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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.21 by root, Wed Jul 13 00:13:09 2005 UTC vs.
Revision 1.71 by root, Tue Oct 24 11:57:30 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	aioreq_pri 4; # give next request a very high priority
		24	my $req = aio_unlink "/tmp/file", sub { };
		25	$req->cancel; # cancel request if still in queue
		26
		27	my $grp = aio_group sub { print "all stats done\n" };
		28	add $grp aio_stat "..." for ...;
		29
		30	# AnyEvent integration
		31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		33
		34	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	35	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	36	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	37	cb => \&IO::AIO::poll_cb);
24		38
25	# Glib/Gtk2	39	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	40	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb, 1 };	41	in => sub { IO::AIO::poll_cb; 1 };
28		42
29	# Tk	43	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	45	readable => \&IO::AIO::poll_cb);
32		46
33	# Danga::Socket	47	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	49	\&IO::AIO::poll_cb);
36		50
37
38	=head1 DESCRIPTION	51	=head1 DESCRIPTION
39		52
40	This module implements asynchronous I/O using whatever means your	53	This module implements asynchronous I/O using whatever means your
41	operating system supports.	54	operating system supports.
42		55
43	Currently, a number of threads are started that execute your read/writes	56	Currently, a number of threads are started that execute your read/writes
44	and signal their completion. You don't need thread support in your libc or	57	and signal their completion. You don't need thread support in perl, and
45	perl, and the threads created by this module will not be visible to the	58	the threads created by this module will not be visible to perl. In the
46	pthreads library. In the future, this module might make use of the native	59	future, this module might make use of the native aio functions available
47	aio functions available on many operating systems. However, they are often	60	on many operating systems. However, they are often not well-supported
48	not well-supported (Linux doesn't allow them on normal files currently,	61	(Linux doesn't allow them on normal files currently, for example),
49	for example), and they would only support aio_read and aio_write, so the	62	and they would only support aio_read and aio_write, so the remaining
50	remaining functionality would have to be implemented using threads anyway.	63	functionality would have to be implemented using threads anyway.
51		64
52	Although the module will work with in the presence of other threads, it is	65	Although the module will work with in the presence of other threads,
53	currently not reentrant, so use appropriate locking yourself.	66	it is currently not reentrant in any way, so use appropriate locking
		67	yourself, always call C<poll_cb> from within the same thread, or never
		68	call C<poll_cb> (or other C<aio_> functions) recursively.
54		69
55	=cut	70	=cut
56		71
57	package IO::AIO;	72	package IO::AIO;
58		73
		74	no warnings;
		75	use strict 'vars';
		76
59	use base 'Exporter';	77	use base 'Exporter';
60		78
61	use Fcntl ();
62
63	BEGIN {	79	BEGIN {
64	$VERSION = 0.9;	80	our $VERSION = '2.0';
65		81
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
67	aio_fsync aio_fdatasync aio_readahead);	83	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	84	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		85	aio_group aio_nop);
		86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		88	min_parallel max_parallel max_outstanding nreqs);
		89
		90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		91
70	require XSLoader;	92	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	93	XSLoader::load ("IO::AIO", $VERSION);
72	}	94	}
73		95
74	=head1 FUNCTIONS	96	=head1 FUNCTIONS
75		97
76	=head2 AIO FUNCTIONS	98	=head2 AIO FUNCTIONS
…		…
81	which must be a code reference. This code reference will get called with	103	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	104	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	105	perl, which usually delivers "false") as it's sole argument when the given
84	syscall has been executed asynchronously.	106	syscall has been executed asynchronously.
85		107
86	All functions that expect a filehandle will also accept a file descriptor.	108	All functions expecting a filehandle keep a copy of the filehandle
		109	internally until the request has finished.
87		110
		111	All requests return objects of type L<IO::AIO::REQ> that allow further
		112	manipulation of those requests while they are in-flight.
		113
88	The filenames you pass to these routines I<must> be absolute. The reason	114	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	115	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	116	request is being executed, the current working directory could have
91	that you never change the current working directory.	117	changed. Alternatively, you can make sure that you never change the
		118	current working directory.
		119
		120	To encode pathnames to byte form, either make sure you either: a)
		121	always pass in filenames you got from outside (command line, readdir
		122	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		123	your pathnames to the locale (or other) encoding in effect in the user
		124	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		125	use something else.
92		126
93	=over 4	127	=over 4
94		128
		129	=item aioreq_pri $pri
		130
		131	Sets the priority for the next aio request. The default priority
		132	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,
		133	respectively. Requests with higher priority will be serviced first.
		134
		135	The priority will be reset to C<0> after each call to one of the C<aio_>
		136	functions.
		137
		138	Example: open a file with low priority, then read something from it with
		139	higher priority so the read request is serviced before other low priority
		140	open requests (potentially spamming the cache):
		141
		142	aioreq_pri -3;
		143	aio_open ..., sub {
		144	return unless $_[0];
		145
		146	aioreq_pri -2;
		147	aio_read $_[0], ..., sub {
		148	...
		149	};
		150	};
		151
		152	=item aioreq_nice $pri_adjust
		153
		154	Similar to C<aioreq_pri>, but subtracts the given value from the current
		155	priority, so effects are cumulative.
		156
95	=item aio_open $pathname, $flags, $mode, $callback	157	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		158
97	Asynchronously open or create a file and call the callback with a newly	159	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	160	created filehandle for the file.
99		161
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	162	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
117	} else {	179	} else {
118	die "open failed: $!\n";	180	die "open failed: $!\n";
119	}	181	}
120	};	182	};
121		183
122	=item aio_close $fh, $callback	184	=item aio_close $fh, $callback->($status)
123		185
124	Asynchronously close a file and call the callback with the result	186	Asynchronously close a file and call the callback with the result
125	code. I<WARNING:> although accepted, you should not pass in a perl	187	code. I<WARNING:> although accepted, you should not pass in a perl
126	filehandle here, as perl will likely close the file descriptor another	188	filehandle here, as perl will likely close the file descriptor another
127	time when the filehandle is destroyed. Normally, you can safely call perls	189	time when the filehandle is destroyed. Normally, you can safely call perls
128	C<close> or just let filehandles go out of scope.	190	C<close> or just let filehandles go out of scope.
129		191
130	This is supposed to be a bug in the API, so that might change. It's	192	This is supposed to be a bug in the API, so that might change. It's
131	therefore best to avoid this function.	193	therefore best to avoid this function.
132		194
133	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	195	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
134		196
135	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	197	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
136		198
137	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	199	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	200	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	201	callback without the actual number of bytes read (or -1 on error, just
140	like the syscall).	202	like the syscall).
141		203
		204	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		205	is outstanding. Modifying it can result in segfaults or WW3 (if the
		206	necessary/optional hardware is installed).
		207
142	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	208	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
143	offset C<0> within the scalar:	209	offset C<0> within the scalar:
144		210
145	aio_read $fh, 7, 15, $buffer, 0, sub {	211	aio_read $fh, 7, 15, $buffer, 0, sub {
146	$_[0] > 0 or die "read error: $!";	212	$_[0] > 0 or die "read error: $!";
147	print "read $_[0] bytes: <$buffer>\n";	213	print "read $_[0] bytes: <$buffer>\n";
148	};	214	};
149		215
		216	=item aio_move $srcpath, $dstpath, $callback->($status)
		217
		218	Try to move the I<file> (directories not supported as either source or
		219	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		220	the C<0> (error) or C<-1> ok.
		221
		222	This is a composite request that tries to rename(2) the file first. If
		223	rename files with C<EXDEV>, it creates the destination file with mode 0200
		224	and copies the contents of the source file into it using C<aio_sendfile>,
		225	followed by restoring atime, mtime, access mode and uid/gid, in that
		226	order, and unlinking the C<$srcpath>.
		227
		228	If an error occurs, the partial destination file will be unlinked, if
		229	possible, except when setting atime, mtime, access mode and uid/gid, where
		230	errors are being ignored.
		231
		232	=cut
		233
		234	sub aio_move($$$) {
		235	my ($src, $dst, $cb) = @_;
		236
		237	my $grp = aio_group $cb;
		238
		239	add $grp aio_rename $src, $dst, sub {
		240	if ($_[0] && $! == EXDEV) {
		241	add $grp aio_open $src, O_RDONLY, 0, sub {
		242	if (my $src_fh = $_[0]) {
		243	my @stat = stat $src_fh;
		244
		245	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		246	if (my $dst_fh = $_[0]) {
		247	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		248	close $src_fh;
		249
		250	if ($_[0] == $stat[7]) {
		251	utime $stat[8], $stat[9], $dst;
		252	chmod $stat[2] & 07777, $dst_fh;
		253	chown $stat[4], $stat[5], $dst_fh;
		254	close $dst_fh;
		255
		256	add $grp aio_unlink $src, sub {
		257	$grp->result ($_[0]);
		258	};
		259	} else {
		260	my $errno = $!;
		261	add $grp aio_unlink $dst, sub {
		262	$! = $errno;
		263	$grp->result (-1);
		264	};
		265	}
		266	};
		267	} else {
		268	$grp->result (-1);
		269	}
		270	},
		271
		272	} else {
		273	$grp->result (-1);
		274	}
		275	};
		276	} else {
		277	$grp->result ($_[0]);
		278	}
		279	};
		280
		281	$grp
		282	}
		283
		284	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		285
		286	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		287	reading at byte offset C<$in_offset>, and starts writing at the current
		288	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		289	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		290	other.
		291
		292	This call tries to make use of a native C<sendfile> syscall to provide
		293	zero-copy operation. For this to work, C<$out_fh> should refer to a
		294	socket, and C<$in_fh> should refer to mmap'able file.
		295
		296	If the native sendfile call fails or is not implemented, it will be
		297	emulated, so you can call C<aio_sendfile> on any type of filehandle
		298	regardless of the limitations of the operating system.
		299
		300	Please note, however, that C<aio_sendfile> can read more bytes from
		301	C<$in_fh> than are written, and there is no way to find out how many
		302	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		303	provides the number of bytes written to C<$out_fh>. Only if the result
		304	value equals C<$length> one can assume that C<$length> bytes have been
		305	read.
		306
150	=item aio_readahead $fh,$offset,$length, $callback	307	=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		308
156	C<aio_readahead> populates the page cache with data from a file so that	309	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>	310	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	311	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	312	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	313	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	314	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	315	(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.	316	file. The current file offset of the file is left unchanged.
164		317
		318	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		319	emulated by simply reading the data, which would have a similar effect.
		320
165	=item aio_stat $fh_or_path, $callback	321	=item aio_stat $fh_or_path, $callback->($status)
166		322
167	=item aio_lstat $fh, $callback	323	=item aio_lstat $fh, $callback->($status)
168		324
169	Works like perl's C<stat> or C<lstat> in void context. The callback will	325	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 _>	326	be called after the stat and the results will be available using C<stat _>
171	or C<-s _> etc...	327	or C<-s _> etc...
172		328
…		…
182	aio_stat "/etc/passwd", sub {	338	aio_stat "/etc/passwd", sub {
183	$_[0] and die "stat failed: $!";	339	$_[0] and die "stat failed: $!";
184	print "size is ", -s _, "\n";	340	print "size is ", -s _, "\n";
185	};	341	};
186		342
187	=item aio_unlink $pathname, $callback	343	=item aio_unlink $pathname, $callback->($status)
188		344
189	Asynchronously unlink (delete) a file and call the callback with the	345	Asynchronously unlink (delete) a file and call the callback with the
190	result code.	346	result code.
191		347
		348	=item aio_link $srcpath, $dstpath, $callback->($status)
		349
		350	Asynchronously create a new link to the existing object at C<$srcpath> at
		351	the path C<$dstpath> and call the callback with the result code.
		352
		353	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		354
		355	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		356	the path C<$dstpath> and call the callback with the result code.
		357
		358	=item aio_rename $srcpath, $dstpath, $callback->($status)
		359
		360	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		361	rename(2) and call the callback with the result code.
		362
		363	=item aio_rmdir $pathname, $callback->($status)
		364
		365	Asynchronously rmdir (delete) a directory and call the callback with the
		366	result code.
		367
		368	=item aio_readdir $pathname, $callback->($entries)
		369
		370	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		371	directory (i.e. opendir + readdir + closedir). The entries will not be
		372	sorted, and will B<NOT> include the C<.> and C<..> entries.
		373
		374	The callback a single argument which is either C<undef> or an array-ref
		375	with the filenames.
		376
		377	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		378
		379	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		380	separate the entries of directory C<$path> into two sets of names, ones
		381	you can recurse into (directories or links to them), and ones you cannot
		382	recurse into (everything else).
		383
		384	C<aio_scandir> is a composite request that creates of many sub requests_
		385	C<$maxreq> specifies the maximum number of outstanding aio requests that
		386	this function generates. If it is C<< <= 0 >>, then a suitable default
		387	will be chosen (currently 6).
		388
		389	On error, the callback is called without arguments, otherwise it receives
		390	two array-refs with path-relative entry names.
		391
		392	Example:
		393
		394	aio_scandir $dir, 0, sub {
		395	my ($dirs, $nondirs) = @_;
		396	print "real directories: @$dirs\n";
		397	print "everything else: @$nondirs\n";
		398	};
		399
		400	Implementation notes.
		401
		402	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		403
		404	After reading the directory, the modification time, size etc. of the
		405	directory before and after the readdir is checked, and if they match (and
		406	isn't the current time), the link count will be used to decide how many
		407	entries are directories (if >= 2). Otherwise, no knowledge of the number
		408	of subdirectories will be assumed.
		409
		410	Then entries will be sorted into likely directories (everything without
		411	a non-initial dot currently) and likely non-directories (everything
		412	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		413	likely directories first. If that succeeds, it assumes that the entry
		414	is a directory or a symlink to directory (which will be checked
		415	seperately). This is often faster than stat'ing the entry itself because
		416	filesystems might detect the type of the entry without reading the inode
		417	data (e.g. ext2fs filetype feature).
		418
		419	If the known number of directories (link count - 2) has been reached, the
		420	rest of the entries is assumed to be non-directories.
		421
		422	This only works with certainty on POSIX (= UNIX) filesystems, which
		423	fortunately are the vast majority of filesystems around.
		424
		425	It will also likely work on non-POSIX filesystems with reduced efficiency
		426	as those tend to return 0 or 1 as link counts, which disables the
		427	directory counting heuristic.
		428
		429	=cut
		430
		431	sub aio_scandir($$$) {
		432	my ($path, $maxreq, $cb) = @_;
		433
		434	my $grp = aio_group $cb;
		435
		436	$maxreq = 6 if $maxreq <= 0;
		437
		438	# stat once
		439	add $grp aio_stat $path, sub {
		440	return $grp->result () if $_[0];
		441	my $now = time;
		442	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		443
		444	# read the directory entries
		445	add $grp aio_readdir $path, sub {
		446	my $entries = shift
		447	or return $grp->result ();
		448
		449	# stat the dir another time
		450	add $grp aio_stat $path, sub {
		451	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		452
		453	my $ndirs;
		454
		455	# take the slow route if anything looks fishy
		456	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		457	$ndirs = -1;
		458	} else {
		459	# if nlink == 2, we are finished
		460	# on non-posix-fs's, we rely on nlink < 2
		461	$ndirs = (stat _)[3] - 2
		462	or return $grp->result ([], $entries);
		463	}
		464
		465	# sort into likely dirs and likely nondirs
		466	# dirs == files without ".", short entries first
		467	$entries = [map $_->[0],
		468	sort { $b->[1] cmp $a->[1] }
		469	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		470	@$entries];
		471
		472	my (@dirs, @nondirs);
		473
		474	my ($statcb, $schedcb);
		475	my $nreq = 0;
		476
		477	my $statgrp = add $grp aio_group;
		478
		479	$schedcb = sub {
		480	if (@$entries) {
		481	if ($nreq < $maxreq) {
		482	my $ent = pop @$entries;
		483	$nreq++;
		484	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		485	}
		486	} elsif (!$nreq) {
		487	# finished
		488	$statgrp->cancel;
		489	undef $statcb;
		490	undef $schedcb;
		491	$grp->result (\@dirs, \@nondirs);
		492	}
		493	};
		494	$statcb = sub {
		495	my ($status, $entry) = @_;
		496
		497	if ($status < 0) {
		498	$nreq--;
		499	push @nondirs, $entry;
		500	&$schedcb;
		501	} else {
		502	# need to check for real directory
		503	add $grp aio_lstat "$path/$entry", sub {
		504	$nreq--;
		505
		506	if (-d _) {
		507	push @dirs, $entry;
		508
		509	if (!--$ndirs) {
		510	push @nondirs, @$entries;
		511	$entries = [];
		512	}
		513	} else {
		514	push @nondirs, $entry;
		515	}
		516
		517	&$schedcb;
		518	}
		519	}
		520	};
		521
		522	&$schedcb while @$entries && $nreq < $maxreq;
		523	};
		524	};
		525	};
		526
		527	$grp
		528	}
		529
192	=item aio_fsync $fh, $callback	530	=item aio_fsync $fh, $callback->($status)
193		531
194	Asynchronously call fsync on the given filehandle and call the callback	532	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	533	with the fsync result code.
196		534
197	=item aio_fdatasync $fh, $callback	535	=item aio_fdatasync $fh, $callback->($status)
198		536
199	Asynchronously call fdatasync on the given filehandle and call the	537	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	538	callback with the fdatasync result code.
201	C<fdatasync> is not available.	539
		540	If this call isn't available because your OS lacks it or it couldn't be
		541	detected, it will be emulated by calling C<fsync> instead.
		542
		543	=item aio_group $callback->(...)
		544
		545	[EXPERIMENTAL]
		546
		547	This is a very special aio request: Instead of doing something, it is a
		548	container for other aio requests, which is useful if you want to bundle
		549	many requests into a single, composite, request with a definite callback
		550	and the ability to cancel the whole request with its subrequests.
		551
		552	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		553	for more info.
		554
		555	Example:
		556
		557	my $grp = aio_group sub {
		558	print "all stats done\n";
		559	};
		560
		561	add $grp
		562	(aio_stat ...),
		563	(aio_stat ...),
		564	...;
		565
		566	=item aio_nop $callback->()
		567
		568	This is a special request - it does nothing in itself and is only used for
		569	side effects, such as when you want to add a dummy request to a group so
		570	that finishing the requests in the group depends on executing the given
		571	code.
		572
		573	While this request does nothing, it still goes through the execution
		574	phase and still requires a worker thread. Thus, the callback will not
		575	be executed immediately but only after other requests in the queue have
		576	entered their execution phase. This can be used to measure request
		577	latency.
		578
		579	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		580
		581	Mainly used for debugging and benchmarking, this aio request puts one of
		582	the request workers to sleep for the given time.
		583
		584	While it is theoretically handy to have simple I/O scheduling requests
		585	like sleep and file handle readable/writable, the overhead this creates is
		586	immense (it blocks a thread for a long time) so do not use this function
		587	except to put your application under artificial I/O pressure.
		588
		589	=back
		590
		591	=head2 IO::AIO::REQ CLASS
		592
		593	All non-aggregate C<aio_*> functions return an object of this class when
		594	called in non-void context.
		595
		596	A request always moves through the following five states in its lifetime,
		597	in order: B<ready> (request has been created, but has not been executed
		598	yet), B<execute> (request is currently being executed), B<pending>
		599	(request has been executed but callback has not been called yet),
		600	B<result> (results are being processed synchronously, includes calling the
		601	callback) and B<done> (request has reached the end of its lifetime and
		602	holds no resources anymore).
		603
		604	=over 4
		605
		606	=item cancel $req
		607
		608	Cancels the request, if possible. Has the effect of skipping execution
		609	when entering the B<execute> state and skipping calling the callback when
		610	entering the the B<result> state, but will leave the request otherwise
		611	untouched. That means that requests that currently execute will not be
		612	stopped and resources held by the request will not be freed prematurely.
		613
		614	=item cb $req $callback->(...)
		615
		616	Replace (or simply set) the callback registered to the request.
		617
		618	=back
		619
		620	=head2 IO::AIO::GRP CLASS
		621
		622	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		623	objects of this class, too.
		624
		625	A IO::AIO::GRP object is a special request that can contain multiple other
		626	aio requests.
		627
		628	You create one by calling the C<aio_group> constructing function with a
		629	callback that will be called when all contained requests have entered the
		630	C<done> state:
		631
		632	my $grp = aio_group sub {
		633	print "all requests are done\n";
		634	};
		635
		636	You add requests by calling the C<add> method with one or more
		637	C<IO::AIO::REQ> objects:
		638
		639	$grp->add (aio_unlink "...");
		640
		641	add $grp aio_stat "...", sub {
		642	$_[0] or return $grp->result ("error");
		643
		644	# add another request dynamically, if first succeeded
		645	add $grp aio_open "...", sub {
		646	$grp->result ("ok");
		647	};
		648	};
		649
		650	This makes it very easy to create composite requests (see the source of
		651	C<aio_move> for an application) that work and feel like simple requests.
		652
		653	=over 4
		654
		655	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		656	C<IO::AIO::poll_cb>, just like any other request.
		657
		658	=item * They can be canceled like any other request. Canceling will cancel not
		659	only the request itself, but also all requests it contains.
		660
		661	=item * They can also can also be added to other IO::AIO::GRP objects.
		662
		663	=item * You must not add requests to a group from within the group callback (or
		664	any later time).
		665
		666	=item * This does not harmonise well with C<max_outstanding>, so best do
		667	not combine C<aio_group> with it. Groups and feeders are recommended for
		668	this kind of concurrency-limiting.
		669
		670	=back
		671
		672	Their lifetime, simplified, looks like this: when they are empty, they
		673	will finish very quickly. If they contain only requests that are in the
		674	C<done> state, they will also finish. Otherwise they will continue to
		675	exist.
		676
		677	That means after creating a group you have some time to add requests. And
		678	in the callbacks of those requests, you can add further requests to the
		679	group. And only when all those requests have finished will the the group
		680	itself finish.
		681
		682	=over 4
		683
		684	=item add $grp ...
		685
		686	=item $grp->add (...)
		687
		688	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		689	be added, including other groups, as long as you do not create circular
		690	dependencies.
		691
		692	Returns all its arguments.
		693
		694	=item $grp->result (...)
		695
		696	Set the result value(s) that will be passed to the group callback when all
		697	subrequests have finished. By default, no argument will be passed.
		698
		699	=item feed $grp $callback->($grp)
		700
		701	[VERY EXPERIMENTAL]
		702
		703	Sets a feeder/generator on this group: every group can have an attached
		704	generator that generates requests if idle. The idea behind this is that,
		705	although you could just queue as many requests as you want in a group,
		706	this might starve other requests for a potentially long time. For
		707	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		708	requests, delaying any later requests for a long time.
		709
		710	To avoid this, and allow incremental generation of requests, you can
		711	instead a group and set a feeder on it that generates those requests. The
		712	feed callback will be called whenever there are few enough (see C<limit>,
		713	below) requests active in the group itself and is expected to queue more
		714	requests.
		715
		716	The feed callback can queue as many requests as it likes (i.e. C<add> does
		717	not impose any limits).
		718
		719	If the feed does not queue more requests when called, it will be
		720	automatically removed from the group.
		721
		722	If the feed limit is C<0>, it will be set to C<2> automatically.
		723
		724	Example:
		725
		726	# stat all files in @files, but only ever use four aio requests concurrently:
		727
		728	my $grp = aio_group sub { print "finished\n" };
		729	limit $grp 4;
		730	feed $grp sub {
		731	my $file = pop @files
		732	or return;
		733
		734	add $grp aio_stat $file, sub { ... };
		735	};
		736
		737	=item limit $grp $num
		738
		739	Sets the feeder limit for the group: The feeder will be called whenever
		740	the group contains less than this many requests.
		741
		742	Setting the limit to C<0> will pause the feeding process.
202		743
203	=back	744	=back
204		745
205	=head2 SUPPORT FUNCTIONS	746	=head2 SUPPORT FUNCTIONS
206		747
…		…
264	IO::AIO::poll_wait, IO::AIO::poll_cb	805	IO::AIO::poll_wait, IO::AIO::poll_cb
265	if IO::AIO::nreqs;	806	if IO::AIO::nreqs;
266		807
267	=item IO::AIO::min_parallel $nthreads	808	=item IO::AIO::min_parallel $nthreads
268		809
269	Set the minimum number of AIO threads to C<$nthreads>. The default is	810	Set the minimum number of AIO threads to C<$nthreads>. The current
270	C<1>, which means a single asynchronous operation can be done at one time	811	default is C<8>, which means eight asynchronous operations can execute
271	(the number of outstanding operations, however, is unlimited).	812	concurrently at any one time (the number of outstanding requests,
		813	however, is unlimited).
272		814
		815	IO::AIO starts threads only on demand, when an AIO request is queued and
		816	no free thread exists.
		817
273	It is recommended to keep the number of threads low, as some Linux	818	It is recommended to keep the number of threads relatively low, as some
274	kernel versions will scale negatively with the number of threads (higher	819	Linux kernel versions will scale negatively with the number of threads
275	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	820	(higher parallelity => MUCH higher latency). With current Linux 2.6
276	threads should be fine.	821	versions, 4-32 threads should be fine.
277		822
278	Under normal circumstances you don't need to call this function, as this	823	Under most circumstances you don't need to call this function, as the
279	module automatically starts some threads (the exact number might change,	824	module selects a default that is suitable for low to moderate load.
280	and is currently 4).
281		825
282	=item IO::AIO::max_parallel $nthreads	826	=item IO::AIO::max_parallel $nthreads
283		827
284	Sets the maximum number of AIO threads to C<$nthreads>. If more than	828	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
285	the specified number of threads are currently running, kill them. This	829	specified number of threads are currently running, this function kills
286	function blocks until the limit is reached.	830	them. This function blocks until the limit is reached.
		831
		832	While C<$nthreads> are zero, aio requests get queued but not executed
		833	until the number of threads has been increased again.
287		834
288	This module automatically runs C<max_parallel 0> at program end, to ensure	835	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.	836	that all threads are killed and that there are no outstanding requests.
290		837
291	Under normal circumstances you don't need to call this function.	838	Under normal circumstances you don't need to call this function.
292		839
293	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	840	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		841
		842	[DEPRECATED]
294		843
295	Sets the maximum number of outstanding requests to C<$nreqs>. If you	844	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	845	try to queue up more than this number of requests, the caller will block until
297	some requests have been handled.	846	some requests have been handled.
298		847
299	The default is very large, so normally there is no practical limit. If you	848	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	849	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>.	850	this to a relatively low number, such as C<100>.
		851
		852	This function does not work well together with C<aio_group>'s, and their
		853	feeder interface is better suited to limiting concurrency, so do not use
		854	this function.
302		855
303	Under normal circumstances you don't need to call this function.	856	Under normal circumstances you don't need to call this function.
304		857
305	=back	858	=back
306		859
…		…
308		861
309	# support function to convert a fd into a perl filehandle	862	# support function to convert a fd into a perl filehandle
310	sub _fd2fh {	863	sub _fd2fh {
311	return undef if $_[0] < 0;	864	return undef if $_[0] < 0;
312		865
313	# try to be perl5.6-compatible	866	# try to generate nice filehandles
314	local *AIO_FH;	867	my $sym = "IO::AIO::fd#$_[0]";
315	open AIO_FH, "+<&=$_[0]"	868	local *$sym;
		869
		870	open *$sym, "+<&=$_[0]" # usually works under any unix
		871	or open *$sym, "<&=$_[0]" # cygwin needs this
		872	or open *$sym, ">&=$_[0]" # or this
316	or return undef;	873	or return undef;
317		874
318	*AIO_FH	875	*$sym
319	}	876	}
320		877
321	min_parallel 4;	878	min_parallel 8;
322		879
323	END {	880	END {
324	max_parallel 0;	881	max_parallel 0;
325	}	882	}
326		883
327	1;	884	1;
328		885
		886	=head2 FORK BEHAVIOUR
		887
		888	This module should do "the right thing" when the process using it forks:
		889
		890	Before the fork, IO::AIO enters a quiescent state where no requests
		891	can be added in other threads and no results will be processed. After
		892	the fork the parent simply leaves the quiescent state and continues
		893	request/result processing, while the child clears the request/result
		894	queue (so the requests started before the fork will only be handled in
		895	the parent). Threads will be started on demand until the limit ste in the
		896	parent process has been reached again.
		897
		898	In short: the parent will, after a short pause, continue as if fork had
		899	not been called, while the child will act as if IO::AIO has not been used
		900	yet.
		901
		902	=head2 MEMORY USAGE
		903
		904	Each aio request uses - depending on your architecture - around 128 bytes
		905	of memory. In addition, stat requests need a stat buffer (possibly a few
		906	hundred bytes). Perl scalars and other data passed into aio requests will
		907	also be locked.
		908
		909	This is now awfully much, so queuing lots of requests is not usually a
		910	problem.
		911
		912	Each thread needs a stack area which is usually around 16k, sometimes much
		913	larger, depending on the OS.
		914
329	=head1 SEE ALSO	915	=head1 SEE ALSO
330		916
331	L<Coro>, L<Linux::AIO>.	917	L<Coro::AIO>.
332		918
333	=head1 AUTHOR	919	=head1 AUTHOR
334		920
335	Marc Lehmann <schmorp@schmorp.de>	921	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	922	http://home.schmorp.de/

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Revision 1.71 by root, Tue Oct 24 11:57:30 2006 UTC