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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
132	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
133	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_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 have to make sure signals are unblocked
		447	when you want to receive them.
		448
		449	This behaviour is useful when you want to do your own signal handling, or
		450	want to handle signals only in specific threads and want to avoid libev
		451	unblocking the signals.
		452
		453	It's also required by POSIX in a threaded program, as libev calls
		454	C<sigprocmask>, whose behaviour is officially unspecified.
		455
		456	This flag's behaviour will become the default in future versions of libev.
		457
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	458	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		459
369	This is your standard select(2) backend. Not I<completely> standard, as	460	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	461	libev tries to roll its own fd_set with no limits on the number of fds,
371	but if that fails, expect a fairly low limit on the number of fds when	462	but if that fails, expect a fairly low limit on the number of fds when
…		…
395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	486	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	487	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		488
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	489	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		490
		491	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		492	kernels).
		493
400	For few fds, this backend is a bit little slower than poll and select,	494	For few fds, this backend is a bit little slower than poll and select, but
401	but it scales phenomenally better. While poll and select usually scale	495	it scales phenomenally better. While poll and select usually scale like
402	like O(total_fds) where n is the total number of fds (or the highest fd),	496	O(total_fds) where total_fds is the total number of fds (or the highest
403	epoll scales either O(1) or O(active_fds).	497	fd), epoll scales either O(1) or O(active_fds).
404		498
405	The epoll mechanism deserves honorable mention as the most misdesigned	499	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	500	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	501	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	502	descriptor (and unnecessary guessing of parameters), problems with dup,
		503	returning before the timeout value, resulting in additional iterations
		504	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	505	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	506	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	507	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	508	and is of course hard to detect.
413		509
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	510	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
415	of course I<doesn't>, and epoll just loves to report events for totally	511	but of course I<doesn't>, and epoll just loves to report events for
416	I<different> file descriptors (even already closed ones, so one cannot	512	totally I<different> file descriptors (even already closed ones, so
417	even remove them from the set) than registered in the set (especially	513	one cannot even remove them from the set) than registered in the set
418	on SMP systems). Libev tries to counter these spurious notifications by	514	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	515	notifications by employing an additional generation counter and comparing
420	events to filter out spurious ones, recreating the set when required.	516	that against the events to filter out spurious ones, recreating the set
		517	when required. Epoll also erroneously rounds down timeouts, but gives you
		518	no way to know when and by how much, so sometimes you have to busy-wait
		519	because epoll returns immediately despite a nonzero timeout. And last
		520	not least, it also refuses to work with some file descriptors which work
		521	perfectly fine with C<select> (files, many character devices...).
		522
		523	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		524	cobbled together in a hurry, no thought to design or interaction with
		525	others. Oh, the pain, will it ever stop...
421		526
422	While stopping, setting and starting an I/O watcher in the same iteration	527	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	528	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	529	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	530	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	596	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		597
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	598	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	599	it's really slow, but it still scales very well (O(active_fds)).
495		600
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	601	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	602	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	603	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	604	might perform better.
504		605
505	On the positive side, with the exception of the spurious readiness	606	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	607	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	608	among the OS-specific backends (I vastly prefer correctness over speed
		609	hacks).
		610
		611	On the negative side, the interface is I<bizarre> - so bizarre that
		612	even sun itself gets it wrong in their code examples: The event polling
		613	function sometimes returns events to the caller even though an error
		614	occurred, but with no indication whether it has done so or not (yes, it's
		615	even documented that way) - deadly for edge-triggered interfaces where you
		616	absolutely have to know whether an event occurred or not because you have
		617	to re-arm the watcher.
		618
		619	Fortunately libev seems to be able to work around these idiocies.
509		620
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	621	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	622	C<EVBACKEND_POLL>.
512		623
513	=item C<EVBACKEND_ALL>	624	=item C<EVBACKEND_ALL>
514		625
515	Try all backends (even potentially broken ones that wouldn't be tried	626	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	627	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	628	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		629
519	It is definitely not recommended to use this flag.	630	It is definitely not recommended to use this flag, use whatever
		631	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		632	at all.
		633
		634	=item C<EVBACKEND_MASK>
		635
		636	Not a backend at all, but a mask to select all backend bits from a
		637	C<flags> value, in case you want to mask out any backends from a flags
		638	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		639
521	=back	640	=back
522		641
523	If one or more of these are or'ed into the flags value, then only these	642	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	643	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	644	here). If none are specified, all backends in C<ev_recommended_backends
526		645	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		646
555	Example: Try to create a event loop that uses epoll and nothing else.	647	Example: Try to create a event loop that uses epoll and nothing else.
556		648
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	649	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	650	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	651	fatal ("no epoll found here, maybe it hides under your chair");
560		652
		653	Example: Use whatever libev has to offer, but make sure that kqueue is
		654	used if available.
		655
		656	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		657
561	=item ev_default_destroy ()	658	=item ev_loop_destroy (loop)
562		659
563	Destroys the default loop again (frees all memory and kernel state	660	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	661	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	662	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	663	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	664	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	665	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		667
571	Note that certain global state, such as signal state (and installed signal	668	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	669	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	670	as signal and child watchers) would need to be stopped manually.
574		671
575	In general it is not advisable to call this function except in the	672	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	673	C<ev_loop_new>, but it can also be used on the default loop returned by
		674	C<ev_default_loop>, in which case it is not thread-safe.
		675
		676	Note that it is not advisable to call this function on the default loop
		677	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	678	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	679	and C<ev_loop_destroy>.
579		680
580	=item ev_loop_destroy (loop)	681	=item ev_loop_fork (loop)
581		682
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	683	This function sets a flag that causes subsequent C<ev_run> iterations to
588	to reinitialise the kernel state for backends that have one. Despite the	684	reinitialise the kernel state for backends that have one. Despite the
589	name, you can call it anytime, but it makes most sense after forking, in	685	name, you can call it anytime, but it makes most sense after forking, in
590	the child process (or both child and parent, but that again makes little	686	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
591	sense). You I<must> call it in the child before using any of the libev	687	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	688
		689	Again, you I<have> to call it on I<any> loop that you want to re-use after
		690	a fork, I<even if you do not plan to use the loop in the parent>. This is
		691	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		692	during fork.
593		693
594	On the other hand, you only need to call this function in the child	694	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	695	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	696	you just fork+exec or create a new loop in the child, you don't have to
		697	call it at all (in fact, C<epoll> is so badly broken that it makes a
		698	difference, but libev will usually detect this case on its own and do a
		699	costly reset of the backend).
597		700
598	The function itself is quite fast and it's usually not a problem to call	701	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	702	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		703
		704	Example: Automate calling C<ev_loop_fork> on the default loop when
		705	using pthreads.
		706
		707	static void
		708	post_fork_child (void)
		709	{
		710	ev_loop_fork (EV_DEFAULT);
		711	}
		712
		713	...
602	pthread_atfork (0, 0, ev_default_fork);	714	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		715
611	=item int ev_is_default_loop (loop)	716	=item int ev_is_default_loop (loop)
612		717
613	Returns true when the given loop is, in fact, the default loop, and false	718	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	719	otherwise.
615		720
616	=item unsigned int ev_loop_count (loop)	721	=item unsigned int ev_iteration (loop)
617		722
618	Returns the count of loop iterations for the loop, which is identical to	723	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	724	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	725	and happily wraps around with enough iterations.
621		726
622	This value can sometimes be useful as a generation counter of sorts (it	727	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	728	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	729	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		730	prepare and check phases.
625		731
626	=item unsigned int ev_loop_depth (loop)	732	=item unsigned int ev_depth (loop)
627		733
628	Returns the number of times C<ev_loop> was entered minus the number of	734	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	735	times C<ev_run> was exited normally, in other words, the recursion depth.
630		736
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	737	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	738	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	739	in which case it is higher.
634		740
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	741	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	742	throwing an exception etc.), doesn't count as "exit" - consider this
		743	as a hint to avoid such ungentleman-like behaviour unless it's really
		744	convenient, in which case it is fully supported.
637		745
638	=item unsigned int ev_backend (loop)	746	=item unsigned int ev_backend (loop)
639		747
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	748	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	749	use.
…		…
650		758
651	=item ev_now_update (loop)	759	=item ev_now_update (loop)
652		760
653	Establishes the current time by querying the kernel, updating the time	761	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	762	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	763	is usually done automatically within C<ev_run ()>.
656		764
657	This function is rarely useful, but when some event callback runs for a	765	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	766	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	767	the current time is a good idea.
660		768
…		…
662		770
663	=item ev_suspend (loop)	771	=item ev_suspend (loop)
664		772
665	=item ev_resume (loop)	773	=item ev_resume (loop)
666		774
667	These two functions suspend and resume a loop, for use when the loop is	775	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	776	loop is not used for a while and timeouts should not be processed.
669		777
670	A typical use case would be an interactive program such as a game: When	778	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	779	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	780	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	781	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	783	C<ev_resume> directly afterwards to resume timer processing.
676		784
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	785	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	786	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	787	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	788	occurred while suspended).
681		789
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	790	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	791	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	792	without a previous call to C<ev_suspend>.
685		793
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	794	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	795	event loop time (see C<ev_now_update>).
688		796
689	=item ev_loop (loop, int flags)	797	=item ev_run (loop, int flags)
690		798
691	Finally, this is it, the event handler. This function usually is called	799	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	800	after you have initialised all your watchers and you want to start
693	events.	801	handling events. It will ask the operating system for any new events, call
		802	the watcher callbacks, an then repeat the whole process indefinitely: This
		803	is why event loops are called I<loops>.
694		804
695	If the flags argument is specified as C<0>, it will not return until	805	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	806	until either no event watchers are active anymore or C<ev_break> was
		807	called.
697		808
698	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
699	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
700	finished (especially in interactive programs), but having a program	811	finished (especially in interactive programs), but having a program
701	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
702	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
703	beauty.	814	beauty.
704		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
705	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
706	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
707	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
708	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.
709		826
710	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
711	necessary) and will handle those and any already outstanding ones. It	828	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	829	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	830	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	831	user-registered callback will be called), and will return after one
715	iteration of the loop.	832	iteration of the loop.
716		833
717	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
718	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
719	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
720	usually a better approach for this kind of thing.	837	usually a better approach for this kind of thing.
721		838
722	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):
723		842
		843	- Increment loop depth.
		844	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	845	- Before the first iteration, call any pending watchers.
		846	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	847	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- 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.
727	- Queue and call all prepare watchers.	849	- Queue and call all prepare watchers.
		850	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	851	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	852	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	853	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	854	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	855	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	856	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	857	any active watchers at all will result in not sleeping).
735	- 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.
736	- Block the process, waiting for any events.	860	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	861	- Queue all outstanding I/O (fd) events.
738	- 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.
739	- Queue all expired timers.	863	- Queue all expired timers.
740	- Queue all expired periodics.	864	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	865	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	866	- Queue all check watchers.
743	- 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).
744	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
745	be handled here by queueing them when their watcher gets executed.	869	be handled here by queueing them when their watcher gets executed.
746	- 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
747	were used, or there are no active watchers, return, otherwise	871	were used, or there are no active watchers, goto FINISH, otherwise
748	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.
749		877
750	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
751	anymore.	879	anymore.
752		880
753	... queue jobs here, make sure they register event watchers as long	881	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	882	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	883	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	884	... jobs done or somebody called break. yeah!
757		885
758	=item ev_unloop (loop, how)	886	=item ev_break (loop, how)
759		887
760	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
761	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
762	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
763	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.
764		892
765	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>.
766		894
767	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.
768		897
769	=item ev_ref (loop)	898	=item ev_ref (loop)
770		899
771	=item ev_unref (loop)	900	=item ev_unref (loop)
772		901
773	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
774	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
775	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.
776		905
777	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
778	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>
779	stopping it.	909	before stopping it.
780		910
781	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
782	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
783	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
784	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
785	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
786	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
787	before, respectively. Note also that libev might stop watchers itself	917	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	918	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	919	in the callback).
790		920
791	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>
792	running when nothing else is active.	922	running when nothing else is active.
793		923
794	ev_signal exitsig;	924	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	925	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	926	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	927	ev_unref (loop);
798		928
799	Example: For some weird reason, unregister the above signal handler again.	929	Example: For some weird reason, unregister the above signal handler again.
800		930
801	ev_ref (loop);	931	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	932	ev_signal_stop (loop, &exitsig);
…		…
822	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.
823		953
824	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
825	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,
826	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
827	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
828	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
829	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
830	once per this interval, on average.	960	once per this interval, on average (as long as the host time resolution is
		961	good enough).
831		962
832	Likewise, by setting a higher I<timeout collect interval> you allow libev	963	Likewise, by setting a higher I<timeout collect interval> you allow libev
833	to spend more time collecting timeouts, at the expense of increased	964	to spend more time collecting timeouts, at the expense of increased
834	latency/jitter/inexactness (the watcher callback will be called	965	latency/jitter/inexactness (the watcher callback will be called
835	later). C<ev_io> watchers will not be affected. Setting this to a non-null	966	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	972	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	973	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	974	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	975	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	976	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	977	then you can't do more than 100 transactions per second).
847		978
848	Setting the I<timeout collect interval> can improve the opportunity for	979	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	980	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	981	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	982	times the process sleeps and wakes up again. Another useful technique to
…		…
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	990	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		991
861	=item ev_invoke_pending (loop)	992	=item ev_invoke_pending (loop)
862		993
863	This call will simply invoke all pending watchers while resetting their	994	This call will simply invoke all pending watchers while resetting their
864	pending state. Normally, C<ev_loop> does this automatically when required,	995	pending state. Normally, C<ev_run> does this automatically when required,
865	but when overriding the invoke callback this call comes handy.	996	but when overriding the invoke callback this call comes handy. This
		997	function can be invoked from a watcher - this can be useful for example
		998	when you want to do some lengthy calculation and want to pass further
		999	event handling to another thread (you still have to make sure only one
		1000	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1001
		1002	=item int ev_pending_count (loop)
		1003
		1004	Returns the number of pending watchers - zero indicates that no watchers
		1005	are pending.
866		1006
867	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1007	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
868		1008
869	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
870	invoking all pending watchers when there are any, C<ev_loop> will call	1010	invoking all pending watchers when there are any, C<ev_run> will call
871	this callback instead. This is useful, for example, when you want to	1011	this callback instead. This is useful, for example, when you want to
872	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
873		1013
874	If you want to reset the callback, use C<ev_invoke_pending> as new	1014	If you want to reset the callback, use C<ev_invoke_pending> as new
875	callback.	1015	callback.
…		…
878		1018
879	Sometimes you want to share the same loop between multiple threads. This	1019	Sometimes you want to share the same loop between multiple threads. This
880	can be done relatively simply by putting mutex_lock/unlock calls around	1020	can be done relatively simply by putting mutex_lock/unlock calls around
881	each call to a libev function.	1021	each call to a libev function.
882		1022
883	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1023	However, C<ev_run> can run an indefinite time, so it is not feasible
884	wait for it to return. One way around this is to wake up the loop via	1024	to wait for it to return. One way around this is to wake up the event
885	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<av_async_send>, another way is to set these
886	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
887		1027
888	When set, then C<release> will be called just before the thread is	1028	When set, then C<release> will be called just before the thread is
889	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
890	afterwards.	1030	afterwards.
891		1031
…		…
894		1034
895	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
896	C<release> and C<acquire> (that's their only purpose after all), no	1036	C<release> and C<acquire> (that's their only purpose after all), no
897	modifications done will affect the event loop, i.e. adding watchers will	1037	modifications done will affect the event loop, i.e. adding watchers will
898	have no effect on the set of file descriptors being watched, or the time	1038	have no effect on the set of file descriptors being watched, or the time
899	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1039	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
900	to take note of any changes you made.	1040	to take note of any changes you made.
901		1041
902	In theory, threads executing C<ev_loop> will be async-cancel safe between	1042	In theory, threads executing C<ev_run> will be async-cancel safe between
903	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
904		1044
905	See also the locking example in the C<THREADS> section later in this	1045	See also the locking example in the C<THREADS> section later in this
906	document.	1046	document.
907		1047
908	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
909		1049
910	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
911		1051
912	Set and retrieve a single C<void *> associated with a loop. When	1052	Set and retrieve a single C<void *> associated with a loop. When
913	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1053	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
914	C<0.>	1054	C<0>.
915		1055
916	These two functions can be used to associate arbitrary data with a loop,	1056	These two functions can be used to associate arbitrary data with a loop,
917	and are intended solely for the C<invoke_pending_cb>, C<release> and	1057	and are intended solely for the C<invoke_pending_cb>, C<release> and
918	C<acquire> callbacks described above, but of course can be (ab-)used for	1058	C<acquire> callbacks described above, but of course can be (ab-)used for
919	any other purpose as well.	1059	any other purpose as well.
920		1060
921	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
922		1062
923	This function only does something when C<EV_VERIFY> support has been	1063	This function only does something when C<EV_VERIFY> support has been
924	compiled in, which is the default for non-minimal builds. It tries to go	1064	compiled in, which is the default for non-minimal builds. It tries to go
925	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
926	is found to be inconsistent, it will print an error message to standard	1066	is found to be inconsistent, it will print an error message to standard
…		…
937		1077
938	In the following description, uppercase C<TYPE> in names stands for the	1078	In the following description, uppercase C<TYPE> in names stands for the
939	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1079	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
940	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
941		1081
942	A watcher is a structure that you create and register to record your	1082	A watcher is an opaque structure that you allocate and register to record
943	interest in some event. For instance, if you want to wait for STDIN to	1083	your interest in some event. To make a concrete example, imagine you want
944	become readable, you would create an C<ev_io> watcher for that:	1084	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1085	for that:
945		1086
946	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1087	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
947	{	1088	{
948	ev_io_stop (w);	1089	ev_io_stop (w);
949	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
950	}	1091	}
951		1092
952	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
953		1094
954	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
955		1096
956	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
957	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
958	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
959		1100
960	ev_loop (loop, 0);	1101	ev_run (loop, 0);
961		1102
962	As you can see, you are responsible for allocating the memory for your	1103	As you can see, you are responsible for allocating the memory for your
963	watcher structures (and it is I<usually> a bad idea to do this on the	1104	watcher structures (and it is I<usually> a bad idea to do this on the
964	stack).	1105	stack).
965		1106
966	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1107	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
967	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1108	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
968		1109
969	Each watcher structure must be initialised by a call to C<ev_init	1110	Each watcher structure must be initialised by a call to C<ev_init (watcher
970	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
971	callback gets invoked each time the event occurs (or, in the case of I/O	1112	invoked each time the event occurs (or, in the case of I/O watchers, each
972	watchers, each time the event loop detects that the file descriptor given	1113	time the event loop detects that the file descriptor given is readable
973	is readable and/or writable).	1114	and/or writable).
974		1115
975	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1116	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
976	macro to configure it, with arguments specific to the watcher type. There	1117	macro to configure it, with arguments specific to the watcher type. There
977	is also a macro to combine initialisation and setting in one call: C<<	1118	is also a macro to combine initialisation and setting in one call: C<<
978	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1001	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1002		1143
1003	The file descriptor in the C<ev_io> watcher has become readable and/or	1144	The file descriptor in the C<ev_io> watcher has become readable and/or
1004	writable.	1145	writable.
1005		1146
1006	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1007		1148
1008	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1009		1150
1010	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1011		1152
…		…
1029		1170
1030	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1031		1172
1032	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1033		1174
1034	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1175	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
1035	to gather new events, and all C<ev_check> watchers are invoked just after	1176	to gather new events, and all C<ev_check> watchers are invoked just after
1036	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1177	C<ev_run> has gathered them, but before it invokes any callbacks for any
1037	received events. Callbacks of both watcher types can start and stop as	1178	received events. Callbacks of both watcher types can start and stop as
1038	many watchers as they want, and all of them will be taken into account	1179	many watchers as they want, and all of them will be taken into account
1039	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1180	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
1040	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1041		1182
1042	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1043		1184
1044	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1185	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1045		1186
1046	=item C<EV_FORK>	1187	=item C<EV_FORK>
1047		1188
1048	The event loop has been resumed in the child process after fork (see	1189	The event loop has been resumed in the child process after fork (see
1049	C<ev_fork>).	1190	C<ev_fork>).
		1191
		1192	=item C<EV_CLEANUP>
		1193
		1194	The event loop is about to be destroyed (see C<ev_cleanup>).
1050		1195
1051	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1052		1197
1053	The given async watcher has been asynchronously notified (see C<ev_async>).	1198	The given async watcher has been asynchronously notified (see C<ev_async>).
1054		1199
…		…
1101		1246
1102	ev_io w;	1247	ev_io w;
1103	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1104	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1105		1250
1106	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1107		1252
1108	This macro initialises the type-specific parts of a watcher. You need to	1253	This macro initialises the type-specific parts of a watcher. You need to
1109	call C<ev_init> at least once before you call this macro, but you can	1254	call C<ev_init> at least once before you call this macro, but you can
1110	call C<ev_TYPE_set> any number of times. You must not, however, call this	1255	call C<ev_TYPE_set> any number of times. You must not, however, call this
1111	macro on a watcher that is active (it can be pending, however, which is a	1256	macro on a watcher that is active (it can be pending, however, which is a
…		…
1124		1269
1125	Example: Initialise and set an C<ev_io> watcher in one step.	1270	Example: Initialise and set an C<ev_io> watcher in one step.
1126		1271
1127	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1128		1273
1129	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1130		1275
1131	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1132	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1133		1278
1134	Example: Start the C<ev_io> watcher that is being abused as example in this	1279	Example: Start the C<ev_io> watcher that is being abused as example in this
1135	whole section.	1280	whole section.
1136		1281
1137	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1138		1283
1139	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1140		1285
1141	Stops the given watcher if active, and clears the pending status (whether	1286	Stops the given watcher if active, and clears the pending status (whether
1142	the watcher was active or not).	1287	the watcher was active or not).
1143		1288
1144	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1169	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1170		1315
1171	Change the callback. You can change the callback at virtually any time	1316	Change the callback. You can change the callback at virtually any time
1172	(modulo threads).	1317	(modulo threads).
1173		1318
1174	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1175		1320
1176	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1177		1322
1178	Set and query the priority of the watcher. The priority is a small	1323	Set and query the priority of the watcher. The priority is a small
1179	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1324	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1211	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1212		1357
1213	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1358	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1214	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1215		1360
		1361	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1362
		1363	Feeds the given event set into the event loop, as if the specified event
		1364	had happened for the specified watcher (which must be a pointer to an
		1365	initialised but not necessarily started event watcher). Obviously you must
		1366	not free the watcher as long as it has pending events.
		1367
		1368	Stopping the watcher, letting libev invoke it, or calling
		1369	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1370	not started in the first place.
		1371
		1372	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1373	functions that do not need a watcher.
		1374
1216	=back	1375	=back
1217		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1218		1379
1219	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1220		1381
1221	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1222	and read at any time: libev will completely ignore it. This can be used	1383	active, pending and so on. In this section these states and the rules to
1223	to associate arbitrary data with your watcher. If you need more data and	1384	transition between them will be described in more detail - and while these
1224	don't want to allocate memory and store a pointer to it in that data	1385	rules might look complicated, they usually do "the right thing".
1225	member, you can also "subclass" the watcher type and provide your own
1226	data:
1227		1386
1228	struct my_io	1387	=over 4
1229	{
1230	ev_io io;
1231	int otherfd;
1232	void *somedata;
1233	struct whatever *mostinteresting;
1234	};
1235		1388
1236	...	1389	=item initialiased
1237	struct my_io w;
1238	ev_io_init (&w.io, my_cb, fd, EV_READ);
1239		1390
1240	And since your callback will be called with a pointer to the watcher, you	1391	Before a watcher can be registered with the event loop it has to be
1241	can cast it back to your own type:	1392	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1393	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1242		1394
1243	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1395	In this state it is simply some block of memory that is suitable for
1244	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1245	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1246	...	1398	C<ev_TYPE_init> again.
1247	}
1248		1399
1249	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1250	instead have been omitted.
1251		1401
1252	Another common scenario is to use some data structure with multiple	1402	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1253	embedded watchers:	1403	property of the event loop, and is actively waiting for events. While in
		1404	this state it cannot be accessed (except in a few documented ways), moved,
		1405	freed or anything else - the only legal thing is to keep a pointer to it,
		1406	and call libev functions on it that are documented to work on active watchers.
1254		1407
1255	struct my_biggy	1408	=item pending
1256	{
1257	int some_data;
1258	ev_timer t1;
1259	ev_timer t2;
1260	}
1261		1409
1262	In this case getting the pointer to C<my_biggy> is a bit more	1410	If a watcher is active and libev determines that an event it is interested
1263	complicated: Either you store the address of your C<my_biggy> struct	1411	in has occurred (such as a timer expiring), it will become pending. It will
1264	in the C<data> member of the watcher (for woozies), or you need to use	1412	stay in this pending state until either it is stopped or its callback is
1265	some pointer arithmetic using C<offsetof> inside your watchers (for real	1413	about to be invoked, so it is not normally pending inside the watcher
1266	programmers):	1414	callback.
1267		1415
1268	#include <stddef.h>	1416	The watcher might or might not be active while it is pending (for example,
		1417	an expired non-repeating timer can be pending but no longer active). If it
		1418	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1419	but it is still property of the event loop at this time, so cannot be
		1420	moved, freed or reused. And if it is active the rules described in the
		1421	previous item still apply.
1269		1422
1270	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1271	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1272	{	1425	active.
1273	struct my_biggy big = (struct my_biggy *)
1274	(((char *)w) - offsetof (struct my_biggy, t1));
1275	}
1276		1426
1277	static void	1427	=item stopped
1278	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1279	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1280	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1281	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1282	}	1432	of whether it was active or not, so stopping a watcher explicitly before
		1433	freeing it is often a good idea.
		1434
		1435	While stopped (and not pending) the watcher is essentially in the
		1436	initialised state, that is, it can be reused, moved, modified in any way
		1437	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1438	it again).
		1439
		1440	=back
1283		1441
1284	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1285		1443
1286	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1287	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1330		1488
1331	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1332	you can associate an C<ev_idle> watcher to each such watcher, and in	1490	you can associate an C<ev_idle> watcher to each such watcher, and in
1333	the normal watcher callback, you just start the idle watcher. The real	1491	the normal watcher callback, you just start the idle watcher. The real
1334	processing is done in the idle watcher callback. This causes libev to	1492	processing is done in the idle watcher callback. This causes libev to
1335	continously poll and process kernel event data for the watcher, but when	1493	continuously poll and process kernel event data for the watcher, but when
1336	the lock-out case is known to be rare (which in turn is rare :), this is	1494	the lock-out case is known to be rare (which in turn is rare :), this is
1337	workable.	1495	workable.
1338		1496
1339	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1340	miserably under the type of load it was designed to handle. In that case,	1498	miserably under the type of load it was designed to handle. In that case,
…		…
1354	{	1512	{
1355	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1356	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1357	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1358		1516
1359	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1360	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1361	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1362	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1363	}	1521	}
1364		1522
…		…
1414	In general you can register as many read and/or write event watchers per	1572	In general you can register as many read and/or write event watchers per
1415	fd as you want (as long as you don't confuse yourself). Setting all file	1573	fd as you want (as long as you don't confuse yourself). Setting all file
1416	descriptors to non-blocking mode is also usually a good idea (but not	1574	descriptors to non-blocking mode is also usually a good idea (but not
1417	required if you know what you are doing).	1575	required if you know what you are doing).
1418		1576
1419	If you cannot use non-blocking mode, then force the use of a
1420	known-to-be-good backend (at the time of this writing, this includes only
1421	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1422	descriptors for which non-blocking operation makes no sense (such as
1423	files) - libev doesn't guarentee any specific behaviour in that case.
1424
1425	Another thing you have to watch out for is that it is quite easy to	1577	Another thing you have to watch out for is that it is quite easy to
1426	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1427	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1579	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1428	because there is no data. Not only are some backends known to create a	1580	because there is no data. It is very easy to get into this situation even
1429	lot of those (for example Solaris ports), it is very easy to get into	1581	with a relatively standard program structure. Thus it is best to always
1430	this situation even with a relatively standard program structure. Thus	1582	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1431	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1432	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1433		1584
1434	If you cannot run the fd in non-blocking mode (for example you should	1585	If you cannot run the fd in non-blocking mode (for example you should
1435	not play around with an Xlib connection), then you have to separately	1586	not play around with an Xlib connection), then you have to separately
1436	re-test whether a file descriptor is really ready with a known-to-be good	1587	re-test whether a file descriptor is really ready with a known-to-be good
1437	interface such as poll (fortunately in our Xlib example, Xlib already	1588	interface such as poll (fortunately in the case of Xlib, it already does
1438	does this on its own, so its quite safe to use). Some people additionally	1589	this on its own, so its quite safe to use). Some people additionally
1439	use C<SIGALRM> and an interval timer, just to be sure you won't block	1590	use C<SIGALRM> and an interval timer, just to be sure you won't block
1440	indefinitely.	1591	indefinitely.
1441		1592
1442	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1443		1594
…		…
1471		1622
1472	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1473	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1474	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1475		1626
		1627	=head3 The special problem of files
		1628
		1629	Many people try to use C<select> (or libev) on file descriptors
		1630	representing files, and expect it to become ready when their program
		1631	doesn't block on disk accesses (which can take a long time on their own).
		1632
		1633	However, this cannot ever work in the "expected" way - you get a readiness
		1634	notification as soon as the kernel knows whether and how much data is
		1635	there, and in the case of open files, that's always the case, so you
		1636	always get a readiness notification instantly, and your read (or possibly
		1637	write) will still block on the disk I/O.
		1638
		1639	Another way to view it is that in the case of sockets, pipes, character
		1640	devices and so on, there is another party (the sender) that delivers data
		1641	on its own, but in the case of files, there is no such thing: the disk
		1642	will not send data on its own, simply because it doesn't know what you
		1643	wish to read - you would first have to request some data.
		1644
		1645	Since files are typically not-so-well supported by advanced notification
		1646	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1647	to files, even though you should not use it. The reason for this is
		1648	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1649	usually a tty, often a pipe, but also sometimes files or special devices
		1650	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1651	F</dev/urandom>), and even though the file might better be served with
		1652	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1653	it "just works" instead of freezing.
		1654
		1655	So avoid file descriptors pointing to files when you know it (e.g. use
		1656	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1657	when you rarely read from a file instead of from a socket, and want to
		1658	reuse the same code path.
		1659
1476	=head3 The special problem of fork	1660	=head3 The special problem of fork
1477		1661
1478	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1662	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1479	useless behaviour. Libev fully supports fork, but needs to be told about	1663	useless behaviour. Libev fully supports fork, but needs to be told about
1480	it in the child.	1664	it in the child if you want to continue to use it in the child.
1481		1665
1482	To support fork in your programs, you either have to call	1666	To support fork in your child processes, you have to call C<ev_loop_fork
1483	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1667	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1484	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1485	C<EVBACKEND_POLL>.
1486		1669
1487	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1488		1671
1489	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1672	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1490	when writing to a pipe whose other end has been closed, your program gets	1673	when writing to a pipe whose other end has been closed, your program gets
…		…
1493		1676
1494	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1495	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1678	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1496	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1497		1680
		1681	=head3 The special problem of accept()ing when you can't
		1682
		1683	Many implementations of the POSIX C<accept> function (for example,
		1684	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1685	connection from the pending queue in all error cases.
		1686
		1687	For example, larger servers often run out of file descriptors (because
		1688	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1689	rejecting the connection, leading to libev signalling readiness on
		1690	the next iteration again (the connection still exists after all), and
		1691	typically causing the program to loop at 100% CPU usage.
		1692
		1693	Unfortunately, the set of errors that cause this issue differs between
		1694	operating systems, there is usually little the app can do to remedy the
		1695	situation, and no known thread-safe method of removing the connection to
		1696	cope with overload is known (to me).
		1697
		1698	One of the easiest ways to handle this situation is to just ignore it
		1699	- when the program encounters an overload, it will just loop until the
		1700	situation is over. While this is a form of busy waiting, no OS offers an
		1701	event-based way to handle this situation, so it's the best one can do.
		1702
		1703	A better way to handle the situation is to log any errors other than
		1704	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1705	messages, and continue as usual, which at least gives the user an idea of
		1706	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1707	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1708	usage.
		1709
		1710	If your program is single-threaded, then you could also keep a dummy file
		1711	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1712	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1713	close that fd, and create a new dummy fd. This will gracefully refuse
		1714	clients under typical overload conditions.
		1715
		1716	The last way to handle it is to simply log the error and C<exit>, as
		1717	is often done with C<malloc> failures, but this results in an easy
		1718	opportunity for a DoS attack.
1498		1719
1499	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1500		1721
1501	=over 4	1722	=over 4
1502		1723
…		…
1534	...	1755	...
1535	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1536	ev_io stdin_readable;	1757	ev_io stdin_readable;
1537	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1758	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1538	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1539	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1540		1761
1541		1762
1542	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1543		1764
1544	Timer watchers are simple relative timers that generate an event after a	1765	Timer watchers are simple relative timers that generate an event after a
…		…
1553	The callback is guaranteed to be invoked only I<after> its timeout has	1774	The callback is guaranteed to be invoked only I<after> its timeout has
1554	passed (not I<at>, so on systems with very low-resolution clocks this	1775	passed (not I<at>, so on systems with very low-resolution clocks this
1555	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay). If multiple timers become ready during the
1556	same loop iteration then the ones with earlier time-out values are invoked	1777	same loop iteration then the ones with earlier time-out values are invoked
1557	before ones of the same priority with later time-out values (but this is	1778	before ones of the same priority with later time-out values (but this is
1558	no longer true when a callback calls C<ev_loop> recursively).	1779	no longer true when a callback calls C<ev_run> recursively).
1559		1780
1560	=head3 Be smart about timeouts	1781	=head3 Be smart about timeouts
1561		1782
1562	Many real-world problems involve some kind of timeout, usually for error	1783	Many real-world problems involve some kind of timeout, usually for error
1563	recovery. A typical example is an HTTP request - if the other side hangs,	1784	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1649	ev_tstamp timeout = last_activity + 60.;	1870	ev_tstamp timeout = last_activity + 60.;
1650		1871
1651	// if last_activity + 60. is older than now, we did time out	1872	// if last_activity + 60. is older than now, we did time out
1652	if (timeout < now)	1873	if (timeout < now)
1653	{	1874	{
1654	// timeout occured, take action	1875	// timeout occurred, take action
1655	}	1876	}
1656	else	1877	else
1657	{	1878	{
1658	// callback was invoked, but there was some activity, re-arm	1879	// callback was invoked, but there was some activity, re-arm
1659	// the watcher to fire in last_activity + 60, which is	1880	// the watcher to fire in last_activity + 60, which is
…		…
1681	to the current time (meaning we just have some activity :), then call the	1902	to the current time (meaning we just have some activity :), then call the
1682	callback, which will "do the right thing" and start the timer:	1903	callback, which will "do the right thing" and start the timer:
1683		1904
1684	ev_init (timer, callback);	1905	ev_init (timer, callback);
1685	last_activity = ev_now (loop);	1906	last_activity = ev_now (loop);
1686	callback (loop, timer, EV_TIMEOUT);	1907	callback (loop, timer, EV_TIMER);
1687		1908
1688	And when there is some activity, simply store the current time in	1909	And when there is some activity, simply store the current time in
1689	C<last_activity>, no libev calls at all:	1910	C<last_activity>, no libev calls at all:
1690		1911
1691	last_actiivty = ev_now (loop);	1912	last_activity = ev_now (loop);
1692		1913
1693	This technique is slightly more complex, but in most cases where the	1914	This technique is slightly more complex, but in most cases where the
1694	time-out is unlikely to be triggered, much more efficient.	1915	time-out is unlikely to be triggered, much more efficient.
1695		1916
1696	Changing the timeout is trivial as well (if it isn't hard-coded in the	1917	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1734		1955
1735	=head3 The special problem of time updates	1956	=head3 The special problem of time updates
1736		1957
1737	Establishing the current time is a costly operation (it usually takes at	1958	Establishing the current time is a costly operation (it usually takes at
1738	least two system calls): EV therefore updates its idea of the current	1959	least two system calls): EV therefore updates its idea of the current
1739	time only before and after C<ev_loop> collects new events, which causes a	1960	time only before and after C<ev_run> collects new events, which causes a
1740	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1961	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1741	lots of events in one iteration.	1962	lots of events in one iteration.
1742		1963
1743	The relative timeouts are calculated relative to the C<ev_now ()>	1964	The relative timeouts are calculated relative to the C<ev_now ()>
1744	time. This is usually the right thing as this timestamp refers to the time	1965	time. This is usually the right thing as this timestamp refers to the time
…		…
1750		1971
1751	If the event loop is suspended for a long time, you can also force an	1972	If the event loop is suspended for a long time, you can also force an
1752	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1973	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1753	()>.	1974	()>.
1754		1975
		1976	=head3 The special problems of suspended animation
		1977
		1978	When you leave the server world it is quite customary to hit machines that
		1979	can suspend/hibernate - what happens to the clocks during such a suspend?
		1980
		1981	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1982	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1983	to run until the system is suspended, but they will not advance while the
		1984	system is suspended. That means, on resume, it will be as if the program
		1985	was frozen for a few seconds, but the suspend time will not be counted
		1986	towards C<ev_timer> when a monotonic clock source is used. The real time
		1987	clock advanced as expected, but if it is used as sole clocksource, then a
		1988	long suspend would be detected as a time jump by libev, and timers would
		1989	be adjusted accordingly.
		1990
		1991	I would not be surprised to see different behaviour in different between
		1992	operating systems, OS versions or even different hardware.
		1993
		1994	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1995	time jump in the monotonic clocks and the realtime clock. If the program
		1996	is suspended for a very long time, and monotonic clock sources are in use,
		1997	then you can expect C<ev_timer>s to expire as the full suspension time
		1998	will be counted towards the timers. When no monotonic clock source is in
		1999	use, then libev will again assume a timejump and adjust accordingly.
		2000
		2001	It might be beneficial for this latter case to call C<ev_suspend>
		2002	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2003	deterministic behaviour in this case (you can do nothing against
		2004	C<SIGSTOP>).
		2005
1755	=head3 Watcher-Specific Functions and Data Members	2006	=head3 Watcher-Specific Functions and Data Members
1756		2007
1757	=over 4	2008	=over 4
1758		2009
1759	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2010	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1772	keep up with the timer (because it takes longer than those 10 seconds to	2023	keep up with the timer (because it takes longer than those 10 seconds to
1773	do stuff) the timer will not fire more than once per event loop iteration.	2024	do stuff) the timer will not fire more than once per event loop iteration.
1774		2025
1775	=item ev_timer_again (loop, ev_timer *)	2026	=item ev_timer_again (loop, ev_timer *)
1776		2027
1777	This will act as if the timer timed out and restart it again if it is	2028	This will act as if the timer timed out and restarts it again if it is
1778	repeating. The exact semantics are:	2029	repeating. The exact semantics are:
1779		2030
1780	If the timer is pending, its pending status is cleared.	2031	If the timer is pending, its pending status is cleared.
1781		2032
1782	If the timer is started but non-repeating, stop it (as if it timed out).	2033	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1784	If the timer is repeating, either start it if necessary (with the	2035	If the timer is repeating, either start it if necessary (with the
1785	C<repeat> value), or reset the running timer to the C<repeat> value.	2036	C<repeat> value), or reset the running timer to the C<repeat> value.
1786		2037
1787	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2038	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1788	usage example.	2039	usage example.
		2040
		2041	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2042
		2043	Returns the remaining time until a timer fires. If the timer is active,
		2044	then this time is relative to the current event loop time, otherwise it's
		2045	the timeout value currently configured.
		2046
		2047	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2048	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2049	will return C<4>. When the timer expires and is restarted, it will return
		2050	roughly C<7> (likely slightly less as callback invocation takes some time,
		2051	too), and so on.
1789		2052
1790	=item ev_tstamp repeat [read-write]	2053	=item ev_tstamp repeat [read-write]
1791		2054
1792	The current C<repeat> value. Will be used each time the watcher times out	2055	The current C<repeat> value. Will be used each time the watcher times out
1793	or C<ev_timer_again> is called, and determines the next timeout (if any),	2056	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1819	}	2082	}
1820		2083
1821	ev_timer mytimer;	2084	ev_timer mytimer;
1822	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2085	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1823	ev_timer_again (&mytimer); /* start timer */	2086	ev_timer_again (&mytimer); /* start timer */
1824	ev_loop (loop, 0);	2087	ev_run (loop, 0);
1825		2088
1826	// and in some piece of code that gets executed on any "activity":	2089	// and in some piece of code that gets executed on any "activity":
1827	// reset the timeout to start ticking again at 10 seconds	2090	// reset the timeout to start ticking again at 10 seconds
1828	ev_timer_again (&mytimer);	2091	ev_timer_again (&mytimer);
1829		2092
…		…
1855		2118
1856	As with timers, the callback is guaranteed to be invoked only when the	2119	As with timers, the callback is guaranteed to be invoked only when the
1857	point in time where it is supposed to trigger has passed. If multiple	2120	point in time where it is supposed to trigger has passed. If multiple
1858	timers become ready during the same loop iteration then the ones with	2121	timers become ready during the same loop iteration then the ones with
1859	earlier time-out values are invoked before ones with later time-out values	2122	earlier time-out values are invoked before ones with later time-out values
1860	(but this is no longer true when a callback calls C<ev_loop> recursively).	2123	(but this is no longer true when a callback calls C<ev_run> recursively).
1861		2124
1862	=head3 Watcher-Specific Functions and Data Members	2125	=head3 Watcher-Specific Functions and Data Members
1863		2126
1864	=over 4	2127	=over 4
1865		2128
…		…
1900		2163
1901	Another way to think about it (for the mathematically inclined) is that	2164	Another way to think about it (for the mathematically inclined) is that
1902	C<ev_periodic> will try to run the callback in this mode at the next possible	2165	C<ev_periodic> will try to run the callback in this mode at the next possible
1903	time where C<time = offset (mod interval)>, regardless of any time jumps.	2166	time where C<time = offset (mod interval)>, regardless of any time jumps.
1904		2167
1905	For numerical stability it is preferable that the C<offset> value is near	2168	The C<interval> I<MUST> be positive, and for numerical stability, the
1906	C<ev_now ()> (the current time), but there is no range requirement for	2169	interval value should be higher than C<1/8192> (which is around 100
1907	this value, and in fact is often specified as zero.	2170	microseconds) and C<offset> should be higher than C<0> and should have
		2171	at most a similar magnitude as the current time (say, within a factor of
		2172	ten). Typical values for offset are, in fact, C<0> or something between
		2173	C<0> and C<interval>, which is also the recommended range.
1908		2174
1909	Note also that there is an upper limit to how often a timer can fire (CPU	2175	Note also that there is an upper limit to how often a timer can fire (CPU
1910	speed for example), so if C<interval> is very small then timing stability	2176	speed for example), so if C<interval> is very small then timing stability
1911	will of course deteriorate. Libev itself tries to be exact to be about one	2177	will of course deteriorate. Libev itself tries to be exact to be about one
1912	millisecond (if the OS supports it and the machine is fast enough).	2178	millisecond (if the OS supports it and the machine is fast enough).
…		…
1993	Example: Call a callback every hour, or, more precisely, whenever the	2259	Example: Call a callback every hour, or, more precisely, whenever the
1994	system time is divisible by 3600. The callback invocation times have	2260	system time is divisible by 3600. The callback invocation times have
1995	potentially a lot of jitter, but good long-term stability.	2261	potentially a lot of jitter, but good long-term stability.
1996		2262
1997	static void	2263	static void
1998	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2264	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1999	{	2265	{
2000	... its now a full hour (UTC, or TAI or whatever your clock follows)	2266	... its now a full hour (UTC, or TAI or whatever your clock follows)
2001	}	2267	}
2002		2268
2003	ev_periodic hourly_tick;	2269	ev_periodic hourly_tick;
…		…
2026		2292
2027	=head2 C<ev_signal> - signal me when a signal gets signalled!	2293	=head2 C<ev_signal> - signal me when a signal gets signalled!
2028		2294
2029	Signal watchers will trigger an event when the process receives a specific	2295	Signal watchers will trigger an event when the process receives a specific
2030	signal one or more times. Even though signals are very asynchronous, libev	2296	signal one or more times. Even though signals are very asynchronous, libev
2031	will try it's best to deliver signals synchronously, i.e. as part of the	2297	will try its best to deliver signals synchronously, i.e. as part of the
2032	normal event processing, like any other event.	2298	normal event processing, like any other event.
2033		2299
2034	If you want signals asynchronously, just use C<sigaction> as you would	2300	If you want signals to be delivered truly asynchronously, just use
2035	do without libev and forget about sharing the signal. You can even use	2301	C<sigaction> as you would do without libev and forget about sharing
2036	C<ev_async> from a signal handler to synchronously wake up an event loop.	2302	the signal. You can even use C<ev_async> from a signal handler to
		2303	synchronously wake up an event loop.
2037		2304
2038	You can configure as many watchers as you like per signal. Only when the	2305	You can configure as many watchers as you like for the same signal, but
		2306	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2307	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2308	C<SIGINT> in both the default loop and another loop at the same time. At
		2309	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2310
2039	first watcher gets started will libev actually register a signal handler	2311	When the first watcher gets started will libev actually register something
2040	with the kernel (thus it coexists with your own signal handlers as long as	2312	with the kernel (thus it coexists with your own signal handlers as long as
2041	you don't register any with libev for the same signal). Similarly, when	2313	you don't register any with libev for the same signal).
2042	the last signal watcher for a signal is stopped, libev will reset the
2043	signal handler to SIG_DFL (regardless of what it was set to before).
2044		2314
2045	If possible and supported, libev will install its handlers with	2315	If possible and supported, libev will install its handlers with
2046	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2316	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2047	interrupted. If you have a problem with system calls getting interrupted by	2317	not be unduly interrupted. If you have a problem with system calls getting
2048	signals you can block all signals in an C<ev_check> watcher and unblock	2318	interrupted by signals you can block all signals in an C<ev_check> watcher
2049	them in an C<ev_prepare> watcher.	2319	and unblock them in an C<ev_prepare> watcher.
		2320
		2321	=head3 The special problem of inheritance over fork/execve/pthread_create
		2322
		2323	Both the signal mask (C<sigprocmask>) and the signal disposition
		2324	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2325	stopping it again), that is, libev might or might not block the signal,
		2326	and might or might not set or restore the installed signal handler (but
		2327	see C<EVFLAG_NOSIGMASK>).
		2328
		2329	While this does not matter for the signal disposition (libev never
		2330	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2331	C<execve>), this matters for the signal mask: many programs do not expect
		2332	certain signals to be blocked.
		2333
		2334	This means that before calling C<exec> (from the child) you should reset
		2335	the signal mask to whatever "default" you expect (all clear is a good
		2336	choice usually).
		2337
		2338	The simplest way to ensure that the signal mask is reset in the child is
		2339	to install a fork handler with C<pthread_atfork> that resets it. That will
		2340	catch fork calls done by libraries (such as the libc) as well.
		2341
		2342	In current versions of libev, the signal will not be blocked indefinitely
		2343	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2344	the window of opportunity for problems, it will not go away, as libev
		2345	I<has> to modify the signal mask, at least temporarily.
		2346
		2347	So I can't stress this enough: I<If you do not reset your signal mask when
		2348	you expect it to be empty, you have a race condition in your code>. This
		2349	is not a libev-specific thing, this is true for most event libraries.
		2350
		2351	=head3 The special problem of threads signal handling
		2352
		2353	POSIX threads has problematic signal handling semantics, specifically,
		2354	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2355	threads in a process block signals, which is hard to achieve.
		2356
		2357	When you want to use sigwait (or mix libev signal handling with your own
		2358	for the same signals), you can tackle this problem by globally blocking
		2359	all signals before creating any threads (or creating them with a fully set
		2360	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2361	loops. Then designate one thread as "signal receiver thread" which handles
		2362	these signals. You can pass on any signals that libev might be interested
		2363	in by calling C<ev_feed_signal>.
2050		2364
2051	=head3 Watcher-Specific Functions and Data Members	2365	=head3 Watcher-Specific Functions and Data Members
2052		2366
2053	=over 4	2367	=over 4
2054		2368
…		…
2070	Example: Try to exit cleanly on SIGINT.	2384	Example: Try to exit cleanly on SIGINT.
2071		2385
2072	static void	2386	static void
2073	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2387	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2074	{	2388	{
2075	ev_unloop (loop, EVUNLOOP_ALL);	2389	ev_break (loop, EVBREAK_ALL);
2076	}	2390	}
2077		2391
2078	ev_signal signal_watcher;	2392	ev_signal signal_watcher;
2079	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2393	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2080	ev_signal_start (loop, &signal_watcher);	2394	ev_signal_start (loop, &signal_watcher);
…		…
2099	libev)	2413	libev)
2100		2414
2101	=head3 Process Interaction	2415	=head3 Process Interaction
2102		2416
2103	Libev grabs C<SIGCHLD> as soon as the default event loop is	2417	Libev grabs C<SIGCHLD> as soon as the default event loop is
2104	initialised. This is necessary to guarantee proper behaviour even if	2418	initialised. This is necessary to guarantee proper behaviour even if the
2105	the first child watcher is started after the child exits. The occurrence	2419	first child watcher is started after the child exits. The occurrence
2106	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2420	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2107	synchronously as part of the event loop processing. Libev always reaps all	2421	synchronously as part of the event loop processing. Libev always reaps all
2108	children, even ones not watched.	2422	children, even ones not watched.
2109		2423
2110	=head3 Overriding the Built-In Processing	2424	=head3 Overriding the Built-In Processing
…		…
2120	=head3 Stopping the Child Watcher	2434	=head3 Stopping the Child Watcher
2121		2435
2122	Currently, the child watcher never gets stopped, even when the	2436	Currently, the child watcher never gets stopped, even when the
2123	child terminates, so normally one needs to stop the watcher in the	2437	child terminates, so normally one needs to stop the watcher in the
2124	callback. Future versions of libev might stop the watcher automatically	2438	callback. Future versions of libev might stop the watcher automatically
2125	when a child exit is detected.	2439	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2440	problem).
2126		2441
2127	=head3 Watcher-Specific Functions and Data Members	2442	=head3 Watcher-Specific Functions and Data Members
2128		2443
2129	=over 4	2444	=over 4
2130		2445
…		…
2465		2780
2466	Prepare and check watchers are usually (but not always) used in pairs:	2781	Prepare and check watchers are usually (but not always) used in pairs:
2467	prepare watchers get invoked before the process blocks and check watchers	2782	prepare watchers get invoked before the process blocks and check watchers
2468	afterwards.	2783	afterwards.
2469		2784
2470	You I<must not> call C<ev_loop> or similar functions that enter	2785	You I<must not> call C<ev_run> or similar functions that enter
2471	the current event loop from either C<ev_prepare> or C<ev_check>	2786	the current event loop from either C<ev_prepare> or C<ev_check>
2472	watchers. Other loops than the current one are fine, however. The	2787	watchers. Other loops than the current one are fine, however. The
2473	rationale behind this is that you do not need to check for recursion in	2788	rationale behind this is that you do not need to check for recursion in
2474	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2789	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2475	C<ev_check> so if you have one watcher of each kind they will always be	2790	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2643		2958
2644	if (timeout >= 0)	2959	if (timeout >= 0)
2645	// create/start timer	2960	// create/start timer
2646		2961
2647	// poll	2962	// poll
2648	ev_loop (EV_A_ 0);	2963	ev_run (EV_A_ 0);
2649		2964
2650	// stop timer again	2965	// stop timer again
2651	if (timeout >= 0)	2966	if (timeout >= 0)
2652	ev_timer_stop (EV_A_ &to);	2967	ev_timer_stop (EV_A_ &to);
2653		2968
…		…
2731	if you do not want that, you need to temporarily stop the embed watcher).	3046	if you do not want that, you need to temporarily stop the embed watcher).
2732		3047
2733	=item ev_embed_sweep (loop, ev_embed *)	3048	=item ev_embed_sweep (loop, ev_embed *)
2734		3049
2735	Make a single, non-blocking sweep over the embedded loop. This works	3050	Make a single, non-blocking sweep over the embedded loop. This works
2736	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3051	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2737	appropriate way for embedded loops.	3052	appropriate way for embedded loops.
2738		3053
2739	=item struct ev_loop *other [read-only]	3054	=item struct ev_loop *other [read-only]
2740		3055
2741	The embedded event loop.	3056	The embedded event loop.
…		…
2801	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3116	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2802	handlers will be invoked, too, of course.	3117	handlers will be invoked, too, of course.
2803		3118
2804	=head3 The special problem of life after fork - how is it possible?	3119	=head3 The special problem of life after fork - how is it possible?
2805		3120
2806	Most uses of C<fork()> consist of forking, then some simple calls to ste	3121	Most uses of C<fork()> consist of forking, then some simple calls to set
2807	up/change the process environment, followed by a call to C<exec()>. This	3122	up/change the process environment, followed by a call to C<exec()>. This
2808	sequence should be handled by libev without any problems.	3123	sequence should be handled by libev without any problems.
2809		3124
2810	This changes when the application actually wants to do event handling	3125	This changes when the application actually wants to do event handling
2811	in the child, or both parent in child, in effect "continuing" after the	3126	in the child, or both parent in child, in effect "continuing" after the
…		…
2827	disadvantage of having to use multiple event loops (which do not support	3142	disadvantage of having to use multiple event loops (which do not support
2828	signal watchers).	3143	signal watchers).
2829		3144
2830	When this is not possible, or you want to use the default loop for	3145	When this is not possible, or you want to use the default loop for
2831	other reasons, then in the process that wants to start "fresh", call	3146	other reasons, then in the process that wants to start "fresh", call
2832	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3147	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2833	the default loop will "orphan" (not stop) all registered watchers, so you	3148	Destroying the default loop will "orphan" (not stop) all registered
2834	have to be careful not to execute code that modifies those watchers. Note	3149	watchers, so you have to be careful not to execute code that modifies
2835	also that in that case, you have to re-register any signal watchers.	3150	those watchers. Note also that in that case, you have to re-register any
		3151	signal watchers.
2836		3152
2837	=head3 Watcher-Specific Functions and Data Members	3153	=head3 Watcher-Specific Functions and Data Members
2838		3154
2839	=over 4	3155	=over 4
2840		3156
2841	=item ev_fork_init (ev_signal *, callback)	3157	=item ev_fork_init (ev_fork *, callback)
2842		3158
2843	Initialises and configures the fork watcher - it has no parameters of any	3159	Initialises and configures the fork watcher - it has no parameters of any
2844	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3160	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2845	believe me.	3161	really.
2846		3162
2847	=back	3163	=back
2848		3164
2849		3165
		3166	=head2 C<ev_cleanup> - even the best things end
		3167
		3168	Cleanup watchers are called just before the event loop is being destroyed
		3169	by a call to C<ev_loop_destroy>.
		3170
		3171	While there is no guarantee that the event loop gets destroyed, cleanup
		3172	watchers provide a convenient method to install cleanup hooks for your
		3173	program, worker threads and so on - you just to make sure to destroy the
		3174	loop when you want them to be invoked.
		3175
		3176	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3177	all other watchers, they do not keep a reference to the event loop (which
		3178	makes a lot of sense if you think about it). Like all other watchers, you
		3179	can call libev functions in the callback, except C<ev_cleanup_start>.
		3180
		3181	=head3 Watcher-Specific Functions and Data Members
		3182
		3183	=over 4
		3184
		3185	=item ev_cleanup_init (ev_cleanup *, callback)
		3186
		3187	Initialises and configures the cleanup watcher - it has no parameters of
		3188	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3189	pointless, I assure you.
		3190
		3191	=back
		3192
		3193	Example: Register an atexit handler to destroy the default loop, so any
		3194	cleanup functions are called.
		3195
		3196	static void
		3197	program_exits (void)
		3198	{
		3199	ev_loop_destroy (EV_DEFAULT_UC);
		3200	}
		3201
		3202	...
		3203	atexit (program_exits);
		3204
		3205
2850	=head2 C<ev_async> - how to wake up another event loop	3206	=head2 C<ev_async> - how to wake up an event loop
2851		3207
2852	In general, you cannot use an C<ev_loop> from multiple threads or other	3208	In general, you cannot use an C<ev_loop> from multiple threads or other
2853	asynchronous sources such as signal handlers (as opposed to multiple event	3209	asynchronous sources such as signal handlers (as opposed to multiple event
2854	loops - those are of course safe to use in different threads).	3210	loops - those are of course safe to use in different threads).
2855		3211
2856	Sometimes, however, you need to wake up another event loop you do not	3212	Sometimes, however, you need to wake up an event loop you do not control,
2857	control, for example because it belongs to another thread. This is what	3213	for example because it belongs to another thread. This is what C<ev_async>
2858	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3214	watchers do: as long as the C<ev_async> watcher is active, you can signal
2859	can signal it by calling C<ev_async_send>, which is thread- and signal	3215	it by calling C<ev_async_send>, which is thread- and signal safe.
2860	safe.
2861		3216
2862	This functionality is very similar to C<ev_signal> watchers, as signals,	3217	This functionality is very similar to C<ev_signal> watchers, as signals,
2863	too, are asynchronous in nature, and signals, too, will be compressed	3218	too, are asynchronous in nature, and signals, too, will be compressed
2864	(i.e. the number of callback invocations may be less than the number of	3219	(i.e. the number of callback invocations may be less than the number of
2865	C<ev_async_sent> calls).	3220	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2866		3221	of "global async watchers" by using a watcher on an otherwise unused
2867	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3222	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2868	just the default loop.	3223	even without knowing which loop owns the signal.
2869		3224
2870	=head3 Queueing	3225	=head3 Queueing
2871		3226
2872	C<ev_async> does not support queueing of data in any way. The reason	3227	C<ev_async> does not support queueing of data in any way. The reason
2873	is that the author does not know of a simple (or any) algorithm for a	3228	is that the author does not know of a simple (or any) algorithm for a
2874	multiple-writer-single-reader queue that works in all cases and doesn't	3229	multiple-writer-single-reader queue that works in all cases and doesn't
2875	need elaborate support such as pthreads.	3230	need elaborate support such as pthreads or unportable memory access
		3231	semantics.
2876		3232
2877	That means that if you want to queue data, you have to provide your own	3233	That means that if you want to queue data, you have to provide your own
2878	queue. But at least I can tell you how to implement locking around your	3234	queue. But at least I can tell you how to implement locking around your
2879	queue:	3235	queue:
2880		3236
…		…
2964	trust me.	3320	trust me.
2965		3321
2966	=item ev_async_send (loop, ev_async *)	3322	=item ev_async_send (loop, ev_async *)
2967		3323
2968	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3324	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2969	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3325	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3326	returns.
		3327
2970	C<ev_feed_event>, this call is safe to do from other threads, signal or	3328	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2971	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3329	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2972	section below on what exactly this means).	3330	embedding section below on what exactly this means).
2973		3331
2974	Note that, as with other watchers in libev, multiple events might get	3332	Note that, as with other watchers in libev, multiple events might get
2975	compressed into a single callback invocation (another way to look at this	3333	compressed into a single callback invocation (another way to look at
2976	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3334	this is that C<ev_async> watchers are level-triggered: they are set on
2977	reset when the event loop detects that).	3335	C<ev_async_send>, reset when the event loop detects that).
2978		3336
2979	This call incurs the overhead of a system call only once per event loop	3337	This call incurs the overhead of at most one extra system call per event
2980	iteration, so while the overhead might be noticeable, it doesn't apply to	3338	loop iteration, if the event loop is blocked, and no syscall at all if
2981	repeated calls to C<ev_async_send> for the same event loop.	3339	the event loop (or your program) is processing events. That means that
		3340	repeated calls are basically free (there is no need to avoid calls for
		3341	performance reasons) and that the overhead becomes smaller (typically
		3342	zero) under load.
2982		3343
2983	=item bool = ev_async_pending (ev_async *)	3344	=item bool = ev_async_pending (ev_async *)
2984		3345
2985	Returns a non-zero value when C<ev_async_send> has been called on the	3346	Returns a non-zero value when C<ev_async_send> has been called on the
2986	watcher but the event has not yet been processed (or even noted) by the	3347	watcher but the event has not yet been processed (or even noted) by the
…		…
3019		3380
3020	If C<timeout> is less than 0, then no timeout watcher will be	3381	If C<timeout> is less than 0, then no timeout watcher will be
3021	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3382	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3022	repeat = 0) will be started. C<0> is a valid timeout.	3383	repeat = 0) will be started. C<0> is a valid timeout.
3023		3384
3024	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3385	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3025	passed an C<revents> set like normal event callbacks (a combination of	3386	passed an C<revents> set like normal event callbacks (a combination of
3026	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3387	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3027	value passed to C<ev_once>. Note that it is possible to receive I<both>	3388	value passed to C<ev_once>. Note that it is possible to receive I<both>
3028	a timeout and an io event at the same time - you probably should give io	3389	a timeout and an io event at the same time - you probably should give io
3029	events precedence.	3390	events precedence.
3030		3391
3031	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3392	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3032		3393
3033	static void stdin_ready (int revents, void *arg)	3394	static void stdin_ready (int revents, void *arg)
3034	{	3395	{
3035	if (revents & EV_READ)	3396	if (revents & EV_READ)
3036	/* stdin might have data for us, joy! */;	3397	/* stdin might have data for us, joy! */;
3037	else if (revents & EV_TIMEOUT)	3398	else if (revents & EV_TIMER)
3038	/* doh, nothing entered */;	3399	/* doh, nothing entered */;
3039	}	3400	}
3040		3401
3041	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3402	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3042		3403
3043	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3044
3045	Feeds the given event set into the event loop, as if the specified event
3046	had happened for the specified watcher (which must be a pointer to an
3047	initialised but not necessarily started event watcher).
3048
3049	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3404	=item ev_feed_fd_event (loop, int fd, int revents)
3050		3405
3051	Feed an event on the given fd, as if a file descriptor backend detected	3406	Feed an event on the given fd, as if a file descriptor backend detected
3052	the given events it.	3407	the given events it.
3053		3408
3054	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3409	=item ev_feed_signal_event (loop, int signum)
3055		3410
3056	Feed an event as if the given signal occurred (C<loop> must be the default	3411	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3057	loop!).	3412	which is async-safe.
3058		3413
3059	=back	3414	=back
		3415
		3416
		3417	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3418
		3419	This section explains some common idioms that are not immediately
		3420	obvious. Note that examples are sprinkled over the whole manual, and this
		3421	section only contains stuff that wouldn't fit anywhere else.
		3422
		3423	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3424
		3425	Each watcher has, by default, a C<void *data> member that you can read
		3426	or modify at any time: libev will completely ignore it. This can be used
		3427	to associate arbitrary data with your watcher. If you need more data and
		3428	don't want to allocate memory separately and store a pointer to it in that
		3429	data member, you can also "subclass" the watcher type and provide your own
		3430	data:
		3431
		3432	struct my_io
		3433	{
		3434	ev_io io;
		3435	int otherfd;
		3436	void *somedata;
		3437	struct whatever *mostinteresting;
		3438	};
		3439
		3440	...
		3441	struct my_io w;
		3442	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3443
		3444	And since your callback will be called with a pointer to the watcher, you
		3445	can cast it back to your own type:
		3446
		3447	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3448	{
		3449	struct my_io *w = (struct my_io *)w_;
		3450	...
		3451	}
		3452
		3453	More interesting and less C-conformant ways of casting your callback
		3454	function type instead have been omitted.
		3455
		3456	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3457
		3458	Another common scenario is to use some data structure with multiple
		3459	embedded watchers, in effect creating your own watcher that combines
		3460	multiple libev event sources into one "super-watcher":
		3461
		3462	struct my_biggy
		3463	{
		3464	int some_data;
		3465	ev_timer t1;
		3466	ev_timer t2;
		3467	}
		3468
		3469	In this case getting the pointer to C<my_biggy> is a bit more
		3470	complicated: Either you store the address of your C<my_biggy> struct in
		3471	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3472	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3473	real programmers):
		3474
		3475	#include <stddef.h>
		3476
		3477	static void
		3478	t1_cb (EV_P_ ev_timer *w, int revents)
		3479	{
		3480	struct my_biggy big = (struct my_biggy *)
		3481	(((char *)w) - offsetof (struct my_biggy, t1));
		3482	}
		3483
		3484	static void
		3485	t2_cb (EV_P_ ev_timer *w, int revents)
		3486	{
		3487	struct my_biggy big = (struct my_biggy *)
		3488	(((char *)w) - offsetof (struct my_biggy, t2));
		3489	}
		3490
		3491	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3492
		3493	Often (especially in GUI toolkits) there are places where you have
		3494	I<modal> interaction, which is most easily implemented by recursively
		3495	invoking C<ev_run>.
		3496
		3497	This brings the problem of exiting - a callback might want to finish the
		3498	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3499	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3500	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3501	other combination: In these cases, C<ev_break> will not work alone.
		3502
		3503	The solution is to maintain "break this loop" variable for each C<ev_run>
		3504	invocation, and use a loop around C<ev_run> until the condition is
		3505	triggered, using C<EVRUN_ONCE>:
		3506
		3507	// main loop
		3508	int exit_main_loop = 0;
		3509
		3510	while (!exit_main_loop)
		3511	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3512
		3513	// in a model watcher
		3514	int exit_nested_loop = 0;
		3515
		3516	while (!exit_nested_loop)
		3517	ev_run (EV_A_ EVRUN_ONCE);
		3518
		3519	To exit from any of these loops, just set the corresponding exit variable:
		3520
		3521	// exit modal loop
		3522	exit_nested_loop = 1;
		3523
		3524	// exit main program, after modal loop is finished
		3525	exit_main_loop = 1;
		3526
		3527	// exit both
		3528	exit_main_loop = exit_nested_loop = 1;
		3529
		3530	=head2 THREAD LOCKING EXAMPLE
		3531
		3532	Here is a fictitious example of how to run an event loop in a different
		3533	thread from where callbacks are being invoked and watchers are
		3534	created/added/removed.
		3535
		3536	For a real-world example, see the C<EV::Loop::Async> perl module,
		3537	which uses exactly this technique (which is suited for many high-level
		3538	languages).
		3539
		3540	The example uses a pthread mutex to protect the loop data, a condition
		3541	variable to wait for callback invocations, an async watcher to notify the
		3542	event loop thread and an unspecified mechanism to wake up the main thread.
		3543
		3544	First, you need to associate some data with the event loop:
		3545
		3546	typedef struct {
		3547	mutex_t lock; /* global loop lock */
		3548	ev_async async_w;
		3549	thread_t tid;
		3550	cond_t invoke_cv;
		3551	} userdata;
		3552
		3553	void prepare_loop (EV_P)
		3554	{
		3555	// for simplicity, we use a static userdata struct.
		3556	static userdata u;
		3557
		3558	ev_async_init (&u->async_w, async_cb);
		3559	ev_async_start (EV_A_ &u->async_w);
		3560
		3561	pthread_mutex_init (&u->lock, 0);
		3562	pthread_cond_init (&u->invoke_cv, 0);
		3563
		3564	// now associate this with the loop
		3565	ev_set_userdata (EV_A_ u);
		3566	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3567	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3568
		3569	// then create the thread running ev_run
		3570	pthread_create (&u->tid, 0, l_run, EV_A);
		3571	}
		3572
		3573	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3574	solely to wake up the event loop so it takes notice of any new watchers
		3575	that might have been added:
		3576
		3577	static void
		3578	async_cb (EV_P_ ev_async *w, int revents)
		3579	{
		3580	// just used for the side effects
		3581	}
		3582
		3583	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3584	protecting the loop data, respectively.
		3585
		3586	static void
		3587	l_release (EV_P)
		3588	{
		3589	userdata *u = ev_userdata (EV_A);
		3590	pthread_mutex_unlock (&u->lock);
		3591	}
		3592
		3593	static void
		3594	l_acquire (EV_P)
		3595	{
		3596	userdata *u = ev_userdata (EV_A);
		3597	pthread_mutex_lock (&u->lock);
		3598	}
		3599
		3600	The event loop thread first acquires the mutex, and then jumps straight
		3601	into C<ev_run>:
		3602
		3603	void *
		3604	l_run (void *thr_arg)
		3605	{
		3606	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3607
		3608	l_acquire (EV_A);
		3609	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3610	ev_run (EV_A_ 0);
		3611	l_release (EV_A);
		3612
		3613	return 0;
		3614	}
		3615
		3616	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3617	signal the main thread via some unspecified mechanism (signals? pipe
		3618	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3619	have been called (in a while loop because a) spurious wakeups are possible
		3620	and b) skipping inter-thread-communication when there are no pending
		3621	watchers is very beneficial):
		3622
		3623	static void
		3624	l_invoke (EV_P)
		3625	{
		3626	userdata *u = ev_userdata (EV_A);
		3627
		3628	while (ev_pending_count (EV_A))
		3629	{
		3630	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3631	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3632	}
		3633	}
		3634
		3635	Now, whenever the main thread gets told to invoke pending watchers, it
		3636	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3637	thread to continue:
		3638
		3639	static void
		3640	real_invoke_pending (EV_P)
		3641	{
		3642	userdata *u = ev_userdata (EV_A);
		3643
		3644	pthread_mutex_lock (&u->lock);
		3645	ev_invoke_pending (EV_A);
		3646	pthread_cond_signal (&u->invoke_cv);
		3647	pthread_mutex_unlock (&u->lock);
		3648	}
		3649
		3650	Whenever you want to start/stop a watcher or do other modifications to an
		3651	event loop, you will now have to lock:
		3652
		3653	ev_timer timeout_watcher;
		3654	userdata *u = ev_userdata (EV_A);
		3655
		3656	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3657
		3658	pthread_mutex_lock (&u->lock);
		3659	ev_timer_start (EV_A_ &timeout_watcher);
		3660	ev_async_send (EV_A_ &u->async_w);
		3661	pthread_mutex_unlock (&u->lock);
		3662
		3663	Note that sending the C<ev_async> watcher is required because otherwise
		3664	an event loop currently blocking in the kernel will have no knowledge
		3665	about the newly added timer. By waking up the loop it will pick up any new
		3666	watchers in the next event loop iteration.
		3667
		3668	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3669
		3670	While the overhead of a callback that e.g. schedules a thread is small, it
		3671	is still an overhead. If you embed libev, and your main usage is with some
		3672	kind of threads or coroutines, you might want to customise libev so that
		3673	doesn't need callbacks anymore.
		3674
		3675	Imagine you have coroutines that you can switch to using a function
		3676	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3677	and that due to some magic, the currently active coroutine is stored in a
		3678	global called C<current_coro>. Then you can build your own "wait for libev
		3679	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3680	the differing C<;> conventions):
		3681
		3682	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3683	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3684
		3685	That means instead of having a C callback function, you store the
		3686	coroutine to switch to in each watcher, and instead of having libev call
		3687	your callback, you instead have it switch to that coroutine.
		3688
		3689	A coroutine might now wait for an event with a function called
		3690	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3691	matter when, or whether the watcher is active or not when this function is
		3692	called):
		3693
		3694	void
		3695	wait_for_event (ev_watcher *w)
		3696	{
		3697	ev_cb_set (w) = current_coro;
		3698	switch_to (libev_coro);
		3699	}
		3700
		3701	That basically suspends the coroutine inside C<wait_for_event> and
		3702	continues the libev coroutine, which, when appropriate, switches back to
		3703	this or any other coroutine. I am sure if you sue this your own :)
		3704
		3705	You can do similar tricks if you have, say, threads with an event queue -
		3706	instead of storing a coroutine, you store the queue object and instead of
		3707	switching to a coroutine, you push the watcher onto the queue and notify
		3708	any waiters.
		3709
		3710	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3711	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3712
		3713	// my_ev.h
		3714	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3715	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3716	#include "../libev/ev.h"
		3717
		3718	// my_ev.c
		3719	#define EV_H "my_ev.h"
		3720	#include "../libev/ev.c"
		3721
		3722	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3723	F<my_ev.c> into your project. When properly specifying include paths, you
		3724	can even use F<ev.h> as header file name directly.
3060		3725
3061		3726
3062	=head1 LIBEVENT EMULATION	3727	=head1 LIBEVENT EMULATION
3063		3728
3064	Libev offers a compatibility emulation layer for libevent. It cannot	3729	Libev offers a compatibility emulation layer for libevent. It cannot
3065	emulate the internals of libevent, so here are some usage hints:	3730	emulate the internals of libevent, so here are some usage hints:
3066		3731
3067	=over 4	3732	=over 4
		3733
		3734	=item * Only the libevent-1.4.1-beta API is being emulated.
		3735
		3736	This was the newest libevent version available when libev was implemented,
		3737	and is still mostly unchanged in 2010.
3068		3738
3069	=item * Use it by including <event.h>, as usual.	3739	=item * Use it by including <event.h>, as usual.
3070		3740
3071	=item * The following members are fully supported: ev_base, ev_callback,	3741	=item * The following members are fully supported: ev_base, ev_callback,
3072	ev_arg, ev_fd, ev_res, ev_events.	3742	ev_arg, ev_fd, ev_res, ev_events.
…		…
3078	=item * Priorities are not currently supported. Initialising priorities	3748	=item * Priorities are not currently supported. Initialising priorities
3079	will fail and all watchers will have the same priority, even though there	3749	will fail and all watchers will have the same priority, even though there
3080	is an ev_pri field.	3750	is an ev_pri field.
3081		3751
3082	=item * In libevent, the last base created gets the signals, in libev, the	3752	=item * In libevent, the last base created gets the signals, in libev, the
3083	first base created (== the default loop) gets the signals.	3753	base that registered the signal gets the signals.
3084		3754
3085	=item * Other members are not supported.	3755	=item * Other members are not supported.
3086		3756
3087	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3757	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3088	to use the libev header file and library.	3758	to use the libev header file and library.
…		…
3107	Care has been taken to keep the overhead low. The only data member the C++	3777	Care has been taken to keep the overhead low. The only data member the C++
3108	classes add (compared to plain C-style watchers) is the event loop pointer	3778	classes add (compared to plain C-style watchers) is the event loop pointer
3109	that the watcher is associated with (or no additional members at all if	3779	that the watcher is associated with (or no additional members at all if
3110	you disable C<EV_MULTIPLICITY> when embedding libev).	3780	you disable C<EV_MULTIPLICITY> when embedding libev).
3111		3781
3112	Currently, functions, and static and non-static member functions can be	3782	Currently, functions, static and non-static member functions and classes
3113	used as callbacks. Other types should be easy to add as long as they only	3783	with C<operator ()> can be used as callbacks. Other types should be easy
3114	need one additional pointer for context. If you need support for other	3784	to add as long as they only need one additional pointer for context. If
3115	types of functors please contact the author (preferably after implementing	3785	you need support for other types of functors please contact the author
3116	it).	3786	(preferably after implementing it).
3117		3787
3118	Here is a list of things available in the C<ev> namespace:	3788	Here is a list of things available in the C<ev> namespace:
3119		3789
3120	=over 4	3790	=over 4
3121		3791
…		…
3139		3809
3140	=over 4	3810	=over 4
3141		3811
3142	=item ev::TYPE::TYPE ()	3812	=item ev::TYPE::TYPE ()
3143		3813
3144	=item ev::TYPE::TYPE (struct ev_loop *)	3814	=item ev::TYPE::TYPE (loop)
3145		3815
3146	=item ev::TYPE::~TYPE	3816	=item ev::TYPE::~TYPE
3147		3817
3148	The constructor (optionally) takes an event loop to associate the watcher	3818	The constructor (optionally) takes an event loop to associate the watcher
3149	with. If it is omitted, it will use C<EV_DEFAULT>.	3819	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3182	myclass obj;	3852	myclass obj;
3183	ev::io iow;	3853	ev::io iow;
3184	iow.set <myclass, &myclass::io_cb> (&obj);	3854	iow.set <myclass, &myclass::io_cb> (&obj);
3185		3855
3186	=item w->set (object *)	3856	=item w->set (object *)
3187
3188	This is an B<experimental> feature that might go away in a future version.
3189		3857
3190	This is a variation of a method callback - leaving out the method to call	3858	This is a variation of a method callback - leaving out the method to call
3191	will default the method to C<operator ()>, which makes it possible to use	3859	will default the method to C<operator ()>, which makes it possible to use
3192	functor objects without having to manually specify the C<operator ()> all	3860	functor objects without having to manually specify the C<operator ()> all
3193	the time. Incidentally, you can then also leave out the template argument	3861	the time. Incidentally, you can then also leave out the template argument
…		…
3226	Example: Use a plain function as callback.	3894	Example: Use a plain function as callback.
3227		3895
3228	static void io_cb (ev::io &w, int revents) { }	3896	static void io_cb (ev::io &w, int revents) { }
3229	iow.set <io_cb> ();	3897	iow.set <io_cb> ();
3230		3898
3231	=item w->set (struct ev_loop *)	3899	=item w->set (loop)
3232		3900
3233	Associates a different C<struct ev_loop> with this watcher. You can only	3901	Associates a different C<struct ev_loop> with this watcher. You can only
3234	do this when the watcher is inactive (and not pending either).	3902	do this when the watcher is inactive (and not pending either).
3235		3903
3236	=item w->set ([arguments])	3904	=item w->set ([arguments])
3237		3905
3238	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3906	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3239	called at least once. Unlike the C counterpart, an active watcher gets	3907	method or a suitable start method must be called at least once. Unlike the
3240	automatically stopped and restarted when reconfiguring it with this	3908	C counterpart, an active watcher gets automatically stopped and restarted
3241	method.	3909	when reconfiguring it with this method.
3242		3910
3243	=item w->start ()	3911	=item w->start ()
3244		3912
3245	Starts the watcher. Note that there is no C<loop> argument, as the	3913	Starts the watcher. Note that there is no C<loop> argument, as the
3246	constructor already stores the event loop.	3914	constructor already stores the event loop.
3247		3915
		3916	=item w->start ([arguments])
		3917
		3918	Instead of calling C<set> and C<start> methods separately, it is often
		3919	convenient to wrap them in one call. Uses the same type of arguments as
		3920	the configure C<set> method of the watcher.
		3921
3248	=item w->stop ()	3922	=item w->stop ()
3249		3923
3250	Stops the watcher if it is active. Again, no C<loop> argument.	3924	Stops the watcher if it is active. Again, no C<loop> argument.
3251		3925
3252	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3926	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3264		3938
3265	=back	3939	=back
3266		3940
3267	=back	3941	=back
3268		3942
3269	Example: Define a class with an IO and idle watcher, start one of them in	3943	Example: Define a class with two I/O and idle watchers, start the I/O
3270	the constructor.	3944	watchers in the constructor.
3271		3945
3272	class myclass	3946	class myclass
3273	{	3947	{
3274	ev::io io ; void io_cb (ev::io &w, int revents);	3948	ev::io io ; void io_cb (ev::io &w, int revents);
		3949	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3275	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3950	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3276		3951
3277	myclass (int fd)	3952	myclass (int fd)
3278	{	3953	{
3279	io .set <myclass, &myclass::io_cb > (this);	3954	io .set <myclass, &myclass::io_cb > (this);
		3955	io2 .set <myclass, &myclass::io2_cb > (this);
3280	idle.set <myclass, &myclass::idle_cb> (this);	3956	idle.set <myclass, &myclass::idle_cb> (this);
3281		3957
3282	io.start (fd, ev::READ);	3958	io.set (fd, ev::WRITE); // configure the watcher
		3959	io.start (); // start it whenever convenient
		3960
		3961	io2.start (fd, ev::READ); // set + start in one call
3283	}	3962	}
3284	};	3963	};
3285		3964
3286		3965
3287	=head1 OTHER LANGUAGE BINDINGS	3966	=head1 OTHER LANGUAGE BINDINGS
…		…
3326	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4005	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3327		4006
3328	=item D	4007	=item D
3329		4008
3330	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4009	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3331	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4010	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3332		4011
3333	=item Ocaml	4012	=item Ocaml
3334		4013
3335	Erkki Seppala has written Ocaml bindings for libev, to be found at	4014	Erkki Seppala has written Ocaml bindings for libev, to be found at
3336	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4015	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4016
		4017	=item Lua
		4018
		4019	Brian Maher has written a partial interface to libev for lua (at the
		4020	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4021	L<http://github.com/brimworks/lua-ev>.
3337		4022
3338	=back	4023	=back
3339		4024
3340		4025
3341	=head1 MACRO MAGIC	4026	=head1 MACRO MAGIC
…		…
3355	loop argument"). The C<EV_A> form is used when this is the sole argument,	4040	loop argument"). The C<EV_A> form is used when this is the sole argument,
3356	C<EV_A_> is used when other arguments are following. Example:	4041	C<EV_A_> is used when other arguments are following. Example:
3357		4042
3358	ev_unref (EV_A);	4043	ev_unref (EV_A);
3359	ev_timer_add (EV_A_ watcher);	4044	ev_timer_add (EV_A_ watcher);
3360	ev_loop (EV_A_ 0);	4045	ev_run (EV_A_ 0);
3361		4046
3362	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4047	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3363	which is often provided by the following macro.	4048	which is often provided by the following macro.
3364		4049
3365	=item C<EV_P>, C<EV_P_>	4050	=item C<EV_P>, C<EV_P_>
…		…
3405	}	4090	}
3406		4091
3407	ev_check check;	4092	ev_check check;
3408	ev_check_init (&check, check_cb);	4093	ev_check_init (&check, check_cb);
3409	ev_check_start (EV_DEFAULT_ &check);	4094	ev_check_start (EV_DEFAULT_ &check);
3410	ev_loop (EV_DEFAULT_ 0);	4095	ev_run (EV_DEFAULT_ 0);
3411		4096
3412	=head1 EMBEDDING	4097	=head1 EMBEDDING
3413		4098
3414	Libev can (and often is) directly embedded into host	4099	Libev can (and often is) directly embedded into host
3415	applications. Examples of applications that embed it include the Deliantra	4100	applications. Examples of applications that embed it include the Deliantra
…		…
3495	libev.m4	4180	libev.m4
3496		4181
3497	=head2 PREPROCESSOR SYMBOLS/MACROS	4182	=head2 PREPROCESSOR SYMBOLS/MACROS
3498		4183
3499	Libev can be configured via a variety of preprocessor symbols you have to	4184	Libev can be configured via a variety of preprocessor symbols you have to
3500	define before including any of its files. The default in the absence of	4185	define before including (or compiling) any of its files. The default in
3501	autoconf is documented for every option.	4186	the absence of autoconf is documented for every option.
		4187
		4188	Symbols marked with "(h)" do not change the ABI, and can have different
		4189	values when compiling libev vs. including F<ev.h>, so it is permissible
		4190	to redefine them before including F<ev.h> without breaking compatibility
		4191	to a compiled library. All other symbols change the ABI, which means all
		4192	users of libev and the libev code itself must be compiled with compatible
		4193	settings.
3502		4194
3503	=over 4	4195	=over 4
3504		4196
		4197	=item EV_COMPAT3 (h)
		4198
		4199	Backwards compatibility is a major concern for libev. This is why this
		4200	release of libev comes with wrappers for the functions and symbols that
		4201	have been renamed between libev version 3 and 4.
		4202
		4203	You can disable these wrappers (to test compatibility with future
		4204	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4205	sources. This has the additional advantage that you can drop the C<struct>
		4206	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4207	typedef in that case.
		4208
		4209	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4210	and in some even more future version the compatibility code will be
		4211	removed completely.
		4212
3505	=item EV_STANDALONE	4213	=item EV_STANDALONE (h)
3506		4214
3507	Must always be C<1> if you do not use autoconf configuration, which	4215	Must always be C<1> if you do not use autoconf configuration, which
3508	keeps libev from including F<config.h>, and it also defines dummy	4216	keeps libev from including F<config.h>, and it also defines dummy
3509	implementations for some libevent functions (such as logging, which is not	4217	implementations for some libevent functions (such as logging, which is not
3510	supported). It will also not define any of the structs usually found in	4218	supported). It will also not define any of the structs usually found in
3511	F<event.h> that are not directly supported by the libev core alone.	4219	F<event.h> that are not directly supported by the libev core alone.
3512		4220
3513	In stanbdalone mode, libev will still try to automatically deduce the	4221	In standalone mode, libev will still try to automatically deduce the
3514	configuration, but has to be more conservative.	4222	configuration, but has to be more conservative.
		4223
		4224	=item EV_USE_FLOOR
		4225
		4226	If defined to be C<1>, libev will use the C<floor ()> function for its
		4227	periodic reschedule calculations, otherwise libev will fall back on a
		4228	portable (slower) implementation. If you enable this, you usually have to
		4229	link against libm or something equivalent. Enabling this when the C<floor>
		4230	function is not available will fail, so the safe default is to not enable
		4231	this.
3515		4232
3516	=item EV_USE_MONOTONIC	4233	=item EV_USE_MONOTONIC
3517		4234
3518	If defined to be C<1>, libev will try to detect the availability of the	4235	If defined to be C<1>, libev will try to detect the availability of the
3519	monotonic clock option at both compile time and runtime. Otherwise no	4236	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3583	be used is the winsock select). This means that it will call	4300	be used is the winsock select). This means that it will call
3584	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4301	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3585	it is assumed that all these functions actually work on fds, even	4302	it is assumed that all these functions actually work on fds, even
3586	on win32. Should not be defined on non-win32 platforms.	4303	on win32. Should not be defined on non-win32 platforms.
3587		4304
3588	=item EV_FD_TO_WIN32_HANDLE	4305	=item EV_FD_TO_WIN32_HANDLE(fd)
3589		4306
3590	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4307	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3591	file descriptors to socket handles. When not defining this symbol (the	4308	file descriptors to socket handles. When not defining this symbol (the
3592	default), then libev will call C<_get_osfhandle>, which is usually	4309	default), then libev will call C<_get_osfhandle>, which is usually
3593	correct. In some cases, programs use their own file descriptor management,	4310	correct. In some cases, programs use their own file descriptor management,
3594	in which case they can provide this function to map fds to socket handles.	4311	in which case they can provide this function to map fds to socket handles.
		4312
		4313	=item EV_WIN32_HANDLE_TO_FD(handle)
		4314
		4315	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4316	using the standard C<_open_osfhandle> function. For programs implementing
		4317	their own fd to handle mapping, overwriting this function makes it easier
		4318	to do so. This can be done by defining this macro to an appropriate value.
		4319
		4320	=item EV_WIN32_CLOSE_FD(fd)
		4321
		4322	If programs implement their own fd to handle mapping on win32, then this
		4323	macro can be used to override the C<close> function, useful to unregister
		4324	file descriptors again. Note that the replacement function has to close
		4325	the underlying OS handle.
3595		4326
3596	=item EV_USE_POLL	4327	=item EV_USE_POLL
3597		4328
3598	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4329	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3599	backend. Otherwise it will be enabled on non-win32 platforms. It	4330	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3638	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4369	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3639		4370
3640	=item EV_ATOMIC_T	4371	=item EV_ATOMIC_T
3641		4372
3642	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4373	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3643	access is atomic with respect to other threads or signal contexts. No such	4374	access is atomic and serialised with respect to other threads or signal
3644	type is easily found in the C language, so you can provide your own type	4375	contexts. No such type is easily found in the C language, so you can
3645	that you know is safe for your purposes. It is used both for signal handler "locking"	4376	provide your own type that you know is safe for your purposes. It is used
3646	as well as for signal and thread safety in C<ev_async> watchers.	4377	both for signal handler "locking" as well as for signal and thread safety
		4378	in C<ev_async> watchers.
3647		4379
3648	In the absence of this define, libev will use C<sig_atomic_t volatile>	4380	In the absence of this define, libev will use C<sig_atomic_t volatile>
3649	(from F<signal.h>), which is usually good enough on most platforms.	4381	(from F<signal.h>), which is usually good enough on most platforms,
		4382	although strictly speaking using a type that also implies a memory fence
		4383	is required.
3650		4384
3651	=item EV_H	4385	=item EV_H (h)
3652		4386
3653	The name of the F<ev.h> header file used to include it. The default if	4387	The name of the F<ev.h> header file used to include it. The default if
3654	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4388	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3655	used to virtually rename the F<ev.h> header file in case of conflicts.	4389	used to virtually rename the F<ev.h> header file in case of conflicts.
3656		4390
3657	=item EV_CONFIG_H	4391	=item EV_CONFIG_H (h)
3658		4392
3659	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4393	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3660	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4394	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3661	C<EV_H>, above.	4395	C<EV_H>, above.
3662		4396
3663	=item EV_EVENT_H	4397	=item EV_EVENT_H (h)
3664		4398
3665	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4399	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3666	of how the F<event.h> header can be found, the default is C<"event.h">.	4400	of how the F<event.h> header can be found, the default is C<"event.h">.
3667		4401
3668	=item EV_PROTOTYPES	4402	=item EV_PROTOTYPES (h)
3669		4403
3670	If defined to be C<0>, then F<ev.h> will not define any function	4404	If defined to be C<0>, then F<ev.h> will not define any function
3671	prototypes, but still define all the structs and other symbols. This is	4405	prototypes, but still define all the structs and other symbols. This is
3672	occasionally useful if you want to provide your own wrapper functions	4406	occasionally useful if you want to provide your own wrapper functions
3673	around libev functions.	4407	around libev functions.
…		…
3695	fine.	4429	fine.
3696		4430
3697	If your embedding application does not need any priorities, defining these	4431	If your embedding application does not need any priorities, defining these
3698	both to C<0> will save some memory and CPU.	4432	both to C<0> will save some memory and CPU.
3699		4433
3700	=item EV_PERIODIC_ENABLE	4434	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4435	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4436	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3701		4437
3702	If undefined or defined to be C<1>, then periodic timers are supported. If	4438	If undefined or defined to be C<1> (and the platform supports it), then
3703	defined to be C<0>, then they are not. Disabling them saves a few kB of	4439	the respective watcher type is supported. If defined to be C<0>, then it
3704	code.	4440	is not. Disabling watcher types mainly saves code size.
3705		4441
3706	=item EV_IDLE_ENABLE	4442	=item EV_FEATURES
3707
3708	If undefined or defined to be C<1>, then idle watchers are supported. If
3709	defined to be C<0>, then they are not. Disabling them saves a few kB of
3710	code.
3711
3712	=item EV_EMBED_ENABLE
3713
3714	If undefined or defined to be C<1>, then embed watchers are supported. If
3715	defined to be C<0>, then they are not. Embed watchers rely on most other
3716	watcher types, which therefore must not be disabled.
3717
3718	=item EV_STAT_ENABLE
3719
3720	If undefined or defined to be C<1>, then stat watchers are supported. If
3721	defined to be C<0>, then they are not.
3722
3723	=item EV_FORK_ENABLE
3724
3725	If undefined or defined to be C<1>, then fork watchers are supported. If
3726	defined to be C<0>, then they are not.
3727
3728	=item EV_ASYNC_ENABLE
3729
3730	If undefined or defined to be C<1>, then async watchers are supported. If
3731	defined to be C<0>, then they are not.
3732
3733	=item EV_MINIMAL
3734		4443
3735	If you need to shave off some kilobytes of code at the expense of some	4444	If you need to shave off some kilobytes of code at the expense of some
3736	speed (but with the full API), define this symbol to C<1>. Currently this	4445	speed (but with the full API), you can define this symbol to request
3737	is used to override some inlining decisions, saves roughly 30% code size	4446	certain subsets of functionality. The default is to enable all features
3738	on amd64. It also selects a much smaller 2-heap for timer management over	4447	that can be enabled on the platform.
3739	the default 4-heap.
3740		4448
3741	You can save even more by disabling watcher types you do not need	4449	A typical way to use this symbol is to define it to C<0> (or to a bitset
3742	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4450	with some broad features you want) and then selectively re-enable
3743	(C<-DNDEBUG>) will usually reduce code size a lot.	4451	additional parts you want, for example if you want everything minimal,
		4452	but multiple event loop support, async and child watchers and the poll
		4453	backend, use this:
3744		4454
3745	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4455	#define EV_FEATURES 0
3746	provide a bare-bones event library. See C<ev.h> for details on what parts	4456	#define EV_MULTIPLICITY 1
3747	of the API are still available, and do not complain if this subset changes	4457	#define EV_USE_POLL 1
3748	over time.	4458	#define EV_CHILD_ENABLE 1
		4459	#define EV_ASYNC_ENABLE 1
		4460
		4461	The actual value is a bitset, it can be a combination of the following
		4462	values:
		4463
		4464	=over 4
		4465
		4466	=item C<1> - faster/larger code
		4467
		4468	Use larger code to speed up some operations.
		4469
		4470	Currently this is used to override some inlining decisions (enlarging the
		4471	code size by roughly 30% on amd64).
		4472
		4473	When optimising for size, use of compiler flags such as C<-Os> with
		4474	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4475	assertions.
		4476
		4477	=item C<2> - faster/larger data structures
		4478
		4479	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4480	hash table sizes and so on. This will usually further increase code size
		4481	and can additionally have an effect on the size of data structures at
		4482	runtime.
		4483
		4484	=item C<4> - full API configuration
		4485
		4486	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4487	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4488
		4489	=item C<8> - full API
		4490
		4491	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4492	details on which parts of the API are still available without this
		4493	feature, and do not complain if this subset changes over time.
		4494
		4495	=item C<16> - enable all optional watcher types
		4496
		4497	Enables all optional watcher types. If you want to selectively enable
		4498	only some watcher types other than I/O and timers (e.g. prepare,
		4499	embed, async, child...) you can enable them manually by defining
		4500	C<EV_watchertype_ENABLE> to C<1> instead.
		4501
		4502	=item C<32> - enable all backends
		4503
		4504	This enables all backends - without this feature, you need to enable at
		4505	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4506
		4507	=item C<64> - enable OS-specific "helper" APIs
		4508
		4509	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4510	default.
		4511
		4512	=back
		4513
		4514	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4515	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4516	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4517	watchers, timers and monotonic clock support.
		4518
		4519	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4520	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4521	your program might be left out as well - a binary starting a timer and an
		4522	I/O watcher then might come out at only 5Kb.
		4523
		4524	=item EV_AVOID_STDIO
		4525
		4526	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4527	functions (printf, scanf, perror etc.). This will increase the code size
		4528	somewhat, but if your program doesn't otherwise depend on stdio and your
		4529	libc allows it, this avoids linking in the stdio library which is quite
		4530	big.
		4531
		4532	Note that error messages might become less precise when this option is
		4533	enabled.
		4534
		4535	=item EV_NSIG
		4536
		4537	The highest supported signal number, +1 (or, the number of
		4538	signals): Normally, libev tries to deduce the maximum number of signals
		4539	automatically, but sometimes this fails, in which case it can be
		4540	specified. Also, using a lower number than detected (C<32> should be
		4541	good for about any system in existence) can save some memory, as libev
		4542	statically allocates some 12-24 bytes per signal number.
3749		4543
3750	=item EV_PID_HASHSIZE	4544	=item EV_PID_HASHSIZE
3751		4545
3752	C<ev_child> watchers use a small hash table to distribute workload by	4546	C<ev_child> watchers use a small hash table to distribute workload by
3753	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4547	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3754	than enough. If you need to manage thousands of children you might want to	4548	usually more than enough. If you need to manage thousands of children you
3755	increase this value (I<must> be a power of two).	4549	might want to increase this value (I<must> be a power of two).
3756		4550
3757	=item EV_INOTIFY_HASHSIZE	4551	=item EV_INOTIFY_HASHSIZE
3758		4552
3759	C<ev_stat> watchers use a small hash table to distribute workload by	4553	C<ev_stat> watchers use a small hash table to distribute workload by
3760	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4554	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3761	usually more than enough. If you need to manage thousands of C<ev_stat>	4555	disabled), usually more than enough. If you need to manage thousands of
3762	watchers you might want to increase this value (I<must> be a power of	4556	C<ev_stat> watchers you might want to increase this value (I<must> be a
3763	two).	4557	power of two).
3764		4558
3765	=item EV_USE_4HEAP	4559	=item EV_USE_4HEAP
3766		4560
3767	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4561	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3768	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4562	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3769	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4563	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3770	faster performance with many (thousands) of watchers.	4564	faster performance with many (thousands) of watchers.
3771		4565
3772	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4566	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3773	(disabled).	4567	will be C<0>.
3774		4568
3775	=item EV_HEAP_CACHE_AT	4569	=item EV_HEAP_CACHE_AT
3776		4570
3777	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4571	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3778	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4572	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3779	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4573	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3780	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4574	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3781	but avoids random read accesses on heap changes. This improves performance	4575	but avoids random read accesses on heap changes. This improves performance
3782	noticeably with many (hundreds) of watchers.	4576	noticeably with many (hundreds) of watchers.
3783		4577
3784	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4578	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3785	(disabled).	4579	will be C<0>.
3786		4580
3787	=item EV_VERIFY	4581	=item EV_VERIFY
3788		4582
3789	Controls how much internal verification (see C<ev_loop_verify ()>) will	4583	Controls how much internal verification (see C<ev_verify ()>) will
3790	be done: If set to C<0>, no internal verification code will be compiled	4584	be done: If set to C<0>, no internal verification code will be compiled
3791	in. If set to C<1>, then verification code will be compiled in, but not	4585	in. If set to C<1>, then verification code will be compiled in, but not
3792	called. If set to C<2>, then the internal verification code will be	4586	called. If set to C<2>, then the internal verification code will be
3793	called once per loop, which can slow down libev. If set to C<3>, then the	4587	called once per loop, which can slow down libev. If set to C<3>, then the
3794	verification code will be called very frequently, which will slow down	4588	verification code will be called very frequently, which will slow down
3795	libev considerably.	4589	libev considerably.
3796		4590
3797	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4591	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3798	C<0>.	4592	will be C<0>.
3799		4593
3800	=item EV_COMMON	4594	=item EV_COMMON
3801		4595
3802	By default, all watchers have a C<void *data> member. By redefining	4596	By default, all watchers have a C<void *data> member. By redefining
3803	this macro to a something else you can include more and other types of	4597	this macro to something else you can include more and other types of
3804	members. You have to define it each time you include one of the files,	4598	members. You have to define it each time you include one of the files,
3805	though, and it must be identical each time.	4599	though, and it must be identical each time.
3806		4600
3807	For example, the perl EV module uses something like this:	4601	For example, the perl EV module uses something like this:
3808		4602
…		…
3861	file.	4655	file.
3862		4656
3863	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4657	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3864	that everybody includes and which overrides some configure choices:	4658	that everybody includes and which overrides some configure choices:
3865		4659
3866	#define EV_MINIMAL 1	4660	#define EV_FEATURES 8
3867	#define EV_USE_POLL 0	4661	#define EV_USE_SELECT 1
3868	#define EV_MULTIPLICITY 0
3869	#define EV_PERIODIC_ENABLE 0	4662	#define EV_PREPARE_ENABLE 1
		4663	#define EV_IDLE_ENABLE 1
3870	#define EV_STAT_ENABLE 0	4664	#define EV_SIGNAL_ENABLE 1
3871	#define EV_FORK_ENABLE 0	4665	#define EV_CHILD_ENABLE 1
		4666	#define EV_USE_STDEXCEPT 0
3872	#define EV_CONFIG_H <config.h>	4667	#define EV_CONFIG_H <config.h>
3873	#define EV_MINPRI 0
3874	#define EV_MAXPRI 0
3875		4668
3876	#include "ev++.h"	4669	#include "ev++.h"
3877		4670
3878	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4671	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3879		4672
3880	#include "ev_cpp.h"	4673	#include "ev_cpp.h"
3881	#include "ev.c"	4674	#include "ev.c"
3882		4675
3883	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4676	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3884		4677
3885	=head2 THREADS AND COROUTINES	4678	=head2 THREADS AND COROUTINES
3886		4679
3887	=head3 THREADS	4680	=head3 THREADS
3888		4681
…		…
3939	default loop and triggering an C<ev_async> watcher from the default loop	4732	default loop and triggering an C<ev_async> watcher from the default loop
3940	watcher callback into the event loop interested in the signal.	4733	watcher callback into the event loop interested in the signal.
3941		4734
3942	=back	4735	=back
3943		4736
3944	=head4 THREAD LOCKING EXAMPLE	4737	See also L<THREAD LOCKING EXAMPLE>.
3945
3946	Here is a fictitious example of how to run an event loop in a different
3947	thread than where callbacks are being invoked and watchers are
3948	created/added/removed.
3949
3950	For a real-world example, see the C<EV::Loop::Async> perl module,
3951	which uses exactly this technique (which is suited for many high-level
3952	languages).
3953
3954	The example uses a pthread mutex to protect the loop data, a condition
3955	variable to wait for callback invocations, an async watcher to notify the
3956	event loop thread and an unspecified mechanism to wake up the main thread.
3957
3958	First, you need to associate some data with the event loop:
3959
3960	typedef struct {
3961	mutex_t lock; /* global loop lock */
3962	ev_async async_w;
3963	thread_t tid;
3964	cond_t invoke_cv;
3965	} userdata;
3966
3967	void prepare_loop (EV_P)
3968	{
3969	// for simplicity, we use a static userdata struct.
3970	static userdata u;
3971
3972	ev_async_init (&u->async_w, async_cb);
3973	ev_async_start (EV_A_ &u->async_w);
3974
3975	pthread_mutex_init (&u->lock, 0);
3976	pthread_cond_init (&u->invoke_cv, 0);
3977
3978	// now associate this with the loop
3979	ev_set_userdata (EV_A_ u);
3980	ev_set_invoke_pending_cb (EV_A_ l_invoke);
3981	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3982
3983	// then create the thread running ev_loop
3984	pthread_create (&u->tid, 0, l_run, EV_A);
3985	}
3986
3987	The callback for the C<ev_async> watcher does nothing: the watcher is used
3988	solely to wake up the event loop so it takes notice of any new watchers
3989	that might have been added:
3990
3991	static void
3992	async_cb (EV_P_ ev_async *w, int revents)
3993	{
3994	// just used for the side effects
3995	}
3996
3997	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
3998	protecting the loop data, respectively.
3999
4000	static void
4001	l_release (EV_P)
4002	{
4003	udat *u = ev_userdata (EV_A);
4004	pthread_mutex_unlock (&u->lock);
4005	}
4006
4007	static void
4008	l_acquire (EV_P)
4009	{
4010	udat *u = ev_userdata (EV_A);
4011	pthread_mutex_lock (&u->lock);
4012	}
4013
4014	The event loop thread first acquires the mutex, and then jumps straight
4015	into C<ev_loop>:
4016
4017	void *
4018	l_run (void *thr_arg)
4019	{
4020	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4021
4022	l_acquire (EV_A);
4023	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4024	ev_loop (EV_A_ 0);
4025	l_release (EV_A);
4026
4027	return 0;
4028	}
4029
4030	Instead of invoking all pending watchers, the C<l_invoke> callback will
4031	signal the main thread via some unspecified mechanism (signals? pipe
4032	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4033	have been called:
4034
4035	static void
4036	l_invoke (EV_P)
4037	{
4038	udat *u = ev_userdata (EV_A);
4039
4040	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4041
4042	pthread_cond_wait (&u->invoke_cv, &u->lock);
4043	}
4044
4045	Now, whenever the main thread gets told to invoke pending watchers, it
4046	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4047	thread to continue:
4048
4049	static void
4050	real_invoke_pending (EV_P)
4051	{
4052	udat *u = ev_userdata (EV_A);
4053
4054	pthread_mutex_lock (&u->lock);
4055	ev_invoke_pending (EV_A);
4056	pthread_cond_signal (&u->invoke_cv);
4057	pthread_mutex_unlock (&u->lock);
4058	}
4059
4060	Whenever you want to start/stop a watcher or do other modifications to an
4061	event loop, you will now have to lock:
4062
4063	ev_timer timeout_watcher;
4064	udat *u = ev_userdata (EV_A);
4065
4066	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4067
4068	pthread_mutex_lock (&u->lock);
4069	ev_timer_start (EV_A_ &timeout_watcher);
4070	ev_async_send (EV_A_ &u->async_w);
4071	pthread_mutex_unlock (&u->lock);
4072
4073	Note that sending the C<ev_async> watcher is required because otherwise
4074	an event loop currently blocking in the kernel will have no knowledge
4075	about the newly added timer. By waking up the loop it will pick up any new
4076	watchers in the next event loop iteration.
4077		4738
4078	=head3 COROUTINES	4739	=head3 COROUTINES
4079		4740
4080	Libev is very accommodating to coroutines ("cooperative threads"):	4741	Libev is very accommodating to coroutines ("cooperative threads"):
4081	libev fully supports nesting calls to its functions from different	4742	libev fully supports nesting calls to its functions from different
4082	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4743	coroutines (e.g. you can call C<ev_run> on the same loop from two
4083	different coroutines, and switch freely between both coroutines running the	4744	different coroutines, and switch freely between both coroutines running
4084	loop, as long as you don't confuse yourself). The only exception is that	4745	the loop, as long as you don't confuse yourself). The only exception is
4085	you must not do this from C<ev_periodic> reschedule callbacks.	4746	that you must not do this from C<ev_periodic> reschedule callbacks.
4086		4747
4087	Care has been taken to ensure that libev does not keep local state inside	4748	Care has been taken to ensure that libev does not keep local state inside
4088	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4749	C<ev_run>, and other calls do not usually allow for coroutine switches as
4089	they do not call any callbacks.	4750	they do not call any callbacks.
4090		4751
4091	=head2 COMPILER WARNINGS	4752	=head2 COMPILER WARNINGS
4092		4753
4093	Depending on your compiler and compiler settings, you might get no or a	4754	Depending on your compiler and compiler settings, you might get no or a
…		…
4104	maintainable.	4765	maintainable.
4105		4766
4106	And of course, some compiler warnings are just plain stupid, or simply	4767	And of course, some compiler warnings are just plain stupid, or simply
4107	wrong (because they don't actually warn about the condition their message	4768	wrong (because they don't actually warn about the condition their message
4108	seems to warn about). For example, certain older gcc versions had some	4769	seems to warn about). For example, certain older gcc versions had some
4109	warnings that resulted an extreme number of false positives. These have	4770	warnings that resulted in an extreme number of false positives. These have
4110	been fixed, but some people still insist on making code warn-free with	4771	been fixed, but some people still insist on making code warn-free with
4111	such buggy versions.	4772	such buggy versions.
4112		4773
4113	While libev is written to generate as few warnings as possible,	4774	While libev is written to generate as few warnings as possible,
4114	"warn-free" code is not a goal, and it is recommended not to build libev	4775	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4150	I suggest using suppression lists.	4811	I suggest using suppression lists.
4151		4812
4152		4813
4153	=head1 PORTABILITY NOTES	4814	=head1 PORTABILITY NOTES
4154		4815
		4816	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4817
		4818	GNU/Linux is the only common platform that supports 64 bit file/large file
		4819	interfaces but I<disables> them by default.
		4820
		4821	That means that libev compiled in the default environment doesn't support
		4822	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4823
		4824	Unfortunately, many programs try to work around this GNU/Linux issue
		4825	by enabling the large file API, which makes them incompatible with the
		4826	standard libev compiled for their system.
		4827
		4828	Likewise, libev cannot enable the large file API itself as this would
		4829	suddenly make it incompatible to the default compile time environment,
		4830	i.e. all programs not using special compile switches.
		4831
		4832	=head2 OS/X AND DARWIN BUGS
		4833
		4834	The whole thing is a bug if you ask me - basically any system interface
		4835	you touch is broken, whether it is locales, poll, kqueue or even the
		4836	OpenGL drivers.
		4837
		4838	=head3 C<kqueue> is buggy
		4839
		4840	The kqueue syscall is broken in all known versions - most versions support
		4841	only sockets, many support pipes.
		4842
		4843	Libev tries to work around this by not using C<kqueue> by default on this
		4844	rotten platform, but of course you can still ask for it when creating a
		4845	loop - embedding a socket-only kqueue loop into a select-based one is
		4846	probably going to work well.
		4847
		4848	=head3 C<poll> is buggy
		4849
		4850	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4851	implementation by something calling C<kqueue> internally around the 10.5.6
		4852	release, so now C<kqueue> I<and> C<poll> are broken.
		4853
		4854	Libev tries to work around this by not using C<poll> by default on
		4855	this rotten platform, but of course you can still ask for it when creating
		4856	a loop.
		4857
		4858	=head3 C<select> is buggy
		4859
		4860	All that's left is C<select>, and of course Apple found a way to fuck this
		4861	one up as well: On OS/X, C<select> actively limits the number of file
		4862	descriptors you can pass in to 1024 - your program suddenly crashes when
		4863	you use more.
		4864
		4865	There is an undocumented "workaround" for this - defining
		4866	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4867	work on OS/X.
		4868
		4869	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4870
		4871	=head3 C<errno> reentrancy
		4872
		4873	The default compile environment on Solaris is unfortunately so
		4874	thread-unsafe that you can't even use components/libraries compiled
		4875	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4876	defined by default. A valid, if stupid, implementation choice.
		4877
		4878	If you want to use libev in threaded environments you have to make sure
		4879	it's compiled with C<_REENTRANT> defined.
		4880
		4881	=head3 Event port backend
		4882
		4883	The scalable event interface for Solaris is called "event
		4884	ports". Unfortunately, this mechanism is very buggy in all major
		4885	releases. If you run into high CPU usage, your program freezes or you get
		4886	a large number of spurious wakeups, make sure you have all the relevant
		4887	and latest kernel patches applied. No, I don't know which ones, but there
		4888	are multiple ones to apply, and afterwards, event ports actually work
		4889	great.
		4890
		4891	If you can't get it to work, you can try running the program by setting
		4892	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4893	C<select> backends.
		4894
		4895	=head2 AIX POLL BUG
		4896
		4897	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4898	this by trying to avoid the poll backend altogether (i.e. it's not even
		4899	compiled in), which normally isn't a big problem as C<select> works fine
		4900	with large bitsets on AIX, and AIX is dead anyway.
		4901
4155	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4902	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4903
		4904	=head3 General issues
4156		4905
4157	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4906	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4158	requires, and its I/O model is fundamentally incompatible with the POSIX	4907	requires, and its I/O model is fundamentally incompatible with the POSIX
4159	model. Libev still offers limited functionality on this platform in	4908	model. Libev still offers limited functionality on this platform in
4160	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4909	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4161	descriptors. This only applies when using Win32 natively, not when using	4910	descriptors. This only applies when using Win32 natively, not when using
4162	e.g. cygwin.	4911	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4912	as every compiler comes with a slightly differently broken/incompatible
		4913	environment.
4163		4914
4164	Lifting these limitations would basically require the full	4915	Lifting these limitations would basically require the full
4165	re-implementation of the I/O system. If you are into these kinds of	4916	re-implementation of the I/O system. If you are into this kind of thing,
4166	things, then note that glib does exactly that for you in a very portable	4917	then note that glib does exactly that for you in a very portable way (note
4167	way (note also that glib is the slowest event library known to man).	4918	also that glib is the slowest event library known to man).
4168		4919
4169	There is no supported compilation method available on windows except	4920	There is no supported compilation method available on windows except
4170	embedding it into other applications.	4921	embedding it into other applications.
4171		4922
4172	Sensible signal handling is officially unsupported by Microsoft - libev	4923	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4200	you do I<not> compile the F<ev.c> or any other embedded source files!):	4951	you do I<not> compile the F<ev.c> or any other embedded source files!):
4201		4952
4202	#include "evwrap.h"	4953	#include "evwrap.h"
4203	#include "ev.c"	4954	#include "ev.c"
4204		4955
4205	=over 4
4206
4207	=item The winsocket select function	4956	=head3 The winsocket C<select> function
4208		4957
4209	The winsocket C<select> function doesn't follow POSIX in that it	4958	The winsocket C<select> function doesn't follow POSIX in that it
4210	requires socket I<handles> and not socket I<file descriptors> (it is	4959	requires socket I<handles> and not socket I<file descriptors> (it is
4211	also extremely buggy). This makes select very inefficient, and also	4960	also extremely buggy). This makes select very inefficient, and also
4212	requires a mapping from file descriptors to socket handles (the Microsoft	4961	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4221	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4970	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4222		4971
4223	Note that winsockets handling of fd sets is O(n), so you can easily get a	4972	Note that winsockets handling of fd sets is O(n), so you can easily get a
4224	complexity in the O(n²) range when using win32.	4973	complexity in the O(n²) range when using win32.
4225		4974
4226	=item Limited number of file descriptors	4975	=head3 Limited number of file descriptors
4227		4976
4228	Windows has numerous arbitrary (and low) limits on things.	4977	Windows has numerous arbitrary (and low) limits on things.
4229		4978
4230	Early versions of winsocket's select only supported waiting for a maximum	4979	Early versions of winsocket's select only supported waiting for a maximum
4231	of C<64> handles (probably owning to the fact that all windows kernels	4980	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4246	runtime libraries. This might get you to about C<512> or C<2048> sockets	4995	runtime libraries. This might get you to about C<512> or C<2048> sockets
4247	(depending on windows version and/or the phase of the moon). To get more,	4996	(depending on windows version and/or the phase of the moon). To get more,
4248	you need to wrap all I/O functions and provide your own fd management, but	4997	you need to wrap all I/O functions and provide your own fd management, but
4249	the cost of calling select (O(n²)) will likely make this unworkable.	4998	the cost of calling select (O(n²)) will likely make this unworkable.
4250		4999
4251	=back
4252
4253	=head2 PORTABILITY REQUIREMENTS	5000	=head2 PORTABILITY REQUIREMENTS
4254		5001
4255	In addition to a working ISO-C implementation and of course the	5002	In addition to a working ISO-C implementation and of course the
4256	backend-specific APIs, libev relies on a few additional extensions:	5003	backend-specific APIs, libev relies on a few additional extensions:
4257		5004
…		…
4263	Libev assumes not only that all watcher pointers have the same internal	5010	Libev assumes not only that all watcher pointers have the same internal
4264	structure (guaranteed by POSIX but not by ISO C for example), but it also	5011	structure (guaranteed by POSIX but not by ISO C for example), but it also
4265	assumes that the same (machine) code can be used to call any watcher	5012	assumes that the same (machine) code can be used to call any watcher
4266	callback: The watcher callbacks have different type signatures, but libev	5013	callback: The watcher callbacks have different type signatures, but libev
4267	calls them using an C<ev_watcher *> internally.	5014	calls them using an C<ev_watcher *> internally.
		5015
		5016	=item pointer accesses must be thread-atomic
		5017
		5018	Accessing a pointer value must be atomic, it must both be readable and
		5019	writable in one piece - this is the case on all current architectures.
4268		5020
4269	=item C<sig_atomic_t volatile> must be thread-atomic as well	5021	=item C<sig_atomic_t volatile> must be thread-atomic as well
4270		5022
4271	The type C<sig_atomic_t volatile> (or whatever is defined as	5023	The type C<sig_atomic_t volatile> (or whatever is defined as
4272	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5024	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4295	watchers.	5047	watchers.
4296		5048
4297	=item C<double> must hold a time value in seconds with enough accuracy	5049	=item C<double> must hold a time value in seconds with enough accuracy
4298		5050
4299	The type C<double> is used to represent timestamps. It is required to	5051	The type C<double> is used to represent timestamps. It is required to
4300	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5052	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4301	enough for at least into the year 4000. This requirement is fulfilled by	5053	good enough for at least into the year 4000 with millisecond accuracy
		5054	(the design goal for libev). This requirement is overfulfilled by
4302	implementations implementing IEEE 754, which is basically all existing	5055	implementations using IEEE 754, which is basically all existing ones.
		5056
4303	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5057	With IEEE 754 doubles, you get microsecond accuracy until at least the
4304	2200.	5058	year 2255 (and millisecond accuray till the year 287396 - by then, libev
		5059	is either obsolete or somebody patched it to use C<long double> or
		5060	something like that, just kidding).
4305		5061
4306	=back	5062	=back
4307		5063
4308	If you know of other additional requirements drop me a note.	5064	If you know of other additional requirements drop me a note.
4309		5065
…		…
4371	=item Processing ev_async_send: O(number_of_async_watchers)	5127	=item Processing ev_async_send: O(number_of_async_watchers)
4372		5128
4373	=item Processing signals: O(max_signal_number)	5129	=item Processing signals: O(max_signal_number)
4374		5130
4375	Sending involves a system call I<iff> there were no other C<ev_async_send>	5131	Sending involves a system call I<iff> there were no other C<ev_async_send>
4376	calls in the current loop iteration. Checking for async and signal events	5132	calls in the current loop iteration and the loop is currently
		5133	blocked. Checking for async and signal events involves iterating over all
4377	involves iterating over all running async watchers or all signal numbers.	5134	running async watchers or all signal numbers.
4378		5135
4379	=back	5136	=back
4380		5137
4381		5138
		5139	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5140
		5141	The major version 4 introduced some incompatible changes to the API.
		5142
		5143	At the moment, the C<ev.h> header file provides compatibility definitions
		5144	for all changes, so most programs should still compile. The compatibility
		5145	layer might be removed in later versions of libev, so better update to the
		5146	new API early than late.
		5147
		5148	=over 4
		5149
		5150	=item C<EV_COMPAT3> backwards compatibility mechanism
		5151
		5152	The backward compatibility mechanism can be controlled by
		5153	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5154	section.
		5155
		5156	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5157
		5158	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5159
		5160	ev_loop_destroy (EV_DEFAULT_UC);
		5161	ev_loop_fork (EV_DEFAULT);
		5162
		5163	=item function/symbol renames
		5164
		5165	A number of functions and symbols have been renamed:
		5166
		5167	ev_loop => ev_run
		5168	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5169	EVLOOP_ONESHOT => EVRUN_ONCE
		5170
		5171	ev_unloop => ev_break
		5172	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5173	EVUNLOOP_ONE => EVBREAK_ONE
		5174	EVUNLOOP_ALL => EVBREAK_ALL
		5175
		5176	EV_TIMEOUT => EV_TIMER
		5177
		5178	ev_loop_count => ev_iteration
		5179	ev_loop_depth => ev_depth
		5180	ev_loop_verify => ev_verify
		5181
		5182	Most functions working on C<struct ev_loop> objects don't have an
		5183	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5184	associated constants have been renamed to not collide with the C<struct
		5185	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5186	as all other watcher types. Note that C<ev_loop_fork> is still called
		5187	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5188	typedef.
		5189
		5190	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5191
		5192	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5193	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5194	and work, but the library code will of course be larger.
		5195
		5196	=back
		5197
		5198
4382	=head1 GLOSSARY	5199	=head1 GLOSSARY
4383		5200
4384	=over 4	5201	=over 4
4385		5202
4386	=item active	5203	=item active
4387		5204
4388	A watcher is active as long as it has been started (has been attached to	5205	A watcher is active as long as it has been started and not yet stopped.
4389	an event loop) but not yet stopped (disassociated from the event loop).	5206	See L<WATCHER STATES> for details.
4390		5207
4391	=item application	5208	=item application
4392		5209
4393	In this document, an application is whatever is using libev.	5210	In this document, an application is whatever is using libev.
		5211
		5212	=item backend
		5213
		5214	The part of the code dealing with the operating system interfaces.
4394		5215
4395	=item callback	5216	=item callback
4396		5217
4397	The address of a function that is called when some event has been	5218	The address of a function that is called when some event has been
4398	detected. Callbacks are being passed the event loop, the watcher that	5219	detected. Callbacks are being passed the event loop, the watcher that
4399	received the event, and the actual event bitset.	5220	received the event, and the actual event bitset.
4400		5221
4401	=item callback invocation	5222	=item callback/watcher invocation
4402		5223
4403	The act of calling the callback associated with a watcher.	5224	The act of calling the callback associated with a watcher.
4404		5225
4405	=item event	5226	=item event
4406		5227
4407	A change of state of some external event, such as data now being available	5228	A change of state of some external event, such as data now being available
4408	for reading on a file descriptor, time having passed or simply not having	5229	for reading on a file descriptor, time having passed or simply not having
4409	any other events happening anymore.	5230	any other events happening anymore.
4410		5231
4411	In libev, events are represented as single bits (such as C<EV_READ> or	5232	In libev, events are represented as single bits (such as C<EV_READ> or
4412	C<EV_TIMEOUT>).	5233	C<EV_TIMER>).
4413		5234
4414	=item event library	5235	=item event library
4415		5236
4416	A software package implementing an event model and loop.	5237	A software package implementing an event model and loop.
4417		5238
…		…
4425	The model used to describe how an event loop handles and processes	5246	The model used to describe how an event loop handles and processes
4426	watchers and events.	5247	watchers and events.
4427		5248
4428	=item pending	5249	=item pending
4429		5250
4430	A watcher is pending as soon as the corresponding event has been detected,	5251	A watcher is pending as soon as the corresponding event has been
4431	and stops being pending as soon as the watcher will be invoked or its	5252	detected. See L<WATCHER STATES> for details.
4432	pending status is explicitly cleared by the application.
4433
4434	A watcher can be pending, but not active. Stopping a watcher also clears
4435	its pending status.
4436		5253
4437	=item real time	5254	=item real time
4438		5255
4439	The physical time that is observed. It is apparently strictly monotonic :)	5256	The physical time that is observed. It is apparently strictly monotonic :)
4440		5257
4441	=item wall-clock time	5258	=item wall-clock time
4442		5259
4443	The time and date as shown on clocks. Unlike real time, it can actually	5260	The time and date as shown on clocks. Unlike real time, it can actually
4444	be wrong and jump forwards and backwards, e.g. when the you adjust your	5261	be wrong and jump forwards and backwards, e.g. when you adjust your
4445	clock.	5262	clock.
4446		5263
4447	=item watcher	5264	=item watcher
4448		5265
4449	A data structure that describes interest in certain events. Watchers need	5266	A data structure that describes interest in certain events. Watchers need
4450	to be started (attached to an event loop) before they can receive events.	5267	to be started (attached to an event loop) before they can receive events.
4451		5268
4452	=item watcher invocation
4453
4454	The act of calling the callback associated with a watcher.
4455
4456	=back	5269	=back
4457		5270
4458	=head1 AUTHOR	5271	=head1 AUTHOR
4459		5272
4460	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5273	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5274	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4461		5275

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