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Revision 1.9 by root, Sun Jul 10 22:20:55 2005 UTC vs.
Revision 1.192 by root, Fri May 20 00:00:03 2011 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
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
21	Event->io (fd => IO::AIO::poll_fileno,	22	use IO::AIO 2;
22	poll => 'r',
23	cb => \&IO::AIO::poll_cb);
24		23
25	# Glib/Gtk2	24	aioreq_pri 4; # give next request a very high priority
26	add_watch Glib::IO IO::AIO::poll_fileno,	25	my $req = aio_unlink "/tmp/file", sub { };
27	\&IO::AIO::poll_cb;	26	$req->cancel; # cancel request if still in queue
28		27
29	# Tk	28	my $grp = aio_group sub { print "all stats done\n" };
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	29	add $grp aio_stat "..." for ...;
31	readable => \&IO::AIO::poll_cb);
32		30
33	=head1 DESCRIPTION	31	=head1 DESCRIPTION
34		32
35	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
36	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>).
37		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
38	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
39	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
40	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
41	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
42	aio functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
43	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
44	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
45	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.
46		62
47	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,
48	currently not reentrant, so use appropriate locking yourself.	64	it is currently not reentrant in any way, so use appropriate locking
		65	yourself, always call C<poll_cb> from within the same thread, or never
		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
49		161
50	=cut	162	=cut
51		163
52	package IO::AIO;	164	package IO::AIO;
53		165
		166	use Carp ();
		167
		168	use common::sense;
		169
54	use base 'Exporter';	170	use base 'Exporter';
55		171
56	use Fcntl ();
57
58	BEGIN {	172	BEGIN {
59	$VERSION = 0.2;	173	our $VERSION = '3.8';
60		174
61	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
62	aio_fsync aio_fdatasync aio_readahead);	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
63	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
		178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		179	aio_rename aio_link aio_move aio_copy aio_group
		180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		181	aio_chmod aio_utime aio_truncate
		182	aio_msync aio_mtouch aio_mlock aio_mlockall
		183	aio_statvfs);
		184
		185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		187	min_parallel max_parallel max_idle idle_timeout
		188	nreqs nready npending nthreads
		189	max_poll_time max_poll_reqs
		190	sendfile fadvise madvise
		191	mmap munmap munlock munlockall);
		192
		193	push @AIO_REQ, qw(aio_busy); # not exported
		194
		195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
64		196
65	require XSLoader;	197	require XSLoader;
66	XSLoader::load IO::AIO, $VERSION;	198	XSLoader::load ("IO::AIO", $VERSION);
67	}	199	}
68		200
69	=head1 FUNCTIONS	201	=head1 FUNCTIONS
70		202
		203	=head2 QUICK OVERVIEW
		204
		205	This section simply lists the prototypes of the most important functions
		206	for quick reference. See the following sections for function-by-function
		207	documentation.
		208
		209	aio_open $pathname, $flags, $mode, $callback->($fh)
		210	aio_close $fh, $callback->($status)
		211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		214	aio_readahead $fh,$offset,$length, $callback->($retval)
		215	aio_stat $fh_or_path, $callback->($status)
		216	aio_lstat $fh, $callback->($status)
		217	aio_statvfs $fh_or_path, $callback->($statvfs)
		218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		220	aio_truncate $fh_or_path, $offset, $callback->($status)
		221	aio_chmod $fh_or_path, $mode, $callback->($status)
		222	aio_unlink $pathname, $callback->($status)
		223	aio_mknod $path, $mode, $dev, $callback->($status)
		224	aio_link $srcpath, $dstpath, $callback->($status)
		225	aio_symlink $srcpath, $dstpath, $callback->($status)
		226	aio_readlink $path, $callback->($link)
		227	aio_rename $srcpath, $dstpath, $callback->($status)
		228	aio_mkdir $pathname, $mode, $callback->($status)
		229	aio_rmdir $pathname, $callback->($status)
		230	aio_readdir $pathname, $callback->($entries)
		231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		234	aio_load $path, $data, $callback->($status)
		235	aio_copy $srcpath, $dstpath, $callback->($status)
		236	aio_move $srcpath, $dstpath, $callback->($status)
		237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		238	aio_rmtree $path, $callback->($status)
		239	aio_sync $callback->($status)
		240	aio_fsync $fh, $callback->($status)
		241	aio_fdatasync $fh, $callback->($status)
		242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		243	aio_pathsync $path, $callback->($status)
		244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		247	aio_mlockall $flags, $callback->($status)
		248	aio_group $callback->(...)
		249	aio_nop $callback->()
		250
		251	$prev_pri = aioreq_pri [$pri]
		252	aioreq_nice $pri_adjust
		253
		254	IO::AIO::poll_wait
		255	IO::AIO::poll_cb
		256	IO::AIO::poll
		257	IO::AIO::flush
		258	IO::AIO::max_poll_reqs $nreqs
		259	IO::AIO::max_poll_time $seconds
		260	IO::AIO::min_parallel $nthreads
		261	IO::AIO::max_parallel $nthreads
		262	IO::AIO::max_idle $nthreads
		263	IO::AIO::idle_timeout $seconds
		264	IO::AIO::max_outstanding $maxreqs
		265	IO::AIO::nreqs
		266	IO::AIO::nready
		267	IO::AIO::npending
		268
		269	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		270	IO::AIO::fadvise $fh, $offset, $len, $advice
		271	IO::AIO::madvise $scalar, $offset, $length, $advice
		272	IO::AIO::mprotect $scalar, $offset, $length, $protect
		273	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		274	IO::AIO::munlockall
		275
71	=head2 AIO FUNCTIONS	276	=head2 AIO REQUEST FUNCTIONS
72		277
73	All the C<aio_*> calls are more or less thin wrappers around the syscall	278	All the C<aio_*> calls are more or less thin wrappers around the syscall
74	with the same name (sans C<aio_>). The arguments are similar or identical,	279	with the same name (sans C<aio_>). The arguments are similar or identical,
75	and they all accept an additional C<$callback> argument which must be	280	and they all accept an additional (and optional) C<$callback> argument
76	a code reference. This code reference will get called with the syscall	281	which must be a code reference. This code reference will get called with
77	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	282	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
78	usually delivers "false") as it's sole argument when the given syscall has	283	perl, which usually delivers "false") as its sole argument after the given
79	been executed asynchronously.	284	syscall has been executed asynchronously.
80		285
81	All functions that expect a filehandle will also accept a file descriptor.	286	All functions expecting a filehandle keep a copy of the filehandle
		287	internally until the request has finished.
82		288
		289	All functions return request objects of type L<IO::AIO::REQ> that allow
		290	further manipulation of those requests while they are in-flight.
		291
83	The filenames you pass to these routines I<must> be absolute. The reason	292	The pathnames you pass to these routines I<must> be absolute and
84	is that at the time the request is being executed, the current working	293	encoded as octets. The reason for the former is that at the time the
85	directory could have changed. Alternatively, you can make sure that you	294	request is being executed, the current working directory could have
86	never change the current working directory.	295	changed. Alternatively, you can make sure that you never change the
		296	current working directory anywhere in the program and then use relative
		297	paths.
		298
		299	To encode pathnames as octets, either make sure you either: a) always pass
		300	in filenames you got from outside (command line, readdir etc.) without
		301	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		302	your pathnames to the locale (or other) encoding in effect in the user
		303	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		304	use something else to ensure your scalar has the correct contents.
		305
		306	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		307	handles correctly whether it is set or not.
87		308
88	=over 4	309	=over 4
89		310
		311	=item $prev_pri = aioreq_pri [$pri]
		312
		313	Returns the priority value that would be used for the next request and, if
		314	C<$pri> is given, sets the priority for the next aio request.
		315
		316	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		317	and C<4>, respectively. Requests with higher priority will be serviced
		318	first.
		319
		320	The priority will be reset to C<0> after each call to one of the C<aio_*>
		321	functions.
		322
		323	Example: open a file with low priority, then read something from it with
		324	higher priority so the read request is serviced before other low priority
		325	open requests (potentially spamming the cache):
		326
		327	aioreq_pri -3;
		328	aio_open ..., sub {
		329	return unless $_[0];
		330
		331	aioreq_pri -2;
		332	aio_read $_[0], ..., sub {
		333	...
		334	};
		335	};
		336
		337
		338	=item aioreq_nice $pri_adjust
		339
		340	Similar to C<aioreq_pri>, but subtracts the given value from the current
		341	priority, so the effect is cumulative.
		342
		343
90	=item aio_open $pathname, $flags, $mode, $callback	344	=item aio_open $pathname, $flags, $mode, $callback->($fh)
91		345
92	Asynchronously open or create a file and call the callback with a newly	346	Asynchronously open or create a file and call the callback with a newly
93	created filehandle for the file.	347	created filehandle for the file.
94		348
95	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	349	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
96	for an explanation.	350	for an explanation.
97		351
98	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	352	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
99	list. They are the same as used in C<sysopen>.	353	list. They are the same as used by C<sysopen>.
		354
		355	Likewise, C<$mode> specifies the mode of the newly created file, if it
		356	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		357	except that it is mandatory (i.e. use C<0> if you don't create new files,
		358	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		359	by the umask in effect then the request is being executed, so better never
		360	change the umask.
100		361
101	Example:	362	Example:
102		363
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	364	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
104	if ($_[0]) {	365	if ($_[0]) {
105	print "open successful, fh is $_[0]\n";	366	print "open successful, fh is $_[0]\n";
106	...	367	...
107	} else {	368	} else {
108	die "open failed: $!\n";	369	die "open failed: $!\n";
109	}	370	}
110	};	371	};
111		372
		373
112	=item aio_close $fh, $callback	374	=item aio_close $fh, $callback->($status)
113		375
114	Asynchronously close a file and call the callback with the result	376	Asynchronously close a file and call the callback with the result
115	code. I<WARNING:> although accepted, you should not pass in a perl	377	code.
116	filehandle here, as perl will likely close the file descriptor itself when
117	the filehandle is destroyed. Normally, you can safely call perls C<close>
118	or just let filehandles go out of scope.
119		378
		379	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
		380	closing the file descriptor associated with the filehandle itself.
		381
		382	Therefore, C<aio_close> will not close the filehandle - instead it will
		383	use dup2 to overwrite the file descriptor with the write-end of a pipe
		384	(the pipe fd will be created on demand and will be cached).
		385
		386	Or in other words: the file descriptor will be closed, but it will not be
		387	free for reuse until the perl filehandle is closed.
		388
		389	=cut
		390
120	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	391	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121		392
122	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	393	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
123		394
124	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	395	Reads or writes C<$length> bytes from or to the specified C<$fh> and
125	into the scalar given by C<data> and offset C<dataoffset> and calls the	396	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
126	callback without the actual number of bytes read (or -1 on error, just	397	and calls the callback without the actual number of bytes read (or -1 on
127	like the syscall).	398	error, just like the syscall).
128		399
		400	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		401	offset plus the actual number of bytes read.
		402
		403	If C<$offset> is undefined, then the current file descriptor offset will
		404	be used (and updated), otherwise the file descriptor offset will not be
		405	changed by these calls.
		406
		407	If C<$length> is undefined in C<aio_write>, use the remaining length of
		408	C<$data>.
		409
		410	If C<$dataoffset> is less than zero, it will be counted from the end of
		411	C<$data>.
		412
		413	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		414	is outstanding. Modifying it can result in segfaults or World War III (if
		415	the necessary/optional hardware is installed).
		416
129	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	417	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
130	offset C<0> within the scalar:	418	offset C<0> within the scalar:
131		419
132	aio_read $fh, 7, 15, $buffer, 0, sub {	420	aio_read $fh, 7, 15, $buffer, 0, sub {
133	$_[0] > 0 or die "read error: $!";	421	$_[0] > 0 or die "read error: $!";
134	print "read $_[0] bytes: <$buffer>\n";	422	print "read $_[0] bytes: <$buffer>\n";
135	};	423	};
136		424
		425
		426	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		427
		428	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		429	reading at byte offset C<$in_offset>, and starts writing at the current
		430	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		431	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		432	other.
		433
		434	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		435	are written, and there is no way to find out how many bytes have been read
		436	from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of
		437	bytes written to C<$out_fh>. Only if the result value equals C<$length>
		438	one can assume that C<$length> bytes have been read.
		439
		440	Unlike with other C<aio_> functions, it makes a lot of sense to use
		441	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		442	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		443	the socket I/O will be non-blocking. Note, however, that you can run into
		444	a trap where C<aio_sendfile> reads some data with readahead, then fails
		445	to write all data, and when the socket is ready the next time, the data
		446	in the cache is already lost, forcing C<aio_sendfile> to again hit the
		447	disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage
		448	much better.
		449
		450	This call tries to make use of a native C<sendfile> syscall to provide
		451	zero-copy operation. For this to work, C<$out_fh> should refer to a
		452	socket, and C<$in_fh> should refer to an mmap'able file.
		453
		454	If a native sendfile cannot be found or it fails with C<ENOSYS>,
		455	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
		456	it will be emulated, so you can call C<aio_sendfile> on any type of
		457	filehandle regardless of the limitations of the operating system.
		458
		459
137	=item aio_readahead $fh,$offset,$length, $callback	460	=item aio_readahead $fh,$offset,$length, $callback->($retval)
138		461
139	Asynchronously reads the specified byte range into the page cache, using
140	the C<readahead> syscall. If that syscall doesn't exist the status will be
141	C<-1> and C<$!> is set to ENOSYS.
142
143	readahead() populates the page cache with data from a file so that	462	C<aio_readahead> populates the page cache with data from a file so that
144	subsequent reads from that file will not block on disk I/O. The C<$offset>	463	subsequent reads from that file will not block on disk I/O. The C<$offset>
145	argument specifies the starting point from which data is to be read and	464	argument specifies the starting point from which data is to be read and
146	C<$length> specifies the number of bytes to be read. I/O is performed in	465	C<$length> specifies the number of bytes to be read. I/O is performed in
147	whole pages, so that offset is effectively rounded down to a page boundary	466	whole pages, so that offset is effectively rounded down to a page boundary
148	and bytes are read up to the next page boundary greater than or equal to	467	and bytes are read up to the next page boundary greater than or equal to
149	(off-set+length). aio_readahead() does not read beyond the end of the	468	(off-set+length). C<aio_readahead> does not read beyond the end of the
150	file. The current file offset of the file is left unchanged.	469	file. The current file offset of the file is left unchanged.
151		470
		471	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		472	emulated by simply reading the data, which would have a similar effect.
		473
		474
152	=item aio_stat $fh_or_path, $callback	475	=item aio_stat $fh_or_path, $callback->($status)
153		476
154	=item aio_lstat $fh, $callback	477	=item aio_lstat $fh, $callback->($status)
155		478
156	Works like perl's C<stat> or C<lstat> in void context. The callback will	479	Works like perl's C<stat> or C<lstat> in void context. The callback will
157	be called after the stat and the results will be available using C<stat _>	480	be called after the stat and the results will be available using C<stat _>
158	or C<-s _> etc...	481	or C<-s _> etc...
