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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and
		88	look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L<WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
132	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
133	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
169		180
170	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
171		182
172	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
173	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
174	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
175		192
176	=item int ev_version_major ()	193	=item int ev_version_major ()
177		194
178	=item int ev_version_minor ()	195	=item int ev_version_minor ()
179		196
…		…
190	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	209	not a problem.
193		210
194	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
196		214
197	assert (("libev version mismatch",	215	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
200		218
…		…
211	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
213		231
214	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
215		233
216	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
222		241
223	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
224		243
225	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
230		249
231	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
232		251
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
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).
866		1001
867	=item int ev_pending_count (loop)	1002	=item int ev_pending_count (loop)
868		1003
869	Returns the number of pending watchers - zero indicates that no watchers	1004	Returns the number of pending watchers - zero indicates that no watchers
870	are pending.	1005	are pending.
871		1006
872	=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))
873		1008
874	This overrides the invoke pending functionality of the loop: Instead of	1009	This overrides the invoke pending functionality of the loop: Instead of
875	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
876	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
877	invoke the actual watchers inside another context (another thread etc.).	1012	invoke the actual watchers inside another context (another thread etc.).
878		1013
879	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
880	callback.	1015	callback.
…		…
883		1018
884	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
885	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
886	each call to a libev function.	1021	each call to a libev function.
887		1022
888	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
889	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
890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1025	loop via C<ev_break> and C<ev_async_send>, another way is to set these
891	and I<acquire> callbacks on the loop.	1026	I<release> and I<acquire> callbacks on the loop.
892		1027
893	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
894	suspended waiting for new events, and C<acquire> is called just	1029	suspended waiting for new events, and C<acquire> is called just
895	afterwards.	1030	afterwards.
896		1031
…		…
899		1034
900	While event loop modifications are allowed between invocations of	1035	While event loop modifications are allowed between invocations of
901	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
902	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
903	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
904	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
905	to take note of any changes you made.	1040	to take note of any changes you made.
906		1041
907	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
908	invocations of C<release> and C<acquire>.	1043	invocations of C<release> and C<acquire>.
909		1044
910	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
911	document.	1046	document.
912		1047
913	=item ev_set_userdata (loop, void *data)	1048	=item ev_set_userdata (loop, void *data)
914		1049
915	=item ev_userdata (loop)	1050	=item void *ev_userdata (loop)
916		1051
917	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
918	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
919	C<0.>	1054	C<0>.
920		1055
921	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,
922	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
923	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
924	any other purpose as well.	1059	any other purpose as well.
925		1060
926	=item ev_loop_verify (loop)	1061	=item ev_verify (loop)
927		1062
928	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
929	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
930	through all internal structures and checks them for validity. If anything	1065	through all internal structures and checks them for validity. If anything
931	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
…		…
942		1077
943	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
944	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
945	watchers and C<ev_io_start> for I/O watchers.	1080	watchers and C<ev_io_start> for I/O watchers.
946		1081
947	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
948	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
949	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:
950		1086
951	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)
952	{	1088	{
953	ev_io_stop (w);	1089	ev_io_stop (w);
954	ev_unloop (loop, EVUNLOOP_ALL);	1090	ev_break (loop, EVBREAK_ALL);
955	}	1091	}
956		1092
957	struct ev_loop *loop = ev_default_loop (0);	1093	struct ev_loop *loop = ev_default_loop (0);
958		1094
959	ev_io stdin_watcher;	1095	ev_io stdin_watcher;
960		1096
961	ev_init (&stdin_watcher, my_cb);	1097	ev_init (&stdin_watcher, my_cb);
962	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1098	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
963	ev_io_start (loop, &stdin_watcher);	1099	ev_io_start (loop, &stdin_watcher);
964		1100
965	ev_loop (loop, 0);	1101	ev_run (loop, 0);
966		1102
967	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
968	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
969	stack).	1105	stack).
970		1106
971	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>
972	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).
973		1109
974	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
975	(watcher *, callback)>, which expects a callback to be provided. This	1111	*, callback)>, which expects a callback to be provided. This callback is
976	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
977	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
978	is readable and/or writable).	1114	and/or writable).
979		1115
980	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 *, ...) >>
981	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
982	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<<
983	ev_TYPE_init (watcher *, callback, ...) >>.	1119	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1006	=item C<EV_WRITE>	1142	=item C<EV_WRITE>
1007		1143
1008	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
1009	writable.	1145	writable.
1010		1146
1011	=item C<EV_TIMEOUT>	1147	=item C<EV_TIMER>
1012		1148
1013	The C<ev_timer> watcher has timed out.	1149	The C<ev_timer> watcher has timed out.
1014		1150
1015	=item C<EV_PERIODIC>	1151	=item C<EV_PERIODIC>
1016		1152
…		…
1034		1170
1035	=item C<EV_PREPARE>	1171	=item C<EV_PREPARE>
1036		1172
1037	=item C<EV_CHECK>	1173	=item C<EV_CHECK>
1038		1174
1039	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
1040	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
1041	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
1042	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
1043	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
1044	(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
1045	C<ev_loop> from blocking).	1181	C<ev_run> from blocking).
1046		1182
1047	=item C<EV_EMBED>	1183	=item C<EV_EMBED>
1048		1184
1049	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.
1050		1186
1051	=item C<EV_FORK>	1187	=item C<EV_FORK>
1052		1188
1053	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
1054	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>).
1055		1195
1056	=item C<EV_ASYNC>	1196	=item C<EV_ASYNC>
1057		1197
1058	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>).
1059		1199
…		…
1106		1246
1107	ev_io w;	1247	ev_io w;
1108	ev_init (&w, my_cb);	1248	ev_init (&w, my_cb);
1109	ev_io_set (&w, STDIN_FILENO, EV_READ);	1249	ev_io_set (&w, STDIN_FILENO, EV_READ);
1110		1250
1111	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1251	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1112		1252
1113	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
1114	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
1115	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
1116	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
…		…
1129		1269
1130	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.
1131		1271
1132	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1272	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1133		1273
1134	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1274	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1135		1275
1136	Starts (activates) the given watcher. Only active watchers will receive	1276	Starts (activates) the given watcher. Only active watchers will receive
1137	events. If the watcher is already active nothing will happen.	1277	events. If the watcher is already active nothing will happen.
1138		1278
1139	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
1140	whole section.	1280	whole section.
1141		1281
1142	ev_io_start (EV_DEFAULT_UC, &w);	1282	ev_io_start (EV_DEFAULT_UC, &w);
1143		1283
1144	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1284	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1145		1285
1146	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
1147	the watcher was active or not).	1287	the watcher was active or not).
1148		1288
1149	It is possible that stopped watchers are pending - for example,	1289	It is possible that stopped watchers are pending - for example,
…		…
1174	=item ev_cb_set (ev_TYPE *watcher, callback)	1314	=item ev_cb_set (ev_TYPE *watcher, callback)
1175		1315
1176	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
1177	(modulo threads).	1317	(modulo threads).
1178		1318
1179	=item ev_set_priority (ev_TYPE *watcher, priority)	1319	=item ev_set_priority (ev_TYPE *watcher, int priority)
1180		1320
1181	=item int ev_priority (ev_TYPE *watcher)	1321	=item int ev_priority (ev_TYPE *watcher)
1182		1322
1183	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
1184	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>
…		…
1216	watcher isn't pending it does nothing and returns C<0>.	1356	watcher isn't pending it does nothing and returns C<0>.
1217		1357
1218	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
1219	callback to be invoked, which can be accomplished with this function.	1359	callback to be invoked, which can be accomplished with this function.
1220		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
1221	=back	1375	=back
1222		1376
		1377	See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR
		1378	OWN COMPOSITE WATCHERS> idioms.
1223		1379
1224	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1380	=head2 WATCHER STATES
1225		1381
1226	Each watcher has, by default, a member C<void *data> that you can change	1382	There are various watcher states mentioned throughout this manual -
1227	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
1228	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
1229	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".
1230	member, you can also "subclass" the watcher type and provide your own
1231	data:
1232		1386
1233	struct my_io	1387	=over 4
1234	{
1235	ev_io io;
1236	int otherfd;
1237	void *somedata;
1238	struct whatever *mostinteresting;
1239	};
1240		1388
1241	...	1389	=item initialiased
1242	struct my_io w;
1243	ev_io_init (&w.io, my_cb, fd, EV_READ);
1244		1390
1245	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
1246	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.
1247		1394
1248	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
1249	{	1396	use in an event loop. It can be moved around, freed, reused etc. at
1250	struct my_io *w = (struct my_io *)w_;	1397	will - as long as you either keep the memory contents intact, or call
1251	...	1398	C<ev_TYPE_init> again.
1252	}
1253		1399
1254	More interesting and less C-conformant ways of casting your callback type	1400	=item started/running/active
1255	instead have been omitted.
1256		1401
1257	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
1258	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.
1259		1407
1260	struct my_biggy	1408	=item pending
1261	{
1262	int some_data;
1263	ev_timer t1;
1264	ev_timer t2;
1265	}
1266		1409
1267	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
1268	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
1269	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
1270	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
1271	programmers):	1414	callback.
1272		1415
1273	#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.
1274		1422
1275	static void	1423	It is also possible to feed an event on a watcher that is not active (e.g.
1276	t1_cb (EV_P_ ev_timer *w, int revents)	1424	via C<ev_feed_event>), in which case it becomes pending without being
1277	{	1425	active.
1278	struct my_biggy big = (struct my_biggy *)
1279	(((char *)w) - offsetof (struct my_biggy, t1));
1280	}
1281		1426
1282	static void	1427	=item stopped
1283	t2_cb (EV_P_ ev_timer *w, int revents)	1428
1284	{	1429	A watcher can be stopped implicitly by libev (in which case it might still
1285	struct my_biggy big = (struct my_biggy *)	1430	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1286	(((char *)w) - offsetof (struct my_biggy, t2));	1431	latter will clear any pending state the watcher might be in, regardless
1287	}	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
1288		1441
1289	=head2 WATCHER PRIORITY MODELS	1442	=head2 WATCHER PRIORITY MODELS
1290		1443
1291	Many event loops support I<watcher priorities>, which are usually small	1444	Many event loops support I<watcher priorities>, which are usually small
1292	integers that influence the ordering of event callback invocation	1445	integers that influence the ordering of event callback invocation
…		…
1335		1488
1336	For example, to emulate how many other event libraries handle priorities,	1489	For example, to emulate how many other event libraries handle priorities,
1337	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
1338	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
1339	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
1340	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
1341	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
1342	workable.	1495	workable.
1343		1496
1344	Usually, however, the lock-out model implemented that way will perform	1497	Usually, however, the lock-out model implemented that way will perform
1345	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,
…		…
1359	{	1512	{
1360	// stop the I/O watcher, we received the event, but	1513	// stop the I/O watcher, we received the event, but
1361	// are not yet ready to handle it.	1514	// are not yet ready to handle it.
1362	ev_io_stop (EV_A_ w);	1515	ev_io_stop (EV_A_ w);
1363		1516
1364	// start the idle watcher to ahndle the actual event.	1517	// start the idle watcher to handle the actual event.
1365	// it will not be executed as long as other watchers	1518	// it will not be executed as long as other watchers
1366	// with the default priority are receiving events.	1519	// with the default priority are receiving events.
1367	ev_idle_start (EV_A_ &idle);	1520	ev_idle_start (EV_A_ &idle);
1368	}	1521	}
1369		1522
…		…
1419	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
1420	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
1421	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
1422	required if you know what you are doing).	1575	required if you know what you are doing).
1423		1576
1424	If you cannot use non-blocking mode, then force the use of a
1425	known-to-be-good backend (at the time of this writing, this includes only
1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1427	descriptors for which non-blocking operation makes no sense (such as
1428	files) - libev doesn't guarentee any specific behaviour in that case.
1429
1430	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
1431	receive "spurious" readiness notifications, that is your callback might	1578	receive "spurious" readiness notifications, that is, your callback might
1432	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
1433	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
1434	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
1435	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
1436	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1437	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1583	preferable to a program hanging until some data arrives.
1438		1584
1439	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
1440	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
1441	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
1442	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
1443	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
1444	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
1445	indefinitely.	1591	indefinitely.
1446		1592
1447	But really, best use non-blocking mode.	1593	But really, best use non-blocking mode.
1448		1594
…		…
1476		1622
1477	There is no workaround possible except not registering events	1623	There is no workaround possible except not registering events
1478	for potentially C<dup ()>'ed file descriptors, or to resort to	1624	for potentially C<dup ()>'ed file descriptors, or to resort to
1479	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1625	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1480		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
1481	=head3 The special problem of fork	1660	=head3 The special problem of fork
1482		1661
1483	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
1484	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
1485	it in the child.	1664	it in the child if you want to continue to use it in the child.
1486		1665
1487	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
1488	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
1489	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1668	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1490	C<EVBACKEND_POLL>.
1491		1669
1492	=head3 The special problem of SIGPIPE	1670	=head3 The special problem of SIGPIPE
1493		1671
1494	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>:
1495	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
…		…
1498		1676
1499	So when you encounter spurious, unexplained daemon exits, make sure you	1677	So when you encounter spurious, unexplained daemon exits, make sure you
1500	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
1501	somewhere, as that would have given you a big clue).	1679	somewhere, as that would have given you a big clue).
1502		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.
1503		1719
1504	=head3 Watcher-Specific Functions	1720	=head3 Watcher-Specific Functions
1505		1721
1506	=over 4	1722	=over 4
1507		1723
…		…
1539	...	1755	...
1540	struct ev_loop *loop = ev_default_init (0);	1756	struct ev_loop *loop = ev_default_init (0);
1541	ev_io stdin_readable;	1757	ev_io stdin_readable;
1542	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);
1543	ev_io_start (loop, &stdin_readable);	1759	ev_io_start (loop, &stdin_readable);
1544	ev_loop (loop, 0);	1760	ev_run (loop, 0);
1545		1761
1546		1762
1547	=head2 C<ev_timer> - relative and optionally repeating timeouts	1763	=head2 C<ev_timer> - relative and optionally repeating timeouts
1548		1764
1549	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
…		…
1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1771	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1556	monotonic clock option helps a lot here).	1772	monotonic clock option helps a lot here).
