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Revision 1.93 by root, Wed Nov 8 01:59:58 2006 UTC vs.
Revision 1.276 by root, Fri Sep 22 05:24:41 2017 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
30	# AnyEvent integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',
37	cb => \&IO::AIO::poll_cb);
38
39	# Glib/Gtk2 integration
40	add_watch Glib::IO IO::AIO::poll_fileno,
41	in => sub { IO::AIO::poll_cb; 1 };
42
43	# Tk integration
44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
45	readable => \&IO::AIO::poll_cb);
46
47	# Danga::Socket integration
48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49	\&IO::AIO::poll_cb);
50
51	=head1 DESCRIPTION	31	=head1 DESCRIPTION
52		32
53	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
54	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
55		36
56	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
57	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
58	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
59	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
61	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
62	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
63	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
64	concurrently.	45	concurrently.
65		46
66	While most of this works on all types of file descriptors (for example	47	While most of this works on all types of file descriptors (for
67	sockets), using these functions on file descriptors that support	48	example sockets), using these functions on file descriptors that
68	nonblocking operation (again, sockets, pipes etc.) is very inefficient or	49	support nonblocking operation (again, sockets, pipes etc.) is
69	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop	50	very inefficient. Use an event loop for that (such as the L<EV>
70	for that (such as the L<Event|Event> module): IO::AIO will naturally fit	51	module): IO::AIO will naturally fit into such an event loop itself.
71	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
76	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
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 with in the presence of other (Perl-)	67	Although the module will work in the presence of other (Perl-) threads,
84	threads, it is currently not reentrant in any way, so use appropriate	68	it is currently not reentrant in any way, so use appropriate locking
85	locking yourself, always call C<poll_cb> from within the same thread, or	69	yourself, always call C<poll_cb> from within the same thread, or never
86	never 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 = $_[0]	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;
109		90
…		…
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.
…		…
183		164
184	=cut	165	=cut
185		166
186	package IO::AIO;	167	package IO::AIO;
187		168
188	no warnings;	169	use Carp ();
189	use strict 'vars';	170
		171	use common::sense;
190		172
191	use base 'Exporter';	173	use base 'Exporter';
192		174
193	BEGIN {	175	BEGIN {
194	our $VERSION = '2.2';	176	our $VERSION = 4.35;
195		177
196	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
197	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
198	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
199	aio_move aio_copy aio_group aio_nop aio_mknod);	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
		184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
		189
200	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
201	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
202	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
203	nreqs nready npending nthreads	193	nreqs nready npending nthreads
204	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
205		199
206	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
207		201
208	require XSLoader;	202	require XSLoader;
209	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
210	}	204	}
211		205
212	=head1 FUNCTIONS	206	=head1 FUNCTIONS
213		207
214	=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_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		239	aio_mkdir $pathname, $mode, $callback->($status)
		240	aio_rmdir $pathname, $callback->($status)
		241	aio_readdir $pathname, $callback->($entries)
		242	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		243	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		244	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		245	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		246	aio_load $pathname, $data, $callback->($status)
		247	aio_copy $srcpath, $dstpath, $callback->($status)
		248	aio_move $srcpath, $dstpath, $callback->($status)
		249	aio_rmtree $pathname, $callback->($status)
		250	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		251	aio_ioctl $fh, $request, $buf, $callback->($status)
		252	aio_sync $callback->($status)
		253	aio_syncfs $fh, $callback->($status)
		254	aio_fsync $fh, $callback->($status)
		255	aio_fdatasync $fh, $callback->($status)
		256	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		257	aio_pathsync $pathname, $callback->($status)
		258	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		259	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		260	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		261	aio_mlockall $flags, $callback->($status)
		262	aio_group $callback->(...)
		263	aio_nop $callback->()
		264
		265	$prev_pri = aioreq_pri [$pri]
		266	aioreq_nice $pri_adjust
		267
		268	IO::AIO::poll_wait
		269	IO::AIO::poll_cb
		270	IO::AIO::poll
		271	IO::AIO::flush
		272	IO::AIO::max_poll_reqs $nreqs
		273	IO::AIO::max_poll_time $seconds
		274	IO::AIO::min_parallel $nthreads
		275	IO::AIO::max_parallel $nthreads
		276	IO::AIO::max_idle $nthreads
		277	IO::AIO::idle_timeout $seconds
		278	IO::AIO::max_outstanding $maxreqs
		279	IO::AIO::nreqs
		280	IO::AIO::nready
		281	IO::AIO::npending
		282	IO::AIO::min_fdlimit $nfd;
		283
		284	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		285	IO::AIO::fadvise $fh, $offset, $len, $advice
		286	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		287	IO::AIO::munmap $scalar
		288	IO::AIO::madvise $scalar, $offset, $length, $advice
		289	IO::AIO::mprotect $scalar, $offset, $length, $protect
		290	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		291	IO::AIO::munlockall
		292
		293	=head2 API NOTES
215		294
216	All the C<aio_*> calls are more or less thin wrappers around the syscall	295	All the C<aio_*> calls are more or less thin wrappers around the syscall
217	with the same name (sans C<aio_>). The arguments are similar or identical,	296	with the same name (sans C<aio_>). The arguments are similar or identical,
218	and they all accept an additional (and optional) C<$callback> argument	297	and they all accept an additional (and optional) C<$callback> argument
219	which must be a code reference. This code reference will get called with	298	which must be a code reference. This code reference will be called after
220	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	299	the syscall has been executed in an asynchronous fashion. The results
221	perl, which usually delivers "false") as it's sole argument when the given	300	of the request will be passed as arguments to the callback (and, if an
222	syscall has been executed asynchronously.	301	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		302	most syscalls return C<-1> on error, unlike perl, which usually delivers
		303	"false").
		304
		305	Some requests (such as C<aio_readdir>) pass the actual results and
		306	communicate failures by passing C<undef>.
223		307
224	All functions expecting a filehandle keep a copy of the filehandle	308	All functions expecting a filehandle keep a copy of the filehandle
225	internally until the request has finished.	309	internally until the request has finished.
226		310
227	All functions return request objects of type L<IO::AIO::REQ> that allow	311	All functions return request objects of type L<IO::AIO::REQ> that allow
228	further manipulation of those requests while they are in-flight.	312	further manipulation of those requests while they are in-flight.
229		313
230	The pathnames you pass to these routines I<must> be absolute and	314	The pathnames you pass to these routines I<should> be absolute. The
231	encoded as octets. The reason for the former is that at the time the	315	reason for this is that at the time the request is being executed, the
232	request is being executed, the current working directory could have	316	current working directory could have changed. Alternatively, you can
233	changed. Alternatively, you can make sure that you never change the	317	make sure that you never change the current working directory anywhere
234	current working directory anywhere in the program and then use relative	318	in the program and then use relative paths. You can also take advantage
235	paths.	319	of IO::AIOs working directory abstraction, that lets you specify paths
		320	relative to some previously-opened "working directory object" - see the
		321	description of the C<IO::AIO::WD> class later in this document.
236		322
237	To encode pathnames as octets, either make sure you either: a) always pass	323	To encode pathnames as octets, either make sure you either: a) always pass
238	in filenames you got from outside (command line, readdir etc.) without	324	in filenames you got from outside (command line, readdir etc.) without
239	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	325	tinkering, b) are in your native filesystem encoding, c) use the Encode
240	your pathnames to the locale (or other) encoding in effect in the user	326	module and encode your pathnames to the locale (or other) encoding in
241	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	327	effect in the user environment, d) use Glib::filename_from_unicode on
242	use something else to ensure your scalar has the correct contents.	328	unicode filenames or e) use something else to ensure your scalar has the
		329	correct contents.
243		330
244	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	331	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
245	handles correctly wether it is set or not.	332	handles correctly whether it is set or not.
		333
		334	=head2 AIO REQUEST FUNCTIONS
246		335
247	=over 4	336	=over 4
248		337
249	=item $prev_pri = aioreq_pri [$pri]	338	=item $prev_pri = aioreq_pri [$pri]
250		339
…		…
270	aio_read $_[0], ..., sub {	359	aio_read $_[0], ..., sub {
271	...	360	...
272	};	361	};
273	};	362	};
274		363
		364
275	=item aioreq_nice $pri_adjust	365	=item aioreq_nice $pri_adjust
276		366
277	Similar to C<aioreq_pri>, but subtracts the given value from the current	367	Similar to C<aioreq_pri>, but subtracts the given value from the current
278	priority, so the effect is cumulative.	368	priority, so the effect is cumulative.
279		369
		370
280	=item aio_open $pathname, $flags, $mode, $callback->($fh)	371	=item aio_open $pathname, $flags, $mode, $callback->($fh)
281		372
282	Asynchronously open or create a file and call the callback with a newly	373	Asynchronously open or create a file and call the callback with a newly
283	created filehandle for the file.	374	created filehandle for the file (or C<undef> in case of an error).
284		375
285	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	376	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
286	for an explanation.	377	for an explanation.
287		378
288	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	379	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
289	list. They are the same as used by C<sysopen>.	380	list. They are the same as used by C<sysopen>.
290		381
291	Likewise, C<$mode> specifies the mode of the newly created file, if it	382	Likewise, C<$mode> specifies the mode of the newly created file, if it
292	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	383	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
293	except that it is mandatory (i.e. use C<0> if you don't create new files,	384	except that it is mandatory (i.e. use C<0> if you don't create new files,
294	and C<0666> or C<0777> if you do).	385	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		386	by the umask in effect then the request is being executed, so better never
		387	change the umask.
295		388
296	Example:	389	Example:
297		390
298	aio_open "/etc/passwd", O_RDONLY, 0, sub {	391	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
299	if ($_[0]) {	392	if ($_[0]) {
300	print "open successful, fh is $_[0]\n";	393	print "open successful, fh is $_[0]\n";
301	...	394	...
302	} else {	395	} else {
303	die "open failed: $!\n";	396	die "open failed: $!\n";
304	}	397	}
305	};	398	};
306		399
		400	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		401	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		402	following POSIX and non-POSIX constants are available (missing ones on
		403	your system are, as usual, C<0>):
		404
		405	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		406	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		407	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		408
		409
307	=item aio_close $fh, $callback->($status)	410	=item aio_close $fh, $callback->($status)
308		411
309	Asynchronously close a file and call the callback with the result	412	Asynchronously close a file and call the callback with the result
310	code. I<WARNING:> although accepted, you should not pass in a perl	413	code.
311	filehandle here, as perl will likely close the file descriptor another
312	time when the filehandle is destroyed. Normally, you can safely call perls
313	C<close> or just let filehandles go out of scope.
314		414
315	This is supposed to be a bug in the API, so that might change. It's	415	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
316	therefore best to avoid this function.	416	closing the file descriptor associated with the filehandle itself.
		417
		418	Therefore, C<aio_close> will not close the filehandle - instead it will
		419	use dup2 to overwrite the file descriptor with the write-end of a pipe
		420	(the pipe fd will be created on demand and will be cached).
		421
		422	Or in other words: the file descriptor will be closed, but it will not be
		423	free for reuse until the perl filehandle is closed.
		424
		425	=cut
		426
		427	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		428
		429	Seeks the filehandle to the new C<$offset>, similarly to perl's
		430	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		431	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		432	C<IO::AIO::SEEK_END>).
		433
		434	The resulting absolute offset will be passed to the callback, or C<-1> in
		435	case of an error.
		436
		437	In theory, the C<$whence> constants could be different than the
		438	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		439	so don't panic.
		440
		441	As a GNU/Linux (and maybe Solaris) extension, also the constants
		442	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		443	could be found. No guarantees about suitability for use in C<aio_seek> or
		444	Perl's C<sysseek> can be made though, although I would naively assume they
		445	"just work".
317		446
318	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
319		448
320	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
321		450
322	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	451	Reads or writes C<$length> bytes from or to the specified C<$fh> and
323	into the scalar given by C<data> and offset C<dataoffset> and calls the	452	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
324	callback without the actual number of bytes read (or -1 on error, just	453	calls the callback with the actual number of bytes transferred (or -1 on
325	like the syscall).	454	error, just like the syscall).
		455
		456	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		457	offset plus the actual number of bytes read.
		458
		459	If C<$offset> is undefined, then the current file descriptor offset will
		460	be used (and updated), otherwise the file descriptor offset will not be
		461	changed by these calls.
		462
		463	If C<$length> is undefined in C<aio_write>, use the remaining length of
		464	C<$data>.
		465
		466	If C<$dataoffset> is less than zero, it will be counted from the end of
		467	C<$data>.
326		468
327	The C<$data> scalar I<MUST NOT> be modified in any way while the request	469	The C<$data> scalar I<MUST NOT> be modified in any way while the request
328	is outstanding. Modifying it can result in segfaults or WW3 (if the	470	is outstanding. Modifying it can result in segfaults or World War III (if
329	necessary/optional hardware is installed).	471	the necessary/optional hardware is installed).
330		472
331	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	473	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
332	offset C<0> within the scalar:	474	offset C<0> within the scalar:
333		475
334	aio_read $fh, 7, 15, $buffer, 0, sub {	476	aio_read $fh, 7, 15, $buffer, 0, sub {
335	$_[0] > 0 or die "read error: $!";	477	$_[0] > 0 or die "read error: $!";
336	print "read $_[0] bytes: <$buffer>\n";	478	print "read $_[0] bytes: <$buffer>\n";
337	};	479	};
338		480
		481
339	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	482	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
340		483
341	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	484	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
342	reading at byte offset C<$in_offset>, and starts writing at the current	485	reading at byte offset C<$in_offset>, and starts writing at the current
343	file offset of C<$out_fh>. Because of that, it is not safe to issue more	486	file offset of C<$out_fh>. Because of that, it is not safe to issue more
344	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	487	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
345	other.	488	other. The same C<$in_fh> works fine though, as this function does not
		489	move or use the file offset of C<$in_fh>.
346		490
		491	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		492	are written, and there is no way to find out how many more bytes have been
		493	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		494	number of bytes written to C<$out_fh>. Only if the result value equals
		495	C<$length> one can assume that C<$length> bytes have been read.
		496
		497	Unlike with other C<aio_> functions, it makes a lot of sense to use
		498	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		499	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		500	the socket I/O will be non-blocking. Note, however, that you can run
		501	into a trap where C<aio_sendfile> reads some data with readahead, then
		502	fails to write all data, and when the socket is ready the next time, the
		503	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		504	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		505	resource usage.
		506
347	This call tries to make use of a native C<sendfile> syscall to provide	507	This call tries to make use of a native C<sendfile>-like syscall to
348	zero-copy operation. For this to work, C<$out_fh> should refer to a	508	provide zero-copy operation. For this to work, C<$out_fh> should refer to
349	socket, and C<$in_fh> should refer to mmap'able file.	509	a socket, and C<$in_fh> should refer to an mmap'able file.
350		510
351	If the native sendfile call fails or is not implemented, it will be	511	If a native sendfile cannot be found or it fails with C<ENOSYS>,
352	emulated, so you can call C<aio_sendfile> on any type of filehandle	512	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		513	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
353	regardless of the limitations of the operating system.	514	type of filehandle regardless of the limitations of the operating system.
354		515
355	Please note, however, that C<aio_sendfile> can read more bytes from	516	As native sendfile syscalls (as practically any non-POSIX interface hacked
356	C<$in_fh> than are written, and there is no way to find out how many	517	together in a hurry to improve benchmark numbers) tend to be rather buggy
357	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	518	on many systems, this implementation tries to work around some known bugs
358	provides the number of bytes written to C<$out_fh>. Only if the result	519	in Linux and FreeBSD kernels (probably others, too), but that might fail,
359	value equals C<$length> one can assume that C<$length> bytes have been	520	so you really really should check the return value of C<aio_sendfile> -
360	read.	521	fewer bytes than expected might have been transferred.
		522
361		523
362	=item aio_readahead $fh,$offset,$length, $callback->($retval)	524	=item aio_readahead $fh,$offset,$length, $callback->($retval)
363		525
364	C<aio_readahead> populates the page cache with data from a file so that	526	C<aio_readahead> populates the page cache with data from a file so that
365	subsequent reads from that file will not block on disk I/O. The C<$offset>	527	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
368	whole pages, so that offset is effectively rounded down to a page boundary	530	whole pages, so that offset is effectively rounded down to a page boundary
369	and bytes are read up to the next page boundary greater than or equal to	531	and bytes are read up to the next page boundary greater than or equal to
370	(off-set+length). C<aio_readahead> does not read beyond the end of the	532	(off-set+length). C<aio_readahead> does not read beyond the end of the
371	file. The current file offset of the file is left unchanged.	533	file. The current file offset of the file is left unchanged.
372		534
373	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	535	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
374	emulated by simply reading the data, which would have a similar effect.	536	be emulated by simply reading the data, which would have a similar effect.
		537
375		538
376	=item aio_stat $fh_or_path, $callback->($status)	539	=item aio_stat $fh_or_path, $callback->($status)
377		540
378	=item aio_lstat $fh, $callback->($status)	541	=item aio_lstat $fh, $callback->($status)
379		542
…		…
385	for an explanation.	548	for an explanation.
386		549
387	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	550	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
388	error when stat'ing a large file, the results will be silently truncated	551	error when stat'ing a large file, the results will be silently truncated
389	unless perl itself is compiled with large file support.	552	unless perl itself is compiled with large file support.
		553
		554	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		555	following constants and functions (if not implemented, the constants will
		556	be C<0> and the functions will either C<croak> or fall back on traditional
		557	behaviour).
		558
		559	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		560	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		561	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
390		562
391	Example: Print the length of F</etc/passwd>:	563	Example: Print the length of F</etc/passwd>:
392		564
393	aio_stat "/etc/passwd", sub {	565	aio_stat "/etc/passwd", sub {
394	$_[0] and die "stat failed: $!";	566	$_[0] and die "stat failed: $!";
395	print "size is ", -s _, "\n";	567	print "size is ", -s _, "\n";
396	};	568	};
397		569
		570
		571	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		572
		573	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		574	whether a file handle or path was passed.
		575
		576	On success, the callback is passed a hash reference with the following
		577	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		578	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		579	is passed.
		580
		581	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		582	C<ST_NOSUID>.
		583
		584	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		585	their correct value when available, or to C<0> on systems that do
		586	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		587	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		588	C<ST_NODIRATIME> and C<ST_RELATIME>.
		589
		590	Example: stat C</wd> and dump out the data if successful.
		591
		592	aio_statvfs "/wd", sub {
		593	my $f = $_[0]
		594	or die "statvfs: $!";
		595
		596	use Data::Dumper;
		597	say Dumper $f;
		598	};
		599
		600	# result:
		601	{
		602	bsize => 1024,
		603	bfree => 4333064312,
		604	blocks => 10253828096,
		605	files => 2050765568,
		606	flag => 4096,
		607	favail => 2042092649,
		608	bavail => 4333064312,
		609	ffree => 2042092649,
		610	namemax => 255,
		611	frsize => 1024,
		612	fsid => 1810
		613	}
		614
		615	Here is a (likely partial - send me updates!) list of fsid values used by
		616	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		617
		618	0x0000adf5 adfs
		619	0x0000adff affs
		620	0x5346414f afs
		621	0x09041934 anon-inode filesystem
		622	0x00000187 autofs
		623	0x42465331 befs
		624	0x1badface bfs
		625	0x42494e4d binfmt_misc
		626	0x9123683e btrfs
		627	0x0027e0eb cgroupfs
		628	0xff534d42 cifs
		629	0x73757245 coda
		630	0x012ff7b7 coh
		631	0x28cd3d45 cramfs
		632	0x453dcd28 cramfs-wend (wrong endianness)
		633	0x64626720 debugfs
		634	0x00001373 devfs
		635	0x00001cd1 devpts
		636	0x0000f15f ecryptfs
		637	0x00414a53 efs
		638	0x0000137d ext
		639	0x0000ef53 ext2/ext3/ext4
		640	0x0000ef51 ext2
		641	0xf2f52010 f2fs
		642	0x00004006 fat
		643	0x65735546 fuseblk
		644	0x65735543 fusectl
		645	0x0bad1dea futexfs
		646	0x01161970 gfs2
		647	0x47504653 gpfs
		648	0x00004244 hfs
		649	0xf995e849 hpfs
		650	0x00c0ffee hostfs
		651	0x958458f6 hugetlbfs
		652	0x2bad1dea inotifyfs
		653	0x00009660 isofs
		654	0x000072b6 jffs2
		655	0x3153464a jfs
		656	0x6b414653 k-afs
		657	0x0bd00bd0 lustre
		658	0x0000137f minix
		659	0x0000138f minix 30 char names
		660	0x00002468 minix v2
		661	0x00002478 minix v2 30 char names
		662	0x00004d5a minix v3
		663	0x19800202 mqueue
		664	0x00004d44 msdos
		665	0x0000564c novell
		666	0x00006969 nfs
		667	0x6e667364 nfsd
		668	0x00003434 nilfs
		669	0x5346544e ntfs
		670	0x00009fa1 openprom
		671	0x7461636F ocfs2
		672	0x00009fa0 proc
		673	0x6165676c pstorefs
		674	0x0000002f qnx4
		675	0x68191122 qnx6
		676	0x858458f6 ramfs
		677	0x52654973 reiserfs
		678	0x00007275 romfs
		679	0x67596969 rpc_pipefs
		680	0x73636673 securityfs
		681	0xf97cff8c selinux
		682	0x0000517b smb
		683	0x534f434b sockfs
		684	0x73717368 squashfs
		685	0x62656572 sysfs
		686	0x012ff7b6 sysv2
		687	0x012ff7b5 sysv4
		688	0x01021994 tmpfs
		689	0x15013346 udf
		690	0x00011954 ufs
		691	0x54190100 ufs byteswapped
		692	0x00009fa2 usbdevfs
		693	0x01021997 v9fs
		694	0xa501fcf5 vxfs
		695	0xabba1974 xenfs
		696	0x012ff7b4 xenix
		697	0x58465342 xfs
		698	0x012fd16d xia
		699
		700	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		701
		702	Works like perl's C<utime> function (including the special case of $atime
		703	and $mtime being undef). Fractional times are supported if the underlying
		704	syscalls support them.
		705
		706	When called with a pathname, uses utimes(2) if available, otherwise
		707	utime(2). If called on a file descriptor, uses futimes(2) if available,
		708	otherwise returns ENOSYS, so this is not portable.
		709
		710	Examples:
		711
		712	# set atime and mtime to current time (basically touch(1)):
		713	aio_utime "path", undef, undef;
		714	# set atime to current time and mtime to beginning of the epoch:
		715	aio_utime "path", time, undef; # undef==0
		716
		717
		718	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		719
		720	Works like perl's C<chown> function, except that C<undef> for either $uid
		721	or $gid is being interpreted as "do not change" (but -1 can also be used).
		722
		723	Examples:
		724
		725	# same as "chown root path" in the shell:
		726	aio_chown "path", 0, -1;
		727	# same as above:
		728	aio_chown "path", 0, undef;
		729
		730
		731	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		732
		733	Works like truncate(2) or ftruncate(2).
		734
		735
		736	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		737
		738	Allocates or frees disk space according to the C<$mode> argument. See the
		739	linux C<fallocate> documentation for details.
		740
		741	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		742	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		743	to deallocate a file range.
		744
		745	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		746	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		747	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		748	to unshare shared blocks (see your L<fallocate(2)> manpage).
		749
		750	The file system block size used by C<fallocate> is presumably the
		751	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		752	can dictate other limitations.
		753
		754	If C<fallocate> isn't available or cannot be emulated (currently no
		755	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		756
		757
		758	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		759
		760	Works like perl's C<chmod> function.
		761
		762
398	=item aio_unlink $pathname, $callback->($status)	763	=item aio_unlink $pathname, $callback->($status)
399		764
400	Asynchronously unlink (delete) a file and call the callback with the	765	Asynchronously unlink (delete) a file and call the callback with the
401	result code.	766	result code.
402		767
		768
403	=item aio_mknod $path, $mode, $dev, $callback->($status)	769	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
404		770
405	[EXPERIMENTAL]	771	[EXPERIMENTAL]
406		772
407	Asynchronously create a device node (or fifo). See mknod(2).	773	Asynchronously create a device node (or fifo). See mknod(2).
408		774
409	The only (POSIX-) portable way of calling this function is:	775	The only (POSIX-) portable way of calling this function is:
410		776
411	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	777	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		778
		779	See C<aio_stat> for info about some potentially helpful extra constants
		780	and functions.
412		781
413	=item aio_link $srcpath, $dstpath, $callback->($status)	782	=item aio_link $srcpath, $dstpath, $callback->($status)
414		783
415	Asynchronously create a new link to the existing object at C<$srcpath> at	784	Asynchronously create a new link to the existing object at C<$srcpath> at
416	the path C<$dstpath> and call the callback with the result code.	785	the path C<$dstpath> and call the callback with the result code.
417		786
		787
418	=item aio_symlink $srcpath, $dstpath, $callback->($status)	788	=item aio_symlink $srcpath, $dstpath, $callback->($status)
419		789
420	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	790	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
421	the path C<$dstpath> and call the callback with the result code.	791	the path C<$dstpath> and call the callback with the result code.
422		792
		793
423	=item aio_readlink $path, $callback->($link)	794	=item aio_readlink $pathname, $callback->($link)
424		795
425	Asynchronously read the symlink specified by C<$path> and pass it to	796	Asynchronously read the symlink specified by C<$path> and pass it to
426	the callback. If an error occurs, nothing or undef gets passed to the	797	the callback. If an error occurs, nothing or undef gets passed to the
427	callback.	798	callback.
428		799
		800
		801	=item aio_realpath $pathname, $callback->($path)
		802
		803	Asynchronously make the path absolute and resolve any symlinks in
		804	C<$path>. The resulting path only consists of directories (same as
		805	L<Cwd::realpath>).
		806
		807	This request can be used to get the absolute path of the current working
		808	directory by passing it a path of F<.> (a single dot).
		809
		810
429	=item aio_rename $srcpath, $dstpath, $callback->($status)	811	=item aio_rename $srcpath, $dstpath, $callback->($status)
430		812
431	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	813	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
432	rename(2) and call the callback with the result code.	814	rename(2) and call the callback with the result code.
433		815
		816	On systems that support the AIO::WD working directory abstraction
		817	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		818	of failing, C<rename> is called on the absolute path of C<$wd>.
		819
		820
		821	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		822
		823	Basically a version of C<aio_rename> with an additional C<$flags>
		824	argument. Calling this with C<$flags=0> is the same as calling
		825	C<aio_rename>.
		826
		827	Non-zero flags are currently only supported on GNU/Linux systems that
		828	support renameat2. Other systems fail with C<ENOSYS> in this case.
		829
		830	The following constants are available (missing ones are, as usual C<0>),
		831	see renameat2(2) for details:
		832
		833	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		834	and C<IO::AIO::RENAME_WHITEOUT>.
		835
		836
		837	=item aio_mkdir $pathname, $mode, $callback->($status)
		838
		839	Asynchronously mkdir (create) a directory and call the callback with
		840	the result code. C<$mode> will be modified by the umask at the time the
		841	request is executed, so do not change your umask.
		842
		843
434	=item aio_rmdir $pathname, $callback->($status)	844	=item aio_rmdir $pathname, $callback->($status)
435		845
436	Asynchronously rmdir (delete) a directory and call the callback with the	846	Asynchronously rmdir (delete) a directory and call the callback with the
437	result code.	847	result code.
		848
		849	On systems that support the AIO::WD working directory abstraction
		850	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		851	C<rmdir> is called on the absolute path of C<$wd>.
		852
438		853
439	=item aio_readdir $pathname, $callback->($entries)	854	=item aio_readdir $pathname, $callback->($entries)
440		855
441	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	856	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
442	directory (i.e. opendir + readdir + closedir). The entries will not be	857	directory (i.e. opendir + readdir + closedir). The entries will not be
443	sorted, and will B<NOT> include the C<.> and C<..> entries.	858	sorted, and will B<NOT> include the C<.> and C<..> entries.
444		859
445	The callback a single argument which is either C<undef> or an array-ref	860	The callback is passed a single argument which is either C<undef> or an
446	with the filenames.	861	array-ref with the filenames.
		862
		863
		864	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		865
		866	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		867	tune behaviour and output format. In case of an error, C<$entries> will be
		868	C<undef>.
		869
		870	The flags are a combination of the following constants, ORed together (the
		871	flags will also be passed to the callback, possibly modified):
		872
		873	=over 4
		874
		875	=item IO::AIO::READDIR_DENTS
		876
		877	When this flag is off, then the callback gets an arrayref consisting of
		878	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		879	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		880	entry in more detail.
		881
		882	C<$name> is the name of the entry.
		883
		884	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		885
		886	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		887	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		888	C<IO::AIO::DT_WHT>.
		889
		890	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		891	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		892	scalars are read-only: you can not modify them.
		893
		894	C<$inode> is the inode number (which might not be exact on systems with 64
		895	bit inode numbers and 32 bit perls). This field has unspecified content on
		896	systems that do not deliver the inode information.
		897
		898	=item IO::AIO::READDIR_DIRS_FIRST
		899
		900	When this flag is set, then the names will be returned in an order where
		901	likely directories come first, in optimal stat order. This is useful when
		902	you need to quickly find directories, or you want to find all directories
		903	while avoiding to stat() each entry.
		904
		905	If the system returns type information in readdir, then this is used
		906	to find directories directly. Otherwise, likely directories are names
		907	beginning with ".", or otherwise names with no dots, of which names with
		908	short names are tried first.
		909
		910	=item IO::AIO::READDIR_STAT_ORDER
		911
		912	When this flag is set, then the names will be returned in an order
		913	suitable for stat()'ing each one. That is, when you plan to stat()
		914	all files in the given directory, then the returned order will likely
		915	be fastest.
		916
		917	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		918	the likely dirs come first, resulting in a less optimal stat order.
		919
		920	=item IO::AIO::READDIR_FOUND_UNKNOWN
		921
		922	This flag should not be set when calling C<aio_readdirx>. Instead, it
		923	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		924	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		925	C<$type>'s are known, which can be used to speed up some algorithms.
		926
		927	=back
		928
		929
		930	=item aio_load $pathname, $data, $callback->($status)
		931
		932	This is a composite request that tries to fully load the given file into
		933	memory. Status is the same as with aio_read.
		934
		935	=cut
		936
		937	sub aio_load($$;$) {
		938	my ($path, undef, $cb) = @_;
		939	my $data = \$_[1];
		940
		941	my $pri = aioreq_pri;
		942	my $grp = aio_group $cb;
		943
		944	aioreq_pri $pri;
		945	add $grp aio_open $path, O_RDONLY, 0, sub {
		946	my $fh = shift
		947	or return $grp->result (-1);
		948
		949	aioreq_pri $pri;
		950	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		951	$grp->result ($_[0]);
		952	};
		953	};
		954
		955	$grp
		956	}
447		957
448	=item aio_copy $srcpath, $dstpath, $callback->($status)	958	=item aio_copy $srcpath, $dstpath, $callback->($status)
449		959
450	Try to copy the I<file> (directories not supported as either source or	960	Try to copy the I<file> (directories not supported as either source or
451	destination) from C<$srcpath> to C<$dstpath> and call the callback with	961	destination) from C<$srcpath> to C<$dstpath> and call the callback with
452	the C<0> (error) or C<-1> ok.	962	a status of C<0> (ok) or C<-1> (error, see C<$!>).
453		963
		964	Existing destination files will be truncated.
		965
454	This is a composite request that it creates the destination file with	966	This is a composite request that creates the destination file with
455	mode 0200 and copies the contents of the source file into it using	967	mode 0200 and copies the contents of the source file into it using
456	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	968	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
457	uid/gid, in that order.	969	uid/gid, in that order.
458		970
459	If an error occurs, the partial destination file will be unlinked, if	971	If an error occurs, the partial destination file will be unlinked, if
…		…
469	my $grp = aio_group $cb;	981	my $grp = aio_group $cb;
470		982
471	aioreq_pri $pri;	983	aioreq_pri $pri;
472	add $grp aio_open $src, O_RDONLY, 0, sub {	984	add $grp aio_open $src, O_RDONLY, 0, sub {
473	if (my $src_fh = $_[0]) {	985	if (my $src_fh = $_[0]) {
474	my @stat = stat $src_fh;	986	my @stat = stat $src_fh; # hmm, might block over nfs?
475		987
476	aioreq_pri $pri;	988	aioreq_pri $pri;
477	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	989	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
478	if (my $dst_fh = $_[0]) {	990	if (my $dst_fh = $_[0]) {
479	aioreq_pri $pri;	991	aioreq_pri $pri;
480	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	992	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
481	if ($_[0] == $stat[7]) {	993	if ($_[0] == $stat[7]) {
482	$grp->result (0);	994	$grp->result (0);
483	close $src_fh;	995	close $src_fh;
484		996
485	# those should not normally block. should. should.	997	my $ch = sub {
		998	aioreq_pri $pri;
		999	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		1000	aioreq_pri $pri;
		1001	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		1002	aioreq_pri $pri;
		1003	add $grp aio_close $dst_fh;
		1004	}
		1005	};
		1006	};
		1007
		1008	aioreq_pri $pri;
		1009	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1010	if ($_[0] < 0 && $! == ENOSYS) {
		1011	aioreq_pri $pri;
486	utime $stat[8], $stat[9], $dst;	1012	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
487	chmod $stat[2] & 07777, $dst_fh;	1013	} else {
488	chown $stat[4], $stat[5], $dst_fh;	1014	$ch->();
		1015	}
489	close $dst_fh;	1016	};
490	} else {	1017	} else {
491	$grp->result (-1);	1018	$grp->result (-1);
492	close $src_fh;	1019	close $src_fh;
493	close $dst_fh;	1020	close $dst_fh;
494		1021
…		…
511		1038
512	=item aio_move $srcpath, $dstpath, $callback->($status)	1039	=item aio_move $srcpath, $dstpath, $callback->($status)
513		1040
514	Try to move the I<file> (directories not supported as either source or	1041	Try to move the I<file> (directories not supported as either source or
515	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1042	destination) from C<$srcpath> to C<$dstpath> and call the callback with
516	the C<0> (error) or C<-1> ok.	1043	a status of C<0> (ok) or C<-1> (error, see C<$!>).
517		1044
518	This is a composite request that tries to rename(2) the file first. If	1045	This is a composite request that tries to rename(2) the file first; if
519	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1046	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
520	that is successful, unlinking the C<$srcpath>.	1047	that is successful, unlinks the C<$srcpath>.
521		1048
522	=cut	1049	=cut
523		1050
524	sub aio_move($$;$) {	1051	sub aio_move($$;$) {
525	my ($src, $dst, $cb) = @_;	1052	my ($src, $dst, $cb) = @_;
…		…
532	if ($_[0] && $! == EXDEV) {	1059	if ($_[0] && $! == EXDEV) {
533	aioreq_pri $pri;	1060	aioreq_pri $pri;
534	add $grp aio_copy $src, $dst, sub {	1061	add $grp aio_copy $src, $dst, sub {
535	$grp->result ($_[0]);	1062	$grp->result ($_[0]);
536		1063
537	if (!$_[0]) {	1064	unless ($_[0]) {
538	aioreq_pri $pri;	1065	aioreq_pri $pri;
539	add $grp aio_unlink $src;	1066	add $grp aio_unlink $src;
540	}	1067	}
541	};	1068	};
542	} else {	1069	} else {
…		…
545	};	1072	};
546		1073
547	$grp	1074	$grp
548	}	1075	}
549		1076
550	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1077	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
551		1078
552	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1079	Scans a directory (similar to C<aio_readdir>) but additionally tries to
553	efficiently separate the entries of directory C<$path> into two sets of	1080	efficiently separate the entries of directory C<$path> into two sets of
554	names, directories you can recurse into (directories), and ones you cannot	1081	names, directories you can recurse into (directories), and ones you cannot
555	recurse into (everything else, including symlinks to directories).	1082	recurse into (everything else, including symlinks to directories).
…		…
572		1099
573	Implementation notes.	1100	Implementation notes.
574		1101
575	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1102	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
576		1103
		1104	If readdir returns file type information, then this is used directly to
		1105	find directories.
		1106
577	After reading the directory, the modification time, size etc. of the	1107	Otherwise, after reading the directory, the modification time, size etc.
578	directory before and after the readdir is checked, and if they match (and	1108	of the directory before and after the readdir is checked, and if they
579	isn't the current time), the link count will be used to decide how many	1109	match (and isn't the current time), the link count will be used to decide
580	entries are directories (if >= 2). Otherwise, no knowledge of the number	1110	how many entries are directories (if >= 2). Otherwise, no knowledge of the
581	of subdirectories will be assumed.	1111	number of subdirectories will be assumed.
582		1112
583	Then entries will be sorted into likely directories (everything without	1113	Then entries will be sorted into likely directories a non-initial dot
584	a non-initial dot currently) and likely non-directories (everything	1114	currently) and likely non-directories (see C<aio_readdirx>). Then every
585	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1115	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
586	likely directories first. If that succeeds, it assumes that the entry	1116	in order of their inode numbers. If that succeeds, it assumes that the
587	is a directory or a symlink to directory (which will be checked	1117	entry is a directory or a symlink to directory (which will be checked
588	seperately). This is often faster than stat'ing the entry itself because	1118	separately). This is often faster than stat'ing the entry itself because
589	filesystems might detect the type of the entry without reading the inode	1119	filesystems might detect the type of the entry without reading the inode
590	data (e.g. ext2fs filetype feature).	1120	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1121	the filetype information on readdir.
591		1122
592	If the known number of directories (link count - 2) has been reached, the	1123	If the known number of directories (link count - 2) has been reached, the
593	rest of the entries is assumed to be non-directories.	1124	rest of the entries is assumed to be non-directories.
594		1125
595	This only works with certainty on POSIX (= UNIX) filesystems, which	1126	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
599	as those tend to return 0 or 1 as link counts, which disables the	1130	as those tend to return 0 or 1 as link counts, which disables the
600	directory counting heuristic.	1131	directory counting heuristic.
601		1132
602	=cut	1133	=cut
603		1134
604	sub aio_scandir($$$) {	1135	sub aio_scandir($$;$) {
605	my ($path, $maxreq, $cb) = @_;	1136	my ($path, $maxreq, $cb) = @_;
606		1137
607	my $pri = aioreq_pri;	1138	my $pri = aioreq_pri;
608		1139
609	my $grp = aio_group $cb;	1140	my $grp = aio_group $cb;
610		1141
611	$maxreq = 4 if $maxreq <= 0;	1142	$maxreq = 4 if $maxreq <= 0;
612		1143
613	# stat once	1144	# get a wd object
614	aioreq_pri $pri;	1145	aioreq_pri $pri;
615	add $grp aio_stat $path, sub {	1146	add $grp aio_wd $path, sub {
		1147	$_[0]
616	return $grp->result () if $_[0];	1148	or return $grp->result ();
617	my $now = time;
618	my $hash1 = join ":", (stat _)[0,1,3,7,9];
619		1149
620	# read the directory entries	1150	my $wd = [shift, "."];
		1151
		1152	# stat once
621	aioreq_pri $pri;	1153	aioreq_pri $pri;
622	add $grp aio_readdir $path, sub {	1154	add $grp aio_stat $wd, sub {
623	my $entries = shift
624	or return $grp->result ();	1155	return $grp->result () if $_[0];
		1156	my $now = time;
		1157	my $hash1 = join ":", (stat _)[0,1,3,7,9];
625		1158
626	# stat the dir another time	1159	# read the directory entries
627	aioreq_pri $pri;	1160	aioreq_pri $pri;
		1161	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1162	my $entries = shift
		1163	or return $grp->result ();
		1164
		1165	# stat the dir another time
		1166	aioreq_pri $pri;
628	add $grp aio_stat $path, sub {	1167	add $grp aio_stat $wd, sub {
629	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1168	my $hash2 = join ":", (stat _)[0,1,3,7,9];
630		1169
631	my $ndirs;	1170	my $ndirs;
632		1171
633	# take the slow route if anything looks fishy	1172	# take the slow route if anything looks fishy
634	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1173	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
635	$ndirs = -1;	1174	$ndirs = -1;
636	} else {	1175	} else {
637	# if nlink == 2, we are finished	1176	# if nlink == 2, we are finished
638	# on non-posix-fs's, we rely on nlink < 2	1177	# for non-posix-fs's, we rely on nlink < 2
639	$ndirs = (stat _)[3] - 2	1178	$ndirs = (stat _)[3] - 2
640	or return $grp->result ([], $entries);	1179	or return $grp->result ([], $entries);
641	}	1180	}
642		1181
643	# sort into likely dirs and likely nondirs
644	# dirs == files without ".", short entries first
645	$entries = [map $_->[0],
646	sort { $b->[1] cmp $a->[1] }
647	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
648	@$entries];
649
650	my (@dirs, @nondirs);	1182	my (@dirs, @nondirs);
651		1183
652	my $statgrp = add $grp aio_group sub {	1184	my $statgrp = add $grp aio_group sub {
653	$grp->result (\@dirs, \@nondirs);	1185	$grp->result (\@dirs, \@nondirs);
654	};	1186	};
655		1187
656	limit $statgrp $maxreq;	1188	limit $statgrp $maxreq;
657	feed $statgrp sub {	1189	feed $statgrp sub {
658	return unless @$entries;	1190	return unless @$entries;
659	my $entry = pop @$entries;	1191	my $entry = shift @$entries;
660		1192
661	aioreq_pri $pri;	1193	aioreq_pri $pri;
		1194	$wd->[1] = "$entry/.";
662	add $statgrp aio_stat "$path/$entry/.", sub {	1195	add $statgrp aio_stat $wd, sub {
663	if ($_[0] < 0) {	1196	if ($_[0] < 0) {
664	push @nondirs, $entry;	1197	push @nondirs, $entry;
665	} else {	1198	} else {
666	# need to check for real directory	1199	# need to check for real directory
667	aioreq_pri $pri;	1200	aioreq_pri $pri;
		1201	$wd->[1] = $entry;
668	add $statgrp aio_lstat "$path/$entry", sub {	1202	add $statgrp aio_lstat $wd, sub {
669	if (-d _) {	1203	if (-d _) {
670	push @dirs, $entry;	1204	push @dirs, $entry;
671		1205
672	unless (--$ndirs) {	1206	unless (--$ndirs) {
673	push @nondirs, @$entries;	1207	push @nondirs, @$entries;
674	feed $statgrp;	1208	feed $statgrp;
		1209	}
		1210	} else {
		1211	push @nondirs, $entry;
675	}	1212	}
676	} else {
677	push @nondirs, $entry;
678	}	1213	}
679	}	1214	}
680	}	1215	};
681	};	1216	};
682	};	1217	};
683	};	1218	};
684	};	1219	};
685	};	1220	};
686		1221
687	$grp	1222	$grp
688	}	1223	}
689		1224
		1225	=item aio_rmtree $pathname, $callback->($status)
		1226
		1227	Delete a directory tree starting (and including) C<$path>, return the
		1228	status of the final C<rmdir> only. This is a composite request that
		1229	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1230	everything else.
		1231
		1232	=cut
		1233
		1234	sub aio_rmtree;
		1235	sub aio_rmtree($;$) {
		1236	my ($path, $cb) = @_;
		1237
		1238	my $pri = aioreq_pri;
		1239	my $grp = aio_group $cb;
		1240
		1241	aioreq_pri $pri;
		1242	add $grp aio_scandir $path, 0, sub {
		1243	my ($dirs, $nondirs) = @_;
		1244
		1245	my $dirgrp = aio_group sub {
		1246	add $grp aio_rmdir $path, sub {
		1247	$grp->result ($_[0]);
		1248	};
		1249	};
		1250
		1251	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1252	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1253
		1254	add $grp $dirgrp;
		1255	};
		1256
		1257	$grp
		1258	}
		1259
		1260	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1261
		1262	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1263
		1264	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1265	they execute asynchronously and pass the return value to the callback.
		1266
		1267	Both calls can be used for a lot of things, some of which make more sense
		1268	to run asynchronously in their own thread, while some others make less
		1269	sense. For example, calls that block waiting for external events, such
		1270	as locking, will also lock down an I/O thread while it is waiting, which
		1271	can deadlock the whole I/O system. At the same time, there might be no
		1272	alternative to using a thread to wait.
		1273
		1274	So in general, you should only use these calls for things that do
		1275	(filesystem) I/O, not for things that wait for other events (network,
		1276	other processes), although if you are careful and know what you are doing,
		1277	you still can.
		1278
		1279	The following constants are available (missing ones are, as usual C<0>):
		1280
		1281	C<F_DUPFD_CLOEXEC>,
		1282
		1283	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1284
		1285	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1286
		1287	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1288	C<FS_IOC_FIEMAP>.
		1289
		1290	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1291	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1292
		1293	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1294	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1295	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1296	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1297	C<FS_FL_USER_MODIFIABLE>.
		1298
		1299	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1300	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1301	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1302	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1303
		1304	=item aio_sync $callback->($status)
		1305
		1306	Asynchronously call sync and call the callback when finished.
		1307
690	=item aio_fsync $fh, $callback->($status)	1308	=item aio_fsync $fh, $callback->($status)
691		1309
692	Asynchronously call fsync on the given filehandle and call the callback	1310	Asynchronously call fsync on the given filehandle and call the callback
693	with the fsync result code.	1311	with the fsync result code.
694		1312
…		…
697	Asynchronously call fdatasync on the given filehandle and call the	1315	Asynchronously call fdatasync on the given filehandle and call the
698	callback with the fdatasync result code.	1316	callback with the fdatasync result code.
699		1317
700	If this call isn't available because your OS lacks it or it couldn't be	1318	If this call isn't available because your OS lacks it or it couldn't be
701	detected, it will be emulated by calling C<fsync> instead.	1319	detected, it will be emulated by calling C<fsync> instead.
		1320
		1321	=item aio_syncfs $fh, $callback->($status)
		1322
		1323	Asynchronously call the syncfs syscall to sync the filesystem associated
		1324	to the given filehandle and call the callback with the syncfs result
		1325	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1326	errno to C<ENOSYS> nevertheless.
		1327
		1328	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1329
		1330	Sync the data portion of the file specified by C<$offset> and C<$length>
		1331	to disk (but NOT the metadata), by calling the Linux-specific
		1332	sync_file_range call. If sync_file_range is not available or it returns
		1333	ENOSYS, then fdatasync or fsync is being substituted.
		1334
		1335	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1336	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1337	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1338	manpage for details.
		1339
		1340	=item aio_pathsync $pathname, $callback->($status)
		1341
		1342	This request tries to open, fsync and close the given path. This is a
		1343	composite request intended to sync directories after directory operations
		1344	(E.g. rename). This might not work on all operating systems or have any
		1345	specific effect, but usually it makes sure that directory changes get
		1346	written to disc. It works for anything that can be opened for read-only,
		1347	not just directories.
		1348
		1349	Future versions of this function might fall back to other methods when
		1350	C<fsync> on the directory fails (such as calling C<sync>).
		1351
		1352	Passes C<0> when everything went ok, and C<-1> on error.
		1353
		1354	=cut
		1355
		1356	sub aio_pathsync($;$) {
		1357	my ($path, $cb) = @_;
		1358
		1359	my $pri = aioreq_pri;
		1360	my $grp = aio_group $cb;
		1361
		1362	aioreq_pri $pri;
		1363	add $grp aio_open $path, O_RDONLY, 0, sub {
		1364	my ($fh) = @_;
		1365	if ($fh) {
		1366	aioreq_pri $pri;
		1367	add $grp aio_fsync $fh, sub {
		1368	$grp->result ($_[0]);
		1369
		1370	aioreq_pri $pri;
		1371	add $grp aio_close $fh;
		1372	};
		1373	} else {
		1374	$grp->result (-1);
		1375	}
		1376	};
		1377
		1378	$grp
		1379	}
		1380
		1381	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1382
		1383	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1384	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1385	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1386	scalar must only be modified in-place while an aio operation is pending on
		1387	it).
		1388
		1389	It calls the C<msync> function of your OS, if available, with the memory
		1390	area starting at C<$offset> in the string and ending C<$length> bytes
		1391	later. If C<$length> is negative, counts from the end, and if C<$length>
		1392	is C<undef>, then it goes till the end of the string. The flags can be
		1393	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1394	C<IO::AIO::MS_INVALIDATE>.
		1395
		1396	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1397
		1398	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1399	scalars.
		1400
		1401	It touches (reads or writes) all memory pages in the specified
		1402	range inside the scalar. All caveats and parameters are the same
		1403	as for C<aio_msync>, above, except for flags, which must be either
		1404	C<0> (which reads all pages and ensures they are instantiated) or
		1405	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1406	writing an octet from it, which dirties the page).
		1407
		1408	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1409
		1410	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1411	scalars.
		1412
		1413	It reads in all the pages of the underlying storage into memory (if any)
		1414	and locks them, so they are not getting swapped/paged out or removed.
		1415
		1416	If C<$length> is undefined, then the scalar will be locked till the end.
		1417
		1418	On systems that do not implement C<mlock>, this function returns C<-1>
		1419	and sets errno to C<ENOSYS>.
		1420
		1421	Note that the corresponding C<munlock> is synchronous and is
		1422	documented under L<MISCELLANEOUS FUNCTIONS>.
		1423
		1424	Example: open a file, mmap and mlock it - both will be undone when
		1425	C<$data> gets destroyed.
		1426
		1427	open my $fh, "<", $path or die "$path: $!";
		1428	my $data;
		1429	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1430	aio_mlock $data; # mlock in background
		1431
		1432	=item aio_mlockall $flags, $callback->($status)
		1433
		1434	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1435	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1436
		1437	On systems that do not implement C<mlockall>, this function returns C<-1>
		1438	and sets errno to C<ENOSYS>.
		1439
		1440	Note that the corresponding C<munlockall> is synchronous and is
		1441	documented under L<MISCELLANEOUS FUNCTIONS>.
		1442
		1443	Example: asynchronously lock all current and future pages into memory.
		1444
		1445	aio_mlockall IO::AIO::MCL_FUTURE;
		1446
		1447	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1448
		1449	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1450	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1451	the ioctl is not available on your OS, then this request will fail with
		1452	C<ENOSYS>.
		1453
		1454	C<$start> is the starting offset to query extents for, C<$length> is the
		1455	size of the range to query - if it is C<undef>, then the whole file will
		1456	be queried.
		1457
		1458	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1459	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1460	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1461	the data portion.
		1462
		1463	C<$count> is the maximum number of extent records to return. If it is
		1464	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1465	case, if it is C<0>, then the callback receives the number of extents
		1466	instead of the extents themselves (which is unreliable, see below).
		1467
		1468	If an error occurs, the callback receives no arguments. The special
		1469	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1470
		1471	Otherwise, the callback receives an array reference with extent
		1472	structures. Each extent structure is an array reference itself, with the
		1473	following members:
		1474
		1475	[$logical, $physical, $length, $flags]
		1476
		1477	Flags is any combination of the following flag values (typically either C<0>
		1478	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1479
		1480	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1481	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1482	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1483	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1484	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1485	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1486
		1487	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1488	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1489	it to return all extents of a range for files with large number of
		1490	extents. The code works around all these issues if C<$count> is undef.
702		1491
703	=item aio_group $callback->(...)	1492	=item aio_group $callback->(...)
704		1493
705	This is a very special aio request: Instead of doing something, it is a	1494	This is a very special aio request: Instead of doing something, it is a
706	container for other aio requests, which is useful if you want to bundle	1495	container for other aio requests, which is useful if you want to bundle
…		…
744	immense (it blocks a thread for a long time) so do not use this function	1533	immense (it blocks a thread for a long time) so do not use this function
745	except to put your application under artificial I/O pressure.	1534	except to put your application under artificial I/O pressure.
746		1535
747	=back	1536	=back
748		1537
		1538
		1539	=head2 IO::AIO::WD - multiple working directories
		1540
		1541	Your process only has one current working directory, which is used by all
		1542	threads. This makes it hard to use relative paths (some other component
		1543	could call C<chdir> at any time, and it is hard to control when the path
		1544	will be used by IO::AIO).
		1545
		1546	One solution for this is to always use absolute paths. This usually works,
		1547	but can be quite slow (the kernel has to walk the whole path on every
		1548	access), and can also be a hassle to implement.
		1549
		1550	Newer POSIX systems have a number of functions (openat, fdopendir,
		1551	futimensat and so on) that make it possible to specify working directories
		1552	per operation.
		1553
		1554	For portability, and because the clowns who "designed", or shall I write,
		1555	perpetrated this new interface were obviously half-drunk, this abstraction
		1556	cannot be perfect, though.
		1557
		1558	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1559	object. This object stores the canonicalised, absolute version of the
		1560	path, and on systems that allow it, also a directory file descriptor.
		1561
		1562	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1563	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1564	object and a pathname instead (or the IO::AIO::WD object alone, which
		1565	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1566	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1567	to that IO::AIO::WD object.
		1568
		1569	For example, to get a wd object for F</etc> and then stat F<passwd>
		1570	inside, you would write:
		1571
		1572	aio_wd "/etc", sub {
		1573	my $etcdir = shift;
		1574
		1575	# although $etcdir can be undef on error, there is generally no reason
		1576	# to check for errors here, as aio_stat will fail with ENOENT
		1577	# when $etcdir is undef.
		1578
		1579	aio_stat [$etcdir, "passwd"], sub {
		1580	# yay
		1581	};
		1582	};
		1583
		1584	The fact that C<aio_wd> is a request and not a normal function shows that
		1585	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1586	which is why it is done asynchronously.
		1587
		1588	To stat the directory obtained with C<aio_wd> above, one could write
		1589	either of the following three request calls:
		1590
		1591	aio_lstat "/etc" , sub { ... # pathname as normal string
		1592	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1593	aio_lstat $wd , sub { ... # shorthand for the previous
		1594
		1595	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1596	object and the pathname string, so you could write the following without
		1597	causing any issues due to C<$path> getting reused:
		1598
		1599	my $path = [$wd, undef];
		1600
		1601	for my $name (qw(abc def ghi)) {
		1602	$path->[1] = $name;
		1603	aio_stat $path, sub {
		1604	# ...
		1605	};
		1606	}
		1607
		1608	There are some caveats: when directories get renamed (or deleted), the
		1609	pathname string doesn't change, so will point to the new directory (or
		1610	nowhere at all), while the directory fd, if available on the system,
		1611	will still point to the original directory. Most functions accepting a
		1612	pathname will use the directory fd on newer systems, and the string on
		1613	older systems. Some functions (such as realpath) will always rely on the
		1614	string form of the pathname.
		1615
		1616	So this functionality is mainly useful to get some protection against
		1617	C<chdir>, to easily get an absolute path out of a relative path for future
		1618	reference, and to speed up doing many operations in the same directory
		1619	(e.g. when stat'ing all files in a directory).
		1620
		1621	The following functions implement this working directory abstraction:
		1622
		1623	=over 4
		1624
		1625	=item aio_wd $pathname, $callback->($wd)
		1626
		1627	Asynchonously canonicalise the given pathname and convert it to an
		1628	IO::AIO::WD object representing it. If possible and supported on the
		1629	system, also open a directory fd to speed up pathname resolution relative
		1630	to this working directory.
		1631
		1632	If something goes wrong, then C<undef> is passwd to the callback instead
		1633	of a working directory object and C<$!> is set appropriately. Since
		1634	passing C<undef> as working directory component of a pathname fails the
		1635	request with C<ENOENT>, there is often no need for error checking in the
		1636	C<aio_wd> callback, as future requests using the value will fail in the
		1637	expected way.
		1638
		1639	=item IO::AIO::CWD
		1640
		1641	This is a compiletime constant (object) that represents the process
		1642	current working directory.
		1643
		1644	Specifying this object as working directory object for a pathname is as if
		1645	the pathname would be specified directly, without a directory object. For
		1646	example, these calls are functionally identical:
		1647
		1648	aio_stat "somefile", sub { ... };
		1649	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1650
		1651	=back
		1652
		1653	To recover the path associated with an IO::AIO::WD object, you can use
		1654	C<aio_realpath>:
		1655
		1656	aio_realpath $wd, sub {
		1657	warn "path is $_[0]\n";
		1658	};
		1659
		1660	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1661	sometimes, fall back to using an absolue path.
		1662
749	=head2 IO::AIO::REQ CLASS	1663	=head2 IO::AIO::REQ CLASS
750		1664
751	All non-aggregate C<aio_*> functions return an object of this class when	1665	All non-aggregate C<aio_*> functions return an object of this class when
752	called in non-void context.	1666	called in non-void context.
753		1667
…		…
756	=item cancel $req	1670	=item cancel $req
757		1671
758	Cancels the request, if possible. Has the effect of skipping execution	1672	Cancels the request, if possible. Has the effect of skipping execution
759	when entering the B<execute> state and skipping calling the callback when	1673	when entering the B<execute> state and skipping calling the callback when
760	entering the the B<result> state, but will leave the request otherwise	1674	entering the the B<result> state, but will leave the request otherwise
761	untouched. That means that requests that currently execute will not be	1675	untouched (with the exception of readdir). That means that requests that
762	stopped and resources held by the request will not be freed prematurely.	1676	currently execute will not be stopped and resources held by the request
		1677	will not be freed prematurely.
763		1678
764	=item cb $req $callback->(...)	1679	=item cb $req $callback->(...)
765		1680
766	Replace (or simply set) the callback registered to the request.	1681	Replace (or simply set) the callback registered to the request.
767		1682
…		…
818	Their lifetime, simplified, looks like this: when they are empty, they	1733	Their lifetime, simplified, looks like this: when they are empty, they
819	will finish very quickly. If they contain only requests that are in the	1734	will finish very quickly. If they contain only requests that are in the
820	C<done> state, they will also finish. Otherwise they will continue to	1735	C<done> state, they will also finish. Otherwise they will continue to
821	exist.	1736	exist.
822		1737
823	That means after creating a group you have some time to add requests. And	1738	That means after creating a group you have some time to add requests
824	in the callbacks of those requests, you can add further requests to the	1739	(precisely before the callback has been invoked, which is only done within
825	group. And only when all those requests have finished will the the group	1740	the C<poll_cb>). And in the callbacks of those requests, you can add
826	itself finish.	1741	further requests to the group. And only when all those requests have
		1742	finished will the the group itself finish.
827		1743
828	=over 4	1744	=over 4
829		1745
830	=item add $grp ...	1746	=item add $grp ...
831		1747
…		…
840	=item $grp->cancel_subs	1756	=item $grp->cancel_subs
841		1757
842	Cancel all subrequests and clears any feeder, but not the group request	1758	Cancel all subrequests and clears any feeder, but not the group request
843	itself. Useful when you queued a lot of events but got a result early.	1759	itself. Useful when you queued a lot of events but got a result early.
844		1760
		1761	The group request will finish normally (you cannot add requests to the
		1762	group).
		1763
845	=item $grp->result (...)	1764	=item $grp->result (...)
846		1765
847	Set the result value(s) that will be passed to the group callback when all	1766	Set the result value(s) that will be passed to the group callback when all
848	subrequests have finished and set thre groups errno to the current value	1767	subrequests have finished and set the groups errno to the current value
849	of errno (just like calling C<errno> without an error number). By default,	1768	of errno (just like calling C<errno> without an error number). By default,
850	no argument will be passed and errno is zero.	1769	no argument will be passed and errno is zero.
851		1770
852	=item $grp->errno ([$errno])	1771	=item $grp->errno ([$errno])
853		1772
…		…
864	=item feed $grp $callback->($grp)	1783	=item feed $grp $callback->($grp)
865		1784
866	Sets a feeder/generator on this group: every group can have an attached	1785	Sets a feeder/generator on this group: every group can have an attached
867	generator that generates requests if idle. The idea behind this is that,	1786	generator that generates requests if idle. The idea behind this is that,
868	although you could just queue as many requests as you want in a group,	1787	although you could just queue as many requests as you want in a group,
869	this might starve other requests for a potentially long time. For	1788	this might starve other requests for a potentially long time. For example,
870	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1789	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
871	requests, delaying any later requests for a long time.	1790	requests, delaying any later requests for a long time.
872		1791
873	To avoid this, and allow incremental generation of requests, you can	1792	To avoid this, and allow incremental generation of requests, you can
874	instead a group and set a feeder on it that generates those requests. The	1793	instead a group and set a feeder on it that generates those requests. The
875	feed callback will be called whenever there are few enough (see C<limit>,	1794	feed callback will be called whenever there are few enough (see C<limit>,
…		…
880	not impose any limits).	1799	not impose any limits).
881		1800
882	If the feed does not queue more requests when called, it will be	1801	If the feed does not queue more requests when called, it will be
883	automatically removed from the group.	1802	automatically removed from the group.
884		1803
885	If the feed limit is C<0>, it will be set to C<2> automatically.	1804	If the feed limit is C<0> when this method is called, it will be set to
		1805	C<2> automatically.
886		1806
887	Example:	1807	Example:
888		1808
889	# stat all files in @files, but only ever use four aio requests concurrently:	1809	# stat all files in @files, but only ever use four aio requests concurrently:
890		1810
…		…
902	Sets the feeder limit for the group: The feeder will be called whenever	1822	Sets the feeder limit for the group: The feeder will be called whenever
903	the group contains less than this many requests.	1823	the group contains less than this many requests.
904		1824
905	Setting the limit to C<0> will pause the feeding process.	1825	Setting the limit to C<0> will pause the feeding process.
906		1826
		1827	The default value for the limit is C<0>, but note that setting a feeder
		1828	automatically bumps it up to C<2>.
		1829
907	=back	1830	=back
908		1831
909	=head2 SUPPORT FUNCTIONS	1832	=head2 SUPPORT FUNCTIONS
910		1833
911	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1834	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
913	=over 4	1836	=over 4
914		1837
915	=item $fileno = IO::AIO::poll_fileno	1838	=item $fileno = IO::AIO::poll_fileno
916		1839
917	Return the I<request result pipe file descriptor>. This filehandle must be	1840	Return the I<request result pipe file descriptor>. This filehandle must be
918	polled for reading by some mechanism outside this module (e.g. Event or	1841	polled for reading by some mechanism outside this module (e.g. EV, Glib,
919	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1842	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
920	to call C<poll_cb> to check the results.	1843	you have to call C<poll_cb> to check the results.
921		1844
922	See C<poll_cb> for an example.	1845	See C<poll_cb> for an example.
923		1846
924	=item IO::AIO::poll_cb	1847	=item IO::AIO::poll_cb
925		1848
926	Process some outstanding events on the result pipe. You have to call this	1849	Process some requests that have reached the result phase (i.e. they have
927	regularly. Returns the number of events processed. Returns immediately	1850	been executed but the results are not yet reported). You have to call
928	when no events are outstanding. The amount of events processed depends on	1851	this "regularly" to finish outstanding requests.
929	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
930		1852
		1853	Returns C<0> if all events could be processed (or there were no
		1854	events to process), or C<-1> if it returned earlier for whatever
		1855	reason. Returns immediately when no events are outstanding. The amount
		1856	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1857	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1858
931	If not all requests were processed for whatever reason, the filehandle	1859	If not all requests were processed for whatever reason, the poll file
932	will still be ready when C<poll_cb> returns.	1860	descriptor will still be ready when C<poll_cb> returns, so normally you
		1861	don't have to do anything special to have it called later.
		1862
		1863	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1864	ready, it can be beneficial to call this function from loops which submit
		1865	a lot of requests, to make sure the results get processed when they become
		1866	available and not just when the loop is finished and the event loop takes
		1867	over again. This function returns very fast when there are no outstanding
		1868	requests.
933		1869
934	Example: Install an Event watcher that automatically calls	1870	Example: Install an Event watcher that automatically calls
935	IO::AIO::poll_cb with high priority:	1871	IO::AIO::poll_cb with high priority (more examples can be found in the
		1872	SYNOPSIS section, at the top of this document):
936		1873
937	Event->io (fd => IO::AIO::poll_fileno,	1874	Event->io (fd => IO::AIO::poll_fileno,
938	poll => 'r', async => 1,	1875	poll => 'r', async => 1,
939	cb => \&IO::AIO::poll_cb);	1876	cb => \&IO::AIO::poll_cb);
		1877
		1878	=item IO::AIO::poll_wait
		1879
		1880	Wait until either at least one request is in the result phase or no
		1881	requests are outstanding anymore.
		1882
		1883	This is useful if you want to synchronously wait for some requests to
		1884	become ready, without actually handling them.
		1885
		1886	See C<nreqs> for an example.
		1887
		1888	=item IO::AIO::poll
		1889
		1890	Waits until some requests have been handled.
		1891
		1892	Returns the number of requests processed, but is otherwise strictly
		1893	equivalent to:
		1894
		1895	IO::AIO::poll_wait, IO::AIO::poll_cb
		1896
		1897	=item IO::AIO::flush
		1898
		1899	Wait till all outstanding AIO requests have been handled.
		1900
		1901	Strictly equivalent to:
		1902
		1903	IO::AIO::poll_wait, IO::AIO::poll_cb
		1904	while IO::AIO::nreqs;
940		1905
941	=item IO::AIO::max_poll_reqs $nreqs	1906	=item IO::AIO::max_poll_reqs $nreqs
942		1907
943	=item IO::AIO::max_poll_time $seconds	1908	=item IO::AIO::max_poll_time $seconds
944		1909
…		…
969	# use a low priority so other tasks have priority	1934	# use a low priority so other tasks have priority
970	Event->io (fd => IO::AIO::poll_fileno,	1935	Event->io (fd => IO::AIO::poll_fileno,
971	poll => 'r', nice => 1,	1936	poll => 'r', nice => 1,
972	cb => &IO::AIO::poll_cb);	1937	cb => &IO::AIO::poll_cb);
973		1938
974	=item IO::AIO::poll_wait	1939	=back
975
976	If there are any outstanding requests and none of them in the result
977	phase, wait till the result filehandle becomes ready for reading (simply
978	does a C<select> on the filehandle. This is useful if you want to
979	synchronously wait for some requests to finish).
980
981	See C<nreqs> for an example.
982
983	=item IO::AIO::poll
984
985	Waits until some requests have been handled.
986
987	Returns the number of requests processed, but is otherwise strictly
988	equivalent to:
989
990	IO::AIO::poll_wait, IO::AIO::poll_cb
991
992	=item IO::AIO::flush
993
994	Wait till all outstanding AIO requests have been handled.
995
996	Strictly equivalent to:
997
998	IO::AIO::poll_wait, IO::AIO::poll_cb
999	while IO::AIO::nreqs;
1000		1940
1001	=head3 CONTROLLING THE NUMBER OF THREADS	1941	=head3 CONTROLLING THE NUMBER OF THREADS
		1942
		1943	=over
1002		1944
1003	=item IO::AIO::min_parallel $nthreads	1945	=item IO::AIO::min_parallel $nthreads
1004		1946
1005	Set the minimum number of AIO threads to C<$nthreads>. The current	1947	Set the minimum number of AIO threads to C<$nthreads>. The current
1006	default is C<8>, which means eight asynchronous operations can execute	1948	default is C<8>, which means eight asynchronous operations can execute
…		…
1034		1976
1035	Under normal circumstances you don't need to call this function.	1977	Under normal circumstances you don't need to call this function.
1036		1978
1037	=item IO::AIO::max_idle $nthreads	1979	=item IO::AIO::max_idle $nthreads
1038		1980
1039	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1981	Limit the number of threads (default: 4) that are allowed to idle
1040	threads that did not get a request to process within 10 seconds). That	1982	(i.e., threads that did not get a request to process within the idle
1041	means if a thread becomes idle while C<$nthreads> other threads are also	1983	timeout (default: 10 seconds). That means if a thread becomes idle while
1042	idle, it will free its resources and exit.	1984	C<$nthreads> other threads are also idle, it will free its resources and
		1985	exit.
1043		1986
1044	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1987	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1045	to allow for extremely high load situations, but want to free resources	1988	to allow for extremely high load situations, but want to free resources
1046	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1989	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1047		1990
1048	The default is probably ok in most situations, especially if thread	1991	The default is probably ok in most situations, especially if thread
1049	creation is fast. If thread creation is very slow on your system you might	1992	creation is fast. If thread creation is very slow on your system you might
1050	want to use larger values.	1993	want to use larger values.
1051		1994
		1995	=item IO::AIO::idle_timeout $seconds
		1996
		1997	Sets the minimum idle timeout (default 10) after which worker threads are
		1998	allowed to exit. SEe C<IO::AIO::max_idle>.
		1999
1052	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	2000	=item IO::AIO::max_outstanding $maxreqs
		2001
		2002	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2003	you do queue up more than this number of requests, the next call to
		2004	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2005	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2006	longer exceeded.
		2007
		2008	In other words, this setting does not enforce a queue limit, but can be
		2009	used to make poll functions block if the limit is exceeded.
1053		2010
1054	This is a very bad function to use in interactive programs because it	2011	This is a very bad function to use in interactive programs because it
1055	blocks, and a bad way to reduce concurrency because it is inexact: Better	2012	blocks, and a bad way to reduce concurrency because it is inexact: Better
1056	use an C<aio_group> together with a feed callback.	2013	use an C<aio_group> together with a feed callback.
1057		2014
1058	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2015	Its main use is in scripts without an event loop - when you want to stat
1059	to queue up more than this number of requests, the next call to the	2016	a lot of files, you can write something like this:
1060	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1061	function will block until the limit is no longer exceeded.
1062		2017
1063	The default value is very large, so there is no practical limit on the	2018	IO::AIO::max_outstanding 32;
1064	number of outstanding requests.
1065		2019
1066	You can still queue as many requests as you want. Therefore,	2020	for my $path (...) {
1067	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	2021	aio_stat $path , ...;
1068	as a stop gap to shield against fatal memory overflow (with large values).	2022	IO::AIO::poll_cb;
		2023	}
		2024
		2025	IO::AIO::flush;
		2026
		2027	The call to C<poll_cb> inside the loop will normally return instantly, but
		2028	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2029	some requests have been handled. This keeps the loop from pushing a large
		2030	number of C<aio_stat> requests onto the queue.
		2031
		2032	The default value for C<max_outstanding> is very large, so there is no
		2033	practical limit on the number of outstanding requests.
		2034
		2035	=back
1069		2036
1070	=head3 STATISTICAL INFORMATION	2037	=head3 STATISTICAL INFORMATION
		2038
		2039	=over
1071		2040
1072	=item IO::AIO::nreqs	2041	=item IO::AIO::nreqs
1073		2042
1074	Returns the number of requests currently in the ready, execute or pending	2043	Returns the number of requests currently in the ready, execute or pending
1075	states (i.e. for which their callback has not been invoked yet).	2044	states (i.e. for which their callback has not been invoked yet).
…		…
1089	Returns the number of requests currently in the pending state (executed,	2058	Returns the number of requests currently in the pending state (executed,
1090	but not yet processed by poll_cb).	2059	but not yet processed by poll_cb).
1091		2060
1092	=back	2061	=back
1093		2062
		2063	=head3 MISCELLANEOUS FUNCTIONS
		2064
		2065	IO::AIO implements some functions that are useful when you want to use
		2066	some "Advanced I/O" function not available to in Perl, without going the
		2067	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2068	counterpart.
		2069
		2070	=over 4
		2071
		2072	=item $numfd = IO::AIO::get_fdlimit
		2073
		2074	Tries to find the current file descriptor limit and returns it, or
		2075	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2076	the highest valid file descriptor number.
		2077
		2078	=item IO::AIO::min_fdlimit [$numfd]
		2079
		2080	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2081	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2082	is missing, it will try to set a very high limit, although this is not
		2083	recommended when you know the actual minimum that you require.
		2084
		2085	If the limit cannot be raised enough, the function makes a best-effort
		2086	attempt to increase the limit as much as possible, using various
		2087	tricks, while still failing. You can query the resulting limit using
		2088	C<IO::AIO::get_fdlimit>.
		2089
		2090	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2091	true.
		2092
		2093	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2094
		2095	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2096	but is blocking (this makes most sense if you know the input data is
		2097	likely cached already and the output filehandle is set to non-blocking
		2098	operations).
		2099
		2100	Returns the number of bytes copied, or C<-1> on error.
		2101
		2102	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2103
		2104	Simply calls the C<posix_fadvise> function (see its
		2105	manpage for details). The following advice constants are
		2106	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2107	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2108	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2109
		2110	On systems that do not implement C<posix_fadvise>, this function returns
		2111	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2112
		2113	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2114
		2115	Simply calls the C<posix_madvise> function (see its
		2116	manpage for details). The following advice constants are
		2117	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2118	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2119	C<IO::AIO::MADV_DONTNEED>.
		2120
		2121	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2122	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2123	will be reduced to fit into the C<$scalar>.
		2124
		2125	On systems that do not implement C<posix_madvise>, this function returns
		2126	ENOSYS, otherwise the return value of C<posix_madvise>.
		2127
		2128	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2129
		2130	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2131	$scalar (see its manpage for details). The following protect
		2132	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2133	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2134
		2135	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2136	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2137	will be reduced to fit into the C<$scalar>.
		2138
		2139	On systems that do not implement C<mprotect>, this function returns
		2140	ENOSYS, otherwise the return value of C<mprotect>.
		2141
		2142	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2143
		2144	Memory-maps a file (or anonymous memory range) and attaches it to the
		2145	given C<$scalar>, which will act like a string scalar. Returns true on
		2146	success, and false otherwise.
		2147
		2148	The scalar must exist, but its contents do not matter - this means you
		2149	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2150	the scalar first.
		2151
		2152	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2153	which don't change the string length, and most read-only operations such
		2154	as copying it or searching it with regexes and so on.
		2155
		2156	Anything else is unsafe and will, at best, result in memory leaks.
		2157
		2158	The memory map associated with the C<$scalar> is automatically removed
		2159	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2160	or C<IO::AIO::munmap> functions are called on it.
		2161
		2162	This calls the C<mmap>(2) function internally. See your system's manual
		2163	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2164
		2165	The C<$length> must be larger than zero and smaller than the actual
		2166	filesize.
		2167
		2168	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2169	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2170
		2171	C<$flags> can be a combination of
		2172	C<IO::AIO::MAP_SHARED> or
		2173	C<IO::AIO::MAP_PRIVATE>,
		2174	or a number of system-specific flags (when not available, the are C<0>):
		2175	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2176	C<IO::AIO::MAP_LOCKED>,
		2177	C<IO::AIO::MAP_NORESERVE>,
		2178	C<IO::AIO::MAP_POPULATE>,
		2179	C<IO::AIO::MAP_NONBLOCK>,
		2180	C<IO::AIO::MAP_FIXED>,
		2181	C<IO::AIO::MAP_GROWSDOWN>,
		2182	C<IO::AIO::MAP_32BIT>,
		2183	C<IO::AIO::MAP_HUGETLB> or
		2184	C<IO::AIO::MAP_STACK>.
		2185
		2186	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2187
		2188	C<$offset> is the offset from the start of the file - it generally must be
		2189	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2190
		2191	Example:
		2192
		2193	use Digest::MD5;
		2194	use IO::AIO;
		2195
		2196	open my $fh, "<verybigfile"
		2197	or die "$!";
		2198
		2199	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2200	or die "verybigfile: $!";
		2201
		2202	my $fast_md5 = md5 $data;
		2203
		2204	=item IO::AIO::munmap $scalar
		2205
		2206	Removes a previous mmap and undefines the C<$scalar>.
		2207
		2208	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2209
		2210	Calls the C<munlock> function, undoing the effects of a previous
		2211	C<aio_mlock> call (see its description for details).
		2212
		2213	=item IO::AIO::munlockall
		2214
		2215	Calls the C<munlockall> function.
		2216
		2217	On systems that do not implement C<munlockall>, this function returns
		2218	ENOSYS, otherwise the return value of C<munlockall>.
		2219
		2220	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2221
		2222	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2223	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2224	should be the file offset.
		2225
		2226	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2227	silently corrupt the data in this case.
		2228
		2229	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2230	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2231	C<IO::AIO::SPLICE_F_GIFT>.
		2232
		2233	See the C<splice(2)> manpage for details.
		2234
		2235	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2236
		2237	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2238	description for C<IO::AIO::splice> above for details.
		2239
		2240	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2241
		2242	Attempts to query or change the pipe buffer size. Obviously works only
		2243	on pipes, and currently works only on GNU/Linux systems, and fails with
		2244	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2245	size on other systems, drop me a note.
		2246
		2247	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2248
		2249	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2250	C<$flags> is missing or C<0>, then this should be the same as a call to
		2251	perl's built-in C<pipe> function and create a new pipe, and works on
		2252	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2253	(..., 4096, O_BINARY)>.
		2254
		2255	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2256	the given flags (Linux 2.6.27, glibc 2.9).
		2257
		2258	On success, the read and write file handles are returned.
		2259
		2260	On error, nothing will be returned. If the pipe2 syscall is missing and
		2261	C<$flags> is non-zero, fails with C<ENOSYS>.
		2262
		2263	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2264	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2265	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2266
		2267	=back
		2268
1094	=cut	2269	=cut
1095		2270
1096	# support function to convert a fd into a perl filehandle
1097	sub _fd2fh {
1098	return undef if $_[0] < 0;
1099
1100	# try to generate nice filehandles
1101	my $sym = "IO::AIO::fd#$_[0]";
1102	local *$sym;
1103
1104	open *$sym, "+<&=$_[0]" # usually works under any unix
1105	or open *$sym, "<&=$_[0]" # cygwin needs this
1106	or open *$sym, ">&=$_[0]" # or this
1107	or return undef;
1108
1109	*$sym
1110	}
1111
1112	min_parallel 8;	2271	min_parallel 8;
1113		2272
1114	END {	2273	END { flush }
1115	min_parallel 1;
1116	flush;
1117	};
1118		2274
1119	1;	2275	1;
1120		2276
		2277	=head1 EVENT LOOP INTEGRATION
		2278
		2279	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2280	automatically into many event loops:
		2281
		2282	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2283	use AnyEvent::AIO;
		2284
		2285	You can also integrate IO::AIO manually into many event loops, here are
		2286	some examples of how to do this:
		2287
		2288	# EV integration
		2289	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2290
		2291	# Event integration
		2292	Event->io (fd => IO::AIO::poll_fileno,
		2293	poll => 'r',
		2294	cb => \&IO::AIO::poll_cb);
		2295
		2296	# Glib/Gtk2 integration
		2297	add_watch Glib::IO IO::AIO::poll_fileno,
		2298	in => sub { IO::AIO::poll_cb; 1 };
		2299
		2300	# Tk integration
		2301	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2302	readable => \&IO::AIO::poll_cb);
		2303
		2304	# Danga::Socket integration
		2305	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2306	\&IO::AIO::poll_cb);
		2307
1121	=head2 FORK BEHAVIOUR	2308	=head2 FORK BEHAVIOUR
1122		2309
1123	This module should do "the right thing" when the process using it forks:	2310	Usage of pthreads in a program changes the semantics of fork
		2311	considerably. Specifically, only async-safe functions can be called after
		2312	fork. Perl doesn't know about this, so in general, you cannot call fork
		2313	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2314	pthreads, so this applies, but many other extensions and (for inexplicable
		2315	reasons) perl itself often is linked against pthreads, so this limitation
		2316	applies to quite a lot of perls.
1124		2317
1125	Before the fork, IO::AIO enters a quiescent state where no requests	2318	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1126	can be added in other threads and no results will be processed. After	2319	only works in the process that loaded it. Forking is fully supported, but
1127	the fork the parent simply leaves the quiescent state and continues	2320	using IO::AIO in the child is not.
1128	request/result processing, while the child frees the request/result queue
1129	(so that the requests started before the fork will only be handled in the
1130	parent). Threads will be started on demand until the limit set in the
1131	parent process has been reached again.
1132		2321
1133	In short: the parent will, after a short pause, continue as if fork had	2322	You might get around by not I<using> IO::AIO before (or after)
1134	not been called, while the child will act as if IO::AIO has not been used	2323	forking. You could also try to call the L<IO::AIO::reinit> function in the
1135	yet.	2324	child:
		2325
		2326	=over 4
		2327
		2328	=item IO::AIO::reinit
		2329
		2330	Abandons all current requests and I/O threads and simply reinitialises all
		2331	data structures. This is not an operation supported by any standards, but
		2332	happens to work on GNU/Linux and some newer BSD systems.
		2333
		2334	The only reasonable use for this function is to call it after forking, if
		2335	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2336	the process will result in undefined behaviour. Calling it at any time
		2337	will also result in any undefined (by POSIX) behaviour.
		2338
		2339	=back
1136		2340
1137	=head2 MEMORY USAGE	2341	=head2 MEMORY USAGE
1138		2342
1139	Per-request usage:	2343	Per-request usage:
1140		2344
…		…
1142	bytes of memory. In addition, stat requests need a stat buffer (possibly	2346	bytes of memory. In addition, stat requests need a stat buffer (possibly
1143	a few hundred bytes), readdir requires a result buffer and so on. Perl	2347	a few hundred bytes), readdir requires a result buffer and so on. Perl
1144	scalars and other data passed into aio requests will also be locked and	2348	scalars and other data passed into aio requests will also be locked and
1145	will consume memory till the request has entered the done state.	2349	will consume memory till the request has entered the done state.
1146		2350
1147	This is now awfully much, so queuing lots of requests is not usually a	2351	This is not awfully much, so queuing lots of requests is not usually a
1148	problem.	2352	problem.
1149		2353
1150	Per-thread usage:	2354	Per-thread usage:
1151		2355
1152	In the execution phase, some aio requests require more memory for	2356	In the execution phase, some aio requests require more memory for
…		…
1157		2361
1158	Known bugs will be fixed in the next release.	2362	Known bugs will be fixed in the next release.
1159		2363
1160	=head1 SEE ALSO	2364	=head1 SEE ALSO
1161		2365
1162	L<Coro::AIO>.	2366	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2367	more natural syntax.
1163		2368
1164	=head1 AUTHOR	2369	=head1 AUTHOR
1165		2370
1166	Marc Lehmann <schmorp@schmorp.de>	2371	Marc Lehmann <schmorp@schmorp.de>
1167	http://home.schmorp.de/	2372	http://home.schmorp.de/

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