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Revision 1.178 by root, Sun Jan 10 23:10:58 2010 UTC vs.
Revision 1.317 by root, Sun Sep 25 16:30:50 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
…		…
58	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
59	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
60	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
61	using threads anyway.	61	using threads anyway.
62		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
63	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,
64	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
65	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
66	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
67		71
68	=head2 EXAMPLE	72	=head2 EXAMPLE
69		73
70	This is a simple example that uses the EV module and loads	74	This is a simple example that uses the EV module and loads
71	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
72		76
73	use Fcntl;
74	use EV;	77	use EV;
75	use IO::AIO;	78	use IO::AIO;
76		79
77	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
79		82
80	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
81	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
82	my $fh = shift	85	my $fh = shift
83	or die "error while opening: $!";	86	or die "error while opening: $!";
84		87
85	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
86	my $size = -s $fh;	89	my $size = -s $fh;
…		…
95		98
96	# file contents now in $contents	99	# file contents now in $contents
97	print $contents;	100	print $contents;
98		101
99	# exit event loop and program	102	# exit event loop and program
100	EV::unloop;	103	EV::break;
101	};	104	};
102	};	105	};
103		106
104	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
105	# check for sockets etc. etc.	108	# check for sockets etc. etc.
106		109
107	# process events as long as there are some:	110	# process events as long as there are some:
108	EV::loop;	111	EV::run;
109		112
110	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
111		114
112	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
113	directly visible to Perl.	116	directly visible to Perl.
…		…
168	use common::sense;	171	use common::sense;
169		172
170	use base 'Exporter';	173	use base 'Exporter';
171		174
172	BEGIN {	175	BEGIN {
173	our $VERSION = '3.6';	176	our $VERSION = 4.79;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
179	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
182	aio_msync aio_mtouch aio_statvfs);	186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
183		190
184	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
185	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
186	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
187	nreqs nready npending nthreads	194	nreqs nready npending nthreads
188	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
189	sendfile fadvise);	196	sendfile fadvise madvise
		197	mmap munmap mremap munlock munlockall
		198
		199	accept4 tee splice pipe2 pipesize
		200	fexecve mount umount memfd_create eventfd
		201	timerfd_create timerfd_settime timerfd_gettime
		202	pidfd_open pidfd_send_signal pidfd_getfd);
190		203
191	push @AIO_REQ, qw(aio_busy); # not exported	204	push @AIO_REQ, qw(aio_busy); # not exported
192		205
193	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
194		207
…		…
198		211
199	=head1 FUNCTIONS	212	=head1 FUNCTIONS
200		213
201	=head2 QUICK OVERVIEW	214	=head2 QUICK OVERVIEW
202		215
203	This section simply lists the prototypes of the most important functions	216	This section simply lists the prototypes most of the functions for
204	for quick reference. See the following sections for function-by-function	217	quick reference. See the following sections for function-by-function
205	documentation.	218	documentation.
206		219
		220	aio_wd $pathname, $callback->($wd)
207	aio_open $pathname, $flags, $mode, $callback->($fh)	221	aio_open $pathname, $flags, $mode, $callback->($fh)
208	aio_close $fh, $callback->($status)	222	aio_close $fh, $callback->($status)
		223	aio_seek $fh,$offset,$whence, $callback->($offs)
209	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	224	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
210	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	225	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
211	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	226	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
212	aio_readahead $fh,$offset,$length, $callback->($retval)	227	aio_readahead $fh,$offset,$length, $callback->($retval)
213	aio_stat $fh_or_path, $callback->($status)	228	aio_stat $fh_or_path, $callback->($status)
214	aio_lstat $fh, $callback->($status)	229	aio_lstat $fh, $callback->($status)
215	aio_statvfs $fh_or_path, $callback->($statvfs)	230	aio_statvfs $fh_or_path, $callback->($statvfs)
216	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	231	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
217	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	232	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		233	aio_chmod $fh_or_path, $mode, $callback->($status)
218	aio_truncate $fh_or_path, $offset, $callback->($status)	234	aio_truncate $fh_or_path, $offset, $callback->($status)
219	aio_chmod $fh_or_path, $mode, $callback->($status)	235	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		236	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
220	aio_unlink $pathname, $callback->($status)	237	aio_unlink $pathname, $callback->($status)
221	aio_mknod $path, $mode, $dev, $callback->($status)	238	aio_mknod $pathname, $mode, $dev, $callback->($status)
222	aio_link $srcpath, $dstpath, $callback->($status)	239	aio_link $srcpath, $dstpath, $callback->($status)
223	aio_symlink $srcpath, $dstpath, $callback->($status)	240	aio_symlink $srcpath, $dstpath, $callback->($status)
224	aio_readlink $path, $callback->($link)	241	aio_readlink $pathname, $callback->($link)
		242	aio_realpath $pathname, $callback->($path)
225	aio_rename $srcpath, $dstpath, $callback->($status)	243	aio_rename $srcpath, $dstpath, $callback->($status)
		244	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
226	aio_mkdir $pathname, $mode, $callback->($status)	245	aio_mkdir $pathname, $mode, $callback->($status)
227	aio_rmdir $pathname, $callback->($status)	246	aio_rmdir $pathname, $callback->($status)
228	aio_readdir $pathname, $callback->($entries)	247	aio_readdir $pathname, $callback->($entries)
229	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	248	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
230	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	249	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
231	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	250	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		251	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
232	aio_load $path, $data, $callback->($status)	252	aio_load $pathname, $data, $callback->($status)
233	aio_copy $srcpath, $dstpath, $callback->($status)	253	aio_copy $srcpath, $dstpath, $callback->($status)
234	aio_move $srcpath, $dstpath, $callback->($status)	254	aio_move $srcpath, $dstpath, $callback->($status)
235	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
236	aio_rmtree $path, $callback->($status)	255	aio_rmtree $pathname, $callback->($status)
		256	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		257	aio_ioctl $fh, $request, $buf, $callback->($status)
237	aio_sync $callback->($status)	258	aio_sync $callback->($status)
		259	aio_syncfs $fh, $callback->($status)
238	aio_fsync $fh, $callback->($status)	260	aio_fsync $fh, $callback->($status)
239	aio_fdatasync $fh, $callback->($status)	261	aio_fdatasync $fh, $callback->($status)
240	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	262	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
241	aio_pathsync $path, $callback->($status)	263	aio_pathsync $pathname, $callback->($status)
242	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	264	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
243	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($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)
244	aio_group $callback->(...)	268	aio_group $callback->(...)
245	aio_nop $callback->()	269	aio_nop $callback->()
246		270
247	$prev_pri = aioreq_pri [$pri]	271	$prev_pri = aioreq_pri [$pri]
248	aioreq_nice $pri_adjust	272	aioreq_nice $pri_adjust
…		…
254	IO::AIO::max_poll_reqs $nreqs	278	IO::AIO::max_poll_reqs $nreqs
255	IO::AIO::max_poll_time $seconds	279	IO::AIO::max_poll_time $seconds
256	IO::AIO::min_parallel $nthreads	280	IO::AIO::min_parallel $nthreads
257	IO::AIO::max_parallel $nthreads	281	IO::AIO::max_parallel $nthreads
258	IO::AIO::max_idle $nthreads	282	IO::AIO::max_idle $nthreads
		283	IO::AIO::idle_timeout $seconds
259	IO::AIO::max_outstanding $maxreqs	284	IO::AIO::max_outstanding $maxreqs
260	IO::AIO::nreqs	285	IO::AIO::nreqs
261	IO::AIO::nready	286	IO::AIO::nready
262	IO::AIO::npending	287	IO::AIO::npending
		288	IO::AIO::reinit
		289
		290	$nfd = IO::AIO::get_fdlimit
		291	IO::AIO::min_fdlimit $nfd
263		292
264	IO::AIO::sendfile $ofh, $ifh, $offset, $count	293	IO::AIO::sendfile $ofh, $ifh, $offset, $count
265	IO::AIO::fadvise $fh, $offset, $len, $advice	294	IO::AIO::fadvise $fh, $offset, $len, $advice
266	IO::AIO::mlockall $flags	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
267	IO::AIO::munlockall	303	IO::AIO::munlockall
268		304
269	=head2 AIO REQUEST FUNCTIONS	305	# stat extensions
		306	$counter = IO::AIO::st_gen
		307	$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		308	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		309	$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		310	$seconds = IO::AIO::st_btimesec
		311	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		312
		313	# very much unportable syscalls
		314	IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
		315	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		316	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		317
		318	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		319	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		320
		321	$fh = IO::AIO::eventfd [$initval, [$flags]]
		322	$fh = IO::AIO::memfd_create $pathname[, $flags]
		323
		324	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		325	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		326	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		327
		328	$fh = IO::AIO::pidfd_open $pid[, $flags]
		329	$status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		330	$fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		331
		332	$retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		333	$retval = IO::AIO::umount $path, $flags = 0
		334
		335	=head2 API NOTES
270		336
271	All the C<aio_*> calls are more or less thin wrappers around the syscall	337	All the C<aio_*> calls are more or less thin wrappers around the syscall
272	with the same name (sans C<aio_>). The arguments are similar or identical,	338	with the same name (sans C<aio_>). The arguments are similar or identical,
273	and they all accept an additional (and optional) C<$callback> argument	339	and they all accept an additional (and optional) C<$callback> argument
274	which must be a code reference. This code reference will get called with	340	which must be a code reference. This code reference will be called after
275	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	341	the syscall has been executed in an asynchronous fashion. The results
276	perl, which usually delivers "false") as its sole argument after the given	342	of the request will be passed as arguments to the callback (and, if an
277	syscall has been executed asynchronously.	343	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		344	most syscalls return C<-1> on error, unlike perl, which usually delivers
		345	"false").
		346
		347	Some requests (such as C<aio_readdir>) pass the actual results and
		348	communicate failures by passing C<undef>.
278		349
279	All functions expecting a filehandle keep a copy of the filehandle	350	All functions expecting a filehandle keep a copy of the filehandle
280	internally until the request has finished.	351	internally until the request has finished.
281		352
282	All functions return request objects of type L<IO::AIO::REQ> that allow	353	All functions return request objects of type L<IO::AIO::REQ> that allow
283	further manipulation of those requests while they are in-flight.	354	further manipulation of those requests while they are in-flight.
284		355
285	The pathnames you pass to these routines I<must> be absolute and	356	The pathnames you pass to these routines I<should> be absolute. The
286	encoded as octets. The reason for the former is that at the time the	357	reason for this is that at the time the request is being executed, the
287	request is being executed, the current working directory could have	358	current working directory could have changed. Alternatively, you can
288	changed. Alternatively, you can make sure that you never change the	359	make sure that you never change the current working directory anywhere
289	current working directory anywhere in the program and then use relative	360	in the program and then use relative paths. You can also take advantage
290	paths.	361	of IO::AIOs working directory abstraction, that lets you specify paths
		362	relative to some previously-opened "working directory object" - see the
		363	description of the C<IO::AIO::WD> class later in this document.
291		364
292	To encode pathnames as octets, either make sure you either: a) always pass	365	To encode pathnames as octets, either make sure you either: a) always pass
293	in filenames you got from outside (command line, readdir etc.) without	366	in filenames you got from outside (command line, readdir etc.) without
294	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	367	tinkering, b) are in your native filesystem encoding, c) use the Encode
295	your pathnames to the locale (or other) encoding in effect in the user	368	module and encode your pathnames to the locale (or other) encoding in
296	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	369	effect in the user environment, d) use Glib::filename_from_unicode on
297	use something else to ensure your scalar has the correct contents.	370	unicode filenames or e) use something else to ensure your scalar has the
		371	correct contents.
298		372
299	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	373	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
300	handles correctly whether it is set or not.	374	handles correctly whether it is set or not.
		375
		376	=head2 AIO REQUEST FUNCTIONS
301		377
302	=over 4	378	=over 4
303		379
304	=item $prev_pri = aioreq_pri [$pri]	380	=item $prev_pri = aioreq_pri [$pri]
305		381
…		…
335		411
336		412
337	=item aio_open $pathname, $flags, $mode, $callback->($fh)	413	=item aio_open $pathname, $flags, $mode, $callback->($fh)
338		414
339	Asynchronously open or create a file and call the callback with a newly	415	Asynchronously open or create a file and call the callback with a newly
340	created filehandle for the file.	416	created filehandle for the file (or C<undef> in case of an error).
341		417
342	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	418	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
343	for an explanation.	419	for an explanation.
344		420
345	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	421	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
352	by the umask in effect then the request is being executed, so better never	428	by the umask in effect then the request is being executed, so better never
353	change the umask.	429	change the umask.
354		430
355	Example:	431	Example:
356		432
357	aio_open "/etc/passwd", O_RDONLY, 0, sub {	433	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
358	if ($_[0]) {	434	if ($_[0]) {
359	print "open successful, fh is $_[0]\n";	435	print "open successful, fh is $_[0]\n";
360	...	436	...
361	} else {	437	} else {
362	die "open failed: $!\n";	438	die "open failed: $!\n";
363	}	439	}
364	};	440	};
365		441
		442	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		443	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		444	following POSIX and non-POSIX constants are available (missing ones on
		445	your system are, as usual, C<0>):
		446
		447	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		448	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		449	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		450
366		451
367	=item aio_close $fh, $callback->($status)	452	=item aio_close $fh, $callback->($status)
368		453
369	Asynchronously close a file and call the callback with the result	454	Asynchronously close a file and call the callback with the result
370	code.	455	code.
…		…
379	Or in other words: the file descriptor will be closed, but it will not be	464	Or in other words: the file descriptor will be closed, but it will not be
380	free for reuse until the perl filehandle is closed.	465	free for reuse until the perl filehandle is closed.
381		466
382	=cut	467	=cut
383		468
		469	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		470
		471	Seeks the filehandle to the new C<$offset>, similarly to perl's
		472	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		473	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		474	C<IO::AIO::SEEK_END>).
		475
		476	The resulting absolute offset will be passed to the callback, or C<-1> in
		477	case of an error.
		478
		479	In theory, the C<$whence> constants could be different than the
		480	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		481	so don't panic.
		482
		483	As a GNU/Linux (and maybe Solaris) extension, also the constants
		484	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		485	could be found. No guarantees about suitability for use in C<aio_seek> or
		486	Perl's C<sysseek> can be made though, although I would naively assume they
		487	"just work".
		488
384	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	489	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
385		490
386	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	491	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
387		492
388	Reads or writes C<$length> bytes from or to the specified C<$fh> and	493	Reads or writes C<$length> bytes from or to the specified C<$fh> and
389	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	494	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
390	and calls the callback without the actual number of bytes read (or -1 on	495	calls the callback with the actual number of bytes transferred (or -1 on
391	error, just like the syscall).	496	error, just like the syscall).
392		497
393	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	498	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
394	offset plus the actual number of bytes read.	499	offset plus the actual number of bytes read.
395		500
…		…
420		525
421	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	526	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
422	reading at byte offset C<$in_offset>, and starts writing at the current	527	reading at byte offset C<$in_offset>, and starts writing at the current
423	file offset of C<$out_fh>. Because of that, it is not safe to issue more	528	file offset of C<$out_fh>. Because of that, it is not safe to issue more
424	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	529	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
425	other.	530	other. The same C<$in_fh> works fine though, as this function does not
		531	move or use the file offset of C<$in_fh>.
426		532
		533	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		534	are written, and there is no way to find out how many more bytes have been
		535	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		536	number of bytes written to C<$out_fh>. Only if the result value equals
		537	C<$length> one can assume that C<$length> bytes have been read.
		538
		539	Unlike with other C<aio_> functions, it makes a lot of sense to use
		540	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		541	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		542	the socket I/O will be non-blocking. Note, however, that you can run
		543	into a trap where C<aio_sendfile> reads some data with readahead, then
		544	fails to write all data, and when the socket is ready the next time, the
		545	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		546	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		547	resource usage.
		548
427	This call tries to make use of a native C<sendfile> syscall to provide	549	This call tries to make use of a native C<sendfile>-like syscall to
428	zero-copy operation. For this to work, C<$out_fh> should refer to a	550	provide zero-copy operation. For this to work, C<$out_fh> should refer to
429	socket, and C<$in_fh> should refer to an mmap'able file.	551	a socket, and C<$in_fh> should refer to an mmap'able file.
430		552
431	If a native sendfile cannot be found or it fails with C<ENOSYS>,	553	If a native sendfile cannot be found or it fails with C<ENOSYS>,
432	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	554	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
433	it will be emulated, so you can call C<aio_sendfile> on any type of	555	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
434	filehandle regardless of the limitations of the operating system.	556	type of filehandle regardless of the limitations of the operating system.
435		557
436	Please note, however, that C<aio_sendfile> can read more bytes from	558	As native sendfile syscalls (as practically any non-POSIX interface hacked
437	C<$in_fh> than are written, and there is no way to find out how many	559	together in a hurry to improve benchmark numbers) tend to be rather buggy
438	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	560	on many systems, this implementation tries to work around some known bugs
439	provides the number of bytes written to C<$out_fh>. Only if the result	561	in Linux and FreeBSD kernels (probably others, too), but that might fail,
440	value equals C<$length> one can assume that C<$length> bytes have been	562	so you really really should check the return value of C<aio_sendfile> -
441	read.	563	fewer bytes than expected might have been transferred.
442		564
443		565
444	=item aio_readahead $fh,$offset,$length, $callback->($retval)	566	=item aio_readahead $fh,$offset,$length, $callback->($retval)
445		567
446	C<aio_readahead> populates the page cache with data from a file so that	568	C<aio_readahead> populates the page cache with data from a file so that
…		…
450	whole pages, so that offset is effectively rounded down to a page boundary	572	whole pages, so that offset is effectively rounded down to a page boundary
451	and bytes are read up to the next page boundary greater than or equal to	573	and bytes are read up to the next page boundary greater than or equal to
452	(off-set+length). C<aio_readahead> does not read beyond the end of the	574	(off-set+length). C<aio_readahead> does not read beyond the end of the
453	file. The current file offset of the file is left unchanged.	575	file. The current file offset of the file is left unchanged.
454		576
455	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	577	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
456	emulated by simply reading the data, which would have a similar effect.	578	be emulated by simply reading the data, which would have a similar effect.
457		579
458		580
459	=item aio_stat $fh_or_path, $callback->($status)	581	=item aio_stat $fh_or_path, $callback->($status)
460		582
461	=item aio_lstat $fh, $callback->($status)	583	=item aio_lstat $fh, $callback->($status)
462		584
463	Works like perl's C<stat> or C<lstat> in void context. The callback will	585	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
464	be called after the stat and the results will be available using C<stat _>	586	callback will be called after the stat and the results will be available
465	or C<-s _> etc...	587	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		588	and C<-T>).
466		589
467	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	590	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
468	for an explanation.	591	for an explanation.
469		592
470	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	593	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
471	error when stat'ing a large file, the results will be silently truncated	594	error when stat'ing a large file, the results will be silently truncated
472	unless perl itself is compiled with large file support.	595	unless perl itself is compiled with large file support.
		596
		597	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		598	following constants and functions (if not implemented, the constants will
		599	be C<0> and the functions will either C<croak> or fall back on traditional
		600	behaviour).
		601
		602	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		603	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		604	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		605
		606	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		607	ACCESS>.
473		608
474	Example: Print the length of F</etc/passwd>:	609	Example: Print the length of F</etc/passwd>:
475		610
476	aio_stat "/etc/passwd", sub {	611	aio_stat "/etc/passwd", sub {
477	$_[0] and die "stat failed: $!";	612	$_[0] and die "stat failed: $!";
…		…
521	namemax => 255,	656	namemax => 255,
522	frsize => 1024,	657	frsize => 1024,
523	fsid => 1810	658	fsid => 1810
524	}	659	}
525		660
526
527	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	661	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
528		662
529	Works like perl's C<utime> function (including the special case of $atime	663	Works like perl's C<utime> function (including the special case of $atime
530	and $mtime being undef). Fractional times are supported if the underlying	664	and $mtime being undef). Fractional times are supported if the underlying
531	syscalls support them.	665	syscalls support them.
532		666
533	When called with a pathname, uses utimes(2) if available, otherwise	667	When called with a pathname, uses utimensat(2) or utimes(2) if available,
534	utime(2). If called on a file descriptor, uses futimes(2) if available,	668	otherwise utime(2). If called on a file descriptor, uses futimens(2)
535	otherwise returns ENOSYS, so this is not portable.	669	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		670	portable.
536		671
537	Examples:	672	Examples:
538		673
539	# set atime and mtime to current time (basically touch(1)):	674	# set atime and mtime to current time (basically touch(1)):
540	aio_utime "path", undef, undef;	675	aio_utime "path", undef, undef;
…		…
558	=item aio_truncate $fh_or_path, $offset, $callback->($status)	693	=item aio_truncate $fh_or_path, $offset, $callback->($status)
559		694
560	Works like truncate(2) or ftruncate(2).	695	Works like truncate(2) or ftruncate(2).
561		696
562		697
		698	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		699
		700	Allocates or frees disk space according to the C<$mode> argument. See the
		701	linux C<fallocate> documentation for details.
		702
		703	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		704	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		705	to deallocate a file range.
		706
		707	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		708	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		709	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		710	to unshare shared blocks (see your L<fallocate(2)> manpage).
		711
		712	The file system block size used by C<fallocate> is presumably the
		713	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		714	can dictate other limitations.
		715
		716	If C<fallocate> isn't available or cannot be emulated (currently no
		717	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		718
		719
563	=item aio_chmod $fh_or_path, $mode, $callback->($status)	720	=item aio_chmod $fh_or_path, $mode, $callback->($status)
564		721
565	Works like perl's C<chmod> function.	722	Works like perl's C<chmod> function.
566		723
567		724
…		…
569		726
570	Asynchronously unlink (delete) a file and call the callback with the	727	Asynchronously unlink (delete) a file and call the callback with the
571	result code.	728	result code.
572		729
573		730
574	=item aio_mknod $path, $mode, $dev, $callback->($status)	731	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
575		732
576	[EXPERIMENTAL]	733	[EXPERIMENTAL]
577		734
578	Asynchronously create a device node (or fifo). See mknod(2).	735	Asynchronously create a device node (or fifo). See mknod(2).
579		736
580	The only (POSIX-) portable way of calling this function is:	737	The only (POSIX-) portable way of calling this function is:
581		738
582	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	739	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
583		740
		741	See C<aio_stat> for info about some potentially helpful extra constants
		742	and functions.
584		743
585	=item aio_link $srcpath, $dstpath, $callback->($status)	744	=item aio_link $srcpath, $dstpath, $callback->($status)
586		745
587	Asynchronously create a new link to the existing object at C<$srcpath> at	746	Asynchronously create a new link to the existing object at C<$srcpath> at
588	the path C<$dstpath> and call the callback with the result code.	747	the path C<$dstpath> and call the callback with the result code.
…		…
592		751
593	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	752	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
594	the path C<$dstpath> and call the callback with the result code.	753	the path C<$dstpath> and call the callback with the result code.
595		754
596		755
597	=item aio_readlink $path, $callback->($link)	756	=item aio_readlink $pathname, $callback->($link)
598		757
599	Asynchronously read the symlink specified by C<$path> and pass it to	758	Asynchronously read the symlink specified by C<$path> and pass it to
600	the callback. If an error occurs, nothing or undef gets passed to the	759	the callback. If an error occurs, nothing or undef gets passed to the
601	callback.	760	callback.
602		761
603		762
		763	=item aio_realpath $pathname, $callback->($path)
		764
		765	Asynchronously make the path absolute and resolve any symlinks in
		766	C<$path>. The resulting path only consists of directories (same as
		767	L<Cwd::realpath>).
		768
		769	This request can be used to get the absolute path of the current working
		770	directory by passing it a path of F<.> (a single dot).
		771
		772
604	=item aio_rename $srcpath, $dstpath, $callback->($status)	773	=item aio_rename $srcpath, $dstpath, $callback->($status)
605		774
606	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	775	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
607	rename(2) and call the callback with the result code.	776	rename(2) and call the callback with the result code.
		777
		778	On systems that support the AIO::WD working directory abstraction
		779	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		780	of failing, C<rename> is called on the absolute path of C<$wd>.
		781
		782
		783	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		784
		785	Basically a version of C<aio_rename> with an additional C<$flags>
		786	argument. Calling this with C<$flags=0> is the same as calling
		787	C<aio_rename>.
		788
		789	Non-zero flags are currently only supported on GNU/Linux systems that
		790	support renameat2. Other systems fail with C<ENOSYS> in this case.
		791
		792	The following constants are available (missing ones are, as usual C<0>),
		793	see renameat2(2) for details:
		794
		795	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		796	and C<IO::AIO::RENAME_WHITEOUT>.
608		797
609		798
610	=item aio_mkdir $pathname, $mode, $callback->($status)	799	=item aio_mkdir $pathname, $mode, $callback->($status)
611		800
612	Asynchronously mkdir (create) a directory and call the callback with	801	Asynchronously mkdir (create) a directory and call the callback with
…		…
617	=item aio_rmdir $pathname, $callback->($status)	806	=item aio_rmdir $pathname, $callback->($status)
618		807
619	Asynchronously rmdir (delete) a directory and call the callback with the	808	Asynchronously rmdir (delete) a directory and call the callback with the
620	result code.	809	result code.
621		810
		811	On systems that support the AIO::WD working directory abstraction
		812	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		813	C<rmdir> is called on the absolute path of C<$wd>.
		814
622		815
623	=item aio_readdir $pathname, $callback->($entries)	816	=item aio_readdir $pathname, $callback->($entries)
624		817
625	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	818	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
626	directory (i.e. opendir + readdir + closedir). The entries will not be	819	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
630	array-ref with the filenames.	823	array-ref with the filenames.
631		824
632		825
633	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	826	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
634		827
635	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	828	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
636	behaviour and output format. In case of an error, C<$entries> will be	829	tune behaviour and output format. In case of an error, C<$entries> will be
637	C<undef>.	830	C<undef>.
638		831
639	The flags are a combination of the following constants, ORed together (the	832	The flags are a combination of the following constants, ORed together (the
640	flags will also be passed to the callback, possibly modified):	833	flags will also be passed to the callback, possibly modified):
641		834
642	=over 4	835	=over 4
643		836
644	=item IO::AIO::READDIR_DENTS	837	=item IO::AIO::READDIR_DENTS
645		838
646	When this flag is off, then the callback gets an arrayref with of names	839	Normally the callback gets an arrayref consisting of names only (as
647	only (as with C<aio_readdir>), otherwise it gets an arrayref with	840	with C<aio_readdir>). If this flag is set, then the callback gets an
648	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	841	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
649	entry in more detail.	842	single directory entry in more detail:
650		843
651	C<$name> is the name of the entry.	844	C<$name> is the name of the entry.
652		845
653	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	846	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
654		847
655	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	848	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
656	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	849	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
657	C<IO::AIO::DT_WHT>.	850	C<IO::AIO::DT_WHT>.
658		851
659	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	852	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
660	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	853	to know, you have to run stat yourself. Also, for speed/memory reasons,
661	scalars are read-only: you can not modify them.	854	the C<$type> scalars are read-only: you must not modify them.
662		855
663	C<$inode> is the inode number (which might not be exact on systems with 64	856	C<$inode> is the inode number (which might not be exact on systems with 64
664	bit inode numbers and 32 bit perls). This field has unspecified content on	857	bit inode numbers and 32 bit perls). This field has unspecified content on
665	systems that do not deliver the inode information.	858	systems that do not deliver the inode information.
666		859
667	=item IO::AIO::READDIR_DIRS_FIRST	860	=item IO::AIO::READDIR_DIRS_FIRST
668		861
669	When this flag is set, then the names will be returned in an order where	862	When this flag is set, then the names will be returned in an order where
670	likely directories come first. This is useful when you need to quickly	863	likely directories come first, in optimal stat order. This is useful when
671	find directories, or you want to find all directories while avoiding to	864	you need to quickly find directories, or you want to find all directories
672	stat() each entry.	865	while avoiding to stat() each entry.
673		866
674	If the system returns type information in readdir, then this is used	867	If the system returns type information in readdir, then this is used
675	to find directories directly. Otherwise, likely directories are files	868	to find directories directly. Otherwise, likely directories are names
676	beginning with ".", or otherwise files with no dots, of which files with	869	beginning with ".", or otherwise names with no dots, of which names with
677	short names are tried first.	870	short names are tried first.
678		871
679	=item IO::AIO::READDIR_STAT_ORDER	872	=item IO::AIO::READDIR_STAT_ORDER
680		873
681	When this flag is set, then the names will be returned in an order	874	When this flag is set, then the names will be returned in an order
682	suitable for stat()'ing each one. That is, when you plan to stat()	875	suitable for stat()'ing each one. That is, when you plan to stat() most or
683	all files in the given directory, then the returned order will likely	876	all files in the given directory, then the returned order will likely be
684	be fastest.	877	faster.
685		878
686	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	879	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
687	the likely dirs come first, resulting in a less optimal stat order.	880	then the likely dirs come first, resulting in a less optimal stat order
		881	for stat'ing all entries, but likely a more optimal order for finding
		882	subdirectories.
688		883
689	=item IO::AIO::READDIR_FOUND_UNKNOWN	884	=item IO::AIO::READDIR_FOUND_UNKNOWN
690		885
691	This flag should not be set when calling C<aio_readdirx>. Instead, it	886	This flag should not be set when calling C<aio_readdirx>. Instead, it
692	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	887	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
693	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	888	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
694	C<$type>'s are known, which can be used to speed up some algorithms.	889	C<$type>'s are known, which can be used to speed up some algorithms.
695		890
696	=back	891	=back
697		892
698		893
		894	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		895
		896	Opens, reads and closes the given file. The data is put into C<$data>,
		897	which is resized as required.
		898
		899	If C<$offset> is negative, then it is counted from the end of the file.
		900
		901	If C<$length> is zero, then the remaining length of the file is
		902	used. Also, in this case, the same limitations to modifying C<$data> apply
		903	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		904	with C<substr>. If the size of the file is known, specifying a non-zero
		905	C<$length> results in a performance advantage.
		906
		907	This request is similar to the older C<aio_load> request, but since it is
		908	a single request, it might be more efficient to use.
		909
		910	Example: load F</etc/passwd> into C<$passwd>.
		911
		912	my $passwd;
		913	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		914	$_[0] >= 0
		915	or die "/etc/passwd: $!\n";
		916
		917	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		918	print $passwd;
		919	};
		920	IO::AIO::flush;
		921
		922
699	=item aio_load $path, $data, $callback->($status)	923	=item aio_load $pathname, $data, $callback->($status)
700		924
701	This is a composite request that tries to fully load the given file into	925	This is a composite request that tries to fully load the given file into
702	memory. Status is the same as with aio_read.	926	memory. Status is the same as with aio_read.
		927
		928	Using C<aio_slurp> might be more efficient, as it is a single request.
703		929
704	=cut	930	=cut
705		931
706	sub aio_load($$;$) {	932	sub aio_load($$;$) {
707	my ($path, undef, $cb) = @_;	933	my ($path, undef, $cb) = @_;
…		…
727	=item aio_copy $srcpath, $dstpath, $callback->($status)	953	=item aio_copy $srcpath, $dstpath, $callback->($status)
728		954
729	Try to copy the I<file> (directories not supported as either source or	955	Try to copy the I<file> (directories not supported as either source or
730	destination) from C<$srcpath> to C<$dstpath> and call the callback with	956	destination) from C<$srcpath> to C<$dstpath> and call the callback with
731	a status of C<0> (ok) or C<-1> (error, see C<$!>).	957	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		958
		959	Existing destination files will be truncated.
732		960
733	This is a composite request that creates the destination file with	961	This is a composite request that creates the destination file with
734	mode 0200 and copies the contents of the source file into it using	962	mode 0200 and copies the contents of the source file into it using
735	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	963	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
736	uid/gid, in that order.	964	uid/gid, in that order.
…		…
826	if ($_[0] && $! == EXDEV) {	1054	if ($_[0] && $! == EXDEV) {
827	aioreq_pri $pri;	1055	aioreq_pri $pri;
828	add $grp aio_copy $src, $dst, sub {	1056	add $grp aio_copy $src, $dst, sub {
829	$grp->result ($_[0]);	1057	$grp->result ($_[0]);
830		1058
831	if (!$_[0]) {	1059	unless ($_[0]) {
832	aioreq_pri $pri;	1060	aioreq_pri $pri;
833	add $grp aio_unlink $src;	1061	add $grp aio_unlink $src;
834	}	1062	}
835	};	1063	};
836	} else {	1064	} else {
…		…
839	};	1067	};
840		1068
841	$grp	1069	$grp
842	}	1070	}
843		1071
844	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1072	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
845		1073
846	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1074	Scans a directory (similar to C<aio_readdir>) but additionally tries to
847	efficiently separate the entries of directory C<$path> into two sets of	1075	efficiently separate the entries of directory C<$path> into two sets of
848	names, directories you can recurse into (directories), and ones you cannot	1076	names, directories you can recurse into (directories), and ones you cannot
849	recurse into (everything else, including symlinks to directories).	1077	recurse into (everything else, including symlinks to directories).
850		1078
851	C<aio_scandir> is a composite request that creates of many sub requests_	1079	C<aio_scandir> is a composite request that generates many sub requests.
852	C<$maxreq> specifies the maximum number of outstanding aio requests that	1080	C<$maxreq> specifies the maximum number of outstanding aio requests that
853	this function generates. If it is C<< <= 0 >>, then a suitable default	1081	this function generates. If it is C<< <= 0 >>, then a suitable default
854	will be chosen (currently 4).	1082	will be chosen (currently 4).
855		1083
856	On error, the callback is called without arguments, otherwise it receives	1084	On error, the callback is called without arguments, otherwise it receives
…		…
880	Then entries will be sorted into likely directories a non-initial dot	1108	Then entries will be sorted into likely directories a non-initial dot
881	currently) and likely non-directories (see C<aio_readdirx>). Then every	1109	currently) and likely non-directories (see C<aio_readdirx>). Then every
882	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1110	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
883	in order of their inode numbers. If that succeeds, it assumes that the	1111	in order of their inode numbers. If that succeeds, it assumes that the
884	entry is a directory or a symlink to directory (which will be checked	1112	entry is a directory or a symlink to directory (which will be checked
885	seperately). This is often faster than stat'ing the entry itself because	1113	separately). This is often faster than stat'ing the entry itself because
886	filesystems might detect the type of the entry without reading the inode	1114	filesystems might detect the type of the entry without reading the inode
887	data (e.g. ext2fs filetype feature), even on systems that cannot return	1115	data (e.g. ext2fs filetype feature), even on systems that cannot return
888	the filetype information on readdir.	1116	the filetype information on readdir.
889		1117
890	If the known number of directories (link count - 2) has been reached, the	1118	If the known number of directories (link count - 2) has been reached, the
…		…
906		1134
907	my $grp = aio_group $cb;	1135	my $grp = aio_group $cb;
908		1136
909	$maxreq = 4 if $maxreq <= 0;	1137	$maxreq = 4 if $maxreq <= 0;
910		1138
911	# stat once	1139	# get a wd object
912	aioreq_pri $pri;	1140	aioreq_pri $pri;
913	add $grp aio_stat $path, sub {	1141	add $grp aio_wd $path, sub {
		1142	$_[0]
914	return $grp->result () if $_[0];	1143	or return $grp->result ();
915	my $now = time;
916	my $hash1 = join ":", (stat _)[0,1,3,7,9];
917		1144
918	# read the directory entries	1145	my $wd = [shift, "."];
		1146
		1147	# stat once
919	aioreq_pri $pri;	1148	aioreq_pri $pri;
920	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1149	add $grp aio_stat $wd, sub {
921	my $entries = shift
922	or return $grp->result ();	1150	return $grp->result () if $_[0];
		1151	my $now = time;
		1152	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1153	my $rdxflags = READDIR_DIRS_FIRST;
923		1154
924	# stat the dir another time	1155	if ((stat _)[3] < 2) {
		1156	# at least one non-POSIX filesystem exists
		1157	# that returns useful DT_type values: btrfs,
		1158	# so optimise for this here by requesting dents
		1159	$rdxflags |= READDIR_DENTS;
		1160	}
		1161
		1162	# read the directory entries
925	aioreq_pri $pri;	1163	aioreq_pri $pri;
926	add $grp aio_stat $path, sub {	1164	add $grp aio_readdirx $wd, $rdxflags, sub {
927	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1165	my ($entries, $flags) = @_
		1166	or return $grp->result ();
928		1167
		1168	if ($rdxflags & READDIR_DENTS) {
		1169	# if we requested type values, see if we can use them directly.
		1170
		1171	# if there were any DT_UNKNOWN entries then we assume we
		1172	# don't know. alternatively, we could assume that if we get
		1173	# one DT_DIR, then all directories are indeed marked with
		1174	# DT_DIR, but this seems not required for btrfs, and this
		1175	# is basically the "btrfs can't get it's act together" code
		1176	# branch.
		1177	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1178	# now we have valid DT_ information for all entries,
		1179	# so use it as an optimisation without further stat's.
		1180	# they must also all be at the beginning of @$entries
		1181	# by now.
		1182
929	my $ndirs;	1183	my $dirs;
930		1184
931	# take the slow route if anything looks fishy
932	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
933	$ndirs = -1;
934	} else {
935	# if nlink == 2, we are finished
936	# for non-posix-fs's, we rely on nlink < 2
937	$ndirs = (stat _)[3] - 2
938	or return $grp->result ([], $entries);
939	}
940
941	my (@dirs, @nondirs);
942
943	my $statgrp = add $grp aio_group sub {
944	$grp->result (\@dirs, \@nondirs);
945	};
946
947	limit $statgrp $maxreq;
948	feed $statgrp sub {
949	return unless @$entries;
950	my $entry = shift @$entries;
951
952	aioreq_pri $pri;
953	add $statgrp aio_stat "$path/$entry/.", sub {
954	if ($_[0] < 0) {	1185	if (@$entries) {
955	push @nondirs, $entry;	1186	for (0 .. $#$entries) {
956	} else {	1187	if ($entries->[$_][1] != DT_DIR) {
957	# need to check for real directory	1188	# splice out directories
958	aioreq_pri $pri;	1189	$dirs = [splice @$entries, 0, $_];
959	add $statgrp aio_lstat "$path/$entry", sub {
960	if (-d _) {
961	push @dirs, $entry;
962
963	unless (--$ndirs) {
964	push @nondirs, @$entries;
965	feed $statgrp;
966	}	1190	last;
967	} else {
968	push @nondirs, $entry;
969	}	1191	}
970	}	1192	}
		1193
		1194	# if we didn't find any non-dir, then all entries are dirs
		1195	unless ($dirs) {
		1196	($dirs, $entries) = ($entries, []);
		1197	}
		1198	} else {
		1199	# directory is empty, so there are no sbdirs
		1200	$dirs = [];
971	}	1201	}
		1202
		1203	# either splice'd the directories out or the dir was empty.
		1204	# convert dents to filenames
		1205	$_ = $_->[0] for @$dirs;
		1206	$_ = $_->[0] for @$entries;
		1207
		1208	return $grp->result ($dirs, $entries);
		1209	}
		1210
		1211	# cannot use, so return to our old ways
		1212	# by pretending we only scanned for names.
		1213	$_ = $_->[0] for @$entries;
		1214	}
		1215
		1216	# stat the dir another time
		1217	aioreq_pri $pri;
		1218	add $grp aio_stat $wd, sub {
		1219	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1220
		1221	my $ndirs;
		1222
		1223	# take the slow route if anything looks fishy
		1224	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1225	$ndirs = -1;
		1226	} else {
		1227	# if nlink == 2, we are finished
		1228	# for non-posix-fs's, we rely on nlink < 2
		1229	$ndirs = (stat _)[3] - 2
		1230	or return $grp->result ([], $entries);
		1231	}
		1232
		1233	my (@dirs, @nondirs);
		1234
		1235	my $statgrp = add $grp aio_group sub {
		1236	$grp->result (\@dirs, \@nondirs);
		1237	};
		1238
		1239	limit $statgrp $maxreq;
		1240	feed $statgrp sub {
		1241	return unless @$entries;
		1242	my $entry = shift @$entries;
		1243
		1244	aioreq_pri $pri;
		1245	$wd->[1] = "$entry/.";
		1246	add $statgrp aio_stat $wd, sub {
		1247	if ($_[0] < 0) {
		1248	push @nondirs, $entry;
		1249	} else {
		1250	# need to check for real directory
		1251	aioreq_pri $pri;
		1252	$wd->[1] = $entry;
		1253	add $statgrp aio_lstat $wd, sub {
		1254	if (-d _) {
		1255	push @dirs, $entry;
		1256
		1257	unless (--$ndirs) {
		1258	push @nondirs, @$entries;
		1259	feed $statgrp;
		1260	}
		1261	} else {
		1262	push @nondirs, $entry;
		1263	}
		1264	}
		1265	}
		1266	};
972	};	1267	};
973	};	1268	};
974	};	1269	};
975	};	1270	};
976	};	1271	};
977		1272
978	$grp	1273	$grp
979	}	1274	}
980		1275
981	=item aio_rmtree $path, $callback->($status)	1276	=item aio_rmtree $pathname, $callback->($status)
982		1277
983	Delete a directory tree starting (and including) C<$path>, return the	1278	Delete a directory tree starting (and including) C<$path>, return the
984	status of the final C<rmdir> only. This is a composite request that	1279	status of the final C<rmdir> only. This is a composite request that
985	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1280	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
986	everything else.	1281	everything else.
987		1282
988	=cut	1283	=cut
989		1284
…		…
1011	};	1306	};
1012		1307
1013	$grp	1308	$grp
1014	}	1309	}
1015		1310
		1311	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1312
		1313	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1314
		1315	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1316	they execute asynchronously and pass the return value to the callback.
		1317
		1318	Both calls can be used for a lot of things, some of which make more sense
		1319	to run asynchronously in their own thread, while some others make less
		1320	sense. For example, calls that block waiting for external events, such
		1321	as locking, will also lock down an I/O thread while it is waiting, which
		1322	can deadlock the whole I/O system. At the same time, there might be no
		1323	alternative to using a thread to wait.
		1324
		1325	So in general, you should only use these calls for things that do
		1326	(filesystem) I/O, not for things that wait for other events (network,
		1327	other processes), although if you are careful and know what you are doing,
		1328	you still can.
		1329
		1330	The following constants are available and can be used for normal C<ioctl>
		1331	and C<fcntl> as well (missing ones are, as usual C<0>):
		1332
		1333	C<F_DUPFD_CLOEXEC>,
		1334
		1335	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1336
		1337	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1338
		1339	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1340	C<F_SEAL_WRITE>.
		1341
		1342	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1343	C<FS_IOC_FIEMAP>.
		1344
		1345	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1346	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1347
		1348	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1349	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1350	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1351	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1352	C<FS_FL_USER_MODIFIABLE>.
		1353
		1354	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1355	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1356	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1357	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1358
		1359	C<BLKROSET>, C<BLKROGET>, C<BLKRRPART>, C<BLKGETSIZE>, C<BLKFLSBUF>, C<BLKRASET>,
		1360	C<BLKRAGET>, C<BLKFRASET>, C<BLKFRAGET>, C<BLKSECTSET>, C<BLKSECTGET>, C<BLKSSZGET>,
		1361	C<BLKBSZGET>, C<BLKBSZSET>, C<BLKGETSIZE64>,
		1362
		1363
1016	=item aio_sync $callback->($status)	1364	=item aio_sync $callback->($status)
1017		1365
1018	Asynchronously call sync and call the callback when finished.	1366	Asynchronously call sync and call the callback when finished.
1019		1367
1020	=item aio_fsync $fh, $callback->($status)	1368	=item aio_fsync $fh, $callback->($status)
…		…
1027	Asynchronously call fdatasync on the given filehandle and call the	1375	Asynchronously call fdatasync on the given filehandle and call the
1028	callback with the fdatasync result code.	1376	callback with the fdatasync result code.
1029		1377
1030	If this call isn't available because your OS lacks it or it couldn't be	1378	If this call isn't available because your OS lacks it or it couldn't be
1031	detected, it will be emulated by calling C<fsync> instead.	1379	detected, it will be emulated by calling C<fsync> instead.
		1380
		1381	=item aio_syncfs $fh, $callback->($status)
		1382
		1383	Asynchronously call the syncfs syscall to sync the filesystem associated
		1384	to the given filehandle and call the callback with the syncfs result
		1385	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1386	errno to C<ENOSYS> nevertheless.
1032		1387
1033	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1388	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1034		1389
1035	Sync the data portion of the file specified by C<$offset> and C<$length>	1390	Sync the data portion of the file specified by C<$offset> and C<$length>
1036	to disk (but NOT the metadata), by calling the Linux-specific	1391	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1040	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1395	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1041	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1396	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1042	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1397	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1043	manpage for details.	1398	manpage for details.
1044		1399
1045	=item aio_pathsync $path, $callback->($status)	1400	=item aio_pathsync $pathname, $callback->($status)
1046		1401
1047	This request tries to open, fsync and close the given path. This is a	1402	This request tries to open, fsync and close the given path. This is a
1048	composite request intended to sync directories after directory operations	1403	composite request intended to sync directories after directory operations
1049	(E.g. rename). This might not work on all operating systems or have any	1404	(E.g. rename). This might not work on all operating systems or have any
1050	specific effect, but usually it makes sure that directory changes get	1405	specific effect, but usually it makes sure that directory changes get
…		…
1081	};	1436	};
1082		1437
1083	$grp	1438	$grp
1084	}	1439	}
1085		1440
1086	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1441	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1087		1442
1088	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1443	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1089	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1444	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1090	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1445	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1091	scalar must only be modified in-place while an aio operation is pending on	1446	scalar must only be modified in-place while an aio operation is pending on
…		…
1093		1448
1094	It calls the C<msync> function of your OS, if available, with the memory	1449	It calls the C<msync> function of your OS, if available, with the memory
1095	area starting at C<$offset> in the string and ending C<$length> bytes	1450	area starting at C<$offset> in the string and ending C<$length> bytes
1096	later. If C<$length> is negative, counts from the end, and if C<$length>	1451	later. If C<$length> is negative, counts from the end, and if C<$length>
1097	is C<undef>, then it goes till the end of the string. The flags can be	1452	is C<undef>, then it goes till the end of the string. The flags can be
1098	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1453	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1099	C<IO::AIO::MS_SYNC>.	1454	C<IO::AIO::MS_INVALIDATE>.
1100		1455
1101	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1456	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1102		1457
1103	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1458	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1104	scalars.	1459	scalars.
1105		1460
1106	It touches (reads or writes) all memory pages in the specified	1461	It touches (reads or writes) all memory pages in the specified
1107	range inside the scalar. All caveats and parameters are the same	1462	range inside the scalar. All caveats and parameters are the same
1108	as for C<aio_msync>, above, except for flags, which must be either	1463	as for C<aio_msync>, above, except for flags, which must be either
1109	C<0> (which reads all pages and ensures they are instantiated) or	1464	C<0> (which reads all pages and ensures they are instantiated) or
1110	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1465	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1111	writing an octet from it, which dirties the page).	1466	writing an octet from it, which dirties the page).
		1467
		1468	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1469
		1470	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1471	scalars.
		1472
		1473	It reads in all the pages of the underlying storage into memory (if any)
		1474	and locks them, so they are not getting swapped/paged out or removed.
		1475
		1476	If C<$length> is undefined, then the scalar will be locked till the end.
		1477
		1478	On systems that do not implement C<mlock>, this function returns C<-1>
		1479	and sets errno to C<ENOSYS>.
		1480
		1481	Note that the corresponding C<munlock> is synchronous and is
		1482	documented under L<MISCELLANEOUS FUNCTIONS>.
		1483
		1484	Example: open a file, mmap and mlock it - both will be undone when
		1485	C<$data> gets destroyed.
		1486
		1487	open my $fh, "<", $path or die "$path: $!";
		1488	my $data;
		1489	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1490	aio_mlock $data; # mlock in background
		1491
		1492	=item aio_mlockall $flags, $callback->($status)
		1493
		1494	Calls the C<mlockall> function with the given C<$flags> (a
		1495	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1496	C<IO::AIO::MCL_ONFAULT>).
		1497
		1498	On systems that do not implement C<mlockall>, this function returns C<-1>
		1499	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1500	by the system result in a return value of C<-1> with errno being set to
		1501	C<EINVAL>.
		1502
		1503	Note that the corresponding C<munlockall> is synchronous and is
		1504	documented under L<MISCELLANEOUS FUNCTIONS>.
		1505
		1506	Example: asynchronously lock all current and future pages into memory.
		1507
		1508	aio_mlockall IO::AIO::MCL_FUTURE;
		1509
		1510	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1511
		1512	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1513	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1514	the ioctl is not available on your OS, then this request will fail with
		1515	C<ENOSYS>.
		1516
		1517	C<$start> is the starting offset to query extents for, C<$length> is the
		1518	size of the range to query - if it is C<undef>, then the whole file will
		1519	be queried.
		1520
		1521	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1522	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1523	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1524	the data portion.
		1525
		1526	C<$count> is the maximum number of extent records to return. If it is
		1527	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1528	case, if it is C<0>, then the callback receives the number of extents
		1529	instead of the extents themselves (which is unreliable, see below).
		1530
		1531	If an error occurs, the callback receives no arguments. The special
		1532	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1533
		1534	Otherwise, the callback receives an array reference with extent
		1535	structures. Each extent structure is an array reference itself, with the
		1536	following members:
		1537
		1538	[$logical, $physical, $length, $flags]
		1539
		1540	Flags is any combination of the following flag values (typically either C<0>
		1541	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1542
		1543	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1544	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1545	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1546	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1547	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1548	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1549
		1550	At the time of this writing (Linux 3.2), this request is unreliable unless
		1551	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1552	it to return all extents of a range for files with a large number of
		1553	extents. The code (only) works around all these issues if C<$count> is
		1554	C<undef>.
1112		1555
1113	=item aio_group $callback->(...)	1556	=item aio_group $callback->(...)
1114		1557
1115	This is a very special aio request: Instead of doing something, it is a	1558	This is a very special aio request: Instead of doing something, it is a
1116	container for other aio requests, which is useful if you want to bundle	1559	container for other aio requests, which is useful if you want to bundle
…		…
1153	like sleep and file handle readable/writable, the overhead this creates is	1596	like sleep and file handle readable/writable, the overhead this creates is
1154	immense (it blocks a thread for a long time) so do not use this function	1597	immense (it blocks a thread for a long time) so do not use this function
1155	except to put your application under artificial I/O pressure.	1598	except to put your application under artificial I/O pressure.
1156		1599
1157	=back	1600	=back
		1601
		1602
		1603	=head2 IO::AIO::WD - multiple working directories
		1604
		1605	Your process only has one current working directory, which is used by all
		1606	threads. This makes it hard to use relative paths (some other component
		1607	could call C<chdir> at any time, and it is hard to control when the path
		1608	will be used by IO::AIO).
		1609
		1610	One solution for this is to always use absolute paths. This usually works,
		1611	but can be quite slow (the kernel has to walk the whole path on every
		1612	access), and can also be a hassle to implement.
		1613
		1614	Newer POSIX systems have a number of functions (openat, fdopendir,
		1615	futimensat and so on) that make it possible to specify working directories
		1616	per operation.
		1617
		1618	For portability, and because the clowns who "designed", or shall I write,
		1619	perpetrated this new interface were obviously half-drunk, this abstraction
		1620	cannot be perfect, though.
		1621
		1622	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1623	object. This object stores the canonicalised, absolute version of the
		1624	path, and on systems that allow it, also a directory file descriptor.
		1625
		1626	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1627	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1628	object and a pathname instead (or the IO::AIO::WD object alone, which
		1629	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1630	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1631	to that IO::AIO::WD object.
		1632
		1633	For example, to get a wd object for F</etc> and then stat F<passwd>
		1634	inside, you would write:
		1635
		1636	aio_wd "/etc", sub {
		1637	my $etcdir = shift;
		1638
		1639	# although $etcdir can be undef on error, there is generally no reason
		1640	# to check for errors here, as aio_stat will fail with ENOENT
		1641	# when $etcdir is undef.
		1642
		1643	aio_stat [$etcdir, "passwd"], sub {
		1644	# yay
		1645	};
		1646	};
		1647
		1648	The fact that C<aio_wd> is a request and not a normal function shows that
		1649	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1650	which is why it is done asynchronously.
		1651
		1652	To stat the directory obtained with C<aio_wd> above, one could write
		1653	either of the following three request calls:
		1654
		1655	aio_lstat "/etc" , sub { ... # pathname as normal string
		1656	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1657	aio_lstat $wd , sub { ... # shorthand for the previous
		1658
		1659	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1660	object and the pathname string, so you could write the following without
		1661	causing any issues due to C<$path> getting reused:
		1662
		1663	my $path = [$wd, undef];
		1664
		1665	for my $name (qw(abc def ghi)) {
		1666	$path->[1] = $name;
		1667	aio_stat $path, sub {
		1668	# ...
		1669	};
		1670	}
		1671
		1672	There are some caveats: when directories get renamed (or deleted), the
		1673	pathname string doesn't change, so will point to the new directory (or
		1674	nowhere at all), while the directory fd, if available on the system,
		1675	will still point to the original directory. Most functions accepting a
		1676	pathname will use the directory fd on newer systems, and the string on
		1677	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1678	the string form of the pathname.
		1679
		1680	So this functionality is mainly useful to get some protection against
		1681	C<chdir>, to easily get an absolute path out of a relative path for future
		1682	reference, and to speed up doing many operations in the same directory
		1683	(e.g. when stat'ing all files in a directory).
		1684
		1685	The following functions implement this working directory abstraction:
		1686
		1687	=over 4
		1688
		1689	=item aio_wd $pathname, $callback->($wd)
		1690
		1691	Asynchonously canonicalise the given pathname and convert it to an
		1692	IO::AIO::WD object representing it. If possible and supported on the
		1693	system, also open a directory fd to speed up pathname resolution relative
		1694	to this working directory.
		1695
		1696	If something goes wrong, then C<undef> is passwd to the callback instead
		1697	of a working directory object and C<$!> is set appropriately. Since
		1698	passing C<undef> as working directory component of a pathname fails the
		1699	request with C<ENOENT>, there is often no need for error checking in the
		1700	C<aio_wd> callback, as future requests using the value will fail in the
		1701	expected way.
		1702
		1703	=item IO::AIO::CWD
		1704
		1705	This is a compile time constant (object) that represents the process
		1706	current working directory.
		1707
		1708	Specifying this object as working directory object for a pathname is as if
		1709	the pathname would be specified directly, without a directory object. For
		1710	example, these calls are functionally identical:
		1711
		1712	aio_stat "somefile", sub { ... };
		1713	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1714
		1715	=back
		1716
		1717	To recover the path associated with an IO::AIO::WD object, you can use
		1718	C<aio_realpath>:
		1719
		1720	aio_realpath $wd, sub {
		1721	warn "path is $_[0]\n";
		1722	};
		1723
		1724	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1725	sometimes, fall back to using an absolue path.
1158		1726
1159	=head2 IO::AIO::REQ CLASS	1727	=head2 IO::AIO::REQ CLASS
1160		1728
1161	All non-aggregate C<aio_*> functions return an object of this class when	1729	All non-aggregate C<aio_*> functions return an object of this class when
1162	called in non-void context.	1730	called in non-void context.
…		…
1280		1848
1281	Sets a feeder/generator on this group: every group can have an attached	1849	Sets a feeder/generator on this group: every group can have an attached
1282	generator that generates requests if idle. The idea behind this is that,	1850	generator that generates requests if idle. The idea behind this is that,
1283	although you could just queue as many requests as you want in a group,	1851	although you could just queue as many requests as you want in a group,
1284	this might starve other requests for a potentially long time. For example,	1852	this might starve other requests for a potentially long time. For example,
1285	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1853	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1286	delaying any later requests for a long time.	1854	requests, delaying any later requests for a long time.
1287		1855
1288	To avoid this, and allow incremental generation of requests, you can	1856	To avoid this, and allow incremental generation of requests, you can
1289	instead a group and set a feeder on it that generates those requests. The	1857	instead a group and set a feeder on it that generates those requests. The
1290	feed callback will be called whenever there are few enough (see C<limit>,	1858	feed callback will be called whenever there are few enough (see C<limit>,
1291	below) requests active in the group itself and is expected to queue more	1859	below) requests active in the group itself and is expected to queue more
…		…
1323	The default value for the limit is C<0>, but note that setting a feeder	1891	The default value for the limit is C<0>, but note that setting a feeder
1324	automatically bumps it up to C<2>.	1892	automatically bumps it up to C<2>.
1325		1893
1326	=back	1894	=back
1327		1895
		1896
1328	=head2 SUPPORT FUNCTIONS	1897	=head2 SUPPORT FUNCTIONS
1329		1898
1330	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1899	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1331		1900
1332	=over 4	1901	=over 4
…		…
1340		1909
1341	See C<poll_cb> for an example.	1910	See C<poll_cb> for an example.
1342		1911
1343	=item IO::AIO::poll_cb	1912	=item IO::AIO::poll_cb
1344		1913
1345	Process some outstanding events on the result pipe. You have to call this	1914	Process some requests that have reached the result phase (i.e. they have
1346	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1915	been executed but the results are not yet reported). You have to call
1347	returned earlier for whatever reason. Returns immediately when no events	1916	this "regularly" to finish outstanding requests.
1348	are outstanding. The amount of events processed depends on the settings of
1349	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1350		1917
		1918	Returns C<0> if all events could be processed (or there were no
		1919	events to process), or C<-1> if it returned earlier for whatever
		1920	reason. Returns immediately when no events are outstanding. The amount
		1921	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1922	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1923
1351	If not all requests were processed for whatever reason, the filehandle	1924	If not all requests were processed for whatever reason, the poll file
1352	will still be ready when C<poll_cb> returns, so normally you don't have to	1925	descriptor will still be ready when C<poll_cb> returns, so normally you
1353	do anything special to have it called later.	1926	don't have to do anything special to have it called later.
		1927
		1928	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1929	ready, it can be beneficial to call this function from loops which submit
		1930	a lot of requests, to make sure the results get processed when they become
		1931	available and not just when the loop is finished and the event loop takes
		1932	over again. This function returns very fast when there are no outstanding
		1933	requests.
1354		1934
1355	Example: Install an Event watcher that automatically calls	1935	Example: Install an Event watcher that automatically calls
1356	IO::AIO::poll_cb with high priority (more examples can be found in the	1936	IO::AIO::poll_cb with high priority (more examples can be found in the
1357	SYNOPSIS section, at the top of this document):	1937	SYNOPSIS section, at the top of this document):
1358		1938
…		…
1360	poll => 'r', async => 1,	1940	poll => 'r', async => 1,
1361	cb => \&IO::AIO::poll_cb);	1941	cb => \&IO::AIO::poll_cb);
1362		1942
1363	=item IO::AIO::poll_wait	1943	=item IO::AIO::poll_wait
1364		1944
1365	If there are any outstanding requests and none of them in the result	1945	Wait until either at least one request is in the result phase or no
1366	phase, wait till the result filehandle becomes ready for reading (simply	1946	requests are outstanding anymore.
1367	does a C<select> on the filehandle. This is useful if you want to	1947
1368	synchronously wait for some requests to finish).	1948	This is useful if you want to synchronously wait for some requests to
		1949	become ready, without actually handling them.
1369		1950
1370	See C<nreqs> for an example.	1951	See C<nreqs> for an example.
1371		1952
1372	=item IO::AIO::poll	1953	=item IO::AIO::poll
1373		1954
…		…
1384		1965
1385	Strictly equivalent to:	1966	Strictly equivalent to:
1386		1967
1387	IO::AIO::poll_wait, IO::AIO::poll_cb	1968	IO::AIO::poll_wait, IO::AIO::poll_cb
1388	while IO::AIO::nreqs;	1969	while IO::AIO::nreqs;
		1970
		1971	This function can be useful at program aborts, to make sure outstanding
		1972	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1973	this function on normal exits), or when you are merely using C<IO::AIO>
		1974	for its more advanced functions, rather than for async I/O, e.g.:
		1975
		1976	my ($dirs, $nondirs);
		1977	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1978	IO::AIO::flush;
		1979	# $dirs, $nondirs are now set
1389		1980
1390	=item IO::AIO::max_poll_reqs $nreqs	1981	=item IO::AIO::max_poll_reqs $nreqs
1391		1982
1392	=item IO::AIO::max_poll_time $seconds	1983	=item IO::AIO::max_poll_time $seconds
1393		1984
…		…
1420	poll => 'r', nice => 1,	2011	poll => 'r', nice => 1,
1421	cb => &IO::AIO::poll_cb);	2012	cb => &IO::AIO::poll_cb);
1422		2013
1423	=back	2014	=back
1424		2015
		2016
1425	=head3 CONTROLLING THE NUMBER OF THREADS	2017	=head3 CONTROLLING THE NUMBER OF THREADS
1426		2018
1427	=over	2019	=over
1428		2020
1429	=item IO::AIO::min_parallel $nthreads	2021	=item IO::AIO::min_parallel $nthreads
…		…
1460		2052
1461	Under normal circumstances you don't need to call this function.	2053	Under normal circumstances you don't need to call this function.
1462		2054
1463	=item IO::AIO::max_idle $nthreads	2055	=item IO::AIO::max_idle $nthreads
1464		2056
1465	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2057	Limit the number of threads (default: 4) that are allowed to idle
1466	threads that did not get a request to process within 10 seconds). That	2058	(i.e., threads that did not get a request to process within the idle
1467	means if a thread becomes idle while C<$nthreads> other threads are also	2059	timeout (default: 10 seconds). That means if a thread becomes idle while
1468	idle, it will free its resources and exit.	2060	C<$nthreads> other threads are also idle, it will free its resources and
		2061	exit.
1469		2062
1470	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2063	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1471	to allow for extremely high load situations, but want to free resources	2064	to allow for extremely high load situations, but want to free resources
1472	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2065	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1473		2066
1474	The default is probably ok in most situations, especially if thread	2067	The default is probably ok in most situations, especially if thread
1475	creation is fast. If thread creation is very slow on your system you might	2068	creation is fast. If thread creation is very slow on your system you might
1476	want to use larger values.	2069	want to use larger values.
1477		2070
		2071	=item IO::AIO::idle_timeout $seconds
		2072
		2073	Sets the minimum idle timeout (default 10) after which worker threads are
		2074	allowed to exit. SEe C<IO::AIO::max_idle>.
		2075
1478	=item IO::AIO::max_outstanding $maxreqs	2076	=item IO::AIO::max_outstanding $maxreqs
1479		2077
1480	This is a very bad function to use in interactive programs because it
1481	blocks, and a bad way to reduce concurrency because it is inexact: Better
1482	use an C<aio_group> together with a feed callback.
1483
1484	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2078	Sets the maximum number of outstanding requests to C<$nreqs>. If
1485	do queue up more than this number of requests, the next call to the	2079	you do queue up more than this number of requests, the next call to
1486	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)	2080	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1487	function will block until the limit is no longer exceeded.	2081	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2082	longer exceeded.
1488		2083
1489	The default value is very large, so there is no practical limit on the	2084	In other words, this setting does not enforce a queue limit, but can be
1490	number of outstanding requests.	2085	used to make poll functions block if the limit is exceeded.
1491		2086
1492	You can still queue as many requests as you want. Therefore,	2087	This is a bad function to use in interactive programs because it blocks,
1493	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2088	and a bad way to reduce concurrency because it is inexact. If you need to
1494	as a stop gap to shield against fatal memory overflow (with large values).	2089	issue many requests without being able to call a poll function on demand,
		2090	it is better to use an C<aio_group> together with a feed callback.
		2091
		2092	Its main use is in scripts without an event loop - when you want to stat a
		2093	lot of files, you can write something like this:
		2094
		2095	IO::AIO::max_outstanding 32;
		2096
		2097	for my $path (...) {
		2098	aio_stat $path , ...;
		2099	IO::AIO::poll_cb;
		2100	}
		2101
		2102	IO::AIO::flush;
		2103
		2104	The call to C<poll_cb> inside the loop will normally return instantly,
		2105	allowing the loop to progress, but as soon as more than C<32> requests
		2106	are in-flight, it will block until some requests have been handled. This
		2107	keeps the loop from pushing a large number of C<aio_stat> requests onto
		2108	the queue (which, with many paths to stat, can use up a lot of memory).
		2109
		2110	The default value for C<max_outstanding> is very large, so there is no
		2111	practical limit on the number of outstanding requests.
1495		2112
1496	=back	2113	=back
		2114
1497		2115
1498	=head3 STATISTICAL INFORMATION	2116	=head3 STATISTICAL INFORMATION
1499		2117
1500	=over	2118	=over
1501		2119
…		…
1519	Returns the number of requests currently in the pending state (executed,	2137	Returns the number of requests currently in the pending state (executed,
1520	but not yet processed by poll_cb).	2138	but not yet processed by poll_cb).
1521		2139
1522	=back	2140	=back
1523		2141
		2142
		2143	=head3 SUBSECOND STAT TIME ACCESS
		2144
		2145	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2146	generally find access/modification and change times with subsecond time
		2147	accuracy of the system supports it, but perl's built-in functions only
		2148	return the integer part.
		2149
		2150	The following functions return the timestamps of the most recent
		2151	stat with subsecond precision on most systems and work both after
		2152	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2153	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2154	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2155
		2156	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2157	full resolution without rounding and work with standard perl C<stat>,
		2158	alleviating the need to call the special C<Time::HiRes> functions, which
		2159	do not act like their perl counterparts.
		2160
		2161	On operating systems or file systems where subsecond time resolution is
		2162	not supported or could not be detected, a fractional part of C<0> is
		2163	returned, so it is always safe to call these functions.
		2164
		2165	=over 4
		2166
		2167	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2168
		2169	Return the access, modication, change or birth time, respectively,
		2170	including fractional part. Due to the limited precision of floating point,
		2171	the accuracy on most platforms is only a bit better than milliseconds
		2172	for times around now - see the I<nsec> function family, below, for full
		2173	accuracy.
		2174
		2175	File birth time is only available when the OS and perl support it (on
		2176	FreeBSD and NetBSD at the time of this writing, although support is
		2177	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2178	it). On systems where it isn't available, C<0> is currently returned, but
		2179	this might change to C<undef> in a future version.
		2180
		2181	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2182
		2183	Returns access, modification, change and birth time all in one go, and
		2184	maybe more times in the future version.
		2185
		2186	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2187
		2188	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2189	as an integer in the range C<0> to C<999999999>.
		2190
		2191	Note that no accessors are provided for access, modification and
		2192	change times - you need to get those from C<stat _> if required (C<int
		2193	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2194	value).
		2195
		2196	=item $seconds = IO::AIO::st_btimesec
		2197
		2198	The (integral) seconds part of the file birth time, if available.
		2199
		2200	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2201
		2202	Like the functions above, but returns all four times in one go (and maybe
		2203	more in future versions).
		2204
		2205	=item $counter = IO::AIO::st_gen
		2206
		2207	Returns the generation counter (in practice this is just a random number)
		2208	of the file. This is only available on platforms which have this member in
		2209	their C<struct stat> (most BSDs at the time of this writing) and generally
		2210	only to the root usert. If unsupported, C<0> is returned, but this might
		2211	change to C<undef> in a future version.
		2212
		2213	=back
		2214
		2215	Example: print the high resolution modification time of F</etc>, using
		2216	C<stat>, and C<IO::AIO::aio_stat>.
		2217
		2218	if (stat "/etc") {
		2219	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2220	}
		2221
		2222	IO::AIO::aio_stat "/etc", sub {
		2223	$_[0]
		2224	and return;
		2225
		2226	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2227	};
		2228
		2229	IO::AIO::flush;
		2230
		2231	Output of the awbove on my system, showing reduced and full accuracy:
		2232
		2233	stat(/etc) mtime: 1534043702.020808
		2234	aio_stat(/etc) mtime: 1534043702.020807792
		2235
		2236
1524	=head3 MISCELLANEOUS FUNCTIONS	2237	=head3 MISCELLANEOUS FUNCTIONS
1525		2238
1526	IO::AIO implements some functions that might be useful, but are not	2239	IO::AIO implements some functions that are useful when you want to use
1527	asynchronous.	2240	some "Advanced I/O" function not available to in Perl, without going the
		2241	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2242	counterpart.
1528		2243
1529	=over 4	2244	=over 4
		2245
		2246	=item $retval = IO::AIO::fexecve $fh, $argv, $envp
		2247
		2248	A more-or-less direct equivalent to the POSIX C<fexecve> functions, which
		2249	allows you to specify the program to be executed via a file descriptor (or
		2250	handle). Returns C<-1> and sets errno to C<ENOSYS> if not available.
		2251
		2252	=item $retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
		2253
		2254	Calls the GNU/Linux mount syscall with the given arguments. All except
		2255	C<$flags> are strings, and if C<$data> is C<undef>, a C<NULL> will be
		2256	passed.
		2257
		2258	The following values for C<$flags> are available:
		2259
		2260	C<IO::AIO::MS_RDONLY>, C<IO::AIO::MS_NOSUID>, C<IO::AIO::MS_NODEV>, C<IO::AIO::MS_NOEXEC>, C<IO::AIO::MS_SYNCHRONOUS>,
		2261	C<IO::AIO::MS_REMOUNT>, C<IO::AIO::MS_MANDLOCK>, C<IO::AIO::MS_DIRSYNC>, C<IO::AIO::MS_NOATIME>,
		2262	C<IO::AIO::MS_NODIRATIME>, C<IO::AIO::MS_BIND>, C<IO::AIO::MS_MOVE>, C<IO::AIO::MS_REC>, C<IO::AIO::MS_SILENT>,
		2263	C<IO::AIO::MS_POSIXACL>, C<IO::AIO::MS_UNBINDABLE>, C<IO::AIO::MS_PRIVATE>, C<IO::AIO::MS_SLAVE>, C<IO::AIO::MS_SHARED>,
		2264	C<IO::AIO::MS_RELATIME>, C<IO::AIO::MS_KERNMOUNT>, C<IO::AIO::MS_I_VERSION>, C<IO::AIO::MS_STRICTATIME>,
		2265	C<IO::AIO::MS_LAZYTIME>, C<IO::AIO::MS_ACTIVE>, C<IO::AIO::MS_NOUSER>, C<IO::AIO::MS_RMT_MASK>, C<IO::AIO::MS_MGC_VAL> and
		2266	C<IO::AIO::MS_MGC_MSK>.
		2267
		2268	=item $retval = IO::AIO::umount $path, $flags = 0
		2269
		2270	Invokes the GNU/Linux C<umount> or C<umount2> syscalls. Always calls
		2271	C<umount> if C<$flags> is C<0>, otherwqise always tries to call
		2272	C<umount2>.
		2273
		2274	The following C<$flags> are available:
		2275
		2276	C<IO::AIO::MNT_FORCE>, C<IO::AIO::MNT_DETACH>, C<IO::AIO::MNT_EXPIRE> and C<IO::AIO::UMOUNT_NOFOLLOW>.
		2277
		2278	=item $numfd = IO::AIO::get_fdlimit
		2279
		2280	Tries to find the current file descriptor limit and returns it, or
		2281	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2282	the highest valid file descriptor number.
		2283
		2284	=item IO::AIO::min_fdlimit [$numfd]
		2285
		2286	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2287	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2288	is missing, it will try to set a very high limit, although this is not
		2289	recommended when you know the actual minimum that you require.
		2290
		2291	If the limit cannot be raised enough, the function makes a best-effort
		2292	attempt to increase the limit as much as possible, using various
		2293	tricks, while still failing. You can query the resulting limit using
		2294	C<IO::AIO::get_fdlimit>.
		2295
		2296	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2297	true.
1530		2298
1531	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2299	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1532		2300
1533	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2301	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1534	but is blocking (this makes most sense if you know the input data is	2302	but is blocking (this makes most sense if you know the input data is
…		…
1537		2305
1538	Returns the number of bytes copied, or C<-1> on error.	2306	Returns the number of bytes copied, or C<-1> on error.
1539		2307
1540	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2308	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1541		2309
1542	Simply calls the C<posix_fadvise> function (see it's	2310	Simply calls the C<posix_fadvise> function (see its
1543	manpage for details). The following advice constants are	2311	manpage for details). The following advice constants are
1544	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2312	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1545	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2313	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1546	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2314	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1547		2315
1548	On systems that do not implement C<posix_fadvise>, this function returns	2316	On systems that do not implement C<posix_fadvise>, this function returns
1549	ENOSYS, otherwise the return value of C<posix_fadvise>.	2317	ENOSYS, otherwise the return value of C<posix_fadvise>.
1550		2318
		2319	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2320
		2321	Simply calls the C<posix_madvise> function (see its
		2322	manpage for details). The following advice constants are
		2323	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2324	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2325	C<IO::AIO::MADV_DONTNEED>.
		2326
		2327	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2328	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2329	will be reduced to fit into the C<$scalar>.
		2330
		2331	On systems that do not implement C<posix_madvise>, this function returns
		2332	ENOSYS, otherwise the return value of C<posix_madvise>.
		2333
		2334	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2335
		2336	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2337	$scalar (see its manpage for details). The following protect
		2338	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2339	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2340
		2341	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2342	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2343	will be reduced to fit into the C<$scalar>.
		2344
		2345	On systems that do not implement C<mprotect>, this function returns
		2346	ENOSYS, otherwise the return value of C<mprotect>.
		2347
1551	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2348	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1552		2349
1553	Memory-maps a file (or anonymous memory range) and attaches it to the	2350	Memory-maps a file (or anonymous memory range) and attaches it to the
1554	given C<$scalar>, which will act like a string scalar.	2351	given C<$scalar>, which will act like a string scalar. Returns true on
		2352	success, and false otherwise.
1555		2353
		2354	The scalar must exist, but its contents do not matter - this means you
		2355	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2356	the scalar first.
		2357
1556	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2358	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1557	change the string length, and most read-only operations such as copying it	2359	which don't change the string length, and most read-only operations such
1558	or searching it with regexes and so on.	2360	as copying it or searching it with regexes and so on.
1559		2361
1560	Anything else is unsafe and will, at best, result in memory leaks.	2362	Anything else is unsafe and will, at best, result in memory leaks.
1561		2363
1562	The memory map associated with the C<$scalar> is automatically removed	2364	The memory map associated with the C<$scalar> is automatically removed
1563	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2365	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1564	C<IO::AIO::munmap> functions are called.	2366	or C<IO::AIO::munmap> functions are called on it.
1565		2367
1566	This calls the C<mmap>(2) function internally. See your system's manual	2368	This calls the C<mmap>(2) function internally. See your system's manual
1567	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2369	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1568		2370
1569	The C<$length> must be larger than zero and smaller than the actual	2371	The C<$length> must be larger than zero and smaller than the actual
1570	filesize.	2372	filesize.
1571		2373
1572	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2374	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1573	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2375	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1574		2376
1575	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2377	C<$flags> can be a combination of
1576	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2378	C<IO::AIO::MAP_SHARED> or
1577	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2379	C<IO::AIO::MAP_PRIVATE>,
		2380	or a number of system-specific flags (when not available, the are C<0>):
1578	(which is set to C<MAP_ANON> if your system only provides this	2381	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1579	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2382	C<IO::AIO::MAP_LOCKED>,
1580	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2383	C<IO::AIO::MAP_NORESERVE>,
		2384	C<IO::AIO::MAP_POPULATE>,
1581	C<IO::AIO::MAP_NONBLOCK>	2385	C<IO::AIO::MAP_NONBLOCK>,
		2386	C<IO::AIO::MAP_FIXED>,
		2387	C<IO::AIO::MAP_GROWSDOWN>,
		2388	C<IO::AIO::MAP_32BIT>,
		2389	C<IO::AIO::MAP_HUGETLB>,
		2390	C<IO::AIO::MAP_STACK>,
		2391	C<IO::AIO::MAP_FIXED_NOREPLACE>,
		2392	C<IO::AIO::MAP_SHARED_VALIDATE>,
		2393	C<IO::AIO::MAP_SYNC> or
		2394	C<IO::AIO::MAP_UNINITIALIZED>.
1582		2395
1583	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2396	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2397
		2398	C<$offset> is the offset from the start of the file - it generally must be
		2399	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
1584		2400
1585	Example:	2401	Example:
1586		2402
1587	use Digest::MD5;	2403	use Digest::MD5;
1588	use IO::AIO;	2404	use IO::AIO;
…		…
1597		2413
1598	=item IO::AIO::munmap $scalar	2414	=item IO::AIO::munmap $scalar
1599		2415
1600	Removes a previous mmap and undefines the C<$scalar>.	2416	Removes a previous mmap and undefines the C<$scalar>.
1601		2417
		2418	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2419
		2420	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2421	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2422	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2423
		2424	Returns true if successful, and false otherwise. If the underlying mmapped
		2425	region has changed address, then the true value has the numerical value
		2426	C<1>, otherwise it has the numerical value C<0>:
		2427
		2428	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2429	or die "mremap: $!";
		2430
		2431	if ($success*1) {
		2432	warn "scalar has chanegd address in memory\n";
		2433	}
		2434
		2435	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2436	implemented, but not supported and might go away in a future version.
		2437
		2438	On systems where this call is not supported or is not emulated, this call
		2439	returns falls and sets C<$!> to C<ENOSYS>.
		2440
1602	=item IO::AIO::mlockall $flags	2441	=item IO::AIO::mlockall $flags
1603		2442
1604	Calls the C<mlockall> function with the given C<$flags> (a combination of	2443	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
1605	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL__FUTURE>).	2444	but is blocking.
1606		2445
1607	On systems that do not implement C<mlockall>, this function returns	2446	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1608	ENOSYS, otherwise the return value of C<mlockall>.	2447
		2448	Calls the C<munlock> function, undoing the effects of a previous
		2449	C<aio_mlock> call (see its description for details).
1609		2450
1610	=item IO::AIO::munlockall	2451	=item IO::AIO::munlockall
1611		2452
1612	Calls the C<munlockall> function.	2453	Calls the C<munlockall> function.
1613		2454
1614	On systems that do not implement C<munlockall>, this function returns	2455	On systems that do not implement C<munlockall>, this function returns
1615	ENOSYS, otherwise the return value of C<munlockall>.	2456	ENOSYS, otherwise the return value of C<munlockall>.
		2457
		2458	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2459
		2460	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2461	and return the new file handle on success, or sets C<$!> and returns
		2462	C<undef> on error.
		2463
		2464	The remote name of the new socket will be stored in C<$sockaddr>, which
		2465	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2466	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2467	by returning a longer string in C<$sockaddr>, which might or might not be
		2468	truncated.
		2469
		2470	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2471	C<$sockaddr_maxlen>.
		2472
		2473	The main reasons to use this syscall rather than portable C<accept(2)>
		2474	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2475	flags and you can accept name-less sockets by specifying C<0> for
		2476	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2477	C<accept>.
		2478
		2479	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2480
		2481	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2482	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2483	should be the file offset.
		2484
		2485	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2486	silently corrupt the data in this case.
		2487
		2488	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2489	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2490	C<IO::AIO::SPLICE_F_GIFT>.
		2491
		2492	See the C<splice(2)> manpage for details.
		2493
		2494	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2495
		2496	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2497	description for C<IO::AIO::splice> above for details.
		2498
		2499	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2500
		2501	Attempts to query or change the pipe buffer size. Obviously works only
		2502	on pipes, and currently works only on GNU/Linux systems, and fails with
		2503	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2504	size on other systems, drop me a note.
		2505
		2506	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2507
		2508	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2509	C<$flags> is missing or C<0>, then this should be the same as a call to
		2510	perl's built-in C<pipe> function and create a new pipe, and works on
		2511	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2512	(..., 4096, O_BINARY)>.
		2513
		2514	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2515	the given flags (Linux 2.6.27, glibc 2.9).
		2516
		2517	On success, the read and write file handles are returned.
		2518
		2519	On error, nothing will be returned. If the pipe2 syscall is missing and
		2520	C<$flags> is non-zero, fails with C<ENOSYS>.
		2521
		2522	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2523	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2524	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2525
		2526	Example: create a pipe race-free w.r.t. threads and fork:
		2527
		2528	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2529	or die "pipe2: $!\n";
		2530
		2531	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2532
		2533	This is a direct interface to the Linux L<memfd_create(2)> system
		2534	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2535	should be C<IO::AIO::MFD_CLOEXEC>.
		2536
		2537	On success, the new memfd filehandle is returned, otherwise returns
		2538	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2539
		2540	Please refer to L<memfd_create(2)> for more info on this call.
		2541
		2542	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2543	C<IO::AIO::MFD_ALLOW_SEALING>, C<IO::AIO::MFD_HUGETLB>,
		2544	C<IO::AIO::MFD_HUGETLB_2MB> and C<IO::AIO::MFD_HUGETLB_1GB>.
		2545
		2546	Example: create a new memfd.
		2547
		2548	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2549	or die "memfd_create: $!\n";
		2550
		2551	=item $fh = IO::AIO::pidfd_open $pid[, $flags]
		2552
		2553	This is an interface to the Linux L<pidfd_open(2)> system call. The
		2554	default for C<$flags> is C<0>.
		2555
		2556	On success, a new pidfd filehandle is returned (that is already set to
		2557	close-on-exec), otherwise returns C<undef>. If the syscall is missing,
		2558	fails with C<ENOSYS>.
		2559
		2560	Example: open pid 6341 as pidfd.
		2561
		2562	my $fh = IO::AIO::pidfd_open 6341
		2563	or die "pidfd_open: $!\n";
		2564
		2565	=item $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
		2566
		2567	This is an interface to the Linux L<pidfd_send_signal> system call. The
		2568	default for C<$siginfo> is C<undef> and the default for C<$flags> is C<0>.
		2569
		2570	Returns the system call status. If the syscall is missing, fails with
		2571	C<ENOSYS>.
		2572
		2573	When specified, C<$siginfo> must be a reference to a hash with one or more
		2574	of the following members:
		2575
		2576	=over
		2577
		2578	=item code - the C<si_code> member
		2579
		2580	=item pid - the C<si_pid> member
		2581
		2582	=item uid - the C<si_uid> member
		2583
		2584	=item value_int - the C<si_value.sival_int> member
		2585
		2586	=item value_ptr - the C<si_value.sival_ptr> member, specified as an integer
		2587
		2588	=back
		2589
		2590	Example: send a SIGKILL to the specified process.
		2591
		2592	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
		2593	and die "pidfd_send_signal: $!\n";
		2594
		2595	Example: send a SIGKILL to the specified process with extra data.
		2596
		2597	my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
		2598	and die "pidfd_send_signal: $!\n";
		2599
		2600	=item $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
		2601
		2602	This is an interface to the Linux L<pidfd_getfd> system call. The default
		2603	for C<$flags> is C<0>.
		2604
		2605	On success, returns a dup'ed copy of the target file descriptor (specified
		2606	as an integer) returned (that is already set to close-on-exec), otherwise
		2607	returns C<undef>. If the syscall is missing, fails with C<ENOSYS>.
		2608
		2609	Example: get a copy of standard error of another process and print soemthing to it.
		2610
		2611	my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
		2612	or die "pidfd_getfd: $!\n";
		2613	print $errfh "stderr\n";
		2614
		2615	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2616
		2617	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2618	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2619
		2620	On success, the new eventfd filehandle is returned, otherwise returns
		2621	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2622
		2623	Please refer to L<eventfd(2)> for more info on this call.
		2624
		2625	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2626	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2627
		2628	Example: create a new eventfd filehandle:
		2629
		2630	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2631	or die "eventfd: $!\n";
		2632
		2633	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2634
		2635	This is a direct interface to the Linux L<timerfd_create(2)> system
		2636	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2637	should be C<IO::AIO::TFD_CLOEXEC>.
		2638
		2639	On success, the new timerfd filehandle is returned, otherwise returns
		2640	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2641
		2642	Please refer to L<timerfd_create(2)> for more info on this call.
		2643
		2644	The following C<$clockid> values are
		2645	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2646	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2647	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2648	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2649
		2650	The following C<$flags> values are available (Linux
		2651	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2652
		2653	Example: create a new timerfd and set it to one-second repeated alarms,
		2654	then wait for two alarms:
		2655
		2656	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2657	or die "timerfd_create: $!\n";
		2658
		2659	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2660	or die "timerfd_settime: $!\n";
		2661
		2662	for (1..2) {
		2663	8 == sysread $fh, my $buf, 8
		2664	or die "timerfd read failure\n";
		2665
		2666	printf "number of expirations (likely 1): %d\n",
		2667	unpack "Q", $buf;
		2668	}
		2669
		2670	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2671
		2672	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2673	call. Please refer to its manpage for more info on this call.
		2674
		2675	The new itimerspec is specified using two (possibly fractional) second
		2676	values, C<$new_interval> and C<$new_value>).
		2677
		2678	On success, the current interval and value are returned (as per
		2679	C<timerfd_gettime>). On failure, the empty list is returned.
		2680
		2681	The following C<$flags> values are
		2682	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2683	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2684
		2685	See C<IO::AIO::timerfd_create> for a full example.
		2686
		2687	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2688
		2689	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2690	call. Please refer to its manpage for more info on this call.
		2691
		2692	On success, returns the current values of interval and value for the given
		2693	timerfd (as potentially fractional second values). On failure, the empty
		2694	list is returned.
1616		2695
1617	=back	2696	=back
1618		2697
1619	=cut	2698	=cut
1620		2699
…		…
1655	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2734	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1656	\&IO::AIO::poll_cb);	2735	\&IO::AIO::poll_cb);
1657		2736
1658	=head2 FORK BEHAVIOUR	2737	=head2 FORK BEHAVIOUR
1659		2738
1660	This module should do "the right thing" when the process using it forks:	2739	Usage of pthreads in a program changes the semantics of fork
		2740	considerably. Specifically, only async-safe functions can be called after
		2741	fork. Perl doesn't know about this, so in general, you cannot call fork
		2742	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2743	pthreads, so this applies, but many other extensions and (for inexplicable
		2744	reasons) perl itself often is linked against pthreads, so this limitation
		2745	applies to quite a lot of perls.
1661		2746
1662	Before the fork, IO::AIO enters a quiescent state where no requests	2747	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1663	can be added in other threads and no results will be processed. After	2748	only works in the process that loaded it. Forking is fully supported, but
1664	the fork the parent simply leaves the quiescent state and continues	2749	using IO::AIO in the child is not.
1665	request/result processing, while the child frees the request/result queue
1666	(so that the requests started before the fork will only be handled in the
1667	parent). Threads will be started on demand until the limit set in the
1668	parent process has been reached again.
1669		2750
1670	In short: the parent will, after a short pause, continue as if fork had	2751	You might get around by not I<using> IO::AIO before (or after)
1671	not been called, while the child will act as if IO::AIO has not been used	2752	forking. You could also try to call the L<IO::AIO::reinit> function in the
1672	yet.	2753	child:
		2754
		2755	=over 4
		2756
		2757	=item IO::AIO::reinit
		2758
		2759	Abandons all current requests and I/O threads and simply reinitialises all
		2760	data structures. This is not an operation supported by any standards, but
		2761	happens to work on GNU/Linux and some newer BSD systems.
		2762
		2763	The only reasonable use for this function is to call it after forking, if
		2764	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2765	the process will result in undefined behaviour. Calling it at any time
		2766	will also result in any undefined (by POSIX) behaviour.
		2767
		2768	=back
		2769
		2770	=head2 LINUX-SPECIFIC CALLS
		2771
		2772	When a call is documented as "linux-specific" then this means it
		2773	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2774	availability and compatibility of such calls regardless of the platform
		2775	it is compiled on, so platforms such as FreeBSD which often implement
		2776	these calls will work. When in doubt, call them and see if they fail wth
		2777	C<ENOSYS>.
1673		2778
1674	=head2 MEMORY USAGE	2779	=head2 MEMORY USAGE
1675		2780
1676	Per-request usage:	2781	Per-request usage:
1677		2782
…		…
1690	temporary buffers, and each thread requires a stack and other data	2795	temporary buffers, and each thread requires a stack and other data
1691	structures (usually around 16k-128k, depending on the OS).	2796	structures (usually around 16k-128k, depending on the OS).
1692		2797
1693	=head1 KNOWN BUGS	2798	=head1 KNOWN BUGS
1694		2799
1695	Known bugs will be fixed in the next release.	2800	Known bugs will be fixed in the next release :)
		2801
		2802	=head1 KNOWN ISSUES
		2803
		2804	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2805	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2806	non-created hash slots or other scalars I didn't think of. It's best to
		2807	avoid such and either use scalar variables or making sure that the scalar
		2808	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2809
		2810	I am not sure anything can be done about this, so this is considered a
		2811	known issue, rather than a bug.
1696		2812
1697	=head1 SEE ALSO	2813	=head1 SEE ALSO
1698		2814
1699	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2815	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1700	more natural syntax.	2816	more natural syntax and L<IO::FDPass> for file descriptor passing.
1701		2817
1702	=head1 AUTHOR	2818	=head1 AUTHOR
1703		2819
1704	Marc Lehmann <schmorp@schmorp.de>	2820	Marc Lehmann <schmorp@schmorp.de>
1705	http://home.schmorp.de/	2821	http://home.schmorp.de/

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