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Revision 1.26 by root, Sun Aug 7 03:34:07 2005 UTC vs.
Revision 1.142 by root, Wed Oct 22 18:15:36 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, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
		34	# EV integration
		35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		36
		37	# Event integration
21	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
22	poll => 'r',	39	poll => 'r',
23	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
24		41
25	# Glib/Gtk2	42	# Glib/Gtk2 integration
26	add_watch Glib::IO IO::AIO::poll_fileno,	43	add_watch Glib::IO IO::AIO::poll_fileno,
27	in => sub { IO::AIO::poll_cb; 1 };	44	in => sub { IO::AIO::poll_cb; 1 };
28		45
29	# Tk	46	# Tk integration
30	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",	47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
31	readable => \&IO::AIO::poll_cb);	48	readable => \&IO::AIO::poll_cb);
32		49
33	# Danga::Socket	50	# Danga::Socket integration
34	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
35	\&IO::AIO::poll_cb);	52	\&IO::AIO::poll_cb);
36		53
37
38	=head1 DESCRIPTION	54	=head1 DESCRIPTION
39		55
40	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
41	operating system supports.	57	operating system supports.
42		58
		59	Asynchronous means that operations that can normally block your program
		60	(e.g. reading from disk) will be done asynchronously: the operation
		61	will still block, but you can do something else in the meantime. This
		62	is extremely useful for programs that need to stay interactive even
		63	when doing heavy I/O (GUI programs, high performance network servers
		64	etc.), but can also be used to easily do operations in parallel that are
		65	normally done sequentially, e.g. stat'ing many files, which is much faster
		66	on a RAID volume or over NFS when you do a number of stat operations
		67	concurrently.
		68
		69	While most of this works on all types of file descriptors (for
		70	example sockets), using these functions on file descriptors that
		71	support nonblocking operation (again, sockets, pipes etc.) is very
		72	inefficient. Use an event loop for that (such as the L<Event|Event>
		73	module): IO::AIO will naturally fit into such an event loop itself.
		74
43	Currently, a number of threads are started that execute your read/writes	75	In this version, a number of threads are started that execute your
44	and signal their completion. You don't need thread support in your libc or	76	requests and signal their completion. You don't need thread support
45	perl, and the threads created by this module will not be visible to the	77	in perl, and the threads created by this module will not be visible
46	pthreads library. In the future, this module might make use of the native	78	to perl. In the future, this module might make use of the native aio
47	aio functions available on many operating systems. However, they are often	79	functions available on many operating systems. However, they are often
48	not well-supported (Linux doesn't allow them on normal files currently,	80	not well-supported or restricted (GNU/Linux doesn't allow them on normal
49	for example), and they would only support aio_read and aio_write, so the	81	files currently, for example), and they would only support aio_read and
50	remaining functionality would have to be implemented using threads anyway.	82	aio_write, so the remaining functionality would have to be implemented
		83	using threads anyway.
51		84
52	Although the module will work with in the presence of other threads, it is	85	Although the module will work in the presence of other (Perl-) threads,
53	currently not reentrant, so use appropriate locking yourself, always call	86	it is currently not reentrant in any way, so use appropriate locking
54	C<poll_cb> from within the same thread, or never call C<poll_cb> (or other	87	yourself, always call C<poll_cb> from within the same thread, or never
55	C<aio_> functions) recursively.	88	call C<poll_cb> (or other C<aio_> functions) recursively.
		89
		90	=head2 EXAMPLE
		91
		92	This is a simple example that uses the Event module and loads
		93	F</etc/passwd> asynchronously:
		94
		95	use Fcntl;
		96	use Event;
		97	use IO::AIO;
		98
		99	# register the IO::AIO callback with Event
		100	Event->io (fd => IO::AIO::poll_fileno,
		101	poll => 'r',
		102	cb => \&IO::AIO::poll_cb);
		103
		104	# queue the request to open /etc/passwd
		105	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		106	my $fh = shift
		107	or die "error while opening: $!";
		108
		109	# stat'ing filehandles is generally non-blocking
		110	my $size = -s $fh;
		111
		112	# queue a request to read the file
		113	my $contents;
		114	aio_read $fh, 0, $size, $contents, 0, sub {
		115	$_[0] == $size
		116	or die "short read: $!";
		117
		118	close $fh;
		119
		120	# file contents now in $contents
		121	print $contents;
		122
		123	# exit event loop and program
		124	Event::unloop;
		125	};
		126	};
		127
		128	# possibly queue up other requests, or open GUI windows,
		129	# check for sockets etc. etc.
		130
		131	# process events as long as there are some:
		132	Event::loop;
		133
		134	=head1 REQUEST ANATOMY AND LIFETIME
		135
		136	Every C<aio_*> function creates a request. which is a C data structure not
		137	directly visible to Perl.
		138
		139	If called in non-void context, every request function returns a Perl
		140	object representing the request. In void context, nothing is returned,
		141	which saves a bit of memory.
		142
		143	The perl object is a fairly standard ref-to-hash object. The hash contents
		144	are not used by IO::AIO so you are free to store anything you like in it.
		145
		146	During their existance, aio requests travel through the following states,
		147	in order:
		148
		149	=over 4
		150
		151	=item ready
		152
		153	Immediately after a request is created it is put into the ready state,
		154	waiting for a thread to execute it.
		155
		156	=item execute
		157
		158	A thread has accepted the request for processing and is currently
		159	executing it (e.g. blocking in read).
		160
		161	=item pending
		162
		163	The request has been executed and is waiting for result processing.
		164
		165	While request submission and execution is fully asynchronous, result
		166	processing is not and relies on the perl interpreter calling C<poll_cb>
		167	(or another function with the same effect).
		168
		169	=item result
		170
		171	The request results are processed synchronously by C<poll_cb>.
		172
		173	The C<poll_cb> function will process all outstanding aio requests by
		174	calling their callbacks, freeing memory associated with them and managing
		175	any groups they are contained in.
		176
		177	=item done
		178
		179	Request has reached the end of its lifetime and holds no resources anymore
		180	(except possibly for the Perl object, but its connection to the actual
		181	aio request is severed and calling its methods will either do nothing or
		182	result in a runtime error).
		183
		184	=back
56		185
57	=cut	186	=cut
58		187
59	package IO::AIO;	188	package IO::AIO;
60		189
		190	use Carp ();
		191
61	no warnings;	192	no warnings;
		193	use strict 'vars';
62		194
63	use base 'Exporter';	195	use base 'Exporter';
64		196
65	use Fcntl ();
66
67	BEGIN {	197	BEGIN {
68	$VERSION = 1.1;	198	our $VERSION = '3.16';
69		199
70	@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink	200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
71	aio_fsync aio_fdatasync aio_readahead);	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir
72	@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
		203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		204	aio_rename aio_link aio_move aio_copy aio_group
		205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		206	aio_chmod aio_utime aio_truncate);
		207
		208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
		209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
		210	min_parallel max_parallel max_idle
		211	nreqs nready npending nthreads
		212	max_poll_time max_poll_reqs);
		213
		214	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
73		215
74	require XSLoader;	216	require XSLoader;
75	XSLoader::load IO::AIO, $VERSION;	217	XSLoader::load ("IO::AIO", $VERSION);
76	}	218	}
77		219
78	=head1 FUNCTIONS	220	=head1 FUNCTIONS
79		221
80	=head2 AIO FUNCTIONS	222	=head2 AIO REQUEST FUNCTIONS
81		223
82	All the C<aio_*> calls are more or less thin wrappers around the syscall	224	All the C<aio_*> calls are more or less thin wrappers around the syscall
83	with the same name (sans C<aio_>). The arguments are similar or identical,	225	with the same name (sans C<aio_>). The arguments are similar or identical,
84	and they all accept an additional (and optional) C<$callback> argument	226	and they all accept an additional (and optional) C<$callback> argument
85	which must be a code reference. This code reference will get called with	227	which must be a code reference. This code reference will get called with
86	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	228	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
87	perl, which usually delivers "false") as it's sole argument when the given	229	perl, which usually delivers "false") as its sole argument after the given
88	syscall has been executed asynchronously.	230	syscall has been executed asynchronously.
89		231
90	All functions expecting a filehandle keep a copy of the filehandle	232	All functions expecting a filehandle keep a copy of the filehandle
91	internally until the request has finished.	233	internally until the request has finished.
92		234
		235	All functions return request objects of type L<IO::AIO::REQ> that allow
		236	further manipulation of those requests while they are in-flight.
		237
93	The filenames you pass to these routines I<must> be absolute. The reason	238	The pathnames you pass to these routines I<must> be absolute and
94	for this is that at the time the request is being executed, the current	239	encoded as octets. The reason for the former is that at the time the
95	working directory could have changed. Alternatively, you can make sure	240	request is being executed, the current working directory could have
96	that you never change the current working directory.	241	changed. Alternatively, you can make sure that you never change the
		242	current working directory anywhere in the program and then use relative
		243	paths.
		244
		245	To encode pathnames as octets, either make sure you either: a) always pass
		246	in filenames you got from outside (command line, readdir etc.) without
		247	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
		248	your pathnames to the locale (or other) encoding in effect in the user
		249	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
		250	use something else to ensure your scalar has the correct contents.
		251
		252	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		253	handles correctly whether it is set or not.
97		254
98	=over 4	255	=over 4
99		256
		257	=item $prev_pri = aioreq_pri [$pri]
		258
		259	Returns the priority value that would be used for the next request and, if
		260	C<$pri> is given, sets the priority for the next aio request.
		261
		262	The default priority is C<0>, the minimum and maximum priorities are C<-4>
		263	and C<4>, respectively. Requests with higher priority will be serviced
		264	first.
		265
		266	The priority will be reset to C<0> after each call to one of the C<aio_*>
		267	functions.
		268
		269	Example: open a file with low priority, then read something from it with
		270	higher priority so the read request is serviced before other low priority
		271	open requests (potentially spamming the cache):
		272
		273	aioreq_pri -3;
		274	aio_open ..., sub {
		275	return unless $_[0];
		276
		277	aioreq_pri -2;
		278	aio_read $_[0], ..., sub {
		279	...
		280	};
		281	};
		282
		283
		284	=item aioreq_nice $pri_adjust
		285
		286	Similar to C<aioreq_pri>, but subtracts the given value from the current
		287	priority, so the effect is cumulative.
		288
		289
100	=item aio_open $pathname, $flags, $mode, $callback	290	=item aio_open $pathname, $flags, $mode, $callback->($fh)
101		291
102	Asynchronously open or create a file and call the callback with a newly	292	Asynchronously open or create a file and call the callback with a newly
103	created filehandle for the file.	293	created filehandle for the file.
104		294
105	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	295	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
…		…
109	list. They are the same as used by C<sysopen>.	299	list. They are the same as used by C<sysopen>.
110		300
111	Likewise, C<$mode> specifies the mode of the newly created file, if it	301	Likewise, C<$mode> specifies the mode of the newly created file, if it
112	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	302	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
113	except that it is mandatory (i.e. use C<0> if you don't create new files,	303	except that it is mandatory (i.e. use C<0> if you don't create new files,
114	and C<0666> or C<0777> if you do).	304	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		305	by the umask in effect then the request is being executed, so better never
		306	change the umask.
115		307
116	Example:	308	Example:
117		309
118	aio_open "/etc/passwd", O_RDONLY, 0, sub {	310	aio_open "/etc/passwd", O_RDONLY, 0, sub {
119	if ($_[0]) {	311	if ($_[0]) {
…		…
122	} else {	314	} else {
123	die "open failed: $!\n";	315	die "open failed: $!\n";
124	}	316	}
125	};	317	};
126		318
		319
127	=item aio_close $fh, $callback	320	=item aio_close $fh, $callback->($status)
128		321
129	Asynchronously close a file and call the callback with the result	322	Asynchronously close a file and call the callback with the result
130	code. I<WARNING:> although accepted, you should not pass in a perl	323	code.
131	filehandle here, as perl will likely close the file descriptor another
132	time when the filehandle is destroyed. Normally, you can safely call perls
133	C<close> or just let filehandles go out of scope.
134		324
135	This is supposed to be a bug in the API, so that might change. It's	325	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
136	therefore best to avoid this function.	326	closing the file descriptor associated with the filehandle itself.
137		327
		328	Therefore, C<aio_close> will not close the filehandle - instead it will
		329	use dup2 to overwrite the file descriptor with the write-end of a pipe
		330	(the pipe fd will be created on demand and will be cached).
		331
		332	Or in other words: the file descriptor will be closed, but it will not be
		333	free for reuse until the perl filehandle is closed.
		334
		335	=cut
		336
138	=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback	337	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
139		338
140	=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback	339	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
141		340
142	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	341	Reads or writes C<$length> bytes from the specified C<$fh> and C<$offset>
143	into the scalar given by C<data> and offset C<dataoffset> and calls the	342	into the scalar given by C<$data> and offset C<$dataoffset> and calls the
144	callback without the actual number of bytes read (or -1 on error, just	343	callback without the actual number of bytes read (or -1 on error, just
145	like the syscall).	344	like the syscall).
		345
		346	If C<$offset> is undefined, then the current file descriptor offset will
		347	be used (and updated), otherwise the file descriptor offset will not be
		348	changed by these calls.
		349
		350	If C<$length> is undefined in C<aio_write>, use the remaining length of C<$data>.
		351
		352	If C<$dataoffset> is less than zero, it will be counted from the end of
		353	C<$data>.
		354
		355	The C<$data> scalar I<MUST NOT> be modified in any way while the request
		356	is outstanding. Modifying it can result in segfaults or World War III (if
		357	the necessary/optional hardware is installed).
146		358
147	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	359	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
148	offset C<0> within the scalar:	360	offset C<0> within the scalar:
149		361
150	aio_read $fh, 7, 15, $buffer, 0, sub {	362	aio_read $fh, 7, 15, $buffer, 0, sub {
151	$_[0] > 0 or die "read error: $!";	363	$_[0] > 0 or die "read error: $!";
152	print "read $_[0] bytes: <$buffer>\n";	364	print "read $_[0] bytes: <$buffer>\n";
153	};	365	};
154		366
		367
		368	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		369
		370	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
		371	reading at byte offset C<$in_offset>, and starts writing at the current
		372	file offset of C<$out_fh>. Because of that, it is not safe to issue more
		373	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
		374	other.
		375
		376	This call tries to make use of a native C<sendfile> syscall to provide
		377	zero-copy operation. For this to work, C<$out_fh> should refer to a
		378	socket, and C<$in_fh> should refer to mmap'able file.
		379
		380	If the native sendfile call fails or is not implemented, it will be
		381	emulated, so you can call C<aio_sendfile> on any type of filehandle
		382	regardless of the limitations of the operating system.
		383
		384	Please note, however, that C<aio_sendfile> can read more bytes from
		385	C<$in_fh> than are written, and there is no way to find out how many
		386	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
		387	provides the number of bytes written to C<$out_fh>. Only if the result
		388	value equals C<$length> one can assume that C<$length> bytes have been
		389	read.
		390
		391
155	=item aio_readahead $fh,$offset,$length, $callback	392	=item aio_readahead $fh,$offset,$length, $callback->($retval)
156		393
157	C<aio_readahead> populates the page cache with data from a file so that	394	C<aio_readahead> populates the page cache with data from a file so that
158	subsequent reads from that file will not block on disk I/O. The C<$offset>	395	subsequent reads from that file will not block on disk I/O. The C<$offset>
159	argument specifies the starting point from which data is to be read and	396	argument specifies the starting point from which data is to be read and
160	C<$length> specifies the number of bytes to be read. I/O is performed in	397	C<$length> specifies the number of bytes to be read. I/O is performed in
…		…
164	file. The current file offset of the file is left unchanged.	401	file. The current file offset of the file is left unchanged.
165		402
166	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	403	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
167	emulated by simply reading the data, which would have a similar effect.	404	emulated by simply reading the data, which would have a similar effect.
168		405
		406
169	=item aio_stat $fh_or_path, $callback	407	=item aio_stat $fh_or_path, $callback->($status)
170		408
171	=item aio_lstat $fh, $callback	409	=item aio_lstat $fh, $callback->($status)
172		410
173	Works like perl's C<stat> or C<lstat> in void context. The callback will	411	Works like perl's C<stat> or C<lstat> in void context. The callback will
174	be called after the stat and the results will be available using C<stat _>	412	be called after the stat and the results will be available using C<stat _>
175	or C<-s _> etc...	413	or C<-s _> etc...
176		414
…		…
186	aio_stat "/etc/passwd", sub {	424	aio_stat "/etc/passwd", sub {
187	$_[0] and die "stat failed: $!";	425	$_[0] and die "stat failed: $!";
188	print "size is ", -s _, "\n";	426	print "size is ", -s _, "\n";
189	};	427	};
190		428
		429
		430	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		431
		432	Works like perl's C<utime> function (including the special case of $atime
		433	and $mtime being undef). Fractional times are supported if the underlying
		434	syscalls support them.
		435
		436	When called with a pathname, uses utimes(2) if available, otherwise
		437	utime(2). If called on a file descriptor, uses futimes(2) if available,
		438	otherwise returns ENOSYS, so this is not portable.
		439
		440	Examples:
		441
		442	# set atime and mtime to current time (basically touch(1)):
		443	aio_utime "path", undef, undef;
		444	# set atime to current time and mtime to beginning of the epoch:
		445	aio_utime "path", time, undef; # undef==0
		446
		447
		448	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		449
		450	Works like perl's C<chown> function, except that C<undef> for either $uid
		451	or $gid is being interpreted as "do not change" (but -1 can also be used).
		452
		453	Examples:
		454
		455	# same as "chown root path" in the shell:
		456	aio_chown "path", 0, -1;
		457	# same as above:
		458	aio_chown "path", 0, undef;
		459
		460
		461	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		462
		463	Works like truncate(2) or ftruncate(2).
		464
		465
		466	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		467
		468	Works like perl's C<chmod> function.
		469
		470
191	=item aio_unlink $pathname, $callback	471	=item aio_unlink $pathname, $callback->($status)
192		472
193	Asynchronously unlink (delete) a file and call the callback with the	473	Asynchronously unlink (delete) a file and call the callback with the
194	result code.	474	result code.
195		475
		476
		477	=item aio_mknod $path, $mode, $dev, $callback->($status)
		478
		479	[EXPERIMENTAL]
		480
		481	Asynchronously create a device node (or fifo). See mknod(2).
		482
		483	The only (POSIX-) portable way of calling this function is:
		484
		485	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		486
		487
		488	=item aio_link $srcpath, $dstpath, $callback->($status)
		489
		490	Asynchronously create a new link to the existing object at C<$srcpath> at
		491	the path C<$dstpath> and call the callback with the result code.
		492
		493
		494	=item aio_symlink $srcpath, $dstpath, $callback->($status)
		495
		496	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
		497	the path C<$dstpath> and call the callback with the result code.
		498
		499
		500	=item aio_readlink $path, $callback->($link)
		501
		502	Asynchronously read the symlink specified by C<$path> and pass it to
		503	the callback. If an error occurs, nothing or undef gets passed to the
		504	callback.
		505
		506
		507	=item aio_rename $srcpath, $dstpath, $callback->($status)
		508
		509	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
		510	rename(2) and call the callback with the result code.
		511
		512
		513	=item aio_mkdir $pathname, $mode, $callback->($status)
		514
		515	Asynchronously mkdir (create) a directory and call the callback with
		516	the result code. C<$mode> will be modified by the umask at the time the
		517	request is executed, so do not change your umask.
		518
		519
		520	=item aio_rmdir $pathname, $callback->($status)
		521
		522	Asynchronously rmdir (delete) a directory and call the callback with the
		523	result code.
		524
		525
		526	=item aio_readdir $pathname, $callback->($entries)
		527
		528	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
		529	directory (i.e. opendir + readdir + closedir). The entries will not be
		530	sorted, and will B<NOT> include the C<.> and C<..> entries.
		531
		532	The callback a single argument which is either C<undef> or an array-ref
		533	with the filenames.
		534
		535
		536	=item aio_load $path, $data, $callback->($status)
		537
		538	This is a composite request that tries to fully load the given file into
		539	memory. Status is the same as with aio_read.
		540
		541	=cut
		542
		543	sub aio_load($$;$) {
		544	my ($path, undef, $cb) = @_;
		545	my $data = \$_[1];
		546
		547	my $pri = aioreq_pri;
		548	my $grp = aio_group $cb;
		549
		550	aioreq_pri $pri;
		551	add $grp aio_open $path, O_RDONLY, 0, sub {
		552	my $fh = shift
		553	or return $grp->result (-1);
		554
		555	aioreq_pri $pri;
		556	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		557	$grp->result ($_[0]);
		558	};
		559	};
		560
		561	$grp
		562	}
		563
		564	=item aio_copy $srcpath, $dstpath, $callback->($status)
		565
		566	Try to copy the I<file> (directories not supported as either source or
		567	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		568	the C<0> (error) or C<-1> ok.
		569
		570	This is a composite request that creates the destination file with
		571	mode 0200 and copies the contents of the source file into it using
		572	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		573	uid/gid, in that order.
		574
		575	If an error occurs, the partial destination file will be unlinked, if
		576	possible, except when setting atime, mtime, access mode and uid/gid, where
		577	errors are being ignored.
		578
		579	=cut
		580
		581	sub aio_copy($$;$) {
		582	my ($src, $dst, $cb) = @_;
		583
		584	my $pri = aioreq_pri;
		585	my $grp = aio_group $cb;
		586
		587	aioreq_pri $pri;
		588	add $grp aio_open $src, O_RDONLY, 0, sub {
		589	if (my $src_fh = $_[0]) {
		590	my @stat = stat $src_fh;
		591
		592	aioreq_pri $pri;
		593	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		594	if (my $dst_fh = $_[0]) {
		595	aioreq_pri $pri;
		596	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		597	if ($_[0] == $stat[7]) {
		598	$grp->result (0);
		599	close $src_fh;
		600
		601	# those should not normally block. should. should.
		602	utime $stat[8], $stat[9], $dst;
		603	chmod $stat[2] & 07777, $dst_fh;
		604	chown $stat[4], $stat[5], $dst_fh;
		605
		606	aioreq_pri $pri;
		607	add $grp aio_close $dst_fh;
		608	} else {
		609	$grp->result (-1);
		610	close $src_fh;
		611	close $dst_fh;
		612
		613	aioreq $pri;
		614	add $grp aio_unlink $dst;
		615	}
		616	};
		617	} else {
		618	$grp->result (-1);
		619	}
		620	},
		621
		622	} else {
		623	$grp->result (-1);
		624	}
		625	};
		626
		627	$grp
		628	}
		629
		630	=item aio_move $srcpath, $dstpath, $callback->($status)
		631
		632	Try to move the I<file> (directories not supported as either source or
		633	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		634	the C<0> (error) or C<-1> ok.
		635
		636	This is a composite request that tries to rename(2) the file first; if
		637	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		638	that is successful, unlinks the C<$srcpath>.
		639
		640	=cut
		641
		642	sub aio_move($$;$) {
		643	my ($src, $dst, $cb) = @_;
		644
		645	my $pri = aioreq_pri;
		646	my $grp = aio_group $cb;
		647
		648	aioreq_pri $pri;
		649	add $grp aio_rename $src, $dst, sub {
		650	if ($_[0] && $! == EXDEV) {
		651	aioreq_pri $pri;
		652	add $grp aio_copy $src, $dst, sub {
		653	$grp->result ($_[0]);
		654
		655	if (!$_[0]) {
		656	aioreq_pri $pri;
		657	add $grp aio_unlink $src;
		658	}
		659	};
		660	} else {
		661	$grp->result ($_[0]);
		662	}
		663	};
		664
		665	$grp
		666	}
		667
		668	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
		669
		670	Scans a directory (similar to C<aio_readdir>) but additionally tries to
		671	efficiently separate the entries of directory C<$path> into two sets of
		672	names, directories you can recurse into (directories), and ones you cannot
		673	recurse into (everything else, including symlinks to directories).
		674
		675	C<aio_scandir> is a composite request that creates of many sub requests_
		676	C<$maxreq> specifies the maximum number of outstanding aio requests that
		677	this function generates. If it is C<< <= 0 >>, then a suitable default
		678	will be chosen (currently 4).
		679
		680	On error, the callback is called without arguments, otherwise it receives
		681	two array-refs with path-relative entry names.
		682
		683	Example:
		684
		685	aio_scandir $dir, 0, sub {
		686	my ($dirs, $nondirs) = @_;
		687	print "real directories: @$dirs\n";
		688	print "everything else: @$nondirs\n";
		689	};
		690
		691	Implementation notes.
		692
		693	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
		694
		695	After reading the directory, the modification time, size etc. of the
		696	directory before and after the readdir is checked, and if they match (and
		697	isn't the current time), the link count will be used to decide how many
		698	entries are directories (if >= 2). Otherwise, no knowledge of the number
		699	of subdirectories will be assumed.
		700
		701	Then entries will be sorted into likely directories (everything without
		702	a non-initial dot currently) and likely non-directories (everything
		703	else). Then every entry plus an appended C</.> will be C<stat>'ed,
		704	likely directories first. If that succeeds, it assumes that the entry
		705	is a directory or a symlink to directory (which will be checked
		706	seperately). This is often faster than stat'ing the entry itself because
		707	filesystems might detect the type of the entry without reading the inode
		708	data (e.g. ext2fs filetype feature).
		709
		710	If the known number of directories (link count - 2) has been reached, the
		711	rest of the entries is assumed to be non-directories.
		712
		713	This only works with certainty on POSIX (= UNIX) filesystems, which
		714	fortunately are the vast majority of filesystems around.
		715
		716	It will also likely work on non-POSIX filesystems with reduced efficiency
		717	as those tend to return 0 or 1 as link counts, which disables the
		718	directory counting heuristic.
		719
		720	=cut
		721
		722	sub aio_scandir($$;$) {
		723	my ($path, $maxreq, $cb) = @_;
		724
		725	my $pri = aioreq_pri;
		726
		727	my $grp = aio_group $cb;
		728
		729	$maxreq = 4 if $maxreq <= 0;
		730
		731	# stat once
		732	aioreq_pri $pri;
		733	add $grp aio_stat $path, sub {
		734	return $grp->result () if $_[0];
		735	my $now = time;
		736	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		737
		738	# read the directory entries
		739	aioreq_pri $pri;
		740	add $grp aio_readdir $path, sub {
		741	my $entries = shift
		742	or return $grp->result ();
		743
		744	# stat the dir another time
		745	aioreq_pri $pri;
		746	add $grp aio_stat $path, sub {
		747	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		748
		749	my $ndirs;
		750
		751	# take the slow route if anything looks fishy
		752	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		753	$ndirs = -1;
		754	} else {
		755	# if nlink == 2, we are finished
		756	# on non-posix-fs's, we rely on nlink < 2
		757	$ndirs = (stat _)[3] - 2
		758	or return $grp->result ([], $entries);
		759	}
		760
		761	# sort into likely dirs and likely nondirs
		762	# dirs == files without ".", short entries first
		763	$entries = [map $_->[0],
		764	sort { $b->[1] cmp $a->[1] }
		765	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
		766	@$entries];
		767
		768	my (@dirs, @nondirs);
		769
		770	my $statgrp = add $grp aio_group sub {
		771	$grp->result (\@dirs, \@nondirs);
		772	};
		773
		774	limit $statgrp $maxreq;
		775	feed $statgrp sub {
		776	return unless @$entries;
		777	my $entry = pop @$entries;
		778
		779	aioreq_pri $pri;
		780	add $statgrp aio_stat "$path/$entry/.", sub {
		781	if ($_[0] < 0) {
		782	push @nondirs, $entry;
		783	} else {
		784	# need to check for real directory
		785	aioreq_pri $pri;
		786	add $statgrp aio_lstat "$path/$entry", sub {
		787	if (-d _) {
		788	push @dirs, $entry;
		789
		790	unless (--$ndirs) {
		791	push @nondirs, @$entries;
		792	feed $statgrp;
		793	}
		794	} else {
		795	push @nondirs, $entry;
		796	}
		797	}
		798	}
		799	};
		800	};
		801	};
		802	};
		803	};
		804
		805	$grp
		806	}
		807
		808	=item aio_rmtree $path, $callback->($status)
		809
		810	Delete a directory tree starting (and including) C<$path>, return the
		811	status of the final C<rmdir> only. This is a composite request that
		812	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		813	everything else.
		814
		815	=cut
		816
		817	sub aio_rmtree;
		818	sub aio_rmtree($;$) {
		819	my ($path, $cb) = @_;
		820
		821	my $pri = aioreq_pri;
		822	my $grp = aio_group $cb;
		823
		824	aioreq_pri $pri;
		825	add $grp aio_scandir $path, 0, sub {
		826	my ($dirs, $nondirs) = @_;
		827
		828	my $dirgrp = aio_group sub {
		829	add $grp aio_rmdir $path, sub {
		830	$grp->result ($_[0]);
		831	};
		832	};
		833
		834	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		835	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		836
		837	add $grp $dirgrp;
		838	};
		839
		840	$grp
		841	}
		842
		843	=item aio_sync $callback->($status)
		844
		845	Asynchronously call sync and call the callback when finished.
		846
196	=item aio_fsync $fh, $callback	847	=item aio_fsync $fh, $callback->($status)
197		848
198	Asynchronously call fsync on the given filehandle and call the callback	849	Asynchronously call fsync on the given filehandle and call the callback
199	with the fsync result code.	850	with the fsync result code.
200		851
201	=item aio_fdatasync $fh, $callback	852	=item aio_fdatasync $fh, $callback->($status)
202		853
203	Asynchronously call fdatasync on the given filehandle and call the	854	Asynchronously call fdatasync on the given filehandle and call the
204	callback with the fdatasync result code.	855	callback with the fdatasync result code.
205		856
206	If this call isn't available because your OS lacks it or it couldn't be	857	If this call isn't available because your OS lacks it or it couldn't be
207	detected, it will be emulated by calling C<fsync> instead.	858	detected, it will be emulated by calling C<fsync> instead.
208		859
		860	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		861
		862	Sync the data portion of the file specified by C<$offset> and C<$length>
		863	to disk (but NOT the metadata), by calling the Linux-specific
		864	sync_file_range call. If sync_file_range is not available or it returns
		865	ENOSYS, then fdatasync or fsync is being substituted.
		866
		867	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		868	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		869	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		870	manpage for details.
		871
		872	=item aio_pathsync $path, $callback->($status)
		873
		874	This request tries to open, fsync and close the given path. This is a
		875	composite request intended to sync directories after directory operations
		876	(E.g. rename). This might not work on all operating systems or have any
		877	specific effect, but usually it makes sure that directory changes get
		878	written to disc. It works for anything that can be opened for read-only,
		879	not just directories.
		880
		881	Passes C<0> when everything went ok, and C<-1> on error.
		882
		883	=cut
		884
		885	sub aio_pathsync($;$) {
		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	=item aio_group $callback->(...)
		911
		912	This is a very special aio request: Instead of doing something, it is a
		913	container for other aio requests, which is useful if you want to bundle
		914	many requests into a single, composite, request with a definite callback
		915	and the ability to cancel the whole request with its subrequests.
		916
		917	Returns an object of class L<IO::AIO::GRP>. See its documentation below
		918	for more info.
		919
		920	Example:
		921
		922	my $grp = aio_group sub {
		923	print "all stats done\n";
		924	};
		925
		926	add $grp
		927	(aio_stat ...),
		928	(aio_stat ...),
		929	...;
		930
		931	=item aio_nop $callback->()
		932
		933	This is a special request - it does nothing in itself and is only used for
		934	side effects, such as when you want to add a dummy request to a group so
		935	that finishing the requests in the group depends on executing the given
		936	code.
		937
		938	While this request does nothing, it still goes through the execution
		939	phase and still requires a worker thread. Thus, the callback will not
		940	be executed immediately but only after other requests in the queue have
		941	entered their execution phase. This can be used to measure request
		942	latency.
		943
		944	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
		945
		946	Mainly used for debugging and benchmarking, this aio request puts one of
		947	the request workers to sleep for the given time.
		948
		949	While it is theoretically handy to have simple I/O scheduling requests
		950	like sleep and file handle readable/writable, the overhead this creates is
		951	immense (it blocks a thread for a long time) so do not use this function
		952	except to put your application under artificial I/O pressure.
		953
209	=back	954	=back
210		955
		956	=head2 IO::AIO::REQ CLASS
		957
		958	All non-aggregate C<aio_*> functions return an object of this class when
		959	called in non-void context.
		960
		961	=over 4
		962
		963	=item cancel $req
		964
		965	Cancels the request, if possible. Has the effect of skipping execution
		966	when entering the B<execute> state and skipping calling the callback when
		967	entering the the B<result> state, but will leave the request otherwise
		968	untouched. That means that requests that currently execute will not be
		969	stopped and resources held by the request will not be freed prematurely.
		970
		971	=item cb $req $callback->(...)
		972
		973	Replace (or simply set) the callback registered to the request.
		974
		975	=back
		976
		977	=head2 IO::AIO::GRP CLASS
		978
		979	This class is a subclass of L<IO::AIO::REQ>, so all its methods apply to
		980	objects of this class, too.
		981
		982	A IO::AIO::GRP object is a special request that can contain multiple other
		983	aio requests.
		984
		985	You create one by calling the C<aio_group> constructing function with a
		986	callback that will be called when all contained requests have entered the
		987	C<done> state:
		988
		989	my $grp = aio_group sub {
		990	print "all requests are done\n";
		991	};
		992
		993	You add requests by calling the C<add> method with one or more
		994	C<IO::AIO::REQ> objects:
		995
		996	$grp->add (aio_unlink "...");
		997
		998	add $grp aio_stat "...", sub {
		999	$_[0] or return $grp->result ("error");
		1000
		1001	# add another request dynamically, if first succeeded
		1002	add $grp aio_open "...", sub {
		1003	$grp->result ("ok");
		1004	};
		1005	};
		1006
		1007	This makes it very easy to create composite requests (see the source of
		1008	C<aio_move> for an application) that work and feel like simple requests.
		1009
		1010	=over 4
		1011
		1012	=item * The IO::AIO::GRP objects will be cleaned up during calls to
		1013	C<IO::AIO::poll_cb>, just like any other request.
		1014
		1015	=item * They can be canceled like any other request. Canceling will cancel not
		1016	only the request itself, but also all requests it contains.
		1017
		1018	=item * They can also can also be added to other IO::AIO::GRP objects.
		1019
		1020	=item * You must not add requests to a group from within the group callback (or
		1021	any later time).
		1022
		1023	=back
		1024
		1025	Their lifetime, simplified, looks like this: when they are empty, they
		1026	will finish very quickly. If they contain only requests that are in the
		1027	C<done> state, they will also finish. Otherwise they will continue to
		1028	exist.
		1029
		1030	That means after creating a group you have some time to add requests
		1031	(precisely before the callback has been invoked, which is only done within
		1032	the C<poll_cb>). And in the callbacks of those requests, you can add
		1033	further requests to the group. And only when all those requests have
		1034	finished will the the group 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 example,
		1078	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
		1079	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> when this method is called, it will be set to
		1094	C<2> automatically.
		1095
		1096	Example:
		1097
		1098	# stat all files in @files, but only ever use four aio requests concurrently:
		1099
		1100	my $grp = aio_group sub { print "finished\n" };
		1101	limit $grp 4;
		1102	feed $grp sub {
		1103	my $file = pop @files
		1104	or return;
		1105
		1106	add $grp aio_stat $file, sub { ... };
		1107	};
		1108
		1109	=item limit $grp $num
		1110
		1111	Sets the feeder limit for the group: The feeder will be called whenever
		1112	the group contains less than this many requests.
		1113
		1114	Setting the limit to C<0> will pause the feeding process.
		1115
		1116	The default value for the limit is C<0>, but note that setting a feeder
		1117	automatically bumps it up to C<2>.
		1118
		1119	=back
		1120
211	=head2 SUPPORT FUNCTIONS	1121	=head2 SUPPORT FUNCTIONS
		1122
		1123	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
212		1124
213	=over 4	1125	=over 4
214		1126
215	=item $fileno = IO::AIO::poll_fileno	1127	=item $fileno = IO::AIO::poll_fileno
216		1128
…		…
221		1133
222	See C<poll_cb> for an example.	1134	See C<poll_cb> for an example.
223		1135
224	=item IO::AIO::poll_cb	1136	=item IO::AIO::poll_cb
225		1137
226	Process all outstanding events on the result pipe. You have to call this	1138	Process some outstanding events on the result pipe. You have to call this
227	regularly. Returns the number of events processed. Returns immediately	1139	regularly. Returns C<0> if all events could be processed, or C<-1> if it
228	when no events are outstanding.	1140	returned earlier for whatever reason. Returns immediately when no events
		1141	are outstanding. The amount of events processed depends on the settings of
		1142	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1143
		1144	If not all requests were processed for whatever reason, the filehandle
		1145	will still be ready when C<poll_cb> returns, so normally you don't have to
		1146	do anything special to have it called later.
229		1147
230	Example: Install an Event watcher that automatically calls	1148	Example: Install an Event watcher that automatically calls
231	IO::AIO::poll_cb with high priority:	1149	IO::AIO::poll_cb with high priority:
232		1150
233	Event->io (fd => IO::AIO::poll_fileno,	1151	Event->io (fd => IO::AIO::poll_fileno,
234	poll => 'r', async => 1,	1152	poll => 'r', async => 1,
235	cb => \&IO::AIO::poll_cb);	1153	cb => \&IO::AIO::poll_cb);
236		1154
		1155	=item IO::AIO::max_poll_reqs $nreqs
		1156
		1157	=item IO::AIO::max_poll_time $seconds
		1158
		1159	These set the maximum number of requests (default C<0>, meaning infinity)
		1160	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1161	the maximum amount of time (default C<0>, meaning infinity) spent in
		1162	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1163	of time C<poll_cb> is allowed to use).
		1164
		1165	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1166	syscall per request processed, which is not normally a problem unless your
		1167	callbacks are really really fast or your OS is really really slow (I am
		1168	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1169
		1170	Setting these is useful if you want to ensure some level of
		1171	interactiveness when perl is not fast enough to process all requests in
		1172	time.
		1173
		1174	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1175
		1176	Example: Install an Event watcher that automatically calls
		1177	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1178	program get the CPU sometimes even under high AIO load.
		1179
		1180	# try not to spend much more than 0.1s in poll_cb
		1181	IO::AIO::max_poll_time 0.1;
		1182
		1183	# use a low priority so other tasks have priority
		1184	Event->io (fd => IO::AIO::poll_fileno,
		1185	poll => 'r', nice => 1,
		1186	cb => &IO::AIO::poll_cb);
		1187
237	=item IO::AIO::poll_wait	1188	=item IO::AIO::poll_wait
238		1189
		1190	If there are any outstanding requests and none of them in the result
239	Wait till the result filehandle becomes ready for reading (simply does a	1191	phase, wait till the result filehandle becomes ready for reading (simply
240	C<select> on the filehandle. This is useful if you want to synchronously wait	1192	does a C<select> on the filehandle. This is useful if you want to
241	for some requests to finish).	1193	synchronously wait for some requests to finish).
242		1194
243	See C<nreqs> for an example.	1195	See C<nreqs> for an example.
244		1196
		1197	=item IO::AIO::poll
		1198
		1199	Waits until some requests have been handled.
		1200
		1201	Returns the number of requests processed, but is otherwise strictly
		1202	equivalent to:
		1203
		1204	IO::AIO::poll_wait, IO::AIO::poll_cb
		1205
245	=item IO::AIO::nreqs	1206	=item IO::AIO::flush
246		1207
247	Returns the number of requests currently outstanding (i.e. for which their	1208	Wait till all outstanding AIO requests have been handled.
248	callback has not been invoked yet).
249		1209
250	Example: wait till there are no outstanding requests anymore:	1210	Strictly equivalent to:
251		1211
252	IO::AIO::poll_wait, IO::AIO::poll_cb	1212	IO::AIO::poll_wait, IO::AIO::poll_cb
253	while IO::AIO::nreqs;	1213	while IO::AIO::nreqs;
254		1214
		1215	=back
		1216
		1217	=head3 CONTROLLING THE NUMBER OF THREADS
		1218
		1219	=over
		1220
		1221	=item IO::AIO::min_parallel $nthreads
		1222
		1223	Set the minimum number of AIO threads to C<$nthreads>. The current
		1224	default is C<8>, which means eight asynchronous operations can execute
		1225	concurrently at any one time (the number of outstanding requests,
		1226	however, is unlimited).
		1227
		1228	IO::AIO starts threads only on demand, when an AIO request is queued and
		1229	no free thread exists. Please note that queueing up a hundred requests can
		1230	create demand for a hundred threads, even if it turns out that everything
		1231	is in the cache and could have been processed faster by a single thread.
		1232
		1233	It is recommended to keep the number of threads relatively low, as some
		1234	Linux kernel versions will scale negatively with the number of threads
		1235	(higher parallelity => MUCH higher latency). With current Linux 2.6
		1236	versions, 4-32 threads should be fine.
		1237
		1238	Under most circumstances you don't need to call this function, as the
		1239	module selects a default that is suitable for low to moderate load.
		1240
		1241	=item IO::AIO::max_parallel $nthreads
		1242
		1243	Sets the maximum number of AIO threads to C<$nthreads>. If more than the
		1244	specified number of threads are currently running, this function kills
		1245	them. This function blocks until the limit is reached.
		1246
		1247	While C<$nthreads> are zero, aio requests get queued but not executed
		1248	until the number of threads has been increased again.
		1249
		1250	This module automatically runs C<max_parallel 0> at program end, to ensure
		1251	that all threads are killed and that there are no outstanding requests.
		1252
		1253	Under normal circumstances you don't need to call this function.
		1254
		1255	=item IO::AIO::max_idle $nthreads
		1256
		1257	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1258	threads that did not get a request to process within 10 seconds). That
		1259	means if a thread becomes idle while C<$nthreads> other threads are also
		1260	idle, it will free its resources and exit.
		1261
		1262	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1263	to allow for extremely high load situations, but want to free resources
		1264	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1265
		1266	The default is probably ok in most situations, especially if thread
		1267	creation is fast. If thread creation is very slow on your system you might
		1268	want to use larger values.
		1269
		1270	=item IO::AIO::max_outstanding $maxreqs
		1271
		1272	This is a very bad function to use in interactive programs because it
		1273	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1274	use an C<aio_group> together with a feed callback.
		1275
		1276	Sets the maximum number of outstanding requests to C<$nreqs>. If you
		1277	do queue up more than this number of requests, the next call to the
		1278	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1279	function will block until the limit is no longer exceeded.
		1280
		1281	The default value is very large, so there is no practical limit on the
		1282	number of outstanding requests.
		1283
		1284	You can still queue as many requests as you want. Therefore,
		1285	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1286	as a stop gap to shield against fatal memory overflow (with large values).
		1287
		1288	=back
		1289
		1290	=head3 STATISTICAL INFORMATION
		1291
		1292	=over
		1293
255	=item IO::AIO::flush	1294	=item IO::AIO::nreqs
256		1295
257	Wait till all outstanding AIO requests have been handled.	1296	Returns the number of requests currently in the ready, execute or pending
		1297	states (i.e. for which their callback has not been invoked yet).
258		1298
259	Strictly equivalent to:	1299	Example: wait till there are no outstanding requests anymore:
260		1300
261	IO::AIO::poll_wait, IO::AIO::poll_cb	1301	IO::AIO::poll_wait, IO::AIO::poll_cb
262	while IO::AIO::nreqs;	1302	while IO::AIO::nreqs;
263		1303
		1304	=item IO::AIO::nready
		1305
		1306	Returns the number of requests currently in the ready state (not yet
		1307	executed).
		1308
264	=item IO::AIO::poll	1309	=item IO::AIO::npending
265		1310
266	Waits until some requests have been handled.	1311	Returns the number of requests currently in the pending state (executed,
267		1312	but not yet processed by poll_cb).
268	Strictly equivalent to:
269
270	IO::AIO::poll_wait, IO::AIO::poll_cb
271	if IO::AIO::nreqs;
272
273	=item IO::AIO::min_parallel $nthreads
274
275	Set the minimum number of AIO threads to C<$nthreads>. The default is
276	C<1>, which means a single asynchronous operation can be done at one time
277	(the number of outstanding operations, however, is unlimited).
278
279	It is recommended to keep the number of threads low, as some Linux
280	kernel versions will scale negatively with the number of threads (higher
281	parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
282	threads should be fine.
283
284	Under normal circumstances you don't need to call this function, as this
285	module automatically starts some threads (the exact number might change,
286	and is currently 4).
287
288	=item IO::AIO::max_parallel $nthreads
289
290	Sets the maximum number of AIO threads to C<$nthreads>. If more than
291	the specified number of threads are currently running, kill them. This
292	function blocks until the limit is reached.
293
294	This module automatically runs C<max_parallel 0> at program end, to ensure
295	that all threads are killed and that there are no outstanding requests.
296
297	Under normal circumstances you don't need to call this function.
298
299	=item $oldnreqs = IO::AIO::max_outstanding $nreqs
300
301	Sets the maximum number of outstanding requests to C<$nreqs>. If you
302	try to queue up more than this number of requests, the caller will block until
303	some requests have been handled.
304
305	The default is very large, so normally there is no practical limit. If you
306	queue up many requests in a loop it it often improves speed if you set
307	this to a relatively low number, such as C<100>.
308
309	Under normal circumstances you don't need to call this function.
310		1313
311	=back	1314	=back
312		1315
313	=cut	1316	=cut
314		1317
315	# support function to convert a fd into a perl filehandle
316	sub _fd2fh {
317	return undef if $_[0] < 0;
318
319	# try to generate nice filehandles
320	my $sym = "IO::AIO::fd#$_[0]";
321	local *$sym;
322
323	open *$sym, "+<&$_[0]" # usually under any unix
324	or open *$sym, "<&$_[0]" # cygwin needs this
325	or open *$sym, ">&$_[0]" # cygwin needs this
326	or return undef;
327
328	*$sym
329	}
330
331	min_parallel 4;	1318	min_parallel 8;
332		1319
333	END {	1320	END { flush }
334	max_parallel 0;
335	}
336		1321
337	1;	1322	1;
338		1323
		1324	=head2 FORK BEHAVIOUR
		1325
		1326	This module should do "the right thing" when the process using it forks:
		1327
		1328	Before the fork, IO::AIO enters a quiescent state where no requests
		1329	can be added in other threads and no results will be processed. After
		1330	the fork the parent simply leaves the quiescent state and continues
		1331	request/result processing, while the child frees the request/result queue
		1332	(so that the requests started before the fork will only be handled in the
		1333	parent). Threads will be started on demand until the limit set in the
		1334	parent process has been reached again.
		1335
		1336	In short: the parent will, after a short pause, continue as if fork had
		1337	not been called, while the child will act as if IO::AIO has not been used
		1338	yet.
		1339
		1340	=head2 MEMORY USAGE
		1341
		1342	Per-request usage:
		1343
		1344	Each aio request uses - depending on your architecture - around 100-200
		1345	bytes of memory. In addition, stat requests need a stat buffer (possibly
		1346	a few hundred bytes), readdir requires a result buffer and so on. Perl
		1347	scalars and other data passed into aio requests will also be locked and
		1348	will consume memory till the request has entered the done state.
		1349
		1350	This is not awfully much, so queuing lots of requests is not usually a
		1351	problem.
		1352
		1353	Per-thread usage:
		1354
		1355	In the execution phase, some aio requests require more memory for
		1356	temporary buffers, and each thread requires a stack and other data
		1357	structures (usually around 16k-128k, depending on the OS).
		1358
		1359	=head1 KNOWN BUGS
		1360
		1361	Known bugs will be fixed in the next release.
		1362
339	=head1 SEE ALSO	1363	=head1 SEE ALSO
340		1364
341	L<Coro>, L<Linux::AIO>.	1365	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1366	more natural syntax.
342		1367
343	=head1 AUTHOR	1368	=head1 AUTHOR
344		1369
345	Marc Lehmann <schmorp@schmorp.de>	1370	Marc Lehmann <schmorp@schmorp.de>
346	http://home.schmorp.de/	1371	http://home.schmorp.de/

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