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Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC vs.
Revision 1.227 by root, Tue May 29 03:58:02 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) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
30	# AnyEvent integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',
37	cb => \&IO::AIO::poll_cb);
38
39	# Glib/Gtk2 integration
40	add_watch Glib::IO IO::AIO::poll_fileno,
41	in => sub { IO::AIO::poll_cb; 1 };
42
43	# Tk integration
44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
45	readable => \&IO::AIO::poll_cb);
46
47	# Danga::Socket integration
48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49	\&IO::AIO::poll_cb);
50
51	=head1 DESCRIPTION	31	=head1 DESCRIPTION
52		32
53	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
54	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>).
		36
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
55		52
56	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
57	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
58	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
59	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
60	functions available on many operating systems. However, they are often	57	functions available on many operating systems. However, they are often
61	not well-supported or restricted (Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	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
63	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
64	using threads anyway.	61	using threads anyway.
65		62
66	Although the module will work with in the presence of other (Perl-)	63	Although the module will work in the presence of other (Perl-) threads,
67	threads, it is currently not reentrant in any way, so use appropriate	64	it is currently not reentrant in any way, so use appropriate locking
68	locking yourself, always call C<poll_cb> from within the same thread, or	65	yourself, always call C<poll_cb> from within the same thread, or never
69	never call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
		67
		68	=head2 EXAMPLE
		69
		70	This is a simple example that uses the EV module and loads
		71	F</etc/passwd> asynchronously:
		72
		73	use Fcntl;
		74	use EV;
		75	use IO::AIO;
		76
		77	# register the IO::AIO callback with EV
		78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		79
		80	# queue the request to open /etc/passwd
		81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		82	my $fh = shift
		83	or die "error while opening: $!";
		84
		85	# stat'ing filehandles is generally non-blocking
		86	my $size = -s $fh;
		87
		88	# queue a request to read the file
		89	my $contents;
		90	aio_read $fh, 0, $size, $contents, 0, sub {
		91	$_[0] == $size
		92	or die "short read: $!";
		93
		94	close $fh;
		95
		96	# file contents now in $contents
		97	print $contents;
		98
		99	# exit event loop and program
		100	EV::unloop;
		101	};
		102	};
		103
		104	# possibly queue up other requests, or open GUI windows,
		105	# check for sockets etc. etc.
		106
		107	# process events as long as there are some:
		108	EV::loop;
70		109
71	=head1 REQUEST ANATOMY AND LIFETIME	110	=head1 REQUEST ANATOMY AND LIFETIME
72		111
73	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
74	directly visible to Perl.	113	directly visible to Perl.
…		…
116	Request has reached the end of its lifetime and holds no resources anymore	155	Request has reached the end of its lifetime and holds no resources anymore
117	(except possibly for the Perl object, but its connection to the actual	156	(except possibly for the Perl object, but its connection to the actual
118	aio request is severed and calling its methods will either do nothing or	157	aio request is severed and calling its methods will either do nothing or
119	result in a runtime error).	158	result in a runtime error).
120		159
		160	=back
		161
121	=cut	162	=cut
122		163
123	package IO::AIO;	164	package IO::AIO;
124		165
125	no warnings;	166	use Carp ();
126	use strict 'vars';	167
		168	use common::sense;
127		169
128	use base 'Exporter';	170	use base 'Exporter';
129		171
130	BEGIN {	172	BEGIN {
131	our $VERSION = '2.0';	173	our $VERSION = '4.15';
132		174
133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	175	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead aio_fiemap
		180	aio_rename aio_link aio_move aio_copy aio_group
		181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
136	aio_group aio_nop);	185	aio_wd);
		186
137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139	min_parallel max_parallel nreqs);	189	min_parallel max_parallel max_idle idle_timeout
		190	nreqs nready npending nthreads
		191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
140		196
141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142		198
143	require XSLoader;	199	require XSLoader;
144	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
145	}	201	}
146		202
147	=head1 FUNCTIONS	203	=head1 FUNCTIONS
148		204
149	=head2 AIO 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_unlink $pathname, $callback->($status)
		227	aio_mknod $pathname, $mode, $dev, $callback->($status)
		228	aio_link $srcpath, $dstpath, $callback->($status)
		229	aio_symlink $srcpath, $dstpath, $callback->($status)
		230	aio_readlink $pathname, $callback->($link)
		231	aio_realpath $pathname, $callback->($link)
		232	aio_rename $srcpath, $dstpath, $callback->($status)
		233	aio_mkdir $pathname, $mode, $callback->($status)
		234	aio_rmdir $pathname, $callback->($status)
		235	aio_readdir $pathname, $callback->($entries)
		236	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		237	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		238	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		239	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		240	aio_load $pathname, $data, $callback->($status)
		241	aio_copy $srcpath, $dstpath, $callback->($status)
		242	aio_move $srcpath, $dstpath, $callback->($status)
		243	aio_rmtree $pathname, $callback->($status)
		244	aio_sync $callback->($status)
		245	aio_syncfs $fh, $callback->($status)
		246	aio_fsync $fh, $callback->($status)
		247	aio_fdatasync $fh, $callback->($status)
		248	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		249	aio_pathsync $pathname, $callback->($status)
		250	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		251	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		252	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		253	aio_mlockall $flags, $callback->($status)
		254	aio_group $callback->(...)
		255	aio_nop $callback->()
		256
		257	$prev_pri = aioreq_pri [$pri]
		258	aioreq_nice $pri_adjust
		259
		260	IO::AIO::poll_wait
		261	IO::AIO::poll_cb
		262	IO::AIO::poll
		263	IO::AIO::flush
		264	IO::AIO::max_poll_reqs $nreqs
		265	IO::AIO::max_poll_time $seconds
		266	IO::AIO::min_parallel $nthreads
		267	IO::AIO::max_parallel $nthreads
		268	IO::AIO::max_idle $nthreads
		269	IO::AIO::idle_timeout $seconds
		270	IO::AIO::max_outstanding $maxreqs
		271	IO::AIO::nreqs
		272	IO::AIO::nready
		273	IO::AIO::npending
		274
		275	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		276	IO::AIO::fadvise $fh, $offset, $len, $advice
		277	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		278	IO::AIO::munmap $scalar
		279	IO::AIO::madvise $scalar, $offset, $length, $advice
		280	IO::AIO::mprotect $scalar, $offset, $length, $protect
		281	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		282	IO::AIO::munlockall
		283
		284	=head2 API NOTES
150		285
151	All the C<aio_*> calls are more or less thin wrappers around the syscall	286	All the C<aio_*> calls are more or less thin wrappers around the syscall
152	with the same name (sans C<aio_>). The arguments are similar or identical,	287	with the same name (sans C<aio_>). The arguments are similar or identical,
153	and they all accept an additional (and optional) C<$callback> argument	288	and they all accept an additional (and optional) C<$callback> argument
154	which must be a code reference. This code reference will get called with	289	which must be a code reference. This code reference will be called after
155	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	290	the syscall has been executed in an asynchronous fashion. The results
156	perl, which usually delivers "false") as it's sole argument when the given	291	of the request will be passed as arguments to the callback (and, if an
157	syscall has been executed asynchronously.	292	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		293	most syscalls return C<-1> on error, unlike perl, which usually delivers
		294	"false").
		295
		296	Some requests (such as C<aio_readdir>) pass the actual results and
		297	communicate failures by passing C<undef>.
158		298
159	All functions expecting a filehandle keep a copy of the filehandle	299	All functions expecting a filehandle keep a copy of the filehandle
160	internally until the request has finished.	300	internally until the request has finished.
161		301
162	All requests return objects of type L<IO::AIO::REQ> that allow further	302	All functions return request objects of type L<IO::AIO::REQ> that allow
163	manipulation of those requests while they are in-flight.	303	further manipulation of those requests while they are in-flight.
164		304
165	The pathnames you pass to these routines I<must> be absolute and	305	The pathnames you pass to these routines I<should> be absolute. The
166	encoded in byte form. The reason for the former is that at the time the	306	reason for this is that at the time the request is being executed, the
167	request is being executed, the current working directory could have	307	current working directory could have changed. Alternatively, you can
168	changed. Alternatively, you can make sure that you never change the	308	make sure that you never change the current working directory anywhere
169	current working directory.	309	in the program and then use relative paths. You can also take advantage
		310	of IO::AIOs working directory abstraction, that lets you specify paths
		311	relative to some previously-opened "working directory object" - see the
		312	description of the C<IO::AIO::WD> class later in this document.
170		313
171	To encode pathnames to byte form, either make sure you either: a)	314	To encode pathnames as octets, either make sure you either: a) always pass
172	always pass in filenames you got from outside (command line, readdir	315	in filenames you got from outside (command line, readdir etc.) without
173	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	316	tinkering, b) are in your native filesystem encoding, c) use the Encode
174	your pathnames to the locale (or other) encoding in effect in the user	317	module and encode your pathnames to the locale (or other) encoding in
175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	318	effect in the user environment, d) use Glib::filename_from_unicode on
176	use something else.	319	unicode filenames or e) use something else to ensure your scalar has the
		320	correct contents.
		321
		322	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		323	handles correctly whether it is set or not.
		324
		325	=head2 AIO REQUEST FUNCTIONS
177		326
178	=over 4	327	=over 4
179		328
180	=item aioreq_pri $pri	329	=item $prev_pri = aioreq_pri [$pri]
181		330
182	Sets the priority for the next aio request. The default priority	331	Returns the priority value that would be used for the next request and, if
		332	C<$pri> is given, sets the priority for the next aio request.
		333
183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,	334	The default priority is C<0>, the minimum and maximum priorities are C<-4>
184	respectively. Requests with higher priority will be serviced first.	335	and C<4>, respectively. Requests with higher priority will be serviced
		336	first.
185		337
186	The priority will be reset to C<0> after each call to one of the C<aio_>	338	The priority will be reset to C<0> after each call to one of the C<aio_*>
187	functions.	339	functions.
188		340
189	Example: open a file with low priority, then read something from it with	341	Example: open a file with low priority, then read something from it with
190	higher priority so the read request is serviced before other low priority	342	higher priority so the read request is serviced before other low priority
191	open requests (potentially spamming the cache):	343	open requests (potentially spamming the cache):
…		…
198	aio_read $_[0], ..., sub {	350	aio_read $_[0], ..., sub {
199	...	351	...
200	};	352	};
201	};	353	};
202		354
		355
203	=item aioreq_nice $pri_adjust	356	=item aioreq_nice $pri_adjust
204		357
205	Similar to C<aioreq_pri>, but subtracts the given value from the current	358	Similar to C<aioreq_pri>, but subtracts the given value from the current
206	priority, so effects are cumulative.	359	priority, so the effect is cumulative.
		360
207		361
208	=item aio_open $pathname, $flags, $mode, $callback->($fh)	362	=item aio_open $pathname, $flags, $mode, $callback->($fh)
209		363
210	Asynchronously open or create a file and call the callback with a newly	364	Asynchronously open or create a file and call the callback with a newly
211	created filehandle for the file.	365	created filehandle for the file.
…		…
217	list. They are the same as used by C<sysopen>.	371	list. They are the same as used by C<sysopen>.
218		372
219	Likewise, C<$mode> specifies the mode of the newly created file, if it	373	Likewise, C<$mode> specifies the mode of the newly created file, if it
220	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	374	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
221	except that it is mandatory (i.e. use C<0> if you don't create new files,	375	except that it is mandatory (i.e. use C<0> if you don't create new files,
222	and C<0666> or C<0777> if you do).	376	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		377	by the umask in effect then the request is being executed, so better never
		378	change the umask.
223		379
224	Example:	380	Example:
225		381
226	aio_open "/etc/passwd", O_RDONLY, 0, sub {	382	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
227	if ($_[0]) {	383	if ($_[0]) {
228	print "open successful, fh is $_[0]\n";	384	print "open successful, fh is $_[0]\n";
229	...	385	...
230	} else {	386	} else {
231	die "open failed: $!\n";	387	die "open failed: $!\n";
232	}	388	}
233	};	389	};
234		390
		391	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		392	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		393	following POSIX and non-POSIX constants are available (missing ones on
		394	your system are, as usual, C<0>):
		395
		396	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		397	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		398	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		399
		400
235	=item aio_close $fh, $callback->($status)	401	=item aio_close $fh, $callback->($status)
236		402
237	Asynchronously close a file and call the callback with the result	403	Asynchronously close a file and call the callback with the result
238	code. I<WARNING:> although accepted, you should not pass in a perl	404	code.
239	filehandle here, as perl will likely close the file descriptor another
240	time when the filehandle is destroyed. Normally, you can safely call perls
241	C<close> or just let filehandles go out of scope.
242		405
243	This is supposed to be a bug in the API, so that might change. It's	406	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
244	therefore best to avoid this function.	407	closing the file descriptor associated with the filehandle itself.
		408
		409	Therefore, C<aio_close> will not close the filehandle - instead it will
		410	use dup2 to overwrite the file descriptor with the write-end of a pipe
		411	(the pipe fd will be created on demand and will be cached).
		412
		413	Or in other words: the file descriptor will be closed, but it will not be
		414	free for reuse until the perl filehandle is closed.
		415
		416	=cut
		417
		418	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		419
		420	Seeks the filehandle to the new C<$offset>, similarly to perl's
		421	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		422	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		423	C<IO::AIO::SEEK_END>).
		424
		425	The resulting absolute offset will be passed to the callback, or C<-1> in
		426	case of an error.
		427
		428	In theory, the C<$whence> constants could be different than the
		429	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		430	so don't panic.
		431
		432	As a GNU/Linux (and maybe Solaris) extension, also the constants
		433	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		434	could be found. No guarantees about suitability for use in C<aio_seek> or
		435	Perl's C<sysseek> can be made though, although I would naively assume they
		436	"just work".
245		437
246	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	438	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
247		439
248	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	440	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
249		441
250	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	442	Reads or writes C<$length> bytes from or to the specified C<$fh> and
251	into the scalar given by C<data> and offset C<dataoffset> and calls the	443	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
252	callback without the actual number of bytes read (or -1 on error, just	444	and calls the callback without the actual number of bytes read (or -1 on
253	like the syscall).	445	error, just like the syscall).
		446
		447	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		448	offset plus the actual number of bytes read.
		449
		450	If C<$offset> is undefined, then the current file descriptor offset will
		451	be used (and updated), otherwise the file descriptor offset will not be
		452	changed by these calls.
		453
		454	If C<$length> is undefined in C<aio_write>, use the remaining length of
		455	C<$data>.
		456
		457	If C<$dataoffset> is less than zero, it will be counted from the end of
		458	C<$data>.
254		459
255	The C<$data> scalar I<MUST NOT> be modified in any way while the request	460	The C<$data> scalar I<MUST NOT> be modified in any way while the request
256	is outstanding. Modifying it can result in segfaults or WW3 (if the	461	is outstanding. Modifying it can result in segfaults or World War III (if
257	necessary/optional hardware is installed).	462	the necessary/optional hardware is installed).
258		463
259	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	464	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
260	offset C<0> within the scalar:	465	offset C<0> within the scalar:
261		466
262	aio_read $fh, 7, 15, $buffer, 0, sub {	467	aio_read $fh, 7, 15, $buffer, 0, sub {
263	$_[0] > 0 or die "read error: $!";	468	$_[0] > 0 or die "read error: $!";
264	print "read $_[0] bytes: <$buffer>\n";	469	print "read $_[0] bytes: <$buffer>\n";
265	};	470	};
266		471
267	=item aio_move $srcpath, $dstpath, $callback->($status)
268
269	Try to move the I<file> (directories not supported as either source or
270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
271	the C<0> (error) or C<-1> ok.
272
273	This is a composite request that tries to rename(2) the file first. If
274	rename files with C<EXDEV>, it creates the destination file with mode 0200
275	and copies the contents of the source file into it using C<aio_sendfile>,
276	followed by restoring atime, mtime, access mode and uid/gid, in that
277	order, and unlinking the C<$srcpath>.
278
279	If an error occurs, the partial destination file will be unlinked, if
280	possible, except when setting atime, mtime, access mode and uid/gid, where
281	errors are being ignored.
282
283	=cut
284
285	sub aio_move($$$) {
286	my ($src, $dst, $cb) = @_;
287
288	my $grp = aio_group $cb;
289
290	add $grp aio_rename $src, $dst, sub {
291	if ($_[0] && $! == EXDEV) {
292	add $grp aio_open $src, O_RDONLY, 0, sub {
293	if (my $src_fh = $_[0]) {
294	my @stat = stat $src_fh;
295
296	add $grp aio_open $dst, O_WRONLY, 0200, sub {
297	if (my $dst_fh = $_[0]) {
298	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
299	close $src_fh;
300
301	if ($_[0] == $stat[7]) {
302	utime $stat[8], $stat[9], $dst;
303	chmod $stat[2] & 07777, $dst_fh;
304	chown $stat[4], $stat[5], $dst_fh;
305	close $dst_fh;
306
307	add $grp aio_unlink $src, sub {
308	$grp->result ($_[0]);
309	};
310	} else {
311	my $errno = $!;
312	add $grp aio_unlink $dst, sub {
313	$! = $errno;
314	$grp->result (-1);
315	};
316	}
317	};
318	} else {
319	$grp->result (-1);
320	}
321	},
322
323	} else {
324	$grp->result (-1);
325	}
326	};
327	} else {
328	$grp->result ($_[0]);
329	}
330	};
331
332	$grp
333	}
334		472
335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	473	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
336		474
337	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	475	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
338	reading at byte offset C<$in_offset>, and starts writing at the current	476	reading at byte offset C<$in_offset>, and starts writing at the current
339	file offset of C<$out_fh>. Because of that, it is not safe to issue more	477	file offset of C<$out_fh>. Because of that, it is not safe to issue more
340	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	478	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
341	other.	479	other. The same C<$in_fh> works fine though, as this function does not
		480	move or use the file offset of C<$in_fh>.
342		481
		482	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		483	are written, and there is no way to find out how many more bytes have been
		484	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		485	number of bytes written to C<$out_fh>. Only if the result value equals
		486	C<$length> one can assume that C<$length> bytes have been read.
		487
		488	Unlike with other C<aio_> functions, it makes a lot of sense to use
		489	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		490	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		491	the socket I/O will be non-blocking. Note, however, that you can run
		492	into a trap where C<aio_sendfile> reads some data with readahead, then
		493	fails to write all data, and when the socket is ready the next time, the
		494	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		495	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		496	resource usage.
		497
343	This call tries to make use of a native C<sendfile> syscall to provide	498	This call tries to make use of a native C<sendfile>-like syscall to
344	zero-copy operation. For this to work, C<$out_fh> should refer to a	499	provide zero-copy operation. For this to work, C<$out_fh> should refer to
345	socket, and C<$in_fh> should refer to mmap'able file.	500	a socket, and C<$in_fh> should refer to an mmap'able file.
346		501
347	If the native sendfile call fails or is not implemented, it will be	502	If a native sendfile cannot be found or it fails with C<ENOSYS>,
348	emulated, so you can call C<aio_sendfile> on any type of filehandle	503	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		504	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
349	regardless of the limitations of the operating system.	505	type of filehandle regardless of the limitations of the operating system.
350		506
351	Please note, however, that C<aio_sendfile> can read more bytes from	507	As native sendfile syscalls (as practically any non-POSIX interface hacked
352	C<$in_fh> than are written, and there is no way to find out how many	508	together in a hurry to improve benchmark numbers) tend to be rather buggy
353	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	509	on many systems, this implementation tries to work around some known bugs
354	provides the number of bytes written to C<$out_fh>. Only if the result	510	in Linux and FreeBSD kernels (probably others, too), but that might fail,
355	value equals C<$length> one can assume that C<$length> bytes have been	511	so you really really should check the return value of C<aio_sendfile> -
356	read.	512	fewre bytes than expected might have been transferred.
		513
357		514
358	=item aio_readahead $fh,$offset,$length, $callback->($retval)	515	=item aio_readahead $fh,$offset,$length, $callback->($retval)
359		516
360	C<aio_readahead> populates the page cache with data from a file so that	517	C<aio_readahead> populates the page cache with data from a file so that
361	subsequent reads from that file will not block on disk I/O. The C<$offset>	518	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
367	file. The current file offset of the file is left unchanged.	524	file. The current file offset of the file is left unchanged.
368		525
369	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	526	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
370	emulated by simply reading the data, which would have a similar effect.	527	emulated by simply reading the data, which would have a similar effect.
371		528
		529
372	=item aio_stat $fh_or_path, $callback->($status)	530	=item aio_stat $fh_or_path, $callback->($status)
373		531
374	=item aio_lstat $fh, $callback->($status)	532	=item aio_lstat $fh, $callback->($status)
375		533
376	Works like perl's C<stat> or C<lstat> in void context. The callback will	534	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
381	for an explanation.	539	for an explanation.
382		540
383	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	541	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
384	error when stat'ing a large file, the results will be silently truncated	542	error when stat'ing a large file, the results will be silently truncated
385	unless perl itself is compiled with large file support.	543	unless perl itself is compiled with large file support.
		544
		545	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		546	following constants and functions (if not implemented, the constants will
		547	be C<0> and the functions will either C<croak> or fall back on traditional
		548	behaviour).
		549
		550	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		551	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		552	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
386		553
387	Example: Print the length of F</etc/passwd>:	554	Example: Print the length of F</etc/passwd>:
388		555
389	aio_stat "/etc/passwd", sub {	556	aio_stat "/etc/passwd", sub {
390	$_[0] and die "stat failed: $!";	557	$_[0] and die "stat failed: $!";
391	print "size is ", -s _, "\n";	558	print "size is ", -s _, "\n";
392	};	559	};
393		560
		561
		562	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		563
		564	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		565	whether a file handle or path was passed.
		566
		567	On success, the callback is passed a hash reference with the following
		568	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		569	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		570	is passed.
		571
		572	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		573	C<ST_NOSUID>.
		574
		575	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		576	their correct value when available, or to C<0> on systems that do
		577	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		578	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		579	C<ST_NODIRATIME> and C<ST_RELATIME>.
		580
		581	Example: stat C</wd> and dump out the data if successful.
		582
		583	aio_statvfs "/wd", sub {
		584	my $f = $_[0]
		585	or die "statvfs: $!";
		586
		587	use Data::Dumper;
		588	say Dumper $f;
		589	};
		590
		591	# result:
		592	{
		593	bsize => 1024,
		594	bfree => 4333064312,
		595	blocks => 10253828096,
		596	files => 2050765568,
		597	flag => 4096,
		598	favail => 2042092649,
		599	bavail => 4333064312,
		600	ffree => 2042092649,
		601	namemax => 255,
		602	frsize => 1024,
		603	fsid => 1810
		604	}
		605
		606
		607	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		608
		609	Works like perl's C<utime> function (including the special case of $atime
		610	and $mtime being undef). Fractional times are supported if the underlying
		611	syscalls support them.
		612
		613	When called with a pathname, uses utimes(2) if available, otherwise
		614	utime(2). If called on a file descriptor, uses futimes(2) if available,
		615	otherwise returns ENOSYS, so this is not portable.
		616
		617	Examples:
		618
		619	# set atime and mtime to current time (basically touch(1)):
		620	aio_utime "path", undef, undef;
		621	# set atime to current time and mtime to beginning of the epoch:
		622	aio_utime "path", time, undef; # undef==0
		623
		624
		625	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		626
		627	Works like perl's C<chown> function, except that C<undef> for either $uid
		628	or $gid is being interpreted as "do not change" (but -1 can also be used).
		629
		630	Examples:
		631
		632	# same as "chown root path" in the shell:
		633	aio_chown "path", 0, -1;
		634	# same as above:
		635	aio_chown "path", 0, undef;
		636
		637
		638	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		639
		640	Works like truncate(2) or ftruncate(2).
		641
		642
		643	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		644
		645	Works like perl's C<chmod> function.
		646
		647
394	=item aio_unlink $pathname, $callback->($status)	648	=item aio_unlink $pathname, $callback->($status)
395		649
396	Asynchronously unlink (delete) a file and call the callback with the	650	Asynchronously unlink (delete) a file and call the callback with the
397	result code.	651	result code.
398		652
		653
		654	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		655
		656	[EXPERIMENTAL]
		657
		658	Asynchronously create a device node (or fifo). See mknod(2).
		659
		660	The only (POSIX-) portable way of calling this function is:
		661
		662	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		663
		664	See C<aio_stat> for info about some potentially helpful extra constants
		665	and functions.
		666
399	=item aio_link $srcpath, $dstpath, $callback->($status)	667	=item aio_link $srcpath, $dstpath, $callback->($status)
400		668
401	Asynchronously create a new link to the existing object at C<$srcpath> at	669	Asynchronously create a new link to the existing object at C<$srcpath> at
402	the path C<$dstpath> and call the callback with the result code.	670	the path C<$dstpath> and call the callback with the result code.
403		671
		672
404	=item aio_symlink $srcpath, $dstpath, $callback->($status)	673	=item aio_symlink $srcpath, $dstpath, $callback->($status)
405		674
406	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	675	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
407	the path C<$dstpath> and call the callback with the result code.	676	the path C<$dstpath> and call the callback with the result code.
408		677
		678
		679	=item aio_readlink $pathname, $callback->($link)
		680
		681	Asynchronously read the symlink specified by C<$path> and pass it to
		682	the callback. If an error occurs, nothing or undef gets passed to the
		683	callback.
		684
		685
		686	=item aio_realpath $pathname, $callback->($path)
		687
		688	Asynchronously make the path absolute and resolve any symlinks in
		689	C<$path>. The resulting path only consists of directories (Same as
		690	L<Cwd::realpath>).
		691
		692	This request can be used to get the absolute path of the current working
		693	directory by passing it a path of F<.> (a single dot).
		694
		695
409	=item aio_rename $srcpath, $dstpath, $callback->($status)	696	=item aio_rename $srcpath, $dstpath, $callback->($status)
410		697
411	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	698	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
412	rename(2) and call the callback with the result code.	699	rename(2) and call the callback with the result code.
413		700
		701
		702	=item aio_mkdir $pathname, $mode, $callback->($status)
		703
		704	Asynchronously mkdir (create) a directory and call the callback with
		705	the result code. C<$mode> will be modified by the umask at the time the
		706	request is executed, so do not change your umask.
		707
		708
414	=item aio_rmdir $pathname, $callback->($status)	709	=item aio_rmdir $pathname, $callback->($status)
415		710
416	Asynchronously rmdir (delete) a directory and call the callback with the	711	Asynchronously rmdir (delete) a directory and call the callback with the
417	result code.	712	result code.
		713
418		714
419	=item aio_readdir $pathname, $callback->($entries)	715	=item aio_readdir $pathname, $callback->($entries)
420		716
421	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	717	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
422	directory (i.e. opendir + readdir + closedir). The entries will not be	718	directory (i.e. opendir + readdir + closedir). The entries will not be
423	sorted, and will B<NOT> include the C<.> and C<..> entries.	719	sorted, and will B<NOT> include the C<.> and C<..> entries.
424		720
425	The callback a single argument which is either C<undef> or an array-ref	721	The callback is passed a single argument which is either C<undef> or an
426	with the filenames.	722	array-ref with the filenames.
427		723
		724
		725	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		726
		727	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		728	tune behaviour and output format. In case of an error, C<$entries> will be
		729	C<undef>.
		730
		731	The flags are a combination of the following constants, ORed together (the
		732	flags will also be passed to the callback, possibly modified):
		733
		734	=over 4
		735
		736	=item IO::AIO::READDIR_DENTS
		737
		738	When this flag is off, then the callback gets an arrayref consisting of
		739	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		740	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		741	entry in more detail.
		742
		743	C<$name> is the name of the entry.
		744
		745	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		746
		747	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		748	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		749	C<IO::AIO::DT_WHT>.
		750
		751	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		752	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		753	scalars are read-only: you can not modify them.
		754
		755	C<$inode> is the inode number (which might not be exact on systems with 64
		756	bit inode numbers and 32 bit perls). This field has unspecified content on
		757	systems that do not deliver the inode information.
		758
		759	=item IO::AIO::READDIR_DIRS_FIRST
		760
		761	When this flag is set, then the names will be returned in an order where
		762	likely directories come first, in optimal stat order. This is useful when
		763	you need to quickly find directories, or you want to find all directories
		764	while avoiding to stat() each entry.
		765
		766	If the system returns type information in readdir, then this is used
		767	to find directories directly. Otherwise, likely directories are names
		768	beginning with ".", or otherwise names with no dots, of which names with
		769	short names are tried first.
		770
		771	=item IO::AIO::READDIR_STAT_ORDER
		772
		773	When this flag is set, then the names will be returned in an order
		774	suitable for stat()'ing each one. That is, when you plan to stat()
		775	all files in the given directory, then the returned order will likely
		776	be fastest.
		777
		778	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		779	the likely dirs come first, resulting in a less optimal stat order.
		780
		781	=item IO::AIO::READDIR_FOUND_UNKNOWN
		782
		783	This flag should not be set when calling C<aio_readdirx>. Instead, it
		784	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		785	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		786	C<$type>'s are known, which can be used to speed up some algorithms.
		787
		788	=back
		789
		790
		791	=item aio_load $pathname, $data, $callback->($status)
		792
		793	This is a composite request that tries to fully load the given file into
		794	memory. Status is the same as with aio_read.
		795
		796	=cut
		797
		798	sub aio_load($$;$) {
		799	my ($path, undef, $cb) = @_;
		800	my $data = \$_[1];
		801
		802	my $pri = aioreq_pri;
		803	my $grp = aio_group $cb;
		804
		805	aioreq_pri $pri;
		806	add $grp aio_open $path, O_RDONLY, 0, sub {
		807	my $fh = shift
		808	or return $grp->result (-1);
		809
		810	aioreq_pri $pri;
		811	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		812	$grp->result ($_[0]);
		813	};
		814	};
		815
		816	$grp
		817	}
		818
		819	=item aio_copy $srcpath, $dstpath, $callback->($status)
		820
		821	Try to copy the I<file> (directories not supported as either source or
		822	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		823	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		824
		825	This is a composite request that creates the destination file with
		826	mode 0200 and copies the contents of the source file into it using
		827	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		828	uid/gid, in that order.
		829
		830	If an error occurs, the partial destination file will be unlinked, if
		831	possible, except when setting atime, mtime, access mode and uid/gid, where
		832	errors are being ignored.
		833
		834	=cut
		835
		836	sub aio_copy($$;$) {
		837	my ($src, $dst, $cb) = @_;
		838
		839	my $pri = aioreq_pri;
		840	my $grp = aio_group $cb;
		841
		842	aioreq_pri $pri;
		843	add $grp aio_open $src, O_RDONLY, 0, sub {
		844	if (my $src_fh = $_[0]) {
		845	my @stat = stat $src_fh; # hmm, might block over nfs?
		846
		847	aioreq_pri $pri;
		848	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		849	if (my $dst_fh = $_[0]) {
		850	aioreq_pri $pri;
		851	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		852	if ($_[0] == $stat[7]) {
		853	$grp->result (0);
		854	close $src_fh;
		855
		856	my $ch = sub {
		857	aioreq_pri $pri;
		858	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		859	aioreq_pri $pri;
		860	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		861	aioreq_pri $pri;
		862	add $grp aio_close $dst_fh;
		863	}
		864	};
		865	};
		866
		867	aioreq_pri $pri;
		868	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		869	if ($_[0] < 0 && $! == ENOSYS) {
		870	aioreq_pri $pri;
		871	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		872	} else {
		873	$ch->();
		874	}
		875	};
		876	} else {
		877	$grp->result (-1);
		878	close $src_fh;
		879	close $dst_fh;
		880
		881	aioreq $pri;
		882	add $grp aio_unlink $dst;
		883	}
		884	};
		885	} else {
		886	$grp->result (-1);
		887	}
		888	},
		889
		890	} else {
		891	$grp->result (-1);
		892	}
		893	};
		894
		895	$grp
		896	}
		897
		898	=item aio_move $srcpath, $dstpath, $callback->($status)
		899
		900	Try to move the I<file> (directories not supported as either source or
		901	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		902	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		903
		904	This is a composite request that tries to rename(2) the file first; if
		905	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		906	that is successful, unlinks the C<$srcpath>.
		907
		908	=cut
		909
		910	sub aio_move($$;$) {
		911	my ($src, $dst, $cb) = @_;
		912
		913	my $pri = aioreq_pri;
		914	my $grp = aio_group $cb;
		915
		916	aioreq_pri $pri;
		917	add $grp aio_rename $src, $dst, sub {
		918	if ($_[0] && $! == EXDEV) {
		919	aioreq_pri $pri;
		920	add $grp aio_copy $src, $dst, sub {
		921	$grp->result ($_[0]);
		922
		923	unless ($_[0]) {
		924	aioreq_pri $pri;
		925	add $grp aio_unlink $src;
		926	}
		927	};
		928	} else {
		929	$grp->result ($_[0]);
		930	}
		931	};
		932
		933	$grp
		934	}
		935
428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	936	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
429		937
430	Scans a directory (similar to C<aio_readdir>) but additionally tries to	938	Scans a directory (similar to C<aio_readdir>) but additionally tries to
431	efficiently separate the entries of directory C<$path> into two sets of	939	efficiently separate the entries of directory C<$path> into two sets of
432	names, directories you can recurse into (directories), and ones you cannot	940	names, directories you can recurse into (directories), and ones you cannot
433	recurse into (everything else, including symlinks to directories).	941	recurse into (everything else, including symlinks to directories).
434		942
435	C<aio_scandir> is a composite request that creates of many sub requests_	943	C<aio_scandir> is a composite request that creates of many sub requests_
436	C<$maxreq> specifies the maximum number of outstanding aio requests that	944	C<$maxreq> specifies the maximum number of outstanding aio requests that
437	this function generates. If it is C<< <= 0 >>, then a suitable default	945	this function generates. If it is C<< <= 0 >>, then a suitable default
438	will be chosen (currently 6).	946	will be chosen (currently 4).
439		947
440	On error, the callback is called without arguments, otherwise it receives	948	On error, the callback is called without arguments, otherwise it receives
441	two array-refs with path-relative entry names.	949	two array-refs with path-relative entry names.
442		950
443	Example:	951	Example:
…		…
450		958
451	Implementation notes.	959	Implementation notes.
452		960
453	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	961	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
454		962
		963	If readdir returns file type information, then this is used directly to
		964	find directories.
		965
455	After reading the directory, the modification time, size etc. of the	966	Otherwise, after reading the directory, the modification time, size etc.
456	directory before and after the readdir is checked, and if they match (and	967	of the directory before and after the readdir is checked, and if they
457	isn't the current time), the link count will be used to decide how many	968	match (and isn't the current time), the link count will be used to decide
458	entries are directories (if >= 2). Otherwise, no knowledge of the number	969	how many entries are directories (if >= 2). Otherwise, no knowledge of the
459	of subdirectories will be assumed.	970	number of subdirectories will be assumed.
460		971
461	Then entries will be sorted into likely directories (everything without	972	Then entries will be sorted into likely directories a non-initial dot
462	a non-initial dot currently) and likely non-directories (everything	973	currently) and likely non-directories (see C<aio_readdirx>). Then every
463	else). Then every entry plus an appended C</.> will be C<stat>'ed,	974	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
464	likely directories first. If that succeeds, it assumes that the entry	975	in order of their inode numbers. If that succeeds, it assumes that the
465	is a directory or a symlink to directory (which will be checked	976	entry is a directory or a symlink to directory (which will be checked
466	seperately). This is often faster than stat'ing the entry itself because	977	separately). This is often faster than stat'ing the entry itself because
467	filesystems might detect the type of the entry without reading the inode	978	filesystems might detect the type of the entry without reading the inode
468	data (e.g. ext2fs filetype feature).	979	data (e.g. ext2fs filetype feature), even on systems that cannot return
		980	the filetype information on readdir.
469		981
470	If the known number of directories (link count - 2) has been reached, the	982	If the known number of directories (link count - 2) has been reached, the
471	rest of the entries is assumed to be non-directories.	983	rest of the entries is assumed to be non-directories.
472		984
473	This only works with certainty on POSIX (= UNIX) filesystems, which	985	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
477	as those tend to return 0 or 1 as link counts, which disables the	989	as those tend to return 0 or 1 as link counts, which disables the
478	directory counting heuristic.	990	directory counting heuristic.
479		991
480	=cut	992	=cut
481		993
482	sub aio_scandir($$$) {	994	sub aio_scandir($$;$) {
483	my ($path, $maxreq, $cb) = @_;	995	my ($path, $maxreq, $cb) = @_;
484		996
		997	my $pri = aioreq_pri;
		998
485	my $grp = aio_group $cb;	999	my $grp = aio_group $cb;
486		1000
487	$maxreq = 6 if $maxreq <= 0;	1001	$maxreq = 4 if $maxreq <= 0;
488		1002
489	# stat once	1003	# get a wd object
		1004	aioreq_pri $pri;
490	add $grp aio_stat $path, sub {	1005	add $grp aio_wd $path, sub {
		1006	$_[0]
		1007	or return $grp->result ();
		1008
		1009	my $wd = [shift, "."];
		1010
		1011	# stat once
		1012	aioreq_pri $pri;
		1013	add $grp aio_stat $wd, sub {
491	return $grp->result () if $_[0];	1014	return $grp->result () if $_[0];
492	my $now = time;	1015	my $now = time;
493	my $hash1 = join ":", (stat _)[0,1,3,7,9];	1016	my $hash1 = join ":", (stat _)[0,1,3,7,9];
494		1017
495	# read the directory entries	1018	# read the directory entries
496	add $grp aio_readdir $path, sub {	1019	aioreq_pri $pri;
		1020	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
497	my $entries = shift	1021	my $entries = shift
498	or return $grp->result ();	1022	or return $grp->result ();
499		1023
500	# stat the dir another time	1024	# stat the dir another time
		1025	aioreq_pri $pri;
501	add $grp aio_stat $path, sub {	1026	add $grp aio_stat $wd, sub {
502	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1027	my $hash2 = join ":", (stat _)[0,1,3,7,9];
503		1028
504	my $ndirs;	1029	my $ndirs;
505		1030
506	# take the slow route if anything looks fishy	1031	# take the slow route if anything looks fishy
507	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1032	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
508	$ndirs = -1;	1033	$ndirs = -1;
509	} else {	1034	} else {
510	# if nlink == 2, we are finished	1035	# if nlink == 2, we are finished
511	# on non-posix-fs's, we rely on nlink < 2	1036	# for non-posix-fs's, we rely on nlink < 2
512	$ndirs = (stat _)[3] - 2	1037	$ndirs = (stat _)[3] - 2
513	or return $grp->result ([], $entries);	1038	or return $grp->result ([], $entries);
514	}	1039	}
515		1040
516	# sort into likely dirs and likely nondirs
517	# dirs == files without ".", short entries first
518	$entries = [map $_->[0],
519	sort { $b->[1] cmp $a->[1] }
520	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
521	@$entries];
522
523	my (@dirs, @nondirs);	1041	my (@dirs, @nondirs);
524		1042
525	my $statgrp = add $grp aio_group sub {	1043	my $statgrp = add $grp aio_group sub {
526	$grp->result (\@dirs, \@nondirs);	1044	$grp->result (\@dirs, \@nondirs);
527	};	1045	};
528		1046
529	limit $statgrp $maxreq;	1047	limit $statgrp $maxreq;
530	feed $statgrp sub {	1048	feed $statgrp sub {
531	return unless @$entries;	1049	return unless @$entries;
532	my $entry = pop @$entries;	1050	my $entry = shift @$entries;
533		1051
		1052	aioreq_pri $pri;
		1053	$wd->[1] = "$entry/.";
534	add $statgrp aio_stat "$path/$entry/.", sub {	1054	add $statgrp aio_stat $wd, sub {
535	if ($_[0] < 0) {	1055	if ($_[0] < 0) {
536	push @nondirs, $entry;	1056	push @nondirs, $entry;
537	} else {	1057	} else {
538	# need to check for real directory	1058	# need to check for real directory
		1059	aioreq_pri $pri;
		1060	$wd->[1] = $entry;
539	add $statgrp aio_lstat "$path/$entry", sub {	1061	add $statgrp aio_lstat $wd, sub {
540	if (-d _) {	1062	if (-d _) {
541	push @dirs, $entry;	1063	push @dirs, $entry;
542		1064
543	unless (--$ndirs) {	1065	unless (--$ndirs) {
544	push @nondirs, @$entries;	1066	push @nondirs, @$entries;
545	feed $statgrp;	1067	feed $statgrp;
		1068	}
		1069	} else {
		1070	push @nondirs, $entry;
546	}	1071	}
547	} else {
548	push @nondirs, $entry;
549	}	1072	}
550	}	1073	}
551	}	1074	};
552	};	1075	};
553	};	1076	};
554	};	1077	};
555	};	1078	};
556	};	1079	};
557		1080
558	$grp	1081	$grp
559	}	1082	}
560		1083
		1084	=item aio_rmtree $pathname, $callback->($status)
		1085
		1086	Delete a directory tree starting (and including) C<$path>, return the
		1087	status of the final C<rmdir> only. This is a composite request that
		1088	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1089	everything else.
		1090
		1091	=cut
		1092
		1093	sub aio_rmtree;
		1094	sub aio_rmtree($;$) {
		1095	my ($path, $cb) = @_;
		1096
		1097	my $pri = aioreq_pri;
		1098	my $grp = aio_group $cb;
		1099
		1100	aioreq_pri $pri;
		1101	add $grp aio_scandir $path, 0, sub {
		1102	my ($dirs, $nondirs) = @_;
		1103
		1104	my $dirgrp = aio_group sub {
		1105	add $grp aio_rmdir $path, sub {
		1106	$grp->result ($_[0]);
		1107	};
		1108	};
		1109
		1110	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1111	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1112
		1113	add $grp $dirgrp;
		1114	};
		1115
		1116	$grp
		1117	}
		1118
		1119	=item aio_sync $callback->($status)
		1120
		1121	Asynchronously call sync and call the callback when finished.
		1122
561	=item aio_fsync $fh, $callback->($status)	1123	=item aio_fsync $fh, $callback->($status)
562		1124
563	Asynchronously call fsync on the given filehandle and call the callback	1125	Asynchronously call fsync on the given filehandle and call the callback
564	with the fsync result code.	1126	with the fsync result code.
565		1127
…		…
568	Asynchronously call fdatasync on the given filehandle and call the	1130	Asynchronously call fdatasync on the given filehandle and call the
569	callback with the fdatasync result code.	1131	callback with the fdatasync result code.
570		1132
571	If this call isn't available because your OS lacks it or it couldn't be	1133	If this call isn't available because your OS lacks it or it couldn't be
572	detected, it will be emulated by calling C<fsync> instead.	1134	detected, it will be emulated by calling C<fsync> instead.
		1135
		1136	=item aio_syncfs $fh, $callback->($status)
		1137
		1138	Asynchronously call the syncfs syscall to sync the filesystem associated
		1139	to the given filehandle and call the callback with the syncfs result
		1140	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1141	errno to C<ENOSYS> nevertheless.
		1142
		1143	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1144
		1145	Sync the data portion of the file specified by C<$offset> and C<$length>
		1146	to disk (but NOT the metadata), by calling the Linux-specific
		1147	sync_file_range call. If sync_file_range is not available or it returns
		1148	ENOSYS, then fdatasync or fsync is being substituted.
		1149
		1150	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1151	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1152	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1153	manpage for details.
		1154
		1155	=item aio_pathsync $pathname, $callback->($status)
		1156
		1157	This request tries to open, fsync and close the given path. This is a
		1158	composite request intended to sync directories after directory operations
		1159	(E.g. rename). This might not work on all operating systems or have any
		1160	specific effect, but usually it makes sure that directory changes get
		1161	written to disc. It works for anything that can be opened for read-only,
		1162	not just directories.
		1163
		1164	Future versions of this function might fall back to other methods when
		1165	C<fsync> on the directory fails (such as calling C<sync>).
		1166
		1167	Passes C<0> when everything went ok, and C<-1> on error.
		1168
		1169	=cut
		1170
		1171	sub aio_pathsync($;$) {
		1172	my ($path, $cb) = @_;
		1173
		1174	my $pri = aioreq_pri;
		1175	my $grp = aio_group $cb;
		1176
		1177	aioreq_pri $pri;
		1178	add $grp aio_open $path, O_RDONLY, 0, sub {
		1179	my ($fh) = @_;
		1180	if ($fh) {
		1181	aioreq_pri $pri;
		1182	add $grp aio_fsync $fh, sub {
		1183	$grp->result ($_[0]);
		1184
		1185	aioreq_pri $pri;
		1186	add $grp aio_close $fh;
		1187	};
		1188	} else {
		1189	$grp->result (-1);
		1190	}
		1191	};
		1192
		1193	$grp
		1194	}
		1195
		1196	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1197
		1198	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1199	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1200	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1201	scalar must only be modified in-place while an aio operation is pending on
		1202	it).
		1203
		1204	It calls the C<msync> function of your OS, if available, with the memory
		1205	area starting at C<$offset> in the string and ending C<$length> bytes
		1206	later. If C<$length> is negative, counts from the end, and if C<$length>
		1207	is C<undef>, then it goes till the end of the string. The flags can be
		1208	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1209	C<IO::AIO::MS_SYNC>.
		1210
		1211	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1212
		1213	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1214	scalars.
		1215
		1216	It touches (reads or writes) all memory pages in the specified
		1217	range inside the scalar. All caveats and parameters are the same
		1218	as for C<aio_msync>, above, except for flags, which must be either
		1219	C<0> (which reads all pages and ensures they are instantiated) or
		1220	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1221	writing an octet from it, which dirties the page).
		1222
		1223	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1224
		1225	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1226	scalars.
		1227
		1228	It reads in all the pages of the underlying storage into memory (if any)
		1229	and locks them, so they are not getting swapped/paged out or removed.
		1230
		1231	If C<$length> is undefined, then the scalar will be locked till the end.
		1232
		1233	On systems that do not implement C<mlock>, this function returns C<-1>
		1234	and sets errno to C<ENOSYS>.
		1235
		1236	Note that the corresponding C<munlock> is synchronous and is
		1237	documented under L<MISCELLANEOUS FUNCTIONS>.
		1238
		1239	Example: open a file, mmap and mlock it - both will be undone when
		1240	C<$data> gets destroyed.
		1241
		1242	open my $fh, "<", $path or die "$path: $!";
		1243	my $data;
		1244	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1245	aio_mlock $data; # mlock in background
		1246
		1247	=item aio_mlockall $flags, $callback->($status)
		1248
		1249	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1250	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1251
		1252	On systems that do not implement C<mlockall>, this function returns C<-1>
		1253	and sets errno to C<ENOSYS>.
		1254
		1255	Note that the corresponding C<munlockall> is synchronous and is
		1256	documented under L<MISCELLANEOUS FUNCTIONS>.
		1257
		1258	Example: asynchronously lock all current and future pages into memory.
		1259
		1260	aio_mlockall IO::AIO::MCL_FUTURE;
		1261
		1262	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1263
		1264	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1265	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1266	C<ioctl> is not available on your OS, then this rquiest will fail with
		1267	C<ENOSYS>.
		1268
		1269	C<$start> is the starting offset to query extents for, C<$length> is the
		1270	size of the range to query - if it is C<undef>, then the whole file will
		1271	be queried.
		1272
		1273	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1274	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1275	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1276	the data portion.
		1277
		1278	C<$count> is the maximum number of extent records to return. If it is
		1279	C<undef>, then IO::AIO queries all extents of the file. As a very special
		1280	case, if it is C<0>, then the callback receives the number of extents
		1281	instead of the extents themselves.
		1282
		1283	If an error occurs, the callback receives no arguments. The special
		1284	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1285
		1286	Otherwise, the callback receives an array reference with extent
		1287	structures. Each extent structure is an array reference itself, with the
		1288	following members:
		1289
		1290	[$logical, $physical, $length, $flags]
		1291
		1292	Flags is any combination of the following flag values (typically either C<0>
		1293	or C<IO::AIO::FIEMAP_EXTENT_LAST>):
		1294
		1295	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1296	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1297	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1298	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1299	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1300	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
573		1301
574	=item aio_group $callback->(...)	1302	=item aio_group $callback->(...)
575		1303
576	This is a very special aio request: Instead of doing something, it is a	1304	This is a very special aio request: Instead of doing something, it is a
577	container for other aio requests, which is useful if you want to bundle	1305	container for other aio requests, which is useful if you want to bundle
…		…
615	immense (it blocks a thread for a long time) so do not use this function	1343	immense (it blocks a thread for a long time) so do not use this function
616	except to put your application under artificial I/O pressure.	1344	except to put your application under artificial I/O pressure.
617		1345
618	=back	1346	=back
619		1347
		1348
		1349	=head2 IO::AIO::WD - multiple working directories
		1350
		1351	Your process only has one current working directory, which is used by all
		1352	threads. This makes it hard to use relative paths (some other component
		1353	could call C<chdir> at any time, and it is hard to control when the path
		1354	will be used by IO::AIO).
		1355
		1356	One solution for this is to always use absolute paths. This usually works,
		1357	but can be quite slow (the kernel has to walk the whole path on every
		1358	access), and can also be a hassle to implement.
		1359
		1360	Newer POSIX systems have a number of functions (openat, fdopendir,
		1361	futimensat and so on) that make it possible to specify working directories
		1362	per operation.
		1363
		1364	For portability, and because the clowns who "designed", or shall I write,
		1365	perpetrated this new interface were obviously half-drunk, this abstraction
		1366	cannot be perfect, though.
		1367
		1368	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1369	object. This object stores the canonicalised, absolute version of the
		1370	path, and on systems that allow it, also a directory file descriptor.
		1371
		1372	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1373	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1374	object and a pathname instead (or the IO::AIO::WD object alone, which
		1375	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1376	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1377	to that IO::AIO::WD object.
		1378
		1379	For example, to get a wd object for F</etc> and then stat F<passwd>
		1380	inside, you would write:
		1381
		1382	aio_wd "/etc", sub {
		1383	my $etcdir = shift;
		1384
		1385	# although $etcdir can be undef on error, there is generally no reason
		1386	# to check for errors here, as aio_stat will fail with ENOENT
		1387	# when $etcdir is undef.
		1388
		1389	aio_stat [$etcdir, "passwd"], sub {
		1390	# yay
		1391	};
		1392	};
		1393
		1394	That C<aio_wd> is a request and not a normal function shows that creating
		1395	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1396	why it is done asynchronously.
		1397
		1398	To stat the directory obtained with C<aio_wd> above, one could write
		1399	either of the following three request calls:
		1400
		1401	aio_lstat "/etc" , sub { ... # pathname as normal string
		1402	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1403	aio_lstat $wd , sub { ... # shorthand for the previous
		1404
		1405	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1406	object and the pathname string, so you could write the following without
		1407	causing any issues due to C<$path> getting reused:
		1408
		1409	my $path = [$wd, undef];
		1410
		1411	for my $name (qw(abc def ghi)) {
		1412	$path->[1] = $name;
		1413	aio_stat $path, sub {
		1414	# ...
		1415	};
		1416	}
		1417
		1418	There are some caveats: when directories get renamed (or deleted), the
		1419	pathname string doesn't change, so will point to the new directory (or
		1420	nowhere at all), while the directory fd, if available on the system,
		1421	will still point to the original directory. Most functions accepting a
		1422	pathname will use the directory fd on newer systems, and the string on
		1423	older systems. Some functions (such as realpath) will always rely on the
		1424	string form of the pathname.
		1425
		1426	So this fucntionality is mainly useful to get some protection against
		1427	C<chdir>, to easily get an absolute path out of a relative path for future
		1428	reference, and to speed up doing many operations in the same directory
		1429	(e.g. when stat'ing all files in a directory).
		1430
		1431	The following functions implement this working directory abstraction:
		1432
		1433	=over 4
		1434
		1435	=item aio_wd $pathname, $callback->($wd)
		1436
		1437	Asynchonously canonicalise the given pathname and convert it to an
		1438	IO::AIO::WD object representing it. If possible and supported on the
		1439	system, also open a directory fd to speed up pathname resolution relative
		1440	to this working directory.
		1441
		1442	If something goes wrong, then C<undef> is passwd to the callback instead
		1443	of a working directory object and C<$!> is set appropriately. Since
		1444	passing C<undef> as working directory component of a pathname fails the
		1445	request with C<ENOENT>, there is often no need for error checking in the
		1446	C<aio_wd> callback, as future requests using the value will fail in the
		1447	expected way.
		1448
		1449	If this call isn't available because your OS lacks it or it couldn't be
		1450	detected, it will be emulated by calling C<fsync> instead.
		1451
		1452	=item IO::AIO::CWD
		1453
		1454	This is a compiletime constant (object) that represents the process
		1455	current working directory.
		1456
		1457	Specifying this object as working directory object for a pathname is as
		1458	if the pathname would be specified directly, without a directory object,
		1459	e.g., these calls are functionally identical:
		1460
		1461	aio_stat "somefile", sub { ... };
		1462	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1463
		1464	=back
		1465
		1466
620	=head2 IO::AIO::REQ CLASS	1467	=head2 IO::AIO::REQ CLASS
621		1468
622	All non-aggregate C<aio_*> functions return an object of this class when	1469	All non-aggregate C<aio_*> functions return an object of this class when
623	called in non-void context.	1470	called in non-void context.
624		1471
…		…
627	=item cancel $req	1474	=item cancel $req
628		1475
629	Cancels the request, if possible. Has the effect of skipping execution	1476	Cancels the request, if possible. Has the effect of skipping execution
630	when entering the B<execute> state and skipping calling the callback when	1477	when entering the B<execute> state and skipping calling the callback when
631	entering the the B<result> state, but will leave the request otherwise	1478	entering the the B<result> state, but will leave the request otherwise
632	untouched. That means that requests that currently execute will not be	1479	untouched (with the exception of readdir). That means that requests that
633	stopped and resources held by the request will not be freed prematurely.	1480	currently execute will not be stopped and resources held by the request
		1481	will not be freed prematurely.
634		1482
635	=item cb $req $callback->(...)	1483	=item cb $req $callback->(...)
636		1484
637	Replace (or simply set) the callback registered to the request.	1485	Replace (or simply set) the callback registered to the request.
638		1486
…		…
689	Their lifetime, simplified, looks like this: when they are empty, they	1537	Their lifetime, simplified, looks like this: when they are empty, they
690	will finish very quickly. If they contain only requests that are in the	1538	will finish very quickly. If they contain only requests that are in the
691	C<done> state, they will also finish. Otherwise they will continue to	1539	C<done> state, they will also finish. Otherwise they will continue to
692	exist.	1540	exist.
693		1541
694	That means after creating a group you have some time to add requests. And	1542	That means after creating a group you have some time to add requests
695	in the callbacks of those requests, you can add further requests to the	1543	(precisely before the callback has been invoked, which is only done within
696	group. And only when all those requests have finished will the the group	1544	the C<poll_cb>). And in the callbacks of those requests, you can add
697	itself finish.	1545	further requests to the group. And only when all those requests have
		1546	finished will the the group itself finish.
698		1547
699	=over 4	1548	=over 4
700		1549
701	=item add $grp ...	1550	=item add $grp ...
702		1551
…		…
711	=item $grp->cancel_subs	1560	=item $grp->cancel_subs
712		1561
713	Cancel all subrequests and clears any feeder, but not the group request	1562	Cancel all subrequests and clears any feeder, but not the group request
714	itself. Useful when you queued a lot of events but got a result early.	1563	itself. Useful when you queued a lot of events but got a result early.
715		1564
		1565	The group request will finish normally (you cannot add requests to the
		1566	group).
		1567
716	=item $grp->result (...)	1568	=item $grp->result (...)
717		1569
718	Set the result value(s) that will be passed to the group callback when all	1570	Set the result value(s) that will be passed to the group callback when all
719	subrequests have finished. By default, no argument will be passed.	1571	subrequests have finished and set the groups errno to the current value
		1572	of errno (just like calling C<errno> without an error number). By default,
		1573	no argument will be passed and errno is zero.
		1574
		1575	=item $grp->errno ([$errno])
		1576
		1577	Sets the group errno value to C<$errno>, or the current value of errno
		1578	when the argument is missing.
		1579
		1580	Every aio request has an associated errno value that is restored when
		1581	the callback is invoked. This method lets you change this value from its
		1582	default (0).
		1583
		1584	Calling C<result> will also set errno, so make sure you either set C<$!>
		1585	before the call to C<result>, or call c<errno> after it.
720		1586
721	=item feed $grp $callback->($grp)	1587	=item feed $grp $callback->($grp)
722		1588
723	Sets a feeder/generator on this group: every group can have an attached	1589	Sets a feeder/generator on this group: every group can have an attached
724	generator that generates requests if idle. The idea behind this is that,	1590	generator that generates requests if idle. The idea behind this is that,
725	although you could just queue as many requests as you want in a group,	1591	although you could just queue as many requests as you want in a group,
726	this might starve other requests for a potentially long time. For	1592	this might starve other requests for a potentially long time. For example,
727	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1593	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
728	requests, delaying any later requests for a long time.	1594	requests, delaying any later requests for a long time.
729		1595
730	To avoid this, and allow incremental generation of requests, you can	1596	To avoid this, and allow incremental generation of requests, you can
731	instead a group and set a feeder on it that generates those requests. The	1597	instead a group and set a feeder on it that generates those requests. The
732	feed callback will be called whenever there are few enough (see C<limit>,	1598	feed callback will be called whenever there are few enough (see C<limit>,
…		…
737	not impose any limits).	1603	not impose any limits).
738		1604
739	If the feed does not queue more requests when called, it will be	1605	If the feed does not queue more requests when called, it will be
740	automatically removed from the group.	1606	automatically removed from the group.
741		1607
742	If the feed limit is C<0>, it will be set to C<2> automatically.	1608	If the feed limit is C<0> when this method is called, it will be set to
		1609	C<2> automatically.
743		1610
744	Example:	1611	Example:
745		1612
746	# stat all files in @files, but only ever use four aio requests concurrently:	1613	# stat all files in @files, but only ever use four aio requests concurrently:
747		1614
…		…
759	Sets the feeder limit for the group: The feeder will be called whenever	1626	Sets the feeder limit for the group: The feeder will be called whenever
760	the group contains less than this many requests.	1627	the group contains less than this many requests.
761		1628
762	Setting the limit to C<0> will pause the feeding process.	1629	Setting the limit to C<0> will pause the feeding process.
763		1630
		1631	The default value for the limit is C<0>, but note that setting a feeder
		1632	automatically bumps it up to C<2>.
		1633
764	=back	1634	=back
765		1635
766	=head2 SUPPORT FUNCTIONS	1636	=head2 SUPPORT FUNCTIONS
767		1637
		1638	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1639
768	=over 4	1640	=over 4
769		1641
770	=item $fileno = IO::AIO::poll_fileno	1642	=item $fileno = IO::AIO::poll_fileno
771		1643
772	Return the I<request result pipe file descriptor>. This filehandle must be	1644	Return the I<request result pipe file descriptor>. This filehandle must be
773	polled for reading by some mechanism outside this module (e.g. Event or	1645	polled for reading by some mechanism outside this module (e.g. EV, Glib,
774	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1646	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
775	to call C<poll_cb> to check the results.	1647	you have to call C<poll_cb> to check the results.
776		1648
777	See C<poll_cb> for an example.	1649	See C<poll_cb> for an example.
778		1650
779	=item IO::AIO::poll_cb	1651	=item IO::AIO::poll_cb
780		1652
781	Process all outstanding events on the result pipe. You have to call this	1653	Process some outstanding events on the result pipe. You have to call
782	regularly. Returns the number of events processed. Returns immediately	1654	this regularly. Returns C<0> if all events could be processed (or there
783	when no events are outstanding.	1655	were no events to process), or C<-1> if it returned earlier for whatever
		1656	reason. Returns immediately when no events are outstanding. The amount of
		1657	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1658	C<IO::AIO::max_poll_time>.
		1659
		1660	If not all requests were processed for whatever reason, the filehandle
		1661	will still be ready when C<poll_cb> returns, so normally you don't have to
		1662	do anything special to have it called later.
		1663
		1664	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1665	ready, it can be beneficial to call this function from loops which submit
		1666	a lot of requests, to make sure the results get processed when they become
		1667	available and not just when the loop is finished and the event loop takes
		1668	over again. This function returns very fast when there are no outstanding
		1669	requests.
784		1670
785	Example: Install an Event watcher that automatically calls	1671	Example: Install an Event watcher that automatically calls
786	IO::AIO::poll_cb with high priority:	1672	IO::AIO::poll_cb with high priority (more examples can be found in the
		1673	SYNOPSIS section, at the top of this document):
787		1674
788	Event->io (fd => IO::AIO::poll_fileno,	1675	Event->io (fd => IO::AIO::poll_fileno,
789	poll => 'r', async => 1,	1676	poll => 'r', async => 1,
790	cb => \&IO::AIO::poll_cb);	1677	cb => \&IO::AIO::poll_cb);
791		1678
792	=item IO::AIO::poll_wait	1679	=item IO::AIO::poll_wait
793		1680
		1681	If there are any outstanding requests and none of them in the result
794	Wait till the result filehandle becomes ready for reading (simply does a	1682	phase, wait till the result filehandle becomes ready for reading (simply
795	C<select> on the filehandle. This is useful if you want to synchronously wait	1683	does a C<select> on the filehandle. This is useful if you want to
796	for some requests to finish).	1684	synchronously wait for some requests to finish).
797		1685
798	See C<nreqs> for an example.	1686	See C<nreqs> for an example.
799		1687
		1688	=item IO::AIO::poll
		1689
		1690	Waits until some requests have been handled.
		1691
		1692	Returns the number of requests processed, but is otherwise strictly
		1693	equivalent to:
		1694
		1695	IO::AIO::poll_wait, IO::AIO::poll_cb
		1696
800	=item IO::AIO::nreqs	1697	=item IO::AIO::flush
801		1698
802	Returns the number of requests currently outstanding (i.e. for which their	1699	Wait till all outstanding AIO requests have been handled.
803	callback has not been invoked yet).
804		1700
805	Example: wait till there are no outstanding requests anymore:	1701	Strictly equivalent to:
806		1702
807	IO::AIO::poll_wait, IO::AIO::poll_cb	1703	IO::AIO::poll_wait, IO::AIO::poll_cb
808	while IO::AIO::nreqs;	1704	while IO::AIO::nreqs;
809		1705
810	=item IO::AIO::flush	1706	=item IO::AIO::max_poll_reqs $nreqs
811		1707
812	Wait till all outstanding AIO requests have been handled.	1708	=item IO::AIO::max_poll_time $seconds
813		1709
814	Strictly equivalent to:	1710	These set the maximum number of requests (default C<0>, meaning infinity)
		1711	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1712	the maximum amount of time (default C<0>, meaning infinity) spent in
		1713	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1714	of time C<poll_cb> is allowed to use).
815		1715
816	IO::AIO::poll_wait, IO::AIO::poll_cb	1716	Setting C<max_poll_time> to a non-zero value creates an overhead of one
817	while IO::AIO::nreqs;	1717	syscall per request processed, which is not normally a problem unless your
		1718	callbacks are really really fast or your OS is really really slow (I am
		1719	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
818		1720
819	=item IO::AIO::poll	1721	Setting these is useful if you want to ensure some level of
		1722	interactiveness when perl is not fast enough to process all requests in
		1723	time.
820		1724
821	Waits until some requests have been handled.	1725	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
822		1726
823	Strictly equivalent to:	1727	Example: Install an Event watcher that automatically calls
		1728	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1729	program get the CPU sometimes even under high AIO load.
824		1730
825	IO::AIO::poll_wait, IO::AIO::poll_cb	1731	# try not to spend much more than 0.1s in poll_cb
826	if IO::AIO::nreqs;	1732	IO::AIO::max_poll_time 0.1;
		1733
		1734	# use a low priority so other tasks have priority
		1735	Event->io (fd => IO::AIO::poll_fileno,
		1736	poll => 'r', nice => 1,
		1737	cb => &IO::AIO::poll_cb);
		1738
		1739	=back
		1740
		1741	=head3 CONTROLLING THE NUMBER OF THREADS
		1742
		1743	=over
827		1744
828	=item IO::AIO::min_parallel $nthreads	1745	=item IO::AIO::min_parallel $nthreads
829		1746
830	Set the minimum number of AIO threads to C<$nthreads>. The current	1747	Set the minimum number of AIO threads to C<$nthreads>. The current
831	default is C<8>, which means eight asynchronous operations can execute	1748	default is C<8>, which means eight asynchronous operations can execute
832	concurrently at any one time (the number of outstanding requests,	1749	concurrently at any one time (the number of outstanding requests,
833	however, is unlimited).	1750	however, is unlimited).
834		1751
835	IO::AIO starts threads only on demand, when an AIO request is queued and	1752	IO::AIO starts threads only on demand, when an AIO request is queued and
836	no free thread exists.	1753	no free thread exists. Please note that queueing up a hundred requests can
		1754	create demand for a hundred threads, even if it turns out that everything
		1755	is in the cache and could have been processed faster by a single thread.
837		1756
838	It is recommended to keep the number of threads relatively low, as some	1757	It is recommended to keep the number of threads relatively low, as some
839	Linux kernel versions will scale negatively with the number of threads	1758	Linux kernel versions will scale negatively with the number of threads
840	(higher parallelity => MUCH higher latency). With current Linux 2.6	1759	(higher parallelity => MUCH higher latency). With current Linux 2.6
841	versions, 4-32 threads should be fine.	1760	versions, 4-32 threads should be fine.
…		…
855	This module automatically runs C<max_parallel 0> at program end, to ensure	1774	This module automatically runs C<max_parallel 0> at program end, to ensure
856	that all threads are killed and that there are no outstanding requests.	1775	that all threads are killed and that there are no outstanding requests.
857		1776
858	Under normal circumstances you don't need to call this function.	1777	Under normal circumstances you don't need to call this function.
859		1778
		1779	=item IO::AIO::max_idle $nthreads
		1780
		1781	Limit the number of threads (default: 4) that are allowed to idle
		1782	(i.e., threads that did not get a request to process within the idle
		1783	timeout (default: 10 seconds). That means if a thread becomes idle while
		1784	C<$nthreads> other threads are also idle, it will free its resources and
		1785	exit.
		1786
		1787	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1788	to allow for extremely high load situations, but want to free resources
		1789	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1790
		1791	The default is probably ok in most situations, especially if thread
		1792	creation is fast. If thread creation is very slow on your system you might
		1793	want to use larger values.
		1794
		1795	=item IO::AIO::idle_timeout $seconds
		1796
		1797	Sets the minimum idle timeout (default 10) after which worker threads are
		1798	allowed to exit. SEe C<IO::AIO::max_idle>.
		1799
860	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1800	=item IO::AIO::max_outstanding $maxreqs
861		1801
862	[REMOVED]
863
864	Pre-2.x versions used max_outstanding for a crude request queue length limit.
865
866	In 2.x+ you are advised to use a group and a feeder to limit
867	concurrency. The max_outstanding feature ran very unstable (endless
868	recursions causing segfaults, bad interaction with groups etc.) and was
869	removed.
870
871	I am deeply sorry, but I am still on the hunt for a good limiting interface.
872
873	Original description was as follows:
874
875	Sets the maximum number of outstanding requests to C<$nreqs>. If you try	1802	Sets the maximum number of outstanding requests to C<$nreqs>. If
876	to queue up more than this number of requests, the caller will block until	1803	you do queue up more than this number of requests, the next call to
877	some requests have been handled.	1804	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1805	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1806	longer exceeded.
		1807
		1808	In other words, this setting does not enforce a queue limit, but can be
		1809	used to make poll functions block if the limit is exceeded.
		1810
		1811	This is a very bad function to use in interactive programs because it
		1812	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1813	use an C<aio_group> together with a feed callback.
		1814
		1815	It's main use is in scripts without an event loop - when you want to stat
		1816	a lot of files, you can write somehting like this:
		1817
		1818	IO::AIO::max_outstanding 32;
		1819
		1820	for my $path (...) {
		1821	aio_stat $path , ...;
		1822	IO::AIO::poll_cb;
		1823	}
		1824
		1825	IO::AIO::flush;
		1826
		1827	The call to C<poll_cb> inside the loop will normally return instantly, but
		1828	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1829	some requests have been handled. This keeps the loop from pushing a large
		1830	number of C<aio_stat> requests onto the queue.
		1831
		1832	The default value for C<max_outstanding> is very large, so there is no
		1833	practical limit on the number of outstanding requests.
878		1834
879	=back	1835	=back
880		1836
		1837	=head3 STATISTICAL INFORMATION
		1838
		1839	=over
		1840
		1841	=item IO::AIO::nreqs
		1842
		1843	Returns the number of requests currently in the ready, execute or pending
		1844	states (i.e. for which their callback has not been invoked yet).
		1845
		1846	Example: wait till there are no outstanding requests anymore:
		1847
		1848	IO::AIO::poll_wait, IO::AIO::poll_cb
		1849	while IO::AIO::nreqs;
		1850
		1851	=item IO::AIO::nready
		1852
		1853	Returns the number of requests currently in the ready state (not yet
		1854	executed).
		1855
		1856	=item IO::AIO::npending
		1857
		1858	Returns the number of requests currently in the pending state (executed,
		1859	but not yet processed by poll_cb).
		1860
		1861	=back
		1862
		1863	=head3 MISCELLANEOUS FUNCTIONS
		1864
		1865	IO::AIO implements some functions that might be useful, but are not
		1866	asynchronous.
		1867
		1868	=over 4
		1869
		1870	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1871
		1872	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1873	but is blocking (this makes most sense if you know the input data is
		1874	likely cached already and the output filehandle is set to non-blocking
		1875	operations).
		1876
		1877	Returns the number of bytes copied, or C<-1> on error.
		1878
		1879	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1880
		1881	Simply calls the C<posix_fadvise> function (see its
		1882	manpage for details). The following advice constants are
		1883	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1884	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1885	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1886
		1887	On systems that do not implement C<posix_fadvise>, this function returns
		1888	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1889
		1890	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1891
		1892	Simply calls the C<posix_madvise> function (see its
		1893	manpage for details). The following advice constants are
		1894	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1895	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1896
		1897	On systems that do not implement C<posix_madvise>, this function returns
		1898	ENOSYS, otherwise the return value of C<posix_madvise>.
		1899
		1900	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1901
		1902	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1903	$scalar (see its manpage for details). The following protect
		1904	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1905	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1906
		1907	On systems that do not implement C<mprotect>, this function returns
		1908	ENOSYS, otherwise the return value of C<mprotect>.
		1909
		1910	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1911
		1912	Memory-maps a file (or anonymous memory range) and attaches it to the
		1913	given C<$scalar>, which will act like a string scalar.
		1914
		1915	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1916	change the string length, and most read-only operations such as copying it
		1917	or searching it with regexes and so on.
		1918
		1919	Anything else is unsafe and will, at best, result in memory leaks.
		1920
		1921	The memory map associated with the C<$scalar> is automatically removed
		1922	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1923	C<IO::AIO::munmap> functions are called.
		1924
		1925	This calls the C<mmap>(2) function internally. See your system's manual
		1926	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1927
		1928	The C<$length> must be larger than zero and smaller than the actual
		1929	filesize.
		1930
		1931	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1932	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1933
		1934	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1935	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1936	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1937	(which is set to C<MAP_ANON> if your system only provides this
		1938	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1939	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1940	C<IO::AIO::MAP_NONBLOCK>
		1941
		1942	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1943
		1944	C<$offset> is the offset from the start of the file - it generally must be
		1945	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1946
		1947	Example:
		1948
		1949	use Digest::MD5;
		1950	use IO::AIO;
		1951
		1952	open my $fh, "<verybigfile"
		1953	or die "$!";
		1954
		1955	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1956	or die "verybigfile: $!";
		1957
		1958	my $fast_md5 = md5 $data;
		1959
		1960	=item IO::AIO::munmap $scalar
		1961
		1962	Removes a previous mmap and undefines the C<$scalar>.
		1963
		1964	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1965
		1966	Calls the C<munlock> function, undoing the effects of a previous
		1967	C<aio_mlock> call (see its description for details).
		1968
		1969	=item IO::AIO::munlockall
		1970
		1971	Calls the C<munlockall> function.
		1972
		1973	On systems that do not implement C<munlockall>, this function returns
		1974	ENOSYS, otherwise the return value of C<munlockall>.
		1975
		1976	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1977
		1978	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		1979	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		1980	should be the file offset.
		1981
		1982	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		1983	silently corrupt the data in this case.
		1984
		1985	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		1986	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		1987	C<IO::AIO::SPLICE_F_GIFT>.
		1988
		1989	See the C<splice(2)> manpage for details.
		1990
		1991	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		1992
		1993	Calls the GNU/Linux C<tee(2)> syscall, see it's manpage and the
		1994	description for C<IO::AIO::splice> above for details.
		1995
		1996	=back
		1997
881	=cut	1998	=cut
882		1999
883	# support function to convert a fd into a perl filehandle
884	sub _fd2fh {
885	return undef if $_[0] < 0;
886
887	# try to generate nice filehandles
888	my $sym = "IO::AIO::fd#$_[0]";
889	local *$sym;
890
891	open *$sym, "+<&=$_[0]" # usually works under any unix
892	or open *$sym, "<&=$_[0]" # cygwin needs this
893	or open *$sym, ">&=$_[0]" # or this
894	or return undef;
895
896	*$sym
897	}
898
899	min_parallel 8;	2000	min_parallel 8;
900		2001
901	END {	2002	END { flush }
902	max_parallel 0;
903	}
904		2003
905	1;	2004	1;
906		2005
		2006	=head1 EVENT LOOP INTEGRATION
		2007
		2008	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2009	automatically into many event loops:
		2010
		2011	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2012	use AnyEvent::AIO;
		2013
		2014	You can also integrate IO::AIO manually into many event loops, here are
		2015	some examples of how to do this:
		2016
		2017	# EV integration
		2018	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2019
		2020	# Event integration
		2021	Event->io (fd => IO::AIO::poll_fileno,
		2022	poll => 'r',
		2023	cb => \&IO::AIO::poll_cb);
		2024
		2025	# Glib/Gtk2 integration
		2026	add_watch Glib::IO IO::AIO::poll_fileno,
		2027	in => sub { IO::AIO::poll_cb; 1 };
		2028
		2029	# Tk integration
		2030	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2031	readable => \&IO::AIO::poll_cb);
		2032
		2033	# Danga::Socket integration
		2034	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2035	\&IO::AIO::poll_cb);
		2036
907	=head2 FORK BEHAVIOUR	2037	=head2 FORK BEHAVIOUR
908		2038
909	This module should do "the right thing" when the process using it forks:	2039	Usage of pthreads in a program changes the semantics of fork
		2040	considerably. Specifically, only async-safe functions can be called after
		2041	fork. Perl doesn't know about this, so in general, you cannot call fork
		2042	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2043	pthreads, so this applies, but many other extensions and (for inexplicable
		2044	reasons) perl itself often is linked against pthreads, so this limitation
		2045	applies to quite a lot of perls.
910		2046
911	Before the fork, IO::AIO enters a quiescent state where no requests	2047	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
912	can be added in other threads and no results will be processed. After	2048	only works in the process that loaded it. Forking is fully supported, but
913	the fork the parent simply leaves the quiescent state and continues	2049	using IO::AIO in the child is not.
914	request/result processing, while the child frees the request/result queue
915	(so that the requests started before the fork will only be handled in the
916	parent). Threads will be started on demand until the limit set in the
917	parent process has been reached again.
918		2050
919	In short: the parent will, after a short pause, continue as if fork had	2051	You might get around by not I<using> IO::AIO before (or after)
920	not been called, while the child will act as if IO::AIO has not been used	2052	forking. You could also try to call the L<IO::AIO::reinit> function in the
921	yet.	2053	child:
		2054
		2055	=over 4
		2056
		2057	=item IO::AIO::reinit
		2058
		2059	Abandons all current requests and I/O threads and simply reinitialises all
		2060	data structures. This is not an operation supported by any standards, but
		2061	happens to work on GNU/Linux and some newer BSD systems.
		2062
		2063	The only reasonable use for this function is to call it after forking, if
		2064	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2065	the process will result in undefined behaviour. Calling it at any time
		2066	will also result in any undefined (by POSIX) behaviour.
		2067
		2068	=back
922		2069
923	=head2 MEMORY USAGE	2070	=head2 MEMORY USAGE
924		2071
925	Per-request usage:	2072	Per-request usage:
926		2073
…		…
928	bytes of memory. In addition, stat requests need a stat buffer (possibly	2075	bytes of memory. In addition, stat requests need a stat buffer (possibly
929	a few hundred bytes), readdir requires a result buffer and so on. Perl	2076	a few hundred bytes), readdir requires a result buffer and so on. Perl
930	scalars and other data passed into aio requests will also be locked and	2077	scalars and other data passed into aio requests will also be locked and
931	will consume memory till the request has entered the done state.	2078	will consume memory till the request has entered the done state.
932		2079
933	This is now awfully much, so queuing lots of requests is not usually a	2080	This is not awfully much, so queuing lots of requests is not usually a
934	problem.	2081	problem.
935		2082
936	Per-thread usage:	2083	Per-thread usage:
937		2084
938	In the execution phase, some aio requests require more memory for	2085	In the execution phase, some aio requests require more memory for
…		…
943		2090
944	Known bugs will be fixed in the next release.	2091	Known bugs will be fixed in the next release.
945		2092
946	=head1 SEE ALSO	2093	=head1 SEE ALSO
947		2094
948	L<Coro::AIO>.	2095	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2096	more natural syntax.
949		2097
950	=head1 AUTHOR	2098	=head1 AUTHOR
951		2099
952	Marc Lehmann <schmorp@schmorp.de>	2100	Marc Lehmann <schmorp@schmorp.de>
953	http://home.schmorp.de/	2101	http://home.schmorp.de/

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