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Revision 1.181 by root, Tue May 4 21:14:01 2010 UTC vs.
Revision 1.304 by root, Wed Apr 3 03:11:45 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 = '3.65';	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_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);
190		198
191	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
192		200
193	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
194		202
…		…
198		206
199	=head1 FUNCTIONS	207	=head1 FUNCTIONS
200		208
201	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
202		210
203	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
204	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
205	documentation.	213	documentation.
206		214
		215	aio_wd $pathname, $callback->($wd)
207	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
208	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
209	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
210	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
211	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
212	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
213	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
214	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
215	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
216	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
217	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)
218	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
219	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)
220	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
221	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
222	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
223	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
224	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
225	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
226	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
227	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
228	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
229	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
230	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
231	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)
232	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
233	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
234	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
235	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
236	aio_rmtree $path, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
237	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
238	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
239	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
240	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
241	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
242	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
243	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
244	aio_group $callback->(...)	263	aio_group $callback->(...)
245	aio_nop $callback->()	264	aio_nop $callback->()
246		265
247	$prev_pri = aioreq_pri [$pri]	266	$prev_pri = aioreq_pri [$pri]
248	aioreq_nice $pri_adjust	267	aioreq_nice $pri_adjust
…		…
254	IO::AIO::max_poll_reqs $nreqs	273	IO::AIO::max_poll_reqs $nreqs
255	IO::AIO::max_poll_time $seconds	274	IO::AIO::max_poll_time $seconds
256	IO::AIO::min_parallel $nthreads	275	IO::AIO::min_parallel $nthreads
257	IO::AIO::max_parallel $nthreads	276	IO::AIO::max_parallel $nthreads
258	IO::AIO::max_idle $nthreads	277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
259	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
260	IO::AIO::nreqs	280	IO::AIO::nreqs
261	IO::AIO::nready	281	IO::AIO::nready
262	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]
263		287
264	IO::AIO::sendfile $ofh, $ifh, $offset, $count	288	IO::AIO::sendfile $ofh, $ifh, $offset, $count
265	IO::AIO::fadvise $fh, $offset, $len, $advice	289	IO::AIO::fadvise $fh, $offset, $len, $advice
266	IO::AIO::mlockall $flags	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]
		294	IO::AIO::madvise $scalar, $offset, $length, $advice
		295	IO::AIO::mprotect $scalar, $offset, $length, $protect
		296	IO::AIO::munlock $scalar, $offset = 0, $length = undef
267	IO::AIO::munlockall	297	IO::AIO::munlockall
268		298
269	=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 $fh
		317
		318	=head2 API NOTES
270		319
271	All the C<aio_*> calls are more or less thin wrappers around the syscall	320	All the C<aio_*> calls are more or less thin wrappers around the syscall
272	with the same name (sans C<aio_>). The arguments are similar or identical,	321	with the same name (sans C<aio_>). The arguments are similar or identical,
273	and they all accept an additional (and optional) C<$callback> argument	322	and they all accept an additional (and optional) C<$callback> argument
274	which must be a code reference. This code reference will get called with	323	which must be a code reference. This code reference will be called after
275	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	324	the syscall has been executed in an asynchronous fashion. The results
276	perl, which usually delivers "false") as its sole argument after the given	325	of the request will be passed as arguments to the callback (and, if an
277	syscall has been executed asynchronously.	326	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		327	most syscalls return C<-1> on error, unlike perl, which usually delivers
		328	"false").
		329
		330	Some requests (such as C<aio_readdir>) pass the actual results and
		331	communicate failures by passing C<undef>.
278		332
279	All functions expecting a filehandle keep a copy of the filehandle	333	All functions expecting a filehandle keep a copy of the filehandle
280	internally until the request has finished.	334	internally until the request has finished.
281		335
282	All functions return request objects of type L<IO::AIO::REQ> that allow	336	All functions return request objects of type L<IO::AIO::REQ> that allow
283	further manipulation of those requests while they are in-flight.	337	further manipulation of those requests while they are in-flight.
284		338
285	The pathnames you pass to these routines I<must> be absolute and	339	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	340	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	341	current working directory could have changed. Alternatively, you can
288	changed. Alternatively, you can make sure that you never change the	342	make sure that you never change the current working directory anywhere
289	current working directory anywhere in the program and then use relative	343	in the program and then use relative paths. You can also take advantage
290	paths.	344	of IO::AIOs working directory abstraction, that lets you specify paths
		345	relative to some previously-opened "working directory object" - see the
		346	description of the C<IO::AIO::WD> class later in this document.
291		347
292	To encode pathnames as octets, either make sure you either: a) always pass	348	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	349	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	350	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	351	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)	352	effect in the user environment, d) use Glib::filename_from_unicode on
297	use something else to ensure your scalar has the correct contents.	353	unicode filenames or e) use something else to ensure your scalar has the
		354	correct contents.
298		355
299	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
300	handles correctly whether it is set or not.	357	handles correctly whether it is set or not.
		358
		359	=head2 AIO REQUEST FUNCTIONS
301		360
302	=over 4	361	=over 4
303		362
304	=item $prev_pri = aioreq_pri [$pri]	363	=item $prev_pri = aioreq_pri [$pri]
305		364
…		…
335		394
336		395
337	=item aio_open $pathname, $flags, $mode, $callback->($fh)	396	=item aio_open $pathname, $flags, $mode, $callback->($fh)
338		397
339	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
340	created filehandle for the file.	399	created filehandle for the file (or C<undef> in case of an error).
341		400
342	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,
343	for an explanation.	402	for an explanation.
344		403
345	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
…		…
361	} else {	420	} else {
362	die "open failed: $!\n";	421	die "open failed: $!\n";
363	}	422	}
364	};	423	};
365		424
		425	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		426	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		427	following POSIX and non-POSIX constants are available (missing ones on
		428	your system are, as usual, C<0>):
		429
		430	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		431	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		432	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		433
366		434
367	=item aio_close $fh, $callback->($status)	435	=item aio_close $fh, $callback->($status)
368		436
369	Asynchronously close a file and call the callback with the result	437	Asynchronously close a file and call the callback with the result
370	code.	438	code.
…		…
379	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
380	free for reuse until the perl filehandle is closed.	448	free for reuse until the perl filehandle is closed.
381		449
382	=cut	450	=cut
383		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
384	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	472	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
385		473
386	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	474	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
387		475
388	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
389	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
390	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
391	error, just like the syscall).	479	error, just like the syscall).
392		480
393	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
394	offset plus the actual number of bytes read.	482	offset plus the actual number of bytes read.
395		483
…		…
420		508
421	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	509	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
422	reading at byte offset C<$in_offset>, and starts writing at the current	510	reading at byte offset C<$in_offset>, and starts writing at the current
423	file offset of C<$out_fh>. Because of that, it is not safe to issue more	511	file offset of C<$out_fh>. Because of that, it is not safe to issue more
424	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	512	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
425	other.	513	other. The same C<$in_fh> works fine though, as this function does not
		514	move or use the file offset of C<$in_fh>.
426		515
		516	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		517	are written, and there is no way to find out how many more bytes have been
		518	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		519	number of bytes written to C<$out_fh>. Only if the result value equals
		520	C<$length> one can assume that C<$length> bytes have been read.
		521
		522	Unlike with other C<aio_> functions, it makes a lot of sense to use
		523	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		524	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		525	the socket I/O will be non-blocking. Note, however, that you can run
		526	into a trap where C<aio_sendfile> reads some data with readahead, then
		527	fails to write all data, and when the socket is ready the next time, the
		528	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		529	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		530	resource usage.
		531
427	This call tries to make use of a native C<sendfile> syscall to provide	532	This call tries to make use of a native C<sendfile>-like syscall to
428	zero-copy operation. For this to work, C<$out_fh> should refer to a	533	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.	534	a socket, and C<$in_fh> should refer to an mmap'able file.
430		535
431	If a native sendfile cannot be found or it fails with C<ENOSYS>,	536	If a native sendfile cannot be found or it fails with C<ENOSYS>,
432	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	537	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
433	it will be emulated, so you can call C<aio_sendfile> on any type of	538	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
434	filehandle regardless of the limitations of the operating system.	539	type of filehandle regardless of the limitations of the operating system.
435		540
436	Please note, however, that C<aio_sendfile> can read more bytes from	541	As native sendfile syscalls (as practically any non-POSIX interface hacked
437	C<$in_fh> than are written, and there is no way to find out how many	542	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	543	on many systems, this implementation tries to work around some known bugs
439	provides the number of bytes written to C<$out_fh>. Only if the result	544	in Linux and FreeBSD kernels (probably others, too), but that might fail,
440	value equals C<$length> one can assume that C<$length> bytes have been	545	so you really really should check the return value of C<aio_sendfile> -
441	read.	546	fewer bytes than expected might have been transferred.
442		547
443		548
444	=item aio_readahead $fh,$offset,$length, $callback->($retval)	549	=item aio_readahead $fh,$offset,$length, $callback->($retval)
445		550
446	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
…		…
450	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
451	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
452	(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
453	file. The current file offset of the file is left unchanged.	558	file. The current file offset of the file is left unchanged.
454		559
455	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
456	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.
457		562
458		563
459	=item aio_stat $fh_or_path, $callback->($status)	564	=item aio_stat $fh_or_path, $callback->($status)
460		565
461	=item aio_lstat $fh, $callback->($status)	566	=item aio_lstat $fh, $callback->($status)
462		567
463	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
464	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
465	or C<-s _> etc...	570	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		571	and C<-T>).
466		572
467	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,
468	for an explanation.	574	for an explanation.
469		575
470	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
471	error when stat'ing a large file, the results will be silently truncated	577	error when stat'ing a large file, the results will be silently truncated
472	unless perl itself is compiled with large file support.	578	unless perl itself is compiled with large file support.
		579
		580	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		581	following constants and functions (if not implemented, the constants will
		582	be C<0> and the functions will either C<croak> or fall back on traditional
		583	behaviour).
		584
		585	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		586	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		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>.
473		591
474	Example: Print the length of F</etc/passwd>:	592	Example: Print the length of F</etc/passwd>:
475		593
476	aio_stat "/etc/passwd", sub {	594	aio_stat "/etc/passwd", sub {
477	$_[0] and die "stat failed: $!";	595	$_[0] and die "stat failed: $!";
…		…
521	namemax => 255,	639	namemax => 255,
522	frsize => 1024,	640	frsize => 1024,
523	fsid => 1810	641	fsid => 1810
524	}	642	}
525		643
526
527	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	644	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
528		645
529	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
530	and $mtime being undef). Fractional times are supported if the underlying	647	and $mtime being undef). Fractional times are supported if the underlying
531	syscalls support them.	648	syscalls support them.
532		649
533	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,
534	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)
535	otherwise returns ENOSYS, so this is not portable.	652	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		653	portable.
536		654
537	Examples:	655	Examples:
538		656
539	# set atime and mtime to current time (basically touch(1)):	657	# set atime and mtime to current time (basically touch(1)):
540	aio_utime "path", undef, undef;	658	aio_utime "path", undef, undef;
…		…
558	=item aio_truncate $fh_or_path, $offset, $callback->($status)	676	=item aio_truncate $fh_or_path, $offset, $callback->($status)
559		677
560	Works like truncate(2) or ftruncate(2).	678	Works like truncate(2) or ftruncate(2).
561		679
562		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
563	=item aio_chmod $fh_or_path, $mode, $callback->($status)	703	=item aio_chmod $fh_or_path, $mode, $callback->($status)
564		704
565	Works like perl's C<chmod> function.	705	Works like perl's C<chmod> function.
566		706
567		707
…		…
569		709
570	Asynchronously unlink (delete) a file and call the callback with the	710	Asynchronously unlink (delete) a file and call the callback with the
571	result code.	711	result code.
572		712
573		713
574	=item aio_mknod $path, $mode, $dev, $callback->($status)	714	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
575		715
576	[EXPERIMENTAL]	716	[EXPERIMENTAL]
577		717
578	Asynchronously create a device node (or fifo). See mknod(2).	718	Asynchronously create a device node (or fifo). See mknod(2).
579		719
580	The only (POSIX-) portable way of calling this function is:	720	The only (POSIX-) portable way of calling this function is:
581		721
582	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	722	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
583		723
		724	See C<aio_stat> for info about some potentially helpful extra constants
		725	and functions.
584		726
585	=item aio_link $srcpath, $dstpath, $callback->($status)	727	=item aio_link $srcpath, $dstpath, $callback->($status)
586		728
587	Asynchronously create a new link to the existing object at C<$srcpath> at	729	Asynchronously create a new link to the existing object at C<$srcpath> at
588	the path C<$dstpath> and call the callback with the result code.	730	the path C<$dstpath> and call the callback with the result code.
…		…
592		734
593	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	735	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
594	the path C<$dstpath> and call the callback with the result code.	736	the path C<$dstpath> and call the callback with the result code.
595		737
596		738
597	=item aio_readlink $path, $callback->($link)	739	=item aio_readlink $pathname, $callback->($link)
598		740
599	Asynchronously read the symlink specified by C<$path> and pass it to	741	Asynchronously read the symlink specified by C<$path> and pass it to
600	the callback. If an error occurs, nothing or undef gets passed to the	742	the callback. If an error occurs, nothing or undef gets passed to the
601	callback.	743	callback.
602		744
603		745
		746	=item aio_realpath $pathname, $callback->($path)
		747
		748	Asynchronously make the path absolute and resolve any symlinks in
		749	C<$path>. The resulting path only consists of directories (same as
		750	L<Cwd::realpath>).
		751
		752	This request can be used to get the absolute path of the current working
		753	directory by passing it a path of F<.> (a single dot).
		754
		755
604	=item aio_rename $srcpath, $dstpath, $callback->($status)	756	=item aio_rename $srcpath, $dstpath, $callback->($status)
605		757
606	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
607	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>.
608		780
609		781
610	=item aio_mkdir $pathname, $mode, $callback->($status)	782	=item aio_mkdir $pathname, $mode, $callback->($status)
611		783
612	Asynchronously mkdir (create) a directory and call the callback with	784	Asynchronously mkdir (create) a directory and call the callback with
…		…
617	=item aio_rmdir $pathname, $callback->($status)	789	=item aio_rmdir $pathname, $callback->($status)
618		790
619	Asynchronously rmdir (delete) a directory and call the callback with the	791	Asynchronously rmdir (delete) a directory and call the callback with the
620	result code.	792	result code.
621		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
622		798
623	=item aio_readdir $pathname, $callback->($entries)	799	=item aio_readdir $pathname, $callback->($entries)
624		800
625	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
626	directory (i.e. opendir + readdir + closedir). The entries will not be	802	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
630	array-ref with the filenames.	806	array-ref with the filenames.
631		807
632		808
633	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	809	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
634		810
635	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	811	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	812	tune behaviour and output format. In case of an error, C<$entries> will be
637	C<undef>.	813	C<undef>.
638		814
639	The flags are a combination of the following constants, ORed together (the	815	The flags are a combination of the following constants, ORed together (the
640	flags will also be passed to the callback, possibly modified):	816	flags will also be passed to the callback, possibly modified):
641		817
642	=over 4	818	=over 4
643		819
644	=item IO::AIO::READDIR_DENTS	820	=item IO::AIO::READDIR_DENTS
645		821
646	When this flag is off, then the callback gets an arrayref with of names	822	Normally the callback gets an arrayref consisting of names only (as
647	only (as with C<aio_readdir>), otherwise it gets an arrayref with	823	with C<aio_readdir>). If this flag is set, then the callback gets an
648	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	824	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
649	entry in more detail.	825	single directory entry in more detail:
650		826
651	C<$name> is the name of the entry.	827	C<$name> is the name of the entry.
652		828
653	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	829	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
654		830
655	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	831	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
656	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	832	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
657	C<IO::AIO::DT_WHT>.	833	C<IO::AIO::DT_WHT>.
658		834
659	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	835	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
660	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	836	to know, you have to run stat yourself. Also, for speed/memory reasons,
661	scalars are read-only: you can not modify them.	837	the C<$type> scalars are read-only: you must not modify them.
662		838
663	C<$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
664	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
665	systems that do not deliver the inode information.	841	systems that do not deliver the inode information.
666		842
667	=item IO::AIO::READDIR_DIRS_FIRST	843	=item IO::AIO::READDIR_DIRS_FIRST
668		844
669	When this flag is set, then the names will be returned in an order where	845	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	846	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	847	you need to quickly find directories, or you want to find all directories
672	stat() each entry.	848	while avoiding to stat() each entry.
673		849
674	If the system returns type information in readdir, then this is used	850	If the system returns type information in readdir, then this is used
675	to find directories directly. Otherwise, likely directories are files	851	to find directories directly. Otherwise, likely directories are names
676	beginning with ".", or otherwise files with no dots, of which files with	852	beginning with ".", or otherwise names with no dots, of which names with
677	short names are tried first.	853	short names are tried first.
678		854
679	=item IO::AIO::READDIR_STAT_ORDER	855	=item IO::AIO::READDIR_STAT_ORDER
680		856
681	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
682	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
683	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
684	be fastest.	860	faster.
685		861
686	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,
687	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.
688		866
689	=item IO::AIO::READDIR_FOUND_UNKNOWN	867	=item IO::AIO::READDIR_FOUND_UNKNOWN
690		868
691	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
692	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<$type>'s found were
693	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	871	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
694	C<$type>'s are known, which can be used to speed up some algorithms.	872	C<$type>'s are known, which can be used to speed up some algorithms.
695		873
696	=back	874	=back
697		875
698		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
699	=item aio_load $path, $data, $callback->($status)	906	=item aio_load $pathname, $data, $callback->($status)
700		907
701	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
702	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.
703		912
704	=cut	913	=cut
705		914
706	sub aio_load($$;$) {	915	sub aio_load($$;$) {
707	my ($path, undef, $cb) = @_;	916	my ($path, undef, $cb) = @_;
…		…
727	=item aio_copy $srcpath, $dstpath, $callback->($status)	936	=item aio_copy $srcpath, $dstpath, $callback->($status)
728		937
729	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
730	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
731	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.
732		943
733	This is a composite request that creates the destination file with	944	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	945	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	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
736	uid/gid, in that order.	947	uid/gid, in that order.
…		…
826	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
827	aioreq_pri $pri;	1038	aioreq_pri $pri;
828	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
829	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
830		1041
831	if (!$_[0]) {	1042	unless ($_[0]) {
832	aioreq_pri $pri;	1043	aioreq_pri $pri;
833	add $grp aio_unlink $src;	1044	add $grp aio_unlink $src;
834	}	1045	}
835	};	1046	};
836	} else {	1047	} else {
…		…
839	};	1050	};
840		1051
841	$grp	1052	$grp
842	}	1053	}
843		1054
844	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
845		1056
846	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
847	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
848	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
849	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
850		1061
851	C<aio_scandir> is a composite request that creates of many sub requests_	1062	C<aio_scandir> is a composite request that generates many sub requests.
852	C<$maxreq> specifies the maximum number of outstanding aio requests that	1063	C<$maxreq> specifies the maximum number of outstanding aio requests that
853	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
854	will be chosen (currently 4).	1065	will be chosen (currently 4).
855		1066
856	On error, the callback is called without arguments, otherwise it receives	1067	On error, the callback is called without arguments, otherwise it receives
…		…
880	Then entries will be sorted into likely directories a non-initial dot	1091	Then entries will be sorted into likely directories a non-initial dot
881	currently) and likely non-directories (see C<aio_readdirx>). Then every	1092	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,	1093	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	1094	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	1095	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	1096	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	1097	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	1098	data (e.g. ext2fs filetype feature), even on systems that cannot return
888	the filetype information on readdir.	1099	the filetype information on readdir.
889		1100
890	If the known number of directories (link count - 2) has been reached, the	1101	If the known number of directories (link count - 2) has been reached, the
…		…
906		1117
907	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
908		1119
909	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
910		1121
911	# stat once	1122	# get a wd object
912	aioreq_pri $pri;	1123	aioreq_pri $pri;
913	add $grp aio_stat $path, sub {	1124	add $grp aio_wd $path, sub {
		1125	$_[0]
914	return $grp->result () if $_[0];	1126	or return $grp->result ();
915	my $now = time;
916	my $hash1 = join ":", (stat _)[0,1,3,7,9];
917		1127
918	# read the directory entries	1128	my $wd = [shift, "."];
		1129
		1130	# stat once
919	aioreq_pri $pri;	1131	aioreq_pri $pri;
920	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1132	add $grp aio_stat $wd, sub {
921	my $entries = shift
922	or return $grp->result ();	1133	return $grp->result () if $_[0];
		1134	my $now = time;
		1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1136	my $rdxflags = READDIR_DIRS_FIRST;
923		1137
924	# stat the dir another time	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	}
		1144
		1145	# read the directory entries
925	aioreq_pri $pri;	1146	aioreq_pri $pri;
926	add $grp aio_stat $path, sub {	1147	add $grp aio_readdirx $wd, $rdxflags, sub {
927	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1148	my ($entries, $flags) = @_
		1149	or return $grp->result ();
928		1150
		1151	if ($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
929	my $ndirs;	1166	my $dirs;
930		1167
931	# take the slow route if anything looks fishy
932	if ($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) {	1168	if (@$entries) {
955	push @nondirs, $entry;	1169	for (0 .. $#$entries) {
956	} else {	1170	if ($entries->[$_][1] != DT_DIR) {
957	# need to check for real directory	1171	# splice out directories
958	aioreq_pri $pri;	1172	$dirs = [splice @$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	}	1173	last;
967	} else {
968	push @nondirs, $entry;
969	}	1174	}
970	}	1175	}
		1176
		1177	# if we didn't find any non-dir, then all entries are dirs
		1178	unless ($dirs) {
		1179	($dirs, $entries) = ($entries, []);
		1180	}
		1181	} else {
		1182	# directory is empty, so there are no sbdirs
		1183	$dirs = [];
971	}	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	}
		1198
		1199	# stat the dir another time
		1200	aioreq_pri $pri;
		1201	add $grp aio_stat $wd, sub {
		1202	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1203
		1204	my $ndirs;
		1205
		1206	# take the slow route if anything looks fishy
		1207	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1208	$ndirs = -1;
		1209	} else {
		1210	# if nlink == 2, we are finished
		1211	# for non-posix-fs's, we rely on nlink < 2
		1212	$ndirs = (stat _)[3] - 2
		1213	or return $grp->result ([], $entries);
		1214	}
		1215
		1216	my (@dirs, @nondirs);
		1217
		1218	my $statgrp = add $grp aio_group sub {
		1219	$grp->result (\@dirs, \@nondirs);
		1220	};
		1221
		1222	limit $statgrp $maxreq;
		1223	feed $statgrp sub {
		1224	return unless @$entries;
		1225	my $entry = shift @$entries;
		1226
		1227	aioreq_pri $pri;
		1228	$wd->[1] = "$entry/.";
		1229	add $statgrp aio_stat $wd, sub {
		1230	if ($_[0] < 0) {
		1231	push @nondirs, $entry;
		1232	} else {
		1233	# need to check for real directory
		1234	aioreq_pri $pri;
		1235	$wd->[1] = $entry;
		1236	add $statgrp aio_lstat $wd, sub {
		1237	if (-d _) {
		1238	push @dirs, $entry;
		1239
		1240	unless (--$ndirs) {
		1241	push @nondirs, @$entries;
		1242	feed $statgrp;
		1243	}
		1244	} else {
		1245	push @nondirs, $entry;
		1246	}
		1247	}
		1248	}
		1249	};
972	};	1250	};
973	};	1251	};
974	};	1252	};
975	};	1253	};
976	};	1254	};
977		1255
978	$grp	1256	$grp
979	}	1257	}
980		1258
981	=item aio_rmtree $path, $callback->($status)	1259	=item aio_rmtree $pathname, $callback->($status)
982		1260
983	Delete a directory tree starting (and including) C<$path>, return the	1261	Delete a directory tree starting (and including) C<$path>, return the
984	status of the final C<rmdir> only. This is a composite request that	1262	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	1263	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
986	everything else.	1264	everything else.
987		1265
988	=cut	1266	=cut
989		1267
…		…
1011	};	1289	};
1012		1290
1013	$grp	1291	$grp
1014	}	1292	}
1015		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 and can be used for normal C<ioctl>
		1314	and C<fcntl> as well (missing ones are, as usual C<0>):
		1315
		1316	C<F_DUPFD_CLOEXEC>,
		1317
		1318	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1319
		1320	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1321
		1322	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1323	C<F_SEAL_WRITE>.
		1324
		1325	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1326	C<FS_IOC_FIEMAP>.
		1327
		1328	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1329	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1330
		1331	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1332	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1333	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1334	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1335	C<FS_FL_USER_MODIFIABLE>.
		1336
		1337	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1338	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1339	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1340	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1341
1016	=item aio_sync $callback->($status)	1342	=item aio_sync $callback->($status)
1017		1343
1018	Asynchronously call sync and call the callback when finished.	1344	Asynchronously call sync and call the callback when finished.
1019		1345
1020	=item aio_fsync $fh, $callback->($status)	1346	=item aio_fsync $fh, $callback->($status)
…		…
1027	Asynchronously call fdatasync on the given filehandle and call the	1353	Asynchronously call fdatasync on the given filehandle and call the
1028	callback with the fdatasync result code.	1354	callback with the fdatasync result code.
1029		1355
1030	If this call isn't available because your OS lacks it or it couldn't be	1356	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.	1357	detected, it will be emulated by calling C<fsync> instead.
		1358
		1359	=item aio_syncfs $fh, $callback->($status)
		1360
		1361	Asynchronously call the syncfs syscall to sync the filesystem associated
		1362	to the given filehandle and call the callback with the syncfs result
		1363	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1364	errno to C<ENOSYS> nevertheless.
1032		1365
1033	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1366	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1034		1367
1035	Sync the data portion of the file specified by C<$offset> and C<$length>	1368	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	1369	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1040	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1373	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1041	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1374	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1042	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1375	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1043	manpage for details.	1376	manpage for details.
1044		1377
1045	=item aio_pathsync $path, $callback->($status)	1378	=item aio_pathsync $pathname, $callback->($status)
1046		1379
1047	This request tries to open, fsync and close the given path. This is a	1380	This request tries to open, fsync and close the given path. This is a
1048	composite request intended to sync directories after directory operations	1381	composite request intended to sync directories after directory operations
1049	(E.g. rename). This might not work on all operating systems or have any	1382	(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	1383	specific effect, but usually it makes sure that directory changes get
…		…
1081	};	1414	};
1082		1415
1083	$grp	1416	$grp
1084	}	1417	}
1085		1418
1086	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1419	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1087		1420
1088	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1421	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	1422	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	1423	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	1424	scalar must only be modified in-place while an aio operation is pending on
…		…
1093		1426
1094	It calls the C<msync> function of your OS, if available, with the memory	1427	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	1428	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>	1429	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	1430	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	1431	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1099	C<IO::AIO::MS_SYNC>.	1432	C<IO::AIO::MS_INVALIDATE>.
1100		1433
1101	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1434	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1102		1435
1103	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1436	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1104	scalars.	1437	scalars.
1105		1438
1106	It touches (reads or writes) all memory pages in the specified	1439	It touches (reads or writes) all memory pages in the specified
1107	range inside the scalar. All caveats and parameters are the same	1440	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	1441	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	1442	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	1443	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1111	writing an octet from it, which dirties the page).	1444	writing an octet from it, which dirties the page).
		1445
		1446	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1447
		1448	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1449	scalars.
		1450
		1451	It reads in all the pages of the underlying storage into memory (if any)
		1452	and locks them, so they are not getting swapped/paged out or removed.
		1453
		1454	If C<$length> is undefined, then the scalar will be locked till the end.
		1455
		1456	On systems that do not implement C<mlock>, this function returns C<-1>
		1457	and sets errno to C<ENOSYS>.
		1458
		1459	Note that the corresponding C<munlock> is synchronous and is
		1460	documented under L<MISCELLANEOUS FUNCTIONS>.
		1461
		1462	Example: open a file, mmap and mlock it - both will be undone when
		1463	C<$data> gets destroyed.
		1464
		1465	open my $fh, "<", $path or die "$path: $!";
		1466	my $data;
		1467	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1468	aio_mlock $data; # mlock in background
		1469
		1470	=item aio_mlockall $flags, $callback->($status)
		1471
		1472	Calls the C<mlockall> function with the given C<$flags> (a
		1473	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1474	C<IO::AIO::MCL_ONFAULT>).
		1475
		1476	On systems that do not implement C<mlockall>, this function returns C<-1>
		1477	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1478	by the system result in a return value of C<-1> with errno being set to
		1479	C<EINVAL>.
		1480
		1481	Note that the corresponding C<munlockall> is synchronous and is
		1482	documented under L<MISCELLANEOUS FUNCTIONS>.
		1483
		1484	Example: asynchronously lock all current and future pages into memory.
		1485
		1486	aio_mlockall IO::AIO::MCL_FUTURE;
		1487
		1488	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1489
		1490	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1491	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1492	the ioctl is not available on your OS, then this request will fail with
		1493	C<ENOSYS>.
		1494
		1495	C<$start> is the starting offset to query extents for, C<$length> is the
		1496	size of the range to query - if it is C<undef>, then the whole file will
		1497	be queried.
		1498
		1499	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1500	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1501	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1502	the data portion.
		1503
		1504	C<$count> is the maximum number of extent records to return. If it is
		1505	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1506	case, if it is C<0>, then the callback receives the number of extents
		1507	instead of the extents themselves (which is unreliable, see below).
		1508
		1509	If an error occurs, the callback receives no arguments. The special
		1510	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1511
		1512	Otherwise, the callback receives an array reference with extent
		1513	structures. Each extent structure is an array reference itself, with the
		1514	following members:
		1515
		1516	[$logical, $physical, $length, $flags]
		1517
		1518	Flags is any combination of the following flag values (typically either C<0>
		1519	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1520
		1521	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1522	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1523	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1524	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1525	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1526	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1527
		1528	At the time of this writing (Linux 3.2), this request is unreliable unless
		1529	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1530	it to return all extents of a range for files with a large number of
		1531	extents. The code (only) works around all these issues if C<$count> is
		1532	C<undef>.
1112		1533
1113	=item aio_group $callback->(...)	1534	=item aio_group $callback->(...)
1114		1535
1115	This is a very special aio request: Instead of doing something, it is a	1536	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	1537	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	1574	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	1575	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.	1576	except to put your application under artificial I/O pressure.
1156		1577
1157	=back	1578	=back
		1579
		1580
		1581	=head2 IO::AIO::WD - multiple working directories
		1582
		1583	Your process only has one current working directory, which is used by all
		1584	threads. This makes it hard to use relative paths (some other component
		1585	could call C<chdir> at any time, and it is hard to control when the path
		1586	will be used by IO::AIO).
		1587
		1588	One solution for this is to always use absolute paths. This usually works,
		1589	but can be quite slow (the kernel has to walk the whole path on every
		1590	access), and can also be a hassle to implement.
		1591
		1592	Newer POSIX systems have a number of functions (openat, fdopendir,
		1593	futimensat and so on) that make it possible to specify working directories
		1594	per operation.
		1595
		1596	For portability, and because the clowns who "designed", or shall I write,
		1597	perpetrated this new interface were obviously half-drunk, this abstraction
		1598	cannot be perfect, though.
		1599
		1600	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1601	object. This object stores the canonicalised, absolute version of the
		1602	path, and on systems that allow it, also a directory file descriptor.
		1603
		1604	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1605	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1606	object and a pathname instead (or the IO::AIO::WD object alone, which
		1607	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1608	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1609	to that IO::AIO::WD object.
		1610
		1611	For example, to get a wd object for F</etc> and then stat F<passwd>
		1612	inside, you would write:
		1613
		1614	aio_wd "/etc", sub {
		1615	my $etcdir = shift;
		1616
		1617	# although $etcdir can be undef on error, there is generally no reason
		1618	# to check for errors here, as aio_stat will fail with ENOENT
		1619	# when $etcdir is undef.
		1620
		1621	aio_stat [$etcdir, "passwd"], sub {
		1622	# yay
		1623	};
		1624	};
		1625
		1626	The fact that C<aio_wd> is a request and not a normal function shows that
		1627	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1628	which is why it is done asynchronously.
		1629
		1630	To stat the directory obtained with C<aio_wd> above, one could write
		1631	either of the following three request calls:
		1632
		1633	aio_lstat "/etc" , sub { ... # pathname as normal string
		1634	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1635	aio_lstat $wd , sub { ... # shorthand for the previous
		1636
		1637	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1638	object and the pathname string, so you could write the following without
		1639	causing any issues due to C<$path> getting reused:
		1640
		1641	my $path = [$wd, undef];
		1642
		1643	for my $name (qw(abc def ghi)) {
		1644	$path->[1] = $name;
		1645	aio_stat $path, sub {
		1646	# ...
		1647	};
		1648	}
		1649
		1650	There are some caveats: when directories get renamed (or deleted), the
		1651	pathname string doesn't change, so will point to the new directory (or
		1652	nowhere at all), while the directory fd, if available on the system,
		1653	will still point to the original directory. Most functions accepting a
		1654	pathname will use the directory fd on newer systems, and the string on
		1655	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1656	the string form of the pathname.
		1657
		1658	So this functionality is mainly useful to get some protection against
		1659	C<chdir>, to easily get an absolute path out of a relative path for future
		1660	reference, and to speed up doing many operations in the same directory
		1661	(e.g. when stat'ing all files in a directory).
		1662
		1663	The following functions implement this working directory abstraction:
		1664
		1665	=over 4
		1666
		1667	=item aio_wd $pathname, $callback->($wd)
		1668
		1669	Asynchonously canonicalise the given pathname and convert it to an
		1670	IO::AIO::WD object representing it. If possible and supported on the
		1671	system, also open a directory fd to speed up pathname resolution relative
		1672	to this working directory.
		1673
		1674	If something goes wrong, then C<undef> is passwd to the callback instead
		1675	of a working directory object and C<$!> is set appropriately. Since
		1676	passing C<undef> as working directory component of a pathname fails the
		1677	request with C<ENOENT>, there is often no need for error checking in the
		1678	C<aio_wd> callback, as future requests using the value will fail in the
		1679	expected way.
		1680
		1681	=item IO::AIO::CWD
		1682
		1683	This is a compiletime constant (object) that represents the process
		1684	current working directory.
		1685
		1686	Specifying this object as working directory object for a pathname is as if
		1687	the pathname would be specified directly, without a directory object. For
		1688	example, these calls are functionally identical:
		1689
		1690	aio_stat "somefile", sub { ... };
		1691	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1692
		1693	=back
		1694
		1695	To recover the path associated with an IO::AIO::WD object, you can use
		1696	C<aio_realpath>:
		1697
		1698	aio_realpath $wd, sub {
		1699	warn "path is $_[0]\n";
		1700	};
		1701
		1702	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1703	sometimes, fall back to using an absolue path.
1158		1704
1159	=head2 IO::AIO::REQ CLASS	1705	=head2 IO::AIO::REQ CLASS
1160		1706
1161	All non-aggregate C<aio_*> functions return an object of this class when	1707	All non-aggregate C<aio_*> functions return an object of this class when
1162	called in non-void context.	1708	called in non-void context.
…		…
1280		1826
1281	Sets a feeder/generator on this group: every group can have an attached	1827	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,	1828	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,	1829	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,	1830	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,	1831	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1286	delaying any later requests for a long time.	1832	requests, delaying any later requests for a long time.
1287		1833
1288	To avoid this, and allow incremental generation of requests, you can	1834	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	1835	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>,	1836	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	1837	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	1869	The default value for the limit is C<0>, but note that setting a feeder
1324	automatically bumps it up to C<2>.	1870	automatically bumps it up to C<2>.
1325		1871
1326	=back	1872	=back
1327		1873
		1874
1328	=head2 SUPPORT FUNCTIONS	1875	=head2 SUPPORT FUNCTIONS
1329		1876
1330	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1877	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1331		1878
1332	=over 4	1879	=over 4
…		…
1340		1887
1341	See C<poll_cb> for an example.	1888	See C<poll_cb> for an example.
1342		1889
1343	=item IO::AIO::poll_cb	1890	=item IO::AIO::poll_cb
1344		1891
1345	Process some outstanding events on the result pipe. You have to call this	1892	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	1893	been executed but the results are not yet reported). You have to call
1347	returned earlier for whatever reason. Returns immediately when no events	1894	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		1895
		1896	Returns C<0> if all events could be processed (or there were no
		1897	events to process), or C<-1> if it returned earlier for whatever
		1898	reason. Returns immediately when no events are outstanding. The amount
		1899	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1900	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1901
1351	If not all requests were processed for whatever reason, the filehandle	1902	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	1903	descriptor will still be ready when C<poll_cb> returns, so normally you
1353	do anything special to have it called later.	1904	don't have to do anything special to have it called later.
		1905
		1906	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1907	ready, it can be beneficial to call this function from loops which submit
		1908	a lot of requests, to make sure the results get processed when they become
		1909	available and not just when the loop is finished and the event loop takes
		1910	over again. This function returns very fast when there are no outstanding
		1911	requests.
1354		1912
1355	Example: Install an Event watcher that automatically calls	1913	Example: Install an Event watcher that automatically calls
1356	IO::AIO::poll_cb with high priority (more examples can be found in the	1914	IO::AIO::poll_cb with high priority (more examples can be found in the
1357	SYNOPSIS section, at the top of this document):	1915	SYNOPSIS section, at the top of this document):
1358		1916
…		…
1360	poll => 'r', async => 1,	1918	poll => 'r', async => 1,
1361	cb => \&IO::AIO::poll_cb);	1919	cb => \&IO::AIO::poll_cb);
1362		1920
1363	=item IO::AIO::poll_wait	1921	=item IO::AIO::poll_wait
1364		1922
1365	If there are any outstanding requests and none of them in the result	1923	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	1924	requests are outstanding anymore.
1367	does a C<select> on the filehandle. This is useful if you want to	1925
1368	synchronously wait for some requests to finish).	1926	This is useful if you want to synchronously wait for some requests to
		1927	become ready, without actually handling them.
1369		1928
1370	See C<nreqs> for an example.	1929	See C<nreqs> for an example.
1371		1930
1372	=item IO::AIO::poll	1931	=item IO::AIO::poll
1373		1932
…		…
1384		1943
1385	Strictly equivalent to:	1944	Strictly equivalent to:
1386		1945
1387	IO::AIO::poll_wait, IO::AIO::poll_cb	1946	IO::AIO::poll_wait, IO::AIO::poll_cb
1388	while IO::AIO::nreqs;	1947	while IO::AIO::nreqs;
		1948
		1949	This function can be useful at program aborts, to make sure outstanding
		1950	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1951	this function on normal exits), or when you are merely using C<IO::AIO>
		1952	for its more advanced functions, rather than for async I/O, e.g.:
		1953
		1954	my ($dirs, $nondirs);
		1955	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1956	IO::AIO::flush;
		1957	# $dirs, $nondirs are now set
1389		1958
1390	=item IO::AIO::max_poll_reqs $nreqs	1959	=item IO::AIO::max_poll_reqs $nreqs
1391		1960
1392	=item IO::AIO::max_poll_time $seconds	1961	=item IO::AIO::max_poll_time $seconds
1393		1962
…		…
1420	poll => 'r', nice => 1,	1989	poll => 'r', nice => 1,
1421	cb => &IO::AIO::poll_cb);	1990	cb => &IO::AIO::poll_cb);
1422		1991
1423	=back	1992	=back
1424		1993
		1994
1425	=head3 CONTROLLING THE NUMBER OF THREADS	1995	=head3 CONTROLLING THE NUMBER OF THREADS
1426		1996
1427	=over	1997	=over
1428		1998
1429	=item IO::AIO::min_parallel $nthreads	1999	=item IO::AIO::min_parallel $nthreads
…		…
1460		2030
1461	Under normal circumstances you don't need to call this function.	2031	Under normal circumstances you don't need to call this function.
1462		2032
1463	=item IO::AIO::max_idle $nthreads	2033	=item IO::AIO::max_idle $nthreads
1464		2034
1465	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2035	Limit the number of threads (default: 4) that are allowed to idle
1466	threads that did not get a request to process within 10 seconds). That	2036	(i.e., threads that did not get a request to process within the idle
1467	means if a thread becomes idle while C<$nthreads> other threads are also	2037	timeout (default: 10 seconds). That means if a thread becomes idle while
1468	idle, it will free its resources and exit.	2038	C<$nthreads> other threads are also idle, it will free its resources and
		2039	exit.
1469		2040
1470	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2041	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	2042	to allow for extremely high load situations, but want to free resources
1472	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2043	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1473		2044
1474	The default is probably ok in most situations, especially if thread	2045	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	2046	creation is fast. If thread creation is very slow on your system you might
1476	want to use larger values.	2047	want to use larger values.
1477		2048
		2049	=item IO::AIO::idle_timeout $seconds
		2050
		2051	Sets the minimum idle timeout (default 10) after which worker threads are
		2052	allowed to exit. SEe C<IO::AIO::max_idle>.
		2053
1478	=item IO::AIO::max_outstanding $maxreqs	2054	=item IO::AIO::max_outstanding $maxreqs
		2055
		2056	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2057	you do queue up more than this number of requests, the next call to
		2058	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2059	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2060	longer exceeded.
		2061
		2062	In other words, this setting does not enforce a queue limit, but can be
		2063	used to make poll functions block if the limit is exceeded.
1479		2064
1480	This is a very bad function to use in interactive programs because it	2065	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	2066	blocks, and a bad way to reduce concurrency because it is inexact: Better
1482	use an C<aio_group> together with a feed callback.	2067	use an C<aio_group> together with a feed callback.
1483		2068
1484	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2069	Its main use is in scripts without an event loop - when you want to stat
1485	do queue up more than this number of requests, the next call to the	2070	a lot of files, you can write something like this:
1486	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1487	function will block until the limit is no longer exceeded.
1488		2071
1489	The default value is very large, so there is no practical limit on the	2072	IO::AIO::max_outstanding 32;
1490	number of outstanding requests.
1491		2073
1492	You can still queue as many requests as you want. Therefore,	2074	for my $path (...) {
1493	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2075	aio_stat $path , ...;
1494	as a stop gap to shield against fatal memory overflow (with large values).	2076	IO::AIO::poll_cb;
		2077	}
		2078
		2079	IO::AIO::flush;
		2080
		2081	The call to C<poll_cb> inside the loop will normally return instantly, but
		2082	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2083	some requests have been handled. This keeps the loop from pushing a large
		2084	number of C<aio_stat> requests onto the queue.
		2085
		2086	The default value for C<max_outstanding> is very large, so there is no
		2087	practical limit on the number of outstanding requests.
1495		2088
1496	=back	2089	=back
		2090
1497		2091
1498	=head3 STATISTICAL INFORMATION	2092	=head3 STATISTICAL INFORMATION
1499		2093
1500	=over	2094	=over
1501		2095
…		…
1519	Returns the number of requests currently in the pending state (executed,	2113	Returns the number of requests currently in the pending state (executed,
1520	but not yet processed by poll_cb).	2114	but not yet processed by poll_cb).
1521		2115
1522	=back	2116	=back
1523		2117
		2118
		2119	=head3 SUBSECOND STAT TIME ACCESS
		2120
		2121	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2122	generally find access/modification and change times with subsecond time
		2123	accuracy of the system supports it, but perl's built-in functions only
		2124	return the integer part.
		2125
		2126	The following functions return the timestamps of the most recent
		2127	stat with subsecond precision on most systems and work both after
		2128	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2129	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2130	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2131
		2132	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2133	full resolution without rounding and work with standard perl C<stat>,
		2134	alleviating the need to call the special C<Time::HiRes> functions, which
		2135	do not act like their perl counterparts.
		2136
		2137	On operating systems or file systems where subsecond time resolution is
		2138	not supported or could not be detected, a fractional part of C<0> is
		2139	returned, so it is always safe to call these functions.
		2140
		2141	=over 4
		2142
		2143	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2144
		2145	Return the access, modication, change or birth time, respectively,
		2146	including fractional part. Due to the limited precision of floating point,
		2147	the accuracy on most platforms is only a bit better than milliseconds
		2148	for times around now - see the I<nsec> function family, below, for full
		2149	accuracy.
		2150
		2151	File birth time is only available when the OS and perl support it (on
		2152	FreeBSD and NetBSD at the time of this writing, although support is
		2153	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2154	it). On systems where it isn't available, C<0> is currently returned, but
		2155	this might change to C<undef> in a future version.
		2156
		2157	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2158
		2159	Returns access, modification, change and birth time all in one go, and
		2160	maybe more times in the future version.
		2161
		2162	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2163
		2164	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2165	as an integer in the range C<0> to C<999999999>.
		2166
		2167	Note that no accessors are provided for access, modification and
		2168	change times - you need to get those from C<stat _> if required (C<int
		2169	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2170	value).
		2171
		2172	=item $seconds = IO::AIO::st_btimesec
		2173
		2174	The (integral) seconds part of the file birth time, if available.
		2175
		2176	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2177
		2178	Like the functions above, but returns all four times in one go (and maybe
		2179	more in future versions).
		2180
		2181	=item $counter = IO::AIO::st_gen
		2182
		2183	Returns the generation counter (in practice this is just a random number)
		2184	of the file. This is only available on platforms which have this member in
		2185	their C<struct stat> (most BSDs at the time of this writing) and generally
		2186	only to the root usert. If unsupported, C<0> is returned, but this might
		2187	change to C<undef> in a future version.
		2188
		2189	=back
		2190
		2191	Example: print the high resolution modification time of F</etc>, using
		2192	C<stat>, and C<IO::AIO::aio_stat>.
		2193
		2194	if (stat "/etc") {
		2195	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2196	}
		2197
		2198	IO::AIO::aio_stat "/etc", sub {
		2199	$_[0]
		2200	and return;
		2201
		2202	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2203	};
		2204
		2205	IO::AIO::flush;
		2206
		2207	Output of the awbove on my system, showing reduced and full accuracy:
		2208
		2209	stat(/etc) mtime: 1534043702.020808
		2210	aio_stat(/etc) mtime: 1534043702.020807792
		2211
		2212
1524	=head3 MISCELLANEOUS FUNCTIONS	2213	=head3 MISCELLANEOUS FUNCTIONS
1525		2214
1526	IO::AIO implements some functions that might be useful, but are not	2215	IO::AIO implements some functions that are useful when you want to use
1527	asynchronous.	2216	some "Advanced I/O" function not available to in Perl, without going the
		2217	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2218	counterpart.
1528		2219
1529	=over 4	2220	=over 4
		2221
		2222	=item $numfd = IO::AIO::get_fdlimit
		2223
		2224	This function is I<EXPERIMENTAL> and subject to change.
		2225
		2226	Tries to find the current file descriptor limit and returns it, or
		2227	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2228	the highest valid file descriptor number.
		2229
		2230	=item IO::AIO::min_fdlimit [$numfd]
		2231
		2232	This function is I<EXPERIMENTAL> and subject to change.
		2233
		2234	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2235	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2236	is missing, it will try to set a very high limit, although this is not
		2237	recommended when you know the actual minimum that you require.
		2238
		2239	If the limit cannot be raised enough, the function makes a best-effort
		2240	attempt to increase the limit as much as possible, using various
		2241	tricks, while still failing. You can query the resulting limit using
		2242	C<IO::AIO::get_fdlimit>.
		2243
		2244	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2245	true.
1530		2246
1531	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2247	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1532		2248
1533	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2249	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	2250	but is blocking (this makes most sense if you know the input data is
…		…
1537		2253
1538	Returns the number of bytes copied, or C<-1> on error.	2254	Returns the number of bytes copied, or C<-1> on error.
1539		2255
1540	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2256	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1541		2257
1542	Simply calls the C<posix_fadvise> function (see it's	2258	Simply calls the C<posix_fadvise> function (see its
1543	manpage for details). The following advice constants are	2259	manpage for details). The following advice constants are
1544	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2260	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1545	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2261	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1546	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2262	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1547		2263
1548	On systems that do not implement C<posix_fadvise>, this function returns	2264	On systems that do not implement C<posix_fadvise>, this function returns
1549	ENOSYS, otherwise the return value of C<posix_fadvise>.	2265	ENOSYS, otherwise the return value of C<posix_fadvise>.
1550		2266
		2267	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2268
		2269	Simply calls the C<posix_madvise> function (see its
		2270	manpage for details). The following advice constants are
		2271	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2272	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2273	C<IO::AIO::MADV_DONTNEED>.
		2274
		2275	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2276	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2277	will be reduced to fit into the C<$scalar>.
		2278
		2279	On systems that do not implement C<posix_madvise>, this function returns
		2280	ENOSYS, otherwise the return value of C<posix_madvise>.
		2281
		2282	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2283
		2284	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2285	$scalar (see its manpage for details). The following protect
		2286	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2287	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2288
		2289	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2290	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2291	will be reduced to fit into the C<$scalar>.
		2292
		2293	On systems that do not implement C<mprotect>, this function returns
		2294	ENOSYS, otherwise the return value of C<mprotect>.
		2295
1551	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2296	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1552		2297
1553	Memory-maps a file (or anonymous memory range) and attaches it to the	2298	Memory-maps a file (or anonymous memory range) and attaches it to the
1554	given C<$scalar>, which will act like a string scalar.	2299	given C<$scalar>, which will act like a string scalar. Returns true on
		2300	success, and false otherwise.
1555		2301
		2302	The scalar must exist, but its contents do not matter - this means you
		2303	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2304	the scalar first.
		2305
1556	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2306	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1557	change the string length, and most read-only operations such as copying it	2307	which don't change the string length, and most read-only operations such
1558	or searching it with regexes and so on.	2308	as copying it or searching it with regexes and so on.
1559		2309
1560	Anything else is unsafe and will, at best, result in memory leaks.	2310	Anything else is unsafe and will, at best, result in memory leaks.
1561		2311
1562	The memory map associated with the C<$scalar> is automatically removed	2312	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	2313	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1564	C<IO::AIO::munmap> functions are called.	2314	or C<IO::AIO::munmap> functions are called on it.
1565		2315
1566	This calls the C<mmap>(2) function internally. See your system's manual	2316	This calls the C<mmap>(2) function internally. See your system's manual
1567	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2317	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1568		2318
1569	The C<$length> must be larger than zero and smaller than the actual	2319	The C<$length> must be larger than zero and smaller than the actual
1570	filesize.	2320	filesize.
1571		2321
1572	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2322	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1573	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2323	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1574		2324
1575	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2325	C<$flags> can be a combination of
1576	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2326	C<IO::AIO::MAP_SHARED> or
1577	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2327	C<IO::AIO::MAP_PRIVATE>,
		2328	or a number of system-specific flags (when not available, the are C<0>):
1578	(which is set to C<MAP_ANON> if your system only provides this	2329	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1579	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2330	C<IO::AIO::MAP_LOCKED>,
1580	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2331	C<IO::AIO::MAP_NORESERVE>,
		2332	C<IO::AIO::MAP_POPULATE>,
1581	C<IO::AIO::MAP_NONBLOCK>	2333	C<IO::AIO::MAP_NONBLOCK>,
		2334	C<IO::AIO::MAP_FIXED>,
		2335	C<IO::AIO::MAP_GROWSDOWN>,
		2336	C<IO::AIO::MAP_32BIT>,
		2337	C<IO::AIO::MAP_HUGETLB> or
		2338	C<IO::AIO::MAP_STACK>.
1582		2339
1583	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2340	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1584		2341
1585	C<$offset> is the offset from the start of the file - it generally must be	2342	C<$offset> is the offset from the start of the file - it generally must be
1586	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2343	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1600		2357
1601	=item IO::AIO::munmap $scalar	2358	=item IO::AIO::munmap $scalar
1602		2359
1603	Removes a previous mmap and undefines the C<$scalar>.	2360	Removes a previous mmap and undefines the C<$scalar>.
1604		2361
		2362	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2363
		2364	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2365	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2366	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2367
		2368	Returns true if successful, and false otherwise. If the underlying mmapped
		2369	region has changed address, then the true value has the numerical value
		2370	C<1>, otherwise it has the numerical value C<0>:
		2371
		2372	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2373	or die "mremap: $!";
		2374
		2375	if ($success*1) {
		2376	warn "scalar has chanegd address in memory\n";
		2377	}
		2378
		2379	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2380	implemented, but not supported and might go away in a future version.
		2381
		2382	On systems where this call is not supported or is not emulated, this call
		2383	returns falls and sets C<$!> to C<ENOSYS>.
		2384
1605	=item IO::AIO::mlockall $flags	2385	=item IO::AIO::mlockall $flags
1606		2386
1607	Calls the C<mlockall> function with the given C<$flags> (a combination of	2387	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
1608	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL__FUTURE>).	2388	but is blocking.
1609		2389
1610	On systems that do not implement C<mlockall>, this function returns	2390	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1611	ENOSYS, otherwise the return value of C<mlockall>.	2391
		2392	Calls the C<munlock> function, undoing the effects of a previous
		2393	C<aio_mlock> call (see its description for details).
1612		2394
1613	=item IO::AIO::munlockall	2395	=item IO::AIO::munlockall
1614		2396
1615	Calls the C<munlockall> function.	2397	Calls the C<munlockall> function.
1616		2398
1617	On systems that do not implement C<munlockall>, this function returns	2399	On systems that do not implement C<munlockall>, this function returns
1618	ENOSYS, otherwise the return value of C<munlockall>.	2400	ENOSYS, otherwise the return value of C<munlockall>.
		2401
		2402	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2403
		2404	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2405	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2406	should be the file offset.
		2407
		2408	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2409	silently corrupt the data in this case.
		2410
		2411	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2412	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2413	C<IO::AIO::SPLICE_F_GIFT>.
		2414
		2415	See the C<splice(2)> manpage for details.
		2416
		2417	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2418
		2419	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2420	description for C<IO::AIO::splice> above for details.
		2421
		2422	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2423
		2424	Attempts to query or change the pipe buffer size. Obviously works only
		2425	on pipes, and currently works only on GNU/Linux systems, and fails with
		2426	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2427	size on other systems, drop me a note.
		2428
		2429	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2430
		2431	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2432	C<$flags> is missing or C<0>, then this should be the same as a call to
		2433	perl's built-in C<pipe> function and create a new pipe, and works on
		2434	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2435	(..., 4096, O_BINARY)>.
		2436
		2437	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2438	the given flags (Linux 2.6.27, glibc 2.9).
		2439
		2440	On success, the read and write file handles are returned.
		2441
		2442	On error, nothing will be returned. If the pipe2 syscall is missing and
		2443	C<$flags> is non-zero, fails with C<ENOSYS>.
		2444
		2445	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2446	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2447	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2448
		2449	Example: create a pipe race-free w.r.t. threads and fork:
		2450
		2451	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2452	or die "pipe2: $!\n";
		2453
		2454	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2455
		2456	This is a direct interface to the Linux L<memfd_create(2)> system
		2457	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2458	should be C<IO::AIO::MFD_CLOEXEC>.
		2459
		2460	On success, the new memfd filehandle is returned, otherwise returns
		2461	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2462
		2463	Please refer to L<memfd_create(2)> for more info on this call.
		2464
		2465	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2466	C<IO::AIO::MFD_ALLOW_SEALING> and C<IO::AIO::MFD_HUGETLB>.
		2467
		2468	Example: create a new memfd.
		2469
		2470	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2471	or die "m,emfd_create: $!\n";
		2472	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2473
		2474	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2475	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2476
		2477	On success, the new eventfd filehandle is returned, otherwise returns
		2478	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2479
		2480	Please refer to L<eventfd(2)> for more info on this call.
		2481
		2482	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2483	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2484
		2485	Example: create a new eventfd filehandle:
		2486
		2487	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2488	or die "eventfd: $!\n";
		2489
		2490	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2491
		2492	This is a direct interface to the Linux L<timerfd_create(2)> system
		2493	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2494	should be C<IO::AIO::TFD_CLOEXEC>.
		2495
		2496	On success, the new timerfd filehandle is returned, otherwise returns
		2497	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2498
		2499	Please refer to L<timerfd_create(2)> for more info on this call.
		2500
		2501	The following C<$clockid> values are
		2502	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2503	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2504	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2505	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2506
		2507	The following C<$flags> values are available (Linux
		2508	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2509
		2510	Example: create a new timerfd and set it to one-second repeated alarms,
		2511	then wait for two alarms:
		2512
		2513	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2514	or die "timerfd_create: $!\n";
		2515
		2516	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2517	or die "timerfd_settime: $!\n";
		2518
		2519	for (1..2) {
		2520	8 == sysread $fh, my $buf, 8
		2521	or die "timerfd read failure\n";
		2522
		2523	printf "number of expirations (likely 1): %d\n",
		2524	unpack "Q", $buf;
		2525	}
		2526
		2527	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2528
		2529	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2530	call. Please refer to its manpage for more info on this call.
		2531
		2532	The new itimerspec is specified using two (possibly fractional) second
		2533	values, C<$new_interval> and C<$new_value>).
		2534
		2535	On success, the current interval and value are returned (as per
		2536	C<timerfd_gettime>). On failure, the empty list is returned.
		2537
		2538	The following C<$flags> values are
		2539	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2540	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2541
		2542	See C<IO::AIO::timerfd_create> for a full example.
		2543
		2544	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2545
		2546	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2547	call. Please refer to its manpage for more info on this call.
		2548
		2549	On success, returns the current values of interval and value for the given
		2550	timerfd (as potentially fractional second values). On failure, the empty
		2551	list is returned.
1619		2552
1620	=back	2553	=back
1621		2554
1622	=cut	2555	=cut
1623		2556
…		…
1658	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2591	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1659	\&IO::AIO::poll_cb);	2592	\&IO::AIO::poll_cb);
1660		2593
1661	=head2 FORK BEHAVIOUR	2594	=head2 FORK BEHAVIOUR
1662		2595
1663	This module should do "the right thing" when the process using it forks:	2596	Usage of pthreads in a program changes the semantics of fork
		2597	considerably. Specifically, only async-safe functions can be called after
		2598	fork. Perl doesn't know about this, so in general, you cannot call fork
		2599	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2600	pthreads, so this applies, but many other extensions and (for inexplicable
		2601	reasons) perl itself often is linked against pthreads, so this limitation
		2602	applies to quite a lot of perls.
1664		2603
1665	Before the fork, IO::AIO enters a quiescent state where no requests	2604	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1666	can be added in other threads and no results will be processed. After	2605	only works in the process that loaded it. Forking is fully supported, but
1667	the fork the parent simply leaves the quiescent state and continues	2606	using IO::AIO in the child is not.
1668	request/result processing, while the child frees the request/result queue
1669	(so that the requests started before the fork will only be handled in the
1670	parent). Threads will be started on demand until the limit set in the
1671	parent process has been reached again.
1672		2607
1673	In short: the parent will, after a short pause, continue as if fork had	2608	You might get around by not I<using> IO::AIO before (or after)
1674	not been called, while the child will act as if IO::AIO has not been used	2609	forking. You could also try to call the L<IO::AIO::reinit> function in the
1675	yet.	2610	child:
		2611
		2612	=over 4
		2613
		2614	=item IO::AIO::reinit
		2615
		2616	Abandons all current requests and I/O threads and simply reinitialises all
		2617	data structures. This is not an operation supported by any standards, but
		2618	happens to work on GNU/Linux and some newer BSD systems.
		2619
		2620	The only reasonable use for this function is to call it after forking, if
		2621	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2622	the process will result in undefined behaviour. Calling it at any time
		2623	will also result in any undefined (by POSIX) behaviour.
		2624
		2625	=back
		2626
		2627	=head2 LINUX-SPECIFIC CALLS
		2628
		2629	When a call is documented as "linux-specific" then this means it
		2630	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2631	availability and compatibility of such calls regardless of the platform
		2632	it is compiled on, so platforms such as FreeBSD which often implement
		2633	these calls will work. When in doubt, call them and see if they fail wth
		2634	C<ENOSYS>.
1676		2635
1677	=head2 MEMORY USAGE	2636	=head2 MEMORY USAGE
1678		2637
1679	Per-request usage:	2638	Per-request usage:
1680		2639
…		…
1693	temporary buffers, and each thread requires a stack and other data	2652	temporary buffers, and each thread requires a stack and other data
1694	structures (usually around 16k-128k, depending on the OS).	2653	structures (usually around 16k-128k, depending on the OS).
1695		2654
1696	=head1 KNOWN BUGS	2655	=head1 KNOWN BUGS
1697		2656
1698	Known bugs will be fixed in the next release.	2657	Known bugs will be fixed in the next release :)
		2658
		2659	=head1 KNOWN ISSUES
		2660
		2661	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2662	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2663	non-created hash slots or other scalars I didn't think of. It's best to
		2664	avoid such and either use scalar variables or making sure that the scalar
		2665	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2666
		2667	I am not sure anything can be done about this, so this is considered a
		2668	known issue, rather than a bug.
1699		2669
1700	=head1 SEE ALSO	2670	=head1 SEE ALSO
1701		2671
1702	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2672	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1703	more natural syntax.	2673	more natural syntax and L<IO::FDPass> for file descriptor passing.
1704		2674
1705	=head1 AUTHOR	2675	=head1 AUTHOR
1706		2676
1707	Marc Lehmann <schmorp@schmorp.de>	2677	Marc Lehmann <schmorp@schmorp.de>
1708	http://home.schmorp.de/	2678	http://home.schmorp.de/

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