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Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC vs.
Revision 1.318 by root, Sat Apr 1 02:14:05 2023 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 = 4.80;
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 mremap munlock munlockall
		198
		199	accept4 tee splice pipe2 pipesize
		200	fexecve mount umount memfd_create eventfd
		201	timerfd_create timerfd_settime timerfd_gettime
		202	pidfd_open pidfd_send_signal pidfd_getfd);
		203
		204	push @AIO_REQ, qw(aio_busy); # not exported
206		205
207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
208		207
209	require XSLoader;	208	require XSLoader;
210	XSLoader::load ("IO::AIO", $VERSION);	209	XSLoader::load ("IO::AIO", $VERSION);
211	}	210	}
212		211
213	=head1 FUNCTIONS	212	=head1 FUNCTIONS
214		213
215	=head2 AIO REQUEST FUNCTIONS	214	=head2 QUICK OVERVIEW
		215
		216	This section simply lists the prototypes most of the functions for
		217	quick reference. See the following sections for function-by-function
		218	documentation.
		219
		220	aio_wd $pathname, $callback->($wd)
		221	aio_open $pathname, $flags, $mode, $callback->($fh)
		222	aio_close $fh, $callback->($status)
		223	aio_seek $fh,$offset,$whence, $callback->($offs)
		224	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		225	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		226	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		227	aio_readahead $fh,$offset,$length, $callback->($retval)
		228	aio_stat $fh_or_path, $callback->($status)
		229	aio_lstat $fh, $callback->($status)
		230	aio_statvfs $fh_or_path, $callback->($statvfs)
		231	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		232	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		233	aio_chmod $fh_or_path, $mode, $callback->($status)
		234	aio_truncate $fh_or_path, $offset, $callback->($status)
		235	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		236	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		237	aio_unlink $pathname, $callback->($status)
		238	aio_mknod $pathname, $mode, $dev, $callback->($status)
		239	aio_link $srcpath, $dstpath, $callback->($status)
		240	aio_symlink $srcpath, $dstpath, $callback->($status)
		241	aio_readlink $pathname, $callback->($link)
		242	aio_realpath $pathname, $callback->($path)
		243	aio_rename $srcpath, $dstpath, $callback->($status)
		244	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		245	aio_mkdir $pathname, $mode, $callback->($status)
		246	aio_rmdir $pathname, $callback->($status)
		247	aio_readdir $pathname, $callback->($entries)
		248	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		249	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		250	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		251	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		252	aio_load $pathname, $data, $callback->($status)
		253	aio_copy $srcpath, $dstpath, $callback->($status)
		254	aio_move $srcpath, $dstpath, $callback->($status)
		255	aio_rmtree $pathname, $callback->($status)
		256	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		257	aio_ioctl $fh, $request, $buf, $callback->($status)
		258	aio_sync $callback->($status)
		259	aio_syncfs $fh, $callback->($status)
		260	aio_fsync $fh, $callback->($status)
		261	aio_fdatasync $fh, $callback->($status)
		262	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		263	aio_pathsync $pathname, $callback->($status)
		264	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		265	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		266	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		267	aio_mlockall $flags, $callback->($status)
		268	aio_group $callback->(...)
		269	aio_nop $callback->()
		270
		271	$prev_pri = aioreq_pri [$pri]
		272	aioreq_nice $pri_adjust
		273
		274	IO::AIO::poll_wait
		275	IO::AIO::poll_cb
		276	IO::AIO::poll
		277	IO::AIO::flush
		278	IO::AIO::max_poll_reqs $nreqs
		279	IO::AIO::max_poll_time $seconds
		280	IO::AIO::min_parallel $nthreads
		281	IO::AIO::max_parallel $nthreads
		282	IO::AIO::max_idle $nthreads
		283	IO::AIO::idle_timeout $seconds
		284	IO::AIO::max_outstanding $maxreqs
		285	IO::AIO::nreqs
		286	IO::AIO::nready
		287	IO::AIO::npending
		288	IO::AIO::reinit
		289
		290	$nfd = IO::AIO::get_fdlimit
		291	IO::AIO::min_fdlimit $nfd
		292
		293	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		294	IO::AIO::fadvise $fh, $offset, $len, $advice
		295	IO::AIO::fexecve $fh, $argv, $envp
		296
		297	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		298	IO::AIO::munmap $scalar
		299	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		300	IO::AIO::madvise $scalar, $offset, $length, $advice
		301	IO::AIO::mprotect $scalar, $offset, $length, $protect
		302	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		303	IO::AIO::munlockall
		304
		305	# stat extensions
		306	$counter = IO::AIO::st_gen
		307	$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		308	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		309	$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		310	$seconds = IO::AIO::st_btimesec
		311	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		312
		313	# very much unportable syscalls
		314	IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
		315	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		316	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		317
		318	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		319	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		320
		321	$fh = IO::AIO::eventfd [$initval, [$flags]]
		322	$fh = IO::AIO::memfd_create $pathname[, $flags]
		323
		324	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		325	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		326	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		327
		328	$fh = IO::AIO::pidfd_open $pid[, $flags]
		329	$status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		330	$fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		331
		332	$retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		333	$retval = IO::AIO::umount $path, $flags = 0
		334
		335	=head2 API NOTES
216		336
217	All the C<aio_*> calls are more or less thin wrappers around the syscall	337	All the C<aio_*> calls are more or less thin wrappers around the syscall
218	with the same name (sans C<aio_>). The arguments are similar or identical,	338	with the same name (sans C<aio_>). The arguments are similar or identical,
219	and they all accept an additional (and optional) C<$callback> argument	339	and they all accept an additional (and optional) C<$callback> argument
220	which must be a code reference. This code reference will get called with	340	which must be a code reference. This code reference will be called after
221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	341	the syscall has been executed in an asynchronous fashion. The results
222	perl, which usually delivers "false") as it's sole argument when the given	342	of the request will be passed as arguments to the callback (and, if an
223	syscall has been executed asynchronously.	343	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		344	most syscalls return C<-1> on error, unlike perl, which usually delivers
		345	"false").
		346
		347	Some requests (such as C<aio_readdir>) pass the actual results and
		348	communicate failures by passing C<undef>.
224		349
225	All functions expecting a filehandle keep a copy of the filehandle	350	All functions expecting a filehandle keep a copy of the filehandle
226	internally until the request has finished.	351	internally until the request has finished.
227		352
228	All functions return request objects of type L<IO::AIO::REQ> that allow	353	All functions return request objects of type L<IO::AIO::REQ> that allow
229	further manipulation of those requests while they are in-flight.	354	further manipulation of those requests while they are in-flight.
230		355
231	The pathnames you pass to these routines I<must> be absolute and	356	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	357	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	358	current working directory could have changed. Alternatively, you can
234	changed. Alternatively, you can make sure that you never change the	359	make sure that you never change the current working directory anywhere
235	current working directory anywhere in the program and then use relative	360	in the program and then use relative paths. You can also take advantage
236	paths.	361	of IO::AIOs working directory abstraction, that lets you specify paths
		362	relative to some previously-opened "working directory object" - see the
		363	description of the C<IO::AIO::WD> class later in this document.
237		364
238	To encode pathnames as octets, either make sure you either: a) always pass	365	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	366	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	367	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	368	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)	369	effect in the user environment, d) use Glib::filename_from_unicode on
243	use something else to ensure your scalar has the correct contents.	370	unicode filenames or e) use something else to ensure your scalar has the
		371	correct contents.
244		372
245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	373	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246	handles correctly wether it is set or not.	374	handles correctly whether it is set or not.
		375
		376	=head2 AIO REQUEST FUNCTIONS
247		377
248	=over 4	378	=over 4
249		379
250	=item $prev_pri = aioreq_pri [$pri]	380	=item $prev_pri = aioreq_pri [$pri]
251		381
…		…
271	aio_read $_[0], ..., sub {	401	aio_read $_[0], ..., sub {
272	...	402	...
273	};	403	};
274	};	404	};
275		405
		406
276	=item aioreq_nice $pri_adjust	407	=item aioreq_nice $pri_adjust
277		408
278	Similar to C<aioreq_pri>, but subtracts the given value from the current	409	Similar to C<aioreq_pri>, but subtracts the given value from the current
279	priority, so the effect is cumulative.	410	priority, so the effect is cumulative.
280		411
		412
281	=item aio_open $pathname, $flags, $mode, $callback->($fh)	413	=item aio_open $pathname, $flags, $mode, $callback->($fh)
282		414
283	Asynchronously open or create a file and call the callback with a newly	415	Asynchronously open or create a file and call the callback with a newly
284	created filehandle for the file.	416	created filehandle for the file (or C<undef> in case of an error).
285
286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
287	for an explanation.
288		417
289	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	418	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
290	list. They are the same as used by C<sysopen>.	419	list. They are the same as used by C<sysopen>.
291		420
292	Likewise, C<$mode> specifies the mode of the newly created file, if it	421	Likewise, C<$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>,	422	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,	423	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).	424	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		425	by the umask in effect then the request is being executed, so better never
		426	change the umask.
296		427
297	Example:	428	Example:
298		429
299	aio_open "/etc/passwd", O_RDONLY, 0, sub {	430	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
300	if ($_[0]) {	431	if ($_[0]) {
301	print "open successful, fh is $_[0]\n";	432	print "open successful, fh is $_[0]\n";
302	...	433	...
303	} else {	434	} else {
304	die "open failed: $!\n";	435	die "open failed: $!\n";
305	}	436	}
306	};	437	};
307		438
		439	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		440	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		441	following POSIX and non-POSIX constants are available (missing ones on
		442	your system are, as usual, C<0>):
		443
		444	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		445	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		446	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		447
		448
308	=item aio_close $fh, $callback->($status)	449	=item aio_close $fh, $callback->($status)
309		450
310	Asynchronously close a file and call the callback with the result	451	Asynchronously close a file and call the callback with the result
311	code. I<WARNING:> although accepted, you should not pass in a perl	452	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		453
316	This is supposed to be a bug in the API, so that might change. It's	454	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
317	therefore best to avoid this function.	455	closing the file descriptor associated with the filehandle itself.
		456
		457	Therefore, C<aio_close> will not close the filehandle - instead it will
		458	use dup2 to overwrite the file descriptor with the write-end of a pipe
		459	(the pipe fd will be created on demand and will be cached).
		460
		461	Or in other words: the file descriptor will be closed, but it will not be
		462	free for reuse until the perl filehandle is closed.
		463
		464	=cut
		465
		466	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		467
		468	Seeks the filehandle to the new C<$offset>, similarly to perl's
		469	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		470	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		471	C<IO::AIO::SEEK_END>).
		472
		473	The resulting absolute offset will be passed to the callback, or C<-1> in
		474	case of an error.
		475
		476	In theory, the C<$whence> constants could be different than the
		477	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		478	so don't panic.
		479
		480	As a GNU/Linux (and maybe Solaris) extension, also the constants
		481	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		482	could be found. No guarantees about suitability for use in C<aio_seek> or
		483	Perl's C<sysseek> can be made though, although I would naively assume they
		484	"just work".
318		485
319	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	486	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
320		487
321	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	488	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322		489
323	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	490	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	491	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
325	callback without the actual number of bytes read (or -1 on error, just	492	calls the callback with the actual number of bytes transferred (or -1 on
326	like the syscall).	493	error, just like the syscall).
		494
		495	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		496	offset plus the actual number of bytes read.
		497
		498	If C<$offset> is undefined, then the current file descriptor offset will
		499	be used (and updated), otherwise the file descriptor offset will not be
		500	changed by these calls.
