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Revision 1.183 by root, Sun Sep 12 03:40:05 2010 UTC vs.
Revision 1.299 by root, Fri Dec 28 12:09:50 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
…		…
58	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
59	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
60	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
61	using threads anyway.	61	using threads anyway.
62		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
63	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
64	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
65	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
66	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
67		71
68	=head2 EXAMPLE	72	=head2 EXAMPLE
69		73
70	This is a simple example that uses the EV module and loads	74	This is a simple example that uses the EV module and loads
71	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
72		76
73	use Fcntl;
74	use EV;	77	use EV;
75	use IO::AIO;	78	use IO::AIO;
76		79
77	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
…		…
95		98
96	# file contents now in $contents	99	# file contents now in $contents
97	print $contents;	100	print $contents;
98		101
99	# exit event loop and program	102	# exit event loop and program
100	EV::unloop;	103	EV::break;
101	};	104	};
102	};	105	};
103		106
104	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
105	# check for sockets etc. etc.	108	# check for sockets etc. etc.
106		109
107	# process events as long as there are some:	110	# process events as long as there are some:
108	EV::loop;	111	EV::run;
109		112
110	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
111		114
112	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
113	directly visible to Perl.	116	directly visible to Perl.
…		…
168	use common::sense;	171	use common::sense;
169		172
170	use base 'Exporter';	173	use base 'Exporter';
171		174
172	BEGIN {	175	BEGIN {
173	our $VERSION = '3.65';	176	our $VERSION = 4.7;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
179	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
182	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
183	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
184		190
185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
188	nreqs nready npending nthreads	194	nreqs nready npending nthreads
189	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
190	sendfile fadvise madvise	196	sendfile fadvise madvise
191	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
192		198
193	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
194		200
195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
196		202
…		…
200		206
201	=head1 FUNCTIONS	207	=head1 FUNCTIONS
202		208
203	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
204		210
205	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
206	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
207	documentation.	213	documentation.
208		214
		215	aio_wd $pathname, $callback->($wd)
209	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
210	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
215	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
216	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
217	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
220	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
221	aio_chmod $fh_or_path, $mode, $callback->($status)	230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
222	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
223	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
224	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
225	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
226	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
227	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
228	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
229	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
230	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
234	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
235	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
236	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238	aio_rmtree $path, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
239	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
240	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
241	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
248	aio_group $callback->(...)	263	aio_group $callback->(...)
249	aio_nop $callback->()	264	aio_nop $callback->()
…		…
258	IO::AIO::max_poll_reqs $nreqs	273	IO::AIO::max_poll_reqs $nreqs
259	IO::AIO::max_poll_time $seconds	274	IO::AIO::max_poll_time $seconds
260	IO::AIO::min_parallel $nthreads	275	IO::AIO::min_parallel $nthreads
261	IO::AIO::max_parallel $nthreads	276	IO::AIO::max_parallel $nthreads
262	IO::AIO::max_idle $nthreads	277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
263	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
264	IO::AIO::nreqs	280	IO::AIO::nreqs
265	IO::AIO::nready	281	IO::AIO::nready
266	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
267		285
268	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
269	IO::AIO::fadvise $fh, $offset, $len, $advice	287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
		291	IO::AIO::madvise $scalar, $offset, $length, $advice
		292	IO::AIO::mprotect $scalar, $offset, $length, $protect
270	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
271	IO::AIO::munlockall	294	IO::AIO::munlockall
272		295
273	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
274		297
275	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
276	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
277	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
278	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
279	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
280	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
281	syscall has been executed asynchronously.	304	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		305	most syscalls return C<-1> on error, unlike perl, which usually delivers
		306	"false").
		307
		308	Some requests (such as C<aio_readdir>) pass the actual results and
		309	communicate failures by passing C<undef>.
282		310
283	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
284	internally until the request has finished.	312	internally until the request has finished.
285		313
286	All functions return request objects of type L<IO::AIO::REQ> that allow	314	All functions return request objects of type L<IO::AIO::REQ> that allow
287	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
288		316
289	The pathnames you pass to these routines I<must> be absolute and	317	The pathnames you pass to these routines I<should> be absolute. The
290	encoded as octets. The reason for the former is that at the time the	318	reason for this is that at the time the request is being executed, the
291	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
292	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
293	current working directory anywhere in the program and then use relative	321	in the program and then use relative paths. You can also take advantage
294	paths.	322	of IO::AIOs working directory abstraction, that lets you specify paths
		323	relative to some previously-opened "working directory object" - see the
		324	description of the C<IO::AIO::WD> class later in this document.
295		325
296	To encode pathnames as octets, either make sure you either: a) always pass	326	To encode pathnames as octets, either make sure you either: a) always pass
297	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
298	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	328	tinkering, b) are in your native filesystem encoding, c) use the Encode
299	your pathnames to the locale (or other) encoding in effect in the user	329	module and encode your pathnames to the locale (or other) encoding in
300	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	330	effect in the user environment, d) use Glib::filename_from_unicode on
301	use something else to ensure your scalar has the correct contents.	331	unicode filenames or e) use something else to ensure your scalar has the
		332	correct contents.
302		333
303	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	334	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
304	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
305		338
306	=over 4	339	=over 4
307		340
308	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
309		342
…		…
339		372
340		373
341	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
342		375
343	Asynchronously open or create a file and call the callback with a newly	376	Asynchronously open or create a file and call the callback with a newly
344	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
345		378
346	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	379	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
347	for an explanation.	380	for an explanation.
348		381
349	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	382	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
365	} else {	398	} else {
366	die "open failed: $!\n";	399	die "open failed: $!\n";
367	}	400	}
368	};	401	};
369		402
		403	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		404	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		405	following POSIX and non-POSIX constants are available (missing ones on
		406	your system are, as usual, C<0>):
		407
		408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		411
370		412
371	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
372		414
373	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
374	code.	416	code.
…		…
383	Or in other words: the file descriptor will be closed, but it will not be	425	Or in other words: the file descriptor will be closed, but it will not be
384	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
385		427
386	=cut	428	=cut
387		429
		430	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		431
		432	Seeks the filehandle to the new C<$offset>, similarly to perl's
		433	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		434	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		435	C<IO::AIO::SEEK_END>).
		436
		437	The resulting absolute offset will be passed to the callback, or C<-1> in
		438	case of an error.
		439
		440	In theory, the C<$whence> constants could be different than the
		441	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		442	so don't panic.
		443
		444	As a GNU/Linux (and maybe Solaris) extension, also the constants
		445	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		446	could be found. No guarantees about suitability for use in C<aio_seek> or
		447	Perl's C<sysseek> can be made though, although I would naively assume they
		448	"just work".
		449
388	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
389		451
390	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
391		453
392	Reads or writes C<$length> bytes from or to the specified C<$fh> and	454	Reads or writes C<$length> bytes from or to the specified C<$fh> and
393	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	455	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
394	and calls the callback without the actual number of bytes read (or -1 on	456	calls the callback with the actual number of bytes transferred (or -1 on
395	error, just like the syscall).	457	error, just like the syscall).
396		458
397	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	459	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
398	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
399		461
…		…
424		486
425	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	487	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
426	reading at byte offset C<$in_offset>, and starts writing at the current	488	reading at byte offset C<$in_offset>, and starts writing at the current
427	file offset of C<$out_fh>. Because of that, it is not safe to issue more	489	file offset of C<$out_fh>. Because of that, it is not safe to issue more
428	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	490	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
429	other.	491	other. The same C<$in_fh> works fine though, as this function does not
		492	move or use the file offset of C<$in_fh>.
430		493
		494	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		495	are written, and there is no way to find out how many more bytes have been
		496	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		497	number of bytes written to C<$out_fh>. Only if the result value equals
		498	C<$length> one can assume that C<$length> bytes have been read.
		499
		500	Unlike with other C<aio_> functions, it makes a lot of sense to use
		501	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		502	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		503	the socket I/O will be non-blocking. Note, however, that you can run
		504	into a trap where C<aio_sendfile> reads some data with readahead, then
		505	fails to write all data, and when the socket is ready the next time, the
		506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		508	resource usage.
		509
431	This call tries to make use of a native C<sendfile> syscall to provide	510	This call tries to make use of a native C<sendfile>-like syscall to
432	zero-copy operation. For this to work, C<$out_fh> should refer to a	511	provide zero-copy operation. For this to work, C<$out_fh> should refer to
433	socket, and C<$in_fh> should refer to an mmap'able file.	512	a socket, and C<$in_fh> should refer to an mmap'able file.
434		513
435	If a native sendfile cannot be found or it fails with C<ENOSYS>,	514	If a native sendfile cannot be found or it fails with C<ENOSYS>,
436	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
437	it will be emulated, so you can call C<aio_sendfile> on any type of	516	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
438	filehandle regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
439		518
440	Please note, however, that C<aio_sendfile> can read more bytes from	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
441	C<$in_fh> than are written, and there is no way to find out how many	520	together in a hurry to improve benchmark numbers) tend to be rather buggy
442	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	521	on many systems, this implementation tries to work around some known bugs
443	provides the number of bytes written to C<$out_fh>. Only if the result	522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
444	value equals C<$length> one can assume that C<$length> bytes have been	523	so you really really should check the return value of C<aio_sendfile> -
445	read.	524	fewer bytes than expected might have been transferred.
446		525
447		526
448	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
449		528
450	C<aio_readahead> populates the page cache with data from a file so that	529	C<aio_readahead> populates the page cache with data from a file so that
…		…
454	whole pages, so that offset is effectively rounded down to a page boundary	533	whole pages, so that offset is effectively rounded down to a page boundary
455	and bytes are read up to the next page boundary greater than or equal to	534	and bytes are read up to the next page boundary greater than or equal to
456	(off-set+length). C<aio_readahead> does not read beyond the end of the	535	(off-set+length). C<aio_readahead> does not read beyond the end of the
457	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
458		537
459	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	538	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
460	emulated by simply reading the data, which would have a similar effect.	539	be emulated by simply reading the data, which would have a similar effect.
461		540
462		541
463	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
464		543
465	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
466		545
467	Works like perl's C<stat> or C<lstat> in void context. The callback will	546	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
468	be called after the stat and the results will be available using C<stat _>	547	callback will be called after the stat and the results will be available
469	or C<-s _> etc...	548	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		549	and C<-T>).
470		550
471	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	551	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
472	for an explanation.	552	for an explanation.
473		553
474	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	554	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
475	error when stat'ing a large file, the results will be silently truncated	555	error when stat'ing a large file, the results will be silently truncated
476	unless perl itself is compiled with large file support.	556	unless perl itself is compiled with large file support.
		557
		558	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		559	following constants and functions (if not implemented, the constants will
		560	be C<0> and the functions will either C<croak> or fall back on traditional
		561	behaviour).
		562
		563	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		564	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		565	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		566
		567	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		568	ACCESS>.
477		569
478	Example: Print the length of F</etc/passwd>:	570	Example: Print the length of F</etc/passwd>:
479		571
480	aio_stat "/etc/passwd", sub {	572	aio_stat "/etc/passwd", sub {
481	$_[0] and die "stat failed: $!";	573	$_[0] and die "stat failed: $!";
…		…
525	namemax => 255,	617	namemax => 255,
526	frsize => 1024,	618	frsize => 1024,
527	fsid => 1810	619	fsid => 1810
528	}	620	}
529		621
530
531	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	622	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
532		623
533	Works like perl's C<utime> function (including the special case of $atime	624	Works like perl's C<utime> function (including the special case of $atime
534	and $mtime being undef). Fractional times are supported if the underlying	625	and $mtime being undef). Fractional times are supported if the underlying
535	syscalls support them.	626	syscalls support them.
536		627
537	When called with a pathname, uses utimes(2) if available, otherwise	628	When called with a pathname, uses utimensat(2) or utimes(2) if available,
538	utime(2). If called on a file descriptor, uses futimes(2) if available,	629	otherwise utime(2). If called on a file descriptor, uses futimens(2)
539	otherwise returns ENOSYS, so this is not portable.	630	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		631	portable.
540		632
541	Examples:	633	Examples:
542		634
543	# set atime and mtime to current time (basically touch(1)):	635	# set atime and mtime to current time (basically touch(1)):
544	aio_utime "path", undef, undef;	636	aio_utime "path", undef, undef;
…		…
562	=item aio_truncate $fh_or_path, $offset, $callback->($status)	654	=item aio_truncate $fh_or_path, $offset, $callback->($status)
563		655
564	Works like truncate(2) or ftruncate(2).	656	Works like truncate(2) or ftruncate(2).
565		657
566		658
		659	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		660
		661	Allocates or frees disk space according to the C<$mode> argument. See the
		662	linux C<fallocate> documentation for details.
		663
		664	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		665	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		666	to deallocate a file range.
		667
		668	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		669	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		670	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		671	to unshare shared blocks (see your L<fallocate(2)> manpage).
		672
		673	The file system block size used by C<fallocate> is presumably the
		674	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		675	can dictate other limitations.
		676
		677	If C<fallocate> isn't available or cannot be emulated (currently no
		678	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		679
		680
567	=item aio_chmod $fh_or_path, $mode, $callback->($status)	681	=item aio_chmod $fh_or_path, $mode, $callback->($status)
568		682
569	Works like perl's C<chmod> function.	683	Works like perl's C<chmod> function.
570		684
571		685
…		…
573		687
574	Asynchronously unlink (delete) a file and call the callback with the	688	Asynchronously unlink (delete) a file and call the callback with the
575	result code.	689	result code.
576		690
577		691
578	=item aio_mknod $path, $mode, $dev, $callback->($status)	692	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
579		693
580	[EXPERIMENTAL]	694	[EXPERIMENTAL]
581		695
582	Asynchronously create a device node (or fifo). See mknod(2).	696	Asynchronously create a device node (or fifo). See mknod(2).
583		697
584	The only (POSIX-) portable way of calling this function is:	698	The only (POSIX-) portable way of calling this function is:
585		699
586	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	700	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
587		701
		702	See C<aio_stat> for info about some potentially helpful extra constants
		703	and functions.
588		704
589	=item aio_link $srcpath, $dstpath, $callback->($status)	705	=item aio_link $srcpath, $dstpath, $callback->($status)
590		706
591	Asynchronously create a new link to the existing object at C<$srcpath> at	707	Asynchronously create a new link to the existing object at C<$srcpath> at
592	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
…		…
596		712
597	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	713	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
598	the path C<$dstpath> and call the callback with the result code.	714	the path C<$dstpath> and call the callback with the result code.
599		715
600		716
601	=item aio_readlink $path, $callback->($link)	717	=item aio_readlink $pathname, $callback->($link)
602		718
603	Asynchronously read the symlink specified by C<$path> and pass it to	719	Asynchronously read the symlink specified by C<$path> and pass it to
604	the callback. If an error occurs, nothing or undef gets passed to the	720	the callback. If an error occurs, nothing or undef gets passed to the
605	callback.	721	callback.
606		722
607		723
		724	=item aio_realpath $pathname, $callback->($path)
		725
		726	Asynchronously make the path absolute and resolve any symlinks in
		727	C<$path>. The resulting path only consists of directories (same as
		728	L<Cwd::realpath>).
		729
		730	This request can be used to get the absolute path of the current working
		731	directory by passing it a path of F<.> (a single dot).
		732
		733
608	=item aio_rename $srcpath, $dstpath, $callback->($status)	734	=item aio_rename $srcpath, $dstpath, $callback->($status)
609		735
610	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	736	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
611	rename(2) and call the callback with the result code.	737	rename(2) and call the callback with the result code.
		738
		739	On systems that support the AIO::WD working directory abstraction
		740	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		741	of failing, C<rename> is called on the absolute path of C<$wd>.
		742
		743
		744	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		745
		746	Basically a version of C<aio_rename> with an additional C<$flags>
		747	argument. Calling this with C<$flags=0> is the same as calling
		748	C<aio_rename>.
		749
		750	Non-zero flags are currently only supported on GNU/Linux systems that
		751	support renameat2. Other systems fail with C<ENOSYS> in this case.
		752
		753	The following constants are available (missing ones are, as usual C<0>),
		754	see renameat2(2) for details:
		755
		756	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		757	and C<IO::AIO::RENAME_WHITEOUT>.
612		758
613		759
614	=item aio_mkdir $pathname, $mode, $callback->($status)	760	=item aio_mkdir $pathname, $mode, $callback->($status)
615		761
616	Asynchronously mkdir (create) a directory and call the callback with	762	Asynchronously mkdir (create) a directory and call the callback with
…		…
621	=item aio_rmdir $pathname, $callback->($status)	767	=item aio_rmdir $pathname, $callback->($status)
622		768
623	Asynchronously rmdir (delete) a directory and call the callback with the	769	Asynchronously rmdir (delete) a directory and call the callback with the
624	result code.	770	result code.
625		771
		772	On systems that support the AIO::WD working directory abstraction
		773	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		774	C<rmdir> is called on the absolute path of C<$wd>.
		775
626		776
627	=item aio_readdir $pathname, $callback->($entries)	777	=item aio_readdir $pathname, $callback->($entries)
628		778
629	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	779	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
630	directory (i.e. opendir + readdir + closedir). The entries will not be	780	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
634	array-ref with the filenames.	784	array-ref with the filenames.
635		785
636		786
637	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	787	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
638		788
639	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	789	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
640	behaviour and output format. In case of an error, C<$entries> will be	790	tune behaviour and output format. In case of an error, C<$entries> will be
641	C<undef>.	791	C<undef>.
642		792
643	The flags are a combination of the following constants, ORed together (the	793	The flags are a combination of the following constants, ORed together (the
644	flags will also be passed to the callback, possibly modified):	794	flags will also be passed to the callback, possibly modified):
645		795
646	=over 4	796	=over 4
647		797
648	=item IO::AIO::READDIR_DENTS	798	=item IO::AIO::READDIR_DENTS
649		799
650	When this flag is off, then the callback gets an arrayref with of names	800	Normally the callback gets an arrayref consisting of names only (as
651	only (as with C<aio_readdir>), otherwise it gets an arrayref with	801	with C<aio_readdir>). If this flag is set, then the callback gets an
652	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	802	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
653	entry in more detail.	803	single directory entry in more detail:
654		804
655	C<$name> is the name of the entry.	805	C<$name> is the name of the entry.
656		806
657	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	807	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
658		808
659	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	809	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
660	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	810	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
661	C<IO::AIO::DT_WHT>.	811	C<IO::AIO::DT_WHT>.
662		812
663	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	813	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
664	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	814	to know, you have to run stat yourself. Also, for speed/memory reasons,
665	scalars are read-only: you can not modify them.	815	the C<$type> scalars are read-only: you must not modify them.
666		816
667	C<$inode> is the inode number (which might not be exact on systems with 64	817	C<$inode> is the inode number (which might not be exact on systems with 64
668	bit inode numbers and 32 bit perls). This field has unspecified content on	818	bit inode numbers and 32 bit perls). This field has unspecified content on
669	systems that do not deliver the inode information.	819	systems that do not deliver the inode information.
670		820
671	=item IO::AIO::READDIR_DIRS_FIRST	821	=item IO::AIO::READDIR_DIRS_FIRST
672		822
673	When this flag is set, then the names will be returned in an order where	823	When this flag is set, then the names will be returned in an order where
674	likely directories come first. This is useful when you need to quickly	824	likely directories come first, in optimal stat order. This is useful when
675	find directories, or you want to find all directories while avoiding to	825	you need to quickly find directories, or you want to find all directories
676	stat() each entry.	826	while avoiding to stat() each entry.
677		827
678	If the system returns type information in readdir, then this is used	828	If the system returns type information in readdir, then this is used
679	to find directories directly. Otherwise, likely directories are files	829	to find directories directly. Otherwise, likely directories are names
680	beginning with ".", or otherwise files with no dots, of which files with	830	beginning with ".", or otherwise names with no dots, of which names with
681	short names are tried first.	831	short names are tried first.
682		832
683	=item IO::AIO::READDIR_STAT_ORDER	833	=item IO::AIO::READDIR_STAT_ORDER
684		834
685	When this flag is set, then the names will be returned in an order	835	When this flag is set, then the names will be returned in an order
686	suitable for stat()'ing each one. That is, when you plan to stat()	836	suitable for stat()'ing each one. That is, when you plan to stat() most or
687	all files in the given directory, then the returned order will likely	837	all files in the given directory, then the returned order will likely be
688	be fastest.	838	faster.
689		839
690	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	840	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
691	the likely dirs come first, resulting in a less optimal stat order.	841	then the likely dirs come first, resulting in a less optimal stat order
		842	for stat'ing all entries, but likely a more optimal order for finding
		843	subdirectories.
692		844
693	=item IO::AIO::READDIR_FOUND_UNKNOWN	845	=item IO::AIO::READDIR_FOUND_UNKNOWN
694		846
695	This flag should not be set when calling C<aio_readdirx>. Instead, it	847	This flag should not be set when calling C<aio_readdirx>. Instead, it
696	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	848	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
697	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	849	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
698	C<$type>'s are known, which can be used to speed up some algorithms.	850	C<$type>'s are known, which can be used to speed up some algorithms.
699		851
700	=back	852	=back
701		853
702		854
		855	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		856
		857	Opens, reads and closes the given file. The data is put into C<$data>,
		858	which is resized as required.
		859
		860	If C<$offset> is negative, then it is counted from the end of the file.
		861
		862	If C<$length> is zero, then the remaining length of the file is
		863	used. Also, in this case, the same limitations to modifying C<$data> apply
		864	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		865	with C<substr>. If the size of the file is known, specifying a non-zero
		866	C<$length> results in a performance advantage.
		867
		868	This request is similar to the older C<aio_load> request, but since it is
		869	a single request, it might be more efficient to use.
		870
		871	Example: load F</etc/passwd> into C<$passwd>.
		872
		873	my $passwd;
		874	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		875	$_[0] >= 0
		876	or die "/etc/passwd: $!\n";
		877
		878	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		879	print $passwd;
		880	};
		881	IO::AIO::flush;
		882
		883
703	=item aio_load $path, $data, $callback->($status)	884	=item aio_load $pathname, $data, $callback->($status)
704		885
705	This is a composite request that tries to fully load the given file into	886	This is a composite request that tries to fully load the given file into
706	memory. Status is the same as with aio_read.	887	memory. Status is the same as with aio_read.
		888
		889	Using C<aio_slurp> might be more efficient, as it is a single request.
707		890
708	=cut	891	=cut
709		892
710	sub aio_load($$;$) {	893	sub aio_load($$;$) {
711	my ($path, undef, $cb) = @_;	894	my ($path, undef, $cb) = @_;
…		…
731	=item aio_copy $srcpath, $dstpath, $callback->($status)	914	=item aio_copy $srcpath, $dstpath, $callback->($status)
732		915
733	Try to copy the I<file> (directories not supported as either source or	916	Try to copy the I<file> (directories not supported as either source or
734	destination) from C<$srcpath> to C<$dstpath> and call the callback with	917	destination) from C<$srcpath> to C<$dstpath> and call the callback with
735	a status of C<0> (ok) or C<-1> (error, see C<$!>).	918	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		919
		920	Existing destination files will be truncated.
736		921
737	This is a composite request that creates the destination file with	922	This is a composite request that creates the destination file with
738	mode 0200 and copies the contents of the source file into it using	923	mode 0200 and copies the contents of the source file into it using
739	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	924	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
740	uid/gid, in that order.	925	uid/gid, in that order.
…		…
830	if ($_[0] && $! == EXDEV) {	1015	if ($_[0] && $! == EXDEV) {
831	aioreq_pri $pri;	1016	aioreq_pri $pri;
832	add $grp aio_copy $src, $dst, sub {	1017	add $grp aio_copy $src, $dst, sub {
833	$grp->result ($_[0]);	1018	$grp->result ($_[0]);
834		1019
835	if (!$_[0]) {	1020	unless ($_[0]) {
836	aioreq_pri $pri;	1021	aioreq_pri $pri;
837	add $grp aio_unlink $src;	1022	add $grp aio_unlink $src;
838	}	1023	}
839	};	1024	};
840	} else {	1025	} else {
…		…
843	};	1028	};
844		1029
845	$grp	1030	$grp
846	}	1031	}
847		1032
848	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1033	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
849		1034
850	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1035	Scans a directory (similar to C<aio_readdir>) but additionally tries to
851	efficiently separate the entries of directory C<$path> into two sets of	1036	efficiently separate the entries of directory C<$path> into two sets of
852	names, directories you can recurse into (directories), and ones you cannot	1037	names, directories you can recurse into (directories), and ones you cannot
853	recurse into (everything else, including symlinks to directories).	1038	recurse into (everything else, including symlinks to directories).
854		1039
855	C<aio_scandir> is a composite request that creates of many sub requests_	1040	C<aio_scandir> is a composite request that generates many sub requests.
856	C<$maxreq> specifies the maximum number of outstanding aio requests that	1041	C<$maxreq> specifies the maximum number of outstanding aio requests that
857	this function generates. If it is C<< <= 0 >>, then a suitable default	1042	this function generates. If it is C<< <= 0 >>, then a suitable default
858	will be chosen (currently 4).	1043	will be chosen (currently 4).
859		1044
860	On error, the callback is called without arguments, otherwise it receives	1045	On error, the callback is called without arguments, otherwise it receives
…		…
884	Then entries will be sorted into likely directories a non-initial dot	1069	Then entries will be sorted into likely directories a non-initial dot
885	currently) and likely non-directories (see C<aio_readdirx>). Then every	1070	currently) and likely non-directories (see C<aio_readdirx>). Then every
886	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1071	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
887	in order of their inode numbers. If that succeeds, it assumes that the	1072	in order of their inode numbers. If that succeeds, it assumes that the
888	entry is a directory or a symlink to directory (which will be checked	1073	entry is a directory or a symlink to directory (which will be checked
889	seperately). This is often faster than stat'ing the entry itself because	1074	separately). This is often faster than stat'ing the entry itself because
890	filesystems might detect the type of the entry without reading the inode	1075	filesystems might detect the type of the entry without reading the inode
891	data (e.g. ext2fs filetype feature), even on systems that cannot return	1076	data (e.g. ext2fs filetype feature), even on systems that cannot return
892	the filetype information on readdir.	1077	the filetype information on readdir.
893		1078
894	If the known number of directories (link count - 2) has been reached, the	1079	If the known number of directories (link count - 2) has been reached, the
…		…
910		1095
911	my $grp = aio_group $cb;	1096	my $grp = aio_group $cb;
912		1097
913	$maxreq = 4 if $maxreq <= 0;	1098	$maxreq = 4 if $maxreq <= 0;
914		1099
915	# stat once	1100	# get a wd object
916	aioreq_pri $pri;	1101	aioreq_pri $pri;
917	add $grp aio_stat $path, sub {	1102	add $grp aio_wd $path, sub {
		1103	$_[0]
918	return $grp->result () if $_[0];	1104	or return $grp->result ();
919	my $now = time;
920	my $hash1 = join ":", (stat _)[0,1,3,7,9];
921		1105
922	# read the directory entries	1106	my $wd = [shift, "."];
		1107
		1108	# stat once
923	aioreq_pri $pri;	1109	aioreq_pri $pri;
924	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1110	add $grp aio_stat $wd, sub {
925	my $entries = shift
926	or return $grp->result ();	1111	return $grp->result () if $_[0];
		1112	my $now = time;
		1113	my $hash1 = join ":", (stat _)[0,1,3,7,9];
		1114	my $rdxflags = READDIR_DIRS_FIRST;
927		1115
928	# stat the dir another time	1116	if ((stat _)[3] < 2) {
		1117	# at least one non-POSIX filesystem exists
		1118	# that returns useful DT_type values: btrfs,
		1119	# so optimise for this here by requesting dents
		1120	$rdxflags |= READDIR_DENTS;
		1121	}
		1122
		1123	# read the directory entries
929	aioreq_pri $pri;	1124	aioreq_pri $pri;
930	add $grp aio_stat $path, sub {	1125	add $grp aio_readdirx $wd, $rdxflags, sub {
931	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1126	my ($entries, $flags) = @_
		1127	or return $grp->result ();
932		1128
		1129	if ($rdxflags & READDIR_DENTS) {
		1130	# if we requested type values, see if we can use them directly.
