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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.59 by root, Sun Oct 22 10:33:26 2006 UTC vs.
Revision 1.118 by root, Thu Nov 29 20:57:02 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 = '2.51';
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_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	[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		414
255	=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)
256		416
257	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
258	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
…		…
272	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
273	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
274	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
275	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
276	read.	436	read.
		437
277		438
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	439	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		440
280	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
281	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>
…		…
287	file. The current file offset of the file is left unchanged.	448	file. The current file offset of the file is left unchanged.
288		449
289	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
290	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.
291		452
		453
292	=item aio_stat $fh_or_path, $callback->($status)	454	=item aio_stat $fh_or_path, $callback->($status)
293		455
294	=item aio_lstat $fh, $callback->($status)	456	=item aio_lstat $fh, $callback->($status)
295		457
296	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
…		…
309	aio_stat "/etc/passwd", sub {	471	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	472	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	473	print "size is ", -s _, "\n";
312	};	474	};
313		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
314	=item aio_unlink $pathname, $callback->($status)	518	=item aio_unlink $pathname, $callback->($status)
315		519
316	Asynchronously unlink (delete) a file and call the callback with the	520	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	521	result code.
318		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
319	=item aio_link $srcpath, $dstpath, $callback->($status)	535	=item aio_link $srcpath, $dstpath, $callback->($status)
320		536
321	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
322	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.
323		539
		540
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	541	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		542
326	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
327	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.
328		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
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	554	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		555
331	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
332	rename(2) and call the callback with the result code.	557	rename(2) and call the callback with the result code.
333		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
334	=item aio_rmdir $pathname, $callback->($status)	567	=item aio_rmdir $pathname, $callback->($status)
335		568
336	Asynchronously rmdir (delete) a directory and call the callback with the	569	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	570	result code.
		571
338		572
339	=item aio_readdir $pathname, $callback->($entries)	573	=item aio_readdir $pathname, $callback->($entries)
340		574
341	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
342	directory (i.e. opendir + readdir + closedir). The entries will not be	576	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	577	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		578
345	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
346	with the filenames.	580	with the filenames.
347		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
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	719	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		720
350	[EXPERIMENTAL due to internal aio_group use]
351
352	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
353	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
354	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
355	recurse into (everything else).	724	recurse into (everything else, including symlinks to directories).
356		725
357	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_
358	requests. C<$maxreq> specifies the maximum number of outstanding aio	727	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	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
360	suitable default will be chosen (currently 8).	729	will be chosen (currently 4).
361		730
362	On error, the callback is called without arguments, otherwise it receives	731	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	732	two array-refs with path-relative entry names.
364		733
365	Example:	734	Example:
…		…
399	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
400	directory counting heuristic.	769	directory counting heuristic.
401		770
402	=cut	771	=cut
403		772
404	sub aio_scandir($$$) {	773	sub aio_scandir($$;$) {
		774	aio_block {
405	my ($path, $maxreq, $cb) = @_;	775	my ($path, $maxreq, $cb) = @_;
406		776
		777	my $pri = aioreq_pri;
		778
407	my $grp = aio_group $cb;	779	my $grp = aio_group $cb;
408		780
409	$maxreq = 8 if $maxreq <= 0;	781	$maxreq = 4 if $maxreq <= 0;
410		782
411	# stat once	783	# stat once
		784	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	785	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	786	return $grp->result () if $_[0];
414	my $now = time;	787	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	788	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		789
417	# read the directory entries	790	# read the directory entries
		791	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	792	add $grp aio_readdir $path, sub {
419	my $entries = shift	793	my $entries = shift
420	or return $grp->result ();	794	or return $grp->result ();
421		795
422	# stat the dir another time	796	# stat the dir another time
		797	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	798	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	799	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		800
426	my $ndirs;	801	my $ndirs;
427		802
428	# take the slow route if anything looks fishy	803	# take the slow route if anything looks fishy
429	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	804	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
430	$ndirs = -1;	805	$ndirs = -1;
431	} else {	806	} else {
432	# if nlink == 2, we are finished	807	# if nlink == 2, we are finished
433	# on non-posix-fs's, we rely on nlink < 2	808	# on non-posix-fs's, we rely on nlink < 2
434	$ndirs = (stat _)[3] - 2	809	$ndirs = (stat _)[3] - 2
435	or return $grp->result ([], $entries);	810	or return $grp->result ([], $entries);
436	}
437
438	# sort into likely dirs and likely nondirs
439	# dirs == files without ".", short entries first
440	$entries = [map $_->[0],
441	sort { $b->[1] cmp $a->[1] }
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];
444
445	my (@dirs, @nondirs);
446
447	my ($statcb, $schedcb);
448	my $nreq = 0;
449
450	$schedcb = sub {
451	if (@$entries) {
452	if ($nreq < $maxreq) {
453	my $ent = pop @$entries;
454	$nreq++;
455	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
456	}
457	} elsif (!$nreq) {
458	# finished
459	undef $statcb;
460	undef $schedcb;
461	$grp->result (\@dirs, \@nondirs) if $cb;
462	undef $cb;
463	}	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	};
464	};	853	};
465	$statcb = sub {
466	my ($status, $entry) = @_;
467
468	if ($status < 0) {
469	$nreq--;
470	push @nondirs, $entry;
471	&$schedcb;
472	} else {
473	# need to check for real directory
474	add $grp aio_lstat "$path/$entry", sub {
475	$nreq--;
476
477	if (-d _) {
478	push @dirs, $entry;
479
480	if (!--$ndirs) {
481	push @nondirs, @$entries;
482	$entries = [];
483	}
484	} else {
485	push @nondirs, $entry;
486	}
487
488	&$schedcb;
489	}
490	}
491	};
492
493	&$schedcb while @$entries && $nreq < $maxreq;
494	};	854	};
495	};	855	};
		856
		857	$grp
496	};	858	}
		859	}
497		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
498	$grp	894	$grp
		895	}
499	}	896	}
500		897
501	=item aio_fsync $fh, $callback->($status)	898	=item aio_fsync $fh, $callback->($status)
502		899
503	Asynchronously call fsync on the given filehandle and call the callback	900	Asynchronously call fsync on the given filehandle and call the callback
…		…
511	If this call isn't available because your OS lacks it or it couldn't be	908	If this call isn't available because your OS lacks it or it couldn't be
512	detected, it will be emulated by calling C<fsync> instead.	909	detected, it will be emulated by calling C<fsync> instead.
513		910
514	=item aio_group $callback->(...)	911	=item aio_group $callback->(...)
515		912
516	[EXPERIMENTAL]
517
518	This is a very special aio request: Instead of doing something, it is a	913	This is a very special aio request: Instead of doing something, it is a
519	container for other aio requests, which is useful if you want to bundle	914	container for other aio requests, which is useful if you want to bundle
520	many requests into a single, composite, request.	915	many requests into a single, composite, request with a definite callback
		916	and the ability to cancel the whole request with its subrequests.
521		917
522	Returns an object of class L<IO::AIO::GRP>. See its documentation below	918	Returns an object of class L<IO::AIO::GRP>. See its documentation below
523	for more info.	919	for more info.
524		920
525	Example:	921	Example:
…		…
531	add $grp	927	add $grp
532	(aio_stat ...),	928	(aio_stat ...),
533	(aio_stat ...),	929	(aio_stat ...),
534	...;	930	...;
535		931
		932	=item aio_nop $callback->()
		933
		934	This is a special request - it does nothing in itself and is only used for
		935	side effects, such as when you want to add a dummy request to a group so
		936	that finishing the requests in the group depends on executing the given
		937	code.
		938
		939	While this request does nothing, it still goes through the execution
		940	phase and still requires a worker thread. Thus, the callback will not
		941	be executed immediately but only after other requests in the queue have
		942	entered their execution phase. This can be used to measure request
		943	latency.
		944
536	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	945	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
537		946
538	Mainly used for debugging and benchmarking, this aio request puts one of	947	Mainly used for debugging and benchmarking, this aio request puts one of
539	the request workers to sleep for the given time.	948	the request workers to sleep for the given time.
540		949
541	While it is theoretically handy to have simple I/O scheduling requests	950	While it is theoretically handy to have simple I/O scheduling requests
542	like sleep and file handle readable/writable, the overhead this creates	951	like sleep and file handle readable/writable, the overhead this creates is
543	is immense, so do not use this function except to put your application	952	immense (it blocks a thread for a long time) so do not use this function
544	under artificial I/O pressure.	953	except to put your application under artificial I/O pressure.
545		954
546	=back	955	=back
547		956
548	=head2 IO::AIO::REQ CLASS	957	=head2 IO::AIO::REQ CLASS
549		958
550	All non-aggregate C<aio_*> functions return an object of this class when	959	All non-aggregate C<aio_*> functions return an object of this class when
551	called in non-void context.	960	called in non-void context.
552		961
553	A request always moves through the following five states in its lifetime,
554	in order: B<ready> (request has been created, but has not been executed
555	yet), B<execute> (request is currently being executed), B<pending>
556	(request has been executed but callback has not been called yet),
557	B<result> (results are being processed synchronously, includes calling the
558	callback) and B<done> (request has reached the end of its lifetime and
559	holds no resources anymore).
560
561	=over 4	962	=over 4
562		963
563	=item $req->cancel	964	=item cancel $req
564		965
565	Cancels the request, if possible. Has the effect of skipping execution	966	Cancels the request, if possible. Has the effect of skipping execution
566	when entering the B<execute> state and skipping calling the callback when	967	when entering the B<execute> state and skipping calling the callback when
567	entering the the B<result> state, but will leave the request otherwise	968	entering the the B<result> state, but will leave the request otherwise
568	untouched. That means that requests that currently execute will not be	969	untouched. That means that requests that currently execute will not be
569	stopped and resources held by the request will not be freed prematurely.	970	stopped and resources held by the request will not be freed prematurely.
570		971
		972	=item cb $req $callback->(...)
		973
		974	Replace (or simply set) the callback registered to the request.
		975
571	=back	976	=back
572		977
573	=head2 IO::AIO::GRP CLASS	978	=head2 IO::AIO::GRP CLASS
574		979
575	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	980	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
601	};	1006	};
602		1007
603	This makes it very easy to create composite requests (see the source of	1008	This makes it very easy to create composite requests (see the source of
604	C<aio_move> for an application) that work and feel like simple requests.	1009	C<aio_move> for an application) that work and feel like simple requests.
605		1010
		1011	=over 4
		1012
606	The IO::AIO::GRP objects will be cleaned up during calls to	1013	=item * The IO::AIO::GRP objects will be cleaned up during calls to
607	C<IO::AIO::poll_cb>, just like any other request.	1014	C<IO::AIO::poll_cb>, just like any other request.
608		1015
609	They can be canceled like any other request. Canceling will cancel not	1016	=item * They can be canceled like any other request. Canceling will cancel not
610	only the request itself, but also all requests it contains.	1017	only the request itself, but also all requests it contains.
611		1018
612	They can also can also be added to other IO::AIO::GRP objects.	1019	=item * They can also can also be added to other IO::AIO::GRP objects.
		1020
		1021	=item * You must not add requests to a group from within the group callback (or
		1022	any later time).
		1023
		1024	=back
613		1025
614	Their lifetime, simplified, looks like this: when they are empty, they	1026	Their lifetime, simplified, looks like this: when they are empty, they
615	will finish very quickly. If they contain only requests that are in the	1027	will finish very quickly. If they contain only requests that are in the
616	C<done> state, they will also finish. Otherwise they will continue to	1028	C<done> state, they will also finish. Otherwise they will continue to
617	exist.	1029	exist.
…		…
621	group. And only when all those requests have finished will the the group	1033	group. And only when all those requests have finished will the the group
622	itself finish.	1034	itself finish.
623		1035
624	=over 4	1036	=over 4
625		1037
		1038	=item add $grp ...
		1039
626	=item $grp->add (...)	1040	=item $grp->add (...)
627
628	=item add $grp ...
629		1041
630	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1042	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
631	be added, including other groups, as long as you do not create circular	1043	be added, including other groups, as long as you do not create circular
632	dependencies.	1044	dependencies.
633		1045
634	Returns all its arguments.	1046	Returns all its arguments.
635		1047
		1048	=item $grp->cancel_subs
		1049
		1050	Cancel all subrequests and clears any feeder, but not the group request
		1051	itself. Useful when you queued a lot of events but got a result early.
		1052
636	=item $grp->result (...)	1053	=item $grp->result (...)
637		1054
638	Set the result value(s) that will be passed to the group callback when all	1055	Set the result value(s) that will be passed to the group callback when all
639	subrequests have finished. By default, no argument will be passed.	1056	subrequests have finished and set thre groups errno to the current value
		1057	of errno (just like calling C<errno> without an error number). By default,
		1058	no argument will be passed and errno is zero.
		1059
		1060	=item $grp->errno ([$errno])
		1061
		1062	Sets the group errno value to C<$errno>, or the current value of errno
		1063	when the argument is missing.
		1064
		1065	Every aio request has an associated errno value that is restored when
		1066	the callback is invoked. This method lets you change this value from its
		1067	default (0).
		1068
		1069	Calling C<result> will also set errno, so make sure you either set C<$!>
		1070	before the call to C<result>, or call c<errno> after it.
		1071
		1072	=item feed $grp $callback->($grp)
		1073
		1074	Sets a feeder/generator on this group: every group can have an attached
		1075	generator that generates requests if idle. The idea behind this is that,
		1076	although you could just queue as many requests as you want in a group,
		1077	this might starve other requests for a potentially long time. For
		1078	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1079	requests, delaying any later requests for a long time.
		1080
		1081	To avoid this, and allow incremental generation of requests, you can
		1082	instead a group and set a feeder on it that generates those requests. The
		1083	feed callback will be called whenever there are few enough (see C<limit>,
		1084	below) requests active in the group itself and is expected to queue more
		1085	requests.
		1086
		1087	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1088	not impose any limits).
		1089
		1090	If the feed does not queue more requests when called, it will be
		1091	automatically removed from the group.
		1092
		1093	If the feed limit is C<0>, it will be set to C<2> automatically.
		1094
		1095	Example:
		1096
		1097	# stat all files in @files, but only ever use four aio requests concurrently:
		1098
		1099	my $grp = aio_group sub { print "finished\n" };
		1100	limit $grp 4;
		1101	feed $grp sub {
		1102	my $file = pop @files
		1103	or return;
		1104
		1105	add $grp aio_stat $file, sub { ... };
		1106	};
		1107
		1108	=item limit $grp $num
		1109
		1110	Sets the feeder limit for the group: The feeder will be called whenever
		1111	the group contains less than this many requests.
		1112
		1113	Setting the limit to C<0> will pause the feeding process.
640		1114
641	=back	1115	=back
642		1116
643	=head2 SUPPORT FUNCTIONS	1117	=head2 SUPPORT FUNCTIONS
		1118
		1119	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
644		1120
645	=over 4	1121	=over 4
646		1122
647	=item $fileno = IO::AIO::poll_fileno	1123	=item $fileno = IO::AIO::poll_fileno
648		1124
…		…
653		1129
654	See C<poll_cb> for an example.	1130	See C<poll_cb> for an example.
655		1131
656	=item IO::AIO::poll_cb	1132	=item IO::AIO::poll_cb
657		1133
658	Process all outstanding events on the result pipe. You have to call this	1134	Process some outstanding events on the result pipe. You have to call this
659	regularly. Returns the number of events processed. Returns immediately	1135	regularly. Returns the number of events processed. Returns immediately
660	when no events are outstanding.	1136	when no events are outstanding. The amount of events processed depends on
		1137	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1138
		1139	If not all requests were processed for whatever reason, the filehandle
		1140	will still be ready when C<poll_cb> returns.
661		1141
662	Example: Install an Event watcher that automatically calls	1142	Example: Install an Event watcher that automatically calls
663	IO::AIO::poll_cb with high priority:	1143	IO::AIO::poll_cb with high priority:
664		1144
665	Event->io (fd => IO::AIO::poll_fileno,	1145	Event->io (fd => IO::AIO::poll_fileno,
666	poll => 'r', async => 1,	1146	poll => 'r', async => 1,
667	cb => \&IO::AIO::poll_cb);	1147	cb => \&IO::AIO::poll_cb);
668		1148
		1149	=item IO::AIO::max_poll_reqs $nreqs
		1150
		1151	=item IO::AIO::max_poll_time $seconds
		1152
		1153	These set the maximum number of requests (default C<0>, meaning infinity)
		1154	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1155	the maximum amount of time (default C<0>, meaning infinity) spent in
		1156	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1157	of time C<poll_cb> is allowed to use).
		1158
		1159	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1160	syscall per request processed, which is not normally a problem unless your
		1161	callbacks are really really fast or your OS is really really slow (I am
		1162	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1163
		1164	Setting these is useful if you want to ensure some level of
		1165	interactiveness when perl is not fast enough to process all requests in
		1166	time.
		1167
		1168	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1169
		1170	Example: Install an Event watcher that automatically calls
		1171	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1172	program get the CPU sometimes even under high AIO load.
		1173
		1174	# try not to spend much more than 0.1s in poll_cb
		1175	IO::AIO::max_poll_time 0.1;
		1176
		1177	# use a low priority so other tasks have priority
		1178	Event->io (fd => IO::AIO::poll_fileno,
		1179	poll => 'r', nice => 1,
		1180	cb => &IO::AIO::poll_cb);
		1181
669	=item IO::AIO::poll_wait	1182	=item IO::AIO::poll_wait
670		1183
		1184	If there are any outstanding requests and none of them in the result
671	Wait till the result filehandle becomes ready for reading (simply does a	1185	phase, wait till the result filehandle becomes ready for reading (simply
672	C<select> on the filehandle. This is useful if you want to synchronously wait	1186	does a C<select> on the filehandle. This is useful if you want to
673	for some requests to finish).	1187	synchronously wait for some requests to finish).
674		1188
675	See C<nreqs> for an example.	1189	See C<nreqs> for an example.
676		1190
		1191	=item IO::AIO::poll
		1192
		1193	Waits until some requests have been handled.
		1194
		1195	Returns the number of requests processed, but is otherwise strictly
		1196	equivalent to:
		1197
		1198	IO::AIO::poll_wait, IO::AIO::poll_cb
		1199
677	=item IO::AIO::nreqs	1200	=item IO::AIO::flush
678		1201
679	Returns the number of requests currently outstanding (i.e. for which their	1202	Wait till all outstanding AIO requests have been handled.
680	callback has not been invoked yet).
681		1203
682	Example: wait till there are no outstanding requests anymore:	1204	Strictly equivalent to:
683		1205
684	IO::AIO::poll_wait, IO::AIO::poll_cb	1206	IO::AIO::poll_wait, IO::AIO::poll_cb
685	while IO::AIO::nreqs;	1207	while IO::AIO::nreqs;
686		1208
687	=item IO::AIO::flush	1209	=back
688		1210
689	Wait till all outstanding AIO requests have been handled.	1211	=head3 CONTROLLING THE NUMBER OF THREADS
690		1212
691	Strictly equivalent to:	1213	=over
692
693	IO::AIO::poll_wait, IO::AIO::poll_cb
694	while IO::AIO::nreqs;
695
696	=item IO::AIO::poll
697
698	Waits until some requests have been handled.
699
700	Strictly equivalent to:
701
702	IO::AIO::poll_wait, IO::AIO::poll_cb
703	if IO::AIO::nreqs;
704		1214
705	=item IO::AIO::min_parallel $nthreads	1215	=item IO::AIO::min_parallel $nthreads
706		1216
707	Set the minimum number of AIO threads to C<$nthreads>. The current default	1217	Set the minimum number of AIO threads to C<$nthreads>. The current
708	is C<4>, which means four asynchronous operations can be done at one time	1218	default is C<8>, which means eight asynchronous operations can execute
709	(the number of outstanding operations, however, is unlimited).	1219	concurrently at any one time (the number of outstanding requests,
		1220	however, is unlimited).
710		1221
711	IO::AIO starts threads only on demand, when an AIO request is queued and	1222	IO::AIO starts threads only on demand, when an AIO request is queued and
712	no free thread exists.	1223	no free thread exists. Please note that queueing up a hundred requests can
		1224	create demand for a hundred threads, even if it turns out that everything
		1225	is in the cache and could have been processed faster by a single thread.
713		1226
714	It is recommended to keep the number of threads low, as some Linux	1227	It is recommended to keep the number of threads relatively low, as some
715	kernel versions will scale negatively with the number of threads (higher	1228	Linux kernel versions will scale negatively with the number of threads
716	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1229	(higher parallelity => MUCH higher latency). With current Linux 2.6
717	threads should be fine.	1230	versions, 4-32 threads should be fine.
718		1231
719	Under most circumstances you don't need to call this function, as the	1232	Under most circumstances you don't need to call this function, as the
720	module selects a default that is suitable for low to moderate load.	1233	module selects a default that is suitable for low to moderate load.
721		1234
722	=item IO::AIO::max_parallel $nthreads	1235	=item IO::AIO::max_parallel $nthreads
…		…
731	This module automatically runs C<max_parallel 0> at program end, to ensure	1244	This module automatically runs C<max_parallel 0> at program end, to ensure
732	that all threads are killed and that there are no outstanding requests.	1245	that all threads are killed and that there are no outstanding requests.
733		1246
734	Under normal circumstances you don't need to call this function.	1247	Under normal circumstances you don't need to call this function.
735		1248
		1249	=item IO::AIO::max_idle $nthreads
		1250
		1251	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1252	threads that did not get a request to process within 10 seconds). That
		1253	means if a thread becomes idle while C<$nthreads> other threads are also
		1254	idle, it will free its resources and exit.
		1255
		1256	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1257	to allow for extremely high load situations, but want to free resources
		1258	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1259
		1260	The default is probably ok in most situations, especially if thread
		1261	creation is fast. If thread creation is very slow on your system you might
		1262	want to use larger values.
		1263
736	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1264	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1265
		1266	This is a very bad function to use in interactive programs because it
		1267	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1268	use an C<aio_group> together with a feed callback.
737		1269
738	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1270	Sets the maximum number of outstanding requests to C<$nreqs>. If you
739	try to queue up more than this number of requests, the caller will block until	1271	do queue up more than this number of requests, the next call to the
740	some requests have been handled.	1272	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1273	function will block until the limit is no longer exceeded.
741		1274
742	The default is very large, so normally there is no practical limit. If you	1275	The default value is very large, so there is no practical limit on the
743	queue up many requests in a loop it often improves speed if you set	1276	number of outstanding requests.
744	this to a relatively low number, such as C<100>.
745		1277
746	Under normal circumstances you don't need to call this function.	1278	You can still queue as many requests as you want. Therefore,
		1279	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1280	as a stop gap to shield against fatal memory overflow (with large values).
747		1281
748	=back	1282	=back
749		1283
		1284	=head3 STATISTICAL INFORMATION
		1285
		1286	=over
		1287
		1288	=item IO::AIO::nreqs
		1289
		1290	Returns the number of requests currently in the ready, execute or pending
		1291	states (i.e. for which their callback has not been invoked yet).
		1292
		1293	Example: wait till there are no outstanding requests anymore:
		1294
		1295	IO::AIO::poll_wait, IO::AIO::poll_cb
		1296	while IO::AIO::nreqs;
		1297
		1298	=item IO::AIO::nready
		1299
		1300	Returns the number of requests currently in the ready state (not yet
		1301	executed).
		1302
		1303	=item IO::AIO::npending
		1304
		1305	Returns the number of requests currently in the pending state (executed,
		1306	but not yet processed by poll_cb).
		1307
		1308	=back
		1309
750	=cut	1310	=cut
751		1311
752	# support function to convert a fd into a perl filehandle
753	sub _fd2fh {
754	return undef if $_[0] < 0;
755
756	# try to generate nice filehandles
757	my $sym = "IO::AIO::fd#$_[0]";
758	local *$sym;
759
760	open *$sym, "+<&=$_[0]" # usually works under any unix
761	or open *$sym, "<&=$_[0]" # cygwin needs this
762	or open *$sym, ">&=$_[0]" # or this
763	or return undef;
764
765	*$sym
766	}
767
768	min_parallel 4;	1312	min_parallel 8;
769		1313
770	END {	1314	END { flush }
771	max_parallel 0;
772	}
773		1315
774	1;	1316	1;
775		1317
776	=head2 FORK BEHAVIOUR	1318	=head2 FORK BEHAVIOUR
777		1319
778	This module should do "the right thing" when the process using it forks:	1320	This module should do "the right thing" when the process using it forks:
779		1321
780	Before the fork, IO::AIO enters a quiescent state where no requests	1322	Before the fork, IO::AIO enters a quiescent state where no requests
781	can be added in other threads and no results will be processed. After	1323	can be added in other threads and no results will be processed. After
782	the fork the parent simply leaves the quiescent state and continues	1324	the fork the parent simply leaves the quiescent state and continues
783	request/result processing, while the child clears the request/result	1325	request/result processing, while the child frees the request/result queue
784	queue (so the requests started before the fork will only be handled in	1326	(so that the requests started before the fork will only be handled in the
785	the parent). Threads will be started on demand until the limit ste in the	1327	parent). Threads will be started on demand until the limit set in the
786	parent process has been reached again.	1328	parent process has been reached again.
787		1329
788	In short: the parent will, after a short pause, continue as if fork had	1330	In short: the parent will, after a short pause, continue as if fork had
789	not been called, while the child will act as if IO::AIO has not been used	1331	not been called, while the child will act as if IO::AIO has not been used
790	yet.	1332	yet.
791		1333
		1334	=head2 MEMORY USAGE
		1335
		1336	Per-request usage:
		1337
		1338	Each aio request uses - depending on your architecture - around 100-200
		1339	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1340	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1341	scalars and other data passed into aio requests will also be locked and
		1342	will consume memory till the request has entered the done state.
		1343
		1344	This is not awfully much, so queuing lots of requests is not usually a
		1345	problem.
		1346
		1347	Per-thread usage:
		1348
		1349	In the execution phase, some aio requests require more memory for
		1350	temporary buffers, and each thread requires a stack and other data
		1351	structures (usually around 16k-128k, depending on the OS).
		1352
		1353	=head1 KNOWN BUGS
		1354
		1355	Known bugs will be fixed in the next release.
		1356
792	=head1 SEE ALSO	1357	=head1 SEE ALSO
793		1358
794	L<Coro>, L<Linux::AIO> (obsolete).	1359	L<Coro::AIO>.
795		1360
796	=head1 AUTHOR	1361	=head1 AUTHOR
797		1362
798	Marc Lehmann <schmorp@schmorp.de>	1363	Marc Lehmann <schmorp@schmorp.de>
799	http://home.schmorp.de/	1364	http://home.schmorp.de/

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