[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 1.54 by root, Sun Oct 22 00:19:05 2006 UTC

…		…
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
		8
		9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		10	my ($fh) = @_;
		11	...
		12	};
		13
		14	aio_unlink "/tmp/file", sub { };
		15
		16	aio_read $fh, 30000, 1024, $buffer, 0, sub {
		17	$_[0] > 0 or die "read error: $!";
		18	};
		19
		20	use IO::AIO 2; # version has aio objects
		21
		22	my $req = aio_unlink "/tmp/file", sub { };
		23	$req->cancel; # cancel request if still in queue
		24
		25	# AnyEvent
		26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		28
		29	# Event
		30	Event->io (fd => IO::AIO::poll_fileno,
		31	poll => 'r',
		32	cb => \&IO::AIO::poll_cb);
		33
		34	# Glib/Gtk2
		35	add_watch Glib::IO IO::AIO::poll_fileno,
		36	in => sub { IO::AIO::poll_cb; 1 };
		37
		38	# Tk
		39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		40	readable => \&IO::AIO::poll_cb);
		41
		42	# Danga::Socket
		43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		44	\&IO::AIO::poll_cb);
		45
8		46
9	=head1 DESCRIPTION	47	=head1 DESCRIPTION
10		48
11	This module implements asynchronous I/O using whatever means your	49	This module implements asynchronous I/O using whatever means your
12	operating system supports.	50	operating system supports.
…		…
19	not well-supported (Linux doesn't allow them on normal files currently,	57	not well-supported (Linux doesn't allow them on normal files currently,
20	for example), and they would only support aio_read and aio_write, so the	58	for example), and they would only support aio_read and aio_write, so the
21	remaining functionality would have to be implemented using threads anyway.	59	remaining functionality would have to be implemented using threads anyway.
22		60
23	Although the module will work with in the presence of other threads, it is	61	Although the module will work with in the presence of other threads, it is
24	currently not reentrant, so use appropriate locking yourself.	62	currently not reentrant, so use appropriate locking yourself, always call
		63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other
		64	C<aio_> functions) recursively.
25		65
26	=cut	66	=cut
27		67
28	package IO::AIO;	68	package IO::AIO;
29		69
		70	no warnings;
		71	use strict 'vars';
		72
30	use base 'Exporter';	73	use base 'Exporter';
31		74
32	use Fcntl ();
33
34	BEGIN {	75	BEGIN {
35	$VERSION = 0.2;	76	our $VERSION = '1.99';
36		77
37	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
		79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
38	aio_fsync aio_fdatasync aio_readahead);	80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		81	aio_group);
39	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
		83
		84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
40		85
41	require XSLoader;	86	require XSLoader;
42	XSLoader::load IO::AIO, $VERSION;	87	XSLoader::load ("IO::AIO", $VERSION);
43	}	88	}
44		89
45	=head1 FUNCTIONS	90	=head1 FUNCTIONS
46		91
47	=head2 AIO FUNCTIONS	92	=head2 AIO FUNCTIONS
48		93
49	All the C<aio_*> calls are more or less thin wrappers around the syscall	94	All the C<aio_*> calls are more or less thin wrappers around the syscall
50	with the same name (sans C<aio_>). The arguments are similar or identical,	95	with the same name (sans C<aio_>). The arguments are similar or identical,
51	and they all accept an additional C<$callback> argument which must be	96	and they all accept an additional (and optional) C<$callback> argument
52	a code reference. This code reference will get called with the syscall	97	which must be a code reference. This code reference will get called with
53	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	98	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
54	usually delivers "false") as it's sole argument when the given syscall has	99	perl, which usually delivers "false") as it's sole argument when the given
55	been executed asynchronously.	100	syscall has been executed asynchronously.
56		101
57	All functions that expect a filehandle will also accept a file descriptor.	102	All functions expecting a filehandle keep a copy of the filehandle
		103	internally until the request has finished.
58		104
		105	All non-composite requests (requests that are not broken down into
		106	multiple requests) return objects of type L<IO::AIO::REQ> that allow
		107	further manipulation of running requests.
		108
59	The filenames you pass to these routines I<must> be absolute. The reason	109	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	110	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	111	request is being executed, the current working directory could have
		112	changed. Alternatively, you can make sure that you never change the
62	never change the current working directory.	113	current working directory.
		114
		115	To encode pathnames to byte form, either make sure you either: a)
		116	always pass in filenames you got from outside (command line, readdir
		117	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		118	your pathnames to the locale (or other) encoding in effect in the user
		119	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		120	use something else.
63		121
64	=over 4	122	=over 4
65		123
66	=item aio_open $pathname, $flags, $mode, $callback	124	=item aio_open $pathname, $flags, $mode, $callback->($fh)
67		125
68	Asynchronously open or create a file and call the callback with a newly	126	Asynchronously open or create a file and call the callback with a newly
69	created filehandle for the file.	127	created filehandle for the file.
70		128
71	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	129	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
72	for an explanation.	130	for an explanation.
73		131
74	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	132	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
75	list. They are the same as used in C<sysopen>.	133	list. They are the same as used by C<sysopen>.
		134
		135	Likewise, C<$mode> specifies the mode of the newly created file, if it
		136	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		137	except that it is mandatory (i.e. use C<0> if you don't create new files,
		138	and C<0666> or C<0777> if you do).
76		139
77	Example:	140	Example:
78		141
79	aio_open "/etc/passwd", O_RDONLY, 0, sub {	142	aio_open "/etc/passwd", O_RDONLY, 0, sub {
80	if ($_[0]) {	143	if ($_[0]) {
…		…
83	} else {	146	} else {
84	die "open failed: $!\n";	147	die "open failed: $!\n";
85	}	148	}
86	};	149	};
87		150
88	=item aio_close $fh, $callback	151	=item aio_close $fh, $callback->($status)
89		152
90	Asynchronously close a file and call the callback with the result	153	Asynchronously close a file and call the callback with the result
91	code. I<WARNING:> although accepted, you should not pass in a perl	154	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	155	filehandle here, as perl will likely close the file descriptor another
93	the filehandle is destroyed. Normally, you can safely call perls C<close>	156	time when the filehandle is destroyed. Normally, you can safely call perls
94	or just let filehandles go out of scope.	157	C<close> or just let filehandles go out of scope.
95		158
		159	This is supposed to be a bug in the API, so that might change. It's
		160	therefore best to avoid this function.
		161
96	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
97		163
98	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
99		165
100	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	166	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	167	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	168	callback without the actual number of bytes read (or -1 on error, just
103	like the syscall).	169	like the syscall).
104		170
		171	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		172	is outstanding. Modifying it can result in segfaults or WW3 (if the
		173	necessary/optional hardware is installed).
		174
105	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	175	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
106	offset C<0> within the scalar:	176	offset C<0> within the scalar:
107		177
108	aio_read $fh, 7, 15, $buffer, 0, sub {	178	aio_read $fh, 7, 15, $buffer, 0, sub {
109	$_[0] >= 0 or die "read error: $!";	179	$_[0] > 0 or die "read error: $!";
110	print "read <$buffer>\n";	180	print "read $_[0] bytes: <$buffer>\n";
111	};	181	};
112		182
		183	=item aio_move $srcpath, $dstpath, $callback->($status)
		184
		185	Try to move the I<file> (directories not supported as either source or
		186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		187	the C<0> (error) or C<-1> ok.
		188
		189	This is a composite request that tries to rename(2) the file first. If
		190	rename files with C<EXDEV>, it creates the destination file with mode 0200
		191	and copies the contents of the source file into it using C<aio_sendfile>,
		192	followed by restoring atime, mtime, access mode and uid/gid, in that
		193	order, and unlinking the C<$srcpath>.
		194
		195	If an error occurs, the partial destination file will be unlinked, if
		196	possible, except when setting atime, mtime, access mode and uid/gid, where
		197	errors are being ignored.
		198
		199	=cut
		200
		201	sub aio_move($$$) {
		202	my ($src, $dst, $cb) = @_;
		203
		204	aio_rename $src, $dst, sub {
		205	if ($_[0] && $! == EXDEV) {
		206	aio_open $src, O_RDONLY, 0, sub {
		207	if (my $src_fh = $_[0]) {
		208	my @stat = stat $src_fh;
		209
		210	aio_open $dst, O_WRONLY, 0200, sub {
		211	if (my $dst_fh = $_[0]) {
		212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		213	close $src_fh;
		214
		215	if ($_[0] == $stat[7]) {
		216	utime $stat[8], $stat[9], $dst;
		217	chmod $stat[2] & 07777, $dst_fh;
		218	chown $stat[4], $stat[5], $dst_fh;
		219	close $dst_fh;
		220
		221	aio_unlink $src, sub {
		222	$cb->($_[0]);
		223	};
		224	} else {
		225	my $errno = $!;
		226	aio_unlink $dst, sub {
		227	$! = $errno;
		228	$cb->(-1);
		229	};
		230	}
		231	};
		232	} else {
		233	$cb->(-1);
		234	}
		235	},
		236
		237	} else {
		238	$cb->(-1);
		239	}
		240	};
		241	} else {
		242	$cb->($_[0]);
		243	}
		244	};
		245	}
		246
		247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		248
		249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		250	reading at byte offset C<$in_offset>, and starts writing at the current
		251	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		252	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		253	other.
		254
		255	This call tries to make use of a native C<sendfile> syscall to provide
		256	zero-copy operation. For this to work, C<$out_fh> should refer to a
		257	socket, and C<$in_fh> should refer to mmap'able file.
		258
		259	If the native sendfile call fails or is not implemented, it will be
		260	emulated, so you can call C<aio_sendfile> on any type of filehandle
		261	regardless of the limitations of the operating system.
		262
		263	Please note, however, that C<aio_sendfile> can read more bytes from
		264	C<$in_fh> than are written, and there is no way to find out how many
		265	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		266	provides the number of bytes written to C<$out_fh>. Only if the result
		267	value equals C<$length> one can assume that C<$length> bytes have been
		268	read.
		269
113	=item aio_readahead $fh,$offset,$length, $callback	270	=item aio_readahead $fh,$offset,$length, $callback->($retval)
114		271
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	272	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>	273	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	274	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	275	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	276	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	277	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	278	(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.	279	file. The current file offset of the file is left unchanged.
127		280
		281	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		282	emulated by simply reading the data, which would have a similar effect.
		283
128	=item aio_stat $fh_or_path, $callback	284	=item aio_stat $fh_or_path, $callback->($status)
129		285
130	=item aio_lstat $fh, $callback	286	=item aio_lstat $fh, $callback->($status)
131		287
132	Works like perl's C<stat> or C<lstat> in void context. The callback will	288	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 _>	289	be called after the stat and the results will be available using C<stat _>
134	or C<-s _> etc...	290	or C<-s _> etc...
135		291
…		…
145	aio_stat "/etc/passwd", sub {	301	aio_stat "/etc/passwd", sub {
146	$_[0] and die "stat failed: $!";	302	$_[0] and die "stat failed: $!";
147	print "size is ", -s _, "\n";	303	print "size is ", -s _, "\n";
148	};	304	};
149		305
150	=item aio_unlink $pathname, $callback	306	=item aio_unlink $pathname, $callback->($status)
151		307
152	Asynchronously unlink (delete) a file and call the callback with the	308	Asynchronously unlink (delete) a file and call the callback with the
153	result code.	309	result code.
154		310
		311	=item aio_link $srcpath, $dstpath, $callback->($status)
		312
		313	Asynchronously create a new link to the existing object at C<$srcpath> at
		314	the path C<$dstpath> and call the callback with the result code.
		315
		316	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		317
		318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		319	the path C<$dstpath> and call the callback with the result code.
		320
		321	=item aio_rename $srcpath, $dstpath, $callback->($status)
		322
		323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		324	rename(2) and call the callback with the result code.
		325
		326	=item aio_rmdir $pathname, $callback->($status)
		327
		328	Asynchronously rmdir (delete) a directory and call the callback with the
		329	result code.
		330
		331	=item aio_readdir $pathname, $callback->($entries)
		332
		333	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		334	directory (i.e. opendir + readdir + closedir). The entries will not be
		335	sorted, and will B<NOT> include the C<.> and C<..> entries.
		336
		337	The callback a single argument which is either C<undef> or an array-ref
		338	with the filenames.
		339
		340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		341
		342	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		343	separate the entries of directory C<$path> into two sets of names, ones
		344	you can recurse into (directories or links to them), and ones you cannot
		345	recurse into (everything else).
		346
		347	C<aio_scandir> is a composite request that consists of many sub
		348	requests. C<$maxreq> specifies the maximum number of outstanding aio
		349	requests that this function generates. If it is C<< <= 0 >>, then a
		350	suitable default will be chosen (currently 8).
		351
		352	On error, the callback is called without arguments, otherwise it receives
		353	two array-refs with path-relative entry names.
		354
		355	Example:
		356
		357	aio_scandir $dir, 0, sub {
		358	my ($dirs, $nondirs) = @_;
		359	print "real directories: @$dirs\n";
		360	print "everything else: @$nondirs\n";
		361	};
		362
		363	Implementation notes.
		364
		365	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		366
		367	After reading the directory, the modification time, size etc. of the
		368	directory before and after the readdir is checked, and if they match (and
		369	isn't the current time), the link count will be used to decide how many
		370	entries are directories (if >= 2). Otherwise, no knowledge of the number
		371	of subdirectories will be assumed.
		372
		373	Then entries will be sorted into likely directories (everything without
		374	a non-initial dot currently) and likely non-directories (everything
		375	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		376	likely directories first. If that succeeds, it assumes that the entry
		377	is a directory or a symlink to directory (which will be checked
		378	seperately). This is often faster than stat'ing the entry itself because
		379	filesystems might detect the type of the entry without reading the inode
		380	data (e.g. ext2fs filetype feature).
		381
		382	If the known number of directories (link count - 2) has been reached, the
		383	rest of the entries is assumed to be non-directories.
		384
		385	This only works with certainty on POSIX (= UNIX) filesystems, which
		386	fortunately are the vast majority of filesystems around.
		387
		388	It will also likely work on non-POSIX filesystems with reduced efficiency
		389	as those tend to return 0 or 1 as link counts, which disables the
		390	directory counting heuristic.
		391
		392	=cut
		393
		394	sub aio_scandir($$$) {
		395	my ($path, $maxreq, $cb) = @_;
		396
		397	$maxreq = 8 if $maxreq <= 0;
		398
		399	# stat once
		400	aio_stat $path, sub {
		401	return $cb->() if $_[0];
		402	my $now = time;
		403	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		404
		405	# read the directory entries
		406	aio_readdir $path, sub {
		407	my $entries = shift
		408	or return $cb->();
		409
		410	# stat the dir another time
		411	aio_stat $path, sub {
		412	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		413
		414	my $ndirs;
		415
		416	# take the slow route if anything looks fishy
		417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		418	$ndirs = -1;
		419	} else {
		420	# if nlink == 2, we are finished
		421	# on non-posix-fs's, we rely on nlink < 2
		422	$ndirs = (stat _)[3] - 2
		423	or return $cb->([], $entries);
		424	}
		425
		426	# sort into likely dirs and likely nondirs
		427	# dirs == files without ".", short entries first
		428	$entries = [map $_->[0],
		429	sort { $b->[1] cmp $a->[1] }
		430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		431	@$entries];
		432
		433	my (@dirs, @nondirs);
		434
		435	my ($statcb, $schedcb);
		436	my $nreq = 0;
		437
		438	$schedcb = sub {
		439	if (@$entries) {
		440	if ($nreq < $maxreq) {
		441	my $ent = pop @$entries;
		442	$nreq++;
		443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		444	}
		445	} elsif (!$nreq) {
		446	# finished
		447	undef $statcb;
		448	undef $schedcb;
		449	$cb->(\@dirs, \@nondirs) if $cb;
		450	undef $cb;
		451	}
		452	};
		453	$statcb = sub {
		454	my ($status, $entry) = @_;
		455
		456	if ($status < 0) {
		457	$nreq--;
		458	push @nondirs, $entry;
		459	&$schedcb;
		460	} else {
		461	# need to check for real directory
		462	aio_lstat "$path/$entry", sub {
		463	$nreq--;
		464
		465	if (-d _) {
		466	push @dirs, $entry;
		467
		468	if (!--$ndirs) {
		469	push @nondirs, @$entries;
		470	$entries = [];
		471	}
		472	} else {
		473	push @nondirs, $entry;
		474	}
		475
		476	&$schedcb;
		477	}
		478	}
		479	};
		480
		481	&$schedcb while @$entries && $nreq < $maxreq;
		482	};
		483	};
		484	};
		485	}
		486
155	=item aio_fsync $fh, $callback	487	=item aio_fsync $fh, $callback->($status)
156		488
157	Asynchronously call fsync on the given filehandle and call the callback	489	Asynchronously call fsync on the given filehandle and call the callback
158	with the fsync result code.	490	with the fsync result code.
159		491
160	=item aio_fdatasync $fh, $callback	492	=item aio_fdatasync $fh, $callback->($status)
161		493
162	Asynchronously call fdatasync on the given filehandle and call the	494	Asynchronously call fdatasync on the given filehandle and call the
163	callback with the fdatasync result code.	495	callback with the fdatasync result code.
164		496
		497	If this call isn't available because your OS lacks it or it couldn't be
		498	detected, it will be emulated by calling C<fsync> instead.
		499
		500	=item aio_group $callback->()
		501
		502	=item aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		503
		504	Mainly used for debugging and benchmarking, this aio request puts one of
		505	the request workers to sleep for the given time.
		506
165	=back	507	=back
166		508
		509	=head2 IO::AIO::REQ CLASS
		510
		511	All non-aggregate C<aio_*> functions return an object of this class when
		512	called in non-void context.
		513
		514	A request always moves through the following five states in its lifetime,
		515	in order: B<ready> (request has been created, but has not been executed
		516	yet), B<execute> (request is currently being executed), B<pending>
		517	(request has been executed but callback has not been called yet),
		518	B<result> (results are being processed synchronously, includes calling the
		519	callback) and B<done> (request has reached the end of its lifetime and
		520	holds no resources anymore).
		521
		522	=over 4
		523
		524	=item $req->cancel
		525
		526	Cancels the request, if possible. Has the effect of skipping execution
		527	when entering the B<execute> state and skipping calling the callback when
		528	entering the the B<result> state, but will leave the request otherwise
		529	untouched. That means that requests that currently execute will not be
		530	stopped and resources held by the request will not be freed prematurely.
		531
		532	=back
		533
167	=head2 SUPPORT FUNCTIONS	534	=head2 SUPPORT FUNCTIONS
168		535
169	=over 4	536	=over 4
170		537
171	=item $fileno = IO::AIO::poll_fileno	538	=item $fileno = IO::AIO::poll_fileno
172		539
173	Return the I<request result pipe filehandle>. This filehandle must be	540	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	541	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	542	select, see below or the SYNOPSIS). If the pipe becomes readable you have
176	C<poll_cb> to check the results.	543	to call C<poll_cb> to check the results.
177		544
178	See C<poll_cb> for an example.	545	See C<poll_cb> for an example.
179		546
180	=item IO::AIO::poll_cb	547	=item IO::AIO::poll_cb
181		548
182	Process all outstanding events on the result pipe. You have to call this	549	Process all outstanding events on the result pipe. You have to call this
183	regularly. Returns the number of events processed. Returns immediately	550	regularly. Returns the number of events processed. Returns immediately
184	when no events are outstanding.	551	when no events are outstanding.
185		552
186	You can use Event to multiplex, e.g.:	553	Example: Install an Event watcher that automatically calls
		554	IO::AIO::poll_cb with high priority:
187		555
188	Event->io (fd => IO::AIO::poll_fileno,	556	Event->io (fd => IO::AIO::poll_fileno,
189	poll => 'r', async => 1,	557	poll => 'r', async => 1,
190	cb => \&IO::AIO::poll_cb);	558	cb => \&IO::AIO::poll_cb);
191		559
192	=item IO::AIO::poll_wait	560	=item IO::AIO::poll_wait
193		561
194	Wait till the result filehandle becomes ready for reading (simply does a	562	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	563	C<select> on the filehandle. This is useful if you want to synchronously wait
196	for some requests to finish).	564	for some requests to finish).
197		565
198	See C<nreqs> for an example.	566	See C<nreqs> for an example.
199		567
200	=item IO::AIO::nreqs	568	=item IO::AIO::nreqs
201		569
202	Returns the number of requests currently outstanding.	570	Returns the number of requests currently outstanding (i.e. for which their
		571	callback has not been invoked yet).
203		572
204	Example: wait till there are no outstanding requests anymore:	573	Example: wait till there are no outstanding requests anymore:
205		574
206	IO::AIO::poll_wait, IO::AIO::poll_cb	575	IO::AIO::poll_wait, IO::AIO::poll_cb
207	while IO::AIO::nreqs;	576	while IO::AIO::nreqs;
208		577
		578	=item IO::AIO::flush
		579
		580	Wait till all outstanding AIO requests have been handled.
		581
		582	Strictly equivalent to:
		583
		584	IO::AIO::poll_wait, IO::AIO::poll_cb
		585	while IO::AIO::nreqs;
		586
		587	=item IO::AIO::poll
		588
		589	Waits until some requests have been handled.
		590
		591	Strictly equivalent to:
		592
		593	IO::AIO::poll_wait, IO::AIO::poll_cb
		594	if IO::AIO::nreqs;
		595
209	=item IO::AIO::min_parallel $nthreads	596	=item IO::AIO::min_parallel $nthreads
210		597
211	Set the minimum number of AIO threads to C<$nthreads>. The default is	598	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	599	is C<4>, which means four asynchronous operations can be done at one time
213	(the number of outstanding operations, however, is unlimited).	600	(the number of outstanding operations, however, is unlimited).
		601
		602	IO::AIO starts threads only on demand, when an AIO request is queued and
		603	no free thread exists.
214		604
215	It is recommended to keep the number of threads low, as some Linux	605	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	606	kernel versions will scale negatively with the number of threads (higher
217	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
218	threads should be fine.	608	threads should be fine.
219		609
220	Under normal circumstances you don't need to call this function, as this	610	Under most circumstances you don't need to call this function, as the
221	module automatically starts some threads (the exact number might change,	611	module selects a default that is suitable for low to moderate load.
222	and is currently 4).
223		612
224	=item IO::AIO::max_parallel $nthreads	613	=item IO::AIO::max_parallel $nthreads
225		614
226	Sets the maximum number of AIO threads to C<$nthreads>. If more than	615	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
227	the specified number of threads are currently running, kill them. This	616	specified number of threads are currently running, this function kills
228	function blocks until the limit is reached.	617	them. This function blocks until the limit is reached.
		618
		619	While C<$nthreads> are zero, aio requests get queued but not executed
		620	until the number of threads has been increased again.
229		621
230	This module automatically runs C<max_parallel 0> at program end, to ensure	622	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.	623	that all threads are killed and that there are no outstanding requests.
232		624
233	Under normal circumstances you don't need to call this function.	625	Under normal circumstances you don't need to call this function.
…		…
237	Sets the maximum number of outstanding requests to C<$nreqs>. If you	629	Sets the maximum number of outstanding requests to C<$nreqs>. If you
238	try to queue up more than this number of requests, the caller will block until	630	try to queue up more than this number of requests, the caller will block until
239	some requests have been handled.	631	some requests have been handled.
240		632
241	The default is very large, so normally there is no practical limit. If you	633	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	634	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>.	635	this to a relatively low number, such as C<100>.
244		636
245	Under normal circumstances you don't need to call this function.	637	Under normal circumstances you don't need to call this function.
246		638
247	=back	639	=back
…		…
250		642
251	# support function to convert a fd into a perl filehandle	643	# support function to convert a fd into a perl filehandle
252	sub _fd2fh {	644	sub _fd2fh {
253	return undef if $_[0] < 0;	645	return undef if $_[0] < 0;
254		646
255	# try to be perl5.6-compatible	647	# try to generate nice filehandles
256	local *AIO_FH;	648	my $sym = "IO::AIO::fd#$_[0]";
257	open AIO_FH, "+<&=$_[0]"	649	local *$sym;
		650
		651	open *$sym, "+<&=$_[0]" # usually works under any unix
		652	or open *$sym, "<&=$_[0]" # cygwin needs this
		653	or open *$sym, ">&=$_[0]" # or this
258	or return undef;	654	or return undef;
259		655
260	*AIO_FH	656	*$sym
261	}	657	}
262		658
263	min_parallel 4;	659	min_parallel 4;
264		660
265	END {	661	END {
266	max_parallel 0;	662	max_parallel 0;
267	}	663	}
268		664
269	1;	665	1;
270		666
		667	=head2 FORK BEHAVIOUR
		668
		669	This module should do "the right thing" when the process using it forks:
		670
		671	Before the fork, IO::AIO enters a quiescent state where no requests
		672	can be added in other threads and no results will be processed. After
		673	the fork the parent simply leaves the quiescent state and continues
		674	request/result processing, while the child clears the request/result
		675	queue (so the requests started before the fork will only be handled in
		676	the parent). Threads will be started on demand until the limit ste in the
		677	parent process has been reached again.
		678
		679	In short: the parent will, after a short pause, continue as if fork had
		680	not been called, while the child will act as if IO::AIO has not been used
		681	yet.
		682
271	=head1 SEE ALSO	683	=head1 SEE ALSO
272		684
273	L<Coro>, L<Linux::AIO>.	685	L<Coro>, L<Linux::AIO> (obsolete).
274		686
275	=head1 AUTHOR	687	=head1 AUTHOR
276		688
277	Marc Lehmann <schmorp@schmorp.de>	689	Marc Lehmann <schmorp@schmorp.de>
278	http://home.schmorp.de/	690	http://home.schmorp.de/

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Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC