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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
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	Returns the current time as libev would use it. Please note that the	178	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	179	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	180	you actually want to know. Also interesting is the combination of
171	C<ev_update_now> and C<ev_now>.	181	C<ev_now_update> and C<ev_now>.
172		182
173	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
174		184
175	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
176	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
177	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
178		194
179	=item int ev_version_major ()	195	=item int ev_version_major ()
180		196
181	=item int ev_version_minor ()	197	=item int ev_version_minor ()
182		198
…		…
193	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
194	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
195	not a problem.	211	not a problem.
196		212
197	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
198	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
199		216
200	assert (("libev version mismatch",	217	assert (("libev version mismatch",
201	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
202	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
203		220
…		…
232	the current system, you would need to look at C<ev_embeddable_backends ()	249	the current system, you would need to look at C<ev_embeddable_backends ()
233	& ev_supported_backends ()>, likewise for recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
234		251
235	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
236		253
237	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
238		255
239	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
240	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
241	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
242	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
248		265
249	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
250	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
251	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
252		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
253	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
254	retries (example requires a standards-compliant C<realloc>).	285	retries.
255		286
256	static void *	287	static void *
257	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
258	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
259	for (;;)	296	for (;;)
260	{	297	{
261	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
262		299
263	if (newptr)	300	if (newptr)
…		…
268	}	305	}
269		306
270	...	307	...
271	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
272		309
273	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
274		311
275	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
276	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
277	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
278	callback is set, then libev will expect it to remedy the situation, no	315	callback is set, then libev will expect it to remedy the situation, no
…		…
290	}	327	}
291		328
292	...	329	...
293	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
294		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
295	=back	345	=back
296		346
297	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
298		348
299	An event loop is described by a C<struct ev_loop *> (the C<struct> is	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
300	I<not> optional in this case unless libev 3 compatibility is disabled, as	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
301	libev 3 had an C<ev_loop> function colliding with the struct name).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
302		352
303	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
304	supports signals and child events, and dynamically created event loops	354	supports child process events, and dynamically created event loops which
305	which do not.	355	do not.
306		356
307	=over 4	357	=over 4
308		358
309	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
310		360
311	This will initialise the default event loop if it hasn't been initialised	361	This returns the "default" event loop object, which is what you should
312	yet and return it. If the default loop could not be initialised, returns	362	normally use when you just need "the event loop". Event loop objects and
313	false. If it already was initialised it simply returns it (and ignores the	363	the C<flags> parameter are described in more detail in the entry for
314	flags. If that is troubling you, check C<ev_backend ()> afterwards).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
315		371
316	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
317	function.	373	function (or via the C<EV_DEFAULT> macro).
318		374
319	Note that this function is I<not> thread-safe, so if you want to use it	375	Note that this function is I<not> thread-safe, so if you want to use it
320	from multiple threads, you have to lock (note also that this is unlikely,	376	from multiple threads, you have to employ some kind of mutex (note also
321	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
322		379
323	The default loop is the only loop that can handle C<ev_signal> and	380	The default loop is the only loop that can handle C<ev_child> watchers,
324	C<ev_child> watchers, and to do this, it always registers a handler	381	and to do this, it always registers a handler for C<SIGCHLD>. If this is
325	for C<SIGCHLD>. If this is a problem for your application you can either	382	a problem for your application you can either create a dynamic loop with
326	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	383	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
327	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
328	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
329		404
330	The flags argument can be used to specify special behaviour or specific	405	The flags argument can be used to specify special behaviour or specific
331	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
332		407
333	The following flags are supported:	408	The following flags are supported:
…		…
343		418
344	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
345	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
346	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
347	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
348	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
349	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
350		427
351	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
352		429
353	Instead of calling C<ev_loop_fork> manually after a fork, you can also	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
354	make libev check for a fork in each iteration by enabling this flag.	431	make libev check for a fork in each iteration by enabling this flag.
355		432
356	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
357	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
358	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
359	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
360	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
361	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
362		440
363	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
364	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
365	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
366		444
367	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
368	environment variable.	446	environment variable.
369		447
370	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
371		449
372	When this flag is specified, then libev will not attempt to use the	450	When this flag is specified, then libev will not attempt to use the
373	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
374	testing, this flag can be useful to conserve inotify file descriptors, as	452	testing, this flag can be useful to conserve inotify file descriptors, as
375	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
376		454
377	=item C<EVFLAG_SIGNALFD>	455	=item C<EVFLAG_SIGNALFD>
378		456
379	When this flag is specified, then libev will attempt to use the	457	When this flag is specified, then libev will attempt to use the
380	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
381	delivers signals synchronously, which makes it both faster and might make	459	delivers signals synchronously, which makes it both faster and might make
382	it possible to get the queued signal data. It can also simplify signal	460	it possible to get the queued signal data. It can also simplify signal
383	handling with threads, as long as you properly block signals in your	461	handling with threads, as long as you properly block signals in your
384	threads that are not interested in handling them.	462	threads that are not interested in handling them.
385		463
386	Signalfd will not be used by default as this changes your signal mask, and	464	Signalfd will not be used by default as this changes your signal mask, and
387	there are a lot of shoddy libraries and programs (glib's threadpool for	465	there are a lot of shoddy libraries and programs (glib's threadpool for
388	example) that can't properly initialise their signal masks.	466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
389		482
390	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
391		484
392	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
393	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
421	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
422		515
423	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
424	kernels).	517	kernels).
425		518
426	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
427	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
428	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
429	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
430		523
431	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
432	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
433	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
434	descriptor (and unnecessary guessing of parameters), problems with dup and	527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
435	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
436	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
437	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
438	hard to detect.	533	and is of course hard to detect.
439		534
440	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
441	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
442	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
443	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
444	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
445	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
446	events to filter out spurious ones, recreating the set when required. Last	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
447	not least, it also refuses to work with some file descriptors which work	545	not least, it also refuses to work with some file descriptors which work
448	perfectly fine with C<select> (files, many character devices...).	546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
449		551
450	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
451	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
452	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
453	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
465	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
466	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
467	the usage. So sad.	569	the usage. So sad.
468		570
469	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
470	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >>) event interface
		580	available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental and only supports a subset of file types), it is the best
		584	event interface available on linux and might be well worth it enabling it
		585	- if it isn't available in your kernel this will be detected and another
		586	backend will be chosen.
		587
		588	This backend can batch oneshot requests and uses a user-space ring buffer
		589	to receive events. It also doesn't suffer from most of the design problems
		590	of epoll (such as not being able to remove event sources from the epoll
		591	set), and generally sounds too good to be true. Because, this being the
		592	linux kernel, of course it suffers from a whole new set of limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to various
		596	arbitrary limits that can be configured in F</proc/sys/fs/aio-max-nr>
		597	and F</proc/sys/fs/aio-nr>), which could lead to it being skipped during
		598	initialisation.
		599
		600	Most problematic in practise, however, is that, like kqueue, it requires
		601	special support from drivers, and, not surprisingly, not all drivers
		602	implement it. For example, in linux 4.19, tcp sockets, pipes, event fds,
		603	files, F</dev/null> and a few others are supported, but ttys are not, so
		604	this is not (yet?) a generic event polling interface but is probably still
		605	be very useful in a web server or similar program.
471		606
472	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
473	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
474		609
475	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	610	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
490		625
491	It scales in the same way as the epoll backend, but the interface to the	626	It scales in the same way as the epoll backend, but the interface to the
492	kernel is more efficient (which says nothing about its actual speed, of	627	kernel is more efficient (which says nothing about its actual speed, of
493	course). While stopping, setting and starting an I/O watcher does never	628	course). While stopping, setting and starting an I/O watcher does never
494	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	629	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
495	two event changes per incident. Support for C<fork ()> is very bad (but	630	two event changes per incident. Support for C<fork ()> is very bad (you
496	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	631	might have to leak fd's on fork, but it's more sane than epoll) and it
497	cases	632	drops fds silently in similarly hard-to-detect cases.
498		633
499	This backend usually performs well under most conditions.	634	This backend usually performs well under most conditions.
500		635
501	While nominally embeddable in other event loops, this doesn't work	636	While nominally embeddable in other event loops, this doesn't work
502	everywhere, so you might need to test for this. And since it is broken	637	everywhere, so you might need to test for this. And since it is broken
…		…
519	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	654	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
520		655
521	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	656	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
522	it's really slow, but it still scales very well (O(active_fds)).	657	it's really slow, but it still scales very well (O(active_fds)).
523		658
524	Please note that Solaris event ports can deliver a lot of spurious
525	notifications, so you need to use non-blocking I/O or other means to avoid
526	blocking when no data (or space) is available.
527
528	While this backend scales well, it requires one system call per active	659	While this backend scales well, it requires one system call per active
529	file descriptor per loop iteration. For small and medium numbers of file	660	file descriptor per loop iteration. For small and medium numbers of file
530	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	661	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
531	might perform better.	662	might perform better.
532		663
533	On the positive side, with the exception of the spurious readiness	664	On the positive side, this backend actually performed fully to
534	notifications, this backend actually performed fully to specification
535	in all tests and is fully embeddable, which is a rare feat among the	665	specification in all tests and is fully embeddable, which is a rare feat
536	OS-specific backends (I vastly prefer correctness over speed hacks).	666	among the OS-specific backends (I vastly prefer correctness over speed
		667	hacks).
		668
		669	On the negative side, the interface is I<bizarre> - so bizarre that
		670	even sun itself gets it wrong in their code examples: The event polling
		671	function sometimes returns events to the caller even though an error
		672	occurred, but with no indication whether it has done so or not (yes, it's
		673	even documented that way) - deadly for edge-triggered interfaces where you
		674	absolutely have to know whether an event occurred or not because you have
		675	to re-arm the watcher.
		676
		677	Fortunately libev seems to be able to work around these idiocies.
537		678
538	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	679	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
539	C<EVBACKEND_POLL>.	680	C<EVBACKEND_POLL>.
540		681
541	=item C<EVBACKEND_ALL>	682	=item C<EVBACKEND_ALL>
542		683
543	Try all backends (even potentially broken ones that wouldn't be tried	684	Try all backends (even potentially broken ones that wouldn't be tried
544	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	685	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
545	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	686	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
546		687
547	It is definitely not recommended to use this flag.	688	It is definitely not recommended to use this flag, use whatever
		689	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		690	at all.
		691
		692	=item C<EVBACKEND_MASK>
		693
		694	Not a backend at all, but a mask to select all backend bits from a
		695	C<flags> value, in case you want to mask out any backends from a flags
		696	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
548		697
549	=back	698	=back
550		699
551	If one or more of the backend flags are or'ed into the flags value,	700	If one or more of the backend flags are or'ed into the flags value,
552	then only these backends will be tried (in the reverse order as listed	701	then only these backends will be tried (in the reverse order as listed
553	here). If none are specified, all backends in C<ev_recommended_backends	702	here). If none are specified, all backends in C<ev_recommended_backends
554	()> will be tried.	703	()> will be tried.
555		704
556	Example: This is the most typical usage.
557
558	if (!ev_default_loop (0))
559	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
560
561	Example: Restrict libev to the select and poll backends, and do not allow
562	environment settings to be taken into account:
563
564	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
565
566	Example: Use whatever libev has to offer, but make sure that kqueue is
567	used if available (warning, breaks stuff, best use only with your own
568	private event loop and only if you know the OS supports your types of
569	fds):
570
571	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
572
573	=item struct ev_loop *ev_loop_new (unsigned int flags)
574
575	Similar to C<ev_default_loop>, but always creates a new event loop that is
576	always distinct from the default loop.
577
578	Note that this function I<is> thread-safe, and one common way to use
579	libev with threads is indeed to create one loop per thread, and using the
580	default loop in the "main" or "initial" thread.
581
582	Example: Try to create a event loop that uses epoll and nothing else.	705	Example: Try to create a event loop that uses epoll and nothing else.
583		706
584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	707	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
585	if (!epoller)	708	if (!epoller)
586	fatal ("no epoll found here, maybe it hides under your chair");	709	fatal ("no epoll found here, maybe it hides under your chair");
587		710
		711	Example: Use whatever libev has to offer, but make sure that kqueue is
		712	used if available.
		713
		714	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		715
		716	Example: Similarly, on linux, you mgiht want to take advantage of the
		717	linux aio backend if possible, but fall back to something else if that
		718	isn't available.
		719
		720	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		721
588	=item ev_default_destroy ()	722	=item ev_loop_destroy (loop)
589		723
590	Destroys the default loop (frees all memory and kernel state etc.). None	724	Destroys an event loop object (frees all memory and kernel state
591	of the active event watchers will be stopped in the normal sense, so	725	etc.). None of the active event watchers will be stopped in the normal
592	e.g. C<ev_is_active> might still return true. It is your responsibility to	726	sense, so e.g. C<ev_is_active> might still return true. It is your
593	either stop all watchers cleanly yourself I<before> calling this function,	727	responsibility to either stop all watchers cleanly yourself I<before>
594	or cope with the fact afterwards (which is usually the easiest thing, you	728	calling this function, or cope with the fact afterwards (which is usually
595	can just ignore the watchers and/or C<free ()> them for example).	729	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		730	for example).
596		731
597	Note that certain global state, such as signal state (and installed signal	732	Note that certain global state, such as signal state (and installed signal
598	handlers), will not be freed by this function, and related watchers (such	733	handlers), will not be freed by this function, and related watchers (such
599	as signal and child watchers) would need to be stopped manually.	734	as signal and child watchers) would need to be stopped manually.
600		735
601	In general it is not advisable to call this function except in the	736	This function is normally used on loop objects allocated by
602	rare occasion where you really need to free e.g. the signal handling	737	C<ev_loop_new>, but it can also be used on the default loop returned by
		738	C<ev_default_loop>, in which case it is not thread-safe.
		739
		740	Note that it is not advisable to call this function on the default loop
		741	except in the rare occasion where you really need to free its resources.
603	pipe fds. If you need dynamically allocated loops it is better to use	742	If you need dynamically allocated loops it is better to use C<ev_loop_new>
604	C<ev_loop_new> and C<ev_loop_destroy>.	743	and C<ev_loop_destroy>.
605		744
606	=item ev_loop_destroy (loop)	745	=item ev_loop_fork (loop)
607
608	Like C<ev_default_destroy>, but destroys an event loop created by an
609	earlier call to C<ev_loop_new>.
610
611	=item ev_default_fork ()
612		746
613	This function sets a flag that causes subsequent C<ev_run> iterations	747	This function sets a flag that causes subsequent C<ev_run> iterations
614	to reinitialise the kernel state for backends that have one. Despite the	748	to reinitialise the kernel state for backends that have one. Despite
615	name, you can call it anytime, but it makes most sense after forking, in	749	the name, you can call it anytime you are allowed to start or stop
616	the child process (or both child and parent, but that again makes little	750	watchers (except inside an C<ev_prepare> callback), but it makes most
617	sense). You I<must> call it in the child before using any of the libev	751	sense after forking, in the child process. You I<must> call it (or use
618	functions, and it will only take effect at the next C<ev_run> iteration.	752	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
619		753
		754	In addition, if you want to reuse a loop (via this function or
		755	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		756
620	Again, you I<have> to call it on I<any> loop that you want to re-use after	757	Again, you I<have> to call it on I<any> loop that you want to re-use after
621	a fork, I<even if you do not plan to use the loop in the parent>. This is	758	a fork, I<even if you do not plan to use the loop in the parent>. This is
622	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	759	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
623	during fork.	760	during fork.
624		761
625	On the other hand, you only need to call this function in the child	762	On the other hand, you only need to call this function in the child
…		…
628	call it at all (in fact, C<epoll> is so badly broken that it makes a	765	call it at all (in fact, C<epoll> is so badly broken that it makes a
629	difference, but libev will usually detect this case on its own and do a	766	difference, but libev will usually detect this case on its own and do a
630	costly reset of the backend).	767	costly reset of the backend).
631		768
632	The function itself is quite fast and it's usually not a problem to call	769	The function itself is quite fast and it's usually not a problem to call
633	it just in case after a fork. To make this easy, the function will fit in	770	it just in case after a fork.
634	quite nicely into a call to C<pthread_atfork>:
635		771
		772	Example: Automate calling C<ev_loop_fork> on the default loop when
		773	using pthreads.
		774
		775	static void
		776	post_fork_child (void)
		777	{
		778	ev_loop_fork (EV_DEFAULT);
		779	}
		780
		781	...
636	pthread_atfork (0, 0, ev_default_fork);	782	pthread_atfork (0, 0, post_fork_child);
637
638	=item ev_loop_fork (loop)
639
640	Like C<ev_default_fork>, but acts on an event loop created by
641	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
642	after fork that you want to re-use in the child, and how you keep track of
643	them is entirely your own problem.
644		783
645	=item int ev_is_default_loop (loop)	784	=item int ev_is_default_loop (loop)
646		785
647	Returns true when the given loop is, in fact, the default loop, and false	786	Returns true when the given loop is, in fact, the default loop, and false
648	otherwise.	787	otherwise.
…		…
659	prepare and check phases.	798	prepare and check phases.
660		799
661	=item unsigned int ev_depth (loop)	800	=item unsigned int ev_depth (loop)
662		801
663	Returns the number of times C<ev_run> was entered minus the number of	802	Returns the number of times C<ev_run> was entered minus the number of
664	times C<ev_run> was exited, in other words, the recursion depth.	803	times C<ev_run> was exited normally, in other words, the recursion depth.
665		804
666	Outside C<ev_run>, this number is zero. In a callback, this number is	805	Outside C<ev_run>, this number is zero. In a callback, this number is
667	C<1>, unless C<ev_run> was invoked recursively (or from another thread),	806	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
668	in which case it is higher.	807	in which case it is higher.
669		808
670	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread	809	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
671	etc.), doesn't count as "exit" - consider this as a hint to avoid such	810	throwing an exception etc.), doesn't count as "exit" - consider this
672	ungentleman-like behaviour unless it's really convenient.	811	as a hint to avoid such ungentleman-like behaviour unless it's really
		812	convenient, in which case it is fully supported.
673		813
674	=item unsigned int ev_backend (loop)	814	=item unsigned int ev_backend (loop)
675		815
676	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	816	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
677	use.	817	use.
…		…
692		832
693	This function is rarely useful, but when some event callback runs for a	833	This function is rarely useful, but when some event callback runs for a
694	very long time without entering the event loop, updating libev's idea of	834	very long time without entering the event loop, updating libev's idea of
695	the current time is a good idea.	835	the current time is a good idea.
696		836
697	See also L<The special problem of time updates> in the C<ev_timer> section.	837	See also L</The special problem of time updates> in the C<ev_timer> section.
698		838
699	=item ev_suspend (loop)	839	=item ev_suspend (loop)
700		840
701	=item ev_resume (loop)	841	=item ev_resume (loop)
702		842
…		…
720	without a previous call to C<ev_suspend>.	860	without a previous call to C<ev_suspend>.
721		861
722	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	862	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
723	event loop time (see C<ev_now_update>).	863	event loop time (see C<ev_now_update>).
724		864
725	=item ev_run (loop, int flags)	865	=item bool ev_run (loop, int flags)
726		866
727	Finally, this is it, the event handler. This function usually is called	867	Finally, this is it, the event handler. This function usually is called
728	after you have initialised all your watchers and you want to start	868	after you have initialised all your watchers and you want to start
729	handling events. It will ask the operating system for any new events, call	869	handling events. It will ask the operating system for any new events, call
730	the watcher callbacks, an then repeat the whole process indefinitely: This	870	the watcher callbacks, and then repeat the whole process indefinitely: This
731	is why event loops are called I<loops>.	871	is why event loops are called I<loops>.
732		872
733	If the flags argument is specified as C<0>, it will keep handling events	873	If the flags argument is specified as C<0>, it will keep handling events
734	until either no event watchers are active anymore or C<ev_break> was	874	until either no event watchers are active anymore or C<ev_break> was
735	called.	875	called.
		876
		877	The return value is false if there are no more active watchers (which
		878	usually means "all jobs done" or "deadlock"), and true in all other cases
		879	(which usually means " you should call C<ev_run> again").
736		880
737	Please note that an explicit C<ev_break> is usually better than	881	Please note that an explicit C<ev_break> is usually better than
738	relying on all watchers to be stopped when deciding when a program has	882	relying on all watchers to be stopped when deciding when a program has
739	finished (especially in interactive programs), but having a program	883	finished (especially in interactive programs), but having a program
740	that automatically loops as long as it has to and no longer by virtue	884	that automatically loops as long as it has to and no longer by virtue
741	of relying on its watchers stopping correctly, that is truly a thing of	885	of relying on its watchers stopping correctly, that is truly a thing of
742	beauty.	886	beauty.
743		887
		888	This function is I<mostly> exception-safe - you can break out of a
		889	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		890	exception and so on. This does not decrement the C<ev_depth> value, nor
		891	will it clear any outstanding C<EVBREAK_ONE> breaks.
		892
744	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle	893	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
745	those events and any already outstanding ones, but will not wait and	894	those events and any already outstanding ones, but will not wait and
746	block your process in case there are no events and will return after one	895	block your process in case there are no events and will return after one
747	iteration of the loop. This is sometimes useful to poll and handle new	896	iteration of the loop. This is sometimes useful to poll and handle new
748	events while doing lengthy calculations, to keep the program responsive.	897	events while doing lengthy calculations, to keep the program responsive.
…		…
757	This is useful if you are waiting for some external event in conjunction	906	This is useful if you are waiting for some external event in conjunction
758	with something not expressible using other libev watchers (i.e. "roll your	907	with something not expressible using other libev watchers (i.e. "roll your
759	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	908	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
760	usually a better approach for this kind of thing.	909	usually a better approach for this kind of thing.
761		910
762	Here are the gory details of what C<ev_run> does:	911	Here are the gory details of what C<ev_run> does (this is for your
		912	understanding, not a guarantee that things will work exactly like this in
		913	future versions):
763		914
764	- Increment loop depth.	915	- Increment loop depth.
765	- Reset the ev_break status.	916	- Reset the ev_break status.
766	- Before the first iteration, call any pending watchers.	917	- Before the first iteration, call any pending watchers.
767	LOOP:	918	LOOP:
…		…
800	anymore.	951	anymore.
801		952
802	... queue jobs here, make sure they register event watchers as long	953	... queue jobs here, make sure they register event watchers as long
803	... as they still have work to do (even an idle watcher will do..)	954	... as they still have work to do (even an idle watcher will do..)
804	ev_run (my_loop, 0);	955	ev_run (my_loop, 0);
805	... jobs done or somebody called unloop. yeah!	956	... jobs done or somebody called break. yeah!
806		957
807	=item ev_break (loop, how)	958	=item ev_break (loop, how)
808		959
809	Can be used to make a call to C<ev_run> return early (but only after it	960	Can be used to make a call to C<ev_run> return early (but only after it
810	has processed all outstanding events). The C<how> argument must be either	961	has processed all outstanding events). The C<how> argument must be either
811	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or	962	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
812	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.	963	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
813		964
814	This "unloop state" will be cleared when entering C<ev_run> again.	965	This "break state" will be cleared on the next call to C<ev_run>.
815		966
816	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##	967	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		968	which case it will have no effect.
817		969
818	=item ev_ref (loop)	970	=item ev_ref (loop)
819		971
820	=item ev_unref (loop)	972	=item ev_unref (loop)
821		973
…		…
842	running when nothing else is active.	994	running when nothing else is active.
843		995
844	ev_signal exitsig;	996	ev_signal exitsig;
845	ev_signal_init (&exitsig, sig_cb, SIGINT);	997	ev_signal_init (&exitsig, sig_cb, SIGINT);
846	ev_signal_start (loop, &exitsig);	998	ev_signal_start (loop, &exitsig);
847	evf_unref (loop);	999	ev_unref (loop);
848		1000
849	Example: For some weird reason, unregister the above signal handler again.	1001	Example: For some weird reason, unregister the above signal handler again.
850		1002
851	ev_ref (loop);	1003	ev_ref (loop);
852	ev_signal_stop (loop, &exitsig);	1004	ev_signal_stop (loop, &exitsig);
…		…
872	overhead for the actual polling but can deliver many events at once.	1024	overhead for the actual polling but can deliver many events at once.
873		1025
874	By setting a higher I<io collect interval> you allow libev to spend more	1026	By setting a higher I<io collect interval> you allow libev to spend more
875	time collecting I/O events, so you can handle more events per iteration,	1027	time collecting I/O events, so you can handle more events per iteration,
876	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1028	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
877	C<ev_timer>) will be not affected. Setting this to a non-null value will	1029	C<ev_timer>) will not be affected. Setting this to a non-null value will
878	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1030	introduce an additional C<ev_sleep ()> call into most loop iterations. The
879	sleep time ensures that libev will not poll for I/O events more often then	1031	sleep time ensures that libev will not poll for I/O events more often then
880	once per this interval, on average.	1032	once per this interval, on average (as long as the host time resolution is
		1033	good enough).
881		1034
882	Likewise, by setting a higher I<timeout collect interval> you allow libev	1035	Likewise, by setting a higher I<timeout collect interval> you allow libev
883	to spend more time collecting timeouts, at the expense of increased	1036	to spend more time collecting timeouts, at the expense of increased
884	latency/jitter/inexactness (the watcher callback will be called	1037	latency/jitter/inexactness (the watcher callback will be called
885	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1038	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
931	invoke the actual watchers inside another context (another thread etc.).	1084	invoke the actual watchers inside another context (another thread etc.).
932		1085
933	If you want to reset the callback, use C<ev_invoke_pending> as new	1086	If you want to reset the callback, use C<ev_invoke_pending> as new
934	callback.	1087	callback.
935		1088
936	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1089	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
937		1090
938	Sometimes you want to share the same loop between multiple threads. This	1091	Sometimes you want to share the same loop between multiple threads. This
939	can be done relatively simply by putting mutex_lock/unlock calls around	1092	can be done relatively simply by putting mutex_lock/unlock calls around
940	each call to a libev function.	1093	each call to a libev function.
941		1094
942	However, C<ev_run> can run an indefinite time, so it is not feasible	1095	However, C<ev_run> can run an indefinite time, so it is not feasible
943	to wait for it to return. One way around this is to wake up the event	1096	to wait for it to return. One way around this is to wake up the event
944	loop via C<ev_break> and C<av_async_send>, another way is to set these	1097	loop via C<ev_break> and C<ev_async_send>, another way is to set these
945	I<release> and I<acquire> callbacks on the loop.	1098	I<release> and I<acquire> callbacks on the loop.
946		1099
947	When set, then C<release> will be called just before the thread is	1100	When set, then C<release> will be called just before the thread is
948	suspended waiting for new events, and C<acquire> is called just	1101	suspended waiting for new events, and C<acquire> is called just
949	afterwards.	1102	afterwards.
…		…
964	See also the locking example in the C<THREADS> section later in this	1117	See also the locking example in the C<THREADS> section later in this
965	document.	1118	document.
966		1119
967	=item ev_set_userdata (loop, void *data)	1120	=item ev_set_userdata (loop, void *data)
968		1121
969	=item ev_userdata (loop)	1122	=item void *ev_userdata (loop)
970		1123
971	Set and retrieve a single C<void *> associated with a loop. When	1124	Set and retrieve a single C<void *> associated with a loop. When
972	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1125	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
973	C<0.>	1126	C<0>.
974		1127
975	These two functions can be used to associate arbitrary data with a loop,	1128	These two functions can be used to associate arbitrary data with a loop,
976	and are intended solely for the C<invoke_pending_cb>, C<release> and	1129	and are intended solely for the C<invoke_pending_cb>, C<release> and
977	C<acquire> callbacks described above, but of course can be (ab-)used for	1130	C<acquire> callbacks described above, but of course can be (ab-)used for
978	any other purpose as well.	1131	any other purpose as well.
…		…
1089		1242
1090	=item C<EV_PREPARE>	1243	=item C<EV_PREPARE>
1091		1244
1092	=item C<EV_CHECK>	1245	=item C<EV_CHECK>
1093		1246
1094	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts	1247	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1095	to gather new events, and all C<ev_check> watchers are invoked just after	1248	gather new events, and all C<ev_check> watchers are queued (not invoked)
1096	C<ev_run> has gathered them, but before it invokes any callbacks for any	1249	just after C<ev_run> has gathered them, but before it queues any callbacks
		1250	for any received events. That means C<ev_prepare> watchers are the last
		1251	watchers invoked before the event loop sleeps or polls for new events, and
		1252	C<ev_check> watchers will be invoked before any other watchers of the same
		1253	or lower priority within an event loop iteration.
		1254
1097	received events. Callbacks of both watcher types can start and stop as	1255	Callbacks of both watcher types can start and stop as many watchers as
1098	many watchers as they want, and all of them will be taken into account	1256	they want, and all of them will be taken into account (for example, a
1099	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1257	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1100	C<ev_run> from blocking).	1258	blocking).
1101		1259
1102	=item C<EV_EMBED>	1260	=item C<EV_EMBED>
1103		1261
1104	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1262	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1105		1263
1106	=item C<EV_FORK>	1264	=item C<EV_FORK>
1107		1265
1108	The event loop has been resumed in the child process after fork (see	1266	The event loop has been resumed in the child process after fork (see
1109	C<ev_fork>).	1267	C<ev_fork>).
		1268
		1269	=item C<EV_CLEANUP>
		1270
		1271	The event loop is about to be destroyed (see C<ev_cleanup>).
1110		1272
1111	=item C<EV_ASYNC>	1273	=item C<EV_ASYNC>
1112		1274
1113	The given async watcher has been asynchronously notified (see C<ev_async>).	1275	The given async watcher has been asynchronously notified (see C<ev_async>).
1114		1276
…		…
1136	programs, though, as the fd could already be closed and reused for another	1298	programs, though, as the fd could already be closed and reused for another
1137	thing, so beware.	1299	thing, so beware.
1138		1300
1139	=back	1301	=back
1140		1302
		1303	=head2 GENERIC WATCHER FUNCTIONS
		1304
		1305	=over 4
		1306
		1307	=item C<ev_init> (ev_TYPE *watcher, callback)
		1308
		1309	This macro initialises the generic portion of a watcher. The contents
		1310	of the watcher object can be arbitrary (so C<malloc> will do). Only
		1311	the generic parts of the watcher are initialised, you I<need> to call
		1312	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		1313	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		1314	which rolls both calls into one.
		1315
		1316	You can reinitialise a watcher at any time as long as it has been stopped
		1317	(or never started) and there are no pending events outstanding.
		1318
		1319	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
		1320	int revents)>.
		1321
		1322	Example: Initialise an C<ev_io> watcher in two steps.
		1323
		1324	ev_io w;
		1325	ev_init (&w, my_cb);
		1326	ev_io_set (&w, STDIN_FILENO, EV_READ);
		1327
		1328	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
		1329
		1330	This macro initialises the type-specific parts of a watcher. You need to
		1331	call C<ev_init> at least once before you call this macro, but you can
		1332	call C<ev_TYPE_set> any number of times. You must not, however, call this
		1333	macro on a watcher that is active (it can be pending, however, which is a
		1334	difference to the C<ev_init> macro).
		1335
		1336	Although some watcher types do not have type-specific arguments
		1337	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		1338
		1339	See C<ev_init>, above, for an example.
		1340
		1341	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		1342
		1343	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		1344	calls into a single call. This is the most convenient method to initialise
		1345	a watcher. The same limitations apply, of course.
		1346
		1347	Example: Initialise and set an C<ev_io> watcher in one step.
		1348
		1349	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1350
		1351	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
		1352
		1353	Starts (activates) the given watcher. Only active watchers will receive
		1354	events. If the watcher is already active nothing will happen.
		1355
		1356	Example: Start the C<ev_io> watcher that is being abused as example in this
		1357	whole section.
		1358
		1359	ev_io_start (EV_DEFAULT_UC, &w);
		1360
		1361	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
		1362
		1363	Stops the given watcher if active, and clears the pending status (whether
		1364	the watcher was active or not).
		1365
		1366	It is possible that stopped watchers are pending - for example,
		1367	non-repeating timers are being stopped when they become pending - but
		1368	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
		1369	pending. If you want to free or reuse the memory used by the watcher it is
		1370	therefore a good idea to always call its C<ev_TYPE_stop> function.
		1371
		1372	=item bool ev_is_active (ev_TYPE *watcher)
		1373
		1374	Returns a true value iff the watcher is active (i.e. it has been started
		1375	and not yet been stopped). As long as a watcher is active you must not modify
		1376	it.
		1377
		1378	=item bool ev_is_pending (ev_TYPE *watcher)
		1379
		1380	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		1381	events but its callback has not yet been invoked). As long as a watcher
		1382	is pending (but not active) you must not call an init function on it (but
		1383	C<ev_TYPE_set> is safe), you must not change its priority, and you must
		1384	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		1385	it).
		1386
		1387	=item callback ev_cb (ev_TYPE *watcher)
		1388
		1389	Returns the callback currently set on the watcher.
		1390
		1391	=item ev_set_cb (ev_TYPE *watcher, callback)
		1392
		1393	Change the callback. You can change the callback at virtually any time
		1394	(modulo threads).
		1395
		1396	=item ev_set_priority (ev_TYPE *watcher, int priority)
		1397
		1398	=item int ev_priority (ev_TYPE *watcher)
		1399
		1400	Set and query the priority of the watcher. The priority is a small
		1401	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		1402	(default: C<-2>). Pending watchers with higher priority will be invoked
		1403	before watchers with lower priority, but priority will not keep watchers
		1404	from being executed (except for C<ev_idle> watchers).
		1405
		1406	If you need to suppress invocation when higher priority events are pending
		1407	you need to look at C<ev_idle> watchers, which provide this functionality.
		1408
		1409	You I<must not> change the priority of a watcher as long as it is active or
		1410	pending.
		1411
		1412	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1413	fine, as long as you do not mind that the priority value you query might
		1414	or might not have been clamped to the valid range.
		1415
		1416	The default priority used by watchers when no priority has been set is
		1417	always C<0>, which is supposed to not be too high and not be too low :).
		1418
		1419	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1420	priorities.
		1421
		1422	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		1423
		1424	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		1425	C<loop> nor C<revents> need to be valid as long as the watcher callback
		1426	can deal with that fact, as both are simply passed through to the
		1427	callback.
		1428
		1429	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		1430
		1431	If the watcher is pending, this function clears its pending status and
		1432	returns its C<revents> bitset (as if its callback was invoked). If the
		1433	watcher isn't pending it does nothing and returns C<0>.
		1434
		1435	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1436	callback to be invoked, which can be accomplished with this function.
		1437
		1438	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1439
		1440	Feeds the given event set into the event loop, as if the specified event
		1441	had happened for the specified watcher (which must be a pointer to an
		1442	initialised but not necessarily started event watcher). Obviously you must
		1443	not free the watcher as long as it has pending events.
		1444
		1445	Stopping the watcher, letting libev invoke it, or calling
		1446	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1447	not started in the first place.
		1448
		1449	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1450	functions that do not need a watcher.
		1451
		1452	=back
		1453
		1454	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1455	OWN COMPOSITE WATCHERS> idioms.
		1456
1141	=head2 WATCHER STATES	1457	=head2 WATCHER STATES
1142		1458
1143	There are various watcher states mentioned throughout this manual -	1459	There are various watcher states mentioned throughout this manual -
1144	active, pending and so on. In this section these states and the rules to	1460	active, pending and so on. In this section these states and the rules to
1145	transition between them will be described in more detail - and while these	1461	transition between them will be described in more detail - and while these
1146	rules might look complicated, they usually do "the right thing".	1462	rules might look complicated, they usually do "the right thing".
1147		1463
1148	=over 4	1464	=over 4
1149		1465
1150	=item initialiased	1466	=item initialised
1151		1467
1152	Before a watcher can be registered with the event looop it has to be	1468	Before a watcher can be registered with the event loop it has to be
1153	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to	1469	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
1154	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.	1470	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1155		1471
1156	In this state it is simply some block of memory that is suitable for use	1472	In this state it is simply some block of memory that is suitable for
1157	in an event loop. It can be moved around, freed, reused etc. at will.	1473	use in an event loop. It can be moved around, freed, reused etc. at
		1474	will - as long as you either keep the memory contents intact, or call
		1475	C<ev_TYPE_init> again.
1158		1476
1159	=item started/running/active	1477	=item started/running/active
1160		1478
1161	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes	1479	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1162	property of the event loop, and is actively waiting for events. While in	1480	property of the event loop, and is actively waiting for events. While in
…		…
1190	latter will clear any pending state the watcher might be in, regardless	1508	latter will clear any pending state the watcher might be in, regardless
1191	of whether it was active or not, so stopping a watcher explicitly before	1509	of whether it was active or not, so stopping a watcher explicitly before
1192	freeing it is often a good idea.	1510	freeing it is often a good idea.
1193		1511
1194	While stopped (and not pending) the watcher is essentially in the	1512	While stopped (and not pending) the watcher is essentially in the
1195	initialised state, that is it can be reused, moved, modified in any way	1513	initialised state, that is, it can be reused, moved, modified in any way
1196	you wish.	1514	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1515	it again).
1197		1516
1198	=back	1517	=back
1199
1200	=head2 GENERIC WATCHER FUNCTIONS
1201
1202	=over 4
1203
1204	=item C<ev_init> (ev_TYPE *watcher, callback)
1205
1206	This macro initialises the generic portion of a watcher. The contents
1207	of the watcher object can be arbitrary (so C<malloc> will do). Only
1208	the generic parts of the watcher are initialised, you I<need> to call
1209	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
1210	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
1211	which rolls both calls into one.
1212
1213	You can reinitialise a watcher at any time as long as it has been stopped
1214	(or never started) and there are no pending events outstanding.
1215
1216	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
1217	int revents)>.
1218
1219	Example: Initialise an C<ev_io> watcher in two steps.
1220
1221	ev_io w;
1222	ev_init (&w, my_cb);
1223	ev_io_set (&w, STDIN_FILENO, EV_READ);
1224
1225	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1226
1227	This macro initialises the type-specific parts of a watcher. You need to
1228	call C<ev_init> at least once before you call this macro, but you can
1229	call C<ev_TYPE_set> any number of times. You must not, however, call this
1230	macro on a watcher that is active (it can be pending, however, which is a
1231	difference to the C<ev_init> macro).
1232
1233	Although some watcher types do not have type-specific arguments
1234	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
1235
1236	See C<ev_init>, above, for an example.
1237
1238	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
1239
1240	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
1241	calls into a single call. This is the most convenient method to initialise
1242	a watcher. The same limitations apply, of course.
1243
1244	Example: Initialise and set an C<ev_io> watcher in one step.
1245
1246	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1247
1248	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1249
1250	Starts (activates) the given watcher. Only active watchers will receive
1251	events. If the watcher is already active nothing will happen.
1252
1253	Example: Start the C<ev_io> watcher that is being abused as example in this
1254	whole section.
1255
1256	ev_io_start (EV_DEFAULT_UC, &w);
1257
1258	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1259
1260	Stops the given watcher if active, and clears the pending status (whether
1261	the watcher was active or not).
1262
1263	It is possible that stopped watchers are pending - for example,
1264	non-repeating timers are being stopped when they become pending - but
1265	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
1266	pending. If you want to free or reuse the memory used by the watcher it is
1267	therefore a good idea to always call its C<ev_TYPE_stop> function.
1268
1269	=item bool ev_is_active (ev_TYPE *watcher)
1270
1271	Returns a true value iff the watcher is active (i.e. it has been started
1272	and not yet been stopped). As long as a watcher is active you must not modify
1273	it.
1274
1275	=item bool ev_is_pending (ev_TYPE *watcher)
1276
1277	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1278	events but its callback has not yet been invoked). As long as a watcher
1279	is pending (but not active) you must not call an init function on it (but
1280	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1281	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1282	it).
1283
1284	=item callback ev_cb (ev_TYPE *watcher)
1285
1286	Returns the callback currently set on the watcher.
1287
1288	=item ev_cb_set (ev_TYPE *watcher, callback)
1289
1290	Change the callback. You can change the callback at virtually any time
1291	(modulo threads).
1292
1293	=item ev_set_priority (ev_TYPE *watcher, int priority)
1294
1295	=item int ev_priority (ev_TYPE *watcher)
1296
1297	Set and query the priority of the watcher. The priority is a small
1298	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1299	(default: C<-2>). Pending watchers with higher priority will be invoked
1300	before watchers with lower priority, but priority will not keep watchers
1301	from being executed (except for C<ev_idle> watchers).
1302
1303	If you need to suppress invocation when higher priority events are pending
1304	you need to look at C<ev_idle> watchers, which provide this functionality.
1305
1306	You I<must not> change the priority of a watcher as long as it is active or
1307	pending.
1308
1309	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1310	fine, as long as you do not mind that the priority value you query might
1311	or might not have been clamped to the valid range.
1312
1313	The default priority used by watchers when no priority has been set is
1314	always C<0>, which is supposed to not be too high and not be too low :).
1315
1316	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1317	priorities.
1318
1319	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1320
1321	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1322	C<loop> nor C<revents> need to be valid as long as the watcher callback
1323	can deal with that fact, as both are simply passed through to the
1324	callback.
1325
1326	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1327
1328	If the watcher is pending, this function clears its pending status and
1329	returns its C<revents> bitset (as if its callback was invoked). If the
1330	watcher isn't pending it does nothing and returns C<0>.
1331
1332	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1333	callback to be invoked, which can be accomplished with this function.
1334
1335	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1336
1337	Feeds the given event set into the event loop, as if the specified event
1338	had happened for the specified watcher (which must be a pointer to an
1339	initialised but not necessarily started event watcher). Obviously you must
1340	not free the watcher as long as it has pending events.
1341
1342	Stopping the watcher, letting libev invoke it, or calling
1343	C<ev_clear_pending> will clear the pending event, even if the watcher was
1344	not started in the first place.
1345
1346	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1347	functions that do not need a watcher.
1348
1349	=back
1350
1351
1352	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1353
1354	Each watcher has, by default, a member C<void *data> that you can change
1355	and read at any time: libev will completely ignore it. This can be used
1356	to associate arbitrary data with your watcher. If you need more data and
1357	don't want to allocate memory and store a pointer to it in that data
1358	member, you can also "subclass" the watcher type and provide your own
1359	data:
1360
1361	struct my_io
1362	{
1363	ev_io io;
1364	int otherfd;
1365	void *somedata;
1366	struct whatever *mostinteresting;
1367	};
1368
1369	...
1370	struct my_io w;
1371	ev_io_init (&w.io, my_cb, fd, EV_READ);
1372
1373	And since your callback will be called with a pointer to the watcher, you
1374	can cast it back to your own type:
1375
1376	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1377	{
1378	struct my_io *w = (struct my_io *)w_;
1379	...
1380	}
1381
1382	More interesting and less C-conformant ways of casting your callback type
1383	instead have been omitted.
1384
1385	Another common scenario is to use some data structure with multiple
1386	embedded watchers:
1387
1388	struct my_biggy
1389	{
1390	int some_data;
1391	ev_timer t1;
1392	ev_timer t2;
1393	}
1394
1395	In this case getting the pointer to C<my_biggy> is a bit more
1396	complicated: Either you store the address of your C<my_biggy> struct
1397	in the C<data> member of the watcher (for woozies), or you need to use
1398	some pointer arithmetic using C<offsetof> inside your watchers (for real
1399	programmers):
1400
1401	#include <stddef.h>
1402
1403	static void
1404	t1_cb (EV_P_ ev_timer *w, int revents)
1405	{
1406	struct my_biggy big = (struct my_biggy *)
1407	(((char *)w) - offsetof (struct my_biggy, t1));
1408	}
1409
1410	static void
1411	t2_cb (EV_P_ ev_timer *w, int revents)
1412	{
1413	struct my_biggy big = (struct my_biggy *)
1414	(((char *)w) - offsetof (struct my_biggy, t2));
1415	}
1416		1518
1417	=head2 WATCHER PRIORITY MODELS	1519	=head2 WATCHER PRIORITY MODELS
1418		1520
1419	Many event loops support I<watcher priorities>, which are usually small	1521	Many event loops support I<watcher priorities>, which are usually small
1420	integers that influence the ordering of event callback invocation	1522	integers that influence the ordering of event callback invocation
…		…
1547	In general you can register as many read and/or write event watchers per	1649	In general you can register as many read and/or write event watchers per
1548	fd as you want (as long as you don't confuse yourself). Setting all file	1650	fd as you want (as long as you don't confuse yourself). Setting all file
1549	descriptors to non-blocking mode is also usually a good idea (but not	1651	descriptors to non-blocking mode is also usually a good idea (but not
1550	required if you know what you are doing).	1652	required if you know what you are doing).
1551		1653
1552	If you cannot use non-blocking mode, then force the use of a
1553	known-to-be-good backend (at the time of this writing, this includes only
1554	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1555	descriptors for which non-blocking operation makes no sense (such as
1556	files) - libev doesn't guarantee any specific behaviour in that case.
1557
1558	Another thing you have to watch out for is that it is quite easy to	1654	Another thing you have to watch out for is that it is quite easy to
1559	receive "spurious" readiness notifications, that is your callback might	1655	receive "spurious" readiness notifications, that is, your callback might
1560	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1656	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1561	because there is no data. Not only are some backends known to create a	1657	because there is no data. It is very easy to get into this situation even
1562	lot of those (for example Solaris ports), it is very easy to get into	1658	with a relatively standard program structure. Thus it is best to always
1563	this situation even with a relatively standard program structure. Thus	1659	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1564	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1565	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1660	preferable to a program hanging until some data arrives.
1566		1661
1567	If you cannot run the fd in non-blocking mode (for example you should	1662	If you cannot run the fd in non-blocking mode (for example you should
1568	not play around with an Xlib connection), then you have to separately	1663	not play around with an Xlib connection), then you have to separately
1569	re-test whether a file descriptor is really ready with a known-to-be good	1664	re-test whether a file descriptor is really ready with a known-to-be good
1570	interface such as poll (fortunately in our Xlib example, Xlib already	1665	interface such as poll (fortunately in the case of Xlib, it already does
1571	does this on its own, so its quite safe to use). Some people additionally	1666	this on its own, so its quite safe to use). Some people additionally
1572	use C<SIGALRM> and an interval timer, just to be sure you won't block	1667	use C<SIGALRM> and an interval timer, just to be sure you won't block
1573	indefinitely.	1668	indefinitely.
1574		1669
1575	But really, best use non-blocking mode.	1670	But really, best use non-blocking mode.
1576		1671
1577	=head3 The special problem of disappearing file descriptors	1672	=head3 The special problem of disappearing file descriptors
1578		1673
1579	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1674	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1580	descriptor (either due to calling C<close> explicitly or any other means,	1675	a file descriptor (either due to calling C<close> explicitly or any other
1581	such as C<dup2>). The reason is that you register interest in some file	1676	means, such as C<dup2>). The reason is that you register interest in some
1582	descriptor, but when it goes away, the operating system will silently drop	1677	file descriptor, but when it goes away, the operating system will silently
1583	this interest. If another file descriptor with the same number then is	1678	drop this interest. If another file descriptor with the same number then
1584	registered with libev, there is no efficient way to see that this is, in	1679	is registered with libev, there is no efficient way to see that this is,
1585	fact, a different file descriptor.	1680	in fact, a different file descriptor.
1586		1681
1587	To avoid having to explicitly tell libev about such cases, libev follows	1682	To avoid having to explicitly tell libev about such cases, libev follows
1588	the following policy: Each time C<ev_io_set> is being called, libev	1683	the following policy: Each time C<ev_io_set> is being called, libev
1589	will assume that this is potentially a new file descriptor, otherwise	1684	will assume that this is potentially a new file descriptor, otherwise
1590	it is assumed that the file descriptor stays the same. That means that	1685	it is assumed that the file descriptor stays the same. That means that
…		…
1604		1699
1605	There is no workaround possible except not registering events	1700	There is no workaround possible except not registering events
1606	for potentially C<dup ()>'ed file descriptors, or to resort to	1701	for potentially C<dup ()>'ed file descriptors, or to resort to
1607	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1702	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1608		1703
		1704	=head3 The special problem of files
		1705
		1706	Many people try to use C<select> (or libev) on file descriptors
		1707	representing files, and expect it to become ready when their program
		1708	doesn't block on disk accesses (which can take a long time on their own).
		1709
		1710	However, this cannot ever work in the "expected" way - you get a readiness
		1711	notification as soon as the kernel knows whether and how much data is
		1712	there, and in the case of open files, that's always the case, so you
		1713	always get a readiness notification instantly, and your read (or possibly
		1714	write) will still block on the disk I/O.
		1715
		1716	Another way to view it is that in the case of sockets, pipes, character
		1717	devices and so on, there is another party (the sender) that delivers data
		1718	on its own, but in the case of files, there is no such thing: the disk
		1719	will not send data on its own, simply because it doesn't know what you
		1720	wish to read - you would first have to request some data.
		1721
		1722	Since files are typically not-so-well supported by advanced notification
		1723	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1724	to files, even though you should not use it. The reason for this is
		1725	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1726	usually a tty, often a pipe, but also sometimes files or special devices
		1727	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1728	F</dev/urandom>), and even though the file might better be served with
		1729	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1730	it "just works" instead of freezing.
		1731
		1732	So avoid file descriptors pointing to files when you know it (e.g. use
		1733	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1734	when you rarely read from a file instead of from a socket, and want to
		1735	reuse the same code path.
		1736
1609	=head3 The special problem of fork	1737	=head3 The special problem of fork
1610		1738
1611	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1739	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1612	useless behaviour. Libev fully supports fork, but needs to be told about	1740	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1613	it in the child.	1741	to be told about it in the child if you want to continue to use it in the
		1742	child.
1614		1743
1615	To support fork in your programs, you either have to call	1744	To support fork in your child processes, you have to call C<ev_loop_fork
1616	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1745	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1617	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1618	C<EVBACKEND_POLL>.
1619		1747
1620	=head3 The special problem of SIGPIPE	1748	=head3 The special problem of SIGPIPE
1621		1749
1622	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1750	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1623	when writing to a pipe whose other end has been closed, your program gets	1751	when writing to a pipe whose other end has been closed, your program gets
…		…
1721	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1849	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1722	monotonic clock option helps a lot here).	1850	monotonic clock option helps a lot here).
1723		1851
1724	The callback is guaranteed to be invoked only I<after> its timeout has	1852	The callback is guaranteed to be invoked only I<after> its timeout has
1725	passed (not I<at>, so on systems with very low-resolution clocks this	1853	passed (not I<at>, so on systems with very low-resolution clocks this
1726	might introduce a small delay). If multiple timers become ready during the	1854	might introduce a small delay, see "the special problem of being too
		1855	early", below). If multiple timers become ready during the same loop
1727	same loop iteration then the ones with earlier time-out values are invoked	1856	iteration then the ones with earlier time-out values are invoked before
1728	before ones of the same priority with later time-out values (but this is	1857	ones of the same priority with later time-out values (but this is no
1729	no longer true when a callback calls C<ev_run> recursively).	1858	longer true when a callback calls C<ev_run> recursively).
1730		1859
1731	=head3 Be smart about timeouts	1860	=head3 Be smart about timeouts
1732		1861
1733	Many real-world problems involve some kind of timeout, usually for error	1862	Many real-world problems involve some kind of timeout, usually for error
1734	recovery. A typical example is an HTTP request - if the other side hangs,	1863	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1809		1938
1810	In this case, it would be more efficient to leave the C<ev_timer> alone,	1939	In this case, it would be more efficient to leave the C<ev_timer> alone,
1811	but remember the time of last activity, and check for a real timeout only	1940	but remember the time of last activity, and check for a real timeout only
1812	within the callback:	1941	within the callback:
1813		1942
		1943	ev_tstamp timeout = 60.;
1814	ev_tstamp last_activity; // time of last activity	1944	ev_tstamp last_activity; // time of last activity
		1945	ev_timer timer;
1815		1946
1816	static void	1947	static void
1817	callback (EV_P_ ev_timer *w, int revents)	1948	callback (EV_P_ ev_timer *w, int revents)
1818	{	1949	{
1819	ev_tstamp now = ev_now (EV_A);	1950	// calculate when the timeout would happen
1820	ev_tstamp timeout = last_activity + 60.;	1951	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1821		1952
1822	// if last_activity + 60. is older than now, we did time out	1953	// if negative, it means we the timeout already occurred
1823	if (timeout < now)	1954	if (after < 0.)
1824	{	1955	{
1825	// timeout occurred, take action	1956	// timeout occurred, take action
1826	}	1957	}
1827	else	1958	else
1828	{	1959	{
1829	// callback was invoked, but there was some activity, re-arm	1960	// callback was invoked, but there was some recent
1830	// the watcher to fire in last_activity + 60, which is	1961	// activity. simply restart the timer to time out
1831	// guaranteed to be in the future, so "again" is positive:	1962	// after "after" seconds, which is the earliest time
1832	w->repeat = timeout - now;	1963	// the timeout can occur.
		1964	ev_timer_set (w, after, 0.);
1833	ev_timer_again (EV_A_ w);	1965	ev_timer_start (EV_A_ w);
1834	}	1966	}
1835	}	1967	}
1836		1968
1837	To summarise the callback: first calculate the real timeout (defined	1969	To summarise the callback: first calculate in how many seconds the
1838	as "60 seconds after the last activity"), then check if that time has	1970	timeout will occur (by calculating the absolute time when it would occur,
1839	been reached, which means something I<did>, in fact, time out. Otherwise	1971	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1840	the callback was invoked too early (C<timeout> is in the future), so	1972	(EV_A)> from that).
1841	re-schedule the timer to fire at that future time, to see if maybe we have
1842	a timeout then.
1843		1973
1844	Note how C<ev_timer_again> is used, taking advantage of the	1974	If this value is negative, then we are already past the timeout, i.e. we
1845	C<ev_timer_again> optimisation when the timer is already running.	1975	timed out, and need to do whatever is needed in this case.
		1976
		1977	Otherwise, we now the earliest time at which the timeout would trigger,
		1978	and simply start the timer with this timeout value.
		1979
		1980	In other words, each time the callback is invoked it will check whether
		1981	the timeout occurred. If not, it will simply reschedule itself to check
		1982	again at the earliest time it could time out. Rinse. Repeat.
1846		1983
1847	This scheme causes more callback invocations (about one every 60 seconds	1984	This scheme causes more callback invocations (about one every 60 seconds
1848	minus half the average time between activity), but virtually no calls to	1985	minus half the average time between activity), but virtually no calls to
1849	libev to change the timeout.	1986	libev to change the timeout.
1850		1987
1851	To start the timer, simply initialise the watcher and set C<last_activity>	1988	To start the machinery, simply initialise the watcher and set
1852	to the current time (meaning we just have some activity :), then call the	1989	C<last_activity> to the current time (meaning there was some activity just
1853	callback, which will "do the right thing" and start the timer:	1990	now), then call the callback, which will "do the right thing" and start
		1991	the timer:
1854		1992
		1993	last_activity = ev_now (EV_A);
1855	ev_init (timer, callback);	1994	ev_init (&timer, callback);
1856	last_activity = ev_now (loop);	1995	callback (EV_A_ &timer, 0);
1857	callback (loop, timer, EV_TIMER);
1858		1996
1859	And when there is some activity, simply store the current time in	1997	When there is some activity, simply store the current time in
1860	C<last_activity>, no libev calls at all:	1998	C<last_activity>, no libev calls at all:
1861		1999
		2000	if (activity detected)
1862	last_activity = ev_now (loop);	2001	last_activity = ev_now (EV_A);
		2002
		2003	When your timeout value changes, then the timeout can be changed by simply
		2004	providing a new value, stopping the timer and calling the callback, which
		2005	will again do the right thing (for example, time out immediately :).
		2006
		2007	timeout = new_value;
		2008	ev_timer_stop (EV_A_ &timer);
		2009	callback (EV_A_ &timer, 0);
1863		2010
1864	This technique is slightly more complex, but in most cases where the	2011	This technique is slightly more complex, but in most cases where the
1865	time-out is unlikely to be triggered, much more efficient.	2012	time-out is unlikely to be triggered, much more efficient.
1866
1867	Changing the timeout is trivial as well (if it isn't hard-coded in the
1868	callback :) - just change the timeout and invoke the callback, which will
1869	fix things for you.
1870		2013
1871	=item 4. Wee, just use a double-linked list for your timeouts.	2014	=item 4. Wee, just use a double-linked list for your timeouts.
1872		2015
1873	If there is not one request, but many thousands (millions...), all	2016	If there is not one request, but many thousands (millions...), all
1874	employing some kind of timeout with the same timeout value, then one can	2017	employing some kind of timeout with the same timeout value, then one can
…		…
1901	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2044	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1902	rather complicated, but extremely efficient, something that really pays	2045	rather complicated, but extremely efficient, something that really pays
1903	off after the first million or so of active timers, i.e. it's usually	2046	off after the first million or so of active timers, i.e. it's usually
1904	overkill :)	2047	overkill :)
1905		2048
		2049	=head3 The special problem of being too early
		2050
		2051	If you ask a timer to call your callback after three seconds, then
		2052	you expect it to be invoked after three seconds - but of course, this
		2053	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2054	guaranteed to any precision by libev - imagine somebody suspending the
		2055	process with a STOP signal for a few hours for example.
		2056
		2057	So, libev tries to invoke your callback as soon as possible I<after> the
		2058	delay has occurred, but cannot guarantee this.
		2059
		2060	A less obvious failure mode is calling your callback too early: many event
		2061	loops compare timestamps with a "elapsed delay >= requested delay", but
		2062	this can cause your callback to be invoked much earlier than you would
		2063	expect.
		2064
		2065	To see why, imagine a system with a clock that only offers full second
		2066	resolution (think windows if you can't come up with a broken enough OS
		2067	yourself). If you schedule a one-second timer at the time 500.9, then the
		2068	event loop will schedule your timeout to elapse at a system time of 500
		2069	(500.9 truncated to the resolution) + 1, or 501.
		2070
		2071	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2072	501" and invoke the callback 0.1s after it was started, even though a
		2073	one-second delay was requested - this is being "too early", despite best
		2074	intentions.
		2075
		2076	This is the reason why libev will never invoke the callback if the elapsed
		2077	delay equals the requested delay, but only when the elapsed delay is
		2078	larger than the requested delay. In the example above, libev would only invoke
		2079	the callback at system time 502, or 1.1s after the timer was started.
		2080
		2081	So, while libev cannot guarantee that your callback will be invoked
		2082	exactly when requested, it I<can> and I<does> guarantee that the requested
		2083	delay has actually elapsed, or in other words, it always errs on the "too
		2084	late" side of things.
		2085
1906	=head3 The special problem of time updates	2086	=head3 The special problem of time updates
1907		2087
1908	Establishing the current time is a costly operation (it usually takes at	2088	Establishing the current time is a costly operation (it usually takes
1909	least two system calls): EV therefore updates its idea of the current	2089	at least one system call): EV therefore updates its idea of the current
1910	time only before and after C<ev_run> collects new events, which causes a	2090	time only before and after C<ev_run> collects new events, which causes a
1911	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2091	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1912	lots of events in one iteration.	2092	lots of events in one iteration.
1913		2093
1914	The relative timeouts are calculated relative to the C<ev_now ()>	2094	The relative timeouts are calculated relative to the C<ev_now ()>
1915	time. This is usually the right thing as this timestamp refers to the time	2095	time. This is usually the right thing as this timestamp refers to the time
1916	of the event triggering whatever timeout you are modifying/starting. If	2096	of the event triggering whatever timeout you are modifying/starting. If
1917	you suspect event processing to be delayed and you I<need> to base the	2097	you suspect event processing to be delayed and you I<need> to base the
1918	timeout on the current time, use something like this to adjust for this:	2098	timeout on the current time, use something like the following to adjust
		2099	for it:
1919		2100
1920	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2101	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1921		2102
1922	If the event loop is suspended for a long time, you can also force an	2103	If the event loop is suspended for a long time, you can also force an
1923	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2104	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1924	()>.	2105	()>, although that will push the event time of all outstanding events
		2106	further into the future.
		2107
		2108	=head3 The special problem of unsynchronised clocks
		2109
		2110	Modern systems have a variety of clocks - libev itself uses the normal
		2111	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2112	jumps).
		2113
		2114	Neither of these clocks is synchronised with each other or any other clock
		2115	on the system, so C<ev_time ()> might return a considerably different time
		2116	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2117	a call to C<gettimeofday> might return a second count that is one higher
		2118	than a directly following call to C<time>.
		2119
		2120	The moral of this is to only compare libev-related timestamps with
		2121	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2122	a second or so.
		2123
		2124	One more problem arises due to this lack of synchronisation: if libev uses
		2125	the system monotonic clock and you compare timestamps from C<ev_time>
		2126	or C<ev_now> from when you started your timer and when your callback is
		2127	invoked, you will find that sometimes the callback is a bit "early".
		2128
		2129	This is because C<ev_timer>s work in real time, not wall clock time, so
		2130	libev makes sure your callback is not invoked before the delay happened,
		2131	I<measured according to the real time>, not the system clock.
		2132
		2133	If your timeouts are based on a physical timescale (e.g. "time out this
		2134	connection after 100 seconds") then this shouldn't bother you as it is
		2135	exactly the right behaviour.
		2136
		2137	If you want to compare wall clock/system timestamps to your timers, then
		2138	you need to use C<ev_periodic>s, as these are based on the wall clock
		2139	time, where your comparisons will always generate correct results.
1925		2140
1926	=head3 The special problems of suspended animation	2141	=head3 The special problems of suspended animation
1927		2142
1928	When you leave the server world it is quite customary to hit machines that	2143	When you leave the server world it is quite customary to hit machines that
1929	can suspend/hibernate - what happens to the clocks during such a suspend?	2144	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1959		2174
1960	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2175	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1961		2176
1962	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2177	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1963		2178
1964	Configure the timer to trigger after C<after> seconds. If C<repeat>	2179	Configure the timer to trigger after C<after> seconds (fractional and
1965	is C<0.>, then it will automatically be stopped once the timeout is	2180	negative values are supported). If C<repeat> is C<0.>, then it will
1966	reached. If it is positive, then the timer will automatically be	2181	automatically be stopped once the timeout is reached. If it is positive,
1967	configured to trigger again C<repeat> seconds later, again, and again,	2182	then the timer will automatically be configured to trigger again C<repeat>
1968	until stopped manually.	2183	seconds later, again, and again, until stopped manually.
1969		2184
1970	The timer itself will do a best-effort at avoiding drift, that is, if	2185	The timer itself will do a best-effort at avoiding drift, that is, if
1971	you configure a timer to trigger every 10 seconds, then it will normally	2186	you configure a timer to trigger every 10 seconds, then it will normally
1972	trigger at exactly 10 second intervals. If, however, your program cannot	2187	trigger at exactly 10 second intervals. If, however, your program cannot
1973	keep up with the timer (because it takes longer than those 10 seconds to	2188	keep up with the timer (because it takes longer than those 10 seconds to
1974	do stuff) the timer will not fire more than once per event loop iteration.	2189	do stuff) the timer will not fire more than once per event loop iteration.
1975		2190
1976	=item ev_timer_again (loop, ev_timer *)	2191	=item ev_timer_again (loop, ev_timer *)
1977		2192
1978	This will act as if the timer timed out and restart it again if it is	2193	This will act as if the timer timed out, and restarts it again if it is
1979	repeating. The exact semantics are:	2194	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2195	timeout to the C<repeat> value and calling C<ev_timer_start>.
1980		2196
		2197	The exact semantics are as in the following rules, all of which will be
		2198	applied to the watcher:
		2199
		2200	=over 4
		2201
1981	If the timer is pending, its pending status is cleared.	2202	=item If the timer is pending, the pending status is always cleared.
1982		2203
1983	If the timer is started but non-repeating, stop it (as if it timed out).	2204	=item If the timer is started but non-repeating, stop it (as if it timed
		2205	out, without invoking it).
1984		2206
1985	If the timer is repeating, either start it if necessary (with the	2207	=item If the timer is repeating, make the C<repeat> value the new timeout
1986	C<repeat> value), or reset the running timer to the C<repeat> value.	2208	and start the timer, if necessary.
1987		2209
		2210	=back
		2211
1988	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2212	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1989	usage example.	2213	usage example.
1990		2214
1991	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2215	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1992		2216
1993	Returns the remaining time until a timer fires. If the timer is active,	2217	Returns the remaining time until a timer fires. If the timer is active,
…		…
2046	Periodic watchers are also timers of a kind, but they are very versatile	2270	Periodic watchers are also timers of a kind, but they are very versatile
2047	(and unfortunately a bit complex).	2271	(and unfortunately a bit complex).
2048		2272
2049	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2273	Unlike C<ev_timer>, periodic watchers are not based on real time (or
2050	relative time, the physical time that passes) but on wall clock time	2274	relative time, the physical time that passes) but on wall clock time
2051	(absolute time, the thing you can read on your calender or clock). The	2275	(absolute time, the thing you can read on your calendar or clock). The
2052	difference is that wall clock time can run faster or slower than real	2276	difference is that wall clock time can run faster or slower than real
2053	time, and time jumps are not uncommon (e.g. when you adjust your	2277	time, and time jumps are not uncommon (e.g. when you adjust your
2054	wrist-watch).	2278	wrist-watch).
2055		2279
2056	You can tell a periodic watcher to trigger after some specific point	2280	You can tell a periodic watcher to trigger after some specific point
…		…
2061	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2285	C<ev_timer>, which would still trigger roughly 10 seconds after starting
2062	it, as it uses a relative timeout).	2286	it, as it uses a relative timeout).
2063		2287
2064	C<ev_periodic> watchers can also be used to implement vastly more complex	2288	C<ev_periodic> watchers can also be used to implement vastly more complex
2065	timers, such as triggering an event on each "midnight, local time", or	2289	timers, such as triggering an event on each "midnight, local time", or
2066	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2290	other complicated rules. This cannot easily be done with C<ev_timer>
2067	those cannot react to time jumps.	2291	watchers, as those cannot react to time jumps.
2068		2292
2069	As with timers, the callback is guaranteed to be invoked only when the	2293	As with timers, the callback is guaranteed to be invoked only when the
2070	point in time where it is supposed to trigger has passed. If multiple	2294	point in time where it is supposed to trigger has passed. If multiple
2071	timers become ready during the same loop iteration then the ones with	2295	timers become ready during the same loop iteration then the ones with
2072	earlier time-out values are invoked before ones with later time-out values	2296	earlier time-out values are invoked before ones with later time-out values
…		…
2113		2337
2114	Another way to think about it (for the mathematically inclined) is that	2338	Another way to think about it (for the mathematically inclined) is that
2115	C<ev_periodic> will try to run the callback in this mode at the next possible	2339	C<ev_periodic> will try to run the callback in this mode at the next possible
2116	time where C<time = offset (mod interval)>, regardless of any time jumps.	2340	time where C<time = offset (mod interval)>, regardless of any time jumps.
2117		2341
2118	For numerical stability it is preferable that the C<offset> value is near	2342	The C<interval> I<MUST> be positive, and for numerical stability, the
2119	C<ev_now ()> (the current time), but there is no range requirement for	2343	interval value should be higher than C<1/8192> (which is around 100
2120	this value, and in fact is often specified as zero.	2344	microseconds) and C<offset> should be higher than C<0> and should have
		2345	at most a similar magnitude as the current time (say, within a factor of
		2346	ten). Typical values for offset are, in fact, C<0> or something between
		2347	C<0> and C<interval>, which is also the recommended range.
2121		2348
2122	Note also that there is an upper limit to how often a timer can fire (CPU	2349	Note also that there is an upper limit to how often a timer can fire (CPU
2123	speed for example), so if C<interval> is very small then timing stability	2350	speed for example), so if C<interval> is very small then timing stability
2124	will of course deteriorate. Libev itself tries to be exact to be about one	2351	will of course deteriorate. Libev itself tries to be exact to be about one
2125	millisecond (if the OS supports it and the machine is fast enough).	2352	millisecond (if the OS supports it and the machine is fast enough).
…		…
2155		2382
2156	NOTE: I<< This callback must always return a time that is higher than or	2383	NOTE: I<< This callback must always return a time that is higher than or
2157	equal to the passed C<now> value >>.	2384	equal to the passed C<now> value >>.
2158		2385
2159	This can be used to create very complex timers, such as a timer that	2386	This can be used to create very complex timers, such as a timer that
2160	triggers on "next midnight, local time". To do this, you would calculate the	2387	triggers on "next midnight, local time". To do this, you would calculate
2161	next midnight after C<now> and return the timestamp value for this. How	2388	the next midnight after C<now> and return the timestamp value for
2162	you do this is, again, up to you (but it is not trivial, which is the main	2389	this. Here is a (completely untested, no error checking) example on how to
2163	reason I omitted it as an example).	2390	do this:
		2391
		2392	#include <time.h>
		2393
		2394	static ev_tstamp
		2395	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2396	{
		2397	time_t tnow = (time_t)now;
		2398	struct tm tm;
		2399	localtime_r (&tnow, &tm);
		2400
		2401	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2402	++tm.tm_mday; // midnight next day
		2403
		2404	return mktime (&tm);
		2405	}
		2406
		2407	Note: this code might run into trouble on days that have more then two
		2408	midnights (beginning and end).
2164		2409
2165	=back	2410	=back
2166		2411
2167	=item ev_periodic_again (loop, ev_periodic *)	2412	=item ev_periodic_again (loop, ev_periodic *)
2168		2413
…		…
2233		2478
2234	ev_periodic hourly_tick;	2479	ev_periodic hourly_tick;
2235	ev_periodic_init (&hourly_tick, clock_cb,	2480	ev_periodic_init (&hourly_tick, clock_cb,
2236	fmod (ev_now (loop), 3600.), 3600., 0);	2481	fmod (ev_now (loop), 3600.), 3600., 0);
2237	ev_periodic_start (loop, &hourly_tick);	2482	ev_periodic_start (loop, &hourly_tick);
2238		2483
2239		2484
2240	=head2 C<ev_signal> - signal me when a signal gets signalled!	2485	=head2 C<ev_signal> - signal me when a signal gets signalled!
2241		2486
2242	Signal watchers will trigger an event when the process receives a specific	2487	Signal watchers will trigger an event when the process receives a specific
2243	signal one or more times. Even though signals are very asynchronous, libev	2488	signal one or more times. Even though signals are very asynchronous, libev
2244	will try it's best to deliver signals synchronously, i.e. as part of the	2489	will try its best to deliver signals synchronously, i.e. as part of the
2245	normal event processing, like any other event.	2490	normal event processing, like any other event.
2246		2491
2247	If you want signals to be delivered truly asynchronously, just use	2492	If you want signals to be delivered truly asynchronously, just use
2248	C<sigaction> as you would do without libev and forget about sharing	2493	C<sigaction> as you would do without libev and forget about sharing
2249	the signal. You can even use C<ev_async> from a signal handler to	2494	the signal. You can even use C<ev_async> from a signal handler to
…		…
2253	only within the same loop, i.e. you can watch for C<SIGINT> in your	2498	only within the same loop, i.e. you can watch for C<SIGINT> in your
2254	default loop and for C<SIGIO> in another loop, but you cannot watch for	2499	default loop and for C<SIGIO> in another loop, but you cannot watch for
2255	C<SIGINT> in both the default loop and another loop at the same time. At	2500	C<SIGINT> in both the default loop and another loop at the same time. At
2256	the moment, C<SIGCHLD> is permanently tied to the default loop.	2501	the moment, C<SIGCHLD> is permanently tied to the default loop.
2257		2502
2258	When the first watcher gets started will libev actually register something	2503	Only after the first watcher for a signal is started will libev actually
2259	with the kernel (thus it coexists with your own signal handlers as long as	2504	register something with the kernel. It thus coexists with your own signal
2260	you don't register any with libev for the same signal).	2505	handlers as long as you don't register any with libev for the same signal.
2261		2506
2262	If possible and supported, libev will install its handlers with	2507	If possible and supported, libev will install its handlers with
2263	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2508	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2264	not be unduly interrupted. If you have a problem with system calls getting	2509	not be unduly interrupted. If you have a problem with system calls getting
2265	interrupted by signals you can block all signals in an C<ev_check> watcher	2510	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2268	=head3 The special problem of inheritance over fork/execve/pthread_create	2513	=head3 The special problem of inheritance over fork/execve/pthread_create
2269		2514
2270	Both the signal mask (C<sigprocmask>) and the signal disposition	2515	Both the signal mask (C<sigprocmask>) and the signal disposition
2271	(C<sigaction>) are unspecified after starting a signal watcher (and after	2516	(C<sigaction>) are unspecified after starting a signal watcher (and after
2272	stopping it again), that is, libev might or might not block the signal,	2517	stopping it again), that is, libev might or might not block the signal,
2273	and might or might not set or restore the installed signal handler.	2518	and might or might not set or restore the installed signal handler (but
		2519	see C<EVFLAG_NOSIGMASK>).
2274		2520
2275	While this does not matter for the signal disposition (libev never	2521	While this does not matter for the signal disposition (libev never
2276	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2522	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2277	C<execve>), this matters for the signal mask: many programs do not expect	2523	C<execve>), this matters for the signal mask: many programs do not expect
2278	certain signals to be blocked.	2524	certain signals to be blocked.
…		…
2291	I<has> to modify the signal mask, at least temporarily.	2537	I<has> to modify the signal mask, at least temporarily.
2292		2538
2293	So I can't stress this enough: I<If you do not reset your signal mask when	2539	So I can't stress this enough: I<If you do not reset your signal mask when
2294	you expect it to be empty, you have a race condition in your code>. This	2540	you expect it to be empty, you have a race condition in your code>. This
2295	is not a libev-specific thing, this is true for most event libraries.	2541	is not a libev-specific thing, this is true for most event libraries.
		2542
		2543	=head3 The special problem of threads signal handling
		2544
		2545	POSIX threads has problematic signal handling semantics, specifically,
		2546	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2547	threads in a process block signals, which is hard to achieve.
		2548
		2549	When you want to use sigwait (or mix libev signal handling with your own
		2550	for the same signals), you can tackle this problem by globally blocking
		2551	all signals before creating any threads (or creating them with a fully set
		2552	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2553	loops. Then designate one thread as "signal receiver thread" which handles
		2554	these signals. You can pass on any signals that libev might be interested
		2555	in by calling C<ev_feed_signal>.
2296		2556
2297	=head3 Watcher-Specific Functions and Data Members	2557	=head3 Watcher-Specific Functions and Data Members
2298		2558
2299	=over 4	2559	=over 4
2300		2560
…		…
2435		2695
2436	=head2 C<ev_stat> - did the file attributes just change?	2696	=head2 C<ev_stat> - did the file attributes just change?
2437		2697
2438	This watches a file system path for attribute changes. That is, it calls	2698	This watches a file system path for attribute changes. That is, it calls
2439	C<stat> on that path in regular intervals (or when the OS says it changed)	2699	C<stat> on that path in regular intervals (or when the OS says it changed)
2440	and sees if it changed compared to the last time, invoking the callback if	2700	and sees if it changed compared to the last time, invoking the callback
2441	it did.	2701	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2702	happen after the watcher has been started will be reported.
2442		2703
2443	The path does not need to exist: changing from "path exists" to "path does	2704	The path does not need to exist: changing from "path exists" to "path does
2444	not exist" is a status change like any other. The condition "path does not	2705	not exist" is a status change like any other. The condition "path does not
2445	exist" (or more correctly "path cannot be stat'ed") is signified by the	2706	exist" (or more correctly "path cannot be stat'ed") is signified by the
2446	C<st_nlink> field being zero (which is otherwise always forced to be at	2707	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2676	Apart from keeping your process non-blocking (which is a useful	2937	Apart from keeping your process non-blocking (which is a useful
2677	effect on its own sometimes), idle watchers are a good place to do	2938	effect on its own sometimes), idle watchers are a good place to do
2678	"pseudo-background processing", or delay processing stuff to after the	2939	"pseudo-background processing", or delay processing stuff to after the
2679	event loop has handled all outstanding events.	2940	event loop has handled all outstanding events.
2680		2941
		2942	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2943
		2944	As long as there is at least one active idle watcher, libev will never
		2945	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2946	For this to work, the idle watcher doesn't need to be invoked at all - the
		2947	lowest priority will do.
		2948
		2949	This mode of operation can be useful together with an C<ev_check> watcher,
		2950	to do something on each event loop iteration - for example to balance load
		2951	between different connections.
		2952
		2953	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2954	example.
		2955
2681	=head3 Watcher-Specific Functions and Data Members	2956	=head3 Watcher-Specific Functions and Data Members
2682		2957
2683	=over 4	2958	=over 4
2684		2959
2685	=item ev_idle_init (ev_idle *, callback)	2960	=item ev_idle_init (ev_idle *, callback)
…		…
2696	callback, free it. Also, use no error checking, as usual.	2971	callback, free it. Also, use no error checking, as usual.
2697		2972
2698	static void	2973	static void
2699	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2974	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2700	{	2975	{
		2976	// stop the watcher
		2977	ev_idle_stop (loop, w);
		2978
		2979	// now we can free it
2701	free (w);	2980	free (w);
		2981
2702	// now do something you wanted to do when the program has	2982	// now do something you wanted to do when the program has
2703	// no longer anything immediate to do.	2983	// no longer anything immediate to do.
2704	}	2984	}
2705		2985
2706	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2986	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2708	ev_idle_start (loop, idle_watcher);	2988	ev_idle_start (loop, idle_watcher);
2709		2989
2710		2990
2711	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2991	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2712		2992
2713	Prepare and check watchers are usually (but not always) used in pairs:	2993	Prepare and check watchers are often (but not always) used in pairs:
2714	prepare watchers get invoked before the process blocks and check watchers	2994	prepare watchers get invoked before the process blocks and check watchers
2715	afterwards.	2995	afterwards.
2716		2996
2717	You I<must not> call C<ev_run> or similar functions that enter	2997	You I<must not> call C<ev_run> (or similar functions that enter the
2718	the current event loop from either C<ev_prepare> or C<ev_check>	2998	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2719	watchers. Other loops than the current one are fine, however. The	2999	C<ev_check> watchers. Other loops than the current one are fine,
2720	rationale behind this is that you do not need to check for recursion in	3000	however. The rationale behind this is that you do not need to check
2721	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3001	for recursion in those watchers, i.e. the sequence will always be
2722	C<ev_check> so if you have one watcher of each kind they will always be	3002	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2723	called in pairs bracketing the blocking call.	3003	kind they will always be called in pairs bracketing the blocking call.
2724		3004
2725	Their main purpose is to integrate other event mechanisms into libev and	3005	Their main purpose is to integrate other event mechanisms into libev and
2726	their use is somewhat advanced. They could be used, for example, to track	3006	their use is somewhat advanced. They could be used, for example, to track
2727	variable changes, implement your own watchers, integrate net-snmp or a	3007	variable changes, implement your own watchers, integrate net-snmp or a
2728	coroutine library and lots more. They are also occasionally useful if	3008	coroutine library and lots more. They are also occasionally useful if
…		…
2746	with priority higher than or equal to the event loop and one coroutine	3026	with priority higher than or equal to the event loop and one coroutine
2747	of lower priority, but only once, using idle watchers to keep the event	3027	of lower priority, but only once, using idle watchers to keep the event
2748	loop from blocking if lower-priority coroutines are active, thus mapping	3028	loop from blocking if lower-priority coroutines are active, thus mapping
2749	low-priority coroutines to idle/background tasks).	3029	low-priority coroutines to idle/background tasks).
2750		3030
2751	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3031	When used for this purpose, it is recommended to give C<ev_check> watchers
2752	priority, to ensure that they are being run before any other watchers	3032	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2753	after the poll (this doesn't matter for C<ev_prepare> watchers).	3033	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3034	watchers).
2754		3035
2755	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3036	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2756	activate ("feed") events into libev. While libev fully supports this, they	3037	activate ("feed") events into libev. While libev fully supports this, they
2757	might get executed before other C<ev_check> watchers did their job. As	3038	might get executed before other C<ev_check> watchers did their job. As
2758	C<ev_check> watchers are often used to embed other (non-libev) event	3039	C<ev_check> watchers are often used to embed other (non-libev) event
2759	loops those other event loops might be in an unusable state until their	3040	loops those other event loops might be in an unusable state until their
2760	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3041	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2761	others).	3042	others).
		3043
		3044	=head3 Abusing an C<ev_check> watcher for its side-effect
		3045
		3046	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3047	useful because they are called once per event loop iteration. For
		3048	example, if you want to handle a large number of connections fairly, you
		3049	normally only do a bit of work for each active connection, and if there
		3050	is more work to do, you wait for the next event loop iteration, so other
		3051	connections have a chance of making progress.
		3052
		3053	Using an C<ev_check> watcher is almost enough: it will be called on the
		3054	next event loop iteration. However, that isn't as soon as possible -
		3055	without external events, your C<ev_check> watcher will not be invoked.
		3056
		3057	This is where C<ev_idle> watchers come in handy - all you need is a
		3058	single global idle watcher that is active as long as you have one active
		3059	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3060	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3061	invoked. Neither watcher alone can do that.
2762		3062
2763	=head3 Watcher-Specific Functions and Data Members	3063	=head3 Watcher-Specific Functions and Data Members
2764		3064
2765	=over 4	3065	=over 4
2766		3066
…		…
2967		3267
2968	=over 4	3268	=over 4
2969		3269
2970	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3270	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2971		3271
2972	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3272	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2973		3273
2974	Configures the watcher to embed the given loop, which must be	3274	Configures the watcher to embed the given loop, which must be
2975	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3275	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2976	invoked automatically, otherwise it is the responsibility of the callback	3276	invoked automatically, otherwise it is the responsibility of the callback
2977	to invoke it (it will continue to be called until the sweep has been done,	3277	to invoke it (it will continue to be called until the sweep has been done,
…		…
2998	used).	3298	used).
2999		3299
3000	struct ev_loop *loop_hi = ev_default_init (0);	3300	struct ev_loop *loop_hi = ev_default_init (0);
3001	struct ev_loop *loop_lo = 0;	3301	struct ev_loop *loop_lo = 0;
3002	ev_embed embed;	3302	ev_embed embed;
3003		3303
3004	// see if there is a chance of getting one that works	3304	// see if there is a chance of getting one that works
3005	// (remember that a flags value of 0 means autodetection)	3305	// (remember that a flags value of 0 means autodetection)
3006	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3306	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3007	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3307	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3008	: 0;	3308	: 0;
…		…
3022	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3322	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
3023		3323
3024	struct ev_loop *loop = ev_default_init (0);	3324	struct ev_loop *loop = ev_default_init (0);
3025	struct ev_loop *loop_socket = 0;	3325	struct ev_loop *loop_socket = 0;
3026	ev_embed embed;	3326	ev_embed embed;
3027		3327
3028	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3328	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3029	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3329	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3030	{	3330	{
3031	ev_embed_init (&embed, 0, loop_socket);	3331	ev_embed_init (&embed, 0, loop_socket);
3032	ev_embed_start (loop, &embed);	3332	ev_embed_start (loop, &embed);
…		…
3040		3340
3041	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3341	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
3042		3342
3043	Fork watchers are called when a C<fork ()> was detected (usually because	3343	Fork watchers are called when a C<fork ()> was detected (usually because
3044	whoever is a good citizen cared to tell libev about it by calling	3344	whoever is a good citizen cared to tell libev about it by calling
3045	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3345	C<ev_loop_fork>). The invocation is done before the event loop blocks next
3046	event loop blocks next and before C<ev_check> watchers are being called,	3346	and before C<ev_check> watchers are being called, and only in the child
3047	and only in the child after the fork. If whoever good citizen calling	3347	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
3048	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3348	and calls it in the wrong process, the fork handlers will be invoked, too,
3049	handlers will be invoked, too, of course.	3349	of course.
3050		3350
3051	=head3 The special problem of life after fork - how is it possible?	3351	=head3 The special problem of life after fork - how is it possible?
3052		3352
3053	Most uses of C<fork()> consist of forking, then some simple calls to set	3353	Most uses of C<fork ()> consist of forking, then some simple calls to set
3054	up/change the process environment, followed by a call to C<exec()>. This	3354	up/change the process environment, followed by a call to C<exec()>. This
3055	sequence should be handled by libev without any problems.	3355	sequence should be handled by libev without any problems.
3056		3356
3057	This changes when the application actually wants to do event handling	3357	This changes when the application actually wants to do event handling
3058	in the child, or both parent in child, in effect "continuing" after the	3358	in the child, or both parent in child, in effect "continuing" after the
…		…
3074	disadvantage of having to use multiple event loops (which do not support	3374	disadvantage of having to use multiple event loops (which do not support
3075	signal watchers).	3375	signal watchers).
3076		3376
3077	When this is not possible, or you want to use the default loop for	3377	When this is not possible, or you want to use the default loop for
3078	other reasons, then in the process that wants to start "fresh", call	3378	other reasons, then in the process that wants to start "fresh", call
3079	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3379	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
3080	the default loop will "orphan" (not stop) all registered watchers, so you	3380	Destroying the default loop will "orphan" (not stop) all registered
3081	have to be careful not to execute code that modifies those watchers. Note	3381	watchers, so you have to be careful not to execute code that modifies
3082	also that in that case, you have to re-register any signal watchers.	3382	those watchers. Note also that in that case, you have to re-register any
		3383	signal watchers.
3083		3384
3084	=head3 Watcher-Specific Functions and Data Members	3385	=head3 Watcher-Specific Functions and Data Members
3085		3386
3086	=over 4	3387	=over 4
3087		3388
3088	=item ev_fork_init (ev_signal *, callback)	3389	=item ev_fork_init (ev_fork *, callback)
3089		3390
3090	Initialises and configures the fork watcher - it has no parameters of any	3391	Initialises and configures the fork watcher - it has no parameters of any
3091	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3392	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3092	believe me.	3393	really.
3093		3394
3094	=back	3395	=back
3095		3396
3096		3397
		3398	=head2 C<ev_cleanup> - even the best things end
		3399
		3400	Cleanup watchers are called just before the event loop is being destroyed
		3401	by a call to C<ev_loop_destroy>.
		3402
		3403	While there is no guarantee that the event loop gets destroyed, cleanup
		3404	watchers provide a convenient method to install cleanup hooks for your
		3405	program, worker threads and so on - you just to make sure to destroy the
		3406	loop when you want them to be invoked.
		3407
		3408	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3409	all other watchers, they do not keep a reference to the event loop (which
		3410	makes a lot of sense if you think about it). Like all other watchers, you
		3411	can call libev functions in the callback, except C<ev_cleanup_start>.
		3412
		3413	=head3 Watcher-Specific Functions and Data Members
		3414
		3415	=over 4
		3416
		3417	=item ev_cleanup_init (ev_cleanup *, callback)
		3418
		3419	Initialises and configures the cleanup watcher - it has no parameters of
		3420	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3421	pointless, I assure you.
		3422
		3423	=back
		3424
		3425	Example: Register an atexit handler to destroy the default loop, so any
		3426	cleanup functions are called.
		3427
		3428	static void
		3429	program_exits (void)
		3430	{
		3431	ev_loop_destroy (EV_DEFAULT_UC);
		3432	}
		3433
		3434	...
		3435	atexit (program_exits);
		3436
		3437
3097	=head2 C<ev_async> - how to wake up an event loop	3438	=head2 C<ev_async> - how to wake up an event loop
3098		3439
3099	In general, you cannot use an C<ev_run> from multiple threads or other	3440	In general, you cannot use an C<ev_loop> from multiple threads or other
3100	asynchronous sources such as signal handlers (as opposed to multiple event	3441	asynchronous sources such as signal handlers (as opposed to multiple event
3101	loops - those are of course safe to use in different threads).	3442	loops - those are of course safe to use in different threads).
3102		3443
3103	Sometimes, however, you need to wake up an event loop you do not control,	3444	Sometimes, however, you need to wake up an event loop you do not control,
3104	for example because it belongs to another thread. This is what C<ev_async>	3445	for example because it belongs to another thread. This is what C<ev_async>
…		…
3106	it by calling C<ev_async_send>, which is thread- and signal safe.	3447	it by calling C<ev_async_send>, which is thread- and signal safe.
3107		3448
3108	This functionality is very similar to C<ev_signal> watchers, as signals,	3449	This functionality is very similar to C<ev_signal> watchers, as signals,
3109	too, are asynchronous in nature, and signals, too, will be compressed	3450	too, are asynchronous in nature, and signals, too, will be compressed
3110	(i.e. the number of callback invocations may be less than the number of	3451	(i.e. the number of callback invocations may be less than the number of
3111	C<ev_async_sent> calls).	3452	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3112		3453	of "global async watchers" by using a watcher on an otherwise unused
3113	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3454	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3114	just the default loop.	3455	even without knowing which loop owns the signal.
3115		3456
3116	=head3 Queueing	3457	=head3 Queueing
3117		3458
3118	C<ev_async> does not support queueing of data in any way. The reason	3459	C<ev_async> does not support queueing of data in any way. The reason
3119	is that the author does not know of a simple (or any) algorithm for a	3460	is that the author does not know of a simple (or any) algorithm for a
…		…
3211	trust me.	3552	trust me.
3212		3553
3213	=item ev_async_send (loop, ev_async *)	3554	=item ev_async_send (loop, ev_async *)
3214		3555
3215	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3556	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3216	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3557	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3558	returns.
		3559
3217	C<ev_feed_event>, this call is safe to do from other threads, signal or	3560	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3218	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3561	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3219	section below on what exactly this means).	3562	embedding section below on what exactly this means).
3220		3563
3221	Note that, as with other watchers in libev, multiple events might get	3564	Note that, as with other watchers in libev, multiple events might get
3222	compressed into a single callback invocation (another way to look at this	3565	compressed into a single callback invocation (another way to look at
3223	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3566	this is that C<ev_async> watchers are level-triggered: they are set on
3224	reset when the event loop detects that).	3567	C<ev_async_send>, reset when the event loop detects that).
3225		3568
3226	This call incurs the overhead of a system call only once per event loop	3569	This call incurs the overhead of at most one extra system call per event
3227	iteration, so while the overhead might be noticeable, it doesn't apply to	3570	loop iteration, if the event loop is blocked, and no syscall at all if
3228	repeated calls to C<ev_async_send> for the same event loop.	3571	the event loop (or your program) is processing events. That means that
		3572	repeated calls are basically free (there is no need to avoid calls for
		3573	performance reasons) and that the overhead becomes smaller (typically
		3574	zero) under load.
3229		3575
3230	=item bool = ev_async_pending (ev_async *)	3576	=item bool = ev_async_pending (ev_async *)
3231		3577
3232	Returns a non-zero value when C<ev_async_send> has been called on the	3578	Returns a non-zero value when C<ev_async_send> has been called on the
3233	watcher but the event has not yet been processed (or even noted) by the	3579	watcher but the event has not yet been processed (or even noted) by the
…		…
3250		3596
3251	There are some other functions of possible interest. Described. Here. Now.	3597	There are some other functions of possible interest. Described. Here. Now.
3252		3598
3253	=over 4	3599	=over 4
3254		3600
3255	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3601	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3256		3602
3257	This function combines a simple timer and an I/O watcher, calls your	3603	This function combines a simple timer and an I/O watcher, calls your
3258	callback on whichever event happens first and automatically stops both	3604	callback on whichever event happens first and automatically stops both
3259	watchers. This is useful if you want to wait for a single event on an fd	3605	watchers. This is useful if you want to wait for a single event on an fd
3260	or timeout without having to allocate/configure/start/stop/free one or	3606	or timeout without having to allocate/configure/start/stop/free one or
…		…
3288	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3634	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3289		3635
3290	=item ev_feed_fd_event (loop, int fd, int revents)	3636	=item ev_feed_fd_event (loop, int fd, int revents)
3291		3637
3292	Feed an event on the given fd, as if a file descriptor backend detected	3638	Feed an event on the given fd, as if a file descriptor backend detected
3293	the given events it.	3639	the given events.
3294		3640
3295	=item ev_feed_signal_event (loop, int signum)	3641	=item ev_feed_signal_event (loop, int signum)
3296		3642
3297	Feed an event as if the given signal occurred (C<loop> must be the default	3643	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3298	loop!).	3644	which is async-safe.
3299		3645
3300	=back	3646	=back
		3647
		3648
		3649	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3650
		3651	This section explains some common idioms that are not immediately
		3652	obvious. Note that examples are sprinkled over the whole manual, and this
		3653	section only contains stuff that wouldn't fit anywhere else.
		3654
		3655	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3656
		3657	Each watcher has, by default, a C<void *data> member that you can read
		3658	or modify at any time: libev will completely ignore it. This can be used
		3659	to associate arbitrary data with your watcher. If you need more data and
		3660	don't want to allocate memory separately and store a pointer to it in that
		3661	data member, you can also "subclass" the watcher type and provide your own
		3662	data:
		3663
		3664	struct my_io
		3665	{
		3666	ev_io io;
		3667	int otherfd;
		3668	void *somedata;
		3669	struct whatever *mostinteresting;
		3670	};
		3671
		3672	...
		3673	struct my_io w;
		3674	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3675
		3676	And since your callback will be called with a pointer to the watcher, you
		3677	can cast it back to your own type:
		3678
		3679	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3680	{
		3681	struct my_io *w = (struct my_io *)w_;
		3682	...
		3683	}
		3684
		3685	More interesting and less C-conformant ways of casting your callback
		3686	function type instead have been omitted.
		3687
		3688	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3689
		3690	Another common scenario is to use some data structure with multiple
		3691	embedded watchers, in effect creating your own watcher that combines
		3692	multiple libev event sources into one "super-watcher":
		3693
		3694	struct my_biggy
		3695	{
		3696	int some_data;
		3697	ev_timer t1;
		3698	ev_timer t2;
		3699	}
		3700
		3701	In this case getting the pointer to C<my_biggy> is a bit more
		3702	complicated: Either you store the address of your C<my_biggy> struct in
		3703	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3704	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3705	real programmers):
		3706
		3707	#include <stddef.h>
		3708
		3709	static void
		3710	t1_cb (EV_P_ ev_timer *w, int revents)
		3711	{
		3712	struct my_biggy big = (struct my_biggy *)
		3713	(((char *)w) - offsetof (struct my_biggy, t1));
		3714	}
		3715
		3716	static void
		3717	t2_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t2));
		3721	}
		3722
		3723	=head2 AVOIDING FINISHING BEFORE RETURNING
		3724
		3725	Often you have structures like this in event-based programs:
		3726
		3727	callback ()
		3728	{
		3729	free (request);
		3730	}
		3731
		3732	request = start_new_request (..., callback);
		3733
		3734	The intent is to start some "lengthy" operation. The C<request> could be
		3735	used to cancel the operation, or do other things with it.
		3736
		3737	It's not uncommon to have code paths in C<start_new_request> that
		3738	immediately invoke the callback, for example, to report errors. Or you add
		3739	some caching layer that finds that it can skip the lengthy aspects of the
		3740	operation and simply invoke the callback with the result.
		3741
		3742	The problem here is that this will happen I<before> C<start_new_request>
		3743	has returned, so C<request> is not set.
		3744
		3745	Even if you pass the request by some safer means to the callback, you
		3746	might want to do something to the request after starting it, such as
		3747	canceling it, which probably isn't working so well when the callback has
		3748	already been invoked.
		3749
		3750	A common way around all these issues is to make sure that
		3751	C<start_new_request> I<always> returns before the callback is invoked. If
		3752	C<start_new_request> immediately knows the result, it can artificially
		3753	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3754	example, or more sneakily, by reusing an existing (stopped) watcher and
		3755	pushing it into the pending queue:
		3756
		3757	ev_set_cb (watcher, callback);
		3758	ev_feed_event (EV_A_ watcher, 0);
		3759
		3760	This way, C<start_new_request> can safely return before the callback is
		3761	invoked, while not delaying callback invocation too much.
		3762
		3763	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3764
		3765	Often (especially in GUI toolkits) there are places where you have
		3766	I<modal> interaction, which is most easily implemented by recursively
		3767	invoking C<ev_run>.
		3768
		3769	This brings the problem of exiting - a callback might want to finish the
		3770	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3771	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3772	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3773	other combination: In these cases, a simple C<ev_break> will not work.
		3774
		3775	The solution is to maintain "break this loop" variable for each C<ev_run>
		3776	invocation, and use a loop around C<ev_run> until the condition is
		3777	triggered, using C<EVRUN_ONCE>:
		3778
		3779	// main loop
		3780	int exit_main_loop = 0;
		3781
		3782	while (!exit_main_loop)
		3783	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3784
		3785	// in a modal watcher
		3786	int exit_nested_loop = 0;
		3787
		3788	while (!exit_nested_loop)
		3789	ev_run (EV_A_ EVRUN_ONCE);
		3790
		3791	To exit from any of these loops, just set the corresponding exit variable:
		3792
		3793	// exit modal loop
		3794	exit_nested_loop = 1;
		3795
		3796	// exit main program, after modal loop is finished
		3797	exit_main_loop = 1;
		3798
		3799	// exit both
		3800	exit_main_loop = exit_nested_loop = 1;
		3801
		3802	=head2 THREAD LOCKING EXAMPLE
		3803
		3804	Here is a fictitious example of how to run an event loop in a different
		3805	thread from where callbacks are being invoked and watchers are
		3806	created/added/removed.
		3807
		3808	For a real-world example, see the C<EV::Loop::Async> perl module,
		3809	which uses exactly this technique (which is suited for many high-level
		3810	languages).
		3811
		3812	The example uses a pthread mutex to protect the loop data, a condition
		3813	variable to wait for callback invocations, an async watcher to notify the
		3814	event loop thread and an unspecified mechanism to wake up the main thread.
		3815
		3816	First, you need to associate some data with the event loop:
		3817
		3818	typedef struct {
		3819	mutex_t lock; /* global loop lock */
		3820	ev_async async_w;
		3821	thread_t tid;
		3822	cond_t invoke_cv;
		3823	} userdata;
		3824
		3825	void prepare_loop (EV_P)
		3826	{
		3827	// for simplicity, we use a static userdata struct.
		3828	static userdata u;
		3829
		3830	ev_async_init (&u->async_w, async_cb);
		3831	ev_async_start (EV_A_ &u->async_w);
		3832
		3833	pthread_mutex_init (&u->lock, 0);
		3834	pthread_cond_init (&u->invoke_cv, 0);
		3835
		3836	// now associate this with the loop
		3837	ev_set_userdata (EV_A_ u);
		3838	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3839	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3840
		3841	// then create the thread running ev_run
		3842	pthread_create (&u->tid, 0, l_run, EV_A);
		3843	}
		3844
		3845	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3846	solely to wake up the event loop so it takes notice of any new watchers
		3847	that might have been added:
		3848
		3849	static void
		3850	async_cb (EV_P_ ev_async *w, int revents)
		3851	{
		3852	// just used for the side effects
		3853	}
		3854
		3855	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3856	protecting the loop data, respectively.
		3857
		3858	static void
		3859	l_release (EV_P)
		3860	{
		3861	userdata *u = ev_userdata (EV_A);
		3862	pthread_mutex_unlock (&u->lock);
		3863	}
		3864
		3865	static void
		3866	l_acquire (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_lock (&u->lock);
		3870	}
		3871
		3872	The event loop thread first acquires the mutex, and then jumps straight
		3873	into C<ev_run>:
		3874
		3875	void *
		3876	l_run (void *thr_arg)
		3877	{
		3878	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3879
		3880	l_acquire (EV_A);
		3881	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3882	ev_run (EV_A_ 0);
		3883	l_release (EV_A);
		3884
		3885	return 0;
		3886	}
		3887
		3888	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3889	signal the main thread via some unspecified mechanism (signals? pipe
		3890	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3891	have been called (in a while loop because a) spurious wakeups are possible
		3892	and b) skipping inter-thread-communication when there are no pending
		3893	watchers is very beneficial):
		3894
		3895	static void
		3896	l_invoke (EV_P)
		3897	{
		3898	userdata *u = ev_userdata (EV_A);
		3899
		3900	while (ev_pending_count (EV_A))
		3901	{
		3902	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3903	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3904	}
		3905	}
		3906
		3907	Now, whenever the main thread gets told to invoke pending watchers, it
		3908	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3909	thread to continue:
		3910
		3911	static void
		3912	real_invoke_pending (EV_P)
		3913	{
		3914	userdata *u = ev_userdata (EV_A);
		3915
		3916	pthread_mutex_lock (&u->lock);
		3917	ev_invoke_pending (EV_A);
		3918	pthread_cond_signal (&u->invoke_cv);
		3919	pthread_mutex_unlock (&u->lock);
		3920	}
		3921
		3922	Whenever you want to start/stop a watcher or do other modifications to an
		3923	event loop, you will now have to lock:
		3924
		3925	ev_timer timeout_watcher;
		3926	userdata *u = ev_userdata (EV_A);
		3927
		3928	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3929
		3930	pthread_mutex_lock (&u->lock);
		3931	ev_timer_start (EV_A_ &timeout_watcher);
		3932	ev_async_send (EV_A_ &u->async_w);
		3933	pthread_mutex_unlock (&u->lock);
		3934
		3935	Note that sending the C<ev_async> watcher is required because otherwise
		3936	an event loop currently blocking in the kernel will have no knowledge
		3937	about the newly added timer. By waking up the loop it will pick up any new
		3938	watchers in the next event loop iteration.
		3939
		3940	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3941
		3942	While the overhead of a callback that e.g. schedules a thread is small, it
		3943	is still an overhead. If you embed libev, and your main usage is with some
		3944	kind of threads or coroutines, you might want to customise libev so that
		3945	doesn't need callbacks anymore.
		3946
		3947	Imagine you have coroutines that you can switch to using a function
		3948	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3949	and that due to some magic, the currently active coroutine is stored in a
		3950	global called C<current_coro>. Then you can build your own "wait for libev
		3951	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3952	the differing C<;> conventions):
		3953
		3954	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3955	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3956
		3957	That means instead of having a C callback function, you store the
		3958	coroutine to switch to in each watcher, and instead of having libev call
		3959	your callback, you instead have it switch to that coroutine.
		3960
		3961	A coroutine might now wait for an event with a function called
		3962	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3963	matter when, or whether the watcher is active or not when this function is
		3964	called):
		3965
		3966	void
		3967	wait_for_event (ev_watcher *w)
		3968	{
		3969	ev_set_cb (w, current_coro);
		3970	switch_to (libev_coro);
		3971	}
		3972
		3973	That basically suspends the coroutine inside C<wait_for_event> and
		3974	continues the libev coroutine, which, when appropriate, switches back to
		3975	this or any other coroutine.
		3976
		3977	You can do similar tricks if you have, say, threads with an event queue -
		3978	instead of storing a coroutine, you store the queue object and instead of
		3979	switching to a coroutine, you push the watcher onto the queue and notify
		3980	any waiters.
		3981
		3982	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3983	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3984
		3985	// my_ev.h
		3986	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3987	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3988	#include "../libev/ev.h"
		3989
		3990	// my_ev.c
		3991	#define EV_H "my_ev.h"
		3992	#include "../libev/ev.c"
		3993
		3994	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3995	F<my_ev.c> into your project. When properly specifying include paths, you
		3996	can even use F<ev.h> as header file name directly.
3301		3997
3302		3998
3303	=head1 LIBEVENT EMULATION	3999	=head1 LIBEVENT EMULATION
3304		4000
3305	Libev offers a compatibility emulation layer for libevent. It cannot	4001	Libev offers a compatibility emulation layer for libevent. It cannot
3306	emulate the internals of libevent, so here are some usage hints:	4002	emulate the internals of libevent, so here are some usage hints:
3307		4003
3308	=over 4	4004	=over 4
		4005
		4006	=item * Only the libevent-1.4.1-beta API is being emulated.
		4007
		4008	This was the newest libevent version available when libev was implemented,
		4009	and is still mostly unchanged in 2010.
3309		4010
3310	=item * Use it by including <event.h>, as usual.	4011	=item * Use it by including <event.h>, as usual.
3311		4012
3312	=item * The following members are fully supported: ev_base, ev_callback,	4013	=item * The following members are fully supported: ev_base, ev_callback,
3313	ev_arg, ev_fd, ev_res, ev_events.	4014	ev_arg, ev_fd, ev_res, ev_events.
…		…
3319	=item * Priorities are not currently supported. Initialising priorities	4020	=item * Priorities are not currently supported. Initialising priorities
3320	will fail and all watchers will have the same priority, even though there	4021	will fail and all watchers will have the same priority, even though there
3321	is an ev_pri field.	4022	is an ev_pri field.
3322		4023
3323	=item * In libevent, the last base created gets the signals, in libev, the	4024	=item * In libevent, the last base created gets the signals, in libev, the
3324	first base created (== the default loop) gets the signals.	4025	base that registered the signal gets the signals.
3325		4026
3326	=item * Other members are not supported.	4027	=item * Other members are not supported.
3327		4028
3328	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4029	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3329	to use the libev header file and library.	4030	to use the libev header file and library.
3330		4031
3331	=back	4032	=back
3332		4033
3333	=head1 C++ SUPPORT	4034	=head1 C++ SUPPORT
		4035
		4036	=head2 C API
		4037
		4038	The normal C API should work fine when used from C++: both ev.h and the
		4039	libev sources can be compiled as C++. Therefore, code that uses the C API
		4040	will work fine.
		4041
		4042	Proper exception specifications might have to be added to callbacks passed
		4043	to libev: exceptions may be thrown only from watcher callbacks, all other
		4044	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4045	callbacks) must not throw exceptions, and might need a C<noexcept>
		4046	specification. If you have code that needs to be compiled as both C and
		4047	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4048
		4049	static void
		4050	fatal_error (const char *msg) EV_NOEXCEPT
		4051	{
		4052	perror (msg);
		4053	abort ();
		4054	}
		4055
		4056	...
		4057	ev_set_syserr_cb (fatal_error);
		4058
		4059	The only API functions that can currently throw exceptions are C<ev_run>,
		4060	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4061	because it runs cleanup watchers).
		4062
		4063	Throwing exceptions in watcher callbacks is only supported if libev itself
		4064	is compiled with a C++ compiler or your C and C++ environments allow
		4065	throwing exceptions through C libraries (most do).
		4066
		4067	=head2 C++ API
3334		4068
3335	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4069	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3336	you to use some convenience methods to start/stop watchers and also change	4070	you to use some convenience methods to start/stop watchers and also change
3337	the callback model to a model using method callbacks on objects.	4071	the callback model to a model using method callbacks on objects.
3338		4072
3339	To use it,	4073	To use it,
3340		4074
3341	#include <ev++.h>	4075	#include <ev++.h>
3342		4076
3343	This automatically includes F<ev.h> and puts all of its definitions (many	4077	This automatically includes F<ev.h> and puts all of its definitions (many
3344	of them macros) into the global namespace. All C++ specific things are	4078	of them macros) into the global namespace. All C++ specific things are
3345	put into the C<ev> namespace. It should support all the same embedding	4079	put into the C<ev> namespace. It should support all the same embedding
…		…
3348	Care has been taken to keep the overhead low. The only data member the C++	4082	Care has been taken to keep the overhead low. The only data member the C++
3349	classes add (compared to plain C-style watchers) is the event loop pointer	4083	classes add (compared to plain C-style watchers) is the event loop pointer
3350	that the watcher is associated with (or no additional members at all if	4084	that the watcher is associated with (or no additional members at all if
3351	you disable C<EV_MULTIPLICITY> when embedding libev).	4085	you disable C<EV_MULTIPLICITY> when embedding libev).
3352		4086
3353	Currently, functions, and static and non-static member functions can be	4087	Currently, functions, static and non-static member functions and classes
3354	used as callbacks. Other types should be easy to add as long as they only	4088	with C<operator ()> can be used as callbacks. Other types should be easy
3355	need one additional pointer for context. If you need support for other	4089	to add as long as they only need one additional pointer for context. If
3356	types of functors please contact the author (preferably after implementing	4090	you need support for other types of functors please contact the author
3357	it).	4091	(preferably after implementing it).
		4092
		4093	For all this to work, your C++ compiler either has to use the same calling
		4094	conventions as your C compiler (for static member functions), or you have
		4095	to embed libev and compile libev itself as C++.
3358		4096
3359	Here is a list of things available in the C<ev> namespace:	4097	Here is a list of things available in the C<ev> namespace:
3360		4098
3361	=over 4	4099	=over 4
3362		4100
…		…
3372	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4110	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3373		4111
3374	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4112	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3375	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4113	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3376	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4114	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3377	defines by many implementations.	4115	defined by many implementations.
3378		4116
3379	All of those classes have these methods:	4117	All of those classes have these methods:
3380		4118
3381	=over 4	4119	=over 4
3382		4120
…		…
3444	void operator() (ev::io &w, int revents)	4182	void operator() (ev::io &w, int revents)
3445	{	4183	{
3446	...	4184	...
3447	}	4185	}
3448	}	4186	}
3449		4187
3450	myfunctor f;	4188	myfunctor f;
3451		4189
3452	ev::io w;	4190	ev::io w;
3453	w.set (&f);	4191	w.set (&f);
3454		4192
…		…
3472	Associates a different C<struct ev_loop> with this watcher. You can only	4210	Associates a different C<struct ev_loop> with this watcher. You can only
3473	do this when the watcher is inactive (and not pending either).	4211	do this when the watcher is inactive (and not pending either).
3474		4212
3475	=item w->set ([arguments])	4213	=item w->set ([arguments])
3476		4214
3477	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this	4215	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
3478	method or a suitable start method must be called at least once. Unlike the	4216	with the same arguments. Either this method or a suitable start method
3479	C counterpart, an active watcher gets automatically stopped and restarted	4217	must be called at least once. Unlike the C counterpart, an active watcher
3480	when reconfiguring it with this method.	4218	gets automatically stopped and restarted when reconfiguring it with this
		4219	method.
		4220
		4221	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4222	clashing with the C<set (loop)> method.
3481		4223
3482	=item w->start ()	4224	=item w->start ()
3483		4225
3484	Starts the watcher. Note that there is no C<loop> argument, as the	4226	Starts the watcher. Note that there is no C<loop> argument, as the
3485	constructor already stores the event loop.	4227	constructor already stores the event loop.
…		…
3515	watchers in the constructor.	4257	watchers in the constructor.
3516		4258
3517	class myclass	4259	class myclass
3518	{	4260	{
3519	ev::io io ; void io_cb (ev::io &w, int revents);	4261	ev::io io ; void io_cb (ev::io &w, int revents);
3520	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);	4262	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3521	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4263	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3522		4264
3523	myclass (int fd)	4265	myclass (int fd)
3524	{	4266	{
3525	io .set <myclass, &myclass::io_cb > (this);	4267	io .set <myclass, &myclass::io_cb > (this);
…		…
3576	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4318	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3577		4319
3578	=item D	4320	=item D
3579		4321
3580	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4322	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3581	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4323	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3582		4324
3583	=item Ocaml	4325	=item Ocaml
3584		4326
3585	Erkki Seppala has written Ocaml bindings for libev, to be found at	4327	Erkki Seppala has written Ocaml bindings for libev, to be found at
3586	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4328	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3589		4331
3590	Brian Maher has written a partial interface to libev for lua (at the	4332	Brian Maher has written a partial interface to libev for lua (at the
3591	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4333	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3592	L<http://github.com/brimworks/lua-ev>.	4334	L<http://github.com/brimworks/lua-ev>.
3593		4335
		4336	=item Javascript
		4337
		4338	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4339
		4340	=item Others
		4341
		4342	There are others, and I stopped counting.
		4343
3594	=back	4344	=back
3595		4345
3596		4346
3597	=head1 MACRO MAGIC	4347	=head1 MACRO MAGIC
3598		4348
…		…
3634	suitable for use with C<EV_A>.	4384	suitable for use with C<EV_A>.
3635		4385
3636	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4386	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3637		4387
3638	Similar to the other two macros, this gives you the value of the default	4388	Similar to the other two macros, this gives you the value of the default
3639	loop, if multiple loops are supported ("ev loop default").	4389	loop, if multiple loops are supported ("ev loop default"). The default loop
		4390	will be initialised if it isn't already initialised.
		4391
		4392	For non-multiplicity builds, these macros do nothing, so you always have
		4393	to initialise the loop somewhere.
3640		4394
3641	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4395	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3642		4396
3643	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4397	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3644	default loop has been initialised (C<UC> == unchecked). Their behaviour	4398	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3711	ev_vars.h	4465	ev_vars.h
3712	ev_wrap.h	4466	ev_wrap.h
3713		4467
3714	ev_win32.c required on win32 platforms only	4468	ev_win32.c required on win32 platforms only
3715		4469
3716	ev_select.c only when select backend is enabled (which is enabled by default)	4470	ev_select.c only when select backend is enabled
3717	ev_poll.c only when poll backend is enabled (disabled by default)	4471	ev_poll.c only when poll backend is enabled
3718	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4472	ev_epoll.c only when the epoll backend is enabled
		4473	ev_linuxaio.c only when the linux aio backend is enabled
3719	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4474	ev_kqueue.c only when the kqueue backend is enabled
3720	ev_port.c only when the solaris port backend is enabled (disabled by default)	4475	ev_port.c only when the solaris port backend is enabled
3721		4476
3722	F<ev.c> includes the backend files directly when enabled, so you only need	4477	F<ev.c> includes the backend files directly when enabled, so you only need
3723	to compile this single file.	4478	to compile this single file.
3724		4479
3725	=head3 LIBEVENT COMPATIBILITY API	4480	=head3 LIBEVENT COMPATIBILITY API
…		…
3789	supported). It will also not define any of the structs usually found in	4544	supported). It will also not define any of the structs usually found in
3790	F<event.h> that are not directly supported by the libev core alone.	4545	F<event.h> that are not directly supported by the libev core alone.
3791		4546
3792	In standalone mode, libev will still try to automatically deduce the	4547	In standalone mode, libev will still try to automatically deduce the
3793	configuration, but has to be more conservative.	4548	configuration, but has to be more conservative.
		4549
		4550	=item EV_USE_FLOOR
		4551
		4552	If defined to be C<1>, libev will use the C<floor ()> function for its
		4553	periodic reschedule calculations, otherwise libev will fall back on a
		4554	portable (slower) implementation. If you enable this, you usually have to
		4555	link against libm or something equivalent. Enabling this when the C<floor>
		4556	function is not available will fail, so the safe default is to not enable
		4557	this.
3794		4558
3795	=item EV_USE_MONOTONIC	4559	=item EV_USE_MONOTONIC
3796		4560
3797	If defined to be C<1>, libev will try to detect the availability of the	4561	If defined to be C<1>, libev will try to detect the availability of the
3798	monotonic clock option at both compile time and runtime. Otherwise no	4562	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3884	If programs implement their own fd to handle mapping on win32, then this	4648	If programs implement their own fd to handle mapping on win32, then this
3885	macro can be used to override the C<close> function, useful to unregister	4649	macro can be used to override the C<close> function, useful to unregister
3886	file descriptors again. Note that the replacement function has to close	4650	file descriptors again. Note that the replacement function has to close
3887	the underlying OS handle.	4651	the underlying OS handle.
3888		4652
		4653	=item EV_USE_WSASOCKET
		4654
		4655	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4656	communication socket, which works better in some environments. Otherwise,
		4657	the normal C<socket> function will be used, which works better in other
		4658	environments.
		4659
3889	=item EV_USE_POLL	4660	=item EV_USE_POLL
3890		4661
3891	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4662	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3892	backend. Otherwise it will be enabled on non-win32 platforms. It	4663	backend. Otherwise it will be enabled on non-win32 platforms. It
3893	takes precedence over select.	4664	takes precedence over select.
…		…
3897	If defined to be C<1>, libev will compile in support for the Linux	4668	If defined to be C<1>, libev will compile in support for the Linux
3898	C<epoll>(7) backend. Its availability will be detected at runtime,	4669	C<epoll>(7) backend. Its availability will be detected at runtime,
3899	otherwise another method will be used as fallback. This is the preferred	4670	otherwise another method will be used as fallback. This is the preferred
3900	backend for GNU/Linux systems. If undefined, it will be enabled if the	4671	backend for GNU/Linux systems. If undefined, it will be enabled if the
3901	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4672	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4673
		4674	=item EV_USE_LINUXAIO
		4675
		4676	If defined to be C<1>, libev will compile in support for the Linux
		4677	aio backend. Due to it's currenbt limitations it has to be requested
		4678	explicitly. If undefined, it will be enabled on linux, otherwise
		4679	disabled.
3902		4680
3903	=item EV_USE_KQUEUE	4681	=item EV_USE_KQUEUE
3904		4682
3905	If defined to be C<1>, libev will compile in support for the BSD style	4683	If defined to be C<1>, libev will compile in support for the BSD style
3906	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4684	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3928	If defined to be C<1>, libev will compile in support for the Linux inotify	4706	If defined to be C<1>, libev will compile in support for the Linux inotify
3929	interface to speed up C<ev_stat> watchers. Its actual availability will	4707	interface to speed up C<ev_stat> watchers. Its actual availability will
3930	be detected at runtime. If undefined, it will be enabled if the headers	4708	be detected at runtime. If undefined, it will be enabled if the headers
3931	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4709	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3932		4710
		4711	=item EV_NO_SMP
		4712
		4713	If defined to be C<1>, libev will assume that memory is always coherent
		4714	between threads, that is, threads can be used, but threads never run on
		4715	different cpus (or different cpu cores). This reduces dependencies
		4716	and makes libev faster.
		4717
		4718	=item EV_NO_THREADS
		4719
		4720	If defined to be C<1>, libev will assume that it will never be called from
		4721	different threads (that includes signal handlers), which is a stronger
		4722	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4723	libev faster.
		4724
3933	=item EV_ATOMIC_T	4725	=item EV_ATOMIC_T
3934		4726
3935	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4727	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3936	access is atomic with respect to other threads or signal contexts. No such	4728	access is atomic with respect to other threads or signal contexts. No
3937	type is easily found in the C language, so you can provide your own type	4729	such type is easily found in the C language, so you can provide your own
3938	that you know is safe for your purposes. It is used both for signal handler "locking"	4730	type that you know is safe for your purposes. It is used both for signal
3939	as well as for signal and thread safety in C<ev_async> watchers.	4731	handler "locking" as well as for signal and thread safety in C<ev_async>
		4732	watchers.
3940		4733
3941	In the absence of this define, libev will use C<sig_atomic_t volatile>	4734	In the absence of this define, libev will use C<sig_atomic_t volatile>
3942	(from F<signal.h>), which is usually good enough on most platforms.	4735	(from F<signal.h>), which is usually good enough on most platforms.
3943		4736
3944	=item EV_H (h)	4737	=item EV_H (h)
…		…
3971	will have the C<struct ev_loop *> as first argument, and you can create	4764	will have the C<struct ev_loop *> as first argument, and you can create
3972	additional independent event loops. Otherwise there will be no support	4765	additional independent event loops. Otherwise there will be no support
3973	for multiple event loops and there is no first event loop pointer	4766	for multiple event loops and there is no first event loop pointer
3974	argument. Instead, all functions act on the single default loop.	4767	argument. Instead, all functions act on the single default loop.
3975		4768
		4769	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4770	default loop when multiplicity is switched off - you always have to
		4771	initialise the loop manually in this case.
		4772
3976	=item EV_MINPRI	4773	=item EV_MINPRI
3977		4774
3978	=item EV_MAXPRI	4775	=item EV_MAXPRI
3979		4776
3980	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4777	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
4016	#define EV_USE_POLL 1	4813	#define EV_USE_POLL 1
4017	#define EV_CHILD_ENABLE 1	4814	#define EV_CHILD_ENABLE 1
4018	#define EV_ASYNC_ENABLE 1	4815	#define EV_ASYNC_ENABLE 1
4019		4816
4020	The actual value is a bitset, it can be a combination of the following	4817	The actual value is a bitset, it can be a combination of the following
4021	values:	4818	values (by default, all of these are enabled):
4022		4819
4023	=over 4	4820	=over 4
4024		4821
4025	=item C<1> - faster/larger code	4822	=item C<1> - faster/larger code
4026		4823
…		…
4030	code size by roughly 30% on amd64).	4827	code size by roughly 30% on amd64).
4031		4828
4032	When optimising for size, use of compiler flags such as C<-Os> with	4829	When optimising for size, use of compiler flags such as C<-Os> with
4033	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4830	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
4034	assertions.	4831	assertions.
		4832
		4833	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4834	(e.g. gcc with C<-Os>).
4035		4835
4036	=item C<2> - faster/larger data structures	4836	=item C<2> - faster/larger data structures
4037		4837
4038	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4838	Replaces the small 2-heap for timer management by a faster 4-heap, larger
4039	hash table sizes and so on. This will usually further increase code size	4839	hash table sizes and so on. This will usually further increase code size
4040	and can additionally have an effect on the size of data structures at	4840	and can additionally have an effect on the size of data structures at
4041	runtime.	4841	runtime.
4042		4842
		4843	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4844	(e.g. gcc with C<-Os>).
		4845
4043	=item C<4> - full API configuration	4846	=item C<4> - full API configuration
4044		4847
4045	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4848	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
4046	enables multiplicity (C<EV_MULTIPLICITY>=1).	4849	enables multiplicity (C<EV_MULTIPLICITY>=1).
4047		4850
…		…
4077		4880
4078	With an intelligent-enough linker (gcc+binutils are intelligent enough	4881	With an intelligent-enough linker (gcc+binutils are intelligent enough
4079	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4882	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
4080	your program might be left out as well - a binary starting a timer and an	4883	your program might be left out as well - a binary starting a timer and an
4081	I/O watcher then might come out at only 5Kb.	4884	I/O watcher then might come out at only 5Kb.
		4885
		4886	=item EV_API_STATIC
		4887
		4888	If this symbol is defined (by default it is not), then all identifiers
		4889	will have static linkage. This means that libev will not export any
		4890	identifiers, and you cannot link against libev anymore. This can be useful
		4891	when you embed libev, only want to use libev functions in a single file,
		4892	and do not want its identifiers to be visible.
		4893
		4894	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4895	wants to use libev.
		4896
		4897	This option only works when libev is compiled with a C compiler, as C++
		4898	doesn't support the required declaration syntax.
4082		4899
4083	=item EV_AVOID_STDIO	4900	=item EV_AVOID_STDIO
4084		4901
4085	If this is set to C<1> at compiletime, then libev will avoid using stdio	4902	If this is set to C<1> at compiletime, then libev will avoid using stdio
4086	functions (printf, scanf, perror etc.). This will increase the code size	4903	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4230	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5047	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4231		5048
4232	#include "ev_cpp.h"	5049	#include "ev_cpp.h"
4233	#include "ev.c"	5050	#include "ev.c"
4234		5051
4235	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5052	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4236		5053
4237	=head2 THREADS AND COROUTINES	5054	=head2 THREADS AND COROUTINES
4238		5055
4239	=head3 THREADS	5056	=head3 THREADS
4240		5057
…		…
4291	default loop and triggering an C<ev_async> watcher from the default loop	5108	default loop and triggering an C<ev_async> watcher from the default loop
4292	watcher callback into the event loop interested in the signal.	5109	watcher callback into the event loop interested in the signal.
4293		5110
4294	=back	5111	=back
4295		5112
4296	=head4 THREAD LOCKING EXAMPLE	5113	See also L</THREAD LOCKING EXAMPLE>.
4297
4298	Here is a fictitious example of how to run an event loop in a different
4299	thread than where callbacks are being invoked and watchers are
4300	created/added/removed.
4301
4302	For a real-world example, see the C<EV::Loop::Async> perl module,
4303	which uses exactly this technique (which is suited for many high-level
4304	languages).
4305
4306	The example uses a pthread mutex to protect the loop data, a condition
4307	variable to wait for callback invocations, an async watcher to notify the
4308	event loop thread and an unspecified mechanism to wake up the main thread.
4309
4310	First, you need to associate some data with the event loop:
4311
4312	typedef struct {
4313	mutex_t lock; /* global loop lock */
4314	ev_async async_w;
4315	thread_t tid;
4316	cond_t invoke_cv;
4317	} userdata;
4318
4319	void prepare_loop (EV_P)
4320	{
4321	// for simplicity, we use a static userdata struct.
4322	static userdata u;
4323
4324	ev_async_init (&u->async_w, async_cb);
4325	ev_async_start (EV_A_ &u->async_w);
4326
4327	pthread_mutex_init (&u->lock, 0);
4328	pthread_cond_init (&u->invoke_cv, 0);
4329
4330	// now associate this with the loop
4331	ev_set_userdata (EV_A_ u);
4332	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4333	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4334
4335	// then create the thread running ev_loop
4336	pthread_create (&u->tid, 0, l_run, EV_A);
4337	}
4338
4339	The callback for the C<ev_async> watcher does nothing: the watcher is used
4340	solely to wake up the event loop so it takes notice of any new watchers
4341	that might have been added:
4342
4343	static void
4344	async_cb (EV_P_ ev_async *w, int revents)
4345	{
4346	// just used for the side effects
4347	}
4348
4349	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4350	protecting the loop data, respectively.
4351
4352	static void
4353	l_release (EV_P)
4354	{
4355	userdata *u = ev_userdata (EV_A);
4356	pthread_mutex_unlock (&u->lock);
4357	}
4358
4359	static void
4360	l_acquire (EV_P)
4361	{
4362	userdata *u = ev_userdata (EV_A);
4363	pthread_mutex_lock (&u->lock);
4364	}
4365
4366	The event loop thread first acquires the mutex, and then jumps straight
4367	into C<ev_run>:
4368
4369	void *
4370	l_run (void *thr_arg)
4371	{
4372	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4373
4374	l_acquire (EV_A);
4375	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4376	ev_run (EV_A_ 0);
4377	l_release (EV_A);
4378
4379	return 0;
4380	}
4381
4382	Instead of invoking all pending watchers, the C<l_invoke> callback will
4383	signal the main thread via some unspecified mechanism (signals? pipe
4384	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4385	have been called (in a while loop because a) spurious wakeups are possible
4386	and b) skipping inter-thread-communication when there are no pending
4387	watchers is very beneficial):
4388
4389	static void
4390	l_invoke (EV_P)
4391	{
4392	userdata *u = ev_userdata (EV_A);
4393
4394	while (ev_pending_count (EV_A))
4395	{
4396	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4397	pthread_cond_wait (&u->invoke_cv, &u->lock);
4398	}
4399	}
4400
4401	Now, whenever the main thread gets told to invoke pending watchers, it
4402	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4403	thread to continue:
4404
4405	static void
4406	real_invoke_pending (EV_P)
4407	{
4408	userdata *u = ev_userdata (EV_A);
4409
4410	pthread_mutex_lock (&u->lock);
4411	ev_invoke_pending (EV_A);
4412	pthread_cond_signal (&u->invoke_cv);
4413	pthread_mutex_unlock (&u->lock);
4414	}
4415
4416	Whenever you want to start/stop a watcher or do other modifications to an
4417	event loop, you will now have to lock:
4418
4419	ev_timer timeout_watcher;
4420	userdata *u = ev_userdata (EV_A);
4421
4422	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4423
4424	pthread_mutex_lock (&u->lock);
4425	ev_timer_start (EV_A_ &timeout_watcher);
4426	ev_async_send (EV_A_ &u->async_w);
4427	pthread_mutex_unlock (&u->lock);
4428
4429	Note that sending the C<ev_async> watcher is required because otherwise
4430	an event loop currently blocking in the kernel will have no knowledge
4431	about the newly added timer. By waking up the loop it will pick up any new
4432	watchers in the next event loop iteration.
4433		5114
4434	=head3 COROUTINES	5115	=head3 COROUTINES
4435		5116
4436	Libev is very accommodating to coroutines ("cooperative threads"):	5117	Libev is very accommodating to coroutines ("cooperative threads"):
4437	libev fully supports nesting calls to its functions from different	5118	libev fully supports nesting calls to its functions from different
…		…
4602	requires, and its I/O model is fundamentally incompatible with the POSIX	5283	requires, and its I/O model is fundamentally incompatible with the POSIX
4603	model. Libev still offers limited functionality on this platform in	5284	model. Libev still offers limited functionality on this platform in
4604	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5285	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4605	descriptors. This only applies when using Win32 natively, not when using	5286	descriptors. This only applies when using Win32 natively, not when using
4606	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5287	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4607	as every compielr comes with a slightly differently broken/incompatible	5288	as every compiler comes with a slightly differently broken/incompatible
4608	environment.	5289	environment.
4609		5290
4610	Lifting these limitations would basically require the full	5291	Lifting these limitations would basically require the full
4611	re-implementation of the I/O system. If you are into this kind of thing,	5292	re-implementation of the I/O system. If you are into this kind of thing,
4612	then note that glib does exactly that for you in a very portable way (note	5293	then note that glib does exactly that for you in a very portable way (note
…		…
4706	structure (guaranteed by POSIX but not by ISO C for example), but it also	5387	structure (guaranteed by POSIX but not by ISO C for example), but it also
4707	assumes that the same (machine) code can be used to call any watcher	5388	assumes that the same (machine) code can be used to call any watcher
4708	callback: The watcher callbacks have different type signatures, but libev	5389	callback: The watcher callbacks have different type signatures, but libev
4709	calls them using an C<ev_watcher *> internally.	5390	calls them using an C<ev_watcher *> internally.
4710		5391
		5392	=item null pointers and integer zero are represented by 0 bytes
		5393
		5394	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5395	relies on this setting pointers and integers to null.
		5396
		5397	=item pointer accesses must be thread-atomic
		5398
		5399	Accessing a pointer value must be atomic, it must both be readable and
		5400	writable in one piece - this is the case on all current architectures.
		5401
4711	=item C<sig_atomic_t volatile> must be thread-atomic as well	5402	=item C<sig_atomic_t volatile> must be thread-atomic as well
4712		5403
4713	The type C<sig_atomic_t volatile> (or whatever is defined as	5404	The type C<sig_atomic_t volatile> (or whatever is defined as
4714	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5405	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4715	threads. This is not part of the specification for C<sig_atomic_t>, but is	5406	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4723	thread" or will block signals process-wide, both behaviours would	5414	thread" or will block signals process-wide, both behaviours would
4724	be compatible with libev. Interaction between C<sigprocmask> and	5415	be compatible with libev. Interaction between C<sigprocmask> and
4725	C<pthread_sigmask> could complicate things, however.	5416	C<pthread_sigmask> could complicate things, however.
4726		5417
4727	The most portable way to handle signals is to block signals in all threads	5418	The most portable way to handle signals is to block signals in all threads
4728	except the initial one, and run the default loop in the initial thread as	5419	except the initial one, and run the signal handling loop in the initial
4729	well.	5420	thread as well.
4730		5421
4731	=item C<long> must be large enough for common memory allocation sizes	5422	=item C<long> must be large enough for common memory allocation sizes
4732		5423
4733	To improve portability and simplify its API, libev uses C<long> internally	5424	To improve portability and simplify its API, libev uses C<long> internally
4734	instead of C<size_t> when allocating its data structures. On non-POSIX	5425	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4740		5431
4741	The type C<double> is used to represent timestamps. It is required to	5432	The type C<double> is used to represent timestamps. It is required to
4742	have at least 51 bits of mantissa (and 9 bits of exponent), which is	5433	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4743	good enough for at least into the year 4000 with millisecond accuracy	5434	good enough for at least into the year 4000 with millisecond accuracy
4744	(the design goal for libev). This requirement is overfulfilled by	5435	(the design goal for libev). This requirement is overfulfilled by
4745	implementations using IEEE 754, which is basically all existing ones. With	5436	implementations using IEEE 754, which is basically all existing ones.
		5437
4746	IEEE 754 doubles, you get microsecond accuracy until at least 2200.	5438	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5439	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5440	is either obsolete or somebody patched it to use C<long double> or
		5441	something like that, just kidding).
4747		5442
4748	=back	5443	=back
4749		5444
4750	If you know of other additional requirements drop me a note.	5445	If you know of other additional requirements drop me a note.
4751		5446
…		…
4813	=item Processing ev_async_send: O(number_of_async_watchers)	5508	=item Processing ev_async_send: O(number_of_async_watchers)
4814		5509
4815	=item Processing signals: O(max_signal_number)	5510	=item Processing signals: O(max_signal_number)
4816		5511
4817	Sending involves a system call I<iff> there were no other C<ev_async_send>	5512	Sending involves a system call I<iff> there were no other C<ev_async_send>
4818	calls in the current loop iteration. Checking for async and signal events	5513	calls in the current loop iteration and the loop is currently
		5514	blocked. Checking for async and signal events involves iterating over all
4819	involves iterating over all running async watchers or all signal numbers.	5515	running async watchers or all signal numbers.
4820		5516
4821	=back	5517	=back
4822		5518
4823		5519
4824	=head1 PORTING FROM LIBEV 3.X TO 4.X	5520	=head1 PORTING FROM LIBEV 3.X TO 4.X
4825		5521
4826	The major version 4 introduced some minor incompatible changes to the API.	5522	The major version 4 introduced some incompatible changes to the API.
4827		5523
4828	At the moment, the C<ev.h> header file tries to implement superficial	5524	At the moment, the C<ev.h> header file provides compatibility definitions
4829	compatibility, so most programs should still compile. Those might be	5525	for all changes, so most programs should still compile. The compatibility
4830	removed in later versions of libev, so better update early than late.	5526	layer might be removed in later versions of libev, so better update to the
		5527	new API early than late.
4831		5528
4832	=over 4	5529	=over 4
		5530
		5531	=item C<EV_COMPAT3> backwards compatibility mechanism
		5532
		5533	The backward compatibility mechanism can be controlled by
		5534	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5535	section.
		5536
		5537	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5538
		5539	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5540
		5541	ev_loop_destroy (EV_DEFAULT_UC);
		5542	ev_loop_fork (EV_DEFAULT);
4833		5543
4834	=item function/symbol renames	5544	=item function/symbol renames
4835		5545
4836	A number of functions and symbols have been renamed:	5546	A number of functions and symbols have been renamed:
4837		5547
…		…
4856	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme	5566	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
4857	as all other watcher types. Note that C<ev_loop_fork> is still called	5567	as all other watcher types. Note that C<ev_loop_fork> is still called
4858	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>	5568	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4859	typedef.	5569	typedef.
4860		5570
4861	=item C<EV_COMPAT3> backwards compatibility mechanism
4862
4863	The backward compatibility mechanism can be controlled by
4864	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
4865	section.
4866
4867	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5571	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4868		5572
4869	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5573	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4870	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5574	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4871	and work, but the library code will of course be larger.	5575	and work, but the library code will of course be larger.
…		…
4878	=over 4	5582	=over 4
4879		5583
4880	=item active	5584	=item active
4881		5585
4882	A watcher is active as long as it has been started and not yet stopped.	5586	A watcher is active as long as it has been started and not yet stopped.
4883	See L<WATCHER STATES> for details.	5587	See L</WATCHER STATES> for details.
4884		5588
4885	=item application	5589	=item application
4886		5590
4887	In this document, an application is whatever is using libev.	5591	In this document, an application is whatever is using libev.
4888		5592
…		…
4924	watchers and events.	5628	watchers and events.
4925		5629
4926	=item pending	5630	=item pending
4927		5631
4928	A watcher is pending as soon as the corresponding event has been	5632	A watcher is pending as soon as the corresponding event has been
4929	detected. See L<WATCHER STATES> for details.	5633	detected. See L</WATCHER STATES> for details.
4930		5634
4931	=item real time	5635	=item real time
4932		5636
4933	The physical time that is observed. It is apparently strictly monotonic :)	5637	The physical time that is observed. It is apparently strictly monotonic :)
4934		5638
4935	=item wall-clock time	5639	=item wall-clock time
4936		5640
4937	The time and date as shown on clocks. Unlike real time, it can actually	5641	The time and date as shown on clocks. Unlike real time, it can actually
4938	be wrong and jump forwards and backwards, e.g. when the you adjust your	5642	be wrong and jump forwards and backwards, e.g. when you adjust your
4939	clock.	5643	clock.
4940		5644
4941	=item watcher	5645	=item watcher
4942		5646
4943	A data structure that describes interest in certain events. Watchers need	5647	A data structure that describes interest in certain events. Watchers need
…		…
4945		5649
4946	=back	5650	=back
4947		5651
4948	=head1 AUTHOR	5652	=head1 AUTHOR
4949		5653
4950	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5654	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5655	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4951		5656

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