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…		…
26	puts ("stdin ready");	26	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	28	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
30		30
31	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
33	}	33	}
34		34
35	// another callback, this time for a time-out	35	// another callback, this time for a time-out
36	static void	36	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	38	{
39	puts ("timeout");	39	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
42	}	42	}
43		43
44	int	44	int
45	main (void)	45	main (void)
46	{	46	{
47	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
49		49
50	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
59		59
60	// now wait for events to arrive	60	// now wait for events to arrive
61	ev_loop (loop, 0);	61	ev_run (loop, 0);
62		62
63	// unloop was called, so exit	63	// break was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 ABOUT THIS DOCUMENT	67	=head1 ABOUT THIS DOCUMENT
68		68
…		…
75	While this document tries to be as complete as possible in documenting	75	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	76	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	77	on event-based programming, nor will it introduce event-based programming
78	with libev.	78	with libev.
79		79
80	Familarity with event based programming techniques in general is assumed	80	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	81	throughout this document.
		82
		83	=head1 WHAT TO READ WHEN IN A HURRY
		84
		85	This manual tries to be very detailed, but unfortunately, this also makes
		86	it very long. If you just want to know the basics of libev, I suggest
		87	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		88	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		89	C<ev_timer> sections in L</WATCHER TYPES>.
82		90
83	=head1 ABOUT LIBEV	91	=head1 ABOUT LIBEV
84		92
85	Libev is an event loop: you register interest in certain events (such as a	93	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	94	file descriptor being readable or a timeout occurring), and it will manage
…		…
98	=head2 FEATURES	106	=head2 FEATURES
99		107
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	108	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	109	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	110	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	111	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	112	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	113	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	114	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	115	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	116	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	117	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		118	limited support for fork events (C<ev_fork>).
110		119
111	It also is quite fast (see this	120	It also is quite fast (see this
112	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	121	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	122	for example).
114		123
…		…
117	Libev is very configurable. In this manual the default (and most common)	126	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	127	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	128	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	129	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	130	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	131	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	132	this argument.
124		133
125	=head2 TIME REPRESENTATION	134	=head2 TIME REPRESENTATION
126		135
127	Libev represents time as a single floating point number, representing	136	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	137	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	138	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	139	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	140	too. It usually aliases to the C<double> type in C. When you need to do
132	on it, you should treat it as some floating point value. Unlike the name	141	any calculations on it, you should treat it as some floating point value.
		142
133	component C<stamp> might indicate, it is also used for time differences	143	Unlike the name component C<stamp> might indicate, it is also used for
134	throughout libev.	144	time differences (e.g. delays) throughout libev.
135		145
136	=head1 ERROR HANDLING	146	=head1 ERROR HANDLING
137		147
138	Libev knows three classes of errors: operating system errors, usage errors	148	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	149	and internal errors (bugs).
…		…
163		173
164	=item ev_tstamp ev_time ()	174	=item ev_tstamp ev_time ()
165		175
166	Returns the current time as libev would use it. Please note that the	176	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	177	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	178	you actually want to know. Also interesting is the combination of
		179	C<ev_now_update> and C<ev_now>.
169		180
170	=item ev_sleep (ev_tstamp interval)	181	=item ev_sleep (ev_tstamp interval)
171		182
172	Sleep for the given interval: The current thread will be blocked until	183	Sleep for the given interval: The current thread will be blocked
173	either it is interrupted or the given time interval has passed. Basically	184	until either it is interrupted or the given time interval has
		185	passed (approximately - it might return a bit earlier even if not
		186	interrupted). Returns immediately if C<< interval <= 0 >>.
		187
174	this is a sub-second-resolution C<sleep ()>.	188	Basically this is a sub-second-resolution C<sleep ()>.
		189
		190	The range of the C<interval> is limited - libev only guarantees to work
		191	with sleep times of up to one day (C<< interval <= 86400 >>).
175		192
176	=item int ev_version_major ()	193	=item int ev_version_major ()
177		194
178	=item int ev_version_minor ()	195	=item int ev_version_minor ()
179		196
…		…
190	as this indicates an incompatible change. Minor versions are usually	207	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	208	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	209	not a problem.
193		210
194	Example: Make sure we haven't accidentally been linked against the wrong	211	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	212	version (note, however, that this will not detect other ABI mismatches,
		213	such as LFS or reentrancy).
196		214
197	assert (("libev version mismatch",	215	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	216	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	217	&& ev_version_minor () >= EV_VERSION_MINOR));
200		218
…		…
211	assert (("sorry, no epoll, no sex",	229	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	230	ev_supported_backends () & EVBACKEND_EPOLL));
213		231
214	=item unsigned int ev_recommended_backends ()	232	=item unsigned int ev_recommended_backends ()
215		233
216	Return the set of all backends compiled into this binary of libev and also	234	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	235	also recommended for this platform, meaning it will work for most file
		236	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	237	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	238	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	239	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	240	probe for if you specify no backends explicitly.
222		241
223	=item unsigned int ev_embeddable_backends ()	242	=item unsigned int ev_embeddable_backends ()
224		243
225	Returns the set of backends that are embeddable in other event loops. This	244	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	245	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	246	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	247	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	248	& ev_supported_backends ()>, likewise for recommended ones.
230		249
231	See the description of C<ev_embed> watchers for more info.	250	See the description of C<ev_embed> watchers for more info.
232		251
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	252	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		253
235	Sets the allocation function to use (the prototype is similar - the	254	Sets the allocation function to use (the prototype is similar - the
236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	255	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
237	used to allocate and free memory (no surprises here). If it returns zero	256	used to allocate and free memory (no surprises here). If it returns zero
238	when memory needs to be allocated (C<size != 0>), the library might abort	257	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
264	}	283	}
265		284
266	...	285	...
267	ev_set_allocator (persistent_realloc);	286	ev_set_allocator (persistent_realloc);
268		287
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	288	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		289
271	Set the callback function to call on a retryable system call error (such	290	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	291	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	292	indicating the system call or subsystem causing the problem. If this
274	callback is set, then libev will expect it to remedy the situation, no	293	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	305	}
287		306
288	...	307	...
289	ev_set_syserr_cb (fatal_error);	308	ev_set_syserr_cb (fatal_error);
290		309
		310	=item ev_feed_signal (int signum)
		311
		312	This function can be used to "simulate" a signal receive. It is completely
		313	safe to call this function at any time, from any context, including signal
		314	handlers or random threads.
		315
		316	Its main use is to customise signal handling in your process, especially
		317	in the presence of threads. For example, you could block signals
		318	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		319	creating any loops), and in one thread, use C<sigwait> or any other
		320	mechanism to wait for signals, then "deliver" them to libev by calling
		321	C<ev_feed_signal>.
		322
291	=back	323	=back
292		324
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	325	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		326
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	327	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	328	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	329	libev 3 had an C<ev_loop> function colliding with the struct name).
298		330
299	The library knows two types of such loops, the I<default> loop, which	331	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	332	supports child process events, and dynamically created event loops which
301	not.	333	do not.
302		334
303	=over 4	335	=over 4
304		336
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	337	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		338
307	This will initialise the default event loop if it hasn't been initialised	339	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	340	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	341	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	342	C<ev_loop_new>.
		343
		344	If the default loop is already initialised then this function simply
		345	returns it (and ignores the flags. If that is troubling you, check
		346	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		347	flags, which should almost always be C<0>, unless the caller is also the
		348	one calling C<ev_run> or otherwise qualifies as "the main program".
311		349
312	If you don't know what event loop to use, use the one returned from this	350	If you don't know what event loop to use, use the one returned from this
313	function.	351	function (or via the C<EV_DEFAULT> macro).
314		352
315	Note that this function is I<not> thread-safe, so if you want to use it	353	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	354	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	355	that this case is unlikely, as loops cannot be shared easily between
		356	threads anyway).
318		357
319	The default loop is the only loop that can handle C<ev_signal> and	358	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	359	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	360	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	361	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	362	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	363
		364	Example: This is the most typical usage.
		365
		366	if (!ev_default_loop (0))
		367	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		368
		369	Example: Restrict libev to the select and poll backends, and do not allow
		370	environment settings to be taken into account:
		371
		372	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		373
		374	=item struct ev_loop *ev_loop_new (unsigned int flags)
		375
		376	This will create and initialise a new event loop object. If the loop
		377	could not be initialised, returns false.
		378
		379	This function is thread-safe, and one common way to use libev with
		380	threads is indeed to create one loop per thread, and using the default
		381	loop in the "main" or "initial" thread.
325		382
326	The flags argument can be used to specify special behaviour or specific	383	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	384	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		385
329	The following flags are supported:	386	The following flags are supported:
…		…
339		396
340	If this flag bit is or'ed into the flag value (or the program runs setuid	397	If this flag bit is or'ed into the flag value (or the program runs setuid
341	or setgid) then libev will I<not> look at the environment variable	398	or setgid) then libev will I<not> look at the environment variable
342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	399	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
343	override the flags completely if it is found in the environment. This is	400	override the flags completely if it is found in the environment. This is
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, to work
345	around bugs.	402	around bugs, or to make libev threadsafe (accessing environment variables
		403	cannot be done in a threadsafe way, but usually it works if no other
		404	thread modifies them).
346		405
347	=item C<EVFLAG_FORKCHECK>	406	=item C<EVFLAG_FORKCHECK>
348		407
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	408	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	409	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		410
353	This works by calling C<getpid ()> on every iteration of the loop,	411	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	412	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	413	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	414	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
362	flag.	420	flag.
363		421
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	422	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	423	environment variable.
366		424
		425	=item C<EVFLAG_NOINOTIFY>
		426
		427	When this flag is specified, then libev will not attempt to use the
		428	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		429	testing, this flag can be useful to conserve inotify file descriptors, as
		430	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		431
		432	=item C<EVFLAG_SIGNALFD>
		433
		434	When this flag is specified, then libev will attempt to use the
		435	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		436	delivers signals synchronously, which makes it both faster and might make
		437	it possible to get the queued signal data. It can also simplify signal
		438	handling with threads, as long as you properly block signals in your
		439	threads that are not interested in handling them.
		440
		441	Signalfd will not be used by default as this changes your signal mask, and
		442	there are a lot of shoddy libraries and programs (glib's threadpool for
		443	example) that can't properly initialise their signal masks.
		444
		445	=item C<EVFLAG_NOSIGMASK>
		446
		447	When this flag is specified, then libev will avoid to modify the signal
		448	mask. Specifically, this means you have to make sure signals are unblocked
		449	when you want to receive them.
		450
		451	This behaviour is useful when you want to do your own signal handling, or
		452	want to handle signals only in specific threads and want to avoid libev
		453	unblocking the signals.
		454
		455	It's also required by POSIX in a threaded program, as libev calls
		456	C<sigprocmask>, whose behaviour is officially unspecified.
		457
		458	This flag's behaviour will become the default in future versions of libev.
		459
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	460	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		461
369	This is your standard select(2) backend. Not I<completely> standard, as	462	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,	463	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	464	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	488	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	489	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		490
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	491	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		492
		493	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		494	kernels).
		495
400	For few fds, this backend is a bit little slower than poll and select,	496	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	497	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),	498	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).	499	fd), epoll scales either O(1) or O(active_fds).
404		500
405	The epoll mechanism deserves honorable mention as the most misdesigned	501	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	502	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	503	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	504	descriptor (and unnecessary guessing of parameters), problems with dup,
		505	returning before the timeout value, resulting in additional iterations
		506	(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	507	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	508	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	509	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	510	and is of course hard to detect.
413		511
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	512	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	513	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	514	totally I<different> file descriptors (even already closed ones, so
417	even remove them from the set) than registered in the set (especially	515	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	516	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	517	notifications by employing an additional generation counter and comparing
420	events to filter out spurious ones, recreating the set when required.	518	that against the events to filter out spurious ones, recreating the set
		519	when required. Epoll also erroneously rounds down timeouts, but gives you
		520	no way to know when and by how much, so sometimes you have to busy-wait
		521	because epoll returns immediately despite a nonzero timeout. And last
		522	not least, it also refuses to work with some file descriptors which work
		523	perfectly fine with C<select> (files, many character devices...).
		524
		525	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		526	cobbled together in a hurry, no thought to design or interaction with
		527	others. Oh, the pain, will it ever stop...
421		528
422	While stopping, setting and starting an I/O watcher in the same iteration	529	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	530	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	531	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	532	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
462		569
463	It scales in the same way as the epoll backend, but the interface to the	570	It scales in the same way as the epoll backend, but the interface to the
464	kernel is more efficient (which says nothing about its actual speed, of	571	kernel is more efficient (which says nothing about its actual speed, of
465	course). While stopping, setting and starting an I/O watcher does never	572	course). While stopping, setting and starting an I/O watcher does never
466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	573	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
467	two event changes per incident. Support for C<fork ()> is very bad (but	574	two event changes per incident. Support for C<fork ()> is very bad (you
468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	575	might have to leak fd's on fork, but it's more sane than epoll) and it
469	cases	576	drops fds silently in similarly hard-to-detect cases.
470		577
471	This backend usually performs well under most conditions.	578	This backend usually performs well under most conditions.
472		579
473	While nominally embeddable in other event loops, this doesn't work	580	While nominally embeddable in other event loops, this doesn't work
474	everywhere, so you might need to test for this. And since it is broken	581	everywhere, so you might need to test for this. And since it is broken
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	598	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		599
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	600	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)).	601	it's really slow, but it still scales very well (O(active_fds)).
495		602
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	603	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	604	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	605	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	606	might perform better.
504		607
505	On the positive side, with the exception of the spurious readiness	608	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	609	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	610	among the OS-specific backends (I vastly prefer correctness over speed
		611	hacks).
		612
		613	On the negative side, the interface is I<bizarre> - so bizarre that
		614	even sun itself gets it wrong in their code examples: The event polling
		615	function sometimes returns events to the caller even though an error
		616	occurred, but with no indication whether it has done so or not (yes, it's
		617	even documented that way) - deadly for edge-triggered interfaces where you
		618	absolutely have to know whether an event occurred or not because you have
		619	to re-arm the watcher.
		620
		621	Fortunately libev seems to be able to work around these idiocies.
509		622
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	623	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	624	C<EVBACKEND_POLL>.
512		625
513	=item C<EVBACKEND_ALL>	626	=item C<EVBACKEND_ALL>
514		627
515	Try all backends (even potentially broken ones that wouldn't be tried	628	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	629	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	630	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		631
519	It is definitely not recommended to use this flag.	632	It is definitely not recommended to use this flag, use whatever
		633	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		634	at all.
		635
		636	=item C<EVBACKEND_MASK>
		637
		638	Not a backend at all, but a mask to select all backend bits from a
		639	C<flags> value, in case you want to mask out any backends from a flags
		640	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		641
521	=back	642	=back
522		643
523	If one or more of these are or'ed into the flags value, then only these	644	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	645	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.	646	here). If none are specified, all backends in C<ev_recommended_backends
526		647	()> 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		648
555	Example: Try to create a event loop that uses epoll and nothing else.	649	Example: Try to create a event loop that uses epoll and nothing else.
556		650
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	651	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	652	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	653	fatal ("no epoll found here, maybe it hides under your chair");
560		654
		655	Example: Use whatever libev has to offer, but make sure that kqueue is
		656	used if available.
		657
		658	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		659
561	=item ev_default_destroy ()	660	=item ev_loop_destroy (loop)
562		661
563	Destroys the default loop again (frees all memory and kernel state	662	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	663	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	664	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>	665	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	666	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	667	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		669
571	Note that certain global state, such as signal state (and installed signal	670	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	671	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	672	as signal and child watchers) would need to be stopped manually.
574		673
575	In general it is not advisable to call this function except in the	674	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	675	C<ev_loop_new>, but it can also be used on the default loop returned by
		676	C<ev_default_loop>, in which case it is not thread-safe.
		677
		678	Note that it is not advisable to call this function on the default loop
		679	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	680	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>).	681	and C<ev_loop_destroy>.
579		682
580	=item ev_loop_destroy (loop)	683	=item ev_loop_fork (loop)
581		684
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	685	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	686	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	687	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	688	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	689	child before resuming or calling C<ev_run>.
592	functions, and it will only take effect at the next C<ev_loop> iteration.	690
		691	Again, you I<have> to call it on I<any> loop that you want to re-use after
		692	a fork, I<even if you do not plan to use the loop in the parent>. This is
		693	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		694	during fork.
593		695
594	On the other hand, you only need to call this function in the child	696	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	697	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.	698	you just fork+exec or create a new loop in the child, you don't have to
		699	call it at all (in fact, C<epoll> is so badly broken that it makes a
		700	difference, but libev will usually detect this case on its own and do a
		701	costly reset of the backend).
597		702
598	The function itself is quite fast and it's usually not a problem to call	703	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	704	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		705
		706	Example: Automate calling C<ev_loop_fork> on the default loop when
		707	using pthreads.
		708
		709	static void
		710	post_fork_child (void)
		711	{
		712	ev_loop_fork (EV_DEFAULT);
		713	}
		714
		715	...
602	pthread_atfork (0, 0, ev_default_fork);	716	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		717
611	=item int ev_is_default_loop (loop)	718	=item int ev_is_default_loop (loop)
612		719
613	Returns true when the given loop is, in fact, the default loop, and false	720	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	721	otherwise.
615		722
616	=item unsigned int ev_loop_count (loop)	723	=item unsigned int ev_iteration (loop)
617		724
618	Returns the count of loop iterations for the loop, which is identical to	725	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	726	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	727	and happily wraps around with enough iterations.
621		728
622	This value can sometimes be useful as a generation counter of sorts (it	729	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	730	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	731	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		732	prepare and check phases.
		733
		734	=item unsigned int ev_depth (loop)
		735
		736	Returns the number of times C<ev_run> was entered minus the number of
		737	times C<ev_run> was exited normally, in other words, the recursion depth.
		738
		739	Outside C<ev_run>, this number is zero. In a callback, this number is
		740	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		741	in which case it is higher.
		742
		743	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		744	throwing an exception etc.), doesn't count as "exit" - consider this
		745	as a hint to avoid such ungentleman-like behaviour unless it's really
		746	convenient, in which case it is fully supported.
625		747
626	=item unsigned int ev_backend (loop)	748	=item unsigned int ev_backend (loop)
627		749
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	750	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	751	use.
…		…
638		760
639	=item ev_now_update (loop)	761	=item ev_now_update (loop)
640		762
641	Establishes the current time by querying the kernel, updating the time	763	Establishes the current time by querying the kernel, updating the time
642	returned by C<ev_now ()> in the progress. This is a costly operation and	764	returned by C<ev_now ()> in the progress. This is a costly operation and
643	is usually done automatically within C<ev_loop ()>.	765	is usually done automatically within C<ev_run ()>.
644		766
645	This function is rarely useful, but when some event callback runs for a	767	This function is rarely useful, but when some event callback runs for a
646	very long time without entering the event loop, updating libev's idea of	768	very long time without entering the event loop, updating libev's idea of
647	the current time is a good idea.	769	the current time is a good idea.
648		770
649	See also L<The special problem of time updates> in the C<ev_timer> section.	771	See also L</The special problem of time updates> in the C<ev_timer> section.
650		772
651	=item ev_suspend (loop)	773	=item ev_suspend (loop)
652		774
653	=item ev_resume (loop)	775	=item ev_resume (loop)
654		776
655	These two functions suspend and resume a loop, for use when the loop is	777	These two functions suspend and resume an event loop, for use when the
656	not used for a while and timeouts should not be processed.	778	loop is not used for a while and timeouts should not be processed.
657		779
658	A typical use case would be an interactive program such as a game: When	780	A typical use case would be an interactive program such as a game: When
659	the user presses C<^Z> to suspend the game and resumes it an hour later it	781	the user presses C<^Z> to suspend the game and resumes it an hour later it
660	would be best to handle timeouts as if no time had actually passed while	782	would be best to handle timeouts as if no time had actually passed while
661	the program was suspended. This can be achieved by calling C<ev_suspend>	783	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
663	C<ev_resume> directly afterwards to resume timer processing.	785	C<ev_resume> directly afterwards to resume timer processing.
664		786
665	Effectively, all C<ev_timer> watchers will be delayed by the time spend	787	Effectively, all C<ev_timer> watchers will be delayed by the time spend
666	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	788	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
667	will be rescheduled (that is, they will lose any events that would have	789	will be rescheduled (that is, they will lose any events that would have
668	occured while suspended).	790	occurred while suspended).
669		791
670	After calling C<ev_suspend> you B<must not> call I<any> function on the	792	After calling C<ev_suspend> you B<must not> call I<any> function on the
671	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	793	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
672	without a previous call to C<ev_suspend>.	794	without a previous call to C<ev_suspend>.
673		795
674	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	796	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
675	event loop time (see C<ev_now_update>).	797	event loop time (see C<ev_now_update>).
676		798
677	=item ev_loop (loop, int flags)	799	=item bool ev_run (loop, int flags)
678		800
679	Finally, this is it, the event handler. This function usually is called	801	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	802	after you have initialised all your watchers and you want to start
681	events.	803	handling events. It will ask the operating system for any new events, call
		804	the watcher callbacks, and then repeat the whole process indefinitely: This
		805	is why event loops are called I<loops>.
682		806
683	If the flags argument is specified as C<0>, it will not return until	807	If the flags argument is specified as C<0>, it will keep handling events
684	either no event watchers are active anymore or C<ev_unloop> was called.	808	until either no event watchers are active anymore or C<ev_break> was
		809	called.
685		810
		811	The return value is false if there are no more active watchers (which
		812	usually means "all jobs done" or "deadlock"), and true in all other cases
		813	(which usually means " you should call C<ev_run> again").
		814
686	Please note that an explicit C<ev_unloop> is usually better than	815	Please note that an explicit C<ev_break> is usually better than
687	relying on all watchers to be stopped when deciding when a program has	816	relying on all watchers to be stopped when deciding when a program has
688	finished (especially in interactive programs), but having a program	817	finished (especially in interactive programs), but having a program
689	that automatically loops as long as it has to and no longer by virtue	818	that automatically loops as long as it has to and no longer by virtue
690	of relying on its watchers stopping correctly, that is truly a thing of	819	of relying on its watchers stopping correctly, that is truly a thing of
691	beauty.	820	beauty.
692		821
		822	This function is I<mostly> exception-safe - you can break out of a
		823	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		824	exception and so on. This does not decrement the C<ev_depth> value, nor
		825	will it clear any outstanding C<EVBREAK_ONE> breaks.
		826
693	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	827	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
694	those events and any already outstanding ones, but will not block your	828	those events and any already outstanding ones, but will not wait and
695	process in case there are no events and will return after one iteration of	829	block your process in case there are no events and will return after one
696	the loop.	830	iteration of the loop. This is sometimes useful to poll and handle new
		831	events while doing lengthy calculations, to keep the program responsive.
697		832
698	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	833	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
699	necessary) and will handle those and any already outstanding ones. It	834	necessary) and will handle those and any already outstanding ones. It
700	will block your process until at least one new event arrives (which could	835	will block your process until at least one new event arrives (which could
701	be an event internal to libev itself, so there is no guarantee that a	836	be an event internal to libev itself, so there is no guarantee that a
702	user-registered callback will be called), and will return after one	837	user-registered callback will be called), and will return after one
703	iteration of the loop.	838	iteration of the loop.
704		839
705	This is useful if you are waiting for some external event in conjunction	840	This is useful if you are waiting for some external event in conjunction
706	with something not expressible using other libev watchers (i.e. "roll your	841	with something not expressible using other libev watchers (i.e. "roll your
707	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	842	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
708	usually a better approach for this kind of thing.	843	usually a better approach for this kind of thing.
709		844
710	Here are the gory details of what C<ev_loop> does:	845	Here are the gory details of what C<ev_run> does (this is for your
		846	understanding, not a guarantee that things will work exactly like this in
		847	future versions):
711		848
		849	- Increment loop depth.
		850	- Reset the ev_break status.
712	- Before the first iteration, call any pending watchers.	851	- Before the first iteration, call any pending watchers.
		852	LOOP:
713	* If EVFLAG_FORKCHECK was used, check for a fork.	853	- If EVFLAG_FORKCHECK was used, check for a fork.
714	- If a fork was detected (by any means), queue and call all fork watchers.	854	- If a fork was detected (by any means), queue and call all fork watchers.
715	- Queue and call all prepare watchers.	855	- Queue and call all prepare watchers.
		856	- If ev_break was called, goto FINISH.
716	- If we have been forked, detach and recreate the kernel state	857	- If we have been forked, detach and recreate the kernel state
717	as to not disturb the other process.	858	as to not disturb the other process.
718	- Update the kernel state with all outstanding changes.	859	- Update the kernel state with all outstanding changes.
719	- Update the "event loop time" (ev_now ()).	860	- Update the "event loop time" (ev_now ()).
720	- Calculate for how long to sleep or block, if at all	861	- Calculate for how long to sleep or block, if at all
721	(active idle watchers, EVLOOP_NONBLOCK or not having	862	(active idle watchers, EVRUN_NOWAIT or not having
722	any active watchers at all will result in not sleeping).	863	any active watchers at all will result in not sleeping).
723	- Sleep if the I/O and timer collect interval say so.	864	- Sleep if the I/O and timer collect interval say so.
		865	- Increment loop iteration counter.
724	- Block the process, waiting for any events.	866	- Block the process, waiting for any events.
725	- Queue all outstanding I/O (fd) events.	867	- Queue all outstanding I/O (fd) events.
726	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	868	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
727	- Queue all expired timers.	869	- Queue all expired timers.
728	- Queue all expired periodics.	870	- Queue all expired periodics.
729	- Unless any events are pending now, queue all idle watchers.	871	- Queue all idle watchers with priority higher than that of pending events.
730	- Queue all check watchers.	872	- Queue all check watchers.
731	- Call all queued watchers in reverse order (i.e. check watchers first).	873	- Call all queued watchers in reverse order (i.e. check watchers first).
732	Signals and child watchers are implemented as I/O watchers, and will	874	Signals and child watchers are implemented as I/O watchers, and will
733	be handled here by queueing them when their watcher gets executed.	875	be handled here by queueing them when their watcher gets executed.
734	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	876	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
735	were used, or there are no active watchers, return, otherwise	877	were used, or there are no active watchers, goto FINISH, otherwise
736	continue with step *.	878	continue with step LOOP.
		879	FINISH:
		880	- Reset the ev_break status iff it was EVBREAK_ONE.
		881	- Decrement the loop depth.
		882	- Return.
737		883
738	Example: Queue some jobs and then loop until no events are outstanding	884	Example: Queue some jobs and then loop until no events are outstanding
739	anymore.	885	anymore.
740		886
741	... queue jobs here, make sure they register event watchers as long	887	... queue jobs here, make sure they register event watchers as long
742	... as they still have work to do (even an idle watcher will do..)	888	... as they still have work to do (even an idle watcher will do..)
743	ev_loop (my_loop, 0);	889	ev_run (my_loop, 0);
744	... jobs done or somebody called unloop. yeah!	890	... jobs done or somebody called break. yeah!
745		891
746	=item ev_unloop (loop, how)	892	=item ev_break (loop, how)
747		893
748	Can be used to make a call to C<ev_loop> return early (but only after it	894	Can be used to make a call to C<ev_run> return early (but only after it
749	has processed all outstanding events). The C<how> argument must be either	895	has processed all outstanding events). The C<how> argument must be either
750	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	896	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
751	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	897	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
752		898
753	This "unloop state" will be cleared when entering C<ev_loop> again.	899	This "break state" will be cleared on the next call to C<ev_run>.
754		900
755	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	901	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		902	which case it will have no effect.
756		903
757	=item ev_ref (loop)	904	=item ev_ref (loop)
758		905
759	=item ev_unref (loop)	906	=item ev_unref (loop)
760		907
761	Ref/unref can be used to add or remove a reference count on the event	908	Ref/unref can be used to add or remove a reference count on the event
762	loop: Every watcher keeps one reference, and as long as the reference	909	loop: Every watcher keeps one reference, and as long as the reference
763	count is nonzero, C<ev_loop> will not return on its own.	910	count is nonzero, C<ev_run> will not return on its own.
764		911
765	If you have a watcher you never unregister that should not keep C<ev_loop>	912	This is useful when you have a watcher that you never intend to
766	from returning, call ev_unref() after starting, and ev_ref() before	913	unregister, but that nevertheless should not keep C<ev_run> from
		914	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
767	stopping it.	915	before stopping it.
768		916
769	As an example, libev itself uses this for its internal signal pipe: It	917	As an example, libev itself uses this for its internal signal pipe: It
770	is not visible to the libev user and should not keep C<ev_loop> from	918	is not visible to the libev user and should not keep C<ev_run> from
771	exiting if no event watchers registered by it are active. It is also an	919	exiting if no event watchers registered by it are active. It is also an
772	excellent way to do this for generic recurring timers or from within	920	excellent way to do this for generic recurring timers or from within
773	third-party libraries. Just remember to I<unref after start> and I<ref	921	third-party libraries. Just remember to I<unref after start> and I<ref
774	before stop> (but only if the watcher wasn't active before, or was active	922	before stop> (but only if the watcher wasn't active before, or was active
775	before, respectively. Note also that libev might stop watchers itself	923	before, respectively. Note also that libev might stop watchers itself
776	(e.g. non-repeating timers) in which case you have to C<ev_ref>	924	(e.g. non-repeating timers) in which case you have to C<ev_ref>
777	in the callback).	925	in the callback).
778		926
779	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	927	Example: Create a signal watcher, but keep it from keeping C<ev_run>
780	running when nothing else is active.	928	running when nothing else is active.
781		929
782	ev_signal exitsig;	930	ev_signal exitsig;
783	ev_signal_init (&exitsig, sig_cb, SIGINT);	931	ev_signal_init (&exitsig, sig_cb, SIGINT);
784	ev_signal_start (loop, &exitsig);	932	ev_signal_start (loop, &exitsig);
785	evf_unref (loop);	933	ev_unref (loop);
786		934
787	Example: For some weird reason, unregister the above signal handler again.	935	Example: For some weird reason, unregister the above signal handler again.
788		936
789	ev_ref (loop);	937	ev_ref (loop);
790	ev_signal_stop (loop, &exitsig);	938	ev_signal_stop (loop, &exitsig);
…		…
810	overhead for the actual polling but can deliver many events at once.	958	overhead for the actual polling but can deliver many events at once.
811		959
812	By setting a higher I<io collect interval> you allow libev to spend more	960	By setting a higher I<io collect interval> you allow libev to spend more
813	time collecting I/O events, so you can handle more events per iteration,	961	time collecting I/O events, so you can handle more events per iteration,
814	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	962	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
815	C<ev_timer>) will be not affected. Setting this to a non-null value will	963	C<ev_timer>) will not be affected. Setting this to a non-null value will
816	introduce an additional C<ev_sleep ()> call into most loop iterations.	964	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		965	sleep time ensures that libev will not poll for I/O events more often then
		966	once per this interval, on average (as long as the host time resolution is
		967	good enough).
817		968
818	Likewise, by setting a higher I<timeout collect interval> you allow libev	969	Likewise, by setting a higher I<timeout collect interval> you allow libev
819	to spend more time collecting timeouts, at the expense of increased	970	to spend more time collecting timeouts, at the expense of increased
820	latency/jitter/inexactness (the watcher callback will be called	971	latency/jitter/inexactness (the watcher callback will be called
821	later). C<ev_io> watchers will not be affected. Setting this to a non-null	972	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
823		974
824	Many (busy) programs can usually benefit by setting the I/O collect	975	Many (busy) programs can usually benefit by setting the I/O collect
825	interval to a value near C<0.1> or so, which is often enough for	976	interval to a value near C<0.1> or so, which is often enough for
826	interactive servers (of course not for games), likewise for timeouts. It	977	interactive servers (of course not for games), likewise for timeouts. It
827	usually doesn't make much sense to set it to a lower value than C<0.01>,	978	usually doesn't make much sense to set it to a lower value than C<0.01>,
828	as this approaches the timing granularity of most systems.	979	as this approaches the timing granularity of most systems. Note that if
		980	you do transactions with the outside world and you can't increase the
		981	parallelity, then this setting will limit your transaction rate (if you
		982	need to poll once per transaction and the I/O collect interval is 0.01,
		983	then you can't do more than 100 transactions per second).
829		984
830	Setting the I<timeout collect interval> can improve the opportunity for	985	Setting the I<timeout collect interval> can improve the opportunity for
831	saving power, as the program will "bundle" timer callback invocations that	986	saving power, as the program will "bundle" timer callback invocations that
832	are "near" in time together, by delaying some, thus reducing the number of	987	are "near" in time together, by delaying some, thus reducing the number of
833	times the process sleeps and wakes up again. Another useful technique to	988	times the process sleeps and wakes up again. Another useful technique to
834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	989	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
835	they fire on, say, one-second boundaries only.	990	they fire on, say, one-second boundaries only.
836		991
		992	Example: we only need 0.1s timeout granularity, and we wish not to poll
		993	more often than 100 times per second:
		994
		995	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		996	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		997
		998	=item ev_invoke_pending (loop)
		999
		1000	This call will simply invoke all pending watchers while resetting their
		1001	pending state. Normally, C<ev_run> does this automatically when required,
		1002	but when overriding the invoke callback this call comes handy. This
		1003	function can be invoked from a watcher - this can be useful for example
		1004	when you want to do some lengthy calculation and want to pass further
		1005	event handling to another thread (you still have to make sure only one
		1006	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1007
		1008	=item int ev_pending_count (loop)
		1009
		1010	Returns the number of pending watchers - zero indicates that no watchers
		1011	are pending.
		1012
		1013	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1014
		1015	This overrides the invoke pending functionality of the loop: Instead of
		1016	invoking all pending watchers when there are any, C<ev_run> will call
		1017	this callback instead. This is useful, for example, when you want to
		1018	invoke the actual watchers inside another context (another thread etc.).
		1019
		1020	If you want to reset the callback, use C<ev_invoke_pending> as new
		1021	callback.
		1022
		1023	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1024
		1025	Sometimes you want to share the same loop between multiple threads. This
		1026	can be done relatively simply by putting mutex_lock/unlock calls around
		1027	each call to a libev function.
		1028
		1029	However, C<ev_run> can run an indefinite time, so it is not feasible
		1030	to wait for it to return. One way around this is to wake up the event
		1031	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1032	I<release> and I<acquire> callbacks on the loop.
		1033
		1034	When set, then C<release> will be called just before the thread is
		1035	suspended waiting for new events, and C<acquire> is called just
		1036	afterwards.
		1037
		1038	Ideally, C<release> will just call your mutex_unlock function, and
		1039	C<acquire> will just call the mutex_lock function again.
		1040
		1041	While event loop modifications are allowed between invocations of
		1042	C<release> and C<acquire> (that's their only purpose after all), no
		1043	modifications done will affect the event loop, i.e. adding watchers will
		1044	have no effect on the set of file descriptors being watched, or the time
		1045	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1046	to take note of any changes you made.
		1047
		1048	In theory, threads executing C<ev_run> will be async-cancel safe between
		1049	invocations of C<release> and C<acquire>.
		1050
		1051	See also the locking example in the C<THREADS> section later in this
		1052	document.
		1053
		1054	=item ev_set_userdata (loop, void *data)
		1055
		1056	=item void *ev_userdata (loop)
		1057
		1058	Set and retrieve a single C<void *> associated with a loop. When
		1059	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1060	C<0>.
		1061
		1062	These two functions can be used to associate arbitrary data with a loop,
		1063	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1064	C<acquire> callbacks described above, but of course can be (ab-)used for
		1065	any other purpose as well.
		1066
837	=item ev_loop_verify (loop)	1067	=item ev_verify (loop)
838		1068
839	This function only does something when C<EV_VERIFY> support has been	1069	This function only does something when C<EV_VERIFY> support has been
840	compiled in, which is the default for non-minimal builds. It tries to go	1070	compiled in, which is the default for non-minimal builds. It tries to go
841	through all internal structures and checks them for validity. If anything	1071	through all internal structures and checks them for validity. If anything
842	is found to be inconsistent, it will print an error message to standard	1072	is found to be inconsistent, it will print an error message to standard
…		…
853		1083
854	In the following description, uppercase C<TYPE> in names stands for the	1084	In the following description, uppercase C<TYPE> in names stands for the
855	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1085	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
856	watchers and C<ev_io_start> for I/O watchers.	1086	watchers and C<ev_io_start> for I/O watchers.
857		1087
858	A watcher is a structure that you create and register to record your	1088	A watcher is an opaque structure that you allocate and register to record
859	interest in some event. For instance, if you want to wait for STDIN to	1089	your interest in some event. To make a concrete example, imagine you want
860	become readable, you would create an C<ev_io> watcher for that:	1090	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1091	for that:
861		1092
862	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1093	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
863	{	1094	{
864	ev_io_stop (w);	1095	ev_io_stop (w);
865	ev_unloop (loop, EVUNLOOP_ALL);	1096	ev_break (loop, EVBREAK_ALL);
866	}	1097	}
867		1098
868	struct ev_loop *loop = ev_default_loop (0);	1099	struct ev_loop *loop = ev_default_loop (0);
869		1100
870	ev_io stdin_watcher;	1101	ev_io stdin_watcher;
871		1102
872	ev_init (&stdin_watcher, my_cb);	1103	ev_init (&stdin_watcher, my_cb);
873	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1104	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
874	ev_io_start (loop, &stdin_watcher);	1105	ev_io_start (loop, &stdin_watcher);
875		1106
876	ev_loop (loop, 0);	1107	ev_run (loop, 0);
877		1108
878	As you can see, you are responsible for allocating the memory for your	1109	As you can see, you are responsible for allocating the memory for your
879	watcher structures (and it is I<usually> a bad idea to do this on the	1110	watcher structures (and it is I<usually> a bad idea to do this on the
880	stack).	1111	stack).
881		1112
882	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1113	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
883	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1114	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
884		1115
885	Each watcher structure must be initialised by a call to C<ev_init	1116	Each watcher structure must be initialised by a call to C<ev_init (watcher
886	(watcher *, callback)>, which expects a callback to be provided. This	1117	*, callback)>, which expects a callback to be provided. This callback is
887	callback gets invoked each time the event occurs (or, in the case of I/O	1118	invoked each time the event occurs (or, in the case of I/O watchers, each
888	watchers, each time the event loop detects that the file descriptor given	1119	time the event loop detects that the file descriptor given is readable
889	is readable and/or writable).	1120	and/or writable).
890		1121
891	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1122	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
892	macro to configure it, with arguments specific to the watcher type. There	1123	macro to configure it, with arguments specific to the watcher type. There
893	is also a macro to combine initialisation and setting in one call: C<<	1124	is also a macro to combine initialisation and setting in one call: C<<
894	ev_TYPE_init (watcher *, callback, ...) >>.	1125	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
917	=item C<EV_WRITE>	1148	=item C<EV_WRITE>
918		1149
919	The file descriptor in the C<ev_io> watcher has become readable and/or	1150	The file descriptor in the C<ev_io> watcher has become readable and/or
920	writable.	1151	writable.
921		1152
922	=item C<EV_TIMEOUT>	1153	=item C<EV_TIMER>
923		1154
924	The C<ev_timer> watcher has timed out.	1155	The C<ev_timer> watcher has timed out.
925		1156
926	=item C<EV_PERIODIC>	1157	=item C<EV_PERIODIC>
927		1158
…		…
945		1176
946	=item C<EV_PREPARE>	1177	=item C<EV_PREPARE>
947		1178
948	=item C<EV_CHECK>	1179	=item C<EV_CHECK>
949		1180
950	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1181	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
951	to gather new events, and all C<ev_check> watchers are invoked just after	1182	gather new events, and all C<ev_check> watchers are queued (not invoked)
952	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1183	just after C<ev_run> has gathered them, but before it queues any callbacks
		1184	for any received events. That means C<ev_prepare> watchers are the last
		1185	watchers invoked before the event loop sleeps or polls for new events, and
		1186	C<ev_check> watchers will be invoked before any other watchers of the same
		1187	or lower priority within an event loop iteration.
		1188
953	received events. Callbacks of both watcher types can start and stop as	1189	Callbacks of both watcher types can start and stop as many watchers as
954	many watchers as they want, and all of them will be taken into account	1190	they want, and all of them will be taken into account (for example, a
955	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1191	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
956	C<ev_loop> from blocking).	1192	blocking).
957		1193
958	=item C<EV_EMBED>	1194	=item C<EV_EMBED>
959		1195
960	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1196	The embedded event loop specified in the C<ev_embed> watcher needs attention.
961		1197
962	=item C<EV_FORK>	1198	=item C<EV_FORK>
963		1199
964	The event loop has been resumed in the child process after fork (see	1200	The event loop has been resumed in the child process after fork (see
965	C<ev_fork>).	1201	C<ev_fork>).
		1202
		1203	=item C<EV_CLEANUP>
		1204
		1205	The event loop is about to be destroyed (see C<ev_cleanup>).
966		1206
967	=item C<EV_ASYNC>	1207	=item C<EV_ASYNC>
968		1208
969	The given async watcher has been asynchronously notified (see C<ev_async>).	1209	The given async watcher has been asynchronously notified (see C<ev_async>).
970		1210
…		…
1017		1257
1018	ev_io w;	1258	ev_io w;
1019	ev_init (&w, my_cb);	1259	ev_init (&w, my_cb);
1020	ev_io_set (&w, STDIN_FILENO, EV_READ);	1260	ev_io_set (&w, STDIN_FILENO, EV_READ);
1021		1261
1022	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1262	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1023		1263
1024	This macro initialises the type-specific parts of a watcher. You need to	1264	This macro initialises the type-specific parts of a watcher. You need to
1025	call C<ev_init> at least once before you call this macro, but you can	1265	call C<ev_init> at least once before you call this macro, but you can
1026	call C<ev_TYPE_set> any number of times. You must not, however, call this	1266	call C<ev_TYPE_set> any number of times. You must not, however, call this
1027	macro on a watcher that is active (it can be pending, however, which is a	1267	macro on a watcher that is active (it can be pending, however, which is a
…		…
1040		1280
1041	Example: Initialise and set an C<ev_io> watcher in one step.	1281	Example: Initialise and set an C<ev_io> watcher in one step.
1042		1282
1043	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1283	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1044		1284
1045	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1285	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1046		1286
1047	Starts (activates) the given watcher. Only active watchers will receive	1287	Starts (activates) the given watcher. Only active watchers will receive
1048	events. If the watcher is already active nothing will happen.	1288	events. If the watcher is already active nothing will happen.
1049		1289
1050	Example: Start the C<ev_io> watcher that is being abused as example in this	1290	Example: Start the C<ev_io> watcher that is being abused as example in this
1051	whole section.	1291	whole section.
1052		1292
1053	ev_io_start (EV_DEFAULT_UC, &w);	1293	ev_io_start (EV_DEFAULT_UC, &w);
1054		1294
1055	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1295	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1056		1296
1057	Stops the given watcher if active, and clears the pending status (whether	1297	Stops the given watcher if active, and clears the pending status (whether
1058	the watcher was active or not).	1298	the watcher was active or not).
1059		1299
1060	It is possible that stopped watchers are pending - for example,	1300	It is possible that stopped watchers are pending - for example,
…		…
1080		1320
1081	=item callback ev_cb (ev_TYPE *watcher)	1321	=item callback ev_cb (ev_TYPE *watcher)
1082		1322
1083	Returns the callback currently set on the watcher.	1323	Returns the callback currently set on the watcher.
1084		1324
1085	=item ev_cb_set (ev_TYPE *watcher, callback)	1325	=item ev_set_cb (ev_TYPE *watcher, callback)
1086		1326
1087	Change the callback. You can change the callback at virtually any time	1327	Change the callback. You can change the callback at virtually any time
1088	(modulo threads).	1328	(modulo threads).
1089		1329
1090	=item ev_set_priority (ev_TYPE *watcher, priority)	1330	=item ev_set_priority (ev_TYPE *watcher, int priority)
1091		1331
1092	=item int ev_priority (ev_TYPE *watcher)	1332	=item int ev_priority (ev_TYPE *watcher)
1093		1333
1094	Set and query the priority of the watcher. The priority is a small	1334	Set and query the priority of the watcher. The priority is a small
1095	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1335	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1108	or might not have been clamped to the valid range.	1348	or might not have been clamped to the valid range.
1109		1349
1110	The default priority used by watchers when no priority has been set is	1350	The default priority used by watchers when no priority has been set is
1111	always C<0>, which is supposed to not be too high and not be too low :).	1351	always C<0>, which is supposed to not be too high and not be too low :).
1112		1352
1113	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1353	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1114	priorities.	1354	priorities.
1115		1355
1116	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1356	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1117		1357
1118	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1358	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1127	watcher isn't pending it does nothing and returns C<0>.	1367	watcher isn't pending it does nothing and returns C<0>.
1128		1368
1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1369	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1130	callback to be invoked, which can be accomplished with this function.	1370	callback to be invoked, which can be accomplished with this function.
1131		1371
		1372	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1373
		1374	Feeds the given event set into the event loop, as if the specified event
		1375	had happened for the specified watcher (which must be a pointer to an
		1376	initialised but not necessarily started event watcher). Obviously you must
		1377	not free the watcher as long as it has pending events.
		1378
		1379	Stopping the watcher, letting libev invoke it, or calling
		1380	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1381	not started in the first place.
		1382
		1383	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1384	functions that do not need a watcher.
		1385
1132	=back	1386	=back
1133		1387
		1388	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1389	OWN COMPOSITE WATCHERS> idioms.
1134		1390
1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1391	=head2 WATCHER STATES
1136		1392
1137	Each watcher has, by default, a member C<void *data> that you can change	1393	There are various watcher states mentioned throughout this manual -
1138	and read at any time: libev will completely ignore it. This can be used	1394	active, pending and so on. In this section these states and the rules to
1139	to associate arbitrary data with your watcher. If you need more data and	1395	transition between them will be described in more detail - and while these
1140	don't want to allocate memory and store a pointer to it in that data	1396	rules might look complicated, they usually do "the right thing".
1141	member, you can also "subclass" the watcher type and provide your own
1142	data:
1143		1397
1144	struct my_io	1398	=over 4
1145	{
1146	ev_io io;
1147	int otherfd;
1148	void *somedata;
1149	struct whatever *mostinteresting;
1150	};
1151		1399
1152	...	1400	=item initialised
1153	struct my_io w;
1154	ev_io_init (&w.io, my_cb, fd, EV_READ);
1155		1401
1156	And since your callback will be called with a pointer to the watcher, you	1402	Before a watcher can be registered with the event loop it has to be
1157	can cast it back to your own type:	1403	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1404	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1158		1405
1159	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1406	In this state it is simply some block of memory that is suitable for
1160	{	1407	use in an event loop. It can be moved around, freed, reused etc. at
1161	struct my_io *w = (struct my_io *)w_;	1408	will - as long as you either keep the memory contents intact, or call
1162	...	1409	C<ev_TYPE_init> again.
1163	}
1164		1410
1165	More interesting and less C-conformant ways of casting your callback type	1411	=item started/running/active
1166	instead have been omitted.
1167		1412
1168	Another common scenario is to use some data structure with multiple	1413	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1169	embedded watchers:	1414	property of the event loop, and is actively waiting for events. While in
		1415	this state it cannot be accessed (except in a few documented ways), moved,
		1416	freed or anything else - the only legal thing is to keep a pointer to it,
		1417	and call libev functions on it that are documented to work on active watchers.
1170		1418
1171	struct my_biggy	1419	=item pending
1172	{
1173	int some_data;
1174	ev_timer t1;
1175	ev_timer t2;
1176	}
1177		1420
1178	In this case getting the pointer to C<my_biggy> is a bit more	1421	If a watcher is active and libev determines that an event it is interested
1179	complicated: Either you store the address of your C<my_biggy> struct	1422	in has occurred (such as a timer expiring), it will become pending. It will
1180	in the C<data> member of the watcher (for woozies), or you need to use	1423	stay in this pending state until either it is stopped or its callback is
1181	some pointer arithmetic using C<offsetof> inside your watchers (for real	1424	about to be invoked, so it is not normally pending inside the watcher
1182	programmers):	1425	callback.
1183		1426
1184	#include <stddef.h>	1427	The watcher might or might not be active while it is pending (for example,
		1428	an expired non-repeating timer can be pending but no longer active). If it
		1429	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1430	but it is still property of the event loop at this time, so cannot be
		1431	moved, freed or reused. And if it is active the rules described in the
		1432	previous item still apply.
1185		1433
1186	static void	1434	It is also possible to feed an event on a watcher that is not active (e.g.
1187	t1_cb (EV_P_ ev_timer *w, int revents)	1435	via C<ev_feed_event>), in which case it becomes pending without being
1188	{	1436	active.
1189	struct my_biggy big = (struct my_biggy *)
1190	(((char *)w) - offsetof (struct my_biggy, t1));
1191	}
1192		1437
1193	static void	1438	=item stopped
1194	t2_cb (EV_P_ ev_timer *w, int revents)	1439
1195	{	1440	A watcher can be stopped implicitly by libev (in which case it might still
1196	struct my_biggy big = (struct my_biggy *)	1441	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1197	(((char *)w) - offsetof (struct my_biggy, t2));	1442	latter will clear any pending state the watcher might be in, regardless
1198	}	1443	of whether it was active or not, so stopping a watcher explicitly before
		1444	freeing it is often a good idea.
		1445
		1446	While stopped (and not pending) the watcher is essentially in the
		1447	initialised state, that is, it can be reused, moved, modified in any way
		1448	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1449	it again).
		1450
		1451	=back
1199		1452
1200	=head2 WATCHER PRIORITY MODELS	1453	=head2 WATCHER PRIORITY MODELS
1201		1454
1202	Many event loops support I<watcher priorities>, which are usually small	1455	Many event loops support I<watcher priorities>, which are usually small
1203	integers that influence the ordering of event callback invocation	1456	integers that influence the ordering of event callback invocation
…		…
1246		1499
1247	For example, to emulate how many other event libraries handle priorities,	1500	For example, to emulate how many other event libraries handle priorities,
1248	you can associate an C<ev_idle> watcher to each such watcher, and in	1501	you can associate an C<ev_idle> watcher to each such watcher, and in
1249	the normal watcher callback, you just start the idle watcher. The real	1502	the normal watcher callback, you just start the idle watcher. The real
1250	processing is done in the idle watcher callback. This causes libev to	1503	processing is done in the idle watcher callback. This causes libev to
1251	continously poll and process kernel event data for the watcher, but when	1504	continuously poll and process kernel event data for the watcher, but when
1252	the lock-out case is known to be rare (which in turn is rare :), this is	1505	the lock-out case is known to be rare (which in turn is rare :), this is
1253	workable.	1506	workable.
1254		1507
1255	Usually, however, the lock-out model implemented that way will perform	1508	Usually, however, the lock-out model implemented that way will perform
1256	miserably under the type of load it was designed to handle. In that case,	1509	miserably under the type of load it was designed to handle. In that case,
…		…
1270	{	1523	{
1271	// stop the I/O watcher, we received the event, but	1524	// stop the I/O watcher, we received the event, but
1272	// are not yet ready to handle it.	1525	// are not yet ready to handle it.
1273	ev_io_stop (EV_A_ w);	1526	ev_io_stop (EV_A_ w);
1274		1527
1275	// start the idle watcher to ahndle the actual event.	1528	// start the idle watcher to handle the actual event.
1276	// it will not be executed as long as other watchers	1529	// it will not be executed as long as other watchers
1277	// with the default priority are receiving events.	1530	// with the default priority are receiving events.
1278	ev_idle_start (EV_A_ &idle);	1531	ev_idle_start (EV_A_ &idle);
1279	}	1532	}
1280		1533
…		…
1330	In general you can register as many read and/or write event watchers per	1583	In general you can register as many read and/or write event watchers per
1331	fd as you want (as long as you don't confuse yourself). Setting all file	1584	fd as you want (as long as you don't confuse yourself). Setting all file
1332	descriptors to non-blocking mode is also usually a good idea (but not	1585	descriptors to non-blocking mode is also usually a good idea (but not
1333	required if you know what you are doing).	1586	required if you know what you are doing).
1334		1587
1335	If you cannot use non-blocking mode, then force the use of a
1336	known-to-be-good backend (at the time of this writing, this includes only
1337	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1338	descriptors for which non-blocking operation makes no sense (such as
1339	files) - libev doesn't guarentee any specific behaviour in that case.
1340
1341	Another thing you have to watch out for is that it is quite easy to	1588	Another thing you have to watch out for is that it is quite easy to
1342	receive "spurious" readiness notifications, that is your callback might	1589	receive "spurious" readiness notifications, that is, your callback might
1343	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1590	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1344	because there is no data. Not only are some backends known to create a	1591	because there is no data. It is very easy to get into this situation even
1345	lot of those (for example Solaris ports), it is very easy to get into	1592	with a relatively standard program structure. Thus it is best to always
1346	this situation even with a relatively standard program structure. Thus	1593	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1347	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1348	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1594	preferable to a program hanging until some data arrives.
1349		1595
1350	If you cannot run the fd in non-blocking mode (for example you should	1596	If you cannot run the fd in non-blocking mode (for example you should
1351	not play around with an Xlib connection), then you have to separately	1597	not play around with an Xlib connection), then you have to separately
1352	re-test whether a file descriptor is really ready with a known-to-be good	1598	re-test whether a file descriptor is really ready with a known-to-be good
1353	interface such as poll (fortunately in our Xlib example, Xlib already	1599	interface such as poll (fortunately in the case of Xlib, it already does
1354	does this on its own, so its quite safe to use). Some people additionally	1600	this on its own, so its quite safe to use). Some people additionally
1355	use C<SIGALRM> and an interval timer, just to be sure you won't block	1601	use C<SIGALRM> and an interval timer, just to be sure you won't block
1356	indefinitely.	1602	indefinitely.
1357		1603
1358	But really, best use non-blocking mode.	1604	But really, best use non-blocking mode.
1359		1605
…		…
1387		1633
1388	There is no workaround possible except not registering events	1634	There is no workaround possible except not registering events
1389	for potentially C<dup ()>'ed file descriptors, or to resort to	1635	for potentially C<dup ()>'ed file descriptors, or to resort to
1390	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1636	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1391		1637
		1638	=head3 The special problem of files
		1639
		1640	Many people try to use C<select> (or libev) on file descriptors
		1641	representing files, and expect it to become ready when their program
		1642	doesn't block on disk accesses (which can take a long time on their own).
		1643
		1644	However, this cannot ever work in the "expected" way - you get a readiness
		1645	notification as soon as the kernel knows whether and how much data is
		1646	there, and in the case of open files, that's always the case, so you
		1647	always get a readiness notification instantly, and your read (or possibly
		1648	write) will still block on the disk I/O.
		1649
		1650	Another way to view it is that in the case of sockets, pipes, character
		1651	devices and so on, there is another party (the sender) that delivers data
		1652	on its own, but in the case of files, there is no such thing: the disk
		1653	will not send data on its own, simply because it doesn't know what you
		1654	wish to read - you would first have to request some data.
		1655
		1656	Since files are typically not-so-well supported by advanced notification
		1657	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1658	to files, even though you should not use it. The reason for this is
		1659	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1660	usually a tty, often a pipe, but also sometimes files or special devices
		1661	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1662	F</dev/urandom>), and even though the file might better be served with
		1663	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1664	it "just works" instead of freezing.
		1665
		1666	So avoid file descriptors pointing to files when you know it (e.g. use
		1667	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1668	when you rarely read from a file instead of from a socket, and want to
		1669	reuse the same code path.
		1670
1392	=head3 The special problem of fork	1671	=head3 The special problem of fork
1393		1672
1394	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1673	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1395	useless behaviour. Libev fully supports fork, but needs to be told about	1674	useless behaviour. Libev fully supports fork, but needs to be told about
1396	it in the child.	1675	it in the child if you want to continue to use it in the child.
1397		1676
1398	To support fork in your programs, you either have to call	1677	To support fork in your child processes, you have to call C<ev_loop_fork
1399	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1678	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1400	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1679	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1401	C<EVBACKEND_POLL>.
1402		1680
1403	=head3 The special problem of SIGPIPE	1681	=head3 The special problem of SIGPIPE
1404		1682
1405	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1683	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1406	when writing to a pipe whose other end has been closed, your program gets	1684	when writing to a pipe whose other end has been closed, your program gets
…		…
1409		1687
1410	So when you encounter spurious, unexplained daemon exits, make sure you	1688	So when you encounter spurious, unexplained daemon exits, make sure you
1411	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1689	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1412	somewhere, as that would have given you a big clue).	1690	somewhere, as that would have given you a big clue).
1413		1691
		1692	=head3 The special problem of accept()ing when you can't
		1693
		1694	Many implementations of the POSIX C<accept> function (for example,
		1695	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1696	connection from the pending queue in all error cases.
		1697
		1698	For example, larger servers often run out of file descriptors (because
		1699	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1700	rejecting the connection, leading to libev signalling readiness on
		1701	the next iteration again (the connection still exists after all), and
		1702	typically causing the program to loop at 100% CPU usage.
		1703
		1704	Unfortunately, the set of errors that cause this issue differs between
		1705	operating systems, there is usually little the app can do to remedy the
		1706	situation, and no known thread-safe method of removing the connection to
		1707	cope with overload is known (to me).
		1708
		1709	One of the easiest ways to handle this situation is to just ignore it
		1710	- when the program encounters an overload, it will just loop until the
		1711	situation is over. While this is a form of busy waiting, no OS offers an
		1712	event-based way to handle this situation, so it's the best one can do.
		1713
		1714	A better way to handle the situation is to log any errors other than
		1715	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1716	messages, and continue as usual, which at least gives the user an idea of
		1717	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1718	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1719	usage.
		1720
		1721	If your program is single-threaded, then you could also keep a dummy file
		1722	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1723	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1724	close that fd, and create a new dummy fd. This will gracefully refuse
		1725	clients under typical overload conditions.
		1726
		1727	The last way to handle it is to simply log the error and C<exit>, as
		1728	is often done with C<malloc> failures, but this results in an easy
		1729	opportunity for a DoS attack.
1414		1730
1415	=head3 Watcher-Specific Functions	1731	=head3 Watcher-Specific Functions
1416		1732
1417	=over 4	1733	=over 4
1418		1734
…		…
1450	...	1766	...
1451	struct ev_loop *loop = ev_default_init (0);	1767	struct ev_loop *loop = ev_default_init (0);
1452	ev_io stdin_readable;	1768	ev_io stdin_readable;
1453	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1769	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1454	ev_io_start (loop, &stdin_readable);	1770	ev_io_start (loop, &stdin_readable);
1455	ev_loop (loop, 0);	1771	ev_run (loop, 0);
1456		1772
1457		1773
1458	=head2 C<ev_timer> - relative and optionally repeating timeouts	1774	=head2 C<ev_timer> - relative and optionally repeating timeouts
1459		1775
1460	Timer watchers are simple relative timers that generate an event after a	1776	Timer watchers are simple relative timers that generate an event after a
…		…
1466	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1782	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1467	monotonic clock option helps a lot here).	1783	monotonic clock option helps a lot here).
1468		1784
1469	The callback is guaranteed to be invoked only I<after> its timeout has	1785	The callback is guaranteed to be invoked only I<after> its timeout has
1470	passed (not I<at>, so on systems with very low-resolution clocks this	1786	passed (not I<at>, so on systems with very low-resolution clocks this
1471	might introduce a small delay). If multiple timers become ready during the	1787	might introduce a small delay, see "the special problem of being too
		1788	early", below). If multiple timers become ready during the same loop
1472	same loop iteration then the ones with earlier time-out values are invoked	1789	iteration then the ones with earlier time-out values are invoked before
1473	before ones with later time-out values (but this is no longer true when a	1790	ones of the same priority with later time-out values (but this is no
1474	callback calls C<ev_loop> recursively).	1791	longer true when a callback calls C<ev_run> recursively).
1475		1792
1476	=head3 Be smart about timeouts	1793	=head3 Be smart about timeouts
1477		1794
1478	Many real-world problems involve some kind of timeout, usually for error	1795	Many real-world problems involve some kind of timeout, usually for error
1479	recovery. A typical example is an HTTP request - if the other side hangs,	1796	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1554		1871
1555	In this case, it would be more efficient to leave the C<ev_timer> alone,	1872	In this case, it would be more efficient to leave the C<ev_timer> alone,
1556	but remember the time of last activity, and check for a real timeout only	1873	but remember the time of last activity, and check for a real timeout only
1557	within the callback:	1874	within the callback:
1558		1875
		1876	ev_tstamp timeout = 60.;
1559	ev_tstamp last_activity; // time of last activity	1877	ev_tstamp last_activity; // time of last activity
		1878	ev_timer timer;
1560		1879
1561	static void	1880	static void
1562	callback (EV_P_ ev_timer *w, int revents)	1881	callback (EV_P_ ev_timer *w, int revents)
1563	{	1882	{
1564	ev_tstamp now = ev_now (EV_A);	1883	// calculate when the timeout would happen
1565	ev_tstamp timeout = last_activity + 60.;	1884	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1566		1885
1567	// if last_activity + 60. is older than now, we did time out	1886	// if negative, it means we the timeout already occurred
1568	if (timeout < now)	1887	if (after < 0.)
1569	{	1888	{
1570	// timeout occured, take action	1889	// timeout occurred, take action
1571	}	1890	}
1572	else	1891	else
1573	{	1892	{
1574	// callback was invoked, but there was some activity, re-arm	1893	// callback was invoked, but there was some recent
1575	// the watcher to fire in last_activity + 60, which is	1894	// activity. simply restart the timer to time out
1576	// guaranteed to be in the future, so "again" is positive:	1895	// after "after" seconds, which is the earliest time
1577	w->repeat = timeout - now;	1896	// the timeout can occur.
		1897	ev_timer_set (w, after, 0.);
1578	ev_timer_again (EV_A_ w);	1898	ev_timer_start (EV_A_ w);
1579	}	1899	}
1580	}	1900	}
1581		1901
1582	To summarise the callback: first calculate the real timeout (defined	1902	To summarise the callback: first calculate in how many seconds the
1583	as "60 seconds after the last activity"), then check if that time has	1903	timeout will occur (by calculating the absolute time when it would occur,
1584	been reached, which means something I<did>, in fact, time out. Otherwise	1904	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1585	the callback was invoked too early (C<timeout> is in the future), so	1905	(EV_A)> from that).
1586	re-schedule the timer to fire at that future time, to see if maybe we have
1587	a timeout then.
1588		1906
1589	Note how C<ev_timer_again> is used, taking advantage of the	1907	If this value is negative, then we are already past the timeout, i.e. we
1590	C<ev_timer_again> optimisation when the timer is already running.	1908	timed out, and need to do whatever is needed in this case.
		1909
		1910	Otherwise, we now the earliest time at which the timeout would trigger,
		1911	and simply start the timer with this timeout value.
		1912
		1913	In other words, each time the callback is invoked it will check whether
		1914	the timeout occurred. If not, it will simply reschedule itself to check
		1915	again at the earliest time it could time out. Rinse. Repeat.
1591		1916
1592	This scheme causes more callback invocations (about one every 60 seconds	1917	This scheme causes more callback invocations (about one every 60 seconds
1593	minus half the average time between activity), but virtually no calls to	1918	minus half the average time between activity), but virtually no calls to
1594	libev to change the timeout.	1919	libev to change the timeout.
1595		1920
1596	To start the timer, simply initialise the watcher and set C<last_activity>	1921	To start the machinery, simply initialise the watcher and set
1597	to the current time (meaning we just have some activity :), then call the	1922	C<last_activity> to the current time (meaning there was some activity just
1598	callback, which will "do the right thing" and start the timer:	1923	now), then call the callback, which will "do the right thing" and start
		1924	the timer:
1599		1925
		1926	last_activity = ev_now (EV_A);
1600	ev_init (timer, callback);	1927	ev_init (&timer, callback);
1601	last_activity = ev_now (loop);	1928	callback (EV_A_ &timer, 0);
1602	callback (loop, timer, EV_TIMEOUT);
1603		1929
1604	And when there is some activity, simply store the current time in	1930	When there is some activity, simply store the current time in
1605	C<last_activity>, no libev calls at all:	1931	C<last_activity>, no libev calls at all:
1606		1932
		1933	if (activity detected)
1607	last_actiivty = ev_now (loop);	1934	last_activity = ev_now (EV_A);
		1935
		1936	When your timeout value changes, then the timeout can be changed by simply
		1937	providing a new value, stopping the timer and calling the callback, which
		1938	will again do the right thing (for example, time out immediately :).
		1939
		1940	timeout = new_value;
		1941	ev_timer_stop (EV_A_ &timer);
		1942	callback (EV_A_ &timer, 0);
1608		1943
1609	This technique is slightly more complex, but in most cases where the	1944	This technique is slightly more complex, but in most cases where the
1610	time-out is unlikely to be triggered, much more efficient.	1945	time-out is unlikely to be triggered, much more efficient.
1611
1612	Changing the timeout is trivial as well (if it isn't hard-coded in the
1613	callback :) - just change the timeout and invoke the callback, which will
1614	fix things for you.
1615		1946
1616	=item 4. Wee, just use a double-linked list for your timeouts.	1947	=item 4. Wee, just use a double-linked list for your timeouts.
1617		1948
1618	If there is not one request, but many thousands (millions...), all	1949	If there is not one request, but many thousands (millions...), all
1619	employing some kind of timeout with the same timeout value, then one can	1950	employing some kind of timeout with the same timeout value, then one can
…		…
1646	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	1977	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1647	rather complicated, but extremely efficient, something that really pays	1978	rather complicated, but extremely efficient, something that really pays
1648	off after the first million or so of active timers, i.e. it's usually	1979	off after the first million or so of active timers, i.e. it's usually
1649	overkill :)	1980	overkill :)
1650		1981
		1982	=head3 The special problem of being too early
		1983
		1984	If you ask a timer to call your callback after three seconds, then
		1985	you expect it to be invoked after three seconds - but of course, this
		1986	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		1987	guaranteed to any precision by libev - imagine somebody suspending the
		1988	process with a STOP signal for a few hours for example.
		1989
		1990	So, libev tries to invoke your callback as soon as possible I<after> the
		1991	delay has occurred, but cannot guarantee this.
		1992
		1993	A less obvious failure mode is calling your callback too early: many event
		1994	loops compare timestamps with a "elapsed delay >= requested delay", but
		1995	this can cause your callback to be invoked much earlier than you would
		1996	expect.
		1997
		1998	To see why, imagine a system with a clock that only offers full second
		1999	resolution (think windows if you can't come up with a broken enough OS
		2000	yourself). If you schedule a one-second timer at the time 500.9, then the
		2001	event loop will schedule your timeout to elapse at a system time of 500
		2002	(500.9 truncated to the resolution) + 1, or 501.
		2003
		2004	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2005	501" and invoke the callback 0.1s after it was started, even though a
		2006	one-second delay was requested - this is being "too early", despite best
		2007	intentions.
		2008
		2009	This is the reason why libev will never invoke the callback if the elapsed
		2010	delay equals the requested delay, but only when the elapsed delay is
		2011	larger than the requested delay. In the example above, libev would only invoke
		2012	the callback at system time 502, or 1.1s after the timer was started.
		2013
		2014	So, while libev cannot guarantee that your callback will be invoked
		2015	exactly when requested, it I<can> and I<does> guarantee that the requested
		2016	delay has actually elapsed, or in other words, it always errs on the "too
		2017	late" side of things.
		2018
1651	=head3 The special problem of time updates	2019	=head3 The special problem of time updates
1652		2020
1653	Establishing the current time is a costly operation (it usually takes at	2021	Establishing the current time is a costly operation (it usually takes
1654	least two system calls): EV therefore updates its idea of the current	2022	at least one system call): EV therefore updates its idea of the current
1655	time only before and after C<ev_loop> collects new events, which causes a	2023	time only before and after C<ev_run> collects new events, which causes a
1656	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2024	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1657	lots of events in one iteration.	2025	lots of events in one iteration.
1658		2026
1659	The relative timeouts are calculated relative to the C<ev_now ()>	2027	The relative timeouts are calculated relative to the C<ev_now ()>
1660	time. This is usually the right thing as this timestamp refers to the time	2028	time. This is usually the right thing as this timestamp refers to the time
…		…
1666		2034
1667	If the event loop is suspended for a long time, you can also force an	2035	If the event loop is suspended for a long time, you can also force an
1668	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2036	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1669	()>.	2037	()>.
1670		2038
		2039	=head3 The special problem of unsynchronised clocks
		2040
		2041	Modern systems have a variety of clocks - libev itself uses the normal
		2042	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2043	jumps).
		2044
		2045	Neither of these clocks is synchronised with each other or any other clock
		2046	on the system, so C<ev_time ()> might return a considerably different time
		2047	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2048	a call to C<gettimeofday> might return a second count that is one higher
		2049	than a directly following call to C<time>.
		2050
		2051	The moral of this is to only compare libev-related timestamps with
		2052	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2053	a second or so.
		2054
		2055	One more problem arises due to this lack of synchronisation: if libev uses
		2056	the system monotonic clock and you compare timestamps from C<ev_time>
		2057	or C<ev_now> from when you started your timer and when your callback is
		2058	invoked, you will find that sometimes the callback is a bit "early".
		2059
		2060	This is because C<ev_timer>s work in real time, not wall clock time, so
		2061	libev makes sure your callback is not invoked before the delay happened,
		2062	I<measured according to the real time>, not the system clock.
		2063
		2064	If your timeouts are based on a physical timescale (e.g. "time out this
		2065	connection after 100 seconds") then this shouldn't bother you as it is
		2066	exactly the right behaviour.
		2067
		2068	If you want to compare wall clock/system timestamps to your timers, then
		2069	you need to use C<ev_periodic>s, as these are based on the wall clock
		2070	time, where your comparisons will always generate correct results.
		2071
		2072	=head3 The special problems of suspended animation
		2073
		2074	When you leave the server world it is quite customary to hit machines that
		2075	can suspend/hibernate - what happens to the clocks during such a suspend?
		2076
		2077	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2078	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2079	to run until the system is suspended, but they will not advance while the
		2080	system is suspended. That means, on resume, it will be as if the program
		2081	was frozen for a few seconds, but the suspend time will not be counted
		2082	towards C<ev_timer> when a monotonic clock source is used. The real time
		2083	clock advanced as expected, but if it is used as sole clocksource, then a
		2084	long suspend would be detected as a time jump by libev, and timers would
		2085	be adjusted accordingly.
		2086
		2087	I would not be surprised to see different behaviour in different between
		2088	operating systems, OS versions or even different hardware.
		2089
		2090	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2091	time jump in the monotonic clocks and the realtime clock. If the program
		2092	is suspended for a very long time, and monotonic clock sources are in use,
		2093	then you can expect C<ev_timer>s to expire as the full suspension time
		2094	will be counted towards the timers. When no monotonic clock source is in
		2095	use, then libev will again assume a timejump and adjust accordingly.
		2096
		2097	It might be beneficial for this latter case to call C<ev_suspend>
		2098	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2099	deterministic behaviour in this case (you can do nothing against
		2100	C<SIGSTOP>).
		2101
1671	=head3 Watcher-Specific Functions and Data Members	2102	=head3 Watcher-Specific Functions and Data Members
1672		2103
1673	=over 4	2104	=over 4
1674		2105
1675	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2106	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1688	keep up with the timer (because it takes longer than those 10 seconds to	2119	keep up with the timer (because it takes longer than those 10 seconds to
1689	do stuff) the timer will not fire more than once per event loop iteration.	2120	do stuff) the timer will not fire more than once per event loop iteration.
1690		2121
1691	=item ev_timer_again (loop, ev_timer *)	2122	=item ev_timer_again (loop, ev_timer *)
1692		2123
1693	This will act as if the timer timed out and restart it again if it is	2124	This will act as if the timer timed out, and restarts it again if it is
1694	repeating. The exact semantics are:	2125	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2126	timeout to the C<repeat> value and calling C<ev_timer_start>.
1695		2127
		2128	The exact semantics are as in the following rules, all of which will be
		2129	applied to the watcher:
		2130
		2131	=over 4
		2132
1696	If the timer is pending, its pending status is cleared.	2133	=item If the timer is pending, the pending status is always cleared.
1697		2134
1698	If the timer is started but non-repeating, stop it (as if it timed out).	2135	=item If the timer is started but non-repeating, stop it (as if it timed
		2136	out, without invoking it).
1699		2137
1700	If the timer is repeating, either start it if necessary (with the	2138	=item If the timer is repeating, make the C<repeat> value the new timeout
1701	C<repeat> value), or reset the running timer to the C<repeat> value.	2139	and start the timer, if necessary.
1702		2140
		2141	=back
		2142
1703	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2143	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1704	usage example.	2144	usage example.
		2145
		2146	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2147
		2148	Returns the remaining time until a timer fires. If the timer is active,
		2149	then this time is relative to the current event loop time, otherwise it's
		2150	the timeout value currently configured.
		2151
		2152	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2153	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2154	will return C<4>. When the timer expires and is restarted, it will return
		2155	roughly C<7> (likely slightly less as callback invocation takes some time,
		2156	too), and so on.
1705		2157
1706	=item ev_tstamp repeat [read-write]	2158	=item ev_tstamp repeat [read-write]
1707		2159
1708	The current C<repeat> value. Will be used each time the watcher times out	2160	The current C<repeat> value. Will be used each time the watcher times out
1709	or C<ev_timer_again> is called, and determines the next timeout (if any),	2161	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1735	}	2187	}
1736		2188
1737	ev_timer mytimer;	2189	ev_timer mytimer;
1738	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2190	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1739	ev_timer_again (&mytimer); /* start timer */	2191	ev_timer_again (&mytimer); /* start timer */
1740	ev_loop (loop, 0);	2192	ev_run (loop, 0);
1741		2193
1742	// and in some piece of code that gets executed on any "activity":	2194	// and in some piece of code that gets executed on any "activity":
1743	// reset the timeout to start ticking again at 10 seconds	2195	// reset the timeout to start ticking again at 10 seconds
1744	ev_timer_again (&mytimer);	2196	ev_timer_again (&mytimer);
1745		2197
…		…
1771		2223
1772	As with timers, the callback is guaranteed to be invoked only when the	2224	As with timers, the callback is guaranteed to be invoked only when the
1773	point in time where it is supposed to trigger has passed. If multiple	2225	point in time where it is supposed to trigger has passed. If multiple
1774	timers become ready during the same loop iteration then the ones with	2226	timers become ready during the same loop iteration then the ones with
1775	earlier time-out values are invoked before ones with later time-out values	2227	earlier time-out values are invoked before ones with later time-out values
1776	(but this is no longer true when a callback calls C<ev_loop> recursively).	2228	(but this is no longer true when a callback calls C<ev_run> recursively).
1777		2229
1778	=head3 Watcher-Specific Functions and Data Members	2230	=head3 Watcher-Specific Functions and Data Members
1779		2231
1780	=over 4	2232	=over 4
1781		2233
…		…
1816		2268
1817	Another way to think about it (for the mathematically inclined) is that	2269	Another way to think about it (for the mathematically inclined) is that
1818	C<ev_periodic> will try to run the callback in this mode at the next possible	2270	C<ev_periodic> will try to run the callback in this mode at the next possible
1819	time where C<time = offset (mod interval)>, regardless of any time jumps.	2271	time where C<time = offset (mod interval)>, regardless of any time jumps.
1820		2272
1821	For numerical stability it is preferable that the C<offset> value is near	2273	The C<interval> I<MUST> be positive, and for numerical stability, the
1822	C<ev_now ()> (the current time), but there is no range requirement for	2274	interval value should be higher than C<1/8192> (which is around 100
1823	this value, and in fact is often specified as zero.	2275	microseconds) and C<offset> should be higher than C<0> and should have
		2276	at most a similar magnitude as the current time (say, within a factor of
		2277	ten). Typical values for offset are, in fact, C<0> or something between
		2278	C<0> and C<interval>, which is also the recommended range.
1824		2279
1825	Note also that there is an upper limit to how often a timer can fire (CPU	2280	Note also that there is an upper limit to how often a timer can fire (CPU
1826	speed for example), so if C<interval> is very small then timing stability	2281	speed for example), so if C<interval> is very small then timing stability
1827	will of course deteriorate. Libev itself tries to be exact to be about one	2282	will of course deteriorate. Libev itself tries to be exact to be about one
1828	millisecond (if the OS supports it and the machine is fast enough).	2283	millisecond (if the OS supports it and the machine is fast enough).
…		…
1909	Example: Call a callback every hour, or, more precisely, whenever the	2364	Example: Call a callback every hour, or, more precisely, whenever the
1910	system time is divisible by 3600. The callback invocation times have	2365	system time is divisible by 3600. The callback invocation times have
1911	potentially a lot of jitter, but good long-term stability.	2366	potentially a lot of jitter, but good long-term stability.
1912		2367
1913	static void	2368	static void
1914	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2369	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1915	{	2370	{
1916	... its now a full hour (UTC, or TAI or whatever your clock follows)	2371	... its now a full hour (UTC, or TAI or whatever your clock follows)
1917	}	2372	}
1918		2373
1919	ev_periodic hourly_tick;	2374	ev_periodic hourly_tick;
…		…
1942		2397
1943	=head2 C<ev_signal> - signal me when a signal gets signalled!	2398	=head2 C<ev_signal> - signal me when a signal gets signalled!
1944		2399
1945	Signal watchers will trigger an event when the process receives a specific	2400	Signal watchers will trigger an event when the process receives a specific
1946	signal one or more times. Even though signals are very asynchronous, libev	2401	signal one or more times. Even though signals are very asynchronous, libev
1947	will try it's best to deliver signals synchronously, i.e. as part of the	2402	will try its best to deliver signals synchronously, i.e. as part of the
1948	normal event processing, like any other event.	2403	normal event processing, like any other event.
1949		2404
1950	If you want signals asynchronously, just use C<sigaction> as you would	2405	If you want signals to be delivered truly asynchronously, just use
1951	do without libev and forget about sharing the signal. You can even use	2406	C<sigaction> as you would do without libev and forget about sharing
1952	C<ev_async> from a signal handler to synchronously wake up an event loop.	2407	the signal. You can even use C<ev_async> from a signal handler to
		2408	synchronously wake up an event loop.
1953		2409
1954	You can configure as many watchers as you like per signal. Only when the	2410	You can configure as many watchers as you like for the same signal, but
		2411	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2412	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2413	C<SIGINT> in both the default loop and another loop at the same time. At
		2414	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2415
1955	first watcher gets started will libev actually register a signal handler	2416	When the first watcher gets started will libev actually register something
1956	with the kernel (thus it coexists with your own signal handlers as long as	2417	with the kernel (thus it coexists with your own signal handlers as long as
1957	you don't register any with libev for the same signal). Similarly, when	2418	you don't register any with libev for the same signal).
1958	the last signal watcher for a signal is stopped, libev will reset the
1959	signal handler to SIG_DFL (regardless of what it was set to before).
1960		2419
1961	If possible and supported, libev will install its handlers with	2420	If possible and supported, libev will install its handlers with
1962	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2421	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1963	interrupted. If you have a problem with system calls getting interrupted by	2422	not be unduly interrupted. If you have a problem with system calls getting
1964	signals you can block all signals in an C<ev_check> watcher and unblock	2423	interrupted by signals you can block all signals in an C<ev_check> watcher
1965	them in an C<ev_prepare> watcher.	2424	and unblock them in an C<ev_prepare> watcher.
		2425
		2426	=head3 The special problem of inheritance over fork/execve/pthread_create
		2427
		2428	Both the signal mask (C<sigprocmask>) and the signal disposition
		2429	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2430	stopping it again), that is, libev might or might not block the signal,
		2431	and might or might not set or restore the installed signal handler (but
		2432	see C<EVFLAG_NOSIGMASK>).
		2433
		2434	While this does not matter for the signal disposition (libev never
		2435	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2436	C<execve>), this matters for the signal mask: many programs do not expect
		2437	certain signals to be blocked.
		2438
		2439	This means that before calling C<exec> (from the child) you should reset
		2440	the signal mask to whatever "default" you expect (all clear is a good
		2441	choice usually).
		2442
		2443	The simplest way to ensure that the signal mask is reset in the child is
		2444	to install a fork handler with C<pthread_atfork> that resets it. That will
		2445	catch fork calls done by libraries (such as the libc) as well.
		2446
		2447	In current versions of libev, the signal will not be blocked indefinitely
		2448	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2449	the window of opportunity for problems, it will not go away, as libev
		2450	I<has> to modify the signal mask, at least temporarily.
		2451
		2452	So I can't stress this enough: I<If you do not reset your signal mask when
		2453	you expect it to be empty, you have a race condition in your code>. This
		2454	is not a libev-specific thing, this is true for most event libraries.
		2455
		2456	=head3 The special problem of threads signal handling
		2457
		2458	POSIX threads has problematic signal handling semantics, specifically,
		2459	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2460	threads in a process block signals, which is hard to achieve.
		2461
		2462	When you want to use sigwait (or mix libev signal handling with your own
		2463	for the same signals), you can tackle this problem by globally blocking
		2464	all signals before creating any threads (or creating them with a fully set
		2465	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2466	loops. Then designate one thread as "signal receiver thread" which handles
		2467	these signals. You can pass on any signals that libev might be interested
		2468	in by calling C<ev_feed_signal>.
1966		2469
1967	=head3 Watcher-Specific Functions and Data Members	2470	=head3 Watcher-Specific Functions and Data Members
1968		2471
1969	=over 4	2472	=over 4
1970		2473
…		…
1986	Example: Try to exit cleanly on SIGINT.	2489	Example: Try to exit cleanly on SIGINT.
1987		2490
1988	static void	2491	static void
1989	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2492	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1990	{	2493	{
1991	ev_unloop (loop, EVUNLOOP_ALL);	2494	ev_break (loop, EVBREAK_ALL);
1992	}	2495	}
1993		2496
1994	ev_signal signal_watcher;	2497	ev_signal signal_watcher;
1995	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2498	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1996	ev_signal_start (loop, &signal_watcher);	2499	ev_signal_start (loop, &signal_watcher);
…		…
2008	in the next callback invocation is not.	2511	in the next callback invocation is not.
2009		2512
2010	Only the default event loop is capable of handling signals, and therefore	2513	Only the default event loop is capable of handling signals, and therefore
2011	you can only register child watchers in the default event loop.	2514	you can only register child watchers in the default event loop.
2012		2515
		2516	Due to some design glitches inside libev, child watchers will always be
		2517	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2518	libev)
		2519
2013	=head3 Process Interaction	2520	=head3 Process Interaction
2014		2521
2015	Libev grabs C<SIGCHLD> as soon as the default event loop is	2522	Libev grabs C<SIGCHLD> as soon as the default event loop is
2016	initialised. This is necessary to guarantee proper behaviour even if	2523	initialised. This is necessary to guarantee proper behaviour even if the
2017	the first child watcher is started after the child exits. The occurrence	2524	first child watcher is started after the child exits. The occurrence
2018	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2525	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2019	synchronously as part of the event loop processing. Libev always reaps all	2526	synchronously as part of the event loop processing. Libev always reaps all
2020	children, even ones not watched.	2527	children, even ones not watched.
2021		2528
2022	=head3 Overriding the Built-In Processing	2529	=head3 Overriding the Built-In Processing
…		…
2032	=head3 Stopping the Child Watcher	2539	=head3 Stopping the Child Watcher
2033		2540
2034	Currently, the child watcher never gets stopped, even when the	2541	Currently, the child watcher never gets stopped, even when the
2035	child terminates, so normally one needs to stop the watcher in the	2542	child terminates, so normally one needs to stop the watcher in the
2036	callback. Future versions of libev might stop the watcher automatically	2543	callback. Future versions of libev might stop the watcher automatically
2037	when a child exit is detected.	2544	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2545	problem).
2038		2546
2039	=head3 Watcher-Specific Functions and Data Members	2547	=head3 Watcher-Specific Functions and Data Members
2040		2548
2041	=over 4	2549	=over 4
2042		2550
…		…
2100		2608
2101	=head2 C<ev_stat> - did the file attributes just change?	2609	=head2 C<ev_stat> - did the file attributes just change?
2102		2610
2103	This watches a file system path for attribute changes. That is, it calls	2611	This watches a file system path for attribute changes. That is, it calls
2104	C<stat> on that path in regular intervals (or when the OS says it changed)	2612	C<stat> on that path in regular intervals (or when the OS says it changed)
2105	and sees if it changed compared to the last time, invoking the callback if	2613	and sees if it changed compared to the last time, invoking the callback
2106	it did.	2614	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2615	happen after the watcher has been started will be reported.
2107		2616
2108	The path does not need to exist: changing from "path exists" to "path does	2617	The path does not need to exist: changing from "path exists" to "path does
2109	not exist" is a status change like any other. The condition "path does not	2618	not exist" is a status change like any other. The condition "path does not
2110	exist" (or more correctly "path cannot be stat'ed") is signified by the	2619	exist" (or more correctly "path cannot be stat'ed") is signified by the
2111	C<st_nlink> field being zero (which is otherwise always forced to be at	2620	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2341	Apart from keeping your process non-blocking (which is a useful	2850	Apart from keeping your process non-blocking (which is a useful
2342	effect on its own sometimes), idle watchers are a good place to do	2851	effect on its own sometimes), idle watchers are a good place to do
2343	"pseudo-background processing", or delay processing stuff to after the	2852	"pseudo-background processing", or delay processing stuff to after the
2344	event loop has handled all outstanding events.	2853	event loop has handled all outstanding events.
2345		2854
		2855	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2856
		2857	As long as there is at least one active idle watcher, libev will never
		2858	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2859	For this to work, the idle watcher doesn't need to be invoked at all - the
		2860	lowest priority will do.
		2861
		2862	This mode of operation can be useful together with an C<ev_check> watcher,
		2863	to do something on each event loop iteration - for example to balance load
		2864	between different connections.
		2865
		2866	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2867	example.
		2868
2346	=head3 Watcher-Specific Functions and Data Members	2869	=head3 Watcher-Specific Functions and Data Members
2347		2870
2348	=over 4	2871	=over 4
2349		2872
2350	=item ev_idle_init (ev_idle *, callback)	2873	=item ev_idle_init (ev_idle *, callback)
…		…
2361	callback, free it. Also, use no error checking, as usual.	2884	callback, free it. Also, use no error checking, as usual.
2362		2885
2363	static void	2886	static void
2364	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2887	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2365	{	2888	{
		2889	// stop the watcher
		2890	ev_idle_stop (loop, w);
		2891
		2892	// now we can free it
2366	free (w);	2893	free (w);
		2894
2367	// now do something you wanted to do when the program has	2895	// now do something you wanted to do when the program has
2368	// no longer anything immediate to do.	2896	// no longer anything immediate to do.
2369	}	2897	}
2370		2898
2371	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2899	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2373	ev_idle_start (loop, idle_watcher);	2901	ev_idle_start (loop, idle_watcher);
2374		2902
2375		2903
2376	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2904	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2377		2905
2378	Prepare and check watchers are usually (but not always) used in pairs:	2906	Prepare and check watchers are often (but not always) used in pairs:
2379	prepare watchers get invoked before the process blocks and check watchers	2907	prepare watchers get invoked before the process blocks and check watchers
2380	afterwards.	2908	afterwards.
2381		2909
2382	You I<must not> call C<ev_loop> or similar functions that enter	2910	You I<must not> call C<ev_run> or similar functions that enter
2383	the current event loop from either C<ev_prepare> or C<ev_check>	2911	the current event loop from either C<ev_prepare> or C<ev_check>
2384	watchers. Other loops than the current one are fine, however. The	2912	watchers. Other loops than the current one are fine, however. The
2385	rationale behind this is that you do not need to check for recursion in	2913	rationale behind this is that you do not need to check for recursion in
2386	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2914	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2387	C<ev_check> so if you have one watcher of each kind they will always be	2915	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2411	with priority higher than or equal to the event loop and one coroutine	2939	with priority higher than or equal to the event loop and one coroutine
2412	of lower priority, but only once, using idle watchers to keep the event	2940	of lower priority, but only once, using idle watchers to keep the event
2413	loop from blocking if lower-priority coroutines are active, thus mapping	2941	loop from blocking if lower-priority coroutines are active, thus mapping
2414	low-priority coroutines to idle/background tasks).	2942	low-priority coroutines to idle/background tasks).
2415		2943
2416	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2944	When used for this purpose, it is recommended to give C<ev_check> watchers
2417	priority, to ensure that they are being run before any other watchers	2945	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2418	after the poll (this doesn't matter for C<ev_prepare> watchers).	2946	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2947	watchers).
2419		2948
2420	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2949	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2421	activate ("feed") events into libev. While libev fully supports this, they	2950	activate ("feed") events into libev. While libev fully supports this, they
2422	might get executed before other C<ev_check> watchers did their job. As	2951	might get executed before other C<ev_check> watchers did their job. As
2423	C<ev_check> watchers are often used to embed other (non-libev) event	2952	C<ev_check> watchers are often used to embed other (non-libev) event
2424	loops those other event loops might be in an unusable state until their	2953	loops those other event loops might be in an unusable state until their
2425	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	2954	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2426	others).	2955	others).
		2956
		2957	=head3 Abusing an C<ev_check> watcher for its side-effect
		2958
		2959	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		2960	useful because they are called once per event loop iteration. For
		2961	example, if you want to handle a large number of connections fairly, you
		2962	normally only do a bit of work for each active connection, and if there
		2963	is more work to do, you wait for the next event loop iteration, so other
		2964	connections have a chance of making progress.
		2965
		2966	Using an C<ev_check> watcher is almost enough: it will be called on the
		2967	next event loop iteration. However, that isn't as soon as possible -
		2968	without external events, your C<ev_check> watcher will not be invoked.
		2969
		2970	This is where C<ev_idle> watchers come in handy - all you need is a
		2971	single global idle watcher that is active as long as you have one active
		2972	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		2973	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		2974	invoked. Neither watcher alone can do that.
2427		2975
2428	=head3 Watcher-Specific Functions and Data Members	2976	=head3 Watcher-Specific Functions and Data Members
2429		2977
2430	=over 4	2978	=over 4
2431		2979
…		…
2555		3103
2556	if (timeout >= 0)	3104	if (timeout >= 0)
2557	// create/start timer	3105	// create/start timer
2558		3106
2559	// poll	3107	// poll
2560	ev_loop (EV_A_ 0);	3108	ev_run (EV_A_ 0);
2561		3109
2562	// stop timer again	3110	// stop timer again
2563	if (timeout >= 0)	3111	if (timeout >= 0)
2564	ev_timer_stop (EV_A_ &to);	3112	ev_timer_stop (EV_A_ &to);
2565		3113
…		…
2632		3180
2633	=over 4	3181	=over 4
2634		3182
2635	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3183	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2636		3184
2637	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3185	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2638		3186
2639	Configures the watcher to embed the given loop, which must be	3187	Configures the watcher to embed the given loop, which must be
2640	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3188	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2641	invoked automatically, otherwise it is the responsibility of the callback	3189	invoked automatically, otherwise it is the responsibility of the callback
2642	to invoke it (it will continue to be called until the sweep has been done,	3190	to invoke it (it will continue to be called until the sweep has been done,
2643	if you do not want that, you need to temporarily stop the embed watcher).	3191	if you do not want that, you need to temporarily stop the embed watcher).
2644		3192
2645	=item ev_embed_sweep (loop, ev_embed *)	3193	=item ev_embed_sweep (loop, ev_embed *)
2646		3194
2647	Make a single, non-blocking sweep over the embedded loop. This works	3195	Make a single, non-blocking sweep over the embedded loop. This works
2648	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3196	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2649	appropriate way for embedded loops.	3197	appropriate way for embedded loops.
2650		3198
2651	=item struct ev_loop *other [read-only]	3199	=item struct ev_loop *other [read-only]
2652		3200
2653	The embedded event loop.	3201	The embedded event loop.
…		…
2705		3253
2706	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3254	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2707		3255
2708	Fork watchers are called when a C<fork ()> was detected (usually because	3256	Fork watchers are called when a C<fork ()> was detected (usually because
2709	whoever is a good citizen cared to tell libev about it by calling	3257	whoever is a good citizen cared to tell libev about it by calling
2710	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3258	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2711	event loop blocks next and before C<ev_check> watchers are being called,	3259	and before C<ev_check> watchers are being called, and only in the child
2712	and only in the child after the fork. If whoever good citizen calling	3260	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2713	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3261	and calls it in the wrong process, the fork handlers will be invoked, too,
2714	handlers will be invoked, too, of course.	3262	of course.
2715		3263
2716	=head3 The special problem of life after fork - how is it possible?	3264	=head3 The special problem of life after fork - how is it possible?
2717		3265
2718	Most uses of C<fork()> consist of forking, then some simple calls to ste	3266	Most uses of C<fork()> consist of forking, then some simple calls to set
2719	up/change the process environment, followed by a call to C<exec()>. This	3267	up/change the process environment, followed by a call to C<exec()>. This
2720	sequence should be handled by libev without any problems.	3268	sequence should be handled by libev without any problems.
2721		3269
2722	This changes when the application actually wants to do event handling	3270	This changes when the application actually wants to do event handling
2723	in the child, or both parent in child, in effect "continuing" after the	3271	in the child, or both parent in child, in effect "continuing" after the
…		…
2739	disadvantage of having to use multiple event loops (which do not support	3287	disadvantage of having to use multiple event loops (which do not support
2740	signal watchers).	3288	signal watchers).
2741		3289
2742	When this is not possible, or you want to use the default loop for	3290	When this is not possible, or you want to use the default loop for
2743	other reasons, then in the process that wants to start "fresh", call	3291	other reasons, then in the process that wants to start "fresh", call
2744	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3292	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2745	the default loop will "orphan" (not stop) all registered watchers, so you	3293	Destroying the default loop will "orphan" (not stop) all registered
2746	have to be careful not to execute code that modifies those watchers. Note	3294	watchers, so you have to be careful not to execute code that modifies
2747	also that in that case, you have to re-register any signal watchers.	3295	those watchers. Note also that in that case, you have to re-register any
		3296	signal watchers.
2748		3297
2749	=head3 Watcher-Specific Functions and Data Members	3298	=head3 Watcher-Specific Functions and Data Members
2750		3299
2751	=over 4	3300	=over 4
2752		3301
2753	=item ev_fork_init (ev_signal *, callback)	3302	=item ev_fork_init (ev_fork *, callback)
2754		3303
2755	Initialises and configures the fork watcher - it has no parameters of any	3304	Initialises and configures the fork watcher - it has no parameters of any
2756	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3305	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2757	believe me.	3306	really.
2758		3307
2759	=back	3308	=back
2760		3309
2761		3310
		3311	=head2 C<ev_cleanup> - even the best things end
		3312
		3313	Cleanup watchers are called just before the event loop is being destroyed
		3314	by a call to C<ev_loop_destroy>.
		3315
		3316	While there is no guarantee that the event loop gets destroyed, cleanup
		3317	watchers provide a convenient method to install cleanup hooks for your
		3318	program, worker threads and so on - you just to make sure to destroy the
		3319	loop when you want them to be invoked.
		3320
		3321	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3322	all other watchers, they do not keep a reference to the event loop (which
		3323	makes a lot of sense if you think about it). Like all other watchers, you
		3324	can call libev functions in the callback, except C<ev_cleanup_start>.
		3325
		3326	=head3 Watcher-Specific Functions and Data Members
		3327
		3328	=over 4
		3329
		3330	=item ev_cleanup_init (ev_cleanup *, callback)
		3331
		3332	Initialises and configures the cleanup watcher - it has no parameters of
		3333	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3334	pointless, I assure you.
		3335
		3336	=back
		3337
		3338	Example: Register an atexit handler to destroy the default loop, so any
		3339	cleanup functions are called.
		3340
		3341	static void
		3342	program_exits (void)
		3343	{
		3344	ev_loop_destroy (EV_DEFAULT_UC);
		3345	}
		3346
		3347	...
		3348	atexit (program_exits);
		3349
		3350
2762	=head2 C<ev_async> - how to wake up another event loop	3351	=head2 C<ev_async> - how to wake up an event loop
2763		3352
2764	In general, you cannot use an C<ev_loop> from multiple threads or other	3353	In general, you cannot use an C<ev_loop> from multiple threads or other
2765	asynchronous sources such as signal handlers (as opposed to multiple event	3354	asynchronous sources such as signal handlers (as opposed to multiple event
2766	loops - those are of course safe to use in different threads).	3355	loops - those are of course safe to use in different threads).
2767		3356
2768	Sometimes, however, you need to wake up another event loop you do not	3357	Sometimes, however, you need to wake up an event loop you do not control,
2769	control, for example because it belongs to another thread. This is what	3358	for example because it belongs to another thread. This is what C<ev_async>
2770	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3359	watchers do: as long as the C<ev_async> watcher is active, you can signal
2771	can signal it by calling C<ev_async_send>, which is thread- and signal	3360	it by calling C<ev_async_send>, which is thread- and signal safe.
2772	safe.
2773		3361
2774	This functionality is very similar to C<ev_signal> watchers, as signals,	3362	This functionality is very similar to C<ev_signal> watchers, as signals,
2775	too, are asynchronous in nature, and signals, too, will be compressed	3363	too, are asynchronous in nature, and signals, too, will be compressed
2776	(i.e. the number of callback invocations may be less than the number of	3364	(i.e. the number of callback invocations may be less than the number of
2777	C<ev_async_sent> calls).	3365	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2778		3366	of "global async watchers" by using a watcher on an otherwise unused
2779	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3367	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2780	just the default loop.	3368	even without knowing which loop owns the signal.
2781		3369
2782	=head3 Queueing	3370	=head3 Queueing
2783		3371
2784	C<ev_async> does not support queueing of data in any way. The reason	3372	C<ev_async> does not support queueing of data in any way. The reason
2785	is that the author does not know of a simple (or any) algorithm for a	3373	is that the author does not know of a simple (or any) algorithm for a
2786	multiple-writer-single-reader queue that works in all cases and doesn't	3374	multiple-writer-single-reader queue that works in all cases and doesn't
2787	need elaborate support such as pthreads.	3375	need elaborate support such as pthreads or unportable memory access
		3376	semantics.
2788		3377
2789	That means that if you want to queue data, you have to provide your own	3378	That means that if you want to queue data, you have to provide your own
2790	queue. But at least I can tell you how to implement locking around your	3379	queue. But at least I can tell you how to implement locking around your
2791	queue:	3380	queue:
2792		3381
…		…
2876	trust me.	3465	trust me.
2877		3466
2878	=item ev_async_send (loop, ev_async *)	3467	=item ev_async_send (loop, ev_async *)
2879		3468
2880	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3469	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2881	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3470	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3471	returns.
		3472
2882	C<ev_feed_event>, this call is safe to do from other threads, signal or	3473	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2883	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3474	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2884	section below on what exactly this means).	3475	embedding section below on what exactly this means).
2885		3476
2886	Note that, as with other watchers in libev, multiple events might get	3477	Note that, as with other watchers in libev, multiple events might get
2887	compressed into a single callback invocation (another way to look at this	3478	compressed into a single callback invocation (another way to look at
2888	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3479	this is that C<ev_async> watchers are level-triggered: they are set on
2889	reset when the event loop detects that).	3480	C<ev_async_send>, reset when the event loop detects that).
2890		3481
2891	This call incurs the overhead of a system call only once per event loop	3482	This call incurs the overhead of at most one extra system call per event
2892	iteration, so while the overhead might be noticeable, it doesn't apply to	3483	loop iteration, if the event loop is blocked, and no syscall at all if
2893	repeated calls to C<ev_async_send> for the same event loop.	3484	the event loop (or your program) is processing events. That means that
		3485	repeated calls are basically free (there is no need to avoid calls for
		3486	performance reasons) and that the overhead becomes smaller (typically
		3487	zero) under load.
2894		3488
2895	=item bool = ev_async_pending (ev_async *)	3489	=item bool = ev_async_pending (ev_async *)
2896		3490
2897	Returns a non-zero value when C<ev_async_send> has been called on the	3491	Returns a non-zero value when C<ev_async_send> has been called on the
2898	watcher but the event has not yet been processed (or even noted) by the	3492	watcher but the event has not yet been processed (or even noted) by the
…		…
2931		3525
2932	If C<timeout> is less than 0, then no timeout watcher will be	3526	If C<timeout> is less than 0, then no timeout watcher will be
2933	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3527	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2934	repeat = 0) will be started. C<0> is a valid timeout.	3528	repeat = 0) will be started. C<0> is a valid timeout.
2935		3529
2936	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3530	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2937	passed an C<revents> set like normal event callbacks (a combination of	3531	passed an C<revents> set like normal event callbacks (a combination of
2938	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3532	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2939	value passed to C<ev_once>. Note that it is possible to receive I<both>	3533	value passed to C<ev_once>. Note that it is possible to receive I<both>
2940	a timeout and an io event at the same time - you probably should give io	3534	a timeout and an io event at the same time - you probably should give io
2941	events precedence.	3535	events precedence.
2942		3536
2943	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3537	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2944		3538
2945	static void stdin_ready (int revents, void *arg)	3539	static void stdin_ready (int revents, void *arg)
2946	{	3540	{
2947	if (revents & EV_READ)	3541	if (revents & EV_READ)
2948	/* stdin might have data for us, joy! */;	3542	/* stdin might have data for us, joy! */;
2949	else if (revents & EV_TIMEOUT)	3543	else if (revents & EV_TIMER)
2950	/* doh, nothing entered */;	3544	/* doh, nothing entered */;
2951	}	3545	}
2952		3546
2953	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3547	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2954		3548
2955	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2956
2957	Feeds the given event set into the event loop, as if the specified event
2958	had happened for the specified watcher (which must be a pointer to an
2959	initialised but not necessarily started event watcher).
2960
2961	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3549	=item ev_feed_fd_event (loop, int fd, int revents)
2962		3550
2963	Feed an event on the given fd, as if a file descriptor backend detected	3551	Feed an event on the given fd, as if a file descriptor backend detected
2964	the given events it.	3552	the given events.
2965		3553
2966	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3554	=item ev_feed_signal_event (loop, int signum)
2967		3555
2968	Feed an event as if the given signal occurred (C<loop> must be the default	3556	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2969	loop!).	3557	which is async-safe.
2970		3558
2971	=back	3559	=back
		3560
		3561
		3562	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3563
		3564	This section explains some common idioms that are not immediately
		3565	obvious. Note that examples are sprinkled over the whole manual, and this
		3566	section only contains stuff that wouldn't fit anywhere else.
		3567
		3568	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3569
		3570	Each watcher has, by default, a C<void *data> member that you can read
		3571	or modify at any time: libev will completely ignore it. This can be used
		3572	to associate arbitrary data with your watcher. If you need more data and
		3573	don't want to allocate memory separately and store a pointer to it in that
		3574	data member, you can also "subclass" the watcher type and provide your own
		3575	data:
		3576
		3577	struct my_io
		3578	{
		3579	ev_io io;
		3580	int otherfd;
		3581	void *somedata;
		3582	struct whatever *mostinteresting;
		3583	};
		3584
		3585	...
		3586	struct my_io w;
		3587	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3588
		3589	And since your callback will be called with a pointer to the watcher, you
		3590	can cast it back to your own type:
		3591
		3592	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3593	{
		3594	struct my_io *w = (struct my_io *)w_;
		3595	...
		3596	}
		3597
		3598	More interesting and less C-conformant ways of casting your callback
		3599	function type instead have been omitted.
		3600
		3601	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3602
		3603	Another common scenario is to use some data structure with multiple
		3604	embedded watchers, in effect creating your own watcher that combines
		3605	multiple libev event sources into one "super-watcher":
		3606
		3607	struct my_biggy
		3608	{
		3609	int some_data;
		3610	ev_timer t1;
		3611	ev_timer t2;
		3612	}
		3613
		3614	In this case getting the pointer to C<my_biggy> is a bit more
		3615	complicated: Either you store the address of your C<my_biggy> struct in
		3616	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3617	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3618	real programmers):
		3619
		3620	#include <stddef.h>
		3621
		3622	static void
		3623	t1_cb (EV_P_ ev_timer *w, int revents)
		3624	{
		3625	struct my_biggy big = (struct my_biggy *)
		3626	(((char *)w) - offsetof (struct my_biggy, t1));
		3627	}
		3628
		3629	static void
		3630	t2_cb (EV_P_ ev_timer *w, int revents)
		3631	{
		3632	struct my_biggy big = (struct my_biggy *)
		3633	(((char *)w) - offsetof (struct my_biggy, t2));
		3634	}
		3635
		3636	=head2 AVOIDING FINISHING BEFORE RETURNING
		3637
		3638	Often you have structures like this in event-based programs:
		3639
		3640	callback ()
		3641	{
		3642	free (request);
		3643	}
		3644
		3645	request = start_new_request (..., callback);
		3646
		3647	The intent is to start some "lengthy" operation. The C<request> could be
		3648	used to cancel the operation, or do other things with it.
		3649
		3650	It's not uncommon to have code paths in C<start_new_request> that
		3651	immediately invoke the callback, for example, to report errors. Or you add
		3652	some caching layer that finds that it can skip the lengthy aspects of the
		3653	operation and simply invoke the callback with the result.
		3654
		3655	The problem here is that this will happen I<before> C<start_new_request>
		3656	has returned, so C<request> is not set.
		3657
		3658	Even if you pass the request by some safer means to the callback, you
		3659	might want to do something to the request after starting it, such as
		3660	canceling it, which probably isn't working so well when the callback has
		3661	already been invoked.
		3662
		3663	A common way around all these issues is to make sure that
		3664	C<start_new_request> I<always> returns before the callback is invoked. If
		3665	C<start_new_request> immediately knows the result, it can artificially
		3666	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3667	example, or more sneakily, by reusing an existing (stopped) watcher and
		3668	pushing it into the pending queue:
		3669
		3670	ev_set_cb (watcher, callback);
		3671	ev_feed_event (EV_A_ watcher, 0);
		3672
		3673	This way, C<start_new_request> can safely return before the callback is
		3674	invoked, while not delaying callback invocation too much.
		3675
		3676	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3677
		3678	Often (especially in GUI toolkits) there are places where you have
		3679	I<modal> interaction, which is most easily implemented by recursively
		3680	invoking C<ev_run>.
		3681
		3682	This brings the problem of exiting - a callback might want to finish the
		3683	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3684	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3685	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3686	other combination: In these cases, a simple C<ev_break> will not work.
		3687
		3688	The solution is to maintain "break this loop" variable for each C<ev_run>
		3689	invocation, and use a loop around C<ev_run> until the condition is
		3690	triggered, using C<EVRUN_ONCE>:
		3691
		3692	// main loop
		3693	int exit_main_loop = 0;
		3694
		3695	while (!exit_main_loop)
		3696	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3697
		3698	// in a modal watcher
		3699	int exit_nested_loop = 0;
		3700
		3701	while (!exit_nested_loop)
		3702	ev_run (EV_A_ EVRUN_ONCE);
		3703
		3704	To exit from any of these loops, just set the corresponding exit variable:
		3705
		3706	// exit modal loop
		3707	exit_nested_loop = 1;
		3708
		3709	// exit main program, after modal loop is finished
		3710	exit_main_loop = 1;
		3711
		3712	// exit both
		3713	exit_main_loop = exit_nested_loop = 1;
		3714
		3715	=head2 THREAD LOCKING EXAMPLE
		3716
		3717	Here is a fictitious example of how to run an event loop in a different
		3718	thread from where callbacks are being invoked and watchers are
		3719	created/added/removed.
		3720
		3721	For a real-world example, see the C<EV::Loop::Async> perl module,
		3722	which uses exactly this technique (which is suited for many high-level
		3723	languages).
		3724
		3725	The example uses a pthread mutex to protect the loop data, a condition
		3726	variable to wait for callback invocations, an async watcher to notify the
		3727	event loop thread and an unspecified mechanism to wake up the main thread.
		3728
		3729	First, you need to associate some data with the event loop:
		3730
		3731	typedef struct {
		3732	mutex_t lock; /* global loop lock */
		3733	ev_async async_w;
		3734	thread_t tid;
		3735	cond_t invoke_cv;
		3736	} userdata;
		3737
		3738	void prepare_loop (EV_P)
		3739	{
		3740	// for simplicity, we use a static userdata struct.
		3741	static userdata u;
		3742
		3743	ev_async_init (&u->async_w, async_cb);
		3744	ev_async_start (EV_A_ &u->async_w);
		3745
		3746	pthread_mutex_init (&u->lock, 0);
		3747	pthread_cond_init (&u->invoke_cv, 0);
		3748
		3749	// now associate this with the loop
		3750	ev_set_userdata (EV_A_ u);
		3751	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3752	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3753
		3754	// then create the thread running ev_run
		3755	pthread_create (&u->tid, 0, l_run, EV_A);
		3756	}
		3757
		3758	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3759	solely to wake up the event loop so it takes notice of any new watchers
		3760	that might have been added:
		3761
		3762	static void
		3763	async_cb (EV_P_ ev_async *w, int revents)
		3764	{
		3765	// just used for the side effects
		3766	}
		3767
		3768	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3769	protecting the loop data, respectively.
		3770
		3771	static void
		3772	l_release (EV_P)
		3773	{
		3774	userdata *u = ev_userdata (EV_A);
		3775	pthread_mutex_unlock (&u->lock);
		3776	}
		3777
		3778	static void
		3779	l_acquire (EV_P)
		3780	{
		3781	userdata *u = ev_userdata (EV_A);
		3782	pthread_mutex_lock (&u->lock);
		3783	}
		3784
		3785	The event loop thread first acquires the mutex, and then jumps straight
		3786	into C<ev_run>:
		3787
		3788	void *
		3789	l_run (void *thr_arg)
		3790	{
		3791	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3792
		3793	l_acquire (EV_A);
		3794	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3795	ev_run (EV_A_ 0);
		3796	l_release (EV_A);
		3797
		3798	return 0;
		3799	}
		3800
		3801	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3802	signal the main thread via some unspecified mechanism (signals? pipe
		3803	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3804	have been called (in a while loop because a) spurious wakeups are possible
		3805	and b) skipping inter-thread-communication when there are no pending
		3806	watchers is very beneficial):
		3807
		3808	static void
		3809	l_invoke (EV_P)
		3810	{
		3811	userdata *u = ev_userdata (EV_A);
		3812
		3813	while (ev_pending_count (EV_A))
		3814	{
		3815	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3816	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3817	}
		3818	}
		3819
		3820	Now, whenever the main thread gets told to invoke pending watchers, it
		3821	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3822	thread to continue:
		3823
		3824	static void
		3825	real_invoke_pending (EV_P)
		3826	{
		3827	userdata *u = ev_userdata (EV_A);
		3828
		3829	pthread_mutex_lock (&u->lock);
		3830	ev_invoke_pending (EV_A);
		3831	pthread_cond_signal (&u->invoke_cv);
		3832	pthread_mutex_unlock (&u->lock);
		3833	}
		3834
		3835	Whenever you want to start/stop a watcher or do other modifications to an
		3836	event loop, you will now have to lock:
		3837
		3838	ev_timer timeout_watcher;
		3839	userdata *u = ev_userdata (EV_A);
		3840
		3841	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3842
		3843	pthread_mutex_lock (&u->lock);
		3844	ev_timer_start (EV_A_ &timeout_watcher);
		3845	ev_async_send (EV_A_ &u->async_w);
		3846	pthread_mutex_unlock (&u->lock);
		3847
		3848	Note that sending the C<ev_async> watcher is required because otherwise
		3849	an event loop currently blocking in the kernel will have no knowledge
		3850	about the newly added timer. By waking up the loop it will pick up any new
		3851	watchers in the next event loop iteration.
		3852
		3853	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3854
		3855	While the overhead of a callback that e.g. schedules a thread is small, it
		3856	is still an overhead. If you embed libev, and your main usage is with some
		3857	kind of threads or coroutines, you might want to customise libev so that
		3858	doesn't need callbacks anymore.
		3859
		3860	Imagine you have coroutines that you can switch to using a function
		3861	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3862	and that due to some magic, the currently active coroutine is stored in a
		3863	global called C<current_coro>. Then you can build your own "wait for libev
		3864	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3865	the differing C<;> conventions):
		3866
		3867	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3868	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3869
		3870	That means instead of having a C callback function, you store the
		3871	coroutine to switch to in each watcher, and instead of having libev call
		3872	your callback, you instead have it switch to that coroutine.
		3873
		3874	A coroutine might now wait for an event with a function called
		3875	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3876	matter when, or whether the watcher is active or not when this function is
		3877	called):
		3878
		3879	void
		3880	wait_for_event (ev_watcher *w)
		3881	{
		3882	ev_set_cb (w, current_coro);
		3883	switch_to (libev_coro);
		3884	}
		3885
		3886	That basically suspends the coroutine inside C<wait_for_event> and
		3887	continues the libev coroutine, which, when appropriate, switches back to
		3888	this or any other coroutine.
		3889
		3890	You can do similar tricks if you have, say, threads with an event queue -
		3891	instead of storing a coroutine, you store the queue object and instead of
		3892	switching to a coroutine, you push the watcher onto the queue and notify
		3893	any waiters.
		3894
		3895	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3896	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3897
		3898	// my_ev.h
		3899	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3900	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb);
		3901	#include "../libev/ev.h"
		3902
		3903	// my_ev.c
		3904	#define EV_H "my_ev.h"
		3905	#include "../libev/ev.c"
		3906
		3907	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3908	F<my_ev.c> into your project. When properly specifying include paths, you
		3909	can even use F<ev.h> as header file name directly.
2972		3910
2973		3911
2974	=head1 LIBEVENT EMULATION	3912	=head1 LIBEVENT EMULATION
2975		3913
2976	Libev offers a compatibility emulation layer for libevent. It cannot	3914	Libev offers a compatibility emulation layer for libevent. It cannot
2977	emulate the internals of libevent, so here are some usage hints:	3915	emulate the internals of libevent, so here are some usage hints:
2978		3916
2979	=over 4	3917	=over 4
		3918
		3919	=item * Only the libevent-1.4.1-beta API is being emulated.
		3920
		3921	This was the newest libevent version available when libev was implemented,
		3922	and is still mostly unchanged in 2010.
2980		3923
2981	=item * Use it by including <event.h>, as usual.	3924	=item * Use it by including <event.h>, as usual.
2982		3925
2983	=item * The following members are fully supported: ev_base, ev_callback,	3926	=item * The following members are fully supported: ev_base, ev_callback,
2984	ev_arg, ev_fd, ev_res, ev_events.	3927	ev_arg, ev_fd, ev_res, ev_events.
…		…
2990	=item * Priorities are not currently supported. Initialising priorities	3933	=item * Priorities are not currently supported. Initialising priorities
2991	will fail and all watchers will have the same priority, even though there	3934	will fail and all watchers will have the same priority, even though there
2992	is an ev_pri field.	3935	is an ev_pri field.
2993		3936
2994	=item * In libevent, the last base created gets the signals, in libev, the	3937	=item * In libevent, the last base created gets the signals, in libev, the
2995	first base created (== the default loop) gets the signals.	3938	base that registered the signal gets the signals.
2996		3939
2997	=item * Other members are not supported.	3940	=item * Other members are not supported.
2998		3941
2999	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3942	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3000	to use the libev header file and library.	3943	to use the libev header file and library.
3001		3944
3002	=back	3945	=back
3003		3946
3004	=head1 C++ SUPPORT	3947	=head1 C++ SUPPORT
		3948
		3949	=head2 C API
		3950
		3951	The normal C API should work fine when used from C++: both ev.h and the
		3952	libev sources can be compiled as C++. Therefore, code that uses the C API
		3953	will work fine.
		3954
		3955	Proper exception specifications might have to be added to callbacks passed
		3956	to libev: exceptions may be thrown only from watcher callbacks, all
		3957	other callbacks (allocator, syserr, loop acquire/release and periodic
		3958	reschedule callbacks) must not throw exceptions, and might need a C<throw
		3959	()> specification. If you have code that needs to be compiled as both C
		3960	and C++ you can use the C<EV_THROW> macro for this:
		3961
		3962	static void
		3963	fatal_error (const char *msg) EV_THROW
		3964	{
		3965	perror (msg);
		3966	abort ();
		3967	}
		3968
		3969	...
		3970	ev_set_syserr_cb (fatal_error);
		3971
		3972	The only API functions that can currently throw exceptions are C<ev_run>,
		3973	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		3974	because it runs cleanup watchers).
		3975
		3976	Throwing exceptions in watcher callbacks is only supported if libev itself
		3977	is compiled with a C++ compiler or your C and C++ environments allow
		3978	throwing exceptions through C libraries (most do).
		3979
		3980	=head2 C++ API
3005		3981
3006	Libev comes with some simplistic wrapper classes for C++ that mainly allow	3982	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3007	you to use some convenience methods to start/stop watchers and also change	3983	you to use some convenience methods to start/stop watchers and also change
3008	the callback model to a model using method callbacks on objects.	3984	the callback model to a model using method callbacks on objects.
3009		3985
…		…
3019	Care has been taken to keep the overhead low. The only data member the C++	3995	Care has been taken to keep the overhead low. The only data member the C++
3020	classes add (compared to plain C-style watchers) is the event loop pointer	3996	classes add (compared to plain C-style watchers) is the event loop pointer
3021	that the watcher is associated with (or no additional members at all if	3997	that the watcher is associated with (or no additional members at all if
3022	you disable C<EV_MULTIPLICITY> when embedding libev).	3998	you disable C<EV_MULTIPLICITY> when embedding libev).
3023		3999
3024	Currently, functions, and static and non-static member functions can be	4000	Currently, functions, static and non-static member functions and classes
3025	used as callbacks. Other types should be easy to add as long as they only	4001	with C<operator ()> can be used as callbacks. Other types should be easy
3026	need one additional pointer for context. If you need support for other	4002	to add as long as they only need one additional pointer for context. If
3027	types of functors please contact the author (preferably after implementing	4003	you need support for other types of functors please contact the author
3028	it).	4004	(preferably after implementing it).
		4005
		4006	For all this to work, your C++ compiler either has to use the same calling
		4007	conventions as your C compiler (for static member functions), or you have
		4008	to embed libev and compile libev itself as C++.
3029		4009
3030	Here is a list of things available in the C<ev> namespace:	4010	Here is a list of things available in the C<ev> namespace:
3031		4011
3032	=over 4	4012	=over 4
3033		4013
…		…
3043	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4023	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3044		4024
3045	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4025	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3046	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4026	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3047	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4027	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3048	defines by many implementations.	4028	defined by many implementations.
3049		4029
3050	All of those classes have these methods:	4030	All of those classes have these methods:
3051		4031
3052	=over 4	4032	=over 4
3053		4033
3054	=item ev::TYPE::TYPE ()	4034	=item ev::TYPE::TYPE ()
3055		4035
3056	=item ev::TYPE::TYPE (struct ev_loop *)	4036	=item ev::TYPE::TYPE (loop)
3057		4037
3058	=item ev::TYPE::~TYPE	4038	=item ev::TYPE::~TYPE
3059		4039
3060	The constructor (optionally) takes an event loop to associate the watcher	4040	The constructor (optionally) takes an event loop to associate the watcher
3061	with. If it is omitted, it will use C<EV_DEFAULT>.	4041	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3094	myclass obj;	4074	myclass obj;
3095	ev::io iow;	4075	ev::io iow;
3096	iow.set <myclass, &myclass::io_cb> (&obj);	4076	iow.set <myclass, &myclass::io_cb> (&obj);
3097		4077
3098	=item w->set (object *)	4078	=item w->set (object *)
3099
3100	This is an B<experimental> feature that might go away in a future version.
3101		4079
3102	This is a variation of a method callback - leaving out the method to call	4080	This is a variation of a method callback - leaving out the method to call
3103	will default the method to C<operator ()>, which makes it possible to use	4081	will default the method to C<operator ()>, which makes it possible to use
3104	functor objects without having to manually specify the C<operator ()> all	4082	functor objects without having to manually specify the C<operator ()> all
3105	the time. Incidentally, you can then also leave out the template argument	4083	the time. Incidentally, you can then also leave out the template argument
…		…
3138	Example: Use a plain function as callback.	4116	Example: Use a plain function as callback.
3139		4117
3140	static void io_cb (ev::io &w, int revents) { }	4118	static void io_cb (ev::io &w, int revents) { }
3141	iow.set <io_cb> ();	4119	iow.set <io_cb> ();
3142		4120
3143	=item w->set (struct ev_loop *)	4121	=item w->set (loop)
3144		4122
3145	Associates a different C<struct ev_loop> with this watcher. You can only	4123	Associates a different C<struct ev_loop> with this watcher. You can only
3146	do this when the watcher is inactive (and not pending either).	4124	do this when the watcher is inactive (and not pending either).
3147		4125
3148	=item w->set ([arguments])	4126	=item w->set ([arguments])
3149		4127
3150	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4128	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4129	with the same arguments. Either this method or a suitable start method
3151	called at least once. Unlike the C counterpart, an active watcher gets	4130	must be called at least once. Unlike the C counterpart, an active watcher
3152	automatically stopped and restarted when reconfiguring it with this	4131	gets automatically stopped and restarted when reconfiguring it with this
3153	method.	4132	method.
		4133
		4134	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4135	clashing with the C<set (loop)> method.
3154		4136
3155	=item w->start ()	4137	=item w->start ()
3156		4138
3157	Starts the watcher. Note that there is no C<loop> argument, as the	4139	Starts the watcher. Note that there is no C<loop> argument, as the
3158	constructor already stores the event loop.	4140	constructor already stores the event loop.
3159		4141
		4142	=item w->start ([arguments])
		4143
		4144	Instead of calling C<set> and C<start> methods separately, it is often
		4145	convenient to wrap them in one call. Uses the same type of arguments as
		4146	the configure C<set> method of the watcher.
		4147
3160	=item w->stop ()	4148	=item w->stop ()
3161		4149
3162	Stops the watcher if it is active. Again, no C<loop> argument.	4150	Stops the watcher if it is active. Again, no C<loop> argument.
3163		4151
3164	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4152	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3176		4164
3177	=back	4165	=back
3178		4166
3179	=back	4167	=back
3180		4168
3181	Example: Define a class with an IO and idle watcher, start one of them in	4169	Example: Define a class with two I/O and idle watchers, start the I/O
3182	the constructor.	4170	watchers in the constructor.
3183		4171
3184	class myclass	4172	class myclass
3185	{	4173	{
3186	ev::io io ; void io_cb (ev::io &w, int revents);	4174	ev::io io ; void io_cb (ev::io &w, int revents);
		4175	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3187	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4176	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3188		4177
3189	myclass (int fd)	4178	myclass (int fd)
3190	{	4179	{
3191	io .set <myclass, &myclass::io_cb > (this);	4180	io .set <myclass, &myclass::io_cb > (this);
		4181	io2 .set <myclass, &myclass::io2_cb > (this);
3192	idle.set <myclass, &myclass::idle_cb> (this);	4182	idle.set <myclass, &myclass::idle_cb> (this);
3193		4183
3194	io.start (fd, ev::READ);	4184	io.set (fd, ev::WRITE); // configure the watcher
		4185	io.start (); // start it whenever convenient
		4186
		4187	io2.start (fd, ev::READ); // set + start in one call
3195	}	4188	}
3196	};	4189	};
3197		4190
3198		4191
3199	=head1 OTHER LANGUAGE BINDINGS	4192	=head1 OTHER LANGUAGE BINDINGS
…		…
3238	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4231	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3239		4232
3240	=item D	4233	=item D
3241		4234
3242	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4235	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3243	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4236	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3244		4237
3245	=item Ocaml	4238	=item Ocaml
3246		4239
3247	Erkki Seppala has written Ocaml bindings for libev, to be found at	4240	Erkki Seppala has written Ocaml bindings for libev, to be found at
3248	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4241	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4242
		4243	=item Lua
		4244
		4245	Brian Maher has written a partial interface to libev for lua (at the
		4246	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4247	L<http://github.com/brimworks/lua-ev>.
		4248
		4249	=item Javascript
		4250
		4251	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4252
		4253	=item Others
		4254
		4255	There are others, and I stopped counting.
3249		4256
3250	=back	4257	=back
3251		4258
3252		4259
3253	=head1 MACRO MAGIC	4260	=head1 MACRO MAGIC
…		…
3267	loop argument"). The C<EV_A> form is used when this is the sole argument,	4274	loop argument"). The C<EV_A> form is used when this is the sole argument,
3268	C<EV_A_> is used when other arguments are following. Example:	4275	C<EV_A_> is used when other arguments are following. Example:
3269		4276
3270	ev_unref (EV_A);	4277	ev_unref (EV_A);
3271	ev_timer_add (EV_A_ watcher);	4278	ev_timer_add (EV_A_ watcher);
3272	ev_loop (EV_A_ 0);	4279	ev_run (EV_A_ 0);
3273		4280
3274	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4281	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3275	which is often provided by the following macro.	4282	which is often provided by the following macro.
3276		4283
3277	=item C<EV_P>, C<EV_P_>	4284	=item C<EV_P>, C<EV_P_>
…		…
3290	suitable for use with C<EV_A>.	4297	suitable for use with C<EV_A>.
3291		4298
3292	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4299	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3293		4300
3294	Similar to the other two macros, this gives you the value of the default	4301	Similar to the other two macros, this gives you the value of the default
3295	loop, if multiple loops are supported ("ev loop default").	4302	loop, if multiple loops are supported ("ev loop default"). The default loop
		4303	will be initialised if it isn't already initialised.
		4304
		4305	For non-multiplicity builds, these macros do nothing, so you always have
		4306	to initialise the loop somewhere.
3296		4307
3297	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4308	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3298		4309
3299	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4310	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3300	default loop has been initialised (C<UC> == unchecked). Their behaviour	4311	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3317	}	4328	}
3318		4329
3319	ev_check check;	4330	ev_check check;
3320	ev_check_init (&check, check_cb);	4331	ev_check_init (&check, check_cb);
3321	ev_check_start (EV_DEFAULT_ &check);	4332	ev_check_start (EV_DEFAULT_ &check);
3322	ev_loop (EV_DEFAULT_ 0);	4333	ev_run (EV_DEFAULT_ 0);
3323		4334
3324	=head1 EMBEDDING	4335	=head1 EMBEDDING
3325		4336
3326	Libev can (and often is) directly embedded into host	4337	Libev can (and often is) directly embedded into host
3327	applications. Examples of applications that embed it include the Deliantra	4338	applications. Examples of applications that embed it include the Deliantra
…		…
3407	libev.m4	4418	libev.m4
3408		4419
3409	=head2 PREPROCESSOR SYMBOLS/MACROS	4420	=head2 PREPROCESSOR SYMBOLS/MACROS
3410		4421
3411	Libev can be configured via a variety of preprocessor symbols you have to	4422	Libev can be configured via a variety of preprocessor symbols you have to
3412	define before including any of its files. The default in the absence of	4423	define before including (or compiling) any of its files. The default in
3413	autoconf is documented for every option.	4424	the absence of autoconf is documented for every option.
		4425
		4426	Symbols marked with "(h)" do not change the ABI, and can have different
		4427	values when compiling libev vs. including F<ev.h>, so it is permissible
		4428	to redefine them before including F<ev.h> without breaking compatibility
		4429	to a compiled library. All other symbols change the ABI, which means all
		4430	users of libev and the libev code itself must be compiled with compatible
		4431	settings.
3414		4432
3415	=over 4	4433	=over 4
3416		4434
		4435	=item EV_COMPAT3 (h)
		4436
		4437	Backwards compatibility is a major concern for libev. This is why this
		4438	release of libev comes with wrappers for the functions and symbols that
		4439	have been renamed between libev version 3 and 4.
		4440
		4441	You can disable these wrappers (to test compatibility with future
		4442	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4443	sources. This has the additional advantage that you can drop the C<struct>
		4444	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4445	typedef in that case.
		4446
		4447	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4448	and in some even more future version the compatibility code will be
		4449	removed completely.
		4450
3417	=item EV_STANDALONE	4451	=item EV_STANDALONE (h)
3418		4452
3419	Must always be C<1> if you do not use autoconf configuration, which	4453	Must always be C<1> if you do not use autoconf configuration, which
3420	keeps libev from including F<config.h>, and it also defines dummy	4454	keeps libev from including F<config.h>, and it also defines dummy
3421	implementations for some libevent functions (such as logging, which is not	4455	implementations for some libevent functions (such as logging, which is not
3422	supported). It will also not define any of the structs usually found in	4456	supported). It will also not define any of the structs usually found in
3423	F<event.h> that are not directly supported by the libev core alone.	4457	F<event.h> that are not directly supported by the libev core alone.
3424		4458
3425	In stanbdalone mode, libev will still try to automatically deduce the	4459	In standalone mode, libev will still try to automatically deduce the
3426	configuration, but has to be more conservative.	4460	configuration, but has to be more conservative.
		4461
		4462	=item EV_USE_FLOOR
		4463
		4464	If defined to be C<1>, libev will use the C<floor ()> function for its
		4465	periodic reschedule calculations, otherwise libev will fall back on a
		4466	portable (slower) implementation. If you enable this, you usually have to
		4467	link against libm or something equivalent. Enabling this when the C<floor>
		4468	function is not available will fail, so the safe default is to not enable
		4469	this.
3427		4470
3428	=item EV_USE_MONOTONIC	4471	=item EV_USE_MONOTONIC
3429		4472
3430	If defined to be C<1>, libev will try to detect the availability of the	4473	If defined to be C<1>, libev will try to detect the availability of the
3431	monotonic clock option at both compile time and runtime. Otherwise no	4474	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3495	be used is the winsock select). This means that it will call	4538	be used is the winsock select). This means that it will call
3496	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4539	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3497	it is assumed that all these functions actually work on fds, even	4540	it is assumed that all these functions actually work on fds, even
3498	on win32. Should not be defined on non-win32 platforms.	4541	on win32. Should not be defined on non-win32 platforms.
3499		4542
3500	=item EV_FD_TO_WIN32_HANDLE	4543	=item EV_FD_TO_WIN32_HANDLE(fd)
3501		4544
3502	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4545	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3503	file descriptors to socket handles. When not defining this symbol (the	4546	file descriptors to socket handles. When not defining this symbol (the
3504	default), then libev will call C<_get_osfhandle>, which is usually	4547	default), then libev will call C<_get_osfhandle>, which is usually
3505	correct. In some cases, programs use their own file descriptor management,	4548	correct. In some cases, programs use their own file descriptor management,
3506	in which case they can provide this function to map fds to socket handles.	4549	in which case they can provide this function to map fds to socket handles.
		4550
		4551	=item EV_WIN32_HANDLE_TO_FD(handle)
		4552
		4553	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4554	using the standard C<_open_osfhandle> function. For programs implementing
		4555	their own fd to handle mapping, overwriting this function makes it easier
		4556	to do so. This can be done by defining this macro to an appropriate value.
		4557
		4558	=item EV_WIN32_CLOSE_FD(fd)
		4559
		4560	If programs implement their own fd to handle mapping on win32, then this
		4561	macro can be used to override the C<close> function, useful to unregister
		4562	file descriptors again. Note that the replacement function has to close
		4563	the underlying OS handle.
		4564
		4565	=item EV_USE_WSASOCKET
		4566
		4567	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4568	communication socket, which works better in some environments. Otherwise,
		4569	the normal C<socket> function will be used, which works better in other
		4570	environments.
3507		4571
3508	=item EV_USE_POLL	4572	=item EV_USE_POLL
3509		4573
3510	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4574	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3511	backend. Otherwise it will be enabled on non-win32 platforms. It	4575	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3547	If defined to be C<1>, libev will compile in support for the Linux inotify	4611	If defined to be C<1>, libev will compile in support for the Linux inotify
3548	interface to speed up C<ev_stat> watchers. Its actual availability will	4612	interface to speed up C<ev_stat> watchers. Its actual availability will
3549	be detected at runtime. If undefined, it will be enabled if the headers	4613	be detected at runtime. If undefined, it will be enabled if the headers
3550	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4614	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3551		4615
		4616	=item EV_NO_SMP
		4617
		4618	If defined to be C<1>, libev will assume that memory is always coherent
		4619	between threads, that is, threads can be used, but threads never run on
		4620	different cpus (or different cpu cores). This reduces dependencies
		4621	and makes libev faster.
		4622
		4623	=item EV_NO_THREADS
		4624
		4625	If defined to be C<1>, libev will assume that it will never be called from
		4626	different threads (that includes signal handlers), which is a stronger
		4627	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4628	libev faster.
		4629
3552	=item EV_ATOMIC_T	4630	=item EV_ATOMIC_T
3553		4631
3554	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4632	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3555	access is atomic with respect to other threads or signal contexts. No such	4633	access is atomic with respect to other threads or signal contexts. No
3556	type is easily found in the C language, so you can provide your own type	4634	such type is easily found in the C language, so you can provide your own
3557	that you know is safe for your purposes. It is used both for signal handler "locking"	4635	type that you know is safe for your purposes. It is used both for signal
3558	as well as for signal and thread safety in C<ev_async> watchers.	4636	handler "locking" as well as for signal and thread safety in C<ev_async>
		4637	watchers.
3559		4638
3560	In the absence of this define, libev will use C<sig_atomic_t volatile>	4639	In the absence of this define, libev will use C<sig_atomic_t volatile>
3561	(from F<signal.h>), which is usually good enough on most platforms.	4640	(from F<signal.h>), which is usually good enough on most platforms.
3562		4641
3563	=item EV_H	4642	=item EV_H (h)
3564		4643
3565	The name of the F<ev.h> header file used to include it. The default if	4644	The name of the F<ev.h> header file used to include it. The default if
3566	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4645	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3567	used to virtually rename the F<ev.h> header file in case of conflicts.	4646	used to virtually rename the F<ev.h> header file in case of conflicts.
3568		4647
3569	=item EV_CONFIG_H	4648	=item EV_CONFIG_H (h)
3570		4649
3571	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4650	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3572	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4651	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3573	C<EV_H>, above.	4652	C<EV_H>, above.
3574		4653
3575	=item EV_EVENT_H	4654	=item EV_EVENT_H (h)
3576		4655
3577	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4656	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3578	of how the F<event.h> header can be found, the default is C<"event.h">.	4657	of how the F<event.h> header can be found, the default is C<"event.h">.
3579		4658
3580	=item EV_PROTOTYPES	4659	=item EV_PROTOTYPES (h)
3581		4660
3582	If defined to be C<0>, then F<ev.h> will not define any function	4661	If defined to be C<0>, then F<ev.h> will not define any function
3583	prototypes, but still define all the structs and other symbols. This is	4662	prototypes, but still define all the structs and other symbols. This is
3584	occasionally useful if you want to provide your own wrapper functions	4663	occasionally useful if you want to provide your own wrapper functions
3585	around libev functions.	4664	around libev functions.
…		…
3590	will have the C<struct ev_loop *> as first argument, and you can create	4669	will have the C<struct ev_loop *> as first argument, and you can create
3591	additional independent event loops. Otherwise there will be no support	4670	additional independent event loops. Otherwise there will be no support
3592	for multiple event loops and there is no first event loop pointer	4671	for multiple event loops and there is no first event loop pointer
3593	argument. Instead, all functions act on the single default loop.	4672	argument. Instead, all functions act on the single default loop.
3594		4673
		4674	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4675	default loop when multiplicity is switched off - you always have to
		4676	initialise the loop manually in this case.
		4677
3595	=item EV_MINPRI	4678	=item EV_MINPRI
3596		4679
3597	=item EV_MAXPRI	4680	=item EV_MAXPRI
3598		4681
3599	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4682	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3607	fine.	4690	fine.
3608		4691
3609	If your embedding application does not need any priorities, defining these	4692	If your embedding application does not need any priorities, defining these
3610	both to C<0> will save some memory and CPU.	4693	both to C<0> will save some memory and CPU.
3611		4694
3612	=item EV_PERIODIC_ENABLE	4695	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4696	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4697	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3613		4698
3614	If undefined or defined to be C<1>, then periodic timers are supported. If	4699	If undefined or defined to be C<1> (and the platform supports it), then
3615	defined to be C<0>, then they are not. Disabling them saves a few kB of	4700	the respective watcher type is supported. If defined to be C<0>, then it
3616	code.	4701	is not. Disabling watcher types mainly saves code size.
3617		4702
3618	=item EV_IDLE_ENABLE	4703	=item EV_FEATURES
3619
3620	If undefined or defined to be C<1>, then idle watchers are supported. If
3621	defined to be C<0>, then they are not. Disabling them saves a few kB of
3622	code.
3623
3624	=item EV_EMBED_ENABLE
3625
3626	If undefined or defined to be C<1>, then embed watchers are supported. If
3627	defined to be C<0>, then they are not. Embed watchers rely on most other
3628	watcher types, which therefore must not be disabled.
3629
3630	=item EV_STAT_ENABLE
3631
3632	If undefined or defined to be C<1>, then stat watchers are supported. If
3633	defined to be C<0>, then they are not.
3634
3635	=item EV_FORK_ENABLE
3636
3637	If undefined or defined to be C<1>, then fork watchers are supported. If
3638	defined to be C<0>, then they are not.
3639
3640	=item EV_ASYNC_ENABLE
3641
3642	If undefined or defined to be C<1>, then async watchers are supported. If
3643	defined to be C<0>, then they are not.
3644
3645	=item EV_MINIMAL
3646		4704
3647	If you need to shave off some kilobytes of code at the expense of some	4705	If you need to shave off some kilobytes of code at the expense of some
3648	speed, define this symbol to C<1>. Currently this is used to override some	4706	speed (but with the full API), you can define this symbol to request
3649	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4707	certain subsets of functionality. The default is to enable all features
3650	much smaller 2-heap for timer management over the default 4-heap.	4708	that can be enabled on the platform.
		4709
		4710	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4711	with some broad features you want) and then selectively re-enable
		4712	additional parts you want, for example if you want everything minimal,
		4713	but multiple event loop support, async and child watchers and the poll
		4714	backend, use this:
		4715
		4716	#define EV_FEATURES 0
		4717	#define EV_MULTIPLICITY 1
		4718	#define EV_USE_POLL 1
		4719	#define EV_CHILD_ENABLE 1
		4720	#define EV_ASYNC_ENABLE 1
		4721
		4722	The actual value is a bitset, it can be a combination of the following
		4723	values (by default, all of these are enabled):
		4724
		4725	=over 4
		4726
		4727	=item C<1> - faster/larger code
		4728
		4729	Use larger code to speed up some operations.
		4730
		4731	Currently this is used to override some inlining decisions (enlarging the
		4732	code size by roughly 30% on amd64).
		4733
		4734	When optimising for size, use of compiler flags such as C<-Os> with
		4735	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4736	assertions.
		4737
		4738	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4739	(e.g. gcc with C<-Os>).
		4740
		4741	=item C<2> - faster/larger data structures
		4742
		4743	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4744	hash table sizes and so on. This will usually further increase code size
		4745	and can additionally have an effect on the size of data structures at
		4746	runtime.
		4747
		4748	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4749	(e.g. gcc with C<-Os>).
		4750
		4751	=item C<4> - full API configuration
		4752
		4753	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4754	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4755
		4756	=item C<8> - full API
		4757
		4758	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4759	details on which parts of the API are still available without this
		4760	feature, and do not complain if this subset changes over time.
		4761
		4762	=item C<16> - enable all optional watcher types
		4763
		4764	Enables all optional watcher types. If you want to selectively enable
		4765	only some watcher types other than I/O and timers (e.g. prepare,
		4766	embed, async, child...) you can enable them manually by defining
		4767	C<EV_watchertype_ENABLE> to C<1> instead.
		4768
		4769	=item C<32> - enable all backends
		4770
		4771	This enables all backends - without this feature, you need to enable at
		4772	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4773
		4774	=item C<64> - enable OS-specific "helper" APIs
		4775
		4776	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4777	default.
		4778
		4779	=back
		4780
		4781	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4782	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4783	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4784	watchers, timers and monotonic clock support.
		4785
		4786	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4787	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4788	your program might be left out as well - a binary starting a timer and an
		4789	I/O watcher then might come out at only 5Kb.
		4790
		4791	=item EV_API_STATIC
		4792
		4793	If this symbol is defined (by default it is not), then all identifiers
		4794	will have static linkage. This means that libev will not export any
		4795	identifiers, and you cannot link against libev anymore. This can be useful
		4796	when you embed libev, only want to use libev functions in a single file,
		4797	and do not want its identifiers to be visible.
		4798
		4799	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4800	wants to use libev.
		4801
		4802	This option only works when libev is compiled with a C compiler, as C++
		4803	doesn't support the required declaration syntax.
		4804
		4805	=item EV_AVOID_STDIO
		4806
		4807	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4808	functions (printf, scanf, perror etc.). This will increase the code size
		4809	somewhat, but if your program doesn't otherwise depend on stdio and your
		4810	libc allows it, this avoids linking in the stdio library which is quite
		4811	big.
		4812
		4813	Note that error messages might become less precise when this option is
		4814	enabled.
		4815
		4816	=item EV_NSIG
		4817
		4818	The highest supported signal number, +1 (or, the number of
		4819	signals): Normally, libev tries to deduce the maximum number of signals
		4820	automatically, but sometimes this fails, in which case it can be
		4821	specified. Also, using a lower number than detected (C<32> should be
		4822	good for about any system in existence) can save some memory, as libev
		4823	statically allocates some 12-24 bytes per signal number.
3651		4824
3652	=item EV_PID_HASHSIZE	4825	=item EV_PID_HASHSIZE
3653		4826
3654	C<ev_child> watchers use a small hash table to distribute workload by	4827	C<ev_child> watchers use a small hash table to distribute workload by
3655	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4828	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3656	than enough. If you need to manage thousands of children you might want to	4829	usually more than enough. If you need to manage thousands of children you
3657	increase this value (I<must> be a power of two).	4830	might want to increase this value (I<must> be a power of two).
3658		4831
3659	=item EV_INOTIFY_HASHSIZE	4832	=item EV_INOTIFY_HASHSIZE
3660		4833
3661	C<ev_stat> watchers use a small hash table to distribute workload by	4834	C<ev_stat> watchers use a small hash table to distribute workload by
3662	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4835	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3663	usually more than enough. If you need to manage thousands of C<ev_stat>	4836	disabled), usually more than enough. If you need to manage thousands of
3664	watchers you might want to increase this value (I<must> be a power of	4837	C<ev_stat> watchers you might want to increase this value (I<must> be a
3665	two).	4838	power of two).
3666		4839
3667	=item EV_USE_4HEAP	4840	=item EV_USE_4HEAP
3668		4841
3669	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4842	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3670	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4843	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3671	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4844	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3672	faster performance with many (thousands) of watchers.	4845	faster performance with many (thousands) of watchers.
3673		4846
3674	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4847	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3675	(disabled).	4848	will be C<0>.
3676		4849
3677	=item EV_HEAP_CACHE_AT	4850	=item EV_HEAP_CACHE_AT
3678		4851
3679	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4852	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3680	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4853	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3681	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4854	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3682	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4855	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3683	but avoids random read accesses on heap changes. This improves performance	4856	but avoids random read accesses on heap changes. This improves performance
3684	noticeably with many (hundreds) of watchers.	4857	noticeably with many (hundreds) of watchers.
3685		4858
3686	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4859	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3687	(disabled).	4860	will be C<0>.
3688		4861
3689	=item EV_VERIFY	4862	=item EV_VERIFY
3690		4863
3691	Controls how much internal verification (see C<ev_loop_verify ()>) will	4864	Controls how much internal verification (see C<ev_verify ()>) will
3692	be done: If set to C<0>, no internal verification code will be compiled	4865	be done: If set to C<0>, no internal verification code will be compiled
3693	in. If set to C<1>, then verification code will be compiled in, but not	4866	in. If set to C<1>, then verification code will be compiled in, but not
3694	called. If set to C<2>, then the internal verification code will be	4867	called. If set to C<2>, then the internal verification code will be
3695	called once per loop, which can slow down libev. If set to C<3>, then the	4868	called once per loop, which can slow down libev. If set to C<3>, then the
3696	verification code will be called very frequently, which will slow down	4869	verification code will be called very frequently, which will slow down
3697	libev considerably.	4870	libev considerably.
3698		4871
3699	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4872	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3700	C<0>.	4873	will be C<0>.
3701		4874
3702	=item EV_COMMON	4875	=item EV_COMMON
3703		4876
3704	By default, all watchers have a C<void *data> member. By redefining	4877	By default, all watchers have a C<void *data> member. By redefining
3705	this macro to a something else you can include more and other types of	4878	this macro to something else you can include more and other types of
3706	members. You have to define it each time you include one of the files,	4879	members. You have to define it each time you include one of the files,
3707	though, and it must be identical each time.	4880	though, and it must be identical each time.
3708		4881
3709	For example, the perl EV module uses something like this:	4882	For example, the perl EV module uses something like this:
3710		4883
…		…
3763	file.	4936	file.
3764		4937
3765	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4938	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3766	that everybody includes and which overrides some configure choices:	4939	that everybody includes and which overrides some configure choices:
3767		4940
3768	#define EV_MINIMAL 1	4941	#define EV_FEATURES 8
3769	#define EV_USE_POLL 0	4942	#define EV_USE_SELECT 1
3770	#define EV_MULTIPLICITY 0
3771	#define EV_PERIODIC_ENABLE 0	4943	#define EV_PREPARE_ENABLE 1
		4944	#define EV_IDLE_ENABLE 1
3772	#define EV_STAT_ENABLE 0	4945	#define EV_SIGNAL_ENABLE 1
3773	#define EV_FORK_ENABLE 0	4946	#define EV_CHILD_ENABLE 1
		4947	#define EV_USE_STDEXCEPT 0
3774	#define EV_CONFIG_H <config.h>	4948	#define EV_CONFIG_H <config.h>
3775	#define EV_MINPRI 0
3776	#define EV_MAXPRI 0
3777		4949
3778	#include "ev++.h"	4950	#include "ev++.h"
3779		4951
3780	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4952	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3781		4953
3782	#include "ev_cpp.h"	4954	#include "ev_cpp.h"
3783	#include "ev.c"	4955	#include "ev.c"
3784		4956
3785	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	4957	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3786		4958
3787	=head2 THREADS AND COROUTINES	4959	=head2 THREADS AND COROUTINES
3788		4960
3789	=head3 THREADS	4961	=head3 THREADS
3790		4962
…		…
3841	default loop and triggering an C<ev_async> watcher from the default loop	5013	default loop and triggering an C<ev_async> watcher from the default loop
3842	watcher callback into the event loop interested in the signal.	5014	watcher callback into the event loop interested in the signal.
3843		5015
3844	=back	5016	=back
3845		5017
		5018	See also L</THREAD LOCKING EXAMPLE>.
		5019
3846	=head3 COROUTINES	5020	=head3 COROUTINES
3847		5021
3848	Libev is very accommodating to coroutines ("cooperative threads"):	5022	Libev is very accommodating to coroutines ("cooperative threads"):
3849	libev fully supports nesting calls to its functions from different	5023	libev fully supports nesting calls to its functions from different
3850	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5024	coroutines (e.g. you can call C<ev_run> on the same loop from two
3851	different coroutines, and switch freely between both coroutines running the	5025	different coroutines, and switch freely between both coroutines running
3852	loop, as long as you don't confuse yourself). The only exception is that	5026	the loop, as long as you don't confuse yourself). The only exception is
3853	you must not do this from C<ev_periodic> reschedule callbacks.	5027	that you must not do this from C<ev_periodic> reschedule callbacks.
3854		5028
3855	Care has been taken to ensure that libev does not keep local state inside	5029	Care has been taken to ensure that libev does not keep local state inside
3856	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5030	C<ev_run>, and other calls do not usually allow for coroutine switches as
3857	they do not call any callbacks.	5031	they do not call any callbacks.
3858		5032
3859	=head2 COMPILER WARNINGS	5033	=head2 COMPILER WARNINGS
3860		5034
3861	Depending on your compiler and compiler settings, you might get no or a	5035	Depending on your compiler and compiler settings, you might get no or a
…		…
3872	maintainable.	5046	maintainable.
3873		5047
3874	And of course, some compiler warnings are just plain stupid, or simply	5048	And of course, some compiler warnings are just plain stupid, or simply
3875	wrong (because they don't actually warn about the condition their message	5049	wrong (because they don't actually warn about the condition their message
3876	seems to warn about). For example, certain older gcc versions had some	5050	seems to warn about). For example, certain older gcc versions had some
3877	warnings that resulted an extreme number of false positives. These have	5051	warnings that resulted in an extreme number of false positives. These have
3878	been fixed, but some people still insist on making code warn-free with	5052	been fixed, but some people still insist on making code warn-free with
3879	such buggy versions.	5053	such buggy versions.
3880		5054
3881	While libev is written to generate as few warnings as possible,	5055	While libev is written to generate as few warnings as possible,
3882	"warn-free" code is not a goal, and it is recommended not to build libev	5056	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3918	I suggest using suppression lists.	5092	I suggest using suppression lists.
3919		5093
3920		5094
3921	=head1 PORTABILITY NOTES	5095	=head1 PORTABILITY NOTES
3922		5096
		5097	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5098
		5099	GNU/Linux is the only common platform that supports 64 bit file/large file
		5100	interfaces but I<disables> them by default.
		5101
		5102	That means that libev compiled in the default environment doesn't support
		5103	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5104
		5105	Unfortunately, many programs try to work around this GNU/Linux issue
		5106	by enabling the large file API, which makes them incompatible with the
		5107	standard libev compiled for their system.
		5108
		5109	Likewise, libev cannot enable the large file API itself as this would
		5110	suddenly make it incompatible to the default compile time environment,
		5111	i.e. all programs not using special compile switches.
		5112
		5113	=head2 OS/X AND DARWIN BUGS
		5114
		5115	The whole thing is a bug if you ask me - basically any system interface
		5116	you touch is broken, whether it is locales, poll, kqueue or even the
		5117	OpenGL drivers.
		5118
		5119	=head3 C<kqueue> is buggy
		5120
		5121	The kqueue syscall is broken in all known versions - most versions support
		5122	only sockets, many support pipes.
		5123
		5124	Libev tries to work around this by not using C<kqueue> by default on this
		5125	rotten platform, but of course you can still ask for it when creating a
		5126	loop - embedding a socket-only kqueue loop into a select-based one is
		5127	probably going to work well.
		5128
		5129	=head3 C<poll> is buggy
		5130
		5131	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5132	implementation by something calling C<kqueue> internally around the 10.5.6
		5133	release, so now C<kqueue> I<and> C<poll> are broken.
		5134
		5135	Libev tries to work around this by not using C<poll> by default on
		5136	this rotten platform, but of course you can still ask for it when creating
		5137	a loop.
		5138
		5139	=head3 C<select> is buggy
		5140
		5141	All that's left is C<select>, and of course Apple found a way to fuck this
		5142	one up as well: On OS/X, C<select> actively limits the number of file
		5143	descriptors you can pass in to 1024 - your program suddenly crashes when
		5144	you use more.
		5145
		5146	There is an undocumented "workaround" for this - defining
		5147	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5148	work on OS/X.
		5149
		5150	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5151
		5152	=head3 C<errno> reentrancy
		5153
		5154	The default compile environment on Solaris is unfortunately so
		5155	thread-unsafe that you can't even use components/libraries compiled
		5156	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5157	defined by default. A valid, if stupid, implementation choice.
		5158
		5159	If you want to use libev in threaded environments you have to make sure
		5160	it's compiled with C<_REENTRANT> defined.
		5161
		5162	=head3 Event port backend
		5163
		5164	The scalable event interface for Solaris is called "event
		5165	ports". Unfortunately, this mechanism is very buggy in all major
		5166	releases. If you run into high CPU usage, your program freezes or you get
		5167	a large number of spurious wakeups, make sure you have all the relevant
		5168	and latest kernel patches applied. No, I don't know which ones, but there
		5169	are multiple ones to apply, and afterwards, event ports actually work
		5170	great.
		5171
		5172	If you can't get it to work, you can try running the program by setting
		5173	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5174	C<select> backends.
		5175
		5176	=head2 AIX POLL BUG
		5177
		5178	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5179	this by trying to avoid the poll backend altogether (i.e. it's not even
		5180	compiled in), which normally isn't a big problem as C<select> works fine
		5181	with large bitsets on AIX, and AIX is dead anyway.
		5182
3923	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5183	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5184
		5185	=head3 General issues
3924		5186
3925	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5187	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3926	requires, and its I/O model is fundamentally incompatible with the POSIX	5188	requires, and its I/O model is fundamentally incompatible with the POSIX
3927	model. Libev still offers limited functionality on this platform in	5189	model. Libev still offers limited functionality on this platform in
3928	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5190	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3929	descriptors. This only applies when using Win32 natively, not when using	5191	descriptors. This only applies when using Win32 natively, not when using
3930	e.g. cygwin.	5192	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5193	as every compiler comes with a slightly differently broken/incompatible
		5194	environment.
3931		5195
3932	Lifting these limitations would basically require the full	5196	Lifting these limitations would basically require the full
3933	re-implementation of the I/O system. If you are into these kinds of	5197	re-implementation of the I/O system. If you are into this kind of thing,
3934	things, then note that glib does exactly that for you in a very portable	5198	then note that glib does exactly that for you in a very portable way (note
3935	way (note also that glib is the slowest event library known to man).	5199	also that glib is the slowest event library known to man).
3936		5200
3937	There is no supported compilation method available on windows except	5201	There is no supported compilation method available on windows except
3938	embedding it into other applications.	5202	embedding it into other applications.
3939		5203
3940	Sensible signal handling is officially unsupported by Microsoft - libev	5204	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3968	you do I<not> compile the F<ev.c> or any other embedded source files!):	5232	you do I<not> compile the F<ev.c> or any other embedded source files!):
3969		5233
3970	#include "evwrap.h"	5234	#include "evwrap.h"
3971	#include "ev.c"	5235	#include "ev.c"
3972		5236
3973	=over 4
3974
3975	=item The winsocket select function	5237	=head3 The winsocket C<select> function
3976		5238
3977	The winsocket C<select> function doesn't follow POSIX in that it	5239	The winsocket C<select> function doesn't follow POSIX in that it
3978	requires socket I<handles> and not socket I<file descriptors> (it is	5240	requires socket I<handles> and not socket I<file descriptors> (it is
3979	also extremely buggy). This makes select very inefficient, and also	5241	also extremely buggy). This makes select very inefficient, and also
3980	requires a mapping from file descriptors to socket handles (the Microsoft	5242	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3989	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5251	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3990		5252
3991	Note that winsockets handling of fd sets is O(n), so you can easily get a	5253	Note that winsockets handling of fd sets is O(n), so you can easily get a
3992	complexity in the O(n²) range when using win32.	5254	complexity in the O(n²) range when using win32.
3993		5255
3994	=item Limited number of file descriptors	5256	=head3 Limited number of file descriptors
3995		5257
3996	Windows has numerous arbitrary (and low) limits on things.	5258	Windows has numerous arbitrary (and low) limits on things.
3997		5259
3998	Early versions of winsocket's select only supported waiting for a maximum	5260	Early versions of winsocket's select only supported waiting for a maximum
3999	of C<64> handles (probably owning to the fact that all windows kernels	5261	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4014	runtime libraries. This might get you to about C<512> or C<2048> sockets	5276	runtime libraries. This might get you to about C<512> or C<2048> sockets
4015	(depending on windows version and/or the phase of the moon). To get more,	5277	(depending on windows version and/or the phase of the moon). To get more,
4016	you need to wrap all I/O functions and provide your own fd management, but	5278	you need to wrap all I/O functions and provide your own fd management, but
4017	the cost of calling select (O(n²)) will likely make this unworkable.	5279	the cost of calling select (O(n²)) will likely make this unworkable.
4018		5280
4019	=back
4020
4021	=head2 PORTABILITY REQUIREMENTS	5281	=head2 PORTABILITY REQUIREMENTS
4022		5282
4023	In addition to a working ISO-C implementation and of course the	5283	In addition to a working ISO-C implementation and of course the
4024	backend-specific APIs, libev relies on a few additional extensions:	5284	backend-specific APIs, libev relies on a few additional extensions:
4025		5285
…		…
4031	Libev assumes not only that all watcher pointers have the same internal	5291	Libev assumes not only that all watcher pointers have the same internal
4032	structure (guaranteed by POSIX but not by ISO C for example), but it also	5292	structure (guaranteed by POSIX but not by ISO C for example), but it also
4033	assumes that the same (machine) code can be used to call any watcher	5293	assumes that the same (machine) code can be used to call any watcher
4034	callback: The watcher callbacks have different type signatures, but libev	5294	callback: The watcher callbacks have different type signatures, but libev
4035	calls them using an C<ev_watcher *> internally.	5295	calls them using an C<ev_watcher *> internally.
		5296
		5297	=item pointer accesses must be thread-atomic
		5298
		5299	Accessing a pointer value must be atomic, it must both be readable and
		5300	writable in one piece - this is the case on all current architectures.
4036		5301
4037	=item C<sig_atomic_t volatile> must be thread-atomic as well	5302	=item C<sig_atomic_t volatile> must be thread-atomic as well
4038		5303
4039	The type C<sig_atomic_t volatile> (or whatever is defined as	5304	The type C<sig_atomic_t volatile> (or whatever is defined as
4040	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5305	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4049	thread" or will block signals process-wide, both behaviours would	5314	thread" or will block signals process-wide, both behaviours would
4050	be compatible with libev. Interaction between C<sigprocmask> and	5315	be compatible with libev. Interaction between C<sigprocmask> and
4051	C<pthread_sigmask> could complicate things, however.	5316	C<pthread_sigmask> could complicate things, however.
4052		5317
4053	The most portable way to handle signals is to block signals in all threads	5318	The most portable way to handle signals is to block signals in all threads
4054	except the initial one, and run the default loop in the initial thread as	5319	except the initial one, and run the signal handling loop in the initial
4055	well.	5320	thread as well.
4056		5321
4057	=item C<long> must be large enough for common memory allocation sizes	5322	=item C<long> must be large enough for common memory allocation sizes
4058		5323
4059	To improve portability and simplify its API, libev uses C<long> internally	5324	To improve portability and simplify its API, libev uses C<long> internally
4060	instead of C<size_t> when allocating its data structures. On non-POSIX	5325	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4063	watchers.	5328	watchers.
4064		5329
4065	=item C<double> must hold a time value in seconds with enough accuracy	5330	=item C<double> must hold a time value in seconds with enough accuracy
4066		5331
4067	The type C<double> is used to represent timestamps. It is required to	5332	The type C<double> is used to represent timestamps. It is required to
4068	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5333	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4069	enough for at least into the year 4000. This requirement is fulfilled by	5334	good enough for at least into the year 4000 with millisecond accuracy
		5335	(the design goal for libev). This requirement is overfulfilled by
4070	implementations implementing IEEE 754 (basically all existing ones).	5336	implementations using IEEE 754, which is basically all existing ones.
		5337
		5338	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5339	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5340	is either obsolete or somebody patched it to use C<long double> or
		5341	something like that, just kidding).
4071		5342
4072	=back	5343	=back
4073		5344
4074	If you know of other additional requirements drop me a note.	5345	If you know of other additional requirements drop me a note.
4075		5346
…		…
4137	=item Processing ev_async_send: O(number_of_async_watchers)	5408	=item Processing ev_async_send: O(number_of_async_watchers)
4138		5409
4139	=item Processing signals: O(max_signal_number)	5410	=item Processing signals: O(max_signal_number)
4140		5411
4141	Sending involves a system call I<iff> there were no other C<ev_async_send>	5412	Sending involves a system call I<iff> there were no other C<ev_async_send>
4142	calls in the current loop iteration. Checking for async and signal events	5413	calls in the current loop iteration and the loop is currently
		5414	blocked. Checking for async and signal events involves iterating over all
4143	involves iterating over all running async watchers or all signal numbers.	5415	running async watchers or all signal numbers.
4144		5416
4145	=back	5417	=back
4146		5418
4147		5419
		5420	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5421
		5422	The major version 4 introduced some incompatible changes to the API.
		5423
		5424	At the moment, the C<ev.h> header file provides compatibility definitions
		5425	for all changes, so most programs should still compile. The compatibility
		5426	layer might be removed in later versions of libev, so better update to the
		5427	new API early than late.
		5428
		5429	=over 4
		5430
		5431	=item C<EV_COMPAT3> backwards compatibility mechanism
		5432
		5433	The backward compatibility mechanism can be controlled by
		5434	C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING>
		5435	section.
		5436
		5437	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5438
		5439	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5440
		5441	ev_loop_destroy (EV_DEFAULT_UC);
		5442	ev_loop_fork (EV_DEFAULT);
		5443
		5444	=item function/symbol renames
		5445
		5446	A number of functions and symbols have been renamed:
		5447
		5448	ev_loop => ev_run
		5449	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5450	EVLOOP_ONESHOT => EVRUN_ONCE
		5451
		5452	ev_unloop => ev_break
		5453	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5454	EVUNLOOP_ONE => EVBREAK_ONE
		5455	EVUNLOOP_ALL => EVBREAK_ALL
		5456
		5457	EV_TIMEOUT => EV_TIMER
		5458
		5459	ev_loop_count => ev_iteration
		5460	ev_loop_depth => ev_depth
		5461	ev_loop_verify => ev_verify
		5462
		5463	Most functions working on C<struct ev_loop> objects don't have an
		5464	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5465	associated constants have been renamed to not collide with the C<struct
		5466	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5467	as all other watcher types. Note that C<ev_loop_fork> is still called
		5468	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5469	typedef.
		5470
		5471	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5472
		5473	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5474	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5475	and work, but the library code will of course be larger.
		5476
		5477	=back
		5478
		5479
4148	=head1 GLOSSARY	5480	=head1 GLOSSARY
4149		5481
4150	=over 4	5482	=over 4
4151		5483
4152	=item active	5484	=item active
4153		5485
4154	A watcher is active as long as it has been started (has been attached to	5486	A watcher is active as long as it has been started and not yet stopped.
4155	an event loop) but not yet stopped (disassociated from the event loop).	5487	See L</WATCHER STATES> for details.
4156		5488
4157	=item application	5489	=item application
4158		5490
4159	In this document, an application is whatever is using libev.	5491	In this document, an application is whatever is using libev.
		5492
		5493	=item backend
		5494
		5495	The part of the code dealing with the operating system interfaces.
4160		5496
4161	=item callback	5497	=item callback
4162		5498
4163	The address of a function that is called when some event has been	5499	The address of a function that is called when some event has been
4164	detected. Callbacks are being passed the event loop, the watcher that	5500	detected. Callbacks are being passed the event loop, the watcher that
4165	received the event, and the actual event bitset.	5501	received the event, and the actual event bitset.
4166		5502
4167	=item callback invocation	5503	=item callback/watcher invocation
4168		5504
4169	The act of calling the callback associated with a watcher.	5505	The act of calling the callback associated with a watcher.
4170		5506
4171	=item event	5507	=item event
4172		5508
4173	A change of state of some external event, such as data now being available	5509	A change of state of some external event, such as data now being available
4174	for reading on a file descriptor, time having passed or simply not having	5510	for reading on a file descriptor, time having passed or simply not having
4175	any other events happening anymore.	5511	any other events happening anymore.
4176		5512
4177	In libev, events are represented as single bits (such as C<EV_READ> or	5513	In libev, events are represented as single bits (such as C<EV_READ> or
4178	C<EV_TIMEOUT>).	5514	C<EV_TIMER>).
4179		5515
4180	=item event library	5516	=item event library
4181		5517
4182	A software package implementing an event model and loop.	5518	A software package implementing an event model and loop.
4183		5519
…		…
4191	The model used to describe how an event loop handles and processes	5527	The model used to describe how an event loop handles and processes
4192	watchers and events.	5528	watchers and events.
4193		5529
4194	=item pending	5530	=item pending
4195		5531
4196	A watcher is pending as soon as the corresponding event has been detected,	5532	A watcher is pending as soon as the corresponding event has been
4197	and stops being pending as soon as the watcher will be invoked or its	5533	detected. See L</WATCHER STATES> for details.
4198	pending status is explicitly cleared by the application.
4199
4200	A watcher can be pending, but not active. Stopping a watcher also clears
4201	its pending status.
4202		5534
4203	=item real time	5535	=item real time
4204		5536
4205	The physical time that is observed. It is apparently strictly monotonic :)	5537	The physical time that is observed. It is apparently strictly monotonic :)
4206		5538
4207	=item wall-clock time	5539	=item wall-clock time
4208		5540
4209	The time and date as shown on clocks. Unlike real time, it can actually	5541	The time and date as shown on clocks. Unlike real time, it can actually
4210	be wrong and jump forwards and backwards, e.g. when the you adjust your	5542	be wrong and jump forwards and backwards, e.g. when you adjust your
4211	clock.	5543	clock.
4212		5544
4213	=item watcher	5545	=item watcher
4214		5546
4215	A data structure that describes interest in certain events. Watchers need	5547	A data structure that describes interest in certain events. Watchers need
4216	to be started (attached to an event loop) before they can receive events.	5548	to be started (attached to an event loop) before they can receive events.
4217		5549
4218	=item watcher invocation
4219
4220	The act of calling the callback associated with a watcher.
4221
4222	=back	5550	=back
4223		5551
4224	=head1 AUTHOR	5552	=head1 AUTHOR
4225		5553
4226	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5554	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5555	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4227		5556

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