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Revision 1.15 by root, Mon Jul 11 03:09:00 2005 UTC vs.
Revision 1.211 by root, Tue Sep 27 12:10:29 2011 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
21	Event->io (fd => IO::AIO::poll_fileno,	22	use IO::AIO 2;
22	poll => 'r',
23	cb => \&IO::AIO::poll_cb);
24		23
25	# Glib/Gtk2	24	aioreq_pri 4; # give next request a very high priority
26	add_watch Glib::IO IO::AIO::poll_fileno,	25	my $req = aio_unlink "/tmp/file", sub { };
27	sub { IO::AIO::poll_cb, 1 };	26	$req->cancel; # cancel request if still in queue
28		27
29	# Tk	28	my $grp = aio_group sub { print "all stats done\n" };
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	29	add $grp aio_stat "..." for ...;
31	readable => \&IO::AIO::poll_cb);
32
33	# Danga::Socket
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);
36
37		30
38	=head1 DESCRIPTION	31	=head1 DESCRIPTION
39		32
40	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
41	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>).
42		36
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
		52
43	Currently, a number of threads are started that execute your read/writes	53	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	54	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	55	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	56	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	59	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	60	aio_write, so the remaining functionality would have to be implemented
		61	using threads anyway.
51		62
52	Although the module will work with in the presence of other threads, it is	63	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself.	64	it is currently not reentrant in any way, so use appropriate locking
		65	yourself, always call C<poll_cb> from within the same thread, or never
		66	call C<poll_cb> (or other C<aio_> functions) recursively.
		67
		68	=head2 EXAMPLE
		69
		70	This is a simple example that uses the EV module and loads
		71	F</etc/passwd> asynchronously:
		72
		73	use Fcntl;
		74	use EV;
		75	use IO::AIO;
		76
		77	# register the IO::AIO callback with EV
		78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		79
		80	# queue the request to open /etc/passwd
		81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		82	my $fh = shift
		83	or die "error while opening: $!";
		84
		85	# stat'ing filehandles is generally non-blocking
		86	my $size = -s $fh;
		87
		88	# queue a request to read the file
		89	my $contents;
		90	aio_read $fh, 0, $size, $contents, 0, sub {
		91	$_[0] == $size
		92	or die "short read: $!";
		93
		94	close $fh;
		95
		96	# file contents now in $contents
		97	print $contents;
		98
		99	# exit event loop and program
		100	EV::unloop;
		101	};
		102	};
		103
		104	# possibly queue up other requests, or open GUI windows,
		105	# check for sockets etc. etc.
		106
		107	# process events as long as there are some:
		108	EV::loop;
		109
		110	=head1 REQUEST ANATOMY AND LIFETIME
		111
		112	Every C<aio_*> function creates a request. which is a C data structure not
		113	directly visible to Perl.
		114
		115	If called in non-void context, every request function returns a Perl
		116	object representing the request. In void context, nothing is returned,
		117	which saves a bit of memory.
		118
		119	The perl object is a fairly standard ref-to-hash object. The hash contents
		120	are not used by IO::AIO so you are free to store anything you like in it.
		121
		122	During their existance, aio requests travel through the following states,
		123	in order:
		124
		125	=over 4
		126
		127	=item ready
		128
		129	Immediately after a request is created it is put into the ready state,
		130	waiting for a thread to execute it.
		131
		132	=item execute
		133
		134	A thread has accepted the request for processing and is currently
		135	executing it (e.g. blocking in read).
		136
		137	=item pending
		138
		139	The request has been executed and is waiting for result processing.
		140
		141	While request submission and execution is fully asynchronous, result
		142	processing is not and relies on the perl interpreter calling C<poll_cb>
		143	(or another function with the same effect).
		144
		145	=item result
		146
		147	The request results are processed synchronously by C<poll_cb>.
		148
		149	The C<poll_cb> function will process all outstanding aio requests by
		150	calling their callbacks, freeing memory associated with them and managing
		151	any groups they are contained in.
		152
		153	=item done
		154
		155	Request has reached the end of its lifetime and holds no resources anymore
		156	(except possibly for the Perl object, but its connection to the actual
		157	aio request is severed and calling its methods will either do nothing or
		158	result in a runtime error).
		159
		160	=back
54		161
55	=cut	162	=cut
56		163
57	package IO::AIO;	164	package IO::AIO;
58		165
		166	use Carp ();
		167
		168	use common::sense;
		169
59	use base 'Exporter';	170	use base 'Exporter';
60		171
61	use Fcntl ();
62
63	BEGIN {	172	BEGIN {
64	$VERSION = 0.3;	173	our $VERSION = '4.0';
65		174
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
67	aio_fsync aio_fdatasync aio_readahead);	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead
		180	aio_rename aio_link aio_move aio_copy aio_group
		181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
		185	aio_wd);
		186
		187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		189	min_parallel max_parallel max_idle idle_timeout
		190	nreqs nready npending nthreads
		191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
		196
		197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		198
70	require XSLoader;	199	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	200	XSLoader::load ("IO::AIO", $VERSION);
72	}	201	}
73		202
74	=head1 FUNCTIONS	203	=head1 FUNCTIONS
75		204
		205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes of the most important functions
		208	for quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		217	aio_readahead $fh,$offset,$length, $callback->($retval)
		218	aio_stat $fh_or_path, $callback->($status)
		219	aio_lstat $fh, $callback->($status)
		220	aio_statvfs $fh_or_path, $callback->($statvfs)
		221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		222	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		223	aio_truncate $fh_or_path, $offset, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_unlink $pathname, $callback->($status)
		226	aio_mknod $pathname, $mode, $dev, $callback->($status)
		227	aio_link $srcpath, $dstpath, $callback->($status)
		228	aio_symlink $srcpath, $dstpath, $callback->($status)
		229	aio_readlink $pathname, $callback->($link)
		230	aio_realpath $pathname, $callback->($link)
		231	aio_rename $srcpath, $dstpath, $callback->($status)
		232	aio_mkdir $pathname, $mode, $callback->($status)
		233	aio_rmdir $pathname, $callback->($status)
		234	aio_readdir $pathname, $callback->($entries)
		235	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		236	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		237	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		238	aio_load $pathname, $data, $callback->($status)
		239	aio_copy $srcpath, $dstpath, $callback->($status)
		240	aio_move $srcpath, $dstpath, $callback->($status)
		241	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		242	aio_rmtree $pathname, $callback->($status)
		243	aio_sync $callback->($status)
		244	aio_syncfs $fh, $callback->($status)
		245	aio_fsync $fh, $callback->($status)
		246	aio_fdatasync $fh, $callback->($status)
		247	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		248	aio_pathsync $pathname, $callback->($status)
		249	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		250	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		251	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		252	aio_mlockall $flags, $callback->($status)
		253	aio_group $callback->(...)
		254	aio_nop $callback->()
		255
		256	$prev_pri = aioreq_pri [$pri]
		257	aioreq_nice $pri_adjust
		258
		259	IO::AIO::poll_wait
		260	IO::AIO::poll_cb
		261	IO::AIO::poll
		262	IO::AIO::flush
		263	IO::AIO::max_poll_reqs $nreqs
		264	IO::AIO::max_poll_time $seconds
		265	IO::AIO::min_parallel $nthreads
		266	IO::AIO::max_parallel $nthreads
		267	IO::AIO::max_idle $nthreads
		268	IO::AIO::idle_timeout $seconds
		269	IO::AIO::max_outstanding $maxreqs
		270	IO::AIO::nreqs
		271	IO::AIO::nready
		272	IO::AIO::npending
		273
		274	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		275	IO::AIO::fadvise $fh, $offset, $len, $advice
		276	IO::AIO::madvise $scalar, $offset, $length, $advice
		277	IO::AIO::mprotect $scalar, $offset, $length, $protect
		278	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		279	IO::AIO::munlockall
		280
76	=head2 AIO FUNCTIONS	281	=head2 AIO REQUEST FUNCTIONS
77		282
78	All the C<aio_*> calls are more or less thin wrappers around the syscall	283	All the C<aio_*> calls are more or less thin wrappers around the syscall
79	with the same name (sans C<aio_>). The arguments are similar or identical,	284	with the same name (sans C<aio_>). The arguments are similar or identical,
80	and they all accept an additional (and optional) C<$callback> argument	285	and they all accept an additional (and optional) C<$callback> argument
81	which must be a code reference. This code reference will get called with	286	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	287	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	288	perl, which usually delivers "false") as its sole argument after the given
84	syscall has been executed asynchronously.	289	syscall has been executed asynchronously.
85		290
86	All functions that expect a filehandle will also accept a file descriptor.	291	All functions expecting a filehandle keep a copy of the filehandle
		292	internally until the request has finished.
87		293
		294	All functions return request objects of type L<IO::AIO::REQ> that allow
		295	further manipulation of those requests while they are in-flight.
		296
88	The filenames you pass to these routines I<must> be absolute. The reason	297	The pathnames you pass to these routines I<should> be absolute. The
89	is that at the time the request is being executed, the current working	298	reason for this is that at the time the request is being executed, the
90	directory could have changed. Alternatively, you can make sure that you	299	current working directory could have changed. Alternatively, you can make
91	never change the current working directory.	300	sure that you never change the current working directory anywhere in
		301	the program and then use relative paths. Lastly, you can take advantage
		302	of IO::AIOs working directory abstraction - see the description of the
		303	C<IO::AIO::WD> class later in this document.
		304
		305	To encode pathnames as octets, either make sure you either: a) always pass
		306	in filenames you got from outside (command line, readdir etc.) without
		307	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		308	your pathnames to the locale (or other) encoding in effect in the user
		309	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		310	use something else to ensure your scalar has the correct contents.
		311
		312	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		313	handles correctly whether it is set or not.
92		314
93	=over 4	315	=over 4
94		316
		317	=item $prev_pri = aioreq_pri [$pri]
		318
		319	Returns the priority value that would be used for the next request and, if
		320	C<$pri> is given, sets the priority for the next aio request.
		321
		322	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		323	and C<4>, respectively. Requests with higher priority will be serviced
		324	first.
		325
		326	The priority will be reset to C<0> after each call to one of the C<aio_*>
		327	functions.
		328
		329	Example: open a file with low priority, then read something from it with
		330	higher priority so the read request is serviced before other low priority
		331	open requests (potentially spamming the cache):
		332
		333	aioreq_pri -3;
		334	aio_open ..., sub {
		335	return unless $_[0];
		336
		337	aioreq_pri -2;
		338	aio_read $_[0], ..., sub {
		339	...
		340	};
		341	};
		342
		343
		344	=item aioreq_nice $pri_adjust
		345
		346	Similar to C<aioreq_pri>, but subtracts the given value from the current
		347	priority, so the effect is cumulative.
		348
		349
95	=item aio_open $pathname, $flags, $mode, $callback	350	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		351
97	Asynchronously open or create a file and call the callback with a newly	352	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	353	created filehandle for the file.
99		354
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	355	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
101	for an explanation.	356	for an explanation.
102		357
103	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	358	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
104	list. They are the same as used in C<sysopen>.	359	list. They are the same as used by C<sysopen>.
		360
		361	Likewise, C<$mode> specifies the mode of the newly created file, if it
		362	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		363	except that it is mandatory (i.e. use C<0> if you don't create new files,
		364	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		365	by the umask in effect then the request is being executed, so better never
		366	change the umask.
105		367
106	Example:	368	Example:
107		369
108	aio_open "/etc/passwd", O_RDONLY, 0, sub {	370	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
109	if ($_[0]) {	371	if ($_[0]) {
110	print "open successful, fh is $_[0]\n";	372	print "open successful, fh is $_[0]\n";
111	...	373	...
112	} else {	374	} else {
113	die "open failed: $!\n";	375	die "open failed: $!\n";
114	}	376	}
115	};	377	};
116		378
		379	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		380	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		381	following POSIX and non-POSIX constants are available (missing ones on
		382	your system are, as usual, C<0>):
		383
		384	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		385	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		386	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		387
		388
117	=item aio_close $fh, $callback	389	=item aio_close $fh, $callback->($status)
118		390
119	Asynchronously close a file and call the callback with the result	391	Asynchronously close a file and call the callback with the result
120	code. I<WARNING:> although accepted, you should not pass in a perl	392	code.
121	filehandle here, as perl will likely close the file descriptor itself when
122	the filehandle is destroyed. Normally, you can safely call perls C<close>
123	or just let filehandles go out of scope.
124		393
		394	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
		395	closing the file descriptor associated with the filehandle itself.
		396
		397	Therefore, C<aio_close> will not close the filehandle - instead it will
		398	use dup2 to overwrite the file descriptor with the write-end of a pipe
		399	(the pipe fd will be created on demand and will be cached).
		400
		401	Or in other words: the file descriptor will be closed, but it will not be
		402	free for reuse until the perl filehandle is closed.
		403
		404	=cut
		405
125	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	406	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
126		407
127	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	408	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128		409
129	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	410	Reads or writes C<$length> bytes from or to the specified C<$fh> and
130	into the scalar given by C<data> and offset C<dataoffset> and calls the	411	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
131	callback without the actual number of bytes read (or -1 on error, just	412	and calls the callback without the actual number of bytes read (or -1 on
132	like the syscall).	413	error, just like the syscall).
133		414
		415	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		416	offset plus the actual number of bytes read.
		417
		418	If C<$offset> is undefined, then the current file descriptor offset will
		419	be used (and updated), otherwise the file descriptor offset will not be
		420	changed by these calls.
		421
		422	If C<$length> is undefined in C<aio_write>, use the remaining length of
		423	C<$data>.
		424
		425	If C<$dataoffset> is less than zero, it will be counted from the end of
		426	C<$data>.
		427
		428	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		429	is outstanding. Modifying it can result in segfaults or World War III (if
		430	the necessary/optional hardware is installed).
		431
134	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	432	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
135	offset C<0> within the scalar:	433	offset C<0> within the scalar:
136		434
137	aio_read $fh, 7, 15, $buffer, 0, sub {	435	aio_read $fh, 7, 15, $buffer, 0, sub {
138	$_[0] > 0 or die "read error: $!";	436	$_[0] > 0 or die "read error: $!";
139	print "read $_[0] bytes: <$buffer>\n";	437	print "read $_[0] bytes: <$buffer>\n";
140	};	438	};
141		439
		440
		441	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		442
		443	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		444	reading at byte offset C<$in_offset>, and starts writing at the current
		445	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		446	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		447	other. The same C<$in_fh> works fine though, as this function does not
		448	move or use the file offset of C<$in_fh>.
		449
		450	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		451	are written, and there is no way to find out how many more bytes have been
		452	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		453	number of bytes written to C<$out_fh>. Only if the result value equals
		454	C<$length> one can assume that C<$length> bytes have been read.
		455
		456	Unlike with other C<aio_> functions, it makes a lot of sense to use
		457	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		458	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		459	the socket I/O will be non-blocking. Note, however, that you can run
		460	into a trap where C<aio_sendfile> reads some data with readahead, then
		461	fails to write all data, and when the socket is ready the next time, the
		462	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		463	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		464	resource usage.
		465
		466	This call tries to make use of a native C<sendfile>-like syscall to
		467	provide zero-copy operation. For this to work, C<$out_fh> should refer to
		468	a socket, and C<$in_fh> should refer to an mmap'able file.
		469
		470	If a native sendfile cannot be found or it fails with C<ENOSYS>,
		471	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		472	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
		473	type of filehandle regardless of the limitations of the operating system.
		474
		475	As native sendfile syscalls (as practically any non-POSIX interface hacked
		476	together in a hurry to improve benchmark numbers) tend to be rather buggy
		477	on many systems, this implementation tries to work around some known bugs
		478	in Linux and FreeBSD kernels (probably others, too), but that might fail,
		479	so you really really should check the return value of C<aio_sendfile> -
		480	fewre bytes than expected might have been transferred.
		481
		482
142	=item aio_readahead $fh,$offset,$length, $callback	483	=item aio_readahead $fh,$offset,$length, $callback->($retval)
143		484
144	Asynchronously reads the specified byte range into the page cache, using
145	the C<readahead> syscall. If that syscall doesn't exist the status will be
146	C<-1> and C<$!> is set to ENOSYS.
147
148	readahead() populates the page cache with data from a file so that	485	C<aio_readahead> populates the page cache with data from a file so that
149	subsequent reads from that file will not block on disk I/O. The C<$offset>	486	subsequent reads from that file will not block on disk I/O. The C<$offset>
150	argument specifies the starting point from which data is to be read and	487	argument specifies the starting point from which data is to be read and
151	C<$length> specifies the number of bytes to be read. I/O is performed in	488	C<$length> specifies the number of bytes to be read. I/O is performed in
152	whole pages, so that offset is effectively rounded down to a page boundary	489	whole pages, so that offset is effectively rounded down to a page boundary
153	and bytes are read up to the next page boundary greater than or equal to	490	and bytes are read up to the next page boundary greater than or equal to
154	(off-set+length). aio_readahead() does not read beyond the end of the	491	(off-set+length). C<aio_readahead> does not read beyond the end of the
155	file. The current file offset of the file is left unchanged.	492	file. The current file offset of the file is left unchanged.
156		493
		494	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		495	emulated by simply reading the data, which would have a similar effect.
		496
		497
157	=item aio_stat $fh_or_path, $callback	498	=item aio_stat $fh_or_path, $callback->($status)
158		499
159	=item aio_lstat $fh, $callback	500	=item aio_lstat $fh, $callback->($status)
160		501
161	Works like perl's C<stat> or C<lstat> in void context. The callback will	502	Works like perl's C<stat> or C<lstat> in void context. The callback will
162	be called after the stat and the results will be available using C<stat _>	503	be called after the stat and the results will be available using C<stat _>
163	or C<-s _> etc...	504	or C<-s _> etc...
164		505
…		…
166	for an explanation.	507	for an explanation.
167		508
168	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	509	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
169	error when stat'ing a large file, the results will be silently truncated	510	error when stat'ing a large file, the results will be silently truncated
170	unless perl itself is compiled with large file support.	511	unless perl itself is compiled with large file support.
		512
		513	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		514	following constants and functions (if not implemented, the constants will
		515	be C<0> and the functions will either C<croak> or fall back on traditional
		516	behaviour).
		517
		518	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		519	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		520	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
171		521
172	Example: Print the length of F</etc/passwd>:	522	Example: Print the length of F</etc/passwd>:
173		523
174	aio_stat "/etc/passwd", sub {	524	aio_stat "/etc/passwd", sub {
175	$_[0] and die "stat failed: $!";	525	$_[0] and die "stat failed: $!";
176	print "size is ", -s _, "\n";	526	print "size is ", -s _, "\n";
177	};	527	};
178		528
		529
		530	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		531
		532	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		533	whether a file handle or path was passed.
		534
		535	On success, the callback is passed a hash reference with the following
		536	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		537	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		538	is passed.
		539
		540	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		541	C<ST_NOSUID>.
		542
		543	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		544	their correct value when available, or to C<0> on systems that do
		545	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		546	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		547	C<ST_NODIRATIME> and C<ST_RELATIME>.
		548
		549	Example: stat C</wd> and dump out the data if successful.
		550
		551	aio_statvfs "/wd", sub {
		552	my $f = $_[0]
		553	or die "statvfs: $!";
		554
		555	use Data::Dumper;
		556	say Dumper $f;
		557	};
		558
		559	# result:
		560	{
		561	bsize => 1024,
		562	bfree => 4333064312,
		563	blocks => 10253828096,
		564	files => 2050765568,
		565	flag => 4096,
		566	favail => 2042092649,
		567	bavail => 4333064312,
		568	ffree => 2042092649,
		569	namemax => 255,
		570	frsize => 1024,
		571	fsid => 1810
		572	}
		573
		574
		575	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		576
		577	Works like perl's C<utime> function (including the special case of $atime
		578	and $mtime being undef). Fractional times are supported if the underlying
		579	syscalls support them.
		580
		581	When called with a pathname, uses utimes(2) if available, otherwise
		582	utime(2). If called on a file descriptor, uses futimes(2) if available,
		583	otherwise returns ENOSYS, so this is not portable.
		584
		585	Examples:
		586
		587	# set atime and mtime to current time (basically touch(1)):
		588	aio_utime "path", undef, undef;
		589	# set atime to current time and mtime to beginning of the epoch:
		590	aio_utime "path", time, undef; # undef==0
		591
		592
		593	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		594
		595	Works like perl's C<chown> function, except that C<undef> for either $uid
		596	or $gid is being interpreted as "do not change" (but -1 can also be used).
		597
		598	Examples:
		599
		600	# same as "chown root path" in the shell:
		601	aio_chown "path", 0, -1;
		602	# same as above:
		603	aio_chown "path", 0, undef;
		604
		605
		606	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		607
		608	Works like truncate(2) or ftruncate(2).
		609
		610
		611	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		612
		613	Works like perl's C<chmod> function.
		614
		615
179	=item aio_unlink $pathname, $callback	616	=item aio_unlink $pathname, $callback->($status)
180		617
181	Asynchronously unlink (delete) a file and call the callback with the	618	Asynchronously unlink (delete) a file and call the callback with the
182	result code.	619	result code.
183		620
		621
		622	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		623
		624	[EXPERIMENTAL]
		625
		626	Asynchronously create a device node (or fifo). See mknod(2).
		627
		628	The only (POSIX-) portable way of calling this function is:
		629
		630	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		631
		632	See C<aio_stat> for info about some potentially helpful extra constants
		633	and functions.
		634
		635	=item aio_link $srcpath, $dstpath, $callback->($status)
		636
		637	Asynchronously create a new link to the existing object at C<$srcpath> at
		638	the path C<$dstpath> and call the callback with the result code.
		639
		640
		641	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		642
		643	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		644	the path C<$dstpath> and call the callback with the result code.
		645
		646
		647	=item aio_readlink $pathname, $callback->($link)
		648
		649	Asynchronously read the symlink specified by C<$path> and pass it to
		650	the callback. If an error occurs, nothing or undef gets passed to the
		651	callback.
		652
		653
		654	=item aio_realpath $pathname, $callback->($path)
		655
		656	Asynchronously make the path absolute and resolve any symlinks in
		657	C<$path>. The resulting path only consists of directories (Same as
		658	L<Cwd::realpath>).
		659
		660	This request can be used to get the absolute path of the current working
		661	directory by passing it a path of F<.> (a single dot).
		662
		663
		664	=item aio_rename $srcpath, $dstpath, $callback->($status)
		665
		666	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		667	rename(2) and call the callback with the result code.
		668
		669
		670	=item aio_mkdir $pathname, $mode, $callback->($status)
		671
		672	Asynchronously mkdir (create) a directory and call the callback with
		673	the result code. C<$mode> will be modified by the umask at the time the
		674	request is executed, so do not change your umask.
		675
		676
		677	=item aio_rmdir $pathname, $callback->($status)
		678
		679	Asynchronously rmdir (delete) a directory and call the callback with the
		680	result code.
		681
		682
		683	=item aio_readdir $pathname, $callback->($entries)
		684
		685	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		686	directory (i.e. opendir + readdir + closedir). The entries will not be
		687	sorted, and will B<NOT> include the C<.> and C<..> entries.
		688
		689	The callback is passed a single argument which is either C<undef> or an
		690	array-ref with the filenames.
		691
		692
		693	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		694
		695	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		696	tune behaviour and output format. In case of an error, C<$entries> will be
		697	C<undef>.
		698
		699	The flags are a combination of the following constants, ORed together (the
		700	flags will also be passed to the callback, possibly modified):
		701
		702	=over 4
		703
		704	=item IO::AIO::READDIR_DENTS
		705
		706	When this flag is off, then the callback gets an arrayref consisting of
		707	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		708	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		709	entry in more detail.
		710
		711	C<$name> is the name of the entry.
		712
		713	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		714
		715	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		716	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		717	C<IO::AIO::DT_WHT>.
		718
		719	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		720	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		721	scalars are read-only: you can not modify them.
		722
		723	C<$inode> is the inode number (which might not be exact on systems with 64
		724	bit inode numbers and 32 bit perls). This field has unspecified content on
		725	systems that do not deliver the inode information.
		726
		727	=item IO::AIO::READDIR_DIRS_FIRST
		728
		729	When this flag is set, then the names will be returned in an order where
		730	likely directories come first, in optimal stat order. This is useful when
		731	you need to quickly find directories, or you want to find all directories
		732	while avoiding to stat() each entry.
		733
		734	If the system returns type information in readdir, then this is used
		735	to find directories directly. Otherwise, likely directories are names
		736	beginning with ".", or otherwise names with no dots, of which names with
		737	short names are tried first.
		738
		739	=item IO::AIO::READDIR_STAT_ORDER
		740
		741	When this flag is set, then the names will be returned in an order
		742	suitable for stat()'ing each one. That is, when you plan to stat()
		743	all files in the given directory, then the returned order will likely
		744	be fastest.
		745
		746	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		747	the likely dirs come first, resulting in a less optimal stat order.
		748
		749	=item IO::AIO::READDIR_FOUND_UNKNOWN
		750
		751	This flag should not be set when calling C<aio_readdirx>. Instead, it
		752	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		753	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		754	C<$type>'s are known, which can be used to speed up some algorithms.
		755
		756	=back
		757
		758
		759	=item aio_load $pathname, $data, $callback->($status)
		760
		761	This is a composite request that tries to fully load the given file into
		762	memory. Status is the same as with aio_read.
		763
		764	=cut
		765
		766	sub aio_load($$;$) {
		767	my ($path, undef, $cb) = @_;
		768	my $data = \$_[1];
		769
		770	my $pri = aioreq_pri;
		771	my $grp = aio_group $cb;
		772
		773	aioreq_pri $pri;
		774	add $grp aio_open $path, O_RDONLY, 0, sub {
		775	my $fh = shift
		776	or return $grp->result (-1);
		777
		778	aioreq_pri $pri;
		779	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		780	$grp->result ($_[0]);
		781	};
		782	};
		783
		784	$grp
		785	}
		786
		787	=item aio_copy $srcpath, $dstpath, $callback->($status)
		788
		789	Try to copy the I<file> (directories not supported as either source or
		790	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		791	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		792
		793	This is a composite request that creates the destination file with
		794	mode 0200 and copies the contents of the source file into it using
		795	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		796	uid/gid, in that order.
		797
		798	If an error occurs, the partial destination file will be unlinked, if
		799	possible, except when setting atime, mtime, access mode and uid/gid, where
		800	errors are being ignored.
		801
		802	=cut
		803
		804	sub aio_copy($$;$) {
		805	my ($src, $dst, $cb) = @_;
		806
		807	my $pri = aioreq_pri;
		808	my $grp = aio_group $cb;
		809
		810	aioreq_pri $pri;
		811	add $grp aio_open $src, O_RDONLY, 0, sub {
		812	if (my $src_fh = $_[0]) {
		813	my @stat = stat $src_fh; # hmm, might block over nfs?
		814
		815	aioreq_pri $pri;
		816	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		817	if (my $dst_fh = $_[0]) {
		818	aioreq_pri $pri;
		819	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		820	if ($_[0] == $stat[7]) {
		821	$grp->result (0);
		822	close $src_fh;
		823
		824	my $ch = sub {
		825	aioreq_pri $pri;
		826	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		827	aioreq_pri $pri;
		828	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		829	aioreq_pri $pri;
		830	add $grp aio_close $dst_fh;
		831	}
		832	};
		833	};
		834
		835	aioreq_pri $pri;
		836	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		837	if ($_[0] < 0 && $! == ENOSYS) {
		838	aioreq_pri $pri;
		839	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		840	} else {
		841	$ch->();
		842	}
		843	};
		844	} else {
		845	$grp->result (-1);
		846	close $src_fh;
		847	close $dst_fh;
		848
		849	aioreq $pri;
		850	add $grp aio_unlink $dst;
		851	}
		852	};
		853	} else {
		854	$grp->result (-1);
		855	}
		856	},
		857
		858	} else {
		859	$grp->result (-1);
		860	}
		861	};
		862
		863	$grp
		864	}
		865
		866	=item aio_move $srcpath, $dstpath, $callback->($status)
		867
		868	Try to move the I<file> (directories not supported as either source or
		869	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		870	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		871
		872	This is a composite request that tries to rename(2) the file first; if
		873	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		874	that is successful, unlinks the C<$srcpath>.
		875
		876	=cut
		877
		878	sub aio_move($$;$) {
		879	my ($src, $dst, $cb) = @_;
		880
		881	my $pri = aioreq_pri;
		882	my $grp = aio_group $cb;
		883
		884	aioreq_pri $pri;
		885	add $grp aio_rename $src, $dst, sub {
		886	if ($_[0] && $! == EXDEV) {
		887	aioreq_pri $pri;
		888	add $grp aio_copy $src, $dst, sub {
		889	$grp->result ($_[0]);
		890
		891	unless ($_[0]) {
		892	aioreq_pri $pri;
		893	add $grp aio_unlink $src;
		894	}
		895	};
		896	} else {
		897	$grp->result ($_[0]);
		898	}
		899	};
		900
		901	$grp
		902	}
		903
		904	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		905
		906	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		907	efficiently separate the entries of directory C<$path> into two sets of
		908	names, directories you can recurse into (directories), and ones you cannot
		909	recurse into (everything else, including symlinks to directories).
		910
		911	C<aio_scandir> is a composite request that creates of many sub requests_
		912	C<$maxreq> specifies the maximum number of outstanding aio requests that
		913	this function generates. If it is C<< <= 0 >>, then a suitable default
		914	will be chosen (currently 4).
		915
		916	On error, the callback is called without arguments, otherwise it receives
		917	two array-refs with path-relative entry names.
		918
		919	Example:
		920
		921	aio_scandir $dir, 0, sub {
		922	my ($dirs, $nondirs) = @_;
		923	print "real directories: @$dirs\n";
		924	print "everything else: @$nondirs\n";
		925	};
		926
		927	Implementation notes.
		928
		929	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		930
		931	If readdir returns file type information, then this is used directly to
		932	find directories.
		933
		934	Otherwise, after reading the directory, the modification time, size etc.
		935	of the directory before and after the readdir is checked, and if they
		936	match (and isn't the current time), the link count will be used to decide
		937	how many entries are directories (if >= 2). Otherwise, no knowledge of the
		938	number of subdirectories will be assumed.
		939
		940	Then entries will be sorted into likely directories a non-initial dot
		941	currently) and likely non-directories (see C<aio_readdirx>). Then every
		942	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		943	in order of their inode numbers. If that succeeds, it assumes that the
		944	entry is a directory or a symlink to directory (which will be checked
		945	separately). This is often faster than stat'ing the entry itself because
		946	filesystems might detect the type of the entry without reading the inode
		947	data (e.g. ext2fs filetype feature), even on systems that cannot return
		948	the filetype information on readdir.
		949
		950	If the known number of directories (link count - 2) has been reached, the
		951	rest of the entries is assumed to be non-directories.
		952
		953	This only works with certainty on POSIX (= UNIX) filesystems, which
		954	fortunately are the vast majority of filesystems around.
		955
		956	It will also likely work on non-POSIX filesystems with reduced efficiency
		957	as those tend to return 0 or 1 as link counts, which disables the
		958	directory counting heuristic.
		959
		960	=cut
		961
		962	sub aio_scandir($$;$) {
		963	my ($path, $maxreq, $cb) = @_;
		964
		965	my $pri = aioreq_pri;
		966
		967	my $grp = aio_group $cb;
		968
		969	$maxreq = 4 if $maxreq <= 0;
		970
		971	# get a wd object
		972
		973	aioreq_pri $pri;
		974	add $grp aio_wd $path, sub {
		975	my $wd = [shift, "."];
		976
		977	# stat once
		978	aioreq_pri $pri;
		979	add $grp aio_stat $wd, sub {
		980	return $grp->result () if $_[0];
		981	my $now = time;
		982	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		983
		984	# read the directory entries
		985	aioreq_pri $pri;
		986	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		987	my $entries = shift
		988	or return $grp->result ();
		989
		990	# stat the dir another time
		991	aioreq_pri $pri;
		992	add $grp aio_stat $wd, sub {
		993	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		994
		995	my $ndirs;
		996
		997	# take the slow route if anything looks fishy
		998	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		999	$ndirs = -1;
		1000	} else {
		1001	# if nlink == 2, we are finished
		1002	# for non-posix-fs's, we rely on nlink < 2
		1003	$ndirs = (stat _)[3] - 2
		1004	or return $grp->result ([], $entries);
		1005	}
		1006
		1007	my (@dirs, @nondirs);
		1008
		1009	my $statgrp = add $grp aio_group sub {
		1010	$grp->result (\@dirs, \@nondirs);
		1011	};
		1012
		1013	limit $statgrp $maxreq;
		1014	feed $statgrp sub {
		1015	return unless @$entries;
		1016	my $entry = shift @$entries;
		1017
		1018	aioreq_pri $pri;
		1019	$wd->[1] = "$entry/.";
		1020	add $statgrp aio_stat $wd, sub {
		1021	if ($_[0] < 0) {
		1022	push @nondirs, $entry;
		1023	} else {
		1024	# need to check for real directory
		1025	aioreq_pri $pri;
		1026	$wd->[1] = $entry;
		1027	add $statgrp aio_lstat $wd, sub {
		1028	if (-d _) {
		1029	push @dirs, $entry;
		1030
		1031	unless (--$ndirs) {
		1032	push @nondirs, @$entries;
		1033	feed $statgrp;
		1034	}
		1035	} else {
		1036	push @nondirs, $entry;
		1037	}
		1038	}
		1039	}
		1040	};
		1041	};
		1042	};
		1043	};
		1044	};
		1045	};
		1046
		1047	$grp
		1048	}
		1049
		1050	=item aio_rmtree $pathname, $callback->($status)
		1051
		1052	Delete a directory tree starting (and including) C<$path>, return the
		1053	status of the final C<rmdir> only. This is a composite request that
		1054	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1055	everything else.
		1056
		1057	=cut
		1058
		1059	sub aio_rmtree;
		1060	sub aio_rmtree($;$) {
		1061	my ($path, $cb) = @_;
		1062
		1063	my $pri = aioreq_pri;
		1064	my $grp = aio_group $cb;
		1065
		1066	aioreq_pri $pri;
		1067	add $grp aio_scandir $path, 0, sub {
		1068	my ($dirs, $nondirs) = @_;
		1069
		1070	my $dirgrp = aio_group sub {
		1071	add $grp aio_rmdir $path, sub {
		1072	$grp->result ($_[0]);
		1073	};
		1074	};
		1075
		1076	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1077	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1078
		1079	add $grp $dirgrp;
		1080	};
		1081
		1082	$grp
		1083	}
		1084
		1085	=item aio_sync $callback->($status)
		1086
		1087	Asynchronously call sync and call the callback when finished.
		1088
184	=item aio_fsync $fh, $callback	1089	=item aio_fsync $fh, $callback->($status)
185		1090
186	Asynchronously call fsync on the given filehandle and call the callback	1091	Asynchronously call fsync on the given filehandle and call the callback
187	with the fsync result code.	1092	with the fsync result code.
188		1093
189	=item aio_fdatasync $fh, $callback	1094	=item aio_fdatasync $fh, $callback->($status)
190		1095
191	Asynchronously call fdatasync on the given filehandle and call the	1096	Asynchronously call fdatasync on the given filehandle and call the
192	callback with the fdatasync result code.	1097	callback with the fdatasync result code.
193		1098
		1099	If this call isn't available because your OS lacks it or it couldn't be
		1100	detected, it will be emulated by calling C<fsync> instead.
		1101
		1102	=item aio_syncfs $fh, $callback->($status)
		1103
		1104	Asynchronously call the syncfs syscall to sync the filesystem associated
		1105	to the given filehandle and call the callback with the syncfs result
		1106	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1107	errno to C<ENOSYS> nevertheless.
		1108
		1109	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1110
		1111	Sync the data portion of the file specified by C<$offset> and C<$length>
		1112	to disk (but NOT the metadata), by calling the Linux-specific
		1113	sync_file_range call. If sync_file_range is not available or it returns
		1114	ENOSYS, then fdatasync or fsync is being substituted.
		1115
		1116	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1117	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1118	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1119	manpage for details.
		1120
		1121	=item aio_pathsync $pathname, $callback->($status)
		1122
		1123	This request tries to open, fsync and close the given path. This is a
		1124	composite request intended to sync directories after directory operations
		1125	(E.g. rename). This might not work on all operating systems or have any
		1126	specific effect, but usually it makes sure that directory changes get
		1127	written to disc. It works for anything that can be opened for read-only,
		1128	not just directories.
		1129
		1130	Future versions of this function might fall back to other methods when
		1131	C<fsync> on the directory fails (such as calling C<sync>).
		1132
		1133	Passes C<0> when everything went ok, and C<-1> on error.
		1134
		1135	=cut
		1136
		1137	sub aio_pathsync($;$) {
		1138	my ($path, $cb) = @_;
		1139
		1140	my $pri = aioreq_pri;
		1141	my $grp = aio_group $cb;
		1142
		1143	aioreq_pri $pri;
		1144	add $grp aio_open $path, O_RDONLY, 0, sub {
		1145	my ($fh) = @_;
		1146	if ($fh) {
		1147	aioreq_pri $pri;
		1148	add $grp aio_fsync $fh, sub {
		1149	$grp->result ($_[0]);
		1150
		1151	aioreq_pri $pri;
		1152	add $grp aio_close $fh;
		1153	};
		1154	} else {
		1155	$grp->result (-1);
		1156	}
		1157	};
		1158
		1159	$grp
		1160	}
		1161
		1162	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1163
		1164	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1165	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1166	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1167	scalar must only be modified in-place while an aio operation is pending on
		1168	it).
		1169
		1170	It calls the C<msync> function of your OS, if available, with the memory
		1171	area starting at C<$offset> in the string and ending C<$length> bytes
		1172	later. If C<$length> is negative, counts from the end, and if C<$length>
		1173	is C<undef>, then it goes till the end of the string. The flags can be
		1174	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1175	C<IO::AIO::MS_SYNC>.
		1176
		1177	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1178
		1179	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1180	scalars.
		1181
		1182	It touches (reads or writes) all memory pages in the specified
		1183	range inside the scalar. All caveats and parameters are the same
		1184	as for C<aio_msync>, above, except for flags, which must be either
		1185	C<0> (which reads all pages and ensures they are instantiated) or
		1186	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1187	writing an octet from it, which dirties the page).
		1188
		1189	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1190
		1191	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1192	scalars.
		1193
		1194	It reads in all the pages of the underlying storage into memory (if any)
		1195	and locks them, so they are not getting swapped/paged out or removed.
		1196
		1197	If C<$length> is undefined, then the scalar will be locked till the end.
		1198
		1199	On systems that do not implement C<mlock>, this function returns C<-1>
		1200	and sets errno to C<ENOSYS>.
		1201
		1202	Note that the corresponding C<munlock> is synchronous and is
		1203	documented under L<MISCELLANEOUS FUNCTIONS>.
		1204
		1205	Example: open a file, mmap and mlock it - both will be undone when
		1206	C<$data> gets destroyed.
		1207
		1208	open my $fh, "<", $path or die "$path: $!";
		1209	my $data;
		1210	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1211	aio_mlock $data; # mlock in background
		1212
		1213	=item aio_mlockall $flags, $callback->($status)
		1214
		1215	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1216	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1217
		1218	On systems that do not implement C<mlockall>, this function returns C<-1>
		1219	and sets errno to C<ENOSYS>.
		1220
		1221	Note that the corresponding C<munlockall> is synchronous and is
		1222	documented under L<MISCELLANEOUS FUNCTIONS>.
		1223
		1224	Example: asynchronously lock all current and future pages into memory.
		1225
		1226	aio_mlockall IO::AIO::MCL_FUTURE;
		1227
		1228	=item aio_group $callback->(...)
		1229
		1230	This is a very special aio request: Instead of doing something, it is a
		1231	container for other aio requests, which is useful if you want to bundle
		1232	many requests into a single, composite, request with a definite callback
		1233	and the ability to cancel the whole request with its subrequests.
		1234
		1235	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		1236	for more info.
		1237
		1238	Example:
		1239
		1240	my $grp = aio_group sub {
		1241	print "all stats done\n";
		1242	};
		1243
		1244	add $grp
		1245	(aio_stat ...),
		1246	(aio_stat ...),
		1247	...;
		1248
		1249	=item aio_nop $callback->()
		1250
		1251	This is a special request - it does nothing in itself and is only used for
		1252	side effects, such as when you want to add a dummy request to a group so
		1253	that finishing the requests in the group depends on executing the given
		1254	code.
		1255
		1256	While this request does nothing, it still goes through the execution
		1257	phase and still requires a worker thread. Thus, the callback will not
		1258	be executed immediately but only after other requests in the queue have
		1259	entered their execution phase. This can be used to measure request
		1260	latency.
		1261
		1262	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1263
		1264	Mainly used for debugging and benchmarking, this aio request puts one of
		1265	the request workers to sleep for the given time.
		1266
		1267	While it is theoretically handy to have simple I/O scheduling requests
		1268	like sleep and file handle readable/writable, the overhead this creates is
		1269	immense (it blocks a thread for a long time) so do not use this function
		1270	except to put your application under artificial I/O pressure.
		1271
194	=back	1272	=back
195		1273
		1274
		1275	=head2 IO::AIO::WD - multiple working directories
		1276
		1277	Your process only has one current working directory, which is used by all
		1278	threads. This makes it hard to use relative paths (some other component
		1279	could call C<chdir> at any time, and it is hard to control when the path
		1280	will be used by IO::AIO).
		1281
		1282	One solution for this is to always use absolute paths. This usually works,
		1283	but can be quite slow (the kernel has to walk the whole path on every
		1284	access), and can also be a hassle to implement.
		1285
		1286	Newer POSIX systems have a number of functions (openat, fdopendir,
		1287	futimensat and so on) that make it possible to specify working directories
		1288	per operation.
		1289
		1290	For portability, and because the clowns who "designed", or shall I write,
		1291	perpetrated this new interface were obviously half-drunk, this abstraction
		1292	cannot be perfect, though.
		1293
		1294	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1295	object. This object stores the canonicalised, absolute version of the
		1296	path, and on systems that allow it, also a directory file descriptor.
		1297
		1298	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1299	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1300	object and a pathname instead. If the pathname is absolute, the
		1301	IO::AIO::WD objetc is ignored, otherwise the pathname is resolved relative
		1302	to that IO::AIO::WD object.
		1303
		1304	For example, to get a wd object for F</etc> and then stat F<passwd>
		1305	inside, you would write:
		1306
		1307	aio_wd "/etc", sub {
		1308	my $etcdir = shift;
		1309
		1310	# although $etcdir can be undef on error, there is generally no reason
		1311	# to check for errors here, as aio_stat will fail with ENOENT
		1312	# when $etcdir is undef.
		1313
		1314	aio_stat [$etcdir, "passwd"], sub {
		1315	# yay
		1316	};
		1317	};
		1318
		1319	This shows that creating an IO::AIO::WD object is itself a potentially
		1320	blocking operation, which is why it is done asynchronously.
		1321
		1322	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1323	object and the pathname string, so you could write the following without
		1324	causing any issues due to C<$path> getting reused:
		1325
		1326	my $path = [$wd, undef];
		1327
		1328	for my $name (qw(abc def ghi)) {
		1329	$path->[1] = $name;
		1330	aio_stat $path, sub {
		1331	# ...
		1332	};
		1333	}
		1334
		1335	There are some caveats: when directories get renamed (or deleted), the
		1336	pathname string doesn't change, so will point to the new directory (or
		1337	nowhere at all), while the directory fd, if available on the system,
		1338	will still point to the original directory. Most functions accepting a
		1339	pathname will use the directory fd on newer systems, and the string on
		1340	older systems. Some functions (such as realpath) will always rely on the
		1341	string form of the pathname.
		1342
		1343	So this fucntionality is mainly useful to get some protection against
		1344	C<chdir>, to easily get an absolute path out of a relative path for future
		1345	reference, and to speed up doing many operations in the same directory
		1346	(e.g. when stat'ing all files in a directory).
		1347
		1348	The following functions implement this working directory abstraction:
		1349
		1350	=over 4
		1351
		1352	=item aio_wd $pathname, $callback->($wd)
		1353
		1354	Asynchonously canonicalise the given pathname and convert it to an
		1355	IO::AIO::WD object representing it. If possible and supported on the
		1356	system, also open a directory fd to speed up pathname resolution relative
		1357	to this working directory.
		1358
		1359	If something goes wrong, then C<undef> is passwd to the callback instead
		1360	of a working directory object and C<$!> is set appropriately. Since
		1361	passing C<undef> as working directory component of a pathname fails the
		1362	request with C<ENOENT>, there is often no need for error checking in the
		1363	C<aio_wd> callback, as future requests using the value will fail in the
		1364	expected way.
		1365
		1366	If this call isn't available because your OS lacks it or it couldn't be
		1367	detected, it will be emulated by calling C<fsync> instead.
		1368
		1369	=item IO::AIO::CWD
		1370
		1371	This is a compiletime constant (object) that represents the process
		1372	current working directory.
		1373
		1374	Specifying this object as working directory object for a pathname is as
		1375	if the pathname would be specified directly, without a directory object,
		1376	e.g., these calls are functionally identical:
		1377
		1378	aio_stat "somefile", sub { ... };
		1379	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1380
		1381	=back
		1382
		1383
		1384	=head2 IO::AIO::REQ CLASS
		1385
		1386	All non-aggregate C<aio_*> functions return an object of this class when
		1387	called in non-void context.
		1388
		1389	=over 4
		1390
		1391	=item cancel $req
		1392
		1393	Cancels the request, if possible. Has the effect of skipping execution
		1394	when entering the B<execute> state and skipping calling the callback when
		1395	entering the the B<result> state, but will leave the request otherwise
		1396	untouched (with the exception of readdir). That means that requests that
		1397	currently execute will not be stopped and resources held by the request
		1398	will not be freed prematurely.
		1399
		1400	=item cb $req $callback->(...)
		1401
		1402	Replace (or simply set) the callback registered to the request.
		1403
		1404	=back
		1405
		1406	=head2 IO::AIO::GRP CLASS
		1407
		1408	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1409	objects of this class, too.
		1410
		1411	A IO::AIO::GRP object is a special request that can contain multiple other
		1412	aio requests.
		1413
		1414	You create one by calling the C<aio_group> constructing function with a
		1415	callback that will be called when all contained requests have entered the
		1416	C<done> state:
		1417
		1418	my $grp = aio_group sub {
		1419	print "all requests are done\n";
		1420	};
		1421
		1422	You add requests by calling the C<add> method with one or more
		1423	C<IO::AIO::REQ> objects:
		1424
		1425	$grp->add (aio_unlink "...");
		1426
		1427	add $grp aio_stat "...", sub {
		1428	$_[0] or return $grp->result ("error");
		1429
		1430	# add another request dynamically, if first succeeded
		1431	add $grp aio_open "...", sub {
		1432	$grp->result ("ok");
		1433	};
		1434	};
		1435
		1436	This makes it very easy to create composite requests (see the source of
		1437	C<aio_move> for an application) that work and feel like simple requests.
		1438
		1439	=over 4
		1440
		1441	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1442	C<IO::AIO::poll_cb>, just like any other request.
		1443
		1444	=item * They can be canceled like any other request. Canceling will cancel not
		1445	only the request itself, but also all requests it contains.
		1446
		1447	=item * They can also can also be added to other IO::AIO::GRP objects.
		1448
		1449	=item * You must not add requests to a group from within the group callback (or
		1450	any later time).
		1451
		1452	=back
		1453
		1454	Their lifetime, simplified, looks like this: when they are empty, they
		1455	will finish very quickly. If they contain only requests that are in the
		1456	C<done> state, they will also finish. Otherwise they will continue to
		1457	exist.
		1458
		1459	That means after creating a group you have some time to add requests
		1460	(precisely before the callback has been invoked, which is only done within
		1461	the C<poll_cb>). And in the callbacks of those requests, you can add
		1462	further requests to the group. And only when all those requests have
		1463	finished will the the group itself finish.
		1464
		1465	=over 4
		1466
		1467	=item add $grp ...
		1468
		1469	=item $grp->add (...)
		1470
		1471	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1472	be added, including other groups, as long as you do not create circular
		1473	dependencies.
		1474
		1475	Returns all its arguments.
		1476
		1477	=item $grp->cancel_subs
		1478
		1479	Cancel all subrequests and clears any feeder, but not the group request
		1480	itself. Useful when you queued a lot of events but got a result early.
		1481
		1482	The group request will finish normally (you cannot add requests to the
		1483	group).
		1484
		1485	=item $grp->result (...)
		1486
		1487	Set the result value(s) that will be passed to the group callback when all
		1488	subrequests have finished and set the groups errno to the current value
		1489	of errno (just like calling C<errno> without an error number). By default,
		1490	no argument will be passed and errno is zero.
		1491
		1492	=item $grp->errno ([$errno])
		1493
		1494	Sets the group errno value to C<$errno>, or the current value of errno
		1495	when the argument is missing.
		1496
		1497	Every aio request has an associated errno value that is restored when
		1498	the callback is invoked. This method lets you change this value from its
		1499	default (0).
		1500
		1501	Calling C<result> will also set errno, so make sure you either set C<$!>
		1502	before the call to C<result>, or call c<errno> after it.
		1503
		1504	=item feed $grp $callback->($grp)
		1505
		1506	Sets a feeder/generator on this group: every group can have an attached
		1507	generator that generates requests if idle. The idea behind this is that,
		1508	although you could just queue as many requests as you want in a group,
		1509	this might starve other requests for a potentially long time. For example,
		1510	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
		1511	requests, delaying any later requests for a long time.
		1512
		1513	To avoid this, and allow incremental generation of requests, you can
		1514	instead a group and set a feeder on it that generates those requests. The
		1515	feed callback will be called whenever there are few enough (see C<limit>,
		1516	below) requests active in the group itself and is expected to queue more
		1517	requests.
		1518
		1519	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1520	not impose any limits).
		1521
		1522	If the feed does not queue more requests when called, it will be
		1523	automatically removed from the group.
		1524
		1525	If the feed limit is C<0> when this method is called, it will be set to
		1526	C<2> automatically.
		1527
		1528	Example:
		1529
		1530	# stat all files in @files, but only ever use four aio requests concurrently:
		1531
		1532	my $grp = aio_group sub { print "finished\n" };
		1533	limit $grp 4;
		1534	feed $grp sub {
		1535	my $file = pop @files
		1536	or return;
		1537
		1538	add $grp aio_stat $file, sub { ... };
		1539	};
		1540
		1541	=item limit $grp $num
		1542
		1543	Sets the feeder limit for the group: The feeder will be called whenever
		1544	the group contains less than this many requests.
		1545
		1546	Setting the limit to C<0> will pause the feeding process.
		1547
		1548	The default value for the limit is C<0>, but note that setting a feeder
		1549	automatically bumps it up to C<2>.
		1550
		1551	=back
		1552
196	=head2 SUPPORT FUNCTIONS	1553	=head2 SUPPORT FUNCTIONS
197		1554
		1555	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1556
198	=over 4	1557	=over 4
199		1558
200	=item $fileno = IO::AIO::poll_fileno	1559	=item $fileno = IO::AIO::poll_fileno
201		1560
202	Return the I<request result pipe filehandle>. This filehandle must be	1561	Return the I<request result pipe file descriptor>. This filehandle must be
203	polled for reading by some mechanism outside this module (e.g. Event	1562	polled for reading by some mechanism outside this module (e.g. EV, Glib,
204	or select, see below). If the pipe becomes readable you have to call	1563	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
205	C<poll_cb> to check the results.	1564	you have to call C<poll_cb> to check the results.
206		1565
207	See C<poll_cb> for an example.	1566	See C<poll_cb> for an example.
208		1567
209	=item IO::AIO::poll_cb	1568	=item IO::AIO::poll_cb
210		1569
211	Process all outstanding events on the result pipe. You have to call this	1570	Process some outstanding events on the result pipe. You have to call
212	regularly. Returns the number of events processed. Returns immediately	1571	this regularly. Returns C<0> if all events could be processed (or there
213	when no events are outstanding.	1572	were no events to process), or C<-1> if it returned earlier for whatever
		1573	reason. Returns immediately when no events are outstanding. The amount of
		1574	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1575	C<IO::AIO::max_poll_time>.
214		1576
215	You can use Event to multiplex, e.g.:	1577	If not all requests were processed for whatever reason, the filehandle
		1578	will still be ready when C<poll_cb> returns, so normally you don't have to
		1579	do anything special to have it called later.
		1580
		1581	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1582	ready, it can be beneficial to call this function from loops which submit
		1583	a lot of requests, to make sure the results get processed when they become
		1584	available and not just when the loop is finished and the event loop takes
		1585	over again. This function returns very fast when there are no outstanding
		1586	requests.
		1587
		1588	Example: Install an Event watcher that automatically calls
		1589	IO::AIO::poll_cb with high priority (more examples can be found in the
		1590	SYNOPSIS section, at the top of this document):
216		1591
217	Event->io (fd => IO::AIO::poll_fileno,	1592	Event->io (fd => IO::AIO::poll_fileno,
218	poll => 'r', async => 1,	1593	poll => 'r', async => 1,
219	cb => \&IO::AIO::poll_cb);	1594	cb => \&IO::AIO::poll_cb);
220		1595
221	=item IO::AIO::poll_wait	1596	=item IO::AIO::poll_wait
222		1597
		1598	If there are any outstanding requests and none of them in the result
223	Wait till the result filehandle becomes ready for reading (simply does a	1599	phase, wait till the result filehandle becomes ready for reading (simply
224	select on the filehandle. This is useful if you want to synchronously wait	1600	does a C<select> on the filehandle. This is useful if you want to
225	for some requests to finish).	1601	synchronously wait for some requests to finish).
226		1602
227	See C<nreqs> for an example.	1603	See C<nreqs> for an example.
228		1604
		1605	=item IO::AIO::poll
		1606
		1607	Waits until some requests have been handled.
		1608
		1609	Returns the number of requests processed, but is otherwise strictly
		1610	equivalent to:
		1611
		1612	IO::AIO::poll_wait, IO::AIO::poll_cb
		1613
229	=item IO::AIO::nreqs	1614	=item IO::AIO::flush
230		1615
231	Returns the number of requests currently outstanding.	1616	Wait till all outstanding AIO requests have been handled.
232		1617
233	Example: wait till there are no outstanding requests anymore:	1618	Strictly equivalent to:
234		1619
235	IO::AIO::poll_wait, IO::AIO::poll_cb	1620	IO::AIO::poll_wait, IO::AIO::poll_cb
236	while IO::AIO::nreqs;	1621	while IO::AIO::nreqs;
237		1622
		1623	=item IO::AIO::max_poll_reqs $nreqs
		1624
		1625	=item IO::AIO::max_poll_time $seconds
		1626
		1627	These set the maximum number of requests (default C<0>, meaning infinity)
		1628	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1629	the maximum amount of time (default C<0>, meaning infinity) spent in
		1630	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1631	of time C<poll_cb> is allowed to use).
		1632
		1633	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1634	syscall per request processed, which is not normally a problem unless your
		1635	callbacks are really really fast or your OS is really really slow (I am
		1636	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1637
		1638	Setting these is useful if you want to ensure some level of
		1639	interactiveness when perl is not fast enough to process all requests in
		1640	time.
		1641
		1642	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1643
		1644	Example: Install an Event watcher that automatically calls
		1645	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1646	program get the CPU sometimes even under high AIO load.
		1647
		1648	# try not to spend much more than 0.1s in poll_cb
		1649	IO::AIO::max_poll_time 0.1;
		1650
		1651	# use a low priority so other tasks have priority
		1652	Event->io (fd => IO::AIO::poll_fileno,
		1653	poll => 'r', nice => 1,
		1654	cb => &IO::AIO::poll_cb);
		1655
		1656	=back
		1657
		1658	=head3 CONTROLLING THE NUMBER OF THREADS
		1659
		1660	=over
		1661
		1662	=item IO::AIO::min_parallel $nthreads
		1663
		1664	Set the minimum number of AIO threads to C<$nthreads>. The current
		1665	default is C<8>, which means eight asynchronous operations can execute
		1666	concurrently at any one time (the number of outstanding requests,
		1667	however, is unlimited).
		1668
		1669	IO::AIO starts threads only on demand, when an AIO request is queued and
		1670	no free thread exists. Please note that queueing up a hundred requests can
		1671	create demand for a hundred threads, even if it turns out that everything
		1672	is in the cache and could have been processed faster by a single thread.
		1673
		1674	It is recommended to keep the number of threads relatively low, as some
		1675	Linux kernel versions will scale negatively with the number of threads
		1676	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1677	versions, 4-32 threads should be fine.
		1678
		1679	Under most circumstances you don't need to call this function, as the
		1680	module selects a default that is suitable for low to moderate load.
		1681
		1682	=item IO::AIO::max_parallel $nthreads
		1683
		1684	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1685	specified number of threads are currently running, this function kills
		1686	them. This function blocks until the limit is reached.
		1687
		1688	While C<$nthreads> are zero, aio requests get queued but not executed
		1689	until the number of threads has been increased again.
		1690
		1691	This module automatically runs C<max_parallel 0> at program end, to ensure
		1692	that all threads are killed and that there are no outstanding requests.
		1693
		1694	Under normal circumstances you don't need to call this function.
		1695
		1696	=item IO::AIO::max_idle $nthreads
		1697
		1698	Limit the number of threads (default: 4) that are allowed to idle
		1699	(i.e., threads that did not get a request to process within the idle
		1700	timeout (default: 10 seconds). That means if a thread becomes idle while
		1701	C<$nthreads> other threads are also idle, it will free its resources and
		1702	exit.
		1703
		1704	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1705	to allow for extremely high load situations, but want to free resources
		1706	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1707
		1708	The default is probably ok in most situations, especially if thread
		1709	creation is fast. If thread creation is very slow on your system you might
		1710	want to use larger values.
		1711
		1712	=item IO::AIO::idle_timeout $seconds
		1713
		1714	Sets the minimum idle timeout (default 10) after which worker threads are
		1715	allowed to exit. SEe C<IO::AIO::max_idle>.
		1716
		1717	=item IO::AIO::max_outstanding $maxreqs
		1718
		1719	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1720	you do queue up more than this number of requests, the next call to
		1721	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1722	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1723	longer exceeded.
		1724
		1725	In other words, this setting does not enforce a queue limit, but can be
		1726	used to make poll functions block if the limit is exceeded.
		1727
		1728	This is a very bad function to use in interactive programs because it
		1729	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1730	use an C<aio_group> together with a feed callback.
		1731
		1732	It's main use is in scripts without an event loop - when you want to stat
		1733	a lot of files, you can write somehting like this:
		1734
		1735	IO::AIO::max_outstanding 32;
		1736
		1737	for my $path (...) {
		1738	aio_stat $path , ...;
		1739	IO::AIO::poll_cb;
		1740	}
		1741
		1742	IO::AIO::flush;
		1743
		1744	The call to C<poll_cb> inside the loop will normally return instantly, but
		1745	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1746	some requests have been handled. This keeps the loop from pushing a large
		1747	number of C<aio_stat> requests onto the queue.
		1748
		1749	The default value for C<max_outstanding> is very large, so there is no
		1750	practical limit on the number of outstanding requests.
		1751
		1752	=back
		1753
		1754	=head3 STATISTICAL INFORMATION
		1755
		1756	=over
		1757
238	=item IO::AIO::flush	1758	=item IO::AIO::nreqs
239		1759
240	Wait till all outstanding AIO requests have been handled.	1760	Returns the number of requests currently in the ready, execute or pending
		1761	states (i.e. for which their callback has not been invoked yet).
241		1762
242	Strictly equivalent to:	1763	Example: wait till there are no outstanding requests anymore:
243		1764
244	IO::AIO::poll_wait, IO::AIO::poll_cb	1765	IO::AIO::poll_wait, IO::AIO::poll_cb
245	while IO::AIO::nreqs;	1766	while IO::AIO::nreqs;
246		1767
		1768	=item IO::AIO::nready
		1769
		1770	Returns the number of requests currently in the ready state (not yet
		1771	executed).
		1772
247	=item IO::AIO::poll	1773	=item IO::AIO::npending
248		1774
249	Waits until some requests have been handled.	1775	Returns the number of requests currently in the pending state (executed,
250		1776	but not yet processed by poll_cb).
251	Strictly equivalent to:
252
253	IO::AIO::poll_wait, IO::AIO::poll_cb
254	if IO::AIO::nreqs;
255
256	=item IO::AIO::min_parallel $nthreads
257
258	Set the minimum number of AIO threads to C<$nthreads>. The default is
259	C<1>, which means a single asynchronous operation can be done at one time
260	(the number of outstanding operations, however, is unlimited).
261
262	It is recommended to keep the number of threads low, as some Linux
263	kernel versions will scale negatively with the number of threads (higher
264	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
265	threads should be fine.
266
267	Under normal circumstances you don't need to call this function, as this
268	module automatically starts some threads (the exact number might change,
269	and is currently 4).
270
271	=item IO::AIO::max_parallel $nthreads
272
273	Sets the maximum number of AIO threads to C<$nthreads>. If more than
274	the specified number of threads are currently running, kill them. This
275	function blocks until the limit is reached.
276
277	This module automatically runs C<max_parallel 0> at program end, to ensure
278	that all threads are killed and that there are no outstanding requests.
279
280	Under normal circumstances you don't need to call this function.
281
282	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
283
284	Sets the maximum number of outstanding requests to C<$nreqs>. If you
285	try to queue up more than this number of requests, the caller will block until
286	some requests have been handled.
287
288	The default is very large, so normally there is no practical limit. If you
289	queue up many requests in a loop it it often improves speed if you set
290	this to a relatively low number, such as C<100>.
291
292	Under normal circumstances you don't need to call this function.
293		1777
294	=back	1778	=back
295		1779
		1780	=head3 MISCELLANEOUS FUNCTIONS
		1781
		1782	IO::AIO implements some functions that might be useful, but are not
		1783	asynchronous.
		1784
		1785	=over 4
		1786
		1787	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1788
		1789	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1790	but is blocking (this makes most sense if you know the input data is
		1791	likely cached already and the output filehandle is set to non-blocking
		1792	operations).
		1793
		1794	Returns the number of bytes copied, or C<-1> on error.
		1795
		1796	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1797
		1798	Simply calls the C<posix_fadvise> function (see its
		1799	manpage for details). The following advice constants are
		1800	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1801	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1802	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1803
		1804	On systems that do not implement C<posix_fadvise>, this function returns
		1805	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1806
		1807	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1808
		1809	Simply calls the C<posix_madvise> function (see its
		1810	manpage for details). The following advice constants are
		1811	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1812	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1813
		1814	On systems that do not implement C<posix_madvise>, this function returns
		1815	ENOSYS, otherwise the return value of C<posix_madvise>.
		1816
		1817	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1818
		1819	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1820	$scalar (see its manpage for details). The following protect
		1821	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1822	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1823
		1824	On systems that do not implement C<mprotect>, this function returns
		1825	ENOSYS, otherwise the return value of C<mprotect>.
		1826
		1827	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1828
		1829	Memory-maps a file (or anonymous memory range) and attaches it to the
		1830	given C<$scalar>, which will act like a string scalar.
		1831
		1832	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1833	change the string length, and most read-only operations such as copying it
		1834	or searching it with regexes and so on.
		1835
		1836	Anything else is unsafe and will, at best, result in memory leaks.
		1837
		1838	The memory map associated with the C<$scalar> is automatically removed
		1839	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1840	C<IO::AIO::munmap> functions are called.
		1841
		1842	This calls the C<mmap>(2) function internally. See your system's manual
		1843	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1844
		1845	The C<$length> must be larger than zero and smaller than the actual
		1846	filesize.
		1847
		1848	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1849	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1850
		1851	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1852	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1853	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1854	(which is set to C<MAP_ANON> if your system only provides this
		1855	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1856	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1857	C<IO::AIO::MAP_NONBLOCK>
		1858
		1859	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1860
		1861	C<$offset> is the offset from the start of the file - it generally must be
		1862	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1863
		1864	Example:
		1865
		1866	use Digest::MD5;
		1867	use IO::AIO;
		1868
		1869	open my $fh, "<verybigfile"
		1870	or die "$!";
		1871
		1872	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1873	or die "verybigfile: $!";
		1874
		1875	my $fast_md5 = md5 $data;
		1876
		1877	=item IO::AIO::munmap $scalar
		1878
		1879	Removes a previous mmap and undefines the C<$scalar>.
		1880
		1881	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1882
		1883	Calls the C<munlock> function, undoing the effects of a previous
		1884	C<aio_mlock> call (see its description for details).
		1885
		1886	=item IO::AIO::munlockall
		1887
		1888	Calls the C<munlockall> function.
		1889
		1890	On systems that do not implement C<munlockall>, this function returns
		1891	ENOSYS, otherwise the return value of C<munlockall>.
		1892
		1893	=back
		1894
296	=cut	1895	=cut
297		1896
298	# support function to convert a fd into a perl filehandle
299	sub _fd2fh {
300	return undef if $_[0] < 0;
301
302	# try to be perl5.6-compatible
303	local *AIO_FH;
304	open AIO_FH, "+<&=$_[0]"
305	or return undef;
306
307	*AIO_FH
308	}
309
310	min_parallel 4;	1897	min_parallel 8;
311		1898
312	END {	1899	END { flush }
313	max_parallel 0;
314	}
315		1900
316	1;	1901	1;
317		1902
		1903	=head1 EVENT LOOP INTEGRATION
		1904
		1905	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1906	automatically into many event loops:
		1907
		1908	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1909	use AnyEvent::AIO;
		1910
		1911	You can also integrate IO::AIO manually into many event loops, here are
		1912	some examples of how to do this:
		1913
		1914	# EV integration
		1915	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1916
		1917	# Event integration
		1918	Event->io (fd => IO::AIO::poll_fileno,
		1919	poll => 'r',
		1920	cb => \&IO::AIO::poll_cb);
		1921
		1922	# Glib/Gtk2 integration
		1923	add_watch Glib::IO IO::AIO::poll_fileno,
		1924	in => sub { IO::AIO::poll_cb; 1 };
		1925
		1926	# Tk integration
		1927	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1928	readable => \&IO::AIO::poll_cb);
		1929
		1930	# Danga::Socket integration
		1931	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1932	\&IO::AIO::poll_cb);
		1933
		1934	=head2 FORK BEHAVIOUR
		1935
		1936	Usage of pthreads in a program changes the semantics of fork
		1937	considerably. Specifically, only async-safe functions can be called after
		1938	fork. Perl doesn't know about this, so in general, you cannot call fork
		1939	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		1940	pthreads, so this applies, but many other extensions and (for inexplicable
		1941	reasons) perl itself often is linked against pthreads, so this limitation
		1942	applies to quite a lot of perls.
		1943
		1944	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
		1945	only works in the process that loaded it. Forking is fully supported, but
		1946	using IO::AIO in the child is not.
		1947
		1948	You might get around by not I<using> IO::AIO before (or after)
		1949	forking. You could also try to call the L<IO::AIO::reinit> function in the
		1950	child:
		1951
		1952	=over 4
		1953
		1954	=item IO::AIO::reinit
		1955
		1956	Abandons all current requests and I/O threads and simply reinitialises all
		1957	data structures. This is not an operation supported by any standards, but
		1958	happens to work on GNU/Linux and some newer BSD systems.
		1959
		1960	The only reasonable use for this function is to call it after forking, if
		1961	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		1962	the process will result in undefined behaviour. Calling it at any time
		1963	will also result in any undefined (by POSIX) behaviour.
		1964
		1965	=back
		1966
		1967	=head2 MEMORY USAGE
		1968
		1969	Per-request usage:
		1970
		1971	Each aio request uses - depending on your architecture - around 100-200
		1972	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1973	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1974	scalars and other data passed into aio requests will also be locked and
		1975	will consume memory till the request has entered the done state.
		1976
		1977	This is not awfully much, so queuing lots of requests is not usually a
		1978	problem.
		1979
		1980	Per-thread usage:
		1981
		1982	In the execution phase, some aio requests require more memory for
		1983	temporary buffers, and each thread requires a stack and other data
		1984	structures (usually around 16k-128k, depending on the OS).
		1985
		1986	=head1 KNOWN BUGS
		1987
		1988	Known bugs will be fixed in the next release.
		1989
318	=head1 SEE ALSO	1990	=head1 SEE ALSO
319		1991
320	L<Coro>, L<Linux::AIO>.	1992	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1993	more natural syntax.
321		1994
322	=head1 AUTHOR	1995	=head1 AUTHOR
323		1996
324	Marc Lehmann <schmorp@schmorp.de>	1997	Marc Lehmann <schmorp@schmorp.de>
325	http://home.schmorp.de/	1998	http://home.schmorp.de/

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