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Revision 1.117 by root, Sat Oct 6 14:05:19 2007 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
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
64	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
68	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
69	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
70	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>
71	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.
72		52
73	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
74	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
75	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
…		…
78	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
79	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
80	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
81	using threads anyway.	61	using threads anyway.
82		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
83	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,
84	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
85	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
86	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
87		71
88	=head2 EXAMPLE	72	=head2 EXAMPLE
89		73
90	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
91	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
92		76
93	use Fcntl;
94	use Event;	77	use EV;
95	use IO::AIO;	78	use IO::AIO;
96		79
97	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
98	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
99	poll => 'r',
100	cb => \&IO::AIO::poll_cb);
101		82
102	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
104	my $fh = shift	85	my $fh = shift
105	or die "error while opening: $!";	86	or die "error while opening: $!";
106		87
107	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
108	my $size = -s $fh;	89	my $size = -s $fh;
…		…
117		98
118	# file contents now in $contents	99	# file contents now in $contents
119	print $contents;	100	print $contents;
120		101
121	# exit event loop and program	102	# exit event loop and program
122	Event::unloop;	103	EV::break;
123	};	104	};
124	};	105	};
125		106
126	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
127	# check for sockets etc. etc.	108	# check for sockets etc. etc.
128		109
129	# process events as long as there are some:	110	# process events as long as there are some:
130	Event::loop;	111	EV::run;
131		112
132	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
133		114
134	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
135	directly visible to Perl.	116	directly visible to Perl.
…		…
185		166
186	package IO::AIO;	167	package IO::AIO;
187		168
188	use Carp ();	169	use Carp ();
189		170
190	no warnings;	171	use common::sense;
191	use strict 'vars';
192		172
193	use base 'Exporter';	173	use base 'Exporter';
194		174
195	BEGIN {	175	BEGIN {
196	our $VERSION = '2.51';	176	our $VERSION = 4.77;
197		177
198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
199	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
200	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
		181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
201	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
202	aio_chown 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);
		190
203	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
204	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
205	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
206	nreqs nready npending nthreads	194	nreqs nready npending nthreads
207	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);
		203
		204	push @AIO_REQ, qw(aio_busy); # not exported
208		205
209	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
210		207
211	require XSLoader;	208	require XSLoader;
212	XSLoader::load ("IO::AIO", $VERSION);	209	XSLoader::load ("IO::AIO", $VERSION);
213	}	210	}
214		211
215	=head1 FUNCTIONS	212	=head1 FUNCTIONS
216		213
217	=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[, $flags]
		331
		332	=head2 API NOTES
218		333
219	All the C<aio_*> calls are more or less thin wrappers around the syscall	334	All the C<aio_*> calls are more or less thin wrappers around the syscall
220	with the same name (sans C<aio_>). The arguments are similar or identical,	335	with the same name (sans C<aio_>). The arguments are similar or identical,
221	and they all accept an additional (and optional) C<$callback> argument	336	and they all accept an additional (and optional) C<$callback> argument
222	which must be a code reference. This code reference will get called with	337	which must be a code reference. This code reference will be called after
223	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	338	the syscall has been executed in an asynchronous fashion. The results
224	perl, which usually delivers "false") as it's sole argument when the given	339	of the request will be passed as arguments to the callback (and, if an
225	syscall has been executed asynchronously.	340	error occured, in C<$!>) - 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>.
226		346
227	All functions expecting a filehandle keep a copy of the filehandle	347	All functions expecting a filehandle keep a copy of the filehandle
228	internally until the request has finished.	348	internally until the request has finished.
229		349
230	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
231	further manipulation of those requests while they are in-flight.	351	further manipulation of those requests while they are in-flight.
232		352
233	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
234	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
235	request is being executed, the current working directory could have	355	current working directory could have changed. Alternatively, you can
236	changed. Alternatively, you can make sure that you never change the	356	make sure that you never change the current working directory anywhere
237	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
238	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.
239		361
240	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
241	in filenames you got from outside (command line, readdir etc.) without	363	in filenames you got from outside (command line, readdir etc.) without
242	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
243	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
244	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
245	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.
246		369
247	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
248	handles correctly wether it is set or not.	371	handles correctly whether it is set or not.
		372
		373	=head2 AIO REQUEST FUNCTIONS
249		374
250	=over 4	375	=over 4
251		376
252	=item $prev_pri = aioreq_pri [$pri]	377	=item $prev_pri = aioreq_pri [$pri]
253		378
…		…
283		408
284		409
285	=item aio_open $pathname, $flags, $mode, $callback->($fh)	410	=item aio_open $pathname, $flags, $mode, $callback->($fh)
286		411
287	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
288	created filehandle for the file.	413	created filehandle for the file (or C<undef> in case of an error).
289		414
290	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,
291	for an explanation.	416	for an explanation.
292		417
293	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
…		…
300	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
301	change the umask.	426	change the umask.
302		427
303	Example:	428	Example:
304		429
305	aio_open "/etc/passwd", O_RDONLY, 0, sub {	430	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
306	if ($_[0]) {	431	if ($_[0]) {
307	print "open successful, fh is $_[0]\n";	432	print "open successful, fh is $_[0]\n";
308	...	433	...
309	} else {	434	} else {
310	die "open failed: $!\n";	435	die "open failed: $!\n";
311	}	436	}
312	};	437	};
313		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
314		448
315	=item aio_close $fh, $callback->($status)	449	=item aio_close $fh, $callback->($status)
316		450
317	Asynchronously close a file and call the callback with the result	451	Asynchronously close a file and call the callback with the result
318	code.	452	code.
319		453
320	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on	454	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
321	closing the file descriptor associated with the filehandle itself. Here is	455	closing the file descriptor associated with the filehandle itself.
322	what aio_close will try:
323		456
324	1. dup()licate the fd	457	Therefore, C<aio_close> will not close the filehandle - instead it will
325	2. asynchronously close() the duplicated fd	458	use dup2 to overwrite the file descriptor with the write-end of a pipe
326	3. dup()licate the fd once more	459	(the pipe fd will be created on demand and will be cached).
327	4. let perl close() the filehandle
328	5. asynchronously close the duplicated fd
329		460
330	The idea is that the first close() flushes stuff to disk that closing an	461	Or in other words: the file descriptor will be closed, but it will not be
331	fd will flush, so when perl closes the fd, nothing much will need to be	462	free for reuse until the perl filehandle is closed.
332	flushed. The second async. close() will then flush stuff to disk that
333	closing the last fd to the file will flush.
334
335	Just FYI, SuSv3 has this to say on close:
336
337	All outstanding record locks owned by the process on the file
338	associated with the file descriptor shall be removed.
339
340	If fildes refers to a socket, close() shall cause the socket to be
341	destroyed. ... close() shall block for up to the current linger
342	interval until all data is transmitted.
343	[this actually sounds like a specification bug, but who knows]
344
345	And at least Linux additionally actually flushes stuff on every close,
346	even when the file itself is still open.
347
348	Sounds enourmously inefficient and complicated? Yes... please show me how
349	to nuke perl's fd out of existence...
350		463
351	=cut	464	=cut
352		465
353	sub aio_close($;$) {	466	=item aio_seek $fh, $offset, $whence, $callback->($offs)
354	aio_block {
355	my ($fh, $cb) = @_;
356		467
357	my $pri = aioreq_pri;	468	Seeks the filehandle to the new C<$offset>, similarly to perl's
358	my $grp = aio_group $cb;	469	C<sysseek>. The C<$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>).
359		472
360	my $fd = fileno $fh;	473	The resulting absolute offset will be passed to the callback, or C<-1> in
		474	case of an error.
361		475
362	defined $fd or Carp::croak "aio_close called with fd-less filehandle";	476	In theory, the C<$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.
363		479
364	# if the dups fail we will simply get EBADF	480	As a GNU/Linux (and maybe Solaris) extension, also the constants
365	my $fd2 = _dup $fd;	481	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
366	aioreq_pri $pri;	482	could be found. No guarantees about suitability for use in C<aio_seek> or
367	add $grp _aio_close $fd2, sub {	483	Perl's C<sysseek> can be made though, although I would naively assume they
368	my $fd2 = _dup $fd;	484	"just work".
369	close $fh;
370	aioreq_pri $pri;
371	add $grp _aio_close $fd2, sub {
372	$grp->result ($_[0]);
373	};
374	};
375
376	$grp
377	}
378	}
379
380		485
381	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	486	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
382		487
383	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	488	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
384		489
385	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>	490	Reads or writes C<$length> bytes from or to the specified C<$fh> and
386	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	491	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
387	callback without the actual number of bytes read (or -1 on error, just	492	calls the callback with the actual number of bytes transferred (or -1 on
388	like the syscall).	493	error, just like the syscall).
		494
		495	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		496	offset plus the actual number of bytes read.
389		497
390	If C<$offset> is undefined, then the current file descriptor offset will	498	If C<$offset> is undefined, then the current file descriptor offset will
391	be used (and updated), otherwise the file descriptor offset will not be	499	be used (and updated), otherwise the file descriptor offset will not be
392	changed by these calls.	500	changed by these calls.
393		501
394	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	502	If C<$length> is undefined in C<aio_write>, use the remaining length of
		503	C<$data>.
395		504
396	If C<$dataoffset> is less than zero, it will be counted from the end of	505	If C<$dataoffset> is less than zero, it will be counted from the end of
397	C<$data>.	506	C<$data>.
398		507
399	The C<$data> scalar I<MUST NOT> be modified in any way while the request	508	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
413		522
414	Tries to copy C<$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<$out_fh>. It starts
415	reading at byte offset C<$in_offset>, and starts writing at the current	524	reading at byte offset C<$in_offset>, and starts writing at the current
416	file offset of C<$out_fh>. Because of that, it is not safe to issue more	525	file offset of C<$out_fh>. Because of that, it is not safe to issue more
417	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	526	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
418	other.	527	other. The same C<$in_fh> works fine though, as this function does not
		528	move or use the file offset of C<$in_fh>.
419		529
		530	Please note that C<aio_sendfile> can read more bytes from C<$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
420	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
421	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
422	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.
423		549
424	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>,
425	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
426	regardless of the limitations of the operating system.	553	type of filehandle regardless of the limitations of the operating system.
427		554
428	Please note, however, that C<aio_sendfile> can read more bytes from	555	As native sendfile syscalls (as practically any non-POSIX interface hacked
429	C<$in_fh> than are written, and there is no way to find out how many	556	together in a hurry to improve benchmark numbers) tend to be rather buggy
430	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	557	on many systems, this implementation tries to work around some known bugs
431	provides the number of bytes written to C<$out_fh>. Only if the result	558	in Linux and FreeBSD kernels (probably others, too), but that might fail,
432	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> -
433	read.	560	fewer bytes than expected might have been transferred.
434		561
435		562
436	=item aio_readahead $fh,$offset,$length, $callback->($retval)	563	=item aio_readahead $fh,$offset,$length, $callback->($retval)
437		564
438	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
…		…
442	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
443	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
444	(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
445	file. The current file offset of the file is left unchanged.	572	file. The current file offset of the file is left unchanged.
446		573
447	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
448	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.
449		576
450		577
451	=item aio_stat $fh_or_path, $callback->($status)	578	=item aio_stat $fh_or_path, $callback->($status)
452		579
453	=item aio_lstat $fh, $callback->($status)	580	=item aio_lstat $fh, $callback->($status)
454		581
455	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
456	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
457	or C<-s _> etc...	584	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		585	and C<-T>).
458		586
459	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,
460	for an explanation.	588	for an explanation.
461		589
462	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
463	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
464	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>.
465		605
466	Example: Print the length of F</etc/passwd>:	606	Example: Print the length of F</etc/passwd>:
467		607
468	aio_stat "/etc/passwd", sub {	608	aio_stat "/etc/passwd", sub {
469	$_[0] and die "stat failed: $!";	609	$_[0] and die "stat failed: $!";
470	print "size is ", -s _, "\n";	610	print "size is ", -s _, "\n";
471	};	611	};
472		612
473		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
474	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	658	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
475		659
476	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
477	and $mtime being undef). Fractional times are supported if the underlying	661	and $mtime being undef). Fractional times are supported if the underlying
478	syscalls support them.	662	syscalls support them.
479		663
480	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,
481	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)
482	otherwise returns ENOSYS, so this is not portable.	666	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		667	portable.
483		668
484	Examples:	669	Examples:
485		670
486	# set atime and mtime to current time (basically touch(1)):	671	# set atime and mtime to current time (basically touch(1)):
487	aio_utime "path", undef, undef;	672	aio_utime "path", undef, undef;
…		…
505	=item aio_truncate $fh_or_path, $offset, $callback->($status)	690	=item aio_truncate $fh_or_path, $offset, $callback->($status)
506		691
507	Works like truncate(2) or ftruncate(2).	692	Works like truncate(2) or ftruncate(2).
508		693
509		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
510	=item aio_chmod $fh_or_path, $mode, $callback->($status)	717	=item aio_chmod $fh_or_path, $mode, $callback->($status)
511		718
512	Works like perl's C<chmod> function.	719	Works like perl's C<chmod> function.
513		720
514		721
…		…
516		723
517	Asynchronously unlink (delete) a file and call the callback with the	724	Asynchronously unlink (delete) a file and call the callback with the
518	result code.	725	result code.
519		726
520		727
521	=item aio_mknod $path, $mode, $dev, $callback->($status)	728	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
522		729
523	[EXPERIMENTAL]	730	[EXPERIMENTAL]
524		731
525	Asynchronously create a device node (or fifo). See mknod(2).	732	Asynchronously create a device node (or fifo). See mknod(2).
526		733
527	The only (POSIX-) portable way of calling this function is:	734	The only (POSIX-) portable way of calling this function is:
528		735
529	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	736	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
530		737
		738	See C<aio_stat> for info about some potentially helpful extra constants
		739	and functions.
531		740
532	=item aio_link $srcpath, $dstpath, $callback->($status)	741	=item aio_link $srcpath, $dstpath, $callback->($status)
533		742
534	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
535	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.
…		…
539		748
540	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
541	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.
542		751
543		752
544	=item aio_readlink $path, $callback->($link)	753	=item aio_readlink $pathname, $callback->($link)
545		754
546	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
547	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
548	callback.	757	callback.
549		758
550		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
551	=item aio_rename $srcpath, $dstpath, $callback->($status)	770	=item aio_rename $srcpath, $dstpath, $callback->($status)
552		771
553	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
554	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>.
555		794
556		795
557	=item aio_mkdir $pathname, $mode, $callback->($status)	796	=item aio_mkdir $pathname, $mode, $callback->($status)
558		797
559	Asynchronously mkdir (create) a directory and call the callback with	798	Asynchronously mkdir (create) a directory and call the callback with
…		…
564	=item aio_rmdir $pathname, $callback->($status)	803	=item aio_rmdir $pathname, $callback->($status)
565		804
566	Asynchronously rmdir (delete) a directory and call the callback with the	805	Asynchronously rmdir (delete) a directory and call the callback with the
567	result code.	806	result code.
568		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
569		812
570	=item aio_readdir $pathname, $callback->($entries)	813	=item aio_readdir $pathname, $callback->($entries)
571		814
572	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
573	directory (i.e. opendir + readdir + closedir). The entries will not be	816	directory (i.e. opendir + readdir + closedir). The entries will not be
574	sorted, and will B<NOT> include the C<.> and C<..> entries.	817	sorted, and will B<NOT> include the C<.> and C<..> entries.
575		818
576	The callback a single argument which is either C<undef> or an array-ref	819	The callback is passed a single argument which is either C<undef> or an
577	with the filenames.	820	array-ref with the filenames.
578		821
579		822
		823	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		824
		825	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		826	tune behaviour and output format. In case of an error, C<$entries> will be
		827	C<undef>.
		828
		829	The flags are a combination of the following constants, ORed together (the
		830	flags will also be passed to the callback, possibly modified):
		831
		832	=over 4
		833
		834	=item IO::AIO::READDIR_DENTS
		835
		836	Normally the callback gets an arrayref consisting of names only (as
		837	with C<aio_readdir>). If this flag is set, then the callback gets an
		838	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
		839	single directory entry in more detail:
		840
		841	C<$name> is the name of the entry.
		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
		853	C<$inode> is the inode number (which might not be exact on systems with 64
		854	bit inode numbers and 32 bit perls). This field has unspecified content on
		855	systems that do not deliver the inode information.
		856
		857	=item IO::AIO::READDIR_DIRS_FIRST
		858
		859	When this flag is set, then the names will be returned in an order where
		860	likely directories come first, in optimal stat order. This is useful when
		861	you need to quickly find directories, or you want to find all directories
		862	while avoiding to stat() each entry.
		863
		864	If the system returns type information in readdir, then this is used
		865	to find directories directly. Otherwise, likely directories are names
		866	beginning with ".", or otherwise names with no dots, of which names with
		867	short names are tried first.
		868
		869	=item IO::AIO::READDIR_STAT_ORDER
		870
		871	When this flag is set, then the names will be returned in an order
		872	suitable for stat()'ing each one. That is, when you plan to stat() most or
		873	all files in the given directory, then the returned order will likely be
		874	faster.
		875
		876	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
		877	then the likely dirs come first, resulting in a less optimal stat order
		878	for stat'ing all entries, but likely a more optimal order for finding
		879	subdirectories.
		880
		881	=item IO::AIO::READDIR_FOUND_UNKNOWN
		882
		883	This flag should not be set when calling C<aio_readdirx>. Instead, it
		884	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		885	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		886	C<$type>'s are known, which can be used to speed up some algorithms.
		887
		888	=back
		889
		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
580	=item aio_load $path, $data, $callback->($status)	920	=item aio_load $pathname, $data, $callback->($status)
581		921
582	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
583	memory. Status is the same as with aio_read.	923	memory. Status is the same as with aio_read.
584		924
		925	Using C<aio_slurp> might be more efficient, as it is a single request.
		926
585	=cut	927	=cut
586		928
587	sub aio_load($$;$) {	929	sub aio_load($$;$) {
588	aio_block {
589	my ($path, undef, $cb) = @_;	930	my ($path, undef, $cb) = @_;
590	my $data = \$_[1];	931	my $data = \$_[1];
591		932
592	my $pri = aioreq_pri;	933	my $pri = aioreq_pri;
593	my $grp = aio_group $cb;	934	my $grp = aio_group $cb;
		935
		936	aioreq_pri $pri;
		937	add $grp aio_open $path, O_RDONLY, 0, sub {
		938	my $fh = shift
		939	or return $grp->result (-1);
594		940
595	aioreq_pri $pri;	941	aioreq_pri $pri;
596	add $grp aio_open $path, O_RDONLY, 0, sub {
597	my $fh = shift
598	or return $grp->result (-1);
599
600	aioreq_pri $pri;
601	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {	942	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
602	$grp->result ($_[0]);	943	$grp->result ($_[0]);
603	};
604	};	944	};
605
606	$grp
607	}	945	};
		946
		947	$grp
608	}	948	}
609		949
610	=item aio_copy $srcpath, $dstpath, $callback->($status)	950	=item aio_copy $srcpath, $dstpath, $callback->($status)
611		951
612	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
613	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
614	the C<0> (error) or C<-1> ok.	954	a status of C<0> (ok) or C<-1> (error, see C<$!>).
615		955
		956	Existing destination files will be truncated.
		957
616	This is a composite request that it creates the destination file with	958	This is a composite request that creates the destination file with
617	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
618	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	960	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
619	uid/gid, in that order.	961	uid/gid, in that order.
620		962
621	If an error occurs, the partial destination file will be unlinked, if	963	If an error occurs, the partial destination file will be unlinked, if
…		…
623	errors are being ignored.	965	errors are being ignored.
624		966
625	=cut	967	=cut
626		968
627	sub aio_copy($$;$) {	969	sub aio_copy($$;$) {
628	aio_block {
629	my ($src, $dst, $cb) = @_;	970	my ($src, $dst, $cb) = @_;
630		971
631	my $pri = aioreq_pri;	972	my $pri = aioreq_pri;
632	my $grp = aio_group $cb;	973	my $grp = aio_group $cb;
633		974
634	aioreq_pri $pri;	975	aioreq_pri $pri;
635	add $grp aio_open $src, O_RDONLY, 0, sub {	976	add $grp aio_open $src, O_RDONLY, 0, sub {
636	if (my $src_fh = $_[0]) {	977	if (my $src_fh = $_[0]) {
637	my @stat = stat $src_fh;	978	my @stat = stat $src_fh; # hmm, might block over nfs?
638		979
639	aioreq_pri $pri;	980	aioreq_pri $pri;
640	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 {
641	if (my $dst_fh = $_[0]) {	982	if (my $dst_fh = $_[0]) {
642	aioreq_pri $pri;	983	aioreq_pri $pri;
643	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	984	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
644	if ($_[0] == $stat[7]) {	985	if ($_[0] == $stat[7]) {
645	$grp->result (0);	986	$grp->result (0);
646	close $src_fh;	987	close $src_fh;
647		988
648	# those should not normally block. should. should.
649	utime $stat[8], $stat[9], $dst;
650	chmod $stat[2] & 07777, $dst_fh;
651	chown $stat[4], $stat[5], $dst_fh;
652	close $dst_fh;
653	} else {	989	my $ch = sub {
654	$grp->result (-1);
655	close $src_fh;
656	close $dst_fh;
657
658	aioreq $pri;	990	aioreq_pri $pri;
		991	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		992	aioreq_pri $pri;
		993	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		994	aioreq_pri $pri;
659	add $grp aio_unlink $dst;	995	add $grp aio_close $dst_fh;
		996	}
		997	};
660	}	998	};
		999
		1000	aioreq_pri $pri;
		1001	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1002	if ($_[0] < 0 && $! == ENOSYS) {
		1003	aioreq_pri $pri;
		1004	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1005	} else {
		1006	$ch->();
		1007	}
		1008	};
		1009	} else {
		1010	$grp->result (-1);
		1011	close $src_fh;
		1012	close $dst_fh;
		1013
		1014	aioreq $pri;
		1015	add $grp aio_unlink $dst;
661	};	1016	}
662	} else {
663	$grp->result (-1);
664	}	1017	};
		1018	} else {
		1019	$grp->result (-1);
665	},	1020	}
666
667	} else {
668	$grp->result (-1);
669	}	1021	},
		1022
		1023	} else {
		1024	$grp->result (-1);
670	};	1025	}
671
672	$grp
673	}	1026	};
		1027
		1028	$grp
674	}	1029	}
675		1030
676	=item aio_move $srcpath, $dstpath, $callback->($status)	1031	=item aio_move $srcpath, $dstpath, $callback->($status)
677		1032
678	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
679	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
680	the C<0> (error) or C<-1> ok.	1035	a status of C<0> (ok) or C<-1> (error, see C<$!>).
681		1036
682	This is a composite request that tries to rename(2) the file first. If	1037	This is a composite request that tries to rename(2) the file first; if
683	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1038	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
684	that is successful, unlinking the C<$srcpath>.	1039	that is successful, unlinks the C<$srcpath>.
685		1040
686	=cut	1041	=cut
687		1042
688	sub aio_move($$;$) {	1043	sub aio_move($$;$) {
689	aio_block {
690	my ($src, $dst, $cb) = @_;	1044	my ($src, $dst, $cb) = @_;
691		1045
692	my $pri = aioreq_pri;	1046	my $pri = aioreq_pri;
693	my $grp = aio_group $cb;	1047	my $grp = aio_group $cb;
694		1048
695	aioreq_pri $pri;	1049	aioreq_pri $pri;
696	add $grp aio_rename $src, $dst, sub {	1050	add $grp aio_rename $src, $dst, sub {
697	if ($_[0] && $! == EXDEV) {	1051	if ($_[0] && $! == EXDEV) {
698	aioreq_pri $pri;	1052	aioreq_pri $pri;
699	add $grp aio_copy $src, $dst, sub {	1053	add $grp aio_copy $src, $dst, sub {
700	$grp->result ($_[0]);
701
702	if (!$_[0]) {
703	aioreq_pri $pri;
704	add $grp aio_unlink $src;
705	}
706	};
707	} else {
708	$grp->result ($_[0]);	1054	$grp->result ($_[0]);
		1055
		1056	unless ($_[0]) {
		1057	aioreq_pri $pri;
		1058	add $grp aio_unlink $src;
		1059	}
709	}	1060	};
		1061	} else {
		1062	$grp->result ($_[0]);
710	};	1063	}
711
712	$grp
713	}	1064	};
		1065
		1066	$grp
714	}	1067	}
715		1068
716	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1069	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
717		1070
718	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1071	Scans a directory (similar to C<aio_readdir>) but additionally tries to
719	efficiently separate the entries of directory C<$path> into two sets of	1072	efficiently separate the entries of directory C<$path> into two sets of
720	names, directories you can recurse into (directories), and ones you cannot	1073	names, directories you can recurse into (directories), and ones you cannot
721	recurse into (everything else, including symlinks to directories).	1074	recurse into (everything else, including symlinks to directories).
722		1075
723	C<aio_scandir> is a composite request that creates of many sub requests_	1076	C<aio_scandir> is a composite request that generates many sub requests.
724	C<$maxreq> specifies the maximum number of outstanding aio requests that	1077	C<$maxreq> specifies the maximum number of outstanding aio requests that
725	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
726	will be chosen (currently 4).	1079	will be chosen (currently 4).
727		1080
728	On error, the callback is called without arguments, otherwise it receives	1081	On error, the callback is called without arguments, otherwise it receives
…		…
738		1091
739	Implementation notes.	1092	Implementation notes.
740		1093
741	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1094	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
742		1095
		1096	If readdir returns file type information, then this is used directly to
		1097	find directories.
		1098
743	After reading the directory, the modification time, size etc. of the	1099	Otherwise, after reading the directory, the modification time, size etc.
744	directory before and after the readdir is checked, and if they match (and	1100	of the directory before and after the readdir is checked, and if they
745	isn't the current time), the link count will be used to decide how many	1101	match (and isn't the current time), the link count will be used to decide
746	entries are directories (if >= 2). Otherwise, no knowledge of the number	1102	how many entries are directories (if >= 2). Otherwise, no knowledge of the
747	of subdirectories will be assumed.	1103	number of subdirectories will be assumed.
748		1104
749	Then entries will be sorted into likely directories (everything without	1105	Then entries will be sorted into likely directories a non-initial dot
750	a non-initial dot currently) and likely non-directories (everything	1106	currently) and likely non-directories (see C<aio_readdirx>). Then every
751	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1107	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
752	likely directories first. If that succeeds, it assumes that the entry	1108	in order of their inode numbers. If that succeeds, it assumes that the
753	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
754	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
755	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
756	data (e.g. ext2fs filetype feature).	1112	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1113	the filetype information on readdir.
757		1114
758	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
759	rest of the entries is assumed to be non-directories.	1116	rest of the entries is assumed to be non-directories.
760		1117
761	This only works with certainty on POSIX (= UNIX) filesystems, which	1118	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
766	directory counting heuristic.	1123	directory counting heuristic.
767		1124
768	=cut	1125	=cut
769		1126
770	sub aio_scandir($$;$) {	1127	sub aio_scandir($$;$) {
771	aio_block {
772	my ($path, $maxreq, $cb) = @_;	1128	my ($path, $maxreq, $cb) = @_;
773		1129
774	my $pri = aioreq_pri;	1130	my $pri = aioreq_pri;
775		1131
776	my $grp = aio_group $cb;	1132	my $grp = aio_group $cb;
777		1133
778	$maxreq = 4 if $maxreq <= 0;	1134	$maxreq = 4 if $maxreq <= 0;
		1135
		1136	# get a wd object
		1137	aioreq_pri $pri;
		1138	add $grp aio_wd $path, sub {
		1139	$_[0]
		1140	or return $grp->result ();
		1141
		1142	my $wd = [shift, "."];
779		1143
780	# stat once	1144	# stat once
781	aioreq_pri $pri;	1145	aioreq_pri $pri;
782	add $grp aio_stat $path, sub {	1146	add $grp aio_stat $wd, sub {
783	return $grp->result () if $_[0];	1147	return $grp->result () if $_[0];
784	my $now = time;	1148	my $now = time;
785	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1149	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1150	my $rdxflags = READDIR_DIRS_FIRST;
		1151
		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	}
786		1158
787	# read the directory entries	1159	# read the directory entries
788	aioreq_pri $pri;	1160	aioreq_pri $pri;
789	add $grp aio_readdir $path, sub {	1161	add $grp aio_readdirx $wd, $rdxflags, sub {
790	my $entries = shift	1162	my ($entries, $flags) = @_
791	or return $grp->result ();	1163	or return $grp->result ();
		1164
		1165	if ($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
		1180	my $dirs;
		1181
		1182	if (@$entries) {
		1183	for (0 .. $#$entries) {
		1184	if ($entries->[$_][1] != DT_DIR) {
		1185	# splice out directories
		1186	$dirs = [splice @$entries, 0, $_];
		1187	last;
		1188	}
		1189	}
		1190
		1191	# if we didn't find any non-dir, then all entries are dirs
		1192	unless ($dirs) {
		1193	($dirs, $entries) = ($entries, []);
		1194	}
		1195	} else {
		1196	# directory is empty, so there are no sbdirs
		1197	$dirs = [];
		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	}
792		1212
793	# stat the dir another time	1213	# stat the dir another time
794	aioreq_pri $pri;	1214	aioreq_pri $pri;
795	add $grp aio_stat $path, sub {	1215	add $grp aio_stat $wd, sub {
796	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1216	my $hash2 = join ":", (stat _)[0,1,3,7,9];
797		1217
798	my $ndirs;	1218	my $ndirs;
799		1219
800	# take the slow route if anything looks fishy	1220	# take the slow route if anything looks fishy
801	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1221	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
802	$ndirs = -1;	1222	$ndirs = -1;
803	} else {	1223	} else {
804	# if nlink == 2, we are finished	1224	# if nlink == 2, we are finished
805	# on non-posix-fs's, we rely on nlink < 2	1225	# for non-posix-fs's, we rely on nlink < 2
806	$ndirs = (stat _)[3] - 2	1226	$ndirs = (stat _)[3] - 2
807	or return $grp->result ([], $entries);	1227	or return $grp->result ([], $entries);
808	}	1228	}
809		1229
810	# sort into likely dirs and likely nondirs
811	# dirs == files without ".", short entries first
812	$entries = [map $_->[0],
813	sort { $b->[1] cmp $a->[1] }
814	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
815	@$entries];
816
817	my (@dirs, @nondirs);	1230	my (@dirs, @nondirs);
818		1231
819	my $statgrp = add $grp aio_group sub {	1232	my $statgrp = add $grp aio_group sub {
820	$grp->result (\@dirs, \@nondirs);	1233	$grp->result (\@dirs, \@nondirs);
821	};	1234	};
822		1235
823	limit $statgrp $maxreq;	1236	limit $statgrp $maxreq;
824	feed $statgrp sub {	1237	feed $statgrp sub {
825	return unless @$entries;	1238	return unless @$entries;
826	my $entry = pop @$entries;	1239	my $entry = shift @$entries;
827		1240
828	aioreq_pri $pri;	1241	aioreq_pri $pri;
		1242	$wd->[1] = "$entry/.";
829	add $statgrp aio_stat "$path/$entry/.", sub {	1243	add $statgrp aio_stat $wd, sub {
830	if ($_[0] < 0) {	1244	if ($_[0] < 0) {
831	push @nondirs, $entry;	1245	push @nondirs, $entry;
832	} else {	1246	} else {
833	# need to check for real directory	1247	# need to check for real directory
834	aioreq_pri $pri;	1248	aioreq_pri $pri;
		1249	$wd->[1] = $entry;
835	add $statgrp aio_lstat "$path/$entry", sub {	1250	add $statgrp aio_lstat $wd, sub {
836	if (-d _) {	1251	if (-d _) {
837	push @dirs, $entry;	1252	push @dirs, $entry;
838		1253
839	unless (--$ndirs) {	1254	unless (--$ndirs) {
840	push @nondirs, @$entries;	1255	push @nondirs, @$entries;
…		…
848	};	1263	};
849	};	1264	};
850	};	1265	};
851	};	1266	};
852	};	1267	};
853
854	$grp
855	}	1268	};
		1269
		1270	$grp
856	}	1271	}
857		1272
858	=item aio_rmtree $path, $callback->($status)	1273	=item aio_rmtree $pathname, $callback->($status)
859		1274
860	Delete a directory tree starting (and including) C<$path>, return the	1275	Delete a directory tree starting (and including) C<$path>, return the
861	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
862	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
863	everything else.	1278	everything else.
864		1279
865	=cut	1280	=cut
866		1281
867	sub aio_rmtree;	1282	sub aio_rmtree;
868	sub aio_rmtree($;$) {	1283	sub aio_rmtree($;$) {
869	aio_block {
870	my ($path, $cb) = @_;	1284	my ($path, $cb) = @_;
871		1285
872	my $pri = aioreq_pri;	1286	my $pri = aioreq_pri;
873	my $grp = aio_group $cb;	1287	my $grp = aio_group $cb;
874		1288
875	aioreq_pri $pri;	1289	aioreq_pri $pri;
876	add $grp aio_scandir $path, 0, sub {	1290	add $grp aio_scandir $path, 0, sub {
877	my ($dirs, $nondirs) = @_;	1291	my ($dirs, $nondirs) = @_;
878		1292
879	my $dirgrp = aio_group sub {	1293	my $dirgrp = aio_group sub {
880	add $grp aio_rmdir $path, sub {	1294	add $grp aio_rmdir $path, sub {
881	$grp->result ($_[0]);	1295	$grp->result ($_[0]);
882	};
883	};	1296	};
884
885	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
886	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
887
888	add $grp $dirgrp;
889	};	1297	};
890		1298
891	$grp	1299	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1300	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1301
		1302	add $grp $dirgrp;
892	}	1303	};
		1304
		1305	$grp
893	}	1306	}
		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
		1356	=item aio_sync $callback->($status)
		1357
		1358	Asynchronously call sync and call the callback when finished.
894		1359
895	=item aio_fsync $fh, $callback->($status)	1360	=item aio_fsync $fh, $callback->($status)
896		1361
897	Asynchronously call fsync on the given filehandle and call the callback	1362	Asynchronously call fsync on the given filehandle and call the callback
898	with the fsync result code.	1363	with the fsync result code.
…		…
902	Asynchronously call fdatasync on the given filehandle and call the	1367	Asynchronously call fdatasync on the given filehandle and call the
903	callback with the fdatasync result code.	1368	callback with the fdatasync result code.
904		1369
905	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
906	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.
		1379
		1380	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1381
		1382	Sync the data portion of the file specified by C<$offset> and C<$length>
		1383	to disk (but NOT the metadata), by calling the Linux-specific
		1384	sync_file_range call. If sync_file_range is not available or it returns
		1385	ENOSYS, then fdatasync or fsync is being substituted.
		1386
		1387	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1388	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1389	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1390	manpage for details.
		1391
		1392	=item aio_pathsync $pathname, $callback->($status)
		1393
		1394	This request tries to open, fsync and close the given path. This is a
		1395	composite request intended to sync directories after directory operations
		1396	(E.g. rename). This might not work on all operating systems or have any
		1397	specific effect, but usually it makes sure that directory changes get
		1398	written to disc. It works for anything that can be opened for read-only,
		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>).
		1403
		1404	Passes C<0> when everything went ok, and C<-1> on error.
		1405
		1406	=cut
		1407
		1408	sub aio_pathsync($;$) {
		1409	my ($path, $cb) = @_;
		1410
		1411	my $pri = aioreq_pri;
		1412	my $grp = aio_group $cb;
		1413
		1414	aioreq_pri $pri;
		1415	add $grp aio_open $path, O_RDONLY, 0, sub {
		1416	my ($fh) = @_;
		1417	if ($fh) {
		1418	aioreq_pri $pri;
		1419	add $grp aio_fsync $fh, sub {
		1420	$grp->result ($_[0]);
		1421
		1422	aioreq_pri $pri;
		1423	add $grp aio_close $fh;
		1424	};
		1425	} else {
		1426	$grp->result (-1);
		1427	}
		1428	};
		1429
		1430	$grp
		1431	}
		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>.
907		1547
908	=item aio_group $callback->(...)	1548	=item aio_group $callback->(...)
909		1549
910	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
911	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
…		…
949	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
950	except to put your application under artificial I/O pressure.	1590	except to put your application under artificial I/O pressure.
951		1591
952	=back	1592	=back
953		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
954	=head2 IO::AIO::REQ CLASS	1719	=head2 IO::AIO::REQ CLASS
955		1720
956	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
957	called in non-void context.	1722	called in non-void context.
958		1723
…		…
961	=item cancel $req	1726	=item cancel $req
962		1727
963	Cancels the request, if possible. Has the effect of skipping execution	1728	Cancels the request, if possible. Has the effect of skipping execution
964	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
965	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
966	untouched. That means that requests that currently execute will not be	1731	untouched (with the exception of readdir). That means that requests that
967	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.
968		1734
969	=item cb $req $callback->(...)	1735	=item cb $req $callback->(...)
970		1736
971	Replace (or simply set) the callback registered to the request.	1737	Replace (or simply set) the callback registered to the request.
972		1738
…		…
1023	Their lifetime, simplified, looks like this: when they are empty, they	1789	Their lifetime, simplified, looks like this: when they are empty, they
1024	will finish very quickly. If they contain only requests that are in the	1790	will finish very quickly. If they contain only requests that are in the
1025	C<done> state, they will also finish. Otherwise they will continue to	1791	C<done> state, they will also finish. Otherwise they will continue to
1026	exist.	1792	exist.
1027		1793
1028	That means after creating a group you have some time to add requests. And	1794	That means after creating a group you have some time to add requests
1029	in the callbacks of those requests, you can add further requests to the	1795	(precisely before the callback has been invoked, which is only done within
1030	group. And only when all those requests have finished will the the group	1796	the C<poll_cb>). And in the callbacks of those requests, you can add
1031	itself finish.	1797	further requests to the group. And only when all those requests have
		1798	finished will the the group itself finish.
1032		1799
1033	=over 4	1800	=over 4
1034		1801
1035	=item add $grp ...	1802	=item add $grp ...
1036		1803
…		…
1045	=item $grp->cancel_subs	1812	=item $grp->cancel_subs
1046		1813
1047	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
1048	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.
1049		1816
		1817	The group request will finish normally (you cannot add requests to the
		1818	group).
		1819
1050	=item $grp->result (...)	1820	=item $grp->result (...)
1051		1821
1052	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
1053	subrequests have finished and set thre groups errno to the current value	1823	subrequests have finished and set the groups errno to the current value
1054	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,
1055	no argument will be passed and errno is zero.	1825	no argument will be passed and errno is zero.
1056		1826
1057	=item $grp->errno ([$errno])	1827	=item $grp->errno ([$errno])
1058		1828
…		…
1069	=item feed $grp $callback->($grp)	1839	=item feed $grp $callback->($grp)
1070		1840
1071	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
1072	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,
1073	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,
1074	this might starve other requests for a potentially long time. For	1844	this might starve other requests for a potentially long time. For example,
1075	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1845	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1076	requests, delaying any later requests for a long time.	1846	requests, delaying any later requests for a long time.
1077		1847
1078	To avoid this, and allow incremental generation of requests, you can	1848	To avoid this, and allow incremental generation of requests, you can
1079	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
1080	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>,
…		…
1085	not impose any limits).	1855	not impose any limits).
1086		1856
1087	If the feed does not queue more requests when called, it will be	1857	If the feed does not queue more requests when called, it will be
1088	automatically removed from the group.	1858	automatically removed from the group.
1089		1859
1090	If the feed limit is C<0>, it will be set to C<2> automatically.	1860	If the feed limit is C<0> when this method is called, it will be set to
		1861	C<2> automatically.
1091		1862
1092	Example:	1863	Example:
1093		1864
1094	# stat all files in @files, but only ever use four aio requests concurrently:	1865	# stat all files in @files, but only ever use four aio requests concurrently:
1095		1866
…		…
1107	Sets the feeder limit for the group: The feeder will be called whenever	1878	Sets the feeder limit for the group: The feeder will be called whenever
1108	the group contains less than this many requests.	1879	the group contains less than this many requests.
1109		1880
1110	Setting the limit to C<0> will pause the feeding process.	1881	Setting the limit to C<0> will pause the feeding process.
1111		1882
		1883	The default value for the limit is C<0>, but note that setting a feeder
		1884	automatically bumps it up to C<2>.
		1885
1112	=back	1886	=back
1113		1887
		1888
1114	=head2 SUPPORT FUNCTIONS	1889	=head2 SUPPORT FUNCTIONS
1115		1890
1116	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1891	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1117		1892
1118	=over 4	1893	=over 4
1119		1894
1120	=item $fileno = IO::AIO::poll_fileno	1895	=item $fileno = IO::AIO::poll_fileno
1121		1896
1122	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
1123	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,
1124	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
1125	to call C<poll_cb> to check the results.	1900	you have to call C<poll_cb> to check the results.
1126		1901
1127	See C<poll_cb> for an example.	1902	See C<poll_cb> for an example.
1128		1903
1129	=item IO::AIO::poll_cb	1904	=item IO::AIO::poll_cb
1130		1905
1131	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
1132	regularly. Returns the number of events processed. Returns immediately	1907	been executed but the results are not yet reported). You have to call
1133	when no events are outstanding. The amount of events processed depends on	1908	this "regularly" to finish outstanding requests.
1134	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1135		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
1136	If not all requests were processed for whatever reason, the filehandle	1916	If not all requests were processed for whatever reason, the poll file
1137	will still be ready when C<poll_cb> returns.	1917	descriptor will still be ready when C<poll_cb> returns, so normally you
		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.
1138		1926
1139	Example: Install an Event watcher that automatically calls	1927	Example: Install an Event watcher that automatically calls
1140	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):
1141		1930
1142	Event->io (fd => IO::AIO::poll_fileno,	1931	Event->io (fd => IO::AIO::poll_fileno,
1143	poll => 'r', async => 1,	1932	poll => 'r', async => 1,
1144	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
1145		1972
1146	=item IO::AIO::max_poll_reqs $nreqs	1973	=item IO::AIO::max_poll_reqs $nreqs
1147		1974
1148	=item IO::AIO::max_poll_time $seconds	1975	=item IO::AIO::max_poll_time $seconds
1149		1976
…		…
1174	# use a low priority so other tasks have priority	2001	# use a low priority so other tasks have priority
1175	Event->io (fd => IO::AIO::poll_fileno,	2002	Event->io (fd => IO::AIO::poll_fileno,
1176	poll => 'r', nice => 1,	2003	poll => 'r', nice => 1,
1177	cb => &IO::AIO::poll_cb);	2004	cb => &IO::AIO::poll_cb);
1178		2005
1179	=item IO::AIO::poll_wait
1180
1181	If there are any outstanding requests and none of them in the result
1182	phase, wait till the result filehandle becomes ready for reading (simply
1183	does a C<select> on the filehandle. This is useful if you want to
1184	synchronously wait for some requests to finish).
1185
1186	See C<nreqs> for an example.
1187
1188	=item IO::AIO::poll
1189
1190	Waits until some requests have been handled.
1191
1192	Returns the number of requests processed, but is otherwise strictly
1193	equivalent to:
1194
1195	IO::AIO::poll_wait, IO::AIO::poll_cb
1196
1197	=item IO::AIO::flush
1198
1199	Wait till all outstanding AIO requests have been handled.
1200
1201	Strictly equivalent to:
1202
1203	IO::AIO::poll_wait, IO::AIO::poll_cb
1204	while IO::AIO::nreqs;
1205
1206	=back	2006	=back
		2007
1207		2008
1208	=head3 CONTROLLING THE NUMBER OF THREADS	2009	=head3 CONTROLLING THE NUMBER OF THREADS
1209		2010
1210	=over	2011	=over
1211		2012
…		…
1243		2044
1244	Under normal circumstances you don't need to call this function.	2045	Under normal circumstances you don't need to call this function.
1245		2046
1246	=item IO::AIO::max_idle $nthreads	2047	=item IO::AIO::max_idle $nthreads
1247		2048
1248	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2049	Limit the number of threads (default: 4) that are allowed to idle
1249	threads that did not get a request to process within 10 seconds). That	2050	(i.e., threads that did not get a request to process within the idle
1250	means if a thread becomes idle while C<$nthreads> other threads are also	2051	timeout (default: 10 seconds). That means if a thread becomes idle while
1251	idle, it will free its resources and exit.	2052	C<$nthreads> other threads are also idle, it will free its resources and
		2053	exit.
1252		2054
1253	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)
1254	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
1255	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2057	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1256		2058
1257	The default is probably ok in most situations, especially if thread	2059	The default is probably ok in most situations, especially if thread
1258	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
1259	want to use larger values.	2061	want to use larger values.
1260		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
1261	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	2068	=item IO::AIO::max_outstanding $maxreqs
1262		2069
1263	This is a very bad function to use in interactive programs because it
1264	blocks, and a bad way to reduce concurrency because it is inexact: Better
1265	use an C<aio_group> together with a feed callback.
1266
1267	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2070	Sets the maximum number of outstanding requests to C<$nreqs>. If
1268	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
1269	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
1270	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.
1271		2075
1272	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
1273	number of outstanding requests.	2077	used to make poll functions block if the limit is exceeded.
1274		2078
1275	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,
1276	C<max_oustsanding> 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
1277	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.
1278		2104
1279	=back	2105	=back
		2106
1280		2107
1281	=head3 STATISTICAL INFORMATION	2108	=head3 STATISTICAL INFORMATION
1282		2109
1283	=over	2110	=over
1284		2111
…		…
1302	Returns the number of requests currently in the pending state (executed,	2129	Returns the number of requests currently in the pending state (executed,
1303	but not yet processed by poll_cb).	2130	but not yet processed by poll_cb).
1304		2131
1305	=back	2132	=back
1306		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
1307	=cut	2664	=cut
1308		2665
1309	min_parallel 8;	2666	min_parallel 8;
1310		2667
1311	END { flush }	2668	END { flush }
1312		2669
1313	1;	2670	1;
1314		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
1315	=head2 FORK BEHAVIOUR	2703	=head2 FORK BEHAVIOUR
1316		2704
1317	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.
1318		2712
1319	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
1320	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
1321	the fork the parent simply leaves the quiescent state and continues	2715	using IO::AIO in the child is not.
1322	request/result processing, while the child frees the request/result queue
1323	(so that the requests started before the fork will only be handled in the
1324	parent). Threads will be started on demand until the limit set in the
1325	parent process has been reached again.
1326		2716
1327	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)
1328	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
1329	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>.
1330		2744
1331	=head2 MEMORY USAGE	2745	=head2 MEMORY USAGE
1332		2746
1333	Per-request usage:	2747	Per-request usage:
1334		2748
…		…
1347	temporary buffers, and each thread requires a stack and other data	2761	temporary buffers, and each thread requires a stack and other data
1348	structures (usually around 16k-128k, depending on the OS).	2762	structures (usually around 16k-128k, depending on the OS).
1349		2763
1350	=head1 KNOWN BUGS	2764	=head1 KNOWN BUGS
1351		2765
1352	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.
1353		2778
1354	=head1 SEE ALSO	2779	=head1 SEE ALSO
1355		2780
1356	L<Coro::AIO>.	2781	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2782	more natural syntax and L<IO::FDPass> for file descriptor passing.
1357		2783
1358	=head1 AUTHOR	2784	=head1 AUTHOR
1359		2785
1360	Marc Lehmann <schmorp@schmorp.de>	2786	Marc Lehmann <schmorp@schmorp.de>
1361	http://home.schmorp.de/	2787	http://home.schmorp.de/

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