ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.125 by root, Sat May 10 22:47:34 2008 UTC vs.
Revision 1.284 by root, Fri Mar 23 01:14:08 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 = '3.0';	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<$callback> argument
227	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
229	perl, which usually delivers "false") as it's sole argument when the given	302	of the request will be passed as arguments to the callback (and, if an
230	syscall has been executed asynchronously.	303	error occured, in C<$!>) - 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 wether 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
430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	617	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
431		618
432	Works like perl's C<utime> function (including the special case of $atime	619	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	620	and $mtime being undef). Fractional times are supported if the underlying
434	syscalls support them.	621	syscalls support them.
…		…
461	=item aio_truncate $fh_or_path, $offset, $callback->($status)	648	=item aio_truncate $fh_or_path, $offset, $callback->($status)
462		649
463	Works like truncate(2) or ftruncate(2).	650	Works like truncate(2) or ftruncate(2).
464		651
465		652
		653	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654
		655	Allocates or frees disk space according to the C<$mode> argument. See the
		656	linux C<fallocate> documentation for details.
		657
		658	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		659	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		660	to deallocate a file range.
		661
		662	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		663	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		664	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		665	to unshare shared blocks (see your L<fallocate(2)> manpage).
		666
		667	The file system block size used by C<fallocate> is presumably the
		668	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		669	can dictate other limitations.
		670
		671	If C<fallocate> isn't available or cannot be emulated (currently no
		672	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		673
		674
466	=item aio_chmod $fh_or_path, $mode, $callback->($status)	675	=item aio_chmod $fh_or_path, $mode, $callback->($status)
467		676
468	Works like perl's C<chmod> function.	677	Works like perl's C<chmod> function.
469		678
470		679
…		…
472		681
473	Asynchronously unlink (delete) a file and call the callback with the	682	Asynchronously unlink (delete) a file and call the callback with the
474	result code.	683	result code.
475		684
476		685
477	=item aio_mknod $path, $mode, $dev, $callback->($status)	686	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
478		687
479	[EXPERIMENTAL]	688	[EXPERIMENTAL]
480		689
481	Asynchronously create a device node (or fifo). See mknod(2).	690	Asynchronously create a device node (or fifo). See mknod(2).
482		691
483	The only (POSIX-) portable way of calling this function is:	692	The only (POSIX-) portable way of calling this function is:
484		693
485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	694	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
486		695
		696	See C<aio_stat> for info about some potentially helpful extra constants
		697	and functions.
487		698
488	=item aio_link $srcpath, $dstpath, $callback->($status)	699	=item aio_link $srcpath, $dstpath, $callback->($status)
489		700
490	Asynchronously create a new link to the existing object at C<$srcpath> at	701	Asynchronously create a new link to the existing object at C<$srcpath> at
491	the path C<$dstpath> and call the callback with the result code.	702	the path C<$dstpath> and call the callback with the result code.
…		…
495		706
496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	707	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
498		709
499		710
500	=item aio_readlink $path, $callback->($link)	711	=item aio_readlink $pathname, $callback->($link)
501		712
502	Asynchronously read the symlink specified by C<$path> and pass it to	713	Asynchronously read the symlink specified by C<$path> and pass it to
503	the callback. If an error occurs, nothing or undef gets passed to the	714	the callback. If an error occurs, nothing or undef gets passed to the
504	callback.	715	callback.
505		716
506		717
		718	=item aio_realpath $pathname, $callback->($path)
		719
		720	Asynchronously make the path absolute and resolve any symlinks in
		721	C<$path>. The resulting path only consists of directories (same as
		722	L<Cwd::realpath>).
		723
		724	This request can be used to get the absolute path of the current working
		725	directory by passing it a path of F<.> (a single dot).
		726
		727
507	=item aio_rename $srcpath, $dstpath, $callback->($status)	728	=item aio_rename $srcpath, $dstpath, $callback->($status)
508		729
509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	730	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
510	rename(2) and call the callback with the result code.	731	rename(2) and call the callback with the result code.
		732
		733	On systems that support the AIO::WD working directory abstraction
		734	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		735	of failing, C<rename> is called on the absolute path of C<$wd>.
		736
		737
		738	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		739
		740	Basically a version of C<aio_rename> with an additional C<$flags>
		741	argument. Calling this with C<$flags=0> is the same as calling
		742	C<aio_rename>.
		743
		744	Non-zero flags are currently only supported on GNU/Linux systems that
		745	support renameat2. Other systems fail with C<ENOSYS> in this case.
		746
		747	The following constants are available (missing ones are, as usual C<0>),
		748	see renameat2(2) for details:
		749
		750	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		751	and C<IO::AIO::RENAME_WHITEOUT>.
511		752
512		753
513	=item aio_mkdir $pathname, $mode, $callback->($status)	754	=item aio_mkdir $pathname, $mode, $callback->($status)
514		755
515	Asynchronously mkdir (create) a directory and call the callback with	756	Asynchronously mkdir (create) a directory and call the callback with
…		…
520	=item aio_rmdir $pathname, $callback->($status)	761	=item aio_rmdir $pathname, $callback->($status)
521		762
522	Asynchronously rmdir (delete) a directory and call the callback with the	763	Asynchronously rmdir (delete) a directory and call the callback with the
523	result code.	764	result code.
524		765
		766	On systems that support the AIO::WD working directory abstraction
		767	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		768	C<rmdir> is called on the absolute path of C<$wd>.
		769
525		770
526	=item aio_readdir $pathname, $callback->($entries)	771	=item aio_readdir $pathname, $callback->($entries)
527		772
528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	773	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	774	directory (i.e. opendir + readdir + closedir). The entries will not be
530	sorted, and will B<NOT> include the C<.> and C<..> entries.	775	sorted, and will B<NOT> include the C<.> and C<..> entries.
531		776
532	The callback a single argument which is either C<undef> or an array-ref	777	The callback is passed a single argument which is either C<undef> or an
533	with the filenames.	778	array-ref with the filenames.
534		779
535		780
		781	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		782
		783	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		784	tune behaviour and output format. In case of an error, C<$entries> will be
		785	C<undef>.
		786
		787	The flags are a combination of the following constants, ORed together (the
		788	flags will also be passed to the callback, possibly modified):
		789
		790	=over 4
		791
		792	=item IO::AIO::READDIR_DENTS
		793
		794	Normally the callback gets an arrayref consisting of names only (as
		795	with C<aio_readdir>). If this flag is set, then the callback gets an
		796	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
		797	single directory entry in more detail:
		798
		799	C<$name> is the name of the entry.
		800
		801	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		802
		803	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		804	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		805	C<IO::AIO::DT_WHT>.
		806
		807	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
		808	to know, you have to run stat yourself. Also, for speed/memory reasons,
		809	the C<$type> scalars are read-only: you must not modify them.
		810
		811	C<$inode> is the inode number (which might not be exact on systems with 64
		812	bit inode numbers and 32 bit perls). This field has unspecified content on
		813	systems that do not deliver the inode information.
		814
		815	=item IO::AIO::READDIR_DIRS_FIRST
		816
		817	When this flag is set, then the names will be returned in an order where
		818	likely directories come first, in optimal stat order. This is useful when
		819	you need to quickly find directories, or you want to find all directories
		820	while avoiding to stat() each entry.
		821
		822	If the system returns type information in readdir, then this is used
		823	to find directories directly. Otherwise, likely directories are names
		824	beginning with ".", or otherwise names with no dots, of which names with
		825	short names are tried first.
		826
		827	=item IO::AIO::READDIR_STAT_ORDER
		828
		829	When this flag is set, then the names will be returned in an order
		830	suitable for stat()'ing each one. That is, when you plan to stat() most or
		831	all files in the given directory, then the returned order will likely be
		832	faster.
		833
		834	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
		835	then the likely dirs come first, resulting in a less optimal stat order
		836	for stat'ing all entries, but likely a more optimal order for finding
		837	subdirectories.
		838
		839	=item IO::AIO::READDIR_FOUND_UNKNOWN
		840
		841	This flag should not be set when calling C<aio_readdirx>. Instead, it
		842	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		843	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		844	C<$type>'s are known, which can be used to speed up some algorithms.
		845
		846	=back
		847
		848
		849	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		850
		851	Opens, reads and closes the given file. The data is put into C<$data>,
		852	which is resized as required.
		853
		854	If C<$offset> is negative, then it is counted from the end of the file.
		855
		856	If C<$length> is zero, then the remaining length of the file is
		857	used. Also, in this case, the same limitations to modifying C<$data> apply
		858	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		859	with C<substr>. If the size of the file is known, specifying a non-zero
		860	C<$length> results in a performance advantage.
		861
		862	This request is similar to the older C<aio_load> request, but since it is
		863	a single request, it might be more efficient to use.
		864
		865	Example: load F</etc/passwd> into C<$passwd>.
		866
		867	my $passwd;
		868	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		869	$_[0] >= 0
		870	or die "/etc/passwd: $!\n";
		871
		872	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		873	print $passwd;
		874	};
		875	IO::AIO::flush;
		876
		877
536	=item aio_load $path, $data, $callback->($status)	878	=item aio_load $pathname, $data, $callback->($status)
537		879
538	This is a composite request that tries to fully load the given file into	880	This is a composite request that tries to fully load the given file into
539	memory. Status is the same as with aio_read.	881	memory. Status is the same as with aio_read.
		882
		883	Using C<aio_slurp> might be more efficient, as it is a single request.
540		884
541	=cut	885	=cut
542		886
543	sub aio_load($$;$) {	887	sub aio_load($$;$) {
544	my ($path, undef, $cb) = @_;	888	my ($path, undef, $cb) = @_;
…		…
563		907
564	=item aio_copy $srcpath, $dstpath, $callback->($status)	908	=item aio_copy $srcpath, $dstpath, $callback->($status)
565		909
566	Try to copy the I<file> (directories not supported as either source or	910	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	911	destination) from C<$srcpath> to C<$dstpath> and call the callback with
568	the C<0> (error) or C<-1> ok.	912	a status of C<0> (ok) or C<-1> (error, see C<$!>).
569		913
		914	Existing destination files will be truncated.
		915
570	This is a composite request that it creates the destination file with	916	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	917	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	918	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
573	uid/gid, in that order.	919	uid/gid, in that order.
574		920
575	If an error occurs, the partial destination file will be unlinked, if	921	If an error occurs, the partial destination file will be unlinked, if
…		…
585	my $grp = aio_group $cb;	931	my $grp = aio_group $cb;
586		932
587	aioreq_pri $pri;	933	aioreq_pri $pri;
588	add $grp aio_open $src, O_RDONLY, 0, sub {	934	add $grp aio_open $src, O_RDONLY, 0, sub {
589	if (my $src_fh = $_[0]) {	935	if (my $src_fh = $_[0]) {
590	my @stat = stat $src_fh;	936	my @stat = stat $src_fh; # hmm, might block over nfs?
591		937
592	aioreq_pri $pri;	938	aioreq_pri $pri;
593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	939	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
594	if (my $dst_fh = $_[0]) {	940	if (my $dst_fh = $_[0]) {
595	aioreq_pri $pri;	941	aioreq_pri $pri;
596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	942	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
597	if ($_[0] == $stat[7]) {	943	if ($_[0] == $stat[7]) {
598	$grp->result (0);	944	$grp->result (0);
599	close $src_fh;	945	close $src_fh;
600		946
601	# those should not normally block. should. should.	947	my $ch = sub {
602	utime $stat[8], $stat[9], $dst;	948	aioreq_pri $pri;
603	chmod $stat[2] & 07777, $dst_fh;	949	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
604	chown $stat[4], $stat[5], $dst_fh;	950	aioreq_pri $pri;
		951	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		952	aioreq_pri $pri;
		953	add $grp aio_close $dst_fh;
		954	}
		955	};
		956	};
605		957
606	aioreq_pri $pri;	958	aioreq_pri $pri;
607	add $grp aio_close $dst_fh;	959	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		960	if ($_[0] < 0 && $! == ENOSYS) {
		961	aioreq_pri $pri;
		962	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		963	} else {
		964	$ch->();
		965	}
		966	};
608	} else {	967	} else {
609	$grp->result (-1);	968	$grp->result (-1);
610	close $src_fh;	969	close $src_fh;
611	close $dst_fh;	970	close $dst_fh;
612		971
…		…
629		988
630	=item aio_move $srcpath, $dstpath, $callback->($status)	989	=item aio_move $srcpath, $dstpath, $callback->($status)
631		990
632	Try to move the I<file> (directories not supported as either source or	991	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	992	destination) from C<$srcpath> to C<$dstpath> and call the callback with
634	the C<0> (error) or C<-1> ok.	993	a status of C<0> (ok) or C<-1> (error, see C<$!>).
635		994
636	This is a composite request that tries to rename(2) the file first. If	995	This is a composite request that tries to rename(2) the file first; if
637	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	996	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
638	that is successful, unlinking the C<$srcpath>.	997	that is successful, unlinks the C<$srcpath>.
639		998
640	=cut	999	=cut
641		1000
642	sub aio_move($$;$) {	1001	sub aio_move($$;$) {
643	my ($src, $dst, $cb) = @_;	1002	my ($src, $dst, $cb) = @_;
…		…
650	if ($_[0] && $! == EXDEV) {	1009	if ($_[0] && $! == EXDEV) {
651	aioreq_pri $pri;	1010	aioreq_pri $pri;
652	add $grp aio_copy $src, $dst, sub {	1011	add $grp aio_copy $src, $dst, sub {
653	$grp->result ($_[0]);	1012	$grp->result ($_[0]);
654		1013
655	if (!$_[0]) {	1014	unless ($_[0]) {
656	aioreq_pri $pri;	1015	aioreq_pri $pri;
657	add $grp aio_unlink $src;	1016	add $grp aio_unlink $src;
658	}	1017	}
659	};	1018	};
660	} else {	1019	} else {
…		…
663	};	1022	};
664		1023
665	$grp	1024	$grp
666	}	1025	}
667		1026
668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1027	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
669		1028
670	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1029	Scans a directory (similar to C<aio_readdir>) but additionally tries to
671	efficiently separate the entries of directory C<$path> into two sets of	1030	efficiently separate the entries of directory C<$path> into two sets of
672	names, directories you can recurse into (directories), and ones you cannot	1031	names, directories you can recurse into (directories), and ones you cannot
673	recurse into (everything else, including symlinks to directories).	1032	recurse into (everything else, including symlinks to directories).
674		1033
675	C<aio_scandir> is a composite request that creates of many sub requests_	1034	C<aio_scandir> is a composite request that generates many sub requests.
676	C<$maxreq> specifies the maximum number of outstanding aio requests that	1035	C<$maxreq> specifies the maximum number of outstanding aio requests that
677	this function generates. If it is C<< <= 0 >>, then a suitable default	1036	this function generates. If it is C<< <= 0 >>, then a suitable default
678	will be chosen (currently 4).	1037	will be chosen (currently 4).
679		1038
680	On error, the callback is called without arguments, otherwise it receives	1039	On error, the callback is called without arguments, otherwise it receives
…		…
690		1049
691	Implementation notes.	1050	Implementation notes.
692		1051
693	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1052	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
694		1053
		1054	If readdir returns file type information, then this is used directly to
		1055	find directories.
		1056
695	After reading the directory, the modification time, size etc. of the	1057	Otherwise, after reading the directory, the modification time, size etc.
696	directory before and after the readdir is checked, and if they match (and	1058	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	1059	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	1060	how many entries are directories (if >= 2). Otherwise, no knowledge of the
699	of subdirectories will be assumed.	1061	number of subdirectories will be assumed.
700		1062
701	Then entries will be sorted into likely directories (everything without	1063	Then entries will be sorted into likely directories a non-initial dot
702	a non-initial dot currently) and likely non-directories (everything	1064	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,	1065	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	1066	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	1067	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	1068	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	1069	filesystems might detect the type of the entry without reading the inode
708	data (e.g. ext2fs filetype feature).	1070	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1071	the filetype information on readdir.
709		1072
710	If the known number of directories (link count - 2) has been reached, the	1073	If the known number of directories (link count - 2) has been reached, the
711	rest of the entries is assumed to be non-directories.	1074	rest of the entries is assumed to be non-directories.
712		1075
713	This only works with certainty on POSIX (= UNIX) filesystems, which	1076	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
726		1089
727	my $grp = aio_group $cb;	1090	my $grp = aio_group $cb;
728		1091
729	$maxreq = 4 if $maxreq <= 0;	1092	$maxreq = 4 if $maxreq <= 0;
730		1093
731	# stat once	1094	# get a wd object
732	aioreq_pri $pri;	1095	aioreq_pri $pri;
733	add $grp aio_stat $path, sub {	1096	add $grp aio_wd $path, sub {
		1097	$_[0]
734	return $grp->result () if $_[0];	1098	or return $grp->result ();
735	my $now = time;
736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
737		1099
738	# read the directory entries	1100	my $wd = [shift, "."];
		1101
		1102	# stat once
739	aioreq_pri $pri;	1103	aioreq_pri $pri;
740	add $grp aio_readdir $path, sub {	1104	add $grp aio_stat $wd, sub {
741	my $entries = shift
742	or return $grp->result ();	1105	return $grp->result () if $_[0];
		1106	my $now = time;
		1107	my $hash1 = join ":", (stat _)[0,1,3,7,9];
743		1108
744	# stat the dir another time	1109	# read the directory entries
745	aioreq_pri $pri;	1110	aioreq_pri $pri;
		1111	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1112	my $entries = shift
		1113	or return $grp->result ();
		1114
		1115	# stat the dir another time
		1116	aioreq_pri $pri;
746	add $grp aio_stat $path, sub {	1117	add $grp aio_stat $wd, sub {
747	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1118	my $hash2 = join ":", (stat _)[0,1,3,7,9];
748		1119
749	my $ndirs;	1120	my $ndirs;
750		1121
751	# take the slow route if anything looks fishy	1122	# take the slow route if anything looks fishy
752	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1123	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
753	$ndirs = -1;	1124	$ndirs = -1;
754	} else {	1125	} else {
755	# if nlink == 2, we are finished	1126	# if nlink == 2, we are finished
756	# on non-posix-fs's, we rely on nlink < 2	1127	# for non-posix-fs's, we rely on nlink < 2
757	$ndirs = (stat _)[3] - 2	1128	$ndirs = (stat _)[3] - 2
758	or return $grp->result ([], $entries);	1129	or return $grp->result ([], $entries);
759	}	1130	}
760		1131
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);	1132	my (@dirs, @nondirs);
769		1133
770	my $statgrp = add $grp aio_group sub {	1134	my $statgrp = add $grp aio_group sub {
771	$grp->result (\@dirs, \@nondirs);	1135	$grp->result (\@dirs, \@nondirs);
772	};	1136	};
773		1137
774	limit $statgrp $maxreq;	1138	limit $statgrp $maxreq;
775	feed $statgrp sub {	1139	feed $statgrp sub {
776	return unless @$entries;	1140	return unless @$entries;
777	my $entry = pop @$entries;	1141	my $entry = shift @$entries;
778		1142
779	aioreq_pri $pri;	1143	aioreq_pri $pri;
		1144	$wd->[1] = "$entry/.";
780	add $statgrp aio_stat "$path/$entry/.", sub {	1145	add $statgrp aio_stat $wd, sub {
781	if ($_[0] < 0) {	1146	if ($_[0] < 0) {
782	push @nondirs, $entry;	1147	push @nondirs, $entry;
783	} else {	1148	} else {
784	# need to check for real directory	1149	# need to check for real directory
785	aioreq_pri $pri;	1150	aioreq_pri $pri;
		1151	$wd->[1] = $entry;
786	add $statgrp aio_lstat "$path/$entry", sub {	1152	add $statgrp aio_lstat $wd, sub {
787	if (-d _) {	1153	if (-d _) {
788	push @dirs, $entry;	1154	push @dirs, $entry;
789		1155
790	unless (--$ndirs) {	1156	unless (--$ndirs) {
791	push @nondirs, @$entries;	1157	push @nondirs, @$entries;
792	feed $statgrp;	1158	feed $statgrp;
		1159	}
		1160	} else {
		1161	push @nondirs, $entry;
793	}	1162	}
794	} else {
795	push @nondirs, $entry;
796	}	1163	}
797	}	1164	}
798	}	1165	};
799	};	1166	};
800	};	1167	};
801	};	1168	};
802	};	1169	};
803	};	1170	};
804		1171
805	$grp	1172	$grp
806	}	1173	}
807		1174
808	=item aio_rmtree $path, $callback->($status)	1175	=item aio_rmtree $pathname, $callback->($status)
809		1176
810	Delete a directory tree starting (and including) C<$path>, return the	1177	Delete a directory tree starting (and including) C<$path>, return the
811	status of the final C<rmdir> only. This is a composite request that	1178	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	1179	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
813	everything else.	1180	everything else.
814		1181
815	=cut	1182	=cut
816		1183
…		…
838	};	1205	};
839		1206
840	$grp	1207	$grp
841	}	1208	}
842		1209
		1210	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1211
		1212	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1213
		1214	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1215	they execute asynchronously and pass the return value to the callback.
		1216
		1217	Both calls can be used for a lot of things, some of which make more sense
		1218	to run asynchronously in their own thread, while some others make less
		1219	sense. For example, calls that block waiting for external events, such
		1220	as locking, will also lock down an I/O thread while it is waiting, which
		1221	can deadlock the whole I/O system. At the same time, there might be no
		1222	alternative to using a thread to wait.
		1223
		1224	So in general, you should only use these calls for things that do
		1225	(filesystem) I/O, not for things that wait for other events (network,
		1226	other processes), although if you are careful and know what you are doing,
		1227	you still can.
		1228
		1229	The following constants are available (missing ones are, as usual C<0>):
		1230
		1231	C<F_DUPFD_CLOEXEC>,
		1232
		1233	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1234
		1235	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1236
		1237	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1238	C<FS_IOC_FIEMAP>.
		1239
		1240	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1241	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1242
		1243	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1244	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1245	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1246	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1247	C<FS_FL_USER_MODIFIABLE>.
		1248
		1249	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1250	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1251	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1252	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1253
843	=item aio_sync $callback->($status)	1254	=item aio_sync $callback->($status)
844		1255
845	Asynchronously call sync and call the callback when finished.	1256	Asynchronously call sync and call the callback when finished.
846		1257
847	=item aio_fsync $fh, $callback->($status)	1258	=item aio_fsync $fh, $callback->($status)
…		…
855	callback with the fdatasync result code.	1266	callback with the fdatasync result code.
856		1267
857	If this call isn't available because your OS lacks it or it couldn't be	1268	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.	1269	detected, it will be emulated by calling C<fsync> instead.
859		1270
		1271	=item aio_syncfs $fh, $callback->($status)
		1272
		1273	Asynchronously call the syncfs syscall to sync the filesystem associated
		1274	to the given filehandle and call the callback with the syncfs result
		1275	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1276	errno to C<ENOSYS> nevertheless.
		1277
		1278	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1279
		1280	Sync the data portion of the file specified by C<$offset> and C<$length>
		1281	to disk (but NOT the metadata), by calling the Linux-specific
		1282	sync_file_range call. If sync_file_range is not available or it returns
		1283	ENOSYS, then fdatasync or fsync is being substituted.
		1284
		1285	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1286	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1287	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1288	manpage for details.
		1289
860	=item aio_pathsync $path, $callback->($status)	1290	=item aio_pathsync $pathname, $callback->($status)
861		1291
862	This request tries to open, fsync and close the given path. This is a	1292	This request tries to open, fsync and close the given path. This is a
863	composite request intended tosync directories after directory operations	1293	composite request intended to sync directories after directory operations
864	(E.g. rename). This might not work on all operating systems or have any	1294	(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	1295	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,	1296	written to disc. It works for anything that can be opened for read-only,
867	not just directories.	1297	not just directories.
		1298
		1299	Future versions of this function might fall back to other methods when
		1300	C<fsync> on the directory fails (such as calling C<sync>).
868		1301
869	Passes C<0> when everything went ok, and C<-1> on error.	1302	Passes C<0> when everything went ok, and C<-1> on error.
870		1303
871	=cut	1304	=cut
872		1305
…		…
893	};	1326	};
894		1327
895	$grp	1328	$grp
896	}	1329	}
897		1330
		1331	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1332
		1333	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1334	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1335	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1336	scalar must only be modified in-place while an aio operation is pending on
		1337	it).
		1338
		1339	It calls the C<msync> function of your OS, if available, with the memory
		1340	area starting at C<$offset> in the string and ending C<$length> bytes
		1341	later. If C<$length> is negative, counts from the end, and if C<$length>
		1342	is C<undef>, then it goes till the end of the string. The flags can be
		1343	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1344	C<IO::AIO::MS_INVALIDATE>.
		1345
		1346	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1347
		1348	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1349	scalars.
		1350
		1351	It touches (reads or writes) all memory pages in the specified
		1352	range inside the scalar. All caveats and parameters are the same
		1353	as for C<aio_msync>, above, except for flags, which must be either
		1354	C<0> (which reads all pages and ensures they are instantiated) or
		1355	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1356	writing an octet from it, which dirties the page).
		1357
		1358	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1359
		1360	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1361	scalars.
		1362
		1363	It reads in all the pages of the underlying storage into memory (if any)
		1364	and locks them, so they are not getting swapped/paged out or removed.
		1365
		1366	If C<$length> is undefined, then the scalar will be locked till the end.
		1367
		1368	On systems that do not implement C<mlock>, this function returns C<-1>
		1369	and sets errno to C<ENOSYS>.
		1370
		1371	Note that the corresponding C<munlock> is synchronous and is
		1372	documented under L<MISCELLANEOUS FUNCTIONS>.
		1373
		1374	Example: open a file, mmap and mlock it - both will be undone when
		1375	C<$data> gets destroyed.
		1376
		1377	open my $fh, "<", $path or die "$path: $!";
		1378	my $data;
		1379	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1380	aio_mlock $data; # mlock in background
		1381
		1382	=item aio_mlockall $flags, $callback->($status)
		1383
		1384	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1385	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1386
		1387	On systems that do not implement C<mlockall>, this function returns C<-1>
		1388	and sets errno to C<ENOSYS>.
		1389
		1390	Note that the corresponding C<munlockall> is synchronous and is
		1391	documented under L<MISCELLANEOUS FUNCTIONS>.
		1392
		1393	Example: asynchronously lock all current and future pages into memory.
		1394
		1395	aio_mlockall IO::AIO::MCL_FUTURE;
		1396
		1397	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1398
		1399	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1400	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1401	the ioctl is not available on your OS, then this request will fail with
		1402	C<ENOSYS>.
		1403
		1404	C<$start> is the starting offset to query extents for, C<$length> is the
		1405	size of the range to query - if it is C<undef>, then the whole file will
		1406	be queried.
		1407
		1408	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1409	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1410	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1411	the data portion.
		1412
		1413	C<$count> is the maximum number of extent records to return. If it is
		1414	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1415	case, if it is C<0>, then the callback receives the number of extents
		1416	instead of the extents themselves (which is unreliable, see below).
		1417
		1418	If an error occurs, the callback receives no arguments. The special
		1419	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1420
		1421	Otherwise, the callback receives an array reference with extent
		1422	structures. Each extent structure is an array reference itself, with the
		1423	following members:
		1424
		1425	[$logical, $physical, $length, $flags]
		1426
		1427	Flags is any combination of the following flag values (typically either C<0>
		1428	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1429
		1430	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1431	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1432	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1433	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1434	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1435	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1436
		1437	At the time of this writing (Linux 3.2), this request is unreliable unless
		1438	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1439	it to return all extents of a range for files with a large number of
		1440	extents. The code (only) works around all these issues if C<$count> is
		1441	C<undef>.
		1442
898	=item aio_group $callback->(...)	1443	=item aio_group $callback->(...)
899		1444
900	This is a very special aio request: Instead of doing something, it is a	1445	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	1446	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	1447	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	1484	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.	1485	except to put your application under artificial I/O pressure.
941		1486
942	=back	1487	=back
943		1488
		1489
		1490	=head2 IO::AIO::WD - multiple working directories
		1491
		1492	Your process only has one current working directory, which is used by all
		1493	threads. This makes it hard to use relative paths (some other component
		1494	could call C<chdir> at any time, and it is hard to control when the path
		1495	will be used by IO::AIO).
		1496
		1497	One solution for this is to always use absolute paths. This usually works,
		1498	but can be quite slow (the kernel has to walk the whole path on every
		1499	access), and can also be a hassle to implement.
		1500
		1501	Newer POSIX systems have a number of functions (openat, fdopendir,
		1502	futimensat and so on) that make it possible to specify working directories
		1503	per operation.
		1504
		1505	For portability, and because the clowns who "designed", or shall I write,
		1506	perpetrated this new interface were obviously half-drunk, this abstraction
		1507	cannot be perfect, though.
		1508
		1509	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1510	object. This object stores the canonicalised, absolute version of the
		1511	path, and on systems that allow it, also a directory file descriptor.
		1512
		1513	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1514	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1515	object and a pathname instead (or the IO::AIO::WD object alone, which
		1516	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1517	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1518	to that IO::AIO::WD object.
		1519
		1520	For example, to get a wd object for F</etc> and then stat F<passwd>
		1521	inside, you would write:
		1522
		1523	aio_wd "/etc", sub {
		1524	my $etcdir = shift;
		1525
		1526	# although $etcdir can be undef on error, there is generally no reason
		1527	# to check for errors here, as aio_stat will fail with ENOENT
		1528	# when $etcdir is undef.
		1529
		1530	aio_stat [$etcdir, "passwd"], sub {
		1531	# yay
		1532	};
		1533	};
		1534
		1535	The fact that C<aio_wd> is a request and not a normal function shows that
		1536	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1537	which is why it is done asynchronously.
		1538
		1539	To stat the directory obtained with C<aio_wd> above, one could write
		1540	either of the following three request calls:
		1541
		1542	aio_lstat "/etc" , sub { ... # pathname as normal string
		1543	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1544	aio_lstat $wd , sub { ... # shorthand for the previous
		1545
		1546	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1547	object and the pathname string, so you could write the following without
		1548	causing any issues due to C<$path> getting reused:
		1549
		1550	my $path = [$wd, undef];
		1551
		1552	for my $name (qw(abc def ghi)) {
		1553	$path->[1] = $name;
		1554	aio_stat $path, sub {
		1555	# ...
		1556	};
		1557	}
		1558
		1559	There are some caveats: when directories get renamed (or deleted), the
		1560	pathname string doesn't change, so will point to the new directory (or
		1561	nowhere at all), while the directory fd, if available on the system,
		1562	will still point to the original directory. Most functions accepting a
		1563	pathname will use the directory fd on newer systems, and the string on
		1564	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1565	the string form of the pathname.
		1566
		1567	So this functionality is mainly useful to get some protection against
		1568	C<chdir>, to easily get an absolute path out of a relative path for future
		1569	reference, and to speed up doing many operations in the same directory
		1570	(e.g. when stat'ing all files in a directory).
		1571
		1572	The following functions implement this working directory abstraction:
		1573
		1574	=over 4
		1575
		1576	=item aio_wd $pathname, $callback->($wd)
		1577
		1578	Asynchonously canonicalise the given pathname and convert it to an
		1579	IO::AIO::WD object representing it. If possible and supported on the
		1580	system, also open a directory fd to speed up pathname resolution relative
		1581	to this working directory.
		1582
		1583	If something goes wrong, then C<undef> is passwd to the callback instead
		1584	of a working directory object and C<$!> is set appropriately. Since
		1585	passing C<undef> as working directory component of a pathname fails the
		1586	request with C<ENOENT>, there is often no need for error checking in the
		1587	C<aio_wd> callback, as future requests using the value will fail in the
		1588	expected way.
		1589
		1590	=item IO::AIO::CWD
		1591
		1592	This is a compiletime constant (object) that represents the process
		1593	current working directory.
		1594
		1595	Specifying this object as working directory object for a pathname is as if
		1596	the pathname would be specified directly, without a directory object. For
		1597	example, these calls are functionally identical:
		1598
		1599	aio_stat "somefile", sub { ... };
		1600	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1601
		1602	=back
		1603
		1604	To recover the path associated with an IO::AIO::WD object, you can use
		1605	C<aio_realpath>:
		1606
		1607	aio_realpath $wd, sub {
		1608	warn "path is $_[0]\n";
		1609	};
		1610
		1611	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1612	sometimes, fall back to using an absolue path.
		1613
944	=head2 IO::AIO::REQ CLASS	1614	=head2 IO::AIO::REQ CLASS
945		1615
946	All non-aggregate C<aio_*> functions return an object of this class when	1616	All non-aggregate C<aio_*> functions return an object of this class when
947	called in non-void context.	1617	called in non-void context.
948		1618
…		…
951	=item cancel $req	1621	=item cancel $req
952		1622
953	Cancels the request, if possible. Has the effect of skipping execution	1623	Cancels the request, if possible. Has the effect of skipping execution
954	when entering the B<execute> state and skipping calling the callback when	1624	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	1625	entering the the B<result> state, but will leave the request otherwise
956	untouched. That means that requests that currently execute will not be	1626	untouched (with the exception of readdir). That means that requests that
957	stopped and resources held by the request will not be freed prematurely.	1627	currently execute will not be stopped and resources held by the request
		1628	will not be freed prematurely.
958		1629
959	=item cb $req $callback->(...)	1630	=item cb $req $callback->(...)
960		1631
961	Replace (or simply set) the callback registered to the request.	1632	Replace (or simply set) the callback registered to the request.
962		1633
…		…
1013	Their lifetime, simplified, looks like this: when they are empty, they	1684	Their lifetime, simplified, looks like this: when they are empty, they
1014	will finish very quickly. If they contain only requests that are in the	1685	will finish very quickly. If they contain only requests that are in the
1015	C<done> state, they will also finish. Otherwise they will continue to	1686	C<done> state, they will also finish. Otherwise they will continue to
1016	exist.	1687	exist.
1017		1688
1018	That means after creating a group you have some time to add requests. And	1689	That means after creating a group you have some time to add requests
1019	in the callbacks of those requests, you can add further requests to the	1690	(precisely before the callback has been invoked, which is only done within
1020	group. And only when all those requests have finished will the the group	1691	the C<poll_cb>). And in the callbacks of those requests, you can add
1021	itself finish.	1692	further requests to the group. And only when all those requests have
		1693	finished will the the group itself finish.
1022		1694
1023	=over 4	1695	=over 4
1024		1696
1025	=item add $grp ...	1697	=item add $grp ...
1026		1698
…		…
1034		1706
1035	=item $grp->cancel_subs	1707	=item $grp->cancel_subs
1036		1708
1037	Cancel all subrequests and clears any feeder, but not the group request	1709	Cancel all subrequests and clears any feeder, but not the group request
1038	itself. Useful when you queued a lot of events but got a result early.	1710	itself. Useful when you queued a lot of events but got a result early.
		1711
		1712	The group request will finish normally (you cannot add requests to the
		1713	group).
1039		1714
1040	=item $grp->result (...)	1715	=item $grp->result (...)
1041		1716
1042	Set the result value(s) that will be passed to the group callback when all	1717	Set the result value(s) that will be passed to the group callback when all
1043	subrequests have finished and set the groups errno to the current value	1718	subrequests have finished and set the groups errno to the current value
…		…
1059	=item feed $grp $callback->($grp)	1734	=item feed $grp $callback->($grp)
1060		1735
1061	Sets a feeder/generator on this group: every group can have an attached	1736	Sets a feeder/generator on this group: every group can have an attached
1062	generator that generates requests if idle. The idea behind this is that,	1737	generator that generates requests if idle. The idea behind this is that,
1063	although you could just queue as many requests as you want in a group,	1738	although you could just queue as many requests as you want in a group,
1064	this might starve other requests for a potentially long time. For	1739	this might starve other requests for a potentially long time. For example,
1065	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1740	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1066	requests, delaying any later requests for a long time.	1741	requests, delaying any later requests for a long time.
1067		1742
1068	To avoid this, and allow incremental generation of requests, you can	1743	To avoid this, and allow incremental generation of requests, you can
1069	instead a group and set a feeder on it that generates those requests. The	1744	instead a group and set a feeder on it that generates those requests. The
1070	feed callback will be called whenever there are few enough (see C<limit>,	1745	feed callback will be called whenever there are few enough (see C<limit>,
…		…
1075	not impose any limits).	1750	not impose any limits).
1076		1751
1077	If the feed does not queue more requests when called, it will be	1752	If the feed does not queue more requests when called, it will be
1078	automatically removed from the group.	1753	automatically removed from the group.
1079		1754
1080	If the feed limit is C<0>, it will be set to C<2> automatically.	1755	If the feed limit is C<0> when this method is called, it will be set to
		1756	C<2> automatically.
1081		1757
1082	Example:	1758	Example:
1083		1759
1084	# stat all files in @files, but only ever use four aio requests concurrently:	1760	# stat all files in @files, but only ever use four aio requests concurrently:
1085		1761
…		…
1097	Sets the feeder limit for the group: The feeder will be called whenever	1773	Sets the feeder limit for the group: The feeder will be called whenever
1098	the group contains less than this many requests.	1774	the group contains less than this many requests.
1099		1775
1100	Setting the limit to C<0> will pause the feeding process.	1776	Setting the limit to C<0> will pause the feeding process.
1101		1777
		1778	The default value for the limit is C<0>, but note that setting a feeder
		1779	automatically bumps it up to C<2>.
		1780
1102	=back	1781	=back
1103		1782
1104	=head2 SUPPORT FUNCTIONS	1783	=head2 SUPPORT FUNCTIONS
1105		1784
1106	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1785	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1108	=over 4	1787	=over 4
1109		1788
1110	=item $fileno = IO::AIO::poll_fileno	1789	=item $fileno = IO::AIO::poll_fileno
1111		1790
1112	Return the I<request result pipe file descriptor>. This filehandle must be	1791	Return the I<request result pipe file descriptor>. This filehandle must be
1113	polled for reading by some mechanism outside this module (e.g. Event or	1792	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1114	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1793	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1115	to call C<poll_cb> to check the results.	1794	you have to call C<poll_cb> to check the results.
1116		1795
1117	See C<poll_cb> for an example.	1796	See C<poll_cb> for an example.
1118		1797
1119	=item IO::AIO::poll_cb	1798	=item IO::AIO::poll_cb
1120		1799
1121	Process some outstanding events on the result pipe. You have to call this	1800	Process some requests that have reached the result phase (i.e. they have
1122	regularly. Returns the number of events processed. Returns immediately	1801	been executed but the results are not yet reported). You have to call
1123	when no events are outstanding. The amount of events processed depends on	1802	this "regularly" to finish outstanding requests.
1124	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1125		1803
		1804	Returns C<0> if all events could be processed (or there were no
		1805	events to process), or C<-1> if it returned earlier for whatever
		1806	reason. Returns immediately when no events are outstanding. The amount
		1807	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1808	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1809
1126	If not all requests were processed for whatever reason, the filehandle	1810	If not all requests were processed for whatever reason, the poll file
1127	will still be ready when C<poll_cb> returns.	1811	descriptor will still be ready when C<poll_cb> returns, so normally you
		1812	don't have to do anything special to have it called later.
		1813
		1814	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1815	ready, it can be beneficial to call this function from loops which submit
		1816	a lot of requests, to make sure the results get processed when they become
		1817	available and not just when the loop is finished and the event loop takes
		1818	over again. This function returns very fast when there are no outstanding
		1819	requests.
1128		1820
1129	Example: Install an Event watcher that automatically calls	1821	Example: Install an Event watcher that automatically calls
1130	IO::AIO::poll_cb with high priority:	1822	IO::AIO::poll_cb with high priority (more examples can be found in the
		1823	SYNOPSIS section, at the top of this document):
1131		1824
1132	Event->io (fd => IO::AIO::poll_fileno,	1825	Event->io (fd => IO::AIO::poll_fileno,
1133	poll => 'r', async => 1,	1826	poll => 'r', async => 1,
1134	cb => \&IO::AIO::poll_cb);	1827	cb => \&IO::AIO::poll_cb);
		1828
		1829	=item IO::AIO::poll_wait
		1830
		1831	Wait until either at least one request is in the result phase or no
		1832	requests are outstanding anymore.
		1833
		1834	This is useful if you want to synchronously wait for some requests to
		1835	become ready, without actually handling them.
		1836
		1837	See C<nreqs> for an example.
		1838
		1839	=item IO::AIO::poll
		1840
		1841	Waits until some requests have been handled.
		1842
		1843	Returns the number of requests processed, but is otherwise strictly
		1844	equivalent to:
		1845
		1846	IO::AIO::poll_wait, IO::AIO::poll_cb
		1847
		1848	=item IO::AIO::flush
		1849
		1850	Wait till all outstanding AIO requests have been handled.
		1851
		1852	Strictly equivalent to:
		1853
		1854	IO::AIO::poll_wait, IO::AIO::poll_cb
		1855	while IO::AIO::nreqs;
1135		1856
1136	=item IO::AIO::max_poll_reqs $nreqs	1857	=item IO::AIO::max_poll_reqs $nreqs
1137		1858
1138	=item IO::AIO::max_poll_time $seconds	1859	=item IO::AIO::max_poll_time $seconds
1139		1860
…		…
1164	# use a low priority so other tasks have priority	1885	# use a low priority so other tasks have priority
1165	Event->io (fd => IO::AIO::poll_fileno,	1886	Event->io (fd => IO::AIO::poll_fileno,
1166	poll => 'r', nice => 1,	1887	poll => 'r', nice => 1,
1167	cb => &IO::AIO::poll_cb);	1888	cb => &IO::AIO::poll_cb);
1168		1889
1169	=item IO::AIO::poll_wait
1170
1171	If there are any outstanding requests and none of them in the result
1172	phase, wait till the result filehandle becomes ready for reading (simply
1173	does a C<select> on the filehandle. This is useful if you want to
1174	synchronously wait for some requests to finish).
1175
1176	See C<nreqs> for an example.
1177
1178	=item IO::AIO::poll
1179
1180	Waits until some requests have been handled.
1181
1182	Returns the number of requests processed, but is otherwise strictly
1183	equivalent to:
1184
1185	IO::AIO::poll_wait, IO::AIO::poll_cb
1186
1187	=item IO::AIO::flush
1188
1189	Wait till all outstanding AIO requests have been handled.
1190
1191	Strictly equivalent to:
1192
1193	IO::AIO::poll_wait, IO::AIO::poll_cb
1194	while IO::AIO::nreqs;
1195
1196	=back	1890	=back
1197		1891
1198	=head3 CONTROLLING THE NUMBER OF THREADS	1892	=head3 CONTROLLING THE NUMBER OF THREADS
1199		1893
1200	=over	1894	=over
…		…
1233		1927
1234	Under normal circumstances you don't need to call this function.	1928	Under normal circumstances you don't need to call this function.
1235		1929
1236	=item IO::AIO::max_idle $nthreads	1930	=item IO::AIO::max_idle $nthreads
1237		1931
1238	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1932	Limit the number of threads (default: 4) that are allowed to idle
1239	threads that did not get a request to process within 10 seconds). That	1933	(i.e., threads that did not get a request to process within the idle
1240	means if a thread becomes idle while C<$nthreads> other threads are also	1934	timeout (default: 10 seconds). That means if a thread becomes idle while
1241	idle, it will free its resources and exit.	1935	C<$nthreads> other threads are also idle, it will free its resources and
		1936	exit.
1242		1937
1243	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1938	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1244	to allow for extremely high load situations, but want to free resources	1939	to allow for extremely high load situations, but want to free resources
1245	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1940	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1246		1941
1247	The default is probably ok in most situations, especially if thread	1942	The default is probably ok in most situations, especially if thread
1248	creation is fast. If thread creation is very slow on your system you might	1943	creation is fast. If thread creation is very slow on your system you might
1249	want to use larger values.	1944	want to use larger values.
1250		1945
		1946	=item IO::AIO::idle_timeout $seconds
		1947
		1948	Sets the minimum idle timeout (default 10) after which worker threads are
		1949	allowed to exit. SEe C<IO::AIO::max_idle>.
		1950
1251	=item IO::AIO::max_outstanding $maxreqs	1951	=item IO::AIO::max_outstanding $maxreqs
		1952
		1953	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1954	you do queue up more than this number of requests, the next call to
		1955	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1956	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1957	longer exceeded.
		1958
		1959	In other words, this setting does not enforce a queue limit, but can be
		1960	used to make poll functions block if the limit is exceeded.
1252		1961
1253	This is a very bad function to use in interactive programs because it	1962	This is a very bad function to use in interactive programs because it
1254	blocks, and a bad way to reduce concurrency because it is inexact: Better	1963	blocks, and a bad way to reduce concurrency because it is inexact: Better
1255	use an C<aio_group> together with a feed callback.	1964	use an C<aio_group> together with a feed callback.
1256		1965
1257	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1966	Its main use is in scripts without an event loop - when you want to stat
1258	do queue up more than this number of requests, the next call to the	1967	a lot of files, you can write something like this:
1259	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1260	function will block until the limit is no longer exceeded.
1261		1968
1262	The default value is very large, so there is no practical limit on the	1969	IO::AIO::max_outstanding 32;
1263	number of outstanding requests.
1264		1970
1265	You can still queue as many requests as you want. Therefore,	1971	for my $path (...) {
1266	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1972	aio_stat $path , ...;
1267	as a stop gap to shield against fatal memory overflow (with large values).	1973	IO::AIO::poll_cb;
		1974	}
		1975
		1976	IO::AIO::flush;
		1977
		1978	The call to C<poll_cb> inside the loop will normally return instantly, but
		1979	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1980	some requests have been handled. This keeps the loop from pushing a large
		1981	number of C<aio_stat> requests onto the queue.
		1982
		1983	The default value for C<max_outstanding> is very large, so there is no
		1984	practical limit on the number of outstanding requests.
1268		1985
1269	=back	1986	=back
1270		1987
1271	=head3 STATISTICAL INFORMATION	1988	=head3 STATISTICAL INFORMATION
1272		1989
…		…
1292	Returns the number of requests currently in the pending state (executed,	2009	Returns the number of requests currently in the pending state (executed,
1293	but not yet processed by poll_cb).	2010	but not yet processed by poll_cb).
1294		2011
1295	=back	2012	=back
1296		2013
		2014	=head3 MISCELLANEOUS FUNCTIONS
		2015
		2016	IO::AIO implements some functions that are useful when you want to use
		2017	some "Advanced I/O" function not available to in Perl, without going the
		2018	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2019	counterpart.
		2020
		2021	=over 4
		2022
		2023	=item $numfd = IO::AIO::get_fdlimit
		2024
		2025	This function is I<EXPERIMENTAL> and subject to change.
		2026
		2027	Tries to find the current file descriptor limit and returns it, or
		2028	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2029	the highest valid file descriptor number.
		2030
		2031	=item IO::AIO::min_fdlimit [$numfd]
		2032
		2033	This function is I<EXPERIMENTAL> and subject to change.
		2034
		2035	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2036	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2037	is missing, it will try to set a very high limit, although this is not
		2038	recommended when you know the actual minimum that you require.
		2039
		2040	If the limit cannot be raised enough, the function makes a best-effort
		2041	attempt to increase the limit as much as possible, using various
		2042	tricks, while still failing. You can query the resulting limit using
		2043	C<IO::AIO::get_fdlimit>.
		2044
		2045	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2046	true.
		2047
		2048	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2049
		2050	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2051	but is blocking (this makes most sense if you know the input data is
		2052	likely cached already and the output filehandle is set to non-blocking
		2053	operations).
		2054
		2055	Returns the number of bytes copied, or C<-1> on error.
		2056
		2057	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2058
		2059	Simply calls the C<posix_fadvise> function (see its
		2060	manpage for details). The following advice constants are
		2061	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2062	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2063	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2064
		2065	On systems that do not implement C<posix_fadvise>, this function returns
		2066	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2067
		2068	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2069
		2070	Simply calls the C<posix_madvise> function (see its
		2071	manpage for details). The following advice constants are
		2072	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2073	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2074	C<IO::AIO::MADV_DONTNEED>.
		2075
		2076	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2077	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2078	will be reduced to fit into the C<$scalar>.
		2079
		2080	On systems that do not implement C<posix_madvise>, this function returns
		2081	ENOSYS, otherwise the return value of C<posix_madvise>.
		2082
		2083	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2084
		2085	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2086	$scalar (see its manpage for details). The following protect
		2087	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2088	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2089
		2090	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2091	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2092	will be reduced to fit into the C<$scalar>.
		2093
		2094	On systems that do not implement C<mprotect>, this function returns
		2095	ENOSYS, otherwise the return value of C<mprotect>.
		2096
		2097	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2098
		2099	Memory-maps a file (or anonymous memory range) and attaches it to the
		2100	given C<$scalar>, which will act like a string scalar. Returns true on
		2101	success, and false otherwise.
		2102
		2103	The scalar must exist, but its contents do not matter - this means you
		2104	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2105	the scalar first.
		2106
		2107	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2108	which don't change the string length, and most read-only operations such
		2109	as copying it or searching it with regexes and so on.
		2110
		2111	Anything else is unsafe and will, at best, result in memory leaks.
		2112
		2113	The memory map associated with the C<$scalar> is automatically removed
		2114	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2115	or C<IO::AIO::munmap> functions are called on it.
		2116
		2117	This calls the C<mmap>(2) function internally. See your system's manual
		2118	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2119
		2120	The C<$length> must be larger than zero and smaller than the actual
		2121	filesize.
		2122
		2123	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2124	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2125
		2126	C<$flags> can be a combination of
		2127	C<IO::AIO::MAP_SHARED> or
		2128	C<IO::AIO::MAP_PRIVATE>,
		2129	or a number of system-specific flags (when not available, the are C<0>):
		2130	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2131	C<IO::AIO::MAP_LOCKED>,
		2132	C<IO::AIO::MAP_NORESERVE>,
		2133	C<IO::AIO::MAP_POPULATE>,
		2134	C<IO::AIO::MAP_NONBLOCK>,
		2135	C<IO::AIO::MAP_FIXED>,
		2136	C<IO::AIO::MAP_GROWSDOWN>,
		2137	C<IO::AIO::MAP_32BIT>,
		2138	C<IO::AIO::MAP_HUGETLB> or
		2139	C<IO::AIO::MAP_STACK>.
		2140
		2141	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2142
		2143	C<$offset> is the offset from the start of the file - it generally must be
		2144	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2145
		2146	Example:
		2147
		2148	use Digest::MD5;
		2149	use IO::AIO;
		2150
		2151	open my $fh, "<verybigfile"
		2152	or die "$!";
		2153
		2154	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2155	or die "verybigfile: $!";
		2156
		2157	my $fast_md5 = md5 $data;
		2158
		2159	=item IO::AIO::munmap $scalar
		2160
		2161	Removes a previous mmap and undefines the C<$scalar>.
		2162
		2163	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2164
		2165	Calls the C<munlock> function, undoing the effects of a previous
		2166	C<aio_mlock> call (see its description for details).
		2167
		2168	=item IO::AIO::munlockall
		2169
		2170	Calls the C<munlockall> function.
		2171
		2172	On systems that do not implement C<munlockall>, this function returns
		2173	ENOSYS, otherwise the return value of C<munlockall>.
		2174
		2175	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2176
		2177	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2178	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2179	should be the file offset.
		2180
		2181	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2182	silently corrupt the data in this case.
		2183
		2184	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2185	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2186	C<IO::AIO::SPLICE_F_GIFT>.
		2187
		2188	See the C<splice(2)> manpage for details.
		2189
		2190	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2191
		2192	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2193	description for C<IO::AIO::splice> above for details.
		2194
		2195	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2196
		2197	Attempts to query or change the pipe buffer size. Obviously works only
		2198	on pipes, and currently works only on GNU/Linux systems, and fails with
		2199	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2200	size on other systems, drop me a note.
		2201
		2202	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2203
		2204	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2205	C<$flags> is missing or C<0>, then this should be the same as a call to
		2206	perl's built-in C<pipe> function and create a new pipe, and works on
		2207	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2208	(..., 4096, O_BINARY)>.
		2209
		2210	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2211	the given flags (Linux 2.6.27, glibc 2.9).
		2212
		2213	On success, the read and write file handles are returned.
		2214
		2215	On error, nothing will be returned. If the pipe2 syscall is missing and
		2216	C<$flags> is non-zero, fails with C<ENOSYS>.
		2217
		2218	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2219	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2220	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2221
		2222	Example: create a pipe race-free w.r.t. threads and fork:
		2223
		2224	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2225	or die "pipe2: $!\n";
		2226
		2227	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2228
		2229	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2230	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2231
		2232	On success, the new eventfd filehandle is returned, otherwise returns
		2233	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2234
		2235	Please refer to L<eventfd(2)> for more info on this call.
		2236
		2237	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2238	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2239
		2240	Example: create a new eventfd filehandle:
		2241
		2242	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2243	or die "eventfd: $!\n";
		2244
		2245	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2246
		2247	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2248	(unhelpful) default for C<$flags> is C<0>.
		2249
		2250	On success, the new timerfd filehandle is returned, otherwise returns
		2251	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2252
		2253	Please refer to L<timerfd_create(2)> for more info on this call.
		2254
		2255	The following C<$clockid> values are
		2256	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2257	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2258	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2259	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2260
		2261	The following C<$flags> values are available (Linux
		2262	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2263
		2264	Example: create a new timerfd and set it to one-second repeated alarms,
		2265	then wait for two alarms:
		2266
		2267	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2268	or die "timerfd_create: $!\n";
		2269
		2270	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2271	or die "timerfd_settime: $!\n";
		2272
		2273	for (1..2) {
		2274	8 == sysread $fh, my $buf, 8
		2275	or die "timerfd read failure\n";
		2276
		2277	printf "number of expirations (likely 1): %d\n",
		2278	unpack "Q", $buf;
		2279	}
		2280
		2281	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2282
		2283	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2284	call. Please refer to its manpage for more info on this call.
		2285
		2286	The new itimerspec is specified using two (possibly fractional) second
		2287	values, C<$new_interval> and C<$new_value>).
		2288
		2289	On success, the current interval and value are returned (as per
		2290	C<timerfd_gettime>). On failure, the empty list is returned.
		2291
		2292	The following C<$flags> values are
		2293	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2294	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2295
		2296	See C<IO::AIO::timerfd_create> for a full example.
		2297
		2298	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2299
		2300	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2301	call. Please refer to its manpage for more info on this call.
		2302
		2303	On success, returns the current values of interval and value for the given
		2304	timerfd (as potentially fractional second values). On failure, the empty
		2305	list is returned.
		2306
		2307	=back
		2308
1297	=cut	2309	=cut
1298		2310
1299	min_parallel 8;	2311	min_parallel 8;
1300		2312
1301	END { flush }	2313	END { flush }
1302		2314
1303	1;	2315	1;
1304		2316
		2317	=head1 EVENT LOOP INTEGRATION
		2318
		2319	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2320	automatically into many event loops:
		2321
		2322	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2323	use AnyEvent::AIO;
		2324
		2325	You can also integrate IO::AIO manually into many event loops, here are
		2326	some examples of how to do this:
		2327
		2328	# EV integration
		2329	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2330
		2331	# Event integration
		2332	Event->io (fd => IO::AIO::poll_fileno,
		2333	poll => 'r',
		2334	cb => \&IO::AIO::poll_cb);
		2335
		2336	# Glib/Gtk2 integration
		2337	add_watch Glib::IO IO::AIO::poll_fileno,
		2338	in => sub { IO::AIO::poll_cb; 1 };
		2339
		2340	# Tk integration
		2341	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2342	readable => \&IO::AIO::poll_cb);
		2343
		2344	# Danga::Socket integration
		2345	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2346	\&IO::AIO::poll_cb);
		2347
1305	=head2 FORK BEHAVIOUR	2348	=head2 FORK BEHAVIOUR
1306		2349
1307	This module should do "the right thing" when the process using it forks:	2350	Usage of pthreads in a program changes the semantics of fork
		2351	considerably. Specifically, only async-safe functions can be called after
		2352	fork. Perl doesn't know about this, so in general, you cannot call fork
		2353	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2354	pthreads, so this applies, but many other extensions and (for inexplicable
		2355	reasons) perl itself often is linked against pthreads, so this limitation
		2356	applies to quite a lot of perls.
1308		2357
1309	Before the fork, IO::AIO enters a quiescent state where no requests	2358	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1310	can be added in other threads and no results will be processed. After	2359	only works in the process that loaded it. Forking is fully supported, but
1311	the fork the parent simply leaves the quiescent state and continues	2360	using IO::AIO in the child is not.
1312	request/result processing, while the child frees the request/result queue
1313	(so that the requests started before the fork will only be handled in the
1314	parent). Threads will be started on demand until the limit set in the
1315	parent process has been reached again.
1316		2361
1317	In short: the parent will, after a short pause, continue as if fork had	2362	You might get around by not I<using> IO::AIO before (or after)
1318	not been called, while the child will act as if IO::AIO has not been used	2363	forking. You could also try to call the L<IO::AIO::reinit> function in the
1319	yet.	2364	child:
		2365
		2366	=over 4
		2367
		2368	=item IO::AIO::reinit
		2369
		2370	Abandons all current requests and I/O threads and simply reinitialises all
		2371	data structures. This is not an operation supported by any standards, but
		2372	happens to work on GNU/Linux and some newer BSD systems.
		2373
		2374	The only reasonable use for this function is to call it after forking, if
		2375	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2376	the process will result in undefined behaviour. Calling it at any time
		2377	will also result in any undefined (by POSIX) behaviour.
		2378
		2379	=back
		2380
		2381	=head2 LINUX-SPECIFIC CALLS
		2382
		2383	When a call is documented as "linux-specific" then this means it
		2384	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2385	availability and compatibility of such calls regardless of the platform
		2386	it is compiled on, so platforms such as FreeBSD which often implement
		2387	these calls will work. When in doubt, call them and see if they fail wth
		2388	C<ENOSYS>.
1320		2389
1321	=head2 MEMORY USAGE	2390	=head2 MEMORY USAGE
1322		2391
1323	Per-request usage:	2392	Per-request usage:
1324		2393
…		…
1337	temporary buffers, and each thread requires a stack and other data	2406	temporary buffers, and each thread requires a stack and other data
1338	structures (usually around 16k-128k, depending on the OS).	2407	structures (usually around 16k-128k, depending on the OS).
1339		2408
1340	=head1 KNOWN BUGS	2409	=head1 KNOWN BUGS
1341		2410
1342	Known bugs will be fixed in the next release.	2411	Known bugs will be fixed in the next release :)
		2412
		2413	=head1 KNOWN ISSUES
		2414
		2415	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2416	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2417	non-created hash slots or other scalars I didn't think of. It's best to
		2418	avoid such and either use scalar variables or making sure that the scalar
		2419	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2420
		2421	I am not sure anything can be done about this, so this is considered a
		2422	known issue, rather than a bug.
1343		2423
1344	=head1 SEE ALSO	2424	=head1 SEE ALSO
1345		2425
1346	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2426	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1347	more natural syntax.	2427	more natural syntax.

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines