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Revision 1.156 by root, Tue Jun 16 23:41:59 2009 UTC vs.
Revision 1.288 by root, Tue Jul 31 22:27:49 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
25	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53		30
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports. It is implemented as an interface to C<libeio>	34	operating system supports. It is implemented as an interface to C<libeio>
…		…
81	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
82	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
83	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
84	using threads anyway.	61	using threads anyway.
85		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
86	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,
87	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
88	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
89	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
90		71
91	=head2 EXAMPLE	72	=head2 EXAMPLE
92		73
93	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
94	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
95		76
96	use Fcntl;
97	use EV;	77	use EV;
98	use IO::AIO;	78	use IO::AIO;
99		79
100	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
101	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;
102		82
103	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
104	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
105	my $fh = shift	85	my $fh = shift
106	or die "error while opening: $!";	86	or die "error while opening: $!";
107		87
108	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
109	my $size = -s $fh;	89	my $size = -s $fh;
…		…
118		98
119	# file contents now in $contents	99	# file contents now in $contents
120	print $contents;	100	print $contents;
121		101
122	# exit event loop and program	102	# exit event loop and program
123	EV::unloop;	103	EV::break;
124	};	104	};
125	};	105	};
126		106
127	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
128	# check for sockets etc. etc.	108	# check for sockets etc. etc.
129		109
130	# process events as long as there are some:	110	# process events as long as there are some:
131	EV::loop;	111	EV::run;
132		112
133	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
134		114
135	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
136	directly visible to Perl.	116	directly visible to Perl.
…		…
186		166
187	package IO::AIO;	167	package IO::AIO;
188		168
189	use Carp ();	169	use Carp ();
190		170
191	no warnings;	171	use common::sense;
192	use strict 'vars';
193		172
194	use base 'Exporter';	173	use base 'Exporter';
195		174
196	BEGIN {	175	BEGIN {
197	our $VERSION = '3.23';	176	our $VERSION = 4.5;
198		177
199	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
200	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
201	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
202	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
203	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
204	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
205	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
206		190
207	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
208	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
209	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
210	nreqs nready npending nthreads	194	nreqs nready npending nthreads
211	max_poll_time max_poll_reqs);	195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap mremap munlock munlockall);
212		198
213	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
214		200
215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
216		202
…		…
218	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
219	}	205	}
220		206
221	=head1 FUNCTIONS	207	=head1 FUNCTIONS
222		208
223	=head2 AIO REQUEST FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		285
		286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		291	IO::AIO::madvise $scalar, $offset, $length, $advice
		292	IO::AIO::mprotect $scalar, $offset, $length, $protect
		293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		294	IO::AIO::munlockall
		295
		296	=head2 API NOTES
224		297
225	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
226	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
227	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
228	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
229	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
230	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
231	syscall has been executed asynchronously.	304	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		305	most syscalls return C<-1> on error, unlike perl, which usually delivers
		306	"false").
		307
		308	Some requests (such as C<aio_readdir>) pass the actual results and
		309	communicate failures by passing C<undef>.
232		310
233	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
234	internally until the request has finished.	312	internally until the request has finished.
235		313
236	All functions return request objects of type L<IO::AIO::REQ> that allow	314	All functions return request objects of type L<IO::AIO::REQ> that allow
237	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
238		316
239	The pathnames you pass to these routines I<must> be absolute and	317	The pathnames you pass to these routines I<should> be absolute. The
240	encoded as octets. The reason for the former is that at the time the	318	reason for this is that at the time the request is being executed, the
241	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
242	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
243	current working directory anywhere in the program and then use relative	321	in the program and then use relative paths. You can also take advantage
244	paths.	322	of IO::AIOs working directory abstraction, that lets you specify paths
		323	relative to some previously-opened "working directory object" - see the
		324	description of the C<IO::AIO::WD> class later in this document.
245		325
246	To encode pathnames as octets, either make sure you either: a) always pass	326	To encode pathnames as octets, either make sure you either: a) always pass
247	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	328	tinkering, b) are in your native filesystem encoding, c) use the Encode
249	your pathnames to the locale (or other) encoding in effect in the user	329	module and encode your pathnames to the locale (or other) encoding in
250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	330	effect in the user environment, d) use Glib::filename_from_unicode on
251	use something else to ensure your scalar has the correct contents.	331	unicode filenames or e) use something else to ensure your scalar has the
		332	correct contents.
252		333
253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	334	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
254	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
255		338
256	=over 4	339	=over 4
257		340
258	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
259		342
…		…
289		372
290		373
291	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
292		375
293	Asynchronously open or create a file and call the callback with a newly	376	Asynchronously open or create a file and call the callback with a newly
294	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
295		378
296	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	379	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
297	for an explanation.	380	for an explanation.
298		381
299	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	382	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
306	by the umask in effect then the request is being executed, so better never	389	by the umask in effect then the request is being executed, so better never
307	change the umask.	390	change the umask.
308		391
309	Example:	392	Example:
310		393
311	aio_open "/etc/passwd", O_RDONLY, 0, sub {	394	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
312	if ($_[0]) {	395	if ($_[0]) {
313	print "open successful, fh is $_[0]\n";	396	print "open successful, fh is $_[0]\n";
314	...	397	...
315	} else {	398	} else {
316	die "open failed: $!\n";	399	die "open failed: $!\n";
317	}	400	}
318	};	401	};
319		402
		403	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		404	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		405	following POSIX and non-POSIX constants are available (missing ones on
		406	your system are, as usual, C<0>):
		407
		408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		411
320		412
321	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
322		414
323	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
324	code.	416	code.
…		…
333	Or in other words: the file descriptor will be closed, but it will not be	425	Or in other words: the file descriptor will be closed, but it will not be
334	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
335		427
336	=cut	428	=cut
337		429
		430	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		431
		432	Seeks the filehandle to the new C<$offset>, similarly to perl's
		433	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		434	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		435	C<IO::AIO::SEEK_END>).
		436
		437	The resulting absolute offset will be passed to the callback, or C<-1> in
		438	case of an error.
		439
		440	In theory, the C<$whence> constants could be different than the
		441	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		442	so don't panic.
		443
		444	As a GNU/Linux (and maybe Solaris) extension, also the constants
		445	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		446	could be found. No guarantees about suitability for use in C<aio_seek> or
		447	Perl's C<sysseek> can be made though, although I would naively assume they
		448	"just work".
		449
338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
339		451
340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
341		453
342	Reads or writes C<$length> bytes from or to the specified C<$fh> and	454	Reads or writes C<$length> bytes from or to the specified C<$fh> and
343	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	455	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
344	and calls the callback without the actual number of bytes read (or -1 on	456	calls the callback with the actual number of bytes transferred (or -1 on
345	error, just like the syscall).	457	error, just like the syscall).
346		458
347	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	459	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
348	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
349		461
…		…
374		486
375	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	487	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
376	reading at byte offset C<$in_offset>, and starts writing at the current	488	reading at byte offset C<$in_offset>, and starts writing at the current
377	file offset of C<$out_fh>. Because of that, it is not safe to issue more	489	file offset of C<$out_fh>. Because of that, it is not safe to issue more
378	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	490	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
379	other.	491	other. The same C<$in_fh> works fine though, as this function does not
		492	move or use the file offset of C<$in_fh>.
380		493
		494	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		495	are written, and there is no way to find out how many more bytes have been
		496	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		497	number of bytes written to C<$out_fh>. Only if the result value equals
		498	C<$length> one can assume that C<$length> bytes have been read.
		499
		500	Unlike with other C<aio_> functions, it makes a lot of sense to use
		501	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		502	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		503	the socket I/O will be non-blocking. Note, however, that you can run
		504	into a trap where C<aio_sendfile> reads some data with readahead, then
		505	fails to write all data, and when the socket is ready the next time, the
		506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		508	resource usage.
		509
381	This call tries to make use of a native C<sendfile> syscall to provide	510	This call tries to make use of a native C<sendfile>-like syscall to
382	zero-copy operation. For this to work, C<$out_fh> should refer to a	511	provide zero-copy operation. For this to work, C<$out_fh> should refer to
383	socket, and C<$in_fh> should refer to mmap'able file.	512	a socket, and C<$in_fh> should refer to an mmap'able file.
384		513
385	If the native sendfile call fails or is not implemented, it will be	514	If a native sendfile cannot be found or it fails with C<ENOSYS>,
386	emulated, so you can call C<aio_sendfile> on any type of filehandle	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		516	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
387	regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
388		518
389	Please note, however, that C<aio_sendfile> can read more bytes from	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
390	C<$in_fh> than are written, and there is no way to find out how many	520	together in a hurry to improve benchmark numbers) tend to be rather buggy
391	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	521	on many systems, this implementation tries to work around some known bugs
392	provides the number of bytes written to C<$out_fh>. Only if the result	522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
393	value equals C<$length> one can assume that C<$length> bytes have been	523	so you really really should check the return value of C<aio_sendfile> -
394	read.	524	fewer bytes than expected might have been transferred.
395		525
396		526
397	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
398		528
399	C<aio_readahead> populates the page cache with data from a file so that	529	C<aio_readahead> populates the page cache with data from a file so that
…		…
403	whole pages, so that offset is effectively rounded down to a page boundary	533	whole pages, so that offset is effectively rounded down to a page boundary
404	and bytes are read up to the next page boundary greater than or equal to	534	and bytes are read up to the next page boundary greater than or equal to
405	(off-set+length). C<aio_readahead> does not read beyond the end of the	535	(off-set+length). C<aio_readahead> does not read beyond the end of the
406	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
407		537
408	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	538	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
409	emulated by simply reading the data, which would have a similar effect.	539	be emulated by simply reading the data, which would have a similar effect.
410		540
411		541
412	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
413		543
414	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
…		…
421	for an explanation.	551	for an explanation.
422		552
423	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	553	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
424	error when stat'ing a large file, the results will be silently truncated	554	error when stat'ing a large file, the results will be silently truncated
425	unless perl itself is compiled with large file support.	555	unless perl itself is compiled with large file support.
		556
		557	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		558	following constants and functions (if not implemented, the constants will
		559	be C<0> and the functions will either C<croak> or fall back on traditional
		560	behaviour).
		561
		562	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		563	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		564	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
426		565
427	Example: Print the length of F</etc/passwd>:	566	Example: Print the length of F</etc/passwd>:
428		567
429	aio_stat "/etc/passwd", sub {	568	aio_stat "/etc/passwd", sub {
430	$_[0] and die "stat failed: $!";	569	$_[0] and die "stat failed: $!";
431	print "size is ", -s _, "\n";	570	print "size is ", -s _, "\n";
432	};	571	};
433		572
434		573
		574	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		575
		576	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		577	whether a file handle or path was passed.
		578
		579	On success, the callback is passed a hash reference with the following
		580	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		581	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		582	is passed.
		583
		584	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		585	C<ST_NOSUID>.
		586
		587	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		588	their correct value when available, or to C<0> on systems that do
		589	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		590	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		591	C<ST_NODIRATIME> and C<ST_RELATIME>.
		592
		593	Example: stat C</wd> and dump out the data if successful.
		594
		595	aio_statvfs "/wd", sub {
		596	my $f = $_[0]
		597	or die "statvfs: $!";
		598
		599	use Data::Dumper;
		600	say Dumper $f;
		601	};
		602
		603	# result:
		604	{
		605	bsize => 1024,
		606	bfree => 4333064312,
		607	blocks => 10253828096,
		608	files => 2050765568,
		609	flag => 4096,
		610	favail => 2042092649,
		611	bavail => 4333064312,
		612	ffree => 2042092649,
		613	namemax => 255,
		614	frsize => 1024,
		615	fsid => 1810
		616	}
		617
435	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	618	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
436		619
437	Works like perl's C<utime> function (including the special case of $atime	620	Works like perl's C<utime> function (including the special case of $atime
438	and $mtime being undef). Fractional times are supported if the underlying	621	and $mtime being undef). Fractional times are supported if the underlying
439	syscalls support them.	622	syscalls support them.
…		…
466	=item aio_truncate $fh_or_path, $offset, $callback->($status)	649	=item aio_truncate $fh_or_path, $offset, $callback->($status)
467		650
468	Works like truncate(2) or ftruncate(2).	651	Works like truncate(2) or ftruncate(2).
469		652
470		653
		654	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		655
		656	Allocates or frees disk space according to the C<$mode> argument. See the
		657	linux C<fallocate> documentation for details.
		658
		659	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		660	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		661	to deallocate a file range.
		662
		663	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		664	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		665	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		666	to unshare shared blocks (see your L<fallocate(2)> manpage).
		667
		668	The file system block size used by C<fallocate> is presumably the
		669	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		670	can dictate other limitations.
		671
		672	If C<fallocate> isn't available or cannot be emulated (currently no
		673	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		674
		675
471	=item aio_chmod $fh_or_path, $mode, $callback->($status)	676	=item aio_chmod $fh_or_path, $mode, $callback->($status)
472		677
473	Works like perl's C<chmod> function.	678	Works like perl's C<chmod> function.
474		679
475		680
…		…
477		682
478	Asynchronously unlink (delete) a file and call the callback with the	683	Asynchronously unlink (delete) a file and call the callback with the
479	result code.	684	result code.
480		685
481		686
482	=item aio_mknod $path, $mode, $dev, $callback->($status)	687	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
483		688
484	[EXPERIMENTAL]	689	[EXPERIMENTAL]
485		690
486	Asynchronously create a device node (or fifo). See mknod(2).	691	Asynchronously create a device node (or fifo). See mknod(2).
487		692
488	The only (POSIX-) portable way of calling this function is:	693	The only (POSIX-) portable way of calling this function is:
489		694
490	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	695	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
491		696
		697	See C<aio_stat> for info about some potentially helpful extra constants
		698	and functions.
492		699
493	=item aio_link $srcpath, $dstpath, $callback->($status)	700	=item aio_link $srcpath, $dstpath, $callback->($status)
494		701
495	Asynchronously create a new link to the existing object at C<$srcpath> at	702	Asynchronously create a new link to the existing object at C<$srcpath> at
496	the path C<$dstpath> and call the callback with the result code.	703	the path C<$dstpath> and call the callback with the result code.
…		…
500		707
501	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	708	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
502	the path C<$dstpath> and call the callback with the result code.	709	the path C<$dstpath> and call the callback with the result code.
503		710
504		711
505	=item aio_readlink $path, $callback->($link)	712	=item aio_readlink $pathname, $callback->($link)
506		713
507	Asynchronously read the symlink specified by C<$path> and pass it to	714	Asynchronously read the symlink specified by C<$path> and pass it to
508	the callback. If an error occurs, nothing or undef gets passed to the	715	the callback. If an error occurs, nothing or undef gets passed to the
509	callback.	716	callback.
510		717
511		718
		719	=item aio_realpath $pathname, $callback->($path)
		720
		721	Asynchronously make the path absolute and resolve any symlinks in
		722	C<$path>. The resulting path only consists of directories (same as
		723	L<Cwd::realpath>).
		724
		725	This request can be used to get the absolute path of the current working
		726	directory by passing it a path of F<.> (a single dot).
		727
		728
512	=item aio_rename $srcpath, $dstpath, $callback->($status)	729	=item aio_rename $srcpath, $dstpath, $callback->($status)
513		730
514	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	731	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
515	rename(2) and call the callback with the result code.	732	rename(2) and call the callback with the result code.
		733
		734	On systems that support the AIO::WD working directory abstraction
		735	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		736	of failing, C<rename> is called on the absolute path of C<$wd>.
		737
		738
		739	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		740
		741	Basically a version of C<aio_rename> with an additional C<$flags>
		742	argument. Calling this with C<$flags=0> is the same as calling
		743	C<aio_rename>.
		744
		745	Non-zero flags are currently only supported on GNU/Linux systems that
		746	support renameat2. Other systems fail with C<ENOSYS> in this case.
		747
		748	The following constants are available (missing ones are, as usual C<0>),
		749	see renameat2(2) for details:
		750
		751	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		752	and C<IO::AIO::RENAME_WHITEOUT>.
516		753
517		754
518	=item aio_mkdir $pathname, $mode, $callback->($status)	755	=item aio_mkdir $pathname, $mode, $callback->($status)
519		756
520	Asynchronously mkdir (create) a directory and call the callback with	757	Asynchronously mkdir (create) a directory and call the callback with
…		…
525	=item aio_rmdir $pathname, $callback->($status)	762	=item aio_rmdir $pathname, $callback->($status)
526		763
527	Asynchronously rmdir (delete) a directory and call the callback with the	764	Asynchronously rmdir (delete) a directory and call the callback with the
528	result code.	765	result code.
529		766
		767	On systems that support the AIO::WD working directory abstraction
		768	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		769	C<rmdir> is called on the absolute path of C<$wd>.
		770
530		771
531	=item aio_readdir $pathname, $callback->($entries)	772	=item aio_readdir $pathname, $callback->($entries)
532		773
533	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	774	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
534	directory (i.e. opendir + readdir + closedir). The entries will not be	775	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
538	array-ref with the filenames.	779	array-ref with the filenames.
539		780
540		781
541	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	782	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
542		783
543	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	784	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
544	behaviour and output format. In case of an error, C<$entries> will be	785	tune behaviour and output format. In case of an error, C<$entries> will be
545	C<undef>.	786	C<undef>.
546		787
547	The flags are a combination of the following constants, ORed together (the	788	The flags are a combination of the following constants, ORed together (the
548	flags will also be passed to the callback, possibly modified):	789	flags will also be passed to the callback, possibly modified):
549		790
550	=over 4	791	=over 4
551		792
552	=item IO::AIO::READDIR_DENTS	793	=item IO::AIO::READDIR_DENTS
553		794
554	When this flag is off, then the callback gets an arrayref with of names	795	Normally the callback gets an arrayref consisting of names only (as
555	only (as with C<aio_readdir>), otherwise it gets an arrayref with	796	with C<aio_readdir>). If this flag is set, then the callback gets an
556	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	797	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
557	entry in more detail.	798	single directory entry in more detail:
558		799
559	C<$name> is the name of the entry.	800	C<$name> is the name of the entry.
560		801
561	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	802	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
562		803
563	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	804	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
564	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	805	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
565	C<IO::AIO::DT_WHT>.	806	C<IO::AIO::DT_WHT>.
566		807
567	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	808	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
568	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	809	to know, you have to run stat yourself. Also, for speed/memory reasons,
569	scalars are read-only: you can not modify them.	810	the C<$type> scalars are read-only: you must not modify them.
570		811
571	C<$inode> is the inode number (which might not be exact on systems with 64	812	C<$inode> is the inode number (which might not be exact on systems with 64
572	bit inode numbers and 32 bit perls). This field has unspecified content on	813	bit inode numbers and 32 bit perls). This field has unspecified content on
573	systems that do not deliver the inode information.	814	systems that do not deliver the inode information.
574		815
575	=item IO::AIO::READDIR_DIRS_FIRST	816	=item IO::AIO::READDIR_DIRS_FIRST
576		817
577	When this flag is set, then the names will be returned in an order where	818	When this flag is set, then the names will be returned in an order where
578	likely directories come first. This is useful when you need to quickly	819	likely directories come first, in optimal stat order. This is useful when
579	find directories, or you want to find all directories while avoiding to	820	you need to quickly find directories, or you want to find all directories
580	stat() each entry.	821	while avoiding to stat() each entry.
581		822
582	If the system returns type information in readdir, then this is used	823	If the system returns type information in readdir, then this is used
583	to find directories directly. Otherwise, likely directories are files	824	to find directories directly. Otherwise, likely directories are names
584	beginning with ".", or otherwise files with no dots, of which files with	825	beginning with ".", or otherwise names with no dots, of which names with
585	short names are tried first.	826	short names are tried first.
586		827
587	=item IO::AIO::READDIR_STAT_ORDER	828	=item IO::AIO::READDIR_STAT_ORDER
588		829
589	When this flag is set, then the names will be returned in an order	830	When this flag is set, then the names will be returned in an order
590	suitable for stat()'ing each one. That is, when you plan to stat()	831	suitable for stat()'ing each one. That is, when you plan to stat() most or
591	all files in the given directory, then the returned order will likely	832	all files in the given directory, then the returned order will likely be
592	be fastest.	833	faster.
593		834
594	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	835	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
595	the likely dirs come first, resulting in a less optimal stat order.	836	then the likely dirs come first, resulting in a less optimal stat order
		837	for stat'ing all entries, but likely a more optimal order for finding
		838	subdirectories.
596		839
597	=item IO::AIO::READDIR_FOUND_UNKNOWN	840	=item IO::AIO::READDIR_FOUND_UNKNOWN
598		841
599	This flag should not be set when calling C<aio_readdirx>. Instead, it	842	This flag should not be set when calling C<aio_readdirx>. Instead, it
600	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	843	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
601	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	844	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
602	C<$type>'s are known, which can be used to speed up some algorithms.	845	C<$type>'s are known, which can be used to speed up some algorithms.
603		846
604	=back	847	=back
605		848
606		849
		850	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		851
		852	Opens, reads and closes the given file. The data is put into C<$data>,
		853	which is resized as required.
		854
		855	If C<$offset> is negative, then it is counted from the end of the file.
		856
		857	If C<$length> is zero, then the remaining length of the file is
		858	used. Also, in this case, the same limitations to modifying C<$data> apply
		859	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		860	with C<substr>. If the size of the file is known, specifying a non-zero
		861	C<$length> results in a performance advantage.
		862
		863	This request is similar to the older C<aio_load> request, but since it is
		864	a single request, it might be more efficient to use.
		865
		866	Example: load F</etc/passwd> into C<$passwd>.
		867
		868	my $passwd;
		869	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		870	$_[0] >= 0
		871	or die "/etc/passwd: $!\n";
		872
		873	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		874	print $passwd;
		875	};
		876	IO::AIO::flush;
		877
		878
607	=item aio_load $path, $data, $callback->($status)	879	=item aio_load $pathname, $data, $callback->($status)
608		880
609	This is a composite request that tries to fully load the given file into	881	This is a composite request that tries to fully load the given file into
610	memory. Status is the same as with aio_read.	882	memory. Status is the same as with aio_read.
		883
		884	Using C<aio_slurp> might be more efficient, as it is a single request.
611		885
612	=cut	886	=cut
613		887
614	sub aio_load($$;$) {	888	sub aio_load($$;$) {
615	my ($path, undef, $cb) = @_;	889	my ($path, undef, $cb) = @_;
…		…
634		908
635	=item aio_copy $srcpath, $dstpath, $callback->($status)	909	=item aio_copy $srcpath, $dstpath, $callback->($status)
636		910
637	Try to copy the I<file> (directories not supported as either source or	911	Try to copy the I<file> (directories not supported as either source or
638	destination) from C<$srcpath> to C<$dstpath> and call the callback with	912	destination) from C<$srcpath> to C<$dstpath> and call the callback with
639	the C<0> (error) or C<-1> ok.	913	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		914
		915	Existing destination files will be truncated.
640		916
641	This is a composite request that creates the destination file with	917	This is a composite request that creates the destination file with
642	mode 0200 and copies the contents of the source file into it using	918	mode 0200 and copies the contents of the source file into it using
643	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	919	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
644	uid/gid, in that order.	920	uid/gid, in that order.
…		…
656	my $grp = aio_group $cb;	932	my $grp = aio_group $cb;
657		933
658	aioreq_pri $pri;	934	aioreq_pri $pri;
659	add $grp aio_open $src, O_RDONLY, 0, sub {	935	add $grp aio_open $src, O_RDONLY, 0, sub {
660	if (my $src_fh = $_[0]) {	936	if (my $src_fh = $_[0]) {
661	my @stat = stat $src_fh; # hmm, might bock over nfs?	937	my @stat = stat $src_fh; # hmm, might block over nfs?
662		938
663	aioreq_pri $pri;	939	aioreq_pri $pri;
664	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	940	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
665	if (my $dst_fh = $_[0]) {	941	if (my $dst_fh = $_[0]) {
666	aioreq_pri $pri;	942	aioreq_pri $pri;
…		…
713		989
714	=item aio_move $srcpath, $dstpath, $callback->($status)	990	=item aio_move $srcpath, $dstpath, $callback->($status)
715		991
716	Try to move the I<file> (directories not supported as either source or	992	Try to move the I<file> (directories not supported as either source or
717	destination) from C<$srcpath> to C<$dstpath> and call the callback with	993	destination) from C<$srcpath> to C<$dstpath> and call the callback with
718	the C<0> (error) or C<-1> ok.	994	a status of C<0> (ok) or C<-1> (error, see C<$!>).
719		995
720	This is a composite request that tries to rename(2) the file first; if	996	This is a composite request that tries to rename(2) the file first; if
721	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	997	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
722	that is successful, unlinks the C<$srcpath>.	998	that is successful, unlinks the C<$srcpath>.
723		999
…		…
734	if ($_[0] && $! == EXDEV) {	1010	if ($_[0] && $! == EXDEV) {
735	aioreq_pri $pri;	1011	aioreq_pri $pri;
736	add $grp aio_copy $src, $dst, sub {	1012	add $grp aio_copy $src, $dst, sub {
737	$grp->result ($_[0]);	1013	$grp->result ($_[0]);
738		1014
739	if (!$_[0]) {	1015	unless ($_[0]) {
740	aioreq_pri $pri;	1016	aioreq_pri $pri;
741	add $grp aio_unlink $src;	1017	add $grp aio_unlink $src;
742	}	1018	}
743	};	1019	};
744	} else {	1020	} else {
…		…
747	};	1023	};
748		1024
749	$grp	1025	$grp
750	}	1026	}
751		1027
752	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1028	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
753		1029
754	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1030	Scans a directory (similar to C<aio_readdir>) but additionally tries to
755	efficiently separate the entries of directory C<$path> into two sets of	1031	efficiently separate the entries of directory C<$path> into two sets of
756	names, directories you can recurse into (directories), and ones you cannot	1032	names, directories you can recurse into (directories), and ones you cannot
757	recurse into (everything else, including symlinks to directories).	1033	recurse into (everything else, including symlinks to directories).
758		1034
759	C<aio_scandir> is a composite request that creates of many sub requests_	1035	C<aio_scandir> is a composite request that generates many sub requests.
760	C<$maxreq> specifies the maximum number of outstanding aio requests that	1036	C<$maxreq> specifies the maximum number of outstanding aio requests that
761	this function generates. If it is C<< <= 0 >>, then a suitable default	1037	this function generates. If it is C<< <= 0 >>, then a suitable default
762	will be chosen (currently 4).	1038	will be chosen (currently 4).
763		1039
764	On error, the callback is called without arguments, otherwise it receives	1040	On error, the callback is called without arguments, otherwise it receives
…		…
788	Then entries will be sorted into likely directories a non-initial dot	1064	Then entries will be sorted into likely directories a non-initial dot
789	currently) and likely non-directories (see C<aio_readdirx>). Then every	1065	currently) and likely non-directories (see C<aio_readdirx>). Then every
790	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1066	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
791	in order of their inode numbers. If that succeeds, it assumes that the	1067	in order of their inode numbers. If that succeeds, it assumes that the
792	entry is a directory or a symlink to directory (which will be checked	1068	entry is a directory or a symlink to directory (which will be checked
793	seperately). This is often faster than stat'ing the entry itself because	1069	separately). This is often faster than stat'ing the entry itself because
794	filesystems might detect the type of the entry without reading the inode	1070	filesystems might detect the type of the entry without reading the inode
795	data (e.g. ext2fs filetype feature), even on systems that cannot return	1071	data (e.g. ext2fs filetype feature), even on systems that cannot return
796	the filetype information on readdir.	1072	the filetype information on readdir.
797		1073
798	If the known number of directories (link count - 2) has been reached, the	1074	If the known number of directories (link count - 2) has been reached, the
…		…
814		1090
815	my $grp = aio_group $cb;	1091	my $grp = aio_group $cb;
816		1092
817	$maxreq = 4 if $maxreq <= 0;	1093	$maxreq = 4 if $maxreq <= 0;
818		1094
819	# stat once	1095	# get a wd object
820	aioreq_pri $pri;	1096	aioreq_pri $pri;
821	add $grp aio_stat $path, sub {	1097	add $grp aio_wd $path, sub {
		1098	$_[0]
822	return $grp->result () if $_[0];	1099	or return $grp->result ();
823	my $now = time;
824	my $hash1 = join ":", (stat _)[0,1,3,7,9];
825		1100
826	# read the directory entries	1101	my $wd = [shift, "."];
		1102
		1103	# stat once
827	aioreq_pri $pri;	1104	aioreq_pri $pri;
828	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1105	add $grp aio_stat $wd, sub {
829	my $entries = shift
830	or return $grp->result ();	1106	return $grp->result () if $_[0];
		1107	my $now = time;
		1108	my $hash1 = join ":", (stat _)[0,1,3,7,9];
831		1109
832	# stat the dir another time	1110	# read the directory entries
833	aioreq_pri $pri;	1111	aioreq_pri $pri;
		1112	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1113	my $entries = shift
		1114	or return $grp->result ();
		1115
		1116	# stat the dir another time
		1117	aioreq_pri $pri;
834	add $grp aio_stat $path, sub {	1118	add $grp aio_stat $wd, sub {
835	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1119	my $hash2 = join ":", (stat _)[0,1,3,7,9];
836		1120
837	my $ndirs;	1121	my $ndirs;
838		1122
839	# take the slow route if anything looks fishy	1123	# take the slow route if anything looks fishy
840	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1124	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
841	$ndirs = -1;	1125	$ndirs = -1;
842	} else {	1126	} else {
843	# if nlink == 2, we are finished	1127	# if nlink == 2, we are finished
844	# for non-posix-fs's, we rely on nlink < 2	1128	# for non-posix-fs's, we rely on nlink < 2
845	$ndirs = (stat _)[3] - 2	1129	$ndirs = (stat _)[3] - 2
846	or return $grp->result ([], $entries);	1130	or return $grp->result ([], $entries);
847	}	1131	}
848		1132
849	my (@dirs, @nondirs);	1133	my (@dirs, @nondirs);
850		1134
851	my $statgrp = add $grp aio_group sub {	1135	my $statgrp = add $grp aio_group sub {
852	$grp->result (\@dirs, \@nondirs);	1136	$grp->result (\@dirs, \@nondirs);
853	};	1137	};
854		1138
855	limit $statgrp $maxreq;	1139	limit $statgrp $maxreq;
856	feed $statgrp sub {	1140	feed $statgrp sub {
857	return unless @$entries;	1141	return unless @$entries;
858	my $entry = shift @$entries;	1142	my $entry = shift @$entries;
859		1143
860	aioreq_pri $pri;	1144	aioreq_pri $pri;
		1145	$wd->[1] = "$entry/.";
861	add $statgrp aio_stat "$path/$entry/.", sub {	1146	add $statgrp aio_stat $wd, sub {
862	if ($_[0] < 0) {	1147	if ($_[0] < 0) {
863	push @nondirs, $entry;	1148	push @nondirs, $entry;
864	} else {	1149	} else {
865	# need to check for real directory	1150	# need to check for real directory
866	aioreq_pri $pri;	1151	aioreq_pri $pri;
		1152	$wd->[1] = $entry;
867	add $statgrp aio_lstat "$path/$entry", sub {	1153	add $statgrp aio_lstat $wd, sub {
868	if (-d _) {	1154	if (-d _) {
869	push @dirs, $entry;	1155	push @dirs, $entry;
870		1156
871	unless (--$ndirs) {	1157	unless (--$ndirs) {
872	push @nondirs, @$entries;	1158	push @nondirs, @$entries;
873	feed $statgrp;	1159	feed $statgrp;
		1160	}
		1161	} else {
		1162	push @nondirs, $entry;
874	}	1163	}
875	} else {
876	push @nondirs, $entry;
877	}	1164	}
878	}	1165	}
879	}	1166	};
880	};	1167	};
881	};	1168	};
882	};	1169	};
883	};	1170	};
884	};	1171	};
885		1172
886	$grp	1173	$grp
887	}	1174	}
888		1175
889	=item aio_rmtree $path, $callback->($status)	1176	=item aio_rmtree $pathname, $callback->($status)
890		1177
891	Delete a directory tree starting (and including) C<$path>, return the	1178	Delete a directory tree starting (and including) C<$path>, return the
892	status of the final C<rmdir> only. This is a composite request that	1179	status of the final C<rmdir> only. This is a composite request that
893	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1180	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
894	everything else.	1181	everything else.
895		1182
896	=cut	1183	=cut
897		1184
…		…
919	};	1206	};
920		1207
921	$grp	1208	$grp
922	}	1209	}
923		1210
		1211	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1212
		1213	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1214
		1215	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1216	they execute asynchronously and pass the return value to the callback.
		1217
		1218	Both calls can be used for a lot of things, some of which make more sense
		1219	to run asynchronously in their own thread, while some others make less
		1220	sense. For example, calls that block waiting for external events, such
		1221	as locking, will also lock down an I/O thread while it is waiting, which
		1222	can deadlock the whole I/O system. At the same time, there might be no
		1223	alternative to using a thread to wait.
		1224
		1225	So in general, you should only use these calls for things that do
		1226	(filesystem) I/O, not for things that wait for other events (network,
		1227	other processes), although if you are careful and know what you are doing,
		1228	you still can.
		1229
		1230	The following constants are available (missing ones are, as usual C<0>):
		1231
		1232	C<F_DUPFD_CLOEXEC>,
		1233
		1234	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1235
		1236	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1237
		1238	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1239	C<FS_IOC_FIEMAP>.
		1240
		1241	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1242	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1243
		1244	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1245	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1246	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1247	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1248	C<FS_FL_USER_MODIFIABLE>.
		1249
		1250	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1251	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1252	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1253	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1254
924	=item aio_sync $callback->($status)	1255	=item aio_sync $callback->($status)
925		1256
926	Asynchronously call sync and call the callback when finished.	1257	Asynchronously call sync and call the callback when finished.
927		1258
928	=item aio_fsync $fh, $callback->($status)	1259	=item aio_fsync $fh, $callback->($status)
…		…
935	Asynchronously call fdatasync on the given filehandle and call the	1266	Asynchronously call fdatasync on the given filehandle and call the
936	callback with the fdatasync result code.	1267	callback with the fdatasync result code.
937		1268
938	If this call isn't available because your OS lacks it or it couldn't be	1269	If this call isn't available because your OS lacks it or it couldn't be
939	detected, it will be emulated by calling C<fsync> instead.	1270	detected, it will be emulated by calling C<fsync> instead.
		1271
		1272	=item aio_syncfs $fh, $callback->($status)
		1273
		1274	Asynchronously call the syncfs syscall to sync the filesystem associated
		1275	to the given filehandle and call the callback with the syncfs result
		1276	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1277	errno to C<ENOSYS> nevertheless.
940		1278
941	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1279	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
942		1280
943	Sync the data portion of the file specified by C<$offset> and C<$length>	1281	Sync the data portion of the file specified by C<$offset> and C<$length>
944	to disk (but NOT the metadata), by calling the Linux-specific	1282	to disk (but NOT the metadata), by calling the Linux-specific
…		…
948	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1286	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
949	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1287	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
950	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1288	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
951	manpage for details.	1289	manpage for details.
952		1290
953	=item aio_pathsync $path, $callback->($status)	1291	=item aio_pathsync $pathname, $callback->($status)
954		1292
955	This request tries to open, fsync and close the given path. This is a	1293	This request tries to open, fsync and close the given path. This is a
956	composite request intended to sync directories after directory operations	1294	composite request intended to sync directories after directory operations
957	(E.g. rename). This might not work on all operating systems or have any	1295	(E.g. rename). This might not work on all operating systems or have any
958	specific effect, but usually it makes sure that directory changes get	1296	specific effect, but usually it makes sure that directory changes get
959	written to disc. It works for anything that can be opened for read-only,	1297	written to disc. It works for anything that can be opened for read-only,
960	not just directories.	1298	not just directories.
		1299
		1300	Future versions of this function might fall back to other methods when
		1301	C<fsync> on the directory fails (such as calling C<sync>).
961		1302
962	Passes C<0> when everything went ok, and C<-1> on error.	1303	Passes C<0> when everything went ok, and C<-1> on error.
963		1304
964	=cut	1305	=cut
965		1306
…		…
986	};	1327	};
987		1328
988	$grp	1329	$grp
989	}	1330	}
990		1331
		1332	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1333
		1334	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1335	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1336	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1337	scalar must only be modified in-place while an aio operation is pending on
		1338	it).
		1339
		1340	It calls the C<msync> function of your OS, if available, with the memory
		1341	area starting at C<$offset> in the string and ending C<$length> bytes
		1342	later. If C<$length> is negative, counts from the end, and if C<$length>
		1343	is C<undef>, then it goes till the end of the string. The flags can be
		1344	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1345	C<IO::AIO::MS_INVALIDATE>.
		1346
		1347	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1348
		1349	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1350	scalars.
		1351
		1352	It touches (reads or writes) all memory pages in the specified
		1353	range inside the scalar. All caveats and parameters are the same
		1354	as for C<aio_msync>, above, except for flags, which must be either
		1355	C<0> (which reads all pages and ensures they are instantiated) or
		1356	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1357	writing an octet from it, which dirties the page).
		1358
		1359	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1360
		1361	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1362	scalars.
		1363
		1364	It reads in all the pages of the underlying storage into memory (if any)
		1365	and locks them, so they are not getting swapped/paged out or removed.
		1366
		1367	If C<$length> is undefined, then the scalar will be locked till the end.
		1368
		1369	On systems that do not implement C<mlock>, this function returns C<-1>
		1370	and sets errno to C<ENOSYS>.
		1371
		1372	Note that the corresponding C<munlock> is synchronous and is
		1373	documented under L<MISCELLANEOUS FUNCTIONS>.
		1374
		1375	Example: open a file, mmap and mlock it - both will be undone when
		1376	C<$data> gets destroyed.
		1377
		1378	open my $fh, "<", $path or die "$path: $!";
		1379	my $data;
		1380	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1381	aio_mlock $data; # mlock in background
		1382
		1383	=item aio_mlockall $flags, $callback->($status)
		1384
		1385	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1386	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1387
		1388	On systems that do not implement C<mlockall>, this function returns C<-1>
		1389	and sets errno to C<ENOSYS>.
		1390
		1391	Note that the corresponding C<munlockall> is synchronous and is
		1392	documented under L<MISCELLANEOUS FUNCTIONS>.
		1393
		1394	Example: asynchronously lock all current and future pages into memory.
		1395
		1396	aio_mlockall IO::AIO::MCL_FUTURE;
		1397
		1398	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1399
		1400	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1401	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1402	the ioctl is not available on your OS, then this request will fail with
		1403	C<ENOSYS>.
		1404
		1405	C<$start> is the starting offset to query extents for, C<$length> is the
		1406	size of the range to query - if it is C<undef>, then the whole file will
		1407	be queried.
		1408
		1409	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1410	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1411	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1412	the data portion.
		1413
		1414	C<$count> is the maximum number of extent records to return. If it is
		1415	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1416	case, if it is C<0>, then the callback receives the number of extents
		1417	instead of the extents themselves (which is unreliable, see below).
		1418
		1419	If an error occurs, the callback receives no arguments. The special
		1420	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1421
		1422	Otherwise, the callback receives an array reference with extent
		1423	structures. Each extent structure is an array reference itself, with the
		1424	following members:
		1425
		1426	[$logical, $physical, $length, $flags]
		1427
		1428	Flags is any combination of the following flag values (typically either C<0>
		1429	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1430
		1431	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1432	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1433	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1434	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1435	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1436	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1437
		1438	At the time of this writing (Linux 3.2), this request is unreliable unless
		1439	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1440	it to return all extents of a range for files with a large number of
		1441	extents. The code (only) works around all these issues if C<$count> is
		1442	C<undef>.
		1443
991	=item aio_group $callback->(...)	1444	=item aio_group $callback->(...)
992		1445
993	This is a very special aio request: Instead of doing something, it is a	1446	This is a very special aio request: Instead of doing something, it is a
994	container for other aio requests, which is useful if you want to bundle	1447	container for other aio requests, which is useful if you want to bundle
995	many requests into a single, composite, request with a definite callback	1448	many requests into a single, composite, request with a definite callback
…		…
1031	like sleep and file handle readable/writable, the overhead this creates is	1484	like sleep and file handle readable/writable, the overhead this creates is
1032	immense (it blocks a thread for a long time) so do not use this function	1485	immense (it blocks a thread for a long time) so do not use this function
1033	except to put your application under artificial I/O pressure.	1486	except to put your application under artificial I/O pressure.
1034		1487
1035	=back	1488	=back
		1489
		1490
		1491	=head2 IO::AIO::WD - multiple working directories
		1492
		1493	Your process only has one current working directory, which is used by all
		1494	threads. This makes it hard to use relative paths (some other component
		1495	could call C<chdir> at any time, and it is hard to control when the path
		1496	will be used by IO::AIO).
		1497
		1498	One solution for this is to always use absolute paths. This usually works,
		1499	but can be quite slow (the kernel has to walk the whole path on every
		1500	access), and can also be a hassle to implement.
		1501
		1502	Newer POSIX systems have a number of functions (openat, fdopendir,
		1503	futimensat and so on) that make it possible to specify working directories
		1504	per operation.
		1505
		1506	For portability, and because the clowns who "designed", or shall I write,
		1507	perpetrated this new interface were obviously half-drunk, this abstraction
		1508	cannot be perfect, though.
		1509
		1510	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1511	object. This object stores the canonicalised, absolute version of the
		1512	path, and on systems that allow it, also a directory file descriptor.
		1513
		1514	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1515	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1516	object and a pathname instead (or the IO::AIO::WD object alone, which
		1517	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1518	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1519	to that IO::AIO::WD object.
		1520
		1521	For example, to get a wd object for F</etc> and then stat F<passwd>
		1522	inside, you would write:
		1523
		1524	aio_wd "/etc", sub {
		1525	my $etcdir = shift;
		1526
		1527	# although $etcdir can be undef on error, there is generally no reason
		1528	# to check for errors here, as aio_stat will fail with ENOENT
		1529	# when $etcdir is undef.
		1530
		1531	aio_stat [$etcdir, "passwd"], sub {
		1532	# yay
		1533	};
		1534	};
		1535
		1536	The fact that C<aio_wd> is a request and not a normal function shows that
		1537	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1538	which is why it is done asynchronously.
		1539
		1540	To stat the directory obtained with C<aio_wd> above, one could write
		1541	either of the following three request calls:
		1542
		1543	aio_lstat "/etc" , sub { ... # pathname as normal string
		1544	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1545	aio_lstat $wd , sub { ... # shorthand for the previous
		1546
		1547	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1548	object and the pathname string, so you could write the following without
		1549	causing any issues due to C<$path> getting reused:
		1550
		1551	my $path = [$wd, undef];
		1552
		1553	for my $name (qw(abc def ghi)) {
		1554	$path->[1] = $name;
		1555	aio_stat $path, sub {
		1556	# ...
		1557	};
		1558	}
		1559
		1560	There are some caveats: when directories get renamed (or deleted), the
		1561	pathname string doesn't change, so will point to the new directory (or
		1562	nowhere at all), while the directory fd, if available on the system,
		1563	will still point to the original directory. Most functions accepting a
		1564	pathname will use the directory fd on newer systems, and the string on
		1565	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1566	the string form of the pathname.
		1567
		1568	So this functionality is mainly useful to get some protection against
		1569	C<chdir>, to easily get an absolute path out of a relative path for future
		1570	reference, and to speed up doing many operations in the same directory
		1571	(e.g. when stat'ing all files in a directory).
		1572
		1573	The following functions implement this working directory abstraction:
		1574
		1575	=over 4
		1576
		1577	=item aio_wd $pathname, $callback->($wd)
		1578
		1579	Asynchonously canonicalise the given pathname and convert it to an
		1580	IO::AIO::WD object representing it. If possible and supported on the
		1581	system, also open a directory fd to speed up pathname resolution relative
		1582	to this working directory.
		1583
		1584	If something goes wrong, then C<undef> is passwd to the callback instead
		1585	of a working directory object and C<$!> is set appropriately. Since
		1586	passing C<undef> as working directory component of a pathname fails the
		1587	request with C<ENOENT>, there is often no need for error checking in the
		1588	C<aio_wd> callback, as future requests using the value will fail in the
		1589	expected way.
		1590
		1591	=item IO::AIO::CWD
		1592
		1593	This is a compiletime constant (object) that represents the process
		1594	current working directory.
		1595
		1596	Specifying this object as working directory object for a pathname is as if
		1597	the pathname would be specified directly, without a directory object. For
		1598	example, these calls are functionally identical:
		1599
		1600	aio_stat "somefile", sub { ... };
		1601	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1602
		1603	=back
		1604
		1605	To recover the path associated with an IO::AIO::WD object, you can use
		1606	C<aio_realpath>:
		1607
		1608	aio_realpath $wd, sub {
		1609	warn "path is $_[0]\n";
		1610	};
		1611
		1612	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1613	sometimes, fall back to using an absolue path.
1036		1614
1037	=head2 IO::AIO::REQ CLASS	1615	=head2 IO::AIO::REQ CLASS
1038		1616
1039	All non-aggregate C<aio_*> functions return an object of this class when	1617	All non-aggregate C<aio_*> functions return an object of this class when
1040	called in non-void context.	1618	called in non-void context.
…		…
1130	=item $grp->cancel_subs	1708	=item $grp->cancel_subs
1131		1709
1132	Cancel all subrequests and clears any feeder, but not the group request	1710	Cancel all subrequests and clears any feeder, but not the group request
1133	itself. Useful when you queued a lot of events but got a result early.	1711	itself. Useful when you queued a lot of events but got a result early.
1134		1712
		1713	The group request will finish normally (you cannot add requests to the
		1714	group).
		1715
1135	=item $grp->result (...)	1716	=item $grp->result (...)
1136		1717
1137	Set the result value(s) that will be passed to the group callback when all	1718	Set the result value(s) that will be passed to the group callback when all
1138	subrequests have finished and set the groups errno to the current value	1719	subrequests have finished and set the groups errno to the current value
1139	of errno (just like calling C<errno> without an error number). By default,	1720	of errno (just like calling C<errno> without an error number). By default,
…		…
1155		1736
1156	Sets a feeder/generator on this group: every group can have an attached	1737	Sets a feeder/generator on this group: every group can have an attached
1157	generator that generates requests if idle. The idea behind this is that,	1738	generator that generates requests if idle. The idea behind this is that,
1158	although you could just queue as many requests as you want in a group,	1739	although you could just queue as many requests as you want in a group,
1159	this might starve other requests for a potentially long time. For example,	1740	this might starve other requests for a potentially long time. For example,
1160	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1741	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1161	delaying any later requests for a long time.	1742	requests, delaying any later requests for a long time.
1162		1743
1163	To avoid this, and allow incremental generation of requests, you can	1744	To avoid this, and allow incremental generation of requests, you can
1164	instead a group and set a feeder on it that generates those requests. The	1745	instead a group and set a feeder on it that generates those requests. The
1165	feed callback will be called whenever there are few enough (see C<limit>,	1746	feed callback will be called whenever there are few enough (see C<limit>,
1166	below) requests active in the group itself and is expected to queue more	1747	below) requests active in the group itself and is expected to queue more
…		…
1215		1796
1216	See C<poll_cb> for an example.	1797	See C<poll_cb> for an example.
1217		1798
1218	=item IO::AIO::poll_cb	1799	=item IO::AIO::poll_cb
1219		1800
1220	Process some outstanding events on the result pipe. You have to call this	1801	Process some requests that have reached the result phase (i.e. they have
1221	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1802	been executed but the results are not yet reported). You have to call
1222	returned earlier for whatever reason. Returns immediately when no events	1803	this "regularly" to finish outstanding requests.
1223	are outstanding. The amount of events processed depends on the settings of
1224	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1225		1804
		1805	Returns C<0> if all events could be processed (or there were no
		1806	events to process), or C<-1> if it returned earlier for whatever
		1807	reason. Returns immediately when no events are outstanding. The amount
		1808	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1809	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1810
1226	If not all requests were processed for whatever reason, the filehandle	1811	If not all requests were processed for whatever reason, the poll file
1227	will still be ready when C<poll_cb> returns, so normally you don't have to	1812	descriptor will still be ready when C<poll_cb> returns, so normally you
1228	do anything special to have it called later.	1813	don't have to do anything special to have it called later.
		1814
		1815	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1816	ready, it can be beneficial to call this function from loops which submit
		1817	a lot of requests, to make sure the results get processed when they become
		1818	available and not just when the loop is finished and the event loop takes
		1819	over again. This function returns very fast when there are no outstanding
		1820	requests.
1229		1821
1230	Example: Install an Event watcher that automatically calls	1822	Example: Install an Event watcher that automatically calls
1231	IO::AIO::poll_cb with high priority (more examples can be found in the	1823	IO::AIO::poll_cb with high priority (more examples can be found in the
1232	SYNOPSIS section, at the top of this document):	1824	SYNOPSIS section, at the top of this document):
1233		1825
1234	Event->io (fd => IO::AIO::poll_fileno,	1826	Event->io (fd => IO::AIO::poll_fileno,
1235	poll => 'r', async => 1,	1827	poll => 'r', async => 1,
1236	cb => \&IO::AIO::poll_cb);	1828	cb => \&IO::AIO::poll_cb);
		1829
		1830	=item IO::AIO::poll_wait
		1831
		1832	Wait until either at least one request is in the result phase or no
		1833	requests are outstanding anymore.
		1834
		1835	This is useful if you want to synchronously wait for some requests to
		1836	become ready, without actually handling them.
		1837
		1838	See C<nreqs> for an example.
		1839
		1840	=item IO::AIO::poll
		1841
		1842	Waits until some requests have been handled.
		1843
		1844	Returns the number of requests processed, but is otherwise strictly
		1845	equivalent to:
		1846
		1847	IO::AIO::poll_wait, IO::AIO::poll_cb
		1848
		1849	=item IO::AIO::flush
		1850
		1851	Wait till all outstanding AIO requests have been handled.
		1852
		1853	Strictly equivalent to:
		1854
		1855	IO::AIO::poll_wait, IO::AIO::poll_cb
		1856	while IO::AIO::nreqs;
1237		1857
1238	=item IO::AIO::max_poll_reqs $nreqs	1858	=item IO::AIO::max_poll_reqs $nreqs
1239		1859
1240	=item IO::AIO::max_poll_time $seconds	1860	=item IO::AIO::max_poll_time $seconds
1241		1861
…		…
1266	# use a low priority so other tasks have priority	1886	# use a low priority so other tasks have priority
1267	Event->io (fd => IO::AIO::poll_fileno,	1887	Event->io (fd => IO::AIO::poll_fileno,
1268	poll => 'r', nice => 1,	1888	poll => 'r', nice => 1,
1269	cb => &IO::AIO::poll_cb);	1889	cb => &IO::AIO::poll_cb);
1270		1890
1271	=item IO::AIO::poll_wait
1272
1273	If there are any outstanding requests and none of them in the result
1274	phase, wait till the result filehandle becomes ready for reading (simply
1275	does a C<select> on the filehandle. This is useful if you want to
1276	synchronously wait for some requests to finish).
1277
1278	See C<nreqs> for an example.
1279
1280	=item IO::AIO::poll
1281
1282	Waits until some requests have been handled.
1283
1284	Returns the number of requests processed, but is otherwise strictly
1285	equivalent to:
1286
1287	IO::AIO::poll_wait, IO::AIO::poll_cb
1288
1289	=item IO::AIO::flush
1290
1291	Wait till all outstanding AIO requests have been handled.
1292
1293	Strictly equivalent to:
1294
1295	IO::AIO::poll_wait, IO::AIO::poll_cb
1296	while IO::AIO::nreqs;
1297
1298	=back	1891	=back
1299		1892
1300	=head3 CONTROLLING THE NUMBER OF THREADS	1893	=head3 CONTROLLING THE NUMBER OF THREADS
1301		1894
1302	=over	1895	=over
…		…
1335		1928
1336	Under normal circumstances you don't need to call this function.	1929	Under normal circumstances you don't need to call this function.
1337		1930
1338	=item IO::AIO::max_idle $nthreads	1931	=item IO::AIO::max_idle $nthreads
1339		1932
1340	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1933	Limit the number of threads (default: 4) that are allowed to idle
1341	threads that did not get a request to process within 10 seconds). That	1934	(i.e., threads that did not get a request to process within the idle
1342	means if a thread becomes idle while C<$nthreads> other threads are also	1935	timeout (default: 10 seconds). That means if a thread becomes idle while
1343	idle, it will free its resources and exit.	1936	C<$nthreads> other threads are also idle, it will free its resources and
		1937	exit.
1344		1938
1345	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1939	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1346	to allow for extremely high load situations, but want to free resources	1940	to allow for extremely high load situations, but want to free resources
1347	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1941	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1348		1942
1349	The default is probably ok in most situations, especially if thread	1943	The default is probably ok in most situations, especially if thread
1350	creation is fast. If thread creation is very slow on your system you might	1944	creation is fast. If thread creation is very slow on your system you might
1351	want to use larger values.	1945	want to use larger values.
1352		1946
		1947	=item IO::AIO::idle_timeout $seconds
		1948
		1949	Sets the minimum idle timeout (default 10) after which worker threads are
		1950	allowed to exit. SEe C<IO::AIO::max_idle>.
		1951
1353	=item IO::AIO::max_outstanding $maxreqs	1952	=item IO::AIO::max_outstanding $maxreqs
		1953
		1954	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1955	you do queue up more than this number of requests, the next call to
		1956	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1957	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1958	longer exceeded.
		1959
		1960	In other words, this setting does not enforce a queue limit, but can be
		1961	used to make poll functions block if the limit is exceeded.
1354		1962
1355	This is a very bad function to use in interactive programs because it	1963	This is a very bad function to use in interactive programs because it
1356	blocks, and a bad way to reduce concurrency because it is inexact: Better	1964	blocks, and a bad way to reduce concurrency because it is inexact: Better
1357	use an C<aio_group> together with a feed callback.	1965	use an C<aio_group> together with a feed callback.
1358		1966
1359	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1967	Its main use is in scripts without an event loop - when you want to stat
1360	do queue up more than this number of requests, the next call to the	1968	a lot of files, you can write something like this:
1361	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1362	function will block until the limit is no longer exceeded.
1363		1969
1364	The default value is very large, so there is no practical limit on the	1970	IO::AIO::max_outstanding 32;
1365	number of outstanding requests.
1366		1971
1367	You can still queue as many requests as you want. Therefore,	1972	for my $path (...) {
1368	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1973	aio_stat $path , ...;
1369	as a stop gap to shield against fatal memory overflow (with large values).	1974	IO::AIO::poll_cb;
		1975	}
		1976
		1977	IO::AIO::flush;
		1978
		1979	The call to C<poll_cb> inside the loop will normally return instantly, but
		1980	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1981	some requests have been handled. This keeps the loop from pushing a large
		1982	number of C<aio_stat> requests onto the queue.
		1983
		1984	The default value for C<max_outstanding> is very large, so there is no
		1985	practical limit on the number of outstanding requests.
1370		1986
1371	=back	1987	=back
1372		1988
1373	=head3 STATISTICAL INFORMATION	1989	=head3 STATISTICAL INFORMATION
1374		1990
…		…
1394	Returns the number of requests currently in the pending state (executed,	2010	Returns the number of requests currently in the pending state (executed,
1395	but not yet processed by poll_cb).	2011	but not yet processed by poll_cb).
1396		2012
1397	=back	2013	=back
1398		2014
		2015	=head3 MISCELLANEOUS FUNCTIONS
		2016
		2017	IO::AIO implements some functions that are useful when you want to use
		2018	some "Advanced I/O" function not available to in Perl, without going the
		2019	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2020	counterpart.
		2021
		2022	=over 4
		2023
		2024	=item $numfd = IO::AIO::get_fdlimit
		2025
		2026	This function is I<EXPERIMENTAL> and subject to change.
		2027
		2028	Tries to find the current file descriptor limit and returns it, or
		2029	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2030	the highest valid file descriptor number.
		2031
		2032	=item IO::AIO::min_fdlimit [$numfd]
		2033
		2034	This function is I<EXPERIMENTAL> and subject to change.
		2035
		2036	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2037	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2038	is missing, it will try to set a very high limit, although this is not
		2039	recommended when you know the actual minimum that you require.
		2040
		2041	If the limit cannot be raised enough, the function makes a best-effort
		2042	attempt to increase the limit as much as possible, using various
		2043	tricks, while still failing. You can query the resulting limit using
		2044	C<IO::AIO::get_fdlimit>.
		2045
		2046	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2047	true.
		2048
		2049	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2050
		2051	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2052	but is blocking (this makes most sense if you know the input data is
		2053	likely cached already and the output filehandle is set to non-blocking
		2054	operations).
		2055
		2056	Returns the number of bytes copied, or C<-1> on error.
		2057
		2058	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2059
		2060	Simply calls the C<posix_fadvise> function (see its
		2061	manpage for details). The following advice constants are
		2062	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2063	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2064	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2065
		2066	On systems that do not implement C<posix_fadvise>, this function returns
		2067	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2068
		2069	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2070
		2071	Simply calls the C<posix_madvise> function (see its
		2072	manpage for details). The following advice constants are
		2073	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2074	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2075	C<IO::AIO::MADV_DONTNEED>.
		2076
		2077	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2078	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2079	will be reduced to fit into the C<$scalar>.
		2080
		2081	On systems that do not implement C<posix_madvise>, this function returns
		2082	ENOSYS, otherwise the return value of C<posix_madvise>.
		2083
		2084	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2085
		2086	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2087	$scalar (see its manpage for details). The following protect
		2088	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2089	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2090
		2091	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2092	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2093	will be reduced to fit into the C<$scalar>.
		2094
		2095	On systems that do not implement C<mprotect>, this function returns
		2096	ENOSYS, otherwise the return value of C<mprotect>.
		2097
		2098	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2099
		2100	Memory-maps a file (or anonymous memory range) and attaches it to the
		2101	given C<$scalar>, which will act like a string scalar. Returns true on
		2102	success, and false otherwise.
		2103
		2104	The scalar must exist, but its contents do not matter - this means you
		2105	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2106	the scalar first.
		2107
		2108	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2109	which don't change the string length, and most read-only operations such
		2110	as copying it or searching it with regexes and so on.
		2111
		2112	Anything else is unsafe and will, at best, result in memory leaks.
		2113
		2114	The memory map associated with the C<$scalar> is automatically removed
		2115	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2116	or C<IO::AIO::munmap> functions are called on it.
		2117
		2118	This calls the C<mmap>(2) function internally. See your system's manual
		2119	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2120
		2121	The C<$length> must be larger than zero and smaller than the actual
		2122	filesize.
		2123
		2124	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2125	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2126
		2127	C<$flags> can be a combination of
		2128	C<IO::AIO::MAP_SHARED> or
		2129	C<IO::AIO::MAP_PRIVATE>,
		2130	or a number of system-specific flags (when not available, the are C<0>):
		2131	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2132	C<IO::AIO::MAP_LOCKED>,
		2133	C<IO::AIO::MAP_NORESERVE>,
		2134	C<IO::AIO::MAP_POPULATE>,
		2135	C<IO::AIO::MAP_NONBLOCK>,
		2136	C<IO::AIO::MAP_FIXED>,
		2137	C<IO::AIO::MAP_GROWSDOWN>,
		2138	C<IO::AIO::MAP_32BIT>,
		2139	C<IO::AIO::MAP_HUGETLB> or
		2140	C<IO::AIO::MAP_STACK>.
		2141
		2142	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2143
		2144	C<$offset> is the offset from the start of the file - it generally must be
		2145	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2146
		2147	Example:
		2148
		2149	use Digest::MD5;
		2150	use IO::AIO;
		2151
		2152	open my $fh, "<verybigfile"
		2153	or die "$!";
		2154
		2155	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2156	or die "verybigfile: $!";
		2157
		2158	my $fast_md5 = md5 $data;
		2159
		2160	=item IO::AIO::munmap $scalar
		2161
		2162	Removes a previous mmap and undefines the C<$scalar>.
		2163
		2164	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2165
		2166	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2167	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2168	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2169
		2170	Returns true if successful, and false otherwise. If the underlying mmapped
		2171	region has changed address, then the true value has the numerical value
		2172	C<1>, otherwise it has the numerical value C<0>:
		2173
		2174	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2175	or die "mremap: $!";
		2176
		2177	if ($success*1) {
		2178	warn "scalar has chanegd address in memory\n";
		2179	}
		2180
		2181	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2182	implemented, but not supported and might go away in a future version.
		2183
		2184	On systems where this call is not supported or is not emulated, this call
		2185	returns falls and sets C<$!> to C<ENOSYS>.
		2186
		2187	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2188
		2189	Calls the C<munlock> function, undoing the effects of a previous
		2190	C<aio_mlock> call (see its description for details).
		2191
		2192	=item IO::AIO::munlockall
		2193
		2194	Calls the C<munlockall> function.
		2195
		2196	On systems that do not implement C<munlockall>, this function returns
		2197	ENOSYS, otherwise the return value of C<munlockall>.
		2198
		2199	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2200
		2201	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2202	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2203	should be the file offset.
		2204
		2205	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2206	silently corrupt the data in this case.
		2207
		2208	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2209	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2210	C<IO::AIO::SPLICE_F_GIFT>.
		2211
		2212	See the C<splice(2)> manpage for details.
		2213
		2214	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2215
		2216	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2217	description for C<IO::AIO::splice> above for details.
		2218
		2219	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2220
		2221	Attempts to query or change the pipe buffer size. Obviously works only
		2222	on pipes, and currently works only on GNU/Linux systems, and fails with
		2223	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2224	size on other systems, drop me a note.
		2225
		2226	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2227
		2228	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2229	C<$flags> is missing or C<0>, then this should be the same as a call to
		2230	perl's built-in C<pipe> function and create a new pipe, and works on
		2231	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2232	(..., 4096, O_BINARY)>.
		2233
		2234	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2235	the given flags (Linux 2.6.27, glibc 2.9).
		2236
		2237	On success, the read and write file handles are returned.
		2238
		2239	On error, nothing will be returned. If the pipe2 syscall is missing and
		2240	C<$flags> is non-zero, fails with C<ENOSYS>.
		2241
		2242	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2243	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2244	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2245
		2246	Example: create a pipe race-free w.r.t. threads and fork:
		2247
		2248	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2249	or die "pipe2: $!\n";
		2250
		2251	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2252
		2253	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2254	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2255
		2256	On success, the new eventfd filehandle is returned, otherwise returns
		2257	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2258
		2259	Please refer to L<eventfd(2)> for more info on this call.
		2260
		2261	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2262	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2263
		2264	Example: create a new eventfd filehandle:
		2265
		2266	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2267	or die "eventfd: $!\n";
		2268
		2269	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2270
		2271	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2272	(unhelpful) default for C<$flags> is C<0>.
		2273
		2274	On success, the new timerfd filehandle is returned, otherwise returns
		2275	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2276
		2277	Please refer to L<timerfd_create(2)> for more info on this call.
		2278
		2279	The following C<$clockid> values are
		2280	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2281	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2282	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2283	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2284
		2285	The following C<$flags> values are available (Linux
		2286	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2287
		2288	Example: create a new timerfd and set it to one-second repeated alarms,
		2289	then wait for two alarms:
		2290
		2291	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2292	or die "timerfd_create: $!\n";
		2293
		2294	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2295	or die "timerfd_settime: $!\n";
		2296
		2297	for (1..2) {
		2298	8 == sysread $fh, my $buf, 8
		2299	or die "timerfd read failure\n";
		2300
		2301	printf "number of expirations (likely 1): %d\n",
		2302	unpack "Q", $buf;
		2303	}
		2304
		2305	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2306
		2307	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2308	call. Please refer to its manpage for more info on this call.
		2309
		2310	The new itimerspec is specified using two (possibly fractional) second
		2311	values, C<$new_interval> and C<$new_value>).
		2312
		2313	On success, the current interval and value are returned (as per
		2314	C<timerfd_gettime>). On failure, the empty list is returned.
		2315
		2316	The following C<$flags> values are
		2317	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2318	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2319
		2320	See C<IO::AIO::timerfd_create> for a full example.
		2321
		2322	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2323
		2324	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2325	call. Please refer to its manpage for more info on this call.
		2326
		2327	On success, returns the current values of interval and value for the given
		2328	timerfd (as potentially fractional second values). On failure, the empty
		2329	list is returned.
		2330
		2331	=back
		2332
1399	=cut	2333	=cut
1400		2334
1401	min_parallel 8;	2335	min_parallel 8;
1402		2336
1403	END { flush }	2337	END { flush }
1404		2338
1405	1;	2339	1;
1406		2340
		2341	=head1 EVENT LOOP INTEGRATION
		2342
		2343	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2344	automatically into many event loops:
		2345
		2346	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2347	use AnyEvent::AIO;
		2348
		2349	You can also integrate IO::AIO manually into many event loops, here are
		2350	some examples of how to do this:
		2351
		2352	# EV integration
		2353	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2354
		2355	# Event integration
		2356	Event->io (fd => IO::AIO::poll_fileno,
		2357	poll => 'r',
		2358	cb => \&IO::AIO::poll_cb);
		2359
		2360	# Glib/Gtk2 integration
		2361	add_watch Glib::IO IO::AIO::poll_fileno,
		2362	in => sub { IO::AIO::poll_cb; 1 };
		2363
		2364	# Tk integration
		2365	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2366	readable => \&IO::AIO::poll_cb);
		2367
		2368	# Danga::Socket integration
		2369	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2370	\&IO::AIO::poll_cb);
		2371
1407	=head2 FORK BEHAVIOUR	2372	=head2 FORK BEHAVIOUR
1408		2373
1409	This module should do "the right thing" when the process using it forks:	2374	Usage of pthreads in a program changes the semantics of fork
		2375	considerably. Specifically, only async-safe functions can be called after
		2376	fork. Perl doesn't know about this, so in general, you cannot call fork
		2377	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2378	pthreads, so this applies, but many other extensions and (for inexplicable
		2379	reasons) perl itself often is linked against pthreads, so this limitation
		2380	applies to quite a lot of perls.
1410		2381
1411	Before the fork, IO::AIO enters a quiescent state where no requests	2382	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1412	can be added in other threads and no results will be processed. After	2383	only works in the process that loaded it. Forking is fully supported, but
1413	the fork the parent simply leaves the quiescent state and continues	2384	using IO::AIO in the child is not.
1414	request/result processing, while the child frees the request/result queue
1415	(so that the requests started before the fork will only be handled in the
1416	parent). Threads will be started on demand until the limit set in the
1417	parent process has been reached again.
1418		2385
1419	In short: the parent will, after a short pause, continue as if fork had	2386	You might get around by not I<using> IO::AIO before (or after)
1420	not been called, while the child will act as if IO::AIO has not been used	2387	forking. You could also try to call the L<IO::AIO::reinit> function in the
1421	yet.	2388	child:
		2389
		2390	=over 4
		2391
		2392	=item IO::AIO::reinit
		2393
		2394	Abandons all current requests and I/O threads and simply reinitialises all
		2395	data structures. This is not an operation supported by any standards, but
		2396	happens to work on GNU/Linux and some newer BSD systems.
		2397
		2398	The only reasonable use for this function is to call it after forking, if
		2399	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2400	the process will result in undefined behaviour. Calling it at any time
		2401	will also result in any undefined (by POSIX) behaviour.
		2402
		2403	=back
		2404
		2405	=head2 LINUX-SPECIFIC CALLS
		2406
		2407	When a call is documented as "linux-specific" then this means it
		2408	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2409	availability and compatibility of such calls regardless of the platform
		2410	it is compiled on, so platforms such as FreeBSD which often implement
		2411	these calls will work. When in doubt, call them and see if they fail wth
		2412	C<ENOSYS>.
1422		2413
1423	=head2 MEMORY USAGE	2414	=head2 MEMORY USAGE
1424		2415
1425	Per-request usage:	2416	Per-request usage:
1426		2417
…		…
1439	temporary buffers, and each thread requires a stack and other data	2430	temporary buffers, and each thread requires a stack and other data
1440	structures (usually around 16k-128k, depending on the OS).	2431	structures (usually around 16k-128k, depending on the OS).
1441		2432
1442	=head1 KNOWN BUGS	2433	=head1 KNOWN BUGS
1443		2434
1444	Known bugs will be fixed in the next release.	2435	Known bugs will be fixed in the next release :)
		2436
		2437	=head1 KNOWN ISSUES
		2438
		2439	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2440	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2441	non-created hash slots or other scalars I didn't think of. It's best to
		2442	avoid such and either use scalar variables or making sure that the scalar
		2443	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2444
		2445	I am not sure anything can be done about this, so this is considered a
		2446	known issue, rather than a bug.
1445		2447
1446	=head1 SEE ALSO	2448	=head1 SEE ALSO
1447		2449
1448	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2450	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1449	more natural syntax.	2451	more natural syntax.

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