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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_run (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
78	with libev.	80	with libev.
79		81
80	Familiarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
82		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	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	96	file descriptor being readable or a timeout occurring), and it will manage
87	these event sources and provide your program with events.	97	these event sources and provide your program with events.
…		…
95	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
149	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
150	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
151	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
152	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
153		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
154	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
155	extensive consistency checking code. These do not trigger under normal
156	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
157		171
158		172
159	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
160		174
161	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
165		179
166	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
167		181
168	Returns the current time as libev would use it. Please note that the	182	Returns the current time as libev would use it. Please note that the
169	C<ev_now> function is usually faster and also often returns the timestamp	183	C<ev_now> function is usually faster and also often returns the timestamp
170	you actually want to know.	184	you actually want to know. Also interesting is the combination of
		185	C<ev_now_update> and C<ev_now>.
171		186
172	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
173		188
174	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
175	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
176	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
177		198
178	=item int ev_version_major ()	199	=item int ev_version_major ()
179		200
180	=item int ev_version_minor ()	201	=item int ev_version_minor ()
181		202
…		…
192	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
193	compatible to older versions, so a larger minor version alone is usually	214	compatible to older versions, so a larger minor version alone is usually
194	not a problem.	215	not a problem.
195		216
196	Example: Make sure we haven't accidentally been linked against the wrong	217	Example: Make sure we haven't accidentally been linked against the wrong
197	version (note, however, that this will not detect ABI mismatches :).	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
198		220
199	assert (("libev version mismatch",	221	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
202		224
…		…
213	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
215		237
216	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
217		239
218	Return the set of all backends compiled into this binary of libev and also	240	Return the set of all backends compiled into this binary of libev and
219	recommended for this platform. This set is often smaller than the one	241	also recommended for this platform, meaning it will work for most file
		242	descriptor types. This set is often smaller than the one returned by
220	returned by C<ev_supported_backends>, as for example kqueue is broken on	243	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
221	most BSDs and will not be auto-detected unless you explicitly request it	244	and will not be auto-detected unless you explicitly request it (assuming
222	(assuming you know what you are doing). This is the set of backends that	245	you know what you are doing). This is the set of backends that libev will
223	libev will probe for if you specify no backends explicitly.	246	probe for if you specify no backends explicitly.
224		247
225	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
226		249
227	Returns the set of backends that are embeddable in other event loops. This	250	Returns the set of backends that are embeddable in other event loops. This
228	is the theoretical, all-platform, value. To find which backends	251	value is platform-specific but can include backends not available on the
229	might be supported on the current system, you would need to look at	252	current system. To find which embeddable backends might be supported on
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
232		255
233	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
234		257
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		259
237	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
238	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	261	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
239	used to allocate and free memory (no surprises here). If it returns zero	262	used to allocate and free memory (no surprises here). If it returns zero
240	when memory needs to be allocated (C<size != 0>), the library might abort	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
246		269
247	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
248	free some memory if it cannot allocate memory, to use a special allocator,	271	free some memory if it cannot allocate memory, to use a special allocator,
249	or even to sleep a while and retry until some memory is available.	272	or even to sleep a while and retry until some memory is available.
250		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
251	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
252	retries (example requires a standards-compliant C<realloc>).	289	retries.
253		290
254	static void *	291	static void *
255	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
256	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
257	for (;;)	300	for (;;)
258	{	301	{
259	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
260		303
261	if (newptr)	304	if (newptr)
…		…
266	}	309	}
267		310
268	...	311	...
269	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
270		313
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		315
273	Set the callback function to call on a retryable system call error (such	316	Set the callback function to call on a retryable system call error (such
274	as failed select, poll, epoll_wait). The message is a printable string	317	as failed select, poll, epoll_wait). The message is a printable string
275	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
276	callback is set, then libev will expect it to remedy the situation, no	319	callback is set, then libev will expect it to remedy the situation, no
…		…
288	}	331	}
289		332
290	...	333	...
291	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
292		335
		336	=item ev_feed_signal (int signum)
		337
		338	This function can be used to "simulate" a signal receive. It is completely
		339	safe to call this function at any time, from any context, including signal
		340	handlers or random threads.
		341
		342	Its main use is to customise signal handling in your process, especially
		343	in the presence of threads. For example, you could block signals
		344	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		345	creating any loops), and in one thread, use C<sigwait> or any other
		346	mechanism to wait for signals, then "deliver" them to libev by calling
		347	C<ev_feed_signal>.
		348
293	=back	349	=back
294		350
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		352
297	An event loop is described by a C<struct ev_loop *> (the C<struct> is	353	An event loop is described by a C<struct ev_loop *> (the C<struct> is
298	I<not> optional in case unless libev 3 compatibility is disabled, as libev	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
299	3 had an C<ev_loop> function colliding with the struct name).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
300		356
301	The library knows two types of such loops, the I<default> loop, which	357	The library knows two types of such loops, the I<default> loop, which
302	supports signals and child events, and dynamically created event loops	358	supports child process events, and dynamically created event loops which
303	which do not.	359	do not.
304		360
305	=over 4	361	=over 4
306		362
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		364
309	This will initialise the default event loop if it hasn't been initialised	365	This returns the "default" event loop object, which is what you should
310	yet and return it. If the default loop could not be initialised, returns	366	normally use when you just need "the event loop". Event loop objects and
311	false. If it already was initialised it simply returns it (and ignores the	367	the C<flags> parameter are described in more detail in the entry for
312	flags. If that is troubling you, check C<ev_backend ()> afterwards).	368	C<ev_loop_new>.
		369
		370	If the default loop is already initialised then this function simply
		371	returns it (and ignores the flags. If that is troubling you, check
		372	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		373	flags, which should almost always be C<0>, unless the caller is also the
		374	one calling C<ev_run> or otherwise qualifies as "the main program".
313		375
314	If you don't know what event loop to use, use the one returned from this	376	If you don't know what event loop to use, use the one returned from this
315	function.	377	function (or via the C<EV_DEFAULT> macro).
316		378
317	Note that this function is I<not> thread-safe, so if you want to use it	379	Note that this function is I<not> thread-safe, so if you want to use it
318	from multiple threads, you have to lock (note also that this is unlikely,	380	from multiple threads, you have to employ some kind of mutex (note also
319	as loops cannot be shared easily between threads anyway).	381	that this case is unlikely, as loops cannot be shared easily between
		382	threads anyway).
320		383
321	The default loop is the only loop that can handle C<ev_signal> and	384	The default loop is the only loop that can handle C<ev_child> watchers,
322	C<ev_child> watchers, and to do this, it always registers a handler	385	and to do this, it always registers a handler for C<SIGCHLD>. If this is
323	for C<SIGCHLD>. If this is a problem for your application you can either	386	a problem for your application you can either create a dynamic loop with
324	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	387	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	C<ev_default_init>.	389
		390	Example: This is the most typical usage.
		391
		392	if (!ev_default_loop (0))
		393	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		394
		395	Example: Restrict libev to the select and poll backends, and do not allow
		396	environment settings to be taken into account:
		397
		398	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		399
		400	=item struct ev_loop *ev_loop_new (unsigned int flags)
		401
		402	This will create and initialise a new event loop object. If the loop
		403	could not be initialised, returns false.
		404
		405	This function is thread-safe, and one common way to use libev with
		406	threads is indeed to create one loop per thread, and using the default
		407	loop in the "main" or "initial" thread.
327		408
328	The flags argument can be used to specify special behaviour or specific	409	The flags argument can be used to specify special behaviour or specific
329	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	410	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
330		411
331	The following flags are supported:	412	The following flags are supported:
…		…
341		422
342	If this flag bit is or'ed into the flag value (or the program runs setuid	423	If this flag bit is or'ed into the flag value (or the program runs setuid
343	or setgid) then libev will I<not> look at the environment variable	424	or setgid) then libev will I<not> look at the environment variable
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	override the flags completely if it is found in the environment. This is	426	override the flags completely if it is found in the environment. This is
346	useful to try out specific backends to test their performance, or to work	427	useful to try out specific backends to test their performance, to work
347	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
348		431
349	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
350		433
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	434	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	435	make libev check for a fork in each iteration by enabling this flag.
353		436
354	This works by calling C<getpid ()> on every iteration of the loop,	437	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	438	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	439	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	440	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
360		444
361	The big advantage of this flag is that you can forget about fork (and	445	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
363	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
364		448
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	450	environment variable.
367		451
368	=item C<EVFLAG_NOINOTIFY>	452	=item C<EVFLAG_NOINOTIFY>
369		453
370	When this flag is specified, then libev will not attempt to use the	454	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	455	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	456	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	457	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		458
375	=item C<EVFLAG_SIGNALFD>	459	=item C<EVFLAG_SIGNALFD>
376		460
377	When this flag is specified, then libev will attempt to use the	461	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	463	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	464	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	465	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	466	threads that are not interested in handling them.
383		467
384	Signalfd will not be used by default as this changes your signal mask, and	468	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	469	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
387		495
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		497
390	This is your standard select(2) backend. Not I<completely> standard, as	498	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	499	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	524	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
418		526
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		528
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	530	kernels).
423		531
424	For few fds, this backend is a bit little slower than poll and select,	532	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	534	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
428		536
429	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	540	descriptor (and unnecessary guessing of parameters), problems with dup,
		541	returning before the timeout value, resulting in additional iterations
		542	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	543	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	544	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	545	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	546	and is of course hard to detect.
437		547
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	549	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	551	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required. Last	554	that against the events to filter out spurious ones, recreating the set
		555	when required. Epoll also erroneously rounds down timeouts, but gives you
		556	no way to know when and by how much, so sometimes you have to busy-wait
		557	because epoll returns immediately despite a nonzero timeout. And last
445	not least, it also refuses to work with some file descriptors which work	558	not least, it also refuses to work with some file descriptors which work
446	perfectly fine with C<select> (files, many character devices...).	559	perfectly fine with C<select> (files, many character devices...).
		560
		561	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		562	cobbled together in a hurry, no thought to design or interaction with
		563	others. Oh, the pain, will it ever stop...
447		564
448	While stopping, setting and starting an I/O watcher in the same iteration	565	While stopping, setting and starting an I/O watcher in the same iteration
449	will result in some caching, there is still a system call per such	566	will result in some caching, there is still a system call per such
450	incident (because the same I<file descriptor> could point to a different	567	incident (because the same I<file descriptor> could point to a different
451	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	568	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
463	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	580	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
464	faster than epoll for maybe up to a hundred file descriptors, depending on	581	faster than epoll for maybe up to a hundred file descriptors, depending on
465	the usage. So sad.	582	the usage. So sad.
466		583
467	While nominally embeddable in other event loops, this feature is broken in	584	While nominally embeddable in other event loops, this feature is broken in
468	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
469		586
470	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	587	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
471	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
472		589
		590	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		591
		592	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		593	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		594	only tries to use it in 4.19+).
		595
		596	This is another Linux train wreck of an event interface.
		597
		598	If this backend works for you (as of this writing, it was very
		599	experimental), it is the best event interface available on Linux and might
		600	be well worth enabling it - if it isn't available in your kernel this will
		601	be detected and this backend will be skipped.
		602
		603	This backend can batch oneshot requests and supports a user-space ring
		604	buffer to receive events. It also doesn't suffer from most of the design
		605	problems of epoll (such as not being able to remove event sources from
		606	the epoll set), and generally sounds too good to be true. Because, this
		607	being the Linux kernel, of course it suffers from a whole new set of
		608	limitations, forcing you to fall back to epoll, inheriting all its design
		609	issues.
		610
		611	For one, it is not easily embeddable (but probably could be done using
		612	an event fd at some extra overhead). It also is subject to a system wide
		613	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		614	requests are left, this backend will be skipped during initialisation, and
		615	will switch to epoll when the loop is active.
		616
		617	Most problematic in practice, however, is that not all file descriptors
		618	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		619	files, F</dev/null> and many others are supported, but ttys do not work
		620	properly (a known bug that the kernel developers don't care about, see
		621	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		622	(yet?) a generic event polling interface.
		623
		624	Overall, it seems the Linux developers just don't want it to have a
		625	generic event handling mechanism other than C<select> or C<poll>.
		626
		627	To work around all these problem, the current version of libev uses its
		628	epoll backend as a fallback for file descriptor types that do not work. Or
		629	falls back completely to epoll if the kernel acts up.
		630
		631	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		632	C<EVBACKEND_POLL>.
		633
473	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
474		635
475	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
476	was broken on all BSDs except NetBSD (usually it doesn't work reliably	637	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
477	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
478	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
479	is by design, these kqueue bugs can (and eventually will) be fixed	640	brokenness is by design, these kqueue bugs can be (and mostly have been)
480	without API changes to existing programs. For this reason it's not being	641	fixed without API changes to existing programs. For this reason it's not
481	"auto-detected" unless you explicitly specify it in the flags (i.e. using	642	being "auto-detected" on all platforms unless you explicitly specify it
482	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	643	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
483	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
484		645
485	You still can embed kqueue into a normal poll or select backend and use it	646	You still can embed kqueue into a normal poll or select backend and use it
486	only for sockets (after having made sure that sockets work with kqueue on	647	only for sockets (after having made sure that sockets work with kqueue on
487	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
488		649
489	It scales in the same way as the epoll backend, but the interface to the	650	It scales in the same way as the epoll backend, but the interface to the
490	kernel is more efficient (which says nothing about its actual speed, of	651	kernel is more efficient (which says nothing about its actual speed, of
491	course). While stopping, setting and starting an I/O watcher does never	652	course). While stopping, setting and starting an I/O watcher does never
492	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	653	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
493	two event changes per incident. Support for C<fork ()> is very bad (but	654	two event changes per incident. Support for C<fork ()> is very bad (you
494	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	655	might have to leak fds on fork, but it's more sane than epoll) and it
495	cases	656	drops fds silently in similarly hard-to-detect cases.
496		657
497	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
498		659
499	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
500	everywhere, so you might need to test for this. And since it is broken	661	everywhere, so you might need to test for this. And since it is broken
…		…
517	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
518		679
519	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	680	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
520	it's really slow, but it still scales very well (O(active_fds)).	681	it's really slow, but it still scales very well (O(active_fds)).
521		682
522	Please note that Solaris event ports can deliver a lot of spurious
523	notifications, so you need to use non-blocking I/O or other means to avoid
524	blocking when no data (or space) is available.
525
526	While this backend scales well, it requires one system call per active	683	While this backend scales well, it requires one system call per active
527	file descriptor per loop iteration. For small and medium numbers of file	684	file descriptor per loop iteration. For small and medium numbers of file
528	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
529	might perform better.	686	might perform better.
530		687
531	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
532	notifications, this backend actually performed fully to specification
533	in all tests and is fully embeddable, which is a rare feat among the	689	specification in all tests and is fully embeddable, which is a rare feat
534	OS-specific backends (I vastly prefer correctness over speed hacks).	690	among the OS-specific backends (I vastly prefer correctness over speed
		691	hacks).
		692
		693	On the negative side, the interface is I<bizarre> - so bizarre that
		694	even sun itself gets it wrong in their code examples: The event polling
		695	function sometimes returns events to the caller even though an error
		696	occurred, but with no indication whether it has done so or not (yes, it's
		697	even documented that way) - deadly for edge-triggered interfaces where you
		698	absolutely have to know whether an event occurred or not because you have
		699	to re-arm the watcher.
		700
		701	Fortunately libev seems to be able to work around these idiocies.
535		702
536	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	703	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
537	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
538		705
539	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
540		707
541	Try all backends (even potentially broken ones that wouldn't be tried	708	Try all backends (even potentially broken ones that wouldn't be tried
542	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	709	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
543	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
544		711
545	It is definitely not recommended to use this flag.	712	It is definitely not recommended to use this flag, use whatever
		713	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		714	at all.
		715
		716	=item C<EVBACKEND_MASK>
		717
		718	Not a backend at all, but a mask to select all backend bits from a
		719	C<flags> value, in case you want to mask out any backends from a flags
		720	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
546		721
547	=back	722	=back
548		723
549	If one or more of the backend flags are or'ed into the flags value,	724	If one or more of the backend flags are or'ed into the flags value,
550	then only these backends will be tried (in the reverse order as listed	725	then only these backends will be tried (in the reverse order as listed
551	here). If none are specified, all backends in C<ev_recommended_backends	726	here). If none are specified, all backends in C<ev_recommended_backends
552	()> will be tried.	727	()> will be tried.
553		728
554	Example: This is the most typical usage.
555
556	if (!ev_default_loop (0))
557	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
558
559	Example: Restrict libev to the select and poll backends, and do not allow
560	environment settings to be taken into account:
561
562	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
563
564	Example: Use whatever libev has to offer, but make sure that kqueue is
565	used if available (warning, breaks stuff, best use only with your own
566	private event loop and only if you know the OS supports your types of
567	fds):
568
569	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
570
571	=item struct ev_loop *ev_loop_new (unsigned int flags)
572
573	Similar to C<ev_default_loop>, but always creates a new event loop that is
574	always distinct from the default loop.
575
576	Note that this function I<is> thread-safe, and one common way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	729	Example: Try to create a event loop that uses epoll and nothing else.
581		730
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	732	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
585		734
		735	Example: Use whatever libev has to offer, but make sure that kqueue is
		736	used if available.
		737
		738	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		739
		740	Example: Similarly, on linux, you mgiht want to take advantage of the
		741	linux aio backend if possible, but fall back to something else if that
		742	isn't available.
		743
		744	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		745
586	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
587		747
588	Destroys the default loop (frees all memory and kernel state etc.). None	748	Destroys an event loop object (frees all memory and kernel state
589	of the active event watchers will be stopped in the normal sense, so	749	etc.). None of the active event watchers will be stopped in the normal
590	e.g. C<ev_is_active> might still return true. It is your responsibility to	750	sense, so e.g. C<ev_is_active> might still return true. It is your
591	either stop all watchers cleanly yourself I<before> calling this function,	751	responsibility to either stop all watchers cleanly yourself I<before>
592	or cope with the fact afterwards (which is usually the easiest thing, you	752	calling this function, or cope with the fact afterwards (which is usually
593	can just ignore the watchers and/or C<free ()> them for example).	753	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		754	for example).
