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Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs.
Revision 1.273 by root, Fri Jun 23 22:33:06 2017 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) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
18	};	19	};
19		20
20	# version 2+ has request and group objects	21	# version 2+ has request and group objects
21	use IO::AIO 2;	22	use IO::AIO 2;
22		23
		24	aioreq_pri 4; # give next request a very high priority
23	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
25		27
26	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
28		30
29	# AnyEvent integration
30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33	# Event integration
34	Event->io (fd => IO::AIO::poll_fileno,
35	poll => 'r',
36	cb => \&IO::AIO::poll_cb);
37
38	# Glib/Gtk2 integration
39	add_watch Glib::IO IO::AIO::poll_fileno,
40	in => sub { IO::AIO::poll_cb; 1 };
41
42	# Tk integration
43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44	readable => \&IO::AIO::poll_cb);
45
46	# Danga::Socket integration
47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48	\&IO::AIO::poll_cb);
49
50	=head1 DESCRIPTION	31	=head1 DESCRIPTION
51		32
52	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
53	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>).
54		36
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
		52
55	Currently, a number of threads are started that execute your read/writes	53	In this version, a number of threads are started that execute your
56	and signal their completion. You don't need thread support in your libc or	54	requests and signal their completion. You don't need thread support
57	perl, and the threads created by this module will not be visible to the	55	in perl, and the threads created by this module will not be visible
58	pthreads library. In the future, this module might make use of the native	56	to perl. In the future, this module might make use of the native aio
59	aio functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
61	for example), and they would only support aio_read and aio_write, so the	59	files currently, for example), and they would only support aio_read and
62	remaining functionality would have to be implemented using threads anyway.	60	aio_write, so the remaining functionality would have to be implemented
		61	using threads anyway.
63		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
64	Although the module will work with in the presence of other threads, it is	67	Although the module will work in the presence of other (Perl-) threads,
65	currently not reentrant, so use appropriate locking yourself, always call	68	it is currently not reentrant in any way, so use appropriate locking
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	69	yourself, always call C<poll_cb> from within the same thread, or never
67	C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
		71
		72	=head2 EXAMPLE
		73
		74	This is a simple example that uses the EV module and loads
		75	F</etc/passwd> asynchronously:
		76
		77	use EV;
		78	use IO::AIO;
		79
		80	# register the IO::AIO callback with EV
		81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		82
		83	# queue the request to open /etc/passwd
		84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		85	my $fh = shift
		86	or die "error while opening: $!";
		87
		88	# stat'ing filehandles is generally non-blocking
		89	my $size = -s $fh;
		90
		91	# queue a request to read the file
		92	my $contents;
		93	aio_read $fh, 0, $size, $contents, 0, sub {
		94	$_[0] == $size
		95	or die "short read: $!";
		96
		97	close $fh;
		98
		99	# file contents now in $contents
		100	print $contents;
		101
		102	# exit event loop and program
		103	EV::break;
		104	};
		105	};
		106
		107	# possibly queue up other requests, or open GUI windows,
		108	# check for sockets etc. etc.
		109
		110	# process events as long as there are some:
		111	EV::run;
		112
		113	=head1 REQUEST ANATOMY AND LIFETIME
		114
		115	Every C<aio_*> function creates a request. which is a C data structure not
		116	directly visible to Perl.
		117
		118	If called in non-void context, every request function returns a Perl
		119	object representing the request. In void context, nothing is returned,
		120	which saves a bit of memory.
		121
		122	The perl object is a fairly standard ref-to-hash object. The hash contents
		123	are not used by IO::AIO so you are free to store anything you like in it.
		124
		125	During their existance, aio requests travel through the following states,
		126	in order:
		127
		128	=over 4
		129
		130	=item ready
		131
		132	Immediately after a request is created it is put into the ready state,
		133	waiting for a thread to execute it.
		134
		135	=item execute
		136
		137	A thread has accepted the request for processing and is currently
		138	executing it (e.g. blocking in read).
		139
		140	=item pending
		141
		142	The request has been executed and is waiting for result processing.
		143
		144	While request submission and execution is fully asynchronous, result
		145	processing is not and relies on the perl interpreter calling C<poll_cb>
		146	(or another function with the same effect).
		147
		148	=item result
		149
		150	The request results are processed synchronously by C<poll_cb>.
		151
		152	The C<poll_cb> function will process all outstanding aio requests by
		153	calling their callbacks, freeing memory associated with them and managing
		154	any groups they are contained in.
		155
		156	=item done
		157
		158	Request has reached the end of its lifetime and holds no resources anymore
		159	(except possibly for the Perl object, but its connection to the actual
		160	aio request is severed and calling its methods will either do nothing or
		161	result in a runtime error).
		162
		163	=back
68		164
69	=cut	165	=cut
70		166
71	package IO::AIO;	167	package IO::AIO;
72		168
73	no warnings;	169	use Carp ();
74	use strict 'vars';	170
		171	use common::sense;
75		172
76	use base 'Exporter';	173	use base 'Exporter';
77		174
78	BEGIN {	175	BEGIN {
79	our $VERSION = '2.0';	176	our $VERSION = 4.35;
80		177
81	our @EXPORT = 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
82	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
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	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
		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
84	aio_group);	188	aio_wd);
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	189
		190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		192	min_parallel max_parallel max_idle idle_timeout
		193	nreqs nready npending nthreads
		194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
		197
		198	push @AIO_REQ, qw(aio_busy); # not exported
86		199
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		201
89	require XSLoader;	202	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
91	}	204	}
92		205
93	=head1 FUNCTIONS	206	=head1 FUNCTIONS
94		207
95	=head2 AIO FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		239	aio_mkdir $pathname, $mode, $callback->($status)
		240	aio_rmdir $pathname, $callback->($status)
		241	aio_readdir $pathname, $callback->($entries)
		242	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		243	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		244	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		245	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		246	aio_load $pathname, $data, $callback->($status)
		247	aio_copy $srcpath, $dstpath, $callback->($status)
		248	aio_move $srcpath, $dstpath, $callback->($status)
		249	aio_rmtree $pathname, $callback->($status)
		250	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		251	aio_ioctl $fh, $request, $buf, $callback->($status)
		252	aio_sync $callback->($status)
		253	aio_syncfs $fh, $callback->($status)
		254	aio_fsync $fh, $callback->($status)
		255	aio_fdatasync $fh, $callback->($status)
		256	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		257	aio_pathsync $pathname, $callback->($status)
		258	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		259	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		260	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		261	aio_mlockall $flags, $callback->($status)
		262	aio_group $callback->(...)
		263	aio_nop $callback->()
		264
		265	$prev_pri = aioreq_pri [$pri]
		266	aioreq_nice $pri_adjust
		267
		268	IO::AIO::poll_wait
		269	IO::AIO::poll_cb
		270	IO::AIO::poll
		271	IO::AIO::flush
		272	IO::AIO::max_poll_reqs $nreqs
		273	IO::AIO::max_poll_time $seconds
		274	IO::AIO::min_parallel $nthreads
		275	IO::AIO::max_parallel $nthreads
		276	IO::AIO::max_idle $nthreads
		277	IO::AIO::idle_timeout $seconds
		278	IO::AIO::max_outstanding $maxreqs
		279	IO::AIO::nreqs
		280	IO::AIO::nready
		281	IO::AIO::npending
		282
		283	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		284	IO::AIO::fadvise $fh, $offset, $len, $advice
		285	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		286	IO::AIO::munmap $scalar
		287	IO::AIO::madvise $scalar, $offset, $length, $advice
		288	IO::AIO::mprotect $scalar, $offset, $length, $protect
		289	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		290	IO::AIO::munlockall
		291
		292	=head2 API NOTES
96		293
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	294	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	295	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	296	and they all accept an additional (and optional) C<$callback> argument
100	which must be a code reference. This code reference will get called with	297	which must be a code reference. This code reference will be called after
101	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	298	the syscall has been executed in an asynchronous fashion. The results
102	perl, which usually delivers "false") as it's sole argument when the given	299	of the request will be passed as arguments to the callback (and, if an
103	syscall has been executed asynchronously.	300	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		301	most syscalls return C<-1> on error, unlike perl, which usually delivers
		302	"false").
		303
		304	Some requests (such as C<aio_readdir>) pass the actual results and
		305	communicate failures by passing C<undef>.
104		306
105	All functions expecting a filehandle keep a copy of the filehandle	307	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	308	internally until the request has finished.
107		309
108	All requests return objects of type L<IO::AIO::REQ> that allow further	310	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	311	further manipulation of those requests while they are in-flight.
110		312
111	The pathnames you pass to these routines I<must> be absolute and	313	The pathnames you pass to these routines I<should> be absolute. The
112	encoded in byte form. The reason for the former is that at the time the	314	reason for this is that at the time the request is being executed, the
113	request is being executed, the current working directory could have	315	current working directory could have changed. Alternatively, you can
114	changed. Alternatively, you can make sure that you never change the	316	make sure that you never change the current working directory anywhere
115	current working directory.	317	in the program and then use relative paths. You can also take advantage
		318	of IO::AIOs working directory abstraction, that lets you specify paths
		319	relative to some previously-opened "working directory object" - see the
		320	description of the C<IO::AIO::WD> class later in this document.
116		321
117	To encode pathnames to byte form, either make sure you either: a)	322	To encode pathnames as octets, either make sure you either: a) always pass
118	always pass in filenames you got from outside (command line, readdir	323	in filenames you got from outside (command line, readdir etc.) without
119	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	324	tinkering, b) are in your native filesystem encoding, c) use the Encode
120	your pathnames to the locale (or other) encoding in effect in the user	325	module and encode your pathnames to the locale (or other) encoding in
121	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	326	effect in the user environment, d) use Glib::filename_from_unicode on
122	use something else.	327	unicode filenames or e) use something else to ensure your scalar has the
		328	correct contents.
		329
		330	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		331	handles correctly whether it is set or not.
		332
		333	=head2 AIO REQUEST FUNCTIONS
123		334
124	=over 4	335	=over 4
125		336
		337	=item $prev_pri = aioreq_pri [$pri]
		338
		339	Returns the priority value that would be used for the next request and, if
		340	C<$pri> is given, sets the priority for the next aio request.
		341
		342	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		343	and C<4>, respectively. Requests with higher priority will be serviced
		344	first.
		345
		346	The priority will be reset to C<0> after each call to one of the C<aio_*>
		347	functions.
		348
		349	Example: open a file with low priority, then read something from it with
		350	higher priority so the read request is serviced before other low priority
		351	open requests (potentially spamming the cache):
		352
		353	aioreq_pri -3;
		354	aio_open ..., sub {
		355	return unless $_[0];
		356
		357	aioreq_pri -2;
		358	aio_read $_[0], ..., sub {
		359	...
		360	};
		361	};
		362
		363
		364	=item aioreq_nice $pri_adjust
		365
		366	Similar to C<aioreq_pri>, but subtracts the given value from the current
		367	priority, so the effect is cumulative.
		368
		369
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	370	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		371
128	Asynchronously open or create a file and call the callback with a newly	372	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	373	created filehandle for the file (or C<undef> in case of an error).
130		374
131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	375	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132	for an explanation.	376	for an explanation.
133		377
134	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	378	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
135	list. They are the same as used by C<sysopen>.	379	list. They are the same as used by C<sysopen>.
136		380
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	381	Likewise, C<$mode> specifies the mode of the newly created file, if it
138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	382	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
139	except that it is mandatory (i.e. use C<0> if you don't create new files,	383	except that it is mandatory (i.e. use C<0> if you don't create new files,
140	and C<0666> or C<0777> if you do).	384	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		385	by the umask in effect then the request is being executed, so better never
		386	change the umask.
141		387
142	Example:	388	Example:
143		389
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	390	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
145	if ($_[0]) {	391	if ($_[0]) {
146	print "open successful, fh is $_[0]\n";	392	print "open successful, fh is $_[0]\n";
147	...	393	...
148	} else {	394	} else {
149	die "open failed: $!\n";	395	die "open failed: $!\n";
150	}	396	}
151	};	397	};
152		398
		399	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		400	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		401	following POSIX and non-POSIX constants are available (missing ones on
		402	your system are, as usual, C<0>):
		403
		404	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		405	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		406	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		407
		408
153	=item aio_close $fh, $callback->($status)	409	=item aio_close $fh, $callback->($status)
154		410
155	Asynchronously close a file and call the callback with the result	411	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	412	code.
157	filehandle here, as perl will likely close the file descriptor another
158	time when the filehandle is destroyed. Normally, you can safely call perls
159	C<close> or just let filehandles go out of scope.
160		413
161	This is supposed to be a bug in the API, so that might change. It's	414	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	415	closing the file descriptor associated with the filehandle itself.
		416
		417	Therefore, C<aio_close> will not close the filehandle - instead it will
		418	use dup2 to overwrite the file descriptor with the write-end of a pipe
		419	(the pipe fd will be created on demand and will be cached).
		420
		421	Or in other words: the file descriptor will be closed, but it will not be
		422	free for reuse until the perl filehandle is closed.
		423
		424	=cut
		425
		426	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		427
		428	Seeks the filehandle to the new C<$offset>, similarly to perl's
		429	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		430	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		431	C<IO::AIO::SEEK_END>).
		432
		433	The resulting absolute offset will be passed to the callback, or C<-1> in
		434	case of an error.
		435
		436	In theory, the C<$whence> constants could be different than the
		437	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		438	so don't panic.
		439
		440	As a GNU/Linux (and maybe Solaris) extension, also the constants
		441	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		442	could be found. No guarantees about suitability for use in C<aio_seek> or
		443	Perl's C<sysseek> can be made though, although I would naively assume they
		444	"just work".
163		445
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	446	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		447
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	448	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		449
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	450	Reads or writes C<$length> bytes from or to the specified C<$fh> and
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	451	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
170	callback without the actual number of bytes read (or -1 on error, just	452	calls the callback with the actual number of bytes transferred (or -1 on
171	like the syscall).	453	error, just like the syscall).
		454
		455	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		456	offset plus the actual number of bytes read.
		457
		458	If C<$offset> is undefined, then the current file descriptor offset will
		459	be used (and updated), otherwise the file descriptor offset will not be
		460	changed by these calls.
		461
		462	If C<$length> is undefined in C<aio_write>, use the remaining length of
		463	C<$data>.
		464
		465	If C<$dataoffset> is less than zero, it will be counted from the end of
		466	C<$data>.
172		467
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	468	The C<$data> scalar I<MUST NOT> be modified in any way while the request
174	is outstanding. Modifying it can result in segfaults or WW3 (if the	469	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	470	the necessary/optional hardware is installed).
176		471
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	472	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	473	offset C<0> within the scalar:
179		474
180	aio_read $fh, 7, 15, $buffer, 0, sub {	475	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	476	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	477	print "read $_[0] bytes: <$buffer>\n";
183	};	478	};
184		479
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.
192
193	This is a composite request that tries to rename(2) the file first. If
194	rename files with C<EXDEV>, it creates the destination file with mode 0200
195	and copies the contents of the source file into it using C<aio_sendfile>,
196	followed by restoring atime, mtime, access mode and uid/gid, in that
197	order, and unlinking the C<$srcpath>.
198
199	If an error occurs, the partial destination file will be unlinked, if
200	possible, except when setting atime, mtime, access mode and uid/gid, where
201	errors are being ignored.
202
203	=cut
204
205	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;
207
208	my $grp = aio_group $cb;
209
210	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {
212	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;
215
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {
218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
219	close $src_fh;
220
221	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;
226
227	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);
229	};
230	} else {
231	my $errno = $!;
232	add $grp aio_unlink $dst, sub {
233	$! = $errno;
234	$grp->result (-1);
235	};
236	}
237	};
238	} else {
239	$grp->result (-1);
240	}
241	},
242
243	} else {
244	$grp->result (-1);
245	}
246	};
247	} else {
248	$grp->result ($_[0]);
249	}
250	};
251
252	$grp
253	}
254		480
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	481	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		482
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	483	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
258	reading at byte offset C<$in_offset>, and starts writing at the current	484	reading at byte offset C<$in_offset>, and starts writing at the current
259	file offset of C<$out_fh>. Because of that, it is not safe to issue more	485	file offset of C<$out_fh>. Because of that, it is not safe to issue more
260	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	486	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
261	other.	487	other. The same C<$in_fh> works fine though, as this function does not
		488	move or use the file offset of C<$in_fh>.
262		489
		490	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		491	are written, and there is no way to find out how many more bytes have been
		492	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		493	number of bytes written to C<$out_fh>. Only if the result value equals
		494	C<$length> one can assume that C<$length> bytes have been read.
		495
		496	Unlike with other C<aio_> functions, it makes a lot of sense to use
		497	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		498	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		499	the socket I/O will be non-blocking. Note, however, that you can run
		500	into a trap where C<aio_sendfile> reads some data with readahead, then
		501	fails to write all data, and when the socket is ready the next time, the
		502	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		503	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		504	resource usage.
		505
263	This call tries to make use of a native C<sendfile> syscall to provide	506	This call tries to make use of a native C<sendfile>-like syscall to
264	zero-copy operation. For this to work, C<$out_fh> should refer to a	507	provide zero-copy operation. For this to work, C<$out_fh> should refer to
265	socket, and C<$in_fh> should refer to mmap'able file.	508	a socket, and C<$in_fh> should refer to an mmap'able file.
266		509
267	If the native sendfile call fails or is not implemented, it will be	510	If a native sendfile cannot be found or it fails with C<ENOSYS>,
268	emulated, so you can call C<aio_sendfile> on any type of filehandle	511	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		512	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
269	regardless of the limitations of the operating system.	513	type of filehandle regardless of the limitations of the operating system.
270		514
271	Please note, however, that C<aio_sendfile> can read more bytes from	515	As native sendfile syscalls (as practically any non-POSIX interface hacked
272	C<$in_fh> than are written, and there is no way to find out how many	516	together in a hurry to improve benchmark numbers) tend to be rather buggy
273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	517	on many systems, this implementation tries to work around some known bugs
274	provides the number of bytes written to C<$out_fh>. Only if the result	518	in Linux and FreeBSD kernels (probably others, too), but that might fail,
275	value equals C<$length> one can assume that C<$length> bytes have been	519	so you really really should check the return value of C<aio_sendfile> -
276	read.	520	fewer bytes than expected might have been transferred.
		521
277		522
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	523	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		524
280	C<aio_readahead> populates the page cache with data from a file so that	525	C<aio_readahead> populates the page cache with data from a file so that
281	subsequent reads from that file will not block on disk I/O. The C<$offset>	526	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
284	whole pages, so that offset is effectively rounded down to a page boundary	529	whole pages, so that offset is effectively rounded down to a page boundary
285	and bytes are read up to the next page boundary greater than or equal to	530	and bytes are read up to the next page boundary greater than or equal to
286	(off-set+length). C<aio_readahead> does not read beyond the end of the	531	(off-set+length). C<aio_readahead> does not read beyond the end of the
287	file. The current file offset of the file is left unchanged.	532	file. The current file offset of the file is left unchanged.
288		533
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	534	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
290	emulated by simply reading the data, which would have a similar effect.	535	be emulated by simply reading the data, which would have a similar effect.
		536
291		537
292	=item aio_stat $fh_or_path, $callback->($status)	538	=item aio_stat $fh_or_path, $callback->($status)
293		539
294	=item aio_lstat $fh, $callback->($status)	540	=item aio_lstat $fh, $callback->($status)
295		541
…		…
301	for an explanation.	547	for an explanation.
302		548
303	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	549	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
304	error when stat'ing a large file, the results will be silently truncated	550	error when stat'ing a large file, the results will be silently truncated
305	unless perl itself is compiled with large file support.	551	unless perl itself is compiled with large file support.
		552
		553	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		554	following constants and functions (if not implemented, the constants will
		555	be C<0> and the functions will either C<croak> or fall back on traditional
		556	behaviour).
		557
		558	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		559	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		560	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
306		561
307	Example: Print the length of F</etc/passwd>:	562	Example: Print the length of F</etc/passwd>:
308		563
309	aio_stat "/etc/passwd", sub {	564	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	565	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	566	print "size is ", -s _, "\n";
312	};	567	};
313		568
		569
		570	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		571
		572	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		573	whether a file handle or path was passed.
		574
		575	On success, the callback is passed a hash reference with the following
		576	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		577	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		578	is passed.
		579
		580	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		581	C<ST_NOSUID>.
		582
		583	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		584	their correct value when available, or to C<0> on systems that do
		585	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		586	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		587	C<ST_NODIRATIME> and C<ST_RELATIME>.
		588
		589	Example: stat C</wd> and dump out the data if successful.
		590
		591	aio_statvfs "/wd", sub {
		592	my $f = $_[0]
		593	or die "statvfs: $!";
		594
		595	use Data::Dumper;
		596	say Dumper $f;
		597	};
		598
		599	# result:
		600	{
		601	bsize => 1024,
		602	bfree => 4333064312,
		603	blocks => 10253828096,
		604	files => 2050765568,
		605	flag => 4096,
		606	favail => 2042092649,
		607	bavail => 4333064312,
		608	ffree => 2042092649,
		609	namemax => 255,
		610	frsize => 1024,
		611	fsid => 1810
		612	}
		613
		614	Here is a (likely partial - send me updates!) list of fsid values used by
		615	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		616
		617	0x0000adf5 adfs
		618	0x0000adff affs
		619	0x5346414f afs
		620	0x09041934 anon-inode filesystem
		621	0x00000187 autofs
		622	0x42465331 befs
		623	0x1badface bfs
		624	0x42494e4d binfmt_misc
		625	0x9123683e btrfs
		626	0x0027e0eb cgroupfs
		627	0xff534d42 cifs
		628	0x73757245 coda
		629	0x012ff7b7 coh
		630	0x28cd3d45 cramfs
		631	0x453dcd28 cramfs-wend (wrong endianness)
		632	0x64626720 debugfs
		633	0x00001373 devfs
		634	0x00001cd1 devpts
		635	0x0000f15f ecryptfs
		636	0x00414a53 efs
		637	0x0000137d ext
		638	0x0000ef53 ext2/ext3/ext4
		639	0x0000ef51 ext2
		640	0xf2f52010 f2fs
		641	0x00004006 fat
		642	0x65735546 fuseblk
		643	0x65735543 fusectl
		644	0x0bad1dea futexfs
		645	0x01161970 gfs2
		646	0x47504653 gpfs
		647	0x00004244 hfs
		648	0xf995e849 hpfs
		649	0x00c0ffee hostfs
		650	0x958458f6 hugetlbfs
		651	0x2bad1dea inotifyfs
		652	0x00009660 isofs
		653	0x000072b6 jffs2
		654	0x3153464a jfs
		655	0x6b414653 k-afs
		656	0x0bd00bd0 lustre
		657	0x0000137f minix
		658	0x0000138f minix 30 char names
		659	0x00002468 minix v2
		660	0x00002478 minix v2 30 char names
		661	0x00004d5a minix v3
		662	0x19800202 mqueue
		663	0x00004d44 msdos
		664	0x0000564c novell
		665	0x00006969 nfs
		666	0x6e667364 nfsd
		667	0x00003434 nilfs
		668	0x5346544e ntfs
		669	0x00009fa1 openprom
		670	0x7461636F ocfs2
		671	0x00009fa0 proc
		672	0x6165676c pstorefs
		673	0x0000002f qnx4
		674	0x68191122 qnx6
		675	0x858458f6 ramfs
		676	0x52654973 reiserfs
		677	0x00007275 romfs
		678	0x67596969 rpc_pipefs
		679	0x73636673 securityfs
		680	0xf97cff8c selinux
		681	0x0000517b smb
		682	0x534f434b sockfs
		683	0x73717368 squashfs
		684	0x62656572 sysfs
		685	0x012ff7b6 sysv2
		686	0x012ff7b5 sysv4
		687	0x01021994 tmpfs
		688	0x15013346 udf
		689	0x00011954 ufs
		690	0x54190100 ufs byteswapped
		691	0x00009fa2 usbdevfs
		692	0x01021997 v9fs
		693	0xa501fcf5 vxfs
		694	0xabba1974 xenfs
		695	0x012ff7b4 xenix
		696	0x58465342 xfs
		697	0x012fd16d xia
		698
		699	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		700
		701	Works like perl's C<utime> function (including the special case of $atime
		702	and $mtime being undef). Fractional times are supported if the underlying
		703	syscalls support them.
		704
		705	When called with a pathname, uses utimes(2) if available, otherwise
		706	utime(2). If called on a file descriptor, uses futimes(2) if available,
		707	otherwise returns ENOSYS, so this is not portable.
		708
		709	Examples:
		710
		711	# set atime and mtime to current time (basically touch(1)):
		712	aio_utime "path", undef, undef;
		713	# set atime to current time and mtime to beginning of the epoch:
		714	aio_utime "path", time, undef; # undef==0
		715
		716
		717	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		718
		719	Works like perl's C<chown> function, except that C<undef> for either $uid
		720	or $gid is being interpreted as "do not change" (but -1 can also be used).
		721
		722	Examples:
		723
		724	# same as "chown root path" in the shell:
		725	aio_chown "path", 0, -1;
		726	# same as above:
		727	aio_chown "path", 0, undef;
		728
		729
		730	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		731
		732	Works like truncate(2) or ftruncate(2).
		733
		734
		735	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		736
		737	Allocates or frees disk space according to the C<$mode> argument. See the
		738	linux C<fallocate> documentation for details.
		739
		740	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		741	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		742	to deallocate a file range.
		743
		744	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		745	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		746	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		747	to unshare shared blocks (see your L<fallocate(2)> manpage).
		748
		749	The file system block size used by C<fallocate> is presumably the
		750	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		751	can dictate other limitations.
		752
		753	If C<fallocate> isn't available or cannot be emulated (currently no
		754	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		755
		756
		757	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		758
		759	Works like perl's C<chmod> function.
		760
		761
314	=item aio_unlink $pathname, $callback->($status)	762	=item aio_unlink $pathname, $callback->($status)
315		763
316	Asynchronously unlink (delete) a file and call the callback with the	764	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	765	result code.
318		766
		767
		768	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		769
		770	[EXPERIMENTAL]
		771
		772	Asynchronously create a device node (or fifo). See mknod(2).
		773
		774	The only (POSIX-) portable way of calling this function is:
		775
		776	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		777
		778	See C<aio_stat> for info about some potentially helpful extra constants
		779	and functions.
		780
319	=item aio_link $srcpath, $dstpath, $callback->($status)	781	=item aio_link $srcpath, $dstpath, $callback->($status)
320		782
321	Asynchronously create a new link to the existing object at C<$srcpath> at	783	Asynchronously create a new link to the existing object at C<$srcpath> at
322	the path C<$dstpath> and call the callback with the result code.	784	the path C<$dstpath> and call the callback with the result code.
323		785
		786
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	787	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		788
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	789	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
327	the path C<$dstpath> and call the callback with the result code.	790	the path C<$dstpath> and call the callback with the result code.
328		791
		792
		793	=item aio_readlink $pathname, $callback->($link)
		794
		795	Asynchronously read the symlink specified by C<$path> and pass it to
		796	the callback. If an error occurs, nothing or undef gets passed to the
		797	callback.
		798
		799
		800	=item aio_realpath $pathname, $callback->($path)
		801
		802	Asynchronously make the path absolute and resolve any symlinks in
		803	C<$path>. The resulting path only consists of directories (same as
		804	L<Cwd::realpath>).
		805
		806	This request can be used to get the absolute path of the current working
		807	directory by passing it a path of F<.> (a single dot).
		808
		809
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	810	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		811
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	812	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	813	rename(2) and call the callback with the result code.
333		814
		815	On systems that support the AIO::WD working directory abstraction
		816	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		817	of failing, C<rename> is called on the absolute path of C<$wd>.
		818
		819
		820	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		821
		822	Basically a version of C<aio_rename> with an additional C<$flags>
		823	argument. Calling this with C<$flags=0> is the same as calling
		824	C<aio_rename>.
		825
		826	Non-zero flags are currently only supported on GNU/Linux systems that
		827	support renameat2. Other systems fail with C<ENOSYS> in this case.
		828
		829	The following constants are available (missing ones are, as usual C<0>),
		830	see renameat2(2) for details:
		831
		832	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		833	and C<IO::AIO::RENAME_WHITEOUT>.
		834
		835
		836	=item aio_mkdir $pathname, $mode, $callback->($status)
		837
		838	Asynchronously mkdir (create) a directory and call the callback with
		839	the result code. C<$mode> will be modified by the umask at the time the
		840	request is executed, so do not change your umask.
		841
		842
334	=item aio_rmdir $pathname, $callback->($status)	843	=item aio_rmdir $pathname, $callback->($status)
335		844
336	Asynchronously rmdir (delete) a directory and call the callback with the	845	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	846	result code.
		847
		848	On systems that support the AIO::WD working directory abstraction
		849	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		850	C<rmdir> is called on the absolute path of C<$wd>.
		851
338		852
339	=item aio_readdir $pathname, $callback->($entries)	853	=item aio_readdir $pathname, $callback->($entries)
340		854
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	855	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
342	directory (i.e. opendir + readdir + closedir). The entries will not be	856	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	857	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		858
345	The callback a single argument which is either C<undef> or an array-ref	859	The callback is passed a single argument which is either C<undef> or an
346	with the filenames.	860	array-ref with the filenames.
347		861
		862
		863	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		864
		865	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		866	tune behaviour and output format. In case of an error, C<$entries> will be
		867	C<undef>.
		868
		869	The flags are a combination of the following constants, ORed together (the
		870	flags will also be passed to the callback, possibly modified):
		871
		872	=over 4
		873
		874	=item IO::AIO::READDIR_DENTS
		875
		876	When this flag is off, then the callback gets an arrayref consisting of
		877	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		878	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		879	entry in more detail.
		880
		881	C<$name> is the name of the entry.
		882
		883	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		884
		885	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		886	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		887	C<IO::AIO::DT_WHT>.
		888
		889	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		890	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		891	scalars are read-only: you can not modify them.
		892
		893	C<$inode> is the inode number (which might not be exact on systems with 64
		894	bit inode numbers and 32 bit perls). This field has unspecified content on
		895	systems that do not deliver the inode information.
		896
		897	=item IO::AIO::READDIR_DIRS_FIRST
		898
		899	When this flag is set, then the names will be returned in an order where
		900	likely directories come first, in optimal stat order. This is useful when
		901	you need to quickly find directories, or you want to find all directories
		902	while avoiding to stat() each entry.
		903
		904	If the system returns type information in readdir, then this is used
		905	to find directories directly. Otherwise, likely directories are names
		906	beginning with ".", or otherwise names with no dots, of which names with
		907	short names are tried first.
		908
		909	=item IO::AIO::READDIR_STAT_ORDER
		910
		911	When this flag is set, then the names will be returned in an order
		912	suitable for stat()'ing each one. That is, when you plan to stat()
		913	all files in the given directory, then the returned order will likely
		914	be fastest.
		915
		916	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		917	the likely dirs come first, resulting in a less optimal stat order.
		918
		919	=item IO::AIO::READDIR_FOUND_UNKNOWN
		920
		921	This flag should not be set when calling C<aio_readdirx>. Instead, it
		922	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		923	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		924	C<$type>'s are known, which can be used to speed up some algorithms.
		925
		926	=back
		927
		928
		929	=item aio_load $pathname, $data, $callback->($status)
		930
		931	This is a composite request that tries to fully load the given file into
		932	memory. Status is the same as with aio_read.
		933
		934	=cut
		935
		936	sub aio_load($$;$) {
		937	my ($path, undef, $cb) = @_;
		938	my $data = \$_[1];
		939
		940	my $pri = aioreq_pri;
		941	my $grp = aio_group $cb;
		942
		943	aioreq_pri $pri;
		944	add $grp aio_open $path, O_RDONLY, 0, sub {
		945	my $fh = shift
		946	or return $grp->result (-1);
		947
		948	aioreq_pri $pri;
		949	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		950	$grp->result ($_[0]);
		951	};
		952	};
		953
		954	$grp
		955	}
		956
		957	=item aio_copy $srcpath, $dstpath, $callback->($status)
		958
		959	Try to copy the I<file> (directories not supported as either source or
		960	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		961	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		962
		963	This is a composite request that creates the destination file with
		964	mode 0200 and copies the contents of the source file into it using
		965	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		966	uid/gid, in that order.
		967
		968	If an error occurs, the partial destination file will be unlinked, if
		969	possible, except when setting atime, mtime, access mode and uid/gid, where
		970	errors are being ignored.
		971
		972	=cut
		973
		974	sub aio_copy($$;$) {
		975	my ($src, $dst, $cb) = @_;
		976
		977	my $pri = aioreq_pri;
		978	my $grp = aio_group $cb;
		979
		980	aioreq_pri $pri;
		981	add $grp aio_open $src, O_RDONLY, 0, sub {
		982	if (my $src_fh = $_[0]) {
		983	my @stat = stat $src_fh; # hmm, might block over nfs?
		984
		985	aioreq_pri $pri;
		986	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		987	if (my $dst_fh = $_[0]) {
		988	aioreq_pri $pri;
		989	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		990	if ($_[0] == $stat[7]) {
		991	$grp->result (0);
		992	close $src_fh;
		993
		994	my $ch = sub {
		995	aioreq_pri $pri;
		996	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		997	aioreq_pri $pri;
		998	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		999	aioreq_pri $pri;
		1000	add $grp aio_close $dst_fh;
		1001	}
		1002	};
		1003	};
		1004
		1005	aioreq_pri $pri;
		1006	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1007	if ($_[0] < 0 && $! == ENOSYS) {
		1008	aioreq_pri $pri;
		1009	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1010	} else {
		1011	$ch->();
		1012	}
		1013	};
		1014	} else {
		1015	$grp->result (-1);
		1016	close $src_fh;
		1017	close $dst_fh;
		1018
		1019	aioreq $pri;
		1020	add $grp aio_unlink $dst;
		1021	}
		1022	};
		1023	} else {
		1024	$grp->result (-1);
		1025	}
		1026	},
		1027
		1028	} else {
		1029	$grp->result (-1);
		1030	}
		1031	};
		1032
		1033	$grp
		1034	}
		1035
		1036	=item aio_move $srcpath, $dstpath, $callback->($status)
		1037
		1038	Try to move the I<file> (directories not supported as either source or
		1039	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		1040	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		1041
		1042	This is a composite request that tries to rename(2) the file first; if
		1043	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		1044	that is successful, unlinks the C<$srcpath>.
		1045
		1046	=cut
		1047
		1048	sub aio_move($$;$) {
		1049	my ($src, $dst, $cb) = @_;
		1050
		1051	my $pri = aioreq_pri;
		1052	my $grp = aio_group $cb;
		1053
		1054	aioreq_pri $pri;
		1055	add $grp aio_rename $src, $dst, sub {
		1056	if ($_[0] && $! == EXDEV) {
		1057	aioreq_pri $pri;
		1058	add $grp aio_copy $src, $dst, sub {
		1059	$grp->result ($_[0]);
		1060
		1061	unless ($_[0]) {
		1062	aioreq_pri $pri;
		1063	add $grp aio_unlink $src;
		1064	}
		1065	};
		1066	} else {
		1067	$grp->result ($_[0]);
		1068	}
		1069	};
		1070
		1071	$grp
		1072	}
		1073
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1074	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
349
350	[EXPERIMENTAL due to internal aio_group use]
351		1075
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1076	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	1077	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	1078	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	1079	recurse into (everything else, including symlinks to directories).
356		1080
357	C<aio_scandir> is a composite request that creates of many sub requests_	1081	C<aio_scandir> is a composite request that creates of many sub requests_
358	C<$maxreq> specifies the maximum number of outstanding aio requests that	1082	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	1083	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	1084	will be chosen (currently 4).
361		1085
362	On error, the callback is called without arguments, otherwise it receives	1086	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	1087	two array-refs with path-relative entry names.
364		1088
365	Example:	1089	Example:
…		…
372		1096
373	Implementation notes.	1097	Implementation notes.
374		1098
375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1099	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
376		1100
		1101	If readdir returns file type information, then this is used directly to
		1102	find directories.
		1103
377	After reading the directory, the modification time, size etc. of the	1104	Otherwise, after reading the directory, the modification time, size etc.
378	directory before and after the readdir is checked, and if they match (and	1105	of the directory before and after the readdir is checked, and if they
379	isn't the current time), the link count will be used to decide how many	1106	match (and isn't the current time), the link count will be used to decide
380	entries are directories (if >= 2). Otherwise, no knowledge of the number	1107	how many entries are directories (if >= 2). Otherwise, no knowledge of the
381	of subdirectories will be assumed.	1108	number of subdirectories will be assumed.
382		1109
383	Then entries will be sorted into likely directories (everything without	1110	Then entries will be sorted into likely directories a non-initial dot
384	a non-initial dot currently) and likely non-directories (everything	1111	currently) and likely non-directories (see C<aio_readdirx>). Then every
385	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1112	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
386	likely directories first. If that succeeds, it assumes that the entry	1113	in order of their inode numbers. If that succeeds, it assumes that the
387	is a directory or a symlink to directory (which will be checked	1114	entry is a directory or a symlink to directory (which will be checked
388	seperately). This is often faster than stat'ing the entry itself because	1115	separately). This is often faster than stat'ing the entry itself because
389	filesystems might detect the type of the entry without reading the inode	1116	filesystems might detect the type of the entry without reading the inode
390	data (e.g. ext2fs filetype feature).	1117	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1118	the filetype information on readdir.
391		1119
392	If the known number of directories (link count - 2) has been reached, the	1120	If the known number of directories (link count - 2) has been reached, the
393	rest of the entries is assumed to be non-directories.	1121	rest of the entries is assumed to be non-directories.
394		1122
395	This only works with certainty on POSIX (= UNIX) filesystems, which	1123	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	1127	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	1128	directory counting heuristic.
401		1129
402	=cut	1130	=cut
403		1131
404	sub aio_scandir($$$) {	1132	sub aio_scandir($$;$) {
405	my ($path, $maxreq, $cb) = @_;	1133	my ($path, $maxreq, $cb) = @_;
406		1134
		1135	my $pri = aioreq_pri;
		1136
407	my $grp = aio_group $cb;	1137	my $grp = aio_group $cb;
408		1138
409	$maxreq = 6 if $maxreq <= 0;	1139	$maxreq = 4 if $maxreq <= 0;
410		1140
411	# stat once	1141	# get a wd object
		1142	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	1143	add $grp aio_wd $path, sub {
		1144	$_[0]
		1145	or return $grp->result ();
		1146
		1147	my $wd = [shift, "."];
		1148
		1149	# stat once
		1150	aioreq_pri $pri;
		1151	add $grp aio_stat $wd, sub {
413	return $grp->result () if $_[0];	1152	return $grp->result () if $_[0];
414	my $now = time;	1153	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1154	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		1155
417	# read the directory entries	1156	# read the directory entries
418	add $grp aio_readdir $path, sub {	1157	aioreq_pri $pri;
		1158	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
419	my $entries = shift	1159	my $entries = shift
420	or return $grp->result ();	1160	or return $grp->result ();
421		1161
422	# stat the dir another time	1162	# stat the dir another time
		1163	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	1164	add $grp aio_stat $wd, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1165	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		1166
426	my $ndirs;	1167	my $ndirs;
427		1168
428	# take the slow route if anything looks fishy	1169	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1170	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	1171	$ndirs = -1;
431	} else {	1172	} else {
432	# if nlink == 2, we are finished	1173	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	1174	# for non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	1175	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	1176	or return $grp->result ([], $entries);
436	}	1177	}
437		1178
438	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];
444
445	my (@dirs, @nondirs);	1179	my (@dirs, @nondirs);
446		1180
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	1181	my $statgrp = add $grp aio_group sub {
451
452	$schedcb = sub {
453	if (@$entries) {
454	if ($nreq < $maxreq) {
455	my $ent = pop @$entries;
456	$nreq++;
457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458	}
459	} elsif (!$nreq) {
460	# finished
461	$statgrp->cancel;
462	undef $statcb;
463	undef $schedcb;
464	$grp->result (\@dirs, \@nondirs);	1182	$grp->result (\@dirs, \@nondirs);
465	}	1183	};
		1184
		1185	limit $statgrp $maxreq;
		1186	feed $statgrp sub {
		1187	return unless @$entries;
		1188	my $entry = shift @$entries;
		1189
		1190	aioreq_pri $pri;
		1191	$wd->[1] = "$entry/.";
		1192	add $statgrp aio_stat $wd, sub {
		1193	if ($_[0] < 0) {
		1194	push @nondirs, $entry;
		1195	} else {
		1196	# need to check for real directory
		1197	aioreq_pri $pri;
		1198	$wd->[1] = $entry;
		1199	add $statgrp aio_lstat $wd, sub {
		1200	if (-d _) {
		1201	push @dirs, $entry;
		1202
		1203	unless (--$ndirs) {
		1204	push @nondirs, @$entries;
		1205	feed $statgrp;
		1206	}
		1207	} else {
		1208	push @nondirs, $entry;
		1209	}
		1210	}
		1211	}
		1212	};
		1213	};
466	};	1214	};
467	$statcb = sub {
468	my ($status, $entry) = @_;
469
470	if ($status < 0) {
471	$nreq--;
472	push @nondirs, $entry;
473	&$schedcb;
474	} else {
475	# need to check for real directory
476	add $grp aio_lstat "$path/$entry", sub {
477	$nreq--;
478
479	if (-d _) {
480	push @dirs, $entry;
481
482	if (!--$ndirs) {
483	push @nondirs, @$entries;
484	$entries = [];
485	}
486	} else {
487	push @nondirs, $entry;
488	}
489
490	&$schedcb;
491	}
492	}
493	};
494
495	&$schedcb while @$entries && $nreq < $maxreq;
496	};	1215	};
497	};	1216	};
498	};	1217	};
499		1218
500	$grp	1219	$grp
501	}	1220	}
502		1221
		1222	=item aio_rmtree $pathname, $callback->($status)
		1223
		1224	Delete a directory tree starting (and including) C<$path>, return the
		1225	status of the final C<rmdir> only. This is a composite request that
		1226	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1227	everything else.
		1228
		1229	=cut
		1230
		1231	sub aio_rmtree;
		1232	sub aio_rmtree($;$) {
		1233	my ($path, $cb) = @_;
		1234
		1235	my $pri = aioreq_pri;
		1236	my $grp = aio_group $cb;
		1237
		1238	aioreq_pri $pri;
		1239	add $grp aio_scandir $path, 0, sub {
		1240	my ($dirs, $nondirs) = @_;
		1241
		1242	my $dirgrp = aio_group sub {
		1243	add $grp aio_rmdir $path, sub {
		1244	$grp->result ($_[0]);
		1245	};
		1246	};
		1247
		1248	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1249	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1250
		1251	add $grp $dirgrp;
		1252	};
		1253
		1254	$grp
		1255	}
		1256
		1257	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1258
		1259	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1260
		1261	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1262	they execute asynchronously and pass the return value to the callback.
		1263
		1264	Both calls can be used for a lot of things, some of which make more sense
		1265	to run asynchronously in their own thread, while some others make less
		1266	sense. For example, calls that block waiting for external events, such
		1267	as locking, will also lock down an I/O thread while it is waiting, which
		1268	can deadlock the whole I/O system. At the same time, there might be no
		1269	alternative to using a thread to wait.
		1270
		1271	So in general, you should only use these calls for things that do
		1272	(filesystem) I/O, not for things that wait for other events (network,
		1273	other processes), although if you are careful and know what you are doing,
		1274	you still can.
		1275
		1276	The following constants are available (missing ones are, as usual C<0>):
		1277
		1278	C<F_DUPFD_CLOEXEC>,
		1279
		1280	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1281
		1282	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1283
		1284	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1285	C<FS_IOC_FIEMAP>.
		1286
		1287	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1288	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1289
		1290	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1291	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1292	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1293	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1294	C<FS_FL_USER_MODIFIABLE>.
		1295
		1296	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1297	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1298	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1299	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1300
		1301	=item aio_sync $callback->($status)
		1302
		1303	Asynchronously call sync and call the callback when finished.
		1304
503	=item aio_fsync $fh, $callback->($status)	1305	=item aio_fsync $fh, $callback->($status)
504		1306
505	Asynchronously call fsync on the given filehandle and call the callback	1307	Asynchronously call fsync on the given filehandle and call the callback
506	with the fsync result code.	1308	with the fsync result code.
507		1309
…		…
511	callback with the fdatasync result code.	1313	callback with the fdatasync result code.
512		1314
513	If this call isn't available because your OS lacks it or it couldn't be	1315	If this call isn't available because your OS lacks it or it couldn't be
514	detected, it will be emulated by calling C<fsync> instead.	1316	detected, it will be emulated by calling C<fsync> instead.
515		1317
		1318	=item aio_syncfs $fh, $callback->($status)
		1319
		1320	Asynchronously call the syncfs syscall to sync the filesystem associated
		1321	to the given filehandle and call the callback with the syncfs result
		1322	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1323	errno to C<ENOSYS> nevertheless.
		1324
		1325	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1326
		1327	Sync the data portion of the file specified by C<$offset> and C<$length>
		1328	to disk (but NOT the metadata), by calling the Linux-specific
		1329	sync_file_range call. If sync_file_range is not available or it returns
		1330	ENOSYS, then fdatasync or fsync is being substituted.
		1331
		1332	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1333	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1334	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1335	manpage for details.
		1336
		1337	=item aio_pathsync $pathname, $callback->($status)
		1338
		1339	This request tries to open, fsync and close the given path. This is a
		1340	composite request intended to sync directories after directory operations
		1341	(E.g. rename). This might not work on all operating systems or have any
		1342	specific effect, but usually it makes sure that directory changes get
		1343	written to disc. It works for anything that can be opened for read-only,
		1344	not just directories.
		1345
		1346	Future versions of this function might fall back to other methods when
		1347	C<fsync> on the directory fails (such as calling C<sync>).
		1348
		1349	Passes C<0> when everything went ok, and C<-1> on error.
		1350
		1351	=cut
		1352
		1353	sub aio_pathsync($;$) {
		1354	my ($path, $cb) = @_;
		1355
		1356	my $pri = aioreq_pri;
		1357	my $grp = aio_group $cb;
		1358
		1359	aioreq_pri $pri;
		1360	add $grp aio_open $path, O_RDONLY, 0, sub {
		1361	my ($fh) = @_;
		1362	if ($fh) {
		1363	aioreq_pri $pri;
		1364	add $grp aio_fsync $fh, sub {
		1365	$grp->result ($_[0]);
		1366
		1367	aioreq_pri $pri;
		1368	add $grp aio_close $fh;
		1369	};
		1370	} else {
		1371	$grp->result (-1);
		1372	}
		1373	};
		1374
		1375	$grp
		1376	}
		1377
		1378	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1379
		1380	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1381	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1382	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1383	scalar must only be modified in-place while an aio operation is pending on
		1384	it).
		1385
		1386	It calls the C<msync> function of your OS, if available, with the memory
		1387	area starting at C<$offset> in the string and ending C<$length> bytes
		1388	later. If C<$length> is negative, counts from the end, and if C<$length>
		1389	is C<undef>, then it goes till the end of the string. The flags can be
		1390	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1391	C<IO::AIO::MS_INVALIDATE>.
		1392
		1393	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1394
		1395	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1396	scalars.
		1397
		1398	It touches (reads or writes) all memory pages in the specified
		1399	range inside the scalar. All caveats and parameters are the same
		1400	as for C<aio_msync>, above, except for flags, which must be either
		1401	C<0> (which reads all pages and ensures they are instantiated) or
		1402	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1403	writing an octet from it, which dirties the page).
		1404
		1405	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1406
		1407	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1408	scalars.
		1409
		1410	It reads in all the pages of the underlying storage into memory (if any)
		1411	and locks them, so they are not getting swapped/paged out or removed.
		1412
		1413	If C<$length> is undefined, then the scalar will be locked till the end.
		1414
		1415	On systems that do not implement C<mlock>, this function returns C<-1>
		1416	and sets errno to C<ENOSYS>.
		1417
		1418	Note that the corresponding C<munlock> is synchronous and is
		1419	documented under L<MISCELLANEOUS FUNCTIONS>.
		1420
		1421	Example: open a file, mmap and mlock it - both will be undone when
		1422	C<$data> gets destroyed.
		1423
		1424	open my $fh, "<", $path or die "$path: $!";
		1425	my $data;
		1426	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1427	aio_mlock $data; # mlock in background
		1428
		1429	=item aio_mlockall $flags, $callback->($status)
		1430
		1431	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1432	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1433
		1434	On systems that do not implement C<mlockall>, this function returns C<-1>
		1435	and sets errno to C<ENOSYS>.
		1436
		1437	Note that the corresponding C<munlockall> is synchronous and is
		1438	documented under L<MISCELLANEOUS FUNCTIONS>.
		1439
		1440	Example: asynchronously lock all current and future pages into memory.
		1441
		1442	aio_mlockall IO::AIO::MCL_FUTURE;
		1443
		1444	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1445
		1446	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1447	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1448	the ioctl is not available on your OS, then this request will fail with
		1449	C<ENOSYS>.
		1450
		1451	C<$start> is the starting offset to query extents for, C<$length> is the
		1452	size of the range to query - if it is C<undef>, then the whole file will
		1453	be queried.
		1454
		1455	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1456	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1457	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1458	the data portion.
		1459
		1460	C<$count> is the maximum number of extent records to return. If it is
		1461	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1462	case, if it is C<0>, then the callback receives the number of extents
		1463	instead of the extents themselves (which is unreliable, see below).
		1464
		1465	If an error occurs, the callback receives no arguments. The special
		1466	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1467
		1468	Otherwise, the callback receives an array reference with extent
		1469	structures. Each extent structure is an array reference itself, with the
		1470	following members:
		1471
		1472	[$logical, $physical, $length, $flags]
		1473
		1474	Flags is any combination of the following flag values (typically either C<0>
		1475	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1476
		1477	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1478	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1479	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1480	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1481	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1482	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1483
		1484	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1485	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1486	it to return all extents of a range for files with large number of
		1487	extents. The code works around all these issues if C<$count> is undef.
		1488
516	=item aio_group $callback->(...)	1489	=item aio_group $callback->(...)
517
518	[EXPERIMENTAL]
519		1490
520	This is a very special aio request: Instead of doing something, it is a	1491	This is a very special aio request: Instead of doing something, it is a
521	container for other aio requests, which is useful if you want to bundle	1492	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	1493	many requests into a single, composite, request with a definite callback
		1494	and the ability to cancel the whole request with its subrequests.
523		1495
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1496	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	1497	for more info.
526		1498
527	Example:	1499	Example:
…		…
533	add $grp	1505	add $grp
534	(aio_stat ...),	1506	(aio_stat ...),
535	(aio_stat ...),	1507	(aio_stat ...),
536	...;	1508	...;
537		1509
		1510	=item aio_nop $callback->()
		1511
		1512	This is a special request - it does nothing in itself and is only used for
		1513	side effects, such as when you want to add a dummy request to a group so
		1514	that finishing the requests in the group depends on executing the given
		1515	code.
		1516
		1517	While this request does nothing, it still goes through the execution
		1518	phase and still requires a worker thread. Thus, the callback will not
		1519	be executed immediately but only after other requests in the queue have
		1520	entered their execution phase. This can be used to measure request
		1521	latency.
		1522
538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1523	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
539		1524
540	Mainly used for debugging and benchmarking, this aio request puts one of	1525	Mainly used for debugging and benchmarking, this aio request puts one of
541	the request workers to sleep for the given time.	1526	the request workers to sleep for the given time.
542		1527
543	While it is theoretically handy to have simple I/O scheduling requests	1528	While it is theoretically handy to have simple I/O scheduling requests
544	like sleep and file handle readable/writable, the overhead this creates	1529	like sleep and file handle readable/writable, the overhead this creates is
545	is immense, so do not use this function except to put your application	1530	immense (it blocks a thread for a long time) so do not use this function
546	under artificial I/O pressure.	1531	except to put your application under artificial I/O pressure.
547		1532
548	=back	1533	=back
		1534
		1535
		1536	=head2 IO::AIO::WD - multiple working directories
		1537
		1538	Your process only has one current working directory, which is used by all
		1539	threads. This makes it hard to use relative paths (some other component
		1540	could call C<chdir> at any time, and it is hard to control when the path
		1541	will be used by IO::AIO).
		1542
		1543	One solution for this is to always use absolute paths. This usually works,
		1544	but can be quite slow (the kernel has to walk the whole path on every
		1545	access), and can also be a hassle to implement.
		1546
		1547	Newer POSIX systems have a number of functions (openat, fdopendir,
		1548	futimensat and so on) that make it possible to specify working directories
		1549	per operation.
		1550
		1551	For portability, and because the clowns who "designed", or shall I write,
		1552	perpetrated this new interface were obviously half-drunk, this abstraction
		1553	cannot be perfect, though.
		1554
		1555	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1556	object. This object stores the canonicalised, absolute version of the
		1557	path, and on systems that allow it, also a directory file descriptor.
		1558
		1559	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1560	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1561	object and a pathname instead (or the IO::AIO::WD object alone, which
		1562	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1563	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1564	to that IO::AIO::WD object.
		1565
		1566	For example, to get a wd object for F</etc> and then stat F<passwd>
		1567	inside, you would write:
		1568
		1569	aio_wd "/etc", sub {
		1570	my $etcdir = shift;
		1571
		1572	# although $etcdir can be undef on error, there is generally no reason
		1573	# to check for errors here, as aio_stat will fail with ENOENT
		1574	# when $etcdir is undef.
		1575
		1576	aio_stat [$etcdir, "passwd"], sub {
		1577	# yay
		1578	};
		1579	};
		1580
		1581	The fact that C<aio_wd> is a request and not a normal function shows that
		1582	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1583	which is why it is done asynchronously.
		1584
		1585	To stat the directory obtained with C<aio_wd> above, one could write
		1586	either of the following three request calls:
		1587
		1588	aio_lstat "/etc" , sub { ... # pathname as normal string
		1589	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1590	aio_lstat $wd , sub { ... # shorthand for the previous
		1591
		1592	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1593	object and the pathname string, so you could write the following without
		1594	causing any issues due to C<$path> getting reused:
		1595
		1596	my $path = [$wd, undef];
		1597
		1598	for my $name (qw(abc def ghi)) {
		1599	$path->[1] = $name;
		1600	aio_stat $path, sub {
		1601	# ...
		1602	};
		1603	}
		1604
		1605	There are some caveats: when directories get renamed (or deleted), the
		1606	pathname string doesn't change, so will point to the new directory (or
		1607	nowhere at all), while the directory fd, if available on the system,
		1608	will still point to the original directory. Most functions accepting a
		1609	pathname will use the directory fd on newer systems, and the string on
		1610	older systems. Some functions (such as realpath) will always rely on the
		1611	string form of the pathname.
		1612
		1613	So this functionality is mainly useful to get some protection against
		1614	C<chdir>, to easily get an absolute path out of a relative path for future
		1615	reference, and to speed up doing many operations in the same directory
		1616	(e.g. when stat'ing all files in a directory).
		1617
		1618	The following functions implement this working directory abstraction:
		1619
		1620	=over 4
		1621
		1622	=item aio_wd $pathname, $callback->($wd)
		1623
		1624	Asynchonously canonicalise the given pathname and convert it to an
		1625	IO::AIO::WD object representing it. If possible and supported on the
		1626	system, also open a directory fd to speed up pathname resolution relative
		1627	to this working directory.
		1628
		1629	If something goes wrong, then C<undef> is passwd to the callback instead
		1630	of a working directory object and C<$!> is set appropriately. Since
		1631	passing C<undef> as working directory component of a pathname fails the
		1632	request with C<ENOENT>, there is often no need for error checking in the
		1633	C<aio_wd> callback, as future requests using the value will fail in the
		1634	expected way.
		1635
		1636	=item IO::AIO::CWD
		1637
		1638	This is a compiletime constant (object) that represents the process
		1639	current working directory.
		1640
		1641	Specifying this object as working directory object for a pathname is as if
		1642	the pathname would be specified directly, without a directory object. For
		1643	example, these calls are functionally identical:
		1644
		1645	aio_stat "somefile", sub { ... };
		1646	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1647
		1648	=back
		1649
		1650	To recover the path associated with an IO::AIO::WD object, you can use
		1651	C<aio_realpath>:
		1652
		1653	aio_realpath $wd, sub {
		1654	warn "path is $_[0]\n";
		1655	};
		1656
		1657	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1658	sometimes, fall back to using an absolue path.
549		1659
550	=head2 IO::AIO::REQ CLASS	1660	=head2 IO::AIO::REQ CLASS
551		1661
552	All non-aggregate C<aio_*> functions return an object of this class when	1662	All non-aggregate C<aio_*> functions return an object of this class when
553	called in non-void context.	1663	called in non-void context.
554		1664
555	A request always moves through the following five states in its lifetime,
556	in order: B<ready> (request has been created, but has not been executed
557	yet), B<execute> (request is currently being executed), B<pending>
558	(request has been executed but callback has not been called yet),
559	B<result> (results are being processed synchronously, includes calling the
560	callback) and B<done> (request has reached the end of its lifetime and
561	holds no resources anymore).
562
563	=over 4	1665	=over 4
564		1666
565	=item $req->cancel	1667	=item cancel $req
566		1668
567	Cancels the request, if possible. Has the effect of skipping execution	1669	Cancels the request, if possible. Has the effect of skipping execution
568	when entering the B<execute> state and skipping calling the callback when	1670	when entering the B<execute> state and skipping calling the callback when
569	entering the the B<result> state, but will leave the request otherwise	1671	entering the the B<result> state, but will leave the request otherwise
570	untouched. That means that requests that currently execute will not be	1672	untouched (with the exception of readdir). That means that requests that
571	stopped and resources held by the request will not be freed prematurely.	1673	currently execute will not be stopped and resources held by the request
		1674	will not be freed prematurely.
		1675
		1676	=item cb $req $callback->(...)
		1677
		1678	Replace (or simply set) the callback registered to the request.
572		1679
573	=back	1680	=back
574		1681
575	=head2 IO::AIO::GRP CLASS	1682	=head2 IO::AIO::GRP CLASS
576		1683
…		…
616	=item * They can also can also be added to other IO::AIO::GRP objects.	1723	=item * They can also can also be added to other IO::AIO::GRP objects.
617		1724
618	=item * You must not add requests to a group from within the group callback (or	1725	=item * You must not add requests to a group from within the group callback (or
619	any later time).	1726	any later time).
620		1727
621	=item * This does not harmonise well with C<max_outstanding>, so best do
622	not combine C<aio_group> with it. Groups and feeders are recommended for
623	this kind of concurrency-limiting.
624
625	=back	1728	=back
626		1729
627	Their lifetime, simplified, looks like this: when they are empty, they	1730	Their lifetime, simplified, looks like this: when they are empty, they
628	will finish very quickly. If they contain only requests that are in the	1731	will finish very quickly. If they contain only requests that are in the
629	C<done> state, they will also finish. Otherwise they will continue to	1732	C<done> state, they will also finish. Otherwise they will continue to
630	exist.	1733	exist.
631		1734
632	That means after creating a group you have some time to add requests. And	1735	That means after creating a group you have some time to add requests
633	in the callbacks of those requests, you can add further requests to the	1736	(precisely before the callback has been invoked, which is only done within
634	group. And only when all those requests have finished will the the group	1737	the C<poll_cb>). And in the callbacks of those requests, you can add
635	itself finish.	1738	further requests to the group. And only when all those requests have
		1739	finished will the the group itself finish.
636		1740
637	=over 4	1741	=over 4
638		1742
		1743	=item add $grp ...
		1744
639	=item $grp->add (...)	1745	=item $grp->add (...)
640
641	=item add $grp ...
642		1746
643	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1747	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
644	be added, including other groups, as long as you do not create circular	1748	be added, including other groups, as long as you do not create circular
645	dependencies.	1749	dependencies.
646		1750
647	Returns all its arguments.	1751	Returns all its arguments.
648		1752
		1753	=item $grp->cancel_subs
		1754
		1755	Cancel all subrequests and clears any feeder, but not the group request
		1756	itself. Useful when you queued a lot of events but got a result early.
		1757
		1758	The group request will finish normally (you cannot add requests to the
		1759	group).
		1760
649	=item $grp->result (...)	1761	=item $grp->result (...)
650		1762
651	Set the result value(s) that will be passed to the group callback when all	1763	Set the result value(s) that will be passed to the group callback when all
652	subrequests have finished. By default, no argument will be passed.	1764	subrequests have finished and set the groups errno to the current value
		1765	of errno (just like calling C<errno> without an error number). By default,
		1766	no argument will be passed and errno is zero.
653		1767
654	=item $grp->set_feeder ($callback->($grp))	1768	=item $grp->errno ([$errno])
655		1769
656	[VERY EXPERIMENTAL]	1770	Sets the group errno value to C<$errno>, or the current value of errno
		1771	when the argument is missing.
		1772
		1773	Every aio request has an associated errno value that is restored when
		1774	the callback is invoked. This method lets you change this value from its
		1775	default (0).
		1776
		1777	Calling C<result> will also set errno, so make sure you either set C<$!>
		1778	before the call to C<result>, or call c<errno> after it.
		1779
		1780	=item feed $grp $callback->($grp)
657		1781
658	Sets a feeder/generator on this group: every group can have an attached	1782	Sets a feeder/generator on this group: every group can have an attached
659	generator that generates requests if idle. The idea behind this is that,	1783	generator that generates requests if idle. The idea behind this is that,
660	although you could just queue as many requests as you want in a group,	1784	although you could just queue as many requests as you want in a group,
661	this might starve other requests for a potentially long time. For	1785	this might starve other requests for a potentially long time. For example,
662	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1786	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
663	requests, delaying any later requests for a long time.	1787	requests, delaying any later requests for a long time.
664		1788
665	To avoid this, and allow incremental generation of requests, you can	1789	To avoid this, and allow incremental generation of requests, you can
666	instead a group and set a feeder on it that generates those requests. The	1790	instead a group and set a feeder on it that generates those requests. The
667	feeder will be called whenever there are few enough (see C<feeder_limit>,	1791	feed callback will be called whenever there are few enough (see C<limit>,
668	below) requests active in the group itself and is expected to queue more	1792	below) requests active in the group itself and is expected to queue more
669	requests.	1793	requests.
670		1794
671	The feeder can queue as many requests as it likes (i.e. C<add> does not	1795	The feed callback can queue as many requests as it likes (i.e. C<add> does
672	impose any limits).	1796	not impose any limits).
673		1797
674	If the feeder does not queue more requests when called, it will be	1798	If the feed does not queue more requests when called, it will be
675	automatically removed from the group.	1799	automatically removed from the group.
676		1800
677	If the feeder limit is C<0>, it will be set to C<2> automatically.	1801	If the feed limit is C<0> when this method is called, it will be set to
		1802	C<2> automatically.
678		1803
679	Example:	1804	Example:
680		1805
681	# stat all files in @files, but only ever use four aio requests concurrently:	1806	# stat all files in @files, but only ever use four aio requests concurrently:
682		1807
683	my $grp = aio_group sub { print "finished\n" };	1808	my $grp = aio_group sub { print "finished\n" };
684	$grp->feeder_limit (4);	1809	limit $grp 4;
685	$grp->set_feeder (sub {	1810	feed $grp sub {
686	my $file = pop @files	1811	my $file = pop @files
687	or return;	1812	or return;
688		1813
689	add $grp aio_stat $file, sub { ... };	1814	add $grp aio_stat $file, sub { ... };
690	});	1815	};
691		1816
692	=item $grp->feeder_limit ($num)	1817	=item limit $grp $num
693		1818
694	Sets the feeder limit for the group: The feeder will be called whenever	1819	Sets the feeder limit for the group: The feeder will be called whenever
695	the group contains less than this many requests.	1820	the group contains less than this many requests.
696		1821
697	Setting the limit to C<0> will pause the feeding process.	1822	Setting the limit to C<0> will pause the feeding process.
698		1823
		1824	The default value for the limit is C<0>, but note that setting a feeder
		1825	automatically bumps it up to C<2>.
		1826
699	=back	1827	=back
700		1828
701	=head2 SUPPORT FUNCTIONS	1829	=head2 SUPPORT FUNCTIONS
702		1830
		1831	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1832
703	=over 4	1833	=over 4
704		1834
705	=item $fileno = IO::AIO::poll_fileno	1835	=item $fileno = IO::AIO::poll_fileno
706		1836
707	Return the I<request result pipe file descriptor>. This filehandle must be	1837	Return the I<request result pipe file descriptor>. This filehandle must be
708	polled for reading by some mechanism outside this module (e.g. Event or	1838	polled for reading by some mechanism outside this module (e.g. EV, Glib,
709	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1839	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
710	to call C<poll_cb> to check the results.	1840	you have to call C<poll_cb> to check the results.
711		1841
712	See C<poll_cb> for an example.	1842	See C<poll_cb> for an example.
713		1843
714	=item IO::AIO::poll_cb	1844	=item IO::AIO::poll_cb
715		1845
716	Process all outstanding events on the result pipe. You have to call this	1846	Process some requests that have reached the result phase (i.e. they have
717	regularly. Returns the number of events processed. Returns immediately	1847	been executed but the results are not yet reported). You have to call
718	when no events are outstanding.	1848	this "regularly" to finish outstanding requests.
		1849
		1850	Returns C<0> if all events could be processed (or there were no
		1851	events to process), or C<-1> if it returned earlier for whatever
		1852	reason. Returns immediately when no events are outstanding. The amount
		1853	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1854	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1855
		1856	If not all requests were processed for whatever reason, the poll file
		1857	descriptor will still be ready when C<poll_cb> returns, so normally you
		1858	don't have to do anything special to have it called later.
		1859
		1860	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1861	ready, it can be beneficial to call this function from loops which submit
		1862	a lot of requests, to make sure the results get processed when they become
		1863	available and not just when the loop is finished and the event loop takes
		1864	over again. This function returns very fast when there are no outstanding
		1865	requests.
719		1866
720	Example: Install an Event watcher that automatically calls	1867	Example: Install an Event watcher that automatically calls
721	IO::AIO::poll_cb with high priority:	1868	IO::AIO::poll_cb with high priority (more examples can be found in the
		1869	SYNOPSIS section, at the top of this document):
722		1870
723	Event->io (fd => IO::AIO::poll_fileno,	1871	Event->io (fd => IO::AIO::poll_fileno,
724	poll => 'r', async => 1,	1872	poll => 'r', async => 1,
725	cb => \&IO::AIO::poll_cb);	1873	cb => \&IO::AIO::poll_cb);
726		1874
727	=item IO::AIO::poll_wait	1875	=item IO::AIO::poll_wait
728		1876
729	Wait till the result filehandle becomes ready for reading (simply does a	1877	Wait until either at least one request is in the result phase or no
730	C<select> on the filehandle. This is useful if you want to synchronously wait	1878	requests are outstanding anymore.
731	for some requests to finish).	1879
		1880	This is useful if you want to synchronously wait for some requests to
		1881	become ready, without actually handling them.
732		1882
733	See C<nreqs> for an example.	1883	See C<nreqs> for an example.
734		1884
		1885	=item IO::AIO::poll
		1886
		1887	Waits until some requests have been handled.
		1888
		1889	Returns the number of requests processed, but is otherwise strictly
		1890	equivalent to:
		1891
		1892	IO::AIO::poll_wait, IO::AIO::poll_cb
		1893
735	=item IO::AIO::nreqs	1894	=item IO::AIO::flush
736		1895
737	Returns the number of requests currently outstanding (i.e. for which their	1896	Wait till all outstanding AIO requests have been handled.
738	callback has not been invoked yet).
739		1897
740	Example: wait till there are no outstanding requests anymore:	1898	Strictly equivalent to:
741		1899
742	IO::AIO::poll_wait, IO::AIO::poll_cb	1900	IO::AIO::poll_wait, IO::AIO::poll_cb
743	while IO::AIO::nreqs;	1901	while IO::AIO::nreqs;
744		1902
745	=item IO::AIO::flush	1903	=item IO::AIO::max_poll_reqs $nreqs
746		1904
747	Wait till all outstanding AIO requests have been handled.	1905	=item IO::AIO::max_poll_time $seconds
748		1906
749	Strictly equivalent to:	1907	These set the maximum number of requests (default C<0>, meaning infinity)
		1908	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1909	the maximum amount of time (default C<0>, meaning infinity) spent in
		1910	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1911	of time C<poll_cb> is allowed to use).
750		1912
751	IO::AIO::poll_wait, IO::AIO::poll_cb	1913	Setting C<max_poll_time> to a non-zero value creates an overhead of one
752	while IO::AIO::nreqs;	1914	syscall per request processed, which is not normally a problem unless your
		1915	callbacks are really really fast or your OS is really really slow (I am
		1916	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
753		1917
754	=item IO::AIO::poll	1918	Setting these is useful if you want to ensure some level of
		1919	interactiveness when perl is not fast enough to process all requests in
		1920	time.
755		1921
756	Waits until some requests have been handled.	1922	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
757		1923
758	Strictly equivalent to:	1924	Example: Install an Event watcher that automatically calls
		1925	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1926	program get the CPU sometimes even under high AIO load.
759		1927
760	IO::AIO::poll_wait, IO::AIO::poll_cb	1928	# try not to spend much more than 0.1s in poll_cb
761	if IO::AIO::nreqs;	1929	IO::AIO::max_poll_time 0.1;
		1930
		1931	# use a low priority so other tasks have priority
		1932	Event->io (fd => IO::AIO::poll_fileno,
		1933	poll => 'r', nice => 1,
		1934	cb => &IO::AIO::poll_cb);
		1935
		1936	=back
		1937
		1938	=head3 CONTROLLING THE NUMBER OF THREADS
		1939
		1940	=over
762		1941
763	=item IO::AIO::min_parallel $nthreads	1942	=item IO::AIO::min_parallel $nthreads
764		1943
765	Set the minimum number of AIO threads to C<$nthreads>. The current	1944	Set the minimum number of AIO threads to C<$nthreads>. The current
766	default is C<8>, which means eight asynchronous operations can execute	1945	default is C<8>, which means eight asynchronous operations can execute
767	concurrently at any one time (the number of outstanding requests,	1946	concurrently at any one time (the number of outstanding requests,
768	however, is unlimited).	1947	however, is unlimited).
769		1948
770	IO::AIO starts threads only on demand, when an AIO request is queued and	1949	IO::AIO starts threads only on demand, when an AIO request is queued and
771	no free thread exists.	1950	no free thread exists. Please note that queueing up a hundred requests can
		1951	create demand for a hundred threads, even if it turns out that everything
		1952	is in the cache and could have been processed faster by a single thread.
772		1953
773	It is recommended to keep the number of threads relatively low, as some	1954	It is recommended to keep the number of threads relatively low, as some
774	Linux kernel versions will scale negatively with the number of threads	1955	Linux kernel versions will scale negatively with the number of threads
775	(higher parallelity => MUCH higher latency). With current Linux 2.6	1956	(higher parallelity => MUCH higher latency). With current Linux 2.6
776	versions, 4-32 threads should be fine.	1957	versions, 4-32 threads should be fine.
…		…
790	This module automatically runs C<max_parallel 0> at program end, to ensure	1971	This module automatically runs C<max_parallel 0> at program end, to ensure
791	that all threads are killed and that there are no outstanding requests.	1972	that all threads are killed and that there are no outstanding requests.
792		1973
793	Under normal circumstances you don't need to call this function.	1974	Under normal circumstances you don't need to call this function.
794		1975
		1976	=item IO::AIO::max_idle $nthreads
		1977
		1978	Limit the number of threads (default: 4) that are allowed to idle
		1979	(i.e., threads that did not get a request to process within the idle
		1980	timeout (default: 10 seconds). That means if a thread becomes idle while
		1981	C<$nthreads> other threads are also idle, it will free its resources and
		1982	exit.
		1983
		1984	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1985	to allow for extremely high load situations, but want to free resources
		1986	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1987
		1988	The default is probably ok in most situations, especially if thread
		1989	creation is fast. If thread creation is very slow on your system you might
		1990	want to use larger values.
		1991
		1992	=item IO::AIO::idle_timeout $seconds
		1993
		1994	Sets the minimum idle timeout (default 10) after which worker threads are
		1995	allowed to exit. SEe C<IO::AIO::max_idle>.
		1996
795	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1997	=item IO::AIO::max_outstanding $maxreqs
796		1998
797	[DEPRECATED]
798
799	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1999	Sets the maximum number of outstanding requests to C<$nreqs>. If
800	try to queue up more than this number of requests, the caller will block until	2000	you do queue up more than this number of requests, the next call to
801	some requests have been handled.	2001	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2002	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2003	longer exceeded.
802		2004
803	The default is very large, so normally there is no practical limit. If you	2005	In other words, this setting does not enforce a queue limit, but can be
804	queue up many requests in a loop it often improves speed if you set	2006	used to make poll functions block if the limit is exceeded.
805	this to a relatively low number, such as C<100>.
806		2007
807	This function does not work well together with C<aio_group>'s, and their	2008	This is a very bad function to use in interactive programs because it
808	feeder interface is better suited to limiting concurrency, so do not use	2009	blocks, and a bad way to reduce concurrency because it is inexact: Better
809	this function.	2010	use an C<aio_group> together with a feed callback.
810		2011
811	Under normal circumstances you don't need to call this function.	2012	Its main use is in scripts without an event loop - when you want to stat
		2013	a lot of files, you can write somehting like this:
		2014
		2015	IO::AIO::max_outstanding 32;
		2016
		2017	for my $path (...) {
		2018	aio_stat $path , ...;
		2019	IO::AIO::poll_cb;
		2020	}
		2021
		2022	IO::AIO::flush;
		2023
		2024	The call to C<poll_cb> inside the loop will normally return instantly, but
		2025	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2026	some requests have been handled. This keeps the loop from pushing a large
		2027	number of C<aio_stat> requests onto the queue.
		2028
		2029	The default value for C<max_outstanding> is very large, so there is no
		2030	practical limit on the number of outstanding requests.
812		2031
813	=back	2032	=back
814		2033
		2034	=head3 STATISTICAL INFORMATION
		2035
		2036	=over
		2037
		2038	=item IO::AIO::nreqs
		2039
		2040	Returns the number of requests currently in the ready, execute or pending
		2041	states (i.e. for which their callback has not been invoked yet).
		2042
		2043	Example: wait till there are no outstanding requests anymore:
		2044
		2045	IO::AIO::poll_wait, IO::AIO::poll_cb
		2046	while IO::AIO::nreqs;
		2047
		2048	=item IO::AIO::nready
		2049
		2050	Returns the number of requests currently in the ready state (not yet
		2051	executed).
		2052
		2053	=item IO::AIO::npending
		2054
		2055	Returns the number of requests currently in the pending state (executed,
		2056	but not yet processed by poll_cb).
		2057
		2058	=back
		2059
		2060	=head3 MISCELLANEOUS FUNCTIONS
		2061
		2062	IO::AIO implements some functions that are useful when you want to use
		2063	some "Advanced I/O" function not available to in Perl, without going the
		2064	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2065	counterpart.
		2066
		2067	=over 4
		2068
		2069	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2070
		2071	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2072	but is blocking (this makes most sense if you know the input data is
		2073	likely cached already and the output filehandle is set to non-blocking
		2074	operations).
		2075
		2076	Returns the number of bytes copied, or C<-1> on error.
		2077
		2078	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2079
		2080	Simply calls the C<posix_fadvise> function (see its
		2081	manpage for details). The following advice constants are
		2082	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2083	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2084	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2085
		2086	On systems that do not implement C<posix_fadvise>, this function returns
		2087	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2088
		2089	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2090
		2091	Simply calls the C<posix_madvise> function (see its
		2092	manpage for details). The following advice constants are
		2093	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2094	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2095	C<IO::AIO::MADV_DONTNEED>.
		2096
		2097	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2098	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2099	will be reduced to fit into the C<$scalar>.
		2100
		2101	On systems that do not implement C<posix_madvise>, this function returns
		2102	ENOSYS, otherwise the return value of C<posix_madvise>.
		2103
		2104	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2105
		2106	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2107	$scalar (see its manpage for details). The following protect
		2108	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2109	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2110
		2111	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2112	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2113	will be reduced to fit into the C<$scalar>.
		2114
		2115	On systems that do not implement C<mprotect>, this function returns
		2116	ENOSYS, otherwise the return value of C<mprotect>.
		2117
		2118	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2119
		2120	Memory-maps a file (or anonymous memory range) and attaches it to the
		2121	given C<$scalar>, which will act like a string scalar. Returns true on
		2122	success, and false otherwise.
		2123
		2124	The scalar must exist, but its contents do not matter - this means you
		2125	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2126	the scalar first.
		2127
		2128	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2129	which don't change the string length, and most read-only operations such
		2130	as copying it or searching it with regexes and so on.
		2131
		2132	Anything else is unsafe and will, at best, result in memory leaks.
		2133
		2134	The memory map associated with the C<$scalar> is automatically removed
		2135	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2136	or C<IO::AIO::munmap> functions are called on it.
		2137
		2138	This calls the C<mmap>(2) function internally. See your system's manual
		2139	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2140
		2141	The C<$length> must be larger than zero and smaller than the actual
		2142	filesize.
		2143
		2144	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2145	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2146
		2147	C<$flags> can be a combination of
		2148	C<IO::AIO::MAP_SHARED> or
		2149	C<IO::AIO::MAP_PRIVATE>,
		2150	or a number of system-specific flags (when not available, the are C<0>):
		2151	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2152	C<IO::AIO::MAP_LOCKED>,
		2153	C<IO::AIO::MAP_NORESERVE>,
		2154	C<IO::AIO::MAP_POPULATE>,
		2155	C<IO::AIO::MAP_NONBLOCK>,
		2156	C<IO::AIO::MAP_FIXED>,
		2157	C<IO::AIO::MAP_GROWSDOWN>,
		2158	C<IO::AIO::MAP_32BIT>,
		2159	C<IO::AIO::MAP_HUGETLB> or
		2160	C<IO::AIO::MAP_STACK>.
		2161
		2162	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2163
		2164	C<$offset> is the offset from the start of the file - it generally must be
		2165	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2166
		2167	Example:
		2168
		2169	use Digest::MD5;
		2170	use IO::AIO;
		2171
		2172	open my $fh, "<verybigfile"
		2173	or die "$!";
		2174
		2175	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2176	or die "verybigfile: $!";
		2177
		2178	my $fast_md5 = md5 $data;
		2179
		2180	=item IO::AIO::munmap $scalar
		2181
		2182	Removes a previous mmap and undefines the C<$scalar>.
		2183
		2184	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2185
		2186	Calls the C<munlock> function, undoing the effects of a previous
		2187	C<aio_mlock> call (see its description for details).
		2188
		2189	=item IO::AIO::munlockall
		2190
		2191	Calls the C<munlockall> function.
		2192
		2193	On systems that do not implement C<munlockall>, this function returns
		2194	ENOSYS, otherwise the return value of C<munlockall>.
		2195
		2196	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2197
		2198	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2199	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2200	should be the file offset.
		2201
		2202	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2203	silently corrupt the data in this case.
		2204
		2205	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2206	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2207	C<IO::AIO::SPLICE_F_GIFT>.
		2208
		2209	See the C<splice(2)> manpage for details.
		2210
		2211	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2212
		2213	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2214	description for C<IO::AIO::splice> above for details.
		2215
		2216	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2217
		2218	Attempts to query or change the pipe buffer size. Obviously works only
		2219	on pipes, and currently works only on GNU/Linux systems, and fails with
		2220	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2221	size on other systems, drop me a note.
		2222
		2223	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2224
		2225	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2226	C<$flags> is missing or C<0>, then this should be the same as a call to
		2227	perl's built-in C<pipe> function and create a new pipe, and works on
		2228	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2229	(..., 4096, O_BINARY)>.
		2230
		2231	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2232	the given flags (Linux 2.6.27, glibc 2.9).
		2233
		2234	On success, the read and write file handles are returned.
		2235
		2236	On error, nothing will be returned. If the pipe2 syscall is missing and
		2237	C<$flags> is non-zero, fails with C<ENOSYS>.
		2238
		2239	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2240	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2241	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2242
		2243	=back
		2244
815	=cut	2245	=cut
816		2246
817	# support function to convert a fd into a perl filehandle
818	sub _fd2fh {
819	return undef if $_[0] < 0;
820
821	# try to generate nice filehandles
822	my $sym = "IO::AIO::fd#$_[0]";
823	local *$sym;
824
825	open *$sym, "+<&=$_[0]" # usually works under any unix
826	or open *$sym, "<&=$_[0]" # cygwin needs this
827	or open *$sym, ">&=$_[0]" # or this
828	or return undef;
829
830	*$sym
831	}
832
833	min_parallel 8;	2247	min_parallel 8;
834		2248
835	END {	2249	END { flush }
836	max_parallel 0;
837	}
838		2250
839	1;	2251	1;
840		2252
		2253	=head1 EVENT LOOP INTEGRATION
		2254
		2255	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2256	automatically into many event loops:
		2257
		2258	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2259	use AnyEvent::AIO;
		2260
		2261	You can also integrate IO::AIO manually into many event loops, here are
		2262	some examples of how to do this:
		2263
		2264	# EV integration
		2265	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2266
		2267	# Event integration
		2268	Event->io (fd => IO::AIO::poll_fileno,
		2269	poll => 'r',
		2270	cb => \&IO::AIO::poll_cb);
		2271
		2272	# Glib/Gtk2 integration
		2273	add_watch Glib::IO IO::AIO::poll_fileno,
		2274	in => sub { IO::AIO::poll_cb; 1 };
		2275
		2276	# Tk integration
		2277	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2278	readable => \&IO::AIO::poll_cb);
		2279
		2280	# Danga::Socket integration
		2281	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2282	\&IO::AIO::poll_cb);
		2283
841	=head2 FORK BEHAVIOUR	2284	=head2 FORK BEHAVIOUR
842		2285
843	This module should do "the right thing" when the process using it forks:	2286	Usage of pthreads in a program changes the semantics of fork
		2287	considerably. Specifically, only async-safe functions can be called after
		2288	fork. Perl doesn't know about this, so in general, you cannot call fork
		2289	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2290	pthreads, so this applies, but many other extensions and (for inexplicable
		2291	reasons) perl itself often is linked against pthreads, so this limitation
		2292	applies to quite a lot of perls.
844		2293
845	Before the fork, IO::AIO enters a quiescent state where no requests	2294	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
846	can be added in other threads and no results will be processed. After	2295	only works in the process that loaded it. Forking is fully supported, but
847	the fork the parent simply leaves the quiescent state and continues	2296	using IO::AIO in the child is not.
848	request/result processing, while the child clears the request/result
849	queue (so the requests started before the fork will only be handled in
850	the parent). Threads will be started on demand until the limit ste in the
851	parent process has been reached again.
852		2297
853	In short: the parent will, after a short pause, continue as if fork had	2298	You might get around by not I<using> IO::AIO before (or after)
854	not been called, while the child will act as if IO::AIO has not been used	2299	forking. You could also try to call the L<IO::AIO::reinit> function in the
855	yet.	2300	child:
		2301
		2302	=over 4
		2303
		2304	=item IO::AIO::reinit
		2305
		2306	Abandons all current requests and I/O threads and simply reinitialises all
		2307	data structures. This is not an operation supported by any standards, but
		2308	happens to work on GNU/Linux and some newer BSD systems.
		2309
		2310	The only reasonable use for this function is to call it after forking, if
		2311	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2312	the process will result in undefined behaviour. Calling it at any time
		2313	will also result in any undefined (by POSIX) behaviour.
		2314
		2315	=back
856		2316
857	=head2 MEMORY USAGE	2317	=head2 MEMORY USAGE
858		2318
		2319	Per-request usage:
		2320
859	Each aio request uses - depending on your architecture - around 128 bytes	2321	Each aio request uses - depending on your architecture - around 100-200
860	of memory. In addition, stat requests need a stat buffer (possibly a few	2322	bytes of memory. In addition, stat requests need a stat buffer (possibly
861	hundred bytes). Perl scalars and other data passed into aio requests will	2323	a few hundred bytes), readdir requires a result buffer and so on. Perl
862	also be locked.	2324	scalars and other data passed into aio requests will also be locked and
		2325	will consume memory till the request has entered the done state.
863		2326
864	This is now awfully much, so queuing lots of requests is not usually a	2327	This is not awfully much, so queuing lots of requests is not usually a
865	problem.	2328	problem.
866		2329
867	Each thread needs a stack area which is usually around 16k, sometimes much	2330	Per-thread usage:
868	larger, depending on the OS.	2331
		2332	In the execution phase, some aio requests require more memory for
		2333	temporary buffers, and each thread requires a stack and other data
		2334	structures (usually around 16k-128k, depending on the OS).
		2335
		2336	=head1 KNOWN BUGS
		2337
		2338	Known bugs will be fixed in the next release.
869		2339
870	=head1 SEE ALSO	2340	=head1 SEE ALSO
871		2341
872	L<Coro>, L<Linux::AIO> (obsolete).	2342	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2343	more natural syntax.
873		2344
874	=head1 AUTHOR	2345	=head1 AUTHOR
875		2346
876	Marc Lehmann <schmorp@schmorp.de>	2347	Marc Lehmann <schmorp@schmorp.de>
877	http://home.schmorp.de/	2348	http://home.schmorp.de/

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