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Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs.
Revision 1.145 by root, Sun Apr 19 19:20:10 2009 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	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" };
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	29	add $grp aio_stat "..." for ...;
27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28		30
29	# Event	31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	39	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
33		41
34	# Glib/Gtk2	42	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	44	in => sub { IO::AIO::poll_cb; 1 };
37		45
38	# Tk	46	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
41		49
42	# Danga::Socket	50	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
45		53
46
47	=head1 DESCRIPTION	54	=head1 DESCRIPTION
48		55
49	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
50	operating system supports.	57	operating system supports.
51		58
		59	Asynchronous means that operations that can normally block your program
		60	(e.g. reading from disk) will be done asynchronously: the operation
		61	will still block, but you can do something else in the meantime. This
		62	is extremely useful for programs that need to stay interactive even
		63	when doing heavy I/O (GUI programs, high performance network servers
		64	etc.), but can also be used to easily do operations in parallel that are
		65	normally done sequentially, e.g. stat'ing many files, which is much faster
		66	on a RAID volume or over NFS when you do a number of stat operations
		67	concurrently.
		68
		69	While most of this works on all types of file descriptors (for
		70	example sockets), using these functions on file descriptors that
		71	support nonblocking operation (again, sockets, pipes etc.) is very
		72	inefficient. Use an event loop for that (such as the L<Event|Event>
		73	module): IO::AIO will naturally fit into such an event loop itself.
		74
52	Currently, a number of threads are started that execute your read/writes	75	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	76	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	77	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	78	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	79	functions available on many operating systems. However, they are often
57	not well-supported (Linux doesn't allow them on normal files currently,	80	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	81	files currently, for example), and they would only support aio_read and
59	remaining functionality would have to be implemented using threads anyway.	82	aio_write, so the remaining functionality would have to be implemented
		83	using threads anyway.
60		84
61	Although the module will work with in the presence of other threads, it is	85	Although the module will work in the presence of other (Perl-) threads,
62	currently not reentrant, so use appropriate locking yourself, always call	86	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	87	yourself, always call C<poll_cb> from within the same thread, or never
64	C<aio_> functions) recursively.	88	call C<poll_cb> (or other C<aio_> functions) recursively.
		89
		90	=head2 EXAMPLE
		91
		92	This is a simple example that uses the Event module and loads
		93	F</etc/passwd> asynchronously:
		94
		95	use Fcntl;
		96	use Event;
		97	use IO::AIO;
		98
		99	# register the IO::AIO callback with Event
		100	Event->io (fd => IO::AIO::poll_fileno,
		101	poll => 'r',
		102	cb => \&IO::AIO::poll_cb);
		103
		104	# queue the request to open /etc/passwd
		105	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		106	my $fh = shift
		107	or die "error while opening: $!";
		108
		109	# stat'ing filehandles is generally non-blocking
		110	my $size = -s $fh;
		111
		112	# queue a request to read the file
		113	my $contents;
		114	aio_read $fh, 0, $size, $contents, 0, sub {
		115	$_[0] == $size
		116	or die "short read: $!";
		117
		118	close $fh;
		119
		120	# file contents now in $contents
		121	print $contents;
		122
		123	# exit event loop and program
		124	Event::unloop;
		125	};
		126	};
		127
		128	# possibly queue up other requests, or open GUI windows,
		129	# check for sockets etc. etc.
		130
		131	# process events as long as there are some:
		132	Event::loop;
		133
		134	=head1 REQUEST ANATOMY AND LIFETIME
		135
		136	Every C<aio_*> function creates a request. which is a C data structure not
		137	directly visible to Perl.
		138
		139	If called in non-void context, every request function returns a Perl
		140	object representing the request. In void context, nothing is returned,
		141	which saves a bit of memory.
		142
		143	The perl object is a fairly standard ref-to-hash object. The hash contents
		144	are not used by IO::AIO so you are free to store anything you like in it.
		145
		146	During their existance, aio requests travel through the following states,
		147	in order:
		148
		149	=over 4
		150
		151	=item ready
		152
		153	Immediately after a request is created it is put into the ready state,
		154	waiting for a thread to execute it.
		155
		156	=item execute
		157
		158	A thread has accepted the request for processing and is currently
		159	executing it (e.g. blocking in read).
		160
		161	=item pending
		162
		163	The request has been executed and is waiting for result processing.
		164
		165	While request submission and execution is fully asynchronous, result
		166	processing is not and relies on the perl interpreter calling C<poll_cb>
		167	(or another function with the same effect).
		168
		169	=item result
		170
		171	The request results are processed synchronously by C<poll_cb>.
		172
		173	The C<poll_cb> function will process all outstanding aio requests by
		174	calling their callbacks, freeing memory associated with them and managing
		175	any groups they are contained in.
		176
		177	=item done
		178
		179	Request has reached the end of its lifetime and holds no resources anymore
		180	(except possibly for the Perl object, but its connection to the actual
		181	aio request is severed and calling its methods will either do nothing or
		182	result in a runtime error).
		183
		184	=back
65		185
66	=cut	186	=cut
67		187
68	package IO::AIO;	188	package IO::AIO;
		189
		190	use Carp ();
69		191
70	no warnings;	192	no warnings;
71	use strict 'vars';	193	use strict 'vars';
72		194
73	use base 'Exporter';	195	use base 'Exporter';
74		196
75	BEGIN {	197	BEGIN {
76	our $VERSION = '1.99';	198	our $VERSION = '3.18';
77		199
78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
81	aio_group);	203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
82	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	204	aio_rename aio_link aio_move aio_copy aio_group
		205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		206	aio_chmod aio_utime aio_truncate);
		207
		208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		210	min_parallel max_parallel max_idle
		211	nreqs nready npending nthreads
		212	max_poll_time max_poll_reqs);
		213
		214	push @AIO_REQ, qw(aio_busy); # not exported
83		215
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		217
86	require XSLoader;	218	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	219	XSLoader::load ("IO::AIO", $VERSION);
88	}	220	}
89		221
90	=head1 FUNCTIONS	222	=head1 FUNCTIONS
91		223
92	=head2 AIO FUNCTIONS	224	=head2 AIO REQUEST FUNCTIONS
93		225
94	All the C<aio_*> calls are more or less thin wrappers around the syscall	226	All the C<aio_*> calls are more or less thin wrappers around the syscall
95	with the same name (sans C<aio_>). The arguments are similar or identical,	227	with the same name (sans C<aio_>). The arguments are similar or identical,
96	and they all accept an additional (and optional) C<$callback> argument	228	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	229	which must be a code reference. This code reference will get called with
98	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
99	perl, which usually delivers "false") as it's sole argument when the given	231	perl, which usually delivers "false") as its sole argument after the given
100	syscall has been executed asynchronously.	232	syscall has been executed asynchronously.
101		233
102	All functions expecting a filehandle keep a copy of the filehandle	234	All functions expecting a filehandle keep a copy of the filehandle
103	internally until the request has finished.	235	internally until the request has finished.
104		236
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	237	All functions return request objects of type L<IO::AIO::REQ> that allow
107	further manipulation of running requests.	238	further manipulation of those requests while they are in-flight.
108		239
109	The pathnames you pass to these routines I<must> be absolute and	240	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	241	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	242	request is being executed, the current working directory could have
112	changed. Alternatively, you can make sure that you never change the	243	changed. Alternatively, you can make sure that you never change the
113	current working directory.	244	current working directory anywhere in the program and then use relative
		245	paths.
114		246
115	To encode pathnames to byte form, either make sure you either: a)	247	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	248	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	249	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	250	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)	251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
120	use something else.	252	use something else to ensure your scalar has the correct contents.
		253
		254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		255	handles correctly whether it is set or not.
121		256
122	=over 4	257	=over 4
		258
		259	=item $prev_pri = aioreq_pri [$pri]
		260
		261	Returns the priority value that would be used for the next request and, if
		262	C<$pri> is given, sets the priority for the next aio request.
		263
		264	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		265	and C<4>, respectively. Requests with higher priority will be serviced
		266	first.
		267
		268	The priority will be reset to C<0> after each call to one of the C<aio_*>
		269	functions.
		270
		271	Example: open a file with low priority, then read something from it with
		272	higher priority so the read request is serviced before other low priority
		273	open requests (potentially spamming the cache):
		274
		275	aioreq_pri -3;
		276	aio_open ..., sub {
		277	return unless $_[0];
		278
		279	aioreq_pri -2;
		280	aio_read $_[0], ..., sub {
		281	...
		282	};
		283	};
		284
		285
		286	=item aioreq_nice $pri_adjust
		287
		288	Similar to C<aioreq_pri>, but subtracts the given value from the current
		289	priority, so the effect is cumulative.
		290
123		291
124	=item aio_open $pathname, $flags, $mode, $callback->($fh)	292	=item aio_open $pathname, $flags, $mode, $callback->($fh)
125		293
126	Asynchronously open or create a file and call the callback with a newly	294	Asynchronously open or create a file and call the callback with a newly
127	created filehandle for the file.	295	created filehandle for the file.
…		…
133	list. They are the same as used by C<sysopen>.	301	list. They are the same as used by C<sysopen>.
134		302
135	Likewise, C<$mode> specifies the mode of the newly created file, if it	303	Likewise, C<$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>,	304	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,	305	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).	306	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		307	by the umask in effect then the request is being executed, so better never
		308	change the umask.
139		309
140	Example:	310	Example:
141		311
142	aio_open "/etc/passwd", O_RDONLY, 0, sub {	312	aio_open "/etc/passwd", O_RDONLY, 0, sub {
143	if ($_[0]) {	313	if ($_[0]) {
…		…
146	} else {	316	} else {
147	die "open failed: $!\n";	317	die "open failed: $!\n";
148	}	318	}
149	};	319	};
150		320
		321
151	=item aio_close $fh, $callback->($status)	322	=item aio_close $fh, $callback->($status)
152		323
153	Asynchronously close a file and call the callback with the result	324	Asynchronously close a file and call the callback with the result
154	code. I<WARNING:> although accepted, you should not pass in a perl	325	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		326
159	This is supposed to be a bug in the API, so that might change. It's	327	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
160	therefore best to avoid this function.	328	closing the file descriptor associated with the filehandle itself.
		329
		330	Therefore, C<aio_close> will not close the filehandle - instead it will
		331	use dup2 to overwrite the file descriptor with the write-end of a pipe
		332	(the pipe fd will be created on demand and will be cached).
		333
		334	Or in other words: the file descriptor will be closed, but it will not be
		335	free for reuse until the perl filehandle is closed.
		336
		337	=cut
161		338
162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163		340
164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		342
166	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	343	Reads or writes C<$length> bytes from or to the specified C<$fh> and
167	into the scalar given by C<data> and offset C<dataoffset> and calls the	344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
168	callback without the actual number of bytes read (or -1 on error, just	345	and calls the callback without the actual number of bytes read (or -1 on
169	like the syscall).	346	error, just like the syscall).
		347
		348	If C<$offset> is undefined, then the current file descriptor offset will
		349	be used (and updated), otherwise the file descriptor offset will not be
		350	changed by these calls.
		351
		352	If C<$length> is undefined in C<aio_write>, use the remaining length of
		353	C<$data>.
		354
		355	If C<$dataoffset> is less than zero, it will be counted from the end of
		356	C<$data>.
170		357
171	The C<$data> scalar I<MUST NOT> be modified in any way while the request	358	The C<$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	359	is outstanding. Modifying it can result in segfaults or World War III (if
173	necessary/optional hardware is installed).	360	the necessary/optional hardware is installed).
174		361
175	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	362	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
176	offset C<0> within the scalar:	363	offset C<0> within the scalar:
177		364
178	aio_read $fh, 7, 15, $buffer, 0, sub {	365	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	366	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	367	print "read $_[0] bytes: <$buffer>\n";
181	};	368	};
182		369
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		370
247	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	371	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
248		372
249	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	373	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	374	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	388	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	389	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	390	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	391	value equals C<$length> one can assume that C<$length> bytes have been
268	read.	392	read.
		393
269		394
270	=item aio_readahead $fh,$offset,$length, $callback->($retval)	395	=item aio_readahead $fh,$offset,$length, $callback->($retval)
271		396
272	C<aio_readahead> populates the page cache with data from a file so that	397	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>	398	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.	404	file. The current file offset of the file is left unchanged.
280		405
281	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	406	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.	407	emulated by simply reading the data, which would have a similar effect.
283		408
		409
284	=item aio_stat $fh_or_path, $callback->($status)	410	=item aio_stat $fh_or_path, $callback->($status)
285		411
286	=item aio_lstat $fh, $callback->($status)	412	=item aio_lstat $fh, $callback->($status)
287		413
288	Works like perl's C<stat> or C<lstat> in void context. The callback will	414	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
301	aio_stat "/etc/passwd", sub {	427	aio_stat "/etc/passwd", sub {
302	$_[0] and die "stat failed: $!";	428	$_[0] and die "stat failed: $!";
303	print "size is ", -s _, "\n";	429	print "size is ", -s _, "\n";
304	};	430	};
305		431
		432
		433	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		434
		435	Works like perl's C<utime> function (including the special case of $atime
		436	and $mtime being undef). Fractional times are supported if the underlying
		437	syscalls support them.
		438
		439	When called with a pathname, uses utimes(2) if available, otherwise
		440	utime(2). If called on a file descriptor, uses futimes(2) if available,
		441	otherwise returns ENOSYS, so this is not portable.
		442
		443	Examples:
		444
		445	# set atime and mtime to current time (basically touch(1)):
		446	aio_utime "path", undef, undef;
		447	# set atime to current time and mtime to beginning of the epoch:
		448	aio_utime "path", time, undef; # undef==0
		449
		450
		451	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		452
		453	Works like perl's C<chown> function, except that C<undef> for either $uid
		454	or $gid is being interpreted as "do not change" (but -1 can also be used).
		455
		456	Examples:
		457
		458	# same as "chown root path" in the shell:
		459	aio_chown "path", 0, -1;
		460	# same as above:
		461	aio_chown "path", 0, undef;
		462
		463
		464	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		465
		466	Works like truncate(2) or ftruncate(2).
		467
		468
		469	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		470
		471	Works like perl's C<chmod> function.
		472
		473
306	=item aio_unlink $pathname, $callback->($status)	474	=item aio_unlink $pathname, $callback->($status)
307		475
308	Asynchronously unlink (delete) a file and call the callback with the	476	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	477	result code.
310		478
		479
		480	=item aio_mknod $path, $mode, $dev, $callback->($status)
		481
		482	[EXPERIMENTAL]
		483
		484	Asynchronously create a device node (or fifo). See mknod(2).
		485
		486	The only (POSIX-) portable way of calling this function is:
		487
		488	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		489
		490
311	=item aio_link $srcpath, $dstpath, $callback->($status)	491	=item aio_link $srcpath, $dstpath, $callback->($status)
312		492
313	Asynchronously create a new link to the existing object at C<$srcpath> at	493	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.	494	the path C<$dstpath> and call the callback with the result code.
315		495
		496
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	497	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		498
318	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	499	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.	500	the path C<$dstpath> and call the callback with the result code.
320		501
		502
		503	=item aio_readlink $path, $callback->($link)
		504
		505	Asynchronously read the symlink specified by C<$path> and pass it to
		506	the callback. If an error occurs, nothing or undef gets passed to the
		507	callback.
		508
		509
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	510	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		511
323	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	512	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
324	rename(2) and call the callback with the result code.	513	rename(2) and call the callback with the result code.
325		514
		515
		516	=item aio_mkdir $pathname, $mode, $callback->($status)
		517
		518	Asynchronously mkdir (create) a directory and call the callback with
		519	the result code. C<$mode> will be modified by the umask at the time the
		520	request is executed, so do not change your umask.
		521
		522
326	=item aio_rmdir $pathname, $callback->($status)	523	=item aio_rmdir $pathname, $callback->($status)
327		524
328	Asynchronously rmdir (delete) a directory and call the callback with the	525	Asynchronously rmdir (delete) a directory and call the callback with the
329	result code.	526	result code.
		527
330		528
331	=item aio_readdir $pathname, $callback->($entries)	529	=item aio_readdir $pathname, $callback->($entries)
332		530
333	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	531	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	532	directory (i.e. opendir + readdir + closedir). The entries will not be
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	533	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		534
337	The callback a single argument which is either C<undef> or an array-ref	535	The callback a single argument which is either C<undef> or an array-ref
338	with the filenames.	536	with the filenames.
339		537
		538
		539	=item aio_load $path, $data, $callback->($status)
		540
		541	This is a composite request that tries to fully load the given file into
		542	memory. Status is the same as with aio_read.
		543
		544	=cut
		545
		546	sub aio_load($$;$) {
		547	my ($path, undef, $cb) = @_;
		548	my $data = \$_[1];
		549
		550	my $pri = aioreq_pri;
		551	my $grp = aio_group $cb;
		552
		553	aioreq_pri $pri;
		554	add $grp aio_open $path, O_RDONLY, 0, sub {
		555	my $fh = shift
		556	or return $grp->result (-1);
		557
		558	aioreq_pri $pri;
		559	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		560	$grp->result ($_[0]);
		561	};
		562	};
		563
		564	$grp
		565	}
		566
		567	=item aio_copy $srcpath, $dstpath, $callback->($status)
		568
		569	Try to copy the I<file> (directories not supported as either source or
		570	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		571	the C<0> (error) or C<-1> ok.
		572
		573	This is a composite request that creates the destination file with
		574	mode 0200 and copies the contents of the source file into it using
		575	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		576	uid/gid, in that order.
		577
		578	If an error occurs, the partial destination file will be unlinked, if
		579	possible, except when setting atime, mtime, access mode and uid/gid, where
		580	errors are being ignored.
		581
		582	=cut
		583
		584	sub aio_copy($$;$) {
		585	my ($src, $dst, $cb) = @_;
		586
		587	my $pri = aioreq_pri;
		588	my $grp = aio_group $cb;
		589
		590	aioreq_pri $pri;
		591	add $grp aio_open $src, O_RDONLY, 0, sub {
		592	if (my $src_fh = $_[0]) {
		593	my @stat = stat $src_fh;
		594
		595	aioreq_pri $pri;
		596	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		597	if (my $dst_fh = $_[0]) {
		598	aioreq_pri $pri;
		599	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		600	if ($_[0] == $stat[7]) {
		601	$grp->result (0);
		602	close $src_fh;
		603
		604	# those should not normally block. should. should.
		605	utime $stat[8], $stat[9], $dst;
		606	chmod $stat[2] & 07777, $dst_fh;
		607	chown $stat[4], $stat[5], $dst_fh;
		608
		609	aioreq_pri $pri;
		610	add $grp aio_close $dst_fh;
		611	} else {
		612	$grp->result (-1);
		613	close $src_fh;
		614	close $dst_fh;
		615
		616	aioreq $pri;
		617	add $grp aio_unlink $dst;
		618	}
		619	};
		620	} else {
		621	$grp->result (-1);
		622	}
		623	},
		624
		625	} else {
		626	$grp->result (-1);
		627	}
		628	};
		629
		630	$grp
		631	}
		632
		633	=item aio_move $srcpath, $dstpath, $callback->($status)
		634
		635	Try to move the I<file> (directories not supported as either source or
		636	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		637	the C<0> (error) or C<-1> ok.
		638
		639	This is a composite request that tries to rename(2) the file first; if
		640	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		641	that is successful, unlinks the C<$srcpath>.
		642
		643	=cut
		644
		645	sub aio_move($$;$) {
		646	my ($src, $dst, $cb) = @_;
		647
		648	my $pri = aioreq_pri;
		649	my $grp = aio_group $cb;
		650
		651	aioreq_pri $pri;
		652	add $grp aio_rename $src, $dst, sub {
		653	if ($_[0] && $! == EXDEV) {
		654	aioreq_pri $pri;
		655	add $grp aio_copy $src, $dst, sub {
		656	$grp->result ($_[0]);
		657
		658	if (!$_[0]) {
		659	aioreq_pri $pri;
		660	add $grp aio_unlink $src;
		661	}
		662	};
		663	} else {
		664	$grp->result ($_[0]);
		665	}
		666	};
		667
		668	$grp
		669	}
		670
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	671	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		672
342	Scans a directory (similar to C<aio_readdir>) but additionally tries to	673	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	674	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	675	names, directories you can recurse into (directories), and ones you cannot
345	recurse into (everything else).	676	recurse into (everything else, including symlinks to directories).
346		677
347	C<aio_scandir> is a composite request that consists of many sub	678	C<aio_scandir> is a composite request that creates of many sub requests_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	679	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	requests that this function generates. If it is C<< <= 0 >>, then a	680	this function generates. If it is C<< <= 0 >>, then a suitable default
350	suitable default will be chosen (currently 8).	681	will be chosen (currently 4).
351		682
352	On error, the callback is called without arguments, otherwise it receives	683	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	684	two array-refs with path-relative entry names.
354		685
355	Example:	686	Example:
…		…
389	as those tend to return 0 or 1 as link counts, which disables the	720	as those tend to return 0 or 1 as link counts, which disables the
390	directory counting heuristic.	721	directory counting heuristic.
391		722
392	=cut	723	=cut
393		724
394	sub aio_scandir($$$) {	725	sub aio_scandir($$;$) {
395	my ($path, $maxreq, $cb) = @_;	726	my ($path, $maxreq, $cb) = @_;
396		727
		728	my $pri = aioreq_pri;
		729
		730	my $grp = aio_group $cb;
		731
397	$maxreq = 8 if $maxreq <= 0;	732	$maxreq = 4 if $maxreq <= 0;
398		733
399	# stat once	734	# stat once
		735	aioreq_pri $pri;
400	aio_stat $path, sub {	736	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	737	return $grp->result () if $_[0];
402	my $now = time;	738	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	739	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		740
405	# read the directory entries	741	# read the directory entries
		742	aioreq_pri $pri;
406	aio_readdir $path, sub {	743	add $grp aio_readdir $path, sub {
407	my $entries = shift	744	my $entries = shift
408	or return $cb->();	745	or return $grp->result ();
409		746
410	# stat the dir another time	747	# stat the dir another time
		748	aioreq_pri $pri;
411	aio_stat $path, sub {	749	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	750	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		751
414	my $ndirs;	752	my $ndirs;
415		753
416	# take the slow route if anything looks fishy	754	# take the slow route if anything looks fishy
…		…
418	$ndirs = -1;	756	$ndirs = -1;
419	} else {	757	} else {
420	# if nlink == 2, we are finished	758	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	759	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	760	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	761	or return $grp->result ([], $entries);
424	}	762	}
425		763
426	# sort into likely dirs and likely nondirs	764	# sort into likely dirs and likely nondirs
427	# dirs == files without ".", short entries first	765	# dirs == files without ".", short entries first
428	$entries = [map $_->[0],	766	$entries = [map $_->[0],
…		…
430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	768	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
431	@$entries];	769	@$entries];
432		770
433	my (@dirs, @nondirs);	771	my (@dirs, @nondirs);
434		772
435	my ($statcb, $schedcb);	773	my $statgrp = add $grp aio_group sub {
436	my $nreq = 0;	774	$grp->result (\@dirs, \@nondirs);
		775	};
437		776
438	$schedcb = sub {	777	limit $statgrp $maxreq;
439	if (@$entries) {	778	feed $statgrp sub {
440	if ($nreq < $maxreq) {	779	return unless @$entries;
441	my $ent = pop @$entries;	780	my $entry = pop @$entries;
		781
		782	aioreq_pri $pri;
		783	add $statgrp aio_stat "$path/$entry/.", sub {
		784	if ($_[0] < 0) {
		785	push @nondirs, $entry;
		786	} else {
		787	# need to check for real directory
		788	aioreq_pri $pri;
		789	add $statgrp aio_lstat "$path/$entry", sub {
		790	if (-d _) {
		791	push @dirs, $entry;
		792
		793	unless (--$ndirs) {
		794	push @nondirs, @$entries;
		795	feed $statgrp;
		796	}
		797	} else {
		798	push @nondirs, $entry;
		799	}
442	$nreq++;	800	}
443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
444	}	801	}
445	} elsif (!$nreq) {
446	# finished
447	undef $statcb;
448	undef $schedcb;
449	$cb->(\@dirs, \@nondirs) if $cb;
450	undef $cb;
451	}	802	};
452	};	803	};
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	};	804	};
483	};	805	};
484	};	806	};
		807
		808	$grp
485	}	809	}
		810
		811	=item aio_rmtree $path, $callback->($status)
		812
		813	Delete a directory tree starting (and including) C<$path>, return the
		814	status of the final C<rmdir> only. This is a composite request that
		815	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		816	everything else.
		817
		818	=cut
		819
		820	sub aio_rmtree;
		821	sub aio_rmtree($;$) {
		822	my ($path, $cb) = @_;
		823
		824	my $pri = aioreq_pri;
		825	my $grp = aio_group $cb;
		826
		827	aioreq_pri $pri;
		828	add $grp aio_scandir $path, 0, sub {
		829	my ($dirs, $nondirs) = @_;
		830
		831	my $dirgrp = aio_group sub {
		832	add $grp aio_rmdir $path, sub {
		833	$grp->result ($_[0]);
		834	};
		835	};
		836
		837	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		838	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		839
		840	add $grp $dirgrp;
		841	};
		842
		843	$grp
		844	}
		845
		846	=item aio_sync $callback->($status)
		847
		848	Asynchronously call sync and call the callback when finished.
486		849
487	=item aio_fsync $fh, $callback->($status)	850	=item aio_fsync $fh, $callback->($status)
488		851
489	Asynchronously call fsync on the given filehandle and call the callback	852	Asynchronously call fsync on the given filehandle and call the callback
490	with the fsync result code.	853	with the fsync result code.
…		…
495	callback with the fdatasync result code.	858	callback with the fdatasync result code.
496		859
497	If this call isn't available because your OS lacks it or it couldn't be	860	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.	861	detected, it will be emulated by calling C<fsync> instead.
499		862
		863	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		864
		865	Sync the data portion of the file specified by C<$offset> and C<$length>
		866	to disk (but NOT the metadata), by calling the Linux-specific
		867	sync_file_range call. If sync_file_range is not available or it returns
		868	ENOSYS, then fdatasync or fsync is being substituted.
		869
		870	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		871	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		872	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		873	manpage for details.
		874
		875	=item aio_pathsync $path, $callback->($status)
		876
		877	This request tries to open, fsync and close the given path. This is a
		878	composite request intended to sync directories after directory operations
		879	(E.g. rename). This might not work on all operating systems or have any
		880	specific effect, but usually it makes sure that directory changes get
		881	written to disc. It works for anything that can be opened for read-only,
		882	not just directories.
		883
		884	Passes C<0> when everything went ok, and C<-1> on error.
		885
		886	=cut
		887
		888	sub aio_pathsync($;$) {
		889	my ($path, $cb) = @_;
		890
		891	my $pri = aioreq_pri;
		892	my $grp = aio_group $cb;
		893
		894	aioreq_pri $pri;
		895	add $grp aio_open $path, O_RDONLY, 0, sub {
		896	my ($fh) = @_;
		897	if ($fh) {
		898	aioreq_pri $pri;
		899	add $grp aio_fsync $fh, sub {
		900	$grp->result ($_[0]);
		901
		902	aioreq_pri $pri;
		903	add $grp aio_close $fh;
		904	};
		905	} else {
		906	$grp->result (-1);
		907	}
		908	};
		909
		910	$grp
		911	}
		912
500	=item aio_group $callback->()	913	=item aio_group $callback->(...)
501		914
		915	This is a very special aio request: Instead of doing something, it is a
		916	container for other aio requests, which is useful if you want to bundle
		917	many requests into a single, composite, request with a definite callback
		918	and the ability to cancel the whole request with its subrequests.
		919
		920	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		921	for more info.
		922
		923	Example:
		924
		925	my $grp = aio_group sub {
		926	print "all stats done\n";
		927	};
		928
		929	add $grp
		930	(aio_stat ...),
		931	(aio_stat ...),
		932	...;
		933
		934	=item aio_nop $callback->()
		935
		936	This is a special request - it does nothing in itself and is only used for
		937	side effects, such as when you want to add a dummy request to a group so
		938	that finishing the requests in the group depends on executing the given
		939	code.
		940
		941	While this request does nothing, it still goes through the execution
		942	phase and still requires a worker thread. Thus, the callback will not
		943	be executed immediately but only after other requests in the queue have
		944	entered their execution phase. This can be used to measure request
		945	latency.
		946
502	=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	947	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
503		948
504	Mainly used for debugging and benchmarking, this aio request puts one of	949	Mainly used for debugging and benchmarking, this aio request puts one of
505	the request workers to sleep for the given time.	950	the request workers to sleep for the given time.
506		951
		952	While it is theoretically handy to have simple I/O scheduling requests
		953	like sleep and file handle readable/writable, the overhead this creates is
		954	immense (it blocks a thread for a long time) so do not use this function
		955	except to put your application under artificial I/O pressure.
		956
507	=back	957	=back
508		958
509	=head2 IO::AIO::REQ CLASS	959	=head2 IO::AIO::REQ CLASS
510		960
511	All non-aggregate C<aio_*> functions return an object of this class when	961	All non-aggregate C<aio_*> functions return an object of this class when
512	called in non-void context.	962	called in non-void context.
513		963
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	964	=over 4
523		965
524	=item $req->cancel	966	=item cancel $req
525		967
526	Cancels the request, if possible. Has the effect of skipping execution	968	Cancels the request, if possible. Has the effect of skipping execution
527	when entering the B<execute> state and skipping calling the callback when	969	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	970	entering the the B<result> state, but will leave the request otherwise
529	untouched. That means that requests that currently execute will not be	971	untouched. That means that requests that currently execute will not be
530	stopped and resources held by the request will not be freed prematurely.	972	stopped and resources held by the request will not be freed prematurely.
531		973
		974	=item cb $req $callback->(...)
		975
		976	Replace (or simply set) the callback registered to the request.
		977
532	=back	978	=back
533		979
		980	=head2 IO::AIO::GRP CLASS
		981
		982	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		983	objects of this class, too.
		984
		985	A IO::AIO::GRP object is a special request that can contain multiple other
		986	aio requests.
		987
		988	You create one by calling the C<aio_group> constructing function with a
		989	callback that will be called when all contained requests have entered the
		990	C<done> state:
		991
		992	my $grp = aio_group sub {
		993	print "all requests are done\n";
		994	};
		995
		996	You add requests by calling the C<add> method with one or more
		997	C<IO::AIO::REQ> objects:
		998
		999	$grp->add (aio_unlink "...");
		1000
		1001	add $grp aio_stat "...", sub {
		1002	$_[0] or return $grp->result ("error");
		1003
		1004	# add another request dynamically, if first succeeded
		1005	add $grp aio_open "...", sub {
		1006	$grp->result ("ok");
		1007	};
		1008	};
		1009
		1010	This makes it very easy to create composite requests (see the source of
		1011	C<aio_move> for an application) that work and feel like simple requests.
		1012
		1013	=over 4
		1014
		1015	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1016	C<IO::AIO::poll_cb>, just like any other request.
		1017
		1018	=item * They can be canceled like any other request. Canceling will cancel not
		1019	only the request itself, but also all requests it contains.
		1020
		1021	=item * They can also can also be added to other IO::AIO::GRP objects.
		1022
		1023	=item * You must not add requests to a group from within the group callback (or
		1024	any later time).
		1025
		1026	=back
		1027
		1028	Their lifetime, simplified, looks like this: when they are empty, they
		1029	will finish very quickly. If they contain only requests that are in the
		1030	C<done> state, they will also finish. Otherwise they will continue to
		1031	exist.
		1032
		1033	That means after creating a group you have some time to add requests
		1034	(precisely before the callback has been invoked, which is only done within
		1035	the C<poll_cb>). And in the callbacks of those requests, you can add
		1036	further requests to the group. And only when all those requests have
		1037	finished will the the group itself finish.
		1038
		1039	=over 4
		1040
		1041	=item add $grp ...
		1042
		1043	=item $grp->add (...)
		1044
		1045	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1046	be added, including other groups, as long as you do not create circular
		1047	dependencies.
		1048
		1049	Returns all its arguments.
		1050
		1051	=item $grp->cancel_subs
		1052
		1053	Cancel all subrequests and clears any feeder, but not the group request
		1054	itself. Useful when you queued a lot of events but got a result early.
		1055
		1056	=item $grp->result (...)
		1057
		1058	Set the result value(s) that will be passed to the group callback when all
		1059	subrequests have finished and set the groups errno to the current value
		1060	of errno (just like calling C<errno> without an error number). By default,
		1061	no argument will be passed and errno is zero.
		1062
		1063	=item $grp->errno ([$errno])
		1064
		1065	Sets the group errno value to C<$errno>, or the current value of errno
		1066	when the argument is missing.
		1067
		1068	Every aio request has an associated errno value that is restored when
		1069	the callback is invoked. This method lets you change this value from its
		1070	default (0).
		1071
		1072	Calling C<result> will also set errno, so make sure you either set C<$!>
		1073	before the call to C<result>, or call c<errno> after it.
		1074
		1075	=item feed $grp $callback->($grp)
		1076
		1077	Sets a feeder/generator on this group: every group can have an attached
		1078	generator that generates requests if idle. The idea behind this is that,
		1079	although you could just queue as many requests as you want in a group,
		1080	this might starve other requests for a potentially long time. For example,
		1081	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1082	delaying any later requests for a long time.
		1083
		1084	To avoid this, and allow incremental generation of requests, you can
		1085	instead a group and set a feeder on it that generates those requests. The
		1086	feed callback will be called whenever there are few enough (see C<limit>,
		1087	below) requests active in the group itself and is expected to queue more
		1088	requests.
		1089
		1090	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1091	not impose any limits).
		1092
		1093	If the feed does not queue more requests when called, it will be
		1094	automatically removed from the group.
		1095
		1096	If the feed limit is C<0> when this method is called, it will be set to
		1097	C<2> automatically.
		1098
		1099	Example:
		1100
		1101	# stat all files in @files, but only ever use four aio requests concurrently:
		1102
		1103	my $grp = aio_group sub { print "finished\n" };
		1104	limit $grp 4;
		1105	feed $grp sub {
		1106	my $file = pop @files
		1107	or return;
		1108
		1109	add $grp aio_stat $file, sub { ... };
		1110	};
		1111
		1112	=item limit $grp $num
		1113
		1114	Sets the feeder limit for the group: The feeder will be called whenever
		1115	the group contains less than this many requests.
		1116
		1117	Setting the limit to C<0> will pause the feeding process.
		1118
		1119	The default value for the limit is C<0>, but note that setting a feeder
		1120	automatically bumps it up to C<2>.
		1121
		1122	=back
		1123
534	=head2 SUPPORT FUNCTIONS	1124	=head2 SUPPORT FUNCTIONS
		1125
		1126	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		1127
536	=over 4	1128	=over 4
537		1129
538	=item $fileno = IO::AIO::poll_fileno	1130	=item $fileno = IO::AIO::poll_fileno
539		1131
…		…
544		1136
545	See C<poll_cb> for an example.	1137	See C<poll_cb> for an example.
546		1138
547	=item IO::AIO::poll_cb	1139	=item IO::AIO::poll_cb
548		1140
549	Process all outstanding events on the result pipe. You have to call this	1141	Process some outstanding events on the result pipe. You have to call this
550	regularly. Returns the number of events processed. Returns immediately	1142	regularly. Returns C<0> if all events could be processed, or C<-1> if it
551	when no events are outstanding.	1143	returned earlier for whatever reason. Returns immediately when no events
		1144	are outstanding. The amount of events processed depends on the settings of
		1145	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1146
		1147	If not all requests were processed for whatever reason, the filehandle
		1148	will still be ready when C<poll_cb> returns, so normally you don't have to
		1149	do anything special to have it called later.
552		1150
553	Example: Install an Event watcher that automatically calls	1151	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1152	IO::AIO::poll_cb with high priority:
555		1153
556	Event->io (fd => IO::AIO::poll_fileno,	1154	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1155	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1156	cb => \&IO::AIO::poll_cb);
559		1157
		1158	=item IO::AIO::max_poll_reqs $nreqs
		1159
		1160	=item IO::AIO::max_poll_time $seconds
		1161
		1162	These set the maximum number of requests (default C<0>, meaning infinity)
		1163	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1164	the maximum amount of time (default C<0>, meaning infinity) spent in
		1165	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1166	of time C<poll_cb> is allowed to use).
		1167
		1168	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1169	syscall per request processed, which is not normally a problem unless your
		1170	callbacks are really really fast or your OS is really really slow (I am
		1171	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1172
		1173	Setting these is useful if you want to ensure some level of
		1174	interactiveness when perl is not fast enough to process all requests in
		1175	time.
		1176
		1177	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1178
		1179	Example: Install an Event watcher that automatically calls
		1180	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1181	program get the CPU sometimes even under high AIO load.
		1182
		1183	# try not to spend much more than 0.1s in poll_cb
		1184	IO::AIO::max_poll_time 0.1;
		1185
		1186	# use a low priority so other tasks have priority
		1187	Event->io (fd => IO::AIO::poll_fileno,
		1188	poll => 'r', nice => 1,
		1189	cb => &IO::AIO::poll_cb);
		1190
560	=item IO::AIO::poll_wait	1191	=item IO::AIO::poll_wait
561		1192
		1193	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	1194	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	1195	does a C<select> on the filehandle. This is useful if you want to
564	for some requests to finish).	1196	synchronously wait for some requests to finish).
565		1197
566	See C<nreqs> for an example.	1198	See C<nreqs> for an example.
567		1199
		1200	=item IO::AIO::poll
		1201
		1202	Waits until some requests have been handled.
		1203
		1204	Returns the number of requests processed, but is otherwise strictly
		1205	equivalent to:
		1206
		1207	IO::AIO::poll_wait, IO::AIO::poll_cb
		1208
568	=item IO::AIO::nreqs	1209	=item IO::AIO::flush
569		1210
570	Returns the number of requests currently outstanding (i.e. for which their	1211	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1212
573	Example: wait till there are no outstanding requests anymore:	1213	Strictly equivalent to:
574		1214
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1215	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1216	while IO::AIO::nreqs;
577		1217
578	=item IO::AIO::flush	1218	=back
579		1219
580	Wait till all outstanding AIO requests have been handled.	1220	=head3 CONTROLLING THE NUMBER OF THREADS
581		1221
582	Strictly equivalent to:	1222	=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		1223
596	=item IO::AIO::min_parallel $nthreads	1224	=item IO::AIO::min_parallel $nthreads
597		1225
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1226	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	1227	default is C<8>, which means eight asynchronous operations can execute
600	(the number of outstanding operations, however, is unlimited).	1228	concurrently at any one time (the number of outstanding requests,
		1229	however, is unlimited).
601		1230
602	IO::AIO starts threads only on demand, when an AIO request is queued and	1231	IO::AIO starts threads only on demand, when an AIO request is queued and
603	no free thread exists.	1232	no free thread exists. Please note that queueing up a hundred requests can
		1233	create demand for a hundred threads, even if it turns out that everything
		1234	is in the cache and could have been processed faster by a single thread.
604		1235
605	It is recommended to keep the number of threads low, as some Linux	1236	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	1237	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1238	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1239	versions, 4-32 threads should be fine.
609		1240
610	Under most circumstances you don't need to call this function, as the	1241	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.	1242	module selects a default that is suitable for low to moderate load.
612		1243
613	=item IO::AIO::max_parallel $nthreads	1244	=item IO::AIO::max_parallel $nthreads
…		…
622	This module automatically runs C<max_parallel 0> at program end, to ensure	1253	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.	1254	that all threads are killed and that there are no outstanding requests.
624		1255
625	Under normal circumstances you don't need to call this function.	1256	Under normal circumstances you don't need to call this function.
626		1257
		1258	=item IO::AIO::max_idle $nthreads
		1259
		1260	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1261	threads that did not get a request to process within 10 seconds). That
		1262	means if a thread becomes idle while C<$nthreads> other threads are also
		1263	idle, it will free its resources and exit.
		1264
		1265	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1266	to allow for extremely high load situations, but want to free resources
		1267	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1268
		1269	The default is probably ok in most situations, especially if thread
		1270	creation is fast. If thread creation is very slow on your system you might
		1271	want to use larger values.
		1272
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1273	=item IO::AIO::max_outstanding $maxreqs
		1274
		1275	This is a very bad function to use in interactive programs because it
		1276	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1277	use an C<aio_group> together with a feed callback.
628		1278
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1279	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	1280	do queue up more than this number of requests, the next call to the
631	some requests have been handled.	1281	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1282	function will block until the limit is no longer exceeded.
632		1283
633	The default is very large, so normally there is no practical limit. If you	1284	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	1285	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1286
637	Under normal circumstances you don't need to call this function.	1287	You can still queue as many requests as you want. Therefore,
		1288	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1289	as a stop gap to shield against fatal memory overflow (with large values).
638		1290
639	=back	1291	=back
640		1292
		1293	=head3 STATISTICAL INFORMATION
		1294
		1295	=over
		1296
		1297	=item IO::AIO::nreqs
		1298
		1299	Returns the number of requests currently in the ready, execute or pending
		1300	states (i.e. for which their callback has not been invoked yet).
		1301
		1302	Example: wait till there are no outstanding requests anymore:
		1303
		1304	IO::AIO::poll_wait, IO::AIO::poll_cb
		1305	while IO::AIO::nreqs;
		1306
		1307	=item IO::AIO::nready
		1308
		1309	Returns the number of requests currently in the ready state (not yet
		1310	executed).
		1311
		1312	=item IO::AIO::npending
		1313
		1314	Returns the number of requests currently in the pending state (executed,
		1315	but not yet processed by poll_cb).
		1316
		1317	=back
		1318
641	=cut	1319	=cut
642		1320
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;	1321	min_parallel 8;
660		1322
661	END {	1323	END { flush }
662	max_parallel 0;
663	}
664		1324
665	1;	1325	1;
666		1326
667	=head2 FORK BEHAVIOUR	1327	=head2 FORK BEHAVIOUR
668		1328
669	This module should do "the right thing" when the process using it forks:	1329	This module should do "the right thing" when the process using it forks:
670		1330
671	Before the fork, IO::AIO enters a quiescent state where no requests	1331	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	1332	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	1333	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1334	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	1335	(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	1336	parent). Threads will be started on demand until the limit set in the
677	parent process has been reached again.	1337	parent process has been reached again.
678		1338
679	In short: the parent will, after a short pause, continue as if fork had	1339	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	1340	not been called, while the child will act as if IO::AIO has not been used
681	yet.	1341	yet.
682		1342
		1343	=head2 MEMORY USAGE
		1344
		1345	Per-request usage:
		1346
		1347	Each aio request uses - depending on your architecture - around 100-200
		1348	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1349	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1350	scalars and other data passed into aio requests will also be locked and
		1351	will consume memory till the request has entered the done state.
		1352
		1353	This is not awfully much, so queuing lots of requests is not usually a
		1354	problem.
		1355
		1356	Per-thread usage:
		1357
		1358	In the execution phase, some aio requests require more memory for
		1359	temporary buffers, and each thread requires a stack and other data
		1360	structures (usually around 16k-128k, depending on the OS).
		1361
		1362	=head1 KNOWN BUGS
		1363
		1364	Known bugs will be fixed in the next release.
		1365
683	=head1 SEE ALSO	1366	=head1 SEE ALSO
684		1367
685	L<Coro>, L<Linux::AIO> (obsolete).	1368	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1369	more natural syntax.
686		1370
687	=head1 AUTHOR	1371	=head1 AUTHOR
688		1372
689	Marc Lehmann <schmorp@schmorp.de>	1373	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1374	http://home.schmorp.de/

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