ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.96 by root, Fri Dec 22 04:05:50 2006 UTC vs.
Revision 1.233 by root, Mon Aug 13 01:01:04 2012 UTC

…		…
4		4
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", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration
32	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
33	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
34
35	# Event integration
36	Event->io (fd => IO::AIO::poll_fileno,
37	poll => 'r',
38	cb => \&IO::AIO::poll_cb);
39
40	# Glib/Gtk2 integration
41	add_watch Glib::IO IO::AIO::poll_fileno,
42	in => sub { IO::AIO::poll_cb; 1 };
43
44	# Tk integration
45	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46	readable => \&IO::AIO::poll_cb);
47
48	# Danga::Socket integration
49	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50	\&IO::AIO::poll_cb);
51
52	=head1 DESCRIPTION	31	=head1 DESCRIPTION
53		32
54	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
55	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
56		36
57	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
58	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
59	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
60	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
62	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
63	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
64	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
65	concurrently.	45	concurrently.
66		46
67	While most of this works on all types of file descriptors (for example	47	While most of this works on all types of file descriptors (for
68	sockets), using these functions on file descriptors that support	48	example sockets), using these functions on file descriptors that
69	nonblocking operation (again, sockets, pipes etc.) is very inefficient or	49	support nonblocking operation (again, sockets, pipes etc.) is
70	might not work (aio_read fails on sockets/pipes/fifos). Use an event loop	50	very inefficient. Use an event loop for that (such as the L<EV>
71	for that (such as the L<Event|Event> module): IO::AIO will naturally fit	51	module): IO::AIO will naturally fit into such an event loop itself.
72	into such an event loop itself.
73		52
74	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
75	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
76	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
77	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
79	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
80	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
81	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
82	using threads anyway.	61	using threads anyway.
83		62
84	Although the module will work with in the presence of other (Perl-)	63	Although the module will work in the presence of other (Perl-) threads,
85	threads, it is currently not reentrant in any way, so use appropriate	64	it is currently not reentrant in any way, so use appropriate locking
86	locking yourself, always call C<poll_cb> from within the same thread, or	65	yourself, always call C<poll_cb> from within the same thread, or never
87	never call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
88		67
89	=head2 EXAMPLE	68	=head2 EXAMPLE
90		69
91	This is a simple example that uses the Event module and loads	70	This is a simple example that uses the EV module and loads
92	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
93		72
94	use Fcntl;	73	use Fcntl;
95	use Event;	74	use EV;
96	use IO::AIO;	75	use IO::AIO;
97		76
98	# register the IO::AIO callback with Event	77	# register the IO::AIO callback with EV
99	Event->io (fd => IO::AIO::poll_fileno,	78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
100	poll => 'r',
101	cb => \&IO::AIO::poll_cb);
102		79
103	# queue the request to open /etc/passwd	80	# queue the request to open /etc/passwd
104	aio_open "/etc/passwd", O_RDONLY, 0, sub {	81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
105	my $fh = shift	82	my $fh = shift
106	or die "error while opening: $!";	83	or die "error while opening: $!";
107		84
108	# stat'ing filehandles is generally non-blocking	85	# stat'ing filehandles is generally non-blocking
109	my $size = -s $fh;	86	my $size = -s $fh;
…		…
118		95
119	# file contents now in $contents	96	# file contents now in $contents
120	print $contents;	97	print $contents;
121		98
122	# exit event loop and program	99	# exit event loop and program
123	Event::unloop;	100	EV::unloop;
124	};	101	};
125	};	102	};
126		103
127	# possibly queue up other requests, or open GUI windows,	104	# possibly queue up other requests, or open GUI windows,
128	# check for sockets etc. etc.	105	# check for sockets etc. etc.
129		106
130	# process events as long as there are some:	107	# process events as long as there are some:
131	Event::loop;	108	EV::loop;
132		109
133	=head1 REQUEST ANATOMY AND LIFETIME	110	=head1 REQUEST ANATOMY AND LIFETIME
134		111
135	Every C<aio_*> function creates a request. which is a C data structure not	112	Every C<aio_*> function creates a request. which is a C data structure not
136	directly visible to Perl.	113	directly visible to Perl.
…		…
184		161
185	=cut	162	=cut
186		163
187	package IO::AIO;	164	package IO::AIO;
188		165
189	no warnings;	166	use Carp ();
190	use strict 'vars';	167
		168	use common::sense;
191		169
192	use base 'Exporter';	170	use base 'Exporter';
193		171
194	BEGIN {	172	BEGIN {
195	our $VERSION = '2.21';	173	our $VERSION = '4.15';
196		174
197	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	175	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
198	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
199	aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
200	aio_move aio_copy aio_group aio_nop aio_mknod);	178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead aio_fiemap
		180	aio_rename aio_link aio_move aio_copy aio_group
		181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
		185	aio_wd);
		186
201	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice aio_block));	187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
202	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
203	min_parallel max_parallel max_idle	189	min_parallel max_parallel max_idle idle_timeout
204	nreqs nready npending nthreads	190	nreqs nready npending nthreads
205	max_poll_time max_poll_reqs);	191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
206		196
207	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
208		198
209	require XSLoader;	199	require XSLoader;
210	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
211	}	201	}
212		202
213	=head1 FUNCTIONS	203	=head1 FUNCTIONS
214		204
215	=head2 AIO REQUEST FUNCTIONS	205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes most of the functions for
		208	quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_seek $fh,$offset,$whence, $callback->($offs)
		215	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		217	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		218	aio_readahead $fh,$offset,$length, $callback->($retval)
		219	aio_stat $fh_or_path, $callback->($status)
		220	aio_lstat $fh, $callback->($status)
		221	aio_statvfs $fh_or_path, $callback->($statvfs)
		222	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		223	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_truncate $fh_or_path, $offset, $callback->($status)
		226	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		227	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		228	aio_unlink $pathname, $callback->($status)
		229	aio_mknod $pathname, $mode, $dev, $callback->($status)
		230	aio_link $srcpath, $dstpath, $callback->($status)
		231	aio_symlink $srcpath, $dstpath, $callback->($status)
		232	aio_readlink $pathname, $callback->($link)
		233	aio_realpath $pathname, $callback->($link)
		234	aio_rename $srcpath, $dstpath, $callback->($status)
		235	aio_mkdir $pathname, $mode, $callback->($status)
		236	aio_rmdir $pathname, $callback->($status)
		237	aio_readdir $pathname, $callback->($entries)
		238	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		239	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		240	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		241	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		242	aio_load $pathname, $data, $callback->($status)
		243	aio_copy $srcpath, $dstpath, $callback->($status)
		244	aio_move $srcpath, $dstpath, $callback->($status)
		245	aio_rmtree $pathname, $callback->($status)
		246	aio_sync $callback->($status)
		247	aio_syncfs $fh, $callback->($status)
		248	aio_fsync $fh, $callback->($status)
		249	aio_fdatasync $fh, $callback->($status)
		250	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		251	aio_pathsync $pathname, $callback->($status)
		252	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		254	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		255	aio_mlockall $flags, $callback->($status)
		256	aio_group $callback->(...)
		257	aio_nop $callback->()
		258
		259	$prev_pri = aioreq_pri [$pri]
		260	aioreq_nice $pri_adjust
		261
		262	IO::AIO::poll_wait
		263	IO::AIO::poll_cb
		264	IO::AIO::poll
		265	IO::AIO::flush
		266	IO::AIO::max_poll_reqs $nreqs
		267	IO::AIO::max_poll_time $seconds
		268	IO::AIO::min_parallel $nthreads
		269	IO::AIO::max_parallel $nthreads
		270	IO::AIO::max_idle $nthreads
		271	IO::AIO::idle_timeout $seconds
		272	IO::AIO::max_outstanding $maxreqs
		273	IO::AIO::nreqs
		274	IO::AIO::nready
		275	IO::AIO::npending
		276
		277	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		278	IO::AIO::fadvise $fh, $offset, $len, $advice
		279	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		280	IO::AIO::munmap $scalar
		281	IO::AIO::madvise $scalar, $offset, $length, $advice
		282	IO::AIO::mprotect $scalar, $offset, $length, $protect
		283	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		284	IO::AIO::munlockall
		285
		286	=head2 API NOTES
216		287
217	All the C<aio_*> calls are more or less thin wrappers around the syscall	288	All the C<aio_*> calls are more or less thin wrappers around the syscall
218	with the same name (sans C<aio_>). The arguments are similar or identical,	289	with the same name (sans C<aio_>). The arguments are similar or identical,
219	and they all accept an additional (and optional) C<$callback> argument	290	and they all accept an additional (and optional) C<$callback> argument
220	which must be a code reference. This code reference will get called with	291	which must be a code reference. This code reference will be called after
221	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	292	the syscall has been executed in an asynchronous fashion. The results
222	perl, which usually delivers "false") as it's sole argument when the given	293	of the request will be passed as arguments to the callback (and, if an
223	syscall has been executed asynchronously.	294	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		295	most syscalls return C<-1> on error, unlike perl, which usually delivers
		296	"false").
		297
		298	Some requests (such as C<aio_readdir>) pass the actual results and
		299	communicate failures by passing C<undef>.
224		300
225	All functions expecting a filehandle keep a copy of the filehandle	301	All functions expecting a filehandle keep a copy of the filehandle
226	internally until the request has finished.	302	internally until the request has finished.
227		303
228	All functions return request objects of type L<IO::AIO::REQ> that allow	304	All functions return request objects of type L<IO::AIO::REQ> that allow
229	further manipulation of those requests while they are in-flight.	305	further manipulation of those requests while they are in-flight.
230		306
231	The pathnames you pass to these routines I<must> be absolute and	307	The pathnames you pass to these routines I<should> be absolute. The
232	encoded as octets. The reason for the former is that at the time the	308	reason for this is that at the time the request is being executed, the
233	request is being executed, the current working directory could have	309	current working directory could have changed. Alternatively, you can
234	changed. Alternatively, you can make sure that you never change the	310	make sure that you never change the current working directory anywhere
235	current working directory anywhere in the program and then use relative	311	in the program and then use relative paths. You can also take advantage
236	paths.	312	of IO::AIOs working directory abstraction, that lets you specify paths
		313	relative to some previously-opened "working directory object" - see the
		314	description of the C<IO::AIO::WD> class later in this document.
237		315
238	To encode pathnames as octets, either make sure you either: a) always pass	316	To encode pathnames as octets, either make sure you either: a) always pass
239	in filenames you got from outside (command line, readdir etc.) without	317	in filenames you got from outside (command line, readdir etc.) without
240	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	318	tinkering, b) are in your native filesystem encoding, c) use the Encode
241	your pathnames to the locale (or other) encoding in effect in the user	319	module and encode your pathnames to the locale (or other) encoding in
242	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	320	effect in the user environment, d) use Glib::filename_from_unicode on
243	use something else to ensure your scalar has the correct contents.	321	unicode filenames or e) use something else to ensure your scalar has the
		322	correct contents.
244		323
245	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	324	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246	handles correctly wether it is set or not.	325	handles correctly whether it is set or not.
		326
		327	=head2 AIO REQUEST FUNCTIONS
247		328
248	=over 4	329	=over 4
249		330
250	=item $prev_pri = aioreq_pri [$pri]	331	=item $prev_pri = aioreq_pri [$pri]
251		332
…		…
271	aio_read $_[0], ..., sub {	352	aio_read $_[0], ..., sub {
272	...	353	...
273	};	354	};
274	};	355	};
275		356
		357
276	=item aioreq_nice $pri_adjust	358	=item aioreq_nice $pri_adjust
277		359
278	Similar to C<aioreq_pri>, but subtracts the given value from the current	360	Similar to C<aioreq_pri>, but subtracts the given value from the current
279	priority, so the effect is cumulative.	361	priority, so the effect is cumulative.
280		362
		363
281	=item aio_open $pathname, $flags, $mode, $callback->($fh)	364	=item aio_open $pathname, $flags, $mode, $callback->($fh)
282		365
283	Asynchronously open or create a file and call the callback with a newly	366	Asynchronously open or create a file and call the callback with a newly
284	created filehandle for the file.	367	created filehandle for the file (or C<undef> in case of an error).
285		368
286	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	369	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
287	for an explanation.	370	for an explanation.
288		371
289	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	372	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
290	list. They are the same as used by C<sysopen>.	373	list. They are the same as used by C<sysopen>.
291		374
292	Likewise, C<$mode> specifies the mode of the newly created file, if it	375	Likewise, C<$mode> specifies the mode of the newly created file, if it
293	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	376	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
294	except that it is mandatory (i.e. use C<0> if you don't create new files,	377	except that it is mandatory (i.e. use C<0> if you don't create new files,
295	and C<0666> or C<0777> if you do).	378	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		379	by the umask in effect then the request is being executed, so better never
		380	change the umask.
296		381
297	Example:	382	Example:
298		383
299	aio_open "/etc/passwd", O_RDONLY, 0, sub {	384	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
300	if ($_[0]) {	385	if ($_[0]) {
301	print "open successful, fh is $_[0]\n";	386	print "open successful, fh is $_[0]\n";
302	...	387	...
303	} else {	388	} else {
304	die "open failed: $!\n";	389	die "open failed: $!\n";
305	}	390	}
306	};	391	};
307		392
		393	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		394	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		395	following POSIX and non-POSIX constants are available (missing ones on
		396	your system are, as usual, C<0>):
		397
		398	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		399	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		400	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		401
		402
308	=item aio_close $fh, $callback->($status)	403	=item aio_close $fh, $callback->($status)
309		404
310	Asynchronously close a file and call the callback with the result	405	Asynchronously close a file and call the callback with the result
311	code. I<WARNING:> although accepted, you should not pass in a perl	406	code.
312	filehandle here, as perl will likely close the file descriptor another
313	time when the filehandle is destroyed. Normally, you can safely call perls
314	C<close> or just let filehandles go out of scope.
315		407
316	This is supposed to be a bug in the API, so that might change. It's	408	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
317	therefore best to avoid this function.	409	closing the file descriptor associated with the filehandle itself.
		410
		411	Therefore, C<aio_close> will not close the filehandle - instead it will
		412	use dup2 to overwrite the file descriptor with the write-end of a pipe
		413	(the pipe fd will be created on demand and will be cached).
		414
		415	Or in other words: the file descriptor will be closed, but it will not be
		416	free for reuse until the perl filehandle is closed.
		417
		418	=cut
		419
		420	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		421
		422	Seeks the filehandle to the new C<$offset>, similarly to perl's
		423	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		424	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		425	C<IO::AIO::SEEK_END>).
		426
		427	The resulting absolute offset will be passed to the callback, or C<-1> in
		428	case of an error.
		429
		430	In theory, the C<$whence> constants could be different than the
		431	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		432	so don't panic.
		433
		434	As a GNU/Linux (and maybe Solaris) extension, also the constants
		435	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		436	could be found. No guarantees about suitability for use in C<aio_seek> or
		437	Perl's C<sysseek> can be made though, although I would naively assume they
		438	"just work".
318		439
319	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	440	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
320		441
321	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	442	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322		443
323	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	444	Reads or writes C<$length> bytes from or to the specified C<$fh> and
324	into the scalar given by C<data> and offset C<dataoffset> and calls the	445	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
325	callback without the actual number of bytes read (or -1 on error, just	446	and calls the callback without the actual number of bytes read (or -1 on
326	like the syscall).	447	error, just like the syscall).
		448
		449	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		450	offset plus the actual number of bytes read.
		451
		452	If C<$offset> is undefined, then the current file descriptor offset will
		453	be used (and updated), otherwise the file descriptor offset will not be
		454	changed by these calls.
		455
		456	If C<$length> is undefined in C<aio_write>, use the remaining length of
		457	C<$data>.
		458
		459	If C<$dataoffset> is less than zero, it will be counted from the end of
		460	C<$data>.
327		461
328	The C<$data> scalar I<MUST NOT> be modified in any way while the request	462	The C<$data> scalar I<MUST NOT> be modified in any way while the request
329	is outstanding. Modifying it can result in segfaults or WW3 (if the	463	is outstanding. Modifying it can result in segfaults or World War III (if
330	necessary/optional hardware is installed).	464	the necessary/optional hardware is installed).
331		465
332	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	466	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
333	offset C<0> within the scalar:	467	offset C<0> within the scalar:
334		468
335	aio_read $fh, 7, 15, $buffer, 0, sub {	469	aio_read $fh, 7, 15, $buffer, 0, sub {
336	$_[0] > 0 or die "read error: $!";	470	$_[0] > 0 or die "read error: $!";
337	print "read $_[0] bytes: <$buffer>\n";	471	print "read $_[0] bytes: <$buffer>\n";
338	};	472	};
339		473
		474
340	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	475	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
341		476
342	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	477	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
343	reading at byte offset C<$in_offset>, and starts writing at the current	478	reading at byte offset C<$in_offset>, and starts writing at the current
344	file offset of C<$out_fh>. Because of that, it is not safe to issue more	479	file offset of C<$out_fh>. Because of that, it is not safe to issue more
345	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	480	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
346	other.	481	other. The same C<$in_fh> works fine though, as this function does not
		482	move or use the file offset of C<$in_fh>.
347		483
		484	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		485	are written, and there is no way to find out how many more bytes have been
		486	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		487	number of bytes written to C<$out_fh>. Only if the result value equals
		488	C<$length> one can assume that C<$length> bytes have been read.
		489
		490	Unlike with other C<aio_> functions, it makes a lot of sense to use
		491	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		492	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		493	the socket I/O will be non-blocking. Note, however, that you can run
		494	into a trap where C<aio_sendfile> reads some data with readahead, then
		495	fails to write all data, and when the socket is ready the next time, the
		496	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		497	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		498	resource usage.
		499
348	This call tries to make use of a native C<sendfile> syscall to provide	500	This call tries to make use of a native C<sendfile>-like syscall to
349	zero-copy operation. For this to work, C<$out_fh> should refer to a	501	provide zero-copy operation. For this to work, C<$out_fh> should refer to
350	socket, and C<$in_fh> should refer to mmap'able file.	502	a socket, and C<$in_fh> should refer to an mmap'able file.
351		503
352	If the native sendfile call fails or is not implemented, it will be	504	If a native sendfile cannot be found or it fails with C<ENOSYS>,
353	emulated, so you can call C<aio_sendfile> on any type of filehandle	505	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		506	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
354	regardless of the limitations of the operating system.	507	type of filehandle regardless of the limitations of the operating system.
355		508
356	Please note, however, that C<aio_sendfile> can read more bytes from	509	As native sendfile syscalls (as practically any non-POSIX interface hacked
357	C<$in_fh> than are written, and there is no way to find out how many	510	together in a hurry to improve benchmark numbers) tend to be rather buggy
358	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	511	on many systems, this implementation tries to work around some known bugs
359	provides the number of bytes written to C<$out_fh>. Only if the result	512	in Linux and FreeBSD kernels (probably others, too), but that might fail,
360	value equals C<$length> one can assume that C<$length> bytes have been	513	so you really really should check the return value of C<aio_sendfile> -
361	read.	514	fewre bytes than expected might have been transferred.
		515
362		516
363	=item aio_readahead $fh,$offset,$length, $callback->($retval)	517	=item aio_readahead $fh,$offset,$length, $callback->($retval)
364		518
365	C<aio_readahead> populates the page cache with data from a file so that	519	C<aio_readahead> populates the page cache with data from a file so that
366	subsequent reads from that file will not block on disk I/O. The C<$offset>	520	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
372	file. The current file offset of the file is left unchanged.	526	file. The current file offset of the file is left unchanged.
373		527
374	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	528	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
375	emulated by simply reading the data, which would have a similar effect.	529	emulated by simply reading the data, which would have a similar effect.
376		530
		531
377	=item aio_stat $fh_or_path, $callback->($status)	532	=item aio_stat $fh_or_path, $callback->($status)
378		533
379	=item aio_lstat $fh, $callback->($status)	534	=item aio_lstat $fh, $callback->($status)
380		535
381	Works like perl's C<stat> or C<lstat> in void context. The callback will	536	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
386	for an explanation.	541	for an explanation.
387		542
388	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	543	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
389	error when stat'ing a large file, the results will be silently truncated	544	error when stat'ing a large file, the results will be silently truncated
390	unless perl itself is compiled with large file support.	545	unless perl itself is compiled with large file support.
		546
		547	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		548	following constants and functions (if not implemented, the constants will
		549	be C<0> and the functions will either C<croak> or fall back on traditional
		550	behaviour).
		551
		552	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		553	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		554	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
391		555
392	Example: Print the length of F</etc/passwd>:	556	Example: Print the length of F</etc/passwd>:
393		557
394	aio_stat "/etc/passwd", sub {	558	aio_stat "/etc/passwd", sub {
395	$_[0] and die "stat failed: $!";	559	$_[0] and die "stat failed: $!";
396	print "size is ", -s _, "\n";	560	print "size is ", -s _, "\n";
397	};	561	};
398		562
		563
		564	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		565
		566	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		567	whether a file handle or path was passed.
		568
		569	On success, the callback is passed a hash reference with the following
		570	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		571	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		572	is passed.
		573
		574	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		575	C<ST_NOSUID>.
		576
		577	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		578	their correct value when available, or to C<0> on systems that do
		579	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		580	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		581	C<ST_NODIRATIME> and C<ST_RELATIME>.
		582
		583	Example: stat C</wd> and dump out the data if successful.
		584
		585	aio_statvfs "/wd", sub {
		586	my $f = $_[0]
		587	or die "statvfs: $!";
		588
		589	use Data::Dumper;
		590	say Dumper $f;
		591	};
		592
		593	# result:
		594	{
		595	bsize => 1024,
		596	bfree => 4333064312,
		597	blocks => 10253828096,
		598	files => 2050765568,
		599	flag => 4096,
		600	favail => 2042092649,
		601	bavail => 4333064312,
		602	ffree => 2042092649,
		603	namemax => 255,
		604	frsize => 1024,
		605	fsid => 1810
		606	}
		607
		608
		609	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		610
		611	Works like perl's C<utime> function (including the special case of $atime
		612	and $mtime being undef). Fractional times are supported if the underlying
		613	syscalls support them.
		614
		615	When called with a pathname, uses utimes(2) if available, otherwise
		616	utime(2). If called on a file descriptor, uses futimes(2) if available,
		617	otherwise returns ENOSYS, so this is not portable.
		618
		619	Examples:
		620
		621	# set atime and mtime to current time (basically touch(1)):
		622	aio_utime "path", undef, undef;
		623	# set atime to current time and mtime to beginning of the epoch:
		624	aio_utime "path", time, undef; # undef==0
		625
		626
		627	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		628
		629	Works like perl's C<chown> function, except that C<undef> for either $uid
		630	or $gid is being interpreted as "do not change" (but -1 can also be used).
		631
		632	Examples:
		633
		634	# same as "chown root path" in the shell:
		635	aio_chown "path", 0, -1;
		636	# same as above:
		637	aio_chown "path", 0, undef;
		638
		639
		640	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		641
		642	Works like truncate(2) or ftruncate(2).
		643
		644
		645	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		646
		647	Allocates or freed disk space according to the C<$mode> argument. See the
		648	linux C<fallocate> docuemntation for details.
		649
		650	C<$mode> can currently be C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE>
		651	to allocate space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE |
		652	IO::AIO::FALLOC_FL_KEEP_SIZE>, to deallocate a file range.
		653
		654	The file system block size used by C<fallocate> is presumably the
		655	C<f_bsize> returned by C<statvfs>.
		656
		657	If C<fallocate> isn't available or cannot be emulated (currently no
		658	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		659
		660
		661	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		662
		663	Works like perl's C<chmod> function.
		664
		665
399	=item aio_unlink $pathname, $callback->($status)	666	=item aio_unlink $pathname, $callback->($status)
400		667
401	Asynchronously unlink (delete) a file and call the callback with the	668	Asynchronously unlink (delete) a file and call the callback with the
402	result code.	669	result code.
403		670
		671
404	=item aio_mknod $path, $mode, $dev, $callback->($status)	672	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
405		673
406	[EXPERIMENTAL]	674	[EXPERIMENTAL]
407		675
408	Asynchronously create a device node (or fifo). See mknod(2).	676	Asynchronously create a device node (or fifo). See mknod(2).
409		677
410	The only (POSIX-) portable way of calling this function is:	678	The only (POSIX-) portable way of calling this function is:
411		679
412	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	680	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		681
		682	See C<aio_stat> for info about some potentially helpful extra constants
		683	and functions.
413		684
414	=item aio_link $srcpath, $dstpath, $callback->($status)	685	=item aio_link $srcpath, $dstpath, $callback->($status)
415		686
416	Asynchronously create a new link to the existing object at C<$srcpath> at	687	Asynchronously create a new link to the existing object at C<$srcpath> at
417	the path C<$dstpath> and call the callback with the result code.	688	the path C<$dstpath> and call the callback with the result code.
418		689
		690
419	=item aio_symlink $srcpath, $dstpath, $callback->($status)	691	=item aio_symlink $srcpath, $dstpath, $callback->($status)
420		692
421	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	693	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
422	the path C<$dstpath> and call the callback with the result code.	694	the path C<$dstpath> and call the callback with the result code.
423		695
		696
424	=item aio_readlink $path, $callback->($link)	697	=item aio_readlink $pathname, $callback->($link)
425		698
426	Asynchronously read the symlink specified by C<$path> and pass it to	699	Asynchronously read the symlink specified by C<$path> and pass it to
427	the callback. If an error occurs, nothing or undef gets passed to the	700	the callback. If an error occurs, nothing or undef gets passed to the
428	callback.	701	callback.
429		702
		703
		704	=item aio_realpath $pathname, $callback->($path)
		705
		706	Asynchronously make the path absolute and resolve any symlinks in
		707	C<$path>. The resulting path only consists of directories (Same as
		708	L<Cwd::realpath>).
		709
		710	This request can be used to get the absolute path of the current working
		711	directory by passing it a path of F<.> (a single dot).
		712
		713
430	=item aio_rename $srcpath, $dstpath, $callback->($status)	714	=item aio_rename $srcpath, $dstpath, $callback->($status)
431		715
432	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	716	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
433	rename(2) and call the callback with the result code.	717	rename(2) and call the callback with the result code.
434		718
		719
		720	=item aio_mkdir $pathname, $mode, $callback->($status)
		721
		722	Asynchronously mkdir (create) a directory and call the callback with
		723	the result code. C<$mode> will be modified by the umask at the time the
		724	request is executed, so do not change your umask.
		725
		726
435	=item aio_rmdir $pathname, $callback->($status)	727	=item aio_rmdir $pathname, $callback->($status)
436		728
437	Asynchronously rmdir (delete) a directory and call the callback with the	729	Asynchronously rmdir (delete) a directory and call the callback with the
438	result code.	730	result code.
		731
439		732
440	=item aio_readdir $pathname, $callback->($entries)	733	=item aio_readdir $pathname, $callback->($entries)
441		734
442	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	735	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
443	directory (i.e. opendir + readdir + closedir). The entries will not be	736	directory (i.e. opendir + readdir + closedir). The entries will not be
444	sorted, and will B<NOT> include the C<.> and C<..> entries.	737	sorted, and will B<NOT> include the C<.> and C<..> entries.
445		738
446	The callback a single argument which is either C<undef> or an array-ref	739	The callback is passed a single argument which is either C<undef> or an
447	with the filenames.	740	array-ref with the filenames.
		741
		742
		743	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		744
		745	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		746	tune behaviour and output format. In case of an error, C<$entries> will be
		747	C<undef>.
		748
		749	The flags are a combination of the following constants, ORed together (the
		750	flags will also be passed to the callback, possibly modified):
		751
		752	=over 4
		753
		754	=item IO::AIO::READDIR_DENTS
		755
		756	When this flag is off, then the callback gets an arrayref consisting of
		757	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		758	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		759	entry in more detail.
		760
		761	C<$name> is the name of the entry.
		762
		763	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		764
		765	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		766	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		767	C<IO::AIO::DT_WHT>.
		768
		769	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		770	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		771	scalars are read-only: you can not modify them.
		772
		773	C<$inode> is the inode number (which might not be exact on systems with 64
		774	bit inode numbers and 32 bit perls). This field has unspecified content on
		775	systems that do not deliver the inode information.
		776
		777	=item IO::AIO::READDIR_DIRS_FIRST
		778
		779	When this flag is set, then the names will be returned in an order where
		780	likely directories come first, in optimal stat order. This is useful when
		781	you need to quickly find directories, or you want to find all directories
		782	while avoiding to stat() each entry.
		783
		784	If the system returns type information in readdir, then this is used
		785	to find directories directly. Otherwise, likely directories are names
		786	beginning with ".", or otherwise names with no dots, of which names with
		787	short names are tried first.
		788
		789	=item IO::AIO::READDIR_STAT_ORDER
		790
		791	When this flag is set, then the names will be returned in an order
		792	suitable for stat()'ing each one. That is, when you plan to stat()
		793	all files in the given directory, then the returned order will likely
		794	be fastest.
		795
		796	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		797	the likely dirs come first, resulting in a less optimal stat order.
		798
		799	=item IO::AIO::READDIR_FOUND_UNKNOWN
		800
		801	This flag should not be set when calling C<aio_readdirx>. Instead, it
		802	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		803	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		804	C<$type>'s are known, which can be used to speed up some algorithms.
		805
		806	=back
		807
		808
		809	=item aio_load $pathname, $data, $callback->($status)
		810
		811	This is a composite request that tries to fully load the given file into
		812	memory. Status is the same as with aio_read.
		813
		814	=cut
		815
		816	sub aio_load($$;$) {
		817	my ($path, undef, $cb) = @_;
		818	my $data = \$_[1];
		819
		820	my $pri = aioreq_pri;
		821	my $grp = aio_group $cb;
		822
		823	aioreq_pri $pri;
		824	add $grp aio_open $path, O_RDONLY, 0, sub {
		825	my $fh = shift
		826	or return $grp->result (-1);
		827
		828	aioreq_pri $pri;
		829	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		830	$grp->result ($_[0]);
		831	};
		832	};
		833
		834	$grp
		835	}
448		836
449	=item aio_copy $srcpath, $dstpath, $callback->($status)	837	=item aio_copy $srcpath, $dstpath, $callback->($status)
450		838
451	Try to copy the I<file> (directories not supported as either source or	839	Try to copy the I<file> (directories not supported as either source or
452	destination) from C<$srcpath> to C<$dstpath> and call the callback with	840	destination) from C<$srcpath> to C<$dstpath> and call the callback with
453	the C<0> (error) or C<-1> ok.	841	a status of C<0> (ok) or C<-1> (error, see C<$!>).
454		842
455	This is a composite request that it creates the destination file with	843	This is a composite request that creates the destination file with
456	mode 0200 and copies the contents of the source file into it using	844	mode 0200 and copies the contents of the source file into it using
457	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	845	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
458	uid/gid, in that order.	846	uid/gid, in that order.
459		847
460	If an error occurs, the partial destination file will be unlinked, if	848	If an error occurs, the partial destination file will be unlinked, if
…		…
462	errors are being ignored.	850	errors are being ignored.
463		851
464	=cut	852	=cut
465		853
466	sub aio_copy($$;$) {	854	sub aio_copy($$;$) {
467	aio_block {
468	my ($src, $dst, $cb) = @_;	855	my ($src, $dst, $cb) = @_;
469		856
470	my $pri = aioreq_pri;	857	my $pri = aioreq_pri;
471	my $grp = aio_group $cb;	858	my $grp = aio_group $cb;
472		859
473	aioreq_pri $pri;	860	aioreq_pri $pri;
474	add $grp aio_open $src, O_RDONLY, 0, sub {	861	add $grp aio_open $src, O_RDONLY, 0, sub {
475	if (my $src_fh = $_[0]) {	862	if (my $src_fh = $_[0]) {
476	my @stat = stat $src_fh;	863	my @stat = stat $src_fh; # hmm, might block over nfs?
477		864
478	aioreq_pri $pri;	865	aioreq_pri $pri;
479	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	866	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
480	if (my $dst_fh = $_[0]) {	867	if (my $dst_fh = $_[0]) {
481	aioreq_pri $pri;	868	aioreq_pri $pri;
482	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	869	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
483	if ($_[0] == $stat[7]) {	870	if ($_[0] == $stat[7]) {
484	$grp->result (0);	871	$grp->result (0);
485	close $src_fh;	872	close $src_fh;
486		873
487	# those should not normally block. should. should.
488	utime $stat[8], $stat[9], $dst;
489	chmod $stat[2] & 07777, $dst_fh;
490	chown $stat[4], $stat[5], $dst_fh;
491	close $dst_fh;
492	} else {	874	my $ch = sub {
493	$grp->result (-1);
494	close $src_fh;
495	close $dst_fh;
496
497	aioreq $pri;	875	aioreq_pri $pri;
		876	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		877	aioreq_pri $pri;
		878	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		879	aioreq_pri $pri;
498	add $grp aio_unlink $dst;	880	add $grp aio_close $dst_fh;
		881	}
		882	};
499	}	883	};
		884
		885	aioreq_pri $pri;
		886	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		887	if ($_[0] < 0 && $! == ENOSYS) {
		888	aioreq_pri $pri;
		889	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		890	} else {
		891	$ch->();
		892	}
		893	};
		894	} else {
		895	$grp->result (-1);
		896	close $src_fh;
		897	close $dst_fh;
		898
		899	aioreq $pri;
		900	add $grp aio_unlink $dst;
500	};	901	}
501	} else {
502	$grp->result (-1);
503	}	902	};
		903	} else {
		904	$grp->result (-1);
504	},	905	}
505
506	} else {
507	$grp->result (-1);
508	}	906	},
		907
		908	} else {
		909	$grp->result (-1);
509	};	910	}
510
511	$grp
512	}	911	};
		912
		913	$grp
513	}	914	}
514		915
515	=item aio_move $srcpath, $dstpath, $callback->($status)	916	=item aio_move $srcpath, $dstpath, $callback->($status)
516		917
517	Try to move the I<file> (directories not supported as either source or	918	Try to move the I<file> (directories not supported as either source or
518	destination) from C<$srcpath> to C<$dstpath> and call the callback with	919	destination) from C<$srcpath> to C<$dstpath> and call the callback with
519	the C<0> (error) or C<-1> ok.	920	a status of C<0> (ok) or C<-1> (error, see C<$!>).
520		921
521	This is a composite request that tries to rename(2) the file first. If	922	This is a composite request that tries to rename(2) the file first; if
522	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	923	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
523	that is successful, unlinking the C<$srcpath>.	924	that is successful, unlinks the C<$srcpath>.
524		925
525	=cut	926	=cut
526		927
527	sub aio_move($$;$) {	928	sub aio_move($$;$) {
528	aio_block {
529	my ($src, $dst, $cb) = @_;	929	my ($src, $dst, $cb) = @_;
530		930
531	my $pri = aioreq_pri;	931	my $pri = aioreq_pri;
532	my $grp = aio_group $cb;	932	my $grp = aio_group $cb;
533		933
534	aioreq_pri $pri;	934	aioreq_pri $pri;
535	add $grp aio_rename $src, $dst, sub {	935	add $grp aio_rename $src, $dst, sub {
536	if ($_[0] && $! == EXDEV) {	936	if ($_[0] && $! == EXDEV) {
537	aioreq_pri $pri;	937	aioreq_pri $pri;
538	add $grp aio_copy $src, $dst, sub {	938	add $grp aio_copy $src, $dst, sub {
539	$grp->result ($_[0]);
540
541	if (!$_[0]) {
542	aioreq_pri $pri;
543	add $grp aio_unlink $src;
544	}
545	};
546	} else {
547	$grp->result ($_[0]);	939	$grp->result ($_[0]);
		940
		941	unless ($_[0]) {
		942	aioreq_pri $pri;
		943	add $grp aio_unlink $src;
		944	}
548	}	945	};
		946	} else {
		947	$grp->result ($_[0]);
549	};	948	}
550
551	$grp
552	}	949	};
		950
		951	$grp
553	}	952	}
554		953
555	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	954	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
556		955
557	Scans a directory (similar to C<aio_readdir>) but additionally tries to	956	Scans a directory (similar to C<aio_readdir>) but additionally tries to
558	efficiently separate the entries of directory C<$path> into two sets of	957	efficiently separate the entries of directory C<$path> into two sets of
559	names, directories you can recurse into (directories), and ones you cannot	958	names, directories you can recurse into (directories), and ones you cannot
560	recurse into (everything else, including symlinks to directories).	959	recurse into (everything else, including symlinks to directories).
…		…
577		976
578	Implementation notes.	977	Implementation notes.
579		978
580	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	979	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
581		980
		981	If readdir returns file type information, then this is used directly to
		982	find directories.
		983
582	After reading the directory, the modification time, size etc. of the	984	Otherwise, after reading the directory, the modification time, size etc.
583	directory before and after the readdir is checked, and if they match (and	985	of the directory before and after the readdir is checked, and if they
584	isn't the current time), the link count will be used to decide how many	986	match (and isn't the current time), the link count will be used to decide
585	entries are directories (if >= 2). Otherwise, no knowledge of the number	987	how many entries are directories (if >= 2). Otherwise, no knowledge of the
586	of subdirectories will be assumed.	988	number of subdirectories will be assumed.
587		989
588	Then entries will be sorted into likely directories (everything without	990	Then entries will be sorted into likely directories a non-initial dot
589	a non-initial dot currently) and likely non-directories (everything	991	currently) and likely non-directories (see C<aio_readdirx>). Then every
590	else). Then every entry plus an appended C</.> will be C<stat>'ed,	992	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
591	likely directories first. If that succeeds, it assumes that the entry	993	in order of their inode numbers. If that succeeds, it assumes that the
592	is a directory or a symlink to directory (which will be checked	994	entry is a directory or a symlink to directory (which will be checked
593	seperately). This is often faster than stat'ing the entry itself because	995	separately). This is often faster than stat'ing the entry itself because
594	filesystems might detect the type of the entry without reading the inode	996	filesystems might detect the type of the entry without reading the inode
595	data (e.g. ext2fs filetype feature).	997	data (e.g. ext2fs filetype feature), even on systems that cannot return
		998	the filetype information on readdir.
596		999
597	If the known number of directories (link count - 2) has been reached, the	1000	If the known number of directories (link count - 2) has been reached, the
598	rest of the entries is assumed to be non-directories.	1001	rest of the entries is assumed to be non-directories.
599		1002
600	This only works with certainty on POSIX (= UNIX) filesystems, which	1003	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
604	as those tend to return 0 or 1 as link counts, which disables the	1007	as those tend to return 0 or 1 as link counts, which disables the
605	directory counting heuristic.	1008	directory counting heuristic.
606		1009
607	=cut	1010	=cut
608		1011
609	sub aio_scandir($$$) {	1012	sub aio_scandir($$;$) {
610	aio_block {
611	my ($path, $maxreq, $cb) = @_;	1013	my ($path, $maxreq, $cb) = @_;
612		1014
613	my $pri = aioreq_pri;	1015	my $pri = aioreq_pri;
614		1016
615	my $grp = aio_group $cb;	1017	my $grp = aio_group $cb;
616		1018
617	$maxreq = 4 if $maxreq <= 0;	1019	$maxreq = 4 if $maxreq <= 0;
		1020
		1021	# get a wd object
		1022	aioreq_pri $pri;
		1023	add $grp aio_wd $path, sub {
		1024	$_[0]
		1025	or return $grp->result ();
		1026
		1027	my $wd = [shift, "."];
618		1028
619	# stat once	1029	# stat once
620	aioreq_pri $pri;	1030	aioreq_pri $pri;
621	add $grp aio_stat $path, sub {	1031	add $grp aio_stat $wd, sub {
622	return $grp->result () if $_[0];	1032	return $grp->result () if $_[0];
623	my $now = time;	1033	my $now = time;
624	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1034	my $hash1 = join ":", (stat _)[0,1,3,7,9];
625		1035
626	# read the directory entries	1036	# read the directory entries
627	aioreq_pri $pri;	1037	aioreq_pri $pri;
628	add $grp aio_readdir $path, sub {	1038	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
629	my $entries = shift	1039	my $entries = shift
630	or return $grp->result ();	1040	or return $grp->result ();
631		1041
632	# stat the dir another time	1042	# stat the dir another time
633	aioreq_pri $pri;	1043	aioreq_pri $pri;
634	add $grp aio_stat $path, sub {	1044	add $grp aio_stat $wd, sub {
635	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1045	my $hash2 = join ":", (stat _)[0,1,3,7,9];
636		1046
637	my $ndirs;	1047	my $ndirs;
638		1048
639	# take the slow route if anything looks fishy	1049	# take the slow route if anything looks fishy
640	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1050	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
641	$ndirs = -1;	1051	$ndirs = -1;
642	} else {	1052	} else {
643	# if nlink == 2, we are finished	1053	# if nlink == 2, we are finished
644	# on non-posix-fs's, we rely on nlink < 2	1054	# for non-posix-fs's, we rely on nlink < 2
645	$ndirs = (stat _)[3] - 2	1055	$ndirs = (stat _)[3] - 2
646	or return $grp->result ([], $entries);	1056	or return $grp->result ([], $entries);
647	}	1057	}
648		1058
649	# sort into likely dirs and likely nondirs
650	# dirs == files without ".", short entries first
651	$entries = [map $_->[0],
652	sort { $b->[1] cmp $a->[1] }
653	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
654	@$entries];
655
656	my (@dirs, @nondirs);	1059	my (@dirs, @nondirs);
657		1060
658	my $statgrp = add $grp aio_group sub {	1061	my $statgrp = add $grp aio_group sub {
659	$grp->result (\@dirs, \@nondirs);	1062	$grp->result (\@dirs, \@nondirs);
660	};	1063	};
661		1064
662	limit $statgrp $maxreq;	1065	limit $statgrp $maxreq;
663	feed $statgrp sub {	1066	feed $statgrp sub {
664	return unless @$entries;	1067	return unless @$entries;
665	my $entry = pop @$entries;	1068	my $entry = shift @$entries;
666		1069
667	aioreq_pri $pri;	1070	aioreq_pri $pri;
		1071	$wd->[1] = "$entry/.";
668	add $statgrp aio_stat "$path/$entry/.", sub {	1072	add $statgrp aio_stat $wd, sub {
669	if ($_[0] < 0) {	1073	if ($_[0] < 0) {
670	push @nondirs, $entry;	1074	push @nondirs, $entry;
671	} else {	1075	} else {
672	# need to check for real directory	1076	# need to check for real directory
673	aioreq_pri $pri;	1077	aioreq_pri $pri;
		1078	$wd->[1] = $entry;
674	add $statgrp aio_lstat "$path/$entry", sub {	1079	add $statgrp aio_lstat $wd, sub {
675	if (-d _) {	1080	if (-d _) {
676	push @dirs, $entry;	1081	push @dirs, $entry;
677		1082
678	unless (--$ndirs) {	1083	unless (--$ndirs) {
679	push @nondirs, @$entries;	1084	push @nondirs, @$entries;
…		…
687	};	1092	};
688	};	1093	};
689	};	1094	};
690	};	1095	};
691	};	1096	};
692
693	$grp
694	}	1097	};
		1098
		1099	$grp
695	}	1100	}
		1101
		1102	=item aio_rmtree $pathname, $callback->($status)
		1103
		1104	Delete a directory tree starting (and including) C<$path>, return the
		1105	status of the final C<rmdir> only. This is a composite request that
		1106	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1107	everything else.
		1108
		1109	=cut
		1110
		1111	sub aio_rmtree;
		1112	sub aio_rmtree($;$) {
		1113	my ($path, $cb) = @_;
		1114
		1115	my $pri = aioreq_pri;
		1116	my $grp = aio_group $cb;
		1117
		1118	aioreq_pri $pri;
		1119	add $grp aio_scandir $path, 0, sub {
		1120	my ($dirs, $nondirs) = @_;
		1121
		1122	my $dirgrp = aio_group sub {
		1123	add $grp aio_rmdir $path, sub {
		1124	$grp->result ($_[0]);
		1125	};
		1126	};
		1127
		1128	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1129	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1130
		1131	add $grp $dirgrp;
		1132	};
		1133
		1134	$grp
		1135	}
		1136
		1137	=item aio_sync $callback->($status)
		1138
		1139	Asynchronously call sync and call the callback when finished.
696		1140
697	=item aio_fsync $fh, $callback->($status)	1141	=item aio_fsync $fh, $callback->($status)
698		1142
699	Asynchronously call fsync on the given filehandle and call the callback	1143	Asynchronously call fsync on the given filehandle and call the callback
700	with the fsync result code.	1144	with the fsync result code.
…		…
704	Asynchronously call fdatasync on the given filehandle and call the	1148	Asynchronously call fdatasync on the given filehandle and call the
705	callback with the fdatasync result code.	1149	callback with the fdatasync result code.
706		1150
707	If this call isn't available because your OS lacks it or it couldn't be	1151	If this call isn't available because your OS lacks it or it couldn't be
708	detected, it will be emulated by calling C<fsync> instead.	1152	detected, it will be emulated by calling C<fsync> instead.
		1153
		1154	=item aio_syncfs $fh, $callback->($status)
		1155
		1156	Asynchronously call the syncfs syscall to sync the filesystem associated
		1157	to the given filehandle and call the callback with the syncfs result
		1158	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1159	errno to C<ENOSYS> nevertheless.
		1160
		1161	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1162
		1163	Sync the data portion of the file specified by C<$offset> and C<$length>
		1164	to disk (but NOT the metadata), by calling the Linux-specific
		1165	sync_file_range call. If sync_file_range is not available or it returns
		1166	ENOSYS, then fdatasync or fsync is being substituted.
		1167
		1168	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1169	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1170	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1171	manpage for details.
		1172
		1173	=item aio_pathsync $pathname, $callback->($status)
		1174
		1175	This request tries to open, fsync and close the given path. This is a
		1176	composite request intended to sync directories after directory operations
		1177	(E.g. rename). This might not work on all operating systems or have any
		1178	specific effect, but usually it makes sure that directory changes get
		1179	written to disc. It works for anything that can be opened for read-only,
		1180	not just directories.
		1181
		1182	Future versions of this function might fall back to other methods when
		1183	C<fsync> on the directory fails (such as calling C<sync>).
		1184
		1185	Passes C<0> when everything went ok, and C<-1> on error.
		1186
		1187	=cut
		1188
		1189	sub aio_pathsync($;$) {
		1190	my ($path, $cb) = @_;
		1191
		1192	my $pri = aioreq_pri;
		1193	my $grp = aio_group $cb;
		1194
		1195	aioreq_pri $pri;
		1196	add $grp aio_open $path, O_RDONLY, 0, sub {
		1197	my ($fh) = @_;
		1198	if ($fh) {
		1199	aioreq_pri $pri;
		1200	add $grp aio_fsync $fh, sub {
		1201	$grp->result ($_[0]);
		1202
		1203	aioreq_pri $pri;
		1204	add $grp aio_close $fh;
		1205	};
		1206	} else {
		1207	$grp->result (-1);
		1208	}
		1209	};
		1210
		1211	$grp
		1212	}
		1213
		1214	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1215
		1216	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1217	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1218	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1219	scalar must only be modified in-place while an aio operation is pending on
		1220	it).
		1221
		1222	It calls the C<msync> function of your OS, if available, with the memory
		1223	area starting at C<$offset> in the string and ending C<$length> bytes
		1224	later. If C<$length> is negative, counts from the end, and if C<$length>
		1225	is C<undef>, then it goes till the end of the string. The flags can be
		1226	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1227	C<IO::AIO::MS_SYNC>.
		1228
		1229	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1230
		1231	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1232	scalars.
		1233
		1234	It touches (reads or writes) all memory pages in the specified
		1235	range inside the scalar. All caveats and parameters are the same
		1236	as for C<aio_msync>, above, except for flags, which must be either
		1237	C<0> (which reads all pages and ensures they are instantiated) or
		1238	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1239	writing an octet from it, which dirties the page).
		1240
		1241	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1242
		1243	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1244	scalars.
		1245
		1246	It reads in all the pages of the underlying storage into memory (if any)
		1247	and locks them, so they are not getting swapped/paged out or removed.
		1248
		1249	If C<$length> is undefined, then the scalar will be locked till the end.
		1250
		1251	On systems that do not implement C<mlock>, this function returns C<-1>
		1252	and sets errno to C<ENOSYS>.
		1253
		1254	Note that the corresponding C<munlock> is synchronous and is
		1255	documented under L<MISCELLANEOUS FUNCTIONS>.
		1256
		1257	Example: open a file, mmap and mlock it - both will be undone when
		1258	C<$data> gets destroyed.
		1259
		1260	open my $fh, "<", $path or die "$path: $!";
		1261	my $data;
		1262	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1263	aio_mlock $data; # mlock in background
		1264
		1265	=item aio_mlockall $flags, $callback->($status)
		1266
		1267	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1268	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1269
		1270	On systems that do not implement C<mlockall>, this function returns C<-1>
		1271	and sets errno to C<ENOSYS>.
		1272
		1273	Note that the corresponding C<munlockall> is synchronous and is
		1274	documented under L<MISCELLANEOUS FUNCTIONS>.
		1275
		1276	Example: asynchronously lock all current and future pages into memory.
		1277
		1278	aio_mlockall IO::AIO::MCL_FUTURE;
		1279
		1280	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1281
		1282	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1283	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1284	C<ioctl> is not available on your OS, then this request will fail with
		1285	C<ENOSYS>.
		1286
		1287	C<$start> is the starting offset to query extents for, C<$length> is the
		1288	size of the range to query - if it is C<undef>, then the whole file will
		1289	be queried.
		1290
		1291	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1292	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1293	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1294	the data portion.
		1295
		1296	C<$count> is the maximum number of extent records to return. If it is
		1297	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1298	case, if it is C<0>, then the callback receives the number of extents
		1299	instead of the extents themselves (which is unreliable, see below).
		1300
		1301	If an error occurs, the callback receives no arguments. The special
		1302	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1303
		1304	Otherwise, the callback receives an array reference with extent
		1305	structures. Each extent structure is an array reference itself, with the
		1306	following members:
		1307
		1308	[$logical, $physical, $length, $flags]
		1309
		1310	Flags is any combination of the following flag values (typically either C<0>
		1311	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1312
		1313	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1314	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1315	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1316	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1317	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1318	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1319
		1320	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1321	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1322	it to return all extents of a range for files with large number of
		1323	extents. The code works around all these issues if C<$count> is undef.
709		1324
710	=item aio_group $callback->(...)	1325	=item aio_group $callback->(...)
711		1326
712	This is a very special aio request: Instead of doing something, it is a	1327	This is a very special aio request: Instead of doing something, it is a
713	container for other aio requests, which is useful if you want to bundle	1328	container for other aio requests, which is useful if you want to bundle
…		…
751	immense (it blocks a thread for a long time) so do not use this function	1366	immense (it blocks a thread for a long time) so do not use this function
752	except to put your application under artificial I/O pressure.	1367	except to put your application under artificial I/O pressure.
753		1368
754	=back	1369	=back
755		1370
		1371
		1372	=head2 IO::AIO::WD - multiple working directories
		1373
		1374	Your process only has one current working directory, which is used by all
		1375	threads. This makes it hard to use relative paths (some other component
		1376	could call C<chdir> at any time, and it is hard to control when the path
		1377	will be used by IO::AIO).
		1378
		1379	One solution for this is to always use absolute paths. This usually works,
		1380	but can be quite slow (the kernel has to walk the whole path on every
		1381	access), and can also be a hassle to implement.
		1382
		1383	Newer POSIX systems have a number of functions (openat, fdopendir,
		1384	futimensat and so on) that make it possible to specify working directories
		1385	per operation.
		1386
		1387	For portability, and because the clowns who "designed", or shall I write,
		1388	perpetrated this new interface were obviously half-drunk, this abstraction
		1389	cannot be perfect, though.
		1390
		1391	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1392	object. This object stores the canonicalised, absolute version of the
		1393	path, and on systems that allow it, also a directory file descriptor.
		1394
		1395	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1396	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1397	object and a pathname instead (or the IO::AIO::WD object alone, which
		1398	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1399	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1400	to that IO::AIO::WD object.
		1401
		1402	For example, to get a wd object for F</etc> and then stat F<passwd>
		1403	inside, you would write:
		1404
		1405	aio_wd "/etc", sub {
		1406	my $etcdir = shift;
		1407
		1408	# although $etcdir can be undef on error, there is generally no reason
		1409	# to check for errors here, as aio_stat will fail with ENOENT
		1410	# when $etcdir is undef.
		1411
		1412	aio_stat [$etcdir, "passwd"], sub {
		1413	# yay
		1414	};
		1415	};
		1416
		1417	That C<aio_wd> is a request and not a normal function shows that creating
		1418	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1419	why it is done asynchronously.
		1420
		1421	To stat the directory obtained with C<aio_wd> above, one could write
		1422	either of the following three request calls:
		1423
		1424	aio_lstat "/etc" , sub { ... # pathname as normal string
		1425	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1426	aio_lstat $wd , sub { ... # shorthand for the previous
		1427
		1428	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1429	object and the pathname string, so you could write the following without
		1430	causing any issues due to C<$path> getting reused:
		1431
		1432	my $path = [$wd, undef];
		1433
		1434	for my $name (qw(abc def ghi)) {
		1435	$path->[1] = $name;
		1436	aio_stat $path, sub {
		1437	# ...
		1438	};
		1439	}
		1440
		1441	There are some caveats: when directories get renamed (or deleted), the
		1442	pathname string doesn't change, so will point to the new directory (or
		1443	nowhere at all), while the directory fd, if available on the system,
		1444	will still point to the original directory. Most functions accepting a
		1445	pathname will use the directory fd on newer systems, and the string on
		1446	older systems. Some functions (such as realpath) will always rely on the
		1447	string form of the pathname.
		1448
		1449	So this fucntionality is mainly useful to get some protection against
		1450	C<chdir>, to easily get an absolute path out of a relative path for future
		1451	reference, and to speed up doing many operations in the same directory
		1452	(e.g. when stat'ing all files in a directory).
		1453
		1454	The following functions implement this working directory abstraction:
		1455
		1456	=over 4
		1457
		1458	=item aio_wd $pathname, $callback->($wd)
		1459
		1460	Asynchonously canonicalise the given pathname and convert it to an
		1461	IO::AIO::WD object representing it. If possible and supported on the
		1462	system, also open a directory fd to speed up pathname resolution relative
		1463	to this working directory.
		1464
		1465	If something goes wrong, then C<undef> is passwd to the callback instead
		1466	of a working directory object and C<$!> is set appropriately. Since
		1467	passing C<undef> as working directory component of a pathname fails the
		1468	request with C<ENOENT>, there is often no need for error checking in the
		1469	C<aio_wd> callback, as future requests using the value will fail in the
		1470	expected way.
		1471
		1472	If this call isn't available because your OS lacks it or it couldn't be
		1473	detected, it will be emulated by calling C<fsync> instead.
		1474
		1475	=item IO::AIO::CWD
		1476
		1477	This is a compiletime constant (object) that represents the process
		1478	current working directory.
		1479
		1480	Specifying this object as working directory object for a pathname is as
		1481	if the pathname would be specified directly, without a directory object,
		1482	e.g., these calls are functionally identical:
		1483
		1484	aio_stat "somefile", sub { ... };
		1485	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1486
		1487	=back
		1488
		1489
756	=head2 IO::AIO::REQ CLASS	1490	=head2 IO::AIO::REQ CLASS
757		1491
758	All non-aggregate C<aio_*> functions return an object of this class when	1492	All non-aggregate C<aio_*> functions return an object of this class when
759	called in non-void context.	1493	called in non-void context.
760		1494
…		…
763	=item cancel $req	1497	=item cancel $req
764		1498
765	Cancels the request, if possible. Has the effect of skipping execution	1499	Cancels the request, if possible. Has the effect of skipping execution
766	when entering the B<execute> state and skipping calling the callback when	1500	when entering the B<execute> state and skipping calling the callback when
767	entering the the B<result> state, but will leave the request otherwise	1501	entering the the B<result> state, but will leave the request otherwise
768	untouched. That means that requests that currently execute will not be	1502	untouched (with the exception of readdir). That means that requests that
769	stopped and resources held by the request will not be freed prematurely.	1503	currently execute will not be stopped and resources held by the request
		1504	will not be freed prematurely.
770		1505
771	=item cb $req $callback->(...)	1506	=item cb $req $callback->(...)
772		1507
773	Replace (or simply set) the callback registered to the request.	1508	Replace (or simply set) the callback registered to the request.
774		1509
…		…
825	Their lifetime, simplified, looks like this: when they are empty, they	1560	Their lifetime, simplified, looks like this: when they are empty, they
826	will finish very quickly. If they contain only requests that are in the	1561	will finish very quickly. If they contain only requests that are in the
827	C<done> state, they will also finish. Otherwise they will continue to	1562	C<done> state, they will also finish. Otherwise they will continue to
828	exist.	1563	exist.
829		1564
830	That means after creating a group you have some time to add requests. And	1565	That means after creating a group you have some time to add requests
831	in the callbacks of those requests, you can add further requests to the	1566	(precisely before the callback has been invoked, which is only done within
832	group. And only when all those requests have finished will the the group	1567	the C<poll_cb>). And in the callbacks of those requests, you can add
833	itself finish.	1568	further requests to the group. And only when all those requests have
		1569	finished will the the group itself finish.
834		1570
835	=over 4	1571	=over 4
836		1572
837	=item add $grp ...	1573	=item add $grp ...
838		1574
…		…
847	=item $grp->cancel_subs	1583	=item $grp->cancel_subs
848		1584
849	Cancel all subrequests and clears any feeder, but not the group request	1585	Cancel all subrequests and clears any feeder, but not the group request
850	itself. Useful when you queued a lot of events but got a result early.	1586	itself. Useful when you queued a lot of events but got a result early.
851		1587
		1588	The group request will finish normally (you cannot add requests to the
		1589	group).
		1590
852	=item $grp->result (...)	1591	=item $grp->result (...)
853		1592
854	Set the result value(s) that will be passed to the group callback when all	1593	Set the result value(s) that will be passed to the group callback when all
855	subrequests have finished and set thre groups errno to the current value	1594	subrequests have finished and set the groups errno to the current value
856	of errno (just like calling C<errno> without an error number). By default,	1595	of errno (just like calling C<errno> without an error number). By default,
857	no argument will be passed and errno is zero.	1596	no argument will be passed and errno is zero.
858		1597
859	=item $grp->errno ([$errno])	1598	=item $grp->errno ([$errno])
860		1599
…		…
871	=item feed $grp $callback->($grp)	1610	=item feed $grp $callback->($grp)
872		1611
873	Sets a feeder/generator on this group: every group can have an attached	1612	Sets a feeder/generator on this group: every group can have an attached
874	generator that generates requests if idle. The idea behind this is that,	1613	generator that generates requests if idle. The idea behind this is that,
875	although you could just queue as many requests as you want in a group,	1614	although you could just queue as many requests as you want in a group,
876	this might starve other requests for a potentially long time. For	1615	this might starve other requests for a potentially long time. For example,
877	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1616	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
878	requests, delaying any later requests for a long time.	1617	requests, delaying any later requests for a long time.
879		1618
880	To avoid this, and allow incremental generation of requests, you can	1619	To avoid this, and allow incremental generation of requests, you can
881	instead a group and set a feeder on it that generates those requests. The	1620	instead a group and set a feeder on it that generates those requests. The
882	feed callback will be called whenever there are few enough (see C<limit>,	1621	feed callback will be called whenever there are few enough (see C<limit>,
…		…
887	not impose any limits).	1626	not impose any limits).
888		1627
889	If the feed does not queue more requests when called, it will be	1628	If the feed does not queue more requests when called, it will be
890	automatically removed from the group.	1629	automatically removed from the group.
891		1630
892	If the feed limit is C<0>, it will be set to C<2> automatically.	1631	If the feed limit is C<0> when this method is called, it will be set to
		1632	C<2> automatically.
893		1633
894	Example:	1634	Example:
895		1635
896	# stat all files in @files, but only ever use four aio requests concurrently:	1636	# stat all files in @files, but only ever use four aio requests concurrently:
897		1637
…		…
909	Sets the feeder limit for the group: The feeder will be called whenever	1649	Sets the feeder limit for the group: The feeder will be called whenever
910	the group contains less than this many requests.	1650	the group contains less than this many requests.
911		1651
912	Setting the limit to C<0> will pause the feeding process.	1652	Setting the limit to C<0> will pause the feeding process.
913		1653
		1654	The default value for the limit is C<0>, but note that setting a feeder
		1655	automatically bumps it up to C<2>.
		1656
914	=back	1657	=back
915		1658
916	=head2 SUPPORT FUNCTIONS	1659	=head2 SUPPORT FUNCTIONS
917		1660
918	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1661	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
920	=over 4	1663	=over 4
921		1664
922	=item $fileno = IO::AIO::poll_fileno	1665	=item $fileno = IO::AIO::poll_fileno
923		1666
924	Return the I<request result pipe file descriptor>. This filehandle must be	1667	Return the I<request result pipe file descriptor>. This filehandle must be
925	polled for reading by some mechanism outside this module (e.g. Event or	1668	polled for reading by some mechanism outside this module (e.g. EV, Glib,
926	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1669	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
927	to call C<poll_cb> to check the results.	1670	you have to call C<poll_cb> to check the results.
928		1671
929	See C<poll_cb> for an example.	1672	See C<poll_cb> for an example.
930		1673
931	=item IO::AIO::poll_cb	1674	=item IO::AIO::poll_cb
932		1675
933	Process some outstanding events on the result pipe. You have to call this	1676	Process some outstanding events on the result pipe. You have to call
934	regularly. Returns the number of events processed. Returns immediately	1677	this regularly. Returns C<0> if all events could be processed (or there
935	when no events are outstanding. The amount of events processed depends on	1678	were no events to process), or C<-1> if it returned earlier for whatever
936	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.	1679	reason. Returns immediately when no events are outstanding. The amount of
		1680	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1681	C<IO::AIO::max_poll_time>.
937		1682
938	If not all requests were processed for whatever reason, the filehandle	1683	If not all requests were processed for whatever reason, the filehandle
939	will still be ready when C<poll_cb> returns.	1684	will still be ready when C<poll_cb> returns, so normally you don't have to
		1685	do anything special to have it called later.
		1686
		1687	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1688	ready, it can be beneficial to call this function from loops which submit
		1689	a lot of requests, to make sure the results get processed when they become
		1690	available and not just when the loop is finished and the event loop takes
		1691	over again. This function returns very fast when there are no outstanding
		1692	requests.
940		1693
941	Example: Install an Event watcher that automatically calls	1694	Example: Install an Event watcher that automatically calls
942	IO::AIO::poll_cb with high priority:	1695	IO::AIO::poll_cb with high priority (more examples can be found in the
		1696	SYNOPSIS section, at the top of this document):
943		1697
944	Event->io (fd => IO::AIO::poll_fileno,	1698	Event->io (fd => IO::AIO::poll_fileno,
945	poll => 'r', async => 1,	1699	poll => 'r', async => 1,
946	cb => \&IO::AIO::poll_cb);	1700	cb => \&IO::AIO::poll_cb);
		1701
		1702	=item IO::AIO::poll_wait
		1703
		1704	If there are any outstanding requests and none of them in the result
		1705	phase, wait till the result filehandle becomes ready for reading (simply
		1706	does a C<select> on the filehandle. This is useful if you want to
		1707	synchronously wait for some requests to finish).
		1708
		1709	See C<nreqs> for an example.
		1710
		1711	=item IO::AIO::poll
		1712
		1713	Waits until some requests have been handled.
		1714
		1715	Returns the number of requests processed, but is otherwise strictly
		1716	equivalent to:
		1717
		1718	IO::AIO::poll_wait, IO::AIO::poll_cb
		1719
		1720	=item IO::AIO::flush
		1721
		1722	Wait till all outstanding AIO requests have been handled.
		1723
		1724	Strictly equivalent to:
		1725
		1726	IO::AIO::poll_wait, IO::AIO::poll_cb
		1727	while IO::AIO::nreqs;
947		1728
948	=item IO::AIO::max_poll_reqs $nreqs	1729	=item IO::AIO::max_poll_reqs $nreqs
949		1730
950	=item IO::AIO::max_poll_time $seconds	1731	=item IO::AIO::max_poll_time $seconds
951		1732
…		…
976	# use a low priority so other tasks have priority	1757	# use a low priority so other tasks have priority
977	Event->io (fd => IO::AIO::poll_fileno,	1758	Event->io (fd => IO::AIO::poll_fileno,
978	poll => 'r', nice => 1,	1759	poll => 'r', nice => 1,
979	cb => &IO::AIO::poll_cb);	1760	cb => &IO::AIO::poll_cb);
980		1761
981	=item IO::AIO::poll_wait	1762	=back
982
983	If there are any outstanding requests and none of them in the result
984	phase, wait till the result filehandle becomes ready for reading (simply
985	does a C<select> on the filehandle. This is useful if you want to
986	synchronously wait for some requests to finish).
987
988	See C<nreqs> for an example.
989
990	=item IO::AIO::poll
991
992	Waits until some requests have been handled.
993
994	Returns the number of requests processed, but is otherwise strictly
995	equivalent to:
996
997	IO::AIO::poll_wait, IO::AIO::poll_cb
998
999	=item IO::AIO::flush
1000
1001	Wait till all outstanding AIO requests have been handled.
1002
1003	Strictly equivalent to:
1004
1005	IO::AIO::poll_wait, IO::AIO::poll_cb
1006	while IO::AIO::nreqs;
1007		1763
1008	=head3 CONTROLLING THE NUMBER OF THREADS	1764	=head3 CONTROLLING THE NUMBER OF THREADS
		1765
		1766	=over
1009		1767
1010	=item IO::AIO::min_parallel $nthreads	1768	=item IO::AIO::min_parallel $nthreads
1011		1769
1012	Set the minimum number of AIO threads to C<$nthreads>. The current	1770	Set the minimum number of AIO threads to C<$nthreads>. The current
1013	default is C<8>, which means eight asynchronous operations can execute	1771	default is C<8>, which means eight asynchronous operations can execute
…		…
1041		1799
1042	Under normal circumstances you don't need to call this function.	1800	Under normal circumstances you don't need to call this function.
1043		1801
1044	=item IO::AIO::max_idle $nthreads	1802	=item IO::AIO::max_idle $nthreads
1045		1803
1046	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1804	Limit the number of threads (default: 4) that are allowed to idle
1047	threads that did not get a request to process within 10 seconds). That	1805	(i.e., threads that did not get a request to process within the idle
1048	means if a thread becomes idle while C<$nthreads> other threads are also	1806	timeout (default: 10 seconds). That means if a thread becomes idle while
1049	idle, it will free its resources and exit.	1807	C<$nthreads> other threads are also idle, it will free its resources and
		1808	exit.
1050		1809
1051	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1810	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1052	to allow for extremely high load situations, but want to free resources	1811	to allow for extremely high load situations, but want to free resources
1053	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1812	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1054		1813
1055	The default is probably ok in most situations, especially if thread	1814	The default is probably ok in most situations, especially if thread
1056	creation is fast. If thread creation is very slow on your system you might	1815	creation is fast. If thread creation is very slow on your system you might
1057	want to use larger values.	1816	want to use larger values.
1058		1817
		1818	=item IO::AIO::idle_timeout $seconds
		1819
		1820	Sets the minimum idle timeout (default 10) after which worker threads are
		1821	allowed to exit. SEe C<IO::AIO::max_idle>.
		1822
1059	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1823	=item IO::AIO::max_outstanding $maxreqs
		1824
		1825	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1826	you do queue up more than this number of requests, the next call to
		1827	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1828	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1829	longer exceeded.
		1830
		1831	In other words, this setting does not enforce a queue limit, but can be
		1832	used to make poll functions block if the limit is exceeded.
1060		1833
1061	This is a very bad function to use in interactive programs because it	1834	This is a very bad function to use in interactive programs because it
1062	blocks, and a bad way to reduce concurrency because it is inexact: Better	1835	blocks, and a bad way to reduce concurrency because it is inexact: Better
1063	use an C<aio_group> together with a feed callback.	1836	use an C<aio_group> together with a feed callback.
1064		1837
1065	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1838	It's main use is in scripts without an event loop - when you want to stat
1066	to queue up more than this number of requests, the next call to the	1839	a lot of files, you can write somehting like this:
1067	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1068	function will block until the limit is no longer exceeded.
1069		1840
1070	The default value is very large, so there is no practical limit on the	1841	IO::AIO::max_outstanding 32;
1071	number of outstanding requests.
1072		1842
1073	You can still queue as many requests as you want. Therefore,	1843	for my $path (...) {
1074	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1844	aio_stat $path , ...;
1075	as a stop gap to shield against fatal memory overflow (with large values).	1845	IO::AIO::poll_cb;
		1846	}
		1847
		1848	IO::AIO::flush;
		1849
		1850	The call to C<poll_cb> inside the loop will normally return instantly, but
		1851	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1852	some requests have been handled. This keeps the loop from pushing a large
		1853	number of C<aio_stat> requests onto the queue.
		1854
		1855	The default value for C<max_outstanding> is very large, so there is no
		1856	practical limit on the number of outstanding requests.
		1857
		1858	=back
1076		1859
1077	=head3 STATISTICAL INFORMATION	1860	=head3 STATISTICAL INFORMATION
		1861
		1862	=over
1078		1863
1079	=item IO::AIO::nreqs	1864	=item IO::AIO::nreqs
1080		1865
1081	Returns the number of requests currently in the ready, execute or pending	1866	Returns the number of requests currently in the ready, execute or pending
1082	states (i.e. for which their callback has not been invoked yet).	1867	states (i.e. for which their callback has not been invoked yet).
…		…
1096	Returns the number of requests currently in the pending state (executed,	1881	Returns the number of requests currently in the pending state (executed,
1097	but not yet processed by poll_cb).	1882	but not yet processed by poll_cb).
1098		1883
1099	=back	1884	=back
1100		1885
		1886	=head3 MISCELLANEOUS FUNCTIONS
		1887
		1888	IO::AIO implements some functions that might be useful, but are not
		1889	asynchronous.
		1890
		1891	=over 4
		1892
		1893	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1894
		1895	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1896	but is blocking (this makes most sense if you know the input data is
		1897	likely cached already and the output filehandle is set to non-blocking
		1898	operations).
		1899
		1900	Returns the number of bytes copied, or C<-1> on error.
		1901
		1902	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1903
		1904	Simply calls the C<posix_fadvise> function (see its
		1905	manpage for details). The following advice constants are
		1906	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1907	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1908	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1909
		1910	On systems that do not implement C<posix_fadvise>, this function returns
		1911	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1912
		1913	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1914
		1915	Simply calls the C<posix_madvise> function (see its
		1916	manpage for details). The following advice constants are
		1917	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1918	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1919
		1920	On systems that do not implement C<posix_madvise>, this function returns
		1921	ENOSYS, otherwise the return value of C<posix_madvise>.
		1922
		1923	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1924
		1925	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1926	$scalar (see its manpage for details). The following protect
		1927	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1928	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1929
		1930	On systems that do not implement C<mprotect>, this function returns
		1931	ENOSYS, otherwise the return value of C<mprotect>.
		1932
		1933	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1934
		1935	Memory-maps a file (or anonymous memory range) and attaches it to the
		1936	given C<$scalar>, which will act like a string scalar. Returns true on
		1937	success, and false otherwise.
		1938
		1939	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1940	change the string length, and most read-only operations such as copying it
		1941	or searching it with regexes and so on.
		1942
		1943	Anything else is unsafe and will, at best, result in memory leaks.
		1944
		1945	The memory map associated with the C<$scalar> is automatically removed
		1946	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1947	C<IO::AIO::munmap> functions are called.
		1948
		1949	This calls the C<mmap>(2) function internally. See your system's manual
		1950	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1951
		1952	The C<$length> must be larger than zero and smaller than the actual
		1953	filesize.
		1954
		1955	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1956	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1957
		1958	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1959	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1960	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1961	(which is set to C<MAP_ANON> if your system only provides this
		1962	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1963	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1964	C<IO::AIO::MAP_NONBLOCK>
		1965
		1966	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1967
		1968	C<$offset> is the offset from the start of the file - it generally must be
		1969	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1970
		1971	Example:
		1972
		1973	use Digest::MD5;
		1974	use IO::AIO;
		1975
		1976	open my $fh, "<verybigfile"
		1977	or die "$!";
		1978
		1979	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1980	or die "verybigfile: $!";
		1981
		1982	my $fast_md5 = md5 $data;
		1983
		1984	=item IO::AIO::munmap $scalar
		1985
		1986	Removes a previous mmap and undefines the C<$scalar>.
		1987
		1988	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1989
		1990	Calls the C<munlock> function, undoing the effects of a previous
		1991	C<aio_mlock> call (see its description for details).
		1992
		1993	=item IO::AIO::munlockall
		1994
		1995	Calls the C<munlockall> function.
		1996
		1997	On systems that do not implement C<munlockall>, this function returns
		1998	ENOSYS, otherwise the return value of C<munlockall>.
		1999
		2000	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2001
		2002	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2003	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2004	should be the file offset.
		2005
		2006	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2007	silently corrupt the data in this case.
		2008
		2009	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2010	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2011	C<IO::AIO::SPLICE_F_GIFT>.
		2012
		2013	See the C<splice(2)> manpage for details.
		2014
		2015	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2016
		2017	Calls the GNU/Linux C<tee(2)> syscall, see it's manpage and the
		2018	description for C<IO::AIO::splice> above for details.
		2019
		2020	=back
		2021
1101	=cut	2022	=cut
1102		2023
1103	# support function to convert a fd into a perl filehandle
1104	sub _fd2fh {
1105	return undef if $_[0] < 0;
1106
1107	# try to generate nice filehandles
1108	my $sym = "IO::AIO::fd#$_[0]";
1109	local *$sym;
1110
1111	open *$sym, "+<&=$_[0]" # usually works under any unix
1112	or open *$sym, "<&=$_[0]" # cygwin needs this
1113	or open *$sym, ">&=$_[0]" # or this
1114	or return undef;
1115
1116	*$sym
1117	}
1118
1119	min_parallel 8;	2024	min_parallel 8;
1120		2025
1121	END { flush }	2026	END { flush }
1122		2027
1123	1;	2028	1;
1124		2029
		2030	=head1 EVENT LOOP INTEGRATION
		2031
		2032	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2033	automatically into many event loops:
		2034
		2035	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2036	use AnyEvent::AIO;
		2037
		2038	You can also integrate IO::AIO manually into many event loops, here are
		2039	some examples of how to do this:
		2040
		2041	# EV integration
		2042	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2043
		2044	# Event integration
		2045	Event->io (fd => IO::AIO::poll_fileno,
		2046	poll => 'r',
		2047	cb => \&IO::AIO::poll_cb);
		2048
		2049	# Glib/Gtk2 integration
		2050	add_watch Glib::IO IO::AIO::poll_fileno,
		2051	in => sub { IO::AIO::poll_cb; 1 };
		2052
		2053	# Tk integration
		2054	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2055	readable => \&IO::AIO::poll_cb);
		2056
		2057	# Danga::Socket integration
		2058	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2059	\&IO::AIO::poll_cb);
		2060
1125	=head2 FORK BEHAVIOUR	2061	=head2 FORK BEHAVIOUR
1126		2062
1127	This module should do "the right thing" when the process using it forks:	2063	Usage of pthreads in a program changes the semantics of fork
		2064	considerably. Specifically, only async-safe functions can be called after
		2065	fork. Perl doesn't know about this, so in general, you cannot call fork
		2066	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2067	pthreads, so this applies, but many other extensions and (for inexplicable
		2068	reasons) perl itself often is linked against pthreads, so this limitation
		2069	applies to quite a lot of perls.
1128		2070
1129	Before the fork, IO::AIO enters a quiescent state where no requests	2071	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1130	can be added in other threads and no results will be processed. After	2072	only works in the process that loaded it. Forking is fully supported, but
1131	the fork the parent simply leaves the quiescent state and continues	2073	using IO::AIO in the child is not.
1132	request/result processing, while the child frees the request/result queue
1133	(so that the requests started before the fork will only be handled in the
1134	parent). Threads will be started on demand until the limit set in the
1135	parent process has been reached again.
1136		2074
1137	In short: the parent will, after a short pause, continue as if fork had	2075	You might get around by not I<using> IO::AIO before (or after)
1138	not been called, while the child will act as if IO::AIO has not been used	2076	forking. You could also try to call the L<IO::AIO::reinit> function in the
1139	yet.	2077	child:
		2078
		2079	=over 4
		2080
		2081	=item IO::AIO::reinit
		2082
		2083	Abandons all current requests and I/O threads and simply reinitialises all
		2084	data structures. This is not an operation supported by any standards, but
		2085	happens to work on GNU/Linux and some newer BSD systems.
		2086
		2087	The only reasonable use for this function is to call it after forking, if
		2088	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2089	the process will result in undefined behaviour. Calling it at any time
		2090	will also result in any undefined (by POSIX) behaviour.
		2091
		2092	=back
1140		2093
1141	=head2 MEMORY USAGE	2094	=head2 MEMORY USAGE
1142		2095
1143	Per-request usage:	2096	Per-request usage:
1144		2097
…		…
1146	bytes of memory. In addition, stat requests need a stat buffer (possibly	2099	bytes of memory. In addition, stat requests need a stat buffer (possibly
1147	a few hundred bytes), readdir requires a result buffer and so on. Perl	2100	a few hundred bytes), readdir requires a result buffer and so on. Perl
1148	scalars and other data passed into aio requests will also be locked and	2101	scalars and other data passed into aio requests will also be locked and
1149	will consume memory till the request has entered the done state.	2102	will consume memory till the request has entered the done state.
1150		2103
1151	This is now awfully much, so queuing lots of requests is not usually a	2104	This is not awfully much, so queuing lots of requests is not usually a
1152	problem.	2105	problem.
1153		2106
1154	Per-thread usage:	2107	Per-thread usage:
1155		2108
1156	In the execution phase, some aio requests require more memory for	2109	In the execution phase, some aio requests require more memory for
…		…
1161		2114
1162	Known bugs will be fixed in the next release.	2115	Known bugs will be fixed in the next release.
1163		2116
1164	=head1 SEE ALSO	2117	=head1 SEE ALSO
1165		2118
1166	L<Coro::AIO>.	2119	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2120	more natural syntax.
1167		2121
1168	=head1 AUTHOR	2122	=head1 AUTHOR
1169		2123
1170	Marc Lehmann <schmorp@schmorp.de>	2124	Marc Lehmann <schmorp@schmorp.de>
1171	http://home.schmorp.de/	2125	http://home.schmorp.de/

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines