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Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC vs.
Revision 1.255 by root, Thu Jun 25 15:20:11 2015 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
30	# AnyEvent integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',
37	cb => \&IO::AIO::poll_cb);
38
39	# Glib/Gtk2 integration
40	add_watch Glib::IO IO::AIO::poll_fileno,
41	in => sub { IO::AIO::poll_cb; 1 };
42
43	# Tk integration
44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
45	readable => \&IO::AIO::poll_cb);
46
47	# Danga::Socket integration
48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49	\&IO::AIO::poll_cb);
50
51	=head1 DESCRIPTION	31	=head1 DESCRIPTION
52		32
53	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
54	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
55		36
56	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
57	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
58	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
59	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
61	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
62	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
63	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
64	concurrently.	45	concurrently.
65		46
66	While this works on all types of file descriptors (for example sockets),	47	While most of this works on all types of file descriptors (for
67	using these functions on file descriptors that support nonblocking	48	example sockets), using these functions on file descriptors that
68	operation (again, sockets, pipes etc.) is very inefficient. Use an event	49	support nonblocking operation (again, sockets, pipes etc.) is
69	loop for that (such as the L<Event|Event> module): IO::AIO will naturally	50	very inefficient. Use an event loop for that (such as the L<EV>
70	fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
71		52
72	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
73	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
74	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
75	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
77	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
78	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
79	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
80	using threads anyway.	61	using threads anyway.
81		62
82	Although the module will work with in the presence of other (Perl-)	63	Although the module will work in the presence of other (Perl-) threads,
83	threads, it is currently not reentrant in any way, so use appropriate	64	it is currently not reentrant in any way, so use appropriate locking
84	locking yourself, always call C<poll_cb> from within the same thread, or	65	yourself, always call C<poll_cb> from within the same thread, or never
85	never call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
86		67
87	=head2 EXAMPLE	68	=head2 EXAMPLE
88		69
89	This is a simple example that uses the Event module and loads	70	This is a simple example that uses the EV module and loads
90	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
91		72
92	use Fcntl;
93	use Event;	73	use EV;
94	use IO::AIO;	74	use IO::AIO;
95		75
96	# register the IO::AIO callback with Event	76	# register the IO::AIO callback with EV
97	Event->io (fd => IO::AIO::poll_fileno,	77	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
98	poll => 'r',
99	cb => \&IO::AIO::poll_cb);
100		78
101	# queue the request to open /etc/passwd	79	# queue the request to open /etc/passwd
102	aio_open "/etc/passwd", O_RDONLY, 0, sub {	80	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
103	my $fh = $_[0]	81	my $fh = shift
104	or die "error while opening: $!";	82	or die "error while opening: $!";
105		83
106	# stat'ing filehandles is generally non-blocking	84	# stat'ing filehandles is generally non-blocking
107	my $size = -s $fh;	85	my $size = -s $fh;
108		86
…		…
116		94
117	# file contents now in $contents	95	# file contents now in $contents
118	print $contents;	96	print $contents;
119		97
120	# exit event loop and program	98	# exit event loop and program
121	Event::unloop;	99	EV::unloop;
122	};	100	};
123	};	101	};
124		102
125	# possibly queue up other requests, or open GUI windows,	103	# possibly queue up other requests, or open GUI windows,
126	# check for sockets etc. etc.	104	# check for sockets etc. etc.
127		105
128	# process events as long as there are some:	106	# process events as long as there are some:
129	Event::loop;	107	EV::loop;
130		108
131	=head1 REQUEST ANATOMY AND LIFETIME	109	=head1 REQUEST ANATOMY AND LIFETIME
132		110
133	Every C<aio_*> function creates a request. which is a C data structure not	111	Every C<aio_*> function creates a request. which is a C data structure not
134	directly visible to Perl.	112	directly visible to Perl.
…		…
176	Request has reached the end of its lifetime and holds no resources anymore	154	Request has reached the end of its lifetime and holds no resources anymore
177	(except possibly for the Perl object, but its connection to the actual	155	(except possibly for the Perl object, but its connection to the actual
178	aio request is severed and calling its methods will either do nothing or	156	aio request is severed and calling its methods will either do nothing or
179	result in a runtime error).	157	result in a runtime error).
180		158
		159	=back
		160
181	=cut	161	=cut
182		162
183	package IO::AIO;	163	package IO::AIO;
184		164
185	no warnings;	165	use Carp ();
186	use strict 'vars';	166
		167	use common::sense;
187		168
188	use base 'Exporter';	169	use base 'Exporter';
189		170
190	BEGIN {	171	BEGIN {
191	our $VERSION = '2.1';	172	our $VERSION = 4.32;
192		173
193	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	174	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
194	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	175	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
195	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	176	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
196	aio_copy aio_group aio_nop aio_mknod);	177	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_allocate
		178	aio_pathsync aio_readahead aio_fiemap
		179	aio_rename aio_link aio_move aio_copy aio_group
		180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		181	aio_chmod aio_utime aio_truncate
		182	aio_msync aio_mtouch aio_mlock aio_mlockall
		183	aio_statvfs
		184	aio_wd);
		185
197	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	186	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
198	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	187	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
199	min_parallel max_parallel max_idle	188	min_parallel max_parallel max_idle idle_timeout
200	nreqs nready npending nthreads	189	nreqs nready npending nthreads
201	max_poll_time max_poll_reqs);	190	max_poll_time max_poll_reqs
		191	sendfile fadvise madvise
		192	mmap munmap munlock munlockall);
		193
		194	push @AIO_REQ, qw(aio_busy); # not exported
202		195
203	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	196	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
204		197
205	require XSLoader;	198	require XSLoader;
206	XSLoader::load ("IO::AIO", $VERSION);	199	XSLoader::load ("IO::AIO", $VERSION);
207	}	200	}
208		201
209	=head1 FUNCTIONS	202	=head1 FUNCTIONS
210		203
211	=head2 AIO FUNCTIONS	204	=head2 QUICK OVERVIEW
		205
		206	This section simply lists the prototypes most of the functions for
		207	quick reference. See the following sections for function-by-function
		208	documentation.
		209
		210	aio_wd $pathname, $callback->($wd)
		211	aio_open $pathname, $flags, $mode, $callback->($fh)
		212	aio_close $fh, $callback->($status)
		213	aio_seek $fh,$offset,$whence, $callback->($offs)
		214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		217	aio_readahead $fh,$offset,$length, $callback->($retval)
		218	aio_stat $fh_or_path, $callback->($status)
		219	aio_lstat $fh, $callback->($status)
		220	aio_statvfs $fh_or_path, $callback->($statvfs)
		221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		222	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		223	aio_chmod $fh_or_path, $mode, $callback->($status)
		224	aio_truncate $fh_or_path, $offset, $callback->($status)
		225	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		226	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		227	aio_unlink $pathname, $callback->($status)
		228	aio_mknod $pathname, $mode, $dev, $callback->($status)
		229	aio_link $srcpath, $dstpath, $callback->($status)
		230	aio_symlink $srcpath, $dstpath, $callback->($status)
		231	aio_readlink $pathname, $callback->($link)
		232	aio_realpath $pathname, $callback->($path)
		233	aio_rename $srcpath, $dstpath, $callback->($status)
		234	aio_mkdir $pathname, $mode, $callback->($status)
		235	aio_rmdir $pathname, $callback->($status)
		236	aio_readdir $pathname, $callback->($entries)
		237	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		238	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		239	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		240	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		241	aio_load $pathname, $data, $callback->($status)
		242	aio_copy $srcpath, $dstpath, $callback->($status)
		243	aio_move $srcpath, $dstpath, $callback->($status)
		244	aio_rmtree $pathname, $callback->($status)
		245	aio_sync $callback->($status)
		246	aio_syncfs $fh, $callback->($status)
		247	aio_fsync $fh, $callback->($status)
		248	aio_fdatasync $fh, $callback->($status)
		249	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		250	aio_pathsync $pathname, $callback->($status)
		251	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		252	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		254	aio_mlockall $flags, $callback->($status)
		255	aio_group $callback->(...)
		256	aio_nop $callback->()
		257
		258	$prev_pri = aioreq_pri [$pri]
		259	aioreq_nice $pri_adjust
		260
		261	IO::AIO::poll_wait
		262	IO::AIO::poll_cb
		263	IO::AIO::poll
		264	IO::AIO::flush
		265	IO::AIO::max_poll_reqs $nreqs
		266	IO::AIO::max_poll_time $seconds
		267	IO::AIO::min_parallel $nthreads
		268	IO::AIO::max_parallel $nthreads
		269	IO::AIO::max_idle $nthreads
		270	IO::AIO::idle_timeout $seconds
		271	IO::AIO::max_outstanding $maxreqs
		272	IO::AIO::nreqs
		273	IO::AIO::nready
		274	IO::AIO::npending
		275
		276	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		277	IO::AIO::fadvise $fh, $offset, $len, $advice
		278	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		279	IO::AIO::munmap $scalar
		280	IO::AIO::madvise $scalar, $offset, $length, $advice
		281	IO::AIO::mprotect $scalar, $offset, $length, $protect
		282	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		283	IO::AIO::munlockall
		284
		285	=head2 API NOTES
212		286
213	All the C<aio_*> calls are more or less thin wrappers around the syscall	287	All the C<aio_*> calls are more or less thin wrappers around the syscall
214	with the same name (sans C<aio_>). The arguments are similar or identical,	288	with the same name (sans C<aio_>). The arguments are similar or identical,
215	and they all accept an additional (and optional) C<$callback> argument	289	and they all accept an additional (and optional) C<$callback> argument
216	which must be a code reference. This code reference will get called with	290	which must be a code reference. This code reference will be called after
217	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	291	the syscall has been executed in an asynchronous fashion. The results
218	perl, which usually delivers "false") as it's sole argument when the given	292	of the request will be passed as arguments to the callback (and, if an
219	syscall has been executed asynchronously.	293	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		294	most syscalls return C<-1> on error, unlike perl, which usually delivers
		295	"false").
		296
		297	Some requests (such as C<aio_readdir>) pass the actual results and
		298	communicate failures by passing C<undef>.
220		299
221	All functions expecting a filehandle keep a copy of the filehandle	300	All functions expecting a filehandle keep a copy of the filehandle
222	internally until the request has finished.	301	internally until the request has finished.
223		302
224	All requests return objects of type L<IO::AIO::REQ> that allow further	303	All functions return request objects of type L<IO::AIO::REQ> that allow
225	manipulation of those requests while they are in-flight.	304	further manipulation of those requests while they are in-flight.
226		305
227	The pathnames you pass to these routines I<must> be absolute and	306	The pathnames you pass to these routines I<should> be absolute. The
228	encoded in byte form. The reason for the former is that at the time the	307	reason for this is that at the time the request is being executed, the
229	request is being executed, the current working directory could have	308	current working directory could have changed. Alternatively, you can
230	changed. Alternatively, you can make sure that you never change the	309	make sure that you never change the current working directory anywhere
231	current working directory.	310	in the program and then use relative paths. You can also take advantage
		311	of IO::AIOs working directory abstraction, that lets you specify paths
		312	relative to some previously-opened "working directory object" - see the
		313	description of the C<IO::AIO::WD> class later in this document.
232		314
233	To encode pathnames to byte form, either make sure you either: a)	315	To encode pathnames as octets, either make sure you either: a) always pass
234	always pass in filenames you got from outside (command line, readdir	316	in filenames you got from outside (command line, readdir etc.) without
235	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	317	tinkering, b) are in your native filesystem encoding, c) use the Encode
236	your pathnames to the locale (or other) encoding in effect in the user	318	module and encode your pathnames to the locale (or other) encoding in
237	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	319	effect in the user environment, d) use Glib::filename_from_unicode on
238	use something else.	320	unicode filenames or e) use something else to ensure your scalar has the
		321	correct contents.
		322
		323	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		324	handles correctly whether it is set or not.
		325
		326	=head2 AIO REQUEST FUNCTIONS
239		327
240	=over 4	328	=over 4
241		329
242	=item $prev_pri = aioreq_pri [$pri]	330	=item $prev_pri = aioreq_pri [$pri]
243		331
…		…
263	aio_read $_[0], ..., sub {	351	aio_read $_[0], ..., sub {
264	...	352	...
265	};	353	};
266	};	354	};
267		355
		356
268	=item aioreq_nice $pri_adjust	357	=item aioreq_nice $pri_adjust
269		358
270	Similar to C<aioreq_pri>, but subtracts the given value from the current	359	Similar to C<aioreq_pri>, but subtracts the given value from the current
271	priority, so effects are cumulative.	360	priority, so the effect is cumulative.
		361
272		362
273	=item aio_open $pathname, $flags, $mode, $callback->($fh)	363	=item aio_open $pathname, $flags, $mode, $callback->($fh)
274		364
275	Asynchronously open or create a file and call the callback with a newly	365	Asynchronously open or create a file and call the callback with a newly
276	created filehandle for the file.	366	created filehandle for the file (or C<undef> in case of an error).
277		367
278	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	368	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
279	for an explanation.	369	for an explanation.
280		370
281	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	371	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
282	list. They are the same as used by C<sysopen>.	372	list. They are the same as used by C<sysopen>.
283		373
284	Likewise, C<$mode> specifies the mode of the newly created file, if it	374	Likewise, C<$mode> specifies the mode of the newly created file, if it
285	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	375	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
286	except that it is mandatory (i.e. use C<0> if you don't create new files,	376	except that it is mandatory (i.e. use C<0> if you don't create new files,
287	and C<0666> or C<0777> if you do).	377	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		378	by the umask in effect then the request is being executed, so better never
		379	change the umask.
288		380
289	Example:	381	Example:
290		382
291	aio_open "/etc/passwd", O_RDONLY, 0, sub {	383	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
292	if ($_[0]) {	384	if ($_[0]) {
293	print "open successful, fh is $_[0]\n";	385	print "open successful, fh is $_[0]\n";
294	...	386	...
295	} else {	387	} else {
296	die "open failed: $!\n";	388	die "open failed: $!\n";
297	}	389	}
298	};	390	};
299		391
		392	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		393	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		394	following POSIX and non-POSIX constants are available (missing ones on
		395	your system are, as usual, C<0>):
		396
		397	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		398	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		399	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		400
		401
300	=item aio_close $fh, $callback->($status)	402	=item aio_close $fh, $callback->($status)
301		403
302	Asynchronously close a file and call the callback with the result	404	Asynchronously close a file and call the callback with the result
303	code. I<WARNING:> although accepted, you should not pass in a perl	405	code.
304	filehandle here, as perl will likely close the file descriptor another
305	time when the filehandle is destroyed. Normally, you can safely call perls
306	C<close> or just let filehandles go out of scope.
307		406
308	This is supposed to be a bug in the API, so that might change. It's	407	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
309	therefore best to avoid this function.	408	closing the file descriptor associated with the filehandle itself.
		409
		410	Therefore, C<aio_close> will not close the filehandle - instead it will
		411	use dup2 to overwrite the file descriptor with the write-end of a pipe
		412	(the pipe fd will be created on demand and will be cached).
		413
		414	Or in other words: the file descriptor will be closed, but it will not be
		415	free for reuse until the perl filehandle is closed.
		416
		417	=cut
		418
		419	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		420
		421	Seeks the filehandle to the new C<$offset>, similarly to perl's
		422	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		423	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		424	C<IO::AIO::SEEK_END>).
		425
		426	The resulting absolute offset will be passed to the callback, or C<-1> in
		427	case of an error.
		428
		429	In theory, the C<$whence> constants could be different than the
		430	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		431	so don't panic.
		432
		433	As a GNU/Linux (and maybe Solaris) extension, also the constants
		434	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		435	could be found. No guarantees about suitability for use in C<aio_seek> or
		436	Perl's C<sysseek> can be made though, although I would naively assume they
		437	"just work".
310		438
311	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	439	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
312		440
313	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	441	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
314		442
315	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	443	Reads or writes C<$length> bytes from or to the specified C<$fh> and
316	into the scalar given by C<data> and offset C<dataoffset> and calls the	444	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
317	callback without the actual number of bytes read (or -1 on error, just	445	and calls the callback without the actual number of bytes read (or -1 on
318	like the syscall).	446	error, just like the syscall).
		447
		448	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		449	offset plus the actual number of bytes read.
		450
		451	If C<$offset> is undefined, then the current file descriptor offset will
		452	be used (and updated), otherwise the file descriptor offset will not be
		453	changed by these calls.
		454
		455	If C<$length> is undefined in C<aio_write>, use the remaining length of
		456	C<$data>.
		457
		458	If C<$dataoffset> is less than zero, it will be counted from the end of
		459	C<$data>.
319		460
320	The C<$data> scalar I<MUST NOT> be modified in any way while the request	461	The C<$data> scalar I<MUST NOT> be modified in any way while the request
321	is outstanding. Modifying it can result in segfaults or WW3 (if the	462	is outstanding. Modifying it can result in segfaults or World War III (if
322	necessary/optional hardware is installed).	463	the necessary/optional hardware is installed).
323		464
324	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	465	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
325	offset C<0> within the scalar:	466	offset C<0> within the scalar:
326		467
327	aio_read $fh, 7, 15, $buffer, 0, sub {	468	aio_read $fh, 7, 15, $buffer, 0, sub {
328	$_[0] > 0 or die "read error: $!";	469	$_[0] > 0 or die "read error: $!";
329	print "read $_[0] bytes: <$buffer>\n";	470	print "read $_[0] bytes: <$buffer>\n";
330	};	471	};
331		472
		473
332	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	474	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
333		475
334	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	476	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
335	reading at byte offset C<$in_offset>, and starts writing at the current	477	reading at byte offset C<$in_offset>, and starts writing at the current
336	file offset of C<$out_fh>. Because of that, it is not safe to issue more	478	file offset of C<$out_fh>. Because of that, it is not safe to issue more
337	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	479	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
338	other.	480	other. The same C<$in_fh> works fine though, as this function does not
		481	move or use the file offset of C<$in_fh>.
339		482
		483	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		484	are written, and there is no way to find out how many more bytes have been
		485	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		486	number of bytes written to C<$out_fh>. Only if the result value equals
		487	C<$length> one can assume that C<$length> bytes have been read.
		488
		489	Unlike with other C<aio_> functions, it makes a lot of sense to use
		490	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		491	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		492	the socket I/O will be non-blocking. Note, however, that you can run
		493	into a trap where C<aio_sendfile> reads some data with readahead, then
		494	fails to write all data, and when the socket is ready the next time, the
		495	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		496	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		497	resource usage.
		498
340	This call tries to make use of a native C<sendfile> syscall to provide	499	This call tries to make use of a native C<sendfile>-like syscall to
341	zero-copy operation. For this to work, C<$out_fh> should refer to a	500	provide zero-copy operation. For this to work, C<$out_fh> should refer to
342	socket, and C<$in_fh> should refer to mmap'able file.	501	a socket, and C<$in_fh> should refer to an mmap'able file.
343		502
344	If the native sendfile call fails or is not implemented, it will be	503	If a native sendfile cannot be found or it fails with C<ENOSYS>,
345	emulated, so you can call C<aio_sendfile> on any type of filehandle	504	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		505	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
346	regardless of the limitations of the operating system.	506	type of filehandle regardless of the limitations of the operating system.
347		507
348	Please note, however, that C<aio_sendfile> can read more bytes from	508	As native sendfile syscalls (as practically any non-POSIX interface hacked
349	C<$in_fh> than are written, and there is no way to find out how many	509	together in a hurry to improve benchmark numbers) tend to be rather buggy
350	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	510	on many systems, this implementation tries to work around some known bugs
351	provides the number of bytes written to C<$out_fh>. Only if the result	511	in Linux and FreeBSD kernels (probably others, too), but that might fail,
352	value equals C<$length> one can assume that C<$length> bytes have been	512	so you really really should check the return value of C<aio_sendfile> -
353	read.	513	fewre bytes than expected might have been transferred.
		514
354		515
355	=item aio_readahead $fh,$offset,$length, $callback->($retval)	516	=item aio_readahead $fh,$offset,$length, $callback->($retval)
356		517
357	C<aio_readahead> populates the page cache with data from a file so that	518	C<aio_readahead> populates the page cache with data from a file so that
358	subsequent reads from that file will not block on disk I/O. The C<$offset>	519	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
364	file. The current file offset of the file is left unchanged.	525	file. The current file offset of the file is left unchanged.
365		526
366	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	527	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
367	emulated by simply reading the data, which would have a similar effect.	528	emulated by simply reading the data, which would have a similar effect.
368		529
		530
369	=item aio_stat $fh_or_path, $callback->($status)	531	=item aio_stat $fh_or_path, $callback->($status)
370		532
371	=item aio_lstat $fh, $callback->($status)	533	=item aio_lstat $fh, $callback->($status)
372		534
373	Works like perl's C<stat> or C<lstat> in void context. The callback will	535	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
378	for an explanation.	540	for an explanation.
379		541
380	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	542	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
381	error when stat'ing a large file, the results will be silently truncated	543	error when stat'ing a large file, the results will be silently truncated
382	unless perl itself is compiled with large file support.	544	unless perl itself is compiled with large file support.
		545
		546	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		547	following constants and functions (if not implemented, the constants will
		548	be C<0> and the functions will either C<croak> or fall back on traditional
		549	behaviour).
		550
		551	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		552	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		553	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
383		554
384	Example: Print the length of F</etc/passwd>:	555	Example: Print the length of F</etc/passwd>:
385		556
386	aio_stat "/etc/passwd", sub {	557	aio_stat "/etc/passwd", sub {
387	$_[0] and die "stat failed: $!";	558	$_[0] and die "stat failed: $!";
388	print "size is ", -s _, "\n";	559	print "size is ", -s _, "\n";
389	};	560	};
390		561
		562
		563	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		564
		565	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		566	whether a file handle or path was passed.
		567
		568	On success, the callback is passed a hash reference with the following
		569	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		570	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		571	is passed.
		572
		573	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		574	C<ST_NOSUID>.
		575
		576	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		577	their correct value when available, or to C<0> on systems that do
		578	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		579	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		580	C<ST_NODIRATIME> and C<ST_RELATIME>.
		581
		582	Example: stat C</wd> and dump out the data if successful.
		583
		584	aio_statvfs "/wd", sub {
		585	my $f = $_[0]
		586	or die "statvfs: $!";
		587
		588	use Data::Dumper;
		589	say Dumper $f;
		590	};
		591
		592	# result:
		593	{
		594	bsize => 1024,
		595	bfree => 4333064312,
		596	blocks => 10253828096,
		597	files => 2050765568,
		598	flag => 4096,
		599	favail => 2042092649,
		600	bavail => 4333064312,
		601	ffree => 2042092649,
		602	namemax => 255,
		603	frsize => 1024,
		604	fsid => 1810
		605	}
		606
		607	Here is a (likely partial - send me updates!) list of fsid values used by
		608	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		609
		610	0x0000adf5 adfs
		611	0x0000adff affs
		612	0x5346414f afs
		613	0x09041934 anon-inode filesystem
		614	0x00000187 autofs
		615	0x42465331 befs
		616	0x1badface bfs
		617	0x42494e4d binfmt_misc
		618	0x9123683e btrfs
		619	0x0027e0eb cgroupfs
		620	0xff534d42 cifs
		621	0x73757245 coda
		622	0x012ff7b7 coh
		623	0x28cd3d45 cramfs
		624	0x453dcd28 cramfs-wend (wrong endianness)
		625	0x64626720 debugfs
		626	0x00001373 devfs
		627	0x00001cd1 devpts
		628	0x0000f15f ecryptfs
		629	0x00414a53 efs
		630	0x0000137d ext
		631	0x0000ef53 ext2/ext3
		632	0x0000ef51 ext2
		633	0x00004006 fat
		634	0x65735546 fuseblk
		635	0x65735543 fusectl
		636	0x0bad1dea futexfs
		637	0x01161970 gfs2
		638	0x47504653 gpfs
		639	0x00004244 hfs
		640	0xf995e849 hpfs
		641	0x958458f6 hugetlbfs
		642	0x2bad1dea inotifyfs
		643	0x00009660 isofs
		644	0x000072b6 jffs2
		645	0x3153464a jfs
		646	0x6b414653 k-afs
		647	0x0bd00bd0 lustre
		648	0x0000137f minix
		649	0x0000138f minix 30 char names
		650	0x00002468 minix v2
		651	0x00002478 minix v2 30 char names
		652	0x00004d5a minix v3
		653	0x19800202 mqueue
		654	0x00004d44 msdos
		655	0x0000564c novell
		656	0x00006969 nfs
		657	0x6e667364 nfsd
		658	0x00003434 nilfs
		659	0x5346544e ntfs
		660	0x00009fa1 openprom
		661	0x7461636F ocfs2
		662	0x00009fa0 proc
		663	0x6165676c pstorefs
		664	0x0000002f qnx4
		665	0x858458f6 ramfs
		666	0x52654973 reiserfs
		667	0x00007275 romfs
		668	0x67596969 rpc_pipefs
		669	0x73636673 securityfs
		670	0xf97cff8c selinux
		671	0x0000517b smb
		672	0x534f434b sockfs
		673	0x73717368 squashfs
		674	0x62656572 sysfs
		675	0x012ff7b6 sysv2
		676	0x012ff7b5 sysv4
		677	0x01021994 tmpfs
		678	0x15013346 udf
		679	0x00011954 ufs
		680	0x54190100 ufs byteswapped
		681	0x00009fa2 usbdevfs
		682	0x01021997 v9fs
		683	0xa501fcf5 vxfs
		684	0xabba1974 xenfs
		685	0x012ff7b4 xenix
		686	0x58465342 xfs
		687	0x012fd16d xia
		688
		689	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		690
		691	Works like perl's C<utime> function (including the special case of $atime
		692	and $mtime being undef). Fractional times are supported if the underlying
		693	syscalls support them.
		694
		695	When called with a pathname, uses utimes(2) if available, otherwise
		696	utime(2). If called on a file descriptor, uses futimes(2) if available,
		697	otherwise returns ENOSYS, so this is not portable.
		698
		699	Examples:
		700
		701	# set atime and mtime to current time (basically touch(1)):
		702	aio_utime "path", undef, undef;
		703	# set atime to current time and mtime to beginning of the epoch:
		704	aio_utime "path", time, undef; # undef==0
		705
		706
		707	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		708
		709	Works like perl's C<chown> function, except that C<undef> for either $uid
		710	or $gid is being interpreted as "do not change" (but -1 can also be used).
		711
		712	Examples:
		713
		714	# same as "chown root path" in the shell:
		715	aio_chown "path", 0, -1;
		716	# same as above:
		717	aio_chown "path", 0, undef;
		718
		719
		720	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		721
		722	Works like truncate(2) or ftruncate(2).
		723
		724
		725	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		726
		727	Allocates or frees disk space according to the C<$mode> argument. See the
		728	linux C<fallocate> documentation for details.
		729
		730	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		731	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		732	to deallocate a file range.
		733
		734	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		735	(without leaving a hole) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see
		736	your L<fallocate(2)> manpage).
		737
		738	The file system block size used by C<fallocate> is presumably the
		739	C<f_bsize> returned by C<statvfs>.
		740
		741	If C<fallocate> isn't available or cannot be emulated (currently no
		742	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		743
		744
		745	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		746
		747	Works like perl's C<chmod> function.
		748
		749
391	=item aio_unlink $pathname, $callback->($status)	750	=item aio_unlink $pathname, $callback->($status)
392		751
393	Asynchronously unlink (delete) a file and call the callback with the	752	Asynchronously unlink (delete) a file and call the callback with the
394	result code.	753	result code.
395		754
		755
396	=item aio_mknod $path, $mode, $dev, $callback->($status)	756	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
397		757
398	[EXPERIMENTAL]	758	[EXPERIMENTAL]
399		759
400	Asynchronously create a device node (or fifo). See mknod(2).	760	Asynchronously create a device node (or fifo). See mknod(2).
401		761
402	The only (POSIX-) portable way of calling this function is:	762	The only (POSIX-) portable way of calling this function is:
403		763
404	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	764	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		765
		766	See C<aio_stat> for info about some potentially helpful extra constants
		767	and functions.
405		768
406	=item aio_link $srcpath, $dstpath, $callback->($status)	769	=item aio_link $srcpath, $dstpath, $callback->($status)
407		770
408	Asynchronously create a new link to the existing object at C<$srcpath> at	771	Asynchronously create a new link to the existing object at C<$srcpath> at
409	the path C<$dstpath> and call the callback with the result code.	772	the path C<$dstpath> and call the callback with the result code.
410		773
		774
411	=item aio_symlink $srcpath, $dstpath, $callback->($status)	775	=item aio_symlink $srcpath, $dstpath, $callback->($status)
412		776
413	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	777	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
414	the path C<$dstpath> and call the callback with the result code.	778	the path C<$dstpath> and call the callback with the result code.
415		779
		780
		781	=item aio_readlink $pathname, $callback->($link)
		782
		783	Asynchronously read the symlink specified by C<$path> and pass it to
		784	the callback. If an error occurs, nothing or undef gets passed to the
		785	callback.
		786
		787
		788	=item aio_realpath $pathname, $callback->($path)
		789
		790	Asynchronously make the path absolute and resolve any symlinks in
		791	C<$path>. The resulting path only consists of directories (same as
		792	L<Cwd::realpath>).
		793
		794	This request can be used to get the absolute path of the current working
		795	directory by passing it a path of F<.> (a single dot).
		796
		797
416	=item aio_rename $srcpath, $dstpath, $callback->($status)	798	=item aio_rename $srcpath, $dstpath, $callback->($status)
417		799
418	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	800	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
419	rename(2) and call the callback with the result code.	801	rename(2) and call the callback with the result code.
420		802
		803	On systems that support the AIO::WD working directory abstraction
		804	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		805	of failing, C<rename> is called on the absolute path of C<$wd>.
		806
		807
		808	=item aio_mkdir $pathname, $mode, $callback->($status)
		809
		810	Asynchronously mkdir (create) a directory and call the callback with
		811	the result code. C<$mode> will be modified by the umask at the time the
		812	request is executed, so do not change your umask.
		813
		814
421	=item aio_rmdir $pathname, $callback->($status)	815	=item aio_rmdir $pathname, $callback->($status)
422		816
423	Asynchronously rmdir (delete) a directory and call the callback with the	817	Asynchronously rmdir (delete) a directory and call the callback with the
424	result code.	818	result code.
		819
		820	On systems that support the AIO::WD working directory abstraction
		821	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		822	C<rmdir> is called on the absolute path of C<$wd>.
		823
425		824
426	=item aio_readdir $pathname, $callback->($entries)	825	=item aio_readdir $pathname, $callback->($entries)
427		826
428	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	827	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
429	directory (i.e. opendir + readdir + closedir). The entries will not be	828	directory (i.e. opendir + readdir + closedir). The entries will not be
430	sorted, and will B<NOT> include the C<.> and C<..> entries.	829	sorted, and will B<NOT> include the C<.> and C<..> entries.
431		830
432	The callback a single argument which is either C<undef> or an array-ref	831	The callback is passed a single argument which is either C<undef> or an
433	with the filenames.	832	array-ref with the filenames.
		833
		834
		835	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		836
		837	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		838	tune behaviour and output format. In case of an error, C<$entries> will be
		839	C<undef>.
		840
		841	The flags are a combination of the following constants, ORed together (the
		842	flags will also be passed to the callback, possibly modified):
		843
		844	=over 4
		845
		846	=item IO::AIO::READDIR_DENTS
		847
		848	When this flag is off, then the callback gets an arrayref consisting of
		849	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		850	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		851	entry in more detail.
		852
		853	C<$name> is the name of the entry.
		854
		855	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		856
		857	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		858	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		859	C<IO::AIO::DT_WHT>.
		860
		861	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		862	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		863	scalars are read-only: you can not modify them.
		864
		865	C<$inode> is the inode number (which might not be exact on systems with 64
		866	bit inode numbers and 32 bit perls). This field has unspecified content on
		867	systems that do not deliver the inode information.
		868
		869	=item IO::AIO::READDIR_DIRS_FIRST
		870
		871	When this flag is set, then the names will be returned in an order where
		872	likely directories come first, in optimal stat order. This is useful when
		873	you need to quickly find directories, or you want to find all directories
		874	while avoiding to stat() each entry.
		875
		876	If the system returns type information in readdir, then this is used
		877	to find directories directly. Otherwise, likely directories are names
		878	beginning with ".", or otherwise names with no dots, of which names with
		879	short names are tried first.
		880
		881	=item IO::AIO::READDIR_STAT_ORDER
		882
		883	When this flag is set, then the names will be returned in an order
		884	suitable for stat()'ing each one. That is, when you plan to stat()
		885	all files in the given directory, then the returned order will likely
		886	be fastest.
		887
		888	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		889	the likely dirs come first, resulting in a less optimal stat order.
		890
		891	=item IO::AIO::READDIR_FOUND_UNKNOWN
		892
		893	This flag should not be set when calling C<aio_readdirx>. Instead, it
		894	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		895	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		896	C<$type>'s are known, which can be used to speed up some algorithms.
		897
		898	=back
		899
		900
		901	=item aio_load $pathname, $data, $callback->($status)
		902
		903	This is a composite request that tries to fully load the given file into
		904	memory. Status is the same as with aio_read.
		905
		906	=cut
		907
		908	sub aio_load($$;$) {
		909	my ($path, undef, $cb) = @_;
		910	my $data = \$_[1];
		911
		912	my $pri = aioreq_pri;
		913	my $grp = aio_group $cb;
		914
		915	aioreq_pri $pri;
		916	add $grp aio_open $path, O_RDONLY, 0, sub {
		917	my $fh = shift
		918	or return $grp->result (-1);
		919
		920	aioreq_pri $pri;
		921	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		922	$grp->result ($_[0]);
		923	};
		924	};
		925
		926	$grp
		927	}
434		928
435	=item aio_copy $srcpath, $dstpath, $callback->($status)	929	=item aio_copy $srcpath, $dstpath, $callback->($status)
436		930
437	Try to copy the I<file> (directories not supported as either source or	931	Try to copy the I<file> (directories not supported as either source or
438	destination) from C<$srcpath> to C<$dstpath> and call the callback with	932	destination) from C<$srcpath> to C<$dstpath> and call the callback with
439	the C<0> (error) or C<-1> ok.	933	a status of C<0> (ok) or C<-1> (error, see C<$!>).
440		934
441	This is a composite request that it creates the destination file with	935	This is a composite request that creates the destination file with
442	mode 0200 and copies the contents of the source file into it using	936	mode 0200 and copies the contents of the source file into it using
443	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	937	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
444	uid/gid, in that order.	938	uid/gid, in that order.
445		939
446	If an error occurs, the partial destination file will be unlinked, if	940	If an error occurs, the partial destination file will be unlinked, if
…		…
456	my $grp = aio_group $cb;	950	my $grp = aio_group $cb;
457		951
458	aioreq_pri $pri;	952	aioreq_pri $pri;
459	add $grp aio_open $src, O_RDONLY, 0, sub {	953	add $grp aio_open $src, O_RDONLY, 0, sub {
460	if (my $src_fh = $_[0]) {	954	if (my $src_fh = $_[0]) {
461	my @stat = stat $src_fh;	955	my @stat = stat $src_fh; # hmm, might block over nfs?
462		956
463	aioreq_pri $pri;	957	aioreq_pri $pri;
464	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	958	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
465	if (my $dst_fh = $_[0]) {	959	if (my $dst_fh = $_[0]) {
466	aioreq_pri $pri;	960	aioreq_pri $pri;
467	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	961	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
468	if ($_[0] == $stat[7]) {	962	if ($_[0] == $stat[7]) {
469	$grp->result (0);	963	$grp->result (0);
470	close $src_fh;	964	close $src_fh;
471		965
472	# those should not normally block. should. should.	966	my $ch = sub {
		967	aioreq_pri $pri;
		968	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		969	aioreq_pri $pri;
		970	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		971	aioreq_pri $pri;
		972	add $grp aio_close $dst_fh;
		973	}
		974	};
		975	};
		976
		977	aioreq_pri $pri;
		978	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		979	if ($_[0] < 0 && $! == ENOSYS) {
		980	aioreq_pri $pri;
473	utime $stat[8], $stat[9], $dst;	981	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
474	chmod $stat[2] & 07777, $dst_fh;	982	} else {
475	chown $stat[4], $stat[5], $dst_fh;	983	$ch->();
		984	}
476	close $dst_fh;	985	};
477	} else {	986	} else {
478	$grp->result (-1);	987	$grp->result (-1);
479	close $src_fh;	988	close $src_fh;
480	close $dst_fh;	989	close $dst_fh;
481		990
…		…
498		1007
499	=item aio_move $srcpath, $dstpath, $callback->($status)	1008	=item aio_move $srcpath, $dstpath, $callback->($status)
500		1009
501	Try to move the I<file> (directories not supported as either source or	1010	Try to move the I<file> (directories not supported as either source or
502	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1011	destination) from C<$srcpath> to C<$dstpath> and call the callback with
503	the C<0> (error) or C<-1> ok.	1012	a status of C<0> (ok) or C<-1> (error, see C<$!>).
504		1013
505	This is a composite request that tries to rename(2) the file first. If	1014	This is a composite request that tries to rename(2) the file first; if
506	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1015	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
507	that is successful, unlinking the C<$srcpath>.	1016	that is successful, unlinks the C<$srcpath>.
508		1017
509	=cut	1018	=cut
510		1019
511	sub aio_move($$;$) {	1020	sub aio_move($$;$) {
512	my ($src, $dst, $cb) = @_;	1021	my ($src, $dst, $cb) = @_;
…		…
519	if ($_[0] && $! == EXDEV) {	1028	if ($_[0] && $! == EXDEV) {
520	aioreq_pri $pri;	1029	aioreq_pri $pri;
521	add $grp aio_copy $src, $dst, sub {	1030	add $grp aio_copy $src, $dst, sub {
522	$grp->result ($_[0]);	1031	$grp->result ($_[0]);
523		1032
524	if (!$_[0]) {	1033	unless ($_[0]) {
525	aioreq_pri $pri;	1034	aioreq_pri $pri;
526	add $grp aio_unlink $src;	1035	add $grp aio_unlink $src;
527	}	1036	}
528	};	1037	};
529	} else {	1038	} else {
…		…
532	};	1041	};
533		1042
534	$grp	1043	$grp
535	}	1044	}
536		1045
537	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1046	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
538		1047
539	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1048	Scans a directory (similar to C<aio_readdir>) but additionally tries to
540	efficiently separate the entries of directory C<$path> into two sets of	1049	efficiently separate the entries of directory C<$path> into two sets of
541	names, directories you can recurse into (directories), and ones you cannot	1050	names, directories you can recurse into (directories), and ones you cannot
542	recurse into (everything else, including symlinks to directories).	1051	recurse into (everything else, including symlinks to directories).
…		…
559		1068
560	Implementation notes.	1069	Implementation notes.
561		1070
562	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1071	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
563		1072
		1073	If readdir returns file type information, then this is used directly to
		1074	find directories.
		1075
564	After reading the directory, the modification time, size etc. of the	1076	Otherwise, after reading the directory, the modification time, size etc.
565	directory before and after the readdir is checked, and if they match (and	1077	of the directory before and after the readdir is checked, and if they
566	isn't the current time), the link count will be used to decide how many	1078	match (and isn't the current time), the link count will be used to decide
567	entries are directories (if >= 2). Otherwise, no knowledge of the number	1079	how many entries are directories (if >= 2). Otherwise, no knowledge of the
568	of subdirectories will be assumed.	1080	number of subdirectories will be assumed.
569		1081
570	Then entries will be sorted into likely directories (everything without	1082	Then entries will be sorted into likely directories a non-initial dot
571	a non-initial dot currently) and likely non-directories (everything	1083	currently) and likely non-directories (see C<aio_readdirx>). Then every
572	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1084	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
573	likely directories first. If that succeeds, it assumes that the entry	1085	in order of their inode numbers. If that succeeds, it assumes that the
574	is a directory or a symlink to directory (which will be checked	1086	entry is a directory or a symlink to directory (which will be checked
575	seperately). This is often faster than stat'ing the entry itself because	1087	separately). This is often faster than stat'ing the entry itself because
576	filesystems might detect the type of the entry without reading the inode	1088	filesystems might detect the type of the entry without reading the inode
577	data (e.g. ext2fs filetype feature).	1089	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1090	the filetype information on readdir.
578		1091
579	If the known number of directories (link count - 2) has been reached, the	1092	If the known number of directories (link count - 2) has been reached, the
580	rest of the entries is assumed to be non-directories.	1093	rest of the entries is assumed to be non-directories.
581		1094
582	This only works with certainty on POSIX (= UNIX) filesystems, which	1095	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
586	as those tend to return 0 or 1 as link counts, which disables the	1099	as those tend to return 0 or 1 as link counts, which disables the
587	directory counting heuristic.	1100	directory counting heuristic.
588		1101
589	=cut	1102	=cut
590		1103
591	sub aio_scandir($$$) {	1104	sub aio_scandir($$;$) {
592	my ($path, $maxreq, $cb) = @_;	1105	my ($path, $maxreq, $cb) = @_;
593		1106
594	my $pri = aioreq_pri;	1107	my $pri = aioreq_pri;
595		1108
596	my $grp = aio_group $cb;	1109	my $grp = aio_group $cb;
597		1110
598	$maxreq = 4 if $maxreq <= 0;	1111	$maxreq = 4 if $maxreq <= 0;
599		1112
600	# stat once	1113	# get a wd object
601	aioreq_pri $pri;	1114	aioreq_pri $pri;
602	add $grp aio_stat $path, sub {	1115	add $grp aio_wd $path, sub {
		1116	$_[0]
603	return $grp->result () if $_[0];	1117	or return $grp->result ();
604	my $now = time;
605	my $hash1 = join ":", (stat _)[0,1,3,7,9];
606		1118
607	# read the directory entries	1119	my $wd = [shift, "."];
		1120
		1121	# stat once
608	aioreq_pri $pri;	1122	aioreq_pri $pri;
609	add $grp aio_readdir $path, sub {	1123	add $grp aio_stat $wd, sub {
610	my $entries = shift
611	or return $grp->result ();	1124	return $grp->result () if $_[0];
		1125	my $now = time;
		1126	my $hash1 = join ":", (stat _)[0,1,3,7,9];
612		1127
613	# stat the dir another time	1128	# read the directory entries
614	aioreq_pri $pri;	1129	aioreq_pri $pri;
		1130	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1131	my $entries = shift
		1132	or return $grp->result ();
		1133
		1134	# stat the dir another time
		1135	aioreq_pri $pri;
615	add $grp aio_stat $path, sub {	1136	add $grp aio_stat $wd, sub {
616	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1137	my $hash2 = join ":", (stat _)[0,1,3,7,9];
617		1138
618	my $ndirs;	1139	my $ndirs;
619		1140
620	# take the slow route if anything looks fishy	1141	# take the slow route if anything looks fishy
621	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1142	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
622	$ndirs = -1;	1143	$ndirs = -1;
623	} else {	1144	} else {
624	# if nlink == 2, we are finished	1145	# if nlink == 2, we are finished
625	# on non-posix-fs's, we rely on nlink < 2	1146	# for non-posix-fs's, we rely on nlink < 2
626	$ndirs = (stat _)[3] - 2	1147	$ndirs = (stat _)[3] - 2
627	or return $grp->result ([], $entries);	1148	or return $grp->result ([], $entries);
628	}	1149	}
629		1150
630	# sort into likely dirs and likely nondirs
631	# dirs == files without ".", short entries first
632	$entries = [map $_->[0],
633	sort { $b->[1] cmp $a->[1] }
634	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
635	@$entries];
636
637	my (@dirs, @nondirs);	1151	my (@dirs, @nondirs);
638		1152
639	my $statgrp = add $grp aio_group sub {	1153	my $statgrp = add $grp aio_group sub {
640	$grp->result (\@dirs, \@nondirs);	1154	$grp->result (\@dirs, \@nondirs);
641	};	1155	};
642		1156
643	limit $statgrp $maxreq;	1157	limit $statgrp $maxreq;
644	feed $statgrp sub {	1158	feed $statgrp sub {
645	return unless @$entries;	1159	return unless @$entries;
646	my $entry = pop @$entries;	1160	my $entry = shift @$entries;
647		1161
648	aioreq_pri $pri;	1162	aioreq_pri $pri;
		1163	$wd->[1] = "$entry/.";
649	add $statgrp aio_stat "$path/$entry/.", sub {	1164	add $statgrp aio_stat $wd, sub {
650	if ($_[0] < 0) {	1165	if ($_[0] < 0) {
651	push @nondirs, $entry;	1166	push @nondirs, $entry;
652	} else {	1167	} else {
653	# need to check for real directory	1168	# need to check for real directory
654	aioreq_pri $pri;	1169	aioreq_pri $pri;
		1170	$wd->[1] = $entry;
655	add $statgrp aio_lstat "$path/$entry", sub {	1171	add $statgrp aio_lstat $wd, sub {
656	if (-d _) {	1172	if (-d _) {
657	push @dirs, $entry;	1173	push @dirs, $entry;
658		1174
659	unless (--$ndirs) {	1175	unless (--$ndirs) {
660	push @nondirs, @$entries;	1176	push @nondirs, @$entries;
661	feed $statgrp;	1177	feed $statgrp;
		1178	}
		1179	} else {
		1180	push @nondirs, $entry;
662	}	1181	}
663	} else {
664	push @nondirs, $entry;
665	}	1182	}
666	}	1183	}
667	}	1184	};
668	};	1185	};
669	};	1186	};
670	};	1187	};
671	};	1188	};
672	};	1189	};
673		1190
674	$grp	1191	$grp
675	}	1192	}
676		1193
		1194	=item aio_rmtree $pathname, $callback->($status)
		1195
		1196	Delete a directory tree starting (and including) C<$path>, return the
		1197	status of the final C<rmdir> only. This is a composite request that
		1198	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1199	everything else.
		1200
		1201	=cut
		1202
		1203	sub aio_rmtree;
		1204	sub aio_rmtree($;$) {
		1205	my ($path, $cb) = @_;
		1206
		1207	my $pri = aioreq_pri;
		1208	my $grp = aio_group $cb;
		1209
		1210	aioreq_pri $pri;
		1211	add $grp aio_scandir $path, 0, sub {
		1212	my ($dirs, $nondirs) = @_;
		1213
		1214	my $dirgrp = aio_group sub {
		1215	add $grp aio_rmdir $path, sub {
		1216	$grp->result ($_[0]);
		1217	};
		1218	};
		1219
		1220	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1221	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1222
		1223	add $grp $dirgrp;
		1224	};
		1225
		1226	$grp
		1227	}
		1228
		1229	=item aio_sync $callback->($status)
		1230
		1231	Asynchronously call sync and call the callback when finished.
		1232
677	=item aio_fsync $fh, $callback->($status)	1233	=item aio_fsync $fh, $callback->($status)
678		1234
679	Asynchronously call fsync on the given filehandle and call the callback	1235	Asynchronously call fsync on the given filehandle and call the callback
680	with the fsync result code.	1236	with the fsync result code.
681		1237
…		…
684	Asynchronously call fdatasync on the given filehandle and call the	1240	Asynchronously call fdatasync on the given filehandle and call the
685	callback with the fdatasync result code.	1241	callback with the fdatasync result code.
686		1242
687	If this call isn't available because your OS lacks it or it couldn't be	1243	If this call isn't available because your OS lacks it or it couldn't be
688	detected, it will be emulated by calling C<fsync> instead.	1244	detected, it will be emulated by calling C<fsync> instead.
		1245
		1246	=item aio_syncfs $fh, $callback->($status)
		1247
		1248	Asynchronously call the syncfs syscall to sync the filesystem associated
		1249	to the given filehandle and call the callback with the syncfs result
		1250	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1251	errno to C<ENOSYS> nevertheless.
		1252
		1253	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1254
		1255	Sync the data portion of the file specified by C<$offset> and C<$length>
		1256	to disk (but NOT the metadata), by calling the Linux-specific
		1257	sync_file_range call. If sync_file_range is not available or it returns
		1258	ENOSYS, then fdatasync or fsync is being substituted.
		1259
		1260	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1261	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1262	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1263	manpage for details.
		1264
		1265	=item aio_pathsync $pathname, $callback->($status)
		1266
		1267	This request tries to open, fsync and close the given path. This is a
		1268	composite request intended to sync directories after directory operations
		1269	(E.g. rename). This might not work on all operating systems or have any
		1270	specific effect, but usually it makes sure that directory changes get
		1271	written to disc. It works for anything that can be opened for read-only,
		1272	not just directories.
		1273
		1274	Future versions of this function might fall back to other methods when
		1275	C<fsync> on the directory fails (such as calling C<sync>).
		1276
		1277	Passes C<0> when everything went ok, and C<-1> on error.
		1278
		1279	=cut
		1280
		1281	sub aio_pathsync($;$) {
		1282	my ($path, $cb) = @_;
		1283
		1284	my $pri = aioreq_pri;
		1285	my $grp = aio_group $cb;
		1286
		1287	aioreq_pri $pri;
		1288	add $grp aio_open $path, O_RDONLY, 0, sub {
		1289	my ($fh) = @_;
		1290	if ($fh) {
		1291	aioreq_pri $pri;
		1292	add $grp aio_fsync $fh, sub {
		1293	$grp->result ($_[0]);
		1294
		1295	aioreq_pri $pri;
		1296	add $grp aio_close $fh;
		1297	};
		1298	} else {
		1299	$grp->result (-1);
		1300	}
		1301	};
		1302
		1303	$grp
		1304	}
		1305
		1306	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1307
		1308	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1309	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1310	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1311	scalar must only be modified in-place while an aio operation is pending on
		1312	it).
		1313
		1314	It calls the C<msync> function of your OS, if available, with the memory
		1315	area starting at C<$offset> in the string and ending C<$length> bytes
		1316	later. If C<$length> is negative, counts from the end, and if C<$length>
		1317	is C<undef>, then it goes till the end of the string. The flags can be
		1318	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1319	C<IO::AIO::MS_SYNC>.
		1320
		1321	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1322
		1323	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1324	scalars.
		1325
		1326	It touches (reads or writes) all memory pages in the specified
		1327	range inside the scalar. All caveats and parameters are the same
		1328	as for C<aio_msync>, above, except for flags, which must be either
		1329	C<0> (which reads all pages and ensures they are instantiated) or
		1330	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1331	writing an octet from it, which dirties the page).
		1332
		1333	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1334
		1335	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1336	scalars.
		1337
		1338	It reads in all the pages of the underlying storage into memory (if any)
		1339	and locks them, so they are not getting swapped/paged out or removed.
		1340
		1341	If C<$length> is undefined, then the scalar will be locked till the end.
		1342
		1343	On systems that do not implement C<mlock>, this function returns C<-1>
		1344	and sets errno to C<ENOSYS>.
		1345
		1346	Note that the corresponding C<munlock> is synchronous and is
		1347	documented under L<MISCELLANEOUS FUNCTIONS>.
		1348
		1349	Example: open a file, mmap and mlock it - both will be undone when
		1350	C<$data> gets destroyed.
		1351
		1352	open my $fh, "<", $path or die "$path: $!";
		1353	my $data;
		1354	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1355	aio_mlock $data; # mlock in background
		1356
		1357	=item aio_mlockall $flags, $callback->($status)
		1358
		1359	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1360	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1361
		1362	On systems that do not implement C<mlockall>, this function returns C<-1>
		1363	and sets errno to C<ENOSYS>.
		1364
		1365	Note that the corresponding C<munlockall> is synchronous and is
		1366	documented under L<MISCELLANEOUS FUNCTIONS>.
		1367
		1368	Example: asynchronously lock all current and future pages into memory.
		1369
		1370	aio_mlockall IO::AIO::MCL_FUTURE;
		1371
		1372	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1373
		1374	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1375	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1376	the ioctl is not available on your OS, then this request will fail with
		1377	C<ENOSYS>.
		1378
		1379	C<$start> is the starting offset to query extents for, C<$length> is the
		1380	size of the range to query - if it is C<undef>, then the whole file will
		1381	be queried.
		1382
		1383	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1384	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1385	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1386	the data portion.
		1387
		1388	C<$count> is the maximum number of extent records to return. If it is
		1389	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1390	case, if it is C<0>, then the callback receives the number of extents
		1391	instead of the extents themselves (which is unreliable, see below).
		1392
		1393	If an error occurs, the callback receives no arguments. The special
		1394	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1395
		1396	Otherwise, the callback receives an array reference with extent
		1397	structures. Each extent structure is an array reference itself, with the
		1398	following members:
		1399
		1400	[$logical, $physical, $length, $flags]
		1401
		1402	Flags is any combination of the following flag values (typically either C<0>
		1403	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1404
		1405	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1406	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1407	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1408	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1409	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1410	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1411
		1412	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1413	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1414	it to return all extents of a range for files with large number of
		1415	extents. The code works around all these issues if C<$count> is undef.
689		1416
690	=item aio_group $callback->(...)	1417	=item aio_group $callback->(...)
691		1418
692	This is a very special aio request: Instead of doing something, it is a	1419	This is a very special aio request: Instead of doing something, it is a
693	container for other aio requests, which is useful if you want to bundle	1420	container for other aio requests, which is useful if you want to bundle
…		…
731	immense (it blocks a thread for a long time) so do not use this function	1458	immense (it blocks a thread for a long time) so do not use this function
732	except to put your application under artificial I/O pressure.	1459	except to put your application under artificial I/O pressure.
733		1460
734	=back	1461	=back
735		1462
		1463
		1464	=head2 IO::AIO::WD - multiple working directories
		1465
		1466	Your process only has one current working directory, which is used by all
		1467	threads. This makes it hard to use relative paths (some other component
		1468	could call C<chdir> at any time, and it is hard to control when the path
		1469	will be used by IO::AIO).
		1470
		1471	One solution for this is to always use absolute paths. This usually works,
		1472	but can be quite slow (the kernel has to walk the whole path on every
		1473	access), and can also be a hassle to implement.
		1474
		1475	Newer POSIX systems have a number of functions (openat, fdopendir,
		1476	futimensat and so on) that make it possible to specify working directories
		1477	per operation.
		1478
		1479	For portability, and because the clowns who "designed", or shall I write,
		1480	perpetrated this new interface were obviously half-drunk, this abstraction
		1481	cannot be perfect, though.
		1482
		1483	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1484	object. This object stores the canonicalised, absolute version of the
		1485	path, and on systems that allow it, also a directory file descriptor.
		1486
		1487	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1488	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1489	object and a pathname instead (or the IO::AIO::WD object alone, which
		1490	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1491	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1492	to that IO::AIO::WD object.
		1493
		1494	For example, to get a wd object for F</etc> and then stat F<passwd>
		1495	inside, you would write:
		1496
		1497	aio_wd "/etc", sub {
		1498	my $etcdir = shift;
		1499
		1500	# although $etcdir can be undef on error, there is generally no reason
		1501	# to check for errors here, as aio_stat will fail with ENOENT
		1502	# when $etcdir is undef.
		1503
		1504	aio_stat [$etcdir, "passwd"], sub {
		1505	# yay
		1506	};
		1507	};
		1508
		1509	The fact that C<aio_wd> is a request and not a normal function shows that
		1510	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1511	which is why it is done asynchronously.
		1512
		1513	To stat the directory obtained with C<aio_wd> above, one could write
		1514	either of the following three request calls:
		1515
		1516	aio_lstat "/etc" , sub { ... # pathname as normal string
		1517	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1518	aio_lstat $wd , sub { ... # shorthand for the previous
		1519
		1520	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1521	object and the pathname string, so you could write the following without
		1522	causing any issues due to C<$path> getting reused:
		1523
		1524	my $path = [$wd, undef];
		1525
		1526	for my $name (qw(abc def ghi)) {
		1527	$path->[1] = $name;
		1528	aio_stat $path, sub {
		1529	# ...
		1530	};
		1531	}
		1532
		1533	There are some caveats: when directories get renamed (or deleted), the
		1534	pathname string doesn't change, so will point to the new directory (or
		1535	nowhere at all), while the directory fd, if available on the system,
		1536	will still point to the original directory. Most functions accepting a
		1537	pathname will use the directory fd on newer systems, and the string on
		1538	older systems. Some functions (such as realpath) will always rely on the
		1539	string form of the pathname.
		1540
		1541	So this functionality is mainly useful to get some protection against
		1542	C<chdir>, to easily get an absolute path out of a relative path for future
		1543	reference, and to speed up doing many operations in the same directory
		1544	(e.g. when stat'ing all files in a directory).
		1545
		1546	The following functions implement this working directory abstraction:
		1547
		1548	=over 4
		1549
		1550	=item aio_wd $pathname, $callback->($wd)
		1551
		1552	Asynchonously canonicalise the given pathname and convert it to an
		1553	IO::AIO::WD object representing it. If possible and supported on the
		1554	system, also open a directory fd to speed up pathname resolution relative
		1555	to this working directory.
		1556
		1557	If something goes wrong, then C<undef> is passwd to the callback instead
		1558	of a working directory object and C<$!> is set appropriately. Since
		1559	passing C<undef> as working directory component of a pathname fails the
		1560	request with C<ENOENT>, there is often no need for error checking in the
		1561	C<aio_wd> callback, as future requests using the value will fail in the
		1562	expected way.
		1563
		1564	=item IO::AIO::CWD
		1565
		1566	This is a compiletime constant (object) that represents the process
		1567	current working directory.
		1568
		1569	Specifying this object as working directory object for a pathname is as if
		1570	the pathname would be specified directly, without a directory object. For
		1571	example, these calls are functionally identical:
		1572
		1573	aio_stat "somefile", sub { ... };
		1574	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1575
		1576	=back
		1577
		1578	To recover the path associated with an IO::AIO::WD object, you can use
		1579	C<aio_realpath>:
		1580
		1581	aio_realpath $wd, sub {
		1582	warn "path is $_[0]\n";
		1583	};
		1584
		1585	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1586	sometimes, fall back to using an absolue path.
		1587
736	=head2 IO::AIO::REQ CLASS	1588	=head2 IO::AIO::REQ CLASS
737		1589
738	All non-aggregate C<aio_*> functions return an object of this class when	1590	All non-aggregate C<aio_*> functions return an object of this class when
739	called in non-void context.	1591	called in non-void context.
740		1592
…		…
743	=item cancel $req	1595	=item cancel $req
744		1596
745	Cancels the request, if possible. Has the effect of skipping execution	1597	Cancels the request, if possible. Has the effect of skipping execution
746	when entering the B<execute> state and skipping calling the callback when	1598	when entering the B<execute> state and skipping calling the callback when
747	entering the the B<result> state, but will leave the request otherwise	1599	entering the the B<result> state, but will leave the request otherwise
748	untouched. That means that requests that currently execute will not be	1600	untouched (with the exception of readdir). That means that requests that
749	stopped and resources held by the request will not be freed prematurely.	1601	currently execute will not be stopped and resources held by the request
		1602	will not be freed prematurely.
750		1603
751	=item cb $req $callback->(...)	1604	=item cb $req $callback->(...)
752		1605
753	Replace (or simply set) the callback registered to the request.	1606	Replace (or simply set) the callback registered to the request.
754		1607
…		…
805	Their lifetime, simplified, looks like this: when they are empty, they	1658	Their lifetime, simplified, looks like this: when they are empty, they
806	will finish very quickly. If they contain only requests that are in the	1659	will finish very quickly. If they contain only requests that are in the
807	C<done> state, they will also finish. Otherwise they will continue to	1660	C<done> state, they will also finish. Otherwise they will continue to
808	exist.	1661	exist.
809		1662
810	That means after creating a group you have some time to add requests. And	1663	That means after creating a group you have some time to add requests
811	in the callbacks of those requests, you can add further requests to the	1664	(precisely before the callback has been invoked, which is only done within
812	group. And only when all those requests have finished will the the group	1665	the C<poll_cb>). And in the callbacks of those requests, you can add
813	itself finish.	1666	further requests to the group. And only when all those requests have
		1667	finished will the the group itself finish.
814		1668
815	=over 4	1669	=over 4
816		1670
817	=item add $grp ...	1671	=item add $grp ...
818		1672
…		…
827	=item $grp->cancel_subs	1681	=item $grp->cancel_subs
828		1682
829	Cancel all subrequests and clears any feeder, but not the group request	1683	Cancel all subrequests and clears any feeder, but not the group request
830	itself. Useful when you queued a lot of events but got a result early.	1684	itself. Useful when you queued a lot of events but got a result early.
831		1685
		1686	The group request will finish normally (you cannot add requests to the
		1687	group).
		1688
832	=item $grp->result (...)	1689	=item $grp->result (...)
833		1690
834	Set the result value(s) that will be passed to the group callback when all	1691	Set the result value(s) that will be passed to the group callback when all
835	subrequests have finished and set thre groups errno to the current value	1692	subrequests have finished and set the groups errno to the current value
836	of errno (just like calling C<errno> without an error number). By default,	1693	of errno (just like calling C<errno> without an error number). By default,
837	no argument will be passed and errno is zero.	1694	no argument will be passed and errno is zero.
838		1695
839	=item $grp->errno ([$errno])	1696	=item $grp->errno ([$errno])
840		1697
…		…
851	=item feed $grp $callback->($grp)	1708	=item feed $grp $callback->($grp)
852		1709
853	Sets a feeder/generator on this group: every group can have an attached	1710	Sets a feeder/generator on this group: every group can have an attached
854	generator that generates requests if idle. The idea behind this is that,	1711	generator that generates requests if idle. The idea behind this is that,
855	although you could just queue as many requests as you want in a group,	1712	although you could just queue as many requests as you want in a group,
856	this might starve other requests for a potentially long time. For	1713	this might starve other requests for a potentially long time. For example,
857	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1714	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
858	requests, delaying any later requests for a long time.	1715	requests, delaying any later requests for a long time.
859		1716
860	To avoid this, and allow incremental generation of requests, you can	1717	To avoid this, and allow incremental generation of requests, you can
861	instead a group and set a feeder on it that generates those requests. The	1718	instead a group and set a feeder on it that generates those requests. The
862	feed callback will be called whenever there are few enough (see C<limit>,	1719	feed callback will be called whenever there are few enough (see C<limit>,
…		…
867	not impose any limits).	1724	not impose any limits).
868		1725
869	If the feed does not queue more requests when called, it will be	1726	If the feed does not queue more requests when called, it will be
870	automatically removed from the group.	1727	automatically removed from the group.
871		1728
872	If the feed limit is C<0>, it will be set to C<2> automatically.	1729	If the feed limit is C<0> when this method is called, it will be set to
		1730	C<2> automatically.
873		1731
874	Example:	1732	Example:
875		1733
876	# stat all files in @files, but only ever use four aio requests concurrently:	1734	# stat all files in @files, but only ever use four aio requests concurrently:
877		1735
…		…
889	Sets the feeder limit for the group: The feeder will be called whenever	1747	Sets the feeder limit for the group: The feeder will be called whenever
890	the group contains less than this many requests.	1748	the group contains less than this many requests.
891		1749
892	Setting the limit to C<0> will pause the feeding process.	1750	Setting the limit to C<0> will pause the feeding process.
893		1751
		1752	The default value for the limit is C<0>, but note that setting a feeder
		1753	automatically bumps it up to C<2>.
		1754
894	=back	1755	=back
895		1756
896	=head2 SUPPORT FUNCTIONS	1757	=head2 SUPPORT FUNCTIONS
897		1758
898	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1759	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
900	=over 4	1761	=over 4
901		1762
902	=item $fileno = IO::AIO::poll_fileno	1763	=item $fileno = IO::AIO::poll_fileno
903		1764
904	Return the I<request result pipe file descriptor>. This filehandle must be	1765	Return the I<request result pipe file descriptor>. This filehandle must be
905	polled for reading by some mechanism outside this module (e.g. Event or	1766	polled for reading by some mechanism outside this module (e.g. EV, Glib,
906	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1767	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
907	to call C<poll_cb> to check the results.	1768	you have to call C<poll_cb> to check the results.
908		1769
909	See C<poll_cb> for an example.	1770	See C<poll_cb> for an example.
910		1771
911	=item IO::AIO::poll_cb	1772	=item IO::AIO::poll_cb
912		1773
913	Process some outstanding events on the result pipe. You have to call this	1774	Process some requests that have reached the result phase (i.e. they have
914	regularly. Returns the number of events processed. Returns immediately	1775	been executed but the results are not yet reported). You have to call
915	when no events are outstanding. The amount of events processed depends on	1776	this "regularly" to finish outstanding requests.
916	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
917		1777
		1778	Returns C<0> if all events could be processed (or there were no
		1779	events to process), or C<-1> if it returned earlier for whatever
		1780	reason. Returns immediately when no events are outstanding. The amount
		1781	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1782	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1783
918	If not all requests were processed for whatever reason, the filehandle	1784	If not all requests were processed for whatever reason, the poll file
919	will still be ready when C<poll_cb> returns.	1785	descriptor will still be ready when C<poll_cb> returns, so normally you
		1786	don't have to do anything special to have it called later.
		1787
		1788	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1789	ready, it can be beneficial to call this function from loops which submit
		1790	a lot of requests, to make sure the results get processed when they become
		1791	available and not just when the loop is finished and the event loop takes
		1792	over again. This function returns very fast when there are no outstanding
		1793	requests.
920		1794
921	Example: Install an Event watcher that automatically calls	1795	Example: Install an Event watcher that automatically calls
922	IO::AIO::poll_cb with high priority:	1796	IO::AIO::poll_cb with high priority (more examples can be found in the
		1797	SYNOPSIS section, at the top of this document):
923		1798
924	Event->io (fd => IO::AIO::poll_fileno,	1799	Event->io (fd => IO::AIO::poll_fileno,
925	poll => 'r', async => 1,	1800	poll => 'r', async => 1,
926	cb => \&IO::AIO::poll_cb);	1801	cb => \&IO::AIO::poll_cb);
		1802
		1803	=item IO::AIO::poll_wait
		1804
		1805	Wait until either at least one request is in the result phase or no
		1806	requests are outstanding anymore.
		1807
		1808	This is useful if you want to synchronously wait for some requests to
		1809	become ready, without actually handling them.
		1810
		1811	See C<nreqs> for an example.
		1812
		1813	=item IO::AIO::poll
		1814
		1815	Waits until some requests have been handled.
		1816
		1817	Returns the number of requests processed, but is otherwise strictly
		1818	equivalent to:
		1819
		1820	IO::AIO::poll_wait, IO::AIO::poll_cb
		1821
		1822	=item IO::AIO::flush
		1823
		1824	Wait till all outstanding AIO requests have been handled.
		1825
		1826	Strictly equivalent to:
		1827
		1828	IO::AIO::poll_wait, IO::AIO::poll_cb
		1829	while IO::AIO::nreqs;
927		1830
928	=item IO::AIO::max_poll_reqs $nreqs	1831	=item IO::AIO::max_poll_reqs $nreqs
929		1832
930	=item IO::AIO::max_poll_time $seconds	1833	=item IO::AIO::max_poll_time $seconds
931		1834
…		…
933	that are being processed by C<IO::AIO::poll_cb> in one call, respectively	1836	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
934	the maximum amount of time (default C<0>, meaning infinity) spent in	1837	the maximum amount of time (default C<0>, meaning infinity) spent in
935	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount	1838	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
936	of time C<poll_cb> is allowed to use).	1839	of time C<poll_cb> is allowed to use).
937		1840
		1841	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1842	syscall per request processed, which is not normally a problem unless your
		1843	callbacks are really really fast or your OS is really really slow (I am
		1844	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1845
938	Setting these is useful if you want to ensure some level of	1846	Setting these is useful if you want to ensure some level of
939	interactiveness when perl is not fast enough to process all requests in	1847	interactiveness when perl is not fast enough to process all requests in
940	time.	1848	time.
941		1849
942	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	1850	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
943		1851
944	Example: Install an Event watcher that automatically calls	1852	Example: Install an Event watcher that automatically calls
945	IO::AIO::poll_some with low priority, to ensure that other parts of the	1853	IO::AIO::poll_cb with low priority, to ensure that other parts of the
946	program get the CPU sometimes even under high AIO load.	1854	program get the CPU sometimes even under high AIO load.
947		1855
948	# try not to spend much more than 0.1s in poll_cb	1856	# try not to spend much more than 0.1s in poll_cb
949	IO::AIO::max_poll_time 0.1;	1857	IO::AIO::max_poll_time 0.1;
950		1858
951	# use a low priority so other tasks have priority	1859	# use a low priority so other tasks have priority
952	Event->io (fd => IO::AIO::poll_fileno,	1860	Event->io (fd => IO::AIO::poll_fileno,
953	poll => 'r', nice => 1,	1861	poll => 'r', nice => 1,
954	cb => &IO::AIO::poll_cb);	1862	cb => &IO::AIO::poll_cb);
955		1863
956	=item IO::AIO::poll_wait	1864	=back
957
958	Wait till the result filehandle becomes ready for reading (simply does a
959	C<select> on the filehandle. This is useful if you want to synchronously
960	wait for some requests to finish).
961
962	See C<nreqs> for an example.
963
964	=item IO::AIO::poll
965
966	Waits until some requests have been handled.
967
968	Strictly equivalent to:
969
970	IO::AIO::poll_wait, IO::AIO::poll_cb
971	if IO::AIO::nreqs;
972
973	=item IO::AIO::flush
974
975	Wait till all outstanding AIO requests have been handled.
976
977	Strictly equivalent to:
978
979	IO::AIO::poll_wait, IO::AIO::poll_cb
980	while IO::AIO::nreqs;
981		1865
982	=head3 CONTROLLING THE NUMBER OF THREADS	1866	=head3 CONTROLLING THE NUMBER OF THREADS
		1867
		1868	=over
983		1869
984	=item IO::AIO::min_parallel $nthreads	1870	=item IO::AIO::min_parallel $nthreads
985		1871
986	Set the minimum number of AIO threads to C<$nthreads>. The current	1872	Set the minimum number of AIO threads to C<$nthreads>. The current
987	default is C<8>, which means eight asynchronous operations can execute	1873	default is C<8>, which means eight asynchronous operations can execute
…		…
1015		1901
1016	Under normal circumstances you don't need to call this function.	1902	Under normal circumstances you don't need to call this function.
1017		1903
1018	=item IO::AIO::max_idle $nthreads	1904	=item IO::AIO::max_idle $nthreads
1019		1905
1020	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1906	Limit the number of threads (default: 4) that are allowed to idle
1021	threads that did not get a request to process within 10 seconds). That	1907	(i.e., threads that did not get a request to process within the idle
1022	means if a thread becomes idle while C<$nthreads> other threads are also	1908	timeout (default: 10 seconds). That means if a thread becomes idle while
1023	idle, it will free its resources and exit.	1909	C<$nthreads> other threads are also idle, it will free its resources and
		1910	exit.
1024		1911
1025	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1912	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1026	to allow for extremely high load situations, but want to free resources	1913	to allow for extremely high load situations, but want to free resources
1027	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1914	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1028		1915
1029	The default is probably ok in most situations, especially if thread	1916	The default is probably ok in most situations, especially if thread
1030	creation is fast. If thread creation is very slow on your system you might	1917	creation is fast. If thread creation is very slow on your system you might
1031	want to use larger values.	1918	want to use larger values.
1032		1919
		1920	=item IO::AIO::idle_timeout $seconds
		1921
		1922	Sets the minimum idle timeout (default 10) after which worker threads are
		1923	allowed to exit. SEe C<IO::AIO::max_idle>.
		1924
1033	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1925	=item IO::AIO::max_outstanding $maxreqs
		1926
		1927	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1928	you do queue up more than this number of requests, the next call to
		1929	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1930	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1931	longer exceeded.
		1932
		1933	In other words, this setting does not enforce a queue limit, but can be
		1934	used to make poll functions block if the limit is exceeded.
1034		1935
1035	This is a very bad function to use in interactive programs because it	1936	This is a very bad function to use in interactive programs because it
1036	blocks, and a bad way to reduce concurrency because it is inexact: Better	1937	blocks, and a bad way to reduce concurrency because it is inexact: Better
1037	use an C<aio_group> together with a feed callback.	1938	use an C<aio_group> together with a feed callback.
1038		1939
1039	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1940	Its main use is in scripts without an event loop - when you want to stat
1040	to queue up more than this number of requests, the next call to the	1941	a lot of files, you can write somehting like this:
1041	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1042	function will block until the limit is no longer exceeded.
1043		1942
1044	The default value is very large, so there is no practical limit on the	1943	IO::AIO::max_outstanding 32;
1045	number of outstanding requests.
1046		1944
1047	You can still queue as many requests as you want. Therefore,	1945	for my $path (...) {
1048	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1946	aio_stat $path , ...;
1049	as a stop gap to shield against fatal memory overflow (with large values).	1947	IO::AIO::poll_cb;
		1948	}
		1949
		1950	IO::AIO::flush;
		1951
		1952	The call to C<poll_cb> inside the loop will normally return instantly, but
		1953	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1954	some requests have been handled. This keeps the loop from pushing a large
		1955	number of C<aio_stat> requests onto the queue.
		1956
		1957	The default value for C<max_outstanding> is very large, so there is no
		1958	practical limit on the number of outstanding requests.
		1959
		1960	=back
1050		1961
1051	=head3 STATISTICAL INFORMATION	1962	=head3 STATISTICAL INFORMATION
		1963
		1964	=over
1052		1965
1053	=item IO::AIO::nreqs	1966	=item IO::AIO::nreqs
1054		1967
1055	Returns the number of requests currently in the ready, execute or pending	1968	Returns the number of requests currently in the ready, execute or pending
1056	states (i.e. for which their callback has not been invoked yet).	1969	states (i.e. for which their callback has not been invoked yet).
…		…
1070	Returns the number of requests currently in the pending state (executed,	1983	Returns the number of requests currently in the pending state (executed,
1071	but not yet processed by poll_cb).	1984	but not yet processed by poll_cb).
1072		1985
1073	=back	1986	=back
1074		1987
		1988	=head3 MISCELLANEOUS FUNCTIONS
		1989
		1990	IO::AIO implements some functions that are useful when you want to use
		1991	some "Advanced I/O" function not available to in Perl, without going the
		1992	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		1993	counterpart.
		1994
		1995	=over 4
		1996
		1997	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1998
		1999	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2000	but is blocking (this makes most sense if you know the input data is
		2001	likely cached already and the output filehandle is set to non-blocking
		2002	operations).
		2003
		2004	Returns the number of bytes copied, or C<-1> on error.
		2005
		2006	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2007
		2008	Simply calls the C<posix_fadvise> function (see its
		2009	manpage for details). The following advice constants are
		2010	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2011	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2012	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2013
		2014	On systems that do not implement C<posix_fadvise>, this function returns
		2015	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2016
		2017	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2018
		2019	Simply calls the C<posix_madvise> function (see its
		2020	manpage for details). The following advice constants are
		2021	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2022	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		2023
		2024	On systems that do not implement C<posix_madvise>, this function returns
		2025	ENOSYS, otherwise the return value of C<posix_madvise>.
		2026
		2027	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2028
		2029	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2030	$scalar (see its manpage for details). The following protect
		2031	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2032	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2033
		2034	On systems that do not implement C<mprotect>, this function returns
		2035	ENOSYS, otherwise the return value of C<mprotect>.
		2036
		2037	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2038
		2039	Memory-maps a file (or anonymous memory range) and attaches it to the
		2040	given C<$scalar>, which will act like a string scalar. Returns true on
		2041	success, and false otherwise.
		2042
		2043	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		2044	change the string length, and most read-only operations such as copying it
		2045	or searching it with regexes and so on.
		2046
		2047	Anything else is unsafe and will, at best, result in memory leaks.
		2048
		2049	The memory map associated with the C<$scalar> is automatically removed
		2050	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		2051	C<IO::AIO::munmap> functions are called.
		2052
		2053	This calls the C<mmap>(2) function internally. See your system's manual
		2054	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2055
		2056	The C<$length> must be larger than zero and smaller than the actual
		2057	filesize.
		2058
		2059	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2060	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2061
		2062	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		2063	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		2064	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		2065	(which is set to C<MAP_ANON> if your system only provides this
		2066	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		2067	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		2068	C<IO::AIO::MAP_NONBLOCK>
		2069
		2070	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2071
		2072	C<$offset> is the offset from the start of the file - it generally must be
		2073	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2074
		2075	Example:
		2076
		2077	use Digest::MD5;
		2078	use IO::AIO;
		2079
		2080	open my $fh, "<verybigfile"
		2081	or die "$!";
		2082
		2083	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2084	or die "verybigfile: $!";
		2085
		2086	my $fast_md5 = md5 $data;
		2087
		2088	=item IO::AIO::munmap $scalar
		2089
		2090	Removes a previous mmap and undefines the C<$scalar>.
		2091
		2092	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2093
		2094	Calls the C<munlock> function, undoing the effects of a previous
		2095	C<aio_mlock> call (see its description for details).
		2096
		2097	=item IO::AIO::munlockall
		2098
		2099	Calls the C<munlockall> function.
		2100
		2101	On systems that do not implement C<munlockall>, this function returns
		2102	ENOSYS, otherwise the return value of C<munlockall>.
		2103
		2104	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2105
		2106	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2107	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2108	should be the file offset.
		2109
		2110	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2111	silently corrupt the data in this case.
		2112
		2113	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2114	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2115	C<IO::AIO::SPLICE_F_GIFT>.
		2116
		2117	See the C<splice(2)> manpage for details.
		2118
		2119	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2120
		2121	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2122	description for C<IO::AIO::splice> above for details.
		2123
		2124	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2125
		2126	Attempts to query or change the pipe buffer size. Obviously works only
		2127	on pipes, and currently works only on GNU/Linux systems, and fails with
		2128	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2129	size on other systems, drop me a note.
		2130
		2131	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2132
		2133	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2134	C<$flags> is missing or C<0>, then this should be the same as a call to
		2135	perl's built-in C<pipe> function and create a new pipe, and works on
		2136	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2137	(..., 4096, O_BINARY)>.
		2138
		2139	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2140	the given flags (Linux 2.6.27, glibc 2.9).
		2141
		2142	On success, the read and write file handles are returned.
		2143
		2144	On error, nothing will be returned. If the pipe2 syscall is missing and
		2145	C<$flags> is non-zero, fails with C<ENOSYS>.
		2146
		2147	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2148	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2149	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2150
		2151	=back
		2152
1075	=cut	2153	=cut
1076		2154
1077	# support function to convert a fd into a perl filehandle
1078	sub _fd2fh {
1079	return undef if $_[0] < 0;
1080
1081	# try to generate nice filehandles
1082	my $sym = "IO::AIO::fd#$_[0]";
1083	local *$sym;
1084
1085	open *$sym, "+<&=$_[0]" # usually works under any unix
1086	or open *$sym, "<&=$_[0]" # cygwin needs this
1087	or open *$sym, ">&=$_[0]" # or this
1088	or return undef;
1089
1090	*$sym
1091	}
1092
1093	min_parallel 8;	2155	min_parallel 8;
1094		2156
1095	END {	2157	END { flush }
1096	min_parallel 1;
1097	flush;
1098	};
1099		2158
1100	1;	2159	1;
1101		2160
		2161	=head1 EVENT LOOP INTEGRATION
		2162
		2163	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2164	automatically into many event loops:
		2165
		2166	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2167	use AnyEvent::AIO;
		2168
		2169	You can also integrate IO::AIO manually into many event loops, here are
		2170	some examples of how to do this:
		2171
		2172	# EV integration
		2173	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2174
		2175	# Event integration
		2176	Event->io (fd => IO::AIO::poll_fileno,
		2177	poll => 'r',
		2178	cb => \&IO::AIO::poll_cb);
		2179
		2180	# Glib/Gtk2 integration
		2181	add_watch Glib::IO IO::AIO::poll_fileno,
		2182	in => sub { IO::AIO::poll_cb; 1 };
		2183
		2184	# Tk integration
		2185	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2186	readable => \&IO::AIO::poll_cb);
		2187
		2188	# Danga::Socket integration
		2189	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2190	\&IO::AIO::poll_cb);
		2191
1102	=head2 FORK BEHAVIOUR	2192	=head2 FORK BEHAVIOUR
1103		2193
1104	This module should do "the right thing" when the process using it forks:	2194	Usage of pthreads in a program changes the semantics of fork
		2195	considerably. Specifically, only async-safe functions can be called after
		2196	fork. Perl doesn't know about this, so in general, you cannot call fork
		2197	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2198	pthreads, so this applies, but many other extensions and (for inexplicable
		2199	reasons) perl itself often is linked against pthreads, so this limitation
		2200	applies to quite a lot of perls.
1105		2201
1106	Before the fork, IO::AIO enters a quiescent state where no requests	2202	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1107	can be added in other threads and no results will be processed. After	2203	only works in the process that loaded it. Forking is fully supported, but
1108	the fork the parent simply leaves the quiescent state and continues	2204	using IO::AIO in the child is not.
1109	request/result processing, while the child frees the request/result queue
1110	(so that the requests started before the fork will only be handled in the
1111	parent). Threads will be started on demand until the limit set in the
1112	parent process has been reached again.
1113		2205
1114	In short: the parent will, after a short pause, continue as if fork had	2206	You might get around by not I<using> IO::AIO before (or after)
1115	not been called, while the child will act as if IO::AIO has not been used	2207	forking. You could also try to call the L<IO::AIO::reinit> function in the
1116	yet.	2208	child:
		2209
		2210	=over 4
		2211
		2212	=item IO::AIO::reinit
		2213
		2214	Abandons all current requests and I/O threads and simply reinitialises all
		2215	data structures. This is not an operation supported by any standards, but
		2216	happens to work on GNU/Linux and some newer BSD systems.
		2217
		2218	The only reasonable use for this function is to call it after forking, if
		2219	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2220	the process will result in undefined behaviour. Calling it at any time
		2221	will also result in any undefined (by POSIX) behaviour.
		2222
		2223	=back
1117		2224
1118	=head2 MEMORY USAGE	2225	=head2 MEMORY USAGE
1119		2226
1120	Per-request usage:	2227	Per-request usage:
1121		2228
…		…
1123	bytes of memory. In addition, stat requests need a stat buffer (possibly	2230	bytes of memory. In addition, stat requests need a stat buffer (possibly
1124	a few hundred bytes), readdir requires a result buffer and so on. Perl	2231	a few hundred bytes), readdir requires a result buffer and so on. Perl
1125	scalars and other data passed into aio requests will also be locked and	2232	scalars and other data passed into aio requests will also be locked and
1126	will consume memory till the request has entered the done state.	2233	will consume memory till the request has entered the done state.
1127		2234
1128	This is now awfully much, so queuing lots of requests is not usually a	2235	This is not awfully much, so queuing lots of requests is not usually a
1129	problem.	2236	problem.
1130		2237
1131	Per-thread usage:	2238	Per-thread usage:
1132		2239
1133	In the execution phase, some aio requests require more memory for	2240	In the execution phase, some aio requests require more memory for
…		…
1138		2245
1139	Known bugs will be fixed in the next release.	2246	Known bugs will be fixed in the next release.
1140		2247
1141	=head1 SEE ALSO	2248	=head1 SEE ALSO
1142		2249
1143	L<Coro::AIO>.	2250	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2251	more natural syntax.
1144		2252
1145	=head1 AUTHOR	2253	=head1 AUTHOR
1146		2254
1147	Marc Lehmann <schmorp@schmorp.de>	2255	Marc Lehmann <schmorp@schmorp.de>
1148	http://home.schmorp.de/	2256	http://home.schmorp.de/

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