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Revision 1.212 by root, Thu Sep 29 22:42:15 2011 UTC vs.
Revision 1.302 by root, Wed Apr 3 03:03:53 2019 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
…		…
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;
…		…
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 = '4.0';	176	our $VERSION = 4.72;
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_realpath aio_sync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
179	aio_pathsync aio_readahead	182	aio_pathsync aio_readahead aio_fiemap aio_allocate
180	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
181	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
182	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
183	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
184	aio_statvfs	187	aio_statvfs
		188	aio_slurp
185	aio_wd);	189	aio_wd);
186		190
187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
189	min_parallel max_parallel max_idle idle_timeout	193	min_parallel max_parallel max_idle idle_timeout
190	nreqs nready npending nthreads	194	nreqs nready npending nthreads
191	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
192	sendfile fadvise madvise	196	sendfile fadvise madvise
193	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
194		198
195	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
196		200
197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
198		202
…		…
202		206
203	=head1 FUNCTIONS	207	=head1 FUNCTIONS
204		208
205	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
206		210
207	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
208	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
209	documentation.	213	documentation.
210		214
211	aio_wd $pathname, $callback->($wd)	215	aio_wd $pathname, $callback->($wd)
212	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
213	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
217	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
218	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
219	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
220	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
222	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
223	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
224	aio_chmod $fh_or_path, $mode, $callback->($status)	230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
225	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
226	aio_mknod $pathname, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
227	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
228	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
229	aio_readlink $pathname, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
230	aio_realpath $pathname, $callback->($link)	237	aio_realpath $pathname, $callback->($path)
231	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
232	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
233	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
234	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
235	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
236	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
237	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
238	aio_load $pathname, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
239	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
240	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
241	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
242	aio_rmtree $pathname, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
243	aio_sync $callback->($status)	253	aio_sync $callback->($status)
244	aio_syncfs $fh, $callback->($status)	254	aio_syncfs $fh, $callback->($status)
245	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
246	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
247	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
248	aio_pathsync $pathname, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
249	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
250	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
251	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
252	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
253	aio_group $callback->(...)	263	aio_group $callback->(...)
254	aio_nop $callback->()	264	aio_nop $callback->()
…		…
268	IO::AIO::idle_timeout $seconds	278	IO::AIO::idle_timeout $seconds
269	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
270	IO::AIO::nreqs	280	IO::AIO::nreqs
271	IO::AIO::nready	281	IO::AIO::nready
272	IO::AIO::npending	282	IO::AIO::npending
		283	IO::AIO::reinit
		284
		285	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		286	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
273		287
274	IO::AIO::sendfile $ofh, $ifh, $offset, $count	288	IO::AIO::sendfile $ofh, $ifh, $offset, $count
275	IO::AIO::fadvise $fh, $offset, $len, $advice	289	IO::AIO::fadvise $fh, $offset, $len, $advice
		290
		291	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		292	IO::AIO::munmap $scalar
		293	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
276	IO::AIO::madvise $scalar, $offset, $length, $advice	294	IO::AIO::madvise $scalar, $offset, $length, $advice
277	IO::AIO::mprotect $scalar, $offset, $length, $protect	295	IO::AIO::mprotect $scalar, $offset, $length, $protect
278	IO::AIO::munlock $scalar, $offset = 0, $length = undef	296	IO::AIO::munlock $scalar, $offset = 0, $length = undef
279	IO::AIO::munlockall	297	IO::AIO::munlockall
280		298
281	=head2 AIO REQUEST FUNCTIONS	299	# stat extensions
		300	$counter = IO::AIO::st_gen
		301	$seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		302	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		303	$nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		304	$seconds = IO::AIO::st_btimesec
		305	($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		306
		307	# very much unportable syscalls
		308	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		309	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		310	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		311	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		312	$fh = IO::AIO::memfd_create $pathname[, $flags]
		313	$fh = IO::AIO::eventfd [$initval, [$flags]]
		314	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		315	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		316	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		317
		318	=head2 API NOTES
282		319
283	All the C<aio_*> calls are more or less thin wrappers around the syscall	320	All the C<aio_*> calls are more or less thin wrappers around the syscall
284	with the same name (sans C<aio_>). The arguments are similar or identical,	321	with the same name (sans C<aio_>). The arguments are similar or identical,
285	and they all accept an additional (and optional) C<$callback> argument	322	and they all accept an additional (and optional) C<$callback> argument
286	which must be a code reference. This code reference will be called after	323	which must be a code reference. This code reference will be called after
…		…
317	correct contents.	354	correct contents.
318		355
319	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	356	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
320	handles correctly whether it is set or not.	357	handles correctly whether it is set or not.
321		358
		359	=head2 AIO REQUEST FUNCTIONS
		360
322	=over 4	361	=over 4
323		362
324	=item $prev_pri = aioreq_pri [$pri]	363	=item $prev_pri = aioreq_pri [$pri]
325		364
326	Returns the priority value that would be used for the next request and, if	365	Returns the priority value that would be used for the next request and, if
…		…
355		394
356		395
357	=item aio_open $pathname, $flags, $mode, $callback->($fh)	396	=item aio_open $pathname, $flags, $mode, $callback->($fh)
358		397
359	Asynchronously open or create a file and call the callback with a newly	398	Asynchronously open or create a file and call the callback with a newly
360	created filehandle for the file.	399	created filehandle for the file (or C<undef> in case of an error).
361		400
362	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	401	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
363	for an explanation.	402	for an explanation.
364		403
365	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	404	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
388	following POSIX and non-POSIX constants are available (missing ones on	427	following POSIX and non-POSIX constants are available (missing ones on
389	your system are, as usual, C<0>):	428	your system are, as usual, C<0>):
390		429
391	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,	430	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
392	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,	431	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
393	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.	432	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
394		433
395		434
396	=item aio_close $fh, $callback->($status)	435	=item aio_close $fh, $callback->($status)
397		436
398	Asynchronously close a file and call the callback with the result	437	Asynchronously close a file and call the callback with the result
…		…
408	Or in other words: the file descriptor will be closed, but it will not be	447	Or in other words: the file descriptor will be closed, but it will not be
409	free for reuse until the perl filehandle is closed.	448	free for reuse until the perl filehandle is closed.
410		449
411	=cut	450	=cut
412		451
		452	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		453
		454	Seeks the filehandle to the new C<$offset>, similarly to perl's
		455	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		456	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		457	C<IO::AIO::SEEK_END>).
		458
		459	The resulting absolute offset will be passed to the callback, or C<-1> in
		460	case of an error.
		461
		462	In theory, the C<$whence> constants could be different than the
		463	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		464	so don't panic.
		465
		466	As a GNU/Linux (and maybe Solaris) extension, also the constants
		467	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		468	could be found. No guarantees about suitability for use in C<aio_seek> or
		469	Perl's C<sysseek> can be made though, although I would naively assume they
		470	"just work".
		471
413	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	472	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
414		473
415	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	474	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
416		475
417	Reads or writes C<$length> bytes from or to the specified C<$fh> and	476	Reads or writes C<$length> bytes from or to the specified C<$fh> and
418	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	477	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
419	and calls the callback without the actual number of bytes read (or -1 on	478	calls the callback with the actual number of bytes transferred (or -1 on
420	error, just like the syscall).	479	error, just like the syscall).
421		480
422	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	481	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
423	offset plus the actual number of bytes read.	482	offset plus the actual number of bytes read.
424		483
…		…
482	As native sendfile syscalls (as practically any non-POSIX interface hacked	541	As native sendfile syscalls (as practically any non-POSIX interface hacked
483	together in a hurry to improve benchmark numbers) tend to be rather buggy	542	together in a hurry to improve benchmark numbers) tend to be rather buggy
484	on many systems, this implementation tries to work around some known bugs	543	on many systems, this implementation tries to work around some known bugs
485	in Linux and FreeBSD kernels (probably others, too), but that might fail,	544	in Linux and FreeBSD kernels (probably others, too), but that might fail,
486	so you really really should check the return value of C<aio_sendfile> -	545	so you really really should check the return value of C<aio_sendfile> -
487	fewre bytes than expected might have been transferred.	546	fewer bytes than expected might have been transferred.
488		547
489		548
490	=item aio_readahead $fh,$offset,$length, $callback->($retval)	549	=item aio_readahead $fh,$offset,$length, $callback->($retval)
491		550
492	C<aio_readahead> populates the page cache with data from a file so that	551	C<aio_readahead> populates the page cache with data from a file so that
…		…
496	whole pages, so that offset is effectively rounded down to a page boundary	555	whole pages, so that offset is effectively rounded down to a page boundary
497	and bytes are read up to the next page boundary greater than or equal to	556	and bytes are read up to the next page boundary greater than or equal to
498	(off-set+length). C<aio_readahead> does not read beyond the end of the	557	(off-set+length). C<aio_readahead> does not read beyond the end of the
499	file. The current file offset of the file is left unchanged.	558	file. The current file offset of the file is left unchanged.
500		559
501	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	560	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
502	emulated by simply reading the data, which would have a similar effect.	561	be emulated by simply reading the data, which would have a similar effect.
503		562
504		563
505	=item aio_stat $fh_or_path, $callback->($status)	564	=item aio_stat $fh_or_path, $callback->($status)
506		565
507	=item aio_lstat $fh, $callback->($status)	566	=item aio_lstat $fh, $callback->($status)
508		567
509	Works like perl's C<stat> or C<lstat> in void context. The callback will	568	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
510	be called after the stat and the results will be available using C<stat _>	569	callback will be called after the stat and the results will be available
511	or C<-s _> etc...	570	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		571	and C<-T>).
512		572
513	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	573	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
514	for an explanation.	574	for an explanation.
515		575
516	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	576	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
…		…
523	behaviour).	583	behaviour).
524		584
525	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,	585	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
526	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,	586	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
527	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.	587	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		588
		589	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		590	ACCESS>.
528		591
529	Example: Print the length of F</etc/passwd>:	592	Example: Print the length of F</etc/passwd>:
530		593
531	aio_stat "/etc/passwd", sub {	594	aio_stat "/etc/passwd", sub {
532	$_[0] and die "stat failed: $!";	595	$_[0] and die "stat failed: $!";
…		…
576	namemax => 255,	639	namemax => 255,
577	frsize => 1024,	640	frsize => 1024,
578	fsid => 1810	641	fsid => 1810
579	}	642	}
580		643
581
582	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	644	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
583		645
584	Works like perl's C<utime> function (including the special case of $atime	646	Works like perl's C<utime> function (including the special case of $atime
585	and $mtime being undef). Fractional times are supported if the underlying	647	and $mtime being undef). Fractional times are supported if the underlying
586	syscalls support them.	648	syscalls support them.
587		649
588	When called with a pathname, uses utimes(2) if available, otherwise	650	When called with a pathname, uses utimensat(2) or utimes(2) if available,
589	utime(2). If called on a file descriptor, uses futimes(2) if available,	651	otherwise utime(2). If called on a file descriptor, uses futimens(2)
590	otherwise returns ENOSYS, so this is not portable.	652	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		653	portable.
591		654
592	Examples:	655	Examples:
593		656
594	# set atime and mtime to current time (basically touch(1)):	657	# set atime and mtime to current time (basically touch(1)):
595	aio_utime "path", undef, undef;	658	aio_utime "path", undef, undef;
…		…
613	=item aio_truncate $fh_or_path, $offset, $callback->($status)	676	=item aio_truncate $fh_or_path, $offset, $callback->($status)
614		677
615	Works like truncate(2) or ftruncate(2).	678	Works like truncate(2) or ftruncate(2).
616		679
617		680
		681	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		682
		683	Allocates or frees disk space according to the C<$mode> argument. See the
		684	linux C<fallocate> documentation for details.
		685
		686	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		687	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		688	to deallocate a file range.
		689
		690	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		691	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		692	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		693	to unshare shared blocks (see your L<fallocate(2)> manpage).
		694
		695	The file system block size used by C<fallocate> is presumably the
		696	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		697	can dictate other limitations.
		698
		699	If C<fallocate> isn't available or cannot be emulated (currently no
		700	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		701
		702
618	=item aio_chmod $fh_or_path, $mode, $callback->($status)	703	=item aio_chmod $fh_or_path, $mode, $callback->($status)
619		704
620	Works like perl's C<chmod> function.	705	Works like perl's C<chmod> function.
621		706
622		707
…		…
659		744
660		745
661	=item aio_realpath $pathname, $callback->($path)	746	=item aio_realpath $pathname, $callback->($path)
662		747
663	Asynchronously make the path absolute and resolve any symlinks in	748	Asynchronously make the path absolute and resolve any symlinks in
664	C<$path>. The resulting path only consists of directories (Same as	749	C<$path>. The resulting path only consists of directories (same as
665	L<Cwd::realpath>).	750	L<Cwd::realpath>).
666		751
667	This request can be used to get the absolute path of the current working	752	This request can be used to get the absolute path of the current working
668	directory by passing it a path of F<.> (a single dot).	753	directory by passing it a path of F<.> (a single dot).
669		754
670		755
671	=item aio_rename $srcpath, $dstpath, $callback->($status)	756	=item aio_rename $srcpath, $dstpath, $callback->($status)
672		757
673	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	758	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
674	rename(2) and call the callback with the result code.	759	rename(2) and call the callback with the result code.
		760
		761	On systems that support the AIO::WD working directory abstraction
		762	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		763	of failing, C<rename> is called on the absolute path of C<$wd>.
		764
		765
		766	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		767
		768	Basically a version of C<aio_rename> with an additional C<$flags>
		769	argument. Calling this with C<$flags=0> is the same as calling
		770	C<aio_rename>.
		771
		772	Non-zero flags are currently only supported on GNU/Linux systems that
		773	support renameat2. Other systems fail with C<ENOSYS> in this case.
		774
		775	The following constants are available (missing ones are, as usual C<0>),
		776	see renameat2(2) for details:
		777
		778	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		779	and C<IO::AIO::RENAME_WHITEOUT>.
675		780
676		781
677	=item aio_mkdir $pathname, $mode, $callback->($status)	782	=item aio_mkdir $pathname, $mode, $callback->($status)
678		783
679	Asynchronously mkdir (create) a directory and call the callback with	784	Asynchronously mkdir (create) a directory and call the callback with
…		…
684	=item aio_rmdir $pathname, $callback->($status)	789	=item aio_rmdir $pathname, $callback->($status)
685		790
686	Asynchronously rmdir (delete) a directory and call the callback with the	791	Asynchronously rmdir (delete) a directory and call the callback with the
687	result code.	792	result code.
688		793
		794	On systems that support the AIO::WD working directory abstraction
		795	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		796	C<rmdir> is called on the absolute path of C<$wd>.
		797
689		798
690	=item aio_readdir $pathname, $callback->($entries)	799	=item aio_readdir $pathname, $callback->($entries)
691		800
692	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	801	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
693	directory (i.e. opendir + readdir + closedir). The entries will not be	802	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
708		817
709	=over 4	818	=over 4
710		819
711	=item IO::AIO::READDIR_DENTS	820	=item IO::AIO::READDIR_DENTS
712		821
713	When this flag is off, then the callback gets an arrayref consisting of	822	Normally the callback gets an arrayref consisting of names only (as
714	names only (as with C<aio_readdir>), otherwise it gets an arrayref with	823	with C<aio_readdir>). If this flag is set, then the callback gets an
715	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	824	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
716	entry in more detail.	825	single directory entry in more detail:
717		826
718	C<$name> is the name of the entry.	827	C<$name> is the name of the entry.
719		828
720	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	829	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
721		830
722	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	831	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
723	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	832	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
724	C<IO::AIO::DT_WHT>.	833	C<IO::AIO::DT_WHT>.
725		834
726	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	835	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
727	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	836	to know, you have to run stat yourself. Also, for speed/memory reasons,
728	scalars are read-only: you can not modify them.	837	the C<$type> scalars are read-only: you must not modify them.
729		838
730	C<$inode> is the inode number (which might not be exact on systems with 64	839	C<$inode> is the inode number (which might not be exact on systems with 64
731	bit inode numbers and 32 bit perls). This field has unspecified content on	840	bit inode numbers and 32 bit perls). This field has unspecified content on
732	systems that do not deliver the inode information.	841	systems that do not deliver the inode information.
733		842
…		…
744	short names are tried first.	853	short names are tried first.
745		854
746	=item IO::AIO::READDIR_STAT_ORDER	855	=item IO::AIO::READDIR_STAT_ORDER
747		856
748	When this flag is set, then the names will be returned in an order	857	When this flag is set, then the names will be returned in an order
749	suitable for stat()'ing each one. That is, when you plan to stat()	858	suitable for stat()'ing each one. That is, when you plan to stat() most or
750	all files in the given directory, then the returned order will likely	859	all files in the given directory, then the returned order will likely be
751	be fastest.	860	faster.
752		861
753	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	862	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
754	the likely dirs come first, resulting in a less optimal stat order.	863	then the likely dirs come first, resulting in a less optimal stat order
		864	for stat'ing all entries, but likely a more optimal order for finding
		865	subdirectories.
755		866
756	=item IO::AIO::READDIR_FOUND_UNKNOWN	867	=item IO::AIO::READDIR_FOUND_UNKNOWN
757		868
758	This flag should not be set when calling C<aio_readdirx>. Instead, it	869	This flag should not be set when calling C<aio_readdirx>. Instead, it
759	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	870	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
…		…
761	C<$type>'s are known, which can be used to speed up some algorithms.	872	C<$type>'s are known, which can be used to speed up some algorithms.
762		873
763	=back	874	=back
764		875
765		876
		877	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		878
		879	Opens, reads and closes the given file. The data is put into C<$data>,
		880	which is resized as required.
		881
		882	If C<$offset> is negative, then it is counted from the end of the file.
		883
		884	If C<$length> is zero, then the remaining length of the file is
		885	used. Also, in this case, the same limitations to modifying C<$data> apply
		886	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		887	with C<substr>. If the size of the file is known, specifying a non-zero
		888	C<$length> results in a performance advantage.
		889
		890	This request is similar to the older C<aio_load> request, but since it is
		891	a single request, it might be more efficient to use.
		892
		893	Example: load F</etc/passwd> into C<$passwd>.
		894
		895	my $passwd;
		896	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		897	$_[0] >= 0
		898	or die "/etc/passwd: $!\n";
		899
		900	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		901	print $passwd;
		902	};
		903	IO::AIO::flush;
		904
		905
766	=item aio_load $pathname, $data, $callback->($status)	906	=item aio_load $pathname, $data, $callback->($status)
767		907
768	This is a composite request that tries to fully load the given file into	908	This is a composite request that tries to fully load the given file into
769	memory. Status is the same as with aio_read.	909	memory. Status is the same as with aio_read.
		910
		911	Using C<aio_slurp> might be more efficient, as it is a single request.
770		912
771	=cut	913	=cut
772		914
773	sub aio_load($$;$) {	915	sub aio_load($$;$) {
774	my ($path, undef, $cb) = @_;	916	my ($path, undef, $cb) = @_;
…		…
794	=item aio_copy $srcpath, $dstpath, $callback->($status)	936	=item aio_copy $srcpath, $dstpath, $callback->($status)
795		937
796	Try to copy the I<file> (directories not supported as either source or	938	Try to copy the I<file> (directories not supported as either source or
797	destination) from C<$srcpath> to C<$dstpath> and call the callback with	939	destination) from C<$srcpath> to C<$dstpath> and call the callback with
798	a status of C<0> (ok) or C<-1> (error, see C<$!>).	940	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		941
		942	Existing destination files will be truncated.
799		943
800	This is a composite request that creates the destination file with	944	This is a composite request that creates the destination file with
801	mode 0200 and copies the contents of the source file into it using	945	mode 0200 and copies the contents of the source file into it using
802	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
803	uid/gid, in that order.	947	uid/gid, in that order.
…		…
913	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
914	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
915	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
916	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
917		1061
918	C<aio_scandir> is a composite request that creates of many sub requests_	1062	C<aio_scandir> is a composite request that generates many sub requests.
919	C<$maxreq> specifies the maximum number of outstanding aio requests that	1063	C<$maxreq> specifies the maximum number of outstanding aio requests that
920	this function generates. If it is C<< <= 0 >>, then a suitable default	1064	this function generates. If it is C<< <= 0 >>, then a suitable default
921	will be chosen (currently 4).	1065	will be chosen (currently 4).
922		1066
923	On error, the callback is called without arguments, otherwise it receives	1067	On error, the callback is called without arguments, otherwise it receives
…		…
987	aioreq_pri $pri;	1131	aioreq_pri $pri;
988	add $grp aio_stat $wd, sub {	1132	add $grp aio_stat $wd, sub {
989	return $grp->result () if $_[0];	1133	return $grp->result () if $_[0];
990	my $now = time;	1134	my $now = time;
991	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1136	my $rdxflags = READDIR_DIRS_FIRST;
		1137
		1138	if ((stat _)[3] < 2) {
		1139	# at least one non-POSIX filesystem exists
		1140	# that returns useful DT_type values: btrfs,
		1141	# so optimise for this here by requesting dents
		1142	$rdxflags |= READDIR_DENTS;
		1143	}
992		1144
993	# read the directory entries	1145	# read the directory entries
994	aioreq_pri $pri;	1146	aioreq_pri $pri;
995	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {	1147	add $grp aio_readdirx $wd, $rdxflags, sub {
996	my $entries = shift	1148	my ($entries, $flags) = @_
997	or return $grp->result ();	1149	or return $grp->result ();
		1150
		1151	if ($rdxflags & READDIR_DENTS) {
		1152	# if we requested type values, see if we can use them directly.
		1153
		1154	# if there were any DT_UNKNOWN entries then we assume we
		1155	# don't know. alternatively, we could assume that if we get
		1156	# one DT_DIR, then all directories are indeed marked with
		1157	# DT_DIR, but this seems not required for btrfs, and this
		1158	# is basically the "btrfs can't get it's act together" code
		1159	# branch.
		1160	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1161	# now we have valid DT_ information for all entries,
		1162	# so use it as an optimisation without further stat's.
		1163	# they must also all be at the beginning of @$entries
		1164	# by now.
		1165
		1166	my $dirs;
		1167
		1168	if (@$entries) {
		1169	for (0 .. $#$entries) {
		1170	if ($entries->[$_][1] != DT_DIR) {
		1171	# splice out directories
		1172	$dirs = [splice @$entries, 0, $_];
		1173	last;
		1174	}
		1175	}
		1176
		1177	# if we didn't find any non-dir, then all entries are dirs
		1178	unless ($dirs) {
		1179	($dirs, $entries) = ($entries, []);
		1180	}
		1181	} else {
		1182	# directory is empty, so there are no sbdirs
		1183	$dirs = [];
		1184	}
		1185
		1186	# either splice'd the directories out or the dir was empty.
		1187	# convert dents to filenames
		1188	$_ = $_->[0] for @$dirs;
		1189	$_ = $_->[0] for @$entries;
		1190
		1191	return $grp->result ($dirs, $entries);
		1192	}
		1193
		1194	# cannot use, so return to our old ways
		1195	# by pretending we only scanned for names.
		1196	$_ = $_->[0] for @$entries;
		1197	}
998		1198
999	# stat the dir another time	1199	# stat the dir another time
1000	aioreq_pri $pri;	1200	aioreq_pri $pri;
1001	add $grp aio_stat $wd, sub {	1201	add $grp aio_stat $wd, sub {
1002	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1202	my $hash2 = join ":", (stat _)[0,1,3,7,9];
…		…
1057	}	1257	}
1058		1258
1059	=item aio_rmtree $pathname, $callback->($status)	1259	=item aio_rmtree $pathname, $callback->($status)
1060		1260
1061	Delete a directory tree starting (and including) C<$path>, return the	1261	Delete a directory tree starting (and including) C<$path>, return the
1062	status of the final C<rmdir> only. This is a composite request that	1262	status of the final C<rmdir> only. This is a composite request that
1063	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1263	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1064	everything else.	1264	everything else.
1065		1265
1066	=cut	1266	=cut
1067		1267
…		…
1088	add $grp $dirgrp;	1288	add $grp $dirgrp;
1089	};	1289	};
1090		1290
1091	$grp	1291	$grp
1092	}	1292	}
		1293
		1294	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1295
		1296	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1297
		1298	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1299	they execute asynchronously and pass the return value to the callback.
		1300
		1301	Both calls can be used for a lot of things, some of which make more sense
		1302	to run asynchronously in their own thread, while some others make less
		1303	sense. For example, calls that block waiting for external events, such
		1304	as locking, will also lock down an I/O thread while it is waiting, which
		1305	can deadlock the whole I/O system. At the same time, there might be no
		1306	alternative to using a thread to wait.
		1307
		1308	So in general, you should only use these calls for things that do
		1309	(filesystem) I/O, not for things that wait for other events (network,
		1310	other processes), although if you are careful and know what you are doing,
		1311	you still can.
		1312
		1313	The following constants are available (missing ones are, as usual C<0>):
		1314
		1315	C<F_DUPFD_CLOEXEC>,
		1316
		1317	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1318
		1319	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1320
		1321	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1322	C<FS_IOC_FIEMAP>.
		1323
		1324	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1325	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1326
		1327	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1328	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1329	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1330	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1331	C<FS_FL_USER_MODIFIABLE>.
		1332
		1333	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1334	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1335	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1336	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
1093		1337
1094	=item aio_sync $callback->($status)	1338	=item aio_sync $callback->($status)
1095		1339
1096	Asynchronously call sync and call the callback when finished.	1340	Asynchronously call sync and call the callback when finished.
1097		1341
…		…
1166	};	1410	};
1167		1411
1168	$grp	1412	$grp
1169	}	1413	}
1170		1414
1171	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1415	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1172		1416
1173	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1417	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1174	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1418	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1175	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1419	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1176	scalar must only be modified in-place while an aio operation is pending on	1420	scalar must only be modified in-place while an aio operation is pending on
…		…
1178		1422
1179	It calls the C<msync> function of your OS, if available, with the memory	1423	It calls the C<msync> function of your OS, if available, with the memory
1180	area starting at C<$offset> in the string and ending C<$length> bytes	1424	area starting at C<$offset> in the string and ending C<$length> bytes
1181	later. If C<$length> is negative, counts from the end, and if C<$length>	1425	later. If C<$length> is negative, counts from the end, and if C<$length>
1182	is C<undef>, then it goes till the end of the string. The flags can be	1426	is C<undef>, then it goes till the end of the string. The flags can be
1183	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1427	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1184	C<IO::AIO::MS_SYNC>.	1428	C<IO::AIO::MS_INVALIDATE>.
1185		1429
1186	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1430	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1187		1431
1188	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1432	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1189	scalars.	1433	scalars.
1190		1434
1191	It touches (reads or writes) all memory pages in the specified	1435	It touches (reads or writes) all memory pages in the specified
1192	range inside the scalar. All caveats and parameters are the same	1436	range inside the scalar. All caveats and parameters are the same
1193	as for C<aio_msync>, above, except for flags, which must be either	1437	as for C<aio_msync>, above, except for flags, which must be either
1194	C<0> (which reads all pages and ensures they are instantiated) or	1438	C<0> (which reads all pages and ensures they are instantiated) or
1195	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1439	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1196	writing an octet from it, which dirties the page).	1440	writing an octet from it, which dirties the page).
1197		1441
1198	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1442	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1199		1443
1200	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1444	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1219	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;	1463	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1220	aio_mlock $data; # mlock in background	1464	aio_mlock $data; # mlock in background
1221		1465
1222	=item aio_mlockall $flags, $callback->($status)	1466	=item aio_mlockall $flags, $callback->($status)
1223		1467
1224	Calls the C<mlockall> function with the given C<$flags> (a combination of	1468	Calls the C<mlockall> function with the given C<$flags> (a
1225	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).	1469	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1470	C<IO::AIO::MCL_ONFAULT>).
1226		1471
1227	On systems that do not implement C<mlockall>, this function returns C<-1>	1472	On systems that do not implement C<mlockall>, this function returns C<-1>
1228	and sets errno to C<ENOSYS>.	1473	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1474	by the system result in a return value of C<-1> with errno being set to
		1475	C<EINVAL>.
1229		1476
1230	Note that the corresponding C<munlockall> is synchronous and is	1477	Note that the corresponding C<munlockall> is synchronous and is
1231	documented under L<MISCELLANEOUS FUNCTIONS>.	1478	documented under L<MISCELLANEOUS FUNCTIONS>.
1232		1479
1233	Example: asynchronously lock all current and future pages into memory.	1480	Example: asynchronously lock all current and future pages into memory.
1234		1481
1235	aio_mlockall IO::AIO::MCL_FUTURE;	1482	aio_mlockall IO::AIO::MCL_FUTURE;
		1483
		1484	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1485
		1486	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1487	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1488	the ioctl is not available on your OS, then this request will fail with
		1489	C<ENOSYS>.
		1490
		1491	C<$start> is the starting offset to query extents for, C<$length> is the
		1492	size of the range to query - if it is C<undef>, then the whole file will
		1493	be queried.
		1494
		1495	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1496	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1497	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1498	the data portion.
		1499
		1500	C<$count> is the maximum number of extent records to return. If it is
		1501	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1502	case, if it is C<0>, then the callback receives the number of extents
		1503	instead of the extents themselves (which is unreliable, see below).
		1504
		1505	If an error occurs, the callback receives no arguments. The special
		1506	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1507
		1508	Otherwise, the callback receives an array reference with extent
		1509	structures. Each extent structure is an array reference itself, with the
		1510	following members:
		1511
		1512	[$logical, $physical, $length, $flags]
		1513
		1514	Flags is any combination of the following flag values (typically either C<0>
		1515	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1516
		1517	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1518	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1519	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1520	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1521	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1522	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1523
		1524	At the time of this writing (Linux 3.2), this request is unreliable unless
		1525	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1526	it to return all extents of a range for files with a large number of
		1527	extents. The code (only) works around all these issues if C<$count> is
		1528	C<undef>.
1236		1529
1237	=item aio_group $callback->(...)	1530	=item aio_group $callback->(...)
1238		1531
1239	This is a very special aio request: Instead of doing something, it is a	1532	This is a very special aio request: Instead of doing something, it is a
1240	container for other aio requests, which is useful if you want to bundle	1533	container for other aio requests, which is useful if you want to bundle
…		…
1304	object. This object stores the canonicalised, absolute version of the	1597	object. This object stores the canonicalised, absolute version of the
1305	path, and on systems that allow it, also a directory file descriptor.	1598	path, and on systems that allow it, also a directory file descriptor.
1306		1599
1307	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>	1600	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
1308	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD	1601	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
1309	object and a pathname instead. If the pathname is absolute, the	1602	object and a pathname instead (or the IO::AIO::WD object alone, which
		1603	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
1310	IO::AIO::WD objetc is ignored, otherwise the pathname is resolved relative	1604	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
1311	to that IO::AIO::WD object.	1605	to that IO::AIO::WD object.
1312		1606
1313	For example, to get a wd object for F</etc> and then stat F<passwd>	1607	For example, to get a wd object for F</etc> and then stat F<passwd>
1314	inside, you would write:	1608	inside, you would write:
1315		1609
…		…
1323	aio_stat [$etcdir, "passwd"], sub {	1617	aio_stat [$etcdir, "passwd"], sub {
1324	# yay	1618	# yay
1325	};	1619	};
1326	};	1620	};
1327		1621
		1622	The fact that C<aio_wd> is a request and not a normal function shows that
1328	This shows that creating an IO::AIO::WD object is itself a potentially	1623	creating an IO::AIO::WD object is itself a potentially blocking operation,
1329	blocking operation, which is why it is done asynchronously.	1624	which is why it is done asynchronously.
		1625
		1626	To stat the directory obtained with C<aio_wd> above, one could write
		1627	either of the following three request calls:
		1628
		1629	aio_lstat "/etc" , sub { ... # pathname as normal string
		1630	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1631	aio_lstat $wd , sub { ... # shorthand for the previous
1330		1632
1331	As with normal pathnames, IO::AIO keeps a copy of the working directory	1633	As with normal pathnames, IO::AIO keeps a copy of the working directory
1332	object and the pathname string, so you could write the following without	1634	object and the pathname string, so you could write the following without
1333	causing any issues due to C<$path> getting reused:	1635	causing any issues due to C<$path> getting reused:
1334		1636
…		…
1344	There are some caveats: when directories get renamed (or deleted), the	1646	There are some caveats: when directories get renamed (or deleted), the
1345	pathname string doesn't change, so will point to the new directory (or	1647	pathname string doesn't change, so will point to the new directory (or
1346	nowhere at all), while the directory fd, if available on the system,	1648	nowhere at all), while the directory fd, if available on the system,
1347	will still point to the original directory. Most functions accepting a	1649	will still point to the original directory. Most functions accepting a
1348	pathname will use the directory fd on newer systems, and the string on	1650	pathname will use the directory fd on newer systems, and the string on
1349	older systems. Some functions (such as realpath) will always rely on the	1651	older systems. Some functions (such as C<aio_realpath>) will always rely on
1350	string form of the pathname.	1652	the string form of the pathname.
1351		1653
1352	So this fucntionality is mainly useful to get some protection against	1654	So this functionality is mainly useful to get some protection against
1353	C<chdir>, to easily get an absolute path out of a relative path for future	1655	C<chdir>, to easily get an absolute path out of a relative path for future
1354	reference, and to speed up doing many operations in the same directory	1656	reference, and to speed up doing many operations in the same directory
1355	(e.g. when stat'ing all files in a directory).	1657	(e.g. when stat'ing all files in a directory).
1356		1658
1357	The following functions implement this working directory abstraction:	1659	The following functions implement this working directory abstraction:
…		…
1370	passing C<undef> as working directory component of a pathname fails the	1672	passing C<undef> as working directory component of a pathname fails the
1371	request with C<ENOENT>, there is often no need for error checking in the	1673	request with C<ENOENT>, there is often no need for error checking in the
1372	C<aio_wd> callback, as future requests using the value will fail in the	1674	C<aio_wd> callback, as future requests using the value will fail in the
1373	expected way.	1675	expected way.
1374		1676
1375	If this call isn't available because your OS lacks it or it couldn't be
1376	detected, it will be emulated by calling C<fsync> instead.
1377
1378	=item IO::AIO::CWD	1677	=item IO::AIO::CWD
1379		1678
1380	This is a compiletime constant (object) that represents the process	1679	This is a compiletime constant (object) that represents the process
1381	current working directory.	1680	current working directory.
1382		1681
1383	Specifying this object as working directory object for a pathname is as	1682	Specifying this object as working directory object for a pathname is as if
1384	if the pathname would be specified directly, without a directory object,	1683	the pathname would be specified directly, without a directory object. For
1385	e.g., these calls are functionally identical:	1684	example, these calls are functionally identical:
1386		1685
1387	aio_stat "somefile", sub { ... };	1686	aio_stat "somefile", sub { ... };
1388	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };	1687	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1389		1688
1390	=back	1689	=back
1391		1690
		1691	To recover the path associated with an IO::AIO::WD object, you can use
		1692	C<aio_realpath>:
		1693
		1694	aio_realpath $wd, sub {
		1695	warn "path is $_[0]\n";
		1696	};
		1697
		1698	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1699	sometimes, fall back to using an absolue path.
1392		1700
1393	=head2 IO::AIO::REQ CLASS	1701	=head2 IO::AIO::REQ CLASS
1394		1702
1395	All non-aggregate C<aio_*> functions return an object of this class when	1703	All non-aggregate C<aio_*> functions return an object of this class when
1396	called in non-void context.	1704	called in non-void context.
…		…
1557	The default value for the limit is C<0>, but note that setting a feeder	1865	The default value for the limit is C<0>, but note that setting a feeder
1558	automatically bumps it up to C<2>.	1866	automatically bumps it up to C<2>.
1559		1867
1560	=back	1868	=back
1561		1869
		1870
1562	=head2 SUPPORT FUNCTIONS	1871	=head2 SUPPORT FUNCTIONS
1563		1872
1564	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1873	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1565		1874
1566	=over 4	1875	=over 4
…		…
1574		1883
1575	See C<poll_cb> for an example.	1884	See C<poll_cb> for an example.
1576		1885
1577	=item IO::AIO::poll_cb	1886	=item IO::AIO::poll_cb
1578		1887
1579	Process some outstanding events on the result pipe. You have to call	1888	Process some requests that have reached the result phase (i.e. they have
		1889	been executed but the results are not yet reported). You have to call
		1890	this "regularly" to finish outstanding requests.
		1891
1580	this regularly. Returns C<0> if all events could be processed (or there	1892	Returns C<0> if all events could be processed (or there were no
1581	were no events to process), or C<-1> if it returned earlier for whatever	1893	events to process), or C<-1> if it returned earlier for whatever
1582	reason. Returns immediately when no events are outstanding. The amount of	1894	reason. Returns immediately when no events are outstanding. The amount
1583	events processed depends on the settings of C<IO::AIO::max_poll_req> and	1895	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
1584	C<IO::AIO::max_poll_time>.	1896	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
1585		1897
1586	If not all requests were processed for whatever reason, the filehandle	1898	If not all requests were processed for whatever reason, the poll file
1587	will still be ready when C<poll_cb> returns, so normally you don't have to	1899	descriptor will still be ready when C<poll_cb> returns, so normally you
1588	do anything special to have it called later.	1900	don't have to do anything special to have it called later.
1589		1901
1590	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes	1902	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
1591	ready, it can be beneficial to call this function from loops which submit	1903	ready, it can be beneficial to call this function from loops which submit
1592	a lot of requests, to make sure the results get processed when they become	1904	a lot of requests, to make sure the results get processed when they become
1593	available and not just when the loop is finished and the event loop takes	1905	available and not just when the loop is finished and the event loop takes
…		…
1602	poll => 'r', async => 1,	1914	poll => 'r', async => 1,
1603	cb => \&IO::AIO::poll_cb);	1915	cb => \&IO::AIO::poll_cb);
1604		1916
1605	=item IO::AIO::poll_wait	1917	=item IO::AIO::poll_wait
1606		1918
1607	If there are any outstanding requests and none of them in the result	1919	Wait until either at least one request is in the result phase or no
1608	phase, wait till the result filehandle becomes ready for reading (simply	1920	requests are outstanding anymore.
1609	does a C<select> on the filehandle. This is useful if you want to	1921
1610	synchronously wait for some requests to finish).	1922	This is useful if you want to synchronously wait for some requests to
		1923	become ready, without actually handling them.
1611		1924
1612	See C<nreqs> for an example.	1925	See C<nreqs> for an example.
1613		1926
1614	=item IO::AIO::poll	1927	=item IO::AIO::poll
1615		1928
…		…
1626		1939
1627	Strictly equivalent to:	1940	Strictly equivalent to:
1628		1941
1629	IO::AIO::poll_wait, IO::AIO::poll_cb	1942	IO::AIO::poll_wait, IO::AIO::poll_cb
1630	while IO::AIO::nreqs;	1943	while IO::AIO::nreqs;
		1944
		1945	This function can be useful at program aborts, to make sure outstanding
		1946	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1947	this function on normal exits), or when you are merely using C<IO::AIO>
		1948	for its more advanced functions, rather than for async I/O, e.g.:
		1949
		1950	my ($dirs, $nondirs);
		1951	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1952	IO::AIO::flush;
		1953	# $dirs, $nondirs are now set
1631		1954
1632	=item IO::AIO::max_poll_reqs $nreqs	1955	=item IO::AIO::max_poll_reqs $nreqs
1633		1956
1634	=item IO::AIO::max_poll_time $seconds	1957	=item IO::AIO::max_poll_time $seconds
1635		1958
…		…
1662	poll => 'r', nice => 1,	1985	poll => 'r', nice => 1,
1663	cb => &IO::AIO::poll_cb);	1986	cb => &IO::AIO::poll_cb);
1664		1987
1665	=back	1988	=back
1666		1989
		1990
1667	=head3 CONTROLLING THE NUMBER OF THREADS	1991	=head3 CONTROLLING THE NUMBER OF THREADS
1668		1992
1669	=over	1993	=over
1670		1994
1671	=item IO::AIO::min_parallel $nthreads	1995	=item IO::AIO::min_parallel $nthreads
…		…
1736		2060
1737	This is a very bad function to use in interactive programs because it	2061	This is a very bad function to use in interactive programs because it
1738	blocks, and a bad way to reduce concurrency because it is inexact: Better	2062	blocks, and a bad way to reduce concurrency because it is inexact: Better
1739	use an C<aio_group> together with a feed callback.	2063	use an C<aio_group> together with a feed callback.
1740		2064
1741	It's main use is in scripts without an event loop - when you want to stat	2065	Its main use is in scripts without an event loop - when you want to stat
1742	a lot of files, you can write somehting like this:	2066	a lot of files, you can write something like this:
1743		2067
1744	IO::AIO::max_outstanding 32;	2068	IO::AIO::max_outstanding 32;
1745		2069
1746	for my $path (...) {	2070	for my $path (...) {
1747	aio_stat $path , ...;	2071	aio_stat $path , ...;
…		…
1758	The default value for C<max_outstanding> is very large, so there is no	2082	The default value for C<max_outstanding> is very large, so there is no
1759	practical limit on the number of outstanding requests.	2083	practical limit on the number of outstanding requests.
1760		2084
1761	=back	2085	=back
1762		2086
		2087
1763	=head3 STATISTICAL INFORMATION	2088	=head3 STATISTICAL INFORMATION
1764		2089
1765	=over	2090	=over
1766		2091
1767	=item IO::AIO::nreqs	2092	=item IO::AIO::nreqs
…		…
1784	Returns the number of requests currently in the pending state (executed,	2109	Returns the number of requests currently in the pending state (executed,
1785	but not yet processed by poll_cb).	2110	but not yet processed by poll_cb).
1786		2111
1787	=back	2112	=back
1788		2113
		2114
		2115	=head3 SUBSECOND STAT TIME ACCESS
		2116
		2117	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2118	generally find access/modification and change times with subsecond time
		2119	accuracy of the system supports it, but perl's built-in functions only
		2120	return the integer part.
		2121
		2122	The following functions return the timestamps of the most recent
		2123	stat with subsecond precision on most systems and work both after
		2124	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2125	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2126	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2127
		2128	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2129	full resolution without rounding and work with standard perl C<stat>,
		2130	alleviating the need to call the special C<Time::HiRes> functions, which
		2131	do not act like their perl counterparts.
		2132
		2133	On operating systems or file systems where subsecond time resolution is
		2134	not supported or could not be detected, a fractional part of C<0> is
		2135	returned, so it is always safe to call these functions.
		2136
		2137	=over 4
		2138
		2139	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2140
		2141	Return the access, modication, change or birth time, respectively,
		2142	including fractional part. Due to the limited precision of floating point,
		2143	the accuracy on most platforms is only a bit better than milliseconds
		2144	for times around now - see the I<nsec> function family, below, for full
		2145	accuracy.
		2146
		2147	File birth time is only available when the OS and perl support it (on
		2148	FreeBSD and NetBSD at the time of this writing, although support is
		2149	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2150	it). On systems where it isn't available, C<0> is currently returned, but
		2151	this might change to C<undef> in a future version.
		2152
		2153	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2154
		2155	Returns access, modification, change and birth time all in one go, and
		2156	maybe more times in the future version.
		2157
		2158	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2159
		2160	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2161	as an integer in the range C<0> to C<999999999>.
		2162
		2163	Note that no accessors are provided for access, modification and
		2164	change times - you need to get those from C<stat _> if required (C<int
		2165	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2166	value).
		2167
		2168	=item $seconds = IO::AIO::st_btimesec
		2169
		2170	The (integral) seconds part of the file birth time, if available.
		2171
		2172	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2173
		2174	Like the functions above, but returns all four times in one go (and maybe
		2175	more in future versions).
		2176
		2177	=item $counter = IO::AIO::st_gen
		2178
		2179	Returns the generation counter (in practice this is just a random number)
		2180	of the file. This is only available on platforms which have this member in
		2181	their C<struct stat> (most BSDs at the time of this writing) and generally
		2182	only to the root usert. If unsupported, C<0> is returned, but this might
		2183	change to C<undef> in a future version.
		2184
		2185	=back
		2186
		2187	Example: print the high resolution modification time of F</etc>, using
		2188	C<stat>, and C<IO::AIO::aio_stat>.
		2189
		2190	if (stat "/etc") {
		2191	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2192	}
		2193
		2194	IO::AIO::aio_stat "/etc", sub {
		2195	$_[0]
		2196	and return;
		2197
		2198	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2199	};
		2200
		2201	IO::AIO::flush;
		2202
		2203	Output of the awbove on my system, showing reduced and full accuracy:
		2204
		2205	stat(/etc) mtime: 1534043702.020808
		2206	aio_stat(/etc) mtime: 1534043702.020807792
		2207
		2208
1789	=head3 MISCELLANEOUS FUNCTIONS	2209	=head3 MISCELLANEOUS FUNCTIONS
1790		2210
1791	IO::AIO implements some functions that might be useful, but are not	2211	IO::AIO implements some functions that are useful when you want to use
1792	asynchronous.	2212	some "Advanced I/O" function not available to in Perl, without going the
		2213	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2214	counterpart.
1793		2215
1794	=over 4	2216	=over 4
		2217
		2218	=item $numfd = IO::AIO::get_fdlimit
		2219
		2220	This function is I<EXPERIMENTAL> and subject to change.
		2221
		2222	Tries to find the current file descriptor limit and returns it, or
		2223	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2224	the highest valid file descriptor number.
		2225
		2226	=item IO::AIO::min_fdlimit [$numfd]
		2227
		2228	This function is I<EXPERIMENTAL> and subject to change.
		2229
		2230	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2231	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2232	is missing, it will try to set a very high limit, although this is not
		2233	recommended when you know the actual minimum that you require.
		2234
		2235	If the limit cannot be raised enough, the function makes a best-effort
		2236	attempt to increase the limit as much as possible, using various
		2237	tricks, while still failing. You can query the resulting limit using
		2238	C<IO::AIO::get_fdlimit>.
		2239
		2240	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2241	true.
1795		2242
1796	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2243	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1797		2244
1798	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2245	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1799	but is blocking (this makes most sense if you know the input data is	2246	but is blocking (this makes most sense if you know the input data is
…		…
1816	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2263	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1817		2264
1818	Simply calls the C<posix_madvise> function (see its	2265	Simply calls the C<posix_madvise> function (see its
1819	manpage for details). The following advice constants are	2266	manpage for details). The following advice constants are
1820	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2267	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1821	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2268	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2269	C<IO::AIO::MADV_DONTNEED>.
		2270
		2271	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2272	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2273	will be reduced to fit into the C<$scalar>.
1822		2274
1823	On systems that do not implement C<posix_madvise>, this function returns	2275	On systems that do not implement C<posix_madvise>, this function returns
1824	ENOSYS, otherwise the return value of C<posix_madvise>.	2276	ENOSYS, otherwise the return value of C<posix_madvise>.
1825		2277
1826	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2278	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
…		…
1828	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2280	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1829	$scalar (see its manpage for details). The following protect	2281	$scalar (see its manpage for details). The following protect
1830	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2282	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1831	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2283	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
1832		2284
		2285	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2286	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2287	will be reduced to fit into the C<$scalar>.
		2288
1833	On systems that do not implement C<mprotect>, this function returns	2289	On systems that do not implement C<mprotect>, this function returns
1834	ENOSYS, otherwise the return value of C<mprotect>.	2290	ENOSYS, otherwise the return value of C<mprotect>.
1835		2291
1836	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2292	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1837		2293
1838	Memory-maps a file (or anonymous memory range) and attaches it to the	2294	Memory-maps a file (or anonymous memory range) and attaches it to the
1839	given C<$scalar>, which will act like a string scalar.	2295	given C<$scalar>, which will act like a string scalar. Returns true on
		2296	success, and false otherwise.
1840		2297
		2298	The scalar must exist, but its contents do not matter - this means you
		2299	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2300	the scalar first.
		2301
1841	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2302	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1842	change the string length, and most read-only operations such as copying it	2303	which don't change the string length, and most read-only operations such
1843	or searching it with regexes and so on.	2304	as copying it or searching it with regexes and so on.
1844		2305
1845	Anything else is unsafe and will, at best, result in memory leaks.	2306	Anything else is unsafe and will, at best, result in memory leaks.
1846		2307
1847	The memory map associated with the C<$scalar> is automatically removed	2308	The memory map associated with the C<$scalar> is automatically removed
1848	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2309	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1849	C<IO::AIO::munmap> functions are called.	2310	or C<IO::AIO::munmap> functions are called on it.
1850		2311
1851	This calls the C<mmap>(2) function internally. See your system's manual	2312	This calls the C<mmap>(2) function internally. See your system's manual
1852	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2313	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1853		2314
1854	The C<$length> must be larger than zero and smaller than the actual	2315	The C<$length> must be larger than zero and smaller than the actual
1855	filesize.	2316	filesize.
1856		2317
1857	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2318	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1858	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2319	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1859		2320
1860	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2321	C<$flags> can be a combination of
1861	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2322	C<IO::AIO::MAP_SHARED> or
1862	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2323	C<IO::AIO::MAP_PRIVATE>,
		2324	or a number of system-specific flags (when not available, the are C<0>):
1863	(which is set to C<MAP_ANON> if your system only provides this	2325	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1864	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2326	C<IO::AIO::MAP_LOCKED>,
1865	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2327	C<IO::AIO::MAP_NORESERVE>,
		2328	C<IO::AIO::MAP_POPULATE>,
1866	C<IO::AIO::MAP_NONBLOCK>	2329	C<IO::AIO::MAP_NONBLOCK>,
		2330	C<IO::AIO::MAP_FIXED>,
		2331	C<IO::AIO::MAP_GROWSDOWN>,
		2332	C<IO::AIO::MAP_32BIT>,
		2333	C<IO::AIO::MAP_HUGETLB> or
		2334	C<IO::AIO::MAP_STACK>.
1867		2335
1868	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2336	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1869		2337
1870	C<$offset> is the offset from the start of the file - it generally must be	2338	C<$offset> is the offset from the start of the file - it generally must be
1871	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2339	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1885		2353
1886	=item IO::AIO::munmap $scalar	2354	=item IO::AIO::munmap $scalar
1887		2355
1888	Removes a previous mmap and undefines the C<$scalar>.	2356	Removes a previous mmap and undefines the C<$scalar>.
1889		2357
		2358	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2359
		2360	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2361	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2362	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2363
		2364	Returns true if successful, and false otherwise. If the underlying mmapped
		2365	region has changed address, then the true value has the numerical value
		2366	C<1>, otherwise it has the numerical value C<0>:
		2367
		2368	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2369	or die "mremap: $!";
		2370
		2371	if ($success*1) {
		2372	warn "scalar has chanegd address in memory\n";
		2373	}
		2374
		2375	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2376	implemented, but not supported and might go away in a future version.
		2377
		2378	On systems where this call is not supported or is not emulated, this call
		2379	returns falls and sets C<$!> to C<ENOSYS>.
		2380
		2381	=item IO::AIO::mlockall $flags
		2382
		2383	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2384	but is blocking.
		2385
1890	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2386	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1891		2387
1892	Calls the C<munlock> function, undoing the effects of a previous	2388	Calls the C<munlock> function, undoing the effects of a previous
1893	C<aio_mlock> call (see its description for details).	2389	C<aio_mlock> call (see its description for details).
1894		2390
…		…
1896		2392
1897	Calls the C<munlockall> function.	2393	Calls the C<munlockall> function.
1898		2394
1899	On systems that do not implement C<munlockall>, this function returns	2395	On systems that do not implement C<munlockall>, this function returns
1900	ENOSYS, otherwise the return value of C<munlockall>.	2396	ENOSYS, otherwise the return value of C<munlockall>.
		2397
		2398	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2399
		2400	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2401	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2402	should be the file offset.
		2403
		2404	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2405	silently corrupt the data in this case.
		2406
		2407	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2408	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2409	C<IO::AIO::SPLICE_F_GIFT>.
		2410
		2411	See the C<splice(2)> manpage for details.
		2412
		2413	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2414
		2415	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2416	description for C<IO::AIO::splice> above for details.
		2417
		2418	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2419
		2420	Attempts to query or change the pipe buffer size. Obviously works only
		2421	on pipes, and currently works only on GNU/Linux systems, and fails with
		2422	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2423	size on other systems, drop me a note.
		2424
		2425	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2426
		2427	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2428	C<$flags> is missing or C<0>, then this should be the same as a call to
		2429	perl's built-in C<pipe> function and create a new pipe, and works on
		2430	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2431	(..., 4096, O_BINARY)>.
		2432
		2433	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2434	the given flags (Linux 2.6.27, glibc 2.9).
		2435
		2436	On success, the read and write file handles are returned.
		2437
		2438	On error, nothing will be returned. If the pipe2 syscall is missing and
		2439	C<$flags> is non-zero, fails with C<ENOSYS>.
		2440
		2441	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2442	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2443	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2444
		2445	Example: create a pipe race-free w.r.t. threads and fork:
		2446
		2447	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2448	or die "pipe2: $!\n";
		2449
		2450	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2451
		2452	This is a direct interface to the Linux L<memfd_create(2)> system
		2453	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2454	should be C<IO::AIO::MFD_CLOEXEC>.
		2455
		2456	On success, the new memfd filehandle is returned, otherwise returns
		2457	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2458
		2459	Please refer to L<memfd_create(2)> for more info on this call.
		2460
		2461	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2462	C<IO::AIO::MFD_ALLOW_SEALING> and C<IO::AIO::MFD_HUGETLB>.
		2463
		2464	Example: create a new memfd.
		2465
		2466	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2467	or die "m,emfd_create: $!\n";
		2468	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2469
		2470	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2471	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2472
		2473	On success, the new eventfd filehandle is returned, otherwise returns
		2474	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2475
		2476	Please refer to L<eventfd(2)> for more info on this call.
		2477
		2478	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2479	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2480
		2481	Example: create a new eventfd filehandle:
		2482
		2483	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2484	or die "eventfd: $!\n";
		2485
		2486	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2487
		2488	This is a direct interface to the Linux L<timerfd_create(2)> system
		2489	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2490	should be C<IO::AIO::TFD_CLOEXEC>.
		2491
		2492	On success, the new timerfd filehandle is returned, otherwise returns
		2493	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2494
		2495	Please refer to L<timerfd_create(2)> for more info on this call.
		2496
		2497	The following C<$clockid> values are
		2498	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2499	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2500	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2501	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2502
		2503	The following C<$flags> values are available (Linux
		2504	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2505
		2506	Example: create a new timerfd and set it to one-second repeated alarms,
		2507	then wait for two alarms:
		2508
		2509	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2510	or die "timerfd_create: $!\n";
		2511
		2512	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2513	or die "timerfd_settime: $!\n";
		2514
		2515	for (1..2) {
		2516	8 == sysread $fh, my $buf, 8
		2517	or die "timerfd read failure\n";
		2518
		2519	printf "number of expirations (likely 1): %d\n",
		2520	unpack "Q", $buf;
		2521	}
		2522
		2523	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2524
		2525	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2526	call. Please refer to its manpage for more info on this call.
		2527
		2528	The new itimerspec is specified using two (possibly fractional) second
		2529	values, C<$new_interval> and C<$new_value>).
		2530
		2531	On success, the current interval and value are returned (as per
		2532	C<timerfd_gettime>). On failure, the empty list is returned.
		2533
		2534	The following C<$flags> values are
		2535	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2536	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2537
		2538	See C<IO::AIO::timerfd_create> for a full example.
		2539
		2540	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2541
		2542	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2543	call. Please refer to its manpage for more info on this call.
		2544
		2545	On success, returns the current values of interval and value for the given
		2546	timerfd (as potentially fractional second values). On failure, the empty
		2547	list is returned.
1901		2548
1902	=back	2549	=back
1903		2550
1904	=cut	2551	=cut
1905		2552
…		…
1971	the process will result in undefined behaviour. Calling it at any time	2618	the process will result in undefined behaviour. Calling it at any time
1972	will also result in any undefined (by POSIX) behaviour.	2619	will also result in any undefined (by POSIX) behaviour.
1973		2620
1974	=back	2621	=back
1975		2622
		2623	=head2 LINUX-SPECIFIC CALLS
		2624
		2625	When a call is documented as "linux-specific" then this means it
		2626	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2627	availability and compatibility of such calls regardless of the platform
		2628	it is compiled on, so platforms such as FreeBSD which often implement
		2629	these calls will work. When in doubt, call them and see if they fail wth
		2630	C<ENOSYS>.
		2631
1976	=head2 MEMORY USAGE	2632	=head2 MEMORY USAGE
1977		2633
1978	Per-request usage:	2634	Per-request usage:
1979		2635
1980	Each aio request uses - depending on your architecture - around 100-200	2636	Each aio request uses - depending on your architecture - around 100-200
…		…
1992	temporary buffers, and each thread requires a stack and other data	2648	temporary buffers, and each thread requires a stack and other data
1993	structures (usually around 16k-128k, depending on the OS).	2649	structures (usually around 16k-128k, depending on the OS).
1994		2650
1995	=head1 KNOWN BUGS	2651	=head1 KNOWN BUGS
1996		2652
1997	Known bugs will be fixed in the next release.	2653	Known bugs will be fixed in the next release :)
		2654
		2655	=head1 KNOWN ISSUES
		2656
		2657	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2658	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2659	non-created hash slots or other scalars I didn't think of. It's best to
		2660	avoid such and either use scalar variables or making sure that the scalar
		2661	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2662
		2663	I am not sure anything can be done about this, so this is considered a
		2664	known issue, rather than a bug.
1998		2665
1999	=head1 SEE ALSO	2666	=head1 SEE ALSO
2000		2667
2001	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2668	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
2002	more natural syntax.	2669	more natural syntax.

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