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Revision 1.149 by root, Sat Jun 6 18:19:35 2009 UTC vs.
Revision 1.315 by root, Mon Sep 5 00:03:32 2022 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 (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	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>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	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
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	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
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	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
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	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
…		…
80	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
81	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
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		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
85	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
86	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
87	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	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
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	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
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.2';	176	our $VERSION = 4.77;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	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);
207		190
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	194	nreqs nready npending nthreads
212	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 memfd_create eventfd
		201	timerfd_create timerfd_settime timerfd_gettime
		202	pidfd_open pidfd_send_signal pidfd_getfd);
213		203
214	push @AIO_REQ, qw(aio_busy); # not exported	204	push @AIO_REQ, qw(aio_busy); # not exported
215		205
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		207
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	209	XSLoader::load ("IO::AIO", $VERSION);
220	}	210	}
221		211
222	=head1 FUNCTIONS	212	=head1 FUNCTIONS
223		213
224	=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[, $flags]
		331
		332	=head2 API NOTES
225		333
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	334	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	335	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	336	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	337	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	338	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	339	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	340	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		341	most syscalls return C<-1> on error, unlike perl, which usually delivers
		342	"false").
		343
		344	Some requests (such as C<aio_readdir>) pass the actual results and
		345	communicate failures by passing C<undef>.
233		346
234	All functions expecting a filehandle keep a copy of the filehandle	347	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	348	internally until the request has finished.
236		349
237	All functions return request objects of type L<IO::AIO::REQ> that allow	350	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	351	further manipulation of those requests while they are in-flight.
239		352
240	The pathnames you pass to these routines I<must> be absolute and	353	The pathnames you pass to these routines I<should> be absolute. The
241	encoded as octets. The reason for the former is that at the time the	354	reason for this is that at the time the request is being executed, the
242	request is being executed, the current working directory could have	355	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	356	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	357	in the program and then use relative paths. You can also take advantage
245	paths.	358	of IO::AIOs working directory abstraction, that lets you specify paths
		359	relative to some previously-opened "working directory object" - see the
		360	description of the C<IO::AIO::WD> class later in this document.
246		361
247	To encode pathnames as octets, either make sure you either: a) always pass	362	To encode pathnames as octets, either make sure you either: a) always pass
248	in filenames you got from outside (command line, readdir etc.) without	363	in filenames you got from outside (command line, readdir etc.) without
249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	364	tinkering, b) are in your native filesystem encoding, c) use the Encode
250	your pathnames to the locale (or other) encoding in effect in the user	365	module and encode your pathnames to the locale (or other) encoding in
251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	366	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	367	unicode filenames or e) use something else to ensure your scalar has the
		368	correct contents.
253		369
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	370	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	371	handles correctly whether it is set or not.
		372
		373	=head2 AIO REQUEST FUNCTIONS
256		374
257	=over 4	375	=over 4
258		376
259	=item $prev_pri = aioreq_pri [$pri]	377	=item $prev_pri = aioreq_pri [$pri]
260		378
…		…
290		408
291		409
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	410	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		411
294	Asynchronously open or create a file and call the callback with a newly	412	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	413	created filehandle for the file (or C<undef> in case of an error).
296		414
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	415	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	416	for an explanation.
299		417
300	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
…		…
307	by the umask in effect then the request is being executed, so better never	425	by the umask in effect then the request is being executed, so better never
308	change the umask.	426	change the umask.
309		427
310	Example:	428	Example:
311		429
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	430	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	431	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	432	print "open successful, fh is $_[0]\n";
315	...	433	...
316	} else {	434	} else {
317	die "open failed: $!\n";	435	die "open failed: $!\n";
318	}	436	}
319	};	437	};
320		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
321		448
322	=item aio_close $fh, $callback->($status)	449	=item aio_close $fh, $callback->($status)
323		450
324	Asynchronously close a file and call the callback with the result	451	Asynchronously close a file and call the callback with the result
325	code.	452	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	461	Or in other words: the file descriptor will be closed, but it will not be
335	free for reuse until the perl filehandle is closed.	462	free for reuse until the perl filehandle is closed.
336		463
337	=cut	464	=cut
338		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".
		485
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	486	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		487
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	488	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		489
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	490	Reads or writes C<$length> bytes from or to the specified C<$fh> and
344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	491	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
345	and calls the callback without the actual number of bytes read (or -1 on	492	calls the callback with the actual number of bytes transferred (or -1 on
346	error, just like the syscall).	493	error, just like the syscall).
347		494
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	495	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	496	offset plus the actual number of bytes read.
350		497
…		…
375		522
376	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
377	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
378	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
379	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
380	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>.
381		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<$in_fh>) is a file - the file I/O will then be asynchronous, while
		539	the socket I/O will be non-blocking. Note, however, that you can run
		540	into a trap where C<aio_sendfile> reads some data with readahead, then
		541	fails to write all data, and when the socket is ready the next time, the
		542	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		543	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		544	resource usage.
		545
382	This call tries to make use of a native C<sendfile> syscall to provide	546	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	547	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	548	a socket, and C<$in_fh> should refer to an mmap'able file.
385		549
386	If the native sendfile call fails or is not implemented, it will be	550	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	551	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		552	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	553	type of filehandle regardless of the limitations of the operating system.
389		554
390	Please note, however, that C<aio_sendfile> can read more bytes from	555	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$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
392	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
393	provides the number of bytes written to C<$out_fh>. Only if the result	558	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	559	so you really really should check the return value of C<aio_sendfile> -
395	read.	560	fewer bytes than expected might have been transferred.
396		561
397		562
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	563	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		564
400	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
…		…
404	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
405	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
406	(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
407	file. The current file offset of the file is left unchanged.	572	file. The current file offset of the file is left unchanged.
408		573
409	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
410	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.
411		576
412		577
413	=item aio_stat $fh_or_path, $callback->($status)	578	=item aio_stat $fh_or_path, $callback->($status)
414		579
415	=item aio_lstat $fh, $callback->($status)	580	=item aio_lstat $fh, $callback->($status)
416		581
417	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
418	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
419	or C<-s _> etc...	584	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		585	and C<-T>).
420		586
421	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	587	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
422	for an explanation.	588	for an explanation.
423		589
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	590	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	591	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	592	unless perl itself is compiled with large file support.
		593
		594	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		595	following constants and functions (if not implemented, the constants will
		596	be C<0> and the functions will either C<croak> or fall back on traditional
		597	behaviour).
		598
		599	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		600	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		601	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		602
		603	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		604	ACCESS>.
427		605
428	Example: Print the length of F</etc/passwd>:	606	Example: Print the length of F</etc/passwd>:
429		607
430	aio_stat "/etc/passwd", sub {	608	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	609	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	610	print "size is ", -s _, "\n";
433	};	611	};
434		612
435		613
		614	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		615
		616	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		617	whether a file handle or path was passed.
		618
		619	On success, the callback is passed a hash reference with the following
		620	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		621	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		622	is passed.
		623
		624	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		625	C<ST_NOSUID>.
		626
		627	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		628	their correct value when available, or to C<0> on systems that do
		629	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		630	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		631	C<ST_NODIRATIME> and C<ST_RELATIME>.
		632
		633	Example: stat C</wd> and dump out the data if successful.
		634
		635	aio_statvfs "/wd", sub {
		636	my $f = $_[0]
		637	or die "statvfs: $!";
		638
		639	use Data::Dumper;
		640	say Dumper $f;
		641	};
		642
		643	# result:
		644	{
		645	bsize => 1024,
		646	bfree => 4333064312,
		647	blocks => 10253828096,
		648	files => 2050765568,
		649	flag => 4096,
		650	favail => 2042092649,
		651	bavail => 4333064312,
		652	ffree => 2042092649,
		653	namemax => 255,
		654	frsize => 1024,
		655	fsid => 1810
		656	}
		657
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	658	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		659
438	Works like perl's C<utime> function (including the special case of $atime	660	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	661	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	662	syscalls support them.
441		663
442	When called with a pathname, uses utimes(2) if available, otherwise	664	When called with a pathname, uses utimensat(2) or utimes(2) if available,
443	utime(2). If called on a file descriptor, uses futimes(2) if available,	665	otherwise utime(2). If called on a file descriptor, uses futimens(2)
444	otherwise returns ENOSYS, so this is not portable.	666	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		667	portable.
445		668
446	Examples:	669	Examples:
447		670
448	# set atime and mtime to current time (basically touch(1)):	671	# set atime and mtime to current time (basically touch(1)):
449	aio_utime "path", undef, undef;	672	aio_utime "path", undef, undef;
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	690	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		691
469	Works like truncate(2) or ftruncate(2).	692	Works like truncate(2) or ftruncate(2).
470		693
471		694
		695	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		696
		697	Allocates or frees disk space according to the C<$mode> argument. See the
		698	linux C<fallocate> documentation for details.
		699
		700	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		701	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		702	to deallocate a file range.
		703
		704	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		705	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		706	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		707	to unshare shared blocks (see your L<fallocate(2)> manpage).
		708
		709	The file system block size used by C<fallocate> is presumably the
		710	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		711	can dictate other limitations.
		712
		713	If C<fallocate> isn't available or cannot be emulated (currently no
		714	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		715
		716
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	717	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		718
474	Works like perl's C<chmod> function.	719	Works like perl's C<chmod> function.
475		720
476		721
…		…
478		723
479	Asynchronously unlink (delete) a file and call the callback with the	724	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	725	result code.
481		726
482		727
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	728	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		729
485	[EXPERIMENTAL]	730	[EXPERIMENTAL]
486		731
487	Asynchronously create a device node (or fifo). See mknod(2).	732	Asynchronously create a device node (or fifo). See mknod(2).
488		733
489	The only (POSIX-) portable way of calling this function is:	734	The only (POSIX-) portable way of calling this function is:
490		735
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	736	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		737
		738	See C<aio_stat> for info about some potentially helpful extra constants
		739	and functions.
493		740
494	=item aio_link $srcpath, $dstpath, $callback->($status)	741	=item aio_link $srcpath, $dstpath, $callback->($status)
495		742
496	Asynchronously create a new link to the existing object at C<$srcpath> at	743	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	744	the path C<$dstpath> and call the callback with the result code.
…		…
501		748
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	749	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	750	the path C<$dstpath> and call the callback with the result code.
504		751
505		752
506	=item aio_readlink $path, $callback->($link)	753	=item aio_readlink $pathname, $callback->($link)
507		754
508	Asynchronously read the symlink specified by C<$path> and pass it to	755	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	756	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	757	callback.
511		758
512		759
		760	=item aio_realpath $pathname, $callback->($path)
		761
		762	Asynchronously make the path absolute and resolve any symlinks in
		763	C<$path>. The resulting path only consists of directories (same as
		764	L<Cwd::realpath>).
		765
		766	This request can be used to get the absolute path of the current working
		767	directory by passing it a path of F<.> (a single dot).
		768
		769
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	770	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		771
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	772	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	773	rename(2) and call the callback with the result code.
		774
		775	On systems that support the AIO::WD working directory abstraction
		776	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		777	of failing, C<rename> is called on the absolute path of C<$wd>.
		778
		779
		780	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		781
		782	Basically a version of C<aio_rename> with an additional C<$flags>
		783	argument. Calling this with C<$flags=0> is the same as calling
		784	C<aio_rename>.
		785
		786	Non-zero flags are currently only supported on GNU/Linux systems that
		787	support renameat2. Other systems fail with C<ENOSYS> in this case.
		788
		789	The following constants are available (missing ones are, as usual C<0>),
		790	see renameat2(2) for details:
		791
		792	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		793	and C<IO::AIO::RENAME_WHITEOUT>.
517		794
518		795
519	=item aio_mkdir $pathname, $mode, $callback->($status)	796	=item aio_mkdir $pathname, $mode, $callback->($status)
520		797
521	Asynchronously mkdir (create) a directory and call the callback with	798	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	803	=item aio_rmdir $pathname, $callback->($status)
527		804
528	Asynchronously rmdir (delete) a directory and call the callback with the	805	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	806	result code.
530		807
		808	On systems that support the AIO::WD working directory abstraction
		809	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		810	C<rmdir> is called on the absolute path of C<$wd>.
		811
531		812
532	=item aio_readdir $pathname, $callback->($entries)	813	=item aio_readdir $pathname, $callback->($entries)
533		814
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	815	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	816	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
539	array-ref with the filenames.	820	array-ref with the filenames.
540		821
541		822
542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	823	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
543		824
544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	825	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
545	behaviour and output format. In case of an error, C<$entries> will be	826	tune behaviour and output format. In case of an error, C<$entries> will be
546	C<undef>.	827	C<undef>.
547		828
548	The flags are a combination of the following constants, ORed together (the	829	The flags are a combination of the following constants, ORed together (the
549	flags will also be passed to the callback, possibly modified):	830	flags will also be passed to the callback, possibly modified):
550		831
551	=over 4	832	=over 4
552		833
553	=item AIO::READDIR_DENTS	834	=item IO::AIO::READDIR_DENTS
554		835
555	When this flag is off, then the callback gets an arrayref with of names	836	Normally the callback gets an arrayref consisting of names only (as
556	only (as with C<aio_readdir>), otherwise it gets an arrayref with	837	with C<aio_readdir>). If this flag is set, then the callback gets an
557	C<[$name, $inode, $type]> arrayrefs, each describing a single directory	838	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
558	entry in more detail.	839	single directory entry in more detail:
559		840
560	C<$name> is the name of the entry.	841	C<$name> is the name of the entry.
561		842
		843	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		844
		845	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		846	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		847	C<IO::AIO::DT_WHT>.
		848
		849	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		850	to know, you have to run stat yourself. Also, for speed/memory reasons,
		851	the C<$type> scalars are read-only: you must not modify them.
		852
562	C<$inode> is the inode number (which might not be exact on systems with 64	853	C<$inode> is the inode number (which might not be exact on systems with 64
563	bit inode numbers and 32 bit perls). On systems that do not deliver the	854	bit inode numbers and 32 bit perls). This field has unspecified content on
564	inode information, this will always be zero.	855	systems that do not deliver the inode information.
565		856
566	C<$type> is one of the C<AIO::DT_xxx> constants:
567
568	C<AIO::DT_UNKNOWN>, C<AIO::DT_FIFO>, C<AIO::DT_CHR>, C<AIO::DT_DIR>,
569	C<AIO::DT_BLK>, C<AIO::DT_REG>, C<AIO::DT_LNK>, C<AIO::DT_SOCK>,
570	C<AIO::DT_WHT>.
571
572	C<AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
573	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
574	scalars are read-only: you can not modify them.
575
576	=item AIO::READDIR_DIRS_FIRST	857	=item IO::AIO::READDIR_DIRS_FIRST
577		858
578	When this flag is set, then the names will be returned in an order where	859	When this flag is set, then the names will be returned in an order where
579	likely directories come first. This is useful when you need to quickly	860	likely directories come first, in optimal stat order. This is useful when
580	find directories, or you want to find all directories while avoiding to	861	you need to quickly find directories, or you want to find all directories
581	stat() each entry.	862	while avoiding to stat() each entry.
582		863
583	If the system returns type information in readdir, then this is used	864	If the system returns type information in readdir, then this is used
584	to find directories directly. Otherwise, likely directories are files	865	to find directories directly. Otherwise, likely directories are names
585	beginning with ".", or otherwise files with no dots, of which files with	866	beginning with ".", or otherwise names with no dots, of which names with
586	short names are tried first.	867	short names are tried first.
587		868
588	=item AIO::READDIR_STAT_ORDER	869	=item IO::AIO::READDIR_STAT_ORDER
589		870
590	When this flag is set, then the names will be returned in an order	871	When this flag is set, then the names will be returned in an order
591	suitable for stat()'ing each one. That is, when you plan to stat()	872	suitable for stat()'ing each one. That is, when you plan to stat() most or
592	all files in the given directory, then the returned order will likely	873	all files in the given directory, then the returned order will likely be
593	be fastest.	874	faster.
594		875
595	If both this flag and IO::READDIR_DIRS_FIRST are specified, then the	876	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
596	likely dirs come first, resulting in a less optimal stat order.	877	then the likely dirs come first, resulting in a less optimal stat order
		878	for stat'ing all entries, but likely a more optimal order for finding
		879	subdirectories.
597		880
598	=item AIO::READDIR_FOUND_UNKNOWN	881	=item IO::AIO::READDIR_FOUND_UNKNOWN
599		882
600	This flag should not be set when calling C<aio_readdirx>. Instead, it	883	This flag should not be set when calling C<aio_readdirx>. Instead, it
601	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	884	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
602	C<AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	885	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
603	C<$type>'s are known, which can be used to speed up some algorithms.	886	C<$type>'s are known, which can be used to speed up some algorithms.
604		887
605	=back	888	=back
606		889
607		890
		891	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		892
		893	Opens, reads and closes the given file. The data is put into C<$data>,
		894	which is resized as required.
		895
		896	If C<$offset> is negative, then it is counted from the end of the file.
		897
		898	If C<$length> is zero, then the remaining length of the file is
		899	used. Also, in this case, the same limitations to modifying C<$data> apply
		900	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		901	with C<substr>. If the size of the file is known, specifying a non-zero
		902	C<$length> results in a performance advantage.
		903
		904	This request is similar to the older C<aio_load> request, but since it is
		905	a single request, it might be more efficient to use.
		906
		907	Example: load F</etc/passwd> into C<$passwd>.
		908
		909	my $passwd;
		910	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		911	$_[0] >= 0
		912	or die "/etc/passwd: $!\n";
		913
		914	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		915	print $passwd;
		916	};
		917	IO::AIO::flush;
		918
		919
608	=item aio_load $path, $data, $callback->($status)	920	=item aio_load $pathname, $data, $callback->($status)
609		921
610	This is a composite request that tries to fully load the given file into	922	This is a composite request that tries to fully load the given file into
611	memory. Status is the same as with aio_read.	923	memory. Status is the same as with aio_read.
		924
		925	Using C<aio_slurp> might be more efficient, as it is a single request.
612		926
613	=cut	927	=cut
614		928
615	sub aio_load($$;$) {	929	sub aio_load($$;$) {
616	my ($path, undef, $cb) = @_;	930	my ($path, undef, $cb) = @_;
…		…
635		949
636	=item aio_copy $srcpath, $dstpath, $callback->($status)	950	=item aio_copy $srcpath, $dstpath, $callback->($status)
637		951
638	Try to copy the I<file> (directories not supported as either source or	952	Try to copy the I<file> (directories not supported as either source or
639	destination) from C<$srcpath> to C<$dstpath> and call the callback with	953	destination) from C<$srcpath> to C<$dstpath> and call the callback with
640	the C<0> (error) or C<-1> ok.	954	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		955
		956	Existing destination files will be truncated.
641		957
642	This is a composite request that creates the destination file with	958	This is a composite request that creates the destination file with
643	mode 0200 and copies the contents of the source file into it using	959	mode 0200 and copies the contents of the source file into it using
644	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	960	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
645	uid/gid, in that order.	961	uid/gid, in that order.
…		…
657	my $grp = aio_group $cb;	973	my $grp = aio_group $cb;
658		974
659	aioreq_pri $pri;	975	aioreq_pri $pri;
660	add $grp aio_open $src, O_RDONLY, 0, sub {	976	add $grp aio_open $src, O_RDONLY, 0, sub {
661	if (my $src_fh = $_[0]) {	977	if (my $src_fh = $_[0]) {
662	my @stat = stat $src_fh; # hmm, might bock over nfs?	978	my @stat = stat $src_fh; # hmm, might block over nfs?
663		979
664	aioreq_pri $pri;	980	aioreq_pri $pri;
665	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	981	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
666	if (my $dst_fh = $_[0]) {	982	if (my $dst_fh = $_[0]) {
667	aioreq_pri $pri;	983	aioreq_pri $pri;
…		…
714		1030
715	=item aio_move $srcpath, $dstpath, $callback->($status)	1031	=item aio_move $srcpath, $dstpath, $callback->($status)
716		1032
717	Try to move the I<file> (directories not supported as either source or	1033	Try to move the I<file> (directories not supported as either source or
718	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1034	destination) from C<$srcpath> to C<$dstpath> and call the callback with
719	the C<0> (error) or C<-1> ok.	1035	a status of C<0> (ok) or C<-1> (error, see C<$!>).
720		1036
721	This is a composite request that tries to rename(2) the file first; if	1037	This is a composite request that tries to rename(2) the file first; if
722	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	1038	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
723	that is successful, unlinks the C<$srcpath>.	1039	that is successful, unlinks the C<$srcpath>.
724		1040
…		…
735	if ($_[0] && $! == EXDEV) {	1051	if ($_[0] && $! == EXDEV) {
736	aioreq_pri $pri;	1052	aioreq_pri $pri;
737	add $grp aio_copy $src, $dst, sub {	1053	add $grp aio_copy $src, $dst, sub {
738	$grp->result ($_[0]);	1054	$grp->result ($_[0]);
739		1055
740	if (!$_[0]) {	1056	unless ($_[0]) {
741	aioreq_pri $pri;	1057	aioreq_pri $pri;
742	add $grp aio_unlink $src;	1058	add $grp aio_unlink $src;
743	}	1059	}
744	};	1060	};
745	} else {	1061	} else {
…		…
748	};	1064	};
749		1065
750	$grp	1066	$grp
751	}	1067	}
752		1068
753	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1069	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
754		1070
755	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1071	Scans a directory (similar to C<aio_readdir>) but additionally tries to
756	efficiently separate the entries of directory C<$path> into two sets of	1072	efficiently separate the entries of directory C<$path> into two sets of
757	names, directories you can recurse into (directories), and ones you cannot	1073	names, directories you can recurse into (directories), and ones you cannot
758	recurse into (everything else, including symlinks to directories).	1074	recurse into (everything else, including symlinks to directories).
759		1075
760	C<aio_scandir> is a composite request that creates of many sub requests_	1076	C<aio_scandir> is a composite request that generates many sub requests.
761	C<$maxreq> specifies the maximum number of outstanding aio requests that	1077	C<$maxreq> specifies the maximum number of outstanding aio requests that
762	this function generates. If it is C<< <= 0 >>, then a suitable default	1078	this function generates. If it is C<< <= 0 >>, then a suitable default
763	will be chosen (currently 4).	1079	will be chosen (currently 4).
764		1080
765	On error, the callback is called without arguments, otherwise it receives	1081	On error, the callback is called without arguments, otherwise it receives
…		…
789	Then entries will be sorted into likely directories a non-initial dot	1105	Then entries will be sorted into likely directories a non-initial dot
790	currently) and likely non-directories (see C<aio_readdirx>). Then every	1106	currently) and likely non-directories (see C<aio_readdirx>). Then every
791	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1107	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
792	in order of their inode numbers. If that succeeds, it assumes that the	1108	in order of their inode numbers. If that succeeds, it assumes that the
793	entry is a directory or a symlink to directory (which will be checked	1109	entry is a directory or a symlink to directory (which will be checked
794	seperately). This is often faster than stat'ing the entry itself because	1110	separately). This is often faster than stat'ing the entry itself because
795	filesystems might detect the type of the entry without reading the inode	1111	filesystems might detect the type of the entry without reading the inode
796	data (e.g. ext2fs filetype feature), even on systems that cannot return	1112	data (e.g. ext2fs filetype feature), even on systems that cannot return
797	the filetype information on readdir.	1113	the filetype information on readdir.
798		1114
799	If the known number of directories (link count - 2) has been reached, the	1115	If the known number of directories (link count - 2) has been reached, the
…		…
815		1131
816	my $grp = aio_group $cb;	1132	my $grp = aio_group $cb;
817		1133
818	$maxreq = 4 if $maxreq <= 0;	1134	$maxreq = 4 if $maxreq <= 0;
819		1135
820	# stat once	1136	# get a wd object
821	aioreq_pri $pri;	1137	aioreq_pri $pri;
822	add $grp aio_stat $path, sub {	1138	add $grp aio_wd $path, sub {
		1139	$_[0]
823	return $grp->result () if $_[0];	1140	or return $grp->result ();
824	my $now = time;
825	my $hash1 = join ":", (stat _)[0,1,3,7,9];
826		1141
827	# read the directory entries	1142	my $wd = [shift, "."];
		1143
		1144	# stat once
828	aioreq_pri $pri;	1145	aioreq_pri $pri;
829	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1146	add $grp aio_stat $wd, sub {
830	my $entries = shift
831	or return $grp->result ();	1147	return $grp->result () if $_[0];
		1148	my $now = time;
		1149	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1150	my $rdxflags = READDIR_DIRS_FIRST;
832		1151
833	# stat the dir another time	1152	if ((stat _)[3] < 2) {
		1153	# at least one non-POSIX filesystem exists
		1154	# that returns useful DT_type values: btrfs,
		1155	# so optimise for this here by requesting dents
		1156	$rdxflags |= READDIR_DENTS;
		1157	}
		1158
		1159	# read the directory entries
834	aioreq_pri $pri;	1160	aioreq_pri $pri;
835	add $grp aio_stat $path, sub {	1161	add $grp aio_readdirx $wd, $rdxflags, sub {
836	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1162	my ($entries, $flags) = @_
		1163	or return $grp->result ();
837		1164
		1165	if ($rdxflags & READDIR_DENTS) {
		1166	# if we requested type values, see if we can use them directly.
		1167
		1168	# if there were any DT_UNKNOWN entries then we assume we
		1169	# don't know. alternatively, we could assume that if we get
		1170	# one DT_DIR, then all directories are indeed marked with
		1171	# DT_DIR, but this seems not required for btrfs, and this
		1172	# is basically the "btrfs can't get it's act together" code
		1173	# branch.
		1174	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1175	# now we have valid DT_ information for all entries,
		1176	# so use it as an optimisation without further stat's.
		1177	# they must also all be at the beginning of @$entries
		1178	# by now.
		1179
838	my $ndirs;	1180	my $dirs;
839		1181
840	# take the slow route if anything looks fishy
841	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
842	$ndirs = -1;
843	} else {
844	# if nlink == 2, we are finished
845	# on non-posix-fs's, we rely on nlink < 2
846	$ndirs = (stat _)[3] - 2
847	or return $grp->result ([], $entries);
848	}
849
850	my (@dirs, @nondirs);
851
852	my $statgrp = add $grp aio_group sub {
853	$grp->result (\@dirs, \@nondirs);
854	};
855
856	limit $statgrp $maxreq;
857	feed $statgrp sub {
858	return unless @$entries;
859	my $entry = pop @$entries;
860
861	aioreq_pri $pri;
862	add $statgrp aio_stat "$path/$entry/.", sub {
863	if ($_[0] < 0) {	1182	if (@$entries) {
864	push @nondirs, $entry;	1183	for (0 .. $#$entries) {
865	} else {	1184	if ($entries->[$_][1] != DT_DIR) {
866	# need to check for real directory	1185	# splice out directories
867	aioreq_pri $pri;	1186	$dirs = [splice @$entries, 0, $_];
868	add $statgrp aio_lstat "$path/$entry", sub {
869	if (-d _) {
870	push @dirs, $entry;
871
872	unless (--$ndirs) {
873	push @nondirs, @$entries;
874	feed $statgrp;
875	}	1187	last;
876	} else {
877	push @nondirs, $entry;
878	}	1188	}
879	}	1189	}
		1190
		1191	# if we didn't find any non-dir, then all entries are dirs
		1192	unless ($dirs) {
		1193	($dirs, $entries) = ($entries, []);
		1194	}
		1195	} else {
		1196	# directory is empty, so there are no sbdirs
		1197	$dirs = [];
880	}	1198	}
		1199
		1200	# either splice'd the directories out or the dir was empty.
		1201	# convert dents to filenames
		1202	$_ = $_->[0] for @$dirs;
		1203	$_ = $_->[0] for @$entries;
		1204
		1205	return $grp->result ($dirs, $entries);
		1206	}
		1207
		1208	# cannot use, so return to our old ways
		1209	# by pretending we only scanned for names.
