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Revision 1.115 by root, Mon Sep 24 18:14:00 2007 UTC vs.
Revision 1.249 by root, Wed Jul 30 22:00:04 2014 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 = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	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>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	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
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
64	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
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
68	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
69	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
70	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
71	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
72		52
73	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
74	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
75	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
85	yourself, always call C<poll_cb> from within the same thread, or never	65	yourself, always call C<poll_cb> from within the same thread, or never
86	call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
87		67
88	=head2 EXAMPLE	68	=head2 EXAMPLE
89		69
90	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
91	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
92		72
93	use Fcntl;
94	use Event;	73	use EV;
95	use IO::AIO;	74	use IO::AIO;
96		75
97	# register the IO::AIO callback with Event	76	# register the IO::AIO callback with EV
98	Event->io (fd => IO::AIO::poll_fileno,	77	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
99	poll => 'r',
100	cb => \&IO::AIO::poll_cb);
101		78
102	# queue the request to open /etc/passwd	79	# queue the request to open /etc/passwd
103	aio_open "/etc/passwd", O_RDONLY, 0, sub {	80	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
104	my $fh = shift	81	my $fh = shift
105	or die "error while opening: $!";	82	or die "error while opening: $!";
106		83
107	# stat'ing filehandles is generally non-blocking	84	# stat'ing filehandles is generally non-blocking
108	my $size = -s $fh;	85	my $size = -s $fh;
…		…
117		94
118	# file contents now in $contents	95	# file contents now in $contents
119	print $contents;	96	print $contents;
120		97
121	# exit event loop and program	98	# exit event loop and program
122	Event::unloop;	99	EV::unloop;
123	};	100	};
124	};	101	};
125		102
126	# possibly queue up other requests, or open GUI windows,	103	# possibly queue up other requests, or open GUI windows,
127	# check for sockets etc. etc.	104	# check for sockets etc. etc.
128		105
129	# process events as long as there are some:	106	# process events as long as there are some:
130	Event::loop;	107	EV::loop;
131		108
132	=head1 REQUEST ANATOMY AND LIFETIME	109	=head1 REQUEST ANATOMY AND LIFETIME
133		110
134	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
135	directly visible to Perl.	112	directly visible to Perl.
…		…
183		160
184	=cut	161	=cut
185		162
186	package IO::AIO;	163	package IO::AIO;
187		164
188	no warnings;	165	use Carp ();
189	use strict 'vars';	166
		167	use common::sense;
190		168
191	use base 'Exporter';	169	use base 'Exporter';
192		170
193	BEGIN {	171	BEGIN {
194	our $VERSION = '2.41';	172	our $VERSION = 4.31;
195		173
196	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
197	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
198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	176	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		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
199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir	180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
200	aio_chown aio_chmod aio_utime aio_truncate);	181	aio_chmod aio_utime aio_truncate
		182	aio_msync aio_mtouch aio_mlock aio_mlockall
		183	aio_statvfs
		184	aio_wd);
		185
201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	186	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	187	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
203	min_parallel max_parallel max_idle	188	min_parallel max_parallel max_idle idle_timeout
204	nreqs nready npending nthreads	189	nreqs nready npending nthreads
205	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
206		195
207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	196	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
208		197
209	require XSLoader;	198	require XSLoader;
210	XSLoader::load ("IO::AIO", $VERSION);	199	XSLoader::load ("IO::AIO", $VERSION);
211	}	200	}
212		201
213	=head1 FUNCTIONS	202	=head1 FUNCTIONS
214		203
215	=head2 AIO REQUEST 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, $length = undef
		283	IO::AIO::munlockall
		284
		285	=head2 API NOTES
216		286
217	All the C<aio_*> calls are more or less thin wrappers around the syscall	287	All the C<aio_*> calls are more or less thin wrappers around the syscall
218	with the same name (sans C<aio_>). The arguments are similar or identical,	288	with the same name (sans C<aio_>). The arguments are similar or identical,
219	and they all accept an additional (and optional) C<$callback> argument	289	and they all accept an additional (and optional) C<$callback> argument
220	which must be a code reference. This code reference will get called with	290	which must be a code reference. This code reference will be called after
221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	291	the syscall has been executed in an asynchronous fashion. The results
222	perl, which usually delivers "false") as it's sole argument when the given	292	of the request will be passed as arguments to the callback (and, if an
223	syscall has been executed asynchronously.	293	error occured, in C<$!>) - 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>.
224		299
225	All functions expecting a filehandle keep a copy of the filehandle	300	All functions expecting a filehandle keep a copy of the filehandle
226	internally until the request has finished.	301	internally until the request has finished.
227		302
228	All functions return request objects of type L<IO::AIO::REQ> that allow	303	All functions return request objects of type L<IO::AIO::REQ> that allow
229	further manipulation of those requests while they are in-flight.	304	further manipulation of those requests while they are in-flight.
230		305
231	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
232	encoded as octets. 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
233	request is being executed, the current working directory could have	308	current working directory could have changed. Alternatively, you can
234	changed. Alternatively, you can make sure that you never change the	309	make sure that you never change the current working directory anywhere
235	current working directory anywhere in the program and then use relative	310	in the program and then use relative paths. You can also take advantage
236	paths.	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.
237		314
238	To encode pathnames as octets, either make sure you either: a) always pass	315	To encode pathnames as octets, either make sure you either: a) always pass
239	in filenames you got from outside (command line, readdir etc.) without	316	in filenames you got from outside (command line, readdir etc.) without
240	tinkering, 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
241	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
242	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
243	use something else to ensure your scalar has the correct contents.	320	unicode filenames or e) use something else to ensure your scalar has the
		321	correct contents.
244		322
245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	323	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246	handles correctly wether it is set or not.	324	handles correctly whether it is set or not.
		325
		326	=head2 AIO REQUEST FUNCTIONS
247		327
248	=over 4	328	=over 4
249		329
250	=item $prev_pri = aioreq_pri [$pri]	330	=item $prev_pri = aioreq_pri [$pri]
251		331
…		…
281		361
282		362
283	=item aio_open $pathname, $flags, $mode, $callback->($fh)	363	=item aio_open $pathname, $flags, $mode, $callback->($fh)
284		364
285	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
286	created filehandle for the file.	366	created filehandle for the file (or C<undef> in case of an error).
287		367
288	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,
289	for an explanation.	369	for an explanation.
290		370
291	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
…		…
298	by the umask in effect then the request is being executed, so better never	378	by the umask in effect then the request is being executed, so better never
299	change the umask.	379	change the umask.
300		380
301	Example:	381	Example:
302		382
303	aio_open "/etc/passwd", O_RDONLY, 0, sub {	383	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
304	if ($_[0]) {	384	if ($_[0]) {
305	print "open successful, fh is $_[0]\n";	385	print "open successful, fh is $_[0]\n";
306	...	386	...
307	} else {	387	} else {
308	die "open failed: $!\n";	388	die "open failed: $!\n";
309	}	389	}
310	};	390	};
311		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> and C<O_TTY_INIT>.
		400
312		401
313	=item aio_close $fh, $callback->($status)	402	=item aio_close $fh, $callback->($status)
314		403
315	Asynchronously close a file and call the callback with the result	404	Asynchronously close a file and call the callback with the result
316	code. I<WARNING:> although accepted, you should not pass in a perl	405	code.
317	filehandle here, as perl will likely close the file descriptor another
318	time when the filehandle is destroyed. Normally, you can safely call perls
319	C<close> or just let filehandles go out of scope.
320		406
321	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
322	therefore best to avoid this function.	408	closing the file descriptor associated with the filehandle itself.
323		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".
324		438
325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	439	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
326		440
327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	441	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
328		442
329	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<$fh> and
330	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	444	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
331	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
332	like the syscall).	446	error, just like the syscall).
		447
		448	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		449	offset plus the actual number of bytes read.
333		450
334	If C<$offset> is undefined, then the current file descriptor offset will	451	If C<$offset> is undefined, then the current file descriptor offset will
335	be used (and updated), otherwise the file descriptor offset will not be	452	be used (and updated), otherwise the file descriptor offset will not be
336	changed by these calls.	453	changed by these calls.
337		454
338	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	455	If C<$length> is undefined in C<aio_write>, use the remaining length of
		456	C<$data>.
339		457
340	If C<$dataoffset> is less than zero, it will be counted from the end of	458	If C<$dataoffset> is less than zero, it will be counted from the end of
341	C<$data>.	459	C<$data>.
342		460
343	The C<$data> scalar I<MUST NOT> be modified in any way while the request	461	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
357		475
358	Tries to copy C<$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<$out_fh>. It starts
359	reading at byte offset C<$in_offset>, and starts writing at the current	477	reading at byte offset C<$in_offset>, and starts writing at the current
360	file offset of C<$out_fh>. Because of that, it is not safe to issue more	478	file offset of C<$out_fh>. Because of that, it is not safe to issue more
361	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	479	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
362	other.	480	other. The same C<$in_fh> works fine though, as this function does not
		481	move or use the file offset of C<$in_fh>.
363		482
		483	Please note that C<aio_sendfile> can read more bytes from C<$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
364	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
365	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
366	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.
367		502
368	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>,
369	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
370	regardless of the limitations of the operating system.	506	type of filehandle regardless of the limitations of the operating system.
371		507
372	Please note, however, that C<aio_sendfile> can read more bytes from	508	As native sendfile syscalls (as practically any non-POSIX interface hacked
373	C<$in_fh> than are written, and there is no way to find out how many	509	together in a hurry to improve benchmark numbers) tend to be rather buggy
374	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	510	on many systems, this implementation tries to work around some known bugs
375	provides the number of bytes written to C<$out_fh>. Only if the result	511	in Linux and FreeBSD kernels (probably others, too), but that might fail,
376	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> -
377	read.	513	fewre bytes than expected might have been transferred.
378		514
379		515
380	=item aio_readahead $fh,$offset,$length, $callback->($retval)	516	=item aio_readahead $fh,$offset,$length, $callback->($retval)
381		517
382	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
…		…
405		541
406	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
407	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
408	unless perl itself is compiled with large file support.	544	unless perl itself is compiled with large file support.
409		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>.
		554
410	Example: Print the length of F</etc/passwd>:	555	Example: Print the length of F</etc/passwd>:
411		556
412	aio_stat "/etc/passwd", sub {	557	aio_stat "/etc/passwd", sub {
413	$_[0] and die "stat failed: $!";	558	$_[0] and die "stat failed: $!";
414	print "size is ", -s _, "\n";	559	print "size is ", -s _, "\n";
415	};	560	};
416		561
417		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
418	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	689	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
419		690
420	Works like perl's C<utime> function (including the special case of $atime	691	Works like perl's C<utime> function (including the special case of $atime
421	and $mtime being undef). Fractional times are supported if the underlying	692	and $mtime being undef). Fractional times are supported if the underlying
422	syscalls support them.	693	syscalls support them.
…		…
449	=item aio_truncate $fh_or_path, $offset, $callback->($status)	720	=item aio_truncate $fh_or_path, $offset, $callback->($status)
450		721
451	Works like truncate(2) or ftruncate(2).	722	Works like truncate(2) or ftruncate(2).
452		723
453		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> can currently be C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE>
		731	to allocate space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE |
		732	IO::AIO::FALLOC_FL_KEEP_SIZE>, to deallocate a file range.
		733
		734	The file system block size used by C<fallocate> is presumably the
		735	C<f_bsize> returned by C<statvfs>.
		736
		737	If C<fallocate> isn't available or cannot be emulated (currently no
		738	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		739
		740
454	=item aio_chmod $fh_or_path, $mode, $callback->($status)	741	=item aio_chmod $fh_or_path, $mode, $callback->($status)
455		742
456	Works like perl's C<chmod> function.	743	Works like perl's C<chmod> function.
457		744
458		745
…		…
460		747
461	Asynchronously unlink (delete) a file and call the callback with the	748	Asynchronously unlink (delete) a file and call the callback with the
462	result code.	749	result code.
463		750
464		751
465	=item aio_mknod $path, $mode, $dev, $callback->($status)	752	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
466		753
467	[EXPERIMENTAL]	754	[EXPERIMENTAL]
468		755
469	Asynchronously create a device node (or fifo). See mknod(2).	756	Asynchronously create a device node (or fifo). See mknod(2).
470		757
471	The only (POSIX-) portable way of calling this function is:	758	The only (POSIX-) portable way of calling this function is:
472		759
473	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	760	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
474		761
		762	See C<aio_stat> for info about some potentially helpful extra constants
		763	and functions.
475		764
476	=item aio_link $srcpath, $dstpath, $callback->($status)	765	=item aio_link $srcpath, $dstpath, $callback->($status)
477		766
478	Asynchronously create a new link to the existing object at C<$srcpath> at	767	Asynchronously create a new link to the existing object at C<$srcpath> at
479	the path C<$dstpath> and call the callback with the result code.	768	the path C<$dstpath> and call the callback with the result code.
…		…
483		772
484	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	773	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
485	the path C<$dstpath> and call the callback with the result code.	774	the path C<$dstpath> and call the callback with the result code.
486		775
487		776
488	=item aio_readlink $path, $callback->($link)	777	=item aio_readlink $pathname, $callback->($link)
489		778
490	Asynchronously read the symlink specified by C<$path> and pass it to	779	Asynchronously read the symlink specified by C<$path> and pass it to
491	the callback. If an error occurs, nothing or undef gets passed to the	780	the callback. If an error occurs, nothing or undef gets passed to the
492	callback.	781	callback.
493		782
494		783
		784	=item aio_realpath $pathname, $callback->($path)
		785
		786	Asynchronously make the path absolute and resolve any symlinks in
		787	C<$path>. The resulting path only consists of directories (same as
		788	L<Cwd::realpath>).
		789
		790	This request can be used to get the absolute path of the current working
		791	directory by passing it a path of F<.> (a single dot).
		792
		793
495	=item aio_rename $srcpath, $dstpath, $callback->($status)	794	=item aio_rename $srcpath, $dstpath, $callback->($status)
496		795
497	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	796	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
498	rename(2) and call the callback with the result code.	797	rename(2) and call the callback with the result code.
		798
		799	On systems that support the AIO::WD working directory abstraction
		800	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		801	of failing, C<rename> is called on the absolute path of C<$wd>.
499		802
500		803
501	=item aio_mkdir $pathname, $mode, $callback->($status)	804	=item aio_mkdir $pathname, $mode, $callback->($status)
502		805
503	Asynchronously mkdir (create) a directory and call the callback with	806	Asynchronously mkdir (create) a directory and call the callback with
…		…
508	=item aio_rmdir $pathname, $callback->($status)	811	=item aio_rmdir $pathname, $callback->($status)
509		812
510	Asynchronously rmdir (delete) a directory and call the callback with the	813	Asynchronously rmdir (delete) a directory and call the callback with the
511	result code.	814	result code.
512		815
		816	On systems that support the AIO::WD working directory abstraction
		817	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		818	C<rmdir> is called on the absolute path of C<$wd>.
		819
513		820
514	=item aio_readdir $pathname, $callback->($entries)	821	=item aio_readdir $pathname, $callback->($entries)
515		822
516	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	823	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
517	directory (i.e. opendir + readdir + closedir). The entries will not be	824	directory (i.e. opendir + readdir + closedir). The entries will not be
518	sorted, and will B<NOT> include the C<.> and C<..> entries.	825	sorted, and will B<NOT> include the C<.> and C<..> entries.
519		826
520	The callback a single argument which is either C<undef> or an array-ref	827	The callback is passed a single argument which is either C<undef> or an
521	with the filenames.	828	array-ref with the filenames.
522		829
523		830
		831	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		832
		833	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		834	tune behaviour and output format. In case of an error, C<$entries> will be
		835	C<undef>.
		836
		837	The flags are a combination of the following constants, ORed together (the
		838	flags will also be passed to the callback, possibly modified):
		839
		840	=over 4
		841
		842	=item IO::AIO::READDIR_DENTS
		843
		844	When this flag is off, then the callback gets an arrayref consisting of
		845	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		846	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		847	entry in more detail.
		848
		849	C<$name> is the name of the entry.
		850
		851	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		852
		853	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		854	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		855	C<IO::AIO::DT_WHT>.
		856
		857	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		858	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		859	scalars are read-only: you can not modify them.
		860
		861	C<$inode> is the inode number (which might not be exact on systems with 64
		862	bit inode numbers and 32 bit perls). This field has unspecified content on
		863	systems that do not deliver the inode information.
		864
		865	=item IO::AIO::READDIR_DIRS_FIRST
		866
		867	When this flag is set, then the names will be returned in an order where
		868	likely directories come first, in optimal stat order. This is useful when
		869	you need to quickly find directories, or you want to find all directories
		870	while avoiding to stat() each entry.
		871
		872	If the system returns type information in readdir, then this is used
		873	to find directories directly. Otherwise, likely directories are names
		874	beginning with ".", or otherwise names with no dots, of which names with
		875	short names are tried first.
		876
		877	=item IO::AIO::READDIR_STAT_ORDER
		878
		879	When this flag is set, then the names will be returned in an order
		880	suitable for stat()'ing each one. That is, when you plan to stat()
		881	all files in the given directory, then the returned order will likely
		882	be fastest.
		883
		884	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		885	the likely dirs come first, resulting in a less optimal stat order.
		886
		887	=item IO::AIO::READDIR_FOUND_UNKNOWN
		888
		889	This flag should not be set when calling C<aio_readdirx>. Instead, it
		890	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		891	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		892	C<$type>'s are known, which can be used to speed up some algorithms.
		893
		894	=back
		895
		896
524	=item aio_load $path, $data, $callback->($status)	897	=item aio_load $pathname, $data, $callback->($status)
525		898
526	This is a composite request that tries to fully load the given file into	899	This is a composite request that tries to fully load the given file into
527	memory. Status is the same as with aio_read.	900	memory. Status is the same as with aio_read.
528		901
529	=cut	902	=cut
530		903
531	sub aio_load($$;$) {	904	sub aio_load($$;$) {
532	aio_block {
533	my ($path, undef, $cb) = @_;	905	my ($path, undef, $cb) = @_;
534	my $data = \$_[1];	906	my $data = \$_[1];
535		907
536	my $pri = aioreq_pri;	908	my $pri = aioreq_pri;
537	my $grp = aio_group $cb;	909	my $grp = aio_group $cb;
		910
		911	aioreq_pri $pri;
		912	add $grp aio_open $path, O_RDONLY, 0, sub {
		913	my $fh = shift
		914	or return $grp->result (-1);
538		915
539	aioreq_pri $pri;	916	aioreq_pri $pri;
540	add $grp aio_open $path, O_RDONLY, 0, sub {
541	my $fh = shift
542	or return $grp->result (-1);
543
544	aioreq_pri $pri;
545	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {	917	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
546	$grp->result ($_[0]);	918	$grp->result ($_[0]);
547	};
548	};	919	};
549
550	$grp
551	}	920	};
		921
		922	$grp
552	}	923	}
553		924
554	=item aio_copy $srcpath, $dstpath, $callback->($status)	925	=item aio_copy $srcpath, $dstpath, $callback->($status)
555		926
556	Try to copy the I<file> (directories not supported as either source or	927	Try to copy the I<file> (directories not supported as either source or
557	destination) from C<$srcpath> to C<$dstpath> and call the callback with	928	destination) from C<$srcpath> to C<$dstpath> and call the callback with
558	the C<0> (error) or C<-1> ok.	929	a status of C<0> (ok) or C<-1> (error, see C<$!>).
559		930
560	This is a composite request that it creates the destination file with	931	This is a composite request that creates the destination file with
561	mode 0200 and copies the contents of the source file into it using	932	mode 0200 and copies the contents of the source file into it using
562	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	933	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
563	uid/gid, in that order.	934	uid/gid, in that order.
564		935
565	If an error occurs, the partial destination file will be unlinked, if	936	If an error occurs, the partial destination file will be unlinked, if
…		…
567	errors are being ignored.	938	errors are being ignored.
568		939
569	=cut	940	=cut
570		941
571	sub aio_copy($$;$) {	942	sub aio_copy($$;$) {
572	aio_block {
573	my ($src, $dst, $cb) = @_;	943	my ($src, $dst, $cb) = @_;
574		944
575	my $pri = aioreq_pri;	945	my $pri = aioreq_pri;
576	my $grp = aio_group $cb;	946	my $grp = aio_group $cb;
577		947
578	aioreq_pri $pri;	948	aioreq_pri $pri;
579	add $grp aio_open $src, O_RDONLY, 0, sub {	949	add $grp aio_open $src, O_RDONLY, 0, sub {
580	if (my $src_fh = $_[0]) {	950	if (my $src_fh = $_[0]) {
581	my @stat = stat $src_fh;	951	my @stat = stat $src_fh; # hmm, might block over nfs?
582		952
583	aioreq_pri $pri;	953	aioreq_pri $pri;
584	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	954	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
585	if (my $dst_fh = $_[0]) {	955	if (my $dst_fh = $_[0]) {
586	aioreq_pri $pri;	956	aioreq_pri $pri;
587	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	957	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
588	if ($_[0] == $stat[7]) {	958	if ($_[0] == $stat[7]) {
589	$grp->result (0);	959	$grp->result (0);
590	close $src_fh;	960	close $src_fh;
591		961
592	# those should not normally block. should. should.
593	utime $stat[8], $stat[9], $dst;
594	chmod $stat[2] & 07777, $dst_fh;
595	chown $stat[4], $stat[5], $dst_fh;
596	close $dst_fh;
597	} else {	962	my $ch = sub {
598	$grp->result (-1);
599	close $src_fh;
600	close $dst_fh;
601
602	aioreq $pri;	963	aioreq_pri $pri;
		964	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		965	aioreq_pri $pri;
		966	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		967	aioreq_pri $pri;
603	add $grp aio_unlink $dst;	968	add $grp aio_close $dst_fh;
		969	}
		970	};
604	}	971	};
		972
		973	aioreq_pri $pri;
		974	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		975	if ($_[0] < 0 && $! == ENOSYS) {
		976	aioreq_pri $pri;
		977	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		978	} else {
		979	$ch->();
		980	}
		981	};
		982	} else {
		983	$grp->result (-1);
		984	close $src_fh;
		985	close $dst_fh;
		986
		987	aioreq $pri;
		988	add $grp aio_unlink $dst;
605	};	989	}
606	} else {
607	$grp->result (-1);
608	}	990	};
		991	} else {
		992	$grp->result (-1);
609	},	993	}
610
611	} else {
612	$grp->result (-1);
613	}	994	},
		995
		996	} else {
		997	$grp->result (-1);
614	};	998	}
615
616	$grp
617	}	999	};
		1000
		1001	$grp
618	}	1002	}
619		1003
620	=item aio_move $srcpath, $dstpath, $callback->($status)	1004	=item aio_move $srcpath, $dstpath, $callback->($status)
621		1005
622	Try to move the I<file> (directories not supported as either source or	1006	Try to move the I<file> (directories not supported as either source or
623	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1007	destination) from C<$srcpath> to C<$dstpath> and call the callback with
624	the C<0> (error) or C<-1> ok.	1008	a status of C<0> (ok) or C<-1> (error, see C<$!>).
625		1009
626	This is a composite request that tries to rename(2) the file first. If	1010	This is a composite request that tries to rename(2) the file first; if
627	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1011	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
628	that is successful, unlinking the C<$srcpath>.	1012	that is successful, unlinks the C<$srcpath>.
629		1013
630	=cut	1014	=cut
631		1015
632	sub aio_move($$;$) {	1016	sub aio_move($$;$) {
633	aio_block {
634	my ($src, $dst, $cb) = @_;	1017	my ($src, $dst, $cb) = @_;
635		1018
636	my $pri = aioreq_pri;	1019	my $pri = aioreq_pri;
637	my $grp = aio_group $cb;	1020	my $grp = aio_group $cb;
638		1021
639	aioreq_pri $pri;	1022	aioreq_pri $pri;
640	add $grp aio_rename $src, $dst, sub {	1023	add $grp aio_rename $src, $dst, sub {
641	if ($_[0] && $! == EXDEV) {	1024	if ($_[0] && $! == EXDEV) {
642	aioreq_pri $pri;	1025	aioreq_pri $pri;
643	add $grp aio_copy $src, $dst, sub {	1026	add $grp aio_copy $src, $dst, sub {
644	$grp->result ($_[0]);
645
646	if (!$_[0]) {
647	aioreq_pri $pri;
648	add $grp aio_unlink $src;
649	}
650	};
651	} else {
652	$grp->result ($_[0]);	1027	$grp->result ($_[0]);
		1028
		1029	unless ($_[0]) {
		1030	aioreq_pri $pri;
		1031	add $grp aio_unlink $src;
		1032	}
653	}	1033	};
		1034	} else {
		1035	$grp->result ($_[0]);
654	};	1036	}
655
656	$grp
657	}	1037	};
		1038
		1039	$grp
658	}	1040	}
659		1041
660	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1042	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
661		1043
662	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1044	Scans a directory (similar to C<aio_readdir>) but additionally tries to
663	efficiently separate the entries of directory C<$path> into two sets of	1045	efficiently separate the entries of directory C<$path> into two sets of
664	names, directories you can recurse into (directories), and ones you cannot	1046	names, directories you can recurse into (directories), and ones you cannot
665	recurse into (everything else, including symlinks to directories).	1047	recurse into (everything else, including symlinks to directories).
…		…
682		1064
683	Implementation notes.	1065	Implementation notes.
684		1066
685	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1067	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
686		1068
		1069	If readdir returns file type information, then this is used directly to
		1070	find directories.
		1071
687	After reading the directory, the modification time, size etc. of the	1072	Otherwise, after reading the directory, the modification time, size etc.
688	directory before and after the readdir is checked, and if they match (and	1073	of the directory before and after the readdir is checked, and if they
689	isn't the current time), the link count will be used to decide how many	1074	match (and isn't the current time), the link count will be used to decide
690	entries are directories (if >= 2). Otherwise, no knowledge of the number	1075	how many entries are directories (if >= 2). Otherwise, no knowledge of the
691	of subdirectories will be assumed.	1076	number of subdirectories will be assumed.
692		1077
693	Then entries will be sorted into likely directories (everything without	1078	Then entries will be sorted into likely directories a non-initial dot
694	a non-initial dot currently) and likely non-directories (everything	1079	currently) and likely non-directories (see C<aio_readdirx>). Then every
695	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1080	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
696	likely directories first. If that succeeds, it assumes that the entry	1081	in order of their inode numbers. If that succeeds, it assumes that the
697	is a directory or a symlink to directory (which will be checked	1082	entry is a directory or a symlink to directory (which will be checked
698	seperately). This is often faster than stat'ing the entry itself because	1083	separately). This is often faster than stat'ing the entry itself because
699	filesystems might detect the type of the entry without reading the inode	1084	filesystems might detect the type of the entry without reading the inode
700	data (e.g. ext2fs filetype feature).	1085	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1086	the filetype information on readdir.
701		1087
702	If the known number of directories (link count - 2) has been reached, the	1088	If the known number of directories (link count - 2) has been reached, the
703	rest of the entries is assumed to be non-directories.	1089	rest of the entries is assumed to be non-directories.
704		1090
705	This only works with certainty on POSIX (= UNIX) filesystems, which	1091	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
710	directory counting heuristic.	1096	directory counting heuristic.
711		1097
712	=cut	1098	=cut
713		1099
714	sub aio_scandir($$;$) {	1100	sub aio_scandir($$;$) {
715	aio_block {
716	my ($path, $maxreq, $cb) = @_;	1101	my ($path, $maxreq, $cb) = @_;
717		1102
718	my $pri = aioreq_pri;	1103	my $pri = aioreq_pri;
719		1104
720	my $grp = aio_group $cb;	1105	my $grp = aio_group $cb;
721		1106
722	$maxreq = 4 if $maxreq <= 0;	1107	$maxreq = 4 if $maxreq <= 0;
		1108
		1109	# get a wd object
		1110	aioreq_pri $pri;
		1111	add $grp aio_wd $path, sub {
		1112	$_[0]
		1113	or return $grp->result ();
		1114
		1115	my $wd = [shift, "."];
723		1116
724	# stat once	1117	# stat once
725	aioreq_pri $pri;	1118	aioreq_pri $pri;
726	add $grp aio_stat $path, sub {	1119	add $grp aio_stat $wd, sub {
727	return $grp->result () if $_[0];	1120	return $grp->result () if $_[0];
728	my $now = time;	1121	my $now = time;
729	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1122	my $hash1 = join ":", (stat _)[0,1,3,7,9];
730		1123
731	# read the directory entries	1124	# read the directory entries
732	aioreq_pri $pri;	1125	aioreq_pri $pri;
733	add $grp aio_readdir $path, sub {	1126	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
734	my $entries = shift	1127	my $entries = shift
735	or return $grp->result ();	1128	or return $grp->result ();
736		1129
737	# stat the dir another time	1130	# stat the dir another time
738	aioreq_pri $pri;	1131	aioreq_pri $pri;
739	add $grp aio_stat $path, sub {	1132	add $grp aio_stat $wd, sub {
740	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1133	my $hash2 = join ":", (stat _)[0,1,3,7,9];
741		1134
742	my $ndirs;	1135	my $ndirs;
743		1136
744	# take the slow route if anything looks fishy	1137	# take the slow route if anything looks fishy
745	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1138	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
746	$ndirs = -1;	1139	$ndirs = -1;
747	} else {	1140	} else {
748	# if nlink == 2, we are finished	1141	# if nlink == 2, we are finished
749	# on non-posix-fs's, we rely on nlink < 2	1142	# for non-posix-fs's, we rely on nlink < 2
750	$ndirs = (stat _)[3] - 2	1143	$ndirs = (stat _)[3] - 2
751	or return $grp->result ([], $entries);	1144	or return $grp->result ([], $entries);
752	}	1145	}
753		1146
754	# sort into likely dirs and likely nondirs
755	# dirs == files without ".", short entries first
756	$entries = [map $_->[0],
757	sort { $b->[1] cmp $a->[1] }
758	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
759	@$entries];
760
761	my (@dirs, @nondirs);	1147	my (@dirs, @nondirs);
762		1148
763	my $statgrp = add $grp aio_group sub {	1149	my $statgrp = add $grp aio_group sub {
764	$grp->result (\@dirs, \@nondirs);	1150	$grp->result (\@dirs, \@nondirs);
765	};	1151	};
766		1152
767	limit $statgrp $maxreq;	1153	limit $statgrp $maxreq;
768	feed $statgrp sub {	1154	feed $statgrp sub {
769	return unless @$entries;	1155	return unless @$entries;
770	my $entry = pop @$entries;	1156	my $entry = shift @$entries;
771		1157
772	aioreq_pri $pri;	1158	aioreq_pri $pri;
		1159	$wd->[1] = "$entry/.";
773	add $statgrp aio_stat "$path/$entry/.", sub {	1160	add $statgrp aio_stat $wd, sub {
774	if ($_[0] < 0) {	1161	if ($_[0] < 0) {
775	push @nondirs, $entry;	1162	push @nondirs, $entry;
776	} else {	1163	} else {
777	# need to check for real directory	1164	# need to check for real directory
778	aioreq_pri $pri;	1165	aioreq_pri $pri;
		1166	$wd->[1] = $entry;
779	add $statgrp aio_lstat "$path/$entry", sub {	1167	add $statgrp aio_lstat $wd, sub {
780	if (-d _) {	1168	if (-d _) {
781	push @dirs, $entry;	1169	push @dirs, $entry;
782		1170
783	unless (--$ndirs) {	1171	unless (--$ndirs) {
784	push @nondirs, @$entries;	1172	push @nondirs, @$entries;
…		…
792	};	1180	};
793	};	1181	};
794	};	1182	};
795	};	1183	};
796	};	1184	};
797
798	$grp
799	}	1185	};
		1186
		1187	$grp
800	}	1188	}
801		1189
802	=item aio_rmtree $path, $callback->($status)	1190	=item aio_rmtree $pathname, $callback->($status)
803		1191
804	Delete a directory tree starting (and including) C<$path>, return the	1192	Delete a directory tree starting (and including) C<$path>, return the
805	status of the final C<rmdir> only. This is a composite request that	1193	status of the final C<rmdir> only. This is a composite request that
806	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1194	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
807	everything else.	1195	everything else.
808		1196
809	=cut	1197	=cut
810		1198
811	sub aio_rmtree;	1199	sub aio_rmtree;
812	sub aio_rmtree($;$) {	1200	sub aio_rmtree($;$) {
813	aio_block {
814	my ($path, $cb) = @_;	1201	my ($path, $cb) = @_;
815		1202
816	my $pri = aioreq_pri;	1203	my $pri = aioreq_pri;
817	my $grp = aio_group $cb;	1204	my $grp = aio_group $cb;
818		1205
819	aioreq_pri $pri;	1206	aioreq_pri $pri;
820	add $grp aio_scandir $path, 0, sub {	1207	add $grp aio_scandir $path, 0, sub {
821	my ($dirs, $nondirs) = @_;	1208	my ($dirs, $nondirs) = @_;
822		1209
823	my $dirgrp = aio_group sub {	1210	my $dirgrp = aio_group sub {
824	add $grp aio_rmdir $path, sub {	1211	add $grp aio_rmdir $path, sub {
825	$grp->result ($_[0]);	1212	$grp->result ($_[0]);
826	};
827	};	1213	};
828
829	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
830	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
831
832	add $grp $dirgrp;
833	};	1214	};
834		1215
835	$grp	1216	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1217	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1218
		1219	add $grp $dirgrp;
836	}	1220	};
		1221
		1222	$grp
837	}	1223	}
		1224
		1225	=item aio_sync $callback->($status)
		1226
		1227	Asynchronously call sync and call the callback when finished.
838		1228
839	=item aio_fsync $fh, $callback->($status)	1229	=item aio_fsync $fh, $callback->($status)
840		1230
841	Asynchronously call fsync on the given filehandle and call the callback	1231	Asynchronously call fsync on the given filehandle and call the callback
842	with the fsync result code.	1232	with the fsync result code.
…		…
846	Asynchronously call fdatasync on the given filehandle and call the	1236	Asynchronously call fdatasync on the given filehandle and call the
847	callback with the fdatasync result code.	1237	callback with the fdatasync result code.
848		1238
849	If this call isn't available because your OS lacks it or it couldn't be	1239	If this call isn't available because your OS lacks it or it couldn't be
850	detected, it will be emulated by calling C<fsync> instead.	1240	detected, it will be emulated by calling C<fsync> instead.
		1241
		1242	=item aio_syncfs $fh, $callback->($status)
		1243
		1244	Asynchronously call the syncfs syscall to sync the filesystem associated
		1245	to the given filehandle and call the callback with the syncfs result
		1246	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1247	errno to C<ENOSYS> nevertheless.
		1248
		1249	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1250
		1251	Sync the data portion of the file specified by C<$offset> and C<$length>
		1252	to disk (but NOT the metadata), by calling the Linux-specific
		1253	sync_file_range call. If sync_file_range is not available or it returns
		1254	ENOSYS, then fdatasync or fsync is being substituted.
		1255
		1256	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1257	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1258	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1259	manpage for details.
		1260
		1261	=item aio_pathsync $pathname, $callback->($status)
		1262
		1263	This request tries to open, fsync and close the given path. This is a
		1264	composite request intended to sync directories after directory operations
		1265	(E.g. rename). This might not work on all operating systems or have any
		1266	specific effect, but usually it makes sure that directory changes get
		1267	written to disc. It works for anything that can be opened for read-only,
		1268	not just directories.
		1269
		1270	Future versions of this function might fall back to other methods when
		1271	C<fsync> on the directory fails (such as calling C<sync>).
		1272
		1273	Passes C<0> when everything went ok, and C<-1> on error.
		1274
		1275	=cut
		1276
		1277	sub aio_pathsync($;$) {
		1278	my ($path, $cb) = @_;
		1279
		1280	my $pri = aioreq_pri;
		1281	my $grp = aio_group $cb;
		1282
		1283	aioreq_pri $pri;
		1284	add $grp aio_open $path, O_RDONLY, 0, sub {
		1285	my ($fh) = @_;
		1286	if ($fh) {
		1287	aioreq_pri $pri;
		1288	add $grp aio_fsync $fh, sub {
		1289	$grp->result ($_[0]);
		1290
		1291	aioreq_pri $pri;
		1292	add $grp aio_close $fh;
		1293	};
		1294	} else {
		1295	$grp->result (-1);
		1296	}
		1297	};
		1298
		1299	$grp
		1300	}
		1301
		1302	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1303
		1304	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1305	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1306	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1307	scalar must only be modified in-place while an aio operation is pending on
		1308	it).
		1309
		1310	It calls the C<msync> function of your OS, if available, with the memory
		1311	area starting at C<$offset> in the string and ending C<$length> bytes
		1312	later. If C<$length> is negative, counts from the end, and if C<$length>
		1313	is C<undef>, then it goes till the end of the string. The flags can be
		1314	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1315	C<IO::AIO::MS_SYNC>.
		1316
		1317	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1318
		1319	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1320	scalars.
		1321
		1322	It touches (reads or writes) all memory pages in the specified
		1323	range inside the scalar. All caveats and parameters are the same
		1324	as for C<aio_msync>, above, except for flags, which must be either
		1325	C<0> (which reads all pages and ensures they are instantiated) or
		1326	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1327	writing an octet from it, which dirties the page).
		1328
		1329	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1330
		1331	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1332	scalars.
		1333
		1334	It reads in all the pages of the underlying storage into memory (if any)
		1335	and locks them, so they are not getting swapped/paged out or removed.
		1336
		1337	If C<$length> is undefined, then the scalar will be locked till the end.
		1338
		1339	On systems that do not implement C<mlock>, this function returns C<-1>
		1340	and sets errno to C<ENOSYS>.
		1341
		1342	Note that the corresponding C<munlock> is synchronous and is
		1343	documented under L<MISCELLANEOUS FUNCTIONS>.
		1344
		1345	Example: open a file, mmap and mlock it - both will be undone when
		1346	C<$data> gets destroyed.
		1347
		1348	open my $fh, "<", $path or die "$path: $!";
		1349	my $data;
		1350	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1351	aio_mlock $data; # mlock in background
		1352
		1353	=item aio_mlockall $flags, $callback->($status)
		1354
		1355	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1356	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1357
		1358	On systems that do not implement C<mlockall>, this function returns C<-1>
		1359	and sets errno to C<ENOSYS>.
		1360
		1361	Note that the corresponding C<munlockall> is synchronous and is
		1362	documented under L<MISCELLANEOUS FUNCTIONS>.
		1363
		1364	Example: asynchronously lock all current and future pages into memory.
		1365
		1366	aio_mlockall IO::AIO::MCL_FUTURE;
		1367
		1368	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1369
		1370	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1371	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1372	the ioctl is not available on your OS, then this request will fail with
		1373	C<ENOSYS>.
		1374
		1375	C<$start> is the starting offset to query extents for, C<$length> is the
		1376	size of the range to query - if it is C<undef>, then the whole file will
		1377	be queried.
		1378
		1379	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1380	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1381	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1382	the data portion.
		1383
		1384	C<$count> is the maximum number of extent records to return. If it is
		1385	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1386	case, if it is C<0>, then the callback receives the number of extents
		1387	instead of the extents themselves (which is unreliable, see below).
		1388
		1389	If an error occurs, the callback receives no arguments. The special
		1390	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1391
		1392	Otherwise, the callback receives an array reference with extent
		1393	structures. Each extent structure is an array reference itself, with the
		1394	following members:
		1395
		1396	[$logical, $physical, $length, $flags]
		1397
		1398	Flags is any combination of the following flag values (typically either C<0>
		1399	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1400
		1401	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1402	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1403	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1404	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1405	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1406	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1407
		1408	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1409	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1410	it to return all extents of a range for files with large number of
		1411	extents. The code works around all these issues if C<$count> is undef.
851		1412
852	=item aio_group $callback->(...)	1413	=item aio_group $callback->(...)
853		1414
854	This is a very special aio request: Instead of doing something, it is a	1415	This is a very special aio request: Instead of doing something, it is a
855	container for other aio requests, which is useful if you want to bundle	1416	container for other aio requests, which is useful if you want to bundle
…		…
893	immense (it blocks a thread for a long time) so do not use this function	1454	immense (it blocks a thread for a long time) so do not use this function
894	except to put your application under artificial I/O pressure.	1455	except to put your application under artificial I/O pressure.
895		1456
896	=back	1457	=back
897		1458
		1459
		1460	=head2 IO::AIO::WD - multiple working directories
		1461
		1462	Your process only has one current working directory, which is used by all
		1463	threads. This makes it hard to use relative paths (some other component
		1464	could call C<chdir> at any time, and it is hard to control when the path
		1465	will be used by IO::AIO).
		1466
		1467	One solution for this is to always use absolute paths. This usually works,
		1468	but can be quite slow (the kernel has to walk the whole path on every
		1469	access), and can also be a hassle to implement.
		1470
		1471	Newer POSIX systems have a number of functions (openat, fdopendir,
		1472	futimensat and so on) that make it possible to specify working directories
		1473	per operation.
		1474
		1475	For portability, and because the clowns who "designed", or shall I write,
		1476	perpetrated this new interface were obviously half-drunk, this abstraction
		1477	cannot be perfect, though.
		1478
		1479	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1480	object. This object stores the canonicalised, absolute version of the
		1481	path, and on systems that allow it, also a directory file descriptor.
		1482
		1483	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1484	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1485	object and a pathname instead (or the IO::AIO::WD object alone, which
		1486	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1487	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1488	to that IO::AIO::WD object.
		1489
		1490	For example, to get a wd object for F</etc> and then stat F<passwd>
		1491	inside, you would write:
		1492
		1493	aio_wd "/etc", sub {
		1494	my $etcdir = shift;
		1495
		1496	# although $etcdir can be undef on error, there is generally no reason
		1497	# to check for errors here, as aio_stat will fail with ENOENT
		1498	# when $etcdir is undef.
		1499
		1500	aio_stat [$etcdir, "passwd"], sub {
		1501	# yay
		1502	};
		1503	};
		1504
		1505	That C<aio_wd> is a request and not a normal function shows that creating
		1506	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1507	why it is done asynchronously.
		1508
		1509	To stat the directory obtained with C<aio_wd> above, one could write
		1510	either of the following three request calls:
		1511
		1512	aio_lstat "/etc" , sub { ... # pathname as normal string
		1513	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1514	aio_lstat $wd , sub { ... # shorthand for the previous
		1515
		1516	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1517	object and the pathname string, so you could write the following without
		1518	causing any issues due to C<$path> getting reused:
		1519
		1520	my $path = [$wd, undef];
		1521
		1522	for my $name (qw(abc def ghi)) {
		1523	$path->[1] = $name;
		1524	aio_stat $path, sub {
		1525	# ...
		1526	};
		1527	}
		1528
		1529	There are some caveats: when directories get renamed (or deleted), the
		1530	pathname string doesn't change, so will point to the new directory (or
		1531	nowhere at all), while the directory fd, if available on the system,
		1532	will still point to the original directory. Most functions accepting a
		1533	pathname will use the directory fd on newer systems, and the string on
		1534	older systems. Some functions (such as realpath) will always rely on the
		1535	string form of the pathname.
		1536
		1537	So this functionality is mainly useful to get some protection against
		1538	C<chdir>, to easily get an absolute path out of a relative path for future
		1539	reference, and to speed up doing many operations in the same directory
		1540	(e.g. when stat'ing all files in a directory).
		1541
		1542	The following functions implement this working directory abstraction:
		1543
		1544	=over 4
		1545
		1546	=item aio_wd $pathname, $callback->($wd)
		1547
		1548	Asynchonously canonicalise the given pathname and convert it to an
		1549	IO::AIO::WD object representing it. If possible and supported on the
		1550	system, also open a directory fd to speed up pathname resolution relative
		1551	to this working directory.
		1552
		1553	If something goes wrong, then C<undef> is passwd to the callback instead
		1554	of a working directory object and C<$!> is set appropriately. Since
		1555	passing C<undef> as working directory component of a pathname fails the
		1556	request with C<ENOENT>, there is often no need for error checking in the
		1557	C<aio_wd> callback, as future requests using the value will fail in the
		1558	expected way.
		1559
		1560	=item IO::AIO::CWD
		1561
		1562	This is a compiletime constant (object) that represents the process
		1563	current working directory.
		1564
		1565	Specifying this object as working directory object for a pathname is as if
		1566	the pathname would be specified directly, without a directory object. For
		1567	example, these calls are functionally identical:
		1568
		1569	aio_stat "somefile", sub { ... };
		1570	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1571
		1572	=back
		1573
		1574	To recover the path associated with an IO::AIO::WD object, you can use
		1575	C<aio_realpath>:
		1576
		1577	aio_realpath $wd, sub {
		1578	warn "path is $_[0]\n";
		1579	};
		1580
		1581	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1582	sometimes, fall back to using an absolue path.
		1583
898	=head2 IO::AIO::REQ CLASS	1584	=head2 IO::AIO::REQ CLASS
899		1585
900	All non-aggregate C<aio_*> functions return an object of this class when	1586	All non-aggregate C<aio_*> functions return an object of this class when
901	called in non-void context.	1587	called in non-void context.
902		1588
…		…
905	=item cancel $req	1591	=item cancel $req
906		1592
907	Cancels the request, if possible. Has the effect of skipping execution	1593	Cancels the request, if possible. Has the effect of skipping execution
908	when entering the B<execute> state and skipping calling the callback when	1594	when entering the B<execute> state and skipping calling the callback when
909	entering the the B<result> state, but will leave the request otherwise	1595	entering the the B<result> state, but will leave the request otherwise
910	untouched. That means that requests that currently execute will not be	1596	untouched (with the exception of readdir). That means that requests that
911	stopped and resources held by the request will not be freed prematurely.	1597	currently execute will not be stopped and resources held by the request
		1598	will not be freed prematurely.
912		1599
913	=item cb $req $callback->(...)	1600	=item cb $req $callback->(...)
914		1601
915	Replace (or simply set) the callback registered to the request.	1602	Replace (or simply set) the callback registered to the request.
916		1603
…		…
967	Their lifetime, simplified, looks like this: when they are empty, they	1654	Their lifetime, simplified, looks like this: when they are empty, they
968	will finish very quickly. If they contain only requests that are in the	1655	will finish very quickly. If they contain only requests that are in the
969	C<done> state, they will also finish. Otherwise they will continue to	1656	C<done> state, they will also finish. Otherwise they will continue to
970	exist.	1657	exist.
971		1658
972	That means after creating a group you have some time to add requests. And	1659	That means after creating a group you have some time to add requests
973	in the callbacks of those requests, you can add further requests to the	1660	(precisely before the callback has been invoked, which is only done within
974	group. And only when all those requests have finished will the the group	1661	the C<poll_cb>). And in the callbacks of those requests, you can add
975	itself finish.	1662	further requests to the group. And only when all those requests have
		1663	finished will the the group itself finish.
976		1664
977	=over 4	1665	=over 4
978		1666
979	=item add $grp ...	1667	=item add $grp ...
980		1668
…		…
989	=item $grp->cancel_subs	1677	=item $grp->cancel_subs
990		1678
991	Cancel all subrequests and clears any feeder, but not the group request	1679	Cancel all subrequests and clears any feeder, but not the group request
992	itself. Useful when you queued a lot of events but got a result early.	1680	itself. Useful when you queued a lot of events but got a result early.
993		1681
		1682	The group request will finish normally (you cannot add requests to the
		1683	group).
		1684
994	=item $grp->result (...)	1685	=item $grp->result (...)
995		1686
996	Set the result value(s) that will be passed to the group callback when all	1687	Set the result value(s) that will be passed to the group callback when all
997	subrequests have finished and set thre groups errno to the current value	1688	subrequests have finished and set the groups errno to the current value
998	of errno (just like calling C<errno> without an error number). By default,	1689	of errno (just like calling C<errno> without an error number). By default,
999	no argument will be passed and errno is zero.	1690	no argument will be passed and errno is zero.
1000		1691
1001	=item $grp->errno ([$errno])	1692	=item $grp->errno ([$errno])
1002		1693
…		…
1013	=item feed $grp $callback->($grp)	1704	=item feed $grp $callback->($grp)
1014		1705
1015	Sets a feeder/generator on this group: every group can have an attached	1706	Sets a feeder/generator on this group: every group can have an attached
1016	generator that generates requests if idle. The idea behind this is that,	1707	generator that generates requests if idle. The idea behind this is that,
1017	although you could just queue as many requests as you want in a group,	1708	although you could just queue as many requests as you want in a group,
1018	this might starve other requests for a potentially long time. For	1709	this might starve other requests for a potentially long time. For example,
1019	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1710	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1020	requests, delaying any later requests for a long time.	1711	requests, delaying any later requests for a long time.
1021		1712
1022	To avoid this, and allow incremental generation of requests, you can	1713	To avoid this, and allow incremental generation of requests, you can
1023	instead a group and set a feeder on it that generates those requests. The	1714	instead a group and set a feeder on it that generates those requests. The
1024	feed callback will be called whenever there are few enough (see C<limit>,	1715	feed callback will be called whenever there are few enough (see C<limit>,
…		…
1029	not impose any limits).	1720	not impose any limits).
1030		1721
1031	If the feed does not queue more requests when called, it will be	1722	If the feed does not queue more requests when called, it will be
1032	automatically removed from the group.	1723	automatically removed from the group.
1033		1724
1034	If the feed limit is C<0>, it will be set to C<2> automatically.	1725	If the feed limit is C<0> when this method is called, it will be set to
		1726	C<2> automatically.
1035		1727
1036	Example:	1728	Example:
1037		1729
1038	# stat all files in @files, but only ever use four aio requests concurrently:	1730	# stat all files in @files, but only ever use four aio requests concurrently:
1039		1731
…		…
1051	Sets the feeder limit for the group: The feeder will be called whenever	1743	Sets the feeder limit for the group: The feeder will be called whenever
1052	the group contains less than this many requests.	1744	the group contains less than this many requests.
1053		1745
1054	Setting the limit to C<0> will pause the feeding process.	1746	Setting the limit to C<0> will pause the feeding process.
1055		1747
		1748	The default value for the limit is C<0>, but note that setting a feeder
		1749	automatically bumps it up to C<2>.
		1750
1056	=back	1751	=back
1057		1752
1058	=head2 SUPPORT FUNCTIONS	1753	=head2 SUPPORT FUNCTIONS
1059		1754
1060	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1755	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1062	=over 4	1757	=over 4
1063		1758
1064	=item $fileno = IO::AIO::poll_fileno	1759	=item $fileno = IO::AIO::poll_fileno
1065		1760
1066	Return the I<request result pipe file descriptor>. This filehandle must be	1761	Return the I<request result pipe file descriptor>. This filehandle must be
1067	polled for reading by some mechanism outside this module (e.g. Event or	1762	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1068	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1763	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1069	to call C<poll_cb> to check the results.	1764	you have to call C<poll_cb> to check the results.
1070		1765
1071	See C<poll_cb> for an example.	1766	See C<poll_cb> for an example.
1072		1767
1073	=item IO::AIO::poll_cb	1768	=item IO::AIO::poll_cb
1074		1769
1075	Process some outstanding events on the result pipe. You have to call this	1770	Process some requests that have reached the result phase (i.e. they have
1076	regularly. Returns the number of events processed. Returns immediately	1771	been executed but the results are not yet reported). You have to call
1077	when no events are outstanding. The amount of events processed depends on	1772	this "regularly" to finish outstanding requests.
1078	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1079		1773
		1774	Returns C<0> if all events could be processed (or there were no
		1775	events to process), or C<-1> if it returned earlier for whatever
		1776	reason. Returns immediately when no events are outstanding. The amount
		1777	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1778	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1779
1080	If not all requests were processed for whatever reason, the filehandle	1780	If not all requests were processed for whatever reason, the poll file
1081	will still be ready when C<poll_cb> returns.	1781	descriptor will still be ready when C<poll_cb> returns, so normally you
		1782	don't have to do anything special to have it called later.
		1783
		1784	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1785	ready, it can be beneficial to call this function from loops which submit
		1786	a lot of requests, to make sure the results get processed when they become
		1787	available and not just when the loop is finished and the event loop takes
		1788	over again. This function returns very fast when there are no outstanding
		1789	requests.
1082		1790
1083	Example: Install an Event watcher that automatically calls	1791	Example: Install an Event watcher that automatically calls
1084	IO::AIO::poll_cb with high priority:	1792	IO::AIO::poll_cb with high priority (more examples can be found in the
		1793	SYNOPSIS section, at the top of this document):
1085		1794
1086	Event->io (fd => IO::AIO::poll_fileno,	1795	Event->io (fd => IO::AIO::poll_fileno,
1087	poll => 'r', async => 1,	1796	poll => 'r', async => 1,
1088	cb => \&IO::AIO::poll_cb);	1797	cb => \&IO::AIO::poll_cb);
		1798
		1799	=item IO::AIO::poll_wait
		1800
		1801	Wait until either at least one request is in the result phase or no
		1802	requests are outstanding anymore.
		1803
		1804	This is useful if you want to synchronously wait for some requests to
		1805	become ready, without actually handling them.
		1806
		1807	See C<nreqs> for an example.
		1808
		1809	=item IO::AIO::poll
		1810
		1811	Waits until some requests have been handled.
		1812
		1813	Returns the number of requests processed, but is otherwise strictly
		1814	equivalent to:
		1815
		1816	IO::AIO::poll_wait, IO::AIO::poll_cb
		1817
		1818	=item IO::AIO::flush
		1819
		1820	Wait till all outstanding AIO requests have been handled.
		1821
		1822	Strictly equivalent to:
		1823
		1824	IO::AIO::poll_wait, IO::AIO::poll_cb
		1825	while IO::AIO::nreqs;
1089		1826
1090	=item IO::AIO::max_poll_reqs $nreqs	1827	=item IO::AIO::max_poll_reqs $nreqs
1091		1828
1092	=item IO::AIO::max_poll_time $seconds	1829	=item IO::AIO::max_poll_time $seconds
1093		1830
…		…
1118	# use a low priority so other tasks have priority	1855	# use a low priority so other tasks have priority
1119	Event->io (fd => IO::AIO::poll_fileno,	1856	Event->io (fd => IO::AIO::poll_fileno,
1120	poll => 'r', nice => 1,	1857	poll => 'r', nice => 1,
1121	cb => &IO::AIO::poll_cb);	1858	cb => &IO::AIO::poll_cb);
1122		1859
1123	=item IO::AIO::poll_wait
1124
1125	If there are any outstanding requests and none of them in the result
1126	phase, wait till the result filehandle becomes ready for reading (simply
1127	does a C<select> on the filehandle. This is useful if you want to
1128	synchronously wait for some requests to finish).
1129
1130	See C<nreqs> for an example.
1131
1132	=item IO::AIO::poll
1133
1134	Waits until some requests have been handled.
1135
1136	Returns the number of requests processed, but is otherwise strictly
1137	equivalent to:
1138
1139	IO::AIO::poll_wait, IO::AIO::poll_cb
1140
1141	=item IO::AIO::flush
1142
1143	Wait till all outstanding AIO requests have been handled.
1144
1145	Strictly equivalent to:
1146
1147	IO::AIO::poll_wait, IO::AIO::poll_cb
1148	while IO::AIO::nreqs;
1149
1150	=back	1860	=back
1151		1861
1152	=head3 CONTROLLING THE NUMBER OF THREADS	1862	=head3 CONTROLLING THE NUMBER OF THREADS
1153		1863
1154	=over	1864	=over
…		…
1187		1897
1188	Under normal circumstances you don't need to call this function.	1898	Under normal circumstances you don't need to call this function.
1189		1899
1190	=item IO::AIO::max_idle $nthreads	1900	=item IO::AIO::max_idle $nthreads
1191		1901
1192	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1902	Limit the number of threads (default: 4) that are allowed to idle
1193	threads that did not get a request to process within 10 seconds). That	1903	(i.e., threads that did not get a request to process within the idle
1194	means if a thread becomes idle while C<$nthreads> other threads are also	1904	timeout (default: 10 seconds). That means if a thread becomes idle while
1195	idle, it will free its resources and exit.	1905	C<$nthreads> other threads are also idle, it will free its resources and
		1906	exit.
1196		1907
1197	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1908	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1198	to allow for extremely high load situations, but want to free resources	1909	to allow for extremely high load situations, but want to free resources
1199	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1910	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1200		1911
1201	The default is probably ok in most situations, especially if thread	1912	The default is probably ok in most situations, especially if thread
1202	creation is fast. If thread creation is very slow on your system you might	1913	creation is fast. If thread creation is very slow on your system you might
1203	want to use larger values.	1914	want to use larger values.
1204		1915
		1916	=item IO::AIO::idle_timeout $seconds
		1917
		1918	Sets the minimum idle timeout (default 10) after which worker threads are
		1919	allowed to exit. SEe C<IO::AIO::max_idle>.
		1920
1205	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1921	=item IO::AIO::max_outstanding $maxreqs
		1922
		1923	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1924	you do queue up more than this number of requests, the next call to
		1925	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1926	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1927	longer exceeded.
		1928
		1929	In other words, this setting does not enforce a queue limit, but can be
		1930	used to make poll functions block if the limit is exceeded.
1206		1931
1207	This is a very bad function to use in interactive programs because it	1932	This is a very bad function to use in interactive programs because it
1208	blocks, and a bad way to reduce concurrency because it is inexact: Better	1933	blocks, and a bad way to reduce concurrency because it is inexact: Better
1209	use an C<aio_group> together with a feed callback.	1934	use an C<aio_group> together with a feed callback.
1210		1935
1211	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1936	Its main use is in scripts without an event loop - when you want to stat
1212	do queue up more than this number of requests, the next call to the	1937	a lot of files, you can write somehting like this:
1213	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1214	function will block until the limit is no longer exceeded.
1215		1938
1216	The default value is very large, so there is no practical limit on the	1939	IO::AIO::max_outstanding 32;
1217	number of outstanding requests.
1218		1940
1219	You can still queue as many requests as you want. Therefore,	1941	for my $path (...) {
1220	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1942	aio_stat $path , ...;
1221	as a stop gap to shield against fatal memory overflow (with large values).	1943	IO::AIO::poll_cb;
		1944	}
		1945
		1946	IO::AIO::flush;
		1947
		1948	The call to C<poll_cb> inside the loop will normally return instantly, but
		1949	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1950	some requests have been handled. This keeps the loop from pushing a large
		1951	number of C<aio_stat> requests onto the queue.
		1952
		1953	The default value for C<max_outstanding> is very large, so there is no
		1954	practical limit on the number of outstanding requests.
1222		1955
1223	=back	1956	=back
1224		1957
1225	=head3 STATISTICAL INFORMATION	1958	=head3 STATISTICAL INFORMATION
1226		1959
…		…
1246	Returns the number of requests currently in the pending state (executed,	1979	Returns the number of requests currently in the pending state (executed,
1247	but not yet processed by poll_cb).	1980	but not yet processed by poll_cb).
1248		1981
1249	=back	1982	=back
1250		1983
		1984	=head3 MISCELLANEOUS FUNCTIONS
		1985
		1986	IO::AIO implements some functions that are useful when you want to use
		1987	some "Advanced I/O" function not available to in Perl, without going the
		1988	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		1989	counterpart.
		1990
		1991	=over 4
		1992
		1993	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1994
		1995	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1996	but is blocking (this makes most sense if you know the input data is
		1997	likely cached already and the output filehandle is set to non-blocking
		1998	operations).
		1999
		2000	Returns the number of bytes copied, or C<-1> on error.
		2001
		2002	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2003
		2004	Simply calls the C<posix_fadvise> function (see its
		2005	manpage for details). The following advice constants are
		2006	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2007	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2008	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2009
		2010	On systems that do not implement C<posix_fadvise>, this function returns
		2011	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2012
		2013	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2014
		2015	Simply calls the C<posix_madvise> function (see its
		2016	manpage for details). The following advice constants are
		2017	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2018	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		2019
		2020	On systems that do not implement C<posix_madvise>, this function returns
		2021	ENOSYS, otherwise the return value of C<posix_madvise>.
		2022
		2023	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2024
		2025	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2026	$scalar (see its manpage for details). The following protect
		2027	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2028	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2029
		2030	On systems that do not implement C<mprotect>, this function returns
		2031	ENOSYS, otherwise the return value of C<mprotect>.
		2032
		2033	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2034
		2035	Memory-maps a file (or anonymous memory range) and attaches it to the
		2036	given C<$scalar>, which will act like a string scalar. Returns true on
		2037	success, and false otherwise.
		2038
		2039	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		2040	change the string length, and most read-only operations such as copying it
		2041	or searching it with regexes and so on.
		2042
		2043	Anything else is unsafe and will, at best, result in memory leaks.
		2044
		2045	The memory map associated with the C<$scalar> is automatically removed
		2046	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		2047	C<IO::AIO::munmap> functions are called.
		2048
		2049	This calls the C<mmap>(2) function internally. See your system's manual
		2050	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2051
		2052	The C<$length> must be larger than zero and smaller than the actual
		2053	filesize.
		2054
		2055	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2056	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2057
		2058	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		2059	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		2060	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		2061	(which is set to C<MAP_ANON> if your system only provides this
		2062	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		2063	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		2064	C<IO::AIO::MAP_NONBLOCK>
		2065
		2066	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2067
		2068	C<$offset> is the offset from the start of the file - it generally must be
		2069	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2070
		2071	Example:
		2072
		2073	use Digest::MD5;
		2074	use IO::AIO;
		2075
		2076	open my $fh, "<verybigfile"
		2077	or die "$!";
		2078
		2079	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2080	or die "verybigfile: $!";
		2081
		2082	my $fast_md5 = md5 $data;
		2083
		2084	=item IO::AIO::munmap $scalar
		2085
		2086	Removes a previous mmap and undefines the C<$scalar>.
		2087
		2088	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2089
		2090	Calls the C<munlock> function, undoing the effects of a previous
		2091	C<aio_mlock> call (see its description for details).
		2092
		2093	=item IO::AIO::munlockall
		2094
		2095	Calls the C<munlockall> function.
		2096
		2097	On systems that do not implement C<munlockall>, this function returns
		2098	ENOSYS, otherwise the return value of C<munlockall>.
		2099
		2100	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2101
		2102	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2103	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2104	should be the file offset.
		2105
		2106	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2107	silently corrupt the data in this case.
		2108
		2109	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2110	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2111	C<IO::AIO::SPLICE_F_GIFT>.
		2112
		2113	See the C<splice(2)> manpage for details.
		2114
		2115	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2116
		2117	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2118	description for C<IO::AIO::splice> above for details.
		2119
		2120	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2121
		2122	Attempts to query or change the pipe buffer size. Obviously works only
		2123	on pipes, and currently works only on GNU/Linux systems, and fails with
		2124	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2125	size on other systems, drop me a note.
		2126
		2127	=back
		2128
1251	=cut	2129	=cut
1252		2130
1253	# support function to convert a fd into a perl filehandle
1254	sub _fd2fh {
1255	return undef if $_[0] < 0;
1256
1257	# try to generate nice filehandles
1258	my $sym = "IO::AIO::fd#$_[0]";
1259	local *$sym;
1260
1261	open *$sym, "+<&=$_[0]" # usually works under any unix
1262	or open *$sym, "<&=$_[0]" # cygwin needs this
1263	or open *$sym, ">&=$_[0]" # or this
1264	or return undef;
1265
1266	*$sym
1267	}
1268
1269	min_parallel 8;	2131	min_parallel 8;
1270		2132
1271	END { flush }	2133	END { flush }
1272		2134
1273	1;	2135	1;
1274		2136
		2137	=head1 EVENT LOOP INTEGRATION
		2138
		2139	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2140	automatically into many event loops:
		2141
		2142	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2143	use AnyEvent::AIO;
		2144
		2145	You can also integrate IO::AIO manually into many event loops, here are
		2146	some examples of how to do this:
		2147
		2148	# EV integration
		2149	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2150
		2151	# Event integration
		2152	Event->io (fd => IO::AIO::poll_fileno,
		2153	poll => 'r',
		2154	cb => \&IO::AIO::poll_cb);
		2155
		2156	# Glib/Gtk2 integration
		2157	add_watch Glib::IO IO::AIO::poll_fileno,
		2158	in => sub { IO::AIO::poll_cb; 1 };
		2159
		2160	# Tk integration
		2161	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2162	readable => \&IO::AIO::poll_cb);
		2163
		2164	# Danga::Socket integration
		2165	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2166	\&IO::AIO::poll_cb);
		2167
1275	=head2 FORK BEHAVIOUR	2168	=head2 FORK BEHAVIOUR
1276		2169
1277	This module should do "the right thing" when the process using it forks:	2170	Usage of pthreads in a program changes the semantics of fork
		2171	considerably. Specifically, only async-safe functions can be called after
		2172	fork. Perl doesn't know about this, so in general, you cannot call fork
		2173	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2174	pthreads, so this applies, but many other extensions and (for inexplicable
		2175	reasons) perl itself often is linked against pthreads, so this limitation
		2176	applies to quite a lot of perls.
1278		2177
1279	Before the fork, IO::AIO enters a quiescent state where no requests	2178	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1280	can be added in other threads and no results will be processed. After	2179	only works in the process that loaded it. Forking is fully supported, but
1281	the fork the parent simply leaves the quiescent state and continues	2180	using IO::AIO in the child is not.
1282	request/result processing, while the child frees the request/result queue
1283	(so that the requests started before the fork will only be handled in the
1284	parent). Threads will be started on demand until the limit set in the
1285	parent process has been reached again.
1286		2181
1287	In short: the parent will, after a short pause, continue as if fork had	2182	You might get around by not I<using> IO::AIO before (or after)
1288	not been called, while the child will act as if IO::AIO has not been used	2183	forking. You could also try to call the L<IO::AIO::reinit> function in the
1289	yet.	2184	child:
		2185
		2186	=over 4
		2187
		2188	=item IO::AIO::reinit
		2189
		2190	Abandons all current requests and I/O threads and simply reinitialises all
		2191	data structures. This is not an operation supported by any standards, but
		2192	happens to work on GNU/Linux and some newer BSD systems.
		2193
		2194	The only reasonable use for this function is to call it after forking, if
		2195	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2196	the process will result in undefined behaviour. Calling it at any time
		2197	will also result in any undefined (by POSIX) behaviour.
		2198
		2199	=back
1290		2200
1291	=head2 MEMORY USAGE	2201	=head2 MEMORY USAGE
1292		2202
1293	Per-request usage:	2203	Per-request usage:
1294		2204
…		…
1311		2221
1312	Known bugs will be fixed in the next release.	2222	Known bugs will be fixed in the next release.
1313		2223
1314	=head1 SEE ALSO	2224	=head1 SEE ALSO
1315		2225
1316	L<Coro::AIO>.	2226	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2227	more natural syntax.
1317		2228
1318	=head1 AUTHOR	2229	=head1 AUTHOR
1319		2230
1320	Marc Lehmann <schmorp@schmorp.de>	2231	Marc Lehmann <schmorp@schmorp.de>
1321	http://home.schmorp.de/	2232	http://home.schmorp.de/

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