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Revision 1.70 by root, Tue Oct 24 03:40:38 2006 UTC vs.
Revision 1.217 by root, Sun Oct 9 22:25:00 2011 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
		37	Asynchronous means that operations that can normally block your program
		38	(e.g. reading from disk) will be done asynchronously: the operation
		39	will still block, but you can do something else in the meantime. This
		40	is extremely useful for programs that need to stay interactive even
		41	when doing heavy I/O (GUI programs, high performance network servers
		42	etc.), but can also be used to easily do operations in parallel that are
		43	normally done sequentially, e.g. stat'ing many files, which is much faster
		44	on a RAID volume or over NFS when you do a number of stat operations
		45	concurrently.
		46
		47	While most of this works on all types of file descriptors (for
		48	example sockets), using these functions on file descriptors that
		49	support nonblocking operation (again, sockets, pipes etc.) is
		50	very inefficient. Use an event loop for that (such as the L<EV>
		51	module): IO::AIO will naturally fit into such an event loop itself.
		52
56	Currently, a number of threads are started that execute your read/writes	53	In this version, a number of threads are started that execute your
57	and signal their completion. You don't need thread support in perl, and	54	requests and signal their completion. You don't need thread support
58	the threads created by this module will not be visible to perl. In the	55	in perl, and the threads created by this module will not be visible
59	future, this module might make use of the native aio functions available	56	to perl. In the future, this module might make use of the native aio
60	on many operating systems. However, they are often not well-supported	57	functions available on many operating systems. However, they are often
61	(Linux doesn't allow them on normal files currently, for example),	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	and they would only support aio_read and aio_write, so the remaining	59	files currently, for example), and they would only support aio_read and
63	functionality would have to be implemented using threads anyway.	60	aio_write, so the remaining functionality would have to be implemented
		61	using threads anyway.
64		62
65	Although the module will work with in the presence of other threads,	63	Although the module will work in the presence of other (Perl-) threads,
66	it is currently not reentrant in any way, so use appropriate locking	64	it is currently not reentrant in any way, so use appropriate locking
67	yourself, always call C<poll_cb> from within the same thread, or never	65	yourself, always call C<poll_cb> from within the same thread, or never
68	call C<poll_cb> (or other C<aio_> functions) recursively.	66	call C<poll_cb> (or other C<aio_> functions) recursively.
69		67
		68	=head2 EXAMPLE
		69
		70	This is a simple example that uses the EV module and loads
		71	F</etc/passwd> asynchronously:
		72
		73	use Fcntl;
		74	use EV;
		75	use IO::AIO;
		76
		77	# register the IO::AIO callback with EV
		78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		79
		80	# queue the request to open /etc/passwd
		81	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		82	my $fh = shift
		83	or die "error while opening: $!";
		84
		85	# stat'ing filehandles is generally non-blocking
		86	my $size = -s $fh;
		87
		88	# queue a request to read the file
		89	my $contents;
		90	aio_read $fh, 0, $size, $contents, 0, sub {
		91	$_[0] == $size
		92	or die "short read: $!";
		93
		94	close $fh;
		95
		96	# file contents now in $contents
		97	print $contents;
		98
		99	# exit event loop and program
		100	EV::unloop;
		101	};
		102	};
		103
		104	# possibly queue up other requests, or open GUI windows,
		105	# check for sockets etc. etc.
		106
		107	# process events as long as there are some:
		108	EV::loop;
		109
		110	=head1 REQUEST ANATOMY AND LIFETIME
		111
		112	Every C<aio_*> function creates a request. which is a C data structure not
		113	directly visible to Perl.
		114
		115	If called in non-void context, every request function returns a Perl
		116	object representing the request. In void context, nothing is returned,
		117	which saves a bit of memory.
		118
		119	The perl object is a fairly standard ref-to-hash object. The hash contents
		120	are not used by IO::AIO so you are free to store anything you like in it.
		121
		122	During their existance, aio requests travel through the following states,
		123	in order:
		124
		125	=over 4
		126
		127	=item ready
		128
		129	Immediately after a request is created it is put into the ready state,
		130	waiting for a thread to execute it.
		131
		132	=item execute
		133
		134	A thread has accepted the request for processing and is currently
		135	executing it (e.g. blocking in read).
		136
		137	=item pending
		138
		139	The request has been executed and is waiting for result processing.
		140
		141	While request submission and execution is fully asynchronous, result
		142	processing is not and relies on the perl interpreter calling C<poll_cb>
		143	(or another function with the same effect).
		144
		145	=item result
		146
		147	The request results are processed synchronously by C<poll_cb>.
		148
		149	The C<poll_cb> function will process all outstanding aio requests by
		150	calling their callbacks, freeing memory associated with them and managing
		151	any groups they are contained in.
		152
		153	=item done
		154
		155	Request has reached the end of its lifetime and holds no resources anymore
		156	(except possibly for the Perl object, but its connection to the actual
		157	aio request is severed and calling its methods will either do nothing or
		158	result in a runtime error).
		159
		160	=back
		161
70	=cut	162	=cut
71		163
72	package IO::AIO;	164	package IO::AIO;
73		165
74	no warnings;	166	use Carp ();
75	use strict 'vars';	167
		168	use common::sense;
76		169
77	use base 'Exporter';	170	use base 'Exporter';
78		171
79	BEGIN {	172	BEGIN {
80	our $VERSION = '2.0';	173	our $VERSION = '4.11';
81		174
82	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
83	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
84	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	177	aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
		178	aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
		179	aio_pathsync aio_readahead
		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
85	aio_group aio_nop);	185	aio_wd);
		186
86	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
87	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
88	min_parallel max_parallel max_outstanding nreqs);	189	min_parallel max_parallel max_idle idle_timeout
		190	nreqs nready npending nthreads
		191	max_poll_time max_poll_reqs
		192	sendfile fadvise madvise
		193	mmap munmap munlock munlockall);
		194
		195	push @AIO_REQ, qw(aio_busy); # not exported
89		196
90	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
91		198
92	require XSLoader;	199	require XSLoader;
93	XSLoader::load ("IO::AIO", $VERSION);	200	XSLoader::load ("IO::AIO", $VERSION);
94	}	201	}
95		202
96	=head1 FUNCTIONS	203	=head1 FUNCTIONS
97		204
		205	=head2 QUICK OVERVIEW
		206
		207	This section simply lists the prototypes of the most important functions
		208	for quick reference. See the following sections for function-by-function
		209	documentation.
		210
		211	aio_wd $pathname, $callback->($wd)
		212	aio_open $pathname, $flags, $mode, $callback->($fh)
		213	aio_close $fh, $callback->($status)
		214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		217	aio_readahead $fh,$offset,$length, $callback->($retval)
		218	aio_stat $fh_or_path, $callback->($status)
		219	aio_lstat $fh, $callback->($status)
		220	aio_statvfs $fh_or_path, $callback->($statvfs)
		221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		222	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		223	aio_truncate $fh_or_path, $offset, $callback->($status)
		224	aio_chmod $fh_or_path, $mode, $callback->($status)
		225	aio_unlink $pathname, $callback->($status)
		226	aio_mknod $pathname, $mode, $dev, $callback->($status)
		227	aio_link $srcpath, $dstpath, $callback->($status)
		228	aio_symlink $srcpath, $dstpath, $callback->($status)
		229	aio_readlink $pathname, $callback->($link)
		230	aio_realpath $pathname, $callback->($link)
		231	aio_rename $srcpath, $dstpath, $callback->($status)
		232	aio_mkdir $pathname, $mode, $callback->($status)
		233	aio_rmdir $pathname, $callback->($status)
		234	aio_readdir $pathname, $callback->($entries)
		235	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		236	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		237	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		238	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		239	aio_load $pathname, $data, $callback->($status)
		240	aio_copy $srcpath, $dstpath, $callback->($status)
		241	aio_move $srcpath, $dstpath, $callback->($status)
		242	aio_rmtree $pathname, $callback->($status)
		243	aio_sync $callback->($status)
		244	aio_syncfs $fh, $callback->($status)
		245	aio_fsync $fh, $callback->($status)
		246	aio_fdatasync $fh, $callback->($status)
		247	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		248	aio_pathsync $pathname, $callback->($status)
		249	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		250	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		251	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		252	aio_mlockall $flags, $callback->($status)
		253	aio_group $callback->(...)
		254	aio_nop $callback->()
		255
		256	$prev_pri = aioreq_pri [$pri]
		257	aioreq_nice $pri_adjust
		258
		259	IO::AIO::poll_wait
		260	IO::AIO::poll_cb
		261	IO::AIO::poll
		262	IO::AIO::flush
		263	IO::AIO::max_poll_reqs $nreqs
		264	IO::AIO::max_poll_time $seconds
		265	IO::AIO::min_parallel $nthreads
		266	IO::AIO::max_parallel $nthreads
		267	IO::AIO::max_idle $nthreads
		268	IO::AIO::idle_timeout $seconds
		269	IO::AIO::max_outstanding $maxreqs
		270	IO::AIO::nreqs
		271	IO::AIO::nready
		272	IO::AIO::npending
		273
		274	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		275	IO::AIO::fadvise $fh, $offset, $len, $advice
		276	IO::AIO::madvise $scalar, $offset, $length, $advice
		277	IO::AIO::mprotect $scalar, $offset, $length, $protect
		278	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		279	IO::AIO::munlockall
		280
98	=head2 AIO FUNCTIONS	281	=head2 AIO REQUEST FUNCTIONS
99		282
100	All the C<aio_*> calls are more or less thin wrappers around the syscall	283	All the C<aio_*> calls are more or less thin wrappers around the syscall
101	with the same name (sans C<aio_>). The arguments are similar or identical,	284	with the same name (sans C<aio_>). The arguments are similar or identical,
102	and they all accept an additional (and optional) C<$callback> argument	285	and they all accept an additional (and optional) C<$callback> argument
103	which must be a code reference. This code reference will get called with	286	which must be a code reference. This code reference will be called after
104	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	287	the syscall has been executed in an asynchronous fashion. The results
105	perl, which usually delivers "false") as it's sole argument when the given	288	of the request will be passed as arguments to the callback (and, if an
106	syscall has been executed asynchronously.	289	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		290	most syscalls return C<-1> on error, unlike perl, which usually delivers
		291	"false").
		292
		293	Some requests (such as C<aio_readdir>) pass the actual results and
		294	communicate failures by passing C<undef>.
107		295
108	All functions expecting a filehandle keep a copy of the filehandle	296	All functions expecting a filehandle keep a copy of the filehandle
109	internally until the request has finished.	297	internally until the request has finished.
110		298
111	All requests return objects of type L<IO::AIO::REQ> that allow further	299	All functions return request objects of type L<IO::AIO::REQ> that allow
112	manipulation of those requests while they are in-flight.	300	further manipulation of those requests while they are in-flight.
113		301
114	The pathnames you pass to these routines I<must> be absolute and	302	The pathnames you pass to these routines I<should> be absolute. The
115	encoded in byte form. The reason for the former is that at the time the	303	reason for this is that at the time the request is being executed, the
116	request is being executed, the current working directory could have	304	current working directory could have changed. Alternatively, you can
117	changed. Alternatively, you can make sure that you never change the	305	make sure that you never change the current working directory anywhere
118	current working directory.	306	in the program and then use relative paths. You can also take advantage
		307	of IO::AIOs working directory abstraction, that lets you specify paths
		308	relative to some previously-opened "working directory object" - see the
		309	description of the C<IO::AIO::WD> class later in this document.
119		310
120	To encode pathnames to byte form, either make sure you either: a)	311	To encode pathnames as octets, either make sure you either: a) always pass
121	always pass in filenames you got from outside (command line, readdir	312	in filenames you got from outside (command line, readdir etc.) without
122	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	313	tinkering, b) are in your native filesystem encoding, c) use the Encode
123	your pathnames to the locale (or other) encoding in effect in the user	314	module and encode your pathnames to the locale (or other) encoding in
124	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	315	effect in the user environment, d) use Glib::filename_from_unicode on
125	use something else.	316	unicode filenames or e) use something else to ensure your scalar has the
		317	correct contents.
		318
		319	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		320	handles correctly whether it is set or not.
126		321
127	=over 4	322	=over 4
128		323
129	=item aioreq_pri $pri	324	=item $prev_pri = aioreq_pri [$pri]
130		325
131	Sets the priority for the next aio request. The default priority	326	Returns the priority value that would be used for the next request and, if
		327	C<$pri> is given, sets the priority for the next aio request.
		328
132	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,	329	The default priority is C<0>, the minimum and maximum priorities are C<-4>
133	respectively. Requests with higher priority will be serviced first.	330	and C<4>, respectively. Requests with higher priority will be serviced
		331	first.
134		332
135	The priority will be reset to C<0> after each call to one of the C<aio_>	333	The priority will be reset to C<0> after each call to one of the C<aio_*>
136	functions.	334	functions.
137		335
138	Example: open a file with low priority, then read something from it with	336	Example: open a file with low priority, then read something from it with
139	higher priority so the read request is serviced before other low priority	337	higher priority so the read request is serviced before other low priority
140	open requests (potentially spamming the cache):	338	open requests (potentially spamming the cache):
…		…
147	aio_read $_[0], ..., sub {	345	aio_read $_[0], ..., sub {
148	...	346	...
149	};	347	};
150	};	348	};
151		349
		350
152	=item aioreq_nice $pri_adjust	351	=item aioreq_nice $pri_adjust
153		352
154	Similar to C<aioreq_pri>, but subtracts the given value from the current	353	Similar to C<aioreq_pri>, but subtracts the given value from the current
155	priority, so effects are cumulative.	354	priority, so the effect is cumulative.
		355
156		356
157	=item aio_open $pathname, $flags, $mode, $callback->($fh)	357	=item aio_open $pathname, $flags, $mode, $callback->($fh)
158		358
159	Asynchronously open or create a file and call the callback with a newly	359	Asynchronously open or create a file and call the callback with a newly
160	created filehandle for the file.	360	created filehandle for the file.
…		…
166	list. They are the same as used by C<sysopen>.	366	list. They are the same as used by C<sysopen>.
167		367
168	Likewise, C<$mode> specifies the mode of the newly created file, if it	368	Likewise, C<$mode> specifies the mode of the newly created file, if it
169	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	369	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
170	except that it is mandatory (i.e. use C<0> if you don't create new files,	370	except that it is mandatory (i.e. use C<0> if you don't create new files,
171	and C<0666> or C<0777> if you do).	371	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		372	by the umask in effect then the request is being executed, so better never
		373	change the umask.
172		374
173	Example:	375	Example:
174		376
175	aio_open "/etc/passwd", O_RDONLY, 0, sub {	377	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
176	if ($_[0]) {	378	if ($_[0]) {
177	print "open successful, fh is $_[0]\n";	379	print "open successful, fh is $_[0]\n";
178	...	380	...
179	} else {	381	} else {
180	die "open failed: $!\n";	382	die "open failed: $!\n";
181	}	383	}
182	};	384	};
183		385
		386	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		387	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		388	following POSIX and non-POSIX constants are available (missing ones on
		389	your system are, as usual, C<0>):
		390
		391	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		392	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		393	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
		394
		395
184	=item aio_close $fh, $callback->($status)	396	=item aio_close $fh, $callback->($status)
185		397
186	Asynchronously close a file and call the callback with the result	398	Asynchronously close a file and call the callback with the result
187	code. I<WARNING:> although accepted, you should not pass in a perl	399	code.
188	filehandle here, as perl will likely close the file descriptor another
189	time when the filehandle is destroyed. Normally, you can safely call perls
190	C<close> or just let filehandles go out of scope.
191		400
192	This is supposed to be a bug in the API, so that might change. It's	401	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
193	therefore best to avoid this function.	402	closing the file descriptor associated with the filehandle itself.
		403
		404	Therefore, C<aio_close> will not close the filehandle - instead it will
		405	use dup2 to overwrite the file descriptor with the write-end of a pipe
		406	(the pipe fd will be created on demand and will be cached).
		407
		408	Or in other words: the file descriptor will be closed, but it will not be
		409	free for reuse until the perl filehandle is closed.
		410
		411	=cut
194		412
195	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	413	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
196		414
197	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	415	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
198		416
199	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	417	Reads or writes C<$length> bytes from or to the specified C<$fh> and
200	into the scalar given by C<data> and offset C<dataoffset> and calls the	418	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
201	callback without the actual number of bytes read (or -1 on error, just	419	and calls the callback without the actual number of bytes read (or -1 on
202	like the syscall).	420	error, just like the syscall).
		421
		422	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		423	offset plus the actual number of bytes read.
		424
		425	If C<$offset> is undefined, then the current file descriptor offset will
		426	be used (and updated), otherwise the file descriptor offset will not be
		427	changed by these calls.
		428
		429	If C<$length> is undefined in C<aio_write>, use the remaining length of
		430	C<$data>.
		431
		432	If C<$dataoffset> is less than zero, it will be counted from the end of
		433	C<$data>.
203		434
204	The C<$data> scalar I<MUST NOT> be modified in any way while the request	435	The C<$data> scalar I<MUST NOT> be modified in any way while the request
205	is outstanding. Modifying it can result in segfaults or WW3 (if the	436	is outstanding. Modifying it can result in segfaults or World War III (if
206	necessary/optional hardware is installed).	437	the necessary/optional hardware is installed).
207		438
208	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	439	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
209	offset C<0> within the scalar:	440	offset C<0> within the scalar:
210		441
211	aio_read $fh, 7, 15, $buffer, 0, sub {	442	aio_read $fh, 7, 15, $buffer, 0, sub {
212	$_[0] > 0 or die "read error: $!";	443	$_[0] > 0 or die "read error: $!";
213	print "read $_[0] bytes: <$buffer>\n";	444	print "read $_[0] bytes: <$buffer>\n";
214	};	445	};
215		446
216	=item aio_move $srcpath, $dstpath, $callback->($status)
217
218	[EXPERIMENTAL due to internal aio_group use]
219
220	Try to move the I<file> (directories not supported as either source or
221	destination) from C<$srcpath> to C<$dstpath> and call the callback with
222	the C<0> (error) or C<-1> ok.
223
224	This is a composite request that tries to rename(2) the file first. If
225	rename files with C<EXDEV>, it creates the destination file with mode 0200
226	and copies the contents of the source file into it using C<aio_sendfile>,
227	followed by restoring atime, mtime, access mode and uid/gid, in that
228	order, and unlinking the C<$srcpath>.
229
230	If an error occurs, the partial destination file will be unlinked, if
231	possible, except when setting atime, mtime, access mode and uid/gid, where
232	errors are being ignored.
233
234	=cut
235
236	sub aio_move($$$) {
237	my ($src, $dst, $cb) = @_;
238
239	my $grp = aio_group $cb;
240
241	add $grp aio_rename $src, $dst, sub {
242	if ($_[0] && $! == EXDEV) {
243	add $grp aio_open $src, O_RDONLY, 0, sub {
244	if (my $src_fh = $_[0]) {
245	my @stat = stat $src_fh;
246
247	add $grp aio_open $dst, O_WRONLY, 0200, sub {
248	if (my $dst_fh = $_[0]) {
249	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
250	close $src_fh;
251
252	if ($_[0] == $stat[7]) {
253	utime $stat[8], $stat[9], $dst;
254	chmod $stat[2] & 07777, $dst_fh;
255	chown $stat[4], $stat[5], $dst_fh;
256	close $dst_fh;
257
258	add $grp aio_unlink $src, sub {
259	$grp->result ($_[0]);
260	};
261	} else {
262	my $errno = $!;
263	add $grp aio_unlink $dst, sub {
264	$! = $errno;
265	$grp->result (-1);
266	};
267	}
268	};
269	} else {
270	$grp->result (-1);
271	}
272	},
273
274	} else {
275	$grp->result (-1);
276	}
277	};
278	} else {
279	$grp->result ($_[0]);
280	}
281	};
282
283	$grp
284	}
285		447
286	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	448	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
287		449
288	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	450	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
289	reading at byte offset C<$in_offset>, and starts writing at the current	451	reading at byte offset C<$in_offset>, and starts writing at the current
290	file offset of C<$out_fh>. Because of that, it is not safe to issue more	452	file offset of C<$out_fh>. Because of that, it is not safe to issue more
291	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	453	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
292	other.	454	other. The same C<$in_fh> works fine though, as this function does not
		455	move or use the file offset of C<$in_fh>.
293		456
		457	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		458	are written, and there is no way to find out how many more bytes have been
		459	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		460	number of bytes written to C<$out_fh>. Only if the result value equals
		461	C<$length> one can assume that C<$length> bytes have been read.
		462
		463	Unlike with other C<aio_> functions, it makes a lot of sense to use
		464	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		465	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		466	the socket I/O will be non-blocking. Note, however, that you can run
		467	into a trap where C<aio_sendfile> reads some data with readahead, then
		468	fails to write all data, and when the socket is ready the next time, the
		469	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		470	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		471	resource usage.
