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Revision 1.183 by root, Sun Sep 12 03:40:05 2010 UTC vs.
Revision 1.306 by root, Wed Oct 16 09:11:35 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 = 4.73;
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::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
		309	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		310	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		311	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		312	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		313	$fh = IO::AIO::memfd_create $pathname[, $flags]
		314	$fh = IO::AIO::eventfd [$initval, [$flags]]
		315	$fh = IO::AIO::timerfd_create $clockid[, $flags]
		316	($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		317	($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		318
		319	=head2 API NOTES
274		320
275	All the C<aio_*> calls are more or less thin wrappers around the syscall	321	All the C<aio_*> calls are more or less thin wrappers around the syscall
276	with the same name (sans C<aio_>). The arguments are similar or identical,	322	with the same name (sans C<aio_>). The arguments are similar or identical,
277	and they all accept an additional (and optional) C<$callback> argument	323	and they all accept an additional (and optional) C<$callback> argument
278	which must be a code reference. This code reference will get called with	324	which must be a code reference. This code reference will be called after
279	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	325	the syscall has been executed in an asynchronous fashion. The results
280	perl, which usually delivers "false") as its sole argument after the given	326	of the request will be passed as arguments to the callback (and, if an
281	syscall has been executed asynchronously.	327	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		328	most syscalls return C<-1> on error, unlike perl, which usually delivers
		329	"false").
		330
		331	Some requests (such as C<aio_readdir>) pass the actual results and
		332	communicate failures by passing C<undef>.
282		333
283	All functions expecting a filehandle keep a copy of the filehandle	334	All functions expecting a filehandle keep a copy of the filehandle
284	internally until the request has finished.	335	internally until the request has finished.
285		336
286	All functions return request objects of type L<IO::AIO::REQ> that allow	337	All functions return request objects of type L<IO::AIO::REQ> that allow
287	further manipulation of those requests while they are in-flight.	338	further manipulation of those requests while they are in-flight.
288		339
289	The pathnames you pass to these routines I<must> be absolute and	340	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	341	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	342	current working directory could have changed. Alternatively, you can
292	changed. Alternatively, you can make sure that you never change the	343	make sure that you never change the current working directory anywhere
293	current working directory anywhere in the program and then use relative	344	in the program and then use relative paths. You can also take advantage
294	paths.	345	of IO::AIOs working directory abstraction, that lets you specify paths
		346	relative to some previously-opened "working directory object" - see the
		347	description of the C<IO::AIO::WD> class later in this document.
295		348
296	To encode pathnames as octets, either make sure you either: a) always pass	349	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	350	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	351	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	352	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)	353	effect in the user environment, d) use Glib::filename_from_unicode on
301	use something else to ensure your scalar has the correct contents.	354	unicode filenames or e) use something else to ensure your scalar has the
		355	correct contents.
302		356
303	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	357	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
304	handles correctly whether it is set or not.	358	handles correctly whether it is set or not.
		359
		360	=head2 AIO REQUEST FUNCTIONS
305		361
306	=over 4	362	=over 4
307		363
308	=item $prev_pri = aioreq_pri [$pri]	364	=item $prev_pri = aioreq_pri [$pri]
309		365
…		…
339		395
340		396
341	=item aio_open $pathname, $flags, $mode, $callback->($fh)	397	=item aio_open $pathname, $flags, $mode, $callback->($fh)
342		398
343	Asynchronously open or create a file and call the callback with a newly	399	Asynchronously open or create a file and call the callback with a newly
344	created filehandle for the file.	400	created filehandle for the file (or C<undef> in case of an error).
345		401
346	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	402	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
347	for an explanation.	403	for an explanation.
348		404
349	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	405	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
365	} else {	421	} else {
366	die "open failed: $!\n";	422	die "open failed: $!\n";
367	}	423	}
368	};	424	};
369		425
		426	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		427	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		428	following POSIX and non-POSIX constants are available (missing ones on
		429	your system are, as usual, C<0>):
		430
		431	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		432	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		433	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		434
370		435
371	=item aio_close $fh, $callback->($status)	436	=item aio_close $fh, $callback->($status)
372		437
373	Asynchronously close a file and call the callback with the result	438	Asynchronously close a file and call the callback with the result
374	code.	439	code.
…		…
383	Or in other words: the file descriptor will be closed, but it will not be	448	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.	449	free for reuse until the perl filehandle is closed.
385		450
386	=cut	451	=cut
387		452
		453	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		454
		455	Seeks the filehandle to the new C<$offset>, similarly to perl's
		456	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		457	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		458	C<IO::AIO::SEEK_END>).
		459
		460	The resulting absolute offset will be passed to the callback, or C<-1> in
		461	case of an error.
		462
		463	In theory, the C<$whence> constants could be different than the
		464	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		465	so don't panic.
		466
		467	As a GNU/Linux (and maybe Solaris) extension, also the constants
		468	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		469	could be found. No guarantees about suitability for use in C<aio_seek> or
		470	Perl's C<sysseek> can be made though, although I would naively assume they
		471	"just work".
		472
388	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	473	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
389		474
390	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	475	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
391		476
392	Reads or writes C<$length> bytes from or to the specified C<$fh> and	477	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<$dataoffset>	478	C<$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	479	calls the callback with the actual number of bytes transferred (or -1 on
395	error, just like the syscall).	480	error, just like the syscall).
396		481
397	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	482	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
398	offset plus the actual number of bytes read.	483	offset plus the actual number of bytes read.
399		484
…		…
424		509
425	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	510	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
426	reading at byte offset C<$in_offset>, and starts writing at the current	511	reading at byte offset C<$in_offset>, and starts writing at the current
427	file offset of C<$out_fh>. Because of that, it is not safe to issue more	512	file offset of C<$out_fh>. Because of that, it is not safe to issue more
428	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	513	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
429	other.	514	other. The same C<$in_fh> works fine though, as this function does not
		515	move or use the file offset of C<$in_fh>.
430		516
		517	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		518	are written, and there is no way to find out how many more bytes have been
		519	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		520	number of bytes written to C<$out_fh>. Only if the result value equals
		521	C<$length> one can assume that C<$length> bytes have been read.
		522
		523	Unlike with other C<aio_> functions, it makes a lot of sense to use
		524	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		525	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		526	the socket I/O will be non-blocking. Note, however, that you can run
		527	into a trap where C<aio_sendfile> reads some data with readahead, then
		528	fails to write all data, and when the socket is ready the next time, the
		529	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		530	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		531	resource usage.
		532
431	This call tries to make use of a native C<sendfile> syscall to provide	533	This call tries to make use of a native C<sendfile>-like syscall to
432	zero-copy operation. For this to work, C<$out_fh> should refer to a	534	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.	535	a socket, and C<$in_fh> should refer to an mmap'able file.
434		536
435	If a native sendfile cannot be found or it fails with C<ENOSYS>,	537	If a native sendfile cannot be found or it fails with C<ENOSYS>,
436	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	538	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
437	it will be emulated, so you can call C<aio_sendfile> on any type of	539	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
438	filehandle regardless of the limitations of the operating system.	540	type of filehandle regardless of the limitations of the operating system.
439		541
440	Please note, however, that C<aio_sendfile> can read more bytes from	542	As native sendfile syscalls (as practically any non-POSIX interface hacked
441	C<$in_fh> than are written, and there is no way to find out how many	543	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	544	on many systems, this implementation tries to work around some known bugs
443	provides the number of bytes written to C<$out_fh>. Only if the result	545	in Linux and FreeBSD kernels (probably others, too), but that might fail,
444	value equals C<$length> one can assume that C<$length> bytes have been	546	so you really really should check the return value of C<aio_sendfile> -
445	read.	547	fewer bytes than expected might have been transferred.
446		548
447		549
448	=item aio_readahead $fh,$offset,$length, $callback->($retval)	550	=item aio_readahead $fh,$offset,$length, $callback->($retval)
449		551
450	C<aio_readahead> populates the page cache with data from a file so that	552	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	556	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	557	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	558	(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.	559	file. The current file offset of the file is left unchanged.
458		560
459	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	561	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.	562	be emulated by simply reading the data, which would have a similar effect.
461		563
462		564
463	=item aio_stat $fh_or_path, $callback->($status)	565	=item aio_stat $fh_or_path, $callback->($status)
464		566
465	=item aio_lstat $fh, $callback->($status)	567	=item aio_lstat $fh, $callback->($status)
466		568
467	Works like perl's C<stat> or C<lstat> in void context. The callback will	569	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 _>	570	callback will be called after the stat and the results will be available
469	or C<-s _> etc...	571	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		572	and C<-T>).
470		573
471	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	574	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
472	for an explanation.	575	for an explanation.
473		576
474	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	577	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	578	error when stat'ing a large file, the results will be silently truncated
476	unless perl itself is compiled with large file support.	579	unless perl itself is compiled with large file support.
		580
		581	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		582	following constants and functions (if not implemented, the constants will
		583	be C<0> and the functions will either C<croak> or fall back on traditional
		584	behaviour).
		585
		586	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		587	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		588	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		589
		590	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		591	ACCESS>.
477		592
478	Example: Print the length of F</etc/passwd>:	593	Example: Print the length of F</etc/passwd>:
479		594
480	aio_stat "/etc/passwd", sub {	595	aio_stat "/etc/passwd", sub {
481	$_[0] and die "stat failed: $!";	596	$_[0] and die "stat failed: $!";
…		…
525	namemax => 255,	640	namemax => 255,
526	frsize => 1024,	641	frsize => 1024,
527	fsid => 1810	642	fsid => 1810
528	}	643	}
529		644
530
531	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	645	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
532		646
533	Works like perl's C<utime> function (including the special case of $atime	647	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	648	and $mtime being undef). Fractional times are supported if the underlying
535	syscalls support them.	649	syscalls support them.
536		650
537	When called with a pathname, uses utimes(2) if available, otherwise	651	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,	652	otherwise utime(2). If called on a file descriptor, uses futimens(2)
539	otherwise returns ENOSYS, so this is not portable.	653	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		654	portable.
540		655
541	Examples:	656	Examples:
542		657
543	# set atime and mtime to current time (basically touch(1)):	658	# set atime and mtime to current time (basically touch(1)):
544	aio_utime "path", undef, undef;	659	aio_utime "path", undef, undef;
…		…
562	=item aio_truncate $fh_or_path, $offset, $callback->($status)	677	=item aio_truncate $fh_or_path, $offset, $callback->($status)
563		678
564	Works like truncate(2) or ftruncate(2).	679	Works like truncate(2) or ftruncate(2).
565		680
566		681
		682	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		683
		684	Allocates or frees disk space according to the C<$mode> argument. See the
		685	linux C<fallocate> documentation for details.
		686
		687	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		688	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		689	to deallocate a file range.
		690
		691	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		692	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		693	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		694	to unshare shared blocks (see your L<fallocate(2)> manpage).
		695
		696	The file system block size used by C<fallocate> is presumably the
		697	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		698	can dictate other limitations.
		699
		700	If C<fallocate> isn't available or cannot be emulated (currently no
		701	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		702
		703
567	=item aio_chmod $fh_or_path, $mode, $callback->($status)	704	=item aio_chmod $fh_or_path, $mode, $callback->($status)
568		705
569	Works like perl's C<chmod> function.	706	Works like perl's C<chmod> function.
570		707
571		708
…		…
573		710
574	Asynchronously unlink (delete) a file and call the callback with the	711	Asynchronously unlink (delete) a file and call the callback with the
575	result code.	712	result code.
576		713
577		714
578	=item aio_mknod $path, $mode, $dev, $callback->($status)	715	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
579		716
580	[EXPERIMENTAL]	717	[EXPERIMENTAL]
581		718
582	Asynchronously create a device node (or fifo). See mknod(2).	719	Asynchronously create a device node (or fifo). See mknod(2).
583		720
584	The only (POSIX-) portable way of calling this function is:	721	The only (POSIX-) portable way of calling this function is:
585		722
586	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	723	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
587		724
		725	See C<aio_stat> for info about some potentially helpful extra constants
		726	and functions.
588		727
589	=item aio_link $srcpath, $dstpath, $callback->($status)	728	=item aio_link $srcpath, $dstpath, $callback->($status)
590		729
591	Asynchronously create a new link to the existing object at C<$srcpath> at	730	Asynchronously create a new link to the existing object at C<$srcpath> at
592	the path C<$dstpath> and call the callback with the result code.	731	the path C<$dstpath> and call the callback with the result code.
…		…
596		735
597	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	736	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
598	the path C<$dstpath> and call the callback with the result code.	737	the path C<$dstpath> and call the callback with the result code.
599		738
600		739
601	=item aio_readlink $path, $callback->($link)	740	=item aio_readlink $pathname, $callback->($link)
602		741
603	Asynchronously read the symlink specified by C<$path> and pass it to	742	Asynchronously read the symlink specified by C<$path> and pass it to
604	the callback. If an error occurs, nothing or undef gets passed to the	743	the callback. If an error occurs, nothing or undef gets passed to the
605	callback.	744	callback.
606		745
607		746
		747	=item aio_realpath $pathname, $callback->($path)
		748
		749	Asynchronously make the path absolute and resolve any symlinks in
		750	C<$path>. The resulting path only consists of directories (same as
		751	L<Cwd::realpath>).
		752
		753	This request can be used to get the absolute path of the current working
		754	directory by passing it a path of F<.> (a single dot).
		755
		756
608	=item aio_rename $srcpath, $dstpath, $callback->($status)	757	=item aio_rename $srcpath, $dstpath, $callback->($status)
609		758
610	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	759	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
611	rename(2) and call the callback with the result code.	760	rename(2) and call the callback with the result code.
		761
		762	On systems that support the AIO::WD working directory abstraction
		763	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		764	of failing, C<rename> is called on the absolute path of C<$wd>.
		765
		766
		767	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		768
		769	Basically a version of C<aio_rename> with an additional C<$flags>
		770	argument. Calling this with C<$flags=0> is the same as calling
		771	C<aio_rename>.
		772
		773	Non-zero flags are currently only supported on GNU/Linux systems that
		774	support renameat2. Other systems fail with C<ENOSYS> in this case.
		775
		776	The following constants are available (missing ones are, as usual C<0>),
		777	see renameat2(2) for details:
		778
		779	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		780	and C<IO::AIO::RENAME_WHITEOUT>.
612		781
613		782
614	=item aio_mkdir $pathname, $mode, $callback->($status)	783	=item aio_mkdir $pathname, $mode, $callback->($status)
615		784
616	Asynchronously mkdir (create) a directory and call the callback with	785	Asynchronously mkdir (create) a directory and call the callback with
…		…
621	=item aio_rmdir $pathname, $callback->($status)	790	=item aio_rmdir $pathname, $callback->($status)
622		791
623	Asynchronously rmdir (delete) a directory and call the callback with the	792	Asynchronously rmdir (delete) a directory and call the callback with the
624	result code.	793	result code.
625		794
		795	On systems that support the AIO::WD working directory abstraction
		796	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		797	C<rmdir> is called on the absolute path of C<$wd>.
		798
626		799
627	=item aio_readdir $pathname, $callback->($entries)	800	=item aio_readdir $pathname, $callback->($entries)
628		801
629	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	802	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	803	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
634	array-ref with the filenames.	807	array-ref with the filenames.
635		808
636		809
637	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	810	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
638		811
639	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	812	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	813	tune behaviour and output format. In case of an error, C<$entries> will be
641	C<undef>.	814	C<undef>.
642		815
643	The flags are a combination of the following constants, ORed together (the	816	The flags are a combination of the following constants, ORed together (the
644	flags will also be passed to the callback, possibly modified):	817	flags will also be passed to the callback, possibly modified):
645		818
646	=over 4	819	=over 4
647		820
648	=item IO::AIO::READDIR_DENTS	821	=item IO::AIO::READDIR_DENTS
649		822
650	When this flag is off, then the callback gets an arrayref with of names	823	Normally the callback gets an arrayref consisting of names only (as
651	only (as with C<aio_readdir>), otherwise it gets an arrayref with	824	with C<aio_readdir>). If this flag is set, then the callback gets an
652	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	825	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
653	entry in more detail.	826	single directory entry in more detail:
654		827
655	C<$name> is the name of the entry.	828	C<$name> is the name of the entry.
656		829
657	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	830	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
658		831
659	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	832	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
660	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	833	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
661	C<IO::AIO::DT_WHT>.	834	C<IO::AIO::DT_WHT>.
662		835
663	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	836	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
664	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	837	to know, you have to run stat yourself. Also, for speed/memory reasons,
665	scalars are read-only: you can not modify them.	838	the C<$type> scalars are read-only: you must not modify them.
666		839
667	C<$inode> is the inode number (which might not be exact on systems with 64	840	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	841	bit inode numbers and 32 bit perls). This field has unspecified content on
669	systems that do not deliver the inode information.	842	systems that do not deliver the inode information.
670		843
671	=item IO::AIO::READDIR_DIRS_FIRST	844	=item IO::AIO::READDIR_DIRS_FIRST
672		845
673	When this flag is set, then the names will be returned in an order where	846	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	847	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	848	you need to quickly find directories, or you want to find all directories
676	stat() each entry.	849	while avoiding to stat() each entry.
677		850
678	If the system returns type information in readdir, then this is used	851	If the system returns type information in readdir, then this is used
679	to find directories directly. Otherwise, likely directories are files	852	to find directories directly. Otherwise, likely directories are names
680	beginning with ".", or otherwise files with no dots, of which files with	853	beginning with ".", or otherwise names with no dots, of which names with
681	short names are tried first.	854	short names are tried first.
682		855
683	=item IO::AIO::READDIR_STAT_ORDER	856	=item IO::AIO::READDIR_STAT_ORDER
684		857
685	When this flag is set, then the names will be returned in an order	858	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()	859	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	860	all files in the given directory, then the returned order will likely be
688	be fastest.	861	faster.
689		862
690	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	863	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.	864	then the likely dirs come first, resulting in a less optimal stat order
		865	for stat'ing all entries, but likely a more optimal order for finding
		866	subdirectories.
692		867
693	=item IO::AIO::READDIR_FOUND_UNKNOWN	868	=item IO::AIO::READDIR_FOUND_UNKNOWN
694		869
695	This flag should not be set when calling C<aio_readdirx>. Instead, it	870	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	871	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
697	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	872	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
698	C<$type>'s are known, which can be used to speed up some algorithms.	873	C<$type>'s are known, which can be used to speed up some algorithms.
699		874
700	=back	875	=back
701		876
702		877
		878	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		879
		880	Opens, reads and closes the given file. The data is put into C<$data>,
		881	which is resized as required.
		882
		883	If C<$offset> is negative, then it is counted from the end of the file.
		884
		885	If C<$length> is zero, then the remaining length of the file is
		886	used. Also, in this case, the same limitations to modifying C<$data> apply
		887	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		888	with C<substr>. If the size of the file is known, specifying a non-zero
		889	C<$length> results in a performance advantage.
		890
		891	This request is similar to the older C<aio_load> request, but since it is
		892	a single request, it might be more efficient to use.
		893
		894	Example: load F</etc/passwd> into C<$passwd>.
		895
		896	my $passwd;
		897	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		898	$_[0] >= 0
		899	or die "/etc/passwd: $!\n";
		900
		901	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		902	print $passwd;
		903	};
		904	IO::AIO::flush;
		905
		906
703	=item aio_load $path, $data, $callback->($status)	907	=item aio_load $pathname, $data, $callback->($status)
704		908
705	This is a composite request that tries to fully load the given file into	909	This is a composite request that tries to fully load the given file into
706	memory. Status is the same as with aio_read.	910	memory. Status is the same as with aio_read.
		911
		912	Using C<aio_slurp> might be more efficient, as it is a single request.
707		913
708	=cut	914	=cut
709		915
710	sub aio_load($$;$) {	916	sub aio_load($$;$) {
711	my ($path, undef, $cb) = @_;	917	my ($path, undef, $cb) = @_;
…		…
731	=item aio_copy $srcpath, $dstpath, $callback->($status)	937	=item aio_copy $srcpath, $dstpath, $callback->($status)
732		938
733	Try to copy the I<file> (directories not supported as either source or	939	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	940	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<$!>).	941	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		942
		943	Existing destination files will be truncated.
736		944
737	This is a composite request that creates the destination file with	945	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	946	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	947	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
740	uid/gid, in that order.	948	uid/gid, in that order.
…		…
830	if ($_[0] && $! == EXDEV) {	1038	if ($_[0] && $! == EXDEV) {
831	aioreq_pri $pri;	1039	aioreq_pri $pri;
832	add $grp aio_copy $src, $dst, sub {	1040	add $grp aio_copy $src, $dst, sub {
833	$grp->result ($_[0]);	1041	$grp->result ($_[0]);
834		1042
835	if (!$_[0]) {	1043	unless ($_[0]) {
836	aioreq_pri $pri;	1044	aioreq_pri $pri;
837	add $grp aio_unlink $src;	1045	add $grp aio_unlink $src;
838	}	1046	}
839	};	1047	};
840	} else {	1048	} else {
…		…
843	};	1051	};
844		1052
845	$grp	1053	$grp
846	}	1054	}
847		1055
848	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1056	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
849		1057
850	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1058	Scans a directory (similar to C<aio_readdir>) but additionally tries to
851	efficiently separate the entries of directory C<$path> into two sets of	1059	efficiently separate the entries of directory C<$path> into two sets of
852	names, directories you can recurse into (directories), and ones you cannot	1060	names, directories you can recurse into (directories), and ones you cannot
853	recurse into (everything else, including symlinks to directories).	1061	recurse into (everything else, including symlinks to directories).
854		1062
855	C<aio_scandir> is a composite request that creates of many sub requests_	1063	C<aio_scandir> is a composite request that generates many sub requests.
856	C<$maxreq> specifies the maximum number of outstanding aio requests that	1064	C<$maxreq> specifies the maximum number of outstanding aio requests that
857	this function generates. If it is C<< <= 0 >>, then a suitable default	1065	this function generates. If it is C<< <= 0 >>, then a suitable default
858	will be chosen (currently 4).	1066	will be chosen (currently 4).
859		1067
860	On error, the callback is called without arguments, otherwise it receives	1068	On error, the callback is called without arguments, otherwise it receives
…		…
884	Then entries will be sorted into likely directories a non-initial dot	1092	Then entries will be sorted into likely directories a non-initial dot
885	currently) and likely non-directories (see C<aio_readdirx>). Then every	1093	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,	1094	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	1095	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	1096	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	1097	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	1098	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	1099	data (e.g. ext2fs filetype feature), even on systems that cannot return
892	the filetype information on readdir.	1100	the filetype information on readdir.
893		1101
894	If the known number of directories (link count - 2) has been reached, the	1102	If the known number of directories (link count - 2) has been reached, the
…		…
910		1118
911	my $grp = aio_group $cb;	1119	my $grp = aio_group $cb;
912		1120
913	$maxreq = 4 if $maxreq <= 0;	1121	$maxreq = 4 if $maxreq <= 0;
914		1122
915	# stat once	1123	# get a wd object
916	aioreq_pri $pri;	1124	aioreq_pri $pri;
917	add $grp aio_stat $path, sub {	1125	add $grp aio_wd $path, sub {
		1126	$_[0]
918	return $grp->result () if $_[0];	1127	or return $grp->result ();
919	my $now = time;
920	my $hash1 = join ":", (stat _)[0,1,3,7,9];
921		1128
922	# read the directory entries	1129	my $wd = [shift, "."];
		1130
		1131	# stat once
923	aioreq_pri $pri;	1132	aioreq_pri $pri;
924	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1133	add $grp aio_stat $wd, sub {
925	my $entries = shift
926	or return $grp->result ();	1134	return $grp->result () if $_[0];
		1135	my $now = time;
		1136	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1137	my $rdxflags = READDIR_DIRS_FIRST;
927		1138
928	# stat the dir another time	1139	if ((stat _)[3] < 2) {
		1140	# at least one non-POSIX filesystem exists
		1141	# that returns useful DT_type values: btrfs,
		1142	# so optimise for this here by requesting dents
		1143	$rdxflags |= READDIR_DENTS;
		1144	}
		1145
		1146	# read the directory entries
929	aioreq_pri $pri;	1147	aioreq_pri $pri;
930	add $grp aio_stat $path, sub {	1148	add $grp aio_readdirx $wd, $rdxflags, sub {
931	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1149	my ($entries, $flags) = @_
		1150	or return $grp->result ();
932		1151
		1152	if ($rdxflags & READDIR_DENTS) {
		1153	# if we requested type values, see if we can use them directly.
		1154
		1155	# if there were any DT_UNKNOWN entries then we assume we
		1156	# don't know. alternatively, we could assume that if we get
		1157	# one DT_DIR, then all directories are indeed marked with
		1158	# DT_DIR, but this seems not required for btrfs, and this
		1159	# is basically the "btrfs can't get it's act together" code
		1160	# branch.
		1161	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1162	# now we have valid DT_ information for all entries,
		1163	# so use it as an optimisation without further stat's.
		1164	# they must also all be at the beginning of @$entries
		1165	# by now.
		1166
933	my $ndirs;	1167	my $dirs;
934		1168
935	# take the slow route if anything looks fishy
936	if ($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) {	1169	if (@$entries) {
959	push @nondirs, $entry;	1170	for (0 .. $#$entries) {
960	} else {	1171	if ($entries->[$_][1] != DT_DIR) {
961	# need to check for real directory	1172	# splice out directories
962	aioreq_pri $pri;	1173	$dirs = [splice @$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	}	1174	last;
971	} else {
972	push @nondirs, $entry;
973	}	1175	}
974	}	1176	}
		1177
		1178	# if we didn't find any non-dir, then all entries are dirs
		1179	unless ($dirs) {
		1180	($dirs, $entries) = ($entries, []);
		1181	}
		1182	} else {
		1183	# directory is empty, so there are no sbdirs
		1184	$dirs = [];
975	}	1185	}
		1186
		1187	# either splice'd the directories out or the dir was empty.
		1188	# convert dents to filenames
		1189	$_ = $_->[0] for @$dirs;
		1190	$_ = $_->[0] for @$entries;
		1191
		1192	return $grp->result ($dirs, $entries);
		1193	}
		1194
		1195	# cannot use, so return to our old ways
		1196	# by pretending we only scanned for names.
		1197	$_ = $_->[0] for @$entries;
		1198	}
		1199
		1200	# stat the dir another time
		1201	aioreq_pri $pri;
		1202	add $grp aio_stat $wd, sub {
		1203	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1204
		1205	my $ndirs;
		1206
		1207	# take the slow route if anything looks fishy
		1208	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1209	$ndirs = -1;
		1210	} else {
		1211	# if nlink == 2, we are finished
		1212	# for non-posix-fs's, we rely on nlink < 2
		1213	$ndirs = (stat _)[3] - 2
		1214	or return $grp->result ([], $entries);
		1215	}
		1216
		1217	my (@dirs, @nondirs);
		1218
		1219	my $statgrp = add $grp aio_group sub {
		1220	$grp->result (\@dirs, \@nondirs);
		1221	};
		1222
		1223	limit $statgrp $maxreq;
		1224	feed $statgrp sub {
		1225	return unless @$entries;
		1226	my $entry = shift @$entries;
		1227
		1228	aioreq_pri $pri;
		1229	$wd->[1] = "$entry/.";
		1230	add $statgrp aio_stat $wd, sub {
		1231	if ($_[0] < 0) {
		1232	push @nondirs, $entry;
		1233	} else {
		1234	# need to check for real directory
		1235	aioreq_pri $pri;
		1236	$wd->[1] = $entry;
		1237	add $statgrp aio_lstat $wd, sub {
		1238	if (-d _) {
		1239	push @dirs, $entry;
		1240
		1241	unless (--$ndirs) {
		1242	push @nondirs, @$entries;
		1243	feed $statgrp;
		1244	}
		1245	} else {
		1246	push @nondirs, $entry;
		1247	}
		1248	}
		1249	}
		1250	};
976	};	1251	};
977	};	1252	};
978	};	1253	};
979	};	1254	};
980	};	1255	};
981		1256
982	$grp	1257	$grp
983	}	1258	}
984		1259
985	=item aio_rmtree $path, $callback->($status)	1260	=item aio_rmtree $pathname, $callback->($status)
986		1261
987	Delete a directory tree starting (and including) C<$path>, return the	1262	Delete a directory tree starting (and including) C<$path>, return the
988	status of the final C<rmdir> only. This is a composite request that	1263	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	1264	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
990	everything else.	1265	everything else.
991		1266
992	=cut	1267	=cut
993		1268
…		…
1015	};	1290	};
1016		1291
1017	$grp	1292	$grp
1018	}	1293	}
1019		1294
		1295	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1296
		1297	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1298
		1299	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1300	they execute asynchronously and pass the return value to the callback.
		1301
		1302	Both calls can be used for a lot of things, some of which make more sense
		1303	to run asynchronously in their own thread, while some others make less
		1304	sense. For example, calls that block waiting for external events, such
		1305	as locking, will also lock down an I/O thread while it is waiting, which
		1306	can deadlock the whole I/O system. At the same time, there might be no
		1307	alternative to using a thread to wait.
		1308
		1309	So in general, you should only use these calls for things that do
		1310	(filesystem) I/O, not for things that wait for other events (network,
		1311	other processes), although if you are careful and know what you are doing,
		1312	you still can.
		1313
		1314	The following constants are available and can be used for normal C<ioctl>
		1315	and C<fcntl> as well (missing ones are, as usual C<0>):
		1316
		1317	C<F_DUPFD_CLOEXEC>,
		1318
		1319	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1320
		1321	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1322
		1323	C<F_ADD_SEALS>, C<F_GET_SEALS>, C<F_SEAL_SEAL>, C<F_SEAL_SHRINK>, C<F_SEAL_GROW> and
		1324	C<F_SEAL_WRITE>.
		1325
		1326	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1327	C<FS_IOC_FIEMAP>.
		1328
		1329	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1330	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1331
		1332	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1333	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1334	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1335	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1336	C<FS_FL_USER_MODIFIABLE>.
		1337
		1338	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1339	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1340	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1341	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1342
1020	=item aio_sync $callback->($status)	1343	=item aio_sync $callback->($status)
1021		1344
1022	Asynchronously call sync and call the callback when finished.	1345	Asynchronously call sync and call the callback when finished.
1023		1346
1024	=item aio_fsync $fh, $callback->($status)	1347	=item aio_fsync $fh, $callback->($status)
…		…
1031	Asynchronously call fdatasync on the given filehandle and call the	1354	Asynchronously call fdatasync on the given filehandle and call the
1032	callback with the fdatasync result code.	1355	callback with the fdatasync result code.
1033		1356
1034	If this call isn't available because your OS lacks it or it couldn't be	1357	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.	1358	detected, it will be emulated by calling C<fsync> instead.
		1359
		1360	=item aio_syncfs $fh, $callback->($status)
		1361
		1362	Asynchronously call the syncfs syscall to sync the filesystem associated
		1363	to the given filehandle and call the callback with the syncfs result
		1364	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1365	errno to C<ENOSYS> nevertheless.
1036		1366
1037	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1367	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1038		1368
1039	Sync the data portion of the file specified by C<$offset> and C<$length>	1369	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	1370	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1044	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1374	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1045	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1375	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1046	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1376	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1047	manpage for details.	1377	manpage for details.
1048		1378
1049	=item aio_pathsync $path, $callback->($status)	1379	=item aio_pathsync $pathname, $callback->($status)
1050		1380
1051	This request tries to open, fsync and close the given path. This is a	1381	This request tries to open, fsync and close the given path. This is a
1052	composite request intended to sync directories after directory operations	1382	composite request intended to sync directories after directory operations
1053	(E.g. rename). This might not work on all operating systems or have any	1383	(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	1384	specific effect, but usually it makes sure that directory changes get
…		…
1085	};	1415	};
1086		1416
1087	$grp	1417	$grp
1088	}	1418	}
1089		1419
1090	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1420	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1091		1421
1092	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1422	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	1423	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	1424	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	1425	scalar must only be modified in-place while an aio operation is pending on
…		…
1097		1427
1098	It calls the C<msync> function of your OS, if available, with the memory	1428	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	1429	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>	1430	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	1431	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	1432	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1103	C<IO::AIO::MS_SYNC>.	1433	C<IO::AIO::MS_INVALIDATE>.
1104		1434
1105	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1435	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1106		1436
1107	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1437	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1108	scalars.	1438	scalars.
1109		1439
1110	It touches (reads or writes) all memory pages in the specified	1440	It touches (reads or writes) all memory pages in the specified
1111	range inside the scalar. All caveats and parameters are the same	1441	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	1442	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	1443	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	1444	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1115	writing an octet from it, which dirties the page).	1445	writing an octet from it, which dirties the page).
1116		1446
1117	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1447	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1118		1448
1119	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1449	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;	1468	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1139	aio_mlock $data; # mlock in background	1469	aio_mlock $data; # mlock in background
1140		1470
1141	=item aio_mlockall $flags, $callback->($status)	1471	=item aio_mlockall $flags, $callback->($status)
1142		1472
1143	Calls the C<mlockall> function with the given C<$flags> (a combination of	1473	Calls the C<mlockall> function with the given C<$flags> (a
1144	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).	1474	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1475	C<IO::AIO::MCL_ONFAULT>).
1145		1476
1146	On systems that do not implement C<mlockall>, this function returns C<-1>	1477	On systems that do not implement C<mlockall>, this function returns C<-1>
1147	and sets errno to C<ENOSYS>.	1478	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1479	by the system result in a return value of C<-1> with errno being set to
		1480	C<EINVAL>.
1148		1481
1149	Note that the corresponding C<munlockall> is synchronous and is	1482	Note that the corresponding C<munlockall> is synchronous and is
1150	documented under L<MISCELLANEOUS FUNCTIONS>.	1483	documented under L<MISCELLANEOUS FUNCTIONS>.
1151		1484
1152	Example: asynchronously lock all current and future pages into memory.	1485	Example: asynchronously lock all current and future pages into memory.
1153		1486
1154	aio_mlockall IO::AIO::MCL_FUTURE;	1487	aio_mlockall IO::AIO::MCL_FUTURE;
		1488
		1489	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1490
		1491	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1492	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1493	the ioctl is not available on your OS, then this request will fail with
		1494	C<ENOSYS>.
		1495
		1496	C<$start> is the starting offset to query extents for, C<$length> is the
		1497	size of the range to query - if it is C<undef>, then the whole file will
		1498	be queried.
		1499
		1500	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1501	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1502	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1503	the data portion.
		1504
		1505	C<$count> is the maximum number of extent records to return. If it is
		1506	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1507	case, if it is C<0>, then the callback receives the number of extents
		1508	instead of the extents themselves (which is unreliable, see below).
		1509
		1510	If an error occurs, the callback receives no arguments. The special
		1511	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1512
		1513	Otherwise, the callback receives an array reference with extent
		1514	structures. Each extent structure is an array reference itself, with the
		1515	following members:
		1516
		1517	[$logical, $physical, $length, $flags]
		1518
		1519	Flags is any combination of the following flag values (typically either C<0>
		1520	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1521
		1522	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1523	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1524	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1525	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1526	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1527	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1528
		1529	At the time of this writing (Linux 3.2), this request is unreliable unless
		1530	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1531	it to return all extents of a range for files with a large number of
		1532	extents. The code (only) works around all these issues if C<$count> is
		1533	C<undef>.
1155		1534
1156	=item aio_group $callback->(...)	1535	=item aio_group $callback->(...)
1157		1536
1158	This is a very special aio request: Instead of doing something, it is a	1537	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	1538	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	1575	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	1576	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.	1577	except to put your application under artificial I/O pressure.
1199		1578
1200	=back	1579	=back
		1580
		1581
		1582	=head2 IO::AIO::WD - multiple working directories
		1583
		1584	Your process only has one current working directory, which is used by all
		1585	threads. This makes it hard to use relative paths (some other component
		1586	could call C<chdir> at any time, and it is hard to control when the path
		1587	will be used by IO::AIO).
		1588
		1589	One solution for this is to always use absolute paths. This usually works,
		1590	but can be quite slow (the kernel has to walk the whole path on every
		1591	access), and can also be a hassle to implement.
		1592
		1593	Newer POSIX systems have a number of functions (openat, fdopendir,
		1594	futimensat and so on) that make it possible to specify working directories
		1595	per operation.
		1596
		1597	For portability, and because the clowns who "designed", or shall I write,
		1598	perpetrated this new interface were obviously half-drunk, this abstraction
		1599	cannot be perfect, though.
		1600
		1601	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1602	object. This object stores the canonicalised, absolute version of the
		1603	path, and on systems that allow it, also a directory file descriptor.
		1604
		1605	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1606	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1607	object and a pathname instead (or the IO::AIO::WD object alone, which
		1608	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1609	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1610	to that IO::AIO::WD object.
		1611
		1612	For example, to get a wd object for F</etc> and then stat F<passwd>
		1613	inside, you would write:
		1614
		1615	aio_wd "/etc", sub {
		1616	my $etcdir = shift;
		1617
		1618	# although $etcdir can be undef on error, there is generally no reason
		1619	# to check for errors here, as aio_stat will fail with ENOENT
		1620	# when $etcdir is undef.
		1621
		1622	aio_stat [$etcdir, "passwd"], sub {
		1623	# yay
		1624	};
		1625	};
		1626
		1627	The fact that C<aio_wd> is a request and not a normal function shows that
		1628	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1629	which is why it is done asynchronously.
		1630
		1631	To stat the directory obtained with C<aio_wd> above, one could write
		1632	either of the following three request calls:
		1633
		1634	aio_lstat "/etc" , sub { ... # pathname as normal string
		1635	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1636	aio_lstat $wd , sub { ... # shorthand for the previous
		1637
		1638	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1639	object and the pathname string, so you could write the following without
		1640	causing any issues due to C<$path> getting reused:
		1641
		1642	my $path = [$wd, undef];
		1643
		1644	for my $name (qw(abc def ghi)) {
		1645	$path->[1] = $name;
		1646	aio_stat $path, sub {
		1647	# ...
		1648	};
		1649	}
		1650
		1651	There are some caveats: when directories get renamed (or deleted), the
		1652	pathname string doesn't change, so will point to the new directory (or
		1653	nowhere at all), while the directory fd, if available on the system,
		1654	will still point to the original directory. Most functions accepting a
		1655	pathname will use the directory fd on newer systems, and the string on
		1656	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1657	the string form of the pathname.
		1658
		1659	So this functionality is mainly useful to get some protection against
		1660	C<chdir>, to easily get an absolute path out of a relative path for future
		1661	reference, and to speed up doing many operations in the same directory
		1662	(e.g. when stat'ing all files in a directory).
		1663
		1664	The following functions implement this working directory abstraction:
		1665
		1666	=over 4
		1667
		1668	=item aio_wd $pathname, $callback->($wd)
		1669
		1670	Asynchonously canonicalise the given pathname and convert it to an
		1671	IO::AIO::WD object representing it. If possible and supported on the
		1672	system, also open a directory fd to speed up pathname resolution relative
		1673	to this working directory.
		1674
		1675	If something goes wrong, then C<undef> is passwd to the callback instead
		1676	of a working directory object and C<$!> is set appropriately. Since
		1677	passing C<undef> as working directory component of a pathname fails the
		1678	request with C<ENOENT>, there is often no need for error checking in the
		1679	C<aio_wd> callback, as future requests using the value will fail in the
		1680	expected way.
		1681
		1682	=item IO::AIO::CWD
		1683
		1684	This is a compile time constant (object) that represents the process
		1685	current working directory.
		1686
		1687	Specifying this object as working directory object for a pathname is as if
		1688	the pathname would be specified directly, without a directory object. For
		1689	example, these calls are functionally identical:
		1690
		1691	aio_stat "somefile", sub { ... };
		1692	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1693
		1694	=back
		1695
		1696	To recover the path associated with an IO::AIO::WD object, you can use
		1697	C<aio_realpath>:
		1698
		1699	aio_realpath $wd, sub {
		1700	warn "path is $_[0]\n";
		1701	};
		1702
		1703	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1704	sometimes, fall back to using an absolue path.
1201		1705
1202	=head2 IO::AIO::REQ CLASS	1706	=head2 IO::AIO::REQ CLASS
1203		1707
1204	All non-aggregate C<aio_*> functions return an object of this class when	1708	All non-aggregate C<aio_*> functions return an object of this class when
1205	called in non-void context.	1709	called in non-void context.
…		…
1323		1827
1324	Sets a feeder/generator on this group: every group can have an attached	1828	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,	1829	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,	1830	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,	1831	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,	1832	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1329	delaying any later requests for a long time.	1833	requests, delaying any later requests for a long time.
1330		1834
1331	To avoid this, and allow incremental generation of requests, you can	1835	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	1836	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>,	1837	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	1838	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	1870	The default value for the limit is C<0>, but note that setting a feeder
1367	automatically bumps it up to C<2>.	1871	automatically bumps it up to C<2>.
1368		1872
1369	=back	1873	=back
1370		1874
		1875
1371	=head2 SUPPORT FUNCTIONS	1876	=head2 SUPPORT FUNCTIONS
1372		1877
1373	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1878	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1374		1879
1375	=over 4	1880	=over 4
…		…
1383		1888
1384	See C<poll_cb> for an example.	1889	See C<poll_cb> for an example.
1385		1890
1386	=item IO::AIO::poll_cb	1891	=item IO::AIO::poll_cb
1387		1892
1388	Process some outstanding events on the result pipe. You have to call this	1893	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	1894	been executed but the results are not yet reported). You have to call
1390	returned earlier for whatever reason. Returns immediately when no events	1895	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		1896
		1897	Returns C<0> if all events could be processed (or there were no
		1898	events to process), or C<-1> if it returned earlier for whatever
		1899	reason. Returns immediately when no events are outstanding. The amount
		1900	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1901	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1902
1394	If not all requests were processed for whatever reason, the filehandle	1903	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	1904	descriptor will still be ready when C<poll_cb> returns, so normally you
1396	do anything special to have it called later.	1905	don't have to do anything special to have it called later.
		1906
		1907	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1908	ready, it can be beneficial to call this function from loops which submit
		1909	a lot of requests, to make sure the results get processed when they become
		1910	available and not just when the loop is finished and the event loop takes
		1911	over again. This function returns very fast when there are no outstanding
		1912	requests.
1397		1913
1398	Example: Install an Event watcher that automatically calls	1914	Example: Install an Event watcher that automatically calls
1399	IO::AIO::poll_cb with high priority (more examples can be found in the	1915	IO::AIO::poll_cb with high priority (more examples can be found in the
1400	SYNOPSIS section, at the top of this document):	1916	SYNOPSIS section, at the top of this document):
1401		1917
…		…
1403	poll => 'r', async => 1,	1919	poll => 'r', async => 1,
1404	cb => \&IO::AIO::poll_cb);	1920	cb => \&IO::AIO::poll_cb);
1405		1921
1406	=item IO::AIO::poll_wait	1922	=item IO::AIO::poll_wait
1407		1923
1408	If there are any outstanding requests and none of them in the result	1924	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	1925	requests are outstanding anymore.
1410	does a C<select> on the filehandle. This is useful if you want to	1926
1411	synchronously wait for some requests to finish).	1927	This is useful if you want to synchronously wait for some requests to
		1928	become ready, without actually handling them.
1412		1929
1413	See C<nreqs> for an example.	1930	See C<nreqs> for an example.
1414		1931
1415	=item IO::AIO::poll	1932	=item IO::AIO::poll
1416		1933
…		…
1427		1944
1428	Strictly equivalent to:	1945	Strictly equivalent to:
1429		1946
1430	IO::AIO::poll_wait, IO::AIO::poll_cb	1947	IO::AIO::poll_wait, IO::AIO::poll_cb
1431	while IO::AIO::nreqs;	1948	while IO::AIO::nreqs;
		1949
		1950	This function can be useful at program aborts, to make sure outstanding
		1951	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1952	this function on normal exits), or when you are merely using C<IO::AIO>
		1953	for its more advanced functions, rather than for async I/O, e.g.:
		1954
		1955	my ($dirs, $nondirs);
		1956	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1957	IO::AIO::flush;
		1958	# $dirs, $nondirs are now set
1432		1959
1433	=item IO::AIO::max_poll_reqs $nreqs	1960	=item IO::AIO::max_poll_reqs $nreqs
1434		1961
1435	=item IO::AIO::max_poll_time $seconds	1962	=item IO::AIO::max_poll_time $seconds
1436		1963
…		…
1463	poll => 'r', nice => 1,	1990	poll => 'r', nice => 1,
1464	cb => &IO::AIO::poll_cb);	1991	cb => &IO::AIO::poll_cb);
1465		1992
1466	=back	1993	=back
1467		1994
		1995
1468	=head3 CONTROLLING THE NUMBER OF THREADS	1996	=head3 CONTROLLING THE NUMBER OF THREADS
1469		1997
1470	=over	1998	=over
1471		1999
1472	=item IO::AIO::min_parallel $nthreads	2000	=item IO::AIO::min_parallel $nthreads
…		…
1503		2031
1504	Under normal circumstances you don't need to call this function.	2032	Under normal circumstances you don't need to call this function.
1505		2033
1506	=item IO::AIO::max_idle $nthreads	2034	=item IO::AIO::max_idle $nthreads
1507		2035
1508	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2036	Limit the number of threads (default: 4) that are allowed to idle
1509	threads that did not get a request to process within 10 seconds). That	2037	(i.e., threads that did not get a request to process within the idle
1510	means if a thread becomes idle while C<$nthreads> other threads are also	2038	timeout (default: 10 seconds). That means if a thread becomes idle while
1511	idle, it will free its resources and exit.	2039	C<$nthreads> other threads are also idle, it will free its resources and
		2040	exit.
1512		2041
1513	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2042	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	2043	to allow for extremely high load situations, but want to free resources
1515	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2044	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1516		2045
1517	The default is probably ok in most situations, especially if thread	2046	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	2047	creation is fast. If thread creation is very slow on your system you might
1519	want to use larger values.	2048	want to use larger values.
1520		2049
		2050	=item IO::AIO::idle_timeout $seconds
		2051
		2052	Sets the minimum idle timeout (default 10) after which worker threads are
		2053	allowed to exit. SEe C<IO::AIO::max_idle>.
		2054
1521	=item IO::AIO::max_outstanding $maxreqs	2055	=item IO::AIO::max_outstanding $maxreqs
		2056
		2057	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2058	you do queue up more than this number of requests, the next call to
		2059	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2060	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2061	longer exceeded.
		2062
		2063	In other words, this setting does not enforce a queue limit, but can be
		2064	used to make poll functions block if the limit is exceeded.
1522		2065
1523	This is a very bad function to use in interactive programs because it	2066	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	2067	blocks, and a bad way to reduce concurrency because it is inexact: Better
1525	use an C<aio_group> together with a feed callback.	2068	use an C<aio_group> together with a feed callback.
1526		2069
1527	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2070	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	2071	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		2072
1532	The default value is very large, so there is no practical limit on the	2073	IO::AIO::max_outstanding 32;
1533	number of outstanding requests.
1534		2074
1535	You can still queue as many requests as you want. Therefore,	2075	for my $path (...) {
1536	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2076	aio_stat $path , ...;
1537	as a stop gap to shield against fatal memory overflow (with large values).	2077	IO::AIO::poll_cb;
		2078	}
		2079
		2080	IO::AIO::flush;
		2081
		2082	The call to C<poll_cb> inside the loop will normally return instantly, but
		2083	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2084	some requests have been handled. This keeps the loop from pushing a large
		2085	number of C<aio_stat> requests onto the queue.
		2086
		2087	The default value for C<max_outstanding> is very large, so there is no
		2088	practical limit on the number of outstanding requests.
1538		2089
1539	=back	2090	=back
		2091
1540		2092
1541	=head3 STATISTICAL INFORMATION	2093	=head3 STATISTICAL INFORMATION
1542		2094
1543	=over	2095	=over
1544		2096
…		…
1562	Returns the number of requests currently in the pending state (executed,	2114	Returns the number of requests currently in the pending state (executed,
1563	but not yet processed by poll_cb).	2115	but not yet processed by poll_cb).
1564		2116
1565	=back	2117	=back
1566		2118
		2119
		2120	=head3 SUBSECOND STAT TIME ACCESS
		2121
		2122	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2123	generally find access/modification and change times with subsecond time
		2124	accuracy of the system supports it, but perl's built-in functions only
		2125	return the integer part.
		2126
		2127	The following functions return the timestamps of the most recent
		2128	stat with subsecond precision on most systems and work both after
		2129	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2130	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2131	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2132
		2133	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2134	full resolution without rounding and work with standard perl C<stat>,
		2135	alleviating the need to call the special C<Time::HiRes> functions, which
		2136	do not act like their perl counterparts.
		2137
		2138	On operating systems or file systems where subsecond time resolution is
		2139	not supported or could not be detected, a fractional part of C<0> is
		2140	returned, so it is always safe to call these functions.
		2141
		2142	=over 4
		2143
		2144	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2145
		2146	Return the access, modication, change or birth time, respectively,
		2147	including fractional part. Due to the limited precision of floating point,
		2148	the accuracy on most platforms is only a bit better than milliseconds
		2149	for times around now - see the I<nsec> function family, below, for full
		2150	accuracy.
		2151
		2152	File birth time is only available when the OS and perl support it (on
		2153	FreeBSD and NetBSD at the time of this writing, although support is
		2154	adaptive, so if your OS/perl gains support, IO::AIO can take advantage of
		2155	it). On systems where it isn't available, C<0> is currently returned, but
		2156	this might change to C<undef> in a future version.
		2157
		2158	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2159
		2160	Returns access, modification, change and birth time all in one go, and
		2161	maybe more times in the future version.
		2162
		2163	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2164
		2165	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2166	as an integer in the range C<0> to C<999999999>.
		2167
		2168	Note that no accessors are provided for access, modification and
		2169	change times - you need to get those from C<stat _> if required (C<int
		2170	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2171	value).
		2172
		2173	=item $seconds = IO::AIO::st_btimesec
		2174
		2175	The (integral) seconds part of the file birth time, if available.
		2176
		2177	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2178
		2179	Like the functions above, but returns all four times in one go (and maybe
		2180	more in future versions).
		2181
		2182	=item $counter = IO::AIO::st_gen
		2183
		2184	Returns the generation counter (in practice this is just a random number)
		2185	of the file. This is only available on platforms which have this member in
		2186	their C<struct stat> (most BSDs at the time of this writing) and generally
		2187	only to the root usert. If unsupported, C<0> is returned, but this might
		2188	change to C<undef> in a future version.
		2189
		2190	=back
		2191
		2192	Example: print the high resolution modification time of F</etc>, using
		2193	C<stat>, and C<IO::AIO::aio_stat>.
		2194
		2195	if (stat "/etc") {
		2196	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2197	}
		2198
		2199	IO::AIO::aio_stat "/etc", sub {
		2200	$_[0]
		2201	and return;
		2202
		2203	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2204	};
		2205
		2206	IO::AIO::flush;
		2207
		2208	Output of the awbove on my system, showing reduced and full accuracy:
		2209
		2210	stat(/etc) mtime: 1534043702.020808
		2211	aio_stat(/etc) mtime: 1534043702.020807792
		2212
		2213
1567	=head3 MISCELLANEOUS FUNCTIONS	2214	=head3 MISCELLANEOUS FUNCTIONS
1568		2215
1569	IO::AIO implements some functions that might be useful, but are not	2216	IO::AIO implements some functions that are useful when you want to use
1570	asynchronous.	2217	some "Advanced I/O" function not available to in Perl, without going the
		2218	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2219	counterpart.
1571		2220
1572	=over 4	2221	=over 4
		2222
		2223	=item $numfd = IO::AIO::get_fdlimit
		2224
		2225	This function is I<EXPERIMENTAL> and subject to change.
		2226
		2227	Tries to find the current file descriptor limit and returns it, or
		2228	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2229	the highest valid file descriptor number.
		2230
		2231	=item IO::AIO::min_fdlimit [$numfd]
		2232
		2233	This function is I<EXPERIMENTAL> and subject to change.
		2234
		2235	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2236	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2237	is missing, it will try to set a very high limit, although this is not
		2238	recommended when you know the actual minimum that you require.
		2239
		2240	If the limit cannot be raised enough, the function makes a best-effort
		2241	attempt to increase the limit as much as possible, using various
		2242	tricks, while still failing. You can query the resulting limit using
		2243	C<IO::AIO::get_fdlimit>.
		2244
		2245	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2246	true.
1573		2247
1574	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2248	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1575		2249
1576	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2250	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	2251	but is blocking (this makes most sense if you know the input data is
…		…
1580		2254
1581	Returns the number of bytes copied, or C<-1> on error.	2255	Returns the number of bytes copied, or C<-1> on error.
1582		2256
1583	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2257	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1584		2258
1585	Simply calls the C<posix_fadvise> function (see it's	2259	Simply calls the C<posix_fadvise> function (see its
1586	manpage for details). The following advice constants are	2260	manpage for details). The following advice constants are
1587	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2261	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1588	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2262	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1589	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2263	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1590		2264
1591	On systems that do not implement C<posix_fadvise>, this function returns	2265	On systems that do not implement C<posix_fadvise>, this function returns
1592	ENOSYS, otherwise the return value of C<posix_fadvise>.	2266	ENOSYS, otherwise the return value of C<posix_fadvise>.
1593		2267
		2268	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2269
		2270	Simply calls the C<posix_madvise> function (see its
		2271	manpage for details). The following advice constants are
		2272	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2273	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2274	C<IO::AIO::MADV_DONTNEED>.
		2275
		2276	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2277	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2278	will be reduced to fit into the C<$scalar>.
		2279
		2280	On systems that do not implement C<posix_madvise>, this function returns
		2281	ENOSYS, otherwise the return value of C<posix_madvise>.
		2282
		2283	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2284
		2285	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2286	$scalar (see its manpage for details). The following protect
		2287	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2288	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2289
		2290	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2291	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2292	will be reduced to fit into the C<$scalar>.
		2293
		2294	On systems that do not implement C<mprotect>, this function returns
		2295	ENOSYS, otherwise the return value of C<mprotect>.
		2296
1594	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2297	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1595		2298
1596	Memory-maps a file (or anonymous memory range) and attaches it to the	2299	Memory-maps a file (or anonymous memory range) and attaches it to the
1597	given C<$scalar>, which will act like a string scalar.	2300	given C<$scalar>, which will act like a string scalar. Returns true on
		2301	success, and false otherwise.
1598		2302
		2303	The scalar must exist, but its contents do not matter - this means you
		2304	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2305	the scalar first.
		2306
1599	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2307	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1600	change the string length, and most read-only operations such as copying it	2308	which don't change the string length, and most read-only operations such
1601	or searching it with regexes and so on.	2309	as copying it or searching it with regexes and so on.
1602		2310
1603	Anything else is unsafe and will, at best, result in memory leaks.	2311	Anything else is unsafe and will, at best, result in memory leaks.
1604		2312
1605	The memory map associated with the C<$scalar> is automatically removed	2313	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	2314	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1607	C<IO::AIO::munmap> functions are called.	2315	or C<IO::AIO::munmap> functions are called on it.
1608		2316
1609	This calls the C<mmap>(2) function internally. See your system's manual	2317	This calls the C<mmap>(2) function internally. See your system's manual
1610	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2318	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1611		2319
1612	The C<$length> must be larger than zero and smaller than the actual	2320	The C<$length> must be larger than zero and smaller than the actual
1613	filesize.	2321	filesize.
1614		2322
1615	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2323	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1616	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2324	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1617		2325
1618	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2326	C<$flags> can be a combination of
1619	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2327	C<IO::AIO::MAP_SHARED> or
1620	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2328	C<IO::AIO::MAP_PRIVATE>,
		2329	or a number of system-specific flags (when not available, the are C<0>):
1621	(which is set to C<MAP_ANON> if your system only provides this	2330	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1622	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2331	C<IO::AIO::MAP_LOCKED>,
1623	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2332	C<IO::AIO::MAP_NORESERVE>,
		2333	C<IO::AIO::MAP_POPULATE>,
1624	C<IO::AIO::MAP_NONBLOCK>	2334	C<IO::AIO::MAP_NONBLOCK>,
		2335	C<IO::AIO::MAP_FIXED>,
		2336	C<IO::AIO::MAP_GROWSDOWN>,
		2337	C<IO::AIO::MAP_32BIT>,
		2338	C<IO::AIO::MAP_HUGETLB> or
		2339	C<IO::AIO::MAP_STACK>.
1625		2340
1626	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2341	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1627		2342
1628	C<$offset> is the offset from the start of the file - it generally must be	2343	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>.	2344	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1643		2358
1644	=item IO::AIO::munmap $scalar	2359	=item IO::AIO::munmap $scalar
1645		2360
1646	Removes a previous mmap and undefines the C<$scalar>.	2361	Removes a previous mmap and undefines the C<$scalar>.
1647		2362
		2363	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2364
		2365	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2366	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2367	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2368
		2369	Returns true if successful, and false otherwise. If the underlying mmapped
		2370	region has changed address, then the true value has the numerical value
		2371	C<1>, otherwise it has the numerical value C<0>:
		2372
		2373	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2374	or die "mremap: $!";
		2375
		2376	if ($success*1) {
		2377	warn "scalar has chanegd address in memory\n";
		2378	}
		2379
		2380	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2381	implemented, but not supported and might go away in a future version.
		2382
		2383	On systems where this call is not supported or is not emulated, this call
		2384	returns falls and sets C<$!> to C<ENOSYS>.
		2385
		2386	=item IO::AIO::mlockall $flags
		2387
		2388	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2389	but is blocking.
		2390
1648	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2391	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1649		2392
1650	Calls the C<munlock> function, undoing the effects of a previous	2393	Calls the C<munlock> function, undoing the effects of a previous
1651	C<aio_mlock> call (see its description for details).	2394	C<aio_mlock> call (see its description for details).
1652		2395
…		…
1654		2397
1655	Calls the C<munlockall> function.	2398	Calls the C<munlockall> function.
1656		2399
1657	On systems that do not implement C<munlockall>, this function returns	2400	On systems that do not implement C<munlockall>, this function returns
1658	ENOSYS, otherwise the return value of C<munlockall>.	2401	ENOSYS, otherwise the return value of C<munlockall>.
		2402
		2403	=item $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
		2404
		2405	Uses the GNU/Linux C<accept4(2)> syscall, if available, to accept a socket
		2406	and return the new file handle on success, or sets C<$!> and returns
		2407	C<undef> on error.
		2408
		2409	The remote name of the new socket will be stored in C<$sockaddr>, which
		2410	will be extended to allow for at least C<$sockaddr_maxlen> octets. If the
		2411	socket name does not fit into C<$sockaddr_maxlen> octets, this is signaled
		2412	by returning a longer string in C<$sockaddr>, which might or might not be
		2413	truncated.
		2414
		2415	To accept name-less sockets, use C<undef> for C<$sockaddr> and C<0> for
		2416	C<$sockaddr_maxlen>.
		2417
		2418	The main reasons to use this syscall rather than portable C«accept(2)>
		2419	are that you can specify C<SOCK_NONBLOCK> and/or C<SOCK_CLOEXEC>
		2420	flags and you can accept name-less sockets by specifying C<0> for
		2421	C<$sockaddr_maxlen>, which is sadly not possible with perl's interface to
		2422	C<accept>.
		2423
		2424	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2425
		2426	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2427	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2428	should be the file offset.
		2429
		2430	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2431	silently corrupt the data in this case.
		2432
		2433	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2434	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2435	C<IO::AIO::SPLICE_F_GIFT>.
		2436
		2437	See the C<splice(2)> manpage for details.
		2438
		2439	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2440
		2441	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2442	description for C<IO::AIO::splice> above for details.
		2443
		2444	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2445
		2446	Attempts to query or change the pipe buffer size. Obviously works only
		2447	on pipes, and currently works only on GNU/Linux systems, and fails with
		2448	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2449	size on other systems, drop me a note.
		2450
		2451	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2452
		2453	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2454	C<$flags> is missing or C<0>, then this should be the same as a call to
		2455	perl's built-in C<pipe> function and create a new pipe, and works on
		2456	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2457	(..., 4096, O_BINARY)>.
		2458
		2459	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2460	the given flags (Linux 2.6.27, glibc 2.9).
		2461
		2462	On success, the read and write file handles are returned.
		2463
		2464	On error, nothing will be returned. If the pipe2 syscall is missing and
		2465	C<$flags> is non-zero, fails with C<ENOSYS>.
		2466
		2467	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2468	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2469	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2470
		2471	Example: create a pipe race-free w.r.t. threads and fork:
		2472
		2473	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2474	or die "pipe2: $!\n";
		2475
		2476	=item $fh = IO::AIO::memfd_create $pathname[, $flags]
		2477
		2478	This is a direct interface to the Linux L<memfd_create(2)> system
		2479	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2480	should be C<IO::AIO::MFD_CLOEXEC>.
		2481
		2482	On success, the new memfd filehandle is returned, otherwise returns
		2483	C<undef>. If the memfd_create syscall is missing, fails with C<ENOSYS>.
		2484
		2485	Please refer to L<memfd_create(2)> for more info on this call.
		2486
		2487	The following C<$flags> values are available: C<IO::AIO::MFD_CLOEXEC>,
		2488	C<IO::AIO::MFD_ALLOW_SEALING> and C<IO::AIO::MFD_HUGETLB>.
		2489
		2490	Example: create a new memfd.
		2491
		2492	my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
		2493	or die "m,emfd_create: $!\n";
		2494	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2495
		2496	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2497	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2498
		2499	On success, the new eventfd filehandle is returned, otherwise returns
		2500	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2501
		2502	Please refer to L<eventfd(2)> for more info on this call.
		2503
		2504	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2505	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2506
		2507	Example: create a new eventfd filehandle:
		2508
		2509	$fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
		2510	or die "eventfd: $!\n";
		2511
		2512	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2513
		2514	This is a direct interface to the Linux L<timerfd_create(2)> system
		2515	call. The (unhelpful) default for C<$flags> is C<0>, but your default
		2516	should be C<IO::AIO::TFD_CLOEXEC>.
		2517
		2518	On success, the new timerfd filehandle is returned, otherwise returns
		2519	C<undef>. If the timerfd_create syscall is missing, fails with C<ENOSYS>.
		2520
		2521	Please refer to L<timerfd_create(2)> for more info on this call.
		2522
		2523	The following C<$clockid> values are
		2524	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2525	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2526	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2527	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2528
		2529	The following C<$flags> values are available (Linux
		2530	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2531
		2532	Example: create a new timerfd and set it to one-second repeated alarms,
		2533	then wait for two alarms:
		2534
		2535	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2536	or die "timerfd_create: $!\n";
		2537
		2538	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2539	or die "timerfd_settime: $!\n";
		2540
		2541	for (1..2) {
		2542	8 == sysread $fh, my $buf, 8
		2543	or die "timerfd read failure\n";
		2544
		2545	printf "number of expirations (likely 1): %d\n",
		2546	unpack "Q", $buf;
		2547	}
		2548
		2549	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2550
		2551	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2552	call. Please refer to its manpage for more info on this call.
		2553
		2554	The new itimerspec is specified using two (possibly fractional) second
		2555	values, C<$new_interval> and C<$new_value>).
		2556
		2557	On success, the current interval and value are returned (as per
		2558	C<timerfd_gettime>). On failure, the empty list is returned.
		2559
		2560	The following C<$flags> values are
		2561	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2562	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2563
		2564	See C<IO::AIO::timerfd_create> for a full example.
		2565
		2566	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2567
		2568	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2569	call. Please refer to its manpage for more info on this call.
		2570
		2571	On success, returns the current values of interval and value for the given
		2572	timerfd (as potentially fractional second values). On failure, the empty
		2573	list is returned.
1659		2574
1660	=back	2575	=back
1661		2576
1662	=cut	2577	=cut
1663		2578
…		…
1698	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2613	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1699	\&IO::AIO::poll_cb);	2614	\&IO::AIO::poll_cb);
1700		2615
1701	=head2 FORK BEHAVIOUR	2616	=head2 FORK BEHAVIOUR
1702		2617
1703	This module should do "the right thing" when the process using it forks:	2618	Usage of pthreads in a program changes the semantics of fork
		2619	considerably. Specifically, only async-safe functions can be called after
		2620	fork. Perl doesn't know about this, so in general, you cannot call fork
		2621	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2622	pthreads, so this applies, but many other extensions and (for inexplicable
		2623	reasons) perl itself often is linked against pthreads, so this limitation
		2624	applies to quite a lot of perls.
1704		2625
1705	Before the fork, IO::AIO enters a quiescent state where no requests	2626	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	2627	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	2628	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		2629
1713	In short: the parent will, after a short pause, continue as if fork had	2630	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	2631	forking. You could also try to call the L<IO::AIO::reinit> function in the
1715	yet.	2632	child:
		2633
		2634	=over 4
		2635
		2636	=item IO::AIO::reinit
		2637
		2638	Abandons all current requests and I/O threads and simply reinitialises all
		2639	data structures. This is not an operation supported by any standards, but
		2640	happens to work on GNU/Linux and some newer BSD systems.
		2641
		2642	The only reasonable use for this function is to call it after forking, if
		2643	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2644	the process will result in undefined behaviour. Calling it at any time
		2645	will also result in any undefined (by POSIX) behaviour.
		2646
		2647	=back
		2648
		2649	=head2 LINUX-SPECIFIC CALLS
		2650
		2651	When a call is documented as "linux-specific" then this means it
		2652	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2653	availability and compatibility of such calls regardless of the platform
		2654	it is compiled on, so platforms such as FreeBSD which often implement
		2655	these calls will work. When in doubt, call them and see if they fail wth
		2656	C<ENOSYS>.
1716		2657
1717	=head2 MEMORY USAGE	2658	=head2 MEMORY USAGE
1718		2659
1719	Per-request usage:	2660	Per-request usage:
1720		2661
…		…
1733	temporary buffers, and each thread requires a stack and other data	2674	temporary buffers, and each thread requires a stack and other data
1734	structures (usually around 16k-128k, depending on the OS).	2675	structures (usually around 16k-128k, depending on the OS).
1735		2676
1736	=head1 KNOWN BUGS	2677	=head1 KNOWN BUGS
1737		2678
1738	Known bugs will be fixed in the next release.	2679	Known bugs will be fixed in the next release :)
		2680
		2681	=head1 KNOWN ISSUES
		2682
		2683	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2684	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2685	non-created hash slots or other scalars I didn't think of. It's best to
		2686	avoid such and either use scalar variables or making sure that the scalar
		2687	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2688
		2689	I am not sure anything can be done about this, so this is considered a
		2690	known issue, rather than a bug.
1739		2691
1740	=head1 SEE ALSO	2692	=head1 SEE ALSO
1741		2693
1742	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2694	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1743	more natural syntax.	2695	more natural syntax and L<IO::FDPass> for file descriptor passing.
1744		2696
1745	=head1 AUTHOR	2697	=head1 AUTHOR
1746		2698
1747	Marc Lehmann <schmorp@schmorp.de>	2699	Marc Lehmann <schmorp@schmorp.de>
1748	http://home.schmorp.de/	2700	http://home.schmorp.de/

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