159		482
…		…
161	for an explanation.	484	for an explanation.
162		485
163	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	486	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
164	error when stat'ing a large file, the results will be silently truncated	487	error when stat'ing a large file, the results will be silently truncated
165	unless perl itself is compiled with large file support.	488	unless perl itself is compiled with large file support.
		489
		490	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		491	following constants and functions (if not implemented, the constants will
		492	be C<0> and the functions will either C<croak> or fall back on traditional
		493	behaviour).
		494
		495	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		496	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		497	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
166		498
167	Example: Print the length of F</etc/passwd>:	499	Example: Print the length of F</etc/passwd>:
168		500
169	aio_stat "/etc/passwd", sub {	501	aio_stat "/etc/passwd", sub {
170	$_[0] and die "stat failed: $!";	502	$_[0] and die "stat failed: $!";
171	print "size is ", -s _, "\n";	503	print "size is ", -s _, "\n";
172	};	504	};
173		505
		506
		507	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		508
		509	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		510	whether a file handle or path was passed.
		511
		512	On success, the callback is passed a hash reference with the following
		513	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		514	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		515	is passed.
		516
		517	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		518	C<ST_NOSUID>.
		519
		520	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		521	their correct value when available, or to C<0> on systems that do
		522	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		523	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		524	C<ST_NODIRATIME> and C<ST_RELATIME>.
		525
		526	Example: stat C</wd> and dump out the data if successful.
		527
		528	aio_statvfs "/wd", sub {
		529	my $f = $_[0]
		530	or die "statvfs: $!";
		531
		532	use Data::Dumper;
		533	say Dumper $f;
		534	};
		535
		536	# result:
		537	{
		538	bsize => 1024,
		539	bfree => 4333064312,
		540	blocks => 10253828096,
		541	files => 2050765568,
		542	flag => 4096,
		543	favail => 2042092649,
		544	bavail => 4333064312,
		545	ffree => 2042092649,
		546	namemax => 255,
		547	frsize => 1024,
		548	fsid => 1810
		549	}
		550
		551
		552	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		553
		554	Works like perl's C<utime> function (including the special case of $atime
		555	and $mtime being undef). Fractional times are supported if the underlying
		556	syscalls support them.
		557
		558	When called with a pathname, uses utimes(2) if available, otherwise
		559	utime(2). If called on a file descriptor, uses futimes(2) if available,
		560	otherwise returns ENOSYS, so this is not portable.
		561
		562	Examples:
		563
		564	# set atime and mtime to current time (basically touch(1)):
		565	aio_utime "path", undef, undef;
		566	# set atime to current time and mtime to beginning of the epoch:
		567	aio_utime "path", time, undef; # undef==0
		568
		569
		570	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		571
		572	Works like perl's C<chown> function, except that C<undef> for either $uid
		573	or $gid is being interpreted as "do not change" (but -1 can also be used).
		574
		575	Examples:
		576
		577	# same as "chown root path" in the shell:
		578	aio_chown "path", 0, -1;
		579	# same as above:
		580	aio_chown "path", 0, undef;
		581
		582
		583	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		584
		585	Works like truncate(2) or ftruncate(2).
		586
		587
		588	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		589
		590	Works like perl's C<chmod> function.
		591
		592
174	=item aio_unlink $pathname, $callback	593	=item aio_unlink $pathname, $callback->($status)
175		594
176	Asynchronously unlink (delete) a file and call the callback with the	595	Asynchronously unlink (delete) a file and call the callback with the
177	result code.	596	result code.
178		597
		598
		599	=item aio_mknod $path, $mode, $dev, $callback->($status)
		600
		601	[EXPERIMENTAL]
		602
		603	Asynchronously create a device node (or fifo). See mknod(2).
		604
		605	The only (POSIX-) portable way of calling this function is:
		606
		607	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		608
		609	See C<aio_stat> for info about some potentially helpful extra constants
		610	and functions.
		611
		612	=item aio_link $srcpath, $dstpath, $callback->($status)
		613
		614	Asynchronously create a new link to the existing object at C<$srcpath> at
		615	the path C<$dstpath> and call the callback with the result code.
		616
		617
		618	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		619
		620	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		621	the path C<$dstpath> and call the callback with the result code.
		622
		623
		624	=item aio_readlink $path, $callback->($link)
		625
		626	Asynchronously read the symlink specified by C<$path> and pass it to
		627	the callback. If an error occurs, nothing or undef gets passed to the
		628	callback.
		629
		630
		631	=item aio_rename $srcpath, $dstpath, $callback->($status)
		632
		633	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		634	rename(2) and call the callback with the result code.
		635
		636
		637	=item aio_mkdir $pathname, $mode, $callback->($status)
		638
		639	Asynchronously mkdir (create) a directory and call the callback with
		640	the result code. C<$mode> will be modified by the umask at the time the
		641	request is executed, so do not change your umask.
		642
		643
		644	=item aio_rmdir $pathname, $callback->($status)
		645
		646	Asynchronously rmdir (delete) a directory and call the callback with the
		647	result code.
		648
		649
		650	=item aio_readdir $pathname, $callback->($entries)
		651
		652	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		653	directory (i.e. opendir + readdir + closedir). The entries will not be
		654	sorted, and will B<NOT> include the C<.> and C<..> entries.
		655
		656	The callback is passed a single argument which is either C<undef> or an
		657	array-ref with the filenames.
		658
		659
		660	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		661
		662	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		663	behaviour and output format. In case of an error, C<$entries> will be
		664	C<undef>.
		665
		666	The flags are a combination of the following constants, ORed together (the
		667	flags will also be passed to the callback, possibly modified):
		668
		669	=over 4
		670
		671	=item IO::AIO::READDIR_DENTS
		672
		673	When this flag is off, then the callback gets an arrayref consisting of
		674	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		675	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		676	entry in more detail.
		677
		678	C<$name> is the name of the entry.
		679
		680	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		681
		682	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		683	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		684	C<IO::AIO::DT_WHT>.
		685
		686	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		687	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		688	scalars are read-only: you can not modify them.
		689
		690	C<$inode> is the inode number (which might not be exact on systems with 64
		691	bit inode numbers and 32 bit perls). This field has unspecified content on
		692	systems that do not deliver the inode information.
		693
		694	=item IO::AIO::READDIR_DIRS_FIRST
		695
		696	When this flag is set, then the names will be returned in an order where
		697	likely directories come first. This is useful when you need to quickly
		698	find directories, or you want to find all directories while avoiding to
		699	stat() each entry.
		700
		701	If the system returns type information in readdir, then this is used
		702	to find directories directly. Otherwise, likely directories are files
		703	beginning with ".", or otherwise files with no dots, of which files with
		704	short names are tried first.
		705
		706	=item IO::AIO::READDIR_STAT_ORDER
		707
		708	When this flag is set, then the names will be returned in an order
		709	suitable for stat()'ing each one. That is, when you plan to stat()
		710	all files in the given directory, then the returned order will likely
		711	be fastest.
		712
		713	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		714	the likely dirs come first, resulting in a less optimal stat order.
		715
		716	=item IO::AIO::READDIR_FOUND_UNKNOWN
		717
		718	This flag should not be set when calling C<aio_readdirx>. Instead, it
		719	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		720	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		721	C<$type>'s are known, which can be used to speed up some algorithms.
		722
		723	=back
		724
		725
		726	=item aio_load $path, $data, $callback->($status)
		727
		728	This is a composite request that tries to fully load the given file into
		729	memory. Status is the same as with aio_read.
		730
		731	=cut
		732
		733	sub aio_load($$;$) {
		734	my ($path, undef, $cb) = @_;
		735	my $data = \$_[1];
		736
		737	my $pri = aioreq_pri;
		738	my $grp = aio_group $cb;
		739
		740	aioreq_pri $pri;
		741	add $grp aio_open $path, O_RDONLY, 0, sub {
		742	my $fh = shift
		743	or return $grp->result (-1);
		744
		745	aioreq_pri $pri;
		746	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		747	$grp->result ($_[0]);
		748	};
		749	};
		750
		751	$grp
		752	}
		753
		754	=item aio_copy $srcpath, $dstpath, $callback->($status)
		755
		756	Try to copy the I<file> (directories not supported as either source or
		757	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		758	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		759
		760	This is a composite request that creates the destination file with
		761	mode 0200 and copies the contents of the source file into it using
		762	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		763	uid/gid, in that order.
		764
		765	If an error occurs, the partial destination file will be unlinked, if
		766	possible, except when setting atime, mtime, access mode and uid/gid, where
		767	errors are being ignored.
		768
		769	=cut
		770
		771	sub aio_copy($$;$) {
		772	my ($src, $dst, $cb) = @_;
		773
		774	my $pri = aioreq_pri;
		775	my $grp = aio_group $cb;
		776
		777	aioreq_pri $pri;
		778	add $grp aio_open $src, O_RDONLY, 0, sub {
		779	if (my $src_fh = $_[0]) {
		780	my @stat = stat $src_fh; # hmm, might block over nfs?
		781
		782	aioreq_pri $pri;
		783	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		784	if (my $dst_fh = $_[0]) {
		785	aioreq_pri $pri;
		786	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		787	if ($_[0] == $stat[7]) {
		788	$grp->result (0);
		789	close $src_fh;
		790
		791	my $ch = sub {
		792	aioreq_pri $pri;
		793	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		794	aioreq_pri $pri;
		795	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		796	aioreq_pri $pri;
		797	add $grp aio_close $dst_fh;
		798	}
		799	};
		800	};
		801
		802	aioreq_pri $pri;
		803	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		804	if ($_[0] < 0 && $! == ENOSYS) {
		805	aioreq_pri $pri;
		806	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		807	} else {
		808	$ch->();
		809	}
		810	};
		811	} else {
		812	$grp->result (-1);
		813	close $src_fh;
		814	close $dst_fh;
		815
		816	aioreq $pri;
		817	add $grp aio_unlink $dst;
		818	}
		819	};
		820	} else {
		821	$grp->result (-1);
		822	}
		823	},
		824
		825	} else {
		826	$grp->result (-1);
		827	}
		828	};
		829
		830	$grp
		831	}
		832
		833	=item aio_move $srcpath, $dstpath, $callback->($status)
		834
		835	Try to move the I<file> (directories not supported as either source or
		836	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		837	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		838
		839	This is a composite request that tries to rename(2) the file first; if
		840	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		841	that is successful, unlinks the C<$srcpath>.
		842
		843	=cut
		844
		845	sub aio_move($$;$) {
		846	my ($src, $dst, $cb) = @_;
		847
		848	my $pri = aioreq_pri;
		849	my $grp = aio_group $cb;
		850
		851	aioreq_pri $pri;
		852	add $grp aio_rename $src, $dst, sub {
		853	if ($_[0] && $! == EXDEV) {
		854	aioreq_pri $pri;
		855	add $grp aio_copy $src, $dst, sub {
		856	$grp->result ($_[0]);
		857
		858	if (!$_[0]) {
		859	aioreq_pri $pri;
		860	add $grp aio_unlink $src;
		861	}
		862	};
		863	} else {
		864	$grp->result ($_[0]);
		865	}
		866	};
		867
		868	$grp
		869	}
		870
		871	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		872
		873	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		874	efficiently separate the entries of directory C<$path> into two sets of
		875	names, directories you can recurse into (directories), and ones you cannot
		876	recurse into (everything else, including symlinks to directories).
		877
		878	C<aio_scandir> is a composite request that creates of many sub requests_
		879	C<$maxreq> specifies the maximum number of outstanding aio requests that
		880	this function generates. If it is C<< <= 0 >>, then a suitable default
		881	will be chosen (currently 4).
		882
		883	On error, the callback is called without arguments, otherwise it receives
		884	two array-refs with path-relative entry names.
		885
		886	Example:
		887
		888	aio_scandir $dir, 0, sub {
		889	my ($dirs, $nondirs) = @_;
		890	print "real directories: @$dirs\n";
		891	print "everything else: @$nondirs\n";
		892	};
		893
		894	Implementation notes.
		895
		896	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		897
		898	If readdir returns file type information, then this is used directly to
		899	find directories.
		900
		901	Otherwise, after reading the directory, the modification time, size etc.
		902	of the directory before and after the readdir is checked, and if they
		903	match (and isn't the current time), the link count will be used to decide
		904	how many entries are directories (if >= 2). Otherwise, no knowledge of the
		905	number of subdirectories will be assumed.
		906
		907	Then entries will be sorted into likely directories a non-initial dot
		908	currently) and likely non-directories (see C<aio_readdirx>). Then every
		909	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		910	in order of their inode numbers. If that succeeds, it assumes that the
		911	entry is a directory or a symlink to directory (which will be checked
		912	seperately). This is often faster than stat'ing the entry itself because
		913	filesystems might detect the type of the entry without reading the inode
		914	data (e.g. ext2fs filetype feature), even on systems that cannot return
		915	the filetype information on readdir.
		916
		917	If the known number of directories (link count - 2) has been reached, the
		918	rest of the entries is assumed to be non-directories.
		919
		920	This only works with certainty on POSIX (= UNIX) filesystems, which
		921	fortunately are the vast majority of filesystems around.
		922
		923	It will also likely work on non-POSIX filesystems with reduced efficiency
		924	as those tend to return 0 or 1 as link counts, which disables the
		925	directory counting heuristic.
		926
		927	=cut
		928
		929	sub aio_scandir($$;$) {
		930	my ($path, $maxreq, $cb) = @_;
		931
		932	my $pri = aioreq_pri;
		933
		934	my $grp = aio_group $cb;
		935
		936	$maxreq = 4 if $maxreq <= 0;
		937
		938	# stat once
		939	aioreq_pri $pri;
		940	add $grp aio_stat $path, sub {
		941	return $grp->result () if $_[0];
		942	my $now = time;
		943	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		944
		945	# read the directory entries
		946	aioreq_pri $pri;
		947	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
		948	my $entries = shift
		949	or return $grp->result ();
		950
		951	# stat the dir another time
		952	aioreq_pri $pri;
		953	add $grp aio_stat $path, sub {
		954	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		955
		956	my $ndirs;
		957
		958	# take the slow route if anything looks fishy
		959	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		960	$ndirs = -1;
		961	} else {
		962	# if nlink == 2, we are finished
		963	# for non-posix-fs's, we rely on nlink < 2
		964	$ndirs = (stat _)[3] - 2
		965	or return $grp->result ([], $entries);
		966	}
		967
		968	my (@dirs, @nondirs);
		969
		970	my $statgrp = add $grp aio_group sub {
		971	$grp->result (\@dirs, \@nondirs);
		972	};
		973
		974	limit $statgrp $maxreq;
		975	feed $statgrp sub {
		976	return unless @$entries;
		977	my $entry = shift @$entries;
		978
		979	aioreq_pri $pri;
		980	add $statgrp aio_stat "$path/$entry/.", sub {
		981	if ($_[0] < 0) {
		982	push @nondirs, $entry;
		983	} else {
		984	# need to check for real directory
		985	aioreq_pri $pri;
		986	add $statgrp aio_lstat "$path/$entry", sub {
		987	if (-d _) {
		988	push @dirs, $entry;
		989
		990	unless (--$ndirs) {
		991	push @nondirs, @$entries;
		992	feed $statgrp;
		993	}
		994	} else {
		995	push @nondirs, $entry;
		996	}
		997	}
		998	}
		999	};
		1000	};
		1001	};
		1002	};
		1003	};
		1004
		1005	$grp
		1006	}
		1007
		1008	=item aio_rmtree $path, $callback->($status)
		1009
		1010	Delete a directory tree starting (and including) C<$path>, return the
		1011	status of the final C<rmdir> only. This is a composite request that
		1012	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1013	everything else.
		1014
		1015	=cut
		1016
		1017	sub aio_rmtree;
		1018	sub aio_rmtree($;$) {
		1019	my ($path, $cb) = @_;
		1020
		1021	my $pri = aioreq_pri;
		1022	my $grp = aio_group $cb;
		1023
		1024	aioreq_pri $pri;
		1025	add $grp aio_scandir $path, 0, sub {
		1026	my ($dirs, $nondirs) = @_;
		1027
		1028	my $dirgrp = aio_group sub {
		1029	add $grp aio_rmdir $path, sub {
		1030	$grp->result ($_[0]);
		1031	};
		1032	};
		1033
		1034	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1035	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1036
		1037	add $grp $dirgrp;
		1038	};
		1039
		1040	$grp
		1041	}
		1042
		1043	=item aio_sync $callback->($status)
		1044
		1045	Asynchronously call sync and call the callback when finished.
		1046
179	=item aio_fsync $fh, $callback	1047	=item aio_fsync $fh, $callback->($status)
180		1048
181	Asynchronously call fsync on the given filehandle and call the callback	1049	Asynchronously call fsync on the given filehandle and call the callback
182	with the fsync result code.	1050	with the fsync result code.
183		1051
184	=item aio_fdatasync $fh, $callback	1052	=item aio_fdatasync $fh, $callback->($status)
185		1053
186	Asynchronously call fdatasync on the given filehandle and call the	1054	Asynchronously call fdatasync on the given filehandle and call the
187	callback with the fdatasync result code.	1055	callback with the fdatasync result code.
188		1056
		1057	If this call isn't available because your OS lacks it or it couldn't be
		1058	detected, it will be emulated by calling C<fsync> instead.
		1059
		1060	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1061
		1062	Sync the data portion of the file specified by C<$offset> and C<$length>
		1063	to disk (but NOT the metadata), by calling the Linux-specific
		1064	sync_file_range call. If sync_file_range is not available or it returns
		1065	ENOSYS, then fdatasync or fsync is being substituted.
		1066
		1067	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1068	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1069	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1070	manpage for details.
		1071
		1072	=item aio_pathsync $path, $callback->($status)
		1073
		1074	This request tries to open, fsync and close the given path. This is a
		1075	composite request intended to sync directories after directory operations
		1076	(E.g. rename). This might not work on all operating systems or have any
		1077	specific effect, but usually it makes sure that directory changes get
		1078	written to disc. It works for anything that can be opened for read-only,
		1079	not just directories.
		1080
		1081	Future versions of this function might fall back to other methods when
		1082	C<fsync> on the directory fails (such as calling C<sync>).
		1083
		1084	Passes C<0> when everything went ok, and C<-1> on error.
		1085
		1086	=cut
		1087
		1088	sub aio_pathsync($;$) {
		1089	my ($path, $cb) = @_;
		1090
		1091	my $pri = aioreq_pri;
		1092	my $grp = aio_group $cb;
		1093
		1094	aioreq_pri $pri;
		1095	add $grp aio_open $path, O_RDONLY, 0, sub {
		1096	my ($fh) = @_;
		1097	if ($fh) {
		1098	aioreq_pri $pri;
		1099	add $grp aio_fsync $fh, sub {
		1100	$grp->result ($_[0]);
		1101
		1102	aioreq_pri $pri;
		1103	add $grp aio_close $fh;
		1104	};
		1105	} else {
		1106	$grp->result (-1);
		1107	}
		1108	};
		1109
		1110	$grp
		1111	}
		1112
		1113	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1114
		1115	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1116	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1117	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1118	scalar must only be modified in-place while an aio operation is pending on
		1119	it).
		1120
		1121	It calls the C<msync> function of your OS, if available, with the memory
		1122	area starting at C<$offset> in the string and ending C<$length> bytes
		1123	later. If C<$length> is negative, counts from the end, and if C<$length>
		1124	is C<undef>, then it goes till the end of the string. The flags can be
		1125	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1126	C<IO::AIO::MS_SYNC>.
		1127
		1128	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1129
		1130	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1131	scalars.
		1132
		1133	It touches (reads or writes) all memory pages in the specified
		1134	range inside the scalar. All caveats and parameters are the same
		1135	as for C<aio_msync>, above, except for flags, which must be either
		1136	C<0> (which reads all pages and ensures they are instantiated) or
		1137	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1138	writing an octet from it, which dirties the page).
		1139
		1140	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1141
		1142	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1143	scalars.
		1144
		1145	It reads in all the pages of the underlying storage into memory (if any)
		1146	and locks them, so they are not getting swapped/paged out or removed.
		1147
		1148	If C<$length> is undefined, then the scalar will be locked till the end.
		1149
		1150	On systems that do not implement C<mlock>, this function returns C<-1>
		1151	and sets errno to C<ENOSYS>.
		1152
		1153	Note that the corresponding C<munlock> is synchronous and is
		1154	documented under L<MISCELLANEOUS FUNCTIONS>.
		1155
		1156	Example: open a file, mmap and mlock it - both will be undone when
		1157	C<$data> gets destroyed.
		1158
		1159	open my $fh, "<", $path or die "$path: $!";
		1160	my $data;
		1161	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1162	aio_mlock $data; # mlock in background
		1163
		1164	=item aio_mlockall $flags, $callback->($status)
		1165
		1166	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1167	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1168
		1169	On systems that do not implement C<mlockall>, this function returns C<-1>
		1170	and sets errno to C<ENOSYS>.
		1171
		1172	Note that the corresponding C<munlockall> is synchronous and is
		1173	documented under L<MISCELLANEOUS FUNCTIONS>.
		1174
		1175	Example: asynchronously lock all current and future pages into memory.
		1176
		1177	aio_mlockall IO::AIO::MCL_FUTURE;
		1178
		1179	=item aio_group $callback->(...)
		1180
		1181	This is a very special aio request: Instead of doing something, it is a
		1182	container for other aio requests, which is useful if you want to bundle
		1183	many requests into a single, composite, request with a definite callback
		1184	and the ability to cancel the whole request with its subrequests.
		1185
		1186	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		1187	for more info.
		1188
		1189	Example:
		1190
		1191	my $grp = aio_group sub {
		1192	print "all stats done\n";
		1193	};
		1194
		1195	add $grp
		1196	(aio_stat ...),
		1197	(aio_stat ...),
		1198	...;
		1199
		1200	=item aio_nop $callback->()
		1201
		1202	This is a special request - it does nothing in itself and is only used for
		1203	side effects, such as when you want to add a dummy request to a group so
		1204	that finishing the requests in the group depends on executing the given
		1205	code.
		1206
		1207	While this request does nothing, it still goes through the execution
		1208	phase and still requires a worker thread. Thus, the callback will not
		1209	be executed immediately but only after other requests in the queue have
		1210	entered their execution phase. This can be used to measure request
		1211	latency.
		1212
		1213	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1214
		1215	Mainly used for debugging and benchmarking, this aio request puts one of
		1216	the request workers to sleep for the given time.
		1217
		1218	While it is theoretically handy to have simple I/O scheduling requests
		1219	like sleep and file handle readable/writable, the overhead this creates is
		1220	immense (it blocks a thread for a long time) so do not use this function
		1221	except to put your application under artificial I/O pressure.
		1222
189	=back	1223	=back
190		1224
		1225	=head2 IO::AIO::REQ CLASS
		1226
		1227	All non-aggregate C<aio_*> functions return an object of this class when
		1228	called in non-void context.
		1229
		1230	=over 4
		1231
		1232	=item cancel $req
		1233
		1234	Cancels the request, if possible. Has the effect of skipping execution
		1235	when entering the B<execute> state and skipping calling the callback when
		1236	entering the the B<result> state, but will leave the request otherwise
		1237	untouched (with the exception of readdir). That means that requests that
		1238	currently execute will not be stopped and resources held by the request
		1239	will not be freed prematurely.
		1240
		1241	=item cb $req $callback->(...)
		1242
		1243	Replace (or simply set) the callback registered to the request.
		1244
		1245	=back
		1246
		1247	=head2 IO::AIO::GRP CLASS
		1248
		1249	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1250	objects of this class, too.
		1251
		1252	A IO::AIO::GRP object is a special request that can contain multiple other
		1253	aio requests.
		1254
		1255	You create one by calling the C<aio_group> constructing function with a
		1256	callback that will be called when all contained requests have entered the
		1257	C<done> state:
		1258
		1259	my $grp = aio_group sub {
		1260	print "all requests are done\n";
		1261	};
		1262
		1263	You add requests by calling the C<add> method with one or more
		1264	C<IO::AIO::REQ> objects:
		1265
		1266	$grp->add (aio_unlink "...");
		1267
		1268	add $grp aio_stat "...", sub {
		1269	$_[0] or return $grp->result ("error");
		1270
		1271	# add another request dynamically, if first succeeded
		1272	add $grp aio_open "...", sub {
		1273	$grp->result ("ok");
		1274	};
		1275	};
		1276
		1277	This makes it very easy to create composite requests (see the source of
		1278	C<aio_move> for an application) that work and feel like simple requests.
		1279
		1280	=over 4
		1281
		1282	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1283	C<IO::AIO::poll_cb>, just like any other request.
		1284
		1285	=item * They can be canceled like any other request. Canceling will cancel not
		1286	only the request itself, but also all requests it contains.
		1287
		1288	=item * They can also can also be added to other IO::AIO::GRP objects.
		1289
		1290	=item * You must not add requests to a group from within the group callback (or
		1291	any later time).
		1292
		1293	=back
		1294
		1295	Their lifetime, simplified, looks like this: when they are empty, they
		1296	will finish very quickly. If they contain only requests that are in the
		1297	C<done> state, they will also finish. Otherwise they will continue to
		1298	exist.
		1299
		1300	That means after creating a group you have some time to add requests
		1301	(precisely before the callback has been invoked, which is only done within
		1302	the C<poll_cb>). And in the callbacks of those requests, you can add
		1303	further requests to the group. And only when all those requests have
		1304	finished will the the group itself finish.
		1305
		1306	=over 4
		1307
		1308	=item add $grp ...
		1309
		1310	=item $grp->add (...)
		1311
		1312	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1313	be added, including other groups, as long as you do not create circular
		1314	dependencies.
		1315
		1316	Returns all its arguments.
		1317
		1318	=item $grp->cancel_subs
		1319
		1320	Cancel all subrequests and clears any feeder, but not the group request
		1321	itself. Useful when you queued a lot of events but got a result early.
		1322
		1323	The group request will finish normally (you cannot add requests to the
		1324	group).
		1325
		1326	=item $grp->result (...)
		1327
		1328	Set the result value(s) that will be passed to the group callback when all
		1329	subrequests have finished and set the groups errno to the current value
		1330	of errno (just like calling C<errno> without an error number). By default,
		1331	no argument will be passed and errno is zero.
		1332
		1333	=item $grp->errno ([$errno])
		1334
		1335	Sets the group errno value to C<$errno>, or the current value of errno
		1336	when the argument is missing.
		1337
		1338	Every aio request has an associated errno value that is restored when
		1339	the callback is invoked. This method lets you change this value from its
		1340	default (0).
		1341
		1342	Calling C<result> will also set errno, so make sure you either set C<$!>
		1343	before the call to C<result>, or call c<errno> after it.
		1344
		1345	=item feed $grp $callback->($grp)
		1346
		1347	Sets a feeder/generator on this group: every group can have an attached
		1348	generator that generates requests if idle. The idea behind this is that,
		1349	although you could just queue as many requests as you want in a group,
		1350	this might starve other requests for a potentially long time. For example,
		1351	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1352	delaying any later requests for a long time.
		1353
		1354	To avoid this, and allow incremental generation of requests, you can
		1355	instead a group and set a feeder on it that generates those requests. The
		1356	feed callback will be called whenever there are few enough (see C<limit>,
		1357	below) requests active in the group itself and is expected to queue more
		1358	requests.
		1359
		1360	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1361	not impose any limits).
		1362
		1363	If the feed does not queue more requests when called, it will be
		1364	automatically removed from the group.
		1365
		1366	If the feed limit is C<0> when this method is called, it will be set to
		1367	C<2> automatically.
		1368
		1369	Example:
		1370
		1371	# stat all files in @files, but only ever use four aio requests concurrently:
		1372
		1373	my $grp = aio_group sub { print "finished\n" };
		1374	limit $grp 4;
		1375	feed $grp sub {
		1376	my $file = pop @files
		1377	or return;
		1378
		1379	add $grp aio_stat $file, sub { ... };
		1380	};
		1381
		1382	=item limit $grp $num
		1383
		1384	Sets the feeder limit for the group: The feeder will be called whenever
		1385	the group contains less than this many requests.
		1386
		1387	Setting the limit to C<0> will pause the feeding process.
		1388
		1389	The default value for the limit is C<0>, but note that setting a feeder
		1390	automatically bumps it up to C<2>.
		1391
		1392	=back
		1393
191	=head2 SUPPORT FUNCTIONS	1394	=head2 SUPPORT FUNCTIONS
192		1395
		1396	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1397
193	=over 4	1398	=over 4
194		1399
195	=item $fileno = IO::AIO::poll_fileno	1400	=item $fileno = IO::AIO::poll_fileno
196		1401
197	Return the I<request result pipe filehandle>. This filehandle must be	1402	Return the I<request result pipe file descriptor>. This filehandle must be
198	polled for reading by some mechanism outside this module (e.g. Event	1403	polled for reading by some mechanism outside this module (e.g. EV, Glib,
199	or select, see below). If the pipe becomes readable you have to call	1404	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
200	C<poll_cb> to check the results.	1405	you have to call C<poll_cb> to check the results.
201		1406
202	See C<poll_cb> for an example.	1407	See C<poll_cb> for an example.
203		1408
204	=item IO::AIO::poll_cb	1409	=item IO::AIO::poll_cb
205		1410
206	Process all outstanding events on the result pipe. You have to call this	1411	Process some outstanding events on the result pipe. You have to call
207	regularly. Returns the number of events processed. Returns immediately	1412	this regularly. Returns C<0> if all events could be processed (or there
208	when no events are outstanding.	1413	were no events to process), or C<-1> if it returned earlier for whatever
		1414	reason. Returns immediately when no events are outstanding. The amount of
		1415	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1416	C<IO::AIO::max_poll_time>.
209		1417
210	You can use Event to multiplex, e.g.:	1418	If not all requests were processed for whatever reason, the filehandle
		1419	will still be ready when C<poll_cb> returns, so normally you don't have to
		1420	do anything special to have it called later.
		1421
		1422	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1423	ready, it can be beneficial to call this function from loops which submit
		1424	a lot of requests, to make sure the results get processed when they become
		1425	available and not just when the loop is finished and the event loop takes
		1426	over again. This function returns very fast when there are no outstanding
		1427	requests.
		1428
		1429	Example: Install an Event watcher that automatically calls
		1430	IO::AIO::poll_cb with high priority (more examples can be found in the
		1431	SYNOPSIS section, at the top of this document):
211		1432
212	Event->io (fd => IO::AIO::poll_fileno,	1433	Event->io (fd => IO::AIO::poll_fileno,
213	poll => 'r', async => 1,	1434	poll => 'r', async => 1,
214	cb => \&IO::AIO::poll_cb);	1435	cb => \&IO::AIO::poll_cb);
215		1436
216	=item IO::AIO::poll_wait	1437	=item IO::AIO::poll_wait
217		1438
		1439	If there are any outstanding requests and none of them in the result
218	Wait till the result filehandle becomes ready for reading (simply does a	1440	phase, wait till the result filehandle becomes ready for reading (simply
219	select on the filehandle. This is useful if you want to synchronously wait	1441	does a C<select> on the filehandle. This is useful if you want to
220	for some requests to finish).	1442	synchronously wait for some requests to finish).
221		1443
222	See C<nreqs> for an example.	1444	See C<nreqs> for an example.
223		1445
		1446	=item IO::AIO::poll
		1447
		1448	Waits until some requests have been handled.
		1449
		1450	Returns the number of requests processed, but is otherwise strictly
		1451	equivalent to:
		1452
		1453	IO::AIO::poll_wait, IO::AIO::poll_cb
		1454
224	=item IO::AIO::nreqs	1455	=item IO::AIO::flush
225		1456
226	Returns the number of requests currently outstanding.	1457	Wait till all outstanding AIO requests have been handled.
227		1458
228	Example: wait till there are no outstanding requests anymore:	1459	Strictly equivalent to:
229		1460
230	IO::AIO::poll_wait, IO::AIO::poll_cb	1461	IO::AIO::poll_wait, IO::AIO::poll_cb
231	while IO::AIO::nreqs;	1462	while IO::AIO::nreqs;
232		1463
		1464	=item IO::AIO::max_poll_reqs $nreqs
		1465
		1466	=item IO::AIO::max_poll_time $seconds
		1467
		1468	These set the maximum number of requests (default C<0>, meaning infinity)
		1469	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1470	the maximum amount of time (default C<0>, meaning infinity) spent in
		1471	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1472	of time C<poll_cb> is allowed to use).
		1473
		1474	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1475	syscall per request processed, which is not normally a problem unless your
		1476	callbacks are really really fast or your OS is really really slow (I am
		1477	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1478
		1479	Setting these is useful if you want to ensure some level of
		1480	interactiveness when perl is not fast enough to process all requests in
		1481	time.
		1482
		1483	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1484
		1485	Example: Install an Event watcher that automatically calls
		1486	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1487	program get the CPU sometimes even under high AIO load.
		1488
		1489	# try not to spend much more than 0.1s in poll_cb
		1490	IO::AIO::max_poll_time 0.1;
		1491
		1492	# use a low priority so other tasks have priority
		1493	Event->io (fd => IO::AIO::poll_fileno,
		1494	poll => 'r', nice => 1,
		1495	cb => &IO::AIO::poll_cb);
		1496
		1497	=back
		1498
		1499	=head3 CONTROLLING THE NUMBER OF THREADS
		1500
		1501	=over
		1502
233	=item IO::AIO::min_parallel $nthreads	1503	=item IO::AIO::min_parallel $nthreads
234		1504
235	Set the minimum number of AIO threads to C<$nthreads>. The default is	1505	Set the minimum number of AIO threads to C<$nthreads>. The current
236	C<1>, which means a single asynchronous operation can be done at one time	1506	default is C<8>, which means eight asynchronous operations can execute
237	(the number of outstanding operations, however, is unlimited).	1507	concurrently at any one time (the number of outstanding requests,
		1508	however, is unlimited).
238		1509
		1510	IO::AIO starts threads only on demand, when an AIO request is queued and
		1511	no free thread exists. Please note that queueing up a hundred requests can
		1512	create demand for a hundred threads, even if it turns out that everything
		1513	is in the cache and could have been processed faster by a single thread.
		1514
239	It is recommended to keep the number of threads low, as some Linux	1515	It is recommended to keep the number of threads relatively low, as some
240	kernel versions will scale negatively with the number of threads (higher	1516	Linux kernel versions will scale negatively with the number of threads
241	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1517	(higher parallelity => MUCH higher latency). With current Linux 2.6
242	threads should be fine.	1518	versions, 4-32 threads should be fine.
243		1519
244	Under normal circumstances you don't need to call this function, as this	1520	Under most circumstances you don't need to call this function, as the
245	module automatically starts some threads (the exact number might change,	1521	module selects a default that is suitable for low to moderate load.
246	and is currently 4).
247		1522
248	=item IO::AIO::max_parallel $nthreads	1523	=item IO::AIO::max_parallel $nthreads
249		1524
250	Sets the maximum number of AIO threads to C<$nthreads>. If more than	1525	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
251	the specified number of threads are currently running, kill them. This	1526	specified number of threads are currently running, this function kills
252	function blocks until the limit is reached.	1527	them. This function blocks until the limit is reached.
		1528
		1529	While C<$nthreads> are zero, aio requests get queued but not executed
		1530	until the number of threads has been increased again.
253		1531
254	This module automatically runs C<max_parallel 0> at program end, to ensure	1532	This module automatically runs C<max_parallel 0> at program end, to ensure
255	that all threads are killed and that there are no outstanding requests.	1533	that all threads are killed and that there are no outstanding requests.
256		1534
257	Under normal circumstances you don't need to call this function.	1535	Under normal circumstances you don't need to call this function.
258		1536
		1537	=item IO::AIO::max_idle $nthreads
		1538
		1539	Limit the number of threads (default: 4) that are allowed to idle
		1540	(i.e., threads that did not get a request to process within the idle
		1541	timeout (default: 10 seconds). That means if a thread becomes idle while
		1542	C<$nthreads> other threads are also idle, it will free its resources and
		1543	exit.
		1544
		1545	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1546	to allow for extremely high load situations, but want to free resources
		1547	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1548
		1549	The default is probably ok in most situations, especially if thread
		1550	creation is fast. If thread creation is very slow on your system you might
		1551	want to use larger values.
		1552
		1553	=item IO::AIO::idle_timeout $seconds
		1554
		1555	Sets the minimum idle timeout (default 10) after which worker threads are
		1556	allowed to exit. SEe C<IO::AIO::max_idle>.
		1557
259	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1558	=item IO::AIO::max_outstanding $maxreqs
		1559
		1560	This is a very bad function to use in interactive programs because it
		1561	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1562	use an C<aio_group> together with a feed callback.
260		1563
261	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1564	Sets the maximum number of outstanding requests to C<$nreqs>. If you
262	try to queue up more than this number of requests, the caller will block until	1565	do queue up more than this number of requests, the next call to the
263	some requests have been handled.	1566	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1567	function will block until the limit is no longer exceeded.
264		1568
265	The default is very large, so normally there is no practical limit. If you	1569	The default value is very large, so there is no practical limit on the
266	queue up many requests in a loop it it often improves speed if you set	1570	number of outstanding requests.
267	this to a relatively low number, such as C<100>.
268		1571
269	Under normal circumstances you don't need to call this function.	1572	You can still queue as many requests as you want. Therefore,
		1573	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1574	as a stop gap to shield against fatal memory overflow (with large values).
270		1575
271	=back	1576	=back
272		1577
		1578	=head3 STATISTICAL INFORMATION
		1579
		1580	=over
		1581
		1582	=item IO::AIO::nreqs
		1583
		1584	Returns the number of requests currently in the ready, execute or pending
		1585	states (i.e. for which their callback has not been invoked yet).
		1586
		1587	Example: wait till there are no outstanding requests anymore:
		1588
		1589	IO::AIO::poll_wait, IO::AIO::poll_cb
		1590	while IO::AIO::nreqs;
		1591
		1592	=item IO::AIO::nready
		1593
		1594	Returns the number of requests currently in the ready state (not yet
		1595	executed).
		1596
		1597	=item IO::AIO::npending
		1598
		1599	Returns the number of requests currently in the pending state (executed,
		1600	but not yet processed by poll_cb).
		1601
		1602	=back
		1603
		1604	=head3 MISCELLANEOUS FUNCTIONS
		1605
		1606	IO::AIO implements some functions that might be useful, but are not
		1607	asynchronous.
		1608
		1609	=over 4
		1610
		1611	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1612
		1613	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1614	but is blocking (this makes most sense if you know the input data is
		1615	likely cached already and the output filehandle is set to non-blocking
		1616	operations).
		1617
		1618	Returns the number of bytes copied, or C<-1> on error.
		1619
		1620	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1621
		1622	Simply calls the C<posix_fadvise> function (see its
		1623	manpage for details). The following advice constants are
		1624	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1625	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1626	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1627
		1628	On systems that do not implement C<posix_fadvise>, this function returns
		1629	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1630
		1631	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1632
		1633	Simply calls the C<posix_madvise> function (see its
		1634	manpage for details). The following advice constants are
		1635	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1636	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1637
		1638	On systems that do not implement C<posix_madvise>, this function returns
		1639	ENOSYS, otherwise the return value of C<posix_madvise>.
		1640
		1641	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1642
		1643	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1644	$scalar (see its manpage for details). The following protect
		1645	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1646	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1647
		1648	On systems that do not implement C<mprotect>, this function returns
		1649	ENOSYS, otherwise the return value of C<mprotect>.
		1650
		1651	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1652
		1653	Memory-maps a file (or anonymous memory range) and attaches it to the
		1654	given C<$scalar>, which will act like a string scalar.
		1655
		1656	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1657	change the string length, and most read-only operations such as copying it
		1658	or searching it with regexes and so on.
		1659
		1660	Anything else is unsafe and will, at best, result in memory leaks.
		1661
		1662	The memory map associated with the C<$scalar> is automatically removed
		1663	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1664	C<IO::AIO::munmap> functions are called.
		1665
		1666	This calls the C<mmap>(2) function internally. See your system's manual
		1667	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1668
		1669	The C<$length> must be larger than zero and smaller than the actual
		1670	filesize.
		1671
		1672	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1673	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1674
		1675	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1676	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1677	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1678	(which is set to C<MAP_ANON> if your system only provides this
		1679	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1680	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1681	C<IO::AIO::MAP_NONBLOCK>
		1682
		1683	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1684
		1685	C<$offset> is the offset from the start of the file - it generally must be
		1686	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1687
		1688	Example:
		1689
		1690	use Digest::MD5;
		1691	use IO::AIO;
		1692
		1693	open my $fh, "<verybigfile"
		1694	or die "$!";
		1695
		1696	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1697	or die "verybigfile: $!";
		1698
		1699	my $fast_md5 = md5 $data;
		1700
		1701	=item IO::AIO::munmap $scalar
		1702
		1703	Removes a previous mmap and undefines the C<$scalar>.
		1704
		1705	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1706
		1707	Calls the C<munlock> function, undoing the effects of a previous
		1708	C<aio_mlock> call (see its description for details).
		1709
		1710	=item IO::AIO::munlockall
		1711
		1712	Calls the C<munlockall> function.
		1713
		1714	On systems that do not implement C<munlockall>, this function returns
		1715	ENOSYS, otherwise the return value of C<munlockall>.
		1716
		1717	=back
		1718
273	=cut	1719	=cut
274		1720
275	# support function to convert a fd into a perl filehandle
276	sub _fd2fh {
277	return undef if $_[0] < 0;
278
279	# try to be perl5.6-compatible
280	local *AIO_FH;
281	open AIO_FH, "+<&=$_[0]"
282	or return undef;
283
284	*AIO_FH
285	}
286
287	min_parallel 4;	1721	min_parallel 8;
288		1722
289	END {	1723	END { flush }
290	max_parallel 0;
291	}
292		1724
293	1;	1725	1;
294		1726
		1727	=head1 EVENT LOOP INTEGRATION
		1728
		1729	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1730	automatically into many event loops:
		1731
		1732	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1733	use AnyEvent::AIO;
		1734
		1735	You can also integrate IO::AIO manually into many event loops, here are
		1736	some examples of how to do this:
		1737
		1738	# EV integration
		1739	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1740
		1741	# Event integration
		1742	Event->io (fd => IO::AIO::poll_fileno,
		1743	poll => 'r',
		1744	cb => \&IO::AIO::poll_cb);
		1745
		1746	# Glib/Gtk2 integration
		1747	add_watch Glib::IO IO::AIO::poll_fileno,
		1748	in => sub { IO::AIO::poll_cb; 1 };
		1749
		1750	# Tk integration
		1751	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1752	readable => \&IO::AIO::poll_cb);
		1753
		1754	# Danga::Socket integration
		1755	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1756	\&IO::AIO::poll_cb);
		1757
		1758	=head2 FORK BEHAVIOUR
		1759
		1760	This module should do "the right thing" when the process using it forks:
		1761
		1762	Before the fork, IO::AIO enters a quiescent state where no requests
		1763	can be added in other threads and no results will be processed. After
		1764	the fork the parent simply leaves the quiescent state and continues
		1765	request/result processing, while the child frees the request/result queue
		1766	(so that the requests started before the fork will only be handled in the
		1767	parent). Threads will be started on demand until the limit set in the
		1768	parent process has been reached again.
		1769
		1770	In short: the parent will, after a short pause, continue as if fork had
		1771	not been called, while the child will act as if IO::AIO has not been used
		1772	yet.
		1773
		1774	=head2 MEMORY USAGE
		1775
		1776	Per-request usage:
		1777
		1778	Each aio request uses - depending on your architecture - around 100-200
		1779	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1780	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1781	scalars and other data passed into aio requests will also be locked and
		1782	will consume memory till the request has entered the done state.
		1783
		1784	This is not awfully much, so queuing lots of requests is not usually a
		1785	problem.
		1786
		1787	Per-thread usage:
		1788
		1789	In the execution phase, some aio requests require more memory for
		1790	temporary buffers, and each thread requires a stack and other data
		1791	structures (usually around 16k-128k, depending on the OS).
		1792
		1793	=head1 KNOWN BUGS
		1794
		1795	Known bugs will be fixed in the next release.
		1796
295	=head1 SEE ALSO	1797	=head1 SEE ALSO
296		1798
297	L<Coro>, L<Linux::AIO>.	1799	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1800	more natural syntax.
298		1801
299	=head1 AUTHOR	1802	=head1 AUTHOR
300		1803
301	Marc Lehmann <schmorp@schmorp.de>	1804	Marc Lehmann <schmorp@schmorp.de>
302	http://home.schmorp.de/	1805	http://home.schmorp.de/

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