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Revision 1.50 by root, Sat Jun 24 16:27:02 2006 UTC vs.
Revision 1.115 by root, Mon Sep 24 18:14:00 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
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# AnyEvent	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
21	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
22	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 });
23		34
24	# Event	35	# Event integration
25	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
26	poll => 'r',	37	poll => 'r',
27	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
28		39
29	# Glib/Gtk2	40	# Glib/Gtk2 integration
30	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
31	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
32		43
33	# Tk	44	# Tk integration
34	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
35	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
36		47
37	# Danga::Socket	48	# Danga::Socket integration
38	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
39	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
40		51
41
42	=head1 DESCRIPTION	52	=head1 DESCRIPTION
43		53
44	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
45	operating system supports.	55	operating system supports.
46		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
47	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
48	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
49	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
50	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
51	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
52	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
53	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
54	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
55		82
56	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
57	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
58	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	85	yourself, always call C<poll_cb> from within the same thread, or never
59	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
60		183
61	=cut	184	=cut
62		185
63	package IO::AIO;	186	package IO::AIO;
64		187
65	no warnings;	188	no warnings;
		189	use strict 'vars';
66		190
67	use base 'Exporter';	191	use base 'Exporter';
68		192
69	use Fcntl ();
70
71	BEGIN {	193	BEGIN {
72	$VERSION = '1.8';	194	our $VERSION = '2.41';
73		195
74	@EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	196	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
75	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	197	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
76	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
77	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel	199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
78	max_outstanding nreqs);	200	aio_chown aio_chmod aio_utime aio_truncate);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
79		208
80	require XSLoader;	209	require XSLoader;
81	XSLoader::load IO::AIO, $VERSION;	210	XSLoader::load ("IO::AIO", $VERSION);
82	}	211	}
83		212
84	=head1 FUNCTIONS	213	=head1 FUNCTIONS
85		214
86	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
87		216
88	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
89	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
90	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
91	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
…		…
94	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
95		224
96	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
97	internally until the request has finished.	226	internally until the request has finished.
98		227
		228	All functions return request objects of type L<IO::AIO::REQ> that allow
		229	further manipulation of those requests while they are in-flight.
		230
99	The pathnames you pass to these routines I<must> be absolute and	231	The pathnames you pass to these routines I<must> be absolute and
100	encoded in byte form. The reason for the former is that at the time the	232	encoded as octets. The reason for the former is that at the time the
101	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
102	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
103	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
104		237
105	To encode pathnames to byte form, either make sure you either: a)	238	To encode pathnames as octets, either make sure you either: a) always pass
106	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
107	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
108	your pathnames to the locale (or other) encoding in effect in the user	241	your pathnames to the locale (or other) encoding in effect in the user
109	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
110	use something else.	243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
111		247
112	=over 4	248	=over 4
		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276
		277	=item aioreq_nice $pri_adjust
		278
		279	Similar to C<aioreq_pri>, but subtracts the given value from the current
		280	priority, so the effect is cumulative.
		281
113		282
114	=item aio_open $pathname, $flags, $mode, $callback->($fh)	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
115		284
116	Asynchronously open or create a file and call the callback with a newly	285	Asynchronously open or create a file and call the callback with a newly
117	created filehandle for the file.	286	created filehandle for the file.
…		…
123	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
124		293
125	Likewise, C<$mode> specifies the mode of the newly created file, if it	294	Likewise, C<$mode> specifies the mode of the newly created file, if it
126	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	295	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
127	except that it is mandatory (i.e. use C<0> if you don't create new files,	296	except that it is mandatory (i.e. use C<0> if you don't create new files,
128	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
129		300
130	Example:	301	Example:
131		302
132	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
133	if ($_[0]) {	304	if ($_[0]) {
…		…
136	} else {	307	} else {
137	die "open failed: $!\n";	308	die "open failed: $!\n";
138	}	309	}
139	};	310	};
140		311
		312
141	=item aio_close $fh, $callback->($status)	313	=item aio_close $fh, $callback->($status)
142		314
143	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
144	code. I<WARNING:> although accepted, you should not pass in a perl	316	code. I<WARNING:> although accepted, you should not pass in a perl
145	filehandle here, as perl will likely close the file descriptor another	317	filehandle here, as perl will likely close the file descriptor another
…		…
147	C<close> or just let filehandles go out of scope.	319	C<close> or just let filehandles go out of scope.
148		320
149	This is supposed to be a bug in the API, so that might change. It's	321	This is supposed to be a bug in the API, so that might change. It's
150	therefore best to avoid this function.	322	therefore best to avoid this function.
151		323
		324
152	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	325	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
153		326
154	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	327	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
155		328
156	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	329	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
157	into the scalar given by C<data> and offset C<dataoffset> and calls the	330	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
158	callback without the actual number of bytes read (or -1 on error, just	331	callback without the actual number of bytes read (or -1 on error, just
159	like the syscall).	332	like the syscall).
160		333
		334	If C<$offset> is undefined, then the current file descriptor offset will
		335	be used (and updated), otherwise the file descriptor offset will not be
		336	changed by these calls.
		337
		338	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		339
		340	If C<$dataoffset> is less than zero, it will be counted from the end of
		341	C<$data>.
		342
161	The C<$data> scalar I<MUST NOT> be modified in any way while the request	343	The C<$data> scalar I<MUST NOT> be modified in any way while the request
162	is outstanding. Modifying it can result in segfaults or WW3 (if the	344	is outstanding. Modifying it can result in segfaults or World War III (if
163	necessary/optional hardware is installed).	345	the necessary/optional hardware is installed).
164		346
165	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	347	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
166	offset C<0> within the scalar:	348	offset C<0> within the scalar:
167		349
168	aio_read $fh, 7, 15, $buffer, 0, sub {	350	aio_read $fh, 7, 15, $buffer, 0, sub {
169	$_[0] > 0 or die "read error: $!";	351	$_[0] > 0 or die "read error: $!";
170	print "read $_[0] bytes: <$buffer>\n";	352	print "read $_[0] bytes: <$buffer>\n";
171	};	353	};
172		354
173	=item aio_move $srcpath, $dstpath, $callback->($status)
174
175	[EXPERIMENTAL]
176
177	Try to move the I<file> (directories not supported as either source or destination)
178	from C<$srcpath> to C<$dstpath> and call the callback with the C<0> (error) or C<-1> ok.
179
180	This is a composite request that tries to rename(2) the file first. If
181	rename files with C<EXDEV>, it creates the destination file with mode 0200
182	and copies the contents of the source file into it using C<aio_sendfile>,
183	followed by restoring atime, mtime, access mode and uid/gid, in that
184	order, and unlinking the C<$srcpath>.
185
186	If an error occurs, the partial destination file will be unlinked, if
187	possible, except when setting atime, mtime, access mode and uid/gid, where
188	errors are being ignored.
189
190	=cut
191
192	sub aio_move($$$) {
193	my ($src, $dst, $cb) = @_;
194
195	aio_rename $src, $dst, sub {
196	if ($_[0] && $! == Errno::EXDEV) {
197	aio_open $src, O_RDONLY, 0, sub {
198	if (my $src_fh = $_[0]) {
199	my @stat = stat $src_fh;
200
201	aio_open $dst, O_WRONLY, 0200, sub {
202	if (my $dst_fh = $_[0]) {
203	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
204	close $src_fh;
205
206	if ($_[0] == $stat[7]) {
207	utime $stat[8], $stat[9], $dst;
208	chmod $stat[2] & 07777, $dst_fh;
209	chown $stat[4], $stat[5], $dst_fh;
210	close $dst_fh;
211
212	aio_unlink $src, sub {
213	$cb->($_[0]);
214	};
215	} else {
216	my $errno = $!;
217	aio_unlink $dst, sub {
218	$! = $errno;
219	$cb->(-1);
220	};
221	}
222	};
223	} else {
224	$cb->(-1);
225	}
226	},
227
228	} else {
229	$cb->(-1);
230	}
231	};
232	} else {
233	$cb->($_[0]);
234	}
235	};
236	}
237		355
238	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	356	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
239		357
240	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	358	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
241	reading at byte offset C<$in_offset>, and starts writing at the current	359	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
255	C<$in_fh> than are written, and there is no way to find out how many	373	C<$in_fh> than are written, and there is no way to find out how many
256	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	374	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
257	provides the number of bytes written to C<$out_fh>. Only if the result	375	provides the number of bytes written to C<$out_fh>. Only if the result
258	value equals C<$length> one can assume that C<$length> bytes have been	376	value equals C<$length> one can assume that C<$length> bytes have been
259	read.	377	read.
		378
260		379
261	=item aio_readahead $fh,$offset,$length, $callback->($retval)	380	=item aio_readahead $fh,$offset,$length, $callback->($retval)
262		381
263	C<aio_readahead> populates the page cache with data from a file so that	382	C<aio_readahead> populates the page cache with data from a file so that
264	subsequent reads from that file will not block on disk I/O. The C<$offset>	383	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
270	file. The current file offset of the file is left unchanged.	389	file. The current file offset of the file is left unchanged.
271		390
272	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	391	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
273	emulated by simply reading the data, which would have a similar effect.	392	emulated by simply reading the data, which would have a similar effect.
274		393
		394
275	=item aio_stat $fh_or_path, $callback->($status)	395	=item aio_stat $fh_or_path, $callback->($status)
276		396
277	=item aio_lstat $fh, $callback->($status)	397	=item aio_lstat $fh, $callback->($status)
278		398
279	Works like perl's C<stat> or C<lstat> in void context. The callback will	399	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
292	aio_stat "/etc/passwd", sub {	412	aio_stat "/etc/passwd", sub {
293	$_[0] and die "stat failed: $!";	413	$_[0] and die "stat failed: $!";
294	print "size is ", -s _, "\n";	414	print "size is ", -s _, "\n";
295	};	415	};
296		416
		417
		418	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		419
		420	Works like perl's C<utime> function (including the special case of $atime
		421	and $mtime being undef). Fractional times are supported if the underlying
		422	syscalls support them.
		423
		424	When called with a pathname, uses utimes(2) if available, otherwise
		425	utime(2). If called on a file descriptor, uses futimes(2) if available,
		426	otherwise returns ENOSYS, so this is not portable.
		427
		428	Examples:
		429
		430	# set atime and mtime to current time (basically touch(1)):
		431	aio_utime "path", undef, undef;
		432	# set atime to current time and mtime to beginning of the epoch:
		433	aio_utime "path", time, undef; # undef==0
		434
		435
		436	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		437
		438	Works like perl's C<chown> function, except that C<undef> for either $uid
		439	or $gid is being interpreted as "do not change" (but -1 can also be used).
		440
		441	Examples:
		442
		443	# same as "chown root path" in the shell:
		444	aio_chown "path", 0, -1;
		445	# same as above:
		446	aio_chown "path", 0, undef;
		447
		448
		449	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		450
		451	Works like truncate(2) or ftruncate(2).
		452
		453
		454	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		455
		456	Works like perl's C<chmod> function.
		457
		458
297	=item aio_unlink $pathname, $callback->($status)	459	=item aio_unlink $pathname, $callback->($status)
298		460
299	Asynchronously unlink (delete) a file and call the callback with the	461	Asynchronously unlink (delete) a file and call the callback with the
300	result code.	462	result code.
301		463
		464
		465	=item aio_mknod $path, $mode, $dev, $callback->($status)
		466
		467	[EXPERIMENTAL]
		468
		469	Asynchronously create a device node (or fifo). See mknod(2).
		470
		471	The only (POSIX-) portable way of calling this function is:
		472
		473	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		474
		475
302	=item aio_link $srcpath, $dstpath, $callback->($status)	476	=item aio_link $srcpath, $dstpath, $callback->($status)
303		477
304	Asynchronously create a new link to the existing object at C<$srcpath> at	478	Asynchronously create a new link to the existing object at C<$srcpath> at
305	the path C<$dstpath> and call the callback with the result code.	479	the path C<$dstpath> and call the callback with the result code.
306		480
		481
307	=item aio_symlink $srcpath, $dstpath, $callback->($status)	482	=item aio_symlink $srcpath, $dstpath, $callback->($status)
308		483
309	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	484	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
310	the path C<$dstpath> and call the callback with the result code.	485	the path C<$dstpath> and call the callback with the result code.
311		486
		487
		488	=item aio_readlink $path, $callback->($link)
		489
		490	Asynchronously read the symlink specified by C<$path> and pass it to
		491	the callback. If an error occurs, nothing or undef gets passed to the
		492	callback.
		493
		494
312	=item aio_rename $srcpath, $dstpath, $callback->($status)	495	=item aio_rename $srcpath, $dstpath, $callback->($status)
313		496
314	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	497	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
315	rename(2) and call the callback with the result code.	498	rename(2) and call the callback with the result code.
316		499
		500
		501	=item aio_mkdir $pathname, $mode, $callback->($status)
		502
		503	Asynchronously mkdir (create) a directory and call the callback with
		504	the result code. C<$mode> will be modified by the umask at the time the
		505	request is executed, so do not change your umask.
		506
		507
317	=item aio_rmdir $pathname, $callback->($status)	508	=item aio_rmdir $pathname, $callback->($status)
318		509
319	Asynchronously rmdir (delete) a directory and call the callback with the	510	Asynchronously rmdir (delete) a directory and call the callback with the
320	result code.	511	result code.
		512
321		513
322	=item aio_readdir $pathname, $callback->($entries)	514	=item aio_readdir $pathname, $callback->($entries)
323		515
324	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	516	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
325	directory (i.e. opendir + readdir + closedir). The entries will not be	517	directory (i.e. opendir + readdir + closedir). The entries will not be
326	sorted, and will B<NOT> include the C<.> and C<..> entries.	518	sorted, and will B<NOT> include the C<.> and C<..> entries.
327		519
328	The callback a single argument which is either C<undef> or an array-ref	520	The callback a single argument which is either C<undef> or an array-ref
329	with the filenames.	521	with the filenames.
330		522
		523
		524	=item aio_load $path, $data, $callback->($status)
		525
		526	This is a composite request that tries to fully load the given file into
		527	memory. Status is the same as with aio_read.
		528
		529	=cut
		530
		531	sub aio_load($$;$) {
		532	aio_block {
		533	my ($path, undef, $cb) = @_;
		534	my $data = \$_[1];
		535
		536	my $pri = aioreq_pri;
		537	my $grp = aio_group $cb;
		538
		539	aioreq_pri $pri;
		540	add $grp aio_open $path, O_RDONLY, 0, sub {
		541	my $fh = shift
		542	or return $grp->result (-1);
		543
		544	aioreq_pri $pri;
		545	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		546	$grp->result ($_[0]);
		547	};
		548	};
		549
		550	$grp
		551	}
		552	}
		553
		554	=item aio_copy $srcpath, $dstpath, $callback->($status)
		555
		556	Try to copy the I<file> (directories not supported as either source or
		557	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		558	the C<0> (error) or C<-1> ok.
		559
		560	This is a composite request that it creates the destination file with
		561	mode 0200 and copies the contents of the source file into it using
		562	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		563	uid/gid, in that order.
		564
		565	If an error occurs, the partial destination file will be unlinked, if
		566	possible, except when setting atime, mtime, access mode and uid/gid, where
		567	errors are being ignored.
		568
		569	=cut
		570
		571	sub aio_copy($$;$) {
		572	aio_block {
		573	my ($src, $dst, $cb) = @_;
		574
		575	my $pri = aioreq_pri;
		576	my $grp = aio_group $cb;
		577
		578	aioreq_pri $pri;
		579	add $grp aio_open $src, O_RDONLY, 0, sub {
		580	if (my $src_fh = $_[0]) {
		581	my @stat = stat $src_fh;
		582
		583	aioreq_pri $pri;
		584	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		585	if (my $dst_fh = $_[0]) {
		586	aioreq_pri $pri;
		587	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		588	if ($_[0] == $stat[7]) {
		589	$grp->result (0);
		590	close $src_fh;
		591
		592	# those should not normally block. should. should.
		593	utime $stat[8], $stat[9], $dst;
		594	chmod $stat[2] & 07777, $dst_fh;
		595	chown $stat[4], $stat[5], $dst_fh;
		596	close $dst_fh;
		597	} else {
		598	$grp->result (-1);
		599	close $src_fh;
		600	close $dst_fh;
		601
		602	aioreq $pri;
		603	add $grp aio_unlink $dst;
		604	}
		605	};
		606	} else {
		607	$grp->result (-1);
		608	}
		609	},
		610
		611	} else {
		612	$grp->result (-1);
		613	}
		614	};
		615
		616	$grp
		617	}
		618	}
		619
		620	=item aio_move $srcpath, $dstpath, $callback->($status)
		621
		622	Try to move the I<file> (directories not supported as either source or
		623	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		624	the C<0> (error) or C<-1> ok.
		625
		626	This is a composite request that tries to rename(2) the file first. If
		627	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		628	that is successful, unlinking the C<$srcpath>.
		629
		630	=cut
		631
		632	sub aio_move($$;$) {
		633	aio_block {
		634	my ($src, $dst, $cb) = @_;
		635
		636	my $pri = aioreq_pri;
		637	my $grp = aio_group $cb;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_rename $src, $dst, sub {
		641	if ($_[0] && $! == EXDEV) {
		642	aioreq_pri $pri;
		643	add $grp aio_copy $src, $dst, sub {
		644	$grp->result ($_[0]);
		645
		646	if (!$_[0]) {
		647	aioreq_pri $pri;
		648	add $grp aio_unlink $src;
		649	}
		650	};
		651	} else {
		652	$grp->result ($_[0]);
		653	}
		654	};
		655
		656	$grp
		657	}
		658	}
		659
331	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	660	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
332		661
333	Scans a directory (similar to C<aio_readdir>) and tries to separate the	662	Scans a directory (similar to C<aio_readdir>) but additionally tries to
334	entries of directory C<$path> into two sets of names, ones you can recurse	663	efficiently separate the entries of directory C<$path> into two sets of
335	into (directories), and ones you cannot recurse into (everything else).	664	names, directories you can recurse into (directories), and ones you cannot
		665	recurse into (everything else, including symlinks to directories).
336		666
337	C<aio_scandir> is a composite request that consists of many	667	C<aio_scandir> is a composite request that creates of many sub requests_
338	aio-primitives. C<$maxreq> specifies the maximum number of outstanding	668	C<$maxreq> specifies the maximum number of outstanding aio requests that
339	aio requests that this function generates. If it is C<< <= 0 >>, then a	669	this function generates. If it is C<< <= 0 >>, then a suitable default
340	suitable default will be chosen (currently 8).	670	will be chosen (currently 4).
341		671
342	On error, the callback is called without arguments, otherwise it receives	672	On error, the callback is called without arguments, otherwise it receives
343	two array-refs with path-relative entry names.	673	two array-refs with path-relative entry names.
344		674
345	Example:	675	Example:
…		…
353	Implementation notes.	683	Implementation notes.
354		684
355	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	685	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
356		686
357	After reading the directory, the modification time, size etc. of the	687	After reading the directory, the modification time, size etc. of the
358	directory before and after the readdir is checked, and if they match, the	688	directory before and after the readdir is checked, and if they match (and
359	link count will be used to decide how many entries are directories (if	689	isn't the current time), the link count will be used to decide how many
360	>= 2). Otherwise, no knowledge of the number of subdirectories will be	690	entries are directories (if >= 2). Otherwise, no knowledge of the number
361	assumed.	691	of subdirectories will be assumed.
362		692
363	Then entires will be sorted into likely directories (everything without a	693	Then entries will be sorted into likely directories (everything without
364	non-initial dot) and likely non-directories (everything else). Then every	694	a non-initial dot currently) and likely non-directories (everything
365	entry + C</.> will be C<stat>'ed, likely directories first. This is often	695	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		696	likely directories first. If that succeeds, it assumes that the entry
		697	is a directory or a symlink to directory (which will be checked
		698	seperately). This is often faster than stat'ing the entry itself because
366	faster because filesystems might detect the type of the entry without	699	filesystems might detect the type of the entry without reading the inode
367	reading the inode data (e.g. ext2fs filetype feature). If that succeeds,	700	data (e.g. ext2fs filetype feature).
368	it assumes that the entry is a directory or a symlink to directory (which
369	will be checked seperately).
370		701
371	If the known number of directories has been reached, the rest of the	702	If the known number of directories (link count - 2) has been reached, the
372	entries is assumed to be non-directories.	703	rest of the entries is assumed to be non-directories.
		704
		705	This only works with certainty on POSIX (= UNIX) filesystems, which
		706	fortunately are the vast majority of filesystems around.
		707
		708	It will also likely work on non-POSIX filesystems with reduced efficiency
		709	as those tend to return 0 or 1 as link counts, which disables the
		710	directory counting heuristic.
373		711
374	=cut	712	=cut
375		713
376	sub aio_scandir($$$) {	714	sub aio_scandir($$;$) {
		715	aio_block {
377	my ($path, $maxreq, $cb) = @_;	716	my ($path, $maxreq, $cb) = @_;
378		717
		718	my $pri = aioreq_pri;
		719
		720	my $grp = aio_group $cb;
		721
379	$maxreq = 8 if $maxreq <= 0;	722	$maxreq = 4 if $maxreq <= 0;
380		723
381	# stat once	724	# stat once
		725	aioreq_pri $pri;
382	aio_stat $path, sub {	726	add $grp aio_stat $path, sub {
383	return $cb->() if $_[0];	727	return $grp->result () if $_[0];
		728	my $now = time;
384	my $hash1 = join ":", (stat _)[0,1,3,7,9];	729	my $hash1 = join ":", (stat _)[0,1,3,7,9];
385		730
386	# read the directory entries	731	# read the directory entries
		732	aioreq_pri $pri;
387	aio_readdir $path, sub {	733	add $grp aio_readdir $path, sub {
388	my $entries = shift	734	my $entries = shift
389	or return $cb->();	735	or return $grp->result ();
390		736
391	# stat the dir another time	737	# stat the dir another time
		738	aioreq_pri $pri;
392	aio_stat $path, sub {	739	add $grp aio_stat $path, sub {
393	my $hash2 = join ":", (stat _)[0,1,3,7,9];	740	my $hash2 = join ":", (stat _)[0,1,3,7,9];
394		741
395	my $ndirs;	742	my $ndirs;
396		743
397	# take the slow route if anything looks fishy	744	# take the slow route if anything looks fishy
398	if ($hash1 ne $hash2) {	745	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
399	$ndirs = -1;	746	$ndirs = -1;
400	} else {	747	} else {
401	# if nlink == 2, we are finished	748	# if nlink == 2, we are finished
402	# on non-posix-fs's, we rely on nlink < 2	749	# on non-posix-fs's, we rely on nlink < 2
403	$ndirs = (stat _)[3] - 2	750	$ndirs = (stat _)[3] - 2
404	or return $cb->([], $entries);	751	or return $grp->result ([], $entries);
405	}
406
407	# sort into likely dirs and likely nondirs
408	# dirs == files without ".", short entries first
409	$entries = [map $_->[0],
410	sort { $b->[1] cmp $a->[1] }
411	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
412	@$entries];
413
414	my (@dirs, @nondirs);
415
416	my ($statcb, $schedcb);
417	my $nreq = 0;
418
419	$schedcb = sub {
420	if (@$entries) {
421	if ($nreq < $maxreq) {
422	my $ent = pop @$entries;
423	$nreq++;
424	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
425	}
426	} elsif (!$nreq) {
427	# finished
428	undef $statcb;
429	undef $schedcb;
430	$cb->(\@dirs, \@nondirs) if $cb;
431	undef $cb;
432	}	752	}
		753
		754	# sort into likely dirs and likely nondirs
		755	# dirs == files without ".", short entries first
		756	$entries = [map $_->[0],
		757	sort { $b->[1] cmp $a->[1] }
		758	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		759	@$entries];
		760
		761	my (@dirs, @nondirs);
		762
		763	my $statgrp = add $grp aio_group sub {
		764	$grp->result (\@dirs, \@nondirs);
		765	};
		766
		767	limit $statgrp $maxreq;
		768	feed $statgrp sub {
		769	return unless @$entries;
		770	my $entry = pop @$entries;
		771
		772	aioreq_pri $pri;
		773	add $statgrp aio_stat "$path/$entry/.", sub {
		774	if ($_[0] < 0) {
		775	push @nondirs, $entry;
		776	} else {
		777	# need to check for real directory
		778	aioreq_pri $pri;
		779	add $statgrp aio_lstat "$path/$entry", sub {
		780	if (-d _) {
		781	push @dirs, $entry;
		782
		783	unless (--$ndirs) {
		784	push @nondirs, @$entries;
		785	feed $statgrp;
		786	}
		787	} else {
		788	push @nondirs, $entry;
		789	}
		790	}
		791	}
		792	};
		793	};
433	};	794	};
434	$statcb = sub {
435	my ($status, $entry) = @_;
436
437	if ($status < 0) {
438	$nreq--;
439	push @nondirs, $entry;
440	&$schedcb;
441	} else {
442	# need to check for real directory
443	aio_lstat "$path/$entry", sub {
444	$nreq--;
445
446	if (-d _) {
447	push @dirs, $entry;
448
449	if (!--$ndirs) {
450	push @nondirs, @$entries;
451	$entries = [];
452	}
453	} else {
454	push @nondirs, $entry;
455	}
456
457	&$schedcb;
458	}
459	}
460	};
461
462	&$schedcb while @$entries && $nreq < $maxreq;
463	};	795	};
464	};	796	};
		797
		798	$grp
465	};	799	}
		800	}
		801
		802	=item aio_rmtree $path, $callback->($status)
		803
		804	Delete a directory tree starting (and including) C<$path>, return the
		805	status of the final C<rmdir> only. This is a composite request that
		806	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		807	everything else.
		808
		809	=cut
		810
		811	sub aio_rmtree;
		812	sub aio_rmtree($;$) {
		813	aio_block {
		814	my ($path, $cb) = @_;
		815
		816	my $pri = aioreq_pri;
		817	my $grp = aio_group $cb;
		818
		819	aioreq_pri $pri;
		820	add $grp aio_scandir $path, 0, sub {
		821	my ($dirs, $nondirs) = @_;
		822
		823	my $dirgrp = aio_group sub {
		824	add $grp aio_rmdir $path, sub {
		825	$grp->result ($_[0]);
		826	};
		827	};
		828
		829	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		830	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		831
		832	add $grp $dirgrp;
		833	};
		834
		835	$grp
		836	}
466	}	837	}
467		838
468	=item aio_fsync $fh, $callback->($status)	839	=item aio_fsync $fh, $callback->($status)
469		840
470	Asynchronously call fsync on the given filehandle and call the callback	841	Asynchronously call fsync on the given filehandle and call the callback
…		…
476	callback with the fdatasync result code.	847	callback with the fdatasync result code.
477		848
478	If this call isn't available because your OS lacks it or it couldn't be	849	If this call isn't available because your OS lacks it or it couldn't be
479	detected, it will be emulated by calling C<fsync> instead.	850	detected, it will be emulated by calling C<fsync> instead.
480		851
		852	=item aio_group $callback->(...)
		853
		854	This is a very special aio request: Instead of doing something, it is a
		855	container for other aio requests, which is useful if you want to bundle
		856	many requests into a single, composite, request with a definite callback
		857	and the ability to cancel the whole request with its subrequests.
		858
		859	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		860	for more info.
		861
		862	Example:
		863
		864	my $grp = aio_group sub {
		865	print "all stats done\n";
		866	};
		867
		868	add $grp
		869	(aio_stat ...),
		870	(aio_stat ...),
		871	...;
		872
		873	=item aio_nop $callback->()
		874
		875	This is a special request - it does nothing in itself and is only used for
		876	side effects, such as when you want to add a dummy request to a group so
		877	that finishing the requests in the group depends on executing the given
		878	code.
		879
		880	While this request does nothing, it still goes through the execution
		881	phase and still requires a worker thread. Thus, the callback will not
		882	be executed immediately but only after other requests in the queue have
		883	entered their execution phase. This can be used to measure request
		884	latency.
		885
		886	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		887
		888	Mainly used for debugging and benchmarking, this aio request puts one of
		889	the request workers to sleep for the given time.
		890
		891	While it is theoretically handy to have simple I/O scheduling requests
		892	like sleep and file handle readable/writable, the overhead this creates is
		893	immense (it blocks a thread for a long time) so do not use this function
		894	except to put your application under artificial I/O pressure.
		895
481	=back	896	=back
482		897
		898	=head2 IO::AIO::REQ CLASS
		899
		900	All non-aggregate C<aio_*> functions return an object of this class when
		901	called in non-void context.
		902
		903	=over 4
		904
		905	=item cancel $req
		906
		907	Cancels the request, if possible. Has the effect of skipping execution
		908	when entering the B<execute> state and skipping calling the callback when
		909	entering the the B<result> state, but will leave the request otherwise
		910	untouched. That means that requests that currently execute will not be
		911	stopped and resources held by the request will not be freed prematurely.
		912
		913	=item cb $req $callback->(...)
		914
		915	Replace (or simply set) the callback registered to the request.
		916
		917	=back
		918
		919	=head2 IO::AIO::GRP CLASS
		920
		921	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		922	objects of this class, too.
		923
		924	A IO::AIO::GRP object is a special request that can contain multiple other
		925	aio requests.
		926
		927	You create one by calling the C<aio_group> constructing function with a
		928	callback that will be called when all contained requests have entered the
		929	C<done> state:
		930
		931	my $grp = aio_group sub {
		932	print "all requests are done\n";
		933	};
		934
		935	You add requests by calling the C<add> method with one or more
		936	C<IO::AIO::REQ> objects:
		937
		938	$grp->add (aio_unlink "...");
		939
		940	add $grp aio_stat "...", sub {
		941	$_[0] or return $grp->result ("error");
		942
		943	# add another request dynamically, if first succeeded
		944	add $grp aio_open "...", sub {
		945	$grp->result ("ok");
		946	};
		947	};
		948
		949	This makes it very easy to create composite requests (see the source of
		950	C<aio_move> for an application) that work and feel like simple requests.
		951
		952	=over 4
		953
		954	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		955	C<IO::AIO::poll_cb>, just like any other request.
		956
		957	=item * They can be canceled like any other request. Canceling will cancel not
		958	only the request itself, but also all requests it contains.
		959
		960	=item * They can also can also be added to other IO::AIO::GRP objects.
		961
		962	=item * You must not add requests to a group from within the group callback (or
		963	any later time).
		964
		965	=back
		966
		967	Their lifetime, simplified, looks like this: when they are empty, they
		968	will finish very quickly. If they contain only requests that are in the
		969	C<done> state, they will also finish. Otherwise they will continue to
		970	exist.
		971
		972	That means after creating a group you have some time to add requests. And
		973	in the callbacks of those requests, you can add further requests to the
		974	group. And only when all those requests have finished will the the group
		975	itself finish.
		976
		977	=over 4
		978
		979	=item add $grp ...
		980
		981	=item $grp->add (...)
		982
		983	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		984	be added, including other groups, as long as you do not create circular
		985	dependencies.
		986
		987	Returns all its arguments.
		988
		989	=item $grp->cancel_subs
		990
		991	Cancel all subrequests and clears any feeder, but not the group request
		992	itself. Useful when you queued a lot of events but got a result early.
		993
		994	=item $grp->result (...)
		995
		996	Set the result value(s) that will be passed to the group callback when all
		997	subrequests have finished and set thre groups errno to the current value
		998	of errno (just like calling C<errno> without an error number). By default,
		999	no argument will be passed and errno is zero.
		1000
		1001	=item $grp->errno ([$errno])
		1002
		1003	Sets the group errno value to C<$errno>, or the current value of errno
		1004	when the argument is missing.
		1005
		1006	Every aio request has an associated errno value that is restored when
		1007	the callback is invoked. This method lets you change this value from its
		1008	default (0).
		1009
		1010	Calling C<result> will also set errno, so make sure you either set C<$!>
		1011	before the call to C<result>, or call c<errno> after it.
		1012
		1013	=item feed $grp $callback->($grp)
		1014
		1015	Sets a feeder/generator on this group: every group can have an attached
		1016	generator that generates requests if idle. The idea behind this is that,
		1017	although you could just queue as many requests as you want in a group,
		1018	this might starve other requests for a potentially long time. For
		1019	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1020	requests, delaying any later requests for a long time.
		1021
		1022	To avoid this, and allow incremental generation of requests, you can
		1023	instead a group and set a feeder on it that generates those requests. The
		1024	feed callback will be called whenever there are few enough (see C<limit>,
		1025	below) requests active in the group itself and is expected to queue more
		1026	requests.
		1027
		1028	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1029	not impose any limits).
		1030
		1031	If the feed does not queue more requests when called, it will be
		1032	automatically removed from the group.
		1033
		1034	If the feed limit is C<0>, it will be set to C<2> automatically.
		1035
		1036	Example:
		1037
		1038	# stat all files in @files, but only ever use four aio requests concurrently:
		1039
		1040	my $grp = aio_group sub { print "finished\n" };
		1041	limit $grp 4;
		1042	feed $grp sub {
		1043	my $file = pop @files
		1044	or return;
		1045
		1046	add $grp aio_stat $file, sub { ... };
		1047	};
		1048
		1049	=item limit $grp $num
		1050
		1051	Sets the feeder limit for the group: The feeder will be called whenever
		1052	the group contains less than this many requests.
		1053
		1054	Setting the limit to C<0> will pause the feeding process.
		1055
		1056	=back
		1057
483	=head2 SUPPORT FUNCTIONS	1058	=head2 SUPPORT FUNCTIONS
		1059
		1060	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
484		1061
485	=over 4	1062	=over 4
486		1063
487	=item $fileno = IO::AIO::poll_fileno	1064	=item $fileno = IO::AIO::poll_fileno
488		1065
…		…
493		1070
494	See C<poll_cb> for an example.	1071	See C<poll_cb> for an example.
495		1072
496	=item IO::AIO::poll_cb	1073	=item IO::AIO::poll_cb
497		1074
498	Process all outstanding events on the result pipe. You have to call this	1075	Process some outstanding events on the result pipe. You have to call this
499	regularly. Returns the number of events processed. Returns immediately	1076	regularly. Returns the number of events processed. Returns immediately
500	when no events are outstanding.	1077	when no events are outstanding. The amount of events processed depends on
		1078	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1079
		1080	If not all requests were processed for whatever reason, the filehandle
		1081	will still be ready when C<poll_cb> returns.
501		1082
502	Example: Install an Event watcher that automatically calls	1083	Example: Install an Event watcher that automatically calls
503	IO::AIO::poll_cb with high priority:	1084	IO::AIO::poll_cb with high priority:
504		1085
505	Event->io (fd => IO::AIO::poll_fileno,	1086	Event->io (fd => IO::AIO::poll_fileno,
506	poll => 'r', async => 1,	1087	poll => 'r', async => 1,
507	cb => \&IO::AIO::poll_cb);	1088	cb => \&IO::AIO::poll_cb);
508		1089
		1090	=item IO::AIO::max_poll_reqs $nreqs
		1091
		1092	=item IO::AIO::max_poll_time $seconds
		1093
		1094	These set the maximum number of requests (default C<0>, meaning infinity)
		1095	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1096	the maximum amount of time (default C<0>, meaning infinity) spent in
		1097	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1098	of time C<poll_cb> is allowed to use).
		1099
		1100	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1101	syscall per request processed, which is not normally a problem unless your
		1102	callbacks are really really fast or your OS is really really slow (I am
		1103	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1104
		1105	Setting these is useful if you want to ensure some level of
		1106	interactiveness when perl is not fast enough to process all requests in
		1107	time.
		1108
		1109	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1110
		1111	Example: Install an Event watcher that automatically calls
		1112	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1113	program get the CPU sometimes even under high AIO load.
		1114
		1115	# try not to spend much more than 0.1s in poll_cb
		1116	IO::AIO::max_poll_time 0.1;
		1117
		1118	# use a low priority so other tasks have priority
		1119	Event->io (fd => IO::AIO::poll_fileno,
		1120	poll => 'r', nice => 1,
		1121	cb => &IO::AIO::poll_cb);
		1122
509	=item IO::AIO::poll_wait	1123	=item IO::AIO::poll_wait
510		1124
		1125	If there are any outstanding requests and none of them in the result
511	Wait till the result filehandle becomes ready for reading (simply does a	1126	phase, wait till the result filehandle becomes ready for reading (simply
512	C<select> on the filehandle. This is useful if you want to synchronously wait	1127	does a C<select> on the filehandle. This is useful if you want to
513	for some requests to finish).	1128	synchronously wait for some requests to finish).
514		1129
515	See C<nreqs> for an example.	1130	See C<nreqs> for an example.
516		1131
		1132	=item IO::AIO::poll
		1133
		1134	Waits until some requests have been handled.
		1135
		1136	Returns the number of requests processed, but is otherwise strictly
		1137	equivalent to:
		1138
		1139	IO::AIO::poll_wait, IO::AIO::poll_cb
		1140
517	=item IO::AIO::nreqs	1141	=item IO::AIO::flush
518		1142
519	Returns the number of requests currently outstanding (i.e. for which their	1143	Wait till all outstanding AIO requests have been handled.
520	callback has not been invoked yet).
521		1144
522	Example: wait till there are no outstanding requests anymore:	1145	Strictly equivalent to:
523		1146
524	IO::AIO::poll_wait, IO::AIO::poll_cb	1147	IO::AIO::poll_wait, IO::AIO::poll_cb
525	while IO::AIO::nreqs;	1148	while IO::AIO::nreqs;
526		1149
527	=item IO::AIO::flush	1150	=back
528		1151
529	Wait till all outstanding AIO requests have been handled.	1152	=head3 CONTROLLING THE NUMBER OF THREADS
530		1153
531	Strictly equivalent to:	1154	=over
532
533	IO::AIO::poll_wait, IO::AIO::poll_cb
534	while IO::AIO::nreqs;
535
536	=item IO::AIO::poll
537
538	Waits until some requests have been handled.
539
540	Strictly equivalent to:
541
542	IO::AIO::poll_wait, IO::AIO::poll_cb
543	if IO::AIO::nreqs;
544		1155
545	=item IO::AIO::min_parallel $nthreads	1156	=item IO::AIO::min_parallel $nthreads
546		1157
547	Set the minimum number of AIO threads to C<$nthreads>. The current default	1158	Set the minimum number of AIO threads to C<$nthreads>. The current
548	is C<4>, which means four asynchronous operations can be done at one time	1159	default is C<8>, which means eight asynchronous operations can execute
549	(the number of outstanding operations, however, is unlimited).	1160	concurrently at any one time (the number of outstanding requests,
		1161	however, is unlimited).
550		1162
551	IO::AIO starts threads only on demand, when an AIO request is queued and	1163	IO::AIO starts threads only on demand, when an AIO request is queued and
552	no free thread exists.	1164	no free thread exists. Please note that queueing up a hundred requests can
		1165	create demand for a hundred threads, even if it turns out that everything
		1166	is in the cache and could have been processed faster by a single thread.
553		1167
554	It is recommended to keep the number of threads low, as some Linux	1168	It is recommended to keep the number of threads relatively low, as some
555	kernel versions will scale negatively with the number of threads (higher	1169	Linux kernel versions will scale negatively with the number of threads
556	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1170	(higher parallelity => MUCH higher latency). With current Linux 2.6
557	threads should be fine.	1171	versions, 4-32 threads should be fine.
558		1172
559	Under most circumstances you don't need to call this function, as the	1173	Under most circumstances you don't need to call this function, as the
560	module selects a default that is suitable for low to moderate load.	1174	module selects a default that is suitable for low to moderate load.
561		1175
562	=item IO::AIO::max_parallel $nthreads	1176	=item IO::AIO::max_parallel $nthreads
…		…
571	This module automatically runs C<max_parallel 0> at program end, to ensure	1185	This module automatically runs C<max_parallel 0> at program end, to ensure
572	that all threads are killed and that there are no outstanding requests.	1186	that all threads are killed and that there are no outstanding requests.
573		1187
574	Under normal circumstances you don't need to call this function.	1188	Under normal circumstances you don't need to call this function.
575		1189
		1190	=item IO::AIO::max_idle $nthreads
		1191
		1192	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1193	threads that did not get a request to process within 10 seconds). That
		1194	means if a thread becomes idle while C<$nthreads> other threads are also
		1195	idle, it will free its resources and exit.
		1196
		1197	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1198	to allow for extremely high load situations, but want to free resources
		1199	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1200
		1201	The default is probably ok in most situations, especially if thread
		1202	creation is fast. If thread creation is very slow on your system you might
		1203	want to use larger values.
		1204
576	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1205	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1206
		1207	This is a very bad function to use in interactive programs because it
		1208	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1209	use an C<aio_group> together with a feed callback.
577		1210
578	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1211	Sets the maximum number of outstanding requests to C<$nreqs>. If you
579	try to queue up more than this number of requests, the caller will block until	1212	do queue up more than this number of requests, the next call to the
580	some requests have been handled.	1213	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1214	function will block until the limit is no longer exceeded.
581		1215
582	The default is very large, so normally there is no practical limit. If you	1216	The default value is very large, so there is no practical limit on the
583	queue up many requests in a loop it often improves speed if you set	1217	number of outstanding requests.
584	this to a relatively low number, such as C<100>.
585		1218
586	Under normal circumstances you don't need to call this function.	1219	You can still queue as many requests as you want. Therefore,
		1220	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1221	as a stop gap to shield against fatal memory overflow (with large values).
		1222
		1223	=back
		1224
		1225	=head3 STATISTICAL INFORMATION
		1226
		1227	=over
		1228
		1229	=item IO::AIO::nreqs
		1230
		1231	Returns the number of requests currently in the ready, execute or pending
		1232	states (i.e. for which their callback has not been invoked yet).
		1233
		1234	Example: wait till there are no outstanding requests anymore:
		1235
		1236	IO::AIO::poll_wait, IO::AIO::poll_cb
		1237	while IO::AIO::nreqs;
		1238
		1239	=item IO::AIO::nready
		1240
		1241	Returns the number of requests currently in the ready state (not yet
		1242	executed).
		1243
		1244	=item IO::AIO::npending
		1245
		1246	Returns the number of requests currently in the pending state (executed,
		1247	but not yet processed by poll_cb).
587		1248
588	=back	1249	=back
589		1250
590	=cut	1251	=cut
591		1252
…		…
603	or return undef;	1264	or return undef;
604		1265
605	*$sym	1266	*$sym
606	}	1267	}
607		1268
608	min_parallel 4;	1269	min_parallel 8;
609		1270
610	END {	1271	END { flush }
611	max_parallel 0;
612	}
613		1272
614	1;	1273	1;
615		1274
616	=head2 FORK BEHAVIOUR	1275	=head2 FORK BEHAVIOUR
		1276
		1277	This module should do "the right thing" when the process using it forks:
617		1278
618	Before the fork, IO::AIO enters a quiescent state where no requests	1279	Before the fork, IO::AIO enters a quiescent state where no requests
619	can be added in other threads and no results will be processed. After	1280	can be added in other threads and no results will be processed. After
620	the fork the parent simply leaves the quiescent state and continues	1281	the fork the parent simply leaves the quiescent state and continues
621	request/result processing, while the child clears the request/result	1282	request/result processing, while the child frees the request/result queue
622	queue (so the requests started before the fork will only be handled in	1283	(so that the requests started before the fork will only be handled in the
623	the parent). Threats will be started on demand until the limit ste in the	1284	parent). Threads will be started on demand until the limit set in the
624	parent process has been reached again.	1285	parent process has been reached again.
625		1286
		1287	In short: the parent will, after a short pause, continue as if fork had
		1288	not been called, while the child will act as if IO::AIO has not been used
		1289	yet.
		1290
		1291	=head2 MEMORY USAGE
		1292
		1293	Per-request usage:
		1294
		1295	Each aio request uses - depending on your architecture - around 100-200
		1296	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1297	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1298	scalars and other data passed into aio requests will also be locked and
		1299	will consume memory till the request has entered the done state.
		1300
		1301	This is not awfully much, so queuing lots of requests is not usually a
		1302	problem.
		1303
		1304	Per-thread usage:
		1305
		1306	In the execution phase, some aio requests require more memory for
		1307	temporary buffers, and each thread requires a stack and other data
		1308	structures (usually around 16k-128k, depending on the OS).
		1309
		1310	=head1 KNOWN BUGS
		1311
		1312	Known bugs will be fixed in the next release.
		1313
626	=head1 SEE ALSO	1314	=head1 SEE ALSO
627		1315
628	L<Coro>, L<Linux::AIO>.	1316	L<Coro::AIO>.
629		1317
630	=head1 AUTHOR	1318	=head1 AUTHOR
631		1319
632	Marc Lehmann <schmorp@schmorp.de>	1320	Marc Lehmann <schmorp@schmorp.de>
633	http://home.schmorp.de/	1321	http://home.schmorp.de/

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