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Revision 1.65 by root, Mon Oct 23 14:49:51 2006 UTC vs.
Revision 1.282 by root, Tue Feb 20 05:23:47 2018 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 = 4.4;
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
		188	aio_slurp
84	aio_group aio_nop);	189	aio_wd);
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	190
		191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		193	min_parallel max_parallel max_idle idle_timeout
		194	nreqs nready npending nthreads
		195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap munlock munlockall);
		198
		199	push @AIO_REQ, qw(aio_busy); # not exported
86		200
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		202
89	require XSLoader;	203	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
91	}	205	}
92		206
93	=head1 FUNCTIONS	207	=head1 FUNCTIONS
94		208
95	=head2 AIO FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		285
		286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::madvise $scalar, $offset, $length, $advice
		291	IO::AIO::mprotect $scalar, $offset, $length, $protect
		292	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		293	IO::AIO::munlockall
		294
		295	=head2 API NOTES
96		296
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	297	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	298	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	299	and they all accept an additional (and optional) C<$callback> argument
100	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
101	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
102	perl, which usually delivers "false") as it's sole argument when the given	302	of the request will be passed as arguments to the callback (and, if an
103	syscall has been executed asynchronously.	303	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		304	most syscalls return C<-1> on error, unlike perl, which usually delivers
		305	"false").
		306
		307	Some requests (such as C<aio_readdir>) pass the actual results and
		308	communicate failures by passing C<undef>.
104		309
105	All functions expecting a filehandle keep a copy of the filehandle	310	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	311	internally until the request has finished.
107		312
108	All requests return objects of type L<IO::AIO::REQ> that allow further	313	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	314	further manipulation of those requests while they are in-flight.
110		315
111	The pathnames you pass to these routines I<must> be absolute and	316	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	317	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	318	current working directory could have changed. Alternatively, you can
114	changed. Alternatively, you can make sure that you never change the	319	make sure that you never change the current working directory anywhere
115	current working directory.	320	in the program and then use relative paths. You can also take advantage
		321	of IO::AIOs working directory abstraction, that lets you specify paths
		322	relative to some previously-opened "working directory object" - see the
		323	description of the C<IO::AIO::WD> class later in this document.
116		324
117	To encode pathnames to byte form, either make sure you either: a)	325	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	326	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	327	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	328	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)	329	effect in the user environment, d) use Glib::filename_from_unicode on
122	use something else.	330	unicode filenames or e) use something else to ensure your scalar has the
		331	correct contents.
		332
		333	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		334	handles correctly whether it is set or not.
		335
		336	=head2 AIO REQUEST FUNCTIONS
123		337
124	=over 4	338	=over 4
125		339
		340	=item $prev_pri = aioreq_pri [$pri]
		341
		342	Returns the priority value that would be used for the next request and, if
		343	C<$pri> is given, sets the priority for the next aio request.
		344
		345	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		346	and C<4>, respectively. Requests with higher priority will be serviced
		347	first.
		348
		349	The priority will be reset to C<0> after each call to one of the C<aio_*>
		350	functions.
		351
		352	Example: open a file with low priority, then read something from it with
		353	higher priority so the read request is serviced before other low priority
		354	open requests (potentially spamming the cache):
		355
		356	aioreq_pri -3;
		357	aio_open ..., sub {
		358	return unless $_[0];
		359
		360	aioreq_pri -2;
		361	aio_read $_[0], ..., sub {
		362	...
		363	};
		364	};
		365
		366
		367	=item aioreq_nice $pri_adjust
		368
		369	Similar to C<aioreq_pri>, but subtracts the given value from the current
		370	priority, so the effect is cumulative.
		371
		372
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	373	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		374
128	Asynchronously open or create a file and call the callback with a newly	375	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	376	created filehandle for the file (or C<undef> in case of an error).
130		377
131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	378	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
132	for an explanation.	379	for an explanation.
133		380
134	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	381	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
135	list. They are the same as used by C<sysopen>.	382	list. They are the same as used by C<sysopen>.
136		383
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	384	Likewise, C<$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>,	385	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,	386	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).	387	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		388	by the umask in effect then the request is being executed, so better never
		389	change the umask.
141		390
142	Example:	391	Example:
143		392
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	393	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
145	if ($_[0]) {	394	if ($_[0]) {
146	print "open successful, fh is $_[0]\n";	395	print "open successful, fh is $_[0]\n";
147	...	396	...
148	} else {	397	} else {
149	die "open failed: $!\n";	398	die "open failed: $!\n";
150	}	399	}
151	};	400	};
152		401
		402	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		403	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		404	following POSIX and non-POSIX constants are available (missing ones on
		405	your system are, as usual, C<0>):
		406
		407	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		408	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		409	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		410
		411
153	=item aio_close $fh, $callback->($status)	412	=item aio_close $fh, $callback->($status)
154		413
155	Asynchronously close a file and call the callback with the result	414	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	415	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		416
161	This is supposed to be a bug in the API, so that might change. It's	417	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	418	closing the file descriptor associated with the filehandle itself.
		419
		420	Therefore, C<aio_close> will not close the filehandle - instead it will
		421	use dup2 to overwrite the file descriptor with the write-end of a pipe
		422	(the pipe fd will be created on demand and will be cached).
		423
		424	Or in other words: the file descriptor will be closed, but it will not be
		425	free for reuse until the perl filehandle is closed.
		426
		427	=cut
		428
		429	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		430
		431	Seeks the filehandle to the new C<$offset>, similarly to perl's
		432	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		433	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		434	C<IO::AIO::SEEK_END>).
		435
		436	The resulting absolute offset will be passed to the callback, or C<-1> in
		437	case of an error.
		438
		439	In theory, the C<$whence> constants could be different than the
		440	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		441	so don't panic.
		442
		443	As a GNU/Linux (and maybe Solaris) extension, also the constants
		444	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		445	could be found. No guarantees about suitability for use in C<aio_seek> or
		446	Perl's C<sysseek> can be made though, although I would naively assume they
		447	"just work".
163		448
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		450
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	451	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		452
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	453	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	454	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
170	callback without the actual number of bytes read (or -1 on error, just	455	calls the callback with the actual number of bytes transferred (or -1 on
171	like the syscall).	456	error, just like the syscall).
		457
		458	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		459	offset plus the actual number of bytes read.
		460
		461	If C<$offset> is undefined, then the current file descriptor offset will
		462	be used (and updated), otherwise the file descriptor offset will not be
		463	changed by these calls.
		464
		465	If C<$length> is undefined in C<aio_write>, use the remaining length of
		466	C<$data>.
		467
		468	If C<$dataoffset> is less than zero, it will be counted from the end of
		469	C<$data>.
172		470
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	471	The C<$data> scalar I<MUST NOT> be modified in any way while the request
174	is outstanding. Modifying it can result in segfaults or WW3 (if the	472	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	473	the necessary/optional hardware is installed).
176		474
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	475	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	476	offset C<0> within the scalar:
179		477
180	aio_read $fh, 7, 15, $buffer, 0, sub {	478	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	479	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	480	print "read $_[0] bytes: <$buffer>\n";
183	};	481	};
184		482
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.
192
193	This is a composite request that tries to rename(2) the file first. If
194	rename files with C<EXDEV>, it creates the destination file with mode 0200
195	and copies the contents of the source file into it using C<aio_sendfile>,
196	followed by restoring atime, mtime, access mode and uid/gid, in that
197	order, and unlinking the C<$srcpath>.
198
199	If an error occurs, the partial destination file will be unlinked, if
200	possible, except when setting atime, mtime, access mode and uid/gid, where
201	errors are being ignored.
202
203	=cut
204
205	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;
207
208	my $grp = aio_group $cb;
209
210	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {
212	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;
215
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {
218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
219	close $src_fh;
220
221	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;
226
227	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);
229	};
230	} else {
231	my $errno = $!;
232	add $grp aio_unlink $dst, sub {
233	$! = $errno;
234	$grp->result (-1);
235	};
236	}
237	};
238	} else {
239	$grp->result (-1);
240	}
241	},
242
243	} else {
244	$grp->result (-1);
245	}
246	};
247	} else {
248	$grp->result ($_[0]);
249	}
250	};
251
252	$grp
253	}
254		483
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	484	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		485
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	486	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
258	reading at byte offset C<$in_offset>, and starts writing at the current	487	reading at byte offset C<$in_offset>, and starts writing at the current
259	file offset of C<$out_fh>. Because of that, it is not safe to issue more	488	file offset of C<$out_fh>. Because of that, it is not safe to issue more
260	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	489	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
261	other.	490	other. The same C<$in_fh> works fine though, as this function does not
		491	move or use the file offset of C<$in_fh>.
262		492
		493	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		494	are written, and there is no way to find out how many more bytes have been
		495	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		496	number of bytes written to C<$out_fh>. Only if the result value equals
		497	C<$length> one can assume that C<$length> bytes have been read.
		498
		499	Unlike with other C<aio_> functions, it makes a lot of sense to use
		500	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		501	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		502	the socket I/O will be non-blocking. Note, however, that you can run
		503	into a trap where C<aio_sendfile> reads some data with readahead, then
		504	fails to write all data, and when the socket is ready the next time, the
		505	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		506	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		507	resource usage.
		508
263	This call tries to make use of a native C<sendfile> syscall to provide	509	This call tries to make use of a native C<sendfile>-like syscall to
264	zero-copy operation. For this to work, C<$out_fh> should refer to a	510	provide zero-copy operation. For this to work, C<$out_fh> should refer to
265	socket, and C<$in_fh> should refer to mmap'able file.	511	a socket, and C<$in_fh> should refer to an mmap'able file.
266		512
267	If the native sendfile call fails or is not implemented, it will be	513	If a native sendfile cannot be found or it fails with C<ENOSYS>,
268	emulated, so you can call C<aio_sendfile> on any type of filehandle	514	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		515	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
269	regardless of the limitations of the operating system.	516	type of filehandle regardless of the limitations of the operating system.
270		517
271	Please note, however, that C<aio_sendfile> can read more bytes from	518	As native sendfile syscalls (as practically any non-POSIX interface hacked
272	C<$in_fh> than are written, and there is no way to find out how many	519	together in a hurry to improve benchmark numbers) tend to be rather buggy
273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	520	on many systems, this implementation tries to work around some known bugs
274	provides the number of bytes written to C<$out_fh>. Only if the result	521	in Linux and FreeBSD kernels (probably others, too), but that might fail,
275	value equals C<$length> one can assume that C<$length> bytes have been	522	so you really really should check the return value of C<aio_sendfile> -
276	read.	523	fewer bytes than expected might have been transferred.
		524
277		525
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	526	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		527
280	C<aio_readahead> populates the page cache with data from a file so that	528	C<aio_readahead> populates the page cache with data from a file so that
281	subsequent reads from that file will not block on disk I/O. The C<$offset>	529	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
284	whole pages, so that offset is effectively rounded down to a page boundary	532	whole pages, so that offset is effectively rounded down to a page boundary
285	and bytes are read up to the next page boundary greater than or equal to	533	and bytes are read up to the next page boundary greater than or equal to
286	(off-set+length). C<aio_readahead> does not read beyond the end of the	534	(off-set+length). C<aio_readahead> does not read beyond the end of the
287	file. The current file offset of the file is left unchanged.	535	file. The current file offset of the file is left unchanged.
288		536
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	537	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
290	emulated by simply reading the data, which would have a similar effect.	538	be emulated by simply reading the data, which would have a similar effect.
		539
291		540
292	=item aio_stat $fh_or_path, $callback->($status)	541	=item aio_stat $fh_or_path, $callback->($status)
293		542
294	=item aio_lstat $fh, $callback->($status)	543	=item aio_lstat $fh, $callback->($status)
295		544
…		…
301	for an explanation.	550	for an explanation.
302		551
303	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	552	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
304	error when stat'ing a large file, the results will be silently truncated	553	error when stat'ing a large file, the results will be silently truncated
305	unless perl itself is compiled with large file support.	554	unless perl itself is compiled with large file support.
		555
		556	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		557	following constants and functions (if not implemented, the constants will
		558	be C<0> and the functions will either C<croak> or fall back on traditional
		559	behaviour).
		560
		561	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		562	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		563	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
306		564
307	Example: Print the length of F</etc/passwd>:	565	Example: Print the length of F</etc/passwd>:
308		566
309	aio_stat "/etc/passwd", sub {	567	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	568	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	569	print "size is ", -s _, "\n";
312	};	570	};
313		571
		572
		573	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		574
		575	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		576	whether a file handle or path was passed.
		577
		578	On success, the callback is passed a hash reference with the following
		579	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		580	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		581	is passed.
		582
		583	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		584	C<ST_NOSUID>.
		585
		586	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		587	their correct value when available, or to C<0> on systems that do
		588	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		589	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		590	C<ST_NODIRATIME> and C<ST_RELATIME>.
		591
		592	Example: stat C</wd> and dump out the data if successful.
		593
		594	aio_statvfs "/wd", sub {
		595	my $f = $_[0]
		596	or die "statvfs: $!";
		597
		598	use Data::Dumper;
		599	say Dumper $f;
		600	};
		601
		602	# result:
		603	{
		604	bsize => 1024,
		605	bfree => 4333064312,
		606	blocks => 10253828096,
		607	files => 2050765568,
		608	flag => 4096,
		609	favail => 2042092649,
		610	bavail => 4333064312,
		611	ffree => 2042092649,
		612	namemax => 255,
		613	frsize => 1024,
		614	fsid => 1810
		615	}
		616
		617	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		618
		619	Works like perl's C<utime> function (including the special case of $atime
		620	and $mtime being undef). Fractional times are supported if the underlying
		621	syscalls support them.
		622
		623	When called with a pathname, uses utimes(2) if available, otherwise
		624	utime(2). If called on a file descriptor, uses futimes(2) if available,
		625	otherwise returns ENOSYS, so this is not portable.
		626
		627	Examples:
		628
		629	# set atime and mtime to current time (basically touch(1)):
		630	aio_utime "path", undef, undef;
		631	# set atime to current time and mtime to beginning of the epoch:
		632	aio_utime "path", time, undef; # undef==0
		633
		634
		635	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		636
		637	Works like perl's C<chown> function, except that C<undef> for either $uid
		638	or $gid is being interpreted as "do not change" (but -1 can also be used).
		639
		640	Examples:
		641
		642	# same as "chown root path" in the shell:
		643	aio_chown "path", 0, -1;
		644	# same as above:
		645	aio_chown "path", 0, undef;
		646
		647
		648	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		649
		650	Works like truncate(2) or ftruncate(2).
		651
		652
		653	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654
		655	Allocates or frees disk space according to the C<$mode> argument. See the
		656	linux C<fallocate> documentation for details.
		657
		658	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		659	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		660	to deallocate a file range.
		661
		662	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		663	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		664	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		665	to unshare shared blocks (see your L<fallocate(2)> manpage).
		666
		667	The file system block size used by C<fallocate> is presumably the
		668	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		669	can dictate other limitations.
		670
		671	If C<fallocate> isn't available or cannot be emulated (currently no
		672	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		673
		674
		675	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		676
		677	Works like perl's C<chmod> function.
		678
		679
314	=item aio_unlink $pathname, $callback->($status)	680	=item aio_unlink $pathname, $callback->($status)
315		681
316	Asynchronously unlink (delete) a file and call the callback with the	682	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	683	result code.
318		684
		685
		686	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		687
		688	[EXPERIMENTAL]
		689
		690	Asynchronously create a device node (or fifo). See mknod(2).
		691
		692	The only (POSIX-) portable way of calling this function is:
		693
		694	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		695
		696	See C<aio_stat> for info about some potentially helpful extra constants
		697	and functions.
		698
319	=item aio_link $srcpath, $dstpath, $callback->($status)	699	=item aio_link $srcpath, $dstpath, $callback->($status)
320		700
321	Asynchronously create a new link to the existing object at C<$srcpath> at	701	Asynchronously create a new link to the existing object at C<$srcpath> at
322	the path C<$dstpath> and call the callback with the result code.	702	the path C<$dstpath> and call the callback with the result code.
323		703
		704
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	705	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		706
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	707	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
327	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
328		709
		710
		711	=item aio_readlink $pathname, $callback->($link)
		712
		713	Asynchronously read the symlink specified by C<$path> and pass it to
		714	the callback. If an error occurs, nothing or undef gets passed to the
		715	callback.
		716
		717
		718	=item aio_realpath $pathname, $callback->($path)
		719
		720	Asynchronously make the path absolute and resolve any symlinks in
		721	C<$path>. The resulting path only consists of directories (same as
		722	L<Cwd::realpath>).
		723
		724	This request can be used to get the absolute path of the current working
		725	directory by passing it a path of F<.> (a single dot).
		726
		727
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	728	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		729
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	730	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	731	rename(2) and call the callback with the result code.
333		732
		733	On systems that support the AIO::WD working directory abstraction
		734	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		735	of failing, C<rename> is called on the absolute path of C<$wd>.
		736
		737
		738	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		739
		740	Basically a version of C<aio_rename> with an additional C<$flags>
		741	argument. Calling this with C<$flags=0> is the same as calling
		742	C<aio_rename>.
		743
		744	Non-zero flags are currently only supported on GNU/Linux systems that
		745	support renameat2. Other systems fail with C<ENOSYS> in this case.
		746
		747	The following constants are available (missing ones are, as usual C<0>),
		748	see renameat2(2) for details:
		749
		750	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		751	and C<IO::AIO::RENAME_WHITEOUT>.
		752
		753
		754	=item aio_mkdir $pathname, $mode, $callback->($status)
		755
		756	Asynchronously mkdir (create) a directory and call the callback with
		757	the result code. C<$mode> will be modified by the umask at the time the
		758	request is executed, so do not change your umask.
		759
		760
334	=item aio_rmdir $pathname, $callback->($status)	761	=item aio_rmdir $pathname, $callback->($status)
335		762
336	Asynchronously rmdir (delete) a directory and call the callback with the	763	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	764	result code.
		765
		766	On systems that support the AIO::WD working directory abstraction
		767	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		768	C<rmdir> is called on the absolute path of C<$wd>.
		769
338		770
339	=item aio_readdir $pathname, $callback->($entries)	771	=item aio_readdir $pathname, $callback->($entries)
340		772
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	773	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
342	directory (i.e. opendir + readdir + closedir). The entries will not be	774	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	775	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		776
345	The callback a single argument which is either C<undef> or an array-ref	777	The callback is passed a single argument which is either C<undef> or an
346	with the filenames.	778	array-ref with the filenames.
347		779
		780
		781	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		782
		783	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		784	tune behaviour and output format. In case of an error, C<$entries> will be
		785	C<undef>.
		786
		787	The flags are a combination of the following constants, ORed together (the
		788	flags will also be passed to the callback, possibly modified):
		789
		790	=over 4
		791
		792	=item IO::AIO::READDIR_DENTS
		793
		794	When this flag is off, then the callback gets an arrayref consisting of
		795	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		796	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		797	entry in more detail.
		798
		799	C<$name> is the name of the entry.
		800
		801	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		802
		803	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		804	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		805	C<IO::AIO::DT_WHT>.
		806
		807	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		808	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		809	scalars are read-only: you can not modify them.
		810
		811	C<$inode> is the inode number (which might not be exact on systems with 64
		812	bit inode numbers and 32 bit perls). This field has unspecified content on
		813	systems that do not deliver the inode information.
		814
		815	=item IO::AIO::READDIR_DIRS_FIRST
		816
		817	When this flag is set, then the names will be returned in an order where
		818	likely directories come first, in optimal stat order. This is useful when
		819	you need to quickly find directories, or you want to find all directories
		820	while avoiding to stat() each entry.
		821
		822	If the system returns type information in readdir, then this is used
		823	to find directories directly. Otherwise, likely directories are names
		824	beginning with ".", or otherwise names with no dots, of which names with
		825	short names are tried first.
		826
		827	=item IO::AIO::READDIR_STAT_ORDER
		828
		829	When this flag is set, then the names will be returned in an order
		830	suitable for stat()'ing each one. That is, when you plan to stat()
		831	all files in the given directory, then the returned order will likely
		832	be fastest.
		833
		834	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		835	the likely dirs come first, resulting in a less optimal stat order.
		836
		837	=item IO::AIO::READDIR_FOUND_UNKNOWN
		838
		839	This flag should not be set when calling C<aio_readdirx>. Instead, it
		840	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		841	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		842	C<$type>'s are known, which can be used to speed up some algorithms.
		843
		844	=back
		845
		846
		847	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		848
		849	Opens, reads and closes the given file. The data is put into C<$data>,
		850	which is resized as required.
		851
		852	If C<$offset> is negative, then it is counted from the end of the file.
		853
		854	If C<$length> is zero, then the remaining length of the file is
		855	used. Also, in this case, the same limitations to modifying C<$data> apply
		856	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		857	with C<substr>. If the size of the file is known, specifying a non-zero
		858	C<$length> results in a performance advantage.
		859
		860	This request is similar to the older C<aio_load> request, but since it is
		861	a single request, it might be more efficient to use.
		862
		863	Example: load F</etc/passwd> into C<$passwd>.
		864
		865	my $passwd;
		866	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		867	$_[0] >= 0
		868	or die "/etc/passwd: $!\n";
		869
		870	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		871	print $passwd;
		872	};
		873	IO::AIO::flush;
		874
		875
		876	=item aio_load $pathname, $data, $callback->($status)
		877
		878	This is a composite request that tries to fully load the given file into
		879	memory. Status is the same as with aio_read.
		880
		881	Using C<aio_slurp> might be more efficient, as it is a single request.
		882
		883	=cut
		884
		885	sub aio_load($$;$) {
		886	my ($path, undef, $cb) = @_;
		887	my $data = \$_[1];
		888
		889	my $pri = aioreq_pri;
		890	my $grp = aio_group $cb;
		891
		892	aioreq_pri $pri;
		893	add $grp aio_open $path, O_RDONLY, 0, sub {
		894	my $fh = shift
		895	or return $grp->result (-1);
		896
		897	aioreq_pri $pri;
		898	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		899	$grp->result ($_[0]);
		900	};
		901	};
		902
		903	$grp
		904	}
		905
		906	=item aio_copy $srcpath, $dstpath, $callback->($status)
		907
		908	Try to copy the I<file> (directories not supported as either source or
		909	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		910	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		911
		912	Existing destination files will be truncated.
		913
		914	This is a composite request that creates the destination file with
		915	mode 0200 and copies the contents of the source file into it using
		916	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		917	uid/gid, in that order.
		918
		919	If an error occurs, the partial destination file will be unlinked, if
		920	possible, except when setting atime, mtime, access mode and uid/gid, where
		921	errors are being ignored.
		922
		923	=cut
		924
		925	sub aio_copy($$;$) {
		926	my ($src, $dst, $cb) = @_;
		927
		928	my $pri = aioreq_pri;
		929	my $grp = aio_group $cb;
		930
		931	aioreq_pri $pri;
		932	add $grp aio_open $src, O_RDONLY, 0, sub {
		933	if (my $src_fh = $_[0]) {
		934	my @stat = stat $src_fh; # hmm, might block over nfs?
		935
		936	aioreq_pri $pri;
		937	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		938	if (my $dst_fh = $_[0]) {
		939	aioreq_pri $pri;
		940	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		941	if ($_[0] == $stat[7]) {
		942	$grp->result (0);
		943	close $src_fh;
		944
		945	my $ch = sub {
		946	aioreq_pri $pri;
		947	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		948	aioreq_pri $pri;
		949	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		950	aioreq_pri $pri;
		951	add $grp aio_close $dst_fh;
		952	}
		953	};
		954	};
		955
		956	aioreq_pri $pri;
		957	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		958	if ($_[0] < 0 && $! == ENOSYS) {
		959	aioreq_pri $pri;
		960	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		961	} else {
		962	$ch->();
		963	}
		964	};
		965	} else {
		966	$grp->result (-1);
		967	close $src_fh;
		968	close $dst_fh;
		969
		970	aioreq $pri;
		971	add $grp aio_unlink $dst;
		972	}
		973	};
		974	} else {
		975	$grp->result (-1);
		976	}
		977	},
		978
		979	} else {
		980	$grp->result (-1);
		981	}
		982	};
		983
		984	$grp
		985	}
		986
		987	=item aio_move $srcpath, $dstpath, $callback->($status)
		988
		989	Try to move the I<file> (directories not supported as either source or
		990	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		991	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		992
		993	This is a composite request that tries to rename(2) the file first; if
		994	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		995	that is successful, unlinks the C<$srcpath>.
		996
		997	=cut
		998
		999	sub aio_move($$;$) {
		1000	my ($src, $dst, $cb) = @_;
		1001
		1002	my $pri = aioreq_pri;
		1003	my $grp = aio_group $cb;
		1004
		1005	aioreq_pri $pri;
		1006	add $grp aio_rename $src, $dst, sub {
		1007	if ($_[0] && $! == EXDEV) {
		1008	aioreq_pri $pri;
		1009	add $grp aio_copy $src, $dst, sub {
		1010	$grp->result ($_[0]);
		1011
		1012	unless ($_[0]) {
		1013	aioreq_pri $pri;
		1014	add $grp aio_unlink $src;
		1015	}
		1016	};
		1017	} else {
		1018	$grp->result ($_[0]);
		1019	}
		1020	};
		1021
		1022	$grp
		1023	}
		1024
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1025	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
349
350	[EXPERIMENTAL due to internal aio_group use]
351		1026
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1027	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	1028	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	1029	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	1030	recurse into (everything else, including symlinks to directories).
356		1031
357	C<aio_scandir> is a composite request that creates of many sub requests_	1032	C<aio_scandir> is a composite request that generates many sub requests.
358	C<$maxreq> specifies the maximum number of outstanding aio requests that	1033	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	1034	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	1035	will be chosen (currently 4).
361		1036
362	On error, the callback is called without arguments, otherwise it receives	1037	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	1038	two array-refs with path-relative entry names.
364		1039
365	Example:	1040	Example:
…		…
372		1047
373	Implementation notes.	1048	Implementation notes.
374		1049
375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1050	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
376		1051
		1052	If readdir returns file type information, then this is used directly to
		1053	find directories.
		1054
377	After reading the directory, the modification time, size etc. of the	1055	Otherwise, after reading the directory, the modification time, size etc.
378	directory before and after the readdir is checked, and if they match (and	1056	of the directory before and after the readdir is checked, and if they
379	isn't the current time), the link count will be used to decide how many	1057	match (and isn't the current time), the link count will be used to decide
380	entries are directories (if >= 2). Otherwise, no knowledge of the number	1058	how many entries are directories (if >= 2). Otherwise, no knowledge of the
381	of subdirectories will be assumed.	1059	number of subdirectories will be assumed.
382		1060
383	Then entries will be sorted into likely directories (everything without	1061	Then entries will be sorted into likely directories a non-initial dot
384	a non-initial dot currently) and likely non-directories (everything	1062	currently) and likely non-directories (see C<aio_readdirx>). Then every
385	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1063	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
386	likely directories first. If that succeeds, it assumes that the entry	1064	in order of their inode numbers. If that succeeds, it assumes that the
387	is a directory or a symlink to directory (which will be checked	1065	entry is a directory or a symlink to directory (which will be checked
388	seperately). This is often faster than stat'ing the entry itself because	1066	separately). This is often faster than stat'ing the entry itself because
389	filesystems might detect the type of the entry without reading the inode	1067	filesystems might detect the type of the entry without reading the inode
390	data (e.g. ext2fs filetype feature).	1068	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1069	the filetype information on readdir.
391		1070
392	If the known number of directories (link count - 2) has been reached, the	1071	If the known number of directories (link count - 2) has been reached, the
393	rest of the entries is assumed to be non-directories.	1072	rest of the entries is assumed to be non-directories.
394		1073
395	This only works with certainty on POSIX (= UNIX) filesystems, which	1074	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	1078	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	1079	directory counting heuristic.
401		1080
402	=cut	1081	=cut
403		1082
404	sub aio_scandir($$$) {	1083	sub aio_scandir($$;$) {
405	my ($path, $maxreq, $cb) = @_;	1084	my ($path, $maxreq, $cb) = @_;
406		1085
		1086	my $pri = aioreq_pri;
		1087
407	my $grp = aio_group $cb;	1088	my $grp = aio_group $cb;
408		1089
409	$maxreq = 6 if $maxreq <= 0;	1090	$maxreq = 4 if $maxreq <= 0;
410		1091
411	# stat once	1092	# get a wd object
		1093	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	1094	add $grp aio_wd $path, sub {
		1095	$_[0]
		1096	or return $grp->result ();
		1097
		1098	my $wd = [shift, "."];
		1099
		1100	# stat once
		1101	aioreq_pri $pri;
		1102	add $grp aio_stat $wd, sub {
413	return $grp->result () if $_[0];	1103	return $grp->result () if $_[0];
414	my $now = time;	1104	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1105	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		1106
417	# read the directory entries	1107	# read the directory entries
418	add $grp aio_readdir $path, sub {	1108	aioreq_pri $pri;
		1109	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
419	my $entries = shift	1110	my $entries = shift
420	or return $grp->result ();	1111	or return $grp->result ();
421		1112
422	# stat the dir another time	1113	# stat the dir another time
		1114	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	1115	add $grp aio_stat $wd, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1116	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		1117
426	my $ndirs;	1118	my $ndirs;
427		1119
428	# take the slow route if anything looks fishy	1120	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1121	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	1122	$ndirs = -1;
431	} else {	1123	} else {
432	# if nlink == 2, we are finished	1124	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	1125	# for non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	1126	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	1127	or return $grp->result ([], $entries);
436	}	1128	}
437		1129
438	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];
444
445	my (@dirs, @nondirs);	1130	my (@dirs, @nondirs);
446		1131
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	1132	my $statgrp = add $grp aio_group sub {
451
452	$schedcb = sub {
453	if (@$entries) {
454	if ($nreq < $maxreq) {
455	my $ent = pop @$entries;
456	$nreq++;
457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458	}
459	} elsif (!$nreq) {
460	# finished
461	$statgrp->cancel;
462	undef $statcb;
463	undef $schedcb;
464	$grp->result (\@dirs, \@nondirs);	1133	$grp->result (\@dirs, \@nondirs);
465	}	1134	};
		1135
		1136	limit $statgrp $maxreq;
		1137	feed $statgrp sub {
		1138	return unless @$entries;
		1139	my $entry = shift @$entries;
		1140
		1141	aioreq_pri $pri;
		1142	$wd->[1] = "$entry/.";
		1143	add $statgrp aio_stat $wd, sub {
		1144	if ($_[0] < 0) {
		1145	push @nondirs, $entry;
		1146	} else {
		1147	# need to check for real directory
		1148	aioreq_pri $pri;
		1149	$wd->[1] = $entry;
		1150	add $statgrp aio_lstat $wd, sub {
		1151	if (-d _) {
		1152	push @dirs, $entry;
		1153
		1154	unless (--$ndirs) {
		1155	push @nondirs, @$entries;
		1156	feed $statgrp;
		1157	}
		1158	} else {
		1159	push @nondirs, $entry;
		1160	}
		1161	}
		1162	}
		1163	};
		1164	};
466	};	1165	};
467	$statcb = sub {
468	my ($status, $entry) = @_;
469
470	if ($status < 0) {
471	$nreq--;
472	push @nondirs, $entry;
473	&$schedcb;
474	} else {
475	# need to check for real directory
476	add $grp aio_lstat "$path/$entry", sub {
477	$nreq--;
478
479	if (-d _) {
480	push @dirs, $entry;
481
482	if (!--$ndirs) {
483	push @nondirs, @$entries;
484	$entries = [];
485	}
486	} else {
487	push @nondirs, $entry;
488	}
489
490	&$schedcb;
491	}
492	}
493	};
494
495	&$schedcb while @$entries && $nreq < $maxreq;
496	};	1166	};
497	};	1167	};
498	};	1168	};
499		1169
500	$grp	1170	$grp
501	}	1171	}
502		1172
		1173	=item aio_rmtree $pathname, $callback->($status)
		1174
		1175	Delete a directory tree starting (and including) C<$path>, return the
		1176	status of the final C<rmdir> only. This is a composite request that
		1177	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1178	everything else.
		1179
		1180	=cut
		1181
		1182	sub aio_rmtree;
		1183	sub aio_rmtree($;$) {
		1184	my ($path, $cb) = @_;
		1185
		1186	my $pri = aioreq_pri;
		1187	my $grp = aio_group $cb;
		1188
		1189	aioreq_pri $pri;
		1190	add $grp aio_scandir $path, 0, sub {
		1191	my ($dirs, $nondirs) = @_;
		1192
		1193	my $dirgrp = aio_group sub {
		1194	add $grp aio_rmdir $path, sub {
		1195	$grp->result ($_[0]);
		1196	};
		1197	};
		1198
		1199	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1200	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1201
		1202	add $grp $dirgrp;
		1203	};
		1204
		1205	$grp
		1206	}
		1207
		1208	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1209
		1210	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1211
		1212	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1213	they execute asynchronously and pass the return value to the callback.
		1214
		1215	Both calls can be used for a lot of things, some of which make more sense
		1216	to run asynchronously in their own thread, while some others make less
		1217	sense. For example, calls that block waiting for external events, such
		1218	as locking, will also lock down an I/O thread while it is waiting, which
		1219	can deadlock the whole I/O system. At the same time, there might be no
		1220	alternative to using a thread to wait.
		1221
		1222	So in general, you should only use these calls for things that do
		1223	(filesystem) I/O, not for things that wait for other events (network,
		1224	other processes), although if you are careful and know what you are doing,
		1225	you still can.
		1226
		1227	The following constants are available (missing ones are, as usual C<0>):
		1228
		1229	C<F_DUPFD_CLOEXEC>,
		1230
		1231	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1232
		1233	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1234
		1235	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1236	C<FS_IOC_FIEMAP>.
		1237
		1238	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1239	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1240
		1241	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1242	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1243	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1244	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1245	C<FS_FL_USER_MODIFIABLE>.
		1246
		1247	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1248	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1249	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1250	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1251
		1252	=item aio_sync $callback->($status)
		1253
		1254	Asynchronously call sync and call the callback when finished.
		1255
503	=item aio_fsync $fh, $callback->($status)	1256	=item aio_fsync $fh, $callback->($status)
504		1257
505	Asynchronously call fsync on the given filehandle and call the callback	1258	Asynchronously call fsync on the given filehandle and call the callback
506	with the fsync result code.	1259	with the fsync result code.
507		1260
…		…
511	callback with the fdatasync result code.	1264	callback with the fdatasync result code.
512		1265
513	If this call isn't available because your OS lacks it or it couldn't be	1266	If this call isn't available because your OS lacks it or it couldn't be
514	detected, it will be emulated by calling C<fsync> instead.	1267	detected, it will be emulated by calling C<fsync> instead.
515		1268
		1269	=item aio_syncfs $fh, $callback->($status)
		1270
		1271	Asynchronously call the syncfs syscall to sync the filesystem associated
		1272	to the given filehandle and call the callback with the syncfs result
		1273	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1274	errno to C<ENOSYS> nevertheless.
		1275
		1276	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1277
		1278	Sync the data portion of the file specified by C<$offset> and C<$length>
		1279	to disk (but NOT the metadata), by calling the Linux-specific
		1280	sync_file_range call. If sync_file_range is not available or it returns
		1281	ENOSYS, then fdatasync or fsync is being substituted.
		1282
		1283	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1284	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1285	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1286	manpage for details.
		1287
		1288	=item aio_pathsync $pathname, $callback->($status)
		1289
		1290	This request tries to open, fsync and close the given path. This is a
		1291	composite request intended to sync directories after directory operations
		1292	(E.g. rename). This might not work on all operating systems or have any
		1293	specific effect, but usually it makes sure that directory changes get
		1294	written to disc. It works for anything that can be opened for read-only,
		1295	not just directories.
		1296
		1297	Future versions of this function might fall back to other methods when
		1298	C<fsync> on the directory fails (such as calling C<sync>).
		1299
		1300	Passes C<0> when everything went ok, and C<-1> on error.
		1301
		1302	=cut
		1303
		1304	sub aio_pathsync($;$) {
		1305	my ($path, $cb) = @_;
		1306
		1307	my $pri = aioreq_pri;
		1308	my $grp = aio_group $cb;
		1309
		1310	aioreq_pri $pri;
		1311	add $grp aio_open $path, O_RDONLY, 0, sub {
		1312	my ($fh) = @_;
		1313	if ($fh) {
		1314	aioreq_pri $pri;
		1315	add $grp aio_fsync $fh, sub {
		1316	$grp->result ($_[0]);
		1317
		1318	aioreq_pri $pri;
		1319	add $grp aio_close $fh;
		1320	};
		1321	} else {
		1322	$grp->result (-1);
		1323	}
		1324	};
		1325
		1326	$grp
		1327	}
		1328
		1329	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1330
		1331	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1332	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1333	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1334	scalar must only be modified in-place while an aio operation is pending on
		1335	it).
		1336
		1337	It calls the C<msync> function of your OS, if available, with the memory
		1338	area starting at C<$offset> in the string and ending C<$length> bytes
		1339	later. If C<$length> is negative, counts from the end, and if C<$length>
		1340	is C<undef>, then it goes till the end of the string. The flags can be
		1341	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1342	C<IO::AIO::MS_INVALIDATE>.
		1343
		1344	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1345
		1346	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1347	scalars.
		1348
		1349	It touches (reads or writes) all memory pages in the specified
		1350	range inside the scalar. All caveats and parameters are the same
		1351	as for C<aio_msync>, above, except for flags, which must be either
		1352	C<0> (which reads all pages and ensures they are instantiated) or
		1353	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1354	writing an octet from it, which dirties the page).
		1355
		1356	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1357
		1358	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1359	scalars.
		1360
		1361	It reads in all the pages of the underlying storage into memory (if any)
		1362	and locks them, so they are not getting swapped/paged out or removed.
		1363
		1364	If C<$length> is undefined, then the scalar will be locked till the end.
		1365
		1366	On systems that do not implement C<mlock>, this function returns C<-1>
		1367	and sets errno to C<ENOSYS>.
		1368
		1369	Note that the corresponding C<munlock> is synchronous and is
		1370	documented under L<MISCELLANEOUS FUNCTIONS>.
		1371
		1372	Example: open a file, mmap and mlock it - both will be undone when
		1373	C<$data> gets destroyed.
		1374
		1375	open my $fh, "<", $path or die "$path: $!";
		1376	my $data;
		1377	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1378	aio_mlock $data; # mlock in background
		1379
		1380	=item aio_mlockall $flags, $callback->($status)
		1381
		1382	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1383	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1384
		1385	On systems that do not implement C<mlockall>, this function returns C<-1>
		1386	and sets errno to C<ENOSYS>.
		1387
		1388	Note that the corresponding C<munlockall> is synchronous and is
		1389	documented under L<MISCELLANEOUS FUNCTIONS>.
		1390
		1391	Example: asynchronously lock all current and future pages into memory.
		1392
		1393	aio_mlockall IO::AIO::MCL_FUTURE;
		1394
		1395	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1396
		1397	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1398	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1399	the ioctl is not available on your OS, then this request will fail with
		1400	C<ENOSYS>.
		1401
		1402	C<$start> is the starting offset to query extents for, C<$length> is the
		1403	size of the range to query - if it is C<undef>, then the whole file will
		1404	be queried.
		1405
		1406	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1407	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1408	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1409	the data portion.
		1410
		1411	C<$count> is the maximum number of extent records to return. If it is
		1412	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1413	case, if it is C<0>, then the callback receives the number of extents
		1414	instead of the extents themselves (which is unreliable, see below).
		1415
		1416	If an error occurs, the callback receives no arguments. The special
		1417	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1418
		1419	Otherwise, the callback receives an array reference with extent
		1420	structures. Each extent structure is an array reference itself, with the
		1421	following members:
		1422
		1423	[$logical, $physical, $length, $flags]
		1424
		1425	Flags is any combination of the following flag values (typically either C<0>
		1426	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1427
		1428	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1429	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1430	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1431	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1432	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1433	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1434
		1435	At the time of this writing (Linux 3.2), this request is unreliable unless
		1436	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1437	it to return all extents of a range for files with a large number of
		1438	extents. The code (only) works around all these issues if C<$count> is
		1439	C<undef>.
		1440
516	=item aio_group $callback->(...)	1441	=item aio_group $callback->(...)
517
518	[EXPERIMENTAL]
519		1442
520	This is a very special aio request: Instead of doing something, it is a	1443	This is a very special aio request: Instead of doing something, it is a
521	container for other aio requests, which is useful if you want to bundle	1444	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	1445	many requests into a single, composite, request with a definite callback
		1446	and the ability to cancel the whole request with its subrequests.
523		1447
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1448	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	1449	for more info.
526		1450
527	Example:	1451	Example:
…		…
546	phase and still requires a worker thread. Thus, the callback will not	1470	phase and still requires a worker thread. Thus, the callback will not
547	be executed immediately but only after other requests in the queue have	1471	be executed immediately but only after other requests in the queue have
548	entered their execution phase. This can be used to measure request	1472	entered their execution phase. This can be used to measure request
549	latency.	1473	latency.
550		1474
551	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1475	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
552		1476
553	Mainly used for debugging and benchmarking, this aio request puts one of	1477	Mainly used for debugging and benchmarking, this aio request puts one of
554	the request workers to sleep for the given time.	1478	the request workers to sleep for the given time.
555		1479
556	While it is theoretically handy to have simple I/O scheduling requests	1480	While it is theoretically handy to have simple I/O scheduling requests
557	like sleep and file handle readable/writable, the overhead this creates	1481	like sleep and file handle readable/writable, the overhead this creates is
558	is immense, so do not use this function except to put your application	1482	immense (it blocks a thread for a long time) so do not use this function
559	under artificial I/O pressure.	1483	except to put your application under artificial I/O pressure.
560		1484
561	=back	1485	=back
		1486
		1487
		1488	=head2 IO::AIO::WD - multiple working directories
		1489
		1490	Your process only has one current working directory, which is used by all
		1491	threads. This makes it hard to use relative paths (some other component
		1492	could call C<chdir> at any time, and it is hard to control when the path
		1493	will be used by IO::AIO).
		1494
		1495	One solution for this is to always use absolute paths. This usually works,
		1496	but can be quite slow (the kernel has to walk the whole path on every
		1497	access), and can also be a hassle to implement.
		1498
		1499	Newer POSIX systems have a number of functions (openat, fdopendir,
		1500	futimensat and so on) that make it possible to specify working directories
		1501	per operation.
		1502
		1503	For portability, and because the clowns who "designed", or shall I write,
		1504	perpetrated this new interface were obviously half-drunk, this abstraction
		1505	cannot be perfect, though.
		1506
		1507	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1508	object. This object stores the canonicalised, absolute version of the
		1509	path, and on systems that allow it, also a directory file descriptor.
		1510
		1511	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1512	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1513	object and a pathname instead (or the IO::AIO::WD object alone, which
		1514	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1515	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1516	to that IO::AIO::WD object.
		1517
		1518	For example, to get a wd object for F</etc> and then stat F<passwd>
		1519	inside, you would write:
		1520
		1521	aio_wd "/etc", sub {
		1522	my $etcdir = shift;
		1523
		1524	# although $etcdir can be undef on error, there is generally no reason
		1525	# to check for errors here, as aio_stat will fail with ENOENT
		1526	# when $etcdir is undef.
		1527
		1528	aio_stat [$etcdir, "passwd"], sub {
		1529	# yay
		1530	};
		1531	};
		1532
		1533	The fact that C<aio_wd> is a request and not a normal function shows that
		1534	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1535	which is why it is done asynchronously.
		1536
		1537	To stat the directory obtained with C<aio_wd> above, one could write
		1538	either of the following three request calls:
		1539
		1540	aio_lstat "/etc" , sub { ... # pathname as normal string
		1541	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1542	aio_lstat $wd , sub { ... # shorthand for the previous
		1543
		1544	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1545	object and the pathname string, so you could write the following without
		1546	causing any issues due to C<$path> getting reused:
		1547
		1548	my $path = [$wd, undef];
		1549
		1550	for my $name (qw(abc def ghi)) {
		1551	$path->[1] = $name;
		1552	aio_stat $path, sub {
		1553	# ...
		1554	};
		1555	}
		1556
		1557	There are some caveats: when directories get renamed (or deleted), the
		1558	pathname string doesn't change, so will point to the new directory (or
		1559	nowhere at all), while the directory fd, if available on the system,
		1560	will still point to the original directory. Most functions accepting a
		1561	pathname will use the directory fd on newer systems, and the string on
		1562	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1563	the string form of the pathname.
		1564
		1565	So this functionality is mainly useful to get some protection against
		1566	C<chdir>, to easily get an absolute path out of a relative path for future
		1567	reference, and to speed up doing many operations in the same directory
		1568	(e.g. when stat'ing all files in a directory).
		1569
		1570	The following functions implement this working directory abstraction:
		1571
		1572	=over 4
		1573
		1574	=item aio_wd $pathname, $callback->($wd)
		1575
		1576	Asynchonously canonicalise the given pathname and convert it to an
		1577	IO::AIO::WD object representing it. If possible and supported on the
		1578	system, also open a directory fd to speed up pathname resolution relative
		1579	to this working directory.
		1580
		1581	If something goes wrong, then C<undef> is passwd to the callback instead
		1582	of a working directory object and C<$!> is set appropriately. Since
		1583	passing C<undef> as working directory component of a pathname fails the
		1584	request with C<ENOENT>, there is often no need for error checking in the
		1585	C<aio_wd> callback, as future requests using the value will fail in the
		1586	expected way.
		1587
		1588	=item IO::AIO::CWD
		1589
		1590	This is a compiletime constant (object) that represents the process
		1591	current working directory.
		1592
		1593	Specifying this object as working directory object for a pathname is as if
		1594	the pathname would be specified directly, without a directory object. For
		1595	example, these calls are functionally identical:
		1596
		1597	aio_stat "somefile", sub { ... };
		1598	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1599
		1600	=back
		1601
		1602	To recover the path associated with an IO::AIO::WD object, you can use
		1603	C<aio_realpath>:
		1604
		1605	aio_realpath $wd, sub {
		1606	warn "path is $_[0]\n";
		1607	};
		1608
		1609	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1610	sometimes, fall back to using an absolue path.
562		1611
563	=head2 IO::AIO::REQ CLASS	1612	=head2 IO::AIO::REQ CLASS
564		1613
565	All non-aggregate C<aio_*> functions return an object of this class when	1614	All non-aggregate C<aio_*> functions return an object of this class when
566	called in non-void context.	1615	called in non-void context.
567
568	A request always moves through the following five states in its lifetime,
569	in order: B<ready> (request has been created, but has not been executed
570	yet), B<execute> (request is currently being executed), B<pending>
571	(request has been executed but callback has not been called yet),
572	B<result> (results are being processed synchronously, includes calling the
573	callback) and B<done> (request has reached the end of its lifetime and
574	holds no resources anymore).
575		1616
576	=over 4	1617	=over 4
577		1618
578	=item cancel $req	1619	=item cancel $req
579		1620
580	Cancels the request, if possible. Has the effect of skipping execution	1621	Cancels the request, if possible. Has the effect of skipping execution
581	when entering the B<execute> state and skipping calling the callback when	1622	when entering the B<execute> state and skipping calling the callback when
582	entering the the B<result> state, but will leave the request otherwise	1623	entering the the B<result> state, but will leave the request otherwise
583	untouched. That means that requests that currently execute will not be	1624	untouched (with the exception of readdir). That means that requests that
584	stopped and resources held by the request will not be freed prematurely.	1625	currently execute will not be stopped and resources held by the request
		1626	will not be freed prematurely.
585		1627
586	=item cb $req $callback->(...)	1628	=item cb $req $callback->(...)
587		1629
588	Replace (or simply set) the callback registered to the request.	1630	Replace (or simply set) the callback registered to the request.
589		1631
…		…
633	=item * They can also can also be added to other IO::AIO::GRP objects.	1675	=item * They can also can also be added to other IO::AIO::GRP objects.
634		1676
635	=item * You must not add requests to a group from within the group callback (or	1677	=item * You must not add requests to a group from within the group callback (or
636	any later time).	1678	any later time).
637		1679
638	=item * This does not harmonise well with C<max_outstanding>, so best do
639	not combine C<aio_group> with it. Groups and feeders are recommended for
640	this kind of concurrency-limiting.
641
642	=back	1680	=back
643		1681
644	Their lifetime, simplified, looks like this: when they are empty, they	1682	Their lifetime, simplified, looks like this: when they are empty, they
645	will finish very quickly. If they contain only requests that are in the	1683	will finish very quickly. If they contain only requests that are in the
646	C<done> state, they will also finish. Otherwise they will continue to	1684	C<done> state, they will also finish. Otherwise they will continue to
647	exist.	1685	exist.
648		1686
649	That means after creating a group you have some time to add requests. And	1687	That means after creating a group you have some time to add requests
650	in the callbacks of those requests, you can add further requests to the	1688	(precisely before the callback has been invoked, which is only done within
651	group. And only when all those requests have finished will the the group	1689	the C<poll_cb>). And in the callbacks of those requests, you can add
652	itself finish.	1690	further requests to the group. And only when all those requests have
		1691	finished will the the group itself finish.
653		1692
654	=over 4	1693	=over 4
655		1694
656	=item add $grp ...	1695	=item add $grp ...
657		1696
…		…
661	be added, including other groups, as long as you do not create circular	1700	be added, including other groups, as long as you do not create circular
662	dependencies.	1701	dependencies.
663		1702
664	Returns all its arguments.	1703	Returns all its arguments.
665		1704
		1705	=item $grp->cancel_subs
		1706
		1707	Cancel all subrequests and clears any feeder, but not the group request
		1708	itself. Useful when you queued a lot of events but got a result early.
		1709
		1710	The group request will finish normally (you cannot add requests to the
		1711	group).
		1712
666	=item $grp->result (...)	1713	=item $grp->result (...)
667		1714
668	Set the result value(s) that will be passed to the group callback when all	1715	Set the result value(s) that will be passed to the group callback when all
669	subrequests have finished. By default, no argument will be passed.	1716	subrequests have finished and set the groups errno to the current value
		1717	of errno (just like calling C<errno> without an error number). By default,
		1718	no argument will be passed and errno is zero.
		1719
		1720	=item $grp->errno ([$errno])
		1721
		1722	Sets the group errno value to C<$errno>, or the current value of errno
		1723	when the argument is missing.
		1724
		1725	Every aio request has an associated errno value that is restored when
		1726	the callback is invoked. This method lets you change this value from its
		1727	default (0).
		1728
		1729	Calling C<result> will also set errno, so make sure you either set C<$!>
		1730	before the call to C<result>, or call c<errno> after it.
670		1731
671	=item feed $grp $callback->($grp)	1732	=item feed $grp $callback->($grp)
672
673	[VERY EXPERIMENTAL]
674		1733
675	Sets a feeder/generator on this group: every group can have an attached	1734	Sets a feeder/generator on this group: every group can have an attached
676	generator that generates requests if idle. The idea behind this is that,	1735	generator that generates requests if idle. The idea behind this is that,
677	although you could just queue as many requests as you want in a group,	1736	although you could just queue as many requests as you want in a group,
678	this might starve other requests for a potentially long time. For	1737	this might starve other requests for a potentially long time. For example,
679	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1738	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
680	requests, delaying any later requests for a long time.	1739	requests, delaying any later requests for a long time.
681		1740
682	To avoid this, and allow incremental generation of requests, you can	1741	To avoid this, and allow incremental generation of requests, you can
683	instead a group and set a feeder on it that generates those requests. The	1742	instead a group and set a feeder on it that generates those requests. The
684	feed callback will be called whenever there are few enough (see C<feed_limit>,	1743	feed callback will be called whenever there are few enough (see C<limit>,
685	below) requests active in the group itself and is expected to queue more	1744	below) requests active in the group itself and is expected to queue more
686	requests.	1745	requests.
687		1746
688	The feed can queue as many requests as it likes (i.e. C<add> does not	1747	The feed callback can queue as many requests as it likes (i.e. C<add> does
689	impose any limits).	1748	not impose any limits).
690		1749
691	If the feed does not queue more requests when called, it will be	1750	If the feed does not queue more requests when called, it will be
692	automatically removed from the group.	1751	automatically removed from the group.
693		1752
694	If the feed limit is C<0>, it will be set to C<2> automatically.	1753	If the feed limit is C<0> when this method is called, it will be set to
		1754	C<2> automatically.
695		1755
696	Example:	1756	Example:
697		1757
698	# stat all files in @files, but only ever use four aio requests concurrently:	1758	# stat all files in @files, but only ever use four aio requests concurrently:
699		1759
700	my $grp = aio_group sub { print "finished\n" };	1760	my $grp = aio_group sub { print "finished\n" };
701	feed_limit $grp 4;	1761	limit $grp 4;
702	feed $grp sub {	1762	feed $grp sub {
703	my $file = pop @files	1763	my $file = pop @files
704	or return;	1764	or return;
705		1765
706	add $grp aio_stat $file, sub { ... };	1766	add $grp aio_stat $file, sub { ... };
707	};	1767	};
708		1768
709	=item feed_limit $grp $num	1769	=item limit $grp $num
710		1770
711	Sets the feeder limit for the group: The feeder will be called whenever	1771	Sets the feeder limit for the group: The feeder will be called whenever
712	the group contains less than this many requests.	1772	the group contains less than this many requests.
713		1773
714	Setting the limit to C<0> will pause the feeding process.	1774	Setting the limit to C<0> will pause the feeding process.
715		1775
		1776	The default value for the limit is C<0>, but note that setting a feeder
		1777	automatically bumps it up to C<2>.
		1778
716	=back	1779	=back
717		1780
718	=head2 SUPPORT FUNCTIONS	1781	=head2 SUPPORT FUNCTIONS
719		1782
		1783	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1784
720	=over 4	1785	=over 4
721		1786
722	=item $fileno = IO::AIO::poll_fileno	1787	=item $fileno = IO::AIO::poll_fileno
723		1788
724	Return the I<request result pipe file descriptor>. This filehandle must be	1789	Return the I<request result pipe file descriptor>. This filehandle must be
725	polled for reading by some mechanism outside this module (e.g. Event or	1790	polled for reading by some mechanism outside this module (e.g. EV, Glib,
726	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1791	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
727	to call C<poll_cb> to check the results.	1792	you have to call C<poll_cb> to check the results.
728		1793
729	See C<poll_cb> for an example.	1794	See C<poll_cb> for an example.
730		1795
731	=item IO::AIO::poll_cb	1796	=item IO::AIO::poll_cb
732		1797
733	Process all outstanding events on the result pipe. You have to call this	1798	Process some requests that have reached the result phase (i.e. they have
734	regularly. Returns the number of events processed. Returns immediately	1799	been executed but the results are not yet reported). You have to call
735	when no events are outstanding.	1800	this "regularly" to finish outstanding requests.
		1801
		1802	Returns C<0> if all events could be processed (or there were no
		1803	events to process), or C<-1> if it returned earlier for whatever
		1804	reason. Returns immediately when no events are outstanding. The amount
		1805	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1806	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1807
		1808	If not all requests were processed for whatever reason, the poll file
		1809	descriptor will still be ready when C<poll_cb> returns, so normally you
		1810	don't have to do anything special to have it called later.
		1811
		1812	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1813	ready, it can be beneficial to call this function from loops which submit
		1814	a lot of requests, to make sure the results get processed when they become
		1815	available and not just when the loop is finished and the event loop takes
		1816	over again. This function returns very fast when there are no outstanding
		1817	requests.
736		1818
737	Example: Install an Event watcher that automatically calls	1819	Example: Install an Event watcher that automatically calls
738	IO::AIO::poll_cb with high priority:	1820	IO::AIO::poll_cb with high priority (more examples can be found in the
		1821	SYNOPSIS section, at the top of this document):
739		1822
740	Event->io (fd => IO::AIO::poll_fileno,	1823	Event->io (fd => IO::AIO::poll_fileno,
741	poll => 'r', async => 1,	1824	poll => 'r', async => 1,
742	cb => \&IO::AIO::poll_cb);	1825	cb => \&IO::AIO::poll_cb);
743		1826
744	=item IO::AIO::poll_wait	1827	=item IO::AIO::poll_wait
745		1828
746	Wait till the result filehandle becomes ready for reading (simply does a	1829	Wait until either at least one request is in the result phase or no
747	C<select> on the filehandle. This is useful if you want to synchronously wait	1830	requests are outstanding anymore.
748	for some requests to finish).	1831
		1832	This is useful if you want to synchronously wait for some requests to
		1833	become ready, without actually handling them.
749		1834
750	See C<nreqs> for an example.	1835	See C<nreqs> for an example.
751		1836
		1837	=item IO::AIO::poll
		1838
		1839	Waits until some requests have been handled.
		1840
		1841	Returns the number of requests processed, but is otherwise strictly
		1842	equivalent to:
		1843
		1844	IO::AIO::poll_wait, IO::AIO::poll_cb
		1845
752	=item IO::AIO::nreqs	1846	=item IO::AIO::flush
753		1847
754	Returns the number of requests currently outstanding (i.e. for which their	1848	Wait till all outstanding AIO requests have been handled.
755	callback has not been invoked yet).
756		1849
757	Example: wait till there are no outstanding requests anymore:	1850	Strictly equivalent to:
758		1851
759	IO::AIO::poll_wait, IO::AIO::poll_cb	1852	IO::AIO::poll_wait, IO::AIO::poll_cb
760	while IO::AIO::nreqs;	1853	while IO::AIO::nreqs;
761		1854
762	=item IO::AIO::flush	1855	=item IO::AIO::max_poll_reqs $nreqs
763		1856
764	Wait till all outstanding AIO requests have been handled.	1857	=item IO::AIO::max_poll_time $seconds
765		1858
766	Strictly equivalent to:	1859	These set the maximum number of requests (default C<0>, meaning infinity)
		1860	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1861	the maximum amount of time (default C<0>, meaning infinity) spent in
		1862	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1863	of time C<poll_cb> is allowed to use).
767		1864
768	IO::AIO::poll_wait, IO::AIO::poll_cb	1865	Setting C<max_poll_time> to a non-zero value creates an overhead of one
769	while IO::AIO::nreqs;	1866	syscall per request processed, which is not normally a problem unless your
		1867	callbacks are really really fast or your OS is really really slow (I am
		1868	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
770		1869
771	=item IO::AIO::poll	1870	Setting these is useful if you want to ensure some level of
		1871	interactiveness when perl is not fast enough to process all requests in
		1872	time.
772		1873
773	Waits until some requests have been handled.	1874	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
774		1875
775	Strictly equivalent to:	1876	Example: Install an Event watcher that automatically calls
		1877	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1878	program get the CPU sometimes even under high AIO load.
776		1879
777	IO::AIO::poll_wait, IO::AIO::poll_cb	1880	# try not to spend much more than 0.1s in poll_cb
778	if IO::AIO::nreqs;	1881	IO::AIO::max_poll_time 0.1;
		1882
		1883	# use a low priority so other tasks have priority
		1884	Event->io (fd => IO::AIO::poll_fileno,
		1885	poll => 'r', nice => 1,
		1886	cb => &IO::AIO::poll_cb);
		1887
		1888	=back
		1889
		1890	=head3 CONTROLLING THE NUMBER OF THREADS
		1891
		1892	=over
779		1893
780	=item IO::AIO::min_parallel $nthreads	1894	=item IO::AIO::min_parallel $nthreads
781		1895
782	Set the minimum number of AIO threads to C<$nthreads>. The current	1896	Set the minimum number of AIO threads to C<$nthreads>. The current
783	default is C<8>, which means eight asynchronous operations can execute	1897	default is C<8>, which means eight asynchronous operations can execute
784	concurrently at any one time (the number of outstanding requests,	1898	concurrently at any one time (the number of outstanding requests,
785	however, is unlimited).	1899	however, is unlimited).
786		1900
787	IO::AIO starts threads only on demand, when an AIO request is queued and	1901	IO::AIO starts threads only on demand, when an AIO request is queued and
788	no free thread exists.	1902	no free thread exists. Please note that queueing up a hundred requests can
		1903	create demand for a hundred threads, even if it turns out that everything
		1904	is in the cache and could have been processed faster by a single thread.
789		1905
790	It is recommended to keep the number of threads relatively low, as some	1906	It is recommended to keep the number of threads relatively low, as some
791	Linux kernel versions will scale negatively with the number of threads	1907	Linux kernel versions will scale negatively with the number of threads
792	(higher parallelity => MUCH higher latency). With current Linux 2.6	1908	(higher parallelity => MUCH higher latency). With current Linux 2.6
793	versions, 4-32 threads should be fine.	1909	versions, 4-32 threads should be fine.
…		…
807	This module automatically runs C<max_parallel 0> at program end, to ensure	1923	This module automatically runs C<max_parallel 0> at program end, to ensure
808	that all threads are killed and that there are no outstanding requests.	1924	that all threads are killed and that there are no outstanding requests.
809		1925
810	Under normal circumstances you don't need to call this function.	1926	Under normal circumstances you don't need to call this function.
811		1927
		1928	=item IO::AIO::max_idle $nthreads
		1929
		1930	Limit the number of threads (default: 4) that are allowed to idle
		1931	(i.e., threads that did not get a request to process within the idle
		1932	timeout (default: 10 seconds). That means if a thread becomes idle while
		1933	C<$nthreads> other threads are also idle, it will free its resources and
		1934	exit.
		1935
		1936	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1937	to allow for extremely high load situations, but want to free resources
		1938	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1939
		1940	The default is probably ok in most situations, especially if thread
		1941	creation is fast. If thread creation is very slow on your system you might
		1942	want to use larger values.
		1943
		1944	=item IO::AIO::idle_timeout $seconds
		1945
		1946	Sets the minimum idle timeout (default 10) after which worker threads are
		1947	allowed to exit. SEe C<IO::AIO::max_idle>.
		1948
812	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1949	=item IO::AIO::max_outstanding $maxreqs
813		1950
814	[DEPRECATED]
815
816	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1951	Sets the maximum number of outstanding requests to C<$nreqs>. If
817	try to queue up more than this number of requests, the caller will block until	1952	you do queue up more than this number of requests, the next call to
818	some requests have been handled.	1953	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1954	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1955	longer exceeded.
819		1956
820	The default is very large, so normally there is no practical limit. If you	1957	In other words, this setting does not enforce a queue limit, but can be
821	queue up many requests in a loop it often improves speed if you set	1958	used to make poll functions block if the limit is exceeded.
822	this to a relatively low number, such as C<100>.
823		1959
824	This function does not work well together with C<aio_group>'s, and their	1960	This is a very bad function to use in interactive programs because it
825	feeder interface is better suited to limiting concurrency, so do not use	1961	blocks, and a bad way to reduce concurrency because it is inexact: Better
826	this function.	1962	use an C<aio_group> together with a feed callback.
827		1963
828	Under normal circumstances you don't need to call this function.	1964	Its main use is in scripts without an event loop - when you want to stat
		1965	a lot of files, you can write something like this:
		1966
		1967	IO::AIO::max_outstanding 32;
		1968
		1969	for my $path (...) {
		1970	aio_stat $path , ...;
		1971	IO::AIO::poll_cb;
		1972	}
		1973
		1974	IO::AIO::flush;
		1975
		1976	The call to C<poll_cb> inside the loop will normally return instantly, but
		1977	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1978	some requests have been handled. This keeps the loop from pushing a large
		1979	number of C<aio_stat> requests onto the queue.
		1980
		1981	The default value for C<max_outstanding> is very large, so there is no
		1982	practical limit on the number of outstanding requests.
829		1983
830	=back	1984	=back
831		1985
		1986	=head3 STATISTICAL INFORMATION
		1987
		1988	=over
		1989
		1990	=item IO::AIO::nreqs
		1991
		1992	Returns the number of requests currently in the ready, execute or pending
		1993	states (i.e. for which their callback has not been invoked yet).
		1994
		1995	Example: wait till there are no outstanding requests anymore:
		1996
		1997	IO::AIO::poll_wait, IO::AIO::poll_cb
		1998	while IO::AIO::nreqs;
		1999
		2000	=item IO::AIO::nready
		2001
		2002	Returns the number of requests currently in the ready state (not yet
		2003	executed).
		2004
		2005	=item IO::AIO::npending
		2006
		2007	Returns the number of requests currently in the pending state (executed,
		2008	but not yet processed by poll_cb).
		2009
		2010	=back
		2011
		2012	=head3 MISCELLANEOUS FUNCTIONS
		2013
		2014	IO::AIO implements some functions that are useful when you want to use
		2015	some "Advanced I/O" function not available to in Perl, without going the
		2016	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2017	counterpart.
		2018
		2019	=over 4
		2020
		2021	=item $numfd = IO::AIO::get_fdlimit
		2022
		2023	This function is I<EXPERIMENTAL> and subject to change.
		2024
		2025	Tries to find the current file descriptor limit and returns it, or
		2026	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2027	the highest valid file descriptor number.
		2028
		2029	=item IO::AIO::min_fdlimit [$numfd]
		2030
		2031	This function is I<EXPERIMENTAL> and subject to change.
		2032
		2033	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2034	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2035	is missing, it will try to set a very high limit, although this is not
		2036	recommended when you know the actual minimum that you require.
		2037
		2038	If the limit cannot be raised enough, the function makes a best-effort
		2039	attempt to increase the limit as much as possible, using various
		2040	tricks, while still failing. You can query the resulting limit using
		2041	C<IO::AIO::get_fdlimit>.
		2042
		2043	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2044	true.
		2045
		2046	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2047
		2048	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2049	but is blocking (this makes most sense if you know the input data is
		2050	likely cached already and the output filehandle is set to non-blocking
		2051	operations).
		2052
		2053	Returns the number of bytes copied, or C<-1> on error.
		2054
		2055	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2056
		2057	Simply calls the C<posix_fadvise> function (see its
		2058	manpage for details). The following advice constants are
		2059	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2060	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2061	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2062
		2063	On systems that do not implement C<posix_fadvise>, this function returns
		2064	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2065
		2066	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2072	C<IO::AIO::MADV_DONTNEED>.
		2073
		2074	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2075	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2076	will be reduced to fit into the C<$scalar>.
		2077
		2078	On systems that do not implement C<posix_madvise>, this function returns
		2079	ENOSYS, otherwise the return value of C<posix_madvise>.
		2080
		2081	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2082
		2083	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2084	$scalar (see its manpage for details). The following protect
		2085	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2086	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2087
		2088	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2089	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2090	will be reduced to fit into the C<$scalar>.
		2091
		2092	On systems that do not implement C<mprotect>, this function returns
		2093	ENOSYS, otherwise the return value of C<mprotect>.
		2094
		2095	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2096
		2097	Memory-maps a file (or anonymous memory range) and attaches it to the
		2098	given C<$scalar>, which will act like a string scalar. Returns true on
		2099	success, and false otherwise.
		2100
		2101	The scalar must exist, but its contents do not matter - this means you
		2102	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2103	the scalar first.
		2104
		2105	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2106	which don't change the string length, and most read-only operations such
		2107	as copying it or searching it with regexes and so on.
		2108
		2109	Anything else is unsafe and will, at best, result in memory leaks.
		2110
		2111	The memory map associated with the C<$scalar> is automatically removed
		2112	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2113	or C<IO::AIO::munmap> functions are called on it.
		2114
		2115	This calls the C<mmap>(2) function internally. See your system's manual
		2116	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2117
		2118	The C<$length> must be larger than zero and smaller than the actual
		2119	filesize.
		2120
		2121	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2122	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2123
		2124	C<$flags> can be a combination of
		2125	C<IO::AIO::MAP_SHARED> or
		2126	C<IO::AIO::MAP_PRIVATE>,
		2127	or a number of system-specific flags (when not available, the are C<0>):
		2128	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2129	C<IO::AIO::MAP_LOCKED>,
		2130	C<IO::AIO::MAP_NORESERVE>,
		2131	C<IO::AIO::MAP_POPULATE>,
		2132	C<IO::AIO::MAP_NONBLOCK>,
		2133	C<IO::AIO::MAP_FIXED>,
		2134	C<IO::AIO::MAP_GROWSDOWN>,
		2135	C<IO::AIO::MAP_32BIT>,
		2136	C<IO::AIO::MAP_HUGETLB> or
		2137	C<IO::AIO::MAP_STACK>.
		2138
		2139	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2140
		2141	C<$offset> is the offset from the start of the file - it generally must be
		2142	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2143
		2144	Example:
		2145
		2146	use Digest::MD5;
		2147	use IO::AIO;
		2148
		2149	open my $fh, "<verybigfile"
		2150	or die "$!";
		2151
		2152	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2153	or die "verybigfile: $!";
		2154
		2155	my $fast_md5 = md5 $data;
		2156
		2157	=item IO::AIO::munmap $scalar
		2158
		2159	Removes a previous mmap and undefines the C<$scalar>.
		2160
		2161	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2162
		2163	Calls the C<munlock> function, undoing the effects of a previous
		2164	C<aio_mlock> call (see its description for details).
		2165
		2166	=item IO::AIO::munlockall
		2167
		2168	Calls the C<munlockall> function.
		2169
		2170	On systems that do not implement C<munlockall>, this function returns
		2171	ENOSYS, otherwise the return value of C<munlockall>.
		2172
		2173	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2174
		2175	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2176	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2177	should be the file offset.
		2178
		2179	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2180	silently corrupt the data in this case.
		2181
		2182	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2183	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2184	C<IO::AIO::SPLICE_F_GIFT>.
		2185
		2186	See the C<splice(2)> manpage for details.
		2187
		2188	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2189
		2190	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2191	description for C<IO::AIO::splice> above for details.
		2192
		2193	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2194
		2195	Attempts to query or change the pipe buffer size. Obviously works only
		2196	on pipes, and currently works only on GNU/Linux systems, and fails with
		2197	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2198	size on other systems, drop me a note.
		2199
		2200	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2201
		2202	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2203	C<$flags> is missing or C<0>, then this should be the same as a call to
		2204	perl's built-in C<pipe> function and create a new pipe, and works on
		2205	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2206	(..., 4096, O_BINARY)>.
		2207
		2208	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2209	the given flags (Linux 2.6.27, glibc 2.9).
		2210
		2211	On success, the read and write file handles are returned.
		2212
		2213	On error, nothing will be returned. If the pipe2 syscall is missing and
		2214	C<$flags> is non-zero, fails with C<ENOSYS>.
		2215
		2216	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2217	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2218	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2219
		2220	Example: create a pipe race-free w.r.t. threads and fork:
		2221
		2222	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2223	or die "pipe2: $!\n";
		2224
		2225	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2226
		2227	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2228	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2229
		2230	On success, the new eventfd filehandle is returned, otherwise returns
		2231	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2232
		2233	Please refer to L<eventfd(2)> for more info on this call.
		2234
		2235	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2236	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2237
		2238	Example: create a new eventfd filehandle:
		2239
		2240	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2241	or die "eventfd: $!\n";
		2242
		2243	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2244
		2245	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2246	(unhelpful) default for C<$flags> is C<0>.
		2247
		2248	On success, the new timerfd filehandle is returned, otherwise returns
		2249	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2250
		2251	Please refer to L<timerfd_create(2)> for more info on this call.
		2252
		2253	The following C<$clockid> values are
		2254	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2255	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2256	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2257	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2258
		2259	The following C<$flags> values are available (Linux
		2260	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2261
		2262	Example: create a new timerfd and set it to one-second repeated alarms,
		2263	then wait for two alarms:
		2264
		2265	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2266	or die "timerfd_create: $!\n";
		2267
		2268	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2269	or die "timerfd_settime: $!\n";
		2270
		2271	for (1..2) {
		2272	8 == sysread $fh, my $buf, 8
		2273	or die "timerfd read failure\n";
		2274
		2275	printf "number of expirations (likely 1): %d\n",
		2276	unpack "Q", $buf;
		2277	}
		2278
		2279	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2280
		2281	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2282	call. Please refer to its manpage for more info on this call.
		2283
		2284	The new itimerspec is specified using two (possibly fractional) second
		2285	values, C<$new_interval> and C<$new_value>).
		2286
		2287	On success, the current interval and value are returned (as per
		2288	C<timerfd_gettime>). On failure, the empty list is returned.
		2289
		2290	The following C<$flags> values are
		2291	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2292	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2293
		2294	See C<IO::AIO::timerfd_create> for a full example.
		2295
		2296	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2297
		2298	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2299	call. Please refer to its manpage for more info on this call.
		2300
		2301	On success, returns the current values of interval and value for the given
		2302	timerfd (as potentially fractional second values). On failure, the empty
		2303	list is returned.
		2304
		2305	=back
		2306
832	=cut	2307	=cut
833		2308
834	# support function to convert a fd into a perl filehandle
835	sub _fd2fh {
836	return undef if $_[0] < 0;
837
838	# try to generate nice filehandles
839	my $sym = "IO::AIO::fd#$_[0]";
840	local *$sym;
841
842	open *$sym, "+<&=$_[0]" # usually works under any unix
843	or open *$sym, "<&=$_[0]" # cygwin needs this
844	or open *$sym, ">&=$_[0]" # or this
845	or return undef;
846
847	*$sym
848	}
849
850	min_parallel 8;	2309	min_parallel 8;
851		2310
852	END {	2311	END { flush }
853	max_parallel 0;
854	}
855		2312
856	1;	2313	1;
857		2314
		2315	=head1 EVENT LOOP INTEGRATION
		2316
		2317	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2318	automatically into many event loops:
		2319
		2320	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2321	use AnyEvent::AIO;
		2322
		2323	You can also integrate IO::AIO manually into many event loops, here are
		2324	some examples of how to do this:
		2325
		2326	# EV integration
		2327	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2328
		2329	# Event integration
		2330	Event->io (fd => IO::AIO::poll_fileno,
		2331	poll => 'r',
		2332	cb => \&IO::AIO::poll_cb);
		2333
		2334	# Glib/Gtk2 integration
		2335	add_watch Glib::IO IO::AIO::poll_fileno,
		2336	in => sub { IO::AIO::poll_cb; 1 };
		2337
		2338	# Tk integration
		2339	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2340	readable => \&IO::AIO::poll_cb);
		2341
		2342	# Danga::Socket integration
		2343	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2344	\&IO::AIO::poll_cb);
		2345
858	=head2 FORK BEHAVIOUR	2346	=head2 FORK BEHAVIOUR
859		2347
860	This module should do "the right thing" when the process using it forks:	2348	Usage of pthreads in a program changes the semantics of fork
		2349	considerably. Specifically, only async-safe functions can be called after
		2350	fork. Perl doesn't know about this, so in general, you cannot call fork
		2351	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2352	pthreads, so this applies, but many other extensions and (for inexplicable
		2353	reasons) perl itself often is linked against pthreads, so this limitation
		2354	applies to quite a lot of perls.
861		2355
862	Before the fork, IO::AIO enters a quiescent state where no requests	2356	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
863	can be added in other threads and no results will be processed. After	2357	only works in the process that loaded it. Forking is fully supported, but
864	the fork the parent simply leaves the quiescent state and continues	2358	using IO::AIO in the child is not.
865	request/result processing, while the child clears the request/result
866	queue (so the requests started before the fork will only be handled in
867	the parent). Threads will be started on demand until the limit ste in the
868	parent process has been reached again.
869		2359
870	In short: the parent will, after a short pause, continue as if fork had	2360	You might get around by not I<using> IO::AIO before (or after)
871	not been called, while the child will act as if IO::AIO has not been used	2361	forking. You could also try to call the L<IO::AIO::reinit> function in the
872	yet.	2362	child:
		2363
		2364	=over 4
		2365
		2366	=item IO::AIO::reinit
		2367
		2368	Abandons all current requests and I/O threads and simply reinitialises all
		2369	data structures. This is not an operation supported by any standards, but
		2370	happens to work on GNU/Linux and some newer BSD systems.
		2371
		2372	The only reasonable use for this function is to call it after forking, if
		2373	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2374	the process will result in undefined behaviour. Calling it at any time
		2375	will also result in any undefined (by POSIX) behaviour.
		2376
		2377	=back
		2378
		2379	=head2 LINUX-SPECIFIC CALLS
		2380
		2381	When a call is documented as "linux-specific" then this means it
		2382	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2383	availability and compatibility of such calls regardless of the platform
		2384	it is compiled on, so platforms such as FreeBSD which often implement
		2385	these calls will work. When in doubt, call them and see if they fail wth
		2386	C<ENOSYS>.
873		2387
874	=head2 MEMORY USAGE	2388	=head2 MEMORY USAGE
875		2389
		2390	Per-request usage:
		2391
876	Each aio request uses - depending on your architecture - around 128 bytes	2392	Each aio request uses - depending on your architecture - around 100-200
877	of memory. In addition, stat requests need a stat buffer (possibly a few	2393	bytes of memory. In addition, stat requests need a stat buffer (possibly
878	hundred bytes). Perl scalars and other data passed into aio requests will	2394	a few hundred bytes), readdir requires a result buffer and so on. Perl
879	also be locked.	2395	scalars and other data passed into aio requests will also be locked and
		2396	will consume memory till the request has entered the done state.
880		2397
881	This is now awfully much, so queuing lots of requests is not usually a	2398	This is not awfully much, so queuing lots of requests is not usually a
882	problem.	2399	problem.
883		2400
884	Each thread needs a stack area which is usually around 16k, sometimes much	2401	Per-thread usage:
885	larger, depending on the OS.	2402
		2403	In the execution phase, some aio requests require more memory for
		2404	temporary buffers, and each thread requires a stack and other data
		2405	structures (usually around 16k-128k, depending on the OS).
		2406
		2407	=head1 KNOWN BUGS
		2408
		2409	Known bugs will be fixed in the next release.
886		2410
887	=head1 SEE ALSO	2411	=head1 SEE ALSO
888		2412
889	L<Coro>, L<Linux::AIO> (obsolete).	2413	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2414	more natural syntax.
890		2415
891	=head1 AUTHOR	2416	=head1 AUTHOR
892		2417
893	Marc Lehmann <schmorp@schmorp.de>	2418	Marc Lehmann <schmorp@schmorp.de>
894	http://home.schmorp.de/	2419	http://home.schmorp.de/

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