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Revision 1.36 by root, Sun Jun 7 18:31:18 2009 UTC vs.
Revision 1.58 by root, Sun May 1 17:19:39 2016 UTC

…		…
2	IO::AIO - Asynchronous Input/Output	2	IO::AIO - Asynchronous Input/Output
3		3
4	SYNOPSIS	4	SYNOPSIS
5	use IO::AIO;	5	use IO::AIO;
6		6
7	aio_open "/etc/passwd", O_RDONLY, 0, sub {	7	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8	my $fh = shift	8	my $fh = shift
9	or die "/etc/passwd: $!";	9	or die "/etc/passwd: $!";
10	...	10	...
11	};	11	};
12		12
…		…
24	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
25		25
26	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
28		28
29	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
30	use AnyEvent::AIO;
31
32	# EV integration
33	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	DESCRIPTION	29	DESCRIPTION
53	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
54	operating system supports.	31	operating system supports. It is implemented as an interface to "libeio"
		32	(<http://software.schmorp.de/pkg/libeio.html>).
55		33
56	Asynchronous means that operations that can normally block your program	34	Asynchronous means that operations that can normally block your program
57	(e.g. reading from disk) will be done asynchronously: the operation will	35	(e.g. reading from disk) will be done asynchronously: the operation will
58	still block, but you can do something else in the meantime. This is	36	still block, but you can do something else in the meantime. This is
59	extremely useful for programs that need to stay interactive even when	37	extremely useful for programs that need to stay interactive even when
…		…
64	operations concurrently.	42	operations concurrently.
65		43
66	While most of this works on all types of file descriptors (for example	44	While most of this works on all types of file descriptors (for example
67	sockets), using these functions on file descriptors that support	45	sockets), using these functions on file descriptors that support
68	nonblocking operation (again, sockets, pipes etc.) is very inefficient.	46	nonblocking operation (again, sockets, pipes etc.) is very inefficient.
69	Use an event loop for that (such as the Event module): IO::AIO will	47	Use an event loop for that (such as the EV module): IO::AIO will
70	naturally fit into such an event loop itself.	48	naturally fit into such an event loop itself.
71		49
72	In this version, a number of threads are started that execute your	50	In this version, a number of threads are started that execute your
73	requests and signal their completion. You don't need thread support in	51	requests and signal their completion. You don't need thread support in
74	perl, and the threads created by this module will not be visible to	52	perl, and the threads created by this module will not be visible to
…		…
83	it is currently not reentrant in any way, so use appropriate locking	61	it is currently not reentrant in any way, so use appropriate locking
84	yourself, always call "poll_cb" from within the same thread, or never	62	yourself, always call "poll_cb" from within the same thread, or never
85	call "poll_cb" (or other "aio_" functions) recursively.	63	call "poll_cb" (or other "aio_" functions) recursively.
86		64
87	EXAMPLE	65	EXAMPLE
88	This is a simple example that uses the Event module and loads	66	This is a simple example that uses the EV module and loads /etc/passwd
89	/etc/passwd asynchronously:	67	asynchronously:
90		68
91	use Fcntl;
92	use Event;	69	use EV;
93	use IO::AIO;	70	use IO::AIO;
94		71
95	# register the IO::AIO callback with Event	72	# register the IO::AIO callback with EV
96	Event->io (fd => IO::AIO::poll_fileno,	73	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
97	poll => 'r',
98	cb => \&IO::AIO::poll_cb);
99		74
100	# queue the request to open /etc/passwd	75	# queue the request to open /etc/passwd
101	aio_open "/etc/passwd", O_RDONLY, 0, sub {	76	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
102	my $fh = shift	77	my $fh = shift
103	or die "error while opening: $!";	78	or die "error while opening: $!";
104		79
105	# stat'ing filehandles is generally non-blocking	80	# stat'ing filehandles is generally non-blocking
106	my $size = -s $fh;	81	my $size = -s $fh;
…		…
115		90
116	# file contents now in $contents	91	# file contents now in $contents
117	print $contents;	92	print $contents;
118		93
119	# exit event loop and program	94	# exit event loop and program
120	Event::unloop;	95	EV::break;
121	};	96	};
122	};	97	};
123		98
124	# possibly queue up other requests, or open GUI windows,	99	# possibly queue up other requests, or open GUI windows,
125	# check for sockets etc. etc.	100	# check for sockets etc. etc.
126		101
127	# process events as long as there are some:	102	# process events as long as there are some:
128	Event::loop;	103	EV::run;
129		104
130	REQUEST ANATOMY AND LIFETIME	105	REQUEST ANATOMY AND LIFETIME
131	Every "aio_*" function creates a request. which is a C data structure	106	Every "aio_*" function creates a request. which is a C data structure
132	not directly visible to Perl.	107	not directly visible to Perl.
133		108
…		…
169	anymore (except possibly for the Perl object, but its connection to	144	anymore (except possibly for the Perl object, but its connection to
170	the actual aio request is severed and calling its methods will	145	the actual aio request is severed and calling its methods will
171	either do nothing or result in a runtime error).	146	either do nothing or result in a runtime error).
172		147
173	FUNCTIONS	148	FUNCTIONS
174	AIO REQUEST FUNCTIONS	149	QUICK OVERVIEW
		150	This section simply lists the prototypes most of the functions for quick
		151	reference. See the following sections for function-by-function
		152	documentation.
		153
		154	aio_wd $pathname, $callback->($wd)
		155	aio_open $pathname, $flags, $mode, $callback->($fh)
		156	aio_close $fh, $callback->($status)
		157	aio_seek $fh,$offset,$whence, $callback->($offs)
		158	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		159	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		160	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		161	aio_readahead $fh,$offset,$length, $callback->($retval)
		162	aio_stat $fh_or_path, $callback->($status)
		163	aio_lstat $fh, $callback->($status)
		164	aio_statvfs $fh_or_path, $callback->($statvfs)
		165	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		166	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		167	aio_chmod $fh_or_path, $mode, $callback->($status)
		168	aio_truncate $fh_or_path, $offset, $callback->($status)
		169	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		170	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		171	aio_unlink $pathname, $callback->($status)
		172	aio_mknod $pathname, $mode, $dev, $callback->($status)
		173	aio_link $srcpath, $dstpath, $callback->($status)
		174	aio_symlink $srcpath, $dstpath, $callback->($status)
		175	aio_readlink $pathname, $callback->($link)
		176	aio_realpath $pathname, $callback->($path)
		177	aio_rename $srcpath, $dstpath, $callback->($status)
		178	aio_mkdir $pathname, $mode, $callback->($status)
		179	aio_rmdir $pathname, $callback->($status)
		180	aio_readdir $pathname, $callback->($entries)
		181	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		182	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		183	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		184	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		185	aio_load $pathname, $data, $callback->($status)
		186	aio_copy $srcpath, $dstpath, $callback->($status)
		187	aio_move $srcpath, $dstpath, $callback->($status)
		188	aio_rmtree $pathname, $callback->($status)
		189	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		190	aio_ioctl $fh, $request, $buf, $callback->($status)
		191	aio_sync $callback->($status)
		192	aio_syncfs $fh, $callback->($status)
		193	aio_fsync $fh, $callback->($status)
		194	aio_fdatasync $fh, $callback->($status)
		195	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		196	aio_pathsync $pathname, $callback->($status)
		197	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		198	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		199	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		200	aio_mlockall $flags, $callback->($status)
		201	aio_group $callback->(...)
		202	aio_nop $callback->()
		203
		204	$prev_pri = aioreq_pri [$pri]
		205	aioreq_nice $pri_adjust
		206
		207	IO::AIO::poll_wait
		208	IO::AIO::poll_cb
		209	IO::AIO::poll
		210	IO::AIO::flush
		211	IO::AIO::max_poll_reqs $nreqs
		212	IO::AIO::max_poll_time $seconds
		213	IO::AIO::min_parallel $nthreads
		214	IO::AIO::max_parallel $nthreads
		215	IO::AIO::max_idle $nthreads
		216	IO::AIO::idle_timeout $seconds
		217	IO::AIO::max_outstanding $maxreqs
		218	IO::AIO::nreqs
		219	IO::AIO::nready
		220	IO::AIO::npending
		221
		222	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		223	IO::AIO::fadvise $fh, $offset, $len, $advice
		224	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		225	IO::AIO::munmap $scalar
		226	IO::AIO::madvise $scalar, $offset, $length, $advice
		227	IO::AIO::mprotect $scalar, $offset, $length, $protect
		228	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		229	IO::AIO::munlockall
		230
		231	API NOTES
175	All the "aio_*" calls are more or less thin wrappers around the syscall	232	All the "aio_*" calls are more or less thin wrappers around the syscall
176	with the same name (sans "aio_"). The arguments are similar or	233	with the same name (sans "aio_"). The arguments are similar or
177	identical, and they all accept an additional (and optional) $callback	234	identical, and they all accept an additional (and optional) $callback
178	argument which must be a code reference. This code reference will get	235	argument which must be a code reference. This code reference will be
179	called with the syscall return code (e.g. most syscalls return -1 on
180	error, unlike perl, which usually delivers "false") as its sole argument
181	after the given syscall has been executed asynchronously.	236	called after the syscall has been executed in an asynchronous fashion.
		237	The results of the request will be passed as arguments to the callback
		238	(and, if an error occured, in $!) - for most requests the syscall return
		239	code (e.g. most syscalls return -1 on error, unlike perl, which usually
		240	delivers "false").
		241
		242	Some requests (such as "aio_readdir") pass the actual results and
		243	communicate failures by passing "undef".
182		244
183	All functions expecting a filehandle keep a copy of the filehandle	245	All functions expecting a filehandle keep a copy of the filehandle
184	internally until the request has finished.	246	internally until the request has finished.
185		247
186	All functions return request objects of type IO::AIO::REQ that allow	248	All functions return request objects of type IO::AIO::REQ that allow
187	further manipulation of those requests while they are in-flight.	249	further manipulation of those requests while they are in-flight.
188		250
189	The pathnames you pass to these routines *must* be absolute and encoded	251	The pathnames you pass to these routines *should* be absolute. The
190	as octets. The reason for the former is that at the time the request is	252	reason for this is that at the time the request is being executed, the
191	being executed, the current working directory could have changed.	253	current working directory could have changed. Alternatively, you can
192	Alternatively, you can make sure that you never change the current	254	make sure that you never change the current working directory anywhere
193	working directory anywhere in the program and then use relative paths.	255	in the program and then use relative paths. You can also take advantage
		256	of IO::AIOs working directory abstraction, that lets you specify paths
		257	relative to some previously-opened "working directory object" - see the
		258	description of the "IO::AIO::WD" class later in this document.
194		259
195	To encode pathnames as octets, either make sure you either: a) always	260	To encode pathnames as octets, either make sure you either: a) always
196	pass in filenames you got from outside (command line, readdir etc.)	261	pass in filenames you got from outside (command line, readdir etc.)
197	without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module	262	without tinkering, b) are in your native filesystem encoding, c) use the
198	and encode your pathnames to the locale (or other) encoding in effect in	263	Encode module and encode your pathnames to the locale (or other)
199	the user environment, d) use Glib::filename_from_unicode on unicode	264	encoding in effect in the user environment, d) use
200	filenames or e) use something else to ensure your scalar has the correct	265	Glib::filename_from_unicode on unicode filenames or e) use something
201	contents.	266	else to ensure your scalar has the correct contents.
202		267
203	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	268	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
204	handles correctly whether it is set or not.	269	handles correctly whether it is set or not.
205		270
		271	AIO REQUEST FUNCTIONS
206	$prev_pri = aioreq_pri [$pri]	272	$prev_pri = aioreq_pri [$pri]
207	Returns the priority value that would be used for the next request	273	Returns the priority value that would be used for the next request
208	and, if $pri is given, sets the priority for the next aio request.	274	and, if $pri is given, sets the priority for the next aio request.
209		275
210	The default priority is 0, the minimum and maximum priorities are -4	276	The default priority is 0, the minimum and maximum priorities are -4
…		…
232	Similar to "aioreq_pri", but subtracts the given value from the	298	Similar to "aioreq_pri", but subtracts the given value from the
233	current priority, so the effect is cumulative.	299	current priority, so the effect is cumulative.
234		300
235	aio_open $pathname, $flags, $mode, $callback->($fh)	301	aio_open $pathname, $flags, $mode, $callback->($fh)
236	Asynchronously open or create a file and call the callback with a	302	Asynchronously open or create a file and call the callback with a
237	newly created filehandle for the file.	303	newly created filehandle for the file (or "undef" in case of an
		304	error).
238		305
239	The pathname passed to "aio_open" must be absolute. See API NOTES,	306	The pathname passed to "aio_open" must be absolute. See API NOTES,
240	above, for an explanation.	307	above, for an explanation.
241		308
242	The $flags argument is a bitmask. See the "Fcntl" module for a list.	309	The $flags argument is a bitmask. See the "Fcntl" module for a list.
…		…
249	will be modified by the umask in effect then the request is being	316	will be modified by the umask in effect then the request is being
250	executed, so better never change the umask.	317	executed, so better never change the umask.
251		318
252	Example:	319	Example:
253		320
254	aio_open "/etc/passwd", O_RDONLY, 0, sub {	321	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
255	if ($_[0]) {	322	if ($_[0]) {
256	print "open successful, fh is $_[0]\n";	323	print "open successful, fh is $_[0]\n";
257	...	324	...
258	} else {	325	} else {
259	die "open failed: $!\n";	326	die "open failed: $!\n";
260	}	327	}
261	};	328	};
262		329
		330	In addition to all the common open modes/flags ("O_RDONLY",
		331	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		332	"O_APPEND"), the following POSIX and non-POSIX constants are
		333	available (missing ones on your system are, as usual, 0):
		334
		335	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		336	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		337	"O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", and
		338	"O_TTY_INIT".
		339
263	aio_close $fh, $callback->($status)	340	aio_close $fh, $callback->($status)
264	Asynchronously close a file and call the callback with the result	341	Asynchronously close a file and call the callback with the result
265	code.	342	code.
266		343
267	Unfortunately, you can't do this to perl. Perl *insists* very	344	Unfortunately, you can't do this to perl. Perl *insists* very
…		…
272	will use dup2 to overwrite the file descriptor with the write-end of	349	will use dup2 to overwrite the file descriptor with the write-end of
273	a pipe (the pipe fd will be created on demand and will be cached).	350	a pipe (the pipe fd will be created on demand and will be cached).
274		351
275	Or in other words: the file descriptor will be closed, but it will	352	Or in other words: the file descriptor will be closed, but it will
276	not be free for reuse until the perl filehandle is closed.	353	not be free for reuse until the perl filehandle is closed.
		354
		355	aio_seek $fh, $offset, $whence, $callback->($offs)
		356	Seeks the filehandle to the new $offset, similarly to perl's
		357	"sysseek". The $whence can use the traditional values (0 for
		358	"IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
		359	"IO::AIO::SEEK_END").
		360
		361	The resulting absolute offset will be passed to the callback, or -1
		362	in case of an error.
		363
		364	In theory, the $whence constants could be different than the
		365	corresponding values from Fcntl, but perl guarantees they are the
		366	same, so don't panic.
		367
		368	As a GNU/Linux (and maybe Solaris) extension, also the constants
		369	"IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
		370	could be found. No guarantees about suitability for use in
		371	"aio_seek" or Perl's "sysseek" can be made though, although I would
		372	naively assume they "just work".
277		373
278	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	374	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
279	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	375	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
280	Reads or writes $length bytes from or to the specified $fh and	376	Reads or writes $length bytes from or to the specified $fh and
281	$offset into the scalar given by $data and offset $dataoffset and	377	$offset into the scalar given by $data and offset $dataoffset and
…		…
310	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	406	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
311	Tries to copy $length bytes from $in_fh to $out_fh. It starts	407	Tries to copy $length bytes from $in_fh to $out_fh. It starts
312	reading at byte offset $in_offset, and starts writing at the current	408	reading at byte offset $in_offset, and starts writing at the current
313	file offset of $out_fh. Because of that, it is not safe to issue	409	file offset of $out_fh. Because of that, it is not safe to issue
314	more than one "aio_sendfile" per $out_fh, as they will interfere	410	more than one "aio_sendfile" per $out_fh, as they will interfere
315	with each other.	411	with each other. The same $in_fh works fine though, as this function
		412	does not move or use the file offset of $in_fh.
316		413
		414	Please note that "aio_sendfile" can read more bytes from $in_fh than
		415	are written, and there is no way to find out how many more bytes
		416	have been read from "aio_sendfile" alone, as "aio_sendfile" only
		417	provides the number of bytes written to $out_fh. Only if the result
		418	value equals $length one can assume that $length bytes have been
		419	read.
		420
		421	Unlike with other "aio_" functions, it makes a lot of sense to use
		422	"aio_sendfile" on non-blocking sockets, as long as one end
		423	(typically the $in_fh) is a file - the file I/O will then be
		424	asynchronous, while the socket I/O will be non-blocking. Note,
		425	however, that you can run into a trap where "aio_sendfile" reads
		426	some data with readahead, then fails to write all data, and when the
		427	socket is ready the next time, the data in the cache is already
		428	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		429	"aio_read" + "aio_write" let's you better control resource usage.
		430
317	This call tries to make use of a native "sendfile" syscall to	431	This call tries to make use of a native "sendfile"-like syscall to
318	provide zero-copy operation. For this to work, $out_fh should refer	432	provide zero-copy operation. For this to work, $out_fh should refer
319	to a socket, and $in_fh should refer to mmap'able file.	433	to a socket, and $in_fh should refer to an mmap'able file.
320		434
321	If the native sendfile call fails or is not implemented, it will be	435	If a native sendfile cannot be found or it fails with "ENOSYS",
322	emulated, so you can call "aio_sendfile" on any type of filehandle	436	"EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
323	regardless of the limitations of the operating system.	437	"ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
		438	any type of filehandle regardless of the limitations of the
		439	operating system.
324		440
325	Please note, however, that "aio_sendfile" can read more bytes from	441	As native sendfile syscalls (as practically any non-POSIX interface
326	$in_fh than are written, and there is no way to find out how many	442	hacked together in a hurry to improve benchmark numbers) tend to be
327	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"	443	rather buggy on many systems, this implementation tries to work
328	only provides the number of bytes written to $out_fh. Only if the	444	around some known bugs in Linux and FreeBSD kernels (probably
329	result value equals $length one can assume that $length bytes have	445	others, too), but that might fail, so you really really should check
330	been read.	446	the return value of "aio_sendfile" - fewre bytes than expected might
		447	have been transferred.
331		448
332	aio_readahead $fh,$offset,$length, $callback->($retval)	449	aio_readahead $fh,$offset,$length, $callback->($retval)
333	"aio_readahead" populates the page cache with data from a file so	450	"aio_readahead" populates the page cache with data from a file so
334	that subsequent reads from that file will not block on disk I/O. The	451	that subsequent reads from that file will not block on disk I/O. The
335	$offset argument specifies the starting point from which data is to	452	$offset argument specifies the starting point from which data is to
…		…
356	Currently, the stats are always 64-bit-stats, i.e. instead of	473	Currently, the stats are always 64-bit-stats, i.e. instead of
357	returning an error when stat'ing a large file, the results will be	474	returning an error when stat'ing a large file, the results will be
358	silently truncated unless perl itself is compiled with large file	475	silently truncated unless perl itself is compiled with large file
359	support.	476	support.
360		477
		478	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		479	the following constants and functions (if not implemented, the
		480	constants will be 0 and the functions will either "croak" or fall
		481	back on traditional behaviour).
		482
		483	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		484	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		485	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		486
361	Example: Print the length of /etc/passwd:	487	Example: Print the length of /etc/passwd:
362		488
363	aio_stat "/etc/passwd", sub {	489	aio_stat "/etc/passwd", sub {
364	$_[0] and die "stat failed: $!";	490	$_[0] and die "stat failed: $!";
365	print "size is ", -s _, "\n";	491	print "size is ", -s _, "\n";
366	};	492	};
367		493
		494	aio_statvfs $fh_or_path, $callback->($statvfs)
		495	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		496	whether a file handle or path was passed.
		497
		498	On success, the callback is passed a hash reference with the
		499	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		500	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		501	failure, "undef" is passed.
		502
		503	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		504	and "ST_NOSUID".
		505
		506	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		507	their correct value when available, or to 0 on systems that do not
		508	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		509	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		510	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		511
		512	Example: stat "/wd" and dump out the data if successful.
		513
		514	aio_statvfs "/wd", sub {
		515	my $f = $_[0]
		516	or die "statvfs: $!";
		517
		518	use Data::Dumper;
		519	say Dumper $f;
		520	};
		521
		522	# result:
		523	{
		524	bsize => 1024,
		525	bfree => 4333064312,
		526	blocks => 10253828096,
		527	files => 2050765568,
		528	flag => 4096,
		529	favail => 2042092649,
		530	bavail => 4333064312,
		531	ffree => 2042092649,
		532	namemax => 255,
		533	frsize => 1024,
		534	fsid => 1810
		535	}
		536
		537	Here is a (likely partial - send me updates!) list of fsid values
		538	used by Linux - it is safe to hardcode these when $^O is "linux":
		539
		540	0x0000adf5 adfs
		541	0x0000adff affs
		542	0x5346414f afs
		543	0x09041934 anon-inode filesystem
		544	0x00000187 autofs
		545	0x42465331 befs
		546	0x1badface bfs
		547	0x42494e4d binfmt_misc
		548	0x9123683e btrfs
		549	0x0027e0eb cgroupfs
		550	0xff534d42 cifs
		551	0x73757245 coda
		552	0x012ff7b7 coh
		553	0x28cd3d45 cramfs
		554	0x453dcd28 cramfs-wend (wrong endianness)
		555	0x64626720 debugfs
		556	0x00001373 devfs
		557	0x00001cd1 devpts
		558	0x0000f15f ecryptfs
		559	0x00414a53 efs
		560	0x0000137d ext
		561	0x0000ef53 ext2/ext3/ext4
		562	0x0000ef51 ext2
		563	0xf2f52010 f2fs
		564	0x00004006 fat
		565	0x65735546 fuseblk
		566	0x65735543 fusectl
		567	0x0bad1dea futexfs
		568	0x01161970 gfs2
		569	0x47504653 gpfs
		570	0x00004244 hfs
		571	0xf995e849 hpfs
		572	0x00c0ffee hostfs
		573	0x958458f6 hugetlbfs
		574	0x2bad1dea inotifyfs
		575	0x00009660 isofs
		576	0x000072b6 jffs2
		577	0x3153464a jfs
		578	0x6b414653 k-afs
		579	0x0bd00bd0 lustre
		580	0x0000137f minix
		581	0x0000138f minix 30 char names
		582	0x00002468 minix v2
		583	0x00002478 minix v2 30 char names
		584	0x00004d5a minix v3
		585	0x19800202 mqueue
		586	0x00004d44 msdos
		587	0x0000564c novell
		588	0x00006969 nfs
		589	0x6e667364 nfsd
		590	0x00003434 nilfs
		591	0x5346544e ntfs
		592	0x00009fa1 openprom
		593	0x7461636F ocfs2
		594	0x00009fa0 proc
		595	0x6165676c pstorefs
		596	0x0000002f qnx4
		597	0x68191122 qnx6
		598	0x858458f6 ramfs
		599	0x52654973 reiserfs
		600	0x00007275 romfs
		601	0x67596969 rpc_pipefs
		602	0x73636673 securityfs
		603	0xf97cff8c selinux
		604	0x0000517b smb
		605	0x534f434b sockfs
		606	0x73717368 squashfs
		607	0x62656572 sysfs
		608	0x012ff7b6 sysv2
		609	0x012ff7b5 sysv4
		610	0x01021994 tmpfs
		611	0x15013346 udf
		612	0x00011954 ufs
		613	0x54190100 ufs byteswapped
		614	0x00009fa2 usbdevfs
		615	0x01021997 v9fs
		616	0xa501fcf5 vxfs
		617	0xabba1974 xenfs
		618	0x012ff7b4 xenix
		619	0x58465342 xfs
		620	0x012fd16d xia
		621
368	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	622	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
369	Works like perl's "utime" function (including the special case of	623	Works like perl's "utime" function (including the special case of
370	$atime and $mtime being undef). Fractional times are supported if	624	$atime and $mtime being undef). Fractional times are supported if
371	the underlying syscalls support them.	625	the underlying syscalls support them.
372		626
…		…
394	aio_chown "path", 0, undef;	648	aio_chown "path", 0, undef;
395		649
396	aio_truncate $fh_or_path, $offset, $callback->($status)	650	aio_truncate $fh_or_path, $offset, $callback->($status)
397	Works like truncate(2) or ftruncate(2).	651	Works like truncate(2) or ftruncate(2).
398		652
		653	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654	Allocates or frees disk space according to the $mode argument. See
		655	the linux "fallocate" documentation for details.
		656
		657	$mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
		658	space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
		659	IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
		660
		661	IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
		662	(without leaving a hole) and "FALLOC_FL_ZERO_RANGE", to zero a range
		663	(see your fallocate(2) manpage).
		664
		665	The file system block size used by "fallocate" is presumably the
		666	"f_bsize" returned by "statvfs".
		667
		668	If "fallocate" isn't available or cannot be emulated (currently no
		669	emulation will be attempted), passes -1 and sets $! to "ENOSYS".
		670
399	aio_chmod $fh_or_path, $mode, $callback->($status)	671	aio_chmod $fh_or_path, $mode, $callback->($status)
400	Works like perl's "chmod" function.	672	Works like perl's "chmod" function.
401		673
402	aio_unlink $pathname, $callback->($status)	674	aio_unlink $pathname, $callback->($status)
403	Asynchronously unlink (delete) a file and call the callback with the	675	Asynchronously unlink (delete) a file and call the callback with the
404	result code.	676	result code.
405		677
406	aio_mknod $path, $mode, $dev, $callback->($status)	678	aio_mknod $pathname, $mode, $dev, $callback->($status)
407	[EXPERIMENTAL]	679	[EXPERIMENTAL]
408		680
409	Asynchronously create a device node (or fifo). See mknod(2).	681	Asynchronously create a device node (or fifo). See mknod(2).
410		682
411	The only (POSIX-) portable way of calling this function is:	683	The only (POSIX-) portable way of calling this function is:
412		684
413	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	685	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		686
		687	See "aio_stat" for info about some potentially helpful extra
		688	constants and functions.
414		689
415	aio_link $srcpath, $dstpath, $callback->($status)	690	aio_link $srcpath, $dstpath, $callback->($status)
416	Asynchronously create a new link to the existing object at $srcpath	691	Asynchronously create a new link to the existing object at $srcpath
417	at the path $dstpath and call the callback with the result code.	692	at the path $dstpath and call the callback with the result code.
418		693
419	aio_symlink $srcpath, $dstpath, $callback->($status)	694	aio_symlink $srcpath, $dstpath, $callback->($status)
420	Asynchronously create a new symbolic link to the existing object at	695	Asynchronously create a new symbolic link to the existing object at
421	$srcpath at the path $dstpath and call the callback with the result	696	$srcpath at the path $dstpath and call the callback with the result
422	code.	697	code.
423		698
424	aio_readlink $path, $callback->($link)	699	aio_readlink $pathname, $callback->($link)
425	Asynchronously read the symlink specified by $path and pass it to	700	Asynchronously read the symlink specified by $path and pass it to
426	the callback. If an error occurs, nothing or undef gets passed to	701	the callback. If an error occurs, nothing or undef gets passed to
427	the callback.	702	the callback.
428		703
		704	aio_realpath $pathname, $callback->($path)
		705	Asynchronously make the path absolute and resolve any symlinks in
		706	$path. The resulting path only consists of directories (same as
		707	Cwd::realpath).
		708
		709	This request can be used to get the absolute path of the current
		710	working directory by passing it a path of . (a single dot).
		711
429	aio_rename $srcpath, $dstpath, $callback->($status)	712	aio_rename $srcpath, $dstpath, $callback->($status)
430	Asynchronously rename the object at $srcpath to $dstpath, just as	713	Asynchronously rename the object at $srcpath to $dstpath, just as
431	rename(2) and call the callback with the result code.	714	rename(2) and call the callback with the result code.
		715
		716	On systems that support the AIO::WD working directory abstraction
		717	natively, the case "[$wd, "."]" as $srcpath is specialcased -
		718	instead of failing, "rename" is called on the absolute path of $wd.
432		719
433	aio_mkdir $pathname, $mode, $callback->($status)	720	aio_mkdir $pathname, $mode, $callback->($status)
434	Asynchronously mkdir (create) a directory and call the callback with	721	Asynchronously mkdir (create) a directory and call the callback with
435	the result code. $mode will be modified by the umask at the time the	722	the result code. $mode will be modified by the umask at the time the
436	request is executed, so do not change your umask.	723	request is executed, so do not change your umask.
437		724
438	aio_rmdir $pathname, $callback->($status)	725	aio_rmdir $pathname, $callback->($status)
439	Asynchronously rmdir (delete) a directory and call the callback with	726	Asynchronously rmdir (delete) a directory and call the callback with
440	the result code.	727	the result code.
441		728
		729	On systems that support the AIO::WD working directory abstraction
		730	natively, the case "[$wd, "."]" is specialcased - instead of
		731	failing, "rmdir" is called on the absolute path of $wd.
		732
442	aio_readdir $pathname, $callback->($entries)	733	aio_readdir $pathname, $callback->($entries)
443	Unlike the POSIX call of the same name, "aio_readdir" reads an	734	Unlike the POSIX call of the same name, "aio_readdir" reads an
444	entire directory (i.e. opendir + readdir + closedir). The entries	735	entire directory (i.e. opendir + readdir + closedir). The entries
445	will not be sorted, and will NOT include the "." and ".." entries.	736	will not be sorted, and will NOT include the "." and ".." entries.
446		737
447	The callback is passed a single argument which is either "undef" or	738	The callback is passed a single argument which is either "undef" or
448	an array-ref with the filenames.	739	an array-ref with the filenames.
449		740
450	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	741	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
451	Quite similar to "aio_readdir", but the $flags argument allows to	742	Quite similar to "aio_readdir", but the $flags argument allows one
452	tune behaviour and output format. In case of an error, $entries will	743	to tune behaviour and output format. In case of an error, $entries
453	be "undef".	744	will be "undef".
454		745
455	The flags are a combination of the following constants, ORed	746	The flags are a combination of the following constants, ORed
456	together (the flags will also be passed to the callback, possibly	747	together (the flags will also be passed to the callback, possibly
457	modified):	748	modified):
458		749
459	IO::AIO::READDIR_DENTS	750	IO::AIO::READDIR_DENTS
460	When this flag is off, then the callback gets an arrayref with	751	When this flag is off, then the callback gets an arrayref
461	of names only (as with "aio_readdir"), otherwise it gets an	752	consisting of names only (as with "aio_readdir"), otherwise it
462	arrayref with "[$name, $type, $inode]" arrayrefs, each	753	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
463	describing a single directory entry in more detail.	754	describing a single directory entry in more detail.
464		755
465	$name is the name of the entry.	756	$name is the name of the entry.
466		757
467	$type is one of the "IO::AIO::DT_xxx" constants:	758	$type is one of the "IO::AIO::DT_xxx" constants:
…		…
474	you need to know, you have to run stat yourself. Also, for speed	765	you need to know, you have to run stat yourself. Also, for speed
475	reasons, the $type scalars are read-only: you can not modify	766	reasons, the $type scalars are read-only: you can not modify
476	them.	767	them.
477		768
478	$inode is the inode number (which might not be exact on systems	769	$inode is the inode number (which might not be exact on systems
479	with 64 bit inode numbers and 32 bit perls). On systems that do	770	with 64 bit inode numbers and 32 bit perls). This field has
480	not deliver the inode information, this will always be zero.	771	unspecified content on systems that do not deliver the inode
		772	information.
481		773
482	IO::AIO::READDIR_DIRS_FIRST	774	IO::AIO::READDIR_DIRS_FIRST
483	When this flag is set, then the names will be returned in an	775	When this flag is set, then the names will be returned in an
484	order where likely directories come first. This is useful when	776	order where likely directories come first, in optimal stat
485	you need to quickly find directories, or you want to find all	777	order. This is useful when you need to quickly find directories,
486	directories while avoiding to stat() each entry.	778	or you want to find all directories while avoiding to stat()
		779	each entry.
487		780
488	If the system returns type information in readdir, then this is	781	If the system returns type information in readdir, then this is
489	used to find directories directly. Otherwise, likely directories	782	used to find directories directly. Otherwise, likely directories
490	are files beginning with ".", or otherwise files with no dots,	783	are names beginning with ".", or otherwise names with no dots,
491	of which files with short names are tried first.	784	of which names with short names are tried first.
492		785
493	IO::AIO::READDIR_STAT_ORDER	786	IO::AIO::READDIR_STAT_ORDER
494	When this flag is set, then the names will be returned in an	787	When this flag is set, then the names will be returned in an
495	order suitable for stat()'ing each one. That is, when you plan	788	order suitable for stat()'ing each one. That is, when you plan
496	to stat() all files in the given directory, then the returned	789	to stat() all files in the given directory, then the returned
…		…
501	optimal stat order.	794	optimal stat order.
502		795
503	IO::AIO::READDIR_FOUND_UNKNOWN	796	IO::AIO::READDIR_FOUND_UNKNOWN
504	This flag should not be set when calling "aio_readdirx".	797	This flag should not be set when calling "aio_readdirx".
505	Instead, it is being set by "aio_readdirx", when any of the	798	Instead, it is being set by "aio_readdirx", when any of the
506	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this	799	$type's found were "IO::AIO::DT_UNKNOWN". The absence of this
507	flag therefore indicates that all $type's are known, which can	800	flag therefore indicates that all $type's are known, which can
508	be used to speed up some algorithms.	801	be used to speed up some algorithms.
509		802
510	aio_load $path, $data, $callback->($status)	803	aio_load $pathname, $data, $callback->($status)
511	This is a composite request that tries to fully load the given file	804	This is a composite request that tries to fully load the given file
512	into memory. Status is the same as with aio_read.	805	into memory. Status is the same as with aio_read.
513		806
514	aio_copy $srcpath, $dstpath, $callback->($status)	807	aio_copy $srcpath, $dstpath, $callback->($status)
515	Try to copy the *file* (directories not supported as either source	808	Try to copy the *file* (directories not supported as either source
516	or destination) from $srcpath to $dstpath and call the callback with	809	or destination) from $srcpath to $dstpath and call the callback with
517	the 0 (error) or -1 ok.	810	a status of 0 (ok) or -1 (error, see $!).
518		811
519	This is a composite request that creates the destination file with	812	This is a composite request that creates the destination file with
520	mode 0200 and copies the contents of the source file into it using	813	mode 0200 and copies the contents of the source file into it using
521	"aio_sendfile", followed by restoring atime, mtime, access mode and	814	"aio_sendfile", followed by restoring atime, mtime, access mode and
522	uid/gid, in that order.	815	uid/gid, in that order.
…		…
526	uid/gid, where errors are being ignored.	819	uid/gid, where errors are being ignored.
527		820
528	aio_move $srcpath, $dstpath, $callback->($status)	821	aio_move $srcpath, $dstpath, $callback->($status)
529	Try to move the *file* (directories not supported as either source	822	Try to move the *file* (directories not supported as either source
530	or destination) from $srcpath to $dstpath and call the callback with	823	or destination) from $srcpath to $dstpath and call the callback with
531	the 0 (error) or -1 ok.	824	a status of 0 (ok) or -1 (error, see $!).
532		825
533	This is a composite request that tries to rename(2) the file first;	826	This is a composite request that tries to rename(2) the file first;
534	if rename fails with "EXDEV", it copies the file with "aio_copy"	827	if rename fails with "EXDEV", it copies the file with "aio_copy"
535	and, if that is successful, unlinks the $srcpath.	828	and, if that is successful, unlinks the $srcpath.
536		829
537	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	830	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
538	Scans a directory (similar to "aio_readdir") but additionally tries	831	Scans a directory (similar to "aio_readdir") but additionally tries
539	to efficiently separate the entries of directory $path into two sets	832	to efficiently separate the entries of directory $path into two sets
540	of names, directories you can recurse into (directories), and ones	833	of names, directories you can recurse into (directories), and ones
541	you cannot recurse into (everything else, including symlinks to	834	you cannot recurse into (everything else, including symlinks to
542	directories).	835	directories).
…		…
575	Then entries will be sorted into likely directories a non-initial	868	Then entries will be sorted into likely directories a non-initial
576	dot currently) and likely non-directories (see "aio_readdirx"). Then	869	dot currently) and likely non-directories (see "aio_readdirx"). Then
577	every entry plus an appended "/." will be "stat"'ed, likely	870	every entry plus an appended "/." will be "stat"'ed, likely
578	directories first, in order of their inode numbers. If that	871	directories first, in order of their inode numbers. If that
579	succeeds, it assumes that the entry is a directory or a symlink to	872	succeeds, it assumes that the entry is a directory or a symlink to
580	directory (which will be checked seperately). This is often faster	873	directory (which will be checked separately). This is often faster
581	than stat'ing the entry itself because filesystems might detect the	874	than stat'ing the entry itself because filesystems might detect the
582	type of the entry without reading the inode data (e.g. ext2fs	875	type of the entry without reading the inode data (e.g. ext2fs
583	filetype feature), even on systems that cannot return the filetype	876	filetype feature), even on systems that cannot return the filetype
584	information on readdir.	877	information on readdir.
585		878
…		…
591		884
592	It will also likely work on non-POSIX filesystems with reduced	885	It will also likely work on non-POSIX filesystems with reduced
593	efficiency as those tend to return 0 or 1 as link counts, which	886	efficiency as those tend to return 0 or 1 as link counts, which
594	disables the directory counting heuristic.	887	disables the directory counting heuristic.
595		888
596	aio_rmtree $path, $callback->($status)	889	aio_rmtree $pathname, $callback->($status)
597	Delete a directory tree starting (and including) $path, return the	890	Delete a directory tree starting (and including) $path, return the
598	status of the final "rmdir" only. This is a composite request that	891	status of the final "rmdir" only. This is a composite request that
599	uses "aio_scandir" to recurse into and rmdir directories, and unlink	892	uses "aio_scandir" to recurse into and rmdir directories, and unlink
600	everything else.	893	everything else.
601		894
		895	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		896	aio_ioctl $fh, $request, $buf, $callback->($status)
		897	These work just like the "fcntl" and "ioctl" built-in functions,
		898	except they execute asynchronously and pass the return value to the
		899	callback.
		900
		901	Both calls can be used for a lot of things, some of which make more
		902	sense to run asynchronously in their own thread, while some others
		903	make less sense. For example, calls that block waiting for external
		904	events, such as locking, will also lock down an I/O thread while it
		905	is waiting, which can deadlock the whole I/O system. At the same
		906	time, there might be no alternative to using a thread to wait.
		907
		908	So in general, you should only use these calls for things that do
		909	(filesystem) I/O, not for things that wait for other events
		910	(network, other processes), although if you are careful and know
		911	what you are doing, you still can.
		912
602	aio_sync $callback->($status)	913	aio_sync $callback->($status)
603	Asynchronously call sync and call the callback when finished.	914	Asynchronously call sync and call the callback when finished.
604		915
605	aio_fsync $fh, $callback->($status)	916	aio_fsync $fh, $callback->($status)
606	Asynchronously call fsync on the given filehandle and call the	917	Asynchronously call fsync on the given filehandle and call the
…		…
610	Asynchronously call fdatasync on the given filehandle and call the	921	Asynchronously call fdatasync on the given filehandle and call the
611	callback with the fdatasync result code.	922	callback with the fdatasync result code.
612		923
613	If this call isn't available because your OS lacks it or it couldn't	924	If this call isn't available because your OS lacks it or it couldn't
614	be detected, it will be emulated by calling "fsync" instead.	925	be detected, it will be emulated by calling "fsync" instead.
		926
		927	aio_syncfs $fh, $callback->($status)
		928	Asynchronously call the syncfs syscall to sync the filesystem
		929	associated to the given filehandle and call the callback with the
		930	syncfs result code. If syncfs is not available, calls sync(), but
		931	returns -1 and sets errno to "ENOSYS" nevertheless.
615		932
616	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	933	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
617	Sync the data portion of the file specified by $offset and $length	934	Sync the data portion of the file specified by $offset and $length
618	to disk (but NOT the metadata), by calling the Linux-specific	935	to disk (but NOT the metadata), by calling the Linux-specific
619	sync_file_range call. If sync_file_range is not available or it	936	sync_file_range call. If sync_file_range is not available or it
…		…
623	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",	940	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
624	"IO::AIO::SYNC_FILE_RANGE_WRITE" and	941	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
625	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range	942	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
626	manpage for details.	943	manpage for details.
627		944
628	aio_pathsync $path, $callback->($status)	945	aio_pathsync $pathname, $callback->($status)
629	This request tries to open, fsync and close the given path. This is	946	This request tries to open, fsync and close the given path. This is
630	a composite request intended to sync directories after directory	947	a composite request intended to sync directories after directory
631	operations (E.g. rename). This might not work on all operating	948	operations (E.g. rename). This might not work on all operating
632	systems or have any specific effect, but usually it makes sure that	949	systems or have any specific effect, but usually it makes sure that
633	directory changes get written to disc. It works for anything that	950	directory changes get written to disc. It works for anything that
634	can be opened for read-only, not just directories.	951	can be opened for read-only, not just directories.
635		952
		953	Future versions of this function might fall back to other methods
		954	when "fsync" on the directory fails (such as calling "sync").
		955
636	Passes 0 when everything went ok, and -1 on error.	956	Passes 0 when everything went ok, and -1 on error.
		957
		958	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		959	$callback->($status)
		960	This is a rather advanced IO::AIO call, which only works on
		961	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		962	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		963	note that the scalar must only be modified in-place while an aio
		964	operation is pending on it).
		965
		966	It calls the "msync" function of your OS, if available, with the
		967	memory area starting at $offset in the string and ending $length
		968	bytes later. If $length is negative, counts from the end, and if
		969	$length is "undef", then it goes till the end of the string. The
		970	flags can be a combination of "IO::AIO::MS_ASYNC",
		971	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		972
		973	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		974	$callback->($status)
		975	This is a rather advanced IO::AIO call, which works best on
		976	mmap(2)ed scalars.
		977
		978	It touches (reads or writes) all memory pages in the specified range
		979	inside the scalar. All caveats and parameters are the same as for
		980	"aio_msync", above, except for flags, which must be either 0 (which
		981	reads all pages and ensures they are instantiated) or
		982	"IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
		983	and writing an octet from it, which dirties the page).
		984
		985	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		986	This is a rather advanced IO::AIO call, which works best on
		987	mmap(2)ed scalars.
		988
		989	It reads in all the pages of the underlying storage into memory (if
		990	any) and locks them, so they are not getting swapped/paged out or
		991	removed.
		992
		993	If $length is undefined, then the scalar will be locked till the
		994	end.
		995
		996	On systems that do not implement "mlock", this function returns -1
		997	and sets errno to "ENOSYS".
		998
		999	Note that the corresponding "munlock" is synchronous and is
		1000	documented under "MISCELLANEOUS FUNCTIONS".
		1001
		1002	Example: open a file, mmap and mlock it - both will be undone when
		1003	$data gets destroyed.
		1004
		1005	open my $fh, "<", $path or die "$path: $!";
		1006	my $data;
		1007	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1008	aio_mlock $data; # mlock in background
		1009
		1010	aio_mlockall $flags, $callback->($status)
		1011	Calls the "mlockall" function with the given $flags (a combination
		1012	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		1013
		1014	On systems that do not implement "mlockall", this function returns
		1015	-1 and sets errno to "ENOSYS".
		1016
		1017	Note that the corresponding "munlockall" is synchronous and is
		1018	documented under "MISCELLANEOUS FUNCTIONS".
		1019
		1020	Example: asynchronously lock all current and future pages into
		1021	memory.
		1022
		1023	aio_mlockall IO::AIO::MCL_FUTURE;
		1024
		1025	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1026	Queries the extents of the given file (by calling the Linux "FIEMAP"
		1027	ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
		1028	details). If the ioctl is not available on your OS, then this
		1029	request will fail with "ENOSYS".
		1030
		1031	$start is the starting offset to query extents for, $length is the
		1032	size of the range to query - if it is "undef", then the whole file
		1033	will be queried.
		1034
		1035	$flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
		1036	"IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
		1037	also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
		1038	query the data portion.
		1039
		1040	$count is the maximum number of extent records to return. If it is
		1041	"undef", then IO::AIO queries all extents of the range. As a very
		1042	special case, if it is 0, then the callback receives the number of
		1043	extents instead of the extents themselves (which is unreliable, see
		1044	below).
		1045
		1046	If an error occurs, the callback receives no arguments. The special
		1047	"errno" value "IO::AIO::EBADR" is available to test for flag errors.
		1048
		1049	Otherwise, the callback receives an array reference with extent
		1050	structures. Each extent structure is an array reference itself, with
		1051	the following members:
		1052
		1053	[$logical, $physical, $length, $flags]
		1054
		1055	Flags is any combination of the following flag values (typically
		1056	either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
		1057
		1058	"IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
		1059	"IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
		1060	"IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
		1061	"IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
		1062	"IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
		1063	"IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
		1064	"IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
		1065	or "IO::AIO::FIEMAP_EXTENT_SHARED".
		1066
		1067	At the time of this writing (Linux 3.2), this requets is unreliable
		1068	unless $count is "undef", as the kernel has all sorts of bugs
		1069	preventing it to return all extents of a range for files with large
		1070	number of extents. The code works around all these issues if $count
		1071	is undef.
637		1072
638	aio_group $callback->(...)	1073	aio_group $callback->(...)
639	This is a very special aio request: Instead of doing something, it	1074	This is a very special aio request: Instead of doing something, it
640	is a container for other aio requests, which is useful if you want	1075	is a container for other aio requests, which is useful if you want
641	to bundle many requests into a single, composite, request with a	1076	to bundle many requests into a single, composite, request with a
…		…
676	requests like sleep and file handle readable/writable, the overhead	1111	requests like sleep and file handle readable/writable, the overhead
677	this creates is immense (it blocks a thread for a long time) so do	1112	this creates is immense (it blocks a thread for a long time) so do
678	not use this function except to put your application under	1113	not use this function except to put your application under
679	artificial I/O pressure.	1114	artificial I/O pressure.
680		1115
		1116	IO::AIO::WD - multiple working directories
		1117	Your process only has one current working directory, which is used by
		1118	all threads. This makes it hard to use relative paths (some other
		1119	component could call "chdir" at any time, and it is hard to control when
		1120	the path will be used by IO::AIO).
		1121
		1122	One solution for this is to always use absolute paths. This usually
		1123	works, but can be quite slow (the kernel has to walk the whole path on
		1124	every access), and can also be a hassle to implement.
		1125
		1126	Newer POSIX systems have a number of functions (openat, fdopendir,
		1127	futimensat and so on) that make it possible to specify working
		1128	directories per operation.
		1129
		1130	For portability, and because the clowns who "designed", or shall I
		1131	write, perpetrated this new interface were obviously half-drunk, this
		1132	abstraction cannot be perfect, though.
		1133
		1134	IO::AIO allows you to convert directory paths into a so-called
		1135	IO::AIO::WD object. This object stores the canonicalised, absolute
		1136	version of the path, and on systems that allow it, also a directory file
		1137	descriptor.
		1138
		1139	Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
		1140	or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
		1141	object and a pathname instead (or the IO::AIO::WD object alone, which
		1142	gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
		1143	IO::AIO::WD object is ignored, otherwise the pathname is resolved
		1144	relative to that IO::AIO::WD object.
		1145
		1146	For example, to get a wd object for /etc and then stat passwd inside,
		1147	you would write:
		1148
		1149	aio_wd "/etc", sub {
		1150	my $etcdir = shift;
		1151
		1152	# although $etcdir can be undef on error, there is generally no reason
		1153	# to check for errors here, as aio_stat will fail with ENOENT
		1154	# when $etcdir is undef.
		1155
		1156	aio_stat [$etcdir, "passwd"], sub {
		1157	# yay
		1158	};
		1159	};
		1160
		1161	The fact that "aio_wd" is a request and not a normal function shows that
		1162	creating an IO::AIO::WD object is itself a potentially blocking
		1163	operation, which is why it is done asynchronously.
		1164
		1165	To stat the directory obtained with "aio_wd" above, one could write
		1166	either of the following three request calls:
		1167
		1168	aio_lstat "/etc" , sub { ... # pathname as normal string
		1169	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1170	aio_lstat $wd , sub { ... # shorthand for the previous
		1171
		1172	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1173	object and the pathname string, so you could write the following without
		1174	causing any issues due to $path getting reused:
		1175
		1176	my $path = [$wd, undef];
		1177
		1178	for my $name (qw(abc def ghi)) {
		1179	$path->[1] = $name;
		1180	aio_stat $path, sub {
		1181	# ...
		1182	};
		1183	}
		1184
		1185	There are some caveats: when directories get renamed (or deleted), the
		1186	pathname string doesn't change, so will point to the new directory (or
		1187	nowhere at all), while the directory fd, if available on the system,
		1188	will still point to the original directory. Most functions accepting a
		1189	pathname will use the directory fd on newer systems, and the string on
		1190	older systems. Some functions (such as realpath) will always rely on the
		1191	string form of the pathname.
		1192
		1193	So this functionality is mainly useful to get some protection against
		1194	"chdir", to easily get an absolute path out of a relative path for
		1195	future reference, and to speed up doing many operations in the same
		1196	directory (e.g. when stat'ing all files in a directory).
		1197
		1198	The following functions implement this working directory abstraction:
		1199
		1200	aio_wd $pathname, $callback->($wd)
		1201	Asynchonously canonicalise the given pathname and convert it to an
		1202	IO::AIO::WD object representing it. If possible and supported on the
		1203	system, also open a directory fd to speed up pathname resolution
		1204	relative to this working directory.
		1205
		1206	If something goes wrong, then "undef" is passwd to the callback
		1207	instead of a working directory object and $! is set appropriately.
		1208	Since passing "undef" as working directory component of a pathname
		1209	fails the request with "ENOENT", there is often no need for error
		1210	checking in the "aio_wd" callback, as future requests using the
		1211	value will fail in the expected way.
		1212
		1213	IO::AIO::CWD
		1214	This is a compiletime constant (object) that represents the process
		1215	current working directory.
		1216
		1217	Specifying this object as working directory object for a pathname is
		1218	as if the pathname would be specified directly, without a directory
		1219	object. For example, these calls are functionally identical:
		1220
		1221	aio_stat "somefile", sub { ... };
		1222	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1223
		1224	To recover the path associated with an IO::AIO::WD object, you can use
		1225	"aio_realpath":
		1226
		1227	aio_realpath $wd, sub {
		1228	warn "path is $_[0]\n";
		1229	};
		1230
		1231	Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
		1232	sometimes, fall back to using an absolue path.
		1233
681	IO::AIO::REQ CLASS	1234	IO::AIO::REQ CLASS
682	All non-aggregate "aio_*" functions return an object of this class when	1235	All non-aggregate "aio_*" functions return an object of this class when
683	called in non-void context.	1236	called in non-void context.
684		1237
685	cancel $req	1238	cancel $req
686	Cancels the request, if possible. Has the effect of skipping	1239	Cancels the request, if possible. Has the effect of skipping
687	execution when entering the execute state and skipping calling the	1240	execution when entering the execute state and skipping calling the
688	callback when entering the the result state, but will leave the	1241	callback when entering the the result state, but will leave the
689	request otherwise untouched. That means that requests that currently	1242	request otherwise untouched (with the exception of readdir). That
690	execute will not be stopped and resources held by the request will	1243	means that requests that currently execute will not be stopped and
691	not be freed prematurely.	1244	resources held by the request will not be freed prematurely.
692		1245
693	cb $req $callback->(...)	1246	cb $req $callback->(...)
694	Replace (or simply set) the callback registered to the request.	1247	Replace (or simply set) the callback registered to the request.
695		1248
696	IO::AIO::GRP CLASS	1249	IO::AIO::GRP CLASS
…		…
757		1310
758	$grp->cancel_subs	1311	$grp->cancel_subs
759	Cancel all subrequests and clears any feeder, but not the group	1312	Cancel all subrequests and clears any feeder, but not the group
760	request itself. Useful when you queued a lot of events but got a	1313	request itself. Useful when you queued a lot of events but got a
761	result early.	1314	result early.
		1315
		1316	The group request will finish normally (you cannot add requests to
		1317	the group).
762		1318
763	$grp->result (...)	1319	$grp->result (...)
764	Set the result value(s) that will be passed to the group callback	1320	Set the result value(s) that will be passed to the group callback
765	when all subrequests have finished and set the groups errno to the	1321	when all subrequests have finished and set the groups errno to the
766	current value of errno (just like calling "errno" without an error	1322	current value of errno (just like calling "errno" without an error
…		…
781	Sets a feeder/generator on this group: every group can have an	1337	Sets a feeder/generator on this group: every group can have an
782	attached generator that generates requests if idle. The idea behind	1338	attached generator that generates requests if idle. The idea behind
783	this is that, although you could just queue as many requests as you	1339	this is that, although you could just queue as many requests as you
784	want in a group, this might starve other requests for a potentially	1340	want in a group, this might starve other requests for a potentially
785	long time. For example, "aio_scandir" might generate hundreds of	1341	long time. For example, "aio_scandir" might generate hundreds of
786	thousands "aio_stat" requests, delaying any later requests for a	1342	thousands of "aio_stat" requests, delaying any later requests for a
787	long time.	1343	long time.
788		1344
789	To avoid this, and allow incremental generation of requests, you can	1345	To avoid this, and allow incremental generation of requests, you can
790	instead a group and set a feeder on it that generates those	1346	instead a group and set a feeder on it that generates those
791	requests. The feed callback will be called whenever there are few	1347	requests. The feed callback will be called whenever there are few
…		…
826	SUPPORT FUNCTIONS	1382	SUPPORT FUNCTIONS
827	EVENT PROCESSING AND EVENT LOOP INTEGRATION	1383	EVENT PROCESSING AND EVENT LOOP INTEGRATION
828	$fileno = IO::AIO::poll_fileno	1384	$fileno = IO::AIO::poll_fileno
829	Return the *request result pipe file descriptor*. This filehandle	1385	Return the *request result pipe file descriptor*. This filehandle
830	must be polled for reading by some mechanism outside this module	1386	must be polled for reading by some mechanism outside this module
831	(e.g. Event or select, see below or the SYNOPSIS). If the pipe	1387	(e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
832	becomes readable you have to call "poll_cb" to check the results.	1388	pipe becomes readable you have to call "poll_cb" to check the
		1389	results.
833		1390
834	See "poll_cb" for an example.	1391	See "poll_cb" for an example.
835		1392
836	IO::AIO::poll_cb	1393	IO::AIO::poll_cb
837	Process some outstanding events on the result pipe. You have to call	1394	Process some requests that have reached the result phase (i.e. they
838	this regularly. Returns 0 if all events could be processed, or -1 if	1395	have been executed but the results are not yet reported). You have
839	it returned earlier for whatever reason. Returns immediately when no	1396	to call this "regularly" to finish outstanding requests.
840	events are outstanding. The amount of events processed depends on
841	the settings of "IO::AIO::max_poll_req" and
842	"IO::AIO::max_poll_time".
843		1397
		1398	Returns 0 if all events could be processed (or there were no events
		1399	to process), or -1 if it returned earlier for whatever reason.
		1400	Returns immediately when no events are outstanding. The amount of
		1401	events processed depends on the settings of "IO::AIO::max_poll_req",
		1402	"IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
		1403
844	If not all requests were processed for whatever reason, the	1404	If not all requests were processed for whatever reason, the poll
845	filehandle will still be ready when "poll_cb" returns, so normally	1405	file descriptor will still be ready when "poll_cb" returns, so
846	you don't have to do anything special to have it called later.	1406	normally you don't have to do anything special to have it called
		1407	later.
		1408
		1409	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1410	becomes ready, it can be beneficial to call this function from loops
		1411	which submit a lot of requests, to make sure the results get
		1412	processed when they become available and not just when the loop is
		1413	finished and the event loop takes over again. This function returns
		1414	very fast when there are no outstanding requests.
847		1415
848	Example: Install an Event watcher that automatically calls	1416	Example: Install an Event watcher that automatically calls
849	IO::AIO::poll_cb with high priority:	1417	IO::AIO::poll_cb with high priority (more examples can be found in
		1418	the SYNOPSIS section, at the top of this document):
850		1419
851	Event->io (fd => IO::AIO::poll_fileno,	1420	Event->io (fd => IO::AIO::poll_fileno,
852	poll => 'r', async => 1,	1421	poll => 'r', async => 1,
853	cb => \&IO::AIO::poll_cb);	1422	cb => \&IO::AIO::poll_cb);
		1423
		1424	IO::AIO::poll_wait
		1425	Wait until either at least one request is in the result phase or no
		1426	requests are outstanding anymore.
		1427
		1428	This is useful if you want to synchronously wait for some requests
		1429	to become ready, without actually handling them.
		1430
		1431	See "nreqs" for an example.
		1432
		1433	IO::AIO::poll
		1434	Waits until some requests have been handled.
		1435
		1436	Returns the number of requests processed, but is otherwise strictly
		1437	equivalent to:
		1438
		1439	IO::AIO::poll_wait, IO::AIO::poll_cb
		1440
		1441	IO::AIO::flush
		1442	Wait till all outstanding AIO requests have been handled.
		1443
		1444	Strictly equivalent to:
		1445
		1446	IO::AIO::poll_wait, IO::AIO::poll_cb
		1447	while IO::AIO::nreqs;
854		1448
855	IO::AIO::max_poll_reqs $nreqs	1449	IO::AIO::max_poll_reqs $nreqs
856	IO::AIO::max_poll_time $seconds	1450	IO::AIO::max_poll_time $seconds
857	These set the maximum number of requests (default 0, meaning	1451	These set the maximum number of requests (default 0, meaning
858	infinity) that are being processed by "IO::AIO::poll_cb" in one	1452	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
882	# use a low priority so other tasks have priority	1476	# use a low priority so other tasks have priority
883	Event->io (fd => IO::AIO::poll_fileno,	1477	Event->io (fd => IO::AIO::poll_fileno,
884	poll => 'r', nice => 1,	1478	poll => 'r', nice => 1,
885	cb => &IO::AIO::poll_cb);	1479	cb => &IO::AIO::poll_cb);
886		1480
887	IO::AIO::poll_wait
888	If there are any outstanding requests and none of them in the result
889	phase, wait till the result filehandle becomes ready for reading
890	(simply does a "select" on the filehandle. This is useful if you
891	want to synchronously wait for some requests to finish).
892
893	See "nreqs" for an example.
894
895	IO::AIO::poll
896	Waits until some requests have been handled.
897
898	Returns the number of requests processed, but is otherwise strictly
899	equivalent to:
900
901	IO::AIO::poll_wait, IO::AIO::poll_cb
902
903	IO::AIO::flush
904	Wait till all outstanding AIO requests have been handled.
905
906	Strictly equivalent to:
907
908	IO::AIO::poll_wait, IO::AIO::poll_cb
909	while IO::AIO::nreqs;
910
911	CONTROLLING THE NUMBER OF THREADS	1481	CONTROLLING THE NUMBER OF THREADS
912	IO::AIO::min_parallel $nthreads	1482	IO::AIO::min_parallel $nthreads
913	Set the minimum number of AIO threads to $nthreads. The current	1483	Set the minimum number of AIO threads to $nthreads. The current
914	default is 8, which means eight asynchronous operations can execute	1484	default is 8, which means eight asynchronous operations can execute
915	concurrently at any one time (the number of outstanding requests,	1485	concurrently at any one time (the number of outstanding requests,
…		…
944		1514
945	Under normal circumstances you don't need to call this function.	1515	Under normal circumstances you don't need to call this function.
946		1516
947	IO::AIO::max_idle $nthreads	1517	IO::AIO::max_idle $nthreads
948	Limit the number of threads (default: 4) that are allowed to idle	1518	Limit the number of threads (default: 4) that are allowed to idle
949	(i.e., threads that did not get a request to process within 10	1519	(i.e., threads that did not get a request to process within the idle
950	seconds). That means if a thread becomes idle while $nthreads other	1520	timeout (default: 10 seconds). That means if a thread becomes idle
951	threads are also idle, it will free its resources and exit.	1521	while $nthreads other threads are also idle, it will free its
		1522	resources and exit.
952		1523
953	This is useful when you allow a large number of threads (e.g. 100 or	1524	This is useful when you allow a large number of threads (e.g. 100 or
954	1000) to allow for extremely high load situations, but want to free	1525	1000) to allow for extremely high load situations, but want to free
955	resources under normal circumstances (1000 threads can easily	1526	resources under normal circumstances (1000 threads can easily
956	consume 30MB of RAM).	1527	consume 30MB of RAM).
957		1528
958	The default is probably ok in most situations, especially if thread	1529	The default is probably ok in most situations, especially if thread
959	creation is fast. If thread creation is very slow on your system you	1530	creation is fast. If thread creation is very slow on your system you
960	might want to use larger values.	1531	might want to use larger values.
961		1532
		1533	IO::AIO::idle_timeout $seconds
		1534	Sets the minimum idle timeout (default 10) after which worker
		1535	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1536
962	IO::AIO::max_outstanding $maxreqs	1537	IO::AIO::max_outstanding $maxreqs
		1538	Sets the maximum number of outstanding requests to $nreqs. If you do
		1539	queue up more than this number of requests, the next call to
		1540	"IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
		1541	"IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
		1542	no longer exceeded.
		1543
		1544	In other words, this setting does not enforce a queue limit, but can
		1545	be used to make poll functions block if the limit is exceeded.
		1546
963	This is a very bad function to use in interactive programs because	1547	This is a very bad function to use in interactive programs because
964	it blocks, and a bad way to reduce concurrency because it is	1548	it blocks, and a bad way to reduce concurrency because it is
965	inexact: Better use an "aio_group" together with a feed callback.	1549	inexact: Better use an "aio_group" together with a feed callback.
966		1550
967	Sets the maximum number of outstanding requests to $nreqs. If you do	1551	Its main use is in scripts without an event loop - when you want to
968	queue up more than this number of requests, the next call to the	1552	stat a lot of files, you can write somehting like this:
969	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
970	function will block until the limit is no longer exceeded.
971		1553
972	The default value is very large, so there is no practical limit on	1554	IO::AIO::max_outstanding 32;
		1555
		1556	for my $path (...) {
		1557	aio_stat $path , ...;
		1558	IO::AIO::poll_cb;
		1559	}
		1560
		1561	IO::AIO::flush;
		1562
		1563	The call to "poll_cb" inside the loop will normally return
		1564	instantly, but as soon as more thna 32 reqeusts are in-flight, it
		1565	will block until some requests have been handled. This keeps the
		1566	loop from pushing a large number of "aio_stat" requests onto the
		1567	queue.
		1568
		1569	The default value for "max_outstanding" is very large, so there is
973	the number of outstanding requests.	1570	no practical limit on the number of outstanding requests.
974
975	You can still queue as many requests as you want. Therefore,
976	"max_outstanding" is mainly useful in simple scripts (with low
977	values) or as a stop gap to shield against fatal memory overflow
978	(with large values).
979		1571
980	STATISTICAL INFORMATION	1572	STATISTICAL INFORMATION
981	IO::AIO::nreqs	1573	IO::AIO::nreqs
982	Returns the number of requests currently in the ready, execute or	1574	Returns the number of requests currently in the ready, execute or
983	pending states (i.e. for which their callback has not been invoked	1575	pending states (i.e. for which their callback has not been invoked
…		…
994		1586
995	IO::AIO::npending	1587	IO::AIO::npending
996	Returns the number of requests currently in the pending state	1588	Returns the number of requests currently in the pending state
997	(executed, but not yet processed by poll_cb).	1589	(executed, but not yet processed by poll_cb).
998		1590
		1591	MISCELLANEOUS FUNCTIONS
		1592	IO::AIO implements some functions that are useful when you want to use
		1593	some "Advanced I/O" function not available to in Perl, without going the
		1594	"Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
		1595	counterpart.
		1596
		1597	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1598	Calls the "eio_sendfile_sync" function, which is like
		1599	"aio_sendfile", but is blocking (this makes most sense if you know
		1600	the input data is likely cached already and the output filehandle is
		1601	set to non-blocking operations).
		1602
		1603	Returns the number of bytes copied, or -1 on error.
		1604
		1605	IO::AIO::fadvise $fh, $offset, $len, $advice
		1606	Simply calls the "posix_fadvise" function (see its manpage for
		1607	details). The following advice constants are available:
		1608	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1609	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1610	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1611
		1612	On systems that do not implement "posix_fadvise", this function
		1613	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1614
		1615	IO::AIO::madvise $scalar, $offset, $len, $advice
		1616	Simply calls the "posix_madvise" function (see its manpage for
		1617	details). The following advice constants are available:
		1618	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1619	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1620	"IO::AIO::MADV_DONTNEED".
		1621
		1622	On systems that do not implement "posix_madvise", this function
		1623	returns ENOSYS, otherwise the return value of "posix_madvise".
		1624
		1625	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1626	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1627	$scalar (see its manpage for details). The following protect
		1628	constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1629	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1630
		1631	On systems that do not implement "mprotect", this function returns
		1632	ENOSYS, otherwise the return value of "mprotect".
		1633
		1634	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1635	Memory-maps a file (or anonymous memory range) and attaches it to
		1636	the given $scalar, which will act like a string scalar. Returns true
		1637	on success, and false otherwise.
		1638
		1639	The only operations allowed on the scalar are "substr"/"vec" that
		1640	don't change the string length, and most read-only operations such
		1641	as copying it or searching it with regexes and so on.
		1642
		1643	Anything else is unsafe and will, at best, result in memory leaks.
		1644
		1645	The memory map associated with the $scalar is automatically removed
		1646	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1647	"IO::AIO::munmap" functions are called.
		1648
		1649	This calls the "mmap"(2) function internally. See your system's
		1650	manual page for details on the $length, $prot and $flags parameters.
		1651
		1652	The $length must be larger than zero and smaller than the actual
		1653	filesize.
		1654
		1655	$prot is a combination of "IO::AIO::PROT_NONE",
		1656	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1657	"IO::AIO::PROT_WRITE",
		1658
		1659	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1660	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1661	not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
		1662	"MAP_ANON" if your system only provides this constant),
		1663	"IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
		1664	"IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
		1665	"IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
		1666	"IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
		1667	"IO::AIO::MAP_STACK".
		1668
		1669	If $fh is "undef", then a file descriptor of -1 is passed.
		1670
		1671	$offset is the offset from the start of the file - it generally must
		1672	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1673
		1674	Example:
		1675
		1676	use Digest::MD5;
		1677	use IO::AIO;
		1678
		1679	open my $fh, "<verybigfile"
		1680	or die "$!";
		1681
		1682	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1683	or die "verybigfile: $!";
		1684
		1685	my $fast_md5 = md5 $data;
		1686
		1687	IO::AIO::munmap $scalar
		1688	Removes a previous mmap and undefines the $scalar.
		1689
		1690	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1691	Calls the "munlock" function, undoing the effects of a previous
		1692	"aio_mlock" call (see its description for details).
		1693
		1694	IO::AIO::munlockall
		1695	Calls the "munlockall" function.
		1696
		1697	On systems that do not implement "munlockall", this function returns
		1698	ENOSYS, otherwise the return value of "munlockall".
		1699
		1700	IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1701	Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
		1702	$w_off are "undef", then "NULL" is passed for these, otherwise they
		1703	should be the file offset.
		1704
		1705	$r_fh and $w_fh should not refer to the same file, as splice might
		1706	silently corrupt the data in this case.
		1707
		1708	The following symbol flag values are available:
		1709	"IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
		1710	"IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
		1711
		1712	See the splice(2) manpage for details.
		1713
		1714	IO::AIO::tee $r_fh, $w_fh, $length, $flags
		1715	Calls the GNU/Linux tee(2) syscall, see its manpage and the
		1716	description for "IO::AIO::splice" above for details.
		1717
		1718	$actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		1719	Attempts to query or change the pipe buffer size. Obviously works
		1720	only on pipes, and currently works only on GNU/Linux systems, and
		1721	fails with -1/"ENOSYS" everywhere else. If anybody knows how to
		1722	influence pipe buffer size on other systems, drop me a note.
		1723
		1724	($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		1725	This is a direct interface to the Linux pipe2(2) system call. If
		1726	$flags is missing or 0, then this should be the same as a call to
		1727	perl's built-in "pipe" function and create a new pipe, and works on
		1728	systems that lack the pipe2 syscall. On win32, this case invokes
		1729	"_pipe (..., 4096, O_BINARY)".
		1730
		1731	If $flags is non-zero, it tries to invoke the pipe2 system call with
		1732	the given flags (Linux 2.6.27, glibc 2.9).
		1733
		1734	On success, the read and write file handles are returned.
		1735
		1736	On error, nothing will be returned. If the pipe2 syscall is missing
		1737	and $flags is non-zero, fails with "ENOSYS".
		1738
		1739	Please refer to pipe2(2) for more info on the $flags, but at the
		1740	time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
		1741	and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
		1742	supported.
		1743
		1744	EVENT LOOP INTEGRATION
		1745	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1746	automatically into many event loops:
		1747
		1748	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1749	use AnyEvent::AIO;
		1750
		1751	You can also integrate IO::AIO manually into many event loops, here are
		1752	some examples of how to do this:
		1753
		1754	# EV integration
		1755	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1756
		1757	# Event integration
		1758	Event->io (fd => IO::AIO::poll_fileno,
		1759	poll => 'r',
		1760	cb => \&IO::AIO::poll_cb);
		1761
		1762	# Glib/Gtk2 integration
		1763	add_watch Glib::IO IO::AIO::poll_fileno,
		1764	in => sub { IO::AIO::poll_cb; 1 };
		1765
		1766	# Tk integration
		1767	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1768	readable => \&IO::AIO::poll_cb);
		1769
		1770	# Danga::Socket integration
		1771	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1772	\&IO::AIO::poll_cb);
		1773
999	FORK BEHAVIOUR	1774	FORK BEHAVIOUR
1000	This module should do "the right thing" when the process using it forks:	1775	Usage of pthreads in a program changes the semantics of fork
		1776	considerably. Specifically, only async-safe functions can be called
		1777	after fork. Perl doesn't know about this, so in general, you cannot call
		1778	fork with defined behaviour in perl if pthreads are involved. IO::AIO
		1779	uses pthreads, so this applies, but many other extensions and (for
		1780	inexplicable reasons) perl itself often is linked against pthreads, so
		1781	this limitation applies to quite a lot of perls.
1001		1782
1002	Before the fork, IO::AIO enters a quiescent state where no requests can	1783	This module no longer tries to fight your OS, or POSIX. That means
1003	be added in other threads and no results will be processed. After the	1784	IO::AIO only works in the process that loaded it. Forking is fully
1004	fork the parent simply leaves the quiescent state and continues	1785	supported, but using IO::AIO in the child is not.
1005	request/result processing, while the child frees the request/result
1006	queue (so that the requests started before the fork will only be handled
1007	in the parent). Threads will be started on demand until the limit set in
1008	the parent process has been reached again.
1009		1786
1010	In short: the parent will, after a short pause, continue as if fork had	1787	You might get around by not *using* IO::AIO before (or after) forking.
1011	not been called, while the child will act as if IO::AIO has not been	1788	You could also try to call the IO::AIO::reinit function in the child:
1012	used yet.	1789
		1790	IO::AIO::reinit
		1791	Abandons all current requests and I/O threads and simply
		1792	reinitialises all data structures. This is not an operation
		1793	supported by any standards, but happens to work on GNU/Linux and
		1794	some newer BSD systems.
		1795
		1796	The only reasonable use for this function is to call it after
		1797	forking, if "IO::AIO" was used in the parent. Calling it while
		1798	IO::AIO is active in the process will result in undefined behaviour.
		1799	Calling it at any time will also result in any undefined (by POSIX)
		1800	behaviour.
1013		1801
1014	MEMORY USAGE	1802	MEMORY USAGE
1015	Per-request usage:	1803	Per-request usage:
1016		1804
1017	Each aio request uses - depending on your architecture - around 100-200	1805	Each aio request uses - depending on your architecture - around 100-200

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