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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.52 by root, Sat Oct 21 23:06:04 2006 UTC vs.
Revision 1.116 by root, Wed Oct 3 21:27:51 2007 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	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" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
26	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
27	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });	33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
28		34
29	# Event	35	# Event integration
30	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
31	poll => 'r',	37	poll => 'r',
32	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
33		39
34	# Glib/Gtk2	40	# Glib/Gtk2 integration
35	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
36	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
37		43
38	# Tk	44	# Tk integration
39	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
40	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
41		47
42	# Danga::Socket	48	# Danga::Socket integration
43	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
44	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
45		51
46
47	=head1 DESCRIPTION	52	=head1 DESCRIPTION
48		53
49	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
50	operating system supports.	55	operating system supports.
51		56
		57	Asynchronous means that operations that can normally block your program
		58	(e.g. reading from disk) will be done asynchronously: the operation
		59	will still block, but you can do something else in the meantime. This
		60	is extremely useful for programs that need to stay interactive even
		61	when doing heavy I/O (GUI programs, high performance network servers
		62	etc.), but can also be used to easily do operations in parallel that are
		63	normally done sequentially, e.g. stat'ing many files, which is much faster
		64	on a RAID volume or over NFS when you do a number of stat operations
		65	concurrently.
		66
		67	While most of this works on all types of file descriptors (for
		68	example sockets), using these functions on file descriptors that
		69	support nonblocking operation (again, sockets, pipes etc.) is very
		70	inefficient. Use an event loop for that (such as the L<Event|Event>
		71	module): IO::AIO will naturally fit into such an event loop itself.
		72
52	Currently, a number of threads are started that execute your read/writes	73	In this version, a number of threads are started that execute your
53	and signal their completion. You don't need thread support in your libc or	74	requests and signal their completion. You don't need thread support
54	perl, and the threads created by this module will not be visible to the	75	in perl, and the threads created by this module will not be visible
55	pthreads library. In the future, this module might make use of the native	76	to perl. In the future, this module might make use of the native aio
56	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
57	not well-supported (Linux doesn't allow them on normal files currently,	78	not well-supported or restricted (GNU/Linux doesn't allow them on normal
58	for example), and they would only support aio_read and aio_write, so the	79	files currently, for example), and they would only support aio_read and
59	remaining functionality would have to be implemented using threads anyway.	80	aio_write, so the remaining functionality would have to be implemented
		81	using threads anyway.
60		82
61	Although the module will work with in the presence of other threads, it is	83	Although the module will work in the presence of other (Perl-) threads,
62	currently not reentrant, so use appropriate locking yourself, always call	84	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	85	yourself, always call C<poll_cb> from within the same thread, or never
64	C<aio_> functions) recursively.	86	call C<poll_cb> (or other C<aio_> functions) recursively.
		87
		88	=head2 EXAMPLE
		89
		90	This is a simple example that uses the Event module and loads
		91	F</etc/passwd> asynchronously:
		92
		93	use Fcntl;
		94	use Event;
		95	use IO::AIO;
		96
		97	# register the IO::AIO callback with Event
		98	Event->io (fd => IO::AIO::poll_fileno,
		99	poll => 'r',
		100	cb => \&IO::AIO::poll_cb);
		101
		102	# queue the request to open /etc/passwd
		103	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		104	my $fh = shift
		105	or die "error while opening: $!";
		106
		107	# stat'ing filehandles is generally non-blocking
		108	my $size = -s $fh;
		109
		110	# queue a request to read the file
		111	my $contents;
		112	aio_read $fh, 0, $size, $contents, 0, sub {
		113	$_[0] == $size
		114	or die "short read: $!";
		115
		116	close $fh;
		117
		118	# file contents now in $contents
		119	print $contents;
		120
		121	# exit event loop and program
		122	Event::unloop;
		123	};
		124	};
		125
		126	# possibly queue up other requests, or open GUI windows,
		127	# check for sockets etc. etc.
		128
		129	# process events as long as there are some:
		130	Event::loop;
		131
		132	=head1 REQUEST ANATOMY AND LIFETIME
		133
		134	Every C<aio_*> function creates a request. which is a C data structure not
		135	directly visible to Perl.
		136
		137	If called in non-void context, every request function returns a Perl
		138	object representing the request. In void context, nothing is returned,
		139	which saves a bit of memory.
		140
		141	The perl object is a fairly standard ref-to-hash object. The hash contents
		142	are not used by IO::AIO so you are free to store anything you like in it.
		143
		144	During their existance, aio requests travel through the following states,
		145	in order:
		146
		147	=over 4
		148
		149	=item ready
		150
		151	Immediately after a request is created it is put into the ready state,
		152	waiting for a thread to execute it.
		153
		154	=item execute
		155
		156	A thread has accepted the request for processing and is currently
		157	executing it (e.g. blocking in read).
		158
		159	=item pending
		160
		161	The request has been executed and is waiting for result processing.
		162
		163	While request submission and execution is fully asynchronous, result
		164	processing is not and relies on the perl interpreter calling C<poll_cb>
		165	(or another function with the same effect).
		166
		167	=item result
		168
		169	The request results are processed synchronously by C<poll_cb>.
		170
		171	The C<poll_cb> function will process all outstanding aio requests by
		172	calling their callbacks, freeing memory associated with them and managing
		173	any groups they are contained in.
		174
		175	=item done
		176
		177	Request has reached the end of its lifetime and holds no resources anymore
		178	(except possibly for the Perl object, but its connection to the actual
		179	aio request is severed and calling its methods will either do nothing or
		180	result in a runtime error).
		181
		182	=back
65		183
66	=cut	184	=cut
67		185
68	package IO::AIO;	186	package IO::AIO;
69		187
…		…
71	use strict 'vars';	189	use strict 'vars';
72		190
73	use base 'Exporter';	191	use base 'Exporter';
74		192
75	BEGIN {	193	BEGIN {
76	our $VERSION = '1.8';	194	our $VERSION = '2.5';
77		195
78	our @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	196	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
79	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	197	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
80	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move);	198	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
81	our @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	199	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
		200	aio_chown aio_chmod aio_utime aio_truncate);
		201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		203	min_parallel max_parallel max_idle
		204	nreqs nready npending nthreads
		205	max_poll_time max_poll_reqs);
		206
		207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
82		208
83	require XSLoader;	209	require XSLoader;
84	XSLoader::load ("IO::AIO", $VERSION);	210	XSLoader::load ("IO::AIO", $VERSION);
85	}	211	}
86		212
87	=head1 FUNCTIONS	213	=head1 FUNCTIONS
88		214
89	=head2 AIO FUNCTIONS	215	=head2 AIO REQUEST FUNCTIONS
90		216
91	All the C<aio_*> calls are more or less thin wrappers around the syscall	217	All the C<aio_*> calls are more or less thin wrappers around the syscall
92	with the same name (sans C<aio_>). The arguments are similar or identical,	218	with the same name (sans C<aio_>). The arguments are similar or identical,
93	and they all accept an additional (and optional) C<$callback> argument	219	and they all accept an additional (and optional) C<$callback> argument
94	which must be a code reference. This code reference will get called with	220	which must be a code reference. This code reference will get called with
…		…
97	syscall has been executed asynchronously.	223	syscall has been executed asynchronously.
98		224
99	All functions expecting a filehandle keep a copy of the filehandle	225	All functions expecting a filehandle keep a copy of the filehandle
100	internally until the request has finished.	226	internally until the request has finished.
101		227
102	All non-composite requests (requests that are not broken down into
103	multiple requests) return objects of type L<IO::AIO::REQ> that allow	228	All functions return request objects of type L<IO::AIO::REQ> that allow
104	further manipulation of running requests.	229	further manipulation of those requests while they are in-flight.
105		230
106	The pathnames you pass to these routines I<must> be absolute and	231	The pathnames you pass to these routines I<must> be absolute and
107	encoded in byte form. The reason for the former is that at the time the	232	encoded as octets. The reason for the former is that at the time the
108	request is being executed, the current working directory could have	233	request is being executed, the current working directory could have
109	changed. Alternatively, you can make sure that you never change the	234	changed. Alternatively, you can make sure that you never change the
110	current working directory.	235	current working directory anywhere in the program and then use relative
		236	paths.
111		237
112	To encode pathnames to byte form, either make sure you either: a)	238	To encode pathnames as octets, either make sure you either: a) always pass
113	always pass in filenames you got from outside (command line, readdir	239	in filenames you got from outside (command line, readdir etc.) without
114	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
115	your pathnames to the locale (or other) encoding in effect in the user	241	your pathnames to the locale (or other) encoding in effect in the user
116	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
117	use something else.	243	use something else to ensure your scalar has the correct contents.
		244
		245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		246	handles correctly wether it is set or not.
118		247
119	=over 4	248	=over 4
		249
		250	=item $prev_pri = aioreq_pri [$pri]
		251
		252	Returns the priority value that would be used for the next request and, if
		253	C<$pri> is given, sets the priority for the next aio request.
		254
		255	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		256	and C<4>, respectively. Requests with higher priority will be serviced
		257	first.
		258
		259	The priority will be reset to C<0> after each call to one of the C<aio_*>
		260	functions.
		261
		262	Example: open a file with low priority, then read something from it with
		263	higher priority so the read request is serviced before other low priority
		264	open requests (potentially spamming the cache):
		265
		266	aioreq_pri -3;
		267	aio_open ..., sub {
		268	return unless $_[0];
		269
		270	aioreq_pri -2;
		271	aio_read $_[0], ..., sub {
		272	...
		273	};
		274	};
		275
		276
		277	=item aioreq_nice $pri_adjust
		278
		279	Similar to C<aioreq_pri>, but subtracts the given value from the current
		280	priority, so the effect is cumulative.
		281
120		282
121	=item aio_open $pathname, $flags, $mode, $callback->($fh)	283	=item aio_open $pathname, $flags, $mode, $callback->($fh)
122		284
123	Asynchronously open or create a file and call the callback with a newly	285	Asynchronously open or create a file and call the callback with a newly
124	created filehandle for the file.	286	created filehandle for the file.
…		…
130	list. They are the same as used by C<sysopen>.	292	list. They are the same as used by C<sysopen>.
131		293
132	Likewise, C<$mode> specifies the mode of the newly created file, if it	294	Likewise, C<$mode> specifies the mode of the newly created file, if it
133	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	295	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
134	except that it is mandatory (i.e. use C<0> if you don't create new files,	296	except that it is mandatory (i.e. use C<0> if you don't create new files,
135	and C<0666> or C<0777> if you do).	297	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		298	by the umask in effect then the request is being executed, so better never
		299	change the umask.
136		300
137	Example:	301	Example:
138		302
139	aio_open "/etc/passwd", O_RDONLY, 0, sub {	303	aio_open "/etc/passwd", O_RDONLY, 0, sub {
140	if ($_[0]) {	304	if ($_[0]) {
…		…
143	} else {	307	} else {
144	die "open failed: $!\n";	308	die "open failed: $!\n";
145	}	309	}
146	};	310	};
147		311
		312
148	=item aio_close $fh, $callback->($status)	313	=item aio_close $fh, $callback->($status)
149		314
150	Asynchronously close a file and call the callback with the result	315	Asynchronously close a file and call the callback with the result
151	code. I<WARNING:> although accepted, you should not pass in a perl	316	code.
152	filehandle here, as perl will likely close the file descriptor another
153	time when the filehandle is destroyed. Normally, you can safely call perls
154	C<close> or just let filehandles go out of scope.
155		317
156	This is supposed to be a bug in the API, so that might change. It's	318	Unlike the other functions operating on files, this function uses the
157	therefore best to avoid this function.	319	PerlIO layer to close the filehandle. The reason is that the PerlIO API
		320	insists on closing the underlying fd itself, no matter what, and doesn't
		321	allow modifications to the fd. Unfortunately, it is not clear that you can
		322	call PerlIO from different threads (actually, its quite clear that this
		323	won't work in some cases), so while it likely works perfectly with simple
		324	file handles (such as the ones created by C<aio_open>) it might fail in
		325	interesting ways for others.
		326
		327	Having said that, aio_close tries to clean up the filehandle as much as
		328	possible before handing it to an io thread, and generally does work.
		329
158		330
159	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	331	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160		332
161	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	333	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
162		334
163	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	335	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
164	into the scalar given by C<data> and offset C<dataoffset> and calls the	336	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
165	callback without the actual number of bytes read (or -1 on error, just	337	callback without the actual number of bytes read (or -1 on error, just
166	like the syscall).	338	like the syscall).
167		339
		340	If C<$offset> is undefined, then the current file descriptor offset will
		341	be used (and updated), otherwise the file descriptor offset will not be
		342	changed by these calls.
		343
		344	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		345
		346	If C<$dataoffset> is less than zero, it will be counted from the end of
		347	C<$data>.
		348
168	The C<$data> scalar I<MUST NOT> be modified in any way while the request	349	The C<$data> scalar I<MUST NOT> be modified in any way while the request
169	is outstanding. Modifying it can result in segfaults or WW3 (if the	350	is outstanding. Modifying it can result in segfaults or World War III (if
170	necessary/optional hardware is installed).	351	the necessary/optional hardware is installed).
171		352
172	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	353	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
173	offset C<0> within the scalar:	354	offset C<0> within the scalar:
174		355
175	aio_read $fh, 7, 15, $buffer, 0, sub {	356	aio_read $fh, 7, 15, $buffer, 0, sub {
176	$_[0] > 0 or die "read error: $!";	357	$_[0] > 0 or die "read error: $!";
177	print "read $_[0] bytes: <$buffer>\n";	358	print "read $_[0] bytes: <$buffer>\n";
178	};	359	};
179		360
180	=item aio_move $srcpath, $dstpath, $callback->($status)
181
182	Try to move the I<file> (directories not supported as either source or
183	destination) from C<$srcpath> to C<$dstpath> and call the callback with
184	the C<0> (error) or C<-1> ok.
185
186	This is a composite request that tries to rename(2) the file first. If
187	rename files with C<EXDEV>, it creates the destination file with mode 0200
188	and copies the contents of the source file into it using C<aio_sendfile>,
189	followed by restoring atime, mtime, access mode and uid/gid, in that
190	order, and unlinking the C<$srcpath>.
191
192	If an error occurs, the partial destination file will be unlinked, if
193	possible, except when setting atime, mtime, access mode and uid/gid, where
194	errors are being ignored.
195
196	=cut
197
198	sub aio_move($$$) {
199	my ($src, $dst, $cb) = @_;
200
201	aio_rename $src, $dst, sub {
202	if ($_[0] && $! == EXDEV) {
203	aio_open $src, O_RDONLY, 0, sub {
204	if (my $src_fh = $_[0]) {
205	my @stat = stat $src_fh;
206
207	aio_open $dst, O_WRONLY, 0200, sub {
208	if (my $dst_fh = $_[0]) {
209	aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
210	close $src_fh;
211
212	if ($_[0] == $stat[7]) {
213	utime $stat[8], $stat[9], $dst;
214	chmod $stat[2] & 07777, $dst_fh;
215	chown $stat[4], $stat[5], $dst_fh;
216	close $dst_fh;
217
218	aio_unlink $src, sub {
219	$cb->($_[0]);
220	};
221	} else {
222	my $errno = $!;
223	aio_unlink $dst, sub {
224	$! = $errno;
225	$cb->(-1);
226	};
227	}
228	};
229	} else {
230	$cb->(-1);
231	}
232	},
233
234	} else {
235	$cb->(-1);
236	}
237	};
238	} else {
239	$cb->($_[0]);
240	}
241	};
242	}
243		361
244	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	362	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
245		363
246	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	364	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
247	reading at byte offset C<$in_offset>, and starts writing at the current	365	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
261	C<$in_fh> than are written, and there is no way to find out how many	379	C<$in_fh> than are written, and there is no way to find out how many
262	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	380	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
263	provides the number of bytes written to C<$out_fh>. Only if the result	381	provides the number of bytes written to C<$out_fh>. Only if the result
264	value equals C<$length> one can assume that C<$length> bytes have been	382	value equals C<$length> one can assume that C<$length> bytes have been
265	read.	383	read.
		384
266		385
267	=item aio_readahead $fh,$offset,$length, $callback->($retval)	386	=item aio_readahead $fh,$offset,$length, $callback->($retval)
268		387
269	C<aio_readahead> populates the page cache with data from a file so that	388	C<aio_readahead> populates the page cache with data from a file so that
270	subsequent reads from that file will not block on disk I/O. The C<$offset>	389	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
276	file. The current file offset of the file is left unchanged.	395	file. The current file offset of the file is left unchanged.
277		396
278	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	397	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
279	emulated by simply reading the data, which would have a similar effect.	398	emulated by simply reading the data, which would have a similar effect.
280		399
		400
281	=item aio_stat $fh_or_path, $callback->($status)	401	=item aio_stat $fh_or_path, $callback->($status)
282		402
283	=item aio_lstat $fh, $callback->($status)	403	=item aio_lstat $fh, $callback->($status)
284		404
285	Works like perl's C<stat> or C<lstat> in void context. The callback will	405	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
298	aio_stat "/etc/passwd", sub {	418	aio_stat "/etc/passwd", sub {
299	$_[0] and die "stat failed: $!";	419	$_[0] and die "stat failed: $!";
300	print "size is ", -s _, "\n";	420	print "size is ", -s _, "\n";
301	};	421	};
302		422
		423
		424	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		425
		426	Works like perl's C<utime> function (including the special case of $atime
		427	and $mtime being undef). Fractional times are supported if the underlying
		428	syscalls support them.
		429
		430	When called with a pathname, uses utimes(2) if available, otherwise
		431	utime(2). If called on a file descriptor, uses futimes(2) if available,
		432	otherwise returns ENOSYS, so this is not portable.
		433
		434	Examples:
		435
		436	# set atime and mtime to current time (basically touch(1)):
		437	aio_utime "path", undef, undef;
		438	# set atime to current time and mtime to beginning of the epoch:
		439	aio_utime "path", time, undef; # undef==0
		440
		441
		442	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		443
		444	Works like perl's C<chown> function, except that C<undef> for either $uid
		445	or $gid is being interpreted as "do not change" (but -1 can also be used).
		446
		447	Examples:
		448
		449	# same as "chown root path" in the shell:
		450	aio_chown "path", 0, -1;
		451	# same as above:
		452	aio_chown "path", 0, undef;
		453
		454
		455	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		456
		457	Works like truncate(2) or ftruncate(2).
		458
		459
		460	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		461
		462	Works like perl's C<chmod> function.
		463
		464
303	=item aio_unlink $pathname, $callback->($status)	465	=item aio_unlink $pathname, $callback->($status)
304		466
305	Asynchronously unlink (delete) a file and call the callback with the	467	Asynchronously unlink (delete) a file and call the callback with the
306	result code.	468	result code.
307		469
		470
		471	=item aio_mknod $path, $mode, $dev, $callback->($status)
		472
		473	[EXPERIMENTAL]
		474
		475	Asynchronously create a device node (or fifo). See mknod(2).
		476
		477	The only (POSIX-) portable way of calling this function is:
		478
		479	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		480
		481
308	=item aio_link $srcpath, $dstpath, $callback->($status)	482	=item aio_link $srcpath, $dstpath, $callback->($status)
309		483
310	Asynchronously create a new link to the existing object at C<$srcpath> at	484	Asynchronously create a new link to the existing object at C<$srcpath> at
311	the path C<$dstpath> and call the callback with the result code.	485	the path C<$dstpath> and call the callback with the result code.
312		486
		487
313	=item aio_symlink $srcpath, $dstpath, $callback->($status)	488	=item aio_symlink $srcpath, $dstpath, $callback->($status)
314		489
315	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	490	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
316	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.
317		492
		493
		494	=item aio_readlink $path, $callback->($link)
		495
		496	Asynchronously read the symlink specified by C<$path> and pass it to
		497	the callback. If an error occurs, nothing or undef gets passed to the
		498	callback.
		499
		500
318	=item aio_rename $srcpath, $dstpath, $callback->($status)	501	=item aio_rename $srcpath, $dstpath, $callback->($status)
319		502
320	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	503	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
321	rename(2) and call the callback with the result code.	504	rename(2) and call the callback with the result code.
322		505
		506
		507	=item aio_mkdir $pathname, $mode, $callback->($status)
		508
		509	Asynchronously mkdir (create) a directory and call the callback with
		510	the result code. C<$mode> will be modified by the umask at the time the
		511	request is executed, so do not change your umask.
		512
		513
323	=item aio_rmdir $pathname, $callback->($status)	514	=item aio_rmdir $pathname, $callback->($status)
324		515
325	Asynchronously rmdir (delete) a directory and call the callback with the	516	Asynchronously rmdir (delete) a directory and call the callback with the
326	result code.	517	result code.
		518
327		519
328	=item aio_readdir $pathname, $callback->($entries)	520	=item aio_readdir $pathname, $callback->($entries)
329		521
330	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	522	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
331	directory (i.e. opendir + readdir + closedir). The entries will not be	523	directory (i.e. opendir + readdir + closedir). The entries will not be
332	sorted, and will B<NOT> include the C<.> and C<..> entries.	524	sorted, and will B<NOT> include the C<.> and C<..> entries.
333		525
334	The callback a single argument which is either C<undef> or an array-ref	526	The callback a single argument which is either C<undef> or an array-ref
335	with the filenames.	527	with the filenames.
336		528
		529
		530	=item aio_load $path, $data, $callback->($status)
		531
		532	This is a composite request that tries to fully load the given file into
		533	memory. Status is the same as with aio_read.
		534
		535	=cut
		536
		537	sub aio_load($$;$) {
		538	aio_block {
		539	my ($path, undef, $cb) = @_;
		540	my $data = \$_[1];
		541
		542	my $pri = aioreq_pri;
		543	my $grp = aio_group $cb;
		544
		545	aioreq_pri $pri;
		546	add $grp aio_open $path, O_RDONLY, 0, sub {
		547	my $fh = shift
		548	or return $grp->result (-1);
		549
		550	aioreq_pri $pri;
		551	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		552	$grp->result ($_[0]);
		553	};
		554	};
		555
		556	$grp
		557	}
		558	}
		559
		560	=item aio_copy $srcpath, $dstpath, $callback->($status)
		561
		562	Try to copy the I<file> (directories not supported as either source or
		563	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		564	the C<0> (error) or C<-1> ok.
		565
		566	This is a composite request that it creates the destination file with
		567	mode 0200 and copies the contents of the source file into it using
		568	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		569	uid/gid, in that order.
		570
		571	If an error occurs, the partial destination file will be unlinked, if
		572	possible, except when setting atime, mtime, access mode and uid/gid, where
		573	errors are being ignored.
		574
		575	=cut
		576
		577	sub aio_copy($$;$) {
		578	aio_block {
		579	my ($src, $dst, $cb) = @_;
		580
		581	my $pri = aioreq_pri;
		582	my $grp = aio_group $cb;
		583
		584	aioreq_pri $pri;
		585	add $grp aio_open $src, O_RDONLY, 0, sub {
		586	if (my $src_fh = $_[0]) {
		587	my @stat = stat $src_fh;
		588
		589	aioreq_pri $pri;
		590	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		591	if (my $dst_fh = $_[0]) {
		592	aioreq_pri $pri;
		593	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		594	if ($_[0] == $stat[7]) {
		595	$grp->result (0);
		596	close $src_fh;
		597
		598	# those should not normally block. should. should.
		599	utime $stat[8], $stat[9], $dst;
		600	chmod $stat[2] & 07777, $dst_fh;
		601	chown $stat[4], $stat[5], $dst_fh;
		602	close $dst_fh;
		603	} else {
		604	$grp->result (-1);
		605	close $src_fh;
		606	close $dst_fh;
		607
		608	aioreq $pri;
		609	add $grp aio_unlink $dst;
		610	}
		611	};
		612	} else {
		613	$grp->result (-1);
		614	}
		615	},
		616
		617	} else {
		618	$grp->result (-1);
		619	}
		620	};
		621
		622	$grp
		623	}
		624	}
		625
		626	=item aio_move $srcpath, $dstpath, $callback->($status)
		627
		628	Try to move the I<file> (directories not supported as either source or
		629	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		630	the C<0> (error) or C<-1> ok.
		631
		632	This is a composite request that tries to rename(2) the file first. If
		633	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		634	that is successful, unlinking the C<$srcpath>.
		635
		636	=cut
		637
		638	sub aio_move($$;$) {
		639	aio_block {
		640	my ($src, $dst, $cb) = @_;
		641
		642	my $pri = aioreq_pri;
		643	my $grp = aio_group $cb;
		644
		645	aioreq_pri $pri;
		646	add $grp aio_rename $src, $dst, sub {
		647	if ($_[0] && $! == EXDEV) {
		648	aioreq_pri $pri;
		649	add $grp aio_copy $src, $dst, sub {
		650	$grp->result ($_[0]);
		651
		652	if (!$_[0]) {
		653	aioreq_pri $pri;
		654	add $grp aio_unlink $src;
		655	}
		656	};
		657	} else {
		658	$grp->result ($_[0]);
		659	}
		660	};
		661
		662	$grp
		663	}
		664	}
		665
337	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	666	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
338		667
339	Scans a directory (similar to C<aio_readdir>) but additionally tries to	668	Scans a directory (similar to C<aio_readdir>) but additionally tries to
340	separate the entries of directory C<$path> into two sets of names, ones	669	efficiently separate the entries of directory C<$path> into two sets of
341	you can recurse into (directories or links to them), and ones you cannot	670	names, directories you can recurse into (directories), and ones you cannot
342	recurse into (everything else).	671	recurse into (everything else, including symlinks to directories).
343		672
344	C<aio_scandir> is a composite request that consists of many sub	673	C<aio_scandir> is a composite request that creates of many sub requests_
345	requests. C<$maxreq> specifies the maximum number of outstanding aio	674	C<$maxreq> specifies the maximum number of outstanding aio requests that
346	requests that this function generates. If it is C<< <= 0 >>, then a	675	this function generates. If it is C<< <= 0 >>, then a suitable default
347	suitable default will be chosen (currently 8).	676	will be chosen (currently 4).
348		677
349	On error, the callback is called without arguments, otherwise it receives	678	On error, the callback is called without arguments, otherwise it receives
350	two array-refs with path-relative entry names.	679	two array-refs with path-relative entry names.
351		680
352	Example:	681	Example:
…		…
386	as those tend to return 0 or 1 as link counts, which disables the	715	as those tend to return 0 or 1 as link counts, which disables the
387	directory counting heuristic.	716	directory counting heuristic.
388		717
389	=cut	718	=cut
390		719
391	sub aio_scandir($$$) {	720	sub aio_scandir($$;$) {
		721	aio_block {
392	my ($path, $maxreq, $cb) = @_;	722	my ($path, $maxreq, $cb) = @_;
393		723
		724	my $pri = aioreq_pri;
		725
		726	my $grp = aio_group $cb;
		727
394	$maxreq = 8 if $maxreq <= 0;	728	$maxreq = 4 if $maxreq <= 0;
395		729
396	# stat once	730	# stat once
		731	aioreq_pri $pri;
397	aio_stat $path, sub {	732	add $grp aio_stat $path, sub {
398	return $cb->() if $_[0];	733	return $grp->result () if $_[0];
399	my $now = time;	734	my $now = time;
400	my $hash1 = join ":", (stat _)[0,1,3,7,9];	735	my $hash1 = join ":", (stat _)[0,1,3,7,9];
401		736
402	# read the directory entries	737	# read the directory entries
		738	aioreq_pri $pri;
403	aio_readdir $path, sub {	739	add $grp aio_readdir $path, sub {
404	my $entries = shift	740	my $entries = shift
405	or return $cb->();	741	or return $grp->result ();
406		742
407	# stat the dir another time	743	# stat the dir another time
		744	aioreq_pri $pri;
408	aio_stat $path, sub {	745	add $grp aio_stat $path, sub {
409	my $hash2 = join ":", (stat _)[0,1,3,7,9];	746	my $hash2 = join ":", (stat _)[0,1,3,7,9];
410		747
411	my $ndirs;	748	my $ndirs;
412		749
413	# take the slow route if anything looks fishy	750	# take the slow route if anything looks fishy
414	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	751	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
415	$ndirs = -1;	752	$ndirs = -1;
416	} else {	753	} else {
417	# if nlink == 2, we are finished	754	# if nlink == 2, we are finished
418	# on non-posix-fs's, we rely on nlink < 2	755	# on non-posix-fs's, we rely on nlink < 2
419	$ndirs = (stat _)[3] - 2	756	$ndirs = (stat _)[3] - 2
420	or return $cb->([], $entries);	757	or return $grp->result ([], $entries);
421	}
422
423	# sort into likely dirs and likely nondirs
424	# dirs == files without ".", short entries first
425	$entries = [map $_->[0],
426	sort { $b->[1] cmp $a->[1] }
427	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
428	@$entries];
429
430	my (@dirs, @nondirs);
431
432	my ($statcb, $schedcb);
433	my $nreq = 0;
434
435	$schedcb = sub {
436	if (@$entries) {
437	if ($nreq < $maxreq) {
438	my $ent = pop @$entries;
439	$nreq++;
440	aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
441	}
442	} elsif (!$nreq) {
443	# finished
444	undef $statcb;
445	undef $schedcb;
446	$cb->(\@dirs, \@nondirs) if $cb;
447	undef $cb;
448	}	758	}
		759
		760	# sort into likely dirs and likely nondirs
		761	# dirs == files without ".", short entries first
		762	$entries = [map $_->[0],
		763	sort { $b->[1] cmp $a->[1] }
		764	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		765	@$entries];
		766
		767	my (@dirs, @nondirs);
		768
		769	my $statgrp = add $grp aio_group sub {
		770	$grp->result (\@dirs, \@nondirs);
		771	};
		772
		773	limit $statgrp $maxreq;
		774	feed $statgrp sub {
		775	return unless @$entries;
		776	my $entry = pop @$entries;
		777
		778	aioreq_pri $pri;
		779	add $statgrp aio_stat "$path/$entry/.", sub {
		780	if ($_[0] < 0) {
		781	push @nondirs, $entry;
		782	} else {
		783	# need to check for real directory
		784	aioreq_pri $pri;
		785	add $statgrp aio_lstat "$path/$entry", sub {
		786	if (-d _) {
		787	push @dirs, $entry;
		788
		789	unless (--$ndirs) {
		790	push @nondirs, @$entries;
		791	feed $statgrp;
		792	}
		793	} else {
		794	push @nondirs, $entry;
		795	}
		796	}
		797	}
		798	};
		799	};
449	};	800	};
450	$statcb = sub {
451	my ($status, $entry) = @_;
452
453	if ($status < 0) {
454	$nreq--;
455	push @nondirs, $entry;
456	&$schedcb;
457	} else {
458	# need to check for real directory
459	aio_lstat "$path/$entry", sub {
460	$nreq--;
461
462	if (-d _) {
463	push @dirs, $entry;
464
465	if (!--$ndirs) {
466	push @nondirs, @$entries;
467	$entries = [];
468	}
469	} else {
470	push @nondirs, $entry;
471	}
472
473	&$schedcb;
474	}
475	}
476	};
477
478	&$schedcb while @$entries && $nreq < $maxreq;
479	};	801	};
480	};	802	};
		803
		804	$grp
481	};	805	}
		806	}
		807
		808	=item aio_rmtree $path, $callback->($status)
		809
		810	Delete a directory tree starting (and including) C<$path>, return the
		811	status of the final C<rmdir> only. This is a composite request that
		812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		813	everything else.
		814
		815	=cut
		816
		817	sub aio_rmtree;
		818	sub aio_rmtree($;$) {
		819	aio_block {
		820	my ($path, $cb) = @_;
		821
		822	my $pri = aioreq_pri;
		823	my $grp = aio_group $cb;
		824
		825	aioreq_pri $pri;
		826	add $grp aio_scandir $path, 0, sub {
		827	my ($dirs, $nondirs) = @_;
		828
		829	my $dirgrp = aio_group sub {
		830	add $grp aio_rmdir $path, sub {
		831	$grp->result ($_[0]);
		832	};
		833	};
		834
		835	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		836	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		837
		838	add $grp $dirgrp;
		839	};
		840
		841	$grp
		842	}
482	}	843	}
483		844
484	=item aio_fsync $fh, $callback->($status)	845	=item aio_fsync $fh, $callback->($status)
485		846
486	Asynchronously call fsync on the given filehandle and call the callback	847	Asynchronously call fsync on the given filehandle and call the callback
…		…
492	callback with the fdatasync result code.	853	callback with the fdatasync result code.
493		854
494	If this call isn't available because your OS lacks it or it couldn't be	855	If this call isn't available because your OS lacks it or it couldn't be
495	detected, it will be emulated by calling C<fsync> instead.	856	detected, it will be emulated by calling C<fsync> instead.
496		857
		858	=item aio_group $callback->(...)
		859
		860	This is a very special aio request: Instead of doing something, it is a
		861	container for other aio requests, which is useful if you want to bundle
		862	many requests into a single, composite, request with a definite callback
		863	and the ability to cancel the whole request with its subrequests.
		864
		865	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		866	for more info.
		867
		868	Example:
		869
		870	my $grp = aio_group sub {
		871	print "all stats done\n";
		872	};
		873
		874	add $grp
		875	(aio_stat ...),
		876	(aio_stat ...),
		877	...;
		878
		879	=item aio_nop $callback->()
		880
		881	This is a special request - it does nothing in itself and is only used for
		882	side effects, such as when you want to add a dummy request to a group so
		883	that finishing the requests in the group depends on executing the given
		884	code.
		885
		886	While this request does nothing, it still goes through the execution
		887	phase and still requires a worker thread. Thus, the callback will not
		888	be executed immediately but only after other requests in the queue have
		889	entered their execution phase. This can be used to measure request
		890	latency.
		891
		892	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		893
		894	Mainly used for debugging and benchmarking, this aio request puts one of
		895	the request workers to sleep for the given time.
		896
		897	While it is theoretically handy to have simple I/O scheduling requests
		898	like sleep and file handle readable/writable, the overhead this creates is
		899	immense (it blocks a thread for a long time) so do not use this function
		900	except to put your application under artificial I/O pressure.
		901
497	=back	902	=back
498		903
499	=head2 IO::AIO::CB CLASS	904	=head2 IO::AIO::REQ CLASS
500		905
501	All non-aggregate C<aio_*> functions return an object of this class when	906	All non-aggregate C<aio_*> functions return an object of this class when
502	called in non-void context.	907	called in non-void context.
503		908
504	A request always moves through the following five states in its lifetime,
505	in order: B<ready> (request has been created, but has not been executed
506	yet), B<execute> (request is currently being executed), B<pending>
507	(request has been executed but callback has not been called yet),
508	B<result> (results are being processed synchronously, includes calling the
509	callback) and B<done> (request has reached the end of its lifetime and
510	holds no resources anymore).
511
512	=over 4	909	=over 4
513		910
514	=item $req->cancel	911	=item cancel $req
515		912
516	Cancels the request, if possible. Has the effect of skipping execution	913	Cancels the request, if possible. Has the effect of skipping execution
517	when entering the B<execute> state and skipping calling the callback when	914	when entering the B<execute> state and skipping calling the callback when
518	entering the the B<result> state, but will leave the request otherwise	915	entering the the B<result> state, but will leave the request otherwise
519	untouched. That means that requests that currently execute will not be	916	untouched. That means that requests that currently execute will not be
520	stopped and resources held by the request will not be freed prematurely.	917	stopped and resources held by the request will not be freed prematurely.
521		918
		919	=item cb $req $callback->(...)
		920
		921	Replace (or simply set) the callback registered to the request.
		922
522	=back	923	=back
523		924
		925	=head2 IO::AIO::GRP CLASS
		926
		927	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		928	objects of this class, too.
		929
		930	A IO::AIO::GRP object is a special request that can contain multiple other
		931	aio requests.
		932
		933	You create one by calling the C<aio_group> constructing function with a
		934	callback that will be called when all contained requests have entered the
		935	C<done> state:
		936
		937	my $grp = aio_group sub {
		938	print "all requests are done\n";
		939	};
		940
		941	You add requests by calling the C<add> method with one or more
		942	C<IO::AIO::REQ> objects:
		943
		944	$grp->add (aio_unlink "...");
		945
		946	add $grp aio_stat "...", sub {
		947	$_[0] or return $grp->result ("error");
		948
		949	# add another request dynamically, if first succeeded
		950	add $grp aio_open "...", sub {
		951	$grp->result ("ok");
		952	};
		953	};
		954
		955	This makes it very easy to create composite requests (see the source of
		956	C<aio_move> for an application) that work and feel like simple requests.
		957
		958	=over 4
		959
		960	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		961	C<IO::AIO::poll_cb>, just like any other request.
		962
		963	=item * They can be canceled like any other request. Canceling will cancel not
		964	only the request itself, but also all requests it contains.
		965
		966	=item * They can also can also be added to other IO::AIO::GRP objects.
		967
		968	=item * You must not add requests to a group from within the group callback (or
		969	any later time).
		970
		971	=back
		972
		973	Their lifetime, simplified, looks like this: when they are empty, they
		974	will finish very quickly. If they contain only requests that are in the
		975	C<done> state, they will also finish. Otherwise they will continue to
		976	exist.
		977
		978	That means after creating a group you have some time to add requests. And
		979	in the callbacks of those requests, you can add further requests to the
		980	group. And only when all those requests have finished will the the group
		981	itself finish.
		982
		983	=over 4
		984
		985	=item add $grp ...
		986
		987	=item $grp->add (...)
		988
		989	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		990	be added, including other groups, as long as you do not create circular
		991	dependencies.
		992
		993	Returns all its arguments.
		994
		995	=item $grp->cancel_subs
		996
		997	Cancel all subrequests and clears any feeder, but not the group request
		998	itself. Useful when you queued a lot of events but got a result early.
		999
		1000	=item $grp->result (...)
		1001
		1002	Set the result value(s) that will be passed to the group callback when all
		1003	subrequests have finished and set thre groups errno to the current value
		1004	of errno (just like calling C<errno> without an error number). By default,
		1005	no argument will be passed and errno is zero.
		1006
		1007	=item $grp->errno ([$errno])
		1008
		1009	Sets the group errno value to C<$errno>, or the current value of errno
		1010	when the argument is missing.
		1011
		1012	Every aio request has an associated errno value that is restored when
		1013	the callback is invoked. This method lets you change this value from its
		1014	default (0).
		1015
		1016	Calling C<result> will also set errno, so make sure you either set C<$!>
		1017	before the call to C<result>, or call c<errno> after it.
		1018
		1019	=item feed $grp $callback->($grp)
		1020
		1021	Sets a feeder/generator on this group: every group can have an attached
		1022	generator that generates requests if idle. The idea behind this is that,
		1023	although you could just queue as many requests as you want in a group,
		1024	this might starve other requests for a potentially long time. For
		1025	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1026	requests, delaying any later requests for a long time.
		1027
		1028	To avoid this, and allow incremental generation of requests, you can
		1029	instead a group and set a feeder on it that generates those requests. The
		1030	feed callback will be called whenever there are few enough (see C<limit>,
		1031	below) requests active in the group itself and is expected to queue more
		1032	requests.
		1033
		1034	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1035	not impose any limits).
		1036
		1037	If the feed does not queue more requests when called, it will be
		1038	automatically removed from the group.
		1039
		1040	If the feed limit is C<0>, it will be set to C<2> automatically.
		1041
		1042	Example:
		1043
		1044	# stat all files in @files, but only ever use four aio requests concurrently:
		1045
		1046	my $grp = aio_group sub { print "finished\n" };
		1047	limit $grp 4;
		1048	feed $grp sub {
		1049	my $file = pop @files
		1050	or return;
		1051
		1052	add $grp aio_stat $file, sub { ... };
		1053	};
		1054
		1055	=item limit $grp $num
		1056
		1057	Sets the feeder limit for the group: The feeder will be called whenever
		1058	the group contains less than this many requests.
		1059
		1060	Setting the limit to C<0> will pause the feeding process.
		1061
		1062	=back
		1063
524	=head2 SUPPORT FUNCTIONS	1064	=head2 SUPPORT FUNCTIONS
		1065
		1066	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
525		1067
526	=over 4	1068	=over 4
527		1069
528	=item $fileno = IO::AIO::poll_fileno	1070	=item $fileno = IO::AIO::poll_fileno
529		1071
…		…
534		1076
535	See C<poll_cb> for an example.	1077	See C<poll_cb> for an example.
536		1078
537	=item IO::AIO::poll_cb	1079	=item IO::AIO::poll_cb
538		1080
539	Process all outstanding events on the result pipe. You have to call this	1081	Process some outstanding events on the result pipe. You have to call this
540	regularly. Returns the number of events processed. Returns immediately	1082	regularly. Returns the number of events processed. Returns immediately
541	when no events are outstanding.	1083	when no events are outstanding. The amount of events processed depends on
		1084	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1085
		1086	If not all requests were processed for whatever reason, the filehandle
		1087	will still be ready when C<poll_cb> returns.
542		1088
543	Example: Install an Event watcher that automatically calls	1089	Example: Install an Event watcher that automatically calls
544	IO::AIO::poll_cb with high priority:	1090	IO::AIO::poll_cb with high priority:
545		1091
546	Event->io (fd => IO::AIO::poll_fileno,	1092	Event->io (fd => IO::AIO::poll_fileno,
547	poll => 'r', async => 1,	1093	poll => 'r', async => 1,
548	cb => \&IO::AIO::poll_cb);	1094	cb => \&IO::AIO::poll_cb);
549		1095
		1096	=item IO::AIO::max_poll_reqs $nreqs
		1097
		1098	=item IO::AIO::max_poll_time $seconds
		1099
		1100	These set the maximum number of requests (default C<0>, meaning infinity)
		1101	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1102	the maximum amount of time (default C<0>, meaning infinity) spent in
		1103	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1104	of time C<poll_cb> is allowed to use).
		1105
		1106	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1107	syscall per request processed, which is not normally a problem unless your
		1108	callbacks are really really fast or your OS is really really slow (I am
		1109	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1110
		1111	Setting these is useful if you want to ensure some level of
		1112	interactiveness when perl is not fast enough to process all requests in
		1113	time.
		1114
		1115	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1116
		1117	Example: Install an Event watcher that automatically calls
		1118	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1119	program get the CPU sometimes even under high AIO load.
		1120
		1121	# try not to spend much more than 0.1s in poll_cb
		1122	IO::AIO::max_poll_time 0.1;
		1123
		1124	# use a low priority so other tasks have priority
		1125	Event->io (fd => IO::AIO::poll_fileno,
		1126	poll => 'r', nice => 1,
		1127	cb => &IO::AIO::poll_cb);
		1128
550	=item IO::AIO::poll_wait	1129	=item IO::AIO::poll_wait
551		1130
		1131	If there are any outstanding requests and none of them in the result
552	Wait till the result filehandle becomes ready for reading (simply does a	1132	phase, wait till the result filehandle becomes ready for reading (simply
553	C<select> on the filehandle. This is useful if you want to synchronously wait	1133	does a C<select> on the filehandle. This is useful if you want to
554	for some requests to finish).	1134	synchronously wait for some requests to finish).
555		1135
556	See C<nreqs> for an example.	1136	See C<nreqs> for an example.
557		1137
		1138	=item IO::AIO::poll
		1139
		1140	Waits until some requests have been handled.
		1141
		1142	Returns the number of requests processed, but is otherwise strictly
		1143	equivalent to:
		1144
		1145	IO::AIO::poll_wait, IO::AIO::poll_cb
		1146
558	=item IO::AIO::nreqs	1147	=item IO::AIO::flush
559		1148
560	Returns the number of requests currently outstanding (i.e. for which their	1149	Wait till all outstanding AIO requests have been handled.
561	callback has not been invoked yet).
562		1150
563	Example: wait till there are no outstanding requests anymore:	1151	Strictly equivalent to:
564		1152
565	IO::AIO::poll_wait, IO::AIO::poll_cb	1153	IO::AIO::poll_wait, IO::AIO::poll_cb
566	while IO::AIO::nreqs;	1154	while IO::AIO::nreqs;
567		1155
568	=item IO::AIO::flush	1156	=back
569		1157
570	Wait till all outstanding AIO requests have been handled.	1158	=head3 CONTROLLING THE NUMBER OF THREADS
571		1159
572	Strictly equivalent to:	1160	=over
573
574	IO::AIO::poll_wait, IO::AIO::poll_cb
575	while IO::AIO::nreqs;
576
577	=item IO::AIO::poll
578
579	Waits until some requests have been handled.
580
581	Strictly equivalent to:
582
583	IO::AIO::poll_wait, IO::AIO::poll_cb
584	if IO::AIO::nreqs;
585		1161
586	=item IO::AIO::min_parallel $nthreads	1162	=item IO::AIO::min_parallel $nthreads
587		1163
588	Set the minimum number of AIO threads to C<$nthreads>. The current default	1164	Set the minimum number of AIO threads to C<$nthreads>. The current
589	is C<4>, which means four asynchronous operations can be done at one time	1165	default is C<8>, which means eight asynchronous operations can execute
590	(the number of outstanding operations, however, is unlimited).	1166	concurrently at any one time (the number of outstanding requests,
		1167	however, is unlimited).
591		1168
592	IO::AIO starts threads only on demand, when an AIO request is queued and	1169	IO::AIO starts threads only on demand, when an AIO request is queued and
593	no free thread exists.	1170	no free thread exists. Please note that queueing up a hundred requests can
		1171	create demand for a hundred threads, even if it turns out that everything
		1172	is in the cache and could have been processed faster by a single thread.
594		1173
595	It is recommended to keep the number of threads low, as some Linux	1174	It is recommended to keep the number of threads relatively low, as some
596	kernel versions will scale negatively with the number of threads (higher	1175	Linux kernel versions will scale negatively with the number of threads
597	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32	1176	(higher parallelity => MUCH higher latency). With current Linux 2.6
598	threads should be fine.	1177	versions, 4-32 threads should be fine.
599		1178
600	Under most circumstances you don't need to call this function, as the	1179	Under most circumstances you don't need to call this function, as the
601	module selects a default that is suitable for low to moderate load.	1180	module selects a default that is suitable for low to moderate load.
602		1181
603	=item IO::AIO::max_parallel $nthreads	1182	=item IO::AIO::max_parallel $nthreads
…		…
612	This module automatically runs C<max_parallel 0> at program end, to ensure	1191	This module automatically runs C<max_parallel 0> at program end, to ensure
613	that all threads are killed and that there are no outstanding requests.	1192	that all threads are killed and that there are no outstanding requests.
614		1193
615	Under normal circumstances you don't need to call this function.	1194	Under normal circumstances you don't need to call this function.
616		1195
		1196	=item IO::AIO::max_idle $nthreads
		1197
		1198	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1199	threads that did not get a request to process within 10 seconds). That
		1200	means if a thread becomes idle while C<$nthreads> other threads are also
		1201	idle, it will free its resources and exit.
		1202
		1203	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1204	to allow for extremely high load situations, but want to free resources
		1205	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1206
		1207	The default is probably ok in most situations, especially if thread
		1208	creation is fast. If thread creation is very slow on your system you might
		1209	want to use larger values.
		1210
617	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1211	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1212
		1213	This is a very bad function to use in interactive programs because it
		1214	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1215	use an C<aio_group> together with a feed callback.
618		1216
619	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1217	Sets the maximum number of outstanding requests to C<$nreqs>. If you
620	try to queue up more than this number of requests, the caller will block until	1218	do queue up more than this number of requests, the next call to the
621	some requests have been handled.	1219	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1220	function will block until the limit is no longer exceeded.
622		1221
623	The default is very large, so normally there is no practical limit. If you	1222	The default value is very large, so there is no practical limit on the
624	queue up many requests in a loop it often improves speed if you set	1223	number of outstanding requests.
625	this to a relatively low number, such as C<100>.
626		1224
627	Under normal circumstances you don't need to call this function.	1225	You can still queue as many requests as you want. Therefore,
		1226	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1227	as a stop gap to shield against fatal memory overflow (with large values).
628		1228
629	=back	1229	=back
630		1230
		1231	=head3 STATISTICAL INFORMATION
		1232
		1233	=over
		1234
		1235	=item IO::AIO::nreqs
		1236
		1237	Returns the number of requests currently in the ready, execute or pending
		1238	states (i.e. for which their callback has not been invoked yet).
		1239
		1240	Example: wait till there are no outstanding requests anymore:
		1241
		1242	IO::AIO::poll_wait, IO::AIO::poll_cb
		1243	while IO::AIO::nreqs;
		1244
		1245	=item IO::AIO::nready
		1246
		1247	Returns the number of requests currently in the ready state (not yet
		1248	executed).
		1249
		1250	=item IO::AIO::npending
		1251
		1252	Returns the number of requests currently in the pending state (executed,
		1253	but not yet processed by poll_cb).
		1254
		1255	=back
		1256
631	=cut	1257	=cut
632		1258
633	# support function to convert a fd into a perl filehandle
634	sub _fd2fh {
635	return undef if $_[0] < 0;
636
637	# try to generate nice filehandles
638	my $sym = "IO::AIO::fd#$_[0]";
639	local *$sym;
640
641	open *$sym, "+<&=$_[0]" # usually works under any unix
642	or open *$sym, "<&=$_[0]" # cygwin needs this
643	or open *$sym, ">&=$_[0]" # or this
644	or return undef;
645
646	*$sym
647	}
648
649	min_parallel 4;	1259	min_parallel 8;
650		1260
651	END {	1261	END { flush }
652	max_parallel 0;
653	}
654		1262
655	1;	1263	1;
656		1264
657	=head2 FORK BEHAVIOUR	1265	=head2 FORK BEHAVIOUR
658		1266
659	This module should do "the right thing" when the process using it forks:	1267	This module should do "the right thing" when the process using it forks:
660		1268
661	Before the fork, IO::AIO enters a quiescent state where no requests	1269	Before the fork, IO::AIO enters a quiescent state where no requests
662	can be added in other threads and no results will be processed. After	1270	can be added in other threads and no results will be processed. After
663	the fork the parent simply leaves the quiescent state and continues	1271	the fork the parent simply leaves the quiescent state and continues
664	request/result processing, while the child clears the request/result	1272	request/result processing, while the child frees the request/result queue
665	queue (so the requests started before the fork will only be handled in	1273	(so that the requests started before the fork will only be handled in the
666	the parent). Threads will be started on demand until the limit ste in the	1274	parent). Threads will be started on demand until the limit set in the
667	parent process has been reached again.	1275	parent process has been reached again.
668		1276
669	In short: the parent will, after a short pause, continue as if fork had	1277	In short: the parent will, after a short pause, continue as if fork had
670	not been called, while the child will act as if IO::AIO has not been used	1278	not been called, while the child will act as if IO::AIO has not been used
671	yet.	1279	yet.
672		1280
		1281	=head2 MEMORY USAGE
		1282
		1283	Per-request usage:
		1284
		1285	Each aio request uses - depending on your architecture - around 100-200
		1286	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1287	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1288	scalars and other data passed into aio requests will also be locked and
		1289	will consume memory till the request has entered the done state.
		1290
		1291	This is not awfully much, so queuing lots of requests is not usually a
		1292	problem.
		1293
		1294	Per-thread usage:
		1295
		1296	In the execution phase, some aio requests require more memory for
		1297	temporary buffers, and each thread requires a stack and other data
		1298	structures (usually around 16k-128k, depending on the OS).
		1299
		1300	=head1 KNOWN BUGS
		1301
		1302	Known bugs will be fixed in the next release.
		1303
673	=head1 SEE ALSO	1304	=head1 SEE ALSO
674		1305
675	L<Coro>, L<Linux::AIO> (obsolete).	1306	L<Coro::AIO>.
676		1307
677	=head1 AUTHOR	1308	=head1 AUTHOR
678		1309
679	Marc Lehmann <schmorp@schmorp.de>	1310	Marc Lehmann <schmorp@schmorp.de>
680	http://home.schmorp.de/	1311	http://home.schmorp.de/

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