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Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC vs.
Revision 1.284 by root, Fri Mar 23 01:14:08 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
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 = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	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>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
62	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
63	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
64	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for example	47	While most of this works on all types of file descriptors (for
68	sockets), using these functions on file descriptors that support	48	example sockets), using these functions on file descriptors that
69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or	49	support nonblocking operation (again, sockets, pipes etc.) is
70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop	50	very inefficient. Use an event loop for that (such as the L<EV>
71	for that (such as the L<Event|Event> module): IO::AIO will naturally fit	51	module): IO::AIO will naturally fit into such an event loop itself.
72	into such an event loop itself.
73		52
74	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
75	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
76	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
77	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
79	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
80	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
81	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
82	using threads anyway.	61	using threads anyway.
83		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
84	Although the module will work with in the presence of other (Perl-)	67	Although the module will work in the presence of other (Perl-) threads,
85	threads, it is currently not reentrant in any way, so use appropriate	68	it is currently not reentrant in any way, so use appropriate locking
86	locking yourself, always call C<poll_cb> from within the same thread, or	69	yourself, always call C<poll_cb> from within the same thread, or never
87	never call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
88		71
89	=head2 EXAMPLE	72	=head2 EXAMPLE
90		73
91	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
92	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
93		76
94	use Fcntl;
95	use Event;	77	use EV;
96	use IO::AIO;	78	use IO::AIO;
97		79
98	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
99	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
100	poll => 'r',
101	cb => \&IO::AIO::poll_cb);
102		82
103	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
104	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
105	my $fh = shift	85	my $fh = shift
106	or die "error while opening: $!";	86	or die "error while opening: $!";
107		87
108	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
109	my $size = -s $fh;	89	my $size = -s $fh;
…		…
118		98
119	# file contents now in $contents	99	# file contents now in $contents
120	print $contents;	100	print $contents;
121		101
122	# exit event loop and program	102	# exit event loop and program
123	Event::unloop;	103	EV::break;
124	};	104	};
125	};	105	};
126		106
127	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
128	# check for sockets etc. etc.	108	# check for sockets etc. etc.
129		109
130	# process events as long as there are some:	110	# process events as long as there are some:
131	Event::loop;	111	EV::run;
132		112
133	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
134		114
135	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
136	directly visible to Perl.	116	directly visible to Perl.
…		…
184		164
185	=cut	165	=cut
186		166
187	package IO::AIO;	167	package IO::AIO;
188		168
189	no warnings;	169	use Carp ();
190	use strict 'vars';	170
		171	use common::sense;
191		172
192	use base 'Exporter';	173	use base 'Exporter';
193		174
194	BEGIN {	175	BEGIN {
195	our $VERSION = '2.21';	176	our $VERSION = 4.4;
196		177
197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
200	aio_move aio_copy aio_group aio_nop aio_mknod);	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
		184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
		190
201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
203	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
204	nreqs nready npending nthreads	194	nreqs nready npending nthreads
205	max_poll_time max_poll_reqs);	195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap munlock munlockall);
		198
		199	push @AIO_REQ, qw(aio_busy); # not exported
206		200
207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
208		202
209	require XSLoader;	203	require XSLoader;
210	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
211	}	205	}
212		206
213	=head1 FUNCTIONS	207	=head1 FUNCTIONS
214		208
215	=head2 AIO REQUEST FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		285
		286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::madvise $scalar, $offset, $length, $advice
		291	IO::AIO::mprotect $scalar, $offset, $length, $protect
		292	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		293	IO::AIO::munlockall
		294
		295	=head2 API NOTES
216		296
217	All the C<aio_*> calls are more or less thin wrappers around the syscall	297	All the C<aio_*> calls are more or less thin wrappers around the syscall
218	with the same name (sans C<aio_>). The arguments are similar or identical,	298	with the same name (sans C<aio_>). The arguments are similar or identical,
219	and they all accept an additional (and optional) C<$callback> argument	299	and they all accept an additional (and optional) C<$callback> argument
220	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
222	perl, which usually delivers "false") as it's sole argument when the given	302	of the request will be passed as arguments to the callback (and, if an
223	syscall has been executed asynchronously.	303	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		304	most syscalls return C<-1> on error, unlike perl, which usually delivers
		305	"false").
		306
		307	Some requests (such as C<aio_readdir>) pass the actual results and
		308	communicate failures by passing C<undef>.
224		309
225	All functions expecting a filehandle keep a copy of the filehandle	310	All functions expecting a filehandle keep a copy of the filehandle
226	internally until the request has finished.	311	internally until the request has finished.
227		312
228	All functions return request objects of type L<IO::AIO::REQ> that allow	313	All functions return request objects of type L<IO::AIO::REQ> that allow
229	further manipulation of those requests while they are in-flight.	314	further manipulation of those requests while they are in-flight.
230		315
231	The pathnames you pass to these routines I<must> be absolute and	316	The pathnames you pass to these routines I<should> be absolute. The
232	encoded as octets. The reason for the former is that at the time the	317	reason for this is that at the time the request is being executed, the
233	request is being executed, the current working directory could have	318	current working directory could have changed. Alternatively, you can
234	changed. Alternatively, you can make sure that you never change the	319	make sure that you never change the current working directory anywhere
235	current working directory anywhere in the program and then use relative	320	in the program and then use relative paths. You can also take advantage
236	paths.	321	of IO::AIOs working directory abstraction, that lets you specify paths
		322	relative to some previously-opened "working directory object" - see the
		323	description of the C<IO::AIO::WD> class later in this document.
237		324
238	To encode pathnames as octets, either make sure you either: a) always pass	325	To encode pathnames as octets, either make sure you either: a) always pass
239	in filenames you got from outside (command line, readdir etc.) without	326	in filenames you got from outside (command line, readdir etc.) without
240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	327	tinkering, b) are in your native filesystem encoding, c) use the Encode
241	your pathnames to the locale (or other) encoding in effect in the user	328	module and encode your pathnames to the locale (or other) encoding in
242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	329	effect in the user environment, d) use Glib::filename_from_unicode on
243	use something else to ensure your scalar has the correct contents.	330	unicode filenames or e) use something else to ensure your scalar has the
		331	correct contents.
244		332
245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	333	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246	handles correctly wether it is set or not.	334	handles correctly whether it is set or not.
		335
		336	=head2 AIO REQUEST FUNCTIONS
247		337
248	=over 4	338	=over 4
249		339
250	=item $prev_pri = aioreq_pri [$pri]	340	=item $prev_pri = aioreq_pri [$pri]
251		341
…		…
271	aio_read $_[0], ..., sub {	361	aio_read $_[0], ..., sub {
272	...	362	...
273	};	363	};
274	};	364	};
275		365
		366
276	=item aioreq_nice $pri_adjust	367	=item aioreq_nice $pri_adjust
277		368
278	Similar to C<aioreq_pri>, but subtracts the given value from the current	369	Similar to C<aioreq_pri>, but subtracts the given value from the current
279	priority, so the effect is cumulative.	370	priority, so the effect is cumulative.
280		371
		372
281	=item aio_open $pathname, $flags, $mode, $callback->($fh)	373	=item aio_open $pathname, $flags, $mode, $callback->($fh)
282		374
283	Asynchronously open or create a file and call the callback with a newly	375	Asynchronously open or create a file and call the callback with a newly
284	created filehandle for the file.	376	created filehandle for the file (or C<undef> in case of an error).
285		377
286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	378	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
287	for an explanation.	379	for an explanation.
288		380
289	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	381	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
290	list. They are the same as used by C<sysopen>.	382	list. They are the same as used by C<sysopen>.
291		383
292	Likewise, C<$mode> specifies the mode of the newly created file, if it	384	Likewise, C<$mode> specifies the mode of the newly created file, if it
293	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	385	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
294	except that it is mandatory (i.e. use C<0> if you don't create new files,	386	except that it is mandatory (i.e. use C<0> if you don't create new files,
295	and C<0666> or C<0777> if you do).	387	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		388	by the umask in effect then the request is being executed, so better never
		389	change the umask.
296		390
297	Example:	391	Example:
298		392
299	aio_open "/etc/passwd", O_RDONLY, 0, sub {	393	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
300	if ($_[0]) {	394	if ($_[0]) {
301	print "open successful, fh is $_[0]\n";	395	print "open successful, fh is $_[0]\n";
302	...	396	...
303	} else {	397	} else {
304	die "open failed: $!\n";	398	die "open failed: $!\n";
305	}	399	}
306	};	400	};
307		401
		402	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		403	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		404	following POSIX and non-POSIX constants are available (missing ones on
		405	your system are, as usual, C<0>):
		406
		407	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		408	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		409	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		410
		411
308	=item aio_close $fh, $callback->($status)	412	=item aio_close $fh, $callback->($status)
309		413
310	Asynchronously close a file and call the callback with the result	414	Asynchronously close a file and call the callback with the result
311	code. I<WARNING:> although accepted, you should not pass in a perl	415	code.
312	filehandle here, as perl will likely close the file descriptor another
313	time when the filehandle is destroyed. Normally, you can safely call perls
314	C<close> or just let filehandles go out of scope.
315		416
316	This is supposed to be a bug in the API, so that might change. It's	417	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
317	therefore best to avoid this function.	418	closing the file descriptor associated with the filehandle itself.
		419
		420	Therefore, C<aio_close> will not close the filehandle - instead it will
		421	use dup2 to overwrite the file descriptor with the write-end of a pipe
		422	(the pipe fd will be created on demand and will be cached).
		423
		424	Or in other words: the file descriptor will be closed, but it will not be
		425	free for reuse until the perl filehandle is closed.
		426
		427	=cut
		428
		429	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		430
		431	Seeks the filehandle to the new C<$offset>, similarly to perl's
		432	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		433	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		434	C<IO::AIO::SEEK_END>).
		435
		436	The resulting absolute offset will be passed to the callback, or C<-1> in
		437	case of an error.
		438
		439	In theory, the C<$whence> constants could be different than the
		440	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		441	so don't panic.
		442
		443	As a GNU/Linux (and maybe Solaris) extension, also the constants
		444	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		445	could be found. No guarantees about suitability for use in C<aio_seek> or
		446	Perl's C<sysseek> can be made though, although I would naively assume they
		447	"just work".
318		448
319	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
320		450
321	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	451	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322		452
323	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	453	Reads or writes C<$length> bytes from or to the specified C<$fh> and
324	into the scalar given by C<data> and offset C<dataoffset> and calls the	454	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
325	callback without the actual number of bytes read (or -1 on error, just	455	calls the callback with the actual number of bytes transferred (or -1 on
326	like the syscall).	456	error, just like the syscall).
		457
		458	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		459	offset plus the actual number of bytes read.
		460
		461	If C<$offset> is undefined, then the current file descriptor offset will
		462	be used (and updated), otherwise the file descriptor offset will not be
		463	changed by these calls.
		464
		465	If C<$length> is undefined in C<aio_write>, use the remaining length of
		466	C<$data>.
		467
		468	If C<$dataoffset> is less than zero, it will be counted from the end of
		469	C<$data>.
327		470
328	The C<$data> scalar I<MUST NOT> be modified in any way while the request	471	The C<$data> scalar I<MUST NOT> be modified in any way while the request
329	is outstanding. Modifying it can result in segfaults or WW3 (if the	472	is outstanding. Modifying it can result in segfaults or World War III (if
330	necessary/optional hardware is installed).	473	the necessary/optional hardware is installed).
331		474
332	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	475	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
333	offset C<0> within the scalar:	476	offset C<0> within the scalar:
334		477
335	aio_read $fh, 7, 15, $buffer, 0, sub {	478	aio_read $fh, 7, 15, $buffer, 0, sub {
336	$_[0] > 0 or die "read error: $!";	479	$_[0] > 0 or die "read error: $!";
337	print "read $_[0] bytes: <$buffer>\n";	480	print "read $_[0] bytes: <$buffer>\n";
338	};	481	};
339		482
		483
340	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	484	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
341		485
342	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	486	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
343	reading at byte offset C<$in_offset>, and starts writing at the current	487	reading at byte offset C<$in_offset>, and starts writing at the current
344	file offset of C<$out_fh>. Because of that, it is not safe to issue more	488	file offset of C<$out_fh>. Because of that, it is not safe to issue more
345	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	489	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
346	other.	490	other. The same C<$in_fh> works fine though, as this function does not
		491	move or use the file offset of C<$in_fh>.
347		492
		493	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		494	are written, and there is no way to find out how many more bytes have been
		495	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		496	number of bytes written to C<$out_fh>. Only if the result value equals
		497	C<$length> one can assume that C<$length> bytes have been read.
		498
		499	Unlike with other C<aio_> functions, it makes a lot of sense to use
		500	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		501	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		502	the socket I/O will be non-blocking. Note, however, that you can run
		503	into a trap where C<aio_sendfile> reads some data with readahead, then
		504	fails to write all data, and when the socket is ready the next time, the
		505	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		506	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		507	resource usage.
		508
348	This call tries to make use of a native C<sendfile> syscall to provide	509	This call tries to make use of a native C<sendfile>-like syscall to
349	zero-copy operation. For this to work, C<$out_fh> should refer to a	510	provide zero-copy operation. For this to work, C<$out_fh> should refer to
350	socket, and C<$in_fh> should refer to mmap'able file.	511	a socket, and C<$in_fh> should refer to an mmap'able file.
351		512
352	If the native sendfile call fails or is not implemented, it will be	513	If a native sendfile cannot be found or it fails with C<ENOSYS>,
353	emulated, so you can call C<aio_sendfile> on any type of filehandle	514	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		515	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
354	regardless of the limitations of the operating system.	516	type of filehandle regardless of the limitations of the operating system.
355		517
356	Please note, however, that C<aio_sendfile> can read more bytes from	518	As native sendfile syscalls (as practically any non-POSIX interface hacked
357	C<$in_fh> than are written, and there is no way to find out how many	519	together in a hurry to improve benchmark numbers) tend to be rather buggy
358	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	520	on many systems, this implementation tries to work around some known bugs
359	provides the number of bytes written to C<$out_fh>. Only if the result	521	in Linux and FreeBSD kernels (probably others, too), but that might fail,
360	value equals C<$length> one can assume that C<$length> bytes have been	522	so you really really should check the return value of C<aio_sendfile> -
361	read.	523	fewer bytes than expected might have been transferred.
		524
362		525
363	=item aio_readahead $fh,$offset,$length, $callback->($retval)	526	=item aio_readahead $fh,$offset,$length, $callback->($retval)
364		527
365	C<aio_readahead> populates the page cache with data from a file so that	528	C<aio_readahead> populates the page cache with data from a file so that
366	subsequent reads from that file will not block on disk I/O. The C<$offset>	529	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
369	whole pages, so that offset is effectively rounded down to a page boundary	532	whole pages, so that offset is effectively rounded down to a page boundary
370	and bytes are read up to the next page boundary greater than or equal to	533	and bytes are read up to the next page boundary greater than or equal to
371	(off-set+length). C<aio_readahead> does not read beyond the end of the	534	(off-set+length). C<aio_readahead> does not read beyond the end of the
372	file. The current file offset of the file is left unchanged.	535	file. The current file offset of the file is left unchanged.
373		536
374	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	537	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
375	emulated by simply reading the data, which would have a similar effect.	538	be emulated by simply reading the data, which would have a similar effect.
		539
376		540
377	=item aio_stat $fh_or_path, $callback->($status)	541	=item aio_stat $fh_or_path, $callback->($status)
378		542
379	=item aio_lstat $fh, $callback->($status)	543	=item aio_lstat $fh, $callback->($status)
380		544
…		…
386	for an explanation.	550	for an explanation.
387		551
388	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	552	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
389	error when stat'ing a large file, the results will be silently truncated	553	error when stat'ing a large file, the results will be silently truncated
390	unless perl itself is compiled with large file support.	554	unless perl itself is compiled with large file support.
		555
		556	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		557	following constants and functions (if not implemented, the constants will
		558	be C<0> and the functions will either C<croak> or fall back on traditional
		559	behaviour).
		560
		561	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		562	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		563	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
391		564
392	Example: Print the length of F</etc/passwd>:	565	Example: Print the length of F</etc/passwd>:
393		566
394	aio_stat "/etc/passwd", sub {	567	aio_stat "/etc/passwd", sub {
395	$_[0] and die "stat failed: $!";	568	$_[0] and die "stat failed: $!";
396	print "size is ", -s _, "\n";	569	print "size is ", -s _, "\n";
397	};	570	};
398		571
		572
		573	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		574
		575	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		576	whether a file handle or path was passed.
		577
		578	On success, the callback is passed a hash reference with the following
		579	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		580	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		581	is passed.
		582
		583	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		584	C<ST_NOSUID>.
		585
		586	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		587	their correct value when available, or to C<0> on systems that do
		588	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		589	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		590	C<ST_NODIRATIME> and C<ST_RELATIME>.
		591
		592	Example: stat C</wd> and dump out the data if successful.
		593
		594	aio_statvfs "/wd", sub {
		595	my $f = $_[0]
		596	or die "statvfs: $!";
		597
		598	use Data::Dumper;
		599	say Dumper $f;
		600	};
		601
		602	# result:
		603	{
		604	bsize => 1024,
		605	bfree => 4333064312,
		606	blocks => 10253828096,
		607	files => 2050765568,
		608	flag => 4096,
		609	favail => 2042092649,
		610	bavail => 4333064312,
		611	ffree => 2042092649,
		612	namemax => 255,
		613	frsize => 1024,
		614	fsid => 1810
		615	}
		616
		617	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		618
		619	Works like perl's C<utime> function (including the special case of $atime
		620	and $mtime being undef). Fractional times are supported if the underlying
		621	syscalls support them.
		622
		623	When called with a pathname, uses utimes(2) if available, otherwise
		624	utime(2). If called on a file descriptor, uses futimes(2) if available,
		625	otherwise returns ENOSYS, so this is not portable.
		626
		627	Examples:
		628
		629	# set atime and mtime to current time (basically touch(1)):
		630	aio_utime "path", undef, undef;
		631	# set atime to current time and mtime to beginning of the epoch:
		632	aio_utime "path", time, undef; # undef==0
		633
		634
		635	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		636
		637	Works like perl's C<chown> function, except that C<undef> for either $uid
		638	or $gid is being interpreted as "do not change" (but -1 can also be used).
		639
		640	Examples:
		641
		642	# same as "chown root path" in the shell:
		643	aio_chown "path", 0, -1;
		644	# same as above:
		645	aio_chown "path", 0, undef;
		646
		647
		648	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		649
		650	Works like truncate(2) or ftruncate(2).
		651
		652
		653	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654
		655	Allocates or frees disk space according to the C<$mode> argument. See the
		656	linux C<fallocate> documentation for details.
		657
		658	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		659	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		660	to deallocate a file range.
		661
		662	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		663	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		664	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		665	to unshare shared blocks (see your L<fallocate(2)> manpage).
		666
		667	The file system block size used by C<fallocate> is presumably the
		668	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		669	can dictate other limitations.
		670
		671	If C<fallocate> isn't available or cannot be emulated (currently no
		672	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		673
		674
		675	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		676
		677	Works like perl's C<chmod> function.
		678
		679
399	=item aio_unlink $pathname, $callback->($status)	680	=item aio_unlink $pathname, $callback->($status)
400		681
401	Asynchronously unlink (delete) a file and call the callback with the	682	Asynchronously unlink (delete) a file and call the callback with the
402	result code.	683	result code.
403		684
		685
404	=item aio_mknod $path, $mode, $dev, $callback->($status)	686	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
405		687
406	[EXPERIMENTAL]	688	[EXPERIMENTAL]
407		689
408	Asynchronously create a device node (or fifo). See mknod(2).	690	Asynchronously create a device node (or fifo). See mknod(2).
409		691
410	The only (POSIX-) portable way of calling this function is:	692	The only (POSIX-) portable way of calling this function is:
411		693
412	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	694	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		695
		696	See C<aio_stat> for info about some potentially helpful extra constants
		697	and functions.
413		698
414	=item aio_link $srcpath, $dstpath, $callback->($status)	699	=item aio_link $srcpath, $dstpath, $callback->($status)
415		700
416	Asynchronously create a new link to the existing object at C<$srcpath> at	701	Asynchronously create a new link to the existing object at C<$srcpath> at
417	the path C<$dstpath> and call the callback with the result code.	702	the path C<$dstpath> and call the callback with the result code.
418		703
		704
419	=item aio_symlink $srcpath, $dstpath, $callback->($status)	705	=item aio_symlink $srcpath, $dstpath, $callback->($status)
420		706
421	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	707	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
422	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
423		709
		710
424	=item aio_readlink $path, $callback->($link)	711	=item aio_readlink $pathname, $callback->($link)
425		712
426	Asynchronously read the symlink specified by C<$path> and pass it to	713	Asynchronously read the symlink specified by C<$path> and pass it to
427	the callback. If an error occurs, nothing or undef gets passed to the	714	the callback. If an error occurs, nothing or undef gets passed to the
428	callback.	715	callback.
429		716
		717
		718	=item aio_realpath $pathname, $callback->($path)
		719
		720	Asynchronously make the path absolute and resolve any symlinks in
		721	C<$path>. The resulting path only consists of directories (same as
		722	L<Cwd::realpath>).
		723
		724	This request can be used to get the absolute path of the current working
		725	directory by passing it a path of F<.> (a single dot).
		726
		727
430	=item aio_rename $srcpath, $dstpath, $callback->($status)	728	=item aio_rename $srcpath, $dstpath, $callback->($status)
431		729
432	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	730	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
433	rename(2) and call the callback with the result code.	731	rename(2) and call the callback with the result code.
434		732
		733	On systems that support the AIO::WD working directory abstraction
		734	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		735	of failing, C<rename> is called on the absolute path of C<$wd>.
		736
		737
		738	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		739
		740	Basically a version of C<aio_rename> with an additional C<$flags>
		741	argument. Calling this with C<$flags=0> is the same as calling
		742	C<aio_rename>.
		743
		744	Non-zero flags are currently only supported on GNU/Linux systems that
		745	support renameat2. Other systems fail with C<ENOSYS> in this case.
		746
		747	The following constants are available (missing ones are, as usual C<0>),
		748	see renameat2(2) for details:
		749
		750	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		751	and C<IO::AIO::RENAME_WHITEOUT>.
		752
		753
		754	=item aio_mkdir $pathname, $mode, $callback->($status)
		755
		756	Asynchronously mkdir (create) a directory and call the callback with
		757	the result code. C<$mode> will be modified by the umask at the time the
		758	request is executed, so do not change your umask.
		759
		760
435	=item aio_rmdir $pathname, $callback->($status)	761	=item aio_rmdir $pathname, $callback->($status)
436		762
437	Asynchronously rmdir (delete) a directory and call the callback with the	763	Asynchronously rmdir (delete) a directory and call the callback with the
438	result code.	764	result code.
		765
		766	On systems that support the AIO::WD working directory abstraction
		767	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		768	C<rmdir> is called on the absolute path of C<$wd>.
		769
439		770
440	=item aio_readdir $pathname, $callback->($entries)	771	=item aio_readdir $pathname, $callback->($entries)
441		772
442	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	773	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
443	directory (i.e. opendir + readdir + closedir). The entries will not be	774	directory (i.e. opendir + readdir + closedir). The entries will not be
444	sorted, and will B<NOT> include the C<.> and C<..> entries.	775	sorted, and will B<NOT> include the C<.> and C<..> entries.
445		776
446	The callback a single argument which is either C<undef> or an array-ref	777	The callback is passed a single argument which is either C<undef> or an
447	with the filenames.	778	array-ref with the filenames.
		779
		780
		781	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		782
		783	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		784	tune behaviour and output format. In case of an error, C<$entries> will be
		785	C<undef>.
		786
		787	The flags are a combination of the following constants, ORed together (the
		788	flags will also be passed to the callback, possibly modified):
		789
		790	=over 4
		791
		792	=item IO::AIO::READDIR_DENTS
		793
		794	Normally the callback gets an arrayref consisting of names only (as
		795	with C<aio_readdir>). If this flag is set, then the callback gets an
		796	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
		797	single directory entry in more detail:
		798
		799	C<$name> is the name of the entry.
		800
		801	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		802
		803	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		804	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		805	C<IO::AIO::DT_WHT>.
		806
		807	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		808	to know, you have to run stat yourself. Also, for speed/memory reasons,
		809	the C<$type> scalars are read-only: you must not modify them.
		810
		811	C<$inode> is the inode number (which might not be exact on systems with 64
		812	bit inode numbers and 32 bit perls). This field has unspecified content on
		813	systems that do not deliver the inode information.
		814
		815	=item IO::AIO::READDIR_DIRS_FIRST
		816
		817	When this flag is set, then the names will be returned in an order where
		818	likely directories come first, in optimal stat order. This is useful when
		819	you need to quickly find directories, or you want to find all directories
		820	while avoiding to stat() each entry.
		821
		822	If the system returns type information in readdir, then this is used
		823	to find directories directly. Otherwise, likely directories are names
		824	beginning with ".", or otherwise names with no dots, of which names with
		825	short names are tried first.
		826
		827	=item IO::AIO::READDIR_STAT_ORDER
		828
		829	When this flag is set, then the names will be returned in an order
		830	suitable for stat()'ing each one. That is, when you plan to stat() most or
		831	all files in the given directory, then the returned order will likely be
		832	faster.
		833
		834	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
		835	then the likely dirs come first, resulting in a less optimal stat order
		836	for stat'ing all entries, but likely a more optimal order for finding
		837	subdirectories.
		838
		839	=item IO::AIO::READDIR_FOUND_UNKNOWN
		840
		841	This flag should not be set when calling C<aio_readdirx>. Instead, it
		842	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		843	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		844	C<$type>'s are known, which can be used to speed up some algorithms.
		845
		846	=back
		847
		848
		849	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		850
		851	Opens, reads and closes the given file. The data is put into C<$data>,
		852	which is resized as required.
		853
		854	If C<$offset> is negative, then it is counted from the end of the file.
		855
		856	If C<$length> is zero, then the remaining length of the file is
		857	used. Also, in this case, the same limitations to modifying C<$data> apply
		858	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		859	with C<substr>. If the size of the file is known, specifying a non-zero
		860	C<$length> results in a performance advantage.
		861
		862	This request is similar to the older C<aio_load> request, but since it is
		863	a single request, it might be more efficient to use.
		864
		865	Example: load F</etc/passwd> into C<$passwd>.
		866
		867	my $passwd;
		868	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		869	$_[0] >= 0
		870	or die "/etc/passwd: $!\n";
		871
		872	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		873	print $passwd;
		874	};
		875	IO::AIO::flush;
		876
		877
		878	=item aio_load $pathname, $data, $callback->($status)
		879
		880	This is a composite request that tries to fully load the given file into
		881	memory. Status is the same as with aio_read.
		882
		883	Using C<aio_slurp> might be more efficient, as it is a single request.
		884
		885	=cut
		886
		887	sub aio_load($$;$) {
		888	my ($path, undef, $cb) = @_;
		889	my $data = \$_[1];
		890
		891	my $pri = aioreq_pri;
		892	my $grp = aio_group $cb;
		893
		894	aioreq_pri $pri;
		895	add $grp aio_open $path, O_RDONLY, 0, sub {
		896	my $fh = shift
		897	or return $grp->result (-1);
		898
		899	aioreq_pri $pri;
		900	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		901	$grp->result ($_[0]);
		902	};
		903	};
		904
		905	$grp
		906	}
448		907
449	=item aio_copy $srcpath, $dstpath, $callback->($status)	908	=item aio_copy $srcpath, $dstpath, $callback->($status)
450		909
451	Try to copy the I<file> (directories not supported as either source or	910	Try to copy the I<file> (directories not supported as either source or
452	destination) from C<$srcpath> to C<$dstpath> and call the callback with	911	destination) from C<$srcpath> to C<$dstpath> and call the callback with
453	the C<0> (error) or C<-1> ok.	912	a status of C<0> (ok) or C<-1> (error, see C<$!>).
454		913
		914	Existing destination files will be truncated.
		915
455	This is a composite request that it creates the destination file with	916	This is a composite request that creates the destination file with
456	mode 0200 and copies the contents of the source file into it using	917	mode 0200 and copies the contents of the source file into it using
457	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	918	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
458	uid/gid, in that order.	919	uid/gid, in that order.
459		920
460	If an error occurs, the partial destination file will be unlinked, if	921	If an error occurs, the partial destination file will be unlinked, if
…		…
462	errors are being ignored.	923	errors are being ignored.
463		924
464	=cut	925	=cut
465		926
466	sub aio_copy($$;$) {	927	sub aio_copy($$;$) {
467	aio_block {
468	my ($src, $dst, $cb) = @_;	928	my ($src, $dst, $cb) = @_;
469		929
470	my $pri = aioreq_pri;	930	my $pri = aioreq_pri;
471	my $grp = aio_group $cb;	931	my $grp = aio_group $cb;
472		932
473	aioreq_pri $pri;	933	aioreq_pri $pri;
474	add $grp aio_open $src, O_RDONLY, 0, sub {	934	add $grp aio_open $src, O_RDONLY, 0, sub {
475	if (my $src_fh = $_[0]) {	935	if (my $src_fh = $_[0]) {
476	my @stat = stat $src_fh;	936	my @stat = stat $src_fh; # hmm, might block over nfs?
477		937
478	aioreq_pri $pri;	938	aioreq_pri $pri;
479	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	939	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
480	if (my $dst_fh = $_[0]) {	940	if (my $dst_fh = $_[0]) {
481	aioreq_pri $pri;	941	aioreq_pri $pri;
482	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	942	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
483	if ($_[0] == $stat[7]) {	943	if ($_[0] == $stat[7]) {
484	$grp->result (0);	944	$grp->result (0);
485	close $src_fh;	945	close $src_fh;
486		946
487	# those should not normally block. should. should.
488	utime $stat[8], $stat[9], $dst;
489	chmod $stat[2] & 07777, $dst_fh;
490	chown $stat[4], $stat[5], $dst_fh;
491	close $dst_fh;
492	} else {	947	my $ch = sub {
493	$grp->result (-1);
494	close $src_fh;
495	close $dst_fh;
496
497	aioreq $pri;	948	aioreq_pri $pri;
		949	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		950	aioreq_pri $pri;
		951	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		952	aioreq_pri $pri;
498	add $grp aio_unlink $dst;	953	add $grp aio_close $dst_fh;
		954	}
		955	};
499	}	956	};
		957
		958	aioreq_pri $pri;
		959	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		960	if ($_[0] < 0 && $! == ENOSYS) {
		961	aioreq_pri $pri;
		962	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		963	} else {
		964	$ch->();
		965	}
		966	};
		967	} else {
		968	$grp->result (-1);
		969	close $src_fh;
		970	close $dst_fh;
		971
		972	aioreq $pri;
		973	add $grp aio_unlink $dst;
500	};	974	}
501	} else {
502	$grp->result (-1);
503	}	975	};
		976	} else {
		977	$grp->result (-1);
504	},	978	}
505
506	} else {
507	$grp->result (-1);
508	}	979	},
		980
		981	} else {
		982	$grp->result (-1);
509	};	983	}
510
511	$grp
512	}	984	};
		985
		986	$grp
513	}	987	}
514		988
515	=item aio_move $srcpath, $dstpath, $callback->($status)	989	=item aio_move $srcpath, $dstpath, $callback->($status)
516		990
517	Try to move the I<file> (directories not supported as either source or	991	Try to move the I<file> (directories not supported as either source or
518	destination) from C<$srcpath> to C<$dstpath> and call the callback with	992	destination) from C<$srcpath> to C<$dstpath> and call the callback with
519	the C<0> (error) or C<-1> ok.	993	a status of C<0> (ok) or C<-1> (error, see C<$!>).
520		994
521	This is a composite request that tries to rename(2) the file first. If	995	This is a composite request that tries to rename(2) the file first; if
522	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	996	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
523	that is successful, unlinking the C<$srcpath>.	997	that is successful, unlinks the C<$srcpath>.
524		998
525	=cut	999	=cut
526		1000
527	sub aio_move($$;$) {	1001	sub aio_move($$;$) {
528	aio_block {
529	my ($src, $dst, $cb) = @_;	1002	my ($src, $dst, $cb) = @_;
530		1003
531	my $pri = aioreq_pri;	1004	my $pri = aioreq_pri;
532	my $grp = aio_group $cb;	1005	my $grp = aio_group $cb;
533		1006
534	aioreq_pri $pri;	1007	aioreq_pri $pri;
535	add $grp aio_rename $src, $dst, sub {	1008	add $grp aio_rename $src, $dst, sub {
536	if ($_[0] && $! == EXDEV) {	1009	if ($_[0] && $! == EXDEV) {
537	aioreq_pri $pri;	1010	aioreq_pri $pri;
538	add $grp aio_copy $src, $dst, sub {	1011	add $grp aio_copy $src, $dst, sub {
539	$grp->result ($_[0]);
540
541	if (!$_[0]) {
542	aioreq_pri $pri;
543	add $grp aio_unlink $src;
544	}
545	};
546	} else {
547	$grp->result ($_[0]);	1012	$grp->result ($_[0]);
		1013
		1014	unless ($_[0]) {
		1015	aioreq_pri $pri;
		1016	add $grp aio_unlink $src;
		1017	}
548	}	1018	};
		1019	} else {
		1020	$grp->result ($_[0]);
549	};	1021	}
550
551	$grp
552	}	1022	};
		1023
		1024	$grp
553	}	1025	}
554		1026
555	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1027	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
556		1028
557	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1029	Scans a directory (similar to C<aio_readdir>) but additionally tries to
558	efficiently separate the entries of directory C<$path> into two sets of	1030	efficiently separate the entries of directory C<$path> into two sets of
559	names, directories you can recurse into (directories), and ones you cannot	1031	names, directories you can recurse into (directories), and ones you cannot
560	recurse into (everything else, including symlinks to directories).	1032	recurse into (everything else, including symlinks to directories).
561		1033
562	C<aio_scandir> is a composite request that creates of many sub requests_	1034	C<aio_scandir> is a composite request that generates many sub requests.
563	C<$maxreq> specifies the maximum number of outstanding aio requests that	1035	C<$maxreq> specifies the maximum number of outstanding aio requests that
564	this function generates. If it is C<< <= 0 >>, then a suitable default	1036	this function generates. If it is C<< <= 0 >>, then a suitable default
565	will be chosen (currently 4).	1037	will be chosen (currently 4).
566		1038
567	On error, the callback is called without arguments, otherwise it receives	1039	On error, the callback is called without arguments, otherwise it receives
…		…
577		1049
578	Implementation notes.	1050	Implementation notes.
579		1051
580	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1052	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
581		1053
		1054	If readdir returns file type information, then this is used directly to
		1055	find directories.
		1056
582	After reading the directory, the modification time, size etc. of the	1057	Otherwise, after reading the directory, the modification time, size etc.
583	directory before and after the readdir is checked, and if they match (and	1058	of the directory before and after the readdir is checked, and if they
584	isn't the current time), the link count will be used to decide how many	1059	match (and isn't the current time), the link count will be used to decide
585	entries are directories (if >= 2). Otherwise, no knowledge of the number	1060	how many entries are directories (if >= 2). Otherwise, no knowledge of the
586	of subdirectories will be assumed.	1061	number of subdirectories will be assumed.
587		1062
588	Then entries will be sorted into likely directories (everything without	1063	Then entries will be sorted into likely directories a non-initial dot
589	a non-initial dot currently) and likely non-directories (everything	1064	currently) and likely non-directories (see C<aio_readdirx>). Then every
590	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1065	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
591	likely directories first. If that succeeds, it assumes that the entry	1066	in order of their inode numbers. If that succeeds, it assumes that the
592	is a directory or a symlink to directory (which will be checked	1067	entry is a directory or a symlink to directory (which will be checked
593	seperately). This is often faster than stat'ing the entry itself because	1068	separately). This is often faster than stat'ing the entry itself because
594	filesystems might detect the type of the entry without reading the inode	1069	filesystems might detect the type of the entry without reading the inode
595	data (e.g. ext2fs filetype feature).	1070	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1071	the filetype information on readdir.
596		1072
597	If the known number of directories (link count - 2) has been reached, the	1073	If the known number of directories (link count - 2) has been reached, the
598	rest of the entries is assumed to be non-directories.	1074	rest of the entries is assumed to be non-directories.
599		1075
600	This only works with certainty on POSIX (= UNIX) filesystems, which	1076	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
604	as those tend to return 0 or 1 as link counts, which disables the	1080	as those tend to return 0 or 1 as link counts, which disables the
605	directory counting heuristic.	1081	directory counting heuristic.
606		1082
607	=cut	1083	=cut
608		1084
609	sub aio_scandir($$$) {	1085	sub aio_scandir($$;$) {
610	aio_block {
611	my ($path, $maxreq, $cb) = @_;	1086	my ($path, $maxreq, $cb) = @_;
612		1087
613	my $pri = aioreq_pri;	1088	my $pri = aioreq_pri;
614		1089
615	my $grp = aio_group $cb;	1090	my $grp = aio_group $cb;
616		1091
617	$maxreq = 4 if $maxreq <= 0;	1092	$maxreq = 4 if $maxreq <= 0;
		1093
		1094	# get a wd object
		1095	aioreq_pri $pri;
		1096	add $grp aio_wd $path, sub {
		1097	$_[0]
		1098	or return $grp->result ();
		1099
		1100	my $wd = [shift, "."];
618		1101
619	# stat once	1102	# stat once
620	aioreq_pri $pri;	1103	aioreq_pri $pri;
621	add $grp aio_stat $path, sub {	1104	add $grp aio_stat $wd, sub {
622	return $grp->result () if $_[0];	1105	return $grp->result () if $_[0];
623	my $now = time;	1106	my $now = time;
624	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1107	my $hash1 = join ":", (stat _)[0,1,3,7,9];
625		1108
626	# read the directory entries	1109	# read the directory entries
627	aioreq_pri $pri;	1110	aioreq_pri $pri;
628	add $grp aio_readdir $path, sub {	1111	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
629	my $entries = shift	1112	my $entries = shift
630	or return $grp->result ();	1113	or return $grp->result ();
631		1114
632	# stat the dir another time	1115	# stat the dir another time
633	aioreq_pri $pri;	1116	aioreq_pri $pri;
634	add $grp aio_stat $path, sub {	1117	add $grp aio_stat $wd, sub {
635	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1118	my $hash2 = join ":", (stat _)[0,1,3,7,9];
636		1119
637	my $ndirs;	1120	my $ndirs;
638		1121
639	# take the slow route if anything looks fishy	1122	# take the slow route if anything looks fishy
640	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1123	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
641	$ndirs = -1;	1124	$ndirs = -1;
642	} else {	1125	} else {
643	# if nlink == 2, we are finished	1126	# if nlink == 2, we are finished
644	# on non-posix-fs's, we rely on nlink < 2	1127	# for non-posix-fs's, we rely on nlink < 2
645	$ndirs = (stat _)[3] - 2	1128	$ndirs = (stat _)[3] - 2
646	or return $grp->result ([], $entries);	1129	or return $grp->result ([], $entries);
647	}	1130	}
648		1131
649	# sort into likely dirs and likely nondirs
650	# dirs == files without ".", short entries first
651	$entries = [map $_->[0],
652	sort { $b->[1] cmp $a->[1] }
653	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
654	@$entries];
655
656	my (@dirs, @nondirs);	1132	my (@dirs, @nondirs);
657		1133
658	my $statgrp = add $grp aio_group sub {	1134	my $statgrp = add $grp aio_group sub {
659	$grp->result (\@dirs, \@nondirs);	1135	$grp->result (\@dirs, \@nondirs);
660	};	1136	};
661		1137
662	limit $statgrp $maxreq;	1138	limit $statgrp $maxreq;
663	feed $statgrp sub {	1139	feed $statgrp sub {
664	return unless @$entries;	1140	return unless @$entries;
665	my $entry = pop @$entries;	1141	my $entry = shift @$entries;
666		1142
667	aioreq_pri $pri;	1143	aioreq_pri $pri;
		1144	$wd->[1] = "$entry/.";
668	add $statgrp aio_stat "$path/$entry/.", sub {	1145	add $statgrp aio_stat $wd, sub {
669	if ($_[0] < 0) {	1146	if ($_[0] < 0) {
670	push @nondirs, $entry;	1147	push @nondirs, $entry;
671	} else {	1148	} else {
672	# need to check for real directory	1149	# need to check for real directory
673	aioreq_pri $pri;	1150	aioreq_pri $pri;
		1151	$wd->[1] = $entry;
674	add $statgrp aio_lstat "$path/$entry", sub {	1152	add $statgrp aio_lstat $wd, sub {
675	if (-d _) {	1153	if (-d _) {
676	push @dirs, $entry;	1154	push @dirs, $entry;
677		1155
678	unless (--$ndirs) {	1156	unless (--$ndirs) {
679	push @nondirs, @$entries;	1157	push @nondirs, @$entries;
…		…
687	};	1165	};
688	};	1166	};
689	};	1167	};
690	};	1168	};
691	};	1169	};
692
693	$grp
694	}	1170	};
		1171
		1172	$grp
695	}	1173	}
		1174
		1175	=item aio_rmtree $pathname, $callback->($status)
		1176
		1177	Delete a directory tree starting (and including) C<$path>, return the
		1178	status of the final C<rmdir> only. This is a composite request that
		1179	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1180	everything else.
		1181
		1182	=cut
		1183
		1184	sub aio_rmtree;
		1185	sub aio_rmtree($;$) {
		1186	my ($path, $cb) = @_;
		1187
		1188	my $pri = aioreq_pri;
		1189	my $grp = aio_group $cb;
		1190
		1191	aioreq_pri $pri;
		1192	add $grp aio_scandir $path, 0, sub {
		1193	my ($dirs, $nondirs) = @_;
		1194
		1195	my $dirgrp = aio_group sub {
		1196	add $grp aio_rmdir $path, sub {
		1197	$grp->result ($_[0]);
		1198	};
		1199	};
		1200
		1201	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1202	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1203
		1204	add $grp $dirgrp;
		1205	};
		1206
		1207	$grp
		1208	}
		1209
		1210	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1211
		1212	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1213
		1214	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1215	they execute asynchronously and pass the return value to the callback.
		1216
		1217	Both calls can be used for a lot of things, some of which make more sense
		1218	to run asynchronously in their own thread, while some others make less
		1219	sense. For example, calls that block waiting for external events, such
		1220	as locking, will also lock down an I/O thread while it is waiting, which
		1221	can deadlock the whole I/O system. At the same time, there might be no
		1222	alternative to using a thread to wait.
		1223
		1224	So in general, you should only use these calls for things that do
		1225	(filesystem) I/O, not for things that wait for other events (network,
		1226	other processes), although if you are careful and know what you are doing,
		1227	you still can.
		1228
		1229	The following constants are available (missing ones are, as usual C<0>):
		1230
		1231	C<F_DUPFD_CLOEXEC>,
		1232
		1233	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1234
		1235	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1236
		1237	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1238	C<FS_IOC_FIEMAP>.
		1239
		1240	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1241	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1242
		1243	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1244	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1245	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1246	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1247	C<FS_FL_USER_MODIFIABLE>.
		1248
		1249	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1250	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1251	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1252	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1253
		1254	=item aio_sync $callback->($status)
		1255
		1256	Asynchronously call sync and call the callback when finished.
696		1257
697	=item aio_fsync $fh, $callback->($status)	1258	=item aio_fsync $fh, $callback->($status)
698		1259
699	Asynchronously call fsync on the given filehandle and call the callback	1260	Asynchronously call fsync on the given filehandle and call the callback
700	with the fsync result code.	1261	with the fsync result code.
…		…
704	Asynchronously call fdatasync on the given filehandle and call the	1265	Asynchronously call fdatasync on the given filehandle and call the
705	callback with the fdatasync result code.	1266	callback with the fdatasync result code.
706		1267
707	If this call isn't available because your OS lacks it or it couldn't be	1268	If this call isn't available because your OS lacks it or it couldn't be
708	detected, it will be emulated by calling C<fsync> instead.	1269	detected, it will be emulated by calling C<fsync> instead.
		1270
		1271	=item aio_syncfs $fh, $callback->($status)
		1272
		1273	Asynchronously call the syncfs syscall to sync the filesystem associated
		1274	to the given filehandle and call the callback with the syncfs result
		1275	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1276	errno to C<ENOSYS> nevertheless.
		1277
		1278	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1279
		1280	Sync the data portion of the file specified by C<$offset> and C<$length>
		1281	to disk (but NOT the metadata), by calling the Linux-specific
		1282	sync_file_range call. If sync_file_range is not available or it returns
		1283	ENOSYS, then fdatasync or fsync is being substituted.
		1284
		1285	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1286	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1287	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1288	manpage for details.
		1289
		1290	=item aio_pathsync $pathname, $callback->($status)
		1291
		1292	This request tries to open, fsync and close the given path. This is a
		1293	composite request intended to sync directories after directory operations
		1294	(E.g. rename). This might not work on all operating systems or have any
		1295	specific effect, but usually it makes sure that directory changes get
		1296	written to disc. It works for anything that can be opened for read-only,
		1297	not just directories.
		1298
		1299	Future versions of this function might fall back to other methods when
		1300	C<fsync> on the directory fails (such as calling C<sync>).
		1301
		1302	Passes C<0> when everything went ok, and C<-1> on error.
		1303
		1304	=cut
		1305
		1306	sub aio_pathsync($;$) {
		1307	my ($path, $cb) = @_;
		1308
		1309	my $pri = aioreq_pri;
		1310	my $grp = aio_group $cb;
		1311
		1312	aioreq_pri $pri;
		1313	add $grp aio_open $path, O_RDONLY, 0, sub {
		1314	my ($fh) = @_;
		1315	if ($fh) {
		1316	aioreq_pri $pri;
		1317	add $grp aio_fsync $fh, sub {
		1318	$grp->result ($_[0]);
		1319
		1320	aioreq_pri $pri;
		1321	add $grp aio_close $fh;
		1322	};
		1323	} else {
		1324	$grp->result (-1);
		1325	}
		1326	};
		1327
		1328	$grp
		1329	}
		1330
		1331	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1332
		1333	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1334	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1335	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1336	scalar must only be modified in-place while an aio operation is pending on
		1337	it).
		1338
		1339	It calls the C<msync> function of your OS, if available, with the memory
		1340	area starting at C<$offset> in the string and ending C<$length> bytes
		1341	later. If C<$length> is negative, counts from the end, and if C<$length>
		1342	is C<undef>, then it goes till the end of the string. The flags can be
		1343	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1344	C<IO::AIO::MS_INVALIDATE>.
		1345
		1346	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1347
		1348	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1349	scalars.
		1350
		1351	It touches (reads or writes) all memory pages in the specified
		1352	range inside the scalar. All caveats and parameters are the same
		1353	as for C<aio_msync>, above, except for flags, which must be either
		1354	C<0> (which reads all pages and ensures they are instantiated) or
		1355	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1356	writing an octet from it, which dirties the page).
		1357
		1358	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1359
		1360	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1361	scalars.
		1362
		1363	It reads in all the pages of the underlying storage into memory (if any)
		1364	and locks them, so they are not getting swapped/paged out or removed.
		1365
		1366	If C<$length> is undefined, then the scalar will be locked till the end.
		1367
		1368	On systems that do not implement C<mlock>, this function returns C<-1>
		1369	and sets errno to C<ENOSYS>.
		1370
		1371	Note that the corresponding C<munlock> is synchronous and is
		1372	documented under L<MISCELLANEOUS FUNCTIONS>.
		1373
		1374	Example: open a file, mmap and mlock it - both will be undone when
		1375	C<$data> gets destroyed.
		1376
		1377	open my $fh, "<", $path or die "$path: $!";
		1378	my $data;
		1379	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1380	aio_mlock $data; # mlock in background
		1381
		1382	=item aio_mlockall $flags, $callback->($status)
		1383
		1384	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1385	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1386
		1387	On systems that do not implement C<mlockall>, this function returns C<-1>
		1388	and sets errno to C<ENOSYS>.
		1389
		1390	Note that the corresponding C<munlockall> is synchronous and is
		1391	documented under L<MISCELLANEOUS FUNCTIONS>.
		1392
		1393	Example: asynchronously lock all current and future pages into memory.
		1394
		1395	aio_mlockall IO::AIO::MCL_FUTURE;
		1396
		1397	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1398
		1399	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1400	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1401	the ioctl is not available on your OS, then this request will fail with
		1402	C<ENOSYS>.
		1403
		1404	C<$start> is the starting offset to query extents for, C<$length> is the
		1405	size of the range to query - if it is C<undef>, then the whole file will
		1406	be queried.
		1407
		1408	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1409	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1410	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1411	the data portion.
		1412
		1413	C<$count> is the maximum number of extent records to return. If it is
		1414	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1415	case, if it is C<0>, then the callback receives the number of extents
		1416	instead of the extents themselves (which is unreliable, see below).
		1417
		1418	If an error occurs, the callback receives no arguments. The special
		1419	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1420
		1421	Otherwise, the callback receives an array reference with extent
		1422	structures. Each extent structure is an array reference itself, with the
		1423	following members:
		1424
		1425	[$logical, $physical, $length, $flags]
		1426
		1427	Flags is any combination of the following flag values (typically either C<0>
		1428	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1429
		1430	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1431	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1432	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1433	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1434	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1435	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1436
		1437	At the time of this writing (Linux 3.2), this request is unreliable unless
		1438	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1439	it to return all extents of a range for files with a large number of
		1440	extents. The code (only) works around all these issues if C<$count> is
		1441	C<undef>.
709		1442
710	=item aio_group $callback->(...)	1443	=item aio_group $callback->(...)
711		1444
712	This is a very special aio request: Instead of doing something, it is a	1445	This is a very special aio request: Instead of doing something, it is a
713	container for other aio requests, which is useful if you want to bundle	1446	container for other aio requests, which is useful if you want to bundle
…		…
751	immense (it blocks a thread for a long time) so do not use this function	1484	immense (it blocks a thread for a long time) so do not use this function
752	except to put your application under artificial I/O pressure.	1485	except to put your application under artificial I/O pressure.
753		1486
754	=back	1487	=back
755		1488
		1489
		1490	=head2 IO::AIO::WD - multiple working directories
		1491
		1492	Your process only has one current working directory, which is used by all
		1493	threads. This makes it hard to use relative paths (some other component
		1494	could call C<chdir> at any time, and it is hard to control when the path
		1495	will be used by IO::AIO).
		1496
		1497	One solution for this is to always use absolute paths. This usually works,
		1498	but can be quite slow (the kernel has to walk the whole path on every
		1499	access), and can also be a hassle to implement.
		1500
		1501	Newer POSIX systems have a number of functions (openat, fdopendir,
		1502	futimensat and so on) that make it possible to specify working directories
		1503	per operation.
		1504
		1505	For portability, and because the clowns who "designed", or shall I write,
		1506	perpetrated this new interface were obviously half-drunk, this abstraction
		1507	cannot be perfect, though.
		1508
		1509	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1510	object. This object stores the canonicalised, absolute version of the
		1511	path, and on systems that allow it, also a directory file descriptor.
		1512
		1513	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1514	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1515	object and a pathname instead (or the IO::AIO::WD object alone, which
		1516	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1517	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1518	to that IO::AIO::WD object.
		1519
		1520	For example, to get a wd object for F</etc> and then stat F<passwd>
		1521	inside, you would write:
		1522
		1523	aio_wd "/etc", sub {
		1524	my $etcdir = shift;
		1525
		1526	# although $etcdir can be undef on error, there is generally no reason
		1527	# to check for errors here, as aio_stat will fail with ENOENT
		1528	# when $etcdir is undef.
		1529
		1530	aio_stat [$etcdir, "passwd"], sub {
		1531	# yay
		1532	};
		1533	};
		1534
		1535	The fact that C<aio_wd> is a request and not a normal function shows that
		1536	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1537	which is why it is done asynchronously.
		1538
		1539	To stat the directory obtained with C<aio_wd> above, one could write
		1540	either of the following three request calls:
		1541
		1542	aio_lstat "/etc" , sub { ... # pathname as normal string
		1543	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1544	aio_lstat $wd , sub { ... # shorthand for the previous
		1545
		1546	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1547	object and the pathname string, so you could write the following without
		1548	causing any issues due to C<$path> getting reused:
		1549
		1550	my $path = [$wd, undef];
		1551
		1552	for my $name (qw(abc def ghi)) {
		1553	$path->[1] = $name;
		1554	aio_stat $path, sub {
		1555	# ...
		1556	};
		1557	}
		1558
		1559	There are some caveats: when directories get renamed (or deleted), the
		1560	pathname string doesn't change, so will point to the new directory (or
		1561	nowhere at all), while the directory fd, if available on the system,
		1562	will still point to the original directory. Most functions accepting a
		1563	pathname will use the directory fd on newer systems, and the string on
		1564	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1565	the string form of the pathname.
		1566
		1567	So this functionality is mainly useful to get some protection against
		1568	C<chdir>, to easily get an absolute path out of a relative path for future
		1569	reference, and to speed up doing many operations in the same directory
		1570	(e.g. when stat'ing all files in a directory).
		1571
		1572	The following functions implement this working directory abstraction:
		1573
		1574	=over 4
		1575
		1576	=item aio_wd $pathname, $callback->($wd)
		1577
		1578	Asynchonously canonicalise the given pathname and convert it to an
		1579	IO::AIO::WD object representing it. If possible and supported on the
		1580	system, also open a directory fd to speed up pathname resolution relative
		1581	to this working directory.
		1582
		1583	If something goes wrong, then C<undef> is passwd to the callback instead
		1584	of a working directory object and C<$!> is set appropriately. Since
		1585	passing C<undef> as working directory component of a pathname fails the
		1586	request with C<ENOENT>, there is often no need for error checking in the
		1587	C<aio_wd> callback, as future requests using the value will fail in the
		1588	expected way.
		1589
		1590	=item IO::AIO::CWD
		1591
		1592	This is a compiletime constant (object) that represents the process
		1593	current working directory.
		1594
		1595	Specifying this object as working directory object for a pathname is as if
		1596	the pathname would be specified directly, without a directory object. For
		1597	example, these calls are functionally identical:
		1598
		1599	aio_stat "somefile", sub { ... };
		1600	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1601
		1602	=back
		1603
		1604	To recover the path associated with an IO::AIO::WD object, you can use
		1605	C<aio_realpath>:
		1606
		1607	aio_realpath $wd, sub {
		1608	warn "path is $_[0]\n";
		1609	};
		1610
		1611	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1612	sometimes, fall back to using an absolue path.
		1613
756	=head2 IO::AIO::REQ CLASS	1614	=head2 IO::AIO::REQ CLASS
757		1615
758	All non-aggregate C<aio_*> functions return an object of this class when	1616	All non-aggregate C<aio_*> functions return an object of this class when
759	called in non-void context.	1617	called in non-void context.
760		1618
…		…
763	=item cancel $req	1621	=item cancel $req
764		1622
765	Cancels the request, if possible. Has the effect of skipping execution	1623	Cancels the request, if possible. Has the effect of skipping execution
766	when entering the B<execute> state and skipping calling the callback when	1624	when entering the B<execute> state and skipping calling the callback when
767	entering the the B<result> state, but will leave the request otherwise	1625	entering the the B<result> state, but will leave the request otherwise
768	untouched. That means that requests that currently execute will not be	1626	untouched (with the exception of readdir). That means that requests that
769	stopped and resources held by the request will not be freed prematurely.	1627	currently execute will not be stopped and resources held by the request
		1628	will not be freed prematurely.
770		1629
771	=item cb $req $callback->(...)	1630	=item cb $req $callback->(...)
772		1631
773	Replace (or simply set) the callback registered to the request.	1632	Replace (or simply set) the callback registered to the request.
774		1633
…		…
825	Their lifetime, simplified, looks like this: when they are empty, they	1684	Their lifetime, simplified, looks like this: when they are empty, they
826	will finish very quickly. If they contain only requests that are in the	1685	will finish very quickly. If they contain only requests that are in the
827	C<done> state, they will also finish. Otherwise they will continue to	1686	C<done> state, they will also finish. Otherwise they will continue to
828	exist.	1687	exist.
829		1688
830	That means after creating a group you have some time to add requests. And	1689	That means after creating a group you have some time to add requests
831	in the callbacks of those requests, you can add further requests to the	1690	(precisely before the callback has been invoked, which is only done within
832	group. And only when all those requests have finished will the the group	1691	the C<poll_cb>). And in the callbacks of those requests, you can add
833	itself finish.	1692	further requests to the group. And only when all those requests have
		1693	finished will the the group itself finish.
834		1694
835	=over 4	1695	=over 4
836		1696
837	=item add $grp ...	1697	=item add $grp ...
838		1698
…		…
847	=item $grp->cancel_subs	1707	=item $grp->cancel_subs
848		1708
849	Cancel all subrequests and clears any feeder, but not the group request	1709	Cancel all subrequests and clears any feeder, but not the group request
850	itself. Useful when you queued a lot of events but got a result early.	1710	itself. Useful when you queued a lot of events but got a result early.
851		1711
		1712	The group request will finish normally (you cannot add requests to the
		1713	group).
		1714
852	=item $grp->result (...)	1715	=item $grp->result (...)
853		1716
854	Set the result value(s) that will be passed to the group callback when all	1717	Set the result value(s) that will be passed to the group callback when all
855	subrequests have finished and set thre groups errno to the current value	1718	subrequests have finished and set the groups errno to the current value
856	of errno (just like calling C<errno> without an error number). By default,	1719	of errno (just like calling C<errno> without an error number). By default,
857	no argument will be passed and errno is zero.	1720	no argument will be passed and errno is zero.
858		1721
859	=item $grp->errno ([$errno])	1722	=item $grp->errno ([$errno])
860		1723
…		…
871	=item feed $grp $callback->($grp)	1734	=item feed $grp $callback->($grp)
872		1735
873	Sets a feeder/generator on this group: every group can have an attached	1736	Sets a feeder/generator on this group: every group can have an attached
874	generator that generates requests if idle. The idea behind this is that,	1737	generator that generates requests if idle. The idea behind this is that,
875	although you could just queue as many requests as you want in a group,	1738	although you could just queue as many requests as you want in a group,
876	this might starve other requests for a potentially long time. For	1739	this might starve other requests for a potentially long time. For example,
877	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1740	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
878	requests, delaying any later requests for a long time.	1741	requests, delaying any later requests for a long time.
879		1742
880	To avoid this, and allow incremental generation of requests, you can	1743	To avoid this, and allow incremental generation of requests, you can
881	instead a group and set a feeder on it that generates those requests. The	1744	instead a group and set a feeder on it that generates those requests. The
882	feed callback will be called whenever there are few enough (see C<limit>,	1745	feed callback will be called whenever there are few enough (see C<limit>,
…		…
887	not impose any limits).	1750	not impose any limits).
888		1751
889	If the feed does not queue more requests when called, it will be	1752	If the feed does not queue more requests when called, it will be
890	automatically removed from the group.	1753	automatically removed from the group.
891		1754
892	If the feed limit is C<0>, it will be set to C<2> automatically.	1755	If the feed limit is C<0> when this method is called, it will be set to
		1756	C<2> automatically.
893		1757
894	Example:	1758	Example:
895		1759
896	# stat all files in @files, but only ever use four aio requests concurrently:	1760	# stat all files in @files, but only ever use four aio requests concurrently:
897		1761
…		…
909	Sets the feeder limit for the group: The feeder will be called whenever	1773	Sets the feeder limit for the group: The feeder will be called whenever
910	the group contains less than this many requests.	1774	the group contains less than this many requests.
911		1775
912	Setting the limit to C<0> will pause the feeding process.	1776	Setting the limit to C<0> will pause the feeding process.
913		1777
		1778	The default value for the limit is C<0>, but note that setting a feeder
		1779	automatically bumps it up to C<2>.
		1780
914	=back	1781	=back
915		1782
916	=head2 SUPPORT FUNCTIONS	1783	=head2 SUPPORT FUNCTIONS
917		1784
918	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1785	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
920	=over 4	1787	=over 4
921		1788
922	=item $fileno = IO::AIO::poll_fileno	1789	=item $fileno = IO::AIO::poll_fileno
923		1790
924	Return the I<request result pipe file descriptor>. This filehandle must be	1791	Return the I<request result pipe file descriptor>. This filehandle must be
925	polled for reading by some mechanism outside this module (e.g. Event or	1792	polled for reading by some mechanism outside this module (e.g. EV, Glib,
926	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1793	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
927	to call C<poll_cb> to check the results.	1794	you have to call C<poll_cb> to check the results.
928		1795
929	See C<poll_cb> for an example.	1796	See C<poll_cb> for an example.
930		1797
931	=item IO::AIO::poll_cb	1798	=item IO::AIO::poll_cb
932		1799
933	Process some outstanding events on the result pipe. You have to call this	1800	Process some requests that have reached the result phase (i.e. they have
934	regularly. Returns the number of events processed. Returns immediately	1801	been executed but the results are not yet reported). You have to call
935	when no events are outstanding. The amount of events processed depends on	1802	this "regularly" to finish outstanding requests.
936	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
937		1803
		1804	Returns C<0> if all events could be processed (or there were no
		1805	events to process), or C<-1> if it returned earlier for whatever
		1806	reason. Returns immediately when no events are outstanding. The amount
		1807	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1808	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1809
938	If not all requests were processed for whatever reason, the filehandle	1810	If not all requests were processed for whatever reason, the poll file
939	will still be ready when C<poll_cb> returns.	1811	descriptor will still be ready when C<poll_cb> returns, so normally you
		1812	don't have to do anything special to have it called later.
		1813
		1814	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1815	ready, it can be beneficial to call this function from loops which submit
		1816	a lot of requests, to make sure the results get processed when they become
		1817	available and not just when the loop is finished and the event loop takes
		1818	over again. This function returns very fast when there are no outstanding
		1819	requests.
940		1820
941	Example: Install an Event watcher that automatically calls	1821	Example: Install an Event watcher that automatically calls
942	IO::AIO::poll_cb with high priority:	1822	IO::AIO::poll_cb with high priority (more examples can be found in the
		1823	SYNOPSIS section, at the top of this document):
943		1824
944	Event->io (fd => IO::AIO::poll_fileno,	1825	Event->io (fd => IO::AIO::poll_fileno,
945	poll => 'r', async => 1,	1826	poll => 'r', async => 1,
946	cb => \&IO::AIO::poll_cb);	1827	cb => \&IO::AIO::poll_cb);
		1828
		1829	=item IO::AIO::poll_wait
		1830
		1831	Wait until either at least one request is in the result phase or no
		1832	requests are outstanding anymore.
		1833
		1834	This is useful if you want to synchronously wait for some requests to
		1835	become ready, without actually handling them.
		1836
		1837	See C<nreqs> for an example.
		1838
		1839	=item IO::AIO::poll
		1840
		1841	Waits until some requests have been handled.
		1842
		1843	Returns the number of requests processed, but is otherwise strictly
		1844	equivalent to:
		1845
		1846	IO::AIO::poll_wait, IO::AIO::poll_cb
		1847
		1848	=item IO::AIO::flush
		1849
		1850	Wait till all outstanding AIO requests have been handled.
		1851
		1852	Strictly equivalent to:
		1853
		1854	IO::AIO::poll_wait, IO::AIO::poll_cb
		1855	while IO::AIO::nreqs;
947		1856
948	=item IO::AIO::max_poll_reqs $nreqs	1857	=item IO::AIO::max_poll_reqs $nreqs
949		1858
950	=item IO::AIO::max_poll_time $seconds	1859	=item IO::AIO::max_poll_time $seconds
951		1860
…		…
976	# use a low priority so other tasks have priority	1885	# use a low priority so other tasks have priority
977	Event->io (fd => IO::AIO::poll_fileno,	1886	Event->io (fd => IO::AIO::poll_fileno,
978	poll => 'r', nice => 1,	1887	poll => 'r', nice => 1,
979	cb => &IO::AIO::poll_cb);	1888	cb => &IO::AIO::poll_cb);
980		1889
981	=item IO::AIO::poll_wait	1890	=back
982
983	If there are any outstanding requests and none of them in the result
984	phase, wait till the result filehandle becomes ready for reading (simply
985	does a C<select> on the filehandle. This is useful if you want to
986	synchronously wait for some requests to finish).
987
988	See C<nreqs> for an example.
989
990	=item IO::AIO::poll
991
992	Waits until some requests have been handled.
993
994	Returns the number of requests processed, but is otherwise strictly
995	equivalent to:
996
997	IO::AIO::poll_wait, IO::AIO::poll_cb
998
999	=item IO::AIO::flush
1000
1001	Wait till all outstanding AIO requests have been handled.
1002
1003	Strictly equivalent to:
1004
1005	IO::AIO::poll_wait, IO::AIO::poll_cb
1006	while IO::AIO::nreqs;
1007		1891
1008	=head3 CONTROLLING THE NUMBER OF THREADS	1892	=head3 CONTROLLING THE NUMBER OF THREADS
		1893
		1894	=over
1009		1895
1010	=item IO::AIO::min_parallel $nthreads	1896	=item IO::AIO::min_parallel $nthreads
1011		1897
1012	Set the minimum number of AIO threads to C<$nthreads>. The current	1898	Set the minimum number of AIO threads to C<$nthreads>. The current
1013	default is C<8>, which means eight asynchronous operations can execute	1899	default is C<8>, which means eight asynchronous operations can execute
…		…
1041		1927
1042	Under normal circumstances you don't need to call this function.	1928	Under normal circumstances you don't need to call this function.
1043		1929
1044	=item IO::AIO::max_idle $nthreads	1930	=item IO::AIO::max_idle $nthreads
1045		1931
1046	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1932	Limit the number of threads (default: 4) that are allowed to idle
1047	threads that did not get a request to process within 10 seconds). That	1933	(i.e., threads that did not get a request to process within the idle
1048	means if a thread becomes idle while C<$nthreads> other threads are also	1934	timeout (default: 10 seconds). That means if a thread becomes idle while
1049	idle, it will free its resources and exit.	1935	C<$nthreads> other threads are also idle, it will free its resources and
		1936	exit.
1050		1937
1051	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1938	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1052	to allow for extremely high load situations, but want to free resources	1939	to allow for extremely high load situations, but want to free resources
1053	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1940	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1054		1941
1055	The default is probably ok in most situations, especially if thread	1942	The default is probably ok in most situations, especially if thread
1056	creation is fast. If thread creation is very slow on your system you might	1943	creation is fast. If thread creation is very slow on your system you might
1057	want to use larger values.	1944	want to use larger values.
1058		1945
		1946	=item IO::AIO::idle_timeout $seconds
		1947
		1948	Sets the minimum idle timeout (default 10) after which worker threads are
		1949	allowed to exit. SEe C<IO::AIO::max_idle>.
		1950
1059	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1951	=item IO::AIO::max_outstanding $maxreqs
		1952
		1953	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1954	you do queue up more than this number of requests, the next call to
		1955	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1956	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1957	longer exceeded.
		1958
		1959	In other words, this setting does not enforce a queue limit, but can be
		1960	used to make poll functions block if the limit is exceeded.
1060		1961
1061	This is a very bad function to use in interactive programs because it	1962	This is a very bad function to use in interactive programs because it
1062	blocks, and a bad way to reduce concurrency because it is inexact: Better	1963	blocks, and a bad way to reduce concurrency because it is inexact: Better
1063	use an C<aio_group> together with a feed callback.	1964	use an C<aio_group> together with a feed callback.
1064		1965
1065	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1966	Its main use is in scripts without an event loop - when you want to stat
1066	to queue up more than this number of requests, the next call to the	1967	a lot of files, you can write something like this:
1067	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1068	function will block until the limit is no longer exceeded.
1069		1968
1070	The default value is very large, so there is no practical limit on the	1969	IO::AIO::max_outstanding 32;
1071	number of outstanding requests.
1072		1970
1073	You can still queue as many requests as you want. Therefore,	1971	for my $path (...) {
1074	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1972	aio_stat $path , ...;
1075	as a stop gap to shield against fatal memory overflow (with large values).	1973	IO::AIO::poll_cb;
		1974	}
		1975
		1976	IO::AIO::flush;
		1977
		1978	The call to C<poll_cb> inside the loop will normally return instantly, but
		1979	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1980	some requests have been handled. This keeps the loop from pushing a large
		1981	number of C<aio_stat> requests onto the queue.
		1982
		1983	The default value for C<max_outstanding> is very large, so there is no
		1984	practical limit on the number of outstanding requests.
		1985
		1986	=back
1076		1987
1077	=head3 STATISTICAL INFORMATION	1988	=head3 STATISTICAL INFORMATION
		1989
		1990	=over
1078		1991
1079	=item IO::AIO::nreqs	1992	=item IO::AIO::nreqs
1080		1993
1081	Returns the number of requests currently in the ready, execute or pending	1994	Returns the number of requests currently in the ready, execute or pending
1082	states (i.e. for which their callback has not been invoked yet).	1995	states (i.e. for which their callback has not been invoked yet).
…		…
1096	Returns the number of requests currently in the pending state (executed,	2009	Returns the number of requests currently in the pending state (executed,
1097	but not yet processed by poll_cb).	2010	but not yet processed by poll_cb).
1098		2011
1099	=back	2012	=back
1100		2013
		2014	=head3 MISCELLANEOUS FUNCTIONS
		2015
		2016	IO::AIO implements some functions that are useful when you want to use
		2017	some "Advanced I/O" function not available to in Perl, without going the
		2018	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2019	counterpart.
		2020
		2021	=over 4
		2022
		2023	=item $numfd = IO::AIO::get_fdlimit
		2024
		2025	This function is I<EXPERIMENTAL> and subject to change.
		2026
		2027	Tries to find the current file descriptor limit and returns it, or
		2028	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2029	the highest valid file descriptor number.
		2030
		2031	=item IO::AIO::min_fdlimit [$numfd]
		2032
		2033	This function is I<EXPERIMENTAL> and subject to change.
		2034
		2035	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2036	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2037	is missing, it will try to set a very high limit, although this is not
		2038	recommended when you know the actual minimum that you require.
		2039
		2040	If the limit cannot be raised enough, the function makes a best-effort
		2041	attempt to increase the limit as much as possible, using various
		2042	tricks, while still failing. You can query the resulting limit using
		2043	C<IO::AIO::get_fdlimit>.
		2044
		2045	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2046	true.
		2047
		2048	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2049
		2050	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2051	but is blocking (this makes most sense if you know the input data is
		2052	likely cached already and the output filehandle is set to non-blocking
		2053	operations).
		2054
		2055	Returns the number of bytes copied, or C<-1> on error.
		2056
		2057	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2058
		2059	Simply calls the C<posix_fadvise> function (see its
		2060	manpage for details). The following advice constants are
		2061	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2062	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2063	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2064
		2065	On systems that do not implement C<posix_fadvise>, this function returns
		2066	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2067
		2068	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2069
		2070	Simply calls the C<posix_madvise> function (see its
		2071	manpage for details). The following advice constants are
		2072	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2073	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2074	C<IO::AIO::MADV_DONTNEED>.
		2075
		2076	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2077	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2078	will be reduced to fit into the C<$scalar>.
		2079
		2080	On systems that do not implement C<posix_madvise>, this function returns
		2081	ENOSYS, otherwise the return value of C<posix_madvise>.
		2082
		2083	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2084
		2085	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2086	$scalar (see its manpage for details). The following protect
		2087	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2088	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2089
		2090	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2091	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2092	will be reduced to fit into the C<$scalar>.
		2093
		2094	On systems that do not implement C<mprotect>, this function returns
		2095	ENOSYS, otherwise the return value of C<mprotect>.
		2096
		2097	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2098
		2099	Memory-maps a file (or anonymous memory range) and attaches it to the
		2100	given C<$scalar>, which will act like a string scalar. Returns true on
		2101	success, and false otherwise.
		2102
		2103	The scalar must exist, but its contents do not matter - this means you
		2104	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2105	the scalar first.
		2106
		2107	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2108	which don't change the string length, and most read-only operations such
		2109	as copying it or searching it with regexes and so on.
		2110
		2111	Anything else is unsafe and will, at best, result in memory leaks.
		2112
		2113	The memory map associated with the C<$scalar> is automatically removed
		2114	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2115	or C<IO::AIO::munmap> functions are called on it.
		2116
		2117	This calls the C<mmap>(2) function internally. See your system's manual
		2118	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2119
		2120	The C<$length> must be larger than zero and smaller than the actual
		2121	filesize.
		2122
		2123	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2124	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2125
		2126	C<$flags> can be a combination of
		2127	C<IO::AIO::MAP_SHARED> or
		2128	C<IO::AIO::MAP_PRIVATE>,
		2129	or a number of system-specific flags (when not available, the are C<0>):
		2130	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2131	C<IO::AIO::MAP_LOCKED>,
		2132	C<IO::AIO::MAP_NORESERVE>,
		2133	C<IO::AIO::MAP_POPULATE>,
		2134	C<IO::AIO::MAP_NONBLOCK>,
		2135	C<IO::AIO::MAP_FIXED>,
		2136	C<IO::AIO::MAP_GROWSDOWN>,
		2137	C<IO::AIO::MAP_32BIT>,
		2138	C<IO::AIO::MAP_HUGETLB> or
		2139	C<IO::AIO::MAP_STACK>.
		2140
		2141	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2142
		2143	C<$offset> is the offset from the start of the file - it generally must be
		2144	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2145
		2146	Example:
		2147
		2148	use Digest::MD5;
		2149	use IO::AIO;
		2150
		2151	open my $fh, "<verybigfile"
		2152	or die "$!";
		2153
		2154	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2155	or die "verybigfile: $!";
		2156
		2157	my $fast_md5 = md5 $data;
		2158
		2159	=item IO::AIO::munmap $scalar
		2160
		2161	Removes a previous mmap and undefines the C<$scalar>.
		2162
		2163	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2164
		2165	Calls the C<munlock> function, undoing the effects of a previous
		2166	C<aio_mlock> call (see its description for details).
		2167
		2168	=item IO::AIO::munlockall
		2169
		2170	Calls the C<munlockall> function.
		2171
		2172	On systems that do not implement C<munlockall>, this function returns
		2173	ENOSYS, otherwise the return value of C<munlockall>.
		2174
		2175	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2176
		2177	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2178	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2179	should be the file offset.
		2180
		2181	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2182	silently corrupt the data in this case.
		2183
		2184	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2185	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2186	C<IO::AIO::SPLICE_F_GIFT>.
		2187
		2188	See the C<splice(2)> manpage for details.
		2189
		2190	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2191
		2192	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2193	description for C<IO::AIO::splice> above for details.
		2194
		2195	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2196
		2197	Attempts to query or change the pipe buffer size. Obviously works only
		2198	on pipes, and currently works only on GNU/Linux systems, and fails with
		2199	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2200	size on other systems, drop me a note.
		2201
		2202	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2203
		2204	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2205	C<$flags> is missing or C<0>, then this should be the same as a call to
		2206	perl's built-in C<pipe> function and create a new pipe, and works on
		2207	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2208	(..., 4096, O_BINARY)>.
		2209
		2210	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2211	the given flags (Linux 2.6.27, glibc 2.9).
		2212
		2213	On success, the read and write file handles are returned.
		2214
		2215	On error, nothing will be returned. If the pipe2 syscall is missing and
		2216	C<$flags> is non-zero, fails with C<ENOSYS>.
		2217
		2218	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2219	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2220	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2221
		2222	Example: create a pipe race-free w.r.t. threads and fork:
		2223
		2224	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2225	or die "pipe2: $!\n";
		2226
		2227	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2228
		2229	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2230	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2231
		2232	On success, the new eventfd filehandle is returned, otherwise returns
		2233	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2234
		2235	Please refer to L<eventfd(2)> for more info on this call.
		2236
		2237	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2238	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2239
		2240	Example: create a new eventfd filehandle:
		2241
		2242	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2243	or die "eventfd: $!\n";
		2244
		2245	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2246
		2247	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2248	(unhelpful) default for C<$flags> is C<0>.
		2249
		2250	On success, the new timerfd filehandle is returned, otherwise returns
		2251	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2252
		2253	Please refer to L<timerfd_create(2)> for more info on this call.
		2254
		2255	The following C<$clockid> values are
		2256	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2257	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2258	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2259	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2260
		2261	The following C<$flags> values are available (Linux
		2262	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2263
		2264	Example: create a new timerfd and set it to one-second repeated alarms,
		2265	then wait for two alarms:
		2266
		2267	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2268	or die "timerfd_create: $!\n";
		2269
		2270	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2271	or die "timerfd_settime: $!\n";
		2272
		2273	for (1..2) {
		2274	8 == sysread $fh, my $buf, 8
		2275	or die "timerfd read failure\n";
		2276
		2277	printf "number of expirations (likely 1): %d\n",
		2278	unpack "Q", $buf;
		2279	}
		2280
		2281	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2282
		2283	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2284	call. Please refer to its manpage for more info on this call.
		2285
		2286	The new itimerspec is specified using two (possibly fractional) second
		2287	values, C<$new_interval> and C<$new_value>).
		2288
		2289	On success, the current interval and value are returned (as per
		2290	C<timerfd_gettime>). On failure, the empty list is returned.
		2291
		2292	The following C<$flags> values are
		2293	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2294	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2295
		2296	See C<IO::AIO::timerfd_create> for a full example.
		2297
		2298	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2299
		2300	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2301	call. Please refer to its manpage for more info on this call.
		2302
		2303	On success, returns the current values of interval and value for the given
		2304	timerfd (as potentially fractional second values). On failure, the empty
		2305	list is returned.
		2306
		2307	=back
		2308
1101	=cut	2309	=cut
1102		2310
1103	# support function to convert a fd into a perl filehandle
1104	sub _fd2fh {
1105	return undef if $_[0] < 0;
1106
1107	# try to generate nice filehandles
1108	my $sym = "IO::AIO::fd#$_[0]";
1109	local *$sym;
1110
1111	open *$sym, "+<&=$_[0]" # usually works under any unix
1112	or open *$sym, "<&=$_[0]" # cygwin needs this
1113	or open *$sym, ">&=$_[0]" # or this
1114	or return undef;
1115
1116	*$sym
1117	}
1118
1119	min_parallel 8;	2311	min_parallel 8;
1120		2312
1121	END { flush }	2313	END { flush }
1122		2314
1123	1;	2315	1;
1124		2316
		2317	=head1 EVENT LOOP INTEGRATION
		2318
		2319	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2320	automatically into many event loops:
		2321
		2322	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2323	use AnyEvent::AIO;
		2324
		2325	You can also integrate IO::AIO manually into many event loops, here are
		2326	some examples of how to do this:
		2327
		2328	# EV integration
		2329	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2330
		2331	# Event integration
		2332	Event->io (fd => IO::AIO::poll_fileno,
		2333	poll => 'r',
		2334	cb => \&IO::AIO::poll_cb);
		2335
		2336	# Glib/Gtk2 integration
		2337	add_watch Glib::IO IO::AIO::poll_fileno,
		2338	in => sub { IO::AIO::poll_cb; 1 };
		2339
		2340	# Tk integration
		2341	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2342	readable => \&IO::AIO::poll_cb);
		2343
		2344	# Danga::Socket integration
		2345	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2346	\&IO::AIO::poll_cb);
		2347
1125	=head2 FORK BEHAVIOUR	2348	=head2 FORK BEHAVIOUR
1126		2349
1127	This module should do "the right thing" when the process using it forks:	2350	Usage of pthreads in a program changes the semantics of fork
		2351	considerably. Specifically, only async-safe functions can be called after
		2352	fork. Perl doesn't know about this, so in general, you cannot call fork
		2353	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2354	pthreads, so this applies, but many other extensions and (for inexplicable
		2355	reasons) perl itself often is linked against pthreads, so this limitation
		2356	applies to quite a lot of perls.
1128		2357
1129	Before the fork, IO::AIO enters a quiescent state where no requests	2358	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1130	can be added in other threads and no results will be processed. After	2359	only works in the process that loaded it. Forking is fully supported, but
1131	the fork the parent simply leaves the quiescent state and continues	2360	using IO::AIO in the child is not.
1132	request/result processing, while the child frees the request/result queue
1133	(so that the requests started before the fork will only be handled in the
1134	parent). Threads will be started on demand until the limit set in the
1135	parent process has been reached again.
1136		2361
1137	In short: the parent will, after a short pause, continue as if fork had	2362	You might get around by not I<using> IO::AIO before (or after)
1138	not been called, while the child will act as if IO::AIO has not been used	2363	forking. You could also try to call the L<IO::AIO::reinit> function in the
1139	yet.	2364	child:
		2365
		2366	=over 4
		2367
		2368	=item IO::AIO::reinit
		2369
		2370	Abandons all current requests and I/O threads and simply reinitialises all
		2371	data structures. This is not an operation supported by any standards, but
		2372	happens to work on GNU/Linux and some newer BSD systems.
		2373
		2374	The only reasonable use for this function is to call it after forking, if
		2375	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2376	the process will result in undefined behaviour. Calling it at any time
		2377	will also result in any undefined (by POSIX) behaviour.
		2378
		2379	=back
		2380
		2381	=head2 LINUX-SPECIFIC CALLS
		2382
		2383	When a call is documented as "linux-specific" then this means it
		2384	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2385	availability and compatibility of such calls regardless of the platform
		2386	it is compiled on, so platforms such as FreeBSD which often implement
		2387	these calls will work. When in doubt, call them and see if they fail wth
		2388	C<ENOSYS>.
1140		2389
1141	=head2 MEMORY USAGE	2390	=head2 MEMORY USAGE
1142		2391
1143	Per-request usage:	2392	Per-request usage:
1144		2393
…		…
1146	bytes of memory. In addition, stat requests need a stat buffer (possibly	2395	bytes of memory. In addition, stat requests need a stat buffer (possibly
1147	a few hundred bytes), readdir requires a result buffer and so on. Perl	2396	a few hundred bytes), readdir requires a result buffer and so on. Perl
1148	scalars and other data passed into aio requests will also be locked and	2397	scalars and other data passed into aio requests will also be locked and
1149	will consume memory till the request has entered the done state.	2398	will consume memory till the request has entered the done state.
1150		2399
1151	This is now awfully much, so queuing lots of requests is not usually a	2400	This is not awfully much, so queuing lots of requests is not usually a
1152	problem.	2401	problem.
1153		2402
1154	Per-thread usage:	2403	Per-thread usage:
1155		2404
1156	In the execution phase, some aio requests require more memory for	2405	In the execution phase, some aio requests require more memory for
1157	temporary buffers, and each thread requires a stack and other data	2406	temporary buffers, and each thread requires a stack and other data
1158	structures (usually around 16k-128k, depending on the OS).	2407	structures (usually around 16k-128k, depending on the OS).
1159		2408
1160	=head1 KNOWN BUGS	2409	=head1 KNOWN BUGS
1161		2410
1162	Known bugs will be fixed in the next release.	2411	Known bugs will be fixed in the next release :)
		2412
		2413	=head1 KNOWN ISSUES
		2414
		2415	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2416	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2417	non-created hash slots or other scalars I didn't think of. It's best to
		2418	avoid such and either use scalar variables or making sure that the scalar
		2419	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2420
		2421	I am not sure anything can be done about this, so this is considered a
		2422	known issue, rather than a bug.
1163		2423
1164	=head1 SEE ALSO	2424	=head1 SEE ALSO
1165		2425
1166	L<Coro::AIO>.	2426	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2427	more natural syntax.
1167		2428
1168	=head1 AUTHOR	2429	=head1 AUTHOR
1169		2430
1170	Marc Lehmann <schmorp@schmorp.de>	2431	Marc Lehmann <schmorp@schmorp.de>
1171	http://home.schmorp.de/	2432	http://home.schmorp.de/

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