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Revision 1.14 by root, Mon Jul 11 02:53:59 2005 UTC vs.
Revision 1.156 by root, Tue Jun 16 23:41:59 2009 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	39	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
24		41
25	# Glib/Gtk2	42	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
27	\&IO::AIO::poll_cb;	44	in => sub { IO::AIO::poll_cb; 1 };
28		45
29	# Tk	46	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
32		49
33	# Danga::Socket	50	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
36		53
37
38	=head1 DESCRIPTION	54	=head1 DESCRIPTION
39		55
40	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
41	operating system supports.	57	operating system supports. It is implemented as an interface to C<libeio>
		58	(L<http://software.schmorp.de/pkg/libeio.html>).
42		59
		60	Asynchronous means that operations that can normally block your program
		61	(e.g. reading from disk) will be done asynchronously: the operation
		62	will still block, but you can do something else in the meantime. This
		63	is extremely useful for programs that need to stay interactive even
		64	when doing heavy I/O (GUI programs, high performance network servers
		65	etc.), but can also be used to easily do operations in parallel that are
		66	normally done sequentially, e.g. stat'ing many files, which is much faster
		67	on a RAID volume or over NFS when you do a number of stat operations
		68	concurrently.
		69
		70	While most of this works on all types of file descriptors (for
		71	example sockets), using these functions on file descriptors that
		72	support nonblocking operation (again, sockets, pipes etc.) is
		73	very inefficient. Use an event loop for that (such as the L<EV>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
43	Currently, a number of threads are started that execute your read/writes	76	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	77	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	78	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	79	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	80	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	81	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	82	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	83	aio_write, so the remaining functionality would have to be implemented
		84	using threads anyway.
51		85
52	Although the module will work with in the presence of other threads, it is	86	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself.	87	it is currently not reentrant in any way, so use appropriate locking
		88	yourself, always call C<poll_cb> from within the same thread, or never
		89	call C<poll_cb> (or other C<aio_> functions) recursively.
		90
		91	=head2 EXAMPLE
		92
		93	This is a simple example that uses the EV module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use EV;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with EV
		101	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		102
		103	# queue the request to open /etc/passwd
		104	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		105	my $fh = shift
		106	or die "error while opening: $!";
		107
		108	# stat'ing filehandles is generally non-blocking
		109	my $size = -s $fh;
		110
		111	# queue a request to read the file
		112	my $contents;
		113	aio_read $fh, 0, $size, $contents, 0, sub {
		114	$_[0] == $size
		115	or die "short read: $!";
		116
		117	close $fh;
		118
		119	# file contents now in $contents
		120	print $contents;
		121
		122	# exit event loop and program
		123	EV::unloop;
		124	};
		125	};
		126
		127	# possibly queue up other requests, or open GUI windows,
		128	# check for sockets etc. etc.
		129
		130	# process events as long as there are some:
		131	EV::loop;
		132
		133	=head1 REQUEST ANATOMY AND LIFETIME
		134
		135	Every C<aio_*> function creates a request. which is a C data structure not
		136	directly visible to Perl.
		137
		138	If called in non-void context, every request function returns a Perl
		139	object representing the request. In void context, nothing is returned,
		140	which saves a bit of memory.
		141
		142	The perl object is a fairly standard ref-to-hash object. The hash contents
		143	are not used by IO::AIO so you are free to store anything you like in it.
		144
		145	During their existance, aio requests travel through the following states,
		146	in order:
		147
		148	=over 4
		149
		150	=item ready
		151
		152	Immediately after a request is created it is put into the ready state,
		153	waiting for a thread to execute it.
		154
		155	=item execute
		156
		157	A thread has accepted the request for processing and is currently
		158	executing it (e.g. blocking in read).
		159
		160	=item pending
		161
		162	The request has been executed and is waiting for result processing.
		163
		164	While request submission and execution is fully asynchronous, result
		165	processing is not and relies on the perl interpreter calling C<poll_cb>
		166	(or another function with the same effect).
		167
		168	=item result
		169
		170	The request results are processed synchronously by C<poll_cb>.
		171
		172	The C<poll_cb> function will process all outstanding aio requests by
		173	calling their callbacks, freeing memory associated with them and managing
		174	any groups they are contained in.
		175
		176	=item done
		177
		178	Request has reached the end of its lifetime and holds no resources anymore
		179	(except possibly for the Perl object, but its connection to the actual
		180	aio request is severed and calling its methods will either do nothing or
		181	result in a runtime error).
		182
		183	=back
54		184
55	=cut	185	=cut
56		186
57	package IO::AIO;	187	package IO::AIO;
58		188
		189	use Carp ();
		190
		191	no warnings;
		192	use strict 'vars';
		193
59	use base 'Exporter';	194	use base 'Exporter';
60		195
61	use Fcntl ();
62
63	BEGIN {	196	BEGIN {
64	$VERSION = 0.3;	197	our $VERSION = '3.23';
65		198
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	199	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
67	aio_fsync aio_fdatasync aio_readahead);	200	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	201	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
		202	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		203	aio_rename aio_link aio_move aio_copy aio_group
		204	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		205	aio_chmod aio_utime aio_truncate);
		206
		207	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		208	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		209	min_parallel max_parallel max_idle
		210	nreqs nready npending nthreads
		211	max_poll_time max_poll_reqs);
		212
		213	push @AIO_REQ, qw(aio_busy); # not exported
		214
		215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		216
70	require XSLoader;	217	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	218	XSLoader::load ("IO::AIO", $VERSION);
72	}	219	}
73		220
74	=head1 FUNCTIONS	221	=head1 FUNCTIONS
75		222
76	=head2 AIO FUNCTIONS	223	=head2 AIO REQUEST FUNCTIONS
77		224
78	All the C<aio_*> calls are more or less thin wrappers around the syscall	225	All the C<aio_*> calls are more or less thin wrappers around the syscall
79	with the same name (sans C<aio_>). The arguments are similar or identical,	226	with the same name (sans C<aio_>). The arguments are similar or identical,
80	and they all accept an additional (and optional) C<$callback> argument	227	and they all accept an additional (and optional) C<$callback> argument
81	which must be a code reference. This code reference will get called with	228	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	229	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	230	perl, which usually delivers "false") as its sole argument after the given
84	syscall has been executed asynchronously.	231	syscall has been executed asynchronously.
85		232
86	All functions that expect a filehandle will also accept a file descriptor.	233	All functions expecting a filehandle keep a copy of the filehandle
		234	internally until the request has finished.
87		235
		236	All functions return request objects of type L<IO::AIO::REQ> that allow
		237	further manipulation of those requests while they are in-flight.
		238
88	The filenames you pass to these routines I<must> be absolute. The reason	239	The pathnames you pass to these routines I<must> be absolute and
89	is that at the time the request is being executed, the current working	240	encoded as octets. The reason for the former is that at the time the
90	directory could have changed. Alternatively, you can make sure that you	241	request is being executed, the current working directory could have
91	never change the current working directory.	242	changed. Alternatively, you can make sure that you never change the
		243	current working directory anywhere in the program and then use relative
		244	paths.
		245
		246	To encode pathnames as octets, either make sure you either: a) always pass
		247	in filenames you got from outside (command line, readdir etc.) without
		248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		249	your pathnames to the locale (or other) encoding in effect in the user
		250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		251	use something else to ensure your scalar has the correct contents.
		252
		253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		254	handles correctly whether it is set or not.
92		255
93	=over 4	256	=over 4
94		257
		258	=item $prev_pri = aioreq_pri [$pri]
		259
		260	Returns the priority value that would be used for the next request and, if
		261	C<$pri> is given, sets the priority for the next aio request.
		262
		263	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		264	and C<4>, respectively. Requests with higher priority will be serviced
		265	first.
		266
		267	The priority will be reset to C<0> after each call to one of the C<aio_*>
		268	functions.
		269
		270	Example: open a file with low priority, then read something from it with
		271	higher priority so the read request is serviced before other low priority
		272	open requests (potentially spamming the cache):
		273
		274	aioreq_pri -3;
		275	aio_open ..., sub {
		276	return unless $_[0];
		277
		278	aioreq_pri -2;
		279	aio_read $_[0], ..., sub {
		280	...
		281	};
		282	};
		283
		284
		285	=item aioreq_nice $pri_adjust
		286
		287	Similar to C<aioreq_pri>, but subtracts the given value from the current
		288	priority, so the effect is cumulative.
		289
		290
95	=item aio_open $pathname, $flags, $mode, $callback	291	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		292
97	Asynchronously open or create a file and call the callback with a newly	293	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	294	created filehandle for the file.
99		295
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	296	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
101	for an explanation.	297	for an explanation.
102		298
103	The C<$mode> argument is a bitmask. See the C<Fcntl> module for a	299	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
104	list. They are the same as used in C<sysopen>.	300	list. They are the same as used by C<sysopen>.
		301
		302	Likewise, C<$mode> specifies the mode of the newly created file, if it
		303	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
		304	except that it is mandatory (i.e. use C<0> if you don't create new files,
		305	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		306	by the umask in effect then the request is being executed, so better never
		307	change the umask.
105		308
106	Example:	309	Example:
107		310
108	aio_open "/etc/passwd", O_RDONLY, 0, sub {	311	aio_open "/etc/passwd", O_RDONLY, 0, sub {
109	if ($_[0]) {	312	if ($_[0]) {
…		…
112	} else {	315	} else {
113	die "open failed: $!\n";	316	die "open failed: $!\n";
114	}	317	}
115	};	318	};
116		319
		320
117	=item aio_close $fh, $callback	321	=item aio_close $fh, $callback->($status)
118		322
119	Asynchronously close a file and call the callback with the result	323	Asynchronously close a file and call the callback with the result
120	code. I<WARNING:> although accepted, you should not pass in a perl	324	code.
121	filehandle here, as perl will likely close the file descriptor itself when
122	the filehandle is destroyed. Normally, you can safely call perls C<close>
123	or just let filehandles go out of scope.
124		325
		326	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
		327	closing the file descriptor associated with the filehandle itself.
		328
		329	Therefore, C<aio_close> will not close the filehandle - instead it will
		330	use dup2 to overwrite the file descriptor with the write-end of a pipe
		331	(the pipe fd will be created on demand and will be cached).
		332
		333	Or in other words: the file descriptor will be closed, but it will not be
		334	free for reuse until the perl filehandle is closed.
		335
		336	=cut
		337
125	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
126		339
127	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128		341
129	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	342	Reads or writes C<$length> bytes from or to the specified C<$fh> and
130	into the scalar given by C<data> and offset C<dataoffset> and calls the	343	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
131	callback without the actual number of bytes read (or -1 on error, just	344	and calls the callback without the actual number of bytes read (or -1 on
132	like the syscall).	345	error, just like the syscall).
133		346
		347	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		348	offset plus the actual number of bytes read.
		349
		350	If C<$offset> is undefined, then the current file descriptor offset will
		351	be used (and updated), otherwise the file descriptor offset will not be
		352	changed by these calls.
		353
		354	If C<$length> is undefined in C<aio_write>, use the remaining length of
		355	C<$data>.
		356
		357	If C<$dataoffset> is less than zero, it will be counted from the end of
		358	C<$data>.
		359
		360	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		361	is outstanding. Modifying it can result in segfaults or World War III (if
		362	the necessary/optional hardware is installed).
		363
134	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, strating at	364	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
135	offset C<0> within the scalar:	365	offset C<0> within the scalar:
136		366
137	aio_read $fh, 7, 15, $buffer, 0, sub {	367	aio_read $fh, 7, 15, $buffer, 0, sub {
138	$_[0] > 0 or die "read error: $!";	368	$_[0] > 0 or die "read error: $!";
139	print "read $_[0] bytes: <$buffer>\n";	369	print "read $_[0] bytes: <$buffer>\n";
140	};	370	};
141		371
		372
		373	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		374
		375	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		376	reading at byte offset C<$in_offset>, and starts writing at the current
		377	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		378	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		379	other.
		380
		381	This call tries to make use of a native C<sendfile> syscall to provide
		382	zero-copy operation. For this to work, C<$out_fh> should refer to a
		383	socket, and C<$in_fh> should refer to mmap'able file.
		384
		385	If the native sendfile call fails or is not implemented, it will be
		386	emulated, so you can call C<aio_sendfile> on any type of filehandle
		387	regardless of the limitations of the operating system.
		388
		389	Please note, however, that C<aio_sendfile> can read more bytes from
		390	C<$in_fh> than are written, and there is no way to find out how many
		391	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		392	provides the number of bytes written to C<$out_fh>. Only if the result
		393	value equals C<$length> one can assume that C<$length> bytes have been
		394	read.
		395
		396
142	=item aio_readahead $fh,$offset,$length, $callback	397	=item aio_readahead $fh,$offset,$length, $callback->($retval)
143		398
144	Asynchronously reads the specified byte range into the page cache, using
145	the C<readahead> syscall. If that syscall doesn't exist the status will be
146	C<-1> and C<$!> is set to ENOSYS.
147
148	readahead() populates the page cache with data from a file so that	399	C<aio_readahead> populates the page cache with data from a file so that
149	subsequent reads from that file will not block on disk I/O. The C<$offset>	400	subsequent reads from that file will not block on disk I/O. The C<$offset>
150	argument specifies the starting point from which data is to be read and	401	argument specifies the starting point from which data is to be read and
151	C<$length> specifies the number of bytes to be read. I/O is performed in	402	C<$length> specifies the number of bytes to be read. I/O is performed in
152	whole pages, so that offset is effectively rounded down to a page boundary	403	whole pages, so that offset is effectively rounded down to a page boundary
153	and bytes are read up to the next page boundary greater than or equal to	404	and bytes are read up to the next page boundary greater than or equal to
154	(off-set+length). aio_readahead() does not read beyond the end of the	405	(off-set+length). C<aio_readahead> does not read beyond the end of the
155	file. The current file offset of the file is left unchanged.	406	file. The current file offset of the file is left unchanged.
156		407
		408	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		409	emulated by simply reading the data, which would have a similar effect.
		410
		411
157	=item aio_stat $fh_or_path, $callback	412	=item aio_stat $fh_or_path, $callback->($status)
158		413
159	=item aio_lstat $fh, $callback	414	=item aio_lstat $fh, $callback->($status)
160		415
161	Works like perl's C<stat> or C<lstat> in void context. The callback will	416	Works like perl's C<stat> or C<lstat> in void context. The callback will
162	be called after the stat and the results will be available using C<stat _>	417	be called after the stat and the results will be available using C<stat _>
163	or C<-s _> etc...	418	or C<-s _> etc...
164		419
…		…
174	aio_stat "/etc/passwd", sub {	429	aio_stat "/etc/passwd", sub {
175	$_[0] and die "stat failed: $!";	430	$_[0] and die "stat failed: $!";
176	print "size is ", -s _, "\n";	431	print "size is ", -s _, "\n";
177	};	432	};
178		433
		434
		435	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		436
		437	Works like perl's C<utime> function (including the special case of $atime
		438	and $mtime being undef). Fractional times are supported if the underlying
		439	syscalls support them.
		440
		441	When called with a pathname, uses utimes(2) if available, otherwise
		442	utime(2). If called on a file descriptor, uses futimes(2) if available,
		443	otherwise returns ENOSYS, so this is not portable.
		444
		445	Examples:
		446
		447	# set atime and mtime to current time (basically touch(1)):
		448	aio_utime "path", undef, undef;
		449	# set atime to current time and mtime to beginning of the epoch:
		450	aio_utime "path", time, undef; # undef==0
		451
		452
		453	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		454
		455	Works like perl's C<chown> function, except that C<undef> for either $uid
		456	or $gid is being interpreted as "do not change" (but -1 can also be used).
		457
		458	Examples:
		459
		460	# same as "chown root path" in the shell:
		461	aio_chown "path", 0, -1;
		462	# same as above:
		463	aio_chown "path", 0, undef;
		464
		465
		466	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		467
		468	Works like truncate(2) or ftruncate(2).
		469
		470
		471	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		472
		473	Works like perl's C<chmod> function.
		474
		475
179	=item aio_unlink $pathname, $callback	476	=item aio_unlink $pathname, $callback->($status)
180		477
181	Asynchronously unlink (delete) a file and call the callback with the	478	Asynchronously unlink (delete) a file and call the callback with the
182	result code.	479	result code.
183		480
		481
		482	=item aio_mknod $path, $mode, $dev, $callback->($status)
		483
		484	[EXPERIMENTAL]
		485
		486	Asynchronously create a device node (or fifo). See mknod(2).
		487
		488	The only (POSIX-) portable way of calling this function is:
		489
		490	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		491
		492
		493	=item aio_link $srcpath, $dstpath, $callback->($status)
		494
		495	Asynchronously create a new link to the existing object at C<$srcpath> at
		496	the path C<$dstpath> and call the callback with the result code.
		497
		498
		499	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		500
		501	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		502	the path C<$dstpath> and call the callback with the result code.
		503
		504
		505	=item aio_readlink $path, $callback->($link)
		506
		507	Asynchronously read the symlink specified by C<$path> and pass it to
		508	the callback. If an error occurs, nothing or undef gets passed to the
		509	callback.
		510
		511
		512	=item aio_rename $srcpath, $dstpath, $callback->($status)
		513
		514	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		515	rename(2) and call the callback with the result code.
		516
		517
		518	=item aio_mkdir $pathname, $mode, $callback->($status)
		519
		520	Asynchronously mkdir (create) a directory and call the callback with
		521	the result code. C<$mode> will be modified by the umask at the time the
		522	request is executed, so do not change your umask.
		523
		524
		525	=item aio_rmdir $pathname, $callback->($status)
		526
		527	Asynchronously rmdir (delete) a directory and call the callback with the
		528	result code.
		529
		530
		531	=item aio_readdir $pathname, $callback->($entries)
		532
		533	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		534	directory (i.e. opendir + readdir + closedir). The entries will not be
		535	sorted, and will B<NOT> include the C<.> and C<..> entries.
		536
		537	The callback is passed a single argument which is either C<undef> or an
		538	array-ref with the filenames.
		539
		540
		541	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		542
		543	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		544	behaviour and output format. In case of an error, C<$entries> will be
		545	C<undef>.
		546
		547	The flags are a combination of the following constants, ORed together (the
		548	flags will also be passed to the callback, possibly modified):
		549
		550	=over 4
		551
		552	=item IO::AIO::READDIR_DENTS
		553
		554	When this flag is off, then the callback gets an arrayref with of names
		555	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		556	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		557	entry in more detail.
		558
		559	C<$name> is the name of the entry.
		560
		561	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		562
		563	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		564	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		565	C<IO::AIO::DT_WHT>.
		566
		567	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		568	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		569	scalars are read-only: you can not modify them.
		570
		571	C<$inode> is the inode number (which might not be exact on systems with 64
		572	bit inode numbers and 32 bit perls). This field has unspecified content on
		573	systems that do not deliver the inode information.
		574
		575	=item IO::AIO::READDIR_DIRS_FIRST
		576
		577	When this flag is set, then the names will be returned in an order where
		578	likely directories come first. This is useful when you need to quickly
		579	find directories, or you want to find all directories while avoiding to
		580	stat() each entry.
		581
		582	If the system returns type information in readdir, then this is used
		583	to find directories directly. Otherwise, likely directories are files
		584	beginning with ".", or otherwise files with no dots, of which files with
		585	short names are tried first.
		586
		587	=item IO::AIO::READDIR_STAT_ORDER
		588
		589	When this flag is set, then the names will be returned in an order
		590	suitable for stat()'ing each one. That is, when you plan to stat()
		591	all files in the given directory, then the returned order will likely
		592	be fastest.
		593
		594	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		595	the likely dirs come first, resulting in a less optimal stat order.
		596
		597	=item IO::AIO::READDIR_FOUND_UNKNOWN
		598
		599	This flag should not be set when calling C<aio_readdirx>. Instead, it
		600	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		601	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		602	C<$type>'s are known, which can be used to speed up some algorithms.
		603
		604	=back
		605
		606
		607	=item aio_load $path, $data, $callback->($status)
		608
		609	This is a composite request that tries to fully load the given file into
		610	memory. Status is the same as with aio_read.
		611
		612	=cut
		613
		614	sub aio_load($$;$) {
		615	my ($path, undef, $cb) = @_;
		616	my $data = \$_[1];
		617
		618	my $pri = aioreq_pri;
		619	my $grp = aio_group $cb;
		620
		621	aioreq_pri $pri;
		622	add $grp aio_open $path, O_RDONLY, 0, sub {
		623	my $fh = shift
		624	or return $grp->result (-1);
		625
		626	aioreq_pri $pri;
		627	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		628	$grp->result ($_[0]);
		629	};
		630	};
		631
		632	$grp
		633	}
		634
		635	=item aio_copy $srcpath, $dstpath, $callback->($status)
		636
		637	Try to copy the I<file> (directories not supported as either source or
		638	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		639	the C<0> (error) or C<-1> ok.
		640
		641	This is a composite request that creates the destination file with
		642	mode 0200 and copies the contents of the source file into it using
		643	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		644	uid/gid, in that order.
		645
		646	If an error occurs, the partial destination file will be unlinked, if
		647	possible, except when setting atime, mtime, access mode and uid/gid, where
		648	errors are being ignored.
		649
		650	=cut
		651
		652	sub aio_copy($$;$) {
		653	my ($src, $dst, $cb) = @_;
		654
		655	my $pri = aioreq_pri;
		656	my $grp = aio_group $cb;
		657
		658	aioreq_pri $pri;
		659	add $grp aio_open $src, O_RDONLY, 0, sub {
		660	if (my $src_fh = $_[0]) {
		661	my @stat = stat $src_fh; # hmm, might bock over nfs?
		662
		663	aioreq_pri $pri;
		664	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		665	if (my $dst_fh = $_[0]) {
		666	aioreq_pri $pri;
		667	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		668	if ($_[0] == $stat[7]) {
		669	$grp->result (0);
		670	close $src_fh;
		671
		672	my $ch = sub {
		673	aioreq_pri $pri;
		674	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		675	aioreq_pri $pri;
		676	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		677	aioreq_pri $pri;
		678	add $grp aio_close $dst_fh;
		679	}
		680	};
		681	};
		682
		683	aioreq_pri $pri;
		684	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		685	if ($_[0] < 0 && $! == ENOSYS) {
		686	aioreq_pri $pri;
		687	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		688	} else {
		689	$ch->();
		690	}
		691	};
		692	} else {
		693	$grp->result (-1);
		694	close $src_fh;
		695	close $dst_fh;
		696
		697	aioreq $pri;
		698	add $grp aio_unlink $dst;
		699	}
		700	};
		701	} else {
		702	$grp->result (-1);
		703	}
		704	},
		705
		706	} else {
		707	$grp->result (-1);
		708	}
		709	};
		710
		711	$grp
		712	}
		713
		714	=item aio_move $srcpath, $dstpath, $callback->($status)
		715
		716	Try to move the I<file> (directories not supported as either source or
		717	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		718	the C<0> (error) or C<-1> ok.
		719
		720	This is a composite request that tries to rename(2) the file first; if
		721	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		722	that is successful, unlinks the C<$srcpath>.
		723
		724	=cut
		725
		726	sub aio_move($$;$) {
		727	my ($src, $dst, $cb) = @_;
		728
		729	my $pri = aioreq_pri;
		730	my $grp = aio_group $cb;
		731
		732	aioreq_pri $pri;
		733	add $grp aio_rename $src, $dst, sub {
		734	if ($_[0] && $! == EXDEV) {
		735	aioreq_pri $pri;
		736	add $grp aio_copy $src, $dst, sub {
		737	$grp->result ($_[0]);
		738
		739	if (!$_[0]) {
		740	aioreq_pri $pri;
		741	add $grp aio_unlink $src;
		742	}
		743	};
		744	} else {
		745	$grp->result ($_[0]);
		746	}
		747	};
		748
		749	$grp
		750	}
		751
		752	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		753
		754	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		755	efficiently separate the entries of directory C<$path> into two sets of
		756	names, directories you can recurse into (directories), and ones you cannot
		757	recurse into (everything else, including symlinks to directories).
		758
		759	C<aio_scandir> is a composite request that creates of many sub requests_
		760	C<$maxreq> specifies the maximum number of outstanding aio requests that
		761	this function generates. If it is C<< <= 0 >>, then a suitable default
		762	will be chosen (currently 4).
		763
		764	On error, the callback is called without arguments, otherwise it receives
		765	two array-refs with path-relative entry names.
		766
		767	Example:
		768
		769	aio_scandir $dir, 0, sub {
		770	my ($dirs, $nondirs) = @_;
		771	print "real directories: @$dirs\n";
		772	print "everything else: @$nondirs\n";
		773	};
		774
		775	Implementation notes.
		776
		777	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		778
		779	If readdir returns file type information, then this is used directly to
		780	find directories.
		781
		782	Otherwise, after reading the directory, the modification time, size etc.
		783	of the directory before and after the readdir is checked, and if they
		784	match (and isn't the current time), the link count will be used to decide
		785	how many entries are directories (if >= 2). Otherwise, no knowledge of the
		786	number of subdirectories will be assumed.
		787
		788	Then entries will be sorted into likely directories a non-initial dot
		789	currently) and likely non-directories (see C<aio_readdirx>). Then every
		790	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
		791	in order of their inode numbers. If that succeeds, it assumes that the
		792	entry is a directory or a symlink to directory (which will be checked
		793	seperately). This is often faster than stat'ing the entry itself because
		794	filesystems might detect the type of the entry without reading the inode
		795	data (e.g. ext2fs filetype feature), even on systems that cannot return
		796	the filetype information on readdir.
		797
		798	If the known number of directories (link count - 2) has been reached, the
		799	rest of the entries is assumed to be non-directories.
		800
		801	This only works with certainty on POSIX (= UNIX) filesystems, which
		802	fortunately are the vast majority of filesystems around.
		803
		804	It will also likely work on non-POSIX filesystems with reduced efficiency
		805	as those tend to return 0 or 1 as link counts, which disables the
		806	directory counting heuristic.
		807
		808	=cut
		809
		810	sub aio_scandir($$;$) {
		811	my ($path, $maxreq, $cb) = @_;
		812
		813	my $pri = aioreq_pri;
		814
		815	my $grp = aio_group $cb;
		816
		817	$maxreq = 4 if $maxreq <= 0;
		818
		819	# stat once
		820	aioreq_pri $pri;
		821	add $grp aio_stat $path, sub {
		822	return $grp->result () if $_[0];
		823	my $now = time;
		824	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		825
		826	# read the directory entries
		827	aioreq_pri $pri;
		828	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
		829	my $entries = shift
		830	or return $grp->result ();
		831
		832	# stat the dir another time
		833	aioreq_pri $pri;
		834	add $grp aio_stat $path, sub {
		835	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		836
		837	my $ndirs;
		838
		839	# take the slow route if anything looks fishy
		840	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		841	$ndirs = -1;
		842	} else {
		843	# if nlink == 2, we are finished
		844	# for non-posix-fs's, we rely on nlink < 2
		845	$ndirs = (stat _)[3] - 2
		846	or return $grp->result ([], $entries);
		847	}
		848
		849	my (@dirs, @nondirs);
		850
		851	my $statgrp = add $grp aio_group sub {
		852	$grp->result (\@dirs, \@nondirs);
		853	};
		854
		855	limit $statgrp $maxreq;
		856	feed $statgrp sub {
		857	return unless @$entries;
		858	my $entry = shift @$entries;
		859
		860	aioreq_pri $pri;
		861	add $statgrp aio_stat "$path/$entry/.", sub {
		862	if ($_[0] < 0) {
		863	push @nondirs, $entry;
		864	} else {
		865	# need to check for real directory
		866	aioreq_pri $pri;
		867	add $statgrp aio_lstat "$path/$entry", sub {
		868	if (-d _) {
		869	push @dirs, $entry;
		870
		871	unless (--$ndirs) {
		872	push @nondirs, @$entries;
		873	feed $statgrp;
		874	}
		875	} else {
		876	push @nondirs, $entry;
		877	}
		878	}
		879	}
		880	};
		881	};
		882	};
		883	};
		884	};
		885
		886	$grp
		887	}
		888
		889	=item aio_rmtree $path, $callback->($status)
		890
		891	Delete a directory tree starting (and including) C<$path>, return the
		892	status of the final C<rmdir> only. This is a composite request that
		893	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		894	everything else.
		895
		896	=cut
		897
		898	sub aio_rmtree;
		899	sub aio_rmtree($;$) {
		900	my ($path, $cb) = @_;
		901
		902	my $pri = aioreq_pri;
		903	my $grp = aio_group $cb;
		904
		905	aioreq_pri $pri;
		906	add $grp aio_scandir $path, 0, sub {
		907	my ($dirs, $nondirs) = @_;
		908
		909	my $dirgrp = aio_group sub {
		910	add $grp aio_rmdir $path, sub {
		911	$grp->result ($_[0]);
		912	};
		913	};
		914
		915	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		916	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		917
		918	add $grp $dirgrp;
		919	};
		920
		921	$grp
		922	}
		923
		924	=item aio_sync $callback->($status)
		925
		926	Asynchronously call sync and call the callback when finished.
		927
184	=item aio_fsync $fh, $callback	928	=item aio_fsync $fh, $callback->($status)
185		929
186	Asynchronously call fsync on the given filehandle and call the callback	930	Asynchronously call fsync on the given filehandle and call the callback
187	with the fsync result code.	931	with the fsync result code.
188		932
189	=item aio_fdatasync $fh, $callback	933	=item aio_fdatasync $fh, $callback->($status)
190		934
191	Asynchronously call fdatasync on the given filehandle and call the	935	Asynchronously call fdatasync on the given filehandle and call the
192	callback with the fdatasync result code.	936	callback with the fdatasync result code.
193		937
		938	If this call isn't available because your OS lacks it or it couldn't be
		939	detected, it will be emulated by calling C<fsync> instead.
		940
		941	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		942
		943	Sync the data portion of the file specified by C<$offset> and C<$length>
		944	to disk (but NOT the metadata), by calling the Linux-specific
		945	sync_file_range call. If sync_file_range is not available or it returns
		946	ENOSYS, then fdatasync or fsync is being substituted.
		947
		948	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		949	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		950	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		951	manpage for details.
		952
		953	=item aio_pathsync $path, $callback->($status)
		954
		955	This request tries to open, fsync and close the given path. This is a
		956	composite request intended to sync directories after directory operations
		957	(E.g. rename). This might not work on all operating systems or have any
		958	specific effect, but usually it makes sure that directory changes get
		959	written to disc. It works for anything that can be opened for read-only,
		960	not just directories.
		961
		962	Passes C<0> when everything went ok, and C<-1> on error.
		963
		964	=cut
		965
		966	sub aio_pathsync($;$) {
		967	my ($path, $cb) = @_;
		968
		969	my $pri = aioreq_pri;
		970	my $grp = aio_group $cb;
		971
		972	aioreq_pri $pri;
		973	add $grp aio_open $path, O_RDONLY, 0, sub {
		974	my ($fh) = @_;
		975	if ($fh) {
		976	aioreq_pri $pri;
		977	add $grp aio_fsync $fh, sub {
		978	$grp->result ($_[0]);
		979
		980	aioreq_pri $pri;
		981	add $grp aio_close $fh;
		982	};
		983	} else {
		984	$grp->result (-1);
		985	}
		986	};
		987
		988	$grp
		989	}
		990
		991	=item aio_group $callback->(...)
		992
		993	This is a very special aio request: Instead of doing something, it is a
		994	container for other aio requests, which is useful if you want to bundle
		995	many requests into a single, composite, request with a definite callback
		996	and the ability to cancel the whole request with its subrequests.
		997
		998	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		999	for more info.
		1000
		1001	Example:
		1002
		1003	my $grp = aio_group sub {
		1004	print "all stats done\n";
		1005	};
		1006
		1007	add $grp
		1008	(aio_stat ...),
		1009	(aio_stat ...),
		1010	...;
		1011
		1012	=item aio_nop $callback->()
		1013
		1014	This is a special request - it does nothing in itself and is only used for
		1015	side effects, such as when you want to add a dummy request to a group so
		1016	that finishing the requests in the group depends on executing the given
		1017	code.
		1018
		1019	While this request does nothing, it still goes through the execution
		1020	phase and still requires a worker thread. Thus, the callback will not
		1021	be executed immediately but only after other requests in the queue have
		1022	entered their execution phase. This can be used to measure request
		1023	latency.
		1024
		1025	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		1026
		1027	Mainly used for debugging and benchmarking, this aio request puts one of
		1028	the request workers to sleep for the given time.
		1029
		1030	While it is theoretically handy to have simple I/O scheduling requests
		1031	like sleep and file handle readable/writable, the overhead this creates is
		1032	immense (it blocks a thread for a long time) so do not use this function
		1033	except to put your application under artificial I/O pressure.
		1034
194	=back	1035	=back
195		1036
		1037	=head2 IO::AIO::REQ CLASS
		1038
		1039	All non-aggregate C<aio_*> functions return an object of this class when
		1040	called in non-void context.
		1041
		1042	=over 4
		1043
		1044	=item cancel $req
		1045
		1046	Cancels the request, if possible. Has the effect of skipping execution
		1047	when entering the B<execute> state and skipping calling the callback when
		1048	entering the the B<result> state, but will leave the request otherwise
		1049	untouched (with the exception of readdir). That means that requests that
		1050	currently execute will not be stopped and resources held by the request
		1051	will not be freed prematurely.
		1052
		1053	=item cb $req $callback->(...)
		1054
		1055	Replace (or simply set) the callback registered to the request.
		1056
		1057	=back
		1058
		1059	=head2 IO::AIO::GRP CLASS
		1060
		1061	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		1062	objects of this class, too.
		1063
		1064	A IO::AIO::GRP object is a special request that can contain multiple other
		1065	aio requests.
		1066
		1067	You create one by calling the C<aio_group> constructing function with a
		1068	callback that will be called when all contained requests have entered the
		1069	C<done> state:
		1070
		1071	my $grp = aio_group sub {
		1072	print "all requests are done\n";
		1073	};
		1074
		1075	You add requests by calling the C<add> method with one or more
		1076	C<IO::AIO::REQ> objects:
		1077
		1078	$grp->add (aio_unlink "...");
		1079
		1080	add $grp aio_stat "...", sub {
		1081	$_[0] or return $grp->result ("error");
		1082
		1083	# add another request dynamically, if first succeeded
		1084	add $grp aio_open "...", sub {
		1085	$grp->result ("ok");
		1086	};
		1087	};
		1088
		1089	This makes it very easy to create composite requests (see the source of
		1090	C<aio_move> for an application) that work and feel like simple requests.
		1091
		1092	=over 4
		1093
		1094	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1095	C<IO::AIO::poll_cb>, just like any other request.
		1096
		1097	=item * They can be canceled like any other request. Canceling will cancel not
		1098	only the request itself, but also all requests it contains.
		1099
		1100	=item * They can also can also be added to other IO::AIO::GRP objects.
		1101
		1102	=item * You must not add requests to a group from within the group callback (or
		1103	any later time).
		1104
		1105	=back
		1106
		1107	Their lifetime, simplified, looks like this: when they are empty, they
		1108	will finish very quickly. If they contain only requests that are in the
		1109	C<done> state, they will also finish. Otherwise they will continue to
		1110	exist.
		1111
		1112	That means after creating a group you have some time to add requests
		1113	(precisely before the callback has been invoked, which is only done within
		1114	the C<poll_cb>). And in the callbacks of those requests, you can add
		1115	further requests to the group. And only when all those requests have
		1116	finished will the the group itself finish.
		1117
		1118	=over 4
		1119
		1120	=item add $grp ...
		1121
		1122	=item $grp->add (...)
		1123
		1124	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1125	be added, including other groups, as long as you do not create circular
		1126	dependencies.
		1127
		1128	Returns all its arguments.
		1129
		1130	=item $grp->cancel_subs
		1131
		1132	Cancel all subrequests and clears any feeder, but not the group request
		1133	itself. Useful when you queued a lot of events but got a result early.
		1134
		1135	=item $grp->result (...)
		1136
		1137	Set the result value(s) that will be passed to the group callback when all
		1138	subrequests have finished and set the groups errno to the current value
		1139	of errno (just like calling C<errno> without an error number). By default,
		1140	no argument will be passed and errno is zero.
		1141
		1142	=item $grp->errno ([$errno])
		1143
		1144	Sets the group errno value to C<$errno>, or the current value of errno
		1145	when the argument is missing.
		1146
		1147	Every aio request has an associated errno value that is restored when
		1148	the callback is invoked. This method lets you change this value from its
		1149	default (0).
		1150
		1151	Calling C<result> will also set errno, so make sure you either set C<$!>
		1152	before the call to C<result>, or call c<errno> after it.
		1153
		1154	=item feed $grp $callback->($grp)
		1155
		1156	Sets a feeder/generator on this group: every group can have an attached
		1157	generator that generates requests if idle. The idea behind this is that,
		1158	although you could just queue as many requests as you want in a group,
		1159	this might starve other requests for a potentially long time. For example,
		1160	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1161	delaying any later requests for a long time.
		1162
		1163	To avoid this, and allow incremental generation of requests, you can
		1164	instead a group and set a feeder on it that generates those requests. The
		1165	feed callback will be called whenever there are few enough (see C<limit>,
		1166	below) requests active in the group itself and is expected to queue more
		1167	requests.
		1168
		1169	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1170	not impose any limits).
		1171
		1172	If the feed does not queue more requests when called, it will be
		1173	automatically removed from the group.
		1174
		1175	If the feed limit is C<0> when this method is called, it will be set to
		1176	C<2> automatically.
		1177
		1178	Example:
		1179
		1180	# stat all files in @files, but only ever use four aio requests concurrently:
		1181
		1182	my $grp = aio_group sub { print "finished\n" };
		1183	limit $grp 4;
		1184	feed $grp sub {
		1185	my $file = pop @files
		1186	or return;
		1187
		1188	add $grp aio_stat $file, sub { ... };
		1189	};
		1190
		1191	=item limit $grp $num
		1192
		1193	Sets the feeder limit for the group: The feeder will be called whenever
		1194	the group contains less than this many requests.
		1195
		1196	Setting the limit to C<0> will pause the feeding process.
		1197
		1198	The default value for the limit is C<0>, but note that setting a feeder
		1199	automatically bumps it up to C<2>.
		1200
		1201	=back
		1202
196	=head2 SUPPORT FUNCTIONS	1203	=head2 SUPPORT FUNCTIONS
197		1204
		1205	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1206
198	=over 4	1207	=over 4
199		1208
200	=item $fileno = IO::AIO::poll_fileno	1209	=item $fileno = IO::AIO::poll_fileno
201		1210
202	Return the I<request result pipe filehandle>. This filehandle must be	1211	Return the I<request result pipe file descriptor>. This filehandle must be
203	polled for reading by some mechanism outside this module (e.g. Event	1212	polled for reading by some mechanism outside this module (e.g. EV, Glib,
204	or select, see below). If the pipe becomes readable you have to call	1213	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
205	C<poll_cb> to check the results.	1214	you have to call C<poll_cb> to check the results.
206		1215
207	See C<poll_cb> for an example.	1216	See C<poll_cb> for an example.
208		1217
209	=item IO::AIO::poll_cb	1218	=item IO::AIO::poll_cb
210		1219
211	Process all outstanding events on the result pipe. You have to call this	1220	Process some outstanding events on the result pipe. You have to call this
212	regularly. Returns the number of events processed. Returns immediately	1221	regularly. Returns C<0> if all events could be processed, or C<-1> if it
213	when no events are outstanding.	1222	returned earlier for whatever reason. Returns immediately when no events
		1223	are outstanding. The amount of events processed depends on the settings of
		1224	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
214		1225
215	You can use Event to multiplex, e.g.:	1226	If not all requests were processed for whatever reason, the filehandle
		1227	will still be ready when C<poll_cb> returns, so normally you don't have to
		1228	do anything special to have it called later.
		1229
		1230	Example: Install an Event watcher that automatically calls
		1231	IO::AIO::poll_cb with high priority (more examples can be found in the
		1232	SYNOPSIS section, at the top of this document):
216		1233
217	Event->io (fd => IO::AIO::poll_fileno,	1234	Event->io (fd => IO::AIO::poll_fileno,
218	poll => 'r', async => 1,	1235	poll => 'r', async => 1,
219	cb => \&IO::AIO::poll_cb);	1236	cb => \&IO::AIO::poll_cb);
220		1237
		1238	=item IO::AIO::max_poll_reqs $nreqs
		1239
		1240	=item IO::AIO::max_poll_time $seconds
		1241
		1242	These set the maximum number of requests (default C<0>, meaning infinity)
		1243	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1244	the maximum amount of time (default C<0>, meaning infinity) spent in
		1245	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1246	of time C<poll_cb> is allowed to use).
		1247
		1248	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1249	syscall per request processed, which is not normally a problem unless your
		1250	callbacks are really really fast or your OS is really really slow (I am
		1251	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1252
		1253	Setting these is useful if you want to ensure some level of
		1254	interactiveness when perl is not fast enough to process all requests in
		1255	time.
		1256
		1257	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1258
		1259	Example: Install an Event watcher that automatically calls
		1260	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1261	program get the CPU sometimes even under high AIO load.
		1262
		1263	# try not to spend much more than 0.1s in poll_cb
		1264	IO::AIO::max_poll_time 0.1;
		1265
		1266	# use a low priority so other tasks have priority
		1267	Event->io (fd => IO::AIO::poll_fileno,
		1268	poll => 'r', nice => 1,
		1269	cb => &IO::AIO::poll_cb);
		1270
221	=item IO::AIO::poll_wait	1271	=item IO::AIO::poll_wait
222		1272
		1273	If there are any outstanding requests and none of them in the result
223	Wait till the result filehandle becomes ready for reading (simply does a	1274	phase, wait till the result filehandle becomes ready for reading (simply
224	select on the filehandle. This is useful if you want to synchronously wait	1275	does a C<select> on the filehandle. This is useful if you want to
225	for some requests to finish).	1276	synchronously wait for some requests to finish).
226		1277
227	See C<nreqs> for an example.	1278	See C<nreqs> for an example.
228		1279
		1280	=item IO::AIO::poll
		1281
		1282	Waits until some requests have been handled.
		1283
		1284	Returns the number of requests processed, but is otherwise strictly
		1285	equivalent to:
		1286
		1287	IO::AIO::poll_wait, IO::AIO::poll_cb
		1288
229	=item IO::AIO::nreqs	1289	=item IO::AIO::flush
230		1290
231	Returns the number of requests currently outstanding.	1291	Wait till all outstanding AIO requests have been handled.
232		1292
233	Example: wait till there are no outstanding requests anymore:	1293	Strictly equivalent to:
234		1294
235	IO::AIO::poll_wait, IO::AIO::poll_cb	1295	IO::AIO::poll_wait, IO::AIO::poll_cb
236	while IO::AIO::nreqs;	1296	while IO::AIO::nreqs;
237		1297
		1298	=back
		1299
		1300	=head3 CONTROLLING THE NUMBER OF THREADS
		1301
		1302	=over
		1303
		1304	=item IO::AIO::min_parallel $nthreads
		1305
		1306	Set the minimum number of AIO threads to C<$nthreads>. The current
		1307	default is C<8>, which means eight asynchronous operations can execute
		1308	concurrently at any one time (the number of outstanding requests,
		1309	however, is unlimited).
		1310
		1311	IO::AIO starts threads only on demand, when an AIO request is queued and
		1312	no free thread exists. Please note that queueing up a hundred requests can
		1313	create demand for a hundred threads, even if it turns out that everything
		1314	is in the cache and could have been processed faster by a single thread.
		1315
		1316	It is recommended to keep the number of threads relatively low, as some
		1317	Linux kernel versions will scale negatively with the number of threads
		1318	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1319	versions, 4-32 threads should be fine.
		1320
		1321	Under most circumstances you don't need to call this function, as the
		1322	module selects a default that is suitable for low to moderate load.
		1323
		1324	=item IO::AIO::max_parallel $nthreads
		1325
		1326	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1327	specified number of threads are currently running, this function kills
		1328	them. This function blocks until the limit is reached.
		1329
		1330	While C<$nthreads> are zero, aio requests get queued but not executed
		1331	until the number of threads has been increased again.
		1332
		1333	This module automatically runs C<max_parallel 0> at program end, to ensure
		1334	that all threads are killed and that there are no outstanding requests.
		1335
		1336	Under normal circumstances you don't need to call this function.
		1337
		1338	=item IO::AIO::max_idle $nthreads
		1339
		1340	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1341	threads that did not get a request to process within 10 seconds). That
		1342	means if a thread becomes idle while C<$nthreads> other threads are also
		1343	idle, it will free its resources and exit.
		1344
		1345	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1346	to allow for extremely high load situations, but want to free resources
		1347	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1348
		1349	The default is probably ok in most situations, especially if thread
		1350	creation is fast. If thread creation is very slow on your system you might
		1351	want to use larger values.
		1352
		1353	=item IO::AIO::max_outstanding $maxreqs
		1354
		1355	This is a very bad function to use in interactive programs because it
		1356	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1357	use an C<aio_group> together with a feed callback.
		1358
		1359	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1360	do queue up more than this number of requests, the next call to the
		1361	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1362	function will block until the limit is no longer exceeded.
		1363
		1364	The default value is very large, so there is no practical limit on the
		1365	number of outstanding requests.
		1366
		1367	You can still queue as many requests as you want. Therefore,
		1368	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1369	as a stop gap to shield against fatal memory overflow (with large values).
		1370
		1371	=back
		1372
		1373	=head3 STATISTICAL INFORMATION
		1374
		1375	=over
		1376
238	=item IO::AIO::flush	1377	=item IO::AIO::nreqs
239		1378
240	Wait till all outstanding AIO requests have been handled.	1379	Returns the number of requests currently in the ready, execute or pending
		1380	states (i.e. for which their callback has not been invoked yet).
241		1381
242	Strictly equivalent to:	1382	Example: wait till there are no outstanding requests anymore:
243		1383
244	IO::AIO::poll_wait, IO::AIO::poll_cb	1384	IO::AIO::poll_wait, IO::AIO::poll_cb
245	while IO::AIO::nreqs;	1385	while IO::AIO::nreqs;
246		1386
		1387	=item IO::AIO::nready
		1388
		1389	Returns the number of requests currently in the ready state (not yet
		1390	executed).
		1391
247	=item IO::AIO::poll	1392	=item IO::AIO::npending
248		1393
249	Waits until some requests have been handled.	1394	Returns the number of requests currently in the pending state (executed,
250		1395	but not yet processed by poll_cb).
251	Strictly equivalent to:
252
253	IO::AIO::poll_wait, IO::AIO::poll_cb
254	if IO::AIO::nreqs;
255
256	=item IO::AIO::min_parallel $nthreads
257
258	Set the minimum number of AIO threads to C<$nthreads>. The default is
259	C<1>, which means a single asynchronous operation can be done at one time
260	(the number of outstanding operations, however, is unlimited).
261
262	It is recommended to keep the number of threads low, as some Linux
263	kernel versions will scale negatively with the number of threads (higher
264	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
265	threads should be fine.
266
267	Under normal circumstances you don't need to call this function, as this
268	module automatically starts some threads (the exact number might change,
269	and is currently 4).
270
271	=item IO::AIO::max_parallel $nthreads
272
273	Sets the maximum number of AIO threads to C<$nthreads>. If more than
274	the specified number of threads are currently running, kill them. This
275	function blocks until the limit is reached.
276
277	This module automatically runs C<max_parallel 0> at program end, to ensure
278	that all threads are killed and that there are no outstanding requests.
279
280	Under normal circumstances you don't need to call this function.
281
282	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
283
284	Sets the maximum number of outstanding requests to C<$nreqs>. If you
285	try to queue up more than this number of requests, the caller will block until
286	some requests have been handled.
287
288	The default is very large, so normally there is no practical limit. If you
289	queue up many requests in a loop it it often improves speed if you set
290	this to a relatively low number, such as C<100>.
291
292	Under normal circumstances you don't need to call this function.
293		1396
294	=back	1397	=back
295		1398
296	=cut	1399	=cut
297		1400
298	# support function to convert a fd into a perl filehandle
299	sub _fd2fh {
300	return undef if $_[0] < 0;
301
302	# try to be perl5.6-compatible
303	local *AIO_FH;
304	open AIO_FH, "+<&=$_[0]"
305	or return undef;
306
307	*AIO_FH
308	}
309
310	min_parallel 4;	1401	min_parallel 8;
311		1402
312	END {	1403	END { flush }
313	max_parallel 0;
314	}
315		1404
316	1;	1405	1;
317		1406
		1407	=head2 FORK BEHAVIOUR
		1408
		1409	This module should do "the right thing" when the process using it forks:
		1410
		1411	Before the fork, IO::AIO enters a quiescent state where no requests
		1412	can be added in other threads and no results will be processed. After
		1413	the fork the parent simply leaves the quiescent state and continues
		1414	request/result processing, while the child frees the request/result queue
		1415	(so that the requests started before the fork will only be handled in the
		1416	parent). Threads will be started on demand until the limit set in the
		1417	parent process has been reached again.
		1418
		1419	In short: the parent will, after a short pause, continue as if fork had
		1420	not been called, while the child will act as if IO::AIO has not been used
		1421	yet.
		1422
		1423	=head2 MEMORY USAGE
		1424
		1425	Per-request usage:
		1426
		1427	Each aio request uses - depending on your architecture - around 100-200
		1428	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1429	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1430	scalars and other data passed into aio requests will also be locked and
		1431	will consume memory till the request has entered the done state.
		1432
		1433	This is not awfully much, so queuing lots of requests is not usually a
		1434	problem.
		1435
		1436	Per-thread usage:
		1437
		1438	In the execution phase, some aio requests require more memory for
		1439	temporary buffers, and each thread requires a stack and other data
		1440	structures (usually around 16k-128k, depending on the OS).
		1441
		1442	=head1 KNOWN BUGS
		1443
		1444	Known bugs will be fixed in the next release.
		1445
318	=head1 SEE ALSO	1446	=head1 SEE ALSO
319		1447
320	L<Coro>, L<Linux::AIO>.	1448	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1449	more natural syntax.
321		1450
322	=head1 AUTHOR	1451	=head1 AUTHOR
323		1452
324	Marc Lehmann <schmorp@schmorp.de>	1453	Marc Lehmann <schmorp@schmorp.de>
325	http://home.schmorp.de/	1454	http://home.schmorp.de/

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