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Revision 1.185 by root, Sat Dec 11 19:06:07 2010 UTC vs.
Revision 1.289 by root, Sun Aug 12 05:21:35 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 = '3.7';	176	our $VERSION = 4.5;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
179	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
182	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
183	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
184		190
185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
188	nreqs nready npending nthreads	194	nreqs nready npending nthreads
189	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
190	sendfile fadvise madvise	196	sendfile fadvise madvise
191	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
192		198
193	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
194		200
195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
196		202
…		…
200		206
201	=head1 FUNCTIONS	207	=head1 FUNCTIONS
202		208
203	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
204		210
205	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
206	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
207	documentation.	213	documentation.
208		214
		215	aio_wd $pathname, $callback->($wd)
209	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
210	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
215	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
216	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
217	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
220	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
221	aio_chmod $fh_or_path, $mode, $callback->($status)	230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
222	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
223	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
224	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
225	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
226	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
227	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
228	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
229	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
230	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
234	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
235	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
236	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238	aio_rmtree $path, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
239	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
240	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
241	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
248	aio_group $callback->(...)	263	aio_group $callback->(...)
249	aio_nop $callback->()	264	aio_nop $callback->()
…		…
258	IO::AIO::max_poll_reqs $nreqs	273	IO::AIO::max_poll_reqs $nreqs
259	IO::AIO::max_poll_time $seconds	274	IO::AIO::max_poll_time $seconds
260	IO::AIO::min_parallel $nthreads	275	IO::AIO::min_parallel $nthreads
261	IO::AIO::max_parallel $nthreads	276	IO::AIO::max_parallel $nthreads
262	IO::AIO::max_idle $nthreads	277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
263	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
264	IO::AIO::nreqs	280	IO::AIO::nreqs
265	IO::AIO::nready	281	IO::AIO::nready
266	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
267		285
268	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
269	IO::AIO::fadvise $fh, $offset, $len, $advice	287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
270	IO::AIO::madvise $scalar, $offset, $length, $advice	291	IO::AIO::madvise $scalar, $offset, $length, $advice
271	IO::AIO::mprotect $scalar, $offset, $length, $protect	292	IO::AIO::mprotect $scalar, $offset, $length, $protect
272	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
273	IO::AIO::munlockall	294	IO::AIO::munlockall
274		295
275	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
276		297
277	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
278	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
279	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
280	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
281	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
282	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
283	syscall has been executed asynchronously.	304	error occured, in C<$!>) - 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>.
284		310
285	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
286	internally until the request has finished.	312	internally until the request has finished.
287		313
288	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
289	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
290		316
291	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
292	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
293	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
294	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
295	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
296	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.
297		325
298	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
299	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
300	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
301	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
302	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
303	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.
304		333
305	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
306	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
307		338
308	=over 4	339	=over 4
309		340
310	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
311		342
…		…
341		372
342		373
343	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
344		375
345	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
346	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
347		378
348	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,
349	for an explanation.	380	for an explanation.
350		381
351	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
…		…
367	} else {	398	} else {
368	die "open failed: $!\n";	399	die "open failed: $!\n";
369	}	400	}
370	};	401	};
371		402
		403	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		404	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		405	following POSIX and non-POSIX constants are available (missing ones on
		406	your system are, as usual, C<0>):
		407
		408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		411
372		412
373	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
374		414
375	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
376	code.	416	code.
…		…
385	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
386	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
387		427
388	=cut	428	=cut
389		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
390	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
391		451
392	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
393		453
394	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
395	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
396	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
397	error, just like the syscall).	457	error, just like the syscall).
398		458
399	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
400	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
401		461
…		…
426		486
427	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
428	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
429	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
430	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
431	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>.
432		493
433	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
434	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
435	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
436	bytes written to C<$out_fh>. Only if the result value equals C<$length>	497	number of bytes written to C<$out_fh>. Only if the result value equals
437	one can assume that C<$length> bytes have been read.	498	C<$length> one can assume that C<$length> bytes have been read.
438		499
439	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
440	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
441	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
442	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
443	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
444	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
445	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
446	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
447	much better.	508	resource usage.
448		509
449	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
450	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
451	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.
452		513
453	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>,
454	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
455	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
456	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.
457		525
458		526
459	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
460		528
461	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
…		…
465	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
466	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
467	(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
468	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
469		537
470	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
471	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.
472		540
473		541
474	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
475		543
476	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
…		…
483	for an explanation.	551	for an explanation.
484		552
485	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	553	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
486	error when stat'ing a large file, the results will be silently truncated	554	error when stat'ing a large file, the results will be silently truncated
487	unless perl itself is compiled with large file support.	555	unless perl itself is compiled with large file support.
		556
		557	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		558	following constants and functions (if not implemented, the constants will
		559	be C<0> and the functions will either C<croak> or fall back on traditional
		560	behaviour).
		561
		562	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		563	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		564	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		565
		566	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		567	ACCESS>.
488		568
489	Example: Print the length of F</etc/passwd>:	569	Example: Print the length of F</etc/passwd>:
490		570
491	aio_stat "/etc/passwd", sub {	571	aio_stat "/etc/passwd", sub {
492	$_[0] and die "stat failed: $!";	572	$_[0] and die "stat failed: $!";
…		…
536	namemax => 255,	616	namemax => 255,
537	frsize => 1024,	617	frsize => 1024,
538	fsid => 1810	618	fsid => 1810
539	}	619	}
540		620
541
542	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	621	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
543		622
544	Works like perl's C<utime> function (including the special case of $atime	623	Works like perl's C<utime> function (including the special case of $atime
545	and $mtime being undef). Fractional times are supported if the underlying	624	and $mtime being undef). Fractional times are supported if the underlying
546	syscalls support them.	625	syscalls support them.
…		…
573	=item aio_truncate $fh_or_path, $offset, $callback->($status)	652	=item aio_truncate $fh_or_path, $offset, $callback->($status)
574		653
575	Works like truncate(2) or ftruncate(2).	654	Works like truncate(2) or ftruncate(2).
576		655
577		656
		657	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		658
		659	Allocates or frees disk space according to the C<$mode> argument. See the
		660	linux C<fallocate> documentation for details.
		661
		662	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		663	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		664	to deallocate a file range.
		665
		666	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		667	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		668	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		669	to unshare shared blocks (see your L<fallocate(2)> manpage).
		670
		671	The file system block size used by C<fallocate> is presumably the
		672	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		673	can dictate other limitations.
		674
		675	If C<fallocate> isn't available or cannot be emulated (currently no
		676	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		677
		678
578	=item aio_chmod $fh_or_path, $mode, $callback->($status)	679	=item aio_chmod $fh_or_path, $mode, $callback->($status)
579		680
580	Works like perl's C<chmod> function.	681	Works like perl's C<chmod> function.
581		682
582		683
…		…
584		685
585	Asynchronously unlink (delete) a file and call the callback with the	686	Asynchronously unlink (delete) a file and call the callback with the
586	result code.	687	result code.
587		688
588		689
589	=item aio_mknod $path, $mode, $dev, $callback->($status)	690	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
590		691
591	[EXPERIMENTAL]	692	[EXPERIMENTAL]
592		693
593	Asynchronously create a device node (or fifo). See mknod(2).	694	Asynchronously create a device node (or fifo). See mknod(2).
594		695
595	The only (POSIX-) portable way of calling this function is:	696	The only (POSIX-) portable way of calling this function is:
596		697
597	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	698	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
598		699
		700	See C<aio_stat> for info about some potentially helpful extra constants
		701	and functions.
599		702
600	=item aio_link $srcpath, $dstpath, $callback->($status)	703	=item aio_link $srcpath, $dstpath, $callback->($status)
601		704
602	Asynchronously create a new link to the existing object at C<$srcpath> at	705	Asynchronously create a new link to the existing object at C<$srcpath> at
603	the path C<$dstpath> and call the callback with the result code.	706	the path C<$dstpath> and call the callback with the result code.
…		…
607		710
608	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	711	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
609	the path C<$dstpath> and call the callback with the result code.	712	the path C<$dstpath> and call the callback with the result code.
610		713
611		714
612	=item aio_readlink $path, $callback->($link)	715	=item aio_readlink $pathname, $callback->($link)
613		716
614	Asynchronously read the symlink specified by C<$path> and pass it to	717	Asynchronously read the symlink specified by C<$path> and pass it to
615	the callback. If an error occurs, nothing or undef gets passed to the	718	the callback. If an error occurs, nothing or undef gets passed to the
616	callback.	719	callback.
617		720
618		721
		722	=item aio_realpath $pathname, $callback->($path)
		723
		724	Asynchronously make the path absolute and resolve any symlinks in
		725	C<$path>. The resulting path only consists of directories (same as
		726	L<Cwd::realpath>).
		727
		728	This request can be used to get the absolute path of the current working
		729	directory by passing it a path of F<.> (a single dot).
		730
		731
619	=item aio_rename $srcpath, $dstpath, $callback->($status)	732	=item aio_rename $srcpath, $dstpath, $callback->($status)
620		733
621	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	734	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
622	rename(2) and call the callback with the result code.	735	rename(2) and call the callback with the result code.
		736
		737	On systems that support the AIO::WD working directory abstraction
		738	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		739	of failing, C<rename> is called on the absolute path of C<$wd>.
		740
		741
		742	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		743
		744	Basically a version of C<aio_rename> with an additional C<$flags>
		745	argument. Calling this with C<$flags=0> is the same as calling
		746	C<aio_rename>.
		747
		748	Non-zero flags are currently only supported on GNU/Linux systems that
		749	support renameat2. Other systems fail with C<ENOSYS> in this case.
		750
		751	The following constants are available (missing ones are, as usual C<0>),
		752	see renameat2(2) for details:
		753
		754	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		755	and C<IO::AIO::RENAME_WHITEOUT>.
623		756
624		757
625	=item aio_mkdir $pathname, $mode, $callback->($status)	758	=item aio_mkdir $pathname, $mode, $callback->($status)
626		759
627	Asynchronously mkdir (create) a directory and call the callback with	760	Asynchronously mkdir (create) a directory and call the callback with
…		…
632	=item aio_rmdir $pathname, $callback->($status)	765	=item aio_rmdir $pathname, $callback->($status)
633		766
634	Asynchronously rmdir (delete) a directory and call the callback with the	767	Asynchronously rmdir (delete) a directory and call the callback with the
635	result code.	768	result code.
636		769
		770	On systems that support the AIO::WD working directory abstraction
		771	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		772	C<rmdir> is called on the absolute path of C<$wd>.
		773
637		774
638	=item aio_readdir $pathname, $callback->($entries)	775	=item aio_readdir $pathname, $callback->($entries)
639		776
640	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	777	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
641	directory (i.e. opendir + readdir + closedir). The entries will not be	778	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
645	array-ref with the filenames.	782	array-ref with the filenames.
646		783
647		784
648	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	785	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
649		786
650	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	787	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
651	behaviour and output format. In case of an error, C<$entries> will be	788	tune behaviour and output format. In case of an error, C<$entries> will be
652	C<undef>.	789	C<undef>.
653		790
654	The flags are a combination of the following constants, ORed together (the	791	The flags are a combination of the following constants, ORed together (the
655	flags will also be passed to the callback, possibly modified):	792	flags will also be passed to the callback, possibly modified):
656		793
657	=over 4	794	=over 4
658		795
659	=item IO::AIO::READDIR_DENTS	796	=item IO::AIO::READDIR_DENTS
660		797
661	When this flag is off, then the callback gets an arrayref with of names	798	Normally the callback gets an arrayref consisting of names only (as
662	only (as with C<aio_readdir>), otherwise it gets an arrayref with	799	with C<aio_readdir>). If this flag is set, then the callback gets an
663	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	800	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
664	entry in more detail.	801	single directory entry in more detail:
665		802
666	C<$name> is the name of the entry.	803	C<$name> is the name of the entry.
667		804
668	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	805	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
669		806
670	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	807	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
671	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	808	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
672	C<IO::AIO::DT_WHT>.	809	C<IO::AIO::DT_WHT>.
673		810
674	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	811	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
675	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	812	to know, you have to run stat yourself. Also, for speed/memory reasons,
676	scalars are read-only: you can not modify them.	813	the C<$type> scalars are read-only: you must not modify them.
677		814
678	C<$inode> is the inode number (which might not be exact on systems with 64	815	C<$inode> is the inode number (which might not be exact on systems with 64
679	bit inode numbers and 32 bit perls). This field has unspecified content on	816	bit inode numbers and 32 bit perls). This field has unspecified content on
680	systems that do not deliver the inode information.	817	systems that do not deliver the inode information.
681		818
682	=item IO::AIO::READDIR_DIRS_FIRST	819	=item IO::AIO::READDIR_DIRS_FIRST
683		820
684	When this flag is set, then the names will be returned in an order where	821	When this flag is set, then the names will be returned in an order where
685	likely directories come first. This is useful when you need to quickly	822	likely directories come first, in optimal stat order. This is useful when
686	find directories, or you want to find all directories while avoiding to	823	you need to quickly find directories, or you want to find all directories
687	stat() each entry.	824	while avoiding to stat() each entry.
688		825
689	If the system returns type information in readdir, then this is used	826	If the system returns type information in readdir, then this is used
690	to find directories directly. Otherwise, likely directories are files	827	to find directories directly. Otherwise, likely directories are names
691	beginning with ".", or otherwise files with no dots, of which files with	828	beginning with ".", or otherwise names with no dots, of which names with
692	short names are tried first.	829	short names are tried first.
693		830
694	=item IO::AIO::READDIR_STAT_ORDER	831	=item IO::AIO::READDIR_STAT_ORDER
695		832
696	When this flag is set, then the names will be returned in an order	833	When this flag is set, then the names will be returned in an order
697	suitable for stat()'ing each one. That is, when you plan to stat()	834	suitable for stat()'ing each one. That is, when you plan to stat() most or
698	all files in the given directory, then the returned order will likely	835	all files in the given directory, then the returned order will likely be
699	be fastest.	836	faster.
700		837
701	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	838	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
702	the likely dirs come first, resulting in a less optimal stat order.	839	then the likely dirs come first, resulting in a less optimal stat order
		840	for stat'ing all entries, but likely a more optimal order for finding
		841	subdirectories.
703		842
704	=item IO::AIO::READDIR_FOUND_UNKNOWN	843	=item IO::AIO::READDIR_FOUND_UNKNOWN
705		844
706	This flag should not be set when calling C<aio_readdirx>. Instead, it	845	This flag should not be set when calling C<aio_readdirx>. Instead, it
707	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	846	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
708	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	847	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
709	C<$type>'s are known, which can be used to speed up some algorithms.	848	C<$type>'s are known, which can be used to speed up some algorithms.
710		849
711	=back	850	=back
712		851
713		852
		853	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		854
		855	Opens, reads and closes the given file. The data is put into C<$data>,
		856	which is resized as required.
		857
		858	If C<$offset> is negative, then it is counted from the end of the file.
		859
		860	If C<$length> is zero, then the remaining length of the file is
		861	used. Also, in this case, the same limitations to modifying C<$data> apply
		862	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		863	with C<substr>. If the size of the file is known, specifying a non-zero
		864	C<$length> results in a performance advantage.
		865
		866	This request is similar to the older C<aio_load> request, but since it is
		867	a single request, it might be more efficient to use.
		868
		869	Example: load F</etc/passwd> into C<$passwd>.
		870
		871	my $passwd;
		872	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		873	$_[0] >= 0
		874	or die "/etc/passwd: $!\n";
		875
		876	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		877	print $passwd;
		878	};
		879	IO::AIO::flush;
		880
		881
714	=item aio_load $path, $data, $callback->($status)	882	=item aio_load $pathname, $data, $callback->($status)
715		883
716	This is a composite request that tries to fully load the given file into	884	This is a composite request that tries to fully load the given file into
717	memory. Status is the same as with aio_read.	885	memory. Status is the same as with aio_read.
		886
		887	Using C<aio_slurp> might be more efficient, as it is a single request.
718		888
719	=cut	889	=cut
720		890
721	sub aio_load($$;$) {	891	sub aio_load($$;$) {
722	my ($path, undef, $cb) = @_;	892	my ($path, undef, $cb) = @_;
…		…
742	=item aio_copy $srcpath, $dstpath, $callback->($status)	912	=item aio_copy $srcpath, $dstpath, $callback->($status)
743		913
744	Try to copy the I<file> (directories not supported as either source or	914	Try to copy the I<file> (directories not supported as either source or
745	destination) from C<$srcpath> to C<$dstpath> and call the callback with	915	destination) from C<$srcpath> to C<$dstpath> and call the callback with
746	a status of C<0> (ok) or C<-1> (error, see C<$!>).	916	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		917
		918	Existing destination files will be truncated.
747		919
748	This is a composite request that creates the destination file with	920	This is a composite request that creates the destination file with
749	mode 0200 and copies the contents of the source file into it using	921	mode 0200 and copies the contents of the source file into it using
750	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	922	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
751	uid/gid, in that order.	923	uid/gid, in that order.
…		…
841	if ($_[0] && $! == EXDEV) {	1013	if ($_[0] && $! == EXDEV) {
842	aioreq_pri $pri;	1014	aioreq_pri $pri;
843	add $grp aio_copy $src, $dst, sub {	1015	add $grp aio_copy $src, $dst, sub {
844	$grp->result ($_[0]);	1016	$grp->result ($_[0]);
845		1017
846	if (!$_[0]) {	1018	unless ($_[0]) {
847	aioreq_pri $pri;	1019	aioreq_pri $pri;
848	add $grp aio_unlink $src;	1020	add $grp aio_unlink $src;
849	}	1021	}
850	};	1022	};
851	} else {	1023	} else {
…		…
854	};	1026	};
855		1027
856	$grp	1028	$grp
857	}	1029	}
858		1030
859	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1031	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
860		1032
861	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1033	Scans a directory (similar to C<aio_readdir>) but additionally tries to
862	efficiently separate the entries of directory C<$path> into two sets of	1034	efficiently separate the entries of directory C<$path> into two sets of
863	names, directories you can recurse into (directories), and ones you cannot	1035	names, directories you can recurse into (directories), and ones you cannot
864	recurse into (everything else, including symlinks to directories).	1036	recurse into (everything else, including symlinks to directories).
865		1037
866	C<aio_scandir> is a composite request that creates of many sub requests_	1038	C<aio_scandir> is a composite request that generates many sub requests.
867	C<$maxreq> specifies the maximum number of outstanding aio requests that	1039	C<$maxreq> specifies the maximum number of outstanding aio requests that
868	this function generates. If it is C<< <= 0 >>, then a suitable default	1040	this function generates. If it is C<< <= 0 >>, then a suitable default
869	will be chosen (currently 4).	1041	will be chosen (currently 4).
870		1042
871	On error, the callback is called without arguments, otherwise it receives	1043	On error, the callback is called without arguments, otherwise it receives
…		…
895	Then entries will be sorted into likely directories a non-initial dot	1067	Then entries will be sorted into likely directories a non-initial dot
896	currently) and likely non-directories (see C<aio_readdirx>). Then every	1068	currently) and likely non-directories (see C<aio_readdirx>). Then every
897	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1069	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
898	in order of their inode numbers. If that succeeds, it assumes that the	1070	in order of their inode numbers. If that succeeds, it assumes that the
899	entry is a directory or a symlink to directory (which will be checked	1071	entry is a directory or a symlink to directory (which will be checked
900	seperately). This is often faster than stat'ing the entry itself because	1072	separately). This is often faster than stat'ing the entry itself because
901	filesystems might detect the type of the entry without reading the inode	1073	filesystems might detect the type of the entry without reading the inode
902	data (e.g. ext2fs filetype feature), even on systems that cannot return	1074	data (e.g. ext2fs filetype feature), even on systems that cannot return
903	the filetype information on readdir.	1075	the filetype information on readdir.
904		1076
905	If the known number of directories (link count - 2) has been reached, the	1077	If the known number of directories (link count - 2) has been reached, the
…		…
921		1093
922	my $grp = aio_group $cb;	1094	my $grp = aio_group $cb;
923		1095
924	$maxreq = 4 if $maxreq <= 0;	1096	$maxreq = 4 if $maxreq <= 0;
925		1097
926	# stat once	1098	# get a wd object
927	aioreq_pri $pri;	1099	aioreq_pri $pri;
928	add $grp aio_stat $path, sub {	1100	add $grp aio_wd $path, sub {
		1101	$_[0]
929	return $grp->result () if $_[0];	1102	or return $grp->result ();
930	my $now = time;
931	my $hash1 = join ":", (stat _)[0,1,3,7,9];
932		1103
933	# read the directory entries	1104	my $wd = [shift, "."];
		1105
		1106	# stat once
934	aioreq_pri $pri;	1107	aioreq_pri $pri;
935	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1108	add $grp aio_stat $wd, sub {
936	my $entries = shift
937	or return $grp->result ();	1109	return $grp->result () if $_[0];
		1110	my $now = time;
		1111	my $hash1 = join ":", (stat _)[0,1,3,7,9];
938		1112
939	# stat the dir another time	1113	# read the directory entries
940	aioreq_pri $pri;	1114	aioreq_pri $pri;
		1115	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1116	my $entries = shift
		1117	or return $grp->result ();
		1118
		1119	# stat the dir another time
		1120	aioreq_pri $pri;
941	add $grp aio_stat $path, sub {	1121	add $grp aio_stat $wd, sub {
942	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1122	my $hash2 = join ":", (stat _)[0,1,3,7,9];
943		1123
944	my $ndirs;	1124	my $ndirs;
945		1125
946	# take the slow route if anything looks fishy	1126	# take the slow route if anything looks fishy
947	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1127	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
948	$ndirs = -1;	1128	$ndirs = -1;
949	} else {	1129	} else {
950	# if nlink == 2, we are finished	1130	# if nlink == 2, we are finished
951	# for non-posix-fs's, we rely on nlink < 2	1131	# for non-posix-fs's, we rely on nlink < 2
952	$ndirs = (stat _)[3] - 2	1132	$ndirs = (stat _)[3] - 2
953	or return $grp->result ([], $entries);	1133	or return $grp->result ([], $entries);
954	}	1134	}
955		1135
956	my (@dirs, @nondirs);	1136	my (@dirs, @nondirs);
957		1137
958	my $statgrp = add $grp aio_group sub {	1138	my $statgrp = add $grp aio_group sub {
959	$grp->result (\@dirs, \@nondirs);	1139	$grp->result (\@dirs, \@nondirs);
960	};	1140	};
961		1141
962	limit $statgrp $maxreq;	1142	limit $statgrp $maxreq;
963	feed $statgrp sub {	1143	feed $statgrp sub {
964	return unless @$entries;	1144	return unless @$entries;
965	my $entry = shift @$entries;	1145	my $entry = shift @$entries;
966		1146
967	aioreq_pri $pri;	1147	aioreq_pri $pri;
		1148	$wd->[1] = "$entry/.";
968	add $statgrp aio_stat "$path/$entry/.", sub {	1149	add $statgrp aio_stat $wd, sub {
969	if ($_[0] < 0) {	1150	if ($_[0] < 0) {
970	push @nondirs, $entry;	1151	push @nondirs, $entry;
971	} else {	1152	} else {
972	# need to check for real directory	1153	# need to check for real directory
973	aioreq_pri $pri;	1154	aioreq_pri $pri;
		1155	$wd->[1] = $entry;
974	add $statgrp aio_lstat "$path/$entry", sub {	1156	add $statgrp aio_lstat $wd, sub {
975	if (-d _) {	1157	if (-d _) {
976	push @dirs, $entry;	1158	push @dirs, $entry;
977		1159
978	unless (--$ndirs) {	1160	unless (--$ndirs) {
979	push @nondirs, @$entries;	1161	push @nondirs, @$entries;
980	feed $statgrp;	1162	feed $statgrp;
		1163	}
		1164	} else {
		1165	push @nondirs, $entry;
981	}	1166	}
982	} else {
983	push @nondirs, $entry;
984	}	1167	}
985	}	1168	}
986	}	1169	};
987	};	1170	};
988	};	1171	};
989	};	1172	};
990	};	1173	};
991	};	1174	};
992		1175
993	$grp	1176	$grp
994	}	1177	}
995		1178
996	=item aio_rmtree $path, $callback->($status)	1179	=item aio_rmtree $pathname, $callback->($status)
997		1180
998	Delete a directory tree starting (and including) C<$path>, return the	1181	Delete a directory tree starting (and including) C<$path>, return the
999	status of the final C<rmdir> only. This is a composite request that	1182	status of the final C<rmdir> only. This is a composite request that
1000	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1183	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1001	everything else.	1184	everything else.
1002		1185
1003	=cut	1186	=cut
1004		1187
…		…
1026	};	1209	};
1027		1210
1028	$grp	1211	$grp
1029	}	1212	}
1030		1213
		1214	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1215
		1216	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1217
		1218	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1219	they execute asynchronously and pass the return value to the callback.
		1220
		1221	Both calls can be used for a lot of things, some of which make more sense
		1222	to run asynchronously in their own thread, while some others make less
		1223	sense. For example, calls that block waiting for external events, such
		1224	as locking, will also lock down an I/O thread while it is waiting, which
		1225	can deadlock the whole I/O system. At the same time, there might be no
		1226	alternative to using a thread to wait.
		1227
		1228	So in general, you should only use these calls for things that do
		1229	(filesystem) I/O, not for things that wait for other events (network,
		1230	other processes), although if you are careful and know what you are doing,
		1231	you still can.
		1232
		1233	The following constants are available (missing ones are, as usual C<0>):
		1234
		1235	C<F_DUPFD_CLOEXEC>,
		1236
		1237	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1238
		1239	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1240
		1241	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1242	C<FS_IOC_FIEMAP>.
		1243
		1244	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1245	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1246
		1247	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1248	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1249	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1250	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1251	C<FS_FL_USER_MODIFIABLE>.
		1252
		1253	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1254	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1255	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1256	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1257
1031	=item aio_sync $callback->($status)	1258	=item aio_sync $callback->($status)
1032		1259
1033	Asynchronously call sync and call the callback when finished.	1260	Asynchronously call sync and call the callback when finished.
1034		1261
1035	=item aio_fsync $fh, $callback->($status)	1262	=item aio_fsync $fh, $callback->($status)
…		…
1042	Asynchronously call fdatasync on the given filehandle and call the	1269	Asynchronously call fdatasync on the given filehandle and call the
1043	callback with the fdatasync result code.	1270	callback with the fdatasync result code.
1044		1271
1045	If this call isn't available because your OS lacks it or it couldn't be	1272	If this call isn't available because your OS lacks it or it couldn't be
1046	detected, it will be emulated by calling C<fsync> instead.	1273	detected, it will be emulated by calling C<fsync> instead.
		1274
		1275	=item aio_syncfs $fh, $callback->($status)
		1276
		1277	Asynchronously call the syncfs syscall to sync the filesystem associated
		1278	to the given filehandle and call the callback with the syncfs result
		1279	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1280	errno to C<ENOSYS> nevertheless.
1047		1281
1048	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1282	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1049		1283
1050	Sync the data portion of the file specified by C<$offset> and C<$length>	1284	Sync the data portion of the file specified by C<$offset> and C<$length>
1051	to disk (but NOT the metadata), by calling the Linux-specific	1285	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1055	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1289	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1056	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1290	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1057	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1291	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1058	manpage for details.	1292	manpage for details.
1059		1293
1060	=item aio_pathsync $path, $callback->($status)	1294	=item aio_pathsync $pathname, $callback->($status)
1061		1295
1062	This request tries to open, fsync and close the given path. This is a	1296	This request tries to open, fsync and close the given path. This is a
1063	composite request intended to sync directories after directory operations	1297	composite request intended to sync directories after directory operations
1064	(E.g. rename). This might not work on all operating systems or have any	1298	(E.g. rename). This might not work on all operating systems or have any
1065	specific effect, but usually it makes sure that directory changes get	1299	specific effect, but usually it makes sure that directory changes get
…		…
1096	};	1330	};
1097		1331
1098	$grp	1332	$grp
1099	}	1333	}
1100		1334
1101	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1335	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1102		1336
1103	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1337	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1104	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1338	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1105	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1339	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1106	scalar must only be modified in-place while an aio operation is pending on	1340	scalar must only be modified in-place while an aio operation is pending on
…		…
1108		1342
1109	It calls the C<msync> function of your OS, if available, with the memory	1343	It calls the C<msync> function of your OS, if available, with the memory
1110	area starting at C<$offset> in the string and ending C<$length> bytes	1344	area starting at C<$offset> in the string and ending C<$length> bytes
1111	later. If C<$length> is negative, counts from the end, and if C<$length>	1345	later. If C<$length> is negative, counts from the end, and if C<$length>
1112	is C<undef>, then it goes till the end of the string. The flags can be	1346	is C<undef>, then it goes till the end of the string. The flags can be
1113	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1347	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1114	C<IO::AIO::MS_SYNC>.	1348	C<IO::AIO::MS_INVALIDATE>.
1115		1349
1116	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1350	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1117		1351
1118	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1352	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1119	scalars.	1353	scalars.
1120		1354
1121	It touches (reads or writes) all memory pages in the specified	1355	It touches (reads or writes) all memory pages in the specified
1122	range inside the scalar. All caveats and parameters are the same	1356	range inside the scalar. All caveats and parameters are the same
1123	as for C<aio_msync>, above, except for flags, which must be either	1357	as for C<aio_msync>, above, except for flags, which must be either
1124	C<0> (which reads all pages and ensures they are instantiated) or	1358	C<0> (which reads all pages and ensures they are instantiated) or
1125	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1359	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1126	writing an octet from it, which dirties the page).	1360	writing an octet from it, which dirties the page).
1127		1361
1128	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1362	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1129		1363
1130	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1364	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1161	documented under L<MISCELLANEOUS FUNCTIONS>.	1395	documented under L<MISCELLANEOUS FUNCTIONS>.
1162		1396
1163	Example: asynchronously lock all current and future pages into memory.	1397	Example: asynchronously lock all current and future pages into memory.
1164		1398
1165	aio_mlockall IO::AIO::MCL_FUTURE;	1399	aio_mlockall IO::AIO::MCL_FUTURE;
		1400
		1401	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1402
		1403	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1404	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1405	the ioctl is not available on your OS, then this request will fail with
		1406	C<ENOSYS>.
		1407
		1408	C<$start> is the starting offset to query extents for, C<$length> is the
		1409	size of the range to query - if it is C<undef>, then the whole file will
		1410	be queried.
		1411
		1412	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1413	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1414	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1415	the data portion.
		1416
		1417	C<$count> is the maximum number of extent records to return. If it is
		1418	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1419	case, if it is C<0>, then the callback receives the number of extents
		1420	instead of the extents themselves (which is unreliable, see below).
		1421
		1422	If an error occurs, the callback receives no arguments. The special
		1423	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1424
		1425	Otherwise, the callback receives an array reference with extent
		1426	structures. Each extent structure is an array reference itself, with the
		1427	following members:
		1428
		1429	[$logical, $physical, $length, $flags]
		1430
		1431	Flags is any combination of the following flag values (typically either C<0>
		1432	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1433
		1434	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1435	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1436	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1437	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1438	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1439	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1440
		1441	At the time of this writing (Linux 3.2), this request is unreliable unless
		1442	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1443	it to return all extents of a range for files with a large number of
		1444	extents. The code (only) works around all these issues if C<$count> is
		1445	C<undef>.
1166		1446
1167	=item aio_group $callback->(...)	1447	=item aio_group $callback->(...)
1168		1448
1169	This is a very special aio request: Instead of doing something, it is a	1449	This is a very special aio request: Instead of doing something, it is a
1170	container for other aio requests, which is useful if you want to bundle	1450	container for other aio requests, which is useful if you want to bundle
…		…
1207	like sleep and file handle readable/writable, the overhead this creates is	1487	like sleep and file handle readable/writable, the overhead this creates is
1208	immense (it blocks a thread for a long time) so do not use this function	1488	immense (it blocks a thread for a long time) so do not use this function
1209	except to put your application under artificial I/O pressure.	1489	except to put your application under artificial I/O pressure.
1210		1490
1211	=back	1491	=back
		1492
		1493
		1494	=head2 IO::AIO::WD - multiple working directories
		1495
		1496	Your process only has one current working directory, which is used by all
		1497	threads. This makes it hard to use relative paths (some other component
		1498	could call C<chdir> at any time, and it is hard to control when the path
		1499	will be used by IO::AIO).
		1500
		1501	One solution for this is to always use absolute paths. This usually works,
		1502	but can be quite slow (the kernel has to walk the whole path on every
		1503	access), and can also be a hassle to implement.
		1504
		1505	Newer POSIX systems have a number of functions (openat, fdopendir,
		1506	futimensat and so on) that make it possible to specify working directories
		1507	per operation.
		1508
		1509	For portability, and because the clowns who "designed", or shall I write,
		1510	perpetrated this new interface were obviously half-drunk, this abstraction
		1511	cannot be perfect, though.
		1512
		1513	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1514	object. This object stores the canonicalised, absolute version of the
		1515	path, and on systems that allow it, also a directory file descriptor.
		1516
		1517	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1518	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1519	object and a pathname instead (or the IO::AIO::WD object alone, which
		1520	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1521	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1522	to that IO::AIO::WD object.
		1523
		1524	For example, to get a wd object for F</etc> and then stat F<passwd>
		1525	inside, you would write:
		1526
		1527	aio_wd "/etc", sub {
		1528	my $etcdir = shift;
		1529
		1530	# although $etcdir can be undef on error, there is generally no reason
		1531	# to check for errors here, as aio_stat will fail with ENOENT
		1532	# when $etcdir is undef.
		1533
		1534	aio_stat [$etcdir, "passwd"], sub {
		1535	# yay
		1536	};
		1537	};
		1538
		1539	The fact that C<aio_wd> is a request and not a normal function shows that
		1540	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1541	which is why it is done asynchronously.
		1542
		1543	To stat the directory obtained with C<aio_wd> above, one could write
		1544	either of the following three request calls:
		1545
		1546	aio_lstat "/etc" , sub { ... # pathname as normal string
		1547	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1548	aio_lstat $wd , sub { ... # shorthand for the previous
		1549
		1550	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1551	object and the pathname string, so you could write the following without
		1552	causing any issues due to C<$path> getting reused:
		1553
		1554	my $path = [$wd, undef];
		1555
		1556	for my $name (qw(abc def ghi)) {
		1557	$path->[1] = $name;
		1558	aio_stat $path, sub {
		1559	# ...
		1560	};
		1561	}
		1562
		1563	There are some caveats: when directories get renamed (or deleted), the
		1564	pathname string doesn't change, so will point to the new directory (or
		1565	nowhere at all), while the directory fd, if available on the system,
		1566	will still point to the original directory. Most functions accepting a
		1567	pathname will use the directory fd on newer systems, and the string on
		1568	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1569	the string form of the pathname.
		1570
		1571	So this functionality is mainly useful to get some protection against
		1572	C<chdir>, to easily get an absolute path out of a relative path for future
		1573	reference, and to speed up doing many operations in the same directory
		1574	(e.g. when stat'ing all files in a directory).
		1575
		1576	The following functions implement this working directory abstraction:
		1577
		1578	=over 4
		1579
		1580	=item aio_wd $pathname, $callback->($wd)
		1581
		1582	Asynchonously canonicalise the given pathname and convert it to an
		1583	IO::AIO::WD object representing it. If possible and supported on the
		1584	system, also open a directory fd to speed up pathname resolution relative
		1585	to this working directory.
		1586
		1587	If something goes wrong, then C<undef> is passwd to the callback instead
		1588	of a working directory object and C<$!> is set appropriately. Since
		1589	passing C<undef> as working directory component of a pathname fails the
		1590	request with C<ENOENT>, there is often no need for error checking in the
		1591	C<aio_wd> callback, as future requests using the value will fail in the
		1592	expected way.
		1593
		1594	=item IO::AIO::CWD
		1595
		1596	This is a compiletime constant (object) that represents the process
		1597	current working directory.
		1598
		1599	Specifying this object as working directory object for a pathname is as if
		1600	the pathname would be specified directly, without a directory object. For
		1601	example, these calls are functionally identical:
		1602
		1603	aio_stat "somefile", sub { ... };
		1604	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1605
		1606	=back
		1607
		1608	To recover the path associated with an IO::AIO::WD object, you can use
		1609	C<aio_realpath>:
		1610
		1611	aio_realpath $wd, sub {
		1612	warn "path is $_[0]\n";
		1613	};
		1614
		1615	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1616	sometimes, fall back to using an absolue path.
1212		1617
1213	=head2 IO::AIO::REQ CLASS	1618	=head2 IO::AIO::REQ CLASS
1214		1619
1215	All non-aggregate C<aio_*> functions return an object of this class when	1620	All non-aggregate C<aio_*> functions return an object of this class when
1216	called in non-void context.	1621	called in non-void context.
…		…
1334		1739
1335	Sets a feeder/generator on this group: every group can have an attached	1740	Sets a feeder/generator on this group: every group can have an attached
1336	generator that generates requests if idle. The idea behind this is that,	1741	generator that generates requests if idle. The idea behind this is that,
1337	although you could just queue as many requests as you want in a group,	1742	although you could just queue as many requests as you want in a group,
1338	this might starve other requests for a potentially long time. For example,	1743	this might starve other requests for a potentially long time. For example,
1339	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1744	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1340	delaying any later requests for a long time.	1745	requests, delaying any later requests for a long time.
1341		1746
1342	To avoid this, and allow incremental generation of requests, you can	1747	To avoid this, and allow incremental generation of requests, you can
1343	instead a group and set a feeder on it that generates those requests. The	1748	instead a group and set a feeder on it that generates those requests. The
1344	feed callback will be called whenever there are few enough (see C<limit>,	1749	feed callback will be called whenever there are few enough (see C<limit>,
1345	below) requests active in the group itself and is expected to queue more	1750	below) requests active in the group itself and is expected to queue more
…		…
1394		1799
1395	See C<poll_cb> for an example.	1800	See C<poll_cb> for an example.
1396		1801
1397	=item IO::AIO::poll_cb	1802	=item IO::AIO::poll_cb
1398		1803
1399	Process some outstanding events on the result pipe. You have to call this	1804	Process some requests that have reached the result phase (i.e. they have
1400	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1805	been executed but the results are not yet reported). You have to call
1401	returned earlier for whatever reason. Returns immediately when no events	1806	this "regularly" to finish outstanding requests.
1402	are outstanding. The amount of events processed depends on the settings of
1403	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1404		1807
		1808	Returns C<0> if all events could be processed (or there were no
		1809	events to process), or C<-1> if it returned earlier for whatever
		1810	reason. Returns immediately when no events are outstanding. The amount
		1811	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1812	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1813
1405	If not all requests were processed for whatever reason, the filehandle	1814	If not all requests were processed for whatever reason, the poll file
1406	will still be ready when C<poll_cb> returns, so normally you don't have to	1815	descriptor will still be ready when C<poll_cb> returns, so normally you
1407	do anything special to have it called later.	1816	don't have to do anything special to have it called later.
		1817
		1818	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1819	ready, it can be beneficial to call this function from loops which submit
		1820	a lot of requests, to make sure the results get processed when they become
		1821	available and not just when the loop is finished and the event loop takes
		1822	over again. This function returns very fast when there are no outstanding
		1823	requests.
1408		1824
1409	Example: Install an Event watcher that automatically calls	1825	Example: Install an Event watcher that automatically calls
1410	IO::AIO::poll_cb with high priority (more examples can be found in the	1826	IO::AIO::poll_cb with high priority (more examples can be found in the
1411	SYNOPSIS section, at the top of this document):	1827	SYNOPSIS section, at the top of this document):
1412		1828
…		…
1414	poll => 'r', async => 1,	1830	poll => 'r', async => 1,
1415	cb => \&IO::AIO::poll_cb);	1831	cb => \&IO::AIO::poll_cb);
1416		1832
1417	=item IO::AIO::poll_wait	1833	=item IO::AIO::poll_wait
1418		1834
1419	If there are any outstanding requests and none of them in the result	1835	Wait until either at least one request is in the result phase or no
1420	phase, wait till the result filehandle becomes ready for reading (simply	1836	requests are outstanding anymore.
1421	does a C<select> on the filehandle. This is useful if you want to	1837
1422	synchronously wait for some requests to finish).	1838	This is useful if you want to synchronously wait for some requests to
		1839	become ready, without actually handling them.
1423		1840
1424	See C<nreqs> for an example.	1841	See C<nreqs> for an example.
1425		1842
1426	=item IO::AIO::poll	1843	=item IO::AIO::poll
1427		1844
…		…
1514		1931
1515	Under normal circumstances you don't need to call this function.	1932	Under normal circumstances you don't need to call this function.
1516		1933
1517	=item IO::AIO::max_idle $nthreads	1934	=item IO::AIO::max_idle $nthreads
1518		1935
1519	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1936	Limit the number of threads (default: 4) that are allowed to idle
1520	threads that did not get a request to process within 10 seconds). That	1937	(i.e., threads that did not get a request to process within the idle
1521	means if a thread becomes idle while C<$nthreads> other threads are also	1938	timeout (default: 10 seconds). That means if a thread becomes idle while
1522	idle, it will free its resources and exit.	1939	C<$nthreads> other threads are also idle, it will free its resources and
		1940	exit.
1523		1941
1524	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1942	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1525	to allow for extremely high load situations, but want to free resources	1943	to allow for extremely high load situations, but want to free resources
1526	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1944	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1527		1945
1528	The default is probably ok in most situations, especially if thread	1946	The default is probably ok in most situations, especially if thread
1529	creation is fast. If thread creation is very slow on your system you might	1947	creation is fast. If thread creation is very slow on your system you might
1530	want to use larger values.	1948	want to use larger values.
1531		1949
		1950	=item IO::AIO::idle_timeout $seconds
		1951
		1952	Sets the minimum idle timeout (default 10) after which worker threads are
		1953	allowed to exit. SEe C<IO::AIO::max_idle>.
		1954
1532	=item IO::AIO::max_outstanding $maxreqs	1955	=item IO::AIO::max_outstanding $maxreqs
		1956
		1957	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1958	you do queue up more than this number of requests, the next call to
		1959	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1960	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1961	longer exceeded.
		1962
		1963	In other words, this setting does not enforce a queue limit, but can be
		1964	used to make poll functions block if the limit is exceeded.
1533		1965
1534	This is a very bad function to use in interactive programs because it	1966	This is a very bad function to use in interactive programs because it
1535	blocks, and a bad way to reduce concurrency because it is inexact: Better	1967	blocks, and a bad way to reduce concurrency because it is inexact: Better
1536	use an C<aio_group> together with a feed callback.	1968	use an C<aio_group> together with a feed callback.
1537		1969
1538	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1970	Its main use is in scripts without an event loop - when you want to stat
1539	do queue up more than this number of requests, the next call to the	1971	a lot of files, you can write something like this:
1540	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1541	function will block until the limit is no longer exceeded.
1542		1972
1543	The default value is very large, so there is no practical limit on the	1973	IO::AIO::max_outstanding 32;
1544	number of outstanding requests.
1545		1974
1546	You can still queue as many requests as you want. Therefore,	1975	for my $path (...) {
1547	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1976	aio_stat $path , ...;
1548	as a stop gap to shield against fatal memory overflow (with large values).	1977	IO::AIO::poll_cb;
		1978	}
		1979
		1980	IO::AIO::flush;
		1981
		1982	The call to C<poll_cb> inside the loop will normally return instantly, but
		1983	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1984	some requests have been handled. This keeps the loop from pushing a large
		1985	number of C<aio_stat> requests onto the queue.
		1986
		1987	The default value for C<max_outstanding> is very large, so there is no
		1988	practical limit on the number of outstanding requests.
1549		1989
1550	=back	1990	=back
1551		1991
1552	=head3 STATISTICAL INFORMATION	1992	=head3 STATISTICAL INFORMATION
1553		1993
…		…
1573	Returns the number of requests currently in the pending state (executed,	2013	Returns the number of requests currently in the pending state (executed,
1574	but not yet processed by poll_cb).	2014	but not yet processed by poll_cb).
1575		2015
1576	=back	2016	=back
1577		2017
		2018	=head3 SUBSECOND STAT TIME ACCESS
		2019
		2020	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2021	generally find access/modification and change times with subsecond time
		2022	accuracy of the system supports it, but perl's built-in functions only
		2023	return the integer part.
		2024
		2025	The following functions return the timestamps of the most recent
		2026	stat with subsecond precision on most systems and work both after
		2027	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2028	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2029	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2030
		2031	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2032	full resolution without rounding and work with standard perl C<stat>,
		2033	alleviating the need to call the special C<Time::HiRes> functions, which
		2034	do not act like their perl counterparts.
		2035
		2036	On operating systems or file systems where subsecond time resolution is
		2037	not supported or could not be detected, a fractional part of C<0> is
		2038	returned, so it is always safe to call these functions.
		2039
		2040	=over 4
		2041
		2042	=item IO::AIO::stat_atime, IO::AIO::stat_mtime, IO::AIO::stat_ctime
		2043
		2044	Return the access, modication or change time, respectively, including
		2045	fractional part. Due to the limited precision of floating point, the
		2046	accuracy on most platforms is only a bit better than milliseconds for
		2047	times around now - see the I<nsec> function family, below, for full
		2048	accuracy.
		2049
		2050	=item ($atime, $mtime, $ctime, ...) = IO::AIO::stat_xtime
		2051
		2052	Returns access, modification and change time all in one go, and maybe more
		2053	times in the future version.
		2054
		2055	=item IO::AIO::stat_atimensec, IO::AIO::stat_mtimensec, IO::AIO::stat_ctimensec
		2056
		2057	Return the fractional access, modifcation or change time, in nanoseconds,
		2058	as an integer in the range C<0> to C<999999999>.
		2059
		2060	=back
		2061
		2062	Example: print the high resolution modification time of F</etc>, using
		2063	C<stat>, and C<IO::AIO::aio_stat>.
		2064
		2065	if (stat "/etc") {
		2066	printf "stat(/etc) mtime: %f\n", IO::AIO::stat_mtime;
		2067	}
		2068
		2069	IO::AIO::aio_stat "/etc", sub {
		2070	$_[0]
		2071	and return;
		2072
		2073	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::stat_mtimensec;
		2074	};
		2075
		2076	IO::AIO::flush;
		2077
		2078	Output of the awbove on my system, showing reduced and full accuracy:
		2079
		2080	stat(/etc) mtime: 1534043702.020808
		2081	aio_stat(/etc) mtime: 1534043702.020807792
		2082
1578	=head3 MISCELLANEOUS FUNCTIONS	2083	=head3 MISCELLANEOUS FUNCTIONS
1579		2084
1580	IO::AIO implements some functions that might be useful, but are not	2085	IO::AIO implements some functions that are useful when you want to use
1581	asynchronous.	2086	some "Advanced I/O" function not available to in Perl, without going the
		2087	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2088	counterpart.
1582		2089
1583	=over 4	2090	=over 4
		2091
		2092	=item $numfd = IO::AIO::get_fdlimit
		2093
		2094	This function is I<EXPERIMENTAL> and subject to change.
		2095
		2096	Tries to find the current file descriptor limit and returns it, or
		2097	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2098	the highest valid file descriptor number.
		2099
		2100	=item IO::AIO::min_fdlimit [$numfd]
		2101
		2102	This function is I<EXPERIMENTAL> and subject to change.
		2103
		2104	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2105	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2106	is missing, it will try to set a very high limit, although this is not
		2107	recommended when you know the actual minimum that you require.
		2108
		2109	If the limit cannot be raised enough, the function makes a best-effort
		2110	attempt to increase the limit as much as possible, using various
		2111	tricks, while still failing. You can query the resulting limit using
		2112	C<IO::AIO::get_fdlimit>.
		2113
		2114	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2115	true.
1584		2116
1585	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2117	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1586		2118
1587	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2119	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1588	but is blocking (this makes most sense if you know the input data is	2120	but is blocking (this makes most sense if you know the input data is
…		…
1593		2125
1594	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2126	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1595		2127
1596	Simply calls the C<posix_fadvise> function (see its	2128	Simply calls the C<posix_fadvise> function (see its
1597	manpage for details). The following advice constants are	2129	manpage for details). The following advice constants are
1598	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2130	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1599	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2131	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1600	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2132	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1601		2133
1602	On systems that do not implement C<posix_fadvise>, this function returns	2134	On systems that do not implement C<posix_fadvise>, this function returns
1603	ENOSYS, otherwise the return value of C<posix_fadvise>.	2135	ENOSYS, otherwise the return value of C<posix_fadvise>.
1604		2136
1605	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2137	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1606		2138
1607	Simply calls the C<posix_madvise> function (see its	2139	Simply calls the C<posix_madvise> function (see its
1608	manpage for details). The following advice constants are	2140	manpage for details). The following advice constants are
1609	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2141	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1610	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2142	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2143	C<IO::AIO::MADV_DONTNEED>.
		2144
		2145	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2146	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2147	will be reduced to fit into the C<$scalar>.
1611		2148
1612	On systems that do not implement C<posix_madvise>, this function returns	2149	On systems that do not implement C<posix_madvise>, this function returns
1613	ENOSYS, otherwise the return value of C<posix_madvise>.	2150	ENOSYS, otherwise the return value of C<posix_madvise>.
1614		2151
1615	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2152	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1616		2153
1617	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2154	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1618	$scalar (see its manpage for details). The following protect	2155	$scalar (see its manpage for details). The following protect
1619	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2156	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1620	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2157	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2158
		2159	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2160	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2161	will be reduced to fit into the C<$scalar>.
1621		2162
1622	On systems that do not implement C<mprotect>, this function returns	2163	On systems that do not implement C<mprotect>, this function returns
1623	ENOSYS, otherwise the return value of C<mprotect>.	2164	ENOSYS, otherwise the return value of C<mprotect>.
1624		2165
1625	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2166	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1626		2167
1627	Memory-maps a file (or anonymous memory range) and attaches it to the	2168	Memory-maps a file (or anonymous memory range) and attaches it to the
1628	given C<$scalar>, which will act like a string scalar.	2169	given C<$scalar>, which will act like a string scalar. Returns true on
		2170	success, and false otherwise.
1629		2171
		2172	The scalar must exist, but its contents do not matter - this means you
		2173	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2174	the scalar first.
		2175
1630	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2176	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1631	change the string length, and most read-only operations such as copying it	2177	which don't change the string length, and most read-only operations such
1632	or searching it with regexes and so on.	2178	as copying it or searching it with regexes and so on.
1633		2179
1634	Anything else is unsafe and will, at best, result in memory leaks.	2180	Anything else is unsafe and will, at best, result in memory leaks.
1635		2181
1636	The memory map associated with the C<$scalar> is automatically removed	2182	The memory map associated with the C<$scalar> is automatically removed
1637	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2183	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1638	C<IO::AIO::munmap> functions are called.	2184	or C<IO::AIO::munmap> functions are called on it.
1639		2185
1640	This calls the C<mmap>(2) function internally. See your system's manual	2186	This calls the C<mmap>(2) function internally. See your system's manual
1641	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2187	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1642		2188
1643	The C<$length> must be larger than zero and smaller than the actual	2189	The C<$length> must be larger than zero and smaller than the actual
1644	filesize.	2190	filesize.
1645		2191
1646	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2192	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1647	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2193	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1648		2194
1649	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2195	C<$flags> can be a combination of
1650	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2196	C<IO::AIO::MAP_SHARED> or
1651	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2197	C<IO::AIO::MAP_PRIVATE>,
		2198	or a number of system-specific flags (when not available, the are C<0>):
1652	(which is set to C<MAP_ANON> if your system only provides this	2199	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1653	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2200	C<IO::AIO::MAP_LOCKED>,
1654	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2201	C<IO::AIO::MAP_NORESERVE>,
		2202	C<IO::AIO::MAP_POPULATE>,
1655	C<IO::AIO::MAP_NONBLOCK>	2203	C<IO::AIO::MAP_NONBLOCK>,
		2204	C<IO::AIO::MAP_FIXED>,
		2205	C<IO::AIO::MAP_GROWSDOWN>,
		2206	C<IO::AIO::MAP_32BIT>,
		2207	C<IO::AIO::MAP_HUGETLB> or
		2208	C<IO::AIO::MAP_STACK>.
1656		2209
1657	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2210	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1658		2211
1659	C<$offset> is the offset from the start of the file - it generally must be	2212	C<$offset> is the offset from the start of the file - it generally must be
1660	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2213	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1674		2227
1675	=item IO::AIO::munmap $scalar	2228	=item IO::AIO::munmap $scalar
1676		2229
1677	Removes a previous mmap and undefines the C<$scalar>.	2230	Removes a previous mmap and undefines the C<$scalar>.
1678		2231
		2232	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2233
		2234	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2235	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2236	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2237
		2238	Returns true if successful, and false otherwise. If the underlying mmapped
		2239	region has changed address, then the true value has the numerical value
		2240	C<1>, otherwise it has the numerical value C<0>:
		2241
		2242	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2243	or die "mremap: $!";
		2244
		2245	if ($success*1) {
		2246	warn "scalar has chanegd address in memory\n";
		2247	}
		2248
		2249	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2250	implemented, but not supported and might go away in a future version.
		2251
		2252	On systems where this call is not supported or is not emulated, this call
		2253	returns falls and sets C<$!> to C<ENOSYS>.
		2254
1679	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2255	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1680		2256
1681	Calls the C<munlock> function, undoing the effects of a previous	2257	Calls the C<munlock> function, undoing the effects of a previous
1682	C<aio_mlock> call (see its description for details).	2258	C<aio_mlock> call (see its description for details).
1683		2259
…		…
1685		2261
1686	Calls the C<munlockall> function.	2262	Calls the C<munlockall> function.
1687		2263
1688	On systems that do not implement C<munlockall>, this function returns	2264	On systems that do not implement C<munlockall>, this function returns
1689	ENOSYS, otherwise the return value of C<munlockall>.	2265	ENOSYS, otherwise the return value of C<munlockall>.
		2266
		2267	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2268
		2269	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2270	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2271	should be the file offset.
		2272
		2273	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2274	silently corrupt the data in this case.
		2275
		2276	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2277	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2278	C<IO::AIO::SPLICE_F_GIFT>.
		2279
		2280	See the C<splice(2)> manpage for details.
		2281
		2282	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2283
		2284	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2285	description for C<IO::AIO::splice> above for details.
		2286
		2287	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2288
		2289	Attempts to query or change the pipe buffer size. Obviously works only
		2290	on pipes, and currently works only on GNU/Linux systems, and fails with
		2291	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2292	size on other systems, drop me a note.
		2293
		2294	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2295
		2296	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2297	C<$flags> is missing or C<0>, then this should be the same as a call to
		2298	perl's built-in C<pipe> function and create a new pipe, and works on
		2299	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2300	(..., 4096, O_BINARY)>.
		2301
		2302	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2303	the given flags (Linux 2.6.27, glibc 2.9).
		2304
		2305	On success, the read and write file handles are returned.
		2306
		2307	On error, nothing will be returned. If the pipe2 syscall is missing and
		2308	C<$flags> is non-zero, fails with C<ENOSYS>.
		2309
		2310	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2311	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2312	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2313
		2314	Example: create a pipe race-free w.r.t. threads and fork:
		2315
		2316	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2317	or die "pipe2: $!\n";
		2318
		2319	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2320
		2321	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2322	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2323
		2324	On success, the new eventfd filehandle is returned, otherwise returns
		2325	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2326
		2327	Please refer to L<eventfd(2)> for more info on this call.
		2328
		2329	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2330	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2331
		2332	Example: create a new eventfd filehandle:
		2333
		2334	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2335	or die "eventfd: $!\n";
		2336
		2337	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2338
		2339	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2340	(unhelpful) default for C<$flags> is C<0>.
		2341
		2342	On success, the new timerfd filehandle is returned, otherwise returns
		2343	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2344
		2345	Please refer to L<timerfd_create(2)> for more info on this call.
		2346
		2347	The following C<$clockid> values are
		2348	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2349	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2350	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2351	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2352
		2353	The following C<$flags> values are available (Linux
		2354	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2355
		2356	Example: create a new timerfd and set it to one-second repeated alarms,
		2357	then wait for two alarms:
		2358
		2359	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2360	or die "timerfd_create: $!\n";
		2361
		2362	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2363	or die "timerfd_settime: $!\n";
		2364
		2365	for (1..2) {
		2366	8 == sysread $fh, my $buf, 8
		2367	or die "timerfd read failure\n";
		2368
		2369	printf "number of expirations (likely 1): %d\n",
		2370	unpack "Q", $buf;
		2371	}
		2372
		2373	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2374
		2375	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2376	call. Please refer to its manpage for more info on this call.
		2377
		2378	The new itimerspec is specified using two (possibly fractional) second
		2379	values, C<$new_interval> and C<$new_value>).
		2380
		2381	On success, the current interval and value are returned (as per
		2382	C<timerfd_gettime>). On failure, the empty list is returned.
		2383
		2384	The following C<$flags> values are
		2385	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2386	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2387
		2388	See C<IO::AIO::timerfd_create> for a full example.
		2389
		2390	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2391
		2392	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2393	call. Please refer to its manpage for more info on this call.
		2394
		2395	On success, returns the current values of interval and value for the given
		2396	timerfd (as potentially fractional second values). On failure, the empty
		2397	list is returned.
1690		2398
1691	=back	2399	=back
1692		2400
1693	=cut	2401	=cut
1694		2402
…		…
1729	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2437	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1730	\&IO::AIO::poll_cb);	2438	\&IO::AIO::poll_cb);
1731		2439
1732	=head2 FORK BEHAVIOUR	2440	=head2 FORK BEHAVIOUR
1733		2441
1734	This module should do "the right thing" when the process using it forks:	2442	Usage of pthreads in a program changes the semantics of fork
		2443	considerably. Specifically, only async-safe functions can be called after
		2444	fork. Perl doesn't know about this, so in general, you cannot call fork
		2445	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2446	pthreads, so this applies, but many other extensions and (for inexplicable
		2447	reasons) perl itself often is linked against pthreads, so this limitation
		2448	applies to quite a lot of perls.
1735		2449
1736	Before the fork, IO::AIO enters a quiescent state where no requests	2450	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1737	can be added in other threads and no results will be processed. After	2451	only works in the process that loaded it. Forking is fully supported, but
1738	the fork the parent simply leaves the quiescent state and continues	2452	using IO::AIO in the child is not.
1739	request/result processing, while the child frees the request/result queue
1740	(so that the requests started before the fork will only be handled in the
1741	parent). Threads will be started on demand until the limit set in the
1742	parent process has been reached again.
1743		2453
1744	In short: the parent will, after a short pause, continue as if fork had	2454	You might get around by not I<using> IO::AIO before (or after)
1745	not been called, while the child will act as if IO::AIO has not been used	2455	forking. You could also try to call the L<IO::AIO::reinit> function in the
1746	yet.	2456	child:
		2457
		2458	=over 4
		2459
		2460	=item IO::AIO::reinit
		2461
		2462	Abandons all current requests and I/O threads and simply reinitialises all
		2463	data structures. This is not an operation supported by any standards, but
		2464	happens to work on GNU/Linux and some newer BSD systems.
		2465
		2466	The only reasonable use for this function is to call it after forking, if
		2467	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2468	the process will result in undefined behaviour. Calling it at any time
		2469	will also result in any undefined (by POSIX) behaviour.
		2470
		2471	=back
		2472
		2473	=head2 LINUX-SPECIFIC CALLS
		2474
		2475	When a call is documented as "linux-specific" then this means it
		2476	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2477	availability and compatibility of such calls regardless of the platform
		2478	it is compiled on, so platforms such as FreeBSD which often implement
		2479	these calls will work. When in doubt, call them and see if they fail wth
		2480	C<ENOSYS>.
1747		2481
1748	=head2 MEMORY USAGE	2482	=head2 MEMORY USAGE
1749		2483
1750	Per-request usage:	2484	Per-request usage:
1751		2485
…		…
1764	temporary buffers, and each thread requires a stack and other data	2498	temporary buffers, and each thread requires a stack and other data
1765	structures (usually around 16k-128k, depending on the OS).	2499	structures (usually around 16k-128k, depending on the OS).
1766		2500
1767	=head1 KNOWN BUGS	2501	=head1 KNOWN BUGS
1768		2502
1769	Known bugs will be fixed in the next release.	2503	Known bugs will be fixed in the next release :)
		2504
		2505	=head1 KNOWN ISSUES
		2506
		2507	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2508	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2509	non-created hash slots or other scalars I didn't think of. It's best to
		2510	avoid such and either use scalar variables or making sure that the scalar
		2511	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2512
		2513	I am not sure anything can be done about this, so this is considered a
		2514	known issue, rather than a bug.
1770		2515
1771	=head1 SEE ALSO	2516	=head1 SEE ALSO
1772		2517
1773	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2518	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1774	more natural syntax.	2519	more natural syntax.

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