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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.19 by root, Tue Jul 12 11:02:54 2005 UTC vs.
Revision 1.61 by root, Sun Oct 22 13:52:11 2006 UTC

…		…
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	in => sub { IO::AIO::poll_cb, 1 };	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);
32		45
33	# Danga::Socket	46	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	48	\&IO::AIO::poll_cb);
36
37		49
38	=head1 DESCRIPTION	50	=head1 DESCRIPTION
39		51
40	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
41	operating system supports.	53	operating system supports.
…		…
48	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,
49	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
50	remaining functionality would have to be implemented using threads anyway.	62	remaining functionality would have to be implemented using threads anyway.
51		63
52	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
53	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.
54		68
55	=cut	69	=cut
56		70
57	package IO::AIO;	71	package IO::AIO;
58		72
		73	no warnings;
		74	use strict 'vars';
		75
59	use base 'Exporter';	76	use base 'Exporter';
60		77
61	use Fcntl ();
62
63	BEGIN {	78	BEGIN {
64	$VERSION = 0.5;	79	our $VERSION = '2.0';
65		80
66	@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
67	aio_fsync aio_fdatasync aio_readahead);	83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group);
68	@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';
69		88
70	require XSLoader;	89	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	90	XSLoader::load ("IO::AIO", $VERSION);
72	}	91	}
73		92
74	=head1 FUNCTIONS	93	=head1 FUNCTIONS
75		94
76	=head2 AIO FUNCTIONS	95	=head2 AIO FUNCTIONS
…		…
81	which must be a code reference. This code reference will get called with	100	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	101	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	102	perl, which usually delivers "false") as it's sole argument when the given
84	syscall has been executed asynchronously.	103	syscall has been executed asynchronously.
85		104
86	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.
87		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
88	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
89	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
90	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
91	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.
92		123
93	=over 4	124	=over 4
94		125
95	=item aio_open $pathname, $flags, $mode, $callback	126	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		127
97	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
98	created filehandle for the file.	129	created filehandle for the file.
99		130
100	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,
101	for an explanation.	132	for an explanation.
102		133
103	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
104	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<$mode> specifies the mode of the newly created file, if it
		138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		139	except that it is mandatory (i.e. use C<0> if you don't create new files,
		140	and C<0666> or C<0777> if you do).
105		141
106	Example:	142	Example:
107		143
108	aio_open "/etc/passwd", O_RDONLY, 0, sub {	144	aio_open "/etc/passwd", O_RDONLY, 0, sub {
109	if ($_[0]) {	145	if ($_[0]) {
…		…
112	} else {	148	} else {
113	die "open failed: $!\n";	149	die "open failed: $!\n";
114	}	150	}
115	};	151	};
116		152
117	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
118		154
119	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
120	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
121	filehandle here, as perl will likely close the file descriptor itself when	157	filehandle here, as perl will likely close the file descriptor another
122	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
123	or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
124		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
125	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
126		165
127	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128		167
129	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>
130	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
131	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
132	like the syscall).	171	like the syscall).
133		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
134	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
135	offset C<0> within the scalar:	178	offset C<0> within the scalar:
136		179
137	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
138	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
139	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
140	};	183	};
141		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
142	=item aio_readahead $fh,$offset,$length, $callback	278	=item aio_readahead $fh,$offset,$length, $callback->($retval)
143		279
144	Asynchronously reads the specified byte range into the page cache, using
145	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
146	isn't Linux) the status will be C<-1> and C<$!> is set to ENOSYS.
147
148	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
149	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>
150	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
151	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
152	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
153	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
154	(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
155	file. The current file offset of the file is left unchanged.	287	file. The current file offset of the file is left unchanged.
156		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
157	=item aio_stat $fh_or_path, $callback	292	=item aio_stat $fh_or_path, $callback->($status)
158		293
159	=item aio_lstat $fh, $callback	294	=item aio_lstat $fh, $callback->($status)
160		295
161	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
162	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 _>
163	or C<-s _> etc...	298	or C<-s _> etc...
164		299
…		…
174	aio_stat "/etc/passwd", sub {	309	aio_stat "/etc/passwd", sub {
175	$_[0] and die "stat failed: $!";	310	$_[0] and die "stat failed: $!";
176	print "size is ", -s _, "\n";	311	print "size is ", -s _, "\n";
177	};	312	};
178		313
179	=item aio_unlink $pathname, $callback	314	=item aio_unlink $pathname, $callback->($status)
180		315
181	Asynchronously unlink (delete) a file and call the callback with the	316	Asynchronously unlink (delete) a file and call the callback with the
182	result code.	317	result code.
183		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 creates of many sub requests_
		358	C<$maxreq> specifies the maximum number of outstanding aio requests that
		359	this function generates. If it is C<< <= 0 >>, then a suitable default
		360	will be chosen (currently 6).
		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 = 6 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	my $statgrp = add $grp aio_group;
		451
		452	$schedcb = sub {
		453	if (@$entries) {
		454	if ($nreq < $maxreq) {
		455	my $ent = pop @$entries;
		456	$nreq++;
		457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		458	}
		459	} elsif (!$nreq) {
		460	# finished
		461	$statgrp->cancel;
		462	undef $statcb;
		463	undef $schedcb;
		464	$grp->result (\@dirs, \@nondirs);
		465	}
		466	};
		467	$statcb = sub {
		468	my ($status, $entry) = @_;
		469
		470	if ($status < 0) {
		471	$nreq--;
		472	push @nondirs, $entry;
		473	&$schedcb;
		474	} else {
		475	# need to check for real directory
		476	add $grp aio_lstat "$path/$entry", sub {
		477	$nreq--;
		478
		479	if (-d _) {
		480	push @dirs, $entry;
		481
		482	if (!--$ndirs) {
		483	push @nondirs, @$entries;
		484	$entries = [];
		485	}
		486	} else {
		487	push @nondirs, $entry;
		488	}
		489
		490	&$schedcb;
		491	}
		492	}
		493	};
		494
		495	&$schedcb while @$entries && $nreq < $maxreq;
		496	};
		497	};
		498	};
		499
		500	$grp
		501	}
		502
184	=item aio_fsync $fh, $callback	503	=item aio_fsync $fh, $callback->($status)
185		504
186	Asynchronously call fsync on the given filehandle and call the callback	505	Asynchronously call fsync on the given filehandle and call the callback
187	with the fsync result code.	506	with the fsync result code.
188		507
189	=item aio_fdatasync $fh, $callback	508	=item aio_fdatasync $fh, $callback->($status)
190		509
191	Asynchronously call fdatasync on the given filehandle and call the	510	Asynchronously call fdatasync on the given filehandle and call the
192	callback with the fdatasync result code.	511	callback with the fdatasync result code.
193		512
		513	If this call isn't available because your OS lacks it or it couldn't be
		514	detected, it will be emulated by calling C<fsync> instead.
		515
		516	=item aio_group $callback->(...)
		517
		518	[EXPERIMENTAL]
		519
		520	This is a very special aio request: Instead of doing something, it is a
		521	container for other aio requests, which is useful if you want to bundle
		522	many requests into a single, composite, request.
		523
		524	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		525	for more info.
		526
		527	Example:
		528
		529	my $grp = aio_group sub {
		530	print "all stats done\n";
		531	};
		532
		533	add $grp
		534	(aio_stat ...),
		535	(aio_stat ...),
		536	...;
		537
		538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		539
		540	Mainly used for debugging and benchmarking, this aio request puts one of
		541	the request workers to sleep for the given time.
		542
		543	While it is theoretically handy to have simple I/O scheduling requests
		544	like sleep and file handle readable/writable, the overhead this creates
		545	is immense, so do not use this function except to put your application
		546	under artificial I/O pressure.
		547
194	=back	548	=back
195		549
		550	=head2 IO::AIO::REQ CLASS
		551
		552	All non-aggregate C<aio_*> functions return an object of this class when
		553	called in non-void context.
		554
		555	A request always moves through the following five states in its lifetime,
		556	in order: B<ready> (request has been created, but has not been executed
		557	yet), B<execute> (request is currently being executed), B<pending>
		558	(request has been executed but callback has not been called yet),
		559	B<result> (results are being processed synchronously, includes calling the
		560	callback) and B<done> (request has reached the end of its lifetime and
		561	holds no resources anymore).
		562
		563	=over 4
		564
		565	=item $req->cancel
		566
		567	Cancels the request, if possible. Has the effect of skipping execution
		568	when entering the B<execute> state and skipping calling the callback when
		569	entering the the B<result> state, but will leave the request otherwise
		570	untouched. That means that requests that currently execute will not be
		571	stopped and resources held by the request will not be freed prematurely.
		572
		573	=back
		574
		575	=head2 IO::AIO::GRP CLASS
		576
		577	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		578	objects of this class, too.
		579
		580	A IO::AIO::GRP object is a special request that can contain multiple other
		581	aio requests.
		582
		583	You create one by calling the C<aio_group> constructing function with a
		584	callback that will be called when all contained requests have entered the
		585	C<done> state:
		586
		587	my $grp = aio_group sub {
		588	print "all requests are done\n";
		589	};
		590
		591	You add requests by calling the C<add> method with one or more
		592	C<IO::AIO::REQ> objects:
		593
		594	$grp->add (aio_unlink "...");
		595
		596	add $grp aio_stat "...", sub {
		597	$_[0] or return $grp->result ("error");
		598
		599	# add another request dynamically, if first succeeded
		600	add $grp aio_open "...", sub {
		601	$grp->result ("ok");
		602	};
		603	};
		604
		605	This makes it very easy to create composite requests (see the source of
		606	C<aio_move> for an application) that work and feel like simple requests.
		607
		608	The IO::AIO::GRP objects will be cleaned up during calls to
		609	C<IO::AIO::poll_cb>, just like any other request.
		610
		611	They can be canceled like any other request. Canceling will cancel not
		612	only the request itself, but also all requests it contains.
		613
		614	They can also can also be added to other IO::AIO::GRP objects.
		615
		616	You must not add requests to a group from within the group callback (or
		617	any later time).
		618
		619	Their lifetime, simplified, looks like this: when they are empty, they
		620	will finish very quickly. If they contain only requests that are in the
		621	C<done> state, they will also finish. Otherwise they will continue to
		622	exist.
		623
		624	That means after creating a group you have some time to add requests. And
		625	in the callbacks of those requests, you can add further requests to the
		626	group. And only when all those requests have finished will the the group
		627	itself finish.
		628
		629	=over 4
		630
		631	=item $grp->add (...)
		632
		633	=item add $grp ...
		634
		635	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		636	be added, including other groups, as long as you do not create circular
		637	dependencies.
		638
		639	Returns all its arguments.
		640
		641	=item $grp->result (...)
		642
		643	Set the result value(s) that will be passed to the group callback when all
		644	subrequests have finished. By default, no argument will be passed.
		645
		646	=item $grp->set_feeder ($callback->($grp))
		647
		648	[VERY EXPERIMENTAL]
		649
		650	Sets a feeder/generator on this group: every group can have an attached
		651	generator that generates requests if idle. The idea behind this is that,
		652	although you could just queue as many requests as you want in a group,
		653	this might starve other requests for a potentially long time. For
		654	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		655	requests, delaying any later requests for a long time.
		656
		657	To avoid this, and allow incremental generation of requests, you can
		658	instead a group and set a feeder on it that generates those requests. The
		659	feeder will be called whenever there are few enough (see C<feeder_limit>,
		660	below) requests active in the group itself and is expected to queue more
		661	requests.
		662
		663	The feeder can queue as many requests as it likes (i.e. C<add> does not
		664	impose any limits).
		665
		666	If the feeder does not queue more requests when called, it will be
		667	automatically removed from the group.
		668
		669	If the feeder limit is C<0>, it will be set to C<2> automatically.
		670
		671	Example:
		672
		673	# stat all files in @files, but only ever use four aio requests concurrently:
		674
		675	my $grp = aio_group sub { print "finished\n" };
		676	$grp->feeder_limit (4);
		677	$grp->set_feeder (sub {
		678	my $file = pop @files
		679	or return;
		680
		681	add $grp aio_stat $file, sub { ... };
		682	});
		683
		684	=item $grp->feeder_limit ($num)
		685
		686	Sets the feeder limit for the group: The feeder will be called whenever
		687	the group contains less than this many requests.
		688
		689	Setting the limit to C<0> will pause the feeding process.
		690
		691	=back
		692
196	=head2 SUPPORT FUNCTIONS	693	=head2 SUPPORT FUNCTIONS
197		694
198	=over 4	695	=over 4
199		696
200	=item $fileno = IO::AIO::poll_fileno	697	=item $fileno = IO::AIO::poll_fileno
201		698
202	Return the I<request result pipe filehandle>. This filehandle must be	699	Return the I<request result pipe file descriptor>. This filehandle must be
203	polled for reading by some mechanism outside this module (e.g. Event	700	polled for reading by some mechanism outside this module (e.g. Event or
204	or select, see below). If the pipe becomes readable you have to call	701	select, see below or the SYNOPSIS). If the pipe becomes readable you have
205	C<poll_cb> to check the results.	702	to call C<poll_cb> to check the results.
206		703
207	See C<poll_cb> for an example.	704	See C<poll_cb> for an example.
208		705
209	=item IO::AIO::poll_cb	706	=item IO::AIO::poll_cb
210		707
211	Process all outstanding events on the result pipe. You have to call this	708	Process all outstanding events on the result pipe. You have to call this
212	regularly. Returns the number of events processed. Returns immediately	709	regularly. Returns the number of events processed. Returns immediately
213	when no events are outstanding.	710	when no events are outstanding.
214		711
215	You can use Event to multiplex, e.g.:	712	Example: Install an Event watcher that automatically calls
		713	IO::AIO::poll_cb with high priority:
216		714
217	Event->io (fd => IO::AIO::poll_fileno,	715	Event->io (fd => IO::AIO::poll_fileno,
218	poll => 'r', async => 1,	716	poll => 'r', async => 1,
219	cb => \&IO::AIO::poll_cb);	717	cb => \&IO::AIO::poll_cb);
220		718
221	=item IO::AIO::poll_wait	719	=item IO::AIO::poll_wait
222		720
223	Wait till the result filehandle becomes ready for reading (simply does a	721	Wait till the result filehandle becomes ready for reading (simply does a
224	select on the filehandle. This is useful if you want to synchronously wait	722	C<select> on the filehandle. This is useful if you want to synchronously wait
225	for some requests to finish).	723	for some requests to finish).
226		724
227	See C<nreqs> for an example.	725	See C<nreqs> for an example.
228		726
229	=item IO::AIO::nreqs	727	=item IO::AIO::nreqs
230		728
231	Returns the number of requests currently outstanding.	729	Returns the number of requests currently outstanding (i.e. for which their
		730	callback has not been invoked yet).
232		731
233	Example: wait till there are no outstanding requests anymore:	732	Example: wait till there are no outstanding requests anymore:
234		733
235	IO::AIO::poll_wait, IO::AIO::poll_cb	734	IO::AIO::poll_wait, IO::AIO::poll_cb
236	while IO::AIO::nreqs;	735	while IO::AIO::nreqs;
…		…
253	IO::AIO::poll_wait, IO::AIO::poll_cb	752	IO::AIO::poll_wait, IO::AIO::poll_cb
254	if IO::AIO::nreqs;	753	if IO::AIO::nreqs;
255		754
256	=item IO::AIO::min_parallel $nthreads	755	=item IO::AIO::min_parallel $nthreads
257		756
258	Set the minimum number of AIO threads to C<$nthreads>. The default is	757	Set the minimum number of AIO threads to C<$nthreads>. The current
259	C<1>, which means a single asynchronous operation can be done at one time	758	default is C<8>, which means eight asynchronous operations can execute
260	(the number of outstanding operations, however, is unlimited).	759	concurrently at any one time (the number of outstanding requests,
		760	however, is unlimited).
261		761
		762	IO::AIO starts threads only on demand, when an AIO request is queued and
		763	no free thread exists.
		764
262	It is recommended to keep the number of threads low, as some Linux	765	It is recommended to keep the number of threads relatively low, as some
263	kernel versions will scale negatively with the number of threads (higher	766	Linux kernel versions will scale negatively with the number of threads
264	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	767	(higher parallelity => MUCH higher latency). With current Linux 2.6
265	threads should be fine.	768	versions, 4-32 threads should be fine.
266		769
267	Under normal circumstances you don't need to call this function, as this	770	Under most circumstances you don't need to call this function, as the
268	module automatically starts some threads (the exact number might change,	771	module selects a default that is suitable for low to moderate load.
269	and is currently 4).
