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Revision 1.62 by root, Sun Oct 22 21:13:47 2006 UTC vs.
Revision 1.120 by root, Sun Dec 2 21:51:36 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
82	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	202	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	203	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
84	aio_group);	204	aio_fdatasync aio_pathsync aio_readahead
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	205	aio_rename aio_link aio_move aio_copy aio_group
		206	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		207	aio_chmod aio_utime aio_truncate);
		208
		209	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		210	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		211	min_parallel max_parallel max_idle
		212	nreqs nready npending nthreads
		213	max_poll_time max_poll_reqs);
86		214
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		216
89	require XSLoader;	217	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	218	XSLoader::load ("IO::AIO", $VERSION);
91	}	219	}
92		220
93	=head1 FUNCTIONS	221	=head1 FUNCTIONS
94		222
95	=head2 AIO FUNCTIONS	223	=head2 AIO REQUEST FUNCTIONS
96		224
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	225	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	226	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	227	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	228	which must be a code reference. This code reference will get called with
…		…
103	syscall has been executed asynchronously.	231	syscall has been executed asynchronously.
104		232
105	All functions expecting a filehandle keep a copy of the filehandle	233	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	234	internally until the request has finished.
107		235
108	All requests return objects of type L<IO::AIO::REQ> that allow further	236	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	237	further manipulation of those requests while they are in-flight.
110		238
111	The pathnames you pass to these routines I<must> be absolute and	239	The pathnames you pass to these routines I<must> be absolute and
112	encoded in byte form. The reason for the former is that at the time the	240	encoded as octets. The reason for the former is that at the time the
113	request is being executed, the current working directory could have	241	request is being executed, the current working directory could have
114	changed. Alternatively, you can make sure that you never change the	242	changed. Alternatively, you can make sure that you never change the
115	current working directory.	243	current working directory anywhere in the program and then use relative
		244	paths.
116		245
117	To encode pathnames to byte form, either make sure you either: a)	246	To encode pathnames as octets, either make sure you either: a) always pass
118	always pass in filenames you got from outside (command line, readdir	247	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	248	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	249	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)	250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
122	use something else.	251	use something else to ensure your scalar has the correct contents.
		252
		253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		254	handles correctly wether it is set or not.
123		255
124	=over 4	256	=over 4
		257
		258	=item $prev_pri = aioreq_pri [$pri]
		259
		260	Returns the priority value that would be used for the next request and, if
		261	C<$pri> is given, sets the priority for the next aio request.
		262
		263	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		264	and C<4>, respectively. Requests with higher priority will be serviced
		265	first.
		266
		267	The priority will be reset to C<0> after each call to one of the C<aio_*>
		268	functions.
		269
		270	Example: open a file with low priority, then read something from it with
		271	higher priority so the read request is serviced before other low priority
		272	open requests (potentially spamming the cache):
		273
		274	aioreq_pri -3;
		275	aio_open ..., sub {
		276	return unless $_[0];
		277
		278	aioreq_pri -2;
		279	aio_read $_[0], ..., sub {
		280	...
		281	};
		282	};
		283
		284
		285	=item aioreq_nice $pri_adjust
		286
		287	Similar to C<aioreq_pri>, but subtracts the given value from the current
		288	priority, so the effect is cumulative.
		289
125		290
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	291	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		292
128	Asynchronously open or create a file and call the callback with a newly	293	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	294	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	300	list. They are the same as used by C<sysopen>.
136		301
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	302	Likewise, C<$mode> specifies the mode of the newly created file, if it
138	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	303	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
139	except that it is mandatory (i.e. use C<0> if you don't create new files,	304	except that it is mandatory (i.e. use C<0> if you don't create new files,
140	and C<0666> or C<0777> if you do).	305	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		306	by the umask in effect then the request is being executed, so better never
		307	change the umask.
141		308
142	Example:	309	Example:
143		310
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	311	aio_open "/etc/passwd", O_RDONLY, 0, sub {
145	if ($_[0]) {	312	if ($_[0]) {
…		…
148	} else {	315	} else {
149	die "open failed: $!\n";	316	die "open failed: $!\n";
150	}	317	}
151	};	318	};
152		319
		320
153	=item aio_close $fh, $callback->($status)	321	=item aio_close $fh, $callback->($status)
154		322
155	Asynchronously close a file and call the callback with the result	323	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	324	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		325
161	This is supposed to be a bug in the API, so that might change. It's	326	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	327	closing the file descriptor associated with the filehandle itself. Here is
		328	what aio_close will try:
		329
		330	1. dup()licate the fd
		331	2. asynchronously close() the duplicated fd
		332	3. dup()licate the fd once more
		333	4. let perl close() the filehandle
		334	5. asynchronously close the duplicated fd
		335
		336	The idea is that the first close() flushes stuff to disk that closing an
		337	fd will flush, so when perl closes the fd, nothing much will need to be
		338	flushed. The second async. close() will then flush stuff to disk that
		339	closing the last fd to the file will flush.
		340
		341	Just FYI, SuSv3 has this to say on close:
		342
		343	All outstanding record locks owned by the process on the file
		344	associated with the file descriptor shall be removed.
		345
		346	If fildes refers to a socket, close() shall cause the socket to be
		347	destroyed. ... close() shall block for up to the current linger
		348	interval until all data is transmitted.
		349	[this actually sounds like a specification bug, but who knows]
		350
		351	And at least Linux additionally actually flushes stuff on every close,
		352	even when the file itself is still open.
		353
		354	Sounds enourmously inefficient and complicated? Yes... please show me how
		355	to nuke perl's fd out of existence...
		356
		357	=cut
		358
		359	sub aio_close($;$) {
		360	aio_block {
		361	my ($fh, $cb) = @_;
		362
		363	my $pri = aioreq_pri;
		364	my $grp = aio_group $cb;
		365
		366	my $fd = fileno $fh;
		367
		368	defined $fd or Carp::croak "aio_close called with fd-less filehandle";
		369
		370	# if the dups fail we will simply get EBADF
		371	my $fd2 = _dup $fd;
		372	aioreq_pri $pri;
		373	add $grp _aio_close $fd2, sub {
		374	my $fd2 = _dup $fd;
		375	close $fh;
		376	aioreq_pri $pri;
		377	add $grp _aio_close $fd2, sub {
		378	$grp->result ($_[0]);
		379	};
		380	};
		381
		382	$grp
		383	}
		384	}
		385
163		386
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	387	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		388
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	389	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		390
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	391	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	392	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	393	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	394	like the syscall).
172		395
		396	If C<$offset> is undefined, then the current file descriptor offset will
		397	be used (and updated), otherwise the file descriptor offset will not be
		398	changed by these calls.
		399
		400	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		401
		402	If C<$dataoffset> is less than zero, it will be counted from the end of
		403	C<$data>.
		404
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	405	The C<$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	406	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	407	the necessary/optional hardware is installed).
176		408
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	409	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	410	offset C<0> within the scalar:
179		411
180	aio_read $fh, 7, 15, $buffer, 0, sub {	412	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	413	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	414	print "read $_[0] bytes: <$buffer>\n";
183	};	415	};
184		416
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.
192
193	This is a composite request that tries to rename(2) the file first. If
194	rename files with C<EXDEV>, it creates the destination file with mode 0200
195	and copies the contents of the source file into it using C<aio_sendfile>,
196	followed by restoring atime, mtime, access mode and uid/gid, in that
197	order, and unlinking the C<$srcpath>.
198
199	If an error occurs, the partial destination file will be unlinked, if
200	possible, except when setting atime, mtime, access mode and uid/gid, where
201	errors are being ignored.
202
203	=cut
204
205	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;
207
208	my $grp = aio_group $cb;
209
210	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {
212	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;
215
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {
218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
219	close $src_fh;
220
221	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;
226
227	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);
229	};
230	} else {
231	my $errno = $!;
232	add $grp aio_unlink $dst, sub {
233	$! = $errno;
234	$grp->result (-1);
235	};
236	}
237	};
238	} else {
239	$grp->result (-1);
240	}
241	},
242
243	} else {
244	$grp->result (-1);
245	}
246	};
247	} else {
248	$grp->result ($_[0]);
249	}
250	};
251
252	$grp
253	}
254		417
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	418	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		419
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	420	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
258	reading at byte offset C<$in_offset>, and starts writing at the current	421	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
272	C<$in_fh> than are written, and there is no way to find out how many	435	C<$in_fh> than are written, and there is no way to find out how many
273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	436	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
274	provides the number of bytes written to C<$out_fh>. Only if the result	437	provides the number of bytes written to C<$out_fh>. Only if the result
275	value equals C<$length> one can assume that C<$length> bytes have been	438	value equals C<$length> one can assume that C<$length> bytes have been
276	read.	439	read.
		440
277		441
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	442	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		443
280	C<aio_readahead> populates the page cache with data from a file so that	444	C<aio_readahead> populates the page cache with data from a file so that
281	subsequent reads from that file will not block on disk I/O. The C<$offset>	445	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
287	file. The current file offset of the file is left unchanged.	451	file. The current file offset of the file is left unchanged.
288		452
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	453	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
290	emulated by simply reading the data, which would have a similar effect.	454	emulated by simply reading the data, which would have a similar effect.
291		455
		456
292	=item aio_stat $fh_or_path, $callback->($status)	457	=item aio_stat $fh_or_path, $callback->($status)
293		458
294	=item aio_lstat $fh, $callback->($status)	459	=item aio_lstat $fh, $callback->($status)
295		460
296	Works like perl's C<stat> or C<lstat> in void context. The callback will	461	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
309	aio_stat "/etc/passwd", sub {	474	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	475	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	476	print "size is ", -s _, "\n";
312	};	477	};
313		478
		479
		480	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		481
		482	Works like perl's C<utime> function (including the special case of $atime
		483	and $mtime being undef). Fractional times are supported if the underlying
		484	syscalls support them.
		485
		486	When called with a pathname, uses utimes(2) if available, otherwise
		487	utime(2). If called on a file descriptor, uses futimes(2) if available,
		488	otherwise returns ENOSYS, so this is not portable.
		489
		490	Examples:
		491
		492	# set atime and mtime to current time (basically touch(1)):
		493	aio_utime "path", undef, undef;
		494	# set atime to current time and mtime to beginning of the epoch:
		495	aio_utime "path", time, undef; # undef==0
		496
		497
		498	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		499
		500	Works like perl's C<chown> function, except that C<undef> for either $uid
		501	or $gid is being interpreted as "do not change" (but -1 can also be used).
		502
		503	Examples:
		504
		505	# same as "chown root path" in the shell:
		506	aio_chown "path", 0, -1;
		507	# same as above:
		508	aio_chown "path", 0, undef;
		509
		510
		511	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		512
		513	Works like truncate(2) or ftruncate(2).
		514
		515
		516	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		517
		518	Works like perl's C<chmod> function.
		519
		520
314	=item aio_unlink $pathname, $callback->($status)	521	=item aio_unlink $pathname, $callback->($status)
315		522
316	Asynchronously unlink (delete) a file and call the callback with the	523	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	524	result code.
318		525
		526
		527	=item aio_mknod $path, $mode, $dev, $callback->($status)
		528
		529	[EXPERIMENTAL]
		530
		531	Asynchronously create a device node (or fifo). See mknod(2).
		532
		533	The only (POSIX-) portable way of calling this function is:
		534
		535	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		536
		537
319	=item aio_link $srcpath, $dstpath, $callback->($status)	538	=item aio_link $srcpath, $dstpath, $callback->($status)
320		539
321	Asynchronously create a new link to the existing object at C<$srcpath> at	540	Asynchronously create a new link to the existing object at C<$srcpath> at
322	the path C<$dstpath> and call the callback with the result code.	541	the path C<$dstpath> and call the callback with the result code.
323		542
		543
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	544	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		545
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	546	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
327	the path C<$dstpath> and call the callback with the result code.	547	the path C<$dstpath> and call the callback with the result code.
328		548
		549
		550	=item aio_readlink $path, $callback->($link)
		551
		552	Asynchronously read the symlink specified by C<$path> and pass it to
		553	the callback. If an error occurs, nothing or undef gets passed to the
		554	callback.
		555
		556
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	557	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		558
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	559	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	560	rename(2) and call the callback with the result code.
333		561
		562
		563	=item aio_mkdir $pathname, $mode, $callback->($status)
		564
		565	Asynchronously mkdir (create) a directory and call the callback with
		566	the result code. C<$mode> will be modified by the umask at the time the
		567	request is executed, so do not change your umask.
		568
		569
334	=item aio_rmdir $pathname, $callback->($status)	570	=item aio_rmdir $pathname, $callback->($status)
335		571
336	Asynchronously rmdir (delete) a directory and call the callback with the	572	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	573	result code.
		574
338		575
339	=item aio_readdir $pathname, $callback->($entries)	576	=item aio_readdir $pathname, $callback->($entries)
340		577
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	578	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
342	directory (i.e. opendir + readdir + closedir). The entries will not be	579	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	580	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		581
345	The callback a single argument which is either C<undef> or an array-ref	582	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	583	with the filenames.
347		584
		585
		586	=item aio_load $path, $data, $callback->($status)
		587
		588	This is a composite request that tries to fully load the given file into
		589	memory. Status is the same as with aio_read.
		590
		591	=cut
		592
		593	sub aio_load($$;$) {
		594	aio_block {
		595	my ($path, undef, $cb) = @_;
		596	my $data = \$_[1];
		597
		598	my $pri = aioreq_pri;
		599	my $grp = aio_group $cb;
		600
		601	aioreq_pri $pri;
		602	add $grp aio_open $path, O_RDONLY, 0, sub {
		603	my $fh = shift
		604	or return $grp->result (-1);
		605
		606	aioreq_pri $pri;
		607	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		608	$grp->result ($_[0]);
		609	};
		610	};
		611
		612	$grp
		613	}
		614	}
		615
		616	=item aio_copy $srcpath, $dstpath, $callback->($status)
		617
		618	Try to copy the I<file> (directories not supported as either source or
		619	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		620	the C<0> (error) or C<-1> ok.
		621
		622	This is a composite request that it creates the destination file with
		623	mode 0200 and copies the contents of the source file into it using
		624	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		625	uid/gid, in that order.
		626
		627	If an error occurs, the partial destination file will be unlinked, if
		628	possible, except when setting atime, mtime, access mode and uid/gid, where
		629	errors are being ignored.
		630
		631	=cut
		632
		633	sub aio_copy($$;$) {
		634	aio_block {
		635	my ($src, $dst, $cb) = @_;
		636
		637	my $pri = aioreq_pri;
		638	my $grp = aio_group $cb;
		639
		640	aioreq_pri $pri;
		641	add $grp aio_open $src, O_RDONLY, 0, sub {
		642	if (my $src_fh = $_[0]) {
		643	my @stat = stat $src_fh;
		644
		645	aioreq_pri $pri;
		646	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		647	if (my $dst_fh = $_[0]) {
		648	aioreq_pri $pri;
		649	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		650	if ($_[0] == $stat[7]) {
		651	$grp->result (0);
		652	close $src_fh;
		653
		654	# those should not normally block. should. should.
		655	utime $stat[8], $stat[9], $dst;
		656	chmod $stat[2] & 07777, $dst_fh;
		657	chown $stat[4], $stat[5], $dst_fh;
		658
		659	aioreq_pri $pri;
		660	add $grp aio_close $dst_fh;
		661	} else {
		662	$grp->result (-1);
		663	close $src_fh;
		664	close $dst_fh;
		665
		666	aioreq $pri;
		667	add $grp aio_unlink $dst;
		668	}
		669	};
		670	} else {
		671	$grp->result (-1);
		672	}
		673	},
		674
		675	} else {
		676	$grp->result (-1);
		677	}
		678	};
		679
		680	$grp
		681	}
		682	}
		683
		684	=item aio_move $srcpath, $dstpath, $callback->($status)
		685
		686	Try to move the I<file> (directories not supported as either source or
		687	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		688	the C<0> (error) or C<-1> ok.
		689
		690	This is a composite request that tries to rename(2) the file first. If
		691	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		692	that is successful, unlinking the C<$srcpath>.
		693
		694	=cut
		695
		696	sub aio_move($$;$) {
		697	aio_block {
		698	my ($src, $dst, $cb) = @_;
		699
		700	my $pri = aioreq_pri;
		701	my $grp = aio_group $cb;
		702
		703	aioreq_pri $pri;
		704	add $grp aio_rename $src, $dst, sub {
		705	if ($_[0] && $! == EXDEV) {
		706	aioreq_pri $pri;
		707	add $grp aio_copy $src, $dst, sub {
		708	$grp->result ($_[0]);
		709
		710	if (!$_[0]) {
		711	aioreq_pri $pri;
		712	add $grp aio_unlink $src;
		713	}
		714	};
		715	} else {
		716	$grp->result ($_[0]);
		717	}
		718	};
		719
		720	$grp
		721	}
		722	}
		723
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	724	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		725
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	726	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	727	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	728	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	729	recurse into (everything else, including symlinks to directories).
356		730
357	C<aio_scandir> is a composite request that creates of many sub requests_	731	C<aio_scandir> is a composite request that creates of many sub requests_
358	C<$maxreq> specifies the maximum number of outstanding aio requests that	732	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	this function generates. If it is C<< <= 0 >>, then a suitable default	733	this function generates. If it is C<< <= 0 >>, then a suitable default
360	will be chosen (currently 6).	734	will be chosen (currently 4).
361		735
362	On error, the callback is called without arguments, otherwise it receives	736	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	737	two array-refs with path-relative entry names.
364		738
365	Example:	739	Example:
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	773	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	774	directory counting heuristic.
401		775
402	=cut	776	=cut
403		777
404	sub aio_scandir($$$) {	778	sub aio_scandir($$;$) {
		779	aio_block {
405	my ($path, $maxreq, $cb) = @_;	780	my ($path, $maxreq, $cb) = @_;
406		781
		782	my $pri = aioreq_pri;
		783
407	my $grp = aio_group $cb;	784	my $grp = aio_group $cb;
408		785
409	$maxreq = 6 if $maxreq <= 0;	786	$maxreq = 4 if $maxreq <= 0;
410		787
411	# stat once	788	# stat once
		789	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	790	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	791	return $grp->result () if $_[0];
414	my $now = time;	792	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	793	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		794
417	# read the directory entries	795	# read the directory entries
		796	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	797	add $grp aio_readdir $path, sub {
419	my $entries = shift	798	my $entries = shift
420	or return $grp->result ();	799	or return $grp->result ();
421		800
422	# stat the dir another time	801	# stat the dir another time
		802	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	803	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	804	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		805
426	my $ndirs;	806	my $ndirs;
427		807
428	# take the slow route if anything looks fishy	808	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	809	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	810	$ndirs = -1;
431	} else {	811	} else {
432	# if nlink == 2, we are finished	812	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	813	# on non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	814	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	815	or return $grp->result ([], $entries);
436	}	816	}
437		817
438	# sort into likely dirs and likely nondirs	818	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first	819	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],	820	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }	821	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	822	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];	823	@$entries];
444		824
445	my (@dirs, @nondirs);	825	my (@dirs, @nondirs);
446		826
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	my $statgrp = add $grp aio_group;	827	my $statgrp = add $grp aio_group sub {
451
452	$schedcb = sub {
453	if (@$entries) {
454	if ($nreq < $maxreq) {
455	my $ent = pop @$entries;
456	$nreq++;
457	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
458	}
459	} elsif (!$nreq) {
460	# finished
461	$statgrp->cancel;
462	undef $statcb;
463	undef $schedcb;
464	$grp->result (\@dirs, \@nondirs);	828	$grp->result (\@dirs, \@nondirs);
465	}	829	};
		830
		831	limit $statgrp $maxreq;
		832	feed $statgrp sub {
		833	return unless @$entries;
		834	my $entry = pop @$entries;
		835
		836	aioreq_pri $pri;
		837	add $statgrp aio_stat "$path/$entry/.", sub {
		838	if ($_[0] < 0) {
		839	push @nondirs, $entry;
		840	} else {
		841	# need to check for real directory
		842	aioreq_pri $pri;
		843	add $statgrp aio_lstat "$path/$entry", sub {
		844	if (-d _) {
		845	push @dirs, $entry;
		846
		847	unless (--$ndirs) {
		848	push @nondirs, @$entries;
		849	feed $statgrp;
		850	}
		851	} else {
		852	push @nondirs, $entry;
		853	}
		854	}
		855	}
		856	};
		857	};
466	};	858	};
467	$statcb = sub {
468	my ($status, $entry) = @_;
469
470	if ($status < 0) {
471	$nreq--;
472	push @nondirs, $entry;
473	&$schedcb;
474	} else {
475	# need to check for real directory
476	add $grp aio_lstat "$path/$entry", sub {
477	$nreq--;
478
479	if (-d _) {
480	push @dirs, $entry;
481
482	if (!--$ndirs) {
483	push @nondirs, @$entries;
484	$entries = [];
485	}
486	} else {
487	push @nondirs, $entry;
488	}
489
490	&$schedcb;
491	}
492	}
493	};
494
495	&$schedcb while @$entries && $nreq < $maxreq;
496	};	859	};
497	};	860	};
		861
		862	$grp
498	};	863	}
499
500	$grp
501	}	864	}
		865
		866	=item aio_rmtree $path, $callback->($status)
		867
		868	Delete a directory tree starting (and including) C<$path>, return the
		869	status of the final C<rmdir> only. This is a composite request that
		870	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		871	everything else.
		872
		873	=cut
		874
		875	sub aio_rmtree;
		876	sub aio_rmtree($;$) {
		877	aio_block {
		878	my ($path, $cb) = @_;
		879
		880	my $pri = aioreq_pri;
		881	my $grp = aio_group $cb;
		882
		883	aioreq_pri $pri;
		884	add $grp aio_scandir $path, 0, sub {
		885	my ($dirs, $nondirs) = @_;
		886
		887	my $dirgrp = aio_group sub {
		888	add $grp aio_rmdir $path, sub {
		889	$grp->result ($_[0]);
		890	};
		891	};
		892
		893	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		894	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		895
		896	add $grp $dirgrp;
		897	};
		898
		899	$grp
		900	}
		901	}
		902
		903	=item aio_sync $callback->($status)
		904
		905	Asynchronously call sync and call the callback when finished.
502		906
503	=item aio_fsync $fh, $callback->($status)	907	=item aio_fsync $fh, $callback->($status)
504		908
505	Asynchronously call fsync on the given filehandle and call the callback	909	Asynchronously call fsync on the given filehandle and call the callback
506	with the fsync result code.	910	with the fsync result code.
…		…
511	callback with the fdatasync result code.	915	callback with the fdatasync result code.
512		916
513	If this call isn't available because your OS lacks it or it couldn't be	917	If this call isn't available because your OS lacks it or it couldn't be
514	detected, it will be emulated by calling C<fsync> instead.	918	detected, it will be emulated by calling C<fsync> instead.
515		919
		920	=item aio_pathsync $path, $callback->($status)
		921
		922	This request tries to open, fsync and close the given path. This is a
		923	composite request intended tosync directories after directory operations
		924	(E.g. rename). This might not work on all operating systems or have any
		925	specific effect, but usually it makes sure that directory changes get
		926	written to disc. It works for anything that can be opened for read-only,
		927	not just directories.
		928
		929	Passes C<0> when everything went ok, and C<-1> on error.
		930
		931	=cut
		932
		933	sub aio_pathsync($;$) {
		934	aio_block {
		935	my ($path, $cb) = @_;
		936
		937	my $pri = aioreq_pri;
		938	my $grp = aio_group $cb;
		939
		940	aioreq_pri $pri;
		941	add $grp aio_open $path, O_RDONLY, 0, sub {
		942	my ($fh) = @_;
		943	if ($fh) {
		944	aioreq_pri $pri;
		945	add $grp aio_fsync $fh, sub {
		946	$grp->result ($_[0]);
		947
		948	aioreq_pri $pri;
		949	add $grp aio_close $fh;
		950	};
		951	} else {
		952	$grp->result (-1);
		953	}
		954	};
		955
		956	$grp
		957	}
		958	}
		959
516	=item aio_group $callback->(...)	960	=item aio_group $callback->(...)
517
518	[EXPERIMENTAL]
519		961
520	This is a very special aio request: Instead of doing something, it is a	962	This is a very special aio request: Instead of doing something, it is a
521	container for other aio requests, which is useful if you want to bundle	963	container for other aio requests, which is useful if you want to bundle
522	many requests into a single, composite, request.	964	many requests into a single, composite, request with a definite callback
		965	and the ability to cancel the whole request with its subrequests.
523		966
524	Returns an object of class L<IO::AIO::GRP>. See its documentation below	967	Returns an object of class L<IO::AIO::GRP>. See its documentation below
525	for more info.	968	for more info.
526		969
527	Example:	970	Example:
…		…
533	add $grp	976	add $grp
534	(aio_stat ...),	977	(aio_stat ...),
535	(aio_stat ...),	978	(aio_stat ...),
536	...;	979	...;
537		980
		981	=item aio_nop $callback->()
		982
		983	This is a special request - it does nothing in itself and is only used for
		984	side effects, such as when you want to add a dummy request to a group so
		985	that finishing the requests in the group depends on executing the given
		986	code.
		987
		988	While this request does nothing, it still goes through the execution
		989	phase and still requires a worker thread. Thus, the callback will not
		990	be executed immediately but only after other requests in the queue have
		991	entered their execution phase. This can be used to measure request
		992	latency.
		993
538	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	994	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
539		995
540	Mainly used for debugging and benchmarking, this aio request puts one of	996	Mainly used for debugging and benchmarking, this aio request puts one of
541	the request workers to sleep for the given time.	997	the request workers to sleep for the given time.
542		998
543	While it is theoretically handy to have simple I/O scheduling requests	999	While it is theoretically handy to have simple I/O scheduling requests
544	like sleep and file handle readable/writable, the overhead this creates	1000	like sleep and file handle readable/writable, the overhead this creates is
545	is immense, so do not use this function except to put your application	1001	immense (it blocks a thread for a long time) so do not use this function
546	under artificial I/O pressure.	1002	except to put your application under artificial I/O pressure.
547		1003
548	=back	1004	=back
549		1005
550	=head2 IO::AIO::REQ CLASS	1006	=head2 IO::AIO::REQ CLASS
551		1007
552	All non-aggregate C<aio_*> functions return an object of this class when	1008	All non-aggregate C<aio_*> functions return an object of this class when
553	called in non-void context.	1009	called in non-void context.
554		1010
555	A request always moves through the following five states in its lifetime,
556	in order: B<ready> (request has been created, but has not been executed
557	yet), B<execute> (request is currently being executed), B<pending>
558	(request has been executed but callback has not been called yet),
559	B<result> (results are being processed synchronously, includes calling the
560	callback) and B<done> (request has reached the end of its lifetime and
561	holds no resources anymore).
562
563	=over 4	1011	=over 4
564		1012
565	=item $req->cancel	1013	=item cancel $req
566		1014
567	Cancels the request, if possible. Has the effect of skipping execution	1015	Cancels the request, if possible. Has the effect of skipping execution
568	when entering the B<execute> state and skipping calling the callback when	1016	when entering the B<execute> state and skipping calling the callback when
569	entering the the B<result> state, but will leave the request otherwise	1017	entering the the B<result> state, but will leave the request otherwise
570	untouched. That means that requests that currently execute will not be	1018	untouched. That means that requests that currently execute will not be
571	stopped and resources held by the request will not be freed prematurely.	1019	stopped and resources held by the request will not be freed prematurely.
572		1020
		1021	=item cb $req $callback->(...)
		1022
		1023	Replace (or simply set) the callback registered to the request.
		1024
573	=back	1025	=back
574		1026
575	=head2 IO::AIO::GRP CLASS	1027	=head2 IO::AIO::GRP CLASS
576		1028
577	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	1029	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
616	=item * They can also can also be added to other IO::AIO::GRP objects.	1068	=item * They can also can also be added to other IO::AIO::GRP objects.
617		1069
618	=item * You must not add requests to a group from within the group callback (or	1070	=item * You must not add requests to a group from within the group callback (or
619	any later time).	1071	any later time).
620		1072
621	=item * This does not harmonise well with C<max_outstanding>, so best do
622	not combine C<aio_group> with it. Groups and feeders are recommended for
623	this kind of concurrency-limiting.
624
625	=back	1073	=back
626		1074
627	Their lifetime, simplified, looks like this: when they are empty, they	1075	Their lifetime, simplified, looks like this: when they are empty, they
628	will finish very quickly. If they contain only requests that are in the	1076	will finish very quickly. If they contain only requests that are in the
629	C<done> state, they will also finish. Otherwise they will continue to	1077	C<done> state, they will also finish. Otherwise they will continue to
…		…
634	group. And only when all those requests have finished will the the group	1082	group. And only when all those requests have finished will the the group
635	itself finish.	1083	itself finish.
636		1084
637	=over 4	1085	=over 4
638		1086
		1087	=item add $grp ...
		1088
639	=item $grp->add (...)	1089	=item $grp->add (...)
640
641	=item add $grp ...
642		1090
643	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1091	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
644	be added, including other groups, as long as you do not create circular	1092	be added, including other groups, as long as you do not create circular
645	dependencies.	1093	dependencies.
646		1094
647	Returns all its arguments.	1095	Returns all its arguments.
648		1096
		1097	=item $grp->cancel_subs
		1098
		1099	Cancel all subrequests and clears any feeder, but not the group request
		1100	itself. Useful when you queued a lot of events but got a result early.
		1101
649	=item $grp->result (...)	1102	=item $grp->result (...)
650		1103
651	Set the result value(s) that will be passed to the group callback when all	1104	Set the result value(s) that will be passed to the group callback when all
652	subrequests have finished. By default, no argument will be passed.	1105	subrequests have finished and set the groups errno to the current value
		1106	of errno (just like calling C<errno> without an error number). By default,
		1107	no argument will be passed and errno is zero.
653		1108
654	=item $grp->set_feeder ($callback->($grp))	1109	=item $grp->errno ([$errno])
655		1110
656	[VERY EXPERIMENTAL]	1111	Sets the group errno value to C<$errno>, or the current value of errno
		1112	when the argument is missing.
		1113
		1114	Every aio request has an associated errno value that is restored when
		1115	the callback is invoked. This method lets you change this value from its
		1116	default (0).
		1117
		1118	Calling C<result> will also set errno, so make sure you either set C<$!>
		1119	before the call to C<result>, or call c<errno> after it.
		1120
		1121	=item feed $grp $callback->($grp)
657		1122
658	Sets a feeder/generator on this group: every group can have an attached	1123	Sets a feeder/generator on this group: every group can have an attached
659	generator that generates requests if idle. The idea behind this is that,	1124	generator that generates requests if idle. The idea behind this is that,
660	although you could just queue as many requests as you want in a group,	1125	although you could just queue as many requests as you want in a group,
661	this might starve other requests for a potentially long time. For	1126	this might starve other requests for a potentially long time. For
662	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1127	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
663	requests, delaying any later requests for a long time.	1128	requests, delaying any later requests for a long time.
664		1129
665	To avoid this, and allow incremental generation of requests, you can	1130	To avoid this, and allow incremental generation of requests, you can
666	instead a group and set a feeder on it that generates those requests. The	1131	instead a group and set a feeder on it that generates those requests. The
667	feeder will be called whenever there are few enough (see C<feeder_limit>,	1132	feed callback will be called whenever there are few enough (see C<limit>,
668	below) requests active in the group itself and is expected to queue more	1133	below) requests active in the group itself and is expected to queue more
669	requests.	1134	requests.
670		1135
671	The feeder can queue as many requests as it likes (i.e. C<add> does not	1136	The feed callback can queue as many requests as it likes (i.e. C<add> does
672	impose any limits).	1137	not impose any limits).
673		1138
674	If the feeder does not queue more requests when called, it will be	1139	If the feed does not queue more requests when called, it will be
675	automatically removed from the group.	1140	automatically removed from the group.
676		1141
677	If the feeder limit is C<0>, it will be set to C<2> automatically.	1142	If the feed limit is C<0>, it will be set to C<2> automatically.
678		1143
679	Example:	1144	Example:
680		1145
681	# stat all files in @files, but only ever use four aio requests concurrently:	1146	# stat all files in @files, but only ever use four aio requests concurrently:
682		1147
683	my $grp = aio_group sub { print "finished\n" };	1148	my $grp = aio_group sub { print "finished\n" };
684	$grp->feeder_limit (4);	1149	limit $grp 4;
685	$grp->set_feeder (sub {	1150	feed $grp sub {
686	my $file = pop @files	1151	my $file = pop @files
687	or return;	1152	or return;
688		1153
689	add $grp aio_stat $file, sub { ... };	1154	add $grp aio_stat $file, sub { ... };
690	});	1155	};
691		1156
692	=item $grp->feeder_limit ($num)	1157	=item limit $grp $num
693		1158
694	Sets the feeder limit for the group: The feeder will be called whenever	1159	Sets the feeder limit for the group: The feeder will be called whenever
695	the group contains less than this many requests.	1160	the group contains less than this many requests.
696		1161
697	Setting the limit to C<0> will pause the feeding process.	1162	Setting the limit to C<0> will pause the feeding process.
698		1163
699	=back	1164	=back
700		1165
701	=head2 SUPPORT FUNCTIONS	1166	=head2 SUPPORT FUNCTIONS
		1167
		1168	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
702		1169
703	=over 4	1170	=over 4
704		1171
705	=item $fileno = IO::AIO::poll_fileno	1172	=item $fileno = IO::AIO::poll_fileno
706		1173
…		…
711		1178
712	See C<poll_cb> for an example.	1179	See C<poll_cb> for an example.
713		1180
714	=item IO::AIO::poll_cb	1181	=item IO::AIO::poll_cb
715		1182
716	Process all outstanding events on the result pipe. You have to call this	1183	Process some outstanding events on the result pipe. You have to call this
717	regularly. Returns the number of events processed. Returns immediately	1184	regularly. Returns the number of events processed. Returns immediately
718	when no events are outstanding.	1185	when no events are outstanding. The amount of events processed depends on
		1186	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1187
		1188	If not all requests were processed for whatever reason, the filehandle
		1189	will still be ready when C<poll_cb> returns.
719		1190
720	Example: Install an Event watcher that automatically calls	1191	Example: Install an Event watcher that automatically calls
721	IO::AIO::poll_cb with high priority:	1192	IO::AIO::poll_cb with high priority:
722		1193
723	Event->io (fd => IO::AIO::poll_fileno,	1194	Event->io (fd => IO::AIO::poll_fileno,
724	poll => 'r', async => 1,	1195	poll => 'r', async => 1,
725	cb => \&IO::AIO::poll_cb);	1196	cb => \&IO::AIO::poll_cb);
726		1197
		1198	=item IO::AIO::max_poll_reqs $nreqs
		1199
		1200	=item IO::AIO::max_poll_time $seconds
		1201
		1202	These set the maximum number of requests (default C<0>, meaning infinity)
		1203	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1204	the maximum amount of time (default C<0>, meaning infinity) spent in
		1205	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1206	of time C<poll_cb> is allowed to use).
		1207
		1208	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1209	syscall per request processed, which is not normally a problem unless your
		1210	callbacks are really really fast or your OS is really really slow (I am
		1211	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1212
		1213	Setting these is useful if you want to ensure some level of
		1214	interactiveness when perl is not fast enough to process all requests in
		1215	time.
		1216
		1217	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1218
		1219	Example: Install an Event watcher that automatically calls
		1220	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1221	program get the CPU sometimes even under high AIO load.
		1222
		1223	# try not to spend much more than 0.1s in poll_cb
		1224	IO::AIO::max_poll_time 0.1;
		1225
		1226	# use a low priority so other tasks have priority
		1227	Event->io (fd => IO::AIO::poll_fileno,
		1228	poll => 'r', nice => 1,
		1229	cb => &IO::AIO::poll_cb);
		1230
727	=item IO::AIO::poll_wait	1231	=item IO::AIO::poll_wait
728		1232
		1233	If there are any outstanding requests and none of them in the result
729	Wait till the result filehandle becomes ready for reading (simply does a	1234	phase, wait till the result filehandle becomes ready for reading (simply
730	C<select> on the filehandle. This is useful if you want to synchronously wait	1235	does a C<select> on the filehandle. This is useful if you want to
731	for some requests to finish).	1236	synchronously wait for some requests to finish).
732		1237
733	See C<nreqs> for an example.	1238	See C<nreqs> for an example.
734		1239
		1240	=item IO::AIO::poll
		1241
		1242	Waits until some requests have been handled.
		1243
		1244	Returns the number of requests processed, but is otherwise strictly
		1245	equivalent to:
		1246
		1247	IO::AIO::poll_wait, IO::AIO::poll_cb
		1248
735	=item IO::AIO::nreqs	1249	=item IO::AIO::flush
736		1250
737	Returns the number of requests currently outstanding (i.e. for which their	1251	Wait till all outstanding AIO requests have been handled.
738	callback has not been invoked yet).
739		1252
740	Example: wait till there are no outstanding requests anymore:	1253	Strictly equivalent to:
741		1254
742	IO::AIO::poll_wait, IO::AIO::poll_cb	1255	IO::AIO::poll_wait, IO::AIO::poll_cb
743	while IO::AIO::nreqs;	1256	while IO::AIO::nreqs;
744		1257
745	=item IO::AIO::flush	1258	=back
746		1259
747	Wait till all outstanding AIO requests have been handled.	1260	=head3 CONTROLLING THE NUMBER OF THREADS
748		1261
749	Strictly equivalent to:	1262	=over
750
751	IO::AIO::poll_wait, IO::AIO::poll_cb
752	while IO::AIO::nreqs;
753
754	=item IO::AIO::poll
755
756	Waits until some requests have been handled.
757
758	Strictly equivalent to:
759
760	IO::AIO::poll_wait, IO::AIO::poll_cb
761	if IO::AIO::nreqs;
762		1263
763	=item IO::AIO::min_parallel $nthreads	1264	=item IO::AIO::min_parallel $nthreads
764		1265
765	Set the minimum number of AIO threads to C<$nthreads>. The current	1266	Set the minimum number of AIO threads to C<$nthreads>. The current
766	default is C<8>, which means eight asynchronous operations can execute	1267	default is C<8>, which means eight asynchronous operations can execute
767	concurrently at any one time (the number of outstanding requests,	1268	concurrently at any one time (the number of outstanding requests,
768	however, is unlimited).	1269	however, is unlimited).
769		1270
770	IO::AIO starts threads only on demand, when an AIO request is queued and	1271	IO::AIO starts threads only on demand, when an AIO request is queued and
771	no free thread exists.	1272	no free thread exists. Please note that queueing up a hundred requests can
		1273	create demand for a hundred threads, even if it turns out that everything
		1274	is in the cache and could have been processed faster by a single thread.
772		1275
773	It is recommended to keep the number of threads relatively low, as some	1276	It is recommended to keep the number of threads relatively low, as some
774	Linux kernel versions will scale negatively with the number of threads	1277	Linux kernel versions will scale negatively with the number of threads
775	(higher parallelity => MUCH higher latency). With current Linux 2.6	1278	(higher parallelity => MUCH higher latency). With current Linux 2.6
776	versions, 4-32 threads should be fine.	1279	versions, 4-32 threads should be fine.
…		…
790	This module automatically runs C<max_parallel 0> at program end, to ensure	1293	This module automatically runs C<max_parallel 0> at program end, to ensure
791	that all threads are killed and that there are no outstanding requests.	1294	that all threads are killed and that there are no outstanding requests.
792		1295
793	Under normal circumstances you don't need to call this function.	1296	Under normal circumstances you don't need to call this function.
794		1297
		1298	=item IO::AIO::max_idle $nthreads
		1299
		1300	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1301	threads that did not get a request to process within 10 seconds). That
		1302	means if a thread becomes idle while C<$nthreads> other threads are also
		1303	idle, it will free its resources and exit.
		1304
		1305	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1306	to allow for extremely high load situations, but want to free resources
		1307	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1308
		1309	The default is probably ok in most situations, especially if thread
		1310	creation is fast. If thread creation is very slow on your system you might
		1311	want to use larger values.
		1312
795	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1313	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
796		1314
797	[DEPRECATED]	1315	This is a very bad function to use in interactive programs because it
		1316	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1317	use an C<aio_group> together with a feed callback.
798		1318
799	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1319	Sets the maximum number of outstanding requests to C<$nreqs>. If you
800	try to queue up more than this number of requests, the caller will block until	1320	do queue up more than this number of requests, the next call to the
801	some requests have been handled.	1321	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1322	function will block until the limit is no longer exceeded.
802		1323
803	The default is very large, so normally there is no practical limit. If you	1324	The default value is very large, so there is no practical limit on the
804	queue up many requests in a loop it often improves speed if you set	1325	number of outstanding requests.
805	this to a relatively low number, such as C<100>.
806		1326
807	This function does not work well together with C<aio_group>'s, and their	1327	You can still queue as many requests as you want. Therefore,
808	feeder interface is better suited to limiting concurrency, so do not use	1328	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
809	this function.	1329	as a stop gap to shield against fatal memory overflow (with large values).
810
811	Under normal circumstances you don't need to call this function.
812		1330
813	=back	1331	=back
814		1332
		1333	=head3 STATISTICAL INFORMATION
		1334
		1335	=over
		1336
		1337	=item IO::AIO::nreqs
		1338
		1339	Returns the number of requests currently in the ready, execute or pending
		1340	states (i.e. for which their callback has not been invoked yet).
		1341
		1342	Example: wait till there are no outstanding requests anymore:
		1343
		1344	IO::AIO::poll_wait, IO::AIO::poll_cb
		1345	while IO::AIO::nreqs;
		1346
		1347	=item IO::AIO::nready
		1348
		1349	Returns the number of requests currently in the ready state (not yet
		1350	executed).
		1351
		1352	=item IO::AIO::npending
		1353
		1354	Returns the number of requests currently in the pending state (executed,
		1355	but not yet processed by poll_cb).
		1356
		1357	=back
		1358
815	=cut	1359	=cut
816		1360
817	# support function to convert a fd into a perl filehandle
818	sub _fd2fh {
819	return undef if $_[0] < 0;
820
821	# try to generate nice filehandles
822	my $sym = "IO::AIO::fd#$_[0]";
823	local *$sym;
824
825	open *$sym, "+<&=$_[0]" # usually works under any unix
826	or open *$sym, "<&=$_[0]" # cygwin needs this
827	or open *$sym, ">&=$_[0]" # or this
828	or return undef;
829
830	*$sym
831	}
832
833	min_parallel 8;	1361	min_parallel 8;
834		1362
835	END {	1363	END { flush }
836	max_parallel 0;
837	}
838		1364
839	1;	1365	1;
840		1366
841	=head2 FORK BEHAVIOUR	1367	=head2 FORK BEHAVIOUR
842		1368
843	This module should do "the right thing" when the process using it forks:	1369	This module should do "the right thing" when the process using it forks:
844		1370
845	Before the fork, IO::AIO enters a quiescent state where no requests	1371	Before the fork, IO::AIO enters a quiescent state where no requests
846	can be added in other threads and no results will be processed. After	1372	can be added in other threads and no results will be processed. After
847	the fork the parent simply leaves the quiescent state and continues	1373	the fork the parent simply leaves the quiescent state and continues
848	request/result processing, while the child clears the request/result	1374	request/result processing, while the child frees the request/result queue
849	queue (so the requests started before the fork will only be handled in	1375	(so that the requests started before the fork will only be handled in the
850	the parent). Threads will be started on demand until the limit ste in the	1376	parent). Threads will be started on demand until the limit set in the
851	parent process has been reached again.	1377	parent process has been reached again.
852		1378
853	In short: the parent will, after a short pause, continue as if fork had	1379	In short: the parent will, after a short pause, continue as if fork had
854	not been called, while the child will act as if IO::AIO has not been used	1380	not been called, while the child will act as if IO::AIO has not been used
855	yet.	1381	yet.
856		1382
857	=head2 MEMORY USAGE	1383	=head2 MEMORY USAGE
858		1384
		1385	Per-request usage:
		1386
859	Each aio request uses - depending on your architecture - around 128 bytes	1387	Each aio request uses - depending on your architecture - around 100-200
860	of memory. In addition, stat requests need a stat buffer (possibly a few	1388	bytes of memory. In addition, stat requests need a stat buffer (possibly
861	hundred bytes). Perl scalars and other data passed into aio requests will	1389	a few hundred bytes), readdir requires a result buffer and so on. Perl
862	also be locked.	1390	scalars and other data passed into aio requests will also be locked and
		1391	will consume memory till the request has entered the done state.
863		1392
864	This is now awfully much, so queuing lots of requests is not usually a	1393	This is not awfully much, so queuing lots of requests is not usually a
865	problem.	1394	problem.
866		1395
867	Each thread needs a stack area which is usually around 16k, sometimes much	1396	Per-thread usage:
868	larger, depending on the OS.	1397
		1398	In the execution phase, some aio requests require more memory for
		1399	temporary buffers, and each thread requires a stack and other data
		1400	structures (usually around 16k-128k, depending on the OS).
		1401
		1402	=head1 KNOWN BUGS
		1403
		1404	Known bugs will be fixed in the next release.
869		1405
870	=head1 SEE ALSO	1406	=head1 SEE ALSO
871		1407
872	L<Coro>, L<Linux::AIO> (obsolete).	1408	L<Coro::AIO>.
873		1409
874	=head1 AUTHOR	1410	=head1 AUTHOR
875		1411
876	Marc Lehmann <schmorp@schmorp.de>	1412	Marc Lehmann <schmorp@schmorp.de>
877	http://home.schmorp.de/	1413	http://home.schmorp.de/

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