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Revision 1.21 by root, Wed Jul 13 00:13:09 2005 UTC vs.
Revision 1.124 by root, Sat May 10 19:25:33 2008 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
16	aio_read $fh, 30000, 1024, $buffer, 0, sub {	17	aio_read $fh, 30000, 1024, $buffer, 0, sub {
17	$_[0] > 0 or die "read error: $!";	18	$_[0] > 0 or die "read error: $!";
18	};	19	};
19		20
20	# 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 (EV, Event, Glib, Tk, urxvt, pureperl...)
		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	# EV integration
		36	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		37
		38	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	39	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	40	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	41	cb => \&IO::AIO::poll_cb);
24		42
25	# Glib/Gtk2	43	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	44	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb, 1 };	45	in => sub { IO::AIO::poll_cb; 1 };
28		46
29	# Tk	47	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	48	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	49	readable => \&IO::AIO::poll_cb);
32		50
33	# Danga::Socket	51	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	52	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	53	\&IO::AIO::poll_cb);
36		54
37
38	=head1 DESCRIPTION	55	=head1 DESCRIPTION
39		56
40	This module implements asynchronous I/O using whatever means your	57	This module implements asynchronous I/O using whatever means your
41	operating system supports.	58	operating system supports.
42		59
		60	Asynchronous means that operations that can normally block your program
		61	(e.g. reading from disk) will be done asynchronously: the operation
		62	will still block, but you can do something else in the meantime. This
		63	is extremely useful for programs that need to stay interactive even
		64	when doing heavy I/O (GUI programs, high performance network servers
		65	etc.), but can also be used to easily do operations in parallel that are
		66	normally done sequentially, e.g. stat'ing many files, which is much faster
		67	on a RAID volume or over NFS when you do a number of stat operations
		68	concurrently.
		69
		70	While most of this works on all types of file descriptors (for
		71	example sockets), using these functions on file descriptors that
		72	support nonblocking operation (again, sockets, pipes etc.) is very
		73	inefficient. Use an event loop for that (such as the L<Event|Event>
		74	module): IO::AIO will naturally fit into such an event loop itself.
		75
43	Currently, a number of threads are started that execute your read/writes	76	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	77	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	78	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	79	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	80	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	81	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	82	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	83	aio_write, so the remaining functionality would have to be implemented
		84	using threads anyway.
51		85
52	Although the module will work with in the presence of other threads, it is	86	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself.	87	it is currently not reentrant in any way, so use appropriate locking
		88	yourself, always call C<poll_cb> from within the same thread, or never
		89	call C<poll_cb> (or other C<aio_> functions) recursively.
		90
		91	=head2 EXAMPLE
		92
		93	This is a simple example that uses the Event module and loads
		94	F</etc/passwd> asynchronously:
		95
		96	use Fcntl;
		97	use Event;
		98	use IO::AIO;
		99
		100	# register the IO::AIO callback with Event
		101	Event->io (fd => IO::AIO::poll_fileno,
		102	poll => 'r',
		103	cb => \&IO::AIO::poll_cb);
		104
		105	# queue the request to open /etc/passwd
		106	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		107	my $fh = shift
		108	or die "error while opening: $!";
		109
		110	# stat'ing filehandles is generally non-blocking
		111	my $size = -s $fh;
		112
		113	# queue a request to read the file
		114	my $contents;
		115	aio_read $fh, 0, $size, $contents, 0, sub {
		116	$_[0] == $size
		117	or die "short read: $!";
		118
		119	close $fh;
		120
		121	# file contents now in $contents
		122	print $contents;
		123
		124	# exit event loop and program
		125	Event::unloop;
		126	};
		127	};
		128
		129	# possibly queue up other requests, or open GUI windows,
		130	# check for sockets etc. etc.
		131
		132	# process events as long as there are some:
		133	Event::loop;
		134
		135	=head1 REQUEST ANATOMY AND LIFETIME
		136
		137	Every C<aio_*> function creates a request. which is a C data structure not
		138	directly visible to Perl.
		139
		140	If called in non-void context, every request function returns a Perl
		141	object representing the request. In void context, nothing is returned,
		142	which saves a bit of memory.
		143
		144	The perl object is a fairly standard ref-to-hash object. The hash contents
		145	are not used by IO::AIO so you are free to store anything you like in it.
		146
		147	During their existance, aio requests travel through the following states,
		148	in order:
		149
		150	=over 4
		151
		152	=item ready
		153
		154	Immediately after a request is created it is put into the ready state,
		155	waiting for a thread to execute it.
		156
		157	=item execute
		158
		159	A thread has accepted the request for processing and is currently
		160	executing it (e.g. blocking in read).
		161
		162	=item pending
		163
		164	The request has been executed and is waiting for result processing.
		165
		166	While request submission and execution is fully asynchronous, result
		167	processing is not and relies on the perl interpreter calling C<poll_cb>
		168	(or another function with the same effect).
		169
		170	=item result
		171
		172	The request results are processed synchronously by C<poll_cb>.
		173
		174	The C<poll_cb> function will process all outstanding aio requests by
		175	calling their callbacks, freeing memory associated with them and managing
		176	any groups they are contained in.
		177
		178	=item done
		179
		180	Request has reached the end of its lifetime and holds no resources anymore
		181	(except possibly for the Perl object, but its connection to the actual
		182	aio request is severed and calling its methods will either do nothing or
		183	result in a runtime error).
		184
		185	=back
54		186
55	=cut	187	=cut
56		188
57	package IO::AIO;	189	package IO::AIO;
58		190
		191	use Carp ();
		192
		193	no warnings;
		194	use strict 'vars';
		195
59	use base 'Exporter';	196	use base 'Exporter';
60		197
61	use Fcntl ();
62
63	BEGIN {	198	BEGIN {
64	$VERSION = 0.9;	199	our $VERSION = '3.0';
65		200
66	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	201	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
		202	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
		203	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
67	aio_fsync aio_fdatasync aio_readahead);	204	aio_fdatasync aio_pathsync aio_readahead
68	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	205	aio_rename aio_link aio_move aio_copy aio_group
		206	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		207	aio_chmod aio_utime aio_truncate);
		208
		209	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		210	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		211	min_parallel max_parallel max_idle
		212	nreqs nready npending nthreads
		213	max_poll_time max_poll_reqs);
		214
		215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
69		216
70	require XSLoader;	217	require XSLoader;
71	XSLoader::load IO::AIO, $VERSION;	218	XSLoader::load ("IO::AIO", $VERSION);
72	}	219	}
73		220
74	=head1 FUNCTIONS	221	=head1 FUNCTIONS
75		222
76	=head2 AIO FUNCTIONS	223	=head2 AIO REQUEST FUNCTIONS
77		224
78	All the C<aio_*> calls are more or less thin wrappers around the syscall	225	All the C<aio_*> calls are more or less thin wrappers around the syscall
79	with the same name (sans C<aio_>). The arguments are similar or identical,	226	with the same name (sans C<aio_>). The arguments are similar or identical,
80	and they all accept an additional (and optional) C<$callback> argument	227	and they all accept an additional (and optional) C<$callback> argument
81	which must be a code reference. This code reference will get called with	228	which must be a code reference. This code reference will get called with
82	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	229	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
83	perl, which usually delivers "false") as it's sole argument when the given	230	perl, which usually delivers "false") as it's sole argument when the given
84	syscall has been executed asynchronously.	231	syscall has been executed asynchronously.
85		232
86	All functions that expect a filehandle will also accept a file descriptor.	233	All functions expecting a filehandle keep a copy of the filehandle
		234	internally until the request has finished.
87		235
		236	All functions return request objects of type L<IO::AIO::REQ> that allow
		237	further manipulation of those requests while they are in-flight.
		238
88	The filenames you pass to these routines I<must> be absolute. The reason	239	The pathnames you pass to these routines I<must> be absolute and
89	for this is that at the time the request is being executed, the current	240	encoded as octets. The reason for the former is that at the time the
90	working directory could have changed. Alternatively, you can make sure	241	request is being executed, the current working directory could have
91	that you never change the current working directory.	242	changed. Alternatively, you can make sure that you never change the
		243	current working directory anywhere in the program and then use relative
		244	paths.
		245
		246	To encode pathnames as octets, either make sure you either: a) always pass
		247	in filenames you got from outside (command line, readdir etc.) without
		248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		249	your pathnames to the locale (or other) encoding in effect in the user
		250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		251	use something else to ensure your scalar has the correct contents.
		252
		253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		254	handles correctly wether it is set or not.
92		255
93	=over 4	256	=over 4
94		257
		258	=item $prev_pri = aioreq_pri [$pri]
		259
		260	Returns the priority value that would be used for the next request and, if
		261	C<$pri> is given, sets the priority for the next aio request.
		262
		263	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		264	and C<4>, respectively. Requests with higher priority will be serviced
		265	first.
		266
		267	The priority will be reset to C<0> after each call to one of the C<aio_*>
		268	functions.
		269
		270	Example: open a file with low priority, then read something from it with
		271	higher priority so the read request is serviced before other low priority
		272	open requests (potentially spamming the cache):
		273
		274	aioreq_pri -3;
		275	aio_open ..., sub {
		276	return unless $_[0];
		277
		278	aioreq_pri -2;
		279	aio_read $_[0], ..., sub {
		280	...
		281	};
		282	};
		283
		284
		285	=item aioreq_nice $pri_adjust
		286
		287	Similar to C<aioreq_pri>, but subtracts the given value from the current
		288	priority, so the effect is cumulative.
		289
		290
95	=item aio_open $pathname, $flags, $mode, $callback	291	=item aio_open $pathname, $flags, $mode, $callback->($fh)
96		292
97	Asynchronously open or create a file and call the callback with a newly	293	Asynchronously open or create a file and call the callback with a newly
98	created filehandle for the file.	294	created filehandle for the file.
99		295
100	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	296	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
104	list. They are the same as used by C<sysopen>.	300	list. They are the same as used by C<sysopen>.
105		301
106	Likewise, C<$mode> specifies the mode of the newly created file, if it	302	Likewise, C<$mode> specifies the mode of the newly created file, if it
107	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	303	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
108	except that it is mandatory (i.e. use C<0> if you don't create new files,	304	except that it is mandatory (i.e. use C<0> if you don't create new files,
109	and C<0666> or C<0777> if you do).	305	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		306	by the umask in effect then the request is being executed, so better never
		307	change the umask.
110		308
111	Example:	309	Example:
112		310
113	aio_open "/etc/passwd", O_RDONLY, 0, sub {	311	aio_open "/etc/passwd", O_RDONLY, 0, sub {
114	if ($_[0]) {	312	if ($_[0]) {
…		…
117	} else {	315	} else {
118	die "open failed: $!\n";	316	die "open failed: $!\n";
119	}	317	}
120	};	318	};
121		319
		320
122	=item aio_close $fh, $callback	321	=item aio_close $fh, $callback->($status)
123		322
124	Asynchronously close a file and call the callback with the result	323	Asynchronously close a file and call the callback with the result
125	code. I<WARNING:> although accepted, you should not pass in a perl	324	code.
126	filehandle here, as perl will likely close the file descriptor another
127	time when the filehandle is destroyed. Normally, you can safely call perls
128	C<close> or just let filehandles go out of scope.
129		325
130	This is supposed to be a bug in the API, so that might change. It's	326	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
131	therefore best to avoid this function.	327	closing the file descriptor associated with the filehandle itself.
132		328
		329	Therefore, C<aio_close> will not close the filehandle - instead it will
		330	use dup2 to overwrite the file descriptor with the write-end of a pipe
		331	(the pipe fd will be created on demand and will be cached).
		332
		333	Or in other words: the file descriptor will be closed, but it will not be
		334	free for reuse until the perl filehandle is closed.
		335
		336	=cut
		337
133	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
134		339
135	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
136		341
137	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	342	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
138	into the scalar given by C<data> and offset C<dataoffset> and calls the	343	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
139	callback without the actual number of bytes read (or -1 on error, just	344	callback without the actual number of bytes read (or -1 on error, just
140	like the syscall).	345	like the syscall).
		346
		347	If C<$offset> is undefined, then the current file descriptor offset will
		348	be used (and updated), otherwise the file descriptor offset will not be
		349	changed by these calls.
		350
		351	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		352
		353	If C<$dataoffset> is less than zero, it will be counted from the end of
		354	C<$data>.
		355
		356	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		357	is outstanding. Modifying it can result in segfaults or World War III (if
		358	the necessary/optional hardware is installed).
141		359
142	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	360	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
143	offset C<0> within the scalar:	361	offset C<0> within the scalar:
144		362
145	aio_read $fh, 7, 15, $buffer, 0, sub {	363	aio_read $fh, 7, 15, $buffer, 0, sub {
146	$_[0] > 0 or die "read error: $!";	364	$_[0] > 0 or die "read error: $!";
147	print "read $_[0] bytes: <$buffer>\n";	365	print "read $_[0] bytes: <$buffer>\n";
148	};	366	};
149		367
		368
		369	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		370
		371	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		372	reading at byte offset C<$in_offset>, and starts writing at the current
		373	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		374	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		375	other.
		376
		377	This call tries to make use of a native C<sendfile> syscall to provide
		378	zero-copy operation. For this to work, C<$out_fh> should refer to a
		379	socket, and C<$in_fh> should refer to mmap'able file.
		380
		381	If the native sendfile call fails or is not implemented, it will be
		382	emulated, so you can call C<aio_sendfile> on any type of filehandle
		383	regardless of the limitations of the operating system.
		384
		385	Please note, however, that C<aio_sendfile> can read more bytes from
		386	C<$in_fh> than are written, and there is no way to find out how many
		387	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		388	provides the number of bytes written to C<$out_fh>. Only if the result
		389	value equals C<$length> one can assume that C<$length> bytes have been
		390	read.
		391
		392
150	=item aio_readahead $fh,$offset,$length, $callback	393	=item aio_readahead $fh,$offset,$length, $callback->($retval)
151
152	Asynchronously reads the specified byte range into the page cache, using
153	the C<readahead> syscall. If that syscall doesn't exist (likely if your OS
154	isn't Linux) the status will be C<-1> and C<$!> is set to C<ENOSYS>.
155		394
156	C<aio_readahead> populates the page cache with data from a file so that	395	C<aio_readahead> populates the page cache with data from a file so that
157	subsequent reads from that file will not block on disk I/O. The C<$offset>	396	subsequent reads from that file will not block on disk I/O. The C<$offset>
158	argument specifies the starting point from which data is to be read and	397	argument specifies the starting point from which data is to be read and
159	C<$length> specifies the number of bytes to be read. I/O is performed in	398	C<$length> specifies the number of bytes to be read. I/O is performed in
160	whole pages, so that offset is effectively rounded down to a page boundary	399	whole pages, so that offset is effectively rounded down to a page boundary
161	and bytes are read up to the next page boundary greater than or equal to	400	and bytes are read up to the next page boundary greater than or equal to
162	(off-set+length). C<aio_readahead> does not read beyond the end of the	401	(off-set+length). C<aio_readahead> does not read beyond the end of the
163	file. The current file offset of the file is left unchanged.	402	file. The current file offset of the file is left unchanged.
164		403
		404	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
		405	emulated by simply reading the data, which would have a similar effect.
		406
		407
165	=item aio_stat $fh_or_path, $callback	408	=item aio_stat $fh_or_path, $callback->($status)
166		409
167	=item aio_lstat $fh, $callback	410	=item aio_lstat $fh, $callback->($status)
168		411
169	Works like perl's C<stat> or C<lstat> in void context. The callback will	412	Works like perl's C<stat> or C<lstat> in void context. The callback will
170	be called after the stat and the results will be available using C<stat _>	413	be called after the stat and the results will be available using C<stat _>
171	or C<-s _> etc...	414	or C<-s _> etc...
172		415
…		…
182	aio_stat "/etc/passwd", sub {	425	aio_stat "/etc/passwd", sub {
183	$_[0] and die "stat failed: $!";	426	$_[0] and die "stat failed: $!";
184	print "size is ", -s _, "\n";	427	print "size is ", -s _, "\n";
185	};	428	};
186		429
		430
		431	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		432
		433	Works like perl's C<utime> function (including the special case of $atime
		434	and $mtime being undef). Fractional times are supported if the underlying
		435	syscalls support them.
		436
		437	When called with a pathname, uses utimes(2) if available, otherwise
		438	utime(2). If called on a file descriptor, uses futimes(2) if available,
		439	otherwise returns ENOSYS, so this is not portable.
		440
		441	Examples:
		442
		443	# set atime and mtime to current time (basically touch(1)):
		444	aio_utime "path", undef, undef;
		445	# set atime to current time and mtime to beginning of the epoch:
		446	aio_utime "path", time, undef; # undef==0
		447
		448
		449	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		450
		451	Works like perl's C<chown> function, except that C<undef> for either $uid
		452	or $gid is being interpreted as "do not change" (but -1 can also be used).
		453
		454	Examples:
		455
		456	# same as "chown root path" in the shell:
		457	aio_chown "path", 0, -1;
		458	# same as above:
		459	aio_chown "path", 0, undef;
		460
		461
		462	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		463
		464	Works like truncate(2) or ftruncate(2).
		465
		466
		467	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		468
		469	Works like perl's C<chmod> function.
		470
		471
187	=item aio_unlink $pathname, $callback	472	=item aio_unlink $pathname, $callback->($status)
188		473
189	Asynchronously unlink (delete) a file and call the callback with the	474	Asynchronously unlink (delete) a file and call the callback with the
190	result code.	475	result code.
191		476
		477
		478	=item aio_mknod $path, $mode, $dev, $callback->($status)
		479
		480	[EXPERIMENTAL]
		481
		482	Asynchronously create a device node (or fifo). See mknod(2).
		483
		484	The only (POSIX-) portable way of calling this function is:
		485
		486	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		487
		488
		489	=item aio_link $srcpath, $dstpath, $callback->($status)
		490
		491	Asynchronously create a new link to the existing object at C<$srcpath> at
		492	the path C<$dstpath> and call the callback with the result code.
		493
		494
		495	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		496
		497	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		498	the path C<$dstpath> and call the callback with the result code.
		499
		500
		501	=item aio_readlink $path, $callback->($link)
		502
		503	Asynchronously read the symlink specified by C<$path> and pass it to
		504	the callback. If an error occurs, nothing or undef gets passed to the
		505	callback.
		506
		507
		508	=item aio_rename $srcpath, $dstpath, $callback->($status)
		509
		510	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		511	rename(2) and call the callback with the result code.
		512
		513
		514	=item aio_mkdir $pathname, $mode, $callback->($status)
		515
		516	Asynchronously mkdir (create) a directory and call the callback with
		517	the result code. C<$mode> will be modified by the umask at the time the
		518	request is executed, so do not change your umask.
		519
		520
		521	=item aio_rmdir $pathname, $callback->($status)
		522
		523	Asynchronously rmdir (delete) a directory and call the callback with the
		524	result code.
		525
		526
		527	=item aio_readdir $pathname, $callback->($entries)
		528
		529	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		530	directory (i.e. opendir + readdir + closedir). The entries will not be
		531	sorted, and will B<NOT> include the C<.> and C<..> entries.
		532
		533	The callback a single argument which is either C<undef> or an array-ref
		534	with the filenames.
		535
		536
		537	=item aio_load $path, $data, $callback->($status)
		538
		539	This is a composite request that tries to fully load the given file into
		540	memory. Status is the same as with aio_read.
		541
		542	=cut
		543
		544	sub aio_load($$;$) {
		545	my ($path, undef, $cb) = @_;
		546	my $data = \$_[1];
		547
		548	my $pri = aioreq_pri;
		549	my $grp = aio_group $cb;
		550
		551	aioreq_pri $pri;
		552	add $grp aio_open $path, O_RDONLY, 0, sub {
		553	my $fh = shift
		554	or return $grp->result (-1);
		555
		556	aioreq_pri $pri;
		557	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		558	$grp->result ($_[0]);
		559	};
		560	};
		561
		562	$grp
		563	}
		564
		565	=item aio_copy $srcpath, $dstpath, $callback->($status)
		566
		567	Try to copy the I<file> (directories not supported as either source or
		568	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		569	the C<0> (error) or C<-1> ok.
		570
		571	This is a composite request that it creates the destination file with
		572	mode 0200 and copies the contents of the source file into it using
		573	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		574	uid/gid, in that order.
		575
		576	If an error occurs, the partial destination file will be unlinked, if
		577	possible, except when setting atime, mtime, access mode and uid/gid, where
		578	errors are being ignored.
		579
		580	=cut
		581
		582	sub aio_copy($$;$) {
		583	my ($src, $dst, $cb) = @_;
		584
		585	my $pri = aioreq_pri;
		586	my $grp = aio_group $cb;
		587
		588	aioreq_pri $pri;
		589	add $grp aio_open $src, O_RDONLY, 0, sub {
		590	if (my $src_fh = $_[0]) {
		591	my @stat = stat $src_fh;
		592
		593	aioreq_pri $pri;
		594	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		595	if (my $dst_fh = $_[0]) {
		596	aioreq_pri $pri;
		597	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		598	if ($_[0] == $stat[7]) {
		599	$grp->result (0);
		600	close $src_fh;
		601
		602	# those should not normally block. should. should.
		603	utime $stat[8], $stat[9], $dst;
		604	chmod $stat[2] & 07777, $dst_fh;
		605	chown $stat[4], $stat[5], $dst_fh;
		606
		607	aioreq_pri $pri;
		608	add $grp aio_close $dst_fh;
		609	} else {
		610	$grp->result (-1);
		611	close $src_fh;
		612	close $dst_fh;
		613
		614	aioreq $pri;
		615	add $grp aio_unlink $dst;
		616	}
		617	};
		618	} else {
		619	$grp->result (-1);
		620	}
		621	},
		622
		623	} else {
		624	$grp->result (-1);
		625	}
		626	};
		627
		628	$grp
		629	}
		630
		631	=item aio_move $srcpath, $dstpath, $callback->($status)
		632
		633	Try to move the I<file> (directories not supported as either source or
		634	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		635	the C<0> (error) or C<-1> ok.
		636
		637	This is a composite request that tries to rename(2) the file first. If
		638	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		639	that is successful, unlinking the C<$srcpath>.
		640
		641	=cut
		642
		643	sub aio_move($$;$) {
		644	my ($src, $dst, $cb) = @_;
		645
		646	my $pri = aioreq_pri;
		647	my $grp = aio_group $cb;
		648
		649	aioreq_pri $pri;
		650	add $grp aio_rename $src, $dst, sub {
		651	if ($_[0] && $! == EXDEV) {
		652	aioreq_pri $pri;
		653	add $grp aio_copy $src, $dst, sub {
		654	$grp->result ($_[0]);
		655
		656	if (!$_[0]) {
		657	aioreq_pri $pri;
		658	add $grp aio_unlink $src;
		659	}
		660	};
		661	} else {
		662	$grp->result ($_[0]);
		663	}
		664	};
		665
		666	$grp
		667	}
		668
		669	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		670
		671	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		672	efficiently separate the entries of directory C<$path> into two sets of
		673	names, directories you can recurse into (directories), and ones you cannot
		674	recurse into (everything else, including symlinks to directories).
		675
		676	C<aio_scandir> is a composite request that creates of many sub requests_
		677	C<$maxreq> specifies the maximum number of outstanding aio requests that
		678	this function generates. If it is C<< <= 0 >>, then a suitable default
		679	will be chosen (currently 4).
		680
		681	On error, the callback is called without arguments, otherwise it receives
		682	two array-refs with path-relative entry names.
		683
		684	Example:
		685
		686	aio_scandir $dir, 0, sub {
		687	my ($dirs, $nondirs) = @_;
		688	print "real directories: @$dirs\n";
		689	print "everything else: @$nondirs\n";
		690	};
		691
		692	Implementation notes.
		693
		694	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		695
		696	After reading the directory, the modification time, size etc. of the
		697	directory before and after the readdir is checked, and if they match (and
		698	isn't the current time), the link count will be used to decide how many
		699	entries are directories (if >= 2). Otherwise, no knowledge of the number
		700	of subdirectories will be assumed.
		701
		702	Then entries will be sorted into likely directories (everything without
		703	a non-initial dot currently) and likely non-directories (everything
		704	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		705	likely directories first. If that succeeds, it assumes that the entry
		706	is a directory or a symlink to directory (which will be checked
		707	seperately). This is often faster than stat'ing the entry itself because
		708	filesystems might detect the type of the entry without reading the inode
		709	data (e.g. ext2fs filetype feature).
		710
		711	If the known number of directories (link count - 2) has been reached, the
		712	rest of the entries is assumed to be non-directories.
		713
		714	This only works with certainty on POSIX (= UNIX) filesystems, which
		715	fortunately are the vast majority of filesystems around.
		716
		717	It will also likely work on non-POSIX filesystems with reduced efficiency
		718	as those tend to return 0 or 1 as link counts, which disables the
		719	directory counting heuristic.
		720
		721	=cut
		722
		723	sub aio_scandir($$;$) {
		724	my ($path, $maxreq, $cb) = @_;
		725
		726	my $pri = aioreq_pri;
		727
		728	my $grp = aio_group $cb;
		729
		730	$maxreq = 4 if $maxreq <= 0;
		731
		732	# stat once
		733	aioreq_pri $pri;
		734	add $grp aio_stat $path, sub {
		735	return $grp->result () if $_[0];
		736	my $now = time;
		737	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		738
		739	# read the directory entries
		740	aioreq_pri $pri;
		741	add $grp aio_readdir $path, sub {
		742	my $entries = shift
		743	or return $grp->result ();
		744
		745	# stat the dir another time
		746	aioreq_pri $pri;
		747	add $grp aio_stat $path, sub {
		748	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		749
		750	my $ndirs;
		751
		752	# take the slow route if anything looks fishy
		753	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		754	$ndirs = -1;
		755	} else {
		756	# if nlink == 2, we are finished
		757	# on non-posix-fs's, we rely on nlink < 2
		758	$ndirs = (stat _)[3] - 2
		759	or return $grp->result ([], $entries);
		760	}
		761
		762	# sort into likely dirs and likely nondirs
		763	# dirs == files without ".", short entries first
		764	$entries = [map $_->[0],
		765	sort { $b->[1] cmp $a->[1] }
		766	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		767	@$entries];
		768
		769	my (@dirs, @nondirs);
		770
		771	my $statgrp = add $grp aio_group sub {
		772	$grp->result (\@dirs, \@nondirs);
		773	};
		774
		775	limit $statgrp $maxreq;
		776	feed $statgrp sub {
		777	return unless @$entries;
		778	my $entry = pop @$entries;
		779
		780	aioreq_pri $pri;
		781	add $statgrp aio_stat "$path/$entry/.", sub {
		782	if ($_[0] < 0) {
		783	push @nondirs, $entry;
		784	} else {
		785	# need to check for real directory
		786	aioreq_pri $pri;
		787	add $statgrp aio_lstat "$path/$entry", sub {
		788	if (-d _) {
		789	push @dirs, $entry;
		790
		791	unless (--$ndirs) {
		792	push @nondirs, @$entries;
		793	feed $statgrp;
		794	}
		795	} else {
		796	push @nondirs, $entry;
		797	}
		798	}
		799	}
		800	};
		801	};
		802	};
		803	};
		804	};
		805
		806	$grp
		807	}
		808
		809	=item aio_rmtree $path, $callback->($status)
		810
		811	Delete a directory tree starting (and including) C<$path>, return the
		812	status of the final C<rmdir> only. This is a composite request that
		813	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		814	everything else.
		815
		816	=cut
		817
		818	sub aio_rmtree;
		819	sub aio_rmtree($;$) {
		820	my ($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	}
		843
		844	=item aio_sync $callback->($status)
		845
		846	Asynchronously call sync and call the callback when finished.
		847
192	=item aio_fsync $fh, $callback	848	=item aio_fsync $fh, $callback->($status)
193		849
194	Asynchronously call fsync on the given filehandle and call the callback	850	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	851	with the fsync result code.
196		852
197	=item aio_fdatasync $fh, $callback	853	=item aio_fdatasync $fh, $callback->($status)
198		854
199	Asynchronously call fdatasync on the given filehandle and call the	855	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	856	callback with the fdatasync result code.
201	C<fdatasync> is not available.	857
		858	If this call isn't available because your OS lacks it or it couldn't be
		859	detected, it will be emulated by calling C<fsync> instead.
		860
		861	=item aio_pathsync $path, $callback->($status)
		862
		863	This request tries to open, fsync and close the given path. This is a
		864	composite request intended tosync directories after directory operations
		865	(E.g. rename). This might not work on all operating systems or have any
		866	specific effect, but usually it makes sure that directory changes get
		867	written to disc. It works for anything that can be opened for read-only,
		868	not just directories.
		869
		870	Passes C<0> when everything went ok, and C<-1> on error.
		871
		872	=cut
		873
		874	sub aio_pathsync($;$) {
		875	my ($path, $cb) = @_;
		876
		877	my $pri = aioreq_pri;
		878	my $grp = aio_group $cb;
		879
		880	aioreq_pri $pri;
		881	add $grp aio_open $path, O_RDONLY, 0, sub {
		882	my ($fh) = @_;
		883	if ($fh) {
		884	aioreq_pri $pri;
		885	add $grp aio_fsync $fh, sub {
		886	$grp->result ($_[0]);
		887
		888	aioreq_pri $pri;
		889	add $grp aio_close $fh;
		890	};
		891	} else {
		892	$grp->result (-1);
		893	}
		894	};
		895
		896	$grp
		897	}
		898
		899	=item aio_group $callback->(...)
		900
		901	This is a very special aio request: Instead of doing something, it is a
		902	container for other aio requests, which is useful if you want to bundle
		903	many requests into a single, composite, request with a definite callback
		904	and the ability to cancel the whole request with its subrequests.
		905
		906	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		907	for more info.
		908
		909	Example:
		910
		911	my $grp = aio_group sub {
		912	print "all stats done\n";
		913	};
		914
		915	add $grp
		916	(aio_stat ...),
		917	(aio_stat ...),
		918	...;
		919
		920	=item aio_nop $callback->()
		921
		922	This is a special request - it does nothing in itself and is only used for
		923	side effects, such as when you want to add a dummy request to a group so
		924	that finishing the requests in the group depends on executing the given
		925	code.
		926
		927	While this request does nothing, it still goes through the execution
		928	phase and still requires a worker thread. Thus, the callback will not
		929	be executed immediately but only after other requests in the queue have
		930	entered their execution phase. This can be used to measure request
		931	latency.
		932
		933	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		934
		935	Mainly used for debugging and benchmarking, this aio request puts one of
		936	the request workers to sleep for the given time.
		937
		938	While it is theoretically handy to have simple I/O scheduling requests
		939	like sleep and file handle readable/writable, the overhead this creates is
		940	immense (it blocks a thread for a long time) so do not use this function
		941	except to put your application under artificial I/O pressure.
202		942
203	=back	943	=back
204		944
		945	=head2 IO::AIO::REQ CLASS
		946
		947	All non-aggregate C<aio_*> functions return an object of this class when
		948	called in non-void context.
		949
		950	=over 4
		951
		952	=item cancel $req
		953
		954	Cancels the request, if possible. Has the effect of skipping execution
		955	when entering the B<execute> state and skipping calling the callback when
		956	entering the the B<result> state, but will leave the request otherwise
		957	untouched. That means that requests that currently execute will not be
		958	stopped and resources held by the request will not be freed prematurely.
		959
		960	=item cb $req $callback->(...)
		961
		962	Replace (or simply set) the callback registered to the request.
		963
		964	=back
		965
		966	=head2 IO::AIO::GRP CLASS
		967
		968	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		969	objects of this class, too.
		970
		971	A IO::AIO::GRP object is a special request that can contain multiple other
		972	aio requests.
		973
		974	You create one by calling the C<aio_group> constructing function with a
		975	callback that will be called when all contained requests have entered the
		976	C<done> state:
		977
		978	my $grp = aio_group sub {
		979	print "all requests are done\n";
		980	};
		981
		982	You add requests by calling the C<add> method with one or more
		983	C<IO::AIO::REQ> objects:
		984
		985	$grp->add (aio_unlink "...");
		986
		987	add $grp aio_stat "...", sub {
		988	$_[0] or return $grp->result ("error");
		989
		990	# add another request dynamically, if first succeeded
		991	add $grp aio_open "...", sub {
		992	$grp->result ("ok");
		993	};
		994	};
		995
		996	This makes it very easy to create composite requests (see the source of
		997	C<aio_move> for an application) that work and feel like simple requests.
		998
		999	=over 4
		1000
		1001	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1002	C<IO::AIO::poll_cb>, just like any other request.
		1003
		1004	=item * They can be canceled like any other request. Canceling will cancel not
		1005	only the request itself, but also all requests it contains.
		1006
		1007	=item * They can also can also be added to other IO::AIO::GRP objects.
		1008
		1009	=item * You must not add requests to a group from within the group callback (or
		1010	any later time).
		1011
		1012	=back
		1013
		1014	Their lifetime, simplified, looks like this: when they are empty, they
		1015	will finish very quickly. If they contain only requests that are in the
		1016	C<done> state, they will also finish. Otherwise they will continue to
		1017	exist.
		1018
		1019	That means after creating a group you have some time to add requests. And
		1020	in the callbacks of those requests, you can add further requests to the
		1021	group. And only when all those requests have finished will the the group
		1022	itself finish.
		1023
		1024	=over 4
		1025
		1026	=item add $grp ...
		1027
		1028	=item $grp->add (...)
		1029
		1030	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1031	be added, including other groups, as long as you do not create circular
		1032	dependencies.
		1033
		1034	Returns all its arguments.
		1035
		1036	=item $grp->cancel_subs
		1037
		1038	Cancel all subrequests and clears any feeder, but not the group request
		1039	itself. Useful when you queued a lot of events but got a result early.
		1040
		1041	=item $grp->result (...)
		1042
		1043	Set the result value(s) that will be passed to the group callback when all
		1044	subrequests have finished and set the groups errno to the current value
		1045	of errno (just like calling C<errno> without an error number). By default,
		1046	no argument will be passed and errno is zero.
		1047
		1048	=item $grp->errno ([$errno])
		1049
		1050	Sets the group errno value to C<$errno>, or the current value of errno
		1051	when the argument is missing.
		1052
		1053	Every aio request has an associated errno value that is restored when
		1054	the callback is invoked. This method lets you change this value from its
		1055	default (0).
		1056
		1057	Calling C<result> will also set errno, so make sure you either set C<$!>
		1058	before the call to C<result>, or call c<errno> after it.
		1059
		1060	=item feed $grp $callback->($grp)
		1061
		1062	Sets a feeder/generator on this group: every group can have an attached
		1063	generator that generates requests if idle. The idea behind this is that,
		1064	although you could just queue as many requests as you want in a group,
		1065	this might starve other requests for a potentially long time. For
		1066	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1067	requests, delaying any later requests for a long time.
		1068
		1069	To avoid this, and allow incremental generation of requests, you can
		1070	instead a group and set a feeder on it that generates those requests. The
		1071	feed callback will be called whenever there are few enough (see C<limit>,
		1072	below) requests active in the group itself and is expected to queue more
		1073	requests.
		1074
		1075	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1076	not impose any limits).
		1077
		1078	If the feed does not queue more requests when called, it will be
		1079	automatically removed from the group.
		1080
		1081	If the feed limit is C<0>, it will be set to C<2> automatically.
		1082
		1083	Example:
		1084
		1085	# stat all files in @files, but only ever use four aio requests concurrently:
		1086
		1087	my $grp = aio_group sub { print "finished\n" };
		1088	limit $grp 4;
		1089	feed $grp sub {
		1090	my $file = pop @files
		1091	or return;
		1092
		1093	add $grp aio_stat $file, sub { ... };
		1094	};
		1095
		1096	=item limit $grp $num
		1097
		1098	Sets the feeder limit for the group: The feeder will be called whenever
		1099	the group contains less than this many requests.
		1100
		1101	Setting the limit to C<0> will pause the feeding process.
		1102
		1103	=back
		1104
205	=head2 SUPPORT FUNCTIONS	1105	=head2 SUPPORT FUNCTIONS
		1106
		1107	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
206		1108
207	=over 4	1109	=over 4
208		1110
209	=item $fileno = IO::AIO::poll_fileno	1111	=item $fileno = IO::AIO::poll_fileno
210		1112
…		…
215		1117
216	See C<poll_cb> for an example.	1118	See C<poll_cb> for an example.
217		1119
218	=item IO::AIO::poll_cb	1120	=item IO::AIO::poll_cb
219		1121
220	Process all outstanding events on the result pipe. You have to call this	1122	Process some outstanding events on the result pipe. You have to call this
221	regularly. Returns the number of events processed. Returns immediately	1123	regularly. Returns the number of events processed. Returns immediately
222	when no events are outstanding.	1124	when no events are outstanding. The amount of events processed depends on
		1125	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1126
		1127	If not all requests were processed for whatever reason, the filehandle
		1128	will still be ready when C<poll_cb> returns.
223		1129
224	Example: Install an Event watcher that automatically calls	1130	Example: Install an Event watcher that automatically calls
225	IO::AIO::poll_cb with high priority:	1131	IO::AIO::poll_cb with high priority:
226		1132
227	Event->io (fd => IO::AIO::poll_fileno,	1133	Event->io (fd => IO::AIO::poll_fileno,
228	poll => 'r', async => 1,	1134	poll => 'r', async => 1,
229	cb => \&IO::AIO::poll_cb);	1135	cb => \&IO::AIO::poll_cb);
230		1136
		1137	=item IO::AIO::max_poll_reqs $nreqs
		1138
		1139	=item IO::AIO::max_poll_time $seconds
		1140
		1141	These set the maximum number of requests (default C<0>, meaning infinity)
		1142	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1143	the maximum amount of time (default C<0>, meaning infinity) spent in
		1144	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1145	of time C<poll_cb> is allowed to use).
		1146
		1147	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1148	syscall per request processed, which is not normally a problem unless your
		1149	callbacks are really really fast or your OS is really really slow (I am
		1150	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1151
		1152	Setting these is useful if you want to ensure some level of
		1153	interactiveness when perl is not fast enough to process all requests in
		1154	time.
		1155
		1156	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1157
		1158	Example: Install an Event watcher that automatically calls
		1159	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1160	program get the CPU sometimes even under high AIO load.
		1161
		1162	# try not to spend much more than 0.1s in poll_cb
		1163	IO::AIO::max_poll_time 0.1;
		1164
		1165	# use a low priority so other tasks have priority
		1166	Event->io (fd => IO::AIO::poll_fileno,
		1167	poll => 'r', nice => 1,
		1168	cb => &IO::AIO::poll_cb);
		1169
231	=item IO::AIO::poll_wait	1170	=item IO::AIO::poll_wait
232		1171
		1172	If there are any outstanding requests and none of them in the result
233	Wait till the result filehandle becomes ready for reading (simply does a	1173	phase, wait till the result filehandle becomes ready for reading (simply
234	C<select> on the filehandle. This is useful if you want to synchronously wait	1174	does a C<select> on the filehandle. This is useful if you want to
235	for some requests to finish).	1175	synchronously wait for some requests to finish).
236		1176
237	See C<nreqs> for an example.	1177	See C<nreqs> for an example.
238		1178
		1179	=item IO::AIO::poll
		1180
		1181	Waits until some requests have been handled.
		1182
		1183	Returns the number of requests processed, but is otherwise strictly
		1184	equivalent to:
		1185
		1186	IO::AIO::poll_wait, IO::AIO::poll_cb
		1187
239	=item IO::AIO::nreqs	1188	=item IO::AIO::flush
240		1189
241	Returns the number of requests currently outstanding (i.e. for which their	1190	Wait till all outstanding AIO requests have been handled.
242	callback has not been invoked yet).
243		1191
244	Example: wait till there are no outstanding requests anymore:	1192	Strictly equivalent to:
245		1193
246	IO::AIO::poll_wait, IO::AIO::poll_cb	1194	IO::AIO::poll_wait, IO::AIO::poll_cb
247	while IO::AIO::nreqs;	1195	while IO::AIO::nreqs;
248		1196
		1197	=back
		1198
		1199	=head3 CONTROLLING THE NUMBER OF THREADS
		1200
		1201	=over
		1202
		1203	=item IO::AIO::min_parallel $nthreads
		1204
		1205	Set the minimum number of AIO threads to C<$nthreads>. The current
		1206	default is C<8>, which means eight asynchronous operations can execute
		1207	concurrently at any one time (the number of outstanding requests,
		1208	however, is unlimited).
		1209
		1210	IO::AIO starts threads only on demand, when an AIO request is queued and
		1211	no free thread exists. Please note that queueing up a hundred requests can
		1212	create demand for a hundred threads, even if it turns out that everything
		1213	is in the cache and could have been processed faster by a single thread.
		1214
		1215	It is recommended to keep the number of threads relatively low, as some
		1216	Linux kernel versions will scale negatively with the number of threads
		1217	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1218	versions, 4-32 threads should be fine.
		1219
		1220	Under most circumstances you don't need to call this function, as the
		1221	module selects a default that is suitable for low to moderate load.
		1222
		1223	=item IO::AIO::max_parallel $nthreads
		1224
		1225	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1226	specified number of threads are currently running, this function kills
		1227	them. This function blocks until the limit is reached.
		1228
		1229	While C<$nthreads> are zero, aio requests get queued but not executed
		1230	until the number of threads has been increased again.
		1231
		1232	This module automatically runs C<max_parallel 0> at program end, to ensure
		1233	that all threads are killed and that there are no outstanding requests.
		1234
		1235	Under normal circumstances you don't need to call this function.
		1236
		1237	=item IO::AIO::max_idle $nthreads
		1238
		1239	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1240	threads that did not get a request to process within 10 seconds). That
		1241	means if a thread becomes idle while C<$nthreads> other threads are also
		1242	idle, it will free its resources and exit.
		1243
		1244	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1245	to allow for extremely high load situations, but want to free resources
		1246	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1247
		1248	The default is probably ok in most situations, especially if thread
		1249	creation is fast. If thread creation is very slow on your system you might
		1250	want to use larger values.
		1251
		1252	=item IO::AIO::max_outstanding $maxreqs
		1253
		1254	This is a very bad function to use in interactive programs because it
		1255	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1256	use an C<aio_group> together with a feed callback.
		1257
		1258	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1259	do queue up more than this number of requests, the next call to the
		1260	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1261	function will block until the limit is no longer exceeded.
		1262
		1263	The default value is very large, so there is no practical limit on the
		1264	number of outstanding requests.
		1265
		1266	You can still queue as many requests as you want. Therefore,
		1267	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1268	as a stop gap to shield against fatal memory overflow (with large values).
		1269
		1270	=back
		1271
		1272	=head3 STATISTICAL INFORMATION
		1273
		1274	=over
		1275
249	=item IO::AIO::flush	1276	=item IO::AIO::nreqs
250		1277
251	Wait till all outstanding AIO requests have been handled.	1278	Returns the number of requests currently in the ready, execute or pending
		1279	states (i.e. for which their callback has not been invoked yet).
252		1280
253	Strictly equivalent to:	1281	Example: wait till there are no outstanding requests anymore:
254		1282
255	IO::AIO::poll_wait, IO::AIO::poll_cb	1283	IO::AIO::poll_wait, IO::AIO::poll_cb
256	while IO::AIO::nreqs;	1284	while IO::AIO::nreqs;
257		1285
		1286	=item IO::AIO::nready
		1287
		1288	Returns the number of requests currently in the ready state (not yet
		1289	executed).
		1290
258	=item IO::AIO::poll	1291	=item IO::AIO::npending
259		1292
260	Waits until some requests have been handled.	1293	Returns the number of requests currently in the pending state (executed,
261		1294	but not yet processed by poll_cb).
262	Strictly equivalent to:
263
264	IO::AIO::poll_wait, IO::AIO::poll_cb
265	if IO::AIO::nreqs;
266
267	=item IO::AIO::min_parallel $nthreads
268
269	Set the minimum number of AIO threads to C<$nthreads>. The default is
270	C<1>, which means a single asynchronous operation can be done at one time
271	(the number of outstanding operations, however, is unlimited).
272
273	It is recommended to keep the number of threads low, as some Linux
274	kernel versions will scale negatively with the number of threads (higher
275	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
276	threads should be fine.
277
278	Under normal circumstances you don't need to call this function, as this
279	module automatically starts some threads (the exact number might change,
280	and is currently 4).
281
282	=item IO::AIO::max_parallel $nthreads
283
284	Sets the maximum number of AIO threads to C<$nthreads>. If more than
285	the specified number of threads are currently running, kill them. This
286	function blocks until the limit is reached.
287
288	This module automatically runs C<max_parallel 0> at program end, to ensure
289	that all threads are killed and that there are no outstanding requests.
290
291	Under normal circumstances you don't need to call this function.
292
293	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
294
295	Sets the maximum number of outstanding requests to C<$nreqs>. If you
296	try to queue up more than this number of requests, the caller will block until
297	some requests have been handled.
298
299	The default is very large, so normally there is no practical limit. If you
300	queue up many requests in a loop it it often improves speed if you set
301	this to a relatively low number, such as C<100>.
302
303	Under normal circumstances you don't need to call this function.
304		1295
305	=back	1296	=back
306		1297
307	=cut	1298	=cut
308		1299
309	# support function to convert a fd into a perl filehandle
310	sub _fd2fh {
311	return undef if $_[0] < 0;
312
313	# try to be perl5.6-compatible
314	local *AIO_FH;
315	open AIO_FH, "+<&=$_[0]"
316	or return undef;
317
318	*AIO_FH
319	}
320
321	min_parallel 4;	1300	min_parallel 8;
322		1301
323	END {	1302	END { flush }
324	max_parallel 0;
325	}
326		1303
327	1;	1304	1;
328		1305
		1306	=head2 FORK BEHAVIOUR
		1307
		1308	This module should do "the right thing" when the process using it forks:
		1309
		1310	Before the fork, IO::AIO enters a quiescent state where no requests
		1311	can be added in other threads and no results will be processed. After
		1312	the fork the parent simply leaves the quiescent state and continues
		1313	request/result processing, while the child frees the request/result queue
		1314	(so that the requests started before the fork will only be handled in the
		1315	parent). Threads will be started on demand until the limit set in the
		1316	parent process has been reached again.
		1317
		1318	In short: the parent will, after a short pause, continue as if fork had
		1319	not been called, while the child will act as if IO::AIO has not been used
		1320	yet.
		1321
		1322	=head2 MEMORY USAGE
		1323
		1324	Per-request usage:
		1325
		1326	Each aio request uses - depending on your architecture - around 100-200
		1327	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1328	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1329	scalars and other data passed into aio requests will also be locked and
		1330	will consume memory till the request has entered the done state.
		1331
		1332	This is not awfully much, so queuing lots of requests is not usually a
		1333	problem.
		1334
		1335	Per-thread usage:
		1336
		1337	In the execution phase, some aio requests require more memory for
		1338	temporary buffers, and each thread requires a stack and other data
		1339	structures (usually around 16k-128k, depending on the OS).
		1340
		1341	=head1 KNOWN BUGS
		1342
		1343	Known bugs will be fixed in the next release.
		1344
329	=head1 SEE ALSO	1345	=head1 SEE ALSO
330		1346
331	L<Coro>, L<Linux::AIO>.	1347	L<Coro::AIO>.
332		1348
333	=head1 AUTHOR	1349	=head1 AUTHOR
334		1350
335	Marc Lehmann <schmorp@schmorp.de>	1351	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	1352	http://home.schmorp.de/

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