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Revision 1.165 by root, Tue Aug 18 04:05:00 2009 UTC vs.
Revision 1.275 by root, Fri Sep 22 05:20:39 2017 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
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
…		…
25	my $req = aio_unlink "/tmp/file", sub { };	25	my $req = aio_unlink "/tmp/file", sub { };
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
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53		30
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports. It is implemented as an interface to C<libeio>	34	operating system supports. It is implemented as an interface to C<libeio>
…		…
81	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
82	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
83	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
84	using threads anyway.	61	using threads anyway.
85		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
86	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
87	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
88	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
89	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
90		71
91	=head2 EXAMPLE	72	=head2 EXAMPLE
92		73
93	This is a simple example that uses the EV module and loads	74	This is a simple example that uses the EV module and loads
94	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
95		76
96	use Fcntl;
97	use EV;	77	use EV;
98	use IO::AIO;	78	use IO::AIO;
99		79
100	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
101	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
102		82
103	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
104	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
105	my $fh = shift	85	my $fh = shift
106	or die "error while opening: $!";	86	or die "error while opening: $!";
107		87
108	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
109	my $size = -s $fh;	89	my $size = -s $fh;
…		…
118		98
119	# file contents now in $contents	99	# file contents now in $contents
120	print $contents;	100	print $contents;
121		101
122	# exit event loop and program	102	# exit event loop and program
123	EV::unloop;	103	EV::break;
124	};	104	};
125	};	105	};
126		106
127	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
128	# check for sockets etc. etc.	108	# check for sockets etc. etc.
129		109
130	# process events as long as there are some:	110	# process events as long as there are some:
131	EV::loop;	111	EV::run;
132		112
133	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
134		114
135	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
136	directly visible to Perl.	116	directly visible to Perl.
…		…
191	use common::sense;	171	use common::sense;
192		172
193	use base 'Exporter';	173	use base 'Exporter';
194		174
195	BEGIN {	175	BEGIN {
196	our $VERSION = '3.3';	176	our $VERSION = 4.35;
197		177
198	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
199	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
200	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
201	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
202	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
203	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
204	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
205		189
206	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
207	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
208	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
209	nreqs nready npending nthreads	193	nreqs nready npending nthreads
210	max_poll_time max_poll_reqs	194	max_poll_time max_poll_reqs
211	sendfile fadvise);	195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
212		197
213	push @AIO_REQ, qw(aio_busy); # not exported	198	push @AIO_REQ, qw(aio_busy); # not exported
214		199
215	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
216		201
…		…
218	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
219	}	204	}
220		205
221	=head1 FUNCTIONS	206	=head1 FUNCTIONS
222		207
223	=head2 AIO REQUEST FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		239	aio_mkdir $pathname, $mode, $callback->($status)
		240	aio_rmdir $pathname, $callback->($status)
		241	aio_readdir $pathname, $callback->($entries)
		242	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		243	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		244	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		245	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		246	aio_load $pathname, $data, $callback->($status)
		247	aio_copy $srcpath, $dstpath, $callback->($status)
		248	aio_move $srcpath, $dstpath, $callback->($status)
		249	aio_rmtree $pathname, $callback->($status)
		250	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		251	aio_ioctl $fh, $request, $buf, $callback->($status)
		252	aio_sync $callback->($status)
		253	aio_syncfs $fh, $callback->($status)
		254	aio_fsync $fh, $callback->($status)
		255	aio_fdatasync $fh, $callback->($status)
		256	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		257	aio_pathsync $pathname, $callback->($status)
		258	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		259	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		260	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		261	aio_mlockall $flags, $callback->($status)
		262	aio_group $callback->(...)
		263	aio_nop $callback->()
		264
		265	$prev_pri = aioreq_pri [$pri]
		266	aioreq_nice $pri_adjust
		267
		268	IO::AIO::poll_wait
		269	IO::AIO::poll_cb
		270	IO::AIO::poll
		271	IO::AIO::flush
		272	IO::AIO::max_poll_reqs $nreqs
		273	IO::AIO::max_poll_time $seconds
		274	IO::AIO::min_parallel $nthreads
		275	IO::AIO::max_parallel $nthreads
		276	IO::AIO::max_idle $nthreads
		277	IO::AIO::idle_timeout $seconds
		278	IO::AIO::max_outstanding $maxreqs
		279	IO::AIO::nreqs
		280	IO::AIO::nready
		281	IO::AIO::npending
		282	IO::AIO::min_fdlimit $nfd;
		283
		284	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		285	IO::AIO::fadvise $fh, $offset, $len, $advice
		286	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		287	IO::AIO::munmap $scalar
		288	IO::AIO::madvise $scalar, $offset, $length, $advice
		289	IO::AIO::mprotect $scalar, $offset, $length, $protect
		290	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		291	IO::AIO::munlockall
		292
		293	=head2 API NOTES
224		294
225	All the C<aio_*> calls are more or less thin wrappers around the syscall	295	All the C<aio_*> calls are more or less thin wrappers around the syscall
226	with the same name (sans C<aio_>). The arguments are similar or identical,	296	with the same name (sans C<aio_>). The arguments are similar or identical,
227	and they all accept an additional (and optional) C<$callback> argument	297	and they all accept an additional (and optional) C<$callback> argument
228	which must be a code reference. This code reference will get called with	298	which must be a code reference. This code reference will be called after
229	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	299	the syscall has been executed in an asynchronous fashion. The results
230	perl, which usually delivers "false") as its sole argument after the given	300	of the request will be passed as arguments to the callback (and, if an
231	syscall has been executed asynchronously.	301	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		302	most syscalls return C<-1> on error, unlike perl, which usually delivers
		303	"false").
		304
		305	Some requests (such as C<aio_readdir>) pass the actual results and
		306	communicate failures by passing C<undef>.
232		307
233	All functions expecting a filehandle keep a copy of the filehandle	308	All functions expecting a filehandle keep a copy of the filehandle
234	internally until the request has finished.	309	internally until the request has finished.
235		310
236	All functions return request objects of type L<IO::AIO::REQ> that allow	311	All functions return request objects of type L<IO::AIO::REQ> that allow
237	further manipulation of those requests while they are in-flight.	312	further manipulation of those requests while they are in-flight.
238		313
239	The pathnames you pass to these routines I<must> be absolute and	314	The pathnames you pass to these routines I<should> be absolute. The
240	encoded as octets. The reason for the former is that at the time the	315	reason for this is that at the time the request is being executed, the
241	request is being executed, the current working directory could have	316	current working directory could have changed. Alternatively, you can
242	changed. Alternatively, you can make sure that you never change the	317	make sure that you never change the current working directory anywhere
243	current working directory anywhere in the program and then use relative	318	in the program and then use relative paths. You can also take advantage
244	paths.	319	of IO::AIOs working directory abstraction, that lets you specify paths
		320	relative to some previously-opened "working directory object" - see the
		321	description of the C<IO::AIO::WD> class later in this document.
245		322
246	To encode pathnames as octets, either make sure you either: a) always pass	323	To encode pathnames as octets, either make sure you either: a) always pass
247	in filenames you got from outside (command line, readdir etc.) without	324	in filenames you got from outside (command line, readdir etc.) without
248	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	325	tinkering, b) are in your native filesystem encoding, c) use the Encode
249	your pathnames to the locale (or other) encoding in effect in the user	326	module and encode your pathnames to the locale (or other) encoding in
250	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	327	effect in the user environment, d) use Glib::filename_from_unicode on
251	use something else to ensure your scalar has the correct contents.	328	unicode filenames or e) use something else to ensure your scalar has the
		329	correct contents.
252		330
253	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	331	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
254	handles correctly whether it is set or not.	332	handles correctly whether it is set or not.
		333
		334	=head2 AIO REQUEST FUNCTIONS
255		335
256	=over 4	336	=over 4
257		337
258	=item $prev_pri = aioreq_pri [$pri]	338	=item $prev_pri = aioreq_pri [$pri]
259		339
…		…
289		369
290		370
291	=item aio_open $pathname, $flags, $mode, $callback->($fh)	371	=item aio_open $pathname, $flags, $mode, $callback->($fh)
292		372
293	Asynchronously open or create a file and call the callback with a newly	373	Asynchronously open or create a file and call the callback with a newly
294	created filehandle for the file.	374	created filehandle for the file (or C<undef> in case of an error).
295		375
296	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	376	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
297	for an explanation.	377	for an explanation.
298		378
299	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	379	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
306	by the umask in effect then the request is being executed, so better never	386	by the umask in effect then the request is being executed, so better never
307	change the umask.	387	change the umask.
308		388
309	Example:	389	Example:
310		390
311	aio_open "/etc/passwd", O_RDONLY, 0, sub {	391	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
312	if ($_[0]) {	392	if ($_[0]) {
313	print "open successful, fh is $_[0]\n";	393	print "open successful, fh is $_[0]\n";
314	...	394	...
315	} else {	395	} else {
316	die "open failed: $!\n";	396	die "open failed: $!\n";
317	}	397	}
318	};	398	};
319		399
		400	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		401	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		402	following POSIX and non-POSIX constants are available (missing ones on
		403	your system are, as usual, C<0>):
		404
		405	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		406	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		407	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		408
320		409
321	=item aio_close $fh, $callback->($status)	410	=item aio_close $fh, $callback->($status)
322		411
323	Asynchronously close a file and call the callback with the result	412	Asynchronously close a file and call the callback with the result
324	code.	413	code.
…		…
333	Or in other words: the file descriptor will be closed, but it will not be	422	Or in other words: the file descriptor will be closed, but it will not be
334	free for reuse until the perl filehandle is closed.	423	free for reuse until the perl filehandle is closed.
335		424
336	=cut	425	=cut
337		426
		427	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		428
		429	Seeks the filehandle to the new C<$offset>, similarly to perl's
		430	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		431	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		432	C<IO::AIO::SEEK_END>).
		433
		434	The resulting absolute offset will be passed to the callback, or C<-1> in
		435	case of an error.
		436
		437	In theory, the C<$whence> constants could be different than the
		438	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		439	so don't panic.
		440
		441	As a GNU/Linux (and maybe Solaris) extension, also the constants
		442	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		443	could be found. No guarantees about suitability for use in C<aio_seek> or
		444	Perl's C<sysseek> can be made though, although I would naively assume they
		445	"just work".
		446
338	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
339		448
340	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
341		450
342	Reads or writes C<$length> bytes from or to the specified C<$fh> and	451	Reads or writes C<$length> bytes from or to the specified C<$fh> and
343	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	452	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
344	and calls the callback without the actual number of bytes read (or -1 on	453	calls the callback with the actual number of bytes transferred (or -1 on
345	error, just like the syscall).	454	error, just like the syscall).
346		455
347	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	456	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
348	offset plus the actual number of bytes read.	457	offset plus the actual number of bytes read.
349		458
…		…
374		483
375	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	484	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
376	reading at byte offset C<$in_offset>, and starts writing at the current	485	reading at byte offset C<$in_offset>, and starts writing at the current
377	file offset of C<$out_fh>. Because of that, it is not safe to issue more	486	file offset of C<$out_fh>. Because of that, it is not safe to issue more
378	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	487	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
379	other.	488	other. The same C<$in_fh> works fine though, as this function does not
		489	move or use the file offset of C<$in_fh>.
380		490
		491	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		492	are written, and there is no way to find out how many more bytes have been
		493	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		494	number of bytes written to C<$out_fh>. Only if the result value equals
		495	C<$length> one can assume that C<$length> bytes have been read.
		496
		497	Unlike with other C<aio_> functions, it makes a lot of sense to use
		498	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		499	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		500	the socket I/O will be non-blocking. Note, however, that you can run
		501	into a trap where C<aio_sendfile> reads some data with readahead, then
		502	fails to write all data, and when the socket is ready the next time, the
		503	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		504	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		505	resource usage.
		506
381	This call tries to make use of a native C<sendfile> syscall to provide	507	This call tries to make use of a native C<sendfile>-like syscall to
382	zero-copy operation. For this to work, C<$out_fh> should refer to a	508	provide zero-copy operation. For this to work, C<$out_fh> should refer to
383	socket, and C<$in_fh> should refer to mmap'able file.	509	a socket, and C<$in_fh> should refer to an mmap'able file.
384		510
385	If the native sendfile call fails or is not implemented, it will be	511	If a native sendfile cannot be found or it fails with C<ENOSYS>,
386	emulated, so you can call C<aio_sendfile> on any type of filehandle	512	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		513	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
387	regardless of the limitations of the operating system.	514	type of filehandle regardless of the limitations of the operating system.
388		515
389	Please note, however, that C<aio_sendfile> can read more bytes from	516	As native sendfile syscalls (as practically any non-POSIX interface hacked
390	C<$in_fh> than are written, and there is no way to find out how many	517	together in a hurry to improve benchmark numbers) tend to be rather buggy
391	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	518	on many systems, this implementation tries to work around some known bugs
392	provides the number of bytes written to C<$out_fh>. Only if the result	519	in Linux and FreeBSD kernels (probably others, too), but that might fail,
393	value equals C<$length> one can assume that C<$length> bytes have been	520	so you really really should check the return value of C<aio_sendfile> -
394	read.	521	fewer bytes than expected might have been transferred.
395		522
396		523
397	=item aio_readahead $fh,$offset,$length, $callback->($retval)	524	=item aio_readahead $fh,$offset,$length, $callback->($retval)
398		525
399	C<aio_readahead> populates the page cache with data from a file so that	526	C<aio_readahead> populates the page cache with data from a file so that
…		…
403	whole pages, so that offset is effectively rounded down to a page boundary	530	whole pages, so that offset is effectively rounded down to a page boundary
404	and bytes are read up to the next page boundary greater than or equal to	531	and bytes are read up to the next page boundary greater than or equal to
405	(off-set+length). C<aio_readahead> does not read beyond the end of the	532	(off-set+length). C<aio_readahead> does not read beyond the end of the
406	file. The current file offset of the file is left unchanged.	533	file. The current file offset of the file is left unchanged.
407		534
408	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	535	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
409	emulated by simply reading the data, which would have a similar effect.	536	be emulated by simply reading the data, which would have a similar effect.
410		537
411		538
412	=item aio_stat $fh_or_path, $callback->($status)	539	=item aio_stat $fh_or_path, $callback->($status)
413		540
414	=item aio_lstat $fh, $callback->($status)	541	=item aio_lstat $fh, $callback->($status)
…		…
421	for an explanation.	548	for an explanation.
422		549
423	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	550	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
424	error when stat'ing a large file, the results will be silently truncated	551	error when stat'ing a large file, the results will be silently truncated
425	unless perl itself is compiled with large file support.	552	unless perl itself is compiled with large file support.
		553
		554	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		555	following constants and functions (if not implemented, the constants will
		556	be C<0> and the functions will either C<croak> or fall back on traditional
		557	behaviour).
		558
		559	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		560	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		561	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
426		562
427	Example: Print the length of F</etc/passwd>:	563	Example: Print the length of F</etc/passwd>:
428		564
429	aio_stat "/etc/passwd", sub {	565	aio_stat "/etc/passwd", sub {
430	$_[0] and die "stat failed: $!";	566	$_[0] and die "stat failed: $!";
431	print "size is ", -s _, "\n";	567	print "size is ", -s _, "\n";
432	};	568	};
433		569
434		570
		571	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		572
		573	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		574	whether a file handle or path was passed.
		575
		576	On success, the callback is passed a hash reference with the following
		577	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		578	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		579	is passed.
		580
		581	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		582	C<ST_NOSUID>.
		583
		584	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		585	their correct value when available, or to C<0> on systems that do
		586	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		587	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		588	C<ST_NODIRATIME> and C<ST_RELATIME>.
		589
		590	Example: stat C</wd> and dump out the data if successful.
		591
		592	aio_statvfs "/wd", sub {
		593	my $f = $_[0]
		594	or die "statvfs: $!";
		595
		596	use Data::Dumper;
		597	say Dumper $f;
		598	};
		599
		600	# result:
		601	{
		602	bsize => 1024,
		603	bfree => 4333064312,
		604	blocks => 10253828096,
		605	files => 2050765568,
		606	flag => 4096,
		607	favail => 2042092649,
		608	bavail => 4333064312,
		609	ffree => 2042092649,
		610	namemax => 255,
		611	frsize => 1024,
		612	fsid => 1810
		613	}
		614
		615	Here is a (likely partial - send me updates!) list of fsid values used by
		616	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		617
		618	0x0000adf5 adfs
		619	0x0000adff affs
		620	0x5346414f afs
		621	0x09041934 anon-inode filesystem
		622	0x00000187 autofs
		623	0x42465331 befs
		624	0x1badface bfs
		625	0x42494e4d binfmt_misc
		626	0x9123683e btrfs
		627	0x0027e0eb cgroupfs
		628	0xff534d42 cifs
		629	0x73757245 coda
		630	0x012ff7b7 coh
		631	0x28cd3d45 cramfs
		632	0x453dcd28 cramfs-wend (wrong endianness)
		633	0x64626720 debugfs
		634	0x00001373 devfs
		635	0x00001cd1 devpts
		636	0x0000f15f ecryptfs
		637	0x00414a53 efs
		638	0x0000137d ext
		639	0x0000ef53 ext2/ext3/ext4
		640	0x0000ef51 ext2
		641	0xf2f52010 f2fs
		642	0x00004006 fat
		643	0x65735546 fuseblk
		644	0x65735543 fusectl
		645	0x0bad1dea futexfs
		646	0x01161970 gfs2
		647	0x47504653 gpfs
		648	0x00004244 hfs
		649	0xf995e849 hpfs
		650	0x00c0ffee hostfs
		651	0x958458f6 hugetlbfs
		652	0x2bad1dea inotifyfs
		653	0x00009660 isofs
		654	0x000072b6 jffs2
		655	0x3153464a jfs
		656	0x6b414653 k-afs
		657	0x0bd00bd0 lustre
		658	0x0000137f minix
		659	0x0000138f minix 30 char names
		660	0x00002468 minix v2
		661	0x00002478 minix v2 30 char names
		662	0x00004d5a minix v3
		663	0x19800202 mqueue
		664	0x00004d44 msdos
		665	0x0000564c novell
		666	0x00006969 nfs
		667	0x6e667364 nfsd
		668	0x00003434 nilfs
		669	0x5346544e ntfs
		670	0x00009fa1 openprom
		671	0x7461636F ocfs2
		672	0x00009fa0 proc
		673	0x6165676c pstorefs
		674	0x0000002f qnx4
		675	0x68191122 qnx6
		676	0x858458f6 ramfs
		677	0x52654973 reiserfs
		678	0x00007275 romfs
		679	0x67596969 rpc_pipefs
		680	0x73636673 securityfs
		681	0xf97cff8c selinux
		682	0x0000517b smb
		683	0x534f434b sockfs
		684	0x73717368 squashfs
		685	0x62656572 sysfs
		686	0x012ff7b6 sysv2
		687	0x012ff7b5 sysv4
		688	0x01021994 tmpfs
		689	0x15013346 udf
		690	0x00011954 ufs
		691	0x54190100 ufs byteswapped
		692	0x00009fa2 usbdevfs
		693	0x01021997 v9fs
		694	0xa501fcf5 vxfs
		695	0xabba1974 xenfs
		696	0x012ff7b4 xenix
		697	0x58465342 xfs
		698	0x012fd16d xia
		699
435	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	700	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
436		701
437	Works like perl's C<utime> function (including the special case of $atime	702	Works like perl's C<utime> function (including the special case of $atime
438	and $mtime being undef). Fractional times are supported if the underlying	703	and $mtime being undef). Fractional times are supported if the underlying
439	syscalls support them.	704	syscalls support them.
…		…
466	=item aio_truncate $fh_or_path, $offset, $callback->($status)	731	=item aio_truncate $fh_or_path, $offset, $callback->($status)
467		732
468	Works like truncate(2) or ftruncate(2).	733	Works like truncate(2) or ftruncate(2).
469		734
470		735
		736	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		737
		738	Allocates or frees disk space according to the C<$mode> argument. See the
		739	linux C<fallocate> documentation for details.
		740
		741	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		742	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		743	to deallocate a file range.
		744
		745	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		746	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		747	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		748	to unshare shared blocks (see your L<fallocate(2)> manpage).
		749
		750	The file system block size used by C<fallocate> is presumably the
		751	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		752	can dictate other limitations.
		753
		754	If C<fallocate> isn't available or cannot be emulated (currently no
		755	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		756
		757
471	=item aio_chmod $fh_or_path, $mode, $callback->($status)	758	=item aio_chmod $fh_or_path, $mode, $callback->($status)
472		759
473	Works like perl's C<chmod> function.	760	Works like perl's C<chmod> function.
474		761
475		762
…		…
477		764
478	Asynchronously unlink (delete) a file and call the callback with the	765	Asynchronously unlink (delete) a file and call the callback with the
479	result code.	766	result code.
480		767
481		768
482	=item aio_mknod $path, $mode, $dev, $callback->($status)	769	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
483		770
484	[EXPERIMENTAL]	771	[EXPERIMENTAL]
485		772
486	Asynchronously create a device node (or fifo). See mknod(2).	773	Asynchronously create a device node (or fifo). See mknod(2).
487		774
488	The only (POSIX-) portable way of calling this function is:	775	The only (POSIX-) portable way of calling this function is:
489		776
490	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	777	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
491		778
		779	See C<aio_stat> for info about some potentially helpful extra constants
		780	and functions.
492		781
493	=item aio_link $srcpath, $dstpath, $callback->($status)	782	=item aio_link $srcpath, $dstpath, $callback->($status)
494		783
495	Asynchronously create a new link to the existing object at C<$srcpath> at	784	Asynchronously create a new link to the existing object at C<$srcpath> at
496	the path C<$dstpath> and call the callback with the result code.	785	the path C<$dstpath> and call the callback with the result code.
…		…
500		789
501	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	790	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
502	the path C<$dstpath> and call the callback with the result code.	791	the path C<$dstpath> and call the callback with the result code.
503		792
504		793
505	=item aio_readlink $path, $callback->($link)	794	=item aio_readlink $pathname, $callback->($link)
506		795
507	Asynchronously read the symlink specified by C<$path> and pass it to	796	Asynchronously read the symlink specified by C<$path> and pass it to
508	the callback. If an error occurs, nothing or undef gets passed to the	797	the callback. If an error occurs, nothing or undef gets passed to the
509	callback.	798	callback.
510		799
511		800
		801	=item aio_realpath $pathname, $callback->($path)
		802
		803	Asynchronously make the path absolute and resolve any symlinks in
		804	C<$path>. The resulting path only consists of directories (same as
		805	L<Cwd::realpath>).
		806
		807	This request can be used to get the absolute path of the current working
		808	directory by passing it a path of F<.> (a single dot).
		809
		810
512	=item aio_rename $srcpath, $dstpath, $callback->($status)	811	=item aio_rename $srcpath, $dstpath, $callback->($status)
513		812
514	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	813	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
515	rename(2) and call the callback with the result code.	814	rename(2) and call the callback with the result code.
		815
		816	On systems that support the AIO::WD working directory abstraction
		817	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		818	of failing, C<rename> is called on the absolute path of C<$wd>.
		819
		820
		821	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		822
		823	Basically a version of C<aio_rename> with an additional C<$flags>
		824	argument. Calling this with C<$flags=0> is the same as calling
		825	C<aio_rename>.
		826
		827	Non-zero flags are currently only supported on GNU/Linux systems that
		828	support renameat2. Other systems fail with C<ENOSYS> in this case.
		829
		830	The following constants are available (missing ones are, as usual C<0>),
		831	see renameat2(2) for details:
		832
		833	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		834	and C<IO::AIO::RENAME_WHITEOUT>.
516		835
517		836
518	=item aio_mkdir $pathname, $mode, $callback->($status)	837	=item aio_mkdir $pathname, $mode, $callback->($status)
519		838
520	Asynchronously mkdir (create) a directory and call the callback with	839	Asynchronously mkdir (create) a directory and call the callback with
…		…
525	=item aio_rmdir $pathname, $callback->($status)	844	=item aio_rmdir $pathname, $callback->($status)
526		845
527	Asynchronously rmdir (delete) a directory and call the callback with the	846	Asynchronously rmdir (delete) a directory and call the callback with the
528	result code.	847	result code.
529		848
		849	On systems that support the AIO::WD working directory abstraction
		850	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		851	C<rmdir> is called on the absolute path of C<$wd>.
		852
530		853
531	=item aio_readdir $pathname, $callback->($entries)	854	=item aio_readdir $pathname, $callback->($entries)
532		855
533	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	856	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
534	directory (i.e. opendir + readdir + closedir). The entries will not be	857	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
538	array-ref with the filenames.	861	array-ref with the filenames.
539		862
540		863
541	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	864	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
542		865
543	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	866	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
544	behaviour and output format. In case of an error, C<$entries> will be	867	tune behaviour and output format. In case of an error, C<$entries> will be
545	C<undef>.	868	C<undef>.
546		869
547	The flags are a combination of the following constants, ORed together (the	870	The flags are a combination of the following constants, ORed together (the
548	flags will also be passed to the callback, possibly modified):	871	flags will also be passed to the callback, possibly modified):
549		872
550	=over 4	873	=over 4
551		874
552	=item IO::AIO::READDIR_DENTS	875	=item IO::AIO::READDIR_DENTS
553		876
554	When this flag is off, then the callback gets an arrayref with of names	877	When this flag is off, then the callback gets an arrayref consisting of
555	only (as with C<aio_readdir>), otherwise it gets an arrayref with	878	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
556	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	879	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
557	entry in more detail.	880	entry in more detail.
558		881
559	C<$name> is the name of the entry.	882	C<$name> is the name of the entry.
560		883
…		…
573	systems that do not deliver the inode information.	896	systems that do not deliver the inode information.
574		897
575	=item IO::AIO::READDIR_DIRS_FIRST	898	=item IO::AIO::READDIR_DIRS_FIRST
576		899
577	When this flag is set, then the names will be returned in an order where	900	When this flag is set, then the names will be returned in an order where
578	likely directories come first. This is useful when you need to quickly	901	likely directories come first, in optimal stat order. This is useful when
579	find directories, or you want to find all directories while avoiding to	902	you need to quickly find directories, or you want to find all directories
580	stat() each entry.	903	while avoiding to stat() each entry.
581		904
582	If the system returns type information in readdir, then this is used	905	If the system returns type information in readdir, then this is used
583	to find directories directly. Otherwise, likely directories are files	906	to find directories directly. Otherwise, likely directories are names
584	beginning with ".", or otherwise files with no dots, of which files with	907	beginning with ".", or otherwise names with no dots, of which names with
585	short names are tried first.	908	short names are tried first.
586		909
587	=item IO::AIO::READDIR_STAT_ORDER	910	=item IO::AIO::READDIR_STAT_ORDER
588		911
589	When this flag is set, then the names will be returned in an order	912	When this flag is set, then the names will be returned in an order
…		…
596		919
597	=item IO::AIO::READDIR_FOUND_UNKNOWN	920	=item IO::AIO::READDIR_FOUND_UNKNOWN
598		921
599	This flag should not be set when calling C<aio_readdirx>. Instead, it	922	This flag should not be set when calling C<aio_readdirx>. Instead, it
600	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	923	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
601	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	924	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
602	C<$type>'s are known, which can be used to speed up some algorithms.	925	C<$type>'s are known, which can be used to speed up some algorithms.
603		926
604	=back	927	=back
605		928
606		929
607	=item aio_load $path, $data, $callback->($status)	930	=item aio_load $pathname, $data, $callback->($status)
608		931
609	This is a composite request that tries to fully load the given file into	932	This is a composite request that tries to fully load the given file into
610	memory. Status is the same as with aio_read.	933	memory. Status is the same as with aio_read.
611		934
612	=cut	935	=cut
…		…
636		959
637	Try to copy the I<file> (directories not supported as either source or	960	Try to copy the I<file> (directories not supported as either source or
638	destination) from C<$srcpath> to C<$dstpath> and call the callback with	961	destination) from C<$srcpath> to C<$dstpath> and call the callback with
639	a status of C<0> (ok) or C<-1> (error, see C<$!>).	962	a status of C<0> (ok) or C<-1> (error, see C<$!>).
640		963
		964	Existing destination files will be truncated.
		965
641	This is a composite request that creates the destination file with	966	This is a composite request that creates the destination file with
642	mode 0200 and copies the contents of the source file into it using	967	mode 0200 and copies the contents of the source file into it using
643	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	968	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
644	uid/gid, in that order.	969	uid/gid, in that order.
645		970
…		…
656	my $grp = aio_group $cb;	981	my $grp = aio_group $cb;
657		982
658	aioreq_pri $pri;	983	aioreq_pri $pri;
659	add $grp aio_open $src, O_RDONLY, 0, sub {	984	add $grp aio_open $src, O_RDONLY, 0, sub {
660	if (my $src_fh = $_[0]) {	985	if (my $src_fh = $_[0]) {
661	my @stat = stat $src_fh; # hmm, might bock over nfs?	986	my @stat = stat $src_fh; # hmm, might block over nfs?
662		987
663	aioreq_pri $pri;	988	aioreq_pri $pri;
664	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	989	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
665	if (my $dst_fh = $_[0]) {	990	if (my $dst_fh = $_[0]) {
666	aioreq_pri $pri;	991	aioreq_pri $pri;
…		…
734	if ($_[0] && $! == EXDEV) {	1059	if ($_[0] && $! == EXDEV) {
735	aioreq_pri $pri;	1060	aioreq_pri $pri;
736	add $grp aio_copy $src, $dst, sub {	1061	add $grp aio_copy $src, $dst, sub {
737	$grp->result ($_[0]);	1062	$grp->result ($_[0]);
738		1063
739	if (!$_[0]) {	1064	unless ($_[0]) {
740	aioreq_pri $pri;	1065	aioreq_pri $pri;
741	add $grp aio_unlink $src;	1066	add $grp aio_unlink $src;
742	}	1067	}
743	};	1068	};
744	} else {	1069	} else {
…		…
747	};	1072	};
748		1073
749	$grp	1074	$grp
750	}	1075	}
751		1076
752	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1077	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
753		1078
754	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1079	Scans a directory (similar to C<aio_readdir>) but additionally tries to
755	efficiently separate the entries of directory C<$path> into two sets of	1080	efficiently separate the entries of directory C<$path> into two sets of
756	names, directories you can recurse into (directories), and ones you cannot	1081	names, directories you can recurse into (directories), and ones you cannot
757	recurse into (everything else, including symlinks to directories).	1082	recurse into (everything else, including symlinks to directories).
…		…
788	Then entries will be sorted into likely directories a non-initial dot	1113	Then entries will be sorted into likely directories a non-initial dot
789	currently) and likely non-directories (see C<aio_readdirx>). Then every	1114	currently) and likely non-directories (see C<aio_readdirx>). Then every
790	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1115	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
791	in order of their inode numbers. If that succeeds, it assumes that the	1116	in order of their inode numbers. If that succeeds, it assumes that the
792	entry is a directory or a symlink to directory (which will be checked	1117	entry is a directory or a symlink to directory (which will be checked
793	seperately). This is often faster than stat'ing the entry itself because	1118	separately). This is often faster than stat'ing the entry itself because
794	filesystems might detect the type of the entry without reading the inode	1119	filesystems might detect the type of the entry without reading the inode
795	data (e.g. ext2fs filetype feature), even on systems that cannot return	1120	data (e.g. ext2fs filetype feature), even on systems that cannot return
796	the filetype information on readdir.	1121	the filetype information on readdir.
797		1122
798	If the known number of directories (link count - 2) has been reached, the	1123	If the known number of directories (link count - 2) has been reached, the
…		…
814		1139
815	my $grp = aio_group $cb;	1140	my $grp = aio_group $cb;
816		1141
817	$maxreq = 4 if $maxreq <= 0;	1142	$maxreq = 4 if $maxreq <= 0;
818		1143
819	# stat once	1144	# get a wd object
820	aioreq_pri $pri;	1145	aioreq_pri $pri;
821	add $grp aio_stat $path, sub {	1146	add $grp aio_wd $path, sub {
		1147	$_[0]
822	return $grp->result () if $_[0];	1148	or return $grp->result ();
823	my $now = time;
824	my $hash1 = join ":", (stat _)[0,1,3,7,9];
825		1149
826	# read the directory entries	1150	my $wd = [shift, "."];
		1151
		1152	# stat once
827	aioreq_pri $pri;	1153	aioreq_pri $pri;
828	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1154	add $grp aio_stat $wd, sub {
829	my $entries = shift
830	or return $grp->result ();	1155	return $grp->result () if $_[0];
		1156	my $now = time;
		1157	my $hash1 = join ":", (stat _)[0,1,3,7,9];
831		1158
832	# stat the dir another time	1159	# read the directory entries
833	aioreq_pri $pri;	1160	aioreq_pri $pri;
		1161	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1162	my $entries = shift
		1163	or return $grp->result ();
		1164
		1165	# stat the dir another time
		1166	aioreq_pri $pri;
834	add $grp aio_stat $path, sub {	1167	add $grp aio_stat $wd, sub {
835	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1168	my $hash2 = join ":", (stat _)[0,1,3,7,9];
836		1169
837	my $ndirs;	1170	my $ndirs;
838		1171
839	# take the slow route if anything looks fishy	1172	# take the slow route if anything looks fishy
840	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1173	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
841	$ndirs = -1;	1174	$ndirs = -1;
842	} else {	1175	} else {
843	# if nlink == 2, we are finished	1176	# if nlink == 2, we are finished
844	# for non-posix-fs's, we rely on nlink < 2	1177	# for non-posix-fs's, we rely on nlink < 2
845	$ndirs = (stat _)[3] - 2	1178	$ndirs = (stat _)[3] - 2
846	or return $grp->result ([], $entries);	1179	or return $grp->result ([], $entries);
847	}	1180	}
848		1181
849	my (@dirs, @nondirs);	1182	my (@dirs, @nondirs);
850		1183
851	my $statgrp = add $grp aio_group sub {	1184	my $statgrp = add $grp aio_group sub {
852	$grp->result (\@dirs, \@nondirs);	1185	$grp->result (\@dirs, \@nondirs);
853	};	1186	};
854		1187
855	limit $statgrp $maxreq;	1188	limit $statgrp $maxreq;
856	feed $statgrp sub {	1189	feed $statgrp sub {
857	return unless @$entries;	1190	return unless @$entries;
858	my $entry = shift @$entries;	1191	my $entry = shift @$entries;
859		1192
860	aioreq_pri $pri;	1193	aioreq_pri $pri;
		1194	$wd->[1] = "$entry/.";
861	add $statgrp aio_stat "$path/$entry/.", sub {	1195	add $statgrp aio_stat $wd, sub {
862	if ($_[0] < 0) {	1196	if ($_[0] < 0) {
863	push @nondirs, $entry;	1197	push @nondirs, $entry;
864	} else {	1198	} else {
865	# need to check for real directory	1199	# need to check for real directory
866	aioreq_pri $pri;	1200	aioreq_pri $pri;
		1201	$wd->[1] = $entry;
867	add $statgrp aio_lstat "$path/$entry", sub {	1202	add $statgrp aio_lstat $wd, sub {
868	if (-d _) {	1203	if (-d _) {
869	push @dirs, $entry;	1204	push @dirs, $entry;
870		1205
871	unless (--$ndirs) {	1206	unless (--$ndirs) {
872	push @nondirs, @$entries;	1207	push @nondirs, @$entries;
873	feed $statgrp;	1208	feed $statgrp;
		1209	}
		1210	} else {
		1211	push @nondirs, $entry;
874	}	1212	}
875	} else {
876	push @nondirs, $entry;
877	}	1213	}
878	}	1214	}
879	}	1215	};
880	};	1216	};
881	};	1217	};
882	};	1218	};
883	};	1219	};
884	};	1220	};
885		1221
886	$grp	1222	$grp
887	}	1223	}
888		1224
889	=item aio_rmtree $path, $callback->($status)	1225	=item aio_rmtree $pathname, $callback->($status)
890		1226
891	Delete a directory tree starting (and including) C<$path>, return the	1227	Delete a directory tree starting (and including) C<$path>, return the
892	status of the final C<rmdir> only. This is a composite request that	1228	status of the final C<rmdir> only. This is a composite request that
893	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1229	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
894	everything else.	1230	everything else.
895		1231
896	=cut	1232	=cut
897		1233
…		…
919	};	1255	};
920		1256
921	$grp	1257	$grp
922	}	1258	}
923		1259
		1260	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1261
		1262	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1263
		1264	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1265	they execute asynchronously and pass the return value to the callback.
		1266
		1267	Both calls can be used for a lot of things, some of which make more sense
		1268	to run asynchronously in their own thread, while some others make less
		1269	sense. For example, calls that block waiting for external events, such
		1270	as locking, will also lock down an I/O thread while it is waiting, which
		1271	can deadlock the whole I/O system. At the same time, there might be no
		1272	alternative to using a thread to wait.
		1273
		1274	So in general, you should only use these calls for things that do
		1275	(filesystem) I/O, not for things that wait for other events (network,
		1276	other processes), although if you are careful and know what you are doing,
		1277	you still can.
		1278
		1279	The following constants are available (missing ones are, as usual C<0>):
		1280
		1281	C<F_DUPFD_CLOEXEC>,
		1282
		1283	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1284
		1285	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1286
		1287	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1288	C<FS_IOC_FIEMAP>.
		1289
		1290	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1291	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1292
		1293	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1294	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1295	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1296	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1297	C<FS_FL_USER_MODIFIABLE>.
		1298
		1299	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1300	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1301	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1302	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1303
924	=item aio_sync $callback->($status)	1304	=item aio_sync $callback->($status)
925		1305
926	Asynchronously call sync and call the callback when finished.	1306	Asynchronously call sync and call the callback when finished.
927		1307
928	=item aio_fsync $fh, $callback->($status)	1308	=item aio_fsync $fh, $callback->($status)
…		…
935	Asynchronously call fdatasync on the given filehandle and call the	1315	Asynchronously call fdatasync on the given filehandle and call the
936	callback with the fdatasync result code.	1316	callback with the fdatasync result code.
937		1317
938	If this call isn't available because your OS lacks it or it couldn't be	1318	If this call isn't available because your OS lacks it or it couldn't be
939	detected, it will be emulated by calling C<fsync> instead.	1319	detected, it will be emulated by calling C<fsync> instead.
		1320
		1321	=item aio_syncfs $fh, $callback->($status)
		1322
		1323	Asynchronously call the syncfs syscall to sync the filesystem associated
		1324	to the given filehandle and call the callback with the syncfs result
		1325	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1326	errno to C<ENOSYS> nevertheless.
940		1327
941	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1328	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
942		1329
943	Sync the data portion of the file specified by C<$offset> and C<$length>	1330	Sync the data portion of the file specified by C<$offset> and C<$length>
944	to disk (but NOT the metadata), by calling the Linux-specific	1331	to disk (but NOT the metadata), by calling the Linux-specific
…		…
948	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1335	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
949	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1336	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
950	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1337	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
951	manpage for details.	1338	manpage for details.
952		1339
953	=item aio_pathsync $path, $callback->($status)	1340	=item aio_pathsync $pathname, $callback->($status)
954		1341
955	This request tries to open, fsync and close the given path. This is a	1342	This request tries to open, fsync and close the given path. This is a
956	composite request intended to sync directories after directory operations	1343	composite request intended to sync directories after directory operations
957	(E.g. rename). This might not work on all operating systems or have any	1344	(E.g. rename). This might not work on all operating systems or have any
958	specific effect, but usually it makes sure that directory changes get	1345	specific effect, but usually it makes sure that directory changes get
…		…
989	};	1376	};
990		1377
991	$grp	1378	$grp
992	}	1379	}
993		1380
		1381	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1382
		1383	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1384	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1385	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1386	scalar must only be modified in-place while an aio operation is pending on
		1387	it).
		1388
		1389	It calls the C<msync> function of your OS, if available, with the memory
		1390	area starting at C<$offset> in the string and ending C<$length> bytes
		1391	later. If C<$length> is negative, counts from the end, and if C<$length>
		1392	is C<undef>, then it goes till the end of the string. The flags can be
		1393	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1394	C<IO::AIO::MS_INVALIDATE>.
		1395
		1396	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1397
		1398	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1399	scalars.
		1400
		1401	It touches (reads or writes) all memory pages in the specified
		1402	range inside the scalar. All caveats and parameters are the same
		1403	as for C<aio_msync>, above, except for flags, which must be either
		1404	C<0> (which reads all pages and ensures they are instantiated) or
		1405	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1406	writing an octet from it, which dirties the page).
		1407
		1408	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1409
		1410	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1411	scalars.
		1412
		1413	It reads in all the pages of the underlying storage into memory (if any)
		1414	and locks them, so they are not getting swapped/paged out or removed.
		1415
		1416	If C<$length> is undefined, then the scalar will be locked till the end.
		1417
		1418	On systems that do not implement C<mlock>, this function returns C<-1>
		1419	and sets errno to C<ENOSYS>.
		1420
		1421	Note that the corresponding C<munlock> is synchronous and is
		1422	documented under L<MISCELLANEOUS FUNCTIONS>.
		1423
		1424	Example: open a file, mmap and mlock it - both will be undone when
		1425	C<$data> gets destroyed.
		1426
		1427	open my $fh, "<", $path or die "$path: $!";
		1428	my $data;
		1429	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1430	aio_mlock $data; # mlock in background
		1431
		1432	=item aio_mlockall $flags, $callback->($status)
		1433
		1434	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1435	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1436
		1437	On systems that do not implement C<mlockall>, this function returns C<-1>
		1438	and sets errno to C<ENOSYS>.
		1439
		1440	Note that the corresponding C<munlockall> is synchronous and is
		1441	documented under L<MISCELLANEOUS FUNCTIONS>.
		1442
		1443	Example: asynchronously lock all current and future pages into memory.
		1444
		1445	aio_mlockall IO::AIO::MCL_FUTURE;
		1446
		1447	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1448
		1449	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1450	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1451	the ioctl is not available on your OS, then this request will fail with
		1452	C<ENOSYS>.
		1453
		1454	C<$start> is the starting offset to query extents for, C<$length> is the
		1455	size of the range to query - if it is C<undef>, then the whole file will
		1456	be queried.
		1457
		1458	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1459	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1460	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1461	the data portion.
		1462
		1463	C<$count> is the maximum number of extent records to return. If it is
		1464	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1465	case, if it is C<0>, then the callback receives the number of extents
		1466	instead of the extents themselves (which is unreliable, see below).
		1467
		1468	If an error occurs, the callback receives no arguments. The special
		1469	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1470
		1471	Otherwise, the callback receives an array reference with extent
		1472	structures. Each extent structure is an array reference itself, with the
		1473	following members:
		1474
		1475	[$logical, $physical, $length, $flags]
		1476
		1477	Flags is any combination of the following flag values (typically either C<0>
		1478	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1479
		1480	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1481	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1482	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1483	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1484	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1485	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1486
		1487	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1488	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1489	it to return all extents of a range for files with large number of
		1490	extents. The code works around all these issues if C<$count> is undef.
		1491
994	=item aio_group $callback->(...)	1492	=item aio_group $callback->(...)
995		1493
996	This is a very special aio request: Instead of doing something, it is a	1494	This is a very special aio request: Instead of doing something, it is a
997	container for other aio requests, which is useful if you want to bundle	1495	container for other aio requests, which is useful if you want to bundle
998	many requests into a single, composite, request with a definite callback	1496	many requests into a single, composite, request with a definite callback
…		…
1034	like sleep and file handle readable/writable, the overhead this creates is	1532	like sleep and file handle readable/writable, the overhead this creates is
1035	immense (it blocks a thread for a long time) so do not use this function	1533	immense (it blocks a thread for a long time) so do not use this function
1036	except to put your application under artificial I/O pressure.	1534	except to put your application under artificial I/O pressure.
1037		1535
1038	=back	1536	=back
		1537
		1538
		1539	=head2 IO::AIO::WD - multiple working directories
		1540
		1541	Your process only has one current working directory, which is used by all
		1542	threads. This makes it hard to use relative paths (some other component
		1543	could call C<chdir> at any time, and it is hard to control when the path
		1544	will be used by IO::AIO).
		1545
		1546	One solution for this is to always use absolute paths. This usually works,
		1547	but can be quite slow (the kernel has to walk the whole path on every
		1548	access), and can also be a hassle to implement.
		1549
		1550	Newer POSIX systems have a number of functions (openat, fdopendir,
		1551	futimensat and so on) that make it possible to specify working directories
		1552	per operation.
		1553
		1554	For portability, and because the clowns who "designed", or shall I write,
		1555	perpetrated this new interface were obviously half-drunk, this abstraction
		1556	cannot be perfect, though.
		1557
		1558	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1559	object. This object stores the canonicalised, absolute version of the
		1560	path, and on systems that allow it, also a directory file descriptor.
		1561
		1562	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1563	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1564	object and a pathname instead (or the IO::AIO::WD object alone, which
		1565	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1566	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1567	to that IO::AIO::WD object.
		1568
		1569	For example, to get a wd object for F</etc> and then stat F<passwd>
		1570	inside, you would write:
		1571
		1572	aio_wd "/etc", sub {
		1573	my $etcdir = shift;
		1574
		1575	# although $etcdir can be undef on error, there is generally no reason
		1576	# to check for errors here, as aio_stat will fail with ENOENT
		1577	# when $etcdir is undef.
		1578
		1579	aio_stat [$etcdir, "passwd"], sub {
		1580	# yay
		1581	};
		1582	};
		1583
		1584	The fact that C<aio_wd> is a request and not a normal function shows that
		1585	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1586	which is why it is done asynchronously.
		1587
		1588	To stat the directory obtained with C<aio_wd> above, one could write
		1589	either of the following three request calls:
		1590
		1591	aio_lstat "/etc" , sub { ... # pathname as normal string
		1592	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1593	aio_lstat $wd , sub { ... # shorthand for the previous
		1594
		1595	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1596	object and the pathname string, so you could write the following without
		1597	causing any issues due to C<$path> getting reused:
		1598
		1599	my $path = [$wd, undef];
		1600
		1601	for my $name (qw(abc def ghi)) {
		1602	$path->[1] = $name;
		1603	aio_stat $path, sub {
		1604	# ...
		1605	};
		1606	}
		1607
		1608	There are some caveats: when directories get renamed (or deleted), the
		1609	pathname string doesn't change, so will point to the new directory (or
		1610	nowhere at all), while the directory fd, if available on the system,
		1611	will still point to the original directory. Most functions accepting a
		1612	pathname will use the directory fd on newer systems, and the string on
		1613	older systems. Some functions (such as realpath) will always rely on the
		1614	string form of the pathname.
		1615
		1616	So this functionality is mainly useful to get some protection against
		1617	C<chdir>, to easily get an absolute path out of a relative path for future
		1618	reference, and to speed up doing many operations in the same directory
		1619	(e.g. when stat'ing all files in a directory).
		1620
		1621	The following functions implement this working directory abstraction:
		1622
		1623	=over 4
		1624
		1625	=item aio_wd $pathname, $callback->($wd)
		1626
		1627	Asynchonously canonicalise the given pathname and convert it to an
		1628	IO::AIO::WD object representing it. If possible and supported on the
		1629	system, also open a directory fd to speed up pathname resolution relative
		1630	to this working directory.
		1631
		1632	If something goes wrong, then C<undef> is passwd to the callback instead
		1633	of a working directory object and C<$!> is set appropriately. Since
		1634	passing C<undef> as working directory component of a pathname fails the
		1635	request with C<ENOENT>, there is often no need for error checking in the
		1636	C<aio_wd> callback, as future requests using the value will fail in the
		1637	expected way.
		1638
		1639	=item IO::AIO::CWD
		1640
		1641	This is a compiletime constant (object) that represents the process
		1642	current working directory.
		1643
		1644	Specifying this object as working directory object for a pathname is as if
		1645	the pathname would be specified directly, without a directory object. For
		1646	example, these calls are functionally identical:
		1647
		1648	aio_stat "somefile", sub { ... };
		1649	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1650
		1651	=back
		1652
		1653	To recover the path associated with an IO::AIO::WD object, you can use
		1654	C<aio_realpath>:
		1655
		1656	aio_realpath $wd, sub {
		1657	warn "path is $_[0]\n";
		1658	};
		1659
		1660	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1661	sometimes, fall back to using an absolue path.
1039		1662
1040	=head2 IO::AIO::REQ CLASS	1663	=head2 IO::AIO::REQ CLASS
1041		1664
1042	All non-aggregate C<aio_*> functions return an object of this class when	1665	All non-aggregate C<aio_*> functions return an object of this class when
1043	called in non-void context.	1666	called in non-void context.
…		…
1133	=item $grp->cancel_subs	1756	=item $grp->cancel_subs
1134		1757
1135	Cancel all subrequests and clears any feeder, but not the group request	1758	Cancel all subrequests and clears any feeder, but not the group request
1136	itself. Useful when you queued a lot of events but got a result early.	1759	itself. Useful when you queued a lot of events but got a result early.
1137		1760
		1761	The group request will finish normally (you cannot add requests to the
		1762	group).
		1763
1138	=item $grp->result (...)	1764	=item $grp->result (...)
1139		1765
1140	Set the result value(s) that will be passed to the group callback when all	1766	Set the result value(s) that will be passed to the group callback when all
1141	subrequests have finished and set the groups errno to the current value	1767	subrequests have finished and set the groups errno to the current value
1142	of errno (just like calling C<errno> without an error number). By default,	1768	of errno (just like calling C<errno> without an error number). By default,
…		…
1158		1784
1159	Sets a feeder/generator on this group: every group can have an attached	1785	Sets a feeder/generator on this group: every group can have an attached
1160	generator that generates requests if idle. The idea behind this is that,	1786	generator that generates requests if idle. The idea behind this is that,
1161	although you could just queue as many requests as you want in a group,	1787	although you could just queue as many requests as you want in a group,
1162	this might starve other requests for a potentially long time. For example,	1788	this might starve other requests for a potentially long time. For example,
1163	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1789	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1164	delaying any later requests for a long time.	1790	requests, delaying any later requests for a long time.
1165		1791
1166	To avoid this, and allow incremental generation of requests, you can	1792	To avoid this, and allow incremental generation of requests, you can
1167	instead a group and set a feeder on it that generates those requests. The	1793	instead a group and set a feeder on it that generates those requests. The
1168	feed callback will be called whenever there are few enough (see C<limit>,	1794	feed callback will be called whenever there are few enough (see C<limit>,
1169	below) requests active in the group itself and is expected to queue more	1795	below) requests active in the group itself and is expected to queue more
…		…
1218		1844
1219	See C<poll_cb> for an example.	1845	See C<poll_cb> for an example.
1220		1846
1221	=item IO::AIO::poll_cb	1847	=item IO::AIO::poll_cb
1222		1848
1223	Process some outstanding events on the result pipe. You have to call this	1849	Process some requests that have reached the result phase (i.e. they have
1224	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1850	been executed but the results are not yet reported). You have to call
1225	returned earlier for whatever reason. Returns immediately when no events	1851	this "regularly" to finish outstanding requests.
1226	are outstanding. The amount of events processed depends on the settings of
1227	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1228		1852
		1853	Returns C<0> if all events could be processed (or there were no
		1854	events to process), or C<-1> if it returned earlier for whatever
		1855	reason. Returns immediately when no events are outstanding. The amount
		1856	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1857	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1858
1229	If not all requests were processed for whatever reason, the filehandle	1859	If not all requests were processed for whatever reason, the poll file
1230	will still be ready when C<poll_cb> returns, so normally you don't have to	1860	descriptor will still be ready when C<poll_cb> returns, so normally you
1231	do anything special to have it called later.	1861	don't have to do anything special to have it called later.
		1862
		1863	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1864	ready, it can be beneficial to call this function from loops which submit
		1865	a lot of requests, to make sure the results get processed when they become
		1866	available and not just when the loop is finished and the event loop takes
		1867	over again. This function returns very fast when there are no outstanding
		1868	requests.
1232		1869
1233	Example: Install an Event watcher that automatically calls	1870	Example: Install an Event watcher that automatically calls
1234	IO::AIO::poll_cb with high priority (more examples can be found in the	1871	IO::AIO::poll_cb with high priority (more examples can be found in the
1235	SYNOPSIS section, at the top of this document):	1872	SYNOPSIS section, at the top of this document):
1236		1873
1237	Event->io (fd => IO::AIO::poll_fileno,	1874	Event->io (fd => IO::AIO::poll_fileno,
1238	poll => 'r', async => 1,	1875	poll => 'r', async => 1,
1239	cb => \&IO::AIO::poll_cb);	1876	cb => \&IO::AIO::poll_cb);
		1877
		1878	=item IO::AIO::poll_wait
		1879
		1880	Wait until either at least one request is in the result phase or no
		1881	requests are outstanding anymore.
		1882
		1883	This is useful if you want to synchronously wait for some requests to
		1884	become ready, without actually handling them.
		1885
		1886	See C<nreqs> for an example.
		1887
		1888	=item IO::AIO::poll
		1889
		1890	Waits until some requests have been handled.
		1891
		1892	Returns the number of requests processed, but is otherwise strictly
		1893	equivalent to:
		1894
		1895	IO::AIO::poll_wait, IO::AIO::poll_cb
		1896
		1897	=item IO::AIO::flush
		1898
		1899	Wait till all outstanding AIO requests have been handled.
		1900
		1901	Strictly equivalent to:
		1902
		1903	IO::AIO::poll_wait, IO::AIO::poll_cb
		1904	while IO::AIO::nreqs;
1240		1905
1241	=item IO::AIO::max_poll_reqs $nreqs	1906	=item IO::AIO::max_poll_reqs $nreqs
1242		1907
1243	=item IO::AIO::max_poll_time $seconds	1908	=item IO::AIO::max_poll_time $seconds
1244		1909
…		…
1269	# use a low priority so other tasks have priority	1934	# use a low priority so other tasks have priority
1270	Event->io (fd => IO::AIO::poll_fileno,	1935	Event->io (fd => IO::AIO::poll_fileno,
1271	poll => 'r', nice => 1,	1936	poll => 'r', nice => 1,
1272	cb => &IO::AIO::poll_cb);	1937	cb => &IO::AIO::poll_cb);
1273		1938
1274	=item IO::AIO::poll_wait
1275
1276	If there are any outstanding requests and none of them in the result
1277	phase, wait till the result filehandle becomes ready for reading (simply
1278	does a C<select> on the filehandle. This is useful if you want to
1279	synchronously wait for some requests to finish).
1280
1281	See C<nreqs> for an example.
1282
1283	=item IO::AIO::poll
1284
1285	Waits until some requests have been handled.
1286
1287	Returns the number of requests processed, but is otherwise strictly
1288	equivalent to:
1289
1290	IO::AIO::poll_wait, IO::AIO::poll_cb
1291
1292	=item IO::AIO::flush
1293
1294	Wait till all outstanding AIO requests have been handled.
1295
1296	Strictly equivalent to:
1297
1298	IO::AIO::poll_wait, IO::AIO::poll_cb
1299	while IO::AIO::nreqs;
1300
1301	=back	1939	=back
1302		1940
1303	=head3 CONTROLLING THE NUMBER OF THREADS	1941	=head3 CONTROLLING THE NUMBER OF THREADS
1304		1942
1305	=over	1943	=over
…		…
1338		1976
1339	Under normal circumstances you don't need to call this function.	1977	Under normal circumstances you don't need to call this function.
1340		1978
1341	=item IO::AIO::max_idle $nthreads	1979	=item IO::AIO::max_idle $nthreads
1342		1980
1343	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1981	Limit the number of threads (default: 4) that are allowed to idle
1344	threads that did not get a request to process within 10 seconds). That	1982	(i.e., threads that did not get a request to process within the idle
1345	means if a thread becomes idle while C<$nthreads> other threads are also	1983	timeout (default: 10 seconds). That means if a thread becomes idle while
1346	idle, it will free its resources and exit.	1984	C<$nthreads> other threads are also idle, it will free its resources and
		1985	exit.
1347		1986
1348	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1987	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1349	to allow for extremely high load situations, but want to free resources	1988	to allow for extremely high load situations, but want to free resources
1350	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1989	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1351		1990
1352	The default is probably ok in most situations, especially if thread	1991	The default is probably ok in most situations, especially if thread
1353	creation is fast. If thread creation is very slow on your system you might	1992	creation is fast. If thread creation is very slow on your system you might
1354	want to use larger values.	1993	want to use larger values.
1355		1994
		1995	=item IO::AIO::idle_timeout $seconds
		1996
		1997	Sets the minimum idle timeout (default 10) after which worker threads are
		1998	allowed to exit. SEe C<IO::AIO::max_idle>.
		1999
1356	=item IO::AIO::max_outstanding $maxreqs	2000	=item IO::AIO::max_outstanding $maxreqs
		2001
		2002	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2003	you do queue up more than this number of requests, the next call to
		2004	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2005	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2006	longer exceeded.
		2007
		2008	In other words, this setting does not enforce a queue limit, but can be
		2009	used to make poll functions block if the limit is exceeded.
1357		2010
1358	This is a very bad function to use in interactive programs because it	2011	This is a very bad function to use in interactive programs because it
1359	blocks, and a bad way to reduce concurrency because it is inexact: Better	2012	blocks, and a bad way to reduce concurrency because it is inexact: Better
1360	use an C<aio_group> together with a feed callback.	2013	use an C<aio_group> together with a feed callback.
1361		2014
1362	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2015	Its main use is in scripts without an event loop - when you want to stat
1363	do queue up more than this number of requests, the next call to the	2016	a lot of files, you can write something like this:
1364	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1365	function will block until the limit is no longer exceeded.
1366		2017
1367	The default value is very large, so there is no practical limit on the	2018	IO::AIO::max_outstanding 32;
1368	number of outstanding requests.
1369		2019
1370	You can still queue as many requests as you want. Therefore,	2020	for my $path (...) {
1371	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2021	aio_stat $path , ...;
1372	as a stop gap to shield against fatal memory overflow (with large values).	2022	IO::AIO::poll_cb;
		2023	}
		2024
		2025	IO::AIO::flush;
		2026
		2027	The call to C<poll_cb> inside the loop will normally return instantly, but
		2028	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2029	some requests have been handled. This keeps the loop from pushing a large
		2030	number of C<aio_stat> requests onto the queue.
		2031
		2032	The default value for C<max_outstanding> is very large, so there is no
		2033	practical limit on the number of outstanding requests.
1373		2034
1374	=back	2035	=back
1375		2036
1376	=head3 STATISTICAL INFORMATION	2037	=head3 STATISTICAL INFORMATION
1377		2038
…		…
1399		2060
1400	=back	2061	=back
1401		2062
1402	=head3 MISCELLANEOUS FUNCTIONS	2063	=head3 MISCELLANEOUS FUNCTIONS
1403		2064
1404	IO::AIO implements some functions that might be useful, but are not	2065	IO::AIO implements some functions that are useful when you want to use
1405	asynchronous.	2066	some "Advanced I/O" function not available to in Perl, without going the
		2067	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2068	counterpart.
1406		2069
1407	=over 4	2070	=over 4
		2071
		2072	=item $numfd = IO::AIO::get_fdlimit
		2073
		2074	Tries to find the current file descriptor limit and returns it, or
		2075	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2076	the highest valid file descriptor number.
		2077
		2078	=item IO::AIO::min_fdlimit [$numfd]
		2079
		2080	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2081	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2082	is missing, it will try to set a very high limit, although this is not
		2083	recommended when you know the actual minimum that you require.
		2084
		2085	If the limit cannot be raised enough, the function makes a best-effort
		2086	attempt to increase the limit as much as possible, using various
		2087	tricks, while still failing. You can query the resulting limit using
		2088	C<IO::AIO::get_fdlimit>.
		2089
		2090	If an error occurs, returns C<undef> and sets C<$!>.
1408		2091
1409	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2092	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1410		2093
1411	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2094	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1412	but is blocking (this makes most sense if you know the input data is	2095	but is blocking (this makes most sense if you know the input data is
…		…
1415		2098
1416	Returns the number of bytes copied, or C<-1> on error.	2099	Returns the number of bytes copied, or C<-1> on error.
1417		2100
1418	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2101	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1419		2102
1420	Simply calls the C<posix_fadvise> function (see it's	2103	Simply calls the C<posix_fadvise> function (see its
1421	manpage for details). The following advice constants are	2104	manpage for details). The following advice constants are
1422	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2105	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1423	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2106	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1424	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2107	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1425		2108
1426	On systems that do not implement C<posix_fadvise>, this function returns	2109	On systems that do not implement C<posix_fadvise>, this function returns
1427	ENOSYS, otherwise the return value of C<posix_fadvise>.	2110	ENOSYS, otherwise the return value of C<posix_fadvise>.
1428		2111
		2112	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2113
		2114	Simply calls the C<posix_madvise> function (see its
		2115	manpage for details). The following advice constants are
		2116	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2117	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2118	C<IO::AIO::MADV_DONTNEED>.
		2119
		2120	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2121	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2122	will be reduced to fit into the C<$scalar>.
		2123
		2124	On systems that do not implement C<posix_madvise>, this function returns
		2125	ENOSYS, otherwise the return value of C<posix_madvise>.
		2126
		2127	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2128
		2129	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2130	$scalar (see its manpage for details). The following protect
		2131	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2132	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2133
		2134	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2135	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2136	will be reduced to fit into the C<$scalar>.
		2137
		2138	On systems that do not implement C<mprotect>, this function returns
		2139	ENOSYS, otherwise the return value of C<mprotect>.
		2140
		2141	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2142
		2143	Memory-maps a file (or anonymous memory range) and attaches it to the
		2144	given C<$scalar>, which will act like a string scalar. Returns true on
		2145	success, and false otherwise.
		2146
		2147	The scalar must exist, but its contents do not matter - this means you
		2148	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2149	the scalar first.
		2150
		2151	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2152	which don't change the string length, and most read-only operations such
		2153	as copying it or searching it with regexes and so on.
		2154
		2155	Anything else is unsafe and will, at best, result in memory leaks.
		2156
		2157	The memory map associated with the C<$scalar> is automatically removed
		2158	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2159	or C<IO::AIO::munmap> functions are called on it.
		2160
		2161	This calls the C<mmap>(2) function internally. See your system's manual
		2162	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2163
		2164	The C<$length> must be larger than zero and smaller than the actual
		2165	filesize.
		2166
		2167	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2168	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2169
		2170	C<$flags> can be a combination of
		2171	C<IO::AIO::MAP_SHARED> or
		2172	C<IO::AIO::MAP_PRIVATE>,
		2173	or a number of system-specific flags (when not available, the are C<0>):
		2174	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2175	C<IO::AIO::MAP_LOCKED>,
		2176	C<IO::AIO::MAP_NORESERVE>,
		2177	C<IO::AIO::MAP_POPULATE>,
		2178	C<IO::AIO::MAP_NONBLOCK>,
		2179	C<IO::AIO::MAP_FIXED>,
		2180	C<IO::AIO::MAP_GROWSDOWN>,
		2181	C<IO::AIO::MAP_32BIT>,
		2182	C<IO::AIO::MAP_HUGETLB> or
		2183	C<IO::AIO::MAP_STACK>.
		2184
		2185	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2186
		2187	C<$offset> is the offset from the start of the file - it generally must be
		2188	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2189
		2190	Example:
		2191
		2192	use Digest::MD5;
		2193	use IO::AIO;
		2194
		2195	open my $fh, "<verybigfile"
		2196	or die "$!";
		2197
		2198	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2199	or die "verybigfile: $!";
		2200
		2201	my $fast_md5 = md5 $data;
		2202
		2203	=item IO::AIO::munmap $scalar
		2204
		2205	Removes a previous mmap and undefines the C<$scalar>.
		2206
		2207	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2208
		2209	Calls the C<munlock> function, undoing the effects of a previous
		2210	C<aio_mlock> call (see its description for details).
		2211
		2212	=item IO::AIO::munlockall
		2213
		2214	Calls the C<munlockall> function.
		2215
		2216	On systems that do not implement C<munlockall>, this function returns
		2217	ENOSYS, otherwise the return value of C<munlockall>.
		2218
		2219	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2220
		2221	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2222	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2223	should be the file offset.
		2224
		2225	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2226	silently corrupt the data in this case.
		2227
		2228	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2229	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2230	C<IO::AIO::SPLICE_F_GIFT>.
		2231
		2232	See the C<splice(2)> manpage for details.
		2233
		2234	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2235
		2236	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2237	description for C<IO::AIO::splice> above for details.
		2238
		2239	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2240
		2241	Attempts to query or change the pipe buffer size. Obviously works only
		2242	on pipes, and currently works only on GNU/Linux systems, and fails with
		2243	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2244	size on other systems, drop me a note.
		2245
		2246	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2247
		2248	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2249	C<$flags> is missing or C<0>, then this should be the same as a call to
		2250	perl's built-in C<pipe> function and create a new pipe, and works on
		2251	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2252	(..., 4096, O_BINARY)>.
		2253
		2254	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2255	the given flags (Linux 2.6.27, glibc 2.9).
		2256
		2257	On success, the read and write file handles are returned.
		2258
		2259	On error, nothing will be returned. If the pipe2 syscall is missing and
		2260	C<$flags> is non-zero, fails with C<ENOSYS>.
		2261
		2262	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2263	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2264	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2265
1429	=back	2266	=back
1430		2267
1431	=cut	2268	=cut
1432		2269
1433	min_parallel 8;	2270	min_parallel 8;
1434		2271
1435	END { flush }	2272	END { flush }
1436		2273
1437	1;	2274	1;
1438		2275
		2276	=head1 EVENT LOOP INTEGRATION
		2277
		2278	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2279	automatically into many event loops:
		2280
		2281	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2282	use AnyEvent::AIO;
		2283
		2284	You can also integrate IO::AIO manually into many event loops, here are
		2285	some examples of how to do this:
		2286
		2287	# EV integration
		2288	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2289
		2290	# Event integration
		2291	Event->io (fd => IO::AIO::poll_fileno,
		2292	poll => 'r',
		2293	cb => \&IO::AIO::poll_cb);
		2294
		2295	# Glib/Gtk2 integration
		2296	add_watch Glib::IO IO::AIO::poll_fileno,
		2297	in => sub { IO::AIO::poll_cb; 1 };
		2298
		2299	# Tk integration
		2300	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2301	readable => \&IO::AIO::poll_cb);
		2302
		2303	# Danga::Socket integration
		2304	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2305	\&IO::AIO::poll_cb);
		2306
1439	=head2 FORK BEHAVIOUR	2307	=head2 FORK BEHAVIOUR
1440		2308
1441	This module should do "the right thing" when the process using it forks:	2309	Usage of pthreads in a program changes the semantics of fork
		2310	considerably. Specifically, only async-safe functions can be called after
		2311	fork. Perl doesn't know about this, so in general, you cannot call fork
		2312	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2313	pthreads, so this applies, but many other extensions and (for inexplicable
		2314	reasons) perl itself often is linked against pthreads, so this limitation
		2315	applies to quite a lot of perls.
1442		2316
1443	Before the fork, IO::AIO enters a quiescent state where no requests	2317	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1444	can be added in other threads and no results will be processed. After	2318	only works in the process that loaded it. Forking is fully supported, but
1445	the fork the parent simply leaves the quiescent state and continues	2319	using IO::AIO in the child is not.
1446	request/result processing, while the child frees the request/result queue
1447	(so that the requests started before the fork will only be handled in the
1448	parent). Threads will be started on demand until the limit set in the
1449	parent process has been reached again.
1450		2320
1451	In short: the parent will, after a short pause, continue as if fork had	2321	You might get around by not I<using> IO::AIO before (or after)
1452	not been called, while the child will act as if IO::AIO has not been used	2322	forking. You could also try to call the L<IO::AIO::reinit> function in the
1453	yet.	2323	child:
		2324
		2325	=over 4
		2326
		2327	=item IO::AIO::reinit
		2328
		2329	Abandons all current requests and I/O threads and simply reinitialises all
		2330	data structures. This is not an operation supported by any standards, but
		2331	happens to work on GNU/Linux and some newer BSD systems.
		2332
		2333	The only reasonable use for this function is to call it after forking, if
		2334	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2335	the process will result in undefined behaviour. Calling it at any time
		2336	will also result in any undefined (by POSIX) behaviour.
		2337
		2338	=back
1454		2339
1455	=head2 MEMORY USAGE	2340	=head2 MEMORY USAGE
1456		2341
1457	Per-request usage:	2342	Per-request usage:
1458		2343

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