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Revision 1.193 by root, Thu May 26 04:15:37 2011 UTC vs.
Revision 1.284 by root, Fri Mar 23 01:14:08 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 = '3.8';	176	our $VERSION = 4.4;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
179	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
182	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
183	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
184		190
185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187	min_parallel max_parallel max_idle idle_timeout	193	min_parallel max_parallel max_idle idle_timeout
188	nreqs nready npending nthreads	194	nreqs nready npending nthreads
…		…
200		206
201	=head1 FUNCTIONS	207	=head1 FUNCTIONS
202		208
203	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
204		210
205	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
206	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
207	documentation.	213	documentation.
208		214
		215	aio_wd $pathname, $callback->($wd)
209	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
210	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
215	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
216	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
217	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
220	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
221	aio_chmod $fh_or_path, $mode, $callback->($status)	230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
222	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
223	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
224	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
225	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
226	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
227	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
228	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
229	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
230	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
234	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
235	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
236	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238	aio_rmtree $path, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
239	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
240	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
241	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
248	aio_group $callback->(...)	263	aio_group $callback->(...)
249	aio_nop $callback->()	264	aio_nop $callback->()
…		…
263	IO::AIO::idle_timeout $seconds	278	IO::AIO::idle_timeout $seconds
264	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
265	IO::AIO::nreqs	280	IO::AIO::nreqs
266	IO::AIO::nready	281	IO::AIO::nready
267	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
268		285
269	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
270	IO::AIO::fadvise $fh, $offset, $len, $advice	287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
271	IO::AIO::madvise $scalar, $offset, $length, $advice	290	IO::AIO::madvise $scalar, $offset, $length, $advice
272	IO::AIO::mprotect $scalar, $offset, $length, $protect	291	IO::AIO::mprotect $scalar, $offset, $length, $protect
273	IO::AIO::munlock $scalar, $offset = 0, $length = undef	292	IO::AIO::munlock $scalar, $offset = 0, $length = undef
274	IO::AIO::munlockall	293	IO::AIO::munlockall
275		294
276	=head2 AIO REQUEST FUNCTIONS	295	=head2 API NOTES
277		296
278	All the C<aio_*> calls are more or less thin wrappers around the syscall	297	All the C<aio_*> calls are more or less thin wrappers around the syscall
279	with the same name (sans C<aio_>). The arguments are similar or identical,	298	with the same name (sans C<aio_>). The arguments are similar or identical,
280	and they all accept an additional (and optional) C<$callback> argument	299	and they all accept an additional (and optional) C<$callback> argument
281	which must be a code reference. This code reference will get called with	300	which must be a code reference. This code reference will be called after
282	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	301	the syscall has been executed in an asynchronous fashion. The results
283	perl, which usually delivers "false") as its sole argument after the given	302	of the request will be passed as arguments to the callback (and, if an
284	syscall has been executed asynchronously.	303	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		304	most syscalls return C<-1> on error, unlike perl, which usually delivers
		305	"false").
		306
		307	Some requests (such as C<aio_readdir>) pass the actual results and
		308	communicate failures by passing C<undef>.
285		309
286	All functions expecting a filehandle keep a copy of the filehandle	310	All functions expecting a filehandle keep a copy of the filehandle
287	internally until the request has finished.	311	internally until the request has finished.
288		312
289	All functions return request objects of type L<IO::AIO::REQ> that allow	313	All functions return request objects of type L<IO::AIO::REQ> that allow
290	further manipulation of those requests while they are in-flight.	314	further manipulation of those requests while they are in-flight.
291		315
292	The pathnames you pass to these routines I<must> be absolute and	316	The pathnames you pass to these routines I<should> be absolute. The
293	encoded as octets. The reason for the former is that at the time the	317	reason for this is that at the time the request is being executed, the
294	request is being executed, the current working directory could have	318	current working directory could have changed. Alternatively, you can
295	changed. Alternatively, you can make sure that you never change the	319	make sure that you never change the current working directory anywhere
296	current working directory anywhere in the program and then use relative	320	in the program and then use relative paths. You can also take advantage
297	paths.	321	of IO::AIOs working directory abstraction, that lets you specify paths
		322	relative to some previously-opened "working directory object" - see the
		323	description of the C<IO::AIO::WD> class later in this document.
298		324
299	To encode pathnames as octets, either make sure you either: a) always pass	325	To encode pathnames as octets, either make sure you either: a) always pass
300	in filenames you got from outside (command line, readdir etc.) without	326	in filenames you got from outside (command line, readdir etc.) without
301	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	327	tinkering, b) are in your native filesystem encoding, c) use the Encode
302	your pathnames to the locale (or other) encoding in effect in the user	328	module and encode your pathnames to the locale (or other) encoding in
303	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	329	effect in the user environment, d) use Glib::filename_from_unicode on
304	use something else to ensure your scalar has the correct contents.	330	unicode filenames or e) use something else to ensure your scalar has the
		331	correct contents.
305		332
306	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	333	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
307	handles correctly whether it is set or not.	334	handles correctly whether it is set or not.
		335
		336	=head2 AIO REQUEST FUNCTIONS
308		337
309	=over 4	338	=over 4
310		339
311	=item $prev_pri = aioreq_pri [$pri]	340	=item $prev_pri = aioreq_pri [$pri]
312		341
…		…
342		371
343		372
344	=item aio_open $pathname, $flags, $mode, $callback->($fh)	373	=item aio_open $pathname, $flags, $mode, $callback->($fh)
345		374
346	Asynchronously open or create a file and call the callback with a newly	375	Asynchronously open or create a file and call the callback with a newly
347	created filehandle for the file.	376	created filehandle for the file (or C<undef> in case of an error).
348		377
349	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	378	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
350	for an explanation.	379	for an explanation.
351		380
352	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	381	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
368	} else {	397	} else {
369	die "open failed: $!\n";	398	die "open failed: $!\n";
370	}	399	}
371	};	400	};
372		401
		402	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		403	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		404	following POSIX and non-POSIX constants are available (missing ones on
		405	your system are, as usual, C<0>):
		406
		407	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		408	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		409	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		410
373		411
374	=item aio_close $fh, $callback->($status)	412	=item aio_close $fh, $callback->($status)
375		413
376	Asynchronously close a file and call the callback with the result	414	Asynchronously close a file and call the callback with the result
377	code.	415	code.
…		…
386	Or in other words: the file descriptor will be closed, but it will not be	424	Or in other words: the file descriptor will be closed, but it will not be
387	free for reuse until the perl filehandle is closed.	425	free for reuse until the perl filehandle is closed.
388		426
389	=cut	427	=cut
390		428
		429	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		430
		431	Seeks the filehandle to the new C<$offset>, similarly to perl's
		432	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		433	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		434	C<IO::AIO::SEEK_END>).
		435
		436	The resulting absolute offset will be passed to the callback, or C<-1> in
		437	case of an error.
		438
		439	In theory, the C<$whence> constants could be different than the
		440	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		441	so don't panic.
		442
		443	As a GNU/Linux (and maybe Solaris) extension, also the constants
		444	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		445	could be found. No guarantees about suitability for use in C<aio_seek> or
		446	Perl's C<sysseek> can be made though, although I would naively assume they
		447	"just work".
		448
391	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	449	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
392		450
393	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	451	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
394		452
395	Reads or writes C<$length> bytes from or to the specified C<$fh> and	453	Reads or writes C<$length> bytes from or to the specified C<$fh> and
396	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	454	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
397	and calls the callback without the actual number of bytes read (or -1 on	455	calls the callback with the actual number of bytes transferred (or -1 on
398	error, just like the syscall).	456	error, just like the syscall).
399		457
400	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	458	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
401	offset plus the actual number of bytes read.	459	offset plus the actual number of bytes read.
402		460
…		…
427		485
428	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	486	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
429	reading at byte offset C<$in_offset>, and starts writing at the current	487	reading at byte offset C<$in_offset>, and starts writing at the current
430	file offset of C<$out_fh>. Because of that, it is not safe to issue more	488	file offset of C<$out_fh>. Because of that, it is not safe to issue more
431	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	489	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
432	other.	490	other. The same C<$in_fh> works fine though, as this function does not
		491	move or use the file offset of C<$in_fh>.
433		492
434	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than	493	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
435	are written, and there is no way to find out how many bytes have been read	494	are written, and there is no way to find out how many more bytes have been
436	from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of	495	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
437	bytes written to C<$out_fh>. Only if the result value equals C<$length>	496	number of bytes written to C<$out_fh>. Only if the result value equals
438	one can assume that C<$length> bytes have been read.	497	C<$length> one can assume that C<$length> bytes have been read.
439		498
440	Unlike with other C<aio_> functions, it makes a lot of sense to use	499	Unlike with other C<aio_> functions, it makes a lot of sense to use
441	C<aio_sendfile> on non-blocking sockets, as long as one end (typically	500	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
442	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while	501	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
443	the socket I/O will be non-blocking. Note, however, that you can run into	502	the socket I/O will be non-blocking. Note, however, that you can run
444	a trap where C<aio_sendfile> reads some data with readahead, then fails	503	into a trap where C<aio_sendfile> reads some data with readahead, then
445	to write all data, and when the socket is ready the next time, the data	504	fails to write all data, and when the socket is ready the next time, the
446	in the cache is already lost, forcing C<aio_sendfile> to again hit the	505	data in the cache is already lost, forcing C<aio_sendfile> to again hit
447	disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage	506	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
448	much better.	507	resource usage.
449		508
450	This call tries to make use of a native C<sendfile> syscall to provide	509	This call tries to make use of a native C<sendfile>-like syscall to
451	zero-copy operation. For this to work, C<$out_fh> should refer to a	510	provide zero-copy operation. For this to work, C<$out_fh> should refer to
452	socket, and C<$in_fh> should refer to an mmap'able file.	511	a socket, and C<$in_fh> should refer to an mmap'able file.
453		512
454	If a native sendfile cannot be found or it fails with C<ENOSYS>,	513	If a native sendfile cannot be found or it fails with C<ENOSYS>,
455	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	514	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
456	it will be emulated, so you can call C<aio_sendfile> on any type of	515	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
457	filehandle regardless of the limitations of the operating system.	516	type of filehandle regardless of the limitations of the operating system.
		517
		518	As native sendfile syscalls (as practically any non-POSIX interface hacked
		519	together in a hurry to improve benchmark numbers) tend to be rather buggy
		520	on many systems, this implementation tries to work around some known bugs
		521	in Linux and FreeBSD kernels (probably others, too), but that might fail,
		522	so you really really should check the return value of C<aio_sendfile> -
		523	fewer bytes than expected might have been transferred.
458		524
459		525
460	=item aio_readahead $fh,$offset,$length, $callback->($retval)	526	=item aio_readahead $fh,$offset,$length, $callback->($retval)
461		527
462	C<aio_readahead> populates the page cache with data from a file so that	528	C<aio_readahead> populates the page cache with data from a file so that
…		…
466	whole pages, so that offset is effectively rounded down to a page boundary	532	whole pages, so that offset is effectively rounded down to a page boundary
467	and bytes are read up to the next page boundary greater than or equal to	533	and bytes are read up to the next page boundary greater than or equal to
468	(off-set+length). C<aio_readahead> does not read beyond the end of the	534	(off-set+length). C<aio_readahead> does not read beyond the end of the
469	file. The current file offset of the file is left unchanged.	535	file. The current file offset of the file is left unchanged.
470		536
471	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	537	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
472	emulated by simply reading the data, which would have a similar effect.	538	be emulated by simply reading the data, which would have a similar effect.
473		539
474		540
475	=item aio_stat $fh_or_path, $callback->($status)	541	=item aio_stat $fh_or_path, $callback->($status)
476		542
477	=item aio_lstat $fh, $callback->($status)	543	=item aio_lstat $fh, $callback->($status)
…		…
546	namemax => 255,	612	namemax => 255,
547	frsize => 1024,	613	frsize => 1024,
548	fsid => 1810	614	fsid => 1810
549	}	615	}
550		616
551
552	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	617	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
553		618
554	Works like perl's C<utime> function (including the special case of $atime	619	Works like perl's C<utime> function (including the special case of $atime
555	and $mtime being undef). Fractional times are supported if the underlying	620	and $mtime being undef). Fractional times are supported if the underlying
556	syscalls support them.	621	syscalls support them.
…		…
583	=item aio_truncate $fh_or_path, $offset, $callback->($status)	648	=item aio_truncate $fh_or_path, $offset, $callback->($status)
584		649
585	Works like truncate(2) or ftruncate(2).	650	Works like truncate(2) or ftruncate(2).
586		651
587		652
		653	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		654
		655	Allocates or frees disk space according to the C<$mode> argument. See the
		656	linux C<fallocate> documentation for details.
		657
		658	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		659	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		660	to deallocate a file range.
		661
		662	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		663	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		664	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		665	to unshare shared blocks (see your L<fallocate(2)> manpage).
		666
		667	The file system block size used by C<fallocate> is presumably the
		668	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		669	can dictate other limitations.
		670
		671	If C<fallocate> isn't available or cannot be emulated (currently no
		672	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		673
		674
588	=item aio_chmod $fh_or_path, $mode, $callback->($status)	675	=item aio_chmod $fh_or_path, $mode, $callback->($status)
589		676
590	Works like perl's C<chmod> function.	677	Works like perl's C<chmod> function.
591		678
592		679
…		…
594		681
595	Asynchronously unlink (delete) a file and call the callback with the	682	Asynchronously unlink (delete) a file and call the callback with the
596	result code.	683	result code.
597		684
598		685
599	=item aio_mknod $path, $mode, $dev, $callback->($status)	686	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
600		687
601	[EXPERIMENTAL]	688	[EXPERIMENTAL]
602		689
603	Asynchronously create a device node (or fifo). See mknod(2).	690	Asynchronously create a device node (or fifo). See mknod(2).
604		691
605	The only (POSIX-) portable way of calling this function is:	692	The only (POSIX-) portable way of calling this function is:
606		693
607	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	694	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
608		695
609	See C<aio_stat> for info about some potentially helpful extra constants	696	See C<aio_stat> for info about some potentially helpful extra constants
610	and functions.	697	and functions.
611		698
612	=item aio_link $srcpath, $dstpath, $callback->($status)	699	=item aio_link $srcpath, $dstpath, $callback->($status)
…		…
619		706
620	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	707	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
621	the path C<$dstpath> and call the callback with the result code.	708	the path C<$dstpath> and call the callback with the result code.
622		709
623		710
624	=item aio_readlink $path, $callback->($link)	711	=item aio_readlink $pathname, $callback->($link)
625		712
626	Asynchronously read the symlink specified by C<$path> and pass it to	713	Asynchronously read the symlink specified by C<$path> and pass it to
627	the callback. If an error occurs, nothing or undef gets passed to the	714	the callback. If an error occurs, nothing or undef gets passed to the
628	callback.	715	callback.
629		716
630		717
		718	=item aio_realpath $pathname, $callback->($path)
		719
		720	Asynchronously make the path absolute and resolve any symlinks in
		721	C<$path>. The resulting path only consists of directories (same as
		722	L<Cwd::realpath>).
		723
		724	This request can be used to get the absolute path of the current working
		725	directory by passing it a path of F<.> (a single dot).
		726
		727
631	=item aio_rename $srcpath, $dstpath, $callback->($status)	728	=item aio_rename $srcpath, $dstpath, $callback->($status)
632		729
633	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	730	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
634	rename(2) and call the callback with the result code.	731	rename(2) and call the callback with the result code.
		732
		733	On systems that support the AIO::WD working directory abstraction
		734	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		735	of failing, C<rename> is called on the absolute path of C<$wd>.
		736
		737
		738	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		739
		740	Basically a version of C<aio_rename> with an additional C<$flags>
		741	argument. Calling this with C<$flags=0> is the same as calling
		742	C<aio_rename>.
		743
		744	Non-zero flags are currently only supported on GNU/Linux systems that
		745	support renameat2. Other systems fail with C<ENOSYS> in this case.
		746
		747	The following constants are available (missing ones are, as usual C<0>),
		748	see renameat2(2) for details:
		749
		750	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		751	and C<IO::AIO::RENAME_WHITEOUT>.
635		752
636		753
637	=item aio_mkdir $pathname, $mode, $callback->($status)	754	=item aio_mkdir $pathname, $mode, $callback->($status)
638		755
639	Asynchronously mkdir (create) a directory and call the callback with	756	Asynchronously mkdir (create) a directory and call the callback with
…		…
644	=item aio_rmdir $pathname, $callback->($status)	761	=item aio_rmdir $pathname, $callback->($status)
645		762
646	Asynchronously rmdir (delete) a directory and call the callback with the	763	Asynchronously rmdir (delete) a directory and call the callback with the
647	result code.	764	result code.
648		765
		766	On systems that support the AIO::WD working directory abstraction
		767	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		768	C<rmdir> is called on the absolute path of C<$wd>.
		769
649		770
650	=item aio_readdir $pathname, $callback->($entries)	771	=item aio_readdir $pathname, $callback->($entries)
651		772
652	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	773	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
653	directory (i.e. opendir + readdir + closedir). The entries will not be	774	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
657	array-ref with the filenames.	778	array-ref with the filenames.
658		779
659		780
660	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	781	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
661		782
662	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	783	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
663	behaviour and output format. In case of an error, C<$entries> will be	784	tune behaviour and output format. In case of an error, C<$entries> will be
664	C<undef>.	785	C<undef>.
665		786
666	The flags are a combination of the following constants, ORed together (the	787	The flags are a combination of the following constants, ORed together (the
667	flags will also be passed to the callback, possibly modified):	788	flags will also be passed to the callback, possibly modified):
668		789
669	=over 4	790	=over 4
670		791
671	=item IO::AIO::READDIR_DENTS	792	=item IO::AIO::READDIR_DENTS
672		793
673	When this flag is off, then the callback gets an arrayref consisting of	794	Normally the callback gets an arrayref consisting of names only (as
674	names only (as with C<aio_readdir>), otherwise it gets an arrayref with	795	with C<aio_readdir>). If this flag is set, then the callback gets an
675	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	796	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
676	entry in more detail.	797	single directory entry in more detail:
677		798
678	C<$name> is the name of the entry.	799	C<$name> is the name of the entry.
679		800
680	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	801	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
681		802
682	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	803	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
683	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	804	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
684	C<IO::AIO::DT_WHT>.	805	C<IO::AIO::DT_WHT>.
685		806
686	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	807	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
687	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	808	to know, you have to run stat yourself. Also, for speed/memory reasons,
688	scalars are read-only: you can not modify them.	809	the C<$type> scalars are read-only: you must not modify them.
689		810
690	C<$inode> is the inode number (which might not be exact on systems with 64	811	C<$inode> is the inode number (which might not be exact on systems with 64
691	bit inode numbers and 32 bit perls). This field has unspecified content on	812	bit inode numbers and 32 bit perls). This field has unspecified content on
692	systems that do not deliver the inode information.	813	systems that do not deliver the inode information.
693		814
…		…
704	short names are tried first.	825	short names are tried first.
705		826
706	=item IO::AIO::READDIR_STAT_ORDER	827	=item IO::AIO::READDIR_STAT_ORDER
707		828
708	When this flag is set, then the names will be returned in an order	829	When this flag is set, then the names will be returned in an order
709	suitable for stat()'ing each one. That is, when you plan to stat()	830	suitable for stat()'ing each one. That is, when you plan to stat() most or
710	all files in the given directory, then the returned order will likely	831	all files in the given directory, then the returned order will likely be
711	be fastest.	832	faster.
712		833
713	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	834	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
714	the likely dirs come first, resulting in a less optimal stat order.	835	then the likely dirs come first, resulting in a less optimal stat order
		836	for stat'ing all entries, but likely a more optimal order for finding
		837	subdirectories.
715		838
716	=item IO::AIO::READDIR_FOUND_UNKNOWN	839	=item IO::AIO::READDIR_FOUND_UNKNOWN
717		840
718	This flag should not be set when calling C<aio_readdirx>. Instead, it	841	This flag should not be set when calling C<aio_readdirx>. Instead, it
719	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	842	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
720	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	843	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
721	C<$type>'s are known, which can be used to speed up some algorithms.	844	C<$type>'s are known, which can be used to speed up some algorithms.
722		845
723	=back	846	=back
724		847
725		848
		849	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		850
		851	Opens, reads and closes the given file. The data is put into C<$data>,
		852	which is resized as required.
		853
		854	If C<$offset> is negative, then it is counted from the end of the file.
		855
		856	If C<$length> is zero, then the remaining length of the file is
		857	used. Also, in this case, the same limitations to modifying C<$data> apply
		858	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		859	with C<substr>. If the size of the file is known, specifying a non-zero
		860	C<$length> results in a performance advantage.
		861
		862	This request is similar to the older C<aio_load> request, but since it is
		863	a single request, it might be more efficient to use.
		864
		865	Example: load F</etc/passwd> into C<$passwd>.
		866
		867	my $passwd;
		868	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		869	$_[0] >= 0
		870	or die "/etc/passwd: $!\n";
		871
		872	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		873	print $passwd;
		874	};
		875	IO::AIO::flush;
		876
		877
726	=item aio_load $path, $data, $callback->($status)	878	=item aio_load $pathname, $data, $callback->($status)
727		879
728	This is a composite request that tries to fully load the given file into	880	This is a composite request that tries to fully load the given file into
729	memory. Status is the same as with aio_read.	881	memory. Status is the same as with aio_read.
		882
		883	Using C<aio_slurp> might be more efficient, as it is a single request.
730		884
731	=cut	885	=cut
732		886
733	sub aio_load($$;$) {	887	sub aio_load($$;$) {
734	my ($path, undef, $cb) = @_;	888	my ($path, undef, $cb) = @_;
…		…
754	=item aio_copy $srcpath, $dstpath, $callback->($status)	908	=item aio_copy $srcpath, $dstpath, $callback->($status)
755		909
756	Try to copy the I<file> (directories not supported as either source or	910	Try to copy the I<file> (directories not supported as either source or
757	destination) from C<$srcpath> to C<$dstpath> and call the callback with	911	destination) from C<$srcpath> to C<$dstpath> and call the callback with
758	a status of C<0> (ok) or C<-1> (error, see C<$!>).	912	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		913
		914	Existing destination files will be truncated.
759		915
760	This is a composite request that creates the destination file with	916	This is a composite request that creates the destination file with
761	mode 0200 and copies the contents of the source file into it using	917	mode 0200 and copies the contents of the source file into it using
762	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	918	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
763	uid/gid, in that order.	919	uid/gid, in that order.
…		…
853	if ($_[0] && $! == EXDEV) {	1009	if ($_[0] && $! == EXDEV) {
854	aioreq_pri $pri;	1010	aioreq_pri $pri;
855	add $grp aio_copy $src, $dst, sub {	1011	add $grp aio_copy $src, $dst, sub {
856	$grp->result ($_[0]);	1012	$grp->result ($_[0]);
857		1013
858	if (!$_[0]) {	1014	unless ($_[0]) {
859	aioreq_pri $pri;	1015	aioreq_pri $pri;
860	add $grp aio_unlink $src;	1016	add $grp aio_unlink $src;
861	}	1017	}
862	};	1018	};
863	} else {	1019	} else {
…		…
866	};	1022	};
867		1023
868	$grp	1024	$grp
869	}	1025	}
870		1026
871	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1027	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
872		1028
873	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1029	Scans a directory (similar to C<aio_readdir>) but additionally tries to
874	efficiently separate the entries of directory C<$path> into two sets of	1030	efficiently separate the entries of directory C<$path> into two sets of
875	names, directories you can recurse into (directories), and ones you cannot	1031	names, directories you can recurse into (directories), and ones you cannot
876	recurse into (everything else, including symlinks to directories).	1032	recurse into (everything else, including symlinks to directories).
877		1033
878	C<aio_scandir> is a composite request that creates of many sub requests_	1034	C<aio_scandir> is a composite request that generates many sub requests.
879	C<$maxreq> specifies the maximum number of outstanding aio requests that	1035	C<$maxreq> specifies the maximum number of outstanding aio requests that
880	this function generates. If it is C<< <= 0 >>, then a suitable default	1036	this function generates. If it is C<< <= 0 >>, then a suitable default
881	will be chosen (currently 4).	1037	will be chosen (currently 4).
882		1038
883	On error, the callback is called without arguments, otherwise it receives	1039	On error, the callback is called without arguments, otherwise it receives
…		…
907	Then entries will be sorted into likely directories a non-initial dot	1063	Then entries will be sorted into likely directories a non-initial dot
908	currently) and likely non-directories (see C<aio_readdirx>). Then every	1064	currently) and likely non-directories (see C<aio_readdirx>). Then every
909	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1065	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
910	in order of their inode numbers. If that succeeds, it assumes that the	1066	in order of their inode numbers. If that succeeds, it assumes that the
911	entry is a directory or a symlink to directory (which will be checked	1067	entry is a directory or a symlink to directory (which will be checked
912	seperately). This is often faster than stat'ing the entry itself because	1068	separately). This is often faster than stat'ing the entry itself because
913	filesystems might detect the type of the entry without reading the inode	1069	filesystems might detect the type of the entry without reading the inode
914	data (e.g. ext2fs filetype feature), even on systems that cannot return	1070	data (e.g. ext2fs filetype feature), even on systems that cannot return
915	the filetype information on readdir.	1071	the filetype information on readdir.
916		1072
917	If the known number of directories (link count - 2) has been reached, the	1073	If the known number of directories (link count - 2) has been reached, the
…		…
933		1089
934	my $grp = aio_group $cb;	1090	my $grp = aio_group $cb;
935		1091
936	$maxreq = 4 if $maxreq <= 0;	1092	$maxreq = 4 if $maxreq <= 0;
937		1093
938	# stat once	1094	# get a wd object
939	aioreq_pri $pri;	1095	aioreq_pri $pri;
940	add $grp aio_stat $path, sub {	1096	add $grp aio_wd $path, sub {
		1097	$_[0]
941	return $grp->result () if $_[0];	1098	or return $grp->result ();
942	my $now = time;
943	my $hash1 = join ":", (stat _)[0,1,3,7,9];
944		1099
945	# read the directory entries	1100	my $wd = [shift, "."];
		1101
		1102	# stat once
946	aioreq_pri $pri;	1103	aioreq_pri $pri;
947	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1104	add $grp aio_stat $wd, sub {
948	my $entries = shift
949	or return $grp->result ();	1105	return $grp->result () if $_[0];
		1106	my $now = time;
		1107	my $hash1 = join ":", (stat _)[0,1,3,7,9];
950		1108
951	# stat the dir another time	1109	# read the directory entries
952	aioreq_pri $pri;	1110	aioreq_pri $pri;
		1111	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1112	my $entries = shift
		1113	or return $grp->result ();
		1114
		1115	# stat the dir another time
		1116	aioreq_pri $pri;
953	add $grp aio_stat $path, sub {	1117	add $grp aio_stat $wd, sub {
954	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1118	my $hash2 = join ":", (stat _)[0,1,3,7,9];
955		1119
956	my $ndirs;	1120	my $ndirs;
957		1121
958	# take the slow route if anything looks fishy	1122	# take the slow route if anything looks fishy
959	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1123	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
960	$ndirs = -1;	1124	$ndirs = -1;
961	} else {	1125	} else {
962	# if nlink == 2, we are finished	1126	# if nlink == 2, we are finished
963	# for non-posix-fs's, we rely on nlink < 2	1127	# for non-posix-fs's, we rely on nlink < 2
964	$ndirs = (stat _)[3] - 2	1128	$ndirs = (stat _)[3] - 2
965	or return $grp->result ([], $entries);	1129	or return $grp->result ([], $entries);
966	}	1130	}
967		1131
968	my (@dirs, @nondirs);	1132	my (@dirs, @nondirs);
969		1133
970	my $statgrp = add $grp aio_group sub {	1134	my $statgrp = add $grp aio_group sub {
971	$grp->result (\@dirs, \@nondirs);	1135	$grp->result (\@dirs, \@nondirs);
972	};	1136	};
973		1137
974	limit $statgrp $maxreq;	1138	limit $statgrp $maxreq;
975	feed $statgrp sub {	1139	feed $statgrp sub {
976	return unless @$entries;	1140	return unless @$entries;
977	my $entry = shift @$entries;	1141	my $entry = shift @$entries;
978		1142
979	aioreq_pri $pri;	1143	aioreq_pri $pri;
		1144	$wd->[1] = "$entry/.";
980	add $statgrp aio_stat "$path/$entry/.", sub {	1145	add $statgrp aio_stat $wd, sub {
981	if ($_[0] < 0) {	1146	if ($_[0] < 0) {
982	push @nondirs, $entry;	1147	push @nondirs, $entry;
983	} else {	1148	} else {
984	# need to check for real directory	1149	# need to check for real directory
985	aioreq_pri $pri;	1150	aioreq_pri $pri;
		1151	$wd->[1] = $entry;
986	add $statgrp aio_lstat "$path/$entry", sub {	1152	add $statgrp aio_lstat $wd, sub {
987	if (-d _) {	1153	if (-d _) {
988	push @dirs, $entry;	1154	push @dirs, $entry;
989		1155
990	unless (--$ndirs) {	1156	unless (--$ndirs) {
991	push @nondirs, @$entries;	1157	push @nondirs, @$entries;
992	feed $statgrp;	1158	feed $statgrp;
		1159	}
		1160	} else {
		1161	push @nondirs, $entry;
993	}	1162	}
994	} else {
995	push @nondirs, $entry;
996	}	1163	}
997	}	1164	}
998	}	1165	};
999	};	1166	};
1000	};	1167	};
1001	};	1168	};
1002	};	1169	};
1003	};	1170	};
1004		1171
1005	$grp	1172	$grp
1006	}	1173	}
1007		1174
1008	=item aio_rmtree $path, $callback->($status)	1175	=item aio_rmtree $pathname, $callback->($status)
1009		1176
1010	Delete a directory tree starting (and including) C<$path>, return the	1177	Delete a directory tree starting (and including) C<$path>, return the
1011	status of the final C<rmdir> only. This is a composite request that	1178	status of the final C<rmdir> only. This is a composite request that
1012	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1179	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1013	everything else.	1180	everything else.
1014		1181
1015	=cut	1182	=cut
1016		1183
…		…
1038	};	1205	};
1039		1206
1040	$grp	1207	$grp
1041	}	1208	}
1042		1209
		1210	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1211
		1212	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1213
		1214	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1215	they execute asynchronously and pass the return value to the callback.
		1216
		1217	Both calls can be used for a lot of things, some of which make more sense
		1218	to run asynchronously in their own thread, while some others make less
		1219	sense. For example, calls that block waiting for external events, such
		1220	as locking, will also lock down an I/O thread while it is waiting, which
		1221	can deadlock the whole I/O system. At the same time, there might be no
		1222	alternative to using a thread to wait.
		1223
		1224	So in general, you should only use these calls for things that do
		1225	(filesystem) I/O, not for things that wait for other events (network,
		1226	other processes), although if you are careful and know what you are doing,
		1227	you still can.
		1228
		1229	The following constants are available (missing ones are, as usual C<0>):
		1230
		1231	C<F_DUPFD_CLOEXEC>,
		1232
		1233	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1234
		1235	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1236
		1237	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1238	C<FS_IOC_FIEMAP>.
		1239
		1240	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1241	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1242
		1243	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1244	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1245	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1246	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1247	C<FS_FL_USER_MODIFIABLE>.
		1248
		1249	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1250	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1251	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1252	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1253
1043	=item aio_sync $callback->($status)	1254	=item aio_sync $callback->($status)
1044		1255
1045	Asynchronously call sync and call the callback when finished.	1256	Asynchronously call sync and call the callback when finished.
1046		1257
1047	=item aio_fsync $fh, $callback->($status)	1258	=item aio_fsync $fh, $callback->($status)
…		…
1054	Asynchronously call fdatasync on the given filehandle and call the	1265	Asynchronously call fdatasync on the given filehandle and call the
1055	callback with the fdatasync result code.	1266	callback with the fdatasync result code.
1056		1267
1057	If this call isn't available because your OS lacks it or it couldn't be	1268	If this call isn't available because your OS lacks it or it couldn't be
1058	detected, it will be emulated by calling C<fsync> instead.	1269	detected, it will be emulated by calling C<fsync> instead.
		1270
		1271	=item aio_syncfs $fh, $callback->($status)
		1272
		1273	Asynchronously call the syncfs syscall to sync the filesystem associated
		1274	to the given filehandle and call the callback with the syncfs result
		1275	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1276	errno to C<ENOSYS> nevertheless.
1059		1277
1060	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1278	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1061		1279
1062	Sync the data portion of the file specified by C<$offset> and C<$length>	1280	Sync the data portion of the file specified by C<$offset> and C<$length>
1063	to disk (but NOT the metadata), by calling the Linux-specific	1281	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1067	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1285	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1068	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1286	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1069	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1287	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1070	manpage for details.	1288	manpage for details.
1071		1289
1072	=item aio_pathsync $path, $callback->($status)	1290	=item aio_pathsync $pathname, $callback->($status)
1073		1291
1074	This request tries to open, fsync and close the given path. This is a	1292	This request tries to open, fsync and close the given path. This is a
1075	composite request intended to sync directories after directory operations	1293	composite request intended to sync directories after directory operations
1076	(E.g. rename). This might not work on all operating systems or have any	1294	(E.g. rename). This might not work on all operating systems or have any
1077	specific effect, but usually it makes sure that directory changes get	1295	specific effect, but usually it makes sure that directory changes get
…		…
1108	};	1326	};
1109		1327
1110	$grp	1328	$grp
1111	}	1329	}
1112		1330
1113	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1331	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1114		1332
1115	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1333	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1116	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1334	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1117	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1335	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1118	scalar must only be modified in-place while an aio operation is pending on	1336	scalar must only be modified in-place while an aio operation is pending on
…		…
1120		1338
1121	It calls the C<msync> function of your OS, if available, with the memory	1339	It calls the C<msync> function of your OS, if available, with the memory
1122	area starting at C<$offset> in the string and ending C<$length> bytes	1340	area starting at C<$offset> in the string and ending C<$length> bytes
1123	later. If C<$length> is negative, counts from the end, and if C<$length>	1341	later. If C<$length> is negative, counts from the end, and if C<$length>
1124	is C<undef>, then it goes till the end of the string. The flags can be	1342	is C<undef>, then it goes till the end of the string. The flags can be
1125	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1343	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1126	C<IO::AIO::MS_SYNC>.	1344	C<IO::AIO::MS_INVALIDATE>.
1127		1345
1128	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1346	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1129		1347
1130	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1348	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1131	scalars.	1349	scalars.
1132		1350
1133	It touches (reads or writes) all memory pages in the specified	1351	It touches (reads or writes) all memory pages in the specified
1134	range inside the scalar. All caveats and parameters are the same	1352	range inside the scalar. All caveats and parameters are the same
1135	as for C<aio_msync>, above, except for flags, which must be either	1353	as for C<aio_msync>, above, except for flags, which must be either
1136	C<0> (which reads all pages and ensures they are instantiated) or	1354	C<0> (which reads all pages and ensures they are instantiated) or
1137	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1355	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1138	writing an octet from it, which dirties the page).	1356	writing an octet from it, which dirties the page).
1139		1357
1140	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1358	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1141		1359
1142	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1360	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1173	documented under L<MISCELLANEOUS FUNCTIONS>.	1391	documented under L<MISCELLANEOUS FUNCTIONS>.
1174		1392
1175	Example: asynchronously lock all current and future pages into memory.	1393	Example: asynchronously lock all current and future pages into memory.
1176		1394
1177	aio_mlockall IO::AIO::MCL_FUTURE;	1395	aio_mlockall IO::AIO::MCL_FUTURE;
		1396
		1397	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1398
		1399	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1400	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1401	the ioctl is not available on your OS, then this request will fail with
		1402	C<ENOSYS>.
		1403
		1404	C<$start> is the starting offset to query extents for, C<$length> is the
		1405	size of the range to query - if it is C<undef>, then the whole file will
		1406	be queried.
		1407
		1408	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1409	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1410	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1411	the data portion.
		1412
		1413	C<$count> is the maximum number of extent records to return. If it is
		1414	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1415	case, if it is C<0>, then the callback receives the number of extents
		1416	instead of the extents themselves (which is unreliable, see below).
		1417
		1418	If an error occurs, the callback receives no arguments. The special
		1419	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1420
		1421	Otherwise, the callback receives an array reference with extent
		1422	structures. Each extent structure is an array reference itself, with the
		1423	following members:
		1424
		1425	[$logical, $physical, $length, $flags]
		1426
		1427	Flags is any combination of the following flag values (typically either C<0>
		1428	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1429
		1430	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1431	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1432	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1433	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1434	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1435	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1436
		1437	At the time of this writing (Linux 3.2), this request is unreliable unless
		1438	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1439	it to return all extents of a range for files with a large number of
		1440	extents. The code (only) works around all these issues if C<$count> is
		1441	C<undef>.
1178		1442
1179	=item aio_group $callback->(...)	1443	=item aio_group $callback->(...)
1180		1444
1181	This is a very special aio request: Instead of doing something, it is a	1445	This is a very special aio request: