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Revision 1.50 by root, Sat Jun 24 16:27:02 2006 UTC vs.
Revision 1.168 by root, Mon Nov 30 22:22:13 2009 UTC

…		…
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", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# AnyEvent	21	# version 2+ has request and group objects
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	22	use IO::AIO 2;
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		23
24	# Event	24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	39	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
28		41
29	# Glib/Gtk2	42	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	44	in => sub { IO::AIO::poll_cb; 1 };
32		45
33	# Tk	46	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
36		49
37	# Danga::Socket	50	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
40		53
41
42	=head1 DESCRIPTION	54	=head1 DESCRIPTION
43		55
44	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
45	operating system supports.	57	operating system supports. It is implemented as an interface to C<libeio>
		58	(L<http://software.schmorp.de/pkg/libeio.html>).
46		59
		60	Asynchronous means that operations that can normally block your program
		61	(e.g. reading from disk) will be done asynchronously: the operation
		62	will still block, but you can do something else in the meantime. This
		63	is extremely useful for programs that need to stay interactive even
		64	when doing heavy I/O (GUI programs, high performance network servers
		65	etc.), but can also be used to easily do operations in parallel that are
		66	normally done sequentially, e.g. stat'ing many files, which is much faster
		67	on a RAID volume or over NFS when you do a number of stat operations
		68	concurrently.
		69
		70	While most of this works on all types of file descriptors (for
		71	example sockets), using these functions on file descriptors that
		72	support nonblocking operation (again, sockets, pipes etc.) is
		73	very inefficient. Use an event loop for that (such as the L<EV>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
47	Currently, a number of threads are started that execute your read/writes	76	In this version, a number of threads are started that execute your
48	and signal their completion. You don't need thread support in your libc or	77	requests and signal their completion. You don't need thread support
49	perl, and the threads created by this module will not be visible to the	78	in perl, and the threads created by this module will not be visible
50	pthreads library. In the future, this module might make use of the native	79	to perl. In the future, this module might make use of the native aio
51	aio functions available on many operating systems. However, they are often	80	functions available on many operating systems. However, they are often
52	not well-supported (Linux doesn't allow them on normal files currently,	81	not well-supported or restricted (GNU/Linux doesn't allow them on normal
53	for example), and they would only support aio_read and aio_write, so the	82	files currently, for example), and they would only support aio_read and
54	remaining functionality would have to be implemented using threads anyway.	83	aio_write, so the remaining functionality would have to be implemented
		84	using threads anyway.
55		85
56	Although the module will work with in the presence of other threads, it is	86	Although the module will work in the presence of other (Perl-) threads,
57	currently not reentrant, so use appropriate locking yourself, always call	87	it is currently not reentrant in any way, so use appropriate locking
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	88	yourself, always call C<poll_cb> from within the same thread, or never
59	C<aio_> functions) recursively.	89	call C<poll_cb> (or other C<aio_> functions) recursively.
		90
		91	=head2 EXAMPLE
		92
		93	This is a simple example that uses the EV module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use EV;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with EV
		101	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	EV::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	EV::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
60		184
61	=cut	185	=cut
62		186
63	package IO::AIO;	187	package IO::AIO;
64		188
65	no warnings;	189	use Carp ();
		190
		191	use common::sense;
66		192
67	use base 'Exporter';	193	use base 'Exporter';
68		194
69	use Fcntl ();
70
71	BEGIN {	195	BEGIN {
72	$VERSION = '1.8';	196	our $VERSION = '3.31';
73		197
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	199	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
76	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);	200	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	201	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
78	max_outstanding nreqs);	202	aio_rename aio_link aio_move aio_copy aio_group
		203	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		204	aio_chmod aio_utime aio_truncate);
		205
		206	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		207	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		208	min_parallel max_parallel max_idle
		209	nreqs nready npending nthreads
		210	max_poll_time max_poll_reqs
		211	sendfile fadvise);
		212
		213	push @AIO_REQ, qw(aio_busy); # not exported
		214
		215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		216
80	require XSLoader;	217	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	218	XSLoader::load ("IO::AIO", $VERSION);
82	}	219	}
83		220
84	=head1 FUNCTIONS	221	=head1 FUNCTIONS
85		222
86	=head2 AIO FUNCTIONS	223	=head2 AIO REQUEST FUNCTIONS
87		224
88	All the C<aio_*> calls are more or less thin wrappers around the syscall	225	All the C<aio_*> calls are more or less thin wrappers around the syscall
89	with the same name (sans C<aio_>). The arguments are similar or identical,	226	with the same name (sans C<aio_>). The arguments are similar or identical,
90	and they all accept an additional (and optional) C<$callback> argument	227	and they all accept an additional (and optional) C<$callback> argument
91	which must be a code reference. This code reference will get called with	228	which must be a code reference. This code reference will get called with
92	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	229	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
93	perl, which usually delivers "false") as it's sole argument when the given	230	perl, which usually delivers "false") as its sole argument after the given
94	syscall has been executed asynchronously.	231	syscall has been executed asynchronously.
95		232
96	All functions expecting a filehandle keep a copy of the filehandle	233	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	234	internally until the request has finished.
98		235
		236	All functions return request objects of type L<IO::AIO::REQ> that allow
		237	further manipulation of those requests while they are in-flight.
		238
99	The pathnames you pass to these routines I<must> be absolute and	239	The pathnames you pass to these routines I<must> be absolute and
100	encoded in byte form. The reason for the former is that at the time the	240	encoded as octets. The reason for the former is that at the time the
101	request is being executed, the current working directory could have	241	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	242	changed. Alternatively, you can make sure that you never change the
103	current working directory.	243	current working directory anywhere in the program and then use relative
		244	paths.
104		245
105	To encode pathnames to byte form, either make sure you either: a)	246	To encode pathnames as octets, either make sure you either: a) always pass
106	always pass in filenames you got from outside (command line, readdir	247	in filenames you got from outside (command line, readdir etc.) without
107	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
108	your pathnames to the locale (or other) encoding in effect in the user	249	your pathnames to the locale (or other) encoding in effect in the user
109	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	251	use something else to ensure your scalar has the correct contents.
		252
		253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		254	handles correctly whether it is set or not.
111		255
112	=over 4	256	=over 4
		257
		258	=item $prev_pri = aioreq_pri [$pri]
		259
		260	Returns the priority value that would be used for the next request and, if
		261	C<$pri> is given, sets the priority for the next aio request.
		262
		263	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		264	and C<4>, respectively. Requests with higher priority will be serviced
		265	first.
		266
		267	The priority will be reset to C<0> after each call to one of the C<aio_*>
		268	functions.
		269
		270	Example: open a file with low priority, then read something from it with
		271	higher priority so the read request is serviced before other low priority
		272	open requests (potentially spamming the cache):
		273
		274	aioreq_pri -3;
		275	aio_open ..., sub {
		276	return unless $_[0];
		277
		278	aioreq_pri -2;
		279	aio_read $_[0], ..., sub {
		280	...
		281	};
		282	};
		283
		284
		285	=item aioreq_nice $pri_adjust
		286
		287	Similar to C<aioreq_pri>, but subtracts the given value from the current
		288	priority, so the effect is cumulative.
		289
113		290
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	291	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		292
116	Asynchronously open or create a file and call the callback with a newly	293	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	294	created filehandle for the file.
…		…
123	list. They are the same as used by C<sysopen>.	300	list. They are the same as used by C<sysopen>.
124		301
125	Likewise, C<$mode> specifies the mode of the newly created file, if it	302	Likewise, C<$mode> specifies the mode of the newly created file, if it
126	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	303	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
127	except that it is mandatory (i.e. use C<0> if you don't create new files,	304	except that it is mandatory (i.e. use C<0> if you don't create new files,
128	and C<0666> or C<0777> if you do).	305	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		306	by the umask in effect then the request is being executed, so better never
		307	change the umask.
129		308
130	Example:	309	Example:
131		310
132	aio_open "/etc/passwd", O_RDONLY, 0, sub {	311	aio_open "/etc/passwd", O_RDONLY, 0, sub {
133	if ($_[0]) {	312	if ($_[0]) {
…		…
136	} else {	315	} else {
137	die "open failed: $!\n";	316	die "open failed: $!\n";
138	}	317	}
139	};	318	};
140		319
		320
141	=item aio_close $fh, $callback->($status)	321	=item aio_close $fh, $callback->($status)
142		322
143	Asynchronously close a file and call the callback with the result	323	Asynchronously close a file and call the callback with the result
144	code. I<WARNING:> although accepted, you should not pass in a perl	324	code.
145	filehandle here, as perl will likely close the file descriptor another
146	time when the filehandle is destroyed. Normally, you can safely call perls
147	C<close> or just let filehandles go out of scope.
148		325
149	This is supposed to be a bug in the API, so that might change. It's	326	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
150	therefore best to avoid this function.	327	closing the file descriptor associated with the filehandle itself.
		328
		329	Therefore, C<aio_close> will not close the filehandle - instead it will
		330	use dup2 to overwrite the file descriptor with the write-end of a pipe
		331	(the pipe fd will be created on demand and will be cached).
		332
		333	Or in other words: the file descriptor will be closed, but it will not be
		334	free for reuse until the perl filehandle is closed.
		335
		336	=cut
151		337
152	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		339
154	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
155		341
156	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	342	Reads or writes C<$length> bytes from or to the specified C<$fh> and
157	into the scalar given by C<data> and offset C<dataoffset> and calls the	343	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
158	callback without the actual number of bytes read (or -1 on error, just	344	and calls the callback without the actual number of bytes read (or -1 on
159	like the syscall).	345	error, just like the syscall).
		346
		347	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		348	offset plus the actual number of bytes read.
		349
		350	If C<$offset> is undefined, then the current file descriptor offset will
		351	be used (and updated), otherwise the file descriptor offset will not be
		352	changed by these calls.
		353
		354	If C<$length> is undefined in C<aio_write>, use the remaining length of
		355	C<$data>.
		356
		357	If C<$dataoffset> is less than zero, it will be counted from the end of
		358	C<$data>.
160		359
161	The C<$data> scalar I<MUST NOT> be modified in any way while the request	360	The C<$data> scalar I<MUST NOT> be modified in any way while the request
162	is outstanding. Modifying it can result in segfaults or WW3 (if the	361	is outstanding. Modifying it can result in segfaults or World War III (if
163	necessary/optional hardware is installed).	362	the necessary/optional hardware is installed).
164		363
165	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	364	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
166	offset C<0> within the scalar:	365	offset C<0> within the scalar:
167		366
168	aio_read $fh, 7, 15, $buffer, 0, sub {	367	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	368	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	369	print "read $_[0] bytes: <$buffer>\n";
171	};	370	};
172		371
173	=item aio_move $srcpath, $dstpath, $callback->($status)
174
175	[EXPERIMENTAL]
176
177	Try to move the I<file> (directories not supported as either source or destination)
178	from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok.
179
180	This is a composite request that tries to rename(2) the file first. If
181	rename files with C<EXDEV>, it creates the destination file with mode 0200
182	and copies the contents of the source file into it using C<aio_sendfile>,
183	followed by restoring atime, mtime, access mode and uid/gid, in that
184	order, and unlinking the C<$srcpath>.
185
186	If an error occurs, the partial destination file will be unlinked, if
187	possible, except when setting atime, mtime, access mode and uid/gid, where
188	errors are being ignored.
189
190	=cut
191
192	sub aio_move($$$) {
193	my ($src, $dst, $cb) = @_;
194
195	aio_rename $src, $dst, sub {
196	if ($_[0] && $! == Errno::EXDEV) {
197	aio_open $src, O_RDONLY, 0, sub {
198	if (my $src_fh = $_[0]) {
199	my @stat = stat $src_fh;
200
201	aio_open $dst, O_WRONLY, 0200, sub {
202	if (my $dst_fh = $_[0]) {
203	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
204	close $src_fh;
205
206	if ($_[0] == $stat[7]) {
207	utime $stat[8], $stat[9], $dst;
208	chmod $stat[2] & 07777, $dst_fh;
209	chown $stat[4], $stat[5], $dst_fh;
210	close $dst_fh;
211
212	aio_unlink $src, sub {
213	$cb->($_[0]);
214	};
215	} else {
216	my $errno = $!;
217	aio_unlink $dst, sub {
218	$! = $errno;
219	$cb->(-1);
220	};
221	}
222	};
223	} else {
224	$cb->(-1);
225	}
226	},
227
228	} else {
229	$cb->(-1);
230	}
231	};
232	} else {
233	$cb->($_[0]);
234	}
235	};
236	}
237		372
238	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	373	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
239		374
240	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	375	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
241	reading at byte offset C<$in_offset>, and starts writing at the current	376	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
255	C<$in_fh> than are written, and there is no way to find out how many	390	C<$in_fh> than are written, and there is no way to find out how many
256	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	391	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
257	provides the number of bytes written to C<$out_fh>. Only if the result	392	provides the number of bytes written to C<$out_fh>. Only if the result
258	value equals C<$length> one can assume that C<$length> bytes have been	393	value equals C<$length> one can assume that C<$length> bytes have been
259	read.	394	read.
		395
260		396
261	=item aio_readahead $fh,$offset,$length, $callback->($retval)	397	=item aio_readahead $fh,$offset,$length, $callback->($retval)
262		398
263	C<aio_readahead> populates the page cache with data from a file so that	399	C<aio_readahead> populates the page cache with data from a file so that
264	subsequent reads from that file will not block on disk I/O. The C<$offset>	400	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
270	file. The current file offset of the file is left unchanged.	406	file. The current file offset of the file is left unchanged.
271		407
272	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	408	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
273	emulated by simply reading the data, which would have a similar effect.	409	emulated by simply reading the data, which would have a similar effect.
274		410
		411
275	=item aio_stat $fh_or_path, $callback->($status)	412	=item aio_stat $fh_or_path, $callback->($status)
276		413
277	=item aio_lstat $fh, $callback->($status)	414	=item aio_lstat $fh, $callback->($status)
278		415
279	Works like perl's C<stat> or C<lstat> in void context. The callback will	416	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
292	aio_stat "/etc/passwd", sub {	429	aio_stat "/etc/passwd", sub {
293	$_[0] and die "stat failed: $!";	430	$_[0] and die "stat failed: $!";
294	print "size is ", -s _, "\n";	431	print "size is ", -s _, "\n";
295	};	432	};
296		433
		434
		435	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		436
		437	Works like perl's C<utime> function (including the special case of $atime
		438	and $mtime being undef). Fractional times are supported if the underlying
		439	syscalls support them.
		440
		441	When called with a pathname, uses utimes(2) if available, otherwise
		442	utime(2). If called on a file descriptor, uses futimes(2) if available,
		443	otherwise returns ENOSYS, so this is not portable.
		444
		445	Examples:
		446
		447	# set atime and mtime to current time (basically touch(1)):
		448	aio_utime "path", undef, undef;
		449	# set atime to current time and mtime to beginning of the epoch:
		450	aio_utime "path", time, undef; # undef==0
		451
		452
		453	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		454
		455	Works like perl's C<chown> function, except that C<undef> for either $uid
		456	or $gid is being interpreted as "do not change" (but -1 can also be used).
		457
		458	Examples:
		459
		460	# same as "chown root path" in the shell:
		461	aio_chown "path", 0, -1;
		462	# same as above:
		463	aio_chown "path", 0, undef;
		464
		465
		466	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		467
		468	Works like truncate(2) or ftruncate(2).
		469
		470
		471	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		472
		473	Works like perl's C<chmod> function.
		474
		475
297	=item aio_unlink $pathname, $callback->($status)	476	=item aio_unlink $pathname, $callback->($status)
298		477
299	Asynchronously unlink (delete) a file and call the callback with the	478	Asynchronously unlink (delete) a file and call the callback with the
300	result code.	479	result code.
301		480
		481
		482	=item aio_mknod $path, $mode, $dev, $callback->($status)
		483
		484	[EXPERIMENTAL]
		485
		486	Asynchronously create a device node (or fifo). See mknod(2).
		487
		488	The only (POSIX-) portable way of calling this function is:
		489
		490	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		491
		492
302	=item aio_link $srcpath, $dstpath, $callback->($status)	493	=item aio_link $srcpath, $dstpath, $callback->($status)
303		494
304	Asynchronously create a new link to the existing object at C<$srcpath> at	495	Asynchronously create a new link to the existing object at C<$srcpath> at
305	the path C<$dstpath> and call the callback with the result code.	496	the path C<$dstpath> and call the callback with the result code.
306		497
		498
307	=item aio_symlink $srcpath, $dstpath, $callback->($status)	499	=item aio_symlink $srcpath, $dstpath, $callback->($status)
308		500
309	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	501	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
310	the path C<$dstpath> and call the callback with the result code.	502	the path C<$dstpath> and call the callback with the result code.
311		503
		504
		505	=item aio_readlink $path, $callback->($link)
		506
		507	Asynchronously read the symlink specified by C<$path> and pass it to
		508	the callback. If an error occurs, nothing or undef gets passed to the
		509	callback.
		510
		511
312	=item aio_rename $srcpath, $dstpath, $callback->($status)	512	=item aio_rename $srcpath, $dstpath, $callback->($status)
313		513
314	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	514	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
315	rename(2) and call the callback with the result code.	515	rename(2) and call the callback with the result code.
316		516
		517
		518	=item aio_mkdir $pathname, $mode, $callback->($status)
		519
		520	Asynchronously mkdir (create) a directory and call the callback with
		521	the result code. C<$mode> will be modified by the umask at the time the
		522	request is executed, so do not change your umask.
		523
		524
317	=item aio_rmdir $pathname, $callback->($status)	525	=item aio_rmdir $pathname, $callback->($status)
318		526
319	Asynchronously rmdir (delete) a directory and call the callback with the	527	Asynchronously rmdir (delete) a directory and call the callback with the
320	result code.	528	result code.
		529
321		530
322	=item aio_readdir $pathname, $callback->($entries)	531	=item aio_readdir $pathname, $callback->($entries)
323		532
324	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	533	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
325	directory (i.e. opendir + readdir + closedir). The entries will not be	534	directory (i.e. opendir + readdir + closedir). The entries will not be
326	sorted, and will B<NOT> include the C<.> and C<..> entries.	535	sorted, and will B<NOT> include the C<.> and C<..> entries.
327		536
328	The callback a single argument which is either C<undef> or an array-ref	537	The callback is passed a single argument which is either C<undef> or an
329	with the filenames.	538	array-ref with the filenames.
		539
		540
		541	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		542
		543	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		544	behaviour and output format. In case of an error, C<$entries> will be
		545	C<undef>.
		546
		547	The flags are a combination of the following constants, ORed together (the
		548	flags will also be passed to the callback, possibly modified):
		549
		550	=over 4
		551
		552	=item IO::AIO::READDIR_DENTS
		553
		554	When this flag is off, then the callback gets an arrayref with of names
		555	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		556	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		557	entry in more detail.
		558
		559	C<$name> is the name of the entry.
		560
		561	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		562
		563	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		564	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		565	C<IO::AIO::DT_WHT>.
		566
		567	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		568	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		569	scalars are read-only: you can not modify them.
		570
		571	C<$inode> is the inode number (which might not be exact on systems with 64
		572	bit inode numbers and 32 bit perls). This field has unspecified content on
		573	systems that do not deliver the inode information.
		574
		575	=item IO::AIO::READDIR_DIRS_FIRST
		576
		577	When this flag is set, then the names will be returned in an order where
		578	likely directories come first. This is useful when you need to quickly
		579	find directories, or you want to find all directories while avoiding to
		580	stat() each entry.
		581
		582	If the system returns type information in readdir, then this is used
		583	to find directories directly. Otherwise, likely directories are files
		584	beginning with ".", or otherwise files with no dots, of which files with
		585	short names are tried first.
		586
		587	=item IO::AIO::READDIR_STAT_ORDER
		588
		589	When this flag is set, then the names will be returned in an order
		590	suitable for stat()'ing each one. That is, when you plan to stat()
		591	all files in the given directory, then the returned order will likely
		592	be fastest.
		593
		594	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		595	the likely dirs come first, resulting in a less optimal stat order.
		596
		597	=item IO::AIO::READDIR_FOUND_UNKNOWN
		598
		599	This flag should not be set when calling C<aio_readdirx>. Instead, it
		600	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		601	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		602	C<$type>'s are known, which can be used to speed up some algorithms.
		603
		604	=back
		605
		606
		607	=item aio_load $path, $data, $callback->($status)
		608
		609	This is a composite request that tries to fully load the given file into
		610	memory. Status is the same as with aio_read.
		611
		612	=cut
		613
		614	sub aio_load($$;$) {
		615	my ($path, undef, $cb) = @_;
		616	my $data = \$_[1];
		617
		618	my $pri = aioreq_pri;
		619	my $grp = aio_group $cb;
		620
		621	aioreq_pri $pri;
		622	add $grp aio_open $path, O_RDONLY, 0, sub {
		623	my $fh = shift
		624	or return $grp->result (-1);
		625
		626	aioreq_pri $pri;
		627	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		628	$grp->result ($_[0]);
		629	};
		630	};
		631
		632	$grp
		633	}
		634
		635	=item aio_copy $srcpath, $dstpath, $callback->($status)
		636
		637	Try to copy the I<file> (directories not supported as either source or
		638	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		639	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		640
		641	This is a composite request that creates the destination file with
		642	mode 0200 and copies the contents of the source file into it using
		643	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		644	uid/gid, in that order.
		645
		646	If an error occurs, the partial destination file will be unlinked, if
		647	possible, except when setting atime, mtime, access mode and uid/gid, where
		648	errors are being ignored.
		649
		650	=cut
		651
		652	sub aio_copy($$;$) {
		653	my ($src, $dst, $cb) = @_;
		654
		655	my $pri = aioreq_pri;
		656	my $grp = aio_group $cb;
		657
		658	aioreq_pri $pri;
		659	add $grp aio_open $src, O_RDONLY, 0, sub {
		660	if (my $src_fh = $_[0]) {
		661	my @stat = stat $src_fh; # hmm, might block over nfs?
		662
		663	aioreq_pri $pri;
		664	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		665	if (my $dst_fh = $_[0]) {
		666	aioreq_pri $pri;
		667	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		668	if ($_[0] == $stat[7]) {
		669	$grp->result (0);
		670	close $src_fh;
		671
		672	my $ch = sub {
		673	aioreq_pri $pri;
		674	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		675	aioreq_pri $pri;
		676	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		677	aioreq_pri $pri;
		678	add $grp aio_close $dst_fh;
		679	}
		680	};
		681	};
		682
		683	aioreq_pri $pri;
		684	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		685	if ($_[0] < 0 && $! == ENOSYS) {
		686	aioreq_pri $pri;
		687	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		688	} else {
		689	$ch->();
		690	}
		691	};
		692	} else {
		693	$grp->result (-1);
		694	close $src_fh;
		695	close $dst_fh;
		696
		697	aioreq $pri;
		698	add $grp aio_unlink $dst;
		699	}
		700	};
		701	} else {
		702	$grp->result (-1);
		703	}
		704	},
		705
		706	} else {
		707	$grp->result (-1);
		708	}
		709	};
		710
		711	$grp
		712	}
		713
		714	=item aio_move $srcpath, $dstpath, $callback->($status)
		715
		716	Try to move the I<file> (directories not supported as either source or
		717	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		718	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		719
		720	This is a composite request that tries to rename(2) the file first; if
		721	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		722	that is successful, unlinks the C<$srcpath>.
		723
		724	=cut
		725
		726	sub aio_move($$;$) {
		727	my ($src, $dst, $cb) = @_;
		728
		729	my $pri = aioreq_pri;
		730	my $grp = aio_group $cb;
		731
		732	aioreq_pri $pri;
		733	add $grp aio_rename $src, $dst, sub {
		734	if ($_[0] && $! == EXDEV) {
		735	aioreq_pri $pri;
		736	add $grp aio_copy $src, $dst, sub {
		737	$grp->result ($_[0]);
		738
		739	if (!$_[0]) {
		740	aioreq_pri $pri;
		741	add $grp aio_unlink $src;
		742	}
		743	};
		744	} else {
		745	$grp->result ($_[0]);
		746	}
		747	};
		748
		749	$grp
		750	}
330		751
331	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	752	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
332		753
333	Scans a directory (similar to C<aio_readdir>) and tries to separate the	754	Scans a directory (similar to C<aio_readdir>) but additionally tries to
334	entries of directory C<$path> into two sets of names, ones you can recurse	755	efficiently separate the entries of directory C<$path> into two sets of
335	into (directories), and ones you cannot recurse into (everything else).	756	names, directories you can recurse into (directories), and ones you cannot
		757	recurse into (everything else, including symlinks to directories).
336		758
337	C<aio_scandir> is a composite request that consists of many	759	C<aio_scandir> is a composite request that creates of many sub requests_
338	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	760	C<$maxreq> specifies the maximum number of outstanding aio requests that
339	aio requests that this function generates. If it is C<< <= 0 >>, then a	761	this function generates. If it is C<< <= 0 >>, then a suitable default
340	suitable default will be chosen (currently 8).	762	will be chosen (currently 4).
341		763
342	On error, the callback is called without arguments, otherwise it receives	764	On error, the callback is called without arguments, otherwise it receives
343	two array-refs with path-relative entry names.	765	two array-refs with path-relative entry names.
344		766
345	Example:	767	Example:
…		…
352		774
353	Implementation notes.	775	Implementation notes.
354		776
355	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	777	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
356		778
		779	If readdir returns file type information, then this is used directly to
		780	find directories.
		781
357	After reading the directory, the modification time, size etc. of the	782	Otherwise, after reading the directory, the modification time, size etc.
358	directory before and after the readdir is checked, and if they match, the	783	of the directory before and after the readdir is checked, and if they
359	link count will be used to decide how many entries are directories (if	784	match (and isn't the current time), the link count will be used to decide
360	>= 2). Otherwise, no knowledge of the number of subdirectories will be	785	how many entries are directories (if >= 2). Otherwise, no knowledge of the
361	assumed.	786	number of subdirectories will be assumed.
362		787
363	Then entires will be sorted into likely directories (everything without a	788	Then entries will be sorted into likely directories a non-initial dot
364	non-initial dot) and likely non-directories (everything else). Then every	789	currently) and likely non-directories (see C<aio_readdirx>). Then every
365	entry + C</.> will be C<stat>'ed, likely directories first. This is often	790	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		791	in order of their inode numbers. If that succeeds, it assumes that the
		792	entry is a directory or a symlink to directory (which will be checked
		793	seperately). This is often faster than stat'ing the entry itself because
366	faster because filesystems might detect the type of the entry without	794	filesystems might detect the type of the entry without reading the inode
367	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,	795	data (e.g. ext2fs filetype feature), even on systems that cannot return
368	it assumes that the entry is a directory or a symlink to directory (which	796	the filetype information on readdir.
369	will be checked seperately).
370		797
371	If the known number of directories has been reached, the rest of the	798	If the known number of directories (link count - 2) has been reached, the
372	entries is assumed to be non-directories.	799	rest of the entries is assumed to be non-directories.
		800
		801	This only works with certainty on POSIX (= UNIX) filesystems, which
		802	fortunately are the vast majority of filesystems around.
		803
		804	It will also likely work on non-POSIX filesystems with reduced efficiency
		805	as those tend to return 0 or 1 as link counts, which disables the
		806	directory counting heuristic.
373		807
374	=cut	808	=cut
375		809
376	sub aio_scandir($$$) {	810	sub aio_scandir($$;$) {
377	my ($path, $maxreq, $cb) = @_;	811	my ($path, $maxreq, $cb) = @_;
378		812
		813	my $pri = aioreq_pri;
		814
		815	my $grp = aio_group $cb;
		816
379	$maxreq = 8 if $maxreq <= 0;	817	$maxreq = 4 if $maxreq <= 0;
380		818
381	# stat once	819	# stat once
		820	aioreq_pri $pri;
382	aio_stat $path, sub {	821	add $grp aio_stat $path, sub {
383	return $cb->() if $_[0];	822	return $grp->result () if $_[0];
		823	my $now = time;
384	my $hash1 = join ":", (stat _)[0,1,3,7,9];	824	my $hash1 = join ":", (stat _)[0,1,3,7,9];
385		825
386	# read the directory entries	826	# read the directory entries
387	aio_readdir $path, sub {	827	aioreq_pri $pri;
		828	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
388	my $entries = shift	829	my $entries = shift
389	or return $cb->();	830	or return $grp->result ();
390		831
391	# stat the dir another time	832	# stat the dir another time
		833	aioreq_pri $pri;
392	aio_stat $path, sub {	834	add $grp aio_stat $path, sub {
393	my $hash2 = join ":", (stat _)[0,1,3,7,9];	835	my $hash2 = join ":", (stat _)[0,1,3,7,9];
394		836
395	my $ndirs;	837	my $ndirs;
396		838
397	# take the slow route if anything looks fishy	839	# take the slow route if anything looks fishy
398	if ($hash1 ne $hash2) {	840	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
399	$ndirs = -1;	841	$ndirs = -1;
400	} else {	842	} else {
401	# if nlink == 2, we are finished	843	# if nlink == 2, we are finished
402	# on non-posix-fs's, we rely on nlink < 2	844	# for non-posix-fs's, we rely on nlink < 2
403	$ndirs = (stat _)[3] - 2	845	$ndirs = (stat _)[3] - 2
404	or return $cb->([], $entries);	846	or return $grp->result ([], $entries);
405	}	847	}
406		848
407	# sort into likely dirs and likely nondirs
408	# dirs == files without ".", short entries first
409	$entries = [map $_->[0],
410	sort { $b->[1] cmp $a->[1] }
411	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
412	@$entries];
413
414	my (@dirs, @nondirs);	849	my (@dirs, @nondirs);
415		850
416	my ($statcb, $schedcb);	851	my $statgrp = add $grp aio_group sub {
417	my $nreq = 0;	852	$grp->result (\@dirs, \@nondirs);
		853	};
418		854
419	$schedcb = sub {	855	limit $statgrp $maxreq;
420	if (@$entries) {	856	feed $statgrp sub {
421	if ($nreq < $maxreq) {	857	return unless @$entries;
422	my $ent = pop @$entries;	858	my $entry = shift @$entries;
		859
		860	aioreq_pri $pri;
		861	add $statgrp aio_stat "$path/$entry/.", sub {
		862	if ($_[0] < 0) {
		863	push @nondirs, $entry;
		864	} else {
		865	# need to check for real directory
		866	aioreq_pri $pri;
		867	add $statgrp aio_lstat "$path/$entry", sub {
		868	if (-d _) {
		869	push @dirs, $entry;
		870
		871	unless (--$ndirs) {
		872	push @nondirs, @$entries;
		873	feed $statgrp;
		874	}
		875	} else {
		876	push @nondirs, $entry;
		877	}
423	$nreq++;	878	}
424	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
425	}	879	}
426	} elsif (!$nreq) {
427	# finished
428	undef $statcb;
429	undef $schedcb;
430	$cb->(\@dirs, \@nondirs) if $cb;
431	undef $cb;
432	}	880	};
433	};	881	};
434	$statcb = sub {
435	my ($status, $entry) = @_;
436
437	if ($status < 0) {
438	$nreq--;
439	push @nondirs, $entry;
440	&$schedcb;
441	} else {
442	# need to check for real directory
443	aio_lstat "$path/$entry", sub {
444	$nreq--;
445
446	if (-d _) {
447	push @dirs, $entry;
448
449	if (!--$ndirs) {
450	push @nondirs, @$entries;
451	$entries = [];
452	}
453	} else {
454	push @nondirs, $entry;
455	}
456
457	&$schedcb;
458	}
459	}
460	};
461
462	&$schedcb while @$entries && $nreq < $maxreq;
463	};	882	};
464	};	883	};
465	};	884	};
		885
		886	$grp
466	}	887	}
		888
		889	=item aio_rmtree $path, $callback->($status)
		890
		891	Delete a directory tree starting (and including) C<$path>, return the
		892	status of the final C<rmdir> only. This is a composite request that
		893	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		894	everything else.
		895
		896	=cut
		897
		898	sub aio_rmtree;
		899	sub aio_rmtree($;$) {
		900	my ($path, $cb) = @_;
		901
		902	my $pri = aioreq_pri;
		903	my $grp = aio_group $cb;
		904
		905	aioreq_pri $pri;
		906	add $grp aio_scandir $path, 0, sub {
		907	my ($dirs, $nondirs) = @_;
		908
		909	my $dirgrp = aio_group sub {
		910	add $grp aio_rmdir $path, sub {
		911	$grp->result ($_[0]);
		912	};
		913	};
		914
		915	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		916	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		917
		918	add $grp $dirgrp;
		919	};
		920
		921	$grp
		922	}
		923
		924	=item aio_sync $callback->($status)
		925
		926	Asynchronously call sync and call the callback when finished.
467		927
468	=item aio_fsync $fh, $callback->($status)	928	=item aio_fsync $fh, $callback->($status)
469		929
470	Asynchronously call fsync on the given filehandle and call the callback	930	Asynchronously call fsync on the given filehandle and call the callback
471	with the fsync result code.	931	with the fsync result code.
…		…
476	callback with the fdatasync result code.	936	callback with the fdatasync result code.
477		937
478	If this call isn't available because your OS lacks it or it couldn't be	938	If this call isn't available because your OS lacks it or it couldn't be
479	detected, it will be emulated by calling C<fsync> instead.	939	detected, it will be emulated by calling C<fsync> instead.
480		940
		941	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		942
		943	Sync the data portion of the file specified by C<$offset> and C<$length>
		944	to disk (but NOT the metadata), by calling the Linux-specific
		945	sync_file_range call. If sync_file_range is not available or it returns
		946	ENOSYS, then fdatasync or fsync is being substituted.
		947
		948	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		949	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		950	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		951	manpage for details.
		952
		953	=item aio_pathsync $path, $callback->($status)
		954
		955	This request tries to open, fsync and close the given path. This is a
		956	composite request intended to sync directories after directory operations
		957	(E.g. rename). This might not work on all operating systems or have any
		958	specific effect, but usually it makes sure that directory changes get
		959	written to disc. It works for anything that can be opened for read-only,
		960	not just directories.
		961
		962	Future versions of this function might fall back to other methods when
		963	C<fsync> on the directory fails (such as calling C<sync>).
		964
		965	Passes C<0> when everything went ok, and C<-1> on error.
		966
		967	=cut
		968
		969	sub aio_pathsync($;$) {
		970	my ($path, $cb) = @_;
		971
		972	my $pri = aioreq_pri;
		973	my $grp = aio_group $cb;
		974
		975	aioreq_pri $pri;
		976	add $grp aio_open $path, O_RDONLY, 0, sub {
		977	my ($fh) = @_;
		978	if ($fh) {
		979	aioreq_pri $pri;
		980	add $grp aio_fsync $fh, sub {
		981	$grp->result ($_[0]);
		982
		983	aioreq_pri $pri;
		984	add $grp aio_close $fh;
		985	};
		986	} else {
		987	$grp->result (-1);
		988	}
		989	};
		990
		991	$grp
		992	}
		993
		994	=item aio_group $callback->(...)
		995
		996	This is a very special aio request: Instead of doing something, it is a
		997	container for other aio requests, which is useful if you want to bundle
		998	many requests into a single, composite, request with a definite callback
		999	and the ability to cancel the whole request with its subrequests.
		1000
		1001	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		1002	for more info.
		1003
		1004	Example:
		1005
		1006	my $grp = aio_group sub {
		1007	print "all stats done\n";
		1008	};
		1009
		1010	add $grp
		1011	(aio_stat ...),
		1012	(aio_stat ...),
		1013	...;
		1014
		1015	=item aio_nop $callback->()
		1016
		1017	This is a special request - it does nothing in itself and is only used for
		1018	side effects, such as when you want to add a dummy request to a group so
		1019	that finishing the requests in the group depends on executing the given
		1020	code.
		1021
		1022	While this request does nothing, it still goes through the execution
		1023	phase and still requires a worker thread. Thus, the callback will not
		1024	be executed immediately but only after other requests in the queue have
		1025	entered their execution phase. This can be used to measure request
		1026	latency.
		1027
		1028	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1029
		1030	Mainly used for debugging and benchmarking, this aio request puts one of
		1031	the request workers to sleep for the given time.
		1032
		1033	While it is theoretically handy to have simple I/O scheduling requests
		1034	like sleep and file handle readable/writable, the overhead this creates is
		1035	immense (it blocks a thread for a long time) so do not use this function
		1036	except to put your application under artificial I/O pressure.
		1037
481	=back	1038	=back
482		1039
		1040	=head2 IO::AIO::REQ CLASS
		1041
		1042	All non-aggregate C<aio_*> functions return an object of this class when
		1043	called in non-void context.
		1044
		1045	=over 4
		1046
		1047	=item cancel $req
		1048
		1049	Cancels the request, if possible. Has the effect of skipping execution
		1050	when entering the B<execute> state and skipping calling the callback when
		1051	entering the the B<result> state, but will leave the request otherwise
		1052	untouched (with the exception of readdir). That means that requests that
		1053	currently execute will not be stopped and resources held by the request
		1054	will not be freed prematurely.
		1055
		1056	=item cb $req $callback->(...)
		1057
		1058	Replace (or simply set) the callback registered to the request.
		1059
		1060	=back
		1061
		1062	=head2 IO::AIO::GRP CLASS
		1063
		1064	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1065	objects of this class, too.
		1066
		1067	A IO::AIO::GRP object is a special request that can contain multiple other
		1068	aio requests.
		1069
		1070	You create one by calling the C<aio_group> constructing function with a
		1071	callback that will be called when all contained requests have entered the
		1072	C<done> state:
		1073
		1074	my $grp = aio_group sub {
		1075	print "all requests are done\n";
		1076	};
		1077
		1078	You add requests by calling the C<add> method with one or more
		1079	C<IO::AIO::REQ> objects:
		1080
		1081	$grp->add (aio_unlink "...");
		1082
		1083	add $grp aio_stat "...", sub {
		1084	$_[0] or return $grp->result ("error");
		1085
		1086	# add another request dynamically, if first succeeded
		1087	add $grp aio_open "...", sub {
		1088	$grp->result ("ok");
		1089	};
		1090	};
		1091
		1092	This makes it very easy to create composite requests (see the source of
		1093	C<aio_move> for an application) that work and feel like simple requests.
		1094
		1095	=over 4
		1096
		1097	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1098	C<IO::AIO::poll_cb>, just like any other request.
		1099
		1100	=item * They can be canceled like any other request. Canceling will cancel not
		1101	only the request itself, but also all requests it contains.
		1102
		1103	=item * They can also can also be added to other IO::AIO::GRP objects.
		1104
		1105	=item * You must not add requests to a group from within the group callback (or
		1106	any later time).
		1107
		1108	=back
		1109
		1110	Their lifetime, simplified, looks like this: when they are empty, they
		1111	will finish very quickly. If they contain only requests that are in the
		1112	C<done> state, they will also finish. Otherwise they will continue to
		1113	exist.
		1114
		1115	That means after creating a group you have some time to add requests
		1116	(precisely before the callback has been invoked, which is only done within
		1117	the C<poll_cb>). And in the callbacks of those requests, you can add
		1118	further requests to the group. And only when all those requests have
		1119	finished will the the group itself finish.
		1120
		1121	=over 4
		1122
		1123	=item add $grp ...
		1124
		1125	=item $grp->add (...)
		1126
		1127	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1128	be added, including other groups, as long as you do not create circular
		1129	dependencies.
		1130
		1131	Returns all its arguments.
		1132
		1133	=item $grp->cancel_subs
		1134
		1135	Cancel all subrequests and clears any feeder, but not the group request
		1136	itself. Useful when you queued a lot of events but got a result early.
		1137
		1138	The group request will finish normally (you cannot add requests to the
		1139	group).
		1140
		1141	=item $grp->result (...)
		1142
		1143	Set the result value(s) that will be passed to the group callback when all
		1144	subrequests have finished and set the groups errno to the current value
		1145	of errno (just like calling C<errno> without an error number). By default,
		1146	no argument will be passed and errno is zero.
		1147
		1148	=item $grp->errno ([$errno])
		1149
		1150	Sets the group errno value to C<$errno>, or the current value of errno
		1151	when the argument is missing.
		1152
		1153	Every aio request has an associated errno value that is restored when
		1154	the callback is invoked. This method lets you change this value from its
		1155	default (0).
		1156
		1157	Calling C<result> will also set errno, so make sure you either set C<$!>
		1158	before the call to C<result>, or call c<errno> after it.
		1159
		1160	=item feed $grp $callback->($grp)
		1161
		1162	Sets a feeder/generator on this group: every group can have an attached
		1163	generator that generates requests if idle. The idea behind this is that,
		1164	although you could just queue as many requests as you want in a group,
		1165	this might starve other requests for a potentially long time. For example,
		1166	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1167	delaying any later requests for a long time.
		1168
		1169	To avoid this, and allow incremental generation of requests, you can
		1170	instead a group and set a feeder on it that generates those requests. The
		1171	feed callback will be called whenever there are few enough (see C<limit>,
		1172	below) requests active in the group itself and is expected to queue more
		1173	requests.
		1174
		1175	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1176	not impose any limits).
		1177
		1178	If the feed does not queue more requests when called, it will be
		1179	automatically removed from the group.
		1180
		1181	If the feed limit is C<0> when this method is called, it will be set to
		1182	C<2> automatically.
		1183
		1184	Example:
		1185
		1186	# stat all files in @files, but only ever use four aio requests concurrently:
		1187
		1188	my $grp = aio_group sub { print "finished\n" };
		1189	limit $grp 4;
		1190	feed $grp sub {
		1191	my $file = pop @files
		1192	or return;
		1193
		1194	add $grp aio_stat $file, sub { ... };
		1195	};
		1196
		1197	=item limit $grp $num
		1198
		1199	Sets the feeder limit for the group: The feeder will be called whenever
		1200	the group contains less than this many requests.
		1201
		1202	Setting the limit to C<0> will pause the feeding process.
		1203
		1204	The default value for the limit is C<0>, but note that setting a feeder
		1205	automatically bumps it up to C<2>.
		1206
		1207	=back
		1208
483	=head2 SUPPORT FUNCTIONS	1209	=head2 SUPPORT FUNCTIONS
484		1210
		1211	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1212
485	=over 4	1213	=over 4
486		1214
487	=item $fileno = IO::AIO::poll_fileno	1215	=item $fileno = IO::AIO::poll_fileno
488		1216
489	Return the I<request result pipe file descriptor>. This filehandle must be	1217	Return the I<request result pipe file descriptor>. This filehandle must be
490	polled for reading by some mechanism outside this module (e.g. Event or	1218	polled for reading by some mechanism outside this module (e.g. EV, Glib,
491	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1219	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
492	to call C<poll_cb> to check the results.	1220	you have to call C<poll_cb> to check the results.
493		1221
494	See C<poll_cb> for an example.	1222	See C<poll_cb> for an example.
495		1223
496	=item IO::AIO::poll_cb	1224	=item IO::AIO::poll_cb
497		1225
498	Process all outstanding events on the result pipe. You have to call this	1226	Process some outstanding events on the result pipe. You have to call this
499	regularly. Returns the number of events processed. Returns immediately	1227	regularly. Returns C<0> if all events could be processed, or C<-1> if it
500	when no events are outstanding.	1228	returned earlier for whatever reason. Returns immediately when no events
		1229	are outstanding. The amount of events processed depends on the settings of
		1230	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1231
		1232	If not all requests were processed for whatever reason, the filehandle
		1233	will still be ready when C<poll_cb> returns, so normally you don't have to
		1234	do anything special to have it called later.
501		1235
502	Example: Install an Event watcher that automatically calls	1236	Example: Install an Event watcher that automatically calls
503	IO::AIO::poll_cb with high priority:	1237	IO::AIO::poll_cb with high priority (more examples can be found in the
		1238	SYNOPSIS section, at the top of this document):
504		1239
505	Event->io (fd => IO::AIO::poll_fileno,	1240	Event->io (fd => IO::AIO::poll_fileno,
506	poll => 'r', async => 1,	1241	poll => 'r', async => 1,
507	cb => \&IO::AIO::poll_cb);	1242	cb => \&IO::AIO::poll_cb);
508		1243
		1244	=item IO::AIO::max_poll_reqs $nreqs
		1245
		1246	=item IO::AIO::max_poll_time $seconds
		1247
		1248	These set the maximum number of requests (default C<0>, meaning infinity)
		1249	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1250	the maximum amount of time (default C<0>, meaning infinity) spent in
		1251	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1252	of time C<poll_cb> is allowed to use).
		1253
		1254	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1255	syscall per request processed, which is not normally a problem unless your
		1256	callbacks are really really fast or your OS is really really slow (I am
		1257	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1258
		1259	Setting these is useful if you want to ensure some level of
		1260	interactiveness when perl is not fast enough to process all requests in
		1261	time.
		1262
		1263	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1264
		1265	Example: Install an Event watcher that automatically calls
		1266	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1267	program get the CPU sometimes even under high AIO load.
		1268
		1269	# try not to spend much more than 0.1s in poll_cb
		1270	IO::AIO::max_poll_time 0.1;
		1271
		1272	# use a low priority so other tasks have priority
		1273	Event->io (fd => IO::AIO::poll_fileno,
		1274	poll => 'r', nice => 1,
		1275	cb => &IO::AIO::poll_cb);
		1276
509	=item IO::AIO::poll_wait	1277	=item IO::AIO::poll_wait
510		1278
		1279	If there are any outstanding requests and none of them in the result
511	Wait till the result filehandle becomes ready for reading (simply does a	1280	phase, wait till the result filehandle becomes ready for reading (simply
512	C<select> on the filehandle. This is useful if you want to synchronously wait	1281	does a C<select> on the filehandle. This is useful if you want to
513	for some requests to finish).	1282	synchronously wait for some requests to finish).
514		1283
515	See C<nreqs> for an example.	1284	See C<nreqs> for an example.
516		1285
		1286	=item IO::AIO::poll
		1287
		1288	Waits until some requests have been handled.
		1289
		1290	Returns the number of requests processed, but is otherwise strictly
		1291	equivalent to:
		1292
		1293	IO::AIO::poll_wait, IO::AIO::poll_cb
		1294
517	=item IO::AIO::nreqs	1295	=item IO::AIO::flush
518		1296
519	Returns the number of requests currently outstanding (i.e. for which their	1297	Wait till all outstanding AIO requests have been handled.
520	callback has not been invoked yet).
521		1298
522	Example: wait till there are no outstanding requests anymore:	1299	Strictly equivalent to:
523		1300
524	IO::AIO::poll_wait, IO::AIO::poll_cb	1301	IO::AIO::poll_wait, IO::AIO::poll_cb
525	while IO::AIO::nreqs;	1302	while IO::AIO::nreqs;
526		1303
527	=item IO::AIO::flush	1304	=back
528		1305
529	Wait till all outstanding AIO requests have been handled.	1306	=head3 CONTROLLING THE NUMBER OF THREADS
530		1307
531	Strictly equivalent to:	1308	=over
532
533	IO::AIO::poll_wait, IO::AIO::poll_cb
534	while IO::AIO::nreqs;
535
536	=item IO::AIO::poll
537
538	Waits until some requests have been handled.
539
540	Strictly equivalent to:
541
542	IO::AIO::poll_wait, IO::AIO::poll_cb
543	if IO::AIO::nreqs;
544		1309
545	=item IO::AIO::min_parallel $nthreads	1310	=item IO::AIO::min_parallel $nthreads
546		1311
547	Set the minimum number of AIO threads to C<$nthreads>. The current default	1312	Set the minimum number of AIO threads to C<$nthreads>. The current
548	is C<4>, which means four asynchronous operations can be done at one time	1313	default is C<8>, which means eight asynchronous operations can execute
549	(the number of outstanding operations, however, is unlimited).	1314	concurrently at any one time (the number of outstanding requests,
		1315	however, is unlimited).
550		1316
551	IO::AIO starts threads only on demand, when an AIO request is queued and	1317	IO::AIO starts threads only on demand, when an AIO request is queued and
552	no free thread exists.	1318	no free thread exists. Please note that queueing up a hundred requests can
		1319	create demand for a hundred threads, even if it turns out that everything
		1320	is in the cache and could have been processed faster by a single thread.
553		1321
554	It is recommended to keep the number of threads low, as some Linux	1322	It is recommended to keep the number of threads relatively low, as some
555	kernel versions will scale negatively with the number of threads (higher	1323	Linux kernel versions will scale negatively with the number of threads
556	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1324	(higher parallelity => MUCH higher latency). With current Linux 2.6
557	threads should be fine.	1325	versions, 4-32 threads should be fine.
558		1326
559	Under most circumstances you don't need to call this function, as the	1327	Under most circumstances you don't need to call this function, as the
560	module selects a default that is suitable for low to moderate load.	1328	module selects a default that is suitable for low to moderate load.
561		1329
562	=item IO::AIO::max_parallel $nthreads	1330	=item IO::AIO::max_parallel $nthreads
…		…
571	This module automatically runs C<max_parallel 0> at program end, to ensure	1339	This module automatically runs C<max_parallel 0> at program end, to ensure
572	that all threads are killed and that there are no outstanding requests.	1340	that all threads are killed and that there are no outstanding requests.
573		1341
574	Under normal circumstances you don't need to call this function.	1342	Under normal circumstances you don't need to call this function.
575		1343
		1344	=item IO::AIO::max_idle $nthreads
		1345
		1346	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1347	threads that did not get a request to process within 10 seconds). That
		1348	means if a thread becomes idle while C<$nthreads> other threads are also
		1349	idle, it will free its resources and exit.
		1350
		1351	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1352	to allow for extremely high load situations, but want to free resources
		1353	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1354
		1355	The default is probably ok in most situations, especially if thread
		1356	creation is fast. If thread creation is very slow on your system you might
		1357	want to use larger values.
		1358
576	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1359	=item IO::AIO::max_outstanding $maxreqs
		1360
		1361	This is a very bad function to use in interactive programs because it
		1362	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1363	use an C<aio_group> together with a feed callback.
577		1364
578	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1365	Sets the maximum number of outstanding requests to C<$nreqs>. If you
579	try to queue up more than this number of requests, the caller will block until	1366	do queue up more than this number of requests, the next call to the
580	some requests have been handled.	1367	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1368	function will block until the limit is no longer exceeded.
581		1369
582	The default is very large, so normally there is no practical limit. If you	1370	The default value is very large, so there is no practical limit on the
583	queue up many requests in a loop it often improves speed if you set	1371	number of outstanding requests.
584	this to a relatively low number, such as C<100>.
585		1372
586	Under normal circumstances you don't need to call this function.	1373	You can still queue as many requests as you want. Therefore,
		1374	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1375	as a stop gap to shield against fatal memory overflow (with large values).
587		1376
588	=back	1377	=back
589		1378
		1379	=head3 STATISTICAL INFORMATION
		1380
		1381	=over
		1382
		1383	=item IO::AIO::nreqs
		1384
		1385	Returns the number of requests currently in the ready, execute or pending
		1386	states (i.e. for which their callback has not been invoked yet).
		1387
		1388	Example: wait till there are no outstanding requests anymore:
		1389
		1390	IO::AIO::poll_wait, IO::AIO::poll_cb
		1391	while IO::AIO::nreqs;
		1392
		1393	=item IO::AIO::nready
		1394
		1395	Returns the number of requests currently in the ready state (not yet
		1396	executed).
		1397
		1398	=item IO::AIO::npending
		1399
		1400	Returns the number of requests currently in the pending state (executed,
		1401	but not yet processed by poll_cb).
		1402
		1403	=back
		1404
		1405	=head3 MISCELLANEOUS FUNCTIONS
		1406
		1407	IO::AIO implements some functions that might be useful, but are not
		1408	asynchronous.
		1409
		1410	=over 4
		1411
		1412	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1413
		1414	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1415	but is blocking (this makes most sense if you know the input data is
		1416	likely cached already and the output filehandle is set to non-blocking
		1417	operations).
		1418
		1419	Returns the number of bytes copied, or C<-1> on error.
		1420
		1421	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1422
		1423	Simply calls the C<posix_fadvise> function (see it's
		1424	manpage for details). The following advice constants are
		1425	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1426	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1427	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1428
		1429	On systems that do not implement C<posix_fadvise>, this function returns
		1430	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1431
		1432	=back
		1433
590	=cut	1434	=cut
591		1435
592	# support function to convert a fd into a perl filehandle
593	sub _fd2fh {
594	return undef if $_[0] < 0;
595
596	# try to generate nice filehandles
597	my $sym = "IO::AIO::fd#$_[0]";
598	local *$sym;
599
600	open *$sym, "+<&=$_[0]" # usually works under any unix
601	or open *$sym, "<&=$_[0]" # cygwin needs this
602	or open *$sym, ">&=$_[0]" # or this
603	or return undef;
604
605	*$sym
606	}
607
608	min_parallel 4;	1436	min_parallel 8;
609		1437
610	END {	1438	END { flush }
611	max_parallel 0;
612	}
613		1439
614	1;	1440	1;
615		1441
616	=head2 FORK BEHAVIOUR	1442	=head2 FORK BEHAVIOUR
		1443
		1444	This module should do "the right thing" when the process using it forks:
617		1445
618	Before the fork, IO::AIO enters a quiescent state where no requests	1446	Before the fork, IO::AIO enters a quiescent state where no requests
619	can be added in other threads and no results will be processed. After	1447	can be added in other threads and no results will be processed. After
620	the fork the parent simply leaves the quiescent state and continues	1448	the fork the parent simply leaves the quiescent state and continues
621	request/result processing, while the child clears the request/result	1449	request/result processing, while the child frees the request/result queue
622	queue (so the requests started before the fork will only be handled in	1450	(so that the requests started before the fork will only be handled in the
623	the parent). Threats will be started on demand until the limit ste in the	1451	parent). Threads will be started on demand until the limit set in the
624	parent process has been reached again.	1452	parent process has been reached again.
625		1453
		1454	In short: the parent will, after a short pause, continue as if fork had
		1455	not been called, while the child will act as if IO::AIO has not been used
		1456	yet.
		1457
		1458	=head2 MEMORY USAGE
		1459
		1460	Per-request usage:
		1461
		1462	Each aio request uses - depending on your architecture - around 100-200
		1463	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1464	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1465	scalars and other data passed into aio requests will also be locked and
		1466	will consume memory till the request has entered the done state.
		1467
		1468	This is not awfully much, so queuing lots of requests is not usually a
		1469	problem.
		1470
		1471	Per-thread usage:
		1472
		1473	In the execution phase, some aio requests require more memory for
		1474	temporary buffers, and each thread requires a stack and other data
		1475	structures (usually around 16k-128k, depending on the OS).
		1476
		1477	=head1 KNOWN BUGS
		1478
		1479	Known bugs will be fixed in the next release.
		1480
626	=head1 SEE ALSO	1481	=head1 SEE ALSO
627		1482
628	L<Coro>, L<Linux::AIO>.	1483	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1484	more natural syntax.
629		1485
630	=head1 AUTHOR	1486	=head1 AUTHOR
631		1487
632	Marc Lehmann <schmorp@schmorp.de>	1488	Marc Lehmann <schmorp@schmorp.de>
633	http://home.schmorp.de/	1489	http://home.schmorp.de/

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