		1210	$_ = $_->[0] for @$entries;
		1211	}
		1212
		1213	# stat the dir another time
		1214	aioreq_pri $pri;
		1215	add $grp aio_stat $wd, sub {
		1216	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1217
		1218	my $ndirs;
		1219
		1220	# take the slow route if anything looks fishy
		1221	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1222	$ndirs = -1;
		1223	} else {
		1224	# if nlink == 2, we are finished
		1225	# for non-posix-fs's, we rely on nlink < 2
		1226	$ndirs = (stat _)[3] - 2
		1227	or return $grp->result ([], $entries);
		1228	}
		1229
		1230	my (@dirs, @nondirs);
		1231
		1232	my $statgrp = add $grp aio_group sub {
		1233	$grp->result (\@dirs, \@nondirs);
		1234	};
		1235
		1236	limit $statgrp $maxreq;
		1237	feed $statgrp sub {
		1238	return unless @$entries;
		1239	my $entry = shift @$entries;
		1240
		1241	aioreq_pri $pri;
		1242	$wd->[1] = "$entry/.";
		1243	add $statgrp aio_stat $wd, sub {
		1244	if ($_[0] < 0) {
		1245	push @nondirs, $entry;
		1246	} else {
		1247	# need to check for real directory
		1248	aioreq_pri $pri;
		1249	$wd->[1] = $entry;
		1250	add $statgrp aio_lstat $wd, sub {
		1251	if (-d _) {
		1252	push @dirs, $entry;
		1253
		1254	unless (--$ndirs) {
		1255	push @nondirs, @$entries;
		1256	feed $statgrp;
		1257	}
		1258	} else {
		1259	push @nondirs, $entry;
		1260	}
		1261	}
		1262	}
		1263	};
881	};	1264	};
882	};	1265	};
883	};	1266	};
884	};	1267	};
885	};	1268	};
886		1269
887	$grp	1270	$grp
888	}	1271	}
889		1272
890	=item aio_rmtree $path, $callback->($status)	1273	=item aio_rmtree $pathname, $callback->($status)
891		1274
892	Delete a directory tree starting (and including) C<$path>, return the	1275	Delete a directory tree starting (and including) C<$path>, return the
893	status of the final C<rmdir> only. This is a composite request that	1276	status of the final C<rmdir> only. This is a composite request that
894	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1277	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
895	everything else.	1278	everything else.
896		1279
897	=cut	1280	=cut
898		1281
…		…
920	};	1303	};
921		1304
922	$grp	1305	$grp
923	}	1306	}
924		1307
		1308	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1309
		1310	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1311
		1312	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1313	they execute asynchronously and pass the return value to the callback.
		1314
		1315	Both calls can be used for a lot of things, some of which make more sense
		1316	to run asynchronously in their own thread, while some others make less
		1317	sense. For example, calls that block waiting for external events, such
		1318	as locking, will also lock down an I/O thread while it is waiting, which
		1319	can deadlock the whole I/O system. At the same time, there might be no
		1320	alternative to using a thread to wait.
		1321
		1322	So in general, you should only use these calls for things that do
		1323	(filesystem) I/O, not for things that wait for other events (network,
		1324	other processes), although if you are careful and know what you are doing,
		1325	you still can.
		1326
		1327	The following constants are available and can be used for normal C<ioctl>
		1328	and C<fcntl> as well (missing ones are, as usual C<0>):
		1329
		1330	C<F_DUPFD_CLOEXEC>,
		1331
		1332	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1333
		1334	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1335
		1336	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1337	C<F_SEAL_WRITE>.
		1338
		1339	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1340	C<FS_IOC_FIEMAP>.
		1341
		1342	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1343	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1344
		1345	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1346	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1347	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1348	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1349	C<FS_FL_USER_MODIFIABLE>.
		1350
		1351	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1352	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1353	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1354	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1355
925	=item aio_sync $callback->($status)	1356	=item aio_sync $callback->($status)
926		1357
927	Asynchronously call sync and call the callback when finished.	1358	Asynchronously call sync and call the callback when finished.
928		1359
929	=item aio_fsync $fh, $callback->($status)	1360	=item aio_fsync $fh, $callback->($status)
…		…
936	Asynchronously call fdatasync on the given filehandle and call the	1367	Asynchronously call fdatasync on the given filehandle and call the
937	callback with the fdatasync result code.	1368	callback with the fdatasync result code.
938		1369
939	If this call isn't available because your OS lacks it or it couldn't be	1370	If this call isn't available because your OS lacks it or it couldn't be
940	detected, it will be emulated by calling C<fsync> instead.	1371	detected, it will be emulated by calling C<fsync> instead.
		1372
		1373	=item aio_syncfs $fh, $callback->($status)
		1374
		1375	Asynchronously call the syncfs syscall to sync the filesystem associated
		1376	to the given filehandle and call the callback with the syncfs result
		1377	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1378	errno to C<ENOSYS> nevertheless.
941		1379
942	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1380	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943		1381
944	Sync the data portion of the file specified by C<$offset> and C<$length>	1382	Sync the data portion of the file specified by C<$offset> and C<$length>
945	to disk (but NOT the metadata), by calling the Linux-specific	1383	to disk (but NOT the metadata), by calling the Linux-specific
…		…
949	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1387	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
950	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1388	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
951	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1389	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
952	manpage for details.	1390	manpage for details.
953		1391
954	=item aio_pathsync $path, $callback->($status)	1392	=item aio_pathsync $pathname, $callback->($status)
955		1393
956	This request tries to open, fsync and close the given path. This is a	1394	This request tries to open, fsync and close the given path. This is a
957	composite request intended to sync directories after directory operations	1395	composite request intended to sync directories after directory operations
958	(E.g. rename). This might not work on all operating systems or have any	1396	(E.g. rename). This might not work on all operating systems or have any
959	specific effect, but usually it makes sure that directory changes get	1397	specific effect, but usually it makes sure that directory changes get
960	written to disc. It works for anything that can be opened for read-only,	1398	written to disc. It works for anything that can be opened for read-only,
961	not just directories.	1399	not just directories.
		1400
		1401	Future versions of this function might fall back to other methods when
		1402	C<fsync> on the directory fails (such as calling C<sync>).
962		1403
963	Passes C<0> when everything went ok, and C<-1> on error.	1404	Passes C<0> when everything went ok, and C<-1> on error.
964		1405
965	=cut	1406	=cut
966		1407
…		…
987	};	1428	};
988		1429
989	$grp	1430	$grp
990	}	1431	}
991		1432
		1433	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1434
		1435	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1436	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1437	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1438	scalar must only be modified in-place while an aio operation is pending on
		1439	it).
		1440
		1441	It calls the C<msync> function of your OS, if available, with the memory
		1442	area starting at C<$offset> in the string and ending C<$length> bytes
		1443	later. If C<$length> is negative, counts from the end, and if C<$length>
		1444	is C<undef>, then it goes till the end of the string. The flags can be
		1445	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1446	C<IO::AIO::MS_INVALIDATE>.
		1447
		1448	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1449
		1450	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1451	scalars.
		1452
		1453	It touches (reads or writes) all memory pages in the specified
		1454	range inside the scalar. All caveats and parameters are the same
		1455	as for C<aio_msync>, above, except for flags, which must be either
		1456	C<0> (which reads all pages and ensures they are instantiated) or
		1457	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1458	writing an octet from it, which dirties the page).
		1459
		1460	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1461
		1462	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1463	scalars.
		1464
		1465	It reads in all the pages of the underlying storage into memory (if any)
		1466	and locks them, so they are not getting swapped/paged out or removed.
		1467
		1468	If C<$length> is undefined, then the scalar will be locked till the end.
		1469
		1470	On systems that do not implement C<mlock>, this function returns C<-1>
		1471	and sets errno to C<ENOSYS>.
		1472
		1473	Note that the corresponding C<munlock> is synchronous and is
		1474	documented under L<MISCELLANEOUS FUNCTIONS>.
		1475
		1476	Example: open a file, mmap and mlock it - both will be undone when
		1477	C<$data> gets destroyed.
		1478
		1479	open my $fh, "<", $path or die "$path: $!";
		1480	my $data;
		1481	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1482	aio_mlock $data; # mlock in background
		1483
		1484	=item aio_mlockall $flags, $callback->($status)
		1485
		1486	Calls the C<mlockall> function with the given C<$flags> (a
		1487	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1488	C<IO::AIO::MCL_ONFAULT>).
		1489
		1490	On systems that do not implement C<mlockall>, this function returns C<-1>
		1491	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1492	by the system result in a return value of C<-1> with errno being set to
		1493	C<EINVAL>.
		1494
		1495	Note that the corresponding C<munlockall> is synchronous and is
		1496	documented under L<MISCELLANEOUS FUNCTIONS>.
		1497
		1498	Example: asynchronously lock all current and future pages into memory.
		1499
		1500	aio_mlockall IO::AIO::MCL_FUTURE;
		1501
		1502	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1503
		1504	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1505	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1506	the ioctl is not available on your OS, then this request will fail with
		1507	C<ENOSYS>.
		1508
		1509	C<$start> is the starting offset to query extents for, C<$length> is the
		1510	size of the range to query - if it is C<undef>, then the whole file will
		1511	be queried.
		1512
		1513	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1514	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1515	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1516	the data portion.
		1517
		1518	C<$count> is the maximum number of extent records to return. If it is
		1519	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1520	case, if it is C<0>, then the callback receives the number of extents
		1521	instead of the extents themselves (which is unreliable, see below).
		1522
		1523	If an error occurs, the callback receives no arguments. The special
		1524	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1525
		1526	Otherwise, the callback receives an array reference with extent
		1527	structures. Each extent structure is an array reference itself, with the
		1528	following members:
		1529
		1530	[$logical, $physical, $length, $flags]
		1531
		1532	Flags is any combination of the following flag values (typically either C<0>
		1533	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1534
		1535	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1536	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1537	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1538	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1539	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1540	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1541
		1542	At the time of this writing (Linux 3.2), this request is unreliable unless
		1543	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1544	it to return all extents of a range for files with a large number of
		1545	extents. The code (only) works around all these issues if C<$count> is
		1546	C<undef>.
		1547
992	=item aio_group $callback->(...)	1548	=item aio_group $callback->(...)
993		1549
994	This is a very special aio request: Instead of doing something, it is a	1550	This is a very special aio request: Instead of doing something, it is a
995	container for other aio requests, which is useful if you want to bundle	1551	container for other aio requests, which is useful if you want to bundle
996	many requests into a single, composite, request with a definite callback	1552	many requests into a single, composite, request with a definite callback
…		…
1033	immense (it blocks a thread for a long time) so do not use this function	1589	immense (it blocks a thread for a long time) so do not use this function
1034	except to put your application under artificial I/O pressure.	1590	except to put your application under artificial I/O pressure.
1035		1591
1036	=back	1592	=back
1037		1593
		1594
		1595	=head2 IO::AIO::WD - multiple working directories
		1596
		1597	Your process only has one current working directory, which is used by all
		1598	threads. This makes it hard to use relative paths (some other component
		1599	could call C<chdir> at any time, and it is hard to control when the path
		1600	will be used by IO::AIO).
		1601
		1602	One solution for this is to always use absolute paths. This usually works,
		1603	but can be quite slow (the kernel has to walk the whole path on every
		1604	access), and can also be a hassle to implement.
		1605
		1606	Newer POSIX systems have a number of functions (openat, fdopendir,
		1607	futimensat and so on) that make it possible to specify working directories
		1608	per operation.
		1609
		1610	For portability, and because the clowns who "designed", or shall I write,
		1611	perpetrated this new interface were obviously half-drunk, this abstraction
		1612	cannot be perfect, though.
		1613
		1614	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1615	object. This object stores the canonicalised, absolute version of the
		1616	path, and on systems that allow it, also a directory file descriptor.
		1617
		1618	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1619	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1620	object and a pathname instead (or the IO::AIO::WD object alone, which
		1621	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1622	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1623	to that IO::AIO::WD object.
		1624
		1625	For example, to get a wd object for F</etc> and then stat F<passwd>
		1626	inside, you would write:
		1627
		1628	aio_wd "/etc", sub {
		1629	my $etcdir = shift;
		1630
		1631	# although $etcdir can be undef on error, there is generally no reason
		1632	# to check for errors here, as aio_stat will fail with ENOENT
		1633	# when $etcdir is undef.
		1634
		1635	aio_stat [$etcdir, "passwd"], sub {
		1636	# yay
		1637	};
		1638	};
		1639
		1640	The fact that C<aio_wd> is a request and not a normal function shows that
		1641	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1642	which is why it is done asynchronously.
		1643
		1644	To stat the directory obtained with C<aio_wd> above, one could write
		1645	either of the following three request calls:
		1646
		1647	aio_lstat "/etc" , sub { ... # pathname as normal string
		1648	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1649	aio_lstat $wd , sub { ... # shorthand for the previous
		1650
		1651	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1652	object and the pathname string, so you could write the following without
		1653	causing any issues due to C<$path> getting reused:
		1654
		1655	my $path = [$wd, undef];
		1656
		1657	for my $name (qw(abc def ghi)) {
		1658	$path->[1] = $name;
		1659	aio_stat $path, sub {
		1660	# ...
		1661	};
		1662	}
		1663
		1664	There are some caveats: when directories get renamed (or deleted), the
		1665	pathname string doesn't change, so will point to the new directory (or
		1666	nowhere at all), while the directory fd, if available on the system,
		1667	will still point to the original directory. Most functions accepting a
		1668	pathname will use the directory fd on newer systems, and the string on
		1669	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1670	the string form of the pathname.
		1671
		1672	So this functionality is mainly useful to get some protection against
		1673	C<chdir>, to easily get an absolute path out of a relative path for future
		1674	reference, and to speed up doing many operations in the same directory
		1675	(e.g. when stat'ing all files in a directory).
		1676
		1677	The following functions implement this working directory abstraction:
		1678
		1679	=over 4
		1680
		1681	=item aio_wd $pathname, $callback->($wd)
		1682
		1683	Asynchonously canonicalise the given pathname and convert it to an
		1684	IO::AIO::WD object representing it. If possible and supported on the
		1685	system, also open a directory fd to speed up pathname resolution relative
		1686	to this working directory.
		1687
		1688	If something goes wrong, then C<undef> is passwd to the callback instead
		1689	of a working directory object and C<$!> is set appropriately. Since
		1690	passing C<undef> as working directory component of a pathname fails the
		1691	request with C<ENOENT>, there is often no need for error checking in the
		1692	C<aio_wd> callback, as future requests using the value will fail in the
		1693	expected way.
		1694
		1695	=item IO::AIO::CWD
		1696
		1697	This is a compile time constant (object) that represents the process
		1698	current working directory.
		1699
		1700	Specifying this object as working directory object for a pathname is as if
		1701	the pathname would be specified directly, without a directory object. For
		1702	example, these calls are functionally identical:
		1703
		1704	aio_stat "somefile", sub { ... };
		1705	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1706
		1707	=back
		1708
		1709	To recover the path associated with an IO::AIO::WD object, you can use
		1710	C<aio_realpath>:
		1711
		1712	aio_realpath $wd, sub {
		1713	warn "path is $_[0]\n";
		1714	};
		1715
		1716	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1717	sometimes, fall back to using an absolue path.
		1718
1038	=head2 IO::AIO::REQ CLASS	1719	=head2 IO::AIO::REQ CLASS
1039		1720
1040	All non-aggregate C<aio_*> functions return an object of this class when	1721	All non-aggregate C<aio_*> functions return an object of this class when
1041	called in non-void context.	1722	called in non-void context.
1042		1723
…		…
1045	=item cancel $req	1726	=item cancel $req
1046		1727
1047	Cancels the request, if possible. Has the effect of skipping execution	1728	Cancels the request, if possible. Has the effect of skipping execution
1048	when entering the B<execute> state and skipping calling the callback when	1729	when entering the B<execute> state and skipping calling the callback when
1049	entering the the B<result> state, but will leave the request otherwise	1730	entering the the B<result> state, but will leave the request otherwise
1050	untouched. That means that requests that currently execute will not be	1731	untouched (with the exception of readdir). That means that requests that
1051	stopped and resources held by the request will not be freed prematurely.	1732	currently execute will not be stopped and resources held by the request
		1733	will not be freed prematurely.
1052		1734
1053	=item cb $req $callback->(...)	1735	=item cb $req $callback->(...)
1054		1736
1055	Replace (or simply set) the callback registered to the request.	1737	Replace (or simply set) the callback registered to the request.
1056		1738
…		…
1130	=item $grp->cancel_subs	1812	=item $grp->cancel_subs
1131		1813
1132	Cancel all subrequests and clears any feeder, but not the group request	1814	Cancel all subrequests and clears any feeder, but not the group request
1133	itself. Useful when you queued a lot of events but got a result early.	1815	itself. Useful when you queued a lot of events but got a result early.
1134		1816
		1817	The group request will finish normally (you cannot add requests to the
		1818	group).
		1819
1135	=item $grp->result (...)	1820	=item $grp->result (...)
1136		1821
1137	Set the result value(s) that will be passed to the group callback when all	1822	Set the result value(s) that will be passed to the group callback when all
1138	subrequests have finished and set the groups errno to the current value	1823	subrequests have finished and set the groups errno to the current value
1139	of errno (just like calling C<errno> without an error number). By default,	1824	of errno (just like calling C<errno> without an error number). By default,
…		…
1155		1840
1156	Sets a feeder/generator on this group: every group can have an attached	1841	Sets a feeder/generator on this group: every group can have an attached
1157	generator that generates requests if idle. The idea behind this is that,	1842	generator that generates requests if idle. The idea behind this is that,
1158	although you could just queue as many requests as you want in a group,	1843	although you could just queue as many requests as you want in a group,
1159	this might starve other requests for a potentially long time. For example,	1844	this might starve other requests for a potentially long time. For example,
1160	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1845	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1161	delaying any later requests for a long time.	1846	requests, delaying any later requests for a long time.
1162		1847
1163	To avoid this, and allow incremental generation of requests, you can	1848	To avoid this, and allow incremental generation of requests, you can
1164	instead a group and set a feeder on it that generates those requests. The	1849	instead a group and set a feeder on it that generates those requests. The
1165	feed callback will be called whenever there are few enough (see C<limit>,	1850	feed callback will be called whenever there are few enough (see C<limit>,
1166	below) requests active in the group itself and is expected to queue more	1851	below) requests active in the group itself and is expected to queue more
…		…
1198	The default value for the limit is C<0>, but note that setting a feeder	1883	The default value for the limit is C<0>, but note that setting a feeder
1199	automatically bumps it up to C<2>.	1884	automatically bumps it up to C<2>.
1200		1885
1201	=back	1886	=back
1202		1887
		1888
1203	=head2 SUPPORT FUNCTIONS	1889	=head2 SUPPORT FUNCTIONS
1204		1890
1205	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1891	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1206		1892
1207	=over 4	1893	=over 4
1208		1894
1209	=item $fileno = IO::AIO::poll_fileno	1895	=item $fileno = IO::AIO::poll_fileno
1210		1896
1211	Return the I<request result pipe file descriptor>. This filehandle must be	1897	Return the I<request result pipe file descriptor>. This filehandle must be
1212	polled for reading by some mechanism outside this module (e.g. Event or	1898	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1213	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1899	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1214	to call C<poll_cb> to check the results.	1900	you have to call C<poll_cb> to check the results.
1215		1901
1216	See C<poll_cb> for an example.	1902	See C<poll_cb> for an example.
1217		1903
1218	=item IO::AIO::poll_cb	1904	=item IO::AIO::poll_cb
1219		1905
1220	Process some outstanding events on the result pipe. You have to call this	1906	Process some requests that have reached the result phase (i.e. they have
1221	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1907	been executed but the results are not yet reported). You have to call
1222	returned earlier for whatever reason. Returns immediately when no events	1908	this "regularly" to finish outstanding requests.
1223	are outstanding. The amount of events processed depends on the settings of
1224	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1225		1909
		1910	Returns C<0> if all events could be processed (or there were no
		1911	events to process), or C<-1> if it returned earlier for whatever
		1912	reason. Returns immediately when no events are outstanding. The amount
		1913	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1914	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1915
1226	If not all requests were processed for whatever reason, the filehandle	1916	If not all requests were processed for whatever reason, the poll file
1227	will still be ready when C<poll_cb> returns, so normally you don't have to	1917	descriptor will still be ready when C<poll_cb> returns, so normally you
1228	do anything special to have it called later.	1918	don't have to do anything special to have it called later.
		1919
		1920	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1921	ready, it can be beneficial to call this function from loops which submit
		1922	a lot of requests, to make sure the results get processed when they become
		1923	available and not just when the loop is finished and the event loop takes
		1924	over again. This function returns very fast when there are no outstanding
		1925	requests.
1229		1926
1230	Example: Install an Event watcher that automatically calls	1927	Example: Install an Event watcher that automatically calls
1231	IO::AIO::poll_cb with high priority:	1928	IO::AIO::poll_cb with high priority (more examples can be found in the
		1929	SYNOPSIS section, at the top of this document):
1232		1930
1233	Event->io (fd => IO::AIO::poll_fileno,	1931	Event->io (fd => IO::AIO::poll_fileno,
1234	poll => 'r', async => 1,	1932	poll => 'r', async => 1,
1235	cb => \&IO::AIO::poll_cb);	1933	cb => \&IO::AIO::poll_cb);
		1934
		1935	=item IO::AIO::poll_wait
		1936
		1937	Wait until either at least one request is in the result phase or no
		1938	requests are outstanding anymore.
		1939
		1940	This is useful if you want to synchronously wait for some requests to
		1941	become ready, without actually handling them.
		1942
		1943	See C<nreqs> for an example.
		1944
		1945	=item IO::AIO::poll
		1946
		1947	Waits until some requests have been handled.
		1948
		1949	Returns the number of requests processed, but is otherwise strictly
		1950	equivalent to:
		1951
		1952	IO::AIO::poll_wait, IO::AIO::poll_cb
		1953
		1954	=item IO::AIO::flush
		1955
		1956	Wait till all outstanding AIO requests have been handled.
		1957
		1958	Strictly equivalent to:
		1959
		1960	IO::AIO::poll_wait, IO::AIO::poll_cb
		1961	while IO::AIO::nreqs;
		1962
		1963	This function can be useful at program aborts, to make sure outstanding
		1964	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1965	this function on normal exits), or when you are merely using C<IO::AIO>
		1966	for its more advanced functions, rather than for async I/O, e.g.:
		1967
		1968	my ($dirs, $nondirs);
		1969	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1970	IO::AIO::flush;
		1971	# $dirs, $nondirs are now set
1236		1972
1237	=item IO::AIO::max_poll_reqs $nreqs	1973	=item IO::AIO::max_poll_reqs $nreqs
1238		1974
1239	=item IO::AIO::max_poll_time $seconds	1975	=item IO::AIO::max_poll_time $seconds
1240		1976
…		…
1265	# use a low priority so other tasks have priority	2001	# use a low priority so other tasks have priority
1266	Event->io (fd => IO::AIO::poll_fileno,	2002	Event->io (fd => IO::AIO::poll_fileno,
1267	poll => 'r', nice => 1,	2003	poll => 'r', nice => 1,
1268	cb => &IO::AIO::poll_cb);	2004	cb => &IO::AIO::poll_cb);
1269		2005
1270	=item IO::AIO::poll_wait
1271
1272	If there are any outstanding requests and none of them in the result
1273	phase, wait till the result filehandle becomes ready for reading (simply
1274	does a C<select> on the filehandle. This is useful if you want to
1275	synchronously wait for some requests to finish).
1276
1277	See C<nreqs> for an example.
1278
1279	=item IO::AIO::poll
1280
1281	Waits until some requests have been handled.
1282
1283	Returns the number of requests processed, but is otherwise strictly
1284	equivalent to:
1285
1286	IO::AIO::poll_wait, IO::AIO::poll_cb
1287
1288	=item IO::AIO::flush
1289
1290	Wait till all outstanding AIO requests have been handled.
1291
1292	Strictly equivalent to:
1293
1294	IO::AIO::poll_wait, IO::AIO::poll_cb
1295	while IO::AIO::nreqs;
1296
1297	=back	2006	=back
		2007
1298		2008
1299	=head3 CONTROLLING THE NUMBER OF THREADS	2009	=head3 CONTROLLING THE NUMBER OF THREADS
1300		2010
1301	=over	2011	=over
1302		2012
…		…
1334		2044
1335	Under normal circumstances you don't need to call this function.	2045	Under normal circumstances you don't need to call this function.
1336		2046
1337	=item IO::AIO::max_idle $nthreads	2047	=item IO::AIO::max_idle $nthreads
1338		2048
1339	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2049	Limit the number of threads (default: 4) that are allowed to idle
1340	threads that did not get a request to process within 10 seconds). That	2050	(i.e., threads that did not get a request to process within the idle
1341	means if a thread becomes idle while C<$nthreads> other threads are also	2051	timeout (default: 10 seconds). That means if a thread becomes idle while
1342	idle, it will free its resources and exit.	2052	C<$nthreads> other threads are also idle, it will free its resources and
		2053	exit.
1343		2054
1344	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2055	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1345	to allow for extremely high load situations, but want to free resources	2056	to allow for extremely high load situations, but want to free resources
1346	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2057	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1347		2058
1348	The default is probably ok in most situations, especially if thread	2059	The default is probably ok in most situations, especially if thread
1349	creation is fast. If thread creation is very slow on your system you might	2060	creation is fast. If thread creation is very slow on your system you might
1350	want to use larger values.	2061	want to use larger values.
1351		2062
		2063	=item IO::AIO::idle_timeout $seconds
		2064
		2065	Sets the minimum idle timeout (default 10) after which worker threads are
		2066	allowed to exit. SEe C<IO::AIO::max_idle>.
		2067
1352	=item IO::AIO::max_outstanding $maxreqs	2068	=item IO::AIO::max_outstanding $maxreqs
1353		2069
1354	This is a very bad function to use in interactive programs because it
1355	blocks, and a bad way to reduce concurrency because it is inexact: Better
1356	use an C<aio_group> together with a feed callback.
1357
1358	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2070	Sets the maximum number of outstanding requests to C<$nreqs>. If
1359	do queue up more than this number of requests, the next call to the	2071	you do queue up more than this number of requests, the next call to
1360	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)	2072	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1361	function will block until the limit is no longer exceeded.	2073	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2074	longer exceeded.
1362		2075
1363	The default value is very large, so there is no practical limit on the	2076	In other words, this setting does not enforce a queue limit, but can be
1364	number of outstanding requests.	2077	used to make poll functions block if the limit is exceeded.
1365		2078
1366	You can still queue as many requests as you want. Therefore,	2079	This is a bad function to use in interactive programs because it blocks,
1367	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2080	and a bad way to reduce concurrency because it is inexact. If you need to
1368	as a stop gap to shield against fatal memory overflow (with large values).	2081	issue many requests without being able to call a poll function on demand,
		2082	it is better to use an C<aio_group> together with a feed callback.
		2083
		2084	Its main use is in scripts without an event loop - when you want to stat a
		2085	lot of files, you can write something like this:
		2086
		2087	IO::AIO::max_outstanding 32;
		2088
		2089	for my $path (...) {
		2090	aio_stat $path , ...;
		2091	IO::AIO::poll_cb;
		2092	}
		2093
		2094	IO::AIO::flush;
		2095
		2096	The call to C<poll_cb> inside the loop will normally return instantly,
		2097	allowing the loop to progress, but as soon as more than C<32> requests
		2098	are in-flight, it will block until some requests have been handled. This
		2099	keeps the loop from pushing a large number of C<aio_stat> requests onto
		2100	the queue (which, with many paths to stat, can use up a lot of memory).
		2101
		2102	The default value for C<max_outstanding> is very large, so there is no
		2103	practical limit on the number of outstanding requests.
1369		2104
1370	=back	2105	=back
		2106
1371		2107
1372	=head3 STATISTICAL INFORMATION	2108	=head3 STATISTICAL INFORMATION
1373		2109
1374	=over	2110	=over
1375		2111
…		…
1393	Returns the number of requests currently in the pending state (executed,	2129	Returns the number of requests currently in the pending state (executed,
1394	but not yet processed by poll_cb).	2130	but not yet processed by poll_cb).
1395		2131
1396	=back	2132	=back
1397		2133
		2134
		2135	=head3 SUBSECOND STAT TIME ACCESS
		2136
		2137	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2138	generally find access/modification and change times with subsecond time
		2139	accuracy of the system supports it, but perl's built-in functions only
		2140	return the integer part.
		2141
		2142	The following functions return the timestamps of the most recent
		2143	stat with subsecond precision on most systems and work both after
		2144	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2145	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2146	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2147
		2148	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2149	full resolution without rounding and work with standard perl C<stat>,
		2150	alleviating the need to call the special C<Time::HiRes> functions, which
		2151	do not act like their perl counterparts.
		2152
		2153	On operating systems or file systems where subsecond time resolution is
		2154	not supported or could not be detected, a fractional part of C<0> is
		2155	returned, so it is always safe to call these functions.
		2156
		2157	=over 4
		2158
		2159	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2160
		2161	Return the access, modication, change or birth time, respectively,
		2162	including fractional part. Due to the limited precision of floating point,
		2163	the accuracy on most platforms is only a bit better than milliseconds
		2164	for times around now - see the I<nsec> function family, below, for full
		2165	accuracy.
		2166
		2167	File birth time is only available when the OS and perl support it (on
		2168	FreeBSD and NetBSD at the time of this writing, although support is
		2169	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2170	it). On systems where it isn't available, C<0> is currently returned, but
		2171	this might change to C<undef> in a future version.
		2172
		2173	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2174
		2175	Returns access, modification, change and birth time all in one go, and
		2176	maybe more times in the future version.
		2177
		2178	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2179
		2180	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2181	as an integer in the range C<0> to C<999999999>.
		2182
		2183	Note that no accessors are provided for access, modification and
		2184	change times - you need to get those from C<stat _> if required (C<int
		2185	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2186	value).
		2187
		2188	=item $seconds = IO::AIO::st_btimesec
		2189
		2190	The (integral) seconds part of the file birth time, if available.
		2191
		2192	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2193
		2194	Like the functions above, but returns all four times in one go (and maybe
		2195	more in future versions).
		2196
		2197	=item $counter = IO::AIO::st_gen
		2198
		2199	Returns the generation counter (in practice this is just a random number)
		2200	of the file. This is only available on platforms which have this member in
		2201	their C<struct stat> (most BSDs at the time of this writing) and generally
		2202	only to the root usert. If unsupported, C<0> is returned, but this might
		2203	change to C<undef> in a future version.
		2204
		2205	=back
		2206
		2207	Example: print the high resolution modification time of F</etc>, using
		2208	C<stat>, and C<IO::AIO::aio_stat>.
		2209
		2210	if (stat "/etc") {
		2211	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2212	}
		2213
		2214	IO::AIO::aio_stat "/etc", sub {
		2215	$_[0]
		2216	and return;
		2217
		2218	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2219	};
		2220
		2221	IO::AIO::flush;
		2222
		2223	Output of the awbove on my system, showing reduced and full accuracy:
		2224
		2225	stat(/etc) mtime: 1534043702.020808
		2226	aio_stat(/etc) mtime: 1534043702.020807792
		2227
		2228
		2229	=head3 MISCELLANEOUS FUNCTIONS
		2230
		2231	IO::AIO implements some functions that are useful when you want to use
		2232	some "Advanced I/O" function not available to in Perl, without going the
		2233	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2234	counterpart.
		2235
		2236	=over 4
		2237
		2238	=item $retval = IO::AIO::fexecve $fh, $argv, $envp
		2239
		2240	A more-or-less direct equivalent to the POSIX C<fexecve> functions, which
		2241	allows you to specify the program to be executed via a file descriptor (or
		2242	handle). Returns C<-1> and sets errno to C<ENOSYS> if not available.
		2243
		2244	=item $numfd = IO::AIO::get_fdlimit
		2245
		2246	Tries to find the current file descriptor limit and returns it, or
		2247	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2248	the highest valid file descriptor number.
		2249
		2250	=item IO::AIO::min_fdlimit [$numfd]
		2251
		2252	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2253	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2254	is missing, it will try to set a very high limit, although this is not
		2255	recommended when you know the actual minimum that you require.
		2256
		2257	If the limit cannot be raised enough, the function makes a best-effort
		2258	attempt to increase the limit as much as possible, using various
		2259	tricks, while still failing. You can query the resulting limit using
		2260	C<IO::AIO::get_fdlimit>.
		2261
		2262	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2263	true.
		2264
		2265	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2266
		2267	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2268	but is blocking (this makes most sense if you know the input data is
		2269	likely cached already and the output filehandle is set to non-blocking
		2270	operations).
		2271
		2272	Returns the number of bytes copied, or C<-1> on error.
		2273
		2274	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2275
		2276	Simply calls the C<posix_fadvise> function (see its
		2277	manpage for details). The following advice constants are
		2278	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2279	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2280	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2281
		2282	On systems that do not implement C<posix_fadvise>, this function returns
		2283	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2284
		2285	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2286
		2287	Simply calls the C<posix_madvise> function (see its
		2288	manpage for details). The following advice constants are
		2289	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2290	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2291	C<IO::AIO::MADV_DONTNEED>.
		2292
		2293	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2294	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2295	will be reduced to fit into the C<$scalar>.
		2296
		2297	On systems that do not implement C<posix_madvise>, this function returns
		2298	ENOSYS, otherwise the return value of C<posix_madvise>.
		2299
		2300	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2301
		2302	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2303	$scalar (see its manpage for details). The following protect
		2304	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2305	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2306
		2307	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2308	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2309	will be reduced to fit into the C<$scalar>.
		2310
		2311	On systems that do not implement C<mprotect>, this function returns
		2312	ENOSYS, otherwise the return value of C<mprotect>.
		2313
		2314	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2315
		2316	Memory-maps a file (or anonymous memory range) and attaches it to the
		2317	given C<$scalar>, which will act like a string scalar. Returns true on
		2318	success, and false otherwise.
		2319
		2320	The scalar must exist, but its contents do not matter - this means you
		2321	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2322	the scalar first.
		2323
		2324	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2325	which don't change the string length, and most read-only operations such
		2326	as copying it or searching it with regexes and so on.
		2327
		2328	Anything else is unsafe and will, at best, result in memory leaks.
		2329
		2330	The memory map associated with the C<$scalar> is automatically removed
		2331	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2332	or C<IO::AIO::munmap> functions are called on it.
		2333
		2334	This calls the C<mmap>(2) function internally. See your system's manual
		2335	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2336
		2337	The C<$length> must be larger than zero and smaller than the actual
		2338	filesize.
		2339
		2340	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2341	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2342
		2343	C<$flags> can be a combination of
		2344	C<IO::AIO::MAP_SHARED> or
		2345	C<IO::AIO::MAP_PRIVATE>,
		2346	or a number of system-specific flags (when not available, the are C<0>):
		2347	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2348	C<IO::AIO::MAP_LOCKED>,
		2349	C<IO::AIO::MAP_NORESERVE>,
		2350	C<IO::AIO::MAP_POPULATE>,
		2351	C<IO::AIO::MAP_NONBLOCK>,
		2352	C<IO::AIO::MAP_FIXED>,
		2353	C<IO::AIO::MAP_GROWSDOWN>,
		2354	C<IO::AIO::MAP_32BIT>,
		2355	C<IO::AIO::MAP_HUGETLB>,
		2356	C<IO::AIO::MAP_STACK>,
		2357	C<IO::AIO::MAP_FIXED_NOREPLACE>,
		2358	C<IO::AIO::MAP_SHARED_VALIDATE>,
		2359	C<IO::AIO::MAP_SYNC> or
		2360	C<IO::AIO::MAP_UNINITIALIZED>.
		2361
		2362	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2363
		2364	C<$offset> is the offset from the start of the file - it generally must be
		2365	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2366
		2367	Example:
		2368
		2369	use Digest::MD5;
		2370	use IO::AIO;
		2371
		2372	open my $fh, "<verybigfile"
		2373	or die "$!";
		2374
		2375	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2376	or die "verybigfile: $!";
		2377
		2378	my $fast_md5 = md5 $data;
		2379
		2380	=item IO::AIO::munmap $scalar
		2381
		2382	Removes a previous mmap and undefines the C<$scalar>.
		2383
		2384	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2385
		2386	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2387	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2388	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2389
		2390	Returns true if successful, and false otherwise. If the underlying mmapped
		2391	region has changed address, then the true value has the numerical value
		2392	C<1>, otherwise it has the numerical value C<0>:
		2393
		2394	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2395	or die "mremap: $!";
		2396
		2397	if ($success*1) {
		2398	warn "scalar has chanegd address in memory\n";
		2399	}
		2400
		2401	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2402	implemented, but not supported and might go away in a future version.
		2403
		2404	On systems where this call is not supported or is not emulated, this call
		2405	returns falls and sets C<$!> to C<ENOSYS>.
		2406
		2407	=item IO::AIO::mlockall $flags
		2408
		2409	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2410	but is blocking.
		2411
		2412	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2413
		2414	Calls the C<munlock> function, undoing the effects of a previous
		2415	C<aio_mlock> call (see its description for details).
		2416
		2417	=item IO::AIO::munlockall
		2418
		2419	Calls the C<munlockall> function.
		2420
		2421	On systems that do not implement C<munlockall>, this function returns
		2422	ENOSYS, otherwise the return value of C<munlockall>.
		2423
		2424	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2425
		2426	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2427	and return the new file handle on success, or sets C<$!> and returns
		2428	C<undef> on error.
		2429
		2430	The remote name of the new socket will be stored in C<$sockaddr>, which
		2431	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2432	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2433	by returning a longer string in C<$sockaddr>, which might or might not be
		2434	truncated.
		2435
		2436	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2437	C<$sockaddr_maxlen>.
		2438
		2439	The main reasons to use this syscall rather than portable C<accept(2)>
		2440	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2441	flags and you can accept name-less sockets by specifying C<0> for
		2442	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2443	C<accept>.
		2444
		2445	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2446
		2447	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2448	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2449	should be the file offset.
		2450
		2451	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2452	silently corrupt the data in this case.
		2453
		2454	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2455	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2456	C<IO::AIO::SPLICE_F_GIFT>.
		2457
		2458	See the C<splice(2)> manpage for details.
		2459
		2460	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2461
		2462	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2463	description for C<IO::AIO::splice> above for details.
		2464
		2465	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2466
		2467	Attempts to query or change the pipe buffer size. Obviously works only
		2468	on pipes, and currently works only on GNU/Linux systems, and fails with
		2469	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2470	size on other systems, drop me a note.
		2471
		2472	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2473
		2474	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2475	C<$flags> is missing or C<0>, then this should be the same as a call to
		2476	perl's built-in C<pipe> function and create a new pipe, and works on
		2477	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2478	(..., 4096, O_BINARY)>.
		2479
		2480	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2481	the given flags (Linux 2.6.27, glibc 2.9).
		2482
		2483	On success, the read and write file handles are returned.
		2484
		2485	On error, nothing will be returned. If the pipe2 syscall is missing and
		2486	C<$flags> is non-zero, fails with C<ENOSYS>.
		2487
		2488	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2489	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2490	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2491
		2492	Example: create a pipe race-free w.r.t. threads and fork:
		2493
		2494	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2495	or die "pipe2: $!\n";
		2496
		2497	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2498
		2499	This is a direct interface to the Linux L<memfd_create(2)> system
		2500	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2501	should be C<IO::AIO::MFD_CLOEXEC>.
		2502
		2503	On success, the new memfd filehandle is returned, otherwise returns
		2504	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2505
		2506	Please refer to L<memfd_create(2)> for more info on this call.
		2507
		2508	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2509	C<IO::AIO::MFD_ALLOW_SEALING>, C<IO::AIO::MFD_HUGETLB>,
		2510	C<IO::AIO::MFD_HUGETLB_2MB> and C<IO::AIO::MFD_HUGETLB_1GB>.
		2511
		2512	Example: create a new memfd.
		2513
		2514	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2515	or die "memfd_create: $!\n";
		2516
		2517	=item $fh = IO::AIO::pidfd_open $pid[, $flags]
		2518
		2519	This is an interface to the Linux L<pidfd_open(2)> system call. The
		2520	default for C<$flags> is C<0>.
		2521
		2522	On success, a new pidfd filehandle is returned (that is already set to
		2523	close-on-exec), otherwise returns C<undef>. If the syscall is missing,
		2524	fails with C<ENOSYS>.
		2525
		2526	Example: open pid 6341 as pidfd.
		2527
		2528	my $fh = IO::AIO::pidfd_open 6341
		2529	or die "pidfd_open: $!\n";
		2530
		2531	=item $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		2532
		2533	This is an interface to the Linux L<pidfd_send_signal> system call. The
		2534	default for C<$siginfo> is C<undef> and the default for C<$flags> is C<0>.
		2535
		2536	Returns the system call status. If the syscall is missing, fails with
		2537	C<ENOSYS>.
		2538
		2539	When specified, C<$siginfo> must be a reference to a hash with one or more
		2540	of the following members:
		2541
		2542	=over
		2543
		2544	=item code - the C<si_code> member
		2545
		2546	=item pid - the C<si_pid> member
		2547
		2548	=item uid - the C<si_uid> member
		2549
		2550	=item value_int - the C<si_value.sival_int> member
		2551
		2552	=item value_ptr - the C<si_value.sival_ptr> member, specified as an integer
		2553
		2554	=back
		2555
		2556	Example: send a SIGKILL to the specified process.
		2557
		2558	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
		2559	and die "pidfd_send_signal: $!\n";
		2560
		2561	Example: send a SIGKILL to the specified process with extra data.
		2562
		2563	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
		2564	and die "pidfd_send_signal: $!\n";
		2565
		2566	=item $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		2567
		2568	This is an interface to the Linux L<pidfd_getfd> system call. The default
		2569	for C<$flags> is C<0>.
		2570
		2571	On success, returns a dup'ed copy of the target file descriptor (specified
		2572	as an integer) returned (that is already set to close-on-exec), otherwise
		2573	returns C<undef>. If the syscall is missing, fails with C<ENOSYS>.
		2574
		2575	Example: get a copy of standard error of another process and print soemthing to it.
		2576
		2577	my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
		2578	or die "pidfd_getfd: $!\n";
		2579	print $errfh "stderr\n";
		2580
		2581	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2582
		2583	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2584	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2585
		2586	On success, the new eventfd filehandle is returned, otherwise returns
		2587	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2588
		2589	Please refer to L<eventfd(2)> for more info on this call.
		2590
		2591	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2592	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2593
		2594	Example: create a new eventfd filehandle:
		2595
		2596	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2597	or die "eventfd: $!\n";
		2598
		2599	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2600
		2601	This is a direct interface to the Linux L<timerfd_create(2)> system
		2602	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2603	should be C<IO::AIO::TFD_CLOEXEC>.
		2604
		2605	On success, the new timerfd filehandle is returned, otherwise returns
		2606	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2607
		2608	Please refer to L<timerfd_create(2)> for more info on this call.
		2609
		2610	The following C<$clockid> values are
		2611	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2612	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2613	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2614	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2615
		2616	The following C<$flags> values are available (Linux
		2617	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2618
		2619	Example: create a new timerfd and set it to one-second repeated alarms,
		2620	then wait for two alarms:
		2621
		2622	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2623	or die "timerfd_create: $!\n";
		2624
		2625	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2626	or die "timerfd_settime: $!\n";
		2627
		2628	for (1..2) {
		2629	8 == sysread $fh, my $buf, 8
		2630	or die "timerfd read failure\n";
		2631
		2632	printf "number of expirations (likely 1): %d\n",
		2633	unpack "Q", $buf;
		2634	}
		2635
		2636	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2637
		2638	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2639	call. Please refer to its manpage for more info on this call.
		2640
		2641	The new itimerspec is specified using two (possibly fractional) second
		2642	values, C<$new_interval> and C<$new_value>).
		2643
		2644	On success, the current interval and value are returned (as per
		2645	C<timerfd_gettime>). On failure, the empty list is returned.
		2646
		2647	The following C<$flags> values are
		2648	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2649	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2650
		2651	See C<IO::AIO::timerfd_create> for a full example.
		2652
		2653	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2654
		2655	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2656	call. Please refer to its manpage for more info on this call.
		2657
		2658	On success, returns the current values of interval and value for the given
		2659	timerfd (as potentially fractional second values). On failure, the empty
		2660	list is returned.
		2661
		2662	=back
		2663
1398	=cut	2664	=cut
1399		2665
1400	min_parallel 8;	2666	min_parallel 8;
1401		2667
1402	END { flush }	2668	END { flush }
1403		2669
1404	1;	2670	1;
1405		2671
		2672	=head1 EVENT LOOP INTEGRATION
		2673
		2674	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2675	automatically into many event loops:
		2676
		2677	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2678	use AnyEvent::AIO;
		2679
		2680	You can also integrate IO::AIO manually into many event loops, here are
		2681	some examples of how to do this:
		2682
		2683	# EV integration
		2684	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2685
		2686	# Event integration
		2687	Event->io (fd => IO::AIO::poll_fileno,
		2688	poll => 'r',
		2689	cb => \&IO::AIO::poll_cb);
		2690
		2691	# Glib/Gtk2 integration
		2692	add_watch Glib::IO IO::AIO::poll_fileno,
		2693	in => sub { IO::AIO::poll_cb; 1 };
		2694
		2695	# Tk integration
		2696	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2697	readable => \&IO::AIO::poll_cb);
		2698
		2699	# Danga::Socket integration
		2700	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2701	\&IO::AIO::poll_cb);
		2702
1406	=head2 FORK BEHAVIOUR	2703	=head2 FORK BEHAVIOUR
1407		2704
1408	This module should do "the right thing" when the process using it forks:	2705	Usage of pthreads in a program changes the semantics of fork
		2706	considerably. Specifically, only async-safe functions can be called after
		2707	fork. Perl doesn't know about this, so in general, you cannot call fork
		2708	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2709	pthreads, so this applies, but many other extensions and (for inexplicable
		2710	reasons) perl itself often is linked against pthreads, so this limitation
		2711	applies to quite a lot of perls.
1409		2712
1410	Before the fork, IO::AIO enters a quiescent state where no requests	2713	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1411	can be added in other threads and no results will be processed. After	2714	only works in the process that loaded it. Forking is fully supported, but
1412	the fork the parent simply leaves the quiescent state and continues	2715	using IO::AIO in the child is not.
1413	request/result processing, while the child frees the request/result queue
1414	(so that the requests started before the fork will only be handled in the
1415	parent). Threads will be started on demand until the limit set in the
1416	parent process has been reached again.
1417		2716
1418	In short: the parent will, after a short pause, continue as if fork had	2717	You might get around by not I<using> IO::AIO before (or after)
1419	not been called, while the child will act as if IO::AIO has not been used	2718	forking. You could also try to call the L<IO::AIO::reinit> function in the
1420	yet.	2719	child:
		2720
		2721	=over 4
		2722
		2723	=item IO::AIO::reinit
		2724
		2725	Abandons all current requests and I/O threads and simply reinitialises all
		2726	data structures. This is not an operation supported by any standards, but
		2727	happens to work on GNU/Linux and some newer BSD systems.
		2728
		2729	The only reasonable use for this function is to call it after forking, if
		2730	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2731	the process will result in undefined behaviour. Calling it at any time
		2732	will also result in any undefined (by POSIX) behaviour.
		2733
		2734	=back
		2735
		2736	=head2 LINUX-SPECIFIC CALLS
		2737
		2738	When a call is documented as "linux-specific" then this means it
		2739	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2740	availability and compatibility of such calls regardless of the platform
		2741	it is compiled on, so platforms such as FreeBSD which often implement
		2742	these calls will work. When in doubt, call them and see if they fail wth
		2743	C<ENOSYS>.
1421		2744
1422	=head2 MEMORY USAGE	2745	=head2 MEMORY USAGE
1423		2746
1424	Per-request usage:	2747	Per-request usage:
1425		2748
…		…
1438	temporary buffers, and each thread requires a stack and other data	2761	temporary buffers, and each thread requires a stack and other data
1439	structures (usually around 16k-128k, depending on the OS).	2762	structures (usually around 16k-128k, depending on the OS).
1440		2763
1441	=head1 KNOWN BUGS	2764	=head1 KNOWN BUGS
1442		2765
1443	Known bugs will be fixed in the next release.	2766	Known bugs will be fixed in the next release :)
		2767
		2768	=head1 KNOWN ISSUES
		2769
		2770	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2771	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2772	non-created hash slots or other scalars I didn't think of. It's best to
		2773	avoid such and either use scalar variables or making sure that the scalar
		2774	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2775
		2776	I am not sure anything can be done about this, so this is considered a
		2777	known issue, rather than a bug.
1444		2778
1445	=head1 SEE ALSO	2779	=head1 SEE ALSO
1446		2780
1447	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2781	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1448	more natural syntax.	2782	more natural syntax and L<IO::FDPass> for file descriptor passing.
1449		2783
1450	=head1 AUTHOR	2784	=head1 AUTHOR
1451		2785
1452	Marc Lehmann <schmorp@schmorp.de>	2786	Marc Lehmann <schmorp@schmorp.de>
1453	http://home.schmorp.de/	2787	http://home.schmorp.de/

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