[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 1.57 by root, Sun Oct 22 01:28:31 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	# version 2+ has request and group objects
		21	use IO::AIO 2;
		22
		23	my $req = aio_unlink "/tmp/file", sub { };
		24	$req->cancel; # cancel request if still in queue
		25
		26	my $grp = aio_group sub { print "all stats done\n" };
		27	add $grp aio_stat "..." for ...;
		28
		29	# AnyEvent integration
		30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		32
		33	# Event integration
		34	Event->io (fd => IO::AIO::poll_fileno,
		35	poll => 'r',
		36	cb => \&IO::AIO::poll_cb);
		37
		38	# Glib/Gtk2 integration
		39	add_watch Glib::IO IO::AIO::poll_fileno,
		40	in => sub { IO::AIO::poll_cb; 1 };
		41
		42	# Tk integration
		43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		44	readable => \&IO::AIO::poll_cb);
		45
		46	# Danga::Socket integration
		47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		48	\&IO::AIO::poll_cb);
8		49
9	=head1 DESCRIPTION	50	=head1 DESCRIPTION
10		51
11	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
12	operating system supports.	53	operating system supports.
…		…
19	not well-supported (Linux doesn't allow them on normal files currently,	60	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	61	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.	62	remaining functionality would have to be implemented using threads anyway.
22		63
23	Although the module will work with in the presence of other threads, it is	64	Although the module will work with in the presence of other threads, it is
24	currently not reentrant, so use appropriate locking yourself.	65	currently not reentrant, so use appropriate locking yourself, always call
		66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		67	C<aio_> functions) recursively.
25		68
26	=cut	69	=cut
27		70
28	package IO::AIO;	71	package IO::AIO;
29		72
		73	no warnings;
		74	use strict 'vars';
		75
30	use base 'Exporter';	76	use base 'Exporter';
31		77
32	use Fcntl ();
33
34	BEGIN {	78	BEGIN {
35	$VERSION = 0.2;	79	our $VERSION = '2.0';
36		80
37	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
38	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group);
39	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		86
		87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
40		88
41	require XSLoader;	89	require XSLoader;
42	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
43	}	91	}
44		92
45	=head1 FUNCTIONS	93	=head1 FUNCTIONS
46		94
47	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
48		96
49	All the C<aio_*> calls are more or less thin wrappers around the syscall	97	All the C<aio_*> calls are more or less thin wrappers around the syscall
50	with the same name (sans C<aio_>). The arguments are similar or identical,	98	with the same name (sans C<aio_>). The arguments are similar or identical,
51	and they all accept an additional C<$callback> argument which must be	99	and they all accept an additional (and optional) C<$callback> argument
52	a code reference. This code reference will get called with the syscall	100	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	101	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	102	perl, which usually delivers "false") as it's sole argument when the given
55	been executed asynchronously.	103	syscall has been executed asynchronously.
56		104
57	All functions that expect a filehandle will also accept a file descriptor.	105	All functions expecting a filehandle keep a copy of the filehandle
		106	internally until the request has finished.
58		107
		108	All requests return objects of type L<IO::AIO::REQ> that allow further
		109	manipulation of those requests while they are in-flight.
		110
59	The filenames you pass to these routines I<must> be absolute. The reason	111	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	112	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	113	request is being executed, the current working directory could have
		114	changed. Alternatively, you can make sure that you never change the
62	never change the current working directory.	115	current working directory.
		116
		117	To encode pathnames to byte form, either make sure you either: a)
		118	always pass in filenames you got from outside (command line, readdir
		119	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		120	your pathnames to the locale (or other) encoding in effect in the user
		121	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		122	use something else.
63		123
64	=over 4	124	=over 4
65		125
66	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
67		127
68	Asynchronously open or create a file and call the callback with a newly	128	Asynchronously open or create a file and call the callback with a newly
69	created filehandle for the file.	129	created filehandle for the file.
70		130
71	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	131	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
72	for an explanation.	132	for an explanation.
73		133
74	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	134	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
75	list. They are the same as used in C<sysopen>.	135	list. They are the same as used by C<sysopen>.
		136
		137	Likewise, C<$mode> specifies the mode of the newly created file, if it
		138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		139	except that it is mandatory (i.e. use C<0> if you don't create new files,
		140	and C<0666> or C<0777> if you do).
76		141
77	Example:	142	Example:
78		143
79	aio_open "/etc/passwd", O_RDONLY, 0, sub {	144	aio_open "/etc/passwd", O_RDONLY, 0, sub {
80	if ($_[0]) {	145	if ($_[0]) {
…		…
83	} else {	148	} else {
84	die "open failed: $!\n";	149	die "open failed: $!\n";
85	}	150	}
86	};	151	};
87		152
88	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
89		154
90	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
91	code. I<WARNING:> although accepted, you should not pass in a perl	156	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	157	filehandle here, as perl will likely close the file descriptor another
93	the filehandle is destroyed. Normally, you can safely call perls C<close>	158	time when the filehandle is destroyed. Normally, you can safely call perls
94	or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
95		160
		161	This is supposed to be a bug in the API, so that might change. It's
		162	therefore best to avoid this function.
		163
96	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
97		165
98	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
99		167
100	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	168	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	169	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	170	callback without the actual number of bytes read (or -1 on error, just
103	like the syscall).	171	like the syscall).
104		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
105	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
106	offset C<0> within the scalar:	178	offset C<0> within the scalar:
107		179
108	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
109	$_[0] >= 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
110	print "read <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
111	};	183	};
112		184
		185	=item aio_move $srcpath, $dstpath, $callback->($status)
		186
		187	Try to move the I<file> (directories not supported as either source or
		188	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		189	the C<0> (error) or C<-1> ok.
		190
		191	This is a composite request that tries to rename(2) the file first. If
		192	rename files with C<EXDEV>, it creates the destination file with mode 0200
		193	and copies the contents of the source file into it using C<aio_sendfile>,
		194	followed by restoring atime, mtime, access mode and uid/gid, in that
		195	order, and unlinking the C<$srcpath>.
		196
		197	If an error occurs, the partial destination file will be unlinked, if
		198	possible, except when setting atime, mtime, access mode and uid/gid, where
		199	errors are being ignored.
		200
		201	=cut
		202
		203	sub aio_move($$$) {
		204	my ($src, $dst, $cb) = @_;
		205
		206	my $grp = aio_group;
		207
		208	add $grp aio_rename $src, $dst, sub {
		209	if ($_[0] && $! == EXDEV) {
		210	add $grp aio_open $src, O_RDONLY, 0, sub {
		211	if (my $src_fh = $_[0]) {
		212	my @stat = stat $src_fh;
		213
		214	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		215	if (my $dst_fh = $_[0]) {
		216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		217	close $src_fh;
		218
		219	if ($_[0] == $stat[7]) {
		220	utime $stat[8], $stat[9], $dst;
		221	chmod $stat[2] & 07777, $dst_fh;
		222	chown $stat[4], $stat[5], $dst_fh;
		223	close $dst_fh;
		224
		225	add $grp aio_unlink $src, sub {
		226	$cb->($_[0]);
		227	};
		228	} else {
		229	my $errno = $!;
		230	add $grp aio_unlink $dst, sub {
		231	$! = $errno;
		232	$cb->(-1);
		233	};
		234	}
		235	};
		236	} else {
		237	$cb->(-1);
		238	}
		239	},
		240
		241	} else {
		242	$cb->(-1);
		243	}
		244	};
		245	} else {
		246	$cb->($_[0]);
		247	}
		248	};
		249
		250	$grp
		251	}
		252
		253	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		254
		255	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		256	reading at byte offset C<$in_offset>, and starts writing at the current
		257	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		258	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		259	other.
		260
		261	This call tries to make use of a native C<sendfile> syscall to provide
		262	zero-copy operation. For this to work, C<$out_fh> should refer to a
		263	socket, and C<$in_fh> should refer to mmap'able file.
		264
		265	If the native sendfile call fails or is not implemented, it will be
		266	emulated, so you can call C<aio_sendfile> on any type of filehandle
		267	regardless of the limitations of the operating system.
		268
		269	Please note, however, that C<aio_sendfile> can read more bytes from
		270	C<$in_fh> than are written, and there is no way to find out how many
		271	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		272	provides the number of bytes written to C<$out_fh>. Only if the result
		273	value equals C<$length> one can assume that C<$length> bytes have been
		274	read.
		275
113	=item aio_readahead $fh,$offset,$length, $callback	276	=item aio_readahead $fh,$offset,$length, $callback->($retval)
114		277
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	278	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>	279	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	280	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	281	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	282	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	283	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	284	(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.	285	file. The current file offset of the file is left unchanged.
127		286
		287	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		288	emulated by simply reading the data, which would have a similar effect.
		289
128	=item aio_stat $fh_or_path, $callback	290	=item aio_stat $fh_or_path, $callback->($status)
129		291
130	=item aio_lstat $fh, $callback	292	=item aio_lstat $fh, $callback->($status)
131		293
132	Works like perl's C<stat> or C<lstat> in void context. The callback will	294	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 _>	295	be called after the stat and the results will be available using C<stat _>
134	or C<-s _> etc...	296	or C<-s _> etc...
135		297
…		…
145	aio_stat "/etc/passwd", sub {	307	aio_stat "/etc/passwd", sub {
146	$_[0] and die "stat failed: $!";	308	$_[0] and die "stat failed: $!";
147	print "size is ", -s _, "\n";	309	print "size is ", -s _, "\n";
148	};	310	};
149		311
150	=item aio_unlink $pathname, $callback	312	=item aio_unlink $pathname, $callback->($status)
151		313
152	Asynchronously unlink (delete) a file and call the callback with the	314	Asynchronously unlink (delete) a file and call the callback with the
153	result code.	315	result code.
154		316
		317	=item aio_link $srcpath, $dstpath, $callback->($status)
		318
		319	Asynchronously create a new link to the existing object at C<$srcpath> at
		320	the path C<$dstpath> and call the callback with the result code.
		321
		322	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		323
		324	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		325	the path C<$dstpath> and call the callback with the result code.
		326
		327	=item aio_rename $srcpath, $dstpath, $callback->($status)
		328
		329	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		330	rename(2) and call the callback with the result code.
		331
		332	=item aio_rmdir $pathname, $callback->($status)
		333
		334	Asynchronously rmdir (delete) a directory and call the callback with the
		335	result code.
		336
		337	=item aio_readdir $pathname, $callback->($entries)
		338
		339	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		340	directory (i.e. opendir + readdir + closedir). The entries will not be
		341	sorted, and will B<NOT> include the C<.> and C<..> entries.
		342
		343	The callback a single argument which is either C<undef> or an array-ref
		344	with the filenames.
		345
		346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		347
		348	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		349	separate the entries of directory C<$path> into two sets of names, ones
		350	you can recurse into (directories or links to them), and ones you cannot
		351	recurse into (everything else).
		352
		353	C<aio_scandir> is a composite request that consists of many sub
		354	requests. C<$maxreq> specifies the maximum number of outstanding aio
		355	requests that this function generates. If it is C<< <= 0 >>, then a
		356	suitable default will be chosen (currently 8).
		357
		358	On error, the callback is called without arguments, otherwise it receives
		359	two array-refs with path-relative entry names.
		360
		361	Example:
		362
		363	aio_scandir $dir, 0, sub {
		364	my ($dirs, $nondirs) = @_;
		365	print "real directories: @$dirs\n";
		366	print "everything else: @$nondirs\n";
		367	};
		368
		369	Implementation notes.
		370
		371	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		372
		373	After reading the directory, the modification time, size etc. of the
		374	directory before and after the readdir is checked, and if they match (and
		375	isn't the current time), the link count will be used to decide how many
		376	entries are directories (if >= 2). Otherwise, no knowledge of the number
		377	of subdirectories will be assumed.
		378
		379	Then entries will be sorted into likely directories (everything without
		380	a non-initial dot currently) and likely non-directories (everything
		381	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		382	likely directories first. If that succeeds, it assumes that the entry
		383	is a directory or a symlink to directory (which will be checked
		384	seperately). This is often faster than stat'ing the entry itself because
		385	filesystems might detect the type of the entry without reading the inode
		386	data (e.g. ext2fs filetype feature).
		387
		388	If the known number of directories (link count - 2) has been reached, the
		389	rest of the entries is assumed to be non-directories.
		390
		391	This only works with certainty on POSIX (= UNIX) filesystems, which
		392	fortunately are the vast majority of filesystems around.
		393
		394	It will also likely work on non-POSIX filesystems with reduced efficiency
		395	as those tend to return 0 or 1 as link counts, which disables the
		396	directory counting heuristic.
		397
		398	=cut
		399
		400	sub aio_scandir($$$) {
		401	my ($path, $maxreq, $cb) = @_;
		402
		403	my $grp = aio_group;
		404
		405	$maxreq = 8 if $maxreq <= 0;
		406
		407	# stat once
		408	add $grp aio_stat $path, sub {
		409	return $cb->() if $_[0];
		410	my $now = time;
		411	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		412
		413	# read the directory entries
		414	add $grp aio_readdir $path, sub {
		415	my $entries = shift
		416	or return $cb->();
		417
		418	# stat the dir another time
		419	add $grp aio_stat $path, sub {
		420	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		421
		422	my $ndirs;
		423
		424	# take the slow route if anything looks fishy
		425	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		426	$ndirs = -1;
		427	} else {
		428	# if nlink == 2, we are finished
		429	# on non-posix-fs's, we rely on nlink < 2
		430	$ndirs = (stat _)[3] - 2
		431	or return $cb->([], $entries);
		432	}
		433
		434	# sort into likely dirs and likely nondirs
		435	# dirs == files without ".", short entries first
		436	$entries = [map $_->[0],
		437	sort { $b->[1] cmp $a->[1] }
		438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		439	@$entries];
		440
		441	my (@dirs, @nondirs);
		442
		443	my ($statcb, $schedcb);
		444	my $nreq = 0;
		445
		446	$schedcb = sub {
		447	if (@$entries) {
		448	if ($nreq < $maxreq) {
		449	my $ent = pop @$entries;
		450	$nreq++;
		451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		452	}
		453	} elsif (!$nreq) {
		454	# finished
		455	undef $statcb;
		456	undef $schedcb;
		457	$cb->(\@dirs, \@nondirs) if $cb;
		458	undef $cb;
		459	}
		460	};
		461	$statcb = sub {
		462	my ($status, $entry) = @_;
		463
		464	if ($status < 0) {
		465	$nreq--;
		466	push @nondirs, $entry;
		467	&$schedcb;
		468	} else {
		469	# need to check for real directory
		470	add $grp aio_lstat "$path/$entry", sub {
		471	$nreq--;
		472
		473	if (-d _) {
		474	push @dirs, $entry;
		475
		476	if (!--$ndirs) {
		477	push @nondirs, @$entries;
		478	$entries = [];
		479	}
		480	} else {
		481	push @nondirs, $entry;
		482	}
		483
		484	&$schedcb;
		485	}
		486	}
		487	};
		488
		489	&$schedcb while @$entries && $nreq < $maxreq;
		490	};
		491	};
		492	};
		493
		494	$grp
		495	}
		496
155	=item aio_fsync $fh, $callback	497	=item aio_fsync $fh, $callback->($status)
156		498
157	Asynchronously call fsync on the given filehandle and call the callback	499	Asynchronously call fsync on the given filehandle and call the callback
158	with the fsync result code.	500	with the fsync result code.
159		501
160	=item aio_fdatasync $fh, $callback	502	=item aio_fdatasync $fh, $callback->($status)
161		503
162	Asynchronously call fdatasync on the given filehandle and call the	504	Asynchronously call fdatasync on the given filehandle and call the
163	callback with the fdatasync result code.	505	callback with the fdatasync result code.
164		506
		507	If this call isn't available because your OS lacks it or it couldn't be
		508	detected, it will be emulated by calling C<fsync> instead.
		509
		510	=item aio_group $callback->()
		511
		512	[EXPERIMENTAL]
		513
		514	This is a very special aio request: Instead of doing something, it is a
		515	container for other aio requests, which is useful if you want to bundle
		516	many requests into a single, composite, request.
		517
		518	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		519	for more info.
		520
		521	Example:
		522
		523	my $grp = aio_group sub {
		524	print "all stats done\n";
		525	};
		526
		527	add $grp
		528	(aio_stat ...),
		529	(aio_stat ...),
		530	...;
		531
		532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		533
		534	Mainly used for debugging and benchmarking, this aio request puts one of
		535	the request workers to sleep for the given time.
		536
		537	While it is theoretically handy to have simple I/O scheduling requests
		538	like sleep and file handle readable/writable, the overhead this creates
		539	is immense, so do not use this function except to put your application
		540	under artificial I/O pressure.
		541
165	=back	542	=back
166		543
		544	=head2 IO::AIO::REQ CLASS
		545
		546	All non-aggregate C<aio_*> functions return an object of this class when
		547	called in non-void context.
		548
		549	A request always moves through the following five states in its lifetime,
		550	in order: B<ready> (request has been created, but has not been executed
		551	yet), B<execute> (request is currently being executed), B<pending>
		552	(request has been executed but callback has not been called yet),
		553	B<result> (results are being processed synchronously, includes calling the
		554	callback) and B<done> (request has reached the end of its lifetime and
		555	holds no resources anymore).
		556
		557	=over 4
		558
		559	=item $req->cancel
		560
		561	Cancels the request, if possible. Has the effect of skipping execution
		562	when entering the B<execute> state and skipping calling the callback when
		563	entering the the B<result> state, but will leave the request otherwise
		564	untouched. That means that requests that currently execute will not be
		565	stopped and resources held by the request will not be freed prematurely.
		566
		567	=back
		568
		569	=head2 IO::AIO::GRP CLASS
		570
		571	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		572	objects of this class, too.
		573
		574	A IO::AIO::GRP object is a special request that can contain multiple other
		575	aio requests.
		576
		577	You create one by calling the C<aio_group> constructing function with a
		578	callback that will be called when all contained requests have entered the
		579	C<done> state:
		580
		581	my $grp = aio_group sub {
		582	print "all requests are done\n";
		583	};
		584
		585	You add requests by calling the C<add> method with one or more
		586	C<IO::AIO::REQ> objects:
		587
		588	$grp->add (aio_unlink "...");
		589
		590	add $grp aio_stat "...", sub { ... };
		591
		592	This makes it very easy to create composite requests (see the source of
		593	C<aio_move> for an application) that work and feel like simple requests.
		594
		595	The IO::AIO::GRP objects will be cleaned up during calls to
		596	C<IO::AIO::poll_cb>, just like any other request.
		597
		598	They can be canceled like any other request. Canceling will cancel not
		599	just the request itself, but also all requests it contains.
		600
		601	They can also can also be added to other IO::AIO::GRP objects.
		602
		603	Their lifetime, simplified, looks like this: when they are empty, they
		604	will finish very quickly. If they contain only requests that are in the
		605	C<done> state, they will also finish. Otherwise they will continue to
		606	exist.
		607
		608	That means after creating a group you have some time to add requests. And
		609	in the callbacks of those requests, you can add further requests to the
		610	group. And only when all those requests have finished will the the group
		611	itself finish.
		612
		613	=over 4
		614
		615	=item $grp->add (...)
		616
		617	=item add $grp ...
		618
		619	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		620	be added, including other groups, as long as you do not create circular
		621	dependencies.
		622
		623	Returns all its arguments.
		624
		625	=back
		626
167	=head2 SUPPORT FUNCTIONS	627	=head2 SUPPORT FUNCTIONS
168		628
169	=over 4	629	=over 4
170		630
171	=item $fileno = IO::AIO::poll_fileno	631	=item $fileno = IO::AIO::poll_fileno
172		632
173	Return the I<request result pipe filehandle>. This filehandle must be	633	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	634	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	635	select, see below or the SYNOPSIS). If the pipe becomes readable you have
176	C<poll_cb> to check the results.	636	to call C<poll_cb> to check the results.
177		637
178	See C<poll_cb> for an example.	638	See C<poll_cb> for an example.
179		639
180	=item IO::AIO::poll_cb	640	=item IO::AIO::poll_cb
181		641
182	Process all outstanding events on the result pipe. You have to call this	642	Process all outstanding events on the result pipe. You have to call this
183	regularly. Returns the number of events processed. Returns immediately	643	regularly. Returns the number of events processed. Returns immediately
184	when no events are outstanding.	644	when no events are outstanding.
185		645
186	You can use Event to multiplex, e.g.:	646	Example: Install an Event watcher that automatically calls
		647	IO::AIO::poll_cb with high priority:
187		648
188	Event->io (fd => IO::AIO::poll_fileno,	649	Event->io (fd => IO::AIO::poll_fileno,
189	poll => 'r', async => 1,	650	poll => 'r', async => 1,
190	cb => \&IO::AIO::poll_cb);	651	cb => \&IO::AIO::poll_cb);
191		652
192	=item IO::AIO::poll_wait	653	=item IO::AIO::poll_wait
193		654
194	Wait till the result filehandle becomes ready for reading (simply does a	655	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	656	C<select> on the filehandle. This is useful if you want to synchronously wait
196	for some requests to finish).	657	for some requests to finish).
197		658
198	See C<nreqs> for an example.	659	See C<nreqs> for an example.
199		660
200	=item IO::AIO::nreqs	661	=item IO::AIO::nreqs
201		662
202	Returns the number of requests currently outstanding.	663	Returns the number of requests currently outstanding (i.e. for which their
		664	callback has not been invoked yet).
203		665
204	Example: wait till there are no outstanding requests anymore:	666	Example: wait till there are no outstanding requests anymore:
205		667
206	IO::AIO::poll_wait, IO::AIO::poll_cb	668	IO::AIO::poll_wait, IO::AIO::poll_cb
207	while IO::AIO::nreqs;	669	while IO::AIO::nreqs;
208		670
		671	=item IO::AIO::flush
		672
		673	Wait till all outstanding AIO requests have been handled.
		674
		675	Strictly equivalent to:
		676
		677	IO::AIO::poll_wait, IO::AIO::poll_cb
		678	while IO::AIO::nreqs;
		679
		680	=item IO::AIO::poll
		681
		682	Waits until some requests have been handled.
		683
		684	Strictly equivalent to:
		685
		686	IO::AIO::poll_wait, IO::AIO::poll_cb
		687	if IO::AIO::nreqs;
		688
209	=item IO::AIO::min_parallel $nthreads	689	=item IO::AIO::min_parallel $nthreads
210		690
211	Set the minimum number of AIO threads to C<$nthreads>. The default is	691	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	692	is C<4>, which means four asynchronous operations can be done at one time
213	(the number of outstanding operations, however, is unlimited).	693	(the number of outstanding operations, however, is unlimited).
		694
		695	IO::AIO starts threads only on demand, when an AIO request is queued and
		696	no free thread exists.
214		697
215	It is recommended to keep the number of threads low, as some Linux	698	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	699	kernel versions will scale negatively with the number of threads (higher
217	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	700	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
218	threads should be fine.	701	threads should be fine.
219		702
220	Under normal circumstances you don't need to call this function, as this	703	Under most circumstances you don't need to call this function, as the
221	module automatically starts some threads (the exact number might change,	704	module selects a default that is suitable for low to moderate load.
222	and is currently 4).
223		705
224	=item IO::AIO::max_parallel $nthreads	706	=item IO::AIO::max_parallel $nthreads
225		707
226	Sets the maximum number of AIO threads to C<$nthreads>. If more than	708	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
227	the specified number of threads are currently running, kill them. This	709	specified number of threads are currently running, this function kills
228	function blocks until the limit is reached.	710	them. This function blocks until the limit is reached.
		711
		712	While C<$nthreads> are zero, aio requests get queued but not executed
		713	until the number of threads has been increased again.
229		714
230	This module automatically runs C<max_parallel 0> at program end, to ensure	715	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.	716	that all threads are killed and that there are no outstanding requests.
232		717
233	Under normal circumstances you don't need to call this function.	718	Under normal circumstances you don't need to call this function.
…		…
237	Sets the maximum number of outstanding requests to C<$nreqs>. If you	722	Sets the maximum number of outstanding requests to C<$nreqs>. If you
238	try to queue up more than this number of requests, the caller will block until	723	try to queue up more than this number of requests, the caller will block until
239	some requests have been handled.	724	some requests have been handled.
240		725
241	The default is very large, so normally there is no practical limit. If you	726	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	727	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>.	728	this to a relatively low number, such as C<100>.
244		729
245	Under normal circumstances you don't need to call this function.	730	Under normal circumstances you don't need to call this function.
246		731
247	=back	732	=back
…		…
250		735
251	# support function to convert a fd into a perl filehandle	736	# support function to convert a fd into a perl filehandle
252	sub _fd2fh {	737	sub _fd2fh {
253	return undef if $_[0] < 0;	738	return undef if $_[0] < 0;
254		739
255	# try to be perl5.6-compatible	740	# try to generate nice filehandles
256	local *AIO_FH;	741	my $sym = "IO::AIO::fd#$_[0]";
257	open AIO_FH, "+<&=$_[0]"	742	local *$sym;
		743
		744	open *$sym, "+<&=$_[0]" # usually works under any unix
		745	or open *$sym, "<&=$_[0]" # cygwin needs this
		746	or open *$sym, ">&=$_[0]" # or this
258	or return undef;	747	or return undef;
259		748
260	*AIO_FH	749	*$sym
261	}	750	}
262		751
263	min_parallel 4;	752	min_parallel 4;
264		753
265	END {	754	END {
266	max_parallel 0;	755	max_parallel 0;
267	}	756	}
268		757
269	1;	758	1;
270		759
		760	=head2 FORK BEHAVIOUR
		761
		762	This module should do "the right thing" when the process using it forks:
		763
		764	Before the fork, IO::AIO enters a quiescent state where no requests
		765	can be added in other threads and no results will be processed. After
		766	the fork the parent simply leaves the quiescent state and continues
		767	request/result processing, while the child clears the request/result
		768	queue (so the requests started before the fork will only be handled in
		769	the parent). Threads will be started on demand until the limit ste in the
		770	parent process has been reached again.
		771
		772	In short: the parent will, after a short pause, continue as if fork had
		773	not been called, while the child will act as if IO::AIO has not been used
		774	yet.
		775
271	=head1 SEE ALSO	776	=head1 SEE ALSO
272		777
273	L<Coro>, L<Linux::AIO>.	778	L<Coro>, L<Linux::AIO> (obsolete).
274		779
275	=head1 AUTHOR	780	=head1 AUTHOR
276		781
277	Marc Lehmann <schmorp@schmorp.de>	782	Marc Lehmann <schmorp@schmorp.de>
278	http://home.schmorp.de/	783	http://home.schmorp.de/

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Revision 1.57 by root, Sun Oct 22 01:28:31 2006 UTC