594		755
595	Note that certain global state, such as signal state (and installed signal	756	Note that certain global state, such as signal state (and installed signal
596	handlers), will not be freed by this function, and related watchers (such	757	handlers), will not be freed by this function, and related watchers (such
597	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
598		759
599	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
600	rare occasion where you really need to free e.g. the signal handling	761	C<ev_loop_new>, but it can also be used on the default loop returned by
		762	C<ev_default_loop>, in which case it is not thread-safe.
		763
		764	Note that it is not advisable to call this function on the default loop
		765	except in the rare occasion where you really need to free its resources.
601	pipe fds. If you need dynamically allocated loops it is better to use	766	If you need dynamically allocated loops it is better to use C<ev_loop_new>
602	C<ev_loop_new> and C<ev_loop_destroy>.	767	and C<ev_loop_destroy>.
603		768
604	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
605
606	Like C<ev_default_destroy>, but destroys an event loop created by an
607	earlier call to C<ev_loop_new>.
608
609	=item ev_default_fork ()
610		770
611	This function sets a flag that causes subsequent C<ev_run> iterations	771	This function sets a flag that causes subsequent C<ev_run> iterations
612	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
613	name, you can call it anytime, but it makes most sense after forking, in	773	the name, you can call it anytime you are allowed to start or stop
614	the child process (or both child and parent, but that again makes little	774	watchers (except inside an C<ev_prepare> callback), but it makes most
615	sense). You I<must> call it in the child before using any of the libev	775	sense after forking, in the child process. You I<must> call it (or use
616	functions, and it will only take effect at the next C<ev_run> iteration.	776	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
617		777
		778	In addition, if you want to reuse a loop (via this function or
		779	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		780
618	Again, you I<have> to call it on I<any> loop that you want to re-use after	781	Again, you I<have> to call it on I<any> loop that you want to re-use after
619	a fork, I<even if you do not plan to use the loop in the parent>. This is	782	a fork, I<even if you do not plan to use the loop in the parent>. This is
620	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621	during fork.	784	during fork.
622		785
623	On the other hand, you only need to call this function in the child	786	On the other hand, you only need to call this function in the child
…		…
626	call it at all (in fact, C<epoll> is so badly broken that it makes a	789	call it at all (in fact, C<epoll> is so badly broken that it makes a
627	difference, but libev will usually detect this case on its own and do a	790	difference, but libev will usually detect this case on its own and do a
628	costly reset of the backend).	791	costly reset of the backend).
629		792
630	The function itself is quite fast and it's usually not a problem to call	793	The function itself is quite fast and it's usually not a problem to call
631	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
632	quite nicely into a call to C<pthread_atfork>:
633		795
		796	Example: Automate calling C<ev_loop_fork> on the default loop when
		797	using pthreads.
		798
		799	static void
		800	post_fork_child (void)
		801	{
		802	ev_loop_fork (EV_DEFAULT);
		803	}
		804
		805	...
634	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
635
636	=item ev_loop_fork (loop)
637
638	Like C<ev_default_fork>, but acts on an event loop created by
639	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
640	after fork that you want to re-use in the child, and how you keep track of
641	them is entirely your own problem.
642		807
643	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
644		809
645	Returns true when the given loop is, in fact, the default loop, and false	810	Returns true when the given loop is, in fact, the default loop, and false
646	otherwise.	811	otherwise.
…		…
657	prepare and check phases.	822	prepare and check phases.
658		823
659	=item unsigned int ev_depth (loop)	824	=item unsigned int ev_depth (loop)
660		825
661	Returns the number of times C<ev_run> was entered minus the number of	826	Returns the number of times C<ev_run> was entered minus the number of
662	times C<ev_run> was exited, in other words, the recursion depth.	827	times C<ev_run> was exited normally, in other words, the recursion depth.
663		828
664	Outside C<ev_run>, this number is zero. In a callback, this number is	829	Outside C<ev_run>, this number is zero. In a callback, this number is
665	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	830	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
666	in which case it is higher.	831	in which case it is higher.
667		832
668	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
669	etc.), doesn't count as "exit" - consider this as a hint to avoid such	834	throwing an exception etc.), doesn't count as "exit" - consider this
670	ungentleman-like behaviour unless it's really convenient.	835	as a hint to avoid such ungentleman-like behaviour unless it's really
		836	convenient, in which case it is fully supported.
671		837
672	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
673		839
674	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	840	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
675	use.	841	use.
…		…
690		856
691	This function is rarely useful, but when some event callback runs for a	857	This function is rarely useful, but when some event callback runs for a
692	very long time without entering the event loop, updating libev's idea of	858	very long time without entering the event loop, updating libev's idea of
693	the current time is a good idea.	859	the current time is a good idea.
694		860
695	See also L<The special problem of time updates> in the C<ev_timer> section.	861	See also L</The special problem of time updates> in the C<ev_timer> section.
696		862
697	=item ev_suspend (loop)	863	=item ev_suspend (loop)
698		864
699	=item ev_resume (loop)	865	=item ev_resume (loop)
700		866
…		…
718	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
719		885
720	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
721	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
722		888
723	=item ev_run (loop, int flags)	889	=item bool ev_run (loop, int flags)
724		890
725	Finally, this is it, the event handler. This function usually is called	891	Finally, this is it, the event handler. This function usually is called
726	after you have initialised all your watchers and you want to start	892	after you have initialised all your watchers and you want to start
727	handling events. It will ask the operating system for any new events, call	893	handling events. It will ask the operating system for any new events, call
728	the watcher callbacks, an then repeat the whole process indefinitely: This	894	the watcher callbacks, and then repeat the whole process indefinitely: This
729	is why event loops are called I<loops>.	895	is why event loops are called I<loops>.
730		896
731	If the flags argument is specified as C<0>, it will keep handling events	897	If the flags argument is specified as C<0>, it will keep handling events
732	until either no event watchers are active anymore or C<ev_break> was	898	until either no event watchers are active anymore or C<ev_break> was
733	called.	899	called.
		900
		901	The return value is false if there are no more active watchers (which
		902	usually means "all jobs done" or "deadlock"), and true in all other cases
		903	(which usually means " you should call C<ev_run> again").
734		904
735	Please note that an explicit C<ev_break> is usually better than	905	Please note that an explicit C<ev_break> is usually better than
736	relying on all watchers to be stopped when deciding when a program has	906	relying on all watchers to be stopped when deciding when a program has
737	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
738	that automatically loops as long as it has to and no longer by virtue	908	that automatically loops as long as it has to and no longer by virtue
739	of relying on its watchers stopping correctly, that is truly a thing of	909	of relying on its watchers stopping correctly, that is truly a thing of
740	beauty.	910	beauty.
741		911
		912	This function is I<mostly> exception-safe - you can break out of a
		913	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		914	exception and so on. This does not decrement the C<ev_depth> value, nor
		915	will it clear any outstanding C<EVBREAK_ONE> breaks.
		916
742	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	917	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
743	those events and any already outstanding ones, but will not wait and	918	those events and any already outstanding ones, but will not wait and
744	block your process in case there are no events and will return after one	919	block your process in case there are no events and will return after one
745	iteration of the loop. This is sometimes useful to poll and handle new	920	iteration of the loop. This is sometimes useful to poll and handle new
746	events while doing lengthy calculations, to keep the program responsive.	921	events while doing lengthy calculations, to keep the program responsive.
…		…
755	This is useful if you are waiting for some external event in conjunction	930	This is useful if you are waiting for some external event in conjunction
756	with something not expressible using other libev watchers (i.e. "roll your	931	with something not expressible using other libev watchers (i.e. "roll your
757	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	932	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
758	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
759		934
760	Here are the gory details of what C<ev_run> does:	935	Here are the gory details of what C<ev_run> does (this is for your
		936	understanding, not a guarantee that things will work exactly like this in
		937	future versions):
761		938
762	- Increment loop depth.	939	- Increment loop depth.
763	- Reset the ev_break status.	940	- Reset the ev_break status.
764	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
765	LOOP:	942	LOOP:
…		…
798	anymore.	975	anymore.
799		976
800	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
801	... as they still have work to do (even an idle watcher will do..)	978	... as they still have work to do (even an idle watcher will do..)
802	ev_run (my_loop, 0);	979	ev_run (my_loop, 0);
803	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
804		981
805	=item ev_break (loop, how)	982	=item ev_break (loop, how)
806		983
807	Can be used to make a call to C<ev_run> return early (but only after it	984	Can be used to make a call to C<ev_run> return early (but only after it
808	has processed all outstanding events). The C<how> argument must be either	985	has processed all outstanding events). The C<how> argument must be either
809	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	986	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
810	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	987	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
811		988
812	This "unloop state" will be cleared when entering C<ev_run> again.	989	This "break state" will be cleared on the next call to C<ev_run>.
813		990
814	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	991	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		992	which case it will have no effect.
815		993
816	=item ev_ref (loop)	994	=item ev_ref (loop)
817		995
818	=item ev_unref (loop)	996	=item ev_unref (loop)
819		997
…		…
840	running when nothing else is active.	1018	running when nothing else is active.
841		1019
842	ev_signal exitsig;	1020	ev_signal exitsig;
843	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
844	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
845	evf_unref (loop);	1023	ev_unref (loop);
846		1024
847	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
848		1026
849	ev_ref (loop);	1027	ev_ref (loop);
850	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
870	overhead for the actual polling but can deliver many events at once.	1048	overhead for the actual polling but can deliver many events at once.
871		1049
872	By setting a higher I<io collect interval> you allow libev to spend more	1050	By setting a higher I<io collect interval> you allow libev to spend more
873	time collecting I/O events, so you can handle more events per iteration,	1051	time collecting I/O events, so you can handle more events per iteration,
874	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1052	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
875	C<ev_timer>) will be not affected. Setting this to a non-null value will	1053	C<ev_timer>) will not be affected. Setting this to a non-null value will
876	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
877	sleep time ensures that libev will not poll for I/O events more often then	1055	sleep time ensures that libev will not poll for I/O events more often then
878	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
879		1058
880	Likewise, by setting a higher I<timeout collect interval> you allow libev	1059	Likewise, by setting a higher I<timeout collect interval> you allow libev
881	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
882	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
883	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1062	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
908		1087
909	=item ev_invoke_pending (loop)	1088	=item ev_invoke_pending (loop)
910		1089
911	This call will simply invoke all pending watchers while resetting their	1090	This call will simply invoke all pending watchers while resetting their
912	pending state. Normally, C<ev_run> does this automatically when required,	1091	pending state. Normally, C<ev_run> does this automatically when required,
913	but when overriding the invoke callback this call comes handy.	1092	but when overriding the invoke callback this call comes handy. This
		1093	function can be invoked from a watcher - this can be useful for example
		1094	when you want to do some lengthy calculation and want to pass further
		1095	event handling to another thread (you still have to make sure only one
		1096	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
914		1097
915	=item int ev_pending_count (loop)	1098	=item int ev_pending_count (loop)
916		1099
917	Returns the number of pending watchers - zero indicates that no watchers	1100	Returns the number of pending watchers - zero indicates that no watchers
918	are pending.	1101	are pending.
…		…
925	invoke the actual watchers inside another context (another thread etc.).	1108	invoke the actual watchers inside another context (another thread etc.).
926		1109
927	If you want to reset the callback, use C<ev_invoke_pending> as new	1110	If you want to reset the callback, use C<ev_invoke_pending> as new
928	callback.	1111	callback.
929		1112
930	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1113	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
931		1114
932	Sometimes you want to share the same loop between multiple threads. This	1115	Sometimes you want to share the same loop between multiple threads. This
933	can be done relatively simply by putting mutex_lock/unlock calls around	1116	can be done relatively simply by putting mutex_lock/unlock calls around
934	each call to a libev function.	1117	each call to a libev function.
935		1118
936	However, C<ev_run> can run an indefinite time, so it is not feasible	1119	However, C<ev_run> can run an indefinite time, so it is not feasible
937	to wait for it to return. One way around this is to wake up the event	1120	to wait for it to return. One way around this is to wake up the event
938	loop via C<ev_break> and C<av_async_send>, another way is to set these	1121	loop via C<ev_break> and C<ev_async_send>, another way is to set these
939	I<release> and I<acquire> callbacks on the loop.	1122	I<release> and I<acquire> callbacks on the loop.
940		1123
941	When set, then C<release> will be called just before the thread is	1124	When set, then C<release> will be called just before the thread is
942	suspended waiting for new events, and C<acquire> is called just	1125	suspended waiting for new events, and C<acquire> is called just
943	afterwards.	1126	afterwards.
…		…
958	See also the locking example in the C<THREADS> section later in this	1141	See also the locking example in the C<THREADS> section later in this
959	document.	1142	document.
960		1143
961	=item ev_set_userdata (loop, void *data)	1144	=item ev_set_userdata (loop, void *data)
962		1145
963	=item ev_userdata (loop)	1146	=item void *ev_userdata (loop)
964		1147
965	Set and retrieve a single C<void *> associated with a loop. When	1148	Set and retrieve a single C<void *> associated with a loop. When
966	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1149	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
967	C<0.>	1150	C<0>.
968		1151
969	These two functions can be used to associate arbitrary data with a loop,	1152	These two functions can be used to associate arbitrary data with a loop,
970	and are intended solely for the C<invoke_pending_cb>, C<release> and	1153	and are intended solely for the C<invoke_pending_cb>, C<release> and
971	C<acquire> callbacks described above, but of course can be (ab-)used for	1154	C<acquire> callbacks described above, but of course can be (ab-)used for
972	any other purpose as well.	1155	any other purpose as well.
…		…
990		1173
991	In the following description, uppercase C<TYPE> in names stands for the	1174	In the following description, uppercase C<TYPE> in names stands for the
992	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1175	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
993	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
994		1177
995	A watcher is a structure that you create and register to record your	1178	A watcher is an opaque structure that you allocate and register to record
996	interest in some event. For instance, if you want to wait for STDIN to	1179	your interest in some event. To make a concrete example, imagine you want
997	become readable, you would create an C<ev_io> watcher for that:	1180	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1181	for that:
998		1182
999	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
1000	{	1184	{
1001	ev_io_stop (w);	1185	ev_io_stop (w);
1002	ev_break (loop, EVBREAK_ALL);	1186	ev_break (loop, EVBREAK_ALL);
…		…
1017	stack).	1201	stack).
1018		1202
1019	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1203	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1020	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1204	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1021		1205
1022	Each watcher structure must be initialised by a call to C<ev_init	1206	Each watcher structure must be initialised by a call to C<ev_init (watcher
1023	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
1024	callback gets invoked each time the event occurs (or, in the case of I/O	1208	invoked each time the event occurs (or, in the case of I/O watchers, each
1025	watchers, each time the event loop detects that the file descriptor given	1209	time the event loop detects that the file descriptor given is readable
1026	is readable and/or writable).	1210	and/or writable).
1027		1211
1028	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1212	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1029	macro to configure it, with arguments specific to the watcher type. There	1213	macro to configure it, with arguments specific to the watcher type. There
1030	is also a macro to combine initialisation and setting in one call: C<<	1214	is also a macro to combine initialisation and setting in one call: C<<
1031	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1034	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher	1218	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
1035	*) >>), and you can stop watching for events at any time by calling the	1219	*) >>), and you can stop watching for events at any time by calling the
1036	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
1037		1221
1038	As long as your watcher is active (has been started but not stopped) you	1222	As long as your watcher is active (has been started but not stopped) you
1039	must not touch the values stored in it. Most specifically you must never	1223	must not touch the values stored in it except when explicitly documented
1040	reinitialise it or call its C<ev_TYPE_set> macro.	1224	otherwise. Most specifically you must never reinitialise it or call its
		1225	C<ev_TYPE_set> macro.
1041		1226
1042	Each and every callback receives the event loop pointer as first, the	1227	Each and every callback receives the event loop pointer as first, the
1043	registered watcher structure as second, and a bitset of received events as	1228	registered watcher structure as second, and a bitset of received events as
1044	third argument.	1229	third argument.
1045		1230
…		…
1082		1267
1083	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
1084		1269
1085	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
1086		1271
1087	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1272	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1088	to gather new events, and all C<ev_check> watchers are invoked just after	1273	gather new events, and all C<ev_check> watchers are queued (not invoked)
1089	C<ev_run> has gathered them, but before it invokes any callbacks for any	1274	just after C<ev_run> has gathered them, but before it queues any callbacks
		1275	for any received events. That means C<ev_prepare> watchers are the last
		1276	watchers invoked before the event loop sleeps or polls for new events, and
		1277	C<ev_check> watchers will be invoked before any other watchers of the same
		1278	or lower priority within an event loop iteration.
		1279
1090	received events. Callbacks of both watcher types can start and stop as	1280	Callbacks of both watcher types can start and stop as many watchers as
1091	many watchers as they want, and all of them will be taken into account	1281	they want, and all of them will be taken into account (for example, a
1092	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1282	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1093	C<ev_run> from blocking).	1283	blocking).
1094		1284
1095	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
1096		1286
1097	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1287	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1098		1288
1099	=item C<EV_FORK>	1289	=item C<EV_FORK>
1100		1290
1101	The event loop has been resumed in the child process after fork (see	1291	The event loop has been resumed in the child process after fork (see
1102	C<ev_fork>).	1292	C<ev_fork>).
		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
1103		1297
1104	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
1105		1299
1106	The given async watcher has been asynchronously notified (see C<ev_async>).	1300	The given async watcher has been asynchronously notified (see C<ev_async>).
1107		1301
…		…
1217		1411
1218	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1219		1413
1220	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1221		1415
1222	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1223		1417
1224	Change the callback. You can change the callback at virtually any time	1418	Change the callback. You can change the callback at virtually any time
1225	(modulo threads).	1419	(modulo threads).
1226		1420
1227	=item ev_set_priority (ev_TYPE *watcher, int priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1245	or might not have been clamped to the valid range.	1439	or might not have been clamped to the valid range.
