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Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs.
Revision 1.229 by root, Wed Jul 25 16:32:30 2012 UTC

…		…
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
64	Although the module will work with in the presence of other threads, it is	63	Although the module will work in the presence of other (Perl-) threads,
65	currently not reentrant, so use appropriate locking yourself, always call	64	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	65	yourself, always call C<poll_cb> from within the same thread, or never
67	C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
		67
		68	=head2 EXAMPLE
		69
		70	This is a simple example that uses the EV module and loads
		71	F</etc/passwd> asynchronously:
		72
		73	use Fcntl;
		74	use EV;
		75	use IO::AIO;
		76
		77	# register the IO::AIO callback with EV
		78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		79
		80	# queue the request to open /etc/passwd
		81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		82	my $fh = shift
		83	or die "error while opening: $!";
		84
		85	# stat'ing filehandles is generally non-blocking
		86	my $size = -s $fh;
		87
		88	# queue a request to read the file
		89	my $contents;
		90	aio_read $fh, 0, $size, $contents, 0, sub {
		91	$_[0] == $size
		92	or die "short read: $!";
		93
		94	close $fh;
		95
		96	# file contents now in $contents
		97	print $contents;
		98
		99	# exit event loop and program
		100	EV::unloop;
		101	};
		102	};
		103
		104	# possibly queue up other requests, or open GUI windows,
		105	# check for sockets etc. etc.
		106
		107	# process events as long as there are some:
		108	EV::loop;
		109
		110	=head1 REQUEST ANATOMY AND LIFETIME
		111
		112	Every C<aio_*> function creates a request. which is a C data structure not
		113	directly visible to Perl.
		114
		115	If called in non-void context, every request function returns a Perl
		116	object representing the request. In void context, nothing is returned,
		117	which saves a bit of memory.
		118
		119	The perl object is a fairly standard ref-to-hash object. The hash contents
		120	are not used by IO::AIO so you are free to store anything you like in it.
		121
		122	During their existance, aio requests travel through the following states,
		123	in order:
		124
		125	=over 4
		126
		127	=item ready
		128
		129	Immediately after a request is created it is put into the ready state,
		130	waiting for a thread to execute it.
		131
		132	=item execute
		133
		134	A thread has accepted the request for processing and is currently
		135	executing it (e.g. blocking in read).
		136
		137	=item pending
		138
		139	The request has been executed and is waiting for result processing.
		140
		141	While request submission and execution is fully asynchronous, result
		142	processing is not and relies on the perl interpreter calling C<poll_cb>
		143	(or another function with the same effect).
		144
		145	=item result
		146
		147	The request results are processed synchronously by C<poll_cb>.
		148
		149	The C<poll_cb> function will process all outstanding aio requests by
		150	calling their callbacks, freeing memory associated with them and managing
		151	any groups they are contained in.
		152
		153	=item done
		154
		155	Request has reached the end of its lifetime and holds no resources anymore
		156	(except possibly for the Perl object, but its connection to the actual
		157	aio request is severed and calling its methods will either do nothing or
		158	result in a runtime error).
		159
		160	=back
68		161
69	=cut	162	=cut
70		163
71	package IO::AIO;	164	package IO::AIO;
72		165
73	no warnings;	166	use Carp ();
74	use strict 'vars';	167
		168	use common::sense;
75		169
76	use base 'Exporter';	170	use base 'Exporter';
77		171
78	BEGIN {	172	BEGIN {
79	our $VERSION = '2.0';	173	our $VERSION = '4.15';
80		174
81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	175	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	176	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	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead aio_fiemap
		180	aio_rename aio_link aio_move aio_copy aio_group
		181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
84	aio_group);	185	aio_wd);
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	186
		187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		189	min_parallel max_parallel max_idle idle_timeout
		190	nreqs nready npending nthreads
		191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
86		196
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		198
89	require XSLoader;	199	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
91	}	201	}
92		202
93	=head1 FUNCTIONS	203	=head1 FUNCTIONS
94		204
95	=head2 AIO FUNCTIONS	205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes of the most important functions
		208	for quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_seek $fh,$offset,$whence, $callback->($offs)
		215	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		217	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		218	aio_readahead $fh,$offset,$length, $callback->($retval)
		219	aio_stat $fh_or_path, $callback->($status)
		220	aio_lstat $fh, $callback->($status)
		221	aio_statvfs $fh_or_path, $callback->($statvfs)
		222	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		223	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_truncate $fh_or_path, $offset, $callback->($status)
		226	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		227	aio_unlink $pathname, $callback->($status)
		228	aio_mknod $pathname, $mode, $dev, $callback->($status)
		229	aio_link $srcpath, $dstpath, $callback->($status)
		230	aio_symlink $srcpath, $dstpath, $callback->($status)
		231	aio_readlink $pathname, $callback->($link)
		232	aio_realpath $pathname, $callback->($link)
		233	aio_rename $srcpath, $dstpath, $callback->($status)
		234	aio_mkdir $pathname, $mode, $callback->($status)
		235	aio_rmdir $pathname, $callback->($status)
		236	aio_readdir $pathname, $callback->($entries)
		237	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		238	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		239	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		240	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		241	aio_load $pathname, $data, $callback->($status)
		242	aio_copy $srcpath, $dstpath, $callback->($status)
		243	aio_move $srcpath, $dstpath, $callback->($status)
		244	aio_rmtree $pathname, $callback->($status)
		245	aio_sync $callback->($status)
		246	aio_syncfs $fh, $callback->($status)
		247	aio_fsync $fh, $callback->($status)
		248	aio_fdatasync $fh, $callback->($status)
		249	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		250	aio_pathsync $pathname, $callback->($status)
		251	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		252	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		254	aio_mlockall $flags, $callback->($status)
		255	aio_group $callback->(...)
		256	aio_nop $callback->()
		257
		258	$prev_pri = aioreq_pri [$pri]
		259	aioreq_nice $pri_adjust
		260
		261	IO::AIO::poll_wait
		262	IO::AIO::poll_cb
		263	IO::AIO::poll
		264	IO::AIO::flush
		265	IO::AIO::max_poll_reqs $nreqs
		266	IO::AIO::max_poll_time $seconds
		267	IO::AIO::min_parallel $nthreads
		268	IO::AIO::max_parallel $nthreads
		269	IO::AIO::max_idle $nthreads
		270	IO::AIO::idle_timeout $seconds
		271	IO::AIO::max_outstanding $maxreqs
		272	IO::AIO::nreqs
		273	IO::AIO::nready
		274	IO::AIO::npending
		275
		276	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		277	IO::AIO::fadvise $fh, $offset, $len, $advice
		278	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		279	IO::AIO::munmap $scalar
		280	IO::AIO::madvise $scalar, $offset, $length, $advice
		281	IO::AIO::mprotect $scalar, $offset, $length, $protect
		282	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		283	IO::AIO::munlockall
		284
		285	=head2 API NOTES
96		286
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	287	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	288	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	289	and they all accept an additional (and optional) C<$callback> argument
100	which must be a code reference. This code reference will get called with	290	which must be a code reference. This code reference will be called after
101	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	291	the syscall has been executed in an asynchronous fashion. The results
102	perl, which usually delivers "false") as it's sole argument when the given	292	of the request will be passed as arguments to the callback (and, if an
103	syscall has been executed asynchronously.	293	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		294	most syscalls return C<-1> on error, unlike perl, which usually delivers
		295	"false").
		296
		297	Some requests (such as C<aio_readdir>) pass the actual results and
		298	communicate failures by passing C<undef>.
104		299
105	All functions expecting a filehandle keep a copy of the filehandle	300	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	301	internally until the request has finished.
107		302
108	All requests return objects of type L<IO::AIO::REQ> that allow further	303	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	304	further manipulation of those requests while they are in-flight.
110		305
111	The pathnames you pass to these routines I<must> be absolute and	306	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	307	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	308	current working directory could have changed. Alternatively, you can
114	changed. Alternatively, you can make sure that you never change the	309	make sure that you never change the current working directory anywhere
115	current working directory.	310	in the program and then use relative paths. You can also take advantage
		311	of IO::AIOs working directory abstraction, that lets you specify paths
		312	relative to some previously-opened "working directory object" - see the
		313	description of the C<IO::AIO::WD> class later in this document.
116		314
117	To encode pathnames to byte form, either make sure you either: a)	315	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	316	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	317	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	318	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)	319	effect in the user environment, d) use Glib::filename_from_unicode on
122	use something else.	320	unicode filenames or e) use something else to ensure your scalar has the
		321	correct contents.
		322
		323	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		324	handles correctly whether it is set or not.
		325
		326	=head2 AIO REQUEST FUNCTIONS
123		327
124	=over 4	328	=over 4
		329
		330	=item $prev_pri = aioreq_pri [$pri]
		331
		332	Returns the priority value that would be used for the next request and, if
		333	C<$pri> is given, sets the priority for the next aio request.
		334
		335	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		336	and C<4>, respectively. Requests with higher priority will be serviced
		337	first.
		338
		339	The priority will be reset to C<0> after each call to one of the C<aio_*>
		340	functions.
		341
		342	Example: open a file with low priority, then read something from it with
		343	higher priority so the read request is serviced before other low priority
		344	open requests (potentially spamming the cache):
		345
		346	aioreq_pri -3;
		347	aio_open ..., sub {
		348	return unless $_[0];
		349
		350	aioreq_pri -2;
		351	aio_read $_[0], ..., sub {
		352	...
		353	};
		354	};
		355
		356
		357	=item aioreq_nice $pri_adjust
		358
		359	Similar to C<aioreq_pri>, but subtracts the given value from the current
		360	priority, so the effect is cumulative.
		361
125		362
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	363	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		364
128	Asynchronously open or create a file and call the callback with a newly	365	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	366	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	372	list. They are the same as used by C<sysopen>.
136		373
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	374	Likewise, C<$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>,	375	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,	376	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).	377	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		378	by the umask in effect then the request is being executed, so better never
		379	change the umask.
141		380
142	Example:	381	Example:
143		382
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	383	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
145	if ($_[0]) {	384	if ($_[0]) {
146	print "open successful, fh is $_[0]\n";	385	print "open successful, fh is $_[0]\n";
147	...	386	...
148	} else {	387	} else {
149	die "open failed: $!\n";	388	die "open failed: $!\n";
150	}	389	}
151	};	390	};
152		391
		392	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		393	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		394	following POSIX and non-POSIX constants are available (missing ones on
		395	your system are, as usual, C<0>):
		396
		397	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		398	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		399	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		400
		401
153	=item aio_close $fh, $callback->($status)	402	=item aio_close $fh, $callback->($status)
154		403
155	Asynchronously close a file and call the callback with the result	404	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	405	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		406
161	This is supposed to be a bug in the API, so that might change. It's	407	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	408	closing the file descriptor associated with the filehandle itself.
		409
		410	Therefore, C<aio_close> will not close the filehandle - instead it will
		411	use dup2 to overwrite the file descriptor with the write-end of a pipe
		412	(the pipe fd will be created on demand and will be cached).
		413
		414	Or in other words: the file descriptor will be closed, but it will not be
		415	free for reuse until the perl filehandle is closed.
		416
		417	=cut
		418
		419	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		420
		421	Seeks the filehandle to the new C<$offset>, similarly to perl's
		422	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		423	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		424	C<IO::AIO::SEEK_END>).
		425
		426	The resulting absolute offset will be passed to the callback, or C<-1> in
		427	case of an error.
		428
		429	In theory, the C<$whence> constants could be different than the
		430	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		431	so don't panic.
		432
		433	As a GNU/Linux (and maybe Solaris) extension, also the constants
		434	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		435	could be found. No guarantees about suitability for use in C<aio_seek> or
		436	Perl's C<sysseek> can be made though, although I would naively assume they
		437	"just work".
163		438
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	439	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		440
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	441	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		442
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	443	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	444	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
170	callback without the actual number of bytes read (or -1 on error, just	445	and calls the callback without the actual number of bytes read (or -1 on
171	like the syscall).	446	error, just like the syscall).
		447
		448	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		449	offset plus the actual number of bytes read.
		450
		451	If C<$offset> is undefined, then the current file descriptor offset will
		452	be used (and updated), otherwise the file descriptor offset will not be
		453	changed by these calls.
		454
		455	If C<$length> is undefined in C<aio_write>, use the remaining length of
		456	C<$data>.
		457
		458	If C<$dataoffset> is less than zero, it will be counted from the end of
		459	C<$data>.
172		460
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	461	The C<$data> scalar I<MUST NOT> be modified in any way while the request
174	is outstanding. Modifying it can result in segfaults or WW3 (if the	462	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	463	the necessary/optional hardware is installed).
176		464
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	465	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	466	offset C<0> within the scalar:
179		467
180	aio_read $fh, 7, 15, $buffer, 0, sub {	468	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	469	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	470	print "read $_[0] bytes: <$buffer>\n";
183	};	471	};
184		472
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		473
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	474	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		475
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	476	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	477	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	478	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	479	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
261	other.	480	other. The same C<$in_fh> works fine though, as this function does not
		481	move or use the file offset of C<$in_fh>.
262		482
		483	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		484	are written, and there is no way to find out how many more bytes have been
		485	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		486	number of bytes written to C<$out_fh>. Only if the result value equals
		487	C<$length> one can assume that C<$length> bytes have been read.
		488
		489	Unlike with other C<aio_> functions, it makes a lot of sense to use
		490	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		491	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		492	the socket I/O will be non-blocking. Note, however, that you can run
		493	into a trap where C<aio_sendfile> reads some data with readahead, then
		494	fails to write all data, and when the socket is ready the next time, the
		495	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		496	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		497	resource usage.
		498
263	This call tries to make use of a native C<sendfile> syscall to provide	499	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	500	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.	501	a socket, and C<$in_fh> should refer to an mmap'able file.
266		502
267	If the native sendfile call fails or is not implemented, it will be	503	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	504	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		505	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
269	regardless of the limitations of the operating system.	506	type of filehandle regardless of the limitations of the operating system.
270		507
271	Please note, however, that C<aio_sendfile> can read more bytes from	508	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	509	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	510	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	511	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	512	so you really really should check the return value of C<aio_sendfile> -
276	read.	513	fewre bytes than expected might have been transferred.
		514
277		515
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	516	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		517
280	C<aio_readahead> populates the page cache with data from a file so that	518	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>	519	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
287	file. The current file offset of the file is left unchanged.	525	file. The current file offset of the file is left unchanged.
288		526
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	527	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
290	emulated by simply reading the data, which would have a similar effect.	528	emulated by simply reading the data, which would have a similar effect.
291		529
		530
292	=item aio_stat $fh_or_path, $callback->($status)	531	=item aio_stat $fh_or_path, $callback->($status)
293		532
294	=item aio_lstat $fh, $callback->($status)	533	=item aio_lstat $fh, $callback->($status)
295		534
296	Works like perl's C<stat> or C<lstat> in void context. The callback will	535	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
301	for an explanation.	540	for an explanation.
302		541
303	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	542	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	543	error when stat'ing a large file, the results will be silently truncated
305	unless perl itself is compiled with large file support.	544	unless perl itself is compiled with large file support.
		545
		546	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		547	following constants and functions (if not implemented, the constants will
		548	be C<0> and the functions will either C<croak> or fall back on traditional
		549	behaviour).
		550
		551	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		552	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		553	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
306		554
307	Example: Print the length of F</etc/passwd>:	555	Example: Print the length of F</etc/passwd>:
308		556
309	aio_stat "/etc/passwd", sub {	557	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	558	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	559	print "size is ", -s _, "\n";
312	};	560	};
313		561
		562
		563	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		564
		565	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		566	whether a file handle or path was passed.
		567
		568	On success, the callback is passed a hash reference with the following
		569	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		570	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		571	is passed.
		572
		573	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		574	C<ST_NOSUID>.
		575
		576	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		577	their correct value when available, or to C<0> on systems that do
		578	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		579	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		580	C<ST_NODIRATIME> and C<ST_RELATIME>.
		581
		582	Example: stat C</wd> and dump out the data if successful.
		583
		584	aio_statvfs "/wd", sub {
		585	my $f = $_[0]
		586	or die "statvfs: $!";
		587
		588	use Data::Dumper;
		589	say Dumper $f;
		590	};
		591
		592	# result:
		593	{
		594	bsize => 1024,
		595	bfree => 4333064312,
		596	blocks => 10253828096,
		597	files => 2050765568,
		598	flag => 4096,
		599	favail => 2042092649,
		600	bavail => 4333064312,
		601	ffree => 2042092649,
		602	namemax => 255,
		603	frsize => 1024,
		604	fsid => 1810
		605	}
		606
		607
		608	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		609
		610	Works like perl's C<utime> function (including the special case of $atime
		611	and $mtime being undef). Fractional times are supported if the underlying
		612	syscalls support them.
		613
		614	When called with a pathname, uses utimes(2) if available, otherwise
		615	utime(2). If called on a file descriptor, uses futimes(2) if available,
		616	otherwise returns ENOSYS, so this is not portable.
		617
		618	Examples:
		619
		620	# set atime and mtime to current time (basically touch(1)):
		621	aio_utime "path", undef, undef;
		622	# set atime to current time and mtime to beginning of the epoch:
		623	aio_utime "path", time, undef; # undef==0
		624
		625
		626	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		627
		628	Works like perl's C<chown> function, except that C<undef> for either $uid
		629	or $gid is being interpreted as "do not change" (but -1 can also be used).
		630
		631	Examples:
		632
		633	# same as "chown root path" in the shell:
		634	aio_chown "path", 0, -1;
		635	# same as above:
		636	aio_chown "path", 0, undef;
		637
		638
		639	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		640
		641	Works like truncate(2) or ftruncate(2).
		642
		643
		644	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		645
		646	Allocates or freed disk space according to the C<$mode> argument. See the
		647	linux C<fallocate> docuemntation for details.
		648
		649	C<$mode> can currently be C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE>
		650	to allocate space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE |
		651	IO::AIO::FALLOC_FL_KEEP_SIZE>, to deallocate a file range.
		652
		653	The file system block size used by C<fallocate> is presumably the
		654	C<f_bsize> returned by C<statvfs>.
		655
		656	If C<fallocate> isn't available or cannot be emulated (currently no
		657	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		658
		659
		660	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		661
		662	Works like perl's C<chmod> function.
		663
		664
314	=item aio_unlink $pathname, $callback->($status)	665	=item aio_unlink $pathname, $callback->($status)
315		666
316	Asynchronously unlink (delete) a file and call the callback with the	667	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	668	result code.
318		669
		670
		671	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		672
		673	[EXPERIMENTAL]
		674
		675	Asynchronously create a device node (or fifo). See mknod(2).
		676
		677	The only (POSIX-) portable way of calling this function is:
		678
		679	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		680
		681	See C<aio_stat> for info about some potentially helpful extra constants
		682	and functions.
		683
319	=item aio_link $srcpath, $dstpath, $callback->($status)	684	=item aio_link $srcpath, $dstpath, $callback->($status)
320		685
321	Asynchronously create a new link to the existing object at C<$srcpath> at	686	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.	687	the path C<$dstpath> and call the callback with the result code.
323		688
		689
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	690	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		691
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	692	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.	693	the path C<$dstpath> and call the callback with the result code.
328		694
		695
		696	=item aio_readlink $pathname, $callback->($link)
		697
		698	Asynchronously read the symlink specified by C<$path> and pass it to
		699	the callback. If an error occurs, nothing or undef gets passed to the
		700	callback.
		701
		702
		703	=item aio_realpath $pathname, $callback->($path)
		704
		705	Asynchronously make the path absolute and resolve any symlinks in
		706	C<$path>. The resulting path only consists of directories (Same as
		707	L<Cwd::realpath>).
		708
		709	This request can be used to get the absolute path of the current working
		710	directory by passing it a path of F<.> (a single dot).
		711
		712
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	713	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		714
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	715	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	716	rename(2) and call the callback with the result code.
333		717
		718
		719	=item aio_mkdir $pathname, $mode, $callback->($status)
		720
		721	Asynchronously mkdir (create) a directory and call the callback with
		722	the result code. C<$mode> will be modified by the umask at the time the
		723	request is executed, so do not change your umask.
		724
		725
334	=item aio_rmdir $pathname, $callback->($status)	726	=item aio_rmdir $pathname, $callback->($status)
335		727
336	Asynchronously rmdir (delete) a directory and call the callback with the	728	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	729	result code.
		730
338		731
339	=item aio_readdir $pathname, $callback->($entries)	732	=item aio_readdir $pathname, $callback->($entries)
340		733
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	734	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	735	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	736	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		737
345	The callback a single argument which is either C<undef> or an array-ref	738	The callback is passed a single argument which is either C<undef> or an
346	with the filenames.	739	array-ref with the filenames.
347		740
		741
		742	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		743
		744	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		745	tune behaviour and output format. In case of an error, C<$entries> will be
		746	C<undef>.
		747
		748	The flags are a combination of the following constants, ORed together (the
		749	flags will also be passed to the callback, possibly modified):
		750
		751	=over 4
		752
		753	=item IO::AIO::READDIR_DENTS
		754
		755	When this flag is off, then the callback gets an arrayref consisting of
		756	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		757	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		758	entry in more detail.
		759
		760	C<$name> is the name of the entry.
		761
		762	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		763
		764	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		765	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		766	C<IO::AIO::DT_WHT>.
		767
		768	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		769	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		770	scalars are read-only: you can not modify them.
		771
		772	C<$inode> is the inode number (which might not be exact on systems with 64
		773	bit inode numbers and 32 bit perls). This field has unspecified content on
		774	systems that do not deliver the inode information.
		775
		776	=item IO::AIO::READDIR_DIRS_FIRST
		777
		778	When this flag is set, then the names will be returned in an order where
		779	likely directories come first, in optimal stat order. This is useful when
		780	you need to quickly find directories, or you want to find all directories
		781	while avoiding to stat() each entry.
		782
		783	If the system returns type information in readdir, then this is used
		784	to find directories directly. Otherwise, likely directories are names
		785	beginning with ".", or otherwise names with no dots, of which names with
		786	short names are tried first.
		787
		788	=item IO::AIO::READDIR_STAT_ORDER
		789
		790	When this flag is set, then the names will be returned in an order
		791	suitable for stat()'ing each one. That is, when you plan to stat()
		792	all files in the given directory, then the returned order will likely
		793	be fastest.
		794
		795	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		796	the likely dirs come first, resulting in a less optimal stat order.
		797
		798	=item IO::AIO::READDIR_FOUND_UNKNOWN
		799
		800	This flag should not be set when calling C<aio_readdirx>. Instead, it
		801	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		802	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		803	C<$type>'s are known, which can be used to speed up some algorithms.
		804
		805	=back
		806
		807
		808	=item aio_load $pathname, $data, $callback->($status)
		809
		810	This is a composite request that tries to fully load the given file into
		811	memory. Status is the same as with aio_read.
		812
		813	=cut
		814
		815	sub aio_load($$;$) {
		816	my ($path, undef, $cb) = @_;
		817	my $data = \$_[1];
		818
		819	my $pri = aioreq_pri;
		820	my $grp = aio_group $cb;
		821
		822	aioreq_pri $pri;
		823	add $grp aio_open $path, O_RDONLY, 0, sub {
		824	my $fh = shift
		825	or return $grp->result (-1);
		826
		827	aioreq_pri $pri;
		828	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		829	$grp->result ($_[0]);
		830	};
		831	};
		832
		833	$grp
		834	}
		835
		836	=item aio_copy $srcpath, $dstpath, $callback->($status)
		837
		838	Try to copy the I<file> (directories not supported as either source or
		839	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		840	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		841
		842	This is a composite request that creates the destination file with
		843	mode 0200 and copies the contents of the source file into it using
		844	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		845	uid/gid, in that order.
		846
		847	If an error occurs, the partial destination file will be unlinked, if
		848	possible, except when setting atime, mtime, access mode and uid/gid, where
		849	errors are being ignored.
		850
		851	=cut
		852
		853	sub aio_copy($$;$) {
		854	my ($src, $dst, $cb) = @_;
		855
		856	my $pri = aioreq_pri;
		857	my $grp = aio_group $cb;
		858
		859	aioreq_pri $pri;
		860	add $grp aio_open $src, O_RDONLY, 0, sub {
		861	if (my $src_fh = $_[0]) {
		862	my @stat = stat $src_fh; # hmm, might block over nfs?
		863
		864	aioreq_pri $pri;
		865	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		866	if (my $dst_fh = $_[0]) {
		867	aioreq_pri $pri;
		868	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		869	if ($_[0] == $stat[7]) {
		870	$grp->result (0);
		871	close $src_fh;
		872
		873	my $ch = sub {
		874	aioreq_pri $pri;
		875	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		876	aioreq_pri $pri;
		877	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		878	aioreq_pri $pri;
		879	add $grp aio_close $dst_fh;
		880	}
		881	};
		882	};
		883
		884	aioreq_pri $pri;
		885	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		886	if ($_[0] < 0 && $! == ENOSYS) {
		887	aioreq_pri $pri;
		888	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		889	} else {
		890	$ch->();
		891	}
		892	};
		893	} else {
		894	$grp->result (-1);
		895	close $src_fh;
		896	close $dst_fh;
		897
		898	aioreq $pri;
		899	add $grp aio_unlink $dst;
		900	}
		901	};
		902	} else {
		903	$grp->result (-1);
		904	}
		905	},
		906
		907	} else {
		908	$grp->result (-1);
		909	}
		910	};
		911
		912	$grp
		913	}
		914
		915	=item aio_move $srcpath, $dstpath, $callback->($status)
		916
		917	Try to move the I<file> (directories not supported as either source or
		918	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		919	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		920
		921	This is a composite request that tries to rename(2) the file first; if
		922	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		923	that is successful, unlinks the C<$srcpath>.
		924
		925	=cut
		926
		927	sub aio_move($$;$) {
		928	my ($src, $dst, $cb) = @_;
		929
		930	my $pri = aioreq_pri;
		931	my $grp = aio_group $cb;
		932
		933	aioreq_pri $pri;
		934	add $grp aio_rename $src, $dst, sub {
		935	if ($_[0] && $! == EXDEV) {
		936	aioreq_pri $pri;
		937	add $grp aio_copy $src, $dst, sub {
		938	$grp->result ($_[0]);
		939
		940	unless ($_[0]) {
		941	aioreq_pri $pri;
		942	add $grp aio_unlink $src;
		943	}
		944	};
		945	} else {
		946	$grp->result ($_[0]);
		947	}
		948	};
		949
		950	$grp
		951	}
		952
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	953	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
349
350	[EXPERIMENTAL due to internal aio_group use]
351		954
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	955	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	956	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	957	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	958	recurse into (everything else, including symlinks to directories).
356		959
357	C<aio_scandir> is a composite request that creates of many sub requests_	960	C<aio_scandir> is a composite request that creates of many sub requests_
358	C<$maxreq> specifies the maximum number of outstanding aio requests that	961	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	962	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	963	will be chosen (currently 4).
361		964
362	On error, the callback is called without arguments, otherwise it receives	965	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	966	two array-refs with path-relative entry names.
364		967
365	Example:	968	Example:
…		…
372		975
373	Implementation notes.	976	Implementation notes.
374		977
375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	978	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
376		979
		980	If readdir returns file type information, then this is used directly to
		981	find directories.
		982
377	After reading the directory, the modification time, size etc. of the	983	Otherwise, after reading the directory, the modification time, size etc.
378	directory before and after the readdir is checked, and if they match (and	984	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	985	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	986	how many entries are directories (if >= 2). Otherwise, no knowledge of the
381	of subdirectories will be assumed.	987	number of subdirectories will be assumed.
382		988
383	Then entries will be sorted into likely directories (everything without	989	Then entries will be sorted into likely directories a non-initial dot
384	a non-initial dot currently) and likely non-directories (everything	990	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,	991	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	992	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	993	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	994	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	995	filesystems might detect the type of the entry without reading the inode
390	data (e.g. ext2fs filetype feature).	996	data (e.g. ext2fs filetype feature), even on systems that cannot return
		997	the filetype information on readdir.
391		998
392	If the known number of directories (link count - 2) has been reached, the	999	If the known number of directories (link count - 2) has been reached, the
393	rest of the entries is assumed to be non-directories.	1000	rest of the entries is assumed to be non-directories.
394		1001
395	This only works with certainty on POSIX (= UNIX) filesystems, which	1002	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	1006	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	1007	directory counting heuristic.
401		1008
402	=cut	1009	=cut
403		1010
404	sub aio_scandir($$$) {	1011	sub aio_scandir($$;$) {
405	my ($path, $maxreq, $cb) = @_;	1012	my ($path, $maxreq, $cb) = @_;
406		1013
		1014	my $pri = aioreq_pri;
		1015
407	my $grp = aio_group $cb;	1016	my $grp = aio_group $cb;
408		1017
409	$maxreq = 6 if $maxreq <= 0;	1018	$maxreq = 4 if $maxreq <= 0;
410		1019
411	# stat once	1020	# get a wd object
		1021	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	1022	add $grp aio_wd $path, sub {
		1023	$_[0]
		1024	or return $grp->result ();
		1025
		1026	my $wd = [shift, "."];
		1027
		1028	# stat once
		1029	aioreq_pri $pri;
		1030	add $grp aio_stat $wd, sub {
413	return $grp->result () if $_[0];	1031	return $grp->result () if $_[0];
414	my $now = time;	1032	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1033	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		1034
417	# read the directory entries	1035	# read the directory entries
418	add $grp aio_readdir $path, sub {	1036	aioreq_pri $pri;
		1037	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
419	my $entries = shift	1038	my $entries = shift
420	or return $grp->result ();	1039	or return $grp->result ();
421		1040
422	# stat the dir another time	1041	# stat the dir another time
		1042	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	1043	add $grp aio_stat $wd, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1044	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		1045
426	my $ndirs;	1046	my $ndirs;
427		1047
428	# take the slow route if anything looks fishy	1048	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1049	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	1050	$ndirs = -1;
431	} else {	1051	} else {
432	# if nlink == 2, we are finished	1052	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	1053	# for non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	1054	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	1055	or return $grp->result ([], $entries);
436	}	1056	}
437		1057
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	@$entries];
444
445	my (@dirs, @nondirs);	1058	my (@dirs, @nondirs);
446		1059
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	1060	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);	1061	$grp->result (\@dirs, \@nondirs);
465	}	1062	};
		1063
		1064	limit $statgrp $maxreq;
		1065	feed $statgrp sub {
		1066	return unless @$entries;
		1067	my $entry = shift @$entries;
		1068
		1069	aioreq_pri $pri;
		1070	$wd->[1] = "$entry/.";
		1071	add $statgrp aio_stat $wd, sub {
		1072	if ($_[0] < 0) {
		1073	push @nondirs, $entry;
		1074	} else {
		1075	# need to check for real directory
		1076	aioreq_pri $pri;
		1077	$wd->[1] = $entry;
		1078	add $statgrp aio_lstat $wd, sub {
		1079	if (-d _) {
		1080	push @dirs, $entry;
		1081
		1082	unless (--$ndirs) {
		1083	push @nondirs, @$entries;
		1084	feed $statgrp;
		1085	}
		1086	} else {
		1087	push @nondirs, $entry;
		1088	}
		1089	}
		1090	}
		1091	};
		1092	};
466	};	1093	};
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	};	1094	};
497	};	1095	};
498	};	1096	};
499		1097
500	$grp	1098	$grp
501	}	1099	}
502		1100
		1101	=item aio_rmtree $pathname, $callback->($status)
		1102
		1103	Delete a directory tree starting (and including) C<$path>, return the
		1104	status of the final C<rmdir> only. This is a composite request that
		1105	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1106	everything else.
		1107
		1108	=cut
		1109
		1110	sub aio_rmtree;
		1111	sub aio_rmtree($;$) {
		1112	my ($path, $cb) = @_;
		1113
		1114	my $pri = aioreq_pri;
		1115	my $grp = aio_group $cb;
		1116
		1117	aioreq_pri $pri;
		1118	add $grp aio_scandir $path, 0, sub {
		1119	my ($dirs, $nondirs) = @_;
		1120
		1121	my $dirgrp = aio_group sub {
		1122	add $grp aio_rmdir $path, sub {
		1123	$grp->result ($_[0]);
		1124	};
		1125	};
		1126
		1127	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1128	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1129
		1130	add $grp $dirgrp;
		1131	};
		1132
		1133	$grp
		1134	}
		1135
		1136	=item aio_sync $callback->($status)
		1137
		1138	Asynchronously call sync and call the callback when finished.
		1139
503	=item aio_fsync $fh, $callback->($status)	1140	=item aio_fsync $fh, $callback->($status)
504		1141
505	Asynchronously call fsync on the given filehandle and call the callback	1142	Asynchronously call fsync on the given filehandle and call the callback
506	with the fsync result code.	1143	with the fsync result code.
507		1144
…		…
511	callback with the fdatasync result code.	1148	callback with the fdatasync result code.
512		1149
513	If this call isn't available because your OS lacks it or it couldn't be	1150	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.	1151	detected, it will be emulated by calling C<fsync> instead.
515		1152
		1153	=item aio_syncfs $fh, $callback->($status)
		1154
		1155	Asynchronously call the syncfs syscall to sync the filesystem associated
		1156	to the given filehandle and call the callback with the syncfs result
		1157	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1158	errno to C<ENOSYS> nevertheless.
		1159
		1160	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1161
		1162	Sync the data portion of the file specified by C<$offset> and C<$length>
		1163	to disk (but NOT the metadata), by calling the Linux-specific
		1164	sync_file_range call. If sync_file_range is not available or it returns
		1165	ENOSYS, then fdatasync or fsync is being substituted.
		1166
		1167	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1168	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1169	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1170	manpage for details.
		1171
		1172	=item aio_pathsync $pathname, $callback->($status)
		1173
		1174	This request tries to open, fsync and close the given path. This is a
		1175	composite request intended to sync directories after directory operations
		1176	(E.g. rename). This might not work on all operating systems or have any
		1177	specific effect, but usually it makes sure that directory changes get
		1178	written to disc. It works for anything that can be opened for read-only,
		1179	not just directories.
		1180
		1181	Future versions of this function might fall back to other methods when
		1182	C<fsync> on the directory fails (such as calling C<sync>).
		1183
		1184	Passes C<0> when everything went ok, and C<-1> on error.
		1185
		1186	=cut
		1187
		1188	sub aio_pathsync($;$) {
		1189	my ($path, $cb) = @_;
		1190
		1191	my $pri = aioreq_pri;
		1192	my $grp = aio_group $cb;
		1193
		1194	aioreq_pri $pri;
		1195	add $grp aio_open $path, O_RDONLY, 0, sub {
		1196	my ($fh) = @_;
		1197	if ($fh) {
		1198	aioreq_pri $pri;
		1199	add $grp aio_fsync $fh, sub {
		1200	$grp->result ($_[0]);
		1201
		1202	aioreq_pri $pri;
		1203	add $grp aio_close $fh;
		1204	};
		1205	} else {
		1206	$grp->result (-1);
		1207	}
		1208	};
		1209
		1210	$grp
		1211	}
		1212
		1213	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1214
		1215	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1216	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1217	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1218	scalar must only be modified in-place while an aio operation is pending on
		1219	it).
		1220
		1221	It calls the C<msync> function of your OS, if available, with the memory
		1222	area starting at C<$offset> in the string and ending C<$length> bytes
		1223	later. If C<$length> is negative, counts from the end, and if C<$length>
		1224	is C<undef>, then it goes till the end of the string. The flags can be
		1225	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1226	C<IO::AIO::MS_SYNC>.
		1227
		1228	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1229
		1230	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1231	scalars.
		1232
		1233	It touches (reads or writes) all memory pages in the specified
		1234	range inside the scalar. All caveats and parameters are the same
		1235	as for C<aio_msync>, above, except for flags, which must be either
		1236	C<0> (which reads all pages and ensures they are instantiated) or
		1237	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1238	writing an octet from it, which dirties the page).
		1239
		1240	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1241
		1242	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1243	scalars.
		1244
		1245	It reads in all the pages of the underlying storage into memory (if any)
		1246	and locks them, so they are not getting swapped/paged out or removed.
		1247
		1248	If C<$length> is undefined, then the scalar will be locked till the end.
		1249
		1250	On systems that do not implement C<mlock>, this function returns C<-1>
		1251	and sets errno to C<ENOSYS>.
		1252
		1253	Note that the corresponding C<munlock> is synchronous and is
		1254	documented under L<MISCELLANEOUS FUNCTIONS>.
		1255
		1256	Example: open a file, mmap and mlock it - both will be undone when
		1257	C<$data> gets destroyed.
		1258
		1259	open my $fh, "<", $path or die "$path: $!";
		1260	my $data;
		1261	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1262	aio_mlock $data; # mlock in background
		1263
		1264	=item aio_mlockall $flags, $callback->($status)
		1265
		1266	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1267	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1268
		1269	On systems that do not implement C<mlockall>, this function returns C<-1>
		1270	and sets errno to C<ENOSYS>.
		1271
		1272	Note that the corresponding C<munlockall> is synchronous and is
		1273	documented under L<MISCELLANEOUS FUNCTIONS>.
		1274
		1275	Example: asynchronously lock all current and future pages into memory.
		1276
		1277	aio_mlockall IO::AIO::MCL_FUTURE;
		1278
		1279	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1280
		1281	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1282	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1283	C<ioctl> is not available on your OS, then this rquiest will fail with
		1284	C<ENOSYS>.
		1285
		1286	C<$start> is the starting offset to query extents for, C<$length> is the
		1287	size of the range to query - if it is C<undef>, then the whole file will
		1288	be queried.
		1289
		1290	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1291	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1292	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1293	the data portion.
		1294
		1295	C<$count> is the maximum number of extent records to return. If it is
		1296	C<undef>, then IO::AIO queries all extents of the file. As a very special
		1297	case, if it is C<0>, then the callback receives the number of extents
		1298	instead of the extents themselves.
		1299
		1300	If an error occurs, the callback receives no arguments. The special
		1301	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1302
		1303	Otherwise, the callback receives an array reference with extent
		1304	structures. Each extent structure is an array reference itself, with the
		1305	following members:
		1306
		1307	[$logical, $physical, $length, $flags]
		1308
		1309	Flags is any combination of the following flag values (typically either C<0>
		1310	or C<IO::AIO::FIEMAP_EXTENT_LAST>):
		1311
		1312	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1313	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1314	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1315	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1316	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1317	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1318
516	=item aio_group $callback->(...)	1319	=item aio_group $callback->(...)
517
518	[EXPERIMENTAL]
519		1320
520	This is a very special aio request: Instead of doing something, it is a	1321	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	1322	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	1323	many requests into a single, composite, request with a definite callback
		1324	and the ability to cancel the whole request with its subrequests.
523		1325
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1326	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	1327	for more info.
526		1328
527	Example:	1329	Example:
…		…
533	add $grp	1335	add $grp
534	(aio_stat ...),	1336	(aio_stat ...),
535	(aio_stat ...),	1337	(aio_stat ...),
536	...;	1338	...;
537		1339
		1340	=item aio_nop $callback->()
		1341
		1342	This is a special request - it does nothing in itself and is only used for
		1343	side effects, such as when you want to add a dummy request to a group so
		1344	that finishing the requests in the group depends on executing the given
		1345	code.
		1346
		1347	While this request does nothing, it still goes through the execution
		1348	phase and still requires a worker thread. Thus, the callback will not
		1349	be executed immediately but only after other requests in the queue have
		1350	entered their execution phase. This can be used to measure request
		1351	latency.
		1352
538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1353	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
539		1354
540	Mainly used for debugging and benchmarking, this aio request puts one of	1355	Mainly used for debugging and benchmarking, this aio request puts one of
541	the request workers to sleep for the given time.	1356	the request workers to sleep for the given time.
542		1357
543	While it is theoretically handy to have simple I/O scheduling requests	1358	While it is theoretically handy to have simple I/O scheduling requests
544	like sleep and file handle readable/writable, the overhead this creates	1359	like sleep and file handle readable/writable, the overhead this creates is
545	is immense, so do not use this function except to put your application	1360	immense (it blocks a thread for a long time) so do not use this function
546	under artificial I/O pressure.	1361	except to put your application under artificial I/O pressure.
547		1362
548	=back	1363	=back
		1364
		1365
		1366	=head2 IO::AIO::WD - multiple working directories
		1367
		1368	Your process only has one current working directory, which is used by all
		1369	threads. This makes it hard to use relative paths (some other component
		1370	could call C<chdir> at any time, and it is hard to control when the path
		1371	will be used by IO::AIO).
		1372
		1373	One solution for this is to always use absolute paths. This usually works,
		1374	but can be quite slow (the kernel has to walk the whole path on every
		1375	access), and can also be a hassle to implement.
		1376
		1377	Newer POSIX systems have a number of functions (openat, fdopendir,
		1378	futimensat and so on) that make it possible to specify working directories
		1379	per operation.
		1380
		1381	For portability, and because the clowns who "designed", or shall I write,
		1382	perpetrated this new interface were obviously half-drunk, this abstraction
		1383	cannot be perfect, though.
		1384
		1385	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1386	object. This object stores the canonicalised, absolute version of the
		1387	path, and on systems that allow it, also a directory file descriptor.
		1388
		1389	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1390	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1391	object and a pathname instead (or the IO::AIO::WD object alone, which
		1392	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1393	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1394	to that IO::AIO::WD object.
		1395
		1396	For example, to get a wd object for F</etc> and then stat F<passwd>
		1397	inside, you would write:
		1398
		1399	aio_wd "/etc", sub {
		1400	my $etcdir = shift;
		1401
		1402	# although $etcdir can be undef on error, there is generally no reason
		1403	# to check for errors here, as aio_stat will fail with ENOENT
		1404	# when $etcdir is undef.
		1405
		1406	aio_stat [$etcdir, "passwd"], sub {
		1407	# yay
		1408	};
		1409	};
		1410
		1411	That C<aio_wd> is a request and not a normal function shows that creating
		1412	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1413	why it is done asynchronously.
		1414
		1415	To stat the directory obtained with C<aio_wd> above, one could write
		1416	either of the following three request calls:
		1417
		1418	aio_lstat "/etc" , sub { ... # pathname as normal string
		1419	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1420	aio_lstat $wd , sub { ... # shorthand for the previous
		1421
		1422	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1423	object and the pathname string, so you could write the following without
		1424	causing any issues due to C<$path> getting reused:
		1425
		1426	my $path = [$wd, undef];
		1427
		1428	for my $name (qw(abc def ghi)) {
		1429	$path->[1] = $name;
		1430	aio_stat $path, sub {
		1431	# ...
		1432	};
		1433	}
		1434
		1435	There are some caveats: when directories get renamed (or deleted), the
		1436	pathname string doesn't change, so will point to the new directory (or
		1437	nowhere at all), while the directory fd, if available on the system,
		1438	will still point to the original directory. Most functions accepting a
		1439	pathname will use the directory fd on newer systems, and the string on
		1440	older systems. Some functions (such as realpath) will always rely on the
		1441	string form of the pathname.
		1442
		1443	So this fucntionality is mainly useful to get some protection against
		1444	C<chdir>, to easily get an absolute path out of a relative path for future
		1445	reference, and to speed up doing many operations in the same directory
		1446	(e.g. when stat'ing all files in a directory).
		1447
		1448	The following functions implement this working directory abstraction:
		1449
		1450	=over 4
		1451
		1452	=item aio_wd $pathname, $callback->($wd)
		1453
		1454	Asynchonously canonicalise the given pathname and convert it to an
		1455	IO::AIO::WD object representing it. If possible and supported on the
		1456	system, also open a directory fd to speed up pathname resolution relative
		1457	to this working directory.
		1458
		1459	If something goes wrong, then C<undef> is passwd to the callback instead
		1460	of a working directory object and C<$!> is set appropriately. Since
		1461	passing C<undef> as working directory component of a pathname fails the
		1462	request with C<ENOENT>, there is often no need for error checking in the
		1463	C<aio_wd> callback, as future requests using the value will fail in the
		1464	expected way.
		1465
		1466	If this call isn't available because your OS lacks it or it couldn't be
		1467	detected, it will be emulated by calling C<fsync> instead.
		1468
		1469	=item IO::AIO::CWD
		1470
		1471	This is a compiletime constant (object) that represents the process
		1472	current working directory.
		1473
		1474	Specifying this object as working directory object for a pathname is as
		1475	if the pathname would be specified directly, without a directory object,
		1476	e.g., these calls are functionally identical:
		1477
		1478	aio_stat "somefile", sub { ... };
		1479	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1480
		1481	=back
		1482
549		1483
550	=head2 IO::AIO::REQ CLASS	1484	=head2 IO::AIO::REQ CLASS
551		1485
552	All non-aggregate C<aio_*> functions return an object of this class when	1486	All non-aggregate C<aio_*> functions return an object of this class when
553	called in non-void context.	1487	called in non-void context.
554		1488
555	A request always moves through the following five states in its lifetime,
556	in order: B<ready> (request has been created, but has not been executed
557	yet), B<execute> (request is currently being executed), B<pending>
558	(request has been executed but callback has not been called yet),
559	B<result> (results are being processed synchronously, includes calling the
560	callback) and B<done> (request has reached the end of its lifetime and
561	holds no resources anymore).
562
563	=over 4	1489	=over 4
564		1490
565	=item $req->cancel	1491	=item cancel $req
566		1492
567	Cancels the request, if possible. Has the effect of skipping execution	1493	Cancels the request, if possible. Has the effect of skipping execution
568	when entering the B<execute> state and skipping calling the callback when	1494	when entering the B<execute> state and skipping calling the callback when
569	entering the the B<result> state, but will leave the request otherwise	1495	entering the the B<result> state, but will leave the request otherwise
570	untouched. That means that requests that currently execute will not be	1496	untouched (with the exception of readdir). That means that requests that
571	stopped and resources held by the request will not be freed prematurely.	1497	currently execute will not be stopped and resources held by the request
		1498	will not be freed prematurely.
		1499
		1500	=item cb $req $callback->(...)
		1501
		1502	Replace (or simply set) the callback registered to the request.
572		1503
573	=back	1504	=back
574		1505
575	=head2 IO::AIO::GRP CLASS	1506	=head2 IO::AIO::GRP CLASS
576		1507
…		…
616	=item * They can also can also be added to other IO::AIO::GRP objects.	1547	=item * They can also can also be added to other IO::AIO::GRP objects.
617		1548
618	=item * You must not add requests to a group from within the group callback (or	1549	=item * You must not add requests to a group from within the group callback (or
619	any later time).	1550	any later time).
620		1551
621	=item * This does not harmonise well with C<max_outstanding>, so best do
622	not combine C<aio_group> with it. Groups and feeders are recommended for
623	this kind of concurrency-limiting.
624
625	=back	1552	=back
626		1553
627	Their lifetime, simplified, looks like this: when they are empty, they	1554	Their lifetime, simplified, looks like this: when they are empty, they
628	will finish very quickly. If they contain only requests that are in the	1555	will finish very quickly. If they contain only requests that are in the
629	C<done> state, they will also finish. Otherwise they will continue to	1556	C<done> state, they will also finish. Otherwise they will continue to
630	exist.	1557	exist.
631		1558
632	That means after creating a group you have some time to add requests. And	1559	That means after creating a group you have some time to add requests
633	in the callbacks of those requests, you can add further requests to the	1560	(precisely before the callback has been invoked, which is only done within
634	group. And only when all those requests have finished will the the group	1561	the C<poll_cb>). And in the callbacks of those requests, you can add
635	itself finish.	1562	further requests to the group. And only when all those requests have
		1563	finished will the the group itself finish.
636		1564
637	=over 4	1565	=over 4
638		1566
		1567	=item add $grp ...
		1568
639	=item $grp->add (...)	1569	=item $grp->add (...)
640
641	=item add $grp ...
642		1570
643	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1571	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
644	be added, including other groups, as long as you do not create circular	1572	be added, including other groups, as long as you do not create circular
645	dependencies.	1573	dependencies.
646		1574
647	Returns all its arguments.	1575	Returns all its arguments.
648		1576
		1577	=item $grp->cancel_subs
		1578
		1579	Cancel all subrequests and clears any feeder, but not the group request
		1580	itself. Useful when you queued a lot of events but got a result early.
		1581
		1582	The group request will finish normally (you cannot add requests to the
		1583	group).
		1584
649	=item $grp->result (...)	1585	=item $grp->result (...)
650		1586
651	Set the result value(s) that will be passed to the group callback when all	1587	Set the result value(s) that will be passed to the group callback when all
652	subrequests have finished. By default, no argument will be passed.	1588	subrequests have finished and set the groups errno to the current value
		1589	of errno (just like calling C<errno> without an error number). By default,
		1590	no argument will be passed and errno is zero.
653		1591
654	=item $grp->set_feeder ($callback->($grp))	1592	=item $grp->errno ([$errno])
655		1593
656	[VERY EXPERIMENTAL]	1594	Sets the group errno value to C<$errno>, or the current value of errno
		1595	when the argument is missing.
		1596
		1597	Every aio request has an associated errno value that is restored when
		1598	the callback is invoked. This method lets you change this value from its
		1599	default (0).
		1600
		1601	Calling C<result> will also set errno, so make sure you either set C<$!>
		1602	before the call to C<result>, or call c<errno> after it.
		1603
		1604	=item feed $grp $callback->($grp)
657		1605
658	Sets a feeder/generator on this group: every group can have an attached	1606	Sets a feeder/generator on this group: every group can have an attached
659	generator that generates requests if idle. The idea behind this is that,	1607	generator that generates requests if idle. The idea behind this is that,
660	although you could just queue as many requests as you want in a group,	1608	although you could just queue as many requests as you want in a group,
661	this might starve other requests for a potentially long time. For	1609	this might starve other requests for a potentially long time. For example,
662	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1610	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
663	requests, delaying any later requests for a long time.	1611	requests, delaying any later requests for a long time.
664		1612
665	To avoid this, and allow incremental generation of requests, you can	1613	To avoid this, and allow incremental generation of requests, you can
666	instead a group and set a feeder on it that generates those requests. The	1614	instead a group and set a feeder on it that generates those requests. The
667	feeder will be called whenever there are few enough (see C<feeder_limit>,	1615	feed callback will be called whenever there are few enough (see C<limit>,
668	below) requests active in the group itself and is expected to queue more	1616	below) requests active in the group itself and is expected to queue more
669	requests.	1617	requests.
670		1618
671	The feeder can queue as many requests as it likes (i.e. C<add> does not	1619	The feed callback can queue as many requests as it likes (i.e. C<add> does
672	impose any limits).	1620	not impose any limits).
673		1621
674	If the feeder does not queue more requests when called, it will be	1622	If the feed does not queue more requests when called, it will be
675	automatically removed from the group.	1623	automatically removed from the group.
676		1624
677	If the feeder limit is C<0>, it will be set to C<2> automatically.	1625	If the feed limit is C<0> when this method is called, it will be set to
		1626	C<2> automatically.
678		1627
679	Example:	1628	Example:
680		1629
681	# stat all files in @files, but only ever use four aio requests concurrently:	1630	# stat all files in @files, but only ever use four aio requests concurrently:
682		1631
683	my $grp = aio_group sub { print "finished\n" };	1632	my $grp = aio_group sub { print "finished\n" };
684	$grp->feeder_limit (4);	1633	limit $grp 4;
685	$grp->set_feeder (sub {	1634	feed $grp sub {
686	my $file = pop @files	1635	my $file = pop @files
687	or return;	1636	or return;
688		1637
689	add $grp aio_stat $file, sub { ... };	1638	add $grp aio_stat $file, sub { ... };
690	});	1639	};
691		1640
692	=item $grp->feeder_limit ($num)	1641	=item limit $grp $num
693		1642
694	Sets the feeder limit for the group: The feeder will be called whenever	1643	Sets the feeder limit for the group: The feeder will be called whenever
695	the group contains less than this many requests.	1644	the group contains less than this many requests.
696		1645
697	Setting the limit to C<0> will pause the feeding process.	1646	Setting the limit to C<0> will pause the feeding process.
698		1647
		1648	The default value for the limit is C<0>, but note that setting a feeder
		1649	automatically bumps it up to C<2>.
		1650
699	=back	1651	=back
700		1652
701	=head2 SUPPORT FUNCTIONS	1653	=head2 SUPPORT FUNCTIONS
702		1654
		1655	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1656
703	=over 4	1657	=over 4
704		1658
705	=item $fileno = IO::AIO::poll_fileno	1659	=item $fileno = IO::AIO::poll_fileno
706		1660
707	Return the I<request result pipe file descriptor>. This filehandle must be	1661	Return the I<request result pipe file descriptor>. This filehandle must be
708	polled for reading by some mechanism outside this module (e.g. Event or	1662	polled for reading by some mechanism outside this module (e.g. EV, Glib,
709	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1663	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
710	to call C<poll_cb> to check the results.	1664	you have to call C<poll_cb> to check the results.
711		1665
712	See C<poll_cb> for an example.	1666	See C<poll_cb> for an example.
713		1667
714	=item IO::AIO::poll_cb	1668	=item IO::AIO::poll_cb
715		1669
716	Process all outstanding events on the result pipe. You have to call this	1670	Process some outstanding events on the result pipe. You have to call
717	regularly. Returns the number of events processed. Returns immediately	1671	this regularly. Returns C<0> if all events could be processed (or there
718	when no events are outstanding.	1672	were no events to process), or C<-1> if it returned earlier for whatever
		1673	reason. Returns immediately when no events are outstanding. The amount of
		1674	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1675	C<IO::AIO::max_poll_time>.
		1676
		1677	If not all requests were processed for whatever reason, the filehandle
		1678	will still be ready when C<poll_cb> returns, so normally you don't have to
		1679	do anything special to have it called later.
		1680
		1681	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1682	ready, it can be beneficial to call this function from loops which submit
		1683	a lot of requests, to make sure the results get processed when they become
		1684	available and not just when the loop is finished and the event loop takes
		1685	over again. This function returns very fast when there are no outstanding
		1686	requests.
719		1687
720	Example: Install an Event watcher that automatically calls	1688	Example: Install an Event watcher that automatically calls
721	IO::AIO::poll_cb with high priority:	1689	IO::AIO::poll_cb with high priority (more examples can be found in the
		1690	SYNOPSIS section, at the top of this document):
722		1691
723	Event->io (fd => IO::AIO::poll_fileno,	1692	Event->io (fd => IO::AIO::poll_fileno,
724	poll => 'r', async => 1,	1693	poll => 'r', async => 1,
725	cb => \&IO::AIO::poll_cb);	1694	cb => \&IO::AIO::poll_cb);
726		1695
727	=item IO::AIO::poll_wait	1696	=item IO::AIO::poll_wait
728		1697
		1698	If there are any outstanding requests and none of them in the result
729	Wait till the result filehandle becomes ready for reading (simply does a	1699	phase, wait till the result filehandle becomes ready for reading (simply
730	C<select> on the filehandle. This is useful if you want to synchronously wait	1700	does a C<select> on the filehandle. This is useful if you want to
731	for some requests to finish).	1701	synchronously wait for some requests to finish).
732		1702
733	See C<nreqs> for an example.	1703	See C<nreqs> for an example.
734		1704
		1705	=item IO::AIO::poll
		1706
		1707	Waits until some requests have been handled.
		1708
		1709	Returns the number of requests processed, but is otherwise strictly
		1710	equivalent to:
		1711
		1712	IO::AIO::poll_wait, IO::AIO::poll_cb
		1713
735	=item IO::AIO::nreqs	1714	=item IO::AIO::flush
736		1715
737	Returns the number of requests currently outstanding (i.e. for which their	1716	Wait till all outstanding AIO requests have been handled.
738	callback has not been invoked yet).
739		1717
740	Example: wait till there are no outstanding requests anymore:	1718	Strictly equivalent to:
741		1719
742	IO::AIO::poll_wait, IO::AIO::poll_cb	1720	IO::AIO::poll_wait, IO::AIO::poll_cb
743	while IO::AIO::nreqs;	1721	while IO::AIO::nreqs;
744		1722
745	=item IO::AIO::flush	1723	=item IO::AIO::max_poll_reqs $nreqs
746		1724
747	Wait till all outstanding AIO requests have been handled.	1725	=item IO::AIO::max_poll_time $seconds
748		1726
749	Strictly equivalent to:	1727	These set the maximum number of requests (default C<0>, meaning infinity)
		1728	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1729	the maximum amount of time (default C<0>, meaning infinity) spent in
		1730	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1731	of time C<poll_cb> is allowed to use).
750		1732
751	IO::AIO::poll_wait, IO::AIO::poll_cb	1733	Setting C<max_poll_time> to a non-zero value creates an overhead of one
752	while IO::AIO::nreqs;	1734	syscall per request processed, which is not normally a problem unless your
		1735	callbacks are really really fast or your OS is really really slow (I am
		1736	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
753		1737
754	=item IO::AIO::poll	1738	Setting these is useful if you want to ensure some level of
		1739	interactiveness when perl is not fast enough to process all requests in
		1740	time.
755		1741
756	Waits until some requests have been handled.	1742	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
757		1743
758	Strictly equivalent to:	1744	Example: Install an Event watcher that automatically calls
		1745	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1746	program get the CPU sometimes even under high AIO load.
759		1747
760	IO::AIO::poll_wait, IO::AIO::poll_cb	1748	# try not to spend much more than 0.1s in poll_cb
761	if IO::AIO::nreqs;	1749	IO::AIO::max_poll_time 0.1;
		1750
		1751	# use a low priority so other tasks have priority
		1752	Event->io (fd => IO::AIO::poll_fileno,
		1753	poll => 'r', nice => 1,
		1754	cb => &IO::AIO::poll_cb);
		1755
		1756	=back
		1757
		1758	=head3 CONTROLLING THE NUMBER OF THREADS
		1759
		1760	=over
762		1761
763	=item IO::AIO::min_parallel $nthreads	1762	=item IO::AIO::min_parallel $nthreads
764		1763
765	Set the minimum number of AIO threads to C<$nthreads>. The current	1764	Set the minimum number of AIO threads to C<$nthreads>. The current
766	default is C<8>, which means eight asynchronous operations can execute	1765	default is C<8>, which means eight asynchronous operations can execute
767	concurrently at any one time (the number of outstanding requests,	1766	concurrently at any one time (the number of outstanding requests,
768	however, is unlimited).	1767	however, is unlimited).
769		1768
770	IO::AIO starts threads only on demand, when an AIO request is queued and	1769	IO::AIO starts threads only on demand, when an AIO request is queued and
771	no free thread exists.	1770	no free thread exists. Please note that queueing up a hundred requests can
		1771	create demand for a hundred threads, even if it turns out that everything
		1772	is in the cache and could have been processed faster by a single thread.
772		1773
773	It is recommended to keep the number of threads relatively low, as some	1774	It is recommended to keep the number of threads relatively low, as some
774	Linux kernel versions will scale negatively with the number of threads	1775	Linux kernel versions will scale negatively with the number of threads
775	(higher parallelity => MUCH higher latency). With current Linux 2.6	1776	(higher parallelity => MUCH higher latency). With current Linux 2.6
776	versions, 4-32 threads should be fine.	1777	versions, 4-32 threads should be fine.
…		…
790	This module automatically runs C<max_parallel 0> at program end, to ensure	1791	This module automatically runs C<max_parallel 0> at program end, to ensure
791	that all threads are killed and that there are no outstanding requests.	1792	that all threads are killed and that there are no outstanding requests.
792		1793
793	Under normal circumstances you don't need to call this function.	1794	Under normal circumstances you don't need to call this function.
794		1795
		1796	=item IO::AIO::max_idle $nthreads
		1797
		1798	Limit the number of threads (default: 4) that are allowed to idle
		1799	(i.e., threads that did not get a request to process within the idle
		1800	timeout (default: 10 seconds). That means if a thread becomes idle while
		1801	C<$nthreads> other threads are also idle, it will free its resources and
		1802	exit.
		1803
		1804	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1805	to allow for extremely high load situations, but want to free resources
		1806	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1807
		1808	The default is probably ok in most situations, especially if thread
		1809	creation is fast. If thread creation is very slow on your system you might
		1810	want to use larger values.
		1811
		1812	=item IO::AIO::idle_timeout $seconds
		1813
		1814	Sets the minimum idle timeout (default 10) after which worker threads are
		1815	allowed to exit. SEe C<IO::AIO::max_idle>.
		1816
795	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1817	=item IO::AIO::max_outstanding $maxreqs
796		1818
797	[DEPRECATED]
798
799	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1819	Sets the maximum number of outstanding requests to C<$nreqs>. If
800	try to queue up more than this number of requests, the caller will block until	1820	you do queue up more than this number of requests, the next call to
801	some requests have been handled.	1821	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1822	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1823	longer exceeded.
802		1824
803	The default is very large, so normally there is no practical limit. If you	1825	In other words, this setting does not enforce a queue limit, but can be
804	queue up many requests in a loop it often improves speed if you set	1826	used to make poll functions block if the limit is exceeded.
805	this to a relatively low number, such as C<100>.
806		1827
807	This function does not work well together with C<aio_group>'s, and their	1828	This is a very bad function to use in interactive programs because it
808	feeder interface is better suited to limiting concurrency, so do not use	1829	blocks, and a bad way to reduce concurrency because it is inexact: Better
809	this function.	1830	use an C<aio_group> together with a feed callback.
810		1831
811	Under normal circumstances you don't need to call this function.	1832	It's main use is in scripts without an event loop - when you want to stat
		1833	a lot of files, you can write somehting like this:
		1834
		1835	IO::AIO::max_outstanding 32;
		1836
		1837	for my $path (...) {
		1838	aio_stat $path , ...;
		1839	IO::AIO::poll_cb;
		1840	}
		1841
		1842	IO::AIO::flush;
		1843
		1844	The call to C<poll_cb> inside the loop will normally return instantly, but
		1845	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1846	some requests have been handled. This keeps the loop from pushing a large
		1847	number of C<aio_stat> requests onto the queue.
		1848
		1849	The default value for C<max_outstanding> is very large, so there is no
		1850	practical limit on the number of outstanding requests.
812		1851
813	=back	1852	=back
814		1853
		1854	=head3 STATISTICAL INFORMATION
		1855
		1856	=over
		1857
		1858	=item IO::AIO::nreqs
		1859
		1860	Returns the number of requests currently in the ready, execute or pending
		1861	states (i.e. for which their callback has not been invoked yet).
		1862
		1863	Example: wait till there are no outstanding requests anymore:
		1864
		1865	IO::AIO::poll_wait, IO::AIO::poll_cb
		1866	while IO::AIO::nreqs;
		1867
		1868	=item IO::AIO::nready
		1869
		1870	Returns the number of requests currently in the ready state (not yet
		1871	executed).
		1872
		1873	=item IO::AIO::npending
		1874
		1875	Returns the number of requests currently in the pending state (executed,
		1876	but not yet processed by poll_cb).
		1877
		1878	=back
		1879
		1880	=head3 MISCELLANEOUS FUNCTIONS
		1881
		1882	IO::AIO implements some functions that might be useful, but are not
		1883	asynchronous.
		1884
		1885	=over 4
		1886
		1887	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1888
		1889	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1890	but is blocking (this makes most sense if you know the input data is
		1891	likely cached already and the output filehandle is set to non-blocking
		1892	operations).
		1893
		1894	Returns the number of bytes copied, or C<-1> on error.
		1895
		1896	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1897
		1898	Simply calls the C<posix_fadvise> function (see its
		1899	manpage for details). The following advice constants are
		1900	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1901	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1902	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1903
		1904	On systems that do not implement C<posix_fadvise>, this function returns
		1905	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1906
		1907	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1908
		1909	Simply calls the C<posix_madvise> function (see its
		1910	manpage for details). The following advice constants are
		1911	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1912	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1913
		1914	On systems that do not implement C<posix_madvise>, this function returns
		1915	ENOSYS, otherwise the return value of C<posix_madvise>.
		1916
		1917	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1918
		1919	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1920	$scalar (see its manpage for details). The following protect
		1921	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1922	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1923
		1924	On systems that do not implement C<mprotect>, this function returns
		1925	ENOSYS, otherwise the return value of C<mprotect>.
		1926
		1927	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1928
		1929	Memory-maps a file (or anonymous memory range) and attaches it to the
		1930	given C<$scalar>, which will act like a string scalar. Returns true on
		1931	success, and false otherwise.
		1932
		1933	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1934	change the string length, and most read-only operations such as copying it
		1935	or searching it with regexes and so on.
		1936
		1937	Anything else is unsafe and will, at best, result in memory leaks.
		1938
		1939	The memory map associated with the C<$scalar> is automatically removed
		1940	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1941	C<IO::AIO::munmap> functions are called.
		1942
		1943	This calls the C<mmap>(2) function internally. See your system's manual
		1944	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1945
		1946	The C<$length> must be larger than zero and smaller than the actual
		1947	filesize.
		1948
		1949	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1950	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1951
		1952	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1953	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1954	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1955	(which is set to C<MAP_ANON> if your system only provides this
		1956	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1957	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1958	C<IO::AIO::MAP_NONBLOCK>
		1959
		1960	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1961
		1962	C<$offset> is the offset from the start of the file - it generally must be
		1963	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1964
		1965	Example:
		1966
		1967	use Digest::MD5;
		1968	use IO::AIO;
		1969
		1970	open my $fh, "<verybigfile"
		1971	or die "$!";
		1972
		1973	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1974	or die "verybigfile: $!";
		1975
		1976	my $fast_md5 = md5 $data;
		1977
		1978	=item IO::AIO::munmap $scalar
		1979
		1980	Removes a previous mmap and undefines the C<$scalar>.
		1981
		1982	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1983
		1984	Calls the C<munlock> function, undoing the effects of a previous
		1985	C<aio_mlock> call (see its description for details).
		1986
		1987	=item IO::AIO::munlockall
		1988
		1989	Calls the C<munlockall> function.
		1990
		1991	On systems that do not implement C<munlockall>, this function returns
		1992	ENOSYS, otherwise the return value of C<munlockall>.
		1993
		1994	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1995
		1996	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		1997	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		1998	should be the file offset.
		1999
		2000	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2001	silently corrupt the data in this case.
		2002
		2003	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2004	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2005	C<IO::AIO::SPLICE_F_GIFT>.
		2006
		2007	See the C<splice(2)> manpage for details.
		2008
		2009	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2010
		2011	Calls the GNU/Linux C<tee(2)> syscall, see it's manpage and the
		2012	description for C<IO::AIO::splice> above for details.
		2013
		2014	=back
		2015
815	=cut	2016	=cut
816		2017
817	# support function to convert a fd into a perl filehandle
818	sub _fd2fh {
819	return undef if $_[0] < 0;
820
821	# try to generate nice filehandles
822	my $sym = "IO::AIO::fd#$_[0]";
823	local *$sym;
824
825	open *$sym, "+<&=$_[0]" # usually works under any unix
826	or open *$sym, "<&=$_[0]" # cygwin needs this
827	or open *$sym, ">&=$_[0]" # or this
828	or return undef;
829
830	*$sym
831	}
832
833	min_parallel 8;	2018	min_parallel 8;
834		2019
835	END {	2020	END { flush }
836	max_parallel 0;
837	}
838		2021
839	1;	2022	1;
840		2023
		2024	=head1 EVENT LOOP INTEGRATION
		2025
		2026	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2027	automatically into many event loops:
		2028
		2029	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2030	use AnyEvent::AIO;
		2031
		2032	You can also integrate IO::AIO manually into many event loops, here are
		2033	some examples of how to do this:
		2034
		2035	# EV integration
		2036	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2037
		2038	# Event integration
		2039	Event->io (fd => IO::AIO::poll_fileno,
		2040	poll => 'r',
		2041	cb => \&IO::AIO::poll_cb);
		2042
		2043	# Glib/Gtk2 integration
		2044	add_watch Glib::IO IO::AIO::poll_fileno,
		2045	in => sub { IO::AIO::poll_cb; 1 };
		2046
		2047	# Tk integration
		2048	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2049	readable => \&IO::AIO::poll_cb);
		2050
		2051	# Danga::Socket integration
		2052	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2053	\&IO::AIO::poll_cb);
		2054
841	=head2 FORK BEHAVIOUR	2055	=head2 FORK BEHAVIOUR
842		2056
843	This module should do "the right thing" when the process using it forks:	2057	Usage of pthreads in a program changes the semantics of fork
		2058	considerably. Specifically, only async-safe functions can be called after
		2059	fork. Perl doesn't know about this, so in general, you cannot call fork
		2060	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2061	pthreads, so this applies, but many other extensions and (for inexplicable
		2062	reasons) perl itself often is linked against pthreads, so this limitation
		2063	applies to quite a lot of perls.
844		2064
845	Before the fork, IO::AIO enters a quiescent state where no requests	2065	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
846	can be added in other threads and no results will be processed. After	2066	only works in the process that loaded it. Forking is fully supported, but
847	the fork the parent simply leaves the quiescent state and continues	2067	using IO::AIO in the child is not.
848	request/result processing, while the child clears the request/result
849	queue (so the requests started before the fork will only be handled in
850	the parent). Threads will be started on demand until the limit ste in the
851	parent process has been reached again.
852		2068
853	In short: the parent will, after a short pause, continue as if fork had	2069	You might get around by not I<using> IO::AIO before (or after)
854	not been called, while the child will act as if IO::AIO has not been used	2070	forking. You could also try to call the L<IO::AIO::reinit> function in the
855	yet.	2071	child:
		2072
		2073	=over 4
		2074
		2075	=item IO::AIO::reinit
		2076
		2077	Abandons all current requests and I/O threads and simply reinitialises all
		2078	data structures. This is not an operation supported by any standards, but
		2079	happens to work on GNU/Linux and some newer BSD systems.
		2080
		2081	The only reasonable use for this function is to call it after forking, if
		2082	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2083	the process will result in undefined behaviour. Calling it at any time
		2084	will also result in any undefined (by POSIX) behaviour.
		2085
		2086	=back
856		2087
857	=head2 MEMORY USAGE	2088	=head2 MEMORY USAGE
858		2089
		2090	Per-request usage:
		2091
859	Each aio request uses - depending on your architecture - around 128 bytes	2092	Each aio request uses - depending on your architecture - around 100-200
860	of memory. In addition, stat requests need a stat buffer (possibly a few	2093	bytes of memory. In addition, stat requests need a stat buffer (possibly
861	hundred bytes). Perl scalars and other data passed into aio requests will	2094	a few hundred bytes), readdir requires a result buffer and so on. Perl
862	also be locked.	2095	scalars and other data passed into aio requests will also be locked and
		2096	will consume memory till the request has entered the done state.
863		2097
864	This is now awfully much, so queuing lots of requests is not usually a	2098	This is not awfully much, so queuing lots of requests is not usually a
865	problem.	2099	problem.
866		2100
867	Each thread needs a stack area which is usually around 16k, sometimes much	2101	Per-thread usage:
868	larger, depending on the OS.	2102
		2103	In the execution phase, some aio requests require more memory for
		2104	temporary buffers, and each thread requires a stack and other data
		2105	structures (usually around 16k-128k, depending on the OS).
		2106
		2107	=head1 KNOWN BUGS
		2108
		2109	Known bugs will be fixed in the next release.
869		2110
870	=head1 SEE ALSO	2111	=head1 SEE ALSO
871		2112
872	L<Coro>, L<Linux::AIO> (obsolete).	2113	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2114	more natural syntax.
873		2115
874	=head1 AUTHOR	2116	=head1 AUTHOR
875		2117
876	Marc Lehmann <schmorp@schmorp.de>	2118	Marc Lehmann <schmorp@schmorp.de>
877	http://home.schmorp.de/	2119	http://home.schmorp.de/

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