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Revision 1.147 by root, Wed Jun 3 12:24:49 2009 UTC vs.
Revision 1.229 by root, Wed Jul 25 16:32:30 2012 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
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
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.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
87	yourself, always call C<poll_cb> from within the same thread, or never	65	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
89		67
90	=head2 EXAMPLE	68	=head2 EXAMPLE
91		69
92	This is a simple example that uses the Event module and loads	70	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
94		72
95	use Fcntl;	73	use Fcntl;
96	use Event;	74	use EV;
97	use IO::AIO;	75	use IO::AIO;
98		76
99	# register the IO::AIO callback with Event	77	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		79
104	# queue the request to open /etc/passwd	80	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	82	my $fh = shift
107	or die "error while opening: $!";	83	or die "error while opening: $!";
108		84
109	# stat'ing filehandles is generally non-blocking	85	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	86	my $size = -s $fh;
…		…
119		95
120	# file contents now in $contents	96	# file contents now in $contents
121	print $contents;	97	print $contents;
122		98
123	# exit event loop and program	99	# exit event loop and program
124	Event::unloop;	100	EV::unloop;
125	};	101	};
126	};	102	};
127		103
128	# possibly queue up other requests, or open GUI windows,	104	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	105	# check for sockets etc. etc.
130		106
131	# process events as long as there are some:	107	# process events as long as there are some:
132	Event::loop;	108	EV::loop;
133		109
134	=head1 REQUEST ANATOMY AND LIFETIME	110	=head1 REQUEST ANATOMY AND LIFETIME
135		111
136	Every C<aio_*> function creates a request. which is a C data structure not	112	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	113	directly visible to Perl.
…		…
187		163
188	package IO::AIO;	164	package IO::AIO;
189		165
190	use Carp ();	166	use Carp ();
191		167
192	no warnings;	168	use common::sense;
193	use strict 'vars';
194		169
195	use base 'Exporter';	170	use base 'Exporter';
196		171
197	BEGIN {	172	BEGIN {
198	our $VERSION = '3.19';	173	our $VERSION = '4.15';
199		174
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	175	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead aio_fiemap
204	aio_rename aio_link aio_move aio_copy aio_group	180	aio_rename aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
		185	aio_wd);
207		186
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	189	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	190	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
213		194
214	push @AIO_REQ, qw(aio_busy); # not exported	195	push @AIO_REQ, qw(aio_busy); # not exported
215		196
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		198
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
220	}	201	}
221		202
222	=head1 FUNCTIONS	203	=head1 FUNCTIONS
223		204
224	=head2 AIO REQUEST FUNCTIONS	205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes of the most important functions
		208	for quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_seek $fh,$offset,$whence, $callback->($offs)
		215	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		217	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		218	aio_readahead $fh,$offset,$length, $callback->($retval)
		219	aio_stat $fh_or_path, $callback->($status)
		220	aio_lstat $fh, $callback->($status)
		221	aio_statvfs $fh_or_path, $callback->($statvfs)
		222	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		223	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_truncate $fh_or_path, $offset, $callback->($status)
		226	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		227	aio_unlink $pathname, $callback->($status)
		228	aio_mknod $pathname, $mode, $dev, $callback->($status)
		229	aio_link $srcpath, $dstpath, $callback->($status)
		230	aio_symlink $srcpath, $dstpath, $callback->($status)
		231	aio_readlink $pathname, $callback->($link)
		232	aio_realpath $pathname, $callback->($link)
		233	aio_rename $srcpath, $dstpath, $callback->($status)
		234	aio_mkdir $pathname, $mode, $callback->($status)
		235	aio_rmdir $pathname, $callback->($status)
		236	aio_readdir $pathname, $callback->($entries)
		237	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		238	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		239	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		240	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		241	aio_load $pathname, $data, $callback->($status)
		242	aio_copy $srcpath, $dstpath, $callback->($status)
		243	aio_move $srcpath, $dstpath, $callback->($status)
		244	aio_rmtree $pathname, $callback->($status)
		245	aio_sync $callback->($status)
		246	aio_syncfs $fh, $callback->($status)
		247	aio_fsync $fh, $callback->($status)
		248	aio_fdatasync $fh, $callback->($status)
		249	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		250	aio_pathsync $pathname, $callback->($status)
		251	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		252	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		254	aio_mlockall $flags, $callback->($status)
		255	aio_group $callback->(...)
		256	aio_nop $callback->()
		257
		258	$prev_pri = aioreq_pri [$pri]
		259	aioreq_nice $pri_adjust
		260
		261	IO::AIO::poll_wait
		262	IO::AIO::poll_cb
		263	IO::AIO::poll
		264	IO::AIO::flush
		265	IO::AIO::max_poll_reqs $nreqs
		266	IO::AIO::max_poll_time $seconds
		267	IO::AIO::min_parallel $nthreads
		268	IO::AIO::max_parallel $nthreads
		269	IO::AIO::max_idle $nthreads
		270	IO::AIO::idle_timeout $seconds
		271	IO::AIO::max_outstanding $maxreqs
		272	IO::AIO::nreqs
		273	IO::AIO::nready
		274	IO::AIO::npending
		275
		276	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		277	IO::AIO::fadvise $fh, $offset, $len, $advice
		278	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		279	IO::AIO::munmap $scalar
		280	IO::AIO::madvise $scalar, $offset, $length, $advice
		281	IO::AIO::mprotect $scalar, $offset, $length, $protect
		282	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		283	IO::AIO::munlockall
		284
		285	=head2 API NOTES
225		286
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	287	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	288	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	289	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	290	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	291	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	292	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	293	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		294	most syscalls return C<-1> on error, unlike perl, which usually delivers
		295	"false").
		296
		297	Some requests (such as C<aio_readdir>) pass the actual results and
		298	communicate failures by passing C<undef>.
233		299
234	All functions expecting a filehandle keep a copy of the filehandle	300	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	301	internally until the request has finished.
236		302
237	All functions return request objects of type L<IO::AIO::REQ> that allow	303	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	304	further manipulation of those requests while they are in-flight.
239		305
240	The pathnames you pass to these routines I<must> be absolute and	306	The pathnames you pass to these routines I<should> be absolute. The
241	encoded as octets. The reason for the former is that at the time the	307	reason for this is that at the time the request is being executed, the
242	request is being executed, the current working directory could have	308	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	309	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	310	in the program and then use relative paths. You can also take advantage
245	paths.	311	of IO::AIOs working directory abstraction, that lets you specify paths
		312	relative to some previously-opened "working directory object" - see the
		313	description of the C<IO::AIO::WD> class later in this document.
246		314
247	To encode pathnames as octets, either make sure you either: a) always pass	315	To encode pathnames as octets, either make sure you either: a) always pass
248	in filenames you got from outside (command line, readdir etc.) without	316	in filenames you got from outside (command line, readdir etc.) without
249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	317	tinkering, b) are in your native filesystem encoding, c) use the Encode
250	your pathnames to the locale (or other) encoding in effect in the user	318	module and encode your pathnames to the locale (or other) encoding in
251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	319	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	320	unicode filenames or e) use something else to ensure your scalar has the
		321	correct contents.
253		322
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	323	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	324	handles correctly whether it is set or not.
		325
		326	=head2 AIO REQUEST FUNCTIONS
256		327
257	=over 4	328	=over 4
258		329
259	=item $prev_pri = aioreq_pri [$pri]	330	=item $prev_pri = aioreq_pri [$pri]
260		331
…		…
307	by the umask in effect then the request is being executed, so better never	378	by the umask in effect then the request is being executed, so better never
308	change the umask.	379	change the umask.
309		380
310	Example:	381	Example:
311		382
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	383	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	384	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	385	print "open successful, fh is $_[0]\n";
315	...	386	...
316	} else {	387	} else {
317	die "open failed: $!\n";	388	die "open failed: $!\n";
318	}	389	}
319	};	390	};
320		391
		392	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		393	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		394	following POSIX and non-POSIX constants are available (missing ones on
		395	your system are, as usual, C<0>):
		396
		397	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		398	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		399	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		400
321		401
322	=item aio_close $fh, $callback->($status)	402	=item aio_close $fh, $callback->($status)
323		403
324	Asynchronously close a file and call the callback with the result	404	Asynchronously close a file and call the callback with the result
325	code.	405	code.
…		…
333		413
334	Or in other words: the file descriptor will be closed, but it will not be	414	Or in other words: the file descriptor will be closed, but it will not be
335	free for reuse until the perl filehandle is closed.	415	free for reuse until the perl filehandle is closed.
336		416
337	=cut	417	=cut
		418
		419	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		420
		421	Seeks the filehandle to the new C<$offset>, similarly to perl's
		422	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		423	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		424	C<IO::AIO::SEEK_END>).
		425
		426	The resulting absolute offset will be passed to the callback, or C<-1> in
		427	case of an error.
		428
		429	In theory, the C<$whence> constants could be different than the
		430	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		431	so don't panic.
		432
		433	As a GNU/Linux (and maybe Solaris) extension, also the constants
		434	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		435	could be found. No guarantees about suitability for use in C<aio_seek> or
		436	Perl's C<sysseek> can be made though, although I would naively assume they
		437	"just work".
338		438
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	439	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		440
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	441	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		442
…		…
375		475
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	476	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	477	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	478	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	479	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	480	other. The same C<$in_fh> works fine though, as this function does not
		481	move or use the file offset of C<$in_fh>.
381		482
		483	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		484	are written, and there is no way to find out how many more bytes have been
		485	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		486	number of bytes written to C<$out_fh>. Only if the result value equals
		487	C<$length> one can assume that C<$length> bytes have been read.
		488
		489	Unlike with other C<aio_> functions, it makes a lot of sense to use
		490	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		491	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		492	the socket I/O will be non-blocking. Note, however, that you can run
		493	into a trap where C<aio_sendfile> reads some data with readahead, then
		494	fails to write all data, and when the socket is ready the next time, the
		495	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		496	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		497	resource usage.
		498
382	This call tries to make use of a native C<sendfile> syscall to provide	499	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	500	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	501	a socket, and C<$in_fh> should refer to an mmap'able file.
385		502
386	If the native sendfile call fails or is not implemented, it will be	503	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	504	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		505	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	506	type of filehandle regardless of the limitations of the operating system.
389		507
390	Please note, however, that C<aio_sendfile> can read more bytes from	508	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	509	together in a hurry to improve benchmark numbers) tend to be rather buggy
392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	510	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	511	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	512	so you really really should check the return value of C<aio_sendfile> -
395	read.	513	fewre bytes than expected might have been transferred.
396		514
397		515
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	516	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		517
400	C<aio_readahead> populates the page cache with data from a file so that	518	C<aio_readahead> populates the page cache with data from a file so that
…		…
423		541
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	542	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	543	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	544	unless perl itself is compiled with large file support.
427		545
		546	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		547	following constants and functions (if not implemented, the constants will
		548	be C<0> and the functions will either C<croak> or fall back on traditional
		549	behaviour).
		550
		551	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		552	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		553	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		554
428	Example: Print the length of F</etc/passwd>:	555	Example: Print the length of F</etc/passwd>:
429		556
430	aio_stat "/etc/passwd", sub {	557	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	558	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	559	print "size is ", -s _, "\n";
433	};	560	};
434		561
435		562
		563	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		564
		565	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		566	whether a file handle or path was passed.
		567
		568	On success, the callback is passed a hash reference with the following
		569	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		570	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		571	is passed.
		572
		573	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		574	C<ST_NOSUID>.
		575
		576	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		577	their correct value when available, or to C<0> on systems that do
		578	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		579	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		580	C<ST_NODIRATIME> and C<ST_RELATIME>.
		581
		582	Example: stat C</wd> and dump out the data if successful.
		583
		584	aio_statvfs "/wd", sub {
		585	my $f = $_[0]
		586	or die "statvfs: $!";
		587
		588	use Data::Dumper;
		589	say Dumper $f;
		590	};
		591
		592	# result:
		593	{
		594	bsize => 1024,
		595	bfree => 4333064312,
		596	blocks => 10253828096,
		597	files => 2050765568,
		598	flag => 4096,
		599	favail => 2042092649,
		600	bavail => 4333064312,
		601	ffree => 2042092649,
		602	namemax => 255,
		603	frsize => 1024,
		604	fsid => 1810
		605	}
		606
		607
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	608	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		609
438	Works like perl's C<utime> function (including the special case of $atime	610	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	611	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	612	syscalls support them.
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	639	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		640
469	Works like truncate(2) or ftruncate(2).	641	Works like truncate(2) or ftruncate(2).
470		642
471		643
		644	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		645
		646	Allocates or freed disk space according to the C<$mode> argument. See the
		647	linux C<fallocate> docuemntation for details.
		648
		649	C<$mode> can currently be C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE>
		650	to allocate space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE |
		651	IO::AIO::FALLOC_FL_KEEP_SIZE>, to deallocate a file range.
		652
		653	The file system block size used by C<fallocate> is presumably the
		654	C<f_bsize> returned by C<statvfs>.
		655
		656	If C<fallocate> isn't available or cannot be emulated (currently no
		657	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		658
		659
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	660	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		661
474	Works like perl's C<chmod> function.	662	Works like perl's C<chmod> function.
475		663
476		664
…		…
478		666
479	Asynchronously unlink (delete) a file and call the callback with the	667	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	668	result code.
481		669
482		670
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	671	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		672
485	[EXPERIMENTAL]	673	[EXPERIMENTAL]
486		674
487	Asynchronously create a device node (or fifo). See mknod(2).	675	Asynchronously create a device node (or fifo). See mknod(2).
488		676
489	The only (POSIX-) portable way of calling this function is:	677	The only (POSIX-) portable way of calling this function is:
490		678
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	679	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		680
		681	See C<aio_stat> for info about some potentially helpful extra constants
		682	and functions.
493		683
494	=item aio_link $srcpath, $dstpath, $callback->($status)	684	=item aio_link $srcpath, $dstpath, $callback->($status)
495		685
496	Asynchronously create a new link to the existing object at C<$srcpath> at	686	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	687	the path C<$dstpath> and call the callback with the result code.
…		…
501		691
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	692	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	693	the path C<$dstpath> and call the callback with the result code.
504		694
505		695
506	=item aio_readlink $path, $callback->($link)	696	=item aio_readlink $pathname, $callback->($link)
507		697
508	Asynchronously read the symlink specified by C<$path> and pass it to	698	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	699	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	700	callback.
511		701
512		702
		703	=item aio_realpath $pathname, $callback->($path)
		704
		705	Asynchronously make the path absolute and resolve any symlinks in
		706	C<$path>. The resulting path only consists of directories (Same as
		707	L<Cwd::realpath>).
		708
		709	This request can be used to get the absolute path of the current working
		710	directory by passing it a path of F<.> (a single dot).
		711
		712
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	713	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		714
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	715	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	716	rename(2) and call the callback with the result code.
517		717
…		…
533		733
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	734	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	735	directory (i.e. opendir + readdir + closedir). The entries will not be
536	sorted, and will B<NOT> include the C<.> and C<..> entries.	736	sorted, and will B<NOT> include the C<.> and C<..> entries.
537		737
538	The callback a single argument which is either C<undef> or an array-ref	738	The callback is passed a single argument which is either C<undef> or an
539	with the filenames.	739	array-ref with the filenames.
540		740
541		741
		742	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		743
		744	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		745	tune behaviour and output format. In case of an error, C<$entries> will be
		746	C<undef>.
		747
		748	The flags are a combination of the following constants, ORed together (the
		749	flags will also be passed to the callback, possibly modified):
		750
		751	=over 4
		752
		753	=item IO::AIO::READDIR_DENTS
		754
		755	When this flag is off, then the callback gets an arrayref consisting of
		756	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		757	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		758	entry in more detail.
		759
		760	C<$name> is the name of the entry.
		761
		762	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		763
		764	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		765	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		766	C<IO::AIO::DT_WHT>.
		767
		768	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		769	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		770	scalars are read-only: you can not modify them.
		771
		772	C<$inode> is the inode number (which might not be exact on systems with 64
		773	bit inode numbers and 32 bit perls). This field has unspecified content on
		774	systems that do not deliver the inode information.
		775
		776	=item IO::AIO::READDIR_DIRS_FIRST
		777
		778	When this flag is set, then the names will be returned in an order where
		779	likely directories come first, in optimal stat order. This is useful when
		780	you need to quickly find directories, or you want to find all directories
		781	while avoiding to stat() each entry.
		782
		783	If the system returns type information in readdir, then this is used
		784	to find directories directly. Otherwise, likely directories are names
		785	beginning with ".", or otherwise names with no dots, of which names with
		786	short names are tried first.
		787
		788	=item IO::AIO::READDIR_STAT_ORDER
		789
		790	When this flag is set, then the names will be returned in an order
		791	suitable for stat()'ing each one. That is, when you plan to stat()
		792	all files in the given directory, then the returned order will likely
		793	be fastest.
		794
		795	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		796	the likely dirs come first, resulting in a less optimal stat order.
		797
		798	=item IO::AIO::READDIR_FOUND_UNKNOWN
		799
		800	This flag should not be set when calling C<aio_readdirx>. Instead, it
		801	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		802	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		803	C<$type>'s are known, which can be used to speed up some algorithms.
		804
		805	=back
		806
		807
542	=item aio_load $path, $data, $callback->($status)	808	=item aio_load $pathname, $data, $callback->($status)
543		809
544	This is a composite request that tries to fully load the given file into	810	This is a composite request that tries to fully load the given file into
545	memory. Status is the same as with aio_read.	811	memory. Status is the same as with aio_read.
546		812
547	=cut	813	=cut
…		…
569		835
570	=item aio_copy $srcpath, $dstpath, $callback->($status)	836	=item aio_copy $srcpath, $dstpath, $callback->($status)
571		837
572	Try to copy the I<file> (directories not supported as either source or	838	Try to copy the I<file> (directories not supported as either source or
573	destination) from C<$srcpath> to C<$dstpath> and call the callback with	839	destination) from C<$srcpath> to C<$dstpath> and call the callback with
574	the C<0> (error) or C<-1> ok.	840	a status of C<0> (ok) or C<-1> (error, see C<$!>).
575		841
576	This is a composite request that creates the destination file with	842	This is a composite request that creates the destination file with
577	mode 0200 and copies the contents of the source file into it using	843	mode 0200 and copies the contents of the source file into it using
578	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	844	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
579	uid/gid, in that order.	845	uid/gid, in that order.
…		…
591	my $grp = aio_group $cb;	857	my $grp = aio_group $cb;
592		858
593	aioreq_pri $pri;	859	aioreq_pri $pri;
594	add $grp aio_open $src, O_RDONLY, 0, sub {	860	add $grp aio_open $src, O_RDONLY, 0, sub {
595	if (my $src_fh = $_[0]) {	861	if (my $src_fh = $_[0]) {
596	my @stat = stat $src_fh; # hmm, might bock over nfs?	862	my @stat = stat $src_fh; # hmm, might block over nfs?
597		863
598	aioreq_pri $pri;	864	aioreq_pri $pri;
599	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	865	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
600	if (my $dst_fh = $_[0]) {	866	if (my $dst_fh = $_[0]) {
601	aioreq_pri $pri;	867	aioreq_pri $pri;
…		…
648		914
649	=item aio_move $srcpath, $dstpath, $callback->($status)	915	=item aio_move $srcpath, $dstpath, $callback->($status)
650		916
651	Try to move the I<file> (directories not supported as either source or	917	Try to move the I<file> (directories not supported as either source or
652	destination) from C<$srcpath> to C<$dstpath> and call the callback with	918	destination) from C<$srcpath> to C<$dstpath> and call the callback with
653	the C<0> (error) or C<-1> ok.	919	a status of C<0> (ok) or C<-1> (error, see C<$!>).
654		920
655	This is a composite request that tries to rename(2) the file first; if	921	This is a composite request that tries to rename(2) the file first; if
656	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	922	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
657	that is successful, unlinks the C<$srcpath>.	923	that is successful, unlinks the C<$srcpath>.
658		924
…		…
669	if ($_[0] && $! == EXDEV) {	935	if ($_[0] && $! == EXDEV) {
670	aioreq_pri $pri;	936	aioreq_pri $pri;
671	add $grp aio_copy $src, $dst, sub {	937	add $grp aio_copy $src, $dst, sub {
672	$grp->result ($_[0]);	938	$grp->result ($_[0]);
673		939
674	if (!$_[0]) {	940	unless ($_[0]) {
675	aioreq_pri $pri;	941	aioreq_pri $pri;
676	add $grp aio_unlink $src;	942	add $grp aio_unlink $src;
677	}	943	}
678	};	944	};
679	} else {	945	} else {
…		…
682	};	948	};
683		949
684	$grp	950	$grp
685	}	951	}
686		952
687	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	953	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
688		954
689	Scans a directory (similar to C<aio_readdir>) but additionally tries to	955	Scans a directory (similar to C<aio_readdir>) but additionally tries to
690	efficiently separate the entries of directory C<$path> into two sets of	956	efficiently separate the entries of directory C<$path> into two sets of
691	names, directories you can recurse into (directories), and ones you cannot	957	names, directories you can recurse into (directories), and ones you cannot
692	recurse into (everything else, including symlinks to directories).	958	recurse into (everything else, including symlinks to directories).
…		…
709		975
710	Implementation notes.	976	Implementation notes.
711		977
712	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	978	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
713		979
		980	If readdir returns file type information, then this is used directly to
		981	find directories.
		982
714	After reading the directory, the modification time, size etc. of the	983	Otherwise, after reading the directory, the modification time, size etc.
715	directory before and after the readdir is checked, and if they match (and	984	of the directory before and after the readdir is checked, and if they
716	isn't the current time), the link count will be used to decide how many	985	match (and isn't the current time), the link count will be used to decide
717	entries are directories (if >= 2). Otherwise, no knowledge of the number	986	how many entries are directories (if >= 2). Otherwise, no knowledge of the
718	of subdirectories will be assumed.	987	number of subdirectories will be assumed.
719		988
720	Then entries will be sorted into likely directories (everything without	989	Then entries will be sorted into likely directories a non-initial dot
721	a non-initial dot currently) and likely non-directories (everything	990	currently) and likely non-directories (see C<aio_readdirx>). Then every
722	else). Then every entry plus an appended C</.> will be C<stat>'ed,	991	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
723	likely directories first. If that succeeds, it assumes that the entry	992	in order of their inode numbers. If that succeeds, it assumes that the
724	is a directory or a symlink to directory (which will be checked	993	entry is a directory or a symlink to directory (which will be checked
725	seperately). This is often faster than stat'ing the entry itself because	994	separately). This is often faster than stat'ing the entry itself because
726	filesystems might detect the type of the entry without reading the inode	995	filesystems might detect the type of the entry without reading the inode
727	data (e.g. ext2fs filetype feature).	996	data (e.g. ext2fs filetype feature), even on systems that cannot return
		997	the filetype information on readdir.
728		998
729	If the known number of directories (link count - 2) has been reached, the	999	If the known number of directories (link count - 2) has been reached, the
730	rest of the entries is assumed to be non-directories.	1000	rest of the entries is assumed to be non-directories.
731		1001
732	This only works with certainty on POSIX (= UNIX) filesystems, which	1002	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
745		1015
746	my $grp = aio_group $cb;	1016	my $grp = aio_group $cb;
747		1017
748	$maxreq = 4 if $maxreq <= 0;	1018	$maxreq = 4 if $maxreq <= 0;
749		1019
750	# stat once	1020	# get a wd object
751	aioreq_pri $pri;	1021	aioreq_pri $pri;
752	add $grp aio_stat $path, sub {	1022	add $grp aio_wd $path, sub {
		1023	$_[0]
753	return $grp->result () if $_[0];	1024	or return $grp->result ();
754	my $now = time;
755	my $hash1 = join ":", (stat _)[0,1,3,7,9];
756		1025
757	# read the directory entries	1026	my $wd = [shift, "."];
		1027
		1028	# stat once
758	aioreq_pri $pri;	1029	aioreq_pri $pri;
759	add $grp aio_readdir $path, sub {	1030	add $grp aio_stat $wd, sub {
760	my $entries = shift
761	or return $grp->result ();	1031	return $grp->result () if $_[0];
		1032	my $now = time;
		1033	my $hash1 = join ":", (stat _)[0,1,3,7,9];
762		1034
763	# stat the dir another time	1035	# read the directory entries
764	aioreq_pri $pri;	1036	aioreq_pri $pri;
		1037	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1038	my $entries = shift
		1039	or return $grp->result ();
		1040
		1041	# stat the dir another time
		1042	aioreq_pri $pri;
765	add $grp aio_stat $path, sub {	1043	add $grp aio_stat $wd, sub {
766	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1044	my $hash2 = join ":", (stat _)[0,1,3,7,9];
767		1045
768	my $ndirs;	1046	my $ndirs;
769		1047
770	# take the slow route if anything looks fishy	1048	# take the slow route if anything looks fishy
771	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1049	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
772	$ndirs = -1;	1050	$ndirs = -1;
773	} else {	1051	} else {
774	# if nlink == 2, we are finished	1052	# if nlink == 2, we are finished
775	# on non-posix-fs's, we rely on nlink < 2	1053	# for non-posix-fs's, we rely on nlink < 2
776	$ndirs = (stat _)[3] - 2	1054	$ndirs = (stat _)[3] - 2
777	or return $grp->result ([], $entries);	1055	or return $grp->result ([], $entries);
778	}	1056	}
779		1057
780	# sort into likely dirs and likely nondirs
781	# dirs == files without ".", short entries first
782	$entries = [map $_->[0],
783	sort { $b->[1] cmp $a->[1] }
784	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
785	@$entries];
786
787	my (@dirs, @nondirs);	1058	my (@dirs, @nondirs);
788		1059
789	my $statgrp = add $grp aio_group sub {	1060	my $statgrp = add $grp aio_group sub {
790	$grp->result (\@dirs, \@nondirs);	1061	$grp->result (\@dirs, \@nondirs);
791	};	1062	};
792		1063
793	limit $statgrp $maxreq;	1064	limit $statgrp $maxreq;
794	feed $statgrp sub {	1065	feed $statgrp sub {
795	return unless @$entries;	1066	return unless @$entries;
796	my $entry = pop @$entries;	1067	my $entry = shift @$entries;
797		1068
798	aioreq_pri $pri;	1069	aioreq_pri $pri;
		1070	$wd->[1] = "$entry/.";
799	add $statgrp aio_stat "$path/$entry/.", sub {	1071	add $statgrp aio_stat $wd, sub {
800	if ($_[0] < 0) {	1072	if ($_[0] < 0) {
801	push @nondirs, $entry;	1073	push @nondirs, $entry;
802	} else {	1074	} else {
803	# need to check for real directory	1075	# need to check for real directory
804	aioreq_pri $pri;	1076	aioreq_pri $pri;
		1077	$wd->[1] = $entry;
805	add $statgrp aio_lstat "$path/$entry", sub {	1078	add $statgrp aio_lstat $wd, sub {
806	if (-d _) {	1079	if (-d _) {
807	push @dirs, $entry;	1080	push @dirs, $entry;
808		1081
809	unless (--$ndirs) {	1082	unless (--$ndirs) {
810	push @nondirs, @$entries;	1083	push @nondirs, @$entries;
811	feed $statgrp;	1084	feed $statgrp;
		1085	}
		1086	} else {
		1087	push @nondirs, $entry;
812	}	1088	}
813	} else {
814	push @nondirs, $entry;
815	}	1089	}
816	}	1090	}
817	}	1091	};
818	};	1092	};
819	};	1093	};
820	};	1094	};
821	};	1095	};
822	};	1096	};
823		1097
824	$grp	1098	$grp
825	}	1099	}
826		1100
827	=item aio_rmtree $path, $callback->($status)	1101	=item aio_rmtree $pathname, $callback->($status)
828		1102
829	Delete a directory tree starting (and including) C<$path>, return the	1103	Delete a directory tree starting (and including) C<$path>, return the
830	status of the final C<rmdir> only. This is a composite request that	1104	status of the final C<rmdir> only. This is a composite request that
831	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1105	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
832	everything else.	1106	everything else.
…		…
874	callback with the fdatasync result code.	1148	callback with the fdatasync result code.
875		1149
876	If this call isn't available because your OS lacks it or it couldn't be	1150	If this call isn't available because your OS lacks it or it couldn't be
877	detected, it will be emulated by calling C<fsync> instead.	1151	detected, it will be emulated by calling C<fsync> instead.
878		1152
		1153	=item aio_syncfs $fh, $callback->($status)
		1154
		1155	Asynchronously call the syncfs syscall to sync the filesystem associated
		1156	to the given filehandle and call the callback with the syncfs result
		1157	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1158	errno to C<ENOSYS> nevertheless.
		1159
879	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1160	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
880		1161
881	Sync the data portion of the file specified by C<$offset> and C<$length>	1162	Sync the data portion of the file specified by C<$offset> and C<$length>
882	to disk (but NOT the metadata), by calling the Linux-specific	1163	to disk (but NOT the metadata), by calling the Linux-specific
883	sync_file_range call. If sync_file_range is not available or it returns	1164	sync_file_range call. If sync_file_range is not available or it returns
…		…
886	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1167	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
887	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1168	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
888	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1169	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
889	manpage for details.	1170	manpage for details.
890		1171
891	=item aio_pathsync $path, $callback->($status)	1172	=item aio_pathsync $pathname, $callback->($status)
892		1173
893	This request tries to open, fsync and close the given path. This is a	1174	This request tries to open, fsync and close the given path. This is a
894	composite request intended to sync directories after directory operations	1175	composite request intended to sync directories after directory operations
895	(E.g. rename). This might not work on all operating systems or have any	1176	(E.g. rename). This might not work on all operating systems or have any
896	specific effect, but usually it makes sure that directory changes get	1177	specific effect, but usually it makes sure that directory changes get
897	written to disc. It works for anything that can be opened for read-only,	1178	written to disc. It works for anything that can be opened for read-only,
898	not just directories.	1179	not just directories.
		1180
		1181	Future versions of this function might fall back to other methods when
		1182	C<fsync> on the directory fails (such as calling C<sync>).
899		1183
900	Passes C<0> when everything went ok, and C<-1> on error.	1184	Passes C<0> when everything went ok, and C<-1> on error.
901		1185
902	=cut	1186	=cut
903		1187
…		…
924	};	1208	};
925		1209
926	$grp	1210	$grp
927	}	1211	}
928		1212
		1213	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1214
		1215	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1216	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1217	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1218	scalar must only be modified in-place while an aio operation is pending on
		1219	it).
		1220
		1221	It calls the C<msync> function of your OS, if available, with the memory
		1222	area starting at C<$offset> in the string and ending C<$length> bytes
		1223	later. If C<$length> is negative, counts from the end, and if C<$length>
		1224	is C<undef>, then it goes till the end of the string. The flags can be
		1225	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1226	C<IO::AIO::MS_SYNC>.
		1227
		1228	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1229
		1230	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1231	scalars.
		1232
		1233	It touches (reads or writes) all memory pages in the specified
		1234	range inside the scalar. All caveats and parameters are the same
		1235	as for C<aio_msync>, above, except for flags, which must be either
		1236	C<0> (which reads all pages and ensures they are instantiated) or
		1237	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1238	writing an octet from it, which dirties the page).
		1239
		1240	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1241
		1242	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1243	scalars.
		1244
		1245	It reads in all the pages of the underlying storage into memory (if any)
		1246	and locks them, so they are not getting swapped/paged out or removed.
		1247
		1248	If C<$length> is undefined, then the scalar will be locked till the end.
		1249
		1250	On systems that do not implement C<mlock>, this function returns C<-1>
		1251	and sets errno to C<ENOSYS>.
		1252
		1253	Note that the corresponding C<munlock> is synchronous and is
		1254	documented under L<MISCELLANEOUS FUNCTIONS>.
		1255
		1256	Example: open a file, mmap and mlock it - both will be undone when
		1257	C<$data> gets destroyed.
		1258
		1259	open my $fh, "<", $path or die "$path: $!";
		1260	my $data;
		1261	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1262	aio_mlock $data; # mlock in background
		1263
		1264	=item aio_mlockall $flags, $callback->($status)
		1265
		1266	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1267	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1268
		1269	On systems that do not implement C<mlockall>, this function returns C<-1>
		1270	and sets errno to C<ENOSYS>.
		1271
		1272	Note that the corresponding C<munlockall> is synchronous and is
		1273	documented under L<MISCELLANEOUS FUNCTIONS>.
		1274
		1275	Example: asynchronously lock all current and future pages into memory.
		1276
		1277	aio_mlockall IO::AIO::MCL_FUTURE;
		1278
		1279	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1280
		1281	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1282	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1283	C<ioctl> is not available on your OS, then this rquiest will fail with
		1284	C<ENOSYS>.
		1285
		1286	C<$start> is the starting offset to query extents for, C<$length> is the
		1287	size of the range to query - if it is C<undef>, then the whole file will
		1288	be queried.
		1289
		1290	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1291	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1292	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1293	the data portion.
		1294
		1295	C<$count> is the maximum number of extent records to return. If it is
		1296	C<undef>, then IO::AIO queries all extents of the file. As a very special
		1297	case, if it is C<0>, then the callback receives the number of extents
		1298	instead of the extents themselves.
		1299
		1300	If an error occurs, the callback receives no arguments. The special
		1301	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1302
		1303	Otherwise, the callback receives an array reference with extent
		1304	structures. Each extent structure is an array reference itself, with the
		1305	following members:
		1306
		1307	[$logical, $physical, $length, $flags]
		1308
		1309	Flags is any combination of the following flag values (typically either C<0>
		1310	or C<IO::AIO::FIEMAP_EXTENT_LAST>):
		1311
		1312	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1313	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1314	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1315	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1316	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1317	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1318
929	=item aio_group $callback->(...)	1319	=item aio_group $callback->(...)
930		1320
931	This is a very special aio request: Instead of doing something, it is a	1321	This is a very special aio request: Instead of doing something, it is a
932	container for other aio requests, which is useful if you want to bundle	1322	container for other aio requests, which is useful if you want to bundle
933	many requests into a single, composite, request with a definite callback	1323	many requests into a single, composite, request with a definite callback
…		…
970	immense (it blocks a thread for a long time) so do not use this function	1360	immense (it blocks a thread for a long time) so do not use this function
971	except to put your application under artificial I/O pressure.	1361	except to put your application under artificial I/O pressure.
972		1362
973	=back	1363	=back
974		1364
		1365
		1366	=head2 IO::AIO::WD - multiple working directories
		1367
		1368	Your process only has one current working directory, which is used by all
		1369	threads. This makes it hard to use relative paths (some other component
		1370	could call C<chdir> at any time, and it is hard to control when the path
		1371	will be used by IO::AIO).
		1372
		1373	One solution for this is to always use absolute paths. This usually works,
		1374	but can be quite slow (the kernel has to walk the whole path on every
		1375	access), and can also be a hassle to implement.
		1376
		1377	Newer POSIX systems have a number of functions (openat, fdopendir,
		1378	futimensat and so on) that make it possible to specify working directories
		1379	per operation.
		1380
		1381	For portability, and because the clowns who "designed", or shall I write,
		1382	perpetrated this new interface were obviously half-drunk, this abstraction
		1383	cannot be perfect, though.
		1384
		1385	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1386	object. This object stores the canonicalised, absolute version of the
		1387	path, and on systems that allow it, also a directory file descriptor.
		1388
		1389	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1390	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1391	object and a pathname instead (or the IO::AIO::WD object alone, which
		1392	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1393	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1394	to that IO::AIO::WD object.
		1395
		1396	For example, to get a wd object for F</etc> and then stat F<passwd>
		1397	inside, you would write:
		1398
		1399	aio_wd "/etc", sub {
		1400	my $etcdir = shift;
		1401
		1402	# although $etcdir can be undef on error, there is generally no reason
		1403	# to check for errors here, as aio_stat will fail with ENOENT
		1404	# when $etcdir is undef.
		1405
		1406	aio_stat [$etcdir, "passwd"], sub {
		1407	# yay
		1408	};
		1409	};
		1410
		1411	That C<aio_wd> is a request and not a normal function shows that creating
		1412	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1413	why it is done asynchronously.
		1414
		1415	To stat the directory obtained with C<aio_wd> above, one could write
		1416	either of the following three request calls:
		1417
		1418	aio_lstat "/etc" , sub { ... # pathname as normal string
		1419	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1420	aio_lstat $wd , sub { ... # shorthand for the previous
		1421
		1422	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1423	object and the pathname string, so you could write the following without
		1424	causing any issues due to C<$path> getting reused:
		1425
		1426	my $path = [$wd, undef];
		1427
		1428	for my $name (qw(abc def ghi)) {
		1429	$path->[1] = $name;
		1430	aio_stat $path, sub {
		1431	# ...
		1432	};
		1433	}
		1434
		1435	There are some caveats: when directories get renamed (or deleted), the
		1436	pathname string doesn't change, so will point to the new directory (or
		1437	nowhere at all), while the directory fd, if available on the system,
		1438	will still point to the original directory. Most functions accepting a
		1439	pathname will use the directory fd on newer systems, and the string on
		1440	older systems. Some functions (such as realpath) will always rely on the
		1441	string form of the pathname.
		1442
		1443	So this fucntionality is mainly useful to get some protection against
		1444	C<chdir>, to easily get an absolute path out of a relative path for future
		1445	reference, and to speed up doing many operations in the same directory
		1446	(e.g. when stat'ing all files in a directory).
		1447
		1448	The following functions implement this working directory abstraction:
		1449
		1450	=over 4
		1451
		1452	=item aio_wd $pathname, $callback->($wd)
		1453
		1454	Asynchonously canonicalise the given pathname and convert it to an
		1455	IO::AIO::WD object representing it. If possible and supported on the
		1456	system, also open a directory fd to speed up pathname resolution relative
		1457	to this working directory.
		1458
		1459	If something goes wrong, then C<undef> is passwd to the callback instead
		1460	of a working directory object and C<$!> is set appropriately. Since
		1461	passing C<undef> as working directory component of a pathname fails the
		1462	request with C<ENOENT>, there is often no need for error checking in the
		1463	C<aio_wd> callback, as future requests using the value will fail in the
		1464	expected way.
		1465
		1466	If this call isn't available because your OS lacks it or it couldn't be
		1467	detected, it will be emulated by calling C<fsync> instead.
		1468
		1469	=item IO::AIO::CWD
		1470
		1471	This is a compiletime constant (object) that represents the process
		1472	current working directory.
		1473
		1474	Specifying this object as working directory object for a pathname is as
		1475	if the pathname would be specified directly, without a directory object,
		1476	e.g., these calls are functionally identical:
		1477
		1478	aio_stat "somefile", sub { ... };
		1479	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1480
		1481	=back
		1482
		1483
975	=head2 IO::AIO::REQ CLASS	1484	=head2 IO::AIO::REQ CLASS
976		1485
977	All non-aggregate C<aio_*> functions return an object of this class when	1486	All non-aggregate C<aio_*> functions return an object of this class when
978	called in non-void context.	1487	called in non-void context.
979		1488
…		…
982	=item cancel $req	1491	=item cancel $req
983		1492
984	Cancels the request, if possible. Has the effect of skipping execution	1493	Cancels the request, if possible. Has the effect of skipping execution
985	when entering the B<execute> state and skipping calling the callback when	1494	when entering the B<execute> state and skipping calling the callback when
986	entering the the B<result> state, but will leave the request otherwise	1495	entering the the B<result> state, but will leave the request otherwise
987	untouched. That means that requests that currently execute will not be	1496	untouched (with the exception of readdir). That means that requests that
988	stopped and resources held by the request will not be freed prematurely.	1497	currently execute will not be stopped and resources held by the request
		1498	will not be freed prematurely.
989		1499
990	=item cb $req $callback->(...)	1500	=item cb $req $callback->(...)
991		1501
992	Replace (or simply set) the callback registered to the request.	1502	Replace (or simply set) the callback registered to the request.
993		1503
…		…
1067	=item $grp->cancel_subs	1577	=item $grp->cancel_subs
1068		1578
1069	Cancel all subrequests and clears any feeder, but not the group request	1579	Cancel all subrequests and clears any feeder, but not the group request
1070	itself. Useful when you queued a lot of events but got a result early.	1580	itself. Useful when you queued a lot of events but got a result early.
1071		1581
		1582	The group request will finish normally (you cannot add requests to the
		1583	group).
		1584
1072	=item $grp->result (...)	1585	=item $grp->result (...)
1073		1586
1074	Set the result value(s) that will be passed to the group callback when all	1587	Set the result value(s) that will be passed to the group callback when all
1075	subrequests have finished and set the groups errno to the current value	1588	subrequests have finished and set the groups errno to the current value
1076	of errno (just like calling C<errno> without an error number). By default,	1589	of errno (just like calling C<errno> without an error number). By default,
…		…
1092		1605
1093	Sets a feeder/generator on this group: every group can have an attached	1606	Sets a feeder/generator on this group: every group can have an attached
1094	generator that generates requests if idle. The idea behind this is that,	1607	generator that generates requests if idle. The idea behind this is that,
1095	although you could just queue as many requests as you want in a group,	1608	although you could just queue as many requests as you want in a group,
1096	this might starve other requests for a potentially long time. For example,	1609	this might starve other requests for a potentially long time. For example,
1097	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1610	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1098	delaying any later requests for a long time.	1611	requests, delaying any later requests for a long time.
1099		1612
1100	To avoid this, and allow incremental generation of requests, you can	1613	To avoid this, and allow incremental generation of requests, you can
1101	instead a group and set a feeder on it that generates those requests. The	1614	instead a group and set a feeder on it that generates those requests. The
1102	feed callback will be called whenever there are few enough (see C<limit>,	1615	feed callback will be called whenever there are few enough (see C<limit>,
1103	below) requests active in the group itself and is expected to queue more	1616	below) requests active in the group itself and is expected to queue more
…		…
1144	=over 4	1657	=over 4
1145		1658
1146	=item $fileno = IO::AIO::poll_fileno	1659	=item $fileno = IO::AIO::poll_fileno
1147		1660
1148	Return the I<request result pipe file descriptor>. This filehandle must be	1661	Return the I<request result pipe file descriptor>. This filehandle must be
1149	polled for reading by some mechanism outside this module (e.g. Event or	1662	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1150	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1663	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1151	to call C<poll_cb> to check the results.	1664	you have to call C<poll_cb> to check the results.
1152		1665
1153	See C<poll_cb> for an example.	1666	See C<poll_cb> for an example.
1154		1667
1155	=item IO::AIO::poll_cb	1668	=item IO::AIO::poll_cb
1156		1669
1157	Process some outstanding events on the result pipe. You have to call this	1670	Process some outstanding events on the result pipe. You have to call
1158	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1671	this regularly. Returns C<0> if all events could be processed (or there
1159	returned earlier for whatever reason. Returns immediately when no events	1672	were no events to process), or C<-1> if it returned earlier for whatever
1160	are outstanding. The amount of events processed depends on the settings of	1673	reason. Returns immediately when no events are outstanding. The amount of
1161	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.	1674	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1675	C<IO::AIO::max_poll_time>.
1162		1676
1163	If not all requests were processed for whatever reason, the filehandle	1677	If not all requests were processed for whatever reason, the filehandle
1164	will still be ready when C<poll_cb> returns, so normally you don't have to	1678	will still be ready when C<poll_cb> returns, so normally you don't have to
1165	do anything special to have it called later.	1679	do anything special to have it called later.
1166		1680
		1681	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1682	ready, it can be beneficial to call this function from loops which submit
		1683	a lot of requests, to make sure the results get processed when they become
		1684	available and not just when the loop is finished and the event loop takes
		1685	over again. This function returns very fast when there are no outstanding
		1686	requests.
		1687
1167	Example: Install an Event watcher that automatically calls	1688	Example: Install an Event watcher that automatically calls
1168	IO::AIO::poll_cb with high priority:	1689	IO::AIO::poll_cb with high priority (more examples can be found in the
		1690	SYNOPSIS section, at the top of this document):
1169		1691
1170	Event->io (fd => IO::AIO::poll_fileno,	1692	Event->io (fd => IO::AIO::poll_fileno,
1171	poll => 'r', async => 1,	1693	poll => 'r', async => 1,
1172	cb => \&IO::AIO::poll_cb);	1694	cb => \&IO::AIO::poll_cb);
		1695
		1696	=item IO::AIO::poll_wait
		1697
		1698	If there are any outstanding requests and none of them in the result
		1699	phase, wait till the result filehandle becomes ready for reading (simply
		1700	does a C<select> on the filehandle. This is useful if you want to
		1701	synchronously wait for some requests to finish).
		1702
		1703	See C<nreqs> for an example.
		1704
		1705	=item IO::AIO::poll
		1706
		1707	Waits until some requests have been handled.
		1708
		1709	Returns the number of requests processed, but is otherwise strictly
		1710	equivalent to:
		1711
		1712	IO::AIO::poll_wait, IO::AIO::poll_cb
		1713
		1714	=item IO::AIO::flush
		1715
		1716	Wait till all outstanding AIO requests have been handled.
		1717
		1718	Strictly equivalent to:
		1719
		1720	IO::AIO::poll_wait, IO::AIO::poll_cb
		1721	while IO::AIO::nreqs;
1173		1722
1174	=item IO::AIO::max_poll_reqs $nreqs	1723	=item IO::AIO::max_poll_reqs $nreqs
1175		1724
1176	=item IO::AIO::max_poll_time $seconds	1725	=item IO::AIO::max_poll_time $seconds
1177		1726
…		…
1202	# use a low priority so other tasks have priority	1751	# use a low priority so other tasks have priority
1203	Event->io (fd => IO::AIO::poll_fileno,	1752	Event->io (fd => IO::AIO::poll_fileno,
1204	poll => 'r', nice => 1,	1753	poll => 'r', nice => 1,
1205	cb => &IO::AIO::poll_cb);	1754	cb => &IO::AIO::poll_cb);
1206		1755
1207	=item IO::AIO::poll_wait
1208
1209	If there are any outstanding requests and none of them in the result
1210	phase, wait till the result filehandle becomes ready for reading (simply
1211	does a C<select> on the filehandle. This is useful if you want to
1212	synchronously wait for some requests to finish).
1213
1214	See C<nreqs> for an example.
1215
1216	=item IO::AIO::poll
1217
1218	Waits until some requests have been handled.
1219
1220	Returns the number of requests processed, but is otherwise strictly
1221	equivalent to:
1222
1223	IO::AIO::poll_wait, IO::AIO::poll_cb
1224
1225	=item IO::AIO::flush
1226
1227	Wait till all outstanding AIO requests have been handled.
1228
1229	Strictly equivalent to:
1230
1231	IO::AIO::poll_wait, IO::AIO::poll_cb
1232	while IO::AIO::nreqs;
1233
1234	=back	1756	=back
1235		1757
1236	=head3 CONTROLLING THE NUMBER OF THREADS	1758	=head3 CONTROLLING THE NUMBER OF THREADS
1237		1759
1238	=over	1760	=over
…		…
1271		1793
1272	Under normal circumstances you don't need to call this function.	1794	Under normal circumstances you don't need to call this function.
1273		1795
1274	=item IO::AIO::max_idle $nthreads	1796	=item IO::AIO::max_idle $nthreads
1275		1797
1276	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1798	Limit the number of threads (default: 4) that are allowed to idle
1277	threads that did not get a request to process within 10 seconds). That	1799	(i.e., threads that did not get a request to process within the idle
1278	means if a thread becomes idle while C<$nthreads> other threads are also	1800	timeout (default: 10 seconds). That means if a thread becomes idle while
1279	idle, it will free its resources and exit.	1801	C<$nthreads> other threads are also idle, it will free its resources and
		1802	exit.
1280		1803
1281	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1804	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1282	to allow for extremely high load situations, but want to free resources	1805	to allow for extremely high load situations, but want to free resources
1283	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1806	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1284		1807
1285	The default is probably ok in most situations, especially if thread	1808	The default is probably ok in most situations, especially if thread
1286	creation is fast. If thread creation is very slow on your system you might	1809	creation is fast. If thread creation is very slow on your system you might
1287	want to use larger values.	1810	want to use larger values.
1288		1811
		1812	=item IO::AIO::idle_timeout $seconds
		1813
		1814	Sets the minimum idle timeout (default 10) after which worker threads are
		1815	allowed to exit. SEe C<IO::AIO::max_idle>.
		1816
1289	=item IO::AIO::max_outstanding $maxreqs	1817	=item IO::AIO::max_outstanding $maxreqs
		1818
		1819	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1820	you do queue up more than this number of requests, the next call to
		1821	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1822	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1823	longer exceeded.
		1824
		1825	In other words, this setting does not enforce a queue limit, but can be
		1826	used to make poll functions block if the limit is exceeded.
1290		1827
1291	This is a very bad function to use in interactive programs because it	1828	This is a very bad function to use in interactive programs because it
1292	blocks, and a bad way to reduce concurrency because it is inexact: Better	1829	blocks, and a bad way to reduce concurrency because it is inexact: Better
1293	use an C<aio_group> together with a feed callback.	1830	use an C<aio_group> together with a feed callback.
1294		1831
1295	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1832	It's main use is in scripts without an event loop - when you want to stat
1296	do queue up more than this number of requests, the next call to the	1833	a lot of files, you can write somehting like this:
1297	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1298	function will block until the limit is no longer exceeded.
1299		1834
1300	The default value is very large, so there is no practical limit on the	1835	IO::AIO::max_outstanding 32;
1301	number of outstanding requests.
1302		1836
1303	You can still queue as many requests as you want. Therefore,	1837	for my $path (...) {
1304	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1838	aio_stat $path , ...;
1305	as a stop gap to shield against fatal memory overflow (with large values).	1839	IO::AIO::poll_cb;
		1840	}
		1841
		1842	IO::AIO::flush;
		1843
		1844	The call to C<poll_cb> inside the loop will normally return instantly, but
		1845	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1846	some requests have been handled. This keeps the loop from pushing a large
		1847	number of C<aio_stat> requests onto the queue.
		1848
		1849	The default value for C<max_outstanding> is very large, so there is no
		1850	practical limit on the number of outstanding requests.
1306		1851
1307	=back	1852	=back
1308		1853
1309	=head3 STATISTICAL INFORMATION	1854	=head3 STATISTICAL INFORMATION
1310		1855
…		…
1330	Returns the number of requests currently in the pending state (executed,	1875	Returns the number of requests currently in the pending state (executed,
1331	but not yet processed by poll_cb).	1876	but not yet processed by poll_cb).
1332		1877
1333	=back	1878	=back
1334		1879
		1880	=head3 MISCELLANEOUS FUNCTIONS
		1881
		1882	IO::AIO implements some functions that might be useful, but are not
		1883	asynchronous.
		1884
		1885	=over 4
		1886
		1887	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1888
		1889	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1890	but is blocking (this makes most sense if you know the input data is
		1891	likely cached already and the output filehandle is set to non-blocking
		1892	operations).
		1893
		1894	Returns the number of bytes copied, or C<-1> on error.
		1895
		1896	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1897
		1898	Simply calls the C<posix_fadvise> function (see its
		1899	manpage for details). The following advice constants are
		1900	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1901	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1902	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1903
		1904	On systems that do not implement C<posix_fadvise>, this function returns
		1905	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1906
		1907	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1908
		1909	Simply calls the C<posix_madvise> function (see its
		1910	manpage for details). The following advice constants are
		1911	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1912	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1913
		1914	On systems that do not implement C<posix_madvise>, this function returns
		1915	ENOSYS, otherwise the return value of C<posix_madvise>.
		1916
		1917	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1918
		1919	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1920	$scalar (see its manpage for details). The following protect
		1921	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1922	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1923
		1924	On systems that do not implement C<mprotect>, this function returns
		1925	ENOSYS, otherwise the return value of C<mprotect>.
		1926
		1927	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1928
		1929	Memory-maps a file (or anonymous memory range) and attaches it to the
		1930	given C<$scalar>, which will act like a string scalar. Returns true on
		1931	success, and false otherwise.
		1932
		1933	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1934	change the string length, and most read-only operations such as copying it
		1935	or searching it with regexes and so on.
		1936
		1937	Anything else is unsafe and will, at best, result in memory leaks.
		1938
		1939	The memory map associated with the C<$scalar> is automatically removed
		1940	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1941	C<IO::AIO::munmap> functions are called.
		1942
		1943	This calls the C<mmap>(2) function internally. See your system's manual
		1944	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1945
		1946	The C<$length> must be larger than zero and smaller than the actual
		1947	filesize.
		1948
		1949	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1950	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1951
		1952	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1953	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1954	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1955	(which is set to C<MAP_ANON> if your system only provides this
		1956	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1957	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1958	C<IO::AIO::MAP_NONBLOCK>
		1959
		1960	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1961
		1962	C<$offset> is the offset from the start of the file - it generally must be
		1963	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1964
		1965	Example:
		1966
		1967	use Digest::MD5;
		1968	use IO::AIO;
		1969
		1970	open my $fh, "<verybigfile"
		1971	or die "$!";
		1972
		1973	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1974	or die "verybigfile: $!";
		1975
		1976	my $fast_md5 = md5 $data;
		1977
		1978	=item IO::AIO::munmap $scalar
		1979
		1980	Removes a previous mmap and undefines the C<$scalar>.
		1981
		1982	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1983
		1984	Calls the C<munlock> function, undoing the effects of a previous
		1985	C<aio_mlock> call (see its description for details).
		1986
		1987	=item IO::AIO::munlockall
		1988
		1989	Calls the C<munlockall> function.
		1990
		1991	On systems that do not implement C<munlockall>, this function returns
		1992	ENOSYS, otherwise the return value of C<munlockall>.
		1993
		1994	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1995
		1996	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		1997	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		1998	should be the file offset.
		1999
		2000	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2001	silently corrupt the data in this case.
		2002
		2003	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2004	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2005	C<IO::AIO::SPLICE_F_GIFT>.
		2006
		2007	See the C<splice(2)> manpage for details.
		2008
		2009	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2010
		2011	Calls the GNU/Linux C<tee(2)> syscall, see it's manpage and the
		2012	description for C<IO::AIO::splice> above for details.
		2013
		2014	=back
		2015
1335	=cut	2016	=cut
1336		2017
1337	min_parallel 8;	2018	min_parallel 8;
1338		2019
1339	END { flush }	2020	END { flush }
1340		2021
1341	1;	2022	1;
1342		2023
		2024	=head1 EVENT LOOP INTEGRATION
		2025
		2026	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2027	automatically into many event loops:
		2028
		2029	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2030	use AnyEvent::AIO;
		2031
		2032	You can also integrate IO::AIO manually into many event loops, here are
		2033	some examples of how to do this:
		2034
		2035	# EV integration
		2036	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2037
		2038	# Event integration
		2039	Event->io (fd => IO::AIO::poll_fileno,
		2040	poll => 'r',
		2041	cb => \&IO::AIO::poll_cb);
		2042
		2043	# Glib/Gtk2 integration
		2044	add_watch Glib::IO IO::AIO::poll_fileno,
		2045	in => sub { IO::AIO::poll_cb; 1 };
		2046
		2047	# Tk integration
		2048	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2049	readable => \&IO::AIO::poll_cb);
		2050
		2051	# Danga::Socket integration
		2052	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2053	\&IO::AIO::poll_cb);
		2054
1343	=head2 FORK BEHAVIOUR	2055	=head2 FORK BEHAVIOUR
1344		2056
1345	This module should do "the right thing" when the process using it forks:	2057	Usage of pthreads in a program changes the semantics of fork
		2058	considerably. Specifically, only async-safe functions can be called after
		2059	fork. Perl doesn't know about this, so in general, you cannot call fork
		2060	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2061	pthreads, so this applies, but many other extensions and (for inexplicable
		2062	reasons) perl itself often is linked against pthreads, so this limitation
		2063	applies to quite a lot of perls.
1346		2064
1347	Before the fork, IO::AIO enters a quiescent state where no requests	2065	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1348	can be added in other threads and no results will be processed. After	2066	only works in the process that loaded it. Forking is fully supported, but
1349	the fork the parent simply leaves the quiescent state and continues	2067	using IO::AIO in the child is not.
1350	request/result processing, while the child frees the request/result queue
1351	(so that the requests started before the fork will only be handled in the
1352	parent). Threads will be started on demand until the limit set in the
1353	parent process has been reached again.
1354		2068
1355	In short: the parent will, after a short pause, continue as if fork had	2069	You might get around by not I<using> IO::AIO before (or after)
1356	not been called, while the child will act as if IO::AIO has not been used	2070	forking. You could also try to call the L<IO::AIO::reinit> function in the
1357	yet.	2071	child:
		2072
		2073	=over 4
		2074
		2075	=item IO::AIO::reinit
		2076
		2077	Abandons all current requests and I/O threads and simply reinitialises all
		2078	data structures. This is not an operation supported by any standards, but
		2079	happens to work on GNU/Linux and some newer BSD systems.
		2080
		2081	The only reasonable use for this function is to call it after forking, if
		2082	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2083	the process will result in undefined behaviour. Calling it at any time
		2084	will also result in any undefined (by POSIX) behaviour.
		2085
		2086	=back
1358		2087
1359	=head2 MEMORY USAGE	2088	=head2 MEMORY USAGE
1360		2089
1361	Per-request usage:	2090	Per-request usage:
1362		2091

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