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Revision 1.54 by root, Sun Oct 22 00:19:05 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 = '1.99';	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	aio_group);	201	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	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);
83		208
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	209	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		210
86	require XSLoader;	211	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	212	XSLoader::load ("IO::AIO", $VERSION);
88	}	213	}
89		214
90	=head1 FUNCTIONS	215	=head1 FUNCTIONS
91		216
92	=head2 AIO FUNCTIONS	217	=head2 AIO REQUEST FUNCTIONS
93		218
94	All the C<aio_*> calls are more or less thin wrappers around the syscall	219	All the C<aio_*> calls are more or less thin wrappers around the syscall
95	with the same name (sans C<aio_>). The arguments are similar or identical,	220	with the same name (sans C<aio_>). The arguments are similar or identical,
96	and they all accept an additional (and optional) C<$callback> argument	221	and they all accept an additional (and optional) C<$callback> argument
97	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
…		…
100	syscall has been executed asynchronously.	225	syscall has been executed asynchronously.
101		226
102	All functions expecting a filehandle keep a copy of the filehandle	227	All functions expecting a filehandle keep a copy of the filehandle
103	internally until the request has finished.	228	internally until the request has finished.
104		229
105	All non-composite requests (requests that are not broken down into
106	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
107	further manipulation of running requests.	231	further manipulation of those requests while they are in-flight.
108		232
109	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
110	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
111	request is being executed, the current working directory could have	235	request is being executed, the current working directory could have
112	changed. Alternatively, you can make sure that you never change the	236	changed. Alternatively, you can make sure that you never change the
113	current working directory.	237	current working directory anywhere in the program and then use relative
		238	paths.
114		239
115	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
116	always pass in filenames you got from outside (command line, readdir	241	in filenames you got from outside (command line, readdir etc.) without
117	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
118	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
119	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)
120	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.
121		249
122	=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
123		284
124	=item aio_open $pathname, $flags, $mode, $callback->($fh)	285	=item aio_open $pathname, $flags, $mode, $callback->($fh)
125		286
126	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
127	created filehandle for the file.	288	created filehandle for the file.
…		…
133	list. They are the same as used by C<sysopen>.	294	list. They are the same as used by C<sysopen>.
134		295
135	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
136	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>,
137	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,
138	and C<0666> or C<0777> if you do).	299	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		300	by the umask in effect then the request is being executed, so better never
		301	change the umask.
139		302
140	Example:	303	Example:
141		304
142	aio_open "/etc/passwd", O_RDONLY, 0, sub {	305	aio_open "/etc/passwd", O_RDONLY, 0, sub {
143	if ($_[0]) {	306	if ($_[0]) {
…		…
146	} else {	309	} else {
147	die "open failed: $!\n";	310	die "open failed: $!\n";
148	}	311	}
149	};	312	};
150		313
		314
151	=item aio_close $fh, $callback->($status)	315	=item aio_close $fh, $callback->($status)
152		316
153	Asynchronously close a file and call the callback with the result	317	Asynchronously close a file and call the callback with the result
154	code. I<WARNING:> although accepted, you should not pass in a perl	318	code.
155	filehandle here, as perl will likely close the file descriptor another
156	time when the filehandle is destroyed. Normally, you can safely call perls
157	C<close> or just let filehandles go out of scope.
158		319
159	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
160	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
161		380
162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	381	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163		382
164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	383	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		384
166	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<$offset>
167	into the scalar given by C<data> and offset C<dataoffset> and calls the	386	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
168	callback without the actual number of bytes read (or -1 on error, just	387	callback without the actual number of bytes read (or -1 on error, just
169	like the syscall).	388	like the syscall).
170		389
		390	If C<$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
171	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
172	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
173	necessary/optional hardware is installed).	401	the necessary/optional hardware is installed).
174		402
175	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
176	offset C<0> within the scalar:	404	offset C<0> within the scalar:
177		405
178	aio_read $fh, 7, 15, $buffer, 0, sub {	406	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	407	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	408	print "read $_[0] bytes: <$buffer>\n";
181	};	409	};
182		410
183	=item aio_move $srcpath, $dstpath, $callback->($status)
184
185	Try to move the I<file> (directories not supported as either source or
186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
187	the C<0> (error) or C<-1> ok.
188
189	This is a composite request that tries to rename(2) the file first. If
190	rename files with C<EXDEV>, it creates the destination file with mode 0200
191	and copies the contents of the source file into it using C<aio_sendfile>,
192	followed by restoring atime, mtime, access mode and uid/gid, in that
193	order, and unlinking the C<$srcpath>.
194
195	If an error occurs, the partial destination file will be unlinked, if
196	possible, except when setting atime, mtime, access mode and uid/gid, where
197	errors are being ignored.
198
199	=cut
200
201	sub aio_move($$$) {
202	my ($src, $dst, $cb) = @_;
203
204	aio_rename $src, $dst, sub {
205	if ($_[0] && $! == EXDEV) {
206	aio_open $src, O_RDONLY, 0, sub {
207	if (my $src_fh = $_[0]) {
208	my @stat = stat $src_fh;
209
210	aio_open $dst, O_WRONLY, 0200, sub {
211	if (my $dst_fh = $_[0]) {
212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
213	close $src_fh;
214
215	if ($_[0] == $stat[7]) {
216	utime $stat[8], $stat[9], $dst;
217	chmod $stat[2] & 07777, $dst_fh;
218	chown $stat[4], $stat[5], $dst_fh;
219	close $dst_fh;
220
221	aio_unlink $src, sub {
222	$cb->($_[0]);
223	};
224	} else {
225	my $errno = $!;
226	aio_unlink $dst, sub {
227	$! = $errno;
228	$cb->(-1);
229	};
230	}
231	};
232	} else {
233	$cb->(-1);
234	}
235	},
236
237	} else {
238	$cb->(-1);
239	}
240	};
241	} else {
242	$cb->($_[0]);
243	}
244	};
245	}
246		411
247	=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)
248		413
249	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
250	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
…		…
264	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
265	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
266	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
267	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
268	read.	433	read.
		434
269		435
270	=item aio_readahead $fh,$offset,$length, $callback->($retval)	436	=item aio_readahead $fh,$offset,$length, $callback->($retval)
271		437
272	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
273	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>
…		…
279	file. The current file offset of the file is left unchanged.	445	file. The current file offset of the file is left unchanged.
280		446
281	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
282	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.
283		449
		450
284	=item aio_stat $fh_or_path, $callback->($status)	451	=item aio_stat $fh_or_path, $callback->($status)
285		452
286	=item aio_lstat $fh, $callback->($status)	453	=item aio_lstat $fh, $callback->($status)
287		454
288	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
…		…
301	aio_stat "/etc/passwd", sub {	468	aio_stat "/etc/passwd", sub {
302	$_[0] and die "stat failed: $!";	469	$_[0] and die "stat failed: $!";
303	print "size is ", -s _, "\n";	470	print "size is ", -s _, "\n";
304	};	471	};
305		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
306	=item aio_unlink $pathname, $callback->($status)	515	=item aio_unlink $pathname, $callback->($status)
307		516
308	Asynchronously unlink (delete) a file and call the callback with the	517	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	518	result code.
310		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
311	=item aio_link $srcpath, $dstpath, $callback->($status)	532	=item aio_link $srcpath, $dstpath, $callback->($status)
312		533
313	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
314	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.
315		536
		537
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	538	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		539
318	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
319	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.
320		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
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	551	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		552
323	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
324	rename(2) and call the callback with the result code.	554	rename(2) and call the callback with the result code.
325		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
326	=item aio_rmdir $pathname, $callback->($status)	564	=item aio_rmdir $pathname, $callback->($status)
327		565
328	Asynchronously rmdir (delete) a directory and call the callback with the	566	Asynchronously rmdir (delete) a directory and call the callback with the
329	result code.	567	result code.
		568
330		569
331	=item aio_readdir $pathname, $callback->($entries)	570	=item aio_readdir $pathname, $callback->($entries)
332		571
333	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
334	directory (i.e. opendir + readdir + closedir). The entries will not be	573	directory (i.e. opendir + readdir + closedir). The entries will not be
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	574	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		575
337	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
338	with the filenames.	577	with the filenames.
339		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
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	716	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		717
342	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
343	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
344	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
345	recurse into (everything else).	721	recurse into (everything else, including symlinks to directories).
346		722
347	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_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	724	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	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
350	suitable default will be chosen (currently 8).	726	will be chosen (currently 4).
351		727
352	On error, the callback is called without arguments, otherwise it receives	728	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	729	two array-refs with path-relative entry names.
354		730
355	Example:	731	Example:
…		…
389	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
390	directory counting heuristic.	766	directory counting heuristic.
391		767
392	=cut	768	=cut
393		769
394	sub aio_scandir($$$) {	770	sub aio_scandir($$;$) {
		771	aio_block {
395	my ($path, $maxreq, $cb) = @_;	772	my ($path, $maxreq, $cb) = @_;
396		773
		774	my $pri = aioreq_pri;
		775
		776	my $grp = aio_group $cb;
		777
397	$maxreq = 8 if $maxreq <= 0;	778	$maxreq = 4 if $maxreq <= 0;
398		779
399	# stat once	780	# stat once
		781	aioreq_pri $pri;
400	aio_stat $path, sub {	782	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	783	return $grp->result () if $_[0];
402	my $now = time;	784	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	785	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		786
405	# read the directory entries	787	# read the directory entries
		788	aioreq_pri $pri;
406	aio_readdir $path, sub {	789	add $grp aio_readdir $path, sub {
407	my $entries = shift	790	my $entries = shift
408	or return $cb->();	791	or return $grp->result ();
409		792
410	# stat the dir another time	793	# stat the dir another time
		794	aioreq_pri $pri;
411	aio_stat $path, sub {	795	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	796	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		797
414	my $ndirs;	798	my $ndirs;
415		799
416	# take the slow route if anything looks fishy	800	# take the slow route if anything looks fishy
417	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	801	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
418	$ndirs = -1;	802	$ndirs = -1;
419	} else {	803	} else {
420	# if nlink == 2, we are finished	804	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	805	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	806	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	807	or return $grp->result ([], $entries);
424	}
425
426	# sort into likely dirs and likely nondirs
427	# dirs == files without ".", short entries first
428	$entries = [map $_->[0],
429	sort { $b->[1] cmp $a->[1] }
430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
431	@$entries];
432
433	my (@dirs, @nondirs);
434
435	my ($statcb, $schedcb);
436	my $nreq = 0;
437
438	$schedcb = sub {
439	if (@$entries) {
440	if ($nreq < $maxreq) {
441	my $ent = pop @$entries;
442	$nreq++;
443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
444	}
445	} elsif (!$nreq) {
446	# finished
447	undef $statcb;
448	undef $schedcb;
449	$cb->(\@dirs, \@nondirs) if $cb;
450	undef $cb;
451	}	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	};
452	};	850	};
453	$statcb = sub {
454	my ($status, $entry) = @_;
455
456	if ($status < 0) {
457	$nreq--;
458	push @nondirs, $entry;
459	&$schedcb;
460	} else {
461	# need to check for real directory
462	aio_lstat "$path/$entry", sub {
463	$nreq--;
464
465	if (-d _) {
466	push @dirs, $entry;
467
468	if (!--$ndirs) {
469	push @nondirs, @$entries;
470	$entries = [];
471	}
472	} else {
473	push @nondirs, $entry;
474	}
475
476	&$schedcb;
477	}
478	}
479	};
480
481	&$schedcb while @$entries && $nreq < $maxreq;
482	};	851	};
483	};	852	};
		853
		854	$grp
484	};	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	}
485	}	893	}
486		894
487	=item aio_fsync $fh, $callback->($status)	895	=item aio_fsync $fh, $callback->($status)
488		896
489	Asynchronously call fsync on the given filehandle and call the callback	897	Asynchronously call fsync on the given filehandle and call the callback
…		…
495	callback with the fdatasync result code.	903	callback with the fdatasync result code.
496		904
497	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
498	detected, it will be emulated by calling C<fsync> instead.	906	detected, it will be emulated by calling C<fsync> instead.
499		907
500	=item aio_group $callback->()	908	=item aio_group $callback->(...)
501		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
502	=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	942	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
503		943
504	Mainly used for debugging and benchmarking, this aio request puts one of	944	Mainly used for debugging and benchmarking, this aio request puts one of
505	the request workers to sleep for the given time.	945	the request workers to sleep for the given time.
506		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
507	=back	952	=back
508		953
509	=head2 IO::AIO::REQ CLASS	954	=head2 IO::AIO::REQ CLASS
510		955
511	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
512	called in non-void context.	957	called in non-void context.
513		958
514	A request always moves through the following five states in its lifetime,
515	in order: B<ready> (request has been created, but has not been executed
516	yet), B<execute> (request is currently being executed), B<pending>
517	(request has been executed but callback has not been called yet),
518	B<result> (results are being processed synchronously, includes calling the
519	callback) and B<done> (request has reached the end of its lifetime and
520	holds no resources anymore).
521
522	=over 4	959	=over 4
523		960
524	=item $req->cancel	961	=item cancel $req
525		962
526	Cancels the request, if possible. Has the effect of skipping execution	963	Cancels the request, if possible. Has the effect of skipping execution
527	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
528	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
529	untouched. That means that requests that currently execute will not be	966	untouched. That means that requests that currently execute will not be
530	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.
531		968
		969	=item cb $req $callback->(...)
		970
		971	Replace (or simply set) the callback registered to the request.
		972
532	=back	973	=back
533		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
534	=head2 SUPPORT FUNCTIONS	1114	=head2 SUPPORT FUNCTIONS
		1115
		1116	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		1117
536	=over 4	1118	=over 4
537		1119
538	=item $fileno = IO::AIO::poll_fileno	1120	=item $fileno = IO::AIO::poll_fileno
539		1121
…		…
544		1126
545	See C<poll_cb> for an example.	1127	See C<poll_cb> for an example.
546		1128
547	=item IO::AIO::poll_cb	1129	=item IO::AIO::poll_cb
548		1130
549	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
550	regularly. Returns the number of events processed. Returns immediately	1132	regularly. Returns the number of events processed. Returns immediately
551	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.
552		1138
553	Example: Install an Event watcher that automatically calls	1139	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1140	IO::AIO::poll_cb with high priority:
555		1141
556	Event->io (fd => IO::AIO::poll_fileno,	1142	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1143	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1144	cb => \&IO::AIO::poll_cb);
559		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
560	=item IO::AIO::poll_wait	1179	=item IO::AIO::poll_wait
561		1180
		1181	If there are any outstanding requests and none of them in the result
562	Wait till the result filehandle becomes ready for reading (simply does a	1182	phase, wait till the result filehandle becomes ready for reading (simply
563	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
564	for some requests to finish).	1184	synchronously wait for some requests to finish).
565		1185
566	See C<nreqs> for an example.	1186	See C<nreqs> for an example.
567		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
568	=item IO::AIO::nreqs	1197	=item IO::AIO::flush
569		1198
570	Returns the number of requests currently outstanding (i.e. for which their	1199	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1200
573	Example: wait till there are no outstanding requests anymore:	1201	Strictly equivalent to:
574		1202
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1203	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1204	while IO::AIO::nreqs;
577		1205
578	=item IO::AIO::flush	1206	=back
579		1207
580	Wait till all outstanding AIO requests have been handled.	1208	=head3 CONTROLLING THE NUMBER OF THREADS
581		1209
582	Strictly equivalent to:	1210	=over
583
584	IO::AIO::poll_wait, IO::AIO::poll_cb
585	while IO::AIO::nreqs;
586
587	=item IO::AIO::poll
588
589	Waits until some requests have been handled.
590
591	Strictly equivalent to:
592
593	IO::AIO::poll_wait, IO::AIO::poll_cb
594	if IO::AIO::nreqs;
595		1211
596	=item IO::AIO::min_parallel $nthreads	1212	=item IO::AIO::min_parallel $nthreads
597		1213
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1214	Set the minimum number of AIO threads to C<$nthreads>. The current
599	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
600	(the number of outstanding operations, however, is unlimited).	1216	concurrently at any one time (the number of outstanding requests,
		1217	however, is unlimited).
601		1218
602	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
603	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.
604		1223
605	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
606	kernel versions will scale negatively with the number of threads (higher	1225	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1226	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1227	versions, 4-32 threads should be fine.
609		1228
610	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
611	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.
612		1231
613	=item IO::AIO::max_parallel $nthreads	1232	=item IO::AIO::max_parallel $nthreads
…		…
622	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
623	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.
624		1243
625	Under normal circumstances you don't need to call this function.	1244	Under normal circumstances you don't need to call this function.
626		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
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1261	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1262
		1263	This is a very bad function to use in interactive programs because it
		1264	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1265	use an C<aio_group> together with a feed callback.
628		1266
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1267	Sets the maximum number of outstanding requests to C<$nreqs>. If you
630	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
631	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.
632		1271
633	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
634	queue up many requests in a loop it often improves speed if you set	1273	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1274
637	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).
638		1278
639	=back	1279	=back
640		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
641	=cut	1307	=cut
642		1308
643	# support function to convert a fd into a perl filehandle
644	sub _fd2fh {
645	return undef if $_[0] < 0;
646
647	# try to generate nice filehandles
648	my $sym = "IO::AIO::fd#$_[0]";
649	local *$sym;
650
651	open *$sym, "+<&=$_[0]" # usually works under any unix
652	or open *$sym, "<&=$_[0]" # cygwin needs this
653	or open *$sym, ">&=$_[0]" # or this
654	or return undef;
655
656	*$sym
657	}
658
659	min_parallel 4;	1309	min_parallel 8;
660		1310
661	END {	1311	END { flush }
662	max_parallel 0;
663	}
664		1312
665	1;	1313	1;
666		1314
667	=head2 FORK BEHAVIOUR	1315	=head2 FORK BEHAVIOUR
668		1316
669	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:
670		1318
671	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
672	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
673	the fork the parent simply leaves the quiescent state and continues	1321	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1322	request/result processing, while the child frees the request/result queue
675	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
676	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
677	parent process has been reached again.	1325	parent process has been reached again.
678		1326
679	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
680	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
681	yet.	1329	yet.
682		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
683	=head1 SEE ALSO	1354	=head1 SEE ALSO
684		1355
685	L<Coro>, L<Linux::AIO> (obsolete).	1356	L<Coro::AIO>.
686		1357
687	=head1 AUTHOR	1358	=head1 AUTHOR
688		1359
689	Marc Lehmann <schmorp@schmorp.de>	1360	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1361	http://home.schmorp.de/

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