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Revision 1.57 by root, Sun Oct 22 01:28:31 2006 UTC vs.
Revision 1.270 by root, Fri Jun 23 03:23:19 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	Try to move the I<file> (directories not supported as either source or
188	destination) from C<$srcpath> to C<$dstpath> and call the callback with
189	the C<0> (error) or C<-1> ok.
190
191	This is a composite request that tries to rename(2) the file first. If
192	rename files with C<EXDEV>, it creates the destination file with mode 0200
193	and copies the contents of the source file into it using C<aio_sendfile>,
194	followed by restoring atime, mtime, access mode and uid/gid, in that
195	order, and unlinking the C<$srcpath>.
196
197	If an error occurs, the partial destination file will be unlinked, if
198	possible, except when setting atime, mtime, access mode and uid/gid, where
199	errors are being ignored.
200
201	=cut
202
203	sub aio_move($$$) {
204	my ($src, $dst, $cb) = @_;
205
206	my $grp = aio_group;
207
208	add $grp aio_rename $src, $dst, sub {
209	if ($_[0] && $! == EXDEV) {
210	add $grp aio_open $src, O_RDONLY, 0, sub {
211	if (my $src_fh = $_[0]) {
212	my @stat = stat $src_fh;
213
214	add $grp aio_open $dst, O_WRONLY, 0200, sub {
215	if (my $dst_fh = $_[0]) {
216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
217	close $src_fh;
218
219	if ($_[0] == $stat[7]) {
220	utime $stat[8], $stat[9], $dst;
221	chmod $stat[2] & 07777, $dst_fh;
222	chown $stat[4], $stat[5], $dst_fh;
223	close $dst_fh;
224
225	add $grp aio_unlink $src, sub {
226	$cb->($_[0]);
227	};
228	} else {
229	my $errno = $!;
230	add $grp aio_unlink $dst, sub {
231	$! = $errno;
232	$cb->(-1);
233	};
234	}
235	};
236	} else {
237	$cb->(-1);
238	}
239	},
240
241	} else {
242	$cb->(-1);
243	}
244	};
245	} else {
246	$cb->($_[0]);
247	}
248	};
249
250	$grp
251	}
252		480
253	=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)
254		482
255	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
256	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
257	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
258	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
259	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>.
260		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
261	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
262	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
263	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.
264		509
265	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>,
266	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
267	regardless of the limitations of the operating system.	513	type of filehandle regardless of the limitations of the operating system.
268		514
269	Please note, however, that C<aio_sendfile> can read more bytes from	515	As native sendfile syscalls (as practically any non-POSIX interface hacked
270	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
271	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
272	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,
273	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> -
274	read.	520	fewer bytes than expected might have been transferred.
		521
275		522
276	=item aio_readahead $fh,$offset,$length, $callback->($retval)	523	=item aio_readahead $fh,$offset,$length, $callback->($retval)
277		524
278	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
279	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>
…		…
282	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
283	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
284	(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
285	file. The current file offset of the file is left unchanged.	532	file. The current file offset of the file is left unchanged.
286		533
287	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
288	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
289		537
290	=item aio_stat $fh_or_path, $callback->($status)	538	=item aio_stat $fh_or_path, $callback->($status)
291		539
292	=item aio_lstat $fh, $callback->($status)	540	=item aio_lstat $fh, $callback->($status)
293		541
…		…
299	for an explanation.	547	for an explanation.
300		548
301	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
302	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
303	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>.
304		561
305	Example: Print the length of F</etc/passwd>:	562	Example: Print the length of F</etc/passwd>:
306		563
307	aio_stat "/etc/passwd", sub {	564	aio_stat "/etc/passwd", sub {
308	$_[0] and die "stat failed: $!";	565	$_[0] and die "stat failed: $!";
309	print "size is ", -s _, "\n";	566	print "size is ", -s _, "\n";
310	};	567	};
311		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) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see
		746	your L<fallocate(2)> manpage).
		747
		748	The file system block size used by C<fallocate> is presumably the
		749	C<f_bsize> returned by C<statvfs>.
		750
		751	If C<fallocate> isn't available or cannot be emulated (currently no
		752	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		753
		754
		755	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		756
		757	Works like perl's C<chmod> function.
		758
		759
312	=item aio_unlink $pathname, $callback->($status)	760	=item aio_unlink $pathname, $callback->($status)
313		761
314	Asynchronously unlink (delete) a file and call the callback with the	762	Asynchronously unlink (delete) a file and call the callback with the
315	result code.	763	result code.
316		764
		765
		766	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		767
		768	[EXPERIMENTAL]
		769
		770	Asynchronously create a device node (or fifo). See mknod(2).
		771
		772	The only (POSIX-) portable way of calling this function is:
		773
		774	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		775
		776	See C<aio_stat> for info about some potentially helpful extra constants
		777	and functions.
		778
317	=item aio_link $srcpath, $dstpath, $callback->($status)	779	=item aio_link $srcpath, $dstpath, $callback->($status)
318		780
319	Asynchronously create a new link to the existing object at C<$srcpath> at	781	Asynchronously create a new link to the existing object at C<$srcpath> at
320	the path C<$dstpath> and call the callback with the result code.	782	the path C<$dstpath> and call the callback with the result code.
321		783
		784
322	=item aio_symlink $srcpath, $dstpath, $callback->($status)	785	=item aio_symlink $srcpath, $dstpath, $callback->($status)
323		786
324	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	787	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
325	the path C<$dstpath> and call the callback with the result code.	788	the path C<$dstpath> and call the callback with the result code.
326		789
		790
		791	=item aio_readlink $pathname, $callback->($link)
		792
		793	Asynchronously read the symlink specified by C<$path> and pass it to
		794	the callback. If an error occurs, nothing or undef gets passed to the
		795	callback.
		796
		797
		798	=item aio_realpath $pathname, $callback->($path)
		799
		800	Asynchronously make the path absolute and resolve any symlinks in
		801	C<$path>. The resulting path only consists of directories (same as
		802	L<Cwd::realpath>).
		803
		804	This request can be used to get the absolute path of the current working
		805	directory by passing it a path of F<.> (a single dot).
		806
		807
327	=item aio_rename $srcpath, $dstpath, $callback->($status)	808	=item aio_rename $srcpath, $dstpath, $callback->($status)
328		809
329	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	810	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
330	rename(2) and call the callback with the result code.	811	rename(2) and call the callback with the result code.
331		812
		813	On systems that support the AIO::WD working directory abstraction
		814	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		815	of failing, C<rename> is called on the absolute path of C<$wd>.
		816
		817
		818	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		819
		820	Basically a version of C<aio_rename> with an additional C<$flags>
		821	argument. Calling this with C<$flags=0> is the same as calling
		822	C<aio_rename>.
		823
		824	Non-zero flags are currently only supported on GNU/Linux systems that
		825	support renameat2. Other systems fail with C<ENOSYS> in this case.
		826
		827	The following constants are available (missing ones are, as usual C<0>),
		828	see renameat2(2) for details:
		829
		830	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		831	and C<IO::AIO::RENAME_WHITEOUT>.
		832
		833
		834	=item aio_mkdir $pathname, $mode, $callback->($status)
		835
		836	Asynchronously mkdir (create) a directory and call the callback with
		837	the result code. C<$mode> will be modified by the umask at the time the
		838	request is executed, so do not change your umask.
		839
		840
332	=item aio_rmdir $pathname, $callback->($status)	841	=item aio_rmdir $pathname, $callback->($status)
333		842
334	Asynchronously rmdir (delete) a directory and call the callback with the	843	Asynchronously rmdir (delete) a directory and call the callback with the
335	result code.	844	result code.
		845
		846	On systems that support the AIO::WD working directory abstraction
		847	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		848	C<rmdir> is called on the absolute path of C<$wd>.
		849
336		850
337	=item aio_readdir $pathname, $callback->($entries)	851	=item aio_readdir $pathname, $callback->($entries)
338		852
339	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	853	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
340	directory (i.e. opendir + readdir + closedir). The entries will not be	854	directory (i.e. opendir + readdir + closedir). The entries will not be
341	sorted, and will B<NOT> include the C<.> and C<..> entries.	855	sorted, and will B<NOT> include the C<.> and C<..> entries.
342		856
343	The callback a single argument which is either C<undef> or an array-ref	857	The callback is passed a single argument which is either C<undef> or an
344	with the filenames.	858	array-ref with the filenames.
345		859
		860
		861	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		862
		863	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		864	tune behaviour and output format. In case of an error, C<$entries> will be
		865	C<undef>.
		866
		867	The flags are a combination of the following constants, ORed together (the
		868	flags will also be passed to the callback, possibly modified):
		869
		870	=over 4
		871
		872	=item IO::AIO::READDIR_DENTS
		873
		874	When this flag is off, then the callback gets an arrayref consisting of
		875	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		876	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		877	entry in more detail.
		878
		879	C<$name> is the name of the entry.
		880
		881	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		882
		883	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		884	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		885	C<IO::AIO::DT_WHT>.
		886
		887	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		888	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		889	scalars are read-only: you can not modify them.
		890
		891	C<$inode> is the inode number (which might not be exact on systems with 64
		892	bit inode numbers and 32 bit perls). This field has unspecified content on
		893	systems that do not deliver the inode information.
		894
		895	=item IO::AIO::READDIR_DIRS_FIRST
		896
		897	When this flag is set, then the names will be returned in an order where
		898	likely directories come first, in optimal stat order. This is useful when
		899	you need to quickly find directories, or you want to find all directories
		900	while avoiding to stat() each entry.
		901
		902	If the system returns type information in readdir, then this is used
		903	to find directories directly. Otherwise, likely directories are names
		904	beginning with ".", or otherwise names with no dots, of which names with
		905	short names are tried first.
		906
		907	=item IO::AIO::READDIR_STAT_ORDER
		908
		909	When this flag is set, then the names will be returned in an order
		910	suitable for stat()'ing each one. That is, when you plan to stat()
		911	all files in the given directory, then the returned order will likely
		912	be fastest.
		913
		914	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		915	the likely dirs come first, resulting in a less optimal stat order.
		916
		917	=item IO::AIO::READDIR_FOUND_UNKNOWN
		918
		919	This flag should not be set when calling C<aio_readdirx>. Instead, it
		920	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		921	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		922	C<$type>'s are known, which can be used to speed up some algorithms.
		923
		924	=back
		925
		926
		927	=item aio_load $pathname, $data, $callback->($status)
		928
		929	This is a composite request that tries to fully load the given file into
		930	memory. Status is the same as with aio_read.
		931
		932	=cut
		933
		934	sub aio_load($$;$) {
		935	my ($path, undef, $cb) = @_;
		936	my $data = \$_[1];
		937
		938	my $pri = aioreq_pri;
		939	my $grp = aio_group $cb;
		940
		941	aioreq_pri $pri;
		942	add $grp aio_open $path, O_RDONLY, 0, sub {
		943	my $fh = shift
		944	or return $grp->result (-1);
		945
		946	aioreq_pri $pri;
		947	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		948	$grp->result ($_[0]);
		949	};
		950	};
		951
		952	$grp
		953	}
		954
		955	=item aio_copy $srcpath, $dstpath, $callback->($status)
		956
		957	Try to copy the I<file> (directories not supported as either source or
		958	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		959	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		960
		961	This is a composite request that creates the destination file with
		962	mode 0200 and copies the contents of the source file into it using
		963	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		964	uid/gid, in that order.
		965
		966	If an error occurs, the partial destination file will be unlinked, if
		967	possible, except when setting atime, mtime, access mode and uid/gid, where
		968	errors are being ignored.
		969
		970	=cut
		971
		972	sub aio_copy($$;$) {
		973	my ($src, $dst, $cb) = @_;
		974
		975	my $pri = aioreq_pri;
		976	my $grp = aio_group $cb;
		977
		978	aioreq_pri $pri;
		979	add $grp aio_open $src, O_RDONLY, 0, sub {
		980	if (my $src_fh = $_[0]) {
		981	my @stat = stat $src_fh; # hmm, might block over nfs?
		982
		983	aioreq_pri $pri;
		984	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		985	if (my $dst_fh = $_[0]) {
		986	aioreq_pri $pri;
		987	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		988	if ($_[0] == $stat[7]) {
		989	$grp->result (0);
		990	close $src_fh;
		991
		992	my $ch = sub {
		993	aioreq_pri $pri;
		994	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		995	aioreq_pri $pri;
		996	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		997	aioreq_pri $pri;
		998	add $grp aio_close $dst_fh;
		999	}
		1000	};
		1001	};
		1002
		1003	aioreq_pri $pri;
		1004	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1005	if ($_[0] < 0 && $! == ENOSYS) {
		1006	aioreq_pri $pri;
		1007	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1008	} else {
		1009	$ch->();
		1010	}
		1011	};
		1012	} else {
		1013	$grp->result (-1);
		1014	close $src_fh;
		1015	close $dst_fh;
		1016
		1017	aioreq $pri;
		1018	add $grp aio_unlink $dst;
		1019	}
		1020	};
		1021	} else {
		1022	$grp->result (-1);
		1023	}
		1024	},
		1025
		1026	} else {
		1027	$grp->result (-1);
		1028	}
		1029	};
		1030
		1031	$grp
		1032	}
		1033
		1034	=item aio_move $srcpath, $dstpath, $callback->($status)
		1035
		1036	Try to move the I<file> (directories not supported as either source or
		1037	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		1038	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		1039
		1040	This is a composite request that tries to rename(2) the file first; if
		1041	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		1042	that is successful, unlinks the C<$srcpath>.
		1043
		1044	=cut
		1045
		1046	sub aio_move($$;$) {
		1047	my ($src, $dst, $cb) = @_;
		1048
		1049	my $pri = aioreq_pri;
		1050	my $grp = aio_group $cb;
		1051
		1052	aioreq_pri $pri;
		1053	add $grp aio_rename $src, $dst, sub {
		1054	if ($_[0] && $! == EXDEV) {
		1055	aioreq_pri $pri;
		1056	add $grp aio_copy $src, $dst, sub {
		1057	$grp->result ($_[0]);
		1058
		1059	unless ($_[0]) {
		1060	aioreq_pri $pri;
		1061	add $grp aio_unlink $src;
		1062	}
		1063	};
		1064	} else {
		1065	$grp->result ($_[0]);
		1066	}
		1067	};
		1068
		1069	$grp
		1070	}
		1071
346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1072	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
347		1073
348	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1074	Scans a directory (similar to C<aio_readdir>) but additionally tries to
349	separate the entries of directory C<$path> into two sets of names, ones	1075	efficiently separate the entries of directory C<$path> into two sets of
350	you can recurse into (directories or links to them), and ones you cannot	1076	names, directories you can recurse into (directories), and ones you cannot
351	recurse into (everything else).	1077	recurse into (everything else, including symlinks to directories).
352		1078
353	C<aio_scandir> is a composite request that consists of many sub	1079	C<aio_scandir> is a composite request that creates of many sub requests_
354	requests. C<$maxreq> specifies the maximum number of outstanding aio	1080	C<$maxreq> specifies the maximum number of outstanding aio requests that
355	requests that this function generates. If it is C<< <= 0 >>, then a	1081	this function generates. If it is C<< <= 0 >>, then a suitable default
356	suitable default will be chosen (currently 8).	1082	will be chosen (currently 4).
357		1083
358	On error, the callback is called without arguments, otherwise it receives	1084	On error, the callback is called without arguments, otherwise it receives
359	two array-refs with path-relative entry names.	1085	two array-refs with path-relative entry names.
360		1086
361	Example:	1087	Example:
…		…
368		1094
369	Implementation notes.	1095	Implementation notes.
370		1096
371	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1097	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
372		1098
		1099	If readdir returns file type information, then this is used directly to
		1100	find directories.
		1101
373	After reading the directory, the modification time, size etc. of the	1102	Otherwise, after reading the directory, the modification time, size etc.
374	directory before and after the readdir is checked, and if they match (and	1103	of the directory before and after the readdir is checked, and if they
375	isn't the current time), the link count will be used to decide how many	1104	match (and isn't the current time), the link count will be used to decide
376	entries are directories (if >= 2). Otherwise, no knowledge of the number	1105	how many entries are directories (if >= 2). Otherwise, no knowledge of the
377	of subdirectories will be assumed.	1106	number of subdirectories will be assumed.
378		1107
379	Then entries will be sorted into likely directories (everything without	1108	Then entries will be sorted into likely directories a non-initial dot
380	a non-initial dot currently) and likely non-directories (everything	1109	currently) and likely non-directories (see C<aio_readdirx>). Then every
381	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1110	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
382	likely directories first. If that succeeds, it assumes that the entry	1111	in order of their inode numbers. If that succeeds, it assumes that the
383	is a directory or a symlink to directory (which will be checked	1112	entry is a directory or a symlink to directory (which will be checked
384	seperately). This is often faster than stat'ing the entry itself because	1113	separately). This is often faster than stat'ing the entry itself because
385	filesystems might detect the type of the entry without reading the inode	1114	filesystems might detect the type of the entry without reading the inode
386	data (e.g. ext2fs filetype feature).	1115	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1116	the filetype information on readdir.
387		1117
388	If the known number of directories (link count - 2) has been reached, the	1118	If the known number of directories (link count - 2) has been reached, the
389	rest of the entries is assumed to be non-directories.	1119	rest of the entries is assumed to be non-directories.
390		1120
391	This only works with certainty on POSIX (= UNIX) filesystems, which	1121	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
395	as those tend to return 0 or 1 as link counts, which disables the	1125	as those tend to return 0 or 1 as link counts, which disables the
396	directory counting heuristic.	1126	directory counting heuristic.
397		1127
398	=cut	1128	=cut
399		1129
400	sub aio_scandir($$$) {	1130	sub aio_scandir($$;$) {
401	my ($path, $maxreq, $cb) = @_;	1131	my ($path, $maxreq, $cb) = @_;
402		1132
		1133	my $pri = aioreq_pri;
		1134
403	my $grp = aio_group;	1135	my $grp = aio_group $cb;
404		1136
405	$maxreq = 8 if $maxreq <= 0;	1137	$maxreq = 4 if $maxreq <= 0;
406		1138
407	# stat once	1139	# get a wd object
		1140	aioreq_pri $pri;
408	add $grp aio_stat $path, sub {	1141	add $grp aio_wd $path, sub {
		1142	$_[0]
		1143	or return $grp->result ();
		1144
		1145	my $wd = [shift, "."];
		1146
		1147	# stat once
		1148	aioreq_pri $pri;
		1149	add $grp aio_stat $wd, sub {
409	return $cb->() if $_[0];	1150	return $grp->result () if $_[0];
410	my $now = time;	1151	my $now = time;
411	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1152	my $hash1 = join ":", (stat _)[0,1,3,7,9];
412		1153
413	# read the directory entries	1154	# read the directory entries
414	add $grp aio_readdir $path, sub {	1155	aioreq_pri $pri;
		1156	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
415	my $entries = shift	1157	my $entries = shift
416	or return $cb->();	1158	or return $grp->result ();
417		1159
418	# stat the dir another time	1160	# stat the dir another time
		1161	aioreq_pri $pri;
419	add $grp aio_stat $path, sub {	1162	add $grp aio_stat $wd, sub {
420	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1163	my $hash2 = join ":", (stat _)[0,1,3,7,9];
421		1164
422	my $ndirs;	1165	my $ndirs;
423		1166
424	# take the slow route if anything looks fishy	1167	# take the slow route if anything looks fishy
425	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1168	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
426	$ndirs = -1;	1169	$ndirs = -1;
427	} else {	1170	} else {
428	# if nlink == 2, we are finished	1171	# if nlink == 2, we are finished
429	# on non-posix-fs's, we rely on nlink < 2	1172	# for non-posix-fs's, we rely on nlink < 2
430	$ndirs = (stat _)[3] - 2	1173	$ndirs = (stat _)[3] - 2
431	or return $cb->([], $entries);	1174	or return $grp->result ([], $entries);
432	}
433
434	# sort into likely dirs and likely nondirs
435	# dirs == files without ".", short entries first
436	$entries = [map $_->[0],
437	sort { $b->[1] cmp $a->[1] }
438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
439	@$entries];
440
441	my (@dirs, @nondirs);
442
443	my ($statcb, $schedcb);
444	my $nreq = 0;
445
446	$schedcb = sub {
447	if (@$entries) {
448	if ($nreq < $maxreq) {
449	my $ent = pop @$entries;
450	$nreq++;
451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
452	}
453	} elsif (!$nreq) {
454	# finished
455	undef $statcb;
456	undef $schedcb;
457	$cb->(\@dirs, \@nondirs) if $cb;
458	undef $cb;
459	}	1175	}
		1176
		1177	my (@dirs, @nondirs);
		1178
		1179	my $statgrp = add $grp aio_group sub {
		1180	$grp->result (\@dirs, \@nondirs);
		1181	};
		1182
		1183	limit $statgrp $maxreq;
		1184	feed $statgrp sub {
		1185	return unless @$entries;
		1186	my $entry = shift @$entries;
		1187
		1188	aioreq_pri $pri;
		1189	$wd->[1] = "$entry/.";
		1190	add $statgrp aio_stat $wd, sub {
		1191	if ($_[0] < 0) {
		1192	push @nondirs, $entry;
		1193	} else {
		1194	# need to check for real directory
		1195	aioreq_pri $pri;
		1196	$wd->[1] = $entry;
		1197	add $statgrp aio_lstat $wd, sub {
		1198	if (-d _) {
		1199	push @dirs, $entry;
		1200
		1201	unless (--$ndirs) {
		1202	push @nondirs, @$entries;
		1203	feed $statgrp;
		1204	}
		1205	} else {
		1206	push @nondirs, $entry;
		1207	}
		1208	}
		1209	}
		1210	};
		1211	};
460	};	1212	};
461	$statcb = sub {
462	my ($status, $entry) = @_;
463
464	if ($status < 0) {
465	$nreq--;
466	push @nondirs, $entry;
467	&$schedcb;
468	} else {
469	# need to check for real directory
470	add $grp aio_lstat "$path/$entry", sub {
471	$nreq--;
472
473	if (-d _) {
474	push @dirs, $entry;
475
476	if (!--$ndirs) {
477	push @nondirs, @$entries;
478	$entries = [];
479	}
480	} else {
481	push @nondirs, $entry;
482	}
483
484	&$schedcb;
485	}
486	}
487	};
488
489	&$schedcb while @$entries && $nreq < $maxreq;
490	};	1213	};
491	};	1214	};
492	};	1215	};
493		1216
494	$grp	1217	$grp
495	}	1218	}
496		1219
		1220	=item aio_rmtree $pathname, $callback->($status)
		1221
		1222	Delete a directory tree starting (and including) C<$path>, return the
		1223	status of the final C<rmdir> only. This is a composite request that
		1224	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1225	everything else.
		1226
		1227	=cut
		1228
		1229	sub aio_rmtree;
		1230	sub aio_rmtree($;$) {
		1231	my ($path, $cb) = @_;
		1232
		1233	my $pri = aioreq_pri;
		1234	my $grp = aio_group $cb;
		1235
		1236	aioreq_pri $pri;
		1237	add $grp aio_scandir $path, 0, sub {
		1238	my ($dirs, $nondirs) = @_;
		1239
		1240	my $dirgrp = aio_group sub {
		1241	add $grp aio_rmdir $path, sub {
		1242	$grp->result ($_[0]);
		1243	};
		1244	};
		1245
		1246	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1247	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1248
		1249	add $grp $dirgrp;
		1250	};
		1251
		1252	$grp
		1253	}
		1254
		1255	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1256
		1257	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1258
		1259	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1260	they execute asynchronously and pass the return value to the callback.
		1261
		1262	Both calls can be used for a lot of things, some of which make more sense
		1263	to run asynchronously in their own thread, while some others make less
		1264	sense. For example, calls that block waiting for external events, such
		1265	as locking, will also lock down an I/O thread while it is waiting, which
		1266	can deadlock the whole I/O system. At the same time, there might be no
		1267	alternative to using a thread to wait.
		1268
		1269	So in general, you should only use these calls for things that do
		1270	(filesystem) I/O, not for things that wait for other events (network,
		1271	other processes), although if you are careful and know what you are doing,
		1272	you still can.
		1273
		1274	The following constants are available (missing ones are, as usual C<0>):
		1275
		1276	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1277
		1278	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1279	C<FS_IOC_FIEMAP>.
		1280
		1281	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1282	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1283
		1284	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1285	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1286	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1287	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1288	C<FS_FL_USER_MODIFIABLE>.
		1289
		1290	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1291	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1292	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1293	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1294
		1295	=item aio_sync $callback->($status)
		1296
		1297	Asynchronously call sync and call the callback when finished.
		1298
497	=item aio_fsync $fh, $callback->($status)	1299	=item aio_fsync $fh, $callback->($status)
498		1300
499	Asynchronously call fsync on the given filehandle and call the callback	1301	Asynchronously call fsync on the given filehandle and call the callback
500	with the fsync result code.	1302	with the fsync result code.
501		1303
…		…
505	callback with the fdatasync result code.	1307	callback with the fdatasync result code.
506		1308
507	If this call isn't available because your OS lacks it or it couldn't be	1309	If this call isn't available because your OS lacks it or it couldn't be
508	detected, it will be emulated by calling C<fsync> instead.	1310	detected, it will be emulated by calling C<fsync> instead.
509		1311
		1312	=item aio_syncfs $fh, $callback->($status)
		1313
		1314	Asynchronously call the syncfs syscall to sync the filesystem associated
		1315	to the given filehandle and call the callback with the syncfs result
		1316	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1317	errno to C<ENOSYS> nevertheless.
		1318
		1319	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1320
		1321	Sync the data portion of the file specified by C<$offset> and C<$length>
		1322	to disk (but NOT the metadata), by calling the Linux-specific
		1323	sync_file_range call. If sync_file_range is not available or it returns
		1324	ENOSYS, then fdatasync or fsync is being substituted.
		1325
		1326	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1327	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1328	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1329	manpage for details.
		1330
		1331	=item aio_pathsync $pathname, $callback->($status)
		1332
		1333	This request tries to open, fsync and close the given path. This is a
		1334	composite request intended to sync directories after directory operations
		1335	(E.g. rename). This might not work on all operating systems or have any
		1336	specific effect, but usually it makes sure that directory changes get
		1337	written to disc. It works for anything that can be opened for read-only,
		1338	not just directories.
		1339
		1340	Future versions of this function might fall back to other methods when
		1341	C<fsync> on the directory fails (such as calling C<sync>).
		1342
		1343	Passes C<0> when everything went ok, and C<-1> on error.
		1344
		1345	=cut
		1346
		1347	sub aio_pathsync($;$) {
		1348	my ($path, $cb) = @_;
		1349
		1350	my $pri = aioreq_pri;
		1351	my $grp = aio_group $cb;
		1352
		1353	aioreq_pri $pri;
		1354	add $grp aio_open $path, O_RDONLY, 0, sub {
		1355	my ($fh) = @_;
		1356	if ($fh) {
		1357	aioreq_pri $pri;
		1358	add $grp aio_fsync $fh, sub {
		1359	$grp->result ($_[0]);
		1360
		1361	aioreq_pri $pri;
		1362	add $grp aio_close $fh;
		1363	};
		1364	} else {
		1365	$grp->result (-1);
		1366	}
		1367	};
		1368
		1369	$grp
		1370	}
		1371
		1372	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1373
		1374	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1375	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1376	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1377	scalar must only be modified in-place while an aio operation is pending on
		1378	it).
		1379
		1380	It calls the C<msync> function of your OS, if available, with the memory
		1381	area starting at C<$offset> in the string and ending C<$length> bytes
		1382	later. If C<$length> is negative, counts from the end, and if C<$length>
		1383	is C<undef>, then it goes till the end of the string. The flags can be
		1384	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1385	C<IO::AIO::MS_INVALIDATE>.
		1386
		1387	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1388
		1389	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1390	scalars.
		1391
		1392	It touches (reads or writes) all memory pages in the specified
		1393	range inside the scalar. All caveats and parameters are the same
		1394	as for C<aio_msync>, above, except for flags, which must be either
		1395	C<0> (which reads all pages and ensures they are instantiated) or
		1396	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1397	writing an octet from it, which dirties the page).
		1398
		1399	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1400
		1401	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1402	scalars.
		1403
		1404	It reads in all the pages of the underlying storage into memory (if any)
		1405	and locks them, so they are not getting swapped/paged out or removed.
		1406
		1407	If C<$length> is undefined, then the scalar will be locked till the end.
		1408
		1409	On systems that do not implement C<mlock>, this function returns C<-1>
		1410	and sets errno to C<ENOSYS>.
		1411
		1412	Note that the corresponding C<munlock> is synchronous and is
		1413	documented under L<MISCELLANEOUS FUNCTIONS>.
		1414
		1415	Example: open a file, mmap and mlock it - both will be undone when
		1416	C<$data> gets destroyed.
		1417
		1418	open my $fh, "<", $path or die "$path: $!";
		1419	my $data;
		1420	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1421	aio_mlock $data; # mlock in background
		1422
		1423	=item aio_mlockall $flags, $callback->($status)
		1424
		1425	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1426	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1427
		1428	On systems that do not implement C<mlockall>, this function returns C<-1>
		1429	and sets errno to C<ENOSYS>.
		1430
		1431	Note that the corresponding C<munlockall> is synchronous and is
		1432	documented under L<MISCELLANEOUS FUNCTIONS>.
		1433
		1434	Example: asynchronously lock all current and future pages into memory.
		1435
		1436	aio_mlockall IO::AIO::MCL_FUTURE;
		1437
		1438	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1439
		1440	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1441	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1442	the ioctl is not available on your OS, then this request will fail with
		1443	C<ENOSYS>.
		1444
		1445	C<$start> is the starting offset to query extents for, C<$length> is the
		1446	size of the range to query - if it is C<undef>, then the whole file will
		1447	be queried.
		1448
		1449	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1450	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1451	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1452	the data portion.
		1453
		1454	C<$count> is the maximum number of extent records to return. If it is
		1455	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1456	case, if it is C<0>, then the callback receives the number of extents
		1457	instead of the extents themselves (which is unreliable, see below).
		1458
		1459	If an error occurs, the callback receives no arguments. The special
		1460	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1461
		1462	Otherwise, the callback receives an array reference with extent
		1463	structures. Each extent structure is an array reference itself, with the
		1464	following members:
		1465
		1466	[$logical, $physical, $length, $flags]
		1467
		1468	Flags is any combination of the following flag values (typically either C<0>
		1469	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1470
		1471	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1472	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1473	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1474	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1475	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1476	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1477
		1478	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1479	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1480	it to return all extents of a range for files with large number of
		1481	extents. The code works around all these issues if C<$count> is undef.
		1482
510	=item aio_group $callback->()	1483	=item aio_group $callback->(...)
511
512	[EXPERIMENTAL]
513		1484
514	This is a very special aio request: Instead of doing something, it is a	1485	This is a very special aio request: Instead of doing something, it is a
515	container for other aio requests, which is useful if you want to bundle	1486	container for other aio requests, which is useful if you want to bundle
516	many requests into a single, composite, request.	1487	many requests into a single, composite, request with a definite callback
		1488	and the ability to cancel the whole request with its subrequests.
517		1489
518	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1490	Returns an object of class L<IO::AIO::GRP>. See its documentation below
519	for more info.	1491	for more info.
520		1492
521	Example:	1493	Example:
…		…
527	add $grp	1499	add $grp
528	(aio_stat ...),	1500	(aio_stat ...),
529	(aio_stat ...),	1501	(aio_stat ...),
530	...;	1502	...;
531		1503
		1504	=item aio_nop $callback->()
		1505
		1506	This is a special request - it does nothing in itself and is only used for
		1507	side effects, such as when you want to add a dummy request to a group so
		1508	that finishing the requests in the group depends on executing the given
		1509	code.
		1510
		1511	While this request does nothing, it still goes through the execution
		1512	phase and still requires a worker thread. Thus, the callback will not
		1513	be executed immediately but only after other requests in the queue have
		1514	entered their execution phase. This can be used to measure request
		1515	latency.
		1516
532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1517	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
533		1518
534	Mainly used for debugging and benchmarking, this aio request puts one of	1519	Mainly used for debugging and benchmarking, this aio request puts one of
535	the request workers to sleep for the given time.	1520	the request workers to sleep for the given time.
536		1521
537	While it is theoretically handy to have simple I/O scheduling requests	1522	While it is theoretically handy to have simple I/O scheduling requests
538	like sleep and file handle readable/writable, the overhead this creates	1523	like sleep and file handle readable/writable, the overhead this creates is
539	is immense, so do not use this function except to put your application	1524	immense (it blocks a thread for a long time) so do not use this function
540	under artificial I/O pressure.	1525	except to put your application under artificial I/O pressure.
541		1526
542	=back	1527	=back
		1528
		1529
		1530	=head2 IO::AIO::WD - multiple working directories
		1531
		1532	Your process only has one current working directory, which is used by all
		1533	threads. This makes it hard to use relative paths (some other component
		1534	could call C<chdir> at any time, and it is hard to control when the path
		1535	will be used by IO::AIO).
		1536
		1537	One solution for this is to always use absolute paths. This usually works,
		1538	but can be quite slow (the kernel has to walk the whole path on every
		1539	access), and can also be a hassle to implement.
		1540
		1541	Newer POSIX systems have a number of functions (openat, fdopendir,
		1542	futimensat and so on) that make it possible to specify working directories
		1543	per operation.
		1544
		1545	For portability, and because the clowns who "designed", or shall I write,
		1546	perpetrated this new interface were obviously half-drunk, this abstraction
		1547	cannot be perfect, though.
		1548
		1549	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1550	object. This object stores the canonicalised, absolute version of the
		1551	path, and on systems that allow it, also a directory file descriptor.
		1552
		1553	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1554	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1555	object and a pathname instead (or the IO::AIO::WD object alone, which
		1556	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1557	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1558	to that IO::AIO::WD object.
		1559
		1560	For example, to get a wd object for F</etc> and then stat F<passwd>
		1561	inside, you would write:
		1562
		1563	aio_wd "/etc", sub {
		1564	my $etcdir = shift;
		1565
		1566	# although $etcdir can be undef on error, there is generally no reason
		1567	# to check for errors here, as aio_stat will fail with ENOENT
		1568	# when $etcdir is undef.
		1569
		1570	aio_stat [$etcdir, "passwd"], sub {
		1571	# yay
		1572	};
		1573	};
		1574
		1575	The fact that C<aio_wd> is a request and not a normal function shows that
		1576	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1577	which is why it is done asynchronously.
		1578
		1579	To stat the directory obtained with C<aio_wd> above, one could write
		1580	either of the following three request calls:
		1581
		1582	aio_lstat "/etc" , sub { ... # pathname as normal string
		1583	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1584	aio_lstat $wd , sub { ... # shorthand for the previous
		1585
		1586	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1587	object and the pathname string, so you could write the following without
		1588	causing any issues due to C<$path> getting reused:
		1589
		1590	my $path = [$wd, undef];
		1591
		1592	for my $name (qw(abc def ghi)) {
		1593	$path->[1] = $name;
		1594	aio_stat $path, sub {
		1595	# ...
		1596	};
		1597	}
		1598
		1599	There are some caveats: when directories get renamed (or deleted), the
		1600	pathname string doesn't change, so will point to the new directory (or
		1601	nowhere at all), while the directory fd, if available on the system,
		1602	will still point to the original directory. Most functions accepting a
		1603	pathname will use the directory fd on newer systems, and the string on
		1604	older systems. Some functions (such as realpath) will always rely on the
		1605	string form of the pathname.
		1606
		1607	So this functionality is mainly useful to get some protection against
		1608	C<chdir>, to easily get an absolute path out of a relative path for future
		1609	reference, and to speed up doing many operations in the same directory
		1610	(e.g. when stat'ing all files in a directory).
		1611
		1612	The following functions implement this working directory abstraction:
		1613
		1614	=over 4
		1615
		1616	=item aio_wd $pathname, $callback->($wd)
		1617
		1618	Asynchonously canonicalise the given pathname and convert it to an
		1619	IO::AIO::WD object representing it. If possible and supported on the
		1620	system, also open a directory fd to speed up pathname resolution relative
		1621	to this working directory.
		1622
		1623	If something goes wrong, then C<undef> is passwd to the callback instead
		1624	of a working directory object and C<$!> is set appropriately. Since
		1625	passing C<undef> as working directory component of a pathname fails the
		1626	request with C<ENOENT>, there is often no need for error checking in the
		1627	C<aio_wd> callback, as future requests using the value will fail in the
		1628	expected way.
		1629
		1630	=item IO::AIO::CWD
		1631
		1632	This is a compiletime constant (object) that represents the process
		1633	current working directory.
		1634
		1635	Specifying this object as working directory object for a pathname is as if
		1636	the pathname would be specified directly, without a directory object. For
		1637	example, these calls are functionally identical:
		1638
		1639	aio_stat "somefile", sub { ... };
		1640	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1641
		1642	=back
		1643
		1644	To recover the path associated with an IO::AIO::WD object, you can use
		1645	C<aio_realpath>:
		1646
		1647	aio_realpath $wd, sub {
		1648	warn "path is $_[0]\n";
		1649	};
		1650
		1651	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1652	sometimes, fall back to using an absolue path.
543		1653
544	=head2 IO::AIO::REQ CLASS	1654	=head2 IO::AIO::REQ CLASS
545		1655
546	All non-aggregate C<aio_*> functions return an object of this class when	1656	All non-aggregate C<aio_*> functions return an object of this class when
547	called in non-void context.	1657	called in non-void context.
548		1658
549	A request always moves through the following five states in its lifetime,
550	in order: B<ready> (request has been created, but has not been executed
551	yet), B<execute> (request is currently being executed), B<pending>
552	(request has been executed but callback has not been called yet),
553	B<result> (results are being processed synchronously, includes calling the
554	callback) and B<done> (request has reached the end of its lifetime and
555	holds no resources anymore).
556
557	=over 4	1659	=over 4
558		1660
559	=item $req->cancel	1661	=item cancel $req
560		1662
561	Cancels the request, if possible. Has the effect of skipping execution	1663	Cancels the request, if possible. Has the effect of skipping execution
562	when entering the B<execute> state and skipping calling the callback when	1664	when entering the B<execute> state and skipping calling the callback when
563	entering the the B<result> state, but will leave the request otherwise	1665	entering the the B<result> state, but will leave the request otherwise
564	untouched. That means that requests that currently execute will not be	1666	untouched (with the exception of readdir). That means that requests that
565	stopped and resources held by the request will not be freed prematurely.	1667	currently execute will not be stopped and resources held by the request
		1668	will not be freed prematurely.
		1669
		1670	=item cb $req $callback->(...)
		1671
		1672	Replace (or simply set) the callback registered to the request.
566		1673
567	=back	1674	=back
568		1675
569	=head2 IO::AIO::GRP CLASS	1676	=head2 IO::AIO::GRP CLASS
570		1677
…		…
585	You add requests by calling the C<add> method with one or more	1692	You add requests by calling the C<add> method with one or more
586	C<IO::AIO::REQ> objects:	1693	C<IO::AIO::REQ> objects:
587		1694
588	$grp->add (aio_unlink "...");	1695	$grp->add (aio_unlink "...");
589		1696
590	add $grp aio_stat "...", sub { ... };	1697	add $grp aio_stat "...", sub {
		1698	$_[0] or return $grp->result ("error");
		1699
		1700	# add another request dynamically, if first succeeded
		1701	add $grp aio_open "...", sub {
		1702	$grp->result ("ok");
		1703	};
		1704	};
591		1705
592	This makes it very easy to create composite requests (see the source of	1706	This makes it very easy to create composite requests (see the source of
593	C<aio_move> for an application) that work and feel like simple requests.	1707	C<aio_move> for an application) that work and feel like simple requests.
594		1708
		1709	=over 4
		1710
595	The IO::AIO::GRP objects will be cleaned up during calls to	1711	=item * The IO::AIO::GRP objects will be cleaned up during calls to
596	C<IO::AIO::poll_cb>, just like any other request.	1712	C<IO::AIO::poll_cb>, just like any other request.
597		1713
598	They can be canceled like any other request. Canceling will cancel not	1714	=item * They can be canceled like any other request. Canceling will cancel not
599	just the request itself, but also all requests it contains.	1715	only the request itself, but also all requests it contains.
600		1716
601	They can also can also be added to other IO::AIO::GRP objects.	1717	=item * They can also can also be added to other IO::AIO::GRP objects.
		1718
		1719	=item * You must not add requests to a group from within the group callback (or
		1720	any later time).
		1721
		1722	=back
602		1723
603	Their lifetime, simplified, looks like this: when they are empty, they	1724	Their lifetime, simplified, looks like this: when they are empty, they
604	will finish very quickly. If they contain only requests that are in the	1725	will finish very quickly. If they contain only requests that are in the
605	C<done> state, they will also finish. Otherwise they will continue to	1726	C<done> state, they will also finish. Otherwise they will continue to
606	exist.	1727	exist.
607		1728
608	That means after creating a group you have some time to add requests. And	1729	That means after creating a group you have some time to add requests
609	in the callbacks of those requests, you can add further requests to the	1730	(precisely before the callback has been invoked, which is only done within
610	group. And only when all those requests have finished will the the group	1731	the C<poll_cb>). And in the callbacks of those requests, you can add
611	itself finish.	1732	further requests to the group. And only when all those requests have
		1733	finished will the the group itself finish.
612		1734
613	=over 4	1735	=over 4
614		1736
		1737	=item add $grp ...
		1738
615	=item $grp->add (...)	1739	=item $grp->add (...)
616
617	=item add $grp ...
618		1740
619	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1741	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
620	be added, including other groups, as long as you do not create circular	1742	be added, including other groups, as long as you do not create circular
621	dependencies.	1743	dependencies.
622		1744
623	Returns all its arguments.	1745	Returns all its arguments.
624		1746
		1747	=item $grp->cancel_subs
		1748
		1749	Cancel all subrequests and clears any feeder, but not the group request
		1750	itself. Useful when you queued a lot of events but got a result early.
		1751
		1752	The group request will finish normally (you cannot add requests to the
		1753	group).
		1754
		1755	=item $grp->result (...)
		1756
		1757	Set the result value(s) that will be passed to the group callback when all
		1758	subrequests have finished and set the groups errno to the current value
		1759	of errno (just like calling C<errno> without an error number). By default,
		1760	no argument will be passed and errno is zero.
		1761
		1762	=item $grp->errno ([$errno])
		1763
		1764	Sets the group errno value to C<$errno>, or the current value of errno
		1765	when the argument is missing.
		1766
		1767	Every aio request has an associated errno value that is restored when
		1768	the callback is invoked. This method lets you change this value from its
		1769	default (0).
		1770
		1771	Calling C<result> will also set errno, so make sure you either set C<$!>
		1772	before the call to C<result>, or call c<errno> after it.
		1773
		1774	=item feed $grp $callback->($grp)
		1775
		1776	Sets a feeder/generator on this group: every group can have an attached
		1777	generator that generates requests if idle. The idea behind this is that,
		1778	although you could just queue as many requests as you want in a group,
		1779	this might starve other requests for a potentially long time. For example,
		1780	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
		1781	requests, delaying any later requests for a long time.
		1782
		1783	To avoid this, and allow incremental generation of requests, you can
		1784	instead a group and set a feeder on it that generates those requests. The
		1785	feed callback will be called whenever there are few enough (see C<limit>,
		1786	below) requests active in the group itself and is expected to queue more
		1787	requests.
		1788
		1789	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1790	not impose any limits).
		1791
		1792	If the feed does not queue more requests when called, it will be
		1793	automatically removed from the group.
		1794
		1795	If the feed limit is C<0> when this method is called, it will be set to
		1796	C<2> automatically.
		1797
		1798	Example:
		1799
		1800	# stat all files in @files, but only ever use four aio requests concurrently:
		1801
		1802	my $grp = aio_group sub { print "finished\n" };
		1803	limit $grp 4;
		1804	feed $grp sub {
		1805	my $file = pop @files
		1806	or return;
		1807
		1808	add $grp aio_stat $file, sub { ... };
		1809	};
		1810
		1811	=item limit $grp $num
		1812
		1813	Sets the feeder limit for the group: The feeder will be called whenever
		1814	the group contains less than this many requests.
		1815
		1816	Setting the limit to C<0> will pause the feeding process.
		1817
		1818	The default value for the limit is C<0>, but note that setting a feeder
		1819	automatically bumps it up to C<2>.
		1820
625	=back	1821	=back
626		1822
627	=head2 SUPPORT FUNCTIONS	1823	=head2 SUPPORT FUNCTIONS
628		1824
		1825	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1826
629	=over 4	1827	=over 4
630		1828
631	=item $fileno = IO::AIO::poll_fileno	1829	=item $fileno = IO::AIO::poll_fileno
632		1830
633	Return the I<request result pipe file descriptor>. This filehandle must be	1831	Return the I<request result pipe file descriptor>. This filehandle must be
634	polled for reading by some mechanism outside this module (e.g. Event or	1832	polled for reading by some mechanism outside this module (e.g. EV, Glib,
635	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1833	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
636	to call C<poll_cb> to check the results.	1834	you have to call C<poll_cb> to check the results.
637		1835
638	See C<poll_cb> for an example.	1836	See C<poll_cb> for an example.
639		1837
640	=item IO::AIO::poll_cb	1838	=item IO::AIO::poll_cb
641		1839
642	Process all outstanding events on the result pipe. You have to call this	1840	Process some requests that have reached the result phase (i.e. they have
643	regularly. Returns the number of events processed. Returns immediately	1841	been executed but the results are not yet reported). You have to call
644	when no events are outstanding.	1842	this "regularly" to finish outstanding requests.
		1843
		1844	Returns C<0> if all events could be processed (or there were no
		1845	events to process), or C<-1> if it returned earlier for whatever
		1846	reason. Returns immediately when no events are outstanding. The amount
		1847	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1848	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1849
		1850	If not all requests were processed for whatever reason, the poll file
		1851	descriptor will still be ready when C<poll_cb> returns, so normally you
		1852	don't have to do anything special to have it called later.
		1853
		1854	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1855	ready, it can be beneficial to call this function from loops which submit
		1856	a lot of requests, to make sure the results get processed when they become
		1857	available and not just when the loop is finished and the event loop takes
		1858	over again. This function returns very fast when there are no outstanding
		1859	requests.
645		1860
646	Example: Install an Event watcher that automatically calls	1861	Example: Install an Event watcher that automatically calls
647	IO::AIO::poll_cb with high priority:	1862	IO::AIO::poll_cb with high priority (more examples can be found in the
		1863	SYNOPSIS section, at the top of this document):
648		1864
649	Event->io (fd => IO::AIO::poll_fileno,	1865	Event->io (fd => IO::AIO::poll_fileno,
650	poll => 'r', async => 1,	1866	poll => 'r', async => 1,
651	cb => \&IO::AIO::poll_cb);	1867	cb => \&IO::AIO::poll_cb);
652		1868
653	=item IO::AIO::poll_wait	1869	=item IO::AIO::poll_wait
654		1870
655	Wait till the result filehandle becomes ready for reading (simply does a	1871	Wait until either at least one request is in the result phase or no
656	C<select> on the filehandle. This is useful if you want to synchronously wait	1872	requests are outstanding anymore.
657	for some requests to finish).	1873
		1874	This is useful if you want to synchronously wait for some requests to
		1875	become ready, without actually handling them.
658		1876
659	See C<nreqs> for an example.	1877	See C<nreqs> for an example.
660		1878
		1879	=item IO::AIO::poll
		1880
		1881	Waits until some requests have been handled.
		1882
		1883	Returns the number of requests processed, but is otherwise strictly
		1884	equivalent to:
		1885
		1886	IO::AIO::poll_wait, IO::AIO::poll_cb
		1887
661	=item IO::AIO::nreqs	1888	=item IO::AIO::flush
662		1889
663	Returns the number of requests currently outstanding (i.e. for which their	1890	Wait till all outstanding AIO requests have been handled.
664	callback has not been invoked yet).
665		1891
666	Example: wait till there are no outstanding requests anymore:	1892	Strictly equivalent to:
667		1893
668	IO::AIO::poll_wait, IO::AIO::poll_cb	1894	IO::AIO::poll_wait, IO::AIO::poll_cb
669	while IO::AIO::nreqs;	1895	while IO::AIO::nreqs;
670		1896
671	=item IO::AIO::flush	1897	=item IO::AIO::max_poll_reqs $nreqs
672		1898
673	Wait till all outstanding AIO requests have been handled.	1899	=item IO::AIO::max_poll_time $seconds
674		1900
675	Strictly equivalent to:	1901	These set the maximum number of requests (default C<0>, meaning infinity)
		1902	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1903	the maximum amount of time (default C<0>, meaning infinity) spent in
		1904	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1905	of time C<poll_cb> is allowed to use).
676		1906
677	IO::AIO::poll_wait, IO::AIO::poll_cb	1907	Setting C<max_poll_time> to a non-zero value creates an overhead of one
678	while IO::AIO::nreqs;	1908	syscall per request processed, which is not normally a problem unless your
		1909	callbacks are really really fast or your OS is really really slow (I am
		1910	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
679		1911
680	=item IO::AIO::poll	1912	Setting these is useful if you want to ensure some level of
		1913	interactiveness when perl is not fast enough to process all requests in
		1914	time.
681		1915
682	Waits until some requests have been handled.	1916	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
683		1917
684	Strictly equivalent to:	1918	Example: Install an Event watcher that automatically calls
		1919	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1920	program get the CPU sometimes even under high AIO load.
685		1921
686	IO::AIO::poll_wait, IO::AIO::poll_cb	1922	# try not to spend much more than 0.1s in poll_cb
687	if IO::AIO::nreqs;	1923	IO::AIO::max_poll_time 0.1;
		1924
		1925	# use a low priority so other tasks have priority
		1926	Event->io (fd => IO::AIO::poll_fileno,
		1927	poll => 'r', nice => 1,
		1928	cb => &IO::AIO::poll_cb);
		1929
		1930	=back
		1931
		1932	=head3 CONTROLLING THE NUMBER OF THREADS
		1933
		1934	=over
688		1935
689	=item IO::AIO::min_parallel $nthreads	1936	=item IO::AIO::min_parallel $nthreads
690		1937
691	Set the minimum number of AIO threads to C<$nthreads>. The current default	1938	Set the minimum number of AIO threads to C<$nthreads>. The current
692	is C<4>, which means four asynchronous operations can be done at one time	1939	default is C<8>, which means eight asynchronous operations can execute
693	(the number of outstanding operations, however, is unlimited).	1940	concurrently at any one time (the number of outstanding requests,
		1941	however, is unlimited).
694		1942
695	IO::AIO starts threads only on demand, when an AIO request is queued and	1943	IO::AIO starts threads only on demand, when an AIO request is queued and
696	no free thread exists.	1944	no free thread exists. Please note that queueing up a hundred requests can
		1945	create demand for a hundred threads, even if it turns out that everything
		1946	is in the cache and could have been processed faster by a single thread.
697		1947
698	It is recommended to keep the number of threads low, as some Linux	1948	It is recommended to keep the number of threads relatively low, as some
699	kernel versions will scale negatively with the number of threads (higher	1949	Linux kernel versions will scale negatively with the number of threads
700	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1950	(higher parallelity => MUCH higher latency). With current Linux 2.6
701	threads should be fine.	1951	versions, 4-32 threads should be fine.
702		1952
703	Under most circumstances you don't need to call this function, as the	1953	Under most circumstances you don't need to call this function, as the
704	module selects a default that is suitable for low to moderate load.	1954	module selects a default that is suitable for low to moderate load.
705		1955
706	=item IO::AIO::max_parallel $nthreads	1956	=item IO::AIO::max_parallel $nthreads
…		…
715	This module automatically runs C<max_parallel 0> at program end, to ensure	1965	This module automatically runs C<max_parallel 0> at program end, to ensure
716	that all threads are killed and that there are no outstanding requests.	1966	that all threads are killed and that there are no outstanding requests.
717		1967
718	Under normal circumstances you don't need to call this function.	1968	Under normal circumstances you don't need to call this function.
719		1969
		1970	=item IO::AIO::max_idle $nthreads
		1971
		1972	Limit the number of threads (default: 4) that are allowed to idle
		1973	(i.e., threads that did not get a request to process within the idle
		1974	timeout (default: 10 seconds). That means if a thread becomes idle while
		1975	C<$nthreads> other threads are also idle, it will free its resources and
		1976	exit.
		1977
		1978	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1979	to allow for extremely high load situations, but want to free resources
		1980	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1981
		1982	The default is probably ok in most situations, especially if thread
		1983	creation is fast. If thread creation is very slow on your system you might
		1984	want to use larger values.
		1985
		1986	=item IO::AIO::idle_timeout $seconds
		1987
		1988	Sets the minimum idle timeout (default 10) after which worker threads are
		1989	allowed to exit. SEe C<IO::AIO::max_idle>.
		1990
720	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1991	=item IO::AIO::max_outstanding $maxreqs
721		1992
722	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1993	Sets the maximum number of outstanding requests to C<$nreqs>. If
723	try to queue up more than this number of requests, the caller will block until	1994	you do queue up more than this number of requests, the next call to
724	some requests have been handled.	1995	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1996	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1997	longer exceeded.
725		1998
726	The default is very large, so normally there is no practical limit. If you	1999	In other words, this setting does not enforce a queue limit, but can be
727	queue up many requests in a loop it often improves speed if you set	2000	used to make poll functions block if the limit is exceeded.
728	this to a relatively low number, such as C<100>.
729		2001
730	Under normal circumstances you don't need to call this function.	2002	This is a very bad function to use in interactive programs because it
		2003	blocks, and a bad way to reduce concurrency because it is inexact: Better
		2004	use an C<aio_group> together with a feed callback.
		2005
		2006	Its main use is in scripts without an event loop - when you want to stat
		2007	a lot of files, you can write somehting like this:
		2008
		2009	IO::AIO::max_outstanding 32;
		2010
		2011	for my $path (...) {
		2012	aio_stat $path , ...;
		2013	IO::AIO::poll_cb;
		2014	}
		2015
		2016	IO::AIO::flush;
		2017
		2018	The call to C<poll_cb> inside the loop will normally return instantly, but
		2019	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2020	some requests have been handled. This keeps the loop from pushing a large
		2021	number of C<aio_stat> requests onto the queue.
		2022
		2023	The default value for C<max_outstanding> is very large, so there is no
		2024	practical limit on the number of outstanding requests.
731		2025
732	=back	2026	=back
733		2027
		2028	=head3 STATISTICAL INFORMATION
		2029
		2030	=over
		2031
		2032	=item IO::AIO::nreqs
		2033
		2034	Returns the number of requests currently in the ready, execute or pending
		2035	states (i.e. for which their callback has not been invoked yet).
		2036
		2037	Example: wait till there are no outstanding requests anymore:
		2038
		2039	IO::AIO::poll_wait, IO::AIO::poll_cb
		2040	while IO::AIO::nreqs;
		2041
		2042	=item IO::AIO::nready
		2043
		2044	Returns the number of requests currently in the ready state (not yet
		2045	executed).
		2046
		2047	=item IO::AIO::npending
		2048
		2049	Returns the number of requests currently in the pending state (executed,
		2050	but not yet processed by poll_cb).
		2051
		2052	=back
		2053
		2054	=head3 MISCELLANEOUS FUNCTIONS
		2055
		2056	IO::AIO implements some functions that are useful when you want to use
		2057	some "Advanced I/O" function not available to in Perl, without going the
		2058	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2059	counterpart.
		2060
		2061	=over 4
		2062
		2063	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2064
		2065	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2066	but is blocking (this makes most sense if you know the input data is
		2067	likely cached already and the output filehandle is set to non-blocking
		2068	operations).
		2069
		2070	Returns the number of bytes copied, or C<-1> on error.
		2071
		2072	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2073
		2074	Simply calls the C<posix_fadvise> function (see its
		2075	manpage for details). The following advice constants are
		2076	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2077	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2078	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2079
		2080	On systems that do not implement C<posix_fadvise>, this function returns
		2081	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2082
		2083	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2084
		2085	Simply calls the C<posix_madvise> function (see its
		2086	manpage for details). The following advice constants are
		2087	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2088	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>,
		2089	C<IO::AIO::MADV_FREE>.
		2090
		2091	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2092	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2093	will be reduced to fit into the C<$scalar>.
		2094
		2095	On systems that do not implement C<posix_madvise>, this function returns
		2096	ENOSYS, otherwise the return value of C<posix_madvise>.
		2097
		2098	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2099
		2100	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2101	$scalar (see its manpage for details). The following protect
		2102	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2103	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2104
		2105	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2106	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2107	will be reduced to fit into the C<$scalar>.
		2108
		2109	On systems that do not implement C<mprotect>, this function returns
		2110	ENOSYS, otherwise the return value of C<mprotect>.
		2111
		2112	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2113
		2114	Memory-maps a file (or anonymous memory range) and attaches it to the
		2115	given C<$scalar>, which will act like a string scalar. Returns true on
		2116	success, and false otherwise.
		2117
		2118	The scalar must exist, but its contents do not matter - this means you
		2119	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2120	the scalar first.
		2121
		2122	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2123	which don't change the string length, and most read-only operations such
		2124	as copying it or searching it with regexes and so on.
		2125
		2126	Anything else is unsafe and will, at best, result in memory leaks.
		2127
		2128	The memory map associated with the C<$scalar> is automatically removed
		2129	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2130	or C<IO::AIO::munmap> functions are called on it.
		2131
		2132	This calls the C<mmap>(2) function internally. See your system's manual
		2133	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2134
		2135	The C<$length> must be larger than zero and smaller than the actual
		2136	filesize.
		2137
		2138	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2139	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2140
		2141	C<$flags> can be a combination of
		2142	C<IO::AIO::MAP_SHARED> or
		2143	C<IO::AIO::MAP_PRIVATE>,
		2144	or a number of system-specific flags (when not available, the are C<0>):
		2145	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2146	C<IO::AIO::MAP_LOCKED>,
		2147	C<IO::AIO::MAP_NORESERVE>,
		2148	C<IO::AIO::MAP_POPULATE>,
		2149	C<IO::AIO::MAP_NONBLOCK>,
		2150	C<IO::AIO::MAP_FIXED>,
		2151	C<IO::AIO::MAP_GROWSDOWN>,
		2152	C<IO::AIO::MAP_32BIT>,
		2153	C<IO::AIO::MAP_HUGETLB> or
		2154	C<IO::AIO::MAP_STACK>.
		2155
		2156	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2157
		2158	C<$offset> is the offset from the start of the file - it generally must be
		2159	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2160
		2161	Example:
		2162
		2163	use Digest::MD5;
		2164	use IO::AIO;
		2165
		2166	open my $fh, "<verybigfile"
		2167	or die "$!";
		2168
		2169	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2170	or die "verybigfile: $!";
		2171
		2172	my $fast_md5 = md5 $data;
		2173
		2174	=item IO::AIO::munmap $scalar
		2175
		2176	Removes a previous mmap and undefines the C<$scalar>.
		2177
		2178	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2179
		2180	Calls the C<munlock> function, undoing the effects of a previous
		2181	C<aio_mlock> call (see its description for details).
		2182
		2183	=item IO::AIO::munlockall
		2184
		2185	Calls the C<munlockall> function.
		2186
		2187	On systems that do not implement C<munlockall>, this function returns
		2188	ENOSYS, otherwise the return value of C<munlockall>.
		2189
		2190	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2191
		2192	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2193	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2194	should be the file offset.
		2195
		2196	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2197	silently corrupt the data in this case.
		2198
		2199	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2200	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2201	C<IO::AIO::SPLICE_F_GIFT>.
		2202
		2203	See the C<splice(2)> manpage for details.
		2204
		2205	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2206
		2207	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2208	description for C<IO::AIO::splice> above for details.
		2209
		2210	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2211
		2212	Attempts to query or change the pipe buffer size. Obviously works only
		2213	on pipes, and currently works only on GNU/Linux systems, and fails with
		2214	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2215	size on other systems, drop me a note.
		2216
		2217	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2218
		2219	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2220	C<$flags> is missing or C<0>, then this should be the same as a call to
		2221	perl's built-in C<pipe> function and create a new pipe, and works on
		2222	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2223	(..., 4096, O_BINARY)>.
		2224
		2225	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2226	the given flags (Linux 2.6.27, glibc 2.9).
		2227
		2228	On success, the read and write file handles are returned.
		2229
		2230	On error, nothing will be returned. If the pipe2 syscall is missing and
		2231	C<$flags> is non-zero, fails with C<ENOSYS>.
		2232
		2233	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2234	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2235	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2236
		2237	=back
		2238
734	=cut	2239	=cut
735		2240
736	# support function to convert a fd into a perl filehandle
737	sub _fd2fh {
738	return undef if $_[0] < 0;
739
740	# try to generate nice filehandles
741	my $sym = "IO::AIO::fd#$_[0]";
742	local *$sym;
743
744	open *$sym, "+<&=$_[0]" # usually works under any unix
745	or open *$sym, "<&=$_[0]" # cygwin needs this
746	or open *$sym, ">&=$_[0]" # or this
747	or return undef;
748
749	*$sym
750	}
751
752	min_parallel 4;	2241	min_parallel 8;
753		2242
754	END {	2243	END { flush }
755	max_parallel 0;
756	}
757		2244
758	1;	2245	1;
759		2246
		2247	=head1 EVENT LOOP INTEGRATION
		2248
		2249	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2250	automatically into many event loops:
		2251
		2252	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2253	use AnyEvent::AIO;
		2254
		2255	You can also integrate IO::AIO manually into many event loops, here are
		2256	some examples of how to do this:
		2257
		2258	# EV integration
		2259	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2260
		2261	# Event integration
		2262	Event->io (fd => IO::AIO::poll_fileno,
		2263	poll => 'r',
		2264	cb => \&IO::AIO::poll_cb);
		2265
		2266	# Glib/Gtk2 integration
		2267	add_watch Glib::IO IO::AIO::poll_fileno,
		2268	in => sub { IO::AIO::poll_cb; 1 };
		2269
		2270	# Tk integration
		2271	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2272	readable => \&IO::AIO::poll_cb);
		2273
		2274	# Danga::Socket integration
		2275	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2276	\&IO::AIO::poll_cb);
		2277
760	=head2 FORK BEHAVIOUR	2278	=head2 FORK BEHAVIOUR
761		2279
762	This module should do "the right thing" when the process using it forks:	2280	Usage of pthreads in a program changes the semantics of fork
		2281	considerably. Specifically, only async-safe functions can be called after
		2282	fork. Perl doesn't know about this, so in general, you cannot call fork
		2283	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2284	pthreads, so this applies, but many other extensions and (for inexplicable
		2285	reasons) perl itself often is linked against pthreads, so this limitation
		2286	applies to quite a lot of perls.
763		2287
764	Before the fork, IO::AIO enters a quiescent state where no requests	2288	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
765	can be added in other threads and no results will be processed. After	2289	only works in the process that loaded it. Forking is fully supported, but
766	the fork the parent simply leaves the quiescent state and continues	2290	using IO::AIO in the child is not.
767	request/result processing, while the child clears the request/result
768	queue (so the requests started before the fork will only be handled in
769	the parent). Threads will be started on demand until the limit ste in the
770	parent process has been reached again.
771		2291
772	In short: the parent will, after a short pause, continue as if fork had	2292	You might get around by not I<using> IO::AIO before (or after)
773	not been called, while the child will act as if IO::AIO has not been used	2293	forking. You could also try to call the L<IO::AIO::reinit> function in the
774	yet.	2294	child:
		2295
		2296	=over 4
		2297
		2298	=item IO::AIO::reinit
		2299
		2300	Abandons all current requests and I/O threads and simply reinitialises all
		2301	data structures. This is not an operation supported by any standards, but
		2302	happens to work on GNU/Linux and some newer BSD systems.
		2303
		2304	The only reasonable use for this function is to call it after forking, if
		2305	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2306	the process will result in undefined behaviour. Calling it at any time
		2307	will also result in any undefined (by POSIX) behaviour.
		2308
		2309	=back
		2310
		2311	=head2 MEMORY USAGE
		2312
		2313	Per-request usage:
		2314
		2315	Each aio request uses - depending on your architecture - around 100-200
		2316	bytes of memory. In addition, stat requests need a stat buffer (possibly
		2317	a few hundred bytes), readdir requires a result buffer and so on. Perl
		2318	scalars and other data passed into aio requests will also be locked and
		2319	will consume memory till the request has entered the done state.
		2320
		2321	This is not awfully much, so queuing lots of requests is not usually a
		2322	problem.
		2323
		2324	Per-thread usage:
		2325
		2326	In the execution phase, some aio requests require more memory for
		2327	temporary buffers, and each thread requires a stack and other data
		2328	structures (usually around 16k-128k, depending on the OS).
		2329
		2330	=head1 KNOWN BUGS
		2331
		2332	Known bugs will be fixed in the next release.
775		2333
776	=head1 SEE ALSO	2334	=head1 SEE ALSO
777		2335
778	L<Coro>, L<Linux::AIO> (obsolete).	2336	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2337	more natural syntax.
779		2338
780	=head1 AUTHOR	2339	=head1 AUTHOR
781		2340
782	Marc Lehmann <schmorp@schmorp.de>	2341	Marc Lehmann <schmorp@schmorp.de>
783	http://home.schmorp.de/	2342	http://home.schmorp.de/

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