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Revision 1.147 by root, Wed Jun 3 12:24:49 2009 UTC vs.
Revision 1.281 by root, Tue Feb 20 04:32:59 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
80	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
81	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
85	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
86	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
87	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.19';	176	our $VERSION = 4.4;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
207		190
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	194	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	195	max_poll_time max_poll_reqs
		196	sendfile fadvise madvise
		197	mmap munmap munlock munlockall);
213		198
214	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
215		200
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		202
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	204	XSLoader::load ("IO::AIO", $VERSION);
220	}	205	}
221		206
222	=head1 FUNCTIONS	207	=head1 FUNCTIONS
223		208
224	=head2 AIO REQUEST FUNCTIONS	209	=head2 QUICK OVERVIEW
		210
		211	This section simply lists the prototypes most of the functions for
		212	quick reference. See the following sections for function-by-function
		213	documentation.
		214
		215	aio_wd $pathname, $callback->($wd)
		216	aio_open $pathname, $flags, $mode, $callback->($fh)
		217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
		219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		222	aio_readahead $fh,$offset,$length, $callback->($retval)
		223	aio_stat $fh_or_path, $callback->($status)
		224	aio_lstat $fh, $callback->($status)
		225	aio_statvfs $fh_or_path, $callback->($statvfs)
		226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
		229	aio_truncate $fh_or_path, $offset, $callback->($status)
		230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		232	aio_unlink $pathname, $callback->($status)
		233	aio_mknod $pathname, $mode, $dev, $callback->($status)
		234	aio_link $srcpath, $dstpath, $callback->($status)
		235	aio_symlink $srcpath, $dstpath, $callback->($status)
		236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
		238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		240	aio_mkdir $pathname, $mode, $callback->($status)
		241	aio_rmdir $pathname, $callback->($status)
		242	aio_readdir $pathname, $callback->($entries)
		243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		247	aio_load $pathname, $data, $callback->($status)
		248	aio_copy $srcpath, $dstpath, $callback->($status)
		249	aio_move $srcpath, $dstpath, $callback->($status)
		250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
		253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
		255	aio_fsync $fh, $callback->($status)
		256	aio_fdatasync $fh, $callback->($status)
		257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		258	aio_pathsync $pathname, $callback->($status)
		259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		262	aio_mlockall $flags, $callback->($status)
		263	aio_group $callback->(...)
		264	aio_nop $callback->()
		265
		266	$prev_pri = aioreq_pri [$pri]
		267	aioreq_nice $pri_adjust
		268
		269	IO::AIO::poll_wait
		270	IO::AIO::poll_cb
		271	IO::AIO::poll
		272	IO::AIO::flush
		273	IO::AIO::max_poll_reqs $nreqs
		274	IO::AIO::max_poll_time $seconds
		275	IO::AIO::min_parallel $nthreads
		276	IO::AIO::max_parallel $nthreads
		277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
		279	IO::AIO::max_outstanding $maxreqs
		280	IO::AIO::nreqs
		281	IO::AIO::nready
		282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		285
		286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::madvise $scalar, $offset, $length, $advice
		291	IO::AIO::mprotect $scalar, $offset, $length, $protect
		292	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		293	IO::AIO::munlockall
		294
		295	=head2 API NOTES
225		296
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	297	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	298	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	299	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	302	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	303	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		304	most syscalls return C<-1> on error, unlike perl, which usually delivers
		305	"false").
		306
		307	Some requests (such as C<aio_readdir>) pass the actual results and
		308	communicate failures by passing C<undef>.
233		309
234	All functions expecting a filehandle keep a copy of the filehandle	310	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	311	internally until the request has finished.
236		312
237	All functions return request objects of type L<IO::AIO::REQ> that allow	313	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	314	further manipulation of those requests while they are in-flight.
239		315
240	The pathnames you pass to these routines I<must> be absolute and	316	The pathnames you pass to these routines I<should> be absolute. The
241	encoded as octets. The reason for the former is that at the time the	317	reason for this is that at the time the request is being executed, the
242	request is being executed, the current working directory could have	318	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	319	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	320	in the program and then use relative paths. You can also take advantage
245	paths.	321	of IO::AIOs working directory abstraction, that lets you specify paths
		322	relative to some previously-opened "working directory object" - see the
		323	description of the C<IO::AIO::WD> class later in this document.
246		324
247	To encode pathnames as octets, either make sure you either: a) always pass	325	To encode pathnames as octets, either make sure you either: a) always pass
248	in filenames you got from outside (command line, readdir etc.) without	326	in filenames you got from outside (command line, readdir etc.) without
249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	327	tinkering, b) are in your native filesystem encoding, c) use the Encode
250	your pathnames to the locale (or other) encoding in effect in the user	328	module and encode your pathnames to the locale (or other) encoding in
251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	329	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	330	unicode filenames or e) use something else to ensure your scalar has the
		331	correct contents.
253		332
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	333	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	334	handles correctly whether it is set or not.
		335
		336	=head2 AIO REQUEST FUNCTIONS
256		337
257	=over 4	338	=over 4
258		339
259	=item $prev_pri = aioreq_pri [$pri]	340	=item $prev_pri = aioreq_pri [$pri]
260		341
…		…
290		371
291		372
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	373	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		374
294	Asynchronously open or create a file and call the callback with a newly	375	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	376	created filehandle for the file (or C<undef> in case of an error).
296		377
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	378	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	379	for an explanation.
299		380
300	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	381	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
307	by the umask in effect then the request is being executed, so better never	388	by the umask in effect then the request is being executed, so better never
308	change the umask.	389	change the umask.
309		390
310	Example:	391	Example:
311		392
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	393	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	394	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	395	print "open successful, fh is $_[0]\n";
315	...	396	...
316	} else {	397	} else {
317	die "open failed: $!\n";	398	die "open failed: $!\n";
318	}	399	}
319	};	400	};
320		401
		402	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		403	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		404	following POSIX and non-POSIX constants are available (missing ones on
		405	your system are, as usual, C<0>):
		406
		407	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		408	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		409	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		410
321		411
322	=item aio_close $fh, $callback->($status)	412	=item aio_close $fh, $callback->($status)
323		413
324	Asynchronously close a file and call the callback with the result	414	Asynchronously close a file and call the callback with the result
325	code.	415	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	424	Or in other words: the file descriptor will be closed, but it will not be
335	free for reuse until the perl filehandle is closed.	425	free for reuse until the perl filehandle is closed.
336		426
337	=cut	427	=cut
338		428
		429	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		430
		431	Seeks the filehandle to the new C<$offset>, similarly to perl's
		432	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		433	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		434	C<IO::AIO::SEEK_END>).
		435
		436	The resulting absolute offset will be passed to the callback, or C<-1> in
		437	case of an error.
		438
		439	In theory, the C<$whence> constants could be different than the
		440	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		441	so don't panic.
		442
		443	As a GNU/Linux (and maybe Solaris) extension, also the constants
		444	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		445	could be found. No guarantees about suitability for use in C<aio_seek> or
		446	Perl's C<sysseek> can be made though, although I would naively assume they
		447	"just work".
		448
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		450
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	451	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		452
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	453	Reads or writes C<$length> bytes from or to the specified C<$fh> and
344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	454	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
345	and calls the callback without the actual number of bytes read (or -1 on	455	calls the callback with the actual number of bytes transferred (or -1 on
346	error, just like the syscall).	456	error, just like the syscall).
347		457
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	458	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	459	offset plus the actual number of bytes read.
350		460
…		…
375		485
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	486	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	487	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	488	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	489	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	490	other. The same C<$in_fh> works fine though, as this function does not
		491	move or use the file offset of C<$in_fh>.
381		492
		493	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		494	are written, and there is no way to find out how many more bytes have been
		495	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		496	number of bytes written to C<$out_fh>. Only if the result value equals
		497	C<$length> one can assume that C<$length> bytes have been read.
		498
		499	Unlike with other C<aio_> functions, it makes a lot of sense to use
		500	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		501	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		502	the socket I/O will be non-blocking. Note, however, that you can run
		503	into a trap where C<aio_sendfile> reads some data with readahead, then
		504	fails to write all data, and when the socket is ready the next time, the
		505	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		506	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		507	resource usage.
		508
382	This call tries to make use of a native C<sendfile> syscall to provide	509	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	510	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	511	a socket, and C<$in_fh> should refer to an mmap'able file.
385		512
386	If the native sendfile call fails or is not implemented, it will be	513	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	514	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		515	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	516	type of filehandle regardless of the limitations of the operating system.
389		517
390	Please note, however, that C<aio_sendfile> can read more bytes from	518	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	519	together in a hurry to improve benchmark numbers) tend to be rather buggy
392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	520	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	521	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	522	so you really really should check the return value of C<aio_sendfile> -
395	read.	523	fewer bytes than expected might have been transferred.
396		524
397		525
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	526	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		527
400	C<aio_readahead> populates the page cache with data from a file so that	528	C<aio_readahead> populates the page cache with data from a file so that
…		…
404	whole pages, so that offset is effectively rounded down to a page boundary	532	whole pages, so that offset is effectively rounded down to a page boundary
405	and bytes are read up to the next page boundary greater than or equal to	533	and bytes are read up to the next page boundary greater than or equal to
406	(off-set+length). C<aio_readahead> does not read beyond the end of the	534	(off-set+length). C<aio_readahead> does not read beyond the end of the
407	file. The current file offset of the file is left unchanged.	535	file. The current file offset of the file is left unchanged.
408		536
409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	537	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
410	emulated by simply reading the data, which would have a similar effect.	538	be emulated by simply reading the data, which would have a similar effect.
411		539
412		540
413	=item aio_stat $fh_or_path, $callback->($status)	541	=item aio_stat $fh_or_path, $callback->($status)
414		542
415	=item aio_lstat $fh, $callback->($status)	543	=item aio_lstat $fh, $callback->($status)
…		…
422	for an explanation.	550	for an explanation.
423		551
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	552	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	553	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	554	unless perl itself is compiled with large file support.
		555
		556	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		557	following constants and functions (if not implemented, the constants will
		558	be C<0> and the functions will either C<croak> or fall back on traditional
		559	behaviour).
		560
		561	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		562	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		563	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
427		564
428	Example: Print the length of F</etc/passwd>:	565	Example: Print the length of F</etc/passwd>:
429		566
430	aio_stat "/etc/passwd", sub {	567	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	568	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	569	print "size is ", -s _, "\n";
433	};	570	};
434		571
435		572
		573	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		574
		575	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		576	whether a file handle or path was passed.
		577
		578	On success, the callback is passed a hash reference with the following
		579	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		580	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		581	is passed.
		582
		583	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		584	C<ST_NOSUID>.
		585
		586	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		587	their correct value when available, or to C<0> on systems that do
		588	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		589	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		590	C<ST_NODIRATIME> and C<ST_RELATIME>.
		591
		592	Example: stat C</wd> and dump out the data if successful.
		593
		594	aio_statvfs "/wd", sub {
		595	my $f = $_[0]
		596	or die "statvfs: $!";
		597
		598	use Data::Dumper;
		599	say Dumper $f;
		600	};
		601
		602	# result:
		603	{
		604	bsize => 1024,
		605	bfree => 4333064312,
		606	blocks => 10253828096,
		607	files => 2050765568,
		608	flag => 4096,
		609	favail => 2042092649,
		610	bavail => 4333064312,
		611	ffree => 2042092649,
		612	namemax => 255,
		613	frsize => 1024,
		614	fsid => 1810
		615	}
		616
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	617	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		618
438	Works like perl's C<utime> function (including the special case of $atime	619	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	620	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	621	syscalls support them.
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	648	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		649
469	Works like truncate(2) or ftruncate(2).	650	Works like truncate(2) or ftruncate(2).
470		651
471		652
		653	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654
		655	Allocates or frees disk space according to the C<$mode> argument. See the
		656	linux C<fallocate> documentation for details.
		657
		658	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		659	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		660	to deallocate a file range.
		661
		662	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		663	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		664	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		665	to unshare shared blocks (see your L<fallocate(2)> manpage).
		666
		667	The file system block size used by C<fallocate> is presumably the
		668	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		669	can dictate other limitations.
		670
		671	If C<fallocate> isn't available or cannot be emulated (currently no
		672	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		673
		674
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	675	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		676
474	Works like perl's C<chmod> function.	677	Works like perl's C<chmod> function.
475		678
476		679
…		…
478		681
479	Asynchronously unlink (delete) a file and call the callback with the	682	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	683	result code.
481		684
482		685
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	686	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		687
485	[EXPERIMENTAL]	688	[EXPERIMENTAL]
486		689
487	Asynchronously create a device node (or fifo). See mknod(2).	690	Asynchronously create a device node (or fifo). See mknod(2).
488		691
489	The only (POSIX-) portable way of calling this function is:	692	The only (POSIX-) portable way of calling this function is:
490		693
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	694	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		695
		696	See C<aio_stat> for info about some potentially helpful extra constants
		697	and functions.
493		698
494	=item aio_link $srcpath, $dstpath, $callback->($status)	699	=item aio_link $srcpath, $dstpath, $callback->($status)
495		700
496	Asynchronously create a new link to the existing object at C<$srcpath> at	701	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	702	the path C<$dstpath> and call the callback with the result code.
…		…
501		706
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	707	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
504		709
505		710
506	=item aio_readlink $path, $callback->($link)	711	=item aio_readlink $pathname, $callback->($link)
507		712
508	Asynchronously read the symlink specified by C<$path> and pass it to	713	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	714	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	715	callback.
511		716
512		717
		718	=item aio_realpath $pathname, $callback->($path)
		719
		720	Asynchronously make the path absolute and resolve any symlinks in
		721	C<$path>. The resulting path only consists of directories (same as
		722	L<Cwd::realpath>).
		723
		724	This request can be used to get the absolute path of the current working
		725	directory by passing it a path of F<.> (a single dot).
		726
		727
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	728	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		729
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	730	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	731	rename(2) and call the callback with the result code.
		732
		733	On systems that support the AIO::WD working directory abstraction
		734	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		735	of failing, C<rename> is called on the absolute path of C<$wd>.
		736
		737
		738	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		739
		740	Basically a version of C<aio_rename> with an additional C<$flags>
		741	argument. Calling this with C<$flags=0> is the same as calling
		742	C<aio_rename>.
		743
		744	Non-zero flags are currently only supported on GNU/Linux systems that
		745	support renameat2. Other systems fail with C<ENOSYS> in this case.
		746
		747	The following constants are available (missing ones are, as usual C<0>),
		748	see renameat2(2) for details:
		749
		750	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		751	and C<IO::AIO::RENAME_WHITEOUT>.
517		752
518		753
519	=item aio_mkdir $pathname, $mode, $callback->($status)	754	=item aio_mkdir $pathname, $mode, $callback->($status)
520		755
521	Asynchronously mkdir (create) a directory and call the callback with	756	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	761	=item aio_rmdir $pathname, $callback->($status)
527		762
528	Asynchronously rmdir (delete) a directory and call the callback with the	763	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	764	result code.
530		765
		766	On systems that support the AIO::WD working directory abstraction
		767	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		768	C<rmdir> is called on the absolute path of C<$wd>.
		769
531		770
532	=item aio_readdir $pathname, $callback->($entries)	771	=item aio_readdir $pathname, $callback->($entries)
533		772
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	773	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	774	directory (i.e. opendir + readdir + closedir). The entries will not be
536	sorted, and will B<NOT> include the C<.> and C<..> entries.	775	sorted, and will B<NOT> include the C<.> and C<..> entries.
537		776
538	The callback a single argument which is either C<undef> or an array-ref	777	The callback is passed a single argument which is either C<undef> or an
539	with the filenames.	778	array-ref with the filenames.
540		779
541		780
		781	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		782
		783	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		784	tune behaviour and output format. In case of an error, C<$entries> will be
		785	C<undef>.
		786
		787	The flags are a combination of the following constants, ORed together (the
		788	flags will also be passed to the callback, possibly modified):
		789
		790	=over 4
		791
		792	=item IO::AIO::READDIR_DENTS
		793
		794	When this flag is off, then the callback gets an arrayref consisting of
		795	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		796	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		797	entry in more detail.
		798
		799	C<$name> is the name of the entry.
		800
		801	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		802
		803	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		804	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		805	C<IO::AIO::DT_WHT>.
		806
		807	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		808	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		809	scalars are read-only: you can not modify them.
		810
		811	C<$inode> is the inode number (which might not be exact on systems with 64
		812	bit inode numbers and 32 bit perls). This field has unspecified content on
		813	systems that do not deliver the inode information.
		814
		815	=item IO::AIO::READDIR_DIRS_FIRST
		816
		817	When this flag is set, then the names will be returned in an order where
		818	likely directories come first, in optimal stat order. This is useful when
		819	you need to quickly find directories, or you want to find all directories
		820	while avoiding to stat() each entry.
		821
		822	If the system returns type information in readdir, then this is used
		823	to find directories directly. Otherwise, likely directories are names
		824	beginning with ".", or otherwise names with no dots, of which names with
		825	short names are tried first.
		826
		827	=item IO::AIO::READDIR_STAT_ORDER
		828
		829	When this flag is set, then the names will be returned in an order
		830	suitable for stat()'ing each one. That is, when you plan to stat()
		831	all files in the given directory, then the returned order will likely
		832	be fastest.
		833
		834	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		835	the likely dirs come first, resulting in a less optimal stat order.
		836
		837	=item IO::AIO::READDIR_FOUND_UNKNOWN
		838
		839	This flag should not be set when calling C<aio_readdirx>. Instead, it
		840	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		841	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		842	C<$type>'s are known, which can be used to speed up some algorithms.
		843
		844	=back
		845
		846
		847	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		848
		849	Opens, reads and closes the given file. The data is put into C<$data>,
		850	which is resized as required.
		851
		852	If C<$offset> is negative, then it is counted from the end of the file.
		853
		854	If C<$length> is zero, then the remaining length of the file is
		855	used. Also, in this case, the same limitations to modifying C<$data> apply
		856	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		857	with C<substr>. If the size of the file is known, specifying a non-zero
		858	C<$length> results in a performance advantage.
		859
		860	This request is similar to the older C<aio_load> request, but since it is
		861	a single request, it might be more efficient to use.
		862
		863	Example: load F</etc/passwd> into C<$passwd>.
		864
		865	my $passwd;
		866	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		867	$_[0] >= 0
		868	or die "/etc/passwd: $!\n";
		869
		870	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		871	print $passwd;
		872	};
		873	IO::AIO::flush;
		874
		875
542	=item aio_load $path, $data, $callback->($status)	876	=item aio_load $pathname, $data, $callback->($status)
543		877
544	This is a composite request that tries to fully load the given file into	878	This is a composite request that tries to fully load the given file into
545	memory. Status is the same as with aio_read.	879	memory. Status is the same as with aio_read.
		880
		881	Using C<aio_slurp> might be more efficient, as it is a single request.
546		882
547	=cut	883	=cut
548		884
549	sub aio_load($$;$) {	885	sub aio_load($$;$) {
550	my ($path, undef, $cb) = @_;	886	my ($path, undef, $cb) = @_;
…		…
569		905
570	=item aio_copy $srcpath, $dstpath, $callback->($status)	906	=item aio_copy $srcpath, $dstpath, $callback->($status)
571		907
572	Try to copy the I<file> (directories not supported as either source or	908	Try to copy the I<file> (directories not supported as either source or
573	destination) from C<$srcpath> to C<$dstpath> and call the callback with	909	destination) from C<$srcpath> to C<$dstpath> and call the callback with
574	the C<0> (error) or C<-1> ok.	910	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		911
		912	Existing destination files will be truncated.
575		913
576	This is a composite request that creates the destination file with	914	This is a composite request that creates the destination file with
577	mode 0200 and copies the contents of the source file into it using	915	mode 0200 and copies the contents of the source file into it using
578	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	916	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
579	uid/gid, in that order.	917	uid/gid, in that order.
…		…
591	my $grp = aio_group $cb;	929	my $grp = aio_group $cb;
592		930
593	aioreq_pri $pri;	931	aioreq_pri $pri;
594	add $grp aio_open $src, O_RDONLY, 0, sub {	932	add $grp aio_open $src, O_RDONLY, 0, sub {
595	if (my $src_fh = $_[0]) {	933	if (my $src_fh = $_[0]) {
596	my @stat = stat $src_fh; # hmm, might bock over nfs?	934	my @stat = stat $src_fh; # hmm, might block over nfs?
597		935
598	aioreq_pri $pri;	936	aioreq_pri $pri;
599	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	937	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
600	if (my $dst_fh = $_[0]) {	938	if (my $dst_fh = $_[0]) {
601	aioreq_pri $pri;	939	aioreq_pri $pri;
…		…
648		986
649	=item aio_move $srcpath, $dstpath, $callback->($status)	987	=item aio_move $srcpath, $dstpath, $callback->($status)
650		988
651	Try to move the I<file> (directories not supported as either source or	989	Try to move the I<file> (directories not supported as either source or
652	destination) from C<$srcpath> to C<$dstpath> and call the callback with	990	destination) from C<$srcpath> to C<$dstpath> and call the callback with
653	the C<0> (error) or C<-1> ok.	991	a status of C<0> (ok) or C<-1> (error, see C<$!>).
654		992
655	This is a composite request that tries to rename(2) the file first; if	993	This is a composite request that tries to rename(2) the file first; if
656	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	994	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
657	that is successful, unlinks the C<$srcpath>.	995	that is successful, unlinks the C<$srcpath>.
658		996
…		…
669	if ($_[0] && $! == EXDEV) {	1007	if ($_[0] && $! == EXDEV) {
670	aioreq_pri $pri;	1008	aioreq_pri $pri;
671	add $grp aio_copy $src, $dst, sub {	1009	add $grp aio_copy $src, $dst, sub {
672	$grp->result ($_[0]);	1010	$grp->result ($_[0]);
673		1011
674	if (!$_[0]) {	1012	unless ($_[0]) {
675	aioreq_pri $pri;	1013	aioreq_pri $pri;
676	add $grp aio_unlink $src;	1014	add $grp aio_unlink $src;
677	}	1015	}
678	};	1016	};
679	} else {	1017	} else {
…		…
682	};	1020	};
683		1021
684	$grp	1022	$grp
685	}	1023	}
686		1024
687	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1025	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
688		1026
689	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1027	Scans a directory (similar to C<aio_readdir>) but additionally tries to
690	efficiently separate the entries of directory C<$path> into two sets of	1028	efficiently separate the entries of directory C<$path> into two sets of
691	names, directories you can recurse into (directories), and ones you cannot	1029	names, directories you can recurse into (directories), and ones you cannot
692	recurse into (everything else, including symlinks to directories).	1030	recurse into (everything else, including symlinks to directories).
693		1031
694	C<aio_scandir> is a composite request that creates of many sub requests_	1032	C<aio_scandir> is a composite request that generates many sub requests.
695	C<$maxreq> specifies the maximum number of outstanding aio requests that	1033	C<$maxreq> specifies the maximum number of outstanding aio requests that
696	this function generates. If it is C<< <= 0 >>, then a suitable default	1034	this function generates. If it is C<< <= 0 >>, then a suitable default
697	will be chosen (currently 4).	1035	will be chosen (currently 4).
698		1036
699	On error, the callback is called without arguments, otherwise it receives	1037	On error, the callback is called without arguments, otherwise it receives
…		…
709		1047
710	Implementation notes.	1048	Implementation notes.
711		1049
712	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1050	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
713		1051
		1052	If readdir returns file type information, then this is used directly to
		1053	find directories.
		1054
714	After reading the directory, the modification time, size etc. of the	1055	Otherwise, after reading the directory, the modification time, size etc.
715	directory before and after the readdir is checked, and if they match (and	1056	of the directory before and after the readdir is checked, and if they
716	isn't the current time), the link count will be used to decide how many	1057	match (and isn't the current time), the link count will be used to decide
717	entries are directories (if >= 2). Otherwise, no knowledge of the number	1058	how many entries are directories (if >= 2). Otherwise, no knowledge of the
718	of subdirectories will be assumed.	1059	number of subdirectories will be assumed.
719		1060
720	Then entries will be sorted into likely directories (everything without	1061	Then entries will be sorted into likely directories a non-initial dot
721	a non-initial dot currently) and likely non-directories (everything	1062	currently) and likely non-directories (see C<aio_readdirx>). Then every
722	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1063	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
723	likely directories first. If that succeeds, it assumes that the entry	1064	in order of their inode numbers. If that succeeds, it assumes that the
724	is a directory or a symlink to directory (which will be checked	1065	entry is a directory or a symlink to directory (which will be checked
725	seperately). This is often faster than stat'ing the entry itself because	1066	separately). This is often faster than stat'ing the entry itself because
726	filesystems might detect the type of the entry without reading the inode	1067	filesystems might detect the type of the entry without reading the inode
727	data (e.g. ext2fs filetype feature).	1068	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1069	the filetype information on readdir.
728		1070
729	If the known number of directories (link count - 2) has been reached, the	1071	If the known number of directories (link count - 2) has been reached, the
730	rest of the entries is assumed to be non-directories.	1072	rest of the entries is assumed to be non-directories.
731		1073
732	This only works with certainty on POSIX (= UNIX) filesystems, which	1074	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
745		1087
746	my $grp = aio_group $cb;	1088	my $grp = aio_group $cb;
747		1089
748	$maxreq = 4 if $maxreq <= 0;	1090	$maxreq = 4 if $maxreq <= 0;
749		1091
750	# stat once	1092	# get a wd object
751	aioreq_pri $pri;	1093	aioreq_pri $pri;
752	add $grp aio_stat $path, sub {	1094	add $grp aio_wd $path, sub {
		1095	$_[0]
753	return $grp->result () if $_[0];	1096	or return $grp->result ();
754	my $now = time;
755	my $hash1 = join ":", (stat _)[0,1,3,7,9];
756		1097
757	# read the directory entries	1098	my $wd = [shift, "."];
		1099
		1100	# stat once
758	aioreq_pri $pri;	1101	aioreq_pri $pri;
759	add $grp aio_readdir $path, sub {	1102	add $grp aio_stat $wd, sub {
760	my $entries = shift
761	or return $grp->result ();	1103	return $grp->result () if $_[0];
		1104	my $now = time;
		1105	my $hash1 = join ":", (stat _)[0,1,3,7,9];
762		1106
763	# stat the dir another time	1107	# read the directory entries
764	aioreq_pri $pri;	1108	aioreq_pri $pri;
		1109	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1110	my $entries = shift
		1111	or return $grp->result ();
		1112
		1113	# stat the dir another time
		1114	aioreq_pri $pri;
765	add $grp aio_stat $path, sub {	1115	add $grp aio_stat $wd, sub {
766	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1116	my $hash2 = join ":", (stat _)[0,1,3,7,9];
767		1117
768	my $ndirs;	1118	my $ndirs;
769		1119
770	# take the slow route if anything looks fishy	1120	# take the slow route if anything looks fishy
771	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1121	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
772	$ndirs = -1;	1122	$ndirs = -1;
773	} else {	1123	} else {
774	# if nlink == 2, we are finished	1124	# if nlink == 2, we are finished
775	# on non-posix-fs's, we rely on nlink < 2	1125	# for non-posix-fs's, we rely on nlink < 2
776	$ndirs = (stat _)[3] - 2	1126	$ndirs = (stat _)[3] - 2
777	or return $grp->result ([], $entries);	1127	or return $grp->result ([], $entries);
778	}	1128	}
779		1129
780	# sort into likely dirs and likely nondirs
781	# dirs == files without ".", short entries first
782	$entries = [map $_->[0],
783	sort { $b->[1] cmp $a->[1] }
784	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
785	@$entries];
786
787	my (@dirs, @nondirs);	1130	my (@dirs, @nondirs);
788		1131
789	my $statgrp = add $grp aio_group sub {	1132	my $statgrp = add $grp aio_group sub {
790	$grp->result (\@dirs, \@nondirs);	1133	$grp->result (\@dirs, \@nondirs);
791	};	1134	};
792		1135
793	limit $statgrp $maxreq;	1136	limit $statgrp $maxreq;
794	feed $statgrp sub {	1137	feed $statgrp sub {
795	return unless @$entries;	1138	return unless @$entries;
796	my $entry = pop @$entries;	1139	my $entry = shift @$entries;
797		1140
798	aioreq_pri $pri;	1141	aioreq_pri $pri;
		1142	$wd->[1] = "$entry/.";
799	add $statgrp aio_stat "$path/$entry/.", sub {	1143	add $statgrp aio_stat $wd, sub {
800	if ($_[0] < 0) {	1144	if ($_[0] < 0) {
801	push @nondirs, $entry;	1145	push @nondirs, $entry;
802	} else {	1146	} else {
803	# need to check for real directory	1147	# need to check for real directory
804	aioreq_pri $pri;	1148	aioreq_pri $pri;
		1149	$wd->[1] = $entry;
805	add $statgrp aio_lstat "$path/$entry", sub {	1150	add $statgrp aio_lstat $wd, sub {
806	if (-d _) {	1151	if (-d _) {
807	push @dirs, $entry;	1152	push @dirs, $entry;
808		1153
809	unless (--$ndirs) {	1154	unless (--$ndirs) {
810	push @nondirs, @$entries;	1155	push @nondirs, @$entries;
811	feed $statgrp;	1156	feed $statgrp;
		1157	}
		1158	} else {
		1159	push @nondirs, $entry;
812	}	1160	}
813	} else {
814	push @nondirs, $entry;
815	}	1161	}
816	}	1162	}
817	}	1163	};
818	};	1164	};
819	};	1165	};
820	};	1166	};
821	};	1167	};
822	};	1168	};
823		1169
824	$grp	1170	$grp
825	}	1171	}
826		1172
827	=item aio_rmtree $path, $callback->($status)	1173	=item aio_rmtree $pathname, $callback->($status)
828		1174
829	Delete a directory tree starting (and including) C<$path>, return the	1175	Delete a directory tree starting (and including) C<$path>, return the
830	status of the final C<rmdir> only. This is a composite request that	1176	status of the final C<rmdir> only. This is a composite request that
831	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1177	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
832	everything else.	1178	everything else.
833		1179
834	=cut	1180	=cut
835		1181
…		…
857	};	1203	};
858		1204
859	$grp	1205	$grp
860	}	1206	}
861		1207
		1208	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1209
		1210	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1211
		1212	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1213	they execute asynchronously and pass the return value to the callback.
		1214
		1215	Both calls can be used for a lot of things, some of which make more sense
		1216	to run asynchronously in their own thread, while some others make less
		1217	sense. For example, calls that block waiting for external events, such
		1218	as locking, will also lock down an I/O thread while it is waiting, which
		1219	can deadlock the whole I/O system. At the same time, there might be no
		1220	alternative to using a thread to wait.
		1221
		1222	So in general, you should only use these calls for things that do
		1223	(filesystem) I/O, not for things that wait for other events (network,
		1224	other processes), although if you are careful and know what you are doing,
		1225	you still can.
		1226
		1227	The following constants are available (missing ones are, as usual C<0>):
		1228
		1229	C<F_DUPFD_CLOEXEC>,
		1230
		1231	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1232
		1233	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1234
		1235	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1236	C<FS_IOC_FIEMAP>.
		1237
		1238	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1239	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1240
		1241	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1242	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1243	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1244	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1245	C<FS_FL_USER_MODIFIABLE>.
		1246
		1247	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1248	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1249	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1250	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1251
862	=item aio_sync $callback->($status)	1252	=item aio_sync $callback->($status)
863		1253
864	Asynchronously call sync and call the callback when finished.	1254	Asynchronously call sync and call the callback when finished.
865		1255
866	=item aio_fsync $fh, $callback->($status)	1256	=item aio_fsync $fh, $callback->($status)
…		…
873	Asynchronously call fdatasync on the given filehandle and call the	1263	Asynchronously call fdatasync on the given filehandle and call the
874	callback with the fdatasync result code.	1264	callback with the fdatasync result code.
875		1265
876	If this call isn't available because your OS lacks it or it couldn't be	1266	If this call isn't available because your OS lacks it or it couldn't be
877	detected, it will be emulated by calling C<fsync> instead.	1267	detected, it will be emulated by calling C<fsync> instead.
		1268
		1269	=item aio_syncfs $fh, $callback->($status)
		1270
		1271	Asynchronously call the syncfs syscall to sync the filesystem associated
		1272	to the given filehandle and call the callback with the syncfs result
		1273	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1274	errno to C<ENOSYS> nevertheless.
878		1275
879	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1276	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
880		1277
881	Sync the data portion of the file specified by C<$offset> and C<$length>	1278	Sync the data portion of the file specified by C<$offset> and C<$length>
882	to disk (but NOT the metadata), by calling the Linux-specific	1279	to disk (but NOT the metadata), by calling the Linux-specific
…		…
886	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1283	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
887	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1284	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
888	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1285	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
889	manpage for details.	1286	manpage for details.
890		1287
891	=item aio_pathsync $path, $callback->($status)	1288	=item aio_pathsync $pathname, $callback->($status)
892		1289
893	This request tries to open, fsync and close the given path. This is a	1290	This request tries to open, fsync and close the given path. This is a
894	composite request intended to sync directories after directory operations	1291	composite request intended to sync directories after directory operations
895	(E.g. rename). This might not work on all operating systems or have any	1292	(E.g. rename). This might not work on all operating systems or have any
896	specific effect, but usually it makes sure that directory changes get	1293	specific effect, but usually it makes sure that directory changes get
897	written to disc. It works for anything that can be opened for read-only,	1294	written to disc. It works for anything that can be opened for read-only,
898	not just directories.	1295	not just directories.
		1296
		1297	Future versions of this function might fall back to other methods when
		1298	C<fsync> on the directory fails (such as calling C<sync>).
899		1299
900	Passes C<0> when everything went ok, and C<-1> on error.	1300	Passes C<0> when everything went ok, and C<-1> on error.
901		1301
902	=cut	1302	=cut
903		1303
…		…
924	};	1324	};
925		1325
926	$grp	1326	$grp
927	}	1327	}
928		1328
		1329	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1330
		1331	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1332	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1333	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1334	scalar must only be modified in-place while an aio operation is pending on
		1335	it).
		1336
		1337	It calls the C<msync> function of your OS, if available, with the memory
		1338	area starting at C<$offset> in the string and ending C<$length> bytes
		1339	later. If C<$length> is negative, counts from the end, and if C<$length>
		1340	is C<undef>, then it goes till the end of the string. The flags can be
		1341	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1342	C<IO::AIO::MS_INVALIDATE>.
		1343
		1344	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1345
		1346	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1347	scalars.
		1348
		1349	It touches (reads or writes) all memory pages in the specified
		1350	range inside the scalar. All caveats and parameters are the same
		1351	as for C<aio_msync>, above, except for flags, which must be either
		1352	C<0> (which reads all pages and ensures they are instantiated) or
		1353	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1354	writing an octet from it, which dirties the page).
		1355
		1356	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1357
		1358	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1359	scalars.
		1360
		1361	It reads in all the pages of the underlying storage into memory (if any)
		1362	and locks them, so they are not getting swapped/paged out or removed.
		1363
		1364	If C<$length> is undefined, then the scalar will be locked till the end.
		1365
		1366	On systems that do not implement C<mlock>, this function returns C<-1>
		1367	and sets errno to C<ENOSYS>.
		1368
		1369	Note that the corresponding C<munlock> is synchronous and is
		1370	documented under L<MISCELLANEOUS FUNCTIONS>.
		1371
		1372	Example: open a file, mmap and mlock it - both will be undone when
		1373	C<$data> gets destroyed.
		1374
		1375	open my $fh, "<", $path or die "$path: $!";
		1376	my $data;
		1377	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1378	aio_mlock $data; # mlock in background
		1379
		1380	=item aio_mlockall $flags, $callback->($status)
		1381
		1382	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1383	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1384
		1385	On systems that do not implement C<mlockall>, this function returns C<-1>
		1386	and sets errno to C<ENOSYS>.
		1387
		1388	Note that the corresponding C<munlockall> is synchronous and is
		1389	documented under L<MISCELLANEOUS FUNCTIONS>.
		1390
		1391	Example: asynchronously lock all current and future pages into memory.
		1392
		1393	aio_mlockall IO::AIO::MCL_FUTURE;
		1394
		1395	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1396
		1397	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1398	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1399	the ioctl is not available on your OS, then this request will fail with
		1400	C<ENOSYS>.
		1401
		1402	C<$start> is the starting offset to query extents for, C<$length> is the
		1403	size of the range to query - if it is C<undef>, then the whole file will
		1404	be queried.
		1405
		1406	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1407	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1408	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1409	the data portion.
		1410
		1411	C<$count> is the maximum number of extent records to return. If it is
		1412	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1413	case, if it is C<0>, then the callback receives the number of extents
		1414	instead of the extents themselves (which is unreliable, see below).
		1415
		1416	If an error occurs, the callback receives no arguments. The special
		1417	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1418
		1419	Otherwise, the callback receives an array reference with extent
		1420	structures. Each extent structure is an array reference itself, with the
		1421	following members:
		1422
		1423	[$logical, $physical, $length, $flags]
		1424
		1425	Flags is any combination of the following flag values (typically either C<0>
		1426	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1427
		1428	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1429	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1430	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1431	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1432	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1433	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1434
		1435	At the time of this writing (Linux 3.2), this request is unreliable unless
		1436	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1437	it to return all extents of a range for files with a large number of
		1438	extents. The code (only) works around all these issues if C<$count> is
		1439	C<undef>.
		1440
929	=item aio_group $callback->(...)	1441	=item aio_group $callback->(...)
930		1442
931	This is a very special aio request: Instead of doing something, it is a	1443	This is a very special aio request: Instead of doing something, it is a
932	container for other aio requests, which is useful if you want to bundle	1444	container for other aio requests, which is useful if you want to bundle
933	many requests into a single, composite, request with a definite callback	1445	many requests into a single, composite, request with a definite callback
…		…
970	immense (it blocks a thread for a long time) so do not use this function	1482	immense (it blocks a thread for a long time) so do not use this function
971	except to put your application under artificial I/O pressure.	1483	except to put your application under artificial I/O pressure.
972		1484
973	=back	1485	=back
974		1486
		1487
		1488	=head2 IO::AIO::WD - multiple working directories
		1489
		1490	Your process only has one current working directory, which is used by all
		1491	threads. This makes it hard to use relative paths (some other component
		1492	could call C<chdir> at any time, and it is hard to control when the path
		1493	will be used by IO::AIO).
		1494
		1495	One solution for this is to always use absolute paths. This usually works,
		1496	but can be quite slow (the kernel has to walk the whole path on every
		1497	access), and can also be a hassle to implement.
		1498
		1499	Newer POSIX systems have a number of functions (openat, fdopendir,
		1500	futimensat and so on) that make it possible to specify working directories
		1501	per operation.
		1502
		1503	For portability, and because the clowns who "designed", or shall I write,
		1504	perpetrated this new interface were obviously half-drunk, this abstraction
		1505	cannot be perfect, though.
		1506
		1507	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1508	object. This object stores the canonicalised, absolute version of the
		1509	path, and on systems that allow it, also a directory file descriptor.
		1510
		1511	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1512	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1513	object and a pathname instead (or the IO::AIO::WD object alone, which
		1514	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1515	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1516	to that IO::AIO::WD object.
		1517
		1518	For example, to get a wd object for F</etc> and then stat F<passwd>
		1519	inside, you would write:
		1520
		1521	aio_wd "/etc", sub {
		1522	my $etcdir = shift;
		1523
		1524	# although $etcdir can be undef on error, there is generally no reason
		1525	# to check for errors here, as aio_stat will fail with ENOENT
		1526	# when $etcdir is undef.
		1527
		1528	aio_stat [$etcdir, "passwd"], sub {
		1529	# yay
		1530	};
		1531	};
		1532
		1533	The fact that C<aio_wd> is a request and not a normal function shows that
		1534	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1535	which is why it is done asynchronously.
		1536
		1537	To stat the directory obtained with C<aio_wd> above, one could write
		1538	either of the following three request calls:
		1539
		1540	aio_lstat "/etc" , sub { ... # pathname as normal string
		1541	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1542	aio_lstat $wd , sub { ... # shorthand for the previous
		1543
		1544	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1545	object and the pathname string, so you could write the following without
		1546	causing any issues due to C<$path> getting reused:
		1547
		1548	my $path = [$wd, undef];
		1549
		1550	for my $name (qw(abc def ghi)) {
		1551	$path->[1] = $name;
		1552	aio_stat $path, sub {
		1553	# ...
		1554	};
		1555	}
		1556
		1557	There are some caveats: when directories get renamed (or deleted), the
		1558	pathname string doesn't change, so will point to the new directory (or
		1559	nowhere at all), while the directory fd, if available on the system,
		1560	will still point to the original directory. Most functions accepting a
		1561	pathname will use the directory fd on newer systems, and the string on
		1562	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1563	the string form of the pathname.
		1564
		1565	So this functionality is mainly useful to get some protection against
		1566	C<chdir>, to easily get an absolute path out of a relative path for future
		1567	reference, and to speed up doing many operations in the same directory
		1568	(e.g. when stat'ing all files in a directory).
		1569
		1570	The following functions implement this working directory abstraction:
		1571
		1572	=over 4
		1573
		1574	=item aio_wd $pathname, $callback->($wd)
		1575
		1576	Asynchonously canonicalise the given pathname and convert it to an
		1577	IO::AIO::WD object representing it. If possible and supported on the
		1578	system, also open a directory fd to speed up pathname resolution relative
		1579	to this working directory.
		1580
		1581	If something goes wrong, then C<undef> is passwd to the callback instead
		1582	of a working directory object and C<$!> is set appropriately. Since
		1583	passing C<undef> as working directory component of a pathname fails the
		1584	request with C<ENOENT>, there is often no need for error checking in the
		1585	C<aio_wd> callback, as future requests using the value will fail in the
		1586	expected way.
		1587
		1588	=item IO::AIO::CWD
		1589
		1590	This is a compiletime constant (object) that represents the process
		1591	current working directory.
		1592
		1593	Specifying this object as working directory object for a pathname is as if
		1594	the pathname would be specified directly, without a directory object. For
		1595	example, these calls are functionally identical:
		1596
		1597	aio_stat "somefile", sub { ... };
		1598	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1599
		1600	=back
		1601
		1602	To recover the path associated with an IO::AIO::WD object, you can use
		1603	C<aio_realpath>:
		1604
		1605	aio_realpath $wd, sub {
		1606	warn "path is $_[0]\n";
		1607	};
		1608
		1609	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1610	sometimes, fall back to using an absolue path.
		1611
975	=head2 IO::AIO::REQ CLASS	1612	=head2 IO::AIO::REQ CLASS
976		1613
977	All non-aggregate C<aio_*> functions return an object of this class when	1614	All non-aggregate C<aio_*> functions return an object of this class when
978	called in non-void context.	1615	called in non-void context.
979		1616
…		…
982	=item cancel $req	1619	=item cancel $req
983		1620
984	Cancels the request, if possible. Has the effect of skipping execution	1621	Cancels the request, if possible. Has the effect of skipping execution
985	when entering the B<execute> state and skipping calling the callback when	1622	when entering the B<execute> state and skipping calling the callback when
986	entering the the B<result> state, but will leave the request otherwise	1623	entering the the B<result> state, but will leave the request otherwise
987	untouched. That means that requests that currently execute will not be	1624	untouched (with the exception of readdir). That means that requests that
988	stopped and resources held by the request will not be freed prematurely.	1625	currently execute will not be stopped and resources held by the request
		1626	will not be freed prematurely.
989		1627
990	=item cb $req $callback->(...)	1628	=item cb $req $callback->(...)
991		1629
992	Replace (or simply set) the callback registered to the request.	1630	Replace (or simply set) the callback registered to the request.
993		1631
…		…
1067	=item $grp->cancel_subs	1705	=item $grp->cancel_subs
1068		1706
1069	Cancel all subrequests and clears any feeder, but not the group request	1707	Cancel all subrequests and clears any feeder, but not the group request
1070	itself. Useful when you queued a lot of events but got a result early.	1708	itself. Useful when you queued a lot of events but got a result early.
1071		1709
		1710	The group request will finish normally (you cannot add requests to the
		1711	group).
		1712
1072	=item $grp->result (...)	1713	=item $grp->result (...)
1073		1714
1074	Set the result value(s) that will be passed to the group callback when all	1715	Set the result value(s) that will be passed to the group callback when all
1075	subrequests have finished and set the groups errno to the current value	1716	subrequests have finished and set the groups errno to the current value
1076	of errno (just like calling C<errno> without an error number). By default,	1717	of errno (just like calling C<errno> without an error number). By default,
…		…
1092		1733
1093	Sets a feeder/generator on this group: every group can have an attached	1734	Sets a feeder/generator on this group: every group can have an attached
1094	generator that generates requests if idle. The idea behind this is that,	1735	generator that generates requests if idle. The idea behind this is that,
1095	although you could just queue as many requests as you want in a group,	1736	although you could just queue as many requests as you want in a group,
1096	this might starve other requests for a potentially long time. For example,	1737	this might starve other requests for a potentially long time. For example,
1097	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1738	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1098	delaying any later requests for a long time.	1739	requests, delaying any later requests for a long time.
1099		1740
1100	To avoid this, and allow incremental generation of requests, you can	1741	To avoid this, and allow incremental generation of requests, you can
1101	instead a group and set a feeder on it that generates those requests. The	1742	instead a group and set a feeder on it that generates those requests. The
1102	feed callback will be called whenever there are few enough (see C<limit>,	1743	feed callback will be called whenever there are few enough (see C<limit>,
1103	below) requests active in the group itself and is expected to queue more	1744	below) requests active in the group itself and is expected to queue more
…		…
1144	=over 4	1785	=over 4
1145		1786
1146	=item $fileno = IO::AIO::poll_fileno	1787	=item $fileno = IO::AIO::poll_fileno
1147		1788
1148	Return the I<request result pipe file descriptor>. This filehandle must be	1789	Return the I<request result pipe file descriptor>. This filehandle must be
1149	polled for reading by some mechanism outside this module (e.g. Event or	1790	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1150	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1791	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1151	to call C<poll_cb> to check the results.	1792	you have to call C<poll_cb> to check the results.
1152		1793
1153	See C<poll_cb> for an example.	1794	See C<poll_cb> for an example.
1154		1795
1155	=item IO::AIO::poll_cb	1796	=item IO::AIO::poll_cb
1156		1797
1157	Process some outstanding events on the result pipe. You have to call this	1798	Process some requests that have reached the result phase (i.e. they have
1158	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1799	been executed but the results are not yet reported). You have to call
1159	returned earlier for whatever reason. Returns immediately when no events	1800	this "regularly" to finish outstanding requests.
1160	are outstanding. The amount of events processed depends on the settings of
1161	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1162		1801
		1802	Returns C<0> if all events could be processed (or there were no
		1803	events to process), or C<-1> if it returned earlier for whatever
		1804	reason. Returns immediately when no events are outstanding. The amount
		1805	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1806	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1807
1163	If not all requests were processed for whatever reason, the filehandle	1808	If not all requests were processed for whatever reason, the poll file
1164	will still be ready when C<poll_cb> returns, so normally you don't have to	1809	descriptor will still be ready when C<poll_cb> returns, so normally you
1165	do anything special to have it called later.	1810	don't have to do anything special to have it called later.
		1811
		1812	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1813	ready, it can be beneficial to call this function from loops which submit
		1814	a lot of requests, to make sure the results get processed when they become
		1815	available and not just when the loop is finished and the event loop takes
		1816	over again. This function returns very fast when there are no outstanding
		1817	requests.
1166		1818
1167	Example: Install an Event watcher that automatically calls	1819	Example: Install an Event watcher that automatically calls
1168	IO::AIO::poll_cb with high priority:	1820	IO::AIO::poll_cb with high priority (more examples can be found in the
		1821	SYNOPSIS section, at the top of this document):
1169		1822
1170	Event->io (fd => IO::AIO::poll_fileno,	1823	Event->io (fd => IO::AIO::poll_fileno,
1171	poll => 'r', async => 1,	1824	poll => 'r', async => 1,
1172	cb => \&IO::AIO::poll_cb);	1825	cb => \&IO::AIO::poll_cb);
		1826
		1827	=item IO::AIO::poll_wait
		1828
		1829	Wait until either at least one request is in the result phase or no
		1830	requests are outstanding anymore.
		1831
		1832	This is useful if you want to synchronously wait for some requests to
		1833	become ready, without actually handling them.
		1834
		1835	See C<nreqs> for an example.
		1836
		1837	=item IO::AIO::poll
		1838
		1839	Waits until some requests have been handled.
		1840
		1841	Returns the number of requests processed, but is otherwise strictly
		1842	equivalent to:
		1843
		1844	IO::AIO::poll_wait, IO::AIO::poll_cb
		1845
		1846	=item IO::AIO::flush
		1847
		1848	Wait till all outstanding AIO requests have been handled.
		1849
		1850	Strictly equivalent to:
		1851
		1852	IO::AIO::poll_wait, IO::AIO::poll_cb
		1853	while IO::AIO::nreqs;
1173		1854
1174	=item IO::AIO::max_poll_reqs $nreqs	1855	=item IO::AIO::max_poll_reqs $nreqs
1175		1856
1176	=item IO::AIO::max_poll_time $seconds	1857	=item IO::AIO::max_poll_time $seconds
1177		1858
…		…
1202	# use a low priority so other tasks have priority	1883	# use a low priority so other tasks have priority
1203	Event->io (fd => IO::AIO::poll_fileno,	1884	Event->io (fd => IO::AIO::poll_fileno,
1204	poll => 'r', nice => 1,	1885	poll => 'r', nice => 1,
1205	cb => &IO::AIO::poll_cb);	1886	cb => &IO::AIO::poll_cb);
1206		1887
1207	=item IO::AIO::poll_wait
1208
1209	If there are any outstanding requests and none of them in the result
1210	phase, wait till the result filehandle becomes ready for reading (simply
1211	does a C<select> on the filehandle. This is useful if you want to
1212	synchronously wait for some requests to finish).
1213
1214	See C<nreqs> for an example.
1215
1216	=item IO::AIO::poll
1217
1218	Waits until some requests have been handled.
1219
1220	Returns the number of requests processed, but is otherwise strictly
1221	equivalent to:
1222
1223	IO::AIO::poll_wait, IO::AIO::poll_cb
1224
1225	=item IO::AIO::flush
1226
1227	Wait till all outstanding AIO requests have been handled.
1228
1229	Strictly equivalent to:
1230
1231	IO::AIO::poll_wait, IO::AIO::poll_cb
1232	while IO::AIO::nreqs;
1233
1234	=back	1888	=back
1235		1889
1236	=head3 CONTROLLING THE NUMBER OF THREADS	1890	=head3 CONTROLLING THE NUMBER OF THREADS
1237		1891
1238	=over	1892	=over
…		…
1271		1925
1272	Under normal circumstances you don't need to call this function.	1926	Under normal circumstances you don't need to call this function.
1273		1927
1274	=item IO::AIO::max_idle $nthreads	1928	=item IO::AIO::max_idle $nthreads
1275		1929
1276	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1930	Limit the number of threads (default: 4) that are allowed to idle
1277	threads that did not get a request to process within 10 seconds). That	1931	(i.e., threads that did not get a request to process within the idle
1278	means if a thread becomes idle while C<$nthreads> other threads are also	1932	timeout (default: 10 seconds). That means if a thread becomes idle while
1279	idle, it will free its resources and exit.	1933	C<$nthreads> other threads are also idle, it will free its resources and
		1934	exit.
1280		1935
1281	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1936	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1282	to allow for extremely high load situations, but want to free resources	1937	to allow for extremely high load situations, but want to free resources
1283	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1938	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1284		1939
1285	The default is probably ok in most situations, especially if thread	1940	The default is probably ok in most situations, especially if thread
1286	creation is fast. If thread creation is very slow on your system you might	1941	creation is fast. If thread creation is very slow on your system you might
1287	want to use larger values.	1942	want to use larger values.
1288		1943
		1944	=item IO::AIO::idle_timeout $seconds
		1945
		1946	Sets the minimum idle timeout (default 10) after which worker threads are
		1947	allowed to exit. SEe C<IO::AIO::max_idle>.
		1948
1289	=item IO::AIO::max_outstanding $maxreqs	1949	=item IO::AIO::max_outstanding $maxreqs
		1950
		1951	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1952	you do queue up more than this number of requests, the next call to
		1953	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1954	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1955	longer exceeded.
		1956
		1957	In other words, this setting does not enforce a queue limit, but can be
		1958	used to make poll functions block if the limit is exceeded.
1290		1959
1291	This is a very bad function to use in interactive programs because it	1960	This is a very bad function to use in interactive programs because it
1292	blocks, and a bad way to reduce concurrency because it is inexact: Better	1961	blocks, and a bad way to reduce concurrency because it is inexact: Better
1293	use an C<aio_group> together with a feed callback.	1962	use an C<aio_group> together with a feed callback.
1294		1963
1295	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1964	Its main use is in scripts without an event loop - when you want to stat
1296	do queue up more than this number of requests, the next call to the	1965	a lot of files, you can write something like this:
1297	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1298	function will block until the limit is no longer exceeded.
1299		1966
1300	The default value is very large, so there is no practical limit on the	1967	IO::AIO::max_outstanding 32;
1301	number of outstanding requests.
1302		1968
1303	You can still queue as many requests as you want. Therefore,	1969	for my $path (...) {
1304	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1970	aio_stat $path , ...;
1305	as a stop gap to shield against fatal memory overflow (with large values).	1971	IO::AIO::poll_cb;
		1972	}
		1973
		1974	IO::AIO::flush;
		1975
		1976	The call to C<poll_cb> inside the loop will normally return instantly, but
		1977	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1978	some requests have been handled. This keeps the loop from pushing a large
		1979	number of C<aio_stat> requests onto the queue.
		1980
		1981	The default value for C<max_outstanding> is very large, so there is no
		1982	practical limit on the number of outstanding requests.
1306		1983
1307	=back	1984	=back
1308		1985
1309	=head3 STATISTICAL INFORMATION	1986	=head3 STATISTICAL INFORMATION
1310		1987
…		…
1330	Returns the number of requests currently in the pending state (executed,	2007	Returns the number of requests currently in the pending state (executed,
1331	but not yet processed by poll_cb).	2008	but not yet processed by poll_cb).
1332		2009
1333	=back	2010	=back
1334		2011
		2012	=head3 MISCELLANEOUS FUNCTIONS
		2013
		2014	IO::AIO implements some functions that are useful when you want to use
		2015	some "Advanced I/O" function not available to in Perl, without going the
		2016	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2017	counterpart.
		2018
		2019	=over 4
		2020
		2021	=item $numfd = IO::AIO::get_fdlimit
		2022
		2023	This function is I<EXPERIMENTAL> and subject to change.
		2024
		2025	Tries to find the current file descriptor limit and returns it, or
		2026	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2027	the highest valid file descriptor number.
		2028
		2029	=item IO::AIO::min_fdlimit [$numfd]
		2030
		2031	This function is I<EXPERIMENTAL> and subject to change.
		2032
		2033	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2034	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2035	is missing, it will try to set a very high limit, although this is not
		2036	recommended when you know the actual minimum that you require.
		2037
		2038	If the limit cannot be raised enough, the function makes a best-effort
		2039	attempt to increase the limit as much as possible, using various
		2040	tricks, while still failing. You can query the resulting limit using
		2041	C<IO::AIO::get_fdlimit>.
		2042
		2043	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2044	true.
		2045
		2046	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2047
		2048	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2049	but is blocking (this makes most sense if you know the input data is
		2050	likely cached already and the output filehandle is set to non-blocking
		2051	operations).
		2052
		2053	Returns the number of bytes copied, or C<-1> on error.
		2054
		2055	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2056
		2057	Simply calls the C<posix_fadvise> function (see its
		2058	manpage for details). The following advice constants are
		2059	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2060	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2061	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2062
		2063	On systems that do not implement C<posix_fadvise>, this function returns
		2064	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2065
		2066	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2072	C<IO::AIO::MADV_DONTNEED>.
		2073
		2074	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2075	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2076	will be reduced to fit into the C<$scalar>.
		2077
		2078	On systems that do not implement C<posix_madvise>, this function returns
		2079	ENOSYS, otherwise the return value of C<posix_madvise>.
		2080
		2081	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2082
		2083	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2084	$scalar (see its manpage for details). The following protect
		2085	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2086	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2087
		2088	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2089	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2090	will be reduced to fit into the C<$scalar>.
		2091
		2092	On systems that do not implement C<mprotect>, this function returns
		2093	ENOSYS, otherwise the return value of C<mprotect>.
		2094
		2095	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2096
		2097	Memory-maps a file (or anonymous memory range) and attaches it to the
		2098	given C<$scalar>, which will act like a string scalar. Returns true on
		2099	success, and false otherwise.
		2100
		2101	The scalar must exist, but its contents do not matter - this means you
		2102	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2103	the scalar first.
		2104
		2105	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2106	which don't change the string length, and most read-only operations such
		2107	as copying it or searching it with regexes and so on.
		2108
		2109	Anything else is unsafe and will, at best, result in memory leaks.
		2110
		2111	The memory map associated with the C<$scalar> is automatically removed
		2112	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2113	or C<IO::AIO::munmap> functions are called on it.
		2114
		2115	This calls the C<mmap>(2) function internally. See your system's manual
		2116	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2117
		2118	The C<$length> must be larger than zero and smaller than the actual
		2119	filesize.
		2120
		2121	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2122	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2123
		2124	C<$flags> can be a combination of
		2125	C<IO::AIO::MAP_SHARED> or
		2126	C<IO::AIO::MAP_PRIVATE>,
		2127	or a number of system-specific flags (when not available, the are C<0>):
		2128	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2129	C<IO::AIO::MAP_LOCKED>,
		2130	C<IO::AIO::MAP_NORESERVE>,
		2131	C<IO::AIO::MAP_POPULATE>,
		2132	C<IO::AIO::MAP_NONBLOCK>,
		2133	C<IO::AIO::MAP_FIXED>,
		2134	C<IO::AIO::MAP_GROWSDOWN>,
		2135	C<IO::AIO::MAP_32BIT>,
		2136	C<IO::AIO::MAP_HUGETLB> or
		2137	C<IO::AIO::MAP_STACK>.
		2138
		2139	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2140
		2141	C<$offset> is the offset from the start of the file - it generally must be
		2142	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2143
		2144	Example:
		2145
		2146	use Digest::MD5;
		2147	use IO::AIO;
		2148
		2149	open my $fh, "<verybigfile"
		2150	or die "$!";
		2151
		2152	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2153	or die "verybigfile: $!";
		2154
		2155	my $fast_md5 = md5 $data;
		2156
		2157	=item IO::AIO::munmap $scalar
		2158
		2159	Removes a previous mmap and undefines the C<$scalar>.
		2160
		2161	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2162
		2163	Calls the C<munlock> function, undoing the effects of a previous
		2164	C<aio_mlock> call (see its description for details).
		2165
		2166	=item IO::AIO::munlockall
		2167
		2168	Calls the C<munlockall> function.
		2169
		2170	On systems that do not implement C<munlockall>, this function returns
		2171	ENOSYS, otherwise the return value of C<munlockall>.
		2172
		2173	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2174
		2175	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2176	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2177	should be the file offset.
		2178
		2179	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2180	silently corrupt the data in this case.
		2181
		2182	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2183	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2184	C<IO::AIO::SPLICE_F_GIFT>.
		2185
		2186	See the C<splice(2)> manpage for details.
		2187
		2188	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2189
		2190	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2191	description for C<IO::AIO::splice> above for details.
		2192
		2193	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2194
		2195	Attempts to query or change the pipe buffer size. Obviously works only
		2196	on pipes, and currently works only on GNU/Linux systems, and fails with
		2197	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2198	size on other systems, drop me a note.
		2199
		2200	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2201
		2202	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2203	C<$flags> is missing or C<0>, then this should be the same as a call to
		2204	perl's built-in C<pipe> function and create a new pipe, and works on
		2205	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2206	(..., 4096, O_BINARY)>.
		2207
		2208	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2209	the given flags (Linux 2.6.27, glibc 2.9).
		2210
		2211	On success, the read and write file handles are returned.
		2212
		2213	On error, nothing will be returned. If the pipe2 syscall is missing and
		2214	C<$flags> is non-zero, fails with C<ENOSYS>.
		2215
		2216	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2217	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2218	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2219
		2220	Example: create a pipe race-free w.r.t. threads and fork:
		2221
		2222	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2223	or die "pipe2: $!\n";
		2224
		2225	=item $fh = IO::AIO::eventfd ([$initval, [$flags]])
		2226
		2227	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2228	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2229
		2230	On success, the new eventfd filehandle is returned, otherwise returns
		2231	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2232
		2233	Please refer to L<eventfd(2)> for more info on this call.
		2234
		2235	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2236	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2237
		2238	=back
		2239
1335	=cut	2240	=cut
1336		2241
1337	min_parallel 8;	2242	min_parallel 8;
1338		2243
1339	END { flush }	2244	END { flush }
1340		2245
1341	1;	2246	1;
1342		2247
		2248	=head1 EVENT LOOP INTEGRATION
		2249
		2250	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2251	automatically into many event loops:
		2252
		2253	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2254	use AnyEvent::AIO;
		2255
		2256	You can also integrate IO::AIO manually into many event loops, here are
		2257	some examples of how to do this:
		2258
		2259	# EV integration
		2260	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2261
		2262	# Event integration
		2263	Event->io (fd => IO::AIO::poll_fileno,
		2264	poll => 'r',
		2265	cb => \&IO::AIO::poll_cb);
		2266
		2267	# Glib/Gtk2 integration
		2268	add_watch Glib::IO IO::AIO::poll_fileno,
		2269	in => sub { IO::AIO::poll_cb; 1 };
		2270
		2271	# Tk integration
		2272	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2273	readable => \&IO::AIO::poll_cb);
		2274
		2275	# Danga::Socket integration
		2276	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2277	\&IO::AIO::poll_cb);
		2278
1343	=head2 FORK BEHAVIOUR	2279	=head2 FORK BEHAVIOUR
1344		2280
1345	This module should do "the right thing" when the process using it forks:	2281	Usage of pthreads in a program changes the semantics of fork
		2282	considerably. Specifically, only async-safe functions can be called after
		2283	fork. Perl doesn't know about this, so in general, you cannot call fork
		2284	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2285	pthreads, so this applies, but many other extensions and (for inexplicable
		2286	reasons) perl itself often is linked against pthreads, so this limitation
		2287	applies to quite a lot of perls.
1346		2288
1347	Before the fork, IO::AIO enters a quiescent state where no requests	2289	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1348	can be added in other threads and no results will be processed. After	2290	only works in the process that loaded it. Forking is fully supported, but
1349	the fork the parent simply leaves the quiescent state and continues	2291	using IO::AIO in the child is not.
1350	request/result processing, while the child frees the request/result queue
1351	(so that the requests started before the fork will only be handled in the
1352	parent). Threads will be started on demand until the limit set in the
1353	parent process has been reached again.
1354		2292
1355	In short: the parent will, after a short pause, continue as if fork had	2293	You might get around by not I<using> IO::AIO before (or after)
1356	not been called, while the child will act as if IO::AIO has not been used	2294	forking. You could also try to call the L<IO::AIO::reinit> function in the
1357	yet.	2295	child:
		2296
		2297	=over 4
		2298
		2299	=item IO::AIO::reinit
		2300
		2301	Abandons all current requests and I/O threads and simply reinitialises all
		2302	data structures. This is not an operation supported by any standards, but
		2303	happens to work on GNU/Linux and some newer BSD systems.
		2304
		2305	The only reasonable use for this function is to call it after forking, if
		2306	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2307	the process will result in undefined behaviour. Calling it at any time
		2308	will also result in any undefined (by POSIX) behaviour.
		2309
		2310	=back
1358		2311
1359	=head2 MEMORY USAGE	2312	=head2 MEMORY USAGE
1360		2313
1361	Per-request usage:	2314	Per-request usage:
1362		2315

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