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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.58 by root, Sun Oct 22 10:33:19 2006 UTC vs.
Revision 1.133 by root, Sat Sep 6 07:14:52 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
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
29	# AnyEvent integration	34	# EV integration
30	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
31	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32		36
33	# Event integration	37	# Event integration
34	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
35	poll => 'r',	39	poll => 'r',
36	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
…		…
50	=head1 DESCRIPTION	54	=head1 DESCRIPTION
51		55
52	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
53	operating system supports.	57	operating system supports.
54		58
		59	Asynchronous means that operations that can normally block your program
		60	(e.g. reading from disk) will be done asynchronously: the operation
		61	will still block, but you can do something else in the meantime. This
		62	is extremely useful for programs that need to stay interactive even
		63	when doing heavy I/O (GUI programs, high performance network servers
		64	etc.), but can also be used to easily do operations in parallel that are
		65	normally done sequentially, e.g. stat'ing many files, which is much faster
		66	on a RAID volume or over NFS when you do a number of stat operations
		67	concurrently.
		68
		69	While most of this works on all types of file descriptors (for
		70	example sockets), using these functions on file descriptors that
		71	support nonblocking operation (again, sockets, pipes etc.) is very
		72	inefficient. Use an event loop for that (such as the L<Event|Event>
		73	module): IO::AIO will naturally fit into such an event loop itself.
		74
55	Currently, a number of threads are started that execute your read/writes	75	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	76	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	77	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	78	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	79	functions available on many operating systems. However, they are often
60	not well-supported (Linux doesn't allow them on normal files currently,	80	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	81	files currently, for example), and they would only support aio_read and
62	remaining functionality would have to be implemented using threads anyway.	82	aio_write, so the remaining functionality would have to be implemented
		83	using threads anyway.
63		84
64	Although the module will work with in the presence of other threads, it is	85	Although the module will work in the presence of other (Perl-) threads,
65	currently not reentrant, so use appropriate locking yourself, always call	86	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	87	yourself, always call C<poll_cb> from within the same thread, or never
67	C<aio_> functions) recursively.	88	call C<poll_cb> (or other C<aio_> functions) recursively.
		89
		90	=head2 EXAMPLE
		91
		92	This is a simple example that uses the Event module and loads
		93	F</etc/passwd> asynchronously:
		94
		95	use Fcntl;
		96	use Event;
		97	use IO::AIO;
		98
		99	# register the IO::AIO callback with Event
		100	Event->io (fd => IO::AIO::poll_fileno,
		101	poll => 'r',
		102	cb => \&IO::AIO::poll_cb);
		103
		104	# queue the request to open /etc/passwd
		105	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		106	my $fh = shift
		107	or die "error while opening: $!";
		108
		109	# stat'ing filehandles is generally non-blocking
		110	my $size = -s $fh;
		111
		112	# queue a request to read the file
		113	my $contents;
		114	aio_read $fh, 0, $size, $contents, 0, sub {
		115	$_[0] == $size
		116	or die "short read: $!";
		117
		118	close $fh;
		119
		120	# file contents now in $contents
		121	print $contents;
		122
		123	# exit event loop and program
		124	Event::unloop;
		125	};
		126	};
		127
		128	# possibly queue up other requests, or open GUI windows,
		129	# check for sockets etc. etc.
		130
		131	# process events as long as there are some:
		132	Event::loop;
		133
		134	=head1 REQUEST ANATOMY AND LIFETIME
		135
		136	Every C<aio_*> function creates a request. which is a C data structure not
		137	directly visible to Perl.
		138
		139	If called in non-void context, every request function returns a Perl
		140	object representing the request. In void context, nothing is returned,
		141	which saves a bit of memory.
		142
		143	The perl object is a fairly standard ref-to-hash object. The hash contents
		144	are not used by IO::AIO so you are free to store anything you like in it.
		145
		146	During their existance, aio requests travel through the following states,
		147	in order:
		148
		149	=over 4
		150
		151	=item ready
		152
		153	Immediately after a request is created it is put into the ready state,
		154	waiting for a thread to execute it.
		155
		156	=item execute
		157
		158	A thread has accepted the request for processing and is currently
		159	executing it (e.g. blocking in read).
		160
		161	=item pending
		162
		163	The request has been executed and is waiting for result processing.
		164
		165	While request submission and execution is fully asynchronous, result
		166	processing is not and relies on the perl interpreter calling C<poll_cb>
		167	(or another function with the same effect).
		168
		169	=item result
		170
		171	The request results are processed synchronously by C<poll_cb>.
		172
		173	The C<poll_cb> function will process all outstanding aio requests by
		174	calling their callbacks, freeing memory associated with them and managing
		175	any groups they are contained in.
		176
		177	=item done
		178
		179	Request has reached the end of its lifetime and holds no resources anymore
		180	(except possibly for the Perl object, but its connection to the actual
		181	aio request is severed and calling its methods will either do nothing or
		182	result in a runtime error).
		183
		184	=back
68		185
69	=cut	186	=cut
70		187
71	package IO::AIO;	188	package IO::AIO;
		189
		190	use Carp ();
72		191
73	no warnings;	192	no warnings;
74	use strict 'vars';	193	use strict 'vars';
75		194
76	use base 'Exporter';	195	use base 'Exporter';
77		196
78	BEGIN {	197	BEGIN {
79	our $VERSION = '2.0';	198	our $VERSION = '3.07';
80		199
81	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	200	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	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
83	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
84	aio_group);	203	aio_fdatasync aio_pathsync aio_readahead
85	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	204	aio_rename aio_link aio_move aio_copy aio_group
		205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		206	aio_chmod aio_utime aio_truncate);
		207
		208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		210	min_parallel max_parallel max_idle
		211	nreqs nready npending nthreads
		212	max_poll_time max_poll_reqs);
86		213
87	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
88		215
89	require XSLoader;	216	require XSLoader;
90	XSLoader::load ("IO::AIO", $VERSION);	217	XSLoader::load ("IO::AIO", $VERSION);
91	}	218	}
92		219
93	=head1 FUNCTIONS	220	=head1 FUNCTIONS
94		221
95	=head2 AIO FUNCTIONS	222	=head2 AIO REQUEST FUNCTIONS
96		223
97	All the C<aio_*> calls are more or less thin wrappers around the syscall	224	All the C<aio_*> calls are more or less thin wrappers around the syscall
98	with the same name (sans C<aio_>). The arguments are similar or identical,	225	with the same name (sans C<aio_>). The arguments are similar or identical,
99	and they all accept an additional (and optional) C<$callback> argument	226	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	227	which must be a code reference. This code reference will get called with
…		…
103	syscall has been executed asynchronously.	230	syscall has been executed asynchronously.
104		231
105	All functions expecting a filehandle keep a copy of the filehandle	232	All functions expecting a filehandle keep a copy of the filehandle
106	internally until the request has finished.	233	internally until the request has finished.
107		234
108	All requests return objects of type L<IO::AIO::REQ> that allow further	235	All functions return request objects of type L<IO::AIO::REQ> that allow
109	manipulation of those requests while they are in-flight.	236	further manipulation of those requests while they are in-flight.
110		237
111	The pathnames you pass to these routines I<must> be absolute and	238	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	239	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	240	request is being executed, the current working directory could have
114	changed. Alternatively, you can make sure that you never change the	241	changed. Alternatively, you can make sure that you never change the
115	current working directory.	242	current working directory anywhere in the program and then use relative
		243	paths.
116		244
117	To encode pathnames to byte form, either make sure you either: a)	245	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	246	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	247	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	248	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)	249	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
122	use something else.	250	use something else to ensure your scalar has the correct contents.
		251
		252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		253	handles correctly wether it is set or not.
123		254
124	=over 4	255	=over 4
		256
		257	=item $prev_pri = aioreq_pri [$pri]
		258
		259	Returns the priority value that would be used for the next request and, if
		260	C<$pri> is given, sets the priority for the next aio request.
		261
		262	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		263	and C<4>, respectively. Requests with higher priority will be serviced
		264	first.
		265
		266	The priority will be reset to C<0> after each call to one of the C<aio_*>
		267	functions.
		268
		269	Example: open a file with low priority, then read something from it with
		270	higher priority so the read request is serviced before other low priority
		271	open requests (potentially spamming the cache):
		272
		273	aioreq_pri -3;
		274	aio_open ..., sub {
		275	return unless $_[0];
		276
		277	aioreq_pri -2;
		278	aio_read $_[0], ..., sub {
		279	...
		280	};
		281	};
		282
		283
		284	=item aioreq_nice $pri_adjust
		285
		286	Similar to C<aioreq_pri>, but subtracts the given value from the current
		287	priority, so the effect is cumulative.
		288
125		289
126	=item aio_open $pathname, $flags, $mode, $callback->($fh)	290	=item aio_open $pathname, $flags, $mode, $callback->($fh)
127		291
128	Asynchronously open or create a file and call the callback with a newly	292	Asynchronously open or create a file and call the callback with a newly
129	created filehandle for the file.	293	created filehandle for the file.
…		…
135	list. They are the same as used by C<sysopen>.	299	list. They are the same as used by C<sysopen>.
136		300
137	Likewise, C<$mode> specifies the mode of the newly created file, if it	301	Likewise, C<$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>,	302	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,	303	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).	304	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		305	by the umask in effect then the request is being executed, so better never
		306	change the umask.
141		307
142	Example:	308	Example:
143		309
144	aio_open "/etc/passwd", O_RDONLY, 0, sub {	310	aio_open "/etc/passwd", O_RDONLY, 0, sub {
145	if ($_[0]) {	311	if ($_[0]) {
…		…
148	} else {	314	} else {
149	die "open failed: $!\n";	315	die "open failed: $!\n";
150	}	316	}
151	};	317	};
152		318
		319
153	=item aio_close $fh, $callback->($status)	320	=item aio_close $fh, $callback->($status)
154		321
155	Asynchronously close a file and call the callback with the result	322	Asynchronously close a file and call the callback with the result
156	code. I<WARNING:> although accepted, you should not pass in a perl	323	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		324
161	This is supposed to be a bug in the API, so that might change. It's	325	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
162	therefore best to avoid this function.	326	closing the file descriptor associated with the filehandle itself.
		327
		328	Therefore, C<aio_close> will not close the filehandle - instead it will
		329	use dup2 to overwrite the file descriptor with the write-end of a pipe
		330	(the pipe fd will be created on demand and will be cached).
		331
		332	Or in other words: the file descriptor will be closed, but it will not be
		333	free for reuse until the perl filehandle is closed.
		334
		335	=cut
163		336
164	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		338
166	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
167		340
168	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	341	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
169	into the scalar given by C<data> and offset C<dataoffset> and calls the	342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
170	callback without the actual number of bytes read (or -1 on error, just	343	callback without the actual number of bytes read (or -1 on error, just
171	like the syscall).	344	like the syscall).
172		345
		346	If C<$offset> is undefined, then the current file descriptor offset will
		347	be used (and updated), otherwise the file descriptor offset will not be
		348	changed by these calls.
		349
		350	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		351
		352	If C<$dataoffset> is less than zero, it will be counted from the end of
		353	C<$data>.
		354
173	The C<$data> scalar I<MUST NOT> be modified in any way while the request	355	The C<$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	356	is outstanding. Modifying it can result in segfaults or World War III (if
175	necessary/optional hardware is installed).	357	the necessary/optional hardware is installed).
176		358
177	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	359	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
178	offset C<0> within the scalar:	360	offset C<0> within the scalar:
179		361
180	aio_read $fh, 7, 15, $buffer, 0, sub {	362	aio_read $fh, 7, 15, $buffer, 0, sub {
181	$_[0] > 0 or die "read error: $!";	363	$_[0] > 0 or die "read error: $!";
182	print "read $_[0] bytes: <$buffer>\n";	364	print "read $_[0] bytes: <$buffer>\n";
183	};	365	};
184		366
185	=item aio_move $srcpath, $dstpath, $callback->($status)
186
187	[EXPERIMENTAL due to internal aio_group use]
188
189	Try to move the I<file> (directories not supported as either source or
190	destination) from C<$srcpath> to C<$dstpath> and call the callback with
191	the C<0> (error) or C<-1> ok.
192
193	This is a composite request that tries to rename(2) the file first. If
194	rename files with C<EXDEV>, it creates the destination file with mode 0200
195	and copies the contents of the source file into it using C<aio_sendfile>,
196	followed by restoring atime, mtime, access mode and uid/gid, in that
197	order, and unlinking the C<$srcpath>.
198
199	If an error occurs, the partial destination file will be unlinked, if
200	possible, except when setting atime, mtime, access mode and uid/gid, where
201	errors are being ignored.
202
203	=cut
204
205	sub aio_move($$$) {
206	my ($src, $dst, $cb) = @_;
207
208	my $grp = aio_group $cb;
209
210	add $grp aio_rename $src, $dst, sub {
211	if ($_[0] && $! == EXDEV) {
212	add $grp aio_open $src, O_RDONLY, 0, sub {
213	if (my $src_fh = $_[0]) {
214	my @stat = stat $src_fh;
215
216	add $grp aio_open $dst, O_WRONLY, 0200, sub {
217	if (my $dst_fh = $_[0]) {
218	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
219	close $src_fh;
220
221	if ($_[0] == $stat[7]) {
222	utime $stat[8], $stat[9], $dst;
223	chmod $stat[2] & 07777, $dst_fh;
224	chown $stat[4], $stat[5], $dst_fh;
225	close $dst_fh;
226
227	add $grp aio_unlink $src, sub {
228	$grp->result ($_[0]);
229	};
230	} else {
231	my $errno = $!;
232	add $grp aio_unlink $dst, sub {
233	$! = $errno;
234	$grp->result (-1);
235	};
236	}
237	};
238	} else {
239	$grp->result (-1);
240	}
241	},
242
243	} else {
244	$grp->result (-1);
245	}
246	};
247	} else {
248	$grp->result ($_[0]);
249	}
250	};
251
252	$grp
253	}
254		367
255	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	368	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
256		369
257	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	370	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
258	reading at byte offset C<$in_offset>, and starts writing at the current	371	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
272	C<$in_fh> than are written, and there is no way to find out how many	385	C<$in_fh> than are written, and there is no way to find out how many
273	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	386	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
274	provides the number of bytes written to C<$out_fh>. Only if the result	387	provides the number of bytes written to C<$out_fh>. Only if the result
275	value equals C<$length> one can assume that C<$length> bytes have been	388	value equals C<$length> one can assume that C<$length> bytes have been
276	read.	389	read.
		390
277		391
278	=item aio_readahead $fh,$offset,$length, $callback->($retval)	392	=item aio_readahead $fh,$offset,$length, $callback->($retval)
279		393
280	C<aio_readahead> populates the page cache with data from a file so that	394	C<aio_readahead> populates the page cache with data from a file so that
281	subsequent reads from that file will not block on disk I/O. The C<$offset>	395	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
287	file. The current file offset of the file is left unchanged.	401	file. The current file offset of the file is left unchanged.
288		402
289	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	403	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
290	emulated by simply reading the data, which would have a similar effect.	404	emulated by simply reading the data, which would have a similar effect.
291		405
		406
292	=item aio_stat $fh_or_path, $callback->($status)	407	=item aio_stat $fh_or_path, $callback->($status)
293		408
294	=item aio_lstat $fh, $callback->($status)	409	=item aio_lstat $fh, $callback->($status)
295		410
296	Works like perl's C<stat> or C<lstat> in void context. The callback will	411	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
309	aio_stat "/etc/passwd", sub {	424	aio_stat "/etc/passwd", sub {
310	$_[0] and die "stat failed: $!";	425	$_[0] and die "stat failed: $!";
311	print "size is ", -s _, "\n";	426	print "size is ", -s _, "\n";
312	};	427	};
313		428
		429
		430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		431
		432	Works like perl's C<utime> function (including the special case of $atime
		433	and $mtime being undef). Fractional times are supported if the underlying
		434	syscalls support them.
		435
		436	When called with a pathname, uses utimes(2) if available, otherwise
		437	utime(2). If called on a file descriptor, uses futimes(2) if available,
		438	otherwise returns ENOSYS, so this is not portable.
		439
		440	Examples:
		441
		442	# set atime and mtime to current time (basically touch(1)):
		443	aio_utime "path", undef, undef;
		444	# set atime to current time and mtime to beginning of the epoch:
		445	aio_utime "path", time, undef; # undef==0
		446
		447
		448	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		449
		450	Works like perl's C<chown> function, except that C<undef> for either $uid
		451	or $gid is being interpreted as "do not change" (but -1 can also be used).
		452
		453	Examples:
		454
		455	# same as "chown root path" in the shell:
		456	aio_chown "path", 0, -1;
		457	# same as above:
		458	aio_chown "path", 0, undef;
		459
		460
		461	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		462
		463	Works like truncate(2) or ftruncate(2).
		464
		465
		466	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		467
		468	Works like perl's C<chmod> function.
		469
		470
314	=item aio_unlink $pathname, $callback->($status)	471	=item aio_unlink $pathname, $callback->($status)
315		472
316	Asynchronously unlink (delete) a file and call the callback with the	473	Asynchronously unlink (delete) a file and call the callback with the
317	result code.	474	result code.
318		475
		476
		477	=item aio_mknod $path, $mode, $dev, $callback->($status)
		478
		479	[EXPERIMENTAL]
		480
		481	Asynchronously create a device node (or fifo). See mknod(2).
		482
		483	The only (POSIX-) portable way of calling this function is:
		484
		485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		486
		487
319	=item aio_link $srcpath, $dstpath, $callback->($status)	488	=item aio_link $srcpath, $dstpath, $callback->($status)
320		489
321	Asynchronously create a new link to the existing object at C<$srcpath> at	490	Asynchronously create a new link to the existing object at C<$srcpath> at
322	the path C<$dstpath> and call the callback with the result code.	491	the path C<$dstpath> and call the callback with the result code.
323		492
		493
324	=item aio_symlink $srcpath, $dstpath, $callback->($status)	494	=item aio_symlink $srcpath, $dstpath, $callback->($status)
325		495
326	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
327	the path C<$dstpath> and call the callback with the result code.	497	the path C<$dstpath> and call the callback with the result code.
328		498
		499
		500	=item aio_readlink $path, $callback->($link)
		501
		502	Asynchronously read the symlink specified by C<$path> and pass it to
		503	the callback. If an error occurs, nothing or undef gets passed to the
		504	callback.
		505
		506
329	=item aio_rename $srcpath, $dstpath, $callback->($status)	507	=item aio_rename $srcpath, $dstpath, $callback->($status)
330		508
331	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
332	rename(2) and call the callback with the result code.	510	rename(2) and call the callback with the result code.
333		511
		512
		513	=item aio_mkdir $pathname, $mode, $callback->($status)
		514
		515	Asynchronously mkdir (create) a directory and call the callback with
		516	the result code. C<$mode> will be modified by the umask at the time the
		517	request is executed, so do not change your umask.
		518
		519
334	=item aio_rmdir $pathname, $callback->($status)	520	=item aio_rmdir $pathname, $callback->($status)
335		521
336	Asynchronously rmdir (delete) a directory and call the callback with the	522	Asynchronously rmdir (delete) a directory and call the callback with the
337	result code.	523	result code.
		524
338		525
339	=item aio_readdir $pathname, $callback->($entries)	526	=item aio_readdir $pathname, $callback->($entries)
340		527
341	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
342	directory (i.e. opendir + readdir + closedir). The entries will not be	529	directory (i.e. opendir + readdir + closedir). The entries will not be
343	sorted, and will B<NOT> include the C<.> and C<..> entries.	530	sorted, and will B<NOT> include the C<.> and C<..> entries.
344		531
345	The callback a single argument which is either C<undef> or an array-ref	532	The callback a single argument which is either C<undef> or an array-ref
346	with the filenames.	533	with the filenames.
347		534
		535
		536	=item aio_load $path, $data, $callback->($status)
		537
		538	This is a composite request that tries to fully load the given file into
		539	memory. Status is the same as with aio_read.
		540
		541	=cut
		542
		543	sub aio_load($$;$) {
		544	my ($path, undef, $cb) = @_;
		545	my $data = \$_[1];
		546
		547	my $pri = aioreq_pri;
		548	my $grp = aio_group $cb;
		549
		550	aioreq_pri $pri;
		551	add $grp aio_open $path, O_RDONLY, 0, sub {
		552	my $fh = shift
		553	or return $grp->result (-1);
		554
		555	aioreq_pri $pri;
		556	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		557	$grp->result ($_[0]);
		558	};
		559	};
		560
		561	$grp
		562	}
		563
		564	=item aio_copy $srcpath, $dstpath, $callback->($status)
		565
		566	Try to copy the I<file> (directories not supported as either source or
		567	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		568	the C<0> (error) or C<-1> ok.
		569
		570	This is a composite request that it creates the destination file with
		571	mode 0200 and copies the contents of the source file into it using
		572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		573	uid/gid, in that order.
		574
		575	If an error occurs, the partial destination file will be unlinked, if
		576	possible, except when setting atime, mtime, access mode and uid/gid, where
		577	errors are being ignored.
		578
		579	=cut
		580
		581	sub aio_copy($$;$) {
		582	my ($src, $dst, $cb) = @_;
		583
		584	my $pri = aioreq_pri;
		585	my $grp = aio_group $cb;
		586
		587	aioreq_pri $pri;
		588	add $grp aio_open $src, O_RDONLY, 0, sub {
		589	if (my $src_fh = $_[0]) {
		590	my @stat = stat $src_fh;
		591
		592	aioreq_pri $pri;
		593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		594	if (my $dst_fh = $_[0]) {
		595	aioreq_pri $pri;
		596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		597	if ($_[0] == $stat[7]) {
		598	$grp->result (0);
		599	close $src_fh;
		600
		601	# those should not normally block. should. should.
		602	utime $stat[8], $stat[9], $dst;
		603	chmod $stat[2] & 07777, $dst_fh;
		604	chown $stat[4], $stat[5], $dst_fh;
		605
		606	aioreq_pri $pri;
		607	add $grp aio_close $dst_fh;
		608	} else {
		609	$grp->result (-1);
		610	close $src_fh;
		611	close $dst_fh;
		612
		613	aioreq $pri;
		614	add $grp aio_unlink $dst;
		615	}
		616	};
		617	} else {
		618	$grp->result (-1);
		619	}
		620	},
		621
		622	} else {
		623	$grp->result (-1);
		624	}
		625	};
		626
		627	$grp
		628	}
		629
		630	=item aio_move $srcpath, $dstpath, $callback->($status)
		631
		632	Try to move the I<file> (directories not supported as either source or
		633	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		634	the C<0> (error) or C<-1> ok.
		635
		636	This is a composite request that tries to rename(2) the file first. If
		637	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		638	that is successful, unlinking the C<$srcpath>.
		639
		640	=cut
		641
		642	sub aio_move($$;$) {
		643	my ($src, $dst, $cb) = @_;
		644
		645	my $pri = aioreq_pri;
		646	my $grp = aio_group $cb;
		647
		648	aioreq_pri $pri;
		649	add $grp aio_rename $src, $dst, sub {
		650	if ($_[0] && $! == EXDEV) {
		651	aioreq_pri $pri;
		652	add $grp aio_copy $src, $dst, sub {
		653	$grp->result ($_[0]);
		654
		655	if (!$_[0]) {
		656	aioreq_pri $pri;
		657	add $grp aio_unlink $src;
		658	}
		659	};
		660	} else {
		661	$grp->result ($_[0]);
		662	}
		663	};
		664
		665	$grp
		666	}
		667
348	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
349		669
350	[EXPERIMENTAL due to internal aio_group use]
351
352	Scans a directory (similar to C<aio_readdir>) but additionally tries to	670	Scans a directory (similar to C<aio_readdir>) but additionally tries to
353	separate the entries of directory C<$path> into two sets of names, ones	671	efficiently separate the entries of directory C<$path> into two sets of
354	you can recurse into (directories or links to them), and ones you cannot	672	names, directories you can recurse into (directories), and ones you cannot
355	recurse into (everything else).	673	recurse into (everything else, including symlinks to directories).
356		674
357	C<aio_scandir> is a composite request that consists of many sub	675	C<aio_scandir> is a composite request that creates of many sub requests_
358	requests. C<$maxreq> specifies the maximum number of outstanding aio	676	C<$maxreq> specifies the maximum number of outstanding aio requests that
359	requests that this function generates. If it is C<< <= 0 >>, then a	677	this function generates. If it is C<< <= 0 >>, then a suitable default
360	suitable default will be chosen (currently 8).	678	will be chosen (currently 4).
361		679
362	On error, the callback is called without arguments, otherwise it receives	680	On error, the callback is called without arguments, otherwise it receives
363	two array-refs with path-relative entry names.	681	two array-refs with path-relative entry names.
364		682
365	Example:	683	Example:
…		…
399	as those tend to return 0 or 1 as link counts, which disables the	717	as those tend to return 0 or 1 as link counts, which disables the
400	directory counting heuristic.	718	directory counting heuristic.
401		719
402	=cut	720	=cut
403		721
404	sub aio_scandir($$$) {	722	sub aio_scandir($$;$) {
405	my ($path, $maxreq, $cb) = @_;	723	my ($path, $maxreq, $cb) = @_;
406		724
		725	my $pri = aioreq_pri;
		726
407	my $grp = aio_group $cb;	727	my $grp = aio_group $cb;
408		728
409	$maxreq = 8 if $maxreq <= 0;	729	$maxreq = 4 if $maxreq <= 0;
410		730
411	# stat once	731	# stat once
		732	aioreq_pri $pri;
412	add $grp aio_stat $path, sub {	733	add $grp aio_stat $path, sub {
413	return $grp->result () if $_[0];	734	return $grp->result () if $_[0];
414	my $now = time;	735	my $now = time;
415	my $hash1 = join ":", (stat _)[0,1,3,7,9];	736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
416		737
417	# read the directory entries	738	# read the directory entries
		739	aioreq_pri $pri;
418	add $grp aio_readdir $path, sub {	740	add $grp aio_readdir $path, sub {
419	my $entries = shift	741	my $entries = shift
420	or return $grp->result ();	742	or return $grp->result ();
421		743
422	# stat the dir another time	744	# stat the dir another time
		745	aioreq_pri $pri;
423	add $grp aio_stat $path, sub {	746	add $grp aio_stat $path, sub {
424	my $hash2 = join ":", (stat _)[0,1,3,7,9];	747	my $hash2 = join ":", (stat _)[0,1,3,7,9];
425		748
426	my $ndirs;	749	my $ndirs;
427		750
…		…
442	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
443	@$entries];	766	@$entries];
444		767
445	my (@dirs, @nondirs);	768	my (@dirs, @nondirs);
446		769
447	my ($statcb, $schedcb);	770	my $statgrp = add $grp aio_group sub {
448	my $nreq = 0;	771	$grp->result (\@dirs, \@nondirs);
		772	};
449		773
450	$schedcb = sub {	774	limit $statgrp $maxreq;
451	if (@$entries) {	775	feed $statgrp sub {
452	if ($nreq < $maxreq) {	776	return unless @$entries;
453	my $ent = pop @$entries;	777	my $entry = pop @$entries;
		778
		779	aioreq_pri $pri;
		780	add $statgrp aio_stat "$path/$entry/.", sub {
		781	if ($_[0] < 0) {
		782	push @nondirs, $entry;
		783	} else {
		784	# need to check for real directory
		785	aioreq_pri $pri;
		786	add $statgrp aio_lstat "$path/$entry", sub {
		787	if (-d _) {
		788	push @dirs, $entry;
		789
		790	unless (--$ndirs) {
		791	push @nondirs, @$entries;
		792	feed $statgrp;
		793	}
		794	} else {
		795	push @nondirs, $entry;
		796	}
454	$nreq++;	797	}
455	add $grp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
456	}	798	}
457	} elsif (!$nreq) {
458	# finished
459	undef $statcb;
460	undef $schedcb;
461	$grp->result (\@dirs, \@nondirs) if $cb;
462	undef $cb;
463	}	799	};
464	};	800	};
465	$statcb = sub {
466	my ($status, $entry) = @_;
467
468	if ($status < 0) {
469	$nreq--;
470	push @nondirs, $entry;
471	&$schedcb;
472	} else {
473	# need to check for real directory
474	add $grp aio_lstat "$path/$entry", sub {
475	$nreq--;
476
477	if (-d _) {
478	push @dirs, $entry;
479
480	if (!--$ndirs) {
481	push @nondirs, @$entries;
482	$entries = [];
483	}
484	} else {
485	push @nondirs, $entry;
486	}
487
488	&$schedcb;
489	}
490	}
491	};
492
493	&$schedcb while @$entries && $nreq < $maxreq;
494	};	801	};
495	};	802	};
496	};	803	};
497		804
498	$grp	805	$grp
499	}	806	}
500		807
		808	=item aio_rmtree $path, $callback->($status)
		809
		810	Delete a directory tree starting (and including) C<$path>, return the
		811	status of the final C<rmdir> only. This is a composite request that
		812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		813	everything else.
		814
		815	=cut
		816
		817	sub aio_rmtree;
		818	sub aio_rmtree($;$) {
		819	my ($path, $cb) = @_;
		820
		821	my $pri = aioreq_pri;
		822	my $grp = aio_group $cb;
		823
		824	aioreq_pri $pri;
		825	add $grp aio_scandir $path, 0, sub {
		826	my ($dirs, $nondirs) = @_;
		827
		828	my $dirgrp = aio_group sub {
		829	add $grp aio_rmdir $path, sub {
		830	$grp->result ($_[0]);
		831	};
		832	};
		833
		834	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		835	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		836
		837	add $grp $dirgrp;
		838	};
		839
		840	$grp
		841	}
		842
		843	=item aio_sync $callback->($status)
		844
		845	Asynchronously call sync and call the callback when finished.
		846
501	=item aio_fsync $fh, $callback->($status)	847	=item aio_fsync $fh, $callback->($status)
502		848
503	Asynchronously call fsync on the given filehandle and call the callback	849	Asynchronously call fsync on the given filehandle and call the callback
504	with the fsync result code.	850	with the fsync result code.
505		851
…		…
509	callback with the fdatasync result code.	855	callback with the fdatasync result code.
510		856
511	If this call isn't available because your OS lacks it or it couldn't be	857	If this call isn't available because your OS lacks it or it couldn't be
512	detected, it will be emulated by calling C<fsync> instead.	858	detected, it will be emulated by calling C<fsync> instead.
513		859
		860	=item aio_pathsync $path, $callback->($status)
		861
		862	This request tries to open, fsync and close the given path. This is a
		863	composite request intended tosync directories after directory operations
		864	(E.g. rename). This might not work on all operating systems or have any
		865	specific effect, but usually it makes sure that directory changes get
		866	written to disc. It works for anything that can be opened for read-only,
		867	not just directories.
		868
		869	Passes C<0> when everything went ok, and C<-1> on error.
		870
		871	=cut
		872
		873	sub aio_pathsync($;$) {
		874	my ($path, $cb) = @_;
		875
		876	my $pri = aioreq_pri;
		877	my $grp = aio_group $cb;
		878
		879	aioreq_pri $pri;
		880	add $grp aio_open $path, O_RDONLY, 0, sub {
		881	my ($fh) = @_;
		882	if ($fh) {
		883	aioreq_pri $pri;
		884	add $grp aio_fsync $fh, sub {
		885	$grp->result ($_[0]);
		886
		887	aioreq_pri $pri;
		888	add $grp aio_close $fh;
		889	};
		890	} else {
		891	$grp->result (-1);
		892	}
		893	};
		894
		895	$grp
		896	}
		897
514	=item aio_group $callback->(...)	898	=item aio_group $callback->(...)
515
516	[EXPERIMENTAL]
517		899
518	This is a very special aio request: Instead of doing something, it is a	900	This is a very special aio request: Instead of doing something, it is a
519	container for other aio requests, which is useful if you want to bundle	901	container for other aio requests, which is useful if you want to bundle
520	many requests into a single, composite, request.	902	many requests into a single, composite, request with a definite callback
		903	and the ability to cancel the whole request with its subrequests.
521		904
522	Returns an object of class L<IO::AIO::GRP>. See its documentation below	905	Returns an object of class L<IO::AIO::GRP>. See its documentation below
523	for more info.	906	for more info.
524		907
525	Example:	908	Example:
…		…
531	add $grp	914	add $grp
532	(aio_stat ...),	915	(aio_stat ...),
533	(aio_stat ...),	916	(aio_stat ...),
534	...;	917	...;
535		918
		919	=item aio_nop $callback->()
		920
		921	This is a special request - it does nothing in itself and is only used for
		922	side effects, such as when you want to add a dummy request to a group so
		923	that finishing the requests in the group depends on executing the given
		924	code.
		925
		926	While this request does nothing, it still goes through the execution
		927	phase and still requires a worker thread. Thus, the callback will not
		928	be executed immediately but only after other requests in the queue have
		929	entered their execution phase. This can be used to measure request
		930	latency.
		931
536	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	932	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
537		933
538	Mainly used for debugging and benchmarking, this aio request puts one of	934	Mainly used for debugging and benchmarking, this aio request puts one of
539	the request workers to sleep for the given time.	935	the request workers to sleep for the given time.
540		936
541	While it is theoretically handy to have simple I/O scheduling requests	937	While it is theoretically handy to have simple I/O scheduling requests
542	like sleep and file handle readable/writable, the overhead this creates	938	like sleep and file handle readable/writable, the overhead this creates is
543	is immense, so do not use this function except to put your application	939	immense (it blocks a thread for a long time) so do not use this function
544	under artificial I/O pressure.	940	except to put your application under artificial I/O pressure.
545		941
546	=back	942	=back
547		943
548	=head2 IO::AIO::REQ CLASS	944	=head2 IO::AIO::REQ CLASS
549		945
550	All non-aggregate C<aio_*> functions return an object of this class when	946	All non-aggregate C<aio_*> functions return an object of this class when
551	called in non-void context.	947	called in non-void context.
552		948
553	A request always moves through the following five states in its lifetime,
554	in order: B<ready> (request has been created, but has not been executed
555	yet), B<execute> (request is currently being executed), B<pending>
556	(request has been executed but callback has not been called yet),
557	B<result> (results are being processed synchronously, includes calling the
558	callback) and B<done> (request has reached the end of its lifetime and
559	holds no resources anymore).
560
561	=over 4	949	=over 4
562		950
563	=item $req->cancel	951	=item cancel $req
564		952
565	Cancels the request, if possible. Has the effect of skipping execution	953	Cancels the request, if possible. Has the effect of skipping execution
566	when entering the B<execute> state and skipping calling the callback when	954	when entering the B<execute> state and skipping calling the callback when
567	entering the the B<result> state, but will leave the request otherwise	955	entering the the B<result> state, but will leave the request otherwise
568	untouched. That means that requests that currently execute will not be	956	untouched. That means that requests that currently execute will not be
569	stopped and resources held by the request will not be freed prematurely.	957	stopped and resources held by the request will not be freed prematurely.
570		958
		959	=item cb $req $callback->(...)
		960
		961	Replace (or simply set) the callback registered to the request.
		962
571	=back	963	=back
572		964
573	=head2 IO::AIO::GRP CLASS	965	=head2 IO::AIO::GRP CLASS
574		966
575	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to	967	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
…		…
601	};	993	};
602		994
603	This makes it very easy to create composite requests (see the source of	995	This makes it very easy to create composite requests (see the source of
604	C<aio_move> for an application) that work and feel like simple requests.	996	C<aio_move> for an application) that work and feel like simple requests.
605		997
		998	=over 4
		999
606	The IO::AIO::GRP objects will be cleaned up during calls to	1000	=item * The IO::AIO::GRP objects will be cleaned up during calls to
607	C<IO::AIO::poll_cb>, just like any other request.	1001	C<IO::AIO::poll_cb>, just like any other request.
608		1002
609	They can be canceled like any other request. Canceling will cancel not	1003	=item * They can be canceled like any other request. Canceling will cancel not
610	just the request itself, but also all requests it contains.	1004	only the request itself, but also all requests it contains.
611		1005
612	They can also can also be added to other IO::AIO::GRP objects.	1006	=item * They can also can also be added to other IO::AIO::GRP objects.
		1007
		1008	=item * You must not add requests to a group from within the group callback (or
		1009	any later time).
		1010
		1011	=back
613		1012
614	Their lifetime, simplified, looks like this: when they are empty, they	1013	Their lifetime, simplified, looks like this: when they are empty, they
615	will finish very quickly. If they contain only requests that are in the	1014	will finish very quickly. If they contain only requests that are in the
616	C<done> state, they will also finish. Otherwise they will continue to	1015	C<done> state, they will also finish. Otherwise they will continue to
617	exist.	1016	exist.
618		1017
619	That means after creating a group you have some time to add requests. And	1018	That means after creating a group you have some time to add requests
620	in the callbacks of those requests, you can add further requests to the	1019	(precisely before the callback has been invoked, which is only done within
621	group. And only when all those requests have finished will the the group	1020	the C<poll_cb>). And in the callbacks of those requests, you can add
622	itself finish.	1021	further requests to the group. And only when all those requests have
		1022	finished will the the group itself finish.
623		1023
624	=over 4	1024	=over 4
625		1025
		1026	=item add $grp ...
		1027
626	=item $grp->add (...)	1028	=item $grp->add (...)
627
628	=item add $grp ...
629		1029
630	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can	1030	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
631	be added, including other groups, as long as you do not create circular	1031	be added, including other groups, as long as you do not create circular
632	dependencies.	1032	dependencies.
633		1033
634	Returns all its arguments.	1034	Returns all its arguments.
635		1035
		1036	=item $grp->cancel_subs
		1037
		1038	Cancel all subrequests and clears any feeder, but not the group request
		1039	itself. Useful when you queued a lot of events but got a result early.
		1040
636	=item $grp->result (...)	1041	=item $grp->result (...)
637		1042
638	Set the result value(s) that will be passed to the group callback when all	1043	Set the result value(s) that will be passed to the group callback when all
639	subrequests have finished. By default, no argument will be passed.	1044	subrequests have finished and set the groups errno to the current value
		1045	of errno (just like calling C<errno> without an error number). By default,
		1046	no argument will be passed and errno is zero.
		1047
		1048	=item $grp->errno ([$errno])
		1049
		1050	Sets the group errno value to C<$errno>, or the current value of errno
		1051	when the argument is missing.
		1052
		1053	Every aio request has an associated errno value that is restored when
		1054	the callback is invoked. This method lets you change this value from its
		1055	default (0).
		1056
		1057	Calling C<result> will also set errno, so make sure you either set C<$!>
		1058	before the call to C<result>, or call c<errno> after it.
		1059
		1060	=item feed $grp $callback->($grp)
		1061
		1062	Sets a feeder/generator on this group: every group can have an attached
		1063	generator that generates requests if idle. The idea behind this is that,
		1064	although you could just queue as many requests as you want in a group,
		1065	this might starve other requests for a potentially long time. For
		1066	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1067	requests, delaying any later requests for a long time.
		1068
		1069	To avoid this, and allow incremental generation of requests, you can
		1070	instead a group and set a feeder on it that generates those requests. The
		1071	feed callback will be called whenever there are few enough (see C<limit>,
		1072	below) requests active in the group itself and is expected to queue more
		1073	requests.
		1074
		1075	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1076	not impose any limits).
		1077
		1078	If the feed does not queue more requests when called, it will be
		1079	automatically removed from the group.
		1080
		1081	If the feed limit is C<0>, it will be set to C<2> automatically.
		1082
		1083	Example:
		1084
		1085	# stat all files in @files, but only ever use four aio requests concurrently:
		1086
		1087	my $grp = aio_group sub { print "finished\n" };
		1088	limit $grp 4;
		1089	feed $grp sub {
		1090	my $file = pop @files
		1091	or return;
		1092
		1093	add $grp aio_stat $file, sub { ... };
		1094	};
		1095
		1096	=item limit $grp $num
		1097
		1098	Sets the feeder limit for the group: The feeder will be called whenever
		1099	the group contains less than this many requests.
		1100
		1101	Setting the limit to C<0> will pause the feeding process.
640		1102
641	=back	1103	=back
642		1104
643	=head2 SUPPORT FUNCTIONS	1105	=head2 SUPPORT FUNCTIONS
		1106
		1107	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
644		1108
645	=over 4	1109	=over 4
646		1110
647	=item $fileno = IO::AIO::poll_fileno	1111	=item $fileno = IO::AIO::poll_fileno
648		1112
…		…
653		1117
654	See C<poll_cb> for an example.	1118	See C<poll_cb> for an example.
655		1119
656	=item IO::AIO::poll_cb	1120	=item IO::AIO::poll_cb
657		1121
658	Process all outstanding events on the result pipe. You have to call this	1122	Process some outstanding events on the result pipe. You have to call this
659	regularly. Returns the number of events processed. Returns immediately	1123	regularly. Returns C<0> if all events could be processed, or C<-1> if it
660	when no events are outstanding.	1124	returned earlier for whatever reason. Returns immediately when no events
		1125	are outstanding. The amount of events processed depends on the settings of
		1126	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1127
		1128	If not all requests were processed for whatever reason, the filehandle
		1129	will still be ready when C<poll_cb> returns, so normally you don't have to
		1130	do anything special to have it called later.
661		1131
662	Example: Install an Event watcher that automatically calls	1132	Example: Install an Event watcher that automatically calls
663	IO::AIO::poll_cb with high priority:	1133	IO::AIO::poll_cb with high priority:
664		1134
665	Event->io (fd => IO::AIO::poll_fileno,	1135	Event->io (fd => IO::AIO::poll_fileno,
666	poll => 'r', async => 1,	1136	poll => 'r', async => 1,
667	cb => \&IO::AIO::poll_cb);	1137	cb => \&IO::AIO::poll_cb);
668		1138
		1139	=item IO::AIO::max_poll_reqs $nreqs
		1140
		1141	=item IO::AIO::max_poll_time $seconds
		1142
		1143	These set the maximum number of requests (default C<0>, meaning infinity)
		1144	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1145	the maximum amount of time (default C<0>, meaning infinity) spent in
		1146	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1147	of time C<poll_cb> is allowed to use).
		1148
		1149	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1150	syscall per request processed, which is not normally a problem unless your
		1151	callbacks are really really fast or your OS is really really slow (I am
		1152	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1153
		1154	Setting these is useful if you want to ensure some level of
		1155	interactiveness when perl is not fast enough to process all requests in
		1156	time.
		1157
		1158	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1159
		1160	Example: Install an Event watcher that automatically calls
		1161	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1162	program get the CPU sometimes even under high AIO load.
		1163
		1164	# try not to spend much more than 0.1s in poll_cb
		1165	IO::AIO::max_poll_time 0.1;
		1166
		1167	# use a low priority so other tasks have priority
		1168	Event->io (fd => IO::AIO::poll_fileno,
		1169	poll => 'r', nice => 1,
		1170	cb => &IO::AIO::poll_cb);
		1171
669	=item IO::AIO::poll_wait	1172	=item IO::AIO::poll_wait
670		1173
		1174	If there are any outstanding requests and none of them in the result
671	Wait till the result filehandle becomes ready for reading (simply does a	1175	phase, wait till the result filehandle becomes ready for reading (simply
672	C<select> on the filehandle. This is useful if you want to synchronously wait	1176	does a C<select> on the filehandle. This is useful if you want to
673	for some requests to finish).	1177	synchronously wait for some requests to finish).
674		1178
675	See C<nreqs> for an example.	1179	See C<nreqs> for an example.
676		1180
		1181	=item IO::AIO::poll
		1182
		1183	Waits until some requests have been handled.
		1184
		1185	Returns the number of requests processed, but is otherwise strictly
		1186	equivalent to:
		1187
		1188	IO::AIO::poll_wait, IO::AIO::poll_cb
		1189
677	=item IO::AIO::nreqs	1190	=item IO::AIO::flush
678		1191
679	Returns the number of requests currently outstanding (i.e. for which their	1192	Wait till all outstanding AIO requests have been handled.
680	callback has not been invoked yet).
681		1193
682	Example: wait till there are no outstanding requests anymore:	1194	Strictly equivalent to:
683		1195
684	IO::AIO::poll_wait, IO::AIO::poll_cb	1196	IO::AIO::poll_wait, IO::AIO::poll_cb
685	while IO::AIO::nreqs;	1197	while IO::AIO::nreqs;
686		1198
687	=item IO::AIO::flush	1199	=back
688		1200
689	Wait till all outstanding AIO requests have been handled.	1201	=head3 CONTROLLING THE NUMBER OF THREADS
690		1202
691	Strictly equivalent to:	1203	=over
692
693	IO::AIO::poll_wait, IO::AIO::poll_cb
694	while IO::AIO::nreqs;
695
696	=item IO::AIO::poll
697
698	Waits until some requests have been handled.
699
700	Strictly equivalent to:
701
702	IO::AIO::poll_wait, IO::AIO::poll_cb
703	if IO::AIO::nreqs;
704		1204
705	=item IO::AIO::min_parallel $nthreads	1205	=item IO::AIO::min_parallel $nthreads
706		1206
707	Set the minimum number of AIO threads to C<$nthreads>. The current default	1207	Set the minimum number of AIO threads to C<$nthreads>. The current
708	is C<4>, which means four asynchronous operations can be done at one time	1208	default is C<8>, which means eight asynchronous operations can execute
709	(the number of outstanding operations, however, is unlimited).	1209	concurrently at any one time (the number of outstanding requests,
		1210	however, is unlimited).
710		1211
711	IO::AIO starts threads only on demand, when an AIO request is queued and	1212	IO::AIO starts threads only on demand, when an AIO request is queued and
712	no free thread exists.	1213	no free thread exists. Please note that queueing up a hundred requests can
		1214	create demand for a hundred threads, even if it turns out that everything
		1215	is in the cache and could have been processed faster by a single thread.
713		1216
714	It is recommended to keep the number of threads low, as some Linux	1217	It is recommended to keep the number of threads relatively low, as some
715	kernel versions will scale negatively with the number of threads (higher	1218	Linux kernel versions will scale negatively with the number of threads
716	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1219	(higher parallelity => MUCH higher latency). With current Linux 2.6
717	threads should be fine.	1220	versions, 4-32 threads should be fine.
718		1221
719	Under most circumstances you don't need to call this function, as the	1222	Under most circumstances you don't need to call this function, as the
720	module selects a default that is suitable for low to moderate load.	1223	module selects a default that is suitable for low to moderate load.
721		1224
722	=item IO::AIO::max_parallel $nthreads	1225	=item IO::AIO::max_parallel $nthreads
…		…
731	This module automatically runs C<max_parallel 0> at program end, to ensure	1234	This module automatically runs C<max_parallel 0> at program end, to ensure
732	that all threads are killed and that there are no outstanding requests.	1235	that all threads are killed and that there are no outstanding requests.
733		1236
734	Under normal circumstances you don't need to call this function.	1237	Under normal circumstances you don't need to call this function.
735		1238
		1239	=item IO::AIO::max_idle $nthreads
		1240
		1241	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1242	threads that did not get a request to process within 10 seconds). That
		1243	means if a thread becomes idle while C<$nthreads> other threads are also
		1244	idle, it will free its resources and exit.
		1245
		1246	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1247	to allow for extremely high load situations, but want to free resources
		1248	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1249
		1250	The default is probably ok in most situations, especially if thread
		1251	creation is fast. If thread creation is very slow on your system you might
		1252	want to use larger values.
		1253
736	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1254	=item IO::AIO::max_outstanding $maxreqs
		1255
		1256	This is a very bad function to use in interactive programs because it
		1257	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1258	use an C<aio_group> together with a feed callback.
737		1259
738	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1260	Sets the maximum number of outstanding requests to C<$nreqs>. If you
739	try to queue up more than this number of requests, the caller will block until	1261	do queue up more than this number of requests, the next call to the
740	some requests have been handled.	1262	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1263	function will block until the limit is no longer exceeded.
741		1264
742	The default is very large, so normally there is no practical limit. If you	1265	The default value is very large, so there is no practical limit on the
743	queue up many requests in a loop it often improves speed if you set	1266	number of outstanding requests.
744	this to a relatively low number, such as C<100>.
745		1267
746	Under normal circumstances you don't need to call this function.	1268	You can still queue as many requests as you want. Therefore,
		1269	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1270	as a stop gap to shield against fatal memory overflow (with large values).
747		1271
748	=back	1272	=back
749		1273
		1274	=head3 STATISTICAL INFORMATION
		1275
		1276	=over
		1277
		1278	=item IO::AIO::nreqs
		1279
		1280	Returns the number of requests currently in the ready, execute or pending
		1281	states (i.e. for which their callback has not been invoked yet).
		1282
		1283	Example: wait till there are no outstanding requests anymore:
		1284
		1285	IO::AIO::poll_wait, IO::AIO::poll_cb
		1286	while IO::AIO::nreqs;
		1287
		1288	=item IO::AIO::nready
		1289
		1290	Returns the number of requests currently in the ready state (not yet
		1291	executed).
		1292
		1293	=item IO::AIO::npending
		1294
		1295	Returns the number of requests currently in the pending state (executed,
		1296	but not yet processed by poll_cb).
		1297
		1298	=back
		1299
750	=cut	1300	=cut
751		1301
752	# support function to convert a fd into a perl filehandle
753	sub _fd2fh {
754	return undef if $_[0] < 0;
755
756	# try to generate nice filehandles
757	my $sym = "IO::AIO::fd#$_[0]";
758	local *$sym;
759
760	open *$sym, "+<&=$_[0]" # usually works under any unix
761	or open *$sym, "<&=$_[0]" # cygwin needs this
762	or open *$sym, ">&=$_[0]" # or this
763	or return undef;
764
765	*$sym
766	}
767
768	min_parallel 4;	1302	min_parallel 8;
769		1303
770	END {	1304	END { flush }
771	max_parallel 0;
772	}
773		1305
774	1;	1306	1;
775		1307
776	=head2 FORK BEHAVIOUR	1308	=head2 FORK BEHAVIOUR
777		1309
778	This module should do "the right thing" when the process using it forks:	1310	This module should do "the right thing" when the process using it forks:
779		1311
780	Before the fork, IO::AIO enters a quiescent state where no requests	1312	Before the fork, IO::AIO enters a quiescent state where no requests
781	can be added in other threads and no results will be processed. After	1313	can be added in other threads and no results will be processed. After
782	the fork the parent simply leaves the quiescent state and continues	1314	the fork the parent simply leaves the quiescent state and continues
783	request/result processing, while the child clears the request/result	1315	request/result processing, while the child frees the request/result queue
784	queue (so the requests started before the fork will only be handled in	1316	(so that the requests started before the fork will only be handled in the
785	the parent). Threads will be started on demand until the limit ste in the	1317	parent). Threads will be started on demand until the limit set in the
786	parent process has been reached again.	1318	parent process has been reached again.
787		1319
788	In short: the parent will, after a short pause, continue as if fork had	1320	In short: the parent will, after a short pause, continue as if fork had
789	not been called, while the child will act as if IO::AIO has not been used	1321	not been called, while the child will act as if IO::AIO has not been used
790	yet.	1322	yet.
791		1323
		1324	=head2 MEMORY USAGE
		1325
		1326	Per-request usage:
		1327
		1328	Each aio request uses - depending on your architecture - around 100-200
		1329	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1330	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1331	scalars and other data passed into aio requests will also be locked and
		1332	will consume memory till the request has entered the done state.
		1333
		1334	This is not awfully much, so queuing lots of requests is not usually a
		1335	problem.
		1336
		1337	Per-thread usage:
		1338
		1339	In the execution phase, some aio requests require more memory for
		1340	temporary buffers, and each thread requires a stack and other data
		1341	structures (usually around 16k-128k, depending on the OS).
		1342
		1343	=head1 KNOWN BUGS
		1344
		1345	Known bugs will be fixed in the next release.
		1346
792	=head1 SEE ALSO	1347	=head1 SEE ALSO
793		1348
794	L<Coro>, L<Linux::AIO> (obsolete).	1349	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1350	more natural syntax.
795		1351
796	=head1 AUTHOR	1352	=head1 AUTHOR
797		1353
798	Marc Lehmann <schmorp@schmorp.de>	1354	Marc Lehmann <schmorp@schmorp.de>
799	http://home.schmorp.de/	1355	http://home.schmorp.de/

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