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

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.6 by root, Sun Jul 10 22:19:48 2005 UTC vs.
Revision 1.105 by root, Sun Mar 25 00:20:27 2007 UTC

…		…
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 {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] >= 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
		32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		34
		35	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r', async => 1,	37	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
24		39
25	# Glib/Gtk2	40	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
27	\&IO::AIO::poll_cb;	42	in => sub { IO::AIO::poll_cb; 1 };
28		43
29	# Tk	44	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
32		47
		48	# Danga::Socket integration
		49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		50	\&IO::AIO::poll_cb);
		51
33	=head1 DESCRIPTION	52	=head1 DESCRIPTION
34		53
35	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
36	operating system supports.	55	operating system supports.
37		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for example
		68	sockets), using these functions on file descriptors that support
		69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or
		70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
		71	for that (such as the L<Event\|Event> module): IO::AIO will naturally fit
		72	into such an event loop itself.
		73
38	Currently, a number of threads are started that execute your read/writes	74	In this version, a number of threads are started that execute your
39	and signal their completion. You don't need thread support in your libc or	75	requests and signal their completion. You don't need thread support
40	perl, and the threads created by this module will not be visible to the	76	in perl, and the threads created by this module will not be visible
41	pthreads library. In the future, this module might make use of the native	77	to perl. In the future, this module might make use of the native aio
42	aio functions available on many operating systems. However, they are often	78	functions available on many operating systems. However, they are often
43	not well-supported (Linux doesn't allow them on normal files currently,	79	not well-supported or restricted (GNU/Linux doesn't allow them on normal
44	for example), and they would only support aio_read and aio_write, so the	80	files currently, for example), and they would only support aio_read and
45	remaining functionality would have to be implemented using threads anyway.	81	aio_write, so the remaining functionality would have to be implemented
		82	using threads anyway.
46		83
47	Although the module will work with in the presence of other threads, it is	84	Although the module will work with in the presence of other (Perl-)
48	currently not reentrant, so use appropriate locking yourself.	85	threads, it is currently not reentrant in any way, so use appropriate
		86	locking yourself, always call C<poll_cb> from within the same thread, or
		87	never call C<poll_cb> (or other C<aio_> functions) recursively.
		88
		89	=head2 EXAMPLE
		90
		91	This is a simple example that uses the Event module and loads
		92	F</etc/passwd> asynchronously:
		93
		94	use Fcntl;
		95	use Event;
		96	use IO::AIO;
		97
		98	# register the IO::AIO callback with Event
		99	Event->io (fd => IO::AIO::poll_fileno,
		100	poll => 'r',
		101	cb => \&IO::AIO::poll_cb);
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	Event::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	Event::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
49		184
50	=cut	185	=cut
51		186
52	package IO::AIO;	187	package IO::AIO;
53		188
		189	no warnings;
		190	use strict 'vars';
		191
54	use base 'Exporter';	192	use base 'Exporter';
55		193
56	use Fcntl ();
57
58	BEGIN {	194	BEGIN {
59	$VERSION = 0.2;	195	our $VERSION = '2.33';
60		196
61	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
62	aio_fsync aio_fdatasync aio_readahead);	198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
63	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
		200	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
64		208
65	require XSLoader;	209	require XSLoader;
66	XSLoader::load IO::AIO, $VERSION;	210	XSLoader::load ("IO::AIO", $VERSION);
67	}	211	}
68		212
69	=head1 FUNCTIONS	213	=head1 FUNCTIONS
70		214
71	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
72		216
73	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
74	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
75	and they all accept an additional C<$callback> argument which must be	219	and they all accept an additional (and optional) C<$callback> argument
76	a code reference. This code reference will get called with the syscall	220	which must be a code reference. This code reference will get called with
77	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
78	usually delivers "false") as it's sole argument when the given syscall has	222	perl, which usually delivers "false") as it's sole argument when the given
79	been executed asynchronously.	223	syscall has been executed asynchronously.
80		224
81	All functions that expect a filehandle will also accept a file descriptor.	225	All functions expecting a filehandle keep a copy of the filehandle
		226	internally until the request has finished.
82		227
		228	All functions return request objects of type L<IO::AIO::REQ> that allow
		229	further manipulation of those requests while they are in-flight.
		230
83	The filenames you pass to these routines I<must> be absolute. The reason	231	The pathnames you pass to these routines I<must> be absolute and
84	is that at the time the request is being executed, the current working	232	encoded as octets. The reason for the former is that at the time the
85	directory could have changed. Alternatively, you can make sure that you	233	request is being executed, the current working directory could have
86	never change the current working directory.	234	changed. Alternatively, you can make sure that you never change the
		235	current working directory anywhere in the program and then use relative
		236	paths.
		237
		238	To encode pathnames as octets, either make sure you either: a) always pass
		239	in filenames you got from outside (command line, readdir etc.) without
		240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		241	your pathnames to the locale (or other) encoding in effect in the user
		242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
87		247
88	=over 4	248	=over 4
89		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276	=item aioreq_nice $pri_adjust
		277
		278	Similar to C<aioreq_pri>, but subtracts the given value from the current
		279	priority, so the effect is cumulative.
		280
90	=item aio_open $pathname, $flags, $mode, $callback	281	=item aio_open $pathname, $flags, $mode, $callback->($fh)
91		282
92	Asynchronously open or create a file and call the callback with a newly	283	Asynchronously open or create a file and call the callback with a newly
93	created filehandle for the file.	284	created filehandle for the file.
94		285
95	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
96	for an explanation.	287	for an explanation.
97		288
98	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	289	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
99	list. They are the same as used in C<sysopen>.	290	list. They are the same as used by C<sysopen>.
		291
		292	Likewise, C<$mode> specifies the mode of the newly created file, if it
		293	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		294	except that it is mandatory (i.e. use C<0> if you don't create new files,
		295	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		296	by the umask in effect then the request is being executed, so better never
		297	change the umask.
100		298
101	Example:	299	Example:
102		300
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	301	aio_open "/etc/passwd", O_RDONLY, 0, sub {
104	if ($_[0]) {	302	if ($_[0]) {
…		…
107	} else {	305	} else {
108	die "open failed: $!\n";	306	die "open failed: $!\n";
109	}	307	}
110	};	308	};
111		309
112	=item aio_close $fh, $callback	310	=item aio_close $fh, $callback->($status)
113		311
114	Asynchronously close a file and call the callback with the result	312	Asynchronously close a file and call the callback with the result
115	code. I<WARNING:> although accepted, you should not pass in a perl	313	code. I<WARNING:> although accepted, you should not pass in a perl
116	filehandle here, as perl will likely close the file descriptor itself when	314	filehandle here, as perl will likely close the file descriptor another
117	the filehandle is destroyed. Normally, you can safely call perls C<close>	315	time when the filehandle is destroyed. Normally, you can safely call perls
118	or just let filehandles go out of scope.	316	C<close> or just let filehandles go out of scope.
119		317
		318	This is supposed to be a bug in the API, so that might change. It's
		319	therefore best to avoid this function.
		320
120	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	321	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121		322
122	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	323	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
123		324
124	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	325	Reads or writes C<length> bytes from the specified C<fh> and C<offset>
125	into the scalar given by C<data> and offset C<dataoffset> and calls the	326	into the scalar given by C<data> and offset C<dataoffset> and calls the
126	callback without the actual number of bytes read (or -1 on error, just	327	callback without the actual number of bytes read (or -1 on error, just
127	like the syscall).	328	like the syscall).
128		329
		330	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		331	is outstanding. Modifying it can result in segfaults or WW3 (if the
		332	necessary/optional hardware is installed).
		333
129	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	334	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
130	offset C<0> within the scalar:	335	offset C<0> within the scalar:
131		336
132	aio_read $fh, 7, 15, $buffer, 0, sub {	337	aio_read $fh, 7, 15, $buffer, 0, sub {
133	$_[0] >= 0 or die "read error: $!";	338	$_[0] > 0 or die "read error: $!";
134	print "read <$buffer>\n";	339	print "read $_[0] bytes: <$buffer>\n";
135	};	340	};
136		341
		342	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		343
		344	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		345	reading at byte offset C<$in_offset>, and starts writing at the current
		346	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		347	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		348	other.
		349
		350	This call tries to make use of a native C<sendfile> syscall to provide
		351	zero-copy operation. For this to work, C<$out_fh> should refer to a
		352	socket, and C<$in_fh> should refer to mmap'able file.
		353
		354	If the native sendfile call fails or is not implemented, it will be
		355	emulated, so you can call C<aio_sendfile> on any type of filehandle
		356	regardless of the limitations of the operating system.
		357
		358	Please note, however, that C<aio_sendfile> can read more bytes from
		359	C<$in_fh> than are written, and there is no way to find out how many
		360	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		361	provides the number of bytes written to C<$out_fh>. Only if the result
		362	value equals C<$length> one can assume that C<$length> bytes have been
		363	read.
		364
137	=item aio_readahead $fh,$offset,$length, $callback	365	=item aio_readahead $fh,$offset,$length, $callback->($retval)
138		366
139	Asynchronously reads the specified byte range into the page cache, using
140	the C<readahead> syscall. If that syscall doesn't exist the status will be
141	C<-1> and C<$!> is set to ENOSYS.
142
143	readahead() populates the page cache with data from a file so that	367	C<aio_readahead> populates the page cache with data from a file so that
144	subsequent reads from that file will not block on disk I/O. The C<$offset>	368	subsequent reads from that file will not block on disk I/O. The C<$offset>
145	argument specifies the starting point from which data is to be read and	369	argument specifies the starting point from which data is to be read and
146	C<$length> specifies the number of bytes to be read. I/O is performed in	370	C<$length> specifies the number of bytes to be read. I/O is performed in
147	whole pages, so that offset is effectively rounded down to a page boundary	371	whole pages, so that offset is effectively rounded down to a page boundary
148	and bytes are read up to the next page boundary greater than or equal to	372	and bytes are read up to the next page boundary greater than or equal to
149	(off-set+length). aio_readahead() does not read beyond the end of the	373	(off-set+length). C<aio_readahead> does not read beyond the end of the
150	file. The current file offset of the file is left unchanged.	374	file. The current file offset of the file is left unchanged.
151		375
		376	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		377	emulated by simply reading the data, which would have a similar effect.
		378
152	=item aio_stat $fh_or_path, $callback	379	=item aio_stat $fh_or_path, $callback->($status)
153		380
154	=item aio_lstat $fh, $callback	381	=item aio_lstat $fh, $callback->($status)
155		382
156	Works like perl's C<stat> or C<lstat> in void context. The callback will	383	Works like perl's C<stat> or C<lstat> in void context. The callback will
157	be called after the stat and the results will be available using C<stat _>	384	be called after the stat and the results will be available using C<stat _>
158	or C<-s _> etc...	385	or C<-s _> etc...
159		386
…		…
169	aio_stat "/etc/passwd", sub {	396	aio_stat "/etc/passwd", sub {
170	$_[0] and die "stat failed: $!";	397	$_[0] and die "stat failed: $!";
171	print "size is ", -s _, "\n";	398	print "size is ", -s _, "\n";
172	};	399	};
173		400
174	=item aio_unlink $pathname, $callback	401	=item aio_unlink $pathname, $callback->($status)
175		402
176	Asynchronously unlink (delete) a file and call the callback with the	403	Asynchronously unlink (delete) a file and call the callback with the
177	result code.	404	result code.
178		405
		406	=item aio_mknod $path, $mode, $dev, $callback->($status)
		407
		408	[EXPERIMENTAL]
		409
		410	Asynchronously create a device node (or fifo). See mknod(2).
		411
		412	The only (POSIX-) portable way of calling this function is:
		413
		414	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		415
		416	=item aio_link $srcpath, $dstpath, $callback->($status)
		417
		418	Asynchronously create a new link to the existing object at C<$srcpath> at
		419	the path C<$dstpath> and call the callback with the result code.
		420
		421	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		422
		423	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		424	the path C<$dstpath> and call the callback with the result code.
		425
		426	=item aio_readlink $path, $callback->($link)
		427
		428	Asynchronously read the symlink specified by C<$path> and pass it to
		429	the callback. If an error occurs, nothing or undef gets passed to the
		430	callback.
		431
		432	=item aio_rename $srcpath, $dstpath, $callback->($status)
		433
		434	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		435	rename(2) and call the callback with the result code.
		436
		437	=item aio_mkdir $pathname, $mode, $callback->($status)
		438
		439	Asynchronously mkdir (create) a directory and call the callback with
		440	the result code. C<$mode> will be modified by the umask at the time the
		441	request is executed, so do not change your umask.
		442
		443	=item aio_rmdir $pathname, $callback->($status)
		444
		445	Asynchronously rmdir (delete) a directory and call the callback with the
		446	result code.
		447
		448	=item aio_readdir $pathname, $callback->($entries)
		449
		450	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		451	directory (i.e. opendir + readdir + closedir). The entries will not be
		452	sorted, and will B<NOT> include the C<.> and C<..> entries.
		453
		454	The callback a single argument which is either C<undef> or an array-ref
		455	with the filenames.
		456
		457	=item aio_load $path, $data, $callback->($status)
		458
		459	This is a composite request that tries to fully load the given file into
		460	memory. Status is the same as with aio_read.
		461
		462	=cut
		463
		464	sub aio_load($$;$) {
		465	aio_block {
		466	my ($path, undef, $cb) = @_;
		467	my $data = \$_[1];
		468
		469	my $pri = aioreq_pri;
		470	my $grp = aio_group $cb;
		471
		472	aioreq_pri $pri;
		473	add $grp aio_open $path, O_RDONLY, 0, sub {
		474	my $fh = shift
		475	or return $grp->result (-1);
		476
		477	aioreq_pri $pri;
		478	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		479	$grp->result ($_[0]);
		480	};
		481	};
		482
		483	$grp
		484	}
		485	}
		486
		487	=item aio_copy $srcpath, $dstpath, $callback->($status)
		488
		489	Try to copy the I<file> (directories not supported as either source or
		490	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		491	the C<0> (error) or C<-1> ok.
		492
		493	This is a composite request that it creates the destination file with
		494	mode 0200 and copies the contents of the source file into it using
		495	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		496	uid/gid, in that order.
		497
		498	If an error occurs, the partial destination file will be unlinked, if
		499	possible, except when setting atime, mtime, access mode and uid/gid, where
		500	errors are being ignored.
		501
		502	=cut
		503
		504	sub aio_copy($$;$) {
		505	aio_block {
		506	my ($src, $dst, $cb) = @_;
		507
		508	my $pri = aioreq_pri;
		509	my $grp = aio_group $cb;
		510
		511	aioreq_pri $pri;
		512	add $grp aio_open $src, O_RDONLY, 0, sub {
		513	if (my $src_fh = $_[0]) {
		514	my @stat = stat $src_fh;
		515
		516	aioreq_pri $pri;
		517	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		518	if (my $dst_fh = $_[0]) {
		519	aioreq_pri $pri;
		520	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		521	if ($_[0] == $stat[7]) {
		522	$grp->result (0);
		523	close $src_fh;
		524
		525	# those should not normally block. should. should.
		526	utime $stat[8], $stat[9], $dst;
		527	chmod $stat[2] & 07777, $dst_fh;
		528	chown $stat[4], $stat[5], $dst_fh;
		529	close $dst_fh;
		530	} else {
		531	$grp->result (-1);
		532	close $src_fh;
		533	close $dst_fh;
		534
		535	aioreq $pri;
		536	add $grp aio_unlink $dst;
		537	}
		538	};
		539	} else {
		540	$grp->result (-1);
		541	}
		542	},
		543
		544	} else {
		545	$grp->result (-1);
		546	}
		547	};
		548
		549	$grp
		550	}
		551	}
		552
		553	=item aio_move $srcpath, $dstpath, $callback->($status)
		554
		555	Try to move the I<file> (directories not supported as either source or
		556	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		557	the C<0> (error) or C<-1> ok.
		558
		559	This is a composite request that tries to rename(2) the file first. If
		560	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		561	that is successful, unlinking the C<$srcpath>.
		562
		563	=cut
		564
		565	sub aio_move($$;$) {
		566	aio_block {
		567	my ($src, $dst, $cb) = @_;
		568
		569	my $pri = aioreq_pri;
		570	my $grp = aio_group $cb;
		571
		572	aioreq_pri $pri;
		573	add $grp aio_rename $src, $dst, sub {
		574	if ($_[0] && $! == EXDEV) {
		575	aioreq_pri $pri;
		576	add $grp aio_copy $src, $dst, sub {
		577	$grp->result ($_[0]);
		578
		579	if (!$_[0]) {
		580	aioreq_pri $pri;
		581	add $grp aio_unlink $src;
		582	}
		583	};
		584	} else {
		585	$grp->result ($_[0]);
		586	}
		587	};
		588
		589	$grp
		590	}
		591	}
		592
		593	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		594
		595	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		596	efficiently separate the entries of directory C<$path> into two sets of
		597	names, directories you can recurse into (directories), and ones you cannot
		598	recurse into (everything else, including symlinks to directories).
		599
		600	C<aio_scandir> is a composite request that creates of many sub requests_
		601	C<$maxreq> specifies the maximum number of outstanding aio requests that
		602	this function generates. If it is C<< <= 0 >>, then a suitable default
		603	will be chosen (currently 4).
		604
		605	On error, the callback is called without arguments, otherwise it receives
		606	two array-refs with path-relative entry names.
		607
		608	Example:
		609
		610	aio_scandir $dir, 0, sub {
		611	my ($dirs, $nondirs) = @_;
		612	print "real directories: @$dirs\n";
		613	print "everything else: @$nondirs\n";
		614	};
		615
		616	Implementation notes.
		617
		618	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		619
		620	After reading the directory, the modification time, size etc. of the
		621	directory before and after the readdir is checked, and if they match (and
		622	isn't the current time), the link count will be used to decide how many
		623	entries are directories (if >= 2). Otherwise, no knowledge of the number
		624	of subdirectories will be assumed.
		625
		626	Then entries will be sorted into likely directories (everything without
		627	a non-initial dot currently) and likely non-directories (everything
		628	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		629	likely directories first. If that succeeds, it assumes that the entry
		630	is a directory or a symlink to directory (which will be checked
		631	seperately). This is often faster than stat'ing the entry itself because
		632	filesystems might detect the type of the entry without reading the inode
		633	data (e.g. ext2fs filetype feature).
		634
		635	If the known number of directories (link count - 2) has been reached, the
		636	rest of the entries is assumed to be non-directories.
		637
		638	This only works with certainty on POSIX (= UNIX) filesystems, which
		639	fortunately are the vast majority of filesystems around.
		640
		641	It will also likely work on non-POSIX filesystems with reduced efficiency
		642	as those tend to return 0 or 1 as link counts, which disables the
		643	directory counting heuristic.
		644
		645	=cut
		646
		647	sub aio_scandir($$;$) {
		648	aio_block {
		649	my ($path, $maxreq, $cb) = @_;
		650
		651	my $pri = aioreq_pri;
		652
		653	my $grp = aio_group $cb;
		654
		655	$maxreq = 4 if $maxreq <= 0;
		656
		657	# stat once
		658	aioreq_pri $pri;
		659	add $grp aio_stat $path, sub {
		660	return $grp->result () if $_[0];
		661	my $now = time;
		662	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		663
		664	# read the directory entries
		665	aioreq_pri $pri;
		666	add $grp aio_readdir $path, sub {
		667	my $entries = shift
		668	or return $grp->result ();
		669
		670	# stat the dir another time
		671	aioreq_pri $pri;
		672	add $grp aio_stat $path, sub {
		673	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		674
		675	my $ndirs;
		676
		677	# take the slow route if anything looks fishy
		678	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		679	$ndirs = -1;
		680	} else {
		681	# if nlink == 2, we are finished
		682	# on non-posix-fs's, we rely on nlink < 2
		683	$ndirs = (stat _)[3] - 2
		684	or return $grp->result ([], $entries);
		685	}
		686
		687	# sort into likely dirs and likely nondirs
		688	# dirs == files without ".", short entries first
		689	$entries = [map $_->[0],
		690	sort { $b->[1] cmp $a->[1] }
		691	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		692	@$entries];
		693
		694	my (@dirs, @nondirs);
		695
		696	my $statgrp = add $grp aio_group sub {
		697	$grp->result (\@dirs, \@nondirs);
		698	};
		699
		700	limit $statgrp $maxreq;
		701	feed $statgrp sub {
		702	return unless @$entries;
		703	my $entry = pop @$entries;
		704
		705	aioreq_pri $pri;
		706	add $statgrp aio_stat "$path/$entry/.", sub {
		707	if ($_[0] < 0) {
		708	push @nondirs, $entry;
		709	} else {
		710	# need to check for real directory
		711	aioreq_pri $pri;
		712	add $statgrp aio_lstat "$path/$entry", sub {
		713	if (-d _) {
		714	push @dirs, $entry;
		715
		716	unless (--$ndirs) {
		717	push @nondirs, @$entries;
		718	feed $statgrp;
		719	}
		720	} else {
		721	push @nondirs, $entry;
		722	}
		723	}
		724	}
		725	};
		726	};
		727	};
		728	};
		729	};
		730
		731	$grp
		732	}
		733	}
		734
		735	=item aio_rmtree $path, $callback->($status)
		736
		737	Delete a directory tree starting (and including) C<$path>, return the
		738	status of the final C<rmdir> only. This is a composite request that
		739	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		740	everything else.
		741
		742	=cut
		743
		744	sub aio_rmtree;
		745	sub aio_rmtree($;$) {
		746	aio_block {
		747	my ($path, $cb) = @_;
		748
		749	my $pri = aioreq_pri;
		750	my $grp = aio_group $cb;
		751
		752	aioreq_pri $pri;
		753	add $grp aio_scandir $path, 0, sub {
		754	my ($dirs, $nondirs) = @_;
		755
		756	my $dirgrp = aio_group sub {
		757	add $grp aio_rmdir $path, sub {
		758	$grp->result ($_[0]);
		759	};
		760	};
		761
		762	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		763	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		764
		765	add $grp $dirgrp;
		766	};
		767
		768	$grp
		769	}
		770	}
		771
179	=item aio_fsync $fh, $callback	772	=item aio_fsync $fh, $callback->($status)
180		773
181	Asynchronously call fsync on the given filehandle and call the callback	774	Asynchronously call fsync on the given filehandle and call the callback
182	with the fsync result code.	775	with the fsync result code.
183		776
184	=item aio_fdatasync $fh, $callback	777	=item aio_fdatasync $fh, $callback->($status)
185		778
186	Asynchronously call fdatasync on the given filehandle and call the	779	Asynchronously call fdatasync on the given filehandle and call the
187	callback with the fdatasync result code.	780	callback with the fdatasync result code.
188		781
		782	If this call isn't available because your OS lacks it or it couldn't be
		783	detected, it will be emulated by calling C<fsync> instead.
		784
		785	=item aio_group $callback->(...)
		786
		787	This is a very special aio request: Instead of doing something, it is a
		788	container for other aio requests, which is useful if you want to bundle
		789	many requests into a single, composite, request with a definite callback
		790	and the ability to cancel the whole request with its subrequests.
		791
		792	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		793	for more info.
		794
		795	Example:
		796
		797	my $grp = aio_group sub {
		798	print "all stats done\n";
		799	};
		800
		801	add $grp
		802	(aio_stat ...),
		803	(aio_stat ...),
		804	...;
		805
		806	=item aio_nop $callback->()
		807
		808	This is a special request - it does nothing in itself and is only used for
		809	side effects, such as when you want to add a dummy request to a group so
		810	that finishing the requests in the group depends on executing the given
		811	code.
		812
		813	While this request does nothing, it still goes through the execution
		814	phase and still requires a worker thread. Thus, the callback will not
		815	be executed immediately but only after other requests in the queue have
		816	entered their execution phase. This can be used to measure request
		817	latency.
		818
		819	=item IO::AIO::aio_busy $fractional_seconds, $callback->() NOT EXPORTED
		820
		821	Mainly used for debugging and benchmarking, this aio request puts one of
		822	the request workers to sleep for the given time.
		823
		824	While it is theoretically handy to have simple I/O scheduling requests
		825	like sleep and file handle readable/writable, the overhead this creates is
		826	immense (it blocks a thread for a long time) so do not use this function
		827	except to put your application under artificial I/O pressure.
		828
189	=back	829	=back
190		830
		831	=head2 IO::AIO::REQ CLASS
		832
		833	All non-aggregate C<aio_*> functions return an object of this class when
		834	called in non-void context.
		835
		836	=over 4
		837
		838	=item cancel $req
		839
		840	Cancels the request, if possible. Has the effect of skipping execution
		841	when entering the B<execute> state and skipping calling the callback when
		842	entering the the B<result> state, but will leave the request otherwise
		843	untouched. That means that requests that currently execute will not be
		844	stopped and resources held by the request will not be freed prematurely.
		845
		846	=item cb $req $callback->(...)
		847
		848	Replace (or simply set) the callback registered to the request.
		849
		850	=back
		851
		852	=head2 IO::AIO::GRP CLASS
		853
		854	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		855	objects of this class, too.
		856
		857	A IO::AIO::GRP object is a special request that can contain multiple other
		858	aio requests.
		859
		860	You create one by calling the C<aio_group> constructing function with a
		861	callback that will be called when all contained requests have entered the
		862	C<done> state:
		863
		864	my $grp = aio_group sub {
		865	print "all requests are done\n";
		866	};
		867
		868	You add requests by calling the C<add> method with one or more
		869	C<IO::AIO::REQ> objects:
		870
		871	$grp->add (aio_unlink "...");
		872
		873	add $grp aio_stat "...", sub {
		874	$_[0] or return $grp->result ("error");
		875
		876	# add another request dynamically, if first succeeded
		877	add $grp aio_open "...", sub {
		878	$grp->result ("ok");
		879	};
		880	};
		881
		882	This makes it very easy to create composite requests (see the source of
		883	C<aio_move> for an application) that work and feel like simple requests.
		884
		885	=over 4
		886
		887	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		888	C<IO::AIO::poll_cb>, just like any other request.
		889
		890	=item * They can be canceled like any other request. Canceling will cancel not
		891	only the request itself, but also all requests it contains.
		892
		893	=item * They can also can also be added to other IO::AIO::GRP objects.
		894
		895	=item * You must not add requests to a group from within the group callback (or
		896	any later time).
		897
		898	=back
		899
		900	Their lifetime, simplified, looks like this: when they are empty, they
		901	will finish very quickly. If they contain only requests that are in the
		902	C<done> state, they will also finish. Otherwise they will continue to
		903	exist.
		904
		905	That means after creating a group you have some time to add requests. And
		906	in the callbacks of those requests, you can add further requests to the
		907	group. And only when all those requests have finished will the the group
		908	itself finish.
		909
		910	=over 4
		911
		912	=item add $grp ...
		913
		914	=item $grp->add (...)
		915
		916	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		917	be added, including other groups, as long as you do not create circular
		918	dependencies.
		919
		920	Returns all its arguments.
		921
		922	=item $grp->cancel_subs
		923
		924	Cancel all subrequests and clears any feeder, but not the group request
		925	itself. Useful when you queued a lot of events but got a result early.
		926
		927	=item $grp->result (...)
		928
		929	Set the result value(s) that will be passed to the group callback when all
		930	subrequests have finished and set thre groups errno to the current value
		931	of errno (just like calling C<errno> without an error number). By default,
		932	no argument will be passed and errno is zero.
		933
		934	=item $grp->errno ([$errno])
		935
		936	Sets the group errno value to C<$errno>, or the current value of errno
		937	when the argument is missing.
		938
		939	Every aio request has an associated errno value that is restored when
		940	the callback is invoked. This method lets you change this value from its
		941	default (0).
		942
		943	Calling C<result> will also set errno, so make sure you either set C<$!>
		944	before the call to C<result>, or call c<errno> after it.
		945
		946	=item feed $grp $callback->($grp)
		947
		948	Sets a feeder/generator on this group: every group can have an attached
		949	generator that generates requests if idle. The idea behind this is that,
		950	although you could just queue as many requests as you want in a group,
		951	this might starve other requests for a potentially long time. For
		952	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		953	requests, delaying any later requests for a long time.
		954
		955	To avoid this, and allow incremental generation of requests, you can
		956	instead a group and set a feeder on it that generates those requests. The
		957	feed callback will be called whenever there are few enough (see C<limit>,
		958	below) requests active in the group itself and is expected to queue more
		959	requests.
		960
		961	The feed callback can queue as many requests as it likes (i.e. C<add> does
		962	not impose any limits).
		963
		964	If the feed does not queue more requests when called, it will be
		965	automatically removed from the group.
		966
		967	If the feed limit is C<0>, it will be set to C<2> automatically.
		968
		969	Example:
		970
		971	# stat all files in @files, but only ever use four aio requests concurrently:
		972
		973	my $grp = aio_group sub { print "finished\n" };
		974	limit $grp 4;
		975	feed $grp sub {
		976	my $file = pop @files
		977	or return;
		978
		979	add $grp aio_stat $file, sub { ... };
		980	};
		981
		982	=item limit $grp $num
		983
		984	Sets the feeder limit for the group: The feeder will be called whenever
		985	the group contains less than this many requests.
		986
		987	Setting the limit to C<0> will pause the feeding process.
		988
		989	=back
		990
191	=head2 SUPPORT FUNCTIONS	991	=head2 SUPPORT FUNCTIONS
192		992
		993	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		994
193	=over 4	995	=over 4
194		996
195	=item $fileno = IO::AIO::poll_fileno	997	=item $fileno = IO::AIO::poll_fileno
196		998
197	Return the I<request result pipe filehandle>. This filehandle must be	999	Return the I<request result pipe file descriptor>. This filehandle must be
198	polled for reading by some mechanism outside this module (e.g. Event	1000	polled for reading by some mechanism outside this module (e.g. Event or
199	or select, see below). If the pipe becomes readable you have to call	1001	select, see below or the SYNOPSIS). If the pipe becomes readable you have
200	C<poll_cb> to check the results.	1002	to call C<poll_cb> to check the results.
201		1003
202	See C<poll_cb> for an example.	1004	See C<poll_cb> for an example.
203		1005
204	=item IO::AIO::poll_cb	1006	=item IO::AIO::poll_cb
205		1007
206	Process all outstanding events on the result pipe. You have to call this	1008	Process some outstanding events on the result pipe. You have to call this
207	regularly. Returns the number of events processed. Returns immediately	1009	regularly. Returns the number of events processed. Returns immediately
208	when no events are outstanding.	1010	when no events are outstanding. The amount of events processed depends on
		1011	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
209		1012
210	You can use Event to multiplex, e.g.:	1013	If not all requests were processed for whatever reason, the filehandle
		1014	will still be ready when C<poll_cb> returns.
		1015
		1016	Example: Install an Event watcher that automatically calls
		1017	IO::AIO::poll_cb with high priority:
211		1018
212	Event->io (fd => IO::AIO::poll_fileno,	1019	Event->io (fd => IO::AIO::poll_fileno,
213	poll => 'r', async => 1,	1020	poll => 'r', async => 1,
214	cb => \&IO::AIO::poll_cb);	1021	cb => \&IO::AIO::poll_cb);
215		1022
		1023	=item IO::AIO::max_poll_reqs $nreqs
		1024
		1025	=item IO::AIO::max_poll_time $seconds
		1026
		1027	These set the maximum number of requests (default C<0>, meaning infinity)
		1028	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1029	the maximum amount of time (default C<0>, meaning infinity) spent in
		1030	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1031	of time C<poll_cb> is allowed to use).
		1032
		1033	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1034	syscall per request processed, which is not normally a problem unless your
		1035	callbacks are really really fast or your OS is really really slow (I am
		1036	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1037
		1038	Setting these is useful if you want to ensure some level of
		1039	interactiveness when perl is not fast enough to process all requests in
		1040	time.
		1041
		1042	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1043
		1044	Example: Install an Event watcher that automatically calls
		1045	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1046	program get the CPU sometimes even under high AIO load.
		1047
		1048	# try not to spend much more than 0.1s in poll_cb
		1049	IO::AIO::max_poll_time 0.1;
		1050
		1051	# use a low priority so other tasks have priority
		1052	Event->io (fd => IO::AIO::poll_fileno,
		1053	poll => 'r', nice => 1,
		1054	cb => &IO::AIO::poll_cb);
		1055
216	=item IO::AIO::poll_wait	1056	=item IO::AIO::poll_wait
217		1057
		1058	If there are any outstanding requests and none of them in the result
218	Wait till the result filehandle becomes ready for reading (simply does a	1059	phase, wait till the result filehandle becomes ready for reading (simply
219	select on the filehandle. This is useful if you want to synchronously wait	1060	does a C<select> on the filehandle. This is useful if you want to
220	for some requests to finish).	1061	synchronously wait for some requests to finish).
221		1062
222	See C<nreqs> for an example.	1063	See C<nreqs> for an example.
223		1064
		1065	=item IO::AIO::poll
		1066
		1067	Waits until some requests have been handled.
		1068
		1069	Returns the number of requests processed, but is otherwise strictly
		1070	equivalent to:
		1071
		1072	IO::AIO::poll_wait, IO::AIO::poll_cb
		1073
224	=item IO::AIO::nreqs	1074	=item IO::AIO::flush
225		1075
226	Returns the number of requests currently outstanding.	1076	Wait till all outstanding AIO requests have been handled.
227		1077
228	Example: wait till there are no outstanding requests anymore:	1078	Strictly equivalent to:
229		1079
230	IO::AIO::poll_wait, IO::AIO::poll_cb	1080	IO::AIO::poll_wait, IO::AIO::poll_cb
231	while IO::AIO::nreqs;	1081	while IO::AIO::nreqs;
232		1082
		1083	=back
		1084
		1085	=head3 CONTROLLING THE NUMBER OF THREADS
		1086
		1087	=over
		1088
233	=item IO::AIO::min_parallel $nthreads	1089	=item IO::AIO::min_parallel $nthreads
234		1090
235	Set the minimum number of AIO threads to C<$nthreads>. The default is	1091	Set the minimum number of AIO threads to C<$nthreads>. The current
236	C<1>, which means a single asynchronous operation can be done at one time	1092	default is C<8>, which means eight asynchronous operations can execute
237	(the number of outstanding operations, however, is unlimited).	1093	concurrently at any one time (the number of outstanding requests,
		1094	however, is unlimited).
238		1095
		1096	IO::AIO starts threads only on demand, when an AIO request is queued and
		1097	no free thread exists. Please note that queueing up a hundred requests can
		1098	create demand for a hundred threads, even if it turns out that everything
		1099	is in the cache and could have been processed faster by a single thread.
		1100
239	It is recommended to keep the number of threads low, as some Linux	1101	It is recommended to keep the number of threads relatively low, as some
240	kernel versions will scale negatively with the number of threads (higher	1102	Linux kernel versions will scale negatively with the number of threads
241	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1103	(higher parallelity => MUCH higher latency). With current Linux 2.6
242	threads should be fine.	1104	versions, 4-32 threads should be fine.
243		1105
244	Under normal circumstances you don't need to call this function, as this	1106	Under most circumstances you don't need to call this function, as the
245	module automatically starts some threads (the exact number might change,	1107	module selects a default that is suitable for low to moderate load.
246	and is currently 4).
247		1108
248	=item IO::AIO::max_parallel $nthreads	1109	=item IO::AIO::max_parallel $nthreads
249		1110
250	Sets the maximum number of AIO threads to C<$nthreads>. If more than	1111	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
251	the specified number of threads are currently running, kill them. This	1112	specified number of threads are currently running, this function kills
252	function blocks until the limit is reached.	1113	them. This function blocks until the limit is reached.
		1114
		1115	While C<$nthreads> are zero, aio requests get queued but not executed
		1116	until the number of threads has been increased again.
253		1117
254	This module automatically runs C<max_parallel 0> at program end, to ensure	1118	This module automatically runs C<max_parallel 0> at program end, to ensure
255	that all threads are killed and that there are no outstanding requests.	1119	that all threads are killed and that there are no outstanding requests.
256		1120
257	Under normal circumstances you don't need to call this function.	1121	Under normal circumstances you don't need to call this function.
258		1122
		1123	=item IO::AIO::max_idle $nthreads
		1124
		1125	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1126	threads that did not get a request to process within 10 seconds). That
		1127	means if a thread becomes idle while C<$nthreads> other threads are also
		1128	idle, it will free its resources and exit.
		1129
		1130	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1131	to allow for extremely high load situations, but want to free resources
		1132	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1133
		1134	The default is probably ok in most situations, especially if thread
		1135	creation is fast. If thread creation is very slow on your system you might
		1136	want to use larger values.
		1137
259	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1138	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1139
		1140	This is a very bad function to use in interactive programs because it
		1141	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1142	use an C<aio_group> together with a feed callback.
260		1143
261	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1144	Sets the maximum number of outstanding requests to C<$nreqs>. If you
262	try to queue up more than this number of requests, the caller will block until	1145	to queue up more than this number of requests, the next call to the
263	some requests have been handled.	1146	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1147	function will block until the limit is no longer exceeded.
264		1148
265	The default is very large, so normally there is no practical limit. If you	1149	The default value is very large, so there is no practical limit on the
266	queue up many requests in a loop it it often improves speed if you set	1150	number of outstanding requests.
267	this to a relatively low number, such as C<100>.
268		1151
269	Under normal circumstances you don't need to call this function.	1152	You can still queue as many requests as you want. Therefore,
		1153	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1154	as a stop gap to shield against fatal memory overflow (with large values).
		1155
		1156	=back
		1157
		1158	=head3 STATISTICAL INFORMATION
		1159
		1160	=over
		1161
		1162	=item IO::AIO::nreqs
		1163
		1164	Returns the number of requests currently in the ready, execute or pending
		1165	states (i.e. for which their callback has not been invoked yet).
		1166
		1167	Example: wait till there are no outstanding requests anymore:
		1168
		1169	IO::AIO::poll_wait, IO::AIO::poll_cb
		1170	while IO::AIO::nreqs;
		1171
		1172	=item IO::AIO::nready
		1173
		1174	Returns the number of requests currently in the ready state (not yet
		1175	executed).
		1176
		1177	=item IO::AIO::npending
		1178
		1179	Returns the number of requests currently in the pending state (executed,
		1180	but not yet processed by poll_cb).
270		1181
271	=back	1182	=back
272		1183
273	=cut	1184	=cut
274		1185
275	# support function to convert a fd into a perl filehandle	1186	# support function to convert a fd into a perl filehandle
276	sub _fd2fh {	1187	sub _fd2fh {
277	return undef if $_[0] < 0;	1188	return undef if $_[0] < 0;
278		1189
279	# try to be perl5.6-compatible	1190	# try to generate nice filehandles
280	local *AIO_FH;	1191	my $sym = "IO::AIO::fd#$_[0]";
281	open AIO_FH, "+<&=$_[0]"	1192	local *$sym;
		1193
		1194	open *$sym, "+<&=$_[0]" # usually works under any unix
		1195	or open *$sym, "<&=$_[0]" # cygwin needs this
		1196	or open *$sym, ">&=$_[0]" # or this
282	or return undef;	1197	or return undef;
283		1198
284	*AIO_FH	1199	*$sym
285	}	1200	}
286		1201
287	min_parallel 4;	1202	min_parallel 8;
288		1203
289	END {	1204	END { flush }
290	max_parallel 0;
291	}
292		1205
293	1;	1206	1;
294		1207
		1208	=head2 FORK BEHAVIOUR
		1209
		1210	This module should do "the right thing" when the process using it forks:
		1211
		1212	Before the fork, IO::AIO enters a quiescent state where no requests
		1213	can be added in other threads and no results will be processed. After
		1214	the fork the parent simply leaves the quiescent state and continues
		1215	request/result processing, while the child frees the request/result queue
		1216	(so that the requests started before the fork will only be handled in the
		1217	parent). Threads will be started on demand until the limit set in the
		1218	parent process has been reached again.
		1219
		1220	In short: the parent will, after a short pause, continue as if fork had
		1221	not been called, while the child will act as if IO::AIO has not been used
		1222	yet.
		1223
		1224	=head2 MEMORY USAGE
		1225
		1226	Per-request usage:
		1227
		1228	Each aio request uses - depending on your architecture - around 100-200
		1229	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1230	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1231	scalars and other data passed into aio requests will also be locked and
		1232	will consume memory till the request has entered the done state.
		1233
		1234	This is now awfully much, so queuing lots of requests is not usually a
		1235	problem.
		1236
		1237	Per-thread usage:
		1238
		1239	In the execution phase, some aio requests require more memory for
		1240	temporary buffers, and each thread requires a stack and other data
		1241	structures (usually around 16k-128k, depending on the OS).
		1242
		1243	=head1 KNOWN BUGS
		1244
		1245	Known bugs will be fixed in the next release.
		1246
295	=head1 SEE ALSO	1247	=head1 SEE ALSO
296		1248
297	L<Coro>, L<Linux::AIO>.	1249	L<Coro::AIO>.
298		1250
299	=head1 AUTHOR	1251	=head1 AUTHOR
300		1252
301	Marc Lehmann <schmorp@schmorp.de>	1253	Marc Lehmann <schmorp@schmorp.de>
302	http://home.schmorp.de/	1254	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.6 by root, Sun Jul 10 22:19:48 2005 UTC vs. Revision 1.105 by root, Sun Mar 25 00:20:27 2007 UTC

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Revision 1.105 by root, Sun Mar 25 00:20:27 2007 UTC