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Revision 1.171 by root, Sat Jan 2 14:24:32 2010 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.
…		…
191	use common::sense;	171	use common::sense;
192		172
193	use base 'Exporter';	173	use base 'Exporter';
194		174
195	BEGIN {	175	BEGIN {
196	our $VERSION = '3.4';	176	our $VERSION = 4.5;
197		177
198	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
199	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
200	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
201	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
202	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
203	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
204	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
205	aio_msync aio_mtouch);	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
212	sendfile fadvise);	196	sendfile fadvise madvise
		197	mmap munmap mremap munlock munlockall);
213		198
214	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
215		200
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		202
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
220	}	205	}
221		206
222	=head1 FUNCTIONS	207	=head1 FUNCTIONS
223		208
224	=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, $length = undef
		294	IO::AIO::munlockall
		295
		296	=head2 API NOTES
225		297
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	304	error occured, in C<$!>) - 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>.
233		310
234	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	312	internally until the request has finished.
236		313
237	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
238	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
239		316
240	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
241	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
242	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
244	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
245	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.
246		325
247	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
248	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
249	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
250	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
251	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
252	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.
253		333
254	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
255	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
256		338
257	=over 4	339	=over 4
258		340
259	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
260		342
…		…
290		372
291		373
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		375
294	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
295	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
296		378
297	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,
298	for an explanation.	380	for an explanation.
299		381
300	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
…		…
307	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
308	change the umask.	390	change the umask.
309		391
310	Example:	392	Example:
311		393
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	394	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	395	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	396	print "open successful, fh is $_[0]\n";
315	...	397	...
316	} else {	398	} else {
317	die "open failed: $!\n";	399	die "open failed: $!\n";
318	}	400	}
319	};	401	};
320		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
321		412
322	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
323		414
324	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
325	code.	416	code.
…		…
334	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
335	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
336		427
337	=cut	428	=cut
338		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
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		451
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		453
343	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
344	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
345	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
346	error, just like the syscall).	457	error, just like the syscall).
347		458
348	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
349	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
350		461
…		…
375		486
376	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
377	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
378	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
379	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
380	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>.
381		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<$in_fh>) is a file - the file I/O will then be asynchronous, while
		503	the socket I/O will be non-blocking. Note, however, that you can run
		504	into a trap where C<aio_sendfile> reads some data with readahead, then
		505	fails to write all data, and when the socket is ready the next time, the
		506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		508	resource usage.
		509
382	This call tries to make use of a native C<sendfile> syscall to provide	510	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	511	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	512	a socket, and C<$in_fh> should refer to an mmap'able file.
385		513
386	If a native sendfile cannot be found or it fails with C<ENOSYS>,	514	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
388	it will be emulated, so you can call C<aio_sendfile> on any type of	516	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
389	filehandle regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
390		518
391	Please note, however, that C<aio_sendfile> can read more bytes from	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
392	C<$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
393	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
394	provides the number of bytes written to C<$out_fh>. Only if the result	522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
395	value equals C<$length> one can assume that C<$length> bytes have been	523	so you really really should check the return value of C<aio_sendfile> -
396	read.	524	fewer bytes than expected might have been transferred.
397		525
398		526
399	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
400		528
401	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
…		…
405	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
406	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
407	(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
408	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
409		537
410	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
411	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.
412		540
413		541
414	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
415		543
416	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
…		…
423	for an explanation.	551	for an explanation.
424		552
425	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
426	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
427	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>.
428		565
429	Example: Print the length of F</etc/passwd>:	566	Example: Print the length of F</etc/passwd>:
430		567
431	aio_stat "/etc/passwd", sub {	568	aio_stat "/etc/passwd", sub {
432	$_[0] and die "stat failed: $!";	569	$_[0] and die "stat failed: $!";
433	print "size is ", -s _, "\n";	570	print "size is ", -s _, "\n";
434	};	571	};
435		572
436		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
437	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	618	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
438		619
439	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
440	and $mtime being undef). Fractional times are supported if the underlying	621	and $mtime being undef). Fractional times are supported if the underlying
441	syscalls support them.	622	syscalls support them.
…		…
468	=item aio_truncate $fh_or_path, $offset, $callback->($status)	649	=item aio_truncate $fh_or_path, $offset, $callback->($status)
469		650
470	Works like truncate(2) or ftruncate(2).	651	Works like truncate(2) or ftruncate(2).
471		652
472		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
473	=item aio_chmod $fh_or_path, $mode, $callback->($status)	676	=item aio_chmod $fh_or_path, $mode, $callback->($status)
474		677
475	Works like perl's C<chmod> function.	678	Works like perl's C<chmod> function.
476		679
477		680
…		…
479		682
480	Asynchronously unlink (delete) a file and call the callback with the	683	Asynchronously unlink (delete) a file and call the callback with the
481	result code.	684	result code.
482		685
483		686
484	=item aio_mknod $path, $mode, $dev, $callback->($status)	687	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
485		688
486	[EXPERIMENTAL]	689	[EXPERIMENTAL]
487		690
488	Asynchronously create a device node (or fifo). See mknod(2).	691	Asynchronously create a device node (or fifo). See mknod(2).
489		692
490	The only (POSIX-) portable way of calling this function is:	693	The only (POSIX-) portable way of calling this function is:
491		694
492	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	695	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
493		696
		697	See C<aio_stat> for info about some potentially helpful extra constants
		698	and functions.
494		699
495	=item aio_link $srcpath, $dstpath, $callback->($status)	700	=item aio_link $srcpath, $dstpath, $callback->($status)
496		701
497	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
498	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.
…		…
502		707
503	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
504	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.
505		710
506		711
507	=item aio_readlink $path, $callback->($link)	712	=item aio_readlink $pathname, $callback->($link)
508		713
509	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
510	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
511	callback.	716	callback.
512		717
513		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
514	=item aio_rename $srcpath, $dstpath, $callback->($status)	729	=item aio_rename $srcpath, $dstpath, $callback->($status)
515		730
516	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
517	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>.
518		753
519		754
520	=item aio_mkdir $pathname, $mode, $callback->($status)	755	=item aio_mkdir $pathname, $mode, $callback->($status)
521		756
522	Asynchronously mkdir (create) a directory and call the callback with	757	Asynchronously mkdir (create) a directory and call the callback with
…		…
527	=item aio_rmdir $pathname, $callback->($status)	762	=item aio_rmdir $pathname, $callback->($status)
528		763
529	Asynchronously rmdir (delete) a directory and call the callback with the	764	Asynchronously rmdir (delete) a directory and call the callback with the
530	result code.	765	result code.
531		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
532		771
533	=item aio_readdir $pathname, $callback->($entries)	772	=item aio_readdir $pathname, $callback->($entries)
534		773
535	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
536	directory (i.e. opendir + readdir + closedir). The entries will not be	775	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
540	array-ref with the filenames.	779	array-ref with the filenames.
541		780
542		781
543	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	782	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
544		783
545	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	784	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
546	behaviour and output format. In case of an error, C<$entries> will be	785	tune behaviour and output format. In case of an error, C<$entries> will be
547	C<undef>.	786	C<undef>.
548		787
549	The flags are a combination of the following constants, ORed together (the	788	The flags are a combination of the following constants, ORed together (the
550	flags will also be passed to the callback, possibly modified):	789	flags will also be passed to the callback, possibly modified):
551		790
552	=over 4	791	=over 4
553		792
554	=item IO::AIO::READDIR_DENTS	793	=item IO::AIO::READDIR_DENTS
555		794
556	When this flag is off, then the callback gets an arrayref with of names	795	Normally the callback gets an arrayref consisting of names only (as
557	only (as with C<aio_readdir>), otherwise it gets an arrayref with	796	with C<aio_readdir>). If this flag is set, then the callback gets an
558	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	797	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
559	entry in more detail.	798	single directory entry in more detail:
560		799
561	C<$name> is the name of the entry.	800	C<$name> is the name of the entry.
562		801
563	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	802	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
564		803
565	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	804	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
566	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	805	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
567	C<IO::AIO::DT_WHT>.	806	C<IO::AIO::DT_WHT>.
568		807
569	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	808	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
570	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	809	to know, you have to run stat yourself. Also, for speed/memory reasons,
571	scalars are read-only: you can not modify them.	810	the C<$type> scalars are read-only: you must not modify them.
572		811
573	C<$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
574	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
575	systems that do not deliver the inode information.	814	systems that do not deliver the inode information.
576		815
577	=item IO::AIO::READDIR_DIRS_FIRST	816	=item IO::AIO::READDIR_DIRS_FIRST
578		817
579	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
580	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
581	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
582	stat() each entry.	821	while avoiding to stat() each entry.
583		822
584	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
585	to find directories directly. Otherwise, likely directories are files	824	to find directories directly. Otherwise, likely directories are names
586	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
587	short names are tried first.	826	short names are tried first.
588		827
589	=item IO::AIO::READDIR_STAT_ORDER	828	=item IO::AIO::READDIR_STAT_ORDER
590		829
591	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
592	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
593	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
594	be fastest.	833	faster.
595		834
596	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,
597	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.
598		839
599	=item IO::AIO::READDIR_FOUND_UNKNOWN	840	=item IO::AIO::READDIR_FOUND_UNKNOWN
600		841
601	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
602	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<$type>'s found were
603	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	844	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
604	C<$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.
605		846
606	=back	847	=back
607		848
608		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
609	=item aio_load $path, $data, $callback->($status)	879	=item aio_load $pathname, $data, $callback->($status)
610		880
611	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
612	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.
613		885
614	=cut	886	=cut
615		887
616	sub aio_load($$;$) {	888	sub aio_load($$;$) {
617	my ($path, undef, $cb) = @_;	889	my ($path, undef, $cb) = @_;
…		…
637	=item aio_copy $srcpath, $dstpath, $callback->($status)	909	=item aio_copy $srcpath, $dstpath, $callback->($status)
638		910
639	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
640	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
641	a status of C<0> (ok) or C<-1> (error, see C<$!>).	913	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		914
		915	Existing destination files will be truncated.
642		916
643	This is a composite request that creates the destination file with	917	This is a composite request that creates the destination file with
644	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
645	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	919	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
646	uid/gid, in that order.	920	uid/gid, in that order.
…		…
736	if ($_[0] && $! == EXDEV) {	1010	if ($_[0] && $! == EXDEV) {
737	aioreq_pri $pri;	1011	aioreq_pri $pri;
738	add $grp aio_copy $src, $dst, sub {	1012	add $grp aio_copy $src, $dst, sub {
739	$grp->result ($_[0]);	1013	$grp->result ($_[0]);
740		1014
741	if (!$_[0]) {	1015	unless ($_[0]) {
742	aioreq_pri $pri;	1016	aioreq_pri $pri;
743	add $grp aio_unlink $src;	1017	add $grp aio_unlink $src;
744	}	1018	}
745	};	1019	};
746	} else {	1020	} else {
…		…
749	};	1023	};
750		1024
751	$grp	1025	$grp
752	}	1026	}
753		1027
754	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1028	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
755		1029
756	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1030	Scans a directory (similar to C<aio_readdir>) but additionally tries to
757	efficiently separate the entries of directory C<$path> into two sets of	1031	efficiently separate the entries of directory C<$path> into two sets of
758	names, directories you can recurse into (directories), and ones you cannot	1032	names, directories you can recurse into (directories), and ones you cannot
759	recurse into (everything else, including symlinks to directories).	1033	recurse into (everything else, including symlinks to directories).
760		1034
761	C<aio_scandir> is a composite request that creates of many sub requests_	1035	C<aio_scandir> is a composite request that generates many sub requests.
762	C<$maxreq> specifies the maximum number of outstanding aio requests that	1036	C<$maxreq> specifies the maximum number of outstanding aio requests that
763	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
764	will be chosen (currently 4).	1038	will be chosen (currently 4).
765		1039
766	On error, the callback is called without arguments, otherwise it receives	1040	On error, the callback is called without arguments, otherwise it receives
…		…
790	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
791	currently) and likely non-directories (see C<aio_readdirx>). Then every	1065	currently) and likely non-directories (see C<aio_readdirx>). Then every
792	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,
793	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
794	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
795	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
796	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
797	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
798	the filetype information on readdir.	1072	the filetype information on readdir.
799		1073
800	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
…		…
816		1090
817	my $grp = aio_group $cb;	1091	my $grp = aio_group $cb;
818		1092
819	$maxreq = 4 if $maxreq <= 0;	1093	$maxreq = 4 if $maxreq <= 0;
820		1094
821	# stat once	1095	# get a wd object
822	aioreq_pri $pri;	1096	aioreq_pri $pri;
823	add $grp aio_stat $path, sub {	1097	add $grp aio_wd $path, sub {
		1098	$_[0]
824	return $grp->result () if $_[0];	1099	or return $grp->result ();
825	my $now = time;
826	my $hash1 = join ":", (stat _)[0,1,3,7,9];
827		1100
828	# read the directory entries	1101	my $wd = [shift, "."];
		1102
		1103	# stat once
829	aioreq_pri $pri;	1104	aioreq_pri $pri;
830	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1105	add $grp aio_stat $wd, sub {
831	my $entries = shift
832	or return $grp->result ();	1106	return $grp->result () if $_[0];
		1107	my $now = time;
		1108	my $hash1 = join ":", (stat _)[0,1,3,7,9];
833		1109
834	# stat the dir another time	1110	# read the directory entries
835	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;
836	add $grp aio_stat $path, sub {	1118	add $grp aio_stat $wd, sub {
837	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1119	my $hash2 = join ":", (stat _)[0,1,3,7,9];
838		1120
839	my $ndirs;	1121	my $ndirs;
840		1122
841	# take the slow route if anything looks fishy	1123	# take the slow route if anything looks fishy
842	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1124	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
843	$ndirs = -1;	1125	$ndirs = -1;
844	} else {	1126	} else {
845	# if nlink == 2, we are finished	1127	# if nlink == 2, we are finished
846	# for non-posix-fs's, we rely on nlink < 2	1128	# for non-posix-fs's, we rely on nlink < 2
847	$ndirs = (stat _)[3] - 2	1129	$ndirs = (stat _)[3] - 2
848	or return $grp->result ([], $entries);	1130	or return $grp->result ([], $entries);
849	}	1131	}
850		1132
851	my (@dirs, @nondirs);	1133	my (@dirs, @nondirs);
852		1134
853	my $statgrp = add $grp aio_group sub {	1135	my $statgrp = add $grp aio_group sub {
854	$grp->result (\@dirs, \@nondirs);	1136	$grp->result (\@dirs, \@nondirs);
855	};	1137	};
856		1138
857	limit $statgrp $maxreq;	1139	limit $statgrp $maxreq;
858	feed $statgrp sub {	1140	feed $statgrp sub {
859	return unless @$entries;	1141	return unless @$entries;
860	my $entry = shift @$entries;	1142	my $entry = shift @$entries;
861		1143
862	aioreq_pri $pri;	1144	aioreq_pri $pri;
		1145	$wd->[1] = "$entry/.";
863	add $statgrp aio_stat "$path/$entry/.", sub {	1146	add $statgrp aio_stat $wd, sub {
864	if ($_[0] < 0) {	1147	if ($_[0] < 0) {
865	push @nondirs, $entry;	1148	push @nondirs, $entry;
866	} else {	1149	} else {
867	# need to check for real directory	1150	# need to check for real directory
868	aioreq_pri $pri;	1151	aioreq_pri $pri;
		1152	$wd->[1] = $entry;
869	add $statgrp aio_lstat "$path/$entry", sub {	1153	add $statgrp aio_lstat $wd, sub {
870	if (-d _) {	1154	if (-d _) {
871	push @dirs, $entry;	1155	push @dirs, $entry;
872		1156
873	unless (--$ndirs) {	1157	unless (--$ndirs) {
874	push @nondirs, @$entries;	1158	push @nondirs, @$entries;
875	feed $statgrp;	1159	feed $statgrp;
		1160	}
		1161	} else {
		1162	push @nondirs, $entry;
876	}	1163	}
877	} else {
878	push @nondirs, $entry;
879	}	1164	}
880	}	1165	}
881	}	1166	};
882	};	1167	};
883	};	1168	};
884	};	1169	};
885	};	1170	};
886	};	1171	};
887		1172
888	$grp	1173	$grp
889	}	1174	}
890		1175
891	=item aio_rmtree $path, $callback->($status)	1176	=item aio_rmtree $pathname, $callback->($status)
892		1177
893	Delete a directory tree starting (and including) C<$path>, return the	1178	Delete a directory tree starting (and including) C<$path>, return the
894	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
895	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
896	everything else.	1181	everything else.
897		1182
898	=cut	1183	=cut
899		1184
…		…
921	};	1206	};
922		1207
923	$grp	1208	$grp
924	}	1209	}
925		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
926	=item aio_sync $callback->($status)	1255	=item aio_sync $callback->($status)
927		1256
928	Asynchronously call sync and call the callback when finished.	1257	Asynchronously call sync and call the callback when finished.
929		1258
930	=item aio_fsync $fh, $callback->($status)	1259	=item aio_fsync $fh, $callback->($status)
…		…
937	Asynchronously call fdatasync on the given filehandle and call the	1266	Asynchronously call fdatasync on the given filehandle and call the
938	callback with the fdatasync result code.	1267	callback with the fdatasync result code.
939		1268
940	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
941	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.
942		1278
943	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1279	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
944		1280
945	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>
946	to disk (but NOT the metadata), by calling the Linux-specific	1282	to disk (but NOT the metadata), by calling the Linux-specific
…		…
950	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>,
951	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1287	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
952	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
953	manpage for details.	1289	manpage for details.
954		1290
955	=item aio_pathsync $path, $callback->($status)	1291	=item aio_pathsync $pathname, $callback->($status)
956		1292
957	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
958	composite request intended to sync directories after directory operations	1294	composite request intended to sync directories after directory operations
959	(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
960	specific effect, but usually it makes sure that directory changes get	1296	specific effect, but usually it makes sure that directory changes get
…		…
991	};	1327	};
992		1328
993	$grp	1329	$grp
994	}	1330	}
995		1331
996	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1332	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
997		1333
998	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1334	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
999	scalars (see the L<Sys::Mmap> or L<Mmap> modules for details on this, note	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
1000	that the scalar must only be modified in-place while an aio operation is	1337	scalar must only be modified in-place while an aio operation is pending on
1001	pending on it).	1338	it).
1002		1339
1003	It calls the C<msync> function of your OS, if available, with the memory	1340	It calls the C<msync> function of your OS, if available, with the memory
1004	area starting at C<$offset> in the string and ending C<$length> bytes	1341	area starting at C<$offset> in the string and ending C<$length> bytes
1005	later. If C<$length> is negative, counts from the end, and if C<$length>	1342	later. If C<$length> is negative, counts from the end, and if C<$length>
1006	is C<undef>, then it goes till the end of the string. The flags can be	1343	is C<undef>, then it goes till the end of the string. The flags can be
1007	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1344	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1008	C<IO::AIO::MS_SYNC>.	1345	C<IO::AIO::MS_INVALIDATE>.
1009		1346
1010	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1347	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1011		1348
1012	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1349	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1013	scalars.	1350	scalars.
1014		1351
1015	It touches (reads or writes) all memory pages in the specified	1352	It touches (reads or writes) all memory pages in the specified
1016	range inside the scalar. All caveats and parameters are the same	1353	range inside the scalar. All caveats and parameters are the same
1017	as for C<aio_msync>, above, except for flags, which must be either	1354	as for C<aio_msync>, above, except for flags, which must be either
1018	C<0> (which reads all pages and ensures they are instantiated) or	1355	C<0> (which reads all pages and ensures they are instantiated) or
1019	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1356	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1020	writing an octet from it, which dirties the page).	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>.
1021		1443
1022	=item aio_group $callback->(...)	1444	=item aio_group $callback->(...)
1023		1445
1024	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
1025	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
…		…
1062	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
1063	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
1064	except to put your application under artificial I/O pressure.	1486	except to put your application under artificial I/O pressure.
1065		1487
1066	=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.
1067		1614
1068	=head2 IO::AIO::REQ CLASS	1615	=head2 IO::AIO::REQ CLASS
1069		1616
1070	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
1071	called in non-void context.	1618	called in non-void context.
…		…
1189		1736
1190	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
1191	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,
1192	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,
1193	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,
1194	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>
1195	delaying any later requests for a long time.	1742	requests, delaying any later requests for a long time.
1196		1743
1197	To avoid this, and allow incremental generation of requests, you can	1744	To avoid this, and allow incremental generation of requests, you can
1198	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
1199	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>,
1200	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
…		…
1249		1796
1250	See C<poll_cb> for an example.	1797	See C<poll_cb> for an example.
1251		1798
1252	=item IO::AIO::poll_cb	1799	=item IO::AIO::poll_cb
1253		1800
1254	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
1255	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
1256	returned earlier for whatever reason. Returns immediately when no events	1803	this "regularly" to finish outstanding requests.
1257	are outstanding. The amount of events processed depends on the settings of
1258	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1259		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
1260	If not all requests were processed for whatever reason, the filehandle	1811	If not all requests were processed for whatever reason, the poll file
1261	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
1262	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.
1263		1821
1264	Example: Install an Event watcher that automatically calls	1822	Example: Install an Event watcher that automatically calls
1265	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
1266	SYNOPSIS section, at the top of this document):	1824	SYNOPSIS section, at the top of this document):
1267		1825
1268	Event->io (fd => IO::AIO::poll_fileno,	1826	Event->io (fd => IO::AIO::poll_fileno,
1269	poll => 'r', async => 1,	1827	poll => 'r', async => 1,
1270	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;
1271		1857
1272	=item IO::AIO::max_poll_reqs $nreqs	1858	=item IO::AIO::max_poll_reqs $nreqs
1273		1859
1274	=item IO::AIO::max_poll_time $seconds	1860	=item IO::AIO::max_poll_time $seconds
1275		1861
…		…
1300	# use a low priority so other tasks have priority	1886	# use a low priority so other tasks have priority
1301	Event->io (fd => IO::AIO::poll_fileno,	1887	Event->io (fd => IO::AIO::poll_fileno,
1302	poll => 'r', nice => 1,	1888	poll => 'r', nice => 1,
1303	cb => &IO::AIO::poll_cb);	1889	cb => &IO::AIO::poll_cb);
1304		1890
1305	=item IO::AIO::poll_wait
1306
1307	If there are any outstanding requests and none of them in the result
1308	phase, wait till the result filehandle becomes ready for reading (simply
1309	does a C<select> on the filehandle. This is useful if you want to
1310	synchronously wait for some requests to finish).
1311
1312	See C<nreqs> for an example.
1313
1314	=item IO::AIO::poll
1315
1316	Waits until some requests have been handled.
1317
1318	Returns the number of requests processed, but is otherwise strictly
1319	equivalent to:
1320
1321	IO::AIO::poll_wait, IO::AIO::poll_cb
1322
1323	=item IO::AIO::flush
1324
1325	Wait till all outstanding AIO requests have been handled.
1326
1327	Strictly equivalent to:
1328
1329	IO::AIO::poll_wait, IO::AIO::poll_cb
1330	while IO::AIO::nreqs;
1331
1332	=back	1891	=back
1333		1892
1334	=head3 CONTROLLING THE NUMBER OF THREADS	1893	=head3 CONTROLLING THE NUMBER OF THREADS
1335		1894
1336	=over	1895	=over
…		…
1369		1928
1370	Under normal circumstances you don't need to call this function.	1929	Under normal circumstances you don't need to call this function.
1371		1930
1372	=item IO::AIO::max_idle $nthreads	1931	=item IO::AIO::max_idle $nthreads
1373		1932
1374	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1933	Limit the number of threads (default: 4) that are allowed to idle
1375	threads that did not get a request to process within 10 seconds). That	1934	(i.e., threads that did not get a request to process within the idle
1376	means if a thread becomes idle while C<$nthreads> other threads are also	1935	timeout (default: 10 seconds). That means if a thread becomes idle while
1377	idle, it will free its resources and exit.	1936	C<$nthreads> other threads are also idle, it will free its resources and
		1937	exit.
1378		1938
1379	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)
1380	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
1381	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1941	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1382		1942
1383	The default is probably ok in most situations, especially if thread	1943	The default is probably ok in most situations, especially if thread
1384	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
1385	want to use larger values.	1945	want to use larger values.
1386		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
1387	=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.
1388		1962
1389	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
1390	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
1391	use an C<aio_group> together with a feed callback.	1965	use an C<aio_group> together with a feed callback.
1392		1966
1393	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
1394	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:
1395	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1396	function will block until the limit is no longer exceeded.
1397		1969
1398	The default value is very large, so there is no practical limit on the	1970	IO::AIO::max_outstanding 32;
1399	number of outstanding requests.
1400		1971
1401	You can still queue as many requests as you want. Therefore,	1972	for my $path (...) {
1402	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1973	aio_stat $path , ...;
1403	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.
1404		1986
1405	=back	1987	=back
1406		1988
1407	=head3 STATISTICAL INFORMATION	1989	=head3 STATISTICAL INFORMATION
1408		1990
…		…
1430		2012
1431	=back	2013	=back
1432		2014
1433	=head3 MISCELLANEOUS FUNCTIONS	2015	=head3 MISCELLANEOUS FUNCTIONS
1434		2016
1435	IO::AIO implements some functions that might be useful, but are not	2017	IO::AIO implements some functions that are useful when you want to use
1436	asynchronous.	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.
1437		2021
1438	=over 4	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.
1439		2048
1440	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2049	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1441		2050
1442	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2051	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1443	but is blocking (this makes most sense if you know the input data is	2052	but is blocking (this makes most sense if you know the input data is
…		…
1446		2055
1447	Returns the number of bytes copied, or C<-1> on error.	2056	Returns the number of bytes copied, or C<-1> on error.
1448		2057
1449	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2058	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1450		2059
1451	Simply calls the C<posix_fadvise> function (see it's	2060	Simply calls the C<posix_fadvise> function (see its
1452	manpage for details). The following advice constants are	2061	manpage for details). The following advice constants are
1453	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2062	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1454	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2063	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1455	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2064	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1456		2065
1457	On systems that do not implement C<posix_fadvise>, this function returns	2066	On systems that do not implement C<posix_fadvise>, this function returns
1458	ENOSYS, otherwise the return value of C<posix_fadvise>.	2067	ENOSYS, otherwise the return value of C<posix_fadvise>.
1459		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
1460	=back	2331	=back
1461		2332
1462	=cut	2333	=cut
1463		2334
1464	min_parallel 8;	2335	min_parallel 8;
1465		2336
1466	END { flush }	2337	END { flush }
1467		2338
1468	1;	2339	1;
1469		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
1470	=head2 FORK BEHAVIOUR	2372	=head2 FORK BEHAVIOUR
1471		2373
1472	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.
1473		2381
1474	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
1475	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
1476	the fork the parent simply leaves the quiescent state and continues	2384	using IO::AIO in the child is not.
1477	request/result processing, while the child frees the request/result queue
1478	(so that the requests started before the fork will only be handled in the
1479	parent). Threads will be started on demand until the limit set in the
1480	parent process has been reached again.
1481		2385
1482	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)
1483	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
1484	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>.
1485		2413
1486	=head2 MEMORY USAGE	2414	=head2 MEMORY USAGE
1487		2415
1488	Per-request usage:	2416	Per-request usage:
1489		2417
…		…
1502	temporary buffers, and each thread requires a stack and other data	2430	temporary buffers, and each thread requires a stack and other data
1503	structures (usually around 16k-128k, depending on the OS).	2431	structures (usually around 16k-128k, depending on the OS).
1504		2432
1505	=head1 KNOWN BUGS	2433	=head1 KNOWN BUGS
1506		2434
1507	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.
1508		2447
1509	=head1 SEE ALSO	2448	=head1 SEE ALSO
1510		2449
1511	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
1512	more natural syntax.	2451	more natural syntax.

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