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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.52 by root, Sat Oct 21 23:06:04 2006 UTC vs.
Revision 1.117 by root, Sat Oct 6 14:05:19 2007 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	use IO::AIO 2; # version has aio objects	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
21		23
		24	aioreq_pri 4; # give next request a very high priority
22	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
23	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
24		27
25	# AnyEvent	28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27	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 });
28		34
29	# Event	35	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	37	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
33		39
34	# Glib/Gtk2	40	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
37		43
38	# Tk	44	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
41		47
42	# Danga::Socket	48	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
45		51
46
47	=head1 DESCRIPTION	52	=head1 DESCRIPTION
48		53
49	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
50	operating system supports.	55	operating system supports.
51		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
52	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
53	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
54	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
55	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
56	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
57	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
58	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
59	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
60		82
61	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
62	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
63	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	85	yourself, always call C<poll_cb> from within the same thread, or never
64	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
65		183
66	=cut	184	=cut
67		185
68	package IO::AIO;	186	package IO::AIO;
		187
		188	use Carp ();
69		189
70	no warnings;	190	no warnings;
71	use strict 'vars';	191	use strict 'vars';
72		192
73	use base 'Exporter';	193	use base 'Exporter';
74		194
75	BEGIN {	195	BEGIN {
76	our $VERSION = '1.8';	196	our $VERSION = '2.51';
77		197
78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	199	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);	200	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	201	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
		202	aio_chown aio_chmod aio_utime aio_truncate);
		203	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		204	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		205	min_parallel max_parallel max_idle
		206	nreqs nready npending nthreads
		207	max_poll_time max_poll_reqs);
		208
		209	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
82		210
83	require XSLoader;	211	require XSLoader;
84	XSLoader::load ("IO::AIO", $VERSION);	212	XSLoader::load ("IO::AIO", $VERSION);
85	}	213	}
86		214
87	=head1 FUNCTIONS	215	=head1 FUNCTIONS
88		216
89	=head2 AIO FUNCTIONS	217	=head2 AIO REQUEST FUNCTIONS
90		218
91	All the C<aio_*> calls are more or less thin wrappers around the syscall	219	All the C<aio_*> calls are more or less thin wrappers around the syscall
92	with the same name (sans C<aio_>). The arguments are similar or identical,	220	with the same name (sans C<aio_>). The arguments are similar or identical,
93	and they all accept an additional (and optional) C<$callback> argument	221	and they all accept an additional (and optional) C<$callback> argument
94	which must be a code reference. This code reference will get called with	222	which must be a code reference. This code reference will get called with
…		…
97	syscall has been executed asynchronously.	225	syscall has been executed asynchronously.
98		226
99	All functions expecting a filehandle keep a copy of the filehandle	227	All functions expecting a filehandle keep a copy of the filehandle
100	internally until the request has finished.	228	internally until the request has finished.
101		229
102	All non-composite requests (requests that are not broken down into
103	multiple requests) return objects of type L<IO::AIO::REQ> that allow	230	All functions return request objects of type L<IO::AIO::REQ> that allow
104	further manipulation of running requests.	231	further manipulation of those requests while they are in-flight.
105		232
106	The pathnames you pass to these routines I<must> be absolute and	233	The pathnames you pass to these routines I<must> be absolute and
107	encoded in byte form. The reason for the former is that at the time the	234	encoded as octets. The reason for the former is that at the time the
108	request is being executed, the current working directory could have	235	request is being executed, the current working directory could have
109	changed. Alternatively, you can make sure that you never change the	236	changed. Alternatively, you can make sure that you never change the
110	current working directory.	237	current working directory anywhere in the program and then use relative
		238	paths.
111		239
112	To encode pathnames to byte form, either make sure you either: a)	240	To encode pathnames as octets, either make sure you either: a) always pass
113	always pass in filenames you got from outside (command line, readdir	241	in filenames you got from outside (command line, readdir etc.) without
114	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	242	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
115	your pathnames to the locale (or other) encoding in effect in the user	243	your pathnames to the locale (or other) encoding in effect in the user
116	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	244	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
117	use something else.	245	use something else to ensure your scalar has the correct contents.
		246
		247	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		248	handles correctly wether it is set or not.
118		249
119	=over 4	250	=over 4
		251
		252	=item $prev_pri = aioreq_pri [$pri]
		253
		254	Returns the priority value that would be used for the next request and, if
		255	C<$pri> is given, sets the priority for the next aio request.
		256
		257	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		258	and C<4>, respectively. Requests with higher priority will be serviced
		259	first.
		260
		261	The priority will be reset to C<0> after each call to one of the C<aio_*>
		262	functions.
		263
		264	Example: open a file with low priority, then read something from it with
		265	higher priority so the read request is serviced before other low priority
		266	open requests (potentially spamming the cache):
		267
		268	aioreq_pri -3;
		269	aio_open ..., sub {
		270	return unless $_[0];
		271
		272	aioreq_pri -2;
		273	aio_read $_[0], ..., sub {
		274	...
		275	};
		276	};
		277
		278
		279	=item aioreq_nice $pri_adjust
		280
		281	Similar to C<aioreq_pri>, but subtracts the given value from the current
		282	priority, so the effect is cumulative.
		283
120		284
121	=item aio_open $pathname, $flags, $mode, $callback->($fh)	285	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		286
123	Asynchronously open or create a file and call the callback with a newly	287	Asynchronously open or create a file and call the callback with a newly
124	created filehandle for the file.	288	created filehandle for the file.
…		…
130	list. They are the same as used by C<sysopen>.	294	list. They are the same as used by C<sysopen>.
131		295
132	Likewise, C<$mode> specifies the mode of the newly created file, if it	296	Likewise, C<$mode> specifies the mode of the newly created file, if it
133	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	297	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
134	except that it is mandatory (i.e. use C<0> if you don't create new files,	298	except that it is mandatory (i.e. use C<0> if you don't create new files,
135	and C<0666> or C<0777> if you do).	299	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		300	by the umask in effect then the request is being executed, so better never
		301	change the umask.
136		302
137	Example:	303	Example:
138		304
139	aio_open "/etc/passwd", O_RDONLY, 0, sub {	305	aio_open "/etc/passwd", O_RDONLY, 0, sub {
140	if ($_[0]) {	306	if ($_[0]) {
…		…
143	} else {	309	} else {
144	die "open failed: $!\n";	310	die "open failed: $!\n";
145	}	311	}
146	};	312	};
147		313
		314
148	=item aio_close $fh, $callback->($status)	315	=item aio_close $fh, $callback->($status)
149		316
150	Asynchronously close a file and call the callback with the result	317	Asynchronously close a file and call the callback with the result
151	code. I<WARNING:> although accepted, you should not pass in a perl	318	code.
152	filehandle here, as perl will likely close the file descriptor another
153	time when the filehandle is destroyed. Normally, you can safely call perls
154	C<close> or just let filehandles go out of scope.
155		319
156	This is supposed to be a bug in the API, so that might change. It's	320	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
157	therefore best to avoid this function.	321	closing the file descriptor associated with the filehandle itself. Here is
		322	what aio_close will try:
		323
		324	1. dup()licate the fd
		325	2. asynchronously close() the duplicated fd
		326	3. dup()licate the fd once more
		327	4. let perl close() the filehandle
		328	5. asynchronously close the duplicated fd
		329
		330	The idea is that the first close() flushes stuff to disk that closing an
		331	fd will flush, so when perl closes the fd, nothing much will need to be
		332	flushed. The second async. close() will then flush stuff to disk that
		333	closing the last fd to the file will flush.
		334
		335	Just FYI, SuSv3 has this to say on close:
		336
		337	All outstanding record locks owned by the process on the file
		338	associated with the file descriptor shall be removed.
		339
		340	If fildes refers to a socket, close() shall cause the socket to be
		341	destroyed. ... close() shall block for up to the current linger
		342	interval until all data is transmitted.
		343	[this actually sounds like a specification bug, but who knows]
		344
		345	And at least Linux additionally actually flushes stuff on every close,
		346	even when the file itself is still open.
		347
		348	Sounds enourmously inefficient and complicated? Yes... please show me how
		349	to nuke perl's fd out of existence...
		350
		351	=cut
		352
		353	sub aio_close($;$) {
		354	aio_block {
		355	my ($fh, $cb) = @_;
		356
		357	my $pri = aioreq_pri;
		358	my $grp = aio_group $cb;
		359
		360	my $fd = fileno $fh;
		361
		362	defined $fd or Carp::croak "aio_close called with fd-less filehandle";
		363
		364	# if the dups fail we will simply get EBADF
		365	my $fd2 = _dup $fd;
		366	aioreq_pri $pri;
		367	add $grp _aio_close $fd2, sub {
		368	my $fd2 = _dup $fd;
		369	close $fh;
		370	aioreq_pri $pri;
		371	add $grp _aio_close $fd2, sub {
		372	$grp->result ($_[0]);
		373	};
		374	};
		375
		376	$grp
		377	}
		378	}
		379
158		380
159	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	381	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160		382
161	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	383	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
162		384
163	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	385	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
164	into the scalar given by C<data> and offset C<dataoffset> and calls the	386	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
165	callback without the actual number of bytes read (or -1 on error, just	387	callback without the actual number of bytes read (or -1 on error, just
166	like the syscall).	388	like the syscall).
167		389
		390	If C<$offset> is undefined, then the current file descriptor offset will
		391	be used (and updated), otherwise the file descriptor offset will not be
		392	changed by these calls.
		393
		394	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		395
		396	If C<$dataoffset> is less than zero, it will be counted from the end of
		397	C<$data>.
		398
168	The C<$data> scalar I<MUST NOT> be modified in any way while the request	399	The C<$data> scalar I<MUST NOT> be modified in any way while the request
169	is outstanding. Modifying it can result in segfaults or WW3 (if the	400	is outstanding. Modifying it can result in segfaults or World War III (if
170	necessary/optional hardware is installed).	401	the necessary/optional hardware is installed).
171		402
172	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	403	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
173	offset C<0> within the scalar:	404	offset C<0> within the scalar:
174		405
175	aio_read $fh, 7, 15, $buffer, 0, sub {	406	aio_read $fh, 7, 15, $buffer, 0, sub {
176	$_[0] > 0 or die "read error: $!";	407	$_[0] > 0 or die "read error: $!";
177	print "read $_[0] bytes: <$buffer>\n";	408	print "read $_[0] bytes: <$buffer>\n";
178	};	409	};
179		410
180	=item aio_move $srcpath, $dstpath, $callback->($status)
181
182	Try to move the I<file> (directories not supported as either source or
183	destination) from C<$srcpath> to C<$dstpath> and call the callback with
184	the C<0> (error) or C<-1> ok.
185
186	This is a composite request that tries to rename(2) the file first. If
187	rename files with C<EXDEV>, it creates the destination file with mode 0200
188	and copies the contents of the source file into it using C<aio_sendfile>,
189	followed by restoring atime, mtime, access mode and uid/gid, in that
190	order, and unlinking the C<$srcpath>.
191
192	If an error occurs, the partial destination file will be unlinked, if
193	possible, except when setting atime, mtime, access mode and uid/gid, where
194	errors are being ignored.
195
196	=cut
197
198	sub aio_move($$$) {
199	my ($src, $dst, $cb) = @_;
200
201	aio_rename $src, $dst, sub {
202	if ($_[0] && $! == EXDEV) {
203	aio_open $src, O_RDONLY, 0, sub {
204	if (my $src_fh = $_[0]) {
205	my @stat = stat $src_fh;
206
207	aio_open $dst, O_WRONLY, 0200, sub {
208	if (my $dst_fh = $_[0]) {
209	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
210	close $src_fh;
211
212	if ($_[0] == $stat[7]) {
213	utime $stat[8], $stat[9], $dst;
214	chmod $stat[2] & 07777, $dst_fh;
215	chown $stat[4], $stat[5], $dst_fh;
216	close $dst_fh;
217
218	aio_unlink $src, sub {
219	$cb->($_[0]);
220	};
221	} else {
222	my $errno = $!;
223	aio_unlink $dst, sub {
224	$! = $errno;
225	$cb->(-1);
226	};
227	}
228	};
229	} else {
230	$cb->(-1);
231	}
232	},
233
234	} else {
235	$cb->(-1);
236	}
237	};
238	} else {
239	$cb->($_[0]);
240	}
241	};
242	}
243		411
244	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	412	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
245		413
246	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	414	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
247	reading at byte offset C<$in_offset>, and starts writing at the current	415	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
261	C<$in_fh> than are written, and there is no way to find out how many	429	C<$in_fh> than are written, and there is no way to find out how many
262	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	430	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
263	provides the number of bytes written to C<$out_fh>. Only if the result	431	provides the number of bytes written to C<$out_fh>. Only if the result
264	value equals C<$length> one can assume that C<$length> bytes have been	432	value equals C<$length> one can assume that C<$length> bytes have been
265	read.	433	read.
		434
266		435
267	=item aio_readahead $fh,$offset,$length, $callback->($retval)	436	=item aio_readahead $fh,$offset,$length, $callback->($retval)
268		437
269	C<aio_readahead> populates the page cache with data from a file so that	438	C<aio_readahead> populates the page cache with data from a file so that
270	subsequent reads from that file will not block on disk I/O. The C<$offset>	439	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
276	file. The current file offset of the file is left unchanged.	445	file. The current file offset of the file is left unchanged.
277		446
278	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	447	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
279	emulated by simply reading the data, which would have a similar effect.	448	emulated by simply reading the data, which would have a similar effect.
280		449
		450
281	=item aio_stat $fh_or_path, $callback->($status)	451	=item aio_stat $fh_or_path, $callback->($status)
282		452
283	=item aio_lstat $fh, $callback->($status)	453	=item aio_lstat $fh, $callback->($status)
284		454
285	Works like perl's C<stat> or C<lstat> in void context. The callback will	455	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
298	aio_stat "/etc/passwd", sub {	468	aio_stat "/etc/passwd", sub {
299	$_[0] and die "stat failed: $!";	469	$_[0] and die "stat failed: $!";
300	print "size is ", -s _, "\n";	470	print "size is ", -s _, "\n";
301	};	471	};
302		472
		473
		474	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		475
		476	Works like perl's C<utime> function (including the special case of $atime
		477	and $mtime being undef). Fractional times are supported if the underlying
		478	syscalls support them.
		479
		480	When called with a pathname, uses utimes(2) if available, otherwise
		481	utime(2). If called on a file descriptor, uses futimes(2) if available,
		482	otherwise returns ENOSYS, so this is not portable.
		483
		484	Examples:
		485
		486	# set atime and mtime to current time (basically touch(1)):
		487	aio_utime "path", undef, undef;
		488	# set atime to current time and mtime to beginning of the epoch:
		489	aio_utime "path", time, undef; # undef==0
		490
		491
		492	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		493
		494	Works like perl's C<chown> function, except that C<undef> for either $uid
		495	or $gid is being interpreted as "do not change" (but -1 can also be used).
		496
		497	Examples:
		498
		499	# same as "chown root path" in the shell:
		500	aio_chown "path", 0, -1;
		501	# same as above:
		502	aio_chown "path", 0, undef;
		503
		504
		505	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		506
		507	Works like truncate(2) or ftruncate(2).
		508
		509
		510	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		511
		512	Works like perl's C<chmod> function.
		513
		514
303	=item aio_unlink $pathname, $callback->($status)	515	=item aio_unlink $pathname, $callback->($status)
304		516
305	Asynchronously unlink (delete) a file and call the callback with the	517	Asynchronously unlink (delete) a file and call the callback with the
306	result code.	518	result code.
307		519
		520
		521	=item aio_mknod $path, $mode, $dev, $callback->($status)
		522
		523	[EXPERIMENTAL]
		524
		525	Asynchronously create a device node (or fifo). See mknod(2).
		526
		527	The only (POSIX-) portable way of calling this function is:
		528
		529	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		530
		531
308	=item aio_link $srcpath, $dstpath, $callback->($status)	532	=item aio_link $srcpath, $dstpath, $callback->($status)
309		533
310	Asynchronously create a new link to the existing object at C<$srcpath> at	534	Asynchronously create a new link to the existing object at C<$srcpath> at
311	the path C<$dstpath> and call the callback with the result code.	535	the path C<$dstpath> and call the callback with the result code.
312		536
		537
313	=item aio_symlink $srcpath, $dstpath, $callback->($status)	538	=item aio_symlink $srcpath, $dstpath, $callback->($status)
314		539
315	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	540	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
316	the path C<$dstpath> and call the callback with the result code.	541	the path C<$dstpath> and call the callback with the result code.
317		542
		543
		544	=item aio_readlink $path, $callback->($link)
		545
		546	Asynchronously read the symlink specified by C<$path> and pass it to
		547	the callback. If an error occurs, nothing or undef gets passed to the
		548	callback.
		549
		550
318	=item aio_rename $srcpath, $dstpath, $callback->($status)	551	=item aio_rename $srcpath, $dstpath, $callback->($status)
319		552
320	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	553	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
321	rename(2) and call the callback with the result code.	554	rename(2) and call the callback with the result code.
322		555
		556
		557	=item aio_mkdir $pathname, $mode, $callback->($status)
		558
		559	Asynchronously mkdir (create) a directory and call the callback with
		560	the result code. C<$mode> will be modified by the umask at the time the
		561	request is executed, so do not change your umask.
		562
		563
323	=item aio_rmdir $pathname, $callback->($status)	564	=item aio_rmdir $pathname, $callback->($status)
324		565
325	Asynchronously rmdir (delete) a directory and call the callback with the	566	Asynchronously rmdir (delete) a directory and call the callback with the
326	result code.	567	result code.
		568
327		569
328	=item aio_readdir $pathname, $callback->($entries)	570	=item aio_readdir $pathname, $callback->($entries)
329		571
330	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	572	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
331	directory (i.e. opendir + readdir + closedir). The entries will not be	573	directory (i.e. opendir + readdir + closedir). The entries will not be
332	sorted, and will B<NOT> include the C<.> and C<..> entries.	574	sorted, and will B<NOT> include the C<.> and C<..> entries.
333		575
334	The callback a single argument which is either C<undef> or an array-ref	576	The callback a single argument which is either C<undef> or an array-ref
335	with the filenames.	577	with the filenames.
336		578
		579
		580	=item aio_load $path, $data, $callback->($status)
		581
		582	This is a composite request that tries to fully load the given file into
		583	memory. Status is the same as with aio_read.
		584
		585	=cut
		586
		587	sub aio_load($$;$) {
		588	aio_block {
		589	my ($path, undef, $cb) = @_;
		590	my $data = \$_[1];
		591
		592	my $pri = aioreq_pri;
		593	my $grp = aio_group $cb;
		594
		595	aioreq_pri $pri;
		596	add $grp aio_open $path, O_RDONLY, 0, sub {
		597	my $fh = shift
		598	or return $grp->result (-1);
		599
		600	aioreq_pri $pri;
		601	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		602	$grp->result ($_[0]);
		603	};
		604	};
		605
		606	$grp
		607	}
		608	}
		609
		610	=item aio_copy $srcpath, $dstpath, $callback->($status)
		611
		612	Try to copy the I<file> (directories not supported as either source or
		613	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		614	the C<0> (error) or C<-1> ok.
		615
		616	This is a composite request that it creates the destination file with
		617	mode 0200 and copies the contents of the source file into it using
		618	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		619	uid/gid, in that order.
		620
		621	If an error occurs, the partial destination file will be unlinked, if
		622	possible, except when setting atime, mtime, access mode and uid/gid, where
		623	errors are being ignored.
		624
		625	=cut
		626
		627	sub aio_copy($$;$) {
		628	aio_block {
		629	my ($src, $dst, $cb) = @_;
		630
		631	my $pri = aioreq_pri;
		632	my $grp = aio_group $cb;
		633
		634	aioreq_pri $pri;
		635	add $grp aio_open $src, O_RDONLY, 0, sub {
		636	if (my $src_fh = $_[0]) {
		637	my @stat = stat $src_fh;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		641	if (my $dst_fh = $_[0]) {
		642	aioreq_pri $pri;
		643	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		644	if ($_[0] == $stat[7]) {
		645	$grp->result (0);
		646	close $src_fh;
		647
		648	# those should not normally block. should. should.
		649	utime $stat[8], $stat[9], $dst;
		650	chmod $stat[2] & 07777, $dst_fh;
		651	chown $stat[4], $stat[5], $dst_fh;
		652	close $dst_fh;
		653	} else {
		654	$grp->result (-1);
		655	close $src_fh;
		656	close $dst_fh;
		657
		658	aioreq $pri;
		659	add $grp aio_unlink $dst;
		660	}
		661	};
		662	} else {
		663	$grp->result (-1);
		664	}
		665	},
		666
		667	} else {
		668	$grp->result (-1);
		669	}
		670	};
		671
		672	$grp
		673	}
		674	}
		675
		676	=item aio_move $srcpath, $dstpath, $callback->($status)
		677
		678	Try to move the I<file> (directories not supported as either source or
		679	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		680	the C<0> (error) or C<-1> ok.
		681
		682	This is a composite request that tries to rename(2) the file first. If
		683	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		684	that is successful, unlinking the C<$srcpath>.
		685
		686	=cut
		687
		688	sub aio_move($$;$) {
		689	aio_block {
		690	my ($src, $dst, $cb) = @_;
		691
		692	my $pri = aioreq_pri;
		693	my $grp = aio_group $cb;
		694
		695	aioreq_pri $pri;
		696	add $grp aio_rename $src, $dst, sub {
		697	if ($_[0] && $! == EXDEV) {
		698	aioreq_pri $pri;
		699	add $grp aio_copy $src, $dst, sub {
		700	$grp->result ($_[0]);
		701
		702	if (!$_[0]) {
		703	aioreq_pri $pri;
		704	add $grp aio_unlink $src;
		705	}
		706	};
		707	} else {
		708	$grp->result ($_[0]);
		709	}
		710	};
		711
		712	$grp
		713	}
		714	}
		715
337	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	716	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
338		717
339	Scans a directory (similar to C<aio_readdir>) but additionally tries to	718	Scans a directory (similar to C<aio_readdir>) but additionally tries to
340	separate the entries of directory C<$path> into two sets of names, ones	719	efficiently separate the entries of directory C<$path> into two sets of
341	you can recurse into (directories or links to them), and ones you cannot	720	names, directories you can recurse into (directories), and ones you cannot
342	recurse into (everything else).	721	recurse into (everything else, including symlinks to directories).
343		722
344	C<aio_scandir> is a composite request that consists of many sub	723	C<aio_scandir> is a composite request that creates of many sub requests_
345	requests. C<$maxreq> specifies the maximum number of outstanding aio	724	C<$maxreq> specifies the maximum number of outstanding aio requests that
346	requests that this function generates. If it is C<< <= 0 >>, then a	725	this function generates. If it is C<< <= 0 >>, then a suitable default
347	suitable default will be chosen (currently 8).	726	will be chosen (currently 4).
348		727
349	On error, the callback is called without arguments, otherwise it receives	728	On error, the callback is called without arguments, otherwise it receives
350	two array-refs with path-relative entry names.	729	two array-refs with path-relative entry names.
351		730
352	Example:	731	Example:
…		…
386	as those tend to return 0 or 1 as link counts, which disables the	765	as those tend to return 0 or 1 as link counts, which disables the
387	directory counting heuristic.	766	directory counting heuristic.
388		767
389	=cut	768	=cut
390		769
391	sub aio_scandir($$$) {	770	sub aio_scandir($$;$) {
		771	aio_block {
392	my ($path, $maxreq, $cb) = @_;	772	my ($path, $maxreq, $cb) = @_;
393		773
		774	my $pri = aioreq_pri;
		775
		776	my $grp = aio_group $cb;
		777
394	$maxreq = 8 if $maxreq <= 0;	778	$maxreq = 4 if $maxreq <= 0;
395		779
396	# stat once	780	# stat once
		781	aioreq_pri $pri;
397	aio_stat $path, sub {	782	add $grp aio_stat $path, sub {
398	return $cb->() if $_[0];	783	return $grp->result () if $_[0];
399	my $now = time;	784	my $now = time;
400	my $hash1 = join ":", (stat _)[0,1,3,7,9];	785	my $hash1 = join ":", (stat _)[0,1,3,7,9];
401		786
402	# read the directory entries	787	# read the directory entries
		788	aioreq_pri $pri;
403	aio_readdir $path, sub {	789	add $grp aio_readdir $path, sub {
404	my $entries = shift	790	my $entries = shift
405	or return $cb->();	791	or return $grp->result ();
406		792
407	# stat the dir another time	793	# stat the dir another time
		794	aioreq_pri $pri;
408	aio_stat $path, sub {	795	add $grp aio_stat $path, sub {
409	my $hash2 = join ":", (stat _)[0,1,3,7,9];	796	my $hash2 = join ":", (stat _)[0,1,3,7,9];
410		797
411	my $ndirs;	798	my $ndirs;
412		799
413	# take the slow route if anything looks fishy	800	# take the slow route if anything looks fishy
414	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	801	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
415	$ndirs = -1;	802	$ndirs = -1;
416	} else {	803	} else {
417	# if nlink == 2, we are finished	804	# if nlink == 2, we are finished
418	# on non-posix-fs's, we rely on nlink < 2	805	# on non-posix-fs's, we rely on nlink < 2
419	$ndirs = (stat _)[3] - 2	806	$ndirs = (stat _)[3] - 2
420	or return $cb->([], $entries);	807	or return $grp->result ([], $entries);
421	}
422
423	# sort into likely dirs and likely nondirs
424	# dirs == files without ".", short entries first
425	$entries = [map $_->[0],
426	sort { $b->[1] cmp $a->[1] }
427	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
428	@$entries];
429
430	my (@dirs, @nondirs);
431
432	my ($statcb, $schedcb);
433	my $nreq = 0;
434
435	$schedcb = sub {
436	if (@$entries) {
437	if ($nreq < $maxreq) {
438	my $ent = pop @$entries;
439	$nreq++;
440	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
441	}
442	} elsif (!$nreq) {
443	# finished
444	undef $statcb;
445	undef $schedcb;
446	$cb->(\@dirs, \@nondirs) if $cb;
447	undef $cb;
448	}	808	}
		809
		810	# sort into likely dirs and likely nondirs
		811	# dirs == files without ".", short entries first
		812	$entries = [map $_->[0],
		813	sort { $b->[1] cmp $a->[1] }
		814	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		815	@$entries];
		816
		817	my (@dirs, @nondirs);
		818
		819	my $statgrp = add $grp aio_group sub {
		820	$grp->result (\@dirs, \@nondirs);
		821	};
		822
		823	limit $statgrp $maxreq;
		824	feed $statgrp sub {
		825	return unless @$entries;
		826	my $entry = pop @$entries;
		827
		828	aioreq_pri $pri;
		829	add $statgrp aio_stat "$path/$entry/.", sub {
		830	if ($_[0] < 0) {
		831	push @nondirs, $entry;
		832	} else {
		833	# need to check for real directory
		834	aioreq_pri $pri;
		835	add $statgrp aio_lstat "$path/$entry", sub {
		836	if (-d _) {
		837	push @dirs, $entry;
		838
		839	unless (--$ndirs) {
		840	push @nondirs, @$entries;
		841	feed $statgrp;
		842	}
		843	} else {
		844	push @nondirs, $entry;
		845	}
		846	}
		847	}
		848	};
		849	};
449	};	850	};
450	$statcb = sub {
451	my ($status, $entry) = @_;
452
453	if ($status < 0) {
454	$nreq--;
455	push @nondirs, $entry;
456	&$schedcb;
457	} else {
458	# need to check for real directory
459	aio_lstat "$path/$entry", sub {
460	$nreq--;
461
462	if (-d _) {
463	push @dirs, $entry;
464
465	if (!--$ndirs) {
466	push @nondirs, @$entries;
467	$entries = [];
468	}
469	} else {
470	push @nondirs, $entry;
471	}
472
473	&$schedcb;
474	}
475	}
476	};
477
478	&$schedcb while @$entries && $nreq < $maxreq;
479	};	851	};
480	};	852	};
		853
		854	$grp
481	};	855	}
		856	}
		857
		858	=item aio_rmtree $path, $callback->($status)
		859
		860	Delete a directory tree starting (and including) C<$path>, return the
		861	status of the final C<rmdir> only. This is a composite request that
		862	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		863	everything else.
		864
		865	=cut
		866
		867	sub aio_rmtree;
		868	sub aio_rmtree($;$) {
		869	aio_block {
		870	my ($path, $cb) = @_;
		871
		872	my $pri = aioreq_pri;
		873	my $grp = aio_group $cb;
		874
		875	aioreq_pri $pri;
		876	add $grp aio_scandir $path, 0, sub {
		877	my ($dirs, $nondirs) = @_;
		878
		879	my $dirgrp = aio_group sub {
		880	add $grp aio_rmdir $path, sub {
		881	$grp->result ($_[0]);
		882	};
		883	};
		884
		885	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		886	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		887
		888	add $grp $dirgrp;
		889	};
		890
		891	$grp
		892	}
482	}	893	}
483		894
484	=item aio_fsync $fh, $callback->($status)	895	=item aio_fsync $fh, $callback->($status)
485		896
486	Asynchronously call fsync on the given filehandle and call the callback	897	Asynchronously call fsync on the given filehandle and call the callback
…		…
492	callback with the fdatasync result code.	903	callback with the fdatasync result code.
493		904
494	If this call isn't available because your OS lacks it or it couldn't be	905	If this call isn't available because your OS lacks it or it couldn't be
495	detected, it will be emulated by calling C<fsync> instead.	906	detected, it will be emulated by calling C<fsync> instead.
496		907
		908	=item aio_group $callback->(...)
		909
		910	This is a very special aio request: Instead of doing something, it is a
		911	container for other aio requests, which is useful if you want to bundle
		912	many requests into a single, composite, request with a definite callback
		913	and the ability to cancel the whole request with its subrequests.
		914
		915	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		916	for more info.
		917
		918	Example:
		919
		920	my $grp = aio_group sub {
		921	print "all stats done\n";
		922	};
		923
		924	add $grp
		925	(aio_stat ...),
		926	(aio_stat ...),
		927	...;
		928
		929	=item aio_nop $callback->()
		930
		931	This is a special request - it does nothing in itself and is only used for
		932	side effects, such as when you want to add a dummy request to a group so
		933	that finishing the requests in the group depends on executing the given
		934	code.
		935
		936	While this request does nothing, it still goes through the execution
		937	phase and still requires a worker thread. Thus, the callback will not
		938	be executed immediately but only after other requests in the queue have
		939	entered their execution phase. This can be used to measure request
		940	latency.
		941
		942	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		943
		944	Mainly used for debugging and benchmarking, this aio request puts one of
		945	the request workers to sleep for the given time.
		946
		947	While it is theoretically handy to have simple I/O scheduling requests
		948	like sleep and file handle readable/writable, the overhead this creates is
		949	immense (it blocks a thread for a long time) so do not use this function
		950	except to put your application under artificial I/O pressure.
		951
497	=back	952	=back
498		953
499	=head2 IO::AIO::CB CLASS	954	=head2 IO::AIO::REQ CLASS
500		955
501	All non-aggregate C<aio_*> functions return an object of this class when	956	All non-aggregate C<aio_*> functions return an object of this class when
502	called in non-void context.	957	called in non-void context.
503		958
504	A request always moves through the following five states in its lifetime,
505	in order: B<ready> (request has been created, but has not been executed
506	yet), B<execute> (request is currently being executed), B<pending>
507	(request has been executed but callback has not been called yet),
508	B<result> (results are being processed synchronously, includes calling the
509	callback) and B<done> (request has reached the end of its lifetime and
510	holds no resources anymore).
511
512	=over 4	959	=over 4
513		960
514	=item $req->cancel	961	=item cancel $req
515		962
516	Cancels the request, if possible. Has the effect of skipping execution	963	Cancels the request, if possible. Has the effect of skipping execution
517	when entering the B<execute> state and skipping calling the callback when	964	when entering the B<execute> state and skipping calling the callback when
518	entering the the B<result> state, but will leave the request otherwise	965	entering the the B<result> state, but will leave the request otherwise
519	untouched. That means that requests that currently execute will not be	966	untouched. That means that requests that currently execute will not be
520	stopped and resources held by the request will not be freed prematurely.	967	stopped and resources held by the request will not be freed prematurely.
521		968
		969	=item cb $req $callback->(...)
		970
		971	Replace (or simply set) the callback registered to the request.
		972
522	=back	973	=back
523		974
		975	=head2 IO::AIO::GRP CLASS
		976
		977	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		978	objects of this class, too.
		979
		980	A IO::AIO::GRP object is a special request that can contain multiple other
		981	aio requests.
		982
		983	You create one by calling the C<aio_group> constructing function with a
		984	callback that will be called when all contained requests have entered the
		985	C<done> state:
		986
		987	my $grp = aio_group sub {
		988	print "all requests are done\n";
		989	};
		990
		991	You add requests by calling the C<add> method with one or more
		992	C<IO::AIO::REQ> objects:
		993
		994	$grp->add (aio_unlink "...");
		995
		996	add $grp aio_stat "...", sub {
		997	$_[0] or return $grp->result ("error");
		998
		999	# add another request dynamically, if first succeeded
		1000	add $grp aio_open "...", sub {
		1001	$grp->result ("ok");
		1002	};
		1003	};
		1004
		1005	This makes it very easy to create composite requests (see the source of
		1006	C<aio_move> for an application) that work and feel like simple requests.
		1007
		1008	=over 4
		1009
		1010	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1011	C<IO::AIO::poll_cb>, just like any other request.
		1012
		1013	=item * They can be canceled like any other request. Canceling will cancel not
		1014	only the request itself, but also all requests it contains.
		1015
		1016	=item * They can also can also be added to other IO::AIO::GRP objects.
		1017
		1018	=item * You must not add requests to a group from within the group callback (or
		1019	any later time).
		1020
		1021	=back
		1022
		1023	Their lifetime, simplified, looks like this: when they are empty, they
		1024	will finish very quickly. If they contain only requests that are in the
		1025	C<done> state, they will also finish. Otherwise they will continue to
		1026	exist.
		1027
		1028	That means after creating a group you have some time to add requests. And
		1029	in the callbacks of those requests, you can add further requests to the
		1030	group. And only when all those requests have finished will the the group
		1031	itself finish.
		1032
		1033	=over 4
		1034
		1035	=item add $grp ...
		1036
		1037	=item $grp->add (...)
		1038
		1039	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1040	be added, including other groups, as long as you do not create circular
		1041	dependencies.
		1042
		1043	Returns all its arguments.
		1044
		1045	=item $grp->cancel_subs
		1046
		1047	Cancel all subrequests and clears any feeder, but not the group request
		1048	itself. Useful when you queued a lot of events but got a result early.
		1049
		1050	=item $grp->result (...)
		1051
		1052	Set the result value(s) that will be passed to the group callback when all
		1053	subrequests have finished and set thre groups errno to the current value
		1054	of errno (just like calling C<errno> without an error number). By default,
		1055	no argument will be passed and errno is zero.
		1056
		1057	=item $grp->errno ([$errno])
		1058
		1059	Sets the group errno value to C<$errno>, or the current value of errno
		1060	when the argument is missing.
		1061
		1062	Every aio request has an associated errno value that is restored when
		1063	the callback is invoked. This method lets you change this value from its
		1064	default (0).
		1065
		1066	Calling C<result> will also set errno, so make sure you either set C<$!>
		1067	before the call to C<result>, or call c<errno> after it.
		1068
		1069	=item feed $grp $callback->($grp)
		1070
		1071	Sets a feeder/generator on this group: every group can have an attached
		1072	generator that generates requests if idle. The idea behind this is that,
		1073	although you could just queue as many requests as you want in a group,
		1074	this might starve other requests for a potentially long time. For
		1075	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1076	requests, delaying any later requests for a long time.
		1077
		1078	To avoid this, and allow incremental generation of requests, you can
		1079	instead a group and set a feeder on it that generates those requests. The
		1080	feed callback will be called whenever there are few enough (see C<limit>,
		1081	below) requests active in the group itself and is expected to queue more
		1082	requests.
		1083
		1084	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1085	not impose any limits).
		1086
		1087	If the feed does not queue more requests when called, it will be
		1088	automatically removed from the group.
		1089
		1090	If the feed limit is C<0>, it will be set to C<2> automatically.
		1091
		1092	Example:
		1093
		1094	# stat all files in @files, but only ever use four aio requests concurrently:
		1095
		1096	my $grp = aio_group sub { print "finished\n" };
		1097	limit $grp 4;
		1098	feed $grp sub {
		1099	my $file = pop @files
		1100	or return;
		1101
		1102	add $grp aio_stat $file, sub { ... };
		1103	};
		1104
		1105	=item limit $grp $num
		1106
		1107	Sets the feeder limit for the group: The feeder will be called whenever
		1108	the group contains less than this many requests.
		1109
		1110	Setting the limit to C<0> will pause the feeding process.
		1111
		1112	=back
		1113
524	=head2 SUPPORT FUNCTIONS	1114	=head2 SUPPORT FUNCTIONS
		1115
		1116	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
525		1117
526	=over 4	1118	=over 4
527		1119
528	=item $fileno = IO::AIO::poll_fileno	1120	=item $fileno = IO::AIO::poll_fileno
529		1121
…		…
534		1126
535	See C<poll_cb> for an example.	1127	See C<poll_cb> for an example.
536		1128
537	=item IO::AIO::poll_cb	1129	=item IO::AIO::poll_cb
538		1130
539	Process all outstanding events on the result pipe. You have to call this	1131	Process some outstanding events on the result pipe. You have to call this
540	regularly. Returns the number of events processed. Returns immediately	1132	regularly. Returns the number of events processed. Returns immediately
541	when no events are outstanding.	1133	when no events are outstanding. The amount of events processed depends on
		1134	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1135
		1136	If not all requests were processed for whatever reason, the filehandle
		1137	will still be ready when C<poll_cb> returns.
542		1138
543	Example: Install an Event watcher that automatically calls	1139	Example: Install an Event watcher that automatically calls
544	IO::AIO::poll_cb with high priority:	1140	IO::AIO::poll_cb with high priority:
545		1141
546	Event->io (fd => IO::AIO::poll_fileno,	1142	Event->io (fd => IO::AIO::poll_fileno,
547	poll => 'r', async => 1,	1143	poll => 'r', async => 1,
548	cb => \&IO::AIO::poll_cb);	1144	cb => \&IO::AIO::poll_cb);
549		1145
		1146	=item IO::AIO::max_poll_reqs $nreqs
		1147
		1148	=item IO::AIO::max_poll_time $seconds
		1149
		1150	These set the maximum number of requests (default C<0>, meaning infinity)
		1151	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1152	the maximum amount of time (default C<0>, meaning infinity) spent in
		1153	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1154	of time C<poll_cb> is allowed to use).
		1155
		1156	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1157	syscall per request processed, which is not normally a problem unless your
		1158	callbacks are really really fast or your OS is really really slow (I am
		1159	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1160
		1161	Setting these is useful if you want to ensure some level of
		1162	interactiveness when perl is not fast enough to process all requests in
		1163	time.
		1164
		1165	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1166
		1167	Example: Install an Event watcher that automatically calls
		1168	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1169	program get the CPU sometimes even under high AIO load.
		1170
		1171	# try not to spend much more than 0.1s in poll_cb
		1172	IO::AIO::max_poll_time 0.1;
		1173
		1174	# use a low priority so other tasks have priority
		1175	Event->io (fd => IO::AIO::poll_fileno,
		1176	poll => 'r', nice => 1,
		1177	cb => &IO::AIO::poll_cb);
		1178
550	=item IO::AIO::poll_wait	1179	=item IO::AIO::poll_wait
551		1180
		1181	If there are any outstanding requests and none of them in the result
552	Wait till the result filehandle becomes ready for reading (simply does a	1182	phase, wait till the result filehandle becomes ready for reading (simply
553	C<select> on the filehandle. This is useful if you want to synchronously wait	1183	does a C<select> on the filehandle. This is useful if you want to
554	for some requests to finish).	1184	synchronously wait for some requests to finish).
555		1185
556	See C<nreqs> for an example.	1186	See C<nreqs> for an example.
557		1187
		1188	=item IO::AIO::poll
		1189
		1190	Waits until some requests have been handled.
		1191
		1192	Returns the number of requests processed, but is otherwise strictly
		1193	equivalent to:
		1194
		1195	IO::AIO::poll_wait, IO::AIO::poll_cb
		1196
558	=item IO::AIO::nreqs	1197	=item IO::AIO::flush
559		1198
560	Returns the number of requests currently outstanding (i.e. for which their	1199	Wait till all outstanding AIO requests have been handled.
561	callback has not been invoked yet).
562		1200
563	Example: wait till there are no outstanding requests anymore:	1201	Strictly equivalent to:
564		1202
565	IO::AIO::poll_wait, IO::AIO::poll_cb	1203	IO::AIO::poll_wait, IO::AIO::poll_cb
566	while IO::AIO::nreqs;	1204	while IO::AIO::nreqs;
567		1205
568	=item IO::AIO::flush	1206	=back
569		1207
570	Wait till all outstanding AIO requests have been handled.	1208	=head3 CONTROLLING THE NUMBER OF THREADS
571		1209
572	Strictly equivalent to:	1210	=over
573
574	IO::AIO::poll_wait, IO::AIO::poll_cb
575	while IO::AIO::nreqs;
576
577	=item IO::AIO::poll
578
579	Waits until some requests have been handled.
580
581	Strictly equivalent to:
582
583	IO::AIO::poll_wait, IO::AIO::poll_cb
584	if IO::AIO::nreqs;
585		1211
586	=item IO::AIO::min_parallel $nthreads	1212	=item IO::AIO::min_parallel $nthreads
587		1213
588	Set the minimum number of AIO threads to C<$nthreads>. The current default	1214	Set the minimum number of AIO threads to C<$nthreads>. The current
589	is C<4>, which means four asynchronous operations can be done at one time	1215	default is C<8>, which means eight asynchronous operations can execute
590	(the number of outstanding operations, however, is unlimited).	1216	concurrently at any one time (the number of outstanding requests,
		1217	however, is unlimited).
591		1218
592	IO::AIO starts threads only on demand, when an AIO request is queued and	1219	IO::AIO starts threads only on demand, when an AIO request is queued and
593	no free thread exists.	1220	no free thread exists. Please note that queueing up a hundred requests can
		1221	create demand for a hundred threads, even if it turns out that everything
		1222	is in the cache and could have been processed faster by a single thread.
594		1223
595	It is recommended to keep the number of threads low, as some Linux	1224	It is recommended to keep the number of threads relatively low, as some
596	kernel versions will scale negatively with the number of threads (higher	1225	Linux kernel versions will scale negatively with the number of threads
597	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1226	(higher parallelity => MUCH higher latency). With current Linux 2.6
598	threads should be fine.	1227	versions, 4-32 threads should be fine.
599		1228
600	Under most circumstances you don't need to call this function, as the	1229	Under most circumstances you don't need to call this function, as the
601	module selects a default that is suitable for low to moderate load.	1230	module selects a default that is suitable for low to moderate load.
602		1231
603	=item IO::AIO::max_parallel $nthreads	1232	=item IO::AIO::max_parallel $nthreads
…		…
612	This module automatically runs C<max_parallel 0> at program end, to ensure	1241	This module automatically runs C<max_parallel 0> at program end, to ensure
613	that all threads are killed and that there are no outstanding requests.	1242	that all threads are killed and that there are no outstanding requests.
614		1243
615	Under normal circumstances you don't need to call this function.	1244	Under normal circumstances you don't need to call this function.
616		1245
		1246	=item IO::AIO::max_idle $nthreads
		1247
		1248	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1249	threads that did not get a request to process within 10 seconds). That
		1250	means if a thread becomes idle while C<$nthreads> other threads are also
		1251	idle, it will free its resources and exit.
		1252
		1253	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1254	to allow for extremely high load situations, but want to free resources
		1255	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1256
		1257	The default is probably ok in most situations, especially if thread
		1258	creation is fast. If thread creation is very slow on your system you might
		1259	want to use larger values.
		1260
617	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1261	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1262
		1263	This is a very bad function to use in interactive programs because it
		1264	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1265	use an C<aio_group> together with a feed callback.
618		1266
619	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1267	Sets the maximum number of outstanding requests to C<$nreqs>. If you
620	try to queue up more than this number of requests, the caller will block until	1268	do queue up more than this number of requests, the next call to the
621	some requests have been handled.	1269	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1270	function will block until the limit is no longer exceeded.
622		1271
623	The default is very large, so normally there is no practical limit. If you	1272	The default value is very large, so there is no practical limit on the
624	queue up many requests in a loop it often improves speed if you set	1273	number of outstanding requests.
625	this to a relatively low number, such as C<100>.
626		1274
627	Under normal circumstances you don't need to call this function.	1275	You can still queue as many requests as you want. Therefore,
		1276	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1277	as a stop gap to shield against fatal memory overflow (with large values).
628		1278
629	=back	1279	=back
630		1280
		1281	=head3 STATISTICAL INFORMATION
		1282
		1283	=over
		1284
		1285	=item IO::AIO::nreqs
		1286
		1287	Returns the number of requests currently in the ready, execute or pending
		1288	states (i.e. for which their callback has not been invoked yet).
		1289
		1290	Example: wait till there are no outstanding requests anymore:
		1291
		1292	IO::AIO::poll_wait, IO::AIO::poll_cb
		1293	while IO::AIO::nreqs;
		1294
		1295	=item IO::AIO::nready
		1296
		1297	Returns the number of requests currently in the ready state (not yet
		1298	executed).
		1299
		1300	=item IO::AIO::npending
		1301
		1302	Returns the number of requests currently in the pending state (executed,
		1303	but not yet processed by poll_cb).
		1304
		1305	=back
		1306
631	=cut	1307	=cut
632		1308
633	# support function to convert a fd into a perl filehandle
634	sub _fd2fh {
635	return undef if $_[0] < 0;
636
637	# try to generate nice filehandles
638	my $sym = "IO::AIO::fd#$_[0]";
639	local *$sym;
640
641	open *$sym, "+<&=$_[0]" # usually works under any unix
642	or open *$sym, "<&=$_[0]" # cygwin needs this
643	or open *$sym, ">&=$_[0]" # or this
644	or return undef;
645
646	*$sym
647	}
648
649	min_parallel 4;	1309	min_parallel 8;
650		1310
651	END {	1311	END { flush }
652	max_parallel 0;
653	}
654		1312
655	1;	1313	1;
656		1314
657	=head2 FORK BEHAVIOUR	1315	=head2 FORK BEHAVIOUR
658		1316
659	This module should do "the right thing" when the process using it forks:	1317	This module should do "the right thing" when the process using it forks:
660		1318
661	Before the fork, IO::AIO enters a quiescent state where no requests	1319	Before the fork, IO::AIO enters a quiescent state where no requests
662	can be added in other threads and no results will be processed. After	1320	can be added in other threads and no results will be processed. After
663	the fork the parent simply leaves the quiescent state and continues	1321	the fork the parent simply leaves the quiescent state and continues
664	request/result processing, while the child clears the request/result	1322	request/result processing, while the child frees the request/result queue
665	queue (so the requests started before the fork will only be handled in	1323	(so that the requests started before the fork will only be handled in the
666	the parent). Threads will be started on demand until the limit ste in the	1324	parent). Threads will be started on demand until the limit set in the
667	parent process has been reached again.	1325	parent process has been reached again.
668		1326
669	In short: the parent will, after a short pause, continue as if fork had	1327	In short: the parent will, after a short pause, continue as if fork had
670	not been called, while the child will act as if IO::AIO has not been used	1328	not been called, while the child will act as if IO::AIO has not been used
671	yet.	1329	yet.
672		1330
		1331	=head2 MEMORY USAGE
		1332
		1333	Per-request usage:
		1334
		1335	Each aio request uses - depending on your architecture - around 100-200
		1336	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1337	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1338	scalars and other data passed into aio requests will also be locked and
		1339	will consume memory till the request has entered the done state.
		1340
		1341	This is not awfully much, so queuing lots of requests is not usually a
		1342	problem.
		1343
		1344	Per-thread usage:
		1345
		1346	In the execution phase, some aio requests require more memory for
		1347	temporary buffers, and each thread requires a stack and other data
		1348	structures (usually around 16k-128k, depending on the OS).
		1349
		1350	=head1 KNOWN BUGS
		1351
		1352	Known bugs will be fixed in the next release.
		1353
673	=head1 SEE ALSO	1354	=head1 SEE ALSO
674		1355
675	L<Coro>, L<Linux::AIO> (obsolete).	1356	L<Coro::AIO>.
676		1357
677	=head1 AUTHOR	1358	=head1 AUTHOR
678		1359
679	Marc Lehmann <schmorp@schmorp.de>	1360	Marc Lehmann <schmorp@schmorp.de>
680	http://home.schmorp.de/	1361	http://home.schmorp.de/

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