270		772
271	=item IO::AIO::max_parallel $nthreads	773	=item IO::AIO::max_parallel $nthreads
272		774
273	Sets the maximum number of AIO threads to C<$nthreads>. If more than	775	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
274	the specified number of threads are currently running, kill them. This	776	specified number of threads are currently running, this function kills
275	function blocks until the limit is reached.	777	them. This function blocks until the limit is reached.
		778
		779	While C<$nthreads> are zero, aio requests get queued but not executed
		780	until the number of threads has been increased again.
276		781
277	This module automatically runs C<max_parallel 0> at program end, to ensure	782	This module automatically runs C<max_parallel 0> at program end, to ensure
278	that all threads are killed and that there are no outstanding requests.	783	that all threads are killed and that there are no outstanding requests.
279		784
280	Under normal circumstances you don't need to call this function.	785	Under normal circumstances you don't need to call this function.
…		…
284	Sets the maximum number of outstanding requests to C<$nreqs>. If you	789	Sets the maximum number of outstanding requests to C<$nreqs>. If you
285	try to queue up more than this number of requests, the caller will block until	790	try to queue up more than this number of requests, the caller will block until
286	some requests have been handled.	791	some requests have been handled.
287		792
288	The default is very large, so normally there is no practical limit. If you	793	The default is very large, so normally there is no practical limit. If you
289	queue up many requests in a loop it it often improves speed if you set	794	queue up many requests in a loop it often improves speed if you set
290	this to a relatively low number, such as C<100>.	795	this to a relatively low number, such as C<100>.
291		796
292	Under normal circumstances you don't need to call this function.	797	Under normal circumstances you don't need to call this function.
293		798
294	=back	799	=back
…		…
297		802
298	# support function to convert a fd into a perl filehandle	803	# support function to convert a fd into a perl filehandle
299	sub _fd2fh {	804	sub _fd2fh {
300	return undef if $_[0] < 0;	805	return undef if $_[0] < 0;
301		806
302	# try to be perl5.6-compatible	807	# try to generate nice filehandles
303	local *AIO_FH;	808	my $sym = "IO::AIO::fd#$_[0]";
304	open AIO_FH, "+<&=$_[0]"	809	local *$sym;
		810
		811	open *$sym, "+<&=$_[0]" # usually works under any unix
		812	or open *$sym, "<&=$_[0]" # cygwin needs this
		813	or open *$sym, ">&=$_[0]" # or this
305	or return undef;	814	or return undef;
306		815
307	*AIO_FH	816	*$sym
308	}	817	}
309		818
310	min_parallel 4;	819	min_parallel 8;
311		820
312	END {	821	END {
313	max_parallel 0;	822	max_parallel 0;
314	}	823	}
315		824
316	1;	825	1;
317		826
		827	=head2 FORK BEHAVIOUR
		828
		829	This module should do "the right thing" when the process using it forks:
		830
		831	Before the fork, IO::AIO enters a quiescent state where no requests
		832	can be added in other threads and no results will be processed. After
		833	the fork the parent simply leaves the quiescent state and continues
		834	request/result processing, while the child clears the request/result
		835	queue (so the requests started before the fork will only be handled in
		836	the parent). Threads will be started on demand until the limit ste in the
		837	parent process has been reached again.
		838
		839	In short: the parent will, after a short pause, continue as if fork had
		840	not been called, while the child will act as if IO::AIO has not been used
		841	yet.
		842
		843	=head2 MEMORY USAGE
		844
		845	Each aio request uses - depending on your architecture - around 128 bytes
		846	of memory. In addition, stat requests need a stat buffer (possibly a few
		847	hundred bytes). Perl scalars and other data passed into aio requests will
		848	also be locked.
		849
		850	This is now awfully much, so queuing lots of requests is not usually a
		851	problem.
		852
		853	Each thread needs a stack area which is usually around 16k, sometimes much
		854	larger, depending on the OS.
		855
318	=head1 SEE ALSO	856	=head1 SEE ALSO
319		857
320	L<Coro>, L<Linux::AIO>.	858	L<Coro>, L<Linux::AIO> (obsolete).
321		859
322	=head1 AUTHOR	860	=head1 AUTHOR
323		861
324	Marc Lehmann <schmorp@schmorp.de>	862	Marc Lehmann <schmorp@schmorp.de>
325	http://home.schmorp.de/	863	http://home.schmorp.de/

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Revision 1.61 by root, Sun Oct 22 13:52:11 2006 UTC