		1131
		1132	# if there were any DT_UNKNOWN entries then we assume we
		1133	# don't know. alternatively, we could assume that if we get
		1134	# one DT_DIR, then all directories are indeed marked with
		1135	# DT_DIR, but this seems not required for btrfs, and this
		1136	# is basically the "btrfs can't get it's act together" code
		1137	# branch.
		1138	unless ($flags & READDIR_FOUND_UNKNOWN) {
		1139	# now we have valid DT_ information for all entries,
		1140	# so use it as an optimisation without further stat's.
		1141	# they must also all be at the beginning of @$entries
		1142	# by now.
		1143
933	my $ndirs;	1144	my $dirs;
934		1145
935	# take the slow route if anything looks fishy
936	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
937	$ndirs = -1;
938	} else {
939	# if nlink == 2, we are finished
940	# for non-posix-fs's, we rely on nlink < 2
941	$ndirs = (stat _)[3] - 2
942	or return $grp->result ([], $entries);
943	}
944
945	my (@dirs, @nondirs);
946
947	my $statgrp = add $grp aio_group sub {
948	$grp->result (\@dirs, \@nondirs);
949	};
950
951	limit $statgrp $maxreq;
952	feed $statgrp sub {
953	return unless @$entries;
954	my $entry = shift @$entries;
955
956	aioreq_pri $pri;
957	add $statgrp aio_stat "$path/$entry/.", sub {
958	if ($_[0] < 0) {	1146	if (@$entries) {
959	push @nondirs, $entry;	1147	for (0 .. $#$entries) {
960	} else {	1148	if ($entries->[$_][1] != DT_DIR) {
961	# need to check for real directory	1149	# splice out directories
962	aioreq_pri $pri;	1150	$dirs = [splice @$entries, 0, $_];
963	add $statgrp aio_lstat "$path/$entry", sub {
964	if (-d _) {
965	push @dirs, $entry;
966
967	unless (--$ndirs) {
968	push @nondirs, @$entries;
969	feed $statgrp;
970	}	1151	last;
971	} else {
972	push @nondirs, $entry;
973	}	1152	}
974	}	1153	}
		1154
		1155	# if we didn't find any non-dir, then all entries are dirs
		1156	unless ($dirs) {
		1157	($dirs, $entries) = ($entries, []);
		1158	}
		1159	} else {
		1160	# directory is empty, so there are no sbdirs
		1161	$dirs = [];
975	}	1162	}
		1163
		1164	# either splice'd the directories out or the dir was empty.
		1165	# convert dents to filenames
		1166	$_ = $_->[0] for @$dirs;
		1167	$_ = $_->[0] for @$entries;
		1168
		1169	return $grp->result ($dirs, $entries);
		1170	}
		1171
		1172	# cannot use, so return to our old ways
		1173	# by pretending we only scanned for names.
		1174	$_ = $_->[0] for @$entries;
		1175	}
		1176
		1177	# stat the dir another time
		1178	aioreq_pri $pri;
		1179	add $grp aio_stat $wd, sub {
		1180	my $hash2 = join ":", (stat _)[0,1,3,7,9];
		1181
		1182	my $ndirs;
		1183
		1184	# take the slow route if anything looks fishy
		1185	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
		1186	$ndirs = -1;
		1187	} else {
		1188	# if nlink == 2, we are finished
		1189	# for non-posix-fs's, we rely on nlink < 2
		1190	$ndirs = (stat _)[3] - 2
		1191	or return $grp->result ([], $entries);
		1192	}
		1193
		1194	my (@dirs, @nondirs);
		1195
		1196	my $statgrp = add $grp aio_group sub {
		1197	$grp->result (\@dirs, \@nondirs);
		1198	};
		1199
		1200	limit $statgrp $maxreq;
		1201	feed $statgrp sub {
		1202	return unless @$entries;
		1203	my $entry = shift @$entries;
		1204
		1205	aioreq_pri $pri;
		1206	$wd->[1] = "$entry/.";
		1207	add $statgrp aio_stat $wd, sub {
		1208	if ($_[0] < 0) {
		1209	push @nondirs, $entry;
		1210	} else {
		1211	# need to check for real directory
		1212	aioreq_pri $pri;
		1213	$wd->[1] = $entry;
		1214	add $statgrp aio_lstat $wd, sub {
		1215	if (-d _) {
		1216	push @dirs, $entry;
		1217
		1218	unless (--$ndirs) {
		1219	push @nondirs, @$entries;
		1220	feed $statgrp;
		1221	}
		1222	} else {
		1223	push @nondirs, $entry;
		1224	}
		1225	}
		1226	}
		1227	};
976	};	1228	};
977	};	1229	};
978	};	1230	};
979	};	1231	};
980	};	1232	};
981		1233
982	$grp	1234	$grp
983	}	1235	}
984		1236
985	=item aio_rmtree $path, $callback->($status)	1237	=item aio_rmtree $pathname, $callback->($status)
986		1238
987	Delete a directory tree starting (and including) C<$path>, return the	1239	Delete a directory tree starting (and including) C<$path>, return the
988	status of the final C<rmdir> only. This is a composite request that	1240	status of the final C<rmdir> only. This is a composite request that
989	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1241	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
990	everything else.	1242	everything else.
991		1243
992	=cut	1244	=cut
993		1245
…		…
1015	};	1267	};
1016		1268
1017	$grp	1269	$grp
1018	}	1270	}
1019		1271
		1272	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1273
		1274	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1275
		1276	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1277	they execute asynchronously and pass the return value to the callback.
		1278
		1279	Both calls can be used for a lot of things, some of which make more sense
		1280	to run asynchronously in their own thread, while some others make less
		1281	sense. For example, calls that block waiting for external events, such
		1282	as locking, will also lock down an I/O thread while it is waiting, which
		1283	can deadlock the whole I/O system. At the same time, there might be no
		1284	alternative to using a thread to wait.
		1285
		1286	So in general, you should only use these calls for things that do
		1287	(filesystem) I/O, not for things that wait for other events (network,
		1288	other processes), although if you are careful and know what you are doing,
		1289	you still can.
		1290
		1291	The following constants are available (missing ones are, as usual C<0>):
		1292
		1293	C<F_DUPFD_CLOEXEC>,
		1294
		1295	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1296
		1297	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1298
		1299	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1300	C<FS_IOC_FIEMAP>.
		1301
		1302	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1303	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1304
		1305	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1306	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1307	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1308	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1309	C<FS_FL_USER_MODIFIABLE>.
		1310
		1311	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1312	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1313	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1314	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1315
1020	=item aio_sync $callback->($status)	1316	=item aio_sync $callback->($status)
1021		1317
1022	Asynchronously call sync and call the callback when finished.	1318	Asynchronously call sync and call the callback when finished.
1023		1319
1024	=item aio_fsync $fh, $callback->($status)	1320	=item aio_fsync $fh, $callback->($status)
…		…
1031	Asynchronously call fdatasync on the given filehandle and call the	1327	Asynchronously call fdatasync on the given filehandle and call the
1032	callback with the fdatasync result code.	1328	callback with the fdatasync result code.
1033		1329
1034	If this call isn't available because your OS lacks it or it couldn't be	1330	If this call isn't available because your OS lacks it or it couldn't be
1035	detected, it will be emulated by calling C<fsync> instead.	1331	detected, it will be emulated by calling C<fsync> instead.
		1332
		1333	=item aio_syncfs $fh, $callback->($status)
		1334
		1335	Asynchronously call the syncfs syscall to sync the filesystem associated
		1336	to the given filehandle and call the callback with the syncfs result
		1337	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1338	errno to C<ENOSYS> nevertheless.
1036		1339
1037	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1340	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1038		1341
1039	Sync the data portion of the file specified by C<$offset> and C<$length>	1342	Sync the data portion of the file specified by C<$offset> and C<$length>
1040	to disk (but NOT the metadata), by calling the Linux-specific	1343	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1044	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1347	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1045	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1348	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1046	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1349	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1047	manpage for details.	1350	manpage for details.
1048		1351
1049	=item aio_pathsync $path, $callback->($status)	1352	=item aio_pathsync $pathname, $callback->($status)
1050		1353
1051	This request tries to open, fsync and close the given path. This is a	1354	This request tries to open, fsync and close the given path. This is a
1052	composite request intended to sync directories after directory operations	1355	composite request intended to sync directories after directory operations
1053	(E.g. rename). This might not work on all operating systems or have any	1356	(E.g. rename). This might not work on all operating systems or have any
1054	specific effect, but usually it makes sure that directory changes get	1357	specific effect, but usually it makes sure that directory changes get
…		…
1085	};	1388	};
1086		1389
1087	$grp	1390	$grp
1088	}	1391	}
1089		1392
1090	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1393	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1091		1394
1092	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1395	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1093	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1396	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1094	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1397	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1095	scalar must only be modified in-place while an aio operation is pending on	1398	scalar must only be modified in-place while an aio operation is pending on
…		…
1097		1400
1098	It calls the C<msync> function of your OS, if available, with the memory	1401	It calls the C<msync> function of your OS, if available, with the memory
1099	area starting at C<$offset> in the string and ending C<$length> bytes	1402	area starting at C<$offset> in the string and ending C<$length> bytes
1100	later. If C<$length> is negative, counts from the end, and if C<$length>	1403	later. If C<$length> is negative, counts from the end, and if C<$length>
1101	is C<undef>, then it goes till the end of the string. The flags can be	1404	is C<undef>, then it goes till the end of the string. The flags can be
1102	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1405	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1103	C<IO::AIO::MS_SYNC>.	1406	C<IO::AIO::MS_INVALIDATE>.
1104		1407
1105	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1408	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1106		1409
1107	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1410	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1108	scalars.	1411	scalars.
1109		1412
1110	It touches (reads or writes) all memory pages in the specified	1413	It touches (reads or writes) all memory pages in the specified
1111	range inside the scalar. All caveats and parameters are the same	1414	range inside the scalar. All caveats and parameters are the same
1112	as for C<aio_msync>, above, except for flags, which must be either	1415	as for C<aio_msync>, above, except for flags, which must be either
1113	C<0> (which reads all pages and ensures they are instantiated) or	1416	C<0> (which reads all pages and ensures they are instantiated) or
1114	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1417	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1115	writing an octet from it, which dirties the page).	1418	writing an octet from it, which dirties the page).
1116		1419
1117	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1420	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1118		1421
1119	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1422	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1138	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;	1441	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1139	aio_mlock $data; # mlock in background	1442	aio_mlock $data; # mlock in background
1140		1443
1141	=item aio_mlockall $flags, $callback->($status)	1444	=item aio_mlockall $flags, $callback->($status)
1142		1445
1143	Calls the C<mlockall> function with the given C<$flags> (a combination of	1446	Calls the C<mlockall> function with the given C<$flags> (a
1144	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).	1447	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1448	C<IO::AIO::MCL_ONFAULT>).
1145		1449
1146	On systems that do not implement C<mlockall>, this function returns C<-1>	1450	On systems that do not implement C<mlockall>, this function returns C<-1>
1147	and sets errno to C<ENOSYS>.	1451	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1452	by the system result in a return value of C<-1> with errno being set to
		1453	C<EINVAL>.
1148		1454
1149	Note that the corresponding C<munlockall> is synchronous and is	1455	Note that the corresponding C<munlockall> is synchronous and is
1150	documented under L<MISCELLANEOUS FUNCTIONS>.	1456	documented under L<MISCELLANEOUS FUNCTIONS>.
1151		1457
1152	Example: asynchronously lock all current and future pages into memory.	1458	Example: asynchronously lock all current and future pages into memory.
1153		1459
1154	aio_mlockall IO::AIO::MCL_FUTURE;	1460	aio_mlockall IO::AIO::MCL_FUTURE;
		1461
		1462	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1463
		1464	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1465	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1466	the ioctl is not available on your OS, then this request will fail with
		1467	C<ENOSYS>.
		1468
		1469	C<$start> is the starting offset to query extents for, C<$length> is the
		1470	size of the range to query - if it is C<undef>, then the whole file will
		1471	be queried.
		1472
		1473	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1474	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1475	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1476	the data portion.
		1477
		1478	C<$count> is the maximum number of extent records to return. If it is
		1479	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1480	case, if it is C<0>, then the callback receives the number of extents
		1481	instead of the extents themselves (which is unreliable, see below).
		1482
		1483	If an error occurs, the callback receives no arguments. The special
		1484	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1485
		1486	Otherwise, the callback receives an array reference with extent
		1487	structures. Each extent structure is an array reference itself, with the
		1488	following members:
		1489
		1490	[$logical, $physical, $length, $flags]
		1491
		1492	Flags is any combination of the following flag values (typically either C<0>
		1493	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1494
		1495	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1496	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1497	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1498	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1499	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1500	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1501
		1502	At the time of this writing (Linux 3.2), this request is unreliable unless
		1503	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1504	it to return all extents of a range for files with a large number of
		1505	extents. The code (only) works around all these issues if C<$count> is
		1506	C<undef>.
1155		1507
1156	=item aio_group $callback->(...)	1508	=item aio_group $callback->(...)
1157		1509
1158	This is a very special aio request: Instead of doing something, it is a	1510	This is a very special aio request: Instead of doing something, it is a
1159	container for other aio requests, which is useful if you want to bundle	1511	container for other aio requests, which is useful if you want to bundle
…		…
1196	like sleep and file handle readable/writable, the overhead this creates is	1548	like sleep and file handle readable/writable, the overhead this creates is
1197	immense (it blocks a thread for a long time) so do not use this function	1549	immense (it blocks a thread for a long time) so do not use this function
1198	except to put your application under artificial I/O pressure.	1550	except to put your application under artificial I/O pressure.
1199		1551
1200	=back	1552	=back
		1553
		1554
		1555	=head2 IO::AIO::WD - multiple working directories
		1556
		1557	Your process only has one current working directory, which is used by all
		1558	threads. This makes it hard to use relative paths (some other component
		1559	could call C<chdir> at any time, and it is hard to control when the path
		1560	will be used by IO::AIO).
		1561
		1562	One solution for this is to always use absolute paths. This usually works,
		1563	but can be quite slow (the kernel has to walk the whole path on every
		1564	access), and can also be a hassle to implement.
		1565
		1566	Newer POSIX systems have a number of functions (openat, fdopendir,
		1567	futimensat and so on) that make it possible to specify working directories
		1568	per operation.
		1569
		1570	For portability, and because the clowns who "designed", or shall I write,
		1571	perpetrated this new interface were obviously half-drunk, this abstraction
		1572	cannot be perfect, though.
		1573
		1574	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1575	object. This object stores the canonicalised, absolute version of the
		1576	path, and on systems that allow it, also a directory file descriptor.
		1577
		1578	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1579	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1580	object and a pathname instead (or the IO::AIO::WD object alone, which
		1581	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1582	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1583	to that IO::AIO::WD object.
		1584
		1585	For example, to get a wd object for F</etc> and then stat F<passwd>
		1586	inside, you would write:
		1587
		1588	aio_wd "/etc", sub {
		1589	my $etcdir = shift;
		1590
		1591	# although $etcdir can be undef on error, there is generally no reason
		1592	# to check for errors here, as aio_stat will fail with ENOENT
		1593	# when $etcdir is undef.
		1594
		1595	aio_stat [$etcdir, "passwd"], sub {
		1596	# yay
		1597	};
		1598	};
		1599
		1600	The fact that C<aio_wd> is a request and not a normal function shows that
		1601	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1602	which is why it is done asynchronously.
		1603
		1604	To stat the directory obtained with C<aio_wd> above, one could write
		1605	either of the following three request calls:
		1606
		1607	aio_lstat "/etc" , sub { ... # pathname as normal string
		1608	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1609	aio_lstat $wd , sub { ... # shorthand for the previous
		1610
		1611	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1612	object and the pathname string, so you could write the following without
		1613	causing any issues due to C<$path> getting reused:
		1614
		1615	my $path = [$wd, undef];
		1616
		1617	for my $name (qw(abc def ghi)) {
		1618	$path->[1] = $name;
		1619	aio_stat $path, sub {
		1620	# ...
		1621	};
		1622	}
		1623
		1624	There are some caveats: when directories get renamed (or deleted), the
		1625	pathname string doesn't change, so will point to the new directory (or
		1626	nowhere at all), while the directory fd, if available on the system,
		1627	will still point to the original directory. Most functions accepting a
		1628	pathname will use the directory fd on newer systems, and the string on
		1629	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1630	the string form of the pathname.
		1631
		1632	So this functionality is mainly useful to get some protection against
		1633	C<chdir>, to easily get an absolute path out of a relative path for future
		1634	reference, and to speed up doing many operations in the same directory
		1635	(e.g. when stat'ing all files in a directory).
		1636
		1637	The following functions implement this working directory abstraction:
		1638
		1639	=over 4
		1640
		1641	=item aio_wd $pathname, $callback->($wd)
		1642
		1643	Asynchonously canonicalise the given pathname and convert it to an
		1644	IO::AIO::WD object representing it. If possible and supported on the
		1645	system, also open a directory fd to speed up pathname resolution relative
		1646	to this working directory.
		1647
		1648	If something goes wrong, then C<undef> is passwd to the callback instead
		1649	of a working directory object and C<$!> is set appropriately. Since
		1650	passing C<undef> as working directory component of a pathname fails the
		1651	request with C<ENOENT>, there is often no need for error checking in the
		1652	C<aio_wd> callback, as future requests using the value will fail in the
		1653	expected way.
		1654
		1655	=item IO::AIO::CWD
		1656
		1657	This is a compiletime constant (object) that represents the process
		1658	current working directory.
		1659
		1660	Specifying this object as working directory object for a pathname is as if
		1661	the pathname would be specified directly, without a directory object. For
		1662	example, these calls are functionally identical:
		1663
		1664	aio_stat "somefile", sub { ... };
		1665	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1666
		1667	=back
		1668
		1669	To recover the path associated with an IO::AIO::WD object, you can use
		1670	C<aio_realpath>:
		1671
		1672	aio_realpath $wd, sub {
		1673	warn "path is $_[0]\n";
		1674	};
		1675
		1676	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1677	sometimes, fall back to using an absolue path.
1201		1678
1202	=head2 IO::AIO::REQ CLASS	1679	=head2 IO::AIO::REQ CLASS
1203		1680
1204	All non-aggregate C<aio_*> functions return an object of this class when	1681	All non-aggregate C<aio_*> functions return an object of this class when
1205	called in non-void context.	1682	called in non-void context.
…		…
1323		1800
1324	Sets a feeder/generator on this group: every group can have an attached	1801	Sets a feeder/generator on this group: every group can have an attached
1325	generator that generates requests if idle. The idea behind this is that,	1802	generator that generates requests if idle. The idea behind this is that,
1326	although you could just queue as many requests as you want in a group,	1803	although you could just queue as many requests as you want in a group,
1327	this might starve other requests for a potentially long time. For example,	1804	this might starve other requests for a potentially long time. For example,
1328	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1805	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1329	delaying any later requests for a long time.	1806	requests, delaying any later requests for a long time.
1330		1807
1331	To avoid this, and allow incremental generation of requests, you can	1808	To avoid this, and allow incremental generation of requests, you can
1332	instead a group and set a feeder on it that generates those requests. The	1809	instead a group and set a feeder on it that generates those requests. The
1333	feed callback will be called whenever there are few enough (see C<limit>,	1810	feed callback will be called whenever there are few enough (see C<limit>,
1334	below) requests active in the group itself and is expected to queue more	1811	below) requests active in the group itself and is expected to queue more
…		…
1366	The default value for the limit is C<0>, but note that setting a feeder	1843	The default value for the limit is C<0>, but note that setting a feeder
1367	automatically bumps it up to C<2>.	1844	automatically bumps it up to C<2>.
1368		1845
1369	=back	1846	=back
1370		1847
		1848
1371	=head2 SUPPORT FUNCTIONS	1849	=head2 SUPPORT FUNCTIONS
1372		1850
1373	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1851	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1374		1852
1375	=over 4	1853	=over 4
…		…
1383		1861
1384	See C<poll_cb> for an example.	1862	See C<poll_cb> for an example.
1385		1863
1386	=item IO::AIO::poll_cb	1864	=item IO::AIO::poll_cb
1387		1865
1388	Process some outstanding events on the result pipe. You have to call this	1866	Process some requests that have reached the result phase (i.e. they have
1389	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1867	been executed but the results are not yet reported). You have to call
1390	returned earlier for whatever reason. Returns immediately when no events	1868	this "regularly" to finish outstanding requests.
1391	are outstanding. The amount of events processed depends on the settings of
1392	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1393		1869
		1870	Returns C<0> if all events could be processed (or there were no
		1871	events to process), or C<-1> if it returned earlier for whatever
		1872	reason. Returns immediately when no events are outstanding. The amount
		1873	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1874	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1875
1394	If not all requests were processed for whatever reason, the filehandle	1876	If not all requests were processed for whatever reason, the poll file
1395	will still be ready when C<poll_cb> returns, so normally you don't have to	1877	descriptor will still be ready when C<poll_cb> returns, so normally you
1396	do anything special to have it called later.	1878	don't have to do anything special to have it called later.
		1879
		1880	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1881	ready, it can be beneficial to call this function from loops which submit
		1882	a lot of requests, to make sure the results get processed when they become
		1883	available and not just when the loop is finished and the event loop takes
		1884	over again. This function returns very fast when there are no outstanding
		1885	requests.
1397		1886
1398	Example: Install an Event watcher that automatically calls	1887	Example: Install an Event watcher that automatically calls
1399	IO::AIO::poll_cb with high priority (more examples can be found in the	1888	IO::AIO::poll_cb with high priority (more examples can be found in the
1400	SYNOPSIS section, at the top of this document):	1889	SYNOPSIS section, at the top of this document):
1401		1890
…		…
1403	poll => 'r', async => 1,	1892	poll => 'r', async => 1,
1404	cb => \&IO::AIO::poll_cb);	1893	cb => \&IO::AIO::poll_cb);
1405		1894
1406	=item IO::AIO::poll_wait	1895	=item IO::AIO::poll_wait
1407		1896
1408	If there are any outstanding requests and none of them in the result	1897	Wait until either at least one request is in the result phase or no
1409	phase, wait till the result filehandle becomes ready for reading (simply	1898	requests are outstanding anymore.
1410	does a C<select> on the filehandle. This is useful if you want to	1899
1411	synchronously wait for some requests to finish).	1900	This is useful if you want to synchronously wait for some requests to
		1901	become ready, without actually handling them.
1412		1902
1413	See C<nreqs> for an example.	1903	See C<nreqs> for an example.
1414		1904
1415	=item IO::AIO::poll	1905	=item IO::AIO::poll
1416		1906
…		…
1427		1917
1428	Strictly equivalent to:	1918	Strictly equivalent to:
1429		1919
1430	IO::AIO::poll_wait, IO::AIO::poll_cb	1920	IO::AIO::poll_wait, IO::AIO::poll_cb
1431	while IO::AIO::nreqs;	1921	while IO::AIO::nreqs;
		1922
		1923	This function can be useful at program aborts, to make sure outstanding
		1924	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1925	this function on normal exits), or when you are merely using C<IO::AIO>
		1926	for its more advanced functions, rather than for async I/O, e.g.:
		1927
		1928	my ($dirs, $nondirs);
		1929	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1930	IO::AIO::flush;
		1931	# $dirs, $nondirs are now set
1432		1932
1433	=item IO::AIO::max_poll_reqs $nreqs	1933	=item IO::AIO::max_poll_reqs $nreqs
1434		1934
1435	=item IO::AIO::max_poll_time $seconds	1935	=item IO::AIO::max_poll_time $seconds
1436		1936
…		…
1463	poll => 'r', nice => 1,	1963	poll => 'r', nice => 1,
1464	cb => &IO::AIO::poll_cb);	1964	cb => &IO::AIO::poll_cb);
1465		1965
1466	=back	1966	=back
1467		1967
		1968
1468	=head3 CONTROLLING THE NUMBER OF THREADS	1969	=head3 CONTROLLING THE NUMBER OF THREADS
1469		1970
1470	=over	1971	=over
1471		1972
1472	=item IO::AIO::min_parallel $nthreads	1973	=item IO::AIO::min_parallel $nthreads
…		…
1503		2004
1504	Under normal circumstances you don't need to call this function.	2005	Under normal circumstances you don't need to call this function.
1505		2006
1506	=item IO::AIO::max_idle $nthreads	2007	=item IO::AIO::max_idle $nthreads
1507		2008
1508	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	2009	Limit the number of threads (default: 4) that are allowed to idle
1509	threads that did not get a request to process within 10 seconds). That	2010	(i.e., threads that did not get a request to process within the idle
1510	means if a thread becomes idle while C<$nthreads> other threads are also	2011	timeout (default: 10 seconds). That means if a thread becomes idle while
1511	idle, it will free its resources and exit.	2012	C<$nthreads> other threads are also idle, it will free its resources and
		2013	exit.
1512		2014
1513	This is useful when you allow a large number of threads (e.g. 100 or 1000)	2015	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1514	to allow for extremely high load situations, but want to free resources	2016	to allow for extremely high load situations, but want to free resources
1515	under normal circumstances (1000 threads can easily consume 30MB of RAM).	2017	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1516		2018
1517	The default is probably ok in most situations, especially if thread	2019	The default is probably ok in most situations, especially if thread
1518	creation is fast. If thread creation is very slow on your system you might	2020	creation is fast. If thread creation is very slow on your system you might
1519	want to use larger values.	2021	want to use larger values.
1520		2022
		2023	=item IO::AIO::idle_timeout $seconds
		2024
		2025	Sets the minimum idle timeout (default 10) after which worker threads are
		2026	allowed to exit. SEe C<IO::AIO::max_idle>.
		2027
1521	=item IO::AIO::max_outstanding $maxreqs	2028	=item IO::AIO::max_outstanding $maxreqs
		2029
		2030	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2031	you do queue up more than this number of requests, the next call to
		2032	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2033	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2034	longer exceeded.
		2035
		2036	In other words, this setting does not enforce a queue limit, but can be
		2037	used to make poll functions block if the limit is exceeded.
1522		2038
1523	This is a very bad function to use in interactive programs because it	2039	This is a very bad function to use in interactive programs because it
1524	blocks, and a bad way to reduce concurrency because it is inexact: Better	2040	blocks, and a bad way to reduce concurrency because it is inexact: Better
1525	use an C<aio_group> together with a feed callback.	2041	use an C<aio_group> together with a feed callback.
1526		2042
1527	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2043	Its main use is in scripts without an event loop - when you want to stat
1528	do queue up more than this number of requests, the next call to the	2044	a lot of files, you can write something like this:
1529	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1530	function will block until the limit is no longer exceeded.
1531		2045
1532	The default value is very large, so there is no practical limit on the	2046	IO::AIO::max_outstanding 32;
1533	number of outstanding requests.
1534		2047
1535	You can still queue as many requests as you want. Therefore,	2048	for my $path (...) {
1536	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2049	aio_stat $path , ...;
1537	as a stop gap to shield against fatal memory overflow (with large values).	2050	IO::AIO::poll_cb;
		2051	}
		2052
		2053	IO::AIO::flush;
		2054
		2055	The call to C<poll_cb> inside the loop will normally return instantly, but
		2056	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2057	some requests have been handled. This keeps the loop from pushing a large
		2058	number of C<aio_stat> requests onto the queue.
		2059
		2060	The default value for C<max_outstanding> is very large, so there is no
		2061	practical limit on the number of outstanding requests.
1538		2062
1539	=back	2063	=back
		2064
1540		2065
1541	=head3 STATISTICAL INFORMATION	2066	=head3 STATISTICAL INFORMATION
1542		2067
1543	=over	2068	=over
1544		2069
…		…
1562	Returns the number of requests currently in the pending state (executed,	2087	Returns the number of requests currently in the pending state (executed,
1563	but not yet processed by poll_cb).	2088	but not yet processed by poll_cb).
1564		2089
1565	=back	2090	=back
1566		2091
		2092
		2093	=head3 SUBSECOND STAT TIME ACCESS
		2094
		2095	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2096	generally find access/modification and change times with subsecond time
		2097	accuracy of the system supports it, but perl's built-in functions only
		2098	return the integer part.
		2099
		2100	The following functions return the timestamps of the most recent
		2101	stat with subsecond precision on most systems and work both after
		2102	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2103	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2104	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2105
		2106	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2107	full resolution without rounding and work with standard perl C<stat>,
		2108	alleviating the need to call the special C<Time::HiRes> functions, which
		2109	do not act like their perl counterparts.
		2110
		2111	On operating systems or file systems where subsecond time resolution is
		2112	not supported or could not be detected, a fractional part of C<0> is
		2113	returned, so it is always safe to call these functions.
		2114
		2115	=over 4
		2116
		2117	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2118
		2119	Return the access, modication, change or birth time, respectively,
		2120	including fractional part. Due to the limited precision of floating point,
		2121	the accuracy on most platforms is only a bit better than milliseconds
		2122	for times around now - see the I<nsec> function family, below, for full
		2123	accuracy.
		2124
		2125	File birth time is only available when the OS and perl support it (on
		2126	FreeBSD and NetBSD at the time of this writing, although support is
		2127	adaptive, so if your OS/perl gains support, IO::AIO can take avdantage of
		2128	it). On systems where it isn't available, C<0> is currently returned, but
		2129	this might change to C<undef> in a future version.
		2130
		2131	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2132
		2133	Returns access, modification, change and birth time all in one go, and
		2134	maybe more times in the future version.
		2135
		2136	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2137
		2138	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2139	as an integer in the range C<0> to C<999999999>.
		2140
		2141	Note that no accessors are provided for access, modification and
		2142	change times - you need to get those from C<stat _> if required (C<int
		2143	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2144	value).
		2145
		2146	=item $seconds = IO::AIO::st_btimesec
		2147
		2148	The (integral) seconds part of the file birth time, if available.
		2149
		2150	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2151
		2152	Like the functions above, but returns all four times in one go (and maybe
		2153	more in future versions).
		2154
		2155	=item $counter = IO::AIO::st_gen
		2156
		2157	Returns the generation counter (in practice this is just a random number)
		2158	of the file. This is only available on platforms which have this member in
		2159	their C<struct stat> (most BSDs at the time of this writing) and generally
		2160	only to the root usert. If unsupported, C<0> is returned, but this might
		2161	change to C<undef> in a future version.
		2162
		2163	=back
		2164
		2165	Example: print the high resolution modification time of F</etc>, using
		2166	C<stat>, and C<IO::AIO::aio_stat>.
		2167
		2168	if (stat "/etc") {
		2169	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2170	}
		2171
		2172	IO::AIO::aio_stat "/etc", sub {
		2173	$_[0]
		2174	and return;
		2175
		2176	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2177	};
		2178
		2179	IO::AIO::flush;
		2180
		2181	Output of the awbove on my system, showing reduced and full accuracy:
		2182
		2183	stat(/etc) mtime: 1534043702.020808
		2184	aio_stat(/etc) mtime: 1534043702.020807792
		2185
		2186
1567	=head3 MISCELLANEOUS FUNCTIONS	2187	=head3 MISCELLANEOUS FUNCTIONS
1568		2188
1569	IO::AIO implements some functions that might be useful, but are not	2189	IO::AIO implements some functions that are useful when you want to use
1570	asynchronous.	2190	some "Advanced I/O" function not available to in Perl, without going the
		2191	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2192	counterpart.
1571		2193
1572	=over 4	2194	=over 4
		2195
		2196	=item $numfd = IO::AIO::get_fdlimit
		2197
		2198	This function is I<EXPERIMENTAL> and subject to change.
		2199
		2200	Tries to find the current file descriptor limit and returns it, or
		2201	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2202	the highest valid file descriptor number.
		2203
		2204	=item IO::AIO::min_fdlimit [$numfd]
		2205
		2206	This function is I<EXPERIMENTAL> and subject to change.
		2207
		2208	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2209	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2210	is missing, it will try to set a very high limit, although this is not
		2211	recommended when you know the actual minimum that you require.
		2212
		2213	If the limit cannot be raised enough, the function makes a best-effort
		2214	attempt to increase the limit as much as possible, using various
		2215	tricks, while still failing. You can query the resulting limit using
		2216	C<IO::AIO::get_fdlimit>.
		2217
		2218	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2219	true.
1573		2220
1574	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2221	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1575		2222
1576	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2223	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1577	but is blocking (this makes most sense if you know the input data is	2224	but is blocking (this makes most sense if you know the input data is
…		…
1580		2227
1581	Returns the number of bytes copied, or C<-1> on error.	2228	Returns the number of bytes copied, or C<-1> on error.
1582		2229
1583	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2230	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1584		2231
1585	Simply calls the C<posix_fadvise> function (see it's	2232	Simply calls the C<posix_fadvise> function (see its
1586	manpage for details). The following advice constants are	2233	manpage for details). The following advice constants are
1587	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2234	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1588	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2235	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1589	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2236	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1590		2237
1591	On systems that do not implement C<posix_fadvise>, this function returns	2238	On systems that do not implement C<posix_fadvise>, this function returns
1592	ENOSYS, otherwise the return value of C<posix_fadvise>.	2239	ENOSYS, otherwise the return value of C<posix_fadvise>.
1593		2240
		2241	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2242
		2243	Simply calls the C<posix_madvise> function (see its
		2244	manpage for details). The following advice constants are
		2245	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2246	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2247	C<IO::AIO::MADV_DONTNEED>.
		2248
		2249	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2250	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2251	will be reduced to fit into the C<$scalar>.
		2252
		2253	On systems that do not implement C<posix_madvise>, this function returns
		2254	ENOSYS, otherwise the return value of C<posix_madvise>.
		2255
		2256	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2257
		2258	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2259	$scalar (see its manpage for details). The following protect
		2260	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2261	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2262
		2263	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2264	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2265	will be reduced to fit into the C<$scalar>.
		2266
		2267	On systems that do not implement C<mprotect>, this function returns
		2268	ENOSYS, otherwise the return value of C<mprotect>.
		2269
1594	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2270	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1595		2271
1596	Memory-maps a file (or anonymous memory range) and attaches it to the	2272	Memory-maps a file (or anonymous memory range) and attaches it to the
1597	given C<$scalar>, which will act like a string scalar.	2273	given C<$scalar>, which will act like a string scalar. Returns true on
		2274	success, and false otherwise.
1598		2275
		2276	The scalar must exist, but its contents do not matter - this means you
		2277	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2278	the scalar first.
		2279
1599	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2280	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1600	change the string length, and most read-only operations such as copying it	2281	which don't change the string length, and most read-only operations such
1601	or searching it with regexes and so on.	2282	as copying it or searching it with regexes and so on.
1602		2283
1603	Anything else is unsafe and will, at best, result in memory leaks.	2284	Anything else is unsafe and will, at best, result in memory leaks.
1604		2285
1605	The memory map associated with the C<$scalar> is automatically removed	2286	The memory map associated with the C<$scalar> is automatically removed
1606	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2287	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1607	C<IO::AIO::munmap> functions are called.	2288	or C<IO::AIO::munmap> functions are called on it.
1608		2289
1609	This calls the C<mmap>(2) function internally. See your system's manual	2290	This calls the C<mmap>(2) function internally. See your system's manual
1610	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2291	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1611		2292
1612	The C<$length> must be larger than zero and smaller than the actual	2293	The C<$length> must be larger than zero and smaller than the actual
1613	filesize.	2294	filesize.
1614		2295
1615	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2296	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1616	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2297	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1617		2298
1618	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2299	C<$flags> can be a combination of
1619	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2300	C<IO::AIO::MAP_SHARED> or
1620	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2301	C<IO::AIO::MAP_PRIVATE>,
		2302	or a number of system-specific flags (when not available, the are C<0>):
1621	(which is set to C<MAP_ANON> if your system only provides this	2303	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1622	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2304	C<IO::AIO::MAP_LOCKED>,
1623	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2305	C<IO::AIO::MAP_NORESERVE>,
		2306	C<IO::AIO::MAP_POPULATE>,
1624	C<IO::AIO::MAP_NONBLOCK>	2307	C<IO::AIO::MAP_NONBLOCK>,
		2308	C<IO::AIO::MAP_FIXED>,
		2309	C<IO::AIO::MAP_GROWSDOWN>,
		2310	C<IO::AIO::MAP_32BIT>,
		2311	C<IO::AIO::MAP_HUGETLB> or
		2312	C<IO::AIO::MAP_STACK>.
1625		2313
1626	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2314	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1627		2315
1628	C<$offset> is the offset from the start of the file - it generally must be	2316	C<$offset> is the offset from the start of the file - it generally must be
1629	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2317	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1643		2331
1644	=item IO::AIO::munmap $scalar	2332	=item IO::AIO::munmap $scalar
1645		2333
1646	Removes a previous mmap and undefines the C<$scalar>.	2334	Removes a previous mmap and undefines the C<$scalar>.
1647		2335
		2336	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2337
		2338	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2339	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2340	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2341
		2342	Returns true if successful, and false otherwise. If the underlying mmapped
		2343	region has changed address, then the true value has the numerical value
		2344	C<1>, otherwise it has the numerical value C<0>:
		2345
		2346	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2347	or die "mremap: $!";
		2348
		2349	if ($success*1) {
		2350	warn "scalar has chanegd address in memory\n";
		2351	}
		2352
		2353	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2354	implemented, but not supported and might go away in a future version.
		2355
		2356	On systems where this call is not supported or is not emulated, this call
		2357	returns falls and sets C<$!> to C<ENOSYS>.
		2358
		2359	=item IO::AIO::mlockall $flags
		2360
		2361	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2362	but is blocking.
		2363
1648	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2364	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1649		2365
1650	Calls the C<munlock> function, undoing the effects of a previous	2366	Calls the C<munlock> function, undoing the effects of a previous
1651	C<aio_mlock> call (see its description for details).	2367	C<aio_mlock> call (see its description for details).
1652		2368
…		…
1654		2370
1655	Calls the C<munlockall> function.	2371	Calls the C<munlockall> function.
1656		2372
1657	On systems that do not implement C<munlockall>, this function returns	2373	On systems that do not implement C<munlockall>, this function returns
1658	ENOSYS, otherwise the return value of C<munlockall>.	2374	ENOSYS, otherwise the return value of C<munlockall>.
		2375
		2376	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2377
		2378	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2379	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2380	should be the file offset.
		2381
		2382	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2383	silently corrupt the data in this case.
		2384
		2385	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2386	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2387	C<IO::AIO::SPLICE_F_GIFT>.
		2388
		2389	See the C<splice(2)> manpage for details.
		2390
		2391	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2392
		2393	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2394	description for C<IO::AIO::splice> above for details.
		2395
		2396	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2397
		2398	Attempts to query or change the pipe buffer size. Obviously works only
		2399	on pipes, and currently works only on GNU/Linux systems, and fails with
		2400	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2401	size on other systems, drop me a note.
		2402
		2403	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2404
		2405	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2406	C<$flags> is missing or C<0>, then this should be the same as a call to
		2407	perl's built-in C<pipe> function and create a new pipe, and works on
		2408	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2409	(..., 4096, O_BINARY)>.
		2410
		2411	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2412	the given flags (Linux 2.6.27, glibc 2.9).
		2413
		2414	On success, the read and write file handles are returned.
		2415
		2416	On error, nothing will be returned. If the pipe2 syscall is missing and
		2417	C<$flags> is non-zero, fails with C<ENOSYS>.
		2418
		2419	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2420	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2421	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2422
		2423	Example: create a pipe race-free w.r.t. threads and fork:
		2424
		2425	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2426	or die "pipe2: $!\n";
		2427
		2428	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2429
		2430	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2431	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2432
		2433	On success, the new eventfd filehandle is returned, otherwise returns
		2434	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2435
		2436	Please refer to L<eventfd(2)> for more info on this call.
		2437
		2438	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2439	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2440
		2441	Example: create a new eventfd filehandle:
		2442
		2443	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2444	or die "eventfd: $!\n";
		2445
		2446	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2447
		2448	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2449	(unhelpful) default for C<$flags> is C<0>.
		2450
		2451	On success, the new timerfd filehandle is returned, otherwise returns
		2452	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2453
		2454	Please refer to L<timerfd_create(2)> for more info on this call.
		2455
		2456	The following C<$clockid> values are
		2457	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2458	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2459	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2460	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2461
		2462	The following C<$flags> values are available (Linux
		2463	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2464
		2465	Example: create a new timerfd and set it to one-second repeated alarms,
		2466	then wait for two alarms:
		2467
		2468	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2469	or die "timerfd_create: $!\n";
		2470
		2471	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2472	or die "timerfd_settime: $!\n";
		2473
		2474	for (1..2) {
		2475	8 == sysread $fh, my $buf, 8
		2476	or die "timerfd read failure\n";
		2477
		2478	printf "number of expirations (likely 1): %d\n",
		2479	unpack "Q", $buf;
		2480	}
		2481
		2482	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2483
		2484	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2485	call. Please refer to its manpage for more info on this call.
		2486
		2487	The new itimerspec is specified using two (possibly fractional) second
		2488	values, C<$new_interval> and C<$new_value>).
		2489
		2490	On success, the current interval and value are returned (as per
		2491	C<timerfd_gettime>). On failure, the empty list is returned.
		2492
		2493	The following C<$flags> values are
		2494	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2495	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2496
		2497	See C<IO::AIO::timerfd_create> for a full example.
		2498
		2499	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2500
		2501	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2502	call. Please refer to its manpage for more info on this call.
		2503
		2504	On success, returns the current values of interval and value for the given
		2505	timerfd (as potentially fractional second values). On failure, the empty
		2506	list is returned.
1659		2507
1660	=back	2508	=back
1661		2509
1662	=cut	2510	=cut
1663		2511
…		…
1698	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2546	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1699	\&IO::AIO::poll_cb);	2547	\&IO::AIO::poll_cb);
1700		2548
1701	=head2 FORK BEHAVIOUR	2549	=head2 FORK BEHAVIOUR
1702		2550
1703	This module should do "the right thing" when the process using it forks:	2551	Usage of pthreads in a program changes the semantics of fork
		2552	considerably. Specifically, only async-safe functions can be called after
		2553	fork. Perl doesn't know about this, so in general, you cannot call fork
		2554	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2555	pthreads, so this applies, but many other extensions and (for inexplicable
		2556	reasons) perl itself often is linked against pthreads, so this limitation
		2557	applies to quite a lot of perls.
1704		2558
1705	Before the fork, IO::AIO enters a quiescent state where no requests	2559	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1706	can be added in other threads and no results will be processed. After	2560	only works in the process that loaded it. Forking is fully supported, but
1707	the fork the parent simply leaves the quiescent state and continues	2561	using IO::AIO in the child is not.
1708	request/result processing, while the child frees the request/result queue
1709	(so that the requests started before the fork will only be handled in the
1710	parent). Threads will be started on demand until the limit set in the
1711	parent process has been reached again.
1712		2562
1713	In short: the parent will, after a short pause, continue as if fork had	2563	You might get around by not I<using> IO::AIO before (or after)
1714	not been called, while the child will act as if IO::AIO has not been used	2564	forking. You could also try to call the L<IO::AIO::reinit> function in the
1715	yet.	2565	child:
		2566
		2567	=over 4
		2568
		2569	=item IO::AIO::reinit
		2570
		2571	Abandons all current requests and I/O threads and simply reinitialises all
		2572	data structures. This is not an operation supported by any standards, but
		2573	happens to work on GNU/Linux and some newer BSD systems.
		2574
		2575	The only reasonable use for this function is to call it after forking, if
		2576	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2577	the process will result in undefined behaviour. Calling it at any time
		2578	will also result in any undefined (by POSIX) behaviour.
		2579
		2580	=back
		2581
		2582	=head2 LINUX-SPECIFIC CALLS
		2583
		2584	When a call is documented as "linux-specific" then this means it
		2585	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2586	availability and compatibility of such calls regardless of the platform
		2587	it is compiled on, so platforms such as FreeBSD which often implement
		2588	these calls will work. When in doubt, call them and see if they fail wth
		2589	C<ENOSYS>.
1716		2590
1717	=head2 MEMORY USAGE	2591	=head2 MEMORY USAGE
1718		2592
1719	Per-request usage:	2593	Per-request usage:
1720		2594
…		…
1733	temporary buffers, and each thread requires a stack and other data	2607	temporary buffers, and each thread requires a stack and other data
1734	structures (usually around 16k-128k, depending on the OS).	2608	structures (usually around 16k-128k, depending on the OS).
1735		2609
1736	=head1 KNOWN BUGS	2610	=head1 KNOWN BUGS
1737		2611
1738	Known bugs will be fixed in the next release.	2612	Known bugs will be fixed in the next release :)
		2613
		2614	=head1 KNOWN ISSUES
		2615
		2616	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2617	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2618	non-created hash slots or other scalars I didn't think of. It's best to
		2619	avoid such and either use scalar variables or making sure that the scalar
		2620	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2621
		2622	I am not sure anything can be done about this, so this is considered a
		2623	known issue, rather than a bug.
1739		2624
1740	=head1 SEE ALSO	2625	=head1 SEE ALSO
1741		2626
1742	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2627	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1743	more natural syntax.	2628	more natural syntax.

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