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Revision 1.12 by root, Mon Jul 11 01:03:17 2005 UTC vs.
Revision 1.183 by root, Sun Sep 12 03:40:05 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	\&IO::AIO::poll_cb;	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.	64	it is currently not reentrant in any way, so use appropriate locking
		65	yourself, always call C<poll_cb> from within the same thread, or never
		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
54		161
55	=cut	162	=cut
56		163
57	package IO::AIO;	164	package IO::AIO;
58		165
		166	use Carp ();
		167
		168	use common::sense;
		169
59	use base 'Exporter';	170	use base 'Exporter';
60		171
61	use Fcntl ();
62
63	BEGIN {	172	BEGIN {
64	$VERSION = 0.3;	173	our $VERSION = '3.65';
65		174
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
67	aio_fsync aio_fdatasync aio_readahead);	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
		178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		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_mlock aio_mlockall
		183	aio_statvfs);
		184
		185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		187	min_parallel max_parallel max_idle
		188	nreqs nready npending nthreads
		189	max_poll_time max_poll_reqs
		190	sendfile fadvise madvise
		191	mmap munmap munlock munlockall);
		192
		193	push @AIO_REQ, qw(aio_busy); # not exported
		194
		195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		196
70	require XSLoader;	197	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	198	XSLoader::load ("IO::AIO", $VERSION);
72	}	199	}
73		200
74	=head1 FUNCTIONS	201	=head1 FUNCTIONS
75		202
		203	=head2 QUICK OVERVIEW
		204
		205	This section simply lists the prototypes of the most important functions
		206	for quick reference. See the following sections for function-by-function
		207	documentation.
		208
		209	aio_open $pathname, $flags, $mode, $callback->($fh)
		210	aio_close $fh, $callback->($status)
		211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		214	aio_readahead $fh,$offset,$length, $callback->($retval)
		215	aio_stat $fh_or_path, $callback->($status)
		216	aio_lstat $fh, $callback->($status)
		217	aio_statvfs $fh_or_path, $callback->($statvfs)
		218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		220	aio_truncate $fh_or_path, $offset, $callback->($status)
		221	aio_chmod $fh_or_path, $mode, $callback->($status)
		222	aio_unlink $pathname, $callback->($status)
		223	aio_mknod $path, $mode, $dev, $callback->($status)
		224	aio_link $srcpath, $dstpath, $callback->($status)
		225	aio_symlink $srcpath, $dstpath, $callback->($status)
		226	aio_readlink $path, $callback->($link)
		227	aio_rename $srcpath, $dstpath, $callback->($status)
		228	aio_mkdir $pathname, $mode, $callback->($status)
		229	aio_rmdir $pathname, $callback->($status)
		230	aio_readdir $pathname, $callback->($entries)
		231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		234	aio_load $path, $data, $callback->($status)
		235	aio_copy $srcpath, $dstpath, $callback->($status)
		236	aio_move $srcpath, $dstpath, $callback->($status)
		237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		238	aio_rmtree $path, $callback->($status)
		239	aio_sync $callback->($status)
		240	aio_fsync $fh, $callback->($status)
		241	aio_fdatasync $fh, $callback->($status)
		242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		243	aio_pathsync $path, $callback->($status)
		244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		247	aio_mlockall $flags, $callback->($status)
		248	aio_group $callback->(...)
		249	aio_nop $callback->()
		250
		251	$prev_pri = aioreq_pri [$pri]
		252	aioreq_nice $pri_adjust
		253
		254	IO::AIO::poll_wait
		255	IO::AIO::poll_cb
		256	IO::AIO::poll
		257	IO::AIO::flush
		258	IO::AIO::max_poll_reqs $nreqs
		259	IO::AIO::max_poll_time $seconds
		260	IO::AIO::min_parallel $nthreads
		261	IO::AIO::max_parallel $nthreads
		262	IO::AIO::max_idle $nthreads
		263	IO::AIO::max_outstanding $maxreqs
		264	IO::AIO::nreqs
		265	IO::AIO::nready
		266	IO::AIO::npending
		267
		268	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		269	IO::AIO::fadvise $fh, $offset, $len, $advice
		270	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		271	IO::AIO::munlockall
		272
76	=head2 AIO FUNCTIONS	273	=head2 AIO REQUEST FUNCTIONS
77		274
78	All the C<aio_*> calls are more or less thin wrappers around the syscall	275	All the C<aio_*> calls are more or less thin wrappers around the syscall
79	with the same name (sans C<aio_>). The arguments are similar or identical,	276	with the same name (sans C<aio_>). The arguments are similar or identical,
80	and they all accept an additional C<$callback> argument which must be	277	and they all accept an additional (and optional) C<$callback> argument
81	a code reference. This code reference will get called with the syscall	278	which must be a code reference. This code reference will get called with
82	return code (e.g. most syscalls return C<-1> on error, unlike perl, which	279	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	usually delivers "false") as it's sole argument when the given syscall has	280	perl, which usually delivers "false") as its sole argument after the given
84	been executed asynchronously.	281	syscall has been executed asynchronously.
85		282
86	All functions that expect a filehandle will also accept a file descriptor.	283	All functions expecting a filehandle keep a copy of the filehandle
		284	internally until the request has finished.
87		285
		286	All functions return request objects of type L<IO::AIO::REQ> that allow
		287	further manipulation of those requests while they are in-flight.
		288
88	The filenames you pass to these routines I<must> be absolute. The reason	289	The pathnames you pass to these routines I<must> be absolute and
89	is that at the time the request is being executed, the current working	290	encoded as octets. The reason for the former is that at the time the
90	directory could have changed. Alternatively, you can make sure that you	291	request is being executed, the current working directory could have
91	never change the current working directory.	292	changed. Alternatively, you can make sure that you never change the
		293	current working directory anywhere in the program and then use relative
		294	paths.
		295
		296	To encode pathnames as octets, either make sure you either: a) always pass
		297	in filenames you got from outside (command line, readdir etc.) without
		298	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		299	your pathnames to the locale (or other) encoding in effect in the user
		300	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		301	use something else to ensure your scalar has the correct contents.
		302
		303	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		304	handles correctly whether it is set or not.
92		305
93	=over 4	306	=over 4
94		307
		308	=item $prev_pri = aioreq_pri [$pri]
		309
		310	Returns the priority value that would be used for the next request and, if
		311	C<$pri> is given, sets the priority for the next aio request.
		312
		313	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		314	and C<4>, respectively. Requests with higher priority will be serviced
		315	first.
		316
		317	The priority will be reset to C<0> after each call to one of the C<aio_*>
		318	functions.
		319
		320	Example: open a file with low priority, then read something from it with
		321	higher priority so the read request is serviced before other low priority
		322	open requests (potentially spamming the cache):
		323
		324	aioreq_pri -3;
		325	aio_open ..., sub {
		326	return unless $_[0];
		327
		328	aioreq_pri -2;
		329	aio_read $_[0], ..., sub {
		330	...
		331	};
		332	};
		333
		334
		335	=item aioreq_nice $pri_adjust
		336
		337	Similar to C<aioreq_pri>, but subtracts the given value from the current
		338	priority, so the effect is cumulative.