1246		1440
1247	The default priority used by watchers when no priority has been set is	1441	The default priority used by watchers when no priority has been set is
1248	always C<0>, which is supposed to not be too high and not be too low :).	1442	always C<0>, which is supposed to not be too high and not be too low :).
1249		1443
1250	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1251	priorities.	1445	priorities.
1252		1446
1253	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1254		1448
1255	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1449	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1280	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1474	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1281	functions that do not need a watcher.	1475	functions that do not need a watcher.
1282		1476
1283	=back	1477	=back
1284		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
1285		1481
1286	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1482	=head2 WATCHER STATES
1287		1483
1288	Each watcher has, by default, a member C<void *data> that you can change	1484	There are various watcher states mentioned throughout this manual -
1289	and read at any time: libev will completely ignore it. This can be used	1485	active, pending and so on. In this section these states and the rules to
1290	to associate arbitrary data with your watcher. If you need more data and	1486	transition between them will be described in more detail - and while these
1291	don't want to allocate memory and store a pointer to it in that data	1487	rules might look complicated, they usually do "the right thing".
1292	member, you can also "subclass" the watcher type and provide your own
1293	data:
1294		1488
1295	struct my_io	1489	=over 4
1296	{
1297	ev_io io;
1298	int otherfd;
1299	void *somedata;
1300	struct whatever *mostinteresting;
1301	};
1302		1490
1303	...	1491	=item initialised
1304	struct my_io w;
1305	ev_io_init (&w.io, my_cb, fd, EV_READ);
1306		1492
1307	And since your callback will be called with a pointer to the watcher, you	1493	Before a watcher can be registered with the event loop it has to be
1308	can cast it back to your own type:	1494	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1495	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1309		1496
1310	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1497	In this state it is simply some block of memory that is suitable for
1311	{	1498	use in an event loop. It can be moved around, freed, reused etc. at
1312	struct my_io *w = (struct my_io *)w_;	1499	will - as long as you either keep the memory contents intact, or call
1313	...	1500	C<ev_TYPE_init> again.
1314	}
1315		1501
1316	More interesting and less C-conformant ways of casting your callback type	1502	=item started/running/active
1317	instead have been omitted.
1318		1503
1319	Another common scenario is to use some data structure with multiple	1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1320	embedded watchers:	1505	property of the event loop, and is actively waiting for events. While in
		1506	this state it cannot be accessed (except in a few documented ways), moved,
		1507	freed or anything else - the only legal thing is to keep a pointer to it,
		1508	and call libev functions on it that are documented to work on active watchers.
1321		1509
1322	struct my_biggy	1510	=item pending
1323	{
1324	int some_data;
1325	ev_timer t1;
1326	ev_timer t2;
1327	}
1328		1511
1329	In this case getting the pointer to C<my_biggy> is a bit more	1512	If a watcher is active and libev determines that an event it is interested
1330	complicated: Either you store the address of your C<my_biggy> struct	1513	in has occurred (such as a timer expiring), it will become pending. It will
1331	in the C<data> member of the watcher (for woozies), or you need to use	1514	stay in this pending state until either it is stopped or its callback is
1332	some pointer arithmetic using C<offsetof> inside your watchers (for real	1515	about to be invoked, so it is not normally pending inside the watcher
1333	programmers):	1516	callback.
1334		1517
1335	#include <stddef.h>	1518	The watcher might or might not be active while it is pending (for example,
		1519	an expired non-repeating timer can be pending but no longer active). If it
		1520	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1521	but it is still property of the event loop at this time, so cannot be
		1522	moved, freed or reused. And if it is active the rules described in the
		1523	previous item still apply.
1336		1524
1337	static void	1525	It is also possible to feed an event on a watcher that is not active (e.g.
1338	t1_cb (EV_P_ ev_timer *w, int revents)	1526	via C<ev_feed_event>), in which case it becomes pending without being
1339	{	1527	active.
1340	struct my_biggy big = (struct my_biggy *)
1341	(((char *)w) - offsetof (struct my_biggy, t1));
1342	}
1343		1528
1344	static void	1529	=item stopped
1345	t2_cb (EV_P_ ev_timer *w, int revents)	1530
1346	{	1531	A watcher can be stopped implicitly by libev (in which case it might still
1347	struct my_biggy big = (struct my_biggy *)	1532	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1348	(((char *)w) - offsetof (struct my_biggy, t2));	1533	latter will clear any pending state the watcher might be in, regardless
1349	}	1534	of whether it was active or not, so stopping a watcher explicitly before
		1535	freeing it is often a good idea.
		1536
		1537	While stopped (and not pending) the watcher is essentially in the
		1538	initialised state, that is, it can be reused, moved, modified in any way
		1539	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1540	it again).
		1541
		1542	=back
1350		1543
1351	=head2 WATCHER PRIORITY MODELS	1544	=head2 WATCHER PRIORITY MODELS
1352		1545
1353	Many event loops support I<watcher priorities>, which are usually small	1546	Many event loops support I<watcher priorities>, which are usually small
1354	integers that influence the ordering of event callback invocation	1547	integers that influence the ordering of event callback invocation
1355	between watchers in some way, all else being equal.	1548	between watchers in some way, all else being equal.
1356		1549
1357	In libev, Watcher priorities can be set using C<ev_set_priority>. See its	1550	In libev, watcher priorities can be set using C<ev_set_priority>. See its
1358	description for the more technical details such as the actual priority	1551	description for the more technical details such as the actual priority
1359	range.	1552	range.
1360		1553
1361	There are two common ways how these these priorities are being interpreted	1554	There are two common ways how these these priorities are being interpreted
1362	by event loops:	1555	by event loops:
…		…
1456		1649
1457	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1458	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1459	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1460		1653
1461	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1462	while the watcher is active, you can look at the member and expect some	1655	that, while the watcher is active, you can look at the member and expect
1463	sensible content, but you must not modify it (you can modify it while the	1656	some sensible content, but you must not modify it (you can modify it while
1464	watcher is stopped to your hearts content), or I<[read-write]>, which	1657	the watcher is stopped to your hearts content), or I<[read-write]>, which
1465	means you can expect it to have some sensible content while the watcher	1658	means you can expect it to have some sensible content while the watcher
1466	is active, but you can also modify it. Modifying it may not do something	1659	is active, but you can also modify it. Modifying it may not do something
1467	sensible or take immediate effect (or do anything at all), but libev will	1660	sensible or take immediate effect (or do anything at all), but libev will
1468	not crash or malfunction in any way.	1661	not crash or malfunction in any way.
1469		1662
		1663	In any case, the documentation for each member will explain what the
		1664	effects are, and if there are any additional access restrictions.
1470		1665
1471	=head2 C<ev_io> - is this file descriptor readable or writable?	1666	=head2 C<ev_io> - is this file descriptor readable or writable?
1472		1667
1473	I/O watchers check whether a file descriptor is readable or writable	1668	I/O watchers check whether a file descriptor is readable or writable
1474	in each iteration of the event loop, or, more precisely, when reading	1669	in each iteration of the event loop, or, more precisely, when reading
…		…
1481	In general you can register as many read and/or write event watchers per	1676	In general you can register as many read and/or write event watchers per
1482	fd as you want (as long as you don't confuse yourself). Setting all file	1677	fd as you want (as long as you don't confuse yourself). Setting all file
1483	descriptors to non-blocking mode is also usually a good idea (but not	1678	descriptors to non-blocking mode is also usually a good idea (but not
1484	required if you know what you are doing).	1679	required if you know what you are doing).
1485		1680
1486	If you cannot use non-blocking mode, then force the use of a
1487	known-to-be-good backend (at the time of this writing, this includes only
1488	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1489	descriptors for which non-blocking operation makes no sense (such as
1490	files) - libev doesn't guarantee any specific behaviour in that case.
1491
1492	Another thing you have to watch out for is that it is quite easy to	1681	Another thing you have to watch out for is that it is quite easy to
1493	receive "spurious" readiness notifications, that is your callback might	1682	receive "spurious" readiness notifications, that is, your callback might
1494	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1683	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1495	because there is no data. Not only are some backends known to create a	1684	because there is no data. It is very easy to get into this situation even
1496	lot of those (for example Solaris ports), it is very easy to get into	1685	with a relatively standard program structure. Thus it is best to always
1497	this situation even with a relatively standard program structure. Thus	1686	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1498	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1499	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1687	preferable to a program hanging until some data arrives.
1500		1688
1501	If you cannot run the fd in non-blocking mode (for example you should	1689	If you cannot run the fd in non-blocking mode (for example you should
1502	not play around with an Xlib connection), then you have to separately	1690	not play around with an Xlib connection), then you have to separately
1503	re-test whether a file descriptor is really ready with a known-to-be good	1691	re-test whether a file descriptor is really ready with a known-to-be good
1504	interface such as poll (fortunately in our Xlib example, Xlib already	1692	interface such as poll (fortunately in the case of Xlib, it already does
1505	does this on its own, so its quite safe to use). Some people additionally	1693	this on its own, so its quite safe to use). Some people additionally
1506	use C<SIGALRM> and an interval timer, just to be sure you won't block	1694	use C<SIGALRM> and an interval timer, just to be sure you won't block
1507	indefinitely.	1695	indefinitely.
1508		1696
1509	But really, best use non-blocking mode.	1697	But really, best use non-blocking mode.
1510		1698
1511	=head3 The special problem of disappearing file descriptors	1699	=head3 The special problem of disappearing file descriptors
1512		1700
1513	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1701	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1514	descriptor (either due to calling C<close> explicitly or any other means,	1702	a file descriptor (either due to calling C<close> explicitly or any other
1515	such as C<dup2>). The reason is that you register interest in some file	1703	means, such as C<dup2>). The reason is that you register interest in some
1516	descriptor, but when it goes away, the operating system will silently drop	1704	file descriptor, but when it goes away, the operating system will silently
1517	this interest. If another file descriptor with the same number then is	1705	drop this interest. If another file descriptor with the same number then
1518	registered with libev, there is no efficient way to see that this is, in	1706	is registered with libev, there is no efficient way to see that this is,
1519	fact, a different file descriptor.	1707	in fact, a different file descriptor.
1520		1708
1521	To avoid having to explicitly tell libev about such cases, libev follows	1709	To avoid having to explicitly tell libev about such cases, libev follows
1522	the following policy: Each time C<ev_io_set> is being called, libev	1710	the following policy: Each time C<ev_io_set> is being called, libev
1523	will assume that this is potentially a new file descriptor, otherwise	1711	will assume that this is potentially a new file descriptor, otherwise
1524	it is assumed that the file descriptor stays the same. That means that	1712	it is assumed that the file descriptor stays the same. That means that
…		…
1538		1726
1539	There is no workaround possible except not registering events	1727	There is no workaround possible except not registering events
1540	for potentially C<dup ()>'ed file descriptors, or to resort to	1728	for potentially C<dup ()>'ed file descriptors, or to resort to
1541	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1729	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1542		1730
		1731	=head3 The special problem of files
		1732
		1733	Many people try to use C<select> (or libev) on file descriptors
		1734	representing files, and expect it to become ready when their program
		1735	doesn't block on disk accesses (which can take a long time on their own).
		1736
		1737	However, this cannot ever work in the "expected" way - you get a readiness
		1738	notification as soon as the kernel knows whether and how much data is
		1739	there, and in the case of open files, that's always the case, so you
		1740	always get a readiness notification instantly, and your read (or possibly
		1741	write) will still block on the disk I/O.
		1742
		1743	Another way to view it is that in the case of sockets, pipes, character
		1744	devices and so on, there is another party (the sender) that delivers data
		1745	on its own, but in the case of files, there is no such thing: the disk
		1746	will not send data on its own, simply because it doesn't know what you
		1747	wish to read - you would first have to request some data.
		1748
		1749	Since files are typically not-so-well supported by advanced notification
		1750	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1751	to files, even though you should not use it. The reason for this is
		1752	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1753	usually a tty, often a pipe, but also sometimes files or special devices
		1754	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1755	F</dev/urandom>), and even though the file might better be served with
		1756	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1757	it "just works" instead of freezing.
		1758
		1759	So avoid file descriptors pointing to files when you know it (e.g. use
		1760	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1761	when you rarely read from a file instead of from a socket, and want to
		1762	reuse the same code path.
		1763
1543	=head3 The special problem of fork	1764	=head3 The special problem of fork
1544		1765
1545	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1766	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1546	useless behaviour. Libev fully supports fork, but needs to be told about	1767	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1547	it in the child.	1768	to be told about it in the child if you want to continue to use it in the
		1769	child.
1548		1770
1549	To support fork in your programs, you either have to call	1771	To support fork in your child processes, you have to call C<ev_loop_fork
1550	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1772	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1551	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1773	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1552	C<EVBACKEND_POLL>.
1553		1774
1554	=head3 The special problem of SIGPIPE	1775	=head3 The special problem of SIGPIPE
1555		1776
1556	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1777	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1557	when writing to a pipe whose other end has been closed, your program gets	1778	when writing to a pipe whose other end has been closed, your program gets
…		…
1611		1832
1612	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1833	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1613	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1834	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1614	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1835	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1615		1836
1616	=item int fd [read-only]	1837	=item ev_io_modify (ev_io *, int events)
1617		1838
1618	The file descriptor being watched.	1839	Similar to C<ev_io_set>, but only changes the event mask. Using this might
		1840	be faster with some backends, as libev can assume that the C<fd> still
		1841	refers to the same underlying file description, something it cannot do
		1842	when using C<ev_io_set>.
1619		1843
		1844	=item int fd [no-modify]
		1845
		1846	The file descriptor being watched. While it can be read at any time, you
		1847	must not modify this member even when the watcher is stopped - always use
		1848	C<ev_io_set> for that.
		1849
1620	=item int events [read-only]	1850	=item int events [no-modify]
1621		1851
1622	The events being watched.	1852	The set of events the fd is being watched for, among other flags. Remember
		1853	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1854	EV_READ >>, and similarly for C<EV_WRITE>.
		1855
		1856	As with C<fd>, you must not modify this member even when the watcher is
		1857	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1623		1858
1624	=back	1859	=back
1625		1860
1626	=head3 Examples	1861	=head3 Examples
1627		1862
…		…
1655	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1890	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1656	monotonic clock option helps a lot here).	1891	monotonic clock option helps a lot here).
1657		1892
1658	The callback is guaranteed to be invoked only I<after> its timeout has	1893	The callback is guaranteed to be invoked only I<after> its timeout has
1659	passed (not I<at>, so on systems with very low-resolution clocks this	1894	passed (not I<at>, so on systems with very low-resolution clocks this
1660	might introduce a small delay). If multiple timers become ready during the	1895	might introduce a small delay, see "the special problem of being too
		1896	early", below). If multiple timers become ready during the same loop
1661	same loop iteration then the ones with earlier time-out values are invoked	1897	iteration then the ones with earlier time-out values are invoked before
1662	before ones of the same priority with later time-out values (but this is	1898	ones of the same priority with later time-out values (but this is no
1663	no longer true when a callback calls C<ev_run> recursively).	1899	longer true when a callback calls C<ev_run> recursively).
1664		1900
1665	=head3 Be smart about timeouts	1901	=head3 Be smart about timeouts
1666		1902
1667	Many real-world problems involve some kind of timeout, usually for error	1903	Many real-world problems involve some kind of timeout, usually for error
1668	recovery. A typical example is an HTTP request - if the other side hangs,	1904	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1743		1979
1744	In this case, it would be more efficient to leave the C<ev_timer> alone,	1980	In this case, it would be more efficient to leave the C<ev_timer> alone,
1745	but remember the time of last activity, and check for a real timeout only	1981	but remember the time of last activity, and check for a real timeout only
1746	within the callback:	1982	within the callback:
1747		1983
		1984	ev_tstamp timeout = 60.;
1748	ev_tstamp last_activity; // time of last activity	1985	ev_tstamp last_activity; // time of last activity
		1986	ev_timer timer;
1749		1987
1750	static void	1988	static void
1751	callback (EV_P_ ev_timer *w, int revents)	1989	callback (EV_P_ ev_timer *w, int revents)
1752	{	1990	{
1753	ev_tstamp now = ev_now (EV_A);	1991	// calculate when the timeout would happen
1754	ev_tstamp timeout = last_activity + 60.;	1992	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1755		1993
1756	// if last_activity + 60. is older than now, we did time out	1994	// if negative, it means we the timeout already occurred
1757	if (timeout < now)	1995	if (after < 0.)
1758	{	1996	{
1759	// timeout occurred, take action	1997	// timeout occurred, take action
1760	}	1998	}
1761	else	1999	else
1762	{	2000	{
1763	// callback was invoked, but there was some activity, re-arm	2001	// callback was invoked, but there was some recent
1764	// the watcher to fire in last_activity + 60, which is	2002	// activity. simply restart the timer to time out
1765	// guaranteed to be in the future, so "again" is positive:	2003	// after "after" seconds, which is the earliest time
1766	w->repeat = timeout - now;	2004	// the timeout can occur.
		2005	ev_timer_set (w, after, 0.);
1767	ev_timer_again (EV_A_ w);	2006	ev_timer_start (EV_A_ w);
1768	}	2007	}
1769	}	2008	}
1770		2009
1771	To summarise the callback: first calculate the real timeout (defined	2010	To summarise the callback: first calculate in how many seconds the
1772	as "60 seconds after the last activity"), then check if that time has	2011	timeout will occur (by calculating the absolute time when it would occur,
1773	been reached, which means something I<did>, in fact, time out. Otherwise	2012	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1774	the callback was invoked too early (C<timeout> is in the future), so	2013	(EV_A)> from that).
1775	re-schedule the timer to fire at that future time, to see if maybe we have
1776	a timeout then.
1777		2014
1778	Note how C<ev_timer_again> is used, taking advantage of the	2015	If this value is negative, then we are already past the timeout, i.e. we
1779	C<ev_timer_again> optimisation when the timer is already running.	2016	timed out, and need to do whatever is needed in this case.
		2017
		2018	Otherwise, we now the earliest time at which the timeout would trigger,
		2019	and simply start the timer with this timeout value.
		2020
		2021	In other words, each time the callback is invoked it will check whether
		2022	the timeout occurred. If not, it will simply reschedule itself to check
		2023	again at the earliest time it could time out. Rinse. Repeat.
1780		2024
1781	This scheme causes more callback invocations (about one every 60 seconds	2025	This scheme causes more callback invocations (about one every 60 seconds
1782	minus half the average time between activity), but virtually no calls to	2026	minus half the average time between activity), but virtually no calls to
1783	libev to change the timeout.	2027	libev to change the timeout.
1784		2028
1785	To start the timer, simply initialise the watcher and set C<last_activity>	2029	To start the machinery, simply initialise the watcher and set
1786	to the current time (meaning we just have some activity :), then call the	2030	C<last_activity> to the current time (meaning there was some activity just
1787	callback, which will "do the right thing" and start the timer:	2031	now), then call the callback, which will "do the right thing" and start
		2032	the timer:
1788		2033
		2034	last_activity = ev_now (EV_A);
1789	ev_init (timer, callback);	2035	ev_init (&timer, callback);
1790	last_activity = ev_now (loop);	2036	callback (EV_A_ &timer, 0);
1791	callback (loop, timer, EV_TIMER);
1792		2037
1793	And when there is some activity, simply store the current time in	2038	When there is some activity, simply store the current time in
1794	C<last_activity>, no libev calls at all:	2039	C<last_activity>, no libev calls at all:
1795		2040
		2041	if (activity detected)
1796	last_activity = ev_now (loop);	2042	last_activity = ev_now (EV_A);
		2043
		2044	When your timeout value changes, then the timeout can be changed by simply
		2045	providing a new value, stopping the timer and calling the callback, which
		2046	will again do the right thing (for example, time out immediately :).
		2047
		2048	timeout = new_value;
		2049	ev_timer_stop (EV_A_ &timer);
		2050	callback (EV_A_ &timer, 0);
1797		2051
1798	This technique is slightly more complex, but in most cases where the	2052	This technique is slightly more complex, but in most cases where the
1799	time-out is unlikely to be triggered, much more efficient.	2053	time-out is unlikely to be triggered, much more efficient.
1800
1801	Changing the timeout is trivial as well (if it isn't hard-coded in the
1802	callback :) - just change the timeout and invoke the callback, which will
1803	fix things for you.
1804		2054
1805	=item 4. Wee, just use a double-linked list for your timeouts.	2055	=item 4. Wee, just use a double-linked list for your timeouts.
1806		2056
1807	If there is not one request, but many thousands (millions...), all	2057	If there is not one request, but many thousands (millions...), all
1808	employing some kind of timeout with the same timeout value, then one can	2058	employing some kind of timeout with the same timeout value, then one can
…		…
1835	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2085	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1836	rather complicated, but extremely efficient, something that really pays	2086	rather complicated, but extremely efficient, something that really pays
1837	off after the first million or so of active timers, i.e. it's usually	2087	off after the first million or so of active timers, i.e. it's usually
1838	overkill :)	2088	overkill :)
1839		2089
		2090	=head3 The special problem of being too early
		2091
		2092	If you ask a timer to call your callback after three seconds, then
		2093	you expect it to be invoked after three seconds - but of course, this
		2094	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2095	guaranteed to any precision by libev - imagine somebody suspending the
		2096	process with a STOP signal for a few hours for example.
		2097
		2098	So, libev tries to invoke your callback as soon as possible I<after> the
		2099	delay has occurred, but cannot guarantee this.
		2100
		2101	A less obvious failure mode is calling your callback too early: many event
		2102	loops compare timestamps with a "elapsed delay >= requested delay", but
		2103	this can cause your callback to be invoked much earlier than you would
		2104	expect.
		2105
		2106	To see why, imagine a system with a clock that only offers full second
		2107	resolution (think windows if you can't come up with a broken enough OS
		2108	yourself). If you schedule a one-second timer at the time 500.9, then the
		2109	event loop will schedule your timeout to elapse at a system time of 500
		2110	(500.9 truncated to the resolution) + 1, or 501.
		2111
		2112	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2113	501" and invoke the callback 0.1s after it was started, even though a
		2114	one-second delay was requested - this is being "too early", despite best
		2115	intentions.
		2116
		2117	This is the reason why libev will never invoke the callback if the elapsed
		2118	delay equals the requested delay, but only when the elapsed delay is
		2119	larger than the requested delay. In the example above, libev would only invoke
		2120	the callback at system time 502, or 1.1s after the timer was started.
		2121
		2122	So, while libev cannot guarantee that your callback will be invoked
		2123	exactly when requested, it I<can> and I<does> guarantee that the requested
		2124	delay has actually elapsed, or in other words, it always errs on the "too
		2125	late" side of things.
		2126
1840	=head3 The special problem of time updates	2127	=head3 The special problem of time updates
1841		2128
1842	Establishing the current time is a costly operation (it usually takes at	2129	Establishing the current time is a costly operation (it usually takes
1843	least two system calls): EV therefore updates its idea of the current	2130	at least one system call): EV therefore updates its idea of the current
1844	time only before and after C<ev_run> collects new events, which causes a	2131	time only before and after C<ev_run> collects new events, which causes a
1845	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2132	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1846	lots of events in one iteration.	2133	lots of events in one iteration.
1847		2134
1848	The relative timeouts are calculated relative to the C<ev_now ()>	2135	The relative timeouts are calculated relative to the C<ev_now ()>
1849	time. This is usually the right thing as this timestamp refers to the time	2136	time. This is usually the right thing as this timestamp refers to the time
1850	of the event triggering whatever timeout you are modifying/starting. If	2137	of the event triggering whatever timeout you are modifying/starting. If
1851	you suspect event processing to be delayed and you I<need> to base the	2138	you suspect event processing to be delayed and you I<need> to base the
1852	timeout on the current time, use something like this to adjust for this:	2139	timeout on the current time, use something like the following to adjust
		2140	for it:
1853		2141
1854	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2142	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1855		2143
1856	If the event loop is suspended for a long time, you can also force an	2144	If the event loop is suspended for a long time, you can also force an
1857	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2145	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1858	()>.	2146	()>, although that will push the event time of all outstanding events
		2147	further into the future.
		2148
		2149	=head3 The special problem of unsynchronised clocks
		2150
		2151	Modern systems have a variety of clocks - libev itself uses the normal
		2152	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2153	jumps).
		2154
		2155	Neither of these clocks is synchronised with each other or any other clock
		2156	on the system, so C<ev_time ()> might return a considerably different time
		2157	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2158	a call to C<gettimeofday> might return a second count that is one higher
		2159	than a directly following call to C<time>.
		2160
		2161	The moral of this is to only compare libev-related timestamps with
		2162	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2163	a second or so.
		2164
		2165	One more problem arises due to this lack of synchronisation: if libev uses
		2166	the system monotonic clock and you compare timestamps from C<ev_time>
		2167	or C<ev_now> from when you started your timer and when your callback is
		2168	invoked, you will find that sometimes the callback is a bit "early".
		2169
		2170	This is because C<ev_timer>s work in real time, not wall clock time, so
		2171	libev makes sure your callback is not invoked before the delay happened,
		2172	I<measured according to the real time>, not the system clock.
		2173
		2174	If your timeouts are based on a physical timescale (e.g. "time out this
		2175	connection after 100 seconds") then this shouldn't bother you as it is
		2176	exactly the right behaviour.
		2177
		2178	If you want to compare wall clock/system timestamps to your timers, then
		2179	you need to use C<ev_periodic>s, as these are based on the wall clock
		2180	time, where your comparisons will always generate correct results.
1859		2181
1860	=head3 The special problems of suspended animation	2182	=head3 The special problems of suspended animation
1861		2183
1862	When you leave the server world it is quite customary to hit machines that	2184	When you leave the server world it is quite customary to hit machines that
1863	can suspend/hibernate - what happens to the clocks during such a suspend?	2185	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1893		2215
1894	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2216	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1895		2217
1896	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2218	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1897		2219
1898	Configure the timer to trigger after C<after> seconds. If C<repeat>	2220	Configure the timer to trigger after C<after> seconds (fractional and
1899	is C<0.>, then it will automatically be stopped once the timeout is	2221	negative values are supported). If C<repeat> is C<0.>, then it will
1900	reached. If it is positive, then the timer will automatically be	2222	automatically be stopped once the timeout is reached. If it is positive,
1901	configured to trigger again C<repeat> seconds later, again, and again,	2223	then the timer will automatically be configured to trigger again C<repeat>
1902	until stopped manually.	2224	seconds later, again, and again, until stopped manually.
1903		2225
1904	The timer itself will do a best-effort at avoiding drift, that is, if	2226	The timer itself will do a best-effort at avoiding drift, that is, if
1905	you configure a timer to trigger every 10 seconds, then it will normally	2227	you configure a timer to trigger every 10 seconds, then it will normally
1906	trigger at exactly 10 second intervals. If, however, your program cannot	2228	trigger at exactly 10 second intervals. If, however, your program cannot
1907	keep up with the timer (because it takes longer than those 10 seconds to	2229	keep up with the timer (because it takes longer than those 10 seconds to
1908	do stuff) the timer will not fire more than once per event loop iteration.	2230	do stuff) the timer will not fire more than once per event loop iteration.
1909		2231
1910	=item ev_timer_again (loop, ev_timer *)	2232	=item ev_timer_again (loop, ev_timer *)
1911		2233
1912	This will act as if the timer timed out and restart it again if it is	2234	This will act as if the timer timed out, and restarts it again if it is
1913	repeating. The exact semantics are:	2235	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2236	timeout to the C<repeat> value and calling C<ev_timer_start>.
1914		2237
		2238	The exact semantics are as in the following rules, all of which will be
		2239	applied to the watcher:
		2240
		2241	=over 4
		2242
1915	If the timer is pending, its pending status is cleared.	2243	=item If the timer is pending, the pending status is always cleared.
1916		2244
1917	If the timer is started but non-repeating, stop it (as if it timed out).	2245	=item If the timer is started but non-repeating, stop it (as if it timed
		2246	out, without invoking it).
1918		2247
1919	If the timer is repeating, either start it if necessary (with the	2248	=item If the timer is repeating, make the C<repeat> value the new timeout
1920	C<repeat> value), or reset the running timer to the C<repeat> value.	2249	and start the timer, if necessary.
1921		2250
		2251	=back
		2252
1922	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2253	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1923	usage example.	2254	usage example.
1924		2255
1925	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2256	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1926		2257
1927	Returns the remaining time until a timer fires. If the timer is active,	2258	Returns the remaining time until a timer fires. If the timer is active,
…		…
1980	Periodic watchers are also timers of a kind, but they are very versatile	2311	Periodic watchers are also timers of a kind, but they are very versatile
1981	(and unfortunately a bit complex).	2312	(and unfortunately a bit complex).
1982		2313
1983	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2314	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1984	relative time, the physical time that passes) but on wall clock time	2315	relative time, the physical time that passes) but on wall clock time
1985	(absolute time, the thing you can read on your calender or clock). The	2316	(absolute time, the thing you can read on your calendar or clock). The
1986	difference is that wall clock time can run faster or slower than real	2317	difference is that wall clock time can run faster or slower than real
1987	time, and time jumps are not uncommon (e.g. when you adjust your	2318	time, and time jumps are not uncommon (e.g. when you adjust your
1988	wrist-watch).	2319	wrist-watch).
1989		2320
1990	You can tell a periodic watcher to trigger after some specific point	2321	You can tell a periodic watcher to trigger after some specific point
…		…
1995	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2326	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1996	it, as it uses a relative timeout).	2327	it, as it uses a relative timeout).
1997		2328
1998	C<ev_periodic> watchers can also be used to implement vastly more complex	2329	C<ev_periodic> watchers can also be used to implement vastly more complex
1999	timers, such as triggering an event on each "midnight, local time", or	2330	timers, such as triggering an event on each "midnight, local time", or
2000	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2331	other complicated rules. This cannot easily be done with C<ev_timer>
2001	those cannot react to time jumps.	2332	watchers, as those cannot react to time jumps.
2002		2333
2003	As with timers, the callback is guaranteed to be invoked only when the	2334	As with timers, the callback is guaranteed to be invoked only when the
2004	point in time where it is supposed to trigger has passed. If multiple	2335	point in time where it is supposed to trigger has passed. If multiple
2005	timers become ready during the same loop iteration then the ones with	2336	timers become ready during the same loop iteration then the ones with
2006	earlier time-out values are invoked before ones with later time-out values	2337	earlier time-out values are invoked before ones with later time-out values
…		…
2047		2378
2048	Another way to think about it (for the mathematically inclined) is that	2379	Another way to think about it (for the mathematically inclined) is that
2049	C<ev_periodic> will try to run the callback in this mode at the next possible	2380	C<ev_periodic> will try to run the callback in this mode at the next possible
2050	time where C<time = offset (mod interval)>, regardless of any time jumps.	2381	time where C<time = offset (mod interval)>, regardless of any time jumps.
2051		2382
2052	For numerical stability it is preferable that the C<offset> value is near	2383	The C<interval> I<MUST> be positive, and for numerical stability, the
2053	C<ev_now ()> (the current time), but there is no range requirement for	2384	interval value should be higher than C<1/8192> (which is around 100
2054	this value, and in fact is often specified as zero.	2385	microseconds) and C<offset> should be higher than C<0> and should have
		2386	at most a similar magnitude as the current time (say, within a factor of
		2387	ten). Typical values for offset are, in fact, C<0> or something between
		2388	C<0> and C<interval>, which is also the recommended range.
2055		2389
2056	Note also that there is an upper limit to how often a timer can fire (CPU	2390	Note also that there is an upper limit to how often a timer can fire (CPU
2057	speed for example), so if C<interval> is very small then timing stability	2391	speed for example), so if C<interval> is very small then timing stability
2058	will of course deteriorate. Libev itself tries to be exact to be about one	2392	will of course deteriorate. Libev itself tries to be exact to be about one
2059	millisecond (if the OS supports it and the machine is fast enough).	2393	millisecond (if the OS supports it and the machine is fast enough).
…		…
2089		2423
2090	NOTE: I<< This callback must always return a time that is higher than or	2424	NOTE: I<< This callback must always return a time that is higher than or
2091	equal to the passed C<now> value >>.	2425	equal to the passed C<now> value >>.
2092		2426
2093	This can be used to create very complex timers, such as a timer that	2427	This can be used to create very complex timers, such as a timer that
2094	triggers on "next midnight, local time". To do this, you would calculate the	2428	triggers on "next midnight, local time". To do this, you would calculate
2095	next midnight after C<now> and return the timestamp value for this. How	2429	the next midnight after C<now> and return the timestamp value for
2096	you do this is, again, up to you (but it is not trivial, which is the main	2430	this. Here is a (completely untested, no error checking) example on how to
2097	reason I omitted it as an example).	2431	do this:
		2432
		2433	#include <time.h>
		2434
		2435	static ev_tstamp
		2436	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2437	{
		2438	time_t tnow = (time_t)now;
		2439	struct tm tm;
		2440	localtime_r (&tnow, &tm);
		2441
		2442	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2443	++tm.tm_mday; // midnight next day
		2444
		2445	return mktime (&tm);
		2446	}
		2447
		2448	Note: this code might run into trouble on days that have more then two
		2449	midnights (beginning and end).
2098		2450
2099	=back	2451	=back
2100		2452
2101	=item ev_periodic_again (loop, ev_periodic *)	2453	=item ev_periodic_again (loop, ev_periodic *)
2102		2454
…		…
2167		2519
2168	ev_periodic hourly_tick;	2520	ev_periodic hourly_tick;
2169	ev_periodic_init (&hourly_tick, clock_cb,	2521	ev_periodic_init (&hourly_tick, clock_cb,
2170	fmod (ev_now (loop), 3600.), 3600., 0);	2522	fmod (ev_now (loop), 3600.), 3600., 0);
2171	ev_periodic_start (loop, &hourly_tick);	2523	ev_periodic_start (loop, &hourly_tick);
2172		2524
2173		2525
2174	=head2 C<ev_signal> - signal me when a signal gets signalled!	2526	=head2 C<ev_signal> - signal me when a signal gets signalled!
2175		2527
2176	Signal watchers will trigger an event when the process receives a specific	2528	Signal watchers will trigger an event when the process receives a specific
2177	signal one or more times. Even though signals are very asynchronous, libev	2529	signal one or more times. Even though signals are very asynchronous, libev
2178	will try it's best to deliver signals synchronously, i.e. as part of the	2530	will try its best to deliver signals synchronously, i.e. as part of the
2179	normal event processing, like any other event.	2531	normal event processing, like any other event.
2180		2532
2181	If you want signals to be delivered truly asynchronously, just use	2533	If you want signals to be delivered truly asynchronously, just use
2182	C<sigaction> as you would do without libev and forget about sharing	2534	C<sigaction> as you would do without libev and forget about sharing
2183	the signal. You can even use C<ev_async> from a signal handler to	2535	the signal. You can even use C<ev_async> from a signal handler to
…		…
2187	only within the same loop, i.e. you can watch for C<SIGINT> in your	2539	only within the same loop, i.e. you can watch for C<SIGINT> in your
2188	default loop and for C<SIGIO> in another loop, but you cannot watch for	2540	default loop and for C<SIGIO> in another loop, but you cannot watch for
2189	C<SIGINT> in both the default loop and another loop at the same time. At	2541	C<SIGINT> in both the default loop and another loop at the same time. At
2190	the moment, C<SIGCHLD> is permanently tied to the default loop.	2542	the moment, C<SIGCHLD> is permanently tied to the default loop.
2191		2543
2192	When the first watcher gets started will libev actually register something	2544	Only after the first watcher for a signal is started will libev actually
2193	with the kernel (thus it coexists with your own signal handlers as long as	2545	register something with the kernel. It thus coexists with your own signal
2194	you don't register any with libev for the same signal).	2546	handlers as long as you don't register any with libev for the same signal.
2195		2547
2196	If possible and supported, libev will install its handlers with	2548	If possible and supported, libev will install its handlers with
2197	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2549	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2198	not be unduly interrupted. If you have a problem with system calls getting	2550	not be unduly interrupted. If you have a problem with system calls getting
2199	interrupted by signals you can block all signals in an C<ev_check> watcher	2551	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2202	=head3 The special problem of inheritance over fork/execve/pthread_create	2554	=head3 The special problem of inheritance over fork/execve/pthread_create
2203		2555
2204	Both the signal mask (C<sigprocmask>) and the signal disposition	2556	Both the signal mask (C<sigprocmask>) and the signal disposition
2205	(C<sigaction>) are unspecified after starting a signal watcher (and after	2557	(C<sigaction>) are unspecified after starting a signal watcher (and after
2206	stopping it again), that is, libev might or might not block the signal,	2558	stopping it again), that is, libev might or might not block the signal,
2207	and might or might not set or restore the installed signal handler.	2559	and might or might not set or restore the installed signal handler (but
		2560	see C<EVFLAG_NOSIGMASK>).
2208		2561
2209	While this does not matter for the signal disposition (libev never	2562	While this does not matter for the signal disposition (libev never
2210	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2563	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2211	C<execve>), this matters for the signal mask: many programs do not expect	2564	C<execve>), this matters for the signal mask: many programs do not expect
2212	certain signals to be blocked.	2565	certain signals to be blocked.
…		…
2225	I<has> to modify the signal mask, at least temporarily.	2578	I<has> to modify the signal mask, at least temporarily.
2226		2579
2227	So I can't stress this enough: I<If you do not reset your signal mask when	2580	So I can't stress this enough: I<If you do not reset your signal mask when
2228	you expect it to be empty, you have a race condition in your code>. This	2581	you expect it to be empty, you have a race condition in your code>. This
2229	is not a libev-specific thing, this is true for most event libraries.	2582	is not a libev-specific thing, this is true for most event libraries.
		2583
		2584	=head3 The special problem of threads signal handling
		2585
		2586	POSIX threads has problematic signal handling semantics, specifically,
		2587	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2588	threads in a process block signals, which is hard to achieve.
		2589
		2590	When you want to use sigwait (or mix libev signal handling with your own
		2591	for the same signals), you can tackle this problem by globally blocking
		2592	all signals before creating any threads (or creating them with a fully set
		2593	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2594	loops. Then designate one thread as "signal receiver thread" which handles
		2595	these signals. You can pass on any signals that libev might be interested
		2596	in by calling C<ev_feed_signal>.
2230		2597
2231	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
2232		2599
2233	=over 4	2600	=over 4
2234		2601
…		…
2369		2736
2370	=head2 C<ev_stat> - did the file attributes just change?	2737	=head2 C<ev_stat> - did the file attributes just change?
2371		2738
2372	This watches a file system path for attribute changes. That is, it calls	2739	This watches a file system path for attribute changes. That is, it calls
2373	C<stat> on that path in regular intervals (or when the OS says it changed)	2740	C<stat> on that path in regular intervals (or when the OS says it changed)
2374	and sees if it changed compared to the last time, invoking the callback if	2741	and sees if it changed compared to the last time, invoking the callback
2375	it did.	2742	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2743	happen after the watcher has been started will be reported.
2376		2744
2377	The path does not need to exist: changing from "path exists" to "path does	2745	The path does not need to exist: changing from "path exists" to "path does
2378	not exist" is a status change like any other. The condition "path does not	2746	not exist" is a status change like any other. The condition "path does not
2379	exist" (or more correctly "path cannot be stat'ed") is signified by the	2747	exist" (or more correctly "path cannot be stat'ed") is signified by the
2380	C<st_nlink> field being zero (which is otherwise always forced to be at	2748	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2610	Apart from keeping your process non-blocking (which is a useful	2978	Apart from keeping your process non-blocking (which is a useful
2611	effect on its own sometimes), idle watchers are a good place to do	2979	effect on its own sometimes), idle watchers are a good place to do
2612	"pseudo-background processing", or delay processing stuff to after the	2980	"pseudo-background processing", or delay processing stuff to after the
2613	event loop has handled all outstanding events.	2981	event loop has handled all outstanding events.
2614		2982
		2983	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2984
		2985	As long as there is at least one active idle watcher, libev will never
		2986	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2987	For this to work, the idle watcher doesn't need to be invoked at all - the
		2988	lowest priority will do.
		2989
		2990	This mode of operation can be useful together with an C<ev_check> watcher,
		2991	to do something on each event loop iteration - for example to balance load
		2992	between different connections.
		2993
		2994	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2995	example.
		2996
2615	=head3 Watcher-Specific Functions and Data Members	2997	=head3 Watcher-Specific Functions and Data Members
2616		2998
2617	=over 4	2999	=over 4
2618		3000
2619	=item ev_idle_init (ev_idle *, callback)	3001	=item ev_idle_init (ev_idle *, callback)
…		…
2630	callback, free it. Also, use no error checking, as usual.	3012	callback, free it. Also, use no error checking, as usual.
2631		3013
2632	static void	3014	static void
2633	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3015	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2634	{	3016	{
		3017	// stop the watcher
		3018	ev_idle_stop (loop, w);
		3019
		3020	// now we can free it
2635	free (w);	3021	free (w);
		3022
2636	// now do something you wanted to do when the program has	3023	// now do something you wanted to do when the program has
2637	// no longer anything immediate to do.	3024	// no longer anything immediate to do.
2638	}	3025	}
2639		3026
2640	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3027	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2642	ev_idle_start (loop, idle_watcher);	3029	ev_idle_start (loop, idle_watcher);
2643		3030
2644		3031
2645	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3032	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2646		3033
2647	Prepare and check watchers are usually (but not always) used in pairs:	3034	Prepare and check watchers are often (but not always) used in pairs:
2648	prepare watchers get invoked before the process blocks and check watchers	3035	prepare watchers get invoked before the process blocks and check watchers
2649	afterwards.	3036	afterwards.
2650		3037
2651	You I<must not> call C<ev_run> or similar functions that enter	3038	You I<must not> call C<ev_run> (or similar functions that enter the
2652	the current event loop from either C<ev_prepare> or C<ev_check>	3039	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2653	watchers. Other loops than the current one are fine, however. The	3040	C<ev_check> watchers. Other loops than the current one are fine,
2654	rationale behind this is that you do not need to check for recursion in	3041	however. The rationale behind this is that you do not need to check
2655	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3042	for recursion in those watchers, i.e. the sequence will always be
2656	C<ev_check> so if you have one watcher of each kind they will always be	3043	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2657	called in pairs bracketing the blocking call.	3044	kind they will always be called in pairs bracketing the blocking call.
2658		3045
2659	Their main purpose is to integrate other event mechanisms into libev and	3046	Their main purpose is to integrate other event mechanisms into libev and
2660	their use is somewhat advanced. They could be used, for example, to track	3047	their use is somewhat advanced. They could be used, for example, to track
2661	variable changes, implement your own watchers, integrate net-snmp or a	3048	variable changes, implement your own watchers, integrate net-snmp or a
2662	coroutine library and lots more. They are also occasionally useful if	3049	coroutine library and lots more. They are also occasionally useful if
…		…
2680	with priority higher than or equal to the event loop and one coroutine	3067	with priority higher than or equal to the event loop and one coroutine
2681	of lower priority, but only once, using idle watchers to keep the event	3068	of lower priority, but only once, using idle watchers to keep the event
2682	loop from blocking if lower-priority coroutines are active, thus mapping	3069	loop from blocking if lower-priority coroutines are active, thus mapping
2683	low-priority coroutines to idle/background tasks).	3070	low-priority coroutines to idle/background tasks).
2684		3071
2685	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3072	When used for this purpose, it is recommended to give C<ev_check> watchers
2686	priority, to ensure that they are being run before any other watchers	3073	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2687	after the poll (this doesn't matter for C<ev_prepare> watchers).	3074	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3075	watchers).
2688		3076
2689	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3077	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2690	activate ("feed") events into libev. While libev fully supports this, they	3078	activate ("feed") events into libev. While libev fully supports this, they
2691	might get executed before other C<ev_check> watchers did their job. As	3079	might get executed before other C<ev_check> watchers did their job. As
2692	C<ev_check> watchers are often used to embed other (non-libev) event	3080	C<ev_check> watchers are often used to embed other (non-libev) event
2693	loops those other event loops might be in an unusable state until their	3081	loops those other event loops might be in an unusable state until their
2694	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3082	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2695	others).	3083	others).
		3084
		3085	=head3 Abusing an C<ev_check> watcher for its side-effect
		3086
		3087	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3088	useful because they are called once per event loop iteration. For
		3089	example, if you want to handle a large number of connections fairly, you
		3090	normally only do a bit of work for each active connection, and if there
		3091	is more work to do, you wait for the next event loop iteration, so other
		3092	connections have a chance of making progress.
		3093
		3094	Using an C<ev_check> watcher is almost enough: it will be called on the
		3095	next event loop iteration. However, that isn't as soon as possible -
		3096	without external events, your C<ev_check> watcher will not be invoked.
		3097
		3098	This is where C<ev_idle> watchers come in handy - all you need is a
		3099	single global idle watcher that is active as long as you have one active
		3100	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3101	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3102	invoked. Neither watcher alone can do that.
2696		3103
2697	=head3 Watcher-Specific Functions and Data Members	3104	=head3 Watcher-Specific Functions and Data Members
2698		3105
2699	=over 4	3106	=over 4
2700		3107
…		…
2901		3308
2902	=over 4	3309	=over 4
2903		3310
2904	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3311	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2905		3312
2906	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3313	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2907		3314
2908	Configures the watcher to embed the given loop, which must be	3315	Configures the watcher to embed the given loop, which must be
2909	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3316	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2910	invoked automatically, otherwise it is the responsibility of the callback	3317	invoked automatically, otherwise it is the responsibility of the callback
2911	to invoke it (it will continue to be called until the sweep has been done,	3318	to invoke it (it will continue to be called until the sweep has been done,
…		…
2932	used).	3339	used).
2933		3340
2934	struct ev_loop *loop_hi = ev_default_init (0);	3341	struct ev_loop *loop_hi = ev_default_init (0);
2935	struct ev_loop *loop_lo = 0;	3342	struct ev_loop *loop_lo = 0;
2936	ev_embed embed;	3343	ev_embed embed;
2937		3344
2938	// see if there is a chance of getting one that works	3345	// see if there is a chance of getting one that works
2939	// (remember that a flags value of 0 means autodetection)	3346	// (remember that a flags value of 0 means autodetection)
2940	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3347	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2941	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3348	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2942	: 0;	3349	: 0;
…		…
2956	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3363	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2957		3364
2958	struct ev_loop *loop = ev_default_init (0);	3365	struct ev_loop *loop = ev_default_init (0);
2959	struct ev_loop *loop_socket = 0;	3366	struct ev_loop *loop_socket = 0;
2960	ev_embed embed;	3367	ev_embed embed;
2961		3368
2962	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3369	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2963	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3370	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2964	{	3371	{
2965	ev_embed_init (&embed, 0, loop_socket);	3372	ev_embed_init (&embed, 0, loop_socket);
2966	ev_embed_start (loop, &embed);	3373	ev_embed_start (loop, &embed);
…		…
2974		3381
2975	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3382	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2976		3383
2977	Fork watchers are called when a C<fork ()> was detected (usually because	3384	Fork watchers are called when a C<fork ()> was detected (usually because
2978	whoever is a good citizen cared to tell libev about it by calling	3385	whoever is a good citizen cared to tell libev about it by calling
2979	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3386	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2980	event loop blocks next and before C<ev_check> watchers are being called,	3387	and before C<ev_check> watchers are being called, and only in the child
2981	and only in the child after the fork. If whoever good citizen calling	3388	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2982	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3389	and calls it in the wrong process, the fork handlers will be invoked, too,
2983	handlers will be invoked, too, of course.	3390	of course.
2984		3391
2985	=head3 The special problem of life after fork - how is it possible?	3392	=head3 The special problem of life after fork - how is it possible?
2986		3393
2987	Most uses of C<fork()> consist of forking, then some simple calls to set	3394	Most uses of C<fork ()> consist of forking, then some simple calls to set
2988	up/change the process environment, followed by a call to C<exec()>. This	3395	up/change the process environment, followed by a call to C<exec()>. This
2989	sequence should be handled by libev without any problems.	3396	sequence should be handled by libev without any problems.
2990		3397
2991	This changes when the application actually wants to do event handling	3398	This changes when the application actually wants to do event handling
2992	in the child, or both parent in child, in effect "continuing" after the	3399	in the child, or both parent in child, in effect "continuing" after the
…		…
3008	disadvantage of having to use multiple event loops (which do not support	3415	disadvantage of having to use multiple event loops (which do not support
3009	signal watchers).	3416	signal watchers).
3010		3417
3011	When this is not possible, or you want to use the default loop for	3418	When this is not possible, or you want to use the default loop for
3012	other reasons, then in the process that wants to start "fresh", call	3419	other reasons, then in the process that wants to start "fresh", call
3013	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3420	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3014	the default loop will "orphan" (not stop) all registered watchers, so you	3421	Destroying the default loop will "orphan" (not stop) all registered
3015	have to be careful not to execute code that modifies those watchers. Note	3422	watchers, so you have to be careful not to execute code that modifies
3016	also that in that case, you have to re-register any signal watchers.	3423	those watchers. Note also that in that case, you have to re-register any
		3424	signal watchers.
3017		3425
3018	=head3 Watcher-Specific Functions and Data Members	3426	=head3 Watcher-Specific Functions and Data Members
3019		3427
3020	=over 4	3428	=over 4
3021		3429
3022	=item ev_fork_init (ev_signal *, callback)	3430	=item ev_fork_init (ev_fork *, callback)
3023		3431
3024	Initialises and configures the fork watcher - it has no parameters of any	3432	Initialises and configures the fork watcher - it has no parameters of any
3025	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3433	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3026	believe me.	3434	really.
3027		3435
3028	=back	3436	=back
3029		3437
3030		3438
		3439	=head2 C<ev_cleanup> - even the best things end
		3440
		3441	Cleanup watchers are called just before the event loop is being destroyed
		3442	by a call to C<ev_loop_destroy>.
		3443
		3444	While there is no guarantee that the event loop gets destroyed, cleanup
		3445	watchers provide a convenient method to install cleanup hooks for your
		3446	program, worker threads and so on - you just to make sure to destroy the
		3447	loop when you want them to be invoked.
		3448
		3449	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3450	all other watchers, they do not keep a reference to the event loop (which
		3451	makes a lot of sense if you think about it). Like all other watchers, you
		3452	can call libev functions in the callback, except C<ev_cleanup_start>.
		3453
		3454	=head3 Watcher-Specific Functions and Data Members
		3455
		3456	=over 4
		3457
		3458	=item ev_cleanup_init (ev_cleanup *, callback)
		3459
		3460	Initialises and configures the cleanup watcher - it has no parameters of
		3461	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3462	pointless, I assure you.
		3463
		3464	=back
		3465
		3466	Example: Register an atexit handler to destroy the default loop, so any
		3467	cleanup functions are called.
		3468
		3469	static void
		3470	program_exits (void)
		3471	{
		3472	ev_loop_destroy (EV_DEFAULT_UC);
		3473	}
		3474
		3475	...
		3476	atexit (program_exits);
		3477
		3478
3031	=head2 C<ev_async> - how to wake up an event loop	3479	=head2 C<ev_async> - how to wake up an event loop
3032		3480
3033	In general, you cannot use an C<ev_run> from multiple threads or other	3481	In general, you cannot use an C<ev_loop> from multiple threads or other
3034	asynchronous sources such as signal handlers (as opposed to multiple event	3482	asynchronous sources such as signal handlers (as opposed to multiple event
3035	loops - those are of course safe to use in different threads).	3483	loops - those are of course safe to use in different threads).
3036		3484
3037	Sometimes, however, you need to wake up an event loop you do not control,	3485	Sometimes, however, you need to wake up an event loop you do not control,
3038	for example because it belongs to another thread. This is what C<ev_async>	3486	for example because it belongs to another thread. This is what C<ev_async>
…		…
3040	it by calling C<ev_async_send>, which is thread- and signal safe.	3488	it by calling C<ev_async_send>, which is thread- and signal safe.
3041		3489
3042	This functionality is very similar to C<ev_signal> watchers, as signals,	3490	This functionality is very similar to C<ev_signal> watchers, as signals,
3043	too, are asynchronous in nature, and signals, too, will be compressed	3491	too, are asynchronous in nature, and signals, too, will be compressed
3044	(i.e. the number of callback invocations may be less than the number of	3492	(i.e. the number of callback invocations may be less than the number of
3045	C<ev_async_sent> calls).	3493	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3046		3494	of "global async watchers" by using a watcher on an otherwise unused
3047	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3495	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3048	just the default loop.	3496	even without knowing which loop owns the signal.
3049		3497
3050	=head3 Queueing	3498	=head3 Queueing
3051		3499
3052	C<ev_async> does not support queueing of data in any way. The reason	3500	C<ev_async> does not support queueing of data in any way. The reason
3053	is that the author does not know of a simple (or any) algorithm for a	3501	is that the author does not know of a simple (or any) algorithm for a
…		…
3145	trust me.	3593	trust me.
3146		3594
3147	=item ev_async_send (loop, ev_async *)	3595	=item ev_async_send (loop, ev_async *)
3148		3596
3149	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3597	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3150	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3598	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3599	returns.
		3600
3151	C<ev_feed_event>, this call is safe to do from other threads, signal or	3601	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3152	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3602	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3153	section below on what exactly this means).	3603	embedding section below on what exactly this means).
3154		3604
3155	Note that, as with other watchers in libev, multiple events might get	3605	Note that, as with other watchers in libev, multiple events might get
3156	compressed into a single callback invocation (another way to look at this	3606	compressed into a single callback invocation (another way to look at
3157	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3607	this is that C<ev_async> watchers are level-triggered: they are set on
3158	reset when the event loop detects that).	3608	C<ev_async_send>, reset when the event loop detects that).
3159		3609
3160	This call incurs the overhead of a system call only once per event loop	3610	This call incurs the overhead of at most one extra system call per event
3161	iteration, so while the overhead might be noticeable, it doesn't apply to	3611	loop iteration, if the event loop is blocked, and no syscall at all if
3162	repeated calls to C<ev_async_send> for the same event loop.	3612	the event loop (or your program) is processing events. That means that
		3613	repeated calls are basically free (there is no need to avoid calls for
		3614	performance reasons) and that the overhead becomes smaller (typically
		3615	zero) under load.
3163		3616
3164	=item bool = ev_async_pending (ev_async *)	3617	=item bool = ev_async_pending (ev_async *)
3165		3618
3166	Returns a non-zero value when C<ev_async_send> has been called on the	3619	Returns a non-zero value when C<ev_async_send> has been called on the
3167	watcher but the event has not yet been processed (or even noted) by the	3620	watcher but the event has not yet been processed (or even noted) by the
…		…
3184		3637
3185	There are some other functions of possible interest. Described. Here. Now.	3638	There are some other functions of possible interest. Described. Here. Now.
3186		3639
3187	=over 4	3640	=over 4
3188		3641
3189	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3642	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3190		3643
3191	This function combines a simple timer and an I/O watcher, calls your	3644	This function combines a simple timer and an I/O watcher, calls your
3192	callback on whichever event happens first and automatically stops both	3645	callback on whichever event happens first and automatically stops both
3193	watchers. This is useful if you want to wait for a single event on an fd	3646	watchers. This is useful if you want to wait for a single event on an fd
3194	or timeout without having to allocate/configure/start/stop/free one or	3647	or timeout without having to allocate/configure/start/stop/free one or
…		…
3222	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3675	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3223		3676
3224	=item ev_feed_fd_event (loop, int fd, int revents)	3677	=item ev_feed_fd_event (loop, int fd, int revents)
3225		3678
3226	Feed an event on the given fd, as if a file descriptor backend detected	3679	Feed an event on the given fd, as if a file descriptor backend detected
3227	the given events it.	3680	the given events.
3228		3681
3229	=item ev_feed_signal_event (loop, int signum)	3682	=item ev_feed_signal_event (loop, int signum)
3230		3683
3231	Feed an event as if the given signal occurred (C<loop> must be the default	3684	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3232	loop!).	3685	which is async-safe.
3233		3686
3234	=back	3687	=back
		3688
		3689
		3690	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3691
		3692	This section explains some common idioms that are not immediately
		3693	obvious. Note that examples are sprinkled over the whole manual, and this
		3694	section only contains stuff that wouldn't fit anywhere else.
		3695
		3696	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3697
		3698	Each watcher has, by default, a C<void *data> member that you can read
		3699	or modify at any time: libev will completely ignore it. This can be used
		3700	to associate arbitrary data with your watcher. If you need more data and
		3701	don't want to allocate memory separately and store a pointer to it in that
		3702	data member, you can also "subclass" the watcher type and provide your own
		3703	data:
		3704
		3705	struct my_io
		3706	{
		3707	ev_io io;
		3708	int otherfd;
		3709	void *somedata;
		3710	struct whatever *mostinteresting;
		3711	};
		3712
		3713	...
		3714	struct my_io w;
		3715	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3716
		3717	And since your callback will be called with a pointer to the watcher, you
		3718	can cast it back to your own type:
		3719
		3720	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3721	{
		3722	struct my_io *w = (struct my_io *)w_;
		3723	...
		3724	}
		3725
		3726	More interesting and less C-conformant ways of casting your callback
		3727	function type instead have been omitted.
		3728
		3729	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3730
		3731	Another common scenario is to use some data structure with multiple
		3732	embedded watchers, in effect creating your own watcher that combines
		3733	multiple libev event sources into one "super-watcher":
		3734
		3735	struct my_biggy
		3736	{
		3737	int some_data;
		3738	ev_timer t1;
		3739	ev_timer t2;
		3740	}
		3741
		3742	In this case getting the pointer to C<my_biggy> is a bit more
		3743	complicated: Either you store the address of your C<my_biggy> struct in
		3744	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3745	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3746	real programmers):
		3747
		3748	#include <stddef.h>
		3749
		3750	static void
		3751	t1_cb (EV_P_ ev_timer *w, int revents)
		3752	{
		3753	struct my_biggy big = (struct my_biggy *)
		3754	(((char *)w) - offsetof (struct my_biggy, t1));
		3755	}
		3756
		3757	static void
		3758	t2_cb (EV_P_ ev_timer *w, int revents)
		3759	{
		3760	struct my_biggy big = (struct my_biggy *)
		3761	(((char *)w) - offsetof (struct my_biggy, t2));
		3762	}
		3763
		3764	=head2 AVOIDING FINISHING BEFORE RETURNING
		3765
		3766	Often you have structures like this in event-based programs:
		3767
		3768	callback ()
		3769	{
		3770	free (request);
		3771	}
		3772
		3773	request = start_new_request (..., callback);
		3774
		3775	The intent is to start some "lengthy" operation. The C<request> could be
		3776	used to cancel the operation, or do other things with it.
		3777
		3778	It's not uncommon to have code paths in C<start_new_request> that
		3779	immediately invoke the callback, for example, to report errors. Or you add
		3780	some caching layer that finds that it can skip the lengthy aspects of the
		3781	operation and simply invoke the callback with the result.
		3782
		3783	The problem here is that this will happen I<before> C<start_new_request>
		3784	has returned, so C<request> is not set.
		3785
		3786	Even if you pass the request by some safer means to the callback, you
		3787	might want to do something to the request after starting it, such as
		3788	canceling it, which probably isn't working so well when the callback has
		3789	already been invoked.
		3790
		3791	A common way around all these issues is to make sure that
		3792	C<start_new_request> I<always> returns before the callback is invoked. If
		3793	C<start_new_request> immediately knows the result, it can artificially
		3794	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3795	example, or more sneakily, by reusing an existing (stopped) watcher and
		3796	pushing it into the pending queue:
		3797
		3798	ev_set_cb (watcher, callback);
		3799	ev_feed_event (EV_A_ watcher, 0);
		3800
		3801	This way, C<start_new_request> can safely return before the callback is
		3802	invoked, while not delaying callback invocation too much.
		3803
		3804	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3805
		3806	Often (especially in GUI toolkits) there are places where you have
		3807	I<modal> interaction, which is most easily implemented by recursively
		3808	invoking C<ev_run>.
		3809
		3810	This brings the problem of exiting - a callback might want to finish the
		3811	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3812	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3813	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3814	other combination: In these cases, a simple C<ev_break> will not work.
		3815
		3816	The solution is to maintain "break this loop" variable for each C<ev_run>
		3817	invocation, and use a loop around C<ev_run> until the condition is
		3818	triggered, using C<EVRUN_ONCE>:
		3819
		3820	// main loop
		3821	int exit_main_loop = 0;
		3822
		3823	while (!exit_main_loop)
		3824	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3825
		3826	// in a modal watcher
		3827	int exit_nested_loop = 0;
		3828
		3829	while (!exit_nested_loop)
		3830	ev_run (EV_A_ EVRUN_ONCE);
		3831
		3832	To exit from any of these loops, just set the corresponding exit variable:
		3833
		3834	// exit modal loop
		3835	exit_nested_loop = 1;
		3836
		3837	// exit main program, after modal loop is finished
		3838	exit_main_loop = 1;
		3839
		3840	// exit both
		3841	exit_main_loop = exit_nested_loop = 1;
		3842
		3843	=head2 THREAD LOCKING EXAMPLE
		3844
		3845	Here is a fictitious example of how to run an event loop in a different
		3846	thread from where callbacks are being invoked and watchers are
		3847	created/added/removed.
		3848
		3849	For a real-world example, see the C<EV::Loop::Async> perl module,
		3850	which uses exactly this technique (which is suited for many high-level
		3851	languages).
		3852
		3853	The example uses a pthread mutex to protect the loop data, a condition
		3854	variable to wait for callback invocations, an async watcher to notify the
		3855	event loop thread and an unspecified mechanism to wake up the main thread.
		3856
		3857	First, you need to associate some data with the event loop:
		3858
		3859	typedef struct {
		3860	mutex_t lock; /* global loop lock */
		3861	ev_async async_w;
		3862	thread_t tid;
		3863	cond_t invoke_cv;
		3864	} userdata;
		3865
		3866	void prepare_loop (EV_P)
		3867	{
		3868	// for simplicity, we use a static userdata struct.
		3869	static userdata u;
		3870
		3871	ev_async_init (&u->async_w, async_cb);
		3872	ev_async_start (EV_A_ &u->async_w);
		3873
		3874	pthread_mutex_init (&u->lock, 0);
		3875	pthread_cond_init (&u->invoke_cv, 0);
		3876
		3877	// now associate this with the loop
		3878	ev_set_userdata (EV_A_ u);
		3879	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3880	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3881
		3882	// then create the thread running ev_run
		3883	pthread_create (&u->tid, 0, l_run, EV_A);
		3884	}
		3885
		3886	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3887	solely to wake up the event loop so it takes notice of any new watchers
		3888	that might have been added:
		3889
		3890	static void
		3891	async_cb (EV_P_ ev_async *w, int revents)
		3892	{
		3893	// just used for the side effects
		3894	}
		3895
		3896	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3897	protecting the loop data, respectively.
		3898
		3899	static void
		3900	l_release (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903	pthread_mutex_unlock (&u->lock);
		3904	}
		3905
		3906	static void
		3907	l_acquire (EV_P)
		3908	{
		3909	userdata *u = ev_userdata (EV_A);
		3910	pthread_mutex_lock (&u->lock);
		3911	}
		3912
		3913	The event loop thread first acquires the mutex, and then jumps straight
		3914	into C<ev_run>:
		3915
		3916	void *
		3917	l_run (void *thr_arg)
		3918	{
		3919	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3920
		3921	l_acquire (EV_A);
		3922	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3923	ev_run (EV_A_ 0);
		3924	l_release (EV_A);
		3925
		3926	return 0;
		3927	}
		3928
		3929	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3930	signal the main thread via some unspecified mechanism (signals? pipe
		3931	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3932	have been called (in a while loop because a) spurious wakeups are possible
		3933	and b) skipping inter-thread-communication when there are no pending
		3934	watchers is very beneficial):
		3935
		3936	static void
		3937	l_invoke (EV_P)
		3938	{
		3939	userdata *u = ev_userdata (EV_A);
		3940
		3941	while (ev_pending_count (EV_A))
		3942	{
		3943	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3944	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3945	}
		3946	}
		3947
		3948	Now, whenever the main thread gets told to invoke pending watchers, it
		3949	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3950	thread to continue:
		3951
		3952	static void
		3953	real_invoke_pending (EV_P)
		3954	{
		3955	userdata *u = ev_userdata (EV_A);
		3956
		3957	pthread_mutex_lock (&u->lock);
		3958	ev_invoke_pending (EV_A);
		3959	pthread_cond_signal (&u->invoke_cv);
		3960	pthread_mutex_unlock (&u->lock);
		3961	}
		3962
		3963	Whenever you want to start/stop a watcher or do other modifications to an
		3964	event loop, you will now have to lock:
		3965
		3966	ev_timer timeout_watcher;
		3967	userdata *u = ev_userdata (EV_A);
		3968
		3969	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3970
		3971	pthread_mutex_lock (&u->lock);
		3972	ev_timer_start (EV_A_ &timeout_watcher);
		3973	ev_async_send (EV_A_ &u->async_w);
		3974	pthread_mutex_unlock (&u->lock);
		3975
		3976	Note that sending the C<ev_async> watcher is required because otherwise
		3977	an event loop currently blocking in the kernel will have no knowledge
		3978	about the newly added timer. By waking up the loop it will pick up any new
		3979	watchers in the next event loop iteration.
		3980
		3981	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3982
		3983	While the overhead of a callback that e.g. schedules a thread is small, it
		3984	is still an overhead. If you embed libev, and your main usage is with some
		3985	kind of threads or coroutines, you might want to customise libev so that
		3986	doesn't need callbacks anymore.
		3987
		3988	Imagine you have coroutines that you can switch to using a function
		3989	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3990	and that due to some magic, the currently active coroutine is stored in a
		3991	global called C<current_coro>. Then you can build your own "wait for libev
		3992	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3993	the differing C<;> conventions):
		3994
		3995	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3996	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3997
		3998	That means instead of having a C callback function, you store the
		3999	coroutine to switch to in each watcher, and instead of having libev call
		4000	your callback, you instead have it switch to that coroutine.
		4001
		4002	A coroutine might now wait for an event with a function called
		4003	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4004	matter when, or whether the watcher is active or not when this function is
		4005	called):
		4006
		4007	void
		4008	wait_for_event (ev_watcher *w)
		4009	{
		4010	ev_set_cb (w, current_coro);
		4011	switch_to (libev_coro);
		4012	}
		4013
		4014	That basically suspends the coroutine inside C<wait_for_event> and
		4015	continues the libev coroutine, which, when appropriate, switches back to
		4016	this or any other coroutine.
		4017
		4018	You can do similar tricks if you have, say, threads with an event queue -
		4019	instead of storing a coroutine, you store the queue object and instead of
		4020	switching to a coroutine, you push the watcher onto the queue and notify
		4021	any waiters.
		4022
		4023	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4024	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4025
		4026	// my_ev.h
		4027	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4028	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4029	#include "../libev/ev.h"
		4030
		4031	// my_ev.c
		4032	#define EV_H "my_ev.h"
		4033	#include "../libev/ev.c"
		4034
		4035	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4036	F<my_ev.c> into your project. When properly specifying include paths, you
		4037	can even use F<ev.h> as header file name directly.
3235		4038
3236		4039
3237	=head1 LIBEVENT EMULATION	4040	=head1 LIBEVENT EMULATION
3238		4041
3239	Libev offers a compatibility emulation layer for libevent. It cannot	4042	Libev offers a compatibility emulation layer for libevent. It cannot
3240	emulate the internals of libevent, so here are some usage hints:	4043	emulate the internals of libevent, so here are some usage hints:
3241		4044
3242	=over 4	4045	=over 4
		4046
		4047	=item * Only the libevent-1.4.1-beta API is being emulated.
		4048
		4049	This was the newest libevent version available when libev was implemented,
		4050	and is still mostly unchanged in 2010.
3243		4051
3244	=item * Use it by including <event.h>, as usual.	4052	=item * Use it by including <event.h>, as usual.
3245		4053
3246	=item * The following members are fully supported: ev_base, ev_callback,	4054	=item * The following members are fully supported: ev_base, ev_callback,
3247	ev_arg, ev_fd, ev_res, ev_events.	4055	ev_arg, ev_fd, ev_res, ev_events.
…		…
3253	=item * Priorities are not currently supported. Initialising priorities	4061	=item * Priorities are not currently supported. Initialising priorities
3254	will fail and all watchers will have the same priority, even though there	4062	will fail and all watchers will have the same priority, even though there
3255	is an ev_pri field.	4063	is an ev_pri field.
3256		4064
3257	=item * In libevent, the last base created gets the signals, in libev, the	4065	=item * In libevent, the last base created gets the signals, in libev, the
3258	first base created (== the default loop) gets the signals.	4066	base that registered the signal gets the signals.
3259		4067
3260	=item * Other members are not supported.	4068	=item * Other members are not supported.
3261		4069
3262	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4070	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3263	to use the libev header file and library.	4071	to use the libev header file and library.
3264		4072
3265	=back	4073	=back
3266		4074
3267	=head1 C++ SUPPORT	4075	=head1 C++ SUPPORT
		4076
		4077	=head2 C API
		4078
		4079	The normal C API should work fine when used from C++: both ev.h and the
		4080	libev sources can be compiled as C++. Therefore, code that uses the C API
		4081	will work fine.
		4082
		4083	Proper exception specifications might have to be added to callbacks passed
		4084	to libev: exceptions may be thrown only from watcher callbacks, all other
		4085	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4086	callbacks) must not throw exceptions, and might need a C<noexcept>
		4087	specification. If you have code that needs to be compiled as both C and
		4088	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4089
		4090	static void
		4091	fatal_error (const char *msg) EV_NOEXCEPT
		4092	{
		4093	perror (msg);
		4094	abort ();
		4095	}
		4096
		4097	...
		4098	ev_set_syserr_cb (fatal_error);
		4099
		4100	The only API functions that can currently throw exceptions are C<ev_run>,
		4101	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4102	because it runs cleanup watchers).
		4103
		4104	Throwing exceptions in watcher callbacks is only supported if libev itself
		4105	is compiled with a C++ compiler or your C and C++ environments allow
		4106	throwing exceptions through C libraries (most do).
		4107
		4108	=head2 C++ API
3268		4109
3269	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4110	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3270	you to use some convenience methods to start/stop watchers and also change	4111	you to use some convenience methods to start/stop watchers and also change
3271	the callback model to a model using method callbacks on objects.	4112	the callback model to a model using method callbacks on objects.
3272		4113
3273	To use it,	4114	To use it,
3274		4115
3275	#include <ev++.h>	4116	#include <ev++.h>
3276		4117
3277	This automatically includes F<ev.h> and puts all of its definitions (many	4118	This automatically includes F<ev.h> and puts all of its definitions (many
3278	of them macros) into the global namespace. All C++ specific things are	4119	of them macros) into the global namespace. All C++ specific things are
3279	put into the C<ev> namespace. It should support all the same embedding	4120	put into the C<ev> namespace. It should support all the same embedding
…		…
3282	Care has been taken to keep the overhead low. The only data member the C++	4123	Care has been taken to keep the overhead low. The only data member the C++
3283	classes add (compared to plain C-style watchers) is the event loop pointer	4124	classes add (compared to plain C-style watchers) is the event loop pointer
3284	that the watcher is associated with (or no additional members at all if	4125	that the watcher is associated with (or no additional members at all if
3285	you disable C<EV_MULTIPLICITY> when embedding libev).	4126	you disable C<EV_MULTIPLICITY> when embedding libev).
3286		4127
3287	Currently, functions, and static and non-static member functions can be	4128	Currently, functions, static and non-static member functions and classes
3288	used as callbacks. Other types should be easy to add as long as they only	4129	with C<operator ()> can be used as callbacks. Other types should be easy
3289	need one additional pointer for context. If you need support for other	4130	to add as long as they only need one additional pointer for context. If
3290	types of functors please contact the author (preferably after implementing	4131	you need support for other types of functors please contact the author
3291	it).	4132	(preferably after implementing it).
		4133
		4134	For all this to work, your C++ compiler either has to use the same calling
		4135	conventions as your C compiler (for static member functions), or you have
		4136	to embed libev and compile libev itself as C++.
3292		4137
3293	Here is a list of things available in the C<ev> namespace:	4138	Here is a list of things available in the C<ev> namespace:
3294		4139
3295	=over 4	4140	=over 4
3296		4141
…		…
3306	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4151	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3307		4152
3308	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4153	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3309	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4154	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3310	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4155	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3311	defines by many implementations.	4156	defined by many implementations.
3312		4157
3313	All of those classes have these methods:	4158	All of those classes have these methods:
3314		4159
3315	=over 4	4160	=over 4
3316		4161
…		…
3378	void operator() (ev::io &w, int revents)	4223	void operator() (ev::io &w, int revents)
3379	{	4224	{
3380	...	4225	...
3381	}	4226	}
3382	}	4227	}
3383		4228
3384	myfunctor f;	4229	myfunctor f;
3385		4230
3386	ev::io w;	4231	ev::io w;
3387	w.set (&f);	4232	w.set (&f);
3388		4233
…		…
3406	Associates a different C<struct ev_loop> with this watcher. You can only	4251	Associates a different C<struct ev_loop> with this watcher. You can only
3407	do this when the watcher is inactive (and not pending either).	4252	do this when the watcher is inactive (and not pending either).
3408		4253
3409	=item w->set ([arguments])	4254	=item w->set ([arguments])
3410		4255
3411	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4256	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3412	method or a suitable start method must be called at least once. Unlike the	4257	with the same arguments. Either this method or a suitable start method
3413	C counterpart, an active watcher gets automatically stopped and restarted	4258	must be called at least once. Unlike the C counterpart, an active watcher
3414	when reconfiguring it with this method.	4259	gets automatically stopped and restarted when reconfiguring it with this
		4260	method.
		4261
		4262	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4263	clashing with the C<set (loop)> method.
		4264
		4265	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4266	new event mask only, and internally calls C<ev_io_modfify>.
3415		4267
3416	=item w->start ()	4268	=item w->start ()
3417		4269
3418	Starts the watcher. Note that there is no C<loop> argument, as the	4270	Starts the watcher. Note that there is no C<loop> argument, as the
3419	constructor already stores the event loop.	4271	constructor already stores the event loop.
…		…
3449	watchers in the constructor.	4301	watchers in the constructor.
3450		4302
3451	class myclass	4303	class myclass
3452	{	4304	{
3453	ev::io io ; void io_cb (ev::io &w, int revents);	4305	ev::io io ; void io_cb (ev::io &w, int revents);
3454	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4306	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3455	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4307	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3456		4308
3457	myclass (int fd)	4309	myclass (int fd)
3458	{	4310	{
3459	io .set <myclass, &myclass::io_cb > (this);	4311	io .set <myclass, &myclass::io_cb > (this);
…		…
3510	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4362	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3511		4363
3512	=item D	4364	=item D
3513		4365
3514	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4366	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3515	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4367	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3516		4368
3517	=item Ocaml	4369	=item Ocaml
3518		4370
3519	Erkki Seppala has written Ocaml bindings for libev, to be found at	4371	Erkki Seppala has written Ocaml bindings for libev, to be found at
3520	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4372	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3523		4375
3524	Brian Maher has written a partial interface to libev for lua (at the	4376	Brian Maher has written a partial interface to libev for lua (at the
3525	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4377	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3526	L<http://github.com/brimworks/lua-ev>.	4378	L<http://github.com/brimworks/lua-ev>.
3527		4379
		4380	=item Javascript
		4381
		4382	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4383
		4384	=item Others
		4385
		4386	There are others, and I stopped counting.
		4387
3528	=back	4388	=back
3529		4389
3530		4390
3531	=head1 MACRO MAGIC	4391	=head1 MACRO MAGIC
3532		4392
…		…
3568	suitable for use with C<EV_A>.	4428	suitable for use with C<EV_A>.
3569		4429
3570	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4430	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3571		4431
3572	Similar to the other two macros, this gives you the value of the default	4432	Similar to the other two macros, this gives you the value of the default
3573	loop, if multiple loops are supported ("ev loop default").	4433	loop, if multiple loops are supported ("ev loop default"). The default loop
		4434	will be initialised if it isn't already initialised.
		4435
		4436	For non-multiplicity builds, these macros do nothing, so you always have
		4437	to initialise the loop somewhere.
3574		4438
3575	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4439	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3576		4440
3577	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4441	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3578	default loop has been initialised (C<UC> == unchecked). Their behaviour	4442	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3645	ev_vars.h	4509	ev_vars.h
3646	ev_wrap.h	4510	ev_wrap.h
3647		4511
3648	ev_win32.c required on win32 platforms only	4512	ev_win32.c required on win32 platforms only
3649		4513
3650	ev_select.c only when select backend is enabled (which is enabled by default)	4514	ev_select.c only when select backend is enabled
3651	ev_poll.c only when poll backend is enabled (disabled by default)	4515	ev_poll.c only when poll backend is enabled
3652	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4516	ev_epoll.c only when the epoll backend is enabled
		4517	ev_linuxaio.c only when the linux aio backend is enabled
		4518	ev_iouring.c only when the linux io_uring backend is enabled
3653	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4519	ev_kqueue.c only when the kqueue backend is enabled
3654	ev_port.c only when the solaris port backend is enabled (disabled by default)	4520	ev_port.c only when the solaris port backend is enabled
3655		4521
3656	F<ev.c> includes the backend files directly when enabled, so you only need	4522	F<ev.c> includes the backend files directly when enabled, so you only need
3657	to compile this single file.	4523	to compile this single file.
3658		4524
3659	=head3 LIBEVENT COMPATIBILITY API	4525	=head3 LIBEVENT COMPATIBILITY API
…		…
3723	supported). It will also not define any of the structs usually found in	4589	supported). It will also not define any of the structs usually found in
3724	F<event.h> that are not directly supported by the libev core alone.	4590	F<event.h> that are not directly supported by the libev core alone.
3725		4591
3726	In standalone mode, libev will still try to automatically deduce the	4592	In standalone mode, libev will still try to automatically deduce the
3727	configuration, but has to be more conservative.	4593	configuration, but has to be more conservative.
		4594
		4595	=item EV_USE_FLOOR
		4596
		4597	If defined to be C<1>, libev will use the C<floor ()> function for its
		4598	periodic reschedule calculations, otherwise libev will fall back on a
		4599	portable (slower) implementation. If you enable this, you usually have to
		4600	link against libm or something equivalent. Enabling this when the C<floor>
		4601	function is not available will fail, so the safe default is to not enable
		4602	this.
3728		4603
3729	=item EV_USE_MONOTONIC	4604	=item EV_USE_MONOTONIC
3730		4605
3731	If defined to be C<1>, libev will try to detect the availability of the	4606	If defined to be C<1>, libev will try to detect the availability of the
3732	monotonic clock option at both compile time and runtime. Otherwise no	4607	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3769	available and will probe for kernel support at runtime. This will improve	4644	available and will probe for kernel support at runtime. This will improve
3770	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4645	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3771	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4646	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3772	2.7 or newer, otherwise disabled.	4647	2.7 or newer, otherwise disabled.
3773		4648
		4649	=item EV_USE_SIGNALFD
		4650
		4651	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4652	available and will probe for kernel support at runtime. This enables
		4653	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4654	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4655	2.7 or newer, otherwise disabled.
		4656
		4657	=item EV_USE_TIMERFD
		4658
		4659	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4660	available and will probe for kernel support at runtime. This allows
		4661	libev to detect time jumps accurately. If undefined, it will be enabled
		4662	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4663	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4664
		4665	=item EV_USE_EVENTFD
		4666
		4667	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4668	available and will probe for kernel support at runtime. This will improve
		4669	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4670	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4671	2.7 or newer, otherwise disabled.
		4672
3774	=item EV_USE_SELECT	4673	=item EV_USE_SELECT
3775		4674
3776	If undefined or defined to be C<1>, libev will compile in support for the	4675	If undefined or defined to be C<1>, libev will compile in support for the
3777	C<select>(2) backend. No attempt at auto-detection will be done: if no	4676	C<select>(2) backend. No attempt at auto-detection will be done: if no
3778	other method takes over, select will be it. Otherwise the select backend	4677	other method takes over, select will be it. Otherwise the select backend
…		…
3818	If programs implement their own fd to handle mapping on win32, then this	4717	If programs implement their own fd to handle mapping on win32, then this
3819	macro can be used to override the C<close> function, useful to unregister	4718	macro can be used to override the C<close> function, useful to unregister
3820	file descriptors again. Note that the replacement function has to close	4719	file descriptors again. Note that the replacement function has to close
3821	the underlying OS handle.	4720	the underlying OS handle.
3822		4721
		4722	=item EV_USE_WSASOCKET
		4723
		4724	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4725	communication socket, which works better in some environments. Otherwise,
		4726	the normal C<socket> function will be used, which works better in other
		4727	environments.
		4728
3823	=item EV_USE_POLL	4729	=item EV_USE_POLL
3824		4730
3825	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4731	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3826	backend. Otherwise it will be enabled on non-win32 platforms. It	4732	backend. Otherwise it will be enabled on non-win32 platforms. It
3827	takes precedence over select.	4733	takes precedence over select.
…		…
3831	If defined to be C<1>, libev will compile in support for the Linux	4737	If defined to be C<1>, libev will compile in support for the Linux
3832	C<epoll>(7) backend. Its availability will be detected at runtime,	4738	C<epoll>(7) backend. Its availability will be detected at runtime,
3833	otherwise another method will be used as fallback. This is the preferred	4739	otherwise another method will be used as fallback. This is the preferred
3834	backend for GNU/Linux systems. If undefined, it will be enabled if the	4740	backend for GNU/Linux systems. If undefined, it will be enabled if the
3835	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4741	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4742
		4743	=item EV_USE_LINUXAIO
		4744
		4745	If defined to be C<1>, libev will compile in support for the Linux aio
		4746	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4747	enabled on linux, otherwise disabled.
		4748
		4749	=item EV_USE_IOURING
		4750
		4751	If defined to be C<1>, libev will compile in support for the Linux
		4752	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4753	current limitations it has to be requested explicitly. If undefined, it
		4754	will be enabled on linux, otherwise disabled.
3836		4755
3837	=item EV_USE_KQUEUE	4756	=item EV_USE_KQUEUE
3838		4757
3839	If defined to be C<1>, libev will compile in support for the BSD style	4758	If defined to be C<1>, libev will compile in support for the BSD style
3840	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4759	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3862	If defined to be C<1>, libev will compile in support for the Linux inotify	4781	If defined to be C<1>, libev will compile in support for the Linux inotify
3863	interface to speed up C<ev_stat> watchers. Its actual availability will	4782	interface to speed up C<ev_stat> watchers. Its actual availability will
3864	be detected at runtime. If undefined, it will be enabled if the headers	4783	be detected at runtime. If undefined, it will be enabled if the headers
3865	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4784	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3866		4785
		4786	=item EV_NO_SMP
		4787
		4788	If defined to be C<1>, libev will assume that memory is always coherent
		4789	between threads, that is, threads can be used, but threads never run on
		4790	different cpus (or different cpu cores). This reduces dependencies
		4791	and makes libev faster.
		4792
		4793	=item EV_NO_THREADS
		4794
		4795	If defined to be C<1>, libev will assume that it will never be called from
		4796	different threads (that includes signal handlers), which is a stronger
		4797	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4798	libev faster.
		4799
3867	=item EV_ATOMIC_T	4800	=item EV_ATOMIC_T
3868		4801
3869	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4802	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3870	access is atomic with respect to other threads or signal contexts. No such	4803	access is atomic with respect to other threads or signal contexts. No
3871	type is easily found in the C language, so you can provide your own type	4804	such type is easily found in the C language, so you can provide your own
3872	that you know is safe for your purposes. It is used both for signal handler "locking"	4805	type that you know is safe for your purposes. It is used both for signal
3873	as well as for signal and thread safety in C<ev_async> watchers.	4806	handler "locking" as well as for signal and thread safety in C<ev_async>
		4807	watchers.
3874		4808
3875	In the absence of this define, libev will use C<sig_atomic_t volatile>	4809	In the absence of this define, libev will use C<sig_atomic_t volatile>
3876	(from F<signal.h>), which is usually good enough on most platforms.	4810	(from F<signal.h>), which is usually good enough on most platforms.
3877		4811
3878	=item EV_H (h)	4812	=item EV_H (h)
…		…
3905	will have the C<struct ev_loop *> as first argument, and you can create	4839	will have the C<struct ev_loop *> as first argument, and you can create
3906	additional independent event loops. Otherwise there will be no support	4840	additional independent event loops. Otherwise there will be no support
3907	for multiple event loops and there is no first event loop pointer	4841	for multiple event loops and there is no first event loop pointer
3908	argument. Instead, all functions act on the single default loop.	4842	argument. Instead, all functions act on the single default loop.
3909		4843
		4844	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4845	default loop when multiplicity is switched off - you always have to
		4846	initialise the loop manually in this case.
		4847
3910	=item EV_MINPRI	4848	=item EV_MINPRI
3911		4849
3912	=item EV_MAXPRI	4850	=item EV_MAXPRI
3913		4851
3914	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4852	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3950	#define EV_USE_POLL 1	4888	#define EV_USE_POLL 1
3951	#define EV_CHILD_ENABLE 1	4889	#define EV_CHILD_ENABLE 1
3952	#define EV_ASYNC_ENABLE 1	4890	#define EV_ASYNC_ENABLE 1
3953		4891
3954	The actual value is a bitset, it can be a combination of the following	4892	The actual value is a bitset, it can be a combination of the following
3955	values:	4893	values (by default, all of these are enabled):
3956		4894
3957	=over 4	4895	=over 4
3958		4896
3959	=item C<1> - faster/larger code	4897	=item C<1> - faster/larger code
3960		4898
…		…
3964	code size by roughly 30% on amd64).	4902	code size by roughly 30% on amd64).
3965		4903
3966	When optimising for size, use of compiler flags such as C<-Os> with	4904	When optimising for size, use of compiler flags such as C<-Os> with
3967	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4905	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3968	assertions.	4906	assertions.
		4907
		4908	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4909	(e.g. gcc with C<-Os>).
3969		4910
3970	=item C<2> - faster/larger data structures	4911	=item C<2> - faster/larger data structures
3971		4912
3972	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4913	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3973	hash table sizes and so on. This will usually further increase code size	4914	hash table sizes and so on. This will usually further increase code size
3974	and can additionally have an effect on the size of data structures at	4915	and can additionally have an effect on the size of data structures at
3975	runtime.	4916	runtime.
3976		4917
		4918	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4919	(e.g. gcc with C<-Os>).
		4920
3977	=item C<4> - full API configuration	4921	=item C<4> - full API configuration
3978		4922
3979	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4923	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3980	enables multiplicity (C<EV_MULTIPLICITY>=1).	4924	enables multiplicity (C<EV_MULTIPLICITY>=1).
3981		4925
…		…
4011		4955
4012	With an intelligent-enough linker (gcc+binutils are intelligent enough	4956	With an intelligent-enough linker (gcc+binutils are intelligent enough
4013	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4957	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4014	your program might be left out as well - a binary starting a timer and an	4958	your program might be left out as well - a binary starting a timer and an
4015	I/O watcher then might come out at only 5Kb.	4959	I/O watcher then might come out at only 5Kb.
		4960
		4961	=item EV_API_STATIC
		4962
		4963	If this symbol is defined (by default it is not), then all identifiers
		4964	will have static linkage. This means that libev will not export any
		4965	identifiers, and you cannot link against libev anymore. This can be useful
		4966	when you embed libev, only want to use libev functions in a single file,
		4967	and do not want its identifiers to be visible.
		4968
		4969	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4970	wants to use libev.
		4971
		4972	This option only works when libev is compiled with a C compiler, as C++
		4973	doesn't support the required declaration syntax.
4016		4974
4017	=item EV_AVOID_STDIO	4975	=item EV_AVOID_STDIO
4018		4976
4019	If this is set to C<1> at compiletime, then libev will avoid using stdio	4977	If this is set to C<1> at compiletime, then libev will avoid using stdio
4020	functions (printf, scanf, perror etc.). This will increase the code size	4978	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4078	in. If set to C<1>, then verification code will be compiled in, but not	5036	in. If set to C<1>, then verification code will be compiled in, but not
4079	called. If set to C<2>, then the internal verification code will be	5037	called. If set to C<2>, then the internal verification code will be
4080	called once per loop, which can slow down libev. If set to C<3>, then the	5038	called once per loop, which can slow down libev. If set to C<3>, then the
4081	verification code will be called very frequently, which will slow down	5039	verification code will be called very frequently, which will slow down
4082	libev considerably.	5040	libev considerably.
		5041
		5042	Verification errors are reported via C's C<assert> mechanism, so if you
		5043	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
4083		5044
4084	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	5045	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4085	will be C<0>.	5046	will be C<0>.
4086		5047
4087	=item EV_COMMON	5048	=item EV_COMMON
…		…
4164	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5125	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4165		5126
4166	#include "ev_cpp.h"	5127	#include "ev_cpp.h"
4167	#include "ev.c"	5128	#include "ev.c"
4168		5129
4169	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5130	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4170		5131
4171	=head2 THREADS AND COROUTINES	5132	=head2 THREADS AND COROUTINES
4172		5133
4173	=head3 THREADS	5134	=head3 THREADS
4174		5135
…		…
4225	default loop and triggering an C<ev_async> watcher from the default loop	5186	default loop and triggering an C<ev_async> watcher from the default loop
4226	watcher callback into the event loop interested in the signal.	5187	watcher callback into the event loop interested in the signal.
4227		5188
4228	=back	5189	=back
4229		5190
4230	=head4 THREAD LOCKING EXAMPLE	5191	See also L</THREAD LOCKING EXAMPLE>.
4231
4232	Here is a fictitious example of how to run an event loop in a different
4233	thread than where callbacks are being invoked and watchers are
4234	created/added/removed.
4235
4236	For a real-world example, see the C<EV::Loop::Async> perl module,
4237	which uses exactly this technique (which is suited for many high-level
4238	languages).
4239
4240	The example uses a pthread mutex to protect the loop data, a condition
4241	variable to wait for callback invocations, an async watcher to notify the
4242	event loop thread and an unspecified mechanism to wake up the main thread.
4243
4244	First, you need to associate some data with the event loop:
4245
4246	typedef struct {
4247	mutex_t lock; /* global loop lock */
4248	ev_async async_w;
4249	thread_t tid;
4250	cond_t invoke_cv;
4251	} userdata;
4252
4253	void prepare_loop (EV_P)
4254	{
4255	// for simplicity, we use a static userdata struct.
4256	static userdata u;
4257
4258	ev_async_init (&u->async_w, async_cb);
4259	ev_async_start (EV_A_ &u->async_w);
4260
4261	pthread_mutex_init (&u->lock, 0);
4262	pthread_cond_init (&u->invoke_cv, 0);
4263
4264	// now associate this with the loop
4265	ev_set_userdata (EV_A_ u);
4266	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4267	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4268
4269	// then create the thread running ev_loop
4270	pthread_create (&u->tid, 0, l_run, EV_A);
4271	}
4272
4273	The callback for the C<ev_async> watcher does nothing: the watcher is used
4274	solely to wake up the event loop so it takes notice of any new watchers
4275	that might have been added:
4276
4277	static void
4278	async_cb (EV_P_ ev_async *w, int revents)
4279	{
4280	// just used for the side effects
4281	}
4282
4283	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4284	protecting the loop data, respectively.
4285
4286	static void
4287	l_release (EV_P)
4288	{
4289	userdata *u = ev_userdata (EV_A);
4290	pthread_mutex_unlock (&u->lock);
4291	}
4292
4293	static void
4294	l_acquire (EV_P)
4295	{
4296	userdata *u = ev_userdata (EV_A);
4297	pthread_mutex_lock (&u->lock);
4298	}
4299
4300	The event loop thread first acquires the mutex, and then jumps straight
4301	into C<ev_run>:
4302
4303	void *
4304	l_run (void *thr_arg)
4305	{
4306	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4307
4308	l_acquire (EV_A);
4309	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4310	ev_run (EV_A_ 0);
4311	l_release (EV_A);
4312
4313	return 0;
4314	}
4315
4316	Instead of invoking all pending watchers, the C<l_invoke> callback will
4317	signal the main thread via some unspecified mechanism (signals? pipe
4318	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4319	have been called (in a while loop because a) spurious wakeups are possible
4320	and b) skipping inter-thread-communication when there are no pending
4321	watchers is very beneficial):
4322
4323	static void
4324	l_invoke (EV_P)
4325	{
4326	userdata *u = ev_userdata (EV_A);
4327
4328	while (ev_pending_count (EV_A))
4329	{
4330	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4331	pthread_cond_wait (&u->invoke_cv, &u->lock);
4332	}
4333	}
4334
4335	Now, whenever the main thread gets told to invoke pending watchers, it
4336	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4337	thread to continue:
4338
4339	static void
4340	real_invoke_pending (EV_P)
4341	{
4342	userdata *u = ev_userdata (EV_A);
4343
4344	pthread_mutex_lock (&u->lock);
4345	ev_invoke_pending (EV_A);
4346	pthread_cond_signal (&u->invoke_cv);
4347	pthread_mutex_unlock (&u->lock);
4348	}
4349
4350	Whenever you want to start/stop a watcher or do other modifications to an
4351	event loop, you will now have to lock:
4352
4353	ev_timer timeout_watcher;
4354	userdata *u = ev_userdata (EV_A);
4355
4356	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4357
4358	pthread_mutex_lock (&u->lock);
4359	ev_timer_start (EV_A_ &timeout_watcher);
4360	ev_async_send (EV_A_ &u->async_w);
4361	pthread_mutex_unlock (&u->lock);
4362
4363	Note that sending the C<ev_async> watcher is required because otherwise
4364	an event loop currently blocking in the kernel will have no knowledge
4365	about the newly added timer. By waking up the loop it will pick up any new
4366	watchers in the next event loop iteration.
4367		5192
4368	=head3 COROUTINES	5193	=head3 COROUTINES
4369		5194
4370	Libev is very accommodating to coroutines ("cooperative threads"):	5195	Libev is very accommodating to coroutines ("cooperative threads"):
4371	libev fully supports nesting calls to its functions from different	5196	libev fully supports nesting calls to its functions from different
…		…
4467	=head3 C<kqueue> is buggy	5292	=head3 C<kqueue> is buggy
4468		5293
4469	The kqueue syscall is broken in all known versions - most versions support	5294	The kqueue syscall is broken in all known versions - most versions support
4470	only sockets, many support pipes.	5295	only sockets, many support pipes.
4471		5296
4472	Libev tries to work around this by not using C<kqueue> by default on	5297	Libev tries to work around this by not using C<kqueue> by default on this
4473	this rotten platform, but of course you can still ask for it when creating	5298	rotten platform, but of course you can still ask for it when creating a
4474	a loop.	5299	loop - embedding a socket-only kqueue loop into a select-based one is
		5300	probably going to work well.
4475		5301
4476	=head3 C<poll> is buggy	5302	=head3 C<poll> is buggy
4477		5303
4478	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5304	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4479	implementation by something calling C<kqueue> internally around the 10.5.6	5305	implementation by something calling C<kqueue> internally around the 10.5.6
…		…
4498		5324
4499	=head3 C<errno> reentrancy	5325	=head3 C<errno> reentrancy
4500		5326
4501	The default compile environment on Solaris is unfortunately so	5327	The default compile environment on Solaris is unfortunately so
4502	thread-unsafe that you can't even use components/libraries compiled	5328	thread-unsafe that you can't even use components/libraries compiled
4503	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5329	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4504	isn't defined by default.	5330	defined by default. A valid, if stupid, implementation choice.
4505		5331
4506	If you want to use libev in threaded environments you have to make sure	5332	If you want to use libev in threaded environments you have to make sure
4507	it's compiled with C<_REENTRANT> defined.	5333	it's compiled with C<_REENTRANT> defined.
4508		5334
4509	=head3 Event port backend	5335	=head3 Event port backend
4510		5336
4511	The scalable event interface for Solaris is called "event ports". Unfortunately,	5337	The scalable event interface for Solaris is called "event
4512	this mechanism is very buggy. If you run into high CPU usage, your program	5338	ports". Unfortunately, this mechanism is very buggy in all major
		5339	releases. If you run into high CPU usage, your program freezes or you get
4513	freezes or you get a large number of spurious wakeups, make sure you have	5340	a large number of spurious wakeups, make sure you have all the relevant
4514	all the relevant and latest kernel patches applied. No, I don't know which	5341	and latest kernel patches applied. No, I don't know which ones, but there
4515	ones, but there are multiple ones.	5342	are multiple ones to apply, and afterwards, event ports actually work
		5343	great.
4516		5344
4517	If you can't get it to work, you can try running the program by setting	5345	If you can't get it to work, you can try running the program by setting
4518	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and	5346	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4519	C<select> backends.	5347	C<select> backends.
4520		5348
4521	=head2 AIX POLL BUG	5349	=head2 AIX POLL BUG
4522		5350
4523	AIX unfortunately has a broken C<poll.h> header. Libev works around	5351	AIX unfortunately has a broken C<poll.h> header. Libev works around
4524	this by trying to avoid the poll backend altogether (i.e. it's not even	5352	this by trying to avoid the poll backend altogether (i.e. it's not even
4525	compiled in), which normally isn't a big problem as C<select> works fine	5353	compiled in), which normally isn't a big problem as C<select> works fine
4526	with large bitsets, and AIX is dead anyway.	5354	with large bitsets on AIX, and AIX is dead anyway.
4527		5355
4528	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5356	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4529		5357
4530	=head3 General issues	5358	=head3 General issues
4531		5359
…		…
4533	requires, and its I/O model is fundamentally incompatible with the POSIX	5361	requires, and its I/O model is fundamentally incompatible with the POSIX
4534	model. Libev still offers limited functionality on this platform in	5362	model. Libev still offers limited functionality on this platform in
4535	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5363	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4536	descriptors. This only applies when using Win32 natively, not when using	5364	descriptors. This only applies when using Win32 natively, not when using
4537	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5365	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4538	as every compielr comes with a slightly differently broken/incompatible	5366	as every compiler comes with a slightly differently broken/incompatible
4539	environment.	5367	environment.
4540		5368
4541	Lifting these limitations would basically require the full	5369	Lifting these limitations would basically require the full
4542	re-implementation of the I/O system. If you are into this kind of thing,	5370	re-implementation of the I/O system. If you are into this kind of thing,
4543	then note that glib does exactly that for you in a very portable way (note	5371	then note that glib does exactly that for you in a very portable way (note
…		…
4637	structure (guaranteed by POSIX but not by ISO C for example), but it also	5465	structure (guaranteed by POSIX but not by ISO C for example), but it also
4638	assumes that the same (machine) code can be used to call any watcher	5466	assumes that the same (machine) code can be used to call any watcher
4639	callback: The watcher callbacks have different type signatures, but libev	5467	callback: The watcher callbacks have different type signatures, but libev
4640	calls them using an C<ev_watcher *> internally.	5468	calls them using an C<ev_watcher *> internally.
4641		5469
		5470	=item null pointers and integer zero are represented by 0 bytes
		5471
		5472	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5473	relies on this setting pointers and integers to null.
		5474
		5475	=item pointer accesses must be thread-atomic
		5476
		5477	Accessing a pointer value must be atomic, it must both be readable and
		5478	writable in one piece - this is the case on all current architectures.
		5479
4642	=item C<sig_atomic_t volatile> must be thread-atomic as well	5480	=item C<sig_atomic_t volatile> must be thread-atomic as well
4643		5481
4644	The type C<sig_atomic_t volatile> (or whatever is defined as	5482	The type C<sig_atomic_t volatile> (or whatever is defined as
4645	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5483	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4646	threads. This is not part of the specification for C<sig_atomic_t>, but is	5484	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4654	thread" or will block signals process-wide, both behaviours would	5492	thread" or will block signals process-wide, both behaviours would
4655	be compatible with libev. Interaction between C<sigprocmask> and	5493	be compatible with libev. Interaction between C<sigprocmask> and
4656	C<pthread_sigmask> could complicate things, however.	5494	C<pthread_sigmask> could complicate things, however.
4657		5495
4658	The most portable way to handle signals is to block signals in all threads	5496	The most portable way to handle signals is to block signals in all threads
4659	except the initial one, and run the default loop in the initial thread as	5497	except the initial one, and run the signal handling loop in the initial
4660	well.	5498	thread as well.
4661		5499
4662	=item C<long> must be large enough for common memory allocation sizes	5500	=item C<long> must be large enough for common memory allocation sizes
4663		5501
4664	To improve portability and simplify its API, libev uses C<long> internally	5502	To improve portability and simplify its API, libev uses C<long> internally
4665	instead of C<size_t> when allocating its data structures. On non-POSIX	5503	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4671		5509
4672	The type C<double> is used to represent timestamps. It is required to	5510	The type C<double> is used to represent timestamps. It is required to
4673	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5511	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4674	good enough for at least into the year 4000 with millisecond accuracy	5512	good enough for at least into the year 4000 with millisecond accuracy
4675	(the design goal for libev). This requirement is overfulfilled by	5513	(the design goal for libev). This requirement is overfulfilled by
4676	implementations using IEEE 754, which is basically all existing ones. With	5514	implementations using IEEE 754, which is basically all existing ones.
		5515
4677	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5516	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5517	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5518	is either obsolete or somebody patched it to use C<long double> or
		5519	something like that, just kidding).
4678		5520
4679	=back	5521	=back
4680		5522
4681	If you know of other additional requirements drop me a note.	5523	If you know of other additional requirements drop me a note.
4682		5524
…		…
4744	=item Processing ev_async_send: O(number_of_async_watchers)	5586	=item Processing ev_async_send: O(number_of_async_watchers)
4745		5587
4746	=item Processing signals: O(max_signal_number)	5588	=item Processing signals: O(max_signal_number)
4747		5589
4748	Sending involves a system call I<iff> there were no other C<ev_async_send>	5590	Sending involves a system call I<iff> there were no other C<ev_async_send>
4749	calls in the current loop iteration. Checking for async and signal events	5591	calls in the current loop iteration and the loop is currently
		5592	blocked. Checking for async and signal events involves iterating over all
4750	involves iterating over all running async watchers or all signal numbers.	5593	running async watchers or all signal numbers.
4751		5594
4752	=back	5595	=back
4753		5596
4754		5597
4755	=head1 PORTING FROM LIBEV 3.X TO 4.X	5598	=head1 PORTING FROM LIBEV 3.X TO 4.X
4756		5599
4757	The major version 4 introduced some minor incompatible changes to the API.	5600	The major version 4 introduced some incompatible changes to the API.
4758		5601
4759	At the moment, the C<ev.h> header file tries to implement superficial	5602	At the moment, the C<ev.h> header file provides compatibility definitions
4760	compatibility, so most programs should still compile. Those might be	5603	for all changes, so most programs should still compile. The compatibility
4761	removed in later versions of libev, so better update early than late.	5604	layer might be removed in later versions of libev, so better update to the
		5605	new API early than late.
4762		5606
4763	=over 4	5607	=over 4
		5608
		5609	=item C<EV_COMPAT3> backwards compatibility mechanism
		5610
		5611	The backward compatibility mechanism can be controlled by
		5612	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5613	section.
		5614
		5615	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5616
		5617	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5618
		5619	ev_loop_destroy (EV_DEFAULT_UC);
		5620	ev_loop_fork (EV_DEFAULT);
4764		5621
4765	=item function/symbol renames	5622	=item function/symbol renames
4766		5623
4767	A number of functions and symbols have been renamed:	5624	A number of functions and symbols have been renamed:
4768		5625
…		…
4787	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5644	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4788	as all other watcher types. Note that C<ev_loop_fork> is still called	5645	as all other watcher types. Note that C<ev_loop_fork> is still called
4789	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5646	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4790	typedef.	5647	typedef.
4791		5648
4792	=item C<EV_COMPAT3> backwards compatibility mechanism
4793
4794	The backward compatibility mechanism can be controlled by
4795	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4796	section.
4797
4798	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5649	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4799		5650
4800	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5651	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4801	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5652	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4802	and work, but the library code will of course be larger.	5653	and work, but the library code will of course be larger.
…		…
4808		5659
4809	=over 4	5660	=over 4
4810		5661
4811	=item active	5662	=item active
4812		5663
4813	A watcher is active as long as it has been started (has been attached to	5664	A watcher is active as long as it has been started and not yet stopped.
4814	an event loop) but not yet stopped (disassociated from the event loop).	5665	See L</WATCHER STATES> for details.
4815		5666
4816	=item application	5667	=item application
4817		5668
4818	In this document, an application is whatever is using libev.	5669	In this document, an application is whatever is using libev.
		5670
		5671	=item backend
		5672
		5673	The part of the code dealing with the operating system interfaces.
4819		5674
4820	=item callback	5675	=item callback
4821		5676
4822	The address of a function that is called when some event has been	5677	The address of a function that is called when some event has been
4823	detected. Callbacks are being passed the event loop, the watcher that	5678	detected. Callbacks are being passed the event loop, the watcher that
4824	received the event, and the actual event bitset.	5679	received the event, and the actual event bitset.
4825		5680
4826	=item callback invocation	5681	=item callback/watcher invocation
4827		5682
4828	The act of calling the callback associated with a watcher.	5683	The act of calling the callback associated with a watcher.
4829		5684
4830	=item event	5685	=item event
4831		5686
…		…
4850	The model used to describe how an event loop handles and processes	5705	The model used to describe how an event loop handles and processes
4851	watchers and events.	5706	watchers and events.
4852		5707
4853	=item pending	5708	=item pending
4854		5709
4855	A watcher is pending as soon as the corresponding event has been detected,	5710	A watcher is pending as soon as the corresponding event has been
4856	and stops being pending as soon as the watcher will be invoked or its	5711	detected. See L</WATCHER STATES> for details.
4857	pending status is explicitly cleared by the application.
4858
4859	A watcher can be pending, but not active. Stopping a watcher also clears
4860	its pending status.
4861		5712
4862	=item real time	5713	=item real time
4863		5714
4864	The physical time that is observed. It is apparently strictly monotonic :)	5715	The physical time that is observed. It is apparently strictly monotonic :)
4865		5716
4866	=item wall-clock time	5717	=item wall-clock time
4867		5718
4868	The time and date as shown on clocks. Unlike real time, it can actually	5719	The time and date as shown on clocks. Unlike real time, it can actually
4869	be wrong and jump forwards and backwards, e.g. when the you adjust your	5720	be wrong and jump forwards and backwards, e.g. when you adjust your
4870	clock.	5721	clock.
4871		5722
4872	=item watcher	5723	=item watcher
4873		5724
4874	A data structure that describes interest in certain events. Watchers need	5725	A data structure that describes interest in certain events. Watchers need
4875	to be started (attached to an event loop) before they can receive events.	5726	to be started (attached to an event loop) before they can receive events.
4876		5727
4877	=item watcher invocation
4878
4879	The act of calling the callback associated with a watcher.
4880
4881	=back	5728	=back
4882		5729
4883	=head1 AUTHOR	5730	=head1 AUTHOR
4884		5731
4885	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5732	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5733	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4886		5734

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