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Revision 1.136 by root, Tue Sep 30 14:07:59 2008 UTC vs.
Revision 1.279 by root, Sat Jan 6 01:04:42 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
80	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
81	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
85	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
86	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
87	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.1';	176	our $VERSION = 4.4;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
207		190
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	194	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap munlock munlockall);
		198
		199	push @AIO_REQ, qw(aio_busy); # not exported
213		200
214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
215		202
216	require XSLoader;	203	require XSLoader;
217	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
218	}	205	}
219		206
220	=head1 FUNCTIONS	207	=head1 FUNCTIONS
221		208
222	=head2 AIO REQUEST FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		285
		286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::madvise $scalar, $offset, $length, $advice
		291	IO::AIO::mprotect $scalar, $offset, $length, $protect
		292	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		293	IO::AIO::munlockall
		294
		295	=head2 API NOTES
223		296
224	All the C<aio_*> calls are more or less thin wrappers around the syscall	297	All the C<aio_*> calls are more or less thin wrappers around the syscall
225	with the same name (sans C<aio_>). The arguments are similar or identical,	298	with the same name (sans C<aio_>). The arguments are similar or identical,
226	and they all accept an additional (and optional) C<$callback> argument	299	and they all accept an additional (and optional) C<$callback> argument
227	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
229	perl, which usually delivers "false") as its sole argument after the given	302	of the request will be passed as arguments to the callback (and, if an
230	syscall has been executed asynchronously.	303	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		304	most syscalls return C<-1> on error, unlike perl, which usually delivers
		305	"false").
		306
		307	Some requests (such as C<aio_readdir>) pass the actual results and
		308	communicate failures by passing C<undef>.
231		309
232	All functions expecting a filehandle keep a copy of the filehandle	310	All functions expecting a filehandle keep a copy of the filehandle
233	internally until the request has finished.	311	internally until the request has finished.
234		312
235	All functions return request objects of type L<IO::AIO::REQ> that allow	313	All functions return request objects of type L<IO::AIO::REQ> that allow
236	further manipulation of those requests while they are in-flight.	314	further manipulation of those requests while they are in-flight.
237		315
238	The pathnames you pass to these routines I<must> be absolute and	316	The pathnames you pass to these routines I<should> be absolute. The
239	encoded as octets. The reason for the former is that at the time the	317	reason for this is that at the time the request is being executed, the
240	request is being executed, the current working directory could have	318	current working directory could have changed. Alternatively, you can
241	changed. Alternatively, you can make sure that you never change the	319	make sure that you never change the current working directory anywhere
242	current working directory anywhere in the program and then use relative	320	in the program and then use relative paths. You can also take advantage
243	paths.	321	of IO::AIOs working directory abstraction, that lets you specify paths
		322	relative to some previously-opened "working directory object" - see the
		323	description of the C<IO::AIO::WD> class later in this document.
244		324
245	To encode pathnames as octets, either make sure you either: a) always pass	325	To encode pathnames as octets, either make sure you either: a) always pass
246	in filenames you got from outside (command line, readdir etc.) without	326	in filenames you got from outside (command line, readdir etc.) without
247	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	327	tinkering, b) are in your native filesystem encoding, c) use the Encode
248	your pathnames to the locale (or other) encoding in effect in the user	328	module and encode your pathnames to the locale (or other) encoding in
249	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	329	effect in the user environment, d) use Glib::filename_from_unicode on
250	use something else to ensure your scalar has the correct contents.	330	unicode filenames or e) use something else to ensure your scalar has the
		331	correct contents.
251		332
252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	333	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
253	handles correctly whether it is set or not.	334	handles correctly whether it is set or not.
		335
		336	=head2 AIO REQUEST FUNCTIONS
254		337
255	=over 4	338	=over 4
256		339
257	=item $prev_pri = aioreq_pri [$pri]	340	=item $prev_pri = aioreq_pri [$pri]
258		341
…		…
288		371
289		372
290	=item aio_open $pathname, $flags, $mode, $callback->($fh)	373	=item aio_open $pathname, $flags, $mode, $callback->($fh)
291		374
292	Asynchronously open or create a file and call the callback with a newly	375	Asynchronously open or create a file and call the callback with a newly
293	created filehandle for the file.	376	created filehandle for the file (or C<undef> in case of an error).
294		377
295	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	378	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
296	for an explanation.	379	for an explanation.
297		380
298	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	381	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
305	by the umask in effect then the request is being executed, so better never	388	by the umask in effect then the request is being executed, so better never
306	change the umask.	389	change the umask.
307		390
308	Example:	391	Example:
309		392
310	aio_open "/etc/passwd", O_RDONLY, 0, sub {	393	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
311	if ($_[0]) {	394	if ($_[0]) {
312	print "open successful, fh is $_[0]\n";	395	print "open successful, fh is $_[0]\n";
313	...	396	...
314	} else {	397	} else {
315	die "open failed: $!\n";	398	die "open failed: $!\n";
316	}	399	}
317	};	400	};
318		401
		402	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		403	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		404	following POSIX and non-POSIX constants are available (missing ones on
		405	your system are, as usual, C<0>):
		406
		407	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		408	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		409	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		410
319		411
320	=item aio_close $fh, $callback->($status)	412	=item aio_close $fh, $callback->($status)
321		413
322	Asynchronously close a file and call the callback with the result	414	Asynchronously close a file and call the callback with the result
323	code.	415	code.
…		…
332	Or in other words: the file descriptor will be closed, but it will not be	424	Or in other words: the file descriptor will be closed, but it will not be
333	free for reuse until the perl filehandle is closed.	425	free for reuse until the perl filehandle is closed.
334		426
335	=cut	427	=cut
336		428
		429	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		430
		431	Seeks the filehandle to the new C<$offset>, similarly to perl's
		432	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		433	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		434	C<IO::AIO::SEEK_END>).
		435
		436	The resulting absolute offset will be passed to the callback, or C<-1> in
		437	case of an error.
		438
		439	In theory, the C<$whence> constants could be different than the
		440	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		441	so don't panic.
		442
		443	As a GNU/Linux (and maybe Solaris) extension, also the constants
		444	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		445	could be found. No guarantees about suitability for use in C<aio_seek> or
		446	Perl's C<sysseek> can be made though, although I would naively assume they
		447	"just work".
		448
337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
338		450
339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	451	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		452
341	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>	453	Reads or writes C<$length> bytes from or to the specified C<$fh> and
342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	454	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
343	callback without the actual number of bytes read (or -1 on error, just	455	calls the callback with the actual number of bytes transferred (or -1 on
344	like the syscall).	456	error, just like the syscall).
		457
		458	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		459	offset plus the actual number of bytes read.
345		460
346	If C<$offset> is undefined, then the current file descriptor offset will	461	If C<$offset> is undefined, then the current file descriptor offset will
347	be used (and updated), otherwise the file descriptor offset will not be	462	be used (and updated), otherwise the file descriptor offset will not be
348	changed by these calls.	463	changed by these calls.
349		464
350	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	465	If C<$length> is undefined in C<aio_write>, use the remaining length of
		466	C<$data>.
351		467
352	If C<$dataoffset> is less than zero, it will be counted from the end of	468	If C<$dataoffset> is less than zero, it will be counted from the end of
353	C<$data>.	469	C<$data>.
354		470
355	The C<$data> scalar I<MUST NOT> be modified in any way while the request	471	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
369		485
370	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	486	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
371	reading at byte offset C<$in_offset>, and starts writing at the current	487	reading at byte offset C<$in_offset>, and starts writing at the current
372	file offset of C<$out_fh>. Because of that, it is not safe to issue more	488	file offset of C<$out_fh>. Because of that, it is not safe to issue more
373	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	489	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
374	other.	490	other. The same C<$in_fh> works fine though, as this function does not
		491	move or use the file offset of C<$in_fh>.
375		492
		493	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		494	are written, and there is no way to find out how many more bytes have been
		495	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		496	number of bytes written to C<$out_fh>. Only if the result value equals
		497	C<$length> one can assume that C<$length> bytes have been read.
		498
		499	Unlike with other C<aio_> functions, it makes a lot of sense to use
		500	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		501	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		502	the socket I/O will be non-blocking. Note, however, that you can run
		503	into a trap where C<aio_sendfile> reads some data with readahead, then
		504	fails to write all data, and when the socket is ready the next time, the
		505	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		506	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		507	resource usage.
		508
376	This call tries to make use of a native C<sendfile> syscall to provide	509	This call tries to make use of a native C<sendfile>-like syscall to
377	zero-copy operation. For this to work, C<$out_fh> should refer to a	510	provide zero-copy operation. For this to work, C<$out_fh> should refer to
378	socket, and C<$in_fh> should refer to mmap'able file.	511	a socket, and C<$in_fh> should refer to an mmap'able file.
379		512
380	If the native sendfile call fails or is not implemented, it will be	513	If a native sendfile cannot be found or it fails with C<ENOSYS>,
381	emulated, so you can call C<aio_sendfile> on any type of filehandle	514	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		515	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
382	regardless of the limitations of the operating system.	516	type of filehandle regardless of the limitations of the operating system.
