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Revision 1.151 by root, Fri Jun 12 00:43:16 2009 UTC vs.
Revision 1.266 by root, Tue Aug 9 11:37:53 2016 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
…		…
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		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $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
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.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
80	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
81	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
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		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
85	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,
86	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
87	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
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	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
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.2';	176	our $VERSION = 4.34;
199		177
200	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
201	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
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	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
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_link aio_move aio_copy aio_group
205	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
206	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
207		189
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	193	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
213		197
214	push @AIO_REQ, qw(aio_busy); # not exported	198	push @AIO_REQ, qw(aio_busy); # not exported
215		199
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		201
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
220	}	204	}
221		205
222	=head1 FUNCTIONS	206	=head1 FUNCTIONS
223		207
224	=head2 AIO REQUEST FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_mkdir $pathname, $mode, $callback->($status)
		239	aio_rmdir $pathname, $callback->($status)
		240	aio_readdir $pathname, $callback->($entries)
		241	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		242	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		243	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		244	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		245	aio_load $pathname, $data, $callback->($status)
		246	aio_copy $srcpath, $dstpath, $callback->($status)
		247	aio_move $srcpath, $dstpath, $callback->($status)
		248	aio_rmtree $pathname, $callback->($status)
		249	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		250	aio_ioctl $fh, $request, $buf, $callback->($status)
		251	aio_sync $callback->($status)
		252	aio_syncfs $fh, $callback->($status)
		253	aio_fsync $fh, $callback->($status)
		254	aio_fdatasync $fh, $callback->($status)
		255	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		256	aio_pathsync $pathname, $callback->($status)
		257	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		258	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		259	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		260	aio_mlockall $flags, $callback->($status)
		261	aio_group $callback->(...)
		262	aio_nop $callback->()
		263
		264	$prev_pri = aioreq_pri [$pri]
		265	aioreq_nice $pri_adjust
		266
		267	IO::AIO::poll_wait
		268	IO::AIO::poll_cb
		269	IO::AIO::poll
		270	IO::AIO::flush
		271	IO::AIO::max_poll_reqs $nreqs
		272	IO::AIO::max_poll_time $seconds
		273	IO::AIO::min_parallel $nthreads
		274	IO::AIO::max_parallel $nthreads
		275	IO::AIO::max_idle $nthreads
		276	IO::AIO::idle_timeout $seconds
		277	IO::AIO::max_outstanding $maxreqs
		278	IO::AIO::nreqs
		279	IO::AIO::nready
		280	IO::AIO::npending
		281
		282	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		283	IO::AIO::fadvise $fh, $offset, $len, $advice
		284	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		285	IO::AIO::munmap $scalar
		286	IO::AIO::madvise $scalar, $offset, $length, $advice
		287	IO::AIO::mprotect $scalar, $offset, $length, $protect
		288	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		289	IO::AIO::munlockall
		290
		291	=head2 API NOTES
225		292
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	293	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	294	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	295	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	296	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	297	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	298	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	299	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		300	most syscalls return C<-1> on error, unlike perl, which usually delivers
		301	"false").
		302
		303	Some requests (such as C<aio_readdir>) pass the actual results and
		304	communicate failures by passing C<undef>.
233		305
234	All functions expecting a filehandle keep a copy of the filehandle	306	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	307	internally until the request has finished.
236		308
237	All functions return request objects of type L<IO::AIO::REQ> that allow	309	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	310	further manipulation of those requests while they are in-flight.
239		311
240	The pathnames you pass to these routines I<must> be absolute and	312	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	313	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	314	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	315	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	316	in the program and then use relative paths. You can also take advantage
245	paths.	317	of IO::AIOs working directory abstraction, that lets you specify paths
		318	relative to some previously-opened "working directory object" - see the
		319	description of the C<IO::AIO::WD> class later in this document.
246		320
247	To encode pathnames as octets, either make sure you either: a) always pass	321	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	322	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	323	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	324	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)	325	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	326	unicode filenames or e) use something else to ensure your scalar has the
		327	correct contents.
253		328
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	329	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	330	handles correctly whether it is set or not.
		331
		332	=head2 AIO REQUEST FUNCTIONS
256		333
257	=over 4	334	=over 4
258		335
259	=item $prev_pri = aioreq_pri [$pri]	336	=item $prev_pri = aioreq_pri [$pri]
260		337
…		…
290		367
291		368
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	369	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		370
294	Asynchronously open or create a file and call the callback with a newly	371	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	372	created filehandle for the file (or C<undef> in case of an error).
296		373
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	374	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	375	for an explanation.
299		376
300	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	377	The C<$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	384	by the umask in effect then the request is being executed, so better never
308	change the umask.	385	change the umask.
309		386
310	Example:	387	Example:
311		388
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	389	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	390	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	391	print "open successful, fh is $_[0]\n";
315	...	392	...
316	} else {	393	} else {
317	die "open failed: $!\n";	394	die "open failed: $!\n";
318	}	395	}
319	};	396	};
320		397
		398	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		399	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		400	following POSIX and non-POSIX constants are available (missing ones on
		401	your system are, as usual, C<0>):
		402
		403	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		404	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		405	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		406
321		407
322	=item aio_close $fh, $callback->($status)	408	=item aio_close $fh, $callback->($status)
323		409
324	Asynchronously close a file and call the callback with the result	410	Asynchronously close a file and call the callback with the result
325	code.	411	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	420	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.	421	free for reuse until the perl filehandle is closed.
336		422
337	=cut	423	=cut
338		424
		425	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		426
		427	Seeks the filehandle to the new C<$offset>, similarly to perl's
		428	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		429	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		430	C<IO::AIO::SEEK_END>).
		431
		432	The resulting absolute offset will be passed to the callback, or C<-1> in
		433	case of an error.
		434
		435	In theory, the C<$whence> constants could be different than the
		436	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		437	so don't panic.
		438
		439	As a GNU/Linux (and maybe Solaris) extension, also the constants
		440	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		441	could be found. No guarantees about suitability for use in C<aio_seek> or
		442	Perl's C<sysseek> can be made though, although I would naively assume they
		443	"just work".
		444
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	445	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		446
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		448
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	449	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<$dataoffset>	450	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
345	and calls the callback without the actual number of bytes read (or -1 on	451	and calls the callback with the actual number of bytes read (or -1 on
346	error, just like the syscall).	452	error, just like the syscall).
347		453
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	454	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	455	offset plus the actual number of bytes read.
350		456
…		…
375		481
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	482	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	483	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	484	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	485	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	486	other. The same C<$in_fh> works fine though, as this function does not
		487	move or use the file offset of C<$in_fh>.
381		488
		489	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		490	are written, and there is no way to find out how many more bytes have been
		491	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		492	number of bytes written to C<$out_fh>. Only if the result value equals
		493	C<$length> one can assume that C<$length> bytes have been read.
		494
		495	Unlike with other C<aio_> functions, it makes a lot of sense to use
		496	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		497	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		498	the socket I/O will be non-blocking. Note, however, that you can run
		499	into a trap where C<aio_sendfile> reads some data with readahead, then
		500	fails to write all data, and when the socket is ready the next time, the
		501	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		502	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		503	resource usage.
		504
382	This call tries to make use of a native C<sendfile> syscall to provide	505	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	506	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.	507	a socket, and C<$in_fh> should refer to an mmap'able file.
385		508
386	If the native sendfile call fails or is not implemented, it will be	509	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	510	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		511	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	512	type of filehandle regardless of the limitations of the operating system.
389		513
390	Please note, however, that C<aio_sendfile> can read more bytes from	514	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	515	together in a hurry to improve benchmark numbers) tend to be rather buggy
392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	516	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	517	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	518	so you really really should check the return value of C<aio_sendfile> -
395	read.	519	fewer bytes than expected might have been transferred.
396		520
397		521
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	522	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		523
400	C<aio_readahead> populates the page cache with data from a file so that	524	C<aio_readahead> populates the page cache with data from a file so that
…		…
404	whole pages, so that offset is effectively rounded down to a page boundary	528	whole pages, so that offset is effectively rounded down to a page boundary
405	and bytes are read up to the next page boundary greater than or equal to	529	and bytes are read up to the next page boundary greater than or equal to
406	(off-set+length). C<aio_readahead> does not read beyond the end of the	530	(off-set+length). C<aio_readahead> does not read beyond the end of the
407	file. The current file offset of the file is left unchanged.	531	file. The current file offset of the file is left unchanged.
408		532
409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	533	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
410	emulated by simply reading the data, which would have a similar effect.	534	be emulated by simply reading the data, which would have a similar effect.
411		535
412		536
413	=item aio_stat $fh_or_path, $callback->($status)	537	=item aio_stat $fh_or_path, $callback->($status)
414		538
415	=item aio_lstat $fh, $callback->($status)	539	=item aio_lstat $fh, $callback->($status)
…		…
422	for an explanation.	546	for an explanation.
423		547
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	548	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	549	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	550	unless perl itself is compiled with large file support.
		551
		552	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		553	following constants and functions (if not implemented, the constants will
		554	be C<0> and the functions will either C<croak> or fall back on traditional
		555	behaviour).
		556
		557	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		558	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		559	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
427		560
428	Example: Print the length of F</etc/passwd>:	561	Example: Print the length of F</etc/passwd>:
429		562
430	aio_stat "/etc/passwd", sub {	563	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	564	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	565	print "size is ", -s _, "\n";
433	};	566	};
434		567
435		568
		569	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		570
		571	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		572	whether a file handle or path was passed.
		573
		574	On success, the callback is passed a hash reference with the following
		575	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		576	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		577	is passed.
		578
		579	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		580	C<ST_NOSUID>.
		581
		582	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		583	their correct value when available, or to C<0> on systems that do
		584	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		585	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		586	C<ST_NODIRATIME> and C<ST_RELATIME>.
		587
		588	Example: stat C</wd> and dump out the data if successful.
		589
		590	aio_statvfs "/wd", sub {
		591	my $f = $_[0]
		592	or die "statvfs: $!";
		593
		594	use Data::Dumper;
		595	say Dumper $f;
		596	};
		597
		598	# result:
		599	{
		600	bsize => 1024,
		601	bfree => 4333064312,
		602	blocks => 10253828096,
		603	files => 2050765568,
		604	flag => 4096,
		605	favail => 2042092649,
		606	bavail => 4333064312,
		607	ffree => 2042092649,
		608	namemax => 255,
		609	frsize => 1024,
		610	fsid => 1810
		611	}
		612
		613	Here is a (likely partial - send me updates!) list of fsid values used by
		614	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		615
		616	0x0000adf5 adfs
		617	0x0000adff affs
		618	0x5346414f afs
		619	0x09041934 anon-inode filesystem
		620	0x00000187 autofs
		621	0x42465331 befs
		622	0x1badface bfs
		623	0x42494e4d binfmt_misc
		624	0x9123683e btrfs
		625	0x0027e0eb cgroupfs
		626	0xff534d42 cifs
		627	0x73757245 coda
		628	0x012ff7b7 coh
		629	0x28cd3d45 cramfs
		630	0x453dcd28 cramfs-wend (wrong endianness)
		631	0x64626720 debugfs
		632	0x00001373 devfs
		633	0x00001cd1 devpts
		634	0x0000f15f ecryptfs
		635	0x00414a53 efs
		636	0x0000137d ext
		637	0x0000ef53 ext2/ext3/ext4
		638	0x0000ef51 ext2
		639	0xf2f52010 f2fs
		640	0x00004006 fat
		641	0x65735546 fuseblk
		642	0x65735543 fusectl
		643	0x0bad1dea futexfs
		644	0x01161970 gfs2
		645	0x47504653 gpfs
		646	0x00004244 hfs
		647	0xf995e849 hpfs
		648	0x00c0ffee hostfs
		649	0x958458f6 hugetlbfs
		650	0x2bad1dea inotifyfs
		651	0x00009660 isofs
		652	0x000072b6 jffs2
		653	0x3153464a jfs
		654	0x6b414653 k-afs
		655	0x0bd00bd0 lustre
		656	0x0000137f minix
		657	0x0000138f minix 30 char names
		658	0x00002468 minix v2
		659	0x00002478 minix v2 30 char names
		660	0x00004d5a minix v3
		661	0x19800202 mqueue
		662	0x00004d44 msdos
		663	0x0000564c novell
		664	0x00006969 nfs
		665	0x6e667364 nfsd
		666	0x00003434 nilfs
		667	0x5346544e ntfs
		668	0x00009fa1 openprom
		669	0x7461636F ocfs2
		670	0x00009fa0 proc
		671	0x6165676c pstorefs
		672	0x0000002f qnx4
		673	0x68191122 qnx6
		674	0x858458f6 ramfs
		675	0x52654973 reiserfs
		676	0x00007275 romfs
		677	0x67596969 rpc_pipefs
		678	0x73636673 securityfs
		679	0xf97cff8c selinux
		680	0x0000517b smb
		681	0x534f434b sockfs
		682	0x73717368 squashfs
		683	0x62656572 sysfs
		684	0x012ff7b6 sysv2
		685	0x012ff7b5 sysv4
		686	0x01021994 tmpfs
		687	0x15013346 udf
		688	0x00011954 ufs
		689	0x54190100 ufs byteswapped
		690	0x00009fa2 usbdevfs
		691	0x01021997 v9fs
		692	0xa501fcf5 vxfs
		693	0xabba1974 xenfs
		694	0x012ff7b4 xenix
		695	0x58465342 xfs
		696	0x012fd16d xia
		697
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	698	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		699
438	Works like perl's C<utime> function (including the special case of $atime	700	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	701	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	702	syscalls support them.
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	729	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		730
469	Works like truncate(2) or ftruncate(2).	731	Works like truncate(2) or ftruncate(2).
470		732
471		733
		734	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		735
		736	Allocates or frees disk space according to the C<$mode> argument. See the
		737	linux C<fallocate> documentation for details.
		738
		739	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		740	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		741	to deallocate a file range.
		742
		743	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		744	(without leaving a hole) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see
		745	your L<fallocate(2)> manpage).
		746
		747	The file system block size used by C<fallocate> is presumably the
		748	C<f_bsize> returned by C<statvfs>.
		749
		750	If C<fallocate> isn't available or cannot be emulated (currently no
		751	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		752
		753
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	754	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		755
474	Works like perl's C<chmod> function.	756	Works like perl's C<chmod> function.
475		757
476		758
…		…
478		760
479	Asynchronously unlink (delete) a file and call the callback with the	761	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	762	result code.
481		763
482		764
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	765	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		766
485	[EXPERIMENTAL]	767	[EXPERIMENTAL]
486		768
487	Asynchronously create a device node (or fifo). See mknod(2).	769	Asynchronously create a device node (or fifo). See mknod(2).
488		770
489	The only (POSIX-) portable way of calling this function is:	771	The only (POSIX-) portable way of calling this function is:
490		772
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	773	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		774
		775	See C<aio_stat> for info about some potentially helpful extra constants
		776	and functions.
493		777
494	=item aio_link $srcpath, $dstpath, $callback->($status)	778	=item aio_link $srcpath, $dstpath, $callback->($status)
495		779
496	Asynchronously create a new link to the existing object at C<$srcpath> at	780	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	781	the path C<$dstpath> and call the callback with the result code.
…		…
501		785
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	786	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	787	the path C<$dstpath> and call the callback with the result code.
504		788
505		789
506	=item aio_readlink $path, $callback->($link)	790	=item aio_readlink $pathname, $callback->($link)
507		791
508	Asynchronously read the symlink specified by C<$path> and pass it to	792	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	793	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	794	callback.
511		795
512		796
		797	=item aio_realpath $pathname, $callback->($path)
		798
		799	Asynchronously make the path absolute and resolve any symlinks in
		800	C<$path>. The resulting path only consists of directories (same as
		801	L<Cwd::realpath>).
		802
		803	This request can be used to get the absolute path of the current working
		804	directory by passing it a path of F<.> (a single dot).
		805
		806
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	807	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		808
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	809	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	810	rename(2) and call the callback with the result code.
		811
		812	On systems that support the AIO::WD working directory abstraction
		813	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		814	of failing, C<rename> is called on the absolute path of C<$wd>.
517		815
518		816
519	=item aio_mkdir $pathname, $mode, $callback->($status)	817	=item aio_mkdir $pathname, $mode, $callback->($status)
520		818
521	Asynchronously mkdir (create) a directory and call the callback with	819	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	824	=item aio_rmdir $pathname, $callback->($status)
527		825
528	Asynchronously rmdir (delete) a directory and call the callback with the	826	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	827	result code.
530		828
		829	On systems that support the AIO::WD working directory abstraction
		830	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		831	C<rmdir> is called on the absolute path of C<$wd>.
		832
531		833
532	=item aio_readdir $pathname, $callback->($entries)	834	=item aio_readdir $pathname, $callback->($entries)
533		835
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	836	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	837	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
539	array-ref with the filenames.	841	array-ref with the filenames.
540		842
541		843
542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	844	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
543		845
544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	846	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
545	behaviour and output format. In case of an error, C<$entries> will be	847	tune behaviour and output format. In case of an error, C<$entries> will be
546	C<undef>.	848	C<undef>.
547		849
548	The flags are a combination of the following constants, ORed together (the	850	The flags are a combination of the following constants, ORed together (the
549	flags will also be passed to the callback, possibly modified):	851	flags will also be passed to the callback, possibly modified):
550		852
551	=over 4	853	=over 4
552		854
553	=item IO::AIO::READDIR_DENTS	855	=item IO::AIO::READDIR_DENTS
554		856
555	When this flag is off, then the callback gets an arrayref with of names	857	When this flag is off, then the callback gets an arrayref consisting of
556	only (as with C<aio_readdir>), otherwise it gets an arrayref with	858	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
557	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	859	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
558	entry in more detail.	860	entry in more detail.
559		861
560	C<$name> is the name of the entry.	862	C<$name> is the name of the entry.
561		863
…		…
568	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	870	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
569	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	871	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
570	scalars are read-only: you can not modify them.	872	scalars are read-only: you can not modify them.
571		873
572	C<$inode> is the inode number (which might not be exact on systems with 64	874	C<$inode> is the inode number (which might not be exact on systems with 64
573	bit inode numbers and 32 bit perls). On systems that do not deliver the	875	bit inode numbers and 32 bit perls). This field has unspecified content on
574	inode information, this will always be zero.	876	systems that do not deliver the inode information.
575		877
576	=item IO::AIO::READDIR_DIRS_FIRST	878	=item IO::AIO::READDIR_DIRS_FIRST
577		879
578	When this flag is set, then the names will be returned in an order where	880	When this flag is set, then the names will be returned in an order where
579	likely directories come first. This is useful when you need to quickly	881	likely directories come first, in optimal stat order. This is useful when
580	find directories, or you want to find all directories while avoiding to	882	you need to quickly find directories, or you want to find all directories
581	stat() each entry.	883	while avoiding to stat() each entry.
582		884
583	If the system returns type information in readdir, then this is used	885	If the system returns type information in readdir, then this is used
584	to find directories directly. Otherwise, likely directories are files	886	to find directories directly. Otherwise, likely directories are names
585	beginning with ".", or otherwise files with no dots, of which files with	887	beginning with ".", or otherwise names with no dots, of which names with
586	short names are tried first.	888	short names are tried first.
587		889
588	=item IO::AIO::READDIR_STAT_ORDER	890	=item IO::AIO::READDIR_STAT_ORDER
589		891
590	When this flag is set, then the names will be returned in an order	892	When this flag is set, then the names will be returned in an order
…		…
597		899
598	=item IO::AIO::READDIR_FOUND_UNKNOWN	900	=item IO::AIO::READDIR_FOUND_UNKNOWN
599		901
600	This flag should not be set when calling C<aio_readdirx>. Instead, it	902	This flag should not be set when calling C<aio_readdirx>. Instead, it
601	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	903	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
602	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	904	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
603	C<$type>'s are known, which can be used to speed up some algorithms.	905	C<$type>'s are known, which can be used to speed up some algorithms.
604		906
605	=back	907	=back
606		908
607		909
608	=item aio_load $path, $data, $callback->($status)	910	=item aio_load $pathname, $data, $callback->($status)
609		911
610	This is a composite request that tries to fully load the given file into	912	This is a composite request that tries to fully load the given file into
611	memory. Status is the same as with aio_read.	913	memory. Status is the same as with aio_read.
612		914
613	=cut	915	=cut
…		…
635		937
636	=item aio_copy $srcpath, $dstpath, $callback->($status)	938	=item aio_copy $srcpath, $dstpath, $callback->($status)
637		939
638	Try to copy the I<file> (directories not supported as either source or	940	Try to copy the I<file> (directories not supported as either source or
639	destination) from C<$srcpath> to C<$dstpath> and call the callback with	941	destination) from C<$srcpath> to C<$dstpath> and call the callback with
640	the C<0> (error) or C<-1> ok.	942	a status of C<0> (ok) or C<-1> (error, see C<$!>).
641		943
642	This is a composite request that creates the destination file with	944	This is a composite request that creates the destination file with
643	mode 0200 and copies the contents of the source file into it using	945	mode 0200 and copies the contents of the source file into it using
644	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
645	uid/gid, in that order.	947	uid/gid, in that order.
…		…
657	my $grp = aio_group $cb;	959	my $grp = aio_group $cb;
658		960
659	aioreq_pri $pri;	961	aioreq_pri $pri;
660	add $grp aio_open $src, O_RDONLY, 0, sub {	962	add $grp aio_open $src, O_RDONLY, 0, sub {
661	if (my $src_fh = $_[0]) {	963	if (my $src_fh = $_[0]) {
662	my @stat = stat $src_fh; # hmm, might bock over nfs?	964	my @stat = stat $src_fh; # hmm, might block over nfs?
663		965
664	aioreq_pri $pri;	966	aioreq_pri $pri;
665	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	967	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
666	if (my $dst_fh = $_[0]) {	968	if (my $dst_fh = $_[0]) {
667	aioreq_pri $pri;	969	aioreq_pri $pri;
…		…
714		1016
715	=item aio_move $srcpath, $dstpath, $callback->($status)	1017	=item aio_move $srcpath, $dstpath, $callback->($status)
716		1018
717	Try to move the I<file> (directories not supported as either source or	1019	Try to move the I<file> (directories not supported as either source or
718	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1020	destination) from C<$srcpath> to C<$dstpath> and call the callback with
719	the C<0> (error) or C<-1> ok.	1021	a status of C<0> (ok) or C<-1> (error, see C<$!>).
720		1022
721	This is a composite request that tries to rename(2) the file first; if	1023	This is a composite request that tries to rename(2) the file first; if
722	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	1024	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
723	that is successful, unlinks the C<$srcpath>.	1025	that is successful, unlinks the C<$srcpath>.
724		1026
…		…
735	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
736	aioreq_pri $pri;	1038	aioreq_pri $pri;
737	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
738	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
739		1041
740	if (!$_[0]) {	1042	unless ($_[0]) {
741	aioreq_pri $pri;	1043	aioreq_pri $pri;
742	add $grp aio_unlink $src;	1044	add $grp aio_unlink $src;
743	}	1045	}
744	};	1046	};
745	} else {	1047	} else {
…		…
748	};	1050	};
749		1051
750	$grp	1052	$grp
751	}	1053	}
752		1054
753	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
754		1056
755	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
756	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
757	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
758	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
…		…
789	Then entries will be sorted into likely directories a non-initial dot	1091	Then entries will be sorted into likely directories a non-initial dot
790	currently) and likely non-directories (see C<aio_readdirx>). Then every	1092	currently) and likely non-directories (see C<aio_readdirx>). Then every
791	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1093	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
792	in order of their inode numbers. If that succeeds, it assumes that the	1094	in order of their inode numbers. If that succeeds, it assumes that the
793	entry is a directory or a symlink to directory (which will be checked	1095	entry is a directory or a symlink to directory (which will be checked
794	seperately). This is often faster than stat'ing the entry itself because	1096	separately). This is often faster than stat'ing the entry itself because
795	filesystems might detect the type of the entry without reading the inode	1097	filesystems might detect the type of the entry without reading the inode
796	data (e.g. ext2fs filetype feature), even on systems that cannot return	1098	data (e.g. ext2fs filetype feature), even on systems that cannot return
797	the filetype information on readdir.	1099	the filetype information on readdir.
798		1100
799	If the known number of directories (link count - 2) has been reached, the	1101	If the known number of directories (link count - 2) has been reached, the
…		…
815		1117
816	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
817		1119
818	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
819		1121
820	# stat once	1122	# get a wd object
821	aioreq_pri $pri;	1123	aioreq_pri $pri;
822	add $grp aio_stat $path, sub {	1124	add $grp aio_wd $path, sub {
		1125	$_[0]
823	return $grp->result () if $_[0];	1126	or return $grp->result ();
824	my $now = time;
825	my $hash1 = join ":", (stat _)[0,1,3,7,9];
826		1127
827	# read the directory entries	1128	my $wd = [shift, "."];
		1129
		1130	# stat once
828	aioreq_pri $pri;	1131	aioreq_pri $pri;
829	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1132	add $grp aio_stat $wd, sub {
830	my $entries = shift
831	or return $grp->result ();	1133	return $grp->result () if $_[0];
		1134	my $now = time;
		1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
832		1136
833	# stat the dir another time	1137	# read the directory entries
834	aioreq_pri $pri;	1138	aioreq_pri $pri;
		1139	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1140	my $entries = shift
		1141	or return $grp->result ();
		1142
		1143	# stat the dir another time
		1144	aioreq_pri $pri;
835	add $grp aio_stat $path, sub {	1145	add $grp aio_stat $wd, sub {
836	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1146	my $hash2 = join ":", (stat _)[0,1,3,7,9];
837		1147
838	my $ndirs;	1148	my $ndirs;
839		1149
840	# take the slow route if anything looks fishy	1150	# take the slow route if anything looks fishy
841	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1151	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
842	$ndirs = -1;	1152	$ndirs = -1;
843	} else {	1153	} else {
844	# if nlink == 2, we are finished	1154	# if nlink == 2, we are finished
845	# for non-posix-fs's, we rely on nlink < 2	1155	# for non-posix-fs's, we rely on nlink < 2
846	$ndirs = (stat _)[3] - 2	1156	$ndirs = (stat _)[3] - 2
847	or return $grp->result ([], $entries);	1157	or return $grp->result ([], $entries);
848	}	1158	}
849		1159
850	my (@dirs, @nondirs);	1160	my (@dirs, @nondirs);
851		1161
852	my $statgrp = add $grp aio_group sub {	1162	my $statgrp = add $grp aio_group sub {
853	$grp->result (\@dirs, \@nondirs);	1163	$grp->result (\@dirs, \@nondirs);
854	};	1164	};
855		1165
856	limit $statgrp $maxreq;	1166	limit $statgrp $maxreq;
857	feed $statgrp sub {	1167	feed $statgrp sub {
858	return unless @$entries;	1168	return unless @$entries;
859	my $entry = shift @$entries;	1169	my $entry = shift @$entries;
860		1170
861	aioreq_pri $pri;	1171	aioreq_pri $pri;
		1172	$wd->[1] = "$entry/.";
862	add $statgrp aio_stat "$path/$entry/.", sub {	1173	add $statgrp aio_stat $wd, sub {
863	if ($_[0] < 0) {	1174	if ($_[0] < 0) {
864	push @nondirs, $entry;	1175	push @nondirs, $entry;
865	} else {	1176	} else {
866	# need to check for real directory	1177	# need to check for real directory
867	aioreq_pri $pri;	1178	aioreq_pri $pri;
		1179	$wd->[1] = $entry;
868	add $statgrp aio_lstat "$path/$entry", sub {	1180	add $statgrp aio_lstat $wd, sub {
869	if (-d _) {	1181	if (-d _) {
870	push @dirs, $entry;	1182	push @dirs, $entry;
871		1183
872	unless (--$ndirs) {	1184	unless (--$ndirs) {
873	push @nondirs, @$entries;	1185	push @nondirs, @$entries;
874	feed $statgrp;	1186	feed $statgrp;
		1187	}
		1188	} else {
		1189	push @nondirs, $entry;
875	}	1190	}
876	} else {
877	push @nondirs, $entry;
878	}	1191	}
879	}	1192	}
880	}	1193	};
881	};	1194	};
882	};	1195	};
883	};	1196	};
884	};	1197	};
885	};	1198	};
886		1199
887	$grp	1200	$grp
888	}	1201	}
889		1202
890	=item aio_rmtree $path, $callback->($status)	1203	=item aio_rmtree $pathname, $callback->($status)
891		1204
892	Delete a directory tree starting (and including) C<$path>, return the	1205	Delete a directory tree starting (and including) C<$path>, return the
893	status of the final C<rmdir> only. This is a composite request that	1206	status of the final C<rmdir> only. This is a composite request that
894	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1207	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
895	everything else.	1208	everything else.
896		1209
897	=cut	1210	=cut
898		1211
…		…
920	};	1233	};
921		1234
922	$grp	1235	$grp
923	}	1236	}
924		1237
		1238	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1239
		1240	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1241
		1242	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1243	they execute asynchronously and pass the return value to the callback.
		1244
		1245	Both calls can be used for a lot of things, some of which make more sense
		1246	to run asynchronously in their own thread, while some others make less
		1247	sense. For example, calls that block waiting for external events, such
		1248	as locking, will also lock down an I/O thread while it is waiting, which
		1249	can deadlock the whole I/O system. At the same time, there might be no
		1250	alternative to using a thread to wait.
		1251
		1252	So in general, you should only use these calls for things that do
		1253	(filesystem) I/O, not for things that wait for other events (network,
		1254	other processes), although if you are careful and know what you are doing,
		1255	you still can.
		1256
		1257	The following constants are available (missing ones are, as usual C<0>):
		1258
		1259	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1260
		1261	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1262	C<FS_IOC_FIEMAP>.
		1263
		1264	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1265	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1266
		1267	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1268	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1269	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1270	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1271	C<FS_FL_USER_MODIFIABLE>.
		1272
		1273	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1274	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1275	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1276	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1277
925	=item aio_sync $callback->($status)	1278	=item aio_sync $callback->($status)
926		1279
927	Asynchronously call sync and call the callback when finished.	1280	Asynchronously call sync and call the callback when finished.
928		1281
929	=item aio_fsync $fh, $callback->($status)	1282	=item aio_fsync $fh, $callback->($status)
…		…
936	Asynchronously call fdatasync on the given filehandle and call the	1289	Asynchronously call fdatasync on the given filehandle and call the
937	callback with the fdatasync result code.	1290	callback with the fdatasync result code.
938		1291
939	If this call isn't available because your OS lacks it or it couldn't be	1292	If this call isn't available because your OS lacks it or it couldn't be
940	detected, it will be emulated by calling C<fsync> instead.	1293	detected, it will be emulated by calling C<fsync> instead.
		1294
		1295	=item aio_syncfs $fh, $callback->($status)
		1296
		1297	Asynchronously call the syncfs syscall to sync the filesystem associated
		1298	to the given filehandle and call the callback with the syncfs result
		1299	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1300	errno to C<ENOSYS> nevertheless.
941		1301
942	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1302	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943		1303
944	Sync the data portion of the file specified by C<$offset> and C<$length>	1304	Sync the data portion of the file specified by C<$offset> and C<$length>
945	to disk (but NOT the metadata), by calling the Linux-specific	1305	to disk (but NOT the metadata), by calling the Linux-specific
…		…
949	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1309	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
950	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1310	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
951	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1311	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
952	manpage for details.	1312	manpage for details.
953		1313
954	=item aio_pathsync $path, $callback->($status)	1314	=item aio_pathsync $pathname, $callback->($status)
955		1315
956	This request tries to open, fsync and close the given path. This is a	1316	This request tries to open, fsync and close the given path. This is a
957	composite request intended to sync directories after directory operations	1317	composite request intended to sync directories after directory operations
958	(E.g. rename). This might not work on all operating systems or have any	1318	(E.g. rename). This might not work on all operating systems or have any
959	specific effect, but usually it makes sure that directory changes get	1319	specific effect, but usually it makes sure that directory changes get
960	written to disc. It works for anything that can be opened for read-only,	1320	written to disc. It works for anything that can be opened for read-only,
961	not just directories.	1321	not just directories.
		1322
		1323	Future versions of this function might fall back to other methods when
		1324	C<fsync> on the directory fails (such as calling C<sync>).
962		1325
963	Passes C<0> when everything went ok, and C<-1> on error.	1326	Passes C<0> when everything went ok, and C<-1> on error.
964		1327
965	=cut	1328	=cut
966		1329
…		…
987	};	1350	};
988		1351
989	$grp	1352	$grp
990	}	1353	}
991		1354
		1355	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1356
		1357	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1358	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1359	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1360	scalar must only be modified in-place while an aio operation is pending on
		1361	it).
		1362
		1363	It calls the C<msync> function of your OS, if available, with the memory
		1364	area starting at C<$offset> in the string and ending C<$length> bytes
		1365	later. If C<$length> is negative, counts from the end, and if C<$length>
		1366	is C<undef>, then it goes till the end of the string. The flags can be
		1367	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1368	C<IO::AIO::MS_SYNC>.
		1369
		1370	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1371
		1372	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1373	scalars.
		1374
		1375	It touches (reads or writes) all memory pages in the specified
		1376	range inside the scalar. All caveats and parameters are the same
		1377	as for C<aio_msync>, above, except for flags, which must be either
		1378	C<0> (which reads all pages and ensures they are instantiated) or
		1379	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1380	writing an octet from it, which dirties the page).
		1381
		1382	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1383
		1384	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1385	scalars.
		1386
		1387	It reads in all the pages of the underlying storage into memory (if any)
		1388	and locks them, so they are not getting swapped/paged out or removed.
		1389
		1390	If C<$length> is undefined, then the scalar will be locked till the end.
		1391
		1392	On systems that do not implement C<mlock>, this function returns C<-1>
		1393	and sets errno to C<ENOSYS>.
		1394
		1395	Note that the corresponding C<munlock> is synchronous and is
		1396	documented under L<MISCELLANEOUS FUNCTIONS>.
		1397
		1398	Example: open a file, mmap and mlock it - both will be undone when
		1399	C<$data> gets destroyed.
		1400
		1401	open my $fh, "<", $path or die "$path: $!";
		1402	my $data;
		1403	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1404	aio_mlock $data; # mlock in background
		1405
		1406	=item aio_mlockall $flags, $callback->($status)
		1407
		1408	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1409	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1410
		1411	On systems that do not implement C<mlockall>, this function returns C<-1>
		1412	and sets errno to C<ENOSYS>.
		1413
		1414	Note that the corresponding C<munlockall> is synchronous and is
		1415	documented under L<MISCELLANEOUS FUNCTIONS>.
		1416
		1417	Example: asynchronously lock all current and future pages into memory.
		1418
		1419	aio_mlockall IO::AIO::MCL_FUTURE;
		1420
		1421	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1422
		1423	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1424	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1425	the ioctl is not available on your OS, then this request will fail with
		1426	C<ENOSYS>.
		1427
		1428	C<$start> is the starting offset to query extents for, C<$length> is the
		1429	size of the range to query - if it is C<undef>, then the whole file will
		1430	be queried.
		1431
		1432	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1433	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1434	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1435	the data portion.
		1436
		1437	C<$count> is the maximum number of extent records to return. If it is
		1438	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1439	case, if it is C<0>, then the callback receives the number of extents
		1440	instead of the extents themselves (which is unreliable, see below).
		1441
		1442	If an error occurs, the callback receives no arguments. The special
		1443	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1444
		1445	Otherwise, the callback receives an array reference with extent
		1446	structures. Each extent structure is an array reference itself, with the
		1447	following members:
		1448
		1449	[$logical, $physical, $length, $flags]
		1450
		1451	Flags is any combination of the following flag values (typically either C<0>
		1452	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1453
		1454	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1455	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1456	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1457	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1458	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1459	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1460
		1461	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1462	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1463	it to return all extents of a range for files with large number of
		1464	extents. The code works around all these issues if C<$count> is undef.
		1465
992	=item aio_group $callback->(...)	1466	=item aio_group $callback->(...)
993		1467
994	This is a very special aio request: Instead of doing something, it is a	1468	This is a very special aio request: Instead of doing something, it is a
995	container for other aio requests, which is useful if you want to bundle	1469	container for other aio requests, which is useful if you want to bundle
996	many requests into a single, composite, request with a definite callback	1470	many requests into a single, composite, request with a definite callback
…		…
1032	like sleep and file handle readable/writable, the overhead this creates is	1506	like sleep and file handle readable/writable, the overhead this creates is
1033	immense (it blocks a thread for a long time) so do not use this function	1507	immense (it blocks a thread for a long time) so do not use this function
1034	except to put your application under artificial I/O pressure.	1508	except to put your application under artificial I/O pressure.
1035		1509
1036	=back	1510	=back
		1511
		1512
		1513	=head2 IO::AIO::WD - multiple working directories
		1514
		1515	Your process only has one current working directory, which is used by all
		1516	threads. This makes it hard to use relative paths (some other component
		1517	could call C<chdir> at any time, and it is hard to control when the path
		1518	will be used by IO::AIO).
		1519
		1520	One solution for this is to always use absolute paths. This usually works,
		1521	but can be quite slow (the kernel has to walk the whole path on every
		1522	access), and can also be a hassle to implement.
		1523
		1524	Newer POSIX systems have a number of functions (openat, fdopendir,
		1525	futimensat and so on) that make it possible to specify working directories
		1526	per operation.
		1527
		1528	For portability, and because the clowns who "designed", or shall I write,
		1529	perpetrated this new interface were obviously half-drunk, this abstraction
		1530	cannot be perfect, though.
		1531
		1532	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1533	object. This object stores the canonicalised, absolute version of the
		1534	path, and on systems that allow it, also a directory file descriptor.
		1535
		1536	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1537	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1538	object and a pathname instead (or the IO::AIO::WD object alone, which
		1539	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1540	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1541	to that IO::AIO::WD object.
		1542
		1543	For example, to get a wd object for F</etc> and then stat F<passwd>
		1544	inside, you would write:
		1545
		1546	aio_wd "/etc", sub {
		1547	my $etcdir = shift;
		1548
		1549	# although $etcdir can be undef on error, there is generally no reason
		1550	# to check for errors here, as aio_stat will fail with ENOENT
		1551	# when $etcdir is undef.
		1552
		1553	aio_stat [$etcdir, "passwd"], sub {
		1554	# yay
		1555	};
		1556	};
		1557
		1558	The fact that C<aio_wd> is a request and not a normal function shows that
		1559	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1560	which is why it is done asynchronously.
		1561
		1562	To stat the directory obtained with C<aio_wd> above, one could write
		1563	either of the following three request calls:
		1564
		1565	aio_lstat "/etc" , sub { ... # pathname as normal string
		1566	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1567	aio_lstat $wd , sub { ... # shorthand for the previous
		1568
		1569	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1570	object and the pathname string, so you could write the following without
		1571	causing any issues due to C<$path> getting reused:
		1572
		1573	my $path = [$wd, undef];
		1574
		1575	for my $name (qw(abc def ghi)) {
		1576	$path->[1] = $name;
		1577	aio_stat $path, sub {
		1578	# ...
		1579	};
		1580	}
		1581
		1582	There are some caveats: when directories get renamed (or deleted), the
		1583	pathname string doesn't change, so will point to the new directory (or
		1584	nowhere at all), while the directory fd, if available on the system,
		1585	will still point to the original directory. Most functions accepting a
		1586	pathname will use the directory fd on newer systems, and the string on
		1587	older systems. Some functions (such as realpath) will always rely on the
		1588	string form of the pathname.
		1589
		1590	So this functionality is mainly useful to get some protection against
		1591	C<chdir>, to easily get an absolute path out of a relative path for future
		1592	reference, and to speed up doing many operations in the same directory
		1593	(e.g. when stat'ing all files in a directory).
		1594
		1595	The following functions implement this working directory abstraction:
		1596
		1597	=over 4
		1598
		1599	=item aio_wd $pathname, $callback->($wd)
		1600
		1601	Asynchonously canonicalise the given pathname and convert it to an
		1602	IO::AIO::WD object representing it. If possible and supported on the
		1603	system, also open a directory fd to speed up pathname resolution relative
		1604	to this working directory.
		1605
		1606	If something goes wrong, then C<undef> is passwd to the callback instead
		1607	of a working directory object and C<$!> is set appropriately. Since
		1608	passing C<undef> as working directory component of a pathname fails the
		1609	request with C<ENOENT>, there is often no need for error checking in the
		1610	C<aio_wd> callback, as future requests using the value will fail in the
		1611	expected way.
		1612
		1613	=item IO::AIO::CWD
		1614
		1615	This is a compiletime constant (object) that represents the process
		1616	current working directory.
		1617
		1618	Specifying this object as working directory object for a pathname is as if
		1619	the pathname would be specified directly, without a directory object. For
		1620	example, these calls are functionally identical:
		1621
		1622	aio_stat "somefile", sub { ... };
		1623	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1624
		1625	=back
		1626
		1627	To recover the path associated with an IO::AIO::WD object, you can use
		1628	C<aio_realpath>:
		1629
		1630	aio_realpath $wd, sub {
		1631	warn "path is $_[0]\n";
		1632	};
		1633
		1634	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1635	sometimes, fall back to using an absolue path.
1037		1636
1038	=head2 IO::AIO::REQ CLASS	1637	=head2 IO::AIO::REQ CLASS
1039		1638
1040	All non-aggregate C<aio_*> functions return an object of this class when	1639	All non-aggregate C<aio_*> functions return an object of this class when
1041	called in non-void context.	1640	called in non-void context.
…		…
1131	=item $grp->cancel_subs	1730	=item $grp->cancel_subs
1132		1731
1133	Cancel all subrequests and clears any feeder, but not the group request	1732	Cancel all subrequests and clears any feeder, but not the group request
1134	itself. Useful when you queued a lot of events but got a result early.	1733	itself. Useful when you queued a lot of events but got a result early.
1135		1734
		1735	The group request will finish normally (you cannot add requests to the
		1736	group).
		1737
1136	=item $grp->result (...)	1738	=item $grp->result (...)
1137		1739
1138	Set the result value(s) that will be passed to the group callback when all	1740	Set the result value(s) that will be passed to the group callback when all
1139	subrequests have finished and set the groups errno to the current value	1741	subrequests have finished and set the groups errno to the current value
1140	of errno (just like calling C<errno> without an error number). By default,	1742	of errno (just like calling C<errno> without an error number). By default,
…		…
1156		1758
1157	Sets a feeder/generator on this group: every group can have an attached	1759	Sets a feeder/generator on this group: every group can have an attached
1158	generator that generates requests if idle. The idea behind this is that,	1760	generator that generates requests if idle. The idea behind this is that,
1159	although you could just queue as many requests as you want in a group,	1761	although you could just queue as many requests as you want in a group,
1160	this might starve other requests for a potentially long time. For example,	1762	this might starve other requests for a potentially long time. For example,
1161	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1763	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1162	delaying any later requests for a long time.	1764	requests, delaying any later requests for a long time.
1163		1765
1164	To avoid this, and allow incremental generation of requests, you can	1766	To avoid this, and allow incremental generation of requests, you can
1165	instead a group and set a feeder on it that generates those requests. The	1767	instead a group and set a feeder on it that generates those requests. The
1166	feed callback will be called whenever there are few enough (see C<limit>,	1768	feed callback will be called whenever there are few enough (see C<limit>,
1167	below) requests active in the group itself and is expected to queue more	1769	below) requests active in the group itself and is expected to queue more
…		…
1208	=over 4	1810	=over 4
1209		1811
1210	=item $fileno = IO::AIO::poll_fileno	1812	=item $fileno = IO::AIO::poll_fileno
1211		1813
1212	Return the I<request result pipe file descriptor>. This filehandle must be	1814	Return the I<request result pipe file descriptor>. This filehandle must be
1213	polled for reading by some mechanism outside this module (e.g. Event or	1815	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1214	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1816	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1215	to call C<poll_cb> to check the results.	1817	you have to call C<poll_cb> to check the results.
1216		1818
1217	See C<poll_cb> for an example.	1819	See C<poll_cb> for an example.
1218		1820
1219	=item IO::AIO::poll_cb	1821	=item IO::AIO::poll_cb
1220		1822
1221	Process some outstanding events on the result pipe. You have to call this	1823	Process some requests that have reached the result phase (i.e. they have
1222	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1824	been executed but the results are not yet reported). You have to call
1223	returned earlier for whatever reason. Returns immediately when no events	1825	this "regularly" to finish outstanding requests.
1224	are outstanding. The amount of events processed depends on the settings of
1225	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1226		1826
		1827	Returns C<0> if all events could be processed (or there were no
		1828	events to process), or C<-1> if it returned earlier for whatever
		1829	reason. Returns immediately when no events are outstanding. The amount
		1830	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1831	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1832
1227	If not all requests were processed for whatever reason, the filehandle	1833	If not all requests were processed for whatever reason, the poll file
1228	will still be ready when C<poll_cb> returns, so normally you don't have to	1834	descriptor will still be ready when C<poll_cb> returns, so normally you
1229	do anything special to have it called later.	1835	don't have to do anything special to have it called later.
		1836
		1837	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1838	ready, it can be beneficial to call this function from loops which submit
		1839	a lot of requests, to make sure the results get processed when they become
		1840	available and not just when the loop is finished and the event loop takes
		1841	over again. This function returns very fast when there are no outstanding
		1842	requests.
1230		1843
1231	Example: Install an Event watcher that automatically calls	1844	Example: Install an Event watcher that automatically calls
1232	IO::AIO::poll_cb with high priority:	1845	IO::AIO::poll_cb with high priority (more examples can be found in the
		1846	SYNOPSIS section, at the top of this document):
1233		1847
1234	Event->io (fd => IO::AIO::poll_fileno,	1848	Event->io (fd => IO::AIO::poll_fileno,
1235	poll => 'r', async => 1,	1849	poll => 'r', async => 1,
1236	cb => \&IO::AIO::poll_cb);	1850	cb => \&IO::AIO::poll_cb);
		1851
		1852	=item IO::AIO::poll_wait
		1853
		1854	Wait until either at least one request is in the result phase or no
		1855	requests are outstanding anymore.
		1856
		1857	This is useful if you want to synchronously wait for some requests to
		1858	become ready, without actually handling them.
		1859
		1860	See C<nreqs> for an example.
		1861
		1862	=item IO::AIO::poll
		1863
		1864	Waits until some requests have been handled.
		1865
		1866	Returns the number of requests processed, but is otherwise strictly
		1867	equivalent to:
		1868
		1869	IO::AIO::poll_wait, IO::AIO::poll_cb
		1870
		1871	=item IO::AIO::flush
		1872
		1873	Wait till all outstanding AIO requests have been handled.
		1874
		1875	Strictly equivalent to:
		1876
		1877	IO::AIO::poll_wait, IO::AIO::poll_cb
		1878	while IO::AIO::nreqs;
1237		1879
1238	=item IO::AIO::max_poll_reqs $nreqs	1880	=item IO::AIO::max_poll_reqs $nreqs
1239		1881
1240	=item IO::AIO::max_poll_time $seconds	1882	=item IO::AIO::max_poll_time $seconds
1241		1883
…		…
1266	# use a low priority so other tasks have priority	1908	# use a low priority so other tasks have priority
1267	Event->io (fd => IO::AIO::poll_fileno,	1909	Event->io (fd => IO::AIO::poll_fileno,
1268	poll => 'r', nice => 1,	1910	poll => 'r', nice => 1,
1269	cb => &IO::AIO::poll_cb);	1911	cb => &IO::AIO::poll_cb);
1270		1912
1271	=item IO::AIO::poll_wait
1272
1273	If there are any outstanding requests and none of them in the result
1274	phase, wait till the result filehandle becomes ready for reading (simply
1275	does a C<select> on the filehandle. This is useful if you want to
1276	synchronously wait for some requests to finish).
1277
1278	See C<nreqs> for an example.
1279
1280	=item IO::AIO::poll
1281
1282	Waits until some requests have been handled.
1283
1284	Returns the number of requests processed, but is otherwise strictly
1285	equivalent to:
1286
1287	IO::AIO::poll_wait, IO::AIO::poll_cb
1288
1289	=item IO::AIO::flush
1290
1291	Wait till all outstanding AIO requests have been handled.
1292
1293	Strictly equivalent to:
1294
1295	IO::AIO::poll_wait, IO::AIO::poll_cb
1296	while IO::AIO::nreqs;
1297
1298	=back	1913	=back
1299		1914
1300	=head3 CONTROLLING THE NUMBER OF THREADS	1915	=head3 CONTROLLING THE NUMBER OF THREADS
1301		1916
1302	=over	1917	=over
…		…
1335		1950
1336	Under normal circumstances you don't need to call this function.	1951	Under normal circumstances you don't need to call this function.
1337		1952
1338	=item IO::AIO::max_idle $nthreads	1953	=item IO::AIO::max_idle $nthreads
1339		1954
1340	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1955	Limit the number of threads (default: 4) that are allowed to idle
1341	threads that did not get a request to process within 10 seconds). That	1956	(i.e., threads that did not get a request to process within the idle
1342	means if a thread becomes idle while C<$nthreads> other threads are also	1957	timeout (default: 10 seconds). That means if a thread becomes idle while
1343	idle, it will free its resources and exit.	1958	C<$nthreads> other threads are also idle, it will free its resources and
		1959	exit.
1344		1960
1345	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1961	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1346	to allow for extremely high load situations, but want to free resources	1962	to allow for extremely high load situations, but want to free resources
1347	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1963	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1348		1964
1349	The default is probably ok in most situations, especially if thread	1965	The default is probably ok in most situations, especially if thread
1350	creation is fast. If thread creation is very slow on your system you might	1966	creation is fast. If thread creation is very slow on your system you might
1351	want to use larger values.	1967	want to use larger values.
1352		1968
		1969	=item IO::AIO::idle_timeout $seconds
		1970
		1971	Sets the minimum idle timeout (default 10) after which worker threads are
		1972	allowed to exit. SEe C<IO::AIO::max_idle>.
		1973
1353	=item IO::AIO::max_outstanding $maxreqs	1974	=item IO::AIO::max_outstanding $maxreqs
		1975
		1976	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1977	you do queue up more than this number of requests, the next call to
		1978	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1979	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1980	longer exceeded.
		1981
		1982	In other words, this setting does not enforce a queue limit, but can be
		1983	used to make poll functions block if the limit is exceeded.
1354		1984
1355	This is a very bad function to use in interactive programs because it	1985	This is a very bad function to use in interactive programs because it
1356	blocks, and a bad way to reduce concurrency because it is inexact: Better	1986	blocks, and a bad way to reduce concurrency because it is inexact: Better
1357	use an C<aio_group> together with a feed callback.	1987	use an C<aio_group> together with a feed callback.
1358		1988
1359	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1989	Its main use is in scripts without an event loop - when you want to stat
1360	do queue up more than this number of requests, the next call to the	1990	a lot of files, you can write somehting like this:
1361	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1362	function will block until the limit is no longer exceeded.
1363		1991
1364	The default value is very large, so there is no practical limit on the	1992	IO::AIO::max_outstanding 32;
1365	number of outstanding requests.
1366		1993
1367	You can still queue as many requests as you want. Therefore,	1994	for my $path (...) {
1368	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1995	aio_stat $path , ...;
1369	as a stop gap to shield against fatal memory overflow (with large values).	1996	IO::AIO::poll_cb;
		1997	}
		1998
		1999	IO::AIO::flush;
		2000
		2001	The call to C<poll_cb> inside the loop will normally return instantly, but
		2002	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2003	some requests have been handled. This keeps the loop from pushing a large
		2004	number of C<aio_stat> requests onto the queue.
		2005
		2006	The default value for C<max_outstanding> is very large, so there is no
		2007	practical limit on the number of outstanding requests.
1370		2008
1371	=back	2009	=back
1372		2010
1373	=head3 STATISTICAL INFORMATION	2011	=head3 STATISTICAL INFORMATION
1374		2012
…		…
1394	Returns the number of requests currently in the pending state (executed,	2032	Returns the number of requests currently in the pending state (executed,
1395	but not yet processed by poll_cb).	2033	but not yet processed by poll_cb).
1396		2034
1397	=back	2035	=back
1398		2036
		2037	=head3 MISCELLANEOUS FUNCTIONS
		2038
		2039	IO::AIO implements some functions that are useful when you want to use
		2040	some "Advanced I/O" function not available to in Perl, without going the
		2041	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2042	counterpart.
		2043
		2044	=over 4
		2045
		2046	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2047
		2048	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2049	but is blocking (this makes most sense if you know the input data is
		2050	likely cached already and the output filehandle is set to non-blocking
		2051	operations).
		2052
		2053	Returns the number of bytes copied, or C<-1> on error.
		2054
		2055	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2056
		2057	Simply calls the C<posix_fadvise> function (see its
		2058	manpage for details). The following advice constants are
		2059	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2060	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2061	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2062
		2063	On systems that do not implement C<posix_fadvise>, this function returns
		2064	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2065
		2066	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>,
		2072	C<IO::AIO::MADV_FREE>.
		2073
		2074	On systems that do not implement C<posix_madvise>, this function returns
		2075	ENOSYS, otherwise the return value of C<posix_madvise>.
		2076
		2077	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2078
		2079	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2080	$scalar (see its manpage for details). The following protect
		2081	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2082	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2083
		2084	On systems that do not implement C<mprotect>, this function returns
		2085	ENOSYS, otherwise the return value of C<mprotect>.
		2086
		2087	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2088
		2089	Memory-maps a file (or anonymous memory range) and attaches it to the
		2090	given C<$scalar>, which will act like a string scalar. Returns true on
		2091	success, and false otherwise.
		2092
		2093	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		2094	change the string length, and most read-only operations such as copying it
		2095	or searching it with regexes and so on.
		2096
		2097	Anything else is unsafe and will, at best, result in memory leaks.
		2098
		2099	The memory map associated with the C<$scalar> is automatically removed
		2100	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		2101	C<IO::AIO::munmap> functions are called.
		2102
		2103	This calls the C<mmap>(2) function internally. See your system's manual
		2104	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2105
		2106	The C<$length> must be larger than zero and smaller than the actual
		2107	filesize.
		2108
		2109	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2110	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2111
		2112	C<$flags> can be a combination of
		2113	C<IO::AIO::MAP_SHARED> or
		2114	C<IO::AIO::MAP_PRIVATE>,
		2115	or a number of system-specific flags (when not available, the are C<0>):
		2116	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2117	C<IO::AIO::MAP_LOCKED>,
		2118	C<IO::AIO::MAP_NORESERVE>,
		2119	C<IO::AIO::MAP_POPULATE>,
		2120	C<IO::AIO::MAP_NONBLOCK>,
		2121	C<IO::AIO::MAP_FIXED>,
		2122	C<IO::AIO::MAP_GROWSDOWN>,
		2123	C<IO::AIO::MAP_32BIT>,
		2124	C<IO::AIO::MAP_HUGETLB> or
		2125	C<IO::AIO::MAP_STACK>.
		2126
		2127	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2128
		2129	C<$offset> is the offset from the start of the file - it generally must be
		2130	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2131
		2132	Example:
		2133
		2134	use Digest::MD5;
		2135	use IO::AIO;
		2136
		2137	open my $fh, "<verybigfile"
		2138	or die "$!";
		2139
		2140	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2141	or die "verybigfile: $!";
		2142
		2143	my $fast_md5 = md5 $data;
		2144
		2145	=item IO::AIO::munmap $scalar
		2146
		2147	Removes a previous mmap and undefines the C<$scalar>.
		2148
		2149	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2150
		2151	Calls the C<munlock> function, undoing the effects of a previous
		2152	C<aio_mlock> call (see its description for details).
		2153
		2154	=item IO::AIO::munlockall
		2155
		2156	Calls the C<munlockall> function.
		2157
		2158	On systems that do not implement C<munlockall>, this function returns
		2159	ENOSYS, otherwise the return value of C<munlockall>.
		2160
		2161	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2162
		2163	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2164	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2165	should be the file offset.
		2166
		2167	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2168	silently corrupt the data in this case.
		2169
		2170	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2171	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2172	C<IO::AIO::SPLICE_F_GIFT>.
		2173
		2174	See the C<splice(2)> manpage for details.
		2175
		2176	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2177
		2178	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2179	description for C<IO::AIO::splice> above for details.
		2180
		2181	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2182
		2183	Attempts to query or change the pipe buffer size. Obviously works only
		2184	on pipes, and currently works only on GNU/Linux systems, and fails with
		2185	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2186	size on other systems, drop me a note.
		2187
		2188	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2189
		2190	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2191	C<$flags> is missing or C<0>, then this should be the same as a call to
		2192	perl's built-in C<pipe> function and create a new pipe, and works on
		2193	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2194	(..., 4096, O_BINARY)>.
		2195
		2196	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2197	the given flags (Linux 2.6.27, glibc 2.9).
		2198
		2199	On success, the read and write file handles are returned.
		2200
		2201	On error, nothing will be returned. If the pipe2 syscall is missing and
		2202	C<$flags> is non-zero, fails with C<ENOSYS>.
		2203
		2204	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2205	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2206	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2207
		2208	=back
		2209
1399	=cut	2210	=cut
1400		2211
1401	min_parallel 8;	2212	min_parallel 8;
1402		2213
1403	END { flush }	2214	END { flush }
1404		2215
1405	1;	2216	1;
1406		2217
		2218	=head1 EVENT LOOP INTEGRATION
		2219
		2220	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2221	automatically into many event loops:
		2222
		2223	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2224	use AnyEvent::AIO;
		2225
		2226	You can also integrate IO::AIO manually into many event loops, here are
		2227	some examples of how to do this:
		2228
		2229	# EV integration
		2230	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2231
		2232	# Event integration
		2233	Event->io (fd => IO::AIO::poll_fileno,
		2234	poll => 'r',
		2235	cb => \&IO::AIO::poll_cb);
		2236
		2237	# Glib/Gtk2 integration
		2238	add_watch Glib::IO IO::AIO::poll_fileno,
		2239	in => sub { IO::AIO::poll_cb; 1 };
		2240
		2241	# Tk integration
		2242	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2243	readable => \&IO::AIO::poll_cb);
		2244
		2245	# Danga::Socket integration
		2246	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2247	\&IO::AIO::poll_cb);
		2248
1407	=head2 FORK BEHAVIOUR	2249	=head2 FORK BEHAVIOUR
1408		2250
1409	This module should do "the right thing" when the process using it forks:	2251	Usage of pthreads in a program changes the semantics of fork
		2252	considerably. Specifically, only async-safe functions can be called after
		2253	fork. Perl doesn't know about this, so in general, you cannot call fork
		2254	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2255	pthreads, so this applies, but many other extensions and (for inexplicable
		2256	reasons) perl itself often is linked against pthreads, so this limitation
		2257	applies to quite a lot of perls.
1410		2258
1411	Before the fork, IO::AIO enters a quiescent state where no requests	2259	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1412	can be added in other threads and no results will be processed. After	2260	only works in the process that loaded it. Forking is fully supported, but
1413	the fork the parent simply leaves the quiescent state and continues	2261	using IO::AIO in the child is not.
1414	request/result processing, while the child frees the request/result queue
1415	(so that the requests started before the fork will only be handled in the
1416	parent). Threads will be started on demand until the limit set in the
1417	parent process has been reached again.
1418		2262
1419	In short: the parent will, after a short pause, continue as if fork had	2263	You might get around by not I<using> IO::AIO before (or after)
1420	not been called, while the child will act as if IO::AIO has not been used	2264	forking. You could also try to call the L<IO::AIO::reinit> function in the
1421	yet.	2265	child:
		2266
		2267	=over 4
		2268
		2269	=item IO::AIO::reinit
		2270
		2271	Abandons all current requests and I/O threads and simply reinitialises all
		2272	data structures. This is not an operation supported by any standards, but
		2273	happens to work on GNU/Linux and some newer BSD systems.
		2274
		2275	The only reasonable use for this function is to call it after forking, if
		2276	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2277	the process will result in undefined behaviour. Calling it at any time
		2278	will also result in any undefined (by POSIX) behaviour.
		2279
		2280	=back
1422		2281
1423	=head2 MEMORY USAGE	2282	=head2 MEMORY USAGE
1424		2283
1425	Per-request usage:	2284	Per-request usage:
1426		2285

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