[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.5 by root, Sun Jul 10 21:04:24 2005 UTC vs.
Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC

…		…
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
		8
		9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		10	my ($fh) = @_;
		11	...
		12	};
		13
		14	aio_unlink "/tmp/file", sub { };
		15
		16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		17	$_[0] > 0 or die "read error: $!";
		18	};
		19
		20	use IO::AIO 2; # version has aio objects
		21
		22	my $req = aio_unlink "/tmp/file", sub { };
		23	$req->cancel; # cancel request if still in queue
		24
		25	# AnyEvent
		26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		28
		29	# Event
		30	Event->io (fd => IO::AIO::poll_fileno,
		31	poll => 'r',
		32	cb => \&IO::AIO::poll_cb);
		33
		34	# Glib/Gtk2
		35	add_watch Glib::IO IO::AIO::poll_fileno,
		36	in => sub { IO::AIO::poll_cb; 1 };
		37
		38	# Tk
		39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		40	readable => \&IO::AIO::poll_cb);
		41
		42	# Danga::Socket
		43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		44	\&IO::AIO::poll_cb);
		45
8		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	This module implements asynchronous I/O using whatever means your	49	This module implements asynchronous I/O using whatever means your
12	operating system supports.	50	operating system supports.
…		…
19	not well-supported (Linux doesn't allow them on normal files currently,	57	not well-supported (Linux doesn't allow them on normal files currently,
20	for example), and they would only support aio_read and aio_write, so the	58	for example), and they would only support aio_read and aio_write, so the
21	remaining functionality would have to be implemented using threads anyway.	59	remaining functionality would have to be implemented using threads anyway.
22		60
23	Although the module will work with in the presence of other threads, it is	61	Although the module will work with in the presence of other threads, it is
24	currently not reentrant, so use appropriate locking yourself.	62	currently not reentrant, so use appropriate locking yourself, always call
		63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		64	C<aio_> functions) recursively.
25		65
26	=cut	66	=cut
27		67
28	package IO::AIO;	68	package IO::AIO;
29		69
		70	no warnings;
		71	use strict 'vars';
		72
30	use base 'Exporter';	73	use base 'Exporter';
31		74
32	use Fcntl ();
33
34	BEGIN {	75	BEGIN {
35	$VERSION = 0.2;	76	our $VERSION = '2.0';
36		77
37	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
38	aio_fsync aio_fdatasync aio_readahead);	80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		81	aio_group);
39	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		83
		84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
40		85
41	require XSLoader;	86	require XSLoader;
42	XSLoader::load IO::AIO, $VERSION;	87	XSLoader::load ("IO::AIO", $VERSION);
43	}	88	}
44		89
45	=head1 FUNCTIONS	90	=head1 FUNCTIONS
46		91
47	=head2 AIO FUNCTIONS	92	=head2 AIO FUNCTIONS
48		93
49	All the C<aio_*> calls are more or less thin wrappers around the syscall	94	All the C<aio_*> calls are more or less thin wrappers around the syscall
50	with the same name (sans C<aio_>). The arguments are similar or identical,	95	with the same name (sans C<aio_>). The arguments are similar or identical,
51	and they all accept an additional C<$callback> argument which must be	96	and they all accept an additional (and optional) C<$callback> argument
52	a code reference. This code reference will get called with the syscall	97	which must be a code reference. This code reference will get called with
53	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	98	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
54	usually delivers "false") as it's sole argument when the given syscall has	99	perl, which usually delivers "false") as it's sole argument when the given
55	been executed asynchronously.	100	syscall has been executed asynchronously.
56		101
57	All functions that expect a filehandle will also accept a file descriptor.	102	All functions expecting a filehandle keep a copy of the filehandle
		103	internally until the request has finished.
58		104
		105	All requests return objects of type L<IO::AIO::REQ> that allow further
		106	manipulation of those requests while they are in-flight.
		107
59	The filenames you pass to these routines I<must> be absolute. The reason	108	The pathnames you pass to these routines I<must> be absolute and
60	is that at the time the request is being executed, the current working	109	encoded in byte form. The reason for the former is that at the time the
61	directory could have changed. Alternatively, you can make sure that you	110	request is being executed, the current working directory could have
		111	changed. Alternatively, you can make sure that you never change the
62	never change the current working directory.	112	current working directory.
		113
		114	To encode pathnames to byte form, either make sure you either: a)
		115	always pass in filenames you got from outside (command line, readdir
		116	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		117	your pathnames to the locale (or other) encoding in effect in the user
		118	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		119	use something else.
63		120
64	=over 4	121	=over 4
65		122
66	=item aio_open $pathname, $flags, $mode, $callback	123	=item aio_open $pathname, $flags, $mode, $callback->($fh)
67		124
68	Asynchronously open or create a file and call the callback with a newly	125	Asynchronously open or create a file and call the callback with a newly
69	created filehandle for the file.	126	created filehandle for the file.
70		127
71	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	128	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
72	for an explanation.	129	for an explanation.
73		130
74	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	131	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
75	list. They are the same as used in C<sysopen>.	132	list. They are the same as used by C<sysopen>.
		133
		134	Likewise, C<$mode> specifies the mode of the newly created file, if it
		135	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		136	except that it is mandatory (i.e. use C<0> if you don't create new files,
		137	and C<0666> or C<0777> if you do).
76		138
77	Example:	139	Example:
78		140
79	aio_open "/etc/passwd", O_RDONLY, 0, sub {	141	aio_open "/etc/passwd", O_RDONLY, 0, sub {
80	if ($_[0]) {	142	if ($_[0]) {
…		…
83	} else {	145	} else {
84	die "open failed: $!\n";	146	die "open failed: $!\n";
85	}	147	}
86	};	148	};
87		149
88	=item aio_close $fh, $callback	150	=item aio_close $fh, $callback->($status)
89		151
90	Asynchronously close a file and call the callback with the result	152	Asynchronously close a file and call the callback with the result
91	code. I<WARNING:> although accepted, you should not pass in a perl	153	code. I<WARNING:> although accepted, you should not pass in a perl
92	filehandle here, as perl will likely close the file descriptor itself when	154	filehandle here, as perl will likely close the file descriptor another
93	the filehandle is destroyed. Normally, you can safely call perls C<close>	155	time when the filehandle is destroyed. Normally, you can safely call perls
94	or just let filehandles go out of scope.	156	C<close> or just let filehandles go out of scope.
95		157
		158	This is supposed to be a bug in the API, so that might change. It's
		159	therefore best to avoid this function.
		160
96	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	161	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
97		162
98	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	163	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
99		164
100	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	165	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
101	into the scalar given by C<data> and offset C<dataoffset> and calls the	166	into the scalar given by C<data> and offset C<dataoffset> and calls the
102	callback without the actual number of bytes read (or -1 on error, just	167	callback without the actual number of bytes read (or -1 on error, just
103	like the syscall).	168	like the syscall).
104		169
		170	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		171	is outstanding. Modifying it can result in segfaults or WW3 (if the
		172	necessary/optional hardware is installed).
		173
105	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	174	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
106	offset C<0> within the scalar:	175	offset C<0> within the scalar:
107		176
108	aio_read $fh, 7, 15, $buffer, 0, sub {	177	aio_read $fh, 7, 15, $buffer, 0, sub {
109	$_[0] >= 0 or die "read error: $!";	178	$_[0] > 0 or die "read error: $!";
110	print "read <$buffer>\n";	179	print "read $_[0] bytes: <$buffer>\n";
111	};	180	};
112		181
		182	=item aio_move $srcpath, $dstpath, $callback->($status)
		183
		184	Try to move the I<file> (directories not supported as either source or
		185	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		186	the C<0> (error) or C<-1> ok.
		187
		188	This is a composite request that tries to rename(2) the file first. If
		189	rename files with C<EXDEV>, it creates the destination file with mode 0200
		190	and copies the contents of the source file into it using C<aio_sendfile>,
		191	followed by restoring atime, mtime, access mode and uid/gid, in that
		192	order, and unlinking the C<$srcpath>.
		193
		194	If an error occurs, the partial destination file will be unlinked, if
		195	possible, except when setting atime, mtime, access mode and uid/gid, where
		196	errors are being ignored.
		197
		198	=cut
		199
		200	sub aio_move($$$) {
		201	my ($src, $dst, $cb) = @_;
		202
		203	my $grp = aio_group;
		204
		205	add $grp aio_rename $src, $dst, sub {
		206	if ($_[0] && $! == EXDEV) {
		207	add $grp aio_open $src, O_RDONLY, 0, sub {
		208	if (my $src_fh = $_[0]) {
		209	my @stat = stat $src_fh;
		210
		211	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		212	if (my $dst_fh = $_[0]) {
		213	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		214	close $src_fh;
		215
		216	if ($_[0] == $stat[7]) {
		217	utime $stat[8], $stat[9], $dst;
		218	chmod $stat[2] & 07777, $dst_fh;
		219	chown $stat[4], $stat[5], $dst_fh;
		220	close $dst_fh;
		221
		222	add $grp aio_unlink $src, sub {
		223	$cb->($_[0]);
		224	};
		225	} else {
		226	my $errno = $!;
		227	add $grp aio_unlink $dst, sub {
		228	$! = $errno;
		229	$cb->(-1);
		230	};
		231	}
		232	};
		233	} else {
		234	$cb->(-1);
		235	}
		236	},
		237
		238	} else {
		239	$cb->(-1);
		240	}
		241	};
		242	} else {
		243	$cb->($_[0]);
		244	}
		245	};
		246
		247	$grp
		248	}
		249
		250	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		251
		252	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		253	reading at byte offset C<$in_offset>, and starts writing at the current
		254	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		255	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		256	other.
		257
		258	This call tries to make use of a native C<sendfile> syscall to provide
		259	zero-copy operation. For this to work, C<$out_fh> should refer to a
		260	socket, and C<$in_fh> should refer to mmap'able file.
		261
		262	If the native sendfile call fails or is not implemented, it will be
		263	emulated, so you can call C<aio_sendfile> on any type of filehandle
		264	regardless of the limitations of the operating system.
		265
		266	Please note, however, that C<aio_sendfile> can read more bytes from
		267	C<$in_fh> than are written, and there is no way to find out how many
		268	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		269	provides the number of bytes written to C<$out_fh>. Only if the result
		270	value equals C<$length> one can assume that C<$length> bytes have been
		271	read.
		272
113	=item aio_readahead $fh,$offset,$length, $callback	273	=item aio_readahead $fh,$offset,$length, $callback->($retval)
114		274
115	Asynchronously reads the specified byte range into the page cache, using
116	the C<readahead> syscall. If that syscall doesn't exist the status will be
117	C<-1> and C<$!> is set to ENOSYS.
118
119	readahead() populates the page cache with data from a file so that	275	C<aio_readahead> populates the page cache with data from a file so that
120	subsequent reads from that file will not block on disk I/O. The C<$offset>	276	subsequent reads from that file will not block on disk I/O. The C<$offset>
121	argument specifies the starting point from which data is to be read and	277	argument specifies the starting point from which data is to be read and
122	C<$length> specifies the number of bytes to be read. I/O is performed in	278	C<$length> specifies the number of bytes to be read. I/O is performed in
123	whole pages, so that offset is effectively rounded down to a page boundary	279	whole pages, so that offset is effectively rounded down to a page boundary
124	and bytes are read up to the next page boundary greater than or equal to	280	and bytes are read up to the next page boundary greater than or equal to
125	(off-set+length). aio_readahead() does not read beyond the end of the	281	(off-set+length). C<aio_readahead> does not read beyond the end of the
126	file. The current file offset of the file is left unchanged.	282	file. The current file offset of the file is left unchanged.
127		283
		284	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		285	emulated by simply reading the data, which would have a similar effect.
		286
128	=item aio_stat $fh_or_path, $callback	287	=item aio_stat $fh_or_path, $callback->($status)
129		288
130	=item aio_lstat $fh, $callback	289	=item aio_lstat $fh, $callback->($status)
131		290
132	Works like perl's C<stat> or C<lstat> in void context. The callback will	291	Works like perl's C<stat> or C<lstat> in void context. The callback will
133	be called after the stat and the results will be available using C<stat _>	292	be called after the stat and the results will be available using C<stat _>
134	or C<-s _> etc...	293	or C<-s _> etc...
135		294
…		…
145	aio_stat "/etc/passwd", sub {	304	aio_stat "/etc/passwd", sub {
146	$_[0] and die "stat failed: $!";	305	$_[0] and die "stat failed: $!";
147	print "size is ", -s _, "\n";	306	print "size is ", -s _, "\n";
148	};	307	};
149		308
150	=item aio_unlink $pathname, $callback	309	=item aio_unlink $pathname, $callback->($status)
151		310
152	Asynchronously unlink (delete) a file and call the callback with the	311	Asynchronously unlink (delete) a file and call the callback with the
153	result code.	312	result code.
154		313
		314	=item aio_link $srcpath, $dstpath, $callback->($status)
		315
		316	Asynchronously create a new link to the existing object at C<$srcpath> at
		317	the path C<$dstpath> and call the callback with the result code.
		318
		319	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		320
		321	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		322	the path C<$dstpath> and call the callback with the result code.
		323
		324	=item aio_rename $srcpath, $dstpath, $callback->($status)
		325
		326	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		327	rename(2) and call the callback with the result code.
		328
		329	=item aio_rmdir $pathname, $callback->($status)
		330
		331	Asynchronously rmdir (delete) a directory and call the callback with the
		332	result code.
		333
		334	=item aio_readdir $pathname, $callback->($entries)
		335
		336	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		337	directory (i.e. opendir + readdir + closedir). The entries will not be
		338	sorted, and will B<NOT> include the C<.> and C<..> entries.
		339
		340	The callback a single argument which is either C<undef> or an array-ref
		341	with the filenames.
		342
		343	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		344
		345	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		346	separate the entries of directory C<$path> into two sets of names, ones
		347	you can recurse into (directories or links to them), and ones you cannot
		348	recurse into (everything else).
		349
		350	C<aio_scandir> is a composite request that consists of many sub
		351	requests. C<$maxreq> specifies the maximum number of outstanding aio
		352	requests that this function generates. If it is C<< <= 0 >>, then a
		353	suitable default will be chosen (currently 8).
		354
		355	On error, the callback is called without arguments, otherwise it receives
		356	two array-refs with path-relative entry names.
		357
		358	Example:
		359
		360	aio_scandir $dir, 0, sub {
		361	my ($dirs, $nondirs) = @_;
		362	print "real directories: @$dirs\n";
		363	print "everything else: @$nondirs\n";
		364	};
		365
		366	Implementation notes.
		367
		368	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		369
		370	After reading the directory, the modification time, size etc. of the
		371	directory before and after the readdir is checked, and if they match (and
		372	isn't the current time), the link count will be used to decide how many
		373	entries are directories (if >= 2). Otherwise, no knowledge of the number
		374	of subdirectories will be assumed.
		375
		376	Then entries will be sorted into likely directories (everything without
		377	a non-initial dot currently) and likely non-directories (everything
		378	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		379	likely directories first. If that succeeds, it assumes that the entry
		380	is a directory or a symlink to directory (which will be checked
		381	seperately). This is often faster than stat'ing the entry itself because
		382	filesystems might detect the type of the entry without reading the inode
		383	data (e.g. ext2fs filetype feature).
		384
		385	If the known number of directories (link count - 2) has been reached, the
		386	rest of the entries is assumed to be non-directories.
		387
		388	This only works with certainty on POSIX (= UNIX) filesystems, which
		389	fortunately are the vast majority of filesystems around.
		390
		391	It will also likely work on non-POSIX filesystems with reduced efficiency
		392	as those tend to return 0 or 1 as link counts, which disables the
		393	directory counting heuristic.
		394
		395	=cut
		396
		397	sub aio_scandir($$$) {
		398	my ($path, $maxreq, $cb) = @_;
		399
		400	my $grp = aio_group;
		401
		402	$maxreq = 8 if $maxreq <= 0;
		403
		404	# stat once
		405	add $grp aio_stat $path, sub {
		406	return $cb->() if $_[0];
		407	my $now = time;
		408	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		409
		410	# read the directory entries
		411	add $grp aio_readdir $path, sub {
		412	my $entries = shift
		413	or return $cb->();
		414
		415	# stat the dir another time
		416	add $grp aio_stat $path, sub {
		417	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		418
		419	my $ndirs;
		420
		421	# take the slow route if anything looks fishy
		422	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		423	$ndirs = -1;
		424	} else {
		425	# if nlink == 2, we are finished
		426	# on non-posix-fs's, we rely on nlink < 2
		427	$ndirs = (stat _)[3] - 2
		428	or return $cb->([], $entries);
		429	}
		430
		431	# sort into likely dirs and likely nondirs
		432	# dirs == files without ".", short entries first
		433	$entries = [map $_->[0],
		434	sort { $b->[1] cmp $a->[1] }
		435	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		436	@$entries];
		437
		438	my (@dirs, @nondirs);
		439
		440	my ($statcb, $schedcb);
		441	my $nreq = 0;
		442
		443	$schedcb = sub {
		444	if (@$entries) {
		445	if ($nreq < $maxreq) {
		446	my $ent = pop @$entries;
		447	$nreq++;
		448	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		449	}
		450	} elsif (!$nreq) {
		451	# finished
		452	undef $statcb;
		453	undef $schedcb;
		454	$cb->(\@dirs, \@nondirs) if $cb;
		455	undef $cb;
		456	}
		457	};
		458	$statcb = sub {
		459	my ($status, $entry) = @_;
		460
		461	if ($status < 0) {
		462	$nreq--;
		463	push @nondirs, $entry;
		464	&$schedcb;
		465	} else {
		466	# need to check for real directory
		467	add $grp aio_lstat "$path/$entry", sub {
		468	$nreq--;
		469
		470	if (-d _) {
		471	push @dirs, $entry;
		472
		473	if (!--$ndirs) {
		474	push @nondirs, @$entries;
		475	$entries = [];
		476	}
		477	} else {
		478	push @nondirs, $entry;
		479	}
		480
		481	&$schedcb;
		482	}
		483	}
		484	};
		485
		486	&$schedcb while @$entries && $nreq < $maxreq;
		487	};
		488	};
		489	};
		490
		491	$grp
		492	}
		493
155	=item aio_fsync $fh, $callback	494	=item aio_fsync $fh, $callback->($status)
156		495
157	Asynchronously call fsync on the given filehandle and call the callback	496	Asynchronously call fsync on the given filehandle and call the callback
158	with the fsync result code.	497	with the fsync result code.
159		498
160	=item aio_fdatasync $fh, $callback	499	=item aio_fdatasync $fh, $callback->($status)
161		500
162	Asynchronously call fdatasync on the given filehandle and call the	501	Asynchronously call fdatasync on the given filehandle and call the
163	callback with the fdatasync result code.	502	callback with the fdatasync result code.
164		503
		504	If this call isn't available because your OS lacks it or it couldn't be
		505	detected, it will be emulated by calling C<fsync> instead.
		506
		507	=item aio_group $callback->()
		508
		509	[EXPERIMENTAL]
		510
		511	This is a very special aio request: Instead of doing something, it is a
		512	container for other aio requests, which is useful if you want to bundle
		513	many requests into a single, composite, request.
		514
		515	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		516	for more info.
		517
		518	Example:
		519
		520	my $grp = aio_group sub {
		521	print "all stats done\n";
		522	};
		523
		524	add $grp
		525	(aio_stat ...),
		526	(aio_stat ...),
		527	...;
		528
		529	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		530
		531	Mainly used for debugging and benchmarking, this aio request puts one of
		532	the request workers to sleep for the given time.
		533
165	=back	534	=back
166		535
		536	=head2 IO::AIO::REQ CLASS
		537
		538	All non-aggregate C<aio_*> functions return an object of this class when
		539	called in non-void context.
		540
		541	A request always moves through the following five states in its lifetime,
		542	in order: B<ready> (request has been created, but has not been executed
		543	yet), B<execute> (request is currently being executed), B<pending>
		544	(request has been executed but callback has not been called yet),
		545	B<result> (results are being processed synchronously, includes calling the
		546	callback) and B<done> (request has reached the end of its lifetime and
		547	holds no resources anymore).
		548
		549	=over 4
		550
		551	=item $req->cancel
		552
		553	Cancels the request, if possible. Has the effect of skipping execution
		554	when entering the B<execute> state and skipping calling the callback when
		555	entering the the B<result> state, but will leave the request otherwise
		556	untouched. That means that requests that currently execute will not be
		557	stopped and resources held by the request will not be freed prematurely.
		558
		559	=back
		560
		561	=head2 IO::AIO::GRP CLASS
		562
		563	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		564	objects of this class, too.
		565
		566	A IO::AIO::GRP object is a special request that can contain multiple other
		567	aio requests.
		568
		569	You create one by calling the C<aio_group> constructing function with a
		570	callback that will be called when all contained requests have entered the
		571	C<done> state:
		572
		573	my $grp = aio_group sub {
		574	print "all requests are done\n";
		575	};
		576
		577	You add requests by calling the C<add> method with one or more
		578	C<IO::AIO::REQ> objects:
		579
		580	$grp->add (aio_unlink "...");
		581
		582	add $grp aio_stat "...", sub { ... };
		583
		584	This makes it very easy to create composite requests (see the source of
		585	C<aio_move> for an application) that work and feel like simple requests.
		586
		587	The IO::AIO::GRP objects will be cleaned up during calls to
		588	C<IO::AIO::poll_cb>, just like any other request.
		589
		590	They can be canceled like any other request. Canceling will cancel not
		591	just the request itself, but also all requests it contains.
		592
		593	They can also can also be added to other IO::AIO::GRP objects.
		594
		595	Their lifetime, simplified, looks like this: when they are empty, they
		596	will finish very quickly. If they contain only requests that are in the
		597	C<done> state, they will also finish. Otherwise they will continue to
		598	exist.
		599
		600	=over 4
		601
		602	=item $grp->add (...)
		603
		604	=item add $grp ...
		605
		606	Add one or more
		607	Cancels the request, if possible. Has the effect of skipping execution
		608	when entering the B<execute> state and skipping calling the callback when
		609	entering the the B<result> state, but will leave the request otherwise
		610	untouched. That means that requests that currently execute will not be
		611	stopped and resources held by the request will not be freed prematurely.
		612
		613	=back
		614
167	=head2 SUPPORT FUNCTIONS	615	=head2 SUPPORT FUNCTIONS
168		616
169	=over 4	617	=over 4
170		618
171	=item $fileno = IO::AIO::poll_fileno	619	=item $fileno = IO::AIO::poll_fileno
172		620
173	Return the I<request result pipe filehandle>. This filehandle must be	621	Return the I<request result pipe file descriptor>. This filehandle must be
174	polled for reading by some mechanism outside this module (e.g. Event	622	polled for reading by some mechanism outside this module (e.g. Event or
175	or select, see below). If the pipe becomes readable you have to call	623	select, see below or the SYNOPSIS). If the pipe becomes readable you have
176	C<poll_cb> to check the results.	624	to call C<poll_cb> to check the results.
177		625
178	See C<poll_cb> for an example.	626	See C<poll_cb> for an example.
179		627
180	=item IO::AIO::poll_cb	628	=item IO::AIO::poll_cb
181		629
182	Process all outstanding events on the result pipe. You have to call this	630	Process all outstanding events on the result pipe. You have to call this
183	regularly. Returns the number of events processed. Returns immediately	631	regularly. Returns the number of events processed. Returns immediately
184	when no events are outstanding.	632	when no events are outstanding.
185		633
186	You can use Event to multiplex, e.g.:	634	Example: Install an Event watcher that automatically calls
		635	IO::AIO::poll_cb with high priority:
187		636
188	Event->io (fd => IO::AIO::poll_fileno,	637	Event->io (fd => IO::AIO::poll_fileno,
189	poll => 'r', async => 1,	638	poll => 'r', async => 1,
190	cb => \&IO::AIO::poll_cb);	639	cb => \&IO::AIO::poll_cb);
191		640
192	=item IO::AIO::poll_wait	641	=item IO::AIO::poll_wait
193		642
194	Wait till the result filehandle becomes ready for reading (simply does a	643	Wait till the result filehandle becomes ready for reading (simply does a
195	select on the filehandle. This is useful if you want to synchronously wait	644	C<select> on the filehandle. This is useful if you want to synchronously wait
196	for some requests to finish).	645	for some requests to finish).
197		646
198	See C<nreqs> for an example.	647	See C<nreqs> for an example.
199		648
200	=item IO::AIO::nreqs	649	=item IO::AIO::nreqs
201		650
202	Returns the number of requests currently outstanding.	651	Returns the number of requests currently outstanding (i.e. for which their
		652	callback has not been invoked yet).
203		653
204	Example: wait till there are no outstanding requests anymore:	654	Example: wait till there are no outstanding requests anymore:
205		655
206	IO::AIO::poll_wait, IO::AIO::poll_cb	656	IO::AIO::poll_wait, IO::AIO::poll_cb
207	while IO::AIO::nreqs;	657	while IO::AIO::nreqs;
208		658
		659	=item IO::AIO::flush
		660
		661	Wait till all outstanding AIO requests have been handled.
		662
		663	Strictly equivalent to:
		664
		665	IO::AIO::poll_wait, IO::AIO::poll_cb
		666	while IO::AIO::nreqs;
		667
		668	=item IO::AIO::poll
		669
		670	Waits until some requests have been handled.
		671
		672	Strictly equivalent to:
		673
		674	IO::AIO::poll_wait, IO::AIO::poll_cb
		675	if IO::AIO::nreqs;
		676
209	=item IO::AIO::min_parallel $nthreads	677	=item IO::AIO::min_parallel $nthreads
210		678
211	Set the minimum number of AIO threads to C<$nthreads>. The default is	679	Set the minimum number of AIO threads to C<$nthreads>. The current default
212	C<1>, which means a single asynchronous operation can be done at one time	680	is C<4>, which means four asynchronous operations can be done at one time
213	(the number of outstanding operations, however, is unlimited).	681	(the number of outstanding operations, however, is unlimited).
		682
		683	IO::AIO starts threads only on demand, when an AIO request is queued and
		684	no free thread exists.
214		685
215	It is recommended to keep the number of threads low, as some Linux	686	It is recommended to keep the number of threads low, as some Linux
216	kernel versions will scale negatively with the number of threads (higher	687	kernel versions will scale negatively with the number of threads (higher
217	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	688	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
218	threads should be fine.	689	threads should be fine.
219		690
220	Under normal circumstances you don't need to call this function, as this	691	Under most circumstances you don't need to call this function, as the
221	module automatically starts some threads (the exact number might change,	692	module selects a default that is suitable for low to moderate load.
222	and is currently 4).
223		693
224	=item IO::AIO::max_parallel $nthreads	694	=item IO::AIO::max_parallel $nthreads
225		695
226	Sets the maximum number of AIO threads to C<$nthreads>. If more than	696	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
227	the specified number of threads are currently running, kill them. This	697	specified number of threads are currently running, this function kills
228	function blocks until the limit is reached.	698	them. This function blocks until the limit is reached.
		699
		700	While C<$nthreads> are zero, aio requests get queued but not executed
		701	until the number of threads has been increased again.
229		702
230	This module automatically runs C<max_parallel 0> at program end, to ensure	703	This module automatically runs C<max_parallel 0> at program end, to ensure
231	that all threads are killed and that there are no outstanding requests.	704	that all threads are killed and that there are no outstanding requests.
232		705
233	Under normal circumstances you don't need to call this function.	706	Under normal circumstances you don't need to call this function.
…		…
237	Sets the maximum number of outstanding requests to C<$nreqs>. If you	710	Sets the maximum number of outstanding requests to C<$nreqs>. If you
238	try to queue up more than this number of requests, the caller will block until	711	try to queue up more than this number of requests, the caller will block until
239	some requests have been handled.	712	some requests have been handled.
240		713
241	The default is very large, so normally there is no practical limit. If you	714	The default is very large, so normally there is no practical limit. If you
242	queue up many requests in a loop it it often improves speed if you set	715	queue up many requests in a loop it often improves speed if you set
243	this to a relatively low number, such as C<100>.	716	this to a relatively low number, such as C<100>.
244		717
245	Under normal circumstances you don't need to call this function.	718	Under normal circumstances you don't need to call this function.
246		719
247	=back	720	=back
…		…
250		723
251	# support function to convert a fd into a perl filehandle	724	# support function to convert a fd into a perl filehandle
252	sub _fd2fh {	725	sub _fd2fh {
253	return undef if $_[0] < 0;	726	return undef if $_[0] < 0;
254		727
255	# try to be perl5.6-compatible	728	# try to generate nice filehandles
256	local *AIO_FH;	729	my $sym = "IO::AIO::fd#$_[0]";
257	open AIO_FH, "+<&=$_[0]"	730	local *$sym;
		731
		732	open *$sym, "+<&=$_[0]" # usually works under any unix
		733	or open *$sym, "<&=$_[0]" # cygwin needs this
		734	or open *$sym, ">&=$_[0]" # or this
258	or return undef;	735	or return undef;
259		736
260	*AIO_FH	737	*$sym
261	}	738	}
262		739
263	min_parallel 4;	740	min_parallel 4;
264		741
265	END {	742	END {
266	max_parallel 0;	743	max_parallel 0;
267	}	744	}
268		745
269	1;	746	1;
270		747
		748	=head2 FORK BEHAVIOUR
		749
		750	This module should do "the right thing" when the process using it forks:
		751
		752	Before the fork, IO::AIO enters a quiescent state where no requests
		753	can be added in other threads and no results will be processed. After
		754	the fork the parent simply leaves the quiescent state and continues
		755	request/result processing, while the child clears the request/result
		756	queue (so the requests started before the fork will only be handled in
		757	the parent). Threads will be started on demand until the limit ste in the
		758	parent process has been reached again.
		759
		760	In short: the parent will, after a short pause, continue as if fork had
		761	not been called, while the child will act as if IO::AIO has not been used
		762	yet.
		763
271	=head1 SEE ALSO	764	=head1 SEE ALSO
272		765
273	L<Coro>, L<Linux::AIO>.	766	L<Coro>, L<Linux::AIO> (obsolete).
274		767
275	=head1 AUTHOR	768	=head1 AUTHOR
276		769
277	Marc Lehmann <schmorp@schmorp.de>	770	Marc Lehmann <schmorp@schmorp.de>
278	http://home.schmorp.de/	771	http://home.schmorp.de/

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Revision 1.55 by root, Sun Oct 22 00:49:29 2006 UTC