ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.245 by root, Tue Jun 30 06:24:38 2009 UTC vs.
Revision 1.372 by root, Sat Jun 4 05:44:16 2011 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_update_now> 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 ahve 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 errornously 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 returning 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
		616	you absolutely have to know whether an event occurred or not because you
		617	have 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. The	958	introduce an additional C<ev_sleep ()> call into most loop iterations. The
817	sleep time ensures that libev will not poll for I/O events more often then	959	sleep time ensures that libev will not poll for I/O events more often then
818	once per this interval, on average.	960	once per this interval, on average.
819		961
820	Likewise, by setting a higher I<timeout collect interval> you allow libev	962	Likewise, by setting a higher I<timeout collect interval> you allow libev
…		…
829	usually doesn't make much sense to set it to a lower value than C<0.01>,	971	usually doesn't make much sense to set it to a lower value than C<0.01>,
830	as this approaches the timing granularity of most systems. Note that if	972	as this approaches the timing granularity of most systems. Note that if
831	you do transactions with the outside world and you can't increase the	973	you do transactions with the outside world and you can't increase the
832	parallelity, then this setting will limit your transaction rate (if you	974	parallelity, then this setting will limit your transaction rate (if you
833	need to poll once per transaction and the I/O collect interval is 0.01,	975	need to poll once per transaction and the I/O collect interval is 0.01,
834	then you can't do more than 100 transations per second).	976	then you can't do more than 100 transactions per second).
835		977
836	Setting the I<timeout collect interval> can improve the opportunity for	978	Setting the I<timeout collect interval> can improve the opportunity for
837	saving power, as the program will "bundle" timer callback invocations that	979	saving power, as the program will "bundle" timer callback invocations that
838	are "near" in time together, by delaying some, thus reducing the number of	980	are "near" in time together, by delaying some, thus reducing the number of
839	times the process sleeps and wakes up again. Another useful technique to	981	times the process sleeps and wakes up again. Another useful technique to
…		…
844	more often than 100 times per second:	986	more often than 100 times per second:
845		987
846	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	988	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
847	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	989	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
848		990
		991	=item ev_invoke_pending (loop)
		992
		993	This call will simply invoke all pending watchers while resetting their
		994	pending state. Normally, C<ev_run> does this automatically when required,
		995	but when overriding the invoke callback this call comes handy. This
		996	function can be invoked from a watcher - this can be useful for example
		997	when you want to do some lengthy calculation and want to pass further
		998	event handling to another thread (you still have to make sure only one
		999	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1000
		1001	=item int ev_pending_count (loop)
		1002
		1003	Returns the number of pending watchers - zero indicates that no watchers
		1004	are pending.
		1005
		1006	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1007
		1008	This overrides the invoke pending functionality of the loop: Instead of
		1009	invoking all pending watchers when there are any, C<ev_run> will call
		1010	this callback instead. This is useful, for example, when you want to
		1011	invoke the actual watchers inside another context (another thread etc.).
		1012
		1013	If you want to reset the callback, use C<ev_invoke_pending> as new
		1014	callback.
		1015
		1016	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		1017
		1018	Sometimes you want to share the same loop between multiple threads. This
		1019	can be done relatively simply by putting mutex_lock/unlock calls around
		1020	each call to a libev function.
		1021
		1022	However, C<ev_run> can run an indefinite time, so it is not feasible
		1023	to wait for it to return. One way around this is to wake up the event
		1024	loop via C<ev_break> and C<av_async_send>, another way is to set these
		1025	I<release> and I<acquire> callbacks on the loop.
		1026
		1027	When set, then C<release> will be called just before the thread is
		1028	suspended waiting for new events, and C<acquire> is called just
		1029	afterwards.
		1030
		1031	Ideally, C<release> will just call your mutex_unlock function, and
		1032	C<acquire> will just call the mutex_lock function again.
		1033
		1034	While event loop modifications are allowed between invocations of
		1035	C<release> and C<acquire> (that's their only purpose after all), no
		1036	modifications done will affect the event loop, i.e. adding watchers will
		1037	have no effect on the set of file descriptors being watched, or the time
		1038	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1039	to take note of any changes you made.
		1040
		1041	In theory, threads executing C<ev_run> will be async-cancel safe between
		1042	invocations of C<release> and C<acquire>.
		1043
		1044	See also the locking example in the C<THREADS> section later in this
		1045	document.
		1046
		1047	=item ev_set_userdata (loop, void *data)
		1048
		1049	=item void *ev_userdata (loop)
		1050
		1051	Set and retrieve a single C<void *> associated with a loop. When
		1052	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1053	C<0>.
		1054
		1055	These two functions can be used to associate arbitrary data with a loop,
		1056	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1057	C<acquire> callbacks described above, but of course can be (ab-)used for
		1058	any other purpose as well.
		1059
849	=item ev_loop_verify (loop)	1060	=item ev_verify (loop)
850		1061
851	This function only does something when C<EV_VERIFY> support has been	1062	This function only does something when C<EV_VERIFY> support has been
852	compiled in, which is the default for non-minimal builds. It tries to go	1063	compiled in, which is the default for non-minimal builds. It tries to go
853	through all internal structures and checks them for validity. If anything	1064	through all internal structures and checks them for validity. If anything
854	is found to be inconsistent, it will print an error message to standard	1065	is found to be inconsistent, it will print an error message to standard
…		…
865		1076
866	In the following description, uppercase C<TYPE> in names stands for the	1077	In the following description, uppercase C<TYPE> in names stands for the
867	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1078	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
868	watchers and C<ev_io_start> for I/O watchers.	1079	watchers and C<ev_io_start> for I/O watchers.
869		1080
870	A watcher is a structure that you create and register to record your	1081	A watcher is an opaque structure that you allocate and register to record
871	interest in some event. For instance, if you want to wait for STDIN to	1082	your interest in some event. To make a concrete example, imagine you want
872	become readable, you would create an C<ev_io> watcher for that:	1083	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1084	for that:
873		1085
874	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1086	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
875	{	1087	{
876	ev_io_stop (w);	1088	ev_io_stop (w);
877	ev_unloop (loop, EVUNLOOP_ALL);	1089	ev_break (loop, EVBREAK_ALL);
878	}	1090	}
879		1091
880	struct ev_loop *loop = ev_default_loop (0);	1092	struct ev_loop *loop = ev_default_loop (0);
881		1093
882	ev_io stdin_watcher;	1094	ev_io stdin_watcher;
883		1095
884	ev_init (&stdin_watcher, my_cb);	1096	ev_init (&stdin_watcher, my_cb);
885	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1097	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
886	ev_io_start (loop, &stdin_watcher);	1098	ev_io_start (loop, &stdin_watcher);
887		1099
888	ev_loop (loop, 0);	1100	ev_run (loop, 0);
889		1101
890	As you can see, you are responsible for allocating the memory for your	1102	As you can see, you are responsible for allocating the memory for your
891	watcher structures (and it is I<usually> a bad idea to do this on the	1103	watcher structures (and it is I<usually> a bad idea to do this on the
892	stack).	1104	stack).
893		1105
894	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1106	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
895	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1107	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
896		1108
897	Each watcher structure must be initialised by a call to C<ev_init	1109	Each watcher structure must be initialised by a call to C<ev_init (watcher
898	(watcher *, callback)>, which expects a callback to be provided. This	1110	*, callback)>, which expects a callback to be provided. This callback is
899	callback gets invoked each time the event occurs (or, in the case of I/O	1111	invoked each time the event occurs (or, in the case of I/O watchers, each
900	watchers, each time the event loop detects that the file descriptor given	1112	time the event loop detects that the file descriptor given is readable
901	is readable and/or writable).	1113	and/or writable).
902		1114
903	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1115	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
904	macro to configure it, with arguments specific to the watcher type. There	1116	macro to configure it, with arguments specific to the watcher type. There
905	is also a macro to combine initialisation and setting in one call: C<<	1117	is also a macro to combine initialisation and setting in one call: C<<
906	ev_TYPE_init (watcher *, callback, ...) >>.	1118	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
929	=item C<EV_WRITE>	1141	=item C<EV_WRITE>
930		1142
931	The file descriptor in the C<ev_io> watcher has become readable and/or	1143	The file descriptor in the C<ev_io> watcher has become readable and/or
932	writable.	1144	writable.
933		1145
934	=item C<EV_TIMEOUT>	1146	=item C<EV_TIMER>
935		1147
936	The C<ev_timer> watcher has timed out.	1148	The C<ev_timer> watcher has timed out.
937		1149
938	=item C<EV_PERIODIC>	1150	=item C<EV_PERIODIC>
939		1151
…		…
957		1169
958	=item C<EV_PREPARE>	1170	=item C<EV_PREPARE>
959		1171
960	=item C<EV_CHECK>	1172	=item C<EV_CHECK>
961		1173
962	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1174	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
963	to gather new events, and all C<ev_check> watchers are invoked just after	1175	to gather new events, and all C<ev_check> watchers are invoked just after
964	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1176	C<ev_run> has gathered them, but before it invokes any callbacks for any
965	received events. Callbacks of both watcher types can start and stop as	1177	received events. Callbacks of both watcher types can start and stop as
966	many watchers as they want, and all of them will be taken into account	1178	many watchers as they want, and all of them will be taken into account
967	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1179	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
968	C<ev_loop> from blocking).	1180	C<ev_run> from blocking).
969		1181
970	=item C<EV_EMBED>	1182	=item C<EV_EMBED>
971		1183
972	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1184	The embedded event loop specified in the C<ev_embed> watcher needs attention.
973		1185
974	=item C<EV_FORK>	1186	=item C<EV_FORK>
975		1187
976	The event loop has been resumed in the child process after fork (see	1188	The event loop has been resumed in the child process after fork (see
977	C<ev_fork>).	1189	C<ev_fork>).
		1190
		1191	=item C<EV_CLEANUP>
		1192
		1193	The event loop is about to be destroyed (see C<ev_cleanup>).
978		1194
979	=item C<EV_ASYNC>	1195	=item C<EV_ASYNC>
980		1196
981	The given async watcher has been asynchronously notified (see C<ev_async>).	1197	The given async watcher has been asynchronously notified (see C<ev_async>).
982		1198
…		…
1029		1245
1030	ev_io w;	1246	ev_io w;
1031	ev_init (&w, my_cb);	1247	ev_init (&w, my_cb);
1032	ev_io_set (&w, STDIN_FILENO, EV_READ);	1248	ev_io_set (&w, STDIN_FILENO, EV_READ);
1033		1249
1034	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1250	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1035		1251
1036	This macro initialises the type-specific parts of a watcher. You need to	1252	This macro initialises the type-specific parts of a watcher. You need to
1037	call C<ev_init> at least once before you call this macro, but you can	1253	call C<ev_init> at least once before you call this macro, but you can
1038	call C<ev_TYPE_set> any number of times. You must not, however, call this	1254	call C<ev_TYPE_set> any number of times. You must not, however, call this
1039	macro on a watcher that is active (it can be pending, however, which is a	1255	macro on a watcher that is active (it can be pending, however, which is a
…		…
1052		1268
1053	Example: Initialise and set an C<ev_io> watcher in one step.	1269	Example: Initialise and set an C<ev_io> watcher in one step.
1054		1270
1055	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1271	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1056		1272
1057	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1273	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1058		1274
1059	Starts (activates) the given watcher. Only active watchers will receive	1275	Starts (activates) the given watcher. Only active watchers will receive
1060	events. If the watcher is already active nothing will happen.	1276	events. If the watcher is already active nothing will happen.
1061		1277
1062	Example: Start the C<ev_io> watcher that is being abused as example in this	1278	Example: Start the C<ev_io> watcher that is being abused as example in this
1063	whole section.	1279	whole section.
1064		1280
1065	ev_io_start (EV_DEFAULT_UC, &w);	1281	ev_io_start (EV_DEFAULT_UC, &w);
1066		1282
1067	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1283	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1068		1284
1069	Stops the given watcher if active, and clears the pending status (whether	1285	Stops the given watcher if active, and clears the pending status (whether
1070	the watcher was active or not).	1286	the watcher was active or not).
1071		1287
1072	It is possible that stopped watchers are pending - for example,	1288	It is possible that stopped watchers are pending - for example,
…		…
1097	=item ev_cb_set (ev_TYPE *watcher, callback)	1313	=item ev_cb_set (ev_TYPE *watcher, callback)
1098		1314
1099	Change the callback. You can change the callback at virtually any time	1315	Change the callback. You can change the callback at virtually any time
1100	(modulo threads).	1316	(modulo threads).
1101		1317
1102	=item ev_set_priority (ev_TYPE *watcher, priority)	1318	=item ev_set_priority (ev_TYPE *watcher, int priority)
1103		1319
1104	=item int ev_priority (ev_TYPE *watcher)	1320	=item int ev_priority (ev_TYPE *watcher)
1105		1321
1106	Set and query the priority of the watcher. The priority is a small	1322	Set and query the priority of the watcher. The priority is a small
1107	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1323	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1139	watcher isn't pending it does nothing and returns C<0>.	1355	watcher isn't pending it does nothing and returns C<0>.
1140		1356
1141	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1357	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1142	callback to be invoked, which can be accomplished with this function.	1358	callback to be invoked, which can be accomplished with this function.
1143		1359
		1360	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1361
		1362	Feeds the given event set into the event loop, as if the specified event
		1363	had happened for the specified watcher (which must be a pointer to an
		1364	initialised but not necessarily started event watcher). Obviously you must
		1365	not free the watcher as long as it has pending events.
		1366
		1367	Stopping the watcher, letting libev invoke it, or calling
		1368	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1369	not started in the first place.
		1370
		1371	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1372	functions that do not need a watcher.
		1373
1144	=back	1374	=back
1145		1375
		1376	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1377	OWN COMPOSITE WATCHERS> idioms.
1146		1378
1147	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1379	=head2 WATCHER STATES
1148		1380
1149	Each watcher has, by default, a member C<void *data> that you can change	1381	There are various watcher states mentioned throughout this manual -
1150	and read at any time: libev will completely ignore it. This can be used	1382	active, pending and so on. In this section these states and the rules to
1151	to associate arbitrary data with your watcher. If you need more data and	1383	transition between them will be described in more detail - and while these
1152	don't want to allocate memory and store a pointer to it in that data	1384	rules might look complicated, they usually do "the right thing".
1153	member, you can also "subclass" the watcher type and provide your own
1154	data:
1155		1385
1156	struct my_io	1386	=over 4
1157	{
1158	ev_io io;
1159	int otherfd;
1160	void *somedata;
1161	struct whatever *mostinteresting;
1162	};
1163		1387
1164	...	1388	=item initialiased
1165	struct my_io w;
1166	ev_io_init (&w.io, my_cb, fd, EV_READ);
1167		1389
1168	And since your callback will be called with a pointer to the watcher, you	1390	Before a watcher can be registered with the event looop it has to be
1169	can cast it back to your own type:	1391	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1392	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1170		1393
1171	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1394	In this state it is simply some block of memory that is suitable for
1172	{	1395	use in an event loop. It can be moved around, freed, reused etc. at
1173	struct my_io *w = (struct my_io *)w_;	1396	will - as long as you either keep the memory contents intact, or call
1174	...	1397	C<ev_TYPE_init> again.
1175	}
1176		1398
1177	More interesting and less C-conformant ways of casting your callback type	1399	=item started/running/active
1178	instead have been omitted.
1179		1400
1180	Another common scenario is to use some data structure with multiple	1401	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1181	embedded watchers:	1402	property of the event loop, and is actively waiting for events. While in
		1403	this state it cannot be accessed (except in a few documented ways), moved,
		1404	freed or anything else - the only legal thing is to keep a pointer to it,
		1405	and call libev functions on it that are documented to work on active watchers.
1182		1406
1183	struct my_biggy	1407	=item pending
1184	{
1185	int some_data;
1186	ev_timer t1;
1187	ev_timer t2;
1188	}
1189		1408
1190	In this case getting the pointer to C<my_biggy> is a bit more	1409	If a watcher is active and libev determines that an event it is interested
1191	complicated: Either you store the address of your C<my_biggy> struct	1410	in has occurred (such as a timer expiring), it will become pending. It will
1192	in the C<data> member of the watcher (for woozies), or you need to use	1411	stay in this pending state until either it is stopped or its callback is
1193	some pointer arithmetic using C<offsetof> inside your watchers (for real	1412	about to be invoked, so it is not normally pending inside the watcher
1194	programmers):	1413	callback.
1195		1414
1196	#include <stddef.h>	1415	The watcher might or might not be active while it is pending (for example,
		1416	an expired non-repeating timer can be pending but no longer active). If it
		1417	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1418	but it is still property of the event loop at this time, so cannot be
		1419	moved, freed or reused. And if it is active the rules described in the
		1420	previous item still apply.
1197		1421
1198	static void	1422	It is also possible to feed an event on a watcher that is not active (e.g.
1199	t1_cb (EV_P_ ev_timer *w, int revents)	1423	via C<ev_feed_event>), in which case it becomes pending without being
1200	{	1424	active.
1201	struct my_biggy big = (struct my_biggy *)
1202	(((char *)w) - offsetof (struct my_biggy, t1));
1203	}
1204		1425
1205	static void	1426	=item stopped
1206	t2_cb (EV_P_ ev_timer *w, int revents)	1427
1207	{	1428	A watcher can be stopped implicitly by libev (in which case it might still
1208	struct my_biggy big = (struct my_biggy *)	1429	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1209	(((char *)w) - offsetof (struct my_biggy, t2));	1430	latter will clear any pending state the watcher might be in, regardless
1210	}	1431	of whether it was active or not, so stopping a watcher explicitly before
		1432	freeing it is often a good idea.
		1433
		1434	While stopped (and not pending) the watcher is essentially in the
		1435	initialised state, that is, it can be reused, moved, modified in any way
		1436	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1437	it again).
		1438
		1439	=back
1211		1440
1212	=head2 WATCHER PRIORITY MODELS	1441	=head2 WATCHER PRIORITY MODELS
1213		1442
1214	Many event loops support I<watcher priorities>, which are usually small	1443	Many event loops support I<watcher priorities>, which are usually small
1215	integers that influence the ordering of event callback invocation	1444	integers that influence the ordering of event callback invocation
…		…
1258		1487
1259	For example, to emulate how many other event libraries handle priorities,	1488	For example, to emulate how many other event libraries handle priorities,
1260	you can associate an C<ev_idle> watcher to each such watcher, and in	1489	you can associate an C<ev_idle> watcher to each such watcher, and in
1261	the normal watcher callback, you just start the idle watcher. The real	1490	the normal watcher callback, you just start the idle watcher. The real
1262	processing is done in the idle watcher callback. This causes libev to	1491	processing is done in the idle watcher callback. This causes libev to
1263	continously poll and process kernel event data for the watcher, but when	1492	continuously poll and process kernel event data for the watcher, but when
1264	the lock-out case is known to be rare (which in turn is rare :), this is	1493	the lock-out case is known to be rare (which in turn is rare :), this is
1265	workable.	1494	workable.
1266		1495
1267	Usually, however, the lock-out model implemented that way will perform	1496	Usually, however, the lock-out model implemented that way will perform
1268	miserably under the type of load it was designed to handle. In that case,	1497	miserably under the type of load it was designed to handle. In that case,
…		…
1282	{	1511	{
1283	// stop the I/O watcher, we received the event, but	1512	// stop the I/O watcher, we received the event, but
1284	// are not yet ready to handle it.	1513	// are not yet ready to handle it.
1285	ev_io_stop (EV_A_ w);	1514	ev_io_stop (EV_A_ w);
1286		1515
1287	// start the idle watcher to ahndle the actual event.	1516	// start the idle watcher to handle the actual event.
1288	// it will not be executed as long as other watchers	1517	// it will not be executed as long as other watchers
1289	// with the default priority are receiving events.	1518	// with the default priority are receiving events.
1290	ev_idle_start (EV_A_ &idle);	1519	ev_idle_start (EV_A_ &idle);
1291	}	1520	}
1292		1521
…		…
1342	In general you can register as many read and/or write event watchers per	1571	In general you can register as many read and/or write event watchers per
1343	fd as you want (as long as you don't confuse yourself). Setting all file	1572	fd as you want (as long as you don't confuse yourself). Setting all file
1344	descriptors to non-blocking mode is also usually a good idea (but not	1573	descriptors to non-blocking mode is also usually a good idea (but not
1345	required if you know what you are doing).	1574	required if you know what you are doing).
1346		1575
1347	If you cannot use non-blocking mode, then force the use of a
1348	known-to-be-good backend (at the time of this writing, this includes only
1349	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1350	descriptors for which non-blocking operation makes no sense (such as
1351	files) - libev doesn't guarentee any specific behaviour in that case.
1352
1353	Another thing you have to watch out for is that it is quite easy to	1576	Another thing you have to watch out for is that it is quite easy to
1354	receive "spurious" readiness notifications, that is your callback might	1577	receive "spurious" readiness notifications, that is, your callback might
1355	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1578	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1356	because there is no data. Not only are some backends known to create a	1579	because there is no data. It is very easy to get into this situation even
1357	lot of those (for example Solaris ports), it is very easy to get into	1580	with a relatively standard program structure. Thus it is best to always
1358	this situation even with a relatively standard program structure. Thus	1581	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1359	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1360	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1582	preferable to a program hanging until some data arrives.
1361		1583
1362	If you cannot run the fd in non-blocking mode (for example you should	1584	If you cannot run the fd in non-blocking mode (for example you should
1363	not play around with an Xlib connection), then you have to separately	1585	not play around with an Xlib connection), then you have to separately
1364	re-test whether a file descriptor is really ready with a known-to-be good	1586	re-test whether a file descriptor is really ready with a known-to-be good
1365	interface such as poll (fortunately in our Xlib example, Xlib already	1587	interface such as poll (fortunately in the case of Xlib, it already does
1366	does this on its own, so its quite safe to use). Some people additionally	1588	this on its own, so its quite safe to use). Some people additionally
1367	use C<SIGALRM> and an interval timer, just to be sure you won't block	1589	use C<SIGALRM> and an interval timer, just to be sure you won't block
1368	indefinitely.	1590	indefinitely.
1369		1591
1370	But really, best use non-blocking mode.	1592	But really, best use non-blocking mode.
1371		1593
…		…
1399		1621
1400	There is no workaround possible except not registering events	1622	There is no workaround possible except not registering events
1401	for potentially C<dup ()>'ed file descriptors, or to resort to	1623	for potentially C<dup ()>'ed file descriptors, or to resort to
1402	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1624	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1403		1625
		1626	=head3 The special problem of files
		1627
		1628	Many people try to use C<select> (or libev) on file descriptors
		1629	representing files, and expect it to become ready when their program
		1630	doesn't block on disk accesses (which can take a long time on their own).
		1631
		1632	However, this cannot ever work in the "expected" way - you get a readiness
		1633	notification as soon as the kernel knows whether and how much data is
		1634	there, and in the case of open files, that's always the case, so you
		1635	always get a readiness notification instantly, and your read (or possibly
		1636	write) will still block on the disk I/O.
		1637
		1638	Another way to view it is that in the case of sockets, pipes, character
		1639	devices and so on, there is another party (the sender) that delivers data
		1640	on its own, but in the case of files, there is no such thing: the disk
		1641	will not send data on its own, simply because it doesn't know what you
		1642	wish to read - you would first have to request some data.
		1643
		1644	Since files are typically not-so-well supported by advanced notification
		1645	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1646	to files, even though you should not use it. The reason for this is
		1647	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1648	usually a tty, often a pipe, but also sometimes files or special devices
		1649	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1650	F</dev/urandom>), and even though the file might better be served with
		1651	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1652	it "just works" instead of freezing.
		1653
		1654	So avoid file descriptors pointing to files when you know it (e.g. use
		1655	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1656	when you rarely read from a file instead of from a socket, and want to
		1657	reuse the same code path.
		1658
1404	=head3 The special problem of fork	1659	=head3 The special problem of fork
1405		1660
1406	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1661	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1407	useless behaviour. Libev fully supports fork, but needs to be told about	1662	useless behaviour. Libev fully supports fork, but needs to be told about
1408	it in the child.	1663	it in the child if you want to continue to use it in the child.
1409		1664
1410	To support fork in your programs, you either have to call	1665	To support fork in your child processes, you have to call C<ev_loop_fork
1411	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1666	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1412	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1667	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1413	C<EVBACKEND_POLL>.
1414		1668
1415	=head3 The special problem of SIGPIPE	1669	=head3 The special problem of SIGPIPE
1416		1670
1417	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1671	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1418	when writing to a pipe whose other end has been closed, your program gets	1672	when writing to a pipe whose other end has been closed, your program gets
…		…
1421		1675
1422	So when you encounter spurious, unexplained daemon exits, make sure you	1676	So when you encounter spurious, unexplained daemon exits, make sure you
1423	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1677	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1424	somewhere, as that would have given you a big clue).	1678	somewhere, as that would have given you a big clue).
1425		1679
		1680	=head3 The special problem of accept()ing when you can't
		1681
		1682	Many implementations of the POSIX C<accept> function (for example,
		1683	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1684	connection from the pending queue in all error cases.
		1685
		1686	For example, larger servers often run out of file descriptors (because
		1687	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1688	rejecting the connection, leading to libev signalling readiness on
		1689	the next iteration again (the connection still exists after all), and
		1690	typically causing the program to loop at 100% CPU usage.
		1691
		1692	Unfortunately, the set of errors that cause this issue differs between
		1693	operating systems, there is usually little the app can do to remedy the
		1694	situation, and no known thread-safe method of removing the connection to
		1695	cope with overload is known (to me).
		1696
		1697	One of the easiest ways to handle this situation is to just ignore it
		1698	- when the program encounters an overload, it will just loop until the
		1699	situation is over. While this is a form of busy waiting, no OS offers an
		1700	event-based way to handle this situation, so it's the best one can do.
		1701
		1702	A better way to handle the situation is to log any errors other than
		1703	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1704	messages, and continue as usual, which at least gives the user an idea of
		1705	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1706	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1707	usage.
		1708
		1709	If your program is single-threaded, then you could also keep a dummy file
		1710	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1711	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1712	close that fd, and create a new dummy fd. This will gracefully refuse
		1713	clients under typical overload conditions.
		1714
		1715	The last way to handle it is to simply log the error and C<exit>, as
		1716	is often done with C<malloc> failures, but this results in an easy
		1717	opportunity for a DoS attack.
1426		1718
1427	=head3 Watcher-Specific Functions	1719	=head3 Watcher-Specific Functions
1428		1720
1429	=over 4	1721	=over 4
1430		1722
…		…
1462	...	1754	...
1463	struct ev_loop *loop = ev_default_init (0);	1755	struct ev_loop *loop = ev_default_init (0);
1464	ev_io stdin_readable;	1756	ev_io stdin_readable;
1465	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1757	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1466	ev_io_start (loop, &stdin_readable);	1758	ev_io_start (loop, &stdin_readable);
1467	ev_loop (loop, 0);	1759	ev_run (loop, 0);
1468		1760
1469		1761
1470	=head2 C<ev_timer> - relative and optionally repeating timeouts	1762	=head2 C<ev_timer> - relative and optionally repeating timeouts
1471		1763
1472	Timer watchers are simple relative timers that generate an event after a	1764	Timer watchers are simple relative timers that generate an event after a
…		…
1480		1772
1481	The callback is guaranteed to be invoked only I<after> its timeout has	1773	The callback is guaranteed to be invoked only I<after> its timeout has
1482	passed (not I<at>, so on systems with very low-resolution clocks this	1774	passed (not I<at>, so on systems with very low-resolution clocks this
1483	might introduce a small delay). If multiple timers become ready during the	1775	might introduce a small delay). If multiple timers become ready during the
1484	same loop iteration then the ones with earlier time-out values are invoked	1776	same loop iteration then the ones with earlier time-out values are invoked
1485	before ones with later time-out values (but this is no longer true when a	1777	before ones of the same priority with later time-out values (but this is
1486	callback calls C<ev_loop> recursively).	1778	no longer true when a callback calls C<ev_run> recursively).
1487		1779
1488	=head3 Be smart about timeouts	1780	=head3 Be smart about timeouts
1489		1781
1490	Many real-world problems involve some kind of timeout, usually for error	1782	Many real-world problems involve some kind of timeout, usually for error
1491	recovery. A typical example is an HTTP request - if the other side hangs,	1783	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1577	ev_tstamp timeout = last_activity + 60.;	1869	ev_tstamp timeout = last_activity + 60.;
1578		1870
1579	// if last_activity + 60. is older than now, we did time out	1871	// if last_activity + 60. is older than now, we did time out
1580	if (timeout < now)	1872	if (timeout < now)
1581	{	1873	{
1582	// timeout occured, take action	1874	// timeout occurred, take action
1583	}	1875	}
1584	else	1876	else
1585	{	1877	{
1586	// callback was invoked, but there was some activity, re-arm	1878	// callback was invoked, but there was some activity, re-arm
1587	// the watcher to fire in last_activity + 60, which is	1879	// the watcher to fire in last_activity + 60, which is
…		…
1609	to the current time (meaning we just have some activity :), then call the	1901	to the current time (meaning we just have some activity :), then call the
1610	callback, which will "do the right thing" and start the timer:	1902	callback, which will "do the right thing" and start the timer:
1611		1903
1612	ev_init (timer, callback);	1904	ev_init (timer, callback);
1613	last_activity = ev_now (loop);	1905	last_activity = ev_now (loop);
1614	callback (loop, timer, EV_TIMEOUT);	1906	callback (loop, timer, EV_TIMER);
1615		1907
1616	And when there is some activity, simply store the current time in	1908	And when there is some activity, simply store the current time in
1617	C<last_activity>, no libev calls at all:	1909	C<last_activity>, no libev calls at all:
1618		1910
1619	last_actiivty = ev_now (loop);	1911	last_activity = ev_now (loop);
1620		1912
1621	This technique is slightly more complex, but in most cases where the	1913	This technique is slightly more complex, but in most cases where the
1622	time-out is unlikely to be triggered, much more efficient.	1914	time-out is unlikely to be triggered, much more efficient.
1623		1915
1624	Changing the timeout is trivial as well (if it isn't hard-coded in the	1916	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1662		1954
1663	=head3 The special problem of time updates	1955	=head3 The special problem of time updates
1664		1956
1665	Establishing the current time is a costly operation (it usually takes at	1957	Establishing the current time is a costly operation (it usually takes at
1666	least two system calls): EV therefore updates its idea of the current	1958	least two system calls): EV therefore updates its idea of the current
1667	time only before and after C<ev_loop> collects new events, which causes a	1959	time only before and after C<ev_run> collects new events, which causes a
1668	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1960	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1669	lots of events in one iteration.	1961	lots of events in one iteration.
1670		1962
1671	The relative timeouts are calculated relative to the C<ev_now ()>	1963	The relative timeouts are calculated relative to the C<ev_now ()>
1672	time. This is usually the right thing as this timestamp refers to the time	1964	time. This is usually the right thing as this timestamp refers to the time
…		…
1678		1970
1679	If the event loop is suspended for a long time, you can also force an	1971	If the event loop is suspended for a long time, you can also force an
1680	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1972	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1681	()>.	1973	()>.
1682		1974
		1975	=head3 The special problems of suspended animation
		1976
		1977	When you leave the server world it is quite customary to hit machines that
		1978	can suspend/hibernate - what happens to the clocks during such a suspend?
		1979
		1980	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1981	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1982	to run until the system is suspended, but they will not advance while the
		1983	system is suspended. That means, on resume, it will be as if the program
		1984	was frozen for a few seconds, but the suspend time will not be counted
		1985	towards C<ev_timer> when a monotonic clock source is used. The real time
		1986	clock advanced as expected, but if it is used as sole clocksource, then a
		1987	long suspend would be detected as a time jump by libev, and timers would
		1988	be adjusted accordingly.
		1989
		1990	I would not be surprised to see different behaviour in different between
		1991	operating systems, OS versions or even different hardware.
		1992
		1993	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1994	time jump in the monotonic clocks and the realtime clock. If the program
		1995	is suspended for a very long time, and monotonic clock sources are in use,
		1996	then you can expect C<ev_timer>s to expire as the full suspension time
		1997	will be counted towards the timers. When no monotonic clock source is in
		1998	use, then libev will again assume a timejump and adjust accordingly.
		1999
		2000	It might be beneficial for this latter case to call C<ev_suspend>
		2001	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2002	deterministic behaviour in this case (you can do nothing against
		2003	C<SIGSTOP>).
		2004
1683	=head3 Watcher-Specific Functions and Data Members	2005	=head3 Watcher-Specific Functions and Data Members
1684		2006
1685	=over 4	2007	=over 4
1686		2008
1687	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2009	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1713	C<repeat> value), or reset the running timer to the C<repeat> value.	2035	C<repeat> value), or reset the running timer to the C<repeat> value.
1714		2036
1715	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2037	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1716	usage example.	2038	usage example.
1717		2039
		2040	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2041
		2042	Returns the remaining time until a timer fires. If the timer is active,
		2043	then this time is relative to the current event loop time, otherwise it's
		2044	the timeout value currently configured.
		2045
		2046	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2047	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2048	will return C<4>. When the timer expires and is restarted, it will return
		2049	roughly C<7> (likely slightly less as callback invocation takes some time,
		2050	too), and so on.
		2051
1718	=item ev_tstamp repeat [read-write]	2052	=item ev_tstamp repeat [read-write]
1719		2053
1720	The current C<repeat> value. Will be used each time the watcher times out	2054	The current C<repeat> value. Will be used each time the watcher times out
1721	or C<ev_timer_again> is called, and determines the next timeout (if any),	2055	or C<ev_timer_again> is called, and determines the next timeout (if any),
1722	which is also when any modifications are taken into account.	2056	which is also when any modifications are taken into account.
…		…
1747	}	2081	}
1748		2082
1749	ev_timer mytimer;	2083	ev_timer mytimer;
1750	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2084	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1751	ev_timer_again (&mytimer); /* start timer */	2085	ev_timer_again (&mytimer); /* start timer */
1752	ev_loop (loop, 0);	2086	ev_run (loop, 0);
1753		2087
1754	// and in some piece of code that gets executed on any "activity":	2088	// and in some piece of code that gets executed on any "activity":
1755	// reset the timeout to start ticking again at 10 seconds	2089	// reset the timeout to start ticking again at 10 seconds
1756	ev_timer_again (&mytimer);	2090	ev_timer_again (&mytimer);
1757		2091
…		…
1783		2117
1784	As with timers, the callback is guaranteed to be invoked only when the	2118	As with timers, the callback is guaranteed to be invoked only when the
1785	point in time where it is supposed to trigger has passed. If multiple	2119	point in time where it is supposed to trigger has passed. If multiple
1786	timers become ready during the same loop iteration then the ones with	2120	timers become ready during the same loop iteration then the ones with
1787	earlier time-out values are invoked before ones with later time-out values	2121	earlier time-out values are invoked before ones with later time-out values
1788	(but this is no longer true when a callback calls C<ev_loop> recursively).	2122	(but this is no longer true when a callback calls C<ev_run> recursively).
1789		2123
1790	=head3 Watcher-Specific Functions and Data Members	2124	=head3 Watcher-Specific Functions and Data Members
1791		2125
1792	=over 4	2126	=over 4
1793		2127
…		…
1828		2162
1829	Another way to think about it (for the mathematically inclined) is that	2163	Another way to think about it (for the mathematically inclined) is that
1830	C<ev_periodic> will try to run the callback in this mode at the next possible	2164	C<ev_periodic> will try to run the callback in this mode at the next possible
1831	time where C<time = offset (mod interval)>, regardless of any time jumps.	2165	time where C<time = offset (mod interval)>, regardless of any time jumps.
1832		2166
1833	For numerical stability it is preferable that the C<offset> value is near	2167	The C<interval> I<MUST> be positive, and for numerical stability, the
1834	C<ev_now ()> (the current time), but there is no range requirement for	2168	interval value should be higher than C<1/8192> (which is around 100
1835	this value, and in fact is often specified as zero.	2169	microseconds) and C<offset> should be higher than C<0> and should have
		2170	at most a similar magnitude as the current time (say, within a factor of
		2171	ten). Typical values for offset are, in fact, C<0> or something between
		2172	C<0> and C<interval>, which is also the recommended range.
1836		2173
1837	Note also that there is an upper limit to how often a timer can fire (CPU	2174	Note also that there is an upper limit to how often a timer can fire (CPU
1838	speed for example), so if C<interval> is very small then timing stability	2175	speed for example), so if C<interval> is very small then timing stability
1839	will of course deteriorate. Libev itself tries to be exact to be about one	2176	will of course deteriorate. Libev itself tries to be exact to be about one
1840	millisecond (if the OS supports it and the machine is fast enough).	2177	millisecond (if the OS supports it and the machine is fast enough).
…		…
1921	Example: Call a callback every hour, or, more precisely, whenever the	2258	Example: Call a callback every hour, or, more precisely, whenever the
1922	system time is divisible by 3600. The callback invocation times have	2259	system time is divisible by 3600. The callback invocation times have
1923	potentially a lot of jitter, but good long-term stability.	2260	potentially a lot of jitter, but good long-term stability.
1924		2261
1925	static void	2262	static void
1926	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2263	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1927	{	2264	{
1928	... its now a full hour (UTC, or TAI or whatever your clock follows)	2265	... its now a full hour (UTC, or TAI or whatever your clock follows)
1929	}	2266	}
1930		2267
1931	ev_periodic hourly_tick;	2268	ev_periodic hourly_tick;
…		…
1954		2291
1955	=head2 C<ev_signal> - signal me when a signal gets signalled!	2292	=head2 C<ev_signal> - signal me when a signal gets signalled!
1956		2293
1957	Signal watchers will trigger an event when the process receives a specific	2294	Signal watchers will trigger an event when the process receives a specific
1958	signal one or more times. Even though signals are very asynchronous, libev	2295	signal one or more times. Even though signals are very asynchronous, libev
1959	will try it's best to deliver signals synchronously, i.e. as part of the	2296	will try its best to deliver signals synchronously, i.e. as part of the
1960	normal event processing, like any other event.	2297	normal event processing, like any other event.
1961		2298
1962	If you want signals asynchronously, just use C<sigaction> as you would	2299	If you want signals to be delivered truly asynchronously, just use
1963	do without libev and forget about sharing the signal. You can even use	2300	C<sigaction> as you would do without libev and forget about sharing
1964	C<ev_async> from a signal handler to synchronously wake up an event loop.	2301	the signal. You can even use C<ev_async> from a signal handler to
		2302	synchronously wake up an event loop.
1965		2303
1966	You can configure as many watchers as you like per signal. Only when the	2304	You can configure as many watchers as you like for the same signal, but
		2305	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2306	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2307	C<SIGINT> in both the default loop and another loop at the same time. At
		2308	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2309
1967	first watcher gets started will libev actually register a signal handler	2310	When the first watcher gets started will libev actually register something
1968	with the kernel (thus it coexists with your own signal handlers as long as	2311	with the kernel (thus it coexists with your own signal handlers as long as
1969	you don't register any with libev for the same signal). Similarly, when	2312	you don't register any with libev for the same signal).
1970	the last signal watcher for a signal is stopped, libev will reset the
1971	signal handler to SIG_DFL (regardless of what it was set to before).
1972		2313
1973	If possible and supported, libev will install its handlers with	2314	If possible and supported, libev will install its handlers with
1974	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2315	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1975	interrupted. If you have a problem with system calls getting interrupted by	2316	not be unduly interrupted. If you have a problem with system calls getting
1976	signals you can block all signals in an C<ev_check> watcher and unblock	2317	interrupted by signals you can block all signals in an C<ev_check> watcher
1977	them in an C<ev_prepare> watcher.	2318	and unblock them in an C<ev_prepare> watcher.
		2319
		2320	=head3 The special problem of inheritance over fork/execve/pthread_create
		2321
		2322	Both the signal mask (C<sigprocmask>) and the signal disposition
		2323	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2324	stopping it again), that is, libev might or might not block the signal,
		2325	and might or might not set or restore the installed signal handler (but
		2326	see C<EVFLAG_NOSIGMASK>).
		2327
		2328	While this does not matter for the signal disposition (libev never
		2329	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2330	C<execve>), this matters for the signal mask: many programs do not expect
		2331	certain signals to be blocked.
		2332
		2333	This means that before calling C<exec> (from the child) you should reset
		2334	the signal mask to whatever "default" you expect (all clear is a good
		2335	choice usually).
		2336
		2337	The simplest way to ensure that the signal mask is reset in the child is
		2338	to install a fork handler with C<pthread_atfork> that resets it. That will
		2339	catch fork calls done by libraries (such as the libc) as well.
		2340
		2341	In current versions of libev, the signal will not be blocked indefinitely
		2342	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2343	the window of opportunity for problems, it will not go away, as libev
		2344	I<has> to modify the signal mask, at least temporarily.
		2345
		2346	So I can't stress this enough: I<If you do not reset your signal mask when
		2347	you expect it to be empty, you have a race condition in your code>. This
		2348	is not a libev-specific thing, this is true for most event libraries.
		2349
		2350	=head3 The special problem of threads signal handling
		2351
		2352	POSIX threads has problematic signal handling semantics, specifically,
		2353	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2354	threads in a process block signals, which is hard to achieve.
		2355
		2356	When you want to use sigwait (or mix libev signal handling with your own
		2357	for the same signals), you can tackle this problem by globally blocking
		2358	all signals before creating any threads (or creating them with a fully set
		2359	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2360	loops. Then designate one thread as "signal receiver thread" which handles
		2361	these signals. You can pass on any signals that libev might be interested
		2362	in by calling C<ev_feed_signal>.
1978		2363
1979	=head3 Watcher-Specific Functions and Data Members	2364	=head3 Watcher-Specific Functions and Data Members
1980		2365
1981	=over 4	2366	=over 4
1982		2367
…		…
1998	Example: Try to exit cleanly on SIGINT.	2383	Example: Try to exit cleanly on SIGINT.
1999		2384
2000	static void	2385	static void
2001	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2386	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2002	{	2387	{
2003	ev_unloop (loop, EVUNLOOP_ALL);	2388	ev_break (loop, EVBREAK_ALL);
2004	}	2389	}
2005		2390
2006	ev_signal signal_watcher;	2391	ev_signal signal_watcher;
2007	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2392	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2008	ev_signal_start (loop, &signal_watcher);	2393	ev_signal_start (loop, &signal_watcher);
…		…
2020	in the next callback invocation is not.	2405	in the next callback invocation is not.
2021		2406
2022	Only the default event loop is capable of handling signals, and therefore	2407	Only the default event loop is capable of handling signals, and therefore
2023	you can only register child watchers in the default event loop.	2408	you can only register child watchers in the default event loop.
2024		2409
		2410	Due to some design glitches inside libev, child watchers will always be
		2411	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2412	libev)
		2413
2025	=head3 Process Interaction	2414	=head3 Process Interaction
2026		2415
2027	Libev grabs C<SIGCHLD> as soon as the default event loop is	2416	Libev grabs C<SIGCHLD> as soon as the default event loop is
2028	initialised. This is necessary to guarantee proper behaviour even if	2417	initialised. This is necessary to guarantee proper behaviour even if the
2029	the first child watcher is started after the child exits. The occurrence	2418	first child watcher is started after the child exits. The occurrence
2030	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2419	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2031	synchronously as part of the event loop processing. Libev always reaps all	2420	synchronously as part of the event loop processing. Libev always reaps all
2032	children, even ones not watched.	2421	children, even ones not watched.
2033		2422
2034	=head3 Overriding the Built-In Processing	2423	=head3 Overriding the Built-In Processing
…		…
2044	=head3 Stopping the Child Watcher	2433	=head3 Stopping the Child Watcher
2045		2434
2046	Currently, the child watcher never gets stopped, even when the	2435	Currently, the child watcher never gets stopped, even when the
2047	child terminates, so normally one needs to stop the watcher in the	2436	child terminates, so normally one needs to stop the watcher in the
2048	callback. Future versions of libev might stop the watcher automatically	2437	callback. Future versions of libev might stop the watcher automatically
2049	when a child exit is detected.	2438	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2439	problem).
2050		2440
2051	=head3 Watcher-Specific Functions and Data Members	2441	=head3 Watcher-Specific Functions and Data Members
2052		2442
2053	=over 4	2443	=over 4
2054		2444
…		…
2389		2779
2390	Prepare and check watchers are usually (but not always) used in pairs:	2780	Prepare and check watchers are usually (but not always) used in pairs:
2391	prepare watchers get invoked before the process blocks and check watchers	2781	prepare watchers get invoked before the process blocks and check watchers
2392	afterwards.	2782	afterwards.
2393		2783
2394	You I<must not> call C<ev_loop> or similar functions that enter	2784	You I<must not> call C<ev_run> or similar functions that enter
2395	the current event loop from either C<ev_prepare> or C<ev_check>	2785	the current event loop from either C<ev_prepare> or C<ev_check>
2396	watchers. Other loops than the current one are fine, however. The	2786	watchers. Other loops than the current one are fine, however. The
2397	rationale behind this is that you do not need to check for recursion in	2787	rationale behind this is that you do not need to check for recursion in
2398	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2788	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2399	C<ev_check> so if you have one watcher of each kind they will always be	2789	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2567		2957
2568	if (timeout >= 0)	2958	if (timeout >= 0)
2569	// create/start timer	2959	// create/start timer
2570		2960
2571	// poll	2961	// poll
2572	ev_loop (EV_A_ 0);	2962	ev_run (EV_A_ 0);
2573		2963
2574	// stop timer again	2964	// stop timer again
2575	if (timeout >= 0)	2965	if (timeout >= 0)
2576	ev_timer_stop (EV_A_ &to);	2966	ev_timer_stop (EV_A_ &to);
2577		2967
…		…
2655	if you do not want that, you need to temporarily stop the embed watcher).	3045	if you do not want that, you need to temporarily stop the embed watcher).
2656		3046
2657	=item ev_embed_sweep (loop, ev_embed *)	3047	=item ev_embed_sweep (loop, ev_embed *)
2658		3048
2659	Make a single, non-blocking sweep over the embedded loop. This works	3049	Make a single, non-blocking sweep over the embedded loop. This works
2660	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3050	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2661	appropriate way for embedded loops.	3051	appropriate way for embedded loops.
2662		3052
2663	=item struct ev_loop *other [read-only]	3053	=item struct ev_loop *other [read-only]
2664		3054
2665	The embedded event loop.	3055	The embedded event loop.
…		…
2725	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3115	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2726	handlers will be invoked, too, of course.	3116	handlers will be invoked, too, of course.
2727		3117
2728	=head3 The special problem of life after fork - how is it possible?	3118	=head3 The special problem of life after fork - how is it possible?
2729		3119
2730	Most uses of C<fork()> consist of forking, then some simple calls to ste	3120	Most uses of C<fork()> consist of forking, then some simple calls to set
2731	up/change the process environment, followed by a call to C<exec()>. This	3121	up/change the process environment, followed by a call to C<exec()>. This
2732	sequence should be handled by libev without any problems.	3122	sequence should be handled by libev without any problems.
2733		3123
2734	This changes when the application actually wants to do event handling	3124	This changes when the application actually wants to do event handling
2735	in the child, or both parent in child, in effect "continuing" after the	3125	in the child, or both parent in child, in effect "continuing" after the
…		…
2751	disadvantage of having to use multiple event loops (which do not support	3141	disadvantage of having to use multiple event loops (which do not support
2752	signal watchers).	3142	signal watchers).
2753		3143
2754	When this is not possible, or you want to use the default loop for	3144	When this is not possible, or you want to use the default loop for
2755	other reasons, then in the process that wants to start "fresh", call	3145	other reasons, then in the process that wants to start "fresh", call
2756	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3146	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2757	the default loop will "orphan" (not stop) all registered watchers, so you	3147	Destroying the default loop will "orphan" (not stop) all registered
2758	have to be careful not to execute code that modifies those watchers. Note	3148	watchers, so you have to be careful not to execute code that modifies
2759	also that in that case, you have to re-register any signal watchers.	3149	those watchers. Note also that in that case, you have to re-register any
		3150	signal watchers.
2760		3151
2761	=head3 Watcher-Specific Functions and Data Members	3152	=head3 Watcher-Specific Functions and Data Members
2762		3153
2763	=over 4	3154	=over 4
2764		3155
2765	=item ev_fork_init (ev_signal *, callback)	3156	=item ev_fork_init (ev_fork *, callback)
2766		3157
2767	Initialises and configures the fork watcher - it has no parameters of any	3158	Initialises and configures the fork watcher - it has no parameters of any
2768	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3159	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2769	believe me.	3160	really.
2770		3161
2771	=back	3162	=back
2772		3163
2773		3164
		3165	=head2 C<ev_cleanup> - even the best things end
		3166
		3167	Cleanup watchers are called just before the event loop is being destroyed
		3168	by a call to C<ev_loop_destroy>.
		3169
		3170	While there is no guarantee that the event loop gets destroyed, cleanup
		3171	watchers provide a convenient method to install cleanup hooks for your
		3172	program, worker threads and so on - you just to make sure to destroy the
		3173	loop when you want them to be invoked.
		3174
		3175	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3176	all other watchers, they do not keep a reference to the event loop (which
		3177	makes a lot of sense if you think about it). Like all other watchers, you
		3178	can call libev functions in the callback, except C<ev_cleanup_start>.
		3179
		3180	=head3 Watcher-Specific Functions and Data Members
		3181
		3182	=over 4
		3183
		3184	=item ev_cleanup_init (ev_cleanup *, callback)
		3185
		3186	Initialises and configures the cleanup watcher - it has no parameters of
		3187	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3188	pointless, I assure you.
		3189
		3190	=back
		3191
		3192	Example: Register an atexit handler to destroy the default loop, so any
		3193	cleanup functions are called.
		3194
		3195	static void
		3196	program_exits (void)
		3197	{
		3198	ev_loop_destroy (EV_DEFAULT_UC);
		3199	}
		3200
		3201	...
		3202	atexit (program_exits);
		3203
		3204
2774	=head2 C<ev_async> - how to wake up another event loop	3205	=head2 C<ev_async> - how to wake up an event loop
2775		3206
2776	In general, you cannot use an C<ev_loop> from multiple threads or other	3207	In general, you cannot use an C<ev_loop> from multiple threads or other
2777	asynchronous sources such as signal handlers (as opposed to multiple event	3208	asynchronous sources such as signal handlers (as opposed to multiple event
2778	loops - those are of course safe to use in different threads).	3209	loops - those are of course safe to use in different threads).
2779		3210
2780	Sometimes, however, you need to wake up another event loop you do not	3211	Sometimes, however, you need to wake up an event loop you do not control,
2781	control, for example because it belongs to another thread. This is what	3212	for example because it belongs to another thread. This is what C<ev_async>
2782	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3213	watchers do: as long as the C<ev_async> watcher is active, you can signal
2783	can signal it by calling C<ev_async_send>, which is thread- and signal	3214	it by calling C<ev_async_send>, which is thread- and signal safe.
2784	safe.
2785		3215
2786	This functionality is very similar to C<ev_signal> watchers, as signals,	3216	This functionality is very similar to C<ev_signal> watchers, as signals,
2787	too, are asynchronous in nature, and signals, too, will be compressed	3217	too, are asynchronous in nature, and signals, too, will be compressed
2788	(i.e. the number of callback invocations may be less than the number of	3218	(i.e. the number of callback invocations may be less than the number of
2789	C<ev_async_sent> calls).	3219	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
		3220	of "global async watchers" by using a watcher on an otherwise unused
		3221	signal, and C<ev_feed_signal> to signal this watcher from another thread,
		3222	even without knowing which loop owns the signal.
2790		3223
2791	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3224	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2792	just the default loop.	3225	just the default loop.
2793		3226
2794	=head3 Queueing	3227	=head3 Queueing
2795		3228
2796	C<ev_async> does not support queueing of data in any way. The reason	3229	C<ev_async> does not support queueing of data in any way. The reason
2797	is that the author does not know of a simple (or any) algorithm for a	3230	is that the author does not know of a simple (or any) algorithm for a
2798	multiple-writer-single-reader queue that works in all cases and doesn't	3231	multiple-writer-single-reader queue that works in all cases and doesn't
2799	need elaborate support such as pthreads.	3232	need elaborate support such as pthreads or unportable memory access
		3233	semantics.
2800		3234
2801	That means that if you want to queue data, you have to provide your own	3235	That means that if you want to queue data, you have to provide your own
2802	queue. But at least I can tell you how to implement locking around your	3236	queue. But at least I can tell you how to implement locking around your
2803	queue:	3237	queue:
2804		3238
…		…
2888	trust me.	3322	trust me.
2889		3323
2890	=item ev_async_send (loop, ev_async *)	3324	=item ev_async_send (loop, ev_async *)
2891		3325
2892	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3326	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2893	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3327	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3328	returns.
		3329
2894	C<ev_feed_event>, this call is safe to do from other threads, signal or	3330	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2895	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3331	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2896	section below on what exactly this means).	3332	embedding section below on what exactly this means).
2897		3333
2898	Note that, as with other watchers in libev, multiple events might get	3334	Note that, as with other watchers in libev, multiple events might get
2899	compressed into a single callback invocation (another way to look at this	3335	compressed into a single callback invocation (another way to look at this
2900	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3336	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
2901	reset when the event loop detects that).	3337	reset when the event loop detects that).
…		…
2943		3379
2944	If C<timeout> is less than 0, then no timeout watcher will be	3380	If C<timeout> is less than 0, then no timeout watcher will be
2945	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3381	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2946	repeat = 0) will be started. C<0> is a valid timeout.	3382	repeat = 0) will be started. C<0> is a valid timeout.
2947		3383
2948	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3384	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2949	passed an C<revents> set like normal event callbacks (a combination of	3385	passed an C<revents> set like normal event callbacks (a combination of
2950	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3386	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2951	value passed to C<ev_once>. Note that it is possible to receive I<both>	3387	value passed to C<ev_once>. Note that it is possible to receive I<both>
2952	a timeout and an io event at the same time - you probably should give io	3388	a timeout and an io event at the same time - you probably should give io
2953	events precedence.	3389	events precedence.
2954		3390
2955	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3391	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2956		3392
2957	static void stdin_ready (int revents, void *arg)	3393	static void stdin_ready (int revents, void *arg)
2958	{	3394	{
2959	if (revents & EV_READ)	3395	if (revents & EV_READ)
2960	/* stdin might have data for us, joy! */;	3396	/* stdin might have data for us, joy! */;
2961	else if (revents & EV_TIMEOUT)	3397	else if (revents & EV_TIMER)
2962	/* doh, nothing entered */;	3398	/* doh, nothing entered */;
2963	}	3399	}
2964		3400
2965	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3401	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2966		3402
2967	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2968
2969	Feeds the given event set into the event loop, as if the specified event
2970	had happened for the specified watcher (which must be a pointer to an
2971	initialised but not necessarily started event watcher).
2972
2973	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3403	=item ev_feed_fd_event (loop, int fd, int revents)
2974		3404
2975	Feed an event on the given fd, as if a file descriptor backend detected	3405	Feed an event on the given fd, as if a file descriptor backend detected
2976	the given events it.	3406	the given events it.
2977		3407
2978	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3408	=item ev_feed_signal_event (loop, int signum)
2979		3409
2980	Feed an event as if the given signal occurred (C<loop> must be the default	3410	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2981	loop!).	3411	which is async-safe.
2982		3412
2983	=back	3413	=back
		3414
		3415
		3416	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3417
		3418	This section explains some common idioms that are not immediately
		3419	obvious. Note that examples are sprinkled over the whole manual, and this
		3420	section only contains stuff that wouldn't fit anywhere else.
		3421
		3422	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3423
		3424	Each watcher has, by default, a C<void *data> member that you can read
		3425	or modify at any time: libev will completely ignore it. This can be used
		3426	to associate arbitrary data with your watcher. If you need more data and
		3427	don't want to allocate memory separately and store a pointer to it in that
		3428	data member, you can also "subclass" the watcher type and provide your own
		3429	data:
		3430
		3431	struct my_io
		3432	{
		3433	ev_io io;
		3434	int otherfd;
		3435	void *somedata;
		3436	struct whatever *mostinteresting;
		3437	};
		3438
		3439	...
		3440	struct my_io w;
		3441	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3442
		3443	And since your callback will be called with a pointer to the watcher, you
		3444	can cast it back to your own type:
		3445
		3446	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3447	{
		3448	struct my_io *w = (struct my_io *)w_;
		3449	...
		3450	}
		3451
		3452	More interesting and less C-conformant ways of casting your callback
		3453	function type instead have been omitted.
		3454
		3455	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3456
		3457	Another common scenario is to use some data structure with multiple
		3458	embedded watchers, in effect creating your own watcher that combines
		3459	multiple libev event sources into one "super-watcher":
		3460
		3461	struct my_biggy
		3462	{
		3463	int some_data;
		3464	ev_timer t1;
		3465	ev_timer t2;
		3466	}
		3467
		3468	In this case getting the pointer to C<my_biggy> is a bit more
		3469	complicated: Either you store the address of your C<my_biggy> struct in
		3470	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3471	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3472	real programmers):
		3473
		3474	#include <stddef.h>
		3475
		3476	static void
		3477	t1_cb (EV_P_ ev_timer *w, int revents)
		3478	{
		3479	struct my_biggy big = (struct my_biggy *)
		3480	(((char *)w) - offsetof (struct my_biggy, t1));
		3481	}
		3482
		3483	static void
		3484	t2_cb (EV_P_ ev_timer *w, int revents)
		3485	{
		3486	struct my_biggy big = (struct my_biggy *)
		3487	(((char *)w) - offsetof (struct my_biggy, t2));
		3488	}
		3489
		3490	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3491
		3492	Often (especially in GUI toolkits) there are places where you have
		3493	I<modal> interaction, which is most easily implemented by recursively
		3494	invoking C<ev_run>.
		3495
		3496	This brings the problem of exiting - a callback might want to finish the
		3497	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3498	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3499	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3500	other combination: In these cases, C<ev_break> will not work alone.
		3501
		3502	The solution is to maintain "break this loop" variable for each C<ev_run>
		3503	invocation, and use a loop around C<ev_run> until the condition is
		3504	triggered, using C<EVRUN_ONCE>:
		3505
		3506	// main loop
		3507	int exit_main_loop = 0;
		3508
		3509	while (!exit_main_loop)
		3510	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3511
		3512	// in a model watcher
		3513	int exit_nested_loop = 0;
		3514
		3515	while (!exit_nested_loop)
		3516	ev_run (EV_A_ EVRUN_ONCE);
		3517
		3518	To exit from any of these loops, just set the corresponding exit variable:
		3519
		3520	// exit modal loop
		3521	exit_nested_loop = 1;
		3522
		3523	// exit main program, after modal loop is finished
		3524	exit_main_loop = 1;
		3525
		3526	// exit both
		3527	exit_main_loop = exit_nested_loop = 1;
		3528
		3529	=head2 THREAD LOCKING EXAMPLE
		3530
		3531	Here is a fictitious example of how to run an event loop in a different
		3532	thread from where callbacks are being invoked and watchers are
		3533	created/added/removed.
		3534
		3535	For a real-world example, see the C<EV::Loop::Async> perl module,
		3536	which uses exactly this technique (which is suited for many high-level
		3537	languages).
		3538
		3539	The example uses a pthread mutex to protect the loop data, a condition
		3540	variable to wait for callback invocations, an async watcher to notify the
		3541	event loop thread and an unspecified mechanism to wake up the main thread.
		3542
		3543	First, you need to associate some data with the event loop:
		3544
		3545	typedef struct {
		3546	mutex_t lock; /* global loop lock */
		3547	ev_async async_w;
		3548	thread_t tid;
		3549	cond_t invoke_cv;
		3550	} userdata;
		3551
		3552	void prepare_loop (EV_P)
		3553	{
		3554	// for simplicity, we use a static userdata struct.
		3555	static userdata u;
		3556
		3557	ev_async_init (&u->async_w, async_cb);
		3558	ev_async_start (EV_A_ &u->async_w);
		3559
		3560	pthread_mutex_init (&u->lock, 0);
		3561	pthread_cond_init (&u->invoke_cv, 0);
		3562
		3563	// now associate this with the loop
		3564	ev_set_userdata (EV_A_ u);
		3565	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3566	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3567
		3568	// then create the thread running ev_run
		3569	pthread_create (&u->tid, 0, l_run, EV_A);
		3570	}
		3571
		3572	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3573	solely to wake up the event loop so it takes notice of any new watchers
		3574	that might have been added:
		3575
		3576	static void
		3577	async_cb (EV_P_ ev_async *w, int revents)
		3578	{
		3579	// just used for the side effects
		3580	}
		3581
		3582	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3583	protecting the loop data, respectively.
		3584
		3585	static void
		3586	l_release (EV_P)
		3587	{
		3588	userdata *u = ev_userdata (EV_A);
		3589	pthread_mutex_unlock (&u->lock);
		3590	}
		3591
		3592	static void
		3593	l_acquire (EV_P)
		3594	{
		3595	userdata *u = ev_userdata (EV_A);
		3596	pthread_mutex_lock (&u->lock);
		3597	}
		3598
		3599	The event loop thread first acquires the mutex, and then jumps straight
		3600	into C<ev_run>:
		3601
		3602	void *
		3603	l_run (void *thr_arg)
		3604	{
		3605	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3606
		3607	l_acquire (EV_A);
		3608	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3609	ev_run (EV_A_ 0);
		3610	l_release (EV_A);
		3611
		3612	return 0;
		3613	}
		3614
		3615	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3616	signal the main thread via some unspecified mechanism (signals? pipe
		3617	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3618	have been called (in a while loop because a) spurious wakeups are possible
		3619	and b) skipping inter-thread-communication when there are no pending
		3620	watchers is very beneficial):
		3621
		3622	static void
		3623	l_invoke (EV_P)
		3624	{
		3625	userdata *u = ev_userdata (EV_A);
		3626
		3627	while (ev_pending_count (EV_A))
		3628	{
		3629	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3630	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3631	}
		3632	}
		3633
		3634	Now, whenever the main thread gets told to invoke pending watchers, it
		3635	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3636	thread to continue:
		3637
		3638	static void
		3639	real_invoke_pending (EV_P)
		3640	{
		3641	userdata *u = ev_userdata (EV_A);
		3642
		3643	pthread_mutex_lock (&u->lock);
		3644	ev_invoke_pending (EV_A);
		3645	pthread_cond_signal (&u->invoke_cv);
		3646	pthread_mutex_unlock (&u->lock);
		3647	}
		3648
		3649	Whenever you want to start/stop a watcher or do other modifications to an
		3650	event loop, you will now have to lock:
		3651
		3652	ev_timer timeout_watcher;
		3653	userdata *u = ev_userdata (EV_A);
		3654
		3655	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3656
		3657	pthread_mutex_lock (&u->lock);
		3658	ev_timer_start (EV_A_ &timeout_watcher);
		3659	ev_async_send (EV_A_ &u->async_w);
		3660	pthread_mutex_unlock (&u->lock);
		3661
		3662	Note that sending the C<ev_async> watcher is required because otherwise
		3663	an event loop currently blocking in the kernel will have no knowledge
		3664	about the newly added timer. By waking up the loop it will pick up any new
		3665	watchers in the next event loop iteration.
		3666
		3667	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3668
		3669	While the overhead of a callback that e.g. schedules a thread is small, it
		3670	is still an overhead. If you embed libev, and your main usage is with some
		3671	kind of threads or coroutines, you might want to customise libev so that
		3672	doesn't need callbacks anymore.
		3673
		3674	Imagine you have coroutines that you can switch to using a function
		3675	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3676	and that due to some magic, the currently active coroutine is stored in a
		3677	global called C<current_coro>. Then you can build your own "wait for libev
		3678	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3679	the differing C<;> conventions):
		3680
		3681	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3682	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3683
		3684	That means instead of having a C callback function, you store the
		3685	coroutine to switch to in each watcher, and instead of having libev call
		3686	your callback, you instead have it switch to that coroutine.
		3687
		3688	A coroutine might now wait for an event with a function called
		3689	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3690	matter when, or whether the watcher is active or not when this function is
		3691	called):
		3692
		3693	void
		3694	wait_for_event (ev_watcher *w)
		3695	{
		3696	ev_cb_set (w) = current_coro;
		3697	switch_to (libev_coro);
		3698	}
		3699
		3700	That basically suspends the coroutine inside C<wait_for_event> and
		3701	continues the libev coroutine, which, when appropriate, switches back to
		3702	this or any other coroutine. I am sure if you sue this your own :)
		3703
		3704	You can do similar tricks if you have, say, threads with an event queue -
		3705	instead of storing a coroutine, you store the queue object and instead of
		3706	switching to a coroutine, you push the watcher onto the queue and notify
		3707	any waiters.
		3708
		3709	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3710	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3711
		3712	// my_ev.h
		3713	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3714	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3715	#include "../libev/ev.h"
		3716
		3717	// my_ev.c
		3718	#define EV_H "my_ev.h"
		3719	#include "../libev/ev.c"
		3720
		3721	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3722	F<my_ev.c> into your project. When properly specifying include paths, you
		3723	can even use F<ev.h> as header file name directly.
2984		3724
2985		3725
2986	=head1 LIBEVENT EMULATION	3726	=head1 LIBEVENT EMULATION
2987		3727
2988	Libev offers a compatibility emulation layer for libevent. It cannot	3728	Libev offers a compatibility emulation layer for libevent. It cannot
2989	emulate the internals of libevent, so here are some usage hints:	3729	emulate the internals of libevent, so here are some usage hints:
2990		3730
2991	=over 4	3731	=over 4
		3732
		3733	=item * Only the libevent-1.4.1-beta API is being emulated.
		3734
		3735	This was the newest libevent version available when libev was implemented,
		3736	and is still mostly unchanged in 2010.
2992		3737
2993	=item * Use it by including <event.h>, as usual.	3738	=item * Use it by including <event.h>, as usual.
2994		3739
2995	=item * The following members are fully supported: ev_base, ev_callback,	3740	=item * The following members are fully supported: ev_base, ev_callback,
2996	ev_arg, ev_fd, ev_res, ev_events.	3741	ev_arg, ev_fd, ev_res, ev_events.
…		…
3002	=item * Priorities are not currently supported. Initialising priorities	3747	=item * Priorities are not currently supported. Initialising priorities
3003	will fail and all watchers will have the same priority, even though there	3748	will fail and all watchers will have the same priority, even though there
3004	is an ev_pri field.	3749	is an ev_pri field.
3005		3750
3006	=item * In libevent, the last base created gets the signals, in libev, the	3751	=item * In libevent, the last base created gets the signals, in libev, the
3007	first base created (== the default loop) gets the signals.	3752	base that registered the signal gets the signals.
3008		3753
3009	=item * Other members are not supported.	3754	=item * Other members are not supported.
3010		3755
3011	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3756	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3012	to use the libev header file and library.	3757	to use the libev header file and library.
…		…
3031	Care has been taken to keep the overhead low. The only data member the C++	3776	Care has been taken to keep the overhead low. The only data member the C++
3032	classes add (compared to plain C-style watchers) is the event loop pointer	3777	classes add (compared to plain C-style watchers) is the event loop pointer
3033	that the watcher is associated with (or no additional members at all if	3778	that the watcher is associated with (or no additional members at all if
3034	you disable C<EV_MULTIPLICITY> when embedding libev).	3779	you disable C<EV_MULTIPLICITY> when embedding libev).
3035		3780
3036	Currently, functions, and static and non-static member functions can be	3781	Currently, functions, static and non-static member functions and classes
3037	used as callbacks. Other types should be easy to add as long as they only	3782	with C<operator ()> can be used as callbacks. Other types should be easy
3038	need one additional pointer for context. If you need support for other	3783	to add as long as they only need one additional pointer for context. If
3039	types of functors please contact the author (preferably after implementing	3784	you need support for other types of functors please contact the author
3040	it).	3785	(preferably after implementing it).
3041		3786
3042	Here is a list of things available in the C<ev> namespace:	3787	Here is a list of things available in the C<ev> namespace:
3043		3788
3044	=over 4	3789	=over 4
3045		3790
…		…
3063		3808
3064	=over 4	3809	=over 4
3065		3810
3066	=item ev::TYPE::TYPE ()	3811	=item ev::TYPE::TYPE ()
3067		3812
3068	=item ev::TYPE::TYPE (struct ev_loop *)	3813	=item ev::TYPE::TYPE (loop)
3069		3814
3070	=item ev::TYPE::~TYPE	3815	=item ev::TYPE::~TYPE
3071		3816
3072	The constructor (optionally) takes an event loop to associate the watcher	3817	The constructor (optionally) takes an event loop to associate the watcher
3073	with. If it is omitted, it will use C<EV_DEFAULT>.	3818	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3106	myclass obj;	3851	myclass obj;
3107	ev::io iow;	3852	ev::io iow;
3108	iow.set <myclass, &myclass::io_cb> (&obj);	3853	iow.set <myclass, &myclass::io_cb> (&obj);
3109		3854
3110	=item w->set (object *)	3855	=item w->set (object *)
3111
3112	This is an B<experimental> feature that might go away in a future version.
3113		3856
3114	This is a variation of a method callback - leaving out the method to call	3857	This is a variation of a method callback - leaving out the method to call
3115	will default the method to C<operator ()>, which makes it possible to use	3858	will default the method to C<operator ()>, which makes it possible to use
3116	functor objects without having to manually specify the C<operator ()> all	3859	functor objects without having to manually specify the C<operator ()> all
3117	the time. Incidentally, you can then also leave out the template argument	3860	the time. Incidentally, you can then also leave out the template argument
…		…
3150	Example: Use a plain function as callback.	3893	Example: Use a plain function as callback.
3151		3894
3152	static void io_cb (ev::io &w, int revents) { }	3895	static void io_cb (ev::io &w, int revents) { }
3153	iow.set <io_cb> ();	3896	iow.set <io_cb> ();
3154		3897
3155	=item w->set (struct ev_loop *)	3898	=item w->set (loop)
3156		3899
3157	Associates a different C<struct ev_loop> with this watcher. You can only	3900	Associates a different C<struct ev_loop> with this watcher. You can only
3158	do this when the watcher is inactive (and not pending either).	3901	do this when the watcher is inactive (and not pending either).
3159		3902
3160	=item w->set ([arguments])	3903	=item w->set ([arguments])
3161		3904
3162	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3905	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3163	called at least once. Unlike the C counterpart, an active watcher gets	3906	method or a suitable start method must be called at least once. Unlike the
3164	automatically stopped and restarted when reconfiguring it with this	3907	C counterpart, an active watcher gets automatically stopped and restarted
3165	method.	3908	when reconfiguring it with this method.
3166		3909
3167	=item w->start ()	3910	=item w->start ()
3168		3911
3169	Starts the watcher. Note that there is no C<loop> argument, as the	3912	Starts the watcher. Note that there is no C<loop> argument, as the
3170	constructor already stores the event loop.	3913	constructor already stores the event loop.
3171		3914
		3915	=item w->start ([arguments])
		3916
		3917	Instead of calling C<set> and C<start> methods separately, it is often
		3918	convenient to wrap them in one call. Uses the same type of arguments as
		3919	the configure C<set> method of the watcher.
		3920
3172	=item w->stop ()	3921	=item w->stop ()
3173		3922
3174	Stops the watcher if it is active. Again, no C<loop> argument.	3923	Stops the watcher if it is active. Again, no C<loop> argument.
3175		3924
3176	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3925	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3188		3937
3189	=back	3938	=back
3190		3939
3191	=back	3940	=back
3192		3941
3193	Example: Define a class with an IO and idle watcher, start one of them in	3942	Example: Define a class with two I/O and idle watchers, start the I/O
3194	the constructor.	3943	watchers in the constructor.
3195		3944
3196	class myclass	3945	class myclass
3197	{	3946	{
3198	ev::io io ; void io_cb (ev::io &w, int revents);	3947	ev::io io ; void io_cb (ev::io &w, int revents);
		3948	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
3199	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3949	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3200		3950
3201	myclass (int fd)	3951	myclass (int fd)
3202	{	3952	{
3203	io .set <myclass, &myclass::io_cb > (this);	3953	io .set <myclass, &myclass::io_cb > (this);
		3954	io2 .set <myclass, &myclass::io2_cb > (this);
3204	idle.set <myclass, &myclass::idle_cb> (this);	3955	idle.set <myclass, &myclass::idle_cb> (this);
3205		3956
3206	io.start (fd, ev::READ);	3957	io.set (fd, ev::WRITE); // configure the watcher
		3958	io.start (); // start it whenever convenient
		3959
		3960	io2.start (fd, ev::READ); // set + start in one call
3207	}	3961	}
3208	};	3962	};
3209		3963
3210		3964
3211	=head1 OTHER LANGUAGE BINDINGS	3965	=head1 OTHER LANGUAGE BINDINGS
…		…
3257	=item Ocaml	4011	=item Ocaml
3258		4012
3259	Erkki Seppala has written Ocaml bindings for libev, to be found at	4013	Erkki Seppala has written Ocaml bindings for libev, to be found at
3260	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4014	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3261		4015
		4016	=item Lua
		4017
		4018	Brian Maher has written a partial interface to libev for lua (at the
		4019	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4020	L<http://github.com/brimworks/lua-ev>.
		4021
3262	=back	4022	=back
3263		4023
3264		4024
3265	=head1 MACRO MAGIC	4025	=head1 MACRO MAGIC
3266		4026
…		…
3279	loop argument"). The C<EV_A> form is used when this is the sole argument,	4039	loop argument"). The C<EV_A> form is used when this is the sole argument,
3280	C<EV_A_> is used when other arguments are following. Example:	4040	C<EV_A_> is used when other arguments are following. Example:
3281		4041
3282	ev_unref (EV_A);	4042	ev_unref (EV_A);
3283	ev_timer_add (EV_A_ watcher);	4043	ev_timer_add (EV_A_ watcher);
3284	ev_loop (EV_A_ 0);	4044	ev_run (EV_A_ 0);
3285		4045
3286	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4046	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3287	which is often provided by the following macro.	4047	which is often provided by the following macro.
3288		4048
3289	=item C<EV_P>, C<EV_P_>	4049	=item C<EV_P>, C<EV_P_>
…		…
3329	}	4089	}
3330		4090
3331	ev_check check;	4091	ev_check check;
3332	ev_check_init (&check, check_cb);	4092	ev_check_init (&check, check_cb);
3333	ev_check_start (EV_DEFAULT_ &check);	4093	ev_check_start (EV_DEFAULT_ &check);
3334	ev_loop (EV_DEFAULT_ 0);	4094	ev_run (EV_DEFAULT_ 0);
3335		4095
3336	=head1 EMBEDDING	4096	=head1 EMBEDDING
3337		4097
3338	Libev can (and often is) directly embedded into host	4098	Libev can (and often is) directly embedded into host
3339	applications. Examples of applications that embed it include the Deliantra	4099	applications. Examples of applications that embed it include the Deliantra
…		…
3419	libev.m4	4179	libev.m4
3420		4180
3421	=head2 PREPROCESSOR SYMBOLS/MACROS	4181	=head2 PREPROCESSOR SYMBOLS/MACROS
3422		4182
3423	Libev can be configured via a variety of preprocessor symbols you have to	4183	Libev can be configured via a variety of preprocessor symbols you have to
3424	define before including any of its files. The default in the absence of	4184	define before including (or compiling) any of its files. The default in
3425	autoconf is documented for every option.	4185	the absence of autoconf is documented for every option.
		4186
		4187	Symbols marked with "(h)" do not change the ABI, and can have different
		4188	values when compiling libev vs. including F<ev.h>, so it is permissible
		4189	to redefine them before including F<ev.h> without breaking compatibility
		4190	to a compiled library. All other symbols change the ABI, which means all
		4191	users of libev and the libev code itself must be compiled with compatible
		4192	settings.
3426		4193
3427	=over 4	4194	=over 4
3428		4195
		4196	=item EV_COMPAT3 (h)
		4197
		4198	Backwards compatibility is a major concern for libev. This is why this
		4199	release of libev comes with wrappers for the functions and symbols that
		4200	have been renamed between libev version 3 and 4.
		4201
		4202	You can disable these wrappers (to test compatibility with future
		4203	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4204	sources. This has the additional advantage that you can drop the C<struct>
		4205	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4206	typedef in that case.
		4207
		4208	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4209	and in some even more future version the compatibility code will be
		4210	removed completely.
		4211
3429	=item EV_STANDALONE	4212	=item EV_STANDALONE (h)
3430		4213
3431	Must always be C<1> if you do not use autoconf configuration, which	4214	Must always be C<1> if you do not use autoconf configuration, which
3432	keeps libev from including F<config.h>, and it also defines dummy	4215	keeps libev from including F<config.h>, and it also defines dummy
3433	implementations for some libevent functions (such as logging, which is not	4216	implementations for some libevent functions (such as logging, which is not
3434	supported). It will also not define any of the structs usually found in	4217	supported). It will also not define any of the structs usually found in
3435	F<event.h> that are not directly supported by the libev core alone.	4218	F<event.h> that are not directly supported by the libev core alone.
3436		4219
3437	In stanbdalone mode, libev will still try to automatically deduce the	4220	In standalone mode, libev will still try to automatically deduce the
3438	configuration, but has to be more conservative.	4221	configuration, but has to be more conservative.
		4222
		4223	=item EV_USE_FLOOR
		4224
		4225	If defined to be C<1>, libev will use the C<floor ()> function for its
		4226	periodic reschedule calculations, otherwise libev will fall back on a
		4227	portable (slower) implementation. If you enable this, you usually have to
		4228	link against libm or something equivalent. Enabling this when the C<floor>
		4229	function is not available will fail, so the safe default is to not enable
		4230	this.
3439		4231
3440	=item EV_USE_MONOTONIC	4232	=item EV_USE_MONOTONIC
3441		4233
3442	If defined to be C<1>, libev will try to detect the availability of the	4234	If defined to be C<1>, libev will try to detect the availability of the
3443	monotonic clock option at both compile time and runtime. Otherwise no	4235	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3507	be used is the winsock select). This means that it will call	4299	be used is the winsock select). This means that it will call
3508	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4300	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3509	it is assumed that all these functions actually work on fds, even	4301	it is assumed that all these functions actually work on fds, even
3510	on win32. Should not be defined on non-win32 platforms.	4302	on win32. Should not be defined on non-win32 platforms.
3511		4303
3512	=item EV_FD_TO_WIN32_HANDLE	4304	=item EV_FD_TO_WIN32_HANDLE(fd)
3513		4305
3514	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4306	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3515	file descriptors to socket handles. When not defining this symbol (the	4307	file descriptors to socket handles. When not defining this symbol (the
3516	default), then libev will call C<_get_osfhandle>, which is usually	4308	default), then libev will call C<_get_osfhandle>, which is usually
3517	correct. In some cases, programs use their own file descriptor management,	4309	correct. In some cases, programs use their own file descriptor management,
3518	in which case they can provide this function to map fds to socket handles.	4310	in which case they can provide this function to map fds to socket handles.
		4311
		4312	=item EV_WIN32_HANDLE_TO_FD(handle)
		4313
		4314	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4315	using the standard C<_open_osfhandle> function. For programs implementing
		4316	their own fd to handle mapping, overwriting this function makes it easier
		4317	to do so. This can be done by defining this macro to an appropriate value.
		4318
		4319	=item EV_WIN32_CLOSE_FD(fd)
		4320
		4321	If programs implement their own fd to handle mapping on win32, then this
		4322	macro can be used to override the C<close> function, useful to unregister
		4323	file descriptors again. Note that the replacement function has to close
		4324	the underlying OS handle.
3519		4325
3520	=item EV_USE_POLL	4326	=item EV_USE_POLL
3521		4327
3522	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4328	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3523	backend. Otherwise it will be enabled on non-win32 platforms. It	4329	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3570	as well as for signal and thread safety in C<ev_async> watchers.	4376	as well as for signal and thread safety in C<ev_async> watchers.
3571		4377
3572	In the absence of this define, libev will use C<sig_atomic_t volatile>	4378	In the absence of this define, libev will use C<sig_atomic_t volatile>
3573	(from F<signal.h>), which is usually good enough on most platforms.	4379	(from F<signal.h>), which is usually good enough on most platforms.
3574		4380
3575	=item EV_H	4381	=item EV_H (h)
3576		4382
3577	The name of the F<ev.h> header file used to include it. The default if	4383	The name of the F<ev.h> header file used to include it. The default if
3578	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4384	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3579	used to virtually rename the F<ev.h> header file in case of conflicts.	4385	used to virtually rename the F<ev.h> header file in case of conflicts.
3580		4386
3581	=item EV_CONFIG_H	4387	=item EV_CONFIG_H (h)
3582		4388
3583	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4389	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3584	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4390	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3585	C<EV_H>, above.	4391	C<EV_H>, above.
3586		4392
3587	=item EV_EVENT_H	4393	=item EV_EVENT_H (h)
3588		4394
3589	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4395	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3590	of how the F<event.h> header can be found, the default is C<"event.h">.	4396	of how the F<event.h> header can be found, the default is C<"event.h">.
3591		4397
3592	=item EV_PROTOTYPES	4398	=item EV_PROTOTYPES (h)
3593		4399
3594	If defined to be C<0>, then F<ev.h> will not define any function	4400	If defined to be C<0>, then F<ev.h> will not define any function
3595	prototypes, but still define all the structs and other symbols. This is	4401	prototypes, but still define all the structs and other symbols. This is
3596	occasionally useful if you want to provide your own wrapper functions	4402	occasionally useful if you want to provide your own wrapper functions
3597	around libev functions.	4403	around libev functions.
…		…
3619	fine.	4425	fine.
3620		4426
3621	If your embedding application does not need any priorities, defining these	4427	If your embedding application does not need any priorities, defining these
3622	both to C<0> will save some memory and CPU.	4428	both to C<0> will save some memory and CPU.
3623		4429
3624	=item EV_PERIODIC_ENABLE	4430	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4431	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4432	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3625		4433
3626	If undefined or defined to be C<1>, then periodic timers are supported. If	4434	If undefined or defined to be C<1> (and the platform supports it), then
3627	defined to be C<0>, then they are not. Disabling them saves a few kB of	4435	the respective watcher type is supported. If defined to be C<0>, then it
3628	code.	4436	is not. Disabling watcher types mainly saves code size.
3629		4437
3630	=item EV_IDLE_ENABLE	4438	=item EV_FEATURES
3631
3632	If undefined or defined to be C<1>, then idle watchers are supported. If
3633	defined to be C<0>, then they are not. Disabling them saves a few kB of
3634	code.
3635
3636	=item EV_EMBED_ENABLE
3637
3638	If undefined or defined to be C<1>, then embed watchers are supported. If
3639	defined to be C<0>, then they are not. Embed watchers rely on most other
3640	watcher types, which therefore must not be disabled.
3641
3642	=item EV_STAT_ENABLE
3643
3644	If undefined or defined to be C<1>, then stat watchers are supported. If
3645	defined to be C<0>, then they are not.
3646
3647	=item EV_FORK_ENABLE
3648
3649	If undefined or defined to be C<1>, then fork watchers are supported. If
3650	defined to be C<0>, then they are not.
3651
3652	=item EV_ASYNC_ENABLE
3653
3654	If undefined or defined to be C<1>, then async watchers are supported. If
3655	defined to be C<0>, then they are not.
3656
3657	=item EV_MINIMAL
3658		4439
3659	If you need to shave off some kilobytes of code at the expense of some	4440	If you need to shave off some kilobytes of code at the expense of some
3660	speed, define this symbol to C<1>. Currently this is used to override some	4441	speed (but with the full API), you can define this symbol to request
3661	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4442	certain subsets of functionality. The default is to enable all features
3662	much smaller 2-heap for timer management over the default 4-heap.	4443	that can be enabled on the platform.
		4444
		4445	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4446	with some broad features you want) and then selectively re-enable
		4447	additional parts you want, for example if you want everything minimal,
		4448	but multiple event loop support, async and child watchers and the poll
		4449	backend, use this:
		4450
		4451	#define EV_FEATURES 0
		4452	#define EV_MULTIPLICITY 1
		4453	#define EV_USE_POLL 1
		4454	#define EV_CHILD_ENABLE 1
		4455	#define EV_ASYNC_ENABLE 1
		4456
		4457	The actual value is a bitset, it can be a combination of the following
		4458	values:
		4459
		4460	=over 4
		4461
		4462	=item C<1> - faster/larger code
		4463
		4464	Use larger code to speed up some operations.
		4465
		4466	Currently this is used to override some inlining decisions (enlarging the
		4467	code size by roughly 30% on amd64).
		4468
		4469	When optimising for size, use of compiler flags such as C<-Os> with
		4470	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4471	assertions.
		4472
		4473	=item C<2> - faster/larger data structures
		4474
		4475	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4476	hash table sizes and so on. This will usually further increase code size
		4477	and can additionally have an effect on the size of data structures at
		4478	runtime.
		4479
		4480	=item C<4> - full API configuration
		4481
		4482	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4483	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4484
		4485	=item C<8> - full API
		4486
		4487	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4488	details on which parts of the API are still available without this
		4489	feature, and do not complain if this subset changes over time.
		4490
		4491	=item C<16> - enable all optional watcher types
		4492
		4493	Enables all optional watcher types. If you want to selectively enable
		4494	only some watcher types other than I/O and timers (e.g. prepare,
		4495	embed, async, child...) you can enable them manually by defining
		4496	C<EV_watchertype_ENABLE> to C<1> instead.
		4497
		4498	=item C<32> - enable all backends
		4499
		4500	This enables all backends - without this feature, you need to enable at
		4501	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4502
		4503	=item C<64> - enable OS-specific "helper" APIs
		4504
		4505	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4506	default.
		4507
		4508	=back
		4509
		4510	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4511	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4512	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4513	watchers, timers and monotonic clock support.
		4514
		4515	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4516	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4517	your program might be left out as well - a binary starting a timer and an
		4518	I/O watcher then might come out at only 5Kb.
		4519
		4520	=item EV_AVOID_STDIO
		4521
		4522	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4523	functions (printf, scanf, perror etc.). This will increase the code size
		4524	somewhat, but if your program doesn't otherwise depend on stdio and your
		4525	libc allows it, this avoids linking in the stdio library which is quite
		4526	big.
		4527
		4528	Note that error messages might become less precise when this option is
		4529	enabled.
		4530
		4531	=item EV_NSIG
		4532
		4533	The highest supported signal number, +1 (or, the number of
		4534	signals): Normally, libev tries to deduce the maximum number of signals
		4535	automatically, but sometimes this fails, in which case it can be
		4536	specified. Also, using a lower number than detected (C<32> should be
		4537	good for about any system in existence) can save some memory, as libev
		4538	statically allocates some 12-24 bytes per signal number.
3663		4539
3664	=item EV_PID_HASHSIZE	4540	=item EV_PID_HASHSIZE
3665		4541
3666	C<ev_child> watchers use a small hash table to distribute workload by	4542	C<ev_child> watchers use a small hash table to distribute workload by
3667	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4543	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3668	than enough. If you need to manage thousands of children you might want to	4544	usually more than enough. If you need to manage thousands of children you
3669	increase this value (I<must> be a power of two).	4545	might want to increase this value (I<must> be a power of two).
3670		4546
3671	=item EV_INOTIFY_HASHSIZE	4547	=item EV_INOTIFY_HASHSIZE
3672		4548
3673	C<ev_stat> watchers use a small hash table to distribute workload by	4549	C<ev_stat> watchers use a small hash table to distribute workload by
3674	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4550	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3675	usually more than enough. If you need to manage thousands of C<ev_stat>	4551	disabled), usually more than enough. If you need to manage thousands of
3676	watchers you might want to increase this value (I<must> be a power of	4552	C<ev_stat> watchers you might want to increase this value (I<must> be a
3677	two).	4553	power of two).
3678		4554
3679	=item EV_USE_4HEAP	4555	=item EV_USE_4HEAP
3680		4556
3681	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4557	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3682	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4558	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3683	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4559	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3684	faster performance with many (thousands) of watchers.	4560	faster performance with many (thousands) of watchers.
3685		4561
3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4562	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3687	(disabled).	4563	will be C<0>.
3688		4564
3689	=item EV_HEAP_CACHE_AT	4565	=item EV_HEAP_CACHE_AT
3690		4566
3691	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4567	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3692	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4568	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3693	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4569	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3694	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4570	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3695	but avoids random read accesses on heap changes. This improves performance	4571	but avoids random read accesses on heap changes. This improves performance
3696	noticeably with many (hundreds) of watchers.	4572	noticeably with many (hundreds) of watchers.
3697		4573
3698	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4574	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3699	(disabled).	4575	will be C<0>.
3700		4576
3701	=item EV_VERIFY	4577	=item EV_VERIFY
3702		4578
3703	Controls how much internal verification (see C<ev_loop_verify ()>) will	4579	Controls how much internal verification (see C<ev_verify ()>) will
3704	be done: If set to C<0>, no internal verification code will be compiled	4580	be done: If set to C<0>, no internal verification code will be compiled
3705	in. If set to C<1>, then verification code will be compiled in, but not	4581	in. If set to C<1>, then verification code will be compiled in, but not
3706	called. If set to C<2>, then the internal verification code will be	4582	called. If set to C<2>, then the internal verification code will be
3707	called once per loop, which can slow down libev. If set to C<3>, then the	4583	called once per loop, which can slow down libev. If set to C<3>, then the
3708	verification code will be called very frequently, which will slow down	4584	verification code will be called very frequently, which will slow down
3709	libev considerably.	4585	libev considerably.
3710		4586
3711	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4587	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3712	C<0>.	4588	will be C<0>.
3713		4589
3714	=item EV_COMMON	4590	=item EV_COMMON
3715		4591
3716	By default, all watchers have a C<void *data> member. By redefining	4592	By default, all watchers have a C<void *data> member. By redefining
3717	this macro to a something else you can include more and other types of	4593	this macro to something else you can include more and other types of
3718	members. You have to define it each time you include one of the files,	4594	members. You have to define it each time you include one of the files,
3719	though, and it must be identical each time.	4595	though, and it must be identical each time.
3720		4596
3721	For example, the perl EV module uses something like this:	4597	For example, the perl EV module uses something like this:
3722		4598
…		…
3775	file.	4651	file.
3776		4652
3777	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4653	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3778	that everybody includes and which overrides some configure choices:	4654	that everybody includes and which overrides some configure choices:
3779		4655
3780	#define EV_MINIMAL 1	4656	#define EV_FEATURES 8
3781	#define EV_USE_POLL 0	4657	#define EV_USE_SELECT 1
3782	#define EV_MULTIPLICITY 0
3783	#define EV_PERIODIC_ENABLE 0	4658	#define EV_PREPARE_ENABLE 1
		4659	#define EV_IDLE_ENABLE 1
3784	#define EV_STAT_ENABLE 0	4660	#define EV_SIGNAL_ENABLE 1
3785	#define EV_FORK_ENABLE 0	4661	#define EV_CHILD_ENABLE 1
		4662	#define EV_USE_STDEXCEPT 0
3786	#define EV_CONFIG_H <config.h>	4663	#define EV_CONFIG_H <config.h>
3787	#define EV_MINPRI 0
3788	#define EV_MAXPRI 0
3789		4664
3790	#include "ev++.h"	4665	#include "ev++.h"
3791		4666
3792	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4667	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3793		4668
3794	#include "ev_cpp.h"	4669	#include "ev_cpp.h"
3795	#include "ev.c"	4670	#include "ev.c"
3796		4671
3797	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4672	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3798		4673
3799	=head2 THREADS AND COROUTINES	4674	=head2 THREADS AND COROUTINES
3800		4675
3801	=head3 THREADS	4676	=head3 THREADS
3802		4677
…		…
3853	default loop and triggering an C<ev_async> watcher from the default loop	4728	default loop and triggering an C<ev_async> watcher from the default loop
3854	watcher callback into the event loop interested in the signal.	4729	watcher callback into the event loop interested in the signal.
3855		4730
3856	=back	4731	=back
3857		4732
		4733	See also L<THREAD LOCKING EXAMPLE>.
		4734
3858	=head3 COROUTINES	4735	=head3 COROUTINES
3859		4736
3860	Libev is very accommodating to coroutines ("cooperative threads"):	4737	Libev is very accommodating to coroutines ("cooperative threads"):
3861	libev fully supports nesting calls to its functions from different	4738	libev fully supports nesting calls to its functions from different
3862	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4739	coroutines (e.g. you can call C<ev_run> on the same loop from two
3863	different coroutines, and switch freely between both coroutines running the	4740	different coroutines, and switch freely between both coroutines running
3864	loop, as long as you don't confuse yourself). The only exception is that	4741	the loop, as long as you don't confuse yourself). The only exception is
3865	you must not do this from C<ev_periodic> reschedule callbacks.	4742	that you must not do this from C<ev_periodic> reschedule callbacks.
3866		4743
3867	Care has been taken to ensure that libev does not keep local state inside	4744	Care has been taken to ensure that libev does not keep local state inside
3868	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4745	C<ev_run>, and other calls do not usually allow for coroutine switches as
3869	they do not call any callbacks.	4746	they do not call any callbacks.
3870		4747
3871	=head2 COMPILER WARNINGS	4748	=head2 COMPILER WARNINGS
3872		4749
3873	Depending on your compiler and compiler settings, you might get no or a	4750	Depending on your compiler and compiler settings, you might get no or a
…		…
3884	maintainable.	4761	maintainable.
3885		4762
3886	And of course, some compiler warnings are just plain stupid, or simply	4763	And of course, some compiler warnings are just plain stupid, or simply
3887	wrong (because they don't actually warn about the condition their message	4764	wrong (because they don't actually warn about the condition their message
3888	seems to warn about). For example, certain older gcc versions had some	4765	seems to warn about). For example, certain older gcc versions had some
3889	warnings that resulted an extreme number of false positives. These have	4766	warnings that resulted in an extreme number of false positives. These have
3890	been fixed, but some people still insist on making code warn-free with	4767	been fixed, but some people still insist on making code warn-free with
3891	such buggy versions.	4768	such buggy versions.
3892		4769
3893	While libev is written to generate as few warnings as possible,	4770	While libev is written to generate as few warnings as possible,
3894	"warn-free" code is not a goal, and it is recommended not to build libev	4771	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3930	I suggest using suppression lists.	4807	I suggest using suppression lists.
3931		4808
3932		4809
3933	=head1 PORTABILITY NOTES	4810	=head1 PORTABILITY NOTES
3934		4811
		4812	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4813
		4814	GNU/Linux is the only common platform that supports 64 bit file/large file
		4815	interfaces but I<disables> them by default.
		4816
		4817	That means that libev compiled in the default environment doesn't support
		4818	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4819
		4820	Unfortunately, many programs try to work around this GNU/Linux issue
		4821	by enabling the large file API, which makes them incompatible with the
		4822	standard libev compiled for their system.
		4823
		4824	Likewise, libev cannot enable the large file API itself as this would
		4825	suddenly make it incompatible to the default compile time environment,
		4826	i.e. all programs not using special compile switches.
		4827
		4828	=head2 OS/X AND DARWIN BUGS
		4829
		4830	The whole thing is a bug if you ask me - basically any system interface
		4831	you touch is broken, whether it is locales, poll, kqueue or even the
		4832	OpenGL drivers.
		4833
		4834	=head3 C<kqueue> is buggy
		4835
		4836	The kqueue syscall is broken in all known versions - most versions support
		4837	only sockets, many support pipes.
		4838
		4839	Libev tries to work around this by not using C<kqueue> by default on this
		4840	rotten platform, but of course you can still ask for it when creating a
		4841	loop - embedding a socket-only kqueue loop into a select-based one is
		4842	probably going to work well.
		4843
		4844	=head3 C<poll> is buggy
		4845
		4846	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4847	implementation by something calling C<kqueue> internally around the 10.5.6
		4848	release, so now C<kqueue> I<and> C<poll> are broken.
		4849
		4850	Libev tries to work around this by not using C<poll> by default on
		4851	this rotten platform, but of course you can still ask for it when creating
		4852	a loop.
		4853
		4854	=head3 C<select> is buggy
		4855
		4856	All that's left is C<select>, and of course Apple found a way to fuck this
		4857	one up as well: On OS/X, C<select> actively limits the number of file
		4858	descriptors you can pass in to 1024 - your program suddenly crashes when
		4859	you use more.
		4860
		4861	There is an undocumented "workaround" for this - defining
		4862	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4863	work on OS/X.
		4864
		4865	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4866
		4867	=head3 C<errno> reentrancy
		4868
		4869	The default compile environment on Solaris is unfortunately so
		4870	thread-unsafe that you can't even use components/libraries compiled
		4871	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4872	defined by default. A valid, if stupid, implementation choice.
		4873
		4874	If you want to use libev in threaded environments you have to make sure
		4875	it's compiled with C<_REENTRANT> defined.
		4876
		4877	=head3 Event port backend
		4878
		4879	The scalable event interface for Solaris is called "event
		4880	ports". Unfortunately, this mechanism is very buggy in all major
		4881	releases. If you run into high CPU usage, your program freezes or you get
		4882	a large number of spurious wakeups, make sure you have all the relevant
		4883	and latest kernel patches applied. No, I don't know which ones, but there
		4884	are multiple ones to apply, and afterwards, event ports actually work
		4885	great.
		4886
		4887	If you can't get it to work, you can try running the program by setting
		4888	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4889	C<select> backends.
		4890
		4891	=head2 AIX POLL BUG
		4892
		4893	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4894	this by trying to avoid the poll backend altogether (i.e. it's not even
		4895	compiled in), which normally isn't a big problem as C<select> works fine
		4896	with large bitsets on AIX, and AIX is dead anyway.
		4897
3935	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4898	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4899
		4900	=head3 General issues
3936		4901
3937	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4902	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3938	requires, and its I/O model is fundamentally incompatible with the POSIX	4903	requires, and its I/O model is fundamentally incompatible with the POSIX
3939	model. Libev still offers limited functionality on this platform in	4904	model. Libev still offers limited functionality on this platform in
3940	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4905	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3941	descriptors. This only applies when using Win32 natively, not when using	4906	descriptors. This only applies when using Win32 natively, not when using
3942	e.g. cygwin.	4907	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4908	as every compielr comes with a slightly differently broken/incompatible
		4909	environment.
3943		4910
3944	Lifting these limitations would basically require the full	4911	Lifting these limitations would basically require the full
3945	re-implementation of the I/O system. If you are into these kinds of	4912	re-implementation of the I/O system. If you are into this kind of thing,
3946	things, then note that glib does exactly that for you in a very portable	4913	then note that glib does exactly that for you in a very portable way (note
3947	way (note also that glib is the slowest event library known to man).	4914	also that glib is the slowest event library known to man).
3948		4915
3949	There is no supported compilation method available on windows except	4916	There is no supported compilation method available on windows except
3950	embedding it into other applications.	4917	embedding it into other applications.
3951		4918
3952	Sensible signal handling is officially unsupported by Microsoft - libev	4919	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3980	you do I<not> compile the F<ev.c> or any other embedded source files!):	4947	you do I<not> compile the F<ev.c> or any other embedded source files!):
3981		4948
3982	#include "evwrap.h"	4949	#include "evwrap.h"
3983	#include "ev.c"	4950	#include "ev.c"
3984		4951
3985	=over 4
3986
3987	=item The winsocket select function	4952	=head3 The winsocket C<select> function
3988		4953
3989	The winsocket C<select> function doesn't follow POSIX in that it	4954	The winsocket C<select> function doesn't follow POSIX in that it
3990	requires socket I<handles> and not socket I<file descriptors> (it is	4955	requires socket I<handles> and not socket I<file descriptors> (it is
3991	also extremely buggy). This makes select very inefficient, and also	4956	also extremely buggy). This makes select very inefficient, and also
3992	requires a mapping from file descriptors to socket handles (the Microsoft	4957	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4001	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4966	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4002		4967
4003	Note that winsockets handling of fd sets is O(n), so you can easily get a	4968	Note that winsockets handling of fd sets is O(n), so you can easily get a
4004	complexity in the O(n²) range when using win32.	4969	complexity in the O(n²) range when using win32.
4005		4970
4006	=item Limited number of file descriptors	4971	=head3 Limited number of file descriptors
4007		4972
4008	Windows has numerous arbitrary (and low) limits on things.	4973	Windows has numerous arbitrary (and low) limits on things.
4009		4974
4010	Early versions of winsocket's select only supported waiting for a maximum	4975	Early versions of winsocket's select only supported waiting for a maximum
4011	of C<64> handles (probably owning to the fact that all windows kernels	4976	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4026	runtime libraries. This might get you to about C<512> or C<2048> sockets	4991	runtime libraries. This might get you to about C<512> or C<2048> sockets
4027	(depending on windows version and/or the phase of the moon). To get more,	4992	(depending on windows version and/or the phase of the moon). To get more,
4028	you need to wrap all I/O functions and provide your own fd management, but	4993	you need to wrap all I/O functions and provide your own fd management, but
4029	the cost of calling select (O(n²)) will likely make this unworkable.	4994	the cost of calling select (O(n²)) will likely make this unworkable.
4030		4995
4031	=back
4032
4033	=head2 PORTABILITY REQUIREMENTS	4996	=head2 PORTABILITY REQUIREMENTS
4034		4997
4035	In addition to a working ISO-C implementation and of course the	4998	In addition to a working ISO-C implementation and of course the
4036	backend-specific APIs, libev relies on a few additional extensions:	4999	backend-specific APIs, libev relies on a few additional extensions:
4037		5000
…		…
4043	Libev assumes not only that all watcher pointers have the same internal	5006	Libev assumes not only that all watcher pointers have the same internal
4044	structure (guaranteed by POSIX but not by ISO C for example), but it also	5007	structure (guaranteed by POSIX but not by ISO C for example), but it also
4045	assumes that the same (machine) code can be used to call any watcher	5008	assumes that the same (machine) code can be used to call any watcher
4046	callback: The watcher callbacks have different type signatures, but libev	5009	callback: The watcher callbacks have different type signatures, but libev
4047	calls them using an C<ev_watcher *> internally.	5010	calls them using an C<ev_watcher *> internally.
		5011
		5012	=item pointer accesses must be thread-atomic
		5013
		5014	Accessing a pointer value must be atomic, it must both be readable and
		5015	writable in one piece - this is the case on all current architectures.
4048		5016
4049	=item C<sig_atomic_t volatile> must be thread-atomic as well	5017	=item C<sig_atomic_t volatile> must be thread-atomic as well
4050		5018
4051	The type C<sig_atomic_t volatile> (or whatever is defined as	5019	The type C<sig_atomic_t volatile> (or whatever is defined as
4052	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5020	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4075	watchers.	5043	watchers.
4076		5044
4077	=item C<double> must hold a time value in seconds with enough accuracy	5045	=item C<double> must hold a time value in seconds with enough accuracy
4078		5046
4079	The type C<double> is used to represent timestamps. It is required to	5047	The type C<double> is used to represent timestamps. It is required to
4080	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5048	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4081	enough for at least into the year 4000. This requirement is fulfilled by	5049	good enough for at least into the year 4000 with millisecond accuracy
		5050	(the design goal for libev). This requirement is overfulfilled by
4082	implementations implementing IEEE 754 (basically all existing ones).	5051	implementations using IEEE 754, which is basically all existing ones. With
		5052	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
4083		5053
4084	=back	5054	=back
4085		5055
4086	If you know of other additional requirements drop me a note.	5056	If you know of other additional requirements drop me a note.
4087		5057
…		…
4155	involves iterating over all running async watchers or all signal numbers.	5125	involves iterating over all running async watchers or all signal numbers.
4156		5126
4157	=back	5127	=back
4158		5128
4159		5129
		5130	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5131
		5132	The major version 4 introduced some incompatible changes to the API.
		5133
		5134	At the moment, the C<ev.h> header file provides compatibility definitions
		5135	for all changes, so most programs should still compile. The compatibility
		5136	layer might be removed in later versions of libev, so better update to the
		5137	new API early than late.
		5138
		5139	=over 4
		5140
		5141	=item C<EV_COMPAT3> backwards compatibility mechanism
		5142
		5143	The backward compatibility mechanism can be controlled by
		5144	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5145	section.
		5146
		5147	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5148
		5149	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5150
		5151	ev_loop_destroy (EV_DEFAULT_UC);
		5152	ev_loop_fork (EV_DEFAULT);
		5153
		5154	=item function/symbol renames
		5155
		5156	A number of functions and symbols have been renamed:
		5157
		5158	ev_loop => ev_run
		5159	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5160	EVLOOP_ONESHOT => EVRUN_ONCE
		5161
		5162	ev_unloop => ev_break
		5163	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5164	EVUNLOOP_ONE => EVBREAK_ONE
		5165	EVUNLOOP_ALL => EVBREAK_ALL
		5166
		5167	EV_TIMEOUT => EV_TIMER
		5168
		5169	ev_loop_count => ev_iteration
		5170	ev_loop_depth => ev_depth
		5171	ev_loop_verify => ev_verify
		5172
		5173	Most functions working on C<struct ev_loop> objects don't have an
		5174	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5175	associated constants have been renamed to not collide with the C<struct
		5176	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5177	as all other watcher types. Note that C<ev_loop_fork> is still called
		5178	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5179	typedef.
		5180
		5181	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5182
		5183	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5184	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5185	and work, but the library code will of course be larger.
		5186
		5187	=back
		5188
		5189
4160	=head1 GLOSSARY	5190	=head1 GLOSSARY
4161		5191
4162	=over 4	5192	=over 4
4163		5193
4164	=item active	5194	=item active
4165		5195
4166	A watcher is active as long as it has been started (has been attached to	5196	A watcher is active as long as it has been started and not yet stopped.
4167	an event loop) but not yet stopped (disassociated from the event loop).	5197	See L<WATCHER STATES> for details.
4168		5198
4169	=item application	5199	=item application
4170		5200
4171	In this document, an application is whatever is using libev.	5201	In this document, an application is whatever is using libev.
		5202
		5203	=item backend
		5204
		5205	The part of the code dealing with the operating system interfaces.
4172		5206
4173	=item callback	5207	=item callback
4174		5208
4175	The address of a function that is called when some event has been	5209	The address of a function that is called when some event has been
4176	detected. Callbacks are being passed the event loop, the watcher that	5210	detected. Callbacks are being passed the event loop, the watcher that
4177	received the event, and the actual event bitset.	5211	received the event, and the actual event bitset.
4178		5212
4179	=item callback invocation	5213	=item callback/watcher invocation
4180		5214
4181	The act of calling the callback associated with a watcher.	5215	The act of calling the callback associated with a watcher.
4182		5216
4183	=item event	5217	=item event
4184		5218
4185	A change of state of some external event, such as data now being available	5219	A change of state of some external event, such as data now being available
4186	for reading on a file descriptor, time having passed or simply not having	5220	for reading on a file descriptor, time having passed or simply not having
4187	any other events happening anymore.	5221	any other events happening anymore.
4188		5222
4189	In libev, events are represented as single bits (such as C<EV_READ> or	5223	In libev, events are represented as single bits (such as C<EV_READ> or
4190	C<EV_TIMEOUT>).	5224	C<EV_TIMER>).
4191		5225
4192	=item event library	5226	=item event library
4193		5227
4194	A software package implementing an event model and loop.	5228	A software package implementing an event model and loop.
4195		5229
…		…
4203	The model used to describe how an event loop handles and processes	5237	The model used to describe how an event loop handles and processes
4204	watchers and events.	5238	watchers and events.
4205		5239
4206	=item pending	5240	=item pending
4207		5241
4208	A watcher is pending as soon as the corresponding event has been detected,	5242	A watcher is pending as soon as the corresponding event has been
4209	and stops being pending as soon as the watcher will be invoked or its	5243	detected. See L<WATCHER STATES> for details.
4210	pending status is explicitly cleared by the application.
4211
4212	A watcher can be pending, but not active. Stopping a watcher also clears
4213	its pending status.
4214		5244
4215	=item real time	5245	=item real time
4216		5246
4217	The physical time that is observed. It is apparently strictly monotonic :)	5247	The physical time that is observed. It is apparently strictly monotonic :)
4218		5248
4219	=item wall-clock time	5249	=item wall-clock time
4220		5250
4221	The time and date as shown on clocks. Unlike real time, it can actually	5251	The time and date as shown on clocks. Unlike real time, it can actually
4222	be wrong and jump forwards and backwards, e.g. when the you adjust your	5252	be wrong and jump forwards and backwards, e.g. when you adjust your
4223	clock.	5253	clock.
4224		5254
4225	=item watcher	5255	=item watcher
4226		5256
4227	A data structure that describes interest in certain events. Watchers need	5257	A data structure that describes interest in certain events. Watchers need
4228	to be started (attached to an event loop) before they can receive events.	5258	to be started (attached to an event loop) before they can receive events.
4229		5259
4230	=item watcher invocation
4231
4232	The act of calling the callback associated with a watcher.
4233
4234	=back	5260	=back
4235		5261
4236	=head1 AUTHOR	5262	=head1 AUTHOR
4237		5263
4238	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5264	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5265	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4239		5266

Diff Legend

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