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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.1 by root, Sun Jul 10 17:07:44 2005 UTC vs.
Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		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	# 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
		34	Event->io (fd => IO::AIO::poll_fileno,
		35	poll => 'r',
		36	cb => \&IO::AIO::poll_cb);
		37
		38	# Glib/Gtk2 integration
		39	add_watch Glib::IO IO::AIO::poll_fileno,
		40	in => sub { IO::AIO::poll_cb; 1 };
		41
		42	# Tk integration
		43	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		44	readable => \&IO::AIO::poll_cb);
		45
		46	# Danga::Socket integration
		47	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		48	\&IO::AIO::poll_cb);
		49
9	=head1 DESCRIPTION	50	=head1 DESCRIPTION
10		51
11	This module implements asynchronous I/O using whatever means your	52	This module implements asynchronous I/O using whatever means your
12	operating system supports. Currently, it falls back to Linux::AIO if that	53	operating system supports.
13	module is available, or uses pthreads to emulato aio functionality.
14		54
15	Currently, in this module a number of threads are started that execute	55	Currently, a number of threads are started that execute your read/writes
16	your read/writes and signal their completion. You don't need thread	56	and signal their completion. You don't need thread support in perl, and
17	support in your libc or perl, and the threads created by this module will	57	the threads created by this module will not be visible to perl. In the
18	not be visible to the pthreads library.	58	future, this module might make use of the native aio functions available
		59	on many operating systems. However, they are often not well-supported
		60	(Linux doesn't allow them on normal files currently, for example),
		61	and they would only support aio_read and aio_write, so the remaining
		62	functionality would have to be implemented using threads anyway.
19		63
20	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
21	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.
22		68
23	=head2 API NOTES	69	=cut
		70
		71	package IO::AIO;
		72
		73	no warnings;
		74	use strict 'vars';
		75
		76	use base 'Exporter';
		77
		78	BEGIN {
		79	our $VERSION = '2.0';
		80
		81	our @AIO_REQ = 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
		83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
		84	aio_group aio_nop);
		85	our @EXPORT = (@AIO_REQ, qw(aioreq_pri));
		86	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		87	min_parallel max_parallel max_outstanding nreqs);
		88
		89	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
		90
		91	require XSLoader;
		92	XSLoader::load ("IO::AIO", $VERSION);
		93	}
		94
		95	=head1 FUNCTIONS
		96
		97	=head2 AIO FUNCTIONS
24		98
25	All the C<aio_*> calls are more or less thin wrappers around the syscall	99	All the C<aio_*> calls are more or less thin wrappers around the syscall
26	with the same name (sans C<aio_>). The arguments are similar or identical,	100	with the same name (sans C<aio_>). The arguments are similar or identical,
27	and they all accept an additional C<$callback> argument which must be	101	and they all accept an additional (and optional) C<$callback> argument
28	a code reference. This code reference will get called with the syscall	102	which must be a code reference. This code reference will get called with
29	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	103	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
30	usually delivers "false") as it's sole argument when the given syscall has	104	perl, which usually delivers "false") as it's sole argument when the given
31	been executed asynchronously.	105	syscall has been executed asynchronously.
32		106
33	All functions that expect a filehandle will also accept a file descriptor.	107	All functions expecting a filehandle keep a copy of the filehandle
		108	internally until the request has finished.
34		109
		110	All requests return objects of type L<IO::AIO::REQ> that allow further
		111	manipulation of those requests while they are in-flight.
		112
35	The filenames you pass to these routines I<must> be absolute. The reason	113	The pathnames you pass to these routines I<must> be absolute and
36	is that at the time the request is being executed, the current working	114	encoded in byte form. The reason for the former is that at the time the
37	directory could have changed. Alternatively, you can make sure that you	115	request is being executed, the current working directory could have
		116	changed. Alternatively, you can make sure that you never change the
38	never change the current working directory.	117	current working directory.
		118
		119	To encode pathnames to byte form, either make sure you either: a)
		120	always pass in filenames you got from outside (command line, readdir
		121	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		122	your pathnames to the locale (or other) encoding in effect in the user
		123	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		124	use something else.
39		125
40	=over 4	126	=over 4
41		127
42	=cut
43
44	package IO::AIO;
45
46	use base 'Exporter';
47
48	BEGIN {
49	$VERSION = 0.1;
50
51	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
52	aio_fsync aio_fdatasync aio_readahead);
53	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs);
54
55	require XSLoader;
56	XSLoader::load IO::AIO, $VERSION;
57	}
58
59	=item IO::AIO::min_parallel $nthreads
60
61	Set the minimum number of AIO threads to C<$nthreads>. The default is
62	C<1>, which means a single asynchronous operation can be done at one time
63	(the number of outstanding operations, however, is unlimited).
64
65	It is recommended to keep the number of threads low, as some linux
66	kernel versions will scale negatively with the number of threads (higher
67	parallelity => MUCH higher latency).
68
69	Under normal circumstances you don't need to call this function, as this
70	module automatically starts a single async thread.
71
72	=item IO::AIO::max_parallel $nthreads
73
74	Sets the maximum number of AIO threads to C<$nthreads>. If more than
75	the specified number of threads are currently running, kill them. This
76	function blocks until the limit is reached.
77
78	This module automatically runs C<max_parallel 0> at program end, to ensure
79	that all threads are killed and that there are no outstanding requests.
80
81	Under normal circumstances you don't need to call this function.
82
83	=item $fileno = IO::AIO::poll_fileno
84
85	Return the I<request result pipe filehandle>. This filehandle must be
86	polled for reading by some mechanism outside this module (e.g. Event
87	or select, see below). If the pipe becomes readable you have to call
88	C<poll_cb> to check the results.
89
90	See C<poll_cb> for an example.
91
92	=item IO::AIO::poll_cb
93
94	Process all outstanding events on the result pipe. You have to call this
95	regularly. Returns the number of events processed. Returns immediately
96	when no events are outstanding.
97
98	You can use Event to multiplex, e.g.:
99
100	Event->io (fd => IO::AIO::poll_fileno,
101	poll => 'r', async => 1,
102	cb => \&IO::AIO::poll_cb);
103
104	=item IO::AIO::poll_wait
105
106	Wait till the result filehandle becomes ready for reading (simply does a
107	select on the filehandle. This is useful if you want to synchronously wait
108	for some requests to finish).
109
110	See C<nreqs> for an example.
111
112	=item IO::AIO::nreqs
113
114	Returns the number of requests currently outstanding.
115
116	Example: wait till there are no outstanding requests anymore:
117
118	IO::AIO::poll_wait, IO::AIO::poll_cb
119	while IO::AIO::nreqs;
120
121	=item aio_open $pathname, $flags, $mode, $callback	128	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		129
123	Asynchronously open or create a file and call the callback with the	130	Asynchronously open or create a file and call the callback with a newly
124	filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this	131	created filehandle for the file.
125	might change in the future).
126		132
127	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	133	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
128	for an explanation.	134	for an explanation.
129		135
130	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	136	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
131	list. They are the same as used in C<sysopen>.	137	list. They are the same as used by C<sysopen>.
		138
		139	Likewise, C<$mode> specifies the mode of the newly created file, if it
		140	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		141	except that it is mandatory (i.e. use C<0> if you don't create new files,
		142	and C<0666> or C<0777> if you do).
132		143
133	Example:	144	Example:
134		145
135	aio_open "/etc/passwd", O_RDONLY, 0, sub {	146	aio_open "/etc/passwd", O_RDONLY, 0, sub {
136	if ($_[0] >= 0) {	147	if ($_[0]) {
137	open my $fh, "<&$_[0]"; # create a copy for perl
138	aio_close $_[0], sub { }; # close the aio handle
139	print "open successful, fh is $fh\n";	148	print "open successful, fh is $_[0]\n";
140	...	149	...
141	} else {	150	} else {
142	die "open failed: $!\n";	151	die "open failed: $!\n";
143	}	152	}
144	};	153	};
145		154
146	=item aio_close $fh, $callback	155	=item aio_close $fh, $callback->($status)
147		156
148	Asynchronously close a file and call the callback with the result code.	157	Asynchronously close a file and call the callback with the result
		158	code. I<WARNING:> although accepted, you should not pass in a perl
		159	filehandle here, as perl will likely close the file descriptor another
		160	time when the filehandle is destroyed. Normally, you can safely call perls
		161	C<close> or just let filehandles go out of scope.
149		162
		163	This is supposed to be a bug in the API, so that might change. It's
		164	therefore best to avoid this function.
		165
150	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	166	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		167
152	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	168	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		169
154	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	170	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
155	into the scalar given by C<data> and offset C<dataoffset> and calls the	171	into the scalar given by C<data> and offset C<dataoffset> and calls the
156	callback without the actual number of bytes read (or -1 on error, just	172	callback without the actual number of bytes read (or -1 on error, just
157	like the syscall).	173	like the syscall).
158		174
		175	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		176	is outstanding. Modifying it can result in segfaults or WW3 (if the
		177	necessary/optional hardware is installed).
		178
159	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	179	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
160	offset C<0> within the scalar:	180	offset C<0> within the scalar:
161		181
162	aio_read $fh, 7, 15, $buffer, 0, sub {	182	aio_read $fh, 7, 15, $buffer, 0, sub {
163	$_[0] >= 0 or die "read error: $!";	183	$_[0] > 0 or die "read error: $!";
164	print "read <$buffer>\n";	184	print "read $_[0] bytes: <$buffer>\n";
165	};	185	};
166		186
		187	=item aio_move $srcpath, $dstpath, $callback->($status)
		188
		189	[EXPERIMENTAL due to internal aio_group use]
		190
		191	Try to move the I<file> (directories not supported as either source or
		192	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		193	the C<0> (error) or C<-1> ok.
		194
		195	This is a composite request that tries to rename(2) the file first. If
		196	rename files with C<EXDEV>, it creates the destination file with mode 0200
		197	and copies the contents of the source file into it using C<aio_sendfile>,
		198	followed by restoring atime, mtime, access mode and uid/gid, in that
		199	order, and unlinking the C<$srcpath>.
		200
		201	If an error occurs, the partial destination file will be unlinked, if
		202	possible, except when setting atime, mtime, access mode and uid/gid, where
		203	errors are being ignored.
		204
		205	=cut
		206
		207	sub aio_move($$$) {
		208	my ($src, $dst, $cb) = @_;
		209
		210	my $grp = aio_group $cb;
		211
		212	add $grp aio_rename $src, $dst, sub {
		213	if ($_[0] && $! == EXDEV) {
		214	add $grp aio_open $src, O_RDONLY, 0, sub {
		215	if (my $src_fh = $_[0]) {
		216	my @stat = stat $src_fh;
		217
		218	add $grp aio_open $dst, O_WRONLY, 0200, sub {
		219	if (my $dst_fh = $_[0]) {
		220	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		221	close $src_fh;
		222
		223	if ($_[0] == $stat[7]) {
		224	utime $stat[8], $stat[9], $dst;
		225	chmod $stat[2] & 07777, $dst_fh;
		226	chown $stat[4], $stat[5], $dst_fh;
		227	close $dst_fh;
		228
		229	add $grp aio_unlink $src, sub {
		230	$grp->result ($_[0]);
		231	};
		232	} else {
		233	my $errno = $!;
		234	add $grp aio_unlink $dst, sub {
		235	$! = $errno;
		236	$grp->result (-1);
		237	};
		238	}
		239	};
		240	} else {
		241	$grp->result (-1);
		242	}
		243	},
		244
		245	} else {
		246	$grp->result (-1);
		247	}
		248	};
		249	} else {
		250	$grp->result ($_[0]);
		251	}
		252	};
		253
		254	$grp
		255	}
		256
		257	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		258
		259	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		260	reading at byte offset C<$in_offset>, and starts writing at the current
		261	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		262	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		263	other.
		264
		265	This call tries to make use of a native C<sendfile> syscall to provide
		266	zero-copy operation. For this to work, C<$out_fh> should refer to a
		267	socket, and C<$in_fh> should refer to mmap'able file.
		268
		269	If the native sendfile call fails or is not implemented, it will be
		270	emulated, so you can call C<aio_sendfile> on any type of filehandle
		271	regardless of the limitations of the operating system.
		272
		273	Please note, however, that C<aio_sendfile> can read more bytes from
		274	C<$in_fh> than are written, and there is no way to find out how many
		275	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		276	provides the number of bytes written to C<$out_fh>. Only if the result
		277	value equals C<$length> one can assume that C<$length> bytes have been
		278	read.
		279
167	=item aio_readahead $fh,$offset,$length, $callback	280	=item aio_readahead $fh,$offset,$length, $callback->($retval)
168		281
169	Asynchronously reads the specified byte range into the page cache, using
170	the C<readahead> syscall. If that syscall doesn't exist the status will be
171	C<-1> and C<$!> is set to ENOSYS.
172
173	readahead() populates the page cache with data from a file so that	282	C<aio_readahead> populates the page cache with data from a file so that
174	subsequent reads from that file will not block on disk I/O. The C<$offset>	283	subsequent reads from that file will not block on disk I/O. The C<$offset>
175	argument specifies the starting point from which data is to be read and	284	argument specifies the starting point from which data is to be read and
176	C<$length> specifies the number of bytes to be read. I/O is performed in	285	C<$length> specifies the number of bytes to be read. I/O is performed in
177	whole pages, so that offset is effectively rounded down to a page boundary	286	whole pages, so that offset is effectively rounded down to a page boundary
178	and bytes are read up to the next page boundary greater than or equal to	287	and bytes are read up to the next page boundary greater than or equal to
179	(off-set+length). aio_readahead() does not read beyond the end of the	288	(off-set+length). C<aio_readahead> does not read beyond the end of the
180	file. The current file offset of the file is left unchanged.	289	file. The current file offset of the file is left unchanged.
181		290
		291	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		292	emulated by simply reading the data, which would have a similar effect.
		293
182	=item aio_stat $fh_or_path, $callback	294	=item aio_stat $fh_or_path, $callback->($status)
183		295
184	=item aio_lstat $fh, $callback	296	=item aio_lstat $fh, $callback->($status)
185		297
186	Works like perl's C<stat> or C<lstat> in void context. The callback will	298	Works like perl's C<stat> or C<lstat> in void context. The callback will
187	be called after the stat and the results will be available using C<stat _>	299	be called after the stat and the results will be available using C<stat _>
188	or C<-s _> etc...	300	or C<-s _> etc...
189		301
…		…
199	aio_stat "/etc/passwd", sub {	311	aio_stat "/etc/passwd", sub {
200	$_[0] and die "stat failed: $!";	312	$_[0] and die "stat failed: $!";
201	print "size is ", -s _, "\n";	313	print "size is ", -s _, "\n";
202	};	314	};
203		315
204	=item aio_unlink $pathname, $callback	316	=item aio_unlink $pathname, $callback->($status)
205		317
206	Asynchronously unlink (delete) a file and call the callback with the	318	Asynchronously unlink (delete) a file and call the callback with the
207	result code.	319	result code.
208		320
		321	=item aio_link $srcpath, $dstpath, $callback->($status)
		322
		323	Asynchronously create a new link to the existing object at C<$srcpath> at
		324	the path C<$dstpath> and call the callback with the result code.
		325
		326	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		327
		328	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		329	the path C<$dstpath> and call the callback with the result code.
		330
		331	=item aio_rename $srcpath, $dstpath, $callback->($status)
		332
		333	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		334	rename(2) and call the callback with the result code.
		335
		336	=item aio_rmdir $pathname, $callback->($status)
		337
		338	Asynchronously rmdir (delete) a directory and call the callback with the
		339	result code.
		340
		341	=item aio_readdir $pathname, $callback->($entries)
		342
		343	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		344	directory (i.e. opendir + readdir + closedir). The entries will not be
		345	sorted, and will B<NOT> include the C<.> and C<..> entries.
		346
		347	The callback a single argument which is either C<undef> or an array-ref
		348	with the filenames.
		349
		350	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		351
		352	[EXPERIMENTAL due to internal aio_group use]
		353
		354	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		355	separate the entries of directory C<$path> into two sets of names, ones
		356	you can recurse into (directories or links to them), and ones you cannot
		357	recurse into (everything else).
		358
		359	C<aio_scandir> is a composite request that creates of many sub requests_
		360	C<$maxreq> specifies the maximum number of outstanding aio requests that
		361	this function generates. If it is C<< <= 0 >>, then a suitable default
		362	will be chosen (currently 6).
		363
		364	On error, the callback is called without arguments, otherwise it receives
		365	two array-refs with path-relative entry names.
		366
		367	Example:
		368
		369	aio_scandir $dir, 0, sub {
		370	my ($dirs, $nondirs) = @_;
		371	print "real directories: @$dirs\n";
		372	print "everything else: @$nondirs\n";
		373	};
		374
		375	Implementation notes.
		376
		377	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		378
		379	After reading the directory, the modification time, size etc. of the
		380	directory before and after the readdir is checked, and if they match (and
		381	isn't the current time), the link count will be used to decide how many
		382	entries are directories (if >= 2). Otherwise, no knowledge of the number
		383	of subdirectories will be assumed.
		384
		385	Then entries will be sorted into likely directories (everything without
		386	a non-initial dot currently) and likely non-directories (everything
		387	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		388	likely directories first. If that succeeds, it assumes that the entry
		389	is a directory or a symlink to directory (which will be checked
		390	seperately). This is often faster than stat'ing the entry itself because
		391	filesystems might detect the type of the entry without reading the inode
		392	data (e.g. ext2fs filetype feature).
		393
		394	If the known number of directories (link count - 2) has been reached, the
		395	rest of the entries is assumed to be non-directories.
		396
		397	This only works with certainty on POSIX (= UNIX) filesystems, which
		398	fortunately are the vast majority of filesystems around.
		399
		400	It will also likely work on non-POSIX filesystems with reduced efficiency
		401	as those tend to return 0 or 1 as link counts, which disables the
		402	directory counting heuristic.
		403
		404	=cut
		405
		406	sub aio_scandir($$$) {
		407	my ($path, $maxreq, $cb) = @_;
		408
		409	my $grp = aio_group $cb;
		410
		411	$maxreq = 6 if $maxreq <= 0;
		412
		413	# stat once
		414	add $grp aio_stat $path, sub {
		415	return $grp->result () if $_[0];
		416	my $now = time;
		417	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		418
		419	# read the directory entries
		420	add $grp aio_readdir $path, sub {
		421	my $entries = shift
		422	or return $grp->result ();
		423
		424	# stat the dir another time
		425	add $grp aio_stat $path, sub {
		426	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		427
		428	my $ndirs;
		429
		430	# take the slow route if anything looks fishy
		431	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		432	$ndirs = -1;
		433	} else {
		434	# if nlink == 2, we are finished
		435	# on non-posix-fs's, we rely on nlink < 2
		436	$ndirs = (stat _)[3] - 2
		437	or return $grp->result ([], $entries);
		438	}
		439
		440	# sort into likely dirs and likely nondirs
		441	# dirs == files without ".", short entries first
		442	$entries = [map $_->[0],
		443	sort { $b->[1] cmp $a->[1] }
		444	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		445	@$entries];
		446
		447	my (@dirs, @nondirs);
		448
		449	my ($statcb, $schedcb);
		450	my $nreq = 0;
		451
		452	my $statgrp = add $grp aio_group;
		453
		454	$schedcb = sub {
		455	if (@$entries) {
		456	if ($nreq < $maxreq) {
		457	my $ent = pop @$entries;
		458	$nreq++;
		459	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
		460	}
		461	} elsif (!$nreq) {
		462	# finished
		463	$statgrp->cancel;
		464	undef $statcb;
		465	undef $schedcb;
		466	$grp->result (\@dirs, \@nondirs);
		467	}
		468	};
		469	$statcb = sub {
		470	my ($status, $entry) = @_;
		471
		472	if ($status < 0) {
		473	$nreq--;
		474	push @nondirs, $entry;
		475	&$schedcb;
		476	} else {
		477	# need to check for real directory
		478	add $grp aio_lstat "$path/$entry", sub {
		479	$nreq--;
		480
		481	if (-d _) {
		482	push @dirs, $entry;
		483
		484	if (!--$ndirs) {
		485	push @nondirs, @$entries;
		486	$entries = [];
		487	}
		488	} else {
		489	push @nondirs, $entry;
		490	}
		491
		492	&$schedcb;
		493	}
		494	}
		495	};
		496
		497	&$schedcb while @$entries && $nreq < $maxreq;
		498	};
		499	};
		500	};
		501
		502	$grp
		503	}
		504
209	=item aio_fsync $fh, $callback	505	=item aio_fsync $fh, $callback->($status)
210		506
211	Asynchronously call fsync on the given filehandle and call the callback	507	Asynchronously call fsync on the given filehandle and call the callback
212	with the fsync result code.	508	with the fsync result code.
213		509
214	=item aio_fdatasync $fh, $callback	510	=item aio_fdatasync $fh, $callback->($status)
215		511
216	Asynchronously call fdatasync on the given filehandle and call the	512	Asynchronously call fdatasync on the given filehandle and call the
217	callback with the fdatasync result code.	513	callback with the fdatasync result code.
218		514
		515	If this call isn't available because your OS lacks it or it couldn't be
		516	detected, it will be emulated by calling C<fsync> instead.
		517
		518	=item aio_group $callback->(...)
		519
		520	[EXPERIMENTAL]
		521
		522	This is a very special aio request: Instead of doing something, it is a
		523	container for other aio requests, which is useful if you want to bundle
		524	many requests into a single, composite, request.
		525
		526	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		527	for more info.
		528
		529	Example:
		530
		531	my $grp = aio_group sub {
		532	print "all stats done\n";
		533	};
		534
		535	add $grp
		536	(aio_stat ...),
		537	(aio_stat ...),
		538	...;
		539
		540	=item aio_nop $callback->()
		541
		542	This is a special request - it does nothing in itself and is only used for
		543	side effects, such as when you want to add a dummy request to a group so
		544	that finishing the requests in the group depends on executing the given
		545	code.
		546
		547	While this request does nothing, it still goes through the execution
		548	phase and still requires a worker thread. Thus, the callback will not
		549	be executed immediately but only after other requests in the queue have
		550	entered their execution phase. This can be used to measure request
		551	latency.
		552
		553	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() NOT EXPORTED
		554
		555	Mainly used for debugging and benchmarking, this aio request puts one of
		556	the request workers to sleep for the given time.
		557
		558	While it is theoretically handy to have simple I/O scheduling requests
		559	like sleep and file handle readable/writable, the overhead this creates
		560	is immense, so do not use this function except to put your application
		561	under artificial I/O pressure.
		562
		563	=back
		564
		565	=head2 IO::AIO::REQ CLASS
		566
		567	All non-aggregate C<aio_*> functions return an object of this class when
		568	called in non-void context.
		569
		570	A request always moves through the following five states in its lifetime,
		571	in order: B<ready> (request has been created, but has not been executed
		572	yet), B<execute> (request is currently being executed), B<pending>
		573	(request has been executed but callback has not been called yet),
		574	B<result> (results are being processed synchronously, includes calling the
		575	callback) and B<done> (request has reached the end of its lifetime and
		576	holds no resources anymore).
		577
		578	=over 4
		579
		580	=item cancel $req
		581
		582	Cancels the request, if possible. Has the effect of skipping execution
		583	when entering the B<execute> state and skipping calling the callback when
		584	entering the the B<result> state, but will leave the request otherwise
		585	untouched. That means that requests that currently execute will not be
		586	stopped and resources held by the request will not be freed prematurely.
		587
		588	=item cb $req $callback->(...)
		589
		590	Replace (or simply set) the callback registered to the request.
		591
		592	=back
		593
		594	=head2 IO::AIO::GRP CLASS
		595
		596	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		597	objects of this class, too.
		598
		599	A IO::AIO::GRP object is a special request that can contain multiple other
		600	aio requests.
		601
		602	You create one by calling the C<aio_group> constructing function with a
		603	callback that will be called when all contained requests have entered the
		604	C<done> state:
		605
		606	my $grp = aio_group sub {
		607	print "all requests are done\n";
		608	};
		609
		610	You add requests by calling the C<add> method with one or more
		611	C<IO::AIO::REQ> objects:
		612
		613	$grp->add (aio_unlink "...");
		614
		615	add $grp aio_stat "...", sub {
		616	$_[0] or return $grp->result ("error");
		617
		618	# add another request dynamically, if first succeeded
		619	add $grp aio_open "...", sub {
		620	$grp->result ("ok");
		621	};
		622	};
		623
		624	This makes it very easy to create composite requests (see the source of
		625	C<aio_move> for an application) that work and feel like simple requests.
		626
		627	=over 4
		628
		629	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		630	C<IO::AIO::poll_cb>, just like any other request.
		631
		632	=item * They can be canceled like any other request. Canceling will cancel not
		633	only the request itself, but also all requests it contains.
		634
		635	=item * They can also can also be added to other IO::AIO::GRP objects.
		636
		637	=item * You must not add requests to a group from within the group callback (or
		638	any later time).
		639
		640	=item * This does not harmonise well with C<max_outstanding>, so best do
		641	not combine C<aio_group> with it. Groups and feeders are recommended for
		642	this kind of concurrency-limiting.
		643
		644	=back
		645
		646	Their lifetime, simplified, looks like this: when they are empty, they
		647	will finish very quickly. If they contain only requests that are in the
		648	C<done> state, they will also finish. Otherwise they will continue to
		649	exist.
		650
		651	That means after creating a group you have some time to add requests. And
		652	in the callbacks of those requests, you can add further requests to the
		653	group. And only when all those requests have finished will the the group
		654	itself finish.
		655
		656	=over 4
		657
		658	=item add $grp ...
		659
		660	=item $grp->add (...)
		661
		662	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		663	be added, including other groups, as long as you do not create circular
		664	dependencies.
		665
		666	Returns all its arguments.
		667
		668	=item $grp->result (...)
		669
		670	Set the result value(s) that will be passed to the group callback when all
		671	subrequests have finished. By default, no argument will be passed.
		672
		673	=item feed $grp $callback->($grp)
		674
		675	[VERY EXPERIMENTAL]
		676
		677	Sets a feeder/generator on this group: every group can have an attached
		678	generator that generates requests if idle. The idea behind this is that,
		679	although you could just queue as many requests as you want in a group,
		680	this might starve other requests for a potentially long time. For
		681	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		682	requests, delaying any later requests for a long time.
		683
		684	To avoid this, and allow incremental generation of requests, you can
		685	instead a group and set a feeder on it that generates those requests. The
		686	feed callback will be called whenever there are few enough (see C<feed_limit>,
		687	below) requests active in the group itself and is expected to queue more
		688	requests.
		689
		690	The feed can queue as many requests as it likes (i.e. C<add> does not
		691	impose any limits).
		692
		693	If the feed does not queue more requests when called, it will be
		694	automatically removed from the group.
		695
		696	If the feed limit is C<0>, it will be set to C<2> automatically.
		697
		698	Example:
		699
		700	# stat all files in @files, but only ever use four aio requests concurrently:
		701
		702	my $grp = aio_group sub { print "finished\n" };
		703	feed_limit $grp 4;
		704	feed $grp sub {
		705	my $file = pop @files
		706	or return;
		707
		708	add $grp aio_stat $file, sub { ... };
		709	};
		710
		711	=item feed_limit $grp $num
		712
		713	Sets the feeder limit for the group: The feeder will be called whenever
		714	the group contains less than this many requests.
		715
		716	Setting the limit to C<0> will pause the feeding process.
		717
		718	=back
		719
		720	=head2 SUPPORT FUNCTIONS
		721
		722	=over 4
		723
		724	=item $fileno = IO::AIO::poll_fileno
		725
		726	Return the I<request result pipe file descriptor>. This filehandle must be
		727	polled for reading by some mechanism outside this module (e.g. Event or
		728	select, see below or the SYNOPSIS). If the pipe becomes readable you have
		729	to call C<poll_cb> to check the results.
		730
		731	See C<poll_cb> for an example.
		732
		733	=item IO::AIO::poll_cb
		734
		735	Process all outstanding events on the result pipe. You have to call this
		736	regularly. Returns the number of events processed. Returns immediately
		737	when no events are outstanding.
		738
		739	Example: Install an Event watcher that automatically calls
		740	IO::AIO::poll_cb with high priority:
		741
		742	Event->io (fd => IO::AIO::poll_fileno,
		743	poll => 'r', async => 1,
		744	cb => \&IO::AIO::poll_cb);
		745
		746	=item IO::AIO::poll_wait
		747
		748	Wait till the result filehandle becomes ready for reading (simply does a
		749	C<select> on the filehandle. This is useful if you want to synchronously wait
		750	for some requests to finish).
		751
		752	See C<nreqs> for an example.
		753
		754	=item IO::AIO::nreqs
		755
		756	Returns the number of requests currently outstanding (i.e. for which their
		757	callback has not been invoked yet).
		758
		759	Example: wait till there are no outstanding requests anymore:
		760
		761	IO::AIO::poll_wait, IO::AIO::poll_cb
		762	while IO::AIO::nreqs;
		763
		764	=item IO::AIO::flush
		765
		766	Wait till all outstanding AIO requests have been handled.
		767
		768	Strictly equivalent to:
		769
		770	IO::AIO::poll_wait, IO::AIO::poll_cb
		771	while IO::AIO::nreqs;
		772
		773	=item IO::AIO::poll
		774
		775	Waits until some requests have been handled.
		776
		777	Strictly equivalent to:
		778
		779	IO::AIO::poll_wait, IO::AIO::poll_cb
		780	if IO::AIO::nreqs;
		781
		782	=item IO::AIO::min_parallel $nthreads
		783
		784	Set the minimum number of AIO threads to C<$nthreads>. The current
		785	default is C<8>, which means eight asynchronous operations can execute
		786	concurrently at any one time (the number of outstanding requests,
		787	however, is unlimited).
		788
		789	IO::AIO starts threads only on demand, when an AIO request is queued and
		790	no free thread exists.
		791
		792	It is recommended to keep the number of threads relatively low, as some
		793	Linux kernel versions will scale negatively with the number of threads
		794	(higher parallelity => MUCH higher latency). With current Linux 2.6
		795	versions, 4-32 threads should be fine.
		796
		797	Under most circumstances you don't need to call this function, as the
		798	module selects a default that is suitable for low to moderate load.
		799
		800	=item IO::AIO::max_parallel $nthreads
		801
		802	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		803	specified number of threads are currently running, this function kills
		804	them. This function blocks until the limit is reached.
		805
		806	While C<$nthreads> are zero, aio requests get queued but not executed
		807	until the number of threads has been increased again.
		808
		809	This module automatically runs C<max_parallel 0> at program end, to ensure
		810	that all threads are killed and that there are no outstanding requests.
		811
		812	Under normal circumstances you don't need to call this function.
		813
		814	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
		815
		816	[DEPRECATED]
		817
		818	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		819	try to queue up more than this number of requests, the caller will block until
		820	some requests have been handled.
		821
		822	The default is very large, so normally there is no practical limit. If you
		823	queue up many requests in a loop it often improves speed if you set
		824	this to a relatively low number, such as C<100>.
		825
		826	This function does not work well together with C<aio_group>'s, and their
		827	feeder interface is better suited to limiting concurrency, so do not use
		828	this function.
		829
		830	Under normal circumstances you don't need to call this function.
		831
		832	=back
		833
219	=cut	834	=cut
220		835
		836	# support function to convert a fd into a perl filehandle
		837	sub _fd2fh {
		838	return undef if $_[0] < 0;
		839
		840	# try to generate nice filehandles
		841	my $sym = "IO::AIO::fd#$_[0]";
		842	local *$sym;
		843
		844	open *$sym, "+<&=$_[0]" # usually works under any unix
		845	or open *$sym, "<&=$_[0]" # cygwin needs this
		846	or open *$sym, ">&=$_[0]" # or this
		847	or return undef;
		848
		849	*$sym
		850	}
		851
221	min_parallel 4;	852	min_parallel 8;
222		853
223	END {	854	END {
224	max_parallel 0;	855	max_parallel 0;
225	}	856	}
226		857
227	1;	858	1;
228		859
229	=back	860	=head2 FORK BEHAVIOUR
230		861
231	=head1 BUGS	862	This module should do "the right thing" when the process using it forks:
232		863
233	- aio_open gives a fd, but all other functions expect a perl filehandle.	864	Before the fork, IO::AIO enters a quiescent state where no requests
		865	can be added in other threads and no results will be processed. After
		866	the fork the parent simply leaves the quiescent state and continues
		867	request/result processing, while the child clears the request/result
		868	queue (so the requests started before the fork will only be handled in
		869	the parent). Threads will be started on demand until the limit ste in the
		870	parent process has been reached again.
		871
		872	In short: the parent will, after a short pause, continue as if fork had
		873	not been called, while the child will act as if IO::AIO has not been used
		874	yet.
		875
		876	=head2 MEMORY USAGE
		877
		878	Each aio request uses - depending on your architecture - around 128 bytes
		879	of memory. In addition, stat requests need a stat buffer (possibly a few
		880	hundred bytes). Perl scalars and other data passed into aio requests will
		881	also be locked.
		882
		883	This is now awfully much, so queuing lots of requests is not usually a
		884	problem.
		885
		886	Each thread needs a stack area which is usually around 16k, sometimes much
		887	larger, depending on the OS.
234		888
235	=head1 SEE ALSO	889	=head1 SEE ALSO
236		890
237	L<Coro>, L<Linux::AIO>.	891	L<Coro>, L<Linux::AIO> (obsolete).
238		892
239	=head1 AUTHOR	893	=head1 AUTHOR
240		894
241	Marc Lehmann <schmorp@schmorp.de>	895	Marc Lehmann <schmorp@schmorp.de>
242	http://home.schmorp.de/	896	http://home.schmorp.de/

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Revision 1.67 by root, Tue Oct 24 02:25:16 2006 UTC