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Revision 1.21 by root, Wed Jul 13 00:13:09 2005 UTC vs.
Revision 1.122 by root, Sat Apr 26 12:00:23 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 = '2.62';
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 aio_block));
		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($$;$) {
		545	aio_block {
		546	my ($path, undef, $cb) = @_;
		547	my $data = \$_[1];
		548
		549	my $pri = aioreq_pri;
		550	my $grp = aio_group $cb;
		551
		552	aioreq_pri $pri;
		553	add $grp aio_open $path, O_RDONLY, 0, sub {
		554	my $fh = shift
		555	or return $grp->result (-1);
		556
		557	aioreq_pri $pri;
		558	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		559	$grp->result ($_[0]);
		560	};
		561	};
		562
		563	$grp
		564	}
		565	}
		566
		567	=item aio_copy $srcpath, $dstpath, $callback->($status)
		568
		569	Try to copy the I<file> (directories not supported as either source or
		570	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		571	the C<0> (error) or C<-1> ok.
		572
		573	This is a composite request that it creates the destination file with
		574	mode 0200 and copies the contents of the source file into it using
		575	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		576	uid/gid, in that order.
		577
		578	If an error occurs, the partial destination file will be unlinked, if
		579	possible, except when setting atime, mtime, access mode and uid/gid, where
		580	errors are being ignored.
		581
		582	=cut
		583
		584	sub aio_copy($$;$) {
		585	aio_block {
		586	my ($src, $dst, $cb) = @_;
		587
		588	my $pri = aioreq_pri;
		589	my $grp = aio_group $cb;
		590
		591	aioreq_pri $pri;
		592	add $grp aio_open $src, O_RDONLY, 0, sub {
		593	if (my $src_fh = $_[0]) {
		594	my @stat = stat $src_fh;
		595
		596	aioreq_pri $pri;
		597	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		598	if (my $dst_fh = $_[0]) {
		599	aioreq_pri $pri;
		600	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		601	if ($_[0] == $stat[7]) {
		602	$grp->result (0);
		603	close $src_fh;
		604
		605	# those should not normally block. should. should.
		606	utime $stat[8], $stat[9], $dst;
		607	chmod $stat[2] & 07777, $dst_fh;
		608	chown $stat[4], $stat[5], $dst_fh;
		609
		610	aioreq_pri $pri;
		611	add $grp aio_close $dst_fh;
		612	} else {
		613	$grp->result (-1);
		614	close $src_fh;
		615	close $dst_fh;
		616
		617	aioreq $pri;
		618	add $grp aio_unlink $dst;
		619	}
		620	};
		621	} else {
		622	$grp->result (-1);
		623	}
		624	},
		625
		626	} else {
		627	$grp->result (-1);
		628	}
		629	};
		630
		631	$grp
		632	}
		633	}
		634
		635	=item aio_move $srcpath, $dstpath, $callback->($status)
		636
		637	Try to move the I<file> (directories not supported as either source or
		638	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		639	the C<0> (error) or C<-1> ok.
		640
		641	This is a composite request that tries to rename(2) the file first. If
		642	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
		643	that is successful, unlinking the C<$srcpath>.
		644
		645	=cut
		646
		647	sub aio_move($$;$) {
		648	aio_block {
		649	my ($src, $dst, $cb) = @_;
		650
		651	my $pri = aioreq_pri;
		652	my $grp = aio_group $cb;
		653
		654	aioreq_pri $pri;
		655	add $grp aio_rename $src, $dst, sub {
		656	if ($_[0] && $! == EXDEV) {
		657	aioreq_pri $pri;
		658	add $grp aio_copy $src, $dst, sub {
		659	$grp->result ($_[0]);
		660
		661	if (!$_[0]) {
		662	aioreq_pri $pri;
		663	add $grp aio_unlink $src;
		664	}
		665	};
		666	} else {
		667	$grp->result ($_[0]);
		668	}
		669	};
		670
		671	$grp
		672	}
		673	}
		674
		675	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		676
		677	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		678	efficiently separate the entries of directory C<$path> into two sets of
		679	names, directories you can recurse into (directories), and ones you cannot
		680	recurse into (everything else, including symlinks to directories).
		681
		682	C<aio_scandir> is a composite request that creates of many sub requests_
		683	C<$maxreq> specifies the maximum number of outstanding aio requests that
		684	this function generates. If it is C<< <= 0 >>, then a suitable default
		685	will be chosen (currently 4).
		686
		687	On error, the callback is called without arguments, otherwise it receives
		688	two array-refs with path-relative entry names.
		689
		690	Example:
		691
		692	aio_scandir $dir, 0, sub {
		693	my ($dirs, $nondirs) = @_;
		694	print "real directories: @$dirs\n";
		695	print "everything else: @$nondirs\n";
		696	};
		697
		698	Implementation notes.
		699
		700	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		701
		702	After reading the directory, the modification time, size etc. of the
		703	directory before and after the readdir is checked, and if they match (and
		704	isn't the current time), the link count will be used to decide how many
		705	entries are directories (if >= 2). Otherwise, no knowledge of the number
		706	of subdirectories will be assumed.
		707
		708	Then entries will be sorted into likely directories (everything without
		709	a non-initial dot currently) and likely non-directories (everything
		710	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		711	likely directories first. If that succeeds, it assumes that the entry
		712	is a directory or a symlink to directory (which will be checked
		713	seperately). This is often faster than stat'ing the entry itself because
		714	filesystems might detect the type of the entry without reading the inode
		715	data (e.g. ext2fs filetype feature).
		716
		717	If the known number of directories (link count - 2) has been reached, the
		718	rest of the entries is assumed to be non-directories.
		719
		720	This only works with certainty on POSIX (= UNIX) filesystems, which
		721	fortunately are the vast majority of filesystems around.
		722
		723	It will also likely work on non-POSIX filesystems with reduced efficiency
		724	as those tend to return 0 or 1 as link counts, which disables the
		725	directory counting heuristic.
		726
		727	=cut
		728
		729	sub aio_scandir($$;$) {
		730	aio_block {
		731	my ($path, $maxreq, $cb) = @_;
		732
		733	my $pri = aioreq_pri;
		734
		735	my $grp = aio_group $cb;
		736
		737	$maxreq = 4 if $maxreq <= 0;
		738
		739	# stat once
		740	aioreq_pri $pri;
		741	add $grp aio_stat $path, sub {
		742	return $grp->result () if $_[0];
		743	my $now = time;
		744	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		745
		746	# read the directory entries
		747	aioreq_pri $pri;
		748	add $grp aio_readdir $path, sub {
		749	my $entries = shift
		750	or return $grp->result ();
		751
		752	# stat the dir another time
		753	aioreq_pri $pri;
		754	add $grp aio_stat $path, sub {
		755	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		756
		757	my $ndirs;
		758
		759	# take the slow route if anything looks fishy
		760	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		761	$ndirs = -1;
		762	} else {
		763	# if nlink == 2, we are finished
		764	# on non-posix-fs's, we rely on nlink < 2
		765	$ndirs = (stat _)[3] - 2
		766	or return $grp->result ([], $entries);
		767	}
		768
		769	# sort into likely dirs and likely nondirs
		770	# dirs == files without ".", short entries first
		771	$entries = [map $_->[0],
		772	sort { $b->[1] cmp $a->[1] }
		773	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		774	@$entries];
		775
		776	my (@dirs, @nondirs);
		777
		778	my $statgrp = add $grp aio_group sub {
		779	$grp->result (\@dirs, \@nondirs);
		780	};
		781
		782	limit $statgrp $maxreq;
		783	feed $statgrp sub {
		784	return unless @$entries;
		785	my $entry = pop @$entries;
		786
		787	aioreq_pri $pri;
		788	add $statgrp aio_stat "$path/$entry/.", sub {
		789	if ($_[0] < 0) {
		790	push @nondirs, $entry;
		791	} else {
		792	# need to check for real directory
		793	aioreq_pri $pri;
		794	add $statgrp aio_lstat "$path/$entry", sub {
		795	if (-d _) {
		796	push @dirs, $entry;
		797
		798	unless (--$ndirs) {
		799	push @nondirs, @$entries;
		800	feed $statgrp;
		801	}
		802	} else {
		803	push @nondirs, $entry;
		804	}
		805	}
		806	}
		807	};
		808	};
		809	};
		810	};
		811	};
		812
		813	$grp
		814	}
		815	}
		816
		817	=item aio_rmtree $path, $callback->($status)
		818
		819	Delete a directory tree starting (and including) C<$path>, return the
		820	status of the final C<rmdir> only. This is a composite request that
		821	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		822	everything else.
		823
		824	=cut
		825
		826	sub aio_rmtree;
		827	sub aio_rmtree($;$) {
		828	aio_block {
		829	my ($path, $cb) = @_;
		830
		831	my $pri = aioreq_pri;
		832	my $grp = aio_group $cb;
		833
		834	aioreq_pri $pri;
		835	add $grp aio_scandir $path, 0, sub {
		836	my ($dirs, $nondirs) = @_;
		837
		838	my $dirgrp = aio_group sub {
		839	add $grp aio_rmdir $path, sub {
		840	$grp->result ($_[0]);
		841	};
		842	};
		843
		844	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		845	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		846
		847	add $grp $dirgrp;
		848	};
		849
		850	$grp
		851	}
		852	}
		853
		854	=item aio_sync $callback->($status)
		855
		856	Asynchronously call sync and call the callback when finished.
		857
192	=item aio_fsync $fh, $callback	858	=item aio_fsync $fh, $callback->($status)
193		859
194	Asynchronously call fsync on the given filehandle and call the callback	860	Asynchronously call fsync on the given filehandle and call the callback
195	with the fsync result code.	861	with the fsync result code.
196		862
197	=item aio_fdatasync $fh, $callback	863	=item aio_fdatasync $fh, $callback->($status)
198		864
199	Asynchronously call fdatasync on the given filehandle and call the	865	Asynchronously call fdatasync on the given filehandle and call the
200	callback with the fdatasync result code. Might set C<$!> to C<ENOSYS> if	866	callback with the fdatasync result code.
201	C<fdatasync> is not available.	867
		868	If this call isn't available because your OS lacks it or it couldn't be
		869	detected, it will be emulated by calling C<fsync> instead.
		870
		871	=item aio_pathsync $path, $callback->($status)
		872
		873	This request tries to open, fsync and close the given path. This is a
		874	composite request intended tosync directories after directory operations
		875	(E.g. rename). This might not work on all operating systems or have any
		876	specific effect, but usually it makes sure that directory changes get
		877	written to disc. It works for anything that can be opened for read-only,
		878	not just directories.
		879
		880	Passes C<0> when everything went ok, and C<-1> on error.
		881
		882	=cut
		883
		884	sub aio_pathsync($;$) {
		885	aio_block {
		886	my ($path, $cb) = @_;
		887
		888	my $pri = aioreq_pri;
		889	my $grp = aio_group $cb;
		890
		891	aioreq_pri $pri;
		892	add $grp aio_open $path, O_RDONLY, 0, sub {
		893	my ($fh) = @_;
		894	if ($fh) {
		895	aioreq_pri $pri;
		896	add $grp aio_fsync $fh, sub {
		897	$grp->result ($_[0]);
		898
		899	aioreq_pri $pri;
		900	add $grp aio_close $fh;
		901	};
		902	} else {
		903	$grp->result (-1);
		904	}
		905	};
		906
		907	$grp
		908	}
		909	}
		910
		911	=item aio_group $callback->(...)
		912
		913	This is a very special aio request: Instead of doing something, it is a
		914	container for other aio requests, which is useful if you want to bundle
		915	many requests into a single, composite, request with a definite callback
		916	and the ability to cancel the whole request with its subrequests.
		917
		918	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		919	for more info.
		920
		921	Example:
		922
		923	my $grp = aio_group sub {
		924	print "all stats done\n";
		925	};
		926
		927	add $grp
		928	(aio_stat ...),
		929	(aio_stat ...),
		930	...;
		931
		932	=item aio_nop $callback->()
		933
		934	This is a special request - it does nothing in itself and is only used for
		935	side effects, such as when you want to add a dummy request to a group so
		936	that finishing the requests in the group depends on executing the given
		937	code.
		938
		939	While this request does nothing, it still goes through the execution
		940	phase and still requires a worker thread. Thus, the callback will not
		941	be executed immediately but only after other requests in the queue have
		942	entered their execution phase. This can be used to measure request
		943	latency.
		944
		945	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		946
		947	Mainly used for debugging and benchmarking, this aio request puts one of
		948	the request workers to sleep for the given time.
		949
		950	While it is theoretically handy to have simple I/O scheduling requests
		951	like sleep and file handle readable/writable, the overhead this creates is
		952	immense (it blocks a thread for a long time) so do not use this function
		953	except to put your application under artificial I/O pressure.
202		954
203	=back	955	=back
204		956
		957	=head2 IO::AIO::REQ CLASS
		958
		959	All non-aggregate C<aio_*> functions return an object of this class when
		960	called in non-void context.
		961
		962	=over 4
		963
		964	=item cancel $req
		965
		966	Cancels the request, if possible. Has the effect of skipping execution
		967	when entering the B<execute> state and skipping calling the callback when
		968	entering the the B<result> state, but will leave the request otherwise
		969	untouched. That means that requests that currently execute will not be
		970	stopped and resources held by the request will not be freed prematurely.
		971
		972	=item cb $req $callback->(...)
		973
		974	Replace (or simply set) the callback registered to the request.
		975
		976	=back
		977
		978	=head2 IO::AIO::GRP CLASS
		979
		980	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		981	objects of this class, too.
		982
		983	A IO::AIO::GRP object is a special request that can contain multiple other
		984	aio requests.
		985
		986	You create one by calling the C<aio_group> constructing function with a
		987	callback that will be called when all contained requests have entered the
		988	C<done> state:
		989
		990	my $grp = aio_group sub {
		991	print "all requests are done\n";
		992	};
		993
		994	You add requests by calling the C<add> method with one or more
		995	C<IO::AIO::REQ> objects:
		996
		997	$grp->add (aio_unlink "...");
		998
		999	add $grp aio_stat "...", sub {
		1000	$_[0] or return $grp->result ("error");
		1001
		1002	# add another request dynamically, if first succeeded
		1003	add $grp aio_open "...", sub {
		1004	$grp->result ("ok");
		1005	};
		1006	};
		1007
		1008	This makes it very easy to create composite requests (see the source of
		1009	C<aio_move> for an application) that work and feel like simple requests.
		1010
		1011	=over 4
		1012
		1013	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1014	C<IO::AIO::poll_cb>, just like any other request.
		1015
		1016	=item * They can be canceled like any other request. Canceling will cancel not
		1017	only the request itself, but also all requests it contains.
		1018
		1019	=item * They can also can also be added to other IO::AIO::GRP objects.
		1020
		1021	=item * You must not add requests to a group from within the group callback (or
		1022	any later time).
		1023
		1024	=back
		1025
		1026	Their lifetime, simplified, looks like this: when they are empty, they
		1027	will finish very quickly. If they contain only requests that are in the
		1028	C<done> state, they will also finish. Otherwise they will continue to
		1029	exist.
		1030
		1031	That means after creating a group you have some time to add requests. And
		1032	in the callbacks of those requests, you can add further requests to the
		1033	group. And only when all those requests have finished will the the group
		1034	itself finish.
		1035
		1036	=over 4
		1037
		1038	=item add $grp ...
		1039
		1040	=item $grp->add (...)
		1041
		1042	Add one or more requests to the group. Any type of L<IO::AIO::REQ> can
		1043	be added, including other groups, as long as you do not create circular
		1044	dependencies.
		1045
		1046	Returns all its arguments.
		1047
		1048	=item $grp->cancel_subs
		1049
		1050	Cancel all subrequests and clears any feeder, but not the group request
		1051	itself. Useful when you queued a lot of events but got a result early.
		1052
		1053	=item $grp->result (...)
		1054
		1055	Set the result value(s) that will be passed to the group callback when all
		1056	subrequests have finished and set the groups errno to the current value
		1057	of errno (just like calling C<errno> without an error number). By default,
		1058	no argument will be passed and errno is zero.
		1059
		1060	=item $grp->errno ([$errno])
		1061
		1062	Sets the group errno value to C<$errno>, or the current value of errno
		1063	when the argument is missing.
		1064
		1065	Every aio request has an associated errno value that is restored when
		1066	the callback is invoked. This method lets you change this value from its
		1067	default (0).
		1068
		1069	Calling C<result> will also set errno, so make sure you either set C<$!>
		1070	before the call to C<result>, or call c<errno> after it.
		1071
		1072	=item feed $grp $callback->($grp)
		1073
		1074	Sets a feeder/generator on this group: every group can have an attached
		1075	generator that generates requests if idle. The idea behind this is that,
		1076	although you could just queue as many requests as you want in a group,
		1077	this might starve other requests for a potentially long time. For
		1078	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>
		1079	requests, delaying any later requests for a long time.
		1080
		1081	To avoid this, and allow incremental generation of requests, you can
		1082	instead a group and set a feeder on it that generates those requests. The
		1083	feed callback will be called whenever there are few enough (see C<limit>,
		1084	below) requests active in the group itself and is expected to queue more
		1085	requests.
		1086
		1087	The feed callback can queue as many requests as it likes (i.e. C<add> does
		1088	not impose any limits).
		1089
		1090	If the feed does not queue more requests when called, it will be
		1091	automatically removed from the group.
		1092
		1093	If the feed limit is C<0>, it will be set to C<2> automatically.
		1094
		1095	Example:
		1096
		1097	# stat all files in @files, but only ever use four aio requests concurrently:
		1098
		1099	my $grp = aio_group sub { print "finished\n" };
		1100	limit $grp 4;
		1101	feed $grp sub {
		1102	my $file = pop @files
		1103	or return;
		1104
		1105	add $grp aio_stat $file, sub { ... };
		1106	};
		1107
		1108	=item limit $grp $num
		1109
		1110	Sets the feeder limit for the group: The feeder will be called whenever
		1111	the group contains less than this many requests.
		1112
		1113	Setting the limit to C<0> will pause the feeding process.
		1114
		1115	=back
		1116
205	=head2 SUPPORT FUNCTIONS	1117	=head2 SUPPORT FUNCTIONS
		1118
		1119	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
206		1120
207	=over 4	1121	=over 4
208		1122
209	=item $fileno = IO::AIO::poll_fileno	1123	=item $fileno = IO::AIO::poll_fileno
210		1124
…		…
215		1129
216	See C<poll_cb> for an example.	1130	See C<poll_cb> for an example.
217		1131
218	=item IO::AIO::poll_cb	1132	=item IO::AIO::poll_cb
219		1133
220	Process all outstanding events on the result pipe. You have to call this	1134	Process some outstanding events on the result pipe. You have to call this
221	regularly. Returns the number of events processed. Returns immediately	1135	regularly. Returns the number of events processed. Returns immediately
222	when no events are outstanding.	1136	when no events are outstanding. The amount of events processed depends on
		1137	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1138
		1139	If not all requests were processed for whatever reason, the filehandle
		1140	will still be ready when C<poll_cb> returns.
223		1141
224	Example: Install an Event watcher that automatically calls	1142	Example: Install an Event watcher that automatically calls
225	IO::AIO::poll_cb with high priority:	1143	IO::AIO::poll_cb with high priority:
226		1144
227	Event->io (fd => IO::AIO::poll_fileno,	1145	Event->io (fd => IO::AIO::poll_fileno,
228	poll => 'r', async => 1,	1146	poll => 'r', async => 1,
229	cb => \&IO::AIO::poll_cb);	1147	cb => \&IO::AIO::poll_cb);
230		1148
		1149	=item IO::AIO::max_poll_reqs $nreqs
		1150
		1151	=item IO::AIO::max_poll_time $seconds
		1152
		1153	These set the maximum number of requests (default C<0>, meaning infinity)
		1154	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1155	the maximum amount of time (default C<0>, meaning infinity) spent in
		1156	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1157	of time C<poll_cb> is allowed to use).
		1158
		1159	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1160	syscall per request processed, which is not normally a problem unless your
		1161	callbacks are really really fast or your OS is really really slow (I am
		1162	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1163
		1164	Setting these is useful if you want to ensure some level of
		1165	interactiveness when perl is not fast enough to process all requests in
		1166	time.
		1167
		1168	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1169
		1170	Example: Install an Event watcher that automatically calls
		1171	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1172	program get the CPU sometimes even under high AIO load.
		1173
		1174	# try not to spend much more than 0.1s in poll_cb
		1175	IO::AIO::max_poll_time 0.1;
		1176
		1177	# use a low priority so other tasks have priority
		1178	Event->io (fd => IO::AIO::poll_fileno,
		1179	poll => 'r', nice => 1,
		1180	cb => &IO::AIO::poll_cb);
		1181
231	=item IO::AIO::poll_wait	1182	=item IO::AIO::poll_wait
232		1183
		1184	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	1185	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	1186	does a C<select> on the filehandle. This is useful if you want to
235	for some requests to finish).	1187	synchronously wait for some requests to finish).
236		1188
237	See C<nreqs> for an example.	1189	See C<nreqs> for an example.
238		1190
		1191	=item IO::AIO::poll
		1192
		1193	Waits until some requests have been handled.
		1194
		1195	Returns the number of requests processed, but is otherwise strictly
		1196	equivalent to:
		1197
		1198	IO::AIO::poll_wait, IO::AIO::poll_cb
		1199
239	=item IO::AIO::nreqs	1200	=item IO::AIO::flush
240		1201
241	Returns the number of requests currently outstanding (i.e. for which their	1202	Wait till all outstanding AIO requests have been handled.
242	callback has not been invoked yet).
243		1203
244	Example: wait till there are no outstanding requests anymore:	1204	Strictly equivalent to:
245		1205
246	IO::AIO::poll_wait, IO::AIO::poll_cb	1206	IO::AIO::poll_wait, IO::AIO::poll_cb
247	while IO::AIO::nreqs;	1207	while IO::AIO::nreqs;
248		1208
		1209	=back
		1210
		1211	=head3 CONTROLLING THE NUMBER OF THREADS
		1212
		1213	=over
		1214
		1215	=item IO::AIO::min_parallel $nthreads
		1216
		1217	Set the minimum number of AIO threads to C<$nthreads>. The current
		1218	default is C<8>, which means eight asynchronous operations can execute
		1219	concurrently at any one time (the number of outstanding requests,
		1220	however, is unlimited).
		1221
		1222	IO::AIO starts threads only on demand, when an AIO request is queued and
		1223	no free thread exists. Please note that queueing up a hundred requests can
		1224	create demand for a hundred threads, even if it turns out that everything
		1225	is in the cache and could have been processed faster by a single thread.
		1226
		1227	It is recommended to keep the number of threads relatively low, as some
		1228	Linux kernel versions will scale negatively with the number of threads
		1229	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1230	versions, 4-32 threads should be fine.
		1231
		1232	Under most circumstances you don't need to call this function, as the
		1233	module selects a default that is suitable for low to moderate load.
		1234
		1235	=item IO::AIO::max_parallel $nthreads
		1236
		1237	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1238	specified number of threads are currently running, this function kills
		1239	them. This function blocks until the limit is reached.
		1240
		1241	While C<$nthreads> are zero, aio requests get queued but not executed
		1242	until the number of threads has been increased again.
		1243
		1244	This module automatically runs C<max_parallel 0> at program end, to ensure
		1245	that all threads are killed and that there are no outstanding requests.
		1246
		1247	Under normal circumstances you don't need to call this function.
		1248
		1249	=item IO::AIO::max_idle $nthreads
		1250
		1251	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1252	threads that did not get a request to process within 10 seconds). That
		1253	means if a thread becomes idle while C<$nthreads> other threads are also
		1254	idle, it will free its resources and exit.
		1255
		1256	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1257	to allow for extremely high load situations, but want to free resources
		1258	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1259
		1260	The default is probably ok in most situations, especially if thread
		1261	creation is fast. If thread creation is very slow on your system you might
		1262	want to use larger values.
		1263
		1264	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
		1265
		1266	This is a very bad function to use in interactive programs because it
		1267	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1268	use an C<aio_group> together with a feed callback.
		1269
		1270	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1271	do queue up more than this number of requests, the next call to the
		1272	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1273	function will block until the limit is no longer exceeded.
		1274
		1275	The default value is very large, so there is no practical limit on the
		1276	number of outstanding requests.
		1277
		1278	You can still queue as many requests as you want. Therefore,
		1279	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
		1280	as a stop gap to shield against fatal memory overflow (with large values).
		1281
		1282	=back
		1283
		1284	=head3 STATISTICAL INFORMATION
		1285
		1286	=over
		1287
249	=item IO::AIO::flush	1288	=item IO::AIO::nreqs
250		1289
251	Wait till all outstanding AIO requests have been handled.	1290	Returns the number of requests currently in the ready, execute or pending
		1291	states (i.e. for which their callback has not been invoked yet).
252		1292
253	Strictly equivalent to:	1293	Example: wait till there are no outstanding requests anymore:
254		1294
255	IO::AIO::poll_wait, IO::AIO::poll_cb	1295	IO::AIO::poll_wait, IO::AIO::poll_cb
256	while IO::AIO::nreqs;	1296	while IO::AIO::nreqs;
257		1297
		1298	=item IO::AIO::nready
		1299
		1300	Returns the number of requests currently in the ready state (not yet
		1301	executed).
		1302
258	=item IO::AIO::poll	1303	=item IO::AIO::npending
259		1304
260	Waits until some requests have been handled.	1305	Returns the number of requests currently in the pending state (executed,
261		1306	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		1307
305	=back	1308	=back
306		1309
307	=cut	1310	=cut
308		1311
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;	1312	min_parallel 8;
322		1313
323	END {	1314	END { flush }
324	max_parallel 0;
325	}
326		1315
327	1;	1316	1;
328		1317
		1318	=head2 FORK BEHAVIOUR
		1319
		1320	This module should do "the right thing" when the process using it forks:
		1321
		1322	Before the fork, IO::AIO enters a quiescent state where no requests
		1323	can be added in other threads and no results will be processed. After
		1324	the fork the parent simply leaves the quiescent state and continues
		1325	request/result processing, while the child frees the request/result queue
		1326	(so that the requests started before the fork will only be handled in the
		1327	parent). Threads will be started on demand until the limit set in the
		1328	parent process has been reached again.
		1329
		1330	In short: the parent will, after a short pause, continue as if fork had
		1331	not been called, while the child will act as if IO::AIO has not been used
		1332	yet.
		1333
		1334	=head2 MEMORY USAGE
		1335
		1336	Per-request usage:
		1337
		1338	Each aio request uses - depending on your architecture - around 100-200
		1339	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1340	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1341	scalars and other data passed into aio requests will also be locked and
		1342	will consume memory till the request has entered the done state.
		1343
		1344	This is not awfully much, so queuing lots of requests is not usually a
		1345	problem.
		1346
		1347	Per-thread usage:
		1348
		1349	In the execution phase, some aio requests require more memory for
		1350	temporary buffers, and each thread requires a stack and other data
		1351	structures (usually around 16k-128k, depending on the OS).
		1352
		1353	=head1 KNOWN BUGS
		1354
		1355	Known bugs will be fixed in the next release.
		1356
329	=head1 SEE ALSO	1357	=head1 SEE ALSO
330		1358
331	L<Coro>, L<Linux::AIO>.	1359	L<Coro::AIO>.
332		1360
333	=head1 AUTHOR	1361	=head1 AUTHOR
334		1362
335	Marc Lehmann <schmorp@schmorp.de>	1363	Marc Lehmann <schmorp@schmorp.de>
336	http://home.schmorp.de/	1364	http://home.schmorp.de/

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