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Revision 1.39 by root, Sun Aug 28 11:05:50 2005 UTC vs.
Revision 1.181 by root, Tue May 4 21:14:01 2010 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 {	9	aio_open "/etc/passwd", IO::AIO::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
21	Event->io (fd => IO::AIO::poll_fileno,	22	use IO::AIO 2;
22	poll => 'r',
23	cb => \&IO::AIO::poll_cb);
24		23
25	# Glib/Gtk2	24	aioreq_pri 4; # give next request a very high priority
26	add_watch Glib::IO IO::AIO::poll_fileno,	25	my $req = aio_unlink "/tmp/file", sub { };
27	in => sub { IO::AIO::poll_cb; 1 };	26	$req->cancel; # cancel request if still in queue
28		27
29	# Tk	28	my $grp = aio_group sub { print "all stats done\n" };
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	29	add $grp aio_stat "..." for ...;
31	readable => \&IO::AIO::poll_cb);
32
33	# Danga::Socket
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);
36
37		30
38	=head1 DESCRIPTION	31	=head1 DESCRIPTION
39		32
40	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
41	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
42		36
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
		52
43	Currently, a number of threads are started that execute your read/writes	53	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	54	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	55	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	56	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	59	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	60	aio_write, so the remaining functionality would have to be implemented
		61	using threads anyway.
51		62
52	Although the module will work with in the presence of other threads, it is	63	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself, always call	64	it is currently not reentrant in any way, so use appropriate locking
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	65	yourself, always call C<poll_cb> from within the same thread, or never
55	C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
		67
		68	=head2 EXAMPLE
		69
		70	This is a simple example that uses the EV module and loads
		71	F</etc/passwd> asynchronously:
		72
		73	use Fcntl;
		74	use EV;
		75	use IO::AIO;
		76
		77	# register the IO::AIO callback with EV
		78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		79
		80	# queue the request to open /etc/passwd
		81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		82	my $fh = shift
		83	or die "error while opening: $!";
		84
		85	# stat'ing filehandles is generally non-blocking
		86	my $size = -s $fh;
		87
		88	# queue a request to read the file
		89	my $contents;
		90	aio_read $fh, 0, $size, $contents, 0, sub {
		91	$_[0] == $size
		92	or die "short read: $!";
		93
		94	close $fh;
		95
		96	# file contents now in $contents
		97	print $contents;
		98
		99	# exit event loop and program
		100	EV::unloop;
		101	};
		102	};
		103
		104	# possibly queue up other requests, or open GUI windows,
		105	# check for sockets etc. etc.
		106
		107	# process events as long as there are some:
		108	EV::loop;
		109
		110	=head1 REQUEST ANATOMY AND LIFETIME
		111
		112	Every C<aio_*> function creates a request. which is a C data structure not
		113	directly visible to Perl.
		114
		115	If called in non-void context, every request function returns a Perl
		116	object representing the request. In void context, nothing is returned,
		117	which saves a bit of memory.
		118
		119	The perl object is a fairly standard ref-to-hash object. The hash contents
		120	are not used by IO::AIO so you are free to store anything you like in it.
		121
		122	During their existance, aio requests travel through the following states,
		123	in order:
		124
		125	=over 4
		126
		127	=item ready
		128
		129	Immediately after a request is created it is put into the ready state,
		130	waiting for a thread to execute it.
		131
		132	=item execute
		133
		134	A thread has accepted the request for processing and is currently
		135	executing it (e.g. blocking in read).
		136
		137	=item pending
		138
		139	The request has been executed and is waiting for result processing.
		140
		141	While request submission and execution is fully asynchronous, result
		142	processing is not and relies on the perl interpreter calling C<poll_cb>
		143	(or another function with the same effect).
		144
		145	=item result
		146
		147	The request results are processed synchronously by C<poll_cb>.
		148
		149	The C<poll_cb> function will process all outstanding aio requests by
		150	calling their callbacks, freeing memory associated with them and managing
		151	any groups they are contained in.
		152
		153	=item done
		154
		155	Request has reached the end of its lifetime and holds no resources anymore
		156	(except possibly for the Perl object, but its connection to the actual
		157	aio request is severed and calling its methods will either do nothing or
		158	result in a runtime error).
		159
		160	=back
56		161
57	=cut	162	=cut
58		163
59	package IO::AIO;	164	package IO::AIO;
60		165
61	no warnings;	166	use Carp ();
		167
		168	use common::sense;
62		169
63	use base 'Exporter';	170	use base 'Exporter';
64		171
65	use Fcntl ();
66
67	BEGIN {	172	BEGIN {
68	$VERSION = 1.6;	173	our $VERSION = '3.65';
69		174
70	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
71	aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
72	aio_fsync aio_fdatasync aio_readahead);	177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
74	max_outstanding nreqs);	179	aio_rename aio_link aio_move aio_copy aio_group
		180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		181	aio_chmod aio_utime aio_truncate
		182	aio_msync aio_mtouch aio_statvfs);
		183
		184	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		185	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		186	min_parallel max_parallel max_idle
		187	nreqs nready npending nthreads
		188	max_poll_time max_poll_reqs
		189	sendfile fadvise);
		190
		191	push @AIO_REQ, qw(aio_busy); # not exported
		192
		193	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
75		194
76	require XSLoader;	195	require XSLoader;
77	XSLoader::load IO::AIO, $VERSION;	196	XSLoader::load ("IO::AIO", $VERSION);
78	}	197	}
79		198
80	=head1 FUNCTIONS	199	=head1 FUNCTIONS
81		200
		201	=head2 QUICK OVERVIEW
		202
		203	This section simply lists the prototypes of the most important functions
		204	for quick reference. See the following sections for function-by-function
		205	documentation.
		206
		207	aio_open $pathname, $flags, $mode, $callback->($fh)
		208	aio_close $fh, $callback->($status)
		209	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		210	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		211	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		212	aio_readahead $fh,$offset,$length, $callback->($retval)
		213	aio_stat $fh_or_path, $callback->($status)
		214	aio_lstat $fh, $callback->($status)
		215	aio_statvfs $fh_or_path, $callback->($statvfs)
		216	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		217	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		218	aio_truncate $fh_or_path, $offset, $callback->($status)
		219	aio_chmod $fh_or_path, $mode, $callback->($status)
		220	aio_unlink $pathname, $callback->($status)
		221	aio_mknod $path, $mode, $dev, $callback->($status)
		222	aio_link $srcpath, $dstpath, $callback->($status)
		223	aio_symlink $srcpath, $dstpath, $callback->($status)
		224	aio_readlink $path, $callback->($link)
		225	aio_rename $srcpath, $dstpath, $callback->($status)
		226	aio_mkdir $pathname, $mode, $callback->($status)
		227	aio_rmdir $pathname, $callback->($status)
		228	aio_readdir $pathname, $callback->($entries)
		229	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		230	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		231	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		232	aio_load $path, $data, $callback->($status)
		233	aio_copy $srcpath, $dstpath, $callback->($status)
		234	aio_move $srcpath, $dstpath, $callback->($status)
		235	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		236	aio_rmtree $path, $callback->($status)
		237	aio_sync $callback->($status)
		238	aio_fsync $fh, $callback->($status)
		239	aio_fdatasync $fh, $callback->($status)
		240	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		241	aio_pathsync $path, $callback->($status)
		242	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		243	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		244	aio_group $callback->(...)
