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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.32 by root, Wed Aug 17 05:26:20 2005 UTC vs.
Revision 1.117 by root, Sat Oct 6 14:05:19 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	# Event	21	# version 2+ has request and group objects
		22	use IO::AIO 2;
		23
		24	aioreq_pri 4; # give next request a very high priority
		25	my $req = aio_unlink "/tmp/file", sub { };
		26	$req->cancel; # cancel request if still in queue
		27
		28	my $grp = aio_group sub { print "all stats done\n" };
		29	add $grp aio_stat "..." for ...;
		30
		31	# AnyEvent integration
		32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
		33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
		34
		35	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	36	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	37	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	38	cb => \&IO::AIO::poll_cb);
24		39
25	# Glib/Gtk2	40	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	41	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	42	in => sub { IO::AIO::poll_cb; 1 };
28		43
29	# Tk	44	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	46	readable => \&IO::AIO::poll_cb);
32		47
33	# Danga::Socket	48	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	50	\&IO::AIO::poll_cb);
36		51
37
38	=head1 DESCRIPTION	52	=head1 DESCRIPTION
39		53
40	This module implements asynchronous I/O using whatever means your	54	This module implements asynchronous I/O using whatever means your
41	operating system supports.	55	operating system supports.
42		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
43	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
44	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
45	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
46	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
47	aio functions available on many operating systems. However, they are often	77	functions available on many operating systems. However, they are often
48	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
49	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
50	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.
51		82
52	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,
53	currently not reentrant, so use appropriate locking yourself, always call	84	it is currently not reentrant in any way, so use appropriate locking
54	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
55	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
56		183
57	=cut	184	=cut
58		185
59	package IO::AIO;	186	package IO::AIO;
60		187
		188	use Carp ();
		189
61	no warnings;	190	no warnings;
		191	use strict 'vars';
62		192
63	use base 'Exporter';	193	use base 'Exporter';
64		194
65	use Fcntl ();
66
67	BEGIN {	195	BEGIN {
68	$VERSION = 1.3;	196	our $VERSION = '2.51';
69		197
70		198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
71	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	199	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
72	aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);	200	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
73	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	201	aio_move aio_copy aio_group aio_nop aio_mknod aio_load aio_rmtree aio_mkdir
		202	aio_chown aio_chmod aio_utime aio_truncate);
		203	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));
		204	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		205	min_parallel max_parallel max_idle
		206	nreqs nready npending nthreads
		207	max_poll_time max_poll_reqs);
		208
		209	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
74		210
75	require XSLoader;	211	require XSLoader;
76	XSLoader::load IO::AIO, $VERSION;	212	XSLoader::load ("IO::AIO", $VERSION);
77	}	213	}
78		214
79	=head1 FUNCTIONS	215	=head1 FUNCTIONS
80		216
81	=head2 AIO FUNCTIONS	217	=head2 AIO REQUEST FUNCTIONS
82		218
83	All the C<aio_*> calls are more or less thin wrappers around the syscall	219	All the C<aio_*> calls are more or less thin wrappers around the syscall
84	with the same name (sans C<aio_>). The arguments are similar or identical,	220	with the same name (sans C<aio_>). The arguments are similar or identical,
85	and they all accept an additional (and optional) C<$callback> argument	221	and they all accept an additional (and optional) C<$callback> argument
86	which must be a code reference. This code reference will get called with	222	which must be a code reference. This code reference will get called with
…		…
89	syscall has been executed asynchronously.	225	syscall has been executed asynchronously.
90		226
91	All functions expecting a filehandle keep a copy of the filehandle	227	All functions expecting a filehandle keep a copy of the filehandle
92	internally until the request has finished.	228	internally until the request has finished.
93		229
		230	All functions return request objects of type L<IO::AIO::REQ> that allow
		231	further manipulation of those requests while they are in-flight.
		232
94	The pathnames you pass to these routines I<must> be absolute and	233	The pathnames you pass to these routines I<must> be absolute and
95	encoded in byte form. The reason for the former is that at the time the	234	encoded as octets. The reason for the former is that at the time the
96	request is being executed, the current working directory could have	235	request is being executed, the current working directory could have
97	changed. Alternatively, you can make sure that you never change the	236	changed. Alternatively, you can make sure that you never change the
98	current working directory.	237	current working directory anywhere in the program and then use relative
		238	paths.
99		239
100	To encode pathnames to byte form, either make sure you either: a)	240	To encode pathnames as octets, either make sure you either: a) always pass
101	always pass in filenames you got from outside (command line, readdir	241	in filenames you got from outside (command line, readdir etc.) without
102	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	242	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
103	your pathnames to the locale (or other) encoding in effect in the user	243	your pathnames to the locale (or other) encoding in effect in the user
104	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	244	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
105	use something else.	245	use something else to ensure your scalar has the correct contents.
		246
		247	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		248	handles correctly wether it is set or not.
106		249
107	=over 4	250	=over 4
108		251
		252	=item $prev_pri = aioreq_pri [$pri]
		253
		254	Returns the priority value that would be used for the next request and, if
		255	C<$pri> is given, sets the priority for the next aio request.
		256
		257	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		258	and C<4>, respectively. Requests with higher priority will be serviced
		259	first.
		260
		261	The priority will be reset to C<0> after each call to one of the C<aio_*>
		262	functions.
		263
		264	Example: open a file with low priority, then read something from it with
		265	higher priority so the read request is serviced before other low priority
		266	open requests (potentially spamming the cache):
		267
		268	aioreq_pri -3;
		269	aio_open ..., sub {
		270	return unless $_[0];
		271
		272	aioreq_pri -2;
		273	aio_read $_[0], ..., sub {
		274	...
		275	};
		276	};
		277
		278
		279	=item aioreq_nice $pri_adjust
		280
		281	Similar to C<aioreq_pri>, but subtracts the given value from the current
		282	priority, so the effect is cumulative.
		283
		284
109	=item aio_open $pathname, $flags, $mode, $callback	285	=item aio_open $pathname, $flags, $mode, $callback->($fh)
110		286
111	Asynchronously open or create a file and call the callback with a newly	287	Asynchronously open or create a file and call the callback with a newly
112	created filehandle for the file.	288	created filehandle for the file.
113		289
114	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	290	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
118	list. They are the same as used by C<sysopen>.	294	list. They are the same as used by C<sysopen>.
119		295
120	Likewise, C<$mode> specifies the mode of the newly created file, if it	296	Likewise, C<$mode> specifies the mode of the newly created file, if it
121	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	297	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
122	except that it is mandatory (i.e. use C<0> if you don't create new files,	298	except that it is mandatory (i.e. use C<0> if you don't create new files,
123	and C<0666> or C<0777> if you do).	299	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		300	by the umask in effect then the request is being executed, so better never
		301	change the umask.
124		302
125	Example:	303	Example:
126		304
127	aio_open "/etc/passwd", O_RDONLY, 0, sub {	305	aio_open "/etc/passwd", O_RDONLY, 0, sub {
128	if ($_[0]) {	306	if ($_[0]) {
…		…
131	} else {	309	} else {
132	die "open failed: $!\n";	310	die "open failed: $!\n";
133	}	311	}
134	};	312	};
135		313
		314
136	=item aio_close $fh, $callback	315	=item aio_close $fh, $callback->($status)
137		316
138	Asynchronously close a file and call the callback with the result	317	Asynchronously close a file and call the callback with the result
139	code. I<WARNING:> although accepted, you should not pass in a perl	318	code.
140	filehandle here, as perl will likely close the file descriptor another
141	time when the filehandle is destroyed. Normally, you can safely call perls
142	C<close> or just let filehandles go out of scope.
143		319
144	This is supposed to be a bug in the API, so that might change. It's	320	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
145	therefore best to avoid this function.	321	closing the file descriptor associated with the filehandle itself. Here is
		322	what aio_close will try:
146		323
		324	1. dup()licate the fd
		325	2. asynchronously close() the duplicated fd
		326	3. dup()licate the fd once more
		327	4. let perl close() the filehandle
		328	5. asynchronously close the duplicated fd
		329
		330	The idea is that the first close() flushes stuff to disk that closing an
		331	fd will flush, so when perl closes the fd, nothing much will need to be
		332	flushed. The second async. close() will then flush stuff to disk that
		333	closing the last fd to the file will flush.
		334
		335	Just FYI, SuSv3 has this to say on close:
		336
		337	All outstanding record locks owned by the process on the file
		338	associated with the file descriptor shall be removed.
		339
		340	If fildes refers to a socket, close() shall cause the socket to be
		341	destroyed. ... close() shall block for up to the current linger
		342	interval until all data is transmitted.
		343	[this actually sounds like a specification bug, but who knows]
		344
		345	And at least Linux additionally actually flushes stuff on every close,
		346	even when the file itself is still open.
		347
		348	Sounds enourmously inefficient and complicated? Yes... please show me how
		349	to nuke perl's fd out of existence...
		350
		351	=cut
		352
		353	sub aio_close($;$) {
		354	aio_block {
		355	my ($fh, $cb) = @_;
		356
		357	my $pri = aioreq_pri;
		358	my $grp = aio_group $cb;
		359
		360	my $fd = fileno $fh;
		361
		362	defined $fd or Carp::croak "aio_close called with fd-less filehandle";
		363
		364	# if the dups fail we will simply get EBADF
		365	my $fd2 = _dup $fd;
		366	aioreq_pri $pri;
		367	add $grp _aio_close $fd2, sub {
		368	my $fd2 = _dup $fd;
		369	close $fh;
		370	aioreq_pri $pri;
		371	add $grp _aio_close $fd2, sub {
		372	$grp->result ($_[0]);
		373	};
		374	};
		375
		376	$grp
		377	}
		378	}
		379
		380
147	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	381	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
148		382
149	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	383	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
150		384
151	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	385	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
152	into the scalar given by C<data> and offset C<dataoffset> and calls the	386	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
153	callback without the actual number of bytes read (or -1 on error, just	387	callback without the actual number of bytes read (or -1 on error, just
154	like the syscall).	388	like the syscall).
155		389
		390	If C<$offset> is undefined, then the current file descriptor offset will
		391	be used (and updated), otherwise the file descriptor offset will not be
		392	changed by these calls.
		393
		394	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		395
		396	If C<$dataoffset> is less than zero, it will be counted from the end of
		397	C<$data>.
		398
156	The C<$data> scalar I<MUST NOT> be modified in any way while the request	399	The C<$data> scalar I<MUST NOT> be modified in any way while the request
157	is outstanding. Modifying it can result in segfaults or WW3 (if the	400	is outstanding. Modifying it can result in segfaults or World War III (if
158	necessary/optional hardware is installed).	401	the necessary/optional hardware is installed).
159		402
160	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	403	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
161	offset C<0> within the scalar:	404	offset C<0> within the scalar:
162		405
163	aio_read $fh, 7, 15, $buffer, 0, sub {	406	aio_read $fh, 7, 15, $buffer, 0, sub {
164	$_[0] > 0 or die "read error: $!";	407	$_[0] > 0 or die "read error: $!";
165	print "read $_[0] bytes: <$buffer>\n";	408	print "read $_[0] bytes: <$buffer>\n";
166	};	409	};
167		410
		411
		412	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		413
		414	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		415	reading at byte offset C<$in_offset>, and starts writing at the current
		416	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		417	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		418	other.
		419
		420	This call tries to make use of a native C<sendfile> syscall to provide
		421	zero-copy operation. For this to work, C<$out_fh> should refer to a
		422	socket, and C<$in_fh> should refer to mmap'able file.
		423
		424	If the native sendfile call fails or is not implemented, it will be
		425	emulated, so you can call C<aio_sendfile> on any type of filehandle
		426	regardless of the limitations of the operating system.
		427
		428	Please note, however, that C<aio_sendfile> can read more bytes from
		429	C<$in_fh> than are written, and there is no way to find out how many
		430	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		431	provides the number of bytes written to C<$out_fh>. Only if the result
		432	value equals C<$length> one can assume that C<$length> bytes have been
		433	read.
		434
		435
168	=item aio_readahead $fh,$offset,$length, $callback	436	=item aio_readahead $fh,$offset,$length, $callback->($retval)
169		437
170	C<aio_readahead> populates the page cache with data from a file so that	438	C<aio_readahead> populates the page cache with data from a file so that
171	subsequent reads from that file will not block on disk I/O. The C<$offset>	439	subsequent reads from that file will not block on disk I/O. The C<$offset>
172	argument specifies the starting point from which data is to be read and	440	argument specifies the starting point from which data is to be read and
173	C<$length> specifies the number of bytes to be read. I/O is performed in	441	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
177	file. The current file offset of the file is left unchanged.	445	file. The current file offset of the file is left unchanged.
178		446
179	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	447	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
180	emulated by simply reading the data, which would have a similar effect.	448	emulated by simply reading the data, which would have a similar effect.
181		449
		450
182	=item aio_stat $fh_or_path, $callback	451	=item aio_stat $fh_or_path, $callback->($status)
183		452
184	=item aio_lstat $fh, $callback	453	=item aio_lstat $fh, $callback->($status)
185		454
186	Works like perl's C<stat> or C<lstat> in void context. The callback will	455	Works like perl's C<stat> or C<lstat> in void context. The callback will
187	be called after the stat and the results will be available using C<stat _>	456	be called after the stat and the results will be available using C<stat _>
188	or C<-s _> etc...	457	or C<-s _> etc...
189		458
…		…
199	aio_stat "/etc/passwd", sub {	468	aio_stat "/etc/passwd", sub {
200	$_[0] and die "stat failed: $!";	469	$_[0] and die "stat failed: $!";
201	print "size is ", -s _, "\n";	470	print "size is ", -s _, "\n";
202	};	471	};
203		472
		473
		474	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		475
		476	Works like perl's C<utime> function (including the special case of $atime
		477	and $mtime being undef). Fractional times are supported if the underlying
		478	syscalls support them.
		479
		480	When called with a pathname, uses utimes(2) if available, otherwise
		481	utime(2). If called on a file descriptor, uses futimes(2) if available,
		482	otherwise returns ENOSYS, so this is not portable.
		483
		484	Examples:
		485
		486	# set atime and mtime to current time (basically touch(1)):
		487	aio_utime "path", undef, undef;
		488	# set atime to current time and mtime to beginning of the epoch:
		489	aio_utime "path", time, undef; # undef==0
		490
		491
		492	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		493
		494	Works like perl's C<chown> function, except that C<undef> for either $uid
		495	or $gid is being interpreted as "do not change" (but -1 can also be used).
		496
		497	Examples:
		498
		499	# same as "chown root path" in the shell:
		500	aio_chown "path", 0, -1;
		501	# same as above:
		502	aio_chown "path", 0, undef;
		503
		504
		505	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		506
		507	Works like truncate(2) or ftruncate(2).
		508
		509
		510	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		511
		512	Works like perl's C<chmod> function.
		513
		514
204	=item aio_unlink $pathname, $callback	515	=item aio_unlink $pathname, $callback->($status)
205		516
206	Asynchronously unlink (delete) a file and call the callback with the	517	Asynchronously unlink (delete) a file and call the callback with the
207	result code.	518	result code.
208		519
		520
		521	=item aio_mknod $path, $mode, $dev, $callback->($status)
		522
		523	[EXPERIMENTAL]
		524
		525	Asynchronously create a device node (or fifo). See mknod(2).
		526
		527	The only (POSIX-) portable way of calling this function is:
		528
		529	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		530
		531
		532	=item aio_link $srcpath, $dstpath, $callback->($status)
		533
		534	Asynchronously create a new link to the existing object at C<$srcpath> at
		535	the path C<$dstpath> and call the callback with the result code.
		536
		537
		538	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		539
		540	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		541	the path C<$dstpath> and call the callback with the result code.
		542
		543
		544	=item aio_readlink $path, $callback->($link)
		545
		546	Asynchronously read the symlink specified by C<$path> and pass it to
		547	the callback. If an error occurs, nothing or undef gets passed to the
		548	callback.
		549
		550
		551	=item aio_rename $srcpath, $dstpath, $callback->($status)
		552
		553	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		554	rename(2) and call the callback with the result code.
		555
		556
		557	=item aio_mkdir $pathname, $mode, $callback->($status)
		558
		559	Asynchronously mkdir (create) a directory and call the callback with
		560	the result code. C<$mode> will be modified by the umask at the time the
		561	request is executed, so do not change your umask.
		562
		563
209	=item aio_rmdir $pathname, $callback	564	=item aio_rmdir $pathname, $callback->($status)
210		565
211	Asynchronously rmdir (delete) a directory and call the callback with the	566	Asynchronously rmdir (delete) a directory and call the callback with the
212	result code.	567	result code.
213		568
		569
		570	=item aio_readdir $pathname, $callback->($entries)
		571
		572	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		573	directory (i.e. opendir + readdir + closedir). The entries will not be
		574	sorted, and will B<NOT> include the C<.> and C<..> entries.
		575
		576	The callback a single argument which is either C<undef> or an array-ref
		577	with the filenames.
		578
		579
		580	=item aio_load $path, $data, $callback->($status)
		581
		582	This is a composite request that tries to fully load the given file into
		583	memory. Status is the same as with aio_read.
		584
		585	=cut
		586
		587	sub aio_load($$;$) {
		588	aio_block {
		589	my ($path, undef, $cb) = @_;
		590	my $data = \$_[1];
		591
		592	my $pri = aioreq_pri;
		593	my $grp = aio_group $cb;
		594
		595	aioreq_pri $pri;
		596	add $grp aio_open $path, O_RDONLY, 0, sub {
		597	my $fh = shift
		598	or return $grp->result (-1);
		599
		600	aioreq_pri $pri;
		601	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		602	$grp->result ($_[0]);
		603	};
		604	};
		605
		606	$grp
		607	}
		608	}
		609
		610	=item aio_copy $srcpath, $dstpath, $callback->($status)
		611
		612	Try to copy the I<file> (directories not supported as either source or
		613	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		614	the C<0> (error) or C<-1> ok.
		615
		616	This is a composite request that it creates the destination file with
		617	mode 0200 and copies the contents of the source file into it using
		618	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		619	uid/gid, in that order.
		620
		621	If an error occurs, the partial destination file will be unlinked, if
		622	possible, except when setting atime, mtime, access mode and uid/gid, where
		623	errors are being ignored.
		624
		625	=cut
		626
		627	sub aio_copy($$;$) {
		628	aio_block {
		629	my ($src, $dst, $cb) = @_;
		630
		631	my $pri = aioreq_pri;
		632	my $grp = aio_group $cb;
		633
		634	aioreq_pri $pri;
		635	add $grp aio_open $src, O_RDONLY, 0, sub {
		636	if (my $src_fh = $_[0]) {
		637	my @stat = stat $src_fh;
		638
		639	aioreq_pri $pri;
		640	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		641	if (my $dst_fh = $_[0]) {
		642	aioreq_pri $pri;
		643	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		644	if ($_[0] == $stat[7]) {
		645	$grp->result (0);
		646	close $src_fh;
		647
		648	# those should not normally block. should. should.
		649	utime $stat[8], $stat[9], $dst;
		650	chmod $stat[2] & 07777, $dst_fh;
		651	chown $stat[4], $stat[5], $dst_fh;
		652	close $dst_fh;
		653	} else {
		654	$grp->result (-1);
		655	close $src_fh;
		656	close $dst_fh;
		657
		658	aioreq $pri;
		659	add $grp aio_unlink $dst;
		660	}
		661	};
		662	} else {
		663	$grp->result (-1);
		664	}
		665	},
		666
		667	} else {
		668	$grp->result (-1);
		669	}
		670	};
		671
		672	$grp
		673	}
		674	}
		675
		676	=item aio_move $srcpath, $dstpath, $callback->($status)
		677
		678	Try to move the I<file> (directories not supported as either source or
		679	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		680	the C<0> (error) or C<-1> ok.
		681
		682	This is a composite request that tries to rename(2) the file first. If
		683	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		684	that is successful, unlinking the C<$srcpath>.
		685
		686	=cut
		687
		688	sub aio_move($$;$) {
		689	aio_block {
		690	my ($src, $dst, $cb) = @_;
		691
		692	my $pri = aioreq_pri;
		693	my $grp = aio_group $cb;
		694
		695	aioreq_pri $pri;
		696	add $grp aio_rename $src, $dst, sub {
		697	if ($_[0] && $! == EXDEV) {
		698	aioreq_pri $pri;
		699	add $grp aio_copy $src, $dst, sub {
		700	$grp->result ($_[0]);
		701
		702	if (!$_[0]) {
		703	aioreq_pri $pri;
		704	add $grp aio_unlink $src;
		705	}
		706	};
		707	} else {
		708	$grp->result ($_[0]);
		709	}
		710	};
		711
		712	$grp
		713	}
		714	}
		715
		716	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		717
		718	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		719	efficiently separate the entries of directory C<$path> into two sets of
		720	names, directories you can recurse into (directories), and ones you cannot
		721	recurse into (everything else, including symlinks to directories).
		722
		723	C<aio_scandir> is a composite request that creates of many sub requests_
		724	C<$maxreq> specifies the maximum number of outstanding aio requests that
		725	this function generates. If it is C<< <= 0 >>, then a suitable default
		726	will be chosen (currently 4).
		727
		728	On error, the callback is called without arguments, otherwise it receives
		729	two array-refs with path-relative entry names.
		730
		731	Example:
		732
		733	aio_scandir $dir, 0, sub {
		734	my ($dirs, $nondirs) = @_;
		735	print "real directories: @$dirs\n";
		736	print "everything else: @$nondirs\n";
		737	};
		738
		739	Implementation notes.
		740
		741	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		742
		743	After reading the directory, the modification time, size etc. of the
		744	directory before and after the readdir is checked, and if they match (and
		745	isn't the current time), the link count will be used to decide how many
		746	entries are directories (if >= 2). Otherwise, no knowledge of the number
		747	of subdirectories will be assumed.
		748
		749	Then entries will be sorted into likely directories (everything without
		750	a non-initial dot currently) and likely non-directories (everything
		751	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		752	likely directories first. If that succeeds, it assumes that the entry
		753	is a directory or a symlink to directory (which will be checked
		754	seperately). This is often faster than stat'ing the entry itself because
		755	filesystems might detect the type of the entry without reading the inode
		756	data (e.g. ext2fs filetype feature).
		757
		758	If the known number of directories (link count - 2) has been reached, the
		759	rest of the entries is assumed to be non-directories.
		760
		761	This only works with certainty on POSIX (= UNIX) filesystems, which
		762	fortunately are the vast majority of filesystems around.
		763
		764	It will also likely work on non-POSIX filesystems with reduced efficiency
		765	as those tend to return 0 or 1 as link counts, which disables the
		766	directory counting heuristic.
		767
		768	=cut
		769
		770	sub aio_scandir($$;$) {
		771	aio_block {
		772	my ($path, $maxreq, $cb) = @_;
		773
		774	my $pri = aioreq_pri;
		775
		776	my $grp = aio_group $cb;
		777
		778	$maxreq = 4 if $maxreq <= 0;
		779
		780	# stat once
		781	aioreq_pri $pri;
		782	add $grp aio_stat $path, sub {
		783	return $grp->result () if $_[0];
		784	my $now = time;
		785	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		786
		787	# read the directory entries
		788	aioreq_pri $pri;
		789	add $grp aio_readdir $path, sub {
		790	my $entries = shift
		791	or return $grp->result ();
		792
		793	# stat the dir another time
		794	aioreq_pri $pri;
		795	add $grp aio_stat $path, sub {
		796	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		797
		798	my $ndirs;
		799
		800	# take the slow route if anything looks fishy
		801	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		802	$ndirs = -1;
		803	} else {
		804	# if nlink == 2, we are finished
		805	# on non-posix-fs's, we rely on nlink < 2
		806	$ndirs = (stat _)[3] - 2
		807	or return $grp->result ([], $entries);
		808	}
		809
		810	# sort into likely dirs and likely nondirs
		811	# dirs == files without ".", short entries first
		812	$entries = [map $_->[0],
		813	sort { $b->[1] cmp $a->[1] }
		814	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		815	@$entries];
		816
		817	my (@dirs, @nondirs);
		818
		819	my $statgrp = add $grp aio_group sub {
		820	$grp->result (\@dirs, \@nondirs);
		821	};
		822
		823	limit $statgrp $maxreq;
		824	feed $statgrp sub {
		825	return unless @$entries;
		826	my $entry = pop @$entries;
		827
		828	aioreq_pri $pri;
		829	add $statgrp aio_stat "$path/$entry/.", sub {
		830	if ($_[0] < 0) {
		831	push @nondirs, $entry;
		832	} else {
		833	# need to check for real directory
		834	aioreq_pri $pri;
		835	add $statgrp aio_lstat "$path/$entry", sub {
		836	if (-d _) {
		837	push @dirs, $entry;
		838
		839	unless (--$ndirs) {
		840	push @nondirs, @$entries;
		841	feed $statgrp;
		842	}
		843	} else {
		844	push @nondirs, $entry;
		845	}
		846	}
		847	}
		848	};
		849	};
		850	};
		851	};
		852	};
		853
		854	$grp
		855	}
		856	}
		857
		858	=item aio_rmtree $path, $callback->($status)
		859
		860	Delete a directory tree starting (and including) C<$path>, return the
		861	status of the final C<rmdir> only. This is a composite request that
		862	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		863	everything else.
		864
		865	=cut
		866
		867	sub aio_rmtree;
		868	sub aio_rmtree($;$) {
		869	aio_block {
		870	my ($path, $cb) = @_;
		871
		872	my $pri = aioreq_pri;
		873	my $grp = aio_group $cb;
		874
		875	aioreq_pri $pri;
		876	add $grp aio_scandir $path, 0, sub {
		877	my ($dirs, $nondirs) = @_;
		878
		879	my $dirgrp = aio_group sub {
		880	add $grp aio_rmdir $path, sub {
		881	$grp->result ($_[0]);
		882	};
		883	};
		884
		885	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		886	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		887
		888	add $grp $dirgrp;
		889	};
		890
		891	$grp
		892	}
		893	}
		894
214	=item aio_fsync $fh, $callback	895	=item aio_fsync $fh, $callback->($status)
215		896
216	Asynchronously call fsync on the given filehandle and call the callback	897	Asynchronously call fsync on the given filehandle and call the callback
217	with the fsync result code.	898	with the fsync result code.
218		899
219	=item aio_fdatasync $fh, $callback	900	=item aio_fdatasync $fh, $callback->($status)
220		901
221	Asynchronously call fdatasync on the given filehandle and call the	902	Asynchronously call fdatasync on the given filehandle and call the
222	callback with the fdatasync result code.	903	callback with the fdatasync result code.
223		904
224	If this call isn't available because your OS lacks it or it couldn't be	905	If this call isn't available because your OS lacks it or it couldn't be
225	detected, it will be emulated by calling C<fsync> instead.	906	detected, it will be emulated by calling C<fsync> instead.
226		907
		908	=item aio_group $callback->(...)
		909
		910	This is a very special aio request: Instead of doing something, it is a
		911	container for other aio requests, which is useful if you want to bundle
		912	many requests into a single, composite, request with a definite callback
		913	and the ability to cancel the whole request with its subrequests.
		914
		915	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		916	for more info.
		917
		918	Example:
		919
		920	my $grp = aio_group sub {
		921	print "all stats done\n";
		922	};
		923
		924	add $grp
		925	(aio_stat ...),
		926	(aio_stat ...),
		927	...;
		928
		929	=item aio_nop $callback->()
		930
		931	This is a special request - it does nothing in itself and is only used for
		932	side effects, such as when you want to add a dummy request to a group so
		933	that finishing the requests in the group depends on executing the given
		934	code.
		935
		936	While this request does nothing, it still goes through the execution
		937	phase and still requires a worker thread. Thus, the callback will not
		938	be executed immediately but only after other requests in the queue have
		939	entered their execution phase. This can be used to measure request
		940	latency.
		941
		942	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		943
		944	Mainly used for debugging and benchmarking, this aio request puts one of
		945	the request workers to sleep for the given time.
		946
		947	While it is theoretically handy to have simple I/O scheduling requests
		948	like sleep and file handle readable/writable, the overhead this creates is
		949	immense (it blocks a thread for a long time) so do not use this function
		950	except to put your application under artificial I/O pressure.
		951
227	=back	952	=back
228		953
		954	=head2 IO::AIO::REQ CLASS
		955
		956	All non-aggregate C<aio_*> functions return an object of this class when
		957	called in non-void context.
		958
		959	=over 4
		960
		961	=item cancel $req
		962
		963	Cancels the request, if possible. Has the effect of skipping execution
		964	when entering the B<execute> state and skipping calling the callback when
		965	entering the the B<result> state, but will leave the request otherwise
		966	untouched. That means that requests that currently execute will not be
		967	stopped and resources held by the request will not be freed prematurely.
		968
		969	=item cb $req $callback->(...)
		970
		971	Replace (or simply set) the callback registered to the request.
		972
		973	=back
		974
		975	=head2 IO::AIO::GRP CLASS
		976
		977	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		978	objects of this class, too.
		979
		980	A IO::AIO::GRP object is a special request that can contain multiple other
		981	aio requests.
		982
		983	You create one by calling the C<aio_group> constructing function with a
		984	callback that will be called when all contained requests have entered the
		985	C<done> state:
		986
		987	my $grp = aio_group sub {
		988	print "all requests are done\n";
		989	};
		990
		991	You add requests by calling the C<add> method with one or more
		992	C<IO::AIO::REQ> objects:
		993
		994	$grp->add (aio_unlink "...");
		995
		996	add $grp aio_stat "...", sub {
		997	$_[0] or return $grp->result ("error");
		998
		999	# add another request dynamically, if first succeeded
		1000	add $grp aio_open "...", sub {
		1001	$grp->result ("ok");
		1002	};
		1003	};
		1004
		1005	This makes it very easy to create composite requests (see the source of
		1006	C<aio_move> for an application) that work and feel like simple requests.
		1007
		1008	=over 4
		1009
		1010	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1011	C<IO::AIO::poll_cb>, just like any other request.
		1012
		1013	=item * They can be canceled like any other request. Canceling will cancel not
		1014	only the request itself, but also all requests it contains.
		1015
		1016	=item * They can also can also be added to other IO::AIO::GRP objects.
		1017
		1018	=item * You must not add requests to a group from within the group callback (or
		1019	any later time).
		1020
		1021	=back
		1022
		1023	Their lifetime, simplified, looks like this: when they are empty, they
		1024	will finish very quickly. If they contain only requests that are in the
		1025	C<done> state, they will also finish. Otherwise they will continue to
		1026	exist.
		1027
		1028	That means after creating a group you have some time to add requests. And
		1029	in the callbacks of those requests, you can add further requests to the
		1030	group. And only when all those requests have finished will the the group
		1031	itself finish.
		1032
		1033	=over 4
		1034
		1035	=item add $grp ...
		1036
		1037	=item $grp->add (...)
		1038
		1039	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1040	be added, including other groups, as long as you do not create circular
		1041	dependencies.
		1042
		1043	Returns all its arguments.
		1044
		1045	=item $grp->cancel_subs
		1046
		1047	Cancel all subrequests and clears any feeder, but not the group request
		1048	itself. Useful when you queued a lot of events but got a result early.
		1049
		1050	=item $grp->result (...)
		1051
		1052	Set the result value(s) that will be passed to the group callback when all
		1053	subrequests have finished and set thre groups errno to the current value
		1054	of errno (just like calling C<errno> without an error number). By default,
		1055	no argument will be passed and errno is zero.
		1056
		1057	=item $grp->errno ([$errno])
		1058
		1059	Sets the group errno value to C<$errno>, or the current value of errno
		1060	when the argument is missing.
		1061
		1062	Every aio request has an associated errno value that is restored when
		1063	the callback is invoked. This method lets you change this value from its
		1064	default (0).
		1065
		1066	Calling C<result> will also set errno, so make sure you either set C<$!>
		1067	before the call to C<result>, or call c<errno> after it.
		1068
		1069	=item feed $grp $callback->($grp)
		1070
		1071	Sets a feeder/generator on this group: every group can have an attached
		1072	generator that generates requests if idle. The idea behind this is that,
		1073	although you could just queue as many requests as you want in a group,
		1074	this might starve other requests for a potentially long time. For
		1075	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1076	requests, delaying any later requests for a long time.
		1077
		1078	To avoid this, and allow incremental generation of requests, you can
		1079	instead a group and set a feeder on it that generates those requests. The
		1080	feed callback will be called whenever there are few enough (see C<limit>,
		1081	below) requests active in the group itself and is expected to queue more
		1082	requests.
		1083
		1084	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1085	not impose any limits).
		1086
		1087	If the feed does not queue more requests when called, it will be
		1088	automatically removed from the group.
		1089
		1090	If the feed limit is C<0>, it will be set to C<2> automatically.
		1091
		1092	Example:
		1093
		1094	# stat all files in @files, but only ever use four aio requests concurrently:
		1095
		1096	my $grp = aio_group sub { print "finished\n" };
		1097	limit $grp 4;
		1098	feed $grp sub {
		1099	my $file = pop @files
		1100	or return;
		1101
		1102	add $grp aio_stat $file, sub { ... };
		1103	};
		1104
		1105	=item limit $grp $num
		1106
		1107	Sets the feeder limit for the group: The feeder will be called whenever
		1108	the group contains less than this many requests.
		1109
		1110	Setting the limit to C<0> will pause the feeding process.
		1111
		1112	=back
		1113
229	=head2 SUPPORT FUNCTIONS	1114	=head2 SUPPORT FUNCTIONS
		1115
		1116	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
230		1117
231	=over 4	1118	=over 4
232		1119
233	=item $fileno = IO::AIO::poll_fileno	1120	=item $fileno = IO::AIO::poll_fileno
234		1121
…		…
239		1126
240	See C<poll_cb> for an example.	1127	See C<poll_cb> for an example.
241		1128
242	=item IO::AIO::poll_cb	1129	=item IO::AIO::poll_cb
243		1130
244	Process all outstanding events on the result pipe. You have to call this	1131	Process some outstanding events on the result pipe. You have to call this
245	regularly. Returns the number of events processed. Returns immediately	1132	regularly. Returns the number of events processed. Returns immediately
246	when no events are outstanding.	1133	when no events are outstanding. The amount of events processed depends on
		1134	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1135
		1136	If not all requests were processed for whatever reason, the filehandle
		1137	will still be ready when C<poll_cb> returns.
247		1138
248	Example: Install an Event watcher that automatically calls	1139	Example: Install an Event watcher that automatically calls
249	IO::AIO::poll_cb with high priority:	1140	IO::AIO::poll_cb with high priority:
250		1141
251	Event->io (fd => IO::AIO::poll_fileno,	1142	Event->io (fd => IO::AIO::poll_fileno,
252	poll => 'r', async => 1,	1143	poll => 'r', async => 1,
253	cb => \&IO::AIO::poll_cb);	1144	cb => \&IO::AIO::poll_cb);
254		1145
		1146	=item IO::AIO::max_poll_reqs $nreqs
		1147
		1148	=item IO::AIO::max_poll_time $seconds
		1149
		1150	These set the maximum number of requests (default C<0>, meaning infinity)
		1151	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1152	the maximum amount of time (default C<0>, meaning infinity) spent in
		1153	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1154	of time C<poll_cb> is allowed to use).
		1155
		1156	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1157	syscall per request processed, which is not normally a problem unless your
		1158	callbacks are really really fast or your OS is really really slow (I am
		1159	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1160
		1161	Setting these is useful if you want to ensure some level of
		1162	interactiveness when perl is not fast enough to process all requests in
		1163	time.
		1164
		1165	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1166
		1167	Example: Install an Event watcher that automatically calls
		1168	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1169	program get the CPU sometimes even under high AIO load.
		1170
		1171	# try not to spend much more than 0.1s in poll_cb
		1172	IO::AIO::max_poll_time 0.1;
		1173
		1174	# use a low priority so other tasks have priority
		1175	Event->io (fd => IO::AIO::poll_fileno,
		1176	poll => 'r', nice => 1,
		1177	cb => &IO::AIO::poll_cb);
		1178
255	=item IO::AIO::poll_wait	1179	=item IO::AIO::poll_wait
256		1180
		1181	If there are any outstanding requests and none of them in the result
257	Wait till the result filehandle becomes ready for reading (simply does a	1182	phase, wait till the result filehandle becomes ready for reading (simply
258	C<select> on the filehandle. This is useful if you want to synchronously wait	1183	does a C<select> on the filehandle. This is useful if you want to
259	for some requests to finish).	1184	synchronously wait for some requests to finish).
260		1185
261	See C<nreqs> for an example.	1186	See C<nreqs> for an example.
262		1187
		1188	=item IO::AIO::poll
		1189
		1190	Waits until some requests have been handled.
		1191
		1192	Returns the number of requests processed, but is otherwise strictly
		1193	equivalent to:
		1194
		1195	IO::AIO::poll_wait, IO::AIO::poll_cb
		1196
263	=item IO::AIO::nreqs	1197	=item IO::AIO::flush
264		1198
265	Returns the number of requests currently outstanding (i.e. for which their	1199	Wait till all outstanding AIO requests have been handled.
266	callback has not been invoked yet).
267		1200
268	Example: wait till there are no outstanding requests anymore:	1201	Strictly equivalent to:
269		1202
270	IO::AIO::poll_wait, IO::AIO::poll_cb	1203	IO::AIO::poll_wait, IO::AIO::poll_cb
271	while IO::AIO::nreqs;	1204	while IO::AIO::nreqs;
272		1205
		1206	=back
		1207
		1208	=head3 CONTROLLING THE NUMBER OF THREADS
		1209
		1210	=over
		1211
		1212	=item IO::AIO::min_parallel $nthreads
		1213
		1214	Set the minimum number of AIO threads to C<$nthreads>. The current
		1215	default is C<8>, which means eight asynchronous operations can execute
		1216	concurrently at any one time (the number of outstanding requests,
		1217	however, is unlimited).
		1218
		1219	IO::AIO starts threads only on demand, when an AIO request is queued and
		1220	no free thread exists. Please note that queueing up a hundred requests can
		1221	create demand for a hundred threads, even if it turns out that everything
		1222	is in the cache and could have been processed faster by a single thread.
		1223
		1224	It is recommended to keep the number of threads relatively low, as some
		1225	Linux kernel versions will scale negatively with the number of threads
		1226	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1227	versions, 4-32 threads should be fine.
		1228
		1229	Under most circumstances you don't need to call this function, as the
		1230	module selects a default that is suitable for low to moderate load.
		1231
		1232	=item IO::AIO::max_parallel $nthreads
		1233
		1234	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1235	specified number of threads are currently running, this function kills
		1236	them. This function blocks until the limit is reached.
		1237
		1238	While C<$nthreads> are zero, aio requests get queued but not executed
		1239	until the number of threads has been increased again.
		1240
		1241	This module automatically runs C<max_parallel 0> at program end, to ensure
		1242	that all threads are killed and that there are no outstanding requests.
		1243
		1244	Under normal circumstances you don't need to call this function.
		1245
		1246	=item IO::AIO::max_idle $nthreads
		1247
		1248	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1249	threads that did not get a request to process within 10 seconds). That
		1250	means if a thread becomes idle while C<$nthreads> other threads are also
		1251	idle, it will free its resources and exit.
		1252
		1253	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1254	to allow for extremely high load situations, but want to free resources
		1255	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1256
		1257	The default is probably ok in most situations, especially if thread
		1258	creation is fast. If thread creation is very slow on your system you might
		1259	want to use larger values.
		1260
		1261	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1262
		1263	This is a very bad function to use in interactive programs because it
		1264	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1265	use an C<aio_group> together with a feed callback.
		1266
		1267	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1268	do queue up more than this number of requests, the next call to the
		1269	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1270	function will block until the limit is no longer exceeded.
		1271
		1272	The default value is very large, so there is no practical limit on the
		1273	number of outstanding requests.
		1274
		1275	You can still queue as many requests as you want. Therefore,
		1276	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1277	as a stop gap to shield against fatal memory overflow (with large values).
		1278
		1279	=back
		1280
		1281	=head3 STATISTICAL INFORMATION
		1282
		1283	=over
		1284
273	=item IO::AIO::flush	1285	=item IO::AIO::nreqs
274		1286
275	Wait till all outstanding AIO requests have been handled.	1287	Returns the number of requests currently in the ready, execute or pending
		1288	states (i.e. for which their callback has not been invoked yet).
276		1289
277	Strictly equivalent to:	1290	Example: wait till there are no outstanding requests anymore:
278		1291
279	IO::AIO::poll_wait, IO::AIO::poll_cb	1292	IO::AIO::poll_wait, IO::AIO::poll_cb
280	while IO::AIO::nreqs;	1293	while IO::AIO::nreqs;
281		1294
		1295	=item IO::AIO::nready
		1296
		1297	Returns the number of requests currently in the ready state (not yet
		1298	executed).
		1299
282	=item IO::AIO::poll	1300	=item IO::AIO::npending
283		1301
284	Waits until some requests have been handled.	1302	Returns the number of requests currently in the pending state (executed,
285		1303	but not yet processed by poll_cb).
286	Strictly equivalent to:
287
288	IO::AIO::poll_wait, IO::AIO::poll_cb
289	if IO::AIO::nreqs;
290
291	=item IO::AIO::min_parallel $nthreads
292
293	Set the minimum number of AIO threads to C<$nthreads>. The default is
294	C<1>, which means a single asynchronous operation can be done at one time
295	(the number of outstanding operations, however, is unlimited).
296
297	It is recommended to keep the number of threads low, as some Linux
298	kernel versions will scale negatively with the number of threads (higher
299	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
300	threads should be fine.
301
302	Under normal circumstances you don't need to call this function, as this
303	module automatically starts some threads (the exact number might change,
304	and is currently 4).
305
306	=item IO::AIO::max_parallel $nthreads
307
308	Sets the maximum number of AIO threads to C<$nthreads>. If more than
309	the specified number of threads are currently running, kill them. This
310	function blocks until the limit is reached.
311
312	This module automatically runs C<max_parallel 0> at program end, to ensure
313	that all threads are killed and that there are no outstanding requests.
314
315	Under normal circumstances you don't need to call this function.
316
317	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
318
319	Sets the maximum number of outstanding requests to C<$nreqs>. If you
320	try to queue up more than this number of requests, the caller will block until
321	some requests have been handled.
322
323	The default is very large, so normally there is no practical limit. If you
324	queue up many requests in a loop it it often improves speed if you set
325	this to a relatively low number, such as C<100>.
326
327	Under normal circumstances you don't need to call this function.
328		1304
329	=back	1305	=back
330		1306
331	=cut	1307	=cut
332		1308
333	# support function to convert a fd into a perl filehandle
334	sub _fd2fh {
335	return undef if $_[0] < 0;
336
337	# try to generate nice filehandles
338	my $sym = "IO::AIO::fd#$_[0]";
339	local *$sym;
340
341	open *$sym, "+<&=$_[0]" # usually works under any unix
342	or open *$sym, "<&=$_[0]" # cygwin needs this
343	or open *$sym, ">&=$_[0]" # or this
344	or return undef;
345
346	*$sym
347	}
348
349	min_parallel 4;	1309	min_parallel 8;
350		1310
351	END {	1311	END { flush }
352	max_parallel 0;
353	}
354		1312
355	1;	1313	1;
356		1314
357	=head2 FORK BEHAVIOUR	1315	=head2 FORK BEHAVIOUR
358		1316
		1317	This module should do "the right thing" when the process using it forks:
		1318
359	Before the fork IO::AIO enters a quiescent state where no requests can be	1319	Before the fork, IO::AIO enters a quiescent state where no requests
360	added in other threads and no results will be processed. After the fork	1320	can be added in other threads and no results will be processed. After
361	the parent simply leaves the quiescent state and continues request/result	1321	the fork the parent simply leaves the quiescent state and continues
362	processing, while the child clears the request/result queue and starts the	1322	request/result processing, while the child frees the request/result queue
363	same number of threads as were in use by the parent.	1323	(so that the requests started before the fork will only be handled in the
		1324	parent). Threads will be started on demand until the limit set in the
		1325	parent process has been reached again.
		1326
		1327	In short: the parent will, after a short pause, continue as if fork had
		1328	not been called, while the child will act as if IO::AIO has not been used
		1329	yet.
		1330
		1331	=head2 MEMORY USAGE
		1332
		1333	Per-request usage:
		1334
		1335	Each aio request uses - depending on your architecture - around 100-200
		1336	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1337	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1338	scalars and other data passed into aio requests will also be locked and
		1339	will consume memory till the request has entered the done state.
		1340
		1341	This is not awfully much, so queuing lots of requests is not usually a
		1342	problem.
		1343
		1344	Per-thread usage:
		1345
		1346	In the execution phase, some aio requests require more memory for
		1347	temporary buffers, and each thread requires a stack and other data
		1348	structures (usually around 16k-128k, depending on the OS).
		1349
		1350	=head1 KNOWN BUGS
		1351
		1352	Known bugs will be fixed in the next release.
364		1353
365	=head1 SEE ALSO	1354	=head1 SEE ALSO
366		1355
367	L<Coro>, L<Linux::AIO>.	1356	L<Coro::AIO>.
368		1357
369	=head1 AUTHOR	1358	=head1 AUTHOR
370		1359
371	Marc Lehmann <schmorp@schmorp.de>	1360	Marc Lehmann <schmorp@schmorp.de>
372	http://home.schmorp.de/	1361	http://home.schmorp.de/

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