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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.51 by root, Sat Jun 24 19:14:04 2006 UTC vs.
Revision 1.124 by root, Sat May 10 19:25:33 2008 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	# AnyEvent	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, urxvt, pureperl...)
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
23		34
24	# Event	35	# EV integration
		36	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		37
		38	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	39	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	40	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	41	cb => \&IO::AIO::poll_cb);
28		42
29	# Glib/Gtk2	43	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	44	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	45	in => sub { IO::AIO::poll_cb; 1 };
32		46
33	# Tk	47	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	48	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	49	readable => \&IO::AIO::poll_cb);
36		50
37	# Danga::Socket	51	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	52	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	53	\&IO::AIO::poll_cb);
40		54
41
42	=head1 DESCRIPTION	55	=head1 DESCRIPTION
43		56
44	This module implements asynchronous I/O using whatever means your	57	This module implements asynchronous I/O using whatever means your
45	operating system supports.	58	operating system supports.
46		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 very
		73	inefficient. Use an event loop for that (such as the L<Event|Event>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
47	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
48	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
49	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
50	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
51	aio functions available on many operating systems. However, they are often	80	functions available on many operating systems. However, they are often
52	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
53	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
54	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.
55		85
56	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,
57	currently not reentrant, so use appropriate locking yourself, always call	87	it is currently not reentrant in any way, so use appropriate locking
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	88	yourself, always call C<poll_cb> from within the same thread, or never
59	C<aio_> functions) recursively.	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 Event module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use Event;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with Event
		101	Event->io (fd => IO::AIO::poll_fileno,
		102	poll => 'r',
		103	cb => \&IO::AIO::poll_cb);
		104
		105	# queue the request to open /etc/passwd
		106	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		107	my $fh = shift
		108	or die "error while opening: $!";
		109
		110	# stat'ing filehandles is generally non-blocking
		111	my $size = -s $fh;
		112
		113	# queue a request to read the file
		114	my $contents;
		115	aio_read $fh, 0, $size, $contents, 0, sub {
		116	$_[0] == $size
		117	or die "short read: $!";
		118
		119	close $fh;
		120
		121	# file contents now in $contents
		122	print $contents;
		123
		124	# exit event loop and program
		125	Event::unloop;
		126	};
		127	};
		128
		129	# possibly queue up other requests, or open GUI windows,
		130	# check for sockets etc. etc.
		131
		132	# process events as long as there are some:
		133	Event::loop;
		134
		135	=head1 REQUEST ANATOMY AND LIFETIME
		136
		137	Every C<aio_*> function creates a request. which is a C data structure not
		138	directly visible to Perl.
		139
		140	If called in non-void context, every request function returns a Perl
		141	object representing the request. In void context, nothing is returned,
		142	which saves a bit of memory.
		143
		144	The perl object is a fairly standard ref-to-hash object. The hash contents
		145	are not used by IO::AIO so you are free to store anything you like in it.
		146
		147	During their existance, aio requests travel through the following states,
		148	in order:
		149
		150	=over 4
		151
		152	=item ready
		153
		154	Immediately after a request is created it is put into the ready state,
		155	waiting for a thread to execute it.
		156
		157	=item execute
		158
		159	A thread has accepted the request for processing and is currently
		160	executing it (e.g. blocking in read).
		161
		162	=item pending
		163
		164	The request has been executed and is waiting for result processing.
		165
		166	While request submission and execution is fully asynchronous, result
		167	processing is not and relies on the perl interpreter calling C<poll_cb>
		168	(or another function with the same effect).
		169
		170	=item result
		171
		172	The request results are processed synchronously by C<poll_cb>.
		173
		174	The C<poll_cb> function will process all outstanding aio requests by
		175	calling their callbacks, freeing memory associated with them and managing
		176	any groups they are contained in.
		177
		178	=item done
		179
		180	Request has reached the end of its lifetime and holds no resources anymore
		181	(except possibly for the Perl object, but its connection to the actual
		182	aio request is severed and calling its methods will either do nothing or
		183	result in a runtime error).
		184
		185	=back
60		186
61	=cut	187	=cut
62		188
63	package IO::AIO;	189	package IO::AIO;
		190
		191	use Carp ();
64		192
65	no warnings;	193	no warnings;
66	use strict 'vars';	194	use strict 'vars';
67		195
68	use base 'Exporter';	196	use base 'Exporter';
69		197
70	BEGIN {	198	BEGIN {
71	our $VERSION = '1.8';	199	our $VERSION = '3.0';
72		200
73	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	201	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
74	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	202	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
75	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);	203	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
76	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	204	aio_fdatasync aio_pathsync aio_readahead
		205	aio_rename aio_link aio_move aio_copy aio_group
		206	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		207	aio_chmod aio_utime aio_truncate);
		208
		209	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		210	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		211	min_parallel max_parallel max_idle
		212	nreqs nready npending nthreads
		213	max_poll_time max_poll_reqs);
		214
		215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
77		216
78	require XSLoader;	217	require XSLoader;
79	XSLoader::load ("IO::AIO", $VERSION);	218	XSLoader::load ("IO::AIO", $VERSION);
80	}	219	}
81		220
82	=head1 FUNCTIONS	221	=head1 FUNCTIONS
83		222
84	=head2 AIO FUNCTIONS	223	=head2 AIO REQUEST FUNCTIONS
85		224
86	All the C<aio_*> calls are more or less thin wrappers around the syscall	225	All the C<aio_*> calls are more or less thin wrappers around the syscall
87	with the same name (sans C<aio_>). The arguments are similar or identical,	226	with the same name (sans C<aio_>). The arguments are similar or identical,
88	and they all accept an additional (and optional) C<$callback> argument	227	and they all accept an additional (and optional) C<$callback> argument
89	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
…		…
92	syscall has been executed asynchronously.	231	syscall has been executed asynchronously.
93		232
94	All functions expecting a filehandle keep a copy of the filehandle	233	All functions expecting a filehandle keep a copy of the filehandle
95	internally until the request has finished.	234	internally until the request has finished.
96		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
97	The pathnames you pass to these routines I<must> be absolute and	239	The pathnames you pass to these routines I<must> be absolute and
98	encoded in byte form. The reason for the former is that at the time the	240	encoded as octets. The reason for the former is that at the time the
99	request is being executed, the current working directory could have	241	request is being executed, the current working directory could have
100	changed. Alternatively, you can make sure that you never change the	242	changed. Alternatively, you can make sure that you never change the
101	current working directory.	243	current working directory anywhere in the program and then use relative
		244	paths.
102		245
103	To encode pathnames to byte form, either make sure you either: a)	246	To encode pathnames as octets, either make sure you either: a) always pass
104	always pass in filenames you got from outside (command line, readdir	247	in filenames you got from outside (command line, readdir etc.) without
105	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
106	your pathnames to the locale (or other) encoding in effect in the user	249	your pathnames to the locale (or other) encoding in effect in the user
107	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
108	use something else.	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 wether it is set or not.
109		255
110	=over 4	256	=over 4
		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
111		290
112	=item aio_open $pathname, $flags, $mode, $callback->($fh)	291	=item aio_open $pathname, $flags, $mode, $callback->($fh)
113		292
114	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
115	created filehandle for the file.	294	created filehandle for the file.
…		…
121	list. They are the same as used by C<sysopen>.	300	list. They are the same as used by C<sysopen>.
122		301
123	Likewise, C<$mode> specifies the mode of the newly created file, if it	302	Likewise, C<$mode> specifies the mode of the newly created file, if it
124	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	303	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
125	except that it is mandatory (i.e. use C<0> if you don't create new files,	304	except that it is mandatory (i.e. use C<0> if you don't create new files,
126	and C<0666> or C<0777> if you do).	305	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		306	by the umask in effect then the request is being executed, so better never
		307	change the umask.
127		308
128	Example:	309	Example:
129		310
130	aio_open "/etc/passwd", O_RDONLY, 0, sub {	311	aio_open "/etc/passwd", O_RDONLY, 0, sub {
131	if ($_[0]) {	312	if ($_[0]) {
…		…
134	} else {	315	} else {
135	die "open failed: $!\n";	316	die "open failed: $!\n";
136	}	317	}
137	};	318	};
138		319
		320
139	=item aio_close $fh, $callback->($status)	321	=item aio_close $fh, $callback->($status)
140		322
141	Asynchronously close a file and call the callback with the result	323	Asynchronously close a file and call the callback with the result
142	code. I<WARNING:> although accepted, you should not pass in a perl	324	code.
143	filehandle here, as perl will likely close the file descriptor another
144	time when the filehandle is destroyed. Normally, you can safely call perls
145	C<close> or just let filehandles go out of scope.
146		325
147	This is supposed to be a bug in the API, so that might change. It's	326	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
148	therefore best to avoid this function.	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
149		337
150	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
151		339
152	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		341
154	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	342	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
155	into the scalar given by C<data> and offset C<dataoffset> and calls the	343	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
156	callback without the actual number of bytes read (or -1 on error, just	344	callback without the actual number of bytes read (or -1 on error, just
157	like the syscall).	345	like the syscall).
158		346
		347	If C<$offset> is undefined, then the current file descriptor offset will
		348	be used (and updated), otherwise the file descriptor offset will not be
		349	changed by these calls.
		350
		351	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		352
		353	If C<$dataoffset> is less than zero, it will be counted from the end of
		354	C<$data>.
		355
159	The C<$data> scalar I<MUST NOT> be modified in any way while the request	356	The C<$data> scalar I<MUST NOT> be modified in any way while the request
160	is outstanding. Modifying it can result in segfaults or WW3 (if the	357	is outstanding. Modifying it can result in segfaults or World War III (if
161	necessary/optional hardware is installed).	358	the necessary/optional hardware is installed).
162		359
163	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	360	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
164	offset C<0> within the scalar:	361	offset C<0> within the scalar:
165		362
166	aio_read $fh, 7, 15, $buffer, 0, sub {	363	aio_read $fh, 7, 15, $buffer, 0, sub {
167	$_[0] > 0 or die "read error: $!";	364	$_[0] > 0 or die "read error: $!";
168	print "read $_[0] bytes: <$buffer>\n";	365	print "read $_[0] bytes: <$buffer>\n";
169	};	366	};
170		367
171	=item aio_move $srcpath, $dstpath, $callback->($status)
172
173	[EXPERIMENTAL]
174
175	Try to move the I<file> (directories not supported as either source or destination)
176	from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok.
177
178	This is a composite request that tries to rename(2) the file first. If
179	rename files with C<EXDEV>, it creates the destination file with mode 0200
180	and copies the contents of the source file into it using C<aio_sendfile>,
181	followed by restoring atime, mtime, access mode and uid/gid, in that
182	order, and unlinking the C<$srcpath>.
183
184	If an error occurs, the partial destination file will be unlinked, if
185	possible, except when setting atime, mtime, access mode and uid/gid, where
186	errors are being ignored.
187
188	=cut
189
190	sub aio_move($$$) {
191	my ($src, $dst, $cb) = @_;
192
193	aio_rename $src, $dst, sub {
194	if ($_[0] && $! == EXDEV) {
195	aio_open $src, O_RDONLY, 0, sub {
196	if (my $src_fh = $_[0]) {
197	my @stat = stat $src_fh;
198
199	aio_open $dst, O_WRONLY, 0200, sub {
200	if (my $dst_fh = $_[0]) {
201	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
202	close $src_fh;
203
204	if ($_[0] == $stat[7]) {
205	utime $stat[8], $stat[9], $dst;
206	chmod $stat[2] & 07777, $dst_fh;
207	chown $stat[4], $stat[5], $dst_fh;
208	close $dst_fh;
209
210	aio_unlink $src, sub {
211	$cb->($_[0]);
212	};
213	} else {
214	my $errno = $!;
215	aio_unlink $dst, sub {
216	$! = $errno;
217	$cb->(-1);
218	};
219	}
220	};
221	} else {
222	$cb->(-1);
223	}
224	},
225
226	} else {
227	$cb->(-1);
228	}
229	};
230	} else {
231	$cb->($_[0]);
232	}
233	};
234	}
235		368
236	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	369	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
237		370
238	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	371	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
239	reading at byte offset C<$in_offset>, and starts writing at the current	372	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
253	C<$in_fh> than are written, and there is no way to find out how many	386	C<$in_fh> than are written, and there is no way to find out how many
254	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	387	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
255	provides the number of bytes written to C<$out_fh>. Only if the result	388	provides the number of bytes written to C<$out_fh>. Only if the result
256	value equals C<$length> one can assume that C<$length> bytes have been	389	value equals C<$length> one can assume that C<$length> bytes have been
257	read.	390	read.
		391
258		392
259	=item aio_readahead $fh,$offset,$length, $callback->($retval)	393	=item aio_readahead $fh,$offset,$length, $callback->($retval)
260		394
261	C<aio_readahead> populates the page cache with data from a file so that	395	C<aio_readahead> populates the page cache with data from a file so that
262	subsequent reads from that file will not block on disk I/O. The C<$offset>	396	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
268	file. The current file offset of the file is left unchanged.	402	file. The current file offset of the file is left unchanged.
269		403
270	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	404	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
271	emulated by simply reading the data, which would have a similar effect.	405	emulated by simply reading the data, which would have a similar effect.
272		406
		407
273	=item aio_stat $fh_or_path, $callback->($status)	408	=item aio_stat $fh_or_path, $callback->($status)
274		409
275	=item aio_lstat $fh, $callback->($status)	410	=item aio_lstat $fh, $callback->($status)
276		411
277	Works like perl's C<stat> or C<lstat> in void context. The callback will	412	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
290	aio_stat "/etc/passwd", sub {	425	aio_stat "/etc/passwd", sub {
291	$_[0] and die "stat failed: $!";	426	$_[0] and die "stat failed: $!";
292	print "size is ", -s _, "\n";	427	print "size is ", -s _, "\n";
293	};	428	};
294		429
		430
		431	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		432
		433	Works like perl's C<utime> function (including the special case of $atime
		434	and $mtime being undef). Fractional times are supported if the underlying
		435	syscalls support them.
		436
		437	When called with a pathname, uses utimes(2) if available, otherwise
		438	utime(2). If called on a file descriptor, uses futimes(2) if available,
		439	otherwise returns ENOSYS, so this is not portable.
		440
		441	Examples:
		442
		443	# set atime and mtime to current time (basically touch(1)):
		444	aio_utime "path", undef, undef;
		445	# set atime to current time and mtime to beginning of the epoch:
		446	aio_utime "path", time, undef; # undef==0
		447
		448
		449	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		450
		451	Works like perl's C<chown> function, except that C<undef> for either $uid
		452	or $gid is being interpreted as "do not change" (but -1 can also be used).
		453
		454	Examples:
		455
		456	# same as "chown root path" in the shell:
		457	aio_chown "path", 0, -1;
		458	# same as above:
		459	aio_chown "path", 0, undef;
		460
		461
		462	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		463
		464	Works like truncate(2) or ftruncate(2).
		465
		466
		467	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		468
		469	Works like perl's C<chmod> function.
		470
		471
295	=item aio_unlink $pathname, $callback->($status)	472	=item aio_unlink $pathname, $callback->($status)
296		473
297	Asynchronously unlink (delete) a file and call the callback with the	474	Asynchronously unlink (delete) a file and call the callback with the
298	result code.	475	result code.
299		476
		477
		478	=item aio_mknod $path, $mode, $dev, $callback->($status)
		479
		480	[EXPERIMENTAL]
		481
		482	Asynchronously create a device node (or fifo). See mknod(2).
		483
		484	The only (POSIX-) portable way of calling this function is:
		485
		486	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		487
		488
300	=item aio_link $srcpath, $dstpath, $callback->($status)	489	=item aio_link $srcpath, $dstpath, $callback->($status)
301		490
302	Asynchronously create a new link to the existing object at C<$srcpath> at	491	Asynchronously create a new link to the existing object at C<$srcpath> at
303	the path C<$dstpath> and call the callback with the result code.	492	the path C<$dstpath> and call the callback with the result code.
304		493
		494
305	=item aio_symlink $srcpath, $dstpath, $callback->($status)	495	=item aio_symlink $srcpath, $dstpath, $callback->($status)
306		496
307	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	497	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
308	the path C<$dstpath> and call the callback with the result code.	498	the path C<$dstpath> and call the callback with the result code.
309		499
		500
		501	=item aio_readlink $path, $callback->($link)
		502
		503	Asynchronously read the symlink specified by C<$path> and pass it to
		504	the callback. If an error occurs, nothing or undef gets passed to the
		505	callback.
		506
		507
310	=item aio_rename $srcpath, $dstpath, $callback->($status)	508	=item aio_rename $srcpath, $dstpath, $callback->($status)
311		509
312	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	510	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
313	rename(2) and call the callback with the result code.	511	rename(2) and call the callback with the result code.
314		512
		513
		514	=item aio_mkdir $pathname, $mode, $callback->($status)
		515
		516	Asynchronously mkdir (create) a directory and call the callback with
		517	the result code. C<$mode> will be modified by the umask at the time the
		518	request is executed, so do not change your umask.
		519
		520
315	=item aio_rmdir $pathname, $callback->($status)	521	=item aio_rmdir $pathname, $callback->($status)
316		522
317	Asynchronously rmdir (delete) a directory and call the callback with the	523	Asynchronously rmdir (delete) a directory and call the callback with the
318	result code.	524	result code.
		525
319		526
320	=item aio_readdir $pathname, $callback->($entries)	527	=item aio_readdir $pathname, $callback->($entries)
321		528
322	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	529	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
323	directory (i.e. opendir + readdir + closedir). The entries will not be	530	directory (i.e. opendir + readdir + closedir). The entries will not be
324	sorted, and will B<NOT> include the C<.> and C<..> entries.	531	sorted, and will B<NOT> include the C<.> and C<..> entries.
325		532
326	The callback a single argument which is either C<undef> or an array-ref	533	The callback a single argument which is either C<undef> or an array-ref
327	with the filenames.	534	with the filenames.
328		535
		536
		537	=item aio_load $path, $data, $callback->($status)
		538
		539	This is a composite request that tries to fully load the given file into
		540	memory. Status is the same as with aio_read.
		541
		542	=cut
		543
		544	sub aio_load($$;$) {
		545	my ($path, undef, $cb) = @_;
		546	my $data = \$_[1];
		547
		548	my $pri = aioreq_pri;
		549	my $grp = aio_group $cb;
		550
		551	aioreq_pri $pri;
		552	add $grp aio_open $path, O_RDONLY, 0, sub {
		553	my $fh = shift
		554	or return $grp->result (-1);
		555
		556	aioreq_pri $pri;
		557	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		558	$grp->result ($_[0]);
		559	};
		560	};
		561
		562	$grp
		563	}
		564
		565	=item aio_copy $srcpath, $dstpath, $callback->($status)
		566
		567	Try to copy the I<file> (directories not supported as either source or
		568	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		569	the C<0> (error) or C<-1> ok.
		570
		571	This is a composite request that it creates the destination file with
		572	mode 0200 and copies the contents of the source file into it using
		573	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		574	uid/gid, in that order.
		575
		576	If an error occurs, the partial destination file will be unlinked, if
		577	possible, except when setting atime, mtime, access mode and uid/gid, where
		578	errors are being ignored.
		579
		580	=cut
		581
		582	sub aio_copy($$;$) {
		583	my ($src, $dst, $cb) = @_;
		584
		585	my $pri = aioreq_pri;
		586	my $grp = aio_group $cb;
		587
		588	aioreq_pri $pri;
		589	add $grp aio_open $src, O_RDONLY, 0, sub {
		590	if (my $src_fh = $_[0]) {
		591	my @stat = stat $src_fh;
		592
		593	aioreq_pri $pri;
		594	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		595	if (my $dst_fh = $_[0]) {
		596	aioreq_pri $pri;
		597	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		598	if ($_[0] == $stat[7]) {
		599	$grp->result (0);
		600	close $src_fh;
		601
		602	# those should not normally block. should. should.
		603	utime $stat[8], $stat[9], $dst;
		604	chmod $stat[2] & 07777, $dst_fh;
		605	chown $stat[4], $stat[5], $dst_fh;
		606
		607	aioreq_pri $pri;
		608	add $grp aio_close $dst_fh;
		609	} else {
		610	$grp->result (-1);
		611	close $src_fh;
		612	close $dst_fh;
		613
		614	aioreq $pri;
		615	add $grp aio_unlink $dst;
		616	}
		617	};
		618	} else {
		619	$grp->result (-1);
		620	}
		621	},
		622
		623	} else {
		624	$grp->result (-1);
		625	}
		626	};
		627
		628	$grp
		629	}
		630
		631	=item aio_move $srcpath, $dstpath, $callback->($status)
		632
		633	Try to move the I<file> (directories not supported as either source or
		634	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		635	the C<0> (error) or C<-1> ok.
		636
		637	This is a composite request that tries to rename(2) the file first. If
		638	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		639	that is successful, unlinking the C<$srcpath>.
		640
		641	=cut
		642
		643	sub aio_move($$;$) {
		644	my ($src, $dst, $cb) = @_;
		645
		646	my $pri = aioreq_pri;
		647	my $grp = aio_group $cb;
		648
		649	aioreq_pri $pri;
		650	add $grp aio_rename $src, $dst, sub {
		651	if ($_[0] && $! == EXDEV) {
		652	aioreq_pri $pri;
		653	add $grp aio_copy $src, $dst, sub {
		654	$grp->result ($_[0]);
		655
		656	if (!$_[0]) {
		657	aioreq_pri $pri;
		658	add $grp aio_unlink $src;
		659	}
		660	};
		661	} else {
		662	$grp->result ($_[0]);
		663	}
		664	};
		665
		666	$grp
		667	}
		668
329	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	669	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
330		670
331	Scans a directory (similar to C<aio_readdir>) and tries to separate the	671	Scans a directory (similar to C<aio_readdir>) but additionally tries to
332	entries of directory C<$path> into two sets of names, ones you can recurse	672	efficiently separate the entries of directory C<$path> into two sets of
333	into (directories), and ones you cannot recurse into (everything else).	673	names, directories you can recurse into (directories), and ones you cannot
		674	recurse into (everything else, including symlinks to directories).
334		675
335	C<aio_scandir> is a composite request that consists of many	676	C<aio_scandir> is a composite request that creates of many sub requests_
336	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	677	C<$maxreq> specifies the maximum number of outstanding aio requests that
337	aio requests that this function generates. If it is C<< <= 0 >>, then a	678	this function generates. If it is C<< <= 0 >>, then a suitable default
338	suitable default will be chosen (currently 8).	679	will be chosen (currently 4).
339		680
340	On error, the callback is called without arguments, otherwise it receives	681	On error, the callback is called without arguments, otherwise it receives
341	two array-refs with path-relative entry names.	682	two array-refs with path-relative entry names.
342		683
343	Example:	684	Example:
…		…
351	Implementation notes.	692	Implementation notes.
352		693
353	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	694	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
354		695
355	After reading the directory, the modification time, size etc. of the	696	After reading the directory, the modification time, size etc. of the
356	directory before and after the readdir is checked, and if they match, the	697	directory before and after the readdir is checked, and if they match (and
357	link count will be used to decide how many entries are directories (if	698	isn't the current time), the link count will be used to decide how many
358	>= 2). Otherwise, no knowledge of the number of subdirectories will be	699	entries are directories (if >= 2). Otherwise, no knowledge of the number
359	assumed.	700	of subdirectories will be assumed.
360		701
361	Then entires will be sorted into likely directories (everything without a	702	Then entries will be sorted into likely directories (everything without
362	non-initial dot) and likely non-directories (everything else). Then every	703	a non-initial dot currently) and likely non-directories (everything
363	entry + C</.> will be C<stat>'ed, likely directories first. This is often	704	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		705	likely directories first. If that succeeds, it assumes that the entry
		706	is a directory or a symlink to directory (which will be checked
		707	seperately). This is often faster than stat'ing the entry itself because
364	faster because filesystems might detect the type of the entry without	708	filesystems might detect the type of the entry without reading the inode
365	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,	709	data (e.g. ext2fs filetype feature).
366	it assumes that the entry is a directory or a symlink to directory (which
367	will be checked seperately).
368		710
369	If the known number of directories has been reached, the rest of the	711	If the known number of directories (link count - 2) has been reached, the
370	entries is assumed to be non-directories.	712	rest of the entries is assumed to be non-directories.
		713
		714	This only works with certainty on POSIX (= UNIX) filesystems, which
		715	fortunately are the vast majority of filesystems around.
		716
		717	It will also likely work on non-POSIX filesystems with reduced efficiency
		718	as those tend to return 0 or 1 as link counts, which disables the
		719	directory counting heuristic.
371		720
372	=cut	721	=cut
373		722
374	sub aio_scandir($$$) {	723	sub aio_scandir($$;$) {
375	my ($path, $maxreq, $cb) = @_;	724	my ($path, $maxreq, $cb) = @_;
376		725
		726	my $pri = aioreq_pri;
		727
		728	my $grp = aio_group $cb;
		729
377	$maxreq = 8 if $maxreq <= 0;	730	$maxreq = 4 if $maxreq <= 0;
378		731
379	# stat once	732	# stat once
		733	aioreq_pri $pri;
380	aio_stat $path, sub {	734	add $grp aio_stat $path, sub {
381	return $cb->() if $_[0];	735	return $grp->result () if $_[0];
		736	my $now = time;
382	my $hash1 = join ":", (stat _)[0,1,3,7,9];	737	my $hash1 = join ":", (stat _)[0,1,3,7,9];
383		738
384	# read the directory entries	739	# read the directory entries
		740	aioreq_pri $pri;
385	aio_readdir $path, sub {	741	add $grp aio_readdir $path, sub {
386	my $entries = shift	742	my $entries = shift
387	or return $cb->();	743	or return $grp->result ();
388		744
389	# stat the dir another time	745	# stat the dir another time
		746	aioreq_pri $pri;
390	aio_stat $path, sub {	747	add $grp aio_stat $path, sub {
391	my $hash2 = join ":", (stat _)[0,1,3,7,9];	748	my $hash2 = join ":", (stat _)[0,1,3,7,9];
392		749
393	my $ndirs;	750	my $ndirs;
394		751
395	# take the slow route if anything looks fishy	752	# take the slow route if anything looks fishy
396	if ($hash1 ne $hash2) {	753	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
397	$ndirs = -1;	754	$ndirs = -1;
398	} else {	755	} else {
399	# if nlink == 2, we are finished	756	# if nlink == 2, we are finished
400	# on non-posix-fs's, we rely on nlink < 2	757	# on non-posix-fs's, we rely on nlink < 2
401	$ndirs = (stat _)[3] - 2	758	$ndirs = (stat _)[3] - 2
402	or return $cb->([], $entries);	759	or return $grp->result ([], $entries);
403	}	760	}
404		761
405	# sort into likely dirs and likely nondirs	762	# sort into likely dirs and likely nondirs
406	# dirs == files without ".", short entries first	763	# dirs == files without ".", short entries first
407	$entries = [map $_->[0],	764	$entries = [map $_->[0],
…		…
409	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	766	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
410	@$entries];	767	@$entries];
411		768
412	my (@dirs, @nondirs);	769	my (@dirs, @nondirs);
413		770
414	my ($statcb, $schedcb);	771	my $statgrp = add $grp aio_group sub {
415	my $nreq = 0;	772	$grp->result (\@dirs, \@nondirs);
		773	};
416		774
417	$schedcb = sub {	775	limit $statgrp $maxreq;
418	if (@$entries) {	776	feed $statgrp sub {
419	if ($nreq < $maxreq) {	777	return unless @$entries;
420	my $ent = pop @$entries;	778	my $entry = pop @$entries;
		779
		780	aioreq_pri $pri;
		781	add $statgrp aio_stat "$path/$entry/.", sub {
		782	if ($_[0] < 0) {
		783	push @nondirs, $entry;
		784	} else {
		785	# need to check for real directory
		786	aioreq_pri $pri;
		787	add $statgrp aio_lstat "$path/$entry", sub {
		788	if (-d _) {
		789	push @dirs, $entry;
		790
		791	unless (--$ndirs) {
		792	push @nondirs, @$entries;
		793	feed $statgrp;
		794	}
		795	} else {
		796	push @nondirs, $entry;
		797	}
421	$nreq++;	798	}
422	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
423	}	799	}
424	} elsif (!$nreq) {
425	# finished
426	undef $statcb;
427	undef $schedcb;
428	$cb->(\@dirs, \@nondirs) if $cb;
429	undef $cb;
430	}	800	};
431	};	801	};
432	$statcb = sub {
433	my ($status, $entry) = @_;
434
435	if ($status < 0) {
436	$nreq--;
437	push @nondirs, $entry;
438	&$schedcb;
439	} else {
440	# need to check for real directory
441	aio_lstat "$path/$entry", sub {
442	$nreq--;
443
444	if (-d _) {
445	push @dirs, $entry;
446
447	if (!--$ndirs) {
448	push @nondirs, @$entries;
449	$entries = [];
450	}
451	} else {
452	push @nondirs, $entry;
453	}
454
455	&$schedcb;
456	}
457	}
458	};
459
460	&$schedcb while @$entries && $nreq < $maxreq;
461	};	802	};
462	};	803	};
463	};	804	};
		805
		806	$grp
464	}	807	}
		808
		809	=item aio_rmtree $path, $callback->($status)
		810
		811	Delete a directory tree starting (and including) C<$path>, return the
		812	status of the final C<rmdir> only. This is a composite request that
		813	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		814	everything else.
		815
		816	=cut
		817
		818	sub aio_rmtree;
		819	sub aio_rmtree($;$) {
		820	my ($path, $cb) = @_;
		821
		822	my $pri = aioreq_pri;
		823	my $grp = aio_group $cb;
		824
		825	aioreq_pri $pri;
		826	add $grp aio_scandir $path, 0, sub {
		827	my ($dirs, $nondirs) = @_;
		828
		829	my $dirgrp = aio_group sub {
		830	add $grp aio_rmdir $path, sub {
		831	$grp->result ($_[0]);
		832	};
		833	};
		834
		835	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		836	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		837
		838	add $grp $dirgrp;
		839	};
		840
		841	$grp
		842	}
		843
		844	=item aio_sync $callback->($status)
		845
		846	Asynchronously call sync and call the callback when finished.
465		847
466	=item aio_fsync $fh, $callback->($status)	848	=item aio_fsync $fh, $callback->($status)
467		849
468	Asynchronously call fsync on the given filehandle and call the callback	850	Asynchronously call fsync on the given filehandle and call the callback
469	with the fsync result code.	851	with the fsync result code.
…		…
474	callback with the fdatasync result code.	856	callback with the fdatasync result code.
475		857
476	If this call isn't available because your OS lacks it or it couldn't be	858	If this call isn't available because your OS lacks it or it couldn't be
477	detected, it will be emulated by calling C<fsync> instead.	859	detected, it will be emulated by calling C<fsync> instead.
478		860
		861	=item aio_pathsync $path, $callback->($status)
		862
		863	This request tries to open, fsync and close the given path. This is a
		864	composite request intended tosync directories after directory operations
		865	(E.g. rename). This might not work on all operating systems or have any
		866	specific effect, but usually it makes sure that directory changes get
		867	written to disc. It works for anything that can be opened for read-only,
		868	not just directories.
		869
		870	Passes C<0> when everything went ok, and C<-1> on error.
		871
		872	=cut
		873
		874	sub aio_pathsync($;$) {
		875	my ($path, $cb) = @_;
		876
		877	my $pri = aioreq_pri;
		878	my $grp = aio_group $cb;
		879
		880	aioreq_pri $pri;
		881	add $grp aio_open $path, O_RDONLY, 0, sub {
		882	my ($fh) = @_;
		883	if ($fh) {
		884	aioreq_pri $pri;
		885	add $grp aio_fsync $fh, sub {
		886	$grp->result ($_[0]);
		887
		888	aioreq_pri $pri;
		889	add $grp aio_close $fh;
		890	};
		891	} else {
		892	$grp->result (-1);
		893	}
		894	};
		895
		896	$grp
		897	}
		898
		899	=item aio_group $callback->(...)
		900
		901	This is a very special aio request: Instead of doing something, it is a
		902	container for other aio requests, which is useful if you want to bundle
		903	many requests into a single, composite, request with a definite callback
		904	and the ability to cancel the whole request with its subrequests.
		905
		906	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		907	for more info.
		908
		909	Example:
		910
		911	my $grp = aio_group sub {
		912	print "all stats done\n";
		913	};
		914
		915	add $grp
		916	(aio_stat ...),
		917	(aio_stat ...),
		918	...;
		919
		920	=item aio_nop $callback->()
		921
		922	This is a special request - it does nothing in itself and is only used for
		923	side effects, such as when you want to add a dummy request to a group so
		924	that finishing the requests in the group depends on executing the given
		925	code.
		926
		927	While this request does nothing, it still goes through the execution
		928	phase and still requires a worker thread. Thus, the callback will not
		929	be executed immediately but only after other requests in the queue have
		930	entered their execution phase. This can be used to measure request
		931	latency.
		932
		933	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		934
		935	Mainly used for debugging and benchmarking, this aio request puts one of
		936	the request workers to sleep for the given time.
		937
		938	While it is theoretically handy to have simple I/O scheduling requests
		939	like sleep and file handle readable/writable, the overhead this creates is
		940	immense (it blocks a thread for a long time) so do not use this function
		941	except to put your application under artificial I/O pressure.
		942
479	=back	943	=back
480		944
		945	=head2 IO::AIO::REQ CLASS
		946
		947	All non-aggregate C<aio_*> functions return an object of this class when
		948	called in non-void context.
		949
		950	=over 4
		951
		952	=item cancel $req
		953
		954	Cancels the request, if possible. Has the effect of skipping execution
		955	when entering the B<execute> state and skipping calling the callback when
		956	entering the the B<result> state, but will leave the request otherwise
		957	untouched. That means that requests that currently execute will not be
		958	stopped and resources held by the request will not be freed prematurely.
		959
		960	=item cb $req $callback->(...)
		961
		962	Replace (or simply set) the callback registered to the request.
		963
		964	=back
		965
		966	=head2 IO::AIO::GRP CLASS
		967
		968	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		969	objects of this class, too.
		970
		971	A IO::AIO::GRP object is a special request that can contain multiple other
		972	aio requests.
		973
		974	You create one by calling the C<aio_group> constructing function with a
		975	callback that will be called when all contained requests have entered the
		976	C<done> state:
		977
		978	my $grp = aio_group sub {
		979	print "all requests are done\n";
		980	};
		981
		982	You add requests by calling the C<add> method with one or more
		983	C<IO::AIO::REQ> objects:
		984
		985	$grp->add (aio_unlink "...");
		986
		987	add $grp aio_stat "...", sub {
		988	$_[0] or return $grp->result ("error");
		989
		990	# add another request dynamically, if first succeeded
		991	add $grp aio_open "...", sub {
		992	$grp->result ("ok");
		993	};
		994	};
		995
		996	This makes it very easy to create composite requests (see the source of
		997	C<aio_move> for an application) that work and feel like simple requests.
		998
		999	=over 4
		1000
		1001	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1002	C<IO::AIO::poll_cb>, just like any other request.
		1003
		1004	=item * They can be canceled like any other request. Canceling will cancel not
		1005	only the request itself, but also all requests it contains.
		1006
		1007	=item * They can also can also be added to other IO::AIO::GRP objects.
		1008
		1009	=item * You must not add requests to a group from within the group callback (or
		1010	any later time).
		1011
		1012	=back
		1013
		1014	Their lifetime, simplified, looks like this: when they are empty, they
		1015	will finish very quickly. If they contain only requests that are in the
		1016	C<done> state, they will also finish. Otherwise they will continue to
		1017	exist.
		1018
		1019	That means after creating a group you have some time to add requests. And
		1020	in the callbacks of those requests, you can add further requests to the
		1021	group. And only when all those requests have finished will the the group
		1022	itself finish.
		1023
		1024	=over 4
		1025
		1026	=item add $grp ...
		1027
		1028	=item $grp->add (...)
		1029
		1030	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1031	be added, including other groups, as long as you do not create circular
		1032	dependencies.
		1033
		1034	Returns all its arguments.
		1035
		1036	=item $grp->cancel_subs
		1037
		1038	Cancel all subrequests and clears any feeder, but not the group request
		1039	itself. Useful when you queued a lot of events but got a result early.
		1040
		1041	=item $grp->result (...)
		1042
		1043	Set the result value(s) that will be passed to the group callback when all
		1044	subrequests have finished and set the groups errno to the current value
		1045	of errno (just like calling C<errno> without an error number). By default,
		1046	no argument will be passed and errno is zero.
		1047
		1048	=item $grp->errno ([$errno])
		1049
		1050	Sets the group errno value to C<$errno>, or the current value of errno
		1051	when the argument is missing.
		1052
		1053	Every aio request has an associated errno value that is restored when
		1054	the callback is invoked. This method lets you change this value from its
		1055	default (0).
		1056
		1057	Calling C<result> will also set errno, so make sure you either set C<$!>
		1058	before the call to C<result>, or call c<errno> after it.
		1059
		1060	=item feed $grp $callback->($grp)
		1061
		1062	Sets a feeder/generator on this group: every group can have an attached
		1063	generator that generates requests if idle. The idea behind this is that,
		1064	although you could just queue as many requests as you want in a group,
		1065	this might starve other requests for a potentially long time. For
		1066	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1067	requests, delaying any later requests for a long time.
		1068
		1069	To avoid this, and allow incremental generation of requests, you can
		1070	instead a group and set a feeder on it that generates those requests. The
		1071	feed callback will be called whenever there are few enough (see C<limit>,
		1072	below) requests active in the group itself and is expected to queue more
		1073	requests.
		1074
		1075	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1076	not impose any limits).
		1077
		1078	If the feed does not queue more requests when called, it will be
		1079	automatically removed from the group.
		1080
		1081	If the feed limit is C<0>, it will be set to C<2> automatically.
		1082
		1083	Example:
		1084
		1085	# stat all files in @files, but only ever use four aio requests concurrently:
		1086
		1087	my $grp = aio_group sub { print "finished\n" };
		1088	limit $grp 4;
		1089	feed $grp sub {
		1090	my $file = pop @files
		1091	or return;
		1092
		1093	add $grp aio_stat $file, sub { ... };
		1094	};
		1095
		1096	=item limit $grp $num
		1097
		1098	Sets the feeder limit for the group: The feeder will be called whenever
		1099	the group contains less than this many requests.
		1100
		1101	Setting the limit to C<0> will pause the feeding process.
		1102
		1103	=back
		1104
481	=head2 SUPPORT FUNCTIONS	1105	=head2 SUPPORT FUNCTIONS
		1106
		1107	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
482		1108
483	=over 4	1109	=over 4
484		1110
485	=item $fileno = IO::AIO::poll_fileno	1111	=item $fileno = IO::AIO::poll_fileno
486		1112
…		…
491		1117
492	See C<poll_cb> for an example.	1118	See C<poll_cb> for an example.
493		1119
494	=item IO::AIO::poll_cb	1120	=item IO::AIO::poll_cb
495		1121
496	Process all outstanding events on the result pipe. You have to call this	1122	Process some outstanding events on the result pipe. You have to call this
497	regularly. Returns the number of events processed. Returns immediately	1123	regularly. Returns the number of events processed. Returns immediately
498	when no events are outstanding.	1124	when no events are outstanding. The amount of events processed depends on
		1125	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1126
		1127	If not all requests were processed for whatever reason, the filehandle
		1128	will still be ready when C<poll_cb> returns.
499		1129
500	Example: Install an Event watcher that automatically calls	1130	Example: Install an Event watcher that automatically calls
501	IO::AIO::poll_cb with high priority:	1131	IO::AIO::poll_cb with high priority:
502		1132
503	Event->io (fd => IO::AIO::poll_fileno,	1133	Event->io (fd => IO::AIO::poll_fileno,
504	poll => 'r', async => 1,	1134	poll => 'r', async => 1,
505	cb => \&IO::AIO::poll_cb);	1135	cb => \&IO::AIO::poll_cb);
506		1136
		1137	=item IO::AIO::max_poll_reqs $nreqs
		1138
		1139	=item IO::AIO::max_poll_time $seconds
		1140
		1141	These set the maximum number of requests (default C<0>, meaning infinity)
		1142	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1143	the maximum amount of time (default C<0>, meaning infinity) spent in
		1144	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1145	of time C<poll_cb> is allowed to use).
		1146
		1147	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1148	syscall per request processed, which is not normally a problem unless your
		1149	callbacks are really really fast or your OS is really really slow (I am
		1150	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1151
		1152	Setting these is useful if you want to ensure some level of
		1153	interactiveness when perl is not fast enough to process all requests in
		1154	time.
		1155
		1156	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1157
		1158	Example: Install an Event watcher that automatically calls
		1159	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1160	program get the CPU sometimes even under high AIO load.
		1161
		1162	# try not to spend much more than 0.1s in poll_cb
		1163	IO::AIO::max_poll_time 0.1;
		1164
		1165	# use a low priority so other tasks have priority
		1166	Event->io (fd => IO::AIO::poll_fileno,
		1167	poll => 'r', nice => 1,
		1168	cb => &IO::AIO::poll_cb);
		1169
507	=item IO::AIO::poll_wait	1170	=item IO::AIO::poll_wait
508		1171
		1172	If there are any outstanding requests and none of them in the result
509	Wait till the result filehandle becomes ready for reading (simply does a	1173	phase, wait till the result filehandle becomes ready for reading (simply
510	C<select> on the filehandle. This is useful if you want to synchronously wait	1174	does a C<select> on the filehandle. This is useful if you want to
511	for some requests to finish).	1175	synchronously wait for some requests to finish).
512		1176
513	See C<nreqs> for an example.	1177	See C<nreqs> for an example.
514		1178
		1179	=item IO::AIO::poll
		1180
		1181	Waits until some requests have been handled.
		1182
		1183	Returns the number of requests processed, but is otherwise strictly
		1184	equivalent to:
		1185
		1186	IO::AIO::poll_wait, IO::AIO::poll_cb
		1187
515	=item IO::AIO::nreqs	1188	=item IO::AIO::flush
516		1189
517	Returns the number of requests currently outstanding (i.e. for which their	1190	Wait till all outstanding AIO requests have been handled.
518	callback has not been invoked yet).
519		1191
520	Example: wait till there are no outstanding requests anymore:	1192	Strictly equivalent to:
521		1193
522	IO::AIO::poll_wait, IO::AIO::poll_cb	1194	IO::AIO::poll_wait, IO::AIO::poll_cb
523	while IO::AIO::nreqs;	1195	while IO::AIO::nreqs;
524		1196
525	=item IO::AIO::flush	1197	=back
526		1198
527	Wait till all outstanding AIO requests have been handled.	1199	=head3 CONTROLLING THE NUMBER OF THREADS
528		1200
529	Strictly equivalent to:	1201	=over
530
531	IO::AIO::poll_wait, IO::AIO::poll_cb
532	while IO::AIO::nreqs;
533
534	=item IO::AIO::poll
535
536	Waits until some requests have been handled.
537
538	Strictly equivalent to:
539
540	IO::AIO::poll_wait, IO::AIO::poll_cb
541	if IO::AIO::nreqs;
542		1202
543	=item IO::AIO::min_parallel $nthreads	1203	=item IO::AIO::min_parallel $nthreads
544		1204
545	Set the minimum number of AIO threads to C<$nthreads>. The current default	1205	Set the minimum number of AIO threads to C<$nthreads>. The current
546	is C<4>, which means four asynchronous operations can be done at one time	1206	default is C<8>, which means eight asynchronous operations can execute
547	(the number of outstanding operations, however, is unlimited).	1207	concurrently at any one time (the number of outstanding requests,
		1208	however, is unlimited).
548		1209
549	IO::AIO starts threads only on demand, when an AIO request is queued and	1210	IO::AIO starts threads only on demand, when an AIO request is queued and
550	no free thread exists.	1211	no free thread exists. Please note that queueing up a hundred requests can
		1212	create demand for a hundred threads, even if it turns out that everything
		1213	is in the cache and could have been processed faster by a single thread.
551		1214
552	It is recommended to keep the number of threads low, as some Linux	1215	It is recommended to keep the number of threads relatively low, as some
553	kernel versions will scale negatively with the number of threads (higher	1216	Linux kernel versions will scale negatively with the number of threads
554	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1217	(higher parallelity => MUCH higher latency). With current Linux 2.6
555	threads should be fine.	1218	versions, 4-32 threads should be fine.
556		1219
557	Under most circumstances you don't need to call this function, as the	1220	Under most circumstances you don't need to call this function, as the
558	module selects a default that is suitable for low to moderate load.	1221	module selects a default that is suitable for low to moderate load.
559		1222
560	=item IO::AIO::max_parallel $nthreads	1223	=item IO::AIO::max_parallel $nthreads
…		…
569	This module automatically runs C<max_parallel 0> at program end, to ensure	1232	This module automatically runs C<max_parallel 0> at program end, to ensure
570	that all threads are killed and that there are no outstanding requests.	1233	that all threads are killed and that there are no outstanding requests.
571		1234
572	Under normal circumstances you don't need to call this function.	1235	Under normal circumstances you don't need to call this function.
573		1236
		1237	=item IO::AIO::max_idle $nthreads
		1238
		1239	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1240	threads that did not get a request to process within 10 seconds). That
		1241	means if a thread becomes idle while C<$nthreads> other threads are also
		1242	idle, it will free its resources and exit.
		1243
		1244	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1245	to allow for extremely high load situations, but want to free resources
		1246	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1247
		1248	The default is probably ok in most situations, especially if thread
		1249	creation is fast. If thread creation is very slow on your system you might
		1250	want to use larger values.
		1251
574	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1252	=item IO::AIO::max_outstanding $maxreqs
		1253
		1254	This is a very bad function to use in interactive programs because it
		1255	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1256	use an C<aio_group> together with a feed callback.
575		1257
576	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1258	Sets the maximum number of outstanding requests to C<$nreqs>. If you
577	try to queue up more than this number of requests, the caller will block until	1259	do queue up more than this number of requests, the next call to the
578	some requests have been handled.	1260	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1261	function will block until the limit is no longer exceeded.
579		1262
580	The default is very large, so normally there is no practical limit. If you	1263	The default value is very large, so there is no practical limit on the
581	queue up many requests in a loop it often improves speed if you set	1264	number of outstanding requests.
582	this to a relatively low number, such as C<100>.
583		1265
584	Under normal circumstances you don't need to call this function.	1266	You can still queue as many requests as you want. Therefore,
		1267	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1268	as a stop gap to shield against fatal memory overflow (with large values).
585		1269
586	=back	1270	=back
587		1271
		1272	=head3 STATISTICAL INFORMATION
		1273
		1274	=over
		1275
		1276	=item IO::AIO::nreqs
		1277
		1278	Returns the number of requests currently in the ready, execute or pending
		1279	states (i.e. for which their callback has not been invoked yet).
		1280
		1281	Example: wait till there are no outstanding requests anymore:
		1282
		1283	IO::AIO::poll_wait, IO::AIO::poll_cb
		1284	while IO::AIO::nreqs;
		1285
		1286	=item IO::AIO::nready
		1287
		1288	Returns the number of requests currently in the ready state (not yet
		1289	executed).
		1290
		1291	=item IO::AIO::npending
		1292
		1293	Returns the number of requests currently in the pending state (executed,
		1294	but not yet processed by poll_cb).
		1295
		1296	=back
		1297
588	=cut	1298	=cut
589		1299
590	# support function to convert a fd into a perl filehandle
591	sub _fd2fh {
592	return undef if $_[0] < 0;
593
594	# try to generate nice filehandles
595	my $sym = "IO::AIO::fd#$_[0]";
596	local *$sym;
597
598	open *$sym, "+<&=$_[0]" # usually works under any unix
599	or open *$sym, "<&=$_[0]" # cygwin needs this
600	or open *$sym, ">&=$_[0]" # or this
601	or return undef;
602
603	*$sym
604	}
605
606	min_parallel 4;	1300	min_parallel 8;
607		1301
608	END {	1302	END { flush }
609	max_parallel 0;
610	}
611		1303
612	1;	1304	1;
613		1305
614	=head2 FORK BEHAVIOUR	1306	=head2 FORK BEHAVIOUR
		1307
		1308	This module should do "the right thing" when the process using it forks:
615		1309
616	Before the fork, IO::AIO enters a quiescent state where no requests	1310	Before the fork, IO::AIO enters a quiescent state where no requests
617	can be added in other threads and no results will be processed. After	1311	can be added in other threads and no results will be processed. After
618	the fork the parent simply leaves the quiescent state and continues	1312	the fork the parent simply leaves the quiescent state and continues
619	request/result processing, while the child clears the request/result	1313	request/result processing, while the child frees the request/result queue
620	queue (so the requests started before the fork will only be handled in	1314	(so that the requests started before the fork will only be handled in the
621	the parent). Threats will be started on demand until the limit ste in the	1315	parent). Threads will be started on demand until the limit set in the
622	parent process has been reached again.	1316	parent process has been reached again.
623		1317
		1318	In short: the parent will, after a short pause, continue as if fork had
		1319	not been called, while the child will act as if IO::AIO has not been used
		1320	yet.
		1321
		1322	=head2 MEMORY USAGE
		1323
		1324	Per-request usage:
		1325
		1326	Each aio request uses - depending on your architecture - around 100-200
		1327	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1328	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1329	scalars and other data passed into aio requests will also be locked and
		1330	will consume memory till the request has entered the done state.
		1331
		1332	This is not awfully much, so queuing lots of requests is not usually a
		1333	problem.
		1334
		1335	Per-thread usage:
		1336
		1337	In the execution phase, some aio requests require more memory for
		1338	temporary buffers, and each thread requires a stack and other data
		1339	structures (usually around 16k-128k, depending on the OS).
		1340
		1341	=head1 KNOWN BUGS
		1342
		1343	Known bugs will be fixed in the next release.
		1344
624	=head1 SEE ALSO	1345	=head1 SEE ALSO
625		1346
626	L<Coro>, L<Linux::AIO>.	1347	L<Coro::AIO>.
627		1348
628	=head1 AUTHOR	1349	=head1 AUTHOR
629		1350
630	Marc Lehmann <schmorp@schmorp.de>	1351	Marc Lehmann <schmorp@schmorp.de>
631	http://home.schmorp.de/	1352	http://home.schmorp.de/

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