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Revision 1.194 by root, Fri May 27 00:44:49 2011 UTC vs.
Revision 1.296 by root, Sun Aug 26 03:17:35 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 = '3.9';	176	our $VERSION = 4.6;
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 idle_timeout	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->()
…		…
263	IO::AIO::idle_timeout $seconds	278	IO::AIO::idle_timeout $seconds
264	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
265	IO::AIO::nreqs	280	IO::AIO::nreqs
266	IO::AIO::nready	281	IO::AIO::nready
267	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
268		285
269	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
270	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]
271	IO::AIO::madvise $scalar, $offset, $length, $advice	291	IO::AIO::madvise $scalar, $offset, $length, $advice
272	IO::AIO::mprotect $scalar, $offset, $length, $protect	292	IO::AIO::mprotect $scalar, $offset, $length, $protect
273	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
274	IO::AIO::munlockall	294	IO::AIO::munlockall
275		295
276	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
277		297
278	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
279	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
280	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
281	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
282	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
283	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
284	syscall has been executed asynchronously.	304	error occured, in C<$!>) - 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>.
285		310
286	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
287	internally until the request has finished.	312	internally until the request has finished.
288		313
289	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
290	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
291		316
292	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
293	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
294	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
295	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
296	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
297	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.
298		325
299	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
300	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
301	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
302	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
303	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
304	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.
305		333
306	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
307	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
308		338
309	=over 4	339	=over 4
310		340
311	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
312		342
…		…
342		372
343		373
344	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
345		375
346	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
347	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
348		378
349	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,
350	for an explanation.	380	for an explanation.
351		381
352	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
…		…
375	following POSIX and non-POSIX constants are available (missing ones on	405	following POSIX and non-POSIX constants are available (missing ones on
376	your system are, as usual, C<0>):	406	your system are, as usual, C<0>):
377		407
378	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,	408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
379	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,	409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
380	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.	410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
381		411
382		412
383	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
384		414
385	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
…		…
395	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
396	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
397		427
398	=cut	428	=cut
399		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
400	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
401		451
402	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
403		453
404	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
405	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
406	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
407	error, just like the syscall).	457	error, just like the syscall).
408		458
409	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
410	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
411		461
…		…
436		486
437	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
438	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
439	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
440	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
441	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>.
442		493
443	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than	494	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
444	are written, and there is no way to find out how many bytes have been read	495	are written, and there is no way to find out how many more bytes have been
445	from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of	496	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
446	bytes written to C<$out_fh>. Only if the result value equals C<$length>	497	number of bytes written to C<$out_fh>. Only if the result value equals
447	one can assume that C<$length> bytes have been read.	498	C<$length> one can assume that C<$length> bytes have been read.
448		499
449	Unlike with other C<aio_> functions, it makes a lot of sense to use	500	Unlike with other C<aio_> functions, it makes a lot of sense to use
450	C<aio_sendfile> on non-blocking sockets, as long as one end (typically	501	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
451	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while	502	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
452	the socket I/O will be non-blocking. Note, however, that you can run into	503	the socket I/O will be non-blocking. Note, however, that you can run
453	a trap where C<aio_sendfile> reads some data with readahead, then fails	504	into a trap where C<aio_sendfile> reads some data with readahead, then
454	to write all data, and when the socket is ready the next time, the data	505	fails to write all data, and when the socket is ready the next time, the
455	in the cache is already lost, forcing C<aio_sendfile> to again hit the	506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
456	disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage	507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
457	much better.	508	resource usage.
458		509
459	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
460	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
461	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.
462		513
463	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>,
464	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
465	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
466	filehandle regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
		518
		519	As native sendfile syscalls (as practically any non-POSIX interface hacked
		520	together in a hurry to improve benchmark numbers) tend to be rather buggy
		521	on many systems, this implementation tries to work around some known bugs
		522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
		523	so you really really should check the return value of C<aio_sendfile> -
		524	fewer bytes than expected might have been transferred.
467		525
468		526
469	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
470		528
471	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
…		…
475	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
476	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
477	(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
478	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
479		537
480	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
481	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.
482		540
483		541
484	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
485		543
486	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
487		545
488	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
489	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
490	or C<-s _> etc...	548	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		549	and C<-T>).
491		550
492	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,
493	for an explanation.	552	for an explanation.
494		553
495	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
…		…
502	behaviour).	561	behaviour).
503		562
504	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,	563	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
505	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,	564	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
506	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.	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>.
507		569
508	Example: Print the length of F</etc/passwd>:	570	Example: Print the length of F</etc/passwd>:
509		571
510	aio_stat "/etc/passwd", sub {	572	aio_stat "/etc/passwd", sub {
511	$_[0] and die "stat failed: $!";	573	$_[0] and die "stat failed: $!";
…		…
555	namemax => 255,	617	namemax => 255,
556	frsize => 1024,	618	frsize => 1024,
557	fsid => 1810	619	fsid => 1810
558	}	620	}
559		621
560
561	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	622	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
562		623
563	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
564	and $mtime being undef). Fractional times are supported if the underlying	625	and $mtime being undef). Fractional times are supported if the underlying
565	syscalls support them.	626	syscalls support them.
566		627
567	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,
568	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)
569	otherwise returns ENOSYS, so this is not portable.	630	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		631	portable.
570		632
571	Examples:	633	Examples:
572		634
573	# set atime and mtime to current time (basically touch(1)):	635	# set atime and mtime to current time (basically touch(1)):
574	aio_utime "path", undef, undef;	636	aio_utime "path", undef, undef;
…		…
592	=item aio_truncate $fh_or_path, $offset, $callback->($status)	654	=item aio_truncate $fh_or_path, $offset, $callback->($status)
593		655
594	Works like truncate(2) or ftruncate(2).	656	Works like truncate(2) or ftruncate(2).
595		657
596		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
597	=item aio_chmod $fh_or_path, $mode, $callback->($status)	681	=item aio_chmod $fh_or_path, $mode, $callback->($status)
598		682
599	Works like perl's C<chmod> function.	683	Works like perl's C<chmod> function.
600		684
601		685
…		…
603		687
604	Asynchronously unlink (delete) a file and call the callback with the	688	Asynchronously unlink (delete) a file and call the callback with the
605	result code.	689	result code.
606		690
607		691
608	=item aio_mknod $path, $mode, $dev, $callback->($status)	692	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
609		693
610	[EXPERIMENTAL]	694	[EXPERIMENTAL]
611		695
612	Asynchronously create a device node (or fifo). See mknod(2).	696	Asynchronously create a device node (or fifo). See mknod(2).
613		697
614	The only (POSIX-) portable way of calling this function is:	698	The only (POSIX-) portable way of calling this function is:
615		699
616	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	700	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
617		701
618	See C<aio_stat> for info about some potentially helpful extra constants	702	See C<aio_stat> for info about some potentially helpful extra constants
619	and functions.	703	and functions.
620		704
621	=item aio_link $srcpath, $dstpath, $callback->($status)	705	=item aio_link $srcpath, $dstpath, $callback->($status)
…		…
628		712
629	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
630	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.
631		715
632		716
633	=item aio_readlink $path, $callback->($link)	717	=item aio_readlink $pathname, $callback->($link)
634		718
635	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
636	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
637	callback.	721	callback.
638		722
639		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
640	=item aio_rename $srcpath, $dstpath, $callback->($status)	734	=item aio_rename $srcpath, $dstpath, $callback->($status)
641		735
642	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
643	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>.
644		758
645		759
646	=item aio_mkdir $pathname, $mode, $callback->($status)	760	=item aio_mkdir $pathname, $mode, $callback->($status)
647		761
648	Asynchronously mkdir (create) a directory and call the callback with	762	Asynchronously mkdir (create) a directory and call the callback with
…		…
653	=item aio_rmdir $pathname, $callback->($status)	767	=item aio_rmdir $pathname, $callback->($status)
654		768
655	Asynchronously rmdir (delete) a directory and call the callback with the	769	Asynchronously rmdir (delete) a directory and call the callback with the
656	result code.	770	result code.
657		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
658		776
659	=item aio_readdir $pathname, $callback->($entries)	777	=item aio_readdir $pathname, $callback->($entries)
660		778
661	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
662	directory (i.e. opendir + readdir + closedir). The entries will not be	780	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
666	array-ref with the filenames.	784	array-ref with the filenames.
667		785
668		786
669	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	787	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
670		788
671	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	789	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
672	behaviour and output format. In case of an error, C<$entries> will be	790	tune behaviour and output format. In case of an error, C<$entries> will be
673	C<undef>.	791	C<undef>.
674		792
675	The flags are a combination of the following constants, ORed together (the	793	The flags are a combination of the following constants, ORed together (the
676	flags will also be passed to the callback, possibly modified):	794	flags will also be passed to the callback, possibly modified):
677		795
678	=over 4	796	=over 4
679		797
680	=item IO::AIO::READDIR_DENTS	798	=item IO::AIO::READDIR_DENTS
681		799
682	When this flag is off, then the callback gets an arrayref consisting of	800	Normally the callback gets an arrayref consisting of names only (as
683	names only (as with C<aio_readdir>), otherwise it gets an arrayref with	801	with C<aio_readdir>). If this flag is set, then the callback gets an
684	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	802	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
685	entry in more detail.	803	single directory entry in more detail:
686		804
687	C<$name> is the name of the entry.	805	C<$name> is the name of the entry.
688		806
689	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	807	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
690		808
691	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	809	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
692	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	810	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
693	C<IO::AIO::DT_WHT>.	811	C<IO::AIO::DT_WHT>.
694		812
695	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	813	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
696	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	814	to know, you have to run stat yourself. Also, for speed/memory reasons,
697	scalars are read-only: you can not modify them.	815	the C<$type> scalars are read-only: you must not modify them.
698		816
699	C<$inode> is the inode number (which might not be exact on systems with 64	817	C<$inode> is the inode number (which might not be exact on systems with 64
700	bit inode numbers and 32 bit perls). This field has unspecified content on	818	bit inode numbers and 32 bit perls). This field has unspecified content on
701	systems that do not deliver the inode information.	819	systems that do not deliver the inode information.
702		820
…		…
713	short names are tried first.	831	short names are tried first.
714		832
715	=item IO::AIO::READDIR_STAT_ORDER	833	=item IO::AIO::READDIR_STAT_ORDER
716		834
717	When this flag is set, then the names will be returned in an order	835	When this flag is set, then the names will be returned in an order
718	suitable for stat()'ing each one. That is, when you plan to stat()	836	suitable for stat()'ing each one. That is, when you plan to stat() most or
719	all files in the given directory, then the returned order will likely	837	all files in the given directory, then the returned order will likely be
720	be fastest.	838	faster.
721		839
722	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	840	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
723	the likely dirs come first, resulting in a less optimal stat order.	841	then the likely dirs come first, resulting in a less optimal stat order
		842	for stat'ing all entries, but likely a more optimal order for finding
		843	subdirectories.
724		844
725	=item IO::AIO::READDIR_FOUND_UNKNOWN	845	=item IO::AIO::READDIR_FOUND_UNKNOWN
726		846
727	This flag should not be set when calling C<aio_readdirx>. Instead, it	847	This flag should not be set when calling C<aio_readdirx>. Instead, it
728	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	848	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
729	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	849	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
730	C<$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.
731		851
732	=back	852	=back
733		853
734		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
735	=item aio_load $path, $data, $callback->($status)	884	=item aio_load $pathname, $data, $callback->($status)
736		885
737	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
738	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.
739		890
740	=cut	891	=cut
741		892
742	sub aio_load($$;$) {	893	sub aio_load($$;$) {
743	my ($path, undef, $cb) = @_;	894	my ($path, undef, $cb) = @_;
…		…
763	=item aio_copy $srcpath, $dstpath, $callback->($status)	914	=item aio_copy $srcpath, $dstpath, $callback->($status)
764		915
765	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
766	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
767	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.
768		921
769	This is a composite request that creates the destination file with	922	This is a composite request that creates the destination file with
770	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
771	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	924	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
772	uid/gid, in that order.	925	uid/gid, in that order.
…		…
862	if ($_[0] && $! == EXDEV) {	1015	if ($_[0] && $! == EXDEV) {
863	aioreq_pri $pri;	1016	aioreq_pri $pri;
864	add $grp aio_copy $src, $dst, sub {	1017	add $grp aio_copy $src, $dst, sub {
865	$grp->result ($_[0]);	1018	$grp->result ($_[0]);
866		1019
867	if (!$_[0]) {	1020	unless ($_[0]) {
868	aioreq_pri $pri;	1021	aioreq_pri $pri;
869	add $grp aio_unlink $src;	1022	add $grp aio_unlink $src;
870	}	1023	}
871	};	1024	};
872	} else {	1025	} else {
…		…
875	};	1028	};
876		1029
877	$grp	1030	$grp
878	}	1031	}
879		1032
880	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1033	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
881		1034
882	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1035	Scans a directory (similar to C<aio_readdir>) but additionally tries to
883	efficiently separate the entries of directory C<$path> into two sets of	1036	efficiently separate the entries of directory C<$path> into two sets of
884	names, directories you can recurse into (directories), and ones you cannot	1037	names, directories you can recurse into (directories), and ones you cannot
885	recurse into (everything else, including symlinks to directories).	1038	recurse into (everything else, including symlinks to directories).
886		1039
887	C<aio_scandir> is a composite request that creates of many sub requests_	1040	C<aio_scandir> is a composite request that generates many sub requests.
888	C<$maxreq> specifies the maximum number of outstanding aio requests that	1041	C<$maxreq> specifies the maximum number of outstanding aio requests that
889	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
890	will be chosen (currently 4).	1043	will be chosen (currently 4).
891		1044
892	On error, the callback is called without arguments, otherwise it receives	1045	On error, the callback is called without arguments, otherwise it receives
…		…
916	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
917	currently) and likely non-directories (see C<aio_readdirx>). Then every	1070	currently) and likely non-directories (see C<aio_readdirx>). Then every
918	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,
919	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
920	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
921	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
922	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
923	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
924	the filetype information on readdir.	1077	the filetype information on readdir.
925		1078
926	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
…		…
942		1095
943	my $grp = aio_group $cb;	1096	my $grp = aio_group $cb;
944		1097
945	$maxreq = 4 if $maxreq <= 0;	1098	$maxreq = 4 if $maxreq <= 0;
946		1099
947	# stat once	1100	# get a wd object
948	aioreq_pri $pri;	1101	aioreq_pri $pri;
949	add $grp aio_stat $path, sub {	1102	add $grp aio_wd $path, sub {
		1103	$_[0]
950	return $grp->result () if $_[0];	1104	or return $grp->result ();
951	my $now = time;
952	my $hash1 = join ":", (stat _)[0,1,3,7,9];
953		1105
954	# read the directory entries	1106	my $wd = [shift, "."];
		1107
		1108	# stat once
955	aioreq_pri $pri;	1109	aioreq_pri $pri;
956	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1110	add $grp aio_stat $wd, sub {
957	my $entries = shift
958	or return $grp->result ();	1111	return $grp->result () if $_[0];
		1112	my $now = time;
		1113	my $hash1 = join ":", (stat _)[0,1,3,7,9];
959		1114
960	# stat the dir another time	1115	# read the directory entries
961	aioreq_pri $pri;	1116	aioreq_pri $pri;
		1117	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1118	my $entries = shift
		1119	or return $grp->result ();
		1120
		1121	# stat the dir another time
		1122	aioreq_pri $pri;
962	add $grp aio_stat $path, sub {	1123	add $grp aio_stat $wd, sub {
963	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1124	my $hash2 = join ":", (stat _)[0,1,3,7,9];
964		1125
965	my $ndirs;	1126	my $ndirs;
966		1127
967	# take the slow route if anything looks fishy	1128	# take the slow route if anything looks fishy
968	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1129	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
969	$ndirs = -1;	1130	$ndirs = -1;
970	} else {	1131	} else {
971	# if nlink == 2, we are finished	1132	# if nlink == 2, we are finished
972	# for non-posix-fs's, we rely on nlink < 2	1133	# for non-posix-fs's, we rely on nlink < 2
973	$ndirs = (stat _)[3] - 2	1134	$ndirs = (stat _)[3] - 2
974	or return $grp->result ([], $entries);	1135	or return $grp->result ([], $entries);
975	}	1136	}
976		1137
977	my (@dirs, @nondirs);	1138	my (@dirs, @nondirs);
978		1139
979	my $statgrp = add $grp aio_group sub {	1140	my $statgrp = add $grp aio_group sub {
980	$grp->result (\@dirs, \@nondirs);	1141	$grp->result (\@dirs, \@nondirs);
981	};	1142	};
982		1143
983	limit $statgrp $maxreq;	1144	limit $statgrp $maxreq;
984	feed $statgrp sub {	1145	feed $statgrp sub {
985	return unless @$entries;	1146	return unless @$entries;
986	my $entry = shift @$entries;	1147	my $entry = shift @$entries;
987		1148
988	aioreq_pri $pri;	1149	aioreq_pri $pri;
		1150	$wd->[1] = "$entry/.";
989	add $statgrp aio_stat "$path/$entry/.", sub {	1151	add $statgrp aio_stat $wd, sub {
990	if ($_[0] < 0) {	1152	if ($_[0] < 0) {
991	push @nondirs, $entry;	1153	push @nondirs, $entry;
992	} else {	1154	} else {
993	# need to check for real directory	1155	# need to check for real directory
994	aioreq_pri $pri;	1156	aioreq_pri $pri;
		1157	$wd->[1] = $entry;
995	add $statgrp aio_lstat "$path/$entry", sub {	1158	add $statgrp aio_lstat $wd, sub {
996	if (-d _) {	1159	if (-d _) {
997	push @dirs, $entry;	1160	push @dirs, $entry;
998		1161
999	unless (--$ndirs) {	1162	unless (--$ndirs) {
1000	push @nondirs, @$entries;	1163	push @nondirs, @$entries;
1001	feed $statgrp;	1164	feed $statgrp;
		1165	}
		1166	} else {
		1167	push @nondirs, $entry;
1002	}	1168	}
1003	} else {
1004	push @nondirs, $entry;
1005	}	1169	}
1006	}	1170	}
1007	}	1171	};
1008	};	1172	};
1009	};	1173	};
1010	};	1174	};
1011	};	1175	};
1012	};	1176	};
1013		1177
1014	$grp	1178	$grp
1015	}	1179	}
1016		1180
1017	=item aio_rmtree $path, $callback->($status)	1181	=item aio_rmtree $pathname, $callback->($status)
1018		1182
1019	Delete a directory tree starting (and including) C<$path>, return the	1183	Delete a directory tree starting (and including) C<$path>, return the
1020	status of the final C<rmdir> only. This is a composite request that	1184	status of the final C<rmdir> only. This is a composite request that
1021	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1185	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1022	everything else.	1186	everything else.
1023		1187
1024	=cut	1188	=cut
1025		1189
…		…
1047	};	1211	};
1048		1212
1049	$grp	1213	$grp
1050	}	1214	}
1051		1215
		1216	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1217
		1218	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1219
		1220	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1221	they execute asynchronously and pass the return value to the callback.
		1222
		1223	Both calls can be used for a lot of things, some of which make more sense
		1224	to run asynchronously in their own thread, while some others make less
		1225	sense. For example, calls that block waiting for external events, such
		1226	as locking, will also lock down an I/O thread while it is waiting, which
		1227	can deadlock the whole I/O system. At the same time, there might be no
		1228	alternative to using a thread to wait.
		1229
		1230	So in general, you should only use these calls for things that do
		1231	(filesystem) I/O, not for things that wait for other events (network,
		1232	other processes), although if you are careful and know what you are doing,
		1233	you still can.
		1234
		1235	The following constants are available (missing ones are, as usual C<0>):
		1236
		1237	C<F_DUPFD_CLOEXEC>,
		1238
		1239	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1240
		1241	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1242
		1243	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1244	C<FS_IOC_FIEMAP>.
		1245
		1246	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1247	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1248
		1249	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1250	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1251	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1252	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1253	C<FS_FL_USER_MODIFIABLE>.
		1254
		1255	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1256	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1257	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1258	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1259
1052	=item aio_sync $callback->($status)	1260	=item aio_sync $callback->($status)
1053		1261
1054	Asynchronously call sync and call the callback when finished.	1262	Asynchronously call sync and call the callback when finished.
1055		1263
1056	=item aio_fsync $fh, $callback->($status)	1264	=item aio_fsync $fh, $callback->($status)
…		…
1063	Asynchronously call fdatasync on the given filehandle and call the	1271	Asynchronously call fdatasync on the given filehandle and call the
1064	callback with the fdatasync result code.	1272	callback with the fdatasync result code.
1065		1273
1066	If this call isn't available because your OS lacks it or it couldn't be	1274	If this call isn't available because your OS lacks it or it couldn't be
1067	detected, it will be emulated by calling C<fsync> instead.	1275	detected, it will be emulated by calling C<fsync> instead.
		1276
		1277	=item aio_syncfs $fh, $callback->($status)
		1278
		1279	Asynchronously call the syncfs syscall to sync the filesystem associated
		1280	to the given filehandle and call the callback with the syncfs result
		1281	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1282	errno to C<ENOSYS> nevertheless.
1068		1283
1069	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1284	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1070		1285
1071	Sync the data portion of the file specified by C<$offset> and C<$length>	1286	Sync the data portion of the file specified by C<$offset> and C<$length>
1072	to disk (but NOT the metadata), by calling the Linux-specific	1287	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1076	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1291	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1077	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1292	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1078	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1293	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1079	manpage for details.	1294	manpage for details.
1080		1295
1081	=item aio_pathsync $path, $callback->($status)	1296	=item aio_pathsync $pathname, $callback->($status)
1082		1297
1083	This request tries to open, fsync and close the given path. This is a	1298	This request tries to open, fsync and close the given path. This is a
1084	composite request intended to sync directories after directory operations	1299	composite request intended to sync directories after directory operations
1085	(E.g. rename). This might not work on all operating systems or have any	1300	(E.g. rename). This might not work on all operating systems or have any
1086	specific effect, but usually it makes sure that directory changes get	1301	specific effect, but usually it makes sure that directory changes get
…		…
1117	};	1332	};
1118		1333
1119	$grp	1334	$grp
1120	}	1335	}
1121		1336
1122	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1337	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1123		1338
1124	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1339	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1125	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1340	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1126	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1341	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1127	scalar must only be modified in-place while an aio operation is pending on	1342	scalar must only be modified in-place while an aio operation is pending on
…		…
1129		1344
1130	It calls the C<msync> function of your OS, if available, with the memory	1345	It calls the C<msync> function of your OS, if available, with the memory
1131	area starting at C<$offset> in the string and ending C<$length> bytes	1346	area starting at C<$offset> in the string and ending C<$length> bytes
1132	later. If C<$length> is negative, counts from the end, and if C<$length>	1347	later. If C<$length> is negative, counts from the end, and if C<$length>
1133	is C<undef>, then it goes till the end of the string. The flags can be	1348	is C<undef>, then it goes till the end of the string. The flags can be
1134	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1349	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1135	C<IO::AIO::MS_SYNC>.	1350	C<IO::AIO::MS_INVALIDATE>.
1136		1351
1137	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1352	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1138		1353
1139	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1354	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1140	scalars.	1355	scalars.
1141		1356
1142	It touches (reads or writes) all memory pages in the specified	1357	It touches (reads or writes) all memory pages in the specified
1143	range inside the scalar. All caveats and parameters are the same	1358	range inside the scalar. All caveats and parameters are the same
1144	as for C<aio_msync>, above, except for flags, which must be either	1359	as for C<aio_msync>, above, except for flags, which must be either
1145	C<0> (which reads all pages and ensures they are instantiated) or	1360	C<0> (which reads all pages and ensures they are instantiated) or
1146	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1361	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1147	writing an octet from it, which dirties the page).	1362	writing an octet from it, which dirties the page).
1148		1363
1149	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1364	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1150		1365
1151	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1366	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1182	documented under L<MISCELLANEOUS FUNCTIONS>.	1397	documented under L<MISCELLANEOUS FUNCTIONS>.
1183		1398
1184	Example: asynchronously lock all current and future pages into memory.	1399	Example: asynchronously lock all current and future pages into memory.
1185		1400
1186	aio_mlockall IO::AIO::MCL_FUTURE;	1401	aio_mlockall IO::AIO::MCL_FUTURE;
		1402
		1403	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1404
		1405	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1406	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1407	the ioctl is not available on your OS, then this request will fail with
		1408	C<ENOSYS>.
		1409
		1410	C<$start> is the starting offset to query extents for, C<$length> is the
		1411	size of the range to query - if it is C<undef>, then the whole file will
		1412	be queried.
		1413
		1414	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1415	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1416	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1417	the data portion.
		1418
		1419	C<$count> is the maximum number of extent records to return. If it is
		1420	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1421	case, if it is C<0>, then the callback receives the number of extents
		1422	instead of the extents themselves (which is unreliable, see below).
		1423
		1424	If an error occurs, the callback receives no arguments. The special
		1425	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1426
		1427	Otherwise, the callback receives an array reference with extent
		1428	structures. Each extent structure is an array reference itself, with the
		1429	following members:
		1430
		1431	[$logical, $physical, $length, $flags]
		1432
		1433	Flags is any combination of the following flag values (typically either C<0>
		1434	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1435
		1436	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1437	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1438	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1439	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1440	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1441	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1442
		1443	At the time of this writing (Linux 3.2), this request is unreliable unless
		1444	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1445	it to return all extents of a range for files with a large number of
		1446	extents. The code (only) works around all these issues if C<$count> is
		1447	C<undef>.
1187		1448
1188	=item aio_group $callback->(...)	1449	=item aio_group $callback->(...)
1189		1450
1190	This is a very special aio request: Instead of doing something, it is a	1451	This is a very special aio request: Instead of doing something, it is a
1191	container for other aio requests, which is useful if you want to bundle	1452	container for other aio requests, which is useful if you want to bundle
…		…
1228	like sleep and file handle readable/writable, the overhead this creates is	1489	like sleep and file handle readable/writable, the overhead this creates is
1229	immense (it blocks a thread for a long time) so do not use this function	1490	immense (it blocks a thread for a long time) so do not use this function
1230	except to put your application under artificial I/O pressure.	1491	except to put your application under artificial I/O pressure.
1231		1492
1232	=back	1493	=back
		1494
		1495
		1496	=head2 IO::AIO::WD - multiple working directories
		1497
		1498	Your process only has one current working directory, which is used by all
		1499	threads. This makes it hard to use relative paths (some other component
		1500	could call C<chdir> at any time, and it is hard to control when the path
		1501	will be used by IO::AIO).
		1502
		1503	One solution for this is to always use absolute paths. This usually works,
		1504	but can be quite slow (the kernel has to walk the whole path on every
		1505	access), and can also be a hassle to implement.
		1506
		1507	Newer POSIX systems have a number of functions (openat, fdopendir,
		1508	futimensat and so on) that make it possible to specify working directories
		1509	per operation.
		1510
		1511	For portability, and because the clowns who "designed", or shall I write,
		1512	perpetrated this new interface were obviously half-drunk, this abstraction
		1513	cannot be perfect, though.
		1514
		1515	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1516	object. This object stores the canonicalised, absolute version of the
		1517	path, and on systems that allow it, also a directory file descriptor.
		1518
		1519	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1520	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1521	object and a pathname instead (or the IO::AIO::WD object alone, which
		1522	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1523	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1524	to that IO::AIO::WD object.
		1525
		1526	For example, to get a wd object for F</etc> and then stat F<passwd>
		1527	inside, you would write:
		1528
		1529	aio_wd "/etc", sub {
		1530	my $etcdir = shift;
		1531
		1532	# although $etcdir can be undef on error, there is generally no reason
		1533	# to check for errors here, as aio_stat will fail with ENOENT
		1534	# when $etcdir is undef.
		1535
		1536	aio_stat [$etcdir, "passwd"], sub {
		1537	# yay
		1538	};
		1539	};
		1540
		1541	The fact that C<aio_wd> is a request and not a normal function shows that
		1542	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1543	which is why it is done asynchronously.
		1544
		1545	To stat the directory obtained with C<aio_wd> above, one could write
		1546	either of the following three request calls:
		1547
		1548	aio_lstat "/etc" , sub { ... # pathname as normal string
		1549	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1550	aio_lstat $wd , sub { ... # shorthand for the previous
		1551
		1552	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1553	object and the pathname string, so you could write the following without
		1554	causing any issues due to C<$path> getting reused:
		1555
		1556	my $path = [$wd, undef];
		1557
		1558	for my $name (qw(abc def ghi)) {
		1559	$path->[1] = $name;
		1560	aio_stat $path, sub {
		1561	# ...
		1562	};
		1563	}
		1564
		1565	There are some caveats: when directories get renamed (or deleted), the
		1566	pathname string doesn't change, so will point to the new directory (or
		1567	nowhere at all), while the directory fd, if available on the system,
		1568	will still point to the original directory. Most functions accepting a
		1569	pathname will use the directory fd on newer systems, and the string on
		1570	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1571	the string form of the pathname.
		1572
		1573	So this functionality is mainly useful to get some protection against
		1574	C<chdir>, to easily get an absolute path out of a relative path for future
		1575	reference, and to speed up doing many operations in the same directory
		1576	(e.g. when stat'ing all files in a directory).
		1577
		1578	The following functions implement this working directory abstraction:
		1579
		1580	=over 4
		1581
		1582	=item aio_wd $pathname, $callback->($wd)
		1583
		1584	Asynchonously canonicalise the given pathname and convert it to an
		1585	IO::AIO::WD object representing it. If possible and supported on the
		1586	system, also open a directory fd to speed up pathname resolution relative
		1587	to this working directory.
		1588
		1589	If something goes wrong, then C<undef> is passwd to the callback instead
		1590	of a working directory object and C<$!> is set appropriately. Since
		1591	passing C<undef> as working directory component of a pathname fails the
		1592	request with C<ENOENT>, there is often no need for error checking in the
		1593	C<aio_wd> callback, as future requests using the value will fail in the
		1594	expected way.
		1595
		1596	=item IO::AIO::CWD
		1597
		1598	This is a compiletime constant (object) that represents the process
		1599	current working directory.
		1600
		1601	Specifying this object as working directory object for a pathname is as if
		1602	the pathname would be specified directly, without a directory object. For
		1603	example, these calls are functionally identical:
		1604
		1605	aio_stat "somefile", sub { ... };
		1606	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1607
		1608	=back
		1609
		1610	To recover the path associated with an IO::AIO::WD object, you can use
		1611	C<aio_realpath>:
		1612
		1613	aio_realpath $wd, sub {
		1614	warn "path is $_[0]\n";
		1615	};
		1616
		1617	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1618	sometimes, fall back to using an absolue path.
1233		1619
1234	=head2 IO::AIO::REQ CLASS	1620	=head2 IO::AIO::REQ CLASS
1235		1621
1236	All non-aggregate C<aio_*> functions return an object of this class when	1622	All non-aggregate C<aio_*> functions return an object of this class when
1237	called in non-void context.	1623	called in non-void context.
…		…
1355		1741
1356	Sets a feeder/generator on this group: every group can have an attached	1742	Sets a feeder/generator on this group: every group can have an attached
1357	generator that generates requests if idle. The idea behind this is that,	1743	generator that generates requests if idle. The idea behind this is that,
1358	although you could just queue as many requests as you want in a group,	1744	although you could just queue as many requests as you want in a group,
1359	this might starve other requests for a potentially long time. For example,	1745	this might starve other requests for a potentially long time. For example,
1360	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1746	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1361	delaying any later requests for a long time.	1747	requests, delaying any later requests for a long time.
1362		1748
1363	To avoid this, and allow incremental generation of requests, you can	1749	To avoid this, and allow incremental generation of requests, you can
1364	instead a group and set a feeder on it that generates those requests. The	1750	instead a group and set a feeder on it that generates those requests. The
1365	feed callback will be called whenever there are few enough (see C<limit>,	1751	feed callback will be called whenever there are few enough (see C<limit>,
1366	below) requests active in the group itself and is expected to queue more	1752	below) requests active in the group itself and is expected to queue more
…		…
1398	The default value for the limit is C<0>, but note that setting a feeder	1784	The default value for the limit is C<0>, but note that setting a feeder
1399	automatically bumps it up to C<2>.	1785	automatically bumps it up to C<2>.
1400		1786
1401	=back	1787	=back
1402		1788
		1789
1403	=head2 SUPPORT FUNCTIONS	1790	=head2 SUPPORT FUNCTIONS
1404		1791
1405	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1792	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1406		1793
1407	=over 4	1794	=over 4
…		…
1415		1802
1416	See C<poll_cb> for an example.	1803	See C<poll_cb> for an example.
1417		1804
1418	=item IO::AIO::poll_cb	1805	=item IO::AIO::poll_cb
1419		1806
1420	Process some outstanding events on the result pipe. You have to call	1807	Process some requests that have reached the result phase (i.e. they have
		1808	been executed but the results are not yet reported). You have to call
		1809	this "regularly" to finish outstanding requests.
		1810
1421	this regularly. Returns C<0> if all events could be processed (or there	1811	Returns C<0> if all events could be processed (or there were no
1422	were no events to process), or C<-1> if it returned earlier for whatever	1812	events to process), or C<-1> if it returned earlier for whatever
1423	reason. Returns immediately when no events are outstanding. The amount of	1813	reason. Returns immediately when no events are outstanding. The amount
1424	events processed depends on the settings of C<IO::AIO::max_poll_req> and	1814	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
1425	C<IO::AIO::max_poll_time>.	1815	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
1426		1816
1427	If not all requests were processed for whatever reason, the filehandle	1817	If not all requests were processed for whatever reason, the poll file
1428	will still be ready when C<poll_cb> returns, so normally you don't have to	1818	descriptor will still be ready when C<poll_cb> returns, so normally you
1429	do anything special to have it called later.	1819	don't have to do anything special to have it called later.
1430		1820
1431	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes	1821	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
1432	ready, it can be beneficial to call this function from loops which submit	1822	ready, it can be beneficial to call this function from loops which submit
1433	a lot of requests, to make sure the results get processed when they become	1823	a lot of requests, to make sure the results get processed when they become
1434	available and not just when the loop is finished and the event loop takes	1824	available and not just when the loop is finished and the event loop takes
…		…
1443	poll => 'r', async => 1,	1833	poll => 'r', async => 1,
1444	cb => \&IO::AIO::poll_cb);	1834	cb => \&IO::AIO::poll_cb);
1445		1835
1446	=item IO::AIO::poll_wait	1836	=item IO::AIO::poll_wait
1447		1837
1448	If there are any outstanding requests and none of them in the result	1838	Wait until either at least one request is in the result phase or no
1449	phase, wait till the result filehandle becomes ready for reading (simply	1839	requests are outstanding anymore.
1450	does a C<select> on the filehandle. This is useful if you want to	1840
1451	synchronously wait for some requests to finish).	1841	This is useful if you want to synchronously wait for some requests to
		1842	become ready, without actually handling them.
1452		1843
1453	See C<nreqs> for an example.	1844	See C<nreqs> for an example.
1454		1845
1455	=item IO::AIO::poll	1846	=item IO::AIO::poll
1456		1847
…		…
1467		1858
1468	Strictly equivalent to:	1859	Strictly equivalent to:
1469		1860
1470	IO::AIO::poll_wait, IO::AIO::poll_cb	1861	IO::AIO::poll_wait, IO::AIO::poll_cb
1471	while IO::AIO::nreqs;	1862	while IO::AIO::nreqs;
		1863
		1864	This function can be useful at program aborts, to make sure outstanding
		1865	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1866	this function on normal exits), or when you are merely using C<IO::AIO>
		1867	for its more advanced functions, rather than for async I/O, e.g.:
		1868
		1869	my ($dirs, $nondirs);
		1870	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1871	IO::AIO::flush;
		1872	# $dirs, $nondirs are now set
1472		1873
1473	=item IO::AIO::max_poll_reqs $nreqs	1874	=item IO::AIO::max_poll_reqs $nreqs
1474		1875
1475	=item IO::AIO::max_poll_time $seconds	1876	=item IO::AIO::max_poll_time $seconds
1476		1877
…		…
1503	poll => 'r', nice => 1,	1904	poll => 'r', nice => 1,
1504	cb => &IO::AIO::poll_cb);	1905	cb => &IO::AIO::poll_cb);
1505		1906
1506	=back	1907	=back
1507		1908
		1909
1508	=head3 CONTROLLING THE NUMBER OF THREADS	1910	=head3 CONTROLLING THE NUMBER OF THREADS
1509		1911
1510	=over	1912	=over
1511		1913
1512	=item IO::AIO::min_parallel $nthreads	1914	=item IO::AIO::min_parallel $nthreads
…		…
1564	Sets the minimum idle timeout (default 10) after which worker threads are	1966	Sets the minimum idle timeout (default 10) after which worker threads are
1565	allowed to exit. SEe C<IO::AIO::max_idle>.	1967	allowed to exit. SEe C<IO::AIO::max_idle>.
1566		1968
1567	=item IO::AIO::max_outstanding $maxreqs	1969	=item IO::AIO::max_outstanding $maxreqs
1568		1970
		1971	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1972	you do queue up more than this number of requests, the next call to
		1973	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1974	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1975	longer exceeded.
		1976
		1977	In other words, this setting does not enforce a queue limit, but can be
		1978	used to make poll functions block if the limit is exceeded.
		1979
1569	This is a very bad function to use in interactive programs because it	1980	This is a very bad function to use in interactive programs because it
1570	blocks, and a bad way to reduce concurrency because it is inexact: Better	1981	blocks, and a bad way to reduce concurrency because it is inexact: Better
1571	use an C<aio_group> together with a feed callback.	1982	use an C<aio_group> together with a feed callback.
1572		1983
1573	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1984	Its main use is in scripts without an event loop - when you want to stat
1574	do queue up more than this number of requests, the next call to the	1985	a lot of files, you can write something like this:
1575	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1576	function will block until the limit is no longer exceeded.
1577		1986
1578	The default value is very large, so there is no practical limit on the	1987	IO::AIO::max_outstanding 32;
1579	number of outstanding requests.
1580		1988
1581	You can still queue as many requests as you want. Therefore,	1989	for my $path (...) {
1582	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1990	aio_stat $path , ...;
1583	as a stop gap to shield against fatal memory overflow (with large values).	1991	IO::AIO::poll_cb;
		1992	}
		1993
		1994	IO::AIO::flush;
		1995
		1996	The call to C<poll_cb> inside the loop will normally return instantly, but
		1997	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1998	some requests have been handled. This keeps the loop from pushing a large
		1999	number of C<aio_stat> requests onto the queue.
		2000
		2001	The default value for C<max_outstanding> is very large, so there is no
		2002	practical limit on the number of outstanding requests.
1584		2003
1585	=back	2004	=back
		2005
1586		2006
1587	=head3 STATISTICAL INFORMATION	2007	=head3 STATISTICAL INFORMATION
1588		2008
1589	=over	2009	=over
1590		2010
…		…
1608	Returns the number of requests currently in the pending state (executed,	2028	Returns the number of requests currently in the pending state (executed,
1609	but not yet processed by poll_cb).	2029	but not yet processed by poll_cb).
1610		2030
1611	=back	2031	=back
1612		2032
		2033
		2034	=head3 SUBSECOND STAT TIME ACCESS
		2035
		2036	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2037	generally find access/modification and change times with subsecond time
		2038	accuracy of the system supports it, but perl's built-in functions only
		2039	return the integer part.
		2040
		2041	The following functions return the timestamps of the most recent
		2042	stat with subsecond precision on most systems and work both after
		2043	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2044	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2045	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2046
		2047	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2048	full resolution without rounding and work with standard perl C<stat>,
		2049	alleviating the need to call the special C<Time::HiRes> functions, which
		2050	do not act like their perl counterparts.
		2051
		2052	On operating systems or file systems where subsecond time resolution is
		2053	not supported or could not be detected, a fractional part of C<0> is
		2054	returned, so it is always safe to call these functions.
		2055
		2056	=over 4
		2057
		2058	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2059
		2060	Return the access, modication, change or birth time, respectively,
		2061	including fractional part. Due to the limited precision of floating point,
		2062	the accuracy on most platforms is only a bit better than milliseconds
		2063	for times around now - see the I<nsec> function family, below, for full
		2064	accuracy.
		2065
		2066	File birth time is only available when the OS and perl support it (on
		2067	FreeBSD and NetBSD at the time of this writing, although support is
		2068	adaptive, so if your OS/perl gains support, IO::AIO can take avdantage of
		2069	it). On systems where it isn't available, C<0> is currently returned, but
		2070	this might change to C<undef> in a future version.
		2071
		2072	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2073
		2074	Returns access, modification, change and birth time all in one go, and
		2075	maybe more times in the future version.
		2076
		2077	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2078
		2079	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2080	as an integer in the range C<0> to C<999999999>.
		2081
		2082	Note that no accessors are provided for access, modification and
		2083	change times - you need to get those from C<stat _> if required (C<int
		2084	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2085	value).
		2086
		2087	=item $seconds = IO::AIO::st_btimesec
		2088
		2089	The (integral) seconds part of the file birth time, if available.
		2090
		2091	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2092
		2093	Like the functions above, but returns all four times in one go (and maybe
		2094	more in future versions).
		2095
		2096	=item $counter = IO::AIO::st_gen
		2097
		2098	Returns the generation counter (in practice this is just a random number)
		2099	of the file. This is only available on platforms which have this member in
		2100	their C<struct stat> (most BSDs at the time of this writing) and generally
		2101	only to the root usert. If unsupported, C<0> is returned, but this might
		2102	change to C<undef> in a future version.
		2103
		2104	=back
		2105
		2106	Example: print the high resolution modification time of F</etc>, using
		2107	C<stat>, and C<IO::AIO::aio_stat>.
		2108
		2109	if (stat "/etc") {
		2110	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2111	}
		2112
		2113	IO::AIO::aio_stat "/etc", sub {
		2114	$_[0]
		2115	and return;
		2116
		2117	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2118	};
		2119
		2120	IO::AIO::flush;
		2121
		2122	Output of the awbove on my system, showing reduced and full accuracy:
		2123
		2124	stat(/etc) mtime: 1534043702.020808
		2125	aio_stat(/etc) mtime: 1534043702.020807792
		2126
		2127
1613	=head3 MISCELLANEOUS FUNCTIONS	2128	=head3 MISCELLANEOUS FUNCTIONS
1614		2129
1615	IO::AIO implements some functions that might be useful, but are not	2130	IO::AIO implements some functions that are useful when you want to use
1616	asynchronous.	2131	some "Advanced I/O" function not available to in Perl, without going the
		2132	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2133	counterpart.
1617		2134
1618	=over 4	2135	=over 4
		2136
		2137	=item $numfd = IO::AIO::get_fdlimit
		2138
		2139	This function is I<EXPERIMENTAL> and subject to change.
		2140
		2141	Tries to find the current file descriptor limit and returns it, or
		2142	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2143	the highest valid file descriptor number.
		2144
		2145	=item IO::AIO::min_fdlimit [$numfd]
		2146
		2147	This function is I<EXPERIMENTAL> and subject to change.
		2148
		2149	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2150	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2151	is missing, it will try to set a very high limit, although this is not
		2152	recommended when you know the actual minimum that you require.
		2153
		2154	If the limit cannot be raised enough, the function makes a best-effort
		2155	attempt to increase the limit as much as possible, using various
		2156	tricks, while still failing. You can query the resulting limit using
		2157	C<IO::AIO::get_fdlimit>.
		2158
		2159	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2160	true.
1619		2161
1620	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2162	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1621		2163
1622	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2164	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1623	but is blocking (this makes most sense if you know the input data is	2165	but is blocking (this makes most sense if you know the input data is
…		…
1628		2170
1629	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2171	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1630		2172
1631	Simply calls the C<posix_fadvise> function (see its	2173	Simply calls the C<posix_fadvise> function (see its
1632	manpage for details). The following advice constants are	2174	manpage for details). The following advice constants are
1633	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2175	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1634	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2176	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1635	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2177	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1636		2178
1637	On systems that do not implement C<posix_fadvise>, this function returns	2179	On systems that do not implement C<posix_fadvise>, this function returns
1638	ENOSYS, otherwise the return value of C<posix_fadvise>.	2180	ENOSYS, otherwise the return value of C<posix_fadvise>.
1639		2181
1640	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2182	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1641		2183
1642	Simply calls the C<posix_madvise> function (see its	2184	Simply calls the C<posix_madvise> function (see its
1643	manpage for details). The following advice constants are	2185	manpage for details). The following advice constants are
1644	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2186	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1645	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2187	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2188	C<IO::AIO::MADV_DONTNEED>.
		2189
		2190	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2191	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2192	will be reduced to fit into the C<$scalar>.
1646		2193
1647	On systems that do not implement C<posix_madvise>, this function returns	2194	On systems that do not implement C<posix_madvise>, this function returns
1648	ENOSYS, otherwise the return value of C<posix_madvise>.	2195	ENOSYS, otherwise the return value of C<posix_madvise>.
1649		2196
1650	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2197	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1651		2198
1652	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2199	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1653	$scalar (see its manpage for details). The following protect	2200	$scalar (see its manpage for details). The following protect
1654	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2201	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1655	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2202	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2203
		2204	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2205	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2206	will be reduced to fit into the C<$scalar>.
1656		2207
1657	On systems that do not implement C<mprotect>, this function returns	2208	On systems that do not implement C<mprotect>, this function returns
1658	ENOSYS, otherwise the return value of C<mprotect>.	2209	ENOSYS, otherwise the return value of C<mprotect>.
1659		2210
1660	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2211	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1661		2212
1662	Memory-maps a file (or anonymous memory range) and attaches it to the	2213	Memory-maps a file (or anonymous memory range) and attaches it to the
1663	given C<$scalar>, which will act like a string scalar.	2214	given C<$scalar>, which will act like a string scalar. Returns true on
		2215	success, and false otherwise.
1664		2216
		2217	The scalar must exist, but its contents do not matter - this means you
		2218	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2219	the scalar first.
		2220
1665	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2221	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1666	change the string length, and most read-only operations such as copying it	2222	which don't change the string length, and most read-only operations such
1667	or searching it with regexes and so on.	2223	as copying it or searching it with regexes and so on.
1668		2224
1669	Anything else is unsafe and will, at best, result in memory leaks.	2225	Anything else is unsafe and will, at best, result in memory leaks.
1670		2226
1671	The memory map associated with the C<$scalar> is automatically removed	2227	The memory map associated with the C<$scalar> is automatically removed
1672	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2228	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1673	C<IO::AIO::munmap> functions are called.	2229	or C<IO::AIO::munmap> functions are called on it.
1674		2230
1675	This calls the C<mmap>(2) function internally. See your system's manual	2231	This calls the C<mmap>(2) function internally. See your system's manual
1676	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2232	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1677		2233
1678	The C<$length> must be larger than zero and smaller than the actual	2234	The C<$length> must be larger than zero and smaller than the actual
1679	filesize.	2235	filesize.
1680		2236
1681	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2237	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1682	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2238	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1683		2239
1684	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2240	C<$flags> can be a combination of
1685	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2241	C<IO::AIO::MAP_SHARED> or
1686	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2242	C<IO::AIO::MAP_PRIVATE>,
		2243	or a number of system-specific flags (when not available, the are C<0>):
1687	(which is set to C<MAP_ANON> if your system only provides this	2244	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1688	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2245	C<IO::AIO::MAP_LOCKED>,
1689	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2246	C<IO::AIO::MAP_NORESERVE>,
		2247	C<IO::AIO::MAP_POPULATE>,
1690	C<IO::AIO::MAP_NONBLOCK>	2248	C<IO::AIO::MAP_NONBLOCK>,
		2249	C<IO::AIO::MAP_FIXED>,
		2250	C<IO::AIO::MAP_GROWSDOWN>,
		2251	C<IO::AIO::MAP_32BIT>,
		2252	C<IO::AIO::MAP_HUGETLB> or
		2253	C<IO::AIO::MAP_STACK>.
1691		2254
1692	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2255	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1693		2256
1694	C<$offset> is the offset from the start of the file - it generally must be	2257	C<$offset> is the offset from the start of the file - it generally must be
1695	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2258	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1709		2272
1710	=item IO::AIO::munmap $scalar	2273	=item IO::AIO::munmap $scalar
1711		2274
1712	Removes a previous mmap and undefines the C<$scalar>.	2275	Removes a previous mmap and undefines the C<$scalar>.
1713		2276
		2277	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2278
		2279	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2280	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2281	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2282
		2283	Returns true if successful, and false otherwise. If the underlying mmapped
		2284	region has changed address, then the true value has the numerical value
		2285	C<1>, otherwise it has the numerical value C<0>:
		2286
		2287	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2288	or die "mremap: $!";
		2289
		2290	if ($success*1) {
		2291	warn "scalar has chanegd address in memory\n";
		2292	}
		2293
		2294	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2295	implemented, but not supported and might go away in a future version.
		2296
		2297	On systems where this call is not supported or is not emulated, this call
		2298	returns falls and sets C<$!> to C<ENOSYS>.
		2299
1714	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2300	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1715		2301
1716	Calls the C<munlock> function, undoing the effects of a previous	2302	Calls the C<munlock> function, undoing the effects of a previous
1717	C<aio_mlock> call (see its description for details).	2303	C<aio_mlock> call (see its description for details).
1718		2304
…		…
1720		2306
1721	Calls the C<munlockall> function.	2307	Calls the C<munlockall> function.
1722		2308
1723	On systems that do not implement C<munlockall>, this function returns	2309	On systems that do not implement C<munlockall>, this function returns
1724	ENOSYS, otherwise the return value of C<munlockall>.	2310	ENOSYS, otherwise the return value of C<munlockall>.
		2311
		2312	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2313
		2314	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2315	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2316	should be the file offset.
		2317
		2318	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2319	silently corrupt the data in this case.
		2320
		2321	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2322	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2323	C<IO::AIO::SPLICE_F_GIFT>.
		2324
		2325	See the C<splice(2)> manpage for details.
		2326
		2327	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2328
		2329	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2330	description for C<IO::AIO::splice> above for details.
		2331
		2332	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2333
		2334	Attempts to query or change the pipe buffer size. Obviously works only
		2335	on pipes, and currently works only on GNU/Linux systems, and fails with
		2336	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2337	size on other systems, drop me a note.
		2338
		2339	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2340
		2341	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2342	C<$flags> is missing or C<0>, then this should be the same as a call to
		2343	perl's built-in C<pipe> function and create a new pipe, and works on
		2344	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2345	(..., 4096, O_BINARY)>.
		2346
		2347	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2348	the given flags (Linux 2.6.27, glibc 2.9).
		2349
		2350	On success, the read and write file handles are returned.
		2351
		2352	On error, nothing will be returned. If the pipe2 syscall is missing and
		2353	C<$flags> is non-zero, fails with C<ENOSYS>.
		2354
		2355	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2356	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2357	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2358
		2359	Example: create a pipe race-free w.r.t. threads and fork:
		2360
		2361	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2362	or die "pipe2: $!\n";
		2363
		2364	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2365
		2366	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2367	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2368
		2369	On success, the new eventfd filehandle is returned, otherwise returns
		2370	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2371
		2372	Please refer to L<eventfd(2)> for more info on this call.
		2373
		2374	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2375	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2376
		2377	Example: create a new eventfd filehandle:
		2378
		2379	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2380	or die "eventfd: $!\n";
		2381
		2382	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2383
		2384	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2385	(unhelpful) default for C<$flags> is C<0>.
		2386
		2387	On success, the new timerfd filehandle is returned, otherwise returns
		2388	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2389
		2390	Please refer to L<timerfd_create(2)> for more info on this call.
		2391
		2392	The following C<$clockid> values are
		2393	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2394	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2395	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2396	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2397
		2398	The following C<$flags> values are available (Linux
		2399	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2400
		2401	Example: create a new timerfd and set it to one-second repeated alarms,
		2402	then wait for two alarms:
		2403
		2404	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2405	or die "timerfd_create: $!\n";
		2406
		2407	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2408	or die "timerfd_settime: $!\n";
		2409
		2410	for (1..2) {
		2411	8 == sysread $fh, my $buf, 8
		2412	or die "timerfd read failure\n";
		2413
		2414	printf "number of expirations (likely 1): %d\n",
		2415	unpack "Q", $buf;
		2416	}
		2417
		2418	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2419
		2420	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2421	call. Please refer to its manpage for more info on this call.
		2422
		2423	The new itimerspec is specified using two (possibly fractional) second
		2424	values, C<$new_interval> and C<$new_value>).
		2425
		2426	On success, the current interval and value are returned (as per
		2427	C<timerfd_gettime>). On failure, the empty list is returned.
		2428
		2429	The following C<$flags> values are
		2430	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2431	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2432
		2433	See C<IO::AIO::timerfd_create> for a full example.
		2434
		2435	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2436
		2437	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2438	call. Please refer to its manpage for more info on this call.
		2439
		2440	On success, returns the current values of interval and value for the given
		2441	timerfd (as potentially fractional second values). On failure, the empty
		2442	list is returned.
1725		2443
1726	=back	2444	=back
1727		2445
1728	=cut	2446	=cut
1729		2447
…		…
1764	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2482	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1765	\&IO::AIO::poll_cb);	2483	\&IO::AIO::poll_cb);
1766		2484
1767	=head2 FORK BEHAVIOUR	2485	=head2 FORK BEHAVIOUR
1768		2486
1769	This module should do "the right thing" when the process using it forks:	2487	Usage of pthreads in a program changes the semantics of fork
		2488	considerably. Specifically, only async-safe functions can be called after
		2489	fork. Perl doesn't know about this, so in general, you cannot call fork
		2490	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2491	pthreads, so this applies, but many other extensions and (for inexplicable
		2492	reasons) perl itself often is linked against pthreads, so this limitation
		2493	applies to quite a lot of perls.
1770		2494
1771	Before the fork, IO::AIO enters a quiescent state where no requests	2495	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1772	can be added in other threads and no results will be processed. After	2496	only works in the process that loaded it. Forking is fully supported, but
1773	the fork the parent simply leaves the quiescent state and continues	2497	using IO::AIO in the child is not.
1774	request/result processing, while the child frees the request/result queue
1775	(so that the requests started before the fork will only be handled in the
1776	parent). Threads will be started on demand until the limit set in the
1777	parent process has been reached again.
1778		2498
1779	In short: the parent will, after a short pause, continue as if fork had	2499	You might get around by not I<using> IO::AIO before (or after)
1780	not been called, while the child will act as if IO::AIO has not been used	2500	forking. You could also try to call the L<IO::AIO::reinit> function in the
1781	yet.	2501	child:
		2502
		2503	=over 4
		2504
		2505	=item IO::AIO::reinit
		2506
		2507	Abandons all current requests and I/O threads and simply reinitialises all
		2508	data structures. This is not an operation supported by any standards, but
		2509	happens to work on GNU/Linux and some newer BSD systems.
		2510
		2511	The only reasonable use for this function is to call it after forking, if
		2512	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2513	the process will result in undefined behaviour. Calling it at any time
		2514	will also result in any undefined (by POSIX) behaviour.
		2515
		2516	=back
		2517
		2518	=head2 LINUX-SPECIFIC CALLS
		2519
		2520	When a call is documented as "linux-specific" then this means it
		2521	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2522	availability and compatibility of such calls regardless of the platform
		2523	it is compiled on, so platforms such as FreeBSD which often implement
		2524	these calls will work. When in doubt, call them and see if they fail wth
		2525	C<ENOSYS>.
1782		2526
1783	=head2 MEMORY USAGE	2527	=head2 MEMORY USAGE
1784		2528
1785	Per-request usage:	2529	Per-request usage:
1786		2530
…		…
1799	temporary buffers, and each thread requires a stack and other data	2543	temporary buffers, and each thread requires a stack and other data
1800	structures (usually around 16k-128k, depending on the OS).	2544	structures (usually around 16k-128k, depending on the OS).
1801		2545
1802	=head1 KNOWN BUGS	2546	=head1 KNOWN BUGS
1803		2547
1804	Known bugs will be fixed in the next release.	2548	Known bugs will be fixed in the next release :)
		2549
		2550	=head1 KNOWN ISSUES
		2551
		2552	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2553	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2554	non-created hash slots or other scalars I didn't think of. It's best to
		2555	avoid such and either use scalar variables or making sure that the scalar
		2556	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2557
		2558	I am not sure anything can be done about this, so this is considered a
		2559	known issue, rather than a bug.
1805		2560
1806	=head1 SEE ALSO	2561	=head1 SEE ALSO
1807		2562
1808	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2563	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1809	more natural syntax.	2564	more natural syntax.

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