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Revision 1.105 by root, Sun Mar 25 00:20:27 2007 UTC vs.
Revision 1.307 by root, Wed Feb 26 15:32:59 2020 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
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	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>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	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
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
62	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
63	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
64	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
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for example	47	While most of this works on all types of file descriptors (for
68	sockets), using these functions on file descriptors that support	48	example sockets), using these functions on file descriptors that
69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or	49	support nonblocking operation (again, sockets, pipes etc.) is
70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop	50	very inefficient. Use an event loop for that (such as the L<EV>
71	for that (such as the L<Event|Event> module): IO::AIO will naturally fit	51	module): IO::AIO will naturally fit into such an event loop itself.
72	into such an event loop itself.
73		52
74	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
75	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
76	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
77	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
79	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
80	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
81	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
82	using threads anyway.	61	using threads anyway.
83		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
84	Although the module will work with in the presence of other (Perl-)	67	Although the module will work in the presence of other (Perl-) threads,
85	threads, it is currently not reentrant in any way, so use appropriate	68	it is currently not reentrant in any way, so use appropriate locking
86	locking yourself, always call C<poll_cb> from within the same thread, or	69	yourself, always call C<poll_cb> from within the same thread, or never
87	never call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
88		71
89	=head2 EXAMPLE	72	=head2 EXAMPLE
90		73
91	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
92	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
93		76
94	use Fcntl;
95	use Event;	77	use EV;
96	use IO::AIO;	78	use IO::AIO;
97		79
98	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
99	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
100	poll => 'r',
101	cb => \&IO::AIO::poll_cb);
102		82
103	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
104	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
105	my $fh = shift	85	my $fh = shift
106	or die "error while opening: $!";	86	or die "error while opening: $!";
107		87
108	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
109	my $size = -s $fh;	89	my $size = -s $fh;
…		…
118		98
119	# file contents now in $contents	99	# file contents now in $contents
120	print $contents;	100	print $contents;
121		101
122	# exit event loop and program	102	# exit event loop and program
123	Event::unloop;	103	EV::break;
124	};	104	};
125	};	105	};
126		106
127	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
128	# check for sockets etc. etc.	108	# check for sockets etc. etc.
129		109
130	# process events as long as there are some:	110	# process events as long as there are some:
131	Event::loop;	111	EV::run;
132		112
133	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
134		114
135	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
136	directly visible to Perl.	116	directly visible to Perl.
…		…
184		164
185	=cut	165	=cut
186		166
187	package IO::AIO;	167	package IO::AIO;
188		168
189	no warnings;	169	use Carp ();
190	use strict 'vars';	170
		171	use common::sense;
191		172
192	use base 'Exporter';	173	use base 'Exporter';
193		174
194	BEGIN {	175	BEGIN {
195	our $VERSION = '2.33';	176	our $VERSION = 4.73;
196		177
197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
		181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir);	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		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);
		190
201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
203	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
204	nreqs nready npending nthreads	194	nreqs nready npending nthreads
205	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	push @AIO_REQ, qw(aio_busy); # not exported
206		200
207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
208		202
209	require XSLoader;	203	require XSLoader;
210	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
211	}	205	}
212		206
213	=head1 FUNCTIONS	207	=head1 FUNCTIONS
214		208
215	=head2 AIO REQUEST FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	IO::AIO::reinit
		284
		285	$nfd = IO::AIO::get_fdlimit
		286	IO::AIO::min_fdlimit $nfd
		287
		288	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		289	IO::AIO::fadvise $fh, $offset, $len, $advice
		290
		291	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		292	IO::AIO::munmap $scalar
		293	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		294	IO::AIO::madvise $scalar, $offset, $length, $advice
		295	IO::AIO::mprotect $scalar, $offset, $length, $protect
		296	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		297	IO::AIO::munlockall
		298
		299	# stat extensions
		300	$counter = IO::AIO::st_gen
		301	$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		302	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		303	$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		304	$seconds = IO::AIO::st_btimesec
		305	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		306
		307	# very much unportable syscalls
		308	IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
		309	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		310	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		311	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		312	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		313	$fh = IO::AIO::memfd_create $pathname[, $flags]
		314	$fh = IO::AIO::eventfd [$initval, [$flags]]
		315	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		316	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		317	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		318
		319	=head2 API NOTES
216		320
217	All the C<aio_*> calls are more or less thin wrappers around the syscall	321	All the C<aio_*> calls are more or less thin wrappers around the syscall
218	with the same name (sans C<aio_>). The arguments are similar or identical,	322	with the same name (sans C<aio_>). The arguments are similar or identical,
219	and they all accept an additional (and optional) C<$callback> argument	323	and they all accept an additional (and optional) C<$callback> argument
220	which must be a code reference. This code reference will get called with	324	which must be a code reference. This code reference will be called after
221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	325	the syscall has been executed in an asynchronous fashion. The results
222	perl, which usually delivers "false") as it's sole argument when the given	326	of the request will be passed as arguments to the callback (and, if an
223	syscall has been executed asynchronously.	327	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		328	most syscalls return C<-1> on error, unlike perl, which usually delivers
		329	"false").
		330
		331	Some requests (such as C<aio_readdir>) pass the actual results and
		332	communicate failures by passing C<undef>.
224		333
225	All functions expecting a filehandle keep a copy of the filehandle	334	All functions expecting a filehandle keep a copy of the filehandle
226	internally until the request has finished.	335	internally until the request has finished.
227		336
228	All functions return request objects of type L<IO::AIO::REQ> that allow	337	All functions return request objects of type L<IO::AIO::REQ> that allow
229	further manipulation of those requests while they are in-flight.	338	further manipulation of those requests while they are in-flight.
230		339
231	The pathnames you pass to these routines I<must> be absolute and	340	The pathnames you pass to these routines I<should> be absolute. The
232	encoded as octets. The reason for the former is that at the time the	341	reason for this is that at the time the request is being executed, the
233	request is being executed, the current working directory could have	342	current working directory could have changed. Alternatively, you can
234	changed. Alternatively, you can make sure that you never change the	343	make sure that you never change the current working directory anywhere
235	current working directory anywhere in the program and then use relative	344	in the program and then use relative paths. You can also take advantage
236	paths.	345	of IO::AIOs working directory abstraction, that lets you specify paths
		346	relative to some previously-opened "working directory object" - see the
		347	description of the C<IO::AIO::WD> class later in this document.
237		348
238	To encode pathnames as octets, either make sure you either: a) always pass	349	To encode pathnames as octets, either make sure you either: a) always pass
239	in filenames you got from outside (command line, readdir etc.) without	350	in filenames you got from outside (command line, readdir etc.) without
240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	351	tinkering, b) are in your native filesystem encoding, c) use the Encode
241	your pathnames to the locale (or other) encoding in effect in the user	352	module and encode your pathnames to the locale (or other) encoding in
242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	353	effect in the user environment, d) use Glib::filename_from_unicode on
243	use something else to ensure your scalar has the correct contents.	354	unicode filenames or e) use something else to ensure your scalar has the
		355	correct contents.
244		356
245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	357	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246	handles correctly wether it is set or not.	358	handles correctly whether it is set or not.
		359
		360	=head2 AIO REQUEST FUNCTIONS
247		361
248	=over 4	362	=over 4
249		363
250	=item $prev_pri = aioreq_pri [$pri]	364	=item $prev_pri = aioreq_pri [$pri]
251		365
…		…
271	aio_read $_[0], ..., sub {	385	aio_read $_[0], ..., sub {
272	...	386	...
273	};	387	};
274	};	388	};
275		389
		390
276	=item aioreq_nice $pri_adjust	391	=item aioreq_nice $pri_adjust
277		392
278	Similar to C<aioreq_pri>, but subtracts the given value from the current	393	Similar to C<aioreq_pri>, but subtracts the given value from the current
279	priority, so the effect is cumulative.	394	priority, so the effect is cumulative.
280		395
		396
281	=item aio_open $pathname, $flags, $mode, $callback->($fh)	397	=item aio_open $pathname, $flags, $mode, $callback->($fh)
282		398
283	Asynchronously open or create a file and call the callback with a newly	399	Asynchronously open or create a file and call the callback with a newly
284	created filehandle for the file.	400	created filehandle for the file (or C<undef> in case of an error).
285		401
286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	402	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
287	for an explanation.	403	for an explanation.
288		404
289	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	405	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
296	by the umask in effect then the request is being executed, so better never	412	by the umask in effect then the request is being executed, so better never
297	change the umask.	413	change the umask.
298		414
299	Example:	415	Example:
300		416
301	aio_open "/etc/passwd", O_RDONLY, 0, sub {	417	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
302	if ($_[0]) {	418	if ($_[0]) {
303	print "open successful, fh is $_[0]\n";	419	print "open successful, fh is $_[0]\n";
304	...	420	...
305	} else {	421	} else {
306	die "open failed: $!\n";	422	die "open failed: $!\n";
307	}	423	}
308	};	424	};
309		425
		426	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		427	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		428	following POSIX and non-POSIX constants are available (missing ones on
		429	your system are, as usual, C<0>):
		430
		431	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		432	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		433	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		434
		435
310	=item aio_close $fh, $callback->($status)	436	=item aio_close $fh, $callback->($status)
311		437
312	Asynchronously close a file and call the callback with the result	438	Asynchronously close a file and call the callback with the result
313	code. I<WARNING:> although accepted, you should not pass in a perl	439	code.
314	filehandle here, as perl will likely close the file descriptor another
315	time when the filehandle is destroyed. Normally, you can safely call perls
316	C<close> or just let filehandles go out of scope.
317		440
318	This is supposed to be a bug in the API, so that might change. It's	441	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
319	therefore best to avoid this function.	442	closing the file descriptor associated with the filehandle itself.
		443
		444	Therefore, C<aio_close> will not close the filehandle - instead it will
		445	use dup2 to overwrite the file descriptor with the write-end of a pipe
		446	(the pipe fd will be created on demand and will be cached).
		447
		448	Or in other words: the file descriptor will be closed, but it will not be
		449	free for reuse until the perl filehandle is closed.
		450
		451	=cut
		452
		453	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		454
		455	Seeks the filehandle to the new C<$offset>, similarly to perl's
		456	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		457	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		458	C<IO::AIO::SEEK_END>).
		459
		460	The resulting absolute offset will be passed to the callback, or C<-1> in
		461	case of an error.
		462
		463	In theory, the C<$whence> constants could be different than the
		464	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		465	so don't panic.
		466
		467	As a GNU/Linux (and maybe Solaris) extension, also the constants
		468	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		469	could be found. No guarantees about suitability for use in C<aio_seek> or
		470	Perl's C<sysseek> can be made though, although I would naively assume they
		471	"just work".
320		472
321	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	473	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322		474
323	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	475	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
324		476
325	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	477	Reads or writes C<$length> bytes from or to the specified C<$fh> and
326	into the scalar given by C<data> and offset C<dataoffset> and calls the	478	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
327	callback without the actual number of bytes read (or -1 on error, just	479	calls the callback with the actual number of bytes transferred (or -1 on
328	like the syscall).	480	error, just like the syscall).
		481
		482	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		483	offset plus the actual number of bytes read.
		484
		485	If C<$offset> is undefined, then the current file descriptor offset will
		486	be used (and updated), otherwise the file descriptor offset will not be
		487	changed by these calls.
		488
		489	If C<$length> is undefined in C<aio_write>, use the remaining length of
		490	C<$data>.
		491
		492	If C<$dataoffset> is less than zero, it will be counted from the end of
		493	C<$data>.
329		494
330	The C<$data> scalar I<MUST NOT> be modified in any way while the request	495	The C<$data> scalar I<MUST NOT> be modified in any way while the request
331	is outstanding. Modifying it can result in segfaults or WW3 (if the	496	is outstanding. Modifying it can result in segfaults or World War III (if
332	necessary/optional hardware is installed).	497	the necessary/optional hardware is installed).
333		498
334	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	499	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
335	offset C<0> within the scalar:	500	offset C<0> within the scalar:
336		501
337	aio_read $fh, 7, 15, $buffer, 0, sub {	502	aio_read $fh, 7, 15, $buffer, 0, sub {
338	$_[0] > 0 or die "read error: $!";	503	$_[0] > 0 or die "read error: $!";
339	print "read $_[0] bytes: <$buffer>\n";	504	print "read $_[0] bytes: <$buffer>\n";
340	};	505	};
341		506
		507
342	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	508	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
343		509
344	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	510	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
345	reading at byte offset C<$in_offset>, and starts writing at the current	511	reading at byte offset C<$in_offset>, and starts writing at the current
346	file offset of C<$out_fh>. Because of that, it is not safe to issue more	512	file offset of C<$out_fh>. Because of that, it is not safe to issue more
347	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	513	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
348	other.	514	other. The same C<$in_fh> works fine though, as this function does not
		515	move or use the file offset of C<$in_fh>.
349		516
		517	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		518	are written, and there is no way to find out how many more bytes have been
		519	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		520	number of bytes written to C<$out_fh>. Only if the result value equals
		521	C<$length> one can assume that C<$length> bytes have been read.
		522
		523	Unlike with other C<aio_> functions, it makes a lot of sense to use
		524	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		525	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		526	the socket I/O will be non-blocking. Note, however, that you can run
		527	into a trap where C<aio_sendfile> reads some data with readahead, then
		528	fails to write all data, and when the socket is ready the next time, the
		529	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		530	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		531	resource usage.
		532
350	This call tries to make use of a native C<sendfile> syscall to provide	533	This call tries to make use of a native C<sendfile>-like syscall to
351	zero-copy operation. For this to work, C<$out_fh> should refer to a	534	provide zero-copy operation. For this to work, C<$out_fh> should refer to
352	socket, and C<$in_fh> should refer to mmap'able file.	535	a socket, and C<$in_fh> should refer to an mmap'able file.
353		536
354	If the native sendfile call fails or is not implemented, it will be	537	If a native sendfile cannot be found or it fails with C<ENOSYS>,
355	emulated, so you can call C<aio_sendfile> on any type of filehandle	538	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		539	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
356	regardless of the limitations of the operating system.	540	type of filehandle regardless of the limitations of the operating system.
357		541
358	Please note, however, that C<aio_sendfile> can read more bytes from	542	As native sendfile syscalls (as practically any non-POSIX interface hacked
359	C<$in_fh> than are written, and there is no way to find out how many	543	together in a hurry to improve benchmark numbers) tend to be rather buggy
360	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	544	on many systems, this implementation tries to work around some known bugs
361	provides the number of bytes written to C<$out_fh>. Only if the result	545	in Linux and FreeBSD kernels (probably others, too), but that might fail,
362	value equals C<$length> one can assume that C<$length> bytes have been	546	so you really really should check the return value of C<aio_sendfile> -
363	read.	547	fewer bytes than expected might have been transferred.
		548
364		549
365	=item aio_readahead $fh,$offset,$length, $callback->($retval)	550	=item aio_readahead $fh,$offset,$length, $callback->($retval)
366		551
367	C<aio_readahead> populates the page cache with data from a file so that	552	C<aio_readahead> populates the page cache with data from a file so that
368	subsequent reads from that file will not block on disk I/O. The C<$offset>	553	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
371	whole pages, so that offset is effectively rounded down to a page boundary	556	whole pages, so that offset is effectively rounded down to a page boundary
372	and bytes are read up to the next page boundary greater than or equal to	557	and bytes are read up to the next page boundary greater than or equal to
373	(off-set+length). C<aio_readahead> does not read beyond the end of the	558	(off-set+length). C<aio_readahead> does not read beyond the end of the
374	file. The current file offset of the file is left unchanged.	559	file. The current file offset of the file is left unchanged.
375		560
376	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	561	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
377	emulated by simply reading the data, which would have a similar effect.	562	be emulated by simply reading the data, which would have a similar effect.
		563
378		564
379	=item aio_stat $fh_or_path, $callback->($status)	565	=item aio_stat $fh_or_path, $callback->($status)
380		566
381	=item aio_lstat $fh, $callback->($status)	567	=item aio_lstat $fh, $callback->($status)
382		568
383	Works like perl's C<stat> or C<lstat> in void context. The callback will	569	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
384	be called after the stat and the results will be available using C<stat _>	570	callback will be called after the stat and the results will be available
385	or C<-s _> etc...	571	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		572	and C<-T>).
386		573
387	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	574	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
388	for an explanation.	575	for an explanation.
389		576
390	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	577	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
391	error when stat'ing a large file, the results will be silently truncated	578	error when stat'ing a large file, the results will be silently truncated
392	unless perl itself is compiled with large file support.	579	unless perl itself is compiled with large file support.
		580
		581	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		582	following constants and functions (if not implemented, the constants will
		583	be C<0> and the functions will either C<croak> or fall back on traditional
		584	behaviour).
		585
		586	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		587	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		588	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		589
		590	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		591	ACCESS>.
393		592
394	Example: Print the length of F</etc/passwd>:	593	Example: Print the length of F</etc/passwd>:
395		594
396	aio_stat "/etc/passwd", sub {	595	aio_stat "/etc/passwd", sub {
397	$_[0] and die "stat failed: $!";	596	$_[0] and die "stat failed: $!";
398	print "size is ", -s _, "\n";	597	print "size is ", -s _, "\n";
399	};	598	};
400		599
		600
		601	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		602
		603	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		604	whether a file handle or path was passed.
		605
		606	On success, the callback is passed a hash reference with the following
		607	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		608	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		609	is passed.
		610
		611	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		612	C<ST_NOSUID>.
		613
		614	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		615	their correct value when available, or to C<0> on systems that do
		616	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		617	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		618	C<ST_NODIRATIME> and C<ST_RELATIME>.
		619
		620	Example: stat C</wd> and dump out the data if successful.
		621
		622	aio_statvfs "/wd", sub {
		623	my $f = $_[0]
		624	or die "statvfs: $!";
		625
		626	use Data::Dumper;
		627	say Dumper $f;
		628	};
		629
		630	# result:
		631	{
		632	bsize => 1024,
		633	bfree => 4333064312,
		634	blocks => 10253828096,
		635	files => 2050765568,
		636	flag => 4096,
		637	favail => 2042092649,
		638	bavail => 4333064312,
		639	ffree => 2042092649,
		640	namemax => 255,
		641	frsize => 1024,
		642	fsid => 1810
		643	}
		644
		645	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		646
		647	Works like perl's C<utime> function (including the special case of $atime
		648	and $mtime being undef). Fractional times are supported if the underlying
		649	syscalls support them.
		650
		651	When called with a pathname, uses utimensat(2) or utimes(2) if available,
		652	otherwise utime(2). If called on a file descriptor, uses futimens(2)
		653	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		654	portable.
		655
		656	Examples:
		657
		658	# set atime and mtime to current time (basically touch(1)):
		659	aio_utime "path", undef, undef;
		660	# set atime to current time and mtime to beginning of the epoch:
		661	aio_utime "path", time, undef; # undef==0
		662
		663
		664	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		665
		666	Works like perl's C<chown> function, except that C<undef> for either $uid
		667	or $gid is being interpreted as "do not change" (but -1 can also be used).
		668
		669	Examples:
		670
		671	# same as "chown root path" in the shell:
		672	aio_chown "path", 0, -1;
		673	# same as above:
		674	aio_chown "path", 0, undef;
		675
		676
		677	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		678
		679	Works like truncate(2) or ftruncate(2).
		680
		681
		682	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		683
		684	Allocates or frees disk space according to the C<$mode> argument. See the
		685	linux C<fallocate> documentation for details.
		686
		687	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		688	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		689	to deallocate a file range.
		690
		691	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		692	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		693	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		694	to unshare shared blocks (see your L<fallocate(2)> manpage).
		695
		696	The file system block size used by C<fallocate> is presumably the
		697	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		698	can dictate other limitations.
		699
		700	If C<fallocate> isn't available or cannot be emulated (currently no
		701	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		702
		703
		704	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		705
		706	Works like perl's C<chmod> function.
		707
		708
401	=item aio_unlink $pathname, $callback->($status)	709	=item aio_unlink $pathname, $callback->($status)
402		710
403	Asynchronously unlink (delete) a file and call the callback with the	711	Asynchronously unlink (delete) a file and call the callback with the
404	result code.	712	result code.
405		713
		714
406	=item aio_mknod $path, $mode, $dev, $callback->($status)	715	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
407		716
408	[EXPERIMENTAL]	717	[EXPERIMENTAL]
409		718
410	Asynchronously create a device node (or fifo). See mknod(2).	719	Asynchronously create a device node (or fifo). See mknod(2).
411		720
412	The only (POSIX-) portable way of calling this function is:	721	The only (POSIX-) portable way of calling this function is:
413		722
414	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	723	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		724
		725	See C<aio_stat> for info about some potentially helpful extra constants
		726	and functions.
415		727
416	=item aio_link $srcpath, $dstpath, $callback->($status)	728	=item aio_link $srcpath, $dstpath, $callback->($status)
417		729
418	Asynchronously create a new link to the existing object at C<$srcpath> at	730	Asynchronously create a new link to the existing object at C<$srcpath> at
419	the path C<$dstpath> and call the callback with the result code.	731	the path C<$dstpath> and call the callback with the result code.
420		732
		733
421	=item aio_symlink $srcpath, $dstpath, $callback->($status)	734	=item aio_symlink $srcpath, $dstpath, $callback->($status)
422		735
423	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	736	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
424	the path C<$dstpath> and call the callback with the result code.	737	the path C<$dstpath> and call the callback with the result code.
425		738
		739
426	=item aio_readlink $path, $callback->($link)	740	=item aio_readlink $pathname, $callback->($link)
427		741
428	Asynchronously read the symlink specified by C<$path> and pass it to	742	Asynchronously read the symlink specified by C<$path> and pass it to
429	the callback. If an error occurs, nothing or undef gets passed to the	743	the callback. If an error occurs, nothing or undef gets passed to the
430	callback.	744	callback.
431		745
		746
		747	=item aio_realpath $pathname, $callback->($path)
		748
		749	Asynchronously make the path absolute and resolve any symlinks in
		750	C<$path>. The resulting path only consists of directories (same as
		751	L<Cwd::realpath>).
		752
		753	This request can be used to get the absolute path of the current working
		754	directory by passing it a path of F<.> (a single dot).
		755
		756
432	=item aio_rename $srcpath, $dstpath, $callback->($status)	757	=item aio_rename $srcpath, $dstpath, $callback->($status)
433		758
434	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	759	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
435	rename(2) and call the callback with the result code.	760	rename(2) and call the callback with the result code.
		761
		762	On systems that support the AIO::WD working directory abstraction
		763	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		764	of failing, C<rename> is called on the absolute path of C<$wd>.
		765
		766
		767	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		768
		769	Basically a version of C<aio_rename> with an additional C<$flags>
		770	argument. Calling this with C<$flags=0> is the same as calling
		771	C<aio_rename>.
		772
		773	Non-zero flags are currently only supported on GNU/Linux systems that
		774	support renameat2. Other systems fail with C<ENOSYS> in this case.
		775
		776	The following constants are available (missing ones are, as usual C<0>),
		777	see renameat2(2) for details:
		778
		779	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		780	and C<IO::AIO::RENAME_WHITEOUT>.
		781
436		782
437	=item aio_mkdir $pathname, $mode, $callback->($status)	783	=item aio_mkdir $pathname, $mode, $callback->($status)
438		784
439	Asynchronously mkdir (create) a directory and call the callback with	785	Asynchronously mkdir (create) a directory and call the callback with
440	the result code. C<$mode> will be modified by the umask at the time the	786	the result code. C<$mode> will be modified by the umask at the time the
441	request is executed, so do not change your umask.	787	request is executed, so do not change your umask.
442		788
		789
443	=item aio_rmdir $pathname, $callback->($status)	790	=item aio_rmdir $pathname, $callback->($status)
444		791
445	Asynchronously rmdir (delete) a directory and call the callback with the	792	Asynchronously rmdir (delete) a directory and call the callback with the
446	result code.	793	result code.
		794
		795	On systems that support the AIO::WD working directory abstraction
		796	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		797	C<rmdir> is called on the absolute path of C<$wd>.
		798
447		799
448	=item aio_readdir $pathname, $callback->($entries)	800	=item aio_readdir $pathname, $callback->($entries)
449		801
450	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	802	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
451	directory (i.e. opendir + readdir + closedir). The entries will not be	803	directory (i.e. opendir + readdir + closedir). The entries will not be
452	sorted, and will B<NOT> include the C<.> and C<..> entries.	804	sorted, and will B<NOT> include the C<.> and C<..> entries.
453		805
454	The callback a single argument which is either C<undef> or an array-ref	806	The callback is passed a single argument which is either C<undef> or an
455	with the filenames.	807	array-ref with the filenames.
456		808
		809
		810	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		811
		812	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		813	tune behaviour and output format. In case of an error, C<$entries> will be
		814	C<undef>.
		815
		816	The flags are a combination of the following constants, ORed together (the
		817	flags will also be passed to the callback, possibly modified):
		818
		819	=over 4
		820
		821	=item IO::AIO::READDIR_DENTS
		822
		823	Normally the callback gets an arrayref consisting of names only (as
		824	with C<aio_readdir>). If this flag is set, then the callback gets an
		825	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
		826	single directory entry in more detail:
		827
		828	C<$name> is the name of the entry.
		829
		830	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		831
		832	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		833	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		834	C<IO::AIO::DT_WHT>.
		835
		836	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		837	to know, you have to run stat yourself. Also, for speed/memory reasons,
		838	the C<$type> scalars are read-only: you must not modify them.
		839
		840	C<$inode> is the inode number (which might not be exact on systems with 64
		841	bit inode numbers and 32 bit perls). This field has unspecified content on
		842	systems that do not deliver the inode information.
		843
		844	=item IO::AIO::READDIR_DIRS_FIRST
		845
		846	When this flag is set, then the names will be returned in an order where
		847	likely directories come first, in optimal stat order. This is useful when
		848	you need to quickly find directories, or you want to find all directories
		849	while avoiding to stat() each entry.
		850
		851	If the system returns type information in readdir, then this is used
		852	to find directories directly. Otherwise, likely directories are names
		853	beginning with ".", or otherwise names with no dots, of which names with
		854	short names are tried first.
		855
		856	=item IO::AIO::READDIR_STAT_ORDER
		857
		858	When this flag is set, then the names will be returned in an order
		859	suitable for stat()'ing each one. That is, when you plan to stat() most or
		860	all files in the given directory, then the returned order will likely be
		861	faster.
		862
		863	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
		864	then the likely dirs come first, resulting in a less optimal stat order
		865	for stat'ing all entries, but likely a more optimal order for finding
		866	subdirectories.
		867
		868	=item IO::AIO::READDIR_FOUND_UNKNOWN
		869
		870	This flag should not be set when calling C<aio_readdirx>. Instead, it
		871	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		872	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		873	C<$type>'s are known, which can be used to speed up some algorithms.
		874
		875	=back
		876
		877
		878	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		879
		880	Opens, reads and closes the given file. The data is put into C<$data>,
		881	which is resized as required.
		882
		883	If C<$offset> is negative, then it is counted from the end of the file.
		884
		885	If C<$length> is zero, then the remaining length of the file is
		886	used. Also, in this case, the same limitations to modifying C<$data> apply
		887	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		888	with C<substr>. If the size of the file is known, specifying a non-zero
		889	C<$length> results in a performance advantage.
		890
		891	This request is similar to the older C<aio_load> request, but since it is
		892	a single request, it might be more efficient to use.
		893
		894	Example: load F</etc/passwd> into C<$passwd>.
		895
		896	my $passwd;
		897	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		898	$_[0] >= 0
		899	or die "/etc/passwd: $!\n";
		900
		901	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		902	print $passwd;
		903	};
		904	IO::AIO::flush;
		905
		906
457	=item aio_load $path, $data, $callback->($status)	907	=item aio_load $pathname, $data, $callback->($status)
458		908
459	This is a composite request that tries to fully load the given file into	909	This is a composite request that tries to fully load the given file into
460	memory. Status is the same as with aio_read.	910	memory. Status is the same as with aio_read.
461		911
		912	Using C<aio_slurp> might be more efficient, as it is a single request.
		913
462	=cut	914	=cut
463		915
464	sub aio_load($$;$) {	916	sub aio_load($$;$) {
465	aio_block {
466	my ($path, undef, $cb) = @_;	917	my ($path, undef, $cb) = @_;
467	my $data = \$_[1];	918	my $data = \$_[1];
468		919
469	my $pri = aioreq_pri;	920	my $pri = aioreq_pri;
470	my $grp = aio_group $cb;	921	my $grp = aio_group $cb;
		922
		923	aioreq_pri $pri;
		924	add $grp aio_open $path, O_RDONLY, 0, sub {
		925	my $fh = shift
		926	or return $grp->result (-1);
471		927
472	aioreq_pri $pri;	928	aioreq_pri $pri;
473	add $grp aio_open $path, O_RDONLY, 0, sub {
474	my $fh = shift
475	or return $grp->result (-1);
476
477	aioreq_pri $pri;
478	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {	929	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
479	$grp->result ($_[0]);	930	$grp->result ($_[0]);
480	};
481	};	931	};
482
483	$grp
484	}	932	};
		933
		934	$grp
485	}	935	}
486		936
487	=item aio_copy $srcpath, $dstpath, $callback->($status)	937	=item aio_copy $srcpath, $dstpath, $callback->($status)
488		938
489	Try to copy the I<file> (directories not supported as either source or	939	Try to copy the I<file> (directories not supported as either source or
490	destination) from C<$srcpath> to C<$dstpath> and call the callback with	940	destination) from C<$srcpath> to C<$dstpath> and call the callback with
491	the C<0> (error) or C<-1> ok.	941	a status of C<0> (ok) or C<-1> (error, see C<$!>).
492		942
		943	Existing destination files will be truncated.
		944
493	This is a composite request that it creates the destination file with	945	This is a composite request that creates the destination file with
494	mode 0200 and copies the contents of the source file into it using	946	mode 0200 and copies the contents of the source file into it using
495	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	947	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
496	uid/gid, in that order.	948	uid/gid, in that order.
497		949
498	If an error occurs, the partial destination file will be unlinked, if	950	If an error occurs, the partial destination file will be unlinked, if
…		…
500	errors are being ignored.	952	errors are being ignored.
501		953
502	=cut	954	=cut
503		955
504	sub aio_copy($$;$) {	956	sub aio_copy($$;$) {
505	aio_block {
506	my ($src, $dst, $cb) = @_;	957	my ($src, $dst, $cb) = @_;
507		958
508	my $pri = aioreq_pri;	959	my $pri = aioreq_pri;
509	my $grp = aio_group $cb;	960	my $grp = aio_group $cb;
510		961
511	aioreq_pri $pri;	962	aioreq_pri $pri;
512	add $grp aio_open $src, O_RDONLY, 0, sub {	963	add $grp aio_open $src, O_RDONLY, 0, sub {
513	if (my $src_fh = $_[0]) {	964	if (my $src_fh = $_[0]) {
514	my @stat = stat $src_fh;	965	my @stat = stat $src_fh; # hmm, might block over nfs?
515		966
516	aioreq_pri $pri;	967	aioreq_pri $pri;
517	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	968	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
518	if (my $dst_fh = $_[0]) {	969	if (my $dst_fh = $_[0]) {
519	aioreq_pri $pri;	970	aioreq_pri $pri;
520	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	971	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
521	if ($_[0] == $stat[7]) {	972	if ($_[0] == $stat[7]) {
522	$grp->result (0);	973	$grp->result (0);
523	close $src_fh;	974	close $src_fh;
524		975
525	# those should not normally block. should. should.
526	utime $stat[8], $stat[9], $dst;
527	chmod $stat[2] & 07777, $dst_fh;
528	chown $stat[4], $stat[5], $dst_fh;
529	close $dst_fh;
530	} else {	976	my $ch = sub {
531	$grp->result (-1);
532	close $src_fh;
533	close $dst_fh;
534
535	aioreq $pri;	977	aioreq_pri $pri;
		978	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		979	aioreq_pri $pri;
		980	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		981	aioreq_pri $pri;
536	add $grp aio_unlink $dst;	982	add $grp aio_close $dst_fh;
		983	}
		984	};
537	}	985	};
		986
		987	aioreq_pri $pri;
		988	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		989	if ($_[0] < 0 && $! == ENOSYS) {
		990	aioreq_pri $pri;
		991	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		992	} else {
		993	$ch->();
		994	}
		995	};
		996	} else {
		997	$grp->result (-1);
		998	close $src_fh;
		999	close $dst_fh;
		1000
		1001	aioreq $pri;
		1002	add $grp aio_unlink $dst;
538	};	1003	}
539	} else {
540	$grp->result (-1);
541	}	1004	};
		1005	} else {
		1006	$grp->result (-1);
542	},	1007	}
543
544	} else {
545	$grp->result (-1);
546	}	1008	},
		1009
		1010	} else {
		1011	$grp->result (-1);
547	};	1012	}
548
549	$grp
550	}	1013	};
		1014
		1015	$grp
551	}	1016	}
552		1017
553	=item aio_move $srcpath, $dstpath, $callback->($status)	1018	=item aio_move $srcpath, $dstpath, $callback->($status)
554		1019
555	Try to move the I<file> (directories not supported as either source or	1020	Try to move the I<file> (directories not supported as either source or
556	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1021	destination) from C<$srcpath> to C<$dstpath> and call the callback with
557	the C<0> (error) or C<-1> ok.	1022	a status of C<0> (ok) or C<-1> (error, see C<$!>).
558		1023
559	This is a composite request that tries to rename(2) the file first. If	1024	This is a composite request that tries to rename(2) the file first; if
560	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1025	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
561	that is successful, unlinking the C<$srcpath>.	1026	that is successful, unlinks the C<$srcpath>.
562		1027
563	=cut	1028	=cut
564		1029
565	sub aio_move($$;$) {	1030	sub aio_move($$;$) {
566	aio_block {
567	my ($src, $dst, $cb) = @_;	1031	my ($src, $dst, $cb) = @_;
568		1032
569	my $pri = aioreq_pri;	1033	my $pri = aioreq_pri;
570	my $grp = aio_group $cb;	1034	my $grp = aio_group $cb;
571		1035
572	aioreq_pri $pri;	1036	aioreq_pri $pri;
573	add $grp aio_rename $src, $dst, sub {	1037	add $grp aio_rename $src, $dst, sub {
574	if ($_[0] && $! == EXDEV) {	1038	if ($_[0] && $! == EXDEV) {
575	aioreq_pri $pri;	1039	aioreq_pri $pri;
576	add $grp aio_copy $src, $dst, sub {	1040	add $grp aio_copy $src, $dst, sub {
577	$grp->result ($_[0]);
578
579	if (!$_[0]) {
580	aioreq_pri $pri;
581	add $grp aio_unlink $src;
582	}
583	};
584	} else {
585	$grp->result ($_[0]);	1041	$grp->result ($_[0]);
		1042
		1043	unless ($_[0]) {
		1044	aioreq_pri $pri;
		1045	add $grp aio_unlink $src;
		1046	}
586	}	1047	};
		1048	} else {
		1049	$grp->result ($_[0]);
587	};	1050	}
588
589	$grp
590	}	1051	};
		1052
		1053	$grp
591	}	1054	}
592		1055
593	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1056	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
594		1057
595	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1058	Scans a directory (similar to C<aio_readdir>) but additionally tries to
596	efficiently separate the entries of directory C<$path> into two sets of	1059	efficiently separate the entries of directory C<$path> into two sets of
597	names, directories you can recurse into (directories), and ones you cannot	1060	names, directories you can recurse into (directories), and ones you cannot
598	recurse into (everything else, including symlinks to directories).	1061	recurse into (everything else, including symlinks to directories).
599		1062
600	C<aio_scandir> is a composite request that creates of many sub requests_	1063	C<aio_scandir> is a composite request that generates many sub requests.
601	C<$maxreq> specifies the maximum number of outstanding aio requests that	1064	C<$maxreq> specifies the maximum number of outstanding aio requests that
602	this function generates. If it is C<< <= 0 >>, then a suitable default	1065	this function generates. If it is C<< <= 0 >>, then a suitable default
603	will be chosen (currently 4).	1066	will be chosen (currently 4).
604		1067
605	On error, the callback is called without arguments, otherwise it receives	1068	On error, the callback is called without arguments, otherwise it receives
…		…
615		1078
616	Implementation notes.	1079	Implementation notes.
617		1080
618	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1081	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
619		1082
		1083	If readdir returns file type information, then this is used directly to
		1084	find directories.
		1085
620	After reading the directory, the modification time, size etc. of the	1086	Otherwise, after reading the directory, the modification time, size etc.
621	directory before and after the readdir is checked, and if they match (and	1087	of the directory before and after the readdir is checked, and if they
622	isn't the current time), the link count will be used to decide how many	1088	match (and isn't the current time), the link count will be used to decide
623	entries are directories (if >= 2). Otherwise, no knowledge of the number	1089	how many entries are directories (if >= 2). Otherwise, no knowledge of the
624	of subdirectories will be assumed.	1090	number of subdirectories will be assumed.
625		1091
626	Then entries will be sorted into likely directories (everything without	1092	Then entries will be sorted into likely directories a non-initial dot
627	a non-initial dot currently) and likely non-directories (everything	1093	currently) and likely non-directories (see C<aio_readdirx>). Then every
628	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1094	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
629	likely directories first. If that succeeds, it assumes that the entry	1095	in order of their inode numbers. If that succeeds, it assumes that the
630	is a directory or a symlink to directory (which will be checked	1096	entry is a directory or a symlink to directory (which will be checked
631	seperately). This is often faster than stat'ing the entry itself because	1097	separately). This is often faster than stat'ing the entry itself because
632	filesystems might detect the type of the entry without reading the inode	1098	filesystems might detect the type of the entry without reading the inode
633	data (e.g. ext2fs filetype feature).	1099	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1100	the filetype information on readdir.
634		1101
635	If the known number of directories (link count - 2) has been reached, the	1102	If the known number of directories (link count - 2) has been reached, the
636	rest of the entries is assumed to be non-directories.	1103	rest of the entries is assumed to be non-directories.
637		1104
638	This only works with certainty on POSIX (= UNIX) filesystems, which	1105	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
643	directory counting heuristic.	1110	directory counting heuristic.
644		1111
645	=cut	1112	=cut
646		1113
647	sub aio_scandir($$;$) {	1114	sub aio_scandir($$;$) {
648	aio_block {
649	my ($path, $maxreq, $cb) = @_;	1115	my ($path, $maxreq, $cb) = @_;
650		1116
651	my $pri = aioreq_pri;	1117	my $pri = aioreq_pri;
652		1118
653	my $grp = aio_group $cb;	1119	my $grp = aio_group $cb;
654		1120
655	$maxreq = 4 if $maxreq <= 0;	1121	$maxreq = 4 if $maxreq <= 0;
		1122
		1123	# get a wd object
		1124	aioreq_pri $pri;
		1125	add $grp aio_wd $path, sub {
		1126	$_[0]
		1127	or return $grp->result ();
		1128
		1129	my $wd = [shift, "."];
656		1130
657	# stat once	1131	# stat once
658	aioreq_pri $pri;	1132	aioreq_pri $pri;
659	add $grp aio_stat $path, sub {	1133	add $grp aio_stat $wd, sub {
660	return $grp->result () if $_[0];	1134	return $grp->result () if $_[0];
661	my $now = time;	1135	my $now = time;
662	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1136	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1137	my $rdxflags = READDIR_DIRS_FIRST;
		1138
		1139	if ((stat _)[3] < 2) {
		1140	# at least one non-POSIX filesystem exists
		1141	# that returns useful DT_type values: btrfs,
		1142	# so optimise for this here by requesting dents
		1143	$rdxflags |= READDIR_DENTS;
		1144	}
663		1145
664	# read the directory entries	1146	# read the directory entries
665	aioreq_pri $pri;	1147	aioreq_pri $pri;
666	add $grp aio_readdir $path, sub {	1148	add $grp aio_readdirx $wd, $rdxflags, sub {
667	my $entries = shift	1149	my ($entries, $flags) = @_
668	or return $grp->result ();	1150	or return $grp->result ();
		1151
		1152	if ($rdxflags & READDIR_DENTS) {
		1153	# if we requested type values, see if we can use them directly.
		1154
		1155	# if there were any DT_UNKNOWN entries then we assume we
		1156	# don't know. alternatively, we could assume that if we get
		1157	# one DT_DIR, then all directories are indeed marked with
		1158	# DT_DIR, but this seems not required for btrfs, and this
		1159	# is basically the "btrfs can't get it's act together" code
		1160	# branch.
		1161	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1162	# now we have valid DT_ information for all entries,
		1163	# so use it as an optimisation without further stat's.
		1164	# they must also all be at the beginning of @$entries
		1165	# by now.
		1166
		1167	my $dirs;
		1168
		1169	if (@$entries) {
		1170	for (0 .. $#$entries) {
		1171	if ($entries->[$_][1] != DT_DIR) {
		1172	# splice out directories
		1173	$dirs = [splice @$entries, 0, $_];
		1174	last;
		1175	}
		1176	}
		1177
		1178	# if we didn't find any non-dir, then all entries are dirs
		1179	unless ($dirs) {
		1180	($dirs, $entries) = ($entries, []);
		1181	}
		1182	} else {
		1183	# directory is empty, so there are no sbdirs
		1184	$dirs = [];
		1185	}
		1186
		1187	# either splice'd the directories out or the dir was empty.
		1188	# convert dents to filenames
		1189	$_ = $_->[0] for @$dirs;
		1190	$_ = $_->[0] for @$entries;
		1191
		1192	return $grp->result ($dirs, $entries);
		1193	}
		1194
		1195	# cannot use, so return to our old ways
		1196	# by pretending we only scanned for names.
		1197	$_ = $_->[0] for @$entries;
		1198	}
669		1199
670	# stat the dir another time	1200	# stat the dir another time
671	aioreq_pri $pri;	1201	aioreq_pri $pri;
672	add $grp aio_stat $path, sub {	1202	add $grp aio_stat $wd, sub {
673	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1203	my $hash2 = join ":", (stat _)[0,1,3,7,9];
674		1204
675	my $ndirs;	1205	my $ndirs;
676		1206
677	# take the slow route if anything looks fishy	1207	# take the slow route if anything looks fishy
678	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1208	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
679	$ndirs = -1;	1209	$ndirs = -1;
680	} else {	1210	} else {
681	# if nlink == 2, we are finished	1211	# if nlink == 2, we are finished
682	# on non-posix-fs's, we rely on nlink < 2	1212	# for non-posix-fs's, we rely on nlink < 2
683	$ndirs = (stat _)[3] - 2	1213	$ndirs = (stat _)[3] - 2
684	or return $grp->result ([], $entries);	1214	or return $grp->result ([], $entries);
685	}	1215	}
686		1216
687	# sort into likely dirs and likely nondirs
688	# dirs == files without ".", short entries first
689	$entries = [map $_->[0],
690	sort { $b->[1] cmp $a->[1] }
691	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
692	@$entries];
693
694	my (@dirs, @nondirs);	1217	my (@dirs, @nondirs);
695		1218
696	my $statgrp = add $grp aio_group sub {	1219	my $statgrp = add $grp aio_group sub {
697	$grp->result (\@dirs, \@nondirs);	1220	$grp->result (\@dirs, \@nondirs);
698	};	1221	};
699		1222
700	limit $statgrp $maxreq;	1223	limit $statgrp $maxreq;
701	feed $statgrp sub {	1224	feed $statgrp sub {
702	return unless @$entries;	1225	return unless @$entries;
703	my $entry = pop @$entries;	1226	my $entry = shift @$entries;
704		1227
705	aioreq_pri $pri;	1228	aioreq_pri $pri;
		1229	$wd->[1] = "$entry/.";
706	add $statgrp aio_stat "$path/$entry/.", sub {	1230	add $statgrp aio_stat $wd, sub {
707	if ($_[0] < 0) {	1231	if ($_[0] < 0) {
708	push @nondirs, $entry;	1232	push @nondirs, $entry;
709	} else {	1233	} else {
710	# need to check for real directory	1234	# need to check for real directory
711	aioreq_pri $pri;	1235	aioreq_pri $pri;
		1236	$wd->[1] = $entry;
712	add $statgrp aio_lstat "$path/$entry", sub {	1237	add $statgrp aio_lstat $wd, sub {
713	if (-d _) {	1238	if (-d _) {
714	push @dirs, $entry;	1239	push @dirs, $entry;
715		1240
716	unless (--$ndirs) {	1241	unless (--$ndirs) {
717	push @nondirs, @$entries;	1242	push @nondirs, @$entries;
…		…
725	};	1250	};
726	};	1251	};
727	};	1252	};
728	};	1253	};
729	};	1254	};
730
731	$grp
732	}	1255	};
		1256
		1257	$grp
733	}	1258	}
734		1259
735	=item aio_rmtree $path, $callback->($status)	1260	=item aio_rmtree $pathname, $callback->($status)
736		1261
737	Delete a directory tree starting (and including) C<$path>, return the	1262	Delete a directory tree starting (and including) C<$path>, return the
738	status of the final C<rmdir> only. This is a composite request that	1263	status of the final C<rmdir> only. This is a composite request that
739	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1264	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
740	everything else.	1265	everything else.
741		1266
742	=cut	1267	=cut
743		1268
744	sub aio_rmtree;	1269	sub aio_rmtree;
745	sub aio_rmtree($;$) {	1270	sub aio_rmtree($;$) {
746	aio_block {
747	my ($path, $cb) = @_;	1271	my ($path, $cb) = @_;
748		1272
749	my $pri = aioreq_pri;	1273	my $pri = aioreq_pri;
750	my $grp = aio_group $cb;	1274	my $grp = aio_group $cb;
751		1275
752	aioreq_pri $pri;	1276	aioreq_pri $pri;
753	add $grp aio_scandir $path, 0, sub {	1277	add $grp aio_scandir $path, 0, sub {
754	my ($dirs, $nondirs) = @_;	1278	my ($dirs, $nondirs) = @_;
755		1279
756	my $dirgrp = aio_group sub {	1280	my $dirgrp = aio_group sub {
757	add $grp aio_rmdir $path, sub {	1281	add $grp aio_rmdir $path, sub {
758	$grp->result ($_[0]);	1282	$grp->result ($_[0]);
759	};
760	};	1283	};
761
762	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
763	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
764
765	add $grp $dirgrp;
766	};	1284	};
767		1285
768	$grp	1286	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1287	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1288
		1289	add $grp $dirgrp;
769	}	1290	};
		1291
		1292	$grp
770	}	1293	}
		1294
		1295	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1296
		1297	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1298
		1299	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1300	they execute asynchronously and pass the return value to the callback.
		1301
		1302	Both calls can be used for a lot of things, some of which make more sense
		1303	to run asynchronously in their own thread, while some others make less
		1304	sense. For example, calls that block waiting for external events, such
		1305	as locking, will also lock down an I/O thread while it is waiting, which
		1306	can deadlock the whole I/O system. At the same time, there might be no
		1307	alternative to using a thread to wait.
		1308
		1309	So in general, you should only use these calls for things that do
		1310	(filesystem) I/O, not for things that wait for other events (network,
		1311	other processes), although if you are careful and know what you are doing,
		1312	you still can.
		1313
		1314	The following constants are available and can be used for normal C<ioctl>
		1315	and C<fcntl> as well (missing ones are, as usual C<0>):
		1316
		1317	C<F_DUPFD_CLOEXEC>,
		1318
		1319	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1320
		1321	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1322
		1323	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1324	C<F_SEAL_WRITE>.
		1325
		1326	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1327	C<FS_IOC_FIEMAP>.
		1328
		1329	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1330	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1331
		1332	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1333	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1334	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1335	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1336	C<FS_FL_USER_MODIFIABLE>.
		1337
		1338	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1339	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1340	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1341	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1342
		1343	=item aio_sync $callback->($status)
		1344
		1345	Asynchronously call sync and call the callback when finished.
771		1346
772	=item aio_fsync $fh, $callback->($status)	1347	=item aio_fsync $fh, $callback->($status)
773		1348
774	Asynchronously call fsync on the given filehandle and call the callback	1349	Asynchronously call fsync on the given filehandle and call the callback
775	with the fsync result code.	1350	with the fsync result code.
…		…
779	Asynchronously call fdatasync on the given filehandle and call the	1354	Asynchronously call fdatasync on the given filehandle and call the
780	callback with the fdatasync result code.	1355	callback with the fdatasync result code.
781		1356
782	If this call isn't available because your OS lacks it or it couldn't be	1357	If this call isn't available because your OS lacks it or it couldn't be
783	detected, it will be emulated by calling C<fsync> instead.	1358	detected, it will be emulated by calling C<fsync> instead.
		1359
		1360	=item aio_syncfs $fh, $callback->($status)
		1361
		1362	Asynchronously call the syncfs syscall to sync the filesystem associated
		1363	to the given filehandle and call the callback with the syncfs result
		1364	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1365	errno to C<ENOSYS> nevertheless.
		1366
		1367	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1368
		1369	Sync the data portion of the file specified by C<$offset> and C<$length>
		1370	to disk (but NOT the metadata), by calling the Linux-specific
		1371	sync_file_range call. If sync_file_range is not available or it returns
		1372	ENOSYS, then fdatasync or fsync is being substituted.
		1373
		1374	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1375	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1376	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1377	manpage for details.
		1378
		1379	=item aio_pathsync $pathname, $callback->($status)
		1380
		1381	This request tries to open, fsync and close the given path. This is a
		1382	composite request intended to sync directories after directory operations
		1383	(E.g. rename). This might not work on all operating systems or have any
		1384	specific effect, but usually it makes sure that directory changes get
		1385	written to disc. It works for anything that can be opened for read-only,
		1386	not just directories.
		1387
		1388	Future versions of this function might fall back to other methods when
		1389	C<fsync> on the directory fails (such as calling C<sync>).
		1390
		1391	Passes C<0> when everything went ok, and C<-1> on error.
		1392
		1393	=cut
		1394
		1395	sub aio_pathsync($;$) {
		1396	my ($path, $cb) = @_;
		1397
		1398	my $pri = aioreq_pri;
		1399	my $grp = aio_group $cb;
		1400
		1401	aioreq_pri $pri;
		1402	add $grp aio_open $path, O_RDONLY, 0, sub {
		1403	my ($fh) = @_;
		1404	if ($fh) {
		1405	aioreq_pri $pri;
		1406	add $grp aio_fsync $fh, sub {
		1407	$grp->result ($_[0]);
		1408
		1409	aioreq_pri $pri;
		1410	add $grp aio_close $fh;
		1411	};
		1412	} else {
		1413	$grp->result (-1);
		1414	}
		1415	};
		1416
		1417	$grp
		1418	}
		1419
		1420	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1421
		1422	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1423	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1424	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1425	scalar must only be modified in-place while an aio operation is pending on
		1426	it).
		1427
		1428	It calls the C<msync> function of your OS, if available, with the memory
		1429	area starting at C<$offset> in the string and ending C<$length> bytes
		1430	later. If C<$length> is negative, counts from the end, and if C<$length>
		1431	is C<undef>, then it goes till the end of the string. The flags can be
		1432	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1433	C<IO::AIO::MS_INVALIDATE>.
		1434
		1435	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1436
		1437	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1438	scalars.
		1439
		1440	It touches (reads or writes) all memory pages in the specified
		1441	range inside the scalar. All caveats and parameters are the same
		1442	as for C<aio_msync>, above, except for flags, which must be either
		1443	C<0> (which reads all pages and ensures they are instantiated) or
		1444	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1445	writing an octet from it, which dirties the page).
		1446
		1447	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1448
		1449	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1450	scalars.
		1451
		1452	It reads in all the pages of the underlying storage into memory (if any)
		1453	and locks them, so they are not getting swapped/paged out or removed.
		1454
		1455	If C<$length> is undefined, then the scalar will be locked till the end.
		1456
		1457	On systems that do not implement C<mlock>, this function returns C<-1>
		1458	and sets errno to C<ENOSYS>.
		1459
		1460	Note that the corresponding C<munlock> is synchronous and is
		1461	documented under L<MISCELLANEOUS FUNCTIONS>.
		1462
		1463	Example: open a file, mmap and mlock it - both will be undone when
		1464	C<$data> gets destroyed.
		1465
		1466	open my $fh, "<", $path or die "$path: $!";
		1467	my $data;
		1468	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1469	aio_mlock $data; # mlock in background
		1470
		1471	=item aio_mlockall $flags, $callback->($status)
		1472
		1473	Calls the C<mlockall> function with the given C<$flags> (a
		1474	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1475	C<IO::AIO::MCL_ONFAULT>).
		1476
		1477	On systems that do not implement C<mlockall>, this function returns C<-1>
		1478	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1479	by the system result in a return value of C<-1> with errno being set to
		1480	C<EINVAL>.
		1481
		1482	Note that the corresponding C<munlockall> is synchronous and is
		1483	documented under L<MISCELLANEOUS FUNCTIONS>.
		1484
		1485	Example: asynchronously lock all current and future pages into memory.
		1486
		1487	aio_mlockall IO::AIO::MCL_FUTURE;
		1488
		1489	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1490
		1491	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1492	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1493	the ioctl is not available on your OS, then this request will fail with
		1494	C<ENOSYS>.
		1495
		1496	C<$start> is the starting offset to query extents for, C<$length> is the
		1497	size of the range to query - if it is C<undef>, then the whole file will
		1498	be queried.
		1499
		1500	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1501	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1502	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1503	the data portion.
		1504
		1505	C<$count> is the maximum number of extent records to return. If it is
		1506	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1507	case, if it is C<0>, then the callback receives the number of extents
		1508	instead of the extents themselves (which is unreliable, see below).
		1509
		1510	If an error occurs, the callback receives no arguments. The special
		1511	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1512
		1513	Otherwise, the callback receives an array reference with extent
		1514	structures. Each extent structure is an array reference itself, with the
		1515	following members:
		1516
		1517	[$logical, $physical, $length, $flags]
		1518
		1519	Flags is any combination of the following flag values (typically either C<0>
		1520	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1521
		1522	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1523	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1524	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1525	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1526	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1527	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1528
		1529	At the time of this writing (Linux 3.2), this request is unreliable unless
		1530	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1531	it to return all extents of a range for files with a large number of
		1532	extents. The code (only) works around all these issues if C<$count> is
		1533	C<undef>.
784		1534
785	=item aio_group $callback->(...)	1535	=item aio_group $callback->(...)
786		1536
787	This is a very special aio request: Instead of doing something, it is a	1537	This is a very special aio request: Instead of doing something, it is a
788	container for other aio requests, which is useful if you want to bundle	1538	container for other aio requests, which is useful if you want to bundle
…		…
826	immense (it blocks a thread for a long time) so do not use this function	1576	immense (it blocks a thread for a long time) so do not use this function
827	except to put your application under artificial I/O pressure.	1577	except to put your application under artificial I/O pressure.
828		1578
829	=back	1579	=back
830		1580
		1581
		1582	=head2 IO::AIO::WD - multiple working directories
		1583
		1584	Your process only has one current working directory, which is used by all
		1585	threads. This makes it hard to use relative paths (some other component
		1586	could call C<chdir> at any time, and it is hard to control when the path
		1587	will be used by IO::AIO).
		1588
		1589	One solution for this is to always use absolute paths. This usually works,
		1590	but can be quite slow (the kernel has to walk the whole path on every
		1591	access), and can also be a hassle to implement.
		1592
		1593	Newer POSIX systems have a number of functions (openat, fdopendir,
		1594	futimensat and so on) that make it possible to specify working directories
		1595	per operation.
		1596
		1597	For portability, and because the clowns who "designed", or shall I write,
		1598	perpetrated this new interface were obviously half-drunk, this abstraction
		1599	cannot be perfect, though.
		1600
		1601	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1602	object. This object stores the canonicalised, absolute version of the
		1603	path, and on systems that allow it, also a directory file descriptor.
		1604
		1605	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1606	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1607	object and a pathname instead (or the IO::AIO::WD object alone, which
		1608	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1609	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1610	to that IO::AIO::WD object.
		1611
		1612	For example, to get a wd object for F</etc> and then stat F<passwd>
		1613	inside, you would write:
		1614
		1615	aio_wd "/etc", sub {
		1616	my $etcdir = shift;
		1617
		1618	# although $etcdir can be undef on error, there is generally no reason
		1619	# to check for errors here, as aio_stat will fail with ENOENT
		1620	# when $etcdir is undef.
		1621
		1622	aio_stat [$etcdir, "passwd"], sub {
		1623	# yay
		1624	};
		1625	};
		1626
		1627	The fact that C<aio_wd> is a request and not a normal function shows that
		1628	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1629	which is why it is done asynchronously.
		1630
		1631	To stat the directory obtained with C<aio_wd> above, one could write
		1632	either of the following three request calls:
		1633
		1634	aio_lstat "/etc" , sub { ... # pathname as normal string
		1635	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1636	aio_lstat $wd , sub { ... # shorthand for the previous
		1637
		1638	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1639	object and the pathname string, so you could write the following without
		1640	causing any issues due to C<$path> getting reused:
		1641
		1642	my $path = [$wd, undef];
		1643
		1644	for my $name (qw(abc def ghi)) {
		1645	$path->[1] = $name;
		1646	aio_stat $path, sub {
		1647	# ...
		1648	};
		1649	}
		1650
		1651	There are some caveats: when directories get renamed (or deleted), the
		1652	pathname string doesn't change, so will point to the new directory (or
		1653	nowhere at all), while the directory fd, if available on the system,
		1654	will still point to the original directory. Most functions accepting a
		1655	pathname will use the directory fd on newer systems, and the string on
		1656	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1657	the string form of the pathname.
		1658
		1659	So this functionality is mainly useful to get some protection against
		1660	C<chdir>, to easily get an absolute path out of a relative path for future
		1661	reference, and to speed up doing many operations in the same directory
		1662	(e.g. when stat'ing all files in a directory).
		1663
		1664	The following functions implement this working directory abstraction:
		1665
		1666	=over 4
		1667
		1668	=item aio_wd $pathname, $callback->($wd)
		1669
		1670	Asynchonously canonicalise the given pathname and convert it to an
		1671	IO::AIO::WD object representing it. If possible and supported on the
		1672	system, also open a directory fd to speed up pathname resolution relative
		1673	to this working directory.
		1674
		1675	If something goes wrong, then C<undef> is passwd to the callback instead
		1676	of a working directory object and C<$!> is set appropriately. Since
		1677	passing C<undef> as working directory component of a pathname fails the
		1678	request with C<ENOENT>, there is often no need for error checking in the
		1679	C<aio_wd> callback, as future requests using the value will fail in the
		1680	expected way.
		1681
		1682	=item IO::AIO::CWD
		1683
		1684	This is a compile time constant (object) that represents the process
		1685	current working directory.
		1686
		1687	Specifying this object as working directory object for a pathname is as if
		1688	the pathname would be specified directly, without a directory object. For
		1689	example, these calls are functionally identical:
		1690
		1691	aio_stat "somefile", sub { ... };
		1692	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1693
		1694	=back
		1695
		1696	To recover the path associated with an IO::AIO::WD object, you can use
		1697	C<aio_realpath>:
		1698
		1699	aio_realpath $wd, sub {
		1700	warn "path is $_[0]\n";
		1701	};
		1702
		1703	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1704	sometimes, fall back to using an absolue path.
		1705
831	=head2 IO::AIO::REQ CLASS	1706	=head2 IO::AIO::REQ CLASS
832		1707
833	All non-aggregate C<aio_*> functions return an object of this class when	1708	All non-aggregate C<aio_*> functions return an object of this class when
834	called in non-void context.	1709	called in non-void context.
835		1710
…		…
838	=item cancel $req	1713	=item cancel $req
839		1714
840	Cancels the request, if possible. Has the effect of skipping execution	1715	Cancels the request, if possible. Has the effect of skipping execution
841	when entering the B<execute> state and skipping calling the callback when	1716	when entering the B<execute> state and skipping calling the callback when
842	entering the the B<result> state, but will leave the request otherwise	1717	entering the the B<result> state, but will leave the request otherwise
843	untouched. That means that requests that currently execute will not be	1718	untouched (with the exception of readdir). That means that requests that
844	stopped and resources held by the request will not be freed prematurely.	1719	currently execute will not be stopped and resources held by the request
		1720	will not be freed prematurely.
845		1721
846	=item cb $req $callback->(...)	1722	=item cb $req $callback->(...)
847		1723
848	Replace (or simply set) the callback registered to the request.	1724	Replace (or simply set) the callback registered to the request.
849		1725
…		…
900	Their lifetime, simplified, looks like this: when they are empty, they	1776	Their lifetime, simplified, looks like this: when they are empty, they
901	will finish very quickly. If they contain only requests that are in the	1777	will finish very quickly. If they contain only requests that are in the
902	C<done> state, they will also finish. Otherwise they will continue to	1778	C<done> state, they will also finish. Otherwise they will continue to
903	exist.	1779	exist.
904		1780
905	That means after creating a group you have some time to add requests. And	1781	That means after creating a group you have some time to add requests
906	in the callbacks of those requests, you can add further requests to the	1782	(precisely before the callback has been invoked, which is only done within
907	group. And only when all those requests have finished will the the group	1783	the C<poll_cb>). And in the callbacks of those requests, you can add
908	itself finish.	1784	further requests to the group. And only when all those requests have
		1785	finished will the the group itself finish.
909		1786
910	=over 4	1787	=over 4
911		1788
912	=item add $grp ...	1789	=item add $grp ...
913		1790
…		…
922	=item $grp->cancel_subs	1799	=item $grp->cancel_subs
923		1800
924	Cancel all subrequests and clears any feeder, but not the group request	1801	Cancel all subrequests and clears any feeder, but not the group request
925	itself. Useful when you queued a lot of events but got a result early.	1802	itself. Useful when you queued a lot of events but got a result early.
926		1803
		1804	The group request will finish normally (you cannot add requests to the
		1805	group).
		1806
927	=item $grp->result (...)	1807	=item $grp->result (...)
928		1808
929	Set the result value(s) that will be passed to the group callback when all	1809	Set the result value(s) that will be passed to the group callback when all
930	subrequests have finished and set thre groups errno to the current value	1810	subrequests have finished and set the groups errno to the current value
931	of errno (just like calling C<errno> without an error number). By default,	1811	of errno (just like calling C<errno> without an error number). By default,
932	no argument will be passed and errno is zero.	1812	no argument will be passed and errno is zero.
933		1813
934	=item $grp->errno ([$errno])	1814	=item $grp->errno ([$errno])
935		1815
…		…
946	=item feed $grp $callback->($grp)	1826	=item feed $grp $callback->($grp)
947		1827
948	Sets a feeder/generator on this group: every group can have an attached	1828	Sets a feeder/generator on this group: every group can have an attached
949	generator that generates requests if idle. The idea behind this is that,	1829	generator that generates requests if idle. The idea behind this is that,
950	although you could just queue as many requests as you want in a group,	1830	although you could just queue as many requests as you want in a group,
951	this might starve other requests for a potentially long time. For	1831	this might starve other requests for a potentially long time. For example,
952	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1832	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
953	requests, delaying any later requests for a long time.	1833	requests, delaying any later requests for a long time.
954		1834
955	To avoid this, and allow incremental generation of requests, you can	1835	To avoid this, and allow incremental generation of requests, you can
956	instead a group and set a feeder on it that generates those requests. The	1836	instead a group and set a feeder on it that generates those requests. The
957	feed callback will be called whenever there are few enough (see C<limit>,	1837	feed callback will be called whenever there are few enough (see C<limit>,
…		…
962	not impose any limits).	1842	not impose any limits).
963		1843
964	If the feed does not queue more requests when called, it will be	1844	If the feed does not queue more requests when called, it will be
965	automatically removed from the group.	1845	automatically removed from the group.
966		1846
967	If the feed limit is C<0>, it will be set to C<2> automatically.	1847	If the feed limit is C<0> when this method is called, it will be set to
		1848	C<2> automatically.
968		1849
969	Example:	1850	Example:
970		1851
971	# stat all files in @files, but only ever use four aio requests concurrently:	1852	# stat all files in @files, but only ever use four aio requests concurrently:
972		1853
…		…
984	Sets the feeder limit for the group: The feeder will be called whenever	1865	Sets the feeder limit for the group: The feeder will be called whenever
985	the group contains less than this many requests.	1866	the group contains less than this many requests.
986		1867
987	Setting the limit to C<0> will pause the feeding process.	1868	Setting the limit to C<0> will pause the feeding process.
988		1869
		1870	The default value for the limit is C<0>, but note that setting a feeder
		1871	automatically bumps it up to C<2>.
		1872
989	=back	1873	=back
990		1874
		1875
991	=head2 SUPPORT FUNCTIONS	1876	=head2 SUPPORT FUNCTIONS
992		1877
993	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1878	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
994		1879
995	=over 4	1880	=over 4
996		1881
997	=item $fileno = IO::AIO::poll_fileno	1882	=item $fileno = IO::AIO::poll_fileno
998		1883
999	Return the I<request result pipe file descriptor>. This filehandle must be	1884	Return the I<request result pipe file descriptor>. This filehandle must be
1000	polled for reading by some mechanism outside this module (e.g. Event or	1885	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1001	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1886	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1002	to call C<poll_cb> to check the results.	1887	you have to call C<poll_cb> to check the results.
1003		1888
1004	See C<poll_cb> for an example.	1889	See C<poll_cb> for an example.
1005		1890
1006	=item IO::AIO::poll_cb	1891	=item IO::AIO::poll_cb
1007		1892
1008	Process some outstanding events on the result pipe. You have to call this	1893	Process some requests that have reached the result phase (i.e. they have
1009	regularly. Returns the number of events processed. Returns immediately	1894	been executed but the results are not yet reported). You have to call
1010	when no events are outstanding. The amount of events processed depends on	1895	this "regularly" to finish outstanding requests.
1011	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1012		1896
		1897	Returns C<0> if all events could be processed (or there were no
		1898	events to process), or C<-1> if it returned earlier for whatever
		1899	reason. Returns immediately when no events are outstanding. The amount
		1900	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1901	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1902
1013	If not all requests were processed for whatever reason, the filehandle	1903	If not all requests were processed for whatever reason, the poll file
1014	will still be ready when C<poll_cb> returns.	1904	descriptor will still be ready when C<poll_cb> returns, so normally you
		1905	don't have to do anything special to have it called later.
		1906
		1907	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1908	ready, it can be beneficial to call this function from loops which submit
		1909	a lot of requests, to make sure the results get processed when they become
		1910	available and not just when the loop is finished and the event loop takes
		1911	over again. This function returns very fast when there are no outstanding
		1912	requests.
1015		1913
1016	Example: Install an Event watcher that automatically calls	1914	Example: Install an Event watcher that automatically calls
1017	IO::AIO::poll_cb with high priority:	1915	IO::AIO::poll_cb with high priority (more examples can be found in the
		1916	SYNOPSIS section, at the top of this document):
1018		1917
1019	Event->io (fd => IO::AIO::poll_fileno,	1918	Event->io (fd => IO::AIO::poll_fileno,
1020	poll => 'r', async => 1,	1919	poll => 'r', async => 1,
1021	cb => \&IO::AIO::poll_cb);	1920	cb => \&IO::AIO::poll_cb);
		1921
		1922	=item IO::AIO::poll_wait
		1923
		1924	Wait until either at least one request is in the result phase or no
		1925	requests are outstanding anymore.
		1926
		1927	This is useful if you want to synchronously wait for some requests to
		1928	become ready, without actually handling them.
		1929
		1930	See C<nreqs> for an example.
		1931
		1932	=item IO::AIO::poll
		1933
		1934	Waits until some requests have been handled.
		1935
		1936	Returns the number of requests processed, but is otherwise strictly
		1937	equivalent to:
		1938
		1939	IO::AIO::poll_wait, IO::AIO::poll_cb
		1940
		1941	=item IO::AIO::flush
		1942
		1943	Wait till all outstanding AIO requests have been handled.
		1944
		1945	Strictly equivalent to:
		1946
		1947	IO::AIO::poll_wait, IO::AIO::poll_cb
		1948	while IO::AIO::nreqs;
		1949
		1950	This function can be useful at program aborts, to make sure outstanding
		1951	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1952	this function on normal exits), or when you are merely using C<IO::AIO>
		1953	for its more advanced functions, rather than for async I/O, e.g.:
		1954
		1955	my ($dirs, $nondirs);
		1956	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1957	IO::AIO::flush;
		1958	# $dirs, $nondirs are now set
1022		1959
1023	=item IO::AIO::max_poll_reqs $nreqs	1960	=item IO::AIO::max_poll_reqs $nreqs
1024		1961
1025	=item IO::AIO::max_poll_time $seconds	1962	=item IO::AIO::max_poll_time $seconds
1026		1963
…		…
1051	# use a low priority so other tasks have priority	1988	# use a low priority so other tasks have priority
1052	Event->io (fd => IO::AIO::poll_fileno,	1989	Event->io (fd => IO::AIO::poll_fileno,
1053	poll => 'r', nice => 1,	1990	poll => 'r', nice => 1,
1054	cb => &IO::AIO::poll_cb);	1991	cb => &IO::AIO::poll_cb);
1055		1992
1056	=item IO::AIO::poll_wait
1057
1058	If there are any outstanding requests and none of them in the result
1059	phase, wait till the result filehandle becomes ready for reading (simply
1060	does a C<select> on the filehandle. This is useful if you want to
1061	synchronously wait for some requests to finish).
1062
1063	See C<nreqs> for an example.
1064
1065	=item IO::AIO::poll
1066
1067	Waits until some requests have been handled.
1068
1069	Returns the number of requests processed, but is otherwise strictly
1070	equivalent to:
1071
1072	IO::AIO::poll_wait, IO::AIO::poll_cb
1073
1074	=item IO::AIO::flush
1075
1076	Wait till all outstanding AIO requests have been handled.
1077
1078	Strictly equivalent to:
1079
1080	IO::AIO::poll_wait, IO::AIO::poll_cb
1081	while IO::AIO::nreqs;
1082
1083	=back	1993	=back
		1994
1084		1995
1085	=head3 CONTROLLING THE NUMBER OF THREADS	1996	=head3 CONTROLLING THE NUMBER OF THREADS
1086		1997
1087	=over	1998	=over
1088		1999
…		…
1120		2031
1121	Under normal circumstances you don't need to call this function.	2032	Under normal circumstances you don't need to call this function.
1122		2033
1123	=item IO::AIO::max_idle $nthreads	2034	=item IO::AIO::max_idle $nthreads
1124		2035
1125	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2036	Limit the number of threads (default: 4) that are allowed to idle
1126	threads that did not get a request to process within 10 seconds). That	2037	(i.e., threads that did not get a request to process within the idle
1127	means if a thread becomes idle while C<$nthreads> other threads are also	2038	timeout (default: 10 seconds). That means if a thread becomes idle while
1128	idle, it will free its resources and exit.	2039	C<$nthreads> other threads are also idle, it will free its resources and
		2040	exit.
1129		2041
1130	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2042	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1131	to allow for extremely high load situations, but want to free resources	2043	to allow for extremely high load situations, but want to free resources
1132	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2044	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1133		2045
1134	The default is probably ok in most situations, especially if thread	2046	The default is probably ok in most situations, especially if thread
1135	creation is fast. If thread creation is very slow on your system you might	2047	creation is fast. If thread creation is very slow on your system you might
1136	want to use larger values.	2048	want to use larger values.
1137		2049
		2050	=item IO::AIO::idle_timeout $seconds
		2051
		2052	Sets the minimum idle timeout (default 10) after which worker threads are
		2053	allowed to exit. SEe C<IO::AIO::max_idle>.
		2054
1138	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	2055	=item IO::AIO::max_outstanding $maxreqs
		2056
		2057	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2058	you do queue up more than this number of requests, the next call to
		2059	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2060	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2061	longer exceeded.
		2062
		2063	In other words, this setting does not enforce a queue limit, but can be
		2064	used to make poll functions block if the limit is exceeded.
1139		2065
1140	This is a very bad function to use in interactive programs because it	2066	This is a very bad function to use in interactive programs because it
1141	blocks, and a bad way to reduce concurrency because it is inexact: Better	2067	blocks, and a bad way to reduce concurrency because it is inexact: Better
1142	use an C<aio_group> together with a feed callback.	2068	use an C<aio_group> together with a feed callback.
1143		2069
1144	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2070	Its main use is in scripts without an event loop - when you want to stat
1145	to queue up more than this number of requests, the next call to the	2071	a lot of files, you can write something like this:
1146	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1147	function will block until the limit is no longer exceeded.
1148		2072
1149	The default value is very large, so there is no practical limit on the	2073	IO::AIO::max_outstanding 32;
1150	number of outstanding requests.
1151		2074
1152	You can still queue as many requests as you want. Therefore,	2075	for my $path (...) {
1153	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	2076	aio_stat $path , ...;
1154	as a stop gap to shield against fatal memory overflow (with large values).	2077	IO::AIO::poll_cb;
		2078	}
		2079
		2080	IO::AIO::flush;
		2081
		2082	The call to C<poll_cb> inside the loop will normally return instantly, but
		2083	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2084	some requests have been handled. This keeps the loop from pushing a large
		2085	number of C<aio_stat> requests onto the queue.
		2086
		2087	The default value for C<max_outstanding> is very large, so there is no
		2088	practical limit on the number of outstanding requests.
1155		2089
1156	=back	2090	=back
		2091
1157		2092
1158	=head3 STATISTICAL INFORMATION	2093	=head3 STATISTICAL INFORMATION
1159		2094
1160	=over	2095	=over
1161		2096
…		…
1179	Returns the number of requests currently in the pending state (executed,	2114	Returns the number of requests currently in the pending state (executed,
1180	but not yet processed by poll_cb).	2115	but not yet processed by poll_cb).
1181		2116
1182	=back	2117	=back
1183		2118
		2119
		2120	=head3 SUBSECOND STAT TIME ACCESS
		2121
		2122	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2123	generally find access/modification and change times with subsecond time
		2124	accuracy of the system supports it, but perl's built-in functions only
		2125	return the integer part.
		2126
		2127	The following functions return the timestamps of the most recent
		2128	stat with subsecond precision on most systems and work both after
		2129	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2130	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2131	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2132
		2133	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2134	full resolution without rounding and work with standard perl C<stat>,
		2135	alleviating the need to call the special C<Time::HiRes> functions, which
		2136	do not act like their perl counterparts.
		2137
		2138	On operating systems or file systems where subsecond time resolution is
		2139	not supported or could not be detected, a fractional part of C<0> is
		2140	returned, so it is always safe to call these functions.
		2141
		2142	=over 4
		2143
		2144	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2145
		2146	Return the access, modication, change or birth time, respectively,
		2147	including fractional part. Due to the limited precision of floating point,
		2148	the accuracy on most platforms is only a bit better than milliseconds
		2149	for times around now - see the I<nsec> function family, below, for full
		2150	accuracy.
		2151
		2152	File birth time is only available when the OS and perl support it (on
		2153	FreeBSD and NetBSD at the time of this writing, although support is
		2154	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2155	it). On systems where it isn't available, C<0> is currently returned, but
		2156	this might change to C<undef> in a future version.
		2157
		2158	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2159
		2160	Returns access, modification, change and birth time all in one go, and
		2161	maybe more times in the future version.
		2162
		2163	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2164
		2165	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2166	as an integer in the range C<0> to C<999999999>.
		2167
		2168	Note that no accessors are provided for access, modification and
		2169	change times - you need to get those from C<stat _> if required (C<int
		2170	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2171	value).
		2172
		2173	=item $seconds = IO::AIO::st_btimesec
		2174
		2175	The (integral) seconds part of the file birth time, if available.
		2176
		2177	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2178
		2179	Like the functions above, but returns all four times in one go (and maybe
		2180	more in future versions).
		2181
		2182	=item $counter = IO::AIO::st_gen
		2183
		2184	Returns the generation counter (in practice this is just a random number)
		2185	of the file. This is only available on platforms which have this member in
		2186	their C<struct stat> (most BSDs at the time of this writing) and generally
		2187	only to the root usert. If unsupported, C<0> is returned, but this might
		2188	change to C<undef> in a future version.
		2189
		2190	=back
		2191
		2192	Example: print the high resolution modification time of F</etc>, using
		2193	C<stat>, and C<IO::AIO::aio_stat>.
		2194
		2195	if (stat "/etc") {
		2196	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2197	}
		2198
		2199	IO::AIO::aio_stat "/etc", sub {
		2200	$_[0]
		2201	and return;
		2202
		2203	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2204	};
		2205
		2206	IO::AIO::flush;
		2207
		2208	Output of the awbove on my system, showing reduced and full accuracy:
		2209
		2210	stat(/etc) mtime: 1534043702.020808
		2211	aio_stat(/etc) mtime: 1534043702.020807792
		2212
		2213
		2214	=head3 MISCELLANEOUS FUNCTIONS
		2215
		2216	IO::AIO implements some functions that are useful when you want to use
		2217	some "Advanced I/O" function not available to in Perl, without going the
		2218	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2219	counterpart.
		2220
		2221	=over 4
		2222
		2223	=item $numfd = IO::AIO::get_fdlimit
		2224
		2225	Tries to find the current file descriptor limit and returns it, or
		2226	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2227	the highest valid file descriptor number.
		2228
		2229	=item IO::AIO::min_fdlimit [$numfd]
		2230
		2231	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2232	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2233	is missing, it will try to set a very high limit, although this is not
		2234	recommended when you know the actual minimum that you require.
		2235
		2236	If the limit cannot be raised enough, the function makes a best-effort
		2237	attempt to increase the limit as much as possible, using various
		2238	tricks, while still failing. You can query the resulting limit using
		2239	C<IO::AIO::get_fdlimit>.
		2240
		2241	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2242	true.
		2243
		2244	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2245
		2246	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2247	but is blocking (this makes most sense if you know the input data is
		2248	likely cached already and the output filehandle is set to non-blocking
		2249	operations).
		2250
		2251	Returns the number of bytes copied, or C<-1> on error.
		2252
		2253	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2254
		2255	Simply calls the C<posix_fadvise> function (see its
		2256	manpage for details). The following advice constants are
		2257	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2258	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2259	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2260
		2261	On systems that do not implement C<posix_fadvise>, this function returns
		2262	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2263
		2264	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2265
		2266	Simply calls the C<posix_madvise> function (see its
		2267	manpage for details). The following advice constants are
		2268	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2269	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2270	C<IO::AIO::MADV_DONTNEED>.
		2271
		2272	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2273	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2274	will be reduced to fit into the C<$scalar>.
		2275
		2276	On systems that do not implement C<posix_madvise>, this function returns
		2277	ENOSYS, otherwise the return value of C<posix_madvise>.
		2278
		2279	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2280
		2281	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2282	$scalar (see its manpage for details). The following protect
		2283	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2284	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2285
		2286	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2287	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2288	will be reduced to fit into the C<$scalar>.
		2289
		2290	On systems that do not implement C<mprotect>, this function returns
		2291	ENOSYS, otherwise the return value of C<mprotect>.
		2292
		2293	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2294
		2295	Memory-maps a file (or anonymous memory range) and attaches it to the
		2296	given C<$scalar>, which will act like a string scalar. Returns true on
		2297	success, and false otherwise.
		2298
		2299	The scalar must exist, but its contents do not matter - this means you
		2300	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2301	the scalar first.
		2302
		2303	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2304	which don't change the string length, and most read-only operations such
		2305	as copying it or searching it with regexes and so on.
		2306
		2307	Anything else is unsafe and will, at best, result in memory leaks.
		2308
		2309	The memory map associated with the C<$scalar> is automatically removed
		2310	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2311	or C<IO::AIO::munmap> functions are called on it.
		2312
		2313	This calls the C<mmap>(2) function internally. See your system's manual
		2314	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2315
		2316	The C<$length> must be larger than zero and smaller than the actual
		2317	filesize.
		2318
		2319	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2320	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2321
		2322	C<$flags> can be a combination of
		2323	C<IO::AIO::MAP_SHARED> or
		2324	C<IO::AIO::MAP_PRIVATE>,
		2325	or a number of system-specific flags (when not available, the are C<0>):
		2326	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2327	C<IO::AIO::MAP_LOCKED>,
		2328	C<IO::AIO::MAP_NORESERVE>,
		2329	C<IO::AIO::MAP_POPULATE>,
		2330	C<IO::AIO::MAP_NONBLOCK>,
		2331	C<IO::AIO::MAP_FIXED>,
		2332	C<IO::AIO::MAP_GROWSDOWN>,
		2333	C<IO::AIO::MAP_32BIT>,
		2334	C<IO::AIO::MAP_HUGETLB> or
		2335	C<IO::AIO::MAP_STACK>.
		2336
		2337	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2338
		2339	C<$offset> is the offset from the start of the file - it generally must be
		2340	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2341
		2342	Example:
		2343
		2344	use Digest::MD5;
		2345	use IO::AIO;
		2346
		2347	open my $fh, "<verybigfile"
		2348	or die "$!";
		2349
		2350	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2351	or die "verybigfile: $!";
		2352
		2353	my $fast_md5 = md5 $data;
		2354
		2355	=item IO::AIO::munmap $scalar
		2356
		2357	Removes a previous mmap and undefines the C<$scalar>.
		2358
		2359	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2360
		2361	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2362	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2363	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2364
		2365	Returns true if successful, and false otherwise. If the underlying mmapped
		2366	region has changed address, then the true value has the numerical value
		2367	C<1>, otherwise it has the numerical value C<0>:
		2368
		2369	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2370	or die "mremap: $!";
		2371
		2372	if ($success*1) {
		2373	warn "scalar has chanegd address in memory\n";
		2374	}
		2375
		2376	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2377	implemented, but not supported and might go away in a future version.
		2378
		2379	On systems where this call is not supported or is not emulated, this call
		2380	returns falls and sets C<$!> to C<ENOSYS>.
		2381
		2382	=item IO::AIO::mlockall $flags
		2383
		2384	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2385	but is blocking.
		2386
		2387	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2388
		2389	Calls the C<munlock> function, undoing the effects of a previous
		2390	C<aio_mlock> call (see its description for details).
		2391
		2392	=item IO::AIO::munlockall
		2393
		2394	Calls the C<munlockall> function.
		2395
		2396	On systems that do not implement C<munlockall>, this function returns
		2397	ENOSYS, otherwise the return value of C<munlockall>.
		2398
		2399	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2400
		2401	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2402	and return the new file handle on success, or sets C<$!> and returns
		2403	C<undef> on error.
		2404
		2405	The remote name of the new socket will be stored in C<$sockaddr>, which
		2406	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2407	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2408	by returning a longer string in C<$sockaddr>, which might or might not be
		2409	truncated.
		2410
		2411	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2412	C<$sockaddr_maxlen>.
		2413
		2414	The main reasons to use this syscall rather than portable C«accept(2)>
		2415	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2416	flags and you can accept name-less sockets by specifying C<0> for
		2417	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2418	C<accept>.
		2419
		2420	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2421
		2422	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2423	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2424	should be the file offset.
		2425
		2426	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2427	silently corrupt the data in this case.
		2428
		2429	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2430	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2431	C<IO::AIO::SPLICE_F_GIFT>.
		2432
		2433	See the C<splice(2)> manpage for details.
		2434
		2435	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2436
		2437	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2438	description for C<IO::AIO::splice> above for details.
		2439
		2440	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2441
		2442	Attempts to query or change the pipe buffer size. Obviously works only
		2443	on pipes, and currently works only on GNU/Linux systems, and fails with
		2444	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2445	size on other systems, drop me a note.
		2446
		2447	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2448
		2449	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2450	C<$flags> is missing or C<0>, then this should be the same as a call to
		2451	perl's built-in C<pipe> function and create a new pipe, and works on
		2452	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2453	(..., 4096, O_BINARY)>.
		2454
		2455	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2456	the given flags (Linux 2.6.27, glibc 2.9).
		2457
		2458	On success, the read and write file handles are returned.
		2459
		2460	On error, nothing will be returned. If the pipe2 syscall is missing and
		2461	C<$flags> is non-zero, fails with C<ENOSYS>.
		2462
		2463	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2464	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2465	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2466
		2467	Example: create a pipe race-free w.r.t. threads and fork:
		2468
		2469	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2470	or die "pipe2: $!\n";
		2471
		2472	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2473
		2474	This is a direct interface to the Linux L<memfd_create(2)> system
		2475	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2476	should be C<IO::AIO::MFD_CLOEXEC>.
		2477
		2478	On success, the new memfd filehandle is returned, otherwise returns
		2479	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2480
		2481	Please refer to L<memfd_create(2)> for more info on this call.
		2482
		2483	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2484	C<IO::AIO::MFD_ALLOW_SEALING> and C<IO::AIO::MFD_HUGETLB>.
		2485
		2486	Example: create a new memfd.
		2487
		2488	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2489	or die "m,emfd_create: $!\n";
		2490	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2491
		2492	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2493	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2494
		2495	On success, the new eventfd filehandle is returned, otherwise returns
		2496	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2497
		2498	Please refer to L<eventfd(2)> for more info on this call.
		2499
		2500	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2501	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2502
		2503	Example: create a new eventfd filehandle:
		2504
		2505	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2506	or die "eventfd: $!\n";
		2507
		2508	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2509
		2510	This is a direct interface to the Linux L<timerfd_create(2)> system
		2511	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2512	should be C<IO::AIO::TFD_CLOEXEC>.
		2513
		2514	On success, the new timerfd filehandle is returned, otherwise returns
		2515	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2516
		2517	Please refer to L<timerfd_create(2)> for more info on this call.
		2518
		2519	The following C<$clockid> values are
		2520	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2521	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2522	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2523	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2524
		2525	The following C<$flags> values are available (Linux
		2526	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2527
		2528	Example: create a new timerfd and set it to one-second repeated alarms,
		2529	then wait for two alarms:
		2530
		2531	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2532	or die "timerfd_create: $!\n";
		2533
		2534	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2535	or die "timerfd_settime: $!\n";
		2536
		2537	for (1..2) {
		2538	8 == sysread $fh, my $buf, 8
		2539	or die "timerfd read failure\n";
		2540
		2541	printf "number of expirations (likely 1): %d\n",
		2542	unpack "Q", $buf;
		2543	}
		2544
		2545	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2546
		2547	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2548	call. Please refer to its manpage for more info on this call.
		2549
		2550	The new itimerspec is specified using two (possibly fractional) second
		2551	values, C<$new_interval> and C<$new_value>).
		2552
		2553	On success, the current interval and value are returned (as per
		2554	C<timerfd_gettime>). On failure, the empty list is returned.
		2555
		2556	The following C<$flags> values are
		2557	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2558	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2559
		2560	See C<IO::AIO::timerfd_create> for a full example.
		2561
		2562	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2563
		2564	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2565	call. Please refer to its manpage for more info on this call.
		2566
		2567	On success, returns the current values of interval and value for the given
		2568	timerfd (as potentially fractional second values). On failure, the empty
		2569	list is returned.
		2570
		2571	=back
		2572
1184	=cut	2573	=cut
1185		2574
1186	# support function to convert a fd into a perl filehandle
1187	sub _fd2fh {
1188	return undef if $_[0] < 0;
1189
1190	# try to generate nice filehandles
1191	my $sym = "IO::AIO::fd#$_[0]";
1192	local *$sym;
1193
1194	open *$sym, "+<&=$_[0]" # usually works under any unix
1195	or open *$sym, "<&=$_[0]" # cygwin needs this
1196	or open *$sym, ">&=$_[0]" # or this
1197	or return undef;
1198
1199	*$sym
1200	}
1201
1202	min_parallel 8;	2575	min_parallel 8;
1203		2576
1204	END { flush }	2577	END { flush }
1205		2578
1206	1;	2579	1;
1207		2580
		2581	=head1 EVENT LOOP INTEGRATION
		2582
		2583	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2584	automatically into many event loops:
		2585
		2586	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2587	use AnyEvent::AIO;
		2588
		2589	You can also integrate IO::AIO manually into many event loops, here are
		2590	some examples of how to do this:
		2591
		2592	# EV integration
		2593	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2594
		2595	# Event integration
		2596	Event->io (fd => IO::AIO::poll_fileno,
		2597	poll => 'r',
		2598	cb => \&IO::AIO::poll_cb);
		2599
		2600	# Glib/Gtk2 integration
		2601	add_watch Glib::IO IO::AIO::poll_fileno,
		2602	in => sub { IO::AIO::poll_cb; 1 };
		2603
		2604	# Tk integration
		2605	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2606	readable => \&IO::AIO::poll_cb);
		2607
		2608	# Danga::Socket integration
		2609	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2610	\&IO::AIO::poll_cb);
		2611
1208	=head2 FORK BEHAVIOUR	2612	=head2 FORK BEHAVIOUR
1209		2613
1210	This module should do "the right thing" when the process using it forks:	2614	Usage of pthreads in a program changes the semantics of fork
		2615	considerably. Specifically, only async-safe functions can be called after
		2616	fork. Perl doesn't know about this, so in general, you cannot call fork
		2617	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2618	pthreads, so this applies, but many other extensions and (for inexplicable
		2619	reasons) perl itself often is linked against pthreads, so this limitation
		2620	applies to quite a lot of perls.
1211		2621
1212	Before the fork, IO::AIO enters a quiescent state where no requests	2622	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1213	can be added in other threads and no results will be processed. After	2623	only works in the process that loaded it. Forking is fully supported, but
1214	the fork the parent simply leaves the quiescent state and continues	2624	using IO::AIO in the child is not.
1215	request/result processing, while the child frees the request/result queue
1216	(so that the requests started before the fork will only be handled in the
1217	parent). Threads will be started on demand until the limit set in the
1218	parent process has been reached again.
1219		2625
1220	In short: the parent will, after a short pause, continue as if fork had	2626	You might get around by not I<using> IO::AIO before (or after)
1221	not been called, while the child will act as if IO::AIO has not been used	2627	forking. You could also try to call the L<IO::AIO::reinit> function in the
1222	yet.	2628	child:
		2629
		2630	=over 4
		2631
		2632	=item IO::AIO::reinit
		2633
		2634	Abandons all current requests and I/O threads and simply reinitialises all
		2635	data structures. This is not an operation supported by any standards, but
		2636	happens to work on GNU/Linux and some newer BSD systems.
		2637
		2638	The only reasonable use for this function is to call it after forking, if
		2639	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2640	the process will result in undefined behaviour. Calling it at any time
		2641	will also result in any undefined (by POSIX) behaviour.
		2642
		2643	=back
		2644
		2645	=head2 LINUX-SPECIFIC CALLS
		2646
		2647	When a call is documented as "linux-specific" then this means it
		2648	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2649	availability and compatibility of such calls regardless of the platform
		2650	it is compiled on, so platforms such as FreeBSD which often implement
		2651	these calls will work. When in doubt, call them and see if they fail wth
		2652	C<ENOSYS>.
1223		2653
1224	=head2 MEMORY USAGE	2654	=head2 MEMORY USAGE
1225		2655
1226	Per-request usage:	2656	Per-request usage:
1227		2657
…		…
1229	bytes of memory. In addition, stat requests need a stat buffer (possibly	2659	bytes of memory. In addition, stat requests need a stat buffer (possibly
1230	a few hundred bytes), readdir requires a result buffer and so on. Perl	2660	a few hundred bytes), readdir requires a result buffer and so on. Perl
1231	scalars and other data passed into aio requests will also be locked and	2661	scalars and other data passed into aio requests will also be locked and
1232	will consume memory till the request has entered the done state.	2662	will consume memory till the request has entered the done state.
1233		2663
1234	This is now awfully much, so queuing lots of requests is not usually a	2664	This is not awfully much, so queuing lots of requests is not usually a
1235	problem.	2665	problem.
1236		2666
1237	Per-thread usage:	2667	Per-thread usage:
1238		2668
1239	In the execution phase, some aio requests require more memory for	2669	In the execution phase, some aio requests require more memory for
1240	temporary buffers, and each thread requires a stack and other data	2670	temporary buffers, and each thread requires a stack and other data
1241	structures (usually around 16k-128k, depending on the OS).	2671	structures (usually around 16k-128k, depending on the OS).
1242		2672
1243	=head1 KNOWN BUGS	2673	=head1 KNOWN BUGS
1244		2674
1245	Known bugs will be fixed in the next release.	2675	Known bugs will be fixed in the next release :)
		2676
		2677	=head1 KNOWN ISSUES
		2678
		2679	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2680	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2681	non-created hash slots or other scalars I didn't think of. It's best to
		2682	avoid such and either use scalar variables or making sure that the scalar
		2683	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2684
		2685	I am not sure anything can be done about this, so this is considered a
		2686	known issue, rather than a bug.
1246		2687
1247	=head1 SEE ALSO	2688	=head1 SEE ALSO
1248		2689
1249	L<Coro::AIO>.	2690	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2691	more natural syntax and L<IO::FDPass> for file descriptor passing.
1250		2692
1251	=head1 AUTHOR	2693	=head1 AUTHOR
1252		2694
1253	Marc Lehmann <schmorp@schmorp.de>	2695	Marc Lehmann <schmorp@schmorp.de>
1254	http://home.schmorp.de/	2696	http://home.schmorp.de/

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