383		517
384	Please note, however, that C<aio_sendfile> can read more bytes from	518	As native sendfile syscalls (as practically any non-POSIX interface hacked
385	C<$in_fh> than are written, and there is no way to find out how many	519	together in a hurry to improve benchmark numbers) tend to be rather buggy
386	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	520	on many systems, this implementation tries to work around some known bugs
387	provides the number of bytes written to C<$out_fh>. Only if the result	521	in Linux and FreeBSD kernels (probably others, too), but that might fail,
388	value equals C<$length> one can assume that C<$length> bytes have been	522	so you really really should check the return value of C<aio_sendfile> -
389	read.	523	fewer bytes than expected might have been transferred.
390		524
391		525
392	=item aio_readahead $fh,$offset,$length, $callback->($retval)	526	=item aio_readahead $fh,$offset,$length, $callback->($retval)
393		527
394	C<aio_readahead> populates the page cache with data from a file so that	528	C<aio_readahead> populates the page cache with data from a file so that
…		…
398	whole pages, so that offset is effectively rounded down to a page boundary	532	whole pages, so that offset is effectively rounded down to a page boundary
399	and bytes are read up to the next page boundary greater than or equal to	533	and bytes are read up to the next page boundary greater than or equal to
400	(off-set+length). C<aio_readahead> does not read beyond the end of the	534	(off-set+length). C<aio_readahead> does not read beyond the end of the
401	file. The current file offset of the file is left unchanged.	535	file. The current file offset of the file is left unchanged.
402		536
403	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	537	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
404	emulated by simply reading the data, which would have a similar effect.	538	be emulated by simply reading the data, which would have a similar effect.
405		539
406		540
407	=item aio_stat $fh_or_path, $callback->($status)	541	=item aio_stat $fh_or_path, $callback->($status)
408		542
409	=item aio_lstat $fh, $callback->($status)	543	=item aio_lstat $fh, $callback->($status)
…		…
416	for an explanation.	550	for an explanation.
417		551
418	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	552	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
419	error when stat'ing a large file, the results will be silently truncated	553	error when stat'ing a large file, the results will be silently truncated
420	unless perl itself is compiled with large file support.	554	unless perl itself is compiled with large file support.
		555
		556	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		557	following constants and functions (if not implemented, the constants will
		558	be C<0> and the functions will either C<croak> or fall back on traditional
		559	behaviour).
		560
		561	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		562	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		563	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
421		564
422	Example: Print the length of F</etc/passwd>:	565	Example: Print the length of F</etc/passwd>:
423		566
424	aio_stat "/etc/passwd", sub {	567	aio_stat "/etc/passwd", sub {
425	$_[0] and die "stat failed: $!";	568	$_[0] and die "stat failed: $!";
426	print "size is ", -s _, "\n";	569	print "size is ", -s _, "\n";
427	};	570	};
428		571
429		572
		573	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		574
		575	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		576	whether a file handle or path was passed.
		577
		578	On success, the callback is passed a hash reference with the following
		579	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		580	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		581	is passed.
		582
		583	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		584	C<ST_NOSUID>.
		585
		586	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		587	their correct value when available, or to C<0> on systems that do
		588	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		589	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		590	C<ST_NODIRATIME> and C<ST_RELATIME>.
		591
		592	Example: stat C</wd> and dump out the data if successful.
		593
		594	aio_statvfs "/wd", sub {
		595	my $f = $_[0]
		596	or die "statvfs: $!";
		597
		598	use Data::Dumper;
		599	say Dumper $f;
		600	};
		601
		602	# result:
		603	{
		604	bsize => 1024,
		605	bfree => 4333064312,
		606	blocks => 10253828096,
		607	files => 2050765568,
		608	flag => 4096,
		609	favail => 2042092649,
		610	bavail => 4333064312,
		611	ffree => 2042092649,
		612	namemax => 255,
		613	frsize => 1024,
		614	fsid => 1810
		615	}
		616
		617	Here is a (likely partial - send me updates!) list of fsid values used by
		618	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		619
		620	0x0000adf5 adfs
		621	0x0000adff affs
		622	0x5346414f afs
		623	0x09041934 anon-inode filesystem
		624	0x00000187 autofs
		625	0x42465331 befs
		626	0x1badface bfs
		627	0x42494e4d binfmt_misc
		628	0x9123683e btrfs
		629	0x0027e0eb cgroupfs
		630	0xff534d42 cifs
		631	0x73757245 coda
		632	0x012ff7b7 coh
		633	0x28cd3d45 cramfs
		634	0x453dcd28 cramfs-wend (wrong endianness)
		635	0x64626720 debugfs
		636	0x00001373 devfs
		637	0x00001cd1 devpts
		638	0x0000f15f ecryptfs
		639	0x00414a53 efs
		640	0x0000137d ext
		641	0x0000ef53 ext2/ext3/ext4
		642	0x0000ef51 ext2
		643	0xf2f52010 f2fs
		644	0x00004006 fat
		645	0x65735546 fuseblk
		646	0x65735543 fusectl
		647	0x0bad1dea futexfs
		648	0x01161970 gfs2
		649	0x47504653 gpfs
		650	0x00004244 hfs
		651	0xf995e849 hpfs
		652	0x00c0ffee hostfs
		653	0x958458f6 hugetlbfs
		654	0x2bad1dea inotifyfs
		655	0x00009660 isofs
		656	0x000072b6 jffs2
		657	0x3153464a jfs
		658	0x6b414653 k-afs
		659	0x0bd00bd0 lustre
		660	0x0000137f minix
		661	0x0000138f minix 30 char names
		662	0x00002468 minix v2
		663	0x00002478 minix v2 30 char names
		664	0x00004d5a minix v3
		665	0x19800202 mqueue
		666	0x00004d44 msdos
		667	0x0000564c novell
		668	0x00006969 nfs
		669	0x6e667364 nfsd
		670	0x00003434 nilfs
		671	0x5346544e ntfs
		672	0x00009fa1 openprom
		673	0x7461636F ocfs2
		674	0x00009fa0 proc
		675	0x6165676c pstorefs
		676	0x0000002f qnx4
		677	0x68191122 qnx6
		678	0x858458f6 ramfs
		679	0x52654973 reiserfs
		680	0x00007275 romfs
		681	0x67596969 rpc_pipefs
		682	0x73636673 securityfs
		683	0xf97cff8c selinux
		684	0x0000517b smb
		685	0x534f434b sockfs
		686	0x73717368 squashfs
		687	0x62656572 sysfs
		688	0x012ff7b6 sysv2
		689	0x012ff7b5 sysv4
		690	0x01021994 tmpfs
		691	0x15013346 udf
		692	0x00011954 ufs
		693	0x54190100 ufs byteswapped
		694	0x00009fa2 usbdevfs
		695	0x01021997 v9fs
		696	0xa501fcf5 vxfs
		697	0xabba1974 xenfs
		698	0x012ff7b4 xenix
		699	0x58465342 xfs
		700	0x012fd16d xia
		701
430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	702	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
431		703
432	Works like perl's C<utime> function (including the special case of $atime	704	Works like perl's C<utime> function (including the special case of $atime
433	and $mtime being undef). Fractional times are supported if the underlying	705	and $mtime being undef). Fractional times are supported if the underlying
434	syscalls support them.	706	syscalls support them.
…		…
461	=item aio_truncate $fh_or_path, $offset, $callback->($status)	733	=item aio_truncate $fh_or_path, $offset, $callback->($status)
462		734
463	Works like truncate(2) or ftruncate(2).	735	Works like truncate(2) or ftruncate(2).
464		736
465		737
		738	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		739
		740	Allocates or frees disk space according to the C<$mode> argument. See the
		741	linux C<fallocate> documentation for details.
		742
		743	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		744	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		745	to deallocate a file range.
		746
		747	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		748	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		749	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		750	to unshare shared blocks (see your L<fallocate(2)> manpage).
		751
		752	The file system block size used by C<fallocate> is presumably the
		753	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		754	can dictate other limitations.
		755
		756	If C<fallocate> isn't available or cannot be emulated (currently no
		757	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		758
		759
466	=item aio_chmod $fh_or_path, $mode, $callback->($status)	760	=item aio_chmod $fh_or_path, $mode, $callback->($status)
467		761
468	Works like perl's C<chmod> function.	762	Works like perl's C<chmod> function.
469		763
470		764
…		…
472		766
473	Asynchronously unlink (delete) a file and call the callback with the	767	Asynchronously unlink (delete) a file and call the callback with the
474	result code.	768	result code.
475		769
476		770
477	=item aio_mknod $path, $mode, $dev, $callback->($status)	771	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
478		772
479	[EXPERIMENTAL]	773	[EXPERIMENTAL]
480		774
481	Asynchronously create a device node (or fifo). See mknod(2).	775	Asynchronously create a device node (or fifo). See mknod(2).
482		776
483	The only (POSIX-) portable way of calling this function is:	777	The only (POSIX-) portable way of calling this function is:
484		778
485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	779	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
486		780
		781	See C<aio_stat> for info about some potentially helpful extra constants
		782	and functions.
487		783
488	=item aio_link $srcpath, $dstpath, $callback->($status)	784	=item aio_link $srcpath, $dstpath, $callback->($status)
489		785
490	Asynchronously create a new link to the existing object at C<$srcpath> at	786	Asynchronously create a new link to the existing object at C<$srcpath> at
491	the path C<$dstpath> and call the callback with the result code.	787	the path C<$dstpath> and call the callback with the result code.
