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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
…		…
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. Also interetsing is the combination of	184	you actually want to know. Also interesting is the combination of
171	C<ev_update_now> and C<ev_now>.	185	C<ev_now_update> and C<ev_now>.
172		186
173	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
174		188
175	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
176	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
177	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 >>).
178		198
179	=item int ev_version_major ()	199	=item int ev_version_major ()
180		200
181	=item int ev_version_minor ()	201	=item int ev_version_minor ()
182		202
…		…
233	the current system, you would need to look at C<ev_embeddable_backends ()	253	the current system, you would need to look at C<ev_embeddable_backends ()
234	& ev_supported_backends ()>, likewise for recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
235		255
236	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
237		257
238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
239		259
240	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
241	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
242	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
243	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
…		…
249		269
250	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
251	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,
252	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.
253		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
254	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
255	retries (example requires a standards-compliant C<realloc>).	289	retries.
256		290
257	static void *	291	static void *
258	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
259	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
260	for (;;)	300	for (;;)
261	{	301	{
262	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
263		303
264	if (newptr)	304	if (newptr)
…		…
269	}	309	}
270		310
271	...	311	...
272	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
273		313
274	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
275		315
276	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
277	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
278	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
279	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
…		…
291	}	331	}
292		332
293	...	333	...
294	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
295		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
296	=back	349	=back
297		350
298	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
299		352
300	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
301	I<not> optional in this case unless libev 3 compatibility is disabled, as	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
302	libev 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).
303		356
304	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
305	supports signals and child events, and dynamically created event loops	358	supports child process events, and dynamically created event loops which
306	which do not.	359	do not.
307		360
308	=over 4	361	=over 4
309		362
310	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
311		364
312	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
313	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
314	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
315	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".
316		375
317	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
318	function.	377	function (or via the C<EV_DEFAULT> macro).
319		378
320	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
321	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
322	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).
323		383
324	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,
325	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
326	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
327	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
328	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
329	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.
330		408
331	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
332	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>).
333		411
334	The following flags are supported:	412	The following flags are supported:
…		…
344		422
345	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
346	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
347	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
348	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
349	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
350	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).
351		431
352	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
353		433
354	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
355	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.
356		436
357	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,
358	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
359	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
360	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
361	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
362	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).
363		444
364	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
365	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
366	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
367		448
368	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>
369	environment variable.	450	environment variable.
370		451
371	=item C<EVFLAG_NOINOTIFY>	452	=item C<EVFLAG_NOINOTIFY>
372		453
373	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
374	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
375	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
376	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.
377		458
378	=item C<EVFLAG_SIGNALFD>	459	=item C<EVFLAG_SIGNALFD>
379		460
380	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
381	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
382	delivers signals synchronously, which makes it both faster and might make	463	delivers signals synchronously, which makes it both faster and might make
383	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
384	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
385	threads that are not interested in handling them.	466	threads that are not interested in handling them.
386		467
387	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
388	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
389	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.
390		495
391	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
392		497
393	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
394	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,
…		…
419	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
420	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
421		526
422	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
423		528
424	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
425	kernels).	530	kernels).
426		531
427	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
428	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
429	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
430	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
431		536
432	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
433	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
434	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
435	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
436	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
437	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
438	take considerable time (one syscall per file descriptor) and is of course	545	set, which can take considerable time (one syscall per file descriptor)
439	hard to detect.	546	and is of course hard to detect.
440		547
441	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
442	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
443	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
444	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
445	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
446	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
447	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
448	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
449	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...
450		564
451	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
452	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
453	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
454	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
…		…
466	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
467	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
468	the usage. So sad.	582	the usage. So sad.
469		583
470	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
471	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
472		586
473	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
474	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
475		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
476	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
477		635
478	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
479	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
480	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
481	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
482	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)
483	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
484	"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
485	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
486	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
487		645
488	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
489	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
490	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
491		649
492	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
493	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
494	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
495	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
496	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
497	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
498	cases	656	drops fds silently in similarly hard-to-detect cases.
499		657
500	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
501		659
502	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
503	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
…		…
520	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
521		679
522	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,
523	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)).
524		682
525	Please note that Solaris event ports can deliver a lot of spurious
526	notifications, so you need to use non-blocking I/O or other means to avoid
527	blocking when no data (or space) is available.
528
529	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
530	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
531	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
532	might perform better.	686	might perform better.
533		687
534	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
535	notifications, this backend actually performed fully to specification
536	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
537	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.
538		702
539	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
540	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
541		705
542	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
543		707
544	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
545	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
546	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
547		711
548	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).
549		721
550	=back	722	=back
551		723
552	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,
553	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
554	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
555	()> will be tried.	727	()> will be tried.
556		728
557	Example: This is the most typical usage.
558
559	if (!ev_default_loop (0))
560	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
561
562	Example: Restrict libev to the select and poll backends, and do not allow
563	environment settings to be taken into account:
564
565	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
566
567	Example: Use whatever libev has to offer, but make sure that kqueue is
568	used if available (warning, breaks stuff, best use only with your own
569	private event loop and only if you know the OS supports your types of
570	fds):
571
572	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
573
574	=item struct ev_loop *ev_loop_new (unsigned int flags)
575
576	Similar to C<ev_default_loop>, but always creates a new event loop that is
577	always distinct from the default loop.
578
579	Note that this function I<is> thread-safe, and one common way to use
580	libev with threads is indeed to create one loop per thread, and using the
581	default loop in the "main" or "initial" thread.
582
583	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.
584		730
585	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
586	if (!epoller)	732	if (!epoller)
587	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
588		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
589	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
590		747
591	Destroys the default loop (frees all memory and kernel state etc.). None	748	Destroys an event loop object (frees all memory and kernel state
592	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
593	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
594	either stop all watchers cleanly yourself I<before> calling this function,	751	responsibility to either stop all watchers cleanly yourself I<before>
595	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
596	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).
597		755
598	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
599	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
600	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
601		759
602	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
603	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.
604	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>
605	C<ev_loop_new> and C<ev_loop_destroy>.	767	and C<ev_loop_destroy>.
606		768
607	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
608
609	Like C<ev_default_destroy>, but destroys an event loop created by an
610	earlier call to C<ev_loop_new>.
611
612	=item ev_default_fork ()
613		770
614	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
615	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
616	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
617	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
618	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
619	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>.
620		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
621	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
622	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
623	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
624	during fork.	784	during fork.
625		785
626	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
…		…
629	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
630	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
631	costly reset of the backend).	791	costly reset of the backend).
632		792
633	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
634	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
635	quite nicely into a call to C<pthread_atfork>:
636		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	...
637	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
638
639	=item ev_loop_fork (loop)
640
641	Like C<ev_default_fork>, but acts on an event loop created by
642	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
643	after fork that you want to re-use in the child, and how you keep track of
644	them is entirely your own problem.
645		807
646	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
647		809
648	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
649	otherwise.	811	otherwise.
…		…
660	prepare and check phases.	822	prepare and check phases.
661		823
662	=item unsigned int ev_depth (loop)	824	=item unsigned int ev_depth (loop)
663		825
664	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
665	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.
666		828
667	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
668	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),
669	in which case it is higher.	831	in which case it is higher.
670		832
671	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
672	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
673	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.
674		837
675	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
676		839
677	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
678	use.	841	use.
…		…
693		856
694	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
695	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
696	the current time is a good idea.	859	the current time is a good idea.
697		860
698	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.
699		862
700	=item ev_suspend (loop)	863	=item ev_suspend (loop)
701		864
702	=item ev_resume (loop)	865	=item ev_resume (loop)
703		866
…		…
721	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
722		885
723	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
724	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
725		888
726	=item ev_run (loop, int flags)	889	=item bool ev_run (loop, int flags)
727		890
728	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
729	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
730	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
731	the watcher callbacks, an then repeat the whole process indefinitely: This	894	the watcher callbacks, and then repeat the whole process indefinitely: This
732	is why event loops are called I<loops>.	895	is why event loops are called I<loops>.
733		896
734	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
735	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
736	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").
737		904
738	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
739	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
740	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
741	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
742	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
743	beauty.	910	beauty.
744		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
745	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
746	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
747	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
748	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
749	events while doing lengthy calculations, to keep the program responsive.	921	events while doing lengthy calculations, to keep the program responsive.
…		…
758	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
759	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
760	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
761	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
762		934
763	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):
764		938
765	- Increment loop depth.	939	- Increment loop depth.
766	- Reset the ev_break status.	940	- Reset the ev_break status.
767	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
768	LOOP:	942	LOOP:
…		…
801	anymore.	975	anymore.
802		976
803	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
804	... 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..)
805	ev_run (my_loop, 0);	979	ev_run (my_loop, 0);
806	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
807		981
808	=item ev_break (loop, how)	982	=item ev_break (loop, how)
809		983
810	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
811	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
812	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
813	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.
814		988
815	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>.
816		990
817	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.
818		993
819	=item ev_ref (loop)	994	=item ev_ref (loop)
820		995
821	=item ev_unref (loop)	996	=item ev_unref (loop)
822		997
…		…
843	running when nothing else is active.	1018	running when nothing else is active.
844		1019
845	ev_signal exitsig;	1020	ev_signal exitsig;
846	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
847	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
848	evf_unref (loop);	1023	ev_unref (loop);
849		1024
850	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
851		1026
852	ev_ref (loop);	1027	ev_ref (loop);
853	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
873	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.
874		1049
875	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
876	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,
877	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
878	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
879	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
880	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
881	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
882		1058
883	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
884	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
885	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
886	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
…		…
932	invoke the actual watchers inside another context (another thread etc.).	1108	invoke the actual watchers inside another context (another thread etc.).
933		1109
934	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
935	callback.	1111	callback.
936		1112
937	=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 ())
938		1114
939	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
940	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
941	each call to a libev function.	1117	each call to a libev function.
942		1118
943	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
944	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
945	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
946	I<release> and I<acquire> callbacks on the loop.	1122	I<release> and I<acquire> callbacks on the loop.
947		1123
948	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
949	suspended waiting for new events, and C<acquire> is called just	1125	suspended waiting for new events, and C<acquire> is called just
950	afterwards.	1126	afterwards.
…		…
965	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
966	document.	1142	document.
967		1143
968	=item ev_set_userdata (loop, void *data)	1144	=item ev_set_userdata (loop, void *data)
969		1145
970	=item ev_userdata (loop)	1146	=item void *ev_userdata (loop)
971		1147
972	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
973	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
974	C<0.>	1150	C<0>.
975		1151
976	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,
977	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
978	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
979	any other purpose as well.	1155	any other purpose as well.
…		…
1042	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
1043	*) >>), 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
1044	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
1045		1221
1046	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
1047	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
1048	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.
1049		1226
1050	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
1051	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
1052	third argument.	1229	third argument.
1053		1230
…		…
1090		1267
1091	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
1092		1269
1093	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
1094		1271
1095	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
1096	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)
1097	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
1098	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
1099	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
1100	(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
1101	C<ev_run> from blocking).	1283	blocking).
1102		1284
1103	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
1104		1286
1105	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.
1106		1288
1107	=item C<EV_FORK>	1289	=item C<EV_FORK>
1108		1290
1109	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
1110	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>).
1111		1297
1112	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
1113		1299
1114	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>).
1115		1301
…		…
1137	programs, though, as the fd could already be closed and reused for another	1323	programs, though, as the fd could already be closed and reused for another
1138	thing, so beware.	1324	thing, so beware.
1139		1325
1140	=back	1326	=back
1141		1327
		1328	=head2 GENERIC WATCHER FUNCTIONS
		1329
		1330	=over 4
		1331
		1332	=item C<ev_init> (ev_TYPE *watcher, callback)
		1333
		1334	This macro initialises the generic portion of a watcher. The contents
		1335	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1336	the generic parts of the watcher are initialised, you I<need> to call
		1337	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1338	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1339	which rolls both calls into one.
		1340
		1341	You can reinitialise a watcher at any time as long as it has been stopped
		1342	(or never started) and there are no pending events outstanding.
		1343
		1344	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1345	int revents)>.
		1346
		1347	Example: Initialise an C<ev_io> watcher in two steps.
		1348
		1349	ev_io w;
		1350	ev_init (&w, my_cb);
		1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1352
		1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1354
		1355	This macro initialises the type-specific parts of a watcher. You need to
		1356	call C<ev_init> at least once before you call this macro, but you can
		1357	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1358	macro on a watcher that is active (it can be pending, however, which is a
		1359	difference to the C<ev_init> macro).
		1360
		1361	Although some watcher types do not have type-specific arguments
		1362	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1363
		1364	See C<ev_init>, above, for an example.
		1365
		1366	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1367
		1368	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1369	calls into a single call. This is the most convenient method to initialise
		1370	a watcher. The same limitations apply, of course.
		1371
		1372	Example: Initialise and set an C<ev_io> watcher in one step.
		1373
		1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1375
		1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1377
		1378	Starts (activates) the given watcher. Only active watchers will receive
		1379	events. If the watcher is already active nothing will happen.
		1380
		1381	Example: Start the C<ev_io> watcher that is being abused as example in this
		1382	whole section.
		1383
		1384	ev_io_start (EV_DEFAULT_UC, &w);
		1385
		1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1387
		1388	Stops the given watcher if active, and clears the pending status (whether
		1389	the watcher was active or not).
		1390
		1391	It is possible that stopped watchers are pending - for example,
		1392	non-repeating timers are being stopped when they become pending - but
		1393	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1394	pending. If you want to free or reuse the memory used by the watcher it is
		1395	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1396
		1397	=item bool ev_is_active (ev_TYPE *watcher)
		1398
		1399	Returns a true value iff the watcher is active (i.e. it has been started
		1400	and not yet been stopped). As long as a watcher is active you must not modify
		1401	it unless documented otherwise.
		1402
		1403	=item bool ev_is_pending (ev_TYPE *watcher)
		1404
		1405	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1406	events but its callback has not yet been invoked). As long as a watcher
		1407	is pending (but not active) you must not call an init function on it (but
		1408	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1409	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1410	it).
		1411
		1412	=item callback ev_cb (ev_TYPE *watcher)
		1413
		1414	Returns the callback currently set on the watcher.
		1415
		1416	=item ev_set_cb (ev_TYPE *watcher, callback)
		1417
		1418	Change the callback. You can change the callback at virtually any time
		1419	(modulo threads).
		1420
		1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1422
		1423	=item int ev_priority (ev_TYPE *watcher)
		1424
		1425	Set and query the priority of the watcher. The priority is a small
		1426	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1427	(default: C<-2>). Pending watchers with higher priority will be invoked
		1428	before watchers with lower priority, but priority will not keep watchers
		1429	from being executed (except for C<ev_idle> watchers).
		1430
		1431	If you need to suppress invocation when higher priority events are pending
		1432	you need to look at C<ev_idle> watchers, which provide this functionality.
		1433
		1434	You I<must not> change the priority of a watcher as long as it is active or
		1435	pending.
		1436
		1437	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1438	fine, as long as you do not mind that the priority value you query might
		1439	or might not have been clamped to the valid range.
		1440
		1441	The default priority used by watchers when no priority has been set is
		1442	always C<0>, which is supposed to not be too high and not be too low :).
		1443
		1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1445	priorities.
		1446
		1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1448
		1449	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1450	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1451	can deal with that fact, as both are simply passed through to the
		1452	callback.
		1453
		1454	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1455
		1456	If the watcher is pending, this function clears its pending status and
		1457	returns its C<revents> bitset (as if its callback was invoked). If the
		1458	watcher isn't pending it does nothing and returns C<0>.
		1459
		1460	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1461	callback to be invoked, which can be accomplished with this function.
		1462
		1463	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1464
		1465	Feeds the given event set into the event loop, as if the specified event
		1466	had happened for the specified watcher (which must be a pointer to an
		1467	initialised but not necessarily started event watcher). Obviously you must
		1468	not free the watcher as long as it has pending events.
		1469
		1470	Stopping the watcher, letting libev invoke it, or calling
		1471	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1472	not started in the first place.
		1473
		1474	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1475	functions that do not need a watcher.
		1476
		1477	=back
		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
		1481
1142	=head2 WATCHER STATES	1482	=head2 WATCHER STATES
1143		1483
1144	There are various watcher states mentioned throughout this manual -	1484	There are various watcher states mentioned throughout this manual -
1145	active, pending and so on. In this section these states and the rules to	1485	active, pending and so on. In this section these states and the rules to
1146	transition between them will be described in more detail - and while these	1486	transition between them will be described in more detail - and while these
1147	rules might look complicated, they usually do "the right thing".	1487	rules might look complicated, they usually do "the right thing".
1148		1488
1149	=over 4	1489	=over 4
1150		1490
1151	=item initialiased	1491	=item initialised
1152		1492
1153	Before a watcher can be registered with the event looop it has to be	1493	Before a watcher can be registered with the event loop it has to be
1154	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1494	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1155	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1495	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1156		1496
1157	In this state it is simply some block of memory that is suitable for use	1497	In this state it is simply some block of memory that is suitable for
1158	in an event loop. It can be moved around, freed, reused etc. at will.	1498	use in an event loop. It can be moved around, freed, reused etc. at
		1499	will - as long as you either keep the memory contents intact, or call
		1500	C<ev_TYPE_init> again.
1159		1501
1160	=item started/running/active	1502	=item started/running/active
1161		1503
1162	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1163	property of the event loop, and is actively waiting for events. While in	1505	property of the event loop, and is actively waiting for events. While in
…		…
1191	latter will clear any pending state the watcher might be in, regardless	1533	latter will clear any pending state the watcher might be in, regardless
1192	of whether it was active or not, so stopping a watcher explicitly before	1534	of whether it was active or not, so stopping a watcher explicitly before
1193	freeing it is often a good idea.	1535	freeing it is often a good idea.
1194		1536
1195	While stopped (and not pending) the watcher is essentially in the	1537	While stopped (and not pending) the watcher is essentially in the
1196	initialised state, that is it can be reused, moved, modified in any way	1538	initialised state, that is, it can be reused, moved, modified in any way
1197	you wish.	1539	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1540	it again).
1198		1541
1199	=back	1542	=back
1200
1201	=head2 GENERIC WATCHER FUNCTIONS
1202
1203	=over 4
1204
1205	=item C<ev_init> (ev_TYPE *watcher, callback)
1206
1207	This macro initialises the generic portion of a watcher. The contents
1208	of the watcher object can be arbitrary (so C<malloc> will do). Only
1209	the generic parts of the watcher are initialised, you I<need> to call
1210	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1211	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1212	which rolls both calls into one.
1213
1214	You can reinitialise a watcher at any time as long as it has been stopped
1215	(or never started) and there are no pending events outstanding.
1216
1217	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1218	int revents)>.
1219
1220	Example: Initialise an C<ev_io> watcher in two steps.
1221
1222	ev_io w;
1223	ev_init (&w, my_cb);
1224	ev_io_set (&w, STDIN_FILENO, EV_READ);
1225
1226	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1227
1228	This macro initialises the type-specific parts of a watcher. You need to
1229	call C<ev_init> at least once before you call this macro, but you can
1230	call C<ev_TYPE_set> any number of times. You must not, however, call this
1231	macro on a watcher that is active (it can be pending, however, which is a
1232	difference to the C<ev_init> macro).
1233
1234	Although some watcher types do not have type-specific arguments
1235	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1236
1237	See C<ev_init>, above, for an example.
1238
1239	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1240
1241	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1242	calls into a single call. This is the most convenient method to initialise
1243	a watcher. The same limitations apply, of course.
1244
1245	Example: Initialise and set an C<ev_io> watcher in one step.
1246
1247	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1248
1249	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1250
1251	Starts (activates) the given watcher. Only active watchers will receive
1252	events. If the watcher is already active nothing will happen.
1253
1254	Example: Start the C<ev_io> watcher that is being abused as example in this
1255	whole section.
1256
1257	ev_io_start (EV_DEFAULT_UC, &w);
1258
1259	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1260
1261	Stops the given watcher if active, and clears the pending status (whether
1262	the watcher was active or not).
1263
1264	It is possible that stopped watchers are pending - for example,
1265	non-repeating timers are being stopped when they become pending - but
1266	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1267	pending. If you want to free or reuse the memory used by the watcher it is
1268	therefore a good idea to always call its C<ev_TYPE_stop> function.
1269
1270	=item bool ev_is_active (ev_TYPE *watcher)
1271
1272	Returns a true value iff the watcher is active (i.e. it has been started
1273	and not yet been stopped). As long as a watcher is active you must not modify
1274	it.
1275
1276	=item bool ev_is_pending (ev_TYPE *watcher)
1277
1278	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1279	events but its callback has not yet been invoked). As long as a watcher
1280	is pending (but not active) you must not call an init function on it (but
1281	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1282	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1283	it).
1284
1285	=item callback ev_cb (ev_TYPE *watcher)
1286
1287	Returns the callback currently set on the watcher.
1288
1289	=item ev_cb_set (ev_TYPE *watcher, callback)
1290
1291	Change the callback. You can change the callback at virtually any time
1292	(modulo threads).
1293
1294	=item ev_set_priority (ev_TYPE *watcher, int priority)
1295
1296	=item int ev_priority (ev_TYPE *watcher)
1297
1298	Set and query the priority of the watcher. The priority is a small
1299	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1300	(default: C<-2>). Pending watchers with higher priority will be invoked
1301	before watchers with lower priority, but priority will not keep watchers
1302	from being executed (except for C<ev_idle> watchers).
1303
1304	If you need to suppress invocation when higher priority events are pending
1305	you need to look at C<ev_idle> watchers, which provide this functionality.
1306
1307	You I<must not> change the priority of a watcher as long as it is active or
1308	pending.
1309
1310	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1311	fine, as long as you do not mind that the priority value you query might
1312	or might not have been clamped to the valid range.
1313
1314	The default priority used by watchers when no priority has been set is
1315	always C<0>, which is supposed to not be too high and not be too low :).
1316
1317	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1318	priorities.
1319
1320	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1321
1322	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1323	C<loop> nor C<revents> need to be valid as long as the watcher callback
1324	can deal with that fact, as both are simply passed through to the
1325	callback.
1326
1327	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1328
1329	If the watcher is pending, this function clears its pending status and
1330	returns its C<revents> bitset (as if its callback was invoked). If the
1331	watcher isn't pending it does nothing and returns C<0>.
1332
1333	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1334	callback to be invoked, which can be accomplished with this function.
1335
1336	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1337
1338	Feeds the given event set into the event loop, as if the specified event
1339	had happened for the specified watcher (which must be a pointer to an
1340	initialised but not necessarily started event watcher). Obviously you must
1341	not free the watcher as long as it has pending events.
1342
1343	Stopping the watcher, letting libev invoke it, or calling
1344	C<ev_clear_pending> will clear the pending event, even if the watcher was
1345	not started in the first place.
1346
1347	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1348	functions that do not need a watcher.
1349
1350	=back
1351
1352
1353	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1354
1355	Each watcher has, by default, a member C<void *data> that you can change
1356	and read at any time: libev will completely ignore it. This can be used
1357	to associate arbitrary data with your watcher. If you need more data and
1358	don't want to allocate memory and store a pointer to it in that data
1359	member, you can also "subclass" the watcher type and provide your own
1360	data:
1361
1362	struct my_io
1363	{
1364	ev_io io;
1365	int otherfd;
1366	void *somedata;
1367	struct whatever *mostinteresting;
1368	};
1369
1370	...
1371	struct my_io w;
1372	ev_io_init (&w.io, my_cb, fd, EV_READ);
1373
1374	And since your callback will be called with a pointer to the watcher, you
1375	can cast it back to your own type:
1376
1377	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1378	{
1379	struct my_io *w = (struct my_io *)w_;
1380	...
1381	}
1382
1383	More interesting and less C-conformant ways of casting your callback type
1384	instead have been omitted.
1385
1386	Another common scenario is to use some data structure with multiple
1387	embedded watchers:
1388
1389	struct my_biggy
1390	{
1391	int some_data;
1392	ev_timer t1;
1393	ev_timer t2;
1394	}
1395
1396	In this case getting the pointer to C<my_biggy> is a bit more
1397	complicated: Either you store the address of your C<my_biggy> struct
1398	in the C<data> member of the watcher (for woozies), or you need to use
1399	some pointer arithmetic using C<offsetof> inside your watchers (for real
1400	programmers):
1401
1402	#include <stddef.h>
1403
1404	static void
1405	t1_cb (EV_P_ ev_timer *w, int revents)
1406	{
1407	struct my_biggy big = (struct my_biggy *)
1408	(((char *)w) - offsetof (struct my_biggy, t1));
1409	}
1410
1411	static void
1412	t2_cb (EV_P_ ev_timer *w, int revents)
1413	{
1414	struct my_biggy big = (struct my_biggy *)
1415	(((char *)w) - offsetof (struct my_biggy, t2));
1416	}
1417		1543
1418	=head2 WATCHER PRIORITY MODELS	1544	=head2 WATCHER PRIORITY MODELS
1419		1545
1420	Many event loops support I<watcher priorities>, which are usually small	1546	Many event loops support I<watcher priorities>, which are usually small
1421	integers that influence the ordering of event callback invocation	1547	integers that influence the ordering of event callback invocation
1422	between watchers in some way, all else being equal.	1548	between watchers in some way, all else being equal.
1423		1549
1424	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
1425	description for the more technical details such as the actual priority	1551	description for the more technical details such as the actual priority
1426	range.	1552	range.
1427		1553
1428	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
1429	by event loops:	1555	by event loops:
…		…
1523		1649
1524	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1525	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1526	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1527		1653
1528	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1529	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
1530	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
1531	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
1532	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 is
1533	is active, but you can also modify it. Modifying it may not do something	1659	active, but you can also modify it (within the same thread as the event
		1660	loop, i.e. without creating data races). Modifying it may not do something
1534	sensible or take immediate effect (or do anything at all), but libev will	1661	sensible or take immediate effect (or do anything at all), but libev will
1535	not crash or malfunction in any way.	1662	not crash or malfunction in any way.
1536		1663
		1664	In any case, the documentation for each member will explain what the
		1665	effects are, and if there are any additional access restrictions.
1537		1666
1538	=head2 C<ev_io> - is this file descriptor readable or writable?	1667	=head2 C<ev_io> - is this file descriptor readable or writable?
1539		1668
1540	I/O watchers check whether a file descriptor is readable or writable	1669	I/O watchers check whether a file descriptor is readable or writable
1541	in each iteration of the event loop, or, more precisely, when reading	1670	in each iteration of the event loop, or, more precisely, when reading
…		…
1548	In general you can register as many read and/or write event watchers per	1677	In general you can register as many read and/or write event watchers per
1549	fd as you want (as long as you don't confuse yourself). Setting all file	1678	fd as you want (as long as you don't confuse yourself). Setting all file
1550	descriptors to non-blocking mode is also usually a good idea (but not	1679	descriptors to non-blocking mode is also usually a good idea (but not
1551	required if you know what you are doing).	1680	required if you know what you are doing).
1552		1681
1553	If you cannot use non-blocking mode, then force the use of a
1554	known-to-be-good backend (at the time of this writing, this includes only
1555	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1556	descriptors for which non-blocking operation makes no sense (such as
1557	files) - libev doesn't guarantee any specific behaviour in that case.
1558
1559	Another thing you have to watch out for is that it is quite easy to	1682	Another thing you have to watch out for is that it is quite easy to
1560	receive "spurious" readiness notifications, that is your callback might	1683	receive "spurious" readiness notifications, that is, your callback might
1561	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1684	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1562	because there is no data. Not only are some backends known to create a	1685	because there is no data. It is very easy to get into this situation even
1563	lot of those (for example Solaris ports), it is very easy to get into	1686	with a relatively standard program structure. Thus it is best to always
1564	this situation even with a relatively standard program structure. Thus	1687	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1565	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1566	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1688	preferable to a program hanging until some data arrives.
1567		1689
1568	If you cannot run the fd in non-blocking mode (for example you should	1690	If you cannot run the fd in non-blocking mode (for example you should
1569	not play around with an Xlib connection), then you have to separately	1691	not play around with an Xlib connection), then you have to separately
1570	re-test whether a file descriptor is really ready with a known-to-be good	1692	re-test whether a file descriptor is really ready with a known-to-be good
1571	interface such as poll (fortunately in our Xlib example, Xlib already	1693	interface such as poll (fortunately in the case of Xlib, it already does
1572	does this on its own, so its quite safe to use). Some people additionally	1694	this on its own, so its quite safe to use). Some people additionally
1573	use C<SIGALRM> and an interval timer, just to be sure you won't block	1695	use C<SIGALRM> and an interval timer, just to be sure you won't block
1574	indefinitely.	1696	indefinitely.
1575		1697
1576	But really, best use non-blocking mode.	1698	But really, best use non-blocking mode.
1577		1699
1578	=head3 The special problem of disappearing file descriptors	1700	=head3 The special problem of disappearing file descriptors
1579		1701
1580	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1702	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1581	descriptor (either due to calling C<close> explicitly or any other means,	1703	a file descriptor (either due to calling C<close> explicitly or any other
1582	such as C<dup2>). The reason is that you register interest in some file	1704	means, such as C<dup2>). The reason is that you register interest in some
1583	descriptor, but when it goes away, the operating system will silently drop	1705	file descriptor, but when it goes away, the operating system will silently
1584	this interest. If another file descriptor with the same number then is	1706	drop this interest. If another file descriptor with the same number then
1585	registered with libev, there is no efficient way to see that this is, in	1707	is registered with libev, there is no efficient way to see that this is,
1586	fact, a different file descriptor.	1708	in fact, a different file descriptor.
1587		1709
1588	To avoid having to explicitly tell libev about such cases, libev follows	1710	To avoid having to explicitly tell libev about such cases, libev follows
1589	the following policy: Each time C<ev_io_set> is being called, libev	1711	the following policy: Each time C<ev_io_set> is being called, libev
1590	will assume that this is potentially a new file descriptor, otherwise	1712	will assume that this is potentially a new file descriptor, otherwise
1591	it is assumed that the file descriptor stays the same. That means that	1713	it is assumed that the file descriptor stays the same. That means that
…		…
1605		1727
1606	There is no workaround possible except not registering events	1728	There is no workaround possible except not registering events
1607	for potentially C<dup ()>'ed file descriptors, or to resort to	1729	for potentially C<dup ()>'ed file descriptors, or to resort to
1608	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1730	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1609		1731
		1732	=head3 The special problem of files
		1733
		1734	Many people try to use C<select> (or libev) on file descriptors
		1735	representing files, and expect it to become ready when their program
		1736	doesn't block on disk accesses (which can take a long time on their own).
		1737
		1738	However, this cannot ever work in the "expected" way - you get a readiness
		1739	notification as soon as the kernel knows whether and how much data is
		1740	there, and in the case of open files, that's always the case, so you
		1741	always get a readiness notification instantly, and your read (or possibly
		1742	write) will still block on the disk I/O.
		1743
		1744	Another way to view it is that in the case of sockets, pipes, character
		1745	devices and so on, there is another party (the sender) that delivers data
		1746	on its own, but in the case of files, there is no such thing: the disk
		1747	will not send data on its own, simply because it doesn't know what you
		1748	wish to read - you would first have to request some data.
		1749
		1750	Since files are typically not-so-well supported by advanced notification
		1751	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1752	to files, even though you should not use it. The reason for this is
		1753	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1754	usually a tty, often a pipe, but also sometimes files or special devices
		1755	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1756	F</dev/urandom>), and even though the file might better be served with
		1757	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1758	it "just works" instead of freezing.
		1759
		1760	So avoid file descriptors pointing to files when you know it (e.g. use
		1761	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1762	when you rarely read from a file instead of from a socket, and want to
		1763	reuse the same code path.
		1764
1610	=head3 The special problem of fork	1765	=head3 The special problem of fork
1611		1766
1612	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1767	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1613	useless behaviour. Libev fully supports fork, but needs to be told about	1768	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1614	it in the child.	1769	to be told about it in the child if you want to continue to use it in the
		1770	child.
1615		1771
1616	To support fork in your programs, you either have to call	1772	To support fork in your child processes, you have to call C<ev_loop_fork
1617	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1773	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1618	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1774	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1619	C<EVBACKEND_POLL>.
1620		1775
1621	=head3 The special problem of SIGPIPE	1776	=head3 The special problem of SIGPIPE
1622		1777
1623	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1778	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1624	when writing to a pipe whose other end has been closed, your program gets	1779	when writing to a pipe whose other end has been closed, your program gets
…		…
1675	=item ev_io_init (ev_io *, callback, int fd, int events)	1830	=item ev_io_init (ev_io *, callback, int fd, int events)
1676		1831
1677	=item ev_io_set (ev_io *, int fd, int events)	1832	=item ev_io_set (ev_io *, int fd, int events)
1678		1833
1679	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1834	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1680	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1835	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE>, both
1681	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1836	C<EV_READ | EV_WRITE> or C<0>, to express the desire to receive the given
		1837	events.
1682		1838
1683	=item int fd [read-only]	1839	Note that setting the C<events> to C<0> and starting the watcher is
		1840	supported, but not specially optimized - if your program sometimes happens
		1841	to generate this combination this is fine, but if it is easy to avoid
		1842	starting an io watcher watching for no events you should do so.
1684		1843
1685	The file descriptor being watched.	1844	=item ev_io_modify (ev_io *, int events)
1686		1845
		1846	Similar to C<ev_io_set>, but only changes the requested events. Using this
		1847	might be faster with some backends, as libev can assume that the C<fd>
		1848	still refers to the same underlying file description, something it cannot
		1849	do when using C<ev_io_set>.
		1850
		1851	=item int fd [no-modify]
		1852
		1853	The file descriptor being watched. While it can be read at any time, you
		1854	must not modify this member even when the watcher is stopped - always use
		1855	C<ev_io_set> for that.
		1856
1687	=item int events [read-only]	1857	=item int events [no-modify]
1688		1858
1689	The events being watched.	1859	The set of events the fd is being watched for, among other flags. Remember
		1860	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1861	EV_READ >>, and similarly for C<EV_WRITE>.
		1862
		1863	As with C<fd>, you must not modify this member even when the watcher is
		1864	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1690		1865
1691	=back	1866	=back
1692		1867
1693	=head3 Examples	1868	=head3 Examples
1694		1869
…		…
1722	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1897	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1723	monotonic clock option helps a lot here).	1898	monotonic clock option helps a lot here).
1724		1899
1725	The callback is guaranteed to be invoked only I<after> its timeout has	1900	The callback is guaranteed to be invoked only I<after> its timeout has
1726	passed (not I<at>, so on systems with very low-resolution clocks this	1901	passed (not I<at>, so on systems with very low-resolution clocks this
1727	might introduce a small delay). If multiple timers become ready during the	1902	might introduce a small delay, see "the special problem of being too
		1903	early", below). If multiple timers become ready during the same loop
1728	same loop iteration then the ones with earlier time-out values are invoked	1904	iteration then the ones with earlier time-out values are invoked before
1729	before ones of the same priority with later time-out values (but this is	1905	ones of the same priority with later time-out values (but this is no
1730	no longer true when a callback calls C<ev_run> recursively).	1906	longer true when a callback calls C<ev_run> recursively).
1731		1907
1732	=head3 Be smart about timeouts	1908	=head3 Be smart about timeouts
1733		1909
1734	Many real-world problems involve some kind of timeout, usually for error	1910	Many real-world problems involve some kind of timeout, usually for error
1735	recovery. A typical example is an HTTP request - if the other side hangs,	1911	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1810		1986
1811	In this case, it would be more efficient to leave the C<ev_timer> alone,	1987	In this case, it would be more efficient to leave the C<ev_timer> alone,
1812	but remember the time of last activity, and check for a real timeout only	1988	but remember the time of last activity, and check for a real timeout only
1813	within the callback:	1989	within the callback:
1814		1990
		1991	ev_tstamp timeout = 60.;
1815	ev_tstamp last_activity; // time of last activity	1992	ev_tstamp last_activity; // time of last activity
		1993	ev_timer timer;
1816		1994
1817	static void	1995	static void
1818	callback (EV_P_ ev_timer *w, int revents)	1996	callback (EV_P_ ev_timer *w, int revents)
1819	{	1997	{
1820	ev_tstamp now = ev_now (EV_A);	1998	// calculate when the timeout would happen
1821	ev_tstamp timeout = last_activity + 60.;	1999	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1822		2000
1823	// if last_activity + 60. is older than now, we did time out	2001	// if negative, it means we the timeout already occurred
1824	if (timeout < now)	2002	if (after < 0.)
1825	{	2003	{
1826	// timeout occurred, take action	2004	// timeout occurred, take action
1827	}	2005	}
1828	else	2006	else
1829	{	2007	{
1830	// callback was invoked, but there was some activity, re-arm	2008	// callback was invoked, but there was some recent
1831	// the watcher to fire in last_activity + 60, which is	2009	// activity. simply restart the timer to time out
1832	// guaranteed to be in the future, so "again" is positive:	2010	// after "after" seconds, which is the earliest time
1833	w->repeat = timeout - now;	2011	// the timeout can occur.
		2012	ev_timer_set (w, after, 0.);
1834	ev_timer_again (EV_A_ w);	2013	ev_timer_start (EV_A_ w);
1835	}	2014	}
1836	}	2015	}
1837		2016
1838	To summarise the callback: first calculate the real timeout (defined	2017	To summarise the callback: first calculate in how many seconds the
1839	as "60 seconds after the last activity"), then check if that time has	2018	timeout will occur (by calculating the absolute time when it would occur,
1840	been reached, which means something I<did>, in fact, time out. Otherwise	2019	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1841	the callback was invoked too early (C<timeout> is in the future), so	2020	(EV_A)> from that).
1842	re-schedule the timer to fire at that future time, to see if maybe we have
1843	a timeout then.
1844		2021
1845	Note how C<ev_timer_again> is used, taking advantage of the	2022	If this value is negative, then we are already past the timeout, i.e. we
1846	C<ev_timer_again> optimisation when the timer is already running.	2023	timed out, and need to do whatever is needed in this case.
		2024
		2025	Otherwise, we now the earliest time at which the timeout would trigger,
		2026	and simply start the timer with this timeout value.
		2027
		2028	In other words, each time the callback is invoked it will check whether
		2029	the timeout occurred. If not, it will simply reschedule itself to check
		2030	again at the earliest time it could time out. Rinse. Repeat.
1847		2031
1848	This scheme causes more callback invocations (about one every 60 seconds	2032	This scheme causes more callback invocations (about one every 60 seconds
1849	minus half the average time between activity), but virtually no calls to	2033	minus half the average time between activity), but virtually no calls to
1850	libev to change the timeout.	2034	libev to change the timeout.
1851		2035
1852	To start the timer, simply initialise the watcher and set C<last_activity>	2036	To start the machinery, simply initialise the watcher and set
1853	to the current time (meaning we just have some activity :), then call the	2037	C<last_activity> to the current time (meaning there was some activity just
1854	callback, which will "do the right thing" and start the timer:	2038	now), then call the callback, which will "do the right thing" and start
		2039	the timer:
1855		2040
		2041	last_activity = ev_now (EV_A);
1856	ev_init (timer, callback);	2042	ev_init (&timer, callback);
1857	last_activity = ev_now (loop);	2043	callback (EV_A_ &timer, 0);
1858	callback (loop, timer, EV_TIMER);
1859		2044
1860	And when there is some activity, simply store the current time in	2045	When there is some activity, simply store the current time in
1861	C<last_activity>, no libev calls at all:	2046	C<last_activity>, no libev calls at all:
1862		2047
		2048	if (activity detected)
1863	last_activity = ev_now (loop);	2049	last_activity = ev_now (EV_A);
		2050
		2051	When your timeout value changes, then the timeout can be changed by simply
		2052	providing a new value, stopping the timer and calling the callback, which
		2053	will again do the right thing (for example, time out immediately :).
		2054
		2055	timeout = new_value;
		2056	ev_timer_stop (EV_A_ &timer);
		2057	callback (EV_A_ &timer, 0);
1864		2058
1865	This technique is slightly more complex, but in most cases where the	2059	This technique is slightly more complex, but in most cases where the
1866	time-out is unlikely to be triggered, much more efficient.	2060	time-out is unlikely to be triggered, much more efficient.
1867
1868	Changing the timeout is trivial as well (if it isn't hard-coded in the
1869	callback :) - just change the timeout and invoke the callback, which will
1870	fix things for you.
1871		2061
1872	=item 4. Wee, just use a double-linked list for your timeouts.	2062	=item 4. Wee, just use a double-linked list for your timeouts.
1873		2063
1874	If there is not one request, but many thousands (millions...), all	2064	If there is not one request, but many thousands (millions...), all
1875	employing some kind of timeout with the same timeout value, then one can	2065	employing some kind of timeout with the same timeout value, then one can
…		…
1902	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2092	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1903	rather complicated, but extremely efficient, something that really pays	2093	rather complicated, but extremely efficient, something that really pays
1904	off after the first million or so of active timers, i.e. it's usually	2094	off after the first million or so of active timers, i.e. it's usually
1905	overkill :)	2095	overkill :)
1906		2096
		2097	=head3 The special problem of being too early
		2098
		2099	If you ask a timer to call your callback after three seconds, then
		2100	you expect it to be invoked after three seconds - but of course, this
		2101	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2102	guaranteed to any precision by libev - imagine somebody suspending the
		2103	process with a STOP signal for a few hours for example.
		2104
		2105	So, libev tries to invoke your callback as soon as possible I<after> the
		2106	delay has occurred, but cannot guarantee this.
		2107
		2108	A less obvious failure mode is calling your callback too early: many event
		2109	loops compare timestamps with a "elapsed delay >= requested delay", but
		2110	this can cause your callback to be invoked much earlier than you would
		2111	expect.
		2112
		2113	To see why, imagine a system with a clock that only offers full second
		2114	resolution (think windows if you can't come up with a broken enough OS
		2115	yourself). If you schedule a one-second timer at the time 500.9, then the
		2116	event loop will schedule your timeout to elapse at a system time of 500
		2117	(500.9 truncated to the resolution) + 1, or 501.
		2118
		2119	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2120	501" and invoke the callback 0.1s after it was started, even though a
		2121	one-second delay was requested - this is being "too early", despite best
		2122	intentions.
		2123
		2124	This is the reason why libev will never invoke the callback if the elapsed
		2125	delay equals the requested delay, but only when the elapsed delay is
		2126	larger than the requested delay. In the example above, libev would only invoke
		2127	the callback at system time 502, or 1.1s after the timer was started.
		2128
		2129	So, while libev cannot guarantee that your callback will be invoked
		2130	exactly when requested, it I<can> and I<does> guarantee that the requested
		2131	delay has actually elapsed, or in other words, it always errs on the "too
		2132	late" side of things.
		2133
1907	=head3 The special problem of time updates	2134	=head3 The special problem of time updates
1908		2135
1909	Establishing the current time is a costly operation (it usually takes at	2136	Establishing the current time is a costly operation (it usually takes
1910	least two system calls): EV therefore updates its idea of the current	2137	at least one system call): EV therefore updates its idea of the current
1911	time only before and after C<ev_run> collects new events, which causes a	2138	time only before and after C<ev_run> collects new events, which causes a
1912	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2139	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1913	lots of events in one iteration.	2140	lots of events in one iteration.
1914		2141
1915	The relative timeouts are calculated relative to the C<ev_now ()>	2142	The relative timeouts are calculated relative to the C<ev_now ()>
1916	time. This is usually the right thing as this timestamp refers to the time	2143	time. This is usually the right thing as this timestamp refers to the time
1917	of the event triggering whatever timeout you are modifying/starting. If	2144	of the event triggering whatever timeout you are modifying/starting. If
1918	you suspect event processing to be delayed and you I<need> to base the	2145	you suspect event processing to be delayed and you I<need> to base the
1919	timeout on the current time, use something like this to adjust for this:	2146	timeout on the current time, use something like the following to adjust
		2147	for it:
1920		2148
1921	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2149	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1922		2150
1923	If the event loop is suspended for a long time, you can also force an	2151	If the event loop is suspended for a long time, you can also force an
1924	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2152	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1925	()>.	2153	()>, although that will push the event time of all outstanding events
		2154	further into the future.
		2155
		2156	=head3 The special problem of unsynchronised clocks
		2157
		2158	Modern systems have a variety of clocks - libev itself uses the normal
		2159	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2160	jumps).
		2161
		2162	Neither of these clocks is synchronised with each other or any other clock
		2163	on the system, so C<ev_time ()> might return a considerably different time
		2164	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2165	a call to C<gettimeofday> might return a second count that is one higher
		2166	than a directly following call to C<time>.
		2167
		2168	The moral of this is to only compare libev-related timestamps with
		2169	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2170	a second or so.
		2171
		2172	One more problem arises due to this lack of synchronisation: if libev uses
		2173	the system monotonic clock and you compare timestamps from C<ev_time>
		2174	or C<ev_now> from when you started your timer and when your callback is
		2175	invoked, you will find that sometimes the callback is a bit "early".
		2176
		2177	This is because C<ev_timer>s work in real time, not wall clock time, so
		2178	libev makes sure your callback is not invoked before the delay happened,
		2179	I<measured according to the real time>, not the system clock.
		2180
		2181	If your timeouts are based on a physical timescale (e.g. "time out this
		2182	connection after 100 seconds") then this shouldn't bother you as it is
		2183	exactly the right behaviour.
		2184
		2185	If you want to compare wall clock/system timestamps to your timers, then
		2186	you need to use C<ev_periodic>s, as these are based on the wall clock
		2187	time, where your comparisons will always generate correct results.
1926		2188
1927	=head3 The special problems of suspended animation	2189	=head3 The special problems of suspended animation
1928		2190
1929	When you leave the server world it is quite customary to hit machines that	2191	When you leave the server world it is quite customary to hit machines that
1930	can suspend/hibernate - what happens to the clocks during such a suspend?	2192	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1960		2222
1961	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2223	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1962		2224
1963	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2225	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1964		2226
1965	Configure the timer to trigger after C<after> seconds. If C<repeat>	2227	Configure the timer to trigger after C<after> seconds (fractional and
1966	is C<0.>, then it will automatically be stopped once the timeout is	2228	negative values are supported). If C<repeat> is C<0.>, then it will
1967	reached. If it is positive, then the timer will automatically be	2229	automatically be stopped once the timeout is reached. If it is positive,
1968	configured to trigger again C<repeat> seconds later, again, and again,	2230	then the timer will automatically be configured to trigger again C<repeat>
1969	until stopped manually.	2231	seconds later, again, and again, until stopped manually.
1970		2232
1971	The timer itself will do a best-effort at avoiding drift, that is, if	2233	The timer itself will do a best-effort at avoiding drift, that is, if
1972	you configure a timer to trigger every 10 seconds, then it will normally	2234	you configure a timer to trigger every 10 seconds, then it will normally
1973	trigger at exactly 10 second intervals. If, however, your program cannot	2235	trigger at exactly 10 second intervals. If, however, your program cannot
1974	keep up with the timer (because it takes longer than those 10 seconds to	2236	keep up with the timer (because it takes longer than those 10 seconds to
1975	do stuff) the timer will not fire more than once per event loop iteration.	2237	do stuff) the timer will not fire more than once per event loop iteration.
1976		2238
1977	=item ev_timer_again (loop, ev_timer *)	2239	=item ev_timer_again (loop, ev_timer *)
1978		2240
1979	This will act as if the timer timed out and restart it again if it is	2241	This will act as if the timer timed out, and restarts it again if it is
1980	repeating. The exact semantics are:	2242	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2243	timeout to the C<repeat> value and calling C<ev_timer_start>.
1981		2244
		2245	The exact semantics are as in the following rules, all of which will be
		2246	applied to the watcher:
		2247
		2248	=over 4
		2249
1982	If the timer is pending, its pending status is cleared.	2250	=item If the timer is pending, the pending status is always cleared.
1983		2251
1984	If the timer is started but non-repeating, stop it (as if it timed out).	2252	=item If the timer is started but non-repeating, stop it (as if it timed
		2253	out, without invoking it).
1985		2254
1986	If the timer is repeating, either start it if necessary (with the	2255	=item If the timer is repeating, make the C<repeat> value the new timeout
1987	C<repeat> value), or reset the running timer to the C<repeat> value.	2256	and start the timer, if necessary.
1988		2257
		2258	=back
		2259
1989	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2260	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1990	usage example.	2261	usage example.
1991		2262
1992	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2263	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1993		2264
1994	Returns the remaining time until a timer fires. If the timer is active,	2265	Returns the remaining time until a timer fires. If the timer is active,
…		…
2047	Periodic watchers are also timers of a kind, but they are very versatile	2318	Periodic watchers are also timers of a kind, but they are very versatile
2048	(and unfortunately a bit complex).	2319	(and unfortunately a bit complex).
2049		2320
2050	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2321	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2051	relative time, the physical time that passes) but on wall clock time	2322	relative time, the physical time that passes) but on wall clock time
2052	(absolute time, the thing you can read on your calender or clock). The	2323	(absolute time, the thing you can read on your calendar or clock). The
2053	difference is that wall clock time can run faster or slower than real	2324	difference is that wall clock time can run faster or slower than real
2054	time, and time jumps are not uncommon (e.g. when you adjust your	2325	time, and time jumps are not uncommon (e.g. when you adjust your
2055	wrist-watch).	2326	wrist-watch).
2056		2327
2057	You can tell a periodic watcher to trigger after some specific point	2328	You can tell a periodic watcher to trigger after some specific point
…		…
2062	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2333	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2063	it, as it uses a relative timeout).	2334	it, as it uses a relative timeout).
2064		2335
2065	C<ev_periodic> watchers can also be used to implement vastly more complex	2336	C<ev_periodic> watchers can also be used to implement vastly more complex
2066	timers, such as triggering an event on each "midnight, local time", or	2337	timers, such as triggering an event on each "midnight, local time", or
2067	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2338	other complicated rules. This cannot easily be done with C<ev_timer>
2068	those cannot react to time jumps.	2339	watchers, as those cannot react to time jumps.
2069		2340
2070	As with timers, the callback is guaranteed to be invoked only when the	2341	As with timers, the callback is guaranteed to be invoked only when the
2071	point in time where it is supposed to trigger has passed. If multiple	2342	point in time where it is supposed to trigger has passed. If multiple
2072	timers become ready during the same loop iteration then the ones with	2343	timers become ready during the same loop iteration then the ones with
2073	earlier time-out values are invoked before ones with later time-out values	2344	earlier time-out values are invoked before ones with later time-out values
…		…
2114		2385
2115	Another way to think about it (for the mathematically inclined) is that	2386	Another way to think about it (for the mathematically inclined) is that
2116	C<ev_periodic> will try to run the callback in this mode at the next possible	2387	C<ev_periodic> will try to run the callback in this mode at the next possible
2117	time where C<time = offset (mod interval)>, regardless of any time jumps.	2388	time where C<time = offset (mod interval)>, regardless of any time jumps.
2118		2389
2119	For numerical stability it is preferable that the C<offset> value is near	2390	The C<interval> I<MUST> be positive, and for numerical stability, the
2120	C<ev_now ()> (the current time), but there is no range requirement for	2391	interval value should be higher than C<1/8192> (which is around 100
2121	this value, and in fact is often specified as zero.	2392	microseconds) and C<offset> should be higher than C<0> and should have
		2393	at most a similar magnitude as the current time (say, within a factor of
		2394	ten). Typical values for offset are, in fact, C<0> or something between
		2395	C<0> and C<interval>, which is also the recommended range.
2122		2396
2123	Note also that there is an upper limit to how often a timer can fire (CPU	2397	Note also that there is an upper limit to how often a timer can fire (CPU
2124	speed for example), so if C<interval> is very small then timing stability	2398	speed for example), so if C<interval> is very small then timing stability
2125	will of course deteriorate. Libev itself tries to be exact to be about one	2399	will of course deteriorate. Libev itself tries to be exact to be about one
2126	millisecond (if the OS supports it and the machine is fast enough).	2400	millisecond (if the OS supports it and the machine is fast enough).
…		…
2156		2430
2157	NOTE: I<< This callback must always return a time that is higher than or	2431	NOTE: I<< This callback must always return a time that is higher than or
2158	equal to the passed C<now> value >>.	2432	equal to the passed C<now> value >>.
2159		2433
2160	This can be used to create very complex timers, such as a timer that	2434	This can be used to create very complex timers, such as a timer that
2161	triggers on "next midnight, local time". To do this, you would calculate the	2435	triggers on "next midnight, local time". To do this, you would calculate
2162	next midnight after C<now> and return the timestamp value for this. How	2436	the next midnight after C<now> and return the timestamp value for
2163	you do this is, again, up to you (but it is not trivial, which is the main	2437	this. Here is a (completely untested, no error checking) example on how to
2164	reason I omitted it as an example).	2438	do this:
		2439
		2440	#include <time.h>
		2441
		2442	static ev_tstamp
		2443	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2444	{
		2445	time_t tnow = (time_t)now;
		2446	struct tm tm;
		2447	localtime_r (&tnow, &tm);
		2448
		2449	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2450	++tm.tm_mday; // midnight next day
		2451
		2452	return mktime (&tm);
		2453	}
		2454
		2455	Note: this code might run into trouble on days that have more then two
		2456	midnights (beginning and end).
2165		2457
2166	=back	2458	=back
2167		2459
2168	=item ev_periodic_again (loop, ev_periodic *)	2460	=item ev_periodic_again (loop, ev_periodic *)
2169		2461
…		…
2234		2526
2235	ev_periodic hourly_tick;	2527	ev_periodic hourly_tick;
2236	ev_periodic_init (&hourly_tick, clock_cb,	2528	ev_periodic_init (&hourly_tick, clock_cb,
2237	fmod (ev_now (loop), 3600.), 3600., 0);	2529	fmod (ev_now (loop), 3600.), 3600., 0);
2238	ev_periodic_start (loop, &hourly_tick);	2530	ev_periodic_start (loop, &hourly_tick);
2239		2531
2240		2532
2241	=head2 C<ev_signal> - signal me when a signal gets signalled!	2533	=head2 C<ev_signal> - signal me when a signal gets signalled!
2242		2534
2243	Signal watchers will trigger an event when the process receives a specific	2535	Signal watchers will trigger an event when the process receives a specific
2244	signal one or more times. Even though signals are very asynchronous, libev	2536	signal one or more times. Even though signals are very asynchronous, libev
2245	will try it's best to deliver signals synchronously, i.e. as part of the	2537	will try its best to deliver signals synchronously, i.e. as part of the
2246	normal event processing, like any other event.	2538	normal event processing, like any other event.
2247		2539
2248	If you want signals to be delivered truly asynchronously, just use	2540	If you want signals to be delivered truly asynchronously, just use
2249	C<sigaction> as you would do without libev and forget about sharing	2541	C<sigaction> as you would do without libev and forget about sharing
2250	the signal. You can even use C<ev_async> from a signal handler to	2542	the signal. You can even use C<ev_async> from a signal handler to
…		…
2254	only within the same loop, i.e. you can watch for C<SIGINT> in your	2546	only within the same loop, i.e. you can watch for C<SIGINT> in your
2255	default loop and for C<SIGIO> in another loop, but you cannot watch for	2547	default loop and for C<SIGIO> in another loop, but you cannot watch for
2256	C<SIGINT> in both the default loop and another loop at the same time. At	2548	C<SIGINT> in both the default loop and another loop at the same time. At
2257	the moment, C<SIGCHLD> is permanently tied to the default loop.	2549	the moment, C<SIGCHLD> is permanently tied to the default loop.
2258		2550
2259	When the first watcher gets started will libev actually register something	2551	Only after the first watcher for a signal is started will libev actually
2260	with the kernel (thus it coexists with your own signal handlers as long as	2552	register something with the kernel. It thus coexists with your own signal
2261	you don't register any with libev for the same signal).	2553	handlers as long as you don't register any with libev for the same signal.
2262		2554
2263	If possible and supported, libev will install its handlers with	2555	If possible and supported, libev will install its handlers with
2264	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2556	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2265	not be unduly interrupted. If you have a problem with system calls getting	2557	not be unduly interrupted. If you have a problem with system calls getting
2266	interrupted by signals you can block all signals in an C<ev_check> watcher	2558	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2269	=head3 The special problem of inheritance over fork/execve/pthread_create	2561	=head3 The special problem of inheritance over fork/execve/pthread_create
2270		2562
2271	Both the signal mask (C<sigprocmask>) and the signal disposition	2563	Both the signal mask (C<sigprocmask>) and the signal disposition
2272	(C<sigaction>) are unspecified after starting a signal watcher (and after	2564	(C<sigaction>) are unspecified after starting a signal watcher (and after
2273	stopping it again), that is, libev might or might not block the signal,	2565	stopping it again), that is, libev might or might not block the signal,
2274	and might or might not set or restore the installed signal handler.	2566	and might or might not set or restore the installed signal handler (but
		2567	see C<EVFLAG_NOSIGMASK>).
2275		2568
2276	While this does not matter for the signal disposition (libev never	2569	While this does not matter for the signal disposition (libev never
2277	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2570	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2278	C<execve>), this matters for the signal mask: many programs do not expect	2571	C<execve>), this matters for the signal mask: many programs do not expect
2279	certain signals to be blocked.	2572	certain signals to be blocked.
…		…
2292	I<has> to modify the signal mask, at least temporarily.	2585	I<has> to modify the signal mask, at least temporarily.
2293		2586
2294	So I can't stress this enough: I<If you do not reset your signal mask when	2587	So I can't stress this enough: I<If you do not reset your signal mask when
2295	you expect it to be empty, you have a race condition in your code>. This	2588	you expect it to be empty, you have a race condition in your code>. This
2296	is not a libev-specific thing, this is true for most event libraries.	2589	is not a libev-specific thing, this is true for most event libraries.
		2590
		2591	=head3 The special problem of threads signal handling
		2592
		2593	POSIX threads has problematic signal handling semantics, specifically,
		2594	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2595	threads in a process block signals, which is hard to achieve.
		2596
		2597	When you want to use sigwait (or mix libev signal handling with your own
		2598	for the same signals), you can tackle this problem by globally blocking
		2599	all signals before creating any threads (or creating them with a fully set
		2600	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2601	loops. Then designate one thread as "signal receiver thread" which handles
		2602	these signals. You can pass on any signals that libev might be interested
		2603	in by calling C<ev_feed_signal>.
2297		2604
2298	=head3 Watcher-Specific Functions and Data Members	2605	=head3 Watcher-Specific Functions and Data Members
2299		2606
2300	=over 4	2607	=over 4
2301		2608
…		…
2436		2743
2437	=head2 C<ev_stat> - did the file attributes just change?	2744	=head2 C<ev_stat> - did the file attributes just change?
2438		2745
2439	This watches a file system path for attribute changes. That is, it calls	2746	This watches a file system path for attribute changes. That is, it calls
2440	C<stat> on that path in regular intervals (or when the OS says it changed)	2747	C<stat> on that path in regular intervals (or when the OS says it changed)
2441	and sees if it changed compared to the last time, invoking the callback if	2748	and sees if it changed compared to the last time, invoking the callback
2442	it did.	2749	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2750	happen after the watcher has been started will be reported.
2443		2751
2444	The path does not need to exist: changing from "path exists" to "path does	2752	The path does not need to exist: changing from "path exists" to "path does
2445	not exist" is a status change like any other. The condition "path does not	2753	not exist" is a status change like any other. The condition "path does not
2446	exist" (or more correctly "path cannot be stat'ed") is signified by the	2754	exist" (or more correctly "path cannot be stat'ed") is signified by the
2447	C<st_nlink> field being zero (which is otherwise always forced to be at	2755	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2677	Apart from keeping your process non-blocking (which is a useful	2985	Apart from keeping your process non-blocking (which is a useful
2678	effect on its own sometimes), idle watchers are a good place to do	2986	effect on its own sometimes), idle watchers are a good place to do
2679	"pseudo-background processing", or delay processing stuff to after the	2987	"pseudo-background processing", or delay processing stuff to after the
2680	event loop has handled all outstanding events.	2988	event loop has handled all outstanding events.
2681		2989
		2990	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2991
		2992	As long as there is at least one active idle watcher, libev will never
		2993	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2994	For this to work, the idle watcher doesn't need to be invoked at all - the
		2995	lowest priority will do.
		2996
		2997	This mode of operation can be useful together with an C<ev_check> watcher,
		2998	to do something on each event loop iteration - for example to balance load
		2999	between different connections.
		3000
		3001	See L</Abusing an ev_check watcher for its side-effect> for a longer
		3002	example.
		3003
2682	=head3 Watcher-Specific Functions and Data Members	3004	=head3 Watcher-Specific Functions and Data Members
2683		3005
2684	=over 4	3006	=over 4
2685		3007
2686	=item ev_idle_init (ev_idle *, callback)	3008	=item ev_idle_init (ev_idle *, callback)
…		…
2697	callback, free it. Also, use no error checking, as usual.	3019	callback, free it. Also, use no error checking, as usual.
2698		3020
2699	static void	3021	static void
2700	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3022	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2701	{	3023	{
		3024	// stop the watcher
		3025	ev_idle_stop (loop, w);
		3026
		3027	// now we can free it
2702	free (w);	3028	free (w);
		3029
2703	// now do something you wanted to do when the program has	3030	// now do something you wanted to do when the program has
2704	// no longer anything immediate to do.	3031	// no longer anything immediate to do.
2705	}	3032	}
2706		3033
2707	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3034	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2709	ev_idle_start (loop, idle_watcher);	3036	ev_idle_start (loop, idle_watcher);
2710		3037
2711		3038
2712	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3039	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2713		3040
2714	Prepare and check watchers are usually (but not always) used in pairs:	3041	Prepare and check watchers are often (but not always) used in pairs:
2715	prepare watchers get invoked before the process blocks and check watchers	3042	prepare watchers get invoked before the process blocks and check watchers
2716	afterwards.	3043	afterwards.
2717		3044
2718	You I<must not> call C<ev_run> or similar functions that enter	3045	You I<must not> call C<ev_run> (or similar functions that enter the
2719	the current event loop from either C<ev_prepare> or C<ev_check>	3046	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2720	watchers. Other loops than the current one are fine, however. The	3047	C<ev_check> watchers. Other loops than the current one are fine,
2721	rationale behind this is that you do not need to check for recursion in	3048	however. The rationale behind this is that you do not need to check
2722	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3049	for recursion in those watchers, i.e. the sequence will always be
2723	C<ev_check> so if you have one watcher of each kind they will always be	3050	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2724	called in pairs bracketing the blocking call.	3051	kind they will always be called in pairs bracketing the blocking call.
2725		3052
2726	Their main purpose is to integrate other event mechanisms into libev and	3053	Their main purpose is to integrate other event mechanisms into libev and
2727	their use is somewhat advanced. They could be used, for example, to track	3054	their use is somewhat advanced. They could be used, for example, to track
2728	variable changes, implement your own watchers, integrate net-snmp or a	3055	variable changes, implement your own watchers, integrate net-snmp or a
2729	coroutine library and lots more. They are also occasionally useful if	3056	coroutine library and lots more. They are also occasionally useful if
…		…
2747	with priority higher than or equal to the event loop and one coroutine	3074	with priority higher than or equal to the event loop and one coroutine
2748	of lower priority, but only once, using idle watchers to keep the event	3075	of lower priority, but only once, using idle watchers to keep the event
2749	loop from blocking if lower-priority coroutines are active, thus mapping	3076	loop from blocking if lower-priority coroutines are active, thus mapping
2750	low-priority coroutines to idle/background tasks).	3077	low-priority coroutines to idle/background tasks).
2751		3078
2752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3079	When used for this purpose, it is recommended to give C<ev_check> watchers
2753	priority, to ensure that they are being run before any other watchers	3080	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2754	after the poll (this doesn't matter for C<ev_prepare> watchers).	3081	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3082	watchers).
2755		3083
2756	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3084	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2757	activate ("feed") events into libev. While libev fully supports this, they	3085	activate ("feed") events into libev. While libev fully supports this, they
2758	might get executed before other C<ev_check> watchers did their job. As	3086	might get executed before other C<ev_check> watchers did their job. As
2759	C<ev_check> watchers are often used to embed other (non-libev) event	3087	C<ev_check> watchers are often used to embed other (non-libev) event
2760	loops those other event loops might be in an unusable state until their	3088	loops those other event loops might be in an unusable state until their
2761	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3089	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2762	others).	3090	others).
		3091
		3092	=head3 Abusing an C<ev_check> watcher for its side-effect
		3093
		3094	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3095	useful because they are called once per event loop iteration. For
		3096	example, if you want to handle a large number of connections fairly, you
		3097	normally only do a bit of work for each active connection, and if there
		3098	is more work to do, you wait for the next event loop iteration, so other
		3099	connections have a chance of making progress.
		3100
		3101	Using an C<ev_check> watcher is almost enough: it will be called on the
		3102	next event loop iteration. However, that isn't as soon as possible -
		3103	without external events, your C<ev_check> watcher will not be invoked.
		3104
		3105	This is where C<ev_idle> watchers come in handy - all you need is a
		3106	single global idle watcher that is active as long as you have one active
		3107	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3108	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3109	invoked. Neither watcher alone can do that.
2763		3110
2764	=head3 Watcher-Specific Functions and Data Members	3111	=head3 Watcher-Specific Functions and Data Members
2765		3112
2766	=over 4	3113	=over 4
2767		3114
…		…
2968		3315
2969	=over 4	3316	=over 4
2970		3317
2971	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3318	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2972		3319
2973	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3320	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2974		3321
2975	Configures the watcher to embed the given loop, which must be	3322	Configures the watcher to embed the given loop, which must be
2976	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3323	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2977	invoked automatically, otherwise it is the responsibility of the callback	3324	invoked automatically, otherwise it is the responsibility of the callback
2978	to invoke it (it will continue to be called until the sweep has been done,	3325	to invoke it (it will continue to be called until the sweep has been done,
…		…
2999	used).	3346	used).
3000		3347
3001	struct ev_loop *loop_hi = ev_default_init (0);	3348	struct ev_loop *loop_hi = ev_default_init (0);
3002	struct ev_loop *loop_lo = 0;	3349	struct ev_loop *loop_lo = 0;
3003	ev_embed embed;	3350	ev_embed embed;
3004		3351
3005	// see if there is a chance of getting one that works	3352	// see if there is a chance of getting one that works
3006	// (remember that a flags value of 0 means autodetection)	3353	// (remember that a flags value of 0 means autodetection)
3007	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3354	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3008	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3355	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3009	: 0;	3356	: 0;
…		…
3023	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3370	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3024		3371
3025	struct ev_loop *loop = ev_default_init (0);	3372	struct ev_loop *loop = ev_default_init (0);
3026	struct ev_loop *loop_socket = 0;	3373	struct ev_loop *loop_socket = 0;
3027	ev_embed embed;	3374	ev_embed embed;
3028		3375
3029	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3376	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3030	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3377	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3031	{	3378	{
3032	ev_embed_init (&embed, 0, loop_socket);	3379	ev_embed_init (&embed, 0, loop_socket);
3033	ev_embed_start (loop, &embed);	3380	ev_embed_start (loop, &embed);
…		…
3041		3388
3042	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3389	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3043		3390
3044	Fork watchers are called when a C<fork ()> was detected (usually because	3391	Fork watchers are called when a C<fork ()> was detected (usually because
3045	whoever is a good citizen cared to tell libev about it by calling	3392	whoever is a good citizen cared to tell libev about it by calling
3046	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3393	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3047	event loop blocks next and before C<ev_check> watchers are being called,	3394	and before C<ev_check> watchers are being called, and only in the child
3048	and only in the child after the fork. If whoever good citizen calling	3395	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3049	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3396	and calls it in the wrong process, the fork handlers will be invoked, too,
3050	handlers will be invoked, too, of course.	3397	of course.
3051		3398
3052	=head3 The special problem of life after fork - how is it possible?	3399	=head3 The special problem of life after fork - how is it possible?
3053		3400
3054	Most uses of C<fork()> consist of forking, then some simple calls to set	3401	Most uses of C<fork ()> consist of forking, then some simple calls to set
3055	up/change the process environment, followed by a call to C<exec()>. This	3402	up/change the process environment, followed by a call to C<exec()>. This
3056	sequence should be handled by libev without any problems.	3403	sequence should be handled by libev without any problems.
3057		3404
3058	This changes when the application actually wants to do event handling	3405	This changes when the application actually wants to do event handling
3059	in the child, or both parent in child, in effect "continuing" after the	3406	in the child, or both parent in child, in effect "continuing" after the
…		…
3075	disadvantage of having to use multiple event loops (which do not support	3422	disadvantage of having to use multiple event loops (which do not support
3076	signal watchers).	3423	signal watchers).
3077		3424
3078	When this is not possible, or you want to use the default loop for	3425	When this is not possible, or you want to use the default loop for
3079	other reasons, then in the process that wants to start "fresh", call	3426	other reasons, then in the process that wants to start "fresh", call
3080	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3427	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3081	the default loop will "orphan" (not stop) all registered watchers, so you	3428	Destroying the default loop will "orphan" (not stop) all registered
3082	have to be careful not to execute code that modifies those watchers. Note	3429	watchers, so you have to be careful not to execute code that modifies
3083	also that in that case, you have to re-register any signal watchers.	3430	those watchers. Note also that in that case, you have to re-register any
		3431	signal watchers.
3084		3432
3085	=head3 Watcher-Specific Functions and Data Members	3433	=head3 Watcher-Specific Functions and Data Members
3086		3434
3087	=over 4	3435	=over 4
3088		3436
3089	=item ev_fork_init (ev_signal *, callback)	3437	=item ev_fork_init (ev_fork *, callback)
3090		3438
3091	Initialises and configures the fork watcher - it has no parameters of any	3439	Initialises and configures the fork watcher - it has no parameters of any
3092	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3440	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3093	believe me.	3441	really.
3094		3442
3095	=back	3443	=back
3096		3444
3097		3445
		3446	=head2 C<ev_cleanup> - even the best things end
		3447
		3448	Cleanup watchers are called just before the event loop is being destroyed
		3449	by a call to C<ev_loop_destroy>.
		3450
		3451	While there is no guarantee that the event loop gets destroyed, cleanup
		3452	watchers provide a convenient method to install cleanup hooks for your
		3453	program, worker threads and so on - you just to make sure to destroy the
		3454	loop when you want them to be invoked.
		3455
		3456	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3457	all other watchers, they do not keep a reference to the event loop (which
		3458	makes a lot of sense if you think about it). Like all other watchers, you
		3459	can call libev functions in the callback, except C<ev_cleanup_start>.
		3460
		3461	=head3 Watcher-Specific Functions and Data Members
		3462
		3463	=over 4
		3464
		3465	=item ev_cleanup_init (ev_cleanup *, callback)
		3466
		3467	Initialises and configures the cleanup watcher - it has no parameters of
		3468	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3469	pointless, I assure you.
		3470
		3471	=back
		3472
		3473	Example: Register an atexit handler to destroy the default loop, so any
		3474	cleanup functions are called.
		3475
		3476	static void
		3477	program_exits (void)
		3478	{
		3479	ev_loop_destroy (EV_DEFAULT_UC);
		3480	}
		3481
		3482	...
		3483	atexit (program_exits);
		3484
		3485
3098	=head2 C<ev_async> - how to wake up an event loop	3486	=head2 C<ev_async> - how to wake up an event loop
3099		3487
3100	In general, you cannot use an C<ev_run> from multiple threads or other	3488	In general, you cannot use an C<ev_loop> from multiple threads or other
3101	asynchronous sources such as signal handlers (as opposed to multiple event	3489	asynchronous sources such as signal handlers (as opposed to multiple event
3102	loops - those are of course safe to use in different threads).	3490	loops - those are of course safe to use in different threads).
3103		3491
3104	Sometimes, however, you need to wake up an event loop you do not control,	3492	Sometimes, however, you need to wake up an event loop you do not control,
3105	for example because it belongs to another thread. This is what C<ev_async>	3493	for example because it belongs to another thread. This is what C<ev_async>
…		…
3107	it by calling C<ev_async_send>, which is thread- and signal safe.	3495	it by calling C<ev_async_send>, which is thread- and signal safe.
3108		3496
3109	This functionality is very similar to C<ev_signal> watchers, as signals,	3497	This functionality is very similar to C<ev_signal> watchers, as signals,
3110	too, are asynchronous in nature, and signals, too, will be compressed	3498	too, are asynchronous in nature, and signals, too, will be compressed
3111	(i.e. the number of callback invocations may be less than the number of	3499	(i.e. the number of callback invocations may be less than the number of
3112	C<ev_async_sent> calls).	3500	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3113		3501	of "global async watchers" by using a watcher on an otherwise unused
3114	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3502	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3115	just the default loop.	3503	even without knowing which loop owns the signal.
3116		3504
3117	=head3 Queueing	3505	=head3 Queueing
3118		3506
3119	C<ev_async> does not support queueing of data in any way. The reason	3507	C<ev_async> does not support queueing of data in any way. The reason
3120	is that the author does not know of a simple (or any) algorithm for a	3508	is that the author does not know of a simple (or any) algorithm for a
…		…
3212	trust me.	3600	trust me.
3213		3601
3214	=item ev_async_send (loop, ev_async *)	3602	=item ev_async_send (loop, ev_async *)
3215		3603
3216	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3604	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3217	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3605	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3606	returns.
		3607
3218	C<ev_feed_event>, this call is safe to do from other threads, signal or	3608	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3219	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3609	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3220	section below on what exactly this means).	3610	embedding section below on what exactly this means).
3221		3611
3222	Note that, as with other watchers in libev, multiple events might get	3612	Note that, as with other watchers in libev, multiple events might get
3223	compressed into a single callback invocation (another way to look at this	3613	compressed into a single callback invocation (another way to look at
3224	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3614	this is that C<ev_async> watchers are level-triggered: they are set on
3225	reset when the event loop detects that).	3615	C<ev_async_send>, reset when the event loop detects that).
3226		3616
3227	This call incurs the overhead of a system call only once per event loop	3617	This call incurs the overhead of at most one extra system call per event
3228	iteration, so while the overhead might be noticeable, it doesn't apply to	3618	loop iteration, if the event loop is blocked, and no syscall at all if
3229	repeated calls to C<ev_async_send> for the same event loop.	3619	the event loop (or your program) is processing events. That means that
		3620	repeated calls are basically free (there is no need to avoid calls for
		3621	performance reasons) and that the overhead becomes smaller (typically
		3622	zero) under load.
3230		3623
3231	=item bool = ev_async_pending (ev_async *)	3624	=item bool = ev_async_pending (ev_async *)
3232		3625
3233	Returns a non-zero value when C<ev_async_send> has been called on the	3626	Returns a non-zero value when C<ev_async_send> has been called on the
3234	watcher but the event has not yet been processed (or even noted) by the	3627	watcher but the event has not yet been processed (or even noted) by the
…		…
3251		3644
3252	There are some other functions of possible interest. Described. Here. Now.	3645	There are some other functions of possible interest. Described. Here. Now.
3253		3646
3254	=over 4	3647	=over 4
3255		3648
3256	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3649	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3257		3650
3258	This function combines a simple timer and an I/O watcher, calls your	3651	This function combines a simple timer and an I/O watcher, calls your
3259	callback on whichever event happens first and automatically stops both	3652	callback on whichever event happens first and automatically stops both
3260	watchers. This is useful if you want to wait for a single event on an fd	3653	watchers. This is useful if you want to wait for a single event on an fd
3261	or timeout without having to allocate/configure/start/stop/free one or	3654	or timeout without having to allocate/configure/start/stop/free one or
…		…
3289	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3682	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3290		3683
3291	=item ev_feed_fd_event (loop, int fd, int revents)	3684	=item ev_feed_fd_event (loop, int fd, int revents)
3292		3685
3293	Feed an event on the given fd, as if a file descriptor backend detected	3686	Feed an event on the given fd, as if a file descriptor backend detected
3294	the given events it.	3687	the given events.
3295		3688
3296	=item ev_feed_signal_event (loop, int signum)	3689	=item ev_feed_signal_event (loop, int signum)
3297		3690
3298	Feed an event as if the given signal occurred (C<loop> must be the default	3691	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3299	loop!).	3692	which is async-safe.
3300		3693
3301	=back	3694	=back
		3695
		3696
		3697	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3698
		3699	This section explains some common idioms that are not immediately
		3700	obvious. Note that examples are sprinkled over the whole manual, and this
		3701	section only contains stuff that wouldn't fit anywhere else.
		3702
		3703	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3704
		3705	Each watcher has, by default, a C<void *data> member that you can read
		3706	or modify at any time: libev will completely ignore it. This can be used
		3707	to associate arbitrary data with your watcher. If you need more data and
		3708	don't want to allocate memory separately and store a pointer to it in that
		3709	data member, you can also "subclass" the watcher type and provide your own
		3710	data:
		3711
		3712	struct my_io
		3713	{
		3714	ev_io io;
		3715	int otherfd;
		3716	void *somedata;
		3717	struct whatever *mostinteresting;
		3718	};
		3719
		3720	...
		3721	struct my_io w;
		3722	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3723
		3724	And since your callback will be called with a pointer to the watcher, you
		3725	can cast it back to your own type:
		3726
		3727	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3728	{
		3729	struct my_io *w = (struct my_io *)w_;
		3730	...
		3731	}
		3732
		3733	More interesting and less C-conformant ways of casting your callback
		3734	function type instead have been omitted.
		3735
		3736	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3737
		3738	Another common scenario is to use some data structure with multiple
		3739	embedded watchers, in effect creating your own watcher that combines
		3740	multiple libev event sources into one "super-watcher":
		3741
		3742	struct my_biggy
		3743	{
		3744	int some_data;
		3745	ev_timer t1;
		3746	ev_timer t2;
		3747	}
		3748
		3749	In this case getting the pointer to C<my_biggy> is a bit more
		3750	complicated: Either you store the address of your C<my_biggy> struct in
		3751	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3752	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3753	real programmers):
		3754
		3755	#include <stddef.h>
		3756
		3757	static void
		3758	t1_cb (EV_P_ ev_timer *w, int revents)
		3759	{
		3760	struct my_biggy big = (struct my_biggy *)
		3761	(((char *)w) - offsetof (struct my_biggy, t1));
		3762	}
		3763
		3764	static void
		3765	t2_cb (EV_P_ ev_timer *w, int revents)
		3766	{
		3767	struct my_biggy big = (struct my_biggy *)
		3768	(((char *)w) - offsetof (struct my_biggy, t2));
		3769	}
		3770
		3771	=head2 AVOIDING FINISHING BEFORE RETURNING
		3772
		3773	Often you have structures like this in event-based programs:
		3774
		3775	callback ()
		3776	{
		3777	free (request);
		3778	}
		3779
		3780	request = start_new_request (..., callback);
		3781
		3782	The intent is to start some "lengthy" operation. The C<request> could be
		3783	used to cancel the operation, or do other things with it.
		3784
		3785	It's not uncommon to have code paths in C<start_new_request> that
		3786	immediately invoke the callback, for example, to report errors. Or you add
		3787	some caching layer that finds that it can skip the lengthy aspects of the
		3788	operation and simply invoke the callback with the result.
		3789
		3790	The problem here is that this will happen I<before> C<start_new_request>
		3791	has returned, so C<request> is not set.
		3792
		3793	Even if you pass the request by some safer means to the callback, you
		3794	might want to do something to the request after starting it, such as
		3795	canceling it, which probably isn't working so well when the callback has
		3796	already been invoked.
		3797
		3798	A common way around all these issues is to make sure that
		3799	C<start_new_request> I<always> returns before the callback is invoked. If
		3800	C<start_new_request> immediately knows the result, it can artificially
		3801	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3802	example, or more sneakily, by reusing an existing (stopped) watcher and
		3803	pushing it into the pending queue:
		3804
		3805	ev_set_cb (watcher, callback);
		3806	ev_feed_event (EV_A_ watcher, 0);
		3807
		3808	This way, C<start_new_request> can safely return before the callback is
		3809	invoked, while not delaying callback invocation too much.
		3810
		3811	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3812
		3813	Often (especially in GUI toolkits) there are places where you have
		3814	I<modal> interaction, which is most easily implemented by recursively
		3815	invoking C<ev_run>.
		3816
		3817	This brings the problem of exiting - a callback might want to finish the
		3818	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3819	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3820	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3821	other combination: In these cases, a simple C<ev_break> will not work.
		3822
		3823	The solution is to maintain "break this loop" variable for each C<ev_run>
		3824	invocation, and use a loop around C<ev_run> until the condition is
		3825	triggered, using C<EVRUN_ONCE>:
		3826
		3827	// main loop
		3828	int exit_main_loop = 0;
		3829
		3830	while (!exit_main_loop)
		3831	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3832
		3833	// in a modal watcher
		3834	int exit_nested_loop = 0;
		3835
		3836	while (!exit_nested_loop)
		3837	ev_run (EV_A_ EVRUN_ONCE);
		3838
		3839	To exit from any of these loops, just set the corresponding exit variable:
		3840
		3841	// exit modal loop
		3842	exit_nested_loop = 1;
		3843
		3844	// exit main program, after modal loop is finished
		3845	exit_main_loop = 1;
		3846
		3847	// exit both
		3848	exit_main_loop = exit_nested_loop = 1;
		3849
		3850	=head2 THREAD LOCKING EXAMPLE
		3851
		3852	Here is a fictitious example of how to run an event loop in a different
		3853	thread from where callbacks are being invoked and watchers are
		3854	created/added/removed.
		3855
		3856	For a real-world example, see the C<EV::Loop::Async> perl module,
		3857	which uses exactly this technique (which is suited for many high-level
		3858	languages).
		3859
		3860	The example uses a pthread mutex to protect the loop data, a condition
		3861	variable to wait for callback invocations, an async watcher to notify the
		3862	event loop thread and an unspecified mechanism to wake up the main thread.
		3863
		3864	First, you need to associate some data with the event loop:
		3865
		3866	typedef struct {
		3867	pthread_mutex_t lock; /* global loop lock */
		3868	pthread_t tid;
		3869	pthread_cond_t invoke_cv;
		3870	ev_async async_w;
		3871	} userdata;
		3872
		3873	void prepare_loop (EV_P)
		3874	{
		3875	// for simplicity, we use a static userdata struct.
		3876	static userdata u;
		3877
		3878	ev_async_init (&u.async_w, async_cb);
		3879	ev_async_start (EV_A_ &u.async_w);
		3880
		3881	pthread_mutex_init (&u.lock, 0);
		3882	pthread_cond_init (&u.invoke_cv, 0);
		3883
		3884	// now associate this with the loop
		3885	ev_set_userdata (EV_A_ &u);
		3886	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3887	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3888
		3889	// then create the thread running ev_run
		3890	pthread_create (&u.tid, 0, l_run, EV_A);
		3891	}
		3892
		3893	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3894	solely to wake up the event loop so it takes notice of any new watchers
		3895	that might have been added:
		3896
		3897	static void
		3898	async_cb (EV_P_ ev_async *w, int revents)
		3899	{
		3900	// just used for the side effects
		3901	}
		3902
		3903	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3904	protecting the loop data, respectively.
		3905
		3906	static void
		3907	l_release (EV_P)
		3908	{
		3909	userdata *u = ev_userdata (EV_A);
		3910	pthread_mutex_unlock (&u->lock);
		3911	}
		3912
		3913	static void
		3914	l_acquire (EV_P)
		3915	{
		3916	userdata *u = ev_userdata (EV_A);
		3917	pthread_mutex_lock (&u->lock);
		3918	}
		3919
		3920	The event loop thread first acquires the mutex, and then jumps straight
		3921	into C<ev_run>:
		3922
		3923	void *
		3924	l_run (void *thr_arg)
		3925	{
		3926	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3927
		3928	l_acquire (EV_A);
		3929	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3930	ev_run (EV_A_ 0);
		3931	l_release (EV_A);
		3932
		3933	return 0;
		3934	}
		3935
		3936	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3937	signal the main thread via some unspecified mechanism (signals? pipe
		3938	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3939	have been called (in a while loop because a) spurious wakeups are possible
		3940	and b) skipping inter-thread-communication when there are no pending
		3941	watchers is very beneficial):
		3942
		3943	static void
		3944	l_invoke (EV_P)
		3945	{
		3946	userdata *u = ev_userdata (EV_A);
		3947
		3948	while (ev_pending_count (EV_A))
		3949	{
		3950	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3951	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3952	}
		3953	}
		3954
		3955	Now, whenever the main thread gets told to invoke pending watchers, it
		3956	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3957	thread to continue:
		3958
		3959	static void
		3960	real_invoke_pending (EV_P)
		3961	{
		3962	userdata *u = ev_userdata (EV_A);
		3963
		3964	pthread_mutex_lock (&u->lock);
		3965	ev_invoke_pending (EV_A);
		3966	pthread_cond_signal (&u->invoke_cv);
		3967	pthread_mutex_unlock (&u->lock);
		3968	}
		3969
		3970	Whenever you want to start/stop a watcher or do other modifications to an
		3971	event loop, you will now have to lock:
		3972
		3973	ev_timer timeout_watcher;
		3974	userdata *u = ev_userdata (EV_A);
		3975
		3976	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3977
		3978	pthread_mutex_lock (&u->lock);
		3979	ev_timer_start (EV_A_ &timeout_watcher);
		3980	ev_async_send (EV_A_ &u->async_w);
		3981	pthread_mutex_unlock (&u->lock);
		3982
		3983	Note that sending the C<ev_async> watcher is required because otherwise
		3984	an event loop currently blocking in the kernel will have no knowledge
		3985	about the newly added timer. By waking up the loop it will pick up any new
		3986	watchers in the next event loop iteration.
		3987
		3988	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3989
		3990	While the overhead of a callback that e.g. schedules a thread is small, it
		3991	is still an overhead. If you embed libev, and your main usage is with some
		3992	kind of threads or coroutines, you might want to customise libev so that
		3993	doesn't need callbacks anymore.
		3994
		3995	Imagine you have coroutines that you can switch to using a function
		3996	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3997	and that due to some magic, the currently active coroutine is stored in a
		3998	global called C<current_coro>. Then you can build your own "wait for libev
		3999	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		4000	the differing C<;> conventions):
		4001
		4002	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4003	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4004
		4005	That means instead of having a C callback function, you store the
		4006	coroutine to switch to in each watcher, and instead of having libev call
		4007	your callback, you instead have it switch to that coroutine.
		4008
		4009	A coroutine might now wait for an event with a function called
		4010	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4011	matter when, or whether the watcher is active or not when this function is
		4012	called):
		4013
		4014	void
		4015	wait_for_event (ev_watcher *w)
		4016	{
		4017	ev_set_cb (w, current_coro);
		4018	switch_to (libev_coro);
		4019	}
		4020
		4021	That basically suspends the coroutine inside C<wait_for_event> and
		4022	continues the libev coroutine, which, when appropriate, switches back to
		4023	this or any other coroutine.
		4024
		4025	You can do similar tricks if you have, say, threads with an event queue -
		4026	instead of storing a coroutine, you store the queue object and instead of
		4027	switching to a coroutine, you push the watcher onto the queue and notify
		4028	any waiters.
		4029
		4030	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4031	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4032
		4033	// my_ev.h
		4034	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4035	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4036	#include "../libev/ev.h"
		4037
		4038	// my_ev.c
		4039	#define EV_H "my_ev.h"
		4040	#include "../libev/ev.c"
		4041
		4042	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4043	F<my_ev.c> into your project. When properly specifying include paths, you
		4044	can even use F<ev.h> as header file name directly.
3302		4045
3303		4046
3304	=head1 LIBEVENT EMULATION	4047	=head1 LIBEVENT EMULATION
3305		4048
3306	Libev offers a compatibility emulation layer for libevent. It cannot	4049	Libev offers a compatibility emulation layer for libevent. It cannot
3307	emulate the internals of libevent, so here are some usage hints:	4050	emulate the internals of libevent, so here are some usage hints:
3308		4051
3309	=over 4	4052	=over 4
		4053
		4054	=item * Only the libevent-1.4.1-beta API is being emulated.
		4055
		4056	This was the newest libevent version available when libev was implemented,
		4057	and is still mostly unchanged in 2010.
3310		4058
3311	=item * Use it by including <event.h>, as usual.	4059	=item * Use it by including <event.h>, as usual.
3312		4060
3313	=item * The following members are fully supported: ev_base, ev_callback,	4061	=item * The following members are fully supported: ev_base, ev_callback,
3314	ev_arg, ev_fd, ev_res, ev_events.	4062	ev_arg, ev_fd, ev_res, ev_events.
…		…
3320	=item * Priorities are not currently supported. Initialising priorities	4068	=item * Priorities are not currently supported. Initialising priorities
3321	will fail and all watchers will have the same priority, even though there	4069	will fail and all watchers will have the same priority, even though there
3322	is an ev_pri field.	4070	is an ev_pri field.
3323		4071
3324	=item * In libevent, the last base created gets the signals, in libev, the	4072	=item * In libevent, the last base created gets the signals, in libev, the
3325	first base created (== the default loop) gets the signals.	4073	base that registered the signal gets the signals.
3326		4074
3327	=item * Other members are not supported.	4075	=item * Other members are not supported.
3328		4076
3329	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4077	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3330	to use the libev header file and library.	4078	to use the libev header file and library.
3331		4079
3332	=back	4080	=back
3333		4081
3334	=head1 C++ SUPPORT	4082	=head1 C++ SUPPORT
		4083
		4084	=head2 C API
		4085
		4086	The normal C API should work fine when used from C++: both ev.h and the
		4087	libev sources can be compiled as C++. Therefore, code that uses the C API
		4088	will work fine.
		4089
		4090	Proper exception specifications might have to be added to callbacks passed
		4091	to libev: exceptions may be thrown only from watcher callbacks, all other
		4092	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4093	callbacks) must not throw exceptions, and might need a C<noexcept>
		4094	specification. If you have code that needs to be compiled as both C and
		4095	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4096
		4097	static void
		4098	fatal_error (const char *msg) EV_NOEXCEPT
		4099	{
		4100	perror (msg);
		4101	abort ();
		4102	}
		4103
		4104	...
		4105	ev_set_syserr_cb (fatal_error);
		4106
		4107	The only API functions that can currently throw exceptions are C<ev_run>,
		4108	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4109	because it runs cleanup watchers).
		4110
		4111	Throwing exceptions in watcher callbacks is only supported if libev itself
		4112	is compiled with a C++ compiler or your C and C++ environments allow
		4113	throwing exceptions through C libraries (most do).
		4114
		4115	=head2 C++ API
3335		4116
3336	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4117	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3337	you to use some convenience methods to start/stop watchers and also change	4118	you to use some convenience methods to start/stop watchers and also change
3338	the callback model to a model using method callbacks on objects.	4119	the callback model to a model using method callbacks on objects.
3339		4120
3340	To use it,	4121	To use it,
3341		4122
3342	#include <ev++.h>	4123	#include <ev++.h>
3343		4124
3344	This automatically includes F<ev.h> and puts all of its definitions (many	4125	This automatically includes F<ev.h> and puts all of its definitions (many
3345	of them macros) into the global namespace. All C++ specific things are	4126	of them macros) into the global namespace. All C++ specific things are
3346	put into the C<ev> namespace. It should support all the same embedding	4127	put into the C<ev> namespace. It should support all the same embedding
…		…
3349	Care has been taken to keep the overhead low. The only data member the C++	4130	Care has been taken to keep the overhead low. The only data member the C++
3350	classes add (compared to plain C-style watchers) is the event loop pointer	4131	classes add (compared to plain C-style watchers) is the event loop pointer
3351	that the watcher is associated with (or no additional members at all if	4132	that the watcher is associated with (or no additional members at all if
3352	you disable C<EV_MULTIPLICITY> when embedding libev).	4133	you disable C<EV_MULTIPLICITY> when embedding libev).
3353		4134
3354	Currently, functions, and static and non-static member functions can be	4135	Currently, functions, static and non-static member functions and classes
3355	used as callbacks. Other types should be easy to add as long as they only	4136	with C<operator ()> can be used as callbacks. Other types should be easy
3356	need one additional pointer for context. If you need support for other	4137	to add as long as they only need one additional pointer for context. If
3357	types of functors please contact the author (preferably after implementing	4138	you need support for other types of functors please contact the author
3358	it).	4139	(preferably after implementing it).
		4140
		4141	For all this to work, your C++ compiler either has to use the same calling
		4142	conventions as your C compiler (for static member functions), or you have
		4143	to embed libev and compile libev itself as C++.
3359		4144
3360	Here is a list of things available in the C<ev> namespace:	4145	Here is a list of things available in the C<ev> namespace:
3361		4146
3362	=over 4	4147	=over 4
3363		4148
…		…
3373	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4158	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3374		4159
3375	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4160	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3376	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4161	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3377	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4162	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3378	defines by many implementations.	4163	defined by many implementations.
3379		4164
3380	All of those classes have these methods:	4165	All of those classes have these methods:
3381		4166
3382	=over 4	4167	=over 4
3383		4168
…		…
3445	void operator() (ev::io &w, int revents)	4230	void operator() (ev::io &w, int revents)
3446	{	4231	{
3447	...	4232	...
3448	}	4233	}
3449	}	4234	}
3450		4235
3451	myfunctor f;	4236	myfunctor f;
3452		4237
3453	ev::io w;	4238	ev::io w;
3454	w.set (&f);	4239	w.set (&f);
3455		4240
…		…
3473	Associates a different C<struct ev_loop> with this watcher. You can only	4258	Associates a different C<struct ev_loop> with this watcher. You can only
3474	do this when the watcher is inactive (and not pending either).	4259	do this when the watcher is inactive (and not pending either).
3475		4260
3476	=item w->set ([arguments])	4261	=item w->set ([arguments])
3477		4262
3478	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4263	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3479	method or a suitable start method must be called at least once. Unlike the	4264	with the same arguments. Either this method or a suitable start method
3480	C counterpart, an active watcher gets automatically stopped and restarted	4265	must be called at least once. Unlike the C counterpart, an active watcher
3481	when reconfiguring it with this method.	4266	gets automatically stopped and restarted when reconfiguring it with this
		4267	method.
		4268
		4269	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4270	clashing with the C<set (loop)> method.
		4271
		4272	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4273	new event mask only, and internally calls C<ev_io_modfify>.
3482		4274
3483	=item w->start ()	4275	=item w->start ()
3484		4276
3485	Starts the watcher. Note that there is no C<loop> argument, as the	4277	Starts the watcher. Note that there is no C<loop> argument, as the
3486	constructor already stores the event loop.	4278	constructor already stores the event loop.
…		…
3516	watchers in the constructor.	4308	watchers in the constructor.
3517		4309
3518	class myclass	4310	class myclass
3519	{	4311	{
3520	ev::io io ; void io_cb (ev::io &w, int revents);	4312	ev::io io ; void io_cb (ev::io &w, int revents);
3521	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4313	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3522	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4314	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3523		4315
3524	myclass (int fd)	4316	myclass (int fd)
3525	{	4317	{
3526	io .set <myclass, &myclass::io_cb > (this);	4318	io .set <myclass, &myclass::io_cb > (this);
…		…
3577	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4369	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3578		4370
3579	=item D	4371	=item D
3580		4372
3581	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4373	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3582	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4374	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3583		4375
3584	=item Ocaml	4376	=item Ocaml
3585		4377
3586	Erkki Seppala has written Ocaml bindings for libev, to be found at	4378	Erkki Seppala has written Ocaml bindings for libev, to be found at
3587	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4379	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3590		4382
3591	Brian Maher has written a partial interface to libev for lua (at the	4383	Brian Maher has written a partial interface to libev for lua (at the
3592	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4384	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3593	L<http://github.com/brimworks/lua-ev>.	4385	L<http://github.com/brimworks/lua-ev>.
3594		4386
		4387	=item Javascript
		4388
		4389	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4390
		4391	=item Others
		4392
		4393	There are others, and I stopped counting.
		4394
3595	=back	4395	=back
3596		4396
3597		4397
3598	=head1 MACRO MAGIC	4398	=head1 MACRO MAGIC
3599		4399
…		…
3635	suitable for use with C<EV_A>.	4435	suitable for use with C<EV_A>.
3636		4436
3637	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4437	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3638		4438
3639	Similar to the other two macros, this gives you the value of the default	4439	Similar to the other two macros, this gives you the value of the default
3640	loop, if multiple loops are supported ("ev loop default").	4440	loop, if multiple loops are supported ("ev loop default"). The default loop
		4441	will be initialised if it isn't already initialised.
		4442
		4443	For non-multiplicity builds, these macros do nothing, so you always have
		4444	to initialise the loop somewhere.
3641		4445
3642	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4446	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3643		4447
3644	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4448	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3645	default loop has been initialised (C<UC> == unchecked). Their behaviour	4449	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3712	ev_vars.h	4516	ev_vars.h
3713	ev_wrap.h	4517	ev_wrap.h
3714		4518
3715	ev_win32.c required on win32 platforms only	4519	ev_win32.c required on win32 platforms only
3716		4520
3717	ev_select.c only when select backend is enabled (which is enabled by default)	4521	ev_select.c only when select backend is enabled
3718	ev_poll.c only when poll backend is enabled (disabled by default)	4522	ev_poll.c only when poll backend is enabled
3719	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4523	ev_epoll.c only when the epoll backend is enabled
		4524	ev_linuxaio.c only when the linux aio backend is enabled
		4525	ev_iouring.c only when the linux io_uring backend is enabled
3720	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4526	ev_kqueue.c only when the kqueue backend is enabled
3721	ev_port.c only when the solaris port backend is enabled (disabled by default)	4527	ev_port.c only when the solaris port backend is enabled
3722		4528
3723	F<ev.c> includes the backend files directly when enabled, so you only need	4529	F<ev.c> includes the backend files directly when enabled, so you only need
3724	to compile this single file.	4530	to compile this single file.
3725		4531
3726	=head3 LIBEVENT COMPATIBILITY API	4532	=head3 LIBEVENT COMPATIBILITY API
…		…
3790	supported). It will also not define any of the structs usually found in	4596	supported). It will also not define any of the structs usually found in
3791	F<event.h> that are not directly supported by the libev core alone.	4597	F<event.h> that are not directly supported by the libev core alone.
3792		4598
3793	In standalone mode, libev will still try to automatically deduce the	4599	In standalone mode, libev will still try to automatically deduce the
3794	configuration, but has to be more conservative.	4600	configuration, but has to be more conservative.
		4601
		4602	=item EV_USE_FLOOR
		4603
		4604	If defined to be C<1>, libev will use the C<floor ()> function for its
		4605	periodic reschedule calculations, otherwise libev will fall back on a
		4606	portable (slower) implementation. If you enable this, you usually have to
		4607	link against libm or something equivalent. Enabling this when the C<floor>
		4608	function is not available will fail, so the safe default is to not enable
		4609	this.
3795		4610
3796	=item EV_USE_MONOTONIC	4611	=item EV_USE_MONOTONIC
3797		4612
3798	If defined to be C<1>, libev will try to detect the availability of the	4613	If defined to be C<1>, libev will try to detect the availability of the
3799	monotonic clock option at both compile time and runtime. Otherwise no	4614	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3836	available and will probe for kernel support at runtime. This will improve	4651	available and will probe for kernel support at runtime. This will improve
3837	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4652	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3838	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4653	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3839	2.7 or newer, otherwise disabled.	4654	2.7 or newer, otherwise disabled.
3840		4655
		4656	=item EV_USE_SIGNALFD
		4657
		4658	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4659	available and will probe for kernel support at runtime. This enables
		4660	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4661	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4662	2.7 or newer, otherwise disabled.
		4663
		4664	=item EV_USE_TIMERFD
		4665
		4666	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4667	available and will probe for kernel support at runtime. This allows
		4668	libev to detect time jumps accurately. If undefined, it will be enabled
		4669	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4670	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4671
		4672	=item EV_USE_EVENTFD
		4673
		4674	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4675	available and will probe for kernel support at runtime. This will improve
		4676	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4677	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4678	2.7 or newer, otherwise disabled.
		4679
3841	=item EV_USE_SELECT	4680	=item EV_USE_SELECT
3842		4681
3843	If undefined or defined to be C<1>, libev will compile in support for the	4682	If undefined or defined to be C<1>, libev will compile in support for the
3844	C<select>(2) backend. No attempt at auto-detection will be done: if no	4683	C<select>(2) backend. No attempt at auto-detection will be done: if no
3845	other method takes over, select will be it. Otherwise the select backend	4684	other method takes over, select will be it. Otherwise the select backend
…		…
3885	If programs implement their own fd to handle mapping on win32, then this	4724	If programs implement their own fd to handle mapping on win32, then this
3886	macro can be used to override the C<close> function, useful to unregister	4725	macro can be used to override the C<close> function, useful to unregister
3887	file descriptors again. Note that the replacement function has to close	4726	file descriptors again. Note that the replacement function has to close
3888	the underlying OS handle.	4727	the underlying OS handle.
3889		4728
		4729	=item EV_USE_WSASOCKET
		4730
		4731	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4732	communication socket, which works better in some environments. Otherwise,
		4733	the normal C<socket> function will be used, which works better in other
		4734	environments.
		4735
3890	=item EV_USE_POLL	4736	=item EV_USE_POLL
3891		4737
3892	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4738	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3893	backend. Otherwise it will be enabled on non-win32 platforms. It	4739	backend. Otherwise it will be enabled on non-win32 platforms. It
3894	takes precedence over select.	4740	takes precedence over select.
…		…
3898	If defined to be C<1>, libev will compile in support for the Linux	4744	If defined to be C<1>, libev will compile in support for the Linux
3899	C<epoll>(7) backend. Its availability will be detected at runtime,	4745	C<epoll>(7) backend. Its availability will be detected at runtime,
3900	otherwise another method will be used as fallback. This is the preferred	4746	otherwise another method will be used as fallback. This is the preferred
3901	backend for GNU/Linux systems. If undefined, it will be enabled if the	4747	backend for GNU/Linux systems. If undefined, it will be enabled if the
3902	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4748	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4749
		4750	=item EV_USE_LINUXAIO
		4751
		4752	If defined to be C<1>, libev will compile in support for the Linux aio
		4753	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4754	enabled on linux, otherwise disabled.
		4755
		4756	=item EV_USE_IOURING
		4757
		4758	If defined to be C<1>, libev will compile in support for the Linux
		4759	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4760	current limitations it has to be requested explicitly. If undefined, it
		4761	will be enabled on linux, otherwise disabled.
3903		4762
3904	=item EV_USE_KQUEUE	4763	=item EV_USE_KQUEUE
3905		4764
3906	If defined to be C<1>, libev will compile in support for the BSD style	4765	If defined to be C<1>, libev will compile in support for the BSD style
3907	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4766	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3929	If defined to be C<1>, libev will compile in support for the Linux inotify	4788	If defined to be C<1>, libev will compile in support for the Linux inotify
3930	interface to speed up C<ev_stat> watchers. Its actual availability will	4789	interface to speed up C<ev_stat> watchers. Its actual availability will
3931	be detected at runtime. If undefined, it will be enabled if the headers	4790	be detected at runtime. If undefined, it will be enabled if the headers
3932	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4791	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3933		4792
		4793	=item EV_NO_SMP
		4794
		4795	If defined to be C<1>, libev will assume that memory is always coherent
		4796	between threads, that is, threads can be used, but threads never run on
		4797	different cpus (or different cpu cores). This reduces dependencies
		4798	and makes libev faster.
		4799
		4800	=item EV_NO_THREADS
		4801
		4802	If defined to be C<1>, libev will assume that it will never be called from
		4803	different threads (that includes signal handlers), which is a stronger
		4804	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4805	libev faster.
		4806
3934	=item EV_ATOMIC_T	4807	=item EV_ATOMIC_T
3935		4808
3936	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4809	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3937	access is atomic with respect to other threads or signal contexts. No such	4810	access is atomic with respect to other threads or signal contexts. No
3938	type is easily found in the C language, so you can provide your own type	4811	such type is easily found in the C language, so you can provide your own
3939	that you know is safe for your purposes. It is used both for signal handler "locking"	4812	type that you know is safe for your purposes. It is used both for signal
3940	as well as for signal and thread safety in C<ev_async> watchers.	4813	handler "locking" as well as for signal and thread safety in C<ev_async>
		4814	watchers.
3941		4815
3942	In the absence of this define, libev will use C<sig_atomic_t volatile>	4816	In the absence of this define, libev will use C<sig_atomic_t volatile>
3943	(from F<signal.h>), which is usually good enough on most platforms.	4817	(from F<signal.h>), which is usually good enough on most platforms.
3944		4818
3945	=item EV_H (h)	4819	=item EV_H (h)
…		…
3972	will have the C<struct ev_loop *> as first argument, and you can create	4846	will have the C<struct ev_loop *> as first argument, and you can create
3973	additional independent event loops. Otherwise there will be no support	4847	additional independent event loops. Otherwise there will be no support
3974	for multiple event loops and there is no first event loop pointer	4848	for multiple event loops and there is no first event loop pointer
3975	argument. Instead, all functions act on the single default loop.	4849	argument. Instead, all functions act on the single default loop.
3976		4850
		4851	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4852	default loop when multiplicity is switched off - you always have to
		4853	initialise the loop manually in this case.
		4854
3977	=item EV_MINPRI	4855	=item EV_MINPRI
3978		4856
3979	=item EV_MAXPRI	4857	=item EV_MAXPRI
3980		4858
3981	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4859	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4017	#define EV_USE_POLL 1	4895	#define EV_USE_POLL 1
4018	#define EV_CHILD_ENABLE 1	4896	#define EV_CHILD_ENABLE 1
4019	#define EV_ASYNC_ENABLE 1	4897	#define EV_ASYNC_ENABLE 1
4020		4898
4021	The actual value is a bitset, it can be a combination of the following	4899	The actual value is a bitset, it can be a combination of the following
4022	values:	4900	values (by default, all of these are enabled):
4023		4901
4024	=over 4	4902	=over 4
4025		4903
4026	=item C<1> - faster/larger code	4904	=item C<1> - faster/larger code
4027		4905
…		…
4031	code size by roughly 30% on amd64).	4909	code size by roughly 30% on amd64).
4032		4910
4033	When optimising for size, use of compiler flags such as C<-Os> with	4911	When optimising for size, use of compiler flags such as C<-Os> with
4034	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4912	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4035	assertions.	4913	assertions.
		4914
		4915	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4916	(e.g. gcc with C<-Os>).
4036		4917
4037	=item C<2> - faster/larger data structures	4918	=item C<2> - faster/larger data structures
4038		4919
4039	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4920	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4040	hash table sizes and so on. This will usually further increase code size	4921	hash table sizes and so on. This will usually further increase code size
4041	and can additionally have an effect on the size of data structures at	4922	and can additionally have an effect on the size of data structures at
4042	runtime.	4923	runtime.
4043		4924
		4925	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4926	(e.g. gcc with C<-Os>).
		4927
4044	=item C<4> - full API configuration	4928	=item C<4> - full API configuration
4045		4929
4046	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4930	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4047	enables multiplicity (C<EV_MULTIPLICITY>=1).	4931	enables multiplicity (C<EV_MULTIPLICITY>=1).
4048		4932
…		…
4078		4962
4079	With an intelligent-enough linker (gcc+binutils are intelligent enough	4963	With an intelligent-enough linker (gcc+binutils are intelligent enough
4080	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4964	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4081	your program might be left out as well - a binary starting a timer and an	4965	your program might be left out as well - a binary starting a timer and an
4082	I/O watcher then might come out at only 5Kb.	4966	I/O watcher then might come out at only 5Kb.
		4967
		4968	=item EV_API_STATIC
		4969
		4970	If this symbol is defined (by default it is not), then all identifiers
		4971	will have static linkage. This means that libev will not export any
		4972	identifiers, and you cannot link against libev anymore. This can be useful
		4973	when you embed libev, only want to use libev functions in a single file,
		4974	and do not want its identifiers to be visible.
		4975
		4976	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4977	wants to use libev.
		4978
		4979	This option only works when libev is compiled with a C compiler, as C++
		4980	doesn't support the required declaration syntax.
4083		4981
4084	=item EV_AVOID_STDIO	4982	=item EV_AVOID_STDIO
4085		4983
4086	If this is set to C<1> at compiletime, then libev will avoid using stdio	4984	If this is set to C<1> at compiletime, then libev will avoid using stdio
4087	functions (printf, scanf, perror etc.). This will increase the code size	4985	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4145	in. If set to C<1>, then verification code will be compiled in, but not	5043	in. If set to C<1>, then verification code will be compiled in, but not
4146	called. If set to C<2>, then the internal verification code will be	5044	called. If set to C<2>, then the internal verification code will be
4147	called once per loop, which can slow down libev. If set to C<3>, then the	5045	called once per loop, which can slow down libev. If set to C<3>, then the
4148	verification code will be called very frequently, which will slow down	5046	verification code will be called very frequently, which will slow down
4149	libev considerably.	5047	libev considerably.
		5048
		5049	Verification errors are reported via C's C<assert> mechanism, so if you
		5050	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
4150		5051
4151	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	5052	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4152	will be C<0>.	5053	will be C<0>.
4153		5054
4154	=item EV_COMMON	5055	=item EV_COMMON
…		…
4231	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5132	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4232		5133
4233	#include "ev_cpp.h"	5134	#include "ev_cpp.h"
4234	#include "ev.c"	5135	#include "ev.c"
4235		5136
4236	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5137	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4237		5138
4238	=head2 THREADS AND COROUTINES	5139	=head2 THREADS AND COROUTINES
4239		5140
4240	=head3 THREADS	5141	=head3 THREADS
4241		5142
…		…
4292	default loop and triggering an C<ev_async> watcher from the default loop	5193	default loop and triggering an C<ev_async> watcher from the default loop
4293	watcher callback into the event loop interested in the signal.	5194	watcher callback into the event loop interested in the signal.
4294		5195
4295	=back	5196	=back
4296		5197
4297	=head4 THREAD LOCKING EXAMPLE	5198	See also L</THREAD LOCKING EXAMPLE>.
4298
4299	Here is a fictitious example of how to run an event loop in a different
4300	thread than where callbacks are being invoked and watchers are
4301	created/added/removed.
4302
4303	For a real-world example, see the C<EV::Loop::Async> perl module,
4304	which uses exactly this technique (which is suited for many high-level
4305	languages).
4306
4307	The example uses a pthread mutex to protect the loop data, a condition
4308	variable to wait for callback invocations, an async watcher to notify the
4309	event loop thread and an unspecified mechanism to wake up the main thread.
4310
4311	First, you need to associate some data with the event loop:
4312
4313	typedef struct {
4314	mutex_t lock; /* global loop lock */
4315	ev_async async_w;
4316	thread_t tid;
4317	cond_t invoke_cv;
4318	} userdata;
4319
4320	void prepare_loop (EV_P)
4321	{
4322	// for simplicity, we use a static userdata struct.
4323	static userdata u;
4324
4325	ev_async_init (&u->async_w, async_cb);
4326	ev_async_start (EV_A_ &u->async_w);
4327
4328	pthread_mutex_init (&u->lock, 0);
4329	pthread_cond_init (&u->invoke_cv, 0);
4330
4331	// now associate this with the loop
4332	ev_set_userdata (EV_A_ u);
4333	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4334	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4335
4336	// then create the thread running ev_loop
4337	pthread_create (&u->tid, 0, l_run, EV_A);
4338	}
4339
4340	The callback for the C<ev_async> watcher does nothing: the watcher is used
4341	solely to wake up the event loop so it takes notice of any new watchers
4342	that might have been added:
4343
4344	static void
4345	async_cb (EV_P_ ev_async *w, int revents)
4346	{
4347	// just used for the side effects
4348	}
4349
4350	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4351	protecting the loop data, respectively.
4352
4353	static void
4354	l_release (EV_P)
4355	{
4356	userdata *u = ev_userdata (EV_A);
4357	pthread_mutex_unlock (&u->lock);
4358	}
4359
4360	static void
4361	l_acquire (EV_P)
4362	{
4363	userdata *u = ev_userdata (EV_A);
4364	pthread_mutex_lock (&u->lock);
4365	}
4366
4367	The event loop thread first acquires the mutex, and then jumps straight
4368	into C<ev_run>:
4369
4370	void *
4371	l_run (void *thr_arg)
4372	{
4373	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4374
4375	l_acquire (EV_A);
4376	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4377	ev_run (EV_A_ 0);
4378	l_release (EV_A);
4379
4380	return 0;
4381	}
4382
4383	Instead of invoking all pending watchers, the C<l_invoke> callback will
4384	signal the main thread via some unspecified mechanism (signals? pipe
4385	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4386	have been called (in a while loop because a) spurious wakeups are possible
4387	and b) skipping inter-thread-communication when there are no pending
4388	watchers is very beneficial):
4389
4390	static void
4391	l_invoke (EV_P)
4392	{
4393	userdata *u = ev_userdata (EV_A);
4394
4395	while (ev_pending_count (EV_A))
4396	{
4397	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4398	pthread_cond_wait (&u->invoke_cv, &u->lock);
4399	}
4400	}
4401
4402	Now, whenever the main thread gets told to invoke pending watchers, it
4403	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4404	thread to continue:
4405
4406	static void
4407	real_invoke_pending (EV_P)
4408	{
4409	userdata *u = ev_userdata (EV_A);
4410
4411	pthread_mutex_lock (&u->lock);
4412	ev_invoke_pending (EV_A);
4413	pthread_cond_signal (&u->invoke_cv);
4414	pthread_mutex_unlock (&u->lock);
4415	}
4416
4417	Whenever you want to start/stop a watcher or do other modifications to an
4418	event loop, you will now have to lock:
4419
4420	ev_timer timeout_watcher;
4421	userdata *u = ev_userdata (EV_A);
4422
4423	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4424
4425	pthread_mutex_lock (&u->lock);
4426	ev_timer_start (EV_A_ &timeout_watcher);
4427	ev_async_send (EV_A_ &u->async_w);
4428	pthread_mutex_unlock (&u->lock);
4429
4430	Note that sending the C<ev_async> watcher is required because otherwise
4431	an event loop currently blocking in the kernel will have no knowledge
4432	about the newly added timer. By waking up the loop it will pick up any new
4433	watchers in the next event loop iteration.
4434		5199
4435	=head3 COROUTINES	5200	=head3 COROUTINES
4436		5201
4437	Libev is very accommodating to coroutines ("cooperative threads"):	5202	Libev is very accommodating to coroutines ("cooperative threads"):
4438	libev fully supports nesting calls to its functions from different	5203	libev fully supports nesting calls to its functions from different
…		…
4603	requires, and its I/O model is fundamentally incompatible with the POSIX	5368	requires, and its I/O model is fundamentally incompatible with the POSIX
4604	model. Libev still offers limited functionality on this platform in	5369	model. Libev still offers limited functionality on this platform in
4605	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5370	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4606	descriptors. This only applies when using Win32 natively, not when using	5371	descriptors. This only applies when using Win32 natively, not when using
4607	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5372	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4608	as every compielr comes with a slightly differently broken/incompatible	5373	as every compiler comes with a slightly differently broken/incompatible
4609	environment.	5374	environment.
4610		5375
4611	Lifting these limitations would basically require the full	5376	Lifting these limitations would basically require the full
4612	re-implementation of the I/O system. If you are into this kind of thing,	5377	re-implementation of the I/O system. If you are into this kind of thing,
4613	then note that glib does exactly that for you in a very portable way (note	5378	then note that glib does exactly that for you in a very portable way (note
…		…
4707	structure (guaranteed by POSIX but not by ISO C for example), but it also	5472	structure (guaranteed by POSIX but not by ISO C for example), but it also
4708	assumes that the same (machine) code can be used to call any watcher	5473	assumes that the same (machine) code can be used to call any watcher
4709	callback: The watcher callbacks have different type signatures, but libev	5474	callback: The watcher callbacks have different type signatures, but libev
4710	calls them using an C<ev_watcher *> internally.	5475	calls them using an C<ev_watcher *> internally.
4711		5476
		5477	=item null pointers and integer zero are represented by 0 bytes
		5478
		5479	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5480	relies on this setting pointers and integers to null.
		5481
		5482	=item pointer accesses must be thread-atomic
		5483
		5484	Accessing a pointer value must be atomic, it must both be readable and
		5485	writable in one piece - this is the case on all current architectures.
		5486
4712	=item C<sig_atomic_t volatile> must be thread-atomic as well	5487	=item C<sig_atomic_t volatile> must be thread-atomic as well
4713		5488
4714	The type C<sig_atomic_t volatile> (or whatever is defined as	5489	The type C<sig_atomic_t volatile> (or whatever is defined as
4715	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5490	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4716	threads. This is not part of the specification for C<sig_atomic_t>, but is	5491	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4724	thread" or will block signals process-wide, both behaviours would	5499	thread" or will block signals process-wide, both behaviours would
4725	be compatible with libev. Interaction between C<sigprocmask> and	5500	be compatible with libev. Interaction between C<sigprocmask> and
4726	C<pthread_sigmask> could complicate things, however.	5501	C<pthread_sigmask> could complicate things, however.
4727		5502
4728	The most portable way to handle signals is to block signals in all threads	5503	The most portable way to handle signals is to block signals in all threads
4729	except the initial one, and run the default loop in the initial thread as	5504	except the initial one, and run the signal handling loop in the initial
4730	well.	5505	thread as well.
4731		5506
4732	=item C<long> must be large enough for common memory allocation sizes	5507	=item C<long> must be large enough for common memory allocation sizes
4733		5508
4734	To improve portability and simplify its API, libev uses C<long> internally	5509	To improve portability and simplify its API, libev uses C<long> internally
4735	instead of C<size_t> when allocating its data structures. On non-POSIX	5510	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4741		5516
4742	The type C<double> is used to represent timestamps. It is required to	5517	The type C<double> is used to represent timestamps. It is required to
4743	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5518	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4744	good enough for at least into the year 4000 with millisecond accuracy	5519	good enough for at least into the year 4000 with millisecond accuracy
4745	(the design goal for libev). This requirement is overfulfilled by	5520	(the design goal for libev). This requirement is overfulfilled by
4746	implementations using IEEE 754, which is basically all existing ones. With	5521	implementations using IEEE 754, which is basically all existing ones.
		5522
4747	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5523	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5524	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5525	is either obsolete or somebody patched it to use C<long double> or
		5526	something like that, just kidding).
4748		5527
4749	=back	5528	=back
4750		5529
4751	If you know of other additional requirements drop me a note.	5530	If you know of other additional requirements drop me a note.
4752		5531
…		…
4814	=item Processing ev_async_send: O(number_of_async_watchers)	5593	=item Processing ev_async_send: O(number_of_async_watchers)
4815		5594
4816	=item Processing signals: O(max_signal_number)	5595	=item Processing signals: O(max_signal_number)
4817		5596
4818	Sending involves a system call I<iff> there were no other C<ev_async_send>	5597	Sending involves a system call I<iff> there were no other C<ev_async_send>
4819	calls in the current loop iteration. Checking for async and signal events	5598	calls in the current loop iteration and the loop is currently
		5599	blocked. Checking for async and signal events involves iterating over all
4820	involves iterating over all running async watchers or all signal numbers.	5600	running async watchers or all signal numbers.
4821		5601
4822	=back	5602	=back
4823		5603
4824		5604
4825	=head1 PORTING FROM LIBEV 3.X TO 4.X	5605	=head1 PORTING FROM LIBEV 3.X TO 4.X
4826		5606
4827	The major version 4 introduced some minor incompatible changes to the API.	5607	The major version 4 introduced some incompatible changes to the API.
4828		5608
4829	At the moment, the C<ev.h> header file tries to implement superficial	5609	At the moment, the C<ev.h> header file provides compatibility definitions
4830	compatibility, so most programs should still compile. Those might be	5610	for all changes, so most programs should still compile. The compatibility
4831	removed in later versions of libev, so better update early than late.	5611	layer might be removed in later versions of libev, so better update to the
		5612	new API early than late.
4832		5613
4833	=over 4	5614	=over 4
		5615
		5616	=item C<EV_COMPAT3> backwards compatibility mechanism
		5617
		5618	The backward compatibility mechanism can be controlled by
		5619	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5620	section.
		5621
		5622	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5623
		5624	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5625
		5626	ev_loop_destroy (EV_DEFAULT_UC);
		5627	ev_loop_fork (EV_DEFAULT);
4834		5628
4835	=item function/symbol renames	5629	=item function/symbol renames
4836		5630
4837	A number of functions and symbols have been renamed:	5631	A number of functions and symbols have been renamed:
4838		5632
…		…
4857	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5651	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4858	as all other watcher types. Note that C<ev_loop_fork> is still called	5652	as all other watcher types. Note that C<ev_loop_fork> is still called
4859	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5653	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4860	typedef.	5654	typedef.
4861		5655
4862	=item C<EV_COMPAT3> backwards compatibility mechanism
4863
4864	The backward compatibility mechanism can be controlled by
4865	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4866	section.
4867
4868	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5656	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4869		5657
4870	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5658	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4871	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5659	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4872	and work, but the library code will of course be larger.	5660	and work, but the library code will of course be larger.
…		…
4879	=over 4	5667	=over 4
4880		5668
4881	=item active	5669	=item active
4882		5670
4883	A watcher is active as long as it has been started and not yet stopped.	5671	A watcher is active as long as it has been started and not yet stopped.
4884	See L<WATCHER STATES> for details.	5672	See L</WATCHER STATES> for details.
4885		5673
4886	=item application	5674	=item application
4887		5675
4888	In this document, an application is whatever is using libev.	5676	In this document, an application is whatever is using libev.
4889		5677
…		…
4925	watchers and events.	5713	watchers and events.
4926		5714
4927	=item pending	5715	=item pending
4928		5716
4929	A watcher is pending as soon as the corresponding event has been	5717	A watcher is pending as soon as the corresponding event has been
4930	detected. See L<WATCHER STATES> for details.	5718	detected. See L</WATCHER STATES> for details.
4931		5719
4932	=item real time	5720	=item real time
4933		5721
4934	The physical time that is observed. It is apparently strictly monotonic :)	5722	The physical time that is observed. It is apparently strictly monotonic :)
4935		5723
4936	=item wall-clock time	5724	=item wall-clock time
4937		5725
4938	The time and date as shown on clocks. Unlike real time, it can actually	5726	The time and date as shown on clocks. Unlike real time, it can actually
4939	be wrong and jump forwards and backwards, e.g. when the you adjust your	5727	be wrong and jump forwards and backwards, e.g. when you adjust your
4940	clock.	5728	clock.
4941		5729
4942	=item watcher	5730	=item watcher
4943		5731
4944	A data structure that describes interest in certain events. Watchers need	5732	A data structure that describes interest in certain events. Watchers need
…		…
4946		5734
4947	=back	5735	=back
4948		5736
4949	=head1 AUTHOR	5737	=head1 AUTHOR
4950		5738
4951	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5739	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5740	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4952		5741

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