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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.7 by root, Sun Jul 10 22:19:54 2005 UTC vs.
Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC

…		…
12	};	12	};
13		13
14	aio_unlink "/tmp/file", sub { };	14	aio_unlink "/tmp/file", sub { };
15		15
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] >= 0 or die "read error: $!";	17	$_[0] > 0 or die "read error: $!";
18	};	18	};
19		19
20	# Event	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
21	Event->io (fd => IO::AIO::poll_fileno,	34	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	35	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	36	cb => \&IO::AIO::poll_cb);
24		37
25	# Glib/Gtk2	38	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	39	add_watch Glib::IO IO::AIO::poll_fileno,
27	\&IO::AIO::poll_cb;	40	in => sub { IO::AIO::poll_cb; 1 };
28		41
29	# Tk	42	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	44	readable => \&IO::AIO::poll_cb);
		45
		46	# Danga::Socket integration
		47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		48	\&IO::AIO::poll_cb);
32		49
33	=head1 DESCRIPTION	50	=head1 DESCRIPTION
34		51
35	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
36	operating system supports.	53	operating system supports.
…		…
43	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,
44	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
45	remaining functionality would have to be implemented using threads anyway.	62	remaining functionality would have to be implemented using threads anyway.
46		63
47	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
48	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.
49		68
50	=cut	69	=cut
51		70
52	package IO::AIO;	71	package IO::AIO;
53		72
		73	no warnings;
		74	use strict 'vars';
		75
54	use base 'Exporter';	76	use base 'Exporter';
55		77
56	use Fcntl ();
57
58	BEGIN {	78	BEGIN {
59	$VERSION = 0.2;	79	our $VERSION = '2.0';
60		80
61	@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
62	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group);
63	@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';
64		88
65	require XSLoader;	89	require XSLoader;
66	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
67	}	91	}
68		92
69	=head1 FUNCTIONS	93	=head1 FUNCTIONS
70		94
71	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
72		96
73	All the C<aio_*> calls are more or less thin wrappers around the syscall	97	All the C<aio_*> calls are more or less thin wrappers around the syscall
74	with the same name (sans C<aio_>). The arguments are similar or identical,	98	with the same name (sans C<aio_>). The arguments are similar or identical,
75	and they all accept an additional C<$callback> argument which must be	99	and they all accept an additional (and optional) C<$callback> argument
76	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
77	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
78	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
79	been executed asynchronously.	103	syscall has been executed asynchronously.
80		104
81	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.
82		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
83	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
84	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
85	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
86	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.
87		123
88	=over 4	124	=over 4
89		125
90	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
91		127
92	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
93	created filehandle for the file.	129	created filehandle for the file.
94		130
95	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,
96	for an explanation.	132	for an explanation.
97		133
98	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
99	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<$mode> specifies the mode of the newly created file, if it
		138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		139	except that it is mandatory (i.e. use C<0> if you don't create new files,
		140	and C<0666> or C<0777> if you do).
100		141
101	Example:	142	Example:
102		143
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	144	aio_open "/etc/passwd", O_RDONLY, 0, sub {
104	if ($_[0]) {	145	if ($_[0]) {
…		…
107	} else {	148	} else {
108	die "open failed: $!\n";	149	die "open failed: $!\n";
109	}	150	}
110	};	151	};
111		152
112	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
113		154
114	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
115	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
116	filehandle here, as perl will likely close the file descriptor itself when	157	filehandle here, as perl will likely close the file descriptor another
117	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
118	or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
119		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
120	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121		165
122	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
123		167
124	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>
125	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
126	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
127	like the syscall).	171	like the syscall).
128		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
129	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
130	offset C<0> within the scalar:	178	offset C<0> within the scalar:
131		179
132	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
133	$_[0] >= 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
134	print "read <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
135	};	183	};
136		184
		185	=item aio_move $srcpath, $dstpath, $callback->($status)
		186
		187	[EXPERIMENTAL due to internal aio_group use]
		188
		189	Try to move the I<file> (directories not supported as either source or
		190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		191	the C<0> (error) or C<-1> ok.
		192
		193	This is a composite request that tries to rename(2) the file first. If
		194	rename files with C<EXDEV>, it creates the destination file with mode 0200
		195	and copies the contents of the source file into it using C<aio_sendfile>,
		196	followed by restoring atime, mtime, access mode and uid/gid, in that
		197	order, and unlinking the C<$srcpath>.
		198
		199	If an error occurs, the partial destination file will be unlinked, if
		200	possible, except when setting atime, mtime, access mode and uid/gid, where
		201	errors are being ignored.
		202
		203	=cut
		204
		205	sub aio_move($$$) {
		206	my ($src, $dst, $cb) = @_;
		207
		208	my $grp = aio_group $cb;
		209
		210	add $grp aio_rename $src, $dst, sub {
		211	if ($_[0] && $! == EXDEV) {
		212	add $grp aio_open $src, O_RDONLY, 0, sub {
		213	if (my $src_fh = $_[0]) {
		214	my @stat = stat $src_fh;
		215
		216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		217	if (my $dst_fh = $_[0]) {
		218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		219	close $src_fh;
		220
		221	if ($_[0] == $stat[7]) {
		222	utime $stat[8], $stat[9], $dst;
		223	chmod $stat[2] & 07777, $dst_fh;
		224	chown $stat[4], $stat[5], $dst_fh;
		225	close $dst_fh;
		226
		227	add $grp aio_unlink $src, sub {
		228	$grp->result ($_[0]);
		229	};
		230	} else {
		231	my $errno = $!;
		232	add $grp aio_unlink $dst, sub {
		233	$! = $errno;
		234	$grp->result (-1);
		235	};
		236	}
		237	};
		238	} else {
		239	$grp->result (-1);
		240	}
		241	},
		242
		243	} else {
		244	$grp->result (-1);
		245	}
		246	};
		247	} else {
		248	$grp->result ($_[0]);
		249	}
		250	};
		251
		252	$grp
		253	}
		254
		255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		256
		257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		258	reading at byte offset C<$in_offset>, and starts writing at the current
		259	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		260	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		261	other.
		262
		263	This call tries to make use of a native C<sendfile> syscall to provide
		264	zero-copy operation. For this to work, C<$out_fh> should refer to a
		265	socket, and C<$in_fh> should refer to mmap'able file.
		266
		267	If the native sendfile call fails or is not implemented, it will be
		268	emulated, so you can call C<aio_sendfile> on any type of filehandle
		269	regardless of the limitations of the operating system.
		270
		271	Please note, however, that C<aio_sendfile> can read more bytes from
		272	C<$in_fh> than are written, and there is no way to find out how many
		273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		274	provides the number of bytes written to C<$out_fh>. Only if the result
		275	value equals C<$length> one can assume that C<$length> bytes have been
		276	read.
		277
137	=item aio_readahead $fh,$offset,$length, $callback	278	=item aio_readahead $fh,$offset,$length, $callback->($retval)
138		279
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	280	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>	281	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	282	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	283	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	284	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	285	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	286	(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.	287	file. The current file offset of the file is left unchanged.
151		288
		289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		290	emulated by simply reading the data, which would have a similar effect.
		291
152	=item aio_stat $fh_or_path, $callback	292	=item aio_stat $fh_or_path, $callback->($status)
153		293
154	=item aio_lstat $fh, $callback	294	=item aio_lstat $fh, $callback->($status)
155		295
156	Works like perl's C<stat> or C<lstat> in void context. The callback will	296	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 _>	297	be called after the stat and the results will be available using C<stat _>
158	or C<-s _> etc...	298	or C<-s _> etc...
159		299
…		…
169	aio_stat "/etc/passwd", sub {	309	aio_stat "/etc/passwd", sub {
170	$_[0] and die "stat failed: $!";	310	$_[0] and die "stat failed: $!";
171	print "size is ", -s _, "\n";	311	print "size is ", -s _, "\n";
172	};	312	};
173		313
174	=item aio_unlink $pathname, $callback	314	=item aio_unlink $pathname, $callback->($status)
175		315
176	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
177	result code.	317	result code.
178		318
		319	=item aio_link $srcpath, $dstpath, $callback->($status)
		320
		321	Asynchronously create a new link to the existing object at C<$srcpath> at
		322	the path C<$dstpath> and call the callback with the result code.
		323
		324	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		325
		326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		327	the path C<$dstpath> and call the callback with the result code.
		328
		329	=item aio_rename $srcpath, $dstpath, $callback->($status)
		330
		331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		332	rename(2) and call the callback with the result code.
		333
		334	=item aio_rmdir $pathname, $callback->($status)
		335
		336	Asynchronously rmdir (delete) a directory and call the callback with the
		337	result code.
		338
		339	=item aio_readdir $pathname, $callback->($entries)
		340
		341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		342	directory (i.e. opendir + readdir + closedir). The entries will not be
		343	sorted, and will B<NOT> include the C<.> and C<..> entries.
		344
		345	The callback a single argument which is either C<undef> or an array-ref
		346	with the filenames.
		347
		348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		349
		350	[EXPERIMENTAL due to internal aio_group use]
		351
		352	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		353	separate the entries of directory C<$path> into two sets of names, ones
		354	you can recurse into (directories or links to them), and ones you cannot
		355	recurse into (everything else).
		356
		357	C<aio_scandir> is a composite request that consists of many sub
		358	requests. C<$maxreq> specifies the maximum number of outstanding aio
		359	requests that this function generates. If it is C<< <= 0 >>, then a
		360	suitable default will be chosen (currently 8).
		361
		362	On error, the callback is called without arguments, otherwise it receives
		363	two array-refs with path-relative entry names.
		364
		365	Example:
		366
		367	aio_scandir $dir, 0, sub {
		368	my ($dirs, $nondirs) = @_;
		369	print "real directories: @$dirs\n";
		370	print "everything else: @$nondirs\n";
		371	};
		372
		373	Implementation notes.
		374
		375	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		376
		377	After reading the directory, the modification time, size etc. of the
		378	directory before and after the readdir is checked, and if they match (and
		379	isn't the current time), the link count will be used to decide how many
		380	entries are directories (if >= 2). Otherwise, no knowledge of the number
		381	of subdirectories will be assumed.
		382
		383	Then entries will be sorted into likely directories (everything without
		384	a non-initial dot currently) and likely non-directories (everything
		385	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		386	likely directories first. If that succeeds, it assumes that the entry
		387	is a directory or a symlink to directory (which will be checked
		388	seperately). This is often faster than stat'ing the entry itself because
		389	filesystems might detect the type of the entry without reading the inode
		390	data (e.g. ext2fs filetype feature).
		391
		392	If the known number of directories (link count - 2) has been reached, the
		393	rest of the entries is assumed to be non-directories.
		394
		395	This only works with certainty on POSIX (= UNIX) filesystems, which
		396	fortunately are the vast majority of filesystems around.
		397
		398	It will also likely work on non-POSIX filesystems with reduced efficiency
		399	as those tend to return 0 or 1 as link counts, which disables the
		400	directory counting heuristic.
		401
		402	=cut
		403
		404	sub aio_scandir($$$) {
		405	my ($path, $maxreq, $cb) = @_;
		406
		407	my $grp = aio_group $cb;
		408
		409	$maxreq = 8 if $maxreq <= 0;
		410
		411	# stat once
		412	add $grp aio_stat $path, sub {
		413	return $grp->result () if $_[0];
		414	my $now = time;
		415	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		416
		417	# read the directory entries
		418	add $grp aio_readdir $path, sub {
		419	my $entries = shift
		420	or return $grp->result ();
		421
		422	# stat the dir another time
		423	add $grp aio_stat $path, sub {
		424	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		425
		426	my $ndirs;
		427
		428	# take the slow route if anything looks fishy
		429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		430	$ndirs = -1;
		431	} else {
		432	# if nlink == 2, we are finished
		433	# on non-posix-fs's, we rely on nlink < 2
		434	$ndirs = (stat _)[3] - 2
		435	or return $grp->result ([], $entries);
		436	}
		437
		438	# sort into likely dirs and likely nondirs
		439	# dirs == files without ".", short entries first
		440	$entries = [map $_->[0],
		441	sort { $b->[1] cmp $a->[1] }
		442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		443	@$entries];
		444
		445	my (@dirs, @nondirs);
		446
		447	my ($statcb, $schedcb);
		448	my $nreq = 0;
		449
		450	$schedcb = sub {
		451	if (@$entries) {
		452	if ($nreq < $maxreq) {
		453	my $ent = pop @$entries;
		454	$nreq++;
		455	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		456	}
		457	} elsif (!$nreq) {
		458	# finished
		459	undef $statcb;
		460	undef $schedcb;
		461	$grp->result (\@dirs, \@nondirs) if $cb;
		462	undef $cb;
		463	}
		464	};
		465	$statcb = sub {
		466	my ($status, $entry) = @_;
		467
		468	if ($status < 0) {
		469	$nreq--;
		470	push @nondirs, $entry;
		471	&$schedcb;
		472	} else {
		473	# need to check for real directory
		474	add $grp aio_lstat "$path/$entry", sub {
		475	$nreq--;
		476
		477	if (-d _) {
		478	push @dirs, $entry;
		479
		480	if (!--$ndirs) {
		481	push @nondirs, @$entries;
		482	$entries = [];
		483	}
		484	} else {
		485	push @nondirs, $entry;
		486	}
		487
		488	&$schedcb;
		489	}
		490	}
		491	};
		492
		493	&$schedcb while @$entries && $nreq < $maxreq;
		494	};
		495	};
		496	};
		497
		498	$grp
		499	}
		500
179	=item aio_fsync $fh, $callback	501	=item aio_fsync $fh, $callback->($status)
180		502
181	Asynchronously call fsync on the given filehandle and call the callback	503	Asynchronously call fsync on the given filehandle and call the callback
182	with the fsync result code.	504	with the fsync result code.
183		505
184	=item aio_fdatasync $fh, $callback	506	=item aio_fdatasync $fh, $callback->($status)
185		507
186	Asynchronously call fdatasync on the given filehandle and call the	508	Asynchronously call fdatasync on the given filehandle and call the
187	callback with the fdatasync result code.	509	callback with the fdatasync result code.
188		510
		511	If this call isn't available because your OS lacks it or it couldn't be
		512	detected, it will be emulated by calling C<fsync> instead.
		513
		514	=item aio_group $callback->(...)
		515
		516	[EXPERIMENTAL]
		517
		518	This is a very special aio request: Instead of doing something, it is a
		519	container for other aio requests, which is useful if you want to bundle
		520	many requests into a single, composite, request.
		521
		522	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		523	for more info.
		524
		525	Example:
		526
		527	my $grp = aio_group sub {
		528	print "all stats done\n";
		529	};
		530
		531	add $grp
		532	(aio_stat ...),
		533	(aio_stat ...),
		534	...;
		535
		536	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		537
		538	Mainly used for debugging and benchmarking, this aio request puts one of
		539	the request workers to sleep for the given time.
		540
		541	While it is theoretically handy to have simple I/O scheduling requests
		542	like sleep and file handle readable/writable, the overhead this creates
		543	is immense, so do not use this function except to put your application
		544	under artificial I/O pressure.
		545
189	=back	546	=back
190		547
		548	=head2 IO::AIO::REQ CLASS
		549
		550	All non-aggregate C<aio_*> functions return an object of this class when
		551	called in non-void context.
		552
		553	A request always moves through the following five states in its lifetime,
		554	in order: B<ready> (request has been created, but has not been executed
		555	yet), B<execute> (request is currently being executed), B<pending>
		556	(request has been executed but callback has not been called yet),
		557	B<result> (results are being processed synchronously, includes calling the
		558	callback) and B<done> (request has reached the end of its lifetime and
		559	holds no resources anymore).
		560
		561	=over 4
		562
		563	=item $req->cancel
		564
		565	Cancels the request, if possible. Has the effect of skipping execution
		566	when entering the B<execute> state and skipping calling the callback when
		567	entering the the B<result> state, but will leave the request otherwise
		568	untouched. That means that requests that currently execute will not be
		569	stopped and resources held by the request will not be freed prematurely.
		570
		571	=back
		572
		573	=head2 IO::AIO::GRP CLASS
		574
		575	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		576	objects of this class, too.
		577
		578	A IO::AIO::GRP object is a special request that can contain multiple other
		579	aio requests.
		580
		581	You create one by calling the C<aio_group> constructing function with a
		582	callback that will be called when all contained requests have entered the
		583	C<done> state:
		584
		585	my $grp = aio_group sub {
		586	print "all requests are done\n";
		587	};
		588
		589	You add requests by calling the C<add> method with one or more
		590	C<IO::AIO::REQ> objects:
		591
		592	$grp->add (aio_unlink "...");
		593
		594	add $grp aio_stat "...", sub {
		595	$_[0] or return $grp->result ("error");
		596
		597	# add another request dynamically, if first succeeded
		598	add $grp aio_open "...", sub {
		599	$grp->result ("ok");
		600	};
		601	};
		602
		603	This makes it very easy to create composite requests (see the source of
		604	C<aio_move> for an application) that work and feel like simple requests.
		605
		606	The IO::AIO::GRP objects will be cleaned up during calls to
		607	C<IO::AIO::poll_cb>, just like any other request.
		608
		609	They can be canceled like any other request. Canceling will cancel not
		610	just the request itself, but also all requests it contains.
		611
		612	They can also can also be added to other IO::AIO::GRP objects.
		613
		614	Their lifetime, simplified, looks like this: when they are empty, they
		615	will finish very quickly. If they contain only requests that are in the
		616	C<done> state, they will also finish. Otherwise they will continue to
		617	exist.
		618
		619	That means after creating a group you have some time to add requests. And
		620	in the callbacks of those requests, you can add further requests to the
		621	group. And only when all those requests have finished will the the group
		622	itself finish.
		623
		624	=over 4
		625
		626	=item $grp->add (...)
		627
		628	=item add $grp ...
		629
		630	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		631	be added, including other groups, as long as you do not create circular
		632	dependencies.
		633
		634	Returns all its arguments.
		635
		636	=item $grp->result (...)
		637
		638	Set the result value(s) that will be passed to the group callback when all
		639	subrequests have finished. By default, no argument will be passed.
		640
		641	=back
		642
191	=head2 SUPPORT FUNCTIONS	643	=head2 SUPPORT FUNCTIONS
192		644
193	=over 4	645	=over 4
194		646
195	=item $fileno = IO::AIO::poll_fileno	647	=item $fileno = IO::AIO::poll_fileno
196		648
197	Return the I<request result pipe filehandle>. This filehandle must be	649	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	650	polled for reading by some mechanism outside this module (e.g. Event or
199	or select, see below). If the pipe becomes readable you have to call	651	select, see below or the SYNOPSIS). If the pipe becomes readable you have
200	C<poll_cb> to check the results.	652	to call C<poll_cb> to check the results.
201		653
202	See C<poll_cb> for an example.	654	See C<poll_cb> for an example.
203		655
204	=item IO::AIO::poll_cb	656	=item IO::AIO::poll_cb
205		657
206	Process all outstanding events on the result pipe. You have to call this	658	Process all outstanding events on the result pipe. You have to call this
207	regularly. Returns the number of events processed. Returns immediately	659	regularly. Returns the number of events processed. Returns immediately
208	when no events are outstanding.	660	when no events are outstanding.
209		661
210	You can use Event to multiplex, e.g.:	662	Example: Install an Event watcher that automatically calls
		663	IO::AIO::poll_cb with high priority:
211		664
212	Event->io (fd => IO::AIO::poll_fileno,	665	Event->io (fd => IO::AIO::poll_fileno,
213	poll => 'r', async => 1,	666	poll => 'r', async => 1,
214	cb => \&IO::AIO::poll_cb);	667	cb => \&IO::AIO::poll_cb);
215		668
216	=item IO::AIO::poll_wait	669	=item IO::AIO::poll_wait
217		670
218	Wait till the result filehandle becomes ready for reading (simply does a	671	Wait till the result filehandle becomes ready for reading (simply does a
219	select on the filehandle. This is useful if you want to synchronously wait	672	C<select> on the filehandle. This is useful if you want to synchronously wait
220	for some requests to finish).	673	for some requests to finish).
221		674
222	See C<nreqs> for an example.	675	See C<nreqs> for an example.
223		676
224	=item IO::AIO::nreqs	677	=item IO::AIO::nreqs
225		678
226	Returns the number of requests currently outstanding.	679	Returns the number of requests currently outstanding (i.e. for which their
		680	callback has not been invoked yet).
227		681
228	Example: wait till there are no outstanding requests anymore:	682	Example: wait till there are no outstanding requests anymore:
229		683
230	IO::AIO::poll_wait, IO::AIO::poll_cb	684	IO::AIO::poll_wait, IO::AIO::poll_cb
231	while IO::AIO::nreqs;	685	while IO::AIO::nreqs;
232		686
		687	=item IO::AIO::flush
		688
		689	Wait till all outstanding AIO requests have been handled.
		690
		691	Strictly equivalent to:
		692
		693	IO::AIO::poll_wait, IO::AIO::poll_cb
		694	while IO::AIO::nreqs;
		695
		696	=item IO::AIO::poll
		697
		698	Waits until some requests have been handled.
		699
		700	Strictly equivalent to:
		701
		702	IO::AIO::poll_wait, IO::AIO::poll_cb
		703	if IO::AIO::nreqs;
		704
233	=item IO::AIO::min_parallel $nthreads	705	=item IO::AIO::min_parallel $nthreads
234		706
235	Set the minimum number of AIO threads to C<$nthreads>. The default is	707	Set the minimum number of AIO threads to C<$nthreads>. The current default
236	C<1>, which means a single asynchronous operation can be done at one time	708	is C<4>, which means four asynchronous operations can be done at one time
237	(the number of outstanding operations, however, is unlimited).	709	(the number of outstanding operations, however, is unlimited).
		710
		711	IO::AIO starts threads only on demand, when an AIO request is queued and
		712	no free thread exists.
238		713
239	It is recommended to keep the number of threads low, as some Linux	714	It is recommended to keep the number of threads low, as some Linux
240	kernel versions will scale negatively with the number of threads (higher	715	kernel versions will scale negatively with the number of threads (higher
241	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	716	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
242	threads should be fine.	717	threads should be fine.
243		718
244	Under normal circumstances you don't need to call this function, as this	719	Under most circumstances you don't need to call this function, as the
245	module automatically starts some threads (the exact number might change,	720	module selects a default that is suitable for low to moderate load.
246	and is currently 4).
247		721
248	=item IO::AIO::max_parallel $nthreads	722	=item IO::AIO::max_parallel $nthreads
249		723
250	Sets the maximum number of AIO threads to C<$nthreads>. If more than	724	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
251	the specified number of threads are currently running, kill them. This	725	specified number of threads are currently running, this function kills
252	function blocks until the limit is reached.	726	them. This function blocks until the limit is reached.
		727
		728	While C<$nthreads> are zero, aio requests get queued but not executed
		729	until the number of threads has been increased again.
253		730
254	This module automatically runs C<max_parallel 0> at program end, to ensure	731	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.	732	that all threads are killed and that there are no outstanding requests.
256		733
257	Under normal circumstances you don't need to call this function.	734	Under normal circumstances you don't need to call this function.
…		…
261	Sets the maximum number of outstanding requests to C<$nreqs>. If you	738	Sets the maximum number of outstanding requests to C<$nreqs>. If you
262	try to queue up more than this number of requests, the caller will block until	739	try to queue up more than this number of requests, the caller will block until
263	some requests have been handled.	740	some requests have been handled.
264		741
265	The default is very large, so normally there is no practical limit. If you	742	The default is very large, so normally there is no practical limit. If you
266	queue up many requests in a loop it it often improves speed if you set	743	queue up many requests in a loop it often improves speed if you set
267	this to a relatively low number, such as C<100>.	744	this to a relatively low number, such as C<100>.
268		745
269	Under normal circumstances you don't need to call this function.	746	Under normal circumstances you don't need to call this function.
270		747
271	=back	748	=back
…		…
274		751
275	# support function to convert a fd into a perl filehandle	752	# support function to convert a fd into a perl filehandle
276	sub _fd2fh {	753	sub _fd2fh {
277	return undef if $_[0] < 0;	754	return undef if $_[0] < 0;
278		755
279	# try to be perl5.6-compatible	756	# try to generate nice filehandles
280	local *AIO_FH;	757	my $sym = "IO::AIO::fd#$_[0]";
281	open AIO_FH, "+<&=$_[0]"	758	local *$sym;
		759
		760	open *$sym, "+<&=$_[0]" # usually works under any unix
		761	or open *$sym, "<&=$_[0]" # cygwin needs this
		762	or open *$sym, ">&=$_[0]" # or this
282	or return undef;	763	or return undef;
283		764
284	*AIO_FH	765	*$sym
285	}	766	}
286		767
287	min_parallel 4;	768	min_parallel 4;
288		769
289	END {	770	END {
290	max_parallel 0;	771	max_parallel 0;
291	}	772	}
292		773
293	1;	774	1;
294		775
		776	=head2 FORK BEHAVIOUR
		777
		778	This module should do "the right thing" when the process using it forks:
		779
		780	Before the fork, IO::AIO enters a quiescent state where no requests
		781	can be added in other threads and no results will be processed. After
		782	the fork the parent simply leaves the quiescent state and continues
		783	request/result processing, while the child clears the request/result
		784	queue (so the requests started before the fork will only be handled in
		785	the parent). Threads will be started on demand until the limit ste in the
		786	parent process has been reached again.
		787
		788	In short: the parent will, after a short pause, continue as if fork had
		789	not been called, while the child will act as if IO::AIO has not been used
		790	yet.
		791
295	=head1 SEE ALSO	792	=head1 SEE ALSO
296		793
297	L<Coro>, L<Linux::AIO>.	794	L<Coro>, L<Linux::AIO> (obsolete).
298		795
299	=head1 AUTHOR	796	=head1 AUTHOR
300		797
301	Marc Lehmann <schmorp@schmorp.de>	798	Marc Lehmann <schmorp@schmorp.de>
302	http://home.schmorp.de/	799	http://home.schmorp.de/

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Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC