ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.54 by root, Sun Oct 22 00:19:05 2006 UTC vs.
Revision 1.138 by root, Sun Oct 12 21:51:33 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
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	use IO::AIO 2; # version has aio objects	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
21		23
		24	aioreq_pri 4; # give next request a very high priority
22	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
23	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
24		27
25	# AnyEvent	28	my $grp = aio_group sub { print "all stats done\n" };
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	29	add $grp aio_stat "..." for ...;
27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28		30
29	# Event	31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	39	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
33		41
34	# Glib/Gtk2	42	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	44	in => sub { IO::AIO::poll_cb; 1 };
37		45
38	# Tk	46	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
41		49
42	# Danga::Socket	50	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
45		53
46
47	=head1 DESCRIPTION	54	=head1 DESCRIPTION
48		55
49	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
50	operating system supports.	57	operating system supports.
51		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
52	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
53	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
54	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
55	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
56	aio functions available on many operating systems. However, they are often	79	functions available on many operating systems. However, they are often
57	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
58	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
59	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.
60		84
61	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,
62	currently not reentrant, so use appropriate locking yourself, always call	86	it is currently not reentrant in any way, so use appropriate locking
63	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
64	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
65		185
66	=cut	186	=cut
67		187
68	package IO::AIO;	188	package IO::AIO;
		189
		190	use Carp ();
69		191
70	no warnings;	192	no warnings;
71	use strict 'vars';	193	use strict 'vars';
72		194
73	use base 'Exporter';	195	use base 'Exporter';
74		196
75	BEGIN {	197	BEGIN {
76	our $VERSION = '1.99';	198	our $VERSION = '3.1';
77		199
78	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
79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
81	aio_group);	203	aio_fdatasync aio_pathsync aio_readahead
82	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);
83		213
84	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
85		215
86	require XSLoader;	216	require XSLoader;
87	XSLoader::load ("IO::AIO", $VERSION);	217	XSLoader::load ("IO::AIO", $VERSION);
88	}	218	}
89		219
90	=head1 FUNCTIONS	220	=head1 FUNCTIONS
91		221
92	=head2 AIO FUNCTIONS	222	=head2 AIO REQUEST FUNCTIONS
93		223
94	All the C<aio_*> calls are more or less thin wrappers around the syscall	224	All the C<aio_*> calls are more or less thin wrappers around the syscall
95	with the same name (sans C<aio_>). The arguments are similar or identical,	225	with the same name (sans C<aio_>). The arguments are similar or identical,
96	and they all accept an additional (and optional) C<$callback> argument	226	and they all accept an additional (and optional) C<$callback> argument
97	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
98	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
99	perl, which usually delivers "false") as it's sole argument when the given	229	perl, which usually delivers "false") as its sole argument after the given
100	syscall has been executed asynchronously.	230	syscall has been executed asynchronously.
101		231
102	All functions expecting a filehandle keep a copy of the filehandle	232	All functions expecting a filehandle keep a copy of the filehandle
103	internally until the request has finished.	233	internally until the request has finished.
104		234
105	All non-composite requests (requests that are not broken down into
106	multiple requests) return objects of type L<IO::AIO::REQ> that allow	235	All functions return request objects of type L<IO::AIO::REQ> that allow
107	further manipulation of running requests.	236	further manipulation of those requests while they are in-flight.
108		237
109	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
110	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
111	request is being executed, the current working directory could have	240	request is being executed, the current working directory could have
112	changed. Alternatively, you can make sure that you never change the	241	changed. Alternatively, you can make sure that you never change the
113	current working directory.	242	current working directory anywhere in the program and then use relative
		243	paths.
114		244
115	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
116	always pass in filenames you got from outside (command line, readdir	246	in filenames you got from outside (command line, readdir etc.) without
117	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
118	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
119	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)
120	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 whether it is set or not.
121		254
122	=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
123		289
124	=item aio_open $pathname, $flags, $mode, $callback->($fh)	290	=item aio_open $pathname, $flags, $mode, $callback->($fh)
125		291
126	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
127	created filehandle for the file.	293	created filehandle for the file.
…		…
133	list. They are the same as used by C<sysopen>.	299	list. They are the same as used by C<sysopen>.
134		300
135	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
136	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>,
137	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,
138	and C<0666> or C<0777> if you do).	304	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		305	by the umask in effect then the request is being executed, so better never
		306	change the umask.
139		307
140	Example:	308	Example:
141		309
142	aio_open "/etc/passwd", O_RDONLY, 0, sub {	310	aio_open "/etc/passwd", O_RDONLY, 0, sub {
143	if ($_[0]) {	311	if ($_[0]) {
…		…
146	} else {	314	} else {
147	die "open failed: $!\n";	315	die "open failed: $!\n";
148	}	316	}
149	};	317	};
150		318
		319
151	=item aio_close $fh, $callback->($status)	320	=item aio_close $fh, $callback->($status)
152		321
153	Asynchronously close a file and call the callback with the result	322	Asynchronously close a file and call the callback with the result
154	code. I<WARNING:> although accepted, you should not pass in a perl	323	code.
155	filehandle here, as perl will likely close the file descriptor another
156	time when the filehandle is destroyed. Normally, you can safely call perls
157	C<close> or just let filehandles go out of scope.
158		324
159	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
160	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
161		336
162	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163		338
164	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
165		340
166	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<$offset>
167	into the scalar given by C<data> and offset C<dataoffset> and calls the	342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
168	callback without the actual number of bytes read (or -1 on error, just	343	callback without the actual number of bytes read (or -1 on error, just
169	like the syscall).	344	like the syscall).
170		345
		346	If C<$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
171	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
172	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
173	necessary/optional hardware is installed).	357	the necessary/optional hardware is installed).
174		358
175	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
176	offset C<0> within the scalar:	360	offset C<0> within the scalar:
177		361
178	aio_read $fh, 7, 15, $buffer, 0, sub {	362	aio_read $fh, 7, 15, $buffer, 0, sub {
179	$_[0] > 0 or die "read error: $!";	363	$_[0] > 0 or die "read error: $!";
180	print "read $_[0] bytes: <$buffer>\n";	364	print "read $_[0] bytes: <$buffer>\n";
181	};	365	};
182		366
183	=item aio_move $srcpath, $dstpath, $callback->($status)
184
185	Try to move the I<file> (directories not supported as either source or
186	destination) from C<$srcpath> to C<$dstpath> and call the callback with
187	the C<0> (error) or C<-1> ok.
188
189	This is a composite request that tries to rename(2) the file first. If
190	rename files with C<EXDEV>, it creates the destination file with mode 0200
191	and copies the contents of the source file into it using C<aio_sendfile>,
192	followed by restoring atime, mtime, access mode and uid/gid, in that
193	order, and unlinking the C<$srcpath>.
194
195	If an error occurs, the partial destination file will be unlinked, if
196	possible, except when setting atime, mtime, access mode and uid/gid, where
197	errors are being ignored.
198
199	=cut
200
201	sub aio_move($$$) {
202	my ($src, $dst, $cb) = @_;
203
204	aio_rename $src, $dst, sub {
205	if ($_[0] && $! == EXDEV) {
206	aio_open $src, O_RDONLY, 0, sub {
207	if (my $src_fh = $_[0]) {
208	my @stat = stat $src_fh;
209
210	aio_open $dst, O_WRONLY, 0200, sub {
211	if (my $dst_fh = $_[0]) {
212	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
213	close $src_fh;
214
215	if ($_[0] == $stat[7]) {
216	utime $stat[8], $stat[9], $dst;
217	chmod $stat[2] & 07777, $dst_fh;
218	chown $stat[4], $stat[5], $dst_fh;
219	close $dst_fh;
220
221	aio_unlink $src, sub {
222	$cb->($_[0]);
223	};
224	} else {
225	my $errno = $!;
226	aio_unlink $dst, sub {
227	$! = $errno;
228	$cb->(-1);
229	};
230	}
231	};
232	} else {
233	$cb->(-1);
234	}
235	},
236
237	} else {
238	$cb->(-1);
239	}
240	};
241	} else {
242	$cb->($_[0]);
243	}
244	};
245	}
246		367
247	=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)
248		369
249	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
250	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
…		…
264	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
265	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
266	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
267	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
268	read.	389	read.
		390
269		391
270	=item aio_readahead $fh,$offset,$length, $callback->($retval)	392	=item aio_readahead $fh,$offset,$length, $callback->($retval)
271		393
272	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
273	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>
…		…
279	file. The current file offset of the file is left unchanged.	401	file. The current file offset of the file is left unchanged.
280		402
281	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
282	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.
283		405
		406
284	=item aio_stat $fh_or_path, $callback->($status)	407	=item aio_stat $fh_or_path, $callback->($status)
285		408
286	=item aio_lstat $fh, $callback->($status)	409	=item aio_lstat $fh, $callback->($status)
287		410
288	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
…		…
301	aio_stat "/etc/passwd", sub {	424	aio_stat "/etc/passwd", sub {
302	$_[0] and die "stat failed: $!";	425	$_[0] and die "stat failed: $!";
303	print "size is ", -s _, "\n";	426	print "size is ", -s _, "\n";
304	};	427	};
305		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
306	=item aio_unlink $pathname, $callback->($status)	471	=item aio_unlink $pathname, $callback->($status)
307		472
308	Asynchronously unlink (delete) a file and call the callback with the	473	Asynchronously unlink (delete) a file and call the callback with the
309	result code.	474	result code.
310		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
311	=item aio_link $srcpath, $dstpath, $callback->($status)	488	=item aio_link $srcpath, $dstpath, $callback->($status)
312		489
313	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
314	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.
315		492
		493
316	=item aio_symlink $srcpath, $dstpath, $callback->($status)	494	=item aio_symlink $srcpath, $dstpath, $callback->($status)
317		495
318	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
319	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.
320		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
321	=item aio_rename $srcpath, $dstpath, $callback->($status)	507	=item aio_rename $srcpath, $dstpath, $callback->($status)
322		508
323	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
324	rename(2) and call the callback with the result code.	510	rename(2) and call the callback with the result code.
325		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
326	=item aio_rmdir $pathname, $callback->($status)	520	=item aio_rmdir $pathname, $callback->($status)
327		521
328	Asynchronously rmdir (delete) a directory and call the callback with the	522	Asynchronously rmdir (delete) a directory and call the callback with the
329	result code.	523	result code.
		524
330		525
331	=item aio_readdir $pathname, $callback->($entries)	526	=item aio_readdir $pathname, $callback->($entries)
332		527
333	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
334	directory (i.e. opendir + readdir + closedir). The entries will not be	529	directory (i.e. opendir + readdir + closedir). The entries will not be
335	sorted, and will B<NOT> include the C<.> and C<..> entries.	530	sorted, and will B<NOT> include the C<.> and C<..> entries.
336		531
337	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
338	with the filenames.	533	with the filenames.
339		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), $$data, 0, sub {
		557	$grp->result ($_[0]);
		558	};
		559	};
		560
		561	$grp
		562	}
		563
		564	=item aio_copy $srcpath, $dstpath, $callback->($status)
		565
		566	Try to copy the I<file> (directories not supported as either source or
		567	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		568	the C<0> (error) or C<-1> ok.
		569
		570	This is a composite request that creates the destination file with
		571	mode 0200 and copies the contents of the source file into it using
		572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		573	uid/gid, in that order.
		574
		575	If an error occurs, the partial destination file will be unlinked, if
		576	possible, except when setting atime, mtime, access mode and uid/gid, where
		577	errors are being ignored.
		578
		579	=cut
		580
		581	sub aio_copy($$;$) {
		582	my ($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 fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		638	that is successful, unlinks 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
340	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
341		669
342	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
343	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
344	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
345	recurse into (everything else).	673	recurse into (everything else, including symlinks to directories).
346		674
347	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_
348	requests. C<$maxreq> specifies the maximum number of outstanding aio	676	C<$maxreq> specifies the maximum number of outstanding aio requests that
349	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
350	suitable default will be chosen (currently 8).	678	will be chosen (currently 4).
351		679
352	On error, the callback is called without arguments, otherwise it receives	680	On error, the callback is called without arguments, otherwise it receives
353	two array-refs with path-relative entry names.	681	two array-refs with path-relative entry names.
354		682
355	Example:	683	Example:
…		…
389	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
390	directory counting heuristic.	718	directory counting heuristic.
391		719
392	=cut	720	=cut
393		721
394	sub aio_scandir($$$) {	722	sub aio_scandir($$;$) {
395	my ($path, $maxreq, $cb) = @_;	723	my ($path, $maxreq, $cb) = @_;
396		724
		725	my $pri = aioreq_pri;
		726
		727	my $grp = aio_group $cb;
		728
397	$maxreq = 8 if $maxreq <= 0;	729	$maxreq = 4 if $maxreq <= 0;
398		730
399	# stat once	731	# stat once
		732	aioreq_pri $pri;
400	aio_stat $path, sub {	733	add $grp aio_stat $path, sub {
401	return $cb->() if $_[0];	734	return $grp->result () if $_[0];
402	my $now = time;	735	my $now = time;
403	my $hash1 = join ":", (stat _)[0,1,3,7,9];	736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
404		737
405	# read the directory entries	738	# read the directory entries
		739	aioreq_pri $pri;
406	aio_readdir $path, sub {	740	add $grp aio_readdir $path, sub {
407	my $entries = shift	741	my $entries = shift
408	or return $cb->();	742	or return $grp->result ();
409		743
410	# stat the dir another time	744	# stat the dir another time
		745	aioreq_pri $pri;
411	aio_stat $path, sub {	746	add $grp aio_stat $path, sub {
412	my $hash2 = join ":", (stat _)[0,1,3,7,9];	747	my $hash2 = join ":", (stat _)[0,1,3,7,9];
413		748
414	my $ndirs;	749	my $ndirs;
415		750
416	# take the slow route if anything looks fishy	751	# take the slow route if anything looks fishy
…		…
418	$ndirs = -1;	753	$ndirs = -1;
419	} else {	754	} else {
420	# if nlink == 2, we are finished	755	# if nlink == 2, we are finished
421	# on non-posix-fs's, we rely on nlink < 2	756	# on non-posix-fs's, we rely on nlink < 2
422	$ndirs = (stat _)[3] - 2	757	$ndirs = (stat _)[3] - 2
423	or return $cb->([], $entries);	758	or return $grp->result ([], $entries);
424	}	759	}
425		760
426	# sort into likely dirs and likely nondirs	761	# sort into likely dirs and likely nondirs
427	# dirs == files without ".", short entries first	762	# dirs == files without ".", short entries first
428	$entries = [map $_->[0],	763	$entries = [map $_->[0],
…		…
430	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],	765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
431	@$entries];	766	@$entries];
432		767
433	my (@dirs, @nondirs);	768	my (@dirs, @nondirs);
434		769
435	my ($statcb, $schedcb);	770	my $statgrp = add $grp aio_group sub {
436	my $nreq = 0;	771	$grp->result (\@dirs, \@nondirs);
		772	};
437		773
438	$schedcb = sub {	774	limit $statgrp $maxreq;
439	if (@$entries) {	775	feed $statgrp sub {
440	if ($nreq < $maxreq) {	776	return unless @$entries;
441	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	}
442	$nreq++;	797	}
443	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
444	}	798	}
445	} elsif (!$nreq) {
446	# finished
447	undef $statcb;
448	undef $schedcb;
449	$cb->(\@dirs, \@nondirs) if $cb;
450	undef $cb;
451	}	799	};
452	};	800	};
453	$statcb = sub {
454	my ($status, $entry) = @_;
455
456	if ($status < 0) {
457	$nreq--;
458	push @nondirs, $entry;
459	&$schedcb;
460	} else {
461	# need to check for real directory
462	aio_lstat "$path/$entry", sub {
463	$nreq--;
464
465	if (-d _) {
466	push @dirs, $entry;
467
468	if (!--$ndirs) {
469	push @nondirs, @$entries;
470	$entries = [];
471	}
472	} else {
473	push @nondirs, $entry;
474	}
475
476	&$schedcb;
477	}
478	}
479	};
480
481	&$schedcb while @$entries && $nreq < $maxreq;
482	};	801	};
483	};	802	};
484	};	803	};
		804
		805	$grp
485	}	806	}
		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.
486		846
487	=item aio_fsync $fh, $callback->($status)	847	=item aio_fsync $fh, $callback->($status)
488		848
489	Asynchronously call fsync on the given filehandle and call the callback	849	Asynchronously call fsync on the given filehandle and call the callback
490	with the fsync result code.	850	with the fsync result code.
…		…
495	callback with the fdatasync result code.	855	callback with the fdatasync result code.
496		856
497	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
498	detected, it will be emulated by calling C<fsync> instead.	858	detected, it will be emulated by calling C<fsync> instead.
499		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 to sync 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
500	=item aio_group $callback->()	898	=item aio_group $callback->(...)
501		899
		900	This is a very special aio request: Instead of doing something, it is a
		901	container for other aio requests, which is useful if you want to bundle
		902	many requests into a single, composite, request with a definite callback
		903	and the ability to cancel the whole request with its subrequests.
		904
		905	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		906	for more info.
		907
		908	Example:
		909
		910	my $grp = aio_group sub {
		911	print "all stats done\n";
		912	};
		913
		914	add $grp
		915	(aio_stat ...),
		916	(aio_stat ...),
		917	...;
		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
502	=item aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	932	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
503		933
504	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
505	the request workers to sleep for the given time.	935	the request workers to sleep for the given time.
506		936
		937	While it is theoretically handy to have simple I/O scheduling requests
		938	like sleep and file handle readable/writable, the overhead this creates is
		939	immense (it blocks a thread for a long time) so do not use this function
		940	except to put your application under artificial I/O pressure.
		941
507	=back	942	=back
508		943
509	=head2 IO::AIO::REQ CLASS	944	=head2 IO::AIO::REQ CLASS
510		945
511	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
512	called in non-void context.	947	called in non-void context.
513		948
514	A request always moves through the following five states in its lifetime,
515	in order: B<ready> (request has been created, but has not been executed
516	yet), B<execute> (request is currently being executed), B<pending>
517	(request has been executed but callback has not been called yet),
518	B<result> (results are being processed synchronously, includes calling the
519	callback) and B<done> (request has reached the end of its lifetime and
520	holds no resources anymore).
521
522	=over 4	949	=over 4
523		950
524	=item $req->cancel	951	=item cancel $req
525		952
526	Cancels the request, if possible. Has the effect of skipping execution	953	Cancels the request, if possible. Has the effect of skipping execution
527	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
528	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
529	untouched. That means that requests that currently execute will not be	956	untouched. That means that requests that currently execute will not be
530	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.
531		958
		959	=item cb $req $callback->(...)
		960
		961	Replace (or simply set) the callback registered to the request.
		962
532	=back	963	=back
533		964
		965	=head2 IO::AIO::GRP CLASS
		966
		967	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		968	objects of this class, too.
		969
		970	A IO::AIO::GRP object is a special request that can contain multiple other
		971	aio requests.
		972
		973	You create one by calling the C<aio_group> constructing function with a
		974	callback that will be called when all contained requests have entered the
		975	C<done> state:
		976
		977	my $grp = aio_group sub {
		978	print "all requests are done\n";
		979	};
		980
		981	You add requests by calling the C<add> method with one or more
		982	C<IO::AIO::REQ> objects:
		983
		984	$grp->add (aio_unlink "...");
		985
		986	add $grp aio_stat "...", sub {
		987	$_[0] or return $grp->result ("error");
		988
		989	# add another request dynamically, if first succeeded
		990	add $grp aio_open "...", sub {
		991	$grp->result ("ok");
		992	};
		993	};
		994
		995	This makes it very easy to create composite requests (see the source of
		996	C<aio_move> for an application) that work and feel like simple requests.
		997
		998	=over 4
		999
		1000	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1001	C<IO::AIO::poll_cb>, just like any other request.
		1002
		1003	=item * They can be canceled like any other request. Canceling will cancel not
		1004	only the request itself, but also all requests it contains.
		1005
		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
		1012
		1013	Their lifetime, simplified, looks like this: when they are empty, they
		1014	will finish very quickly. If they contain only requests that are in the
		1015	C<done> state, they will also finish. Otherwise they will continue to
		1016	exist.
		1017
		1018	That means after creating a group you have some time to add requests
		1019	(precisely before the callback has been invoked, which is only done within
		1020	the C<poll_cb>). And in the callbacks of those requests, you can add
		1021	further requests to the group. And only when all those requests have
		1022	finished will the the group itself finish.
		1023
		1024	=over 4
		1025
		1026	=item add $grp ...
		1027
		1028	=item $grp->add (...)
		1029
		1030	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1031	be added, including other groups, as long as you do not create circular
		1032	dependencies.
		1033
		1034	Returns all its arguments.
		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
		1041	=item $grp->result (...)
		1042
		1043	Set the result value(s) that will be passed to the group callback when all
		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> when this method is called, it will be set to
		1082	C<2> automatically.
		1083
		1084	Example:
		1085
		1086	# stat all files in @files, but only ever use four aio requests concurrently:
		1087
		1088	my $grp = aio_group sub { print "finished\n" };
		1089	limit $grp 4;
		1090	feed $grp sub {
		1091	my $file = pop @files
		1092	or return;
		1093
		1094	add $grp aio_stat $file, sub { ... };
		1095	};
		1096
		1097	=item limit $grp $num
		1098
		1099	Sets the feeder limit for the group: The feeder will be called whenever
		1100	the group contains less than this many requests.
		1101
		1102	Setting the limit to C<0> will pause the feeding process.
		1103
		1104	The default value for the limit is C<0>, but note that setting a feeder
		1105	automatically bumps it up to C<2>.
		1106
		1107	=back
		1108
534	=head2 SUPPORT FUNCTIONS	1109	=head2 SUPPORT FUNCTIONS
		1110
		1111	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
535		1112
536	=over 4	1113	=over 4
537		1114
538	=item $fileno = IO::AIO::poll_fileno	1115	=item $fileno = IO::AIO::poll_fileno
539		1116
…		…
544		1121
545	See C<poll_cb> for an example.	1122	See C<poll_cb> for an example.
546		1123
547	=item IO::AIO::poll_cb	1124	=item IO::AIO::poll_cb
548		1125
549	Process all outstanding events on the result pipe. You have to call this	1126	Process some outstanding events on the result pipe. You have to call this
550	regularly. Returns the number of events processed. Returns immediately	1127	regularly. Returns C<0> if all events could be processed, or C<-1> if it
551	when no events are outstanding.	1128	returned earlier for whatever reason. Returns immediately when no events
		1129	are outstanding. The amount of events processed depends on the settings of
		1130	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1131
		1132	If not all requests were processed for whatever reason, the filehandle
		1133	will still be ready when C<poll_cb> returns, so normally you don't have to
		1134	do anything special to have it called later.
552		1135
553	Example: Install an Event watcher that automatically calls	1136	Example: Install an Event watcher that automatically calls
554	IO::AIO::poll_cb with high priority:	1137	IO::AIO::poll_cb with high priority:
555		1138
556	Event->io (fd => IO::AIO::poll_fileno,	1139	Event->io (fd => IO::AIO::poll_fileno,
557	poll => 'r', async => 1,	1140	poll => 'r', async => 1,
558	cb => \&IO::AIO::poll_cb);	1141	cb => \&IO::AIO::poll_cb);
559		1142
		1143	=item IO::AIO::max_poll_reqs $nreqs
		1144
		1145	=item IO::AIO::max_poll_time $seconds
		1146
		1147	These set the maximum number of requests (default C<0>, meaning infinity)
		1148	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1149	the maximum amount of time (default C<0>, meaning infinity) spent in
		1150	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1151	of time C<poll_cb> is allowed to use).
		1152
		1153	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1154	syscall per request processed, which is not normally a problem unless your
		1155	callbacks are really really fast or your OS is really really slow (I am
		1156	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1157
		1158	Setting these is useful if you want to ensure some level of
		1159	interactiveness when perl is not fast enough to process all requests in
		1160	time.
		1161
		1162	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1163
		1164	Example: Install an Event watcher that automatically calls
		1165	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1166	program get the CPU sometimes even under high AIO load.
		1167
		1168	# try not to spend much more than 0.1s in poll_cb
		1169	IO::AIO::max_poll_time 0.1;
		1170
		1171	# use a low priority so other tasks have priority
		1172	Event->io (fd => IO::AIO::poll_fileno,
		1173	poll => 'r', nice => 1,
		1174	cb => &IO::AIO::poll_cb);
		1175
560	=item IO::AIO::poll_wait	1176	=item IO::AIO::poll_wait
561		1177
		1178	If there are any outstanding requests and none of them in the result
562	Wait till the result filehandle becomes ready for reading (simply does a	1179	phase, wait till the result filehandle becomes ready for reading (simply
563	C<select> on the filehandle. This is useful if you want to synchronously wait	1180	does a C<select> on the filehandle. This is useful if you want to
564	for some requests to finish).	1181	synchronously wait for some requests to finish).
565		1182
566	See C<nreqs> for an example.	1183	See C<nreqs> for an example.
567		1184
		1185	=item IO::AIO::poll
		1186
		1187	Waits until some requests have been handled.
		1188
		1189	Returns the number of requests processed, but is otherwise strictly
		1190	equivalent to:
		1191
		1192	IO::AIO::poll_wait, IO::AIO::poll_cb
		1193
568	=item IO::AIO::nreqs	1194	=item IO::AIO::flush
569		1195
570	Returns the number of requests currently outstanding (i.e. for which their	1196	Wait till all outstanding AIO requests have been handled.
571	callback has not been invoked yet).
572		1197
573	Example: wait till there are no outstanding requests anymore:	1198	Strictly equivalent to:
574		1199
575	IO::AIO::poll_wait, IO::AIO::poll_cb	1200	IO::AIO::poll_wait, IO::AIO::poll_cb
576	while IO::AIO::nreqs;	1201	while IO::AIO::nreqs;
577		1202
578	=item IO::AIO::flush	1203	=back
579		1204
580	Wait till all outstanding AIO requests have been handled.	1205	=head3 CONTROLLING THE NUMBER OF THREADS
581		1206
582	Strictly equivalent to:	1207	=over
583
584	IO::AIO::poll_wait, IO::AIO::poll_cb
585	while IO::AIO::nreqs;
586
587	=item IO::AIO::poll
588
589	Waits until some requests have been handled.
590
591	Strictly equivalent to:
592
593	IO::AIO::poll_wait, IO::AIO::poll_cb
594	if IO::AIO::nreqs;
595		1208
596	=item IO::AIO::min_parallel $nthreads	1209	=item IO::AIO::min_parallel $nthreads
597		1210
598	Set the minimum number of AIO threads to C<$nthreads>. The current default	1211	Set the minimum number of AIO threads to C<$nthreads>. The current
599	is C<4>, which means four asynchronous operations can be done at one time	1212	default is C<8>, which means eight asynchronous operations can execute
600	(the number of outstanding operations, however, is unlimited).	1213	concurrently at any one time (the number of outstanding requests,
		1214	however, is unlimited).
601		1215
602	IO::AIO starts threads only on demand, when an AIO request is queued and	1216	IO::AIO starts threads only on demand, when an AIO request is queued and
603	no free thread exists.	1217	no free thread exists. Please note that queueing up a hundred requests can
		1218	create demand for a hundred threads, even if it turns out that everything
		1219	is in the cache and could have been processed faster by a single thread.
604		1220
605	It is recommended to keep the number of threads low, as some Linux	1221	It is recommended to keep the number of threads relatively low, as some
606	kernel versions will scale negatively with the number of threads (higher	1222	Linux kernel versions will scale negatively with the number of threads
607	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1223	(higher parallelity => MUCH higher latency). With current Linux 2.6
608	threads should be fine.	1224	versions, 4-32 threads should be fine.
609		1225
610	Under most circumstances you don't need to call this function, as the	1226	Under most circumstances you don't need to call this function, as the
611	module selects a default that is suitable for low to moderate load.	1227	module selects a default that is suitable for low to moderate load.
612		1228
613	=item IO::AIO::max_parallel $nthreads	1229	=item IO::AIO::max_parallel $nthreads
…		…
622	This module automatically runs C<max_parallel 0> at program end, to ensure	1238	This module automatically runs C<max_parallel 0> at program end, to ensure
623	that all threads are killed and that there are no outstanding requests.	1239	that all threads are killed and that there are no outstanding requests.
624		1240
625	Under normal circumstances you don't need to call this function.	1241	Under normal circumstances you don't need to call this function.
626		1242
		1243	=item IO::AIO::max_idle $nthreads
		1244
		1245	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1246	threads that did not get a request to process within 10 seconds). That
		1247	means if a thread becomes idle while C<$nthreads> other threads are also
		1248	idle, it will free its resources and exit.
		1249
		1250	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1251	to allow for extremely high load situations, but want to free resources
		1252	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1253
		1254	The default is probably ok in most situations, especially if thread
		1255	creation is fast. If thread creation is very slow on your system you might
		1256	want to use larger values.
		1257
627	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1258	=item IO::AIO::max_outstanding $maxreqs
		1259
		1260	This is a very bad function to use in interactive programs because it
		1261	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1262	use an C<aio_group> together with a feed callback.
628		1263
629	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1264	Sets the maximum number of outstanding requests to C<$nreqs>. If you
630	try to queue up more than this number of requests, the caller will block until	1265	do queue up more than this number of requests, the next call to the
631	some requests have been handled.	1266	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1267	function will block until the limit is no longer exceeded.
632		1268
633	The default is very large, so normally there is no practical limit. If you	1269	The default value is very large, so there is no practical limit on the
634	queue up many requests in a loop it often improves speed if you set	1270	number of outstanding requests.
635	this to a relatively low number, such as C<100>.
636		1271
637	Under normal circumstances you don't need to call this function.	1272	You can still queue as many requests as you want. Therefore,
		1273	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1274	as a stop gap to shield against fatal memory overflow (with large values).
638		1275
639	=back	1276	=back
640		1277
		1278	=head3 STATISTICAL INFORMATION
		1279
		1280	=over
		1281
		1282	=item IO::AIO::nreqs
		1283
		1284	Returns the number of requests currently in the ready, execute or pending
		1285	states (i.e. for which their callback has not been invoked yet).
		1286
		1287	Example: wait till there are no outstanding requests anymore:
		1288
		1289	IO::AIO::poll_wait, IO::AIO::poll_cb
		1290	while IO::AIO::nreqs;
		1291
		1292	=item IO::AIO::nready
		1293
		1294	Returns the number of requests currently in the ready state (not yet
		1295	executed).
		1296
		1297	=item IO::AIO::npending
		1298
		1299	Returns the number of requests currently in the pending state (executed,
		1300	but not yet processed by poll_cb).
		1301
		1302	=back
		1303
641	=cut	1304	=cut
642		1305
643	# support function to convert a fd into a perl filehandle
644	sub _fd2fh {
645	return undef if $_[0] < 0;
646
647	# try to generate nice filehandles
648	my $sym = "IO::AIO::fd#$_[0]";
649	local *$sym;
650
651	open *$sym, "+<&=$_[0]" # usually works under any unix
652	or open *$sym, "<&=$_[0]" # cygwin needs this
653	or open *$sym, ">&=$_[0]" # or this
654	or return undef;
655
656	*$sym
657	}
658
659	min_parallel 4;	1306	min_parallel 8;
660		1307
661	END {	1308	END { flush }
662	max_parallel 0;
663	}
664		1309
665	1;	1310	1;
666		1311
667	=head2 FORK BEHAVIOUR	1312	=head2 FORK BEHAVIOUR
668		1313
669	This module should do "the right thing" when the process using it forks:	1314	This module should do "the right thing" when the process using it forks:
670		1315
671	Before the fork, IO::AIO enters a quiescent state where no requests	1316	Before the fork, IO::AIO enters a quiescent state where no requests
672	can be added in other threads and no results will be processed. After	1317	can be added in other threads and no results will be processed. After
673	the fork the parent simply leaves the quiescent state and continues	1318	the fork the parent simply leaves the quiescent state and continues
674	request/result processing, while the child clears the request/result	1319	request/result processing, while the child frees the request/result queue
675	queue (so the requests started before the fork will only be handled in	1320	(so that the requests started before the fork will only be handled in the
676	the parent). Threads will be started on demand until the limit ste in the	1321	parent). Threads will be started on demand until the limit set in the
677	parent process has been reached again.	1322	parent process has been reached again.
678		1323
679	In short: the parent will, after a short pause, continue as if fork had	1324	In short: the parent will, after a short pause, continue as if fork had
680	not been called, while the child will act as if IO::AIO has not been used	1325	not been called, while the child will act as if IO::AIO has not been used
681	yet.	1326	yet.
682		1327
		1328	=head2 MEMORY USAGE
		1329
		1330	Per-request usage:
		1331
		1332	Each aio request uses - depending on your architecture - around 100-200
		1333	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1334	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1335	scalars and other data passed into aio requests will also be locked and
		1336	will consume memory till the request has entered the done state.
		1337
		1338	This is not awfully much, so queuing lots of requests is not usually a
		1339	problem.
		1340
		1341	Per-thread usage:
		1342
		1343	In the execution phase, some aio requests require more memory for
		1344	temporary buffers, and each thread requires a stack and other data
		1345	structures (usually around 16k-128k, depending on the OS).
		1346
		1347	=head1 KNOWN BUGS
		1348
		1349	Known bugs will be fixed in the next release.
		1350
683	=head1 SEE ALSO	1351	=head1 SEE ALSO
684		1352
685	L<Coro>, L<Linux::AIO> (obsolete).	1353	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1354	more natural syntax.
686		1355
687	=head1 AUTHOR	1356	=head1 AUTHOR
688		1357
689	Marc Lehmann <schmorp@schmorp.de>	1358	Marc Lehmann <schmorp@schmorp.de>
690	http://home.schmorp.de/	1359	http://home.schmorp.de/

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines