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Revision 1.57 by root, Sun Oct 22 01:28:31 2006 UTC vs.
Revision 1.119 by root, Sun Dec 2 20:54:33 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
…		…
18	};	19	};
19		20
20	# version 2+ has request and group objects	21	# version 2+ has request and group objects
21	use IO::AIO 2;	22	use IO::AIO 2;
22		23
		24	aioreq_pri 4; # give next request a very high priority
23	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
24	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
25		27
26	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
27	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
28		30
29	# AnyEvent integration	31	# AnyEvent integration (EV, Event, Glib, Tk, urxvt, pureperl...)
30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31	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 });
		34
		35	# EV integration
		36	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
32		37
33	# Event integration	38	# Event integration
34	Event->io (fd => IO::AIO::poll_fileno,	39	Event->io (fd => IO::AIO::poll_fileno,
35	poll => 'r',	40	poll => 'r',
36	cb => \&IO::AIO::poll_cb);	41	cb => \&IO::AIO::poll_cb);
…		…
50	=head1 DESCRIPTION	55	=head1 DESCRIPTION
51		56
52	This module implements asynchronous I/O using whatever means your	57	This module implements asynchronous I/O using whatever means your
53	operating system supports.	58	operating system supports.
54		59
		60	Asynchronous means that operations that can normally block your program
		61	(e.g. reading from disk) will be done asynchronously: the operation
		62	will still block, but you can do something else in the meantime. This
		63	is extremely useful for programs that need to stay interactive even
		64	when doing heavy I/O (GUI programs, high performance network servers
		65	etc.), but can also be used to easily do operations in parallel that are
		66	normally done sequentially, e.g. stat'ing many files, which is much faster
		67	on a RAID volume or over NFS when you do a number of stat operations
		68	concurrently.
		69
		70	While most of this works on all types of file descriptors (for
		71	example sockets), using these functions on file descriptors that
		72	support nonblocking operation (again, sockets, pipes etc.) is very
		73	inefficient. Use an event loop for that (such as the L<Event|Event>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
55	Currently, a number of threads are started that execute your read/writes	76	In this version, a number of threads are started that execute your
56	and signal their completion. You don't need thread support in your libc or	77	requests and signal their completion. You don't need thread support
57	perl, and the threads created by this module will not be visible to the	78	in perl, and the threads created by this module will not be visible
58	pthreads library. In the future, this module might make use of the native	79	to perl. In the future, this module might make use of the native aio
59	aio functions available on many operating systems. However, they are often	80	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	81	not well-supported or restricted (GNU/Linux doesn't allow them on normal
61	for example), and they would only support aio_read and aio_write, so the	82	files currently, for example), and they would only support aio_read and
62	remaining functionality would have to be implemented using threads anyway.	83	aio_write, so the remaining functionality would have to be implemented
		84	using threads anyway.
63		85
64	Although the module will work with in the presence of other threads, it is	86	Although the module will work in the presence of other (Perl-) threads,
65	currently not reentrant, so use appropriate locking yourself, always call	87	it is currently not reentrant in any way, so use appropriate locking
66	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	88	yourself, always call C<poll_cb> from within the same thread, or never
67	C<aio_> functions) recursively.	89	call C<poll_cb> (or other C<aio_> functions) recursively.
		90
		91	=head2 EXAMPLE
		92
		93	This is a simple example that uses the Event module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use Event;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with Event
		101	Event->io (fd => IO::AIO::poll_fileno,
		102	poll => 'r',
		103	cb => \&IO::AIO::poll_cb);
		104
		105	# queue the request to open /etc/passwd
		106	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		107	my $fh = shift
		108	or die "error while opening: $!";
		109
		110	# stat'ing filehandles is generally non-blocking
		111	my $size = -s $fh;
		112
		113	# queue a request to read the file
		114	my $contents;
		115	aio_read $fh, 0, $size, $contents, 0, sub {
		116	$_[0] == $size
		117	or die "short read: $!";
		118
		119	close $fh;
		120
		121	# file contents now in $contents
		122	print $contents;
		123
		124	# exit event loop and program
		125	Event::unloop;
		126	};
		127	};
		128
		129	# possibly queue up other requests, or open GUI windows,
		130	# check for sockets etc. etc.
		131
		132	# process events as long as there are some:
		133	Event::loop;
		134
		135	=head1 REQUEST ANATOMY AND LIFETIME
		136
		137	Every C<aio_*> function creates a request. which is a C data structure not
		138	directly visible to Perl.
		139
		140	If called in non-void context, every request function returns a Perl
		141	object representing the request. In void context, nothing is returned,
		142	which saves a bit of memory.
		143
		144	The perl object is a fairly standard ref-to-hash object. The hash contents
		145	are not used by IO::AIO so you are free to store anything you like in it.
		146
		147	During their existance, aio requests travel through the following states,
		148	in order:
		149
		150	=over 4
		151
		152	=item ready
		153
		154	Immediately after a request is created it is put into the ready state,
		155	waiting for a thread to execute it.
		156
		157	=item execute
		158
		159	A thread has accepted the request for processing and is currently
		160	executing it (e.g. blocking in read).
		161
		162	=item pending
		163
		164	The request has been executed and is waiting for result processing.
		165
		166	While request submission and execution is fully asynchronous, result
		167	processing is not and relies on the perl interpreter calling C<poll_cb>
		168	(or another function with the same effect).
		169
		170	=item result
		171
		172	The request results are processed synchronously by C<poll_cb>.
		173
		174	The C<poll_cb> function will process all outstanding aio requests by
		175	calling their callbacks, freeing memory associated with them and managing
		176	any groups they are contained in.
		177
		178	=item done
		179
		180	Request has reached the end of its lifetime and holds no resources anymore
		181	(except possibly for the Perl object, but its connection to the actual
		182	aio request is severed and calling its methods will either do nothing or
		183	result in a runtime error).
		184
		185	=back
68		186
69	=cut	187	=cut
70		188
71	package IO::AIO;	189	package IO::AIO;
		190
		191	use Carp ();
72		192
73	no warnings;	193	no warnings;
74	use strict 'vars';	194	use strict 'vars';
75		195
76	use base 'Exporter';	196	use base 'Exporter';
77		197
78	BEGIN {	198	BEGIN {
79	our $VERSION = '2.0';	199	our $VERSION = '2.6';
80		200
81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	201	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	202	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	203	aio_readlink aio_sync aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
84	aio_group);	204	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	205	aio_chown aio_chmod aio_utime aio_truncate);
		206	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		207	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		208	min_parallel max_parallel max_idle
		209	nreqs nready npending nthreads
		210	max_poll_time max_poll_reqs);
86		211
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	212	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		213
89	require XSLoader;	214	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	215	XSLoader::load ("IO::AIO", $VERSION);
91	}	216	}
92		217
93	=head1 FUNCTIONS	218	=head1 FUNCTIONS
94		219
95	=head2 AIO FUNCTIONS	220	=head2 AIO REQUEST FUNCTIONS
96		221
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	222	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	223	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	224	and they all accept an additional (and optional) C<$callback> argument
100	which must be a code reference. This code reference will get called with	225	which must be a code reference. This code reference will get called with
…		…
103	syscall has been executed asynchronously.	228	syscall has been executed asynchronously.
104		229
105	All functions expecting a filehandle keep a copy of the filehandle	230	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	231	internally until the request has finished.
107		232
108	All requests return objects of type L<IO::AIO::REQ> that allow further	233	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	234	further manipulation of those requests while they are in-flight.
110		235
111	The pathnames you pass to these routines I<must> be absolute and	236	The pathnames you pass to these routines I<must> be absolute and
112	encoded in byte form. The reason for the former is that at the time the	237	encoded as octets. The reason for the former is that at the time the
113	request is being executed, the current working directory could have	238	request is being executed, the current working directory could have
114	changed. Alternatively, you can make sure that you never change the	239	changed. Alternatively, you can make sure that you never change the
115	current working directory.	240	current working directory anywhere in the program and then use relative
		241	paths.
116		242
117	To encode pathnames to byte form, either make sure you either: a)	243	To encode pathnames as octets, either make sure you either: a) always pass
118	always pass in filenames you got from outside (command line, readdir	244	in filenames you got from outside (command line, readdir etc.) without
119	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	245	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
120	your pathnames to the locale (or other) encoding in effect in the user	246	your pathnames to the locale (or other) encoding in effect in the user
121	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	247	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
122	use something else.	248	use something else to ensure your scalar has the correct contents.
		249
		250	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		251	handles correctly wether it is set or not.
123		252
124	=over 4	253	=over 4
		254
		255	=item $prev_pri = aioreq_pri [$pri]
		256
		257	Returns the priority value that would be used for the next request and, if
		258	C<$pri> is given, sets the priority for the next aio request.
		259
		260	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		261	and C<4>, respectively. Requests with higher priority will be serviced
		262	first.
		263
		264	The priority will be reset to C<0> after each call to one of the C<aio_*>
		265	functions.
		266
		267	Example: open a file with low priority, then read something from it with
		268	higher priority so the read request is serviced before other low priority
		269	open requests (potentially spamming the cache):
		270
		271	aioreq_pri -3;
		272	aio_open ..., sub {
		273	return unless $_[0];
		274
		275	aioreq_pri -2;
		276	aio_read $_[0], ..., sub {
		277	...
		278	};
		279	};
		280
		281
		282	=item aioreq_nice $pri_adjust
		283
		284	Similar to C<aioreq_pri>, but subtracts the given value from the current
		285	priority, so the effect is cumulative.
		286
125		287
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	288	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		289
128	Asynchronously open or create a file and call the callback with a newly	290	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	291	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	297	list. They are the same as used by C<sysopen>.
136		298
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	299	Likewise, C<$mode> specifies the mode of the newly created file, if it
138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	300	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
139	except that it is mandatory (i.e. use C<0> if you don't create new files,	301	except that it is mandatory (i.e. use C<0> if you don't create new files,
140	and C<0666> or C<0777> if you do).	302	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		303	by the umask in effect then the request is being executed, so better never
		304	change the umask.
141		305
142	Example:	306	Example:
143		307
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	308	aio_open "/etc/passwd", O_RDONLY, 0, sub {
145	if ($_[0]) {	309	if ($_[0]) {
…		…
148	} else {	312	} else {
149	die "open failed: $!\n";	313	die "open failed: $!\n";
150	}	314	}
151	};	315	};
152		316
		317
153	=item aio_close $fh, $callback->($status)	318	=item aio_close $fh, $callback->($status)
154		319
155	Asynchronously close a file and call the callback with the result	320	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	321	code.
157	filehandle here, as perl will likely close the file descriptor another
158	time when the filehandle is destroyed. Normally, you can safely call perls
159	C<close> or just let filehandles go out of scope.
160		322
161	This is supposed to be a bug in the API, so that might change. It's	323	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	324	closing the file descriptor associated with the filehandle itself. Here is
		325	what aio_close will try:
		326
		327	1. dup()licate the fd
		328	2. asynchronously close() the duplicated fd
		329	3. dup()licate the fd once more
		330	4. let perl close() the filehandle
		331	5. asynchronously close the duplicated fd
		332
		333	The idea is that the first close() flushes stuff to disk that closing an
		334	fd will flush, so when perl closes the fd, nothing much will need to be
		335	flushed. The second async. close() will then flush stuff to disk that
		336	closing the last fd to the file will flush.
		337
		338	Just FYI, SuSv3 has this to say on close:
		339
		340	All outstanding record locks owned by the process on the file
		341	associated with the file descriptor shall be removed.
		342
		343	If fildes refers to a socket, close() shall cause the socket to be
		344	destroyed. ... close() shall block for up to the current linger
		345	interval until all data is transmitted.
		346	[this actually sounds like a specification bug, but who knows]
		347
		348	And at least Linux additionally actually flushes stuff on every close,
		349	even when the file itself is still open.
		350
		351	Sounds enourmously inefficient and complicated? Yes... please show me how
		352	to nuke perl's fd out of existence...
		353
		354	=cut
		355
		356	sub aio_close($;$) {
		357	aio_block {
		358	my ($fh, $cb) = @_;
		359
		360	my $pri = aioreq_pri;
		361	my $grp = aio_group $cb;
		362
		363	my $fd = fileno $fh;
		364
		365	defined $fd or Carp::croak "aio_close called with fd-less filehandle";
		366
		367	# if the dups fail we will simply get EBADF
		368	my $fd2 = _dup $fd;
		369	aioreq_pri $pri;
		370	add $grp _aio_close $fd2, sub {
		371	my $fd2 = _dup $fd;
		372	close $fh;
		373	aioreq_pri $pri;
		374	add $grp _aio_close $fd2, sub {
		375	$grp->result ($_[0]);
		376	};
		377	};
		378
		379	$grp
		380	}
		381	}
		382
163		383
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	384	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		385
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	386	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		387
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	388	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	389	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	390	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	391	like the syscall).
172		392
		393	If C<$offset> is undefined, then the current file descriptor offset will
		394	be used (and updated), otherwise the file descriptor offset will not be
		395	changed by these calls.
		396
		397	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		398
		399	If C<$dataoffset> is less than zero, it will be counted from the end of
		400	C<$data>.
		401
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	402	The C<$data> scalar I<MUST NOT> be modified in any way while the request
174	is outstanding. Modifying it can result in segfaults or WW3 (if the	403	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	404	the necessary/optional hardware is installed).
176		405
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	406	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	407	offset C<0> within the scalar:
179		408
180	aio_read $fh, 7, 15, $buffer, 0, sub {	409	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	410	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	411	print "read $_[0] bytes: <$buffer>\n";
183	};	412	};
184		413
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	Try to move the I<file> (directories not supported as either source or
188	destination) from C<$srcpath> to C<$dstpath> and call the callback with
189	the C<0> (error) or C<-1> ok.
190
191	This is a composite request that tries to rename(2) the file first. If
192	rename files with C<EXDEV>, it creates the destination file with mode 0200
193	and copies the contents of the source file into it using C<aio_sendfile>,
194	followed by restoring atime, mtime, access mode and uid/gid, in that
195	order, and unlinking the C<$srcpath>.
196
197	If an error occurs, the partial destination file will be unlinked, if
198	possible, except when setting atime, mtime, access mode and uid/gid, where
199	errors are being ignored.
200
201	=cut
202
203	sub aio_move($$$) {
204	my ($src, $dst, $cb) = @_;
205
206	my $grp = aio_group;
207
208	add $grp aio_rename $src, $dst, sub {
209	if ($_[0] && $! == EXDEV) {
210	add $grp aio_open $src, O_RDONLY, 0, sub {
211	if (my $src_fh = $_[0]) {
212	my @stat = stat $src_fh;
213
214	add $grp aio_open $dst, O_WRONLY, 0200, sub {
215	if (my $dst_fh = $_[0]) {
216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
217	close $src_fh;
218
219	if ($_[0] == $stat[7]) {
220	utime $stat[8], $stat[9], $dst;
221	chmod $stat[2] & 07777, $dst_fh;
222	chown $stat[4], $stat[5], $dst_fh;
223	close $dst_fh;
224
225	add $grp aio_unlink $src, sub {
226	$cb->($_[0]);
227	};
228	} else {
229	my $errno = $!;
230	add $grp aio_unlink $dst, sub {
231	$! = $errno;
232	$cb->(-1);
233	};
234	}
235	};
236	} else {
237	$cb->(-1);
238	}
239	},
240
241	} else {
242	$cb->(-1);
243	}
244	};
245	} else {
246	$cb->($_[0]);
247	}
248	};
249
250	$grp
251	}
252		414
253	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	415	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
254		416
255	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	417	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
256	reading at byte offset C<$in_offset>, and starts writing at the current	418	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
270	C<$in_fh> than are written, and there is no way to find out how many	432	C<$in_fh> than are written, and there is no way to find out how many
271	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	433	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
272	provides the number of bytes written to C<$out_fh>. Only if the result	434	provides the number of bytes written to C<$out_fh>. Only if the result
273	value equals C<$length> one can assume that C<$length> bytes have been	435	value equals C<$length> one can assume that C<$length> bytes have been
274	read.	436	read.
		437
275		438
276	=item aio_readahead $fh,$offset,$length, $callback->($retval)	439	=item aio_readahead $fh,$offset,$length, $callback->($retval)
277		440
278	C<aio_readahead> populates the page cache with data from a file so that	441	C<aio_readahead> populates the page cache with data from a file so that
279	subsequent reads from that file will not block on disk I/O. The C<$offset>	442	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
285	file. The current file offset of the file is left unchanged.	448	file. The current file offset of the file is left unchanged.
286		449
287	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	450	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
288	emulated by simply reading the data, which would have a similar effect.	451	emulated by simply reading the data, which would have a similar effect.
289		452
		453
290	=item aio_stat $fh_or_path, $callback->($status)	454	=item aio_stat $fh_or_path, $callback->($status)
291		455
292	=item aio_lstat $fh, $callback->($status)	456	=item aio_lstat $fh, $callback->($status)
293		457
294	Works like perl's C<stat> or C<lstat> in void context. The callback will	458	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
307	aio_stat "/etc/passwd", sub {	471	aio_stat "/etc/passwd", sub {
308	$_[0] and die "stat failed: $!";	472	$_[0] and die "stat failed: $!";
309	print "size is ", -s _, "\n";	473	print "size is ", -s _, "\n";
310	};	474	};
311		475
		476
		477	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		478
		479	Works like perl's C<utime> function (including the special case of $atime
		480	and $mtime being undef). Fractional times are supported if the underlying
		481	syscalls support them.
		482
		483	When called with a pathname, uses utimes(2) if available, otherwise
		484	utime(2). If called on a file descriptor, uses futimes(2) if available,
		485	otherwise returns ENOSYS, so this is not portable.
		486
		487	Examples:
		488
		489	# set atime and mtime to current time (basically touch(1)):
		490	aio_utime "path", undef, undef;
		491	# set atime to current time and mtime to beginning of the epoch:
		492	aio_utime "path", time, undef; # undef==0
		493
		494
		495	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		496
		497	Works like perl's C<chown> function, except that C<undef> for either $uid
		498	or $gid is being interpreted as "do not change" (but -1 can also be used).
		499
		500	Examples:
		501
		502	# same as "chown root path" in the shell:
		503	aio_chown "path", 0, -1;
		504	# same as above:
		505	aio_chown "path", 0, undef;
		506
		507
		508	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		509
		510	Works like truncate(2) or ftruncate(2).
		511
		512
		513	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		514
		515	Works like perl's C<chmod> function.
		516
		517
312	=item aio_unlink $pathname, $callback->($status)	518	=item aio_unlink $pathname, $callback->($status)
313		519
314	Asynchronously unlink (delete) a file and call the callback with the	520	Asynchronously unlink (delete) a file and call the callback with the
315	result code.	521	result code.
316		522
		523
		524	=item aio_mknod $path, $mode, $dev, $callback->($status)
		525
		526	[EXPERIMENTAL]
		527
		528	Asynchronously create a device node (or fifo). See mknod(2).
		529
		530	The only (POSIX-) portable way of calling this function is:
		531
		532	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		533
		534
317	=item aio_link $srcpath, $dstpath, $callback->($status)	535	=item aio_link $srcpath, $dstpath, $callback->($status)
318		536
319	Asynchronously create a new link to the existing object at C<$srcpath> at	537	Asynchronously create a new link to the existing object at C<$srcpath> at
320	the path C<$dstpath> and call the callback with the result code.	538	the path C<$dstpath> and call the callback with the result code.
321		539
		540
322	=item aio_symlink $srcpath, $dstpath, $callback->($status)	541	=item aio_symlink $srcpath, $dstpath, $callback->($status)
323		542
324	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	543	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
325	the path C<$dstpath> and call the callback with the result code.	544	the path C<$dstpath> and call the callback with the result code.
326		545
		546
		547	=item aio_readlink $path, $callback->($link)
		548
		549	Asynchronously read the symlink specified by C<$path> and pass it to
		550	the callback. If an error occurs, nothing or undef gets passed to the
		551	callback.
		552
		553
327	=item aio_rename $srcpath, $dstpath, $callback->($status)	554	=item aio_rename $srcpath, $dstpath, $callback->($status)
328		555
329	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	556	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
330	rename(2) and call the callback with the result code.	557	rename(2) and call the callback with the result code.
331		558
		559
		560	=item aio_mkdir $pathname, $mode, $callback->($status)
		561
		562	Asynchronously mkdir (create) a directory and call the callback with
		563	the result code. C<$mode> will be modified by the umask at the time the
		564	request is executed, so do not change your umask.
		565
		566
332	=item aio_rmdir $pathname, $callback->($status)	567	=item aio_rmdir $pathname, $callback->($status)
333		568
334	Asynchronously rmdir (delete) a directory and call the callback with the	569	Asynchronously rmdir (delete) a directory and call the callback with the
335	result code.	570	result code.
		571
336		572
337	=item aio_readdir $pathname, $callback->($entries)	573	=item aio_readdir $pathname, $callback->($entries)
338		574
339	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	575	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
340	directory (i.e. opendir + readdir + closedir). The entries will not be	576	directory (i.e. opendir + readdir + closedir). The entries will not be
341	sorted, and will B<NOT> include the C<.> and C<..> entries.	577	sorted, and will B<NOT> include the C<.> and C<..> entries.
342		578
343	The callback a single argument which is either C<undef> or an array-ref	579	The callback a single argument which is either C<undef> or an array-ref
344	with the filenames.	580	with the filenames.
345		581
		582
		583	=item aio_load $path, $data, $callback->($status)
		584
		585	This is a composite request that tries to fully load the given file into
		586	memory. Status is the same as with aio_read.
		587
		588	=cut
		589
		590	sub aio_load($$;$) {
		591	aio_block {
		592	my ($path, undef, $cb) = @_;
		593	my $data = \$_[1];
		594
		595	my $pri = aioreq_pri;
		596	my $grp = aio_group $cb;
		597
		598	aioreq_pri $pri;
		599	add $grp aio_open $path, O_RDONLY, 0, sub {
		600	my $fh = shift
		601	or return $grp->result (-1);
		602
		603	aioreq_pri $pri;
		604	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		605	$grp->result ($_[0]);
		606	};
		607	};
		608
		609	$grp
		610	}
		611	}
		612
		613	=item aio_copy $srcpath, $dstpath, $callback->($status)
		614
		615	Try to copy the I<file> (directories not supported as either source or
		616	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		617	the C<0> (error) or C<-1> ok.
		618
		619	This is a composite request that it creates the destination file with
		620	mode 0200 and copies the contents of the source file into it using
		621	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		622	uid/gid, in that order.
		623
		624	If an error occurs, the partial destination file will be unlinked, if
		625	possible, except when setting atime, mtime, access mode and uid/gid, where
		626	errors are being ignored.
		627
		628	=cut
		629
		630	sub aio_copy($$;$) {
		631	aio_block {
		632	my ($src, $dst, $cb) = @_;
		633
		634	my $pri = aioreq_pri;
		635	my $grp = aio_group $cb;
		636
		637	aioreq_pri $pri;
		638	add $grp aio_open $src, O_RDONLY, 0, sub {
		639	if (my $src_fh = $_[0]) {
		640	my @stat = stat $src_fh;
		641
		642	aioreq_pri $pri;
		643	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		644	if (my $dst_fh = $_[0]) {
		645	aioreq_pri $pri;
		646	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		647	if ($_[0] == $stat[7]) {
		648	$grp->result (0);
		649	close $src_fh;
		650
		651	# those should not normally block. should. should.
		652	utime $stat[8], $stat[9], $dst;
		653	chmod $stat[2] & 07777, $dst_fh;
		654	chown $stat[4], $stat[5], $dst_fh;
		655	close $dst_fh;
		656	} else {
		657	$grp->result (-1);
		658	close $src_fh;
		659	close $dst_fh;
		660
		661	aioreq $pri;
		662	add $grp aio_unlink $dst;
		663	}
		664	};
		665	} else {
		666	$grp->result (-1);
		667	}
		668	},
		669
		670	} else {
		671	$grp->result (-1);
		672	}
		673	};
		674
		675	$grp
		676	}
		677	}
		678
		679	=item aio_move $srcpath, $dstpath, $callback->($status)
		680
		681	Try to move the I<file> (directories not supported as either source or
		682	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		683	the C<0> (error) or C<-1> ok.
		684
		685	This is a composite request that tries to rename(2) the file first. If
		686	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		687	that is successful, unlinking the C<$srcpath>.
		688
		689	=cut
		690
		691	sub aio_move($$;$) {
		692	aio_block {
		693	my ($src, $dst, $cb) = @_;
		694
		695	my $pri = aioreq_pri;
		696	my $grp = aio_group $cb;
		697
		698	aioreq_pri $pri;
		699	add $grp aio_rename $src, $dst, sub {
		700	if ($_[0] && $! == EXDEV) {
		701	aioreq_pri $pri;
		702	add $grp aio_copy $src, $dst, sub {
		703	$grp->result ($_[0]);
		704
		705	if (!$_[0]) {
		706	aioreq_pri $pri;
		707	add $grp aio_unlink $src;
		708	}
		709	};
		710	} else {
		711	$grp->result ($_[0]);
		712	}
		713	};
		714
		715	$grp
		716	}
		717	}
		718
346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	719	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
347		720
348	Scans a directory (similar to C<aio_readdir>) but additionally tries to	721	Scans a directory (similar to C<aio_readdir>) but additionally tries to
349	separate the entries of directory C<$path> into two sets of names, ones	722	efficiently separate the entries of directory C<$path> into two sets of
350	you can recurse into (directories or links to them), and ones you cannot	723	names, directories you can recurse into (directories), and ones you cannot
351	recurse into (everything else).	724	recurse into (everything else, including symlinks to directories).
352		725
353	C<aio_scandir> is a composite request that consists of many sub	726	C<aio_scandir> is a composite request that creates of many sub requests_
354	requests. C<$maxreq> specifies the maximum number of outstanding aio	727	C<$maxreq> specifies the maximum number of outstanding aio requests that
355	requests that this function generates. If it is C<< <= 0 >>, then a	728	this function generates. If it is C<< <= 0 >>, then a suitable default
356	suitable default will be chosen (currently 8).	729	will be chosen (currently 4).
357		730
358	On error, the callback is called without arguments, otherwise it receives	731	On error, the callback is called without arguments, otherwise it receives
359	two array-refs with path-relative entry names.	732	two array-refs with path-relative entry names.
360		733
361	Example:	734	Example:
…		…
395	as those tend to return 0 or 1 as link counts, which disables the	768	as those tend to return 0 or 1 as link counts, which disables the
396	directory counting heuristic.	769	directory counting heuristic.
397		770
398	=cut	771	=cut
399		772
400	sub aio_scandir($$$) {	773	sub aio_scandir($$;$) {
		774	aio_block {
401	my ($path, $maxreq, $cb) = @_;	775	my ($path, $maxreq, $cb) = @_;
402		776
		777	my $pri = aioreq_pri;
		778
403	my $grp = aio_group;	779	my $grp = aio_group $cb;
404		780
405	$maxreq = 8 if $maxreq <= 0;	781	$maxreq = 4 if $maxreq <= 0;
406		782
407	# stat once	783	# stat once
		784	aioreq_pri $pri;
408	add $grp aio_stat $path, sub {	785	add $grp aio_stat $path, sub {
409	return $cb->() if $_[0];	786	return $grp->result () if $_[0];
410	my $now = time;	787	my $now = time;
411	my $hash1 = join ":", (stat _)[0,1,3,7,9];	788	my $hash1 = join ":", (stat _)[0,1,3,7,9];
412		789
413	# read the directory entries	790	# read the directory entries
		791	aioreq_pri $pri;
414	add $grp aio_readdir $path, sub {	792	add $grp aio_readdir $path, sub {
415	my $entries = shift	793	my $entries = shift
416	or return $cb->();	794	or return $grp->result ();
417		795
418	# stat the dir another time	796	# stat the dir another time
		797	aioreq_pri $pri;
419	add $grp aio_stat $path, sub {	798	add $grp aio_stat $path, sub {
420	my $hash2 = join ":", (stat _)[0,1,3,7,9];	799	my $hash2 = join ":", (stat _)[0,1,3,7,9];
421		800
422	my $ndirs;	801	my $ndirs;
423		802
424	# take the slow route if anything looks fishy	803	# take the slow route if anything looks fishy
425	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	804	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
426	$ndirs = -1;	805	$ndirs = -1;
427	} else {	806	} else {
428	# if nlink == 2, we are finished	807	# if nlink == 2, we are finished
429	# on non-posix-fs's, we rely on nlink < 2	808	# on non-posix-fs's, we rely on nlink < 2
430	$ndirs = (stat _)[3] - 2	809	$ndirs = (stat _)[3] - 2
431	or return $cb->([], $entries);	810	or return $grp->result ([], $entries);
432	}
433
434	# sort into likely dirs and likely nondirs
435	# dirs == files without ".", short entries first
436	$entries = [map $_->[0],
437	sort { $b->[1] cmp $a->[1] }
438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
439	@$entries];
440
441	my (@dirs, @nondirs);
442
443	my ($statcb, $schedcb);
444	my $nreq = 0;
445
446	$schedcb = sub {
447	if (@$entries) {
448	if ($nreq < $maxreq) {
449	my $ent = pop @$entries;
450	$nreq++;
451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
452	}
453	} elsif (!$nreq) {
454	# finished
455	undef $statcb;
456	undef $schedcb;
457	$cb->(\@dirs, \@nondirs) if $cb;
458	undef $cb;
459	}	811	}
		812
		813	# sort into likely dirs and likely nondirs
		814	# dirs == files without ".", short entries first
		815	$entries = [map $_->[0],
		816	sort { $b->[1] cmp $a->[1] }
		817	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		818	@$entries];
		819
		820	my (@dirs, @nondirs);
		821
		822	my $statgrp = add $grp aio_group sub {
		823	$grp->result (\@dirs, \@nondirs);
		824	};
		825
		826	limit $statgrp $maxreq;
		827	feed $statgrp sub {
		828	return unless @$entries;
		829	my $entry = pop @$entries;
		830
		831	aioreq_pri $pri;
		832	add $statgrp aio_stat "$path/$entry/.", sub {
		833	if ($_[0] < 0) {
		834	push @nondirs, $entry;
		835	} else {
		836	# need to check for real directory
		837	aioreq_pri $pri;
		838	add $statgrp aio_lstat "$path/$entry", sub {
		839	if (-d _) {
		840	push @dirs, $entry;
		841
		842	unless (--$ndirs) {
		843	push @nondirs, @$entries;
		844	feed $statgrp;
		845	}
		846	} else {
		847	push @nondirs, $entry;
		848	}
		849	}
		850	}
		851	};
		852	};
460	};	853	};
461	$statcb = sub {
462	my ($status, $entry) = @_;
463
464	if ($status < 0) {
465	$nreq--;
466	push @nondirs, $entry;
467	&$schedcb;
468	} else {
469	# need to check for real directory
470	add $grp aio_lstat "$path/$entry", sub {
471	$nreq--;
472
473	if (-d _) {
474	push @dirs, $entry;
475
476	if (!--$ndirs) {
477	push @nondirs, @$entries;
478	$entries = [];
479	}
480	} else {
481	push @nondirs, $entry;
482	}
483
484	&$schedcb;
485	}
486	}
487	};
488
489	&$schedcb while @$entries && $nreq < $maxreq;
490	};	854	};
491	};	855	};
		856
		857	$grp
492	};	858	}
493
494	$grp
495	}	859	}
		860
		861	=item aio_rmtree $path, $callback->($status)
		862
		863	Delete a directory tree starting (and including) C<$path>, return the
		864	status of the final C<rmdir> only. This is a composite request that
		865	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		866	everything else.
		867
		868	=cut
		869
		870	sub aio_rmtree;
		871	sub aio_rmtree($;$) {
		872	aio_block {
		873	my ($path, $cb) = @_;
		874
		875	my $pri = aioreq_pri;
		876	my $grp = aio_group $cb;
		877
		878	aioreq_pri $pri;
		879	add $grp aio_scandir $path, 0, sub {
		880	my ($dirs, $nondirs) = @_;
		881
		882	my $dirgrp = aio_group sub {
		883	add $grp aio_rmdir $path, sub {
		884	$grp->result ($_[0]);
		885	};
		886	};
		887
		888	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		889	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		890
		891	add $grp $dirgrp;
		892	};
		893
		894	$grp
		895	}
		896	}
		897
		898	=item aio_sync $callback->($status)
		899
		900	Asynchronously call sync and call the callback when finished.
496		901
497	=item aio_fsync $fh, $callback->($status)	902	=item aio_fsync $fh, $callback->($status)
498		903
499	Asynchronously call fsync on the given filehandle and call the callback	904	Asynchronously call fsync on the given filehandle and call the callback
500	with the fsync result code.	905	with the fsync result code.
…		…
505	callback with the fdatasync result code.	910	callback with the fdatasync result code.
506		911
507	If this call isn't available because your OS lacks it or it couldn't be	912	If this call isn't available because your OS lacks it or it couldn't be
508	detected, it will be emulated by calling C<fsync> instead.	913	detected, it will be emulated by calling C<fsync> instead.
509		914
510	=item aio_group $callback->()	915	=item aio_group $callback->(...)
511
512	[EXPERIMENTAL]
513		916
514	This is a very special aio request: Instead of doing something, it is a	917	This is a very special aio request: Instead of doing something, it is a
515	container for other aio requests, which is useful if you want to bundle	918	container for other aio requests, which is useful if you want to bundle
516	many requests into a single, composite, request.	919	many requests into a single, composite, request with a definite callback
		920	and the ability to cancel the whole request with its subrequests.
517		921
518	Returns an object of class L<IO::AIO::GRP>. See its documentation below	922	Returns an object of class L<IO::AIO::GRP>. See its documentation below
519	for more info.	923	for more info.
520		924
521	Example:	925	Example:
…		…
527	add $grp	931	add $grp
528	(aio_stat ...),	932	(aio_stat ...),
529	(aio_stat ...),	933	(aio_stat ...),
530	...;	934	...;
531		935
		936	=item aio_nop $callback->()
		937
		938	This is a special request - it does nothing in itself and is only used for
		939	side effects, such as when you want to add a dummy request to a group so
		940	that finishing the requests in the group depends on executing the given
		941	code.
		942
		943	While this request does nothing, it still goes through the execution
		944	phase and still requires a worker thread. Thus, the callback will not
		945	be executed immediately but only after other requests in the queue have
		946	entered their execution phase. This can be used to measure request
		947	latency.
		948
532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	949	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
533		950
534	Mainly used for debugging and benchmarking, this aio request puts one of	951	Mainly used for debugging and benchmarking, this aio request puts one of
535	the request workers to sleep for the given time.	952	the request workers to sleep for the given time.
536		953
537	While it is theoretically handy to have simple I/O scheduling requests	954	While it is theoretically handy to have simple I/O scheduling requests
538	like sleep and file handle readable/writable, the overhead this creates	955	like sleep and file handle readable/writable, the overhead this creates is
539	is immense, so do not use this function except to put your application	956	immense (it blocks a thread for a long time) so do not use this function
540	under artificial I/O pressure.	957	except to put your application under artificial I/O pressure.
541		958
542	=back	959	=back
543		960
544	=head2 IO::AIO::REQ CLASS	961	=head2 IO::AIO::REQ CLASS
545		962
546	All non-aggregate C<aio_*> functions return an object of this class when	963	All non-aggregate C<aio_*> functions return an object of this class when
547	called in non-void context.	964	called in non-void context.
548		965
549	A request always moves through the following five states in its lifetime,
550	in order: B<ready> (request has been created, but has not been executed
551	yet), B<execute> (request is currently being executed), B<pending>
552	(request has been executed but callback has not been called yet),
553	B<result> (results are being processed synchronously, includes calling the
554	callback) and B<done> (request has reached the end of its lifetime and
555	holds no resources anymore).
556
557	=over 4	966	=over 4
558		967
559	=item $req->cancel	968	=item cancel $req
560		969
561	Cancels the request, if possible. Has the effect of skipping execution	970	Cancels the request, if possible. Has the effect of skipping execution
562	when entering the B<execute> state and skipping calling the callback when	971	when entering the B<execute> state and skipping calling the callback when
563	entering the the B<result> state, but will leave the request otherwise	972	entering the the B<result> state, but will leave the request otherwise
564	untouched. That means that requests that currently execute will not be	973	untouched. That means that requests that currently execute will not be
565	stopped and resources held by the request will not be freed prematurely.	974	stopped and resources held by the request will not be freed prematurely.
566		975
		976	=item cb $req $callback->(...)
		977
		978	Replace (or simply set) the callback registered to the request.
		979
567	=back	980	=back
568		981
569	=head2 IO::AIO::GRP CLASS	982	=head2 IO::AIO::GRP CLASS
570		983
571	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	984	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
585	You add requests by calling the C<add> method with one or more	998	You add requests by calling the C<add> method with one or more
586	C<IO::AIO::REQ> objects:	999	C<IO::AIO::REQ> objects:
587		1000
588	$grp->add (aio_unlink "...");	1001	$grp->add (aio_unlink "...");
589		1002
590	add $grp aio_stat "...", sub { ... };	1003	add $grp aio_stat "...", sub {
		1004	$_[0] or return $grp->result ("error");
		1005
		1006	# add another request dynamically, if first succeeded
		1007	add $grp aio_open "...", sub {
		1008	$grp->result ("ok");
		1009	};
		1010	};
591		1011
592	This makes it very easy to create composite requests (see the source of	1012	This makes it very easy to create composite requests (see the source of
593	C<aio_move> for an application) that work and feel like simple requests.	1013	C<aio_move> for an application) that work and feel like simple requests.
594		1014
		1015	=over 4
		1016
595	The IO::AIO::GRP objects will be cleaned up during calls to	1017	=item * The IO::AIO::GRP objects will be cleaned up during calls to
596	C<IO::AIO::poll_cb>, just like any other request.	1018	C<IO::AIO::poll_cb>, just like any other request.
597		1019
598	They can be canceled like any other request. Canceling will cancel not	1020	=item * They can be canceled like any other request. Canceling will cancel not
599	just the request itself, but also all requests it contains.	1021	only the request itself, but also all requests it contains.
600		1022
601	They can also can also be added to other IO::AIO::GRP objects.	1023	=item * They can also can also be added to other IO::AIO::GRP objects.
		1024
		1025	=item * You must not add requests to a group from within the group callback (or
		1026	any later time).
		1027
		1028	=back
602		1029
603	Their lifetime, simplified, looks like this: when they are empty, they	1030	Their lifetime, simplified, looks like this: when they are empty, they
604	will finish very quickly. If they contain only requests that are in the	1031	will finish very quickly. If they contain only requests that are in the
605	C<done> state, they will also finish. Otherwise they will continue to	1032	C<done> state, they will also finish. Otherwise they will continue to
606	exist.	1033	exist.
…		…
610	group. And only when all those requests have finished will the the group	1037	group. And only when all those requests have finished will the the group
611	itself finish.	1038	itself finish.
612		1039
613	=over 4	1040	=over 4
614		1041
		1042	=item add $grp ...
		1043
615	=item $grp->add (...)	1044	=item $grp->add (...)
616
617	=item add $grp ...
618		1045
619	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1046	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
620	be added, including other groups, as long as you do not create circular	1047	be added, including other groups, as long as you do not create circular
621	dependencies.	1048	dependencies.
622		1049
623	Returns all its arguments.	1050	Returns all its arguments.
624		1051
		1052	=item $grp->cancel_subs
		1053
		1054	Cancel all subrequests and clears any feeder, but not the group request
		1055	itself. Useful when you queued a lot of events but got a result early.
		1056
		1057	=item $grp->result (...)
		1058
		1059	Set the result value(s) that will be passed to the group callback when all
		1060	subrequests have finished and set thre groups errno to the current value
		1061	of errno (just like calling C<errno> without an error number). By default,
		1062	no argument will be passed and errno is zero.
		1063
		1064	=item $grp->errno ([$errno])
		1065
		1066	Sets the group errno value to C<$errno>, or the current value of errno
		1067	when the argument is missing.
		1068
		1069	Every aio request has an associated errno value that is restored when
		1070	the callback is invoked. This method lets you change this value from its
		1071	default (0).
		1072
		1073	Calling C<result> will also set errno, so make sure you either set C<$!>
		1074	before the call to C<result>, or call c<errno> after it.
		1075
		1076	=item feed $grp $callback->($grp)
		1077
		1078	Sets a feeder/generator on this group: every group can have an attached
		1079	generator that generates requests if idle. The idea behind this is that,
		1080	although you could just queue as many requests as you want in a group,
		1081	this might starve other requests for a potentially long time. For
		1082	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1083	requests, delaying any later requests for a long time.
		1084
		1085	To avoid this, and allow incremental generation of requests, you can
		1086	instead a group and set a feeder on it that generates those requests. The
		1087	feed callback will be called whenever there are few enough (see C<limit>,
		1088	below) requests active in the group itself and is expected to queue more
		1089	requests.
		1090
		1091	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1092	not impose any limits).
		1093
		1094	If the feed does not queue more requests when called, it will be
		1095	automatically removed from the group.
		1096
		1097	If the feed limit is C<0>, it will be set to 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
625	=back	1119	=back
626		1120
627	=head2 SUPPORT FUNCTIONS	1121	=head2 SUPPORT FUNCTIONS
		1122
		1123	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
628		1124
629	=over 4	1125	=over 4
630		1126
631	=item $fileno = IO::AIO::poll_fileno	1127	=item $fileno = IO::AIO::poll_fileno
632		1128
…		…
637		1133
638	See C<poll_cb> for an example.	1134	See C<poll_cb> for an example.
639		1135
640	=item IO::AIO::poll_cb	1136	=item IO::AIO::poll_cb
641		1137
642	Process all outstanding events on the result pipe. You have to call this	1138	Process some outstanding events on the result pipe. You have to call this
643	regularly. Returns the number of events processed. Returns immediately	1139	regularly. Returns the number of events processed. Returns immediately
644	when no events are outstanding.	1140	when no events are outstanding. The amount of events processed depends on
		1141	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1142
		1143	If not all requests were processed for whatever reason, the filehandle
		1144	will still be ready when C<poll_cb> returns.
645		1145
646	Example: Install an Event watcher that automatically calls	1146	Example: Install an Event watcher that automatically calls
647	IO::AIO::poll_cb with high priority:	1147	IO::AIO::poll_cb with high priority:
648		1148
649	Event->io (fd => IO::AIO::poll_fileno,	1149	Event->io (fd => IO::AIO::poll_fileno,
650	poll => 'r', async => 1,	1150	poll => 'r', async => 1,
651	cb => \&IO::AIO::poll_cb);	1151	cb => \&IO::AIO::poll_cb);
652		1152
		1153	=item IO::AIO::max_poll_reqs $nreqs
		1154
		1155	=item IO::AIO::max_poll_time $seconds
		1156
		1157	These set the maximum number of requests (default C<0>, meaning infinity)
		1158	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1159	the maximum amount of time (default C<0>, meaning infinity) spent in
		1160	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1161	of time C<poll_cb> is allowed to use).
		1162
		1163	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1164	syscall per request processed, which is not normally a problem unless your
		1165	callbacks are really really fast or your OS is really really slow (I am
		1166	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1167
		1168	Setting these is useful if you want to ensure some level of
		1169	interactiveness when perl is not fast enough to process all requests in
		1170	time.
		1171
		1172	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1173
		1174	Example: Install an Event watcher that automatically calls
		1175	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1176	program get the CPU sometimes even under high AIO load.
		1177
		1178	# try not to spend much more than 0.1s in poll_cb
		1179	IO::AIO::max_poll_time 0.1;
		1180
		1181	# use a low priority so other tasks have priority
		1182	Event->io (fd => IO::AIO::poll_fileno,
		1183	poll => 'r', nice => 1,
		1184	cb => &IO::AIO::poll_cb);
		1185
653	=item IO::AIO::poll_wait	1186	=item IO::AIO::poll_wait
654		1187
		1188	If there are any outstanding requests and none of them in the result
655	Wait till the result filehandle becomes ready for reading (simply does a	1189	phase, wait till the result filehandle becomes ready for reading (simply
656	C<select> on the filehandle. This is useful if you want to synchronously wait	1190	does a C<select> on the filehandle. This is useful if you want to
657	for some requests to finish).	1191	synchronously wait for some requests to finish).
658		1192
659	See C<nreqs> for an example.	1193	See C<nreqs> for an example.
660		1194
		1195	=item IO::AIO::poll
		1196
		1197	Waits until some requests have been handled.
		1198
		1199	Returns the number of requests processed, but is otherwise strictly
		1200	equivalent to:
		1201
		1202	IO::AIO::poll_wait, IO::AIO::poll_cb
		1203
661	=item IO::AIO::nreqs	1204	=item IO::AIO::flush
662		1205
663	Returns the number of requests currently outstanding (i.e. for which their	1206	Wait till all outstanding AIO requests have been handled.
664	callback has not been invoked yet).
665		1207
666	Example: wait till there are no outstanding requests anymore:	1208	Strictly equivalent to:
667		1209
668	IO::AIO::poll_wait, IO::AIO::poll_cb	1210	IO::AIO::poll_wait, IO::AIO::poll_cb
669	while IO::AIO::nreqs;	1211	while IO::AIO::nreqs;
670		1212
671	=item IO::AIO::flush	1213	=back
672		1214
673	Wait till all outstanding AIO requests have been handled.	1215	=head3 CONTROLLING THE NUMBER OF THREADS
674		1216
675	Strictly equivalent to:	1217	=over
676
677	IO::AIO::poll_wait, IO::AIO::poll_cb
678	while IO::AIO::nreqs;
679
680	=item IO::AIO::poll
681
682	Waits until some requests have been handled.
683
684	Strictly equivalent to:
685
686	IO::AIO::poll_wait, IO::AIO::poll_cb
687	if IO::AIO::nreqs;
688		1218
689	=item IO::AIO::min_parallel $nthreads	1219	=item IO::AIO::min_parallel $nthreads
690		1220
691	Set the minimum number of AIO threads to C<$nthreads>. The current default	1221	Set the minimum number of AIO threads to C<$nthreads>. The current
692	is C<4>, which means four asynchronous operations can be done at one time	1222	default is C<8>, which means eight asynchronous operations can execute
693	(the number of outstanding operations, however, is unlimited).	1223	concurrently at any one time (the number of outstanding requests,
		1224	however, is unlimited).
694		1225
695	IO::AIO starts threads only on demand, when an AIO request is queued and	1226	IO::AIO starts threads only on demand, when an AIO request is queued and
696	no free thread exists.	1227	no free thread exists. Please note that queueing up a hundred requests can
		1228	create demand for a hundred threads, even if it turns out that everything
		1229	is in the cache and could have been processed faster by a single thread.
697		1230
698	It is recommended to keep the number of threads low, as some Linux	1231	It is recommended to keep the number of threads relatively low, as some
699	kernel versions will scale negatively with the number of threads (higher	1232	Linux kernel versions will scale negatively with the number of threads
700	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1233	(higher parallelity => MUCH higher latency). With current Linux 2.6
701	threads should be fine.	1234	versions, 4-32 threads should be fine.
702		1235
703	Under most circumstances you don't need to call this function, as the	1236	Under most circumstances you don't need to call this function, as the
704	module selects a default that is suitable for low to moderate load.	1237	module selects a default that is suitable for low to moderate load.
705		1238
706	=item IO::AIO::max_parallel $nthreads	1239	=item IO::AIO::max_parallel $nthreads
…		…
715	This module automatically runs C<max_parallel 0> at program end, to ensure	1248	This module automatically runs C<max_parallel 0> at program end, to ensure
716	that all threads are killed and that there are no outstanding requests.	1249	that all threads are killed and that there are no outstanding requests.
717		1250
718	Under normal circumstances you don't need to call this function.	1251	Under normal circumstances you don't need to call this function.
719		1252
		1253	=item IO::AIO::max_idle $nthreads
		1254
		1255	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1256	threads that did not get a request to process within 10 seconds). That
		1257	means if a thread becomes idle while C<$nthreads> other threads are also
		1258	idle, it will free its resources and exit.
		1259
		1260	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1261	to allow for extremely high load situations, but want to free resources
		1262	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1263
		1264	The default is probably ok in most situations, especially if thread
		1265	creation is fast. If thread creation is very slow on your system you might
		1266	want to use larger values.
		1267
720	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1268	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1269
		1270	This is a very bad function to use in interactive programs because it
		1271	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1272	use an C<aio_group> together with a feed callback.
721		1273
722	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1274	Sets the maximum number of outstanding requests to C<$nreqs>. If you
723	try to queue up more than this number of requests, the caller will block until	1275	do queue up more than this number of requests, the next call to the
724	some requests have been handled.	1276	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1277	function will block until the limit is no longer exceeded.
725		1278
726	The default is very large, so normally there is no practical limit. If you	1279	The default value is very large, so there is no practical limit on the
727	queue up many requests in a loop it often improves speed if you set	1280	number of outstanding requests.
728	this to a relatively low number, such as C<100>.
729		1281
730	Under normal circumstances you don't need to call this function.	1282	You can still queue as many requests as you want. Therefore,
		1283	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1284	as a stop gap to shield against fatal memory overflow (with large values).
731		1285
732	=back	1286	=back
733		1287
		1288	=head3 STATISTICAL INFORMATION
		1289
		1290	=over
		1291
		1292	=item IO::AIO::nreqs
		1293
		1294	Returns the number of requests currently in the ready, execute or pending
		1295	states (i.e. for which their callback has not been invoked yet).
		1296
		1297	Example: wait till there are no outstanding requests anymore:
		1298
		1299	IO::AIO::poll_wait, IO::AIO::poll_cb
		1300	while IO::AIO::nreqs;
		1301
		1302	=item IO::AIO::nready
		1303
		1304	Returns the number of requests currently in the ready state (not yet
		1305	executed).
		1306
		1307	=item IO::AIO::npending
		1308
		1309	Returns the number of requests currently in the pending state (executed,
		1310	but not yet processed by poll_cb).
		1311
		1312	=back
		1313
734	=cut	1314	=cut
735		1315
736	# support function to convert a fd into a perl filehandle
737	sub _fd2fh {
738	return undef if $_[0] < 0;
739
740	# try to generate nice filehandles
741	my $sym = "IO::AIO::fd#$_[0]";
742	local *$sym;
743
744	open *$sym, "+<&=$_[0]" # usually works under any unix
745	or open *$sym, "<&=$_[0]" # cygwin needs this
746	or open *$sym, ">&=$_[0]" # or this
747	or return undef;
748
749	*$sym
750	}
751
752	min_parallel 4;	1316	min_parallel 8;
753		1317
754	END {	1318	END { flush }
755	max_parallel 0;
756	}
757		1319
758	1;	1320	1;
759		1321
760	=head2 FORK BEHAVIOUR	1322	=head2 FORK BEHAVIOUR
761		1323
762	This module should do "the right thing" when the process using it forks:	1324	This module should do "the right thing" when the process using it forks:
763		1325
764	Before the fork, IO::AIO enters a quiescent state where no requests	1326	Before the fork, IO::AIO enters a quiescent state where no requests
765	can be added in other threads and no results will be processed. After	1327	can be added in other threads and no results will be processed. After
766	the fork the parent simply leaves the quiescent state and continues	1328	the fork the parent simply leaves the quiescent state and continues
767	request/result processing, while the child clears the request/result	1329	request/result processing, while the child frees the request/result queue
768	queue (so the requests started before the fork will only be handled in	1330	(so that the requests started before the fork will only be handled in the
769	the parent). Threads will be started on demand until the limit ste in the	1331	parent). Threads will be started on demand until the limit set in the
770	parent process has been reached again.	1332	parent process has been reached again.
771		1333
772	In short: the parent will, after a short pause, continue as if fork had	1334	In short: the parent will, after a short pause, continue as if fork had
773	not been called, while the child will act as if IO::AIO has not been used	1335	not been called, while the child will act as if IO::AIO has not been used
774	yet.	1336	yet.
775		1337
		1338	=head2 MEMORY USAGE
		1339
		1340	Per-request usage:
		1341
		1342	Each aio request uses - depending on your architecture - around 100-200
		1343	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1344	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1345	scalars and other data passed into aio requests will also be locked and
		1346	will consume memory till the request has entered the done state.
		1347
		1348	This is not awfully much, so queuing lots of requests is not usually a
		1349	problem.
		1350
		1351	Per-thread usage:
		1352
		1353	In the execution phase, some aio requests require more memory for
		1354	temporary buffers, and each thread requires a stack and other data
		1355	structures (usually around 16k-128k, depending on the OS).
		1356
		1357	=head1 KNOWN BUGS
		1358
		1359	Known bugs will be fixed in the next release.
		1360
776	=head1 SEE ALSO	1361	=head1 SEE ALSO
777		1362
778	L<Coro>, L<Linux::AIO> (obsolete).	1363	L<Coro::AIO>.
779		1364
780	=head1 AUTHOR	1365	=head1 AUTHOR
781		1366
782	Marc Lehmann <schmorp@schmorp.de>	1367	Marc Lehmann <schmorp@schmorp.de>
783	http://home.schmorp.de/	1368	http://home.schmorp.de/

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