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Revision 1.84 by root, Sat Oct 28 00:17:30 2006 UTC vs.
Revision 1.269 by root, Tue Jun 6 04:29:35 2017 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) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
30	# AnyEvent integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',
37	cb => \&IO::AIO::poll_cb);
38
39	# Glib/Gtk2 integration
40	add_watch Glib::IO IO::AIO::poll_fileno,
41	in => sub { IO::AIO::poll_cb; 1 };
42
43	# Tk integration
44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
45	readable => \&IO::AIO::poll_cb);
46
47	# Danga::Socket integration
48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49	\&IO::AIO::poll_cb);
50
51	=head1 DESCRIPTION	31	=head1 DESCRIPTION
52		32
53	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
54	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>).
		36
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
55		52
56	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
57	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
58	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
59	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
60	functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
61	not well-supported or restricted (Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	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
63	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
64	using threads anyway.	61	using threads anyway.
65		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
66	Although the module will work with in the presence of other (Perl-)	67	Although the module will work in the presence of other (Perl-) threads,
67	threads, it is currently not reentrant in any way, so use appropriate	68	it is currently not reentrant in any way, so use appropriate locking
68	locking yourself, always call C<poll_cb> from within the same thread, or	69	yourself, always call C<poll_cb> from within the same thread, or never
69	never call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
		71
		72	=head2 EXAMPLE
		73
		74	This is a simple example that uses the EV module and loads
		75	F</etc/passwd> asynchronously:
		76
		77	use EV;
		78	use IO::AIO;
		79
		80	# register the IO::AIO callback with EV
		81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		82
		83	# queue the request to open /etc/passwd
		84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		85	my $fh = shift
		86	or die "error while opening: $!";
		87
		88	# stat'ing filehandles is generally non-blocking
		89	my $size = -s $fh;
		90
		91	# queue a request to read the file
		92	my $contents;
		93	aio_read $fh, 0, $size, $contents, 0, sub {
		94	$_[0] == $size
		95	or die "short read: $!";
		96
		97	close $fh;
		98
		99	# file contents now in $contents
		100	print $contents;
		101
		102	# exit event loop and program
		103	EV::break;
		104	};
		105	};
		106
		107	# possibly queue up other requests, or open GUI windows,
		108	# check for sockets etc. etc.
		109
		110	# process events as long as there are some:
		111	EV::run;
70		112
71	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
72		114
73	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
74	directly visible to Perl.	116	directly visible to Perl.
…		…
116	Request has reached the end of its lifetime and holds no resources anymore	158	Request has reached the end of its lifetime and holds no resources anymore
117	(except possibly for the Perl object, but its connection to the actual	159	(except possibly for the Perl object, but its connection to the actual
118	aio request is severed and calling its methods will either do nothing or	160	aio request is severed and calling its methods will either do nothing or
119	result in a runtime error).	161	result in a runtime error).
120		162
		163	=back
		164
121	=cut	165	=cut
122		166
123	package IO::AIO;	167	package IO::AIO;
124		168
125	no warnings;	169	use Carp ();
126	use strict 'vars';	170
		171	use common::sense;
127		172
128	use base 'Exporter';	173	use base 'Exporter';
129		174
130	BEGIN {	175	BEGIN {
131	our $VERSION = '2.0';	176	our $VERSION = 4.35;
132		177
133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
136	aio_copy aio_group aio_nop aio_mknod);	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_link aio_move aio_copy aio_group
		184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
		189
137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139	min_parallel max_parallel nreqs nready npending);	192	min_parallel max_parallel max_idle idle_timeout
		193	nreqs nready npending nthreads
		194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
		197
		198	push @AIO_REQ, qw(aio_busy); # not exported
140		199
141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142		201
143	require XSLoader;	202	require XSLoader;
144	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
145	}	204	}
146		205
147	=head1 FUNCTIONS	206	=head1 FUNCTIONS
148		207
149	=head2 AIO 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 = MS_SYNC, $callback->($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, $length = undef
		289	IO::AIO::munlockall
		290
		291	=head2 API NOTES
150		292
151	All the C<aio_*> calls are more or less thin wrappers around the syscall	293	All the C<aio_*> calls are more or less thin wrappers around the syscall
152	with the same name (sans C<aio_>). The arguments are similar or identical,	294	with the same name (sans C<aio_>). The arguments are similar or identical,
153	and they all accept an additional (and optional) C<$callback> argument	295	and they all accept an additional (and optional) C<$callback> argument
154	which must be a code reference. This code reference will get called with	296	which must be a code reference. This code reference will be called after
155	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	297	the syscall has been executed in an asynchronous fashion. The results
156	perl, which usually delivers "false") as it's sole argument when the given	298	of the request will be passed as arguments to the callback (and, if an
157	syscall has been executed asynchronously.	299	error occured, in C<$!>) - 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>.
158		305
159	All functions expecting a filehandle keep a copy of the filehandle	306	All functions expecting a filehandle keep a copy of the filehandle
160	internally until the request has finished.	307	internally until the request has finished.
161		308
162	All requests return objects of type L<IO::AIO::REQ> that allow further	309	All functions return request objects of type L<IO::AIO::REQ> that allow
163	manipulation of those requests while they are in-flight.	310	further manipulation of those requests while they are in-flight.
164		311
165	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
166	encoded in byte form. 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
167	request is being executed, the current working directory could have	314	current working directory could have changed. Alternatively, you can
168	changed. Alternatively, you can make sure that you never change the	315	make sure that you never change the current working directory anywhere
169	current working directory.	316	in the program and then use relative paths. You can also take advantage
		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.
170		320
171	To encode pathnames to byte form, either make sure you either: a)	321	To encode pathnames as octets, either make sure you either: a) always pass
172	always pass in filenames you got from outside (command line, readdir	322	in filenames you got from outside (command line, readdir etc.) without
173	etc.), 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
174	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
175	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
176	use something else.	326	unicode filenames or e) use something else to ensure your scalar has the
		327	correct contents.
		328
		329	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		330	handles correctly whether it is set or not.
		331
		332	=head2 AIO REQUEST FUNCTIONS
177		333
178	=over 4	334	=over 4
179		335
180	=item $prev_pri = aioreq_pri [$pri]	336	=item $prev_pri = aioreq_pri [$pri]
181		337
…		…
201	aio_read $_[0], ..., sub {	357	aio_read $_[0], ..., sub {
202	...	358	...
203	};	359	};
204	};	360	};
205		361
		362
206	=item aioreq_nice $pri_adjust	363	=item aioreq_nice $pri_adjust
207		364
208	Similar to C<aioreq_pri>, but subtracts the given value from the current	365	Similar to C<aioreq_pri>, but subtracts the given value from the current
209	priority, so effects are cumulative.	366	priority, so the effect is cumulative.
		367
210		368
211	=item aio_open $pathname, $flags, $mode, $callback->($fh)	369	=item aio_open $pathname, $flags, $mode, $callback->($fh)
212		370
213	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
214	created filehandle for the file.	372	created filehandle for the file (or C<undef> in case of an error).
215		373
216	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,
217	for an explanation.	375	for an explanation.
218		376
219	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
220	list. They are the same as used by C<sysopen>.	378	list. They are the same as used by C<sysopen>.
221		379
222	Likewise, C<$mode> specifies the mode of the newly created file, if it	380	Likewise, C<$mode> specifies the mode of the newly created file, if it
223	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	381	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
224	except that it is mandatory (i.e. use C<0> if you don't create new files,	382	except that it is mandatory (i.e. use C<0> if you don't create new files,
225	and C<0666> or C<0777> if you do).	383	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		384	by the umask in effect then the request is being executed, so better never
		385	change the umask.
226		386
227	Example:	387	Example:
228		388
229	aio_open "/etc/passwd", O_RDONLY, 0, sub {	389	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
230	if ($_[0]) {	390	if ($_[0]) {
231	print "open successful, fh is $_[0]\n";	391	print "open successful, fh is $_[0]\n";
232	...	392	...
233	} else {	393	} else {
234	die "open failed: $!\n";	394	die "open failed: $!\n";
235	}	395	}
236	};	396	};
237		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
		407
238	=item aio_close $fh, $callback->($status)	408	=item aio_close $fh, $callback->($status)
239		409
240	Asynchronously close a file and call the callback with the result	410	Asynchronously close a file and call the callback with the result
241	code. I<WARNING:> although accepted, you should not pass in a perl	411	code.
242	filehandle here, as perl will likely close the file descriptor another
243	time when the filehandle is destroyed. Normally, you can safely call perls
244	C<close> or just let filehandles go out of scope.
245		412
246	This is supposed to be a bug in the API, so that might change. It's	413	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
247	therefore best to avoid this function.	414	closing the file descriptor associated with the filehandle itself.
		415
		416	Therefore, C<aio_close> will not close the filehandle - instead it will
		417	use dup2 to overwrite the file descriptor with the write-end of a pipe
		418	(the pipe fd will be created on demand and will be cached).
		419
		420	Or in other words: the file descriptor will be closed, but it will not be
		421	free for reuse until the perl filehandle is closed.
		422
		423	=cut
		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".
248		444
249	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	445	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
250		446
251	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
252		448
253	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	449	Reads or writes C<$length> bytes from or to the specified C<$fh> and
254	into the scalar given by C<data> and offset C<dataoffset> and calls the	450	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
255	callback without the actual number of bytes read (or -1 on error, just	451	calls the callback with the actual number of bytes transferred (or -1 on
256	like the syscall).	452	error, just like the syscall).
		453
		454	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		455	offset plus the actual number of bytes read.
		456
		457	If C<$offset> is undefined, then the current file descriptor offset will
		458	be used (and updated), otherwise the file descriptor offset will not be
		459	changed by these calls.
		460
		461	If C<$length> is undefined in C<aio_write>, use the remaining length of
		462	C<$data>.
		463
		464	If C<$dataoffset> is less than zero, it will be counted from the end of
		465	C<$data>.
257		466
258	The C<$data> scalar I<MUST NOT> be modified in any way while the request	467	The C<$data> scalar I<MUST NOT> be modified in any way while the request
259	is outstanding. Modifying it can result in segfaults or WW3 (if the	468	is outstanding. Modifying it can result in segfaults or World War III (if
260	necessary/optional hardware is installed).	469	the necessary/optional hardware is installed).
261		470
262	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	471	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
263	offset C<0> within the scalar:	472	offset C<0> within the scalar:
264		473
265	aio_read $fh, 7, 15, $buffer, 0, sub {	474	aio_read $fh, 7, 15, $buffer, 0, sub {
266	$_[0] > 0 or die "read error: $!";	475	$_[0] > 0 or die "read error: $!";
267	print "read $_[0] bytes: <$buffer>\n";	476	print "read $_[0] bytes: <$buffer>\n";
268	};	477	};
269		478
		479
270	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	480	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
271		481
272	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
273	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
274	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
275	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
276	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>.
277		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<$in_fh>) is a file - the file I/O will then be asynchronous, while
		498	the socket I/O will be non-blocking. Note, however, that you can run
		499	into a trap where C<aio_sendfile> reads some data with readahead, then
		500	fails to write all data, and when the socket is ready the next time, the
		501	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		502	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		503	resource usage.
		504
278	This call tries to make use of a native C<sendfile> syscall to provide	505	This call tries to make use of a native C<sendfile>-like syscall to
279	zero-copy operation. For this to work, C<$out_fh> should refer to a	506	provide zero-copy operation. For this to work, C<$out_fh> should refer to
280	socket, and C<$in_fh> should refer to mmap'able file.	507	a socket, and C<$in_fh> should refer to an mmap'able file.
281		508
282	If the native sendfile call fails or is not implemented, it will be	509	If a native sendfile cannot be found or it fails with C<ENOSYS>,
283	emulated, so you can call C<aio_sendfile> on any type of filehandle	510	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		511	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
284	regardless of the limitations of the operating system.	512	type of filehandle regardless of the limitations of the operating system.
285		513
286	Please note, however, that C<aio_sendfile> can read more bytes from	514	As native sendfile syscalls (as practically any non-POSIX interface hacked
287	C<$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
288	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
289	provides the number of bytes written to C<$out_fh>. Only if the result	517	in Linux and FreeBSD kernels (probably others, too), but that might fail,
290	value equals C<$length> one can assume that C<$length> bytes have been	518	so you really really should check the return value of C<aio_sendfile> -
291	read.	519	fewer bytes than expected might have been transferred.
		520
292		521
293	=item aio_readahead $fh,$offset,$length, $callback->($retval)	522	=item aio_readahead $fh,$offset,$length, $callback->($retval)
294		523
295	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
296	subsequent reads from that file will not block on disk I/O. The C<$offset>	525	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
299	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
300	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
301	(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
302	file. The current file offset of the file is left unchanged.	531	file. The current file offset of the file is left unchanged.
303		532
304	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
305	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.
		535
306		536
307	=item aio_stat $fh_or_path, $callback->($status)	537	=item aio_stat $fh_or_path, $callback->($status)
308		538
309	=item aio_lstat $fh, $callback->($status)	539	=item aio_lstat $fh, $callback->($status)
310		540
…		…
316	for an explanation.	546	for an explanation.
317		547
318	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
319	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
320	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>.
321		560
322	Example: Print the length of F</etc/passwd>:	561	Example: Print the length of F</etc/passwd>:
323		562
324	aio_stat "/etc/passwd", sub {	563	aio_stat "/etc/passwd", sub {
325	$_[0] and die "stat failed: $!";	564	$_[0] and die "stat failed: $!";
326	print "size is ", -s _, "\n";	565	print "size is ", -s _, "\n";
327	};	566	};
328		567
		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
		698	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		699
		700	Works like perl's C<utime> function (including the special case of $atime
		701	and $mtime being undef). Fractional times are supported if the underlying
		702	syscalls support them.
		703
		704	When called with a pathname, uses utimes(2) if available, otherwise
		705	utime(2). If called on a file descriptor, uses futimes(2) if available,
		706	otherwise returns ENOSYS, so this is not portable.
		707
		708	Examples:
		709
		710	# set atime and mtime to current time (basically touch(1)):
		711	aio_utime "path", undef, undef;
		712	# set atime to current time and mtime to beginning of the epoch:
		713	aio_utime "path", time, undef; # undef==0
		714
		715
		716	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		717
		718	Works like perl's C<chown> function, except that C<undef> for either $uid
		719	or $gid is being interpreted as "do not change" (but -1 can also be used).
		720
		721	Examples:
		722
		723	# same as "chown root path" in the shell:
		724	aio_chown "path", 0, -1;
		725	# same as above:
		726	aio_chown "path", 0, undef;
		727
		728
		729	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		730
		731	Works like truncate(2) or ftruncate(2).
		732
		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
		754	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		755
		756	Works like perl's C<chmod> function.
		757
		758
329	=item aio_unlink $pathname, $callback->($status)	759	=item aio_unlink $pathname, $callback->($status)
330		760
331	Asynchronously unlink (delete) a file and call the callback with the	761	Asynchronously unlink (delete) a file and call the callback with the
332	result code.	762	result code.
333		763
		764
334	=item aio_mknod $path, $mode, $dev, $callback->($status)	765	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		766
		767	[EXPERIMENTAL]
335		768
336	Asynchronously create a device node (or fifo). See mknod(2).	769	Asynchronously create a device node (or fifo). See mknod(2).
337		770
338	The only portable (POSIX) way of calling this function is:	771	The only (POSIX-) portable way of calling this function is:
339		772
340	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	773	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		774
		775	See C<aio_stat> for info about some potentially helpful extra constants
		776	and functions.
341		777
342	=item aio_link $srcpath, $dstpath, $callback->($status)	778	=item aio_link $srcpath, $dstpath, $callback->($status)
343		779
344	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
345	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.
346		782
		783
347	=item aio_symlink $srcpath, $dstpath, $callback->($status)	784	=item aio_symlink $srcpath, $dstpath, $callback->($status)
348		785
349	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
350	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.
351		788
		789
		790	=item aio_readlink $pathname, $callback->($link)
		791
		792	Asynchronously read the symlink specified by C<$path> and pass it to
		793	the callback. If an error occurs, nothing or undef gets passed to the
		794	callback.
		795
		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
352	=item aio_rename $srcpath, $dstpath, $callback->($status)	807	=item aio_rename $srcpath, $dstpath, $callback->($status)
353		808
354	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
355	rename(2) and call the callback with the result code.	810	rename(2) and call the callback with the result code.
356		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>.
		815
		816
		817	=item aio_mkdir $pathname, $mode, $callback->($status)
		818
		819	Asynchronously mkdir (create) a directory and call the callback with
		820	the result code. C<$mode> will be modified by the umask at the time the
		821	request is executed, so do not change your umask.
		822
		823
357	=item aio_rmdir $pathname, $callback->($status)	824	=item aio_rmdir $pathname, $callback->($status)
358		825
359	Asynchronously rmdir (delete) a directory and call the callback with the	826	Asynchronously rmdir (delete) a directory and call the callback with the
360	result code.	827	result code.
		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
361		833
362	=item aio_readdir $pathname, $callback->($entries)	834	=item aio_readdir $pathname, $callback->($entries)
363		835
364	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
365	directory (i.e. opendir + readdir + closedir). The entries will not be	837	directory (i.e. opendir + readdir + closedir). The entries will not be
366	sorted, and will B<NOT> include the C<.> and C<..> entries.	838	sorted, and will B<NOT> include the C<.> and C<..> entries.
367		839
368	The callback a single argument which is either C<undef> or an array-ref	840	The callback is passed a single argument which is either C<undef> or an
369	with the filenames.	841	array-ref with the filenames.
		842
		843
		844	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		845
		846	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		847	tune behaviour and output format. In case of an error, C<$entries> will be
		848	C<undef>.
		849
		850	The flags are a combination of the following constants, ORed together (the
		851	flags will also be passed to the callback, possibly modified):
		852
		853	=over 4
		854
		855	=item IO::AIO::READDIR_DENTS
		856
		857	When this flag is off, then the callback gets an arrayref consisting of
		858	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		859	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		860	entry in more detail.
		861
		862	C<$name> is the name of the entry.
		863
		864	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		865
		866	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		867	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		868	C<IO::AIO::DT_WHT>.
		869
		870	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		871	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		872	scalars are read-only: you can not modify them.
		873
		874	C<$inode> is the inode number (which might not be exact on systems with 64
		875	bit inode numbers and 32 bit perls). This field has unspecified content on
		876	systems that do not deliver the inode information.
		877
		878	=item IO::AIO::READDIR_DIRS_FIRST
		879
		880	When this flag is set, then the names will be returned in an order where
		881	likely directories come first, in optimal stat order. This is useful when
		882	you need to quickly find directories, or you want to find all directories
		883	while avoiding to stat() each entry.
		884
		885	If the system returns type information in readdir, then this is used
		886	to find directories directly. Otherwise, likely directories are names
		887	beginning with ".", or otherwise names with no dots, of which names with
		888	short names are tried first.
		889
		890	=item IO::AIO::READDIR_STAT_ORDER
		891
		892	When this flag is set, then the names will be returned in an order
		893	suitable for stat()'ing each one. That is, when you plan to stat()
		894	all files in the given directory, then the returned order will likely
		895	be fastest.
		896
		897	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		898	the likely dirs come first, resulting in a less optimal stat order.
		899
		900	=item IO::AIO::READDIR_FOUND_UNKNOWN
		901
		902	This flag should not be set when calling C<aio_readdirx>. Instead, it
		903	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		904	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		905	C<$type>'s are known, which can be used to speed up some algorithms.
		906
		907	=back
		908
		909
		910	=item aio_load $pathname, $data, $callback->($status)
		911
		912	This is a composite request that tries to fully load the given file into
		913	memory. Status is the same as with aio_read.
		914
		915	=cut
		916
		917	sub aio_load($$;$) {
		918	my ($path, undef, $cb) = @_;
		919	my $data = \$_[1];
		920
		921	my $pri = aioreq_pri;
		922	my $grp = aio_group $cb;
		923
		924	aioreq_pri $pri;
		925	add $grp aio_open $path, O_RDONLY, 0, sub {
		926	my $fh = shift
		927	or return $grp->result (-1);
		928
		929	aioreq_pri $pri;
		930	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		931	$grp->result ($_[0]);
		932	};
		933	};
		934
		935	$grp
		936	}
370		937
371	=item aio_copy $srcpath, $dstpath, $callback->($status)	938	=item aio_copy $srcpath, $dstpath, $callback->($status)
372		939
373	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
374	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
375	the C<0> (error) or C<-1> ok.	942	a status of C<0> (ok) or C<-1> (error, see C<$!>).
376		943
377	This is a composite request that it creates the destination file with	944	This is a composite request that creates the destination file with
378	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
379	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
380	uid/gid, in that order.	947	uid/gid, in that order.
381		948
382	If an error occurs, the partial destination file will be unlinked, if	949	If an error occurs, the partial destination file will be unlinked, if
…		…
392	my $grp = aio_group $cb;	959	my $grp = aio_group $cb;
393		960
394	aioreq_pri $pri;	961	aioreq_pri $pri;
395	add $grp aio_open $src, O_RDONLY, 0, sub {	962	add $grp aio_open $src, O_RDONLY, 0, sub {
396	if (my $src_fh = $_[0]) {	963	if (my $src_fh = $_[0]) {
397	my @stat = stat $src_fh;	964	my @stat = stat $src_fh; # hmm, might block over nfs?
398		965
399	aioreq_pri $pri;	966	aioreq_pri $pri;
400	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 {
401	if (my $dst_fh = $_[0]) {	968	if (my $dst_fh = $_[0]) {
402	aioreq_pri $pri;	969	aioreq_pri $pri;
403	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	970	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
404	if ($_[0] == $stat[7]) {	971	if ($_[0] == $stat[7]) {
405	$grp->result (0);	972	$grp->result (0);
406	close $src_fh;	973	close $src_fh;
407		974
408	# those should not normally block. should. should.	975	my $ch = sub {
		976	aioreq_pri $pri;
		977	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		978	aioreq_pri $pri;
		979	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		980	aioreq_pri $pri;
		981	add $grp aio_close $dst_fh;
		982	}
		983	};
		984	};
		985
		986	aioreq_pri $pri;
		987	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		988	if ($_[0] < 0 && $! == ENOSYS) {
		989	aioreq_pri $pri;
409	utime $stat[8], $stat[9], $dst;	990	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
410	chmod $stat[2] & 07777, $dst_fh;	991	} else {
411	chown $stat[4], $stat[5], $dst_fh;	992	$ch->();
		993	}
412	close $dst_fh;	994	};
413	} else {	995	} else {
414	$grp->result (-1);	996	$grp->result (-1);
415	close $src_fh;	997	close $src_fh;
416	close $dst_fh;	998	close $dst_fh;
417		999
…		…
434		1016
435	=item aio_move $srcpath, $dstpath, $callback->($status)	1017	=item aio_move $srcpath, $dstpath, $callback->($status)
436		1018
437	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
438	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
439	the C<0> (error) or C<-1> ok.	1021	a status of C<0> (ok) or C<-1> (error, see C<$!>).
440		1022
441	This is a composite request that tries to rename(2) the file first. If	1023	This is a composite request that tries to rename(2) the file first; if
442	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1024	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
443	that is successful, unlinking the C<$srcpath>.	1025	that is successful, unlinks the C<$srcpath>.
444		1026
445	=cut	1027	=cut
446		1028
447	sub aio_move($$;$) {	1029	sub aio_move($$;$) {
448	my ($src, $dst, $cb) = @_;	1030	my ($src, $dst, $cb) = @_;
…		…
455	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
456	aioreq_pri $pri;	1038	aioreq_pri $pri;
457	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
458	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
459		1041
460	if (!$_[0]) {	1042	unless ($_[0]) {
461	aioreq_pri $pri;	1043	aioreq_pri $pri;
462	add $grp aio_unlink $src;	1044	add $grp aio_unlink $src;
463	}	1045	}
464	};	1046	};
465	} else {	1047	} else {
…		…
468	};	1050	};
469		1051
470	$grp	1052	$grp
471	}	1053	}
472		1054
473	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
474		1056
475	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
476	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
477	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
478	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
…		…
495		1077
496	Implementation notes.	1078	Implementation notes.
497		1079
498	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1080	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
499		1081
		1082	If readdir returns file type information, then this is used directly to
		1083	find directories.
		1084
500	After reading the directory, the modification time, size etc. of the	1085	Otherwise, after reading the directory, the modification time, size etc.
501	directory before and after the readdir is checked, and if they match (and	1086	of the directory before and after the readdir is checked, and if they
502	isn't the current time), the link count will be used to decide how many	1087	match (and isn't the current time), the link count will be used to decide
503	entries are directories (if >= 2). Otherwise, no knowledge of the number	1088	how many entries are directories (if >= 2). Otherwise, no knowledge of the
504	of subdirectories will be assumed.	1089	number of subdirectories will be assumed.
505		1090
506	Then entries will be sorted into likely directories (everything without	1091	Then entries will be sorted into likely directories a non-initial dot
507	a non-initial dot currently) and likely non-directories (everything	1092	currently) and likely non-directories (see C<aio_readdirx>). Then every
508	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1093	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
509	likely directories first. If that succeeds, it assumes that the entry	1094	in order of their inode numbers. If that succeeds, it assumes that the
510	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
511	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
512	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
513	data (e.g. ext2fs filetype feature).	1098	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1099	the filetype information on readdir.
514		1100
515	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
516	rest of the entries is assumed to be non-directories.	1102	rest of the entries is assumed to be non-directories.
517		1103
518	This only works with certainty on POSIX (= UNIX) filesystems, which	1104	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
522	as those tend to return 0 or 1 as link counts, which disables the	1108	as those tend to return 0 or 1 as link counts, which disables the
523	directory counting heuristic.	1109	directory counting heuristic.
524		1110
525	=cut	1111	=cut
526		1112
527	sub aio_scandir($$$) {	1113	sub aio_scandir($$;$) {
528	my ($path, $maxreq, $cb) = @_;	1114	my ($path, $maxreq, $cb) = @_;
529		1115
530	my $pri = aioreq_pri;	1116	my $pri = aioreq_pri;
531		1117
532	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
533		1119
534	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
535		1121
536	# stat once	1122	# get a wd object
537	aioreq_pri $pri;	1123	aioreq_pri $pri;
538	add $grp aio_stat $path, sub {	1124	add $grp aio_wd $path, sub {
		1125	$_[0]
539	return $grp->result () if $_[0];	1126	or return $grp->result ();
540	my $now = time;
541	my $hash1 = join ":", (stat _)[0,1,3,7,9];
542		1127
543	# read the directory entries	1128	my $wd = [shift, "."];
		1129
		1130	# stat once
544	aioreq_pri $pri;	1131	aioreq_pri $pri;
545	add $grp aio_readdir $path, sub {	1132	add $grp aio_stat $wd, sub {
546	my $entries = shift
547	or return $grp->result ();	1133	return $grp->result () if $_[0];
		1134	my $now = time;
		1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
548		1136
549	# stat the dir another time	1137	# read the directory entries
550	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;
551	add $grp aio_stat $path, sub {	1145	add $grp aio_stat $wd, sub {
552	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1146	my $hash2 = join ":", (stat _)[0,1,3,7,9];
553		1147
554	my $ndirs;	1148	my $ndirs;
555		1149
556	# take the slow route if anything looks fishy	1150	# take the slow route if anything looks fishy
557	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1151	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
558	$ndirs = -1;	1152	$ndirs = -1;
559	} else {	1153	} else {
560	# if nlink == 2, we are finished	1154	# if nlink == 2, we are finished
561	# on non-posix-fs's, we rely on nlink < 2	1155	# for non-posix-fs's, we rely on nlink < 2
562	$ndirs = (stat _)[3] - 2	1156	$ndirs = (stat _)[3] - 2
563	or return $grp->result ([], $entries);	1157	or return $grp->result ([], $entries);
564	}	1158	}
565		1159
566	# sort into likely dirs and likely nondirs
567	# dirs == files without ".", short entries first
568	$entries = [map $_->[0],
569	sort { $b->[1] cmp $a->[1] }
570	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
571	@$entries];
572
573	my (@dirs, @nondirs);	1160	my (@dirs, @nondirs);
574		1161
575	my $statgrp = add $grp aio_group sub {	1162	my $statgrp = add $grp aio_group sub {
576	$grp->result (\@dirs, \@nondirs);	1163	$grp->result (\@dirs, \@nondirs);
577	};	1164	};
578		1165
579	limit $statgrp $maxreq;	1166	limit $statgrp $maxreq;
580	feed $statgrp sub {	1167	feed $statgrp sub {
581	return unless @$entries;	1168	return unless @$entries;
582	my $entry = pop @$entries;	1169	my $entry = shift @$entries;
583		1170
584	aioreq_pri $pri;	1171	aioreq_pri $pri;
		1172	$wd->[1] = "$entry/.";
585	add $statgrp aio_stat "$path/$entry/.", sub {	1173	add $statgrp aio_stat $wd, sub {
586	if ($_[0] < 0) {	1174	if ($_[0] < 0) {
587	push @nondirs, $entry;	1175	push @nondirs, $entry;
588	} else {	1176	} else {
589	# need to check for real directory	1177	# need to check for real directory
590	aioreq_pri $pri;	1178	aioreq_pri $pri;
		1179	$wd->[1] = $entry;
591	add $statgrp aio_lstat "$path/$entry", sub {	1180	add $statgrp aio_lstat $wd, sub {
592	if (-d _) {	1181	if (-d _) {
593	push @dirs, $entry;	1182	push @dirs, $entry;
594		1183
595	unless (--$ndirs) {	1184	unless (--$ndirs) {
596	push @nondirs, @$entries;	1185	push @nondirs, @$entries;
597	feed $statgrp;	1186	feed $statgrp;
		1187	}
		1188	} else {
		1189	push @nondirs, $entry;
598	}	1190	}
599	} else {
600	push @nondirs, $entry;
601	}	1191	}
602	}	1192	}
603	}	1193	};
604	};	1194	};
605	};	1195	};
606	};	1196	};
607	};	1197	};
608	};	1198	};
609		1199
610	$grp	1200	$grp
611	}	1201	}
612		1202
		1203	=item aio_rmtree $pathname, $callback->($status)
		1204
		1205	Delete a directory tree starting (and including) C<$path>, return the
		1206	status of the final C<rmdir> only. This is a composite request that
		1207	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1208	everything else.
		1209
		1210	=cut
		1211
		1212	sub aio_rmtree;
		1213	sub aio_rmtree($;$) {
		1214	my ($path, $cb) = @_;
		1215
		1216	my $pri = aioreq_pri;
		1217	my $grp = aio_group $cb;
		1218
		1219	aioreq_pri $pri;
		1220	add $grp aio_scandir $path, 0, sub {
		1221	my ($dirs, $nondirs) = @_;
		1222
		1223	my $dirgrp = aio_group sub {
		1224	add $grp aio_rmdir $path, sub {
		1225	$grp->result ($_[0]);
		1226	};
		1227	};
		1228
		1229	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1230	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1231
		1232	add $grp $dirgrp;
		1233	};
		1234
		1235	$grp
		1236	}
		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
		1278	=item aio_sync $callback->($status)
		1279
		1280	Asynchronously call sync and call the callback when finished.
		1281
613	=item aio_fsync $fh, $callback->($status)	1282	=item aio_fsync $fh, $callback->($status)
614		1283
615	Asynchronously call fsync on the given filehandle and call the callback	1284	Asynchronously call fsync on the given filehandle and call the callback
616	with the fsync result code.	1285	with the fsync result code.
617		1286
…		…
620	Asynchronously call fdatasync on the given filehandle and call the	1289	Asynchronously call fdatasync on the given filehandle and call the
621	callback with the fdatasync result code.	1290	callback with the fdatasync result code.
622		1291
623	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
624	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.
		1301
		1302	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1303
		1304	Sync the data portion of the file specified by C<$offset> and C<$length>
		1305	to disk (but NOT the metadata), by calling the Linux-specific
		1306	sync_file_range call. If sync_file_range is not available or it returns
		1307	ENOSYS, then fdatasync or fsync is being substituted.
		1308
		1309	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1310	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1311	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1312	manpage for details.
		1313
		1314	=item aio_pathsync $pathname, $callback->($status)
		1315
		1316	This request tries to open, fsync and close the given path. This is a
		1317	composite request intended to sync directories after directory operations
		1318	(E.g. rename). This might not work on all operating systems or have any
		1319	specific effect, but usually it makes sure that directory changes get
		1320	written to disc. It works for anything that can be opened for read-only,
		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>).
		1325
		1326	Passes C<0> when everything went ok, and C<-1> on error.
		1327
		1328	=cut
		1329
		1330	sub aio_pathsync($;$) {
		1331	my ($path, $cb) = @_;
		1332
		1333	my $pri = aioreq_pri;
		1334	my $grp = aio_group $cb;
		1335
		1336	aioreq_pri $pri;
		1337	add $grp aio_open $path, O_RDONLY, 0, sub {
		1338	my ($fh) = @_;
		1339	if ($fh) {
		1340	aioreq_pri $pri;
		1341	add $grp aio_fsync $fh, sub {
		1342	$grp->result ($_[0]);
		1343
		1344	aioreq_pri $pri;
		1345	add $grp aio_close $fh;
		1346	};
		1347	} else {
		1348	$grp->result (-1);
		1349	}
		1350	};
		1351
		1352	$grp
		1353	}
		1354
		1355	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($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	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1368	C<IO::AIO::MS_INVALIDATE>.
		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.
625		1465
626	=item aio_group $callback->(...)	1466	=item aio_group $callback->(...)
627		1467
628	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
629	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
…		…
667	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
668	except to put your application under artificial I/O pressure.	1508	except to put your application under artificial I/O pressure.
669		1509
670	=back	1510	=back
671		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.
		1636
672	=head2 IO::AIO::REQ CLASS	1637	=head2 IO::AIO::REQ CLASS
673		1638
674	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
675	called in non-void context.	1640	called in non-void context.
676		1641
…		…
679	=item cancel $req	1644	=item cancel $req
680		1645
681	Cancels the request, if possible. Has the effect of skipping execution	1646	Cancels the request, if possible. Has the effect of skipping execution
682	when entering the B<execute> state and skipping calling the callback when	1647	when entering the B<execute> state and skipping calling the callback when
683	entering the the B<result> state, but will leave the request otherwise	1648	entering the the B<result> state, but will leave the request otherwise
684	untouched. That means that requests that currently execute will not be	1649	untouched (with the exception of readdir). That means that requests that
685	stopped and resources held by the request will not be freed prematurely.	1650	currently execute will not be stopped and resources held by the request
		1651	will not be freed prematurely.
686		1652
687	=item cb $req $callback->(...)	1653	=item cb $req $callback->(...)
688		1654
689	Replace (or simply set) the callback registered to the request.	1655	Replace (or simply set) the callback registered to the request.
690		1656
…		…
741	Their lifetime, simplified, looks like this: when they are empty, they	1707	Their lifetime, simplified, looks like this: when they are empty, they
742	will finish very quickly. If they contain only requests that are in the	1708	will finish very quickly. If they contain only requests that are in the
743	C<done> state, they will also finish. Otherwise they will continue to	1709	C<done> state, they will also finish. Otherwise they will continue to
744	exist.	1710	exist.
745		1711
746	That means after creating a group you have some time to add requests. And	1712	That means after creating a group you have some time to add requests
747	in the callbacks of those requests, you can add further requests to the	1713	(precisely before the callback has been invoked, which is only done within
748	group. And only when all those requests have finished will the the group	1714	the C<poll_cb>). And in the callbacks of those requests, you can add
749	itself finish.	1715	further requests to the group. And only when all those requests have
		1716	finished will the the group itself finish.
750		1717
751	=over 4	1718	=over 4
752		1719
753	=item add $grp ...	1720	=item add $grp ...
754		1721
…		…
763	=item $grp->cancel_subs	1730	=item $grp->cancel_subs
764		1731
765	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
766	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.
767		1734
		1735	The group request will finish normally (you cannot add requests to the
		1736	group).
		1737
768	=item $grp->result (...)	1738	=item $grp->result (...)
769		1739
770	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
771	subrequests have finished and set thre groups errno to the current value	1741	subrequests have finished and set the groups errno to the current value
772	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,
773	no argument will be passed and errno is zero.	1743	no argument will be passed and errno is zero.
774		1744
775	=item $grp->errno ([$errno])	1745	=item $grp->errno ([$errno])
776		1746
…		…
787	=item feed $grp $callback->($grp)	1757	=item feed $grp $callback->($grp)
788		1758
789	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
790	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,
791	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,
792	this might starve other requests for a potentially long time. For	1762	this might starve other requests for a potentially long time. For example,
793	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1763	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
794	requests, delaying any later requests for a long time.	1764	requests, delaying any later requests for a long time.
795		1765
796	To avoid this, and allow incremental generation of requests, you can	1766	To avoid this, and allow incremental generation of requests, you can
797	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
798	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>,
…		…
803	not impose any limits).	1773	not impose any limits).
804		1774
805	If the feed does not queue more requests when called, it will be	1775	If the feed does not queue more requests when called, it will be
806	automatically removed from the group.	1776	automatically removed from the group.
807		1777
808	If the feed limit is C<0>, it will be set to C<2> automatically.	1778	If the feed limit is C<0> when this method is called, it will be set to
		1779	C<2> automatically.
809		1780
810	Example:	1781	Example:
811		1782
812	# stat all files in @files, but only ever use four aio requests concurrently:	1783	# stat all files in @files, but only ever use four aio requests concurrently:
813		1784
…		…
825	Sets the feeder limit for the group: The feeder will be called whenever	1796	Sets the feeder limit for the group: The feeder will be called whenever
826	the group contains less than this many requests.	1797	the group contains less than this many requests.
827		1798
828	Setting the limit to C<0> will pause the feeding process.	1799	Setting the limit to C<0> will pause the feeding process.
829		1800
		1801	The default value for the limit is C<0>, but note that setting a feeder
		1802	automatically bumps it up to C<2>.
		1803
830	=back	1804	=back
831		1805
832	=head2 SUPPORT FUNCTIONS	1806	=head2 SUPPORT FUNCTIONS
833		1807
		1808	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1809
834	=over 4	1810	=over 4
835		1811
836	=item $fileno = IO::AIO::poll_fileno	1812	=item $fileno = IO::AIO::poll_fileno
837		1813
838	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
839	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,
840	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
841	to call C<poll_cb> to check the results.	1817	you have to call C<poll_cb> to check the results.
842		1818
843	See C<poll_cb> for an example.	1819	See C<poll_cb> for an example.
844		1820
845	=item IO::AIO::poll_cb	1821	=item IO::AIO::poll_cb
846		1822
847	Process all 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
848	regularly. Returns the number of events processed. Returns immediately	1824	been executed but the results are not yet reported). You have to call
849	when no events are outstanding.	1825	this "regularly" to finish outstanding requests.
850		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
851	If not all requests were processed for whatever reason, the filehandle	1833	If not all requests were processed for whatever reason, the poll file
852	will still be ready when C<poll_cb> returns.	1834	descriptor will still be ready when C<poll_cb> returns, so normally you
		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.
853		1843
854	Example: Install an Event watcher that automatically calls	1844	Example: Install an Event watcher that automatically calls
855	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):
856		1847
857	Event->io (fd => IO::AIO::poll_fileno,	1848	Event->io (fd => IO::AIO::poll_fileno,
858	poll => 'r', async => 1,	1849	poll => 'r', async => 1,
859	cb => \&IO::AIO::poll_cb);	1850	cb => \&IO::AIO::poll_cb);
860		1851
861	=item IO::AIO::poll_some $max_requests	1852	=item IO::AIO::poll_wait
862		1853
863	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests	1854	Wait until either at least one request is in the result phase or no
864	at a time.	1855	requests are outstanding anymore.
865		1856
866	Useful if you want to ensure some level of interactiveness when perl is	1857	This is useful if you want to synchronously wait for some requests to
867	not fast enough to process all requests in time.	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;
		1879
		1880	=item IO::AIO::max_poll_reqs $nreqs
		1881
		1882	=item IO::AIO::max_poll_time $seconds
		1883
		1884	These set the maximum number of requests (default C<0>, meaning infinity)
		1885	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1886	the maximum amount of time (default C<0>, meaning infinity) spent in
		1887	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1888	of time C<poll_cb> is allowed to use).
		1889
		1890	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1891	syscall per request processed, which is not normally a problem unless your
		1892	callbacks are really really fast or your OS is really really slow (I am
		1893	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1894
		1895	Setting these is useful if you want to ensure some level of
		1896	interactiveness when perl is not fast enough to process all requests in
		1897	time.
		1898
		1899	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
868		1900
869	Example: Install an Event watcher that automatically calls	1901	Example: Install an Event watcher that automatically calls
870	IO::AIO::poll_some with low priority, to ensure that other parts of the	1902	IO::AIO::poll_cb with low priority, to ensure that other parts of the
871	program get the CPU sometimes even under high AIO load.	1903	program get the CPU sometimes even under high AIO load.
872		1904
		1905	# try not to spend much more than 0.1s in poll_cb
		1906	IO::AIO::max_poll_time 0.1;
		1907
		1908	# use a low priority so other tasks have priority
873	Event->io (fd => IO::AIO::poll_fileno,	1909	Event->io (fd => IO::AIO::poll_fileno,
874	poll => 'r', nice => 1,	1910	poll => 'r', nice => 1,
875	cb => sub { IO::AIO::poll_some 256 });	1911	cb => &IO::AIO::poll_cb);
876		1912
877	=item IO::AIO::poll_wait	1913	=back
878		1914
879	Wait till the result filehandle becomes ready for reading (simply does a	1915	=head3 CONTROLLING THE NUMBER OF THREADS
880	C<select> on the filehandle. This is useful if you want to synchronously wait
881	for some requests to finish).
882		1916
883	See C<nreqs> for an example.	1917	=over
884
885	=item IO::AIO::nreqs
886
887	Returns the number of requests currently in the ready, execute or pending
888	states (i.e. for which their callback has not been invoked yet).
889
890	Example: wait till there are no outstanding requests anymore:
891
892	IO::AIO::poll_wait, IO::AIO::poll_cb
893	while IO::AIO::nreqs;
894
895	=item IO::AIO::nready
896
897	Returns the number of requests currently in the ready state (not yet
898	executed).
899
900	=item IO::AIO::npending
901
902	Returns the number of requests currently in the pending state (executed,
903	but not yet processed by poll_cb).
904
905	=item IO::AIO::flush
906
907	Wait till all outstanding AIO requests have been handled.
908
909	Strictly equivalent to:
910
911	IO::AIO::poll_wait, IO::AIO::poll_cb
912	while IO::AIO::nreqs;
913
914	=item IO::AIO::poll
915
916	Waits until some requests have been handled.
917
918	Strictly equivalent to:
919
920	IO::AIO::poll_wait, IO::AIO::poll_cb
921	if IO::AIO::nreqs;
922		1918
923	=item IO::AIO::min_parallel $nthreads	1919	=item IO::AIO::min_parallel $nthreads
924		1920
925	Set the minimum number of AIO threads to C<$nthreads>. The current	1921	Set the minimum number of AIO threads to C<$nthreads>. The current
926	default is C<8>, which means eight asynchronous operations can execute	1922	default is C<8>, which means eight asynchronous operations can execute
927	concurrently at any one time (the number of outstanding requests,	1923	concurrently at any one time (the number of outstanding requests,
928	however, is unlimited).	1924	however, is unlimited).
929		1925
930	IO::AIO starts threads only on demand, when an AIO request is queued and	1926	IO::AIO starts threads only on demand, when an AIO request is queued and
931	no free thread exists.	1927	no free thread exists. Please note that queueing up a hundred requests can
		1928	create demand for a hundred threads, even if it turns out that everything
		1929	is in the cache and could have been processed faster by a single thread.
932		1930
933	It is recommended to keep the number of threads relatively low, as some	1931	It is recommended to keep the number of threads relatively low, as some
934	Linux kernel versions will scale negatively with the number of threads	1932	Linux kernel versions will scale negatively with the number of threads
935	(higher parallelity => MUCH higher latency). With current Linux 2.6	1933	(higher parallelity => MUCH higher latency). With current Linux 2.6
936	versions, 4-32 threads should be fine.	1934	versions, 4-32 threads should be fine.
…		…
950	This module automatically runs C<max_parallel 0> at program end, to ensure	1948	This module automatically runs C<max_parallel 0> at program end, to ensure
951	that all threads are killed and that there are no outstanding requests.	1949	that all threads are killed and that there are no outstanding requests.
952		1950
953	Under normal circumstances you don't need to call this function.	1951	Under normal circumstances you don't need to call this function.
954		1952
		1953	=item IO::AIO::max_idle $nthreads
		1954
		1955	Limit the number of threads (default: 4) that are allowed to idle
		1956	(i.e., threads that did not get a request to process within the idle
		1957	timeout (default: 10 seconds). That means if a thread becomes idle while
		1958	C<$nthreads> other threads are also idle, it will free its resources and
		1959	exit.
		1960
		1961	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1962	to allow for extremely high load situations, but want to free resources
		1963	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1964
		1965	The default is probably ok in most situations, especially if thread
		1966	creation is fast. If thread creation is very slow on your system you might
		1967	want to use larger values.
		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
955	=item $oldmaxreqs = 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.
956		1984
957	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
958	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
959	use an C<aio_group> together with a feed callback.	1987	use an C<aio_group> together with a feed callback.
960		1988
961	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
962	to queue up more than this number of requests, the next call to the	1990	a lot of files, you can write somehting like this:
963	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
964	function will block until the limit is no longer exceeded.
965		1991
966	The default value is very large, so there is no practical limit on the	1992	IO::AIO::max_outstanding 32;
967	number of outstanding requests.
968		1993
969	You can still queue as many requests as you want. Therefore,	1994	for my $path (...) {
970	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1995	aio_stat $path , ...;
971	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.
972		2008
973	=back	2009	=back
974		2010
		2011	=head3 STATISTICAL INFORMATION
		2012
		2013	=over
		2014
		2015	=item IO::AIO::nreqs
		2016
		2017	Returns the number of requests currently in the ready, execute or pending
		2018	states (i.e. for which their callback has not been invoked yet).
		2019
		2020	Example: wait till there are no outstanding requests anymore:
		2021
		2022	IO::AIO::poll_wait, IO::AIO::poll_cb
		2023	while IO::AIO::nreqs;
		2024
		2025	=item IO::AIO::nready
		2026
		2027	Returns the number of requests currently in the ready state (not yet
		2028	executed).
		2029
		2030	=item IO::AIO::npending
		2031
		2032	Returns the number of requests currently in the pending state (executed,
		2033	but not yet processed by poll_cb).
		2034
		2035	=back
		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, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>,
		2072	C<IO::AIO::MADV_FREE>.
		2073
		2074	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2075	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2076	will be reduced to fit into the C<$scalar>.
		2077
		2078	On systems that do not implement C<posix_madvise>, this function returns
		2079	ENOSYS, otherwise the return value of C<posix_madvise>.
		2080
		2081	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2082
		2083	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2084	$scalar (see its manpage for details). The following protect
		2085	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2086	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2087
		2088	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2089	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2090	will be reduced to fit into the C<$scalar>.
		2091
		2092	On systems that do not implement C<mprotect>, this function returns
		2093	ENOSYS, otherwise the return value of C<mprotect>.
		2094
		2095	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2096
		2097	Memory-maps a file (or anonymous memory range) and attaches it to the
		2098	given C<$scalar>, which will act like a string scalar. Returns true on
		2099	success, and false otherwise.
		2100
		2101	The scalar must exist, but its contents do not matter - this means you
		2102	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2103	the scalar first.
		2104
		2105	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2106	which don't change the string length, and most read-only operations such
		2107	as copying it or searching it with regexes and so on.
		2108
		2109	Anything else is unsafe and will, at best, result in memory leaks.
		2110
		2111	The memory map associated with the C<$scalar> is automatically removed
		2112	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2113	or C<IO::AIO::munmap> functions are called on it.
		2114
		2115	This calls the C<mmap>(2) function internally. See your system's manual
		2116	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2117
		2118	The C<$length> must be larger than zero and smaller than the actual
		2119	filesize.
		2120
		2121	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2122	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2123
		2124	C<$flags> can be a combination of
		2125	C<IO::AIO::MAP_SHARED> or
		2126	C<IO::AIO::MAP_PRIVATE>,
		2127	or a number of system-specific flags (when not available, the are C<0>):
		2128	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2129	C<IO::AIO::MAP_LOCKED>,
		2130	C<IO::AIO::MAP_NORESERVE>,
		2131	C<IO::AIO::MAP_POPULATE>,
		2132	C<IO::AIO::MAP_NONBLOCK>,
		2133	C<IO::AIO::MAP_FIXED>,
		2134	C<IO::AIO::MAP_GROWSDOWN>,
		2135	C<IO::AIO::MAP_32BIT>,
		2136	C<IO::AIO::MAP_HUGETLB> or
		2137	C<IO::AIO::MAP_STACK>.
		2138
		2139	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2140
		2141	C<$offset> is the offset from the start of the file - it generally must be
		2142	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2143
		2144	Example:
		2145
		2146	use Digest::MD5;
		2147	use IO::AIO;
		2148
		2149	open my $fh, "<verybigfile"
		2150	or die "$!";
		2151
		2152	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2153	or die "verybigfile: $!";
		2154
		2155	my $fast_md5 = md5 $data;
		2156
		2157	=item IO::AIO::munmap $scalar
		2158
		2159	Removes a previous mmap and undefines the C<$scalar>.
		2160
		2161	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2162
		2163	Calls the C<munlock> function, undoing the effects of a previous
		2164	C<aio_mlock> call (see its description for details).
		2165
		2166	=item IO::AIO::munlockall
		2167
		2168	Calls the C<munlockall> function.
		2169
		2170	On systems that do not implement C<munlockall>, this function returns
		2171	ENOSYS, otherwise the return value of C<munlockall>.
		2172
		2173	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2174
		2175	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2176	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2177	should be the file offset.
		2178
		2179	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2180	silently corrupt the data in this case.
		2181
		2182	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2183	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2184	C<IO::AIO::SPLICE_F_GIFT>.
		2185
		2186	See the C<splice(2)> manpage for details.
		2187
		2188	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2189
		2190	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2191	description for C<IO::AIO::splice> above for details.
		2192
		2193	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2194
		2195	Attempts to query or change the pipe buffer size. Obviously works only
		2196	on pipes, and currently works only on GNU/Linux systems, and fails with
		2197	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2198	size on other systems, drop me a note.
		2199
		2200	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2201
		2202	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2203	C<$flags> is missing or C<0>, then this should be the same as a call to
		2204	perl's built-in C<pipe> function and create a new pipe, and works on
		2205	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2206	(..., 4096, O_BINARY)>.
		2207
		2208	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2209	the given flags (Linux 2.6.27, glibc 2.9).
		2210
		2211	On success, the read and write file handles are returned.
		2212
		2213	On error, nothing will be returned. If the pipe2 syscall is missing and
		2214	C<$flags> is non-zero, fails with C<ENOSYS>.
		2215
		2216	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2217	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2218	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2219
		2220	=back
		2221
975	=cut	2222	=cut
976		2223
977	# support function to convert a fd into a perl filehandle
978	sub _fd2fh {
979	return undef if $_[0] < 0;
980
981	# try to generate nice filehandles
982	my $sym = "IO::AIO::fd#$_[0]";
983	local *$sym;
984
985	open *$sym, "+<&=$_[0]" # usually works under any unix
986	or open *$sym, "<&=$_[0]" # cygwin needs this
987	or open *$sym, ">&=$_[0]" # or this
988	or return undef;
989
990	*$sym
991	}
992
993	min_parallel 8;	2224	min_parallel 8;
994		2225
995	END {	2226	END { flush }
996	min_parallel 1;
997	flush;
998	};
999		2227
1000	1;	2228	1;
1001		2229
		2230	=head1 EVENT LOOP INTEGRATION
		2231
		2232	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2233	automatically into many event loops:
		2234
		2235	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2236	use AnyEvent::AIO;
		2237
		2238	You can also integrate IO::AIO manually into many event loops, here are
		2239	some examples of how to do this:
		2240
		2241	# EV integration
		2242	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2243
		2244	# Event integration
		2245	Event->io (fd => IO::AIO::poll_fileno,
		2246	poll => 'r',
		2247	cb => \&IO::AIO::poll_cb);
		2248
		2249	# Glib/Gtk2 integration
		2250	add_watch Glib::IO IO::AIO::poll_fileno,
		2251	in => sub { IO::AIO::poll_cb; 1 };
		2252
		2253	# Tk integration
		2254	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2255	readable => \&IO::AIO::poll_cb);
		2256
		2257	# Danga::Socket integration
		2258	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2259	\&IO::AIO::poll_cb);
		2260
1002	=head2 FORK BEHAVIOUR	2261	=head2 FORK BEHAVIOUR
1003		2262
1004	This module should do "the right thing" when the process using it forks:	2263	Usage of pthreads in a program changes the semantics of fork
		2264	considerably. Specifically, only async-safe functions can be called after
		2265	fork. Perl doesn't know about this, so in general, you cannot call fork
		2266	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2267	pthreads, so this applies, but many other extensions and (for inexplicable
		2268	reasons) perl itself often is linked against pthreads, so this limitation
		2269	applies to quite a lot of perls.
1005		2270
1006	Before the fork, IO::AIO enters a quiescent state where no requests	2271	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1007	can be added in other threads and no results will be processed. After	2272	only works in the process that loaded it. Forking is fully supported, but
1008	the fork the parent simply leaves the quiescent state and continues	2273	using IO::AIO in the child is not.
1009	request/result processing, while the child frees the request/result queue
1010	(so that the requests started before the fork will only be handled in the
1011	parent). Threads will be started on demand until the limit set in the
1012	parent process has been reached again.
1013		2274
1014	In short: the parent will, after a short pause, continue as if fork had	2275	You might get around by not I<using> IO::AIO before (or after)
1015	not been called, while the child will act as if IO::AIO has not been used	2276	forking. You could also try to call the L<IO::AIO::reinit> function in the
1016	yet.	2277	child:
		2278
		2279	=over 4
		2280
		2281	=item IO::AIO::reinit
		2282
		2283	Abandons all current requests and I/O threads and simply reinitialises all
		2284	data structures. This is not an operation supported by any standards, but
		2285	happens to work on GNU/Linux and some newer BSD systems.
		2286
		2287	The only reasonable use for this function is to call it after forking, if
		2288	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2289	the process will result in undefined behaviour. Calling it at any time
		2290	will also result in any undefined (by POSIX) behaviour.
		2291
		2292	=back
1017		2293
1018	=head2 MEMORY USAGE	2294	=head2 MEMORY USAGE
1019		2295
1020	Per-request usage:	2296	Per-request usage:
1021		2297
…		…
1023	bytes of memory. In addition, stat requests need a stat buffer (possibly	2299	bytes of memory. In addition, stat requests need a stat buffer (possibly
1024	a few hundred bytes), readdir requires a result buffer and so on. Perl	2300	a few hundred bytes), readdir requires a result buffer and so on. Perl
1025	scalars and other data passed into aio requests will also be locked and	2301	scalars and other data passed into aio requests will also be locked and
1026	will consume memory till the request has entered the done state.	2302	will consume memory till the request has entered the done state.
1027		2303
1028	This is now awfully much, so queuing lots of requests is not usually a	2304	This is not awfully much, so queuing lots of requests is not usually a
1029	problem.	2305	problem.
1030		2306
1031	Per-thread usage:	2307	Per-thread usage:
1032		2308
1033	In the execution phase, some aio requests require more memory for	2309	In the execution phase, some aio requests require more memory for
…		…
1038		2314
1039	Known bugs will be fixed in the next release.	2315	Known bugs will be fixed in the next release.
1040		2316
1041	=head1 SEE ALSO	2317	=head1 SEE ALSO
1042		2318
1043	L<Coro::AIO>.	2319	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2320	more natural syntax.
1044		2321
1045	=head1 AUTHOR	2322	=head1 AUTHOR
1046		2323
1047	Marc Lehmann <schmorp@schmorp.de>	2324	Marc Lehmann <schmorp@schmorp.de>
1048	http://home.schmorp.de/	2325	http://home.schmorp.de/

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