		501
		502	If C<$length> is undefined in C<aio_write>, use the remaining length of
		503	C<$data>.
		504
		505	If C<$dataoffset> is less than zero, it will be counted from the end of
		506	C<$data>.
327		507
328	The C<$data> scalar I<MUST NOT> be modified in any way while the request	508	The C<$data> scalar I<MUST NOT> be modified in any way while the request
329	is outstanding. Modifying it can result in segfaults or WW3 (if the	509	is outstanding. Modifying it can result in segfaults or World War III (if
330	necessary/optional hardware is installed).	510	the necessary/optional hardware is installed).
331		511
332	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	512	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
333	offset C<0> within the scalar:	513	offset C<0> within the scalar:
334		514
335	aio_read $fh, 7, 15, $buffer, 0, sub {	515	aio_read $fh, 7, 15, $buffer, 0, sub {
336	$_[0] > 0 or die "read error: $!";	516	$_[0] > 0 or die "read error: $!";
337	print "read $_[0] bytes: <$buffer>\n";	517	print "read $_[0] bytes: <$buffer>\n";
338	};	518	};
339		519
		520
340	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	521	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
341		522
342	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	523	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
343	reading at byte offset C<$in_offset>, and starts writing at the current	524	reading at byte offset C<$in_offset>, and starts writing at the current
344	file offset of C<$out_fh>. Because of that, it is not safe to issue more	525	file offset of C<$out_fh>. Because of that, it is not safe to issue more
345	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	526	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
346	other.	527	other. The same C<$in_fh> works fine though, as this function does not
		528	move or use the file offset of C<$in_fh>.
347		529
		530	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		531	are written, and there is no way to find out how many more bytes have been
		532	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		533	number of bytes written to C<$out_fh>. Only if the result value equals
		534	C<$length> one can assume that C<$length> bytes have been read.
		535
		536	Unlike with other C<aio_> functions, it makes a lot of sense to use
		537	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		538	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		539	the socket I/O will be non-blocking. Note, however, that you can run
		540	into a trap where C<aio_sendfile> reads some data with readahead, then
		541	fails to write all data, and when the socket is ready the next time, the
		542	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		543	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		544	resource usage.
		545
348	This call tries to make use of a native C<sendfile> syscall to provide	546	This call tries to make use of a native C<sendfile>-like syscall to
349	zero-copy operation. For this to work, C<$out_fh> should refer to a	547	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.	548	a socket, and C<$in_fh> should refer to an mmap'able file.
351		549
352	If the native sendfile call fails or is not implemented, it will be	550	If a native sendfile cannot be found or it fails with C<ENOSYS>,
353	emulated, so you can call C<aio_sendfile> on any type of filehandle	551	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		552	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
354	regardless of the limitations of the operating system.	553	type of filehandle regardless of the limitations of the operating system.
355		554
356	Please note, however, that C<aio_sendfile> can read more bytes from	555	As native sendfile syscalls (as practically any non-POSIX interface hacked
357	C<$in_fh> than are written, and there is no way to find out how many	556	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	557	on many systems, this implementation tries to work around some known bugs
359	provides the number of bytes written to C<$out_fh>. Only if the result	558	in Linux and FreeBSD kernels (probably others, too), but that might fail,
360	value equals C<$length> one can assume that C<$length> bytes have been	559	so you really really should check the return value of C<aio_sendfile> -
361	read.	560	fewer bytes than expected might have been transferred.
		561
362		562
363	=item aio_readahead $fh,$offset,$length, $callback->($retval)	563	=item aio_readahead $fh,$offset,$length, $callback->($retval)
364		564
365	C<aio_readahead> populates the page cache with data from a file so that	565	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<$offset>	566	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
369	whole pages, so that offset is effectively rounded down to a page boundary	569	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	570	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	571	(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.	572	file. The current file offset of the file is left unchanged.
373		573
374	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	574	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.	575	be emulated by simply reading the data, which would have a similar effect.
		576
376		577
377	=item aio_stat $fh_or_path, $callback->($status)	578	=item aio_stat $fh_or_path, $callback->($status)
378		579
379	=item aio_lstat $fh, $callback->($status)	580	=item aio_lstat $fh, $callback->($status)
380		581
381	Works like perl's C<stat> or C<lstat> in void context. The callback will	582	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
382	be called after the stat and the results will be available using C<stat _>	583	callback will be called after the stat and the results will be available
383	or C<-s _> etc...	584	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
384		585	and C<-T>).
385	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
386	for an explanation.
387		586
388	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	587	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	588	error when stat'ing a large file, the results will be silently truncated
390	unless perl itself is compiled with large file support.	589	unless perl itself is compiled with large file support.
		590
		591	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		592	following constants and functions (if not implemented, the constants will
		593	be C<0> and the functions will either C<croak> or fall back on traditional
		594	behaviour).
		595
		596	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		597	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		598	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		599
		600	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		601	ACCESS>.
391		602
392	Example: Print the length of F</etc/passwd>:	603	Example: Print the length of F</etc/passwd>:
393		604
394	aio_stat "/etc/passwd", sub {	605	aio_stat "/etc/passwd", sub {
395	$_[0] and die "stat failed: $!";	606	$_[0] and die "stat failed: $!";
396	print "size is ", -s _, "\n";	607	print "size is ", -s _, "\n";
397	};	608	};
398		609
		610
		611	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		612
		613	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		614	whether a file handle or path was passed.
		615
		616	On success, the callback is passed a hash reference with the following
		617	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		618	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		619	is passed.
		620
		621	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		622	C<ST_NOSUID>.
		623
		624	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		625	their correct value when available, or to C<0> on systems that do
		626	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		627	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		628	C<ST_NODIRATIME> and C<ST_RELATIME>.
		629
		630	Example: stat C</wd> and dump out the data if successful.
		631
		632	aio_statvfs "/wd", sub {
		633	my $f = $_[0]
		634	or die "statvfs: $!";
		635
		636	use Data::Dumper;
		637	say Dumper $f;
		638	};
		639
		640	# result:
		641	{
		642	bsize => 1024,
		643	bfree => 4333064312,
		644	blocks => 10253828096,
		645	files => 2050765568,
		646	flag => 4096,
		647	favail => 2042092649,
		648	bavail => 4333064312,
		649	ffree => 2042092649,
		650	namemax => 255,
		651	frsize => 1024,
		652	fsid => 1810
		653	}
		654
		655	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		656
		657	Works like perl's C<utime> function (including the special case of $atime
		658	and $mtime being undef). Fractional times are supported if the underlying
		659	syscalls support them.
		660
		661	When called with a pathname, uses utimensat(2) or utimes(2) if available,
		662	otherwise utime(2). If called on a file descriptor, uses futimens(2)
		663	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		664	portable.
		665
		666	Examples:
		667
		668	# set atime and mtime to current time (basically touch(1)):
		669	aio_utime "path", undef, undef;
		670	# set atime to current time and mtime to beginning of the epoch:
		671	aio_utime "path", time, undef; # undef==0
		672
		673
		674	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		675
		676	Works like perl's C<chown> function, except that C<undef> for either $uid
		677	or $gid is being interpreted as "do not change" (but -1 can also be used).
		678
		679	Examples:
		680
		681	# same as "chown root path" in the shell:
		682	aio_chown "path", 0, -1;
		683	# same as above:
		684	aio_chown "path", 0, undef;
		685
		686
		687	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		688
		689	Works like truncate(2) or ftruncate(2).
		690
		691
		692	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		693
		694	Allocates or frees disk space according to the C<$mode> argument. See the
		695	linux C<fallocate> documentation for details.
		696
		697	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		698	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		699	to deallocate a file range.
		700
		701	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		702	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		703	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		704	to unshare shared blocks (see your L<fallocate(2)> manpage).
		705
		706	The file system block size used by C<fallocate> is presumably the
		707	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		708	can dictate other limitations.
		709
		710	If C<fallocate> isn't available or cannot be emulated (currently no
		711	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		712
		713
		714	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		715
		716	Works like perl's C<chmod> function.
		717
		718
399	=item aio_unlink $pathname, $callback->($status)	719	=item aio_unlink $pathname, $callback->($status)
400		720
401	Asynchronously unlink (delete) a file and call the callback with the	721	Asynchronously unlink (delete) a file and call the callback with the
402	result code.	722	result code.
403		723
		724
404	=item aio_mknod $path, $mode, $dev, $callback->($status)	725	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
405		726
406	[EXPERIMENTAL]	727	[EXPERIMENTAL]
407		728
408	Asynchronously create a device node (or fifo). See mknod(2).	729	Asynchronously create a device node (or fifo). See mknod(2).
409		730
410	The only (POSIX-) portable way of calling this function is:	731	The only (POSIX-) portable way of calling this function is:
411		732
412	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	733	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		734
		735	See C<aio_stat> for info about some potentially helpful extra constants
		736	and functions.
413		737
414	=item aio_link $srcpath, $dstpath, $callback->($status)	738	=item aio_link $srcpath, $dstpath, $callback->($status)
415		739
416	Asynchronously create a new link to the existing object at C<$srcpath> at	740	Asynchronously create a new link to the existing object at C<$srcpath> at
417	the path C<$dstpath> and call the callback with the result code.	741	the path C<$dstpath> and call the callback with the result code.
418		742
		743
419	=item aio_symlink $srcpath, $dstpath, $callback->($status)	744	=item aio_symlink $srcpath, $dstpath, $callback->($status)
420		745
421	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	746	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
422	the path C<$dstpath> and call the callback with the result code.	747	the path C<$dstpath> and call the callback with the result code.
423		748
		749
424	=item aio_readlink $path, $callback->($link)	750	=item aio_readlink $pathname, $callback->($link)
425		751
426	Asynchronously read the symlink specified by C<$path> and pass it to	752	Asynchronously read the symlink specified by C<$path> and pass it to
427	the callback. If an error occurs, nothing or undef gets passed to the	753	the callback. If an error occurs, nothing or undef gets passed to the
428	callback.	754	callback.
429		755
		756
		757	=item aio_realpath $pathname, $callback->($path)
		758
		759	Asynchronously make the path absolute and resolve any symlinks in
		760	C<$path>. The resulting path only consists of directories (same as
		761	L<Cwd::realpath>).
		762
		763	This request can be used to get the absolute path of the current working
		764	directory by passing it a path of F<.> (a single dot).
		765
		766
430	=item aio_rename $srcpath, $dstpath, $callback->($status)	767	=item aio_rename $srcpath, $dstpath, $callback->($status)
431		768
432	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	769	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
433	rename(2) and call the callback with the result code.	770	rename(2) and call the callback with the result code.
434		771
		772	On systems that support the AIO::WD working directory abstraction
		773	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		774	of failing, C<rename> is called on the absolute path of C<$wd>.
		775
		776
		777	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		778
		779	Basically a version of C<aio_rename> with an additional C<$flags>
		780	argument. Calling this with C<$flags=0> is the same as calling
		781	C<aio_rename>.
		782
		783	Non-zero flags are currently only supported on GNU/Linux systems that
		784	support renameat2. Other systems fail with C<ENOSYS> in this case.
		785
		786	The following constants are available (missing ones are, as usual C<0>),
		787	see renameat2(2) for details:
		788
		789	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		790	and C<IO::AIO::RENAME_WHITEOUT>.
		791
		792
		793	=item aio_mkdir $pathname, $mode, $callback->($status)
		794
		795	Asynchronously mkdir (create) a directory and call the callback with
		796	the result code. C<$mode> will be modified by the umask at the time the
		797	request is executed, so do not change your umask.
		798
		799
435	=item aio_rmdir $pathname, $callback->($status)	800	=item aio_rmdir $pathname, $callback->($status)
436		801
437	Asynchronously rmdir (delete) a directory and call the callback with the	802	Asynchronously rmdir (delete) a directory and call the callback with the
438	result code.	803	result code.
		804
		805	On systems that support the AIO::WD working directory abstraction
		806	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		807	C<rmdir> is called on the absolute path of C<$wd>.
		808
439		809
440	=item aio_readdir $pathname, $callback->($entries)	810	=item aio_readdir $pathname, $callback->($entries)
441		811
442	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	812	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	813	directory (i.e. opendir + readdir + closedir). The entries will not be
444	sorted, and will B<NOT> include the C<.> and C<..> entries.	814	sorted, and will B<NOT> include the C<.> and C<..> entries.
445		815
446	The callback a single argument which is either C<undef> or an array-ref	816	The callback is passed a single argument which is either C<undef> or an
447	with the filenames.	817	array-ref with the filenames.
		818
		819
		820	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		821
		822	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		823	tune behaviour and output format. In case of an error, C<$entries> will be
		824	C<undef>.
		825
		826	The flags are a combination of the following constants, ORed together (the
		827	flags will also be passed to the callback, possibly modified):
		828
		829	=over 4
		830
		831	=item IO::AIO::READDIR_DENTS
		832
		833	Normally the callback gets an arrayref consisting of names only (as
		834	with C<aio_readdir>). If this flag is set, then the callback gets an
		835	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
		836	single directory entry in more detail:
		837
		838	C<$name> is the name of the entry.
		839
		840	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		841
		842	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		843	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		844	C<IO::AIO::DT_WHT>.
		845
		846	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		847	to know, you have to run stat yourself. Also, for speed/memory reasons,
		848	the C<$type> scalars are read-only: you must not modify them.
		849
		850	C<$inode> is the inode number (which might not be exact on systems with 64
		851	bit inode numbers and 32 bit perls). This field has unspecified content on
		852	systems that do not deliver the inode information.
		853
		854	=item IO::AIO::READDIR_DIRS_FIRST
		855
		856	When this flag is set, then the names will be returned in an order where
		857	likely directories come first, in optimal stat order. This is useful when
		858	you need to quickly find directories, or you want to find all directories
		859	while avoiding to stat() each entry.
		860
		861	If the system returns type information in readdir, then this is used
		862	to find directories directly. Otherwise, likely directories are names
		863	beginning with ".", or otherwise names with no dots, of which names with
		864	short names are tried first.
		865
		866	=item IO::AIO::READDIR_STAT_ORDER
		867
		868	When this flag is set, then the names will be returned in an order
		869	suitable for stat()'ing each one. That is, when you plan to stat() most or
		870	all files in the given directory, then the returned order will likely be
		871	faster.
		872
		873	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
		874	then the likely dirs come first, resulting in a less optimal stat order
		875	for stat'ing all entries, but likely a more optimal order for finding
		876	subdirectories.
		877
		878	=item IO::AIO::READDIR_FOUND_UNKNOWN
		879
		880	This flag should not be set when calling C<aio_readdirx>. Instead, it
		881	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		882	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		883	C<$type>'s are known, which can be used to speed up some algorithms.
		884
		885	=back
		886
		887
		888	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		889
		890	Opens, reads and closes the given file. The data is put into C<$data>,
		891	which is resized as required.
		892
		893	If C<$offset> is negative, then it is counted from the end of the file.
		894
		895	If C<$length> is zero, then the remaining length of the file is
		896	used. Also, in this case, the same limitations to modifying C<$data> apply
		897	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		898	with C<substr>. If the size of the file is known, specifying a non-zero
		899	C<$length> results in a performance advantage.
		900
		901	This request is similar to the older C<aio_load> request, but since it is
		902	a single request, it might be more efficient to use.
		903
		904	Example: load F</etc/passwd> into C<$passwd>.
		905
		906	my $passwd;
		907	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		908	$_[0] >= 0
		909	or die "/etc/passwd: $!\n";
		910
		911	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		912	print $passwd;
		913	};
		914	IO::AIO::flush;
		915
		916
		917	=item aio_load $pathname, $data, $callback->($status)
		918
		919	This is a composite request that tries to fully load the given file into
		920	memory. Status is the same as with aio_read.
		921
		922	Using C<aio_slurp> might be more efficient, as it is a single request.
		923
		924	=cut
		925
		926	sub aio_load($$;$) {
		927	my ($path, undef, $cb) = @_;
		928	my $data = \$_[1];
		929
		930	my $pri = aioreq_pri;
		931	my $grp = aio_group $cb;
		932
		933	aioreq_pri $pri;
		934	add $grp aio_open $path, O_RDONLY, 0, sub {
		935	my $fh = shift
		936	or return $grp->result (-1);
		937
		938	aioreq_pri $pri;
		939	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		940	$grp->result ($_[0]);
		941	};
		942	};
		943
		944	$grp
		945	}
448		946
449	=item aio_copy $srcpath, $dstpath, $callback->($status)	947	=item aio_copy $srcpath, $dstpath, $callback->($status)
450		948
451	Try to copy the I<file> (directories not supported as either source or	949	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	950	destination) from C<$srcpath> to C<$dstpath> and call the callback with
453	the C<0> (error) or C<-1> ok.	951	a status of C<0> (ok) or C<-1> (error, see C<$!>).
454		952
		953	Existing destination files will be truncated.
		954
455	This is a composite request that it creates the destination file with	955	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	956	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	957	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
458	uid/gid, in that order.	958	uid/gid, in that order.
459		959
460	If an error occurs, the partial destination file will be unlinked, if	960	If an error occurs, the partial destination file will be unlinked, if
…		…
462	errors are being ignored.	962	errors are being ignored.
463		963
464	=cut	964	=cut
465		965
466	sub aio_copy($$;$) {	966	sub aio_copy($$;$) {
467	aio_block {
468	my ($src, $dst, $cb) = @_;	967	my ($src, $dst, $cb) = @_;
469		968
470	my $pri = aioreq_pri;	969	my $pri = aioreq_pri;
471	my $grp = aio_group $cb;	970	my $grp = aio_group $cb;
472		971
473	aioreq_pri $pri;	972	aioreq_pri $pri;
474	add $grp aio_open $src, O_RDONLY, 0, sub {	973	add $grp aio_open $src, O_RDONLY, 0, sub {
475	if (my $src_fh = $_[0]) {	974	if (my $src_fh = $_[0]) {
476	my @stat = stat $src_fh;	975	my @stat = stat $src_fh; # hmm, might block over nfs?
477		976
478	aioreq_pri $pri;	977	aioreq_pri $pri;
479	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	978	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
480	if (my $dst_fh = $_[0]) {	979	if (my $dst_fh = $_[0]) {
481	aioreq_pri $pri;	980	aioreq_pri $pri;
482	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	981	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
483	if ($_[0] == $stat[7]) {	982	if ($_[0] == $stat[7]) {
484	$grp->result (0);	983	$grp->result (0);
485	close $src_fh;	984	close $src_fh;
486		985
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 {	986	my $ch = sub {
493	$grp->result (-1);
494	close $src_fh;
495	close $dst_fh;
496
497	aioreq $pri;	987	aioreq_pri $pri;
		988	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		989	aioreq_pri $pri;
		990	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		991	aioreq_pri $pri;
498	add $grp aio_unlink $dst;	992	add $grp aio_close $dst_fh;
		993	}
		994	};
499	}	995	};
		996
		997	aioreq_pri $pri;
		998	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		999	if ($_[0] < 0 && $! == ENOSYS) {
		1000	aioreq_pri $pri;
		1001	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1002	} else {
		1003	$ch->();
		1004	}
		1005	};
		1006	} else {
		1007	$grp->result (-1);
		1008	close $src_fh;
		1009	close $dst_fh;
		1010
		1011	aioreq $pri;
		1012	add $grp aio_unlink $dst;
500	};	1013	}
501	} else {
502	$grp->result (-1);
503	}	1014	};
		1015	} else {
		1016	$grp->result (-1);
504	},	1017	}
505
506	} else {
507	$grp->result (-1);
508	}	1018	},
		1019
		1020	} else {
		1021	$grp->result (-1);
509	};	1022	}
510
511	$grp
512	}	1023	};
		1024
		1025	$grp
513	}	1026	}
514		1027
515	=item aio_move $srcpath, $dstpath, $callback->($status)	1028	=item aio_move $srcpath, $dstpath, $callback->($status)
516		1029
517	Try to move the I<file> (directories not supported as either source or	1030	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	1031	destination) from C<$srcpath> to C<$dstpath> and call the callback with
519	the C<0> (error) or C<-1> ok.	1032	a status of C<0> (ok) or C<-1> (error, see C<$!>).
520		1033
521	This is a composite request that tries to rename(2) the file first. If	1034	This is a composite request that tries to rename(2) the file first; if
522	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1035	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
523	that is successful, unlinking the C<$srcpath>.	1036	that is successful, unlinks the C<$srcpath>.
524		1037
525	=cut	1038	=cut
526		1039
527	sub aio_move($$;$) {	1040	sub aio_move($$;$) {
528	aio_block {
529	my ($src, $dst, $cb) = @_;	1041	my ($src, $dst, $cb) = @_;
530		1042
531	my $pri = aioreq_pri;	1043	my $pri = aioreq_pri;
532	my $grp = aio_group $cb;	1044	my $grp = aio_group $cb;
533		1045
534	aioreq_pri $pri;	1046	aioreq_pri $pri;
535	add $grp aio_rename $src, $dst, sub {	1047	add $grp aio_rename $src, $dst, sub {
536	if ($_[0] && $! == EXDEV) {	1048	if ($_[0] && $! == EXDEV) {
537	aioreq_pri $pri;	1049	aioreq_pri $pri;
538	add $grp aio_copy $src, $dst, sub {	1050	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]);	1051	$grp->result ($_[0]);
		1052
		1053	unless ($_[0]) {
		1054	aioreq_pri $pri;
		1055	add $grp aio_unlink $src;
		1056	}
548	}	1057	};
		1058	} else {
		1059	$grp->result ($_[0]);
549	};	1060	}
550
551	$grp
552	}	1061	};
		1062
		1063	$grp
553	}	1064	}
554		1065
555	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1066	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
556		1067
557	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1068	Scans a directory (similar to C<aio_readdir>) but additionally tries to
558	efficiently separate the entries of directory C<$path> into two sets of	1069	efficiently separate the entries of directory C<$path> into two sets of
559	names, directories you can recurse into (directories), and ones you cannot	1070	names, directories you can recurse into (directories), and ones you cannot
560	recurse into (everything else, including symlinks to directories).	1071	recurse into (everything else, including symlinks to directories).
561		1072
562	C<aio_scandir> is a composite request that creates of many sub requests_	1073	C<aio_scandir> is a composite request that generates many sub requests.
563	C<$maxreq> specifies the maximum number of outstanding aio requests that	1074	C<$maxreq> specifies the maximum number of outstanding aio requests that
564	this function generates. If it is C<< <= 0 >>, then a suitable default	1075	this function generates. If it is C<< <= 0 >>, then a suitable default
565	will be chosen (currently 4).	1076	will be chosen (currently 4).
566		1077
567	On error, the callback is called without arguments, otherwise it receives	1078	On error, the callback is called without arguments, otherwise it receives
…		…
577		1088
578	Implementation notes.	1089	Implementation notes.
579		1090
580	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1091	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
581		1092
		1093	If readdir returns file type information, then this is used directly to
		1094	find directories.
		1095
582	After reading the directory, the modification time, size etc. of the	1096	Otherwise, after reading the directory, the modification time, size etc.
583	directory before and after the readdir is checked, and if they match (and	1097	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	1098	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	1099	how many entries are directories (if >= 2). Otherwise, no knowledge of the
586	of subdirectories will be assumed.	1100	number of subdirectories will be assumed.
587		1101
588	Then entries will be sorted into likely directories (everything without	1102	Then entries will be sorted into likely directories a non-initial dot
589	a non-initial dot currently) and likely non-directories (everything	1103	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,	1104	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	1105	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	1106	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	1107	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	1108	filesystems might detect the type of the entry without reading the inode
595	data (e.g. ext2fs filetype feature).	1109	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1110	the filetype information on readdir.
596		1111
597	If the known number of directories (link count - 2) has been reached, the	1112	If the known number of directories (link count - 2) has been reached, the
598	rest of the entries is assumed to be non-directories.	1113	rest of the entries is assumed to be non-directories.
599		1114
600	This only works with certainty on POSIX (= UNIX) filesystems, which	1115	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	1119	as those tend to return 0 or 1 as link counts, which disables the
605	directory counting heuristic.	1120	directory counting heuristic.
606		1121
607	=cut	1122	=cut
608		1123
609	sub aio_scandir($$$) {	1124	sub aio_scandir($$;$) {
610	aio_block {
611	my ($path, $maxreq, $cb) = @_;	1125	my ($path, $maxreq, $cb) = @_;
612		1126
613	my $pri = aioreq_pri;	1127	my $pri = aioreq_pri;
614		1128
615	my $grp = aio_group $cb;	1129	my $grp = aio_group $cb;
616		1130
617	$maxreq = 4 if $maxreq <= 0;	1131	$maxreq = 4 if $maxreq <= 0;
		1132
		1133	# get a wd object
		1134	aioreq_pri $pri;
		1135	add $grp aio_wd $path, sub {
		1136	$_[0]
		1137	or return $grp->result ();
		1138
		1139	my $wd = [shift, "."];
618		1140
619	# stat once	1141	# stat once
620	aioreq_pri $pri;	1142	aioreq_pri $pri;
621	add $grp aio_stat $path, sub {	1143	add $grp aio_stat $wd, sub {
622	return $grp->result () if $_[0];	1144	return $grp->result () if $_[0];
623	my $now = time;	1145	my $now = time;
624	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1146	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1147	my $rdxflags = READDIR_DIRS_FIRST;
		1148
		1149	if ((stat _)[3] < 2) {
		1150	# at least one non-POSIX filesystem exists
		1151	# that returns useful DT_type values: btrfs,
		1152	# so optimise for this here by requesting dents
		1153	$rdxflags |= READDIR_DENTS;
		1154	}
625		1155
626	# read the directory entries	1156	# read the directory entries
627	aioreq_pri $pri;	1157	aioreq_pri $pri;
628	add $grp aio_readdir $path, sub {	1158	add $grp aio_readdirx $wd, $rdxflags, sub {
629	my $entries = shift	1159	my ($entries, $flags) = @_
630	or return $grp->result ();	1160	or return $grp->result ();
		1161
		1162	if ($rdxflags & READDIR_DENTS) {
		1163	# if we requested type values, see if we can use them directly.
		1164
		1165	# if there were any DT_UNKNOWN entries then we assume we
		1166	# don't know. alternatively, we could assume that if we get
		1167	# one DT_DIR, then all directories are indeed marked with
		1168	# DT_DIR, but this seems not required for btrfs, and this
		1169	# is basically the "btrfs can't get it's act together" code
		1170	# branch.
		1171	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1172	# now we have valid DT_ information for all entries,
		1173	# so use it as an optimisation without further stat's.
		1174	# they must also all be at the beginning of @$entries
		1175	# by now.
		1176
		1177	my $dirs;
		1178
		1179	if (@$entries) {
		1180	for (0 .. $#$entries) {
		1181	if ($entries->[$_][1] != DT_DIR) {
		1182	# splice out directories
		1183	$dirs = [splice @$entries, 0, $_];
		1184	last;
		1185	}
		1186	}
		1187
		1188	# if we didn't find any non-dir, then all entries are dirs
		1189	unless ($dirs) {
		1190	($dirs, $entries) = ($entries, []);
		1191	}
		1192	} else {
		1193	# directory is empty, so there are no sbdirs
		1194	$dirs = [];
		1195	}
		1196
		1197	# either splice'd the directories out or the dir was empty.
		1198	# convert dents to filenames
		1199	$_ = $_->[0] for @$dirs;
		1200	$_ = $_->[0] for @$entries;
		1201
		1202	return $grp->result ($dirs, $entries);
		1203	}
		1204
		1205	# cannot use, so return to our old ways
		1206	# by pretending we only scanned for names.
		1207	$_ = $_->[0] for @$entries;
		1208	}
631		1209
632	# stat the dir another time	1210	# stat the dir another time
633	aioreq_pri $pri;	1211	aioreq_pri $pri;
634	add $grp aio_stat $path, sub {	1212	add $grp aio_stat $wd, sub {
635	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1213	my $hash2 = join ":", (stat _)[0,1,3,7,9];
636		1214
637	my $ndirs;	1215	my $ndirs;
638		1216
639	# take the slow route if anything looks fishy	1217	# take the slow route if anything looks fishy
640	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1218	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
641	$ndirs = -1;	1219	$ndirs = -1;
642	} else {	1220	} else {
643	# if nlink == 2, we are finished	1221	# if nlink == 2, we are finished
644	# on non-posix-fs's, we rely on nlink < 2	1222	# for non-posix-fs's, we rely on nlink < 2
645	$ndirs = (stat _)[3] - 2	1223	$ndirs = (stat _)[3] - 2
646	or return $grp->result ([], $entries);	1224	or return $grp->result ([], $entries);
647	}	1225	}
648		1226
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);	1227	my (@dirs, @nondirs);
657		1228
658	my $statgrp = add $grp aio_group sub {	1229	my $statgrp = add $grp aio_group sub {
659	$grp->result (\@dirs, \@nondirs);	1230	$grp->result (\@dirs, \@nondirs);
660	};	1231	};
661		1232
662	limit $statgrp $maxreq;	1233	limit $statgrp $maxreq;
663	feed $statgrp sub {	1234	feed $statgrp sub {
664	return unless @$entries;	1235	return unless @$entries;
665	my $entry = pop @$entries;	1236	my $entry = shift @$entries;
666		1237
667	aioreq_pri $pri;	1238	aioreq_pri $pri;
		1239	$wd->[1] = "$entry/.";
668	add $statgrp aio_stat "$path/$entry/.", sub {	1240	add $statgrp aio_stat $wd, sub {
669	if ($_[0] < 0) {	1241	if ($_[0] < 0) {
670	push @nondirs, $entry;	1242	push @nondirs, $entry;
671	} else {	1243	} else {
672	# need to check for real directory	1244	# need to check for real directory
673	aioreq_pri $pri;	1245	aioreq_pri $pri;
		1246	$wd->[1] = $entry;
674	add $statgrp aio_lstat "$path/$entry", sub {	1247	add $statgrp aio_lstat $wd, sub {
675	if (-d _) {	1248	if (-d _) {
676	push @dirs, $entry;	1249	push @dirs, $entry;
677		1250
678	unless (--$ndirs) {	1251	unless (--$ndirs) {
679	push @nondirs, @$entries;	1252	push @nondirs, @$entries;
…		…
687	};	1260	};
688	};	1261	};
689	};	1262	};
690	};	1263	};
691	};	1264	};
692
693	$grp
694	}	1265	};
		1266
		1267	$grp
695	}	1268	}
		1269
		1270	=item aio_rmtree $pathname, $callback->($status)
		1271
		1272	Delete a directory tree starting (and including) C<$path>, return the
		1273	status of the final C<rmdir> only. This is a composite request that
		1274	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1275	everything else.
		1276
		1277	=cut
		1278
		1279	sub aio_rmtree;
		1280	sub aio_rmtree($;$) {
		1281	my ($path, $cb) = @_;
		1282
		1283	my $pri = aioreq_pri;
		1284	my $grp = aio_group $cb;
		1285
		1286	aioreq_pri $pri;
		1287	add $grp aio_scandir $path, 0, sub {
		1288	my ($dirs, $nondirs) = @_;
		1289
		1290	my $dirgrp = aio_group sub {
		1291	add $grp aio_rmdir $path, sub {
		1292	$grp->result ($_[0]);
		1293	};
		1294	};
		1295
		1296	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1297	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1298
		1299	add $grp $dirgrp;
		1300	};
		1301
		1302	$grp
		1303	}
		1304
		1305	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1306
		1307	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1308
		1309	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1310	they execute asynchronously and pass the return value to the callback.
		1311
		1312	Both calls can be used for a lot of things, some of which make more sense
		1313	to run asynchronously in their own thread, while some others make less
		1314	sense. For example, calls that block waiting for external events, such
		1315	as locking, will also lock down an I/O thread while it is waiting, which
		1316	can deadlock the whole I/O system. At the same time, there might be no
		1317	alternative to using a thread to wait.
		1318
		1319	So in general, you should only use these calls for things that do
		1320	(filesystem) I/O, not for things that wait for other events (network,
		1321	other processes), although if you are careful and know what you are doing,
		1322	you still can.
		1323
		1324	The following constants are available and can be used for normal C<ioctl>
		1325	and C<fcntl> as well (missing ones are, as usual C<0>):
		1326
		1327	C<F_DUPFD_CLOEXEC>,
		1328
		1329	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1330
		1331	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1332
		1333	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1334	C<F_SEAL_WRITE>.
		1335
		1336	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1337	C<FS_IOC_FIEMAP>.
		1338
		1339	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1340	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1341
		1342	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1343	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1344	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1345	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1346	C<FS_FL_USER_MODIFIABLE>.
		1347
		1348	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1349	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1350	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1351	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1352
		1353	C<BLKROSET>, C<BLKROGET>, C<BLKRRPART>, C<BLKGETSIZE>, C<BLKFLSBUF>, C<BLKRASET>,
		1354	C<BLKRAGET>, C<BLKFRASET>, C<BLKFRAGET>, C<BLKSECTSET>, C<BLKSECTGET>, C<BLKSSZGET>,
		1355	C<BLKBSZGET>, C<BLKBSZSET>, C<BLKGETSIZE64>,
		1356
		1357
		1358	=item aio_sync $callback->($status)
		1359
		1360	Asynchronously call sync and call the callback when finished.
696		1361
697	=item aio_fsync $fh, $callback->($status)	1362	=item aio_fsync $fh, $callback->($status)
698		1363
699	Asynchronously call fsync on the given filehandle and call the callback	1364	Asynchronously call fsync on the given filehandle and call the callback
700	with the fsync result code.	1365	with the fsync result code.
…		…
704	Asynchronously call fdatasync on the given filehandle and call the	1369	Asynchronously call fdatasync on the given filehandle and call the
705	callback with the fdatasync result code.	1370	callback with the fdatasync result code.
706		1371
707	If this call isn't available because your OS lacks it or it couldn't be	1372	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.	1373	detected, it will be emulated by calling C<fsync> instead.
		1374
		1375	=item aio_syncfs $fh, $callback->($status)
		1376
		1377	Asynchronously call the syncfs syscall to sync the filesystem associated
		1378	to the given filehandle and call the callback with the syncfs result
		1379	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1380	errno to C<ENOSYS> nevertheless.
		1381
		1382	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1383
		1384	Sync the data portion of the file specified by C<$offset> and C<$length>
		1385	to disk (but NOT the metadata), by calling the Linux-specific
		1386	sync_file_range call. If sync_file_range is not available or it returns
		1387	ENOSYS, then fdatasync or fsync is being substituted.
		1388
		1389	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1390	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1391	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1392	manpage for details.
		1393
		1394	=item aio_pathsync $pathname, $callback->($status)
		1395
		1396	This request tries to open, fsync and close the given path. This is a
		1397	composite request intended to sync directories after directory operations
		1398	(E.g. rename). This might not work on all operating systems or have any
		1399	specific effect, but usually it makes sure that directory changes get
		1400	written to disc. It works for anything that can be opened for read-only,
		1401	not just directories.
		1402
		1403	Future versions of this function might fall back to other methods when
		1404	C<fsync> on the directory fails (such as calling C<sync>).
		1405
		1406	Passes C<0> when everything went ok, and C<-1> on error.
		1407
		1408	=cut
		1409
		1410	sub aio_pathsync($;$) {
		1411	my ($path, $cb) = @_;
		1412
		1413	my $pri = aioreq_pri;
		1414	my $grp = aio_group $cb;
		1415
		1416	aioreq_pri $pri;
		1417	add $grp aio_open $path, O_RDONLY, 0, sub {
		1418	my ($fh) = @_;
		1419	if ($fh) {
		1420	aioreq_pri $pri;
		1421	add $grp aio_fsync $fh, sub {
		1422	$grp->result ($_[0]);
		1423
		1424	aioreq_pri $pri;
		1425	add $grp aio_close $fh;
		1426	};
		1427	} else {
		1428	$grp->result (-1);
		1429	}
		1430	};
		1431
		1432	$grp
		1433	}
		1434
		1435	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1436
		1437	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1438	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1439	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1440	scalar must only be modified in-place while an aio operation is pending on
		1441	it).
		1442
		1443	It calls the C<msync> function of your OS, if available, with the memory
		1444	area starting at C<$offset> in the string and ending C<$length> bytes
		1445	later. If C<$length> is negative, counts from the end, and if C<$length>
		1446	is C<undef>, then it goes till the end of the string. The flags can be
		1447	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1448	C<IO::AIO::MS_INVALIDATE>.
		1449
		1450	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1451
		1452	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1453	scalars.
		1454
		1455	It touches (reads or writes) all memory pages in the specified
		1456	range inside the scalar. All caveats and parameters are the same
		1457	as for C<aio_msync>, above, except for flags, which must be either
		1458	C<0> (which reads all pages and ensures they are instantiated) or
		1459	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1460	writing an octet from it, which dirties the page).
		1461
		1462	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1463
		1464	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1465	scalars.
		1466
		1467	It reads in all the pages of the underlying storage into memory (if any)
		1468	and locks them, so they are not getting swapped/paged out or removed.
		1469
		1470	If C<$length> is undefined, then the scalar will be locked till the end.
		1471
		1472	On systems that do not implement C<mlock>, this function returns C<-1>
		1473	and sets errno to C<ENOSYS>.
		1474
		1475	Note that the corresponding C<munlock> is synchronous and is
		1476	documented under L<MISCELLANEOUS FUNCTIONS>.
		1477
		1478	Example: open a file, mmap and mlock it - both will be undone when
		1479	C<$data> gets destroyed.
		1480
		1481	open my $fh, "<", $path or die "$path: $!";
		1482	my $data;
		1483	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1484	aio_mlock $data; # mlock in background
		1485
		1486	=item aio_mlockall $flags, $callback->($status)
		1487
		1488	Calls the C<mlockall> function with the given C<$flags> (a
		1489	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1490	C<IO::AIO::MCL_ONFAULT>).
		1491
		1492	On systems that do not implement C<mlockall>, this function returns C<-1>
		1493	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1494	by the system result in a return value of C<-1> with errno being set to
		1495	C<EINVAL>.
		1496
		1497	Note that the corresponding C<munlockall> is synchronous and is
		1498	documented under L<MISCELLANEOUS FUNCTIONS>.
		1499
		1500	Example: asynchronously lock all current and future pages into memory.
		1501
		1502	aio_mlockall IO::AIO::MCL_FUTURE;
		1503
		1504	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1505
		1506	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1507	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1508	the ioctl is not available on your OS, then this request will fail with
		1509	C<ENOSYS>.
		1510
		1511	C<$start> is the starting offset to query extents for, C<$length> is the
		1512	size of the range to query - if it is C<undef>, then the whole file will
		1513	be queried.
		1514
		1515	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1516	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1517	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1518	the data portion.
		1519
		1520	C<$count> is the maximum number of extent records to return. If it is
		1521	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1522	case, if it is C<0>, then the callback receives the number of extents
		1523	instead of the extents themselves (which is unreliable, see below).
		1524
		1525	If an error occurs, the callback receives no arguments. The special
		1526	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1527
		1528	Otherwise, the callback receives an array reference with extent
		1529	structures. Each extent structure is an array reference itself, with the
		1530	following members:
		1531
		1532	[$logical, $physical, $length, $flags]
		1533
		1534	Flags is any combination of the following flag values (typically either C<0>
		1535	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1536
		1537	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1538	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1539	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1540	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1541	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1542	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1543
		1544	At the time of this writing (Linux 3.2), this request is unreliable unless
		1545	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1546	it to return all extents of a range for files with a large number of
		1547	extents. The code (only) works around all these issues if C<$count> is
		1548	C<undef>.
709		1549
710	=item aio_group $callback->(...)	1550	=item aio_group $callback->(...)
711		1551
712	This is a very special aio request: Instead of doing something, it is a	1552	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	1553	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	1591	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.	1592	except to put your application under artificial I/O pressure.
753		1593
754	=back	1594	=back
755		1595
		1596
		1597	=head2 IO::AIO::WD - multiple working directories
		1598
		1599	Your process only has one current working directory, which is used by all
		1600	threads. This makes it hard to use relative paths (some other component
		1601	could call C<chdir> at any time, and it is hard to control when the path
		1602	will be used by IO::AIO).
		1603
		1604	One solution for this is to always use absolute paths. This usually works,
		1605	but can be quite slow (the kernel has to walk the whole path on every
		1606	access), and can also be a hassle to implement.
		1607
		1608	Newer POSIX systems have a number of functions (openat, fdopendir,
		1609	futimensat and so on) that make it possible to specify working directories
		1610	per operation.
		1611
		1612	For portability, and because the clowns who "designed", or shall I write,
		1613	perpetrated this new interface were obviously half-drunk, this abstraction
		1614	cannot be perfect, though.
		1615
		1616	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1617	object. This object stores the canonicalised, absolute version of the
		1618	path, and on systems that allow it, also a directory file descriptor.
		1619
		1620	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1621	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1622	object and a pathname instead (or the IO::AIO::WD object alone, which
		1623	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1624	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1625	to that IO::AIO::WD object.
		1626
		1627	For example, to get a wd object for F</etc> and then stat F<passwd>
		1628	inside, you would write:
		1629
		1630	aio_wd "/etc", sub {
		1631	my $etcdir = shift;
		1632
		1633	# although $etcdir can be undef on error, there is generally no reason
		1634	# to check for errors here, as aio_stat will fail with ENOENT
		1635	# when $etcdir is undef.
		1636
		1637	aio_stat [$etcdir, "passwd"], sub {
		1638	# yay
		1639	};
		1640	};
		1641
		1642	The fact that C<aio_wd> is a request and not a normal function shows that
		1643	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1644	which is why it is done asynchronously.
		1645
		1646	To stat the directory obtained with C<aio_wd> above, one could write
		1647	either of the following three request calls:
		1648
		1649	aio_lstat "/etc" , sub { ... # pathname as normal string
		1650	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1651	aio_lstat $wd , sub { ... # shorthand for the previous
		1652
		1653	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1654	object and the pathname string, so you could write the following without
		1655	causing any issues due to C<$path> getting reused:
		1656
		1657	my $path = [$wd, undef];
		1658
		1659	for my $name (qw(abc def ghi)) {
		1660	$path->[1] = $name;
		1661	aio_stat $path, sub {
		1662	# ...
		1663	};
		1664	}
		1665
		1666	There are some caveats: when directories get renamed (or deleted), the
		1667	pathname string doesn't change, so will point to the new directory (or
		1668	nowhere at all), while the directory fd, if available on the system,
		1669	will still point to the original directory. Most functions accepting a
		1670	pathname will use the directory fd on newer systems, and the string on
		1671	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1672	the string form of the pathname.
		1673
		1674	So this functionality is mainly useful to get some protection against
		1675	C<chdir>, to easily get an absolute path out of a relative path for future
		1676	reference, and to speed up doing many operations in the same directory
		1677	(e.g. when stat'ing all files in a directory).
		1678
		1679	The following functions implement this working directory abstraction:
		1680
		1681	=over 4
		1682
		1683	=item aio_wd $pathname, $callback->($wd)
		1684
		1685	Asynchonously canonicalise the given pathname and convert it to an
		1686	IO::AIO::WD object representing it. If possible and supported on the
		1687	system, also open a directory fd to speed up pathname resolution relative
		1688	to this working directory.
		1689
		1690	If something goes wrong, then C<undef> is passwd to the callback instead
		1691	of a working directory object and C<$!> is set appropriately. Since
		1692	passing C<undef> as working directory component of a pathname fails the
		1693	request with C<ENOENT>, there is often no need for error checking in the
		1694	C<aio_wd> callback, as future requests using the value will fail in the
		1695	expected way.
		1696
		1697	=item IO::AIO::CWD
		1698
		1699	This is a compile time constant (object) that represents the process
		1700	current working directory.
		1701
		1702	Specifying this object as working directory object for a pathname is as if
		1703	the pathname would be specified directly, without a directory object. For
		1704	example, these calls are functionally identical:
		1705
		1706	aio_stat "somefile", sub { ... };
		1707	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1708
		1709	=back
		1710
		1711	To recover the path associated with an IO::AIO::WD object, you can use
		1712	C<aio_realpath>:
		1713
		1714	aio_realpath $wd, sub {
		1715	warn "path is $_[0]\n";
		1716	};
		1717
		1718	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1719	sometimes, fall back to using an absolue path.
		1720
756	=head2 IO::AIO::REQ CLASS	1721	=head2 IO::AIO::REQ CLASS
757		1722
758	All non-aggregate C<aio_*> functions return an object of this class when	1723	All non-aggregate C<aio_*> functions return an object of this class when
759	called in non-void context.	1724	called in non-void context.
760		1725
…		…
763	=item cancel $req	1728	=item cancel $req
764		1729
765	Cancels the request, if possible. Has the effect of skipping execution	1730	Cancels the request, if possible. Has the effect of skipping execution
766	when entering the B<execute> state and skipping calling the callback when	1731	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	1732	entering the the B<result> state, but will leave the request otherwise
768	untouched. That means that requests that currently execute will not be	1733	untouched (with the exception of readdir). That means that requests that
769	stopped and resources held by the request will not be freed prematurely.	1734	currently execute will not be stopped and resources held by the request
		1735	will not be freed prematurely.
770		1736
771	=item cb $req $callback->(...)	1737	=item cb $req $callback->(...)
772		1738
773	Replace (or simply set) the callback registered to the request.	1739	Replace (or simply set) the callback registered to the request.
774		1740
…		…
825	Their lifetime, simplified, looks like this: when they are empty, they	1791	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	1792	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	1793	C<done> state, they will also finish. Otherwise they will continue to
828	exist.	1794	exist.
829		1795
830	That means after creating a group you have some time to add requests. And	1796	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	1797	(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	1798	the C<poll_cb>). And in the callbacks of those requests, you can add
833	itself finish.	1799	further requests to the group. And only when all those requests have
		1800	finished will the the group itself finish.
834		1801
835	=over 4	1802	=over 4
836		1803
837	=item add $grp ...	1804	=item add $grp ...
838		1805
…		…
847	=item $grp->cancel_subs	1814	=item $grp->cancel_subs
848		1815
849	Cancel all subrequests and clears any feeder, but not the group request	1816	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.	1817	itself. Useful when you queued a lot of events but got a result early.
851		1818
		1819	The group request will finish normally (you cannot add requests to the
		1820	group).
		1821
852	=item $grp->result (...)	1822	=item $grp->result (...)
853		1823
854	Set the result value(s) that will be passed to the group callback when all	1824	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	1825	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,	1826	of errno (just like calling C<errno> without an error number). By default,
857	no argument will be passed and errno is zero.	1827	no argument will be passed and errno is zero.
858		1828
859	=item $grp->errno ([$errno])	1829	=item $grp->errno ([$errno])
860		1830
…		…
871	=item feed $grp $callback->($grp)	1841	=item feed $grp $callback->($grp)
872		1842
873	Sets a feeder/generator on this group: every group can have an attached	1843	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,	1844	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,	1845	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	1846	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>	1847	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
878	requests, delaying any later requests for a long time.	1848	requests, delaying any later requests for a long time.
879		1849
880	To avoid this, and allow incremental generation of requests, you can	1850	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	1851	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>,	1852	feed callback will be called whenever there are few enough (see C<limit>,
…		…
887	not impose any limits).	1857	not impose any limits).
888		1858
889	If the feed does not queue more requests when called, it will be	1859	If the feed does not queue more requests when called, it will be
890	automatically removed from the group.	1860	automatically removed from the group.
891		1861
892	If the feed limit is C<0>, it will be set to C<2> automatically.	1862	If the feed limit is C<0> when this method is called, it will be set to
		1863	C<2> automatically.
893		1864
894	Example:	1865	Example:
895		1866
896	# stat all files in @files, but only ever use four aio requests concurrently:	1867	# stat all files in @files, but only ever use four aio requests concurrently:
897		1868
…		…
909	Sets the feeder limit for the group: The feeder will be called whenever	1880	Sets the feeder limit for the group: The feeder will be called whenever
910	the group contains less than this many requests.	1881	the group contains less than this many requests.
911		1882
912	Setting the limit to C<0> will pause the feeding process.	1883	Setting the limit to C<0> will pause the feeding process.
913		1884
		1885	The default value for the limit is C<0>, but note that setting a feeder
		1886	automatically bumps it up to C<2>.
		1887
914	=back	1888	=back
915		1889
		1890
916	=head2 SUPPORT FUNCTIONS	1891	=head2 SUPPORT FUNCTIONS
917		1892
918	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1893	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
919		1894
920	=over 4	1895	=over 4
921		1896
922	=item $fileno = IO::AIO::poll_fileno	1897	=item $fileno = IO::AIO::poll_fileno
923		1898
924	Return the I<request result pipe file descriptor>. This filehandle must be	1899	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	1900	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	1901	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
927	to call C<poll_cb> to check the results.	1902	you have to call C<poll_cb> to check the results.
928		1903
929	See C<poll_cb> for an example.	1904	See C<poll_cb> for an example.
930		1905
931	=item IO::AIO::poll_cb	1906	=item IO::AIO::poll_cb
932		1907
933	Process some outstanding events on the result pipe. You have to call this	1908	Process some requests that have reached the result phase (i.e. they have
934	regularly. Returns the number of events processed. Returns immediately	1909	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	1910	this "regularly" to finish outstanding requests.
936	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
937		1911
		1912	Returns C<0> if all events could be processed (or there were no
		1913	events to process), or C<-1> if it returned earlier for whatever
		1914	reason. Returns immediately when no events are outstanding. The amount
		1915	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1916	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1917
938	If not all requests were processed for whatever reason, the filehandle	1918	If not all requests were processed for whatever reason, the poll file
939	will still be ready when C<poll_cb> returns.	1919	descriptor will still be ready when C<poll_cb> returns, so normally you
		1920	don't have to do anything special to have it called later.
		1921
		1922	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1923	ready, it can be beneficial to call this function from loops which submit
		1924	a lot of requests, to make sure the results get processed when they become
		1925	available and not just when the loop is finished and the event loop takes
		1926	over again. This function returns very fast when there are no outstanding
		1927	requests.
940		1928
941	Example: Install an Event watcher that automatically calls	1929	Example: Install an Event watcher that automatically calls
942	IO::AIO::poll_cb with high priority:	1930	IO::AIO::poll_cb with high priority (more examples can be found in the
		1931	SYNOPSIS section, at the top of this document):
943		1932
944	Event->io (fd => IO::AIO::poll_fileno,	1933	Event->io (fd => IO::AIO::poll_fileno,
945	poll => 'r', async => 1,	1934	poll => 'r', async => 1,
946	cb => \&IO::AIO::poll_cb);	1935	cb => \&IO::AIO::poll_cb);
		1936
		1937	=item IO::AIO::poll_wait
		1938
		1939	Wait until either at least one request is in the result phase or no
		1940	requests are outstanding anymore.
		1941
		1942	This is useful if you want to synchronously wait for some requests to
		1943	become ready, without actually handling them.
		1944
		1945	See C<nreqs> for an example.
		1946
		1947	=item IO::AIO::poll
		1948
		1949	Waits until some requests have been handled.
		1950
		1951	Returns the number of requests processed, but is otherwise strictly
		1952	equivalent to:
		1953
		1954	IO::AIO::poll_wait, IO::AIO::poll_cb
		1955
		1956	=item IO::AIO::flush
		1957
		1958	Wait till all outstanding AIO requests have been handled.
		1959
		1960	Strictly equivalent to:
		1961
		1962	IO::AIO::poll_wait, IO::AIO::poll_cb
		1963	while IO::AIO::nreqs;
		1964
		1965	This function can be useful at program aborts, to make sure outstanding
		1966	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1967	this function on normal exits), or when you are merely using C<IO::AIO>
		1968	for its more advanced functions, rather than for async I/O, e.g.:
		1969
		1970	my ($dirs, $nondirs);
		1971	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1972	IO::AIO::flush;
		1973	# $dirs, $nondirs are now set
947		1974
948	=item IO::AIO::max_poll_reqs $nreqs	1975	=item IO::AIO::max_poll_reqs $nreqs
949		1976
950	=item IO::AIO::max_poll_time $seconds	1977	=item IO::AIO::max_poll_time $seconds
951		1978
…		…
976	# use a low priority so other tasks have priority	2003	# use a low priority so other tasks have priority
977	Event->io (fd => IO::AIO::poll_fileno,	2004	Event->io (fd => IO::AIO::poll_fileno,
978	poll => 'r', nice => 1,	2005	poll => 'r', nice => 1,
979	cb => &IO::AIO::poll_cb);	2006	cb => &IO::AIO::poll_cb);
980		2007
981	=item IO::AIO::poll_wait	2008	=back
982		2009
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		2010
1008	=head3 CONTROLLING THE NUMBER OF THREADS	2011	=head3 CONTROLLING THE NUMBER OF THREADS
		2012
		2013	=over
1009		2014
1010	=item IO::AIO::min_parallel $nthreads	2015	=item IO::AIO::min_parallel $nthreads
1011		2016
1012	Set the minimum number of AIO threads to C<$nthreads>. The current	2017	Set the minimum number of AIO threads to C<$nthreads>. The current
1013	default is C<8>, which means eight asynchronous operations can execute	2018	default is C<8>, which means eight asynchronous operations can execute
…		…
1041		2046
1042	Under normal circumstances you don't need to call this function.	2047	Under normal circumstances you don't need to call this function.
1043		2048
1044	=item IO::AIO::max_idle $nthreads	2049	=item IO::AIO::max_idle $nthreads
1045		2050
1046	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2051	Limit the number of threads (default: 4) that are allowed to idle
1047	threads that did not get a request to process within 10 seconds). That	2052	(i.e., threads that did not get a request to process within the idle
1048	means if a thread becomes idle while C<$nthreads> other threads are also	2053	timeout (default: 10 seconds). That means if a thread becomes idle while
1049	idle, it will free its resources and exit.	2054	C<$nthreads> other threads are also idle, it will free its resources and
		2055	exit.
1050		2056
1051	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2057	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	2058	to allow for extremely high load situations, but want to free resources
1053	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2059	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1054		2060
1055	The default is probably ok in most situations, especially if thread	2061	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	2062	creation is fast. If thread creation is very slow on your system you might
1057	want to use larger values.	2063	want to use larger values.
1058		2064
		2065	=item IO::AIO::idle_timeout $seconds
		2066
		2067	Sets the minimum idle timeout (default 10) after which worker threads are
		2068	allowed to exit. SEe C<IO::AIO::max_idle>.
		2069
1059	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	2070	=item IO::AIO::max_outstanding $maxreqs
1060		2071
1061	This is a very bad function to use in interactive programs because it
1062	blocks, and a bad way to reduce concurrency because it is inexact: Better
1063	use an C<aio_group> together with a feed callback.
1064
1065	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2072	Sets the maximum number of outstanding requests to C<$nreqs>. If
1066	to queue up more than this number of requests, the next call to the	2073	you do queue up more than this number of requests, the next call to
1067	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)	2074	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1068	function will block until the limit is no longer exceeded.	2075	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2076	longer exceeded.
1069		2077
1070	The default value is very large, so there is no practical limit on the	2078	In other words, this setting does not enforce a queue limit, but can be
1071	number of outstanding requests.	2079	used to make poll functions block if the limit is exceeded.
1072		2080
1073	You can still queue as many requests as you want. Therefore,	2081	This is a bad function to use in interactive programs because it blocks,
1074	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	2082	and a bad way to reduce concurrency because it is inexact. If you need to
1075	as a stop gap to shield against fatal memory overflow (with large values).	2083	issue many requests without being able to call a poll function on demand,
		2084	it is better to use an C<aio_group> together with a feed callback.
		2085
		2086	Its main use is in scripts without an event loop - when you want to stat a
		2087	lot of files, you can write something like this:
		2088
		2089	IO::AIO::max_outstanding 32;
		2090
		2091	for my $path (...) {
		2092	aio_stat $path , ...;
		2093	IO::AIO::poll_cb;
		2094	}
		2095
		2096	IO::AIO::flush;
		2097
		2098	The call to C<poll_cb> inside the loop will normally return instantly,
		2099	allowing the loop to progress, but as soon as more than C<32> requests
		2100	are in-flight, it will block until some requests have been handled. This
		2101	keeps the loop from pushing a large number of C<aio_stat> requests onto
		2102	the queue (which, with many paths to stat, can use up a lot of memory).
		2103
		2104	The default value for C<max_outstanding> is very large, so there is no
		2105	practical limit on the number of outstanding requests.
		2106
		2107	=back
		2108
1076		2109
1077	=head3 STATISTICAL INFORMATION	2110	=head3 STATISTICAL INFORMATION
		2111
		2112	=over
1078		2113
1079	=item IO::AIO::nreqs	2114	=item IO::AIO::nreqs
1080		2115
1081	Returns the number of requests currently in the ready, execute or pending	2116	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).	2117	states (i.e. for which their callback has not been invoked yet).
…		…
1096	Returns the number of requests currently in the pending state (executed,	2131	Returns the number of requests currently in the pending state (executed,
1097	but not yet processed by poll_cb).	2132	but not yet processed by poll_cb).
1098		2133
1099	=back	2134	=back
1100		2135
		2136
		2137	=head3 SUBSECOND STAT TIME ACCESS
		2138
		2139	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2140	generally find access/modification and change times with subsecond time
		2141	accuracy of the system supports it, but perl's built-in functions only
		2142	return the integer part.
		2143
		2144	The following functions return the timestamps of the most recent
		2145	stat with subsecond precision on most systems and work both after
		2146	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2147	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2148	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2149
		2150	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2151	full resolution without rounding and work with standard perl C<stat>,
		2152	alleviating the need to call the special C<Time::HiRes> functions, which
		2153	do not act like their perl counterparts.
		2154
		2155	On operating systems or file systems where subsecond time resolution is
		2156	not supported or could not be detected, a fractional part of C<0> is
		2157	returned, so it is always safe to call these functions.
		2158
		2159	=over 4
		2160
		2161	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2162
		2163	Return the access, modication, change or birth time, respectively,
		2164	including fractional part. Due to the limited precision of floating point,
		2165	the accuracy on most platforms is only a bit better than milliseconds
		2166	for times around now - see the I<nsec> function family, below, for full
		2167	accuracy.
		2168
		2169	File birth time is only available when the OS and perl support it (on
		2170	FreeBSD and NetBSD at the time of this writing, although support is
		2171	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2172	it). On systems where it isn't available, C<0> is currently returned, but
		2173	this might change to C<undef> in a future version.
		2174
		2175	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2176
		2177	Returns access, modification, change and birth time all in one go, and
		2178	maybe more times in the future version.
		2179
		2180	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2181
		2182	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2183	as an integer in the range C<0> to C<999999999>.
		2184
		2185	Note that no accessors are provided for access, modification and
		2186	change times - you need to get those from C<stat _> if required (C<int
		2187	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2188	value).
		2189
		2190	=item $seconds = IO::AIO::st_btimesec
		2191
		2192	The (integral) seconds part of the file birth time, if available.
		2193
		2194	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2195
		2196	Like the functions above, but returns all four times in one go (and maybe
		2197	more in future versions).
		2198
		2199	=item $counter = IO::AIO::st_gen
		2200
		2201	Returns the generation counter (in practice this is just a random number)
		2202	of the file. This is only available on platforms which have this member in
		2203	their C<struct stat> (most BSDs at the time of this writing) and generally
		2204	only to the root usert. If unsupported, C<0> is returned, but this might
		2205	change to C<undef> in a future version.
		2206
		2207	=back
		2208
		2209	Example: print the high resolution modification time of F</etc>, using
		2210	C<stat>, and C<IO::AIO::aio_stat>.
		2211
		2212	if (stat "/etc") {
		2213	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2214	}
		2215
		2216	IO::AIO::aio_stat "/etc", sub {
		2217	$_[0]
		2218	and return;
		2219
		2220	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2221	};
		2222
		2223	IO::AIO::flush;
		2224
		2225	Output of the awbove on my system, showing reduced and full accuracy:
		2226
		2227	stat(/etc) mtime: 1534043702.020808
		2228	aio_stat(/etc) mtime: 1534043702.020807792
		2229
		2230
		2231	=head3 MISCELLANEOUS FUNCTIONS
		2232
		2233	IO::AIO implements some functions that are useful when you want to use
		2234	some "Advanced I/O" function not available to in Perl, without going the
		2235	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2236	counterpart.
		2237
		2238	=over 4
		2239
		2240	=item $retval = IO::AIO::fexecve $fh, $argv, $envp
		2241
		2242	A more-or-less direct equivalent to the POSIX C<fexecve> functions, which
		2243	allows you to specify the program to be executed via a file descriptor (or
		2244	handle). Returns C<-1> and sets errno to C<ENOSYS> if not available.
		2245
		2246	=item $retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		2247
		2248	Calls the GNU/Linux mount syscall with the given arguments. All except
		2249	C<$flags> are strings, and if C<$data> is C<undef>, a C<NULL> will be
		2250	passed.
		2251
		2252	The following values for C<$flags> are available:
		2253
		2254	C<IO::AIO::MS_RDONLY>, C<IO::AIO::MS_NOSUID>, C<IO::AIO::MS_NODEV>, C<IO::AIO::MS_NOEXEC>, C<IO::AIO::MS_SYNCHRONOUS>,
		2255	C<IO::AIO::MS_REMOUNT>, C<IO::AIO::MS_MANDLOCK>, C<IO::AIO::MS_DIRSYNC>, C<IO::AIO::MS_NOATIME>,
		2256	C<IO::AIO::MS_NODIRATIME>, C<IO::AIO::MS_BIND>, C<IO::AIO::MS_MOVE>, C<IO::AIO::MS_REC>, C<IO::AIO::MS_SILENT>,
		2257	C<IO::AIO::MS_POSIXACL>, C<IO::AIO::MS_UNBINDABLE>, C<IO::AIO::MS_PRIVATE>, C<IO::AIO::MS_SLAVE>, C<IO::AIO::MS_SHARED>,
		2258	C<IO::AIO::MS_RELATIME>, C<IO::AIO::MS_KERNMOUNT>, C<IO::AIO::MS_I_VERSION>, C<IO::AIO::MS_STRICTATIME>,
		2259	C<IO::AIO::MS_LAZYTIME>, C<IO::AIO::MS_ACTIVE>, C<IO::AIO::MS_NOUSER>, C<IO::AIO::MS_RMT_MASK>, C<IO::AIO::MS_MGC_VAL> and
		2260	C<IO::AIO::MS_MGC_MSK>.
		2261
		2262	=item $retval = IO::AIO::umount $path, $flags = 0
		2263
		2264	Invokes the GNU/Linux C<umount> or C<umount2> syscalls. Always calls
		2265	C<umount> if C<$flags> is C<0>, otherwqise always tries to call
		2266	C<umount2>.
		2267
		2268	The following C<$flags> are available:
		2269
		2270	C<IO::AIO::MNT_FORCE>, C<IO::AIO::MNT_DETACH>, C<IO::AIO::MNT_EXPIRE> and C<IO::AIO::UMOUNT_NOFOLLOW>.
		2271
		2272	=item $numfd = IO::AIO::get_fdlimit
		2273
		2274	Tries to find the current file descriptor limit and returns it, or
		2275	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2276	the highest valid file descriptor number.
		2277
		2278	=item IO::AIO::min_fdlimit [$numfd]
		2279
		2280	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2281	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2282	is missing, it will try to set a very high limit, although this is not
		2283	recommended when you know the actual minimum that you require.
		2284
		2285	If the limit cannot be raised enough, the function makes a best-effort
		2286	attempt to increase the limit as much as possible, using various
		2287	tricks, while still failing. You can query the resulting limit using
		2288	C<IO::AIO::get_fdlimit>.
		2289
		2290	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2291	true.
		2292
		2293	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2294
		2295	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2296	but is blocking (this makes most sense if you know the input data is
		2297	likely cached already and the output filehandle is set to non-blocking
		2298	operations).
		2299
		2300	Returns the number of bytes copied, or C<-1> on error.
		2301
		2302	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2303
		2304	Simply calls the C<posix_fadvise> function (see its
		2305	manpage for details). The following advice constants are
		2306	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2307	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2308	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2309
		2310	On systems that do not implement C<posix_fadvise>, this function returns
		2311	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2312
		2313	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2314
		2315	Simply calls the C<posix_madvise> function (see its
		2316	manpage for details). The following advice constants are
		2317	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2318	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2319	C<IO::AIO::MADV_DONTNEED>.
		2320
		2321	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2322	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2323	will be reduced to fit into the C<$scalar>.
		2324
		2325	On systems that do not implement C<posix_madvise>, this function returns
		2326	ENOSYS, otherwise the return value of C<posix_madvise>.
		2327
		2328	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2329
		2330	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2331	$scalar (see its manpage for details). The following protect
		2332	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2333	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2334
		2335	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2336	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2337	will be reduced to fit into the C<$scalar>.
		2338
		2339	On systems that do not implement C<mprotect>, this function returns
		2340	ENOSYS, otherwise the return value of C<mprotect>.
		2341
		2342	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2343
		2344	Memory-maps a file (or anonymous memory range) and attaches it to the
		2345	given C<$scalar>, which will act like a string scalar. Returns true on
		2346	success, and false otherwise.
		2347
		2348	The scalar must exist, but its contents do not matter - this means you
		2349	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2350	the scalar first.
		2351
		2352	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2353	which don't change the string length, and most read-only operations such
		2354	as copying it or searching it with regexes and so on.
		2355
		2356	Anything else is unsafe and will, at best, result in memory leaks.
		2357
		2358	The memory map associated with the C<$scalar> is automatically removed
		2359	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2360	or C<IO::AIO::munmap> functions are called on it.
		2361
		2362	This calls the C<mmap>(2) function internally. See your system's manual
		2363	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2364
		2365	The C<$length> must be larger than zero and smaller than the actual
		2366	filesize.
		2367
		2368	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2369	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2370
		2371	C<$flags> can be a combination of
		2372	C<IO::AIO::MAP_SHARED> or
		2373	C<IO::AIO::MAP_PRIVATE>,
		2374	or a number of system-specific flags (when not available, the are C<0>):
		2375	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2376	C<IO::AIO::MAP_LOCKED>,
		2377	C<IO::AIO::MAP_NORESERVE>,
		2378	C<IO::AIO::MAP_POPULATE>,
		2379	C<IO::AIO::MAP_NONBLOCK>,
		2380	C<IO::AIO::MAP_FIXED>,
		2381	C<IO::AIO::MAP_GROWSDOWN>,
		2382	C<IO::AIO::MAP_32BIT>,
		2383	C<IO::AIO::MAP_HUGETLB>,
		2384	C<IO::AIO::MAP_STACK>,
		2385	C<IO::AIO::MAP_FIXED_NOREPLACE>,
		2386	C<IO::AIO::MAP_SHARED_VALIDATE>,
		2387	C<IO::AIO::MAP_SYNC> or
		2388	C<IO::AIO::MAP_UNINITIALIZED>.
		2389
		2390	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2391
		2392	C<$offset> is the offset from the start of the file - it generally must be
		2393	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2394
		2395	Example:
		2396
		2397	use Digest::MD5;
		2398	use IO::AIO;
		2399
		2400	open my $fh, "<verybigfile"
		2401	or die "$!";
		2402
		2403	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2404	or die "verybigfile: $!";
		2405
		2406	my $fast_md5 = md5 $data;
		2407
		2408	=item IO::AIO::munmap $scalar
		2409
		2410	Removes a previous mmap and undefines the C<$scalar>.
		2411
		2412	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2413
		2414	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2415	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2416	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2417
		2418	Returns true if successful, and false otherwise. If the underlying mmapped
		2419	region has changed address, then the true value has the numerical value
		2420	C<1>, otherwise it has the numerical value C<0>:
		2421
		2422	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2423	or die "mremap: $!";
		2424
		2425	if ($success*1) {
		2426	warn "scalar has chanegd address in memory\n";
		2427	}
		2428
		2429	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2430	implemented, but not supported and might go away in a future version.
		2431
		2432	On systems where this call is not supported or is not emulated, this call
		2433	returns falls and sets C<$!> to C<ENOSYS>.
		2434
		2435	=item IO::AIO::mlockall $flags
		2436
		2437	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2438	but is blocking.
		2439
		2440	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2441
		2442	Calls the C<munlock> function, undoing the effects of a previous
		2443	C<aio_mlock> call (see its description for details).
		2444
		2445	=item IO::AIO::munlockall
		2446
		2447	Calls the C<munlockall> function.
		2448
		2449	On systems that do not implement C<munlockall>, this function returns
		2450	ENOSYS, otherwise the return value of C<munlockall>.
		2451
		2452	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2453
		2454	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2455	and return the new file handle on success, or sets C<$!> and returns
		2456	C<undef> on error.
		2457
		2458	The remote name of the new socket will be stored in C<$sockaddr>, which
		2459	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2460	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2461	by returning a longer string in C<$sockaddr>, which might or might not be
		2462	truncated.
		2463
		2464	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2465	C<$sockaddr_maxlen>.
		2466
		2467	The main reasons to use this syscall rather than portable C<accept(2)>
		2468	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2469	flags and you can accept name-less sockets by specifying C<0> for
		2470	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2471	C<accept>.
		2472
		2473	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2474
		2475	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2476	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2477	should be the file offset.
		2478
		2479	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2480	silently corrupt the data in this case.
		2481
		2482	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2483	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2484	C<IO::AIO::SPLICE_F_GIFT>.
		2485
		2486	See the C<splice(2)> manpage for details.
		2487
		2488	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2489
		2490	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2491	description for C<IO::AIO::splice> above for details.
		2492
		2493	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2494
		2495	Attempts to query or change the pipe buffer size. Obviously works only
		2496	on pipes, and currently works only on GNU/Linux systems, and fails with
		2497	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2498	size on other systems, drop me a note.
		2499
		2500	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2501
		2502	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2503	C<$flags> is missing or C<0>, then this should be the same as a call to
		2504	perl's built-in C<pipe> function and create a new pipe, and works on
		2505	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2506	(..., 4096, O_BINARY)>.
		2507
		2508	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2509	the given flags (Linux 2.6.27, glibc 2.9).
		2510
		2511	On success, the read and write file handles are returned.
		2512
		2513	On error, nothing will be returned. If the pipe2 syscall is missing and
		2514	C<$flags> is non-zero, fails with C<ENOSYS>.
		2515
		2516	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2517	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2518	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2519
		2520	Example: create a pipe race-free w.r.t. threads and fork:
		2521
		2522	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2523	or die "pipe2: $!\n";
		2524
		2525	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2526
		2527	This is a direct interface to the Linux L<memfd_create(2)> system
		2528	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2529	should be C<IO::AIO::MFD_CLOEXEC>.
		2530
		2531	On success, the new memfd filehandle is returned, otherwise returns
		2532	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2533
		2534	Please refer to L<memfd_create(2)> for more info on this call.
		2535
		2536	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2537	C<IO::AIO::MFD_ALLOW_SEALING>, C<IO::AIO::MFD_HUGETLB>,
		2538	C<IO::AIO::MFD_HUGETLB_2MB> and C<IO::AIO::MFD_HUGETLB_1GB>.
		2539
		2540	Example: create a new memfd.
		2541
		2542	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2543	or die "memfd_create: $!\n";
		2544
		2545	=item $fh = IO::AIO::pidfd_open $pid[, $flags]
		2546
		2547	This is an interface to the Linux L<pidfd_open(2)> system call. The
		2548	default for C<$flags> is C<0>.
		2549
		2550	On success, a new pidfd filehandle is returned (that is already set to
		2551	close-on-exec), otherwise returns C<undef>. If the syscall is missing,
		2552	fails with C<ENOSYS>.
		2553
		2554	Example: open pid 6341 as pidfd.
		2555
		2556	my $fh = IO::AIO::pidfd_open 6341
		2557	or die "pidfd_open: $!\n";
		2558
		2559	=item $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		2560
		2561	This is an interface to the Linux L<pidfd_send_signal> system call. The
		2562	default for C<$siginfo> is C<undef> and the default for C<$flags> is C<0>.
		2563
		2564	Returns the system call status. If the syscall is missing, fails with
		2565	C<ENOSYS>.
		2566
		2567	When specified, C<$siginfo> must be a reference to a hash with one or more
		2568	of the following members:
		2569
		2570	=over
		2571
		2572	=item code - the C<si_code> member
		2573
		2574	=item pid - the C<si_pid> member
		2575
		2576	=item uid - the C<si_uid> member
		2577
		2578	=item value_int - the C<si_value.sival_int> member
		2579
		2580	=item value_ptr - the C<si_value.sival_ptr> member, specified as an integer
		2581
		2582	=back
		2583
		2584	Example: send a SIGKILL to the specified process.
		2585
		2586	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
		2587	and die "pidfd_send_signal: $!\n";
		2588
		2589	Example: send a SIGKILL to the specified process with extra data.
		2590
		2591	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
		2592	and die "pidfd_send_signal: $!\n";
		2593
		2594	=item $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		2595
		2596	This is an interface to the Linux L<pidfd_getfd> system call. The default
		2597	for C<$flags> is C<0>.
		2598
		2599	On success, returns a dup'ed copy of the target file descriptor (specified
		2600	as an integer) returned (that is already set to close-on-exec), otherwise
		2601	returns C<undef>. If the syscall is missing, fails with C<ENOSYS>.
		2602
		2603	Example: get a copy of standard error of another process and print soemthing to it.
		2604
		2605	my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
		2606	or die "pidfd_getfd: $!\n";
		2607	print $errfh "stderr\n";
		2608
		2609	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2610
		2611	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2612	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2613
		2614	On success, the new eventfd filehandle is returned, otherwise returns
		2615	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2616
		2617	Please refer to L<eventfd(2)> for more info on this call.
		2618
		2619	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2620	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2621
		2622	Example: create a new eventfd filehandle:
		2623
		2624	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2625	or die "eventfd: $!\n";
		2626
		2627	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2628
		2629	This is a direct interface to the Linux L<timerfd_create(2)> system
		2630	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2631	should be C<IO::AIO::TFD_CLOEXEC>.
		2632
		2633	On success, the new timerfd filehandle is returned, otherwise returns
		2634	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2635
		2636	Please refer to L<timerfd_create(2)> for more info on this call.
		2637
		2638	The following C<$clockid> values are
		2639	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2640	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2641	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2642	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2643
		2644	The following C<$flags> values are available (Linux
		2645	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2646
		2647	Example: create a new timerfd and set it to one-second repeated alarms,
		2648	then wait for two alarms:
		2649
		2650	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2651	or die "timerfd_create: $!\n";
		2652
		2653	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2654	or die "timerfd_settime: $!\n";
		2655
		2656	for (1..2) {
		2657	8 == sysread $fh, my $buf, 8
		2658	or die "timerfd read failure\n";
		2659
		2660	printf "number of expirations (likely 1): %d\n",
		2661	unpack "Q", $buf;
		2662	}
		2663
		2664	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2665
		2666	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2667	call. Please refer to its manpage for more info on this call.
		2668
		2669	The new itimerspec is specified using two (possibly fractional) second
		2670	values, C<$new_interval> and C<$new_value>).
		2671
		2672	On success, the current interval and value are returned (as per
		2673	C<timerfd_gettime>). On failure, the empty list is returned.
		2674
		2675	The following C<$flags> values are
		2676	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2677	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2678
		2679	See C<IO::AIO::timerfd_create> for a full example.
		2680
		2681	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2682
		2683	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2684	call. Please refer to its manpage for more info on this call.
		2685
		2686	On success, returns the current values of interval and value for the given
		2687	timerfd (as potentially fractional second values). On failure, the empty
		2688	list is returned.
		2689
		2690	=back
		2691
1101	=cut	2692	=cut
1102		2693
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;	2694	min_parallel 8;
1120		2695
1121	END { flush }	2696	END { flush }
1122		2697
1123	1;	2698	1;
1124		2699
		2700	=head1 EVENT LOOP INTEGRATION
		2701
		2702	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2703	automatically into many event loops:
		2704
		2705	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2706	use AnyEvent::AIO;
		2707
		2708	You can also integrate IO::AIO manually into many event loops, here are
		2709	some examples of how to do this:
		2710
		2711	# EV integration
		2712	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2713
		2714	# Event integration
		2715	Event->io (fd => IO::AIO::poll_fileno,
		2716	poll => 'r',
		2717	cb => \&IO::AIO::poll_cb);
		2718
		2719	# Glib/Gtk2 integration
		2720	add_watch Glib::IO IO::AIO::poll_fileno,
		2721	in => sub { IO::AIO::poll_cb; 1 };
		2722
		2723	# Tk integration
		2724	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2725	readable => \&IO::AIO::poll_cb);
		2726
		2727	# Danga::Socket integration
		2728	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2729	\&IO::AIO::poll_cb);
		2730
1125	=head2 FORK BEHAVIOUR	2731	=head2 FORK BEHAVIOUR
1126		2732
1127	This module should do "the right thing" when the process using it forks:	2733	Usage of pthreads in a program changes the semantics of fork
		2734	considerably. Specifically, only async-safe functions can be called after
		2735	fork. Perl doesn't know about this, so in general, you cannot call fork
		2736	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2737	pthreads, so this applies, but many other extensions and (for inexplicable
		2738	reasons) perl itself often is linked against pthreads, so this limitation
		2739	applies to quite a lot of perls.
1128		2740
1129	Before the fork, IO::AIO enters a quiescent state where no requests	2741	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	2742	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	2743	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		2744
1137	In short: the parent will, after a short pause, continue as if fork had	2745	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	2746	forking. You could also try to call the L<IO::AIO::reinit> function in the
1139	yet.	2747	child:
		2748
		2749	=over 4
		2750
		2751	=item IO::AIO::reinit
		2752
		2753	Abandons all current requests and I/O threads and simply reinitialises all
		2754	data structures. This is not an operation supported by any standards, but
		2755	happens to work on GNU/Linux and some newer BSD systems.
		2756
		2757	The only reasonable use for this function is to call it after forking, if
		2758	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2759	the process will result in undefined behaviour. Calling it at any time
		2760	will also result in any undefined (by POSIX) behaviour.
		2761
		2762	=back
		2763
		2764	=head2 LINUX-SPECIFIC CALLS
		2765
		2766	When a call is documented as "linux-specific" then this means it
		2767	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2768	availability and compatibility of such calls regardless of the platform
		2769	it is compiled on, so platforms such as FreeBSD which often implement
		2770	these calls will work. When in doubt, call them and see if they fail wth
		2771	C<ENOSYS>.
1140		2772
1141	=head2 MEMORY USAGE	2773	=head2 MEMORY USAGE
1142		2774
1143	Per-request usage:	2775	Per-request usage:
1144		2776
…		…
1146	bytes of memory. In addition, stat requests need a stat buffer (possibly	2778	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	2779	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	2780	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.	2781	will consume memory till the request has entered the done state.
1150		2782
1151	This is now awfully much, so queuing lots of requests is not usually a	2783	This is not awfully much, so queuing lots of requests is not usually a
1152	problem.	2784	problem.
1153		2785
1154	Per-thread usage:	2786	Per-thread usage:
1155		2787
1156	In the execution phase, some aio requests require more memory for	2788	In the execution phase, some aio requests require more memory for
1157	temporary buffers, and each thread requires a stack and other data	2789	temporary buffers, and each thread requires a stack and other data
1158	structures (usually around 16k-128k, depending on the OS).	2790	structures (usually around 16k-128k, depending on the OS).
1159		2791
1160	=head1 KNOWN BUGS	2792	=head1 KNOWN BUGS
1161		2793
1162	Known bugs will be fixed in the next release.	2794	Known bugs will be fixed in the next release :)
		2795
		2796	=head1 KNOWN ISSUES
		2797
		2798	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2799	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2800	non-created hash slots or other scalars I didn't think of. It's best to
		2801	avoid such and either use scalar variables or making sure that the scalar
		2802	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2803
		2804	I am not sure anything can be done about this, so this is considered a
		2805	known issue, rather than a bug.
1163		2806
1164	=head1 SEE ALSO	2807	=head1 SEE ALSO
1165		2808
1166	L<Coro::AIO>.	2809	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2810	more natural syntax and L<IO::FDPass> for file descriptor passing.
1167		2811
1168	=head1 AUTHOR	2812	=head1 AUTHOR
1169		2813
1170	Marc Lehmann <schmorp@schmorp.de>	2814	Marc Lehmann <schmorp@schmorp.de>
1171	http://home.schmorp.de/	2815	http://home.schmorp.de/

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