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Revision 1.117 by root, Sat Oct 6 14:05:19 2007 UTC vs.
Revision 1.266 by root, Tue Aug 9 11:37:53 2016 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	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>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
64	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
68	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
69	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
70	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
71	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
72		52
73	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
74	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
75	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
…		…
78	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
79	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
80	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
81	using threads anyway.	61	using threads anyway.
82		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
83	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
84	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
85	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
86	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
87		71
88	=head2 EXAMPLE	72	=head2 EXAMPLE
89		73
90	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
91	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
92		76
93	use Fcntl;
94	use Event;	77	use EV;
95	use IO::AIO;	78	use IO::AIO;
96		79
97	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
98	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
99	poll => 'r',
100	cb => \&IO::AIO::poll_cb);
101		82
102	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
104	my $fh = shift	85	my $fh = shift
105	or die "error while opening: $!";	86	or die "error while opening: $!";
106		87
107	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
108	my $size = -s $fh;	89	my $size = -s $fh;
…		…
117		98
118	# file contents now in $contents	99	# file contents now in $contents
119	print $contents;	100	print $contents;
120		101
121	# exit event loop and program	102	# exit event loop and program
122	Event::unloop;	103	EV::break;
123	};	104	};
124	};	105	};
125		106
126	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
127	# check for sockets etc. etc.	108	# check for sockets etc. etc.
128		109
129	# process events as long as there are some:	110	# process events as long as there are some:
130	Event::loop;	111	EV::run;
131		112
132	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
133		114
134	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
135	directly visible to Perl.	116	directly visible to Perl.
…		…
185		166
186	package IO::AIO;	167	package IO::AIO;
187		168
188	use Carp ();	169	use Carp ();
189		170
190	no warnings;	171	use common::sense;
191	use strict 'vars';
192		172
193	use base 'Exporter';	173	use base 'Exporter';
194		174
195	BEGIN {	175	BEGIN {
196	our $VERSION = '2.51';	176	our $VERSION = 4.34;
197		177
198	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
199	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
200	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
		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
201	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
202	aio_chown aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
		189
203	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
204	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
205	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
206	nreqs nready npending nthreads	193	nreqs nready npending nthreads
207	max_poll_time max_poll_reqs);	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
208		199
209	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
210		201
211	require XSLoader;	202	require XSLoader;
212	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
213	}	204	}
214		205
215	=head1 FUNCTIONS	206	=head1 FUNCTIONS
216		207
217	=head2 AIO REQUEST FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_mkdir $pathname, $mode, $callback->($status)
		239	aio_rmdir $pathname, $callback->($status)
		240	aio_readdir $pathname, $callback->($entries)
		241	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		242	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		243	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		244	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		245	aio_load $pathname, $data, $callback->($status)
		246	aio_copy $srcpath, $dstpath, $callback->($status)
		247	aio_move $srcpath, $dstpath, $callback->($status)
		248	aio_rmtree $pathname, $callback->($status)
		249	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		250	aio_ioctl $fh, $request, $buf, $callback->($status)
		251	aio_sync $callback->($status)
		252	aio_syncfs $fh, $callback->($status)
		253	aio_fsync $fh, $callback->($status)
		254	aio_fdatasync $fh, $callback->($status)
		255	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		256	aio_pathsync $pathname, $callback->($status)
		257	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		258	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		259	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		260	aio_mlockall $flags, $callback->($status)
		261	aio_group $callback->(...)
		262	aio_nop $callback->()
		263
		264	$prev_pri = aioreq_pri [$pri]
		265	aioreq_nice $pri_adjust
		266
		267	IO::AIO::poll_wait
		268	IO::AIO::poll_cb
		269	IO::AIO::poll
		270	IO::AIO::flush
		271	IO::AIO::max_poll_reqs $nreqs
		272	IO::AIO::max_poll_time $seconds
		273	IO::AIO::min_parallel $nthreads
		274	IO::AIO::max_parallel $nthreads
		275	IO::AIO::max_idle $nthreads
		276	IO::AIO::idle_timeout $seconds
		277	IO::AIO::max_outstanding $maxreqs
		278	IO::AIO::nreqs
		279	IO::AIO::nready
		280	IO::AIO::npending
		281
		282	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		283	IO::AIO::fadvise $fh, $offset, $len, $advice
		284	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		285	IO::AIO::munmap $scalar
		286	IO::AIO::madvise $scalar, $offset, $length, $advice
		287	IO::AIO::mprotect $scalar, $offset, $length, $protect
		288	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		289	IO::AIO::munlockall
		290
		291	=head2 API NOTES
218		292
219	All the C<aio_*> calls are more or less thin wrappers around the syscall	293	All the C<aio_*> calls are more or less thin wrappers around the syscall
220	with the same name (sans C<aio_>). The arguments are similar or identical,	294	with the same name (sans C<aio_>). The arguments are similar or identical,
221	and they all accept an additional (and optional) C<$callback> argument	295	and they all accept an additional (and optional) C<$callback> argument
222	which must be a code reference. This code reference will get called with	296	which must be a code reference. This code reference will be called after
223	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	297	the syscall has been executed in an asynchronous fashion. The results
224	perl, which usually delivers "false") as it's sole argument when the given	298	of the request will be passed as arguments to the callback (and, if an
225	syscall has been executed asynchronously.	299	error occured, in C<$!>) - 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>.
226		305
227	All functions expecting a filehandle keep a copy of the filehandle	306	All functions expecting a filehandle keep a copy of the filehandle
228	internally until the request has finished.	307	internally until the request has finished.
229		308
230	All functions return request objects of type L<IO::AIO::REQ> that allow	309	All functions return request objects of type L<IO::AIO::REQ> that allow
231	further manipulation of those requests while they are in-flight.	310	further manipulation of those requests while they are in-flight.
232		311
233	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
234	encoded as octets. The reason for the former is that at the time the	313	reason for this is that at the time the request is being executed, the
235	request is being executed, the current working directory could have	314	current working directory could have changed. Alternatively, you can
236	changed. Alternatively, you can make sure that you never change the	315	make sure that you never change the current working directory anywhere
237	current working directory anywhere in the program and then use relative	316	in the program and then use relative paths. You can also take advantage
238	paths.	317	of IO::AIOs working directory abstraction, that lets you specify paths
		318	relative to some previously-opened "working directory object" - see the
		319	description of the C<IO::AIO::WD> class later in this document.
239		320
240	To encode pathnames as octets, either make sure you either: a) always pass	321	To encode pathnames as octets, either make sure you either: a) always pass
241	in filenames you got from outside (command line, readdir etc.) without	322	in filenames you got from outside (command line, readdir etc.) without
242	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	323	tinkering, b) are in your native filesystem encoding, c) use the Encode
243	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
244	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
245	use something else to ensure your scalar has the correct contents.	326	unicode filenames or e) use something else to ensure your scalar has the
		327	correct contents.
246		328
247	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	329	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
248	handles correctly wether it is set or not.	330	handles correctly whether it is set or not.
		331
		332	=head2 AIO REQUEST FUNCTIONS
249		333
250	=over 4	334	=over 4
251		335
252	=item $prev_pri = aioreq_pri [$pri]	336	=item $prev_pri = aioreq_pri [$pri]
253		337
…		…
283		367
284		368
285	=item aio_open $pathname, $flags, $mode, $callback->($fh)	369	=item aio_open $pathname, $flags, $mode, $callback->($fh)
286		370
287	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
288	created filehandle for the file.	372	created filehandle for the file (or C<undef> in case of an error).
289		373
290	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,
291	for an explanation.	375	for an explanation.
292		376
293	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
…		…
300	by the umask in effect then the request is being executed, so better never	384	by the umask in effect then the request is being executed, so better never
301	change the umask.	385	change the umask.
302		386
303	Example:	387	Example:
304		388
305	aio_open "/etc/passwd", O_RDONLY, 0, sub {	389	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
306	if ($_[0]) {	390	if ($_[0]) {
307	print "open successful, fh is $_[0]\n";	391	print "open successful, fh is $_[0]\n";
308	...	392	...
309	} else {	393	} else {
310	die "open failed: $!\n";	394	die "open failed: $!\n";
311	}	395	}
312	};	396	};
313		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
314		407
315	=item aio_close $fh, $callback->($status)	408	=item aio_close $fh, $callback->($status)
316		409
317	Asynchronously close a file and call the callback with the result	410	Asynchronously close a file and call the callback with the result
318	code.	411	code.
319		412
320	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on	413	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
321	closing the file descriptor associated with the filehandle itself. Here is	414	closing the file descriptor associated with the filehandle itself.
322	what aio_close will try:
323		415
324	1. dup()licate the fd	416	Therefore, C<aio_close> will not close the filehandle - instead it will
325	2. asynchronously close() the duplicated fd	417	use dup2 to overwrite the file descriptor with the write-end of a pipe
326	3. dup()licate the fd once more	418	(the pipe fd will be created on demand and will be cached).
327	4. let perl close() the filehandle
328	5. asynchronously close the duplicated fd
329		419
330	The idea is that the first close() flushes stuff to disk that closing an	420	Or in other words: the file descriptor will be closed, but it will not be
331	fd will flush, so when perl closes the fd, nothing much will need to be	421	free for reuse until the perl filehandle is closed.
332	flushed. The second async. close() will then flush stuff to disk that
333	closing the last fd to the file will flush.
334
335	Just FYI, SuSv3 has this to say on close:
336
337	All outstanding record locks owned by the process on the file
338	associated with the file descriptor shall be removed.
339
340	If fildes refers to a socket, close() shall cause the socket to be
341	destroyed. ... close() shall block for up to the current linger
342	interval until all data is transmitted.
343	[this actually sounds like a specification bug, but who knows]
344
345	And at least Linux additionally actually flushes stuff on every close,
346	even when the file itself is still open.
347
348	Sounds enourmously inefficient and complicated? Yes... please show me how
349	to nuke perl's fd out of existence...
350		422
351	=cut	423	=cut
352		424
353	sub aio_close($;$) {	425	=item aio_seek $fh, $offset, $whence, $callback->($offs)
354	aio_block {
355	my ($fh, $cb) = @_;
356		426
357	my $pri = aioreq_pri;	427	Seeks the filehandle to the new C<$offset>, similarly to perl's
358	my $grp = aio_group $cb;	428	C<sysseek>. The C<$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>).
359		431
360	my $fd = fileno $fh;	432	The resulting absolute offset will be passed to the callback, or C<-1> in
		433	case of an error.
361		434
362	defined $fd or Carp::croak "aio_close called with fd-less filehandle";	435	In theory, the C<$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.
363		438
364	# if the dups fail we will simply get EBADF	439	As a GNU/Linux (and maybe Solaris) extension, also the constants
365	my $fd2 = _dup $fd;	440	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
366	aioreq_pri $pri;	441	could be found. No guarantees about suitability for use in C<aio_seek> or
367	add $grp _aio_close $fd2, sub {	442	Perl's C<sysseek> can be made though, although I would naively assume they
368	my $fd2 = _dup $fd;	443	"just work".
369	close $fh;
370	aioreq_pri $pri;
371	add $grp _aio_close $fd2, sub {
372	$grp->result ($_[0]);
373	};
374	};
375
376	$grp
377	}
378	}
379
380		444
381	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	445	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
382		446
383	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
384		448
385	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<$fh> and
386	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	450	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
387	callback without the actual number of bytes read (or -1 on error, just	451	and calls the callback with the actual number of bytes read (or -1 on
388	like the syscall).	452	error, just like the syscall).
		453
		454	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		455	offset plus the actual number of bytes read.
389		456
390	If C<$offset> is undefined, then the current file descriptor offset will	457	If C<$offset> is undefined, then the current file descriptor offset will
391	be used (and updated), otherwise the file descriptor offset will not be	458	be used (and updated), otherwise the file descriptor offset will not be
392	changed by these calls.	459	changed by these calls.
393		460
394	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	461	If C<$length> is undefined in C<aio_write>, use the remaining length of
		462	C<$data>.
395		463
396	If C<$dataoffset> is less than zero, it will be counted from the end of	464	If C<$dataoffset> is less than zero, it will be counted from the end of
397	C<$data>.	465	C<$data>.
398		466
399	The C<$data> scalar I<MUST NOT> be modified in any way while the request	467	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
413		481
414	Tries to copy C<$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<$out_fh>. It starts
415	reading at byte offset C<$in_offset>, and starts writing at the current	483	reading at byte offset C<$in_offset>, and starts writing at the current
416	file offset of C<$out_fh>. Because of that, it is not safe to issue more	484	file offset of C<$out_fh>. Because of that, it is not safe to issue more
417	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	485	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
418	other.	486	other. The same C<$in_fh> works fine though, as this function does not
		487	move or use the file offset of C<$in_fh>.
419		488
		489	Please note that C<aio_sendfile> can read more bytes from C<$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
420	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
421	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
422	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.
423		508
424	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>,
425	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
426	regardless of the limitations of the operating system.	512	type of filehandle regardless of the limitations of the operating system.
427		513
428	Please note, however, that C<aio_sendfile> can read more bytes from	514	As native sendfile syscalls (as practically any non-POSIX interface hacked
429	C<$in_fh> than are written, and there is no way to find out how many	515	together in a hurry to improve benchmark numbers) tend to be rather buggy
430	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	516	on many systems, this implementation tries to work around some known bugs
431	provides the number of bytes written to C<$out_fh>. Only if the result	517	in Linux and FreeBSD kernels (probably others, too), but that might fail,
432	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> -
433	read.	519	fewer bytes than expected might have been transferred.
434		520
435		521
436	=item aio_readahead $fh,$offset,$length, $callback->($retval)	522	=item aio_readahead $fh,$offset,$length, $callback->($retval)
437		523
438	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
…		…
442	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
443	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
444	(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
445	file. The current file offset of the file is left unchanged.	531	file. The current file offset of the file is left unchanged.
446		532
447	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
448	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.
449		535
450		536
451	=item aio_stat $fh_or_path, $callback->($status)	537	=item aio_stat $fh_or_path, $callback->($status)
452		538
453	=item aio_lstat $fh, $callback->($status)	539	=item aio_lstat $fh, $callback->($status)
…		…
460	for an explanation.	546	for an explanation.
461		547
462	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
463	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
464	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>.
465		560
466	Example: Print the length of F</etc/passwd>:	561	Example: Print the length of F</etc/passwd>:
467		562
468	aio_stat "/etc/passwd", sub {	563	aio_stat "/etc/passwd", sub {
469	$_[0] and die "stat failed: $!";	564	$_[0] and die "stat failed: $!";
470	print "size is ", -s _, "\n";	565	print "size is ", -s _, "\n";
471	};	566	};
472		567
473		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
474	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	698	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
475		699
476	Works like perl's C<utime> function (including the special case of $atime	700	Works like perl's C<utime> function (including the special case of $atime
477	and $mtime being undef). Fractional times are supported if the underlying	701	and $mtime being undef). Fractional times are supported if the underlying
478	syscalls support them.	702	syscalls support them.
…		…
505	=item aio_truncate $fh_or_path, $offset, $callback->($status)	729	=item aio_truncate $fh_or_path, $offset, $callback->($status)
506		730
507	Works like truncate(2) or ftruncate(2).	731	Works like truncate(2) or ftruncate(2).
508		732
509		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
510	=item aio_chmod $fh_or_path, $mode, $callback->($status)	754	=item aio_chmod $fh_or_path, $mode, $callback->($status)
511		755
512	Works like perl's C<chmod> function.	756	Works like perl's C<chmod> function.
513		757
514		758
…		…
516		760
517	Asynchronously unlink (delete) a file and call the callback with the	761	Asynchronously unlink (delete) a file and call the callback with the
518	result code.	762	result code.
519		763
520		764
521	=item aio_mknod $path, $mode, $dev, $callback->($status)	765	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
522		766
523	[EXPERIMENTAL]	767	[EXPERIMENTAL]
524		768
525	Asynchronously create a device node (or fifo). See mknod(2).	769	Asynchronously create a device node (or fifo). See mknod(2).
526		770
527	The only (POSIX-) portable way of calling this function is:	771	The only (POSIX-) portable way of calling this function is:
528		772
529	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	773	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
530		774
		775	See C<aio_stat> for info about some potentially helpful extra constants
		776	and functions.
531		777
532	=item aio_link $srcpath, $dstpath, $callback->($status)	778	=item aio_link $srcpath, $dstpath, $callback->($status)
533		779
534	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
535	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.
…		…
539		785
540	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
541	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.
542		788
543		789
544	=item aio_readlink $path, $callback->($link)	790	=item aio_readlink $pathname, $callback->($link)
545		791
546	Asynchronously read the symlink specified by C<$path> and pass it to	792	Asynchronously read the symlink specified by C<$path> and pass it to
547	the callback. If an error occurs, nothing or undef gets passed to the	793	the callback. If an error occurs, nothing or undef gets passed to the
548	callback.	794	callback.
549		795
550		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
551	=item aio_rename $srcpath, $dstpath, $callback->($status)	807	=item aio_rename $srcpath, $dstpath, $callback->($status)
552		808
553	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
554	rename(2) and call the callback with the result code.	810	rename(2) and call the callback with the result code.
		811
		812	On systems that support the AIO::WD working directory abstraction
		813	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		814	of failing, C<rename> is called on the absolute path of C<$wd>.
555		815
556		816
557	=item aio_mkdir $pathname, $mode, $callback->($status)	817	=item aio_mkdir $pathname, $mode, $callback->($status)
558		818
559	Asynchronously mkdir (create) a directory and call the callback with	819	Asynchronously mkdir (create) a directory and call the callback with
…		…
564	=item aio_rmdir $pathname, $callback->($status)	824	=item aio_rmdir $pathname, $callback->($status)
565		825
566	Asynchronously rmdir (delete) a directory and call the callback with the	826	Asynchronously rmdir (delete) a directory and call the callback with the
567	result code.	827	result code.
568		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
569		833
570	=item aio_readdir $pathname, $callback->($entries)	834	=item aio_readdir $pathname, $callback->($entries)
571		835
572	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
573	directory (i.e. opendir + readdir + closedir). The entries will not be	837	directory (i.e. opendir + readdir + closedir). The entries will not be
574	sorted, and will B<NOT> include the C<.> and C<..> entries.	838	sorted, and will B<NOT> include the C<.> and C<..> entries.
575		839
576	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
577	with the filenames.	841	array-ref with the filenames.
578		842
579		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
580	=item aio_load $path, $data, $callback->($status)	910	=item aio_load $pathname, $data, $callback->($status)
581		911
582	This is a composite request that tries to fully load the given file into	912	This is a composite request that tries to fully load the given file into
583	memory. Status is the same as with aio_read.	913	memory. Status is the same as with aio_read.
584		914
585	=cut	915	=cut
586		916
587	sub aio_load($$;$) {	917	sub aio_load($$;$) {
588	aio_block {
589	my ($path, undef, $cb) = @_;	918	my ($path, undef, $cb) = @_;
590	my $data = \$_[1];	919	my $data = \$_[1];
591		920
592	my $pri = aioreq_pri;	921	my $pri = aioreq_pri;
593	my $grp = aio_group $cb;	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);
594		928
595	aioreq_pri $pri;	929	aioreq_pri $pri;
596	add $grp aio_open $path, O_RDONLY, 0, sub {
597	my $fh = shift
598	or return $grp->result (-1);
599
600	aioreq_pri $pri;
601	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {	930	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
602	$grp->result ($_[0]);	931	$grp->result ($_[0]);
603	};
604	};	932	};
605
606	$grp
607	}	933	};
		934
		935	$grp
608	}	936	}
609		937
610	=item aio_copy $srcpath, $dstpath, $callback->($status)	938	=item aio_copy $srcpath, $dstpath, $callback->($status)
611		939
612	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
613	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
614	the C<0> (error) or C<-1> ok.	942	a status of C<0> (ok) or C<-1> (error, see C<$!>).
615		943
616	This is a composite request that it creates the destination file with	944	This is a composite request that creates the destination file with
617	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
618	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
619	uid/gid, in that order.	947	uid/gid, in that order.
620		948
621	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
…		…
623	errors are being ignored.	951	errors are being ignored.
624		952
625	=cut	953	=cut
626		954
627	sub aio_copy($$;$) {	955	sub aio_copy($$;$) {
628	aio_block {
629	my ($src, $dst, $cb) = @_;	956	my ($src, $dst, $cb) = @_;
630		957
631	my $pri = aioreq_pri;	958	my $pri = aioreq_pri;
632	my $grp = aio_group $cb;	959	my $grp = aio_group $cb;
633		960
634	aioreq_pri $pri;	961	aioreq_pri $pri;
635	add $grp aio_open $src, O_RDONLY, 0, sub {	962	add $grp aio_open $src, O_RDONLY, 0, sub {
636	if (my $src_fh = $_[0]) {	963	if (my $src_fh = $_[0]) {
637	my @stat = stat $src_fh;	964	my @stat = stat $src_fh; # hmm, might block over nfs?
638		965
639	aioreq_pri $pri;	966	aioreq_pri $pri;
640	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 {
641	if (my $dst_fh = $_[0]) {	968	if (my $dst_fh = $_[0]) {
642	aioreq_pri $pri;	969	aioreq_pri $pri;
643	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	970	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
644	if ($_[0] == $stat[7]) {	971	if ($_[0] == $stat[7]) {
645	$grp->result (0);	972	$grp->result (0);
646	close $src_fh;	973	close $src_fh;
647		974
648	# those should not normally block. should. should.
649	utime $stat[8], $stat[9], $dst;
650	chmod $stat[2] & 07777, $dst_fh;
651	chown $stat[4], $stat[5], $dst_fh;
652	close $dst_fh;
653	} else {	975	my $ch = sub {
654	$grp->result (-1);
655	close $src_fh;
656	close $dst_fh;
657
658	aioreq $pri;	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;
659	add $grp aio_unlink $dst;	981	add $grp aio_close $dst_fh;
		982	}
		983	};
660	}	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;
		990	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		991	} else {
		992	$ch->();
		993	}
		994	};
		995	} else {
		996	$grp->result (-1);
		997	close $src_fh;
		998	close $dst_fh;
		999
		1000	aioreq $pri;
		1001	add $grp aio_unlink $dst;
661	};	1002	}
662	} else {
663	$grp->result (-1);
664	}	1003	};
		1004	} else {
		1005	$grp->result (-1);
665	},	1006	}
666
667	} else {
668	$grp->result (-1);
669	}	1007	},
		1008
		1009	} else {
		1010	$grp->result (-1);
670	};	1011	}
671
672	$grp
673	}	1012	};
		1013
		1014	$grp
674	}	1015	}
675		1016
676	=item aio_move $srcpath, $dstpath, $callback->($status)	1017	=item aio_move $srcpath, $dstpath, $callback->($status)
677		1018
678	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
679	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
680	the C<0> (error) or C<-1> ok.	1021	a status of C<0> (ok) or C<-1> (error, see C<$!>).
681		1022
682	This is a composite request that tries to rename(2) the file first. If	1023	This is a composite request that tries to rename(2) the file first; if
683	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1024	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
684	that is successful, unlinking the C<$srcpath>.	1025	that is successful, unlinks the C<$srcpath>.
685		1026
686	=cut	1027	=cut
687		1028
688	sub aio_move($$;$) {	1029	sub aio_move($$;$) {
689	aio_block {
690	my ($src, $dst, $cb) = @_;	1030	my ($src, $dst, $cb) = @_;
691		1031
692	my $pri = aioreq_pri;	1032	my $pri = aioreq_pri;
693	my $grp = aio_group $cb;	1033	my $grp = aio_group $cb;
694		1034
695	aioreq_pri $pri;	1035	aioreq_pri $pri;
696	add $grp aio_rename $src, $dst, sub {	1036	add $grp aio_rename $src, $dst, sub {
697	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
698	aioreq_pri $pri;	1038	aioreq_pri $pri;
699	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
700	$grp->result ($_[0]);
701
702	if (!$_[0]) {
703	aioreq_pri $pri;
704	add $grp aio_unlink $src;
705	}
706	};
707	} else {
708	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
		1041
		1042	unless ($_[0]) {
		1043	aioreq_pri $pri;
		1044	add $grp aio_unlink $src;
		1045	}
709	}	1046	};
		1047	} else {
		1048	$grp->result ($_[0]);
710	};	1049	}
711
712	$grp
713	}	1050	};
		1051
		1052	$grp
714	}	1053	}
715		1054
716	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
717		1056
718	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
719	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
720	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
721	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
…		…
738		1077
739	Implementation notes.	1078	Implementation notes.
740		1079
741	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.
742		1081
		1082	If readdir returns file type information, then this is used directly to
		1083	find directories.
		1084
743	After reading the directory, the modification time, size etc. of the	1085	Otherwise, after reading the directory, the modification time, size etc.
744	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
745	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
746	entries are directories (if >= 2). Otherwise, no knowledge of the number	1088	how many entries are directories (if >= 2). Otherwise, no knowledge of the
747	of subdirectories will be assumed.	1089	number of subdirectories will be assumed.
748		1090
749	Then entries will be sorted into likely directories (everything without	1091	Then entries will be sorted into likely directories a non-initial dot
750	a non-initial dot currently) and likely non-directories (everything	1092	currently) and likely non-directories (see C<aio_readdirx>). Then every
751	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,
752	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
753	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
754	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
755	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
756	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.
757		1100
758	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
759	rest of the entries is assumed to be non-directories.	1102	rest of the entries is assumed to be non-directories.
760		1103
761	This only works with certainty on POSIX (= UNIX) filesystems, which	1104	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
766	directory counting heuristic.	1109	directory counting heuristic.
767		1110
768	=cut	1111	=cut
769		1112
770	sub aio_scandir($$;$) {	1113	sub aio_scandir($$;$) {
771	aio_block {
772	my ($path, $maxreq, $cb) = @_;	1114	my ($path, $maxreq, $cb) = @_;
773		1115
774	my $pri = aioreq_pri;	1116	my $pri = aioreq_pri;
775		1117
776	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
777		1119
778	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
		1121
		1122	# get a wd object
		1123	aioreq_pri $pri;
		1124	add $grp aio_wd $path, sub {
		1125	$_[0]
		1126	or return $grp->result ();
		1127
		1128	my $wd = [shift, "."];
779		1129
780	# stat once	1130	# stat once
781	aioreq_pri $pri;	1131	aioreq_pri $pri;
782	add $grp aio_stat $path, sub {	1132	add $grp aio_stat $wd, sub {
783	return $grp->result () if $_[0];	1133	return $grp->result () if $_[0];
784	my $now = time;	1134	my $now = time;
785	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
786		1136
787	# read the directory entries	1137	# read the directory entries
788	aioreq_pri $pri;	1138	aioreq_pri $pri;
789	add $grp aio_readdir $path, sub {	1139	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
790	my $entries = shift	1140	my $entries = shift
791	or return $grp->result ();	1141	or return $grp->result ();
792		1142
793	# stat the dir another time	1143	# stat the dir another time
794	aioreq_pri $pri;	1144	aioreq_pri $pri;
795	add $grp aio_stat $path, sub {	1145	add $grp aio_stat $wd, sub {
796	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1146	my $hash2 = join ":", (stat _)[0,1,3,7,9];
797		1147
798	my $ndirs;	1148	my $ndirs;
799		1149
800	# take the slow route if anything looks fishy	1150	# take the slow route if anything looks fishy
801	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1151	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
802	$ndirs = -1;	1152	$ndirs = -1;
803	} else {	1153	} else {
804	# if nlink == 2, we are finished	1154	# if nlink == 2, we are finished
805	# on non-posix-fs's, we rely on nlink < 2	1155	# for non-posix-fs's, we rely on nlink < 2
806	$ndirs = (stat _)[3] - 2	1156	$ndirs = (stat _)[3] - 2
807	or return $grp->result ([], $entries);	1157	or return $grp->result ([], $entries);
808	}	1158	}
809		1159
810	# sort into likely dirs and likely nondirs
811	# dirs == files without ".", short entries first
812	$entries = [map $_->[0],
813	sort { $b->[1] cmp $a->[1] }
814	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
815	@$entries];
816
817	my (@dirs, @nondirs);	1160	my (@dirs, @nondirs);
818		1161
819	my $statgrp = add $grp aio_group sub {	1162	my $statgrp = add $grp aio_group sub {
820	$grp->result (\@dirs, \@nondirs);	1163	$grp->result (\@dirs, \@nondirs);
821	};	1164	};
822		1165
823	limit $statgrp $maxreq;	1166	limit $statgrp $maxreq;
824	feed $statgrp sub {	1167	feed $statgrp sub {
825	return unless @$entries;	1168	return unless @$entries;
826	my $entry = pop @$entries;	1169	my $entry = shift @$entries;
827		1170
828	aioreq_pri $pri;	1171	aioreq_pri $pri;
		1172	$wd->[1] = "$entry/.";
829	add $statgrp aio_stat "$path/$entry/.", sub {	1173	add $statgrp aio_stat $wd, sub {
830	if ($_[0] < 0) {	1174	if ($_[0] < 0) {
831	push @nondirs, $entry;	1175	push @nondirs, $entry;
832	} else {	1176	} else {
833	# need to check for real directory	1177	# need to check for real directory
834	aioreq_pri $pri;	1178	aioreq_pri $pri;
		1179	$wd->[1] = $entry;
835	add $statgrp aio_lstat "$path/$entry", sub {	1180	add $statgrp aio_lstat $wd, sub {
836	if (-d _) {	1181	if (-d _) {
837	push @dirs, $entry;	1182	push @dirs, $entry;
838		1183
839	unless (--$ndirs) {	1184	unless (--$ndirs) {
840	push @nondirs, @$entries;	1185	push @nondirs, @$entries;
…		…
848	};	1193	};
849	};	1194	};
850	};	1195	};
851	};	1196	};
852	};	1197	};
853
854	$grp
855	}	1198	};
		1199
		1200	$grp
856	}	1201	}
857		1202
858	=item aio_rmtree $path, $callback->($status)	1203	=item aio_rmtree $pathname, $callback->($status)
859		1204
860	Delete a directory tree starting (and including) C<$path>, return the	1205	Delete a directory tree starting (and including) C<$path>, return the
861	status of the final C<rmdir> only. This is a composite request that	1206	status of the final C<rmdir> only. This is a composite request that
862	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1207	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
863	everything else.	1208	everything else.
864		1209
865	=cut	1210	=cut
866		1211
867	sub aio_rmtree;	1212	sub aio_rmtree;
868	sub aio_rmtree($;$) {	1213	sub aio_rmtree($;$) {
869	aio_block {
870	my ($path, $cb) = @_;	1214	my ($path, $cb) = @_;
871		1215
872	my $pri = aioreq_pri;	1216	my $pri = aioreq_pri;
873	my $grp = aio_group $cb;	1217	my $grp = aio_group $cb;
874		1218
875	aioreq_pri $pri;	1219	aioreq_pri $pri;
876	add $grp aio_scandir $path, 0, sub {	1220	add $grp aio_scandir $path, 0, sub {
877	my ($dirs, $nondirs) = @_;	1221	my ($dirs, $nondirs) = @_;
878		1222
879	my $dirgrp = aio_group sub {	1223	my $dirgrp = aio_group sub {
880	add $grp aio_rmdir $path, sub {	1224	add $grp aio_rmdir $path, sub {
881	$grp->result ($_[0]);	1225	$grp->result ($_[0]);
882	};
883	};	1226	};
884
885	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
886	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
887
888	add $grp $dirgrp;
889	};	1227	};
890		1228
891	$grp	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;
892	}	1233	};
		1234
		1235	$grp
893	}	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.
894		1281
895	=item aio_fsync $fh, $callback->($status)	1282	=item aio_fsync $fh, $callback->($status)
896		1283
897	Asynchronously call fsync on the given filehandle and call the callback	1284	Asynchronously call fsync on the given filehandle and call the callback
898	with the fsync result code.	1285	with the fsync result code.
…		…
902	Asynchronously call fdatasync on the given filehandle and call the	1289	Asynchronously call fdatasync on the given filehandle and call the
903	callback with the fdatasync result code.	1290	callback with the fdatasync result code.
904		1291
905	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
906	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 = 0, $callback->($status)
		1356
		1357	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1358	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1359	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1360	scalar must only be modified in-place while an aio operation is pending on
		1361	it).
		1362
		1363	It calls the C<msync> function of your OS, if available, with the memory
		1364	area starting at C<$offset> in the string and ending C<$length> bytes
		1365	later. If C<$length> is negative, counts from the end, and if C<$length>
		1366	is C<undef>, then it goes till the end of the string. The flags can be
		1367	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1368	C<IO::AIO::MS_SYNC>.
		1369
		1370	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1371
		1372	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1373	scalars.
		1374
		1375	It touches (reads or writes) all memory pages in the specified
		1376	range inside the scalar. All caveats and parameters are the same
		1377	as for C<aio_msync>, above, except for flags, which must be either
		1378	C<0> (which reads all pages and ensures they are instantiated) or
		1379	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1380	writing an octet from it, which dirties the page).
		1381
		1382	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1383
		1384	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1385	scalars.
		1386
		1387	It reads in all the pages of the underlying storage into memory (if any)
		1388	and locks them, so they are not getting swapped/paged out or removed.
		1389
		1390	If C<$length> is undefined, then the scalar will be locked till the end.
		1391
		1392	On systems that do not implement C<mlock>, this function returns C<-1>
		1393	and sets errno to C<ENOSYS>.
		1394
		1395	Note that the corresponding C<munlock> is synchronous and is
		1396	documented under L<MISCELLANEOUS FUNCTIONS>.
		1397
		1398	Example: open a file, mmap and mlock it - both will be undone when
		1399	C<$data> gets destroyed.
		1400
		1401	open my $fh, "<", $path or die "$path: $!";
		1402	my $data;
		1403	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1404	aio_mlock $data; # mlock in background
		1405
		1406	=item aio_mlockall $flags, $callback->($status)
		1407
		1408	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1409	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1410
		1411	On systems that do not implement C<mlockall>, this function returns C<-1>
		1412	and sets errno to C<ENOSYS>.
		1413
		1414	Note that the corresponding C<munlockall> is synchronous and is
		1415	documented under L<MISCELLANEOUS FUNCTIONS>.
		1416
		1417	Example: asynchronously lock all current and future pages into memory.
		1418
		1419	aio_mlockall IO::AIO::MCL_FUTURE;
		1420
		1421	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1422
		1423	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1424	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1425	the ioctl is not available on your OS, then this request will fail with
		1426	C<ENOSYS>.
		1427
		1428	C<$start> is the starting offset to query extents for, C<$length> is the
		1429	size of the range to query - if it is C<undef>, then the whole file will
		1430	be queried.
		1431
		1432	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1433	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1434	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1435	the data portion.
		1436
		1437	C<$count> is the maximum number of extent records to return. If it is
		1438	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1439	case, if it is C<0>, then the callback receives the number of extents
		1440	instead of the extents themselves (which is unreliable, see below).
		1441
		1442	If an error occurs, the callback receives no arguments. The special
		1443	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1444
		1445	Otherwise, the callback receives an array reference with extent
		1446	structures. Each extent structure is an array reference itself, with the
		1447	following members:
		1448
		1449	[$logical, $physical, $length, $flags]
		1450
		1451	Flags is any combination of the following flag values (typically either C<0>
		1452	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1453
		1454	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1455	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1456	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1457	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1458	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1459	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1460
		1461	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1462	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1463	it to return all extents of a range for files with large number of
		1464	extents. The code works around all these issues if C<$count> is undef.
907		1465
908	=item aio_group $callback->(...)	1466	=item aio_group $callback->(...)
909		1467
910	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
911	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
…		…
949	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
950	except to put your application under artificial I/O pressure.	1508	except to put your application under artificial I/O pressure.
951		1509
952	=back	1510	=back
953		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
954	=head2 IO::AIO::REQ CLASS	1637	=head2 IO::AIO::REQ CLASS
955		1638
956	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
957	called in non-void context.	1640	called in non-void context.
958		1641
…		…
961	=item cancel $req	1644	=item cancel $req
962		1645
963	Cancels the request, if possible. Has the effect of skipping execution	1646	Cancels the request, if possible. Has the effect of skipping execution
964	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
965	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
966	untouched. That means that requests that currently execute will not be	1649	untouched (with the exception of readdir). That means that requests that
967	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.
968		1652
969	=item cb $req $callback->(...)	1653	=item cb $req $callback->(...)
970		1654
971	Replace (or simply set) the callback registered to the request.	1655	Replace (or simply set) the callback registered to the request.
972		1656
…		…
1023	Their lifetime, simplified, looks like this: when they are empty, they	1707	Their lifetime, simplified, looks like this: when they are empty, they
1024	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
1025	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
1026	exist.	1710	exist.
1027		1711
1028	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
1029	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
1030	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
1031	itself finish.	1715	further requests to the group. And only when all those requests have
		1716	finished will the the group itself finish.
1032		1717
1033	=over 4	1718	=over 4
1034		1719
1035	=item add $grp ...	1720	=item add $grp ...
1036		1721
…		…
1045	=item $grp->cancel_subs	1730	=item $grp->cancel_subs
1046		1731
1047	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
1048	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.
1049		1734
		1735	The group request will finish normally (you cannot add requests to the
		1736	group).
		1737
1050	=item $grp->result (...)	1738	=item $grp->result (...)
1051		1739
1052	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
1053	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
1054	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,
1055	no argument will be passed and errno is zero.	1743	no argument will be passed and errno is zero.
1056		1744
1057	=item $grp->errno ([$errno])	1745	=item $grp->errno ([$errno])
1058		1746
…		…
1069	=item feed $grp $callback->($grp)	1757	=item feed $grp $callback->($grp)
1070		1758
1071	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
1072	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,
1073	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,
1074	this might starve other requests for a potentially long time. For	1762	this might starve other requests for a potentially long time. For example,
1075	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>
1076	requests, delaying any later requests for a long time.	1764	requests, delaying any later requests for a long time.
1077		1765
1078	To avoid this, and allow incremental generation of requests, you can	1766	To avoid this, and allow incremental generation of requests, you can
1079	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
1080	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>,
…		…
1085	not impose any limits).	1773	not impose any limits).
1086		1774
1087	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
1088	automatically removed from the group.	1776	automatically removed from the group.
1089		1777
1090	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.
1091		1780
1092	Example:	1781	Example:
1093		1782
1094	# 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:
1095		1784
…		…
1107	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
1108	the group contains less than this many requests.	1797	the group contains less than this many requests.
1109		1798
1110	Setting the limit to C<0> will pause the feeding process.	1799	Setting the limit to C<0> will pause the feeding process.
1111		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
1112	=back	1804	=back
1113		1805
1114	=head2 SUPPORT FUNCTIONS	1806	=head2 SUPPORT FUNCTIONS
1115		1807
1116	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1808	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1118	=over 4	1810	=over 4
1119		1811
1120	=item $fileno = IO::AIO::poll_fileno	1812	=item $fileno = IO::AIO::poll_fileno
1121		1813
1122	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
1123	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,
1124	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
1125	to call C<poll_cb> to check the results.	1817	you have to call C<poll_cb> to check the results.
1126		1818
1127	See C<poll_cb> for an example.	1819	See C<poll_cb> for an example.
1128		1820
1129	=item IO::AIO::poll_cb	1821	=item IO::AIO::poll_cb
1130		1822
1131	Process some outstanding events on the result pipe. You have to call this	1823	Process some requests that have reached the result phase (i.e. they have
1132	regularly. Returns the number of events processed. Returns immediately	1824	been executed but the results are not yet reported). You have to call
1133	when no events are outstanding. The amount of events processed depends on	1825	this "regularly" to finish outstanding requests.
1134	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1135		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
1136	If not all requests were processed for whatever reason, the filehandle	1833	If not all requests were processed for whatever reason, the poll file
1137	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.
1138		1843
1139	Example: Install an Event watcher that automatically calls	1844	Example: Install an Event watcher that automatically calls
1140	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):
1141		1847
1142	Event->io (fd => IO::AIO::poll_fileno,	1848	Event->io (fd => IO::AIO::poll_fileno,
1143	poll => 'r', async => 1,	1849	poll => 'r', async => 1,
1144	cb => \&IO::AIO::poll_cb);	1850	cb => \&IO::AIO::poll_cb);
		1851
		1852	=item IO::AIO::poll_wait
		1853
		1854	Wait until either at least one request is in the result phase or no
		1855	requests are outstanding anymore.
		1856
		1857	This is useful if you want to synchronously wait for some requests to
		1858	become ready, without actually handling them.
		1859
		1860	See C<nreqs> for an example.
		1861
		1862	=item IO::AIO::poll
		1863
		1864	Waits until some requests have been handled.
		1865
		1866	Returns the number of requests processed, but is otherwise strictly
		1867	equivalent to:
		1868
		1869	IO::AIO::poll_wait, IO::AIO::poll_cb
		1870
		1871	=item IO::AIO::flush
		1872
		1873	Wait till all outstanding AIO requests have been handled.
		1874
		1875	Strictly equivalent to:
		1876
		1877	IO::AIO::poll_wait, IO::AIO::poll_cb
		1878	while IO::AIO::nreqs;
1145		1879
1146	=item IO::AIO::max_poll_reqs $nreqs	1880	=item IO::AIO::max_poll_reqs $nreqs
1147		1881
1148	=item IO::AIO::max_poll_time $seconds	1882	=item IO::AIO::max_poll_time $seconds
1149		1883
…		…
1174	# use a low priority so other tasks have priority	1908	# use a low priority so other tasks have priority
1175	Event->io (fd => IO::AIO::poll_fileno,	1909	Event->io (fd => IO::AIO::poll_fileno,
1176	poll => 'r', nice => 1,	1910	poll => 'r', nice => 1,
1177	cb => &IO::AIO::poll_cb);	1911	cb => &IO::AIO::poll_cb);
1178		1912
1179	=item IO::AIO::poll_wait
1180
1181	If there are any outstanding requests and none of them in the result
1182	phase, wait till the result filehandle becomes ready for reading (simply
1183	does a C<select> on the filehandle. This is useful if you want to
1184	synchronously wait for some requests to finish).
1185
1186	See C<nreqs> for an example.
1187
1188	=item IO::AIO::poll
1189
1190	Waits until some requests have been handled.
1191
1192	Returns the number of requests processed, but is otherwise strictly
1193	equivalent to:
1194
1195	IO::AIO::poll_wait, IO::AIO::poll_cb
1196
1197	=item IO::AIO::flush
1198
1199	Wait till all outstanding AIO requests have been handled.
1200
1201	Strictly equivalent to:
1202
1203	IO::AIO::poll_wait, IO::AIO::poll_cb
1204	while IO::AIO::nreqs;
1205
1206	=back	1913	=back
1207		1914
1208	=head3 CONTROLLING THE NUMBER OF THREADS	1915	=head3 CONTROLLING THE NUMBER OF THREADS
1209		1916
1210	=over	1917	=over
…		…
1243		1950
1244	Under normal circumstances you don't need to call this function.	1951	Under normal circumstances you don't need to call this function.
1245		1952
1246	=item IO::AIO::max_idle $nthreads	1953	=item IO::AIO::max_idle $nthreads
1247		1954
1248	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1955	Limit the number of threads (default: 4) that are allowed to idle
1249	threads that did not get a request to process within 10 seconds). That	1956	(i.e., threads that did not get a request to process within the idle
1250	means if a thread becomes idle while C<$nthreads> other threads are also	1957	timeout (default: 10 seconds). That means if a thread becomes idle while
1251	idle, it will free its resources and exit.	1958	C<$nthreads> other threads are also idle, it will free its resources and
		1959	exit.
1252		1960
1253	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1961	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1254	to allow for extremely high load situations, but want to free resources	1962	to allow for extremely high load situations, but want to free resources
1255	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1963	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1256		1964
1257	The default is probably ok in most situations, especially if thread	1965	The default is probably ok in most situations, especially if thread
1258	creation is fast. If thread creation is very slow on your system you might	1966	creation is fast. If thread creation is very slow on your system you might
1259	want to use larger values.	1967	want to use larger values.
1260		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
1261	=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.
1262		1984
1263	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
1264	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
1265	use an C<aio_group> together with a feed callback.	1987	use an C<aio_group> together with a feed callback.
1266		1988
1267	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
1268	do queue up more than this number of requests, the next call to the	1990	a lot of files, you can write somehting like this:
1269	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1270	function will block until the limit is no longer exceeded.
1271		1991
1272	The default value is very large, so there is no practical limit on the	1992	IO::AIO::max_outstanding 32;
1273	number of outstanding requests.
1274		1993
1275	You can still queue as many requests as you want. Therefore,	1994	for my $path (...) {
1276	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1995	aio_stat $path , ...;
1277	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.
1278		2008
1279	=back	2009	=back
1280		2010
1281	=head3 STATISTICAL INFORMATION	2011	=head3 STATISTICAL INFORMATION
1282		2012
…		…
1302	Returns the number of requests currently in the pending state (executed,	2032	Returns the number of requests currently in the pending state (executed,
1303	but not yet processed by poll_cb).	2033	but not yet processed by poll_cb).
1304		2034
1305	=back	2035	=back
1306		2036
		2037	=head3 MISCELLANEOUS FUNCTIONS
		2038
		2039	IO::AIO implements some functions that are useful when you want to use
		2040	some "Advanced I/O" function not available to in Perl, without going the
		2041	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2042	counterpart.
		2043
		2044	=over 4
		2045
		2046	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2047
		2048	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2049	but is blocking (this makes most sense if you know the input data is
		2050	likely cached already and the output filehandle is set to non-blocking
		2051	operations).
		2052
		2053	Returns the number of bytes copied, or C<-1> on error.
		2054
		2055	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2056
		2057	Simply calls the C<posix_fadvise> function (see its
		2058	manpage for details). The following advice constants are
		2059	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2060	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2061	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2062
		2063	On systems that do not implement C<posix_fadvise>, this function returns
		2064	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2065
		2066	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>,
		2072	C<IO::AIO::MADV_FREE>.
		2073
		2074	On systems that do not implement C<posix_madvise>, this function returns
		2075	ENOSYS, otherwise the return value of C<posix_madvise>.
		2076
		2077	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2078
		2079	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2080	$scalar (see its manpage for details). The following protect
		2081	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2082	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2083
		2084	On systems that do not implement C<mprotect>, this function returns
		2085	ENOSYS, otherwise the return value of C<mprotect>.
		2086
		2087	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2088
		2089	Memory-maps a file (or anonymous memory range) and attaches it to the
		2090	given C<$scalar>, which will act like a string scalar. Returns true on
		2091	success, and false otherwise.
		2092
		2093	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		2094	change the string length, and most read-only operations such as copying it
		2095	or searching it with regexes and so on.
		2096
		2097	Anything else is unsafe and will, at best, result in memory leaks.
		2098
		2099	The memory map associated with the C<$scalar> is automatically removed
		2100	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		2101	C<IO::AIO::munmap> functions are called.
		2102
		2103	This calls the C<mmap>(2) function internally. See your system's manual
		2104	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2105
		2106	The C<$length> must be larger than zero and smaller than the actual
		2107	filesize.
		2108
		2109	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2110	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2111
		2112	C<$flags> can be a combination of
		2113	C<IO::AIO::MAP_SHARED> or
		2114	C<IO::AIO::MAP_PRIVATE>,
		2115	or a number of system-specific flags (when not available, the are C<0>):
		2116	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2117	C<IO::AIO::MAP_LOCKED>,
		2118	C<IO::AIO::MAP_NORESERVE>,
		2119	C<IO::AIO::MAP_POPULATE>,
		2120	C<IO::AIO::MAP_NONBLOCK>,
		2121	C<IO::AIO::MAP_FIXED>,
		2122	C<IO::AIO::MAP_GROWSDOWN>,
		2123	C<IO::AIO::MAP_32BIT>,
		2124	C<IO::AIO::MAP_HUGETLB> or
		2125	C<IO::AIO::MAP_STACK>.
		2126
		2127	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2128
		2129	C<$offset> is the offset from the start of the file - it generally must be
		2130	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2131
		2132	Example:
		2133
		2134	use Digest::MD5;
		2135	use IO::AIO;
		2136
		2137	open my $fh, "<verybigfile"
		2138	or die "$!";
		2139
		2140	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2141	or die "verybigfile: $!";
		2142
		2143	my $fast_md5 = md5 $data;
		2144
		2145	=item IO::AIO::munmap $scalar
		2146
		2147	Removes a previous mmap and undefines the C<$scalar>.
		2148
		2149	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2150
		2151	Calls the C<munlock> function, undoing the effects of a previous
		2152	C<aio_mlock> call (see its description for details).
		2153
		2154	=item IO::AIO::munlockall
		2155
		2156	Calls the C<munlockall> function.
		2157
		2158	On systems that do not implement C<munlockall>, this function returns
		2159	ENOSYS, otherwise the return value of C<munlockall>.
		2160
		2161	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2162
		2163	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2164	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2165	should be the file offset.
		2166
		2167	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2168	silently corrupt the data in this case.
		2169
		2170	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2171	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2172	C<IO::AIO::SPLICE_F_GIFT>.
		2173
		2174	See the C<splice(2)> manpage for details.
		2175
		2176	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2177
		2178	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2179	description for C<IO::AIO::splice> above for details.
		2180
		2181	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2182
		2183	Attempts to query or change the pipe buffer size. Obviously works only
		2184	on pipes, and currently works only on GNU/Linux systems, and fails with
		2185	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2186	size on other systems, drop me a note.
		2187
		2188	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2189
		2190	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2191	C<$flags> is missing or C<0>, then this should be the same as a call to
		2192	perl's built-in C<pipe> function and create a new pipe, and works on
		2193	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2194	(..., 4096, O_BINARY)>.
		2195
		2196	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2197	the given flags (Linux 2.6.27, glibc 2.9).
		2198
		2199	On success, the read and write file handles are returned.
		2200
		2201	On error, nothing will be returned. If the pipe2 syscall is missing and
		2202	C<$flags> is non-zero, fails with C<ENOSYS>.
		2203
		2204	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2205	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2206	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2207
		2208	=back
		2209
1307	=cut	2210	=cut
1308		2211
1309	min_parallel 8;	2212	min_parallel 8;
1310		2213
1311	END { flush }	2214	END { flush }
1312		2215
1313	1;	2216	1;
1314		2217
		2218	=head1 EVENT LOOP INTEGRATION
		2219
		2220	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2221	automatically into many event loops:
		2222
		2223	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2224	use AnyEvent::AIO;
		2225
		2226	You can also integrate IO::AIO manually into many event loops, here are
		2227	some examples of how to do this:
		2228
		2229	# EV integration
		2230	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2231
		2232	# Event integration
		2233	Event->io (fd => IO::AIO::poll_fileno,
		2234	poll => 'r',
		2235	cb => \&IO::AIO::poll_cb);
		2236
		2237	# Glib/Gtk2 integration
		2238	add_watch Glib::IO IO::AIO::poll_fileno,
		2239	in => sub { IO::AIO::poll_cb; 1 };
		2240
		2241	# Tk integration
		2242	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2243	readable => \&IO::AIO::poll_cb);
		2244
		2245	# Danga::Socket integration
		2246	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2247	\&IO::AIO::poll_cb);
		2248
1315	=head2 FORK BEHAVIOUR	2249	=head2 FORK BEHAVIOUR
1316		2250
1317	This module should do "the right thing" when the process using it forks:	2251	Usage of pthreads in a program changes the semantics of fork
		2252	considerably. Specifically, only async-safe functions can be called after
		2253	fork. Perl doesn't know about this, so in general, you cannot call fork
		2254	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2255	pthreads, so this applies, but many other extensions and (for inexplicable
		2256	reasons) perl itself often is linked against pthreads, so this limitation
		2257	applies to quite a lot of perls.
1318		2258
1319	Before the fork, IO::AIO enters a quiescent state where no requests	2259	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1320	can be added in other threads and no results will be processed. After	2260	only works in the process that loaded it. Forking is fully supported, but
1321	the fork the parent simply leaves the quiescent state and continues	2261	using IO::AIO in the child is not.
1322	request/result processing, while the child frees the request/result queue
1323	(so that the requests started before the fork will only be handled in the
1324	parent). Threads will be started on demand until the limit set in the
1325	parent process has been reached again.
1326		2262
1327	In short: the parent will, after a short pause, continue as if fork had	2263	You might get around by not I<using> IO::AIO before (or after)
1328	not been called, while the child will act as if IO::AIO has not been used	2264	forking. You could also try to call the L<IO::AIO::reinit> function in the
1329	yet.	2265	child:
		2266
		2267	=over 4
		2268
		2269	=item IO::AIO::reinit
		2270
		2271	Abandons all current requests and I/O threads and simply reinitialises all
		2272	data structures. This is not an operation supported by any standards, but
		2273	happens to work on GNU/Linux and some newer BSD systems.
		2274
		2275	The only reasonable use for this function is to call it after forking, if
		2276	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2277	the process will result in undefined behaviour. Calling it at any time
		2278	will also result in any undefined (by POSIX) behaviour.
		2279
		2280	=back
1330		2281
1331	=head2 MEMORY USAGE	2282	=head2 MEMORY USAGE
1332		2283
1333	Per-request usage:	2284	Per-request usage:
1334		2285
…		…
1351		2302
1352	Known bugs will be fixed in the next release.	2303	Known bugs will be fixed in the next release.
1353		2304
1354	=head1 SEE ALSO	2305	=head1 SEE ALSO
1355		2306
1356	L<Coro::AIO>.	2307	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2308	more natural syntax.
1357		2309
1358	=head1 AUTHOR	2310	=head1 AUTHOR
1359		2311
1360	Marc Lehmann <schmorp@schmorp.de>	2312	Marc Lehmann <schmorp@schmorp.de>
1361	http://home.schmorp.de/	2313	http://home.schmorp.de/

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