1557		1773
1558	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
1559	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
1560	might introduce a small delay). If multiple timers become ready during the	1776	might introduce a small delay, see "the special problem of being too
		1777	early", below). If multiple timers become ready during the same loop
1561	same loop iteration then the ones with earlier time-out values are invoked	1778	iteration then the ones with earlier time-out values are invoked before
1562	before ones of the same priority with later time-out values (but this is	1779	ones of the same priority with later time-out values (but this is no
1563	no longer true when a callback calls C<ev_loop> recursively).	1780	longer true when a callback calls C<ev_run> recursively).
1564		1781
1565	=head3 Be smart about timeouts	1782	=head3 Be smart about timeouts
1566		1783
1567	Many real-world problems involve some kind of timeout, usually for error	1784	Many real-world problems involve some kind of timeout, usually for error
1568	recovery. A typical example is an HTTP request - if the other side hangs,	1785	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1643		1860
1644	In this case, it would be more efficient to leave the C<ev_timer> alone,	1861	In this case, it would be more efficient to leave the C<ev_timer> alone,
1645	but remember the time of last activity, and check for a real timeout only	1862	but remember the time of last activity, and check for a real timeout only
1646	within the callback:	1863	within the callback:
1647		1864
		1865	ev_tstamp timeout = 60.;
1648	ev_tstamp last_activity; // time of last activity	1866	ev_tstamp last_activity; // time of last activity
		1867	ev_timer timer;
1649		1868
1650	static void	1869	static void
1651	callback (EV_P_ ev_timer *w, int revents)	1870	callback (EV_P_ ev_timer *w, int revents)
1652	{	1871	{
1653	ev_tstamp now = ev_now (EV_A);	1872	// calculate when the timeout would happen
1654	ev_tstamp timeout = last_activity + 60.;	1873	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1655		1874
1656	// if last_activity + 60. is older than now, we did time out	1875	// if negative, it means we the timeout already occured
1657	if (timeout < now)	1876	if (after < 0.)
1658	{	1877	{
1659	// timeout occured, take action	1878	// timeout occurred, take action
1660	}	1879	}
1661	else	1880	else
1662	{	1881	{
1663	// callback was invoked, but there was some activity, re-arm	1882	// callback was invoked, but there was some recent
1664	// the watcher to fire in last_activity + 60, which is	1883	// activity. simply restart the timer to time out
1665	// guaranteed to be in the future, so "again" is positive:	1884	// after "after" seconds, which is the earliest time
1666	w->repeat = timeout - now;	1885	// the timeout can occur.
		1886	ev_timer_set (w, after, 0.);
1667	ev_timer_again (EV_A_ w);	1887	ev_timer_start (EV_A_ w);
1668	}	1888	}
1669	}	1889	}
1670		1890
1671	To summarise the callback: first calculate the real timeout (defined	1891	To summarise the callback: first calculate in how many seconds the
1672	as "60 seconds after the last activity"), then check if that time has	1892	timeout will occur (by calculating the absolute time when it would occur,
1673	been reached, which means something I<did>, in fact, time out. Otherwise	1893	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1674	the callback was invoked too early (C<timeout> is in the future), so	1894	(EV_A)> from that).
1675	re-schedule the timer to fire at that future time, to see if maybe we have
1676	a timeout then.
1677		1895
1678	Note how C<ev_timer_again> is used, taking advantage of the	1896	If this value is negative, then we are already past the timeout, i.e. we
1679	C<ev_timer_again> optimisation when the timer is already running.	1897	timed out, and need to do whatever is needed in this case.
		1898
		1899	Otherwise, we now the earliest time at which the timeout would trigger,
		1900	and simply start the timer with this timeout value.
		1901
		1902	In other words, each time the callback is invoked it will check whether
		1903	the timeout cocured. If not, it will simply reschedule itself to check
		1904	again at the earliest time it could time out. Rinse. Repeat.
1680		1905
1681	This scheme causes more callback invocations (about one every 60 seconds	1906	This scheme causes more callback invocations (about one every 60 seconds
1682	minus half the average time between activity), but virtually no calls to	1907	minus half the average time between activity), but virtually no calls to
1683	libev to change the timeout.	1908	libev to change the timeout.
1684		1909
1685	To start the timer, simply initialise the watcher and set C<last_activity>	1910	To start the machinery, simply initialise the watcher and set
1686	to the current time (meaning we just have some activity :), then call the	1911	C<last_activity> to the current time (meaning there was some activity just
1687	callback, which will "do the right thing" and start the timer:	1912	now), then call the callback, which will "do the right thing" and start
		1913	the timer:
1688		1914
		1915	last_activity = ev_now (EV_A);
1689	ev_init (timer, callback);	1916	ev_init (&timer, callback);
1690	last_activity = ev_now (loop);	1917	callback (EV_A_ &timer, 0);
1691	callback (loop, timer, EV_TIMEOUT);
1692		1918
1693	And when there is some activity, simply store the current time in	1919	When there is some activity, simply store the current time in
1694	C<last_activity>, no libev calls at all:	1920	C<last_activity>, no libev calls at all:
1695		1921
		1922	if (activity detected)
1696	last_actiivty = ev_now (loop);	1923	last_activity = ev_now (EV_A);
		1924
		1925	When your timeout value changes, then the timeout can be changed by simply
		1926	providing a new value, stopping the timer and calling the callback, which
		1927	will agaion do the right thing (for example, time out immediately :).
		1928
		1929	timeout = new_value;
		1930	ev_timer_stop (EV_A_ &timer);
		1931	callback (EV_A_ &timer, 0);
1697		1932
1698	This technique is slightly more complex, but in most cases where the	1933	This technique is slightly more complex, but in most cases where the
1699	time-out is unlikely to be triggered, much more efficient.	1934	time-out is unlikely to be triggered, much more efficient.
1700
1701	Changing the timeout is trivial as well (if it isn't hard-coded in the
1702	callback :) - just change the timeout and invoke the callback, which will
1703	fix things for you.
1704		1935
1705	=item 4. Wee, just use a double-linked list for your timeouts.	1936	=item 4. Wee, just use a double-linked list for your timeouts.
1706		1937
1707	If there is not one request, but many thousands (millions...), all	1938	If there is not one request, but many thousands (millions...), all
1708	employing some kind of timeout with the same timeout value, then one can	1939	employing some kind of timeout with the same timeout value, then one can
…		…
1735	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1966	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1736	rather complicated, but extremely efficient, something that really pays	1967	rather complicated, but extremely efficient, something that really pays
1737	off after the first million or so of active timers, i.e. it's usually	1968	off after the first million or so of active timers, i.e. it's usually
1738	overkill :)	1969	overkill :)
1739		1970
		1971	=head3 The special problem of being too early
		1972
		1973	If you ask a timer to call your callback after three seconds, then
		1974	you expect it to be invoked after three seconds - but of course, this
		1975	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1976	guaranteed to any precision by libev - imagine somebody suspending the
		1977	process with a STOP signal for a few hours for example.
		1978
		1979	So, libev tries to invoke your callback as soon as possible I<after> the
		1980	delay has occurred, but cannot guarantee this.
		1981
		1982	A less obvious failure mode is calling your callback too early: many event
		1983	loops compare timestamps with a "elapsed delay >= requested delay", but
		1984	this can cause your callback to be invoked much earlier than you would
		1985	expect.
		1986
		1987	To see why, imagine a system with a clock that only offers full second
		1988	resolution (think windows if you can't come up with a broken enough OS
		1989	yourself). If you schedule a one-second timer at the time 500.9, then the
		1990	event loop will schedule your timeout to elapse at a system time of 500
		1991	(500.9 truncated to the resolution) + 1, or 501.
		1992
		1993	If an event library looks at the timeout 0.1s later, it will see "501 >=
		1994	501" and invoke the callback 0.1s after it was started, even though a
		1995	one-second delay was requested - this is being "too early", despite best
		1996	intentions.
		1997
		1998	This is the reason why libev will never invoke the callback if the elapsed
		1999	delay equals the requested delay, but only when the elapsed delay is
		2000	larger than the requested delay. In the example above, libev would only invoke
		2001	the callback at system time 502, or 1.1s after the timer was started.
		2002
		2003	So, while libev cannot guarantee that your callback will be invoked
		2004	exactly when requested, it I<can> and I<does> guarantee that the requested
		2005	delay has actually elapsed, or in other words, it always errs on the "too
		2006	late" side of things.
		2007
1740	=head3 The special problem of time updates	2008	=head3 The special problem of time updates
1741		2009
1742	Establishing the current time is a costly operation (it usually takes at	2010	Establishing the current time is a costly operation (it usually takes
1743	least two system calls): EV therefore updates its idea of the current	2011	at least one system call): EV therefore updates its idea of the current
1744	time only before and after C<ev_loop> collects new events, which causes a	2012	time only before and after C<ev_run> collects new events, which causes a
1745	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2013	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1746	lots of events in one iteration.	2014	lots of events in one iteration.
1747		2015
1748	The relative timeouts are calculated relative to the C<ev_now ()>	2016	The relative timeouts are calculated relative to the C<ev_now ()>
1749	time. This is usually the right thing as this timestamp refers to the time	2017	time. This is usually the right thing as this timestamp refers to the time
…		…
1754	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2022	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1755		2023
1756	If the event loop is suspended for a long time, you can also force an	2024	If the event loop is suspended for a long time, you can also force an
1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2025	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1758	()>.	2026	()>.
		2027
		2028	=head3 The special problem of unsynchronised clocks
		2029
		2030	Modern systems have a variety of clocks - libev itself uses the normal
		2031	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2032	jumps).
		2033
		2034	Neither of these clocks is synchronised with each other or any other clock
		2035	on the system, so C<ev_time ()> might return a considerably different time
		2036	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2037	a call to C<gettimeofday> might return a second count that is one higher
		2038	than a directly following call to C<time>.
		2039
		2040	The moral of this is to only compare libev-related timestamps with
		2041	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2042	a second or so.
		2043
		2044	One more problem arises due to this lack of synchronisation: if libev uses
		2045	the system monotonic clock and you compare timestamps from C<ev_time>
		2046	or C<ev_now> from when you started your timer and when your callback is
		2047	invoked, you will find that sometimes the callback is a bit "early".
		2048
		2049	This is because C<ev_timer>s work in real time, not wall clock time, so
		2050	libev makes sure your callback is not invoked before the delay happened,
		2051	I<measured according to the real time>, not the system clock.
		2052
		2053	If your timeouts are based on a physical timescale (e.g. "time out this
		2054	connection after 100 seconds") then this shouldn't bother you as it is
		2055	exactly the right behaviour.
		2056
		2057	If you want to compare wall clock/system timestamps to your timers, then
		2058	you need to use C<ev_periodic>s, as these are based on the wall clock
		2059	time, where your comparisons will always generate correct results.
1759		2060
1760	=head3 The special problems of suspended animation	2061	=head3 The special problems of suspended animation
1761		2062
1762	When you leave the server world it is quite customary to hit machines that	2063	When you leave the server world it is quite customary to hit machines that
1763	can suspend/hibernate - what happens to the clocks during such a suspend?	2064	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1807	keep up with the timer (because it takes longer than those 10 seconds to	2108	keep up with the timer (because it takes longer than those 10 seconds to
1808	do stuff) the timer will not fire more than once per event loop iteration.	2109	do stuff) the timer will not fire more than once per event loop iteration.
1809		2110
1810	=item ev_timer_again (loop, ev_timer *)	2111	=item ev_timer_again (loop, ev_timer *)
1811		2112
1812	This will act as if the timer timed out and restart it again if it is	2113	This will act as if the timer timed out and restarts it again if it is
1813	repeating. The exact semantics are:	2114	repeating. The exact semantics are:
1814		2115
1815	If the timer is pending, its pending status is cleared.	2116	If the timer is pending, its pending status is cleared.
1816		2117
1817	If the timer is started but non-repeating, stop it (as if it timed out).	2118	If the timer is started but non-repeating, stop it (as if it timed out).
…		…
1819	If the timer is repeating, either start it if necessary (with the	2120	If the timer is repeating, either start it if necessary (with the
1820	C<repeat> value), or reset the running timer to the C<repeat> value.	2121	C<repeat> value), or reset the running timer to the C<repeat> value.
1821		2122
1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2123	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1823	usage example.	2124	usage example.
		2125
		2126	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2127
		2128	Returns the remaining time until a timer fires. If the timer is active,
		2129	then this time is relative to the current event loop time, otherwise it's
		2130	the timeout value currently configured.
		2131
		2132	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2133	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2134	will return C<4>. When the timer expires and is restarted, it will return
		2135	roughly C<7> (likely slightly less as callback invocation takes some time,
		2136	too), and so on.
1824		2137
1825	=item ev_tstamp repeat [read-write]	2138	=item ev_tstamp repeat [read-write]
1826		2139
1827	The current C<repeat> value. Will be used each time the watcher times out	2140	The current C<repeat> value. Will be used each time the watcher times out
1828	or C<ev_timer_again> is called, and determines the next timeout (if any),	2141	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1854	}	2167	}
1855		2168
1856	ev_timer mytimer;	2169	ev_timer mytimer;
1857	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2170	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1858	ev_timer_again (&mytimer); /* start timer */	2171	ev_timer_again (&mytimer); /* start timer */
1859	ev_loop (loop, 0);	2172	ev_run (loop, 0);
1860		2173
1861	// and in some piece of code that gets executed on any "activity":	2174	// and in some piece of code that gets executed on any "activity":
1862	// reset the timeout to start ticking again at 10 seconds	2175	// reset the timeout to start ticking again at 10 seconds
1863	ev_timer_again (&mytimer);	2176	ev_timer_again (&mytimer);
1864		2177
…		…
1890		2203
1891	As with timers, the callback is guaranteed to be invoked only when the	2204	As with timers, the callback is guaranteed to be invoked only when the
1892	point in time where it is supposed to trigger has passed. If multiple	2205	point in time where it is supposed to trigger has passed. If multiple
1893	timers become ready during the same loop iteration then the ones with	2206	timers become ready during the same loop iteration then the ones with
1894	earlier time-out values are invoked before ones with later time-out values	2207	earlier time-out values are invoked before ones with later time-out values
1895	(but this is no longer true when a callback calls C<ev_loop> recursively).	2208	(but this is no longer true when a callback calls C<ev_run> recursively).
1896		2209
1897	=head3 Watcher-Specific Functions and Data Members	2210	=head3 Watcher-Specific Functions and Data Members
1898		2211
1899	=over 4	2212	=over 4
1900		2213
…		…
1935		2248
1936	Another way to think about it (for the mathematically inclined) is that	2249	Another way to think about it (for the mathematically inclined) is that
1937	C<ev_periodic> will try to run the callback in this mode at the next possible	2250	C<ev_periodic> will try to run the callback in this mode at the next possible
1938	time where C<time = offset (mod interval)>, regardless of any time jumps.	2251	time where C<time = offset (mod interval)>, regardless of any time jumps.
1939		2252
1940	For numerical stability it is preferable that the C<offset> value is near	2253	The C<interval> I<MUST> be positive, and for numerical stability, the
1941	C<ev_now ()> (the current time), but there is no range requirement for	2254	interval value should be higher than C<1/8192> (which is around 100
1942	this value, and in fact is often specified as zero.	2255	microseconds) and C<offset> should be higher than C<0> and should have
		2256	at most a similar magnitude as the current time (say, within a factor of
		2257	ten). Typical values for offset are, in fact, C<0> or something between
		2258	C<0> and C<interval>, which is also the recommended range.
1943		2259
1944	Note also that there is an upper limit to how often a timer can fire (CPU	2260	Note also that there is an upper limit to how often a timer can fire (CPU
1945	speed for example), so if C<interval> is very small then timing stability	2261	speed for example), so if C<interval> is very small then timing stability
1946	will of course deteriorate. Libev itself tries to be exact to be about one	2262	will of course deteriorate. Libev itself tries to be exact to be about one
1947	millisecond (if the OS supports it and the machine is fast enough).	2263	millisecond (if the OS supports it and the machine is fast enough).
…		…
2028	Example: Call a callback every hour, or, more precisely, whenever the	2344	Example: Call a callback every hour, or, more precisely, whenever the
2029	system time is divisible by 3600. The callback invocation times have	2345	system time is divisible by 3600. The callback invocation times have
2030	potentially a lot of jitter, but good long-term stability.	2346	potentially a lot of jitter, but good long-term stability.
2031		2347
2032	static void	2348	static void
2033	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2349	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2034	{	2350	{
2035	... its now a full hour (UTC, or TAI or whatever your clock follows)	2351	... its now a full hour (UTC, or TAI or whatever your clock follows)
2036	}	2352	}
2037		2353
2038	ev_periodic hourly_tick;	2354	ev_periodic hourly_tick;
…		…
2061		2377
2062	=head2 C<ev_signal> - signal me when a signal gets signalled!	2378	=head2 C<ev_signal> - signal me when a signal gets signalled!
2063		2379
2064	Signal watchers will trigger an event when the process receives a specific	2380	Signal watchers will trigger an event when the process receives a specific
2065	signal one or more times. Even though signals are very asynchronous, libev	2381	signal one or more times. Even though signals are very asynchronous, libev
2066	will try it's best to deliver signals synchronously, i.e. as part of the	2382	will try its best to deliver signals synchronously, i.e. as part of the
2067	normal event processing, like any other event.	2383	normal event processing, like any other event.
2068		2384
2069	If you want signals asynchronously, just use C<sigaction> as you would	2385	If you want signals to be delivered truly asynchronously, just use
2070	do without libev and forget about sharing the signal. You can even use	2386	C<sigaction> as you would do without libev and forget about sharing
2071	C<ev_async> from a signal handler to synchronously wake up an event loop.	2387	the signal. You can even use C<ev_async> from a signal handler to
		2388	synchronously wake up an event loop.
2072		2389
2073	You can configure as many watchers as you like per signal. Only when the	2390	You can configure as many watchers as you like for the same signal, but
		2391	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2392	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2393	C<SIGINT> in both the default loop and another loop at the same time. At
		2394	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2395
2074	first watcher gets started will libev actually register a signal handler	2396	When the first watcher gets started will libev actually register something
2075	with the kernel (thus it coexists with your own signal handlers as long as	2397	with the kernel (thus it coexists with your own signal handlers as long as
2076	you don't register any with libev for the same signal). Similarly, when	2398	you don't register any with libev for the same signal).
2077	the last signal watcher for a signal is stopped, libev will reset the
2078	signal handler to SIG_DFL (regardless of what it was set to before).
2079		2399
2080	If possible and supported, libev will install its handlers with	2400	If possible and supported, libev will install its handlers with
2081	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2401	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2082	interrupted. If you have a problem with system calls getting interrupted by	2402	not be unduly interrupted. If you have a problem with system calls getting
2083	signals you can block all signals in an C<ev_check> watcher and unblock	2403	interrupted by signals you can block all signals in an C<ev_check> watcher
2084	them in an C<ev_prepare> watcher.	2404	and unblock them in an C<ev_prepare> watcher.
		2405
		2406	=head3 The special problem of inheritance over fork/execve/pthread_create
		2407
		2408	Both the signal mask (C<sigprocmask>) and the signal disposition
		2409	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2410	stopping it again), that is, libev might or might not block the signal,
		2411	and might or might not set or restore the installed signal handler (but
		2412	see C<EVFLAG_NOSIGMASK>).
		2413
		2414	While this does not matter for the signal disposition (libev never
		2415	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2416	C<execve>), this matters for the signal mask: many programs do not expect
		2417	certain signals to be blocked.
		2418
		2419	This means that before calling C<exec> (from the child) you should reset
		2420	the signal mask to whatever "default" you expect (all clear is a good
		2421	choice usually).
		2422
		2423	The simplest way to ensure that the signal mask is reset in the child is
		2424	to install a fork handler with C<pthread_atfork> that resets it. That will
		2425	catch fork calls done by libraries (such as the libc) as well.
		2426
		2427	In current versions of libev, the signal will not be blocked indefinitely
		2428	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2429	the window of opportunity for problems, it will not go away, as libev
		2430	I<has> to modify the signal mask, at least temporarily.
		2431
		2432	So I can't stress this enough: I<If you do not reset your signal mask when
		2433	you expect it to be empty, you have a race condition in your code>. This
		2434	is not a libev-specific thing, this is true for most event libraries.
		2435
		2436	=head3 The special problem of threads signal handling
		2437
		2438	POSIX threads has problematic signal handling semantics, specifically,
		2439	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2440	threads in a process block signals, which is hard to achieve.
		2441
		2442	When you want to use sigwait (or mix libev signal handling with your own
		2443	for the same signals), you can tackle this problem by globally blocking
		2444	all signals before creating any threads (or creating them with a fully set
		2445	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2446	loops. Then designate one thread as "signal receiver thread" which handles
		2447	these signals. You can pass on any signals that libev might be interested
		2448	in by calling C<ev_feed_signal>.
2085		2449
2086	=head3 Watcher-Specific Functions and Data Members	2450	=head3 Watcher-Specific Functions and Data Members
2087		2451
2088	=over 4	2452	=over 4
2089		2453
…		…
2105	Example: Try to exit cleanly on SIGINT.	2469	Example: Try to exit cleanly on SIGINT.
2106		2470
2107	static void	2471	static void
2108	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2472	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2109	{	2473	{
2110	ev_unloop (loop, EVUNLOOP_ALL);	2474	ev_break (loop, EVBREAK_ALL);
2111	}	2475	}
2112		2476
2113	ev_signal signal_watcher;	2477	ev_signal signal_watcher;
2114	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2478	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2115	ev_signal_start (loop, &signal_watcher);	2479	ev_signal_start (loop, &signal_watcher);
…		…
2134	libev)	2498	libev)
2135		2499
2136	=head3 Process Interaction	2500	=head3 Process Interaction
2137		2501
2138	Libev grabs C<SIGCHLD> as soon as the default event loop is	2502	Libev grabs C<SIGCHLD> as soon as the default event loop is
2139	initialised. This is necessary to guarantee proper behaviour even if	2503	initialised. This is necessary to guarantee proper behaviour even if the
2140	the first child watcher is started after the child exits. The occurrence	2504	first child watcher is started after the child exits. The occurrence
2141	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2505	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2142	synchronously as part of the event loop processing. Libev always reaps all	2506	synchronously as part of the event loop processing. Libev always reaps all
2143	children, even ones not watched.	2507	children, even ones not watched.
2144		2508
2145	=head3 Overriding the Built-In Processing	2509	=head3 Overriding the Built-In Processing
…		…
2155	=head3 Stopping the Child Watcher	2519	=head3 Stopping the Child Watcher
2156		2520
2157	Currently, the child watcher never gets stopped, even when the	2521	Currently, the child watcher never gets stopped, even when the
2158	child terminates, so normally one needs to stop the watcher in the	2522	child terminates, so normally one needs to stop the watcher in the
2159	callback. Future versions of libev might stop the watcher automatically	2523	callback. Future versions of libev might stop the watcher automatically
2160	when a child exit is detected.	2524	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2525	problem).
2161		2526
2162	=head3 Watcher-Specific Functions and Data Members	2527	=head3 Watcher-Specific Functions and Data Members
2163		2528
2164	=over 4	2529	=over 4
2165		2530
…		…
2500		2865
2501	Prepare and check watchers are usually (but not always) used in pairs:	2866	Prepare and check watchers are usually (but not always) used in pairs:
2502	prepare watchers get invoked before the process blocks and check watchers	2867	prepare watchers get invoked before the process blocks and check watchers
2503	afterwards.	2868	afterwards.
2504		2869
2505	You I<must not> call C<ev_loop> or similar functions that enter	2870	You I<must not> call C<ev_run> or similar functions that enter
2506	the current event loop from either C<ev_prepare> or C<ev_check>	2871	the current event loop from either C<ev_prepare> or C<ev_check>
2507	watchers. Other loops than the current one are fine, however. The	2872	watchers. Other loops than the current one are fine, however. The
2508	rationale behind this is that you do not need to check for recursion in	2873	rationale behind this is that you do not need to check for recursion in
2509	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2874	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2510	C<ev_check> so if you have one watcher of each kind they will always be	2875	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2678		3043
2679	if (timeout >= 0)	3044	if (timeout >= 0)
2680	// create/start timer	3045	// create/start timer
2681		3046
2682	// poll	3047	// poll
2683	ev_loop (EV_A_ 0);	3048	ev_run (EV_A_ 0);
2684		3049
2685	// stop timer again	3050	// stop timer again
2686	if (timeout >= 0)	3051	if (timeout >= 0)
2687	ev_timer_stop (EV_A_ &to);	3052	ev_timer_stop (EV_A_ &to);
2688		3053
…		…
2766	if you do not want that, you need to temporarily stop the embed watcher).	3131	if you do not want that, you need to temporarily stop the embed watcher).
2767		3132
2768	=item ev_embed_sweep (loop, ev_embed *)	3133	=item ev_embed_sweep (loop, ev_embed *)
2769		3134
2770	Make a single, non-blocking sweep over the embedded loop. This works	3135	Make a single, non-blocking sweep over the embedded loop. This works
2771	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3136	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2772	appropriate way for embedded loops.	3137	appropriate way for embedded loops.
2773		3138
2774	=item struct ev_loop *other [read-only]	3139	=item struct ev_loop *other [read-only]
2775		3140
2776	The embedded event loop.	3141	The embedded event loop.
…		…
2836	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3201	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2837	handlers will be invoked, too, of course.	3202	handlers will be invoked, too, of course.
2838		3203
2839	=head3 The special problem of life after fork - how is it possible?	3204	=head3 The special problem of life after fork - how is it possible?
2840		3205
2841	Most uses of C<fork()> consist of forking, then some simple calls to ste	3206	Most uses of C<fork()> consist of forking, then some simple calls to set
2842	up/change the process environment, followed by a call to C<exec()>. This	3207	up/change the process environment, followed by a call to C<exec()>. This
2843	sequence should be handled by libev without any problems.	3208	sequence should be handled by libev without any problems.
2844		3209
2845	This changes when the application actually wants to do event handling	3210	This changes when the application actually wants to do event handling
2846	in the child, or both parent in child, in effect "continuing" after the	3211	in the child, or both parent in child, in effect "continuing" after the
…		…
2862	disadvantage of having to use multiple event loops (which do not support	3227	disadvantage of having to use multiple event loops (which do not support
2863	signal watchers).	3228	signal watchers).
2864		3229
2865	When this is not possible, or you want to use the default loop for	3230	When this is not possible, or you want to use the default loop for
2866	other reasons, then in the process that wants to start "fresh", call	3231	other reasons, then in the process that wants to start "fresh", call
2867	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3232	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2868	the default loop will "orphan" (not stop) all registered watchers, so you	3233	Destroying the default loop will "orphan" (not stop) all registered
2869	have to be careful not to execute code that modifies those watchers. Note	3234	watchers, so you have to be careful not to execute code that modifies
2870	also that in that case, you have to re-register any signal watchers.	3235	those watchers. Note also that in that case, you have to re-register any
		3236	signal watchers.
2871		3237
2872	=head3 Watcher-Specific Functions and Data Members	3238	=head3 Watcher-Specific Functions and Data Members
2873		3239
2874	=over 4	3240	=over 4
2875		3241
2876	=item ev_fork_init (ev_signal *, callback)	3242	=item ev_fork_init (ev_fork *, callback)
2877		3243
2878	Initialises and configures the fork watcher - it has no parameters of any	3244	Initialises and configures the fork watcher - it has no parameters of any
2879	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3245	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2880	believe me.	3246	really.
2881		3247
2882	=back	3248	=back
2883		3249
2884		3250
		3251	=head2 C<ev_cleanup> - even the best things end
		3252
		3253	Cleanup watchers are called just before the event loop is being destroyed
		3254	by a call to C<ev_loop_destroy>.
		3255
		3256	While there is no guarantee that the event loop gets destroyed, cleanup
		3257	watchers provide a convenient method to install cleanup hooks for your
		3258	program, worker threads and so on - you just to make sure to destroy the
		3259	loop when you want them to be invoked.
		3260
		3261	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3262	all other watchers, they do not keep a reference to the event loop (which
		3263	makes a lot of sense if you think about it). Like all other watchers, you
		3264	can call libev functions in the callback, except C<ev_cleanup_start>.
		3265
		3266	=head3 Watcher-Specific Functions and Data Members
		3267
		3268	=over 4
		3269
		3270	=item ev_cleanup_init (ev_cleanup *, callback)
		3271
		3272	Initialises and configures the cleanup watcher - it has no parameters of
		3273	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3274	pointless, I assure you.
		3275
		3276	=back
		3277
		3278	Example: Register an atexit handler to destroy the default loop, so any
		3279	cleanup functions are called.
		3280
		3281	static void
		3282	program_exits (void)
		3283	{
		3284	ev_loop_destroy (EV_DEFAULT_UC);
		3285	}
		3286
		3287	...
		3288	atexit (program_exits);
		3289
		3290
2885	=head2 C<ev_async> - how to wake up another event loop	3291	=head2 C<ev_async> - how to wake up an event loop
2886		3292
2887	In general, you cannot use an C<ev_loop> from multiple threads or other	3293	In general, you cannot use an C<ev_loop> from multiple threads or other
2888	asynchronous sources such as signal handlers (as opposed to multiple event	3294	asynchronous sources such as signal handlers (as opposed to multiple event
2889	loops - those are of course safe to use in different threads).	3295	loops - those are of course safe to use in different threads).
2890		3296
2891	Sometimes, however, you need to wake up another event loop you do not	3297	Sometimes, however, you need to wake up an event loop you do not control,
2892	control, for example because it belongs to another thread. This is what	3298	for example because it belongs to another thread. This is what C<ev_async>
2893	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3299	watchers do: as long as the C<ev_async> watcher is active, you can signal
2894	can signal it by calling C<ev_async_send>, which is thread- and signal	3300	it by calling C<ev_async_send>, which is thread- and signal safe.
2895	safe.
2896		3301
2897	This functionality is very similar to C<ev_signal> watchers, as signals,	3302	This functionality is very similar to C<ev_signal> watchers, as signals,
2898	too, are asynchronous in nature, and signals, too, will be compressed	3303	too, are asynchronous in nature, and signals, too, will be compressed
2899	(i.e. the number of callback invocations may be less than the number of	3304	(i.e. the number of callback invocations may be less than the number of
2900	C<ev_async_sent> calls).	3305	C<ev_async_sent> calls). In fact, you could use signal watchers as a kind
2901		3306	of "global async watchers" by using a watcher on an otherwise unused
2902	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3307	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2903	just the default loop.	3308	even without knowing which loop owns the signal.
2904		3309
2905	=head3 Queueing	3310	=head3 Queueing
2906		3311
2907	C<ev_async> does not support queueing of data in any way. The reason	3312	C<ev_async> does not support queueing of data in any way. The reason
2908	is that the author does not know of a simple (or any) algorithm for a	3313	is that the author does not know of a simple (or any) algorithm for a
2909	multiple-writer-single-reader queue that works in all cases and doesn't	3314	multiple-writer-single-reader queue that works in all cases and doesn't
2910	need elaborate support such as pthreads.	3315	need elaborate support such as pthreads or unportable memory access
		3316	semantics.
2911		3317
2912	That means that if you want to queue data, you have to provide your own	3318	That means that if you want to queue data, you have to provide your own
2913	queue. But at least I can tell you how to implement locking around your	3319	queue. But at least I can tell you how to implement locking around your
2914	queue:	3320	queue:
2915		3321
…		…
2999	trust me.	3405	trust me.
3000		3406
3001	=item ev_async_send (loop, ev_async *)	3407	=item ev_async_send (loop, ev_async *)
3002		3408
3003	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3409	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3004	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3410	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3411	returns.
		3412
3005	C<ev_feed_event>, this call is safe to do from other threads, signal or	3413	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3006	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3414	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3007	section below on what exactly this means).	3415	embedding section below on what exactly this means).
3008		3416
3009	Note that, as with other watchers in libev, multiple events might get	3417	Note that, as with other watchers in libev, multiple events might get
3010	compressed into a single callback invocation (another way to look at this	3418	compressed into a single callback invocation (another way to look at
3011	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3419	this is that C<ev_async> watchers are level-triggered: they are set on
3012	reset when the event loop detects that).	3420	C<ev_async_send>, reset when the event loop detects that).
3013		3421
3014	This call incurs the overhead of a system call only once per event loop	3422	This call incurs the overhead of at most one extra system call per event
3015	iteration, so while the overhead might be noticeable, it doesn't apply to	3423	loop iteration, if the event loop is blocked, and no syscall at all if
3016	repeated calls to C<ev_async_send> for the same event loop.	3424	the event loop (or your program) is processing events. That means that
		3425	repeated calls are basically free (there is no need to avoid calls for
		3426	performance reasons) and that the overhead becomes smaller (typically
		3427	zero) under load.
3017		3428
3018	=item bool = ev_async_pending (ev_async *)	3429	=item bool = ev_async_pending (ev_async *)
3019		3430
3020	Returns a non-zero value when C<ev_async_send> has been called on the	3431	Returns a non-zero value when C<ev_async_send> has been called on the
3021	watcher but the event has not yet been processed (or even noted) by the	3432	watcher but the event has not yet been processed (or even noted) by the
…		…
3054		3465
3055	If C<timeout> is less than 0, then no timeout watcher will be	3466	If C<timeout> is less than 0, then no timeout watcher will be
3056	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3467	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3057	repeat = 0) will be started. C<0> is a valid timeout.	3468	repeat = 0) will be started. C<0> is a valid timeout.
3058		3469
3059	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3470	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3060	passed an C<revents> set like normal event callbacks (a combination of	3471	passed an C<revents> set like normal event callbacks (a combination of
3061	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3472	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3062	value passed to C<ev_once>. Note that it is possible to receive I<both>	3473	value passed to C<ev_once>. Note that it is possible to receive I<both>
3063	a timeout and an io event at the same time - you probably should give io	3474	a timeout and an io event at the same time - you probably should give io
3064	events precedence.	3475	events precedence.
3065		3476
3066	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3477	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3067		3478
3068	static void stdin_ready (int revents, void *arg)	3479	static void stdin_ready (int revents, void *arg)
3069	{	3480	{
3070	if (revents & EV_READ)	3481	if (revents & EV_READ)
3071	/* stdin might have data for us, joy! */;	3482	/* stdin might have data for us, joy! */;
3072	else if (revents & EV_TIMEOUT)	3483	else if (revents & EV_TIMER)
3073	/* doh, nothing entered */;	3484	/* doh, nothing entered */;
3074	}	3485	}
3075		3486
3076	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3487	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3077		3488
3078	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3079
3080	Feeds the given event set into the event loop, as if the specified event
3081	had happened for the specified watcher (which must be a pointer to an
3082	initialised but not necessarily started event watcher).
3083
3084	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3489	=item ev_feed_fd_event (loop, int fd, int revents)
3085		3490
3086	Feed an event on the given fd, as if a file descriptor backend detected	3491	Feed an event on the given fd, as if a file descriptor backend detected
3087	the given events it.	3492	the given events.
3088		3493
3089	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3494	=item ev_feed_signal_event (loop, int signum)
3090		3495
3091	Feed an event as if the given signal occurred (C<loop> must be the default	3496	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3092	loop!).	3497	which is async-safe.
3093		3498
3094	=back	3499	=back
		3500
		3501
		3502	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3503
		3504	This section explains some common idioms that are not immediately
		3505	obvious. Note that examples are sprinkled over the whole manual, and this
		3506	section only contains stuff that wouldn't fit anywhere else.
		3507
		3508	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3509
		3510	Each watcher has, by default, a C<void *data> member that you can read
		3511	or modify at any time: libev will completely ignore it. This can be used
		3512	to associate arbitrary data with your watcher. If you need more data and
		3513	don't want to allocate memory separately and store a pointer to it in that
		3514	data member, you can also "subclass" the watcher type and provide your own
		3515	data:
		3516
		3517	struct my_io
		3518	{
		3519	ev_io io;
		3520	int otherfd;
		3521	void *somedata;
		3522	struct whatever *mostinteresting;
		3523	};
		3524
		3525	...
		3526	struct my_io w;
		3527	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3528
		3529	And since your callback will be called with a pointer to the watcher, you
		3530	can cast it back to your own type:
		3531
		3532	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3533	{
		3534	struct my_io *w = (struct my_io *)w_;
		3535	...
		3536	}
		3537
		3538	More interesting and less C-conformant ways of casting your callback
		3539	function type instead have been omitted.
		3540
		3541	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3542
		3543	Another common scenario is to use some data structure with multiple
		3544	embedded watchers, in effect creating your own watcher that combines
		3545	multiple libev event sources into one "super-watcher":
		3546
		3547	struct my_biggy
		3548	{
		3549	int some_data;
		3550	ev_timer t1;
		3551	ev_timer t2;
		3552	}
		3553
		3554	In this case getting the pointer to C<my_biggy> is a bit more
		3555	complicated: Either you store the address of your C<my_biggy> struct in
		3556	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3557	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3558	real programmers):
		3559
		3560	#include <stddef.h>
		3561
		3562	static void
		3563	t1_cb (EV_P_ ev_timer *w, int revents)
		3564	{
		3565	struct my_biggy big = (struct my_biggy *)
		3566	(((char *)w) - offsetof (struct my_biggy, t1));
		3567	}
		3568
		3569	static void
		3570	t2_cb (EV_P_ ev_timer *w, int revents)
		3571	{
		3572	struct my_biggy big = (struct my_biggy *)
		3573	(((char *)w) - offsetof (struct my_biggy, t2));
		3574	}
		3575
		3576	=head2 AVOIDING FINISHING BEFORE RETURNING
		3577
		3578	Often you have structures like this in event-based programs:
		3579
		3580	callback ()
		3581	{
		3582	free (request);
		3583	}
		3584
		3585	request = start_new_request (..., callback);
		3586
		3587	The intent is to start some "lengthy" operation. The C<request> could be
		3588	used to cancel the operation, or do other things with it.
		3589
		3590	It's not uncommon to have code paths in C<start_new_request> that
		3591	immediately invoke the callback, for example, to report errors. Or you add
		3592	some caching layer that finds that it can skip the lengthy aspects of the
		3593	operation and simply invoke the callback with the result.
		3594
		3595	The problem here is that this will happen I<before> C<start_new_request>
		3596	has returned, so C<request> is not set.
		3597
		3598	Even if you pass the request by some safer means to the callback, you
		3599	might want to do something to the request after starting it, such as
		3600	canceling it, which probably isn't working so well when the callback has
		3601	already been invoked.
		3602
		3603	A common way around all these issues is to make sure that
		3604	C<start_new_request> I<always> returns before the callback is invoked. If
		3605	C<start_new_request> immediately knows the result, it can artificially
		3606	delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher
		3607	for example, or more sneakily, by reusing an existing (stopped) watcher
		3608	and pushing it into the pending queue:
		3609
		3610	ev_set_cb (watcher, callback);
		3611	ev_feed_event (EV_A_ watcher, 0);
		3612
		3613	This way, C<start_new_request> can safely return before the callback is
		3614	invoked, while not delaying callback invocation too much.
		3615
		3616	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3617
		3618	Often (especially in GUI toolkits) there are places where you have
		3619	I<modal> interaction, which is most easily implemented by recursively
		3620	invoking C<ev_run>.
		3621
		3622	This brings the problem of exiting - a callback might want to finish the
		3623	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3624	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3625	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3626	other combination: In these cases, C<ev_break> will not work alone.
		3627
		3628	The solution is to maintain "break this loop" variable for each C<ev_run>
		3629	invocation, and use a loop around C<ev_run> until the condition is
		3630	triggered, using C<EVRUN_ONCE>:
		3631
		3632	// main loop
		3633	int exit_main_loop = 0;
		3634
		3635	while (!exit_main_loop)
		3636	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3637
		3638	// in a model watcher
		3639	int exit_nested_loop = 0;
		3640
		3641	while (!exit_nested_loop)
		3642	ev_run (EV_A_ EVRUN_ONCE);
		3643
		3644	To exit from any of these loops, just set the corresponding exit variable:
		3645
		3646	// exit modal loop
		3647	exit_nested_loop = 1;
		3648
		3649	// exit main program, after modal loop is finished
		3650	exit_main_loop = 1;
		3651
		3652	// exit both
		3653	exit_main_loop = exit_nested_loop = 1;
		3654
		3655	=head2 THREAD LOCKING EXAMPLE
		3656
		3657	Here is a fictitious example of how to run an event loop in a different
		3658	thread from where callbacks are being invoked and watchers are
		3659	created/added/removed.
		3660
		3661	For a real-world example, see the C<EV::Loop::Async> perl module,
		3662	which uses exactly this technique (which is suited for many high-level
		3663	languages).
		3664
		3665	The example uses a pthread mutex to protect the loop data, a condition
		3666	variable to wait for callback invocations, an async watcher to notify the
		3667	event loop thread and an unspecified mechanism to wake up the main thread.
		3668
		3669	First, you need to associate some data with the event loop:
		3670
		3671	typedef struct {
		3672	mutex_t lock; /* global loop lock */
		3673	ev_async async_w;
		3674	thread_t tid;
		3675	cond_t invoke_cv;
		3676	} userdata;
		3677
		3678	void prepare_loop (EV_P)
		3679	{
		3680	// for simplicity, we use a static userdata struct.
		3681	static userdata u;
		3682
		3683	ev_async_init (&u->async_w, async_cb);
		3684	ev_async_start (EV_A_ &u->async_w);
		3685
		3686	pthread_mutex_init (&u->lock, 0);
		3687	pthread_cond_init (&u->invoke_cv, 0);
		3688
		3689	// now associate this with the loop
		3690	ev_set_userdata (EV_A_ u);
		3691	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3692	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3693
		3694	// then create the thread running ev_run
		3695	pthread_create (&u->tid, 0, l_run, EV_A);
		3696	}
		3697
		3698	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3699	solely to wake up the event loop so it takes notice of any new watchers
		3700	that might have been added:
		3701
		3702	static void
		3703	async_cb (EV_P_ ev_async *w, int revents)
		3704	{
		3705	// just used for the side effects
		3706	}
		3707
		3708	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3709	protecting the loop data, respectively.
		3710
		3711	static void
		3712	l_release (EV_P)
		3713	{
		3714	userdata *u = ev_userdata (EV_A);
		3715	pthread_mutex_unlock (&u->lock);
		3716	}
		3717
		3718	static void
		3719	l_acquire (EV_P)
		3720	{
		3721	userdata *u = ev_userdata (EV_A);
		3722	pthread_mutex_lock (&u->lock);
		3723	}
		3724
		3725	The event loop thread first acquires the mutex, and then jumps straight
		3726	into C<ev_run>:
		3727
		3728	void *
		3729	l_run (void *thr_arg)
		3730	{
		3731	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3732
		3733	l_acquire (EV_A);
		3734	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3735	ev_run (EV_A_ 0);
		3736	l_release (EV_A);
		3737
		3738	return 0;
		3739	}
		3740
		3741	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3742	signal the main thread via some unspecified mechanism (signals? pipe
		3743	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3744	have been called (in a while loop because a) spurious wakeups are possible
		3745	and b) skipping inter-thread-communication when there are no pending
		3746	watchers is very beneficial):
		3747
		3748	static void
		3749	l_invoke (EV_P)
		3750	{
		3751	userdata *u = ev_userdata (EV_A);
		3752
		3753	while (ev_pending_count (EV_A))
		3754	{
		3755	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3756	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3757	}
		3758	}
		3759
		3760	Now, whenever the main thread gets told to invoke pending watchers, it
		3761	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3762	thread to continue:
		3763
		3764	static void
		3765	real_invoke_pending (EV_P)
		3766	{
		3767	userdata *u = ev_userdata (EV_A);
		3768
		3769	pthread_mutex_lock (&u->lock);
		3770	ev_invoke_pending (EV_A);
		3771	pthread_cond_signal (&u->invoke_cv);
		3772	pthread_mutex_unlock (&u->lock);
		3773	}
		3774
		3775	Whenever you want to start/stop a watcher or do other modifications to an
		3776	event loop, you will now have to lock:
		3777
		3778	ev_timer timeout_watcher;
		3779	userdata *u = ev_userdata (EV_A);
		3780
		3781	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3782
		3783	pthread_mutex_lock (&u->lock);
		3784	ev_timer_start (EV_A_ &timeout_watcher);
		3785	ev_async_send (EV_A_ &u->async_w);
		3786	pthread_mutex_unlock (&u->lock);
		3787
		3788	Note that sending the C<ev_async> watcher is required because otherwise
		3789	an event loop currently blocking in the kernel will have no knowledge
		3790	about the newly added timer. By waking up the loop it will pick up any new
		3791	watchers in the next event loop iteration.
		3792
		3793	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3794
		3795	While the overhead of a callback that e.g. schedules a thread is small, it
		3796	is still an overhead. If you embed libev, and your main usage is with some
		3797	kind of threads or coroutines, you might want to customise libev so that
		3798	doesn't need callbacks anymore.
		3799
		3800	Imagine you have coroutines that you can switch to using a function
		3801	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3802	and that due to some magic, the currently active coroutine is stored in a
		3803	global called C<current_coro>. Then you can build your own "wait for libev
		3804	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3805	the differing C<;> conventions):
		3806
		3807	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3808	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3809
		3810	That means instead of having a C callback function, you store the
		3811	coroutine to switch to in each watcher, and instead of having libev call
		3812	your callback, you instead have it switch to that coroutine.
		3813
		3814	A coroutine might now wait for an event with a function called
		3815	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3816	matter when, or whether the watcher is active or not when this function is
		3817	called):
		3818
		3819	void
		3820	wait_for_event (ev_watcher *w)
		3821	{
		3822	ev_cb_set (w) = current_coro;
		3823	switch_to (libev_coro);
		3824	}
		3825
		3826	That basically suspends the coroutine inside C<wait_for_event> and
		3827	continues the libev coroutine, which, when appropriate, switches back to
		3828	this or any other coroutine. I am sure if you sue this your own :)
		3829
		3830	You can do similar tricks if you have, say, threads with an event queue -
		3831	instead of storing a coroutine, you store the queue object and instead of
		3832	switching to a coroutine, you push the watcher onto the queue and notify
		3833	any waiters.
		3834
		3835	To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two
		3836	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3837
		3838	// my_ev.h
		3839	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3840	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3841	#include "../libev/ev.h"
		3842
		3843	// my_ev.c
		3844	#define EV_H "my_ev.h"
		3845	#include "../libev/ev.c"
		3846
		3847	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3848	F<my_ev.c> into your project. When properly specifying include paths, you
		3849	can even use F<ev.h> as header file name directly.
3095		3850
3096		3851
3097	=head1 LIBEVENT EMULATION	3852	=head1 LIBEVENT EMULATION
3098		3853
3099	Libev offers a compatibility emulation layer for libevent. It cannot	3854	Libev offers a compatibility emulation layer for libevent. It cannot
3100	emulate the internals of libevent, so here are some usage hints:	3855	emulate the internals of libevent, so here are some usage hints:
3101		3856
3102	=over 4	3857	=over 4
		3858
		3859	=item * Only the libevent-1.4.1-beta API is being emulated.
		3860
		3861	This was the newest libevent version available when libev was implemented,
		3862	and is still mostly unchanged in 2010.
3103		3863
3104	=item * Use it by including <event.h>, as usual.	3864	=item * Use it by including <event.h>, as usual.
3105		3865
3106	=item * The following members are fully supported: ev_base, ev_callback,	3866	=item * The following members are fully supported: ev_base, ev_callback,
3107	ev_arg, ev_fd, ev_res, ev_events.	3867	ev_arg, ev_fd, ev_res, ev_events.
…		…
3113	=item * Priorities are not currently supported. Initialising priorities	3873	=item * Priorities are not currently supported. Initialising priorities
3114	will fail and all watchers will have the same priority, even though there	3874	will fail and all watchers will have the same priority, even though there
3115	is an ev_pri field.	3875	is an ev_pri field.
3116		3876
3117	=item * In libevent, the last base created gets the signals, in libev, the	3877	=item * In libevent, the last base created gets the signals, in libev, the
3118	first base created (== the default loop) gets the signals.	3878	base that registered the signal gets the signals.
3119		3879
3120	=item * Other members are not supported.	3880	=item * Other members are not supported.
3121		3881
3122	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3882	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3123	to use the libev header file and library.	3883	to use the libev header file and library.
…		…
3142	Care has been taken to keep the overhead low. The only data member the C++	3902	Care has been taken to keep the overhead low. The only data member the C++
3143	classes add (compared to plain C-style watchers) is the event loop pointer	3903	classes add (compared to plain C-style watchers) is the event loop pointer
3144	that the watcher is associated with (or no additional members at all if	3904	that the watcher is associated with (or no additional members at all if
3145	you disable C<EV_MULTIPLICITY> when embedding libev).	3905	you disable C<EV_MULTIPLICITY> when embedding libev).
3146		3906
3147	Currently, functions, and static and non-static member functions can be	3907	Currently, functions, static and non-static member functions and classes
3148	used as callbacks. Other types should be easy to add as long as they only	3908	with C<operator ()> can be used as callbacks. Other types should be easy
3149	need one additional pointer for context. If you need support for other	3909	to add as long as they only need one additional pointer for context. If
3150	types of functors please contact the author (preferably after implementing	3910	you need support for other types of functors please contact the author
3151	it).	3911	(preferably after implementing it).
3152		3912
3153	Here is a list of things available in the C<ev> namespace:	3913	Here is a list of things available in the C<ev> namespace:
3154		3914
3155	=over 4	3915	=over 4
3156		3916
…		…
3174		3934
3175	=over 4	3935	=over 4
3176		3936
3177	=item ev::TYPE::TYPE ()	3937	=item ev::TYPE::TYPE ()
3178		3938
3179	=item ev::TYPE::TYPE (struct ev_loop *)	3939	=item ev::TYPE::TYPE (loop)
3180		3940
3181	=item ev::TYPE::~TYPE	3941	=item ev::TYPE::~TYPE
3182		3942
3183	The constructor (optionally) takes an event loop to associate the watcher	3943	The constructor (optionally) takes an event loop to associate the watcher
3184	with. If it is omitted, it will use C<EV_DEFAULT>.	3944	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3217	myclass obj;	3977	myclass obj;
3218	ev::io iow;	3978	ev::io iow;
3219	iow.set <myclass, &myclass::io_cb> (&obj);	3979	iow.set <myclass, &myclass::io_cb> (&obj);
3220		3980
3221	=item w->set (object *)	3981	=item w->set (object *)
3222
3223	This is an B<experimental> feature that might go away in a future version.
3224		3982
3225	This is a variation of a method callback - leaving out the method to call	3983	This is a variation of a method callback - leaving out the method to call
3226	will default the method to C<operator ()>, which makes it possible to use	3984	will default the method to C<operator ()>, which makes it possible to use
3227	functor objects without having to manually specify the C<operator ()> all	3985	functor objects without having to manually specify the C<operator ()> all
3228	the time. Incidentally, you can then also leave out the template argument	3986	the time. Incidentally, you can then also leave out the template argument
…		…
3261	Example: Use a plain function as callback.	4019	Example: Use a plain function as callback.
3262		4020
3263	static void io_cb (ev::io &w, int revents) { }	4021	static void io_cb (ev::io &w, int revents) { }
3264	iow.set <io_cb> ();	4022	iow.set <io_cb> ();
3265		4023
3266	=item w->set (struct ev_loop *)	4024	=item w->set (loop)
3267		4025
3268	Associates a different C<struct ev_loop> with this watcher. You can only	4026	Associates a different C<struct ev_loop> with this watcher. You can only
3269	do this when the watcher is inactive (and not pending either).	4027	do this when the watcher is inactive (and not pending either).
3270		4028
3271	=item w->set ([arguments])	4029	=item w->set ([arguments])
3272		4030
3273	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4031	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
3274	called at least once. Unlike the C counterpart, an active watcher gets	4032	method or a suitable start method must be called at least once. Unlike the
3275	automatically stopped and restarted when reconfiguring it with this	4033	C counterpart, an active watcher gets automatically stopped and restarted
3276	method.	4034	when reconfiguring it with this method.
3277		4035
3278	=item w->start ()	4036	=item w->start ()
3279		4037
3280	Starts the watcher. Note that there is no C<loop> argument, as the	4038	Starts the watcher. Note that there is no C<loop> argument, as the
3281	constructor already stores the event loop.	4039	constructor already stores the event loop.
3282		4040
		4041	=item w->start ([arguments])
		4042
		4043	Instead of calling C<set> and C<start> methods separately, it is often
		4044	convenient to wrap them in one call. Uses the same type of arguments as
		4045	the configure C<set> method of the watcher.
		4046
3283	=item w->stop ()	4047	=item w->stop ()
3284		4048
3285	Stops the watcher if it is active. Again, no C<loop> argument.	4049	Stops the watcher if it is active. Again, no C<loop> argument.
3286		4050
3287	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4051	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3299		4063
3300	=back	4064	=back
3301		4065
3302	=back	4066	=back
3303		4067
3304	Example: Define a class with an IO and idle watcher, start one of them in	4068	Example: Define a class with two I/O and idle watchers, start the I/O
3305	the constructor.	4069	watchers in the constructor.
3306		4070
3307	class myclass	4071	class myclass
3308	{	4072	{
3309	ev::io io ; void io_cb (ev::io &w, int revents);	4073	ev::io io ; void io_cb (ev::io &w, int revents);
		4074	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3310	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4075	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3311		4076
3312	myclass (int fd)	4077	myclass (int fd)
3313	{	4078	{
3314	io .set <myclass, &myclass::io_cb > (this);	4079	io .set <myclass, &myclass::io_cb > (this);
		4080	io2 .set <myclass, &myclass::io2_cb > (this);
3315	idle.set <myclass, &myclass::idle_cb> (this);	4081	idle.set <myclass, &myclass::idle_cb> (this);
3316		4082
3317	io.start (fd, ev::READ);	4083	io.set (fd, ev::WRITE); // configure the watcher
		4084	io.start (); // start it whenever convenient
		4085
		4086	io2.start (fd, ev::READ); // set + start in one call
3318	}	4087	}
3319	};	4088	};
3320		4089
3321		4090
3322	=head1 OTHER LANGUAGE BINDINGS	4091	=head1 OTHER LANGUAGE BINDINGS
…		…
3361	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4130	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3362		4131
3363	=item D	4132	=item D
3364		4133
3365	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4134	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3366	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4135	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3367		4136
3368	=item Ocaml	4137	=item Ocaml
3369		4138
3370	Erkki Seppala has written Ocaml bindings for libev, to be found at	4139	Erkki Seppala has written Ocaml bindings for libev, to be found at
3371	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4140	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4141
		4142	=item Lua
		4143
		4144	Brian Maher has written a partial interface to libev for lua (at the
		4145	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4146	L<http://github.com/brimworks/lua-ev>.
3372		4147
3373	=back	4148	=back
3374		4149
3375		4150
3376	=head1 MACRO MAGIC	4151	=head1 MACRO MAGIC
…		…
3390	loop argument"). The C<EV_A> form is used when this is the sole argument,	4165	loop argument"). The C<EV_A> form is used when this is the sole argument,
3391	C<EV_A_> is used when other arguments are following. Example:	4166	C<EV_A_> is used when other arguments are following. Example:
3392		4167
3393	ev_unref (EV_A);	4168	ev_unref (EV_A);
3394	ev_timer_add (EV_A_ watcher);	4169	ev_timer_add (EV_A_ watcher);
3395	ev_loop (EV_A_ 0);	4170	ev_run (EV_A_ 0);
3396		4171
3397	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4172	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3398	which is often provided by the following macro.	4173	which is often provided by the following macro.
3399		4174
3400	=item C<EV_P>, C<EV_P_>	4175	=item C<EV_P>, C<EV_P_>
…		…
3413	suitable for use with C<EV_A>.	4188	suitable for use with C<EV_A>.
3414		4189
3415	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4190	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3416		4191
3417	Similar to the other two macros, this gives you the value of the default	4192	Similar to the other two macros, this gives you the value of the default
3418	loop, if multiple loops are supported ("ev loop default").	4193	loop, if multiple loops are supported ("ev loop default"). The default loop
		4194	will be initialised if it isn't already initialised.
		4195
		4196	For non-multiplicity builds, these macros do nothing, so you always have
		4197	to initialise the loop somewhere.
3419		4198
3420	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4199	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3421		4200
3422	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4201	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3423	default loop has been initialised (C<UC> == unchecked). Their behaviour	4202	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3440	}	4219	}
3441		4220
3442	ev_check check;	4221	ev_check check;
3443	ev_check_init (&check, check_cb);	4222	ev_check_init (&check, check_cb);
3444	ev_check_start (EV_DEFAULT_ &check);	4223	ev_check_start (EV_DEFAULT_ &check);
3445	ev_loop (EV_DEFAULT_ 0);	4224	ev_run (EV_DEFAULT_ 0);
3446		4225
3447	=head1 EMBEDDING	4226	=head1 EMBEDDING
3448		4227
3449	Libev can (and often is) directly embedded into host	4228	Libev can (and often is) directly embedded into host
3450	applications. Examples of applications that embed it include the Deliantra	4229	applications. Examples of applications that embed it include the Deliantra
…		…
3530	libev.m4	4309	libev.m4
3531		4310
3532	=head2 PREPROCESSOR SYMBOLS/MACROS	4311	=head2 PREPROCESSOR SYMBOLS/MACROS
3533		4312
3534	Libev can be configured via a variety of preprocessor symbols you have to	4313	Libev can be configured via a variety of preprocessor symbols you have to
3535	define before including any of its files. The default in the absence of	4314	define before including (or compiling) any of its files. The default in
3536	autoconf is documented for every option.	4315	the absence of autoconf is documented for every option.
		4316
		4317	Symbols marked with "(h)" do not change the ABI, and can have different
		4318	values when compiling libev vs. including F<ev.h>, so it is permissible
		4319	to redefine them before including F<ev.h> without breaking compatibility
		4320	to a compiled library. All other symbols change the ABI, which means all
		4321	users of libev and the libev code itself must be compiled with compatible
		4322	settings.
3537		4323
3538	=over 4	4324	=over 4
3539		4325
		4326	=item EV_COMPAT3 (h)
		4327
		4328	Backwards compatibility is a major concern for libev. This is why this
		4329	release of libev comes with wrappers for the functions and symbols that
		4330	have been renamed between libev version 3 and 4.
		4331
		4332	You can disable these wrappers (to test compatibility with future
		4333	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4334	sources. This has the additional advantage that you can drop the C<struct>
		4335	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4336	typedef in that case.
		4337
		4338	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4339	and in some even more future version the compatibility code will be
		4340	removed completely.
		4341
3540	=item EV_STANDALONE	4342	=item EV_STANDALONE (h)
3541		4343
3542	Must always be C<1> if you do not use autoconf configuration, which	4344	Must always be C<1> if you do not use autoconf configuration, which
3543	keeps libev from including F<config.h>, and it also defines dummy	4345	keeps libev from including F<config.h>, and it also defines dummy
3544	implementations for some libevent functions (such as logging, which is not	4346	implementations for some libevent functions (such as logging, which is not
3545	supported). It will also not define any of the structs usually found in	4347	supported). It will also not define any of the structs usually found in
3546	F<event.h> that are not directly supported by the libev core alone.	4348	F<event.h> that are not directly supported by the libev core alone.
3547		4349
3548	In stanbdalone mode, libev will still try to automatically deduce the	4350	In standalone mode, libev will still try to automatically deduce the
3549	configuration, but has to be more conservative.	4351	configuration, but has to be more conservative.
		4352
		4353	=item EV_USE_FLOOR
		4354
		4355	If defined to be C<1>, libev will use the C<floor ()> function for its
		4356	periodic reschedule calculations, otherwise libev will fall back on a
		4357	portable (slower) implementation. If you enable this, you usually have to
		4358	link against libm or something equivalent. Enabling this when the C<floor>
		4359	function is not available will fail, so the safe default is to not enable
		4360	this.
3550		4361
3551	=item EV_USE_MONOTONIC	4362	=item EV_USE_MONOTONIC
3552		4363
3553	If defined to be C<1>, libev will try to detect the availability of the	4364	If defined to be C<1>, libev will try to detect the availability of the
3554	monotonic clock option at both compile time and runtime. Otherwise no	4365	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3618	be used is the winsock select). This means that it will call	4429	be used is the winsock select). This means that it will call
3619	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4430	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3620	it is assumed that all these functions actually work on fds, even	4431	it is assumed that all these functions actually work on fds, even
3621	on win32. Should not be defined on non-win32 platforms.	4432	on win32. Should not be defined on non-win32 platforms.
3622		4433
3623	=item EV_FD_TO_WIN32_HANDLE	4434	=item EV_FD_TO_WIN32_HANDLE(fd)
3624		4435
3625	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4436	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3626	file descriptors to socket handles. When not defining this symbol (the	4437	file descriptors to socket handles. When not defining this symbol (the
3627	default), then libev will call C<_get_osfhandle>, which is usually	4438	default), then libev will call C<_get_osfhandle>, which is usually
3628	correct. In some cases, programs use their own file descriptor management,	4439	correct. In some cases, programs use their own file descriptor management,
3629	in which case they can provide this function to map fds to socket handles.	4440	in which case they can provide this function to map fds to socket handles.
		4441
		4442	=item EV_WIN32_HANDLE_TO_FD(handle)
		4443
		4444	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4445	using the standard C<_open_osfhandle> function. For programs implementing
		4446	their own fd to handle mapping, overwriting this function makes it easier
		4447	to do so. This can be done by defining this macro to an appropriate value.
		4448
		4449	=item EV_WIN32_CLOSE_FD(fd)
		4450
		4451	If programs implement their own fd to handle mapping on win32, then this
		4452	macro can be used to override the C<close> function, useful to unregister
		4453	file descriptors again. Note that the replacement function has to close
		4454	the underlying OS handle.
3630		4455
3631	=item EV_USE_POLL	4456	=item EV_USE_POLL
3632		4457
3633	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4458	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3634	backend. Otherwise it will be enabled on non-win32 platforms. It	4459	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3673	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4498	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3674		4499
3675	=item EV_ATOMIC_T	4500	=item EV_ATOMIC_T
3676		4501
3677	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4502	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3678	access is atomic with respect to other threads or signal contexts. No such	4503	access is atomic and serialised with respect to other threads or signal
3679	type is easily found in the C language, so you can provide your own type	4504	contexts. No such type is easily found in the C language, so you can
3680	that you know is safe for your purposes. It is used both for signal handler "locking"	4505	provide your own type that you know is safe for your purposes. It is used
3681	as well as for signal and thread safety in C<ev_async> watchers.	4506	both for signal handler "locking" as well as for signal and thread safety
		4507	in C<ev_async> watchers.
3682		4508
3683	In the absence of this define, libev will use C<sig_atomic_t volatile>	4509	In the absence of this define, libev will use C<sig_atomic_t volatile>
3684	(from F<signal.h>), which is usually good enough on most platforms.	4510	(from F<signal.h>), which is usually good enough on most platforms,
		4511	although strictly speaking using a type that also implies a memory fence
		4512	is required.
3685		4513
3686	=item EV_H	4514	=item EV_H (h)
3687		4515
3688	The name of the F<ev.h> header file used to include it. The default if	4516	The name of the F<ev.h> header file used to include it. The default if
3689	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4517	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3690	used to virtually rename the F<ev.h> header file in case of conflicts.	4518	used to virtually rename the F<ev.h> header file in case of conflicts.
3691		4519
3692	=item EV_CONFIG_H	4520	=item EV_CONFIG_H (h)
3693		4521
3694	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4522	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3695	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4523	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3696	C<EV_H>, above.	4524	C<EV_H>, above.
3697		4525
3698	=item EV_EVENT_H	4526	=item EV_EVENT_H (h)
3699		4527
3700	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4528	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3701	of how the F<event.h> header can be found, the default is C<"event.h">.	4529	of how the F<event.h> header can be found, the default is C<"event.h">.
3702		4530
3703	=item EV_PROTOTYPES	4531	=item EV_PROTOTYPES (h)
3704		4532
3705	If defined to be C<0>, then F<ev.h> will not define any function	4533	If defined to be C<0>, then F<ev.h> will not define any function
3706	prototypes, but still define all the structs and other symbols. This is	4534	prototypes, but still define all the structs and other symbols. This is
3707	occasionally useful if you want to provide your own wrapper functions	4535	occasionally useful if you want to provide your own wrapper functions
3708	around libev functions.	4536	around libev functions.
…		…
3713	will have the C<struct ev_loop *> as first argument, and you can create	4541	will have the C<struct ev_loop *> as first argument, and you can create
3714	additional independent event loops. Otherwise there will be no support	4542	additional independent event loops. Otherwise there will be no support
3715	for multiple event loops and there is no first event loop pointer	4543	for multiple event loops and there is no first event loop pointer
3716	argument. Instead, all functions act on the single default loop.	4544	argument. Instead, all functions act on the single default loop.
3717		4545
		4546	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4547	default loop when multiplicity is switched off - you always have to
		4548	initialise the loop manually in this case.
		4549
3718	=item EV_MINPRI	4550	=item EV_MINPRI
3719		4551
3720	=item EV_MAXPRI	4552	=item EV_MAXPRI
3721		4553
3722	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4554	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3730	fine.	4562	fine.
3731		4563
3732	If your embedding application does not need any priorities, defining these	4564	If your embedding application does not need any priorities, defining these
3733	both to C<0> will save some memory and CPU.	4565	both to C<0> will save some memory and CPU.
3734		4566
3735	=item EV_PERIODIC_ENABLE	4567	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4568	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4569	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3736		4570
3737	If undefined or defined to be C<1>, then periodic timers are supported. If	4571	If undefined or defined to be C<1> (and the platform supports it), then
3738	defined to be C<0>, then they are not. Disabling them saves a few kB of	4572	the respective watcher type is supported. If defined to be C<0>, then it
3739	code.	4573	is not. Disabling watcher types mainly saves code size.
3740		4574
3741	=item EV_IDLE_ENABLE	4575	=item EV_FEATURES
3742
3743	If undefined or defined to be C<1>, then idle watchers are supported. If
3744	defined to be C<0>, then they are not. Disabling them saves a few kB of
3745	code.
3746
3747	=item EV_EMBED_ENABLE
3748
3749	If undefined or defined to be C<1>, then embed watchers are supported. If
3750	defined to be C<0>, then they are not. Embed watchers rely on most other
3751	watcher types, which therefore must not be disabled.
3752
3753	=item EV_STAT_ENABLE
3754
3755	If undefined or defined to be C<1>, then stat watchers are supported. If
3756	defined to be C<0>, then they are not.
3757
3758	=item EV_FORK_ENABLE
3759
3760	If undefined or defined to be C<1>, then fork watchers are supported. If
3761	defined to be C<0>, then they are not.
3762
3763	=item EV_ASYNC_ENABLE
3764
3765	If undefined or defined to be C<1>, then async watchers are supported. If
3766	defined to be C<0>, then they are not.
3767
3768	=item EV_MINIMAL
3769		4576
3770	If you need to shave off some kilobytes of code at the expense of some	4577	If you need to shave off some kilobytes of code at the expense of some
3771	speed (but with the full API), define this symbol to C<1>. Currently this	4578	speed (but with the full API), you can define this symbol to request
3772	is used to override some inlining decisions, saves roughly 30% code size	4579	certain subsets of functionality. The default is to enable all features
3773	on amd64. It also selects a much smaller 2-heap for timer management over	4580	that can be enabled on the platform.
3774	the default 4-heap.
3775		4581
3776	You can save even more by disabling watcher types you do not need	4582	A typical way to use this symbol is to define it to C<0> (or to a bitset
3777	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4583	with some broad features you want) and then selectively re-enable
3778	(C<-DNDEBUG>) will usually reduce code size a lot.	4584	additional parts you want, for example if you want everything minimal,
		4585	but multiple event loop support, async and child watchers and the poll
		4586	backend, use this:
3779		4587
3780	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4588	#define EV_FEATURES 0
3781	provide a bare-bones event library. See C<ev.h> for details on what parts	4589	#define EV_MULTIPLICITY 1
3782	of the API are still available, and do not complain if this subset changes	4590	#define EV_USE_POLL 1
3783	over time.	4591	#define EV_CHILD_ENABLE 1
		4592	#define EV_ASYNC_ENABLE 1
		4593
		4594	The actual value is a bitset, it can be a combination of the following
		4595	values:
		4596
		4597	=over 4
		4598
		4599	=item C<1> - faster/larger code
		4600
		4601	Use larger code to speed up some operations.
		4602
		4603	Currently this is used to override some inlining decisions (enlarging the
		4604	code size by roughly 30% on amd64).
		4605
		4606	When optimising for size, use of compiler flags such as C<-Os> with
		4607	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4608	assertions.
		4609
		4610	=item C<2> - faster/larger data structures
		4611
		4612	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4613	hash table sizes and so on. This will usually further increase code size
		4614	and can additionally have an effect on the size of data structures at
		4615	runtime.
		4616
		4617	=item C<4> - full API configuration
		4618
		4619	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4620	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4621
		4622	=item C<8> - full API
		4623
		4624	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4625	details on which parts of the API are still available without this
		4626	feature, and do not complain if this subset changes over time.
		4627
		4628	=item C<16> - enable all optional watcher types
		4629
		4630	Enables all optional watcher types. If you want to selectively enable
		4631	only some watcher types other than I/O and timers (e.g. prepare,
		4632	embed, async, child...) you can enable them manually by defining
		4633	C<EV_watchertype_ENABLE> to C<1> instead.
		4634
		4635	=item C<32> - enable all backends
		4636
		4637	This enables all backends - without this feature, you need to enable at
		4638	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4639
		4640	=item C<64> - enable OS-specific "helper" APIs
		4641
		4642	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4643	default.
		4644
		4645	=back
		4646
		4647	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4648	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4649	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4650	watchers, timers and monotonic clock support.
		4651
		4652	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4653	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4654	your program might be left out as well - a binary starting a timer and an
		4655	I/O watcher then might come out at only 5Kb.
		4656
		4657	=item EV_API_STATIC
		4658
		4659	If this symbol is defined (by default it is not), then all identifiers
		4660	will have static linkage. This means that libev will not export any
		4661	identifiers, and you cannot link against libev anymore. This can be useful
		4662	when you embed libev, only want to use libev functions in a single file,
		4663	and do not want its identifiers to be visible.
		4664
		4665	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4666	wants to use libev.
		4667
		4668	=item EV_AVOID_STDIO
		4669
		4670	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4671	functions (printf, scanf, perror etc.). This will increase the code size
		4672	somewhat, but if your program doesn't otherwise depend on stdio and your
		4673	libc allows it, this avoids linking in the stdio library which is quite
		4674	big.
		4675
		4676	Note that error messages might become less precise when this option is
		4677	enabled.
		4678
		4679	=item EV_NSIG
		4680
		4681	The highest supported signal number, +1 (or, the number of
		4682	signals): Normally, libev tries to deduce the maximum number of signals
		4683	automatically, but sometimes this fails, in which case it can be
		4684	specified. Also, using a lower number than detected (C<32> should be
		4685	good for about any system in existence) can save some memory, as libev
		4686	statically allocates some 12-24 bytes per signal number.
3784		4687
3785	=item EV_PID_HASHSIZE	4688	=item EV_PID_HASHSIZE
3786		4689
3787	C<ev_child> watchers use a small hash table to distribute workload by	4690	C<ev_child> watchers use a small hash table to distribute workload by
3788	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4691	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3789	than enough. If you need to manage thousands of children you might want to	4692	usually more than enough. If you need to manage thousands of children you
3790	increase this value (I<must> be a power of two).	4693	might want to increase this value (I<must> be a power of two).
3791		4694
3792	=item EV_INOTIFY_HASHSIZE	4695	=item EV_INOTIFY_HASHSIZE
3793		4696
3794	C<ev_stat> watchers use a small hash table to distribute workload by	4697	C<ev_stat> watchers use a small hash table to distribute workload by
3795	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4698	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3796	usually more than enough. If you need to manage thousands of C<ev_stat>	4699	disabled), usually more than enough. If you need to manage thousands of
3797	watchers you might want to increase this value (I<must> be a power of	4700	C<ev_stat> watchers you might want to increase this value (I<must> be a
3798	two).	4701	power of two).
3799		4702
3800	=item EV_USE_4HEAP	4703	=item EV_USE_4HEAP
3801		4704
3802	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4705	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3803	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4706	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3804	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4707	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3805	faster performance with many (thousands) of watchers.	4708	faster performance with many (thousands) of watchers.
3806		4709
3807	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4710	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3808	(disabled).	4711	will be C<0>.
3809		4712
3810	=item EV_HEAP_CACHE_AT	4713	=item EV_HEAP_CACHE_AT
3811		4714
3812	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4715	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3813	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4716	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3814	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4717	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3815	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4718	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3816	but avoids random read accesses on heap changes. This improves performance	4719	but avoids random read accesses on heap changes. This improves performance
3817	noticeably with many (hundreds) of watchers.	4720	noticeably with many (hundreds) of watchers.
3818		4721
3819	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4722	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3820	(disabled).	4723	will be C<0>.
3821		4724
3822	=item EV_VERIFY	4725	=item EV_VERIFY
3823		4726
3824	Controls how much internal verification (see C<ev_loop_verify ()>) will	4727	Controls how much internal verification (see C<ev_verify ()>) will
3825	be done: If set to C<0>, no internal verification code will be compiled	4728	be done: If set to C<0>, no internal verification code will be compiled
3826	in. If set to C<1>, then verification code will be compiled in, but not	4729	in. If set to C<1>, then verification code will be compiled in, but not
3827	called. If set to C<2>, then the internal verification code will be	4730	called. If set to C<2>, then the internal verification code will be
3828	called once per loop, which can slow down libev. If set to C<3>, then the	4731	called once per loop, which can slow down libev. If set to C<3>, then the
3829	verification code will be called very frequently, which will slow down	4732	verification code will be called very frequently, which will slow down
3830	libev considerably.	4733	libev considerably.
3831		4734
3832	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4735	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3833	C<0>.	4736	will be C<0>.
3834		4737
3835	=item EV_COMMON	4738	=item EV_COMMON
3836		4739
3837	By default, all watchers have a C<void *data> member. By redefining	4740	By default, all watchers have a C<void *data> member. By redefining
3838	this macro to a something else you can include more and other types of	4741	this macro to something else you can include more and other types of
3839	members. You have to define it each time you include one of the files,	4742	members. You have to define it each time you include one of the files,
3840	though, and it must be identical each time.	4743	though, and it must be identical each time.
3841		4744
3842	For example, the perl EV module uses something like this:	4745	For example, the perl EV module uses something like this:
3843		4746
…		…
3896	file.	4799	file.
3897		4800
3898	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4801	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3899	that everybody includes and which overrides some configure choices:	4802	that everybody includes and which overrides some configure choices:
3900		4803
3901	#define EV_MINIMAL 1	4804	#define EV_FEATURES 8
3902	#define EV_USE_POLL 0	4805	#define EV_USE_SELECT 1
3903	#define EV_MULTIPLICITY 0
3904	#define EV_PERIODIC_ENABLE 0	4806	#define EV_PREPARE_ENABLE 1
		4807	#define EV_IDLE_ENABLE 1
3905	#define EV_STAT_ENABLE 0	4808	#define EV_SIGNAL_ENABLE 1
3906	#define EV_FORK_ENABLE 0	4809	#define EV_CHILD_ENABLE 1
		4810	#define EV_USE_STDEXCEPT 0
3907	#define EV_CONFIG_H <config.h>	4811	#define EV_CONFIG_H <config.h>
3908	#define EV_MINPRI 0
3909	#define EV_MAXPRI 0
3910		4812
3911	#include "ev++.h"	4813	#include "ev++.h"
3912		4814
3913	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4815	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3914		4816
3915	#include "ev_cpp.h"	4817	#include "ev_cpp.h"
3916	#include "ev.c"	4818	#include "ev.c"
3917		4819
3918	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4820	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3919		4821
3920	=head2 THREADS AND COROUTINES	4822	=head2 THREADS AND COROUTINES
3921		4823
3922	=head3 THREADS	4824	=head3 THREADS
3923		4825
…		…
3974	default loop and triggering an C<ev_async> watcher from the default loop	4876	default loop and triggering an C<ev_async> watcher from the default loop
3975	watcher callback into the event loop interested in the signal.	4877	watcher callback into the event loop interested in the signal.
3976		4878
3977	=back	4879	=back
3978		4880
3979	=head4 THREAD LOCKING EXAMPLE	4881	See also L<THREAD LOCKING EXAMPLE>.
3980
3981	Here is a fictitious example of how to run an event loop in a different
3982	thread than where callbacks are being invoked and watchers are
3983	created/added/removed.
3984
3985	For a real-world example, see the C<EV::Loop::Async> perl module,
3986	which uses exactly this technique (which is suited for many high-level
3987	languages).
3988
3989	The example uses a pthread mutex to protect the loop data, a condition
3990	variable to wait for callback invocations, an async watcher to notify the
3991	event loop thread and an unspecified mechanism to wake up the main thread.
3992
3993	First, you need to associate some data with the event loop:
3994
3995	typedef struct {
3996	mutex_t lock; /* global loop lock */
3997	ev_async async_w;
3998	thread_t tid;
3999	cond_t invoke_cv;
4000	} userdata;
4001
4002	void prepare_loop (EV_P)
4003	{
4004	// for simplicity, we use a static userdata struct.
4005	static userdata u;
4006
4007	ev_async_init (&u->async_w, async_cb);
4008	ev_async_start (EV_A_ &u->async_w);
4009
4010	pthread_mutex_init (&u->lock, 0);
4011	pthread_cond_init (&u->invoke_cv, 0);
4012
4013	// now associate this with the loop
4014	ev_set_userdata (EV_A_ u);
4015	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4016	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4017
4018	// then create the thread running ev_loop
4019	pthread_create (&u->tid, 0, l_run, EV_A);
4020	}
4021
4022	The callback for the C<ev_async> watcher does nothing: the watcher is used
4023	solely to wake up the event loop so it takes notice of any new watchers
4024	that might have been added:
4025
4026	static void
4027	async_cb (EV_P_ ev_async *w, int revents)
4028	{
4029	// just used for the side effects
4030	}
4031
4032	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4033	protecting the loop data, respectively.
4034
4035	static void
4036	l_release (EV_P)
4037	{
4038	userdata *u = ev_userdata (EV_A);
4039	pthread_mutex_unlock (&u->lock);
4040	}
4041
4042	static void
4043	l_acquire (EV_P)
4044	{
4045	userdata *u = ev_userdata (EV_A);
4046	pthread_mutex_lock (&u->lock);
4047	}
4048
4049	The event loop thread first acquires the mutex, and then jumps straight
4050	into C<ev_loop>:
4051
4052	void *
4053	l_run (void *thr_arg)
4054	{
4055	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4056
4057	l_acquire (EV_A);
4058	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4059	ev_loop (EV_A_ 0);
4060	l_release (EV_A);
4061
4062	return 0;
4063	}
4064
4065	Instead of invoking all pending watchers, the C<l_invoke> callback will
4066	signal the main thread via some unspecified mechanism (signals? pipe
4067	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4068	have been called (in a while loop because a) spurious wakeups are possible
4069	and b) skipping inter-thread-communication when there are no pending
4070	watchers is very beneficial):
4071
4072	static void
4073	l_invoke (EV_P)
4074	{
4075	userdata *u = ev_userdata (EV_A);
4076
4077	while (ev_pending_count (EV_A))
4078	{
4079	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4080	pthread_cond_wait (&u->invoke_cv, &u->lock);
4081	}
4082	}
4083
4084	Now, whenever the main thread gets told to invoke pending watchers, it
4085	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4086	thread to continue:
4087
4088	static void
4089	real_invoke_pending (EV_P)
4090	{
4091	userdata *u = ev_userdata (EV_A);
4092
4093	pthread_mutex_lock (&u->lock);
4094	ev_invoke_pending (EV_A);
4095	pthread_cond_signal (&u->invoke_cv);
4096	pthread_mutex_unlock (&u->lock);
4097	}
4098
4099	Whenever you want to start/stop a watcher or do other modifications to an
4100	event loop, you will now have to lock:
4101
4102	ev_timer timeout_watcher;
4103	userdata *u = ev_userdata (EV_A);
4104
4105	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4106
4107	pthread_mutex_lock (&u->lock);
4108	ev_timer_start (EV_A_ &timeout_watcher);
4109	ev_async_send (EV_A_ &u->async_w);
4110	pthread_mutex_unlock (&u->lock);
4111
4112	Note that sending the C<ev_async> watcher is required because otherwise
4113	an event loop currently blocking in the kernel will have no knowledge
4114	about the newly added timer. By waking up the loop it will pick up any new
4115	watchers in the next event loop iteration.
4116		4882
4117	=head3 COROUTINES	4883	=head3 COROUTINES
4118		4884
4119	Libev is very accommodating to coroutines ("cooperative threads"):	4885	Libev is very accommodating to coroutines ("cooperative threads"):
4120	libev fully supports nesting calls to its functions from different	4886	libev fully supports nesting calls to its functions from different
4121	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4887	coroutines (e.g. you can call C<ev_run> on the same loop from two
4122	different coroutines, and switch freely between both coroutines running	4888	different coroutines, and switch freely between both coroutines running
4123	the loop, as long as you don't confuse yourself). The only exception is	4889	the loop, as long as you don't confuse yourself). The only exception is
4124	that you must not do this from C<ev_periodic> reschedule callbacks.	4890	that you must not do this from C<ev_periodic> reschedule callbacks.
4125		4891
4126	Care has been taken to ensure that libev does not keep local state inside	4892	Care has been taken to ensure that libev does not keep local state inside
4127	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4893	C<ev_run>, and other calls do not usually allow for coroutine switches as
4128	they do not call any callbacks.	4894	they do not call any callbacks.
4129		4895
4130	=head2 COMPILER WARNINGS	4896	=head2 COMPILER WARNINGS
4131		4897
4132	Depending on your compiler and compiler settings, you might get no or a	4898	Depending on your compiler and compiler settings, you might get no or a
…		…
4143	maintainable.	4909	maintainable.
4144		4910
4145	And of course, some compiler warnings are just plain stupid, or simply	4911	And of course, some compiler warnings are just plain stupid, or simply
4146	wrong (because they don't actually warn about the condition their message	4912	wrong (because they don't actually warn about the condition their message
4147	seems to warn about). For example, certain older gcc versions had some	4913	seems to warn about). For example, certain older gcc versions had some
4148	warnings that resulted an extreme number of false positives. These have	4914	warnings that resulted in an extreme number of false positives. These have
4149	been fixed, but some people still insist on making code warn-free with	4915	been fixed, but some people still insist on making code warn-free with
4150	such buggy versions.	4916	such buggy versions.
4151		4917
4152	While libev is written to generate as few warnings as possible,	4918	While libev is written to generate as few warnings as possible,
4153	"warn-free" code is not a goal, and it is recommended not to build libev	4919	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4189	I suggest using suppression lists.	4955	I suggest using suppression lists.
4190		4956
4191		4957
4192	=head1 PORTABILITY NOTES	4958	=head1 PORTABILITY NOTES
4193		4959
		4960	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4961
		4962	GNU/Linux is the only common platform that supports 64 bit file/large file
		4963	interfaces but I<disables> them by default.
		4964
		4965	That means that libev compiled in the default environment doesn't support
		4966	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4967
		4968	Unfortunately, many programs try to work around this GNU/Linux issue
		4969	by enabling the large file API, which makes them incompatible with the
		4970	standard libev compiled for their system.
		4971
		4972	Likewise, libev cannot enable the large file API itself as this would
		4973	suddenly make it incompatible to the default compile time environment,
		4974	i.e. all programs not using special compile switches.
		4975
		4976	=head2 OS/X AND DARWIN BUGS
		4977
		4978	The whole thing is a bug if you ask me - basically any system interface
		4979	you touch is broken, whether it is locales, poll, kqueue or even the
		4980	OpenGL drivers.
		4981
		4982	=head3 C<kqueue> is buggy
		4983
		4984	The kqueue syscall is broken in all known versions - most versions support
		4985	only sockets, many support pipes.
		4986
		4987	Libev tries to work around this by not using C<kqueue> by default on this
		4988	rotten platform, but of course you can still ask for it when creating a
		4989	loop - embedding a socket-only kqueue loop into a select-based one is
		4990	probably going to work well.
		4991
		4992	=head3 C<poll> is buggy
		4993
		4994	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4995	implementation by something calling C<kqueue> internally around the 10.5.6
		4996	release, so now C<kqueue> I<and> C<poll> are broken.
		4997
		4998	Libev tries to work around this by not using C<poll> by default on
		4999	this rotten platform, but of course you can still ask for it when creating
		5000	a loop.
		5001
		5002	=head3 C<select> is buggy
		5003
		5004	All that's left is C<select>, and of course Apple found a way to fuck this
		5005	one up as well: On OS/X, C<select> actively limits the number of file
		5006	descriptors you can pass in to 1024 - your program suddenly crashes when
		5007	you use more.
		5008
		5009	There is an undocumented "workaround" for this - defining
		5010	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5011	work on OS/X.
		5012
		5013	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5014
		5015	=head3 C<errno> reentrancy
		5016
		5017	The default compile environment on Solaris is unfortunately so
		5018	thread-unsafe that you can't even use components/libraries compiled
		5019	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5020	defined by default. A valid, if stupid, implementation choice.
		5021
		5022	If you want to use libev in threaded environments you have to make sure
		5023	it's compiled with C<_REENTRANT> defined.
		5024
		5025	=head3 Event port backend
		5026
		5027	The scalable event interface for Solaris is called "event
		5028	ports". Unfortunately, this mechanism is very buggy in all major
		5029	releases. If you run into high CPU usage, your program freezes or you get
		5030	a large number of spurious wakeups, make sure you have all the relevant
		5031	and latest kernel patches applied. No, I don't know which ones, but there
		5032	are multiple ones to apply, and afterwards, event ports actually work
		5033	great.
		5034
		5035	If you can't get it to work, you can try running the program by setting
		5036	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5037	C<select> backends.
		5038
		5039	=head2 AIX POLL BUG
		5040
		5041	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5042	this by trying to avoid the poll backend altogether (i.e. it's not even
		5043	compiled in), which normally isn't a big problem as C<select> works fine
		5044	with large bitsets on AIX, and AIX is dead anyway.
		5045
4194	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5046	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5047
		5048	=head3 General issues
4195		5049
4196	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5050	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4197	requires, and its I/O model is fundamentally incompatible with the POSIX	5051	requires, and its I/O model is fundamentally incompatible with the POSIX
4198	model. Libev still offers limited functionality on this platform in	5052	model. Libev still offers limited functionality on this platform in
4199	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5053	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4200	descriptors. This only applies when using Win32 natively, not when using	5054	descriptors. This only applies when using Win32 natively, not when using
4201	e.g. cygwin.	5055	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5056	as every compiler comes with a slightly differently broken/incompatible
		5057	environment.
4202		5058
4203	Lifting these limitations would basically require the full	5059	Lifting these limitations would basically require the full
4204	re-implementation of the I/O system. If you are into these kinds of	5060	re-implementation of the I/O system. If you are into this kind of thing,
4205	things, then note that glib does exactly that for you in a very portable	5061	then note that glib does exactly that for you in a very portable way (note
4206	way (note also that glib is the slowest event library known to man).	5062	also that glib is the slowest event library known to man).
4207		5063
4208	There is no supported compilation method available on windows except	5064	There is no supported compilation method available on windows except
4209	embedding it into other applications.	5065	embedding it into other applications.
4210		5066
4211	Sensible signal handling is officially unsupported by Microsoft - libev	5067	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4239	you do I<not> compile the F<ev.c> or any other embedded source files!):	5095	you do I<not> compile the F<ev.c> or any other embedded source files!):
4240		5096
4241	#include "evwrap.h"	5097	#include "evwrap.h"
4242	#include "ev.c"	5098	#include "ev.c"
4243		5099
4244	=over 4
4245
4246	=item The winsocket select function	5100	=head3 The winsocket C<select> function
4247		5101
4248	The winsocket C<select> function doesn't follow POSIX in that it	5102	The winsocket C<select> function doesn't follow POSIX in that it
4249	requires socket I<handles> and not socket I<file descriptors> (it is	5103	requires socket I<handles> and not socket I<file descriptors> (it is
4250	also extremely buggy). This makes select very inefficient, and also	5104	also extremely buggy). This makes select very inefficient, and also
4251	requires a mapping from file descriptors to socket handles (the Microsoft	5105	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4260	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5114	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4261		5115
4262	Note that winsockets handling of fd sets is O(n), so you can easily get a	5116	Note that winsockets handling of fd sets is O(n), so you can easily get a
4263	complexity in the O(n²) range when using win32.	5117	complexity in the O(n²) range when using win32.
4264		5118
4265	=item Limited number of file descriptors	5119	=head3 Limited number of file descriptors
4266		5120
4267	Windows has numerous arbitrary (and low) limits on things.	5121	Windows has numerous arbitrary (and low) limits on things.
4268		5122
4269	Early versions of winsocket's select only supported waiting for a maximum	5123	Early versions of winsocket's select only supported waiting for a maximum
4270	of C<64> handles (probably owning to the fact that all windows kernels	5124	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4285	runtime libraries. This might get you to about C<512> or C<2048> sockets	5139	runtime libraries. This might get you to about C<512> or C<2048> sockets
4286	(depending on windows version and/or the phase of the moon). To get more,	5140	(depending on windows version and/or the phase of the moon). To get more,
4287	you need to wrap all I/O functions and provide your own fd management, but	5141	you need to wrap all I/O functions and provide your own fd management, but
4288	the cost of calling select (O(n²)) will likely make this unworkable.	5142	the cost of calling select (O(n²)) will likely make this unworkable.
4289		5143
4290	=back
4291
4292	=head2 PORTABILITY REQUIREMENTS	5144	=head2 PORTABILITY REQUIREMENTS
4293		5145
4294	In addition to a working ISO-C implementation and of course the	5146	In addition to a working ISO-C implementation and of course the
4295	backend-specific APIs, libev relies on a few additional extensions:	5147	backend-specific APIs, libev relies on a few additional extensions:
4296		5148
…		…
4302	Libev assumes not only that all watcher pointers have the same internal	5154	Libev assumes not only that all watcher pointers have the same internal
4303	structure (guaranteed by POSIX but not by ISO C for example), but it also	5155	structure (guaranteed by POSIX but not by ISO C for example), but it also
4304	assumes that the same (machine) code can be used to call any watcher	5156	assumes that the same (machine) code can be used to call any watcher
4305	callback: The watcher callbacks have different type signatures, but libev	5157	callback: The watcher callbacks have different type signatures, but libev
4306	calls them using an C<ev_watcher *> internally.	5158	calls them using an C<ev_watcher *> internally.
		5159
		5160	=item pointer accesses must be thread-atomic
		5161
		5162	Accessing a pointer value must be atomic, it must both be readable and
		5163	writable in one piece - this is the case on all current architectures.
4307		5164
4308	=item C<sig_atomic_t volatile> must be thread-atomic as well	5165	=item C<sig_atomic_t volatile> must be thread-atomic as well
4309		5166
4310	The type C<sig_atomic_t volatile> (or whatever is defined as	5167	The type C<sig_atomic_t volatile> (or whatever is defined as
4311	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5168	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4334	watchers.	5191	watchers.
4335		5192
4336	=item C<double> must hold a time value in seconds with enough accuracy	5193	=item C<double> must hold a time value in seconds with enough accuracy
4337		5194
4338	The type C<double> is used to represent timestamps. It is required to	5195	The type C<double> is used to represent timestamps. It is required to
4339	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5196	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4340	enough for at least into the year 4000. This requirement is fulfilled by	5197	good enough for at least into the year 4000 with millisecond accuracy
		5198	(the design goal for libev). This requirement is overfulfilled by
4341	implementations implementing IEEE 754, which is basically all existing	5199	implementations using IEEE 754, which is basically all existing ones.
		5200
4342	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5201	With IEEE 754 doubles, you get microsecond accuracy until at least the
4343	2200.	5202	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5203	is either obsolete or somebody patched it to use C<long double> or
		5204	something like that, just kidding).
4344		5205
4345	=back	5206	=back
4346		5207
4347	If you know of other additional requirements drop me a note.	5208	If you know of other additional requirements drop me a note.
4348		5209
…		…
4410	=item Processing ev_async_send: O(number_of_async_watchers)	5271	=item Processing ev_async_send: O(number_of_async_watchers)
4411		5272
4412	=item Processing signals: O(max_signal_number)	5273	=item Processing signals: O(max_signal_number)
4413		5274
4414	Sending involves a system call I<iff> there were no other C<ev_async_send>	5275	Sending involves a system call I<iff> there were no other C<ev_async_send>
4415	calls in the current loop iteration. Checking for async and signal events	5276	calls in the current loop iteration and the loop is currently
		5277	blocked. Checking for async and signal events involves iterating over all
4416	involves iterating over all running async watchers or all signal numbers.	5278	running async watchers or all signal numbers.
4417		5279
4418	=back	5280	=back
4419		5281
4420		5282
		5283	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5284
		5285	The major version 4 introduced some incompatible changes to the API.
		5286
		5287	At the moment, the C<ev.h> header file provides compatibility definitions
		5288	for all changes, so most programs should still compile. The compatibility
		5289	layer might be removed in later versions of libev, so better update to the
		5290	new API early than late.
		5291
		5292	=over 4
		5293
		5294	=item C<EV_COMPAT3> backwards compatibility mechanism
		5295
		5296	The backward compatibility mechanism can be controlled by
		5297	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		5298	section.
		5299
		5300	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5301
		5302	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5303
		5304	ev_loop_destroy (EV_DEFAULT_UC);
		5305	ev_loop_fork (EV_DEFAULT);
		5306
		5307	=item function/symbol renames
		5308
		5309	A number of functions and symbols have been renamed:
		5310
		5311	ev_loop => ev_run
		5312	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5313	EVLOOP_ONESHOT => EVRUN_ONCE
		5314
		5315	ev_unloop => ev_break
		5316	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5317	EVUNLOOP_ONE => EVBREAK_ONE
		5318	EVUNLOOP_ALL => EVBREAK_ALL
		5319
		5320	EV_TIMEOUT => EV_TIMER
		5321
		5322	ev_loop_count => ev_iteration
		5323	ev_loop_depth => ev_depth
		5324	ev_loop_verify => ev_verify
		5325
		5326	Most functions working on C<struct ev_loop> objects don't have an
		5327	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5328	associated constants have been renamed to not collide with the C<struct
		5329	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5330	as all other watcher types. Note that C<ev_loop_fork> is still called
		5331	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5332	typedef.
		5333
		5334	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5335
		5336	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5337	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5338	and work, but the library code will of course be larger.
		5339
		5340	=back
		5341
		5342
4421	=head1 GLOSSARY	5343	=head1 GLOSSARY
4422		5344
4423	=over 4	5345	=over 4
4424		5346
4425	=item active	5347	=item active
4426		5348
4427	A watcher is active as long as it has been started (has been attached to	5349	A watcher is active as long as it has been started and not yet stopped.
4428	an event loop) but not yet stopped (disassociated from the event loop).	5350	See L<WATCHER STATES> for details.
4429		5351
4430	=item application	5352	=item application
4431		5353
4432	In this document, an application is whatever is using libev.	5354	In this document, an application is whatever is using libev.
		5355
		5356	=item backend
		5357
		5358	The part of the code dealing with the operating system interfaces.
4433		5359
4434	=item callback	5360	=item callback
4435		5361
4436	The address of a function that is called when some event has been	5362	The address of a function that is called when some event has been
4437	detected. Callbacks are being passed the event loop, the watcher that	5363	detected. Callbacks are being passed the event loop, the watcher that
4438	received the event, and the actual event bitset.	5364	received the event, and the actual event bitset.
4439		5365
4440	=item callback invocation	5366	=item callback/watcher invocation
4441		5367
4442	The act of calling the callback associated with a watcher.	5368	The act of calling the callback associated with a watcher.
4443		5369
4444	=item event	5370	=item event
4445		5371
4446	A change of state of some external event, such as data now being available	5372	A change of state of some external event, such as data now being available
4447	for reading on a file descriptor, time having passed or simply not having	5373	for reading on a file descriptor, time having passed or simply not having
4448	any other events happening anymore.	5374	any other events happening anymore.
4449		5375
4450	In libev, events are represented as single bits (such as C<EV_READ> or	5376	In libev, events are represented as single bits (such as C<EV_READ> or
4451	C<EV_TIMEOUT>).	5377	C<EV_TIMER>).
4452		5378
4453	=item event library	5379	=item event library
4454		5380
4455	A software package implementing an event model and loop.	5381	A software package implementing an event model and loop.
4456		5382
…		…
4464	The model used to describe how an event loop handles and processes	5390	The model used to describe how an event loop handles and processes
4465	watchers and events.	5391	watchers and events.
4466		5392
4467	=item pending	5393	=item pending
4468		5394
4469	A watcher is pending as soon as the corresponding event has been detected,	5395	A watcher is pending as soon as the corresponding event has been
4470	and stops being pending as soon as the watcher will be invoked or its	5396	detected. See L<WATCHER STATES> for details.
4471	pending status is explicitly cleared by the application.
4472
4473	A watcher can be pending, but not active. Stopping a watcher also clears
4474	its pending status.
4475		5397
4476	=item real time	5398	=item real time
4477		5399
4478	The physical time that is observed. It is apparently strictly monotonic :)	5400	The physical time that is observed. It is apparently strictly monotonic :)
4479		5401
4480	=item wall-clock time	5402	=item wall-clock time
4481		5403
4482	The time and date as shown on clocks. Unlike real time, it can actually	5404	The time and date as shown on clocks. Unlike real time, it can actually
4483	be wrong and jump forwards and backwards, e.g. when the you adjust your	5405	be wrong and jump forwards and backwards, e.g. when you adjust your
4484	clock.	5406	clock.
4485		5407
4486	=item watcher	5408	=item watcher
4487		5409
4488	A data structure that describes interest in certain events. Watchers need	5410	A data structure that describes interest in certain events. Watchers need
4489	to be started (attached to an event loop) before they can receive events.	5411	to be started (attached to an event loop) before they can receive events.
4490		5412
4491	=item watcher invocation
4492
4493	The act of calling the callback associated with a watcher.
4494
4495	=back	5413	=back
4496		5414
4497	=head1 AUTHOR	5415	=head1 AUTHOR
4498		5416
4499	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5417	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5418	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4500		5419

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