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Revision 1.56 by root, Sun Oct 22 00:53:47 2006 UTC vs.
Revision 1.122 by root, Sat Apr 26 12:00:23 2008 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 = '2.62';
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.
		328
		329	Therefore, C<aio_close> will not close the filehandle - instead it will
		330	use dup2 to overwrite the file descriptor with the write-end of a pipe
		331	(the pipe fd will be created on demand and will be cached).
		332
		333	Or in other words: the file descriptor will be closed, but it will not be
		334	free for reuse until the perl filehandle is closed.
		335
		336	=cut
163		337
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		339
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		341
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	342	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	343	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	344	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	345	like the syscall).
172		346
		347	If C<$offset> is undefined, then the current file descriptor offset will
		348	be used (and updated), otherwise the file descriptor offset will not be
		349	changed by these calls.
		350
		351	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		352
		353	If C<$dataoffset> is less than zero, it will be counted from the end of
		354	C<$data>.
		355
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	356	The C<$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	357	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	358	the necessary/optional hardware is installed).
176		359
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	360	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	361	offset C<0> within the scalar:
179		362
180	aio_read $fh, 7, 15, $buffer, 0, sub {	363	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	364	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	365	print "read $_[0] bytes: <$buffer>\n";
183	};	366	};
184		367
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	Try to move the I<file> (directories not supported as either source or
188	destination) from C<$srcpath> to C<$dstpath> and call the callback with
189	the C<0> (error) or C<-1> ok.
190
191	This is a composite request that tries to rename(2) the file first. If
192	rename files with C<EXDEV>, it creates the destination file with mode 0200
193	and copies the contents of the source file into it using C<aio_sendfile>,
194	followed by restoring atime, mtime, access mode and uid/gid, in that
195	order, and unlinking the C<$srcpath>.
196
197	If an error occurs, the partial destination file will be unlinked, if
198	possible, except when setting atime, mtime, access mode and uid/gid, where
199	errors are being ignored.
200
201	=cut
202
203	sub aio_move($$$) {
204	my ($src, $dst, $cb) = @_;
205
206	my $grp = aio_group;
207
208	add $grp aio_rename $src, $dst, sub {
209	if ($_[0] && $! == EXDEV) {
210	add $grp aio_open $src, O_RDONLY, 0, sub {
211	if (my $src_fh = $_[0]) {
212	my @stat = stat $src_fh;
213
214	add $grp aio_open $dst, O_WRONLY, 0200, sub {
215	if (my $dst_fh = $_[0]) {
216	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
217	close $src_fh;
218
219	if ($_[0] == $stat[7]) {
220	utime $stat[8], $stat[9], $dst;
221	chmod $stat[2] & 07777, $dst_fh;
222	chown $stat[4], $stat[5], $dst_fh;
223	close $dst_fh;
224
225	add $grp aio_unlink $src, sub {
226	$cb->($_[0]);
227	};
228	} else {
229	my $errno = $!;
230	add $grp aio_unlink $dst, sub {
231	$! = $errno;
232	$cb->(-1);
233	};
234	}
235	};
236	} else {
237	$cb->(-1);
238	}
239	},
240
241	} else {
242	$cb->(-1);
243	}
244	};
245	} else {
246	$cb->($_[0]);
247	}
248	};
249
250	$grp
251	}
252		368
253	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	369	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
254		370
255	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	371	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
256	reading at byte offset C<$in_offset>, and starts writing at the current	372	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
270	C<$in_fh> than are written, and there is no way to find out how many	386	C<$in_fh> than are written, and there is no way to find out how many
271	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	387	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
272	provides the number of bytes written to C<$out_fh>. Only if the result	388	provides the number of bytes written to C<$out_fh>. Only if the result
273	value equals C<$length> one can assume that C<$length> bytes have been	389	value equals C<$length> one can assume that C<$length> bytes have been
274	read.	390	read.
		391
275		392
276	=item aio_readahead $fh,$offset,$length, $callback->($retval)	393	=item aio_readahead $fh,$offset,$length, $callback->($retval)
277		394
278	C<aio_readahead> populates the page cache with data from a file so that	395	C<aio_readahead> populates the page cache with data from a file so that
279	subsequent reads from that file will not block on disk I/O. The C<$offset>	396	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
285	file. The current file offset of the file is left unchanged.	402	file. The current file offset of the file is left unchanged.
286		403
287	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	404	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
288	emulated by simply reading the data, which would have a similar effect.	405	emulated by simply reading the data, which would have a similar effect.
289		406
		407
290	=item aio_stat $fh_or_path, $callback->($status)	408	=item aio_stat $fh_or_path, $callback->($status)
291		409
292	=item aio_lstat $fh, $callback->($status)	410	=item aio_lstat $fh, $callback->($status)
293		411
294	Works like perl's C<stat> or C<lstat> in void context. The callback will	412	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
307	aio_stat "/etc/passwd", sub {	425	aio_stat "/etc/passwd", sub {
308	$_[0] and die "stat failed: $!";	426	$_[0] and die "stat failed: $!";
309	print "size is ", -s _, "\n";	427	print "size is ", -s _, "\n";
310	};	428	};
311		429
		430
		431	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		432
		433	Works like perl's C<utime> function (including the special case of $atime
		434	and $mtime being undef). Fractional times are supported if the underlying
		435	syscalls support them.
		436
		437	When called with a pathname, uses utimes(2) if available, otherwise
		438	utime(2). If called on a file descriptor, uses futimes(2) if available,
		439	otherwise returns ENOSYS, so this is not portable.
		440
		441	Examples:
		442
		443	# set atime and mtime to current time (basically touch(1)):
		444	aio_utime "path", undef, undef;
		445	# set atime to current time and mtime to beginning of the epoch:
		446	aio_utime "path", time, undef; # undef==0
		447
		448
		449	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		450
		451	Works like perl's C<chown> function, except that C<undef> for either $uid
		452	or $gid is being interpreted as "do not change" (but -1 can also be used).
		453
		454	Examples:
		455
		456	# same as "chown root path" in the shell:
		457	aio_chown "path", 0, -1;
		458	# same as above:
		459	aio_chown "path", 0, undef;
		460
		461
		462	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		463
		464	Works like truncate(2) or ftruncate(2).
		465
		466
		467	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		468
		469	Works like perl's C<chmod> function.
		470
		471
312	=item aio_unlink $pathname, $callback->($status)	472	=item aio_unlink $pathname, $callback->($status)
313		473
314	Asynchronously unlink (delete) a file and call the callback with the	474	Asynchronously unlink (delete) a file and call the callback with the
315	result code.	475	result code.
316		476
		477
		478	=item aio_mknod $path, $mode, $dev, $callback->($status)
		479
		480	[EXPERIMENTAL]
		481
		482	Asynchronously create a device node (or fifo). See mknod(2).
		483
		484	The only (POSIX-) portable way of calling this function is:
		485
		486	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		487
		488
317	=item aio_link $srcpath, $dstpath, $callback->($status)	489	=item aio_link $srcpath, $dstpath, $callback->($status)
318		490
319	Asynchronously create a new link to the existing object at C<$srcpath> at	491	Asynchronously create a new link to the existing object at C<$srcpath> at
320	the path C<$dstpath> and call the callback with the result code.	492	the path C<$dstpath> and call the callback with the result code.
321		493
		494
322	=item aio_symlink $srcpath, $dstpath, $callback->($status)	495	=item aio_symlink $srcpath, $dstpath, $callback->($status)
323		496
324	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	497	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
325	the path C<$dstpath> and call the callback with the result code.	498	the path C<$dstpath> and call the callback with the result code.
326		499
		500
		501	=item aio_readlink $path, $callback->($link)
		502
		503	Asynchronously read the symlink specified by C<$path> and pass it to
		504	the callback. If an error occurs, nothing or undef gets passed to the
		505	callback.
		506
		507
327	=item aio_rename $srcpath, $dstpath, $callback->($status)	508	=item aio_rename $srcpath, $dstpath, $callback->($status)
328		509
329	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	510	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
330	rename(2) and call the callback with the result code.	511	rename(2) and call the callback with the result code.
331		512
		513
		514	=item aio_mkdir $pathname, $mode, $callback->($status)
		515
		516	Asynchronously mkdir (create) a directory and call the callback with
		517	the result code. C<$mode> will be modified by the umask at the time the
		518	request is executed, so do not change your umask.
		519
		520
332	=item aio_rmdir $pathname, $callback->($status)	521	=item aio_rmdir $pathname, $callback->($status)
333		522
334	Asynchronously rmdir (delete) a directory and call the callback with the	523	Asynchronously rmdir (delete) a directory and call the callback with the
335	result code.	524	result code.
		525
336		526
337	=item aio_readdir $pathname, $callback->($entries)	527	=item aio_readdir $pathname, $callback->($entries)
338		528
339	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	529	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
340	directory (i.e. opendir + readdir + closedir). The entries will not be	530	directory (i.e. opendir + readdir + closedir). The entries will not be
341	sorted, and will B<NOT> include the C<.> and C<..> entries.	531	sorted, and will B<NOT> include the C<.> and C<..> entries.
342		532
343	The callback a single argument which is either C<undef> or an array-ref	533	The callback a single argument which is either C<undef> or an array-ref
344	with the filenames.	534	with the filenames.
345		535
		536
		537	=item aio_load $path, $data, $callback->($status)
		538
		539	This is a composite request that tries to fully load the given file into
		540	memory. Status is the same as with aio_read.
		541
		542	=cut
		543
		544	sub aio_load($$;$) {
		545	aio_block {
		546	my ($path, undef, $cb) = @_;
		547	my $data = \$_[1];
		548
		549	my $pri = aioreq_pri;
		550	my $grp = aio_group $cb;
		551
		552	aioreq_pri $pri;
		553	add $grp aio_open $path, O_RDONLY, 0, sub {
		554	my $fh = shift
		555	or return $grp->result (-1);
		556
		557	aioreq_pri $pri;
		558	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		559	$grp->result ($_[0]);
		560	};
		561	};
		562
		563	$grp
		564	}
		565	}
		566
		567	=item aio_copy $srcpath, $dstpath, $callback->($status)
		568
		569	Try to copy the I<file> (directories not supported as either source or
		570	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		571	the C<0> (error) or C<-1> ok.
		572
		573	This is a composite request that it creates the destination file with
		574	mode 0200 and copies the contents of the source file into it using
		575	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		576	uid/gid, in that order.
		577
		578	If an error occurs, the partial destination file will be unlinked, if
		579	possible, except when setting atime, mtime, access mode and uid/gid, where
		580	errors are being ignored.
		581
		582	=cut
		583
		584	sub aio_copy($$;$) {
		585	aio_block {
		586	my ($src, $dst, $cb) = @_;
		587
		588	my $pri = aioreq_pri;
		589	my $grp = aio_group $cb;
		590
		591	aioreq_pri $pri;
		592	add $grp aio_open $src, O_RDONLY, 0, sub {
		593	if (my $src_fh = $_[0]) {
		594	my @stat = stat $src_fh;
		595
		596	aioreq_pri $pri;
		597	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		598	if (my $dst_fh = $_[0]) {
		599	aioreq_pri $pri;
		600	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		601	if ($_[0] == $stat[7]) {
		602	$grp->result (0);
		603	close $src_fh;
		604
		605	# those should not normally block. should. should.
		606	utime $stat[8], $stat[9], $dst;
		607	chmod $stat[2] & 07777, $dst_fh;
		608	chown $stat[4], $stat[5], $dst_fh;
		609
		610	aioreq_pri $pri;
		611	add $grp aio_close $dst_fh;
		612	} else {
		613	$grp->result (-1);
		614	close $src_fh;
		615	close $dst_fh;
		616
		617	aioreq $pri;
		618	add $grp aio_unlink $dst;
		619	}
		620	};
		621	} else {
		622	$grp->result (-1);
		623	}
		624	},
		625
		626	} else {
		627	$grp->result (-1);
		628	}
		629	};
		630
		631	$grp
		632	}
		633	}
		634
		635	=item aio_move $srcpath, $dstpath, $callback->($status)
		636
		637	Try to move the I<file> (directories not supported as either source or
		638	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		639	the C<0> (error) or C<-1> ok.
		640
		641	This is a composite request that tries to rename(2) the file first. If
		642	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		643	that is successful, unlinking the C<$srcpath>.
		644
		645	=cut
		646
		647	sub aio_move($$;$) {
		648	aio_block {
		649	my ($src, $dst, $cb) = @_;
		650
		651	my $pri = aioreq_pri;
		652	my $grp = aio_group $cb;
		653
		654	aioreq_pri $pri;
		655	add $grp aio_rename $src, $dst, sub {
		656	if ($_[0] && $! == EXDEV) {
		657	aioreq_pri $pri;
		658	add $grp aio_copy $src, $dst, sub {
		659	$grp->result ($_[0]);
		660
		661	if (!$_[0]) {
		662	aioreq_pri $pri;
		663	add $grp aio_unlink $src;
		664	}
		665	};
		666	} else {
		667	$grp->result ($_[0]);
		668	}
		669	};
		670
		671	$grp
		672	}
		673	}
		674
346	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	675	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
347		676
348	Scans a directory (similar to C<aio_readdir>) but additionally tries to	677	Scans a directory (similar to C<aio_readdir>) but additionally tries to
349	separate the entries of directory C<$path> into two sets of names, ones	678	efficiently separate the entries of directory C<$path> into two sets of
350	you can recurse into (directories or links to them), and ones you cannot	679	names, directories you can recurse into (directories), and ones you cannot
351	recurse into (everything else).	680	recurse into (everything else, including symlinks to directories).
352		681
353	C<aio_scandir> is a composite request that consists of many sub	682	C<aio_scandir> is a composite request that creates of many sub requests_
354	requests. C<$maxreq> specifies the maximum number of outstanding aio	683	C<$maxreq> specifies the maximum number of outstanding aio requests that
355	requests that this function generates. If it is C<< <= 0 >>, then a	684	this function generates. If it is C<< <= 0 >>, then a suitable default
356	suitable default will be chosen (currently 8).	685	will be chosen (currently 4).
357		686
358	On error, the callback is called without arguments, otherwise it receives	687	On error, the callback is called without arguments, otherwise it receives
359	two array-refs with path-relative entry names.	688	two array-refs with path-relative entry names.
360		689
361	Example:	690	Example:
…		…
395	as those tend to return 0 or 1 as link counts, which disables the	724	as those tend to return 0 or 1 as link counts, which disables the
396	directory counting heuristic.	725	directory counting heuristic.
397		726
398	=cut	727	=cut
399		728
400	sub aio_scandir($$$) {	729	sub aio_scandir($$;$) {
		730	aio_block {
401	my ($path, $maxreq, $cb) = @_;	731	my ($path, $maxreq, $cb) = @_;
402		732
		733	my $pri = aioreq_pri;
		734
403	my $grp = aio_group;	735	my $grp = aio_group $cb;
404		736
405	$maxreq = 8 if $maxreq <= 0;	737	$maxreq = 4 if $maxreq <= 0;
406		738
407	# stat once	739	# stat once
		740	aioreq_pri $pri;
408	add $grp aio_stat $path, sub {	741	add $grp aio_stat $path, sub {
409	return $cb->() if $_[0];	742	return $grp->result () if $_[0];
410	my $now = time;	743	my $now = time;
411	my $hash1 = join ":", (stat _)[0,1,3,7,9];	744	my $hash1 = join ":", (stat _)[0,1,3,7,9];
412		745
413	# read the directory entries	746	# read the directory entries
		747	aioreq_pri $pri;
414	add $grp aio_readdir $path, sub {	748	add $grp aio_readdir $path, sub {
415	my $entries = shift	749	my $entries = shift
416	or return $cb->();	750	or return $grp->result ();
417		751
418	# stat the dir another time	752	# stat the dir another time
		753	aioreq_pri $pri;
419	add $grp aio_stat $path, sub {	754	add $grp aio_stat $path, sub {
420	my $hash2 = join ":", (stat _)[0,1,3,7,9];	755	my $hash2 = join ":", (stat _)[0,1,3,7,9];
421		756
422	my $ndirs;	757	my $ndirs;
423		758
424	# take the slow route if anything looks fishy	759	# take the slow route if anything looks fishy
425	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	760	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
426	$ndirs = -1;	761	$ndirs = -1;
427	} else {	762	} else {
428	# if nlink == 2, we are finished	763	# if nlink == 2, we are finished
429	# on non-posix-fs's, we rely on nlink < 2	764	# on non-posix-fs's, we rely on nlink < 2
430	$ndirs = (stat _)[3] - 2	765	$ndirs = (stat _)[3] - 2
431	or return $cb->([], $entries);	766	or return $grp->result ([], $entries);
432	}
433
434	# sort into likely dirs and likely nondirs
435	# dirs == files without ".", short entries first
436	$entries = [map $_->[0],
437	sort { $b->[1] cmp $a->[1] }
438	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
439	@$entries];
440
441	my (@dirs, @nondirs);
442
443	my ($statcb, $schedcb);
444	my $nreq = 0;
445
446	$schedcb = sub {
447	if (@$entries) {
448	if ($nreq < $maxreq) {
449	my $ent = pop @$entries;
450	$nreq++;
451	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
452	}
453	} elsif (!$nreq) {
454	# finished
455	undef $statcb;
456	undef $schedcb;
457	$cb->(\@dirs, \@nondirs) if $cb;
458	undef $cb;
459	}	767	}
		768
		769	# sort into likely dirs and likely nondirs
		770	# dirs == files without ".", short entries first
		771	$entries = [map $_->[0],
		772	sort { $b->[1] cmp $a->[1] }
		773	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		774	@$entries];
		775
		776	my (@dirs, @nondirs);
		777
		778	my $statgrp = add $grp aio_group sub {
		779	$grp->result (\@dirs, \@nondirs);
		780	};
		781
		782	limit $statgrp $maxreq;
		783	feed $statgrp sub {
		784	return unless @$entries;
		785	my $entry = pop @$entries;
		786
		787	aioreq_pri $pri;
		788	add $statgrp aio_stat "$path/$entry/.", sub {
		789	if ($_[0] < 0) {
		790	push @nondirs, $entry;
		791	} else {
		792	# need to check for real directory
		793	aioreq_pri $pri;
		794	add $statgrp aio_lstat "$path/$entry", sub {
		795	if (-d _) {
		796	push @dirs, $entry;
		797
		798	unless (--$ndirs) {
		799	push @nondirs, @$entries;
		800	feed $statgrp;
		801	}
		802	} else {
		803	push @nondirs, $entry;
		804	}
		805	}
		806	}
		807	};
		808	};
460	};	809	};
461	$statcb = sub {
462	my ($status, $entry) = @_;
463
464	if ($status < 0) {
465	$nreq--;
466	push @nondirs, $entry;
467	&$schedcb;
468	} else {
469	# need to check for real directory
470	add $grp aio_lstat "$path/$entry", sub {
471	$nreq--;
472
473	if (-d _) {
474	push @dirs, $entry;
475
476	if (!--$ndirs) {
477	push @nondirs, @$entries;
478	$entries = [];
479	}
480	} else {
481	push @nondirs, $entry;
482	}
483
484	&$schedcb;
485	}
486	}
487	};
488
489	&$schedcb while @$entries && $nreq < $maxreq;
490	};	810	};
491	};	811	};
		812
		813	$grp
492	};	814	}
493
494	$grp
495	}	815	}
		816
		817	=item aio_rmtree $path, $callback->($status)
		818
		819	Delete a directory tree starting (and including) C<$path>, return the
		820	status of the final C<rmdir> only. This is a composite request that
		821	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		822	everything else.
		823
		824	=cut
		825
		826	sub aio_rmtree;
		827	sub aio_rmtree($;$) {
		828	aio_block {
		829	my ($path, $cb) = @_;
		830
		831	my $pri = aioreq_pri;
		832	my $grp = aio_group $cb;
		833
		834	aioreq_pri $pri;
		835	add $grp aio_scandir $path, 0, sub {
		836	my ($dirs, $nondirs) = @_;
		837
		838	my $dirgrp = aio_group sub {
		839	add $grp aio_rmdir $path, sub {
		840	$grp->result ($_[0]);
		841	};
		842	};
		843
		844	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		845	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		846
		847	add $grp $dirgrp;
		848	};
		849
		850	$grp
		851	}
		852	}
		853
		854	=item aio_sync $callback->($status)
		855
		856	Asynchronously call sync and call the callback when finished.
496		857
497	=item aio_fsync $fh, $callback->($status)	858	=item aio_fsync $fh, $callback->($status)
498		859
499	Asynchronously call fsync on the given filehandle and call the callback	860	Asynchronously call fsync on the given filehandle and call the callback
500	with the fsync result code.	861	with the fsync result code.
…		…
505	callback with the fdatasync result code.	866	callback with the fdatasync result code.
506		867
507	If this call isn't available because your OS lacks it or it couldn't be	868	If this call isn't available because your OS lacks it or it couldn't be
508	detected, it will be emulated by calling C<fsync> instead.	869	detected, it will be emulated by calling C<fsync> instead.
509		870
		871	=item aio_pathsync $path, $callback->($status)
		872
		873	This request tries to open, fsync and close the given path. This is a
		874	composite request intended tosync directories after directory operations
		875	(E.g. rename). This might not work on all operating systems or have any
		876	specific effect, but usually it makes sure that directory changes get
		877	written to disc. It works for anything that can be opened for read-only,
		878	not just directories.
		879
		880	Passes C<0> when everything went ok, and C<-1> on error.
		881
		882	=cut
		883
		884	sub aio_pathsync($;$) {
		885	aio_block {
		886	my ($path, $cb) = @_;
		887
		888	my $pri = aioreq_pri;
		889	my $grp = aio_group $cb;
		890
		891	aioreq_pri $pri;
		892	add $grp aio_open $path, O_RDONLY, 0, sub {
		893	my ($fh) = @_;
		894	if ($fh) {
		895	aioreq_pri $pri;
		896	add $grp aio_fsync $fh, sub {
		897	$grp->result ($_[0]);
		898
		899	aioreq_pri $pri;
		900	add $grp aio_close $fh;
		901	};
		902	} else {
		903	$grp->result (-1);
		904	}
		905	};
		906
		907	$grp
		908	}
		909	}
		910
510	=item aio_group $callback->()	911	=item aio_group $callback->(...)
511
512	[EXPERIMENTAL]
513		912
514	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
515	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
516	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.
517		917
518	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
519	for more info.	919	for more info.
520		920
521	Example:	921	Example:
…		…
527	add $grp	927	add $grp
528	(aio_stat ...),	928	(aio_stat ...),
529	(aio_stat ...),	929	(aio_stat ...),
530	...;	930	...;
531		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
532	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	945	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
533		946
534	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
535	the request workers to sleep for the given time.	948	the request workers to sleep for the given time.
536		949
537	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
538	like sleep and file handle readable/writable, the overhead this creates	951	like sleep and file handle readable/writable, the overhead this creates is
539	is immense, so do not use this function except to put your application	952	immense (it blocks a thread for a long time) so do not use this function
540	under artificial I/O pressure.	953	except to put your application under artificial I/O pressure.
541		954
542	=back	955	=back
543		956
544	=head2 IO::AIO::REQ CLASS	957	=head2 IO::AIO::REQ CLASS
545		958
546	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
547	called in non-void context.	960	called in non-void context.
548		961
549	A request always moves through the following five states in its lifetime,
550	in order: B<ready> (request has been created, but has not been executed
551	yet), B<execute> (request is currently being executed), B<pending>
552	(request has been executed but callback has not been called yet),
553	B<result> (results are being processed synchronously, includes calling the
554	callback) and B<done> (request has reached the end of its lifetime and
555	holds no resources anymore).
556
557	=over 4	962	=over 4
558		963
559	=item $req->cancel	964	=item cancel $req
560		965
561	Cancels the request, if possible. Has the effect of skipping execution	966	Cancels the request, if possible. Has the effect of skipping execution
562	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
563	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
564	untouched. That means that requests that currently execute will not be	969	untouched. That means that requests that currently execute will not be
565	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.
566		971
		972	=item cb $req $callback->(...)
		973
		974	Replace (or simply set) the callback registered to the request.
		975
567	=back	976	=back
568		977
569	=head2 IO::AIO::GRP CLASS	978	=head2 IO::AIO::GRP CLASS
570		979
571	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
…		…
585	You add requests by calling the C<add> method with one or more	994	You add requests by calling the C<add> method with one or more
586	C<IO::AIO::REQ> objects:	995	C<IO::AIO::REQ> objects:
587		996
588	$grp->add (aio_unlink "...");	997	$grp->add (aio_unlink "...");
589		998
590	add $grp aio_stat "...", sub { ... };	999	add $grp aio_stat "...", sub {
		1000	$_[0] or return $grp->result ("error");
		1001
		1002	# add another request dynamically, if first succeeded
		1003	add $grp aio_open "...", sub {
		1004	$grp->result ("ok");
		1005	};
		1006	};
591		1007
592	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
593	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.
594		1010
		1011	=over 4
		1012
595	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
596	C<IO::AIO::poll_cb>, just like any other request.	1014	C<IO::AIO::poll_cb>, just like any other request.
597		1015
598	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
599	just the request itself, but also all requests it contains.	1017	only the request itself, but also all requests it contains.
600		1018
601	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
602		1025
603	Their lifetime, simplified, looks like this: when they are empty, they	1026	Their lifetime, simplified, looks like this: when they are empty, they
604	will finish very quickly. If they contain only requests that are in the	1027	will finish very quickly. If they contain only requests that are in the
605	C<done> state, they will also finish. Otherwise they will continue to	1028	C<done> state, they will also finish. Otherwise they will continue to
606	exist.	1029	exist.
607		1030
		1031	That means after creating a group you have some time to add requests. And
		1032	in the callbacks of those requests, you can add further requests to the
		1033	group. And only when all those requests have finished will the the group
		1034	itself finish.
		1035
608	=over 4	1036	=over 4
609		1037
		1038	=item add $grp ...
		1039
610	=item $grp->add (...)	1040	=item $grp->add (...)
611		1041
612	=item add $grp ...	1042	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1043	be added, including other groups, as long as you do not create circular
		1044	dependencies.
613		1045
614	Add one or more	1046	Returns all its arguments.
615	Cancels the request, if possible. Has the effect of skipping execution	1047
616	when entering the B<execute> state and skipping calling the callback when	1048	=item $grp->cancel_subs
617	entering the the B<result> state, but will leave the request otherwise	1049
618	untouched. That means that requests that currently execute will not be	1050	Cancel all subrequests and clears any feeder, but not the group request
619	stopped and resources held by the request will not be freed prematurely.	1051	itself. Useful when you queued a lot of events but got a result early.
		1052
		1053	=item $grp->result (...)
		1054
		1055	Set the result value(s) that will be passed to the group callback when all
		1056	subrequests have finished and set the 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.
620		1114
621	=back	1115	=back
622		1116
623	=head2 SUPPORT FUNCTIONS	1117	=head2 SUPPORT FUNCTIONS
		1118
		1119	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
624		1120
625	=over 4	1121	=over 4
626		1122
627	=item $fileno = IO::AIO::poll_fileno	1123	=item $fileno = IO::AIO::poll_fileno
628		1124
…		…
633		1129
634	See C<poll_cb> for an example.	1130	See C<poll_cb> for an example.
635		1131
636	=item IO::AIO::poll_cb	1132	=item IO::AIO::poll_cb
637		1133
638	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
639	regularly. Returns the number of events processed. Returns immediately	1135	regularly. Returns the number of events processed. Returns immediately
640	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.
641		1141
642	Example: Install an Event watcher that automatically calls	1142	Example: Install an Event watcher that automatically calls
643	IO::AIO::poll_cb with high priority:	1143	IO::AIO::poll_cb with high priority:
644		1144
645	Event->io (fd => IO::AIO::poll_fileno,	1145	Event->io (fd => IO::AIO::poll_fileno,
646	poll => 'r', async => 1,	1146	poll => 'r', async => 1,
647	cb => \&IO::AIO::poll_cb);	1147	cb => \&IO::AIO::poll_cb);
648		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
649	=item IO::AIO::poll_wait	1182	=item IO::AIO::poll_wait
650		1183
		1184	If there are any outstanding requests and none of them in the result
651	Wait till the result filehandle becomes ready for reading (simply does a	1185	phase, wait till the result filehandle becomes ready for reading (simply
652	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
653	for some requests to finish).	1187	synchronously wait for some requests to finish).
654		1188
655	See C<nreqs> for an example.	1189	See C<nreqs> for an example.
656		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
657	=item IO::AIO::nreqs	1200	=item IO::AIO::flush
658		1201
659	Returns the number of requests currently outstanding (i.e. for which their	1202	Wait till all outstanding AIO requests have been handled.
660	callback has not been invoked yet).
661		1203
662	Example: wait till there are no outstanding requests anymore:	1204	Strictly equivalent to:
663		1205
664	IO::AIO::poll_wait, IO::AIO::poll_cb	1206	IO::AIO::poll_wait, IO::AIO::poll_cb
665	while IO::AIO::nreqs;	1207	while IO::AIO::nreqs;
666		1208
667	=item IO::AIO::flush	1209	=back
668		1210
669	Wait till all outstanding AIO requests have been handled.	1211	=head3 CONTROLLING THE NUMBER OF THREADS
670		1212
671	Strictly equivalent to:	1213	=over
672
673	IO::AIO::poll_wait, IO::AIO::poll_cb
674	while IO::AIO::nreqs;
675
676	=item IO::AIO::poll
677
678	Waits until some requests have been handled.
679
680	Strictly equivalent to:
681
682	IO::AIO::poll_wait, IO::AIO::poll_cb
683	if IO::AIO::nreqs;
684		1214
685	=item IO::AIO::min_parallel $nthreads	1215	=item IO::AIO::min_parallel $nthreads
686		1216
687	Set the minimum number of AIO threads to C<$nthreads>. The current default	1217	Set the minimum number of AIO threads to C<$nthreads>. The current
688	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
689	(the number of outstanding operations, however, is unlimited).	1219	concurrently at any one time (the number of outstanding requests,
		1220	however, is unlimited).
690		1221
691	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
692	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.
693		1226
694	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
695	kernel versions will scale negatively with the number of threads (higher	1228	Linux kernel versions will scale negatively with the number of threads
696	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1229	(higher parallelity => MUCH higher latency). With current Linux 2.6
697	threads should be fine.	1230	versions, 4-32 threads should be fine.
698		1231
699	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
700	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.
701		1234
702	=item IO::AIO::max_parallel $nthreads	1235	=item IO::AIO::max_parallel $nthreads
…		…
711	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
712	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.
713		1246
714	Under normal circumstances you don't need to call this function.	1247	Under normal circumstances you don't need to call this function.
715		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
716	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1264	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1265
		1266	This is a very bad function to use in interactive programs because it
		1267	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1268	use an C<aio_group> together with a feed callback.
717		1269
718	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1270	Sets the maximum number of outstanding requests to C<$nreqs>. If you
719	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
720	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.
721		1274
722	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
723	queue up many requests in a loop it often improves speed if you set	1276	number of outstanding requests.
724	this to a relatively low number, such as C<100>.
725		1277
726	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).
727		1281
728	=back	1282	=back
729		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
730	=cut	1310	=cut
731		1311
732	# support function to convert a fd into a perl filehandle
733	sub _fd2fh {
734	return undef if $_[0] < 0;
735
736	# try to generate nice filehandles
737	my $sym = "IO::AIO::fd#$_[0]";
738	local *$sym;
739
740	open *$sym, "+<&=$_[0]" # usually works under any unix
741	or open *$sym, "<&=$_[0]" # cygwin needs this
742	or open *$sym, ">&=$_[0]" # or this
743	or return undef;
744
745	*$sym
746	}
747
748	min_parallel 4;	1312	min_parallel 8;
749		1313
750	END {	1314	END { flush }
751	max_parallel 0;
752	}
753		1315
754	1;	1316	1;
755		1317
756	=head2 FORK BEHAVIOUR	1318	=head2 FORK BEHAVIOUR
757		1319
758	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:
759		1321
760	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
761	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
762	the fork the parent simply leaves the quiescent state and continues	1324	the fork the parent simply leaves the quiescent state and continues
763	request/result processing, while the child clears the request/result	1325	request/result processing, while the child frees the request/result queue
764	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
765	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
766	parent process has been reached again.	1328	parent process has been reached again.
767		1329
768	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
769	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
770	yet.	1332	yet.
771		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
772	=head1 SEE ALSO	1357	=head1 SEE ALSO
773		1358
774	L<Coro>, L<Linux::AIO> (obsolete).	1359	L<Coro::AIO>.
775		1360
776	=head1 AUTHOR	1361	=head1 AUTHOR
777		1362
778	Marc Lehmann <schmorp@schmorp.de>	1363	Marc Lehmann <schmorp@schmorp.de>
779	http://home.schmorp.de/	1364	http://home.schmorp.de/

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