[ViewVC] Diff of: cvs/IO-AIO/README

Comparing IO-AIO/README (file contents):
Revision 1.20 by root, Tue Oct 31 00:45:41 2006 UTC vs.
Revision 1.47 by root, Fri May 27 00:44:49 2011 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) = @_;	8	my $fh = shift
		9	or die "/etc/passwd: $!";
9	...	10	...
10	};	11	};
11		12
12	aio_unlink "/tmp/file", sub { };	13	aio_unlink "/tmp/file", sub { };
13		14
…		…
23	$req->cancel; # cancel request if still in queue	24	$req->cancel; # cancel request if still in queue
24		25
25	my $grp = aio_group sub { print "all stats done\n" };	26	my $grp = aio_group sub { print "all stats done\n" };
26	add $grp aio_stat "..." for ...;	27	add $grp aio_stat "..." for ...;
27		28
28	# AnyEvent integration
29	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
30	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
31
32	# Event integration
33	Event->io (fd => IO::AIO::poll_fileno,
34	poll => 'r',
35	cb => \&IO::AIO::poll_cb);
36
37	# Glib/Gtk2 integration
38	add_watch Glib::IO IO::AIO::poll_fileno,
39	in => sub { IO::AIO::poll_cb; 1 };
40
41	# Tk integration
42	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
43	readable => \&IO::AIO::poll_cb);
44
45	# Danga::Socket integration
46	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
47	\&IO::AIO::poll_cb);
48
49	DESCRIPTION	29	DESCRIPTION
50	This module implements asynchronous I/O using whatever means your	30	This module implements asynchronous I/O using whatever means your
51	operating system supports.	31	operating system supports. It is implemented as an interface to "libeio"
		32	(<http://software.schmorp.de/pkg/libeio.html>).
52		33
53	Asynchronous means that operations that can normally block your program	34	Asynchronous means that operations that can normally block your program
54	(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
55	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
56	extremely useful for programs that need to stay interactive even when	37	extremely useful for programs that need to stay interactive even when
…		…
60	faster on a RAID volume or over NFS when you do a number of stat	41	faster on a RAID volume or over NFS when you do a number of stat
61	operations concurrently.	42	operations concurrently.
62		43
63	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
64	sockets), using these functions on file descriptors that support	45	sockets), using these functions on file descriptors that support
65	nonblocking operation (again, sockets, pipes etc.) is very inefficient	46	nonblocking operation (again, sockets, pipes etc.) is very inefficient.
66	or might not work (aio_read fails on sockets/pipes/fifos). Use an event
67	loop for that (such as the Event module): IO::AIO will naturally fit	47	Use an event loop for that (such as the EV module): IO::AIO will
68	into such an event loop itself.	48	naturally fit into such an event loop itself.
69		49
70	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
71	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
72	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
73	perl. In the future, this module might make use of the native aio	53	perl. In the future, this module might make use of the native aio
…		…
75	not well-supported or restricted (GNU/Linux doesn't allow them on normal	55	not well-supported or restricted (GNU/Linux doesn't allow them on normal
76	files currently, for example), and they would only support aio_read and	56	files currently, for example), and they would only support aio_read and
77	aio_write, so the remaining functionality would have to be implemented	57	aio_write, so the remaining functionality would have to be implemented
78	using threads anyway.	58	using threads anyway.
79		59
80	Although the module will work with in the presence of other (Perl-)	60	Although the module will work in the presence of other (Perl-) threads,
81	threads, it is currently not reentrant in any way, so use appropriate	61	it is currently not reentrant in any way, so use appropriate locking
82	locking yourself, always call "poll_cb" from within the same thread, or	62	yourself, always call "poll_cb" from within the same thread, or never
83	never call "poll_cb" (or other "aio_" functions) recursively.	63	call "poll_cb" (or other "aio_" functions) recursively.
84		64
85	EXAMPLE	65	EXAMPLE
86	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
87	/etc/passwd asynchronously:	67	asynchronously:
88		68
89	use Fcntl;	69	use Fcntl;
90	use Event;	70	use EV;
91	use IO::AIO;	71	use IO::AIO;
92		72
93	# register the IO::AIO callback with Event	73	# register the IO::AIO callback with EV
94	Event->io (fd => IO::AIO::poll_fileno,	74	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
95	poll => 'r',
96	cb => \&IO::AIO::poll_cb);
97		75
98	# queue the request to open /etc/passwd	76	# queue the request to open /etc/passwd
99	aio_open "/etc/passwd", O_RDONLY, 0, sub {	77	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
100	my $fh = $_[0]	78	my $fh = shift
101	or die "error while opening: $!";	79	or die "error while opening: $!";
102		80
103	# stat'ing filehandles is generally non-blocking	81	# stat'ing filehandles is generally non-blocking
104	my $size = -s $fh;	82	my $size = -s $fh;
105		83
…		…
113		91
114	# file contents now in $contents	92	# file contents now in $contents
115	print $contents;	93	print $contents;
116		94
117	# exit event loop and program	95	# exit event loop and program
118	Event::unloop;	96	EV::unloop;
119	};	97	};
120	};	98	};
121		99
122	# possibly queue up other requests, or open GUI windows,	100	# possibly queue up other requests, or open GUI windows,
123	# check for sockets etc. etc.	101	# check for sockets etc. etc.
124		102
125	# process events as long as there are some:	103	# process events as long as there are some:
126	Event::loop;	104	EV::loop;
127		105
128	REQUEST ANATOMY AND LIFETIME	106	REQUEST ANATOMY AND LIFETIME
129	Every "aio_*" function creates a request. which is a C data structure	107	Every "aio_*" function creates a request. which is a C data structure
130	not directly visible to Perl.	108	not directly visible to Perl.
131		109
…		…
167	anymore (except possibly for the Perl object, but its connection to	145	anymore (except possibly for the Perl object, but its connection to
168	the actual aio request is severed and calling its methods will	146	the actual aio request is severed and calling its methods will
169	either do nothing or result in a runtime error).	147	either do nothing or result in a runtime error).
170		148
171	FUNCTIONS	149	FUNCTIONS
		150	QUICK OVERVIEW
		151	This section simply lists the prototypes of the most important functions
		152	for quick reference. See the following sections for function-by-function
		153	documentation.
		154
		155	aio_open $pathname, $flags, $mode, $callback->($fh)
		156	aio_close $fh, $callback->($status)
		157	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		158	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		159	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		160	aio_readahead $fh,$offset,$length, $callback->($retval)
		161	aio_stat $fh_or_path, $callback->($status)
		162	aio_lstat $fh, $callback->($status)
		163	aio_statvfs $fh_or_path, $callback->($statvfs)
		164	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		165	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		166	aio_truncate $fh_or_path, $offset, $callback->($status)
		167	aio_chmod $fh_or_path, $mode, $callback->($status)
		168	aio_unlink $pathname, $callback->($status)
		169	aio_mknod $path, $mode, $dev, $callback->($status)
		170	aio_link $srcpath, $dstpath, $callback->($status)
		171	aio_symlink $srcpath, $dstpath, $callback->($status)
		172	aio_readlink $path, $callback->($link)
		173	aio_rename $srcpath, $dstpath, $callback->($status)
		174	aio_mkdir $pathname, $mode, $callback->($status)
		175	aio_rmdir $pathname, $callback->($status)
		176	aio_readdir $pathname, $callback->($entries)
		177	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		178	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		179	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		180	aio_load $path, $data, $callback->($status)
		181	aio_copy $srcpath, $dstpath, $callback->($status)
		182	aio_move $srcpath, $dstpath, $callback->($status)
		183	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		184	aio_rmtree $path, $callback->($status)
		185	aio_sync $callback->($status)
		186	aio_fsync $fh, $callback->($status)
		187	aio_fdatasync $fh, $callback->($status)
		188	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		189	aio_pathsync $path, $callback->($status)
		190	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		191	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		192	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		193	aio_mlockall $flags, $callback->($status)
		194	aio_group $callback->(...)
		195	aio_nop $callback->()
		196
		197	$prev_pri = aioreq_pri [$pri]
		198	aioreq_nice $pri_adjust
		199
		200	IO::AIO::poll_wait
		201	IO::AIO::poll_cb
		202	IO::AIO::poll
		203	IO::AIO::flush
		204	IO::AIO::max_poll_reqs $nreqs
		205	IO::AIO::max_poll_time $seconds
		206	IO::AIO::min_parallel $nthreads
		207	IO::AIO::max_parallel $nthreads
		208	IO::AIO::max_idle $nthreads
		209	IO::AIO::idle_timeout $seconds
		210	IO::AIO::max_outstanding $maxreqs
		211	IO::AIO::nreqs
		212	IO::AIO::nready
		213	IO::AIO::npending
		214
		215	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		216	IO::AIO::fadvise $fh, $offset, $len, $advice
		217	IO::AIO::madvise $scalar, $offset, $length, $advice
		218	IO::AIO::mprotect $scalar, $offset, $length, $protect
		219	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		220	IO::AIO::munlockall
		221
172	AIO REQUEST FUNCTIONS	222	AIO REQUEST FUNCTIONS
173	All the "aio_*" calls are more or less thin wrappers around the syscall	223	All the "aio_*" calls are more or less thin wrappers around the syscall
174	with the same name (sans "aio_"). The arguments are similar or	224	with the same name (sans "aio_"). The arguments are similar or
175	identical, and they all accept an additional (and optional) $callback	225	identical, and they all accept an additional (and optional) $callback
176	argument which must be a code reference. This code reference will get	226	argument which must be a code reference. This code reference will get
177	called with the syscall return code (e.g. most syscalls return -1 on	227	called with the syscall return code (e.g. most syscalls return -1 on
178	error, unlike perl, which usually delivers "false") as it's sole	228	error, unlike perl, which usually delivers "false") as its sole argument
179	argument when the given syscall has been executed asynchronously.	229	after the given syscall has been executed asynchronously.
180		230
181	All functions expecting a filehandle keep a copy of the filehandle	231	All functions expecting a filehandle keep a copy of the filehandle
182	internally until the request has finished.	232	internally until the request has finished.
183		233
184	All functions return request objects of type IO::AIO::REQ that allow	234	All functions return request objects of type IO::AIO::REQ that allow
…		…
197	the user environment, d) use Glib::filename_from_unicode on unicode	247	the user environment, d) use Glib::filename_from_unicode on unicode
198	filenames or e) use something else to ensure your scalar has the correct	248	filenames or e) use something else to ensure your scalar has the correct
199	contents.	249	contents.
200		250
201	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	251	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
202	handles correctly wether it is set or not.	252	handles correctly whether it is set or not.
203		253
204	$prev_pri = aioreq_pri [$pri]	254	$prev_pri = aioreq_pri [$pri]
205	Returns the priority value that would be used for the next request	255	Returns the priority value that would be used for the next request
206	and, if $pri is given, sets the priority for the next aio request.	256	and, if $pri is given, sets the priority for the next aio request.
207		257
…		…
241	They are the same as used by "sysopen".	291	They are the same as used by "sysopen".
242		292
243	Likewise, $mode specifies the mode of the newly created file, if it	293	Likewise, $mode specifies the mode of the newly created file, if it
244	didn't exist and "O_CREAT" has been given, just like perl's	294	didn't exist and "O_CREAT" has been given, just like perl's
245	"sysopen", except that it is mandatory (i.e. use 0 if you don't	295	"sysopen", except that it is mandatory (i.e. use 0 if you don't
246	create new files, and 0666 or 0777 if you do).	296	create new files, and 0666 or 0777 if you do). Note that the $mode
		297	will be modified by the umask in effect then the request is being
		298	executed, so better never change the umask.
247		299
248	Example:	300	Example:
249		301
250	aio_open "/etc/passwd", O_RDONLY, 0, sub {	302	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
251	if ($_[0]) {	303	if ($_[0]) {
252	print "open successful, fh is $_[0]\n";	304	print "open successful, fh is $_[0]\n";
253	...	305	...
254	} else {	306	} else {
255	die "open failed: $!\n";	307	die "open failed: $!\n";
256	}	308	}
257	};	309	};
258		310
		311	In addition to all the common open modes/flags ("O_RDONLY",
		312	"O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
		313	"O_APPEND"), the following POSIX and non-POSIX constants are
		314	available (missing ones on your system are, as usual, 0):
		315
		316	"O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
		317	"O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
		318	"O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
		319
259	aio_close $fh, $callback->($status)	320	aio_close $fh, $callback->($status)
260	Asynchronously close a file and call the callback with the result	321	Asynchronously close a file and call the callback with the result
261	code. WARNING: although accepted, you should not pass in a perl	322	code.
262	filehandle here, as perl will likely close the file descriptor
263	another time when the filehandle is destroyed. Normally, you can
264	safely call perls "close" or just let filehandles go out of scope.
265		323
266	This is supposed to be a bug in the API, so that might change. It's	324	Unfortunately, you can't do this to perl. Perl insists very
267	therefore best to avoid this function.	325	strongly on closing the file descriptor associated with the
		326	filehandle itself.
		327
		328	Therefore, "aio_close" will not close the filehandle - instead it
		329	will use dup2 to overwrite the file descriptor with the write-end of
		330	a pipe (the pipe fd will be created on demand and will be cached).
		331
		332	Or in other words: the file descriptor will be closed, but it will
		333	not be free for reuse until the perl filehandle is closed.
268		334
269	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	335	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
270	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	336	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271	Reads or writes "length" bytes from the specified "fh" and "offset"	337	Reads or writes $length bytes from or to the specified $fh and
272	into the scalar given by "data" and offset "dataoffset" and calls	338	$offset into the scalar given by $data and offset $dataoffset and
273	the callback without the actual number of bytes read (or -1 on	339	calls the callback without the actual number of bytes read (or -1 on
274	error, just like the syscall).	340	error, just like the syscall).
275		341
		342	"aio_read" will, like "sysread", shrink or grow the $data scalar to
		343	offset plus the actual number of bytes read.
		344
		345	If $offset is undefined, then the current file descriptor offset
		346	will be used (and updated), otherwise the file descriptor offset
		347	will not be changed by these calls.
		348
		349	If $length is undefined in "aio_write", use the remaining length of
		350	$data.
		351
		352	If $dataoffset is less than zero, it will be counted from the end of
		353	$data.