		472
294	This call tries to make use of a native C<sendfile> syscall to provide	473	This call tries to make use of a native C<sendfile>-like syscall to
295	zero-copy operation. For this to work, C<$out_fh> should refer to a	474	provide zero-copy operation. For this to work, C<$out_fh> should refer to
296	socket, and C<$in_fh> should refer to mmap'able file.	475	a socket, and C<$in_fh> should refer to an mmap'able file.
297		476
298	If the native sendfile call fails or is not implemented, it will be	477	If a native sendfile cannot be found or it fails with C<ENOSYS>,
299	emulated, so you can call C<aio_sendfile> on any type of filehandle	478	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		479	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
300	regardless of the limitations of the operating system.	480	type of filehandle regardless of the limitations of the operating system.
301		481
302	Please note, however, that C<aio_sendfile> can read more bytes from	482	As native sendfile syscalls (as practically any non-POSIX interface hacked
303	C<$in_fh> than are written, and there is no way to find out how many	483	together in a hurry to improve benchmark numbers) tend to be rather buggy
304	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	484	on many systems, this implementation tries to work around some known bugs
305	provides the number of bytes written to C<$out_fh>. Only if the result	485	in Linux and FreeBSD kernels (probably others, too), but that might fail,
306	value equals C<$length> one can assume that C<$length> bytes have been	486	so you really really should check the return value of C<aio_sendfile> -
307	read.	487	fewre bytes than expected might have been transferred.
		488
308		489
309	=item aio_readahead $fh,$offset,$length, $callback->($retval)	490	=item aio_readahead $fh,$offset,$length, $callback->($retval)
310		491
311	C<aio_readahead> populates the page cache with data from a file so that	492	C<aio_readahead> populates the page cache with data from a file so that
312	subsequent reads from that file will not block on disk I/O. The C<$offset>	493	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
318	file. The current file offset of the file is left unchanged.	499	file. The current file offset of the file is left unchanged.
319		500
320	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	501	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
321	emulated by simply reading the data, which would have a similar effect.	502	emulated by simply reading the data, which would have a similar effect.
322		503
		504
323	=item aio_stat $fh_or_path, $callback->($status)	505	=item aio_stat $fh_or_path, $callback->($status)
324		506
325	=item aio_lstat $fh, $callback->($status)	507	=item aio_lstat $fh, $callback->($status)
326		508
327	Works like perl's C<stat> or C<lstat> in void context. The callback will	509	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
332	for an explanation.	514	for an explanation.
333		515
334	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	516	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
335	error when stat'ing a large file, the results will be silently truncated	517	error when stat'ing a large file, the results will be silently truncated
336	unless perl itself is compiled with large file support.	518	unless perl itself is compiled with large file support.
		519
		520	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		521	following constants and functions (if not implemented, the constants will
		522	be C<0> and the functions will either C<croak> or fall back on traditional
		523	behaviour).
		524
		525	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		526	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		527	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
337		528
338	Example: Print the length of F</etc/passwd>:	529	Example: Print the length of F</etc/passwd>:
339		530
340	aio_stat "/etc/passwd", sub {	531	aio_stat "/etc/passwd", sub {
341	$_[0] and die "stat failed: $!";	532	$_[0] and die "stat failed: $!";
342	print "size is ", -s _, "\n";	533	print "size is ", -s _, "\n";
343	};	534	};
344		535
		536
		537	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		538
		539	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		540	whether a file handle or path was passed.
		541
		542	On success, the callback is passed a hash reference with the following
		543	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		544	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		545	is passed.
		546
		547	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		548	C<ST_NOSUID>.
		549
		550	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		551	their correct value when available, or to C<0> on systems that do
		552	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		553	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		554	C<ST_NODIRATIME> and C<ST_RELATIME>.
		555
		556	Example: stat C</wd> and dump out the data if successful.
		557
		558	aio_statvfs "/wd", sub {
		559	my $f = $_[0]
		560	or die "statvfs: $!";
		561
		562	use Data::Dumper;
		563	say Dumper $f;
		564	};
		565
		566	# result:
		567	{
		568	bsize => 1024,
		569	bfree => 4333064312,
		570	blocks => 10253828096,
		571	files => 2050765568,
		572	flag => 4096,
		573	favail => 2042092649,
		574	bavail => 4333064312,
		575	ffree => 2042092649,
		576	namemax => 255,
		577	frsize => 1024,
		578	fsid => 1810
		579	}
		580
		581
		582	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		583
		584	Works like perl's C<utime> function (including the special case of $atime
		585	and $mtime being undef). Fractional times are supported if the underlying
		586	syscalls support them.
		587
		588	When called with a pathname, uses utimes(2) if available, otherwise
		589	utime(2). If called on a file descriptor, uses futimes(2) if available,
		590	otherwise returns ENOSYS, so this is not portable.
		591
		592	Examples:
		593
		594	# set atime and mtime to current time (basically touch(1)):
		595	aio_utime "path", undef, undef;
		596	# set atime to current time and mtime to beginning of the epoch:
		597	aio_utime "path", time, undef; # undef==0
		598
		599
		600	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		601
		602	Works like perl's C<chown> function, except that C<undef> for either $uid
		603	or $gid is being interpreted as "do not change" (but -1 can also be used).
		604
		605	Examples:
		606
		607	# same as "chown root path" in the shell:
		608	aio_chown "path", 0, -1;
		609	# same as above:
		610	aio_chown "path", 0, undef;
		611
		612
		613	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		614
		615	Works like truncate(2) or ftruncate(2).
		616
		617
		618	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		619
		620	Works like perl's C<chmod> function.
		621
		622
345	=item aio_unlink $pathname, $callback->($status)	623	=item aio_unlink $pathname, $callback->($status)
346		624
347	Asynchronously unlink (delete) a file and call the callback with the	625	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	626	result code.
349		627
		628
		629	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		630
		631	[EXPERIMENTAL]
		632
		633	Asynchronously create a device node (or fifo). See mknod(2).
		634
		635	The only (POSIX-) portable way of calling this function is:
		636
		637	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		638
		639	See C<aio_stat> for info about some potentially helpful extra constants
		640	and functions.
		641
350	=item aio_link $srcpath, $dstpath, $callback->($status)	642	=item aio_link $srcpath, $dstpath, $callback->($status)
351		643
352	Asynchronously create a new link to the existing object at C<$srcpath> at	644	Asynchronously create a new link to the existing object at C<$srcpath> at
353	the path C<$dstpath> and call the callback with the result code.	645	the path C<$dstpath> and call the callback with the result code.
354		646
		647
355	=item aio_symlink $srcpath, $dstpath, $callback->($status)	648	=item aio_symlink $srcpath, $dstpath, $callback->($status)
356		649
357	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	650	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
358	the path C<$dstpath> and call the callback with the result code.	651	the path C<$dstpath> and call the callback with the result code.
359		652
		653
		654	=item aio_readlink $pathname, $callback->($link)
		655
		656	Asynchronously read the symlink specified by C<$path> and pass it to
		657	the callback. If an error occurs, nothing or undef gets passed to the
		658	callback.
		659
		660
		661	=item aio_realpath $pathname, $callback->($path)
		662
		663	Asynchronously make the path absolute and resolve any symlinks in
		664	C<$path>. The resulting path only consists of directories (Same as
		665	L<Cwd::realpath>).
		666
		667	This request can be used to get the absolute path of the current working
		668	directory by passing it a path of F<.> (a single dot).
		669
		670
360	=item aio_rename $srcpath, $dstpath, $callback->($status)	671	=item aio_rename $srcpath, $dstpath, $callback->($status)
361		672
362	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	673	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
363	rename(2) and call the callback with the result code.	674	rename(2) and call the callback with the result code.
364		675
		676
		677	=item aio_mkdir $pathname, $mode, $callback->($status)
		678
		679	Asynchronously mkdir (create) a directory and call the callback with
		680	the result code. C<$mode> will be modified by the umask at the time the
		681	request is executed, so do not change your umask.
		682
		683
365	=item aio_rmdir $pathname, $callback->($status)	684	=item aio_rmdir $pathname, $callback->($status)
366		685
367	Asynchronously rmdir (delete) a directory and call the callback with the	686	Asynchronously rmdir (delete) a directory and call the callback with the
368	result code.	687	result code.
		688
369		689
370	=item aio_readdir $pathname, $callback->($entries)	690	=item aio_readdir $pathname, $callback->($entries)
371		691
372	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	692	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
373	directory (i.e. opendir + readdir + closedir). The entries will not be	693	directory (i.e. opendir + readdir + closedir). The entries will not be
374	sorted, and will B<NOT> include the C<.> and C<..> entries.	694	sorted, and will B<NOT> include the C<.> and C<..> entries.
375		695
376	The callback a single argument which is either C<undef> or an array-ref	696	The callback is passed a single argument which is either C<undef> or an
377	with the filenames.	697	array-ref with the filenames.
378		698
		699
		700	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		701
		702	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		703	tune behaviour and output format. In case of an error, C<$entries> will be
		704	C<undef>.
		705
		706	The flags are a combination of the following constants, ORed together (the
		707	flags will also be passed to the callback, possibly modified):
		708
		709	=over 4
		710
		711	=item IO::AIO::READDIR_DENTS
		712
		713	When this flag is off, then the callback gets an arrayref consisting of
		714	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		715	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		716	entry in more detail.
		717
		718	C<$name> is the name of the entry.
		719
		720	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		721
		722	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		723	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		724	C<IO::AIO::DT_WHT>.
		725
		726	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		727	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		728	scalars are read-only: you can not modify them.
		729
		730	C<$inode> is the inode number (which might not be exact on systems with 64
		731	bit inode numbers and 32 bit perls). This field has unspecified content on
		732	systems that do not deliver the inode information.
		733
		734	=item IO::AIO::READDIR_DIRS_FIRST
		735
		736	When this flag is set, then the names will be returned in an order where
		737	likely directories come first, in optimal stat order. This is useful when
		738	you need to quickly find directories, or you want to find all directories
		739	while avoiding to stat() each entry.
		740
		741	If the system returns type information in readdir, then this is used
		742	to find directories directly. Otherwise, likely directories are names
		743	beginning with ".", or otherwise names with no dots, of which names with
		744	short names are tried first.
		745
		746	=item IO::AIO::READDIR_STAT_ORDER
		747
		748	When this flag is set, then the names will be returned in an order
		749	suitable for stat()'ing each one. That is, when you plan to stat()
		750	all files in the given directory, then the returned order will likely
		751	be fastest.
		752
		753	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		754	the likely dirs come first, resulting in a less optimal stat order.
		755
		756	=item IO::AIO::READDIR_FOUND_UNKNOWN
		757
		758	This flag should not be set when calling C<aio_readdirx>. Instead, it
		759	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		760	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		761	C<$type>'s are known, which can be used to speed up some algorithms.
		762
		763	=back
		764
		765
		766	=item aio_load $pathname, $data, $callback->($status)
		767
		768	This is a composite request that tries to fully load the given file into
		769	memory. Status is the same as with aio_read.
		770
		771	=cut
		772
		773	sub aio_load($$;$) {
		774	my ($path, undef, $cb) = @_;
		775	my $data = \$_[1];
		776
		777	my $pri = aioreq_pri;
		778	my $grp = aio_group $cb;
		779
		780	aioreq_pri $pri;
		781	add $grp aio_open $path, O_RDONLY, 0, sub {
		782	my $fh = shift
		783	or return $grp->result (-1);
		784
		785	aioreq_pri $pri;
		786	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		787	$grp->result ($_[0]);
		788	};
		789	};
		790
		791	$grp
		792	}
		793
		794	=item aio_copy $srcpath, $dstpath, $callback->($status)
		795
		796	Try to copy the I<file> (directories not supported as either source or
		797	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		798	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		799
		800	This is a composite request that creates the destination file with
		801	mode 0200 and copies the contents of the source file into it using
		802	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		803	uid/gid, in that order.
		804
		805	If an error occurs, the partial destination file will be unlinked, if
		806	possible, except when setting atime, mtime, access mode and uid/gid, where
		807	errors are being ignored.
		808
		809	=cut
		810
		811	sub aio_copy($$;$) {
		812	my ($src, $dst, $cb) = @_;
		813
		814	my $pri = aioreq_pri;
		815	my $grp = aio_group $cb;
		816
		817	aioreq_pri $pri;
		818	add $grp aio_open $src, O_RDONLY, 0, sub {
		819	if (my $src_fh = $_[0]) {
		820	my @stat = stat $src_fh; # hmm, might block over nfs?
		821
		822	aioreq_pri $pri;
		823	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
		824	if (my $dst_fh = $_[0]) {
		825	aioreq_pri $pri;
		826	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		827	if ($_[0] == $stat[7]) {
		828	$grp->result (0);
		829	close $src_fh;
		830
		831	my $ch = sub {
		832	aioreq_pri $pri;
		833	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		834	aioreq_pri $pri;
		835	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		836	aioreq_pri $pri;
		837	add $grp aio_close $dst_fh;
		838	}
		839	};
		840	};
		841
		842	aioreq_pri $pri;
		843	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		844	if ($_[0] < 0 && $! == ENOSYS) {
		845	aioreq_pri $pri;
		846	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		847	} else {
		848	$ch->();
		849	}
		850	};
		851	} else {
		852	$grp->result (-1);
		853	close $src_fh;
		854	close $dst_fh;
		855
		856	aioreq $pri;
		857	add $grp aio_unlink $dst;
		858	}
		859	};
		860	} else {
		861	$grp->result (-1);
		862	}
		863	},
		864
		865	} else {
		866	$grp->result (-1);
		867	}
		868	};
		869
		870	$grp
		871	}
		872
		873	=item aio_move $srcpath, $dstpath, $callback->($status)
		874
		875	Try to move the I<file> (directories not supported as either source or
		876	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		877	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		878
		879	This is a composite request that tries to rename(2) the file first; if
		880	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		881	that is successful, unlinks the C<$srcpath>.
		882
		883	=cut
		884
		885	sub aio_move($$;$) {
		886	my ($src, $dst, $cb) = @_;
		887
		888	my $pri = aioreq_pri;
		889	my $grp = aio_group $cb;
		890
		891	aioreq_pri $pri;
		892	add $grp aio_rename $src, $dst, sub {
		893	if ($_[0] && $! == EXDEV) {
		894	aioreq_pri $pri;
		895	add $grp aio_copy $src, $dst, sub {
		896	$grp->result ($_[0]);
		897
		898	unless ($_[0]) {
		899	aioreq_pri $pri;
		900	add $grp aio_unlink $src;
		901	}
		902	};
		903	} else {
		904	$grp->result ($_[0]);
		905	}
		906	};
		907
		908	$grp
		909	}
		910
379	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	911	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
380
381	[EXPERIMENTAL due to internal aio_group use]
382		912
383	Scans a directory (similar to C<aio_readdir>) but additionally tries to	913	Scans a directory (similar to C<aio_readdir>) but additionally tries to
384	separate the entries of directory C<$path> into two sets of names, ones	914	efficiently separate the entries of directory C<$path> into two sets of
385	you can recurse into (directories or links to them), and ones you cannot	915	names, directories you can recurse into (directories), and ones you cannot
386	recurse into (everything else).	916	recurse into (everything else, including symlinks to directories).
387		917
388	C<aio_scandir> is a composite request that creates of many sub requests_	918	C<aio_scandir> is a composite request that creates of many sub requests_
389	C<$maxreq> specifies the maximum number of outstanding aio requests that	919	C<$maxreq> specifies the maximum number of outstanding aio requests that
390	this function generates. If it is C<< <= 0 >>, then a suitable default	920	this function generates. If it is C<< <= 0 >>, then a suitable default
391	will be chosen (currently 6).	921	will be chosen (currently 4).
392		922
393	On error, the callback is called without arguments, otherwise it receives	923	On error, the callback is called without arguments, otherwise it receives
394	two array-refs with path-relative entry names.	924	two array-refs with path-relative entry names.
395		925
396	Example:	926	Example:
…		…
403		933
404	Implementation notes.	934	Implementation notes.
405		935
406	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	936	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
407		937
		938	If readdir returns file type information, then this is used directly to
		939	find directories.
		940
408	After reading the directory, the modification time, size etc. of the	941	Otherwise, after reading the directory, the modification time, size etc.
409	directory before and after the readdir is checked, and if they match (and	942	of the directory before and after the readdir is checked, and if they
410	isn't the current time), the link count will be used to decide how many	943	match (and isn't the current time), the link count will be used to decide
411	entries are directories (if >= 2). Otherwise, no knowledge of the number	944	how many entries are directories (if >= 2). Otherwise, no knowledge of the
412	of subdirectories will be assumed.	945	number of subdirectories will be assumed.
413		946
414	Then entries will be sorted into likely directories (everything without	947	Then entries will be sorted into likely directories a non-initial dot
415	a non-initial dot currently) and likely non-directories (everything	948	currently) and likely non-directories (see C<aio_readdirx>). Then every
416	else). Then every entry plus an appended C</.> will be C<stat>'ed,	949	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
417	likely directories first. If that succeeds, it assumes that the entry	950	in order of their inode numbers. If that succeeds, it assumes that the
418	is a directory or a symlink to directory (which will be checked	951	entry is a directory or a symlink to directory (which will be checked
419	seperately). This is often faster than stat'ing the entry itself because	952	separately). This is often faster than stat'ing the entry itself because
420	filesystems might detect the type of the entry without reading the inode	953	filesystems might detect the type of the entry without reading the inode
421	data (e.g. ext2fs filetype feature).	954	data (e.g. ext2fs filetype feature), even on systems that cannot return
		955	the filetype information on readdir.
422		956
423	If the known number of directories (link count - 2) has been reached, the	957	If the known number of directories (link count - 2) has been reached, the
424	rest of the entries is assumed to be non-directories.	958	rest of the entries is assumed to be non-directories.
425		959
426	This only works with certainty on POSIX (= UNIX) filesystems, which	960	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
430	as those tend to return 0 or 1 as link counts, which disables the	964	as those tend to return 0 or 1 as link counts, which disables the
431	directory counting heuristic.	965	directory counting heuristic.
432		966
433	=cut	967	=cut
434		968
435	sub aio_scandir($$$) {	969	sub aio_scandir($$;$) {
436	my ($path, $maxreq, $cb) = @_;	970	my ($path, $maxreq, $cb) = @_;
437		971
		972	my $pri = aioreq_pri;
		973
438	my $grp = aio_group $cb;	974	my $grp = aio_group $cb;
439		975
440	$maxreq = 6 if $maxreq <= 0;	976	$maxreq = 4 if $maxreq <= 0;
441		977
442	# stat once	978	# get a wd object
		979	aioreq_pri $pri;
443	add $grp aio_stat $path, sub {	980	add $grp aio_wd $path, sub {
		981	$_[0]
		982	or return $grp->result ();
		983
		984	my $wd = [shift, "."];
		985
		986	# stat once
		987	aioreq_pri $pri;
		988	add $grp aio_stat $wd, sub {
444	return $grp->result () if $_[0];	989	return $grp->result () if $_[0];
445	my $now = time;	990	my $now = time;
446	my $hash1 = join ":", (stat _)[0,1,3,7,9];	991	my $hash1 = join ":", (stat _)[0,1,3,7,9];
447		992
448	# read the directory entries	993	# read the directory entries
449	add $grp aio_readdir $path, sub {	994	aioreq_pri $pri;
		995	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
450	my $entries = shift	996	my $entries = shift
451	or return $grp->result ();	997	or return $grp->result ();
452		998
453	# stat the dir another time	999	# stat the dir another time
		1000	aioreq_pri $pri;
454	add $grp aio_stat $path, sub {	1001	add $grp aio_stat $wd, sub {
455	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1002	my $hash2 = join ":", (stat _)[0,1,3,7,9];
456		1003
457	my $ndirs;	1004	my $ndirs;
458		1005
459	# take the slow route if anything looks fishy	1006	# take the slow route if anything looks fishy
460	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1007	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
461	$ndirs = -1;	1008	$ndirs = -1;
462	} else {	1009	} else {
463	# if nlink == 2, we are finished	1010	# if nlink == 2, we are finished
464	# on non-posix-fs's, we rely on nlink < 2	1011	# for non-posix-fs's, we rely on nlink < 2
465	$ndirs = (stat _)[3] - 2	1012	$ndirs = (stat _)[3] - 2
466	or return $grp->result ([], $entries);	1013	or return $grp->result ([], $entries);
467	}	1014	}
468		1015
469	# sort into likely dirs and likely nondirs
470	# dirs == files without ".", short entries first
471	$entries = [map $_->[0],
472	sort { $b->[1] cmp $a->[1] }
473	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
474	@$entries];
475
476	my (@dirs, @nondirs);	1016	my (@dirs, @nondirs);
477		1017
478	my ($statcb, $schedcb);
479	my $nreq = 0;
480
481	my $statgrp = add $grp aio_group;	1018	my $statgrp = add $grp aio_group sub {
482
483	$schedcb = sub {
484	if (@$entries) {
485	if ($nreq < $maxreq) {
486	my $ent = pop @$entries;
487	$nreq++;
488	add $statgrp aio_stat "$path/$ent/.", sub { $statcb->($_[0], $ent) };
489	}
490	} elsif (!$nreq) {
491	# finished
492	$statgrp->cancel;
493	undef $statcb;
494	undef $schedcb;
495	$grp->result (\@dirs, \@nondirs);	1019	$grp->result (\@dirs, \@nondirs);
496	}	1020	};
		1021
		1022	limit $statgrp $maxreq;
		1023	feed $statgrp sub {
		1024	return unless @$entries;
		1025	my $entry = shift @$entries;
		1026
		1027	aioreq_pri $pri;
		1028	$wd->[1] = "$entry/.";
		1029	add $statgrp aio_stat $wd, sub {
		1030	if ($_[0] < 0) {
		1031	push @nondirs, $entry;
		1032	} else {
		1033	# need to check for real directory
		1034	aioreq_pri $pri;
		1035	$wd->[1] = $entry;
		1036	add $statgrp aio_lstat $wd, sub {
		1037	if (-d _) {
		1038	push @dirs, $entry;
		1039
		1040	unless (--$ndirs) {
		1041	push @nondirs, @$entries;
		1042	feed $statgrp;
		1043	}
		1044	} else {
		1045	push @nondirs, $entry;
		1046	}
		1047	}
		1048	}
		1049	};
		1050	};
497	};	1051	};
498	$statcb = sub {
499	my ($status, $entry) = @_;
500
501	if ($status < 0) {
502	$nreq--;
503	push @nondirs, $entry;
504	&$schedcb;
505	} else {
506	# need to check for real directory
507	add $grp aio_lstat "$path/$entry", sub {
508	$nreq--;
509
510	if (-d _) {
511	push @dirs, $entry;
512
513	if (!--$ndirs) {
514	push @nondirs, @$entries;
515	$entries = [];
516	}
517	} else {
518	push @nondirs, $entry;
519	}
520
521	&$schedcb;
522	}
523	}
524	};
525
526	&$schedcb while @$entries && $nreq < $maxreq;
527	};	1052	};
528	};	1053	};
529	};	1054	};
530		1055
531	$grp	1056	$grp
532	}	1057	}
533		1058
		1059	=item aio_rmtree $pathname, $callback->($status)
		1060
		1061	Delete a directory tree starting (and including) C<$path>, return the
		1062	status of the final C<rmdir> only. This is a composite request that
		1063	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1064	everything else.
		1065
		1066	=cut
		1067
		1068	sub aio_rmtree;
		1069	sub aio_rmtree($;$) {
		1070	my ($path, $cb) = @_;
		1071
		1072	my $pri = aioreq_pri;
		1073	my $grp = aio_group $cb;
		1074
		1075	aioreq_pri $pri;
		1076	add $grp aio_scandir $path, 0, sub {
		1077	my ($dirs, $nondirs) = @_;
		1078
		1079	my $dirgrp = aio_group sub {
		1080	add $grp aio_rmdir $path, sub {
		1081	$grp->result ($_[0]);
		1082	};
		1083	};
		1084
		1085	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1086	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1087
		1088	add $grp $dirgrp;
		1089	};
		1090
		1091	$grp
		1092	}
		1093
		1094	=item aio_sync $callback->($status)
		1095
		1096	Asynchronously call sync and call the callback when finished.
		1097
534	=item aio_fsync $fh, $callback->($status)	1098	=item aio_fsync $fh, $callback->($status)
535		1099
536	Asynchronously call fsync on the given filehandle and call the callback	1100	Asynchronously call fsync on the given filehandle and call the callback
537	with the fsync result code.	1101	with the fsync result code.
538		1102
…		…
542	callback with the fdatasync result code.	1106	callback with the fdatasync result code.
543		1107
544	If this call isn't available because your OS lacks it or it couldn't be	1108	If this call isn't available because your OS lacks it or it couldn't be
545	detected, it will be emulated by calling C<fsync> instead.	1109	detected, it will be emulated by calling C<fsync> instead.
546		1110
		1111	=item aio_syncfs $fh, $callback->($status)
		1112
		1113	Asynchronously call the syncfs syscall to sync the filesystem associated
		1114	to the given filehandle and call the callback with the syncfs result
		1115	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1116	errno to C<ENOSYS> nevertheless.
		1117
		1118	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1119
		1120	Sync the data portion of the file specified by C<$offset> and C<$length>
		1121	to disk (but NOT the metadata), by calling the Linux-specific
		1122	sync_file_range call. If sync_file_range is not available or it returns
		1123	ENOSYS, then fdatasync or fsync is being substituted.
		1124
		1125	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1126	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1127	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1128	manpage for details.
		1129
		1130	=item aio_pathsync $pathname, $callback->($status)
		1131
		1132	This request tries to open, fsync and close the given path. This is a
		1133	composite request intended to sync directories after directory operations
		1134	(E.g. rename). This might not work on all operating systems or have any
		1135	specific effect, but usually it makes sure that directory changes get
		1136	written to disc. It works for anything that can be opened for read-only,
		1137	not just directories.
		1138
		1139	Future versions of this function might fall back to other methods when
		1140	C<fsync> on the directory fails (such as calling C<sync>).
		1141
		1142	Passes C<0> when everything went ok, and C<-1> on error.
		1143
		1144	=cut
		1145
		1146	sub aio_pathsync($;$) {
		1147	my ($path, $cb) = @_;
		1148
		1149	my $pri = aioreq_pri;
		1150	my $grp = aio_group $cb;
		1151
		1152	aioreq_pri $pri;
		1153	add $grp aio_open $path, O_RDONLY, 0, sub {
		1154	my ($fh) = @_;
		1155	if ($fh) {
		1156	aioreq_pri $pri;
		1157	add $grp aio_fsync $fh, sub {
		1158	$grp->result ($_[0]);
		1159
		1160	aioreq_pri $pri;
		1161	add $grp aio_close $fh;
		1162	};
		1163	} else {
		1164	$grp->result (-1);
		1165	}
		1166	};
		1167
		1168	$grp
		1169	}
		1170
		1171	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1172
		1173	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1174	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1175	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1176	scalar must only be modified in-place while an aio operation is pending on
		1177	it).
		1178
		1179	It calls the C<msync> function of your OS, if available, with the memory
		1180	area starting at C<$offset> in the string and ending C<$length> bytes
		1181	later. If C<$length> is negative, counts from the end, and if C<$length>
		1182	is C<undef>, then it goes till the end of the string. The flags can be
		1183	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
		1184	C<IO::AIO::MS_SYNC>.
		1185
		1186	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1187
		1188	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1189	scalars.
		1190
		1191	It touches (reads or writes) all memory pages in the specified
		1192	range inside the scalar. All caveats and parameters are the same
		1193	as for C<aio_msync>, above, except for flags, which must be either
		1194	C<0> (which reads all pages and ensures they are instantiated) or
		1195	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
		1196	writing an octet from it, which dirties the page).
		1197
		1198	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1199
		1200	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1201	scalars.
		1202
		1203	It reads in all the pages of the underlying storage into memory (if any)
		1204	and locks them, so they are not getting swapped/paged out or removed.
		1205
		1206	If C<$length> is undefined, then the scalar will be locked till the end.
		1207
		1208	On systems that do not implement C<mlock>, this function returns C<-1>
		1209	and sets errno to C<ENOSYS>.
		1210
		1211	Note that the corresponding C<munlock> is synchronous and is
		1212	documented under L<MISCELLANEOUS FUNCTIONS>.
		1213
		1214	Example: open a file, mmap and mlock it - both will be undone when
		1215	C<$data> gets destroyed.
		1216
		1217	open my $fh, "<", $path or die "$path: $!";
		1218	my $data;
		1219	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1220	aio_mlock $data; # mlock in background
		1221
		1222	=item aio_mlockall $flags, $callback->($status)
		1223
		1224	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1225	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1226
		1227	On systems that do not implement C<mlockall>, this function returns C<-1>
		1228	and sets errno to C<ENOSYS>.
		1229
		1230	Note that the corresponding C<munlockall> is synchronous and is
		1231	documented under L<MISCELLANEOUS FUNCTIONS>.
		1232
		1233	Example: asynchronously lock all current and future pages into memory.
		1234
		1235	aio_mlockall IO::AIO::MCL_FUTURE;
		1236
547	=item aio_group $callback->(...)	1237	=item aio_group $callback->(...)
548
549	[EXPERIMENTAL]
550		1238
551	This is a very special aio request: Instead of doing something, it is a	1239	This is a very special aio request: Instead of doing something, it is a
552	container for other aio requests, which is useful if you want to bundle	1240	container for other aio requests, which is useful if you want to bundle
553	many requests into a single, composite, request.	1241	many requests into a single, composite, request with a definite callback
		1242	and the ability to cancel the whole request with its subrequests.
554		1243
555	Returns an object of class L<IO::AIO::GRP>. See its documentation below	1244	Returns an object of class L<IO::AIO::GRP>. See its documentation below
556	for more info.	1245	for more info.
557		1246
558	Example:	1247	Example:
…		…
577	phase and still requires a worker thread. Thus, the callback will not	1266	phase and still requires a worker thread. Thus, the callback will not
578	be executed immediately but only after other requests in the queue have	1267	be executed immediately but only after other requests in the queue have
579	entered their execution phase. This can be used to measure request	1268	entered their execution phase. This can be used to measure request
580	latency.	1269	latency.
581		1270
582	=item IO::AIO::aio_sleep $fractional_seconds, $callback->() *NOT EXPORTED*	1271	=item IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
583		1272
584	Mainly used for debugging and benchmarking, this aio request puts one of	1273	Mainly used for debugging and benchmarking, this aio request puts one of
585	the request workers to sleep for the given time.	1274	the request workers to sleep for the given time.
586		1275
587	While it is theoretically handy to have simple I/O scheduling requests	1276	While it is theoretically handy to have simple I/O scheduling requests
588	like sleep and file handle readable/writable, the overhead this creates	1277	like sleep and file handle readable/writable, the overhead this creates is
589	is immense, so do not use this function except to put your application	1278	immense (it blocks a thread for a long time) so do not use this function
590	under artificial I/O pressure.	1279	except to put your application under artificial I/O pressure.
591		1280
592	=back	1281	=back
		1282
		1283
		1284	=head2 IO::AIO::WD - multiple working directories
		1285
		1286	Your process only has one current working directory, which is used by all
		1287	threads. This makes it hard to use relative paths (some other component
		1288	could call C<chdir> at any time, and it is hard to control when the path
		1289	will be used by IO::AIO).
		1290
		1291	One solution for this is to always use absolute paths. This usually works,
		1292	but can be quite slow (the kernel has to walk the whole path on every
		1293	access), and can also be a hassle to implement.
		1294
		1295	Newer POSIX systems have a number of functions (openat, fdopendir,
		1296	futimensat and so on) that make it possible to specify working directories
		1297	per operation.
		1298
		1299	For portability, and because the clowns who "designed", or shall I write,
		1300	perpetrated this new interface were obviously half-drunk, this abstraction
		1301	cannot be perfect, though.
		1302
		1303	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1304	object. This object stores the canonicalised, absolute version of the
		1305	path, and on systems that allow it, also a directory file descriptor.
		1306
		1307	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1308	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1309	object and a pathname instead (or the IO::AIO::WD object alone, which
		1310	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1311	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1312	to that IO::AIO::WD object.
		1313
		1314	For example, to get a wd object for F</etc> and then stat F<passwd>
		1315	inside, you would write:
		1316
		1317	aio_wd "/etc", sub {
		1318	my $etcdir = shift;
		1319
		1320	# although $etcdir can be undef on error, there is generally no reason
		1321	# to check for errors here, as aio_stat will fail with ENOENT
		1322	# when $etcdir is undef.
		1323
		1324	aio_stat [$etcdir, "passwd"], sub {
		1325	# yay
		1326	};
		1327	};
		1328
		1329	That C<aio_wd> is a request and not a normal function shows that creating
		1330	an IO::AIO::WD object is itself a potentially blocking operation, which is
		1331	why it is done asynchronously.
		1332
		1333	To stat the directory obtained with C<aio_wd> above, one could write
		1334	either of the following three request calls:
		1335
		1336	aio_lstat "/etc" , sub { ... # pathname as normal string
		1337	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1338	aio_lstat $wd , sub { ... # shorthand for the previous
		1339
		1340	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1341	object and the pathname string, so you could write the following without
		1342	causing any issues due to C<$path> getting reused:
		1343
		1344	my $path = [$wd, undef];
		1345
		1346	for my $name (qw(abc def ghi)) {
		1347	$path->[1] = $name;
		1348	aio_stat $path, sub {
		1349	# ...
		1350	};
		1351	}
		1352
		1353	There are some caveats: when directories get renamed (or deleted), the
		1354	pathname string doesn't change, so will point to the new directory (or
		1355	nowhere at all), while the directory fd, if available on the system,
		1356	will still point to the original directory. Most functions accepting a
		1357	pathname will use the directory fd on newer systems, and the string on
		1358	older systems. Some functions (such as realpath) will always rely on the
		1359	string form of the pathname.
		1360
		1361	So this fucntionality is mainly useful to get some protection against
		1362	C<chdir>, to easily get an absolute path out of a relative path for future
		1363	reference, and to speed up doing many operations in the same directory
		1364	(e.g. when stat'ing all files in a directory).
		1365
		1366	The following functions implement this working directory abstraction:
		1367
		1368	=over 4
		1369
		1370	=item aio_wd $pathname, $callback->($wd)
		1371
		1372	Asynchonously canonicalise the given pathname and convert it to an
		1373	IO::AIO::WD object representing it. If possible and supported on the
		1374	system, also open a directory fd to speed up pathname resolution relative
		1375	to this working directory.
		1376
		1377	If something goes wrong, then C<undef> is passwd to the callback instead
		1378	of a working directory object and C<$!> is set appropriately. Since
		1379	passing C<undef> as working directory component of a pathname fails the
		1380	request with C<ENOENT>, there is often no need for error checking in the
		1381	C<aio_wd> callback, as future requests using the value will fail in the
		1382	expected way.
		1383
		1384	If this call isn't available because your OS lacks it or it couldn't be
		1385	detected, it will be emulated by calling C<fsync> instead.
		1386
		1387	=item IO::AIO::CWD
		1388
		1389	This is a compiletime constant (object) that represents the process
		1390	current working directory.
		1391
		1392	Specifying this object as working directory object for a pathname is as
		1393	if the pathname would be specified directly, without a directory object,
		1394	e.g., these calls are functionally identical:
		1395
		1396	aio_stat "somefile", sub { ... };
		1397	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1398
		1399	=back
		1400
593		1401
594	=head2 IO::AIO::REQ CLASS	1402	=head2 IO::AIO::REQ CLASS
595		1403
596	All non-aggregate C<aio_*> functions return an object of this class when	1404	All non-aggregate C<aio_*> functions return an object of this class when
597	called in non-void context.	1405	called in non-void context.
598
599	A request always moves through the following five states in its lifetime,
600	in order: B<ready> (request has been created, but has not been executed
601	yet), B<execute> (request is currently being executed), B<pending>
602	(request has been executed but callback has not been called yet),
603	B<result> (results are being processed synchronously, includes calling the
604	callback) and B<done> (request has reached the end of its lifetime and
605	holds no resources anymore).
606		1406
607	=over 4	1407	=over 4
608		1408
609	=item cancel $req	1409	=item cancel $req
610		1410
611	Cancels the request, if possible. Has the effect of skipping execution	1411	Cancels the request, if possible. Has the effect of skipping execution
612	when entering the B<execute> state and skipping calling the callback when	1412	when entering the B<execute> state and skipping calling the callback when
613	entering the the B<result> state, but will leave the request otherwise	1413	entering the the B<result> state, but will leave the request otherwise
614	untouched. That means that requests that currently execute will not be	1414	untouched (with the exception of readdir). That means that requests that
615	stopped and resources held by the request will not be freed prematurely.	1415	currently execute will not be stopped and resources held by the request
		1416	will not be freed prematurely.
616		1417
617	=item cb $req $callback->(...)	1418	=item cb $req $callback->(...)
618		1419
619	Replace (or simply set) the callback registered to the request.	1420	Replace (or simply set) the callback registered to the request.
620		1421
…		…
664	=item * They can also can also be added to other IO::AIO::GRP objects.	1465	=item * They can also can also be added to other IO::AIO::GRP objects.
665		1466
666	=item * You must not add requests to a group from within the group callback (or	1467	=item * You must not add requests to a group from within the group callback (or
667	any later time).	1468	any later time).
668		1469
669	=item * This does not harmonise well with C<max_outstanding>, so best do
670	not combine C<aio_group> with it. Groups and feeders are recommended for
671	this kind of concurrency-limiting.
672
673	=back	1470	=back
674		1471
675	Their lifetime, simplified, looks like this: when they are empty, they	1472	Their lifetime, simplified, looks like this: when they are empty, they
676	will finish very quickly. If they contain only requests that are in the	1473	will finish very quickly. If they contain only requests that are in the
677	C<done> state, they will also finish. Otherwise they will continue to	1474	C<done> state, they will also finish. Otherwise they will continue to
678	exist.	1475	exist.
679		1476
680	That means after creating a group you have some time to add requests. And	1477	That means after creating a group you have some time to add requests
681	in the callbacks of those requests, you can add further requests to the	1478	(precisely before the callback has been invoked, which is only done within
682	group. And only when all those requests have finished will the the group	1479	the C<poll_cb>). And in the callbacks of those requests, you can add
683	itself finish.	1480	further requests to the group. And only when all those requests have
		1481	finished will the the group itself finish.
684		1482
685	=over 4	1483	=over 4
686		1484
687	=item add $grp ...	1485	=item add $grp ...
688		1486
…		…
692	be added, including other groups, as long as you do not create circular	1490	be added, including other groups, as long as you do not create circular
693	dependencies.	1491	dependencies.
694		1492
695	Returns all its arguments.	1493	Returns all its arguments.
696		1494
		1495	=item $grp->cancel_subs
		1496
		1497	Cancel all subrequests and clears any feeder, but not the group request
		1498	itself. Useful when you queued a lot of events but got a result early.
		1499
		1500	The group request will finish normally (you cannot add requests to the
		1501	group).
		1502
697	=item $grp->result (...)	1503	=item $grp->result (...)
698		1504
699	Set the result value(s) that will be passed to the group callback when all	1505	Set the result value(s) that will be passed to the group callback when all
700	subrequests have finished. By default, no argument will be passed.	1506	subrequests have finished and set the groups errno to the current value
		1507	of errno (just like calling C<errno> without an error number). By default,
		1508	no argument will be passed and errno is zero.
		1509
		1510	=item $grp->errno ([$errno])
		1511
		1512	Sets the group errno value to C<$errno>, or the current value of errno
		1513	when the argument is missing.
		1514
		1515	Every aio request has an associated errno value that is restored when
		1516	the callback is invoked. This method lets you change this value from its
		1517	default (0).
		1518
		1519	Calling C<result> will also set errno, so make sure you either set C<$!>
		1520	before the call to C<result>, or call c<errno> after it.
701		1521
702	=item feed $grp $callback->($grp)	1522	=item feed $grp $callback->($grp)
703
704	[VERY EXPERIMENTAL]
705		1523
706	Sets a feeder/generator on this group: every group can have an attached	1524	Sets a feeder/generator on this group: every group can have an attached
707	generator that generates requests if idle. The idea behind this is that,	1525	generator that generates requests if idle. The idea behind this is that,
708	although you could just queue as many requests as you want in a group,	1526	although you could just queue as many requests as you want in a group,
709	this might starve other requests for a potentially long time. For	1527	this might starve other requests for a potentially long time. For example,
710	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1528	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
711	requests, delaying any later requests for a long time.	1529	requests, delaying any later requests for a long time.
712		1530
713	To avoid this, and allow incremental generation of requests, you can	1531	To avoid this, and allow incremental generation of requests, you can
714	instead a group and set a feeder on it that generates those requests. The	1532	instead a group and set a feeder on it that generates those requests. The
715	feed callback will be called whenever there are few enough (see C<limit>,	1533	feed callback will be called whenever there are few enough (see C<limit>,
…		…
720	not impose any limits).	1538	not impose any limits).
721		1539
722	If the feed does not queue more requests when called, it will be	1540	If the feed does not queue more requests when called, it will be
723	automatically removed from the group.	1541	automatically removed from the group.
724		1542
725	If the feed limit is C<0>, it will be set to C<2> automatically.	1543	If the feed limit is C<0> when this method is called, it will be set to
		1544	C<2> automatically.
726		1545
727	Example:	1546	Example:
728		1547
729	# stat all files in @files, but only ever use four aio requests concurrently:	1548	# stat all files in @files, but only ever use four aio requests concurrently:
730		1549
…		…
742	Sets the feeder limit for the group: The feeder will be called whenever	1561	Sets the feeder limit for the group: The feeder will be called whenever
743	the group contains less than this many requests.	1562	the group contains less than this many requests.
744		1563
745	Setting the limit to C<0> will pause the feeding process.	1564	Setting the limit to C<0> will pause the feeding process.
746		1565
		1566	The default value for the limit is C<0>, but note that setting a feeder
		1567	automatically bumps it up to C<2>.
		1568
747	=back	1569	=back
748		1570
749	=head2 SUPPORT FUNCTIONS	1571	=head2 SUPPORT FUNCTIONS
750		1572
		1573	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1574
751	=over 4	1575	=over 4
752		1576
753	=item $fileno = IO::AIO::poll_fileno	1577	=item $fileno = IO::AIO::poll_fileno
754		1578
755	Return the I<request result pipe file descriptor>. This filehandle must be	1579	Return the I<request result pipe file descriptor>. This filehandle must be
756	polled for reading by some mechanism outside this module (e.g. Event or	1580	polled for reading by some mechanism outside this module (e.g. EV, Glib,
757	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1581	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
758	to call C<poll_cb> to check the results.	1582	you have to call C<poll_cb> to check the results.
759		1583
760	See C<poll_cb> for an example.	1584	See C<poll_cb> for an example.
761		1585
762	=item IO::AIO::poll_cb	1586	=item IO::AIO::poll_cb
763		1587
764	Process all outstanding events on the result pipe. You have to call this	1588	Process some outstanding events on the result pipe. You have to call
765	regularly. Returns the number of events processed. Returns immediately	1589	this regularly. Returns C<0> if all events could be processed (or there
766	when no events are outstanding.	1590	were no events to process), or C<-1> if it returned earlier for whatever
		1591	reason. Returns immediately when no events are outstanding. The amount of
		1592	events processed depends on the settings of C<IO::AIO::max_poll_req> and
		1593	C<IO::AIO::max_poll_time>.
		1594
		1595	If not all requests were processed for whatever reason, the filehandle
		1596	will still be ready when C<poll_cb> returns, so normally you don't have to
		1597	do anything special to have it called later.
		1598
		1599	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1600	ready, it can be beneficial to call this function from loops which submit
		1601	a lot of requests, to make sure the results get processed when they become
		1602	available and not just when the loop is finished and the event loop takes
		1603	over again. This function returns very fast when there are no outstanding
		1604	requests.
767		1605
768	Example: Install an Event watcher that automatically calls	1606	Example: Install an Event watcher that automatically calls
769	IO::AIO::poll_cb with high priority:	1607	IO::AIO::poll_cb with high priority (more examples can be found in the
		1608	SYNOPSIS section, at the top of this document):
770		1609
771	Event->io (fd => IO::AIO::poll_fileno,	1610	Event->io (fd => IO::AIO::poll_fileno,
772	poll => 'r', async => 1,	1611	poll => 'r', async => 1,
773	cb => \&IO::AIO::poll_cb);	1612	cb => \&IO::AIO::poll_cb);
774		1613
775	=item IO::AIO::poll_wait	1614	=item IO::AIO::poll_wait
776		1615
		1616	If there are any outstanding requests and none of them in the result
777	Wait till the result filehandle becomes ready for reading (simply does a	1617	phase, wait till the result filehandle becomes ready for reading (simply
778	C<select> on the filehandle. This is useful if you want to synchronously wait	1618	does a C<select> on the filehandle. This is useful if you want to
779	for some requests to finish).	1619	synchronously wait for some requests to finish).
780		1620
781	See C<nreqs> for an example.	1621	See C<nreqs> for an example.
782		1622
		1623	=item IO::AIO::poll
		1624
		1625	Waits until some requests have been handled.
		1626
		1627	Returns the number of requests processed, but is otherwise strictly
		1628	equivalent to:
		1629
		1630	IO::AIO::poll_wait, IO::AIO::poll_cb
		1631
783	=item IO::AIO::nreqs	1632	=item IO::AIO::flush
784		1633
785	Returns the number of requests currently outstanding (i.e. for which their	1634	Wait till all outstanding AIO requests have been handled.
786	callback has not been invoked yet).
787		1635
788	Example: wait till there are no outstanding requests anymore:	1636	Strictly equivalent to:
789		1637
790	IO::AIO::poll_wait, IO::AIO::poll_cb	1638	IO::AIO::poll_wait, IO::AIO::poll_cb
791	while IO::AIO::nreqs;	1639	while IO::AIO::nreqs;
792		1640
793	=item IO::AIO::flush	1641	=item IO::AIO::max_poll_reqs $nreqs
794		1642
795	Wait till all outstanding AIO requests have been handled.	1643	=item IO::AIO::max_poll_time $seconds
796		1644
797	Strictly equivalent to:	1645	These set the maximum number of requests (default C<0>, meaning infinity)
		1646	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1647	the maximum amount of time (default C<0>, meaning infinity) spent in
		1648	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1649	of time C<poll_cb> is allowed to use).
798		1650
799	IO::AIO::poll_wait, IO::AIO::poll_cb	1651	Setting C<max_poll_time> to a non-zero value creates an overhead of one
800	while IO::AIO::nreqs;	1652	syscall per request processed, which is not normally a problem unless your
		1653	callbacks are really really fast or your OS is really really slow (I am
		1654	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
801		1655
802	=item IO::AIO::poll	1656	Setting these is useful if you want to ensure some level of
		1657	interactiveness when perl is not fast enough to process all requests in
		1658	time.
803		1659
804	Waits until some requests have been handled.	1660	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
805		1661
806	Strictly equivalent to:	1662	Example: Install an Event watcher that automatically calls
		1663	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1664	program get the CPU sometimes even under high AIO load.
807		1665
808	IO::AIO::poll_wait, IO::AIO::poll_cb	1666	# try not to spend much more than 0.1s in poll_cb
809	if IO::AIO::nreqs;	1667	IO::AIO::max_poll_time 0.1;
		1668
		1669	# use a low priority so other tasks have priority
		1670	Event->io (fd => IO::AIO::poll_fileno,
		1671	poll => 'r', nice => 1,
		1672	cb => &IO::AIO::poll_cb);
		1673
		1674	=back
		1675
		1676	=head3 CONTROLLING THE NUMBER OF THREADS
		1677
		1678	=over
810		1679
811	=item IO::AIO::min_parallel $nthreads	1680	=item IO::AIO::min_parallel $nthreads
812		1681
813	Set the minimum number of AIO threads to C<$nthreads>. The current	1682	Set the minimum number of AIO threads to C<$nthreads>. The current
814	default is C<8>, which means eight asynchronous operations can execute	1683	default is C<8>, which means eight asynchronous operations can execute
815	concurrently at any one time (the number of outstanding requests,	1684	concurrently at any one time (the number of outstanding requests,
816	however, is unlimited).	1685	however, is unlimited).
817		1686
818	IO::AIO starts threads only on demand, when an AIO request is queued and	1687	IO::AIO starts threads only on demand, when an AIO request is queued and
819	no free thread exists.	1688	no free thread exists. Please note that queueing up a hundred requests can
		1689	create demand for a hundred threads, even if it turns out that everything
		1690	is in the cache and could have been processed faster by a single thread.
820		1691
821	It is recommended to keep the number of threads relatively low, as some	1692	It is recommended to keep the number of threads relatively low, as some
822	Linux kernel versions will scale negatively with the number of threads	1693	Linux kernel versions will scale negatively with the number of threads
823	(higher parallelity => MUCH higher latency). With current Linux 2.6	1694	(higher parallelity => MUCH higher latency). With current Linux 2.6
824	versions, 4-32 threads should be fine.	1695	versions, 4-32 threads should be fine.
…		…
838	This module automatically runs C<max_parallel 0> at program end, to ensure	1709	This module automatically runs C<max_parallel 0> at program end, to ensure
839	that all threads are killed and that there are no outstanding requests.	1710	that all threads are killed and that there are no outstanding requests.
840		1711
841	Under normal circumstances you don't need to call this function.	1712	Under normal circumstances you don't need to call this function.
842		1713
		1714	=item IO::AIO::max_idle $nthreads
		1715
		1716	Limit the number of threads (default: 4) that are allowed to idle
		1717	(i.e., threads that did not get a request to process within the idle
		1718	timeout (default: 10 seconds). That means if a thread becomes idle while
		1719	C<$nthreads> other threads are also idle, it will free its resources and
		1720	exit.
		1721
		1722	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1723	to allow for extremely high load situations, but want to free resources
		1724	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1725
		1726	The default is probably ok in most situations, especially if thread
		1727	creation is fast. If thread creation is very slow on your system you might
		1728	want to use larger values.
		1729
		1730	=item IO::AIO::idle_timeout $seconds
		1731
		1732	Sets the minimum idle timeout (default 10) after which worker threads are
		1733	allowed to exit. SEe C<IO::AIO::max_idle>.
		1734
843	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1735	=item IO::AIO::max_outstanding $maxreqs
844		1736
845	[DEPRECATED]
846
847	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1737	Sets the maximum number of outstanding requests to C<$nreqs>. If
848	try to queue up more than this number of requests, the caller will block until	1738	you do queue up more than this number of requests, the next call to
849	some requests have been handled.	1739	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1740	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1741	longer exceeded.
850		1742
851	The default is very large, so normally there is no practical limit. If you	1743	In other words, this setting does not enforce a queue limit, but can be
852	queue up many requests in a loop it often improves speed if you set	1744	used to make poll functions block if the limit is exceeded.
853	this to a relatively low number, such as C<100>.
854		1745
855	This function does not work well together with C<aio_group>'s, and their	1746	This is a very bad function to use in interactive programs because it
856	feeder interface is better suited to limiting concurrency, so do not use	1747	blocks, and a bad way to reduce concurrency because it is inexact: Better
857	this function.	1748	use an C<aio_group> together with a feed callback.
858		1749
859	Under normal circumstances you don't need to call this function.	1750	It's main use is in scripts without an event loop - when you want to stat
		1751	a lot of files, you can write somehting like this:
		1752
		1753	IO::AIO::max_outstanding 32;
		1754
		1755	for my $path (...) {
		1756	aio_stat $path , ...;
		1757	IO::AIO::poll_cb;
		1758	}
		1759
		1760	IO::AIO::flush;
		1761
		1762	The call to C<poll_cb> inside the loop will normally return instantly, but
		1763	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1764	some requests have been handled. This keeps the loop from pushing a large
		1765	number of C<aio_stat> requests onto the queue.
		1766
		1767	The default value for C<max_outstanding> is very large, so there is no
		1768	practical limit on the number of outstanding requests.
860		1769
861	=back	1770	=back
862		1771
		1772	=head3 STATISTICAL INFORMATION
		1773
		1774	=over
		1775
		1776	=item IO::AIO::nreqs
		1777
		1778	Returns the number of requests currently in the ready, execute or pending
		1779	states (i.e. for which their callback has not been invoked yet).
		1780
		1781	Example: wait till there are no outstanding requests anymore:
		1782
		1783	IO::AIO::poll_wait, IO::AIO::poll_cb
		1784	while IO::AIO::nreqs;
		1785
		1786	=item IO::AIO::nready
		1787
		1788	Returns the number of requests currently in the ready state (not yet
		1789	executed).
		1790
		1791	=item IO::AIO::npending
		1792
		1793	Returns the number of requests currently in the pending state (executed,
		1794	but not yet processed by poll_cb).
		1795
		1796	=back
		1797
		1798	=head3 MISCELLANEOUS FUNCTIONS
		1799
		1800	IO::AIO implements some functions that might be useful, but are not
		1801	asynchronous.
		1802
		1803	=over 4
		1804
		1805	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		1806
		1807	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		1808	but is blocking (this makes most sense if you know the input data is
		1809	likely cached already and the output filehandle is set to non-blocking
		1810	operations).
		1811
		1812	Returns the number of bytes copied, or C<-1> on error.
		1813
		1814	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		1815
		1816	Simply calls the C<posix_fadvise> function (see its
		1817	manpage for details). The following advice constants are
		1818	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		1819	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		1820	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		1821
		1822	On systems that do not implement C<posix_fadvise>, this function returns
		1823	ENOSYS, otherwise the return value of C<posix_fadvise>.
		1824
		1825	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		1826
		1827	Simply calls the C<posix_madvise> function (see its
		1828	manpage for details). The following advice constants are
		1829	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		1830	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
		1831
		1832	On systems that do not implement C<posix_madvise>, this function returns
		1833	ENOSYS, otherwise the return value of C<posix_madvise>.
		1834
		1835	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		1836
		1837	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		1838	$scalar (see its manpage for details). The following protect
		1839	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		1840	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		1841
		1842	On systems that do not implement C<mprotect>, this function returns
		1843	ENOSYS, otherwise the return value of C<mprotect>.
		1844
		1845	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		1846
		1847	Memory-maps a file (or anonymous memory range) and attaches it to the
		1848	given C<$scalar>, which will act like a string scalar.
		1849
		1850	The only operations allowed on the scalar are C<substr>/C<vec> that don't
		1851	change the string length, and most read-only operations such as copying it
		1852	or searching it with regexes and so on.
		1853
		1854	Anything else is unsafe and will, at best, result in memory leaks.
		1855
		1856	The memory map associated with the C<$scalar> is automatically removed
		1857	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
		1858	C<IO::AIO::munmap> functions are called.
		1859
		1860	This calls the C<mmap>(2) function internally. See your system's manual
		1861	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		1862
		1863	The C<$length> must be larger than zero and smaller than the actual
		1864	filesize.
		1865
		1866	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		1867	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		1868
		1869	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
		1870	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
		1871	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
		1872	(which is set to C<MAP_ANON> if your system only provides this
		1873	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
		1874	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
		1875	C<IO::AIO::MAP_NONBLOCK>
		1876
		1877	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		1878
		1879	C<$offset> is the offset from the start of the file - it generally must be
		1880	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		1881
		1882	Example:
		1883
		1884	use Digest::MD5;
		1885	use IO::AIO;
		1886
		1887	open my $fh, "<verybigfile"
		1888	or die "$!";
		1889
		1890	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		1891	or die "verybigfile: $!";
		1892
		1893	my $fast_md5 = md5 $data;
		1894
		1895	=item IO::AIO::munmap $scalar
		1896
		1897	Removes a previous mmap and undefines the C<$scalar>.
		1898
		1899	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		1900
		1901	Calls the C<munlock> function, undoing the effects of a previous
		1902	C<aio_mlock> call (see its description for details).
		1903
		1904	=item IO::AIO::munlockall
		1905
		1906	Calls the C<munlockall> function.
		1907
		1908	On systems that do not implement C<munlockall>, this function returns
		1909	ENOSYS, otherwise the return value of C<munlockall>.
		1910
		1911	=back
		1912
863	=cut	1913	=cut
864		1914
865	# support function to convert a fd into a perl filehandle
866	sub _fd2fh {
867	return undef if $_[0] < 0;
868
869	# try to generate nice filehandles
870	my $sym = "IO::AIO::fd#$_[0]";
871	local *$sym;
872
873	open *$sym, "+<&=$_[0]" # usually works under any unix
874	or open *$sym, "<&=$_[0]" # cygwin needs this
875	or open *$sym, ">&=$_[0]" # or this
876	or return undef;
877
878	*$sym
879	}
880
881	min_parallel 8;	1915	min_parallel 8;
882		1916
883	END {	1917	END { flush }
884	max_parallel 0;
885	}
886		1918
887	1;	1919	1;
888		1920
		1921	=head1 EVENT LOOP INTEGRATION
		1922
		1923	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		1924	automatically into many event loops:
		1925
		1926	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		1927	use AnyEvent::AIO;
		1928
		1929	You can also integrate IO::AIO manually into many event loops, here are
		1930	some examples of how to do this:
		1931
		1932	# EV integration
		1933	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		1934
		1935	# Event integration
		1936	Event->io (fd => IO::AIO::poll_fileno,
		1937	poll => 'r',
		1938	cb => \&IO::AIO::poll_cb);
		1939
		1940	# Glib/Gtk2 integration
		1941	add_watch Glib::IO IO::AIO::poll_fileno,
		1942	in => sub { IO::AIO::poll_cb; 1 };
		1943
		1944	# Tk integration
		1945	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		1946	readable => \&IO::AIO::poll_cb);
		1947
		1948	# Danga::Socket integration
		1949	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		1950	\&IO::AIO::poll_cb);
		1951
889	=head2 FORK BEHAVIOUR	1952	=head2 FORK BEHAVIOUR
890		1953
891	This module should do "the right thing" when the process using it forks:	1954	Usage of pthreads in a program changes the semantics of fork
		1955	considerably. Specifically, only async-safe functions can be called after
		1956	fork. Perl doesn't know about this, so in general, you cannot call fork
		1957	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		1958	pthreads, so this applies, but many other extensions and (for inexplicable
		1959	reasons) perl itself often is linked against pthreads, so this limitation
		1960	applies to quite a lot of perls.
892		1961
893	Before the fork, IO::AIO enters a quiescent state where no requests	1962	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
894	can be added in other threads and no results will be processed. After	1963	only works in the process that loaded it. Forking is fully supported, but
895	the fork the parent simply leaves the quiescent state and continues	1964	using IO::AIO in the child is not.
896	request/result processing, while the child clears the request/result
897	queue (so the requests started before the fork will only be handled in
898	the parent). Threads will be started on demand until the limit ste in the
899	parent process has been reached again.
900		1965
901	In short: the parent will, after a short pause, continue as if fork had	1966	You might get around by not I<using> IO::AIO before (or after)
902	not been called, while the child will act as if IO::AIO has not been used	1967	forking. You could also try to call the L<IO::AIO::reinit> function in the
903	yet.	1968	child:
		1969
		1970	=over 4
		1971
		1972	=item IO::AIO::reinit
		1973
		1974	Abandons all current requests and I/O threads and simply reinitialises all
		1975	data structures. This is not an operation supported by any standards, but
		1976	happens to work on GNU/Linux and some newer BSD systems.
		1977
		1978	The only reasonable use for this function is to call it after forking, if
		1979	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		1980	the process will result in undefined behaviour. Calling it at any time
		1981	will also result in any undefined (by POSIX) behaviour.
		1982
		1983	=back
904		1984
905	=head2 MEMORY USAGE	1985	=head2 MEMORY USAGE
906		1986
		1987	Per-request usage:
		1988
907	Each aio request uses - depending on your architecture - around 128 bytes	1989	Each aio request uses - depending on your architecture - around 100-200
908	of memory. In addition, stat requests need a stat buffer (possibly a few	1990	bytes of memory. In addition, stat requests need a stat buffer (possibly
909	hundred bytes). Perl scalars and other data passed into aio requests will	1991	a few hundred bytes), readdir requires a result buffer and so on. Perl
910	also be locked.	1992	scalars and other data passed into aio requests will also be locked and
		1993	will consume memory till the request has entered the done state.
911		1994
912	This is now awfully much, so queuing lots of requests is not usually a	1995	This is not awfully much, so queuing lots of requests is not usually a
913	problem.	1996	problem.
914		1997
915	Each thread needs a stack area which is usually around 16k, sometimes much	1998	Per-thread usage:
916	larger, depending on the OS.	1999
		2000	In the execution phase, some aio requests require more memory for
		2001	temporary buffers, and each thread requires a stack and other data
		2002	structures (usually around 16k-128k, depending on the OS).
		2003
		2004	=head1 KNOWN BUGS
		2005
		2006	Known bugs will be fixed in the next release.
917		2007
918	=head1 SEE ALSO	2008	=head1 SEE ALSO
919		2009
920	L<Coro::AIO>.	2010	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2011	more natural syntax.
921		2012
922	=head1 AUTHOR	2013	=head1 AUTHOR
923		2014
924	Marc Lehmann <schmorp@schmorp.de>	2015	Marc Lehmann <schmorp@schmorp.de>
925	http://home.schmorp.de/	2016	http://home.schmorp.de/

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