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Revision 1.183 by root, Sun Sep 12 03:40:05 2010 UTC vs.
Revision 1.302 by root, Wed Apr 3 03:03:53 2019 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
…		…
58	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
59	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
60	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
61	using threads anyway.	61	using threads anyway.
62		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
63	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
64	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
65	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
66	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
67		71
68	=head2 EXAMPLE	72	=head2 EXAMPLE
69		73
70	This is a simple example that uses the EV module and loads	74	This is a simple example that uses the EV module and loads
71	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
72		76
73	use Fcntl;
74	use EV;	77	use EV;
75	use IO::AIO;	78	use IO::AIO;
76		79
77	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
…		…
95		98
96	# file contents now in $contents	99	# file contents now in $contents
97	print $contents;	100	print $contents;
98		101
99	# exit event loop and program	102	# exit event loop and program
100	EV::unloop;	103	EV::break;
101	};	104	};
102	};	105	};
103		106
104	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
105	# check for sockets etc. etc.	108	# check for sockets etc. etc.
106		109
107	# process events as long as there are some:	110	# process events as long as there are some:
108	EV::loop;	111	EV::run;
109		112
110	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
111		114
112	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
113	directly visible to Perl.	116	directly visible to Perl.
…		…
168	use common::sense;	171	use common::sense;
169		172
170	use base 'Exporter';	173	use base 'Exporter';
171		174
172	BEGIN {	175	BEGIN {
173	our $VERSION = '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_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
183	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
184		190
185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
188	nreqs nready npending nthreads	194	nreqs nready npending nthreads
189	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
190	sendfile fadvise madvise	196	sendfile fadvise madvise
191	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
192		198
193	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
194		200
195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
196		202
…		…
200		206
201	=head1 FUNCTIONS	207	=head1 FUNCTIONS
202		208
203	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
204		210
205	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
206	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
207	documentation.	213	documentation.
208		214
		215	aio_wd $pathname, $callback->($wd)
209	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
210	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
215	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
216	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
217	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219	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)
220	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
221	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)
222	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
223	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
224	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
225	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
226	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
227	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
228	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
229	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
230	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233	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)
234	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
235	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
236	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238	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)
239	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
240	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
241	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
248	aio_group $callback->(...)	263	aio_group $callback->(...)
249	aio_nop $callback->()	264	aio_nop $callback->()
…		…
258	IO::AIO::max_poll_reqs $nreqs	273	IO::AIO::max_poll_reqs $nreqs
259	IO::AIO::max_poll_time $seconds	274	IO::AIO::max_poll_time $seconds
260	IO::AIO::min_parallel $nthreads	275	IO::AIO::min_parallel $nthreads
261	IO::AIO::max_parallel $nthreads	276	IO::AIO::max_parallel $nthreads
262	IO::AIO::max_idle $nthreads	277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
263	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
264	IO::AIO::nreqs	280	IO::AIO::nreqs
265	IO::AIO::nready	281	IO::AIO::nready
266	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]
267		287
268	IO::AIO::sendfile $ofh, $ifh, $offset, $count	288	IO::AIO::sendfile $ofh, $ifh, $offset, $count
269	IO::AIO::fadvise $fh, $offset, $len, $advice	289	IO::AIO::fadvise $fh, $offset, $len, $advice
		290
		291	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		292	IO::AIO::munmap $scalar
		293	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		294	IO::AIO::madvise $scalar, $offset, $length, $advice
		295	IO::AIO::mprotect $scalar, $offset, $length, $protect
270	IO::AIO::munlock $scalar, $offset = 0, $length = undef	296	IO::AIO::munlock $scalar, $offset = 0, $length = undef
271	IO::AIO::munlockall	297	IO::AIO::munlockall
272		298
273	=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 $fh
		317
		318	=head2 API NOTES
274		319
275	All the C<aio_*> calls are more or less thin wrappers around the syscall	320	All the C<aio_*> calls are more or less thin wrappers around the syscall
276	with the same name (sans C<aio_>). The arguments are similar or identical,	321	with the same name (sans C<aio_>). The arguments are similar or identical,
277	and they all accept an additional (and optional) C<$callback> argument	322	and they all accept an additional (and optional) C<$callback> argument
278	which must be a code reference. This code reference will get called with	323	which must be a code reference. This code reference will be called after
279	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	324	the syscall has been executed in an asynchronous fashion. The results
280	perl, which usually delivers "false") as its sole argument after the given	325	of the request will be passed as arguments to the callback (and, if an
281	syscall has been executed asynchronously.	326	error occured, in C<$!>) - 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>.
282		332
283	All functions expecting a filehandle keep a copy of the filehandle	333	All functions expecting a filehandle keep a copy of the filehandle
284	internally until the request has finished.	334	internally until the request has finished.
285		335
286	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
287	further manipulation of those requests while they are in-flight.	337	further manipulation of those requests while they are in-flight.
288		338
289	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
290	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
291	request is being executed, the current working directory could have	341	current working directory could have changed. Alternatively, you can
292	changed. Alternatively, you can make sure that you never change the	342	make sure that you never change the current working directory anywhere
293	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
294	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.
295		347
296	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
297	in filenames you got from outside (command line, readdir etc.) without	349	in filenames you got from outside (command line, readdir etc.) without
298	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
299	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
300	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
301	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.
302		355
303	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
304	handles correctly whether it is set or not.	357	handles correctly whether it is set or not.
		358
		359	=head2 AIO REQUEST FUNCTIONS
305		360
306	=over 4	361	=over 4
307		362
308	=item $prev_pri = aioreq_pri [$pri]	363	=item $prev_pri = aioreq_pri [$pri]
309		364
…		…
339		394
340		395
341	=item aio_open $pathname, $flags, $mode, $callback->($fh)	396	=item aio_open $pathname, $flags, $mode, $callback->($fh)
342		397
343	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
344	created filehandle for the file.	399	created filehandle for the file (or C<undef> in case of an error).
345		400
346	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,
347	for an explanation.	402	for an explanation.
348		403
349	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
…		…
365	} else {	420	} else {
366	die "open failed: $!\n";	421	die "open failed: $!\n";
367	}	422	}
368	};	423	};
369		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
370		434
371	=item aio_close $fh, $callback->($status)	435	=item aio_close $fh, $callback->($status)
372		436
373	Asynchronously close a file and call the callback with the result	437	Asynchronously close a file and call the callback with the result
374	code.	438	code.
…		…
383	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
384	free for reuse until the perl filehandle is closed.	448	free for reuse until the perl filehandle is closed.
385		449
386	=cut	450	=cut
387		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
388	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	472	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
389		473
390	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	474	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
391		475
392	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
393	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
394	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
395	error, just like the syscall).	479	error, just like the syscall).
396		480
397	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
398	offset plus the actual number of bytes read.	482	offset plus the actual number of bytes read.
399		483
…		…
424		508
425	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
426	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
427	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
428	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
429	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>.
430		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<$in_fh>) is a file - the file I/O will then be asynchronous, while
		525	the socket I/O will be non-blocking. Note, however, that you can run
		526	into a trap where C<aio_sendfile> reads some data with readahead, then
		527	fails to write all data, and when the socket is ready the next time, the
		528	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		529	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		530	resource usage.
		531
431	This call tries to make use of a native C<sendfile> syscall to provide	532	This call tries to make use of a native C<sendfile>-like syscall to
432	zero-copy operation. For this to work, C<$out_fh> should refer to a	533	provide zero-copy operation. For this to work, C<$out_fh> should refer to
433	socket, and C<$in_fh> should refer to an mmap'able file.	534	a socket, and C<$in_fh> should refer to an mmap'able file.
434		535
435	If a native sendfile cannot be found or it fails with C<ENOSYS>,	536	If a native sendfile cannot be found or it fails with C<ENOSYS>,
436	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	537	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
437	it will be emulated, so you can call C<aio_sendfile> on any type of	538	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
438	filehandle regardless of the limitations of the operating system.	539	type of filehandle regardless of the limitations of the operating system.
439		540
440	Please note, however, that C<aio_sendfile> can read more bytes from	541	As native sendfile syscalls (as practically any non-POSIX interface hacked
441	C<$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
442	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
443	provides the number of bytes written to C<$out_fh>. Only if the result	544	in Linux and FreeBSD kernels (probably others, too), but that might fail,
444	value equals C<$length> one can assume that C<$length> bytes have been	545	so you really really should check the return value of C<aio_sendfile> -
445	read.	546	fewer bytes than expected might have been transferred.
446		547
447		548
448	=item aio_readahead $fh,$offset,$length, $callback->($retval)	549	=item aio_readahead $fh,$offset,$length, $callback->($retval)
449		550
450	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
…		…
454	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
455	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
456	(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
457	file. The current file offset of the file is left unchanged.	558	file. The current file offset of the file is left unchanged.
458		559
459	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
460	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.
461		562
462		563
463	=item aio_stat $fh_or_path, $callback->($status)	564	=item aio_stat $fh_or_path, $callback->($status)
464		565
465	=item aio_lstat $fh, $callback->($status)	566	=item aio_lstat $fh, $callback->($status)
466		567
467	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
468	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
469	or C<-s _> etc...	570	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		571	and C<-T>).
470		572
471	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,
472	for an explanation.	574	for an explanation.
473		575
474	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
475	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
476	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>.
477		591
478	Example: Print the length of F</etc/passwd>:	592	Example: Print the length of F</etc/passwd>:
479		593
480	aio_stat "/etc/passwd", sub {	594	aio_stat "/etc/passwd", sub {
481	$_[0] and die "stat failed: $!";	595	$_[0] and die "stat failed: $!";
…		…
525	namemax => 255,	639	namemax => 255,
526	frsize => 1024,	640	frsize => 1024,
527	fsid => 1810	641	fsid => 1810
528	}	642	}
529		643
530
531	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	644	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
532		645
533	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
534	and $mtime being undef). Fractional times are supported if the underlying	647	and $mtime being undef). Fractional times are supported if the underlying
535	syscalls support them.	648	syscalls support them.
536		649
537	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,
538	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)
539	otherwise returns ENOSYS, so this is not portable.	652	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		653	portable.
540		654
541	Examples:	655	Examples:
542		656
543	# set atime and mtime to current time (basically touch(1)):	657	# set atime and mtime to current time (basically touch(1)):
544	aio_utime "path", undef, undef;	658	aio_utime "path", undef, undef;
…		…
562	=item aio_truncate $fh_or_path, $offset, $callback->($status)	676	=item aio_truncate $fh_or_path, $offset, $callback->($status)
563		677
564	Works like truncate(2) or ftruncate(2).	678	Works like truncate(2) or ftruncate(2).
565		679
566		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
567	=item aio_chmod $fh_or_path, $mode, $callback->($status)	703	=item aio_chmod $fh_or_path, $mode, $callback->($status)
568		704
569	Works like perl's C<chmod> function.	705	Works like perl's C<chmod> function.
570		706
571		707
…		…
573		709
574	Asynchronously unlink (delete) a file and call the callback with the	710	Asynchronously unlink (delete) a file and call the callback with the
575	result code.	711	result code.
576		712
577		713
578	=item aio_mknod $path, $mode, $dev, $callback->($status)	714	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
579		715
580	[EXPERIMENTAL]	716	[EXPERIMENTAL]
581		717
582	Asynchronously create a device node (or fifo). See mknod(2).	718	Asynchronously create a device node (or fifo). See mknod(2).
583		719
584	The only (POSIX-) portable way of calling this function is:	720	The only (POSIX-) portable way of calling this function is:
585		721
586	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	722	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
587		723
		724	See C<aio_stat> for info about some potentially helpful extra constants
		725	and functions.
588		726
589	=item aio_link $srcpath, $dstpath, $callback->($status)	727	=item aio_link $srcpath, $dstpath, $callback->($status)
590		728
591	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
592	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.
…		…
596		734
597	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
598	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.
599		737
600		738
601	=item aio_readlink $path, $callback->($link)	739	=item aio_readlink $pathname, $callback->($link)
602		740
603	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
604	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
605	callback.	743	callback.
606		744
607		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
608	=item aio_rename $srcpath, $dstpath, $callback->($status)	756	=item aio_rename $srcpath, $dstpath, $callback->($status)
609		757
610	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
611	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>.
612		780
613		781
614	=item aio_mkdir $pathname, $mode, $callback->($status)	782	=item aio_mkdir $pathname, $mode, $callback->($status)
615		783
616	Asynchronously mkdir (create) a directory and call the callback with	784	Asynchronously mkdir (create) a directory and call the callback with
…		…
621	=item aio_rmdir $pathname, $callback->($status)	789	=item aio_rmdir $pathname, $callback->($status)
622		790
623	Asynchronously rmdir (delete) a directory and call the callback with the	791	Asynchronously rmdir (delete) a directory and call the callback with the
624	result code.	792	result code.
625		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
626		798
627	=item aio_readdir $pathname, $callback->($entries)	799	=item aio_readdir $pathname, $callback->($entries)
628		800
629	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
630	directory (i.e. opendir + readdir + closedir). The entries will not be	802	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
634	array-ref with the filenames.	806	array-ref with the filenames.
635		807
636		808
637	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	809	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
638		810
639	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	811	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
640	behaviour and output format. In case of an error, C<$entries> will be	812	tune behaviour and output format. In case of an error, C<$entries> will be
641	C<undef>.	813	C<undef>.
642		814
643	The flags are a combination of the following constants, ORed together (the	815	The flags are a combination of the following constants, ORed together (the
644	flags will also be passed to the callback, possibly modified):	816	flags will also be passed to the callback, possibly modified):
645		817
646	=over 4	818	=over 4
647		819
648	=item IO::AIO::READDIR_DENTS	820	=item IO::AIO::READDIR_DENTS
649		821
650	When this flag is off, then the callback gets an arrayref with of names	822	Normally the callback gets an arrayref consisting of names only (as
651	only (as with C<aio_readdir>), otherwise it gets an arrayref with	823	with C<aio_readdir>). If this flag is set, then the callback gets an
652	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	824	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
653	entry in more detail.	825	single directory entry in more detail:
654		826
655	C<$name> is the name of the entry.	827	C<$name> is the name of the entry.
656		828
657	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	829	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
658		830
659	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	831	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
660	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	832	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
661	C<IO::AIO::DT_WHT>.	833	C<IO::AIO::DT_WHT>.
662		834
663	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	835	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
664	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	836	to know, you have to run stat yourself. Also, for speed/memory reasons,
665	scalars are read-only: you can not modify them.	837	the C<$type> scalars are read-only: you must not modify them.
666		838
667	C<$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
668	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
669	systems that do not deliver the inode information.	841	systems that do not deliver the inode information.
670		842
671	=item IO::AIO::READDIR_DIRS_FIRST	843	=item IO::AIO::READDIR_DIRS_FIRST
672		844
673	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
674	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
675	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
676	stat() each entry.	848	while avoiding to stat() each entry.
677		849
678	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
679	to find directories directly. Otherwise, likely directories are files	851	to find directories directly. Otherwise, likely directories are names
680	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
681	short names are tried first.	853	short names are tried first.
682		854
683	=item IO::AIO::READDIR_STAT_ORDER	855	=item IO::AIO::READDIR_STAT_ORDER
684		856
685	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
686	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
687	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
688	be fastest.	860	faster.
689		861
690	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,
691	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.
692		866
693	=item IO::AIO::READDIR_FOUND_UNKNOWN	867	=item IO::AIO::READDIR_FOUND_UNKNOWN
694		868
695	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
696	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<$type>'s found were
697	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	871	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
698	C<$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.
699		873
700	=back	874	=back
701		875
702		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
703	=item aio_load $path, $data, $callback->($status)	906	=item aio_load $pathname, $data, $callback->($status)
704		907
705	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
706	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.
707		912
708	=cut	913	=cut
709		914
710	sub aio_load($$;$) {	915	sub aio_load($$;$) {
711	my ($path, undef, $cb) = @_;	916	my ($path, undef, $cb) = @_;
…		…
731	=item aio_copy $srcpath, $dstpath, $callback->($status)	936	=item aio_copy $srcpath, $dstpath, $callback->($status)
732		937
733	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
734	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
735	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.
736		943
737	This is a composite request that creates the destination file with	944	This is a composite request that creates the destination file with
738	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
739	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
740	uid/gid, in that order.	947	uid/gid, in that order.
…		…
830	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
831	aioreq_pri $pri;	1038	aioreq_pri $pri;
832	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
833	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
834		1041
835	if (!$_[0]) {	1042	unless ($_[0]) {
836	aioreq_pri $pri;	1043	aioreq_pri $pri;
837	add $grp aio_unlink $src;	1044	add $grp aio_unlink $src;
838	}	1045	}
839	};	1046	};
840	} else {	1047	} else {
…		…
843	};	1050	};
844		1051
845	$grp	1052	$grp
846	}	1053	}
847		1054
848	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
849		1056
850	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
851	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
852	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
853	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
854		1061
855	C<aio_scandir> is a composite request that creates of many sub requests_	1062	C<aio_scandir> is a composite request that generates many sub requests.
856	C<$maxreq> specifies the maximum number of outstanding aio requests that	1063	C<$maxreq> specifies the maximum number of outstanding aio requests that
857	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
858	will be chosen (currently 4).	1065	will be chosen (currently 4).
859		1066
860	On error, the callback is called without arguments, otherwise it receives	1067	On error, the callback is called without arguments, otherwise it receives
…		…
884	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
885	currently) and likely non-directories (see C<aio_readdirx>). Then every	1092	currently) and likely non-directories (see C<aio_readdirx>). Then every
886	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,
887	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
888	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
889	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
890	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
891	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
892	the filetype information on readdir.	1099	the filetype information on readdir.
893		1100
894	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
…		…
910		1117
911	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
912		1119
913	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
914		1121
915	# stat once	1122	# get a wd object
916	aioreq_pri $pri;	1123	aioreq_pri $pri;
917	add $grp aio_stat $path, sub {	1124	add $grp aio_wd $path, sub {
		1125	$_[0]
918	return $grp->result () if $_[0];	1126	or return $grp->result ();
919	my $now = time;
920	my $hash1 = join ":", (stat _)[0,1,3,7,9];
921		1127
922	# read the directory entries	1128	my $wd = [shift, "."];
		1129
		1130	# stat once
923	aioreq_pri $pri;	1131	aioreq_pri $pri;
924	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1132	add $grp aio_stat $wd, sub {
925	my $entries = shift
926	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;
927		1137
928	# 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
929	aioreq_pri $pri;	1146	aioreq_pri $pri;
930	add $grp aio_stat $path, sub {	1147	add $grp aio_readdirx $wd, $rdxflags, sub {
931	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1148	my ($entries, $flags) = @_
		1149	or return $grp->result ();
932		1150
		1151	if ($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
933	my $ndirs;	1166	my $dirs;
934		1167
935	# take the slow route if anything looks fishy
936	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
937	$ndirs = -1;
938	} else {
939	# if nlink == 2, we are finished
940	# for non-posix-fs's, we rely on nlink < 2
941	$ndirs = (stat _)[3] - 2
942	or return $grp->result ([], $entries);
943	}
944
945	my (@dirs, @nondirs);
946
947	my $statgrp = add $grp aio_group sub {
948	$grp->result (\@dirs, \@nondirs);
949	};
950
951	limit $statgrp $maxreq;
952	feed $statgrp sub {
953	return unless @$entries;
954	my $entry = shift @$entries;
955
956	aioreq_pri $pri;
957	add $statgrp aio_stat "$path/$entry/.", sub {
958	if ($_[0] < 0) {	1168	if (@$entries) {
959	push @nondirs, $entry;	1169	for (0 .. $#$entries) {
960	} else {	1170	if ($entries->[$_][1] != DT_DIR) {
961	# need to check for real directory	1171	# splice out directories
962	aioreq_pri $pri;	1172	$dirs = [splice @$entries, 0, $_];
963	add $statgrp aio_lstat "$path/$entry", sub {
964	if (-d _) {
965	push @dirs, $entry;
966
967	unless (--$ndirs) {
968	push @nondirs, @$entries;
969	feed $statgrp;
970	}	1173	last;
971	} else {
972	push @nondirs, $entry;
973	}	1174	}
974	}	1175	}
		1176
		1177	# if we didn't find any non-dir, then all entries are dirs
		1178	unless ($dirs) {
		1179	($dirs, $entries) = ($entries, []);
		1180	}
		1181	} else {
		1182	# directory is empty, so there are no sbdirs
		1183	$dirs = [];
975	}	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	};
976	};	1250	};
977	};	1251	};
978	};	1252	};
979	};	1253	};
980	};	1254	};
981		1255
982	$grp	1256	$grp
983	}	1257	}
984		1258
985	=item aio_rmtree $path, $callback->($status)	1259	=item aio_rmtree $pathname, $callback->($status)
986		1260
987	Delete a directory tree starting (and including) C<$path>, return the	1261	Delete a directory tree starting (and including) C<$path>, return the
988	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
989	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
990	everything else.	1264	everything else.
991		1265
992	=cut	1266	=cut
993		1267
…		…
1015	};	1289	};
1016		1290
1017	$grp	1291	$grp
1018	}	1292	}
1019		1293
		1294	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1295
		1296	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1297
		1298	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1299	they execute asynchronously and pass the return value to the callback.
		1300
		1301	Both calls can be used for a lot of things, some of which make more sense
		1302	to run asynchronously in their own thread, while some others make less
		1303	sense. For example, calls that block waiting for external events, such
		1304	as locking, will also lock down an I/O thread while it is waiting, which
		1305	can deadlock the whole I/O system. At the same time, there might be no
		1306	alternative to using a thread to wait.
		1307
		1308	So in general, you should only use these calls for things that do
		1309	(filesystem) I/O, not for things that wait for other events (network,
		1310	other processes), although if you are careful and know what you are doing,
		1311	you still can.
		1312
		1313	The following constants are available (missing ones are, as usual C<0>):
		1314
		1315	C<F_DUPFD_CLOEXEC>,
		1316
		1317	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1318
		1319	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1320
		1321	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1322	C<FS_IOC_FIEMAP>.
		1323
		1324	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1325	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1326
		1327	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1328	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1329	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1330	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1331	C<FS_FL_USER_MODIFIABLE>.
		1332
		1333	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1334	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1335	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1336	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1337
1020	=item aio_sync $callback->($status)	1338	=item aio_sync $callback->($status)
1021		1339
1022	Asynchronously call sync and call the callback when finished.	1340	Asynchronously call sync and call the callback when finished.
1023		1341
1024	=item aio_fsync $fh, $callback->($status)	1342	=item aio_fsync $fh, $callback->($status)
…		…
1031	Asynchronously call fdatasync on the given filehandle and call the	1349	Asynchronously call fdatasync on the given filehandle and call the
1032	callback with the fdatasync result code.	1350	callback with the fdatasync result code.
1033		1351
1034	If this call isn't available because your OS lacks it or it couldn't be	1352	If this call isn't available because your OS lacks it or it couldn't be
1035	detected, it will be emulated by calling C<fsync> instead.	1353	detected, it will be emulated by calling C<fsync> instead.
		1354
		1355	=item aio_syncfs $fh, $callback->($status)
		1356
		1357	Asynchronously call the syncfs syscall to sync the filesystem associated
		1358	to the given filehandle and call the callback with the syncfs result
		1359	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1360	errno to C<ENOSYS> nevertheless.
1036		1361
1037	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1362	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1038		1363
1039	Sync the data portion of the file specified by C<$offset> and C<$length>	1364	Sync the data portion of the file specified by C<$offset> and C<$length>
1040	to disk (but NOT the metadata), by calling the Linux-specific	1365	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1044	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1369	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1045	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1370	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1046	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1371	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1047	manpage for details.	1372	manpage for details.
1048		1373
1049	=item aio_pathsync $path, $callback->($status)	1374	=item aio_pathsync $pathname, $callback->($status)
1050		1375
1051	This request tries to open, fsync and close the given path. This is a	1376	This request tries to open, fsync and close the given path. This is a
1052	composite request intended to sync directories after directory operations	1377	composite request intended to sync directories after directory operations
1053	(E.g. rename). This might not work on all operating systems or have any	1378	(E.g. rename). This might not work on all operating systems or have any
1054	specific effect, but usually it makes sure that directory changes get	1379	specific effect, but usually it makes sure that directory changes get
…		…
1085	};	1410	};
1086		1411
1087	$grp	1412	$grp
1088	}	1413	}
1089		1414
1090	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1415	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1091		1416
1092	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1417	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1093	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1418	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1094	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1419	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1095	scalar must only be modified in-place while an aio operation is pending on	1420	scalar must only be modified in-place while an aio operation is pending on
…		…
1097		1422
1098	It calls the C<msync> function of your OS, if available, with the memory	1423	It calls the C<msync> function of your OS, if available, with the memory
1099	area starting at C<$offset> in the string and ending C<$length> bytes	1424	area starting at C<$offset> in the string and ending C<$length> bytes
1100	later. If C<$length> is negative, counts from the end, and if C<$length>	1425	later. If C<$length> is negative, counts from the end, and if C<$length>
1101	is C<undef>, then it goes till the end of the string. The flags can be	1426	is C<undef>, then it goes till the end of the string. The flags can be
1102	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1427	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1103	C<IO::AIO::MS_SYNC>.	1428	C<IO::AIO::MS_INVALIDATE>.
1104		1429
1105	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1430	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1106		1431
1107	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1432	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1108	scalars.	1433	scalars.
1109		1434
1110	It touches (reads or writes) all memory pages in the specified	1435	It touches (reads or writes) all memory pages in the specified
1111	range inside the scalar. All caveats and parameters are the same	1436	range inside the scalar. All caveats and parameters are the same
1112	as for C<aio_msync>, above, except for flags, which must be either	1437	as for C<aio_msync>, above, except for flags, which must be either
1113	C<0> (which reads all pages and ensures they are instantiated) or	1438	C<0> (which reads all pages and ensures they are instantiated) or
1114	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1439	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1115	writing an octet from it, which dirties the page).	1440	writing an octet from it, which dirties the page).
1116		1441
1117	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1442	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1118		1443
1119	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1444	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1138	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;	1463	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1139	aio_mlock $data; # mlock in background	1464	aio_mlock $data; # mlock in background
1140		1465
1141	=item aio_mlockall $flags, $callback->($status)	1466	=item aio_mlockall $flags, $callback->($status)
1142		1467
1143	Calls the C<mlockall> function with the given C<$flags> (a combination of	1468	Calls the C<mlockall> function with the given C<$flags> (a
1144	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).	1469	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1470	C<IO::AIO::MCL_ONFAULT>).
1145		1471
1146	On systems that do not implement C<mlockall>, this function returns C<-1>	1472	On systems that do not implement C<mlockall>, this function returns C<-1>
1147	and sets errno to C<ENOSYS>.	1473	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1474	by the system result in a return value of C<-1> with errno being set to
		1475	C<EINVAL>.
1148		1476
1149	Note that the corresponding C<munlockall> is synchronous and is	1477	Note that the corresponding C<munlockall> is synchronous and is
1150	documented under L<MISCELLANEOUS FUNCTIONS>.	1478	documented under L<MISCELLANEOUS FUNCTIONS>.
1151		1479
1152	Example: asynchronously lock all current and future pages into memory.	1480	Example: asynchronously lock all current and future pages into memory.
1153		1481
1154	aio_mlockall IO::AIO::MCL_FUTURE;	1482	aio_mlockall IO::AIO::MCL_FUTURE;
		1483
		1484	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1485
		1486	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1487	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1488	the ioctl is not available on your OS, then this request will fail with
		1489	C<ENOSYS>.
		1490
		1491	C<$start> is the starting offset to query extents for, C<$length> is the
		1492	size of the range to query - if it is C<undef>, then the whole file will
		1493	be queried.
		1494
		1495	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1496	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1497	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1498	the data portion.
		1499
		1500	C<$count> is the maximum number of extent records to return. If it is
		1501	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1502	case, if it is C<0>, then the callback receives the number of extents
		1503	instead of the extents themselves (which is unreliable, see below).
		1504
		1505	If an error occurs, the callback receives no arguments. The special
		1506	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1507
		1508	Otherwise, the callback receives an array reference with extent
		1509	structures. Each extent structure is an array reference itself, with the
		1510	following members:
		1511
		1512	[$logical, $physical, $length, $flags]
		1513
		1514	Flags is any combination of the following flag values (typically either C<0>
		1515	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1516
		1517	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1518	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1519	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1520	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1521	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1522	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1523
		1524	At the time of this writing (Linux 3.2), this request is unreliable unless
		1525	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1526	it to return all extents of a range for files with a large number of
		1527	extents. The code (only) works around all these issues if C<$count> is
		1528	C<undef>.
1155		1529
1156	=item aio_group $callback->(...)	1530	=item aio_group $callback->(...)
1157		1531
1158	This is a very special aio request: Instead of doing something, it is a	1532	This is a very special aio request: Instead of doing something, it is a
1159	container for other aio requests, which is useful if you want to bundle	1533	container for other aio requests, which is useful if you want to bundle
…		…
1196	like sleep and file handle readable/writable, the overhead this creates is	1570	like sleep and file handle readable/writable, the overhead this creates is
1197	immense (it blocks a thread for a long time) so do not use this function	1571	immense (it blocks a thread for a long time) so do not use this function
1198	except to put your application under artificial I/O pressure.	1572	except to put your application under artificial I/O pressure.
1199		1573
1200	=back	1574	=back
		1575
		1576
		1577	=head2 IO::AIO::WD - multiple working directories
		1578
		1579	Your process only has one current working directory, which is used by all
		1580	threads. This makes it hard to use relative paths (some other component
		1581	could call C<chdir> at any time, and it is hard to control when the path
		1582	will be used by IO::AIO).
		1583
		1584	One solution for this is to always use absolute paths. This usually works,
		1585	but can be quite slow (the kernel has to walk the whole path on every
		1586	access), and can also be a hassle to implement.
		1587
		1588	Newer POSIX systems have a number of functions (openat, fdopendir,
		1589	futimensat and so on) that make it possible to specify working directories
		1590	per operation.
		1591
		1592	For portability, and because the clowns who "designed", or shall I write,
		1593	perpetrated this new interface were obviously half-drunk, this abstraction
		1594	cannot be perfect, though.
		1595
		1596	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1597	object. This object stores the canonicalised, absolute version of the
		1598	path, and on systems that allow it, also a directory file descriptor.
		1599
		1600	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1601	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1602	object and a pathname instead (or the IO::AIO::WD object alone, which
		1603	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1604	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1605	to that IO::AIO::WD object.
		1606
		1607	For example, to get a wd object for F</etc> and then stat F<passwd>
		1608	inside, you would write:
		1609
		1610	aio_wd "/etc", sub {
		1611	my $etcdir = shift;
		1612
		1613	# although $etcdir can be undef on error, there is generally no reason
		1614	# to check for errors here, as aio_stat will fail with ENOENT
		1615	# when $etcdir is undef.
		1616
		1617	aio_stat [$etcdir, "passwd"], sub {
		1618	# yay
		1619	};
		1620	};
		1621
		1622	The fact that C<aio_wd> is a request and not a normal function shows that
		1623	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1624	which is why it is done asynchronously.
		1625
		1626	To stat the directory obtained with C<aio_wd> above, one could write
		1627	either of the following three request calls:
		1628
		1629	aio_lstat "/etc" , sub { ... # pathname as normal string
		1630	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1631	aio_lstat $wd , sub { ... # shorthand for the previous
		1632
		1633	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1634	object and the pathname string, so you could write the following without
		1635	causing any issues due to C<$path> getting reused:
		1636
		1637	my $path = [$wd, undef];
		1638
		1639	for my $name (qw(abc def ghi)) {
		1640	$path->[1] = $name;
		1641	aio_stat $path, sub {
		1642	# ...
		1643	};
		1644	}
		1645
		1646	There are some caveats: when directories get renamed (or deleted), the
		1647	pathname string doesn't change, so will point to the new directory (or
		1648	nowhere at all), while the directory fd, if available on the system,
		1649	will still point to the original directory. Most functions accepting a
		1650	pathname will use the directory fd on newer systems, and the string on
		1651	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1652	the string form of the pathname.
		1653
		1654	So this functionality is mainly useful to get some protection against
		1655	C<chdir>, to easily get an absolute path out of a relative path for future
		1656	reference, and to speed up doing many operations in the same directory
		1657	(e.g. when stat'ing all files in a directory).
		1658
		1659	The following functions implement this working directory abstraction:
		1660
		1661	=over 4
		1662
		1663	=item aio_wd $pathname, $callback->($wd)
		1664
		1665	Asynchonously canonicalise the given pathname and convert it to an
		1666	IO::AIO::WD object representing it. If possible and supported on the
		1667	system, also open a directory fd to speed up pathname resolution relative
		1668	to this working directory.
		1669
		1670	If something goes wrong, then C<undef> is passwd to the callback instead
		1671	of a working directory object and C<$!> is set appropriately. Since
		1672	passing C<undef> as working directory component of a pathname fails the
		1673	request with C<ENOENT>, there is often no need for error checking in the
		1674	C<aio_wd> callback, as future requests using the value will fail in the
		1675	expected way.
		1676
		1677	=item IO::AIO::CWD
		1678
		1679	This is a compiletime constant (object) that represents the process
		1680	current working directory.
		1681
		1682	Specifying this object as working directory object for a pathname is as if
		1683	the pathname would be specified directly, without a directory object. For
		1684	example, these calls are functionally identical:
		1685
		1686	aio_stat "somefile", sub { ... };
		1687	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1688
		1689	=back
		1690
		1691	To recover the path associated with an IO::AIO::WD object, you can use
		1692	C<aio_realpath>:
		1693
		1694	aio_realpath $wd, sub {
		1695	warn "path is $_[0]\n";
		1696	};
		1697
		1698	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1699	sometimes, fall back to using an absolue path.
1201		1700
1202	=head2 IO::AIO::REQ CLASS	1701	=head2 IO::AIO::REQ CLASS
1203		1702
1204	All non-aggregate C<aio_*> functions return an object of this class when	1703	All non-aggregate C<aio_*> functions return an object of this class when
1205	called in non-void context.	1704	called in non-void context.
…		…
1323		1822
1324	Sets a feeder/generator on this group: every group can have an attached	1823	Sets a feeder/generator on this group: every group can have an attached
1325	generator that generates requests if idle. The idea behind this is that,	1824	generator that generates requests if idle. The idea behind this is that,
1326	although you could just queue as many requests as you want in a group,	1825	although you could just queue as many requests as you want in a group,
1327	this might starve other requests for a potentially long time. For example,	1826	this might starve other requests for a potentially long time. For example,
1328	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1827	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1329	delaying any later requests for a long time.	1828	requests, delaying any later requests for a long time.
1330		1829
1331	To avoid this, and allow incremental generation of requests, you can	1830	To avoid this, and allow incremental generation of requests, you can
1332	instead a group and set a feeder on it that generates those requests. The	1831	instead a group and set a feeder on it that generates those requests. The
1333	feed callback will be called whenever there are few enough (see C<limit>,	1832	feed callback will be called whenever there are few enough (see C<limit>,
1334	below) requests active in the group itself and is expected to queue more	1833	below) requests active in the group itself and is expected to queue more
…		…
1366	The default value for the limit is C<0>, but note that setting a feeder	1865	The default value for the limit is C<0>, but note that setting a feeder
1367	automatically bumps it up to C<2>.	1866	automatically bumps it up to C<2>.
1368		1867
1369	=back	1868	=back
1370		1869
		1870
1371	=head2 SUPPORT FUNCTIONS	1871	=head2 SUPPORT FUNCTIONS
1372		1872
1373	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1873	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1374		1874
1375	=over 4	1875	=over 4
…		…
1383		1883
1384	See C<poll_cb> for an example.	1884	See C<poll_cb> for an example.
1385		1885
1386	=item IO::AIO::poll_cb	1886	=item IO::AIO::poll_cb
1387		1887
1388	Process some outstanding events on the result pipe. You have to call this	1888	Process some requests that have reached the result phase (i.e. they have
1389	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1889	been executed but the results are not yet reported). You have to call
1390	returned earlier for whatever reason. Returns immediately when no events	1890	this "regularly" to finish outstanding requests.
1391	are outstanding. The amount of events processed depends on the settings of
1392	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1393		1891
		1892	Returns C<0> if all events could be processed (or there were no
		1893	events to process), or C<-1> if it returned earlier for whatever
		1894	reason. Returns immediately when no events are outstanding. The amount
		1895	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1896	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1897
1394	If not all requests were processed for whatever reason, the filehandle	1898	If not all requests were processed for whatever reason, the poll file
1395	will still be ready when C<poll_cb> returns, so normally you don't have to	1899	descriptor will still be ready when C<poll_cb> returns, so normally you
1396	do anything special to have it called later.	1900	don't have to do anything special to have it called later.
		1901
		1902	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1903	ready, it can be beneficial to call this function from loops which submit
		1904	a lot of requests, to make sure the results get processed when they become
		1905	available and not just when the loop is finished and the event loop takes
		1906	over again. This function returns very fast when there are no outstanding
		1907	requests.
1397		1908
1398	Example: Install an Event watcher that automatically calls	1909	Example: Install an Event watcher that automatically calls
1399	IO::AIO::poll_cb with high priority (more examples can be found in the	1910	IO::AIO::poll_cb with high priority (more examples can be found in the
1400	SYNOPSIS section, at the top of this document):	1911	SYNOPSIS section, at the top of this document):
1401		1912
…		…
1403	poll => 'r', async => 1,	1914	poll => 'r', async => 1,
1404	cb => \&IO::AIO::poll_cb);	1915	cb => \&IO::AIO::poll_cb);
1405		1916
1406	=item IO::AIO::poll_wait	1917	=item IO::AIO::poll_wait
1407		1918
1408	If there are any outstanding requests and none of them in the result	1919	Wait until either at least one request is in the result phase or no
1409	phase, wait till the result filehandle becomes ready for reading (simply	1920	requests are outstanding anymore.
1410	does a C<select> on the filehandle. This is useful if you want to	1921
1411	synchronously wait for some requests to finish).	1922	This is useful if you want to synchronously wait for some requests to
		1923	become ready, without actually handling them.
1412		1924
1413	See C<nreqs> for an example.	1925	See C<nreqs> for an example.
1414		1926
1415	=item IO::AIO::poll	1927	=item IO::AIO::poll
1416		1928
…		…
1427		1939
1428	Strictly equivalent to:	1940	Strictly equivalent to:
1429		1941
1430	IO::AIO::poll_wait, IO::AIO::poll_cb	1942	IO::AIO::poll_wait, IO::AIO::poll_cb
1431	while IO::AIO::nreqs;	1943	while IO::AIO::nreqs;
		1944
		1945	This function can be useful at program aborts, to make sure outstanding
		1946	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1947	this function on normal exits), or when you are merely using C<IO::AIO>
		1948	for its more advanced functions, rather than for async I/O, e.g.:
		1949
		1950	my ($dirs, $nondirs);
		1951	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1952	IO::AIO::flush;
		1953	# $dirs, $nondirs are now set
1432		1954
1433	=item IO::AIO::max_poll_reqs $nreqs	1955	=item IO::AIO::max_poll_reqs $nreqs
1434		1956
1435	=item IO::AIO::max_poll_time $seconds	1957	=item IO::AIO::max_poll_time $seconds
1436		1958
…		…
1463	poll => 'r', nice => 1,	1985	poll => 'r', nice => 1,
1464	cb => &IO::AIO::poll_cb);	1986	cb => &IO::AIO::poll_cb);
1465		1987
1466	=back	1988	=back
1467		1989
		1990
1468	=head3 CONTROLLING THE NUMBER OF THREADS	1991	=head3 CONTROLLING THE NUMBER OF THREADS
1469		1992
1470	=over	1993	=over
1471		1994
1472	=item IO::AIO::min_parallel $nthreads	1995	=item IO::AIO::min_parallel $nthreads
…		…
1503		2026
1504	Under normal circumstances you don't need to call this function.	2027	Under normal circumstances you don't need to call this function.
1505		2028
1506	=item IO::AIO::max_idle $nthreads	2029	=item IO::AIO::max_idle $nthreads
1507		2030
1508	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2031	Limit the number of threads (default: 4) that are allowed to idle
1509	threads that did not get a request to process within 10 seconds). That	2032	(i.e., threads that did not get a request to process within the idle
1510	means if a thread becomes idle while C<$nthreads> other threads are also	2033	timeout (default: 10 seconds). That means if a thread becomes idle while
1511	idle, it will free its resources and exit.	2034	C<$nthreads> other threads are also idle, it will free its resources and
		2035	exit.
1512		2036
1513	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2037	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1514	to allow for extremely high load situations, but want to free resources	2038	to allow for extremely high load situations, but want to free resources
1515	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2039	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1516		2040
1517	The default is probably ok in most situations, especially if thread	2041	The default is probably ok in most situations, especially if thread
1518	creation is fast. If thread creation is very slow on your system you might	2042	creation is fast. If thread creation is very slow on your system you might
1519	want to use larger values.	2043	want to use larger values.
1520		2044
		2045	=item IO::AIO::idle_timeout $seconds
		2046
		2047	Sets the minimum idle timeout (default 10) after which worker threads are
		2048	allowed to exit. SEe C<IO::AIO::max_idle>.
		2049
1521	=item IO::AIO::max_outstanding $maxreqs	2050	=item IO::AIO::max_outstanding $maxreqs
		2051
		2052	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2053	you do queue up more than this number of requests, the next call to
		2054	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2055	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2056	longer exceeded.
		2057
		2058	In other words, this setting does not enforce a queue limit, but can be
		2059	used to make poll functions block if the limit is exceeded.
1522		2060
1523	This is a very bad function to use in interactive programs because it	2061	This is a very bad function to use in interactive programs because it
1524	blocks, and a bad way to reduce concurrency because it is inexact: Better	2062	blocks, and a bad way to reduce concurrency because it is inexact: Better
1525	use an C<aio_group> together with a feed callback.	2063	use an C<aio_group> together with a feed callback.
1526		2064
1527	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2065	Its main use is in scripts without an event loop - when you want to stat
1528	do queue up more than this number of requests, the next call to the	2066	a lot of files, you can write something like this:
1529	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1530	function will block until the limit is no longer exceeded.
1531		2067
1532	The default value is very large, so there is no practical limit on the	2068	IO::AIO::max_outstanding 32;
1533	number of outstanding requests.
1534		2069
1535	You can still queue as many requests as you want. Therefore,	2070	for my $path (...) {
1536	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2071	aio_stat $path , ...;
1537	as a stop gap to shield against fatal memory overflow (with large values).	2072	IO::AIO::poll_cb;
		2073	}
		2074
		2075	IO::AIO::flush;
		2076
		2077	The call to C<poll_cb> inside the loop will normally return instantly, but
		2078	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2079	some requests have been handled. This keeps the loop from pushing a large
		2080	number of C<aio_stat> requests onto the queue.
		2081
		2082	The default value for C<max_outstanding> is very large, so there is no
		2083	practical limit on the number of outstanding requests.
1538		2084
1539	=back	2085	=back
		2086
1540		2087
1541	=head3 STATISTICAL INFORMATION	2088	=head3 STATISTICAL INFORMATION
1542		2089
1543	=over	2090	=over
1544		2091
…		…
1562	Returns the number of requests currently in the pending state (executed,	2109	Returns the number of requests currently in the pending state (executed,
1563	but not yet processed by poll_cb).	2110	but not yet processed by poll_cb).
1564		2111
1565	=back	2112	=back
1566		2113
		2114
		2115	=head3 SUBSECOND STAT TIME ACCESS
		2116
		2117	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2118	generally find access/modification and change times with subsecond time
		2119	accuracy of the system supports it, but perl's built-in functions only
		2120	return the integer part.
		2121
		2122	The following functions return the timestamps of the most recent
		2123	stat with subsecond precision on most systems and work both after
		2124	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2125	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2126	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2127
		2128	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2129	full resolution without rounding and work with standard perl C<stat>,
		2130	alleviating the need to call the special C<Time::HiRes> functions, which
		2131	do not act like their perl counterparts.
		2132
		2133	On operating systems or file systems where subsecond time resolution is
		2134	not supported or could not be detected, a fractional part of C<0> is
		2135	returned, so it is always safe to call these functions.
		2136
		2137	=over 4
		2138
		2139	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2140
		2141	Return the access, modication, change or birth time, respectively,
		2142	including fractional part. Due to the limited precision of floating point,
		2143	the accuracy on most platforms is only a bit better than milliseconds
		2144	for times around now - see the I<nsec> function family, below, for full
		2145	accuracy.
		2146
		2147	File birth time is only available when the OS and perl support it (on
		2148	FreeBSD and NetBSD at the time of this writing, although support is
		2149	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2150	it). On systems where it isn't available, C<0> is currently returned, but
		2151	this might change to C<undef> in a future version.
		2152
		2153	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2154
		2155	Returns access, modification, change and birth time all in one go, and
		2156	maybe more times in the future version.
		2157
		2158	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2159
		2160	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2161	as an integer in the range C<0> to C<999999999>.
		2162
		2163	Note that no accessors are provided for access, modification and
		2164	change times - you need to get those from C<stat _> if required (C<int
		2165	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2166	value).
		2167
		2168	=item $seconds = IO::AIO::st_btimesec
		2169
		2170	The (integral) seconds part of the file birth time, if available.
		2171
		2172	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2173
		2174	Like the functions above, but returns all four times in one go (and maybe
		2175	more in future versions).
		2176
		2177	=item $counter = IO::AIO::st_gen
		2178
		2179	Returns the generation counter (in practice this is just a random number)
		2180	of the file. This is only available on platforms which have this member in
		2181	their C<struct stat> (most BSDs at the time of this writing) and generally
		2182	only to the root usert. If unsupported, C<0> is returned, but this might
		2183	change to C<undef> in a future version.
		2184
		2185	=back
		2186
		2187	Example: print the high resolution modification time of F</etc>, using
		2188	C<stat>, and C<IO::AIO::aio_stat>.
		2189
		2190	if (stat "/etc") {
		2191	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2192	}
		2193
		2194	IO::AIO::aio_stat "/etc", sub {
		2195	$_[0]
		2196	and return;
		2197
		2198	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2199	};
		2200
		2201	IO::AIO::flush;
		2202
		2203	Output of the awbove on my system, showing reduced and full accuracy:
		2204
		2205	stat(/etc) mtime: 1534043702.020808
		2206	aio_stat(/etc) mtime: 1534043702.020807792
		2207
		2208
1567	=head3 MISCELLANEOUS FUNCTIONS	2209	=head3 MISCELLANEOUS FUNCTIONS
1568		2210
1569	IO::AIO implements some functions that might be useful, but are not	2211	IO::AIO implements some functions that are useful when you want to use
1570	asynchronous.	2212	some "Advanced I/O" function not available to in Perl, without going the
		2213	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2214	counterpart.
1571		2215
1572	=over 4	2216	=over 4
		2217
		2218	=item $numfd = IO::AIO::get_fdlimit
		2219
		2220	This function is I<EXPERIMENTAL> and subject to change.
		2221
		2222	Tries to find the current file descriptor limit and returns it, or
		2223	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2224	the highest valid file descriptor number.
		2225
		2226	=item IO::AIO::min_fdlimit [$numfd]
		2227
		2228	This function is I<EXPERIMENTAL> and subject to change.
		2229
		2230	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2231	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2232	is missing, it will try to set a very high limit, although this is not
		2233	recommended when you know the actual minimum that you require.
		2234
		2235	If the limit cannot be raised enough, the function makes a best-effort
		2236	attempt to increase the limit as much as possible, using various
		2237	tricks, while still failing. You can query the resulting limit using
		2238	C<IO::AIO::get_fdlimit>.
		2239
		2240	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2241	true.
1573		2242
1574	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2243	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1575		2244
1576	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2245	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1577	but is blocking (this makes most sense if you know the input data is	2246	but is blocking (this makes most sense if you know the input data is
…		…
1580		2249
1581	Returns the number of bytes copied, or C<-1> on error.	2250	Returns the number of bytes copied, or C<-1> on error.
1582		2251
1583	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2252	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1584		2253
1585	Simply calls the C<posix_fadvise> function (see it's	2254	Simply calls the C<posix_fadvise> function (see its
1586	manpage for details). The following advice constants are	2255	manpage for details). The following advice constants are
1587	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2256	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1588	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2257	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1589	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2258	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1590		2259
1591	On systems that do not implement C<posix_fadvise>, this function returns	2260	On systems that do not implement C<posix_fadvise>, this function returns
1592	ENOSYS, otherwise the return value of C<posix_fadvise>.	2261	ENOSYS, otherwise the return value of C<posix_fadvise>.
1593		2262
		2263	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2264
		2265	Simply calls the C<posix_madvise> function (see its
		2266	manpage for details). The following advice constants are
		2267	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2268	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2269	C<IO::AIO::MADV_DONTNEED>.
		2270
		2271	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2272	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2273	will be reduced to fit into the C<$scalar>.
		2274
		2275	On systems that do not implement C<posix_madvise>, this function returns
		2276	ENOSYS, otherwise the return value of C<posix_madvise>.
		2277
		2278	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2279
		2280	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2281	$scalar (see its manpage for details). The following protect
		2282	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2283	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2284
		2285	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2286	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2287	will be reduced to fit into the C<$scalar>.
		2288
		2289	On systems that do not implement C<mprotect>, this function returns
		2290	ENOSYS, otherwise the return value of C<mprotect>.
		2291
1594	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2292	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1595		2293
1596	Memory-maps a file (or anonymous memory range) and attaches it to the	2294	Memory-maps a file (or anonymous memory range) and attaches it to the
1597	given C<$scalar>, which will act like a string scalar.	2295	given C<$scalar>, which will act like a string scalar. Returns true on
		2296	success, and false otherwise.
1598		2297
		2298	The scalar must exist, but its contents do not matter - this means you
		2299	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2300	the scalar first.
		2301
1599	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2302	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1600	change the string length, and most read-only operations such as copying it	2303	which don't change the string length, and most read-only operations such
1601	or searching it with regexes and so on.	2304	as copying it or searching it with regexes and so on.
1602		2305
1603	Anything else is unsafe and will, at best, result in memory leaks.	2306	Anything else is unsafe and will, at best, result in memory leaks.
1604		2307
1605	The memory map associated with the C<$scalar> is automatically removed	2308	The memory map associated with the C<$scalar> is automatically removed
1606	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2309	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1607	C<IO::AIO::munmap> functions are called.	2310	or C<IO::AIO::munmap> functions are called on it.
1608		2311
1609	This calls the C<mmap>(2) function internally. See your system's manual	2312	This calls the C<mmap>(2) function internally. See your system's manual
1610	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2313	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1611		2314
1612	The C<$length> must be larger than zero and smaller than the actual	2315	The C<$length> must be larger than zero and smaller than the actual
1613	filesize.	2316	filesize.
1614		2317
1615	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2318	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1616	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2319	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1617		2320
1618	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2321	C<$flags> can be a combination of
1619	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2322	C<IO::AIO::MAP_SHARED> or
1620	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2323	C<IO::AIO::MAP_PRIVATE>,
		2324	or a number of system-specific flags (when not available, the are C<0>):
1621	(which is set to C<MAP_ANON> if your system only provides this	2325	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1622	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2326	C<IO::AIO::MAP_LOCKED>,
1623	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2327	C<IO::AIO::MAP_NORESERVE>,
		2328	C<IO::AIO::MAP_POPULATE>,
1624	C<IO::AIO::MAP_NONBLOCK>	2329	C<IO::AIO::MAP_NONBLOCK>,
		2330	C<IO::AIO::MAP_FIXED>,
		2331	C<IO::AIO::MAP_GROWSDOWN>,
		2332	C<IO::AIO::MAP_32BIT>,
		2333	C<IO::AIO::MAP_HUGETLB> or
		2334	C<IO::AIO::MAP_STACK>.
1625		2335
1626	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2336	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1627		2337
1628	C<$offset> is the offset from the start of the file - it generally must be	2338	C<$offset> is the offset from the start of the file - it generally must be
1629	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2339	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1643		2353
1644	=item IO::AIO::munmap $scalar	2354	=item IO::AIO::munmap $scalar
1645		2355
1646	Removes a previous mmap and undefines the C<$scalar>.	2356	Removes a previous mmap and undefines the C<$scalar>.
1647		2357
		2358	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2359
		2360	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2361	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2362	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2363
		2364	Returns true if successful, and false otherwise. If the underlying mmapped
		2365	region has changed address, then the true value has the numerical value
		2366	C<1>, otherwise it has the numerical value C<0>:
		2367
		2368	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2369	or die "mremap: $!";
		2370
		2371	if ($success*1) {
		2372	warn "scalar has chanegd address in memory\n";
		2373	}
		2374
		2375	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2376	implemented, but not supported and might go away in a future version.
		2377
		2378	On systems where this call is not supported or is not emulated, this call
		2379	returns falls and sets C<$!> to C<ENOSYS>.
		2380
		2381	=item IO::AIO::mlockall $flags
		2382
		2383	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2384	but is blocking.
		2385
1648	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2386	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1649		2387
1650	Calls the C<munlock> function, undoing the effects of a previous	2388	Calls the C<munlock> function, undoing the effects of a previous
1651	C<aio_mlock> call (see its description for details).	2389	C<aio_mlock> call (see its description for details).
1652		2390
…		…
1654		2392
1655	Calls the C<munlockall> function.	2393	Calls the C<munlockall> function.
1656		2394
1657	On systems that do not implement C<munlockall>, this function returns	2395	On systems that do not implement C<munlockall>, this function returns
1658	ENOSYS, otherwise the return value of C<munlockall>.	2396	ENOSYS, otherwise the return value of C<munlockall>.
		2397
		2398	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2399
		2400	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2401	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2402	should be the file offset.
		2403
		2404	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2405	silently corrupt the data in this case.
		2406
		2407	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2408	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2409	C<IO::AIO::SPLICE_F_GIFT>.
		2410
		2411	See the C<splice(2)> manpage for details.
		2412
		2413	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2414
		2415	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2416	description for C<IO::AIO::splice> above for details.
		2417
		2418	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2419
		2420	Attempts to query or change the pipe buffer size. Obviously works only
		2421	on pipes, and currently works only on GNU/Linux systems, and fails with
		2422	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2423	size on other systems, drop me a note.
		2424
		2425	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2426
		2427	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2428	C<$flags> is missing or C<0>, then this should be the same as a call to
		2429	perl's built-in C<pipe> function and create a new pipe, and works on
		2430	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2431	(..., 4096, O_BINARY)>.
		2432
		2433	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2434	the given flags (Linux 2.6.27, glibc 2.9).
		2435
		2436	On success, the read and write file handles are returned.
		2437
		2438	On error, nothing will be returned. If the pipe2 syscall is missing and
		2439	C<$flags> is non-zero, fails with C<ENOSYS>.
		2440
		2441	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2442	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2443	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2444
		2445	Example: create a pipe race-free w.r.t. threads and fork:
		2446
		2447	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2448	or die "pipe2: $!\n";
		2449
		2450	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2451
		2452	This is a direct interface to the Linux L<memfd_create(2)> system
		2453	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2454	should be C<IO::AIO::MFD_CLOEXEC>.
		2455
		2456	On success, the new memfd filehandle is returned, otherwise returns
		2457	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2458
		2459	Please refer to L<memfd_create(2)> for more info on this call.
		2460
		2461	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2462	C<IO::AIO::MFD_ALLOW_SEALING> and C<IO::AIO::MFD_HUGETLB>.
		2463
		2464	Example: create a new memfd.
		2465
		2466	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2467	or die "m,emfd_create: $!\n";
		2468	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2469
		2470	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2471	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2472
		2473	On success, the new eventfd filehandle is returned, otherwise returns
		2474	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2475
		2476	Please refer to L<eventfd(2)> for more info on this call.
		2477
		2478	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2479	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2480
		2481	Example: create a new eventfd filehandle:
		2482
		2483	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2484	or die "eventfd: $!\n";
		2485
		2486	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2487
		2488	This is a direct interface to the Linux L<timerfd_create(2)> system
		2489	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2490	should be C<IO::AIO::TFD_CLOEXEC>.
		2491
		2492	On success, the new timerfd filehandle is returned, otherwise returns
		2493	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2494
		2495	Please refer to L<timerfd_create(2)> for more info on this call.
		2496
		2497	The following C<$clockid> values are
		2498	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2499	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2500	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2501	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2502
		2503	The following C<$flags> values are available (Linux
		2504	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2505
		2506	Example: create a new timerfd and set it to one-second repeated alarms,
		2507	then wait for two alarms:
		2508
		2509	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2510	or die "timerfd_create: $!\n";
		2511
		2512	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2513	or die "timerfd_settime: $!\n";
		2514
		2515	for (1..2) {
		2516	8 == sysread $fh, my $buf, 8
		2517	or die "timerfd read failure\n";
		2518
		2519	printf "number of expirations (likely 1): %d\n",
		2520	unpack "Q", $buf;
		2521	}
		2522
		2523	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2524
		2525	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2526	call. Please refer to its manpage for more info on this call.
		2527
		2528	The new itimerspec is specified using two (possibly fractional) second
		2529	values, C<$new_interval> and C<$new_value>).
		2530
		2531	On success, the current interval and value are returned (as per
		2532	C<timerfd_gettime>). On failure, the empty list is returned.
		2533
		2534	The following C<$flags> values are
		2535	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2536	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2537
		2538	See C<IO::AIO::timerfd_create> for a full example.
		2539
		2540	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2541
		2542	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2543	call. Please refer to its manpage for more info on this call.
		2544
		2545	On success, returns the current values of interval and value for the given
		2546	timerfd (as potentially fractional second values). On failure, the empty
		2547	list is returned.
1659		2548
1660	=back	2549	=back
1661		2550
1662	=cut	2551	=cut
1663		2552
…		…
1698	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2587	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1699	\&IO::AIO::poll_cb);	2588	\&IO::AIO::poll_cb);
1700		2589
1701	=head2 FORK BEHAVIOUR	2590	=head2 FORK BEHAVIOUR
1702		2591
1703	This module should do "the right thing" when the process using it forks:	2592	Usage of pthreads in a program changes the semantics of fork
		2593	considerably. Specifically, only async-safe functions can be called after
		2594	fork. Perl doesn't know about this, so in general, you cannot call fork
		2595	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2596	pthreads, so this applies, but many other extensions and (for inexplicable
		2597	reasons) perl itself often is linked against pthreads, so this limitation
		2598	applies to quite a lot of perls.
1704		2599
1705	Before the fork, IO::AIO enters a quiescent state where no requests	2600	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1706	can be added in other threads and no results will be processed. After	2601	only works in the process that loaded it. Forking is fully supported, but
1707	the fork the parent simply leaves the quiescent state and continues	2602	using IO::AIO in the child is not.
1708	request/result processing, while the child frees the request/result queue
1709	(so that the requests started before the fork will only be handled in the
1710	parent). Threads will be started on demand until the limit set in the
1711	parent process has been reached again.
1712		2603
1713	In short: the parent will, after a short pause, continue as if fork had	2604	You might get around by not I<using> IO::AIO before (or after)
1714	not been called, while the child will act as if IO::AIO has not been used	2605	forking. You could also try to call the L<IO::AIO::reinit> function in the
1715	yet.	2606	child:
		2607
		2608	=over 4
		2609
		2610	=item IO::AIO::reinit
		2611
		2612	Abandons all current requests and I/O threads and simply reinitialises all
		2613	data structures. This is not an operation supported by any standards, but
		2614	happens to work on GNU/Linux and some newer BSD systems.
		2615
		2616	The only reasonable use for this function is to call it after forking, if
		2617	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2618	the process will result in undefined behaviour. Calling it at any time
		2619	will also result in any undefined (by POSIX) behaviour.
		2620
		2621	=back
		2622
		2623	=head2 LINUX-SPECIFIC CALLS
		2624
		2625	When a call is documented as "linux-specific" then this means it
		2626	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2627	availability and compatibility of such calls regardless of the platform
		2628	it is compiled on, so platforms such as FreeBSD which often implement
		2629	these calls will work. When in doubt, call them and see if they fail wth
		2630	C<ENOSYS>.
1716		2631
1717	=head2 MEMORY USAGE	2632	=head2 MEMORY USAGE
1718		2633
1719	Per-request usage:	2634	Per-request usage:
1720		2635
…		…
1733	temporary buffers, and each thread requires a stack and other data	2648	temporary buffers, and each thread requires a stack and other data
1734	structures (usually around 16k-128k, depending on the OS).	2649	structures (usually around 16k-128k, depending on the OS).
1735		2650
1736	=head1 KNOWN BUGS	2651	=head1 KNOWN BUGS
1737		2652
1738	Known bugs will be fixed in the next release.	2653	Known bugs will be fixed in the next release :)
		2654
		2655	=head1 KNOWN ISSUES
		2656
		2657	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2658	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2659	non-created hash slots or other scalars I didn't think of. It's best to
		2660	avoid such and either use scalar variables or making sure that the scalar
		2661	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2662
		2663	I am not sure anything can be done about this, so this is considered a
		2664	known issue, rather than a bug.
1739		2665
1740	=head1 SEE ALSO	2666	=head1 SEE ALSO
1741		2667
1742	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2668	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1743	more natural syntax.	2669	more natural syntax.

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