		245	aio_nop $callback->()
		246
		247	$prev_pri = aioreq_pri [$pri]
		248	aioreq_nice $pri_adjust
		249
		250	IO::AIO::poll_wait
		251	IO::AIO::poll_cb
		252	IO::AIO::poll
		253	IO::AIO::flush
		254	IO::AIO::max_poll_reqs $nreqs
		255	IO::AIO::max_poll_time $seconds
		256	IO::AIO::min_parallel $nthreads
		257	IO::AIO::max_parallel $nthreads
		258	IO::AIO::max_idle $nthreads
		259	IO::AIO::max_outstanding $maxreqs
		260	IO::AIO::nreqs
		261	IO::AIO::nready
		262	IO::AIO::npending
		263
		264	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		265	IO::AIO::fadvise $fh, $offset, $len, $advice
		266	IO::AIO::mlockall $flags
		267	IO::AIO::munlockall
		268
82	=head2 AIO FUNCTIONS	269	=head2 AIO REQUEST FUNCTIONS
83		270
84	All the C<aio_*> calls are more or less thin wrappers around the syscall	271	All the C<aio_*> calls are more or less thin wrappers around the syscall
85	with the same name (sans C<aio_>). The arguments are similar or identical,	272	with the same name (sans C<aio_>). The arguments are similar or identical,
86	and they all accept an additional (and optional) C<$callback> argument	273	and they all accept an additional (and optional) C<$callback> argument
87	which must be a code reference. This code reference will get called with	274	which must be a code reference. This code reference will get called with
88	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	275	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
89	perl, which usually delivers "false") as it's sole argument when the given	276	perl, which usually delivers "false") as its sole argument after the given
90	syscall has been executed asynchronously.	277	syscall has been executed asynchronously.
91		278
92	All functions expecting a filehandle keep a copy of the filehandle	279	All functions expecting a filehandle keep a copy of the filehandle
93	internally until the request has finished.	280	internally until the request has finished.
94		281
		282	All functions return request objects of type L<IO::AIO::REQ> that allow
		283	further manipulation of those requests while they are in-flight.
		284
95	The pathnames you pass to these routines I<must> be absolute and	285	The pathnames you pass to these routines I<must> be absolute and
96	encoded in byte form. The reason for the former is that at the time the	286	encoded as octets. The reason for the former is that at the time the
97	request is being executed, the current working directory could have	287	request is being executed, the current working directory could have
98	changed. Alternatively, you can make sure that you never change the	288	changed. Alternatively, you can make sure that you never change the
99	current working directory.	289	current working directory anywhere in the program and then use relative
		290	paths.
100		291
101	To encode pathnames to byte form, either make sure you either: a)	292	To encode pathnames as octets, either make sure you either: a) always pass
102	always pass in filenames you got from outside (command line, readdir	293	in filenames you got from outside (command line, readdir etc.) without
103	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	294	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
104	your pathnames to the locale (or other) encoding in effect in the user	295	your pathnames to the locale (or other) encoding in effect in the user
105	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	296	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
106	use something else.	297	use something else to ensure your scalar has the correct contents.
		298
		299	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		300	handles correctly whether it is set or not.
107		301
108	=over 4	302	=over 4
109		303
		304	=item $prev_pri = aioreq_pri [$pri]
		305
		306	Returns the priority value that would be used for the next request and, if
		307	C<$pri> is given, sets the priority for the next aio request.
		308
		309	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		310	and C<4>, respectively. Requests with higher priority will be serviced
		311	first.
		312
		313	The priority will be reset to C<0> after each call to one of the C<aio_*>
		314	functions.
		315
		316	Example: open a file with low priority, then read something from it with
		317	higher priority so the read request is serviced before other low priority
		318	open requests (potentially spamming the cache):
		319
		320	aioreq_pri -3;
		321	aio_open ..., sub {
		322	return unless $_[0];
		323
		324	aioreq_pri -2;
		325	aio_read $_[0], ..., sub {
		326	...
		327	};
		328	};
		329
		330
		331	=item aioreq_nice $pri_adjust
		332
		333	Similar to C<aioreq_pri>, but subtracts the given value from the current
		334	priority, so the effect is cumulative.
		335
		336
110	=item aio_open $pathname, $flags, $mode, $callback	337	=item aio_open $pathname, $flags, $mode, $callback->($fh)
111		338
112	Asynchronously open or create a file and call the callback with a newly	339	Asynchronously open or create a file and call the callback with a newly
113	created filehandle for the file.	340	created filehandle for the file.
114		341
115	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	342	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
119	list. They are the same as used by C<sysopen>.	346	list. They are the same as used by C<sysopen>.
120		347
121	Likewise, C<$mode> specifies the mode of the newly created file, if it	348	Likewise, C<$mode> specifies the mode of the newly created file, if it
122	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	349	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
123	except that it is mandatory (i.e. use C<0> if you don't create new files,	350	except that it is mandatory (i.e. use C<0> if you don't create new files,
124	and C<0666> or C<0777> if you do).	351	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		352	by the umask in effect then the request is being executed, so better never
		353	change the umask.
125		354
126	Example:	355	Example:
127		356
128	aio_open "/etc/passwd", O_RDONLY, 0, sub {	357	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
129	if ($_[0]) {	358	if ($_[0]) {
130	print "open successful, fh is $_[0]\n";	359	print "open successful, fh is $_[0]\n";
131	...	360	...
132	} else {	361	} else {
133	die "open failed: $!\n";	362	die "open failed: $!\n";
134	}	363	}
135	};	364	};
136		365
		366
137	=item aio_close $fh, $callback	367	=item aio_close $fh, $callback->($status)
138		368
139	Asynchronously close a file and call the callback with the result	369	Asynchronously close a file and call the callback with the result
140	code. I<WARNING:> although accepted, you should not pass in a perl	370	code.
141	filehandle here, as perl will likely close the file descriptor another
142	time when the filehandle is destroyed. Normally, you can safely call perls
143	C<close> or just let filehandles go out of scope.
144		371
145	This is supposed to be a bug in the API, so that might change. It's	372	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
146	therefore best to avoid this function.	373	closing the file descriptor associated with the filehandle itself.
147		374
		375	Therefore, C<aio_close> will not close the filehandle - instead it will
		376	use dup2 to overwrite the file descriptor with the write-end of a pipe
		377	(the pipe fd will be created on demand and will be cached).
		378
		379	Or in other words: the file descriptor will be closed, but it will not be
		380	free for reuse until the perl filehandle is closed.
		381
		382	=cut
		383
148	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	384	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
149		385
150	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	386	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		387
152	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	388	Reads or writes C<$length> bytes from or to the specified C<$fh> and
153	into the scalar given by C<data> and offset C<dataoffset> and calls the	389	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
154	callback without the actual number of bytes read (or -1 on error, just	390	and calls the callback without the actual number of bytes read (or -1 on
155	like the syscall).	391	error, just like the syscall).
		392
		393	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		394	offset plus the actual number of bytes read.
		395
		396	If C<$offset> is undefined, then the current file descriptor offset will
		397	be used (and updated), otherwise the file descriptor offset will not be
		398	changed by these calls.
		399
		400	If C<$length> is undefined in C<aio_write>, use the remaining length of
		401	C<$data>.
		402
		403	If C<$dataoffset> is less than zero, it will be counted from the end of
		404	C<$data>.
156		405
157	The C<$data> scalar I<MUST NOT> be modified in any way while the request	406	The C<$data> scalar I<MUST NOT> be modified in any way while the request
158	is outstanding. Modifying it can result in segfaults or WW3 (if the	407	is outstanding. Modifying it can result in segfaults or World War III (if
159	necessary/optional hardware is installed).	408	the necessary/optional hardware is installed).
160		409
161	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	410	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
162	offset C<0> within the scalar:	411	offset C<0> within the scalar:
163		412
164	aio_read $fh, 7, 15, $buffer, 0, sub {	413	aio_read $fh, 7, 15, $buffer, 0, sub {
165	$_[0] > 0 or die "read error: $!";	414	$_[0] > 0 or die "read error: $!";
166	print "read $_[0] bytes: <$buffer>\n";	415	print "read $_[0] bytes: <$buffer>\n";
167	};	416	};
168		417
		418
169	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback	419	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
170		420
171	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	421	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172	reading at byte offset C<$in_offset>, and starts writing at the current	422	reading at byte offset C<$in_offset>, and starts writing at the current
173	file offset of C<$out_fh>. Because of that, it is not safe to issue more	423	file offset of C<$out_fh>. Because of that, it is not safe to issue more
174	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	424	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
175	other.	425	other.
176		426
177	This call tries to make use of a native C<sendfile> syscall to provide	427	This call tries to make use of a native C<sendfile> syscall to provide
178	zero-copy operation. For this to work, C<$out_fh> should refer to a	428	zero-copy operation. For this to work, C<$out_fh> should refer to a
179	socket, and C<$in_fh> should refer to mmap'able file.	429	socket, and C<$in_fh> should refer to an mmap'able file.
180		430
181	If the native sendfile call fails or is not implemented, it will be	431	If a native sendfile cannot be found or it fails with C<ENOSYS>,
		432	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
182	emulated, so you can call C<aio_sendfile> on any type of filehandle	433	it will be emulated, so you can call C<aio_sendfile> on any type of
183	regardless of the limitations of the operating system.	434	filehandle regardless of the limitations of the operating system.
184		435
185	Please note, however, that C<aio_sendfile> can read more bytes from	436	Please note, however, that C<aio_sendfile> can read more bytes from
186	C<$in_fh> than are written, and there is no way to find out how many	437	C<$in_fh> than are written, and there is no way to find out how many
187	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	438	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188	provides the number of bytes written to C<$out_fh>. Only if the result	439	provides the number of bytes written to C<$out_fh>. Only if the result
189	value equals C<$length> one can assume that C<$length> bytes have been	440	value equals C<$length> one can assume that C<$length> bytes have been
190	read.	441	read.
191		442
		443
192	=item aio_readahead $fh,$offset,$length, $callback	444	=item aio_readahead $fh,$offset,$length, $callback->($retval)
193		445
194	C<aio_readahead> populates the page cache with data from a file so that	446	C<aio_readahead> populates the page cache with data from a file so that
195	subsequent reads from that file will not block on disk I/O. The C<$offset>	447	subsequent reads from that file will not block on disk I/O. The C<$offset>
196	argument specifies the starting point from which data is to be read and	448	argument specifies the starting point from which data is to be read and
197	C<$length> specifies the number of bytes to be read. I/O is performed in	449	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
201	file. The current file offset of the file is left unchanged.	453	file. The current file offset of the file is left unchanged.
202		454
203	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	455	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
204	emulated by simply reading the data, which would have a similar effect.	456	emulated by simply reading the data, which would have a similar effect.
205		457
		458
206	=item aio_stat $fh_or_path, $callback	459	=item aio_stat $fh_or_path, $callback->($status)
207		460
208	=item aio_lstat $fh, $callback	461	=item aio_lstat $fh, $callback->($status)
209		462
210	Works like perl's C<stat> or C<lstat> in void context. The callback will	463	Works like perl's C<stat> or C<lstat> in void context. The callback will
211	be called after the stat and the results will be available using C<stat _>	464	be called after the stat and the results will be available using C<stat _>
212	or C<-s _> etc...	465	or C<-s _> etc...
213		466
…		…
223	aio_stat "/etc/passwd", sub {	476	aio_stat "/etc/passwd", sub {
224	$_[0] and die "stat failed: $!";	477	$_[0] and die "stat failed: $!";
225	print "size is ", -s _, "\n";	478	print "size is ", -s _, "\n";
226	};	479	};
227		480
		481
		482	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		483
		484	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		485	whether a file handle or path was passed.
		486
		487	On success, the callback is passed a hash reference with the following
		488	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		489	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		490	is passed.
		491
		492	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		493	C<ST_NOSUID>.
		494
		495	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		496	their correct value when available, or to C<0> on systems that do
		497	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		498	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		499	C<ST_NODIRATIME> and C<ST_RELATIME>.
		500
		501	Example: stat C</wd> and dump out the data if successful.
		502
		503	aio_statvfs "/wd", sub {
		504	my $f = $_[0]
		505	or die "statvfs: $!";
		506
		507	use Data::Dumper;
		508	say Dumper $f;
		509	};
		510
		511	# result:
		512	{
		513	bsize => 1024,
		514	bfree => 4333064312,
		515	blocks => 10253828096,
		516	files => 2050765568,
		517	flag => 4096,
		518	favail => 2042092649,
		519	bavail => 4333064312,
		520	ffree => 2042092649,
		521	namemax => 255,
		522	frsize => 1024,
		523	fsid => 1810
		524	}
		525
		526
		527	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		528
		529	Works like perl's C<utime> function (including the special case of $atime
		530	and $mtime being undef). Fractional times are supported if the underlying
		531	syscalls support them.
		532
		533	When called with a pathname, uses utimes(2) if available, otherwise
		534	utime(2). If called on a file descriptor, uses futimes(2) if available,
		535	otherwise returns ENOSYS, so this is not portable.
		536
		537	Examples:
		538
		539	# set atime and mtime to current time (basically touch(1)):
		540	aio_utime "path", undef, undef;
		541	# set atime to current time and mtime to beginning of the epoch:
		542	aio_utime "path", time, undef; # undef==0
		543
		544
		545	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		546
		547	Works like perl's C<chown> function, except that C<undef> for either $uid
		548	or $gid is being interpreted as "do not change" (but -1 can also be used).
		549
		550	Examples:
		551
		552	# same as "chown root path" in the shell:
		553	aio_chown "path", 0, -1;
		554	# same as above:
		555	aio_chown "path", 0, undef;
		556
		557
		558	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		559
		560	Works like truncate(2) or ftruncate(2).
		561
		562
		563	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		564
		565	Works like perl's C<chmod> function.
		566
		567
228	=item aio_unlink $pathname, $callback	568	=item aio_unlink $pathname, $callback->($status)
229		569
230	Asynchronously unlink (delete) a file and call the callback with the	570	Asynchronously unlink (delete) a file and call the callback with the
231	result code.	571	result code.
232		572
		573
		574	=item aio_mknod $path, $mode, $dev, $callback->($status)
		575
		576	[EXPERIMENTAL]
		577
		578	Asynchronously create a device node (or fifo). See mknod(2).
		579
		580	The only (POSIX-) portable way of calling this function is:
		581
		582	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		583
		584
		585	=item aio_link $srcpath, $dstpath, $callback->($status)
		586
		587	Asynchronously create a new link to the existing object at C<$srcpath> at
		588	the path C<$dstpath> and call the callback with the result code.
		589
		590
		591	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		592
		593	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		594	the path C<$dstpath> and call the callback with the result code.
		595
		596
		597	=item aio_readlink $path, $callback->($link)
		598
		599	Asynchronously read the symlink specified by C<$path> and pass it to
		600	the callback. If an error occurs, nothing or undef gets passed to the
		601	callback.
		602
		603
		604	=item aio_rename $srcpath, $dstpath, $callback->($status)
		605
		606	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		607	rename(2) and call the callback with the result code.
		608
		609
		610	=item aio_mkdir $pathname, $mode, $callback->($status)
		611
		612	Asynchronously mkdir (create) a directory and call the callback with
		613	the result code. C<$mode> will be modified by the umask at the time the
		614	request is executed, so do not change your umask.
		615
		616
233	=item aio_rmdir $pathname, $callback	617	=item aio_rmdir $pathname, $callback->($status)
234		618
235	Asynchronously rmdir (delete) a directory and call the callback with the	619	Asynchronously rmdir (delete) a directory and call the callback with the
236	result code.	620	result code.
237		621
		622
238	=item aio_readdir $pathname $callback	623	=item aio_readdir $pathname, $callback->($entries)
239		624
240	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	625	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241	directory (i.e. opendir + readdir + closedir). The entries will not be	626	directory (i.e. opendir + readdir + closedir). The entries will not be
242	sorted, and will B<NOT> include the C<.> and C<..> entries.	627	sorted, and will B<NOT> include the C<.> and C<..> entries.
243		628
244	The callback a single argument which is either C<undef> or an array-ref	629	The callback is passed a single argument which is either C<undef> or an
245	with the filenames.	630	array-ref with the filenames.
246		631
		632
		633	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		634
		635	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		636	behaviour and output format. In case of an error, C<$entries> will be
		637	C<undef>.
		638
		639	The flags are a combination of the following constants, ORed together (the
		640	flags will also be passed to the callback, possibly modified):
		641
		642	=over 4
		643
		644	=item IO::AIO::READDIR_DENTS
		645
		646	When this flag is off, then the callback gets an arrayref with of names
		647	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		648	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		649	entry in more detail.
		650
		651	C<$name> is the name of the entry.
		652
		653	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		654
		655	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		656	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		657	C<IO::AIO::DT_WHT>.
		658
		659	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		660	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		661	scalars are read-only: you can not modify them.
		662
		663	C<$inode> is the inode number (which might not be exact on systems with 64
		664	bit inode numbers and 32 bit perls). This field has unspecified content on
		665	systems that do not deliver the inode information.
		666
		667	=item IO::AIO::READDIR_DIRS_FIRST
		668
		669	When this flag is set, then the names will be returned in an order where
		670	likely directories come first. This is useful when you need to quickly
		671	find directories, or you want to find all directories while avoiding to
		672	stat() each entry.
		673
		674	If the system returns type information in readdir, then this is used
		675	to find directories directly. Otherwise, likely directories are files
		676	beginning with ".", or otherwise files with no dots, of which files with
		677	short names are tried first.
		678
		679	=item IO::AIO::READDIR_STAT_ORDER
		680
		681	When this flag is set, then the names will be returned in an order
		682	suitable for stat()'ing each one. That is, when you plan to stat()
		683	all files in the given directory, then the returned order will likely
		684	be fastest.
		685
		686	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		687	the likely dirs come first, resulting in a less optimal stat order.
		688
		689	=item IO::AIO::READDIR_FOUND_UNKNOWN
		690
		691	This flag should not be set when calling C<aio_readdirx>. Instead, it
		692	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		693	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		694	C<$type>'s are known, which can be used to speed up some algorithms.
		695
		696	=back
		697
		698
		699	=item aio_load $path, $data, $callback->($status)
		700
		701	This is a composite request that tries to fully load the given file into
		702	memory. Status is the same as with aio_read.
		703
		704	=cut
		705
		706	sub aio_load($$;$) {
		707	my ($path, undef, $cb) = @_;
		708	my $data = \$_[1];
		709
		710	my $pri = aioreq_pri;
		711	my $grp = aio_group $cb;
		712
		713	aioreq_pri $pri;
		714	add $grp aio_open $path, O_RDONLY, 0, sub {
		715	my $fh = shift
		716	or return $grp->result (-1);
		717
		718	aioreq_pri $pri;
		719	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		720	$grp->result ($_[0]);
		721	};
		722	};
		723
		724	$grp
		725	}
		726
		727	=item aio_copy $srcpath, $dstpath, $callback->($status)
		728
		729	Try to copy the I<file> (directories not supported as either source or
		730	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		731	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		732
		733	This is a composite request that creates the destination file with
		734	mode 0200 and copies the contents of the source file into it using
		735	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		736	uid/gid, in that order.
		737
		738	If an error occurs, the partial destination file will be unlinked, if
		739	possible, except when setting atime, mtime, access mode and uid/gid, where
		740	errors are being ignored.
		741
		742	=cut
		743
		744	sub aio_copy($$;$) {
		745	my ($src, $dst, $cb) = @_;
		746
		747	my $pri = aioreq_pri;
		748	my $grp = aio_group $cb;
		749
		750	aioreq_pri $pri;
		751	add $grp aio_open $src, O_RDONLY, 0, sub {
		752	if (my $src_fh = $_[0]) {
		753	my @stat = stat $src_fh; # hmm, might block over nfs?
		754
		755	aioreq_pri $pri;
		756	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		757	if (my $dst_fh = $_[0]) {
		758	aioreq_pri $pri;
		759	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		760	if ($_[0] == $stat[7]) {
		761	$grp->result (0);
		762	close $src_fh;
		763
		764	my $ch = sub {
		765	aioreq_pri $pri;
		766	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		767	aioreq_pri $pri;
		768	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		769	aioreq_pri $pri;
		770	add $grp aio_close $dst_fh;
		771	}
		772	};
		773	};
		774
		775	aioreq_pri $pri;
		776	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		777	if ($_[0] < 0 && $! == ENOSYS) {
		778	aioreq_pri $pri;
		779	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		780	} else {
		781	$ch->();
		782	}
		783	};
		784	} else {
		785	$grp->result (-1);
		786	close $src_fh;
		787	close $dst_fh;
		788
		789	aioreq $pri;
		790	add $grp aio_unlink $dst;
		791	}
		792	};
		793	} else {
		794	$grp->result (-1);
		795	}
		796	},
		797
		798	} else {
		799	$grp->result (-1);
		800	}
		801	};
		802
		803	$grp
		804	}
		805
		806	=item aio_move $srcpath, $dstpath, $callback->($status)
		807
		808	Try to move the I<file> (directories not supported as either source or
		809	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		810	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		811
		812	This is a composite request that tries to rename(2) the file first; if
		813	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		814	that is successful, unlinks the C<$srcpath>.
		815
		816	=cut
		817
		818	sub aio_move($$;$) {
		819	my ($src, $dst, $cb) = @_;
		820
		821	my $pri = aioreq_pri;
		822	my $grp = aio_group $cb;
		823
		824	aioreq_pri $pri;
		825	add $grp aio_rename $src, $dst, sub {
		826	if ($_[0] && $! == EXDEV) {
		827	aioreq_pri $pri;
		828	add $grp aio_copy $src, $dst, sub {
		829	$grp->result ($_[0]);
		830
		831	if (!$_[0]) {
		832	aioreq_pri $pri;
		833	add $grp aio_unlink $src;
		834	}
		835	};
		836	} else {
		837	$grp->result ($_[0]);
		838	}
		839	};
		840
		841	$grp
		842	}
		843
		844	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		845
		846	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		847	efficiently separate the entries of directory C<$path> into two sets of
		848	names, directories you can recurse into (directories), and ones you cannot
		849	recurse into (everything else, including symlinks to directories).
		850
		851	C<aio_scandir> is a composite request that creates of many sub requests_
		852	C<$maxreq> specifies the maximum number of outstanding aio requests that
		853	this function generates. If it is C<< <= 0 >>, then a suitable default
		854	will be chosen (currently 4).
		855
		856	On error, the callback is called without arguments, otherwise it receives
		857	two array-refs with path-relative entry names.
		858
		859	Example:
		860
		861	aio_scandir $dir, 0, sub {
		862	my ($dirs, $nondirs) = @_;
		863	print "real directories: @$dirs\n";
		864	print "everything else: @$nondirs\n";
		865	};
		866
		867	Implementation notes.
		868
		869	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		870
		871	If readdir returns file type information, then this is used directly to
		872	find directories.
		873
		874	Otherwise, after reading the directory, the modification time, size etc.
		875	of the directory before and after the readdir is checked, and if they
		876	match (and isn't the current time), the link count will be used to decide
		877	how many entries are directories (if >= 2). Otherwise, no knowledge of the
		878	number of subdirectories will be assumed.
		879
		880	Then entries will be sorted into likely directories a non-initial dot
		881	currently) and likely non-directories (see C<aio_readdirx>). Then every
		882	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		883	in order of their inode numbers. If that succeeds, it assumes that the
		884	entry is a directory or a symlink to directory (which will be checked
		885	seperately). This is often faster than stat'ing the entry itself because
		886	filesystems might detect the type of the entry without reading the inode
		887	data (e.g. ext2fs filetype feature), even on systems that cannot return
		888	the filetype information on readdir.
		889
		890	If the known number of directories (link count - 2) has been reached, the
		891	rest of the entries is assumed to be non-directories.
		892
		893	This only works with certainty on POSIX (= UNIX) filesystems, which
		894	fortunately are the vast majority of filesystems around.
		895
		896	It will also likely work on non-POSIX filesystems with reduced efficiency
		897	as those tend to return 0 or 1 as link counts, which disables the
		898	directory counting heuristic.
		899
		900	=cut
		901
		902	sub aio_scandir($$;$) {
		903	my ($path, $maxreq, $cb) = @_;
		904
		905	my $pri = aioreq_pri;
		906
		907	my $grp = aio_group $cb;
		908
		909	$maxreq = 4 if $maxreq <= 0;
		910
		911	# stat once
		912	aioreq_pri $pri;
		913	add $grp aio_stat $path, sub {
		914	return $grp->result () if $_[0];
		915	my $now = time;
		916	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		917
		918	# read the directory entries
		919	aioreq_pri $pri;
		920	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
		921	my $entries = shift
		922	or return $grp->result ();
		923
		924	# stat the dir another time
		925	aioreq_pri $pri;
		926	add $grp aio_stat $path, sub {
		927	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		928
		929	my $ndirs;
		930
		931	# take the slow route if anything looks fishy
		932	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		933	$ndirs = -1;
		934	} else {
		935	# if nlink == 2, we are finished
		936	# for non-posix-fs's, we rely on nlink < 2
		937	$ndirs = (stat _)[3] - 2
		938	or return $grp->result ([], $entries);
		939	}
		940
		941	my (@dirs, @nondirs);
		942
		943	my $statgrp = add $grp aio_group sub {
		944	$grp->result (\@dirs, \@nondirs);
		945	};
		946
		947	limit $statgrp $maxreq;
		948	feed $statgrp sub {
		949	return unless @$entries;
		950	my $entry = shift @$entries;
		951
		952	aioreq_pri $pri;
		953	add $statgrp aio_stat "$path/$entry/.", sub {
		954	if ($_[0] < 0) {
		955	push @nondirs, $entry;
		956	} else {
		957	# need to check for real directory
		958	aioreq_pri $pri;
		959	add $statgrp aio_lstat "$path/$entry", sub {
		960	if (-d _) {
		961	push @dirs, $entry;
		962
		963	unless (--$ndirs) {
		964	push @nondirs, @$entries;
		965	feed $statgrp;
		966	}
		967	} else {
		968	push @nondirs, $entry;
		969	}
		970	}
		971	}
		972	};
		973	};
		974	};
		975	};
		976	};
		977
		978	$grp
		979	}
		980
		981	=item aio_rmtree $path, $callback->($status)
		982
		983	Delete a directory tree starting (and including) C<$path>, return the
		984	status of the final C<rmdir> only. This is a composite request that
		985	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		986	everything else.
		987
		988	=cut
		989
		990	sub aio_rmtree;
		991	sub aio_rmtree($;$) {
		992	my ($path, $cb) = @_;
		993
		994	my $pri = aioreq_pri;
		995	my $grp = aio_group $cb;
		996
		997	aioreq_pri $pri;
		998	add $grp aio_scandir $path, 0, sub {
		999	my ($dirs, $nondirs) = @_;
		1000
		1001	my $dirgrp = aio_group sub {
		1002	add $grp aio_rmdir $path, sub {
		1003	$grp->result ($_[0]);
		1004	};
		1005	};
		1006
		1007	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1008	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1009
		1010	add $grp $dirgrp;
		1011	};
		1012
		1013	$grp
		1014	}
		1015
		1016	=item aio_sync $callback->($status)
		1017
		1018	Asynchronously call sync and call the callback when finished.
		1019
247	=item aio_fsync $fh, $callback	1020	=item aio_fsync $fh, $callback->($status)
248		1021
249	Asynchronously call fsync on the given filehandle and call the callback	1022	Asynchronously call fsync on the given filehandle and call the callback
250	with the fsync result code.	1023	with the fsync result code.
251		1024
252	=item aio_fdatasync $fh, $callback	1025	=item aio_fdatasync $fh, $callback->($status)
253		1026
254	Asynchronously call fdatasync on the given filehandle and call the	1027	Asynchronously call fdatasync on the given filehandle and call the
255	callback with the fdatasync result code.	1028	callback with the fdatasync result code.
256		1029
257	If this call isn't available because your OS lacks it or it couldn't be	1030	If this call isn't available because your OS lacks it or it couldn't be
258	detected, it will be emulated by calling C<fsync> instead.	1031	detected, it will be emulated by calling C<fsync> instead.
259		1032
		1033	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1034
		1035	Sync the data portion of the file specified by C<$offset> and C<$length>
		1036	to disk (but NOT the metadata), by calling the Linux-specific
		1037	sync_file_range call. If sync_file_range is not available or it returns
		1038	ENOSYS, then fdatasync or fsync is being substituted.
		1039
		1040	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1041	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1042	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1043	manpage for details.
		1044
		1045	=item aio_pathsync $path, $callback->($status)
		1046
		1047	This request tries to open, fsync and close the given path. This is a
		1048	composite request intended to sync directories after directory operations
		1049	(E.g. rename). This might not work on all operating systems or have any
		1050	specific effect, but usually it makes sure that directory changes get
		1051	written to disc. It works for anything that can be opened for read-only,
		1052	not just directories.
		1053
		1054	Future versions of this function might fall back to other methods when
		1055	C<fsync> on the directory fails (such as calling C<sync>).
		1056
		1057	Passes C<0> when everything went ok, and C<-1> on error.
		1058
		1059	=cut
		1060
		1061	sub aio_pathsync($;$) {
		1062	my ($path, $cb) = @_;
		1063
		1064	my $pri = aioreq_pri;
		1065	my $grp = aio_group $cb;
		1066
		1067	aioreq_pri $pri;
		1068	add $grp aio_open $path, O_RDONLY, 0, sub {
		1069	my ($fh) = @_;
		1070	if ($fh) {
		1071	aioreq_pri $pri;
		1072	add $grp aio_fsync $fh, sub {
		1073	$grp->result ($_[0]);
		1074
		1075	aioreq_pri $pri;
		1076	add $grp aio_close $fh;
		1077	};
		1078	} else {
		1079	$grp->result (-1);
		1080	}
		1081	};
		1082
		1083	$grp
		1084	}
		1085
		1086	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1087
		1088	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1089	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1090	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1091	scalar must only be modified in-place while an aio operation is pending on
		1092	it).
		1093
		1094	It calls the C<msync> function of your OS, if available, with the memory
		1095	area starting at C<$offset> in the string and ending C<$length> bytes
		1096	later. If C<$length> is negative, counts from the end, and if C<$length>
		1097	is C<undef>, then it goes till the end of the string. The flags can be
		1098	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1099	C<IO::AIO::MS_SYNC>.
		1100
		1101	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1102
		1103	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1104	scalars.
		1105
		1106	It touches (reads or writes) all memory pages in the specified
		1107	range inside the scalar. All caveats and parameters are the same
		1108	as for C<aio_msync>, above, except for flags, which must be either
		1109	C<0> (which reads all pages and ensures they are instantiated) or
		1110	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1111	writing an octet from it, which dirties the page).
		1112
		1113	=item aio_group $callback->(...)
		1114
		1115	This is a very special aio request: Instead of doing something, it is a
		1116	container for other aio requests, which is useful if you want to bundle
		1117	many requests into a single, composite, request with a definite callback
		1118	and the ability to cancel the whole request with its subrequests.
		1119
		1120	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		1121	for more info.
		1122
		1123	Example:
		1124
		1125	my $grp = aio_group sub {
		1126	print "all stats done\n";
		1127	};
		1128
		1129	add $grp
		1130	(aio_stat ...),
		1131	(aio_stat ...),
		1132	...;
		1133
		1134	=item aio_nop $callback->()
		1135
		1136	This is a special request - it does nothing in itself and is only used for
		1137	side effects, such as when you want to add a dummy request to a group so
		1138	that finishing the requests in the group depends on executing the given
		1139	code.
		1140
		1141	While this request does nothing, it still goes through the execution
		1142	phase and still requires a worker thread. Thus, the callback will not
		1143	be executed immediately but only after other requests in the queue have
		1144	entered their execution phase. This can be used to measure request
		1145	latency.
		1146
		1147	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1148
		1149	Mainly used for debugging and benchmarking, this aio request puts one of
		1150	the request workers to sleep for the given time.
		1151
		1152	While it is theoretically handy to have simple I/O scheduling requests
		1153	like sleep and file handle readable/writable, the overhead this creates is
		1154	immense (it blocks a thread for a long time) so do not use this function
		1155	except to put your application under artificial I/O pressure.
		1156
260	=back	1157	=back
261		1158
		1159	=head2 IO::AIO::REQ CLASS
		1160
		1161	All non-aggregate C<aio_*> functions return an object of this class when
		1162	called in non-void context.
		1163
		1164	=over 4
		1165
		1166	=item cancel $req
		1167
		1168	Cancels the request, if possible. Has the effect of skipping execution
		1169	when entering the B<execute> state and skipping calling the callback when
		1170	entering the the B<result> state, but will leave the request otherwise
		1171	untouched (with the exception of readdir). That means that requests that
		1172	currently execute will not be stopped and resources held by the request
		1173	will not be freed prematurely.
		1174
		1175	=item cb $req $callback->(...)
		1176
		1177	Replace (or simply set) the callback registered to the request.
		1178
		1179	=back
		1180
		1181	=head2 IO::AIO::GRP CLASS
		1182
		1183	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1184	objects of this class, too.
		1185
		1186	A IO::AIO::GRP object is a special request that can contain multiple other
		1187	aio requests.
		1188
		1189	You create one by calling the C<aio_group> constructing function with a
		1190	callback that will be called when all contained requests have entered the
		1191	C<done> state:
		1192
		1193	my $grp = aio_group sub {
		1194	print "all requests are done\n";
		1195	};
		1196
		1197	You add requests by calling the C<add> method with one or more
		1198	C<IO::AIO::REQ> objects:
		1199
		1200	$grp->add (aio_unlink "...");
		1201
		1202	add $grp aio_stat "...", sub {
		1203	$_[0] or return $grp->result ("error");
		1204
		1205	# add another request dynamically, if first succeeded
		1206	add $grp aio_open "...", sub {
		1207	$grp->result ("ok");
		1208	};
		1209	};
		1210
		1211	This makes it very easy to create composite requests (see the source of
		1212	C<aio_move> for an application) that work and feel like simple requests.
		1213
		1214	=over 4
		1215
		1216	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1217	C<IO::AIO::poll_cb>, just like any other request.
		1218
		1219	=item * They can be canceled like any other request. Canceling will cancel not
		1220	only the request itself, but also all requests it contains.
		1221
		1222	=item * They can also can also be added to other IO::AIO::GRP objects.
		1223
		1224	=item * You must not add requests to a group from within the group callback (or
		1225	any later time).
		1226
		1227	=back
		1228
		1229	Their lifetime, simplified, looks like this: when they are empty, they
		1230	will finish very quickly. If they contain only requests that are in the
		1231	C<done> state, they will also finish. Otherwise they will continue to
		1232	exist.
		1233
		1234	That means after creating a group you have some time to add requests
		1235	(precisely before the callback has been invoked, which is only done within
		1236	the C<poll_cb>). And in the callbacks of those requests, you can add
		1237	further requests to the group. And only when all those requests have
		1238	finished will the the group itself finish.
		1239
		1240	=over 4
		1241
		1242	=item add $grp ...
		1243
		1244	=item $grp->add (...)
		1245
		1246	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1247	be added, including other groups, as long as you do not create circular
		1248	dependencies.
		1249
		1250	Returns all its arguments.
		1251
		1252	=item $grp->cancel_subs
		1253
		1254	Cancel all subrequests and clears any feeder, but not the group request
		1255	itself. Useful when you queued a lot of events but got a result early.
		1256
		1257	The group request will finish normally (you cannot add requests to the
		1258	group).
		1259
		1260	=item $grp->result (...)
		1261
		1262	Set the result value(s) that will be passed to the group callback when all
		1263	subrequests have finished and set the groups errno to the current value
		1264	of errno (just like calling C<errno> without an error number). By default,
		1265	no argument will be passed and errno is zero.
		1266
		1267	=item $grp->errno ([$errno])
		1268
		1269	Sets the group errno value to C<$errno>, or the current value of errno
		1270	when the argument is missing.
		1271
		1272	Every aio request has an associated errno value that is restored when
		1273	the callback is invoked. This method lets you change this value from its
		1274	default (0).
		1275
		1276	Calling C<result> will also set errno, so make sure you either set C<$!>
		1277	before the call to C<result>, or call c<errno> after it.
		1278
		1279	=item feed $grp $callback->($grp)
		1280
		1281	Sets a feeder/generator on this group: every group can have an attached
		1282	generator that generates requests if idle. The idea behind this is that,
		1283	although you could just queue as many requests as you want in a group,
		1284	this might starve other requests for a potentially long time. For example,
		1285	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1286	delaying any later requests for a long time.
		1287
		1288	To avoid this, and allow incremental generation of requests, you can
		1289	instead a group and set a feeder on it that generates those requests. The
		1290	feed callback will be called whenever there are few enough (see C<limit>,
		1291	below) requests active in the group itself and is expected to queue more
		1292	requests.
		1293
		1294	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1295	not impose any limits).
		1296
		1297	If the feed does not queue more requests when called, it will be
		1298	automatically removed from the group.
		1299
		1300	If the feed limit is C<0> when this method is called, it will be set to
		1301	C<2> automatically.
		1302
		1303	Example:
		1304
		1305	# stat all files in @files, but only ever use four aio requests concurrently:
		1306
		1307	my $grp = aio_group sub { print "finished\n" };
		1308	limit $grp 4;
		1309	feed $grp sub {
		1310	my $file = pop @files
		1311	or return;
		1312
		1313	add $grp aio_stat $file, sub { ... };
		1314	};
		1315
		1316	=item limit $grp $num
		1317
		1318	Sets the feeder limit for the group: The feeder will be called whenever
		1319	the group contains less than this many requests.
		1320
		1321	Setting the limit to C<0> will pause the feeding process.
		1322
		1323	The default value for the limit is C<0>, but note that setting a feeder
		1324	automatically bumps it up to C<2>.
		1325
		1326	=back
		1327
262	=head2 SUPPORT FUNCTIONS	1328	=head2 SUPPORT FUNCTIONS
263		1329
		1330	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1331
264	=over 4	1332	=over 4
265		1333
266	=item $fileno = IO::AIO::poll_fileno	1334	=item $fileno = IO::AIO::poll_fileno
267		1335
268	Return the I<request result pipe file descriptor>. This filehandle must be	1336	Return the I<request result pipe file descriptor>. This filehandle must be
269	polled for reading by some mechanism outside this module (e.g. Event or	1337	polled for reading by some mechanism outside this module (e.g. EV, Glib,
270	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1338	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
271	to call C<poll_cb> to check the results.	1339	you have to call C<poll_cb> to check the results.
272		1340
273	See C<poll_cb> for an example.	1341	See C<poll_cb> for an example.
274		1342
275	=item IO::AIO::poll_cb	1343	=item IO::AIO::poll_cb
276		1344
277	Process all outstanding events on the result pipe. You have to call this	1345	Process some outstanding events on the result pipe. You have to call this
278	regularly. Returns the number of events processed. Returns immediately	1346	regularly. Returns C<0> if all events could be processed, or C<-1> if it
279	when no events are outstanding.	1347	returned earlier for whatever reason. Returns immediately when no events
		1348	are outstanding. The amount of events processed depends on the settings of
		1349	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1350
		1351	If not all requests were processed for whatever reason, the filehandle
		1352	will still be ready when C<poll_cb> returns, so normally you don't have to
		1353	do anything special to have it called later.
280		1354
281	Example: Install an Event watcher that automatically calls	1355	Example: Install an Event watcher that automatically calls
282	IO::AIO::poll_cb with high priority:	1356	IO::AIO::poll_cb with high priority (more examples can be found in the
		1357	SYNOPSIS section, at the top of this document):
283		1358
284	Event->io (fd => IO::AIO::poll_fileno,	1359	Event->io (fd => IO::AIO::poll_fileno,
285	poll => 'r', async => 1,	1360	poll => 'r', async => 1,
286	cb => \&IO::AIO::poll_cb);	1361	cb => \&IO::AIO::poll_cb);
287		1362
288	=item IO::AIO::poll_wait	1363	=item IO::AIO::poll_wait
289		1364
		1365	If there are any outstanding requests and none of them in the result
290	Wait till the result filehandle becomes ready for reading (simply does a	1366	phase, wait till the result filehandle becomes ready for reading (simply
291	C<select> on the filehandle. This is useful if you want to synchronously wait	1367	does a C<select> on the filehandle. This is useful if you want to
292	for some requests to finish).	1368	synchronously wait for some requests to finish).
293		1369
294	See C<nreqs> for an example.	1370	See C<nreqs> for an example.
295		1371
		1372	=item IO::AIO::poll
		1373
		1374	Waits until some requests have been handled.
		1375
		1376	Returns the number of requests processed, but is otherwise strictly
		1377	equivalent to:
		1378
		1379	IO::AIO::poll_wait, IO::AIO::poll_cb
		1380
296	=item IO::AIO::nreqs	1381	=item IO::AIO::flush
297		1382
298	Returns the number of requests currently outstanding (i.e. for which their	1383	Wait till all outstanding AIO requests have been handled.
299	callback has not been invoked yet).
300		1384
301	Example: wait till there are no outstanding requests anymore:	1385	Strictly equivalent to:
302		1386
303	IO::AIO::poll_wait, IO::AIO::poll_cb	1387	IO::AIO::poll_wait, IO::AIO::poll_cb
304	while IO::AIO::nreqs;	1388	while IO::AIO::nreqs;
305		1389
306	=item IO::AIO::flush	1390	=item IO::AIO::max_poll_reqs $nreqs
307		1391
308	Wait till all outstanding AIO requests have been handled.	1392	=item IO::AIO::max_poll_time $seconds
309		1393
310	Strictly equivalent to:	1394	These set the maximum number of requests (default C<0>, meaning infinity)
		1395	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1396	the maximum amount of time (default C<0>, meaning infinity) spent in
		1397	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1398	of time C<poll_cb> is allowed to use).
311		1399
312	IO::AIO::poll_wait, IO::AIO::poll_cb	1400	Setting C<max_poll_time> to a non-zero value creates an overhead of one
313	while IO::AIO::nreqs;	1401	syscall per request processed, which is not normally a problem unless your
		1402	callbacks are really really fast or your OS is really really slow (I am
		1403	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
314		1404
315	=item IO::AIO::poll	1405	Setting these is useful if you want to ensure some level of
		1406	interactiveness when perl is not fast enough to process all requests in
		1407	time.
316		1408
317	Waits until some requests have been handled.	1409	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
318		1410
319	Strictly equivalent to:	1411	Example: Install an Event watcher that automatically calls
		1412	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1413	program get the CPU sometimes even under high AIO load.
320		1414
321	IO::AIO::poll_wait, IO::AIO::poll_cb	1415	# try not to spend much more than 0.1s in poll_cb
322	if IO::AIO::nreqs;	1416	IO::AIO::max_poll_time 0.1;
		1417
		1418	# use a low priority so other tasks have priority
		1419	Event->io (fd => IO::AIO::poll_fileno,
		1420	poll => 'r', nice => 1,
		1421	cb => &IO::AIO::poll_cb);
		1422
		1423	=back
		1424
		1425	=head3 CONTROLLING THE NUMBER OF THREADS
		1426
		1427	=over
323		1428
324	=item IO::AIO::min_parallel $nthreads	1429	=item IO::AIO::min_parallel $nthreads
325		1430
326	Set the minimum number of AIO threads to C<$nthreads>. The current default	1431	Set the minimum number of AIO threads to C<$nthreads>. The current
327	is C<4>, which means four asynchronous operations can be done at one time	1432	default is C<8>, which means eight asynchronous operations can execute
328	(the number of outstanding operations, however, is unlimited).	1433	concurrently at any one time (the number of outstanding requests,
		1434	however, is unlimited).
329		1435
330	IO::AIO starts threads only on demand, when an AIO request is queued and	1436	IO::AIO starts threads only on demand, when an AIO request is queued and
331	no free thread exists.	1437	no free thread exists. Please note that queueing up a hundred requests can
		1438	create demand for a hundred threads, even if it turns out that everything
		1439	is in the cache and could have been processed faster by a single thread.
332		1440
333	It is recommended to keep the number of threads low, as some Linux	1441	It is recommended to keep the number of threads relatively low, as some
334	kernel versions will scale negatively with the number of threads (higher	1442	Linux kernel versions will scale negatively with the number of threads
335	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1443	(higher parallelity => MUCH higher latency). With current Linux 2.6
336	threads should be fine.	1444	versions, 4-32 threads should be fine.
337		1445
338	Under most circumstances you don't need to call this function, as the	1446	Under most circumstances you don't need to call this function, as the
339	module selects a default that is suitable for low to moderate load.	1447	module selects a default that is suitable for low to moderate load.
340		1448
341	=item IO::AIO::max_parallel $nthreads	1449	=item IO::AIO::max_parallel $nthreads
…		…
350	This module automatically runs C<max_parallel 0> at program end, to ensure	1458	This module automatically runs C<max_parallel 0> at program end, to ensure
351	that all threads are killed and that there are no outstanding requests.	1459	that all threads are killed and that there are no outstanding requests.
352		1460
353	Under normal circumstances you don't need to call this function.	1461	Under normal circumstances you don't need to call this function.
354		1462
		1463	=item IO::AIO::max_idle $nthreads
		1464
		1465	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1466	threads that did not get a request to process within 10 seconds). That
		1467	means if a thread becomes idle while C<$nthreads> other threads are also
		1468	idle, it will free its resources and exit.
		1469
		1470	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1471	to allow for extremely high load situations, but want to free resources
		1472	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1473
		1474	The default is probably ok in most situations, especially if thread
		1475	creation is fast. If thread creation is very slow on your system you might
		1476	want to use larger values.
		1477
355	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1478	=item IO::AIO::max_outstanding $maxreqs
		1479
		1480	This is a very bad function to use in interactive programs because it
		1481	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1482	use an C<aio_group> together with a feed callback.
356		1483
357	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1484	Sets the maximum number of outstanding requests to C<$nreqs>. If you
358	try to queue up more than this number of requests, the caller will block until	1485	do queue up more than this number of requests, the next call to the
359	some requests have been handled.	1486	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1487	function will block until the limit is no longer exceeded.
360		1488
361	The default is very large, so normally there is no practical limit. If you	1489	The default value is very large, so there is no practical limit on the
362	queue up many requests in a loop it often improves speed if you set	1490	number of outstanding requests.
363	this to a relatively low number, such as C<100>.
364		1491
365	Under normal circumstances you don't need to call this function.	1492	You can still queue as many requests as you want. Therefore,
		1493	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1494	as a stop gap to shield against fatal memory overflow (with large values).
366		1495
367	=back	1496	=back
368		1497
		1498	=head3 STATISTICAL INFORMATION
		1499
		1500	=over
		1501
		1502	=item IO::AIO::nreqs
		1503
		1504	Returns the number of requests currently in the ready, execute or pending
		1505	states (i.e. for which their callback has not been invoked yet).
		1506
		1507	Example: wait till there are no outstanding requests anymore:
		1508
		1509	IO::AIO::poll_wait, IO::AIO::poll_cb
		1510	while IO::AIO::nreqs;
		1511
		1512	=item IO::AIO::nready
		1513
		1514	Returns the number of requests currently in the ready state (not yet
		1515	executed).
		1516
		1517	=item IO::AIO::npending
		1518
		1519	Returns the number of requests currently in the pending state (executed,
		1520	but not yet processed by poll_cb).
		1521
		1522	=back
		1523
		1524	=head3 MISCELLANEOUS FUNCTIONS
		1525
		1526	IO::AIO implements some functions that might be useful, but are not
		1527	asynchronous.
		1528
		1529	=over 4
		1530
		1531	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1532
		1533	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1534	but is blocking (this makes most sense if you know the input data is
		1535	likely cached already and the output filehandle is set to non-blocking
		1536	operations).
		1537
		1538	Returns the number of bytes copied, or C<-1> on error.
		1539
		1540	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1541
		1542	Simply calls the C<posix_fadvise> function (see it's
		1543	manpage for details). The following advice constants are
		1544	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1545	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1546	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1547
		1548	On systems that do not implement C<posix_fadvise>, this function returns
		1549	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1550
		1551	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1552
		1553	Memory-maps a file (or anonymous memory range) and attaches it to the
		1554	given C<$scalar>, which will act like a string scalar.
		1555
		1556	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1557	change the string length, and most read-only operations such as copying it
		1558	or searching it with regexes and so on.
		1559
		1560	Anything else is unsafe and will, at best, result in memory leaks.
		1561
		1562	The memory map associated with the C<$scalar> is automatically removed
		1563	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1564	C<IO::AIO::munmap> functions are called.
		1565
		1566	This calls the C<mmap>(2) function internally. See your system's manual
		1567	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1568
		1569	The C<$length> must be larger than zero and smaller than the actual
		1570	filesize.
		1571
		1572	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1573	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1574
		1575	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1576	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1577	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1578	(which is set to C<MAP_ANON> if your system only provides this
		1579	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1580	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1581	C<IO::AIO::MAP_NONBLOCK>
		1582
		1583	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1584
		1585	C<$offset> is the offset from the start of the file - it generally must be
		1586	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1587
		1588	Example:
		1589
		1590	use Digest::MD5;
		1591	use IO::AIO;
		1592
		1593	open my $fh, "<verybigfile"
		1594	or die "$!";
		1595
		1596	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1597	or die "verybigfile: $!";
		1598
		1599	my $fast_md5 = md5 $data;
		1600
		1601	=item IO::AIO::munmap $scalar
		1602
		1603	Removes a previous mmap and undefines the C<$scalar>.
		1604
		1605	=item IO::AIO::mlockall $flags
		1606
		1607	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1608	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL__FUTURE>).
		1609
		1610	On systems that do not implement C<mlockall>, this function returns
		1611	ENOSYS, otherwise the return value of C<mlockall>.
		1612
		1613	=item IO::AIO::munlockall
		1614
		1615	Calls the C<munlockall> function.
		1616
		1617	On systems that do not implement C<munlockall>, this function returns
		1618	ENOSYS, otherwise the return value of C<munlockall>.
		1619
		1620	=back
		1621
369	=cut	1622	=cut
370		1623
371	# support function to convert a fd into a perl filehandle
372	sub _fd2fh {
373	return undef if $_[0] < 0;
374
375	# try to generate nice filehandles
376	my $sym = "IO::AIO::fd#$_[0]";
377	local *$sym;
378
379	open *$sym, "+<&=$_[0]" # usually works under any unix
380	or open *$sym, "<&=$_[0]" # cygwin needs this
381	or open *$sym, ">&=$_[0]" # or this
382	or return undef;
383
384	*$sym
385	}
386
387	min_parallel 4;	1624	min_parallel 8;
388		1625
389	END {	1626	END { flush }
390	max_parallel 0;
391	}
392		1627
393	1;	1628	1;
394		1629
		1630	=head1 EVENT LOOP INTEGRATION
		1631
		1632	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1633	automatically into many event loops:
		1634
		1635	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1636	use AnyEvent::AIO;
		1637
		1638	You can also integrate IO::AIO manually into many event loops, here are
		1639	some examples of how to do this:
		1640
		1641	# EV integration
		1642	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1643
		1644	# Event integration
		1645	Event->io (fd => IO::AIO::poll_fileno,
		1646	poll => 'r',
		1647	cb => \&IO::AIO::poll_cb);
		1648
		1649	# Glib/Gtk2 integration
		1650	add_watch Glib::IO IO::AIO::poll_fileno,
		1651	in => sub { IO::AIO::poll_cb; 1 };
		1652
		1653	# Tk integration
		1654	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1655	readable => \&IO::AIO::poll_cb);
		1656
		1657	# Danga::Socket integration
		1658	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1659	\&IO::AIO::poll_cb);
		1660
395	=head2 FORK BEHAVIOUR	1661	=head2 FORK BEHAVIOUR
		1662
		1663	This module should do "the right thing" when the process using it forks:
396		1664
397	Before the fork, IO::AIO enters a quiescent state where no requests	1665	Before the fork, IO::AIO enters a quiescent state where no requests
398	can be added in other threads and no results will be processed. After	1666	can be added in other threads and no results will be processed. After
399	the fork the parent simply leaves the quiescent state and continues	1667	the fork the parent simply leaves the quiescent state and continues
400	request/result processing, while the child clears the request/result	1668	request/result processing, while the child frees the request/result queue
401	queue (so the requests started before the fork will only be handled in	1669	(so that the requests started before the fork will only be handled in the
402	the parent). Threats will be started on demand until the limit ste in the	1670	parent). Threads will be started on demand until the limit set in the
403	parent process has been reached again.	1671	parent process has been reached again.
404		1672
		1673	In short: the parent will, after a short pause, continue as if fork had
		1674	not been called, while the child will act as if IO::AIO has not been used
		1675	yet.
		1676
		1677	=head2 MEMORY USAGE
		1678
		1679	Per-request usage:
		1680
		1681	Each aio request uses - depending on your architecture - around 100-200
		1682	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1683	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1684	scalars and other data passed into aio requests will also be locked and
		1685	will consume memory till the request has entered the done state.
		1686
		1687	This is not awfully much, so queuing lots of requests is not usually a
		1688	problem.
		1689
		1690	Per-thread usage:
		1691
		1692	In the execution phase, some aio requests require more memory for
		1693	temporary buffers, and each thread requires a stack and other data
		1694	structures (usually around 16k-128k, depending on the OS).
		1695
		1696	=head1 KNOWN BUGS
		1697
		1698	Known bugs will be fixed in the next release.
		1699
405	=head1 SEE ALSO	1700	=head1 SEE ALSO
406		1701
407	L<Coro>, L<Linux::AIO>.	1702	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1703	more natural syntax.
408		1704
409	=head1 AUTHOR	1705	=head1 AUTHOR
410		1706
411	Marc Lehmann <schmorp@schmorp.de>	1707	Marc Lehmann <schmorp@schmorp.de>
412	http://home.schmorp.de/	1708	http://home.schmorp.de/

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