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Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC vs.
Revision 1.317 by root, Sun Sep 25 16:30:50 2022 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
80	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
81	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
85	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
86	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
87	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.19';	176	our $VERSION = 4.79;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
207		190
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	194	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap mremap munlock munlockall
		198
		199	accept4 tee splice pipe2 pipesize
		200	fexecve mount umount memfd_create eventfd
		201	timerfd_create timerfd_settime timerfd_gettime
		202	pidfd_open pidfd_send_signal pidfd_getfd);
213		203
214	push @AIO_REQ, qw(aio_busy); # not exported	204	push @AIO_REQ, qw(aio_busy); # not exported
215		205
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		207
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	209	XSLoader::load ("IO::AIO", $VERSION);
220	}	210	}
221		211
222	=head1 FUNCTIONS	212	=head1 FUNCTIONS
223		213
224	=head2 AIO REQUEST FUNCTIONS	214	=head2 QUICK OVERVIEW
		215
		216	This section simply lists the prototypes most of the functions for
		217	quick reference. See the following sections for function-by-function
		218	documentation.
		219
		220	aio_wd $pathname, $callback->($wd)
		221	aio_open $pathname, $flags, $mode, $callback->($fh)
		222	aio_close $fh, $callback->($status)
		223	aio_seek $fh,$offset,$whence, $callback->($offs)
		224	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		225	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		226	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		227	aio_readahead $fh,$offset,$length, $callback->($retval)
		228	aio_stat $fh_or_path, $callback->($status)
		229	aio_lstat $fh, $callback->($status)
		230	aio_statvfs $fh_or_path, $callback->($statvfs)
		231	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		232	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		233	aio_chmod $fh_or_path, $mode, $callback->($status)
		234	aio_truncate $fh_or_path, $offset, $callback->($status)
		235	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		236	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		237	aio_unlink $pathname, $callback->($status)
		238	aio_mknod $pathname, $mode, $dev, $callback->($status)
		239	aio_link $srcpath, $dstpath, $callback->($status)
		240	aio_symlink $srcpath, $dstpath, $callback->($status)
		241	aio_readlink $pathname, $callback->($link)
		242	aio_realpath $pathname, $callback->($path)
		243	aio_rename $srcpath, $dstpath, $callback->($status)
		244	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		245	aio_mkdir $pathname, $mode, $callback->($status)
		246	aio_rmdir $pathname, $callback->($status)
		247	aio_readdir $pathname, $callback->($entries)
		248	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		249	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		250	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		251	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		252	aio_load $pathname, $data, $callback->($status)
		253	aio_copy $srcpath, $dstpath, $callback->($status)
		254	aio_move $srcpath, $dstpath, $callback->($status)
		255	aio_rmtree $pathname, $callback->($status)
		256	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		257	aio_ioctl $fh, $request, $buf, $callback->($status)
		258	aio_sync $callback->($status)
		259	aio_syncfs $fh, $callback->($status)
		260	aio_fsync $fh, $callback->($status)
		261	aio_fdatasync $fh, $callback->($status)
		262	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		263	aio_pathsync $pathname, $callback->($status)
		264	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		265	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		266	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		267	aio_mlockall $flags, $callback->($status)
		268	aio_group $callback->(...)
		269	aio_nop $callback->()
		270
		271	$prev_pri = aioreq_pri [$pri]
		272	aioreq_nice $pri_adjust
		273
		274	IO::AIO::poll_wait
		275	IO::AIO::poll_cb
		276	IO::AIO::poll
		277	IO::AIO::flush
		278	IO::AIO::max_poll_reqs $nreqs
		279	IO::AIO::max_poll_time $seconds
		280	IO::AIO::min_parallel $nthreads
		281	IO::AIO::max_parallel $nthreads
		282	IO::AIO::max_idle $nthreads
		283	IO::AIO::idle_timeout $seconds
		284	IO::AIO::max_outstanding $maxreqs
		285	IO::AIO::nreqs
		286	IO::AIO::nready
		287	IO::AIO::npending
		288	IO::AIO::reinit
		289
		290	$nfd = IO::AIO::get_fdlimit
		291	IO::AIO::min_fdlimit $nfd
		292
		293	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		294	IO::AIO::fadvise $fh, $offset, $len, $advice
		295	IO::AIO::fexecve $fh, $argv, $envp
		296
		297	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		298	IO::AIO::munmap $scalar
		299	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		300	IO::AIO::madvise $scalar, $offset, $length, $advice
		301	IO::AIO::mprotect $scalar, $offset, $length, $protect
		302	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		303	IO::AIO::munlockall
		304
		305	# stat extensions
		306	$counter = IO::AIO::st_gen
		307	$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		308	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		309	$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		310	$seconds = IO::AIO::st_btimesec
		311	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		312
		313	# very much unportable syscalls
		314	IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
		315	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		316	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		317
		318	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		319	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		320
		321	$fh = IO::AIO::eventfd [$initval, [$flags]]
		322	$fh = IO::AIO::memfd_create $pathname[, $flags]
		323
		324	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		325	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		326	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		327
		328	$fh = IO::AIO::pidfd_open $pid[, $flags]
		329	$status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		330	$fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		331
		332	$retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		333	$retval = IO::AIO::umount $path, $flags = 0
		334
		335	=head2 API NOTES
225		336
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	337	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	338	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	339	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	340	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	341	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	342	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	343	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		344	most syscalls return C<-1> on error, unlike perl, which usually delivers
		345	"false").
		346
		347	Some requests (such as C<aio_readdir>) pass the actual results and
		348	communicate failures by passing C<undef>.
233		349
234	All functions expecting a filehandle keep a copy of the filehandle	350	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	351	internally until the request has finished.
236		352
237	All functions return request objects of type L<IO::AIO::REQ> that allow	353	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	354	further manipulation of those requests while they are in-flight.
239		355
240	The pathnames you pass to these routines I<must> be absolute and	356	The pathnames you pass to these routines I<should> be absolute. The
241	encoded as octets. The reason for the former is that at the time the	357	reason for this is that at the time the request is being executed, the
242	request is being executed, the current working directory could have	358	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	359	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	360	in the program and then use relative paths. You can also take advantage
245	paths.	361	of IO::AIOs working directory abstraction, that lets you specify paths
		362	relative to some previously-opened "working directory object" - see the
		363	description of the C<IO::AIO::WD> class later in this document.
246		364
247	To encode pathnames as octets, either make sure you either: a) always pass	365	To encode pathnames as octets, either make sure you either: a) always pass
248	in filenames you got from outside (command line, readdir etc.) without	366	in filenames you got from outside (command line, readdir etc.) without
249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	367	tinkering, b) are in your native filesystem encoding, c) use the Encode
250	your pathnames to the locale (or other) encoding in effect in the user	368	module and encode your pathnames to the locale (or other) encoding in
251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	369	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	370	unicode filenames or e) use something else to ensure your scalar has the
		371	correct contents.
253		372
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	373	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	374	handles correctly whether it is set or not.
		375
		376	=head2 AIO REQUEST FUNCTIONS
256		377
257	=over 4	378	=over 4
258		379
259	=item $prev_pri = aioreq_pri [$pri]	380	=item $prev_pri = aioreq_pri [$pri]
260		381
…		…
290		411
291		412
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	413	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		414
294	Asynchronously open or create a file and call the callback with a newly	415	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	416	created filehandle for the file (or C<undef> in case of an error).
296		417
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	418	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	419	for an explanation.
299		420
300	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	421	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
307	by the umask in effect then the request is being executed, so better never	428	by the umask in effect then the request is being executed, so better never
308	change the umask.	429	change the umask.
309		430
310	Example:	431	Example:
311		432
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	433	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	434	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	435	print "open successful, fh is $_[0]\n";
315	...	436	...
316	} else {	437	} else {
317	die "open failed: $!\n";	438	die "open failed: $!\n";
318	}	439	}
319	};	440	};
320		441
		442	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		443	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		444	following POSIX and non-POSIX constants are available (missing ones on
		445	your system are, as usual, C<0>):
		446
		447	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		448	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		449	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		450
321		451
322	=item aio_close $fh, $callback->($status)	452	=item aio_close $fh, $callback->($status)
323		453
324	Asynchronously close a file and call the callback with the result	454	Asynchronously close a file and call the callback with the result
325	code.	455	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	464	Or in other words: the file descriptor will be closed, but it will not be
335	free for reuse until the perl filehandle is closed.	465	free for reuse until the perl filehandle is closed.
336		466
337	=cut	467	=cut
338		468
		469	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		470
		471	Seeks the filehandle to the new C<$offset>, similarly to perl's
		472	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		473	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		474	C<IO::AIO::SEEK_END>).
		475
		476	The resulting absolute offset will be passed to the callback, or C<-1> in
		477	case of an error.
		478
		479	In theory, the C<$whence> constants could be different than the
		480	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		481	so don't panic.
		482
		483	As a GNU/Linux (and maybe Solaris) extension, also the constants
		484	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		485	could be found. No guarantees about suitability for use in C<aio_seek> or
		486	Perl's C<sysseek> can be made though, although I would naively assume they
		487	"just work".
		488
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	489	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		490
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	491	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		492
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	493	Reads or writes C<$length> bytes from or to the specified C<$fh> and
344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	494	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
345	and calls the callback without the actual number of bytes read (or -1 on	495	calls the callback with the actual number of bytes transferred (or -1 on
346	error, just like the syscall).	496	error, just like the syscall).
347		497
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	498	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	499	offset plus the actual number of bytes read.
350		500
…		…
375		525
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	526	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	527	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	528	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	529	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	530	other. The same C<$in_fh> works fine though, as this function does not
		531	move or use the file offset of C<$in_fh>.
381		532
		533	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		534	are written, and there is no way to find out how many more bytes have been
		535	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		536	number of bytes written to C<$out_fh>. Only if the result value equals
		537	C<$length> one can assume that C<$length> bytes have been read.
		538
		539	Unlike with other C<aio_> functions, it makes a lot of sense to use
		540	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		541	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		542	the socket I/O will be non-blocking. Note, however, that you can run
		543	into a trap where C<aio_sendfile> reads some data with readahead, then
		544	fails to write all data, and when the socket is ready the next time, the
		545	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		546	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		547	resource usage.
		548
382	This call tries to make use of a native C<sendfile> syscall to provide	549	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	550	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	551	a socket, and C<$in_fh> should refer to an mmap'able file.
385		552
386	If the native sendfile call fails or is not implemented, it will be	553	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	554	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		555	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	556	type of filehandle regardless of the limitations of the operating system.
389		557
390	Please note, however, that C<aio_sendfile> can read more bytes from	558	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	559	together in a hurry to improve benchmark numbers) tend to be rather buggy
392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	560	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	561	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	562	so you really really should check the return value of C<aio_sendfile> -
395	read.	563	fewer bytes than expected might have been transferred.
396		564
397		565
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	566	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		567
400	C<aio_readahead> populates the page cache with data from a file so that	568	C<aio_readahead> populates the page cache with data from a file so that
…		…
404	whole pages, so that offset is effectively rounded down to a page boundary	572	whole pages, so that offset is effectively rounded down to a page boundary
405	and bytes are read up to the next page boundary greater than or equal to	573	and bytes are read up to the next page boundary greater than or equal to
406	(off-set+length). C<aio_readahead> does not read beyond the end of the	574	(off-set+length). C<aio_readahead> does not read beyond the end of the
407	file. The current file offset of the file is left unchanged.	575	file. The current file offset of the file is left unchanged.
408		576
409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	577	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
410	emulated by simply reading the data, which would have a similar effect.	578	be emulated by simply reading the data, which would have a similar effect.
411		579
412		580
413	=item aio_stat $fh_or_path, $callback->($status)	581	=item aio_stat $fh_or_path, $callback->($status)
414		582
415	=item aio_lstat $fh, $callback->($status)	583	=item aio_lstat $fh, $callback->($status)
416		584
417	Works like perl's C<stat> or C<lstat> in void context. The callback will	585	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
418	be called after the stat and the results will be available using C<stat _>	586	callback will be called after the stat and the results will be available
419	or C<-s _> etc...	587	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		588	and C<-T>).
420		589
421	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	590	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
422	for an explanation.	591	for an explanation.
423		592
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	593	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	594	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	595	unless perl itself is compiled with large file support.
		596
		597	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		598	following constants and functions (if not implemented, the constants will
		599	be C<0> and the functions will either C<croak> or fall back on traditional
		600	behaviour).
		601
		602	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		603	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		604	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		605
		606	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		607	ACCESS>.
427		608
428	Example: Print the length of F</etc/passwd>:	609	Example: Print the length of F</etc/passwd>:
429		610
430	aio_stat "/etc/passwd", sub {	611	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	612	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	613	print "size is ", -s _, "\n";
433	};	614	};
434		615
435		616
		617	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		618
		619	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		620	whether a file handle or path was passed.
		621
		622	On success, the callback is passed a hash reference with the following
		623	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		624	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		625	is passed.
		626
		627	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		628	C<ST_NOSUID>.
		629
		630	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		631	their correct value when available, or to C<0> on systems that do
		632	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		633	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		634	C<ST_NODIRATIME> and C<ST_RELATIME>.
		635
		636	Example: stat C</wd> and dump out the data if successful.
		637
		638	aio_statvfs "/wd", sub {
		639	my $f = $_[0]
		640	or die "statvfs: $!";
		641
		642	use Data::Dumper;
		643	say Dumper $f;
		644	};
		645
		646	# result:
		647	{
		648	bsize => 1024,
		649	bfree => 4333064312,
		650	blocks => 10253828096,
		651	files => 2050765568,
		652	flag => 4096,
		653	favail => 2042092649,
		654	bavail => 4333064312,
		655	ffree => 2042092649,
		656	namemax => 255,
		657	frsize => 1024,
		658	fsid => 1810
		659	}
		660
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	661	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		662
438	Works like perl's C<utime> function (including the special case of $atime	663	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	664	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	665	syscalls support them.
441		666
442	When called with a pathname, uses utimes(2) if available, otherwise	667	When called with a pathname, uses utimensat(2) or utimes(2) if available,
443	utime(2). If called on a file descriptor, uses futimes(2) if available,	668	otherwise utime(2). If called on a file descriptor, uses futimens(2)
444	otherwise returns ENOSYS, so this is not portable.	669	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		670	portable.
445		671
446	Examples:	672	Examples:
447		673
448	# set atime and mtime to current time (basically touch(1)):	674	# set atime and mtime to current time (basically touch(1)):
449	aio_utime "path", undef, undef;	675	aio_utime "path", undef, undef;
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	693	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		694
469	Works like truncate(2) or ftruncate(2).	695	Works like truncate(2) or ftruncate(2).
470		696
471		697
		698	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		699
		700	Allocates or frees disk space according to the C<$mode> argument. See the
		701	linux C<fallocate> documentation for details.
		702
		703	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		704	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		705	to deallocate a file range.
		706
		707	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		708	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		709	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		710	to unshare shared blocks (see your L<fallocate(2)> manpage).
		711
		712	The file system block size used by C<fallocate> is presumably the
		713	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		714	can dictate other limitations.
		715
		716	If C<fallocate> isn't available or cannot be emulated (currently no
		717	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		718
		719
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	720	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		721
474	Works like perl's C<chmod> function.	722	Works like perl's C<chmod> function.
475		723
476		724
…		…
478		726
479	Asynchronously unlink (delete) a file and call the callback with the	727	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	728	result code.
481		729
482		730
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	731	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		732
485	[EXPERIMENTAL]	733	[EXPERIMENTAL]
486		734
487	Asynchronously create a device node (or fifo). See mknod(2).	735	Asynchronously create a device node (or fifo). See mknod(2).
488		736
489	The only (POSIX-) portable way of calling this function is:	737	The only (POSIX-) portable way of calling this function is:
490		738
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	739	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		740
		741	See C<aio_stat> for info about some potentially helpful extra constants
		742	and functions.
493		743
494	=item aio_link $srcpath, $dstpath, $callback->($status)	744	=item aio_link $srcpath, $dstpath, $callback->($status)
495		745
496	Asynchronously create a new link to the existing object at C<$srcpath> at	746	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	747	the path C<$dstpath> and call the callback with the result code.
…		…
501		751
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	752	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	753	the path C<$dstpath> and call the callback with the result code.
504		754
505		755
506	=item aio_readlink $path, $callback->($link)	756	=item aio_readlink $pathname, $callback->($link)
507		757
508	Asynchronously read the symlink specified by C<$path> and pass it to	758	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	759	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	760	callback.
511		761
512		762
		763	=item aio_realpath $pathname, $callback->($path)
		764
		765	Asynchronously make the path absolute and resolve any symlinks in
		766	C<$path>. The resulting path only consists of directories (same as
		767	L<Cwd::realpath>).
		768
		769	This request can be used to get the absolute path of the current working
		770	directory by passing it a path of F<.> (a single dot).
		771
		772
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	773	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		774
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	775	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	776	rename(2) and call the callback with the result code.
		777
		778	On systems that support the AIO::WD working directory abstraction
		779	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		780	of failing, C<rename> is called on the absolute path of C<$wd>.
		781
		782
		783	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		784
		785	Basically a version of C<aio_rename> with an additional C<$flags>
		786	argument. Calling this with C<$flags=0> is the same as calling
		787	C<aio_rename>.
		788
		789	Non-zero flags are currently only supported on GNU/Linux systems that
		790	support renameat2. Other systems fail with C<ENOSYS> in this case.
		791
		792	The following constants are available (missing ones are, as usual C<0>),
		793	see renameat2(2) for details:
		794
		795	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		796	and C<IO::AIO::RENAME_WHITEOUT>.
517		797
518		798
519	=item aio_mkdir $pathname, $mode, $callback->($status)	799	=item aio_mkdir $pathname, $mode, $callback->($status)
520		800
521	Asynchronously mkdir (create) a directory and call the callback with	801	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	806	=item aio_rmdir $pathname, $callback->($status)
527		807
528	Asynchronously rmdir (delete) a directory and call the callback with the	808	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	809	result code.
530		810
		811	On systems that support the AIO::WD working directory abstraction
		812	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		813	C<rmdir> is called on the absolute path of C<$wd>.
		814
531		815
532	=item aio_readdir $pathname, $callback->($entries)	816	=item aio_readdir $pathname, $callback->($entries)
533		817
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	818	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	819	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
539	array-ref with the filenames.	823	array-ref with the filenames.
540		824
541		825
542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	826	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
543		827
544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	828	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
545	behaviour and output format. In case of an error, C<$entries> will be	829	tune behaviour and output format. In case of an error, C<$entries> will be
546	C<undef>.	830	C<undef>.
547		831
548	The flags are a combination of the following constants, ORed together (the	832	The flags are a combination of the following constants, ORed together (the
549	flags will also be passed to the callback, possibly modified):	833	flags will also be passed to the callback, possibly modified):
550		834
551	=over 4	835	=over 4
552		836
553	=item AIO::READDIR_DENTS	837	=item IO::AIO::READDIR_DENTS
554		838
555	When this flag is off, then the callback gets an arrayref with of names	839	Normally the callback gets an arrayref consisting of names only (as
556	only (as with C<aio_readdir>), otherwise it gets an arrayref with	840	with C<aio_readdir>). If this flag is set, then the callback gets an
557	C<[$name, $inode, $type]> arrayrefs, each describing a single directory	841	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
558	entry in more detail.	842	single directory entry in more detail:
559		843
560	C<$name> is the name of the entry.	844	C<$name> is the name of the entry.
561		845
		846	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		847
		848	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		849	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		850	C<IO::AIO::DT_WHT>.
		851
		852	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		853	to know, you have to run stat yourself. Also, for speed/memory reasons,
		854	the C<$type> scalars are read-only: you must not modify them.
		855
562	C<$inode> is the inode number (which might not be exact on systems with 64	856	C<$inode> is the inode number (which might not be exact on systems with 64
563	bit inode numbers and 32 bit perls). On systems that do not deliver the	857	bit inode numbers and 32 bit perls). This field has unspecified content on
564	inode information, this will always be zero.	858	systems that do not deliver the inode information.
565		859
566	C<$type> is one of the C<AIO::DT_xxx> constants:
567
568	C<AIO::DT_UNKNOWN>, C<AIO::DT_FIFO>, C<AIO::DT_CHR>, C<AIO::DT_DIR>,
569	C<AIO::DT_BLK>, C<AIO::DT_REG>, C<AIO::DT_LNK>, C<AIO::DT_SOCK>,
570	C<AIO::DT_WHT>.
571
572	C<AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
573	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
574	scalars are read-only: you can not modify them.
575
576	=item AIO::READDIR_DIRS_FIRST	860	=item IO::AIO::READDIR_DIRS_FIRST
577		861
578	When this flag is set, then the names will be returned in an order where	862	When this flag is set, then the names will be returned in an order where
579	likely directories come first. This is useful when you need to quickly	863	likely directories come first, in optimal stat order. This is useful when
580	find directories, or you want to find all directories while avoiding to	864	you need to quickly find directories, or you want to find all directories
581	stat() each entry.	865	while avoiding to stat() each entry.
582		866
		867	If the system returns type information in readdir, then this is used
		868	to find directories directly. Otherwise, likely directories are names
		869	beginning with ".", or otherwise names with no dots, of which names with
		870	short names are tried first.
		871
583	=item AIO::READDIR_STAT_ORDER	872	=item IO::AIO::READDIR_STAT_ORDER
584		873
585	When this flag is set, then the names will be returned in an order	874	When this flag is set, then the names will be returned in an order
586	suitable for stat()'ing each one. That is, when you plan to stat()	875	suitable for stat()'ing each one. That is, when you plan to stat() most or
587	all files in the given directory, then the returned order will likely	876	all files in the given directory, then the returned order will likely be
588	be fastest.	877	faster.
589		878
590	If both this flag and IO::READDIR_DIRS_FIRST are specified, then the	879	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
591	likely dirs come first, resulting in a less optimal stat order.	880	then the likely dirs come first, resulting in a less optimal stat order
		881	for stat'ing all entries, but likely a more optimal order for finding
		882	subdirectories.
592		883
593	=item AIO::READDIR_FOUND_UNKNOWN	884	=item IO::AIO::READDIR_FOUND_UNKNOWN
594		885
595	This flag should not be set when calling C<aio_readdirx>. Instead, it	886	This flag should not be set when calling C<aio_readdirx>. Instead, it
596	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	887	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
597	C<AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	888	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
598	C<$type>'s are known, which can be used to speed up some algorithms.	889	C<$type>'s are known, which can be used to speed up some algorithms.
599		890
600	=back	891	=back
601		892
602		893
		894	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		895
		896	Opens, reads and closes the given file. The data is put into C<$data>,
		897	which is resized as required.
		898
		899	If C<$offset> is negative, then it is counted from the end of the file.
		900
		901	If C<$length> is zero, then the remaining length of the file is
		902	used. Also, in this case, the same limitations to modifying C<$data> apply
		903	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		904	with C<substr>. If the size of the file is known, specifying a non-zero
		905	C<$length> results in a performance advantage.
		906
		907	This request is similar to the older C<aio_load> request, but since it is
		908	a single request, it might be more efficient to use.
		909
		910	Example: load F</etc/passwd> into C<$passwd>.
		911
		912	my $passwd;
		913	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		914	$_[0] >= 0
		915	or die "/etc/passwd: $!\n";
		916
		917	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		918	print $passwd;
		919	};
		920	IO::AIO::flush;
		921
		922
603	=item aio_load $path, $data, $callback->($status)	923	=item aio_load $pathname, $data, $callback->($status)
604		924
605	This is a composite request that tries to fully load the given file into	925	This is a composite request that tries to fully load the given file into
606	memory. Status is the same as with aio_read.	926	memory. Status is the same as with aio_read.
		927
		928	Using C<aio_slurp> might be more efficient, as it is a single request.
607		929
608	=cut	930	=cut
609		931
610	sub aio_load($$;$) {	932	sub aio_load($$;$) {
611	my ($path, undef, $cb) = @_;	933	my ($path, undef, $cb) = @_;
…		…
630		952
631	=item aio_copy $srcpath, $dstpath, $callback->($status)	953	=item aio_copy $srcpath, $dstpath, $callback->($status)
632		954
633	Try to copy the I<file> (directories not supported as either source or	955	Try to copy the I<file> (directories not supported as either source or
634	destination) from C<$srcpath> to C<$dstpath> and call the callback with	956	destination) from C<$srcpath> to C<$dstpath> and call the callback with
635	the C<0> (error) or C<-1> ok.	957	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		958
		959	Existing destination files will be truncated.
636		960
637	This is a composite request that creates the destination file with	961	This is a composite request that creates the destination file with
638	mode 0200 and copies the contents of the source file into it using	962	mode 0200 and copies the contents of the source file into it using
639	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	963	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
640	uid/gid, in that order.	964	uid/gid, in that order.
…		…
652	my $grp = aio_group $cb;	976	my $grp = aio_group $cb;
653		977
654	aioreq_pri $pri;	978	aioreq_pri $pri;
655	add $grp aio_open $src, O_RDONLY, 0, sub {	979	add $grp aio_open $src, O_RDONLY, 0, sub {
656	if (my $src_fh = $_[0]) {	980	if (my $src_fh = $_[0]) {
657	my @stat = stat $src_fh; # hmm, might bock over nfs?	981	my @stat = stat $src_fh; # hmm, might block over nfs?
658		982
659	aioreq_pri $pri;	983	aioreq_pri $pri;
660	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	984	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
661	if (my $dst_fh = $_[0]) {	985	if (my $dst_fh = $_[0]) {
662	aioreq_pri $pri;	986	aioreq_pri $pri;
…		…
709		1033
710	=item aio_move $srcpath, $dstpath, $callback->($status)	1034	=item aio_move $srcpath, $dstpath, $callback->($status)
711		1035
712	Try to move the I<file> (directories not supported as either source or	1036	Try to move the I<file> (directories not supported as either source or
713	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1037	destination) from C<$srcpath> to C<$dstpath> and call the callback with
714	the C<0> (error) or C<-1> ok.	1038	a status of C<0> (ok) or C<-1> (error, see C<$!>).
715		1039
716	This is a composite request that tries to rename(2) the file first; if	1040	This is a composite request that tries to rename(2) the file first; if
717	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	1041	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
718	that is successful, unlinks the C<$srcpath>.	1042	that is successful, unlinks the C<$srcpath>.
719		1043
…		…
730	if ($_[0] && $! == EXDEV) {	1054	if ($_[0] && $! == EXDEV) {
731	aioreq_pri $pri;	1055	aioreq_pri $pri;
732	add $grp aio_copy $src, $dst, sub {	1056	add $grp aio_copy $src, $dst, sub {
733	$grp->result ($_[0]);	1057	$grp->result ($_[0]);
734		1058
735	if (!$_[0]) {	1059	unless ($_[0]) {
736	aioreq_pri $pri;	1060	aioreq_pri $pri;
737	add $grp aio_unlink $src;	1061	add $grp aio_unlink $src;
738	}	1062	}
739	};	1063	};
740	} else {	1064	} else {
…		…
743	};	1067	};
744		1068
745	$grp	1069	$grp
746	}	1070	}
747		1071
748	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1072	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
749		1073
750	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1074	Scans a directory (similar to C<aio_readdir>) but additionally tries to
751	efficiently separate the entries of directory C<$path> into two sets of	1075	efficiently separate the entries of directory C<$path> into two sets of
752	names, directories you can recurse into (directories), and ones you cannot	1076	names, directories you can recurse into (directories), and ones you cannot
753	recurse into (everything else, including symlinks to directories).	1077	recurse into (everything else, including symlinks to directories).
754		1078
755	C<aio_scandir> is a composite request that creates of many sub requests_	1079	C<aio_scandir> is a composite request that generates many sub requests.
756	C<$maxreq> specifies the maximum number of outstanding aio requests that	1080	C<$maxreq> specifies the maximum number of outstanding aio requests that
757	this function generates. If it is C<< <= 0 >>, then a suitable default	1081	this function generates. If it is C<< <= 0 >>, then a suitable default
758	will be chosen (currently 4).	1082	will be chosen (currently 4).
759		1083
760	On error, the callback is called without arguments, otherwise it receives	1084	On error, the callback is called without arguments, otherwise it receives
…		…
770		1094
771	Implementation notes.	1095	Implementation notes.
772		1096
773	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1097	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
774		1098
		1099	If readdir returns file type information, then this is used directly to
		1100	find directories.
		1101
775	After reading the directory, the modification time, size etc. of the	1102	Otherwise, after reading the directory, the modification time, size etc.
776	directory before and after the readdir is checked, and if they match (and	1103	of the directory before and after the readdir is checked, and if they
777	isn't the current time), the link count will be used to decide how many	1104	match (and isn't the current time), the link count will be used to decide
778	entries are directories (if >= 2). Otherwise, no knowledge of the number	1105	how many entries are directories (if >= 2). Otherwise, no knowledge of the
779	of subdirectories will be assumed.	1106	number of subdirectories will be assumed.
780		1107
781	Then entries will be sorted into likely directories (everything without	1108	Then entries will be sorted into likely directories a non-initial dot
782	a non-initial dot currently) and likely non-directories (everything	1109	currently) and likely non-directories (see C<aio_readdirx>). Then every
783	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1110	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
784	likely directories first. If that succeeds, it assumes that the entry	1111	in order of their inode numbers. If that succeeds, it assumes that the
785	is a directory or a symlink to directory (which will be checked	1112	entry is a directory or a symlink to directory (which will be checked
786	seperately). This is often faster than stat'ing the entry itself because	1113	separately). This is often faster than stat'ing the entry itself because
787	filesystems might detect the type of the entry without reading the inode	1114	filesystems might detect the type of the entry without reading the inode
788	data (e.g. ext2fs filetype feature).	1115	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1116	the filetype information on readdir.
789		1117
790	If the known number of directories (link count - 2) has been reached, the	1118	If the known number of directories (link count - 2) has been reached, the
791	rest of the entries is assumed to be non-directories.	1119	rest of the entries is assumed to be non-directories.
792		1120
793	This only works with certainty on POSIX (= UNIX) filesystems, which	1121	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
806		1134
807	my $grp = aio_group $cb;	1135	my $grp = aio_group $cb;
808		1136
809	$maxreq = 4 if $maxreq <= 0;	1137	$maxreq = 4 if $maxreq <= 0;
810		1138
811	# stat once	1139	# get a wd object
812	aioreq_pri $pri;	1140	aioreq_pri $pri;
813	add $grp aio_stat $path, sub {	1141	add $grp aio_wd $path, sub {
		1142	$_[0]
814	return $grp->result () if $_[0];	1143	or return $grp->result ();
815	my $now = time;
816	my $hash1 = join ":", (stat _)[0,1,3,7,9];
817		1144
818	# read the directory entries	1145	my $wd = [shift, "."];
		1146
		1147	# stat once
819	aioreq_pri $pri;	1148	aioreq_pri $pri;
820	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1149	add $grp aio_stat $wd, sub {
821	my $entries = shift
822	or return $grp->result ();	1150	return $grp->result () if $_[0];
		1151	my $now = time;
		1152	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1153	my $rdxflags = READDIR_DIRS_FIRST;
823		1154
824	# stat the dir another time	1155	if ((stat _)[3] < 2) {
		1156	# at least one non-POSIX filesystem exists
		1157	# that returns useful DT_type values: btrfs,
		1158	# so optimise for this here by requesting dents
		1159	$rdxflags |= READDIR_DENTS;
		1160	}
		1161
		1162	# read the directory entries
825	aioreq_pri $pri;	1163	aioreq_pri $pri;
826	add $grp aio_stat $path, sub {	1164	add $grp aio_readdirx $wd, $rdxflags, sub {
827	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1165	my ($entries, $flags) = @_
		1166	or return $grp->result ();
828		1167
		1168	if ($rdxflags & READDIR_DENTS) {
		1169	# if we requested type values, see if we can use them directly.
		1170
		1171	# if there were any DT_UNKNOWN entries then we assume we
		1172	# don't know. alternatively, we could assume that if we get
		1173	# one DT_DIR, then all directories are indeed marked with
		1174	# DT_DIR, but this seems not required for btrfs, and this
		1175	# is basically the "btrfs can't get it's act together" code
		1176	# branch.
		1177	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1178	# now we have valid DT_ information for all entries,
		1179	# so use it as an optimisation without further stat's.
		1180	# they must also all be at the beginning of @$entries
		1181	# by now.
		1182
829	my $ndirs;	1183	my $dirs;
830		1184
831	# take the slow route if anything looks fishy
832	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
833	$ndirs = -1;
834	} else {
835	# if nlink == 2, we are finished
836	# on non-posix-fs's, we rely on nlink < 2
837	$ndirs = (stat _)[3] - 2
838	or return $grp->result ([], $entries);
839	}
840
841	# sort into likely dirs and likely nondirs
842	# dirs == files without ".", short entries first
843	$entries = [map $_->[0],
844	sort { $b->[1] cmp $a->[1] }
845	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
846	@$entries];
847
848	my (@dirs, @nondirs);
849
850	my $statgrp = add $grp aio_group sub {
851	$grp->result (\@dirs, \@nondirs);
852	};
853
854	limit $statgrp $maxreq;
855	feed $statgrp sub {
856	return unless @$entries;
857	my $entry = pop @$entries;
858
859	aioreq_pri $pri;
860	add $statgrp aio_stat "$path/$entry/.", sub {
861	if ($_[0] < 0) {	1185	if (@$entries) {
862	push @nondirs, $entry;	1186	for (0 .. $#$entries) {
863	} else {	1187	if ($entries->[$_][1] != DT_DIR) {
864	# need to check for real directory	1188	# splice out directories
865	aioreq_pri $pri;	1189	$dirs = [splice @$entries, 0, $_];
866	add $statgrp aio_lstat "$path/$entry", sub {
867	if (-d _) {
868	push @dirs, $entry;
869
870	unless (--$ndirs) {
871	push @nondirs, @$entries;
872	feed $statgrp;
873	}	1190	last;
874	} else {
875	push @nondirs, $entry;
876	}	1191	}
877	}	1192	}
		1193
		1194	# if we didn't find any non-dir, then all entries are dirs
		1195	unless ($dirs) {
		1196	($dirs, $entries) = ($entries, []);
		1197	}
		1198	} else {
		1199	# directory is empty, so there are no sbdirs
		1200	$dirs = [];
878	}	1201	}
		1202
		1203	# either splice'd the directories out or the dir was empty.
		1204	# convert dents to filenames
		1205	$_ = $_->[0] for @$dirs;
		1206	$_ = $_->[0] for @$entries;
		1207
		1208	return $grp->result ($dirs, $entries);
		1209	}
		1210
		1211	# cannot use, so return to our old ways
		1212	# by pretending we only scanned for names.
		1213	$_ = $_->[0] for @$entries;
		1214	}
		1215
		1216	# stat the dir another time
		1217	aioreq_pri $pri;
		1218	add $grp aio_stat $wd, sub {
		1219	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1220
		1221	my $ndirs;
		1222
		1223	# take the slow route if anything looks fishy
		1224	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1225	$ndirs = -1;
		1226	} else {
		1227	# if nlink == 2, we are finished
		1228	# for non-posix-fs's, we rely on nlink < 2
		1229	$ndirs = (stat _)[3] - 2
		1230	or return $grp->result ([], $entries);
		1231	}
		1232
		1233	my (@dirs, @nondirs);
		1234
		1235	my $statgrp = add $grp aio_group sub {
		1236	$grp->result (\@dirs, \@nondirs);
		1237	};
		1238
		1239	limit $statgrp $maxreq;
		1240	feed $statgrp sub {
		1241	return unless @$entries;
		1242	my $entry = shift @$entries;
		1243
		1244	aioreq_pri $pri;
		1245	$wd->[1] = "$entry/.";
		1246	add $statgrp aio_stat $wd, sub {
		1247	if ($_[0] < 0) {
		1248	push @nondirs, $entry;
		1249	} else {
		1250	# need to check for real directory
		1251	aioreq_pri $pri;
		1252	$wd->[1] = $entry;
		1253	add $statgrp aio_lstat $wd, sub {
		1254	if (-d _) {
		1255	push @dirs, $entry;
		1256
		1257	unless (--$ndirs) {
		1258	push @nondirs, @$entries;
		1259	feed $statgrp;
		1260	}
		1261	} else {
		1262	push @nondirs, $entry;
		1263	}
		1264	}
		1265	}
		1266	};
879	};	1267	};
880	};	1268	};
881	};	1269	};
882	};	1270	};
883	};	1271	};
884		1272
885	$grp	1273	$grp
886	}	1274	}
887		1275
888	=item aio_rmtree $path, $callback->($status)	1276	=item aio_rmtree $pathname, $callback->($status)
889		1277
890	Delete a directory tree starting (and including) C<$path>, return the	1278	Delete a directory tree starting (and including) C<$path>, return the
891	status of the final C<rmdir> only. This is a composite request that	1279	status of the final C<rmdir> only. This is a composite request that
892	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1280	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
893	everything else.	1281	everything else.
894		1282
895	=cut	1283	=cut
896		1284
…		…
918	};	1306	};
919		1307
920	$grp	1308	$grp
921	}	1309	}
922		1310
		1311	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1312
		1313	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1314
		1315	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1316	they execute asynchronously and pass the return value to the callback.
		1317
		1318	Both calls can be used for a lot of things, some of which make more sense
		1319	to run asynchronously in their own thread, while some others make less
		1320	sense. For example, calls that block waiting for external events, such
		1321	as locking, will also lock down an I/O thread while it is waiting, which
		1322	can deadlock the whole I/O system. At the same time, there might be no
		1323	alternative to using a thread to wait.
		1324
		1325	So in general, you should only use these calls for things that do
		1326	(filesystem) I/O, not for things that wait for other events (network,
		1327	other processes), although if you are careful and know what you are doing,
		1328	you still can.
		1329
		1330	The following constants are available and can be used for normal C<ioctl>
		1331	and C<fcntl> as well (missing ones are, as usual C<0>):
		1332
		1333	C<F_DUPFD_CLOEXEC>,
		1334
		1335	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1336
		1337	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1338
		1339	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1340	C<F_SEAL_WRITE>.
		1341
		1342	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1343	C<FS_IOC_FIEMAP>.
		1344
		1345	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1346	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1347
		1348	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1349	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1350	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1351	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1352	C<FS_FL_USER_MODIFIABLE>.
		1353
		1354	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1355	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1356	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1357	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1358
		1359	C<BLKROSET>, C<BLKROGET>, C<BLKRRPART>, C<BLKGETSIZE>, C<BLKFLSBUF>, C<BLKRASET>,
		1360	C<BLKRAGET>, C<BLKFRASET>, C<BLKFRAGET>, C<BLKSECTSET>, C<BLKSECTGET>, C<BLKSSZGET>,
		1361	C<BLKBSZGET>, C<BLKBSZSET>, C<BLKGETSIZE64>,
		1362
		1363
923	=item aio_sync $callback->($status)	1364	=item aio_sync $callback->($status)
924		1365
925	Asynchronously call sync and call the callback when finished.	1366	Asynchronously call sync and call the callback when finished.
926		1367
927	=item aio_fsync $fh, $callback->($status)	1368	=item aio_fsync $fh, $callback->($status)
…		…
934	Asynchronously call fdatasync on the given filehandle and call the	1375	Asynchronously call fdatasync on the given filehandle and call the
935	callback with the fdatasync result code.	1376	callback with the fdatasync result code.
936		1377
937	If this call isn't available because your OS lacks it or it couldn't be	1378	If this call isn't available because your OS lacks it or it couldn't be
938	detected, it will be emulated by calling C<fsync> instead.	1379	detected, it will be emulated by calling C<fsync> instead.
		1380
		1381	=item aio_syncfs $fh, $callback->($status)
		1382
		1383	Asynchronously call the syncfs syscall to sync the filesystem associated
		1384	to the given filehandle and call the callback with the syncfs result
		1385	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1386	errno to C<ENOSYS> nevertheless.
939		1387
940	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1388	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
941		1389
942	Sync the data portion of the file specified by C<$offset> and C<$length>	1390	Sync the data portion of the file specified by C<$offset> and C<$length>
943	to disk (but NOT the metadata), by calling the Linux-specific	1391	to disk (but NOT the metadata), by calling the Linux-specific
…		…
947	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1395	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
948	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1396	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
949	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1397	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
950	manpage for details.	1398	manpage for details.
951		1399
952	=item aio_pathsync $path, $callback->($status)	1400	=item aio_pathsync $pathname, $callback->($status)
953		1401
954	This request tries to open, fsync and close the given path. This is a	1402	This request tries to open, fsync and close the given path. This is a
955	composite request intended to sync directories after directory operations	1403	composite request intended to sync directories after directory operations
956	(E.g. rename). This might not work on all operating systems or have any	1404	(E.g. rename). This might not work on all operating systems or have any
957	specific effect, but usually it makes sure that directory changes get	1405	specific effect, but usually it makes sure that directory changes get
958	written to disc. It works for anything that can be opened for read-only,	1406	written to disc. It works for anything that can be opened for read-only,
959	not just directories.	1407	not just directories.
		1408
		1409	Future versions of this function might fall back to other methods when
		1410	C<fsync> on the directory fails (such as calling C<sync>).
960		1411
961	Passes C<0> when everything went ok, and C<-1> on error.	1412	Passes C<0> when everything went ok, and C<-1> on error.
962		1413
963	=cut	1414	=cut
964		1415
…		…
985	};	1436	};
986		1437
987	$grp	1438	$grp
988	}	1439	}
989		1440
		1441	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1442
		1443	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1444	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1445	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1446	scalar must only be modified in-place while an aio operation is pending on
		1447	it).
		1448
		1449	It calls the C<msync> function of your OS, if available, with the memory
		1450	area starting at C<$offset> in the string and ending C<$length> bytes
		1451	later. If C<$length> is negative, counts from the end, and if C<$length>
		1452	is C<undef>, then it goes till the end of the string. The flags can be
		1453	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1454	C<IO::AIO::MS_INVALIDATE>.
		1455
		1456	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1457
		1458	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1459	scalars.
		1460
		1461	It touches (reads or writes) all memory pages in the specified
		1462	range inside the scalar. All caveats and parameters are the same
		1463	as for C<aio_msync>, above, except for flags, which must be either
		1464	C<0> (which reads all pages and ensures they are instantiated) or
		1465	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1466	writing an octet from it, which dirties the page).
		1467
		1468	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1469
		1470	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1471	scalars.
		1472
		1473	It reads in all the pages of the underlying storage into memory (if any)
		1474	and locks them, so they are not getting swapped/paged out or removed.
		1475
		1476	If C<$length> is undefined, then the scalar will be locked till the end.
		1477
		1478	On systems that do not implement C<mlock>, this function returns C<-1>
		1479	and sets errno to C<ENOSYS>.
		1480
		1481	Note that the corresponding C<munlock> is synchronous and is
		1482	documented under L<MISCELLANEOUS FUNCTIONS>.
		1483
		1484	Example: open a file, mmap and mlock it - both will be undone when
		1485	C<$data> gets destroyed.
		1486
		1487	open my $fh, "<", $path or die "$path: $!";
		1488	my $data;
		1489	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1490	aio_mlock $data; # mlock in background
		1491
		1492	=item aio_mlockall $flags, $callback->($status)
		1493
		1494	Calls the C<mlockall> function with the given C<$flags> (a
		1495	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1496	C<IO::AIO::MCL_ONFAULT>).
		1497
		1498	On systems that do not implement C<mlockall>, this function returns C<-1>
		1499	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1500	by the system result in a return value of C<-1> with errno being set to
		1501	C<EINVAL>.
		1502
		1503	Note that the corresponding C<munlockall> is synchronous and is
		1504	documented under L<MISCELLANEOUS FUNCTIONS>.
		1505
		1506	Example: asynchronously lock all current and future pages into memory.
		1507
		1508	aio_mlockall IO::AIO::MCL_FUTURE;
		1509
		1510	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1511
		1512	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1513	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1514	the ioctl is not available on your OS, then this request will fail with
		1515	C<ENOSYS>.
		1516
		1517	C<$start> is the starting offset to query extents for, C<$length> is the
		1518	size of the range to query - if it is C<undef>, then the whole file will
		1519	be queried.
		1520
		1521	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1522	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1523	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1524	the data portion.
		1525
		1526	C<$count> is the maximum number of extent records to return. If it is
		1527	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1528	case, if it is C<0>, then the callback receives the number of extents
		1529	instead of the extents themselves (which is unreliable, see below).
		1530
		1531	If an error occurs, the callback receives no arguments. The special
		1532	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1533
		1534	Otherwise, the callback receives an array reference with extent
		1535	structures. Each extent structure is an array reference itself, with the
		1536	following members:
		1537
		1538	[$logical, $physical, $length, $flags]
		1539
		1540	Flags is any combination of the following flag values (typically either C<0>
		1541	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1542
		1543	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1544	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1545	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1546	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1547	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1548	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1549
		1550	At the time of this writing (Linux 3.2), this request is unreliable unless
		1551	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1552	it to return all extents of a range for files with a large number of
		1553	extents. The code (only) works around all these issues if C<$count> is
		1554	C<undef>.
		1555
990	=item aio_group $callback->(...)	1556	=item aio_group $callback->(...)
991		1557
992	This is a very special aio request: Instead of doing something, it is a	1558	This is a very special aio request: Instead of doing something, it is a
993	container for other aio requests, which is useful if you want to bundle	1559	container for other aio requests, which is useful if you want to bundle
994	many requests into a single, composite, request with a definite callback	1560	many requests into a single, composite, request with a definite callback
…		…
1031	immense (it blocks a thread for a long time) so do not use this function	1597	immense (it blocks a thread for a long time) so do not use this function
1032	except to put your application under artificial I/O pressure.	1598	except to put your application under artificial I/O pressure.
1033		1599
1034	=back	1600	=back
1035		1601
		1602
		1603	=head2 IO::AIO::WD - multiple working directories
		1604
		1605	Your process only has one current working directory, which is used by all
		1606	threads. This makes it hard to use relative paths (some other component
		1607	could call C<chdir> at any time, and it is hard to control when the path
		1608	will be used by IO::AIO).
		1609
		1610	One solution for this is to always use absolute paths. This usually works,
		1611	but can be quite slow (the kernel has to walk the whole path on every
		1612	access), and can also be a hassle to implement.
		1613
		1614	Newer POSIX systems have a number of functions (openat, fdopendir,
		1615	futimensat and so on) that make it possible to specify working directories
		1616	per operation.
		1617
		1618	For portability, and because the clowns who "designed", or shall I write,
		1619	perpetrated this new interface were obviously half-drunk, this abstraction
		1620	cannot be perfect, though.
		1621
		1622	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1623	object. This object stores the canonicalised, absolute version of the
		1624	path, and on systems that allow it, also a directory file descriptor.
		1625
		1626	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1627	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1628	object and a pathname instead (or the IO::AIO::WD object alone, which
		1629	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1630	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1631	to that IO::AIO::WD object.
		1632
		1633	For example, to get a wd object for F</etc> and then stat F<passwd>
		1634	inside, you would write:
		1635
		1636	aio_wd "/etc", sub {
		1637	my $etcdir = shift;
		1638
		1639	# although $etcdir can be undef on error, there is generally no reason
		1640	# to check for errors here, as aio_stat will fail with ENOENT
		1641	# when $etcdir is undef.
		1642
		1643	aio_stat [$etcdir, "passwd"], sub {
		1644	# yay
		1645	};
		1646	};
		1647
		1648	The fact that C<aio_wd> is a request and not a normal function shows that
		1649	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1650	which is why it is done asynchronously.
		1651
		1652	To stat the directory obtained with C<aio_wd> above, one could write
		1653	either of the following three request calls:
		1654
		1655	aio_lstat "/etc" , sub { ... # pathname as normal string
		1656	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1657	aio_lstat $wd , sub { ... # shorthand for the previous
		1658
		1659	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1660	object and the pathname string, so you could write the following without
		1661	causing any issues due to C<$path> getting reused:
		1662
		1663	my $path = [$wd, undef];
		1664
		1665	for my $name (qw(abc def ghi)) {
		1666	$path->[1] = $name;
		1667	aio_stat $path, sub {
		1668	# ...
		1669	};
		1670	}
		1671
		1672	There are some caveats: when directories get renamed (or deleted), the
		1673	pathname string doesn't change, so will point to the new directory (or
		1674	nowhere at all), while the directory fd, if available on the system,
		1675	will still point to the original directory. Most functions accepting a
		1676	pathname will use the directory fd on newer systems, and the string on
		1677	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1678	the string form of the pathname.
		1679
		1680	So this functionality is mainly useful to get some protection against
		1681	C<chdir>, to easily get an absolute path out of a relative path for future
		1682	reference, and to speed up doing many operations in the same directory
		1683	(e.g. when stat'ing all files in a directory).
		1684
		1685	The following functions implement this working directory abstraction:
		1686
		1687	=over 4
		1688
		1689	=item aio_wd $pathname, $callback->($wd)
		1690
		1691	Asynchonously canonicalise the given pathname and convert it to an
		1692	IO::AIO::WD object representing it. If possible and supported on the
		1693	system, also open a directory fd to speed up pathname resolution relative
		1694	to this working directory.
		1695
		1696	If something goes wrong, then C<undef> is passwd to the callback instead
		1697	of a working directory object and C<$!> is set appropriately. Since
		1698	passing C<undef> as working directory component of a pathname fails the
		1699	request with C<ENOENT>, there is often no need for error checking in the
		1700	C<aio_wd> callback, as future requests using the value will fail in the
		1701	expected way.
		1702
		1703	=item IO::AIO::CWD
		1704
		1705	This is a compile time constant (object) that represents the process
		1706	current working directory.
		1707
		1708	Specifying this object as working directory object for a pathname is as if
		1709	the pathname would be specified directly, without a directory object. For
		1710	example, these calls are functionally identical:
		1711
		1712	aio_stat "somefile", sub { ... };
		1713	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1714
		1715	=back
		1716
		1717	To recover the path associated with an IO::AIO::WD object, you can use
		1718	C<aio_realpath>:
		1719
		1720	aio_realpath $wd, sub {
		1721	warn "path is $_[0]\n";
		1722	};
		1723
		1724	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1725	sometimes, fall back to using an absolue path.
		1726
1036	=head2 IO::AIO::REQ CLASS	1727	=head2 IO::AIO::REQ CLASS
1037		1728
1038	All non-aggregate C<aio_*> functions return an object of this class when	1729	All non-aggregate C<aio_*> functions return an object of this class when
1039	called in non-void context.	1730	called in non-void context.
1040		1731
…		…
1043	=item cancel $req	1734	=item cancel $req
1044		1735
1045	Cancels the request, if possible. Has the effect of skipping execution	1736	Cancels the request, if possible. Has the effect of skipping execution
1046	when entering the B<execute> state and skipping calling the callback when	1737	when entering the B<execute> state and skipping calling the callback when
1047	entering the the B<result> state, but will leave the request otherwise	1738	entering the the B<result> state, but will leave the request otherwise
1048	untouched. That means that requests that currently execute will not be	1739	untouched (with the exception of readdir). That means that requests that
1049	stopped and resources held by the request will not be freed prematurely.	1740	currently execute will not be stopped and resources held by the request
		1741	will not be freed prematurely.
1050		1742
1051	=item cb $req $callback->(...)	1743	=item cb $req $callback->(...)
1052		1744
1053	Replace (or simply set) the callback registered to the request.	1745	Replace (or simply set) the callback registered to the request.
1054		1746
…		…
1128	=item $grp->cancel_subs	1820	=item $grp->cancel_subs
1129		1821
1130	Cancel all subrequests and clears any feeder, but not the group request	1822	Cancel all subrequests and clears any feeder, but not the group request
1131	itself. Useful when you queued a lot of events but got a result early.	1823	itself. Useful when you queued a lot of events but got a result early.
1132		1824
		1825	The group request will finish normally (you cannot add requests to the
		1826	group).
		1827
1133	=item $grp->result (...)	1828	=item $grp->result (...)
1134		1829
1135	Set the result value(s) that will be passed to the group callback when all	1830	Set the result value(s) that will be passed to the group callback when all
1136	subrequests have finished and set the groups errno to the current value	1831	subrequests have finished and set the groups errno to the current value
1137	of errno (just like calling C<errno> without an error number). By default,	1832	of errno (just like calling C<errno> without an error number). By default,
…		…
1153		1848
1154	Sets a feeder/generator on this group: every group can have an attached	1849	Sets a feeder/generator on this group: every group can have an attached
1155	generator that generates requests if idle. The idea behind this is that,	1850	generator that generates requests if idle. The idea behind this is that,
1156	although you could just queue as many requests as you want in a group,	1851	although you could just queue as many requests as you want in a group,
1157	this might starve other requests for a potentially long time. For example,	1852	this might starve other requests for a potentially long time. For example,
1158	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1853	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1159	delaying any later requests for a long time.	1854	requests, delaying any later requests for a long time.
1160		1855
1161	To avoid this, and allow incremental generation of requests, you can	1856	To avoid this, and allow incremental generation of requests, you can
1162	instead a group and set a feeder on it that generates those requests. The	1857	instead a group and set a feeder on it that generates those requests. The
1163	feed callback will be called whenever there are few enough (see C<limit>,	1858	feed callback will be called whenever there are few enough (see C<limit>,
1164	below) requests active in the group itself and is expected to queue more	1859	below) requests active in the group itself and is expected to queue more
…		…
1196	The default value for the limit is C<0>, but note that setting a feeder	1891	The default value for the limit is C<0>, but note that setting a feeder
1197	automatically bumps it up to C<2>.	1892	automatically bumps it up to C<2>.
1198		1893
1199	=back	1894	=back
1200		1895
		1896
1201	=head2 SUPPORT FUNCTIONS	1897	=head2 SUPPORT FUNCTIONS
1202		1898
1203	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1899	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1204		1900
1205	=over 4	1901	=over 4
1206		1902
1207	=item $fileno = IO::AIO::poll_fileno	1903	=item $fileno = IO::AIO::poll_fileno
1208		1904
1209	Return the I<request result pipe file descriptor>. This filehandle must be	1905	Return the I<request result pipe file descriptor>. This filehandle must be
1210	polled for reading by some mechanism outside this module (e.g. Event or	1906	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1211	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1907	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1212	to call C<poll_cb> to check the results.	1908	you have to call C<poll_cb> to check the results.
1213		1909
1214	See C<poll_cb> for an example.	1910	See C<poll_cb> for an example.
1215		1911
1216	=item IO::AIO::poll_cb	1912	=item IO::AIO::poll_cb
1217		1913
1218	Process some outstanding events on the result pipe. You have to call this	1914	Process some requests that have reached the result phase (i.e. they have
1219	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1915	been executed but the results are not yet reported). You have to call
1220	returned earlier for whatever reason. Returns immediately when no events	1916	this "regularly" to finish outstanding requests.
1221	are outstanding. The amount of events processed depends on the settings of
1222	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1223		1917
		1918	Returns C<0> if all events could be processed (or there were no
		1919	events to process), or C<-1> if it returned earlier for whatever
		1920	reason. Returns immediately when no events are outstanding. The amount
		1921	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1922	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1923
1224	If not all requests were processed for whatever reason, the filehandle	1924	If not all requests were processed for whatever reason, the poll file
1225	will still be ready when C<poll_cb> returns, so normally you don't have to	1925	descriptor will still be ready when C<poll_cb> returns, so normally you
1226	do anything special to have it called later.	1926	don't have to do anything special to have it called later.
		1927
		1928	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1929	ready, it can be beneficial to call this function from loops which submit
		1930	a lot of requests, to make sure the results get processed when they become
		1931	available and not just when the loop is finished and the event loop takes
		1932	over again. This function returns very fast when there are no outstanding
		1933	requests.
1227		1934
1228	Example: Install an Event watcher that automatically calls	1935	Example: Install an Event watcher that automatically calls
1229	IO::AIO::poll_cb with high priority:	1936	IO::AIO::poll_cb with high priority (more examples can be found in the
		1937	SYNOPSIS section, at the top of this document):
1230		1938
1231	Event->io (fd => IO::AIO::poll_fileno,	1939	Event->io (fd => IO::AIO::poll_fileno,
1232	poll => 'r', async => 1,	1940	poll => 'r', async => 1,
1233	cb => \&IO::AIO::poll_cb);	1941	cb => \&IO::AIO::poll_cb);
		1942
		1943	=item IO::AIO::poll_wait
		1944
		1945	Wait until either at least one request is in the result phase or no
		1946	requests are outstanding anymore.
		1947
		1948	This is useful if you want to synchronously wait for some requests to
		1949	become ready, without actually handling them.
		1950
		1951	See C<nreqs> for an example.
		1952
		1953	=item IO::AIO::poll
		1954
		1955	Waits until some requests have been handled.
		1956
		1957	Returns the number of requests processed, but is otherwise strictly
		1958	equivalent to:
		1959
		1960	IO::AIO::poll_wait, IO::AIO::poll_cb
		1961
		1962	=item IO::AIO::flush
		1963
		1964	Wait till all outstanding AIO requests have been handled.
		1965
		1966	Strictly equivalent to:
		1967
		1968	IO::AIO::poll_wait, IO::AIO::poll_cb
		1969	while IO::AIO::nreqs;
		1970
		1971	This function can be useful at program aborts, to make sure outstanding
		1972	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1973	this function on normal exits), or when you are merely using C<IO::AIO>
		1974	for its more advanced functions, rather than for async I/O, e.g.:
		1975
		1976	my ($dirs, $nondirs);
		1977	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1978	IO::AIO::flush;
		1979	# $dirs, $nondirs are now set
1234		1980
1235	=item IO::AIO::max_poll_reqs $nreqs	1981	=item IO::AIO::max_poll_reqs $nreqs
1236		1982
1237	=item IO::AIO::max_poll_time $seconds	1983	=item IO::AIO::max_poll_time $seconds
1238		1984
…		…
1263	# use a low priority so other tasks have priority	2009	# use a low priority so other tasks have priority
1264	Event->io (fd => IO::AIO::poll_fileno,	2010	Event->io (fd => IO::AIO::poll_fileno,
1265	poll => 'r', nice => 1,	2011	poll => 'r', nice => 1,
1266	cb => &IO::AIO::poll_cb);	2012	cb => &IO::AIO::poll_cb);
1267		2013
1268	=item IO::AIO::poll_wait
1269
1270	If there are any outstanding requests and none of them in the result
1271	phase, wait till the result filehandle becomes ready for reading (simply
1272	does a C<select> on the filehandle. This is useful if you want to
1273	synchronously wait for some requests to finish).
1274
1275	See C<nreqs> for an example.
1276
1277	=item IO::AIO::poll
1278
1279	Waits until some requests have been handled.
1280
1281	Returns the number of requests processed, but is otherwise strictly
1282	equivalent to:
1283
1284	IO::AIO::poll_wait, IO::AIO::poll_cb
1285
1286	=item IO::AIO::flush
1287
1288	Wait till all outstanding AIO requests have been handled.
1289
1290	Strictly equivalent to:
1291
1292	IO::AIO::poll_wait, IO::AIO::poll_cb
1293	while IO::AIO::nreqs;
1294
1295	=back	2014	=back
		2015
1296		2016
1297	=head3 CONTROLLING THE NUMBER OF THREADS	2017	=head3 CONTROLLING THE NUMBER OF THREADS
1298		2018
1299	=over	2019	=over
1300		2020
…		…
1332		2052
1333	Under normal circumstances you don't need to call this function.	2053	Under normal circumstances you don't need to call this function.
1334		2054
1335	=item IO::AIO::max_idle $nthreads	2055	=item IO::AIO::max_idle $nthreads
1336		2056
1337	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2057	Limit the number of threads (default: 4) that are allowed to idle
1338	threads that did not get a request to process within 10 seconds). That	2058	(i.e., threads that did not get a request to process within the idle
1339	means if a thread becomes idle while C<$nthreads> other threads are also	2059	timeout (default: 10 seconds). That means if a thread becomes idle while
1340	idle, it will free its resources and exit.	2060	C<$nthreads> other threads are also idle, it will free its resources and
		2061	exit.
1341		2062
1342	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2063	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1343	to allow for extremely high load situations, but want to free resources	2064	to allow for extremely high load situations, but want to free resources
1344	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2065	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1345		2066
1346	The default is probably ok in most situations, especially if thread	2067	The default is probably ok in most situations, especially if thread
1347	creation is fast. If thread creation is very slow on your system you might	2068	creation is fast. If thread creation is very slow on your system you might
1348	want to use larger values.	2069	want to use larger values.
1349		2070
		2071	=item IO::AIO::idle_timeout $seconds
		2072
		2073	Sets the minimum idle timeout (default 10) after which worker threads are
		2074	allowed to exit. SEe C<IO::AIO::max_idle>.
		2075
1350	=item IO::AIO::max_outstanding $maxreqs	2076	=item IO::AIO::max_outstanding $maxreqs
1351		2077
1352	This is a very bad function to use in interactive programs because it
1353	blocks, and a bad way to reduce concurrency because it is inexact: Better
1354	use an C<aio_group> together with a feed callback.
1355
1356	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2078	Sets the maximum number of outstanding requests to C<$nreqs>. If
1357	do queue up more than this number of requests, the next call to the	2079	you do queue up more than this number of requests, the next call to
1358	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)	2080	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1359	function will block until the limit is no longer exceeded.	2081	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2082	longer exceeded.
1360		2083
1361	The default value is very large, so there is no practical limit on the	2084	In other words, this setting does not enforce a queue limit, but can be
1362	number of outstanding requests.	2085	used to make poll functions block if the limit is exceeded.
1363		2086
1364	You can still queue as many requests as you want. Therefore,	2087	This is a bad function to use in interactive programs because it blocks,
1365	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2088	and a bad way to reduce concurrency because it is inexact. If you need to
1366	as a stop gap to shield against fatal memory overflow (with large values).	2089	issue many requests without being able to call a poll function on demand,
		2090	it is better to use an C<aio_group> together with a feed callback.
		2091
		2092	Its main use is in scripts without an event loop - when you want to stat a
		2093	lot of files, you can write something like this:
		2094
		2095	IO::AIO::max_outstanding 32;
		2096
		2097	for my $path (...) {
		2098	aio_stat $path , ...;
		2099	IO::AIO::poll_cb;
		2100	}
		2101
		2102	IO::AIO::flush;
		2103
		2104	The call to C<poll_cb> inside the loop will normally return instantly,
		2105	allowing the loop to progress, but as soon as more than C<32> requests
		2106	are in-flight, it will block until some requests have been handled. This
		2107	keeps the loop from pushing a large number of C<aio_stat> requests onto
		2108	the queue (which, with many paths to stat, can use up a lot of memory).
		2109
		2110	The default value for C<max_outstanding> is very large, so there is no
		2111	practical limit on the number of outstanding requests.
1367		2112
1368	=back	2113	=back
		2114
1369		2115
1370	=head3 STATISTICAL INFORMATION	2116	=head3 STATISTICAL INFORMATION
1371		2117
1372	=over	2118	=over
1373		2119
…		…
1391	Returns the number of requests currently in the pending state (executed,	2137	Returns the number of requests currently in the pending state (executed,
1392	but not yet processed by poll_cb).	2138	but not yet processed by poll_cb).
1393		2139
1394	=back	2140	=back
1395		2141
		2142
		2143	=head3 SUBSECOND STAT TIME ACCESS
		2144
		2145	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2146	generally find access/modification and change times with subsecond time
		2147	accuracy of the system supports it, but perl's built-in functions only
		2148	return the integer part.
		2149
		2150	The following functions return the timestamps of the most recent
		2151	stat with subsecond precision on most systems and work both after
		2152	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2153	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2154	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2155
		2156	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2157	full resolution without rounding and work with standard perl C<stat>,
		2158	alleviating the need to call the special C<Time::HiRes> functions, which
		2159	do not act like their perl counterparts.
		2160
		2161	On operating systems or file systems where subsecond time resolution is
		2162	not supported or could not be detected, a fractional part of C<0> is
		2163	returned, so it is always safe to call these functions.
		2164
		2165	=over 4
		2166
		2167	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2168
		2169	Return the access, modication, change or birth time, respectively,
		2170	including fractional part. Due to the limited precision of floating point,
		2171	the accuracy on most platforms is only a bit better than milliseconds
		2172	for times around now - see the I<nsec> function family, below, for full
		2173	accuracy.
		2174
		2175	File birth time is only available when the OS and perl support it (on
		2176	FreeBSD and NetBSD at the time of this writing, although support is
		2177	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2178	it). On systems where it isn't available, C<0> is currently returned, but
		2179	this might change to C<undef> in a future version.
		2180
		2181	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2182
		2183	Returns access, modification, change and birth time all in one go, and
		2184	maybe more times in the future version.
		2185
		2186	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2187
		2188	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2189	as an integer in the range C<0> to C<999999999>.
		2190
		2191	Note that no accessors are provided for access, modification and
		2192	change times - you need to get those from C<stat _> if required (C<int
		2193	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2194	value).
		2195
		2196	=item $seconds = IO::AIO::st_btimesec
		2197
		2198	The (integral) seconds part of the file birth time, if available.
		2199
		2200	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2201
		2202	Like the functions above, but returns all four times in one go (and maybe
		2203	more in future versions).
		2204
		2205	=item $counter = IO::AIO::st_gen
		2206
		2207	Returns the generation counter (in practice this is just a random number)
		2208	of the file. This is only available on platforms which have this member in
		2209	their C<struct stat> (most BSDs at the time of this writing) and generally
		2210	only to the root usert. If unsupported, C<0> is returned, but this might
		2211	change to C<undef> in a future version.
		2212
		2213	=back
		2214
		2215	Example: print the high resolution modification time of F</etc>, using
		2216	C<stat>, and C<IO::AIO::aio_stat>.
		2217
		2218	if (stat "/etc") {
		2219	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2220	}
		2221
		2222	IO::AIO::aio_stat "/etc", sub {
		2223	$_[0]
		2224	and return;
		2225
		2226	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2227	};
		2228
		2229	IO::AIO::flush;
		2230
		2231	Output of the awbove on my system, showing reduced and full accuracy:
		2232
		2233	stat(/etc) mtime: 1534043702.020808
		2234	aio_stat(/etc) mtime: 1534043702.020807792
		2235
		2236
		2237	=head3 MISCELLANEOUS FUNCTIONS
		2238
		2239	IO::AIO implements some functions that are useful when you want to use
		2240	some "Advanced I/O" function not available to in Perl, without going the
		2241	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2242	counterpart.
		2243
		2244	=over 4
		2245
		2246	=item $retval = IO::AIO::fexecve $fh, $argv, $envp
		2247
		2248	A more-or-less direct equivalent to the POSIX C<fexecve> functions, which
		2249	allows you to specify the program to be executed via a file descriptor (or
		2250	handle). Returns C<-1> and sets errno to C<ENOSYS> if not available.
		2251
		2252	=item $retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		2253
		2254	Calls the GNU/Linux mount syscall with the given arguments. All except
		2255	C<$flags> are strings, and if C<$data> is C<undef>, a C<NULL> will be
		2256	passed.
		2257
		2258	The following values for C<$flags> are available:
		2259
		2260	C<IO::AIO::MS_RDONLY>, C<IO::AIO::MS_NOSUID>, C<IO::AIO::MS_NODEV>, C<IO::AIO::MS_NOEXEC>, C<IO::AIO::MS_SYNCHRONOUS>,
		2261	C<IO::AIO::MS_REMOUNT>, C<IO::AIO::MS_MANDLOCK>, C<IO::AIO::MS_DIRSYNC>, C<IO::AIO::MS_NOATIME>,
		2262	C<IO::AIO::MS_NODIRATIME>, C<IO::AIO::MS_BIND>, C<IO::AIO::MS_MOVE>, C<IO::AIO::MS_REC>, C<IO::AIO::MS_SILENT>,
		2263	C<IO::AIO::MS_POSIXACL>, C<IO::AIO::MS_UNBINDABLE>, C<IO::AIO::MS_PRIVATE>, C<IO::AIO::MS_SLAVE>, C<IO::AIO::MS_SHARED>,
		2264	C<IO::AIO::MS_RELATIME>, C<IO::AIO::MS_KERNMOUNT>, C<IO::AIO::MS_I_VERSION>, C<IO::AIO::MS_STRICTATIME>,
		2265	C<IO::AIO::MS_LAZYTIME>, C<IO::AIO::MS_ACTIVE>, C<IO::AIO::MS_NOUSER>, C<IO::AIO::MS_RMT_MASK>, C<IO::AIO::MS_MGC_VAL> and
		2266	C<IO::AIO::MS_MGC_MSK>.
		2267
		2268	=item $retval = IO::AIO::umount $path, $flags = 0
		2269
		2270	Invokes the GNU/Linux C<umount> or C<umount2> syscalls. Always calls
		2271	C<umount> if C<$flags> is C<0>, otherwqise always tries to call
		2272	C<umount2>.
		2273
		2274	The following C<$flags> are available:
		2275
		2276	C<IO::AIO::MNT_FORCE>, C<IO::AIO::MNT_DETACH>, C<IO::AIO::MNT_EXPIRE> and C<IO::AIO::UMOUNT_NOFOLLOW>.
		2277
		2278	=item $numfd = IO::AIO::get_fdlimit
		2279
		2280	Tries to find the current file descriptor limit and returns it, or
		2281	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2282	the highest valid file descriptor number.
		2283
		2284	=item IO::AIO::min_fdlimit [$numfd]
		2285
		2286	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2287	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2288	is missing, it will try to set a very high limit, although this is not
		2289	recommended when you know the actual minimum that you require.
		2290
		2291	If the limit cannot be raised enough, the function makes a best-effort
		2292	attempt to increase the limit as much as possible, using various
		2293	tricks, while still failing. You can query the resulting limit using
		2294	C<IO::AIO::get_fdlimit>.
		2295
		2296	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2297	true.
		2298
		2299	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2300
		2301	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2302	but is blocking (this makes most sense if you know the input data is
		2303	likely cached already and the output filehandle is set to non-blocking
		2304	operations).
		2305
		2306	Returns the number of bytes copied, or C<-1> on error.
		2307
		2308	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2309
		2310	Simply calls the C<posix_fadvise> function (see its
		2311	manpage for details). The following advice constants are
		2312	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2313	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2314	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2315
		2316	On systems that do not implement C<posix_fadvise>, this function returns
		2317	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2318
		2319	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2320
		2321	Simply calls the C<posix_madvise> function (see its
		2322	manpage for details). The following advice constants are
		2323	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2324	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2325	C<IO::AIO::MADV_DONTNEED>.
		2326
		2327	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2328	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2329	will be reduced to fit into the C<$scalar>.
		2330
		2331	On systems that do not implement C<posix_madvise>, this function returns
		2332	ENOSYS, otherwise the return value of C<posix_madvise>.
		2333
		2334	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2335
		2336	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2337	$scalar (see its manpage for details). The following protect
		2338	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2339	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2340
		2341	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2342	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2343	will be reduced to fit into the C<$scalar>.
		2344
		2345	On systems that do not implement C<mprotect>, this function returns
		2346	ENOSYS, otherwise the return value of C<mprotect>.
		2347
		2348	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2349
		2350	Memory-maps a file (or anonymous memory range) and attaches it to the
		2351	given C<$scalar>, which will act like a string scalar. Returns true on
		2352	success, and false otherwise.
		2353
		2354	The scalar must exist, but its contents do not matter - this means you
		2355	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2356	the scalar first.
		2357
		2358	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2359	which don't change the string length, and most read-only operations such
		2360	as copying it or searching it with regexes and so on.
		2361
		2362	Anything else is unsafe and will, at best, result in memory leaks.
		2363
		2364	The memory map associated with the C<$scalar> is automatically removed
		2365	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2366	or C<IO::AIO::munmap> functions are called on it.
		2367
		2368	This calls the C<mmap>(2) function internally. See your system's manual
		2369	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2370
		2371	The C<$length> must be larger than zero and smaller than the actual
		2372	filesize.
		2373
		2374	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2375	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2376
		2377	C<$flags> can be a combination of
		2378	C<IO::AIO::MAP_SHARED> or
		2379	C<IO::AIO::MAP_PRIVATE>,
		2380	or a number of system-specific flags (when not available, the are C<0>):
		2381	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2382	C<IO::AIO::MAP_LOCKED>,
		2383	C<IO::AIO::MAP_NORESERVE>,
		2384	C<IO::AIO::MAP_POPULATE>,
		2385	C<IO::AIO::MAP_NONBLOCK>,
		2386	C<IO::AIO::MAP_FIXED>,
		2387	C<IO::AIO::MAP_GROWSDOWN>,
		2388	C<IO::AIO::MAP_32BIT>,
		2389	C<IO::AIO::MAP_HUGETLB>,
		2390	C<IO::AIO::MAP_STACK>,
		2391	C<IO::AIO::MAP_FIXED_NOREPLACE>,
		2392	C<IO::AIO::MAP_SHARED_VALIDATE>,
		2393	C<IO::AIO::MAP_SYNC> or
		2394	C<IO::AIO::MAP_UNINITIALIZED>.
		2395
		2396	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2397
		2398	C<$offset> is the offset from the start of the file - it generally must be
		2399	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2400
		2401	Example:
		2402
		2403	use Digest::MD5;
		2404	use IO::AIO;
		2405
		2406	open my $fh, "<verybigfile"
		2407	or die "$!";
		2408
		2409	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2410	or die "verybigfile: $!";
		2411
		2412	my $fast_md5 = md5 $data;
		2413
		2414	=item IO::AIO::munmap $scalar
		2415
		2416	Removes a previous mmap and undefines the C<$scalar>.
		2417
		2418	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2419
		2420	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2421	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2422	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2423
		2424	Returns true if successful, and false otherwise. If the underlying mmapped
		2425	region has changed address, then the true value has the numerical value
		2426	C<1>, otherwise it has the numerical value C<0>:
		2427
		2428	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2429	or die "mremap: $!";
		2430
		2431	if ($success*1) {
		2432	warn "scalar has chanegd address in memory\n";
		2433	}
		2434
		2435	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2436	implemented, but not supported and might go away in a future version.
		2437
		2438	On systems where this call is not supported or is not emulated, this call
		2439	returns falls and sets C<$!> to C<ENOSYS>.
		2440
		2441	=item IO::AIO::mlockall $flags
		2442
		2443	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2444	but is blocking.
		2445
		2446	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2447
		2448	Calls the C<munlock> function, undoing the effects of a previous
		2449	C<aio_mlock> call (see its description for details).
		2450
		2451	=item IO::AIO::munlockall
		2452
		2453	Calls the C<munlockall> function.
		2454
		2455	On systems that do not implement C<munlockall>, this function returns
		2456	ENOSYS, otherwise the return value of C<munlockall>.
		2457
		2458	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2459
		2460	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2461	and return the new file handle on success, or sets C<$!> and returns
		2462	C<undef> on error.
		2463
		2464	The remote name of the new socket will be stored in C<$sockaddr>, which
		2465	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2466	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2467	by returning a longer string in C<$sockaddr>, which might or might not be
		2468	truncated.
		2469
		2470	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2471	C<$sockaddr_maxlen>.
		2472
		2473	The main reasons to use this syscall rather than portable C<accept(2)>
		2474	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2475	flags and you can accept name-less sockets by specifying C<0> for
		2476	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2477	C<accept>.
		2478
		2479	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2480
		2481	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2482	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2483	should be the file offset.
		2484
		2485	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2486	silently corrupt the data in this case.
		2487
		2488	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2489	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2490	C<IO::AIO::SPLICE_F_GIFT>.
		2491
		2492	See the C<splice(2)> manpage for details.
		2493
		2494	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2495
		2496	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2497	description for C<IO::AIO::splice> above for details.
		2498
		2499	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2500
		2501	Attempts to query or change the pipe buffer size. Obviously works only
		2502	on pipes, and currently works only on GNU/Linux systems, and fails with
		2503	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2504	size on other systems, drop me a note.
		2505
		2506	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2507
		2508	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2509	C<$flags> is missing or C<0>, then this should be the same as a call to
		2510	perl's built-in C<pipe> function and create a new pipe, and works on
		2511	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2512	(..., 4096, O_BINARY)>.
		2513
		2514	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2515	the given flags (Linux 2.6.27, glibc 2.9).
		2516
		2517	On success, the read and write file handles are returned.
		2518
		2519	On error, nothing will be returned. If the pipe2 syscall is missing and
		2520	C<$flags> is non-zero, fails with C<ENOSYS>.
		2521
		2522	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2523	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2524	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2525
		2526	Example: create a pipe race-free w.r.t. threads and fork:
		2527
		2528	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2529	or die "pipe2: $!\n";
		2530
		2531	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2532
		2533	This is a direct interface to the Linux L<memfd_create(2)> system
		2534	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2535	should be C<IO::AIO::MFD_CLOEXEC>.
		2536
		2537	On success, the new memfd filehandle is returned, otherwise returns
		2538	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2539
		2540	Please refer to L<memfd_create(2)> for more info on this call.
		2541
		2542	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2543	C<IO::AIO::MFD_ALLOW_SEALING>, C<IO::AIO::MFD_HUGETLB>,
		2544	C<IO::AIO::MFD_HUGETLB_2MB> and C<IO::AIO::MFD_HUGETLB_1GB>.
		2545
		2546	Example: create a new memfd.
		2547
		2548	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2549	or die "memfd_create: $!\n";
		2550
		2551	=item $fh = IO::AIO::pidfd_open $pid[, $flags]
		2552
		2553	This is an interface to the Linux L<pidfd_open(2)> system call. The
		2554	default for C<$flags> is C<0>.
		2555
		2556	On success, a new pidfd filehandle is returned (that is already set to
		2557	close-on-exec), otherwise returns C<undef>. If the syscall is missing,
		2558	fails with C<ENOSYS>.
		2559
		2560	Example: open pid 6341 as pidfd.
		2561
		2562	my $fh = IO::AIO::pidfd_open 6341
		2563	or die "pidfd_open: $!\n";
		2564
		2565	=item $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		2566
		2567	This is an interface to the Linux L<pidfd_send_signal> system call. The
		2568	default for C<$siginfo> is C<undef> and the default for C<$flags> is C<0>.
		2569
		2570	Returns the system call status. If the syscall is missing, fails with
		2571	C<ENOSYS>.
		2572
		2573	When specified, C<$siginfo> must be a reference to a hash with one or more
		2574	of the following members:
		2575
		2576	=over
		2577
		2578	=item code - the C<si_code> member
		2579
		2580	=item pid - the C<si_pid> member
		2581
		2582	=item uid - the C<si_uid> member
		2583
		2584	=item value_int - the C<si_value.sival_int> member
		2585
		2586	=item value_ptr - the C<si_value.sival_ptr> member, specified as an integer
		2587
		2588	=back
		2589
		2590	Example: send a SIGKILL to the specified process.
		2591
		2592	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
		2593	and die "pidfd_send_signal: $!\n";
		2594
		2595	Example: send a SIGKILL to the specified process with extra data.
		2596
		2597	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
		2598	and die "pidfd_send_signal: $!\n";
		2599
		2600	=item $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		2601
		2602	This is an interface to the Linux L<pidfd_getfd> system call. The default
		2603	for C<$flags> is C<0>.
		2604
		2605	On success, returns a dup'ed copy of the target file descriptor (specified
		2606	as an integer) returned (that is already set to close-on-exec), otherwise
		2607	returns C<undef>. If the syscall is missing, fails with C<ENOSYS>.
		2608
		2609	Example: get a copy of standard error of another process and print soemthing to it.
		2610
		2611	my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
		2612	or die "pidfd_getfd: $!\n";
		2613	print $errfh "stderr\n";
		2614
		2615	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2616
		2617	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2618	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2619
		2620	On success, the new eventfd filehandle is returned, otherwise returns
		2621	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2622
		2623	Please refer to L<eventfd(2)> for more info on this call.
		2624
		2625	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2626	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2627
		2628	Example: create a new eventfd filehandle:
		2629
		2630	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2631	or die "eventfd: $!\n";
		2632
		2633	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2634
		2635	This is a direct interface to the Linux L<timerfd_create(2)> system
		2636	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2637	should be C<IO::AIO::TFD_CLOEXEC>.
		2638
		2639	On success, the new timerfd filehandle is returned, otherwise returns
		2640	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2641
		2642	Please refer to L<timerfd_create(2)> for more info on this call.
		2643
		2644	The following C<$clockid> values are
		2645	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2646	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2647	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2648	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2649
		2650	The following C<$flags> values are available (Linux
		2651	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2652
		2653	Example: create a new timerfd and set it to one-second repeated alarms,
		2654	then wait for two alarms:
		2655
		2656	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2657	or die "timerfd_create: $!\n";
		2658
		2659	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2660	or die "timerfd_settime: $!\n";
		2661
		2662	for (1..2) {
		2663	8 == sysread $fh, my $buf, 8
		2664	or die "timerfd read failure\n";
		2665
		2666	printf "number of expirations (likely 1): %d\n",
		2667	unpack "Q", $buf;
		2668	}
		2669
		2670	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2671
		2672	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2673	call. Please refer to its manpage for more info on this call.
		2674
		2675	The new itimerspec is specified using two (possibly fractional) second
		2676	values, C<$new_interval> and C<$new_value>).
		2677
		2678	On success, the current interval and value are returned (as per
		2679	C<timerfd_gettime>). On failure, the empty list is returned.
		2680
		2681	The following C<$flags> values are
		2682	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2683	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2684
		2685	See C<IO::AIO::timerfd_create> for a full example.
		2686
		2687	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2688
		2689	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2690	call. Please refer to its manpage for more info on this call.
		2691
		2692	On success, returns the current values of interval and value for the given
		2693	timerfd (as potentially fractional second values). On failure, the empty
		2694	list is returned.
		2695
		2696	=back
		2697
1396	=cut	2698	=cut
1397		2699
1398	min_parallel 8;	2700	min_parallel 8;
1399		2701
1400	END { flush }	2702	END { flush }
1401		2703
1402	1;	2704	1;
1403		2705
		2706	=head1 EVENT LOOP INTEGRATION
		2707
		2708	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2709	automatically into many event loops:
		2710
		2711	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2712	use AnyEvent::AIO;
		2713
		2714	You can also integrate IO::AIO manually into many event loops, here are
		2715	some examples of how to do this:
		2716
		2717	# EV integration
		2718	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2719
		2720	# Event integration
		2721	Event->io (fd => IO::AIO::poll_fileno,
		2722	poll => 'r',
		2723	cb => \&IO::AIO::poll_cb);
		2724
		2725	# Glib/Gtk2 integration
		2726	add_watch Glib::IO IO::AIO::poll_fileno,
		2727	in => sub { IO::AIO::poll_cb; 1 };
		2728
		2729	# Tk integration
		2730	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2731	readable => \&IO::AIO::poll_cb);
		2732
		2733	# Danga::Socket integration
		2734	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2735	\&IO::AIO::poll_cb);
		2736
1404	=head2 FORK BEHAVIOUR	2737	=head2 FORK BEHAVIOUR
1405		2738
1406	This module should do "the right thing" when the process using it forks:	2739	Usage of pthreads in a program changes the semantics of fork
		2740	considerably. Specifically, only async-safe functions can be called after
		2741	fork. Perl doesn't know about this, so in general, you cannot call fork
		2742	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2743	pthreads, so this applies, but many other extensions and (for inexplicable
		2744	reasons) perl itself often is linked against pthreads, so this limitation
		2745	applies to quite a lot of perls.
1407		2746
1408	Before the fork, IO::AIO enters a quiescent state where no requests	2747	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1409	can be added in other threads and no results will be processed. After	2748	only works in the process that loaded it. Forking is fully supported, but
1410	the fork the parent simply leaves the quiescent state and continues	2749	using IO::AIO in the child is not.
1411	request/result processing, while the child frees the request/result queue
1412	(so that the requests started before the fork will only be handled in the
1413	parent). Threads will be started on demand until the limit set in the
1414	parent process has been reached again.
1415		2750
1416	In short: the parent will, after a short pause, continue as if fork had	2751	You might get around by not I<using> IO::AIO before (or after)
1417	not been called, while the child will act as if IO::AIO has not been used	2752	forking. You could also try to call the L<IO::AIO::reinit> function in the
1418	yet.	2753	child:
		2754
		2755	=over 4
		2756
		2757	=item IO::AIO::reinit
		2758
		2759	Abandons all current requests and I/O threads and simply reinitialises all
		2760	data structures. This is not an operation supported by any standards, but
		2761	happens to work on GNU/Linux and some newer BSD systems.
		2762
		2763	The only reasonable use for this function is to call it after forking, if
		2764	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2765	the process will result in undefined behaviour. Calling it at any time
		2766	will also result in any undefined (by POSIX) behaviour.
		2767
		2768	=back
		2769
		2770	=head2 LINUX-SPECIFIC CALLS
		2771
		2772	When a call is documented as "linux-specific" then this means it
		2773	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2774	availability and compatibility of such calls regardless of the platform
		2775	it is compiled on, so platforms such as FreeBSD which often implement
		2776	these calls will work. When in doubt, call them and see if they fail wth
		2777	C<ENOSYS>.
1419		2778
1420	=head2 MEMORY USAGE	2779	=head2 MEMORY USAGE
1421		2780
1422	Per-request usage:	2781	Per-request usage:
1423		2782
…		…
1436	temporary buffers, and each thread requires a stack and other data	2795	temporary buffers, and each thread requires a stack and other data
1437	structures (usually around 16k-128k, depending on the OS).	2796	structures (usually around 16k-128k, depending on the OS).
1438		2797
1439	=head1 KNOWN BUGS	2798	=head1 KNOWN BUGS
1440		2799
1441	Known bugs will be fixed in the next release.	2800	Known bugs will be fixed in the next release :)
		2801
		2802	=head1 KNOWN ISSUES
		2803
		2804	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2805	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2806	non-created hash slots or other scalars I didn't think of. It's best to
		2807	avoid such and either use scalar variables or making sure that the scalar
		2808	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2809
		2810	I am not sure anything can be done about this, so this is considered a
		2811	known issue, rather than a bug.
1442		2812
1443	=head1 SEE ALSO	2813	=head1 SEE ALSO
1444		2814
1445	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2815	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1446	more natural syntax.	2816	more natural syntax and L<IO::FDPass> for file descriptor passing.
1447		2817
1448	=head1 AUTHOR	2818	=head1 AUTHOR
1449		2819
1450	Marc Lehmann <schmorp@schmorp.de>	2820	Marc Lehmann <schmorp@schmorp.de>
1451	http://home.schmorp.de/	2821	http://home.schmorp.de/

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