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Revision 1.88 by root, Sun Oct 29 01:50:29 2006 UTC vs.
Revision 1.230 by root, Fri Jul 27 17:24:06 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 = '4.15';
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 most of the functions for
		208	quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_seek $fh,$offset,$whence, $callback->($offs)
		215	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		217	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		218	aio_readahead $fh,$offset,$length, $callback->($retval)
		219	aio_stat $fh_or_path, $callback->($status)
		220	aio_lstat $fh, $callback->($status)
		221	aio_statvfs $fh_or_path, $callback->($statvfs)
		222	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		223	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_truncate $fh_or_path, $offset, $callback->($status)
		226	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		227	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		228	aio_unlink $pathname, $callback->($status)
		229	aio_mknod $pathname, $mode, $dev, $callback->($status)
		230	aio_link $srcpath, $dstpath, $callback->($status)
		231	aio_symlink $srcpath, $dstpath, $callback->($status)
		232	aio_readlink $pathname, $callback->($link)
		233	aio_realpath $pathname, $callback->($link)
		234	aio_rename $srcpath, $dstpath, $callback->($status)
		235	aio_mkdir $pathname, $mode, $callback->($status)
		236	aio_rmdir $pathname, $callback->($status)
		237	aio_readdir $pathname, $callback->($entries)
		238	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		239	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		240	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		241	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		242	aio_load $pathname, $data, $callback->($status)
		243	aio_copy $srcpath, $dstpath, $callback->($status)
		244	aio_move $srcpath, $dstpath, $callback->($status)
		245	aio_rmtree $pathname, $callback->($status)
		246	aio_sync $callback->($status)
		247	aio_syncfs $fh, $callback->($status)
		248	aio_fsync $fh, $callback->($status)
		249	aio_fdatasync $fh, $callback->($status)
		250	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		251	aio_pathsync $pathname, $callback->($status)
		252	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		253	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		254	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		255	aio_mlockall $flags, $callback->($status)
		256	aio_group $callback->(...)
		257	aio_nop $callback->()
		258
		259	$prev_pri = aioreq_pri [$pri]
		260	aioreq_nice $pri_adjust
		261
		262	IO::AIO::poll_wait
		263	IO::AIO::poll_cb
		264	IO::AIO::poll
		265	IO::AIO::flush
		266	IO::AIO::max_poll_reqs $nreqs
		267	IO::AIO::max_poll_time $seconds
		268	IO::AIO::min_parallel $nthreads
		269	IO::AIO::max_parallel $nthreads
		270	IO::AIO::max_idle $nthreads
		271	IO::AIO::idle_timeout $seconds
		272	IO::AIO::max_outstanding $maxreqs
		273	IO::AIO::nreqs
		274	IO::AIO::nready
		275	IO::AIO::npending
		276
		277	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		278	IO::AIO::fadvise $fh, $offset, $len, $advice
		279	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		280	IO::AIO::munmap $scalar
		281	IO::AIO::madvise $scalar, $offset, $length, $advice
		282	IO::AIO::mprotect $scalar, $offset, $length, $protect
		283	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		284	IO::AIO::munlockall
		285
		286	=head2 API NOTES
214		287
215	All the C<aio_*> calls are more or less thin wrappers around the syscall	288	All the C<aio_*> calls are more or less thin wrappers around the syscall
216	with the same name (sans C<aio_>). The arguments are similar or identical,	289	with the same name (sans C<aio_>). The arguments are similar or identical,
217	and they all accept an additional (and optional) C<$callback> argument	290	and they all accept an additional (and optional) C<$callback> argument
218	which must be a code reference. This code reference will get called with	291	which must be a code reference. This code reference will be called after
219	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	292	the syscall has been executed in an asynchronous fashion. The results
220	perl, which usually delivers "false") as it's sole argument when the given	293	of the request will be passed as arguments to the callback (and, if an
221	syscall has been executed asynchronously.	294	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		295	most syscalls return C<-1> on error, unlike perl, which usually delivers
		296	"false").
		297
		298	Some requests (such as C<aio_readdir>) pass the actual results and
		299	communicate failures by passing C<undef>.
222		300
223	All functions expecting a filehandle keep a copy of the filehandle	301	All functions expecting a filehandle keep a copy of the filehandle
224	internally until the request has finished.	302	internally until the request has finished.
225		303
226	All functions return request objects of type L<IO::AIO::REQ> that allow	304	All functions return request objects of type L<IO::AIO::REQ> that allow
227	further manipulation of those requests while they are in-flight.	305	further manipulation of those requests while they are in-flight.
228		306
229	The pathnames you pass to these routines I<must> be absolute and	307	The pathnames you pass to these routines I<should> be absolute. The
230	encoded as octets. The reason for the former is that at the time the	308	reason for this is that at the time the request is being executed, the
231	request is being executed, the current working directory could have	309	current working directory could have changed. Alternatively, you can
232	changed. Alternatively, you can make sure that you never change the	310	make sure that you never change the current working directory anywhere
233	current working directory anywhere in the program and then use relative	311	in the program and then use relative paths. You can also take advantage
234	paths.	312	of IO::AIOs working directory abstraction, that lets you specify paths
		313	relative to some previously-opened "working directory object" - see the
		314	description of the C<IO::AIO::WD> class later in this document.
235		315
236	To encode pathnames as octets, either make sure you either: a) always pass	316	To encode pathnames as octets, either make sure you either: a) always pass
237	in filenames you got from outside (command line, readdir etc.) without	317	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	318	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	319	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)	320	effect in the user environment, d) use Glib::filename_from_unicode on
241	use something else to ensure your scalar has the correct contents.	321	unicode filenames or e) use something else to ensure your scalar has the
		322	correct contents.
242		323
243	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	324	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
244	handles correctly wether it is set or not.	325	handles correctly whether it is set or not.
		326
		327	=head2 AIO REQUEST FUNCTIONS
245		328
246	=over 4	329	=over 4
247		330
248	=item $prev_pri = aioreq_pri [$pri]	331	=item $prev_pri = aioreq_pri [$pri]
249		332
…		…
269	aio_read $_[0], ..., sub {	352	aio_read $_[0], ..., sub {
270	...	353	...
271	};	354	};
272	};	355	};
273		356
		357
274	=item aioreq_nice $pri_adjust	358	=item aioreq_nice $pri_adjust
275		359
276	Similar to C<aioreq_pri>, but subtracts the given value from the current	360	Similar to C<aioreq_pri>, but subtracts the given value from the current
277	priority, so the effect is cumulative.	361	priority, so the effect is cumulative.
		362
278		363
279	=item aio_open $pathname, $flags, $mode, $callback->($fh)	364	=item aio_open $pathname, $flags, $mode, $callback->($fh)
280		365
281	Asynchronously open or create a file and call the callback with a newly	366	Asynchronously open or create a file and call the callback with a newly
282	created filehandle for the file.	367	created filehandle for the file.
…		…
288	list. They are the same as used by C<sysopen>.	373	list. They are the same as used by C<sysopen>.
289		374
290	Likewise, C<$mode> specifies the mode of the newly created file, if it	375	Likewise, C<$mode> specifies the mode of the newly created file, if it
291	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	376	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
292	except that it is mandatory (i.e. use C<0> if you don't create new files,	377	except that it is mandatory (i.e. use C<0> if you don't create new files,
293	and C<0666> or C<0777> if you do).	378	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		379	by the umask in effect then the request is being executed, so better never
		380	change the umask.
294		381
295	Example:	382	Example:
296		383
297	aio_open "/etc/passwd", O_RDONLY, 0, sub {	384	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
298	if ($_[0]) {	385	if ($_[0]) {
299	print "open successful, fh is $_[0]\n";	386	print "open successful, fh is $_[0]\n";
300	...	387	...
301	} else {	388	} else {
302	die "open failed: $!\n";	389	die "open failed: $!\n";
303	}	390	}
304	};	391	};
305		392
		393	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		394	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		395	following POSIX and non-POSIX constants are available (missing ones on
		396	your system are, as usual, C<0>):
		397
		398	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		399	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		400	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		401
		402
306	=item aio_close $fh, $callback->($status)	403	=item aio_close $fh, $callback->($status)
307		404
308	Asynchronously close a file and call the callback with the result	405	Asynchronously close a file and call the callback with the result
309	code. I<WARNING:> although accepted, you should not pass in a perl	406	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		407
314	This is supposed to be a bug in the API, so that might change. It's	408	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
315	therefore best to avoid this function.	409	closing the file descriptor associated with the filehandle itself.
		410
		411	Therefore, C<aio_close> will not close the filehandle - instead it will
		412	use dup2 to overwrite the file descriptor with the write-end of a pipe
		413	(the pipe fd will be created on demand and will be cached).
		414
		415	Or in other words: the file descriptor will be closed, but it will not be
		416	free for reuse until the perl filehandle is closed.
		417
		418	=cut
		419
		420	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		421
		422	Seeks the filehandle to the new C<$offset>, similarly to perl's
		423	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		424	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		425	C<IO::AIO::SEEK_END>).
		426
		427	The resulting absolute offset will be passed to the callback, or C<-1> in
		428	case of an error.
		429
		430	In theory, the C<$whence> constants could be different than the
		431	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		432	so don't panic.
		433
		434	As a GNU/Linux (and maybe Solaris) extension, also the constants
		435	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		436	could be found. No guarantees about suitability for use in C<aio_seek> or
		437	Perl's C<sysseek> can be made though, although I would naively assume they
		438	"just work".
316		439
317	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	440	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
318		441
319	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	442	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
320		443
321	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	444	Reads or writes C<$length> bytes from or to the specified C<$fh> and
322	into the scalar given by C<data> and offset C<dataoffset> and calls the	445	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
323	callback without the actual number of bytes read (or -1 on error, just	446	and calls the callback without the actual number of bytes read (or -1 on
324	like the syscall).	447	error, just like the syscall).
		448
		449	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		450	offset plus the actual number of bytes read.
		451
		452	If C<$offset> is undefined, then the current file descriptor offset will
		453	be used (and updated), otherwise the file descriptor offset will not be
		454	changed by these calls.
		455
		456	If C<$length> is undefined in C<aio_write>, use the remaining length of
		457	C<$data>.
		458
		459	If C<$dataoffset> is less than zero, it will be counted from the end of
		460	C<$data>.
325		461
326	The C<$data> scalar I<MUST NOT> be modified in any way while the request	462	The C<$data> scalar I<MUST NOT> be modified in any way while the request
327	is outstanding. Modifying it can result in segfaults or WW3 (if the	463	is outstanding. Modifying it can result in segfaults or World War III (if
328	necessary/optional hardware is installed).	464	the necessary/optional hardware is installed).
329		465
330	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	466	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
331	offset C<0> within the scalar:	467	offset C<0> within the scalar:
332		468
333	aio_read $fh, 7, 15, $buffer, 0, sub {	469	aio_read $fh, 7, 15, $buffer, 0, sub {
334	$_[0] > 0 or die "read error: $!";	470	$_[0] > 0 or die "read error: $!";
335	print "read $_[0] bytes: <$buffer>\n";	471	print "read $_[0] bytes: <$buffer>\n";
336	};	472	};
337		473
		474
338	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	475	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
339		476
340	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	477	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
341	reading at byte offset C<$in_offset>, and starts writing at the current	478	reading at byte offset C<$in_offset>, and starts writing at the current
342	file offset of C<$out_fh>. Because of that, it is not safe to issue more	479	file offset of C<$out_fh>. Because of that, it is not safe to issue more
343	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	480	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
344	other.	481	other. The same C<$in_fh> works fine though, as this function does not
		482	move or use the file offset of C<$in_fh>.
345		483
		484	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		485	are written, and there is no way to find out how many more bytes have been
		486	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		487	number of bytes written to C<$out_fh>. Only if the result value equals
		488	C<$length> one can assume that C<$length> bytes have been read.
		489
		490	Unlike with other C<aio_> functions, it makes a lot of sense to use
		491	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		492	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		493	the socket I/O will be non-blocking. Note, however, that you can run
		494	into a trap where C<aio_sendfile> reads some data with readahead, then
		495	fails to write all data, and when the socket is ready the next time, the
		496	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		497	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		498	resource usage.
		499
346	This call tries to make use of a native C<sendfile> syscall to provide	500	This call tries to make use of a native C<sendfile>-like syscall to
347	zero-copy operation. For this to work, C<$out_fh> should refer to a	501	provide zero-copy operation. For this to work, C<$out_fh> should refer to
348	socket, and C<$in_fh> should refer to mmap'able file.	502	a socket, and C<$in_fh> should refer to an mmap'able file.
349		503
350	If the native sendfile call fails or is not implemented, it will be	504	If a native sendfile cannot be found or it fails with C<ENOSYS>,
351	emulated, so you can call C<aio_sendfile> on any type of filehandle	505	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		506	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
352	regardless of the limitations of the operating system.	507	type of filehandle regardless of the limitations of the operating system.
353		508
354	Please note, however, that C<aio_sendfile> can read more bytes from	509	As native sendfile syscalls (as practically any non-POSIX interface hacked
355	C<$in_fh> than are written, and there is no way to find out how many	510	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	511	on many systems, this implementation tries to work around some known bugs
357	provides the number of bytes written to C<$out_fh>. Only if the result	512	in Linux and FreeBSD kernels (probably others, too), but that might fail,
358	value equals C<$length> one can assume that C<$length> bytes have been	513	so you really really should check the return value of C<aio_sendfile> -
359	read.	514	fewre bytes than expected might have been transferred.
		515
360		516
361	=item aio_readahead $fh,$offset,$length, $callback->($retval)	517	=item aio_readahead $fh,$offset,$length, $callback->($retval)
362		518
363	C<aio_readahead> populates the page cache with data from a file so that	519	C<aio_readahead> populates the page cache with data from a file so that
364	subsequent reads from that file will not block on disk I/O. The C<$offset>	520	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
370	file. The current file offset of the file is left unchanged.	526	file. The current file offset of the file is left unchanged.
371		527
372	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	528	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
373	emulated by simply reading the data, which would have a similar effect.	529	emulated by simply reading the data, which would have a similar effect.
374		530
		531
375	=item aio_stat $fh_or_path, $callback->($status)	532	=item aio_stat $fh_or_path, $callback->($status)
376		533
377	=item aio_lstat $fh, $callback->($status)	534	=item aio_lstat $fh, $callback->($status)
378		535
379	Works like perl's C<stat> or C<lstat> in void context. The callback will	536	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
384	for an explanation.	541	for an explanation.
385		542
386	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	543	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
387	error when stat'ing a large file, the results will be silently truncated	544	error when stat'ing a large file, the results will be silently truncated
388	unless perl itself is compiled with large file support.	545	unless perl itself is compiled with large file support.
		546
		547	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		548	following constants and functions (if not implemented, the constants will
		549	be C<0> and the functions will either C<croak> or fall back on traditional
		550	behaviour).
		551
		552	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		553	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		554	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
389		555
390	Example: Print the length of F</etc/passwd>:	556	Example: Print the length of F</etc/passwd>:
391		557
392	aio_stat "/etc/passwd", sub {	558	aio_stat "/etc/passwd", sub {
393	$_[0] and die "stat failed: $!";	559	$_[0] and die "stat failed: $!";
394	print "size is ", -s _, "\n";	560	print "size is ", -s _, "\n";
395	};	561	};
396		562
		563
		564	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		565
		566	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		567	whether a file handle or path was passed.
		568
		569	On success, the callback is passed a hash reference with the following
		570	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		571	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		572	is passed.
		573
		574	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		575	C<ST_NOSUID>.
		576
		577	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		578	their correct value when available, or to C<0> on systems that do
		579	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		580	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		581	C<ST_NODIRATIME> and C<ST_RELATIME>.
		582
		583	Example: stat C</wd> and dump out the data if successful.
		584
		585	aio_statvfs "/wd", sub {
		586	my $f = $_[0]
		587	or die "statvfs: $!";
		588
		589	use Data::Dumper;
		590	say Dumper $f;
		591	};
		592
		593	# result:
		594	{
		595	bsize => 1024,
		596	bfree => 4333064312,
		597	blocks => 10253828096,
		598	files => 2050765568,
		599	flag => 4096,
		600	favail => 2042092649,
		601	bavail => 4333064312,
		602	ffree => 2042092649,
		603	namemax => 255,
		604	frsize => 1024,
		605	fsid => 1810
		606	}
		607
		608
		609	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		610
		611	Works like perl's C<utime> function (including the special case of $atime
		612	and $mtime being undef). Fractional times are supported if the underlying
		613	syscalls support them.
		614
		615	When called with a pathname, uses utimes(2) if available, otherwise
		616	utime(2). If called on a file descriptor, uses futimes(2) if available,
		617	otherwise returns ENOSYS, so this is not portable.
		618
		619	Examples:
		620
		621	# set atime and mtime to current time (basically touch(1)):
		622	aio_utime "path", undef, undef;
		623	# set atime to current time and mtime to beginning of the epoch:
		624	aio_utime "path", time, undef; # undef==0
		625
		626
		627	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		628
		629	Works like perl's C<chown> function, except that C<undef> for either $uid
		630	or $gid is being interpreted as "do not change" (but -1 can also be used).
		631
		632	Examples:
		633
		634	# same as "chown root path" in the shell:
		635	aio_chown "path", 0, -1;
		636	# same as above:
		637	aio_chown "path", 0, undef;
		638
		639
		640	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		641
		642	Works like truncate(2) or ftruncate(2).
		643
		644
		645	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		646
		647	Allocates or freed disk space according to the C<$mode> argument. See the
		648	linux C<fallocate> docuemntation for details.
		649
		650	C<$mode> can currently be C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE>
		651	to allocate space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE |
		652	IO::AIO::FALLOC_FL_KEEP_SIZE>, to deallocate a file range.
		653
		654	The file system block size used by C<fallocate> is presumably the
		655	C<f_bsize> returned by C<statvfs>.
		656
		657	If C<fallocate> isn't available or cannot be emulated (currently no
		658	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		659
		660
		661	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		662
		663	Works like perl's C<chmod> function.
		664
		665
397	=item aio_unlink $pathname, $callback->($status)	666	=item aio_unlink $pathname, $callback->($status)
398		667
399	Asynchronously unlink (delete) a file and call the callback with the	668	Asynchronously unlink (delete) a file and call the callback with the
400	result code.	669	result code.
401		670
		671
402	=item aio_mknod $path, $mode, $dev, $callback->($status)	672	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
403		673
404	[EXPERIMENTAL]	674	[EXPERIMENTAL]
405		675
406	Asynchronously create a device node (or fifo). See mknod(2).	676	Asynchronously create a device node (or fifo). See mknod(2).
407		677
408	The only (POSIX-) portable way of calling this function is:	678	The only (POSIX-) portable way of calling this function is:
409		679
410	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	680	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		681
		682	See C<aio_stat> for info about some potentially helpful extra constants
		683	and functions.
411		684
412	=item aio_link $srcpath, $dstpath, $callback->($status)	685	=item aio_link $srcpath, $dstpath, $callback->($status)
413		686
414	Asynchronously create a new link to the existing object at C<$srcpath> at	687	Asynchronously create a new link to the existing object at C<$srcpath> at
415	the path C<$dstpath> and call the callback with the result code.	688	the path C<$dstpath> and call the callback with the result code.
416		689
		690
417	=item aio_symlink $srcpath, $dstpath, $callback->($status)	691	=item aio_symlink $srcpath, $dstpath, $callback->($status)
418		692
419	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	693	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
420	the path C<$dstpath> and call the callback with the result code.	694	the path C<$dstpath> and call the callback with the result code.
421		695
		696
		697	=item aio_readlink $pathname, $callback->($link)
		698
		699	Asynchronously read the symlink specified by C<$path> and pass it to
		700	the callback. If an error occurs, nothing or undef gets passed to the
		701	callback.
		702
		703
		704	=item aio_realpath $pathname, $callback->($path)
		705
		706	Asynchronously make the path absolute and resolve any symlinks in
		707	C<$path>. The resulting path only consists of directories (Same as
		708	L<Cwd::realpath>).
		709
		710	This request can be used to get the absolute path of the current working
		711	directory by passing it a path of F<.> (a single dot).
		712
		713
422	=item aio_rename $srcpath, $dstpath, $callback->($status)	714	=item aio_rename $srcpath, $dstpath, $callback->($status)
423		715
424	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	716	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
425	rename(2) and call the callback with the result code.	717	rename(2) and call the callback with the result code.
426		718
		719
		720	=item aio_mkdir $pathname, $mode, $callback->($status)
		721
		722	Asynchronously mkdir (create) a directory and call the callback with
		723	the result code. C<$mode> will be modified by the umask at the time the
		724	request is executed, so do not change your umask.
		725
		726
427	=item aio_rmdir $pathname, $callback->($status)	727	=item aio_rmdir $pathname, $callback->($status)
428		728
429	Asynchronously rmdir (delete) a directory and call the callback with the	729	Asynchronously rmdir (delete) a directory and call the callback with the
430	result code.	730	result code.
		731
431		732
432	=item aio_readdir $pathname, $callback->($entries)	733	=item aio_readdir $pathname, $callback->($entries)
433		734
434	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	735	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
435	directory (i.e. opendir + readdir + closedir). The entries will not be	736	directory (i.e. opendir + readdir + closedir). The entries will not be
436	sorted, and will B<NOT> include the C<.> and C<..> entries.	737	sorted, and will B<NOT> include the C<.> and C<..> entries.
437		738
438	The callback a single argument which is either C<undef> or an array-ref	739	The callback is passed a single argument which is either C<undef> or an
439	with the filenames.	740	array-ref with the filenames.
		741
		742
		743	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		744
		745	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		746	tune behaviour and output format. In case of an error, C<$entries> will be
		747	C<undef>.
		748
		749	The flags are a combination of the following constants, ORed together (the
		750	flags will also be passed to the callback, possibly modified):
		751
		752	=over 4
		753
		754	=item IO::AIO::READDIR_DENTS
		755
		756	When this flag is off, then the callback gets an arrayref consisting of
		757	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		758	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		759	entry in more detail.
		760
		761	C<$name> is the name of the entry.
		762
		763	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		764
		765	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		766	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		767	C<IO::AIO::DT_WHT>.
		768
		769	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		770	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		771	scalars are read-only: you can not modify them.
		772
		773	C<$inode> is the inode number (which might not be exact on systems with 64
		774	bit inode numbers and 32 bit perls). This field has unspecified content on
		775	systems that do not deliver the inode information.
		776
		777	=item IO::AIO::READDIR_DIRS_FIRST
		778
		779	When this flag is set, then the names will be returned in an order where
		780	likely directories come first, in optimal stat order. This is useful when
		781	you need to quickly find directories, or you want to find all directories
		782	while avoiding to stat() each entry.
		783
		784	If the system returns type information in readdir, then this is used
		785	to find directories directly. Otherwise, likely directories are names
		786	beginning with ".", or otherwise names with no dots, of which names with
		787	short names are tried first.
		788
		789	=item IO::AIO::READDIR_STAT_ORDER
		790
		791	When this flag is set, then the names will be returned in an order
		792	suitable for stat()'ing each one. That is, when you plan to stat()
		793	all files in the given directory, then the returned order will likely
		794	be fastest.
		795
		796	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		797	the likely dirs come first, resulting in a less optimal stat order.
		798
		799	=item IO::AIO::READDIR_FOUND_UNKNOWN
		800
		801	This flag should not be set when calling C<aio_readdirx>. Instead, it
		802	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		803	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		804	C<$type>'s are known, which can be used to speed up some algorithms.
		805
		806	=back
		807
		808
		809	=item aio_load $pathname, $data, $callback->($status)
		810
		811	This is a composite request that tries to fully load the given file into
		812	memory. Status is the same as with aio_read.
		813
		814	=cut
		815
		816	sub aio_load($$;$) {
		817	my ($path, undef, $cb) = @_;
		818	my $data = \$_[1];
		819
		820	my $pri = aioreq_pri;
		821	my $grp = aio_group $cb;
		822
		823	aioreq_pri $pri;
		824	add $grp aio_open $path, O_RDONLY, 0, sub {
		825	my $fh = shift
		826	or return $grp->result (-1);
		827
		828	aioreq_pri $pri;
		829	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		830	$grp->result ($_[0]);
		831	};
		832	};
		833
		834	$grp
		835	}
440		836
441	=item aio_copy $srcpath, $dstpath, $callback->($status)	837	=item aio_copy $srcpath, $dstpath, $callback->($status)
442		838
443	Try to copy the I<file> (directories not supported as either source or	839	Try to copy the I<file> (directories not supported as either source or
444	destination) from C<$srcpath> to C<$dstpath> and call the callback with	840	destination) from C<$srcpath> to C<$dstpath> and call the callback with
445	the C<0> (error) or C<-1> ok.	841	a status of C<0> (ok) or C<-1> (error, see C<$!>).
446		842
447	This is a composite request that it creates the destination file with	843	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	844	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	845	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
450	uid/gid, in that order.	846	uid/gid, in that order.
451		847
452	If an error occurs, the partial destination file will be unlinked, if	848	If an error occurs, the partial destination file will be unlinked, if
…		…
462	my $grp = aio_group $cb;	858	my $grp = aio_group $cb;
463		859
464	aioreq_pri $pri;	860	aioreq_pri $pri;
465	add $grp aio_open $src, O_RDONLY, 0, sub {	861	add $grp aio_open $src, O_RDONLY, 0, sub {
466	if (my $src_fh = $_[0]) {	862	if (my $src_fh = $_[0]) {
467	my @stat = stat $src_fh;	863	my @stat = stat $src_fh; # hmm, might block over nfs?
468		864
469	aioreq_pri $pri;	865	aioreq_pri $pri;
470	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	866	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
471	if (my $dst_fh = $_[0]) {	867	if (my $dst_fh = $_[0]) {
472	aioreq_pri $pri;	868	aioreq_pri $pri;
473	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	869	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
474	if ($_[0] == $stat[7]) {	870	if ($_[0] == $stat[7]) {
475	$grp->result (0);	871	$grp->result (0);
476	close $src_fh;	872	close $src_fh;
477		873
478	# those should not normally block. should. should.	874	my $ch = sub {
		875	aioreq_pri $pri;
		876	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		877	aioreq_pri $pri;
		878	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		879	aioreq_pri $pri;
		880	add $grp aio_close $dst_fh;
		881	}
		882	};
		883	};
		884
		885	aioreq_pri $pri;
		886	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		887	if ($_[0] < 0 && $! == ENOSYS) {
		888	aioreq_pri $pri;
479	utime $stat[8], $stat[9], $dst;	889	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
480	chmod $stat[2] & 07777, $dst_fh;	890	} else {
481	chown $stat[4], $stat[5], $dst_fh;	891	$ch->();
		892	}
482	close $dst_fh;	893	};
483	} else {	894	} else {
484	$grp->result (-1);	895	$grp->result (-1);
485	close $src_fh;	896	close $src_fh;
486	close $dst_fh;	897	close $dst_fh;
487		898
…		…
504		915
505	=item aio_move $srcpath, $dstpath, $callback->($status)	916	=item aio_move $srcpath, $dstpath, $callback->($status)
506		917
507	Try to move the I<file> (directories not supported as either source or	918	Try to move the I<file> (directories not supported as either source or
508	destination) from C<$srcpath> to C<$dstpath> and call the callback with	919	destination) from C<$srcpath> to C<$dstpath> and call the callback with
509	the C<0> (error) or C<-1> ok.	920	a status of C<0> (ok) or C<-1> (error, see C<$!>).
510		921
511	This is a composite request that tries to rename(2) the file first. If	922	This is a composite request that tries to rename(2) the file first; if
512	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	923	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
513	that is successful, unlinking the C<$srcpath>.	924	that is successful, unlinks the C<$srcpath>.
514		925
515	=cut	926	=cut
516		927
517	sub aio_move($$;$) {	928	sub aio_move($$;$) {
518	my ($src, $dst, $cb) = @_;	929	my ($src, $dst, $cb) = @_;
…		…
525	if ($_[0] && $! == EXDEV) {	936	if ($_[0] && $! == EXDEV) {
526	aioreq_pri $pri;	937	aioreq_pri $pri;
527	add $grp aio_copy $src, $dst, sub {	938	add $grp aio_copy $src, $dst, sub {
528	$grp->result ($_[0]);	939	$grp->result ($_[0]);
529		940
530	if (!$_[0]) {	941	unless ($_[0]) {
531	aioreq_pri $pri;	942	aioreq_pri $pri;
532	add $grp aio_unlink $src;	943	add $grp aio_unlink $src;
533	}	944	}
534	};	945	};
535	} else {	946	} else {
…		…
538	};	949	};
539		950
540	$grp	951	$grp
541	}	952	}
542		953
543	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	954	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
544		955
545	Scans a directory (similar to C<aio_readdir>) but additionally tries to	956	Scans a directory (similar to C<aio_readdir>) but additionally tries to
546	efficiently separate the entries of directory C<$path> into two sets of	957	efficiently separate the entries of directory C<$path> into two sets of
547	names, directories you can recurse into (directories), and ones you cannot	958	names, directories you can recurse into (directories), and ones you cannot
548	recurse into (everything else, including symlinks to directories).	959	recurse into (everything else, including symlinks to directories).
…		…
565		976
566	Implementation notes.	977	Implementation notes.
567		978
568	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	979	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
569		980
		981	If readdir returns file type information, then this is used directly to
		982	find directories.
		983
570	After reading the directory, the modification time, size etc. of the	984	Otherwise, after reading the directory, the modification time, size etc.
571	directory before and after the readdir is checked, and if they match (and	985	of the directory before and after the readdir is checked, and if they
572	isn't the current time), the link count will be used to decide how many	986	match (and isn't the current time), the link count will be used to decide
573	entries are directories (if >= 2). Otherwise, no knowledge of the number	987	how many entries are directories (if >= 2). Otherwise, no knowledge of the
574	of subdirectories will be assumed.	988	number of subdirectories will be assumed.
575		989
576	Then entries will be sorted into likely directories (everything without	990	Then entries will be sorted into likely directories a non-initial dot
577	a non-initial dot currently) and likely non-directories (everything	991	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,	992	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	993	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	994	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	995	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	996	filesystems might detect the type of the entry without reading the inode
583	data (e.g. ext2fs filetype feature).	997	data (e.g. ext2fs filetype feature), even on systems that cannot return
		998	the filetype information on readdir.
584		999
585	If the known number of directories (link count - 2) has been reached, the	1000	If the known number of directories (link count - 2) has been reached, the
586	rest of the entries is assumed to be non-directories.	1001	rest of the entries is assumed to be non-directories.
587		1002
588	This only works with certainty on POSIX (= UNIX) filesystems, which	1003	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	1007	as those tend to return 0 or 1 as link counts, which disables the
593	directory counting heuristic.	1008	directory counting heuristic.
594		1009
595	=cut	1010	=cut
596		1011
597	sub aio_scandir($$$) {	1012	sub aio_scandir($$;$) {
598	my ($path, $maxreq, $cb) = @_;	1013	my ($path, $maxreq, $cb) = @_;
599		1014
600	my $pri = aioreq_pri;	1015	my $pri = aioreq_pri;
601		1016
602	my $grp = aio_group $cb;	1017	my $grp = aio_group $cb;
603		1018
604	$maxreq = 4 if $maxreq <= 0;	1019	$maxreq = 4 if $maxreq <= 0;
605		1020
606	# stat once	1021	# get a wd object
607	aioreq_pri $pri;	1022	aioreq_pri $pri;
608	add $grp aio_stat $path, sub {	1023	add $grp aio_wd $path, sub {
		1024	$_[0]
609	return $grp->result () if $_[0];	1025	or return $grp->result ();
610	my $now = time;
611	my $hash1 = join ":", (stat _)[0,1,3,7,9];
612		1026
613	# read the directory entries	1027	my $wd = [shift, "."];
		1028
		1029	# stat once
614	aioreq_pri $pri;	1030	aioreq_pri $pri;
615	add $grp aio_readdir $path, sub {	1031	add $grp aio_stat $wd, sub {
616	my $entries = shift
617	or return $grp->result ();	1032	return $grp->result () if $_[0];
		1033	my $now = time;
		1034	my $hash1 = join ":", (stat _)[0,1,3,7,9];
618		1035
619	# stat the dir another time	1036	# read the directory entries
620	aioreq_pri $pri;	1037	aioreq_pri $pri;
		1038	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1039	my $entries = shift
		1040	or return $grp->result ();
		1041
		1042	# stat the dir another time
		1043	aioreq_pri $pri;
621	add $grp aio_stat $path, sub {	1044	add $grp aio_stat $wd, sub {
622	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1045	my $hash2 = join ":", (stat _)[0,1,3,7,9];
623		1046
624	my $ndirs;	1047	my $ndirs;
625		1048
626	# take the slow route if anything looks fishy	1049	# take the slow route if anything looks fishy
627	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1050	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
628	$ndirs = -1;	1051	$ndirs = -1;
629	} else {	1052	} else {
630	# if nlink == 2, we are finished	1053	# if nlink == 2, we are finished
631	# on non-posix-fs's, we rely on nlink < 2	1054	# for non-posix-fs's, we rely on nlink < 2
632	$ndirs = (stat _)[3] - 2	1055	$ndirs = (stat _)[3] - 2
633	or return $grp->result ([], $entries);	1056	or return $grp->result ([], $entries);
634	}	1057	}
635		1058
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);	1059	my (@dirs, @nondirs);
644		1060
645	my $statgrp = add $grp aio_group sub {	1061	my $statgrp = add $grp aio_group sub {
646	$grp->result (\@dirs, \@nondirs);	1062	$grp->result (\@dirs, \@nondirs);
647	};	1063	};
648		1064
649	limit $statgrp $maxreq;	1065	limit $statgrp $maxreq;
650	feed $statgrp sub {	1066	feed $statgrp sub {
651	return unless @$entries;	1067	return unless @$entries;
652	my $entry = pop @$entries;	1068	my $entry = shift @$entries;
653		1069
654	aioreq_pri $pri;	1070	aioreq_pri $pri;
		1071	$wd->[1] = "$entry/.";
655	add $statgrp aio_stat "$path/$entry/.", sub {	1072	add $statgrp aio_stat $wd, sub {
656	if ($_[0] < 0) {	1073	if ($_[0] < 0) {
657	push @nondirs, $entry;	1074	push @nondirs, $entry;
658	} else {	1075	} else {
659	# need to check for real directory	1076	# need to check for real directory
660	aioreq_pri $pri;	1077	aioreq_pri $pri;
		1078	$wd->[1] = $entry;
661	add $statgrp aio_lstat "$path/$entry", sub {	1079	add $statgrp aio_lstat $wd, sub {
662	if (-d _) {	1080	if (-d _) {
663	push @dirs, $entry;	1081	push @dirs, $entry;
664		1082
665	unless (--$ndirs) {	1083	unless (--$ndirs) {
666	push @nondirs, @$entries;	1084	push @nondirs, @$entries;
667	feed $statgrp;	1085	feed $statgrp;
		1086	}
		1087	} else {
		1088	push @nondirs, $entry;
668	}	1089	}
669	} else {
670	push @nondirs, $entry;
671	}	1090	}
672	}	1091	}
673	}	1092	};
674	};	1093	};
675	};	1094	};
676	};	1095	};
677	};	1096	};
678	};	1097	};
679		1098
680	$grp	1099	$grp
681	}	1100	}
682		1101
		1102	=item aio_rmtree $pathname, $callback->($status)
		1103
		1104	Delete a directory tree starting (and including) C<$path>, return the
		1105	status of the final C<rmdir> only. This is a composite request that
		1106	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1107	everything else.
		1108
		1109	=cut
		1110
		1111	sub aio_rmtree;
		1112	sub aio_rmtree($;$) {
		1113	my ($path, $cb) = @_;
		1114
		1115	my $pri = aioreq_pri;
		1116	my $grp = aio_group $cb;
		1117
		1118	aioreq_pri $pri;
		1119	add $grp aio_scandir $path, 0, sub {
		1120	my ($dirs, $nondirs) = @_;
		1121
		1122	my $dirgrp = aio_group sub {
		1123	add $grp aio_rmdir $path, sub {
		1124	$grp->result ($_[0]);
		1125	};
		1126	};
		1127
		1128	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1129	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1130
		1131	add $grp $dirgrp;
		1132	};
		1133
		1134	$grp
		1135	}
		1136
		1137	=item aio_sync $callback->($status)
		1138
		1139	Asynchronously call sync and call the callback when finished.
		1140
683	=item aio_fsync $fh, $callback->($status)	1141	=item aio_fsync $fh, $callback->($status)
684		1142
685	Asynchronously call fsync on the given filehandle and call the callback	1143	Asynchronously call fsync on the given filehandle and call the callback
686	with the fsync result code.	1144	with the fsync result code.
687		1145
…		…
690	Asynchronously call fdatasync on the given filehandle and call the	1148	Asynchronously call fdatasync on the given filehandle and call the
691	callback with the fdatasync result code.	1149	callback with the fdatasync result code.
692		1150
693	If this call isn't available because your OS lacks it or it couldn't be	1151	If this call isn't available because your OS lacks it or it couldn't be
694	detected, it will be emulated by calling C<fsync> instead.	1152	detected, it will be emulated by calling C<fsync> instead.
		1153
		1154	=item aio_syncfs $fh, $callback->($status)
		1155
		1156	Asynchronously call the syncfs syscall to sync the filesystem associated
		1157	to the given filehandle and call the callback with the syncfs result
		1158	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1159	errno to C<ENOSYS> nevertheless.
		1160
		1161	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1162
		1163	Sync the data portion of the file specified by C<$offset> and C<$length>
		1164	to disk (but NOT the metadata), by calling the Linux-specific
		1165	sync_file_range call. If sync_file_range is not available or it returns
		1166	ENOSYS, then fdatasync or fsync is being substituted.
		1167
		1168	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1169	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1170	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1171	manpage for details.
		1172
		1173	=item aio_pathsync $pathname, $callback->($status)
		1174
		1175	This request tries to open, fsync and close the given path. This is a
		1176	composite request intended to sync directories after directory operations
		1177	(E.g. rename). This might not work on all operating systems or have any
		1178	specific effect, but usually it makes sure that directory changes get
		1179	written to disc. It works for anything that can be opened for read-only,
		1180	not just directories.
		1181
		1182	Future versions of this function might fall back to other methods when
		1183	C<fsync> on the directory fails (such as calling C<sync>).
		1184
		1185	Passes C<0> when everything went ok, and C<-1> on error.
		1186
		1187	=cut
		1188
		1189	sub aio_pathsync($;$) {
		1190	my ($path, $cb) = @_;
		1191
		1192	my $pri = aioreq_pri;
		1193	my $grp = aio_group $cb;
		1194
		1195	aioreq_pri $pri;
		1196	add $grp aio_open $path, O_RDONLY, 0, sub {
		1197	my ($fh) = @_;
		1198	if ($fh) {
		1199	aioreq_pri $pri;
		1200	add $grp aio_fsync $fh, sub {
		1201	$grp->result ($_[0]);
		1202
		1203	aioreq_pri $pri;
		1204	add $grp aio_close $fh;
		1205	};
		1206	} else {
		1207	$grp->result (-1);
		1208	}
		1209	};
		1210
		1211	$grp
		1212	}
		1213
		1214	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1215
		1216	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1217	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1218	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1219	scalar must only be modified in-place while an aio operation is pending on
		1220	it).
		1221
		1222	It calls the C<msync> function of your OS, if available, with the memory
		1223	area starting at C<$offset> in the string and ending C<$length> bytes
		1224	later. If C<$length> is negative, counts from the end, and if C<$length>
		1225	is C<undef>, then it goes till the end of the string. The flags can be
		1226	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1227	C<IO::AIO::MS_SYNC>.
		1228
		1229	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1230
		1231	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1232	scalars.
		1233
		1234	It touches (reads or writes) all memory pages in the specified
		1235	range inside the scalar. All caveats and parameters are the same
		1236	as for C<aio_msync>, above, except for flags, which must be either
		1237	C<0> (which reads all pages and ensures they are instantiated) or
		1238	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1239	writing an octet from it, which dirties the page).
		1240
		1241	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1242
		1243	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1244	scalars.
		1245
		1246	It reads in all the pages of the underlying storage into memory (if any)
		1247	and locks them, so they are not getting swapped/paged out or removed.
		1248
		1249	If C<$length> is undefined, then the scalar will be locked till the end.
		1250
		1251	On systems that do not implement C<mlock>, this function returns C<-1>
		1252	and sets errno to C<ENOSYS>.
		1253
		1254	Note that the corresponding C<munlock> is synchronous and is
		1255	documented under L<MISCELLANEOUS FUNCTIONS>.
		1256
		1257	Example: open a file, mmap and mlock it - both will be undone when
		1258	C<$data> gets destroyed.
		1259
		1260	open my $fh, "<", $path or die "$path: $!";
		1261	my $data;
		1262	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1263	aio_mlock $data; # mlock in background
		1264
		1265	=item aio_mlockall $flags, $callback->($status)
		1266
		1267	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1268	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1269
		1270	On systems that do not implement C<mlockall>, this function returns C<-1>
		1271	and sets errno to C<ENOSYS>.
		1272
		1273	Note that the corresponding C<munlockall> is synchronous and is
		1274	documented under L<MISCELLANEOUS FUNCTIONS>.
		1275
		1276	Example: asynchronously lock all current and future pages into memory.
		1277
		1278	aio_mlockall IO::AIO::MCL_FUTURE;
		1279
		1280	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1281
		1282	Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
		1283	see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
		1284	C<ioctl> is not available on your OS, then this request will fail with
		1285	C<ENOSYS>.
		1286
		1287	C<$start> is the starting offset to query extents for, C<$length> is the
		1288	size of the range to query - if it is C<undef>, then the whole file will
		1289	be queried.
		1290
		1291	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1292	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1293	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1294	the data portion.
		1295
		1296	C<$count> is the maximum number of extent records to return. If it is
		1297	C<undef>, then IO::AIO queries all extents of the file. As a very special
		1298	case, if it is C<0>, then the callback receives the number of extents
		1299	instead of the extents themselves.
		1300
		1301	If an error occurs, the callback receives no arguments. The special
		1302	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1303
		1304	Otherwise, the callback receives an array reference with extent
		1305	structures. Each extent structure is an array reference itself, with the
		1306	following members:
		1307
		1308	[$logical, $physical, $length, $flags]
		1309
		1310	Flags is any combination of the following flag values (typically either C<0>
		1311	or C<IO::AIO::FIEMAP_EXTENT_LAST>):
		1312
		1313	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1314	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1315	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1316	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1317	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1318	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
695		1319
696	=item aio_group $callback->(...)	1320	=item aio_group $callback->(...)
697		1321
698	This is a very special aio request: Instead of doing something, it is a	1322	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	1323	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	1361	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.	1362	except to put your application under artificial I/O pressure.
739		1363
740	=back	1364	=back
741		1365
		1366
		1367	=head2 IO::AIO::WD - multiple working directories
		1368
		1369	Your process only has one current working directory, which is used by all
		1370	threads. This makes it hard to use relative paths (some other component
		1371	could call C<chdir> at any time, and it is hard to control when the path
		1372	will be used by IO::AIO).
		1373
		1374	One solution for this is to always use absolute paths. This usually works,
		1375	but can be quite slow (the kernel has to walk the whole path on every
		1376	access), and can also be a hassle to implement.
		1377
		1378	Newer POSIX systems have a number of functions (openat, fdopendir,
		1379	futimensat and so on) that make it possible to specify working directories
		1380	per operation.
		1381
		1382	For portability, and because the clowns who "designed", or shall I write,
		1383	perpetrated this new interface were obviously half-drunk, this abstraction
		1384	cannot be perfect, though.
		1385
		1386	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1387	object. This object stores the canonicalised, absolute version of the
		1388	path, and on systems that allow it, also a directory file descriptor.
		1389
		1390	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1391	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1392	object and a pathname instead (or the IO::AIO::WD object alone, which
		1393	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1394	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1395	to that IO::AIO::WD object.
		1396
		1397	For example, to get a wd object for F</etc> and then stat F<passwd>
		1398	inside, you would write:
		1399
		1400	aio_wd "/etc", sub {
		1401	my $etcdir = shift;
		1402
		1403	# although $etcdir can be undef on error, there is generally no reason
		1404	# to check for errors here, as aio_stat will fail with ENOENT
		1405	# when $etcdir is undef.
		1406
		1407	aio_stat [$etcdir, "passwd"], sub {
		1408	# yay
		1409	};
		1410	};
		1411
		1412	That C<aio_wd> is a request and not a normal function shows that creating
		1413	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1414	why it is done asynchronously.
		1415
		1416	To stat the directory obtained with C<aio_wd> above, one could write
		1417	either of the following three request calls:
		1418
		1419	aio_lstat "/etc" , sub { ... # pathname as normal string
		1420	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1421	aio_lstat $wd , sub { ... # shorthand for the previous
		1422
		1423	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1424	object and the pathname string, so you could write the following without
		1425	causing any issues due to C<$path> getting reused:
		1426
		1427	my $path = [$wd, undef];
		1428
		1429	for my $name (qw(abc def ghi)) {
		1430	$path->[1] = $name;
		1431	aio_stat $path, sub {
		1432	# ...
		1433	};
		1434	}
		1435
		1436	There are some caveats: when directories get renamed (or deleted), the
		1437	pathname string doesn't change, so will point to the new directory (or
		1438	nowhere at all), while the directory fd, if available on the system,
		1439	will still point to the original directory. Most functions accepting a
		1440	pathname will use the directory fd on newer systems, and the string on
		1441	older systems. Some functions (such as realpath) will always rely on the
		1442	string form of the pathname.
		1443
		1444	So this fucntionality is mainly useful to get some protection against
		1445	C<chdir>, to easily get an absolute path out of a relative path for future
		1446	reference, and to speed up doing many operations in the same directory
		1447	(e.g. when stat'ing all files in a directory).
		1448
		1449	The following functions implement this working directory abstraction:
		1450
		1451	=over 4
		1452
		1453	=item aio_wd $pathname, $callback->($wd)
		1454
		1455	Asynchonously canonicalise the given pathname and convert it to an
		1456	IO::AIO::WD object representing it. If possible and supported on the
		1457	system, also open a directory fd to speed up pathname resolution relative
		1458	to this working directory.
		1459
		1460	If something goes wrong, then C<undef> is passwd to the callback instead
		1461	of a working directory object and C<$!> is set appropriately. Since
		1462	passing C<undef> as working directory component of a pathname fails the
		1463	request with C<ENOENT>, there is often no need for error checking in the
		1464	C<aio_wd> callback, as future requests using the value will fail in the
		1465	expected way.
		1466
		1467	If this call isn't available because your OS lacks it or it couldn't be
		1468	detected, it will be emulated by calling C<fsync> instead.
		1469
		1470	=item IO::AIO::CWD
		1471
		1472	This is a compiletime constant (object) that represents the process
		1473	current working directory.
		1474
		1475	Specifying this object as working directory object for a pathname is as
		1476	if the pathname would be specified directly, without a directory object,
		1477	e.g., these calls are functionally identical:
		1478
		1479	aio_stat "somefile", sub { ... };
		1480	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1481
		1482	=back
		1483
		1484
742	=head2 IO::AIO::REQ CLASS	1485	=head2 IO::AIO::REQ CLASS
743		1486
744	All non-aggregate C<aio_*> functions return an object of this class when	1487	All non-aggregate C<aio_*> functions return an object of this class when
745	called in non-void context.	1488	called in non-void context.
746		1489
…		…
749	=item cancel $req	1492	=item cancel $req
750		1493
751	Cancels the request, if possible. Has the effect of skipping execution	1494	Cancels the request, if possible. Has the effect of skipping execution
752	when entering the B<execute> state and skipping calling the callback when	1495	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	1496	entering the the B<result> state, but will leave the request otherwise
754	untouched. That means that requests that currently execute will not be	1497	untouched (with the exception of readdir). That means that requests that
755	stopped and resources held by the request will not be freed prematurely.	1498	currently execute will not be stopped and resources held by the request
		1499	will not be freed prematurely.
756		1500
757	=item cb $req $callback->(...)	1501	=item cb $req $callback->(...)
758		1502
759	Replace (or simply set) the callback registered to the request.	1503	Replace (or simply set) the callback registered to the request.
760		1504
…		…
811	Their lifetime, simplified, looks like this: when they are empty, they	1555	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	1556	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	1557	C<done> state, they will also finish. Otherwise they will continue to
814	exist.	1558	exist.
815		1559
816	That means after creating a group you have some time to add requests. And	1560	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	1561	(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	1562	the C<poll_cb>). And in the callbacks of those requests, you can add
819	itself finish.	1563	further requests to the group. And only when all those requests have
		1564	finished will the the group itself finish.
820		1565
821	=over 4	1566	=over 4
822		1567
823	=item add $grp ...	1568	=item add $grp ...
824		1569
…		…
833	=item $grp->cancel_subs	1578	=item $grp->cancel_subs
834		1579
835	Cancel all subrequests and clears any feeder, but not the group request	1580	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.	1581	itself. Useful when you queued a lot of events but got a result early.
837		1582
		1583	The group request will finish normally (you cannot add requests to the
		1584	group).
		1585
838	=item $grp->result (...)	1586	=item $grp->result (...)
839		1587
840	Set the result value(s) that will be passed to the group callback when all	1588	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	1589	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,	1590	of errno (just like calling C<errno> without an error number). By default,
843	no argument will be passed and errno is zero.	1591	no argument will be passed and errno is zero.
844		1592
845	=item $grp->errno ([$errno])	1593	=item $grp->errno ([$errno])
846		1594
…		…
857	=item feed $grp $callback->($grp)	1605	=item feed $grp $callback->($grp)
858		1606
859	Sets a feeder/generator on this group: every group can have an attached	1607	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,	1608	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,	1609	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	1610	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>	1611	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
864	requests, delaying any later requests for a long time.	1612	requests, delaying any later requests for a long time.
865		1613
866	To avoid this, and allow incremental generation of requests, you can	1614	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	1615	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>,	1616	feed callback will be called whenever there are few enough (see C<limit>,
…		…
873	not impose any limits).	1621	not impose any limits).
874		1622
875	If the feed does not queue more requests when called, it will be	1623	If the feed does not queue more requests when called, it will be
876	automatically removed from the group.	1624	automatically removed from the group.
877		1625
878	If the feed limit is C<0>, it will be set to C<2> automatically.	1626	If the feed limit is C<0> when this method is called, it will be set to
		1627	C<2> automatically.
879		1628
880	Example:	1629	Example:
881		1630
882	# stat all files in @files, but only ever use four aio requests concurrently:	1631	# stat all files in @files, but only ever use four aio requests concurrently:
883		1632
…		…
895	Sets the feeder limit for the group: The feeder will be called whenever	1644	Sets the feeder limit for the group: The feeder will be called whenever
896	the group contains less than this many requests.	1645	the group contains less than this many requests.
897		1646
898	Setting the limit to C<0> will pause the feeding process.	1647	Setting the limit to C<0> will pause the feeding process.
899		1648
		1649	The default value for the limit is C<0>, but note that setting a feeder
		1650	automatically bumps it up to C<2>.
		1651
900	=back	1652	=back
901		1653
902	=head2 SUPPORT FUNCTIONS	1654	=head2 SUPPORT FUNCTIONS
903		1655
904	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1656	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
…		…
906	=over 4	1658	=over 4
907		1659
908	=item $fileno = IO::AIO::poll_fileno	1660	=item $fileno = IO::AIO::poll_fileno
909		1661
910	Return the I<request result pipe file descriptor>. This filehandle must be	1662	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	1663	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	1664	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
913	to call C<poll_cb> to check the results.	1665	you have to call C<poll_cb> to check the results.
914		1666
915	See C<poll_cb> for an example.	1667	See C<poll_cb> for an example.
916		1668
917	=item IO::AIO::poll_cb	1669	=item IO::AIO::poll_cb
918		1670
919	Process some outstanding events on the result pipe. You have to call this	1671	Process some outstanding events on the result pipe. You have to call
920	regularly. Returns the number of events processed. Returns immediately	1672	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	1673	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>.	1674	reason. Returns immediately when no events are outstanding. The amount of
		1675	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1676	C<IO::AIO::max_poll_time>.
923		1677
924	If not all requests were processed for whatever reason, the filehandle	1678	If not all requests were processed for whatever reason, the filehandle
925	will still be ready when C<poll_cb> returns.	1679	will still be ready when C<poll_cb> returns, so normally you don't have to
		1680	do anything special to have it called later.
		1681
		1682	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1683	ready, it can be beneficial to call this function from loops which submit
		1684	a lot of requests, to make sure the results get processed when they become
		1685	available and not just when the loop is finished and the event loop takes
		1686	over again. This function returns very fast when there are no outstanding
		1687	requests.
926		1688
927	Example: Install an Event watcher that automatically calls	1689	Example: Install an Event watcher that automatically calls
928	IO::AIO::poll_cb with high priority:	1690	IO::AIO::poll_cb with high priority (more examples can be found in the
		1691	SYNOPSIS section, at the top of this document):
929		1692
930	Event->io (fd => IO::AIO::poll_fileno,	1693	Event->io (fd => IO::AIO::poll_fileno,
931	poll => 'r', async => 1,	1694	poll => 'r', async => 1,
932	cb => \&IO::AIO::poll_cb);	1695	cb => \&IO::AIO::poll_cb);
		1696
		1697	=item IO::AIO::poll_wait
		1698
		1699	If there are any outstanding requests and none of them in the result
		1700	phase, wait till the result filehandle becomes ready for reading (simply
		1701	does a C<select> on the filehandle. This is useful if you want to
		1702	synchronously wait for some requests to finish).
		1703
		1704	See C<nreqs> for an example.
		1705
		1706	=item IO::AIO::poll
		1707
		1708	Waits until some requests have been handled.
		1709
		1710	Returns the number of requests processed, but is otherwise strictly
		1711	equivalent to:
		1712
		1713	IO::AIO::poll_wait, IO::AIO::poll_cb
		1714
		1715	=item IO::AIO::flush
		1716
		1717	Wait till all outstanding AIO requests have been handled.
		1718
		1719	Strictly equivalent to:
		1720
		1721	IO::AIO::poll_wait, IO::AIO::poll_cb
		1722	while IO::AIO::nreqs;
933		1723
934	=item IO::AIO::max_poll_reqs $nreqs	1724	=item IO::AIO::max_poll_reqs $nreqs
935		1725
936	=item IO::AIO::max_poll_time $seconds	1726	=item IO::AIO::max_poll_time $seconds
937		1727
…		…
939	that are being processed by C<IO::AIO::poll_cb> in one call, respectively	1729	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	1730	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	1731	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
942	of time C<poll_cb> is allowed to use).	1732	of time C<poll_cb> is allowed to use).
943		1733
		1734	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1735	syscall per request processed, which is not normally a problem unless your
		1736	callbacks are really really fast or your OS is really really slow (I am
		1737	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1738
944	Setting these is useful if you want to ensure some level of	1739	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	1740	interactiveness when perl is not fast enough to process all requests in
946	time.	1741	time.
947		1742
948	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	1743	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
949		1744
950	Example: Install an Event watcher that automatically calls	1745	Example: Install an Event watcher that automatically calls
951	IO::AIO::poll_some with low priority, to ensure that other parts of the	1746	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.	1747	program get the CPU sometimes even under high AIO load.
953		1748
954	# try not to spend much more than 0.1s in poll_cb	1749	# try not to spend much more than 0.1s in poll_cb
955	IO::AIO::max_poll_time 0.1;	1750	IO::AIO::max_poll_time 0.1;
956		1751
957	# use a low priority so other tasks have priority	1752	# use a low priority so other tasks have priority
958	Event->io (fd => IO::AIO::poll_fileno,	1753	Event->io (fd => IO::AIO::poll_fileno,
959	poll => 'r', nice => 1,	1754	poll => 'r', nice => 1,
960	cb => &IO::AIO::poll_cb);	1755	cb => &IO::AIO::poll_cb);
961		1756
962	=item IO::AIO::poll_wait	1757	=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		1758
988	=head3 CONTROLLING THE NUMBER OF THREADS	1759	=head3 CONTROLLING THE NUMBER OF THREADS
		1760
		1761	=over
989		1762
990	=item IO::AIO::min_parallel $nthreads	1763	=item IO::AIO::min_parallel $nthreads
991		1764
992	Set the minimum number of AIO threads to C<$nthreads>. The current	1765	Set the minimum number of AIO threads to C<$nthreads>. The current
993	default is C<8>, which means eight asynchronous operations can execute	1766	default is C<8>, which means eight asynchronous operations can execute
…		…
1021		1794
1022	Under normal circumstances you don't need to call this function.	1795	Under normal circumstances you don't need to call this function.
1023		1796
1024	=item IO::AIO::max_idle $nthreads	1797	=item IO::AIO::max_idle $nthreads
1025		1798
1026	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1799	Limit the number of threads (default: 4) that are allowed to idle
1027	threads that did not get a request to process within 10 seconds). That	1800	(i.e., threads that did not get a request to process within the idle
1028	means if a thread becomes idle while C<$nthreads> other threads are also	1801	timeout (default: 10 seconds). That means if a thread becomes idle while
1029	idle, it will free its resources and exit.	1802	C<$nthreads> other threads are also idle, it will free its resources and
		1803	exit.
1030		1804
1031	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1805	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	1806	to allow for extremely high load situations, but want to free resources
1033	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1807	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1034		1808
1035	The default is probably ok in most situations, especially if thread	1809	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	1810	creation is fast. If thread creation is very slow on your system you might
1037	want to use larger values.	1811	want to use larger values.
1038		1812
		1813	=item IO::AIO::idle_timeout $seconds
		1814
		1815	Sets the minimum idle timeout (default 10) after which worker threads are
		1816	allowed to exit. SEe C<IO::AIO::max_idle>.
		1817
1039	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1818	=item IO::AIO::max_outstanding $maxreqs
		1819
		1820	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1821	you do queue up more than this number of requests, the next call to
		1822	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1823	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1824	longer exceeded.
		1825
		1826	In other words, this setting does not enforce a queue limit, but can be
		1827	used to make poll functions block if the limit is exceeded.
1040		1828
1041	This is a very bad function to use in interactive programs because it	1829	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	1830	blocks, and a bad way to reduce concurrency because it is inexact: Better
1043	use an C<aio_group> together with a feed callback.	1831	use an C<aio_group> together with a feed callback.
1044		1832
1045	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1833	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	1834	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		1835
1050	The default value is very large, so there is no practical limit on the	1836	IO::AIO::max_outstanding 32;
1051	number of outstanding requests.
1052		1837
1053	You can still queue as many requests as you want. Therefore,	1838	for my $path (...) {
1054	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1839	aio_stat $path , ...;
1055	as a stop gap to shield against fatal memory overflow (with large values).	1840	IO::AIO::poll_cb;
		1841	}
		1842
		1843	IO::AIO::flush;
		1844
		1845	The call to C<poll_cb> inside the loop will normally return instantly, but
		1846	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1847	some requests have been handled. This keeps the loop from pushing a large
		1848	number of C<aio_stat> requests onto the queue.
		1849
		1850	The default value for C<max_outstanding> is very large, so there is no
		1851	practical limit on the number of outstanding requests.
		1852
		1853	=back
1056		1854
1057	=head3 STATISTICAL INFORMATION	1855	=head3 STATISTICAL INFORMATION
		1856
		1857	=over
1058		1858
1059	=item IO::AIO::nreqs	1859	=item IO::AIO::nreqs
1060		1860
1061	Returns the number of requests currently in the ready, execute or pending	1861	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).	1862	states (i.e. for which their callback has not been invoked yet).
…		…
1076	Returns the number of requests currently in the pending state (executed,	1876	Returns the number of requests currently in the pending state (executed,
1077	but not yet processed by poll_cb).	1877	but not yet processed by poll_cb).
1078		1878
1079	=back	1879	=back
1080		1880
		1881	=head3 MISCELLANEOUS FUNCTIONS
		1882
		1883	IO::AIO implements some functions that might be useful, but are not
		1884	asynchronous.
		1885
		1886	=over 4
		1887
		1888	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1889
		1890	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1891	but is blocking (this makes most sense if you know the input data is
		1892	likely cached already and the output filehandle is set to non-blocking
		1893	operations).
		1894
		1895	Returns the number of bytes copied, or C<-1> on error.
		1896
		1897	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1898
		1899	Simply calls the C<posix_fadvise> function (see its
		1900	manpage for details). The following advice constants are
		1901	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1902	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1903	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1904
		1905	On systems that do not implement C<posix_fadvise>, this function returns
		1906	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1907
		1908	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1909
		1910	Simply calls the C<posix_madvise> function (see its
		1911	manpage for details). The following advice constants are
		1912	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1913	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1914
		1915	On systems that do not implement C<posix_madvise>, this function returns
		1916	ENOSYS, otherwise the return value of C<posix_madvise>.
		1917
		1918	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1919
		1920	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1921	$scalar (see its manpage for details). The following protect
		1922	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1923	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1924
		1925	On systems that do not implement C<mprotect>, this function returns
		1926	ENOSYS, otherwise the return value of C<mprotect>.
		1927
		1928	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1929
		1930	Memory-maps a file (or anonymous memory range) and attaches it to the
		1931	given C<$scalar>, which will act like a string scalar. Returns true on
		1932	success, and false otherwise.
		1933
		1934	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1935	change the string length, and most read-only operations such as copying it
		1936	or searching it with regexes and so on.
		1937
		1938	Anything else is unsafe and will, at best, result in memory leaks.
		1939
		1940	The memory map associated with the C<$scalar> is automatically removed
		1941	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1942	C<IO::AIO::munmap> functions are called.
		1943
		1944	This calls the C<mmap>(2) function internally. See your system's manual
		1945	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1946
		1947	The C<$length> must be larger than zero and smaller than the actual
		1948	filesize.
		1949
		1950	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1951	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1952
		1953	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1954	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1955	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1956	(which is set to C<MAP_ANON> if your system only provides this
		1957	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1958	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1959	C<IO::AIO::MAP_NONBLOCK>
		1960
		1961	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1962
		1963	C<$offset> is the offset from the start of the file - it generally must be
		1964	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1965
		1966	Example:
		1967
		1968	use Digest::MD5;
		1969	use IO::AIO;
		1970
		1971	open my $fh, "<verybigfile"
		1972	or die "$!";
		1973
		1974	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1975	or die "verybigfile: $!";
		1976
		1977	my $fast_md5 = md5 $data;
		1978
		1979	=item IO::AIO::munmap $scalar
		1980
		1981	Removes a previous mmap and undefines the C<$scalar>.
		1982
		1983	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1984
		1985	Calls the C<munlock> function, undoing the effects of a previous
		1986	C<aio_mlock> call (see its description for details).
		1987
		1988	=item IO::AIO::munlockall
		1989
		1990	Calls the C<munlockall> function.
		1991
		1992	On systems that do not implement C<munlockall>, this function returns
		1993	ENOSYS, otherwise the return value of C<munlockall>.
		1994
		1995	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		1996
		1997	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		1998	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		1999	should be the file offset.
		2000
		2001	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2002	silently corrupt the data in this case.
		2003
		2004	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2005	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2006	C<IO::AIO::SPLICE_F_GIFT>.
		2007
		2008	See the C<splice(2)> manpage for details.
		2009
		2010	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2011
		2012	Calls the GNU/Linux C<tee(2)> syscall, see it's manpage and the
		2013	description for C<IO::AIO::splice> above for details.
		2014
		2015	=back
		2016
1081	=cut	2017	=cut
1082		2018
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;	2019	min_parallel 8;
1100		2020
1101	END {	2021	END { flush }
1102	min_parallel 1;
1103	flush;
1104	};
1105		2022
1106	1;	2023	1;
1107		2024
		2025	=head1 EVENT LOOP INTEGRATION
		2026
		2027	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2028	automatically into many event loops:
		2029
		2030	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2031	use AnyEvent::AIO;
		2032
		2033	You can also integrate IO::AIO manually into many event loops, here are
		2034	some examples of how to do this:
		2035
		2036	# EV integration
		2037	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2038
		2039	# Event integration
		2040	Event->io (fd => IO::AIO::poll_fileno,
		2041	poll => 'r',
		2042	cb => \&IO::AIO::poll_cb);
		2043
		2044	# Glib/Gtk2 integration
		2045	add_watch Glib::IO IO::AIO::poll_fileno,
		2046	in => sub { IO::AIO::poll_cb; 1 };
		2047
		2048	# Tk integration
		2049	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2050	readable => \&IO::AIO::poll_cb);
		2051
		2052	# Danga::Socket integration
		2053	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2054	\&IO::AIO::poll_cb);
		2055
1108	=head2 FORK BEHAVIOUR	2056	=head2 FORK BEHAVIOUR
1109		2057
1110	This module should do "the right thing" when the process using it forks:	2058	Usage of pthreads in a program changes the semantics of fork
		2059	considerably. Specifically, only async-safe functions can be called after
		2060	fork. Perl doesn't know about this, so in general, you cannot call fork
		2061	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2062	pthreads, so this applies, but many other extensions and (for inexplicable
		2063	reasons) perl itself often is linked against pthreads, so this limitation
		2064	applies to quite a lot of perls.
1111		2065
1112	Before the fork, IO::AIO enters a quiescent state where no requests	2066	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	2067	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	2068	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		2069
1120	In short: the parent will, after a short pause, continue as if fork had	2070	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	2071	forking. You could also try to call the L<IO::AIO::reinit> function in the
1122	yet.	2072	child:
		2073
		2074	=over 4
		2075
		2076	=item IO::AIO::reinit
		2077
		2078	Abandons all current requests and I/O threads and simply reinitialises all
		2079	data structures. This is not an operation supported by any standards, but
		2080	happens to work on GNU/Linux and some newer BSD systems.
		2081
		2082	The only reasonable use for this function is to call it after forking, if
		2083	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2084	the process will result in undefined behaviour. Calling it at any time
		2085	will also result in any undefined (by POSIX) behaviour.
		2086
		2087	=back
1123		2088
1124	=head2 MEMORY USAGE	2089	=head2 MEMORY USAGE
1125		2090
1126	Per-request usage:	2091	Per-request usage:
1127		2092
…		…
1129	bytes of memory. In addition, stat requests need a stat buffer (possibly	2094	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	2095	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	2096	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.	2097	will consume memory till the request has entered the done state.
1133		2098
1134	This is now awfully much, so queuing lots of requests is not usually a	2099	This is not awfully much, so queuing lots of requests is not usually a
1135	problem.	2100	problem.
1136		2101
1137	Per-thread usage:	2102	Per-thread usage:
1138		2103
1139	In the execution phase, some aio requests require more memory for	2104	In the execution phase, some aio requests require more memory for
…		…
1144		2109
1145	Known bugs will be fixed in the next release.	2110	Known bugs will be fixed in the next release.
1146		2111
1147	=head1 SEE ALSO	2112	=head1 SEE ALSO
1148		2113
1149	L<Coro::AIO>.	2114	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2115	more natural syntax.
1150		2116
1151	=head1 AUTHOR	2117	=head1 AUTHOR
1152		2118
1153	Marc Lehmann <schmorp@schmorp.de>	2119	Marc Lehmann <schmorp@schmorp.de>
1154	http://home.schmorp.de/	2120	http://home.schmorp.de/

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