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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.20 by root, Tue Jul 12 11:29:40 2005 UTC vs.
Revision 1.57 by root, Sun Oct 22 01:28:31 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	for this is that at the time the request is being executed, the current	112	encoded in byte form. The reason for the former is that at the time the
90	working directory could have changed. Alternatively, you can make sure	113	request is being executed, the current working directory could have
91	that you never change the current working directory.	114	changed. Alternatively, you can make sure that you never change the
		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,
…		…
117	} else {	148	} else {
118	die "open failed: $!\n";	149	die "open failed: $!\n";
119	}	150	}
120	};	151	};
121		152
122	=item aio_close $fh, $callback	153	=item aio_close $fh, $callback->($status)
123		154
124	Asynchronously close a file and call the callback with the result	155	Asynchronously close a file and call the callback with the result
125	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
126	filehandle here, as perl will likely close the file descriptor another	157	filehandle here, as perl will likely close the file descriptor another
127	time when the filehandle is destroyed. Normally, you can safely call perls	158	time when the filehandle is destroyed. Normally, you can safely call perls
128	C<close> or just let filehandles go out of scope.	159	C<close> or just let filehandles go out of scope.
129		160
130	This is supposed to be a bug in the API, so that might change. It's	161	This is supposed to be a bug in the API, so that might change. It's
131	therefore best to avoid this function.	162	therefore best to avoid this function.
132		163
133	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
134		165
135	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
136		167
137	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>
138	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
139	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
140	like the syscall).	171	like the syscall).
141		172
		173	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		174	is outstanding. Modifying it can result in segfaults or WW3 (if the
		175	necessary/optional hardware is installed).
		176
142	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
143	offset C<0> within the scalar:	178	offset C<0> within the scalar:
144		179
145	aio_read $fh, 7, 15, $buffer, 0, sub {	180	aio_read $fh, 7, 15, $buffer, 0, sub {
146	$_[0] > 0 or die "read error: $!";	181	$_[0] > 0 or die "read error: $!";
147	print "read $_[0] bytes: <$buffer>\n";	182	print "read $_[0] bytes: <$buffer>\n";
148	};	183	};
149		184
		185	=item aio_move $srcpath, $dstpath, $callback->($status)
		186
		187	Try to move the I<file> (directories not supported as either source or
		188	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		189	the C<0> (error) or C<-1> ok.
		190
		191	This is a composite request that tries to rename(2) the file first. If
		192	rename files with C<EXDEV>, it creates the destination file with mode 0200
		193	and copies the contents of the source file into it using C<aio_sendfile>,
		194	followed by restoring atime, mtime, access mode and uid/gid, in that
		195	order, and unlinking the C<$srcpath>.
		196
		197	If an error occurs, the partial destination file will be unlinked, if
		198	possible, except when setting atime, mtime, access mode and uid/gid, where
		199	errors are being ignored.
		200
		201	=cut
		202
		203	sub aio_move($$$) {
		204	my ($src, $dst, $cb) = @_;
		205
		206	my $grp = aio_group;
		207
		208	add $grp aio_rename $src, $dst, sub {
		209	if ($_[0] && $! == EXDEV) {
		210	add $grp aio_open $src, O_RDONLY, 0, sub {
		211	if (my $src_fh = $_[0]) {
		212	my @stat = stat $src_fh;
		213
		214	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		215	if (my $dst_fh = $_[0]) {
		216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		217	close $src_fh;
		218
		219	if ($_[0] == $stat[7]) {
		220	utime $stat[8], $stat[9], $dst;
		221	chmod $stat[2] & 07777, $dst_fh;
		222	chown $stat[4], $stat[5], $dst_fh;
		223	close $dst_fh;
		224
		225	add $grp aio_unlink $src, sub {
		226	$cb->($_[0]);
		227	};
		228	} else {
		229	my $errno = $!;
		230	add $grp aio_unlink $dst, sub {
		231	$! = $errno;
		232	$cb->(-1);
		233	};
		234	}
		235	};
		236	} else {
		237	$cb->(-1);
		238	}
		239	},
		240
		241	} else {
		242	$cb->(-1);
		243	}
		244	};
		245	} else {
		246	$cb->($_[0]);
		247	}
		248	};
		249
		250	$grp
		251	}
		252
		253	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		254
		255	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		256	reading at byte offset C<$in_offset>, and starts writing at the current
		257	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		258	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		259	other.
		260
		261	This call tries to make use of a native C<sendfile> syscall to provide
		262	zero-copy operation. For this to work, C<$out_fh> should refer to a
		263	socket, and C<$in_fh> should refer to mmap'able file.
		264
		265	If the native sendfile call fails or is not implemented, it will be
		266	emulated, so you can call C<aio_sendfile> on any type of filehandle
		267	regardless of the limitations of the operating system.
		268
		269	Please note, however, that C<aio_sendfile> can read more bytes from
		270	C<$in_fh> than are written, and there is no way to find out how many
		271	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		272	provides the number of bytes written to C<$out_fh>. Only if the result
		273	value equals C<$length> one can assume that C<$length> bytes have been
		274	read.
		275
150	=item aio_readahead $fh,$offset,$length, $callback	276	=item aio_readahead $fh,$offset,$length, $callback->($retval)
151
152	Asynchronously reads the specified byte range into the page cache, using
153	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
154	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
155		277
156	C<aio_readahead> populates the page cache with data from a file so that	278	C<aio_readahead> populates the page cache with data from a file so that
157	subsequent reads from that file will not block on disk I/O. The C<$offset>	279	subsequent reads from that file will not block on disk I/O. The C<$offset>
158	argument specifies the starting point from which data is to be read and	280	argument specifies the starting point from which data is to be read and
159	C<$length> specifies the number of bytes to be read. I/O is performed in	281	C<$length> specifies the number of bytes to be read. I/O is performed in
160	whole pages, so that offset is effectively rounded down to a page boundary	282	whole pages, so that offset is effectively rounded down to a page boundary
161	and bytes are read up to the next page boundary greater than or equal to	283	and bytes are read up to the next page boundary greater than or equal to
162	(off-set+length). C<aio_readahead> does not read beyond the end of the	284	(off-set+length). C<aio_readahead> does not read beyond the end of the
163	file. The current file offset of the file is left unchanged.	285	file. The current file offset of the file is left unchanged.
164		286
		287	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		288	emulated by simply reading the data, which would have a similar effect.
		289
165	=item aio_stat $fh_or_path, $callback	290	=item aio_stat $fh_or_path, $callback->($status)
166		291
167	=item aio_lstat $fh, $callback	292	=item aio_lstat $fh, $callback->($status)
168		293
169	Works like perl's C<stat> or C<lstat> in void context. The callback will	294	Works like perl's C<stat> or C<lstat> in void context. The callback will
170	be called after the stat and the results will be available using C<stat _>	295	be called after the stat and the results will be available using C<stat _>
171	or C<-s _> etc...	296	or C<-s _> etc...
172		297
…		…
182	aio_stat "/etc/passwd", sub {	307	aio_stat "/etc/passwd", sub {
183	$_[0] and die "stat failed: $!";	308	$_[0] and die "stat failed: $!";
184	print "size is ", -s _, "\n";	309	print "size is ", -s _, "\n";
185	};	310	};
186		311
187	=item aio_unlink $pathname, $callback	312	=item aio_unlink $pathname, $callback->($status)
188		313
189	Asynchronously unlink (delete) a file and call the callback with the	314	Asynchronously unlink (delete) a file and call the callback with the
190	result code.	315	result code.
191		316
		317	=item aio_link $srcpath, $dstpath, $callback->($status)
		318
		319	Asynchronously create a new link to the existing object at C<$srcpath> at
		320	the path C<$dstpath> and call the callback with the result code.
		321
		322	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		323
		324	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		325	the path C<$dstpath> and call the callback with the result code.
		326
		327	=item aio_rename $srcpath, $dstpath, $callback->($status)
		328
		329	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		330	rename(2) and call the callback with the result code.
		331
		332	=item aio_rmdir $pathname, $callback->($status)
		333
		334	Asynchronously rmdir (delete) a directory and call the callback with the
		335	result code.
		336
		337	=item aio_readdir $pathname, $callback->($entries)
		338
		339	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		340	directory (i.e. opendir + readdir + closedir). The entries will not be
		341	sorted, and will B<NOT> include the C<.> and C<..> entries.
		342
		343	The callback a single argument which is either C<undef> or an array-ref
		344	with the filenames.
		345
		346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		347
		348	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		349	separate the entries of directory C<$path> into two sets of names, ones
		350	you can recurse into (directories or links to them), and ones you cannot
		351	recurse into (everything else).
		352
		353	C<aio_scandir> is a composite request that consists of many sub
		354	requests. C<$maxreq> specifies the maximum number of outstanding aio
		355	requests that this function generates. If it is C<< <= 0 >>, then a
		356	suitable default will be chosen (currently 8).
		357
		358	On error, the callback is called without arguments, otherwise it receives
		359	two array-refs with path-relative entry names.
		360
		361	Example:
		362
		363	aio_scandir $dir, 0, sub {
		364	my ($dirs, $nondirs) = @_;
		365	print "real directories: @$dirs\n";
		366	print "everything else: @$nondirs\n";
		367	};
		368
		369	Implementation notes.
		370
		371	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		372
		373	After reading the directory, the modification time, size etc. of the
		374	directory before and after the readdir is checked, and if they match (and
		375	isn't the current time), the link count will be used to decide how many
		376	entries are directories (if >= 2). Otherwise, no knowledge of the number
		377	of subdirectories will be assumed.
		378
		379	Then entries will be sorted into likely directories (everything without
		380	a non-initial dot currently) and likely non-directories (everything
		381	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		382	likely directories first. If that succeeds, it assumes that the entry
		383	is a directory or a symlink to directory (which will be checked
		384	seperately). This is often faster than stat'ing the entry itself because
		385	filesystems might detect the type of the entry without reading the inode
		386	data (e.g. ext2fs filetype feature).
		387
		388	If the known number of directories (link count - 2) has been reached, the
		389	rest of the entries is assumed to be non-directories.
		390
		391	This only works with certainty on POSIX (= UNIX) filesystems, which
		392	fortunately are the vast majority of filesystems around.
		393
		394	It will also likely work on non-POSIX filesystems with reduced efficiency
		395	as those tend to return 0 or 1 as link counts, which disables the
		396	directory counting heuristic.
		397
		398	=cut
		399
		400	sub aio_scandir($$$) {
		401	my ($path, $maxreq, $cb) = @_;
		402
		403	my $grp = aio_group;
		404
		405	$maxreq = 8 if $maxreq <= 0;
		406
		407	# stat once
		408	add $grp aio_stat $path, sub {
		409	return $cb->() if $_[0];
		410	my $now = time;
		411	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		412
		413	# read the directory entries
		414	add $grp aio_readdir $path, sub {
		415	my $entries = shift
		416	or return $cb->();
		417
		418	# stat the dir another time
		419	add $grp aio_stat $path, sub {
		420	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		421
		422	my $ndirs;
		423
		424	# take the slow route if anything looks fishy
		425	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		426	$ndirs = -1;
		427	} else {
		428	# if nlink == 2, we are finished
		429	# on non-posix-fs's, we rely on nlink < 2
		430	$ndirs = (stat _)[3] - 2
		431	or return $cb->([], $entries);
		432	}
		433
		434	# sort into likely dirs and likely nondirs
		435	# dirs == files without ".", short entries first
		436	$entries = [map $_->[0],
		437	sort { $b->[1] cmp $a->[1] }
		438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		439	@$entries];
		440
		441	my (@dirs, @nondirs);
		442
		443	my ($statcb, $schedcb);
		444	my $nreq = 0;
		445
		446	$schedcb = sub {
		447	if (@$entries) {
		448	if ($nreq < $maxreq) {
		449	my $ent = pop @$entries;
		450	$nreq++;
		451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		452	}
		453	} elsif (!$nreq) {
		454	# finished
		455	undef $statcb;
		456	undef $schedcb;
		457	$cb->(\@dirs, \@nondirs) if $cb;
		458	undef $cb;
		459	}
		460	};
		461	$statcb = sub {
		462	my ($status, $entry) = @_;
		463
		464	if ($status < 0) {
		465	$nreq--;
		466	push @nondirs, $entry;
		467	&$schedcb;
		468	} else {
		469	# need to check for real directory
		470	add $grp aio_lstat "$path/$entry", sub {
		471	$nreq--;
		472
		473	if (-d _) {
		474	push @dirs, $entry;
		475
		476	if (!--$ndirs) {
		477	push @nondirs, @$entries;
		478	$entries = [];
		479	}
		480	} else {
		481	push @nondirs, $entry;
		482	}
		483
		484	&$schedcb;
		485	}
		486	}
		487	};
		488
		489	&$schedcb while @$entries && $nreq < $maxreq;
		490	};
		491	};
		492	};
		493
		494	$grp
		495	}
		496
192	=item aio_fsync $fh, $callback	497	=item aio_fsync $fh, $callback->($status)
193		498
194	Asynchronously call fsync on the given filehandle and call the callback	499	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	500	with the fsync result code.
196		501
197	=item aio_fdatasync $fh, $callback	502	=item aio_fdatasync $fh, $callback->($status)
198		503
199	Asynchronously call fdatasync on the given filehandle and call the	504	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	505	callback with the fdatasync result code.
201	C<fdatasync> is not available.	506
		507	If this call isn't available because your OS lacks it or it couldn't be
		508	detected, it will be emulated by calling C<fsync> instead.
		509
		510	=item aio_group $callback->()
		511
		512	[EXPERIMENTAL]
		513
		514	This is a very special aio request: Instead of doing something, it is a
		515	container for other aio requests, which is useful if you want to bundle
		516	many requests into a single, composite, request.
		517
		518	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		519	for more info.
		520
		521	Example:
		522
		523	my $grp = aio_group sub {
		524	print "all stats done\n";
		525	};
		526
		527	add $grp
		528	(aio_stat ...),
		529	(aio_stat ...),
		530	...;
		531
		532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		533
		534	Mainly used for debugging and benchmarking, this aio request puts one of
		535	the request workers to sleep for the given time.
		536
		537	While it is theoretically handy to have simple I/O scheduling requests
		538	like sleep and file handle readable/writable, the overhead this creates
		539	is immense, so do not use this function except to put your application
		540	under artificial I/O pressure.
		541
		542	=back
		543
		544	=head2 IO::AIO::REQ CLASS
		545
		546	All non-aggregate C<aio_*> functions return an object of this class when
		547	called in non-void context.
		548
		549	A request always moves through the following five states in its lifetime,
		550	in order: B<ready> (request has been created, but has not been executed
		551	yet), B<execute> (request is currently being executed), B<pending>
		552	(request has been executed but callback has not been called yet),
		553	B<result> (results are being processed synchronously, includes calling the
		554	callback) and B<done> (request has reached the end of its lifetime and
		555	holds no resources anymore).
		556
		557	=over 4
		558
		559	=item $req->cancel
		560
		561	Cancels the request, if possible. Has the effect of skipping execution
		562	when entering the B<execute> state and skipping calling the callback when
		563	entering the the B<result> state, but will leave the request otherwise
		564	untouched. That means that requests that currently execute will not be
		565	stopped and resources held by the request will not be freed prematurely.
		566
		567	=back
		568
		569	=head2 IO::AIO::GRP CLASS
		570
		571	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		572	objects of this class, too.
		573
		574	A IO::AIO::GRP object is a special request that can contain multiple other
		575	aio requests.
		576
		577	You create one by calling the C<aio_group> constructing function with a
		578	callback that will be called when all contained requests have entered the
		579	C<done> state:
		580
		581	my $grp = aio_group sub {
		582	print "all requests are done\n";
		583	};
		584
		585	You add requests by calling the C<add> method with one or more
		586	C<IO::AIO::REQ> objects:
		587
		588	$grp->add (aio_unlink "...");
		589
		590	add $grp aio_stat "...", sub { ... };
		591
		592	This makes it very easy to create composite requests (see the source of
		593	C<aio_move> for an application) that work and feel like simple requests.
		594
		595	The IO::AIO::GRP objects will be cleaned up during calls to
		596	C<IO::AIO::poll_cb>, just like any other request.
		597
		598	They can be canceled like any other request. Canceling will cancel not
		599	just the request itself, but also all requests it contains.
		600
		601	They can also can also be added to other IO::AIO::GRP objects.
		602
		603	Their lifetime, simplified, looks like this: when they are empty, they
		604	will finish very quickly. If they contain only requests that are in the
		605	C<done> state, they will also finish. Otherwise they will continue to
		606	exist.
		607
		608	That means after creating a group you have some time to add requests. And
		609	in the callbacks of those requests, you can add further requests to the
		610	group. And only when all those requests have finished will the the group
		611	itself finish.
		612
		613	=over 4
		614
		615	=item $grp->add (...)
		616
		617	=item add $grp ...
		618
		619	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		620	be added, including other groups, as long as you do not create circular
		621	dependencies.
		622
		623	Returns all its arguments.
202		624
203	=back	625	=back
204		626
205	=head2 SUPPORT FUNCTIONS	627	=head2 SUPPORT FUNCTIONS
206		628
…		…
264	IO::AIO::poll_wait, IO::AIO::poll_cb	686	IO::AIO::poll_wait, IO::AIO::poll_cb
265	if IO::AIO::nreqs;	687	if IO::AIO::nreqs;
266		688
267	=item IO::AIO::min_parallel $nthreads	689	=item IO::AIO::min_parallel $nthreads
268		690
269	Set the minimum number of AIO threads to C<$nthreads>. The default is	691	Set the minimum number of AIO threads to C<$nthreads>. The current default
270	C<1>, which means a single asynchronous operation can be done at one time	692	is C<4>, which means four asynchronous operations can be done at one time
271	(the number of outstanding operations, however, is unlimited).	693	(the number of outstanding operations, however, is unlimited).
		694
		695	IO::AIO starts threads only on demand, when an AIO request is queued and
		696	no free thread exists.
272		697
273	It is recommended to keep the number of threads low, as some Linux	698	It is recommended to keep the number of threads low, as some Linux
274	kernel versions will scale negatively with the number of threads (higher	699	kernel versions will scale negatively with the number of threads (higher
275	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	700	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
276	threads should be fine.	701	threads should be fine.
277		702
278	Under normal circumstances you don't need to call this function, as this	703	Under most circumstances you don't need to call this function, as the
279	module automatically starts some threads (the exact number might change,	704	module selects a default that is suitable for low to moderate load.
280	and is currently 4).
281		705
282	=item IO::AIO::max_parallel $nthreads	706	=item IO::AIO::max_parallel $nthreads
283		707
284	Sets the maximum number of AIO threads to C<$nthreads>. If more than	708	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
285	the specified number of threads are currently running, kill them. This	709	specified number of threads are currently running, this function kills
286	function blocks until the limit is reached.	710	them. This function blocks until the limit is reached.
		711
		712	While C<$nthreads> are zero, aio requests get queued but not executed
		713	until the number of threads has been increased again.
287		714
288	This module automatically runs C<max_parallel 0> at program end, to ensure	715	This module automatically runs C<max_parallel 0> at program end, to ensure
289	that all threads are killed and that there are no outstanding requests.	716	that all threads are killed and that there are no outstanding requests.
290		717
291	Under normal circumstances you don't need to call this function.	718	Under normal circumstances you don't need to call this function.
…		…
295	Sets the maximum number of outstanding requests to C<$nreqs>. If you	722	Sets the maximum number of outstanding requests to C<$nreqs>. If you
296	try to queue up more than this number of requests, the caller will block until	723	try to queue up more than this number of requests, the caller will block until
297	some requests have been handled.	724	some requests have been handled.
298		725
299	The default is very large, so normally there is no practical limit. If you	726	The default is very large, so normally there is no practical limit. If you
300	queue up many requests in a loop it it often improves speed if you set	727	queue up many requests in a loop it often improves speed if you set
301	this to a relatively low number, such as C<100>.	728	this to a relatively low number, such as C<100>.
302		729
303	Under normal circumstances you don't need to call this function.	730	Under normal circumstances you don't need to call this function.
304		731
305	=back	732	=back
…		…
308		735
309	# support function to convert a fd into a perl filehandle	736	# support function to convert a fd into a perl filehandle
310	sub _fd2fh {	737	sub _fd2fh {
311	return undef if $_[0] < 0;	738	return undef if $_[0] < 0;
312		739
313	# try to be perl5.6-compatible	740	# try to generate nice filehandles
314	local *AIO_FH;	741	my $sym = "IO::AIO::fd#$_[0]";
315	open AIO_FH, "+<&=$_[0]"	742	local *$sym;
		743
		744	open *$sym, "+<&=$_[0]" # usually works under any unix
		745	or open *$sym, "<&=$_[0]" # cygwin needs this
		746	or open *$sym, ">&=$_[0]" # or this
316	or return undef;	747	or return undef;
317		748
318	*AIO_FH	749	*$sym
319	}	750	}
320		751
321	min_parallel 4;	752	min_parallel 4;
322		753
323	END {	754	END {
324	max_parallel 0;	755	max_parallel 0;
325	}	756	}
326		757
327	1;	758	1;
328		759
		760	=head2 FORK BEHAVIOUR
		761
		762	This module should do "the right thing" when the process using it forks:
		763
		764	Before the fork, IO::AIO enters a quiescent state where no requests
		765	can be added in other threads and no results will be processed. After
		766	the fork the parent simply leaves the quiescent state and continues
		767	request/result processing, while the child clears the request/result
		768	queue (so the requests started before the fork will only be handled in
		769	the parent). Threads will be started on demand until the limit ste in the
		770	parent process has been reached again.
		771
		772	In short: the parent will, after a short pause, continue as if fork had
		773	not been called, while the child will act as if IO::AIO has not been used
		774	yet.
		775
329	=head1 SEE ALSO	776	=head1 SEE ALSO
330		777
331	L<Coro>, L<Linux::AIO>.	778	L<Coro>, L<Linux::AIO> (obsolete).
332		779
333	=head1 AUTHOR	780	=head1 AUTHOR
334		781
335	Marc Lehmann <schmorp@schmorp.de>	782	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	783	http://home.schmorp.de/

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