		354
276	The $data scalar MUST NOT be modified in any way while the request	355	The $data scalar MUST NOT be modified in any way while the request
277	is outstanding. Modifying it can result in segfaults or WW3 (if the	356	is outstanding. Modifying it can result in segfaults or World War
278	necessary/optional hardware is installed).	357	III (if the necessary/optional hardware is installed).
279		358
280	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at	359	Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
281	offset 0 within the scalar:	360	offset 0 within the scalar:
282		361
283	aio_read $fh, 7, 15, $buffer, 0, sub {	362	aio_read $fh, 7, 15, $buffer, 0, sub {
…		…
290	reading at byte offset $in_offset, and starts writing at the current	369	reading at byte offset $in_offset, and starts writing at the current
291	file offset of $out_fh. Because of that, it is not safe to issue	370	file offset of $out_fh. Because of that, it is not safe to issue
292	more than one "aio_sendfile" per $out_fh, as they will interfere	371	more than one "aio_sendfile" per $out_fh, as they will interfere
293	with each other.	372	with each other.
294		373
		374	Please note that "aio_sendfile" can read more bytes from $in_fh than
		375	are written, and there is no way to find out how many bytes have
		376	been read from "aio_sendfile" alone, as "aio_sendfile" only provides
		377	the number of bytes written to $out_fh. Only if the result value
		378	equals $length one can assume that $length bytes have been read.
		379
		380	Unlike with other "aio_" functions, it makes a lot of sense to use
		381	"aio_sendfile" on non-blocking sockets, as long as one end
		382	(typically the $in_fh) is a file - the file I/O will then be
		383	asynchronous, while the socket I/O will be non-blocking. Note,
		384	however, that you can run into a trap where "aio_sendfile" reads
		385	some data with readahead, then fails to write all data, and when the
		386	socket is ready the next time, the data in the cache is already
		387	lost, forcing "aio_sendfile" to again hit the disk. Explicit
		388	"aio_read" + "aio_write" let's you control resource usage much
		389	better.
		390
295	This call tries to make use of a native "sendfile" syscall to	391	This call tries to make use of a native "sendfile" syscall to
296	provide zero-copy operation. For this to work, $out_fh should refer	392	provide zero-copy operation. For this to work, $out_fh should refer
297	to a socket, and $in_fh should refer to mmap'able file.	393	to a socket, and $in_fh should refer to an mmap'able file.
298		394
299	If the native sendfile call fails or is not implemented, it will be	395	If a native sendfile cannot be found or it fails with "ENOSYS",
		396	"ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
300	emulated, so you can call "aio_sendfile" on any type of filehandle	397	it will be emulated, so you can call "aio_sendfile" on any type of
301	regardless of the limitations of the operating system.	398	filehandle regardless of the limitations of the operating system.
302
303	Please note, however, that "aio_sendfile" can read more bytes from
304	$in_fh than are written, and there is no way to find out how many
305	bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
306	only provides the number of bytes written to $out_fh. Only if the
307	result value equals $length one can assume that $length bytes have
308	been read.
309		399
310	aio_readahead $fh,$offset,$length, $callback->($retval)	400	aio_readahead $fh,$offset,$length, $callback->($retval)
311	"aio_readahead" populates the page cache with data from a file so	401	"aio_readahead" populates the page cache with data from a file so
312	that subsequent reads from that file will not block on disk I/O. The	402	that subsequent reads from that file will not block on disk I/O. The
313	$offset argument specifies the starting point from which data is to	403	$offset argument specifies the starting point from which data is to
…		…
334	Currently, the stats are always 64-bit-stats, i.e. instead of	424	Currently, the stats are always 64-bit-stats, i.e. instead of
335	returning an error when stat'ing a large file, the results will be	425	returning an error when stat'ing a large file, the results will be
336	silently truncated unless perl itself is compiled with large file	426	silently truncated unless perl itself is compiled with large file
337	support.	427	support.
338		428
		429	To help interpret the mode and dev/rdev stat values, IO::AIO offers
		430	the following constants and functions (if not implemented, the
		431	constants will be 0 and the functions will either "croak" or fall
		432	back on traditional behaviour).
		433
		434	"S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
		435	"S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
		436	"IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
		437
339	Example: Print the length of /etc/passwd:	438	Example: Print the length of /etc/passwd:
340		439
341	aio_stat "/etc/passwd", sub {	440	aio_stat "/etc/passwd", sub {
342	$_[0] and die "stat failed: $!";	441	$_[0] and die "stat failed: $!";
343	print "size is ", -s _, "\n";	442	print "size is ", -s _, "\n";
344	};	443	};
345		444
		445	aio_statvfs $fh_or_path, $callback->($statvfs)
		446	Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
		447	whether a file handle or path was passed.
		448
		449	On success, the callback is passed a hash reference with the
		450	following members: "bsize", "frsize", "blocks", "bfree", "bavail",
		451	"files", "ffree", "favail", "fsid", "flag" and "namemax". On
		452	failure, "undef" is passed.
		453
		454	The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
		455	and "ST_NOSUID".
		456
		457	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		458	their correct value when available, or to 0 on systems that do not
		459	support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
		460	"ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
		461	"ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
		462
		463	Example: stat "/wd" and dump out the data if successful.
		464
		465	aio_statvfs "/wd", sub {
		466	my $f = $_[0]
		467	or die "statvfs: $!";
		468
		469	use Data::Dumper;
		470	say Dumper $f;
		471	};
		472
		473	# result:
		474	{
		475	bsize => 1024,
		476	bfree => 4333064312,
		477	blocks => 10253828096,
		478	files => 2050765568,
		479	flag => 4096,
		480	favail => 2042092649,
		481	bavail => 4333064312,
		482	ffree => 2042092649,
		483	namemax => 255,
		484	frsize => 1024,
		485	fsid => 1810
		486	}
		487
		488	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		489	Works like perl's "utime" function (including the special case of
		490	$atime and $mtime being undef). Fractional times are supported if
		491	the underlying syscalls support them.
		492
		493	When called with a pathname, uses utimes(2) if available, otherwise
		494	utime(2). If called on a file descriptor, uses futimes(2) if
		495	available, otherwise returns ENOSYS, so this is not portable.
		496
		497	Examples:
		498
		499	# set atime and mtime to current time (basically touch(1)):
		500	aio_utime "path", undef, undef;
		501	# set atime to current time and mtime to beginning of the epoch:
		502	aio_utime "path", time, undef; # undef==0
		503
		504	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		505	Works like perl's "chown" function, except that "undef" for either
		506	$uid or $gid is being interpreted as "do not change" (but -1 can
		507	also be used).
		508
		509	Examples:
		510
		511	# same as "chown root path" in the shell:
		512	aio_chown "path", 0, -1;
		513	# same as above:
		514	aio_chown "path", 0, undef;
		515
		516	aio_truncate $fh_or_path, $offset, $callback->($status)
		517	Works like truncate(2) or ftruncate(2).
		518
		519	aio_chmod $fh_or_path, $mode, $callback->($status)
		520	Works like perl's "chmod" function.
		521
346	aio_unlink $pathname, $callback->($status)	522	aio_unlink $pathname, $callback->($status)
347	Asynchronously unlink (delete) a file and call the callback with the	523	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	524	result code.
349		525
350	aio_mknod $path, $mode, $dev, $callback->($status)	526	aio_mknod $path, $mode, $dev, $callback->($status)
…		…
353	Asynchronously create a device node (or fifo). See mknod(2).	529	Asynchronously create a device node (or fifo). See mknod(2).
354		530
355	The only (POSIX-) portable way of calling this function is:	531	The only (POSIX-) portable way of calling this function is:
356		532
357	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...	533	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		534
		535	See "aio_stat" for info about some potentially helpful extra
		536	constants and functions.
358		537
359	aio_link $srcpath, $dstpath, $callback->($status)	538	aio_link $srcpath, $dstpath, $callback->($status)
360	Asynchronously create a new link to the existing object at $srcpath	539	Asynchronously create a new link to the existing object at $srcpath
361	at the path $dstpath and call the callback with the result code.	540	at the path $dstpath and call the callback with the result code.
362		541
…		…
372		551
373	aio_rename $srcpath, $dstpath, $callback->($status)	552	aio_rename $srcpath, $dstpath, $callback->($status)
374	Asynchronously rename the object at $srcpath to $dstpath, just as	553	Asynchronously rename the object at $srcpath to $dstpath, just as
375	rename(2) and call the callback with the result code.	554	rename(2) and call the callback with the result code.
376		555
		556	aio_mkdir $pathname, $mode, $callback->($status)
		557	Asynchronously mkdir (create) a directory and call the callback with
		558	the result code. $mode will be modified by the umask at the time the
		559	request is executed, so do not change your umask.
		560
377	aio_rmdir $pathname, $callback->($status)	561	aio_rmdir $pathname, $callback->($status)
378	Asynchronously rmdir (delete) a directory and call the callback with	562	Asynchronously rmdir (delete) a directory and call the callback with
379	the result code.	563	the result code.
380		564
381	aio_readdir $pathname, $callback->($entries)	565	aio_readdir $pathname, $callback->($entries)
382	Unlike the POSIX call of the same name, "aio_readdir" reads an	566	Unlike the POSIX call of the same name, "aio_readdir" reads an
383	entire directory (i.e. opendir + readdir + closedir). The entries	567	entire directory (i.e. opendir + readdir + closedir). The entries
384	will not be sorted, and will NOT include the "." and ".." entries.	568	will not be sorted, and will NOT include the "." and ".." entries.
385		569
386	The callback a single argument which is either "undef" or an	570	The callback is passed a single argument which is either "undef" or
387	array-ref with the filenames.	571	an array-ref with the filenames.
		572
		573	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		574	Quite similar to "aio_readdir", but the $flags argument allows to
		575	tune behaviour and output format. In case of an error, $entries will
		576	be "undef".
		577
		578	The flags are a combination of the following constants, ORed
		579	together (the flags will also be passed to the callback, possibly
		580	modified):
		581
		582	IO::AIO::READDIR_DENTS
		583	When this flag is off, then the callback gets an arrayref
		584	consisting of names only (as with "aio_readdir"), otherwise it
		585	gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
		586	describing a single directory entry in more detail.
		587
		588	$name is the name of the entry.
		589
		590	$type is one of the "IO::AIO::DT_xxx" constants:
		591
		592	"IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
		593	"IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
		594	"IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
		595
		596	"IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
		597	you need to know, you have to run stat yourself. Also, for speed
		598	reasons, the $type scalars are read-only: you can not modify
		599	them.
		600
		601	$inode is the inode number (which might not be exact on systems
		602	with 64 bit inode numbers and 32 bit perls). This field has
		603	unspecified content on systems that do not deliver the inode
		604	information.
		605
		606	IO::AIO::READDIR_DIRS_FIRST
		607	When this flag is set, then the names will be returned in an
		608	order where likely directories come first, in optimal stat
		609	order. This is useful when you need to quickly find directories,
		610	or you want to find all directories while avoiding to stat()
		611	each entry.
		612
		613	If the system returns type information in readdir, then this is
		614	used to find directories directly. Otherwise, likely directories
		615	are names beginning with ".", or otherwise names with no dots,
		616	of which names with short names are tried first.
		617
		618	IO::AIO::READDIR_STAT_ORDER
		619	When this flag is set, then the names will be returned in an
		620	order suitable for stat()'ing each one. That is, when you plan
		621	to stat() all files in the given directory, then the returned
		622	order will likely be fastest.
		623
		624	If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
		625	specified, then the likely dirs come first, resulting in a less
		626	optimal stat order.
		627
		628	IO::AIO::READDIR_FOUND_UNKNOWN
		629	This flag should not be set when calling "aio_readdirx".
		630	Instead, it is being set by "aio_readdirx", when any of the
		631	$type's found were "IO::AIO::DT_UNKNOWN". The absense of this
		632	flag therefore indicates that all $type's are known, which can
		633	be used to speed up some algorithms.
		634
		635	aio_load $path, $data, $callback->($status)
		636	This is a composite request that tries to fully load the given file
		637	into memory. Status is the same as with aio_read.
388		638
389	aio_copy $srcpath, $dstpath, $callback->($status)	639	aio_copy $srcpath, $dstpath, $callback->($status)
390	Try to copy the file (directories not supported as either source	640	Try to copy the file (directories not supported as either source
391	or destination) from $srcpath to $dstpath and call the callback with	641	or destination) from $srcpath to $dstpath and call the callback with
392	the 0 (error) or -1 ok.	642	a status of 0 (ok) or -1 (error, see $!).
393		643
394	This is a composite request that it creates the destination file	644	This is a composite request that creates the destination file with
395	with mode 0200 and copies the contents of the source file into it	645	mode 0200 and copies the contents of the source file into it using
396	using "aio_sendfile", followed by restoring atime, mtime, access	646	"aio_sendfile", followed by restoring atime, mtime, access mode and
397	mode and uid/gid, in that order.	647	uid/gid, in that order.
398		648
399	If an error occurs, the partial destination file will be unlinked,	649	If an error occurs, the partial destination file will be unlinked,
400	if possible, except when setting atime, mtime, access mode and	650	if possible, except when setting atime, mtime, access mode and
401	uid/gid, where errors are being ignored.	651	uid/gid, where errors are being ignored.
402		652
403	aio_move $srcpath, $dstpath, $callback->($status)	653	aio_move $srcpath, $dstpath, $callback->($status)
404	Try to move the file (directories not supported as either source	654	Try to move the file (directories not supported as either source
405	or destination) from $srcpath to $dstpath and call the callback with	655	or destination) from $srcpath to $dstpath and call the callback with
406	the 0 (error) or -1 ok.	656	a status of 0 (ok) or -1 (error, see $!).
407		657
408	This is a composite request that tries to rename(2) the file first.	658	This is a composite request that tries to rename(2) the file first;
409	If rename files with "EXDEV", it copies the file with "aio_copy"	659	if rename fails with "EXDEV", it copies the file with "aio_copy"
410	and, if that is successful, unlinking the $srcpath.	660	and, if that is successful, unlinks the $srcpath.
411		661
412	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	662	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
413	Scans a directory (similar to "aio_readdir") but additionally tries	663	Scans a directory (similar to "aio_readdir") but additionally tries
414	to efficiently separate the entries of directory $path into two sets	664	to efficiently separate the entries of directory $path into two sets
415	of names, directories you can recurse into (directories), and ones	665	of names, directories you can recurse into (directories), and ones
…		…
435	Implementation notes.	685	Implementation notes.
436		686
437	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry	687	The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
438	can.	688	can.
439		689
		690	If readdir returns file type information, then this is used directly
		691	to find directories.
		692
440	After reading the directory, the modification time, size etc. of the	693	Otherwise, after reading the directory, the modification time, size
441	directory before and after the readdir is checked, and if they match	694	etc. of the directory before and after the readdir is checked, and
442	(and isn't the current time), the link count will be used to decide	695	if they match (and isn't the current time), the link count will be
443	how many entries are directories (if >= 2). Otherwise, no knowledge	696	used to decide how many entries are directories (if >= 2).
444	of the number of subdirectories will be assumed.	697	Otherwise, no knowledge of the number of subdirectories will be
		698	assumed.
445		699
446	Then entries will be sorted into likely directories (everything	700	Then entries will be sorted into likely directories a non-initial
447	without a non-initial dot currently) and likely non-directories	701	dot currently) and likely non-directories (see "aio_readdirx"). Then
448	(everything else). Then every entry plus an appended "/." will be	702	every entry plus an appended "/." will be "stat"'ed, likely
449	"stat"'ed, likely directories first. If that succeeds, it assumes	703	directories first, in order of their inode numbers. If that
450	that the entry is a directory or a symlink to directory (which will	704	succeeds, it assumes that the entry is a directory or a symlink to
451	be checked seperately). This is often faster than stat'ing the entry	705	directory (which will be checked seperately). This is often faster
452	itself because filesystems might detect the type of the entry	706	than stat'ing the entry itself because filesystems might detect the
453	without reading the inode data (e.g. ext2fs filetype feature).	707	type of the entry without reading the inode data (e.g. ext2fs
		708	filetype feature), even on systems that cannot return the filetype
		709	information on readdir.
454		710
455	If the known number of directories (link count - 2) has been	711	If the known number of directories (link count - 2) has been
456	reached, the rest of the entries is assumed to be non-directories.	712	reached, the rest of the entries is assumed to be non-directories.
457		713
458	This only works with certainty on POSIX (= UNIX) filesystems, which	714	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
460		716
461	It will also likely work on non-POSIX filesystems with reduced	717	It will also likely work on non-POSIX filesystems with reduced
462	efficiency as those tend to return 0 or 1 as link counts, which	718	efficiency as those tend to return 0 or 1 as link counts, which
463	disables the directory counting heuristic.	719	disables the directory counting heuristic.
464		720
		721	aio_rmtree $path, $callback->($status)
		722	Delete a directory tree starting (and including) $path, return the
		723	status of the final "rmdir" only. This is a composite request that
		724	uses "aio_scandir" to recurse into and rmdir directories, and unlink
		725	everything else.
		726
		727	aio_sync $callback->($status)
		728	Asynchronously call sync and call the callback when finished.
		729
465	aio_fsync $fh, $callback->($status)	730	aio_fsync $fh, $callback->($status)
466	Asynchronously call fsync on the given filehandle and call the	731	Asynchronously call fsync on the given filehandle and call the
467	callback with the fsync result code.	732	callback with the fsync result code.
468		733
469	aio_fdatasync $fh, $callback->($status)	734	aio_fdatasync $fh, $callback->($status)
470	Asynchronously call fdatasync on the given filehandle and call the	735	Asynchronously call fdatasync on the given filehandle and call the
471	callback with the fdatasync result code.	736	callback with the fdatasync result code.
472		737
473	If this call isn't available because your OS lacks it or it couldn't	738	If this call isn't available because your OS lacks it or it couldn't
474	be detected, it will be emulated by calling "fsync" instead.	739	be detected, it will be emulated by calling "fsync" instead.
		740
		741	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		742	Sync the data portion of the file specified by $offset and $length
		743	to disk (but NOT the metadata), by calling the Linux-specific
		744	sync_file_range call. If sync_file_range is not available or it
		745	returns ENOSYS, then fdatasync or fsync is being substituted.
		746
		747	$flags can be a combination of
		748	"IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
		749	"IO::AIO::SYNC_FILE_RANGE_WRITE" and
		750	"IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
		751	manpage for details.
		752
		753	aio_pathsync $path, $callback->($status)
		754	This request tries to open, fsync and close the given path. This is
		755	a composite request intended to sync directories after directory
		756	operations (E.g. rename). This might not work on all operating
		757	systems or have any specific effect, but usually it makes sure that
		758	directory changes get written to disc. It works for anything that
		759	can be opened for read-only, not just directories.
		760
		761	Future versions of this function might fall back to other methods
		762	when "fsync" on the directory fails (such as calling "sync").
		763
		764	Passes 0 when everything went ok, and -1 on error.
		765
		766	aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
		767	$callback->($status)
		768	This is a rather advanced IO::AIO call, which only works on
		769	mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
		770	also works on data scalars managed by the Sys::Mmap or Mmap modules,
		771	note that the scalar must only be modified in-place while an aio
		772	operation is pending on it).
		773
		774	It calls the "msync" function of your OS, if available, with the
		775	memory area starting at $offset in the string and ending $length
		776	bytes later. If $length is negative, counts from the end, and if
		777	$length is "undef", then it goes till the end of the string. The
		778	flags can be a combination of "IO::AIO::MS_ASYNC",
		779	"IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
		780
		781	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
		782	$callback->($status)
		783	This is a rather advanced IO::AIO call, which works best on
		784	mmap(2)ed scalars.
		785
		786	It touches (reads or writes) all memory pages in the specified range
		787	inside the scalar. All caveats and parameters are the same as for
		788	"aio_msync", above, except for flags, which must be either 0 (which
		789	reads all pages and ensures they are instantiated) or
		790	"IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
		791	and writing an octet from it, which dirties the page).
		792
		793	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		794	This is a rather advanced IO::AIO call, which works best on
		795	mmap(2)ed scalars.
		796
		797	It reads in all the pages of the underlying storage into memory (if
		798	any) and locks them, so they are not getting swapped/paged out or
		799	removed.
		800
		801	If $length is undefined, then the scalar will be locked till the
		802	end.
		803
		804	On systems that do not implement "mlock", this function returns -1
		805	and sets errno to "ENOSYS".
		806
		807	Note that the corresponding "munlock" is synchronous and is
		808	documented under "MISCELLANEOUS FUNCTIONS".
		809
		810	Example: open a file, mmap and mlock it - both will be undone when
		811	$data gets destroyed.
		812
		813	open my $fh, "<", $path or die "$path: $!";
		814	my $data;
		815	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		816	aio_mlock $data; # mlock in background
		817
		818	aio_mlockall $flags, $callback->($status)
		819	Calls the "mlockall" function with the given $flags (a combination
		820	of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
		821
		822	On systems that do not implement "mlockall", this function returns
		823	-1 and sets errno to "ENOSYS".
		824
		825	Note that the corresponding "munlockall" is synchronous and is
		826	documented under "MISCELLANEOUS FUNCTIONS".
		827
		828	Example: asynchronously lock all current and future pages into
		829	memory.
		830
		831	aio_mlockall IO::AIO::MCL_FUTURE;
475		832
476	aio_group $callback->(...)	833	aio_group $callback->(...)
477	This is a very special aio request: Instead of doing something, it	834	This is a very special aio request: Instead of doing something, it
478	is a container for other aio requests, which is useful if you want	835	is a container for other aio requests, which is useful if you want
479	to bundle many requests into a single, composite, request with a	836	to bundle many requests into a single, composite, request with a
…		…
522		879
523	cancel $req	880	cancel $req
524	Cancels the request, if possible. Has the effect of skipping	881	Cancels the request, if possible. Has the effect of skipping
525	execution when entering the execute state and skipping calling the	882	execution when entering the execute state and skipping calling the
526	callback when entering the the result state, but will leave the	883	callback when entering the the result state, but will leave the
527	request otherwise untouched. That means that requests that currently	884	request otherwise untouched (with the exception of readdir). That
528	execute will not be stopped and resources held by the request will	885	means that requests that currently execute will not be stopped and
529	not be freed prematurely.	886	resources held by the request will not be freed prematurely.
530		887
531	cb $req $callback->(...)	888	cb $req $callback->(...)
532	Replace (or simply set) the callback registered to the request.	889	Replace (or simply set) the callback registered to the request.
533		890
534	IO::AIO::GRP CLASS	891	IO::AIO::GRP CLASS
…		…
561	};	918	};
562		919
563	This makes it very easy to create composite requests (see the source of	920	This makes it very easy to create composite requests (see the source of
564	"aio_move" for an application) that work and feel like simple requests.	921	"aio_move" for an application) that work and feel like simple requests.
565		922
566	* The IO::AIO::GRP objects will be cleaned up during calls to	923	* The IO::AIO::GRP objects will be cleaned up during calls to
567	"IO::AIO::poll_cb", just like any other request.	924	"IO::AIO::poll_cb", just like any other request.
		925
568	* They can be canceled like any other request. Canceling will cancel not	926	* They can be canceled like any other request. Canceling will cancel
569	only the request itself, but also all requests it contains.	927	not only the request itself, but also all requests it contains.
		928
570	* They can also can also be added to other IO::AIO::GRP objects.	929	* They can also can also be added to other IO::AIO::GRP objects.
		930
571	* You must not add requests to a group from within the group callback	931	* You must not add requests to a group from within the group callback
572	(or any later time).	932	(or any later time).
573		933
574	Their lifetime, simplified, looks like this: when they are empty, they	934	Their lifetime, simplified, looks like this: when they are empty, they
575	will finish very quickly. If they contain only requests that are in the	935	will finish very quickly. If they contain only requests that are in the
576	"done" state, they will also finish. Otherwise they will continue to	936	"done" state, they will also finish. Otherwise they will continue to
577	exist.	937	exist.
578		938
579	That means after creating a group you have some time to add requests.	939	That means after creating a group you have some time to add requests
580	And in the callbacks of those requests, you can add further requests to	940	(precisely before the callback has been invoked, which is only done
581	the group. And only when all those requests have finished will the the	941	within the "poll_cb"). And in the callbacks of those requests, you can
582	group itself finish.	942	add further requests to the group. And only when all those requests have
		943	finished will the the group itself finish.
583		944
584	add $grp ...	945	add $grp ...
585	$grp->add (...)	946	$grp->add (...)
586	Add one or more requests to the group. Any type of IO::AIO::REQ can	947	Add one or more requests to the group. Any type of IO::AIO::REQ can
587	be added, including other groups, as long as you do not create	948	be added, including other groups, as long as you do not create
…		…
592	$grp->cancel_subs	953	$grp->cancel_subs
593	Cancel all subrequests and clears any feeder, but not the group	954	Cancel all subrequests and clears any feeder, but not the group
594	request itself. Useful when you queued a lot of events but got a	955	request itself. Useful when you queued a lot of events but got a
595	result early.	956	result early.
596		957
		958	The group request will finish normally (you cannot add requests to
		959	the group).
		960
597	$grp->result (...)	961	$grp->result (...)
598	Set the result value(s) that will be passed to the group callback	962	Set the result value(s) that will be passed to the group callback
599	when all subrequests have finished and set thre groups errno to the	963	when all subrequests have finished and set the groups errno to the
600	current value of errno (just like calling "errno" without an error	964	current value of errno (just like calling "errno" without an error
601	number). By default, no argument will be passed and errno is zero.	965	number). By default, no argument will be passed and errno is zero.
602		966
603	$grp->errno ([$errno])	967	$grp->errno ([$errno])
604	Sets the group errno value to $errno, or the current value of errno	968	Sets the group errno value to $errno, or the current value of errno
…		…
630	does not impose any limits).	994	does not impose any limits).
631		995
632	If the feed does not queue more requests when called, it will be	996	If the feed does not queue more requests when called, it will be
633	automatically removed from the group.	997	automatically removed from the group.
634		998
635	If the feed limit is 0, it will be set to 2 automatically.	999	If the feed limit is 0 when this method is called, it will be set to
		1000	2 automatically.
636		1001
637	Example:	1002	Example:
638		1003
639	# stat all files in @files, but only ever use four aio requests concurrently:	1004	# stat all files in @files, but only ever use four aio requests concurrently:
640		1005
…		…
651	Sets the feeder limit for the group: The feeder will be called	1016	Sets the feeder limit for the group: The feeder will be called
652	whenever the group contains less than this many requests.	1017	whenever the group contains less than this many requests.
653		1018
654	Setting the limit to 0 will pause the feeding process.	1019	Setting the limit to 0 will pause the feeding process.
655		1020
		1021	The default value for the limit is 0, but note that setting a feeder
		1022	automatically bumps it up to 2.
		1023
656	SUPPORT FUNCTIONS	1024	SUPPORT FUNCTIONS
657	EVENT PROCESSING AND EVENT LOOP INTEGRATION	1025	EVENT PROCESSING AND EVENT LOOP INTEGRATION
658	$fileno = IO::AIO::poll_fileno	1026	$fileno = IO::AIO::poll_fileno
659	Return the request result pipe file descriptor. This filehandle	1027	Return the request result pipe file descriptor. This filehandle
660	must be polled for reading by some mechanism outside this module	1028	must be polled for reading by some mechanism outside this module
661	(e.g. Event or select, see below or the SYNOPSIS). If the pipe	1029	(e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
662	becomes readable you have to call "poll_cb" to check the results.	1030	pipe becomes readable you have to call "poll_cb" to check the
		1031	results.
663		1032
664	See "poll_cb" for an example.	1033	See "poll_cb" for an example.
665		1034
666	IO::AIO::poll_cb	1035	IO::AIO::poll_cb
667	Process some outstanding events on the result pipe. You have to call	1036	Process some outstanding events on the result pipe. You have to call
668	this regularly. Returns the number of events processed. Returns	1037	this regularly. Returns 0 if all events could be processed (or there
669	immediately when no events are outstanding. The amount of events	1038	were no events to process), or -1 if it returned earlier for
670	processed depends on the settings of "IO::AIO::max_poll_req" and	1039	whatever reason. Returns immediately when no events are outstanding.
671	"IO::AIO::max_poll_time".	1040	The amount of events processed depends on the settings of
		1041	"IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
672		1042
673	If not all requests were processed for whatever reason, the	1043	If not all requests were processed for whatever reason, the
674	filehandle will still be ready when "poll_cb" returns.	1044	filehandle will still be ready when "poll_cb" returns, so normally
		1045	you don't have to do anything special to have it called later.
		1046
		1047	Apart from calling "IO::AIO::poll_cb" when the event filehandle
		1048	becomes ready, it can be beneficial to call this function from loops
		1049	which submit a lot of requests, to make sure the results get
		1050	processed when they become available and not just when the loop is
		1051	finished and the event loop takes over again. This function returns
		1052	very fast when there are no outstanding requests.
675		1053
676	Example: Install an Event watcher that automatically calls	1054	Example: Install an Event watcher that automatically calls
677	IO::AIO::poll_cb with high priority:	1055	IO::AIO::poll_cb with high priority (more examples can be found in
		1056	the SYNOPSIS section, at the top of this document):
678		1057
679	Event->io (fd => IO::AIO::poll_fileno,	1058	Event->io (fd => IO::AIO::poll_fileno,
680	poll => 'r', async => 1,	1059	poll => 'r', async => 1,
681	cb => \&IO::AIO::poll_cb);	1060	cb => \&IO::AIO::poll_cb);
		1061
		1062	IO::AIO::poll_wait
		1063	If there are any outstanding requests and none of them in the result
		1064	phase, wait till the result filehandle becomes ready for reading
		1065	(simply does a "select" on the filehandle. This is useful if you
		1066	want to synchronously wait for some requests to finish).
		1067
		1068	See "nreqs" for an example.
		1069
		1070	IO::AIO::poll
		1071	Waits until some requests have been handled.
		1072
		1073	Returns the number of requests processed, but is otherwise strictly
		1074	equivalent to:
		1075
		1076	IO::AIO::poll_wait, IO::AIO::poll_cb
		1077
		1078	IO::AIO::flush
		1079	Wait till all outstanding AIO requests have been handled.
		1080
		1081	Strictly equivalent to:
		1082
		1083	IO::AIO::poll_wait, IO::AIO::poll_cb
		1084	while IO::AIO::nreqs;
682		1085
683	IO::AIO::max_poll_reqs $nreqs	1086	IO::AIO::max_poll_reqs $nreqs
684	IO::AIO::max_poll_time $seconds	1087	IO::AIO::max_poll_time $seconds
685	These set the maximum number of requests (default 0, meaning	1088	These set the maximum number of requests (default 0, meaning
686	infinity) that are being processed by "IO::AIO::poll_cb" in one	1089	infinity) that are being processed by "IO::AIO::poll_cb" in one
…		…
710	# use a low priority so other tasks have priority	1113	# use a low priority so other tasks have priority
711	Event->io (fd => IO::AIO::poll_fileno,	1114	Event->io (fd => IO::AIO::poll_fileno,
712	poll => 'r', nice => 1,	1115	poll => 'r', nice => 1,
713	cb => &IO::AIO::poll_cb);	1116	cb => &IO::AIO::poll_cb);
714		1117
715	IO::AIO::poll_wait
716	Wait till the result filehandle becomes ready for reading (simply
717	does a "select" on the filehandle. This is useful if you want to
718	synchronously wait for some requests to finish).
719
720	See "nreqs" for an example.
721
722	IO::AIO::poll
723	Waits until some requests have been handled.
724
725	Strictly equivalent to:
726
727	IO::AIO::poll_wait, IO::AIO::poll_cb
728	if IO::AIO::nreqs;
729
730	IO::AIO::flush
731	Wait till all outstanding AIO requests have been handled.
732
733	Strictly equivalent to:
734
735	IO::AIO::poll_wait, IO::AIO::poll_cb
736	while IO::AIO::nreqs;
737
738	CONTROLLING THE NUMBER OF THREADS	1118	CONTROLLING THE NUMBER OF THREADS
739	IO::AIO::min_parallel $nthreads	1119	IO::AIO::min_parallel $nthreads
740	Set the minimum number of AIO threads to $nthreads. The current	1120	Set the minimum number of AIO threads to $nthreads. The current
741	default is 8, which means eight asynchronous operations can execute	1121	default is 8, which means eight asynchronous operations can execute
742	concurrently at any one time (the number of outstanding requests,	1122	concurrently at any one time (the number of outstanding requests,
…		…
771		1151
772	Under normal circumstances you don't need to call this function.	1152	Under normal circumstances you don't need to call this function.
773		1153
774	IO::AIO::max_idle $nthreads	1154	IO::AIO::max_idle $nthreads
775	Limit the number of threads (default: 4) that are allowed to idle	1155	Limit the number of threads (default: 4) that are allowed to idle
776	(i.e., threads that did not get a request to process within 10	1156	(i.e., threads that did not get a request to process within the idle
777	seconds). That means if a thread becomes idle while $nthreads other	1157	timeout (default: 10 seconds). That means if a thread becomes idle
778	threads are also idle, it will free its resources and exit.	1158	while $nthreads other threads are also idle, it will free its
		1159	resources and exit.
779		1160
780	This is useful when you allow a large number of threads (e.g. 100 or	1161	This is useful when you allow a large number of threads (e.g. 100 or
781	1000) to allow for extremely high load situations, but want to free	1162	1000) to allow for extremely high load situations, but want to free
782	resources under normal circumstances (1000 threads can easily	1163	resources under normal circumstances (1000 threads can easily
783	consume 30MB of RAM).	1164	consume 30MB of RAM).
784		1165
785	The default is probably ok in most situations, especially if thread	1166	The default is probably ok in most situations, especially if thread
786	creation is fast. If thread creation is very slow on your system you	1167	creation is fast. If thread creation is very slow on your system you
787	might want to use larger values.	1168	might want to use larger values.
788		1169
		1170	IO::AIO::idle_timeout $seconds
		1171	Sets the minimum idle timeout (default 10) after which worker
		1172	threads are allowed to exit. SEe "IO::AIO::max_idle".
		1173
789	$oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1174	IO::AIO::max_outstanding $maxreqs
790	This is a very bad function to use in interactive programs because	1175	This is a very bad function to use in interactive programs because
791	it blocks, and a bad way to reduce concurrency because it is	1176	it blocks, and a bad way to reduce concurrency because it is
792	inexact: Better use an "aio_group" together with a feed callback.	1177	inexact: Better use an "aio_group" together with a feed callback.
793		1178
794	Sets the maximum number of outstanding requests to $nreqs. If you to	1179	Sets the maximum number of outstanding requests to $nreqs. If you do
795	queue up more than this number of requests, the next call to the	1180	queue up more than this number of requests, the next call to the
796	"poll_cb" (and "poll_some" and other functions calling "poll_cb")	1181	"poll_cb" (and "poll_some" and other functions calling "poll_cb")
797	function will block until the limit is no longer exceeded.	1182	function will block until the limit is no longer exceeded.
798		1183
799	The default value is very large, so there is no practical limit on	1184	The default value is very large, so there is no practical limit on
800	the number of outstanding requests.	1185	the number of outstanding requests.
801		1186
802	You can still queue as many requests as you want. Therefore,	1187	You can still queue as many requests as you want. Therefore,
803	"max_oustsanding" is mainly useful in simple scripts (with low	1188	"max_outstanding" is mainly useful in simple scripts (with low
804	values) or as a stop gap to shield against fatal memory overflow	1189	values) or as a stop gap to shield against fatal memory overflow
805	(with large values).	1190	(with large values).
806		1191
807	STATISTICAL INFORMATION	1192	STATISTICAL INFORMATION
808	IO::AIO::nreqs	1193	IO::AIO::nreqs
…		…
820	executed).	1205	executed).
821		1206
822	IO::AIO::npending	1207	IO::AIO::npending
823	Returns the number of requests currently in the pending state	1208	Returns the number of requests currently in the pending state
824	(executed, but not yet processed by poll_cb).	1209	(executed, but not yet processed by poll_cb).
		1210
		1211	MISCELLANEOUS FUNCTIONS
		1212	IO::AIO implements some functions that might be useful, but are not
		1213	asynchronous.
		1214
		1215	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1216	Calls the "eio_sendfile_sync" function, which is like
		1217	"aio_sendfile", but is blocking (this makes most sense if you know
		1218	the input data is likely cached already and the output filehandle is
		1219	set to non-blocking operations).
		1220
		1221	Returns the number of bytes copied, or -1 on error.
		1222
		1223	IO::AIO::fadvise $fh, $offset, $len, $advice
		1224	Simply calls the "posix_fadvise" function (see its manpage for
		1225	details). The following advice constants are avaiable:
		1226	"IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
		1227	"IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
		1228	"IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
		1229
		1230	On systems that do not implement "posix_fadvise", this function
		1231	returns ENOSYS, otherwise the return value of "posix_fadvise".
		1232
		1233	IO::AIO::madvise $scalar, $offset, $len, $advice
		1234	Simply calls the "posix_madvise" function (see its manpage for
		1235	details). The following advice constants are avaiable:
		1236	"IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
		1237	"IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
		1238	"IO::AIO::MADV_DONTNEED".
		1239
		1240	On systems that do not implement "posix_madvise", this function
		1241	returns ENOSYS, otherwise the return value of "posix_madvise".
		1242
		1243	IO::AIO::mprotect $scalar, $offset, $len, $protect
		1244	Simply calls the "mprotect" function on the preferably AIO::mmap'ed
		1245	$scalar (see its manpage for details). The following protect
		1246	constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
		1247	"IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
		1248
		1249	On systems that do not implement "mprotect", this function returns
		1250	ENOSYS, otherwise the return value of "mprotect".
		1251
		1252	IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1253	Memory-maps a file (or anonymous memory range) and attaches it to
		1254	the given $scalar, which will act like a string scalar.
		1255
		1256	The only operations allowed on the scalar are "substr"/"vec" that
		1257	don't change the string length, and most read-only operations such
		1258	as copying it or searching it with regexes and so on.
		1259
		1260	Anything else is unsafe and will, at best, result in memory leaks.
		1261
		1262	The memory map associated with the $scalar is automatically removed
		1263	when the $scalar is destroyed, or when the "IO::AIO::mmap" or
		1264	"IO::AIO::munmap" functions are called.
		1265
		1266	This calls the "mmap"(2) function internally. See your system's
		1267	manual page for details on the $length, $prot and $flags parameters.
		1268
		1269	The $length must be larger than zero and smaller than the actual
		1270	filesize.
		1271
		1272	$prot is a combination of "IO::AIO::PROT_NONE",
		1273	"IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
		1274	"IO::AIO::PROT_WRITE",
		1275
		1276	$flags can be a combination of "IO::AIO::MAP_SHARED" or
		1277	"IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
		1278	not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
		1279	(which is set to "MAP_ANON" if your system only provides this
		1280	constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
		1281	"IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
		1282	"IO::AIO::MAP_NONBLOCK"
		1283
		1284	If $fh is "undef", then a file descriptor of -1 is passed.
		1285
		1286	$offset is the offset from the start of the file - it generally must
		1287	be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
		1288
		1289	Example:
		1290
		1291	use Digest::MD5;
		1292	use IO::AIO;
		1293
		1294	open my $fh, "<verybigfile"
		1295	or die "$!";
		1296
		1297	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1298	or die "verybigfile: $!";
		1299
		1300	my $fast_md5 = md5 $data;
		1301
		1302	IO::AIO::munmap $scalar
		1303	Removes a previous mmap and undefines the $scalar.
		1304
		1305	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1306	Calls the "munlock" function, undoing the effects of a previous
		1307	"aio_mlock" call (see its description for details).
		1308
		1309	IO::AIO::munlockall
		1310	Calls the "munlockall" function.
		1311
		1312	On systems that do not implement "munlockall", this function returns
		1313	ENOSYS, otherwise the return value of "munlockall".
		1314
		1315	EVENT LOOP INTEGRATION
		1316	It is recommended to use AnyEvent::AIO to integrate IO::AIO
		1317	automatically into many event loops:
		1318
		1319	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1320	use AnyEvent::AIO;
		1321
		1322	You can also integrate IO::AIO manually into many event loops, here are
		1323	some examples of how to do this:
		1324
		1325	# EV integration
		1326	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1327
		1328	# Event integration
		1329	Event->io (fd => IO::AIO::poll_fileno,
		1330	poll => 'r',
		1331	cb => \&IO::AIO::poll_cb);
		1332
		1333	# Glib/Gtk2 integration
		1334	add_watch Glib::IO IO::AIO::poll_fileno,
		1335	in => sub { IO::AIO::poll_cb; 1 };
		1336
		1337	# Tk integration
		1338	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1339	readable => \&IO::AIO::poll_cb);
		1340
		1341	# Danga::Socket integration
		1342	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1343	\&IO::AIO::poll_cb);
825		1344
826	FORK BEHAVIOUR	1345	FORK BEHAVIOUR
827	This module should do "the right thing" when the process using it forks:	1346	This module should do "the right thing" when the process using it forks:
828		1347
829	Before the fork, IO::AIO enters a quiescent state where no requests can	1348	Before the fork, IO::AIO enters a quiescent state where no requests can
…		…
845	bytes of memory. In addition, stat requests need a stat buffer (possibly	1364	bytes of memory. In addition, stat requests need a stat buffer (possibly
846	a few hundred bytes), readdir requires a result buffer and so on. Perl	1365	a few hundred bytes), readdir requires a result buffer and so on. Perl
847	scalars and other data passed into aio requests will also be locked and	1366	scalars and other data passed into aio requests will also be locked and
848	will consume memory till the request has entered the done state.	1367	will consume memory till the request has entered the done state.
849		1368
850	This is now awfully much, so queuing lots of requests is not usually a	1369	This is not awfully much, so queuing lots of requests is not usually a
851	problem.	1370	problem.
852		1371
853	Per-thread usage:	1372	Per-thread usage:
854		1373
855	In the execution phase, some aio requests require more memory for	1374	In the execution phase, some aio requests require more memory for
…		…
858		1377
859	KNOWN BUGS	1378	KNOWN BUGS
860	Known bugs will be fixed in the next release.	1379	Known bugs will be fixed in the next release.
861		1380
862	SEE ALSO	1381	SEE ALSO
863	Coro::AIO.	1382	AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
		1383	more natural syntax.
864		1384
865	AUTHOR	1385	AUTHOR
866	Marc Lehmann <schmorp@schmorp.de>	1386	Marc Lehmann <schmorp@schmorp.de>
867	http://home.schmorp.de/	1387	http://home.schmorp.de/
868		1388

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Revision 1.20 by root, Tue Oct 31 00:45:41 2006 UTC vs.
Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC