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Revision 1.88 by root, Sun Oct 29 01:50:29 2006 UTC vs.
Revision 1.223 by root, Fri Apr 6 22:51:02 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>).
55		36
56	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
57	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
58	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
59	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
61	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
62	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
63	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
64	concurrently.	45	concurrently.
65		46
66	While this works on all types of file descriptors (for example sockets),	47	While most of this works on all types of file descriptors (for
67	using these functions on file descriptors that support nonblocking	48	example sockets), using these functions on file descriptors that
68	operation (again, sockets, pipes etc.) is very inefficient. Use an event	49	support nonblocking operation (again, sockets, pipes etc.) is
69	loop for that (such as the L<Event|Event> module): IO::AIO will naturally	50	very inefficient. Use an event loop for that (such as the L<EV>
70	fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
71		52
72	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
73	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
74	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
75	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
…		…
77	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
78	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
79	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
80	using threads anyway.	61	using threads anyway.
81		62
82	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,
83	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
84	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
85	never call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
86		67
87	=head2 EXAMPLE	68	=head2 EXAMPLE
88		69
89	This is a simple example that uses the Event module and loads	70	This is a simple example that uses the EV module and loads
90	F</etc/passwd> asynchronously:	71	F</etc/passwd> asynchronously:
91		72
92	use Fcntl;	73	use Fcntl;
93	use Event;	74	use EV;
94	use IO::AIO;	75	use IO::AIO;
95		76
96	# register the IO::AIO callback with Event	77	# register the IO::AIO callback with EV
97	Event->io (fd => IO::AIO::poll_fileno,	78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
98	poll => 'r',
99	cb => \&IO::AIO::poll_cb);
100		79
101	# queue the request to open /etc/passwd	80	# queue the request to open /etc/passwd
102	aio_open "/etc/passwd", O_RDONLY, 0, sub {	81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
103	my $fh = $_[0]	82	my $fh = shift
104	or die "error while opening: $!";	83	or die "error while opening: $!";
105		84
106	# stat'ing filehandles is generally non-blocking	85	# stat'ing filehandles is generally non-blocking
107	my $size = -s $fh;	86	my $size = -s $fh;
108		87
…		…
116		95
117	# file contents now in $contents	96	# file contents now in $contents
118	print $contents;	97	print $contents;
119		98
120	# exit event loop and program	99	# exit event loop and program
121	Event::unloop;	100	EV::unloop;
122	};	101	};
123	};	102	};
124		103
125	# possibly queue up other requests, or open GUI windows,	104	# possibly queue up other requests, or open GUI windows,
126	# check for sockets etc. etc.	105	# check for sockets etc. etc.
127		106
128	# process events as long as there are some:	107	# process events as long as there are some:
129	Event::loop;	108	EV::loop;
130		109
131	=head1 REQUEST ANATOMY AND LIFETIME	110	=head1 REQUEST ANATOMY AND LIFETIME
132		111
133	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
134	directly visible to Perl.	113	directly visible to Perl.
…		…
182		161
183	=cut	162	=cut
184		163
185	package IO::AIO;	164	package IO::AIO;
186		165
187	no warnings;	166	use Carp ();
188	use strict 'vars';	167
		168	use common::sense;
189		169
190	use base 'Exporter';	170	use base 'Exporter';
191		171
192	BEGIN {	172	BEGIN {
193	our $VERSION = '2.1';	173	our $VERSION = '4.13';
194		174
195	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
196	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
197	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
198	aio_copy aio_group aio_nop aio_mknod);	178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead aio_fiemap
		180	aio_rename aio_link aio_move aio_copy aio_group
		181	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		182	aio_chmod aio_utime aio_truncate
		183	aio_msync aio_mtouch aio_mlock aio_mlockall
		184	aio_statvfs
		185	aio_wd);
		186
199	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
200	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
201	min_parallel max_parallel max_idle	189	min_parallel max_parallel max_idle idle_timeout
202	nreqs nready npending nthreads	190	nreqs nready npending nthreads
203	max_poll_time max_poll_reqs);	191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
204		196
205	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
206		198
207	require XSLoader;	199	require XSLoader;
208	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
209	}	201	}
210		202
211	=head1 FUNCTIONS	203	=head1 FUNCTIONS
212		204
213	=head2 AIO REQUEST FUNCTIONS	205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes of the most important functions
		208	for quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_seek $fh,$offset,$whence, $callback->($offs)
		215	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		217	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		218	aio_readahead $fh,$offset,$length, $callback->($retval)
		219	aio_stat $fh_or_path, $callback->($status)
		220	aio_lstat $fh, $callback->($status)
		221	aio_statvfs $fh_or_path, $callback->($statvfs)
		222	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		223	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_truncate $fh_or_path, $offset, $callback->($status)
		226	aio_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::madvise $scalar, $offset, $length, $advice
		278	IO::AIO::mprotect $scalar, $offset, $length, $protect
		279	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		280	IO::AIO::munlockall
		281
		282	=head2 API NOTES
214		283
215	All the C<aio_*> calls are more or less thin wrappers around the syscall	284	All the C<aio_*> calls are more or less thin wrappers around the syscall
216	with the same name (sans C<aio_>). The arguments are similar or identical,	285	with the same name (sans C<aio_>). The arguments are similar or identical,
217	and they all accept an additional (and optional) C<$callback> argument	286	and they all accept an additional (and optional) C<$callback> argument
218	which must be a code reference. This code reference will get called with	287	which must be a code reference. This code reference will be called after
219	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	288	the syscall has been executed in an asynchronous fashion. The results
220	perl, which usually delivers "false") as it's sole argument when the given	289	of the request will be passed as arguments to the callback (and, if an
221	syscall has been executed asynchronously.	290	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		291	most syscalls return C<-1> on error, unlike perl, which usually delivers
		292	"false").
		293
		294	Some requests (such as C<aio_readdir>) pass the actual results and
		295	communicate failures by passing C<undef>.
222		296
223	All functions expecting a filehandle keep a copy of the filehandle	297	All functions expecting a filehandle keep a copy of the filehandle
224	internally until the request has finished.	298	internally until the request has finished.
225		299
226	All functions return request objects of type L<IO::AIO::REQ> that allow	300	All functions return request objects of type L<IO::AIO::REQ> that allow
227	further manipulation of those requests while they are in-flight.	301	further manipulation of those requests while they are in-flight.
228		302
229	The pathnames you pass to these routines I<must> be absolute and	303	The pathnames you pass to these routines I<should> be absolute. The
230	encoded as octets. The reason for the former is that at the time the	304	reason for this is that at the time the request is being executed, the
231	request is being executed, the current working directory could have	305	current working directory could have changed. Alternatively, you can
232	changed. Alternatively, you can make sure that you never change the	306	make sure that you never change the current working directory anywhere
233	current working directory anywhere in the program and then use relative	307	in the program and then use relative paths. You can also take advantage
234	paths.	308	of IO::AIOs working directory abstraction, that lets you specify paths
		309	relative to some previously-opened "working directory object" - see the
		310	description of the C<IO::AIO::WD> class later in this document.
235		311
236	To encode pathnames as octets, either make sure you either: a) always pass	312	To encode pathnames as octets, either make sure you either: a) always pass
237	in filenames you got from outside (command line, readdir etc.) without	313	in filenames you got from outside (command line, readdir etc.) without
238	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	314	tinkering, b) are in your native filesystem encoding, c) use the Encode
239	your pathnames to the locale (or other) encoding in effect in the user	315	module and encode your pathnames to the locale (or other) encoding in
240	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	316	effect in the user environment, d) use Glib::filename_from_unicode on
241	use something else to ensure your scalar has the correct contents.	317	unicode filenames or e) use something else to ensure your scalar has the
		318	correct contents.
242		319
243	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	320	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
244	handles correctly wether it is set or not.	321	handles correctly whether it is set or not.
		322
		323	=head2 AIO REQUEST FUNCTIONS
245		324
246	=over 4	325	=over 4
247		326
248	=item $prev_pri = aioreq_pri [$pri]	327	=item $prev_pri = aioreq_pri [$pri]
249		328
…		…
269	aio_read $_[0], ..., sub {	348	aio_read $_[0], ..., sub {
270	...	349	...
271	};	350	};
272	};	351	};
273		352
		353
274	=item aioreq_nice $pri_adjust	354	=item aioreq_nice $pri_adjust
275		355
276	Similar to C<aioreq_pri>, but subtracts the given value from the current	356	Similar to C<aioreq_pri>, but subtracts the given value from the current
277	priority, so the effect is cumulative.	357	priority, so the effect is cumulative.
		358
278		359
279	=item aio_open $pathname, $flags, $mode, $callback->($fh)	360	=item aio_open $pathname, $flags, $mode, $callback->($fh)
280		361
281	Asynchronously open or create a file and call the callback with a newly	362	Asynchronously open or create a file and call the callback with a newly
282	created filehandle for the file.	363	created filehandle for the file.
…		…
288	list. They are the same as used by C<sysopen>.	369	list. They are the same as used by C<sysopen>.
289		370
290	Likewise, C<$mode> specifies the mode of the newly created file, if it	371	Likewise, C<$mode> specifies the mode of the newly created file, if it
291	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	372	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
292	except that it is mandatory (i.e. use C<0> if you don't create new files,	373	except that it is mandatory (i.e. use C<0> if you don't create new files,
293	and C<0666> or C<0777> if you do).	374	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		375	by the umask in effect then the request is being executed, so better never
		376	change the umask.
294		377
295	Example:	378	Example:
296		379
297	aio_open "/etc/passwd", O_RDONLY, 0, sub {	380	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
298	if ($_[0]) {	381	if ($_[0]) {
299	print "open successful, fh is $_[0]\n";	382	print "open successful, fh is $_[0]\n";
300	...	383	...
301	} else {	384	} else {
302	die "open failed: $!\n";	385	die "open failed: $!\n";
303	}	386	}
304	};	387	};
305		388
		389	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		390	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		391	following POSIX and non-POSIX constants are available (missing ones on
		392	your system are, as usual, C<0>):
		393
		394	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		395	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		396	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		397
		398
306	=item aio_close $fh, $callback->($status)	399	=item aio_close $fh, $callback->($status)
307		400
308	Asynchronously close a file and call the callback with the result	401	Asynchronously close a file and call the callback with the result
309	code. I<WARNING:> although accepted, you should not pass in a perl	402	code.
310	filehandle here, as perl will likely close the file descriptor another
311	time when the filehandle is destroyed. Normally, you can safely call perls
312	C<close> or just let filehandles go out of scope.
313		403
314	This is supposed to be a bug in the API, so that might change. It's	404	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
315	therefore best to avoid this function.	405	closing the file descriptor associated with the filehandle itself.
		406
		407	Therefore, C<aio_close> will not close the filehandle - instead it will
		408	use dup2 to overwrite the file descriptor with the write-end of a pipe
		409	(the pipe fd will be created on demand and will be cached).
		410
		411	Or in other words: the file descriptor will be closed, but it will not be
		412	free for reuse until the perl filehandle is closed.
		413
		414	=cut
		415
		416	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		417
		418	Seeks the filehandle to the new C<$offset>, similarly to perl's
		419	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		420	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		421	C<IO::AIO::SEEK_END>).
		422
		423	The resulting absolute offset will be passed to the callback, or C<-1> in
		424	case of an error.
		425
		426	In theory, the C<$whence> constants could be different than the
		427	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		428	so don't panic.
316		429
317	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	430	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
318		431
319	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	432	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
320		433
321	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	434	Reads or writes C<$length> bytes from or to the specified C<$fh> and
322	into the scalar given by C<data> and offset C<dataoffset> and calls the	435	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
323	callback without the actual number of bytes read (or -1 on error, just	436	and calls the callback without the actual number of bytes read (or -1 on
324	like the syscall).	437	error, just like the syscall).
		438
		439	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		440	offset plus the actual number of bytes read.
		441
		442	If C<$offset> is undefined, then the current file descriptor offset will
		443	be used (and updated), otherwise the file descriptor offset will not be
		444	changed by these calls.
		445
		446	If C<$length> is undefined in C<aio_write>, use the remaining length of
		447	C<$data>.
		448
		449	If C<$dataoffset> is less than zero, it will be counted from the end of
		450	C<$data>.
325		451
326	The C<$data> scalar I<MUST NOT> be modified in any way while the request	452	The C<$data> scalar I<MUST NOT> be modified in any way while the request
327	is outstanding. Modifying it can result in segfaults or WW3 (if the	453	is outstanding. Modifying it can result in segfaults or World War III (if
328	necessary/optional hardware is installed).	454	the necessary/optional hardware is installed).
329		455
330	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	456	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
331	offset C<0> within the scalar:	457	offset C<0> within the scalar:
332		458
333	aio_read $fh, 7, 15, $buffer, 0, sub {	459	aio_read $fh, 7, 15, $buffer, 0, sub {
334	$_[0] > 0 or die "read error: $!";	460	$_[0] > 0 or die "read error: $!";
335	print "read $_[0] bytes: <$buffer>\n";	461	print "read $_[0] bytes: <$buffer>\n";
336	};	462	};
337		463
		464
338	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	465	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
339		466
340	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	467	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
341	reading at byte offset C<$in_offset>, and starts writing at the current	468	reading at byte offset C<$in_offset>, and starts writing at the current
342	file offset of C<$out_fh>. Because of that, it is not safe to issue more	469	file offset of C<$out_fh>. Because of that, it is not safe to issue more
343	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	470	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
344	other.	471	other. The same C<$in_fh> works fine though, as this function does not
		472	move or use the file offset of C<$in_fh>.
345		473
		474	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		475	are written, and there is no way to find out how many more bytes have been
		476	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		477	number of bytes written to C<$out_fh>. Only if the result value equals
		478	C<$length> one can assume that C<$length> bytes have been read.
		479
		480	Unlike with other C<aio_> functions, it makes a lot of sense to use
		481	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		482	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		483	the socket I/O will be non-blocking. Note, however, that you can run
		484	into a trap where C<aio_sendfile> reads some data with readahead, then
		485	fails to write all data, and when the socket is ready the next time, the
		486	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		487	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		488	resource usage.
		489
346	This call tries to make use of a native C<sendfile> syscall to provide	490	This call tries to make use of a native C<sendfile>-like syscall to
347	zero-copy operation. For this to work, C<$out_fh> should refer to a	491	provide zero-copy operation. For this to work, C<$out_fh> should refer to
348	socket, and C<$in_fh> should refer to mmap'able file.	492	a socket, and C<$in_fh> should refer to an mmap'able file.
349		493
350	If the native sendfile call fails or is not implemented, it will be	494	If a native sendfile cannot be found or it fails with C<ENOSYS>,
351	emulated, so you can call C<aio_sendfile> on any type of filehandle	495	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		496	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
352	regardless of the limitations of the operating system.	497	type of filehandle regardless of the limitations of the operating system.
353		498
354	Please note, however, that C<aio_sendfile> can read more bytes from	499	As native sendfile syscalls (as practically any non-POSIX interface hacked
355	C<$in_fh> than are written, and there is no way to find out how many	500	together in a hurry to improve benchmark numbers) tend to be rather buggy
356	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	501	on many systems, this implementation tries to work around some known bugs
357	provides the number of bytes written to C<$out_fh>. Only if the result	502	in Linux and FreeBSD kernels (probably others, too), but that might fail,
358	value equals C<$length> one can assume that C<$length> bytes have been	503	so you really really should check the return value of C<aio_sendfile> -
359	read.	504	fewre bytes than expected might have been transferred.
		505
360		506
361	=item aio_readahead $fh,$offset,$length, $callback->($retval)	507	=item aio_readahead $fh,$offset,$length, $callback->($retval)
362		508
363	C<aio_readahead> populates the page cache with data from a file so that	509	C<aio_readahead> populates the page cache with data from a file so that
364	subsequent reads from that file will not block on disk I/O. The C<$offset>	510	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
370	file. The current file offset of the file is left unchanged.	516	file. The current file offset of the file is left unchanged.
371		517
372	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	518	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
373	emulated by simply reading the data, which would have a similar effect.	519	emulated by simply reading the data, which would have a similar effect.
374		520
		521
375	=item aio_stat $fh_or_path, $callback->($status)	522	=item aio_stat $fh_or_path, $callback->($status)
376		523
377	=item aio_lstat $fh, $callback->($status)	524	=item aio_lstat $fh, $callback->($status)
378		525
379	Works like perl's C<stat> or C<lstat> in void context. The callback will	526	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
384	for an explanation.	531	for an explanation.
385		532
386	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	533	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
387	error when stat'ing a large file, the results will be silently truncated	534	error when stat'ing a large file, the results will be silently truncated
388	unless perl itself is compiled with large file support.	535	unless perl itself is compiled with large file support.
		536
		537	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		538	following constants and functions (if not implemented, the constants will
		539	be C<0> and the functions will either C<croak> or fall back on traditional
		540	behaviour).
		541
		542	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		543	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		544	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
389		545
390	Example: Print the length of F</etc/passwd>:	546	Example: Print the length of F</etc/passwd>:
391		547
392	aio_stat "/etc/passwd", sub {	548	aio_stat "/etc/passwd", sub {
393	$_[0] and die "stat failed: $!";	549	$_[0] and die "stat failed: $!";
394	print "size is ", -s _, "\n";	550	print "size is ", -s _, "\n";
395	};	551	};
396		552
		553
		554	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		555
		556	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		557	whether a file handle or path was passed.
		558
		559	On success, the callback is passed a hash reference with the following
		560	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		561	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		562	is passed.
		563
		564	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		565	C<ST_NOSUID>.
		566
		567	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		568	their correct value when available, or to C<0> on systems that do
		569	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		570	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		571	C<ST_NODIRATIME> and C<ST_RELATIME>.
		572
		573	Example: stat C</wd> and dump out the data if successful.
		574
		575	aio_statvfs "/wd", sub {
		576	my $f = $_[0]
		577	or die "statvfs: $!";
		578
		579	use Data::Dumper;
		580	say Dumper $f;
		581	};
		582
		583	# result:
		584	{
		585	bsize => 1024,
		586	bfree => 4333064312,
		587	blocks => 10253828096,
		588	files => 2050765568,
		589	flag => 4096,
		590	favail => 2042092649,
		591	bavail => 4333064312,
		592	ffree => 2042092649,
		593	namemax => 255,
		594	frsize => 1024,
		595	fsid => 1810
		596	}
		597
		598
		599	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		600
		601	Works like perl's C<utime> function (including the special case of $atime
		602	and $mtime being undef). Fractional times are supported if the underlying
		603	syscalls support them.
		604
		605	When called with a pathname, uses utimes(2) if available, otherwise
		606	utime(2). If called on a file descriptor, uses futimes(2) if available,
		607	otherwise returns ENOSYS, so this is not portable.
		608
		609	Examples:
		610
		611	# set atime and mtime to current time (basically touch(1)):
		612	aio_utime "path", undef, undef;
		613	# set atime to current time and mtime to beginning of the epoch:
		614	aio_utime "path", time, undef; # undef==0
		615
		616
		617	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		618
		619	Works like perl's C<chown> function, except that C<undef> for either $uid
		620	or $gid is being interpreted as "do not change" (but -1 can also be used).
		621
		622	Examples:
		623
		624	# same as "chown root path" in the shell:
		625	aio_chown "path", 0, -1;
		626	# same as above:
		627	aio_chown "path", 0, undef;
		628
		629
		630	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		631
		632	Works like truncate(2) or ftruncate(2).
		633
		634
		635	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		636
		637	Works like perl's C<chmod> function.
		638
		639
397	=item aio_unlink $pathname, $callback->($status)	640	=item aio_unlink $pathname, $callback->($status)
398		641
399	Asynchronously unlink (delete) a file and call the callback with the	642	Asynchronously unlink (delete) a file and call the callback with the
400	result code.	643	result code.
401		644
		645
402	=item aio_mknod $path, $mode, $dev, $callback->($status)	646	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
403		647
404	[EXPERIMENTAL]	648	[EXPERIMENTAL]
405		649
406	Asynchronously create a device node (or fifo). See mknod(2).	650	Asynchronously create a device node (or fifo). See mknod(2).
407		651
408	The only (POSIX-) portable way of calling this function is:	652	The only (POSIX-) portable way of calling this function is:
409		653
410	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	654	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		655
		656	See C<aio_stat> for info about some potentially helpful extra constants
		657	and functions.
411		658
412	=item aio_link $srcpath, $dstpath, $callback->($status)	659	=item aio_link $srcpath, $dstpath, $callback->($status)
413		660
414	Asynchronously create a new link to the existing object at C<$srcpath> at	661	Asynchronously create a new link to the existing object at C<$srcpath> at
415	the path C<$dstpath> and call the callback with the result code.	662	the path C<$dstpath> and call the callback with the result code.
416		663
		664
417	=item aio_symlink $srcpath, $dstpath, $callback->($status)	665	=item aio_symlink $srcpath, $dstpath, $callback->($status)
418		666
419	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	667	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
420	the path C<$dstpath> and call the callback with the result code.	668	the path C<$dstpath> and call the callback with the result code.
421		669
		670
		671	=item aio_readlink $pathname, $callback->($link)
		672
		673	Asynchronously read the symlink specified by C<$path> and pass it to
		674	the callback. If an error occurs, nothing or undef gets passed to the
		675	callback.
		676
		677
		678	=item aio_realpath $pathname, $callback->($path)
		679
		680	Asynchronously make the path absolute and resolve any symlinks in
		681	C<$path>. The resulting path only consists of directories (Same as
		682	L<Cwd::realpath>).
		683
		684	This request can be used to get the absolute path of the current working
		685	directory by passing it a path of F<.> (a single dot).
		686
		687
422	=item aio_rename $srcpath, $dstpath, $callback->($status)	688	=item aio_rename $srcpath, $dstpath, $callback->($status)
423		689
424	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	690	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
425	rename(2) and call the callback with the result code.	691	rename(2) and call the callback with the result code.
426		692
		693
		694	=item aio_mkdir $pathname, $mode, $callback->($status)
		695
		696	Asynchronously mkdir (create) a directory and call the callback with
		697	the result code. C<$mode> will be modified by the umask at the time the
		698	request is executed, so do not change your umask.
		699
		700
427	=item aio_rmdir $pathname, $callback->($status)	701	=item aio_rmdir $pathname, $callback->($status)
428		702
429	Asynchronously rmdir (delete) a directory and call the callback with the	703	Asynchronously rmdir (delete) a directory and call the callback with the
430	result code.	704	result code.
		705
431		706
432	=item aio_readdir $pathname, $callback->($entries)	707	=item aio_readdir $pathname, $callback->($entries)
433		708
434	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	709	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
435	directory (i.e. opendir + readdir + closedir). The entries will not be	710	directory (i.e. opendir + readdir + closedir). The entries will not be
436	sorted, and will B<NOT> include the C<.> and C<..> entries.	711	sorted, and will B<NOT> include the C<.> and C<..> entries.
437		712
438	The callback a single argument which is either C<undef> or an array-ref	713	The callback is passed a single argument which is either C<undef> or an
439	with the filenames.	714	array-ref with the filenames.
		715
		716
		717	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		718
		719	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		720	tune behaviour and output format. In case of an error, C<$entries> will be
		721	C<undef>.
		722
		723	The flags are a combination of the following constants, ORed together (the
		724	flags will also be passed to the callback, possibly modified):
		725
		726	=over 4
		727
		728	=item IO::AIO::READDIR_DENTS
		729
		730	When this flag is off, then the callback gets an arrayref consisting of
		731	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		732	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		733	entry in more detail.
		734
		735	C<$name> is the name of the entry.
		736
		737	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		738
		739	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		740	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		741	C<IO::AIO::DT_WHT>.
		742
		743	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		744	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		745	scalars are read-only: you can not modify them.
		746
		747	C<$inode> is the inode number (which might not be exact on systems with 64
		748	bit inode numbers and 32 bit perls). This field has unspecified content on
		749	systems that do not deliver the inode information.
		750
		751	=item IO::AIO::READDIR_DIRS_FIRST
		752
		753	When this flag is set, then the names will be returned in an order where
		754	likely directories come first, in optimal stat order. This is useful when
		755	you need to quickly find directories, or you want to find all directories
		756	while avoiding to stat() each entry.
		757
		758	If the system returns type information in readdir, then this is used
		759	to find directories directly. Otherwise, likely directories are names
		760	beginning with ".", or otherwise names with no dots, of which names with
		761	short names are tried first.
		762
		763	=item IO::AIO::READDIR_STAT_ORDER
		764
		765	When this flag is set, then the names will be returned in an order
		766	suitable for stat()'ing each one. That is, when you plan to stat()
		767	all files in the given directory, then the returned order will likely
		768	be fastest.
		769
		770	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		771	the likely dirs come first, resulting in a less optimal stat order.
		772
		773	=item IO::AIO::READDIR_FOUND_UNKNOWN
		774
		775	This flag should not be set when calling C<aio_readdirx>. Instead, it
		776	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		777	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		778	C<$type>'s are known, which can be used to speed up some algorithms.
		779
		780	=back
		781
		782
		783	=item aio_load $pathname, $data, $callback->($status)
		784
		785	This is a composite request that tries to fully load the given file into
		786	memory. Status is the same as with aio_read.
		787
		788	=cut
		789
		790	sub aio_load($$;$) {
		791	my ($path, undef, $cb) = @_;
		792	my $data = \$_[1];
		793
		794	my $pri = aioreq_pri;
		795	my $grp = aio_group $cb;
		796
		797	aioreq_pri $pri;
		798	add $grp aio_open $path, O_RDONLY, 0, sub {
		799	my $fh = shift
		800	or return $grp->result (-1);
		801
		802	aioreq_pri $pri;
		803	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		804	$grp->result ($_[0]);
		805	};
		806	};
		807
		808	$grp
		809	}
440		810
441	=item aio_copy $srcpath, $dstpath, $callback->($status)	811	=item aio_copy $srcpath, $dstpath, $callback->($status)
442		812
443	Try to copy the I<file> (directories not supported as either source or	813	Try to copy the I<file> (directories not supported as either source or
444	destination) from C<$srcpath> to C<$dstpath> and call the callback with	814	destination) from C<$srcpath> to C<$dstpath> and call the callback with
445	the C<0> (error) or C<-1> ok.	815	a status of C<0> (ok) or C<-1> (error, see C<$!>).
446		816
447	This is a composite request that it creates the destination file with	817	This is a composite request that creates the destination file with
448	mode 0200 and copies the contents of the source file into it using	818	mode 0200 and copies the contents of the source file into it using
449	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	819	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
450	uid/gid, in that order.	820	uid/gid, in that order.
451		821
452	If an error occurs, the partial destination file will be unlinked, if	822	If an error occurs, the partial destination file will be unlinked, if
…		…
462	my $grp = aio_group $cb;	832	my $grp = aio_group $cb;
463		833
464	aioreq_pri $pri;	834	aioreq_pri $pri;
465	add $grp aio_open $src, O_RDONLY, 0, sub {	835	add $grp aio_open $src, O_RDONLY, 0, sub {
466	if (my $src_fh = $_[0]) {	836	if (my $src_fh = $_[0]) {
467	my @stat = stat $src_fh;	837	my @stat = stat $src_fh; # hmm, might block over nfs?
468		838
469	aioreq_pri $pri;	839	aioreq_pri $pri;
470	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	840	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
471	if (my $dst_fh = $_[0]) {	841	if (my $dst_fh = $_[0]) {
472	aioreq_pri $pri;	842	aioreq_pri $pri;
473	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	843	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
474	if ($_[0] == $stat[7]) {	844	if ($_[0] == $stat[7]) {
475	$grp->result (0);	845	$grp->result (0);
476	close $src_fh;	846	close $src_fh;
477		847
478	# those should not normally block. should. should.	848	my $ch = sub {
		849	aioreq_pri $pri;
		850	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		851	aioreq_pri $pri;
		852	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		853	aioreq_pri $pri;
		854	add $grp aio_close $dst_fh;
		855	}
		856	};
		857	};
		858
		859	aioreq_pri $pri;
		860	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		861	if ($_[0] < 0 && $! == ENOSYS) {
		862	aioreq_pri $pri;
479	utime $stat[8], $stat[9], $dst;	863	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
480	chmod $stat[2] & 07777, $dst_fh;	864	} else {
481	chown $stat[4], $stat[5], $dst_fh;	865	$ch->();
		866	}
482	close $dst_fh;	867	};
483	} else {	868	} else {
484	$grp->result (-1);	869	$grp->result (-1);
485	close $src_fh;	870	close $src_fh;
486	close $dst_fh;	871	close $dst_fh;
487		872
…		…
504		889
505	=item aio_move $srcpath, $dstpath, $callback->($status)	890	=item aio_move $srcpath, $dstpath, $callback->($status)
506		891
507	Try to move the I<file> (directories not supported as either source or	892	Try to move the I<file> (directories not supported as either source or
508	destination) from C<$srcpath> to C<$dstpath> and call the callback with	893	destination) from C<$srcpath> to C<$dstpath> and call the callback with
509	the C<0> (error) or C<-1> ok.	894	a status of C<0> (ok) or C<-1> (error, see C<$!>).
510		895
511	This is a composite request that tries to rename(2) the file first. If	896	This is a composite request that tries to rename(2) the file first; if
512	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	897	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
513	that is successful, unlinking the C<$srcpath>.	898	that is successful, unlinks the C<$srcpath>.
514		899
515	=cut	900	=cut
516		901
517	sub aio_move($$;$) {	902	sub aio_move($$;$) {
518	my ($src, $dst, $cb) = @_;	903	my ($src, $dst, $cb) = @_;
…		…
525	if ($_[0] && $! == EXDEV) {	910	if ($_[0] && $! == EXDEV) {
526	aioreq_pri $pri;	911	aioreq_pri $pri;
527	add $grp aio_copy $src, $dst, sub {	912	add $grp aio_copy $src, $dst, sub {
528	$grp->result ($_[0]);	913	$grp->result ($_[0]);
529		914
530	if (!$_[0]) {	915	unless ($_[0]) {
531	aioreq_pri $pri;	916	aioreq_pri $pri;
532	add $grp aio_unlink $src;	917	add $grp aio_unlink $src;
533	}	918	}
534	};	919	};
535	} else {	920	} else {
…		…
538	};	923	};
539		924
540	$grp	925	$grp
541	}	926	}
542		927
543	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	928	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
544		929
545	Scans a directory (similar to C<aio_readdir>) but additionally tries to	930	Scans a directory (similar to C<aio_readdir>) but additionally tries to
546	efficiently separate the entries of directory C<$path> into two sets of	931	efficiently separate the entries of directory C<$path> into two sets of
547	names, directories you can recurse into (directories), and ones you cannot	932	names, directories you can recurse into (directories), and ones you cannot
548	recurse into (everything else, including symlinks to directories).	933	recurse into (everything else, including symlinks to directories).
…		…
565		950
566	Implementation notes.	951	Implementation notes.
567		952
568	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	953	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
569		954
		955	If readdir returns file type information, then this is used directly to
		956	find directories.
		957
570	After reading the directory, the modification time, size etc. of the	958	Otherwise, after reading the directory, the modification time, size etc.
571	directory before and after the readdir is checked, and if they match (and	959	of the directory before and after the readdir is checked, and if they
572	isn't the current time), the link count will be used to decide how many	960	match (and isn't the current time), the link count will be used to decide
573	entries are directories (if >= 2). Otherwise, no knowledge of the number	961	how many entries are directories (if >= 2). Otherwise, no knowledge of the
574	of subdirectories will be assumed.	962	number of subdirectories will be assumed.
575		963
576	Then entries will be sorted into likely directories (everything without	964	Then entries will be sorted into likely directories a non-initial dot
577	a non-initial dot currently) and likely non-directories (everything	965	currently) and likely non-directories (see C<aio_readdirx>). Then every
578	else). Then every entry plus an appended C</.> will be C<stat>'ed,	966	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
579	likely directories first. If that succeeds, it assumes that the entry	967	in order of their inode numbers. If that succeeds, it assumes that the
580	is a directory or a symlink to directory (which will be checked	968	entry is a directory or a symlink to directory (which will be checked
581	seperately). This is often faster than stat'ing the entry itself because	969	separately). This is often faster than stat'ing the entry itself because
582	filesystems might detect the type of the entry without reading the inode	970	filesystems might detect the type of the entry without reading the inode
583	data (e.g. ext2fs filetype feature).	971	data (e.g. ext2fs filetype feature), even on systems that cannot return
		972	the filetype information on readdir.
584		973
585	If the known number of directories (link count - 2) has been reached, the	974	If the known number of directories (link count - 2) has been reached, the
586	rest of the entries is assumed to be non-directories.	975	rest of the entries is assumed to be non-directories.
587		976
588	This only works with certainty on POSIX (= UNIX) filesystems, which	977	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
592	as those tend to return 0 or 1 as link counts, which disables the	981	as those tend to return 0 or 1 as link counts, which disables the
593	directory counting heuristic.	982	directory counting heuristic.
594		983
595	=cut	984	=cut
596		985
597	sub aio_scandir($$$) {	986	sub aio_scandir($$;$) {
598	my ($path, $maxreq, $cb) = @_;	987	my ($path, $maxreq, $cb) = @_;
599		988
600	my $pri = aioreq_pri;	989	my $pri = aioreq_pri;
601		990
602	my $grp = aio_group $cb;	991	my $grp = aio_group $cb;
603		992
604	$maxreq = 4 if $maxreq <= 0;	993	$maxreq = 4 if $maxreq <= 0;
605		994
606	# stat once	995	# get a wd object
607	aioreq_pri $pri;	996	aioreq_pri $pri;
608	add $grp aio_stat $path, sub {	997	add $grp aio_wd $path, sub {
		998	$_[0]
609	return $grp->result () if $_[0];	999	or return $grp->result ();
610	my $now = time;
611	my $hash1 = join ":", (stat _)[0,1,3,7,9];
612		1000
613	# read the directory entries	1001	my $wd = [shift, "."];
		1002
		1003	# stat once
614	aioreq_pri $pri;	1004	aioreq_pri $pri;
615	add $grp aio_readdir $path, sub {	1005	add $grp aio_stat $wd, sub {
616	my $entries = shift
617	or return $grp->result ();	1006	return $grp->result () if $_[0];
		1007	my $now = time;
		1008	my $hash1 = join ":", (stat _)[0,1,3,7,9];
618		1009
619	# stat the dir another time	1010	# read the directory entries
620	aioreq_pri $pri;	1011	aioreq_pri $pri;
		1012	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1013	my $entries = shift
		1014	or return $grp->result ();
		1015
		1016	# stat the dir another time
		1017	aioreq_pri $pri;
621	add $grp aio_stat $path, sub {	1018	add $grp aio_stat $wd, sub {
622	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1019	my $hash2 = join ":", (stat _)[0,1,3,7,9];
623		1020
624	my $ndirs;	1021	my $ndirs;
625		1022
626	# take the slow route if anything looks fishy	1023	# take the slow route if anything looks fishy
627	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1024	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
628	$ndirs = -1;	1025	$ndirs = -1;
629	} else {	1026	} else {
630	# if nlink == 2, we are finished	1027	# if nlink == 2, we are finished
631	# on non-posix-fs's, we rely on nlink < 2	1028	# for non-posix-fs's, we rely on nlink < 2
632	$ndirs = (stat _)[3] - 2	1029	$ndirs = (stat _)[3] - 2
633	or return $grp->result ([], $entries);	1030	or return $grp->result ([], $entries);
634	}	1031	}
635		1032
636	# sort into likely dirs and likely nondirs
637	# dirs == files without ".", short entries first
638	$entries = [map $_->[0],
639	sort { $b->[1] cmp $a->[1] }
640	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
641	@$entries];
642
643	my (@dirs, @nondirs);	1033	my (@dirs, @nondirs);
644		1034
645	my $statgrp = add $grp aio_group sub {	1035	my $statgrp = add $grp aio_group sub {
646	$grp->result (\@dirs, \@nondirs);	1036	$grp->result (\@dirs, \@nondirs);
647	};	1037	};
648		1038
649	limit $statgrp $maxreq;	1039	limit $statgrp $maxreq;
650	feed $statgrp sub {	1040	feed $statgrp sub {
651	return unless @$entries;	1041	return unless @$entries;
652	my $entry = pop @$entries;	1042	my $entry = shift @$entries;
653		1043
654	aioreq_pri $pri;	1044	aioreq_pri $pri;
		1045	$wd->[1] = "$entry/.";
655	add $statgrp aio_stat "$path/$entry/.", sub {	1046	add $statgrp aio_stat $wd, sub {
656	if ($_[0] < 0) {	1047	if ($_[0] < 0) {
657	push @nondirs, $entry;	1048	push @nondirs, $entry;
658	} else {	1049	} else {
659	# need to check for real directory	1050	# need to check for real directory
660	aioreq_pri $pri;	1051	aioreq_pri $pri;
		1052	$wd->[1] = $entry;
661	add $statgrp aio_lstat "$path/$entry", sub {	1053	add $statgrp aio_lstat $wd, sub {
662	if (-d _) {	1054	if (-d _) {
663	push @dirs, $entry;	1055	push @dirs, $entry;
664		1056
665	unless (--$ndirs) {	1057	unless (--$ndirs) {
666	push @nondirs, @$entries;	1058	push @nondirs, @$entries;
667	feed $statgrp;	1059	feed $statgrp;
		1060	}
		1061	} else {
		1062	push @nondirs, $entry;
668	}	1063	}
669	} else {
670	push @nondirs, $entry;
671	}	1064	}
672	}	1065	}
673	}	1066	};
674	};	1067	};
675	};	1068	};
676	};	1069	};
677	};	1070	};
678	};	1071	};
679		1072
680	$grp	1073	$grp
681	}	1074	}
682		1075
		1076	=item aio_rmtree $pathname, $callback->($status)
		1077
		1078	Delete a directory tree starting (and including) C<$path>, return the
		1079	status of the final C<rmdir> only. This is a composite request that
		1080	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1081	everything else.
		1082
		1083	=cut
		1084
		1085	sub aio_rmtree;
		1086	sub aio_rmtree($;$) {
		1087	my ($path, $cb) = @_;
		1088
		1089	my $pri = aioreq_pri;
		1090	my $grp = aio_group $cb;
		1091
		1092	aioreq_pri $pri;
		1093	add $grp aio_scandir $path, 0, sub {
		1094	my ($dirs, $nondirs) = @_;
		1095
		1096	my $dirgrp = aio_group sub {
		1097	add $grp aio_rmdir $path, sub {
		1098	$grp->result ($_[0]);
		1099	};
		1100	};
		1101
		1102	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1103	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1104
		1105	add $grp $dirgrp;
		1106	};
		1107
		1108	$grp
		1109	}
		1110
		1111	=item aio_sync $callback->($status)
		1112
		1113	Asynchronously call sync and call the callback when finished.
		1114
683	=item aio_fsync $fh, $callback->($status)	1115	=item aio_fsync $fh, $callback->($status)
684		1116
685	Asynchronously call fsync on the given filehandle and call the callback	1117	Asynchronously call fsync on the given filehandle and call the callback
686	with the fsync result code.	1118	with the fsync result code.
687		1119
…		…
690	Asynchronously call fdatasync on the given filehandle and call the	1122	Asynchronously call fdatasync on the given filehandle and call the
691	callback with the fdatasync result code.	1123	callback with the fdatasync result code.
692		1124
693	If this call isn't available because your OS lacks it or it couldn't be	1125	If this call isn't available because your OS lacks it or it couldn't be
694	detected, it will be emulated by calling C<fsync> instead.	1126	detected, it will be emulated by calling C<fsync> instead.
		1127
		1128	=item aio_syncfs $fh, $callback->($status)
		1129
		1130	Asynchronously call the syncfs syscall to sync the filesystem associated
		1131	to the given filehandle and call the callback with the syncfs result
		1132	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1133	errno to C<ENOSYS> nevertheless.
		1134
		1135	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1136
		1137	Sync the data portion of the file specified by C<$offset> and C<$length>
		1138	to disk (but NOT the metadata), by calling the Linux-specific
		1139	sync_file_range call. If sync_file_range is not available or it returns
		1140	ENOSYS, then fdatasync or fsync is being substituted.
		1141
		1142	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1143	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1144	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1145	manpage for details.
		1146
		1147	=item aio_pathsync $pathname, $callback->($status)
		1148
		1149	This request tries to open, fsync and close the given path. This is a
		1150	composite request intended to sync directories after directory operations
		1151	(E.g. rename). This might not work on all operating systems or have any
		1152	specific effect, but usually it makes sure that directory changes get
		1153	written to disc. It works for anything that can be opened for read-only,
		1154	not just directories.
		1155
		1156	Future versions of this function might fall back to other methods when
		1157	C<fsync> on the directory fails (such as calling C<sync>).
		1158
		1159	Passes C<0> when everything went ok, and C<-1> on error.
		1160
		1161	=cut
		1162
		1163	sub aio_pathsync($;$) {
		1164	my ($path, $cb) = @_;
		1165
		1166	my $pri = aioreq_pri;
		1167	my $grp = aio_group $cb;
		1168
		1169	aioreq_pri $pri;
		1170	add $grp aio_open $path, O_RDONLY, 0, sub {
		1171	my ($fh) = @_;
		1172	if ($fh) {
		1173	aioreq_pri $pri;
		1174	add $grp aio_fsync $fh, sub {
		1175	$grp->result ($_[0]);
		1176
		1177	aioreq_pri $pri;
		1178	add $grp aio_close $fh;
		1179	};
		1180	} else {
		1181	$grp->result (-1);
		1182	}
		1183	};
		1184
		1185	$grp
		1186	}
		1187
		1188	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1189
		1190	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1191	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1192	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1193	scalar must only be modified in-place while an aio operation is pending on
		1194	it).
		1195
		1196	It calls the C<msync> function of your OS, if available, with the memory
		1197	area starting at C<$offset> in the string and ending C<$length> bytes
		1198	later. If C<$length> is negative, counts from the end, and if C<$length>
		1199	is C<undef>, then it goes till the end of the string. The flags can be
		1200	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1201	C<IO::AIO::MS_SYNC>.
		1202
		1203	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1204
		1205	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1206	scalars.
		1207
		1208	It touches (reads or writes) all memory pages in the specified
		1209	range inside the scalar. All caveats and parameters are the same
		1210	as for C<aio_msync>, above, except for flags, which must be either
		1211	C<0> (which reads all pages and ensures they are instantiated) or
		1212	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1213	writing an octet from it, which dirties the page).
		1214
		1215	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1216
		1217	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1218	scalars.
		1219
		1220	It reads in all the pages of the underlying storage into memory (if any)
		1221	and locks them, so they are not getting swapped/paged out or removed.
		1222
		1223	If C<$length> is undefined, then the scalar will be locked till the end.
		1224
		1225	On systems that do not implement C<mlock>, this function returns C<-1>
		1226	and sets errno to C<ENOSYS>.
		1227
		1228	Note that the corresponding C<munlock> is synchronous and is
		1229	documented under L<MISCELLANEOUS FUNCTIONS>.
		1230
		1231	Example: open a file, mmap and mlock it - both will be undone when
		1232	C<$data> gets destroyed.
		1233
		1234	open my $fh, "<", $path or die "$path: $!";
		1235	my $data;
		1236	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1237	aio_mlock $data; # mlock in background
		1238
		1239	=item aio_mlockall $flags, $callback->($status)
		1240
		1241	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1242	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1243
		1244	On systems that do not implement C<mlockall>, this function returns C<-1>
		1245	and sets errno to C<ENOSYS>.
		1246
		1247	Note that the corresponding C<munlockall> is synchronous and is
		1248	documented under L<MISCELLANEOUS FUNCTIONS>.
		1249
		1250	Example: asynchronously lock all current and future pages into memory.
		1251
		1252	aio_mlockall IO::AIO::MCL_FUTURE;
		1253
		1254	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1255
		1256	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1257	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1258	C<ioctl> is not available on your OS, then this rquiest will fail with
		1259	C<ENOSYS>.
		1260
		1261	C<$start> is the starting offset to query extents for, C<$length> is the
		1262	size of the range to query - if it is C<undef>, then the whole file will
		1263	be queried.
		1264
		1265	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1266	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1267	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1268	the data portion.
		1269
		1270	C<$count> is the maximum number of extent records to return. If it is
		1271	C<undef>, then IO::AIO queries all extents of the file. As a very special
		1272	case, if it is C<0>, then the callback receives the number of extents
		1273	instead of the extents themselves.
		1274
		1275	If an error occurs, the callback receives no arguments. The special
		1276	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1277
		1278	Otherwise, the callback receives an array reference with extent
		1279	structures. Each extent structure is an array reference itself, with the
		1280	following members:
		1281
		1282	[$logical, $physical, $length, $flags]
		1283
		1284	Flags is any combination of the following flag values (typically either C<0>
		1285	or C<IO::AIO::FIEMAP_EXTENT_LAST>):
		1286
		1287	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1288	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1289	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1290	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1291	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1292	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
695		1293
696	=item aio_group $callback->(...)	1294	=item aio_group $callback->(...)
697		1295
698	This is a very special aio request: Instead of doing something, it is a	1296	This is a very special aio request: Instead of doing something, it is a
699	container for other aio requests, which is useful if you want to bundle	1297	container for other aio requests, which is useful if you want to bundle
…		…
737	immense (it blocks a thread for a long time) so do not use this function	1335	immense (it blocks a thread for a long time) so do not use this function
738	except to put your application under artificial I/O pressure.	1336	except to put your application under artificial I/O pressure.
739		1337
740	=back	1338	=back
741		1339
		1340
		1341	=head2 IO::AIO::WD - multiple working directories
		1342
		1343	Your process only has one current working directory, which is used by all
		1344	threads. This makes it hard to use relative paths (some other component
		1345	could call C<chdir> at any time, and it is hard to control when the path
		1346	will be used by IO::AIO).
		1347
		1348	One solution for this is to always use absolute paths. This usually works,
		1349	but can be quite slow (the kernel has to walk the whole path on every
		1350	access), and can also be a hassle to implement.
		1351
		1352	Newer POSIX systems have a number of functions (openat, fdopendir,
		1353	futimensat and so on) that make it possible to specify working directories
		1354	per operation.
		1355
		1356	For portability, and because the clowns who "designed", or shall I write,
		1357	perpetrated this new interface were obviously half-drunk, this abstraction
		1358	cannot be perfect, though.
		1359
		1360	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1361	object. This object stores the canonicalised, absolute version of the
		1362	path, and on systems that allow it, also a directory file descriptor.
		1363
		1364	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1365	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1366	object and a pathname instead (or the IO::AIO::WD object alone, which
		1367	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1368	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1369	to that IO::AIO::WD object.
		1370
		1371	For example, to get a wd object for F</etc> and then stat F<passwd>
		1372	inside, you would write:
		1373
		1374	aio_wd "/etc", sub {
		1375	my $etcdir = shift;
		1376
		1377	# although $etcdir can be undef on error, there is generally no reason
		1378	# to check for errors here, as aio_stat will fail with ENOENT
		1379	# when $etcdir is undef.
		1380
		1381	aio_stat [$etcdir, "passwd"], sub {
		1382	# yay
		1383	};
		1384	};
		1385
		1386	That C<aio_wd> is a request and not a normal function shows that creating
		1387	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1388	why it is done asynchronously.
		1389
		1390	To stat the directory obtained with C<aio_wd> above, one could write
		1391	either of the following three request calls:
		1392
		1393	aio_lstat "/etc" , sub { ... # pathname as normal string
		1394	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1395	aio_lstat $wd , sub { ... # shorthand for the previous
		1396
		1397	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1398	object and the pathname string, so you could write the following without
		1399	causing any issues due to C<$path> getting reused:
		1400
		1401	my $path = [$wd, undef];
		1402
		1403	for my $name (qw(abc def ghi)) {
		1404	$path->[1] = $name;
		1405	aio_stat $path, sub {
		1406	# ...
		1407	};
		1408	}
		1409
		1410	There are some caveats: when directories get renamed (or deleted), the
		1411	pathname string doesn't change, so will point to the new directory (or
		1412	nowhere at all), while the directory fd, if available on the system,
		1413	will still point to the original directory. Most functions accepting a
		1414	pathname will use the directory fd on newer systems, and the string on
		1415	older systems. Some functions (such as realpath) will always rely on the
		1416	string form of the pathname.
		1417
		1418	So this fucntionality is mainly useful to get some protection against
		1419	C<chdir>, to easily get an absolute path out of a relative path for future
		1420	reference, and to speed up doing many operations in the same directory
		1421	(e.g. when stat'ing all files in a directory).
		1422
		1423	The following functions implement this working directory abstraction:
		1424
		1425	=over 4
		1426
		1427	=item aio_wd $pathname, $callback->($wd)
		1428
		1429	Asynchonously canonicalise the given pathname and convert it to an
		1430	IO::AIO::WD object representing it. If possible and supported on the
		1431	system, also open a directory fd to speed up pathname resolution relative
		1432	to this working directory.
		1433
		1434	If something goes wrong, then C<undef> is passwd to the callback instead
		1435	of a working directory object and C<$!> is set appropriately. Since
		1436	passing C<undef> as working directory component of a pathname fails the
		1437	request with C<ENOENT>, there is often no need for error checking in the
		1438	C<aio_wd> callback, as future requests using the value will fail in the
		1439	expected way.
		1440
		1441	If this call isn't available because your OS lacks it or it couldn't be
		1442	detected, it will be emulated by calling C<fsync> instead.
		1443
		1444	=item IO::AIO::CWD
		1445
		1446	This is a compiletime constant (object) that represents the process
		1447	current working directory.
		1448
		1449	Specifying this object as working directory object for a pathname is as
		1450	if the pathname would be specified directly, without a directory object,
		1451	e.g., these calls are functionally identical:
		1452
		1453	aio_stat "somefile", sub { ... };
		1454	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1455
		1456	=back
		1457
		1458
742	=head2 IO::AIO::REQ CLASS	1459	=head2 IO::AIO::REQ CLASS
743		1460
744	All non-aggregate C<aio_*> functions return an object of this class when	1461	All non-aggregate C<aio_*> functions return an object of this class when
745	called in non-void context.	1462	called in non-void context.
746		1463
…		…
749	=item cancel $req	1466	=item cancel $req
750		1467
751	Cancels the request, if possible. Has the effect of skipping execution	1468	Cancels the request, if possible. Has the effect of skipping execution
752	when entering the B<execute> state and skipping calling the callback when	1469	when entering the B<execute> state and skipping calling the callback when
753	entering the the B<result> state, but will leave the request otherwise	1470	entering the the B<result> state, but will leave the request otherwise
754	untouched. That means that requests that currently execute will not be	1471	untouched (with the exception of readdir). That means that requests that
755	stopped and resources held by the request will not be freed prematurely.	1472	currently execute will not be stopped and resources held by the request
		1473	will not be freed prematurely.
756		1474
757	=item cb $req $callback->(...)	1475	=item cb $req $callback->(...)
758		1476
759	Replace (or simply set) the callback registered to the request.	1477	Replace (or simply set) the callback registered to the request.
760		1478
…		…
811	Their lifetime, simplified, looks like this: when they are empty, they	1529	Their lifetime, simplified, looks like this: when they are empty, they
812	will finish very quickly. If they contain only requests that are in the	1530	will finish very quickly. If they contain only requests that are in the
813	C<done> state, they will also finish. Otherwise they will continue to	1531	C<done> state, they will also finish. Otherwise they will continue to
814	exist.	1532	exist.
815		1533
816	That means after creating a group you have some time to add requests. And	1534	That means after creating a group you have some time to add requests
817	in the callbacks of those requests, you can add further requests to the	1535	(precisely before the callback has been invoked, which is only done within
818	group. And only when all those requests have finished will the the group	1536	the C<poll_cb>). And in the callbacks of those requests, you can add
819	itself finish.	1537	further requests to the group. And only when all those requests have
		1538	finished will the the group itself finish.
820		1539
821	=over 4	1540	=over 4
822		1541
823	=item add $grp ...	1542	=item add $grp ...
824		1543
…		…
833	=item $grp->cancel_subs	1552	=item $grp->cancel_subs
834		1553
835	Cancel all subrequests and clears any feeder, but not the group request	1554	Cancel all subrequests and clears any feeder, but not the group request
836	itself. Useful when you queued a lot of events but got a result early.	1555	itself. Useful when you queued a lot of events but got a result early.
837		1556
		1557	The group request will finish normally (you cannot add requests to the
		1558	group).
		1559
838	=item $grp->result (...)	1560	=item $grp->result (...)
839		1561
840	Set the result value(s) that will be passed to the group callback when all	1562	Set the result value(s) that will be passed to the group callback when all
841	subrequests have finished and set thre groups errno to the current value	1563	subrequests have finished and set the groups errno to the current value
842	of errno (just like calling C<errno> without an error number). By default,	1564	of errno (just like calling C<errno> without an error number). By default,
843	no argument will be passed and errno is zero.	1565	no argument will be passed and errno is zero.
844		1566
845	=item $grp->errno ([$errno])	1567	=item $grp->errno ([$errno])
846		1568
…		…
857	=item feed $grp $callback->($grp)	1579	=item feed $grp $callback->($grp)
858		1580
859	Sets a feeder/generator on this group: every group can have an attached	1581	Sets a feeder/generator on this group: every group can have an attached
860	generator that generates requests if idle. The idea behind this is that,	1582	generator that generates requests if idle. The idea behind this is that,
861	although you could just queue as many requests as you want in a group,	1583	although you could just queue as many requests as you want in a group,
862	this might starve other requests for a potentially long time. For	1584	this might starve other requests for a potentially long time. For example,
863	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1585	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
864	requests, delaying any later requests for a long time.	1586	requests, delaying any later requests for a long time.
865		1587
866	To avoid this, and allow incremental generation of requests, you can	1588	To avoid this, and allow incremental generation of requests, you can
867	instead a group and set a feeder on it that generates those requests. The	1589	instead a group and set a feeder on it that generates those requests. The
868	feed callback will be called whenever there are few enough (see C<limit>,	1590	feed callback will be called whenever there are few enough (see C<limit>,
…		…
873	not impose any limits).	1595	not impose any limits).
874		1596
875	If the feed does not queue more requests when called, it will be	1597	If the feed does not queue more requests when called, it will be
876	automatically removed from the group.	1598	automatically removed from the group.
877		1599
878	If the feed limit is C<0>, it will be set to C<2> automatically.	1600	If the feed limit is C<0> when this method is called, it will be set to
		1601	C<2> automatically.
879		1602
880	Example:	1603	Example:
881		1604
882	# stat all files in @files, but only ever use four aio requests concurrently:	1605	# stat all files in @files, but only ever use four aio requests concurrently:
883		1606
…		…
895	Sets the feeder limit for the group: The feeder will be called whenever	1618	Sets the feeder limit for the group: The feeder will be called whenever
896	the group contains less than this many requests.	1619	the group contains less than this many requests.
897		1620
898	Setting the limit to C<0> will pause the feeding process.	1621	Setting the limit to C<0> will pause the feeding process.
899		1622
		1623	The default value for the limit is C<0>, but note that setting a feeder
		1624	automatically bumps it up to C<2>.
		1625
900	=back	1626	=back
901		1627
902	=head2 SUPPORT FUNCTIONS	1628	=head2 SUPPORT FUNCTIONS
903		1629
904	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1630	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
906	=over 4	1632	=over 4
907		1633
908	=item $fileno = IO::AIO::poll_fileno	1634	=item $fileno = IO::AIO::poll_fileno
909		1635
910	Return the I<request result pipe file descriptor>. This filehandle must be	1636	Return the I<request result pipe file descriptor>. This filehandle must be
911	polled for reading by some mechanism outside this module (e.g. Event or	1637	polled for reading by some mechanism outside this module (e.g. EV, Glib,
912	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1638	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
913	to call C<poll_cb> to check the results.	1639	you have to call C<poll_cb> to check the results.
914		1640
915	See C<poll_cb> for an example.	1641	See C<poll_cb> for an example.
916		1642
917	=item IO::AIO::poll_cb	1643	=item IO::AIO::poll_cb
918		1644
919	Process some outstanding events on the result pipe. You have to call this	1645	Process some outstanding events on the result pipe. You have to call
920	regularly. Returns the number of events processed. Returns immediately	1646	this regularly. Returns C<0> if all events could be processed (or there
921	when no events are outstanding. The amount of events processed depends on	1647	were no events to process), or C<-1> if it returned earlier for whatever
922	the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.	1648	reason. Returns immediately when no events are outstanding. The amount of
		1649	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1650	C<IO::AIO::max_poll_time>.
923		1651
924	If not all requests were processed for whatever reason, the filehandle	1652	If not all requests were processed for whatever reason, the filehandle
925	will still be ready when C<poll_cb> returns.	1653	will still be ready when C<poll_cb> returns, so normally you don't have to
		1654	do anything special to have it called later.
		1655
		1656	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1657	ready, it can be beneficial to call this function from loops which submit
		1658	a lot of requests, to make sure the results get processed when they become
		1659	available and not just when the loop is finished and the event loop takes
		1660	over again. This function returns very fast when there are no outstanding
		1661	requests.
926		1662
927	Example: Install an Event watcher that automatically calls	1663	Example: Install an Event watcher that automatically calls
928	IO::AIO::poll_cb with high priority:	1664	IO::AIO::poll_cb with high priority (more examples can be found in the
		1665	SYNOPSIS section, at the top of this document):
929		1666
930	Event->io (fd => IO::AIO::poll_fileno,	1667	Event->io (fd => IO::AIO::poll_fileno,
931	poll => 'r', async => 1,	1668	poll => 'r', async => 1,
932	cb => \&IO::AIO::poll_cb);	1669	cb => \&IO::AIO::poll_cb);
		1670
		1671	=item IO::AIO::poll_wait
		1672
		1673	If there are any outstanding requests and none of them in the result
		1674	phase, wait till the result filehandle becomes ready for reading (simply
		1675	does a C<select> on the filehandle. This is useful if you want to
		1676	synchronously wait for some requests to finish).
		1677
		1678	See C<nreqs> for an example.
		1679
		1680	=item IO::AIO::poll
		1681
		1682	Waits until some requests have been handled.
		1683
		1684	Returns the number of requests processed, but is otherwise strictly
		1685	equivalent to:
		1686
		1687	IO::AIO::poll_wait, IO::AIO::poll_cb
		1688
		1689	=item IO::AIO::flush
		1690
		1691	Wait till all outstanding AIO requests have been handled.
		1692
		1693	Strictly equivalent to:
		1694
		1695	IO::AIO::poll_wait, IO::AIO::poll_cb
		1696	while IO::AIO::nreqs;
933		1697
934	=item IO::AIO::max_poll_reqs $nreqs	1698	=item IO::AIO::max_poll_reqs $nreqs
935		1699
936	=item IO::AIO::max_poll_time $seconds	1700	=item IO::AIO::max_poll_time $seconds
937		1701
…		…
939	that are being processed by C<IO::AIO::poll_cb> in one call, respectively	1703	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
940	the maximum amount of time (default C<0>, meaning infinity) spent in	1704	the maximum amount of time (default C<0>, meaning infinity) spent in
941	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount	1705	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
942	of time C<poll_cb> is allowed to use).	1706	of time C<poll_cb> is allowed to use).
943		1707
		1708	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1709	syscall per request processed, which is not normally a problem unless your
		1710	callbacks are really really fast or your OS is really really slow (I am
		1711	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1712
944	Setting these is useful if you want to ensure some level of	1713	Setting these is useful if you want to ensure some level of
945	interactiveness when perl is not fast enough to process all requests in	1714	interactiveness when perl is not fast enough to process all requests in
946	time.	1715	time.
947		1716
948	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	1717	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
949		1718
950	Example: Install an Event watcher that automatically calls	1719	Example: Install an Event watcher that automatically calls
951	IO::AIO::poll_some with low priority, to ensure that other parts of the	1720	IO::AIO::poll_cb with low priority, to ensure that other parts of the
952	program get the CPU sometimes even under high AIO load.	1721	program get the CPU sometimes even under high AIO load.
953		1722
954	# try not to spend much more than 0.1s in poll_cb	1723	# try not to spend much more than 0.1s in poll_cb
955	IO::AIO::max_poll_time 0.1;	1724	IO::AIO::max_poll_time 0.1;
956		1725
957	# use a low priority so other tasks have priority	1726	# use a low priority so other tasks have priority
958	Event->io (fd => IO::AIO::poll_fileno,	1727	Event->io (fd => IO::AIO::poll_fileno,
959	poll => 'r', nice => 1,	1728	poll => 'r', nice => 1,
960	cb => &IO::AIO::poll_cb);	1729	cb => &IO::AIO::poll_cb);
961		1730
962	=item IO::AIO::poll_wait	1731	=back
963
964	Wait till the result filehandle becomes ready for reading (simply does a
965	C<select> on the filehandle. This is useful if you want to synchronously
966	wait for some requests to finish).
967
968	See C<nreqs> for an example.
969
970	=item IO::AIO::poll
971
972	Waits until some requests have been handled.
973
974	Strictly equivalent to:
975
976	IO::AIO::poll_wait, IO::AIO::poll_cb
977	if IO::AIO::nreqs;
978
979	=item IO::AIO::flush
980
981	Wait till all outstanding AIO requests have been handled.
982
983	Strictly equivalent to:
984
985	IO::AIO::poll_wait, IO::AIO::poll_cb
986	while IO::AIO::nreqs;
987		1732
988	=head3 CONTROLLING THE NUMBER OF THREADS	1733	=head3 CONTROLLING THE NUMBER OF THREADS
		1734
		1735	=over
989		1736
990	=item IO::AIO::min_parallel $nthreads	1737	=item IO::AIO::min_parallel $nthreads
991		1738
992	Set the minimum number of AIO threads to C<$nthreads>. The current	1739	Set the minimum number of AIO threads to C<$nthreads>. The current
993	default is C<8>, which means eight asynchronous operations can execute	1740	default is C<8>, which means eight asynchronous operations can execute
…		…
1021		1768
1022	Under normal circumstances you don't need to call this function.	1769	Under normal circumstances you don't need to call this function.
1023		1770
1024	=item IO::AIO::max_idle $nthreads	1771	=item IO::AIO::max_idle $nthreads
1025		1772
1026	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1773	Limit the number of threads (default: 4) that are allowed to idle
1027	threads that did not get a request to process within 10 seconds). That	1774	(i.e., threads that did not get a request to process within the idle
1028	means if a thread becomes idle while C<$nthreads> other threads are also	1775	timeout (default: 10 seconds). That means if a thread becomes idle while
1029	idle, it will free its resources and exit.	1776	C<$nthreads> other threads are also idle, it will free its resources and
		1777	exit.
1030		1778
1031	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1779	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1032	to allow for extremely high load situations, but want to free resources	1780	to allow for extremely high load situations, but want to free resources
1033	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1781	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1034		1782
1035	The default is probably ok in most situations, especially if thread	1783	The default is probably ok in most situations, especially if thread
1036	creation is fast. If thread creation is very slow on your system you might	1784	creation is fast. If thread creation is very slow on your system you might
1037	want to use larger values.	1785	want to use larger values.
1038		1786
		1787	=item IO::AIO::idle_timeout $seconds
		1788
		1789	Sets the minimum idle timeout (default 10) after which worker threads are
		1790	allowed to exit. SEe C<IO::AIO::max_idle>.
		1791
1039	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1792	=item IO::AIO::max_outstanding $maxreqs
		1793
		1794	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1795	you do queue up more than this number of requests, the next call to
		1796	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1797	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1798	longer exceeded.
		1799
		1800	In other words, this setting does not enforce a queue limit, but can be
		1801	used to make poll functions block if the limit is exceeded.
1040		1802
1041	This is a very bad function to use in interactive programs because it	1803	This is a very bad function to use in interactive programs because it
1042	blocks, and a bad way to reduce concurrency because it is inexact: Better	1804	blocks, and a bad way to reduce concurrency because it is inexact: Better
1043	use an C<aio_group> together with a feed callback.	1805	use an C<aio_group> together with a feed callback.
1044		1806
1045	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1807	It's main use is in scripts without an event loop - when you want to stat
1046	to queue up more than this number of requests, the next call to the	1808	a lot of files, you can write somehting like this:
1047	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1048	function will block until the limit is no longer exceeded.
1049		1809
1050	The default value is very large, so there is no practical limit on the	1810	IO::AIO::max_outstanding 32;
1051	number of outstanding requests.
1052		1811
1053	You can still queue as many requests as you want. Therefore,	1812	for my $path (...) {
1054	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1813	aio_stat $path , ...;
1055	as a stop gap to shield against fatal memory overflow (with large values).	1814	IO::AIO::poll_cb;
		1815	}
		1816
		1817	IO::AIO::flush;
		1818
		1819	The call to C<poll_cb> inside the loop will normally return instantly, but
		1820	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1821	some requests have been handled. This keeps the loop from pushing a large
		1822	number of C<aio_stat> requests onto the queue.
		1823
		1824	The default value for C<max_outstanding> is very large, so there is no
		1825	practical limit on the number of outstanding requests.
		1826
		1827	=back
1056		1828
1057	=head3 STATISTICAL INFORMATION	1829	=head3 STATISTICAL INFORMATION
		1830
		1831	=over
1058		1832
1059	=item IO::AIO::nreqs	1833	=item IO::AIO::nreqs
1060		1834
1061	Returns the number of requests currently in the ready, execute or pending	1835	Returns the number of requests currently in the ready, execute or pending
1062	states (i.e. for which their callback has not been invoked yet).	1836	states (i.e. for which their callback has not been invoked yet).
…		…
1076	Returns the number of requests currently in the pending state (executed,	1850	Returns the number of requests currently in the pending state (executed,
1077	but not yet processed by poll_cb).	1851	but not yet processed by poll_cb).
1078		1852
1079	=back	1853	=back
1080		1854
		1855	=head3 MISCELLANEOUS FUNCTIONS
		1856
		1857	IO::AIO implements some functions that might be useful, but are not
		1858	asynchronous.
		1859
		1860	=over 4
		1861
		1862	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1863
		1864	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1865	but is blocking (this makes most sense if you know the input data is
		1866	likely cached already and the output filehandle is set to non-blocking
		1867	operations).
		1868
		1869	Returns the number of bytes copied, or C<-1> on error.
		1870
		1871	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1872
		1873	Simply calls the C<posix_fadvise> function (see its
		1874	manpage for details). The following advice constants are
		1875	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1876	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1877	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1878
		1879	On systems that do not implement C<posix_fadvise>, this function returns
		1880	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1881
		1882	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1883
		1884	Simply calls the C<posix_madvise> function (see its
		1885	manpage for details). The following advice constants are
		1886	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1887	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1888
		1889	On systems that do not implement C<posix_madvise>, this function returns
		1890	ENOSYS, otherwise the return value of C<posix_madvise>.
		1891
		1892	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1893
		1894	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1895	$scalar (see its manpage for details). The following protect
		1896	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1897	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1898
		1899	On systems that do not implement C<mprotect>, this function returns
		1900	ENOSYS, otherwise the return value of C<mprotect>.
		1901
		1902	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1903
		1904	Memory-maps a file (or anonymous memory range) and attaches it to the
		1905	given C<$scalar>, which will act like a string scalar.
		1906
		1907	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1908	change the string length, and most read-only operations such as copying it
		1909	or searching it with regexes and so on.
		1910
		1911	Anything else is unsafe and will, at best, result in memory leaks.
		1912
		1913	The memory map associated with the C<$scalar> is automatically removed
		1914	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1915	C<IO::AIO::munmap> functions are called.
		1916
		1917	This calls the C<mmap>(2) function internally. See your system's manual
		1918	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1919
		1920	The C<$length> must be larger than zero and smaller than the actual
		1921	filesize.
		1922
		1923	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1924	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1925
		1926	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1927	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1928	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1929	(which is set to C<MAP_ANON> if your system only provides this
		1930	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1931	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1932	C<IO::AIO::MAP_NONBLOCK>
		1933
		1934	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1935
		1936	C<$offset> is the offset from the start of the file - it generally must be
		1937	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1938
		1939	Example:
		1940
		1941	use Digest::MD5;
		1942	use IO::AIO;
		1943
		1944	open my $fh, "<verybigfile"
		1945	or die "$!";
		1946
		1947	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1948	or die "verybigfile: $!";
		1949
		1950	my $fast_md5 = md5 $data;
		1951
		1952	=item IO::AIO::munmap $scalar
		1953
		1954	Removes a previous mmap and undefines the C<$scalar>.
		1955
		1956	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1957
		1958	Calls the C<munlock> function, undoing the effects of a previous
		1959	C<aio_mlock> call (see its description for details).
		1960
		1961	=item IO::AIO::munlockall
		1962
		1963	Calls the C<munlockall> function.
		1964
		1965	On systems that do not implement C<munlockall>, this function returns
		1966	ENOSYS, otherwise the return value of C<munlockall>.
		1967
		1968	=back
		1969
1081	=cut	1970	=cut
1082		1971
1083	# support function to convert a fd into a perl filehandle
1084	sub _fd2fh {
1085	return undef if $_[0] < 0;
1086
1087	# try to generate nice filehandles
1088	my $sym = "IO::AIO::fd#$_[0]";
1089	local *$sym;
1090
1091	open *$sym, "+<&=$_[0]" # usually works under any unix
1092	or open *$sym, "<&=$_[0]" # cygwin needs this
1093	or open *$sym, ">&=$_[0]" # or this
1094	or return undef;
1095
1096	*$sym
1097	}
1098
1099	min_parallel 8;	1972	min_parallel 8;
1100		1973
1101	END {	1974	END { flush }
1102	min_parallel 1;
1103	flush;
1104	};
1105		1975
1106	1;	1976	1;
1107		1977
		1978	=head1 EVENT LOOP INTEGRATION
		1979
		1980	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1981	automatically into many event loops:
		1982
		1983	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1984	use AnyEvent::AIO;
		1985
		1986	You can also integrate IO::AIO manually into many event loops, here are
		1987	some examples of how to do this:
		1988
		1989	# EV integration
		1990	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1991
		1992	# Event integration
		1993	Event->io (fd => IO::AIO::poll_fileno,
		1994	poll => 'r',
		1995	cb => \&IO::AIO::poll_cb);
		1996
		1997	# Glib/Gtk2 integration
		1998	add_watch Glib::IO IO::AIO::poll_fileno,
		1999	in => sub { IO::AIO::poll_cb; 1 };
		2000
		2001	# Tk integration
		2002	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2003	readable => \&IO::AIO::poll_cb);
		2004
		2005	# Danga::Socket integration
		2006	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2007	\&IO::AIO::poll_cb);
		2008
1108	=head2 FORK BEHAVIOUR	2009	=head2 FORK BEHAVIOUR
1109		2010
1110	This module should do "the right thing" when the process using it forks:	2011	Usage of pthreads in a program changes the semantics of fork
		2012	considerably. Specifically, only async-safe functions can be called after
		2013	fork. Perl doesn't know about this, so in general, you cannot call fork
		2014	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2015	pthreads, so this applies, but many other extensions and (for inexplicable
		2016	reasons) perl itself often is linked against pthreads, so this limitation
		2017	applies to quite a lot of perls.
1111		2018
1112	Before the fork, IO::AIO enters a quiescent state where no requests	2019	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1113	can be added in other threads and no results will be processed. After	2020	only works in the process that loaded it. Forking is fully supported, but
1114	the fork the parent simply leaves the quiescent state and continues	2021	using IO::AIO in the child is not.
1115	request/result processing, while the child frees the request/result queue
1116	(so that the requests started before the fork will only be handled in the
1117	parent). Threads will be started on demand until the limit set in the
1118	parent process has been reached again.
1119		2022
1120	In short: the parent will, after a short pause, continue as if fork had	2023	You might get around by not I<using> IO::AIO before (or after)
1121	not been called, while the child will act as if IO::AIO has not been used	2024	forking. You could also try to call the L<IO::AIO::reinit> function in the
1122	yet.	2025	child:
		2026
		2027	=over 4
		2028
		2029	=item IO::AIO::reinit
		2030
		2031	Abandons all current requests and I/O threads and simply reinitialises all
		2032	data structures. This is not an operation supported by any standards, but
		2033	happens to work on GNU/Linux and some newer BSD systems.
		2034
		2035	The only reasonable use for this function is to call it after forking, if
		2036	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2037	the process will result in undefined behaviour. Calling it at any time
		2038	will also result in any undefined (by POSIX) behaviour.
		2039
		2040	=back
1123		2041
1124	=head2 MEMORY USAGE	2042	=head2 MEMORY USAGE
1125		2043
1126	Per-request usage:	2044	Per-request usage:
1127		2045
…		…
1129	bytes of memory. In addition, stat requests need a stat buffer (possibly	2047	bytes of memory. In addition, stat requests need a stat buffer (possibly
1130	a few hundred bytes), readdir requires a result buffer and so on. Perl	2048	a few hundred bytes), readdir requires a result buffer and so on. Perl
1131	scalars and other data passed into aio requests will also be locked and	2049	scalars and other data passed into aio requests will also be locked and
1132	will consume memory till the request has entered the done state.	2050	will consume memory till the request has entered the done state.
1133		2051
1134	This is now awfully much, so queuing lots of requests is not usually a	2052	This is not awfully much, so queuing lots of requests is not usually a
1135	problem.	2053	problem.
1136		2054
1137	Per-thread usage:	2055	Per-thread usage:
1138		2056
1139	In the execution phase, some aio requests require more memory for	2057	In the execution phase, some aio requests require more memory for
…		…
1144		2062
1145	Known bugs will be fixed in the next release.	2063	Known bugs will be fixed in the next release.
1146		2064
1147	=head1 SEE ALSO	2065	=head1 SEE ALSO
1148		2066
1149	L<Coro::AIO>.	2067	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2068	more natural syntax.
1150		2069
1151	=head1 AUTHOR	2070	=head1 AUTHOR
1152		2071
1153	Marc Lehmann <schmorp@schmorp.de>	2072	Marc Lehmann <schmorp@schmorp.de>
1154	http://home.schmorp.de/	2073	http://home.schmorp.de/

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