		339
		340
95	=item aio_open $pathname, $flags, $mode, $callback	341	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		342
97	Asynchronously open or create a file and call the callback with a newly	343	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	344	created filehandle for the file.
99		345
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	346	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
101	for an explanation.	347	for an explanation.
102		348
103	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	349	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
104	list. They are the same as used in C<sysopen>.	350	list. They are the same as used by C<sysopen>.
		351
		352	Likewise, C<$mode> specifies the mode of the newly created file, if it
		353	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		354	except that it is mandatory (i.e. use C<0> if you don't create new files,
		355	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		356	by the umask in effect then the request is being executed, so better never
		357	change the umask.
105		358
106	Example:	359	Example:
107		360
108	aio_open "/etc/passwd", O_RDONLY, 0, sub {	361	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
109	if ($_[0]) {	362	if ($_[0]) {
110	print "open successful, fh is $_[0]\n";	363	print "open successful, fh is $_[0]\n";
111	...	364	...
112	} else {	365	} else {
113	die "open failed: $!\n";	366	die "open failed: $!\n";
114	}	367	}
115	};	368	};
116		369
		370
117	=item aio_close $fh, $callback	371	=item aio_close $fh, $callback->($status)
118		372
119	Asynchronously close a file and call the callback with the result	373	Asynchronously close a file and call the callback with the result
120	code. I<WARNING:> although accepted, you should not pass in a perl	374	code.
121	filehandle here, as perl will likely close the file descriptor itself when
122	the filehandle is destroyed. Normally, you can safely call perls C<close>
123	or just let filehandles go out of scope.
124		375
		376	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
		377	closing the file descriptor associated with the filehandle itself.
		378
		379	Therefore, C<aio_close> will not close the filehandle - instead it will
		380	use dup2 to overwrite the file descriptor with the write-end of a pipe
		381	(the pipe fd will be created on demand and will be cached).
		382
		383	Or in other words: the file descriptor will be closed, but it will not be
		384	free for reuse until the perl filehandle is closed.
		385
		386	=cut
		387
125	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	388	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
126		389
127	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	390	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128		391
129	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	392	Reads or writes C<$length> bytes from or to the specified C<$fh> and
130	into the scalar given by C<data> and offset C<dataoffset> and calls the	393	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
131	callback without the actual number of bytes read (or -1 on error, just	394	and calls the callback without the actual number of bytes read (or -1 on
132	like the syscall).	395	error, just like the syscall).
133		396
		397	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		398	offset plus the actual number of bytes read.
		399
		400	If C<$offset> is undefined, then the current file descriptor offset will
		401	be used (and updated), otherwise the file descriptor offset will not be
		402	changed by these calls.
		403
		404	If C<$length> is undefined in C<aio_write>, use the remaining length of
		405	C<$data>.
		406
		407	If C<$dataoffset> is less than zero, it will be counted from the end of
		408	C<$data>.
		409
		410	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		411	is outstanding. Modifying it can result in segfaults or World War III (if
		412	the necessary/optional hardware is installed).
		413
134	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	414	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
135	offset C<0> within the scalar:	415	offset C<0> within the scalar:
136		416
137	aio_read $fh, 7, 15, $buffer, 0, sub {	417	aio_read $fh, 7, 15, $buffer, 0, sub {
138	$_[0] > 0 or die "read error: $!";	418	$_[0] > 0 or die "read error: $!";
139	print "read $_[0] bytes: <$buffer>\n";	419	print "read $_[0] bytes: <$buffer>\n";
140	};	420	};
141		421
		422
		423	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		424
		425	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		426	reading at byte offset C<$in_offset>, and starts writing at the current
		427	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		428	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		429	other.
		430
		431	This call tries to make use of a native C<sendfile> syscall to provide
		432	zero-copy operation. For this to work, C<$out_fh> should refer to a
		433	socket, and C<$in_fh> should refer to an mmap'able file.
		434
		435	If a native sendfile cannot be found or it fails with C<ENOSYS>,
		436	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
		437	it will be emulated, so you can call C<aio_sendfile> on any type of
		438	filehandle regardless of the limitations of the operating system.
		439
		440	Please note, however, that C<aio_sendfile> can read more bytes from
		441	C<$in_fh> than are written, and there is no way to find out how many
		442	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		443	provides the number of bytes written to C<$out_fh>. Only if the result
		444	value equals C<$length> one can assume that C<$length> bytes have been
		445	read.
		446
		447
142	=item aio_readahead $fh,$offset,$length, $callback	448	=item aio_readahead $fh,$offset,$length, $callback->($retval)
143		449
144	Asynchronously reads the specified byte range into the page cache, using
145	the C<readahead> syscall. If that syscall doesn't exist the status will be
146	C<-1> and C<$!> is set to ENOSYS.
147
148	readahead() populates the page cache with data from a file so that	450	C<aio_readahead> populates the page cache with data from a file so that
149	subsequent reads from that file will not block on disk I/O. The C<$offset>	451	subsequent reads from that file will not block on disk I/O. The C<$offset>
150	argument specifies the starting point from which data is to be read and	452	argument specifies the starting point from which data is to be read and
151	C<$length> specifies the number of bytes to be read. I/O is performed in	453	C<$length> specifies the number of bytes to be read. I/O is performed in
152	whole pages, so that offset is effectively rounded down to a page boundary	454	whole pages, so that offset is effectively rounded down to a page boundary
153	and bytes are read up to the next page boundary greater than or equal to	455	and bytes are read up to the next page boundary greater than or equal to
154	(off-set+length). aio_readahead() does not read beyond the end of the	456	(off-set+length). C<aio_readahead> does not read beyond the end of the
155	file. The current file offset of the file is left unchanged.	457	file. The current file offset of the file is left unchanged.
156		458
		459	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		460	emulated by simply reading the data, which would have a similar effect.
		461
		462
157	=item aio_stat $fh_or_path, $callback	463	=item aio_stat $fh_or_path, $callback->($status)
158		464
159	=item aio_lstat $fh, $callback	465	=item aio_lstat $fh, $callback->($status)
160		466
161	Works like perl's C<stat> or C<lstat> in void context. The callback will	467	Works like perl's C<stat> or C<lstat> in void context. The callback will
162	be called after the stat and the results will be available using C<stat _>	468	be called after the stat and the results will be available using C<stat _>
163	or C<-s _> etc...	469	or C<-s _> etc...
164		470
…		…
174	aio_stat "/etc/passwd", sub {	480	aio_stat "/etc/passwd", sub {
175	$_[0] and die "stat failed: $!";	481	$_[0] and die "stat failed: $!";
176	print "size is ", -s _, "\n";	482	print "size is ", -s _, "\n";
177	};	483	};
178		484
		485
		486	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		487
		488	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		489	whether a file handle or path was passed.
		490
		491	On success, the callback is passed a hash reference with the following
		492	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		493	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		494	is passed.
		495
		496	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		497	C<ST_NOSUID>.
		498
		499	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		500	their correct value when available, or to C<0> on systems that do
		501	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		502	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		503	C<ST_NODIRATIME> and C<ST_RELATIME>.
		504
		505	Example: stat C</wd> and dump out the data if successful.
		506
		507	aio_statvfs "/wd", sub {
		508	my $f = $_[0]
		509	or die "statvfs: $!";
		510
		511	use Data::Dumper;
		512	say Dumper $f;
		513	};
		514
		515	# result:
		516	{
		517	bsize => 1024,
		518	bfree => 4333064312,
		519	blocks => 10253828096,
		520	files => 2050765568,
		521	flag => 4096,
		522	favail => 2042092649,
		523	bavail => 4333064312,
		524	ffree => 2042092649,
		525	namemax => 255,
		526	frsize => 1024,
		527	fsid => 1810
		528	}
		529
		530
		531	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		532
		533	Works like perl's C<utime> function (including the special case of $atime
		534	and $mtime being undef). Fractional times are supported if the underlying
		535	syscalls support them.
		536
		537	When called with a pathname, uses utimes(2) if available, otherwise
		538	utime(2). If called on a file descriptor, uses futimes(2) if available,
		539	otherwise returns ENOSYS, so this is not portable.
		540
		541	Examples:
		542
		543	# set atime and mtime to current time (basically touch(1)):
		544	aio_utime "path", undef, undef;
		545	# set atime to current time and mtime to beginning of the epoch:
		546	aio_utime "path", time, undef; # undef==0
		547
		548
		549	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		550
		551	Works like perl's C<chown> function, except that C<undef> for either $uid
		552	or $gid is being interpreted as "do not change" (but -1 can also be used).
		553
		554	Examples:
		555
		556	# same as "chown root path" in the shell:
		557	aio_chown "path", 0, -1;
		558	# same as above:
		559	aio_chown "path", 0, undef;
		560
		561
		562	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		563
		564	Works like truncate(2) or ftruncate(2).
		565
		566
		567	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		568
		569	Works like perl's C<chmod> function.
		570
		571
179	=item aio_unlink $pathname, $callback	572	=item aio_unlink $pathname, $callback->($status)
180		573
181	Asynchronously unlink (delete) a file and call the callback with the	574	Asynchronously unlink (delete) a file and call the callback with the
182	result code.	575	result code.
183		576
		577
		578	=item aio_mknod $path, $mode, $dev, $callback->($status)
		579
		580	[EXPERIMENTAL]
		581
		582	Asynchronously create a device node (or fifo). See mknod(2).
		583
		584	The only (POSIX-) portable way of calling this function is:
		585
		586	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		587
		588
		589	=item aio_link $srcpath, $dstpath, $callback->($status)
		590
		591	Asynchronously create a new link to the existing object at C<$srcpath> at
		592	the path C<$dstpath> and call the callback with the result code.
		593
		594
		595	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		596
		597	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		598	the path C<$dstpath> and call the callback with the result code.
		599
		600
		601	=item aio_readlink $path, $callback->($link)
		602
		603	Asynchronously read the symlink specified by C<$path> and pass it to
		604	the callback. If an error occurs, nothing or undef gets passed to the
		605	callback.
		606
		607
		608	=item aio_rename $srcpath, $dstpath, $callback->($status)
		609
		610	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		611	rename(2) and call the callback with the result code.
		612
		613
		614	=item aio_mkdir $pathname, $mode, $callback->($status)
		615
		616	Asynchronously mkdir (create) a directory and call the callback with
		617	the result code. C<$mode> will be modified by the umask at the time the
		618	request is executed, so do not change your umask.
		619
		620
		621	=item aio_rmdir $pathname, $callback->($status)
		622
		623	Asynchronously rmdir (delete) a directory and call the callback with the
		624	result code.
		625
		626
		627	=item aio_readdir $pathname, $callback->($entries)
		628
		629	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		630	directory (i.e. opendir + readdir + closedir). The entries will not be
		631	sorted, and will B<NOT> include the C<.> and C<..> entries.
		632
		633	The callback is passed a single argument which is either C<undef> or an
		634	array-ref with the filenames.
		635
		636
		637	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		638
		639	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		640	behaviour and output format. In case of an error, C<$entries> will be
		641	C<undef>.
		642
		643	The flags are a combination of the following constants, ORed together (the
		644	flags will also be passed to the callback, possibly modified):
		645
		646	=over 4
		647
		648	=item IO::AIO::READDIR_DENTS
		649
		650	When this flag is off, then the callback gets an arrayref with of names
		651	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		652	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		653	entry in more detail.
		654
		655	C<$name> is the name of the entry.
		656
		657	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		658
		659	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		660	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		661	C<IO::AIO::DT_WHT>.
		662
		663	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		664	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		665	scalars are read-only: you can not modify them.
		666
		667	C<$inode> is the inode number (which might not be exact on systems with 64
		668	bit inode numbers and 32 bit perls). This field has unspecified content on
		669	systems that do not deliver the inode information.
		670
		671	=item IO::AIO::READDIR_DIRS_FIRST
		672
		673	When this flag is set, then the names will be returned in an order where
		674	likely directories come first. This is useful when you need to quickly
		675	find directories, or you want to find all directories while avoiding to
		676	stat() each entry.
		677
		678	If the system returns type information in readdir, then this is used
		679	to find directories directly. Otherwise, likely directories are files
		680	beginning with ".", or otherwise files with no dots, of which files with
		681	short names are tried first.
		682
		683	=item IO::AIO::READDIR_STAT_ORDER
		684
		685	When this flag is set, then the names will be returned in an order
		686	suitable for stat()'ing each one. That is, when you plan to stat()
		687	all files in the given directory, then the returned order will likely
		688	be fastest.
		689
		690	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		691	the likely dirs come first, resulting in a less optimal stat order.
		692
		693	=item IO::AIO::READDIR_FOUND_UNKNOWN
		694
		695	This flag should not be set when calling C<aio_readdirx>. Instead, it
		696	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		697	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		698	C<$type>'s are known, which can be used to speed up some algorithms.
		699
		700	=back
		701
		702
		703	=item aio_load $path, $data, $callback->($status)
		704
		705	This is a composite request that tries to fully load the given file into
		706	memory. Status is the same as with aio_read.
		707
		708	=cut
		709
		710	sub aio_load($$;$) {
		711	my ($path, undef, $cb) = @_;
		712	my $data = \$_[1];
		713
		714	my $pri = aioreq_pri;
		715	my $grp = aio_group $cb;
		716
		717	aioreq_pri $pri;
		718	add $grp aio_open $path, O_RDONLY, 0, sub {
		719	my $fh = shift
		720	or return $grp->result (-1);
		721
		722	aioreq_pri $pri;
		723	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		724	$grp->result ($_[0]);
		725	};
		726	};
		727
		728	$grp
		729	}
		730
		731	=item aio_copy $srcpath, $dstpath, $callback->($status)
		732
		733	Try to copy the I<file> (directories not supported as either source or
		734	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		735	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		736
		737	This is a composite request that creates the destination file with
		738	mode 0200 and copies the contents of the source file into it using
		739	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		740	uid/gid, in that order.
		741
		742	If an error occurs, the partial destination file will be unlinked, if
		743	possible, except when setting atime, mtime, access mode and uid/gid, where
		744	errors are being ignored.
		745
		746	=cut
		747
		748	sub aio_copy($$;$) {
		749	my ($src, $dst, $cb) = @_;
		750
		751	my $pri = aioreq_pri;
		752	my $grp = aio_group $cb;
		753
		754	aioreq_pri $pri;
		755	add $grp aio_open $src, O_RDONLY, 0, sub {
		756	if (my $src_fh = $_[0]) {
		757	my @stat = stat $src_fh; # hmm, might block over nfs?
		758
		759	aioreq_pri $pri;
		760	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		761	if (my $dst_fh = $_[0]) {
		762	aioreq_pri $pri;
		763	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		764	if ($_[0] == $stat[7]) {
		765	$grp->result (0);
		766	close $src_fh;
		767
		768	my $ch = sub {
		769	aioreq_pri $pri;
		770	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		771	aioreq_pri $pri;
		772	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		773	aioreq_pri $pri;
		774	add $grp aio_close $dst_fh;
		775	}
		776	};
		777	};
		778
		779	aioreq_pri $pri;
		780	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		781	if ($_[0] < 0 && $! == ENOSYS) {
		782	aioreq_pri $pri;
		783	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		784	} else {
		785	$ch->();
		786	}
		787	};
		788	} else {
		789	$grp->result (-1);
		790	close $src_fh;
		791	close $dst_fh;
		792
		793	aioreq $pri;
		794	add $grp aio_unlink $dst;
		795	}
		796	};
		797	} else {
		798	$grp->result (-1);
		799	}
		800	},
		801
		802	} else {
		803	$grp->result (-1);
		804	}
		805	};
		806
		807	$grp
		808	}
		809
		810	=item aio_move $srcpath, $dstpath, $callback->($status)
		811
		812	Try to move the I<file> (directories not supported as either source or
		813	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		814	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		815
		816	This is a composite request that tries to rename(2) the file first; if
		817	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		818	that is successful, unlinks the C<$srcpath>.
		819
		820	=cut
		821
		822	sub aio_move($$;$) {
		823	my ($src, $dst, $cb) = @_;
		824
		825	my $pri = aioreq_pri;
		826	my $grp = aio_group $cb;
		827
		828	aioreq_pri $pri;
		829	add $grp aio_rename $src, $dst, sub {
		830	if ($_[0] && $! == EXDEV) {
		831	aioreq_pri $pri;
		832	add $grp aio_copy $src, $dst, sub {
		833	$grp->result ($_[0]);
		834
		835	if (!$_[0]) {
		836	aioreq_pri $pri;
		837	add $grp aio_unlink $src;
		838	}
		839	};
		840	} else {
		841	$grp->result ($_[0]);
		842	}
		843	};
		844
		845	$grp
		846	}
		847
		848	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		849
		850	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		851	efficiently separate the entries of directory C<$path> into two sets of
		852	names, directories you can recurse into (directories), and ones you cannot
		853	recurse into (everything else, including symlinks to directories).
		854
		855	C<aio_scandir> is a composite request that creates of many sub requests_
		856	C<$maxreq> specifies the maximum number of outstanding aio requests that
		857	this function generates. If it is C<< <= 0 >>, then a suitable default
		858	will be chosen (currently 4).
		859
		860	On error, the callback is called without arguments, otherwise it receives
		861	two array-refs with path-relative entry names.
		862
		863	Example:
		864
		865	aio_scandir $dir, 0, sub {
		866	my ($dirs, $nondirs) = @_;
		867	print "real directories: @$dirs\n";
		868	print "everything else: @$nondirs\n";
		869	};
		870
		871	Implementation notes.
		872
		873	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		874
		875	If readdir returns file type information, then this is used directly to
		876	find directories.
		877
		878	Otherwise, after reading the directory, the modification time, size etc.
		879	of the directory before and after the readdir is checked, and if they
		880	match (and isn't the current time), the link count will be used to decide
		881	how many entries are directories (if >= 2). Otherwise, no knowledge of the
		882	number of subdirectories will be assumed.
		883
		884	Then entries will be sorted into likely directories a non-initial dot
		885	currently) and likely non-directories (see C<aio_readdirx>). Then every
		886	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		887	in order of their inode numbers. If that succeeds, it assumes that the
		888	entry is a directory or a symlink to directory (which will be checked
		889	seperately). This is often faster than stat'ing the entry itself because
		890	filesystems might detect the type of the entry without reading the inode
		891	data (e.g. ext2fs filetype feature), even on systems that cannot return
		892	the filetype information on readdir.
		893
		894	If the known number of directories (link count - 2) has been reached, the
		895	rest of the entries is assumed to be non-directories.
		896
		897	This only works with certainty on POSIX (= UNIX) filesystems, which
		898	fortunately are the vast majority of filesystems around.
		899
		900	It will also likely work on non-POSIX filesystems with reduced efficiency
		901	as those tend to return 0 or 1 as link counts, which disables the
		902	directory counting heuristic.
		903
		904	=cut
		905
		906	sub aio_scandir($$;$) {
		907	my ($path, $maxreq, $cb) = @_;
		908
		909	my $pri = aioreq_pri;
		910
		911	my $grp = aio_group $cb;
		912
		913	$maxreq = 4 if $maxreq <= 0;
		914
		915	# stat once
		916	aioreq_pri $pri;
		917	add $grp aio_stat $path, sub {
		918	return $grp->result () if $_[0];
		919	my $now = time;
		920	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		921
		922	# read the directory entries
		923	aioreq_pri $pri;
		924	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
		925	my $entries = shift
		926	or return $grp->result ();
		927
		928	# stat the dir another time
		929	aioreq_pri $pri;
		930	add $grp aio_stat $path, sub {
		931	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		932
		933	my $ndirs;
		934
		935	# take the slow route if anything looks fishy
		936	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		937	$ndirs = -1;
		938	} else {
		939	# if nlink == 2, we are finished
		940	# for non-posix-fs's, we rely on nlink < 2
		941	$ndirs = (stat _)[3] - 2
		942	or return $grp->result ([], $entries);
		943	}
		944
		945	my (@dirs, @nondirs);
		946
		947	my $statgrp = add $grp aio_group sub {
		948	$grp->result (\@dirs, \@nondirs);
		949	};
		950
		951	limit $statgrp $maxreq;
		952	feed $statgrp sub {
		953	return unless @$entries;
		954	my $entry = shift @$entries;
		955
		956	aioreq_pri $pri;
		957	add $statgrp aio_stat "$path/$entry/.", sub {
		958	if ($_[0] < 0) {
		959	push @nondirs, $entry;
		960	} else {
		961	# need to check for real directory
		962	aioreq_pri $pri;
		963	add $statgrp aio_lstat "$path/$entry", sub {
		964	if (-d _) {
		965	push @dirs, $entry;
		966
		967	unless (--$ndirs) {
		968	push @nondirs, @$entries;
		969	feed $statgrp;
		970	}
		971	} else {
		972	push @nondirs, $entry;
		973	}
		974	}
		975	}
		976	};
		977	};
		978	};
		979	};
		980	};
		981
		982	$grp
		983	}
		984
		985	=item aio_rmtree $path, $callback->($status)
		986
		987	Delete a directory tree starting (and including) C<$path>, return the
		988	status of the final C<rmdir> only. This is a composite request that
		989	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		990	everything else.
		991
		992	=cut
		993
		994	sub aio_rmtree;
		995	sub aio_rmtree($;$) {
		996	my ($path, $cb) = @_;
		997
		998	my $pri = aioreq_pri;
		999	my $grp = aio_group $cb;
		1000
		1001	aioreq_pri $pri;
		1002	add $grp aio_scandir $path, 0, sub {
		1003	my ($dirs, $nondirs) = @_;
		1004
		1005	my $dirgrp = aio_group sub {
		1006	add $grp aio_rmdir $path, sub {
		1007	$grp->result ($_[0]);
		1008	};
		1009	};
		1010
		1011	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1012	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1013
		1014	add $grp $dirgrp;
		1015	};
		1016
		1017	$grp
		1018	}
		1019
		1020	=item aio_sync $callback->($status)
		1021
		1022	Asynchronously call sync and call the callback when finished.
		1023
184	=item aio_fsync $fh, $callback	1024	=item aio_fsync $fh, $callback->($status)
185		1025
186	Asynchronously call fsync on the given filehandle and call the callback	1026	Asynchronously call fsync on the given filehandle and call the callback
187	with the fsync result code.	1027	with the fsync result code.
188		1028
189	=item aio_fdatasync $fh, $callback	1029	=item aio_fdatasync $fh, $callback->($status)
190		1030
191	Asynchronously call fdatasync on the given filehandle and call the	1031	Asynchronously call fdatasync on the given filehandle and call the
192	callback with the fdatasync result code.	1032	callback with the fdatasync result code.
193		1033
		1034	If this call isn't available because your OS lacks it or it couldn't be
		1035	detected, it will be emulated by calling C<fsync> instead.
		1036
		1037	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1038
		1039	Sync the data portion of the file specified by C<$offset> and C<$length>
		1040	to disk (but NOT the metadata), by calling the Linux-specific
		1041	sync_file_range call. If sync_file_range is not available or it returns
		1042	ENOSYS, then fdatasync or fsync is being substituted.
		1043
		1044	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1045	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1046	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1047	manpage for details.
		1048
		1049	=item aio_pathsync $path, $callback->($status)
		1050
		1051	This request tries to open, fsync and close the given path. This is a
		1052	composite request intended to sync directories after directory operations
		1053	(E.g. rename). This might not work on all operating systems or have any
		1054	specific effect, but usually it makes sure that directory changes get
		1055	written to disc. It works for anything that can be opened for read-only,
		1056	not just directories.
		1057
		1058	Future versions of this function might fall back to other methods when
		1059	C<fsync> on the directory fails (such as calling C<sync>).
		1060
		1061	Passes C<0> when everything went ok, and C<-1> on error.
		1062
		1063	=cut
		1064
		1065	sub aio_pathsync($;$) {
		1066	my ($path, $cb) = @_;
		1067
		1068	my $pri = aioreq_pri;
		1069	my $grp = aio_group $cb;
		1070
		1071	aioreq_pri $pri;
		1072	add $grp aio_open $path, O_RDONLY, 0, sub {
		1073	my ($fh) = @_;
		1074	if ($fh) {
		1075	aioreq_pri $pri;
		1076	add $grp aio_fsync $fh, sub {
		1077	$grp->result ($_[0]);
		1078
		1079	aioreq_pri $pri;
		1080	add $grp aio_close $fh;
		1081	};
		1082	} else {
		1083	$grp->result (-1);
		1084	}
		1085	};
		1086
		1087	$grp
		1088	}
		1089
		1090	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1091
		1092	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1093	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1094	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1095	scalar must only be modified in-place while an aio operation is pending on
		1096	it).
		1097
		1098	It calls the C<msync> function of your OS, if available, with the memory
		1099	area starting at C<$offset> in the string and ending C<$length> bytes
		1100	later. If C<$length> is negative, counts from the end, and if C<$length>
		1101	is C<undef>, then it goes till the end of the string. The flags can be
		1102	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1103	C<IO::AIO::MS_SYNC>.
		1104
		1105	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1106
		1107	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1108	scalars.
		1109
		1110	It touches (reads or writes) all memory pages in the specified
		1111	range inside the scalar. All caveats and parameters are the same
		1112	as for C<aio_msync>, above, except for flags, which must be either
		1113	C<0> (which reads all pages and ensures they are instantiated) or
		1114	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1115	writing an octet from it, which dirties the page).
		1116
		1117	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1118
		1119	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1120	scalars.
		1121
		1122	It reads in all the pages of the underlying storage into memory (if any)
		1123	and locks them, so they are not getting swapped/paged out or removed.
		1124
		1125	If C<$length> is undefined, then the scalar will be locked till the end.
		1126
		1127	On systems that do not implement C<mlock>, this function returns C<-1>
		1128	and sets errno to C<ENOSYS>.
		1129
		1130	Note that the corresponding C<munlock> is synchronous and is
		1131	documented under L<MISCELLANEOUS FUNCTIONS>.
		1132
		1133	Example: open a file, mmap and mlock it - both will be undone when
		1134	C<$data> gets destroyed.
		1135
		1136	open my $fh, "<", $path or die "$path: $!";
		1137	my $data;
		1138	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1139	aio_mlock $data; # mlock in background
		1140
		1141	=item aio_mlockall $flags, $callback->($status)
		1142
		1143	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1144	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1145
		1146	On systems that do not implement C<mlockall>, this function returns C<-1>
		1147	and sets errno to C<ENOSYS>.
		1148
		1149	Note that the corresponding C<munlockall> is synchronous and is
		1150	documented under L<MISCELLANEOUS FUNCTIONS>.
		1151
		1152	Example: asynchronously lock all current and future pages into memory.
		1153
		1154	aio_mlockall IO::AIO::MCL_FUTURE;
		1155
		1156	=item aio_group $callback->(...)
		1157
		1158	This is a very special aio request: Instead of doing something, it is a
		1159	container for other aio requests, which is useful if you want to bundle
		1160	many requests into a single, composite, request with a definite callback
		1161	and the ability to cancel the whole request with its subrequests.
		1162
		1163	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		1164	for more info.
		1165
		1166	Example:
		1167
		1168	my $grp = aio_group sub {
		1169	print "all stats done\n";
		1170	};
		1171
		1172	add $grp
		1173	(aio_stat ...),
		1174	(aio_stat ...),
		1175	...;
		1176
		1177	=item aio_nop $callback->()
		1178
		1179	This is a special request - it does nothing in itself and is only used for
		1180	side effects, such as when you want to add a dummy request to a group so
		1181	that finishing the requests in the group depends on executing the given
		1182	code.
		1183
		1184	While this request does nothing, it still goes through the execution
		1185	phase and still requires a worker thread. Thus, the callback will not
		1186	be executed immediately but only after other requests in the queue have
		1187	entered their execution phase. This can be used to measure request
		1188	latency.
		1189
		1190	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1191
		1192	Mainly used for debugging and benchmarking, this aio request puts one of
		1193	the request workers to sleep for the given time.
		1194
		1195	While it is theoretically handy to have simple I/O scheduling requests
		1196	like sleep and file handle readable/writable, the overhead this creates is
		1197	immense (it blocks a thread for a long time) so do not use this function
		1198	except to put your application under artificial I/O pressure.
		1199
194	=back	1200	=back
195		1201
		1202	=head2 IO::AIO::REQ CLASS
		1203
		1204	All non-aggregate C<aio_*> functions return an object of this class when
		1205	called in non-void context.
		1206
		1207	=over 4
		1208
		1209	=item cancel $req
		1210
		1211	Cancels the request, if possible. Has the effect of skipping execution
		1212	when entering the B<execute> state and skipping calling the callback when
		1213	entering the the B<result> state, but will leave the request otherwise
		1214	untouched (with the exception of readdir). That means that requests that
		1215	currently execute will not be stopped and resources held by the request
		1216	will not be freed prematurely.
		1217
		1218	=item cb $req $callback->(...)
		1219
		1220	Replace (or simply set) the callback registered to the request.
		1221
		1222	=back
		1223
		1224	=head2 IO::AIO::GRP CLASS
		1225
		1226	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1227	objects of this class, too.
		1228
		1229	A IO::AIO::GRP object is a special request that can contain multiple other
		1230	aio requests.
		1231
		1232	You create one by calling the C<aio_group> constructing function with a
		1233	callback that will be called when all contained requests have entered the
		1234	C<done> state:
		1235
		1236	my $grp = aio_group sub {
		1237	print "all requests are done\n";
		1238	};
		1239
		1240	You add requests by calling the C<add> method with one or more
		1241	C<IO::AIO::REQ> objects:
		1242
		1243	$grp->add (aio_unlink "...");
		1244
		1245	add $grp aio_stat "...", sub {
		1246	$_[0] or return $grp->result ("error");
		1247
		1248	# add another request dynamically, if first succeeded
		1249	add $grp aio_open "...", sub {
		1250	$grp->result ("ok");
		1251	};
		1252	};
		1253
		1254	This makes it very easy to create composite requests (see the source of
		1255	C<aio_move> for an application) that work and feel like simple requests.
		1256
		1257	=over 4
		1258
		1259	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1260	C<IO::AIO::poll_cb>, just like any other request.
		1261
		1262	=item * They can be canceled like any other request. Canceling will cancel not
		1263	only the request itself, but also all requests it contains.
		1264
		1265	=item * They can also can also be added to other IO::AIO::GRP objects.
		1266
		1267	=item * You must not add requests to a group from within the group callback (or
		1268	any later time).
		1269
		1270	=back
		1271
		1272	Their lifetime, simplified, looks like this: when they are empty, they
		1273	will finish very quickly. If they contain only requests that are in the
		1274	C<done> state, they will also finish. Otherwise they will continue to
		1275	exist.
		1276
		1277	That means after creating a group you have some time to add requests
		1278	(precisely before the callback has been invoked, which is only done within
		1279	the C<poll_cb>). And in the callbacks of those requests, you can add
		1280	further requests to the group. And only when all those requests have
		1281	finished will the the group itself finish.
		1282
		1283	=over 4
		1284
		1285	=item add $grp ...
		1286
		1287	=item $grp->add (...)
		1288
		1289	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1290	be added, including other groups, as long as you do not create circular
		1291	dependencies.
		1292
		1293	Returns all its arguments.
		1294
		1295	=item $grp->cancel_subs
		1296
		1297	Cancel all subrequests and clears any feeder, but not the group request
		1298	itself. Useful when you queued a lot of events but got a result early.
		1299
		1300	The group request will finish normally (you cannot add requests to the
		1301	group).
		1302
		1303	=item $grp->result (...)
		1304
		1305	Set the result value(s) that will be passed to the group callback when all
		1306	subrequests have finished and set the groups errno to the current value
		1307	of errno (just like calling C<errno> without an error number). By default,
		1308	no argument will be passed and errno is zero.
		1309
		1310	=item $grp->errno ([$errno])
		1311
		1312	Sets the group errno value to C<$errno>, or the current value of errno
		1313	when the argument is missing.
		1314
		1315	Every aio request has an associated errno value that is restored when
		1316	the callback is invoked. This method lets you change this value from its
		1317	default (0).
		1318
		1319	Calling C<result> will also set errno, so make sure you either set C<$!>
		1320	before the call to C<result>, or call c<errno> after it.
		1321
		1322	=item feed $grp $callback->($grp)
		1323
		1324	Sets a feeder/generator on this group: every group can have an attached
		1325	generator that generates requests if idle. The idea behind this is that,
		1326	although you could just queue as many requests as you want in a group,
		1327	this might starve other requests for a potentially long time. For example,
		1328	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1329	delaying any later requests for a long time.
		1330
		1331	To avoid this, and allow incremental generation of requests, you can
		1332	instead a group and set a feeder on it that generates those requests. The
		1333	feed callback will be called whenever there are few enough (see C<limit>,
		1334	below) requests active in the group itself and is expected to queue more
		1335	requests.
		1336
		1337	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1338	not impose any limits).
		1339
		1340	If the feed does not queue more requests when called, it will be
		1341	automatically removed from the group.
		1342
		1343	If the feed limit is C<0> when this method is called, it will be set to
		1344	C<2> automatically.
		1345
		1346	Example:
		1347
		1348	# stat all files in @files, but only ever use four aio requests concurrently:
		1349
		1350	my $grp = aio_group sub { print "finished\n" };
		1351	limit $grp 4;
		1352	feed $grp sub {
		1353	my $file = pop @files
		1354	or return;
		1355
		1356	add $grp aio_stat $file, sub { ... };
		1357	};
		1358
		1359	=item limit $grp $num
		1360
		1361	Sets the feeder limit for the group: The feeder will be called whenever
		1362	the group contains less than this many requests.
		1363
		1364	Setting the limit to C<0> will pause the feeding process.
		1365
		1366	The default value for the limit is C<0>, but note that setting a feeder
		1367	automatically bumps it up to C<2>.
		1368
		1369	=back
		1370
196	=head2 SUPPORT FUNCTIONS	1371	=head2 SUPPORT FUNCTIONS
197		1372
		1373	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1374
198	=over 4	1375	=over 4
199		1376
200	=item $fileno = IO::AIO::poll_fileno	1377	=item $fileno = IO::AIO::poll_fileno
201		1378
202	Return the I<request result pipe filehandle>. This filehandle must be	1379	Return the I<request result pipe file descriptor>. This filehandle must be
203	polled for reading by some mechanism outside this module (e.g. Event	1380	polled for reading by some mechanism outside this module (e.g. EV, Glib,
204	or select, see below). If the pipe becomes readable you have to call	1381	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
205	C<poll_cb> to check the results.	1382	you have to call C<poll_cb> to check the results.
206		1383
207	See C<poll_cb> for an example.	1384	See C<poll_cb> for an example.
208		1385
209	=item IO::AIO::poll_cb	1386	=item IO::AIO::poll_cb
210		1387
211	Process all outstanding events on the result pipe. You have to call this	1388	Process some outstanding events on the result pipe. You have to call this
212	regularly. Returns the number of events processed. Returns immediately	1389	regularly. Returns C<0> if all events could be processed, or C<-1> if it
213	when no events are outstanding.	1390	returned earlier for whatever reason. Returns immediately when no events
		1391	are outstanding. The amount of events processed depends on the settings of
		1392	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
214		1393
215	You can use Event to multiplex, e.g.:	1394	If not all requests were processed for whatever reason, the filehandle
		1395	will still be ready when C<poll_cb> returns, so normally you don't have to
		1396	do anything special to have it called later.
		1397
		1398	Example: Install an Event watcher that automatically calls
		1399	IO::AIO::poll_cb with high priority (more examples can be found in the
		1400	SYNOPSIS section, at the top of this document):
216		1401
217	Event->io (fd => IO::AIO::poll_fileno,	1402	Event->io (fd => IO::AIO::poll_fileno,
218	poll => 'r', async => 1,	1403	poll => 'r', async => 1,
219	cb => \&IO::AIO::poll_cb);	1404	cb => \&IO::AIO::poll_cb);
220		1405
221	=item IO::AIO::poll_wait	1406	=item IO::AIO::poll_wait
222		1407
		1408	If there are any outstanding requests and none of them in the result
223	Wait till the result filehandle becomes ready for reading (simply does a	1409	phase, wait till the result filehandle becomes ready for reading (simply
224	select on the filehandle. This is useful if you want to synchronously wait	1410	does a C<select> on the filehandle. This is useful if you want to
225	for some requests to finish).	1411	synchronously wait for some requests to finish).
226		1412
227	See C<nreqs> for an example.	1413	See C<nreqs> for an example.
228		1414
		1415	=item IO::AIO::poll
		1416
		1417	Waits until some requests have been handled.
		1418
		1419	Returns the number of requests processed, but is otherwise strictly
		1420	equivalent to:
		1421
		1422	IO::AIO::poll_wait, IO::AIO::poll_cb
		1423
229	=item IO::AIO::nreqs	1424	=item IO::AIO::flush
230		1425
231	Returns the number of requests currently outstanding.	1426	Wait till all outstanding AIO requests have been handled.
232		1427
233	Example: wait till there are no outstanding requests anymore:	1428	Strictly equivalent to:
234		1429
235	IO::AIO::poll_wait, IO::AIO::poll_cb	1430	IO::AIO::poll_wait, IO::AIO::poll_cb
236	while IO::AIO::nreqs;	1431	while IO::AIO::nreqs;
237		1432
238	=item IO::AIO::flush	1433	=item IO::AIO::max_poll_reqs $nreqs
239		1434
240	Wait till all outstanding AIO requests have been handled.	1435	=item IO::AIO::max_poll_time $seconds
		1436
		1437	These set the maximum number of requests (default C<0>, meaning infinity)
		1438	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1439	the maximum amount of time (default C<0>, meaning infinity) spent in
		1440	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1441	of time C<poll_cb> is allowed to use).
		1442
		1443	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1444	syscall per request processed, which is not normally a problem unless your
		1445	callbacks are really really fast or your OS is really really slow (I am
		1446	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1447
		1448	Setting these is useful if you want to ensure some level of
		1449	interactiveness when perl is not fast enough to process all requests in
		1450	time.
		1451
		1452	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1453
		1454	Example: Install an Event watcher that automatically calls
		1455	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1456	program get the CPU sometimes even under high AIO load.
		1457
		1458	# try not to spend much more than 0.1s in poll_cb
		1459	IO::AIO::max_poll_time 0.1;
		1460
		1461	# use a low priority so other tasks have priority
		1462	Event->io (fd => IO::AIO::poll_fileno,
		1463	poll => 'r', nice => 1,
		1464	cb => &IO::AIO::poll_cb);
		1465
		1466	=back
		1467
		1468	=head3 CONTROLLING THE NUMBER OF THREADS
		1469
		1470	=over
241		1471
242	=item IO::AIO::min_parallel $nthreads	1472	=item IO::AIO::min_parallel $nthreads
243		1473
244	Set the minimum number of AIO threads to C<$nthreads>. The default is	1474	Set the minimum number of AIO threads to C<$nthreads>. The current
245	C<1>, which means a single asynchronous operation can be done at one time	1475	default is C<8>, which means eight asynchronous operations can execute
246	(the number of outstanding operations, however, is unlimited).	1476	concurrently at any one time (the number of outstanding requests,
		1477	however, is unlimited).
247		1478
		1479	IO::AIO starts threads only on demand, when an AIO request is queued and
		1480	no free thread exists. Please note that queueing up a hundred requests can
		1481	create demand for a hundred threads, even if it turns out that everything
		1482	is in the cache and could have been processed faster by a single thread.
		1483
248	It is recommended to keep the number of threads low, as some Linux	1484	It is recommended to keep the number of threads relatively low, as some
249	kernel versions will scale negatively with the number of threads (higher	1485	Linux kernel versions will scale negatively with the number of threads
250	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1486	(higher parallelity => MUCH higher latency). With current Linux 2.6
251	threads should be fine.	1487	versions, 4-32 threads should be fine.
252		1488
253	Under normal circumstances you don't need to call this function, as this	1489	Under most circumstances you don't need to call this function, as the
254	module automatically starts some threads (the exact number might change,	1490	module selects a default that is suitable for low to moderate load.
255	and is currently 4).
256		1491
257	=item IO::AIO::max_parallel $nthreads	1492	=item IO::AIO::max_parallel $nthreads
258		1493
259	Sets the maximum number of AIO threads to C<$nthreads>. If more than	1494	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
260	the specified number of threads are currently running, kill them. This	1495	specified number of threads are currently running, this function kills
261	function blocks until the limit is reached.	1496	them. This function blocks until the limit is reached.
		1497
		1498	While C<$nthreads> are zero, aio requests get queued but not executed
		1499	until the number of threads has been increased again.
262		1500
263	This module automatically runs C<max_parallel 0> at program end, to ensure	1501	This module automatically runs C<max_parallel 0> at program end, to ensure
264	that all threads are killed and that there are no outstanding requests.	1502	that all threads are killed and that there are no outstanding requests.
265		1503
266	Under normal circumstances you don't need to call this function.	1504	Under normal circumstances you don't need to call this function.
267		1505
		1506	=item IO::AIO::max_idle $nthreads
		1507
		1508	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1509	threads that did not get a request to process within 10 seconds). That
		1510	means if a thread becomes idle while C<$nthreads> other threads are also
		1511	idle, it will free its resources and exit.
		1512
		1513	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1514	to allow for extremely high load situations, but want to free resources
		1515	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1516
		1517	The default is probably ok in most situations, especially if thread
		1518	creation is fast. If thread creation is very slow on your system you might
		1519	want to use larger values.
		1520
268	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1521	=item IO::AIO::max_outstanding $maxreqs
		1522
		1523	This is a very bad function to use in interactive programs because it
		1524	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1525	use an C<aio_group> together with a feed callback.
269		1526
270	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1527	Sets the maximum number of outstanding requests to C<$nreqs>. If you
271	try to queue up more than this number of requests, the caller will block until	1528	do queue up more than this number of requests, the next call to the
272	some requests have been handled.	1529	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1530	function will block until the limit is no longer exceeded.
273		1531
274	The default is very large, so normally there is no practical limit. If you	1532	The default value is very large, so there is no practical limit on the
275	queue up many requests in a loop it it often improves speed if you set	1533	number of outstanding requests.
276	this to a relatively low number, such as C<100>.
277		1534
278	Under normal circumstances you don't need to call this function.	1535	You can still queue as many requests as you want. Therefore,
		1536	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1537	as a stop gap to shield against fatal memory overflow (with large values).
279		1538
280	=back	1539	=back
281		1540
		1541	=head3 STATISTICAL INFORMATION
		1542
		1543	=over
		1544
		1545	=item IO::AIO::nreqs
		1546
		1547	Returns the number of requests currently in the ready, execute or pending
		1548	states (i.e. for which their callback has not been invoked yet).
		1549
		1550	Example: wait till there are no outstanding requests anymore:
		1551
		1552	IO::AIO::poll_wait, IO::AIO::poll_cb
		1553	while IO::AIO::nreqs;
		1554
		1555	=item IO::AIO::nready
		1556
		1557	Returns the number of requests currently in the ready state (not yet
		1558	executed).
		1559
		1560	=item IO::AIO::npending
		1561
		1562	Returns the number of requests currently in the pending state (executed,
		1563	but not yet processed by poll_cb).
		1564
		1565	=back
		1566
		1567	=head3 MISCELLANEOUS FUNCTIONS
		1568
		1569	IO::AIO implements some functions that might be useful, but are not
		1570	asynchronous.
		1571
		1572	=over 4
		1573
		1574	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1575
		1576	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1577	but is blocking (this makes most sense if you know the input data is
		1578	likely cached already and the output filehandle is set to non-blocking
		1579	operations).
		1580
		1581	Returns the number of bytes copied, or C<-1> on error.
		1582
		1583	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1584
		1585	Simply calls the C<posix_fadvise> function (see it's
		1586	manpage for details). The following advice constants are
		1587	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1588	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1589	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1590
		1591	On systems that do not implement C<posix_fadvise>, this function returns
		1592	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1593
		1594	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1595
		1596	Memory-maps a file (or anonymous memory range) and attaches it to the
		1597	given C<$scalar>, which will act like a string scalar.
		1598
		1599	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1600	change the string length, and most read-only operations such as copying it
		1601	or searching it with regexes and so on.
		1602
		1603	Anything else is unsafe and will, at best, result in memory leaks.
		1604
		1605	The memory map associated with the C<$scalar> is automatically removed
		1606	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1607	C<IO::AIO::munmap> functions are called.
		1608
		1609	This calls the C<mmap>(2) function internally. See your system's manual
		1610	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1611
		1612	The C<$length> must be larger than zero and smaller than the actual
		1613	filesize.
		1614
		1615	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1616	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1617
		1618	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1619	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1620	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1621	(which is set to C<MAP_ANON> if your system only provides this
		1622	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1623	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1624	C<IO::AIO::MAP_NONBLOCK>
		1625
		1626	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1627
		1628	C<$offset> is the offset from the start of the file - it generally must be
		1629	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1630
		1631	Example:
		1632
		1633	use Digest::MD5;
		1634	use IO::AIO;
		1635
		1636	open my $fh, "<verybigfile"
		1637	or die "$!";
		1638
		1639	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1640	or die "verybigfile: $!";
		1641
		1642	my $fast_md5 = md5 $data;
		1643
		1644	=item IO::AIO::munmap $scalar
		1645
		1646	Removes a previous mmap and undefines the C<$scalar>.
		1647
		1648	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1649
		1650	Calls the C<munlock> function, undoing the effects of a previous
		1651	C<aio_mlock> call (see its description for details).
		1652
		1653	=item IO::AIO::munlockall
		1654
		1655	Calls the C<munlockall> function.
		1656
		1657	On systems that do not implement C<munlockall>, this function returns
		1658	ENOSYS, otherwise the return value of C<munlockall>.
		1659
		1660	=back
		1661
282	=cut	1662	=cut
283		1663
284	# support function to convert a fd into a perl filehandle
285	sub _fd2fh {
286	return undef if $_[0] < 0;
287
288	# try to be perl5.6-compatible
289	local *AIO_FH;
290	open AIO_FH, "+<&=$_[0]"
291	or return undef;
292
293	*AIO_FH
294	}
295
296	min_parallel 4;	1664	min_parallel 8;
297		1665
298	END {	1666	END { flush }
299	max_parallel 0;
300	}
301		1667
302	1;	1668	1;
303		1669
		1670	=head1 EVENT LOOP INTEGRATION
		1671
		1672	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1673	automatically into many event loops:
		1674
		1675	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1676	use AnyEvent::AIO;
		1677
		1678	You can also integrate IO::AIO manually into many event loops, here are
		1679	some examples of how to do this:
		1680
		1681	# EV integration
		1682	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1683
		1684	# Event integration
		1685	Event->io (fd => IO::AIO::poll_fileno,
		1686	poll => 'r',
		1687	cb => \&IO::AIO::poll_cb);
		1688
		1689	# Glib/Gtk2 integration
		1690	add_watch Glib::IO IO::AIO::poll_fileno,
		1691	in => sub { IO::AIO::poll_cb; 1 };
		1692
		1693	# Tk integration
		1694	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1695	readable => \&IO::AIO::poll_cb);
		1696
		1697	# Danga::Socket integration
		1698	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1699	\&IO::AIO::poll_cb);
		1700
		1701	=head2 FORK BEHAVIOUR
		1702
		1703	This module should do "the right thing" when the process using it forks:
		1704
		1705	Before the fork, IO::AIO enters a quiescent state where no requests
		1706	can be added in other threads and no results will be processed. After
		1707	the fork the parent simply leaves the quiescent state and continues
		1708	request/result processing, while the child frees the request/result queue
		1709	(so that the requests started before the fork will only be handled in the
		1710	parent). Threads will be started on demand until the limit set in the
		1711	parent process has been reached again.
		1712
		1713	In short: the parent will, after a short pause, continue as if fork had
		1714	not been called, while the child will act as if IO::AIO has not been used
		1715	yet.
		1716
		1717	=head2 MEMORY USAGE
		1718
		1719	Per-request usage:
		1720
		1721	Each aio request uses - depending on your architecture - around 100-200
		1722	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1723	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1724	scalars and other data passed into aio requests will also be locked and
		1725	will consume memory till the request has entered the done state.
		1726
		1727	This is not awfully much, so queuing lots of requests is not usually a
		1728	problem.
		1729
		1730	Per-thread usage:
		1731
		1732	In the execution phase, some aio requests require more memory for
		1733	temporary buffers, and each thread requires a stack and other data
		1734	structures (usually around 16k-128k, depending on the OS).
		1735
		1736	=head1 KNOWN BUGS
		1737
		1738	Known bugs will be fixed in the next release.
		1739
304	=head1 SEE ALSO	1740	=head1 SEE ALSO
305		1741
306	L<Coro>, L<Linux::AIO>.	1742	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1743	more natural syntax.
307		1744
308	=head1 AUTHOR	1745	=head1 AUTHOR
309		1746
310	Marc Lehmann <schmorp@schmorp.de>	1747	Marc Lehmann <schmorp@schmorp.de>
311	http://home.schmorp.de/	1748	http://home.schmorp.de/

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