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Revision 1.128 by root, Thu May 29 03:20:40 2008 UTC vs.
Revision 1.275 by root, Fri Sep 22 05:20:39 2017 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 = '3.03';	176	our $VERSION = 4.35;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_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_wd);
207		189
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	193	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
		197
		198	push @AIO_REQ, qw(aio_busy); # not exported
213		199
214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
215		201
216	require XSLoader;	202	require XSLoader;
217	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
218	}	204	}
219		205
220	=head1 FUNCTIONS	206	=head1 FUNCTIONS
221		207
222	=head2 AIO REQUEST FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		239	aio_mkdir $pathname, $mode, $callback->($status)
		240	aio_rmdir $pathname, $callback->($status)
		241	aio_readdir $pathname, $callback->($entries)
		242	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		243	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		244	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		245	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		246	aio_load $pathname, $data, $callback->($status)
		247	aio_copy $srcpath, $dstpath, $callback->($status)
		248	aio_move $srcpath, $dstpath, $callback->($status)
		249	aio_rmtree $pathname, $callback->($status)
		250	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		251	aio_ioctl $fh, $request, $buf, $callback->($status)
		252	aio_sync $callback->($status)
		253	aio_syncfs $fh, $callback->($status)
		254	aio_fsync $fh, $callback->($status)
		255	aio_fdatasync $fh, $callback->($status)
		256	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		257	aio_pathsync $pathname, $callback->($status)
		258	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		259	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		260	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		261	aio_mlockall $flags, $callback->($status)
		262	aio_group $callback->(...)
		263	aio_nop $callback->()
		264
		265	$prev_pri = aioreq_pri [$pri]
		266	aioreq_nice $pri_adjust
		267
		268	IO::AIO::poll_wait
		269	IO::AIO::poll_cb
		270	IO::AIO::poll
		271	IO::AIO::flush
		272	IO::AIO::max_poll_reqs $nreqs
		273	IO::AIO::max_poll_time $seconds
		274	IO::AIO::min_parallel $nthreads
		275	IO::AIO::max_parallel $nthreads
		276	IO::AIO::max_idle $nthreads
		277	IO::AIO::idle_timeout $seconds
		278	IO::AIO::max_outstanding $maxreqs
		279	IO::AIO::nreqs
		280	IO::AIO::nready
		281	IO::AIO::npending
		282	IO::AIO::min_fdlimit $nfd;
		283
		284	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		285	IO::AIO::fadvise $fh, $offset, $len, $advice
		286	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		287	IO::AIO::munmap $scalar
		288	IO::AIO::madvise $scalar, $offset, $length, $advice
		289	IO::AIO::mprotect $scalar, $offset, $length, $protect
		290	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		291	IO::AIO::munlockall
		292
		293	=head2 API NOTES
223		294
224	All the C<aio_*> calls are more or less thin wrappers around the syscall	295	All the C<aio_*> calls are more or less thin wrappers around the syscall
225	with the same name (sans C<aio_>). The arguments are similar or identical,	296	with the same name (sans C<aio_>). The arguments are similar or identical,
226	and they all accept an additional (and optional) C<$callback> argument	297	and they all accept an additional (and optional) C<$callback> argument
227	which must be a code reference. This code reference will get called with	298	which must be a code reference. This code reference will be called after
228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	299	the syscall has been executed in an asynchronous fashion. The results
229	perl, which usually delivers "false") as it's sole argument when the given	300	of the request will be passed as arguments to the callback (and, if an
230	syscall has been executed asynchronously.	301	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		302	most syscalls return C<-1> on error, unlike perl, which usually delivers
		303	"false").
		304
		305	Some requests (such as C<aio_readdir>) pass the actual results and
		306	communicate failures by passing C<undef>.
231		307
232	All functions expecting a filehandle keep a copy of the filehandle	308	All functions expecting a filehandle keep a copy of the filehandle
233	internally until the request has finished.	309	internally until the request has finished.
234		310
235	All functions return request objects of type L<IO::AIO::REQ> that allow	311	All functions return request objects of type L<IO::AIO::REQ> that allow
236	further manipulation of those requests while they are in-flight.	312	further manipulation of those requests while they are in-flight.
237		313
238	The pathnames you pass to these routines I<must> be absolute and	314	The pathnames you pass to these routines I<should> be absolute. The
239	encoded as octets. The reason for the former is that at the time the	315	reason for this is that at the time the request is being executed, the
240	request is being executed, the current working directory could have	316	current working directory could have changed. Alternatively, you can
241	changed. Alternatively, you can make sure that you never change the	317	make sure that you never change the current working directory anywhere
242	current working directory anywhere in the program and then use relative	318	in the program and then use relative paths. You can also take advantage
243	paths.	319	of IO::AIOs working directory abstraction, that lets you specify paths
		320	relative to some previously-opened "working directory object" - see the
		321	description of the C<IO::AIO::WD> class later in this document.
244		322
245	To encode pathnames as octets, either make sure you either: a) always pass	323	To encode pathnames as octets, either make sure you either: a) always pass
246	in filenames you got from outside (command line, readdir etc.) without	324	in filenames you got from outside (command line, readdir etc.) without
247	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	325	tinkering, b) are in your native filesystem encoding, c) use the Encode
248	your pathnames to the locale (or other) encoding in effect in the user	326	module and encode your pathnames to the locale (or other) encoding in
249	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	327	effect in the user environment, d) use Glib::filename_from_unicode on
250	use something else to ensure your scalar has the correct contents.	328	unicode filenames or e) use something else to ensure your scalar has the
		329	correct contents.
251		330
252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	331	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
253	handles correctly wether it is set or not.	332	handles correctly whether it is set or not.
		333
		334	=head2 AIO REQUEST FUNCTIONS
254		335
255	=over 4	336	=over 4
256		337
257	=item $prev_pri = aioreq_pri [$pri]	338	=item $prev_pri = aioreq_pri [$pri]
258		339
…		…
288		369
289		370
290	=item aio_open $pathname, $flags, $mode, $callback->($fh)	371	=item aio_open $pathname, $flags, $mode, $callback->($fh)
291		372
292	Asynchronously open or create a file and call the callback with a newly	373	Asynchronously open or create a file and call the callback with a newly
293	created filehandle for the file.	374	created filehandle for the file (or C<undef> in case of an error).
294		375
295	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	376	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
296	for an explanation.	377	for an explanation.
297		378
298	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	379	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
305	by the umask in effect then the request is being executed, so better never	386	by the umask in effect then the request is being executed, so better never
306	change the umask.	387	change the umask.
307		388
308	Example:	389	Example:
309		390
310	aio_open "/etc/passwd", O_RDONLY, 0, sub {	391	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
311	if ($_[0]) {	392	if ($_[0]) {
312	print "open successful, fh is $_[0]\n";	393	print "open successful, fh is $_[0]\n";
313	...	394	...
314	} else {	395	} else {
315	die "open failed: $!\n";	396	die "open failed: $!\n";
316	}	397	}
317	};	398	};
318		399
		400	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		401	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		402	following POSIX and non-POSIX constants are available (missing ones on
		403	your system are, as usual, C<0>):
		404
		405	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		406	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		407	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		408
319		409
320	=item aio_close $fh, $callback->($status)	410	=item aio_close $fh, $callback->($status)
321		411
322	Asynchronously close a file and call the callback with the result	412	Asynchronously close a file and call the callback with the result
323	code.	413	code.
…		…
332	Or in other words: the file descriptor will be closed, but it will not be	422	Or in other words: the file descriptor will be closed, but it will not be
333	free for reuse until the perl filehandle is closed.	423	free for reuse until the perl filehandle is closed.
334		424
335	=cut	425	=cut
336		426
		427	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		428
		429	Seeks the filehandle to the new C<$offset>, similarly to perl's
		430	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		431	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		432	C<IO::AIO::SEEK_END>).
		433
		434	The resulting absolute offset will be passed to the callback, or C<-1> in
		435	case of an error.
		436
		437	In theory, the C<$whence> constants could be different than the
		438	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		439	so don't panic.
		440
		441	As a GNU/Linux (and maybe Solaris) extension, also the constants
		442	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		443	could be found. No guarantees about suitability for use in C<aio_seek> or
		444	Perl's C<sysseek> can be made though, although I would naively assume they
		445	"just work".
		446
337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
338		448
339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		450
341	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>	451	Reads or writes C<$length> bytes from or to the specified C<$fh> and
342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the	452	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
343	callback without the actual number of bytes read (or -1 on error, just	453	calls the callback with the actual number of bytes transferred (or -1 on
344	like the syscall).	454	error, just like the syscall).
		455
		456	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		457	offset plus the actual number of bytes read.
345		458
346	If C<$offset> is undefined, then the current file descriptor offset will	459	If C<$offset> is undefined, then the current file descriptor offset will
347	be used (and updated), otherwise the file descriptor offset will not be	460	be used (and updated), otherwise the file descriptor offset will not be
348	changed by these calls.	461	changed by these calls.
349		462
350	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.	463	If C<$length> is undefined in C<aio_write>, use the remaining length of
		464	C<$data>.
351		465
352	If C<$dataoffset> is less than zero, it will be counted from the end of	466	If C<$dataoffset> is less than zero, it will be counted from the end of
353	C<$data>.	467	C<$data>.
354		468
355	The C<$data> scalar I<MUST NOT> be modified in any way while the request	469	The C<$data> scalar I<MUST NOT> be modified in any way while the request
…		…
369		483
370	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	484	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
371	reading at byte offset C<$in_offset>, and starts writing at the current	485	reading at byte offset C<$in_offset>, and starts writing at the current
372	file offset of C<$out_fh>. Because of that, it is not safe to issue more	486	file offset of C<$out_fh>. Because of that, it is not safe to issue more
373	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	487	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
374	other.	488	other. The same C<$in_fh> works fine though, as this function does not
		489	move or use the file offset of C<$in_fh>.
375		490
		491	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		492	are written, and there is no way to find out how many more bytes have been
		493	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		494	number of bytes written to C<$out_fh>. Only if the result value equals
		495	C<$length> one can assume that C<$length> bytes have been read.
		496
		497	Unlike with other C<aio_> functions, it makes a lot of sense to use
		498	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		499	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		500	the socket I/O will be non-blocking. Note, however, that you can run
		501	into a trap where C<aio_sendfile> reads some data with readahead, then
		502	fails to write all data, and when the socket is ready the next time, the
		503	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		504	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		505	resource usage.
		506
376	This call tries to make use of a native C<sendfile> syscall to provide	507	This call tries to make use of a native C<sendfile>-like syscall to
377	zero-copy operation. For this to work, C<$out_fh> should refer to a	508	provide zero-copy operation. For this to work, C<$out_fh> should refer to
378	socket, and C<$in_fh> should refer to mmap'able file.	509	a socket, and C<$in_fh> should refer to an mmap'able file.
379		510
380	If the native sendfile call fails or is not implemented, it will be	511	If a native sendfile cannot be found or it fails with C<ENOSYS>,
381	emulated, so you can call C<aio_sendfile> on any type of filehandle	512	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		513	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
382	regardless of the limitations of the operating system.	514	type of filehandle regardless of the limitations of the operating system.
383		515
384	Please note, however, that C<aio_sendfile> can read more bytes from	516	As native sendfile syscalls (as practically any non-POSIX interface hacked
385	C<$in_fh> than are written, and there is no way to find out how many	517	together in a hurry to improve benchmark numbers) tend to be rather buggy
386	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	518	on many systems, this implementation tries to work around some known bugs
387	provides the number of bytes written to C<$out_fh>. Only if the result	519	in Linux and FreeBSD kernels (probably others, too), but that might fail,
388	value equals C<$length> one can assume that C<$length> bytes have been	520	so you really really should check the return value of C<aio_sendfile> -
389	read.	521	fewer bytes than expected might have been transferred.
390		522
391		523
392	=item aio_readahead $fh,$offset,$length, $callback->($retval)	524	=item aio_readahead $fh,$offset,$length, $callback->($retval)
393		525
394	C<aio_readahead> populates the page cache with data from a file so that	526	C<aio_readahead> populates the page cache with data from a file so that
…		…
398	whole pages, so that offset is effectively rounded down to a page boundary	530	whole pages, so that offset is effectively rounded down to a page boundary
399	and bytes are read up to the next page boundary greater than or equal to	531	and bytes are read up to the next page boundary greater than or equal to
400	(off-set+length). C<aio_readahead> does not read beyond the end of the	532	(off-set+length). C<aio_readahead> does not read beyond the end of the
401	file. The current file offset of the file is left unchanged.	533	file. The current file offset of the file is left unchanged.
402		534
403	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	535	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
404	emulated by simply reading the data, which would have a similar effect.	536	be emulated by simply reading the data, which would have a similar effect.
405		537
406		538
407	=item aio_stat $fh_or_path, $callback->($status)	539	=item aio_stat $fh_or_path, $callback->($status)
408		540
409	=item aio_lstat $fh, $callback->($status)	541	=item aio_lstat $fh, $callback->($status)
…		…
416	for an explanation.	548	for an explanation.
417		549
418	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	550	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
419	error when stat'ing a large file, the results will be silently truncated	551	error when stat'ing a large file, the results will be silently truncated
420	unless perl itself is compiled with large file support.	552	unless perl itself is compiled with large file support.
		553
		554	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		555	following constants and functions (if not implemented, the constants will
		556	be C<0> and the functions will either C<croak> or fall back on traditional
		557	behaviour).
		558
		559	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		560	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		561	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
421		562
422	Example: Print the length of F</etc/passwd>:	563	Example: Print the length of F</etc/passwd>:
423		564
424	aio_stat "/etc/passwd", sub {	565	aio_stat "/etc/passwd", sub {
425	$_[0] and die "stat failed: $!";	566	$_[0] and die "stat failed: $!";
426	print "size is ", -s _, "\n";	567	print "size is ", -s _, "\n";
427	};	568	};
428		569
429		570
		571	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		572
		573	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		574	whether a file handle or path was passed.
		575
		576	On success, the callback is passed a hash reference with the following
		577	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		578	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		579	is passed.
		580
		581	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		582	C<ST_NOSUID>.
		583
		584	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		585	their correct value when available, or to C<0> on systems that do
		586	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		587	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		588	C<ST_NODIRATIME> and C<ST_RELATIME>.
		589
		590	Example: stat C</wd> and dump out the data if successful.
		591
		592	aio_statvfs "/wd", sub {
		593	my $f = $_[0]
		594	or die "statvfs: $!";
		595
		596	use Data::Dumper;
		597	say Dumper $f;
		598	};
		599
		600	# result:
		601	{
		602	bsize => 1024,
		603	bfree => 4333064312,
		604	blocks => 10253828096,
		605	files => 2050765568,
		606	flag => 4096,
		607	favail => 2042092649,
		608	bavail => 4333064312,
		609	ffree => 2042092649,
		610	namemax => 255,
		611	frsize => 1024,
		612	fsid => 1810
		613	}
		614
		615	Here is a (likely partial - send me updates!) list of fsid values used by
		616	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		617
		618	0x0000adf5 adfs
		619	0x0000adff affs
		620	0x5346414f afs
		621	0x09041934 anon-inode filesystem
		622	0x00000187 autofs
		623	0x42465331 befs
		624	0x1badface bfs
		625	0x42494e4d binfmt_misc
		626	0x9123683e btrfs
		627	0x0027e0eb cgroupfs
		628	0xff534d42 cifs
		629	0x73757245 coda
		630	0x012ff7b7 coh
		631	0x28cd3d45 cramfs
		632	0x453dcd28 cramfs-wend (wrong endianness)
		633	0x64626720 debugfs
		634	0x00001373 devfs
		635	0x00001cd1 devpts
		636	0x0000f15f ecryptfs
		637	0x00414a53 efs
		638	0x0000137d ext
		639	0x0000ef53 ext2/ext3/ext4
		640	0x0000ef51 ext2
		641	0xf2f52010 f2fs
		642	0x00004006 fat
		643	0x65735546 fuseblk
		644	0x65735543 fusectl
		645	0x0bad1dea futexfs
		646	0x01161970 gfs2
		647	0x47504653 gpfs
		648	0x00004244 hfs
		649	0xf995e849 hpfs
		650	0x00c0ffee hostfs
		651	0x958458f6 hugetlbfs
		652	0x2bad1dea inotifyfs
		653	0x00009660 isofs
		654	0x000072b6 jffs2
		655	0x3153464a jfs
		656	0x6b414653 k-afs
		657	0x0bd00bd0 lustre
		658	0x0000137f minix
		659	0x0000138f minix 30 char names
		660	0x00002468 minix v2
		661	0x00002478 minix v2 30 char names
		662	0x00004d5a minix v3
		663	0x19800202 mqueue
		664	0x00004d44 msdos
		665	0x0000564c novell
		666	0x00006969 nfs
		667	0x6e667364 nfsd
		668	0x00003434 nilfs
		669	0x5346544e ntfs
		670	0x00009fa1 openprom
		671	0x7461636F ocfs2
		672	0x00009fa0 proc
		673	0x6165676c pstorefs
		674	0x0000002f qnx4
		675	0x68191122 qnx6
		676	0x858458f6 ramfs
		677	0x52654973 reiserfs
		678	0x00007275 romfs
		679	0x67596969 rpc_pipefs
		680	0x73636673 securityfs
		681	0xf97cff8c selinux
		682	0x0000517b smb
		683	0x534f434b sockfs
		684	0x73717368 squashfs
		685	0x62656572 sysfs
		686	0x012ff7b6 sysv2
		687	0x012ff7b5 sysv4
		688	0x01021994 tmpfs
		689	0x15013346 udf
		690	0x00011954 ufs
		691	0x54190100 ufs byteswapped
		692	0x00009fa2 usbdevfs
		693	0x01021997 v9fs
		694	0xa501fcf5 vxfs
		695	0xabba1974 xenfs
		696	0x012ff7b4 xenix
		697	0x58465342 xfs
		698	0x012fd16d xia
		699
430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	700	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
431		701
432	Works like perl's C<utime> function (including the special case of $atime	702	Works like perl's C<utime> function (including the special case of $atime
433	and $mtime being undef). Fractional times are supported if the underlying	703	and $mtime being undef). Fractional times are supported if the underlying
434	syscalls support them.	704	syscalls support them.
…		…
461	=item aio_truncate $fh_or_path, $offset, $callback->($status)	731	=item aio_truncate $fh_or_path, $offset, $callback->($status)
462		732
463	Works like truncate(2) or ftruncate(2).	733	Works like truncate(2) or ftruncate(2).
464		734
465		735
		736	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		737
		738	Allocates or frees disk space according to the C<$mode> argument. See the
		739	linux C<fallocate> documentation for details.
		740
		741	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		742	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		743	to deallocate a file range.
		744
		745	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		746	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		747	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		748	to unshare shared blocks (see your L<fallocate(2)> manpage).
		749
		750	The file system block size used by C<fallocate> is presumably the
		751	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		752	can dictate other limitations.
		753
		754	If C<fallocate> isn't available or cannot be emulated (currently no
		755	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		756
		757
466	=item aio_chmod $fh_or_path, $mode, $callback->($status)	758	=item aio_chmod $fh_or_path, $mode, $callback->($status)
467		759
468	Works like perl's C<chmod> function.	760	Works like perl's C<chmod> function.
469		761
470		762
…		…
472		764
473	Asynchronously unlink (delete) a file and call the callback with the	765	Asynchronously unlink (delete) a file and call the callback with the
474	result code.	766	result code.
475		767
476		768
477	=item aio_mknod $path, $mode, $dev, $callback->($status)	769	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
478		770
479	[EXPERIMENTAL]	771	[EXPERIMENTAL]
480		772
481	Asynchronously create a device node (or fifo). See mknod(2).	773	Asynchronously create a device node (or fifo). See mknod(2).
482		774
483	The only (POSIX-) portable way of calling this function is:	775	The only (POSIX-) portable way of calling this function is:
484		776
485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	777	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
486		778
		779	See C<aio_stat> for info about some potentially helpful extra constants
		780	and functions.
487		781
488	=item aio_link $srcpath, $dstpath, $callback->($status)	782	=item aio_link $srcpath, $dstpath, $callback->($status)
489		783
490	Asynchronously create a new link to the existing object at C<$srcpath> at	784	Asynchronously create a new link to the existing object at C<$srcpath> at
491	the path C<$dstpath> and call the callback with the result code.	785	the path C<$dstpath> and call the callback with the result code.
…		…
495		789
496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	790	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	791	the path C<$dstpath> and call the callback with the result code.
498		792
499		793
500	=item aio_readlink $path, $callback->($link)	794	=item aio_readlink $pathname, $callback->($link)
501		795
502	Asynchronously read the symlink specified by C<$path> and pass it to	796	Asynchronously read the symlink specified by C<$path> and pass it to
503	the callback. If an error occurs, nothing or undef gets passed to the	797	the callback. If an error occurs, nothing or undef gets passed to the
504	callback.	798	callback.
505		799
506		800
		801	=item aio_realpath $pathname, $callback->($path)
		802
		803	Asynchronously make the path absolute and resolve any symlinks in
		804	C<$path>. The resulting path only consists of directories (same as
		805	L<Cwd::realpath>).
		806
		807	This request can be used to get the absolute path of the current working
		808	directory by passing it a path of F<.> (a single dot).
		809
		810
507	=item aio_rename $srcpath, $dstpath, $callback->($status)	811	=item aio_rename $srcpath, $dstpath, $callback->($status)
508		812
509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	813	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
510	rename(2) and call the callback with the result code.	814	rename(2) and call the callback with the result code.
		815
		816	On systems that support the AIO::WD working directory abstraction
		817	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		818	of failing, C<rename> is called on the absolute path of C<$wd>.
		819
		820
		821	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		822
		823	Basically a version of C<aio_rename> with an additional C<$flags>
		824	argument. Calling this with C<$flags=0> is the same as calling
		825	C<aio_rename>.
		826
		827	Non-zero flags are currently only supported on GNU/Linux systems that
		828	support renameat2. Other systems fail with C<ENOSYS> in this case.
		829
		830	The following constants are available (missing ones are, as usual C<0>),
		831	see renameat2(2) for details:
		832
		833	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		834	and C<IO::AIO::RENAME_WHITEOUT>.
511		835
512		836
513	=item aio_mkdir $pathname, $mode, $callback->($status)	837	=item aio_mkdir $pathname, $mode, $callback->($status)
514		838
515	Asynchronously mkdir (create) a directory and call the callback with	839	Asynchronously mkdir (create) a directory and call the callback with
…		…
520	=item aio_rmdir $pathname, $callback->($status)	844	=item aio_rmdir $pathname, $callback->($status)
521		845
522	Asynchronously rmdir (delete) a directory and call the callback with the	846	Asynchronously rmdir (delete) a directory and call the callback with the
523	result code.	847	result code.
524		848
		849	On systems that support the AIO::WD working directory abstraction
		850	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		851	C<rmdir> is called on the absolute path of C<$wd>.
		852
525		853
526	=item aio_readdir $pathname, $callback->($entries)	854	=item aio_readdir $pathname, $callback->($entries)
527		855
528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	856	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
529	directory (i.e. opendir + readdir + closedir). The entries will not be	857	directory (i.e. opendir + readdir + closedir). The entries will not be
530	sorted, and will B<NOT> include the C<.> and C<..> entries.	858	sorted, and will B<NOT> include the C<.> and C<..> entries.
531		859
532	The callback a single argument which is either C<undef> or an array-ref	860	The callback is passed a single argument which is either C<undef> or an
533	with the filenames.	861	array-ref with the filenames.
534		862
535		863
		864	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		865
		866	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		867	tune behaviour and output format. In case of an error, C<$entries> will be
		868	C<undef>.
		869
		870	The flags are a combination of the following constants, ORed together (the
		871	flags will also be passed to the callback, possibly modified):
		872
		873	=over 4
		874
		875	=item IO::AIO::READDIR_DENTS
		876
		877	When this flag is off, then the callback gets an arrayref consisting of
		878	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		879	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		880	entry in more detail.
		881
		882	C<$name> is the name of the entry.
		883
		884	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		885
		886	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		887	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		888	C<IO::AIO::DT_WHT>.
		889
		890	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		891	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		892	scalars are read-only: you can not modify them.
		893
		894	C<$inode> is the inode number (which might not be exact on systems with 64
		895	bit inode numbers and 32 bit perls). This field has unspecified content on
		896	systems that do not deliver the inode information.
		897
		898	=item IO::AIO::READDIR_DIRS_FIRST
		899
		900	When this flag is set, then the names will be returned in an order where
		901	likely directories come first, in optimal stat order. This is useful when
		902	you need to quickly find directories, or you want to find all directories
		903	while avoiding to stat() each entry.
		904
		905	If the system returns type information in readdir, then this is used
		906	to find directories directly. Otherwise, likely directories are names
		907	beginning with ".", or otherwise names with no dots, of which names with
		908	short names are tried first.
		909
		910	=item IO::AIO::READDIR_STAT_ORDER
		911
		912	When this flag is set, then the names will be returned in an order
		913	suitable for stat()'ing each one. That is, when you plan to stat()
		914	all files in the given directory, then the returned order will likely
		915	be fastest.
		916
		917	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		918	the likely dirs come first, resulting in a less optimal stat order.
		919
		920	=item IO::AIO::READDIR_FOUND_UNKNOWN
		921
		922	This flag should not be set when calling C<aio_readdirx>. Instead, it
		923	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		924	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		925	C<$type>'s are known, which can be used to speed up some algorithms.
		926
		927	=back
		928
		929
536	=item aio_load $path, $data, $callback->($status)	930	=item aio_load $pathname, $data, $callback->($status)
537		931
538	This is a composite request that tries to fully load the given file into	932	This is a composite request that tries to fully load the given file into
539	memory. Status is the same as with aio_read.	933	memory. Status is the same as with aio_read.
540		934
541	=cut	935	=cut
…		…
563		957
564	=item aio_copy $srcpath, $dstpath, $callback->($status)	958	=item aio_copy $srcpath, $dstpath, $callback->($status)
565		959
566	Try to copy the I<file> (directories not supported as either source or	960	Try to copy the I<file> (directories not supported as either source or
567	destination) from C<$srcpath> to C<$dstpath> and call the callback with	961	destination) from C<$srcpath> to C<$dstpath> and call the callback with
568	the C<0> (error) or C<-1> ok.	962	a status of C<0> (ok) or C<-1> (error, see C<$!>).
569		963
		964	Existing destination files will be truncated.
		965
570	This is a composite request that it creates the destination file with	966	This is a composite request that creates the destination file with
571	mode 0200 and copies the contents of the source file into it using	967	mode 0200 and copies the contents of the source file into it using
572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	968	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
573	uid/gid, in that order.	969	uid/gid, in that order.
574		970
575	If an error occurs, the partial destination file will be unlinked, if	971	If an error occurs, the partial destination file will be unlinked, if
…		…
585	my $grp = aio_group $cb;	981	my $grp = aio_group $cb;
586		982
587	aioreq_pri $pri;	983	aioreq_pri $pri;
588	add $grp aio_open $src, O_RDONLY, 0, sub {	984	add $grp aio_open $src, O_RDONLY, 0, sub {
589	if (my $src_fh = $_[0]) {	985	if (my $src_fh = $_[0]) {
590	my @stat = stat $src_fh;	986	my @stat = stat $src_fh; # hmm, might block over nfs?
591		987
592	aioreq_pri $pri;	988	aioreq_pri $pri;
593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	989	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
594	if (my $dst_fh = $_[0]) {	990	if (my $dst_fh = $_[0]) {
595	aioreq_pri $pri;	991	aioreq_pri $pri;
596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	992	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
597	if ($_[0] == $stat[7]) {	993	if ($_[0] == $stat[7]) {
598	$grp->result (0);	994	$grp->result (0);
599	close $src_fh;	995	close $src_fh;
600		996
601	# those should not normally block. should. should.	997	my $ch = sub {
602	utime $stat[8], $stat[9], $dst;	998	aioreq_pri $pri;
603	chmod $stat[2] & 07777, $dst_fh;	999	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
604	chown $stat[4], $stat[5], $dst_fh;	1000	aioreq_pri $pri;
		1001	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		1002	aioreq_pri $pri;
		1003	add $grp aio_close $dst_fh;
		1004	}
		1005	};
		1006	};
605		1007
606	aioreq_pri $pri;	1008	aioreq_pri $pri;
607	add $grp aio_close $dst_fh;	1009	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		1010	if ($_[0] < 0 && $! == ENOSYS) {
		1011	aioreq_pri $pri;
		1012	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		1013	} else {
		1014	$ch->();
		1015	}
		1016	};
608	} else {	1017	} else {
609	$grp->result (-1);	1018	$grp->result (-1);
610	close $src_fh;	1019	close $src_fh;
611	close $dst_fh;	1020	close $dst_fh;
612		1021
…		…
629		1038
630	=item aio_move $srcpath, $dstpath, $callback->($status)	1039	=item aio_move $srcpath, $dstpath, $callback->($status)
631		1040
632	Try to move the I<file> (directories not supported as either source or	1041	Try to move the I<file> (directories not supported as either source or
633	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1042	destination) from C<$srcpath> to C<$dstpath> and call the callback with
634	the C<0> (error) or C<-1> ok.	1043	a status of C<0> (ok) or C<-1> (error, see C<$!>).
635		1044
636	This is a composite request that tries to rename(2) the file first. If	1045	This is a composite request that tries to rename(2) the file first; if
637	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1046	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
638	that is successful, unlinking the C<$srcpath>.	1047	that is successful, unlinks the C<$srcpath>.
639		1048
640	=cut	1049	=cut
641		1050
642	sub aio_move($$;$) {	1051	sub aio_move($$;$) {
643	my ($src, $dst, $cb) = @_;	1052	my ($src, $dst, $cb) = @_;
…		…
650	if ($_[0] && $! == EXDEV) {	1059	if ($_[0] && $! == EXDEV) {
651	aioreq_pri $pri;	1060	aioreq_pri $pri;
652	add $grp aio_copy $src, $dst, sub {	1061	add $grp aio_copy $src, $dst, sub {
653	$grp->result ($_[0]);	1062	$grp->result ($_[0]);
654		1063
655	if (!$_[0]) {	1064	unless ($_[0]) {
656	aioreq_pri $pri;	1065	aioreq_pri $pri;
657	add $grp aio_unlink $src;	1066	add $grp aio_unlink $src;
658	}	1067	}
659	};	1068	};
660	} else {	1069	} else {
…		…
663	};	1072	};
664		1073
665	$grp	1074	$grp
666	}	1075	}
667		1076
668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1077	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
669		1078
670	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1079	Scans a directory (similar to C<aio_readdir>) but additionally tries to
671	efficiently separate the entries of directory C<$path> into two sets of	1080	efficiently separate the entries of directory C<$path> into two sets of
672	names, directories you can recurse into (directories), and ones you cannot	1081	names, directories you can recurse into (directories), and ones you cannot
673	recurse into (everything else, including symlinks to directories).	1082	recurse into (everything else, including symlinks to directories).
…		…
690		1099
691	Implementation notes.	1100	Implementation notes.
692		1101
693	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1102	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
694		1103
		1104	If readdir returns file type information, then this is used directly to
		1105	find directories.
		1106
695	After reading the directory, the modification time, size etc. of the	1107	Otherwise, after reading the directory, the modification time, size etc.
696	directory before and after the readdir is checked, and if they match (and	1108	of the directory before and after the readdir is checked, and if they
697	isn't the current time), the link count will be used to decide how many	1109	match (and isn't the current time), the link count will be used to decide
698	entries are directories (if >= 2). Otherwise, no knowledge of the number	1110	how many entries are directories (if >= 2). Otherwise, no knowledge of the
699	of subdirectories will be assumed.	1111	number of subdirectories will be assumed.
700		1112
701	Then entries will be sorted into likely directories (everything without	1113	Then entries will be sorted into likely directories a non-initial dot
702	a non-initial dot currently) and likely non-directories (everything	1114	currently) and likely non-directories (see C<aio_readdirx>). Then every
703	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1115	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
704	likely directories first. If that succeeds, it assumes that the entry	1116	in order of their inode numbers. If that succeeds, it assumes that the
705	is a directory or a symlink to directory (which will be checked	1117	entry is a directory or a symlink to directory (which will be checked
706	seperately). This is often faster than stat'ing the entry itself because	1118	separately). This is often faster than stat'ing the entry itself because
707	filesystems might detect the type of the entry without reading the inode	1119	filesystems might detect the type of the entry without reading the inode
708	data (e.g. ext2fs filetype feature).	1120	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1121	the filetype information on readdir.
709		1122
710	If the known number of directories (link count - 2) has been reached, the	1123	If the known number of directories (link count - 2) has been reached, the
711	rest of the entries is assumed to be non-directories.	1124	rest of the entries is assumed to be non-directories.
712		1125
713	This only works with certainty on POSIX (= UNIX) filesystems, which	1126	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
726		1139
727	my $grp = aio_group $cb;	1140	my $grp = aio_group $cb;
728		1141
729	$maxreq = 4 if $maxreq <= 0;	1142	$maxreq = 4 if $maxreq <= 0;
730		1143
731	# stat once	1144	# get a wd object
732	aioreq_pri $pri;	1145	aioreq_pri $pri;
733	add $grp aio_stat $path, sub {	1146	add $grp aio_wd $path, sub {
		1147	$_[0]
734	return $grp->result () if $_[0];	1148	or return $grp->result ();
735	my $now = time;
736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
737		1149
738	# read the directory entries	1150	my $wd = [shift, "."];
		1151
		1152	# stat once
739	aioreq_pri $pri;	1153	aioreq_pri $pri;
740	add $grp aio_readdir $path, sub {	1154	add $grp aio_stat $wd, sub {
741	my $entries = shift
742	or return $grp->result ();	1155	return $grp->result () if $_[0];
		1156	my $now = time;
		1157	my $hash1 = join ":", (stat _)[0,1,3,7,9];
743		1158
744	# stat the dir another time	1159	# read the directory entries
745	aioreq_pri $pri;	1160	aioreq_pri $pri;
		1161	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1162	my $entries = shift
		1163	or return $grp->result ();
		1164
		1165	# stat the dir another time
		1166	aioreq_pri $pri;
746	add $grp aio_stat $path, sub {	1167	add $grp aio_stat $wd, sub {
747	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1168	my $hash2 = join ":", (stat _)[0,1,3,7,9];
748		1169
749	my $ndirs;	1170	my $ndirs;
750		1171
751	# take the slow route if anything looks fishy	1172	# take the slow route if anything looks fishy
752	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1173	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
753	$ndirs = -1;	1174	$ndirs = -1;
754	} else {	1175	} else {
755	# if nlink == 2, we are finished	1176	# if nlink == 2, we are finished
756	# on non-posix-fs's, we rely on nlink < 2	1177	# for non-posix-fs's, we rely on nlink < 2
757	$ndirs = (stat _)[3] - 2	1178	$ndirs = (stat _)[3] - 2
758	or return $grp->result ([], $entries);	1179	or return $grp->result ([], $entries);
759	}	1180	}
760		1181
761	# sort into likely dirs and likely nondirs
762	# dirs == files without ".", short entries first
763	$entries = [map $_->[0],
764	sort { $b->[1] cmp $a->[1] }
765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
766	@$entries];
767
768	my (@dirs, @nondirs);	1182	my (@dirs, @nondirs);
769		1183
770	my $statgrp = add $grp aio_group sub {	1184	my $statgrp = add $grp aio_group sub {
771	$grp->result (\@dirs, \@nondirs);	1185	$grp->result (\@dirs, \@nondirs);
772	};	1186	};
773		1187
774	limit $statgrp $maxreq;	1188	limit $statgrp $maxreq;
775	feed $statgrp sub {	1189	feed $statgrp sub {
776	return unless @$entries;	1190	return unless @$entries;
777	my $entry = pop @$entries;	1191	my $entry = shift @$entries;
778		1192
779	aioreq_pri $pri;	1193	aioreq_pri $pri;
		1194	$wd->[1] = "$entry/.";
780	add $statgrp aio_stat "$path/$entry/.", sub {	1195	add $statgrp aio_stat $wd, sub {
781	if ($_[0] < 0) {	1196	if ($_[0] < 0) {
782	push @nondirs, $entry;	1197	push @nondirs, $entry;
783	} else {	1198	} else {
784	# need to check for real directory	1199	# need to check for real directory
785	aioreq_pri $pri;	1200	aioreq_pri $pri;
		1201	$wd->[1] = $entry;
786	add $statgrp aio_lstat "$path/$entry", sub {	1202	add $statgrp aio_lstat $wd, sub {
787	if (-d _) {	1203	if (-d _) {
788	push @dirs, $entry;	1204	push @dirs, $entry;
789		1205
790	unless (--$ndirs) {	1206	unless (--$ndirs) {
791	push @nondirs, @$entries;	1207	push @nondirs, @$entries;
792	feed $statgrp;	1208	feed $statgrp;
		1209	}
		1210	} else {
		1211	push @nondirs, $entry;
793	}	1212	}
794	} else {
795	push @nondirs, $entry;
796	}	1213	}
797	}	1214	}
798	}	1215	};
799	};	1216	};
800	};	1217	};
801	};	1218	};
802	};	1219	};
803	};	1220	};
804		1221
805	$grp	1222	$grp
806	}	1223	}
807		1224
808	=item aio_rmtree $path, $callback->($status)	1225	=item aio_rmtree $pathname, $callback->($status)
809		1226
810	Delete a directory tree starting (and including) C<$path>, return the	1227	Delete a directory tree starting (and including) C<$path>, return the
811	status of the final C<rmdir> only. This is a composite request that	1228	status of the final C<rmdir> only. This is a composite request that
812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1229	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
813	everything else.	1230	everything else.
814		1231
815	=cut	1232	=cut
816		1233
…		…
838	};	1255	};
839		1256
840	$grp	1257	$grp
841	}	1258	}
842		1259
		1260	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1261
		1262	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1263
		1264	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1265	they execute asynchronously and pass the return value to the callback.
		1266
		1267	Both calls can be used for a lot of things, some of which make more sense
		1268	to run asynchronously in their own thread, while some others make less
		1269	sense. For example, calls that block waiting for external events, such
		1270	as locking, will also lock down an I/O thread while it is waiting, which
		1271	can deadlock the whole I/O system. At the same time, there might be no
		1272	alternative to using a thread to wait.
		1273
		1274	So in general, you should only use these calls for things that do
		1275	(filesystem) I/O, not for things that wait for other events (network,
		1276	other processes), although if you are careful and know what you are doing,
		1277	you still can.
		1278
		1279	The following constants are available (missing ones are, as usual C<0>):
		1280
		1281	C<F_DUPFD_CLOEXEC>,
		1282
		1283	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1284
		1285	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1286
		1287	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1288	C<FS_IOC_FIEMAP>.
		1289
		1290	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1291	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1292
		1293	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1294	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1295	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1296	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1297	C<FS_FL_USER_MODIFIABLE>.
		1298
		1299	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1300	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1301	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1302	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1303
843	=item aio_sync $callback->($status)	1304	=item aio_sync $callback->($status)
844		1305
845	Asynchronously call sync and call the callback when finished.	1306	Asynchronously call sync and call the callback when finished.
846		1307
847	=item aio_fsync $fh, $callback->($status)	1308	=item aio_fsync $fh, $callback->($status)
…		…
855	callback with the fdatasync result code.	1316	callback with the fdatasync result code.
856		1317
857	If this call isn't available because your OS lacks it or it couldn't be	1318	If this call isn't available because your OS lacks it or it couldn't be
858	detected, it will be emulated by calling C<fsync> instead.	1319	detected, it will be emulated by calling C<fsync> instead.
859		1320
		1321	=item aio_syncfs $fh, $callback->($status)
		1322
		1323	Asynchronously call the syncfs syscall to sync the filesystem associated
		1324	to the given filehandle and call the callback with the syncfs result
		1325	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1326	errno to C<ENOSYS> nevertheless.
		1327
		1328	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1329
		1330	Sync the data portion of the file specified by C<$offset> and C<$length>
		1331	to disk (but NOT the metadata), by calling the Linux-specific
		1332	sync_file_range call. If sync_file_range is not available or it returns
		1333	ENOSYS, then fdatasync or fsync is being substituted.
		1334
		1335	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1336	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1337	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1338	manpage for details.
		1339
860	=item aio_pathsync $path, $callback->($status)	1340	=item aio_pathsync $pathname, $callback->($status)
861		1341
862	This request tries to open, fsync and close the given path. This is a	1342	This request tries to open, fsync and close the given path. This is a
863	composite request intended tosync directories after directory operations	1343	composite request intended to sync directories after directory operations
864	(E.g. rename). This might not work on all operating systems or have any	1344	(E.g. rename). This might not work on all operating systems or have any
865	specific effect, but usually it makes sure that directory changes get	1345	specific effect, but usually it makes sure that directory changes get
866	written to disc. It works for anything that can be opened for read-only,	1346	written to disc. It works for anything that can be opened for read-only,
867	not just directories.	1347	not just directories.
		1348
		1349	Future versions of this function might fall back to other methods when
		1350	C<fsync> on the directory fails (such as calling C<sync>).
868		1351
869	Passes C<0> when everything went ok, and C<-1> on error.	1352	Passes C<0> when everything went ok, and C<-1> on error.
870		1353
871	=cut	1354	=cut
872		1355
…		…
893	};	1376	};
894		1377
895	$grp	1378	$grp
896	}	1379	}
897		1380
		1381	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1382
		1383	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1384	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1385	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1386	scalar must only be modified in-place while an aio operation is pending on
		1387	it).
		1388
		1389	It calls the C<msync> function of your OS, if available, with the memory
		1390	area starting at C<$offset> in the string and ending C<$length> bytes
		1391	later. If C<$length> is negative, counts from the end, and if C<$length>
		1392	is C<undef>, then it goes till the end of the string. The flags can be
		1393	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1394	C<IO::AIO::MS_INVALIDATE>.
		1395
		1396	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1397
		1398	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1399	scalars.
		1400
		1401	It touches (reads or writes) all memory pages in the specified
		1402	range inside the scalar. All caveats and parameters are the same
		1403	as for C<aio_msync>, above, except for flags, which must be either
		1404	C<0> (which reads all pages and ensures they are instantiated) or
		1405	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1406	writing an octet from it, which dirties the page).
		1407
		1408	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1409
		1410	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1411	scalars.
		1412
		1413	It reads in all the pages of the underlying storage into memory (if any)
		1414	and locks them, so they are not getting swapped/paged out or removed.
		1415
		1416	If C<$length> is undefined, then the scalar will be locked till the end.
		1417
		1418	On systems that do not implement C<mlock>, this function returns C<-1>
		1419	and sets errno to C<ENOSYS>.
		1420
		1421	Note that the corresponding C<munlock> is synchronous and is
		1422	documented under L<MISCELLANEOUS FUNCTIONS>.
		1423
		1424	Example: open a file, mmap and mlock it - both will be undone when
		1425	C<$data> gets destroyed.
		1426
		1427	open my $fh, "<", $path or die "$path: $!";
		1428	my $data;
		1429	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1430	aio_mlock $data; # mlock in background
		1431
		1432	=item aio_mlockall $flags, $callback->($status)
		1433
		1434	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1435	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1436
		1437	On systems that do not implement C<mlockall>, this function returns C<-1>
		1438	and sets errno to C<ENOSYS>.
		1439
		1440	Note that the corresponding C<munlockall> is synchronous and is
		1441	documented under L<MISCELLANEOUS FUNCTIONS>.
		1442
		1443	Example: asynchronously lock all current and future pages into memory.
		1444
		1445	aio_mlockall IO::AIO::MCL_FUTURE;
		1446
		1447	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1448
		1449	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1450	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1451	the ioctl is not available on your OS, then this request will fail with
		1452	C<ENOSYS>.
		1453
		1454	C<$start> is the starting offset to query extents for, C<$length> is the
		1455	size of the range to query - if it is C<undef>, then the whole file will
		1456	be queried.
		1457
		1458	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1459	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1460	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1461	the data portion.
		1462
		1463	C<$count> is the maximum number of extent records to return. If it is
		1464	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1465	case, if it is C<0>, then the callback receives the number of extents
		1466	instead of the extents themselves (which is unreliable, see below).
		1467
		1468	If an error occurs, the callback receives no arguments. The special
		1469	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1470
		1471	Otherwise, the callback receives an array reference with extent
		1472	structures. Each extent structure is an array reference itself, with the
		1473	following members:
		1474
		1475	[$logical, $physical, $length, $flags]
		1476
		1477	Flags is any combination of the following flag values (typically either C<0>
		1478	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1479
		1480	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1481	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1482	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1483	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1484	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1485	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1486
		1487	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1488	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1489	it to return all extents of a range for files with large number of
		1490	extents. The code works around all these issues if C<$count> is undef.
		1491
898	=item aio_group $callback->(...)	1492	=item aio_group $callback->(...)
899		1493
900	This is a very special aio request: Instead of doing something, it is a	1494	This is a very special aio request: Instead of doing something, it is a
901	container for other aio requests, which is useful if you want to bundle	1495	container for other aio requests, which is useful if you want to bundle
902	many requests into a single, composite, request with a definite callback	1496	many requests into a single, composite, request with a definite callback
…		…
939	immense (it blocks a thread for a long time) so do not use this function	1533	immense (it blocks a thread for a long time) so do not use this function
940	except to put your application under artificial I/O pressure.	1534	except to put your application under artificial I/O pressure.
941		1535
942	=back	1536	=back
943		1537
		1538
		1539	=head2 IO::AIO::WD - multiple working directories
		1540
		1541	Your process only has one current working directory, which is used by all
		1542	threads. This makes it hard to use relative paths (some other component
		1543	could call C<chdir> at any time, and it is hard to control when the path
		1544	will be used by IO::AIO).
		1545
		1546	One solution for this is to always use absolute paths. This usually works,
		1547	but can be quite slow (the kernel has to walk the whole path on every
		1548	access), and can also be a hassle to implement.
		1549
		1550	Newer POSIX systems have a number of functions (openat, fdopendir,
		1551	futimensat and so on) that make it possible to specify working directories
		1552	per operation.
		1553
		1554	For portability, and because the clowns who "designed", or shall I write,
		1555	perpetrated this new interface were obviously half-drunk, this abstraction
		1556	cannot be perfect, though.
		1557
		1558	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1559	object. This object stores the canonicalised, absolute version of the
		1560	path, and on systems that allow it, also a directory file descriptor.
		1561
		1562	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1563	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1564	object and a pathname instead (or the IO::AIO::WD object alone, which
		1565	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1566	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1567	to that IO::AIO::WD object.
		1568
		1569	For example, to get a wd object for F</etc> and then stat F<passwd>
		1570	inside, you would write:
		1571
		1572	aio_wd "/etc", sub {
		1573	my $etcdir = shift;
		1574
		1575	# although $etcdir can be undef on error, there is generally no reason
		1576	# to check for errors here, as aio_stat will fail with ENOENT
		1577	# when $etcdir is undef.
		1578
		1579	aio_stat [$etcdir, "passwd"], sub {
		1580	# yay
		1581	};
		1582	};
		1583
		1584	The fact that C<aio_wd> is a request and not a normal function shows that
		1585	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1586	which is why it is done asynchronously.
		1587
		1588	To stat the directory obtained with C<aio_wd> above, one could write
		1589	either of the following three request calls:
		1590
		1591	aio_lstat "/etc" , sub { ... # pathname as normal string
		1592	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1593	aio_lstat $wd , sub { ... # shorthand for the previous
		1594
		1595	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1596	object and the pathname string, so you could write the following without
		1597	causing any issues due to C<$path> getting reused:
		1598
		1599	my $path = [$wd, undef];
		1600
		1601	for my $name (qw(abc def ghi)) {
		1602	$path->[1] = $name;
		1603	aio_stat $path, sub {
		1604	# ...
		1605	};
		1606	}
		1607
		1608	There are some caveats: when directories get renamed (or deleted), the
		1609	pathname string doesn't change, so will point to the new directory (or
		1610	nowhere at all), while the directory fd, if available on the system,
		1611	will still point to the original directory. Most functions accepting a
		1612	pathname will use the directory fd on newer systems, and the string on
		1613	older systems. Some functions (such as realpath) will always rely on the
		1614	string form of the pathname.
		1615
		1616	So this functionality is mainly useful to get some protection against
		1617	C<chdir>, to easily get an absolute path out of a relative path for future
		1618	reference, and to speed up doing many operations in the same directory
		1619	(e.g. when stat'ing all files in a directory).
		1620
		1621	The following functions implement this working directory abstraction:
		1622
		1623	=over 4
		1624
		1625	=item aio_wd $pathname, $callback->($wd)
		1626
		1627	Asynchonously canonicalise the given pathname and convert it to an
		1628	IO::AIO::WD object representing it. If possible and supported on the
		1629	system, also open a directory fd to speed up pathname resolution relative
		1630	to this working directory.
		1631
		1632	If something goes wrong, then C<undef> is passwd to the callback instead
		1633	of a working directory object and C<$!> is set appropriately. Since
		1634	passing C<undef> as working directory component of a pathname fails the
		1635	request with C<ENOENT>, there is often no need for error checking in the
		1636	C<aio_wd> callback, as future requests using the value will fail in the
		1637	expected way.
		1638
		1639	=item IO::AIO::CWD
		1640
		1641	This is a compiletime constant (object) that represents the process
		1642	current working directory.
		1643
		1644	Specifying this object as working directory object for a pathname is as if
		1645	the pathname would be specified directly, without a directory object. For
		1646	example, these calls are functionally identical:
		1647
		1648	aio_stat "somefile", sub { ... };
		1649	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1650
		1651	=back
		1652
		1653	To recover the path associated with an IO::AIO::WD object, you can use
		1654	C<aio_realpath>:
		1655
		1656	aio_realpath $wd, sub {
		1657	warn "path is $_[0]\n";
		1658	};
		1659
		1660	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1661	sometimes, fall back to using an absolue path.
		1662
944	=head2 IO::AIO::REQ CLASS	1663	=head2 IO::AIO::REQ CLASS
945		1664
946	All non-aggregate C<aio_*> functions return an object of this class when	1665	All non-aggregate C<aio_*> functions return an object of this class when
947	called in non-void context.	1666	called in non-void context.
948		1667
…		…
951	=item cancel $req	1670	=item cancel $req
952		1671
953	Cancels the request, if possible. Has the effect of skipping execution	1672	Cancels the request, if possible. Has the effect of skipping execution
954	when entering the B<execute> state and skipping calling the callback when	1673	when entering the B<execute> state and skipping calling the callback when
955	entering the the B<result> state, but will leave the request otherwise	1674	entering the the B<result> state, but will leave the request otherwise
956	untouched. That means that requests that currently execute will not be	1675	untouched (with the exception of readdir). That means that requests that
957	stopped and resources held by the request will not be freed prematurely.	1676	currently execute will not be stopped and resources held by the request
		1677	will not be freed prematurely.
958		1678
959	=item cb $req $callback->(...)	1679	=item cb $req $callback->(...)
960		1680
961	Replace (or simply set) the callback registered to the request.	1681	Replace (or simply set) the callback registered to the request.
962		1682
…		…
1013	Their lifetime, simplified, looks like this: when they are empty, they	1733	Their lifetime, simplified, looks like this: when they are empty, they
1014	will finish very quickly. If they contain only requests that are in the	1734	will finish very quickly. If they contain only requests that are in the
1015	C<done> state, they will also finish. Otherwise they will continue to	1735	C<done> state, they will also finish. Otherwise they will continue to
1016	exist.	1736	exist.
1017		1737
1018	That means after creating a group you have some time to add requests. And	1738	That means after creating a group you have some time to add requests
1019	in the callbacks of those requests, you can add further requests to the	1739	(precisely before the callback has been invoked, which is only done within
1020	group. And only when all those requests have finished will the the group	1740	the C<poll_cb>). And in the callbacks of those requests, you can add
1021	itself finish.	1741	further requests to the group. And only when all those requests have
		1742	finished will the the group itself finish.
1022		1743
1023	=over 4	1744	=over 4
1024		1745
1025	=item add $grp ...	1746	=item add $grp ...
1026		1747
…		…
1034		1755
1035	=item $grp->cancel_subs	1756	=item $grp->cancel_subs
1036		1757
1037	Cancel all subrequests and clears any feeder, but not the group request	1758	Cancel all subrequests and clears any feeder, but not the group request
1038	itself. Useful when you queued a lot of events but got a result early.	1759	itself. Useful when you queued a lot of events but got a result early.
		1760
		1761	The group request will finish normally (you cannot add requests to the
		1762	group).
1039		1763
1040	=item $grp->result (...)	1764	=item $grp->result (...)
1041		1765
1042	Set the result value(s) that will be passed to the group callback when all	1766	Set the result value(s) that will be passed to the group callback when all
1043	subrequests have finished and set the groups errno to the current value	1767	subrequests have finished and set the groups errno to the current value
…		…
1059	=item feed $grp $callback->($grp)	1783	=item feed $grp $callback->($grp)
1060		1784
1061	Sets a feeder/generator on this group: every group can have an attached	1785	Sets a feeder/generator on this group: every group can have an attached
1062	generator that generates requests if idle. The idea behind this is that,	1786	generator that generates requests if idle. The idea behind this is that,
1063	although you could just queue as many requests as you want in a group,	1787	although you could just queue as many requests as you want in a group,
1064	this might starve other requests for a potentially long time. For	1788	this might starve other requests for a potentially long time. For example,
1065	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1789	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1066	requests, delaying any later requests for a long time.	1790	requests, delaying any later requests for a long time.
1067		1791
1068	To avoid this, and allow incremental generation of requests, you can	1792	To avoid this, and allow incremental generation of requests, you can
1069	instead a group and set a feeder on it that generates those requests. The	1793	instead a group and set a feeder on it that generates those requests. The
1070	feed callback will be called whenever there are few enough (see C<limit>,	1794	feed callback will be called whenever there are few enough (see C<limit>,
…		…
1075	not impose any limits).	1799	not impose any limits).
1076		1800
1077	If the feed does not queue more requests when called, it will be	1801	If the feed does not queue more requests when called, it will be
1078	automatically removed from the group.	1802	automatically removed from the group.
1079		1803
1080	If the feed limit is C<0>, it will be set to C<2> automatically.	1804	If the feed limit is C<0> when this method is called, it will be set to
		1805	C<2> automatically.
1081		1806
1082	Example:	1807	Example:
1083		1808
1084	# stat all files in @files, but only ever use four aio requests concurrently:	1809	# stat all files in @files, but only ever use four aio requests concurrently:
1085		1810
…		…
1097	Sets the feeder limit for the group: The feeder will be called whenever	1822	Sets the feeder limit for the group: The feeder will be called whenever
1098	the group contains less than this many requests.	1823	the group contains less than this many requests.
1099		1824
1100	Setting the limit to C<0> will pause the feeding process.	1825	Setting the limit to C<0> will pause the feeding process.
1101		1826
		1827	The default value for the limit is C<0>, but note that setting a feeder
		1828	automatically bumps it up to C<2>.
		1829
1102	=back	1830	=back
1103		1831
1104	=head2 SUPPORT FUNCTIONS	1832	=head2 SUPPORT FUNCTIONS
1105		1833
1106	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1834	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
1108	=over 4	1836	=over 4
1109		1837
1110	=item $fileno = IO::AIO::poll_fileno	1838	=item $fileno = IO::AIO::poll_fileno
1111		1839
1112	Return the I<request result pipe file descriptor>. This filehandle must be	1840	Return the I<request result pipe file descriptor>. This filehandle must be
1113	polled for reading by some mechanism outside this module (e.g. Event or	1841	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1114	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1842	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1115	to call C<poll_cb> to check the results.	1843	you have to call C<poll_cb> to check the results.
1116		1844
1117	See C<poll_cb> for an example.	1845	See C<poll_cb> for an example.
1118		1846
1119	=item IO::AIO::poll_cb	1847	=item IO::AIO::poll_cb
1120		1848
1121	Process some outstanding events on the result pipe. You have to call this	1849	Process some requests that have reached the result phase (i.e. they have
1122	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1850	been executed but the results are not yet reported). You have to call
1123	returned earlier for whatever reason. Returns immediately when no events	1851	this "regularly" to finish outstanding requests.
1124	are outstanding. The amount of events processed depends on the settings of
1125	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1126		1852
		1853	Returns C<0> if all events could be processed (or there were no
		1854	events to process), or C<-1> if it returned earlier for whatever
		1855	reason. Returns immediately when no events are outstanding. The amount
		1856	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1857	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1858
1127	If not all requests were processed for whatever reason, the filehandle	1859	If not all requests were processed for whatever reason, the poll file
1128	will still be ready when C<poll_cb> returns, so normally you don't have to	1860	descriptor will still be ready when C<poll_cb> returns, so normally you
1129	do anything special to have it called later.	1861	don't have to do anything special to have it called later.
		1862
		1863	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1864	ready, it can be beneficial to call this function from loops which submit
		1865	a lot of requests, to make sure the results get processed when they become
		1866	available and not just when the loop is finished and the event loop takes
		1867	over again. This function returns very fast when there are no outstanding
		1868	requests.
1130		1869
1131	Example: Install an Event watcher that automatically calls	1870	Example: Install an Event watcher that automatically calls
1132	IO::AIO::poll_cb with high priority:	1871	IO::AIO::poll_cb with high priority (more examples can be found in the
		1872	SYNOPSIS section, at the top of this document):
1133		1873
1134	Event->io (fd => IO::AIO::poll_fileno,	1874	Event->io (fd => IO::AIO::poll_fileno,
1135	poll => 'r', async => 1,	1875	poll => 'r', async => 1,
1136	cb => \&IO::AIO::poll_cb);	1876	cb => \&IO::AIO::poll_cb);
		1877
		1878	=item IO::AIO::poll_wait
		1879
		1880	Wait until either at least one request is in the result phase or no
		1881	requests are outstanding anymore.
		1882
		1883	This is useful if you want to synchronously wait for some requests to
		1884	become ready, without actually handling them.
		1885
		1886	See C<nreqs> for an example.
		1887
		1888	=item IO::AIO::poll
		1889
		1890	Waits until some requests have been handled.
		1891
		1892	Returns the number of requests processed, but is otherwise strictly
		1893	equivalent to:
		1894
		1895	IO::AIO::poll_wait, IO::AIO::poll_cb
		1896
		1897	=item IO::AIO::flush
		1898
		1899	Wait till all outstanding AIO requests have been handled.
		1900
		1901	Strictly equivalent to:
		1902
		1903	IO::AIO::poll_wait, IO::AIO::poll_cb
		1904	while IO::AIO::nreqs;
1137		1905
1138	=item IO::AIO::max_poll_reqs $nreqs	1906	=item IO::AIO::max_poll_reqs $nreqs
1139		1907
1140	=item IO::AIO::max_poll_time $seconds	1908	=item IO::AIO::max_poll_time $seconds
1141		1909
…		…
1166	# use a low priority so other tasks have priority	1934	# use a low priority so other tasks have priority
1167	Event->io (fd => IO::AIO::poll_fileno,	1935	Event->io (fd => IO::AIO::poll_fileno,
1168	poll => 'r', nice => 1,	1936	poll => 'r', nice => 1,
1169	cb => &IO::AIO::poll_cb);	1937	cb => &IO::AIO::poll_cb);
1170		1938
1171	=item IO::AIO::poll_wait
1172
1173	If there are any outstanding requests and none of them in the result
1174	phase, wait till the result filehandle becomes ready for reading (simply
1175	does a C<select> on the filehandle. This is useful if you want to
1176	synchronously wait for some requests to finish).
1177
1178	See C<nreqs> for an example.
1179
1180	=item IO::AIO::poll
1181
1182	Waits until some requests have been handled.
1183
1184	Returns the number of requests processed, but is otherwise strictly
1185	equivalent to:
1186
1187	IO::AIO::poll_wait, IO::AIO::poll_cb
1188
1189	=item IO::AIO::flush
1190
1191	Wait till all outstanding AIO requests have been handled.
1192
1193	Strictly equivalent to:
1194
1195	IO::AIO::poll_wait, IO::AIO::poll_cb
1196	while IO::AIO::nreqs;
1197
1198	=back	1939	=back
1199		1940
1200	=head3 CONTROLLING THE NUMBER OF THREADS	1941	=head3 CONTROLLING THE NUMBER OF THREADS
1201		1942
1202	=over	1943	=over
…		…
1235		1976
1236	Under normal circumstances you don't need to call this function.	1977	Under normal circumstances you don't need to call this function.
1237		1978
1238	=item IO::AIO::max_idle $nthreads	1979	=item IO::AIO::max_idle $nthreads
1239		1980
1240	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1981	Limit the number of threads (default: 4) that are allowed to idle
1241	threads that did not get a request to process within 10 seconds). That	1982	(i.e., threads that did not get a request to process within the idle
1242	means if a thread becomes idle while C<$nthreads> other threads are also	1983	timeout (default: 10 seconds). That means if a thread becomes idle while
1243	idle, it will free its resources and exit.	1984	C<$nthreads> other threads are also idle, it will free its resources and
		1985	exit.
1244		1986
1245	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1987	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1246	to allow for extremely high load situations, but want to free resources	1988	to allow for extremely high load situations, but want to free resources
1247	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1989	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1248		1990
1249	The default is probably ok in most situations, especially if thread	1991	The default is probably ok in most situations, especially if thread
1250	creation is fast. If thread creation is very slow on your system you might	1992	creation is fast. If thread creation is very slow on your system you might
1251	want to use larger values.	1993	want to use larger values.
1252		1994
		1995	=item IO::AIO::idle_timeout $seconds
		1996
		1997	Sets the minimum idle timeout (default 10) after which worker threads are
		1998	allowed to exit. SEe C<IO::AIO::max_idle>.
		1999
1253	=item IO::AIO::max_outstanding $maxreqs	2000	=item IO::AIO::max_outstanding $maxreqs
		2001
		2002	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2003	you do queue up more than this number of requests, the next call to
		2004	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2005	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2006	longer exceeded.
		2007
		2008	In other words, this setting does not enforce a queue limit, but can be
		2009	used to make poll functions block if the limit is exceeded.
1254		2010
1255	This is a very bad function to use in interactive programs because it	2011	This is a very bad function to use in interactive programs because it
1256	blocks, and a bad way to reduce concurrency because it is inexact: Better	2012	blocks, and a bad way to reduce concurrency because it is inexact: Better
1257	use an C<aio_group> together with a feed callback.	2013	use an C<aio_group> together with a feed callback.
1258		2014
1259	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2015	Its main use is in scripts without an event loop - when you want to stat
1260	do queue up more than this number of requests, the next call to the	2016	a lot of files, you can write something like this:
1261	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1262	function will block until the limit is no longer exceeded.
1263		2017
1264	The default value is very large, so there is no practical limit on the	2018	IO::AIO::max_outstanding 32;
1265	number of outstanding requests.
1266		2019
1267	You can still queue as many requests as you want. Therefore,	2020	for my $path (...) {
1268	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2021	aio_stat $path , ...;
1269	as a stop gap to shield against fatal memory overflow (with large values).	2022	IO::AIO::poll_cb;
		2023	}
		2024
		2025	IO::AIO::flush;
		2026
		2027	The call to C<poll_cb> inside the loop will normally return instantly, but
		2028	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2029	some requests have been handled. This keeps the loop from pushing a large
		2030	number of C<aio_stat> requests onto the queue.
		2031
		2032	The default value for C<max_outstanding> is very large, so there is no
		2033	practical limit on the number of outstanding requests.
1270		2034
1271	=back	2035	=back
1272		2036
1273	=head3 STATISTICAL INFORMATION	2037	=head3 STATISTICAL INFORMATION
1274		2038
…		…
1294	Returns the number of requests currently in the pending state (executed,	2058	Returns the number of requests currently in the pending state (executed,
1295	but not yet processed by poll_cb).	2059	but not yet processed by poll_cb).
1296		2060
1297	=back	2061	=back
1298		2062
		2063	=head3 MISCELLANEOUS FUNCTIONS
		2064
		2065	IO::AIO implements some functions that are useful when you want to use
		2066	some "Advanced I/O" function not available to in Perl, without going the
		2067	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2068	counterpart.
		2069
		2070	=over 4
		2071
		2072	=item $numfd = IO::AIO::get_fdlimit
		2073
		2074	Tries to find the current file descriptor limit and returns it, or
		2075	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2076	the highest valid file descriptor number.
		2077
		2078	=item IO::AIO::min_fdlimit [$numfd]
		2079
		2080	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2081	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2082	is missing, it will try to set a very high limit, although this is not
		2083	recommended when you know the actual minimum that you require.
		2084
		2085	If the limit cannot be raised enough, the function makes a best-effort
		2086	attempt to increase the limit as much as possible, using various
		2087	tricks, while still failing. You can query the resulting limit using
		2088	C<IO::AIO::get_fdlimit>.
		2089
		2090	If an error occurs, returns C<undef> and sets C<$!>.
		2091
		2092	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2093
		2094	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2095	but is blocking (this makes most sense if you know the input data is
		2096	likely cached already and the output filehandle is set to non-blocking
		2097	operations).
		2098
		2099	Returns the number of bytes copied, or C<-1> on error.
		2100
		2101	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2102
		2103	Simply calls the C<posix_fadvise> function (see its
		2104	manpage for details). The following advice constants are
		2105	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2106	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2107	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2108
		2109	On systems that do not implement C<posix_fadvise>, this function returns
		2110	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2111
		2112	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2113
		2114	Simply calls the C<posix_madvise> function (see its
		2115	manpage for details). The following advice constants are
		2116	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2117	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2118	C<IO::AIO::MADV_DONTNEED>.
		2119
		2120	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2121	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2122	will be reduced to fit into the C<$scalar>.
		2123
		2124	On systems that do not implement C<posix_madvise>, this function returns
		2125	ENOSYS, otherwise the return value of C<posix_madvise>.
		2126
		2127	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2128
		2129	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2130	$scalar (see its manpage for details). The following protect
		2131	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2132	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2133
		2134	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2135	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2136	will be reduced to fit into the C<$scalar>.
		2137
		2138	On systems that do not implement C<mprotect>, this function returns
		2139	ENOSYS, otherwise the return value of C<mprotect>.
		2140
		2141	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2142
		2143	Memory-maps a file (or anonymous memory range) and attaches it to the
		2144	given C<$scalar>, which will act like a string scalar. Returns true on
		2145	success, and false otherwise.
		2146
		2147	The scalar must exist, but its contents do not matter - this means you
		2148	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2149	the scalar first.
		2150
		2151	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2152	which don't change the string length, and most read-only operations such
		2153	as copying it or searching it with regexes and so on.
		2154
		2155	Anything else is unsafe and will, at best, result in memory leaks.
		2156
		2157	The memory map associated with the C<$scalar> is automatically removed
		2158	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2159	or C<IO::AIO::munmap> functions are called on it.
		2160
		2161	This calls the C<mmap>(2) function internally. See your system's manual
		2162	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2163
		2164	The C<$length> must be larger than zero and smaller than the actual
		2165	filesize.
		2166
		2167	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2168	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2169
		2170	C<$flags> can be a combination of
		2171	C<IO::AIO::MAP_SHARED> or
		2172	C<IO::AIO::MAP_PRIVATE>,
		2173	or a number of system-specific flags (when not available, the are C<0>):
		2174	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2175	C<IO::AIO::MAP_LOCKED>,
		2176	C<IO::AIO::MAP_NORESERVE>,
		2177	C<IO::AIO::MAP_POPULATE>,
		2178	C<IO::AIO::MAP_NONBLOCK>,
		2179	C<IO::AIO::MAP_FIXED>,
		2180	C<IO::AIO::MAP_GROWSDOWN>,
		2181	C<IO::AIO::MAP_32BIT>,
		2182	C<IO::AIO::MAP_HUGETLB> or
		2183	C<IO::AIO::MAP_STACK>.
		2184
		2185	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2186
		2187	C<$offset> is the offset from the start of the file - it generally must be
		2188	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2189
		2190	Example:
		2191
		2192	use Digest::MD5;
		2193	use IO::AIO;
		2194
		2195	open my $fh, "<verybigfile"
		2196	or die "$!";
		2197
		2198	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2199	or die "verybigfile: $!";
		2200
		2201	my $fast_md5 = md5 $data;
		2202
		2203	=item IO::AIO::munmap $scalar
		2204
		2205	Removes a previous mmap and undefines the C<$scalar>.
		2206
		2207	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2208
		2209	Calls the C<munlock> function, undoing the effects of a previous
		2210	C<aio_mlock> call (see its description for details).
		2211
		2212	=item IO::AIO::munlockall
		2213
		2214	Calls the C<munlockall> function.
		2215
		2216	On systems that do not implement C<munlockall>, this function returns
		2217	ENOSYS, otherwise the return value of C<munlockall>.
		2218
		2219	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2220
		2221	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2222	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2223	should be the file offset.
		2224
		2225	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2226	silently corrupt the data in this case.
		2227
		2228	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2229	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2230	C<IO::AIO::SPLICE_F_GIFT>.
		2231
		2232	See the C<splice(2)> manpage for details.
		2233
		2234	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2235
		2236	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2237	description for C<IO::AIO::splice> above for details.
		2238
		2239	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2240
		2241	Attempts to query or change the pipe buffer size. Obviously works only
		2242	on pipes, and currently works only on GNU/Linux systems, and fails with
		2243	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2244	size on other systems, drop me a note.
		2245
		2246	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2247
		2248	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2249	C<$flags> is missing or C<0>, then this should be the same as a call to
		2250	perl's built-in C<pipe> function and create a new pipe, and works on
		2251	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2252	(..., 4096, O_BINARY)>.
		2253
		2254	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2255	the given flags (Linux 2.6.27, glibc 2.9).
		2256
		2257	On success, the read and write file handles are returned.
		2258
		2259	On error, nothing will be returned. If the pipe2 syscall is missing and
		2260	C<$flags> is non-zero, fails with C<ENOSYS>.
		2261
		2262	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2263	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2264	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2265
		2266	=back
		2267
1299	=cut	2268	=cut
1300		2269
1301	min_parallel 8;	2270	min_parallel 8;
1302		2271
1303	END { flush }	2272	END { flush }
1304		2273
1305	1;	2274	1;
1306		2275
		2276	=head1 EVENT LOOP INTEGRATION
		2277
		2278	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2279	automatically into many event loops:
		2280
		2281	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2282	use AnyEvent::AIO;
		2283
		2284	You can also integrate IO::AIO manually into many event loops, here are
		2285	some examples of how to do this:
		2286
		2287	# EV integration
		2288	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2289
		2290	# Event integration
		2291	Event->io (fd => IO::AIO::poll_fileno,
		2292	poll => 'r',
		2293	cb => \&IO::AIO::poll_cb);
		2294
		2295	# Glib/Gtk2 integration
		2296	add_watch Glib::IO IO::AIO::poll_fileno,
		2297	in => sub { IO::AIO::poll_cb; 1 };
		2298
		2299	# Tk integration
		2300	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2301	readable => \&IO::AIO::poll_cb);
		2302
		2303	# Danga::Socket integration
		2304	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2305	\&IO::AIO::poll_cb);
		2306
1307	=head2 FORK BEHAVIOUR	2307	=head2 FORK BEHAVIOUR
1308		2308
1309	This module should do "the right thing" when the process using it forks:	2309	Usage of pthreads in a program changes the semantics of fork
		2310	considerably. Specifically, only async-safe functions can be called after
		2311	fork. Perl doesn't know about this, so in general, you cannot call fork
		2312	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2313	pthreads, so this applies, but many other extensions and (for inexplicable
		2314	reasons) perl itself often is linked against pthreads, so this limitation
		2315	applies to quite a lot of perls.
1310		2316
1311	Before the fork, IO::AIO enters a quiescent state where no requests	2317	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1312	can be added in other threads and no results will be processed. After	2318	only works in the process that loaded it. Forking is fully supported, but
1313	the fork the parent simply leaves the quiescent state and continues	2319	using IO::AIO in the child is not.
1314	request/result processing, while the child frees the request/result queue
1315	(so that the requests started before the fork will only be handled in the
1316	parent). Threads will be started on demand until the limit set in the
1317	parent process has been reached again.
1318		2320
1319	In short: the parent will, after a short pause, continue as if fork had	2321	You might get around by not I<using> IO::AIO before (or after)
1320	not been called, while the child will act as if IO::AIO has not been used	2322	forking. You could also try to call the L<IO::AIO::reinit> function in the
1321	yet.	2323	child:
		2324
		2325	=over 4
		2326
		2327	=item IO::AIO::reinit
		2328
		2329	Abandons all current requests and I/O threads and simply reinitialises all
		2330	data structures. This is not an operation supported by any standards, but
		2331	happens to work on GNU/Linux and some newer BSD systems.
		2332
		2333	The only reasonable use for this function is to call it after forking, if
		2334	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2335	the process will result in undefined behaviour. Calling it at any time
		2336	will also result in any undefined (by POSIX) behaviour.
		2337
		2338	=back
1322		2339
1323	=head2 MEMORY USAGE	2340	=head2 MEMORY USAGE
1324		2341
1325	Per-request usage:	2342	Per-request usage:
1326		2343

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