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Revision 1.92 by root, Wed Nov 8 01:57:42 2006 UTC vs.
Revision 1.278 by root, Sun Oct 1 07:24:34 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	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		283	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		284
		285	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		286	IO::AIO::fadvise $fh, $offset, $len, $advice
		287	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		288	IO::AIO::munmap $scalar
		289	IO::AIO::madvise $scalar, $offset, $length, $advice
		290	IO::AIO::mprotect $scalar, $offset, $length, $protect
		291	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		292	IO::AIO::munlockall
		293
		294	=head2 API NOTES
215		295
216	All the C<aio_*> calls are more or less thin wrappers around the syscall	296	All the C<aio_*> calls are more or less thin wrappers around the syscall
217	with the same name (sans C<aio_>). The arguments are similar or identical,	297	with the same name (sans C<aio_>). The arguments are similar or identical,
218	and they all accept an additional (and optional) C<$callback> argument	298	and they all accept an additional (and optional) C<$callback> argument
219	which must be a code reference. This code reference will get called with	299	which must be a code reference. This code reference will be called after
220	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	300	the syscall has been executed in an asynchronous fashion. The results
221	perl, which usually delivers "false") as it's sole argument when the given	301	of the request will be passed as arguments to the callback (and, if an
222	syscall has been executed asynchronously.	302	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		303	most syscalls return C<-1> on error, unlike perl, which usually delivers
		304	"false").
		305
		306	Some requests (such as C<aio_readdir>) pass the actual results and
		307	communicate failures by passing C<undef>.
223		308
224	All functions expecting a filehandle keep a copy of the filehandle	309	All functions expecting a filehandle keep a copy of the filehandle
225	internally until the request has finished.	310	internally until the request has finished.
226		311
227	All functions return request objects of type L<IO::AIO::REQ> that allow	312	All functions return request objects of type L<IO::AIO::REQ> that allow
228	further manipulation of those requests while they are in-flight.	313	further manipulation of those requests while they are in-flight.
229		314
230	The pathnames you pass to these routines I<must> be absolute and	315	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	316	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	317	current working directory could have changed. Alternatively, you can
233	changed. Alternatively, you can make sure that you never change the	318	make sure that you never change the current working directory anywhere
234	current working directory anywhere in the program and then use relative	319	in the program and then use relative paths. You can also take advantage
235	paths.	320	of IO::AIOs working directory abstraction, that lets you specify paths
		321	relative to some previously-opened "working directory object" - see the
		322	description of the C<IO::AIO::WD> class later in this document.
236		323
237	To encode pathnames as octets, either make sure you either: a) always pass	324	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	325	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	326	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	327	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)	328	effect in the user environment, d) use Glib::filename_from_unicode on
242	use something else to ensure your scalar has the correct contents.	329	unicode filenames or e) use something else to ensure your scalar has the
		330	correct contents.
243		331
244	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	332	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
245	handles correctly wether it is set or not.	333	handles correctly whether it is set or not.
		334
		335	=head2 AIO REQUEST FUNCTIONS
246		336
247	=over 4	337	=over 4
248		338
249	=item $prev_pri = aioreq_pri [$pri]	339	=item $prev_pri = aioreq_pri [$pri]
250		340
…		…
270	aio_read $_[0], ..., sub {	360	aio_read $_[0], ..., sub {
271	...	361	...
272	};	362	};
273	};	363	};
274		364
		365
275	=item aioreq_nice $pri_adjust	366	=item aioreq_nice $pri_adjust
276		367
277	Similar to C<aioreq_pri>, but subtracts the given value from the current	368	Similar to C<aioreq_pri>, but subtracts the given value from the current
278	priority, so the effect is cumulative.	369	priority, so the effect is cumulative.
279		370
		371
280	=item aio_open $pathname, $flags, $mode, $callback->($fh)	372	=item aio_open $pathname, $flags, $mode, $callback->($fh)
281		373
282	Asynchronously open or create a file and call the callback with a newly	374	Asynchronously open or create a file and call the callback with a newly
283	created filehandle for the file.	375	created filehandle for the file (or C<undef> in case of an error).
284		376
285	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	377	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
286	for an explanation.	378	for an explanation.
287		379
288	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	380	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
289	list. They are the same as used by C<sysopen>.	381	list. They are the same as used by C<sysopen>.
290		382
291	Likewise, C<$mode> specifies the mode of the newly created file, if it	383	Likewise, C<$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>,	384	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,	385	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).	386	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		387	by the umask in effect then the request is being executed, so better never
		388	change the umask.
295		389
296	Example:	390	Example:
297		391
298	aio_open "/etc/passwd", O_RDONLY, 0, sub {	392	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
299	if ($_[0]) {	393	if ($_[0]) {
300	print "open successful, fh is $_[0]\n";	394	print "open successful, fh is $_[0]\n";
301	...	395	...
302	} else {	396	} else {
303	die "open failed: $!\n";	397	die "open failed: $!\n";
304	}	398	}
305	};	399	};
306		400
		401	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		402	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		403	following POSIX and non-POSIX constants are available (missing ones on
		404	your system are, as usual, C<0>):
		405
		406	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		407	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		408	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		409
		410
307	=item aio_close $fh, $callback->($status)	411	=item aio_close $fh, $callback->($status)
308		412
309	Asynchronously close a file and call the callback with the result	413	Asynchronously close a file and call the callback with the result
310	code. I<WARNING:> although accepted, you should not pass in a perl	414	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		415
315	This is supposed to be a bug in the API, so that might change. It's	416	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
316	therefore best to avoid this function.	417	closing the file descriptor associated with the filehandle itself.
		418
		419	Therefore, C<aio_close> will not close the filehandle - instead it will
		420	use dup2 to overwrite the file descriptor with the write-end of a pipe
		421	(the pipe fd will be created on demand and will be cached).
		422
		423	Or in other words: the file descriptor will be closed, but it will not be
		424	free for reuse until the perl filehandle is closed.
		425
		426	=cut
		427
		428	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		429
		430	Seeks the filehandle to the new C<$offset>, similarly to perl's
		431	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		432	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		433	C<IO::AIO::SEEK_END>).
		434
		435	The resulting absolute offset will be passed to the callback, or C<-1> in
		436	case of an error.
		437
		438	In theory, the C<$whence> constants could be different than the
		439	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		440	so don't panic.
		441
		442	As a GNU/Linux (and maybe Solaris) extension, also the constants
		443	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		444	could be found. No guarantees about suitability for use in C<aio_seek> or
		445	Perl's C<sysseek> can be made though, although I would naively assume they
		446	"just work".
317		447
318	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	448	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
319		449
320	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
321		451
322	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	452	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	453	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
324	callback without the actual number of bytes read (or -1 on error, just	454	calls the callback with the actual number of bytes transferred (or -1 on
325	like the syscall).	455	error, just like the syscall).
		456
		457	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		458	offset plus the actual number of bytes read.
		459
		460	If C<$offset> is undefined, then the current file descriptor offset will
		461	be used (and updated), otherwise the file descriptor offset will not be
		462	changed by these calls.
		463
		464	If C<$length> is undefined in C<aio_write>, use the remaining length of
		465	C<$data>.
		466
		467	If C<$dataoffset> is less than zero, it will be counted from the end of
		468	C<$data>.
326		469
327	The C<$data> scalar I<MUST NOT> be modified in any way while the request	470	The C<$data> scalar I<MUST NOT> be modified in any way while the request
328	is outstanding. Modifying it can result in segfaults or WW3 (if the	471	is outstanding. Modifying it can result in segfaults or World War III (if
329	necessary/optional hardware is installed).	472	the necessary/optional hardware is installed).
330		473
331	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	474	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
332	offset C<0> within the scalar:	475	offset C<0> within the scalar:
333		476
334	aio_read $fh, 7, 15, $buffer, 0, sub {	477	aio_read $fh, 7, 15, $buffer, 0, sub {
335	$_[0] > 0 or die "read error: $!";	478	$_[0] > 0 or die "read error: $!";
336	print "read $_[0] bytes: <$buffer>\n";	479	print "read $_[0] bytes: <$buffer>\n";
337	};	480	};
338		481
		482
339	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	483	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
340		484
341	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	485	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
342	reading at byte offset C<$in_offset>, and starts writing at the current	486	reading at byte offset C<$in_offset>, and starts writing at the current
343	file offset of C<$out_fh>. Because of that, it is not safe to issue more	487	file offset of C<$out_fh>. Because of that, it is not safe to issue more
344	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	488	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
345	other.	489	other. The same C<$in_fh> works fine though, as this function does not
		490	move or use the file offset of C<$in_fh>.
346		491
		492	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		493	are written, and there is no way to find out how many more bytes have been
		494	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		495	number of bytes written to C<$out_fh>. Only if the result value equals
		496	C<$length> one can assume that C<$length> bytes have been read.
		497
		498	Unlike with other C<aio_> functions, it makes a lot of sense to use
		499	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		500	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		501	the socket I/O will be non-blocking. Note, however, that you can run
		502	into a trap where C<aio_sendfile> reads some data with readahead, then
		503	fails to write all data, and when the socket is ready the next time, the
		504	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		505	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		506	resource usage.
		507
347	This call tries to make use of a native C<sendfile> syscall to provide	508	This call tries to make use of a native C<sendfile>-like syscall to
348	zero-copy operation. For this to work, C<$out_fh> should refer to a	509	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.	510	a socket, and C<$in_fh> should refer to an mmap'able file.
350		511
351	If the native sendfile call fails or is not implemented, it will be	512	If a native sendfile cannot be found or it fails with C<ENOSYS>,
352	emulated, so you can call C<aio_sendfile> on any type of filehandle	513	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		514	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
353	regardless of the limitations of the operating system.	515	type of filehandle regardless of the limitations of the operating system.
354		516
355	Please note, however, that C<aio_sendfile> can read more bytes from	517	As native sendfile syscalls (as practically any non-POSIX interface hacked
356	C<$in_fh> than are written, and there is no way to find out how many	518	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	519	on many systems, this implementation tries to work around some known bugs
358	provides the number of bytes written to C<$out_fh>. Only if the result	520	in Linux and FreeBSD kernels (probably others, too), but that might fail,
359	value equals C<$length> one can assume that C<$length> bytes have been	521	so you really really should check the return value of C<aio_sendfile> -
360	read.	522	fewer bytes than expected might have been transferred.
		523
361		524
362	=item aio_readahead $fh,$offset,$length, $callback->($retval)	525	=item aio_readahead $fh,$offset,$length, $callback->($retval)
363		526
364	C<aio_readahead> populates the page cache with data from a file so that	527	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<$offset>	528	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
368	whole pages, so that offset is effectively rounded down to a page boundary	531	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	532	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	533	(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.	534	file. The current file offset of the file is left unchanged.
372		535
373	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	536	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.	537	be emulated by simply reading the data, which would have a similar effect.
		538
375		539
376	=item aio_stat $fh_or_path, $callback->($status)	540	=item aio_stat $fh_or_path, $callback->($status)
377		541
378	=item aio_lstat $fh, $callback->($status)	542	=item aio_lstat $fh, $callback->($status)
379		543
…		…
385	for an explanation.	549	for an explanation.
386		550
387	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	551	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	552	error when stat'ing a large file, the results will be silently truncated
389	unless perl itself is compiled with large file support.	553	unless perl itself is compiled with large file support.
		554
		555	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		556	following constants and functions (if not implemented, the constants will
		557	be C<0> and the functions will either C<croak> or fall back on traditional
		558	behaviour).
		559
		560	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		561	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		562	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
390		563
391	Example: Print the length of F</etc/passwd>:	564	Example: Print the length of F</etc/passwd>:
392		565
393	aio_stat "/etc/passwd", sub {	566	aio_stat "/etc/passwd", sub {
394	$_[0] and die "stat failed: $!";	567	$_[0] and die "stat failed: $!";
395	print "size is ", -s _, "\n";	568	print "size is ", -s _, "\n";
396	};	569	};
397		570
		571
		572	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		573
		574	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		575	whether a file handle or path was passed.
		576
		577	On success, the callback is passed a hash reference with the following
		578	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		579	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		580	is passed.
		581
		582	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		583	C<ST_NOSUID>.
		584
		585	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		586	their correct value when available, or to C<0> on systems that do
		587	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		588	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		589	C<ST_NODIRATIME> and C<ST_RELATIME>.
		590
		591	Example: stat C</wd> and dump out the data if successful.
		592
		593	aio_statvfs "/wd", sub {
		594	my $f = $_[0]
		595	or die "statvfs: $!";
		596
		597	use Data::Dumper;
		598	say Dumper $f;
		599	};
		600
		601	# result:
		602	{
		603	bsize => 1024,
		604	bfree => 4333064312,
		605	blocks => 10253828096,
		606	files => 2050765568,
		607	flag => 4096,
		608	favail => 2042092649,
		609	bavail => 4333064312,
		610	ffree => 2042092649,
		611	namemax => 255,
		612	frsize => 1024,
		613	fsid => 1810
		614	}
		615
		616	Here is a (likely partial - send me updates!) list of fsid values used by
		617	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		618
		619	0x0000adf5 adfs
		620	0x0000adff affs
		621	0x5346414f afs
		622	0x09041934 anon-inode filesystem
		623	0x00000187 autofs
		624	0x42465331 befs
		625	0x1badface bfs
		626	0x42494e4d binfmt_misc
		627	0x9123683e btrfs
		628	0x0027e0eb cgroupfs
		629	0xff534d42 cifs
		630	0x73757245 coda
		631	0x012ff7b7 coh
		632	0x28cd3d45 cramfs
		633	0x453dcd28 cramfs-wend (wrong endianness)
		634	0x64626720 debugfs
		635	0x00001373 devfs
		636	0x00001cd1 devpts
		637	0x0000f15f ecryptfs
		638	0x00414a53 efs
		639	0x0000137d ext
		640	0x0000ef53 ext2/ext3/ext4
		641	0x0000ef51 ext2
		642	0xf2f52010 f2fs
		643	0x00004006 fat
		644	0x65735546 fuseblk
		645	0x65735543 fusectl
		646	0x0bad1dea futexfs
		647	0x01161970 gfs2
		648	0x47504653 gpfs
		649	0x00004244 hfs
		650	0xf995e849 hpfs
		651	0x00c0ffee hostfs
		652	0x958458f6 hugetlbfs
		653	0x2bad1dea inotifyfs
		654	0x00009660 isofs
		655	0x000072b6 jffs2
		656	0x3153464a jfs
		657	0x6b414653 k-afs
		658	0x0bd00bd0 lustre
		659	0x0000137f minix
		660	0x0000138f minix 30 char names
		661	0x00002468 minix v2
		662	0x00002478 minix v2 30 char names
		663	0x00004d5a minix v3
		664	0x19800202 mqueue
		665	0x00004d44 msdos
		666	0x0000564c novell
		667	0x00006969 nfs
		668	0x6e667364 nfsd
		669	0x00003434 nilfs
		670	0x5346544e ntfs
		671	0x00009fa1 openprom
		672	0x7461636F ocfs2
		673	0x00009fa0 proc
		674	0x6165676c pstorefs
		675	0x0000002f qnx4
		676	0x68191122 qnx6
		677	0x858458f6 ramfs
		678	0x52654973 reiserfs
		679	0x00007275 romfs
		680	0x67596969 rpc_pipefs
		681	0x73636673 securityfs
		682	0xf97cff8c selinux
		683	0x0000517b smb
		684	0x534f434b sockfs
		685	0x73717368 squashfs
		686	0x62656572 sysfs
		687	0x012ff7b6 sysv2
		688	0x012ff7b5 sysv4
		689	0x01021994 tmpfs
		690	0x15013346 udf
		691	0x00011954 ufs
		692	0x54190100 ufs byteswapped
		693	0x00009fa2 usbdevfs
		694	0x01021997 v9fs
		695	0xa501fcf5 vxfs
		696	0xabba1974 xenfs
		697	0x012ff7b4 xenix
		698	0x58465342 xfs
		699	0x012fd16d xia
		700
		701	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		702
		703	Works like perl's C<utime> function (including the special case of $atime
		704	and $mtime being undef). Fractional times are supported if the underlying
		705	syscalls support them.
		706
		707	When called with a pathname, uses utimes(2) if available, otherwise
		708	utime(2). If called on a file descriptor, uses futimes(2) if available,
		709	otherwise returns ENOSYS, so this is not portable.
		710
		711	Examples:
		712
		713	# set atime and mtime to current time (basically touch(1)):
		714	aio_utime "path", undef, undef;
		715	# set atime to current time and mtime to beginning of the epoch:
		716	aio_utime "path", time, undef; # undef==0
		717
		718
		719	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		720
		721	Works like perl's C<chown> function, except that C<undef> for either $uid
		722	or $gid is being interpreted as "do not change" (but -1 can also be used).
		723
		724	Examples:
		725
		726	# same as "chown root path" in the shell:
		727	aio_chown "path", 0, -1;
		728	# same as above:
		729	aio_chown "path", 0, undef;
		730
		731
		732	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		733
		734	Works like truncate(2) or ftruncate(2).
		735
		736
		737	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		738
		739	Allocates or frees disk space according to the C<$mode> argument. See the
		740	linux C<fallocate> documentation for details.
		741
		742	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		743	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		744	to deallocate a file range.
		745
		746	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		747	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		748	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		749	to unshare shared blocks (see your L<fallocate(2)> manpage).
		750
		751	The file system block size used by C<fallocate> is presumably the
		752	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		753	can dictate other limitations.
		754
		755	If C<fallocate> isn't available or cannot be emulated (currently no
		756	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		757
		758
		759	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		760
		761	Works like perl's C<chmod> function.
		762
		763
398	=item aio_unlink $pathname, $callback->($status)	764	=item aio_unlink $pathname, $callback->($status)
399		765
400	Asynchronously unlink (delete) a file and call the callback with the	766	Asynchronously unlink (delete) a file and call the callback with the
401	result code.	767	result code.
402		768
		769
403	=item aio_mknod $path, $mode, $dev, $callback->($status)	770	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
404		771
405	[EXPERIMENTAL]	772	[EXPERIMENTAL]
406		773
407	Asynchronously create a device node (or fifo). See mknod(2).	774	Asynchronously create a device node (or fifo). See mknod(2).
408		775
409	The only (POSIX-) portable way of calling this function is:	776	The only (POSIX-) portable way of calling this function is:
410		777
411	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	778	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		779
		780	See C<aio_stat> for info about some potentially helpful extra constants
		781	and functions.
412		782
413	=item aio_link $srcpath, $dstpath, $callback->($status)	783	=item aio_link $srcpath, $dstpath, $callback->($status)
414		784
415	Asynchronously create a new link to the existing object at C<$srcpath> at	785	Asynchronously create a new link to the existing object at C<$srcpath> at
416	the path C<$dstpath> and call the callback with the result code.	786	the path C<$dstpath> and call the callback with the result code.
417		787
		788
418	=item aio_symlink $srcpath, $dstpath, $callback->($status)	789	=item aio_symlink $srcpath, $dstpath, $callback->($status)
419		790
420	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	791	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
421	the path C<$dstpath> and call the callback with the result code.	792	the path C<$dstpath> and call the callback with the result code.
422		793
		794
423	=item aio_readlink $path, $callback->($link)	795	=item aio_readlink $pathname, $callback->($link)
424		796
425	Asynchronously read the symlink specified by C<$path> and pass it to	797	Asynchronously read the symlink specified by C<$path> and pass it to
426	the callback. If an error occurs, nothing or undef gets passed to the	798	the callback. If an error occurs, nothing or undef gets passed to the
427	callback.	799	callback.
428		800
		801
		802	=item aio_realpath $pathname, $callback->($path)
		803
		804	Asynchronously make the path absolute and resolve any symlinks in
		805	C<$path>. The resulting path only consists of directories (same as
		806	L<Cwd::realpath>).
		807
		808	This request can be used to get the absolute path of the current working
		809	directory by passing it a path of F<.> (a single dot).
		810
		811
429	=item aio_rename $srcpath, $dstpath, $callback->($status)	812	=item aio_rename $srcpath, $dstpath, $callback->($status)
430		813
431	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	814	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
432	rename(2) and call the callback with the result code.	815	rename(2) and call the callback with the result code.
433		816
		817	On systems that support the AIO::WD working directory abstraction
		818	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		819	of failing, C<rename> is called on the absolute path of C<$wd>.
		820
		821
		822	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		823
		824	Basically a version of C<aio_rename> with an additional C<$flags>
		825	argument. Calling this with C<$flags=0> is the same as calling
		826	C<aio_rename>.
		827
		828	Non-zero flags are currently only supported on GNU/Linux systems that
		829	support renameat2. Other systems fail with C<ENOSYS> in this case.
		830
		831	The following constants are available (missing ones are, as usual C<0>),
		832	see renameat2(2) for details:
		833
		834	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		835	and C<IO::AIO::RENAME_WHITEOUT>.
		836
		837
		838	=item aio_mkdir $pathname, $mode, $callback->($status)
		839
		840	Asynchronously mkdir (create) a directory and call the callback with
		841	the result code. C<$mode> will be modified by the umask at the time the
		842	request is executed, so do not change your umask.
		843
		844
434	=item aio_rmdir $pathname, $callback->($status)	845	=item aio_rmdir $pathname, $callback->($status)
435		846
436	Asynchronously rmdir (delete) a directory and call the callback with the	847	Asynchronously rmdir (delete) a directory and call the callback with the
437	result code.	848	result code.
		849
		850	On systems that support the AIO::WD working directory abstraction
		851	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		852	C<rmdir> is called on the absolute path of C<$wd>.
		853
438		854
439	=item aio_readdir $pathname, $callback->($entries)	855	=item aio_readdir $pathname, $callback->($entries)
440		856
441	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	857	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	858	directory (i.e. opendir + readdir + closedir). The entries will not be
443	sorted, and will B<NOT> include the C<.> and C<..> entries.	859	sorted, and will B<NOT> include the C<.> and C<..> entries.
444		860
445	The callback a single argument which is either C<undef> or an array-ref	861	The callback is passed a single argument which is either C<undef> or an
446	with the filenames.	862	array-ref with the filenames.
		863
		864
		865	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		866
		867	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		868	tune behaviour and output format. In case of an error, C<$entries> will be
		869	C<undef>.
		870
		871	The flags are a combination of the following constants, ORed together (the
		872	flags will also be passed to the callback, possibly modified):
		873
		874	=over 4
		875
		876	=item IO::AIO::READDIR_DENTS
		877
		878	When this flag is off, then the callback gets an arrayref consisting of
		879	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		880	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		881	entry in more detail.
		882
		883	C<$name> is the name of the entry.
		884
		885	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		886
		887	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		888	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		889	C<IO::AIO::DT_WHT>.
		890
		891	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		892	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		893	scalars are read-only: you can not modify them.
		894
		895	C<$inode> is the inode number (which might not be exact on systems with 64
		896	bit inode numbers and 32 bit perls). This field has unspecified content on
		897	systems that do not deliver the inode information.
		898
		899	=item IO::AIO::READDIR_DIRS_FIRST
		900
		901	When this flag is set, then the names will be returned in an order where
		902	likely directories come first, in optimal stat order. This is useful when
		903	you need to quickly find directories, or you want to find all directories
		904	while avoiding to stat() each entry.
		905
		906	If the system returns type information in readdir, then this is used
		907	to find directories directly. Otherwise, likely directories are names
		908	beginning with ".", or otherwise names with no dots, of which names with
		909	short names are tried first.
		910
		911	=item IO::AIO::READDIR_STAT_ORDER
		912
		913	When this flag is set, then the names will be returned in an order
		914	suitable for stat()'ing each one. That is, when you plan to stat()
		915	all files in the given directory, then the returned order will likely
		916	be fastest.
		917
		918	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		919	the likely dirs come first, resulting in a less optimal stat order.
		920
		921	=item IO::AIO::READDIR_FOUND_UNKNOWN
		922
		923	This flag should not be set when calling C<aio_readdirx>. Instead, it
		924	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		925	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		926	C<$type>'s are known, which can be used to speed up some algorithms.
		927
		928	=back
		929
		930
		931	=item aio_load $pathname, $data, $callback->($status)
		932
		933	This is a composite request that tries to fully load the given file into
		934	memory. Status is the same as with aio_read.
		935
		936	=cut
		937
		938	sub aio_load($$;$) {
		939	my ($path, undef, $cb) = @_;
		940	my $data = \$_[1];
		941
		942	my $pri = aioreq_pri;
		943	my $grp = aio_group $cb;
		944
		945	aioreq_pri $pri;
		946	add $grp aio_open $path, O_RDONLY, 0, sub {
		947	my $fh = shift
		948	or return $grp->result (-1);
		949
		950	aioreq_pri $pri;
		951	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		952	$grp->result ($_[0]);
		953	};
		954	};
		955
		956	$grp
		957	}
447		958
448	=item aio_copy $srcpath, $dstpath, $callback->($status)	959	=item aio_copy $srcpath, $dstpath, $callback->($status)
449		960
450	Try to copy the I<file> (directories not supported as either source or	961	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	962	destination) from C<$srcpath> to C<$dstpath> and call the callback with
452	the C<0> (error) or C<-1> ok.	963	a status of C<0> (ok) or C<-1> (error, see C<$!>).
453		964
		965	Existing destination files will be truncated.
		966
454	This is a composite request that it creates the destination file with	967	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	968	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	969	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
457	uid/gid, in that order.	970	uid/gid, in that order.
458		971
459	If an error occurs, the partial destination file will be unlinked, if	972	If an error occurs, the partial destination file will be unlinked, if
…		…
469	my $grp = aio_group $cb;	982	my $grp = aio_group $cb;
470		983
471	aioreq_pri $pri;	984	aioreq_pri $pri;
472	add $grp aio_open $src, O_RDONLY, 0, sub {	985	add $grp aio_open $src, O_RDONLY, 0, sub {
473	if (my $src_fh = $_[0]) {	986	if (my $src_fh = $_[0]) {
474	my @stat = stat $src_fh;	987	my @stat = stat $src_fh; # hmm, might block over nfs?
475		988
476	aioreq_pri $pri;	989	aioreq_pri $pri;
477	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	990	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
478	if (my $dst_fh = $_[0]) {	991	if (my $dst_fh = $_[0]) {
479	aioreq_pri $pri;	992	aioreq_pri $pri;
480	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	993	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
481	if ($_[0] == $stat[7]) {	994	if ($_[0] == $stat[7]) {
482	$grp->result (0);	995	$grp->result (0);
483	close $src_fh;	996	close $src_fh;
484		997
485	# those should not normally block. should. should.	998	my $ch = sub {
		999	aioreq_pri $pri;
		1000	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		1001	aioreq_pri $pri;
		1002	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		1003	aioreq_pri $pri;
		1004	add $grp aio_close $dst_fh;
		1005	}
		1006	};
		1007	};
		1008
		1009	aioreq_pri $pri;
		1010	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1011	if ($_[0] < 0 && $! == ENOSYS) {
		1012	aioreq_pri $pri;
486	utime $stat[8], $stat[9], $dst;	1013	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
487	chmod $stat[2] & 07777, $dst_fh;	1014	} else {
488	chown $stat[4], $stat[5], $dst_fh;	1015	$ch->();
		1016	}
489	close $dst_fh;	1017	};
490	} else {	1018	} else {
491	$grp->result (-1);	1019	$grp->result (-1);
492	close $src_fh;	1020	close $src_fh;
493	close $dst_fh;	1021	close $dst_fh;
494		1022
…		…
511		1039
512	=item aio_move $srcpath, $dstpath, $callback->($status)	1040	=item aio_move $srcpath, $dstpath, $callback->($status)
513		1041
514	Try to move the I<file> (directories not supported as either source or	1042	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	1043	destination) from C<$srcpath> to C<$dstpath> and call the callback with
516	the C<0> (error) or C<-1> ok.	1044	a status of C<0> (ok) or C<-1> (error, see C<$!>).
517		1045
518	This is a composite request that tries to rename(2) the file first. If	1046	This is a composite request that tries to rename(2) the file first; if
519	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1047	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
520	that is successful, unlinking the C<$srcpath>.	1048	that is successful, unlinks the C<$srcpath>.
521		1049
522	=cut	1050	=cut
523		1051
524	sub aio_move($$;$) {	1052	sub aio_move($$;$) {
525	my ($src, $dst, $cb) = @_;	1053	my ($src, $dst, $cb) = @_;
…		…
532	if ($_[0] && $! == EXDEV) {	1060	if ($_[0] && $! == EXDEV) {
533	aioreq_pri $pri;	1061	aioreq_pri $pri;
534	add $grp aio_copy $src, $dst, sub {	1062	add $grp aio_copy $src, $dst, sub {
535	$grp->result ($_[0]);	1063	$grp->result ($_[0]);
536		1064
537	if (!$_[0]) {	1065	unless ($_[0]) {
538	aioreq_pri $pri;	1066	aioreq_pri $pri;
539	add $grp aio_unlink $src;	1067	add $grp aio_unlink $src;
540	}	1068	}
541	};	1069	};
542	} else {	1070	} else {
…		…
545	};	1073	};
546		1074
547	$grp	1075	$grp
548	}	1076	}
549		1077
550	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1078	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
551		1079
552	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1080	Scans a directory (similar to C<aio_readdir>) but additionally tries to
553	efficiently separate the entries of directory C<$path> into two sets of	1081	efficiently separate the entries of directory C<$path> into two sets of
554	names, directories you can recurse into (directories), and ones you cannot	1082	names, directories you can recurse into (directories), and ones you cannot
555	recurse into (everything else, including symlinks to directories).	1083	recurse into (everything else, including symlinks to directories).
556		1084
557	C<aio_scandir> is a composite request that creates of many sub requests_	1085	C<aio_scandir> is a composite request that generates many sub requests.
558	C<$maxreq> specifies the maximum number of outstanding aio requests that	1086	C<$maxreq> specifies the maximum number of outstanding aio requests that
559	this function generates. If it is C<< <= 0 >>, then a suitable default	1087	this function generates. If it is C<< <= 0 >>, then a suitable default
560	will be chosen (currently 4).	1088	will be chosen (currently 4).
561		1089
562	On error, the callback is called without arguments, otherwise it receives	1090	On error, the callback is called without arguments, otherwise it receives
…		…
572		1100
573	Implementation notes.	1101	Implementation notes.
574		1102
575	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1103	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
576		1104
		1105	If readdir returns file type information, then this is used directly to
		1106	find directories.
		1107
577	After reading the directory, the modification time, size etc. of the	1108	Otherwise, after reading the directory, the modification time, size etc.
578	directory before and after the readdir is checked, and if they match (and	1109	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	1110	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	1111	how many entries are directories (if >= 2). Otherwise, no knowledge of the
581	of subdirectories will be assumed.	1112	number of subdirectories will be assumed.
582		1113
583	Then entries will be sorted into likely directories (everything without	1114	Then entries will be sorted into likely directories a non-initial dot
584	a non-initial dot currently) and likely non-directories (everything	1115	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,	1116	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	1117	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	1118	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	1119	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	1120	filesystems might detect the type of the entry without reading the inode
590	data (e.g. ext2fs filetype feature).	1121	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1122	the filetype information on readdir.
591		1123
592	If the known number of directories (link count - 2) has been reached, the	1124	If the known number of directories (link count - 2) has been reached, the
593	rest of the entries is assumed to be non-directories.	1125	rest of the entries is assumed to be non-directories.
594		1126
595	This only works with certainty on POSIX (= UNIX) filesystems, which	1127	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	1131	as those tend to return 0 or 1 as link counts, which disables the
600	directory counting heuristic.	1132	directory counting heuristic.
601		1133
602	=cut	1134	=cut
603		1135
604	sub aio_scandir($$$) {	1136	sub aio_scandir($$;$) {
605	my ($path, $maxreq, $cb) = @_;	1137	my ($path, $maxreq, $cb) = @_;
606		1138
607	my $pri = aioreq_pri;	1139	my $pri = aioreq_pri;
608		1140
609	my $grp = aio_group $cb;	1141	my $grp = aio_group $cb;
610		1142
611	$maxreq = 4 if $maxreq <= 0;	1143	$maxreq = 4 if $maxreq <= 0;
612		1144
613	# stat once	1145	# get a wd object
614	aioreq_pri $pri;	1146	aioreq_pri $pri;
615	add $grp aio_stat $path, sub {	1147	add $grp aio_wd $path, sub {
		1148	$_[0]
616	return $grp->result () if $_[0];	1149	or return $grp->result ();
617	my $now = time;
618	my $hash1 = join ":", (stat _)[0,1,3,7,9];
619		1150
620	# read the directory entries	1151	my $wd = [shift, "."];
		1152
		1153	# stat once
621	aioreq_pri $pri;	1154	aioreq_pri $pri;
622	add $grp aio_readdir $path, sub {	1155	add $grp aio_stat $wd, sub {
623	my $entries = shift
624	or return $grp->result ();	1156	return $grp->result () if $_[0];
		1157	my $now = time;
		1158	my $hash1 = join ":", (stat _)[0,1,3,7,9];
625		1159
626	# stat the dir another time	1160	# read the directory entries
627	aioreq_pri $pri;	1161	aioreq_pri $pri;
		1162	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1163	my $entries = shift
		1164	or return $grp->result ();
		1165
		1166	# stat the dir another time
		1167	aioreq_pri $pri;
628	add $grp aio_stat $path, sub {	1168	add $grp aio_stat $wd, sub {
629	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1169	my $hash2 = join ":", (stat _)[0,1,3,7,9];
630		1170
631	my $ndirs;	1171	my $ndirs;
632		1172
633	# take the slow route if anything looks fishy	1173	# take the slow route if anything looks fishy
634	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1174	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
635	$ndirs = -1;	1175	$ndirs = -1;
636	} else {	1176	} else {
637	# if nlink == 2, we are finished	1177	# if nlink == 2, we are finished
638	# on non-posix-fs's, we rely on nlink < 2	1178	# for non-posix-fs's, we rely on nlink < 2
639	$ndirs = (stat _)[3] - 2	1179	$ndirs = (stat _)[3] - 2
640	or return $grp->result ([], $entries);	1180	or return $grp->result ([], $entries);
641	}	1181	}
642		1182
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);	1183	my (@dirs, @nondirs);
651		1184
652	my $statgrp = add $grp aio_group sub {	1185	my $statgrp = add $grp aio_group sub {
653	$grp->result (\@dirs, \@nondirs);	1186	$grp->result (\@dirs, \@nondirs);
654	};	1187	};
655		1188
656	limit $statgrp $maxreq;	1189	limit $statgrp $maxreq;
657	feed $statgrp sub {	1190	feed $statgrp sub {
658	return unless @$entries;	1191	return unless @$entries;
659	my $entry = pop @$entries;	1192	my $entry = shift @$entries;
660		1193
661	aioreq_pri $pri;	1194	aioreq_pri $pri;
		1195	$wd->[1] = "$entry/.";
662	add $statgrp aio_stat "$path/$entry/.", sub {	1196	add $statgrp aio_stat $wd, sub {
663	if ($_[0] < 0) {	1197	if ($_[0] < 0) {
664	push @nondirs, $entry;	1198	push @nondirs, $entry;
665	} else {	1199	} else {
666	# need to check for real directory	1200	# need to check for real directory
667	aioreq_pri $pri;	1201	aioreq_pri $pri;
		1202	$wd->[1] = $entry;
668	add $statgrp aio_lstat "$path/$entry", sub {	1203	add $statgrp aio_lstat $wd, sub {
669	if (-d _) {	1204	if (-d _) {
670	push @dirs, $entry;	1205	push @dirs, $entry;
671		1206
672	unless (--$ndirs) {	1207	unless (--$ndirs) {
673	push @nondirs, @$entries;	1208	push @nondirs, @$entries;
674	feed $statgrp;	1209	feed $statgrp;
		1210	}
		1211	} else {
		1212	push @nondirs, $entry;
675	}	1213	}
676	} else {
677	push @nondirs, $entry;
678	}	1214	}
679	}	1215	}
680	}	1216	};
681	};	1217	};
682	};	1218	};
683	};	1219	};
684	};	1220	};
685	};	1221	};
686		1222
687	$grp	1223	$grp
688	}	1224	}
689		1225
		1226	=item aio_rmtree $pathname, $callback->($status)
		1227
		1228	Delete a directory tree starting (and including) C<$path>, return the
		1229	status of the final C<rmdir> only. This is a composite request that
		1230	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1231	everything else.
		1232
		1233	=cut
		1234
		1235	sub aio_rmtree;
		1236	sub aio_rmtree($;$) {
		1237	my ($path, $cb) = @_;
		1238
		1239	my $pri = aioreq_pri;
		1240	my $grp = aio_group $cb;
		1241
		1242	aioreq_pri $pri;
		1243	add $grp aio_scandir $path, 0, sub {
		1244	my ($dirs, $nondirs) = @_;
		1245
		1246	my $dirgrp = aio_group sub {
		1247	add $grp aio_rmdir $path, sub {
		1248	$grp->result ($_[0]);
		1249	};
		1250	};
		1251
		1252	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1253	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1254
		1255	add $grp $dirgrp;
		1256	};
		1257
		1258	$grp
		1259	}
		1260
		1261	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1262
		1263	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1264
		1265	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1266	they execute asynchronously and pass the return value to the callback.
		1267
		1268	Both calls can be used for a lot of things, some of which make more sense
		1269	to run asynchronously in their own thread, while some others make less
		1270	sense. For example, calls that block waiting for external events, such
		1271	as locking, will also lock down an I/O thread while it is waiting, which
		1272	can deadlock the whole I/O system. At the same time, there might be no
		1273	alternative to using a thread to wait.
		1274
		1275	So in general, you should only use these calls for things that do
		1276	(filesystem) I/O, not for things that wait for other events (network,
		1277	other processes), although if you are careful and know what you are doing,
		1278	you still can.
		1279
		1280	The following constants are available (missing ones are, as usual C<0>):
		1281
		1282	C<F_DUPFD_CLOEXEC>,
		1283
		1284	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1285
		1286	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1287
		1288	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1289	C<FS_IOC_FIEMAP>.
		1290
		1291	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1292	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1293
		1294	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1295	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1296	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1297	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1298	C<FS_FL_USER_MODIFIABLE>.
		1299
		1300	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1301	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1302	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1303	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1304
		1305	=item aio_sync $callback->($status)
		1306
		1307	Asynchronously call sync and call the callback when finished.
		1308
690	=item aio_fsync $fh, $callback->($status)	1309	=item aio_fsync $fh, $callback->($status)
691		1310
692	Asynchronously call fsync on the given filehandle and call the callback	1311	Asynchronously call fsync on the given filehandle and call the callback
693	with the fsync result code.	1312	with the fsync result code.
694		1313
…		…
697	Asynchronously call fdatasync on the given filehandle and call the	1316	Asynchronously call fdatasync on the given filehandle and call the
698	callback with the fdatasync result code.	1317	callback with the fdatasync result code.
699		1318
700	If this call isn't available because your OS lacks it or it couldn't be	1319	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.	1320	detected, it will be emulated by calling C<fsync> instead.
		1321
		1322	=item aio_syncfs $fh, $callback->($status)
		1323
		1324	Asynchronously call the syncfs syscall to sync the filesystem associated
		1325	to the given filehandle and call the callback with the syncfs result
		1326	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1327	errno to C<ENOSYS> nevertheless.
		1328
		1329	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1330
		1331	Sync the data portion of the file specified by C<$offset> and C<$length>
		1332	to disk (but NOT the metadata), by calling the Linux-specific
		1333	sync_file_range call. If sync_file_range is not available or it returns
		1334	ENOSYS, then fdatasync or fsync is being substituted.
		1335
		1336	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1337	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1338	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1339	manpage for details.
		1340
		1341	=item aio_pathsync $pathname, $callback->($status)
		1342
		1343	This request tries to open, fsync and close the given path. This is a
		1344	composite request intended to sync directories after directory operations
		1345	(E.g. rename). This might not work on all operating systems or have any
		1346	specific effect, but usually it makes sure that directory changes get
		1347	written to disc. It works for anything that can be opened for read-only,
		1348	not just directories.
		1349
		1350	Future versions of this function might fall back to other methods when
		1351	C<fsync> on the directory fails (such as calling C<sync>).
		1352
		1353	Passes C<0> when everything went ok, and C<-1> on error.
		1354
		1355	=cut
		1356
		1357	sub aio_pathsync($;$) {
		1358	my ($path, $cb) = @_;
		1359
		1360	my $pri = aioreq_pri;
		1361	my $grp = aio_group $cb;
		1362
		1363	aioreq_pri $pri;
		1364	add $grp aio_open $path, O_RDONLY, 0, sub {
		1365	my ($fh) = @_;
		1366	if ($fh) {
		1367	aioreq_pri $pri;
		1368	add $grp aio_fsync $fh, sub {
		1369	$grp->result ($_[0]);
		1370
		1371	aioreq_pri $pri;
		1372	add $grp aio_close $fh;
		1373	};
		1374	} else {
		1375	$grp->result (-1);
		1376	}
		1377	};
		1378
		1379	$grp
		1380	}
		1381
		1382	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1383
		1384	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1385	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1386	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1387	scalar must only be modified in-place while an aio operation is pending on
		1388	it).
		1389
		1390	It calls the C<msync> function of your OS, if available, with the memory
		1391	area starting at C<$offset> in the string and ending C<$length> bytes
		1392	later. If C<$length> is negative, counts from the end, and if C<$length>
		1393	is C<undef>, then it goes till the end of the string. The flags can be
		1394	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1395	C<IO::AIO::MS_INVALIDATE>.
		1396
		1397	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1398
		1399	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1400	scalars.
		1401
		1402	It touches (reads or writes) all memory pages in the specified
		1403	range inside the scalar. All caveats and parameters are the same
		1404	as for C<aio_msync>, above, except for flags, which must be either
		1405	C<0> (which reads all pages and ensures they are instantiated) or
		1406	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1407	writing an octet from it, which dirties the page).
		1408
		1409	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1410
		1411	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1412	scalars.
		1413
		1414	It reads in all the pages of the underlying storage into memory (if any)
		1415	and locks them, so they are not getting swapped/paged out or removed.
		1416
		1417	If C<$length> is undefined, then the scalar will be locked till the end.
		1418
		1419	On systems that do not implement C<mlock>, this function returns C<-1>
		1420	and sets errno to C<ENOSYS>.
		1421
		1422	Note that the corresponding C<munlock> is synchronous and is
		1423	documented under L<MISCELLANEOUS FUNCTIONS>.
		1424
		1425	Example: open a file, mmap and mlock it - both will be undone when
		1426	C<$data> gets destroyed.
		1427
		1428	open my $fh, "<", $path or die "$path: $!";
		1429	my $data;
		1430	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1431	aio_mlock $data; # mlock in background
		1432
		1433	=item aio_mlockall $flags, $callback->($status)
		1434
		1435	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1436	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1437
		1438	On systems that do not implement C<mlockall>, this function returns C<-1>
		1439	and sets errno to C<ENOSYS>.
		1440
		1441	Note that the corresponding C<munlockall> is synchronous and is
		1442	documented under L<MISCELLANEOUS FUNCTIONS>.
		1443
		1444	Example: asynchronously lock all current and future pages into memory.
		1445
		1446	aio_mlockall IO::AIO::MCL_FUTURE;
		1447
		1448	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1449
		1450	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1451	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1452	the ioctl is not available on your OS, then this request will fail with
		1453	C<ENOSYS>.
		1454
		1455	C<$start> is the starting offset to query extents for, C<$length> is the
		1456	size of the range to query - if it is C<undef>, then the whole file will
		1457	be queried.
		1458
		1459	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1460	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1461	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1462	the data portion.
		1463
		1464	C<$count> is the maximum number of extent records to return. If it is
		1465	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1466	case, if it is C<0>, then the callback receives the number of extents
		1467	instead of the extents themselves (which is unreliable, see below).
		1468
		1469	If an error occurs, the callback receives no arguments. The special
		1470	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1471
		1472	Otherwise, the callback receives an array reference with extent
		1473	structures. Each extent structure is an array reference itself, with the
		1474	following members:
		1475
		1476	[$logical, $physical, $length, $flags]
		1477
		1478	Flags is any combination of the following flag values (typically either C<0>
		1479	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1480
		1481	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1482	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1483	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1484	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1485	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1486	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1487
		1488	At the time of this writing (Linux 3.2), this request is unreliable unless
		1489	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1490	it to return all extents of a range for files with a large number of
		1491	extents. The code (only) works around all these issues if C<$count> is
		1492	C<undef>.
702		1493
703	=item aio_group $callback->(...)	1494	=item aio_group $callback->(...)
704		1495
705	This is a very special aio request: Instead of doing something, it is a	1496	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	1497	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	1535	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.	1536	except to put your application under artificial I/O pressure.
746		1537
747	=back	1538	=back
748		1539
		1540
		1541	=head2 IO::AIO::WD - multiple working directories
		1542
		1543	Your process only has one current working directory, which is used by all
		1544	threads. This makes it hard to use relative paths (some other component
		1545	could call C<chdir> at any time, and it is hard to control when the path
		1546	will be used by IO::AIO).
		1547
		1548	One solution for this is to always use absolute paths. This usually works,
		1549	but can be quite slow (the kernel has to walk the whole path on every
		1550	access), and can also be a hassle to implement.
		1551
		1552	Newer POSIX systems have a number of functions (openat, fdopendir,
		1553	futimensat and so on) that make it possible to specify working directories
		1554	per operation.
		1555
		1556	For portability, and because the clowns who "designed", or shall I write,
		1557	perpetrated this new interface were obviously half-drunk, this abstraction
		1558	cannot be perfect, though.
		1559
		1560	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1561	object. This object stores the canonicalised, absolute version of the
		1562	path, and on systems that allow it, also a directory file descriptor.
		1563
		1564	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1565	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1566	object and a pathname instead (or the IO::AIO::WD object alone, which
		1567	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1568	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1569	to that IO::AIO::WD object.
		1570
		1571	For example, to get a wd object for F</etc> and then stat F<passwd>
		1572	inside, you would write:
		1573
		1574	aio_wd "/etc", sub {
		1575	my $etcdir = shift;
		1576
		1577	# although $etcdir can be undef on error, there is generally no reason
		1578	# to check for errors here, as aio_stat will fail with ENOENT
		1579	# when $etcdir is undef.
		1580
		1581	aio_stat [$etcdir, "passwd"], sub {
		1582	# yay
		1583	};
		1584	};
		1585
		1586	The fact that C<aio_wd> is a request and not a normal function shows that
		1587	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1588	which is why it is done asynchronously.
		1589
		1590	To stat the directory obtained with C<aio_wd> above, one could write
		1591	either of the following three request calls:
		1592
		1593	aio_lstat "/etc" , sub { ... # pathname as normal string
		1594	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1595	aio_lstat $wd , sub { ... # shorthand for the previous
		1596
		1597	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1598	object and the pathname string, so you could write the following without
		1599	causing any issues due to C<$path> getting reused:
		1600
		1601	my $path = [$wd, undef];
		1602
		1603	for my $name (qw(abc def ghi)) {
		1604	$path->[1] = $name;
		1605	aio_stat $path, sub {
		1606	# ...
		1607	};
		1608	}
		1609
		1610	There are some caveats: when directories get renamed (or deleted), the
		1611	pathname string doesn't change, so will point to the new directory (or
		1612	nowhere at all), while the directory fd, if available on the system,
		1613	will still point to the original directory. Most functions accepting a
		1614	pathname will use the directory fd on newer systems, and the string on
		1615	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1616	the string form of the pathname.
		1617
		1618	So this functionality is mainly useful to get some protection against
		1619	C<chdir>, to easily get an absolute path out of a relative path for future
		1620	reference, and to speed up doing many operations in the same directory
		1621	(e.g. when stat'ing all files in a directory).
		1622
		1623	The following functions implement this working directory abstraction:
		1624
		1625	=over 4
		1626
		1627	=item aio_wd $pathname, $callback->($wd)
		1628
		1629	Asynchonously canonicalise the given pathname and convert it to an
		1630	IO::AIO::WD object representing it. If possible and supported on the
		1631	system, also open a directory fd to speed up pathname resolution relative
		1632	to this working directory.
		1633
		1634	If something goes wrong, then C<undef> is passwd to the callback instead
		1635	of a working directory object and C<$!> is set appropriately. Since
		1636	passing C<undef> as working directory component of a pathname fails the
		1637	request with C<ENOENT>, there is often no need for error checking in the
		1638	C<aio_wd> callback, as future requests using the value will fail in the
		1639	expected way.
		1640
		1641	=item IO::AIO::CWD
		1642
		1643	This is a compiletime constant (object) that represents the process
		1644	current working directory.
		1645
		1646	Specifying this object as working directory object for a pathname is as if
		1647	the pathname would be specified directly, without a directory object. For
		1648	example, these calls are functionally identical:
		1649
		1650	aio_stat "somefile", sub { ... };
		1651	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1652
		1653	=back
		1654
		1655	To recover the path associated with an IO::AIO::WD object, you can use
		1656	C<aio_realpath>:
		1657
		1658	aio_realpath $wd, sub {
		1659	warn "path is $_[0]\n";
		1660	};
		1661
		1662	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1663	sometimes, fall back to using an absolue path.
		1664
749	=head2 IO::AIO::REQ CLASS	1665	=head2 IO::AIO::REQ CLASS
750		1666
751	All non-aggregate C<aio_*> functions return an object of this class when	1667	All non-aggregate C<aio_*> functions return an object of this class when
752	called in non-void context.	1668	called in non-void context.
753		1669
…		…
756	=item cancel $req	1672	=item cancel $req
757		1673
758	Cancels the request, if possible. Has the effect of skipping execution	1674	Cancels the request, if possible. Has the effect of skipping execution
759	when entering the B<execute> state and skipping calling the callback when	1675	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	1676	entering the the B<result> state, but will leave the request otherwise
761	untouched. That means that requests that currently execute will not be	1677	untouched (with the exception of readdir). That means that requests that
762	stopped and resources held by the request will not be freed prematurely.	1678	currently execute will not be stopped and resources held by the request
		1679	will not be freed prematurely.
763		1680
764	=item cb $req $callback->(...)	1681	=item cb $req $callback->(...)
765		1682
766	Replace (or simply set) the callback registered to the request.	1683	Replace (or simply set) the callback registered to the request.
767		1684
…		…
818	Their lifetime, simplified, looks like this: when they are empty, they	1735	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	1736	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	1737	C<done> state, they will also finish. Otherwise they will continue to
821	exist.	1738	exist.
822		1739
823	That means after creating a group you have some time to add requests. And	1740	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	1741	(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	1742	the C<poll_cb>). And in the callbacks of those requests, you can add
826	itself finish.	1743	further requests to the group. And only when all those requests have
		1744	finished will the the group itself finish.
827		1745
828	=over 4	1746	=over 4
829		1747
830	=item add $grp ...	1748	=item add $grp ...
831		1749
…		…
840	=item $grp->cancel_subs	1758	=item $grp->cancel_subs
841		1759
842	Cancel all subrequests and clears any feeder, but not the group request	1760	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.	1761	itself. Useful when you queued a lot of events but got a result early.
844		1762
		1763	The group request will finish normally (you cannot add requests to the
		1764	group).
		1765
845	=item $grp->result (...)	1766	=item $grp->result (...)
846		1767
847	Set the result value(s) that will be passed to the group callback when all	1768	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	1769	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,	1770	of errno (just like calling C<errno> without an error number). By default,
850	no argument will be passed and errno is zero.	1771	no argument will be passed and errno is zero.
851		1772
852	=item $grp->errno ([$errno])	1773	=item $grp->errno ([$errno])
853		1774
…		…
864	=item feed $grp $callback->($grp)	1785	=item feed $grp $callback->($grp)
865		1786
866	Sets a feeder/generator on this group: every group can have an attached	1787	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,	1788	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,	1789	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	1790	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>	1791	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
871	requests, delaying any later requests for a long time.	1792	requests, delaying any later requests for a long time.
872		1793
873	To avoid this, and allow incremental generation of requests, you can	1794	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	1795	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>,	1796	feed callback will be called whenever there are few enough (see C<limit>,
…		…
880	not impose any limits).	1801	not impose any limits).
881		1802
882	If the feed does not queue more requests when called, it will be	1803	If the feed does not queue more requests when called, it will be
883	automatically removed from the group.	1804	automatically removed from the group.
884		1805
885	If the feed limit is C<0>, it will be set to C<2> automatically.	1806	If the feed limit is C<0> when this method is called, it will be set to
		1807	C<2> automatically.
886		1808
887	Example:	1809	Example:
888		1810
889	# stat all files in @files, but only ever use four aio requests concurrently:	1811	# stat all files in @files, but only ever use four aio requests concurrently:
890		1812
…		…
902	Sets the feeder limit for the group: The feeder will be called whenever	1824	Sets the feeder limit for the group: The feeder will be called whenever
903	the group contains less than this many requests.	1825	the group contains less than this many requests.
904		1826
905	Setting the limit to C<0> will pause the feeding process.	1827	Setting the limit to C<0> will pause the feeding process.
906		1828
		1829	The default value for the limit is C<0>, but note that setting a feeder
		1830	automatically bumps it up to C<2>.
		1831
907	=back	1832	=back
908		1833
909	=head2 SUPPORT FUNCTIONS	1834	=head2 SUPPORT FUNCTIONS
910		1835
911	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1836	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
913	=over 4	1838	=over 4
914		1839
915	=item $fileno = IO::AIO::poll_fileno	1840	=item $fileno = IO::AIO::poll_fileno
916		1841
917	Return the I<request result pipe file descriptor>. This filehandle must be	1842	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	1843	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	1844	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
920	to call C<poll_cb> to check the results.	1845	you have to call C<poll_cb> to check the results.
921		1846
922	See C<poll_cb> for an example.	1847	See C<poll_cb> for an example.
923		1848
924	=item IO::AIO::poll_cb	1849	=item IO::AIO::poll_cb
925		1850
926	Process some outstanding events on the result pipe. You have to call this	1851	Process some requests that have reached the result phase (i.e. they have
927	regularly. Returns the number of events processed. Returns immediately	1852	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	1853	this "regularly" to finish outstanding requests.
929	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
930		1854
		1855	Returns C<0> if all events could be processed (or there were no
		1856	events to process), or C<-1> if it returned earlier for whatever
		1857	reason. Returns immediately when no events are outstanding. The amount
		1858	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1859	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1860
931	If not all requests were processed for whatever reason, the filehandle	1861	If not all requests were processed for whatever reason, the poll file
932	will still be ready when C<poll_cb> returns.	1862	descriptor will still be ready when C<poll_cb> returns, so normally you
		1863	don't have to do anything special to have it called later.
		1864
		1865	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1866	ready, it can be beneficial to call this function from loops which submit
		1867	a lot of requests, to make sure the results get processed when they become
		1868	available and not just when the loop is finished and the event loop takes
		1869	over again. This function returns very fast when there are no outstanding
		1870	requests.
933		1871
934	Example: Install an Event watcher that automatically calls	1872	Example: Install an Event watcher that automatically calls
935	IO::AIO::poll_cb with high priority:	1873	IO::AIO::poll_cb with high priority (more examples can be found in the
		1874	SYNOPSIS section, at the top of this document):
936		1875
937	Event->io (fd => IO::AIO::poll_fileno,	1876	Event->io (fd => IO::AIO::poll_fileno,
938	poll => 'r', async => 1,	1877	poll => 'r', async => 1,
939	cb => \&IO::AIO::poll_cb);	1878	cb => \&IO::AIO::poll_cb);
		1879
		1880	=item IO::AIO::poll_wait
		1881
		1882	Wait until either at least one request is in the result phase or no
		1883	requests are outstanding anymore.
		1884
		1885	This is useful if you want to synchronously wait for some requests to
		1886	become ready, without actually handling them.
		1887
		1888	See C<nreqs> for an example.
		1889
		1890	=item IO::AIO::poll
		1891
		1892	Waits until some requests have been handled.
		1893
		1894	Returns the number of requests processed, but is otherwise strictly
		1895	equivalent to:
		1896
		1897	IO::AIO::poll_wait, IO::AIO::poll_cb
		1898
		1899	=item IO::AIO::flush
		1900
		1901	Wait till all outstanding AIO requests have been handled.
		1902
		1903	Strictly equivalent to:
		1904
		1905	IO::AIO::poll_wait, IO::AIO::poll_cb
		1906	while IO::AIO::nreqs;
940		1907
941	=item IO::AIO::max_poll_reqs $nreqs	1908	=item IO::AIO::max_poll_reqs $nreqs
942		1909
943	=item IO::AIO::max_poll_time $seconds	1910	=item IO::AIO::max_poll_time $seconds
944		1911
…		…
969	# use a low priority so other tasks have priority	1936	# use a low priority so other tasks have priority
970	Event->io (fd => IO::AIO::poll_fileno,	1937	Event->io (fd => IO::AIO::poll_fileno,
971	poll => 'r', nice => 1,	1938	poll => 'r', nice => 1,
972	cb => &IO::AIO::poll_cb);	1939	cb => &IO::AIO::poll_cb);
973		1940
974	=item IO::AIO::poll_wait	1941	=back
975
976	If there are any outstanding requests, wait till the result filehandle
977	becomes ready for reading (simply does a C<select> on the filehandle. This
978	is useful if you want to synchronously wait for some requests to finish).
979
980	See C<nreqs> for an example.
981
982	=item IO::AIO::poll
983
984	Waits until some requests have been handled.
985
986	Returns the number of requests processed, but is otherwise strictly
987	equivalent to:
988
989	IO::AIO::poll_wait, IO::AIO::poll_cb
990	if IO::AIO::nreqs;
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		1942
1001	=head3 CONTROLLING THE NUMBER OF THREADS	1943	=head3 CONTROLLING THE NUMBER OF THREADS
		1944
		1945	=over
1002		1946
1003	=item IO::AIO::min_parallel $nthreads	1947	=item IO::AIO::min_parallel $nthreads
1004		1948
1005	Set the minimum number of AIO threads to C<$nthreads>. The current	1949	Set the minimum number of AIO threads to C<$nthreads>. The current
1006	default is C<8>, which means eight asynchronous operations can execute	1950	default is C<8>, which means eight asynchronous operations can execute
…		…
1034		1978
1035	Under normal circumstances you don't need to call this function.	1979	Under normal circumstances you don't need to call this function.
1036		1980
1037	=item IO::AIO::max_idle $nthreads	1981	=item IO::AIO::max_idle $nthreads
1038		1982
1039	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1983	Limit the number of threads (default: 4) that are allowed to idle
1040	threads that did not get a request to process within 10 seconds). That	1984	(i.e., threads that did not get a request to process within the idle
1041	means if a thread becomes idle while C<$nthreads> other threads are also	1985	timeout (default: 10 seconds). That means if a thread becomes idle while
1042	idle, it will free its resources and exit.	1986	C<$nthreads> other threads are also idle, it will free its resources and
		1987	exit.
1043		1988
1044	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1989	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	1990	to allow for extremely high load situations, but want to free resources
1046	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1991	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1047		1992
1048	The default is probably ok in most situations, especially if thread	1993	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	1994	creation is fast. If thread creation is very slow on your system you might
1050	want to use larger values.	1995	want to use larger values.
1051		1996
		1997	=item IO::AIO::idle_timeout $seconds
		1998
		1999	Sets the minimum idle timeout (default 10) after which worker threads are
		2000	allowed to exit. SEe C<IO::AIO::max_idle>.
		2001
1052	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	2002	=item IO::AIO::max_outstanding $maxreqs
		2003
		2004	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2005	you do queue up more than this number of requests, the next call to
		2006	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2007	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2008	longer exceeded.
		2009
		2010	In other words, this setting does not enforce a queue limit, but can be
		2011	used to make poll functions block if the limit is exceeded.
1053		2012
1054	This is a very bad function to use in interactive programs because it	2013	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	2014	blocks, and a bad way to reduce concurrency because it is inexact: Better
1056	use an C<aio_group> together with a feed callback.	2015	use an C<aio_group> together with a feed callback.
1057		2016
1058	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2017	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	2018	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		2019
1063	The default value is very large, so there is no practical limit on the	2020	IO::AIO::max_outstanding 32;
1064	number of outstanding requests.
1065		2021
1066	You can still queue as many requests as you want. Therefore,	2022	for my $path (...) {
1067	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	2023	aio_stat $path , ...;
1068	as a stop gap to shield against fatal memory overflow (with large values).	2024	IO::AIO::poll_cb;
		2025	}
		2026
		2027	IO::AIO::flush;
		2028
		2029	The call to C<poll_cb> inside the loop will normally return instantly, but
		2030	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2031	some requests have been handled. This keeps the loop from pushing a large
		2032	number of C<aio_stat> requests onto the queue.
		2033
		2034	The default value for C<max_outstanding> is very large, so there is no
		2035	practical limit on the number of outstanding requests.
		2036
		2037	=back
1069		2038
1070	=head3 STATISTICAL INFORMATION	2039	=head3 STATISTICAL INFORMATION
		2040
		2041	=over
1071		2042
1072	=item IO::AIO::nreqs	2043	=item IO::AIO::nreqs
1073		2044
1074	Returns the number of requests currently in the ready, execute or pending	2045	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).	2046	states (i.e. for which their callback has not been invoked yet).
…		…
1089	Returns the number of requests currently in the pending state (executed,	2060	Returns the number of requests currently in the pending state (executed,
1090	but not yet processed by poll_cb).	2061	but not yet processed by poll_cb).
1091		2062
1092	=back	2063	=back
1093		2064
		2065	=head3 MISCELLANEOUS FUNCTIONS
		2066
		2067	IO::AIO implements some functions that are useful when you want to use
		2068	some "Advanced I/O" function not available to in Perl, without going the
		2069	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2070	counterpart.
		2071
		2072	=over 4
		2073
		2074	=item $numfd = IO::AIO::get_fdlimit
		2075
		2076	This function is I<EXPERIMENTAL> and subject to change.
		2077
		2078	Tries to find the current file descriptor limit and returns it, or
		2079	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2080	the highest valid file descriptor number.
		2081
		2082	=item IO::AIO::min_fdlimit [$numfd]
		2083
		2084	This function is I<EXPERIMENTAL> and subject to change.
		2085
		2086	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2087	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2088	is missing, it will try to set a very high limit, although this is not
		2089	recommended when you know the actual minimum that you require.
		2090
		2091	If the limit cannot be raised enough, the function makes a best-effort
		2092	attempt to increase the limit as much as possible, using various
		2093	tricks, while still failing. You can query the resulting limit using
		2094	C<IO::AIO::get_fdlimit>.
		2095
		2096	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2097	true.
		2098
		2099	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2100
		2101	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2102	but is blocking (this makes most sense if you know the input data is
		2103	likely cached already and the output filehandle is set to non-blocking
		2104	operations).
		2105
		2106	Returns the number of bytes copied, or C<-1> on error.
		2107
		2108	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2109
		2110	Simply calls the C<posix_fadvise> function (see its
		2111	manpage for details). The following advice constants are
		2112	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2113	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2114	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2115
		2116	On systems that do not implement C<posix_fadvise>, this function returns
		2117	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2118
		2119	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2120
		2121	Simply calls the C<posix_madvise> function (see its
		2122	manpage for details). The following advice constants are
		2123	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2124	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2125	C<IO::AIO::MADV_DONTNEED>.
		2126
		2127	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2128	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2129	will be reduced to fit into the C<$scalar>.
		2130
		2131	On systems that do not implement C<posix_madvise>, this function returns
		2132	ENOSYS, otherwise the return value of C<posix_madvise>.
		2133
		2134	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2135
		2136	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2137	$scalar (see its manpage for details). The following protect
		2138	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2139	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2140
		2141	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2142	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2143	will be reduced to fit into the C<$scalar>.
		2144
		2145	On systems that do not implement C<mprotect>, this function returns
		2146	ENOSYS, otherwise the return value of C<mprotect>.
		2147
		2148	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2149
		2150	Memory-maps a file (or anonymous memory range) and attaches it to the
		2151	given C<$scalar>, which will act like a string scalar. Returns true on
		2152	success, and false otherwise.
		2153
		2154	The scalar must exist, but its contents do not matter - this means you
		2155	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2156	the scalar first.
		2157
		2158	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2159	which don't change the string length, and most read-only operations such
		2160	as copying it or searching it with regexes and so on.
		2161
		2162	Anything else is unsafe and will, at best, result in memory leaks.
		2163
		2164	The memory map associated with the C<$scalar> is automatically removed
		2165	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2166	or C<IO::AIO::munmap> functions are called on it.
		2167
		2168	This calls the C<mmap>(2) function internally. See your system's manual
		2169	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2170
		2171	The C<$length> must be larger than zero and smaller than the actual
		2172	filesize.
		2173
		2174	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2175	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2176
		2177	C<$flags> can be a combination of
		2178	C<IO::AIO::MAP_SHARED> or
		2179	C<IO::AIO::MAP_PRIVATE>,
		2180	or a number of system-specific flags (when not available, the are C<0>):
		2181	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2182	C<IO::AIO::MAP_LOCKED>,
		2183	C<IO::AIO::MAP_NORESERVE>,
		2184	C<IO::AIO::MAP_POPULATE>,
		2185	C<IO::AIO::MAP_NONBLOCK>,
		2186	C<IO::AIO::MAP_FIXED>,
		2187	C<IO::AIO::MAP_GROWSDOWN>,
		2188	C<IO::AIO::MAP_32BIT>,
		2189	C<IO::AIO::MAP_HUGETLB> or
		2190	C<IO::AIO::MAP_STACK>.
		2191
		2192	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2193
		2194	C<$offset> is the offset from the start of the file - it generally must be
		2195	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2196
		2197	Example:
		2198
		2199	use Digest::MD5;
		2200	use IO::AIO;
		2201
		2202	open my $fh, "<verybigfile"
		2203	or die "$!";
		2204
		2205	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2206	or die "verybigfile: $!";
		2207
		2208	my $fast_md5 = md5 $data;
		2209
		2210	=item IO::AIO::munmap $scalar
		2211
		2212	Removes a previous mmap and undefines the C<$scalar>.
		2213
		2214	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2215
		2216	Calls the C<munlock> function, undoing the effects of a previous
		2217	C<aio_mlock> call (see its description for details).
		2218
		2219	=item IO::AIO::munlockall
		2220
		2221	Calls the C<munlockall> function.
		2222
		2223	On systems that do not implement C<munlockall>, this function returns
		2224	ENOSYS, otherwise the return value of C<munlockall>.
		2225
		2226	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2227
		2228	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2229	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2230	should be the file offset.
		2231
		2232	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2233	silently corrupt the data in this case.
		2234
		2235	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2236	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2237	C<IO::AIO::SPLICE_F_GIFT>.
		2238
		2239	See the C<splice(2)> manpage for details.
		2240
		2241	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2242
		2243	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2244	description for C<IO::AIO::splice> above for details.
		2245
		2246	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2247
		2248	Attempts to query or change the pipe buffer size. Obviously works only
		2249	on pipes, and currently works only on GNU/Linux systems, and fails with
		2250	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2251	size on other systems, drop me a note.
		2252
		2253	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2254
		2255	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2256	C<$flags> is missing or C<0>, then this should be the same as a call to
		2257	perl's built-in C<pipe> function and create a new pipe, and works on
		2258	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2259	(..., 4096, O_BINARY)>.
		2260
		2261	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2262	the given flags (Linux 2.6.27, glibc 2.9).
		2263
		2264	On success, the read and write file handles are returned.
		2265
		2266	On error, nothing will be returned. If the pipe2 syscall is missing and
		2267	C<$flags> is non-zero, fails with C<ENOSYS>.
		2268
		2269	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2270	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2271	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2272
		2273	=back
		2274
1094	=cut	2275	=cut
1095		2276
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;	2277	min_parallel 8;
1113		2278
1114	END {	2279	END { flush }
1115	min_parallel 1;
1116	flush;
1117	};
1118		2280
1119	1;	2281	1;
1120		2282
		2283	=head1 EVENT LOOP INTEGRATION
		2284
		2285	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2286	automatically into many event loops:
		2287
		2288	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2289	use AnyEvent::AIO;
		2290
		2291	You can also integrate IO::AIO manually into many event loops, here are
		2292	some examples of how to do this:
		2293
		2294	# EV integration
		2295	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2296
		2297	# Event integration
		2298	Event->io (fd => IO::AIO::poll_fileno,
		2299	poll => 'r',
		2300	cb => \&IO::AIO::poll_cb);
		2301
		2302	# Glib/Gtk2 integration
		2303	add_watch Glib::IO IO::AIO::poll_fileno,
		2304	in => sub { IO::AIO::poll_cb; 1 };
		2305
		2306	# Tk integration
		2307	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2308	readable => \&IO::AIO::poll_cb);
		2309
		2310	# Danga::Socket integration
		2311	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2312	\&IO::AIO::poll_cb);
		2313
1121	=head2 FORK BEHAVIOUR	2314	=head2 FORK BEHAVIOUR
1122		2315
1123	This module should do "the right thing" when the process using it forks:	2316	Usage of pthreads in a program changes the semantics of fork
		2317	considerably. Specifically, only async-safe functions can be called after
		2318	fork. Perl doesn't know about this, so in general, you cannot call fork
		2319	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2320	pthreads, so this applies, but many other extensions and (for inexplicable
		2321	reasons) perl itself often is linked against pthreads, so this limitation
		2322	applies to quite a lot of perls.
1124		2323
1125	Before the fork, IO::AIO enters a quiescent state where no requests	2324	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	2325	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	2326	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		2327
1133	In short: the parent will, after a short pause, continue as if fork had	2328	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	2329	forking. You could also try to call the L<IO::AIO::reinit> function in the
1135	yet.	2330	child:
		2331
		2332	=over 4
		2333
		2334	=item IO::AIO::reinit
		2335
		2336	Abandons all current requests and I/O threads and simply reinitialises all
		2337	data structures. This is not an operation supported by any standards, but
		2338	happens to work on GNU/Linux and some newer BSD systems.
		2339
		2340	The only reasonable use for this function is to call it after forking, if
		2341	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2342	the process will result in undefined behaviour. Calling it at any time
		2343	will also result in any undefined (by POSIX) behaviour.
		2344
		2345	=back
1136		2346
1137	=head2 MEMORY USAGE	2347	=head2 MEMORY USAGE
1138		2348
1139	Per-request usage:	2349	Per-request usage:
1140		2350
…		…
1142	bytes of memory. In addition, stat requests need a stat buffer (possibly	2352	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	2353	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	2354	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.	2355	will consume memory till the request has entered the done state.
1146		2356
1147	This is now awfully much, so queuing lots of requests is not usually a	2357	This is not awfully much, so queuing lots of requests is not usually a
1148	problem.	2358	problem.
1149		2359
1150	Per-thread usage:	2360	Per-thread usage:
1151		2361
1152	In the execution phase, some aio requests require more memory for	2362	In the execution phase, some aio requests require more memory for
…		…
1157		2367
1158	Known bugs will be fixed in the next release.	2368	Known bugs will be fixed in the next release.
1159		2369
1160	=head1 SEE ALSO	2370	=head1 SEE ALSO
1161		2371
1162	L<Coro::AIO>.	2372	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2373	more natural syntax.
1163		2374
1164	=head1 AUTHOR	2375	=head1 AUTHOR
1165		2376
1166	Marc Lehmann <schmorp@schmorp.de>	2377	Marc Lehmann <schmorp@schmorp.de>
1167	http://home.schmorp.de/	2378	http://home.schmorp.de/

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