…		…
495		791
496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	792	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	793	the path C<$dstpath> and call the callback with the result code.
498		794
499		795
500	=item aio_readlink $path, $callback->($link)	796	=item aio_readlink $pathname, $callback->($link)
501		797
502	Asynchronously read the symlink specified by C<$path> and pass it to	798	Asynchronously read the symlink specified by C<$path> and pass it to
503	the callback. If an error occurs, nothing or undef gets passed to the	799	the callback. If an error occurs, nothing or undef gets passed to the
504	callback.	800	callback.
505		801
506		802
		803	=item aio_realpath $pathname, $callback->($path)
		804
		805	Asynchronously make the path absolute and resolve any symlinks in
		806	C<$path>. The resulting path only consists of directories (same as
		807	L<Cwd::realpath>).
		808
		809	This request can be used to get the absolute path of the current working
		810	directory by passing it a path of F<.> (a single dot).
		811
		812
507	=item aio_rename $srcpath, $dstpath, $callback->($status)	813	=item aio_rename $srcpath, $dstpath, $callback->($status)
508		814
509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	815	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
510	rename(2) and call the callback with the result code.	816	rename(2) and call the callback with the result code.
		817
		818	On systems that support the AIO::WD working directory abstraction
		819	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		820	of failing, C<rename> is called on the absolute path of C<$wd>.
		821
		822
		823	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		824
		825	Basically a version of C<aio_rename> with an additional C<$flags>
		826	argument. Calling this with C<$flags=0> is the same as calling
		827	C<aio_rename>.
		828
		829	Non-zero flags are currently only supported on GNU/Linux systems that
		830	support renameat2. Other systems fail with C<ENOSYS> in this case.
		831
		832	The following constants are available (missing ones are, as usual C<0>),
		833	see renameat2(2) for details:
		834
		835	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		836	and C<IO::AIO::RENAME_WHITEOUT>.
511		837
512		838
513	=item aio_mkdir $pathname, $mode, $callback->($status)	839	=item aio_mkdir $pathname, $mode, $callback->($status)
514		840
515	Asynchronously mkdir (create) a directory and call the callback with	841	Asynchronously mkdir (create) a directory and call the callback with
…		…
520	=item aio_rmdir $pathname, $callback->($status)	846	=item aio_rmdir $pathname, $callback->($status)
521		847
522	Asynchronously rmdir (delete) a directory and call the callback with the	848	Asynchronously rmdir (delete) a directory and call the callback with the
523	result code.	849	result code.
524		850
		851	On systems that support the AIO::WD working directory abstraction
		852	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		853	C<rmdir> is called on the absolute path of C<$wd>.
		854
525		855
526	=item aio_readdir $pathname, $callback->($entries)	856	=item aio_readdir $pathname, $callback->($entries)
527		857
528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	858	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
529	directory (i.e. opendir + readdir + closedir). The entries will not be	859	directory (i.e. opendir + readdir + closedir). The entries will not be
530	sorted, and will B<NOT> include the C<.> and C<..> entries.	860	sorted, and will B<NOT> include the C<.> and C<..> entries.
531		861
532	The callback a single argument which is either C<undef> or an array-ref	862	The callback is passed a single argument which is either C<undef> or an
533	with the filenames.	863	array-ref with the filenames.
534		864
535		865
		866	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		867
		868	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		869	tune behaviour and output format. In case of an error, C<$entries> will be
		870	C<undef>.
		871
		872	The flags are a combination of the following constants, ORed together (the
		873	flags will also be passed to the callback, possibly modified):
		874
		875	=over 4
		876
		877	=item IO::AIO::READDIR_DENTS
		878
		879	When this flag is off, then the callback gets an arrayref consisting of
		880	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		881	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		882	entry in more detail.
		883
		884	C<$name> is the name of the entry.
		885
		886	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		887
		888	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		889	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		890	C<IO::AIO::DT_WHT>.
		891
		892	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		893	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		894	scalars are read-only: you can not modify them.
		895
		896	C<$inode> is the inode number (which might not be exact on systems with 64
		897	bit inode numbers and 32 bit perls). This field has unspecified content on
		898	systems that do not deliver the inode information.
		899
		900	=item IO::AIO::READDIR_DIRS_FIRST
		901
		902	When this flag is set, then the names will be returned in an order where
		903	likely directories come first, in optimal stat order. This is useful when
		904	you need to quickly find directories, or you want to find all directories
		905	while avoiding to stat() each entry.
		906
		907	If the system returns type information in readdir, then this is used
		908	to find directories directly. Otherwise, likely directories are names
		909	beginning with ".", or otherwise names with no dots, of which names with
		910	short names are tried first.
		911
		912	=item IO::AIO::READDIR_STAT_ORDER
		913
		914	When this flag is set, then the names will be returned in an order
		915	suitable for stat()'ing each one. That is, when you plan to stat()
		916	all files in the given directory, then the returned order will likely
		917	be fastest.
		918
		919	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		920	the likely dirs come first, resulting in a less optimal stat order.
		921
		922	=item IO::AIO::READDIR_FOUND_UNKNOWN
		923
		924	This flag should not be set when calling C<aio_readdirx>. Instead, it
		925	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		926	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		927	C<$type>'s are known, which can be used to speed up some algorithms.
		928
		929	=back
		930
		931
		932	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		933
		934	Opens, reads and closes the given file. The data is put into C<$data>,
		935	which is resized as required.
		936
		937	If C<$offset> is negative, then it is counted from the end of the file.
		938
		939	If C<$length> is zero, then the remaining length of the file is
		940	used. Also, in this case, the same limitations to modifying C<$data> apply
		941	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		942	with C<substr>. If the size of the file is known, specifying a non-zero
		943	C<$length> results in a performance advantage.
		944
		945	This request is similar to the older C<aio_load> request, but since it is
		946	a single request, it might be more efficient to use.
		947
		948	Example: load F</etc/passwd> into C<$passwd>.
		949
		950	my $passwd;
		951	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		952	$_[0] >= 0
		953	or die "/etc/passwd: $!\n";
		954
		955	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		956	print $passwd;
		957	};
		958	IO::AIO::flush;
		959
		960
536	=item aio_load $path, $data, $callback->($status)	961	=item aio_load $pathname, $data, $callback->($status)
537		962
538	This is a composite request that tries to fully load the given file into	963	This is a composite request that tries to fully load the given file into
539	memory. Status is the same as with aio_read.	964	memory. Status is the same as with aio_read.
		965
		966	Using C<aio_slurp> might be more efficient, as it is a single request.
540		967
541	=cut	968	=cut
542		969
543	sub aio_load($$;$) {	970	sub aio_load($$;$) {
544	my ($path, undef, $cb) = @_;	971	my ($path, undef, $cb) = @_;
…		…
563		990
564	=item aio_copy $srcpath, $dstpath, $callback->($status)	991	=item aio_copy $srcpath, $dstpath, $callback->($status)
565		992
566	Try to copy the I<file> (directories not supported as either source or	993	Try to copy the I<file> (directories not supported as either source or
567	destination) from C<$srcpath> to C<$dstpath> and call the callback with	994	destination) from C<$srcpath> to C<$dstpath> and call the callback with
568	the C<0> (error) or C<-1> ok.	995	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		996
		997	Existing destination files will be truncated.
569		998
570	This is a composite request that creates the destination file with	999	This is a composite request that creates the destination file with
571	mode 0200 and copies the contents of the source file into it using	1000	mode 0200 and copies the contents of the source file into it using
572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	1001	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
573	uid/gid, in that order.	1002	uid/gid, in that order.
…		…
585	my $grp = aio_group $cb;	1014	my $grp = aio_group $cb;
586		1015
587	aioreq_pri $pri;	1016	aioreq_pri $pri;
588	add $grp aio_open $src, O_RDONLY, 0, sub {	1017	add $grp aio_open $src, O_RDONLY, 0, sub {
589	if (my $src_fh = $_[0]) {	1018	if (my $src_fh = $_[0]) {
590	my @stat = stat $src_fh;	1019	my @stat = stat $src_fh; # hmm, might block over nfs?
591		1020
592	aioreq_pri $pri;	1021	aioreq_pri $pri;
593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	1022	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
594	if (my $dst_fh = $_[0]) {	1023	if (my $dst_fh = $_[0]) {
595	aioreq_pri $pri;	1024	aioreq_pri $pri;
596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	1025	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
597	if ($_[0] == $stat[7]) {	1026	if ($_[0] == $stat[7]) {
598	$grp->result (0);	1027	$grp->result (0);
599	close $src_fh;	1028	close $src_fh;
600		1029
601	# those should not normally block. should. should.	1030	my $ch = sub {
602	utime $stat[8], $stat[9], $dst;	1031	aioreq_pri $pri;
603	chmod $stat[2] & 07777, $dst_fh;	1032	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
604	chown $stat[4], $stat[5], $dst_fh;	1033	aioreq_pri $pri;
		1034	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		1035	aioreq_pri $pri;
		1036	add $grp aio_close $dst_fh;
		1037	}
		1038	};
		1039	};
605		1040
606	aioreq_pri $pri;	1041	aioreq_pri $pri;
607	add $grp aio_close $dst_fh;	1042	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1043	if ($_[0] < 0 && $! == ENOSYS) {
		1044	aioreq_pri $pri;
		1045	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1046	} else {
		1047	$ch->();
		1048	}
		1049	};
608	} else {	1050	} else {
609	$grp->result (-1);	1051	$grp->result (-1);
610	close $src_fh;	1052	close $src_fh;
611	close $dst_fh;	1053	close $dst_fh;
612		1054
…		…
629		1071
630	=item aio_move $srcpath, $dstpath, $callback->($status)	1072	=item aio_move $srcpath, $dstpath, $callback->($status)
631		1073
632	Try to move the I<file> (directories not supported as either source or	1074	Try to move the I<file> (directories not supported as either source or
633	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1075	destination) from C<$srcpath> to C<$dstpath> and call the callback with
634	the C<0> (error) or C<-1> ok.	1076	a status of C<0> (ok) or C<-1> (error, see C<$!>).
635		1077
636	This is a composite request that tries to rename(2) the file first. If	1078	This is a composite request that tries to rename(2) the file first; if
637	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1079	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
638	that is successful, unlinking the C<$srcpath>.	1080	that is successful, unlinks the C<$srcpath>.
639		1081
640	=cut	1082	=cut
641		1083
642	sub aio_move($$;$) {	1084	sub aio_move($$;$) {
643	my ($src, $dst, $cb) = @_;	1085	my ($src, $dst, $cb) = @_;
…		…
650	if ($_[0] && $! == EXDEV) {	1092	if ($_[0] && $! == EXDEV) {
651	aioreq_pri $pri;	1093	aioreq_pri $pri;
652	add $grp aio_copy $src, $dst, sub {	1094	add $grp aio_copy $src, $dst, sub {
653	$grp->result ($_[0]);	1095	$grp->result ($_[0]);
654		1096
655	if (!$_[0]) {	1097	unless ($_[0]) {
656	aioreq_pri $pri;	1098	aioreq_pri $pri;
657	add $grp aio_unlink $src;	1099	add $grp aio_unlink $src;
658	}	1100	}
659	};	1101	};
660	} else {	1102	} else {
…		…
663	};	1105	};
664		1106
665	$grp	1107	$grp
666	}	1108	}
667		1109
668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1110	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
669		1111
670	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1112	Scans a directory (similar to C<aio_readdir>) but additionally tries to
671	efficiently separate the entries of directory C<$path> into two sets of	1113	efficiently separate the entries of directory C<$path> into two sets of
672	names, directories you can recurse into (directories), and ones you cannot	1114	names, directories you can recurse into (directories), and ones you cannot
673	recurse into (everything else, including symlinks to directories).	1115	recurse into (everything else, including symlinks to directories).
674		1116
675	C<aio_scandir> is a composite request that creates of many sub requests_	1117	C<aio_scandir> is a composite request that generates many sub requests.
676	C<$maxreq> specifies the maximum number of outstanding aio requests that	1118	C<$maxreq> specifies the maximum number of outstanding aio requests that
677	this function generates. If it is C<< <= 0 >>, then a suitable default	1119	this function generates. If it is C<< <= 0 >>, then a suitable default
678	will be chosen (currently 4).	1120	will be chosen (currently 4).
679		1121
680	On error, the callback is called without arguments, otherwise it receives	1122	On error, the callback is called without arguments, otherwise it receives
…		…
690		1132
691	Implementation notes.	1133	Implementation notes.
692		1134
693	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1135	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
694		1136
		1137	If readdir returns file type information, then this is used directly to
		1138	find directories.
		1139
695	After reading the directory, the modification time, size etc. of the	1140	Otherwise, after reading the directory, the modification time, size etc.
696	directory before and after the readdir is checked, and if they match (and	1141	of the directory before and after the readdir is checked, and if they
697	isn't the current time), the link count will be used to decide how many	1142	match (and isn't the current time), the link count will be used to decide
698	entries are directories (if >= 2). Otherwise, no knowledge of the number	1143	how many entries are directories (if >= 2). Otherwise, no knowledge of the
699	of subdirectories will be assumed.	1144	number of subdirectories will be assumed.
700		1145
701	Then entries will be sorted into likely directories (everything without	1146	Then entries will be sorted into likely directories a non-initial dot
702	a non-initial dot currently) and likely non-directories (everything	1147	currently) and likely non-directories (see C<aio_readdirx>). Then every
703	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1148	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
704	likely directories first. If that succeeds, it assumes that the entry	1149	in order of their inode numbers. If that succeeds, it assumes that the
705	is a directory or a symlink to directory (which will be checked	1150	entry is a directory or a symlink to directory (which will be checked
706	seperately). This is often faster than stat'ing the entry itself because	1151	separately). This is often faster than stat'ing the entry itself because
707	filesystems might detect the type of the entry without reading the inode	1152	filesystems might detect the type of the entry without reading the inode
708	data (e.g. ext2fs filetype feature).	1153	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1154	the filetype information on readdir.
709		1155
710	If the known number of directories (link count - 2) has been reached, the	1156	If the known number of directories (link count - 2) has been reached, the
711	rest of the entries is assumed to be non-directories.	1157	rest of the entries is assumed to be non-directories.
712		1158
713	This only works with certainty on POSIX (= UNIX) filesystems, which	1159	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
726		1172
727	my $grp = aio_group $cb;	1173	my $grp = aio_group $cb;
728		1174
729	$maxreq = 4 if $maxreq <= 0;	1175	$maxreq = 4 if $maxreq <= 0;
730		1176
731	# stat once	1177	# get a wd object
732	aioreq_pri $pri;	1178	aioreq_pri $pri;
733	add $grp aio_stat $path, sub {	1179	add $grp aio_wd $path, sub {
		1180	$_[0]
734	return $grp->result () if $_[0];	1181	or return $grp->result ();
735	my $now = time;
736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
737		1182
738	# read the directory entries	1183	my $wd = [shift, "."];
		1184
		1185	# stat once
739	aioreq_pri $pri;	1186	aioreq_pri $pri;
740	add $grp aio_readdir $path, sub {	1187	add $grp aio_stat $wd, sub {
741	my $entries = shift
742	or return $grp->result ();	1188	return $grp->result () if $_[0];
		1189	my $now = time;
		1190	my $hash1 = join ":", (stat _)[0,1,3,7,9];
743		1191
744	# stat the dir another time	1192	# read the directory entries
745	aioreq_pri $pri;	1193	aioreq_pri $pri;
		1194	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1195	my $entries = shift
		1196	or return $grp->result ();
		1197
		1198	# stat the dir another time
		1199	aioreq_pri $pri;
746	add $grp aio_stat $path, sub {	1200	add $grp aio_stat $wd, sub {
747	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1201	my $hash2 = join ":", (stat _)[0,1,3,7,9];
748		1202
749	my $ndirs;	1203	my $ndirs;
750		1204
751	# take the slow route if anything looks fishy	1205	# take the slow route if anything looks fishy
752	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1206	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
753	$ndirs = -1;	1207	$ndirs = -1;
754	} else {	1208	} else {
755	# if nlink == 2, we are finished	1209	# if nlink == 2, we are finished
756	# on non-posix-fs's, we rely on nlink < 2	1210	# for non-posix-fs's, we rely on nlink < 2
757	$ndirs = (stat _)[3] - 2	1211	$ndirs = (stat _)[3] - 2
758	or return $grp->result ([], $entries);	1212	or return $grp->result ([], $entries);
759	}	1213	}
760		1214
761	# sort into likely dirs and likely nondirs
762	# dirs == files without ".", short entries first
763	$entries = [map $_->[0],
764	sort { $b->[1] cmp $a->[1] }
765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
766	@$entries];
767
768	my (@dirs, @nondirs);	1215	my (@dirs, @nondirs);
769		1216
770	my $statgrp = add $grp aio_group sub {	1217	my $statgrp = add $grp aio_group sub {
771	$grp->result (\@dirs, \@nondirs);	1218	$grp->result (\@dirs, \@nondirs);
772	};	1219	};
773		1220
774	limit $statgrp $maxreq;	1221	limit $statgrp $maxreq;
775	feed $statgrp sub {	1222	feed $statgrp sub {
776	return unless @$entries;	1223	return unless @$entries;
777	my $entry = pop @$entries;	1224	my $entry = shift @$entries;
778		1225
779	aioreq_pri $pri;	1226	aioreq_pri $pri;
		1227	$wd->[1] = "$entry/.";
780	add $statgrp aio_stat "$path/$entry/.", sub {	1228	add $statgrp aio_stat $wd, sub {
781	if ($_[0] < 0) {	1229	if ($_[0] < 0) {
782	push @nondirs, $entry;	1230	push @nondirs, $entry;
783	} else {	1231	} else {
784	# need to check for real directory	1232	# need to check for real directory
785	aioreq_pri $pri;	1233	aioreq_pri $pri;
		1234	$wd->[1] = $entry;
786	add $statgrp aio_lstat "$path/$entry", sub {	1235	add $statgrp aio_lstat $wd, sub {
787	if (-d _) {	1236	if (-d _) {
788	push @dirs, $entry;	1237	push @dirs, $entry;
789		1238
790	unless (--$ndirs) {	1239	unless (--$ndirs) {
791	push @nondirs, @$entries;	1240	push @nondirs, @$entries;
792	feed $statgrp;	1241	feed $statgrp;
		1242	}
		1243	} else {
		1244	push @nondirs, $entry;
793	}	1245	}
794	} else {
795	push @nondirs, $entry;
796	}	1246	}
797	}	1247	}
798	}	1248	};
799	};	1249	};
800	};	1250	};
801	};	1251	};
802	};	1252	};
803	};	1253	};
804		1254
805	$grp	1255	$grp
806	}	1256	}
807		1257
808	=item aio_rmtree $path, $callback->($status)	1258	=item aio_rmtree $pathname, $callback->($status)
809		1259
810	Delete a directory tree starting (and including) C<$path>, return the	1260	Delete a directory tree starting (and including) C<$path>, return the
811	status of the final C<rmdir> only. This is a composite request that	1261	status of the final C<rmdir> only. This is a composite request that
812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1262	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
813	everything else.	1263	everything else.
814		1264
815	=cut	1265	=cut
816		1266
…		…
838	};	1288	};
839		1289
840	$grp	1290	$grp
841	}	1291	}
842		1292
		1293	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1294
		1295	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1296
		1297	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1298	they execute asynchronously and pass the return value to the callback.
		1299
		1300	Both calls can be used for a lot of things, some of which make more sense
		1301	to run asynchronously in their own thread, while some others make less
		1302	sense. For example, calls that block waiting for external events, such
		1303	as locking, will also lock down an I/O thread while it is waiting, which
		1304	can deadlock the whole I/O system. At the same time, there might be no
		1305	alternative to using a thread to wait.
		1306
		1307	So in general, you should only use these calls for things that do
		1308	(filesystem) I/O, not for things that wait for other events (network,
		1309	other processes), although if you are careful and know what you are doing,
		1310	you still can.
		1311
		1312	The following constants are available (missing ones are, as usual C<0>):
		1313
		1314	C<F_DUPFD_CLOEXEC>,
		1315
		1316	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1317
		1318	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1319
		1320	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1321	C<FS_IOC_FIEMAP>.
		1322
		1323	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1324	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1325
		1326	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1327	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1328	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1329	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1330	C<FS_FL_USER_MODIFIABLE>.
		1331
		1332	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1333	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1334	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1335	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1336
843	=item aio_sync $callback->($status)	1337	=item aio_sync $callback->($status)
844		1338
845	Asynchronously call sync and call the callback when finished.	1339	Asynchronously call sync and call the callback when finished.
846		1340
847	=item aio_fsync $fh, $callback->($status)	1341	=item aio_fsync $fh, $callback->($status)
…		…
855	callback with the fdatasync result code.	1349	callback with the fdatasync result code.
856		1350
857	If this call isn't available because your OS lacks it or it couldn't be	1351	If this call isn't available because your OS lacks it or it couldn't be
858	detected, it will be emulated by calling C<fsync> instead.	1352	detected, it will be emulated by calling C<fsync> instead.
859		1353
		1354	=item aio_syncfs $fh, $callback->($status)
		1355
		1356	Asynchronously call the syncfs syscall to sync the filesystem associated
		1357	to the given filehandle and call the callback with the syncfs result
		1358	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1359	errno to C<ENOSYS> nevertheless.
		1360
		1361	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1362
		1363	Sync the data portion of the file specified by C<$offset> and C<$length>
		1364	to disk (but NOT the metadata), by calling the Linux-specific
		1365	sync_file_range call. If sync_file_range is not available or it returns
		1366	ENOSYS, then fdatasync or fsync is being substituted.
		1367
		1368	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1369	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1370	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1371	manpage for details.
		1372
860	=item aio_pathsync $path, $callback->($status)	1373	=item aio_pathsync $pathname, $callback->($status)
861		1374
862	This request tries to open, fsync and close the given path. This is a	1375	This request tries to open, fsync and close the given path. This is a
863	composite request intended to sync directories after directory operations	1376	composite request intended to sync directories after directory operations
864	(E.g. rename). This might not work on all operating systems or have any	1377	(E.g. rename). This might not work on all operating systems or have any
865	specific effect, but usually it makes sure that directory changes get	1378	specific effect, but usually it makes sure that directory changes get
866	written to disc. It works for anything that can be opened for read-only,	1379	written to disc. It works for anything that can be opened for read-only,
867	not just directories.	1380	not just directories.
		1381
		1382	Future versions of this function might fall back to other methods when
		1383	C<fsync> on the directory fails (such as calling C<sync>).
868		1384
869	Passes C<0> when everything went ok, and C<-1> on error.	1385	Passes C<0> when everything went ok, and C<-1> on error.
870		1386
871	=cut	1387	=cut
872		1388
…		…
893	};	1409	};
894		1410
895	$grp	1411	$grp
896	}	1412	}
897		1413
		1414	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1415
		1416	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1417	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1418	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1419	scalar must only be modified in-place while an aio operation is pending on
		1420	it).
		1421
		1422	It calls the C<msync> function of your OS, if available, with the memory
		1423	area starting at C<$offset> in the string and ending C<$length> bytes
		1424	later. If C<$length> is negative, counts from the end, and if C<$length>
		1425	is C<undef>, then it goes till the end of the string. The flags can be
		1426	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1427	C<IO::AIO::MS_INVALIDATE>.
		1428
		1429	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1430
		1431	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1432	scalars.
		1433
		1434	It touches (reads or writes) all memory pages in the specified
		1435	range inside the scalar. All caveats and parameters are the same
		1436	as for C<aio_msync>, above, except for flags, which must be either
		1437	C<0> (which reads all pages and ensures they are instantiated) or
		1438	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1439	writing an octet from it, which dirties the page).
		1440
		1441	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1442
		1443	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1444	scalars.
		1445
		1446	It reads in all the pages of the underlying storage into memory (if any)
		1447	and locks them, so they are not getting swapped/paged out or removed.
		1448
		1449	If C<$length> is undefined, then the scalar will be locked till the end.
		1450
		1451	On systems that do not implement C<mlock>, this function returns C<-1>
		1452	and sets errno to C<ENOSYS>.
		1453
		1454	Note that the corresponding C<munlock> is synchronous and is
		1455	documented under L<MISCELLANEOUS FUNCTIONS>.
		1456
		1457	Example: open a file, mmap and mlock it - both will be undone when
		1458	C<$data> gets destroyed.
		1459
		1460	open my $fh, "<", $path or die "$path: $!";
		1461	my $data;
		1462	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1463	aio_mlock $data; # mlock in background
		1464
		1465	=item aio_mlockall $flags, $callback->($status)
		1466
		1467	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1468	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1469
		1470	On systems that do not implement C<mlockall>, this function returns C<-1>
		1471	and sets errno to C<ENOSYS>.
		1472
		1473	Note that the corresponding C<munlockall> is synchronous and is
		1474	documented under L<MISCELLANEOUS FUNCTIONS>.
		1475
		1476	Example: asynchronously lock all current and future pages into memory.
		1477
		1478	aio_mlockall IO::AIO::MCL_FUTURE;
		1479
		1480	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1481
		1482	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1483	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1484	the ioctl is not available on your OS, then this request will fail with
		1485	C<ENOSYS>.
		1486
		1487	C<$start> is the starting offset to query extents for, C<$length> is the
		1488	size of the range to query - if it is C<undef>, then the whole file will
		1489	be queried.
		1490
		1491	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1492	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1493	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1494	the data portion.
		1495
		1496	C<$count> is the maximum number of extent records to return. If it is
		1497	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1498	case, if it is C<0>, then the callback receives the number of extents
		1499	instead of the extents themselves (which is unreliable, see below).
		1500
		1501	If an error occurs, the callback receives no arguments. The special
		1502	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1503
		1504	Otherwise, the callback receives an array reference with extent
		1505	structures. Each extent structure is an array reference itself, with the
		1506	following members:
		1507
		1508	[$logical, $physical, $length, $flags]
		1509
		1510	Flags is any combination of the following flag values (typically either C<0>
		1511	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1512
		1513	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1514	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1515	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1516	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1517	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1518	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1519
		1520	At the time of this writing (Linux 3.2), this request is unreliable unless
		1521	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1522	it to return all extents of a range for files with a large number of
		1523	extents. The code (only) works around all these issues if C<$count> is
		1524	C<undef>.
		1525
898	=item aio_group $callback->(...)	1526	=item aio_group $callback->(...)
899		1527
900	This is a very special aio request: Instead of doing something, it is a	1528	This is a very special aio request: Instead of doing something, it is a
901	container for other aio requests, which is useful if you want to bundle	1529	container for other aio requests, which is useful if you want to bundle
902	many requests into a single, composite, request with a definite callback	1530	many requests into a single, composite, request with a definite callback
…		…
939	immense (it blocks a thread for a long time) so do not use this function	1567	immense (it blocks a thread for a long time) so do not use this function
940	except to put your application under artificial I/O pressure.	1568	except to put your application under artificial I/O pressure.
941		1569
942	=back	1570	=back
943		1571
		1572
		1573	=head2 IO::AIO::WD - multiple working directories
		1574
		1575	Your process only has one current working directory, which is used by all
		1576	threads. This makes it hard to use relative paths (some other component
		1577	could call C<chdir> at any time, and it is hard to control when the path
		1578	will be used by IO::AIO).
		1579
		1580	One solution for this is to always use absolute paths. This usually works,
		1581	but can be quite slow (the kernel has to walk the whole path on every
		1582	access), and can also be a hassle to implement.
		1583
		1584	Newer POSIX systems have a number of functions (openat, fdopendir,
		1585	futimensat and so on) that make it possible to specify working directories
		1586	per operation.
		1587
		1588	For portability, and because the clowns who "designed", or shall I write,
		1589	perpetrated this new interface were obviously half-drunk, this abstraction
		1590	cannot be perfect, though.
		1591
		1592	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1593	object. This object stores the canonicalised, absolute version of the
		1594	path, and on systems that allow it, also a directory file descriptor.
		1595
		1596	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1597	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1598	object and a pathname instead (or the IO::AIO::WD object alone, which
		1599	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1600	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1601	to that IO::AIO::WD object.
		1602
		1603	For example, to get a wd object for F</etc> and then stat F<passwd>
		1604	inside, you would write:
		1605
		1606	aio_wd "/etc", sub {
		1607	my $etcdir = shift;
		1608
		1609	# although $etcdir can be undef on error, there is generally no reason
		1610	# to check for errors here, as aio_stat will fail with ENOENT
		1611	# when $etcdir is undef.
		1612
		1613	aio_stat [$etcdir, "passwd"], sub {
		1614	# yay
		1615	};
		1616	};
		1617
		1618	The fact that C<aio_wd> is a request and not a normal function shows that
		1619	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1620	which is why it is done asynchronously.
		1621
		1622	To stat the directory obtained with C<aio_wd> above, one could write
		1623	either of the following three request calls:
		1624
		1625	aio_lstat "/etc" , sub { ... # pathname as normal string
		1626	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1627	aio_lstat $wd , sub { ... # shorthand for the previous
		1628
		1629	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1630	object and the pathname string, so you could write the following without
		1631	causing any issues due to C<$path> getting reused:
		1632
		1633	my $path = [$wd, undef];
		1634
		1635	for my $name (qw(abc def ghi)) {
		1636	$path->[1] = $name;
		1637	aio_stat $path, sub {
		1638	# ...
		1639	};
		1640	}
		1641
		1642	There are some caveats: when directories get renamed (or deleted), the
		1643	pathname string doesn't change, so will point to the new directory (or
		1644	nowhere at all), while the directory fd, if available on the system,
		1645	will still point to the original directory. Most functions accepting a
		1646	pathname will use the directory fd on newer systems, and the string on
		1647	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1648	the string form of the pathname.
		1649
		1650	So this functionality is mainly useful to get some protection against
		1651	C<chdir>, to easily get an absolute path out of a relative path for future
		1652	reference, and to speed up doing many operations in the same directory
		1653	(e.g. when stat'ing all files in a directory).
		1654
		1655	The following functions implement this working directory abstraction:
		1656
		1657	=over 4
		1658
		1659	=item aio_wd $pathname, $callback->($wd)
		1660
		1661	Asynchonously canonicalise the given pathname and convert it to an
		1662	IO::AIO::WD object representing it. If possible and supported on the
		1663	system, also open a directory fd to speed up pathname resolution relative
		1664	to this working directory.
		1665
		1666	If something goes wrong, then C<undef> is passwd to the callback instead
		1667	of a working directory object and C<$!> is set appropriately. Since
		1668	passing C<undef> as working directory component of a pathname fails the
		1669	request with C<ENOENT>, there is often no need for error checking in the
		1670	C<aio_wd> callback, as future requests using the value will fail in the
		1671	expected way.
		1672
		1673	=item IO::AIO::CWD
		1674
		1675	This is a compiletime constant (object) that represents the process
		1676	current working directory.
		1677
		1678	Specifying this object as working directory object for a pathname is as if
		1679	the pathname would be specified directly, without a directory object. For
		1680	example, these calls are functionally identical:
		1681
		1682	aio_stat "somefile", sub { ... };
		1683	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1684
		1685	=back
		1686
		1687	To recover the path associated with an IO::AIO::WD object, you can use
		1688	C<aio_realpath>:
		1689
		1690	aio_realpath $wd, sub {
		1691	warn "path is $_[0]\n";
		1692	};
		1693
		1694	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1695	sometimes, fall back to using an absolue path.
		1696
944	=head2 IO::AIO::REQ CLASS	1697	=head2 IO::AIO::REQ CLASS
945		1698
946	All non-aggregate C<aio_*> functions return an object of this class when	1699	All non-aggregate C<aio_*> functions return an object of this class when
947	called in non-void context.	1700	called in non-void context.
948		1701
…		…
951	=item cancel $req	1704	=item cancel $req
952		1705
953	Cancels the request, if possible. Has the effect of skipping execution	1706	Cancels the request, if possible. Has the effect of skipping execution
954	when entering the B<execute> state and skipping calling the callback when	1707	when entering the B<execute> state and skipping calling the callback when
955	entering the the B<result> state, but will leave the request otherwise	1708	entering the the B<result> state, but will leave the request otherwise
956	untouched. That means that requests that currently execute will not be	1709	untouched (with the exception of readdir). That means that requests that
957	stopped and resources held by the request will not be freed prematurely.	1710	currently execute will not be stopped and resources held by the request
		1711	will not be freed prematurely.
958		1712
959	=item cb $req $callback->(...)	1713	=item cb $req $callback->(...)
960		1714
961	Replace (or simply set) the callback registered to the request.	1715	Replace (or simply set) the callback registered to the request.
962		1716
…		…
1036	=item $grp->cancel_subs	1790	=item $grp->cancel_subs
1037		1791
1038	Cancel all subrequests and clears any feeder, but not the group request	1792	Cancel all subrequests and clears any feeder, but not the group request
1039	itself. Useful when you queued a lot of events but got a result early.	1793	itself. Useful when you queued a lot of events but got a result early.
1040		1794
		1795	The group request will finish normally (you cannot add requests to the
		1796	group).
		1797
1041	=item $grp->result (...)	1798	=item $grp->result (...)
1042		1799
1043	Set the result value(s) that will be passed to the group callback when all	1800	Set the result value(s) that will be passed to the group callback when all
1044	subrequests have finished and set the groups errno to the current value	1801	subrequests have finished and set the groups errno to the current value
1045	of errno (just like calling C<errno> without an error number). By default,	1802	of errno (just like calling C<errno> without an error number). By default,
…		…
1060	=item feed $grp $callback->($grp)	1817	=item feed $grp $callback->($grp)
1061		1818
1062	Sets a feeder/generator on this group: every group can have an attached	1819	Sets a feeder/generator on this group: every group can have an attached
1063	generator that generates requests if idle. The idea behind this is that,	1820	generator that generates requests if idle. The idea behind this is that,
1064	although you could just queue as many requests as you want in a group,	1821	although you could just queue as many requests as you want in a group,
1065	this might starve other requests for a potentially long time. For	1822	this might starve other requests for a potentially long time. For example,
1066	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1823	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1067	requests, delaying any later requests for a long time.	1824	requests, delaying any later requests for a long time.
1068		1825
1069	To avoid this, and allow incremental generation of requests, you can	1826	To avoid this, and allow incremental generation of requests, you can
1070	instead a group and set a feeder on it that generates those requests. The	1827	instead a group and set a feeder on it that generates those requests. The
1071	feed callback will be called whenever there are few enough (see C<limit>,	1828	feed callback will be called whenever there are few enough (see C<limit>,
…		…
1076	not impose any limits).	1833	not impose any limits).
1077		1834
1078	If the feed does not queue more requests when called, it will be	1835	If the feed does not queue more requests when called, it will be
1079	automatically removed from the group.	1836	automatically removed from the group.
1080		1837
1081	If the feed limit is C<0>, it will be set to C<2> automatically.	1838	If the feed limit is C<0> when this method is called, it will be set to
		1839	C<2> automatically.
1082		1840
1083	Example:	1841	Example:
1084		1842
1085	# stat all files in @files, but only ever use four aio requests concurrently:	1843	# stat all files in @files, but only ever use four aio requests concurrently:
1086		1844
…		…
1098	Sets the feeder limit for the group: The feeder will be called whenever	1856	Sets the feeder limit for the group: The feeder will be called whenever
1099	the group contains less than this many requests.	1857	the group contains less than this many requests.
1100		1858
1101	Setting the limit to C<0> will pause the feeding process.	1859	Setting the limit to C<0> will pause the feeding process.
1102		1860
		1861	The default value for the limit is C<0>, but note that setting a feeder
		1862	automatically bumps it up to C<2>.
		1863
1103	=back	1864	=back
1104		1865
1105	=head2 SUPPORT FUNCTIONS	1866	=head2 SUPPORT FUNCTIONS
1106		1867
1107	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1868	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1109	=over 4	1870	=over 4
1110		1871
1111	=item $fileno = IO::AIO::poll_fileno	1872	=item $fileno = IO::AIO::poll_fileno
1112		1873
1113	Return the I<request result pipe file descriptor>. This filehandle must be	1874	Return the I<request result pipe file descriptor>. This filehandle must be
1114	polled for reading by some mechanism outside this module (e.g. Event or	1875	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1115	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1876	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1116	to call C<poll_cb> to check the results.	1877	you have to call C<poll_cb> to check the results.
1117		1878
1118	See C<poll_cb> for an example.	1879	See C<poll_cb> for an example.
1119		1880
1120	=item IO::AIO::poll_cb	1881	=item IO::AIO::poll_cb
1121		1882
1122	Process some outstanding events on the result pipe. You have to call this	1883	Process some requests that have reached the result phase (i.e. they have
1123	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1884	been executed but the results are not yet reported). You have to call
1124	returned earlier for whatever reason. Returns immediately when no events	1885	this "regularly" to finish outstanding requests.
1125	are outstanding. The amount of events processed depends on the settings of
1126	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1127		1886
		1887	Returns C<0> if all events could be processed (or there were no
		1888	events to process), or C<-1> if it returned earlier for whatever
		1889	reason. Returns immediately when no events are outstanding. The amount
		1890	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1891	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1892
1128	If not all requests were processed for whatever reason, the filehandle	1893	If not all requests were processed for whatever reason, the poll file
1129	will still be ready when C<poll_cb> returns, so normally you don't have to	1894	descriptor will still be ready when C<poll_cb> returns, so normally you
1130	do anything special to have it called later.	1895	don't have to do anything special to have it called later.
		1896
		1897	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1898	ready, it can be beneficial to call this function from loops which submit
		1899	a lot of requests, to make sure the results get processed when they become
		1900	available and not just when the loop is finished and the event loop takes
		1901	over again. This function returns very fast when there are no outstanding
		1902	requests.
1131		1903
1132	Example: Install an Event watcher that automatically calls	1904	Example: Install an Event watcher that automatically calls
1133	IO::AIO::poll_cb with high priority:	1905	IO::AIO::poll_cb with high priority (more examples can be found in the
		1906	SYNOPSIS section, at the top of this document):
1134		1907
1135	Event->io (fd => IO::AIO::poll_fileno,	1908	Event->io (fd => IO::AIO::poll_fileno,
1136	poll => 'r', async => 1,	1909	poll => 'r', async => 1,
1137	cb => \&IO::AIO::poll_cb);	1910	cb => \&IO::AIO::poll_cb);
		1911
		1912	=item IO::AIO::poll_wait
		1913
		1914	Wait until either at least one request is in the result phase or no
		1915	requests are outstanding anymore.
		1916
		1917	This is useful if you want to synchronously wait for some requests to
		1918	become ready, without actually handling them.
		1919
		1920	See C<nreqs> for an example.
		1921
		1922	=item IO::AIO::poll
		1923
		1924	Waits until some requests have been handled.
		1925
		1926	Returns the number of requests processed, but is otherwise strictly
		1927	equivalent to:
		1928
		1929	IO::AIO::poll_wait, IO::AIO::poll_cb
		1930
		1931	=item IO::AIO::flush
		1932
		1933	Wait till all outstanding AIO requests have been handled.
		1934
		1935	Strictly equivalent to:
		1936
		1937	IO::AIO::poll_wait, IO::AIO::poll_cb
		1938	while IO::AIO::nreqs;
1138		1939
1139	=item IO::AIO::max_poll_reqs $nreqs	1940	=item IO::AIO::max_poll_reqs $nreqs
1140		1941
1141	=item IO::AIO::max_poll_time $seconds	1942	=item IO::AIO::max_poll_time $seconds
1142		1943
…		…
1167	# use a low priority so other tasks have priority	1968	# use a low priority so other tasks have priority
1168	Event->io (fd => IO::AIO::poll_fileno,	1969	Event->io (fd => IO::AIO::poll_fileno,
1169	poll => 'r', nice => 1,	1970	poll => 'r', nice => 1,
1170	cb => &IO::AIO::poll_cb);	1971	cb => &IO::AIO::poll_cb);
1171		1972
1172	=item IO::AIO::poll_wait
1173
1174	If there are any outstanding requests and none of them in the result
1175	phase, wait till the result filehandle becomes ready for reading (simply
1176	does a C<select> on the filehandle. This is useful if you want to
1177	synchronously wait for some requests to finish).
1178
1179	See C<nreqs> for an example.
1180
1181	=item IO::AIO::poll
1182
1183	Waits until some requests have been handled.
1184
1185	Returns the number of requests processed, but is otherwise strictly
1186	equivalent to:
1187
1188	IO::AIO::poll_wait, IO::AIO::poll_cb
1189
1190	=item IO::AIO::flush
1191
1192	Wait till all outstanding AIO requests have been handled.
1193
1194	Strictly equivalent to:
1195
1196	IO::AIO::poll_wait, IO::AIO::poll_cb
1197	while IO::AIO::nreqs;
1198
1199	=back	1973	=back
1200		1974
1201	=head3 CONTROLLING THE NUMBER OF THREADS	1975	=head3 CONTROLLING THE NUMBER OF THREADS
1202		1976
1203	=over	1977	=over
…		…
1236		2010
1237	Under normal circumstances you don't need to call this function.	2011	Under normal circumstances you don't need to call this function.
1238		2012
1239	=item IO::AIO::max_idle $nthreads	2013	=item IO::AIO::max_idle $nthreads
1240		2014
1241	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2015	Limit the number of threads (default: 4) that are allowed to idle
1242	threads that did not get a request to process within 10 seconds). That	2016	(i.e., threads that did not get a request to process within the idle
1243	means if a thread becomes idle while C<$nthreads> other threads are also	2017	timeout (default: 10 seconds). That means if a thread becomes idle while
1244	idle, it will free its resources and exit.	2018	C<$nthreads> other threads are also idle, it will free its resources and
		2019	exit.
1245		2020
1246	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2021	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1247	to allow for extremely high load situations, but want to free resources	2022	to allow for extremely high load situations, but want to free resources
1248	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2023	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1249		2024
1250	The default is probably ok in most situations, especially if thread	2025	The default is probably ok in most situations, especially if thread
1251	creation is fast. If thread creation is very slow on your system you might	2026	creation is fast. If thread creation is very slow on your system you might
1252	want to use larger values.	2027	want to use larger values.
1253		2028
		2029	=item IO::AIO::idle_timeout $seconds
		2030
		2031	Sets the minimum idle timeout (default 10) after which worker threads are
		2032	allowed to exit. SEe C<IO::AIO::max_idle>.
		2033
1254	=item IO::AIO::max_outstanding $maxreqs	2034	=item IO::AIO::max_outstanding $maxreqs
		2035
		2036	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2037	you do queue up more than this number of requests, the next call to
		2038	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2039	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2040	longer exceeded.
		2041
		2042	In other words, this setting does not enforce a queue limit, but can be
		2043	used to make poll functions block if the limit is exceeded.
1255		2044
1256	This is a very bad function to use in interactive programs because it	2045	This is a very bad function to use in interactive programs because it
1257	blocks, and a bad way to reduce concurrency because it is inexact: Better	2046	blocks, and a bad way to reduce concurrency because it is inexact: Better
1258	use an C<aio_group> together with a feed callback.	2047	use an C<aio_group> together with a feed callback.
1259		2048
1260	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2049	Its main use is in scripts without an event loop - when you want to stat
1261	do queue up more than this number of requests, the next call to the	2050	a lot of files, you can write something like this:
1262	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1263	function will block until the limit is no longer exceeded.
1264		2051
1265	The default value is very large, so there is no practical limit on the	2052	IO::AIO::max_outstanding 32;
1266	number of outstanding requests.
1267		2053
1268	You can still queue as many requests as you want. Therefore,	2054	for my $path (...) {
1269	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2055	aio_stat $path , ...;
1270	as a stop gap to shield against fatal memory overflow (with large values).	2056	IO::AIO::poll_cb;
		2057	}
		2058
		2059	IO::AIO::flush;
		2060
		2061	The call to C<poll_cb> inside the loop will normally return instantly, but
		2062	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2063	some requests have been handled. This keeps the loop from pushing a large
		2064	number of C<aio_stat> requests onto the queue.
		2065
		2066	The default value for C<max_outstanding> is very large, so there is no
		2067	practical limit on the number of outstanding requests.
1271		2068
1272	=back	2069	=back
1273		2070
1274	=head3 STATISTICAL INFORMATION	2071	=head3 STATISTICAL INFORMATION
1275		2072
…		…
1295	Returns the number of requests currently in the pending state (executed,	2092	Returns the number of requests currently in the pending state (executed,
1296	but not yet processed by poll_cb).	2093	but not yet processed by poll_cb).
1297		2094
1298	=back	2095	=back
1299		2096
		2097	=head3 MISCELLANEOUS FUNCTIONS
		2098
		2099	IO::AIO implements some functions that are useful when you want to use
		2100	some "Advanced I/O" function not available to in Perl, without going the
		2101	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2102	counterpart.
		2103
		2104	=over 4
		2105
		2106	=item $numfd = IO::AIO::get_fdlimit
		2107
		2108	This function is I<EXPERIMENTAL> and subject to change.
		2109
		2110	Tries to find the current file descriptor limit and returns it, or
		2111	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2112	the highest valid file descriptor number.
		2113
		2114	=item IO::AIO::min_fdlimit [$numfd]
		2115
		2116	This function is I<EXPERIMENTAL> and subject to change.
		2117
		2118	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2119	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2120	is missing, it will try to set a very high limit, although this is not
		2121	recommended when you know the actual minimum that you require.
		2122
		2123	If the limit cannot be raised enough, the function makes a best-effort
		2124	attempt to increase the limit as much as possible, using various
		2125	tricks, while still failing. You can query the resulting limit using
		2126	C<IO::AIO::get_fdlimit>.
		2127
		2128	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2129	true.
		2130
		2131	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2132
		2133	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2134	but is blocking (this makes most sense if you know the input data is
		2135	likely cached already and the output filehandle is set to non-blocking
		2136	operations).
		2137
		2138	Returns the number of bytes copied, or C<-1> on error.
		2139
		2140	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2141
		2142	Simply calls the C<posix_fadvise> function (see its
		2143	manpage for details). The following advice constants are
		2144	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2145	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2146	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2147
		2148	On systems that do not implement C<posix_fadvise>, this function returns
		2149	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2150
		2151	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2152
		2153	Simply calls the C<posix_madvise> function (see its
		2154	manpage for details). The following advice constants are
		2155	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2156	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2157	C<IO::AIO::MADV_DONTNEED>.
		2158
		2159	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2160	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2161	will be reduced to fit into the C<$scalar>.
		2162
		2163	On systems that do not implement C<posix_madvise>, this function returns
		2164	ENOSYS, otherwise the return value of C<posix_madvise>.
		2165
		2166	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2167
		2168	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2169	$scalar (see its manpage for details). The following protect
		2170	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2171	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2172
		2173	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2174	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2175	will be reduced to fit into the C<$scalar>.
		2176
		2177	On systems that do not implement C<mprotect>, this function returns
		2178	ENOSYS, otherwise the return value of C<mprotect>.
		2179
		2180	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2181
		2182	Memory-maps a file (or anonymous memory range) and attaches it to the
		2183	given C<$scalar>, which will act like a string scalar. Returns true on
		2184	success, and false otherwise.
		2185
		2186	The scalar must exist, but its contents do not matter - this means you
		2187	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2188	the scalar first.
		2189
		2190	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2191	which don't change the string length, and most read-only operations such
		2192	as copying it or searching it with regexes and so on.
		2193
		2194	Anything else is unsafe and will, at best, result in memory leaks.
		2195
		2196	The memory map associated with the C<$scalar> is automatically removed
		2197	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2198	or C<IO::AIO::munmap> functions are called on it.
		2199
		2200	This calls the C<mmap>(2) function internally. See your system's manual
		2201	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2202
		2203	The C<$length> must be larger than zero and smaller than the actual
		2204	filesize.
		2205
		2206	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2207	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2208
		2209	C<$flags> can be a combination of
		2210	C<IO::AIO::MAP_SHARED> or
		2211	C<IO::AIO::MAP_PRIVATE>,
		2212	or a number of system-specific flags (when not available, the are C<0>):
		2213	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2214	C<IO::AIO::MAP_LOCKED>,
		2215	C<IO::AIO::MAP_NORESERVE>,
		2216	C<IO::AIO::MAP_POPULATE>,
		2217	C<IO::AIO::MAP_NONBLOCK>,
		2218	C<IO::AIO::MAP_FIXED>,
		2219	C<IO::AIO::MAP_GROWSDOWN>,
		2220	C<IO::AIO::MAP_32BIT>,
		2221	C<IO::AIO::MAP_HUGETLB> or
		2222	C<IO::AIO::MAP_STACK>.
		2223
		2224	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2225
		2226	C<$offset> is the offset from the start of the file - it generally must be
		2227	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2228
		2229	Example:
		2230
		2231	use Digest::MD5;
		2232	use IO::AIO;
		2233
		2234	open my $fh, "<verybigfile"
		2235	or die "$!";
		2236
		2237	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2238	or die "verybigfile: $!";
		2239
		2240	my $fast_md5 = md5 $data;
		2241
		2242	=item IO::AIO::munmap $scalar
		2243
		2244	Removes a previous mmap and undefines the C<$scalar>.
		2245
		2246	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2247
		2248	Calls the C<munlock> function, undoing the effects of a previous
		2249	C<aio_mlock> call (see its description for details).
		2250
		2251	=item IO::AIO::munlockall
		2252
		2253	Calls the C<munlockall> function.
		2254
		2255	On systems that do not implement C<munlockall>, this function returns
		2256	ENOSYS, otherwise the return value of C<munlockall>.
		2257
		2258	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2259
		2260	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2261	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2262	should be the file offset.
		2263
		2264	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2265	silently corrupt the data in this case.
		2266
		2267	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2268	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2269	C<IO::AIO::SPLICE_F_GIFT>.
		2270
		2271	See the C<splice(2)> manpage for details.
		2272
		2273	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2274
		2275	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2276	description for C<IO::AIO::splice> above for details.
		2277
		2278	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2279
		2280	Attempts to query or change the pipe buffer size. Obviously works only
		2281	on pipes, and currently works only on GNU/Linux systems, and fails with
		2282	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2283	size on other systems, drop me a note.
		2284
		2285	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2286
		2287	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2288	C<$flags> is missing or C<0>, then this should be the same as a call to
		2289	perl's built-in C<pipe> function and create a new pipe, and works on
		2290	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2291	(..., 4096, O_BINARY)>.
		2292
		2293	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2294	the given flags (Linux 2.6.27, glibc 2.9).
		2295
		2296	On success, the read and write file handles are returned.
		2297
		2298	On error, nothing will be returned. If the pipe2 syscall is missing and
		2299	C<$flags> is non-zero, fails with C<ENOSYS>.
		2300
		2301	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2302	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2303	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2304
		2305	=back
		2306
1300	=cut	2307	=cut
1301		2308
1302	min_parallel 8;	2309	min_parallel 8;
1303		2310
1304	END { flush }	2311	END { flush }
1305		2312
1306	1;	2313	1;
1307		2314
		2315	=head1 EVENT LOOP INTEGRATION
		2316
		2317	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2318	automatically into many event loops:
		2319
		2320	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2321	use AnyEvent::AIO;
		2322
		2323	You can also integrate IO::AIO manually into many event loops, here are
		2324	some examples of how to do this:
		2325
		2326	# EV integration
		2327	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2328
		2329	# Event integration
		2330	Event->io (fd => IO::AIO::poll_fileno,
		2331	poll => 'r',
		2332	cb => \&IO::AIO::poll_cb);
		2333
		2334	# Glib/Gtk2 integration
		2335	add_watch Glib::IO IO::AIO::poll_fileno,
		2336	in => sub { IO::AIO::poll_cb; 1 };
		2337
		2338	# Tk integration
		2339	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2340	readable => \&IO::AIO::poll_cb);
		2341
		2342	# Danga::Socket integration
		2343	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2344	\&IO::AIO::poll_cb);
		2345
1308	=head2 FORK BEHAVIOUR	2346	=head2 FORK BEHAVIOUR
1309		2347
1310	This module should do "the right thing" when the process using it forks:	2348	Usage of pthreads in a program changes the semantics of fork
		2349	considerably. Specifically, only async-safe functions can be called after
		2350	fork. Perl doesn't know about this, so in general, you cannot call fork
		2351	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2352	pthreads, so this applies, but many other extensions and (for inexplicable
		2353	reasons) perl itself often is linked against pthreads, so this limitation
		2354	applies to quite a lot of perls.
1311		2355
1312	Before the fork, IO::AIO enters a quiescent state where no requests	2356	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1313	can be added in other threads and no results will be processed. After	2357	only works in the process that loaded it. Forking is fully supported, but
1314	the fork the parent simply leaves the quiescent state and continues	2358	using IO::AIO in the child is not.
1315	request/result processing, while the child frees the request/result queue
1316	(so that the requests started before the fork will only be handled in the
1317	parent). Threads will be started on demand until the limit set in the
1318	parent process has been reached again.
1319		2359
1320	In short: the parent will, after a short pause, continue as if fork had	2360	You might get around by not I<using> IO::AIO before (or after)
1321	not been called, while the child will act as if IO::AIO has not been used	2361	forking. You could also try to call the L<IO::AIO::reinit> function in the
1322	yet.	2362	child:
		2363
		2364	=over 4
		2365
		2366	=item IO::AIO::reinit
		2367
		2368	Abandons all current requests and I/O threads and simply reinitialises all
		2369	data structures. This is not an operation supported by any standards, but
		2370	happens to work on GNU/Linux and some newer BSD systems.
		2371
		2372	The only reasonable use for this function is to call it after forking, if
		2373	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2374	the process will result in undefined behaviour. Calling it at any time
		2375	will also result in any undefined (by POSIX) behaviour.
		2376
		2377	=back
1323		2378
1324	=head2 MEMORY USAGE	2379	=head2 MEMORY USAGE
1325		2380
1326	Per-request usage:	2381	Per-request usage:
1327		2382

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