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Revision 1.152 by root, Fri Jun 12 16:48:08 2009 UTC vs.
Revision 1.289 by root, Sun Aug 12 05:21:35 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 = '3.21';	176	our $VERSION = 4.5;
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 aio_readdirx	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 mremap 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::mremap $scalar, $new_length, $flags[, $new_address]
		291	IO::AIO::madvise $scalar, $offset, $length, $advice
		292	IO::AIO::mprotect $scalar, $offset, $length, $protect
		293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		294	IO::AIO::munlockall
		295
		296	=head2 API NOTES
225		297
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	304	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		305	most syscalls return C<-1> on error, unlike perl, which usually delivers
		306	"false").
		307
		308	Some requests (such as C<aio_readdir>) pass the actual results and
		309	communicate failures by passing C<undef>.
233		310
234	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	312	internally until the request has finished.
236		313
237	All functions return request objects of type L<IO::AIO::REQ> that allow	314	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
239		316
240	The pathnames you pass to these routines I<must> be absolute and	317	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	318	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	319	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	321	in the program and then use relative paths. You can also take advantage
245	paths.	322	of IO::AIOs working directory abstraction, that lets you specify paths
		323	relative to some previously-opened "working directory object" - see the
		324	description of the C<IO::AIO::WD> class later in this document.
246		325
247	To encode pathnames as octets, either make sure you either: a) always pass	326	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	327	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	328	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	329	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)	330	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	331	unicode filenames or e) use something else to ensure your scalar has the
		332	correct contents.
253		333
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	334	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
256		338
257	=over 4	339	=over 4
258		340
259	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
260		342
…		…
290		372
291		373
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		375
294	Asynchronously open or create a file and call the callback with a newly	376	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
296		378
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	379	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	380	for an explanation.
299		381
300	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	382	The C<$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	389	by the umask in effect then the request is being executed, so better never
308	change the umask.	390	change the umask.
309		391
310	Example:	392	Example:
311		393
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	394	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	395	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	396	print "open successful, fh is $_[0]\n";
315	...	397	...
316	} else {	398	} else {
317	die "open failed: $!\n";	399	die "open failed: $!\n";
318	}	400	}
319	};	401	};
320		402
		403	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		404	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		405	following POSIX and non-POSIX constants are available (missing ones on
		406	your system are, as usual, C<0>):
		407
		408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		411
321		412
322	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
323		414
324	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
325	code.	416	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	425	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.	426	free for reuse until the perl filehandle is closed.
336		427
337	=cut	428	=cut
338		429
		430	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		431
		432	Seeks the filehandle to the new C<$offset>, similarly to perl's
		433	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		434	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		435	C<IO::AIO::SEEK_END>).
		436
		437	The resulting absolute offset will be passed to the callback, or C<-1> in
		438	case of an error.
		439
		440	In theory, the C<$whence> constants could be different than the
		441	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		442	so don't panic.
		443
		444	As a GNU/Linux (and maybe Solaris) extension, also the constants
		445	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		446	could be found. No guarantees about suitability for use in C<aio_seek> or
		447	Perl's C<sysseek> can be made though, although I would naively assume they
		448	"just work".
		449
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		451
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		453
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	454	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<$dataoffset>	455	C<$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	456	calls the callback with the actual number of bytes transferred (or -1 on
346	error, just like the syscall).	457	error, just like the syscall).
347		458
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	459	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
350		461
…		…
375		486
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	487	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	488	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	489	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	490	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	491	other. The same C<$in_fh> works fine though, as this function does not
		492	move or use the file offset of C<$in_fh>.
381		493
		494	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		495	are written, and there is no way to find out how many more bytes have been
		496	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		497	number of bytes written to C<$out_fh>. Only if the result value equals
		498	C<$length> one can assume that C<$length> bytes have been read.
		499
		500	Unlike with other C<aio_> functions, it makes a lot of sense to use
		501	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		502	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		503	the socket I/O will be non-blocking. Note, however, that you can run
		504	into a trap where C<aio_sendfile> reads some data with readahead, then
		505	fails to write all data, and when the socket is ready the next time, the
		506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		508	resource usage.
		509
382	This call tries to make use of a native C<sendfile> syscall to provide	510	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	511	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.	512	a socket, and C<$in_fh> should refer to an mmap'able file.
385		513
386	If the native sendfile call fails or is not implemented, it will be	514	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		516	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
389		518
390	Please note, however, that C<aio_sendfile> can read more bytes from	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	520	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	521	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	523	so you really really should check the return value of C<aio_sendfile> -
395	read.	524	fewer bytes than expected might have been transferred.
396		525
397		526
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		528
400	C<aio_readahead> populates the page cache with data from a file so that	529	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	533	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	534	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	535	(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.	536	file. The current file offset of the file is left unchanged.
408		537
409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	538	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.	539	be emulated by simply reading the data, which would have a similar effect.
411		540
412		541
413	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
414		543
415	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
…		…
422	for an explanation.	551	for an explanation.
423		552
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	553	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	554	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	555	unless perl itself is compiled with large file support.
		556
		557	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		558	following constants and functions (if not implemented, the constants will
		559	be C<0> and the functions will either C<croak> or fall back on traditional
		560	behaviour).
		561
		562	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		563	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		564	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		565
		566	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		567	ACCESS>.
427		568
428	Example: Print the length of F</etc/passwd>:	569	Example: Print the length of F</etc/passwd>:
429		570
430	aio_stat "/etc/passwd", sub {	571	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	572	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	573	print "size is ", -s _, "\n";
433	};	574	};
434		575
435		576
		577	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		578
		579	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		580	whether a file handle or path was passed.
		581
		582	On success, the callback is passed a hash reference with the following
		583	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		584	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		585	is passed.
		586
		587	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		588	C<ST_NOSUID>.
		589
		590	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		591	their correct value when available, or to C<0> on systems that do
		592	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		593	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		594	C<ST_NODIRATIME> and C<ST_RELATIME>.
		595
		596	Example: stat C</wd> and dump out the data if successful.
		597
		598	aio_statvfs "/wd", sub {
		599	my $f = $_[0]
		600	or die "statvfs: $!";
		601
		602	use Data::Dumper;
		603	say Dumper $f;
		604	};
		605
		606	# result:
		607	{
		608	bsize => 1024,
		609	bfree => 4333064312,
		610	blocks => 10253828096,
		611	files => 2050765568,
		612	flag => 4096,
		613	favail => 2042092649,
		614	bavail => 4333064312,
		615	ffree => 2042092649,
		616	namemax => 255,
		617	frsize => 1024,
		618	fsid => 1810
		619	}
		620
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	621	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		622
438	Works like perl's C<utime> function (including the special case of $atime	623	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	624	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	625	syscalls support them.
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	652	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		653
469	Works like truncate(2) or ftruncate(2).	654	Works like truncate(2) or ftruncate(2).
470		655
471		656
		657	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		658
		659	Allocates or frees disk space according to the C<$mode> argument. See the
		660	linux C<fallocate> documentation for details.
		661
		662	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		663	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		664	to deallocate a file range.
		665
		666	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		667	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		668	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		669	to unshare shared blocks (see your L<fallocate(2)> manpage).
		670
		671	The file system block size used by C<fallocate> is presumably the
		672	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		673	can dictate other limitations.
		674
		675	If C<fallocate> isn't available or cannot be emulated (currently no
		676	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		677
		678
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	679	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		680
474	Works like perl's C<chmod> function.	681	Works like perl's C<chmod> function.
475		682
476		683
…		…
478		685
479	Asynchronously unlink (delete) a file and call the callback with the	686	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	687	result code.
481		688
482		689
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	690	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		691
485	[EXPERIMENTAL]	692	[EXPERIMENTAL]
486		693
487	Asynchronously create a device node (or fifo). See mknod(2).	694	Asynchronously create a device node (or fifo). See mknod(2).
488		695
489	The only (POSIX-) portable way of calling this function is:	696	The only (POSIX-) portable way of calling this function is:
490		697
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	698	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		699
		700	See C<aio_stat> for info about some potentially helpful extra constants
		701	and functions.
493		702
494	=item aio_link $srcpath, $dstpath, $callback->($status)	703	=item aio_link $srcpath, $dstpath, $callback->($status)
495		704
496	Asynchronously create a new link to the existing object at C<$srcpath> at	705	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	706	the path C<$dstpath> and call the callback with the result code.
…		…
501		710
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	711	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	712	the path C<$dstpath> and call the callback with the result code.
504		713
505		714
506	=item aio_readlink $path, $callback->($link)	715	=item aio_readlink $pathname, $callback->($link)
507		716
508	Asynchronously read the symlink specified by C<$path> and pass it to	717	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	718	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	719	callback.
511		720
512		721
		722	=item aio_realpath $pathname, $callback->($path)
		723
		724	Asynchronously make the path absolute and resolve any symlinks in
		725	C<$path>. The resulting path only consists of directories (same as
		726	L<Cwd::realpath>).
		727
		728	This request can be used to get the absolute path of the current working
		729	directory by passing it a path of F<.> (a single dot).
		730
		731
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	732	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		733
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	734	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	735	rename(2) and call the callback with the result code.
		736
		737	On systems that support the AIO::WD working directory abstraction
		738	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		739	of failing, C<rename> is called on the absolute path of C<$wd>.
		740
		741
		742	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		743
		744	Basically a version of C<aio_rename> with an additional C<$flags>
		745	argument. Calling this with C<$flags=0> is the same as calling
		746	C<aio_rename>.
		747
		748	Non-zero flags are currently only supported on GNU/Linux systems that
		749	support renameat2. Other systems fail with C<ENOSYS> in this case.
		750
		751	The following constants are available (missing ones are, as usual C<0>),
		752	see renameat2(2) for details:
		753
		754	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		755	and C<IO::AIO::RENAME_WHITEOUT>.
517		756
518		757
519	=item aio_mkdir $pathname, $mode, $callback->($status)	758	=item aio_mkdir $pathname, $mode, $callback->($status)
520		759
521	Asynchronously mkdir (create) a directory and call the callback with	760	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	765	=item aio_rmdir $pathname, $callback->($status)
527		766
528	Asynchronously rmdir (delete) a directory and call the callback with the	767	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	768	result code.
530		769
		770	On systems that support the AIO::WD working directory abstraction
		771	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		772	C<rmdir> is called on the absolute path of C<$wd>.
		773
531		774
532	=item aio_readdir $pathname, $callback->($entries)	775	=item aio_readdir $pathname, $callback->($entries)
533		776
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	777	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	778	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
539	array-ref with the filenames.	782	array-ref with the filenames.
540		783
541		784
542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	785	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
543		786
544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	787	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
545	behaviour and output format. In case of an error, C<$entries> will be	788	tune behaviour and output format. In case of an error, C<$entries> will be
546	C<undef>.	789	C<undef>.
547		790
548	The flags are a combination of the following constants, ORed together (the	791	The flags are a combination of the following constants, ORed together (the
549	flags will also be passed to the callback, possibly modified):	792	flags will also be passed to the callback, possibly modified):
550		793
551	=over 4	794	=over 4
552		795
553	=item IO::AIO::READDIR_DENTS	796	=item IO::AIO::READDIR_DENTS
554		797
555	When this flag is off, then the callback gets an arrayref with of names	798	Normally the callback gets an arrayref consisting of names only (as
556	only (as with C<aio_readdir>), otherwise it gets an arrayref with	799	with C<aio_readdir>). If this flag is set, then the callback gets an
557	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	800	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
558	entry in more detail.	801	single directory entry in more detail:
559		802
560	C<$name> is the name of the entry.	803	C<$name> is the name of the entry.
561		804
562	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	805	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
563		806
564	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	807	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
565	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	808	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
566	C<IO::AIO::DT_WHT>.	809	C<IO::AIO::DT_WHT>.
567		810
568	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	811	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
569	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	812	to know, you have to run stat yourself. Also, for speed/memory reasons,
570	scalars are read-only: you can not modify them.	813	the C<$type> scalars are read-only: you must not modify them.
571		814
572	C<$inode> is the inode number (which might not be exact on systems with 64	815	C<$inode> is the inode number (which might not be exact on systems with 64
573	bit inode numbers and 32 bit perls). On systems that do not deliver the	816	bit inode numbers and 32 bit perls). This field has unspecified content on
574	inode information, this will always be zero.	817	systems that do not deliver the inode information.
575		818
576	=item IO::AIO::READDIR_DIRS_FIRST	819	=item IO::AIO::READDIR_DIRS_FIRST
577		820
578	When this flag is set, then the names will be returned in an order where	821	When this flag is set, then the names will be returned in an order where
579	likely directories come first. This is useful when you need to quickly	822	likely directories come first, in optimal stat order. This is useful when
580	find directories, or you want to find all directories while avoiding to	823	you need to quickly find directories, or you want to find all directories
581	stat() each entry.	824	while avoiding to stat() each entry.
582		825
583	If the system returns type information in readdir, then this is used	826	If the system returns type information in readdir, then this is used
584	to find directories directly. Otherwise, likely directories are files	827	to find directories directly. Otherwise, likely directories are names
585	beginning with ".", or otherwise files with no dots, of which files with	828	beginning with ".", or otherwise names with no dots, of which names with
586	short names are tried first.	829	short names are tried first.
587		830
588	=item IO::AIO::READDIR_STAT_ORDER	831	=item IO::AIO::READDIR_STAT_ORDER
589		832
590	When this flag is set, then the names will be returned in an order	833	When this flag is set, then the names will be returned in an order
591	suitable for stat()'ing each one. That is, when you plan to stat()	834	suitable for stat()'ing each one. That is, when you plan to stat() most or
592	all files in the given directory, then the returned order will likely	835	all files in the given directory, then the returned order will likely be
593	be fastest.	836	faster.
594		837
595	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	838	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
596	the likely dirs come first, resulting in a less optimal stat order.	839	then the likely dirs come first, resulting in a less optimal stat order
		840	for stat'ing all entries, but likely a more optimal order for finding
		841	subdirectories.
597		842
598	=item IO::AIO::READDIR_FOUND_UNKNOWN	843	=item IO::AIO::READDIR_FOUND_UNKNOWN
599		844
600	This flag should not be set when calling C<aio_readdirx>. Instead, it	845	This flag should not be set when calling C<aio_readdirx>. Instead, it
601	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	846	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
602	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	847	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
603	C<$type>'s are known, which can be used to speed up some algorithms.	848	C<$type>'s are known, which can be used to speed up some algorithms.
604		849
605	=back	850	=back
606		851
607		852
		853	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		854
		855	Opens, reads and closes the given file. The data is put into C<$data>,
		856	which is resized as required.
		857
		858	If C<$offset> is negative, then it is counted from the end of the file.
		859
		860	If C<$length> is zero, then the remaining length of the file is
		861	used. Also, in this case, the same limitations to modifying C<$data> apply
		862	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		863	with C<substr>. If the size of the file is known, specifying a non-zero
		864	C<$length> results in a performance advantage.
		865
		866	This request is similar to the older C<aio_load> request, but since it is
		867	a single request, it might be more efficient to use.
		868
		869	Example: load F</etc/passwd> into C<$passwd>.
		870
		871	my $passwd;
		872	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		873	$_[0] >= 0
		874	or die "/etc/passwd: $!\n";
		875
		876	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		877	print $passwd;
		878	};
		879	IO::AIO::flush;
		880
		881
608	=item aio_load $path, $data, $callback->($status)	882	=item aio_load $pathname, $data, $callback->($status)
609		883
610	This is a composite request that tries to fully load the given file into	884	This is a composite request that tries to fully load the given file into
611	memory. Status is the same as with aio_read.	885	memory. Status is the same as with aio_read.
		886
		887	Using C<aio_slurp> might be more efficient, as it is a single request.
612		888
613	=cut	889	=cut
614		890
615	sub aio_load($$;$) {	891	sub aio_load($$;$) {
616	my ($path, undef, $cb) = @_;	892	my ($path, undef, $cb) = @_;
…		…
635		911
636	=item aio_copy $srcpath, $dstpath, $callback->($status)	912	=item aio_copy $srcpath, $dstpath, $callback->($status)
637		913
638	Try to copy the I<file> (directories not supported as either source or	914	Try to copy the I<file> (directories not supported as either source or
639	destination) from C<$srcpath> to C<$dstpath> and call the callback with	915	destination) from C<$srcpath> to C<$dstpath> and call the callback with
640	the C<0> (error) or C<-1> ok.	916	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		917
		918	Existing destination files will be truncated.
641		919
642	This is a composite request that creates the destination file with	920	This is a composite request that creates the destination file with
643	mode 0200 and copies the contents of the source file into it using	921	mode 0200 and copies the contents of the source file into it using
644	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	922	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
645	uid/gid, in that order.	923	uid/gid, in that order.
…		…
657	my $grp = aio_group $cb;	935	my $grp = aio_group $cb;
658		936
659	aioreq_pri $pri;	937	aioreq_pri $pri;
660	add $grp aio_open $src, O_RDONLY, 0, sub {	938	add $grp aio_open $src, O_RDONLY, 0, sub {
661	if (my $src_fh = $_[0]) {	939	if (my $src_fh = $_[0]) {
662	my @stat = stat $src_fh; # hmm, might bock over nfs?	940	my @stat = stat $src_fh; # hmm, might block over nfs?
663		941
664	aioreq_pri $pri;	942	aioreq_pri $pri;
665	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	943	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
666	if (my $dst_fh = $_[0]) {	944	if (my $dst_fh = $_[0]) {
667	aioreq_pri $pri;	945	aioreq_pri $pri;
…		…
714		992
715	=item aio_move $srcpath, $dstpath, $callback->($status)	993	=item aio_move $srcpath, $dstpath, $callback->($status)
716		994
717	Try to move the I<file> (directories not supported as either source or	995	Try to move the I<file> (directories not supported as either source or
718	destination) from C<$srcpath> to C<$dstpath> and call the callback with	996	destination) from C<$srcpath> to C<$dstpath> and call the callback with
719	the C<0> (error) or C<-1> ok.	997	a status of C<0> (ok) or C<-1> (error, see C<$!>).
720		998
721	This is a composite request that tries to rename(2) the file first; if	999	This is a composite request that tries to rename(2) the file first; if
722	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	1000	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
723	that is successful, unlinks the C<$srcpath>.	1001	that is successful, unlinks the C<$srcpath>.
724		1002
…		…
735	if ($_[0] && $! == EXDEV) {	1013	if ($_[0] && $! == EXDEV) {
736	aioreq_pri $pri;	1014	aioreq_pri $pri;
737	add $grp aio_copy $src, $dst, sub {	1015	add $grp aio_copy $src, $dst, sub {
738	$grp->result ($_[0]);	1016	$grp->result ($_[0]);
739		1017
740	if (!$_[0]) {	1018	unless ($_[0]) {
741	aioreq_pri $pri;	1019	aioreq_pri $pri;
742	add $grp aio_unlink $src;	1020	add $grp aio_unlink $src;
743	}	1021	}
744	};	1022	};
745	} else {	1023	} else {
…		…
748	};	1026	};
749		1027
750	$grp	1028	$grp
751	}	1029	}
752		1030
753	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1031	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
754		1032
755	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1033	Scans a directory (similar to C<aio_readdir>) but additionally tries to
756	efficiently separate the entries of directory C<$path> into two sets of	1034	efficiently separate the entries of directory C<$path> into two sets of
757	names, directories you can recurse into (directories), and ones you cannot	1035	names, directories you can recurse into (directories), and ones you cannot
758	recurse into (everything else, including symlinks to directories).	1036	recurse into (everything else, including symlinks to directories).
759		1037
760	C<aio_scandir> is a composite request that creates of many sub requests_	1038	C<aio_scandir> is a composite request that generates many sub requests.
761	C<$maxreq> specifies the maximum number of outstanding aio requests that	1039	C<$maxreq> specifies the maximum number of outstanding aio requests that
762	this function generates. If it is C<< <= 0 >>, then a suitable default	1040	this function generates. If it is C<< <= 0 >>, then a suitable default
763	will be chosen (currently 4).	1041	will be chosen (currently 4).
764		1042
765	On error, the callback is called without arguments, otherwise it receives	1043	On error, the callback is called without arguments, otherwise it receives
…		…
789	Then entries will be sorted into likely directories a non-initial dot	1067	Then entries will be sorted into likely directories a non-initial dot
790	currently) and likely non-directories (see C<aio_readdirx>). Then every	1068	currently) and likely non-directories (see C<aio_readdirx>). Then every
791	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1069	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
792	in order of their inode numbers. If that succeeds, it assumes that the	1070	in order of their inode numbers. If that succeeds, it assumes that the
793	entry is a directory or a symlink to directory (which will be checked	1071	entry is a directory or a symlink to directory (which will be checked
794	seperately). This is often faster than stat'ing the entry itself because	1072	separately). This is often faster than stat'ing the entry itself because
795	filesystems might detect the type of the entry without reading the inode	1073	filesystems might detect the type of the entry without reading the inode
796	data (e.g. ext2fs filetype feature), even on systems that cannot return	1074	data (e.g. ext2fs filetype feature), even on systems that cannot return
797	the filetype information on readdir.	1075	the filetype information on readdir.
798		1076
799	If the known number of directories (link count - 2) has been reached, the	1077	If the known number of directories (link count - 2) has been reached, the
…		…
815		1093
816	my $grp = aio_group $cb;	1094	my $grp = aio_group $cb;
817		1095
818	$maxreq = 4 if $maxreq <= 0;	1096	$maxreq = 4 if $maxreq <= 0;
819		1097
820	# stat once	1098	# get a wd object
821	aioreq_pri $pri;	1099	aioreq_pri $pri;
822	add $grp aio_stat $path, sub {	1100	add $grp aio_wd $path, sub {
		1101	$_[0]
823	return $grp->result () if $_[0];	1102	or return $grp->result ();
824	my $now = time;
825	my $hash1 = join ":", (stat _)[0,1,3,7,9];
826		1103
827	# read the directory entries	1104	my $wd = [shift, "."];
		1105
		1106	# stat once
828	aioreq_pri $pri;	1107	aioreq_pri $pri;
829	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1108	add $grp aio_stat $wd, sub {
830	my $entries = shift
831	or return $grp->result ();	1109	return $grp->result () if $_[0];
		1110	my $now = time;
		1111	my $hash1 = join ":", (stat _)[0,1,3,7,9];
832		1112
833	# stat the dir another time	1113	# read the directory entries
834	aioreq_pri $pri;	1114	aioreq_pri $pri;
		1115	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1116	my $entries = shift
		1117	or return $grp->result ();
		1118
		1119	# stat the dir another time
		1120	aioreq_pri $pri;
835	add $grp aio_stat $path, sub {	1121	add $grp aio_stat $wd, sub {
836	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1122	my $hash2 = join ":", (stat _)[0,1,3,7,9];
837		1123
838	my $ndirs;	1124	my $ndirs;
839		1125
840	# take the slow route if anything looks fishy	1126	# take the slow route if anything looks fishy
841	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1127	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
842	$ndirs = -1;	1128	$ndirs = -1;
843	} else {	1129	} else {
844	# if nlink == 2, we are finished	1130	# if nlink == 2, we are finished
845	# for non-posix-fs's, we rely on nlink < 2	1131	# for non-posix-fs's, we rely on nlink < 2
846	$ndirs = (stat _)[3] - 2	1132	$ndirs = (stat _)[3] - 2
847	or return $grp->result ([], $entries);	1133	or return $grp->result ([], $entries);
848	}	1134	}
849		1135
850	my (@dirs, @nondirs);	1136	my (@dirs, @nondirs);
851		1137
852	my $statgrp = add $grp aio_group sub {	1138	my $statgrp = add $grp aio_group sub {
853	$grp->result (\@dirs, \@nondirs);	1139	$grp->result (\@dirs, \@nondirs);
854	};	1140	};
855		1141
856	limit $statgrp $maxreq;	1142	limit $statgrp $maxreq;
857	feed $statgrp sub {	1143	feed $statgrp sub {
858	return unless @$entries;	1144	return unless @$entries;
859	my $entry = shift @$entries;	1145	my $entry = shift @$entries;
860		1146
861	aioreq_pri $pri;	1147	aioreq_pri $pri;
		1148	$wd->[1] = "$entry/.";
862	add $statgrp aio_stat "$path/$entry/.", sub {	1149	add $statgrp aio_stat $wd, sub {
863	if ($_[0] < 0) {	1150	if ($_[0] < 0) {
864	push @nondirs, $entry;	1151	push @nondirs, $entry;
865	} else {	1152	} else {
866	# need to check for real directory	1153	# need to check for real directory
867	aioreq_pri $pri;	1154	aioreq_pri $pri;
		1155	$wd->[1] = $entry;
868	add $statgrp aio_lstat "$path/$entry", sub {	1156	add $statgrp aio_lstat $wd, sub {
869	if (-d _) {	1157	if (-d _) {
870	push @dirs, $entry;	1158	push @dirs, $entry;
871		1159
872	unless (--$ndirs) {	1160	unless (--$ndirs) {
873	push @nondirs, @$entries;	1161	push @nondirs, @$entries;
874	feed $statgrp;	1162	feed $statgrp;
		1163	}
		1164	} else {
		1165	push @nondirs, $entry;
875	}	1166	}
876	} else {
877	push @nondirs, $entry;
878	}	1167	}
879	}	1168	}
880	}	1169	};
881	};	1170	};
882	};	1171	};
883	};	1172	};
884	};	1173	};
885	};	1174	};
886		1175
887	$grp	1176	$grp
888	}	1177	}
889		1178
890	=item aio_rmtree $path, $callback->($status)	1179	=item aio_rmtree $pathname, $callback->($status)
891		1180
892	Delete a directory tree starting (and including) C<$path>, return the	1181	Delete a directory tree starting (and including) C<$path>, return the
893	status of the final C<rmdir> only. This is a composite request that	1182	status of the final C<rmdir> only. This is a composite request that
894	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1183	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
895	everything else.	1184	everything else.
896		1185
897	=cut	1186	=cut
898		1187
…		…
920	};	1209	};
921		1210
922	$grp	1211	$grp
923	}	1212	}
924		1213
		1214	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1215
		1216	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1217
		1218	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1219	they execute asynchronously and pass the return value to the callback.
		1220
		1221	Both calls can be used for a lot of things, some of which make more sense
		1222	to run asynchronously in their own thread, while some others make less
		1223	sense. For example, calls that block waiting for external events, such
		1224	as locking, will also lock down an I/O thread while it is waiting, which
		1225	can deadlock the whole I/O system. At the same time, there might be no
		1226	alternative to using a thread to wait.
		1227
		1228	So in general, you should only use these calls for things that do
		1229	(filesystem) I/O, not for things that wait for other events (network,
		1230	other processes), although if you are careful and know what you are doing,
		1231	you still can.
		1232
		1233	The following constants are available (missing ones are, as usual C<0>):
		1234
		1235	C<F_DUPFD_CLOEXEC>,
		1236
		1237	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1238
		1239	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1240
		1241	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1242	C<FS_IOC_FIEMAP>.
		1243
		1244	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1245	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1246
		1247	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1248	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1249	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1250	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1251	C<FS_FL_USER_MODIFIABLE>.
		1252
		1253	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1254	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1255	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1256	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1257
925	=item aio_sync $callback->($status)	1258	=item aio_sync $callback->($status)
926		1259
927	Asynchronously call sync and call the callback when finished.	1260	Asynchronously call sync and call the callback when finished.
928		1261
929	=item aio_fsync $fh, $callback->($status)	1262	=item aio_fsync $fh, $callback->($status)
…		…
936	Asynchronously call fdatasync on the given filehandle and call the	1269	Asynchronously call fdatasync on the given filehandle and call the
937	callback with the fdatasync result code.	1270	callback with the fdatasync result code.
938		1271
939	If this call isn't available because your OS lacks it or it couldn't be	1272	If this call isn't available because your OS lacks it or it couldn't be
940	detected, it will be emulated by calling C<fsync> instead.	1273	detected, it will be emulated by calling C<fsync> instead.
		1274
		1275	=item aio_syncfs $fh, $callback->($status)
		1276
		1277	Asynchronously call the syncfs syscall to sync the filesystem associated
		1278	to the given filehandle and call the callback with the syncfs result
		1279	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1280	errno to C<ENOSYS> nevertheless.
941		1281
942	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1282	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943		1283
944	Sync the data portion of the file specified by C<$offset> and C<$length>	1284	Sync the data portion of the file specified by C<$offset> and C<$length>
945	to disk (but NOT the metadata), by calling the Linux-specific	1285	to disk (but NOT the metadata), by calling the Linux-specific
…		…
949	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1289	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
950	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1290	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
951	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1291	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
952	manpage for details.	1292	manpage for details.
953		1293
954	=item aio_pathsync $path, $callback->($status)	1294	=item aio_pathsync $pathname, $callback->($status)
955		1295
956	This request tries to open, fsync and close the given path. This is a	1296	This request tries to open, fsync and close the given path. This is a
957	composite request intended to sync directories after directory operations	1297	composite request intended to sync directories after directory operations
958	(E.g. rename). This might not work on all operating systems or have any	1298	(E.g. rename). This might not work on all operating systems or have any
959	specific effect, but usually it makes sure that directory changes get	1299	specific effect, but usually it makes sure that directory changes get
960	written to disc. It works for anything that can be opened for read-only,	1300	written to disc. It works for anything that can be opened for read-only,
961	not just directories.	1301	not just directories.
		1302
		1303	Future versions of this function might fall back to other methods when
		1304	C<fsync> on the directory fails (such as calling C<sync>).
962		1305
963	Passes C<0> when everything went ok, and C<-1> on error.	1306	Passes C<0> when everything went ok, and C<-1> on error.
964		1307
965	=cut	1308	=cut
966		1309
…		…
987	};	1330	};
988		1331
989	$grp	1332	$grp
990	}	1333	}
991		1334
		1335	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1336
		1337	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1338	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1339	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1340	scalar must only be modified in-place while an aio operation is pending on
		1341	it).
		1342
		1343	It calls the C<msync> function of your OS, if available, with the memory
		1344	area starting at C<$offset> in the string and ending C<$length> bytes
		1345	later. If C<$length> is negative, counts from the end, and if C<$length>
		1346	is C<undef>, then it goes till the end of the string. The flags can be
		1347	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1348	C<IO::AIO::MS_INVALIDATE>.
		1349
		1350	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1351
		1352	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1353	scalars.
		1354
		1355	It touches (reads or writes) all memory pages in the specified
		1356	range inside the scalar. All caveats and parameters are the same
		1357	as for C<aio_msync>, above, except for flags, which must be either
		1358	C<0> (which reads all pages and ensures they are instantiated) or
		1359	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1360	writing an octet from it, which dirties the page).
		1361
		1362	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1363
		1364	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1365	scalars.
		1366
		1367	It reads in all the pages of the underlying storage into memory (if any)
		1368	and locks them, so they are not getting swapped/paged out or removed.
		1369
		1370	If C<$length> is undefined, then the scalar will be locked till the end.
		1371
		1372	On systems that do not implement C<mlock>, this function returns C<-1>
		1373	and sets errno to C<ENOSYS>.
		1374
		1375	Note that the corresponding C<munlock> is synchronous and is
		1376	documented under L<MISCELLANEOUS FUNCTIONS>.
		1377
		1378	Example: open a file, mmap and mlock it - both will be undone when
		1379	C<$data> gets destroyed.
		1380
		1381	open my $fh, "<", $path or die "$path: $!";
		1382	my $data;
		1383	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1384	aio_mlock $data; # mlock in background
		1385
		1386	=item aio_mlockall $flags, $callback->($status)
		1387
		1388	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1389	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1390
		1391	On systems that do not implement C<mlockall>, this function returns C<-1>
		1392	and sets errno to C<ENOSYS>.
		1393
		1394	Note that the corresponding C<munlockall> is synchronous and is
		1395	documented under L<MISCELLANEOUS FUNCTIONS>.
		1396
		1397	Example: asynchronously lock all current and future pages into memory.
		1398
		1399	aio_mlockall IO::AIO::MCL_FUTURE;
		1400
		1401	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1402
		1403	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1404	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1405	the ioctl is not available on your OS, then this request will fail with
		1406	C<ENOSYS>.
		1407
		1408	C<$start> is the starting offset to query extents for, C<$length> is the
		1409	size of the range to query - if it is C<undef>, then the whole file will
		1410	be queried.
		1411
		1412	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1413	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1414	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1415	the data portion.
		1416
		1417	C<$count> is the maximum number of extent records to return. If it is
		1418	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1419	case, if it is C<0>, then the callback receives the number of extents
		1420	instead of the extents themselves (which is unreliable, see below).
		1421
		1422	If an error occurs, the callback receives no arguments. The special
		1423	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1424
		1425	Otherwise, the callback receives an array reference with extent
		1426	structures. Each extent structure is an array reference itself, with the
		1427	following members:
		1428
		1429	[$logical, $physical, $length, $flags]
		1430
		1431	Flags is any combination of the following flag values (typically either C<0>
		1432	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1433
		1434	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1435	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1436	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1437	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1438	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1439	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1440
		1441	At the time of this writing (Linux 3.2), this request is unreliable unless
		1442	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1443	it to return all extents of a range for files with a large number of
		1444	extents. The code (only) works around all these issues if C<$count> is
		1445	C<undef>.
		1446
992	=item aio_group $callback->(...)	1447	=item aio_group $callback->(...)
993		1448
994	This is a very special aio request: Instead of doing something, it is a	1449	This is a very special aio request: Instead of doing something, it is a
995	container for other aio requests, which is useful if you want to bundle	1450	container for other aio requests, which is useful if you want to bundle
996	many requests into a single, composite, request with a definite callback	1451	many requests into a single, composite, request with a definite callback
…		…
1032	like sleep and file handle readable/writable, the overhead this creates is	1487	like sleep and file handle readable/writable, the overhead this creates is
1033	immense (it blocks a thread for a long time) so do not use this function	1488	immense (it blocks a thread for a long time) so do not use this function
1034	except to put your application under artificial I/O pressure.	1489	except to put your application under artificial I/O pressure.
1035		1490
1036	=back	1491	=back
		1492
		1493
		1494	=head2 IO::AIO::WD - multiple working directories
		1495
		1496	Your process only has one current working directory, which is used by all
		1497	threads. This makes it hard to use relative paths (some other component
		1498	could call C<chdir> at any time, and it is hard to control when the path
		1499	will be used by IO::AIO).
		1500
		1501	One solution for this is to always use absolute paths. This usually works,
		1502	but can be quite slow (the kernel has to walk the whole path on every
		1503	access), and can also be a hassle to implement.
		1504
		1505	Newer POSIX systems have a number of functions (openat, fdopendir,
		1506	futimensat and so on) that make it possible to specify working directories
		1507	per operation.
		1508
		1509	For portability, and because the clowns who "designed", or shall I write,
		1510	perpetrated this new interface were obviously half-drunk, this abstraction
		1511	cannot be perfect, though.
		1512
		1513	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1514	object. This object stores the canonicalised, absolute version of the
		1515	path, and on systems that allow it, also a directory file descriptor.
		1516
		1517	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1518	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1519	object and a pathname instead (or the IO::AIO::WD object alone, which
		1520	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1521	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1522	to that IO::AIO::WD object.
		1523
		1524	For example, to get a wd object for F</etc> and then stat F<passwd>
		1525	inside, you would write:
		1526
		1527	aio_wd "/etc", sub {
		1528	my $etcdir = shift;
		1529
		1530	# although $etcdir can be undef on error, there is generally no reason
		1531	# to check for errors here, as aio_stat will fail with ENOENT
		1532	# when $etcdir is undef.
		1533
		1534	aio_stat [$etcdir, "passwd"], sub {
		1535	# yay
		1536	};
		1537	};
		1538
		1539	The fact that C<aio_wd> is a request and not a normal function shows that
		1540	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1541	which is why it is done asynchronously.
		1542
		1543	To stat the directory obtained with C<aio_wd> above, one could write
		1544	either of the following three request calls:
		1545
		1546	aio_lstat "/etc" , sub { ... # pathname as normal string
		1547	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1548	aio_lstat $wd , sub { ... # shorthand for the previous
		1549
		1550	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1551	object and the pathname string, so you could write the following without
		1552	causing any issues due to C<$path> getting reused:
		1553
		1554	my $path = [$wd, undef];
		1555
		1556	for my $name (qw(abc def ghi)) {
		1557	$path->[1] = $name;
		1558	aio_stat $path, sub {
		1559	# ...
		1560	};
		1561	}
		1562
		1563	There are some caveats: when directories get renamed (or deleted), the
		1564	pathname string doesn't change, so will point to the new directory (or
		1565	nowhere at all), while the directory fd, if available on the system,
		1566	will still point to the original directory. Most functions accepting a
		1567	pathname will use the directory fd on newer systems, and the string on
		1568	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1569	the string form of the pathname.
		1570
		1571	So this functionality is mainly useful to get some protection against
		1572	C<chdir>, to easily get an absolute path out of a relative path for future
		1573	reference, and to speed up doing many operations in the same directory
		1574	(e.g. when stat'ing all files in a directory).
		1575
		1576	The following functions implement this working directory abstraction:
		1577
		1578	=over 4
		1579
		1580	=item aio_wd $pathname, $callback->($wd)
		1581
		1582	Asynchonously canonicalise the given pathname and convert it to an
		1583	IO::AIO::WD object representing it. If possible and supported on the
		1584	system, also open a directory fd to speed up pathname resolution relative
		1585	to this working directory.
		1586
		1587	If something goes wrong, then C<undef> is passwd to the callback instead
		1588	of a working directory object and C<$!> is set appropriately. Since
		1589	passing C<undef> as working directory component of a pathname fails the
		1590	request with C<ENOENT>, there is often no need for error checking in the
		1591	C<aio_wd> callback, as future requests using the value will fail in the
		1592	expected way.
		1593
		1594	=item IO::AIO::CWD
		1595
		1596	This is a compiletime constant (object) that represents the process
		1597	current working directory.
		1598
		1599	Specifying this object as working directory object for a pathname is as if
		1600	the pathname would be specified directly, without a directory object. For
		1601	example, these calls are functionally identical:
		1602
		1603	aio_stat "somefile", sub { ... };
		1604	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1605
		1606	=back
		1607
		1608	To recover the path associated with an IO::AIO::WD object, you can use
		1609	C<aio_realpath>:
		1610
		1611	aio_realpath $wd, sub {
		1612	warn "path is $_[0]\n";
		1613	};
		1614
		1615	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1616	sometimes, fall back to using an absolue path.
1037		1617
1038	=head2 IO::AIO::REQ CLASS	1618	=head2 IO::AIO::REQ CLASS
1039		1619
1040	All non-aggregate C<aio_*> functions return an object of this class when	1620	All non-aggregate C<aio_*> functions return an object of this class when
1041	called in non-void context.	1621	called in non-void context.
…		…
1131	=item $grp->cancel_subs	1711	=item $grp->cancel_subs
1132		1712
1133	Cancel all subrequests and clears any feeder, but not the group request	1713	Cancel all subrequests and clears any feeder, but not the group request
1134	itself. Useful when you queued a lot of events but got a result early.	1714	itself. Useful when you queued a lot of events but got a result early.
1135		1715
		1716	The group request will finish normally (you cannot add requests to the
		1717	group).
		1718
1136	=item $grp->result (...)	1719	=item $grp->result (...)
1137		1720
1138	Set the result value(s) that will be passed to the group callback when all	1721	Set the result value(s) that will be passed to the group callback when all
1139	subrequests have finished and set the groups errno to the current value	1722	subrequests have finished and set the groups errno to the current value
1140	of errno (just like calling C<errno> without an error number). By default,	1723	of errno (just like calling C<errno> without an error number). By default,
…		…
1156		1739
1157	Sets a feeder/generator on this group: every group can have an attached	1740	Sets a feeder/generator on this group: every group can have an attached
1158	generator that generates requests if idle. The idea behind this is that,	1741	generator that generates requests if idle. The idea behind this is that,
1159	although you could just queue as many requests as you want in a group,	1742	although you could just queue as many requests as you want in a group,
1160	this might starve other requests for a potentially long time. For example,	1743	this might starve other requests for a potentially long time. For example,
1161	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1744	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1162	delaying any later requests for a long time.	1745	requests, delaying any later requests for a long time.
1163		1746
1164	To avoid this, and allow incremental generation of requests, you can	1747	To avoid this, and allow incremental generation of requests, you can
1165	instead a group and set a feeder on it that generates those requests. The	1748	instead a group and set a feeder on it that generates those requests. The
1166	feed callback will be called whenever there are few enough (see C<limit>,	1749	feed callback will be called whenever there are few enough (see C<limit>,
1167	below) requests active in the group itself and is expected to queue more	1750	below) requests active in the group itself and is expected to queue more
…		…
1208	=over 4	1791	=over 4
1209		1792
1210	=item $fileno = IO::AIO::poll_fileno	1793	=item $fileno = IO::AIO::poll_fileno
1211		1794
1212	Return the I<request result pipe file descriptor>. This filehandle must be	1795	Return the I<request result pipe file descriptor>. This filehandle must be
1213	polled for reading by some mechanism outside this module (e.g. Event or	1796	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1214	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1797	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1215	to call C<poll_cb> to check the results.	1798	you have to call C<poll_cb> to check the results.
1216		1799
1217	See C<poll_cb> for an example.	1800	See C<poll_cb> for an example.
1218		1801
1219	=item IO::AIO::poll_cb	1802	=item IO::AIO::poll_cb
1220		1803
1221	Process some outstanding events on the result pipe. You have to call this	1804	Process some requests that have reached the result phase (i.e. they have
1222	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1805	been executed but the results are not yet reported). You have to call
1223	returned earlier for whatever reason. Returns immediately when no events	1806	this "regularly" to finish outstanding requests.
1224	are outstanding. The amount of events processed depends on the settings of
1225	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1226		1807
		1808	Returns C<0> if all events could be processed (or there were no
		1809	events to process), or C<-1> if it returned earlier for whatever
		1810	reason. Returns immediately when no events are outstanding. The amount
		1811	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1812	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1813
1227	If not all requests were processed for whatever reason, the filehandle	1814	If not all requests were processed for whatever reason, the poll file
1228	will still be ready when C<poll_cb> returns, so normally you don't have to	1815	descriptor will still be ready when C<poll_cb> returns, so normally you
1229	do anything special to have it called later.	1816	don't have to do anything special to have it called later.
		1817
		1818	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1819	ready, it can be beneficial to call this function from loops which submit
		1820	a lot of requests, to make sure the results get processed when they become
		1821	available and not just when the loop is finished and the event loop takes
		1822	over again. This function returns very fast when there are no outstanding
		1823	requests.
1230		1824
1231	Example: Install an Event watcher that automatically calls	1825	Example: Install an Event watcher that automatically calls
1232	IO::AIO::poll_cb with high priority:	1826	IO::AIO::poll_cb with high priority (more examples can be found in the
		1827	SYNOPSIS section, at the top of this document):
1233		1828
1234	Event->io (fd => IO::AIO::poll_fileno,	1829	Event->io (fd => IO::AIO::poll_fileno,
1235	poll => 'r', async => 1,	1830	poll => 'r', async => 1,
1236	cb => \&IO::AIO::poll_cb);	1831	cb => \&IO::AIO::poll_cb);
		1832
		1833	=item IO::AIO::poll_wait
		1834
		1835	Wait until either at least one request is in the result phase or no
		1836	requests are outstanding anymore.
		1837
		1838	This is useful if you want to synchronously wait for some requests to
		1839	become ready, without actually handling them.
		1840
		1841	See C<nreqs> for an example.
		1842
		1843	=item IO::AIO::poll
		1844
		1845	Waits until some requests have been handled.
		1846
		1847	Returns the number of requests processed, but is otherwise strictly
		1848	equivalent to:
		1849
		1850	IO::AIO::poll_wait, IO::AIO::poll_cb
		1851
		1852	=item IO::AIO::flush
		1853
		1854	Wait till all outstanding AIO requests have been handled.
		1855
		1856	Strictly equivalent to:
		1857
		1858	IO::AIO::poll_wait, IO::AIO::poll_cb
		1859	while IO::AIO::nreqs;
1237		1860
1238	=item IO::AIO::max_poll_reqs $nreqs	1861	=item IO::AIO::max_poll_reqs $nreqs
1239		1862
1240	=item IO::AIO::max_poll_time $seconds	1863	=item IO::AIO::max_poll_time $seconds
1241		1864
…		…
1266	# use a low priority so other tasks have priority	1889	# use a low priority so other tasks have priority
1267	Event->io (fd => IO::AIO::poll_fileno,	1890	Event->io (fd => IO::AIO::poll_fileno,
1268	poll => 'r', nice => 1,	1891	poll => 'r', nice => 1,
1269	cb => &IO::AIO::poll_cb);	1892	cb => &IO::AIO::poll_cb);
1270		1893
1271	=item IO::AIO::poll_wait
1272
1273	If there are any outstanding requests and none of them in the result
1274	phase, wait till the result filehandle becomes ready for reading (simply
1275	does a C<select> on the filehandle. This is useful if you want to
1276	synchronously wait for some requests to finish).
1277
1278	See C<nreqs> for an example.
1279
1280	=item IO::AIO::poll
1281
1282	Waits until some requests have been handled.
1283
1284	Returns the number of requests processed, but is otherwise strictly
1285	equivalent to:
1286
1287	IO::AIO::poll_wait, IO::AIO::poll_cb
1288
1289	=item IO::AIO::flush
1290
1291	Wait till all outstanding AIO requests have been handled.
1292
1293	Strictly equivalent to:
1294
1295	IO::AIO::poll_wait, IO::AIO::poll_cb
1296	while IO::AIO::nreqs;
1297
1298	=back	1894	=back
1299		1895
1300	=head3 CONTROLLING THE NUMBER OF THREADS	1896	=head3 CONTROLLING THE NUMBER OF THREADS
1301		1897
1302	=over	1898	=over
…		…
1335		1931
1336	Under normal circumstances you don't need to call this function.	1932	Under normal circumstances you don't need to call this function.
1337		1933
1338	=item IO::AIO::max_idle $nthreads	1934	=item IO::AIO::max_idle $nthreads
1339		1935
1340	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1936	Limit the number of threads (default: 4) that are allowed to idle
1341	threads that did not get a request to process within 10 seconds). That	1937	(i.e., threads that did not get a request to process within the idle
1342	means if a thread becomes idle while C<$nthreads> other threads are also	1938	timeout (default: 10 seconds). That means if a thread becomes idle while
1343	idle, it will free its resources and exit.	1939	C<$nthreads> other threads are also idle, it will free its resources and
		1940	exit.
1344		1941
1345	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1942	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1346	to allow for extremely high load situations, but want to free resources	1943	to allow for extremely high load situations, but want to free resources
1347	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1944	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1348		1945
1349	The default is probably ok in most situations, especially if thread	1946	The default is probably ok in most situations, especially if thread
1350	creation is fast. If thread creation is very slow on your system you might	1947	creation is fast. If thread creation is very slow on your system you might
1351	want to use larger values.	1948	want to use larger values.
1352		1949
		1950	=item IO::AIO::idle_timeout $seconds
		1951
		1952	Sets the minimum idle timeout (default 10) after which worker threads are
		1953	allowed to exit. SEe C<IO::AIO::max_idle>.
		1954
1353	=item IO::AIO::max_outstanding $maxreqs	1955	=item IO::AIO::max_outstanding $maxreqs
		1956
		1957	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1958	you do queue up more than this number of requests, the next call to
		1959	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1960	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1961	longer exceeded.
		1962
		1963	In other words, this setting does not enforce a queue limit, but can be
		1964	used to make poll functions block if the limit is exceeded.
1354		1965
1355	This is a very bad function to use in interactive programs because it	1966	This is a very bad function to use in interactive programs because it
1356	blocks, and a bad way to reduce concurrency because it is inexact: Better	1967	blocks, and a bad way to reduce concurrency because it is inexact: Better
1357	use an C<aio_group> together with a feed callback.	1968	use an C<aio_group> together with a feed callback.
1358		1969
1359	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1970	Its main use is in scripts without an event loop - when you want to stat
1360	do queue up more than this number of requests, the next call to the	1971	a lot of files, you can write something like this:
1361	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1362	function will block until the limit is no longer exceeded.
1363		1972
1364	The default value is very large, so there is no practical limit on the	1973	IO::AIO::max_outstanding 32;
1365	number of outstanding requests.
1366		1974
1367	You can still queue as many requests as you want. Therefore,	1975	for my $path (...) {
1368	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1976	aio_stat $path , ...;
1369	as a stop gap to shield against fatal memory overflow (with large values).	1977	IO::AIO::poll_cb;
		1978	}
		1979
		1980	IO::AIO::flush;
		1981
		1982	The call to C<poll_cb> inside the loop will normally return instantly, but
		1983	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1984	some requests have been handled. This keeps the loop from pushing a large
		1985	number of C<aio_stat> requests onto the queue.
		1986
		1987	The default value for C<max_outstanding> is very large, so there is no
		1988	practical limit on the number of outstanding requests.
1370		1989
1371	=back	1990	=back
1372		1991
1373	=head3 STATISTICAL INFORMATION	1992	=head3 STATISTICAL INFORMATION
1374		1993
…		…
1394	Returns the number of requests currently in the pending state (executed,	2013	Returns the number of requests currently in the pending state (executed,
1395	but not yet processed by poll_cb).	2014	but not yet processed by poll_cb).
1396		2015
1397	=back	2016	=back
1398		2017
		2018	=head3 SUBSECOND STAT TIME ACCESS
		2019
		2020	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2021	generally find access/modification and change times with subsecond time
		2022	accuracy of the system supports it, but perl's built-in functions only
		2023	return the integer part.
		2024
		2025	The following functions return the timestamps of the most recent
		2026	stat with subsecond precision on most systems and work both after
		2027	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2028	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2029	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2030
		2031	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2032	full resolution without rounding and work with standard perl C<stat>,
		2033	alleviating the need to call the special C<Time::HiRes> functions, which
		2034	do not act like their perl counterparts.
		2035
		2036	On operating systems or file systems where subsecond time resolution is
		2037	not supported or could not be detected, a fractional part of C<0> is
		2038	returned, so it is always safe to call these functions.
		2039
		2040	=over 4
		2041
		2042	=item IO::AIO::stat_atime, IO::AIO::stat_mtime, IO::AIO::stat_ctime
		2043
		2044	Return the access, modication or change time, respectively, including
		2045	fractional part. Due to the limited precision of floating point, the
		2046	accuracy on most platforms is only a bit better than milliseconds for
		2047	times around now - see the I<nsec> function family, below, for full
		2048	accuracy.
		2049
		2050	=item ($atime, $mtime, $ctime, ...) = IO::AIO::stat_xtime
		2051
		2052	Returns access, modification and change time all in one go, and maybe more
		2053	times in the future version.
		2054
		2055	=item IO::AIO::stat_atimensec, IO::AIO::stat_mtimensec, IO::AIO::stat_ctimensec
		2056
		2057	Return the fractional access, modifcation or change time, in nanoseconds,
		2058	as an integer in the range C<0> to C<999999999>.
		2059
		2060	=back
		2061
		2062	Example: print the high resolution modification time of F</etc>, using
		2063	C<stat>, and C<IO::AIO::aio_stat>.
		2064
		2065	if (stat "/etc") {
		2066	printf "stat(/etc) mtime: %f\n", IO::AIO::stat_mtime;
		2067	}
		2068
		2069	IO::AIO::aio_stat "/etc", sub {
		2070	$_[0]
		2071	and return;
		2072
		2073	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::stat_mtimensec;
		2074	};
		2075
		2076	IO::AIO::flush;
		2077
		2078	Output of the awbove on my system, showing reduced and full accuracy:
		2079
		2080	stat(/etc) mtime: 1534043702.020808
		2081	aio_stat(/etc) mtime: 1534043702.020807792
		2082
		2083	=head3 MISCELLANEOUS FUNCTIONS
		2084
		2085	IO::AIO implements some functions that are useful when you want to use
		2086	some "Advanced I/O" function not available to in Perl, without going the
		2087	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2088	counterpart.
		2089
		2090	=over 4
		2091
		2092	=item $numfd = IO::AIO::get_fdlimit
		2093
		2094	This function is I<EXPERIMENTAL> and subject to change.
		2095
		2096	Tries to find the current file descriptor limit and returns it, or
		2097	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2098	the highest valid file descriptor number.
		2099
		2100	=item IO::AIO::min_fdlimit [$numfd]
		2101
		2102	This function is I<EXPERIMENTAL> and subject to change.
		2103
		2104	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2105	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2106	is missing, it will try to set a very high limit, although this is not
		2107	recommended when you know the actual minimum that you require.
		2108
		2109	If the limit cannot be raised enough, the function makes a best-effort
		2110	attempt to increase the limit as much as possible, using various
		2111	tricks, while still failing. You can query the resulting limit using
		2112	C<IO::AIO::get_fdlimit>.
		2113
		2114	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2115	true.
		2116
		2117	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2118
		2119	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2120	but is blocking (this makes most sense if you know the input data is
		2121	likely cached already and the output filehandle is set to non-blocking
		2122	operations).
		2123
		2124	Returns the number of bytes copied, or C<-1> on error.
		2125
		2126	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2127
		2128	Simply calls the C<posix_fadvise> function (see its
		2129	manpage for details). The following advice constants are
		2130	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2131	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2132	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2133
		2134	On systems that do not implement C<posix_fadvise>, this function returns
		2135	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2136
		2137	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2138
		2139	Simply calls the C<posix_madvise> function (see its
		2140	manpage for details). The following advice constants are
		2141	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2142	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2143	C<IO::AIO::MADV_DONTNEED>.
		2144
		2145	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2146	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2147	will be reduced to fit into the C<$scalar>.
		2148
		2149	On systems that do not implement C<posix_madvise>, this function returns
		2150	ENOSYS, otherwise the return value of C<posix_madvise>.
		2151
		2152	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2153
		2154	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2155	$scalar (see its manpage for details). The following protect
		2156	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2157	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2158
		2159	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2160	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2161	will be reduced to fit into the C<$scalar>.
		2162
		2163	On systems that do not implement C<mprotect>, this function returns
		2164	ENOSYS, otherwise the return value of C<mprotect>.
		2165
		2166	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2167
		2168	Memory-maps a file (or anonymous memory range) and attaches it to the
		2169	given C<$scalar>, which will act like a string scalar. Returns true on
		2170	success, and false otherwise.
		2171
		2172	The scalar must exist, but its contents do not matter - this means you
		2173	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2174	the scalar first.
		2175
		2176	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2177	which don't change the string length, and most read-only operations such
		2178	as copying it or searching it with regexes and so on.
		2179
		2180	Anything else is unsafe and will, at best, result in memory leaks.
		2181
		2182	The memory map associated with the C<$scalar> is automatically removed
		2183	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2184	or C<IO::AIO::munmap> functions are called on it.
		2185
		2186	This calls the C<mmap>(2) function internally. See your system's manual
		2187	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2188
		2189	The C<$length> must be larger than zero and smaller than the actual
		2190	filesize.
		2191
		2192	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2193	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2194
		2195	C<$flags> can be a combination of
		2196	C<IO::AIO::MAP_SHARED> or
		2197	C<IO::AIO::MAP_PRIVATE>,
		2198	or a number of system-specific flags (when not available, the are C<0>):
		2199	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2200	C<IO::AIO::MAP_LOCKED>,
		2201	C<IO::AIO::MAP_NORESERVE>,
		2202	C<IO::AIO::MAP_POPULATE>,
		2203	C<IO::AIO::MAP_NONBLOCK>,
		2204	C<IO::AIO::MAP_FIXED>,
		2205	C<IO::AIO::MAP_GROWSDOWN>,
		2206	C<IO::AIO::MAP_32BIT>,
		2207	C<IO::AIO::MAP_HUGETLB> or
		2208	C<IO::AIO::MAP_STACK>.
		2209
		2210	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2211
		2212	C<$offset> is the offset from the start of the file - it generally must be
		2213	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2214
		2215	Example:
		2216
		2217	use Digest::MD5;
		2218	use IO::AIO;
		2219
		2220	open my $fh, "<verybigfile"
		2221	or die "$!";
		2222
		2223	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2224	or die "verybigfile: $!";
		2225
		2226	my $fast_md5 = md5 $data;
		2227
		2228	=item IO::AIO::munmap $scalar
		2229
		2230	Removes a previous mmap and undefines the C<$scalar>.
		2231
		2232	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2233
		2234	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2235	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2236	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2237
		2238	Returns true if successful, and false otherwise. If the underlying mmapped
		2239	region has changed address, then the true value has the numerical value
		2240	C<1>, otherwise it has the numerical value C<0>:
		2241
		2242	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2243	or die "mremap: $!";
		2244
		2245	if ($success*1) {
		2246	warn "scalar has chanegd address in memory\n";
		2247	}
		2248
		2249	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2250	implemented, but not supported and might go away in a future version.
		2251
		2252	On systems where this call is not supported or is not emulated, this call
		2253	returns falls and sets C<$!> to C<ENOSYS>.
		2254
		2255	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2256
		2257	Calls the C<munlock> function, undoing the effects of a previous
		2258	C<aio_mlock> call (see its description for details).
		2259
		2260	=item IO::AIO::munlockall
		2261
		2262	Calls the C<munlockall> function.
		2263
		2264	On systems that do not implement C<munlockall>, this function returns
		2265	ENOSYS, otherwise the return value of C<munlockall>.
		2266
		2267	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2268
		2269	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2270	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2271	should be the file offset.
		2272
		2273	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2274	silently corrupt the data in this case.
		2275
		2276	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2277	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2278	C<IO::AIO::SPLICE_F_GIFT>.
		2279
		2280	See the C<splice(2)> manpage for details.
		2281
		2282	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2283
		2284	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2285	description for C<IO::AIO::splice> above for details.
		2286
		2287	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2288
		2289	Attempts to query or change the pipe buffer size. Obviously works only
		2290	on pipes, and currently works only on GNU/Linux systems, and fails with
		2291	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2292	size on other systems, drop me a note.
		2293
		2294	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2295
		2296	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2297	C<$flags> is missing or C<0>, then this should be the same as a call to
		2298	perl's built-in C<pipe> function and create a new pipe, and works on
		2299	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2300	(..., 4096, O_BINARY)>.
		2301
		2302	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2303	the given flags (Linux 2.6.27, glibc 2.9).
		2304
		2305	On success, the read and write file handles are returned.
		2306
		2307	On error, nothing will be returned. If the pipe2 syscall is missing and
		2308	C<$flags> is non-zero, fails with C<ENOSYS>.
		2309
		2310	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2311	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2312	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2313
		2314	Example: create a pipe race-free w.r.t. threads and fork:
		2315
		2316	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2317	or die "pipe2: $!\n";
		2318
		2319	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2320
		2321	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2322	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2323
		2324	On success, the new eventfd filehandle is returned, otherwise returns
		2325	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2326
		2327	Please refer to L<eventfd(2)> for more info on this call.
		2328
		2329	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2330	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2331
		2332	Example: create a new eventfd filehandle:
		2333
		2334	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2335	or die "eventfd: $!\n";
		2336
		2337	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2338
		2339	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2340	(unhelpful) default for C<$flags> is C<0>.
		2341
		2342	On success, the new timerfd filehandle is returned, otherwise returns
		2343	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2344
		2345	Please refer to L<timerfd_create(2)> for more info on this call.
		2346
		2347	The following C<$clockid> values are
		2348	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2349	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2350	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2351	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2352
		2353	The following C<$flags> values are available (Linux
		2354	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2355
		2356	Example: create a new timerfd and set it to one-second repeated alarms,
		2357	then wait for two alarms:
		2358
		2359	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2360	or die "timerfd_create: $!\n";
		2361
		2362	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2363	or die "timerfd_settime: $!\n";
		2364
		2365	for (1..2) {
		2366	8 == sysread $fh, my $buf, 8
		2367	or die "timerfd read failure\n";
		2368
		2369	printf "number of expirations (likely 1): %d\n",
		2370	unpack "Q", $buf;
		2371	}
		2372
		2373	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2374
		2375	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2376	call. Please refer to its manpage for more info on this call.
		2377
		2378	The new itimerspec is specified using two (possibly fractional) second
		2379	values, C<$new_interval> and C<$new_value>).
		2380
		2381	On success, the current interval and value are returned (as per
		2382	C<timerfd_gettime>). On failure, the empty list is returned.
		2383
		2384	The following C<$flags> values are
		2385	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2386	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2387
		2388	See C<IO::AIO::timerfd_create> for a full example.
		2389
		2390	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2391
		2392	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2393	call. Please refer to its manpage for more info on this call.
		2394
		2395	On success, returns the current values of interval and value for the given
		2396	timerfd (as potentially fractional second values). On failure, the empty
		2397	list is returned.
		2398
		2399	=back
		2400
1399	=cut	2401	=cut
1400		2402
1401	min_parallel 8;	2403	min_parallel 8;
1402		2404
1403	END { flush }	2405	END { flush }
1404		2406
1405	1;	2407	1;
1406		2408
		2409	=head1 EVENT LOOP INTEGRATION
		2410
		2411	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2412	automatically into many event loops:
		2413
		2414	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2415	use AnyEvent::AIO;
		2416
		2417	You can also integrate IO::AIO manually into many event loops, here are
		2418	some examples of how to do this:
		2419
		2420	# EV integration
		2421	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2422
		2423	# Event integration
		2424	Event->io (fd => IO::AIO::poll_fileno,
		2425	poll => 'r',
		2426	cb => \&IO::AIO::poll_cb);
		2427
		2428	# Glib/Gtk2 integration
		2429	add_watch Glib::IO IO::AIO::poll_fileno,
		2430	in => sub { IO::AIO::poll_cb; 1 };
		2431
		2432	# Tk integration
		2433	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2434	readable => \&IO::AIO::poll_cb);
		2435
		2436	# Danga::Socket integration
		2437	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2438	\&IO::AIO::poll_cb);
		2439
1407	=head2 FORK BEHAVIOUR	2440	=head2 FORK BEHAVIOUR
1408		2441
1409	This module should do "the right thing" when the process using it forks:	2442	Usage of pthreads in a program changes the semantics of fork
		2443	considerably. Specifically, only async-safe functions can be called after
		2444	fork. Perl doesn't know about this, so in general, you cannot call fork
		2445	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2446	pthreads, so this applies, but many other extensions and (for inexplicable
		2447	reasons) perl itself often is linked against pthreads, so this limitation
		2448	applies to quite a lot of perls.
1410		2449
1411	Before the fork, IO::AIO enters a quiescent state where no requests	2450	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1412	can be added in other threads and no results will be processed. After	2451	only works in the process that loaded it. Forking is fully supported, but
1413	the fork the parent simply leaves the quiescent state and continues	2452	using IO::AIO in the child is not.
1414	request/result processing, while the child frees the request/result queue
1415	(so that the requests started before the fork will only be handled in the
1416	parent). Threads will be started on demand until the limit set in the
1417	parent process has been reached again.
1418		2453
1419	In short: the parent will, after a short pause, continue as if fork had	2454	You might get around by not I<using> IO::AIO before (or after)
1420	not been called, while the child will act as if IO::AIO has not been used	2455	forking. You could also try to call the L<IO::AIO::reinit> function in the
1421	yet.	2456	child:
		2457
		2458	=over 4
		2459
		2460	=item IO::AIO::reinit
		2461
		2462	Abandons all current requests and I/O threads and simply reinitialises all
		2463	data structures. This is not an operation supported by any standards, but
		2464	happens to work on GNU/Linux and some newer BSD systems.
		2465
		2466	The only reasonable use for this function is to call it after forking, if
		2467	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2468	the process will result in undefined behaviour. Calling it at any time
		2469	will also result in any undefined (by POSIX) behaviour.
		2470
		2471	=back
		2472
		2473	=head2 LINUX-SPECIFIC CALLS
		2474
		2475	When a call is documented as "linux-specific" then this means it
		2476	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2477	availability and compatibility of such calls regardless of the platform
		2478	it is compiled on, so platforms such as FreeBSD which often implement
		2479	these calls will work. When in doubt, call them and see if they fail wth
		2480	C<ENOSYS>.
1422		2481
1423	=head2 MEMORY USAGE	2482	=head2 MEMORY USAGE
1424		2483
1425	Per-request usage:	2484	Per-request usage:
1426		2485
…		…
1439	temporary buffers, and each thread requires a stack and other data	2498	temporary buffers, and each thread requires a stack and other data
1440	structures (usually around 16k-128k, depending on the OS).	2499	structures (usually around 16k-128k, depending on the OS).
1441		2500
1442	=head1 KNOWN BUGS	2501	=head1 KNOWN BUGS
1443		2502
1444	Known bugs will be fixed in the next release.	2503	Known bugs will be fixed in the next release :)
		2504
		2505	=head1 KNOWN ISSUES
		2506
		2507	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2508	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2509	non-created hash slots or other scalars I didn't think of. It's best to
		2510	avoid such and either use scalar variables or making sure that the scalar
		2511	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2512
		2513	I am not sure anything can be done about this, so this is considered a
		2514	known issue, rather than a bug.
1445		2515
1446	=head1 SEE ALSO	2516	=head1 SEE ALSO
1447		2517
1448	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2518	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1449	more natural syntax.	2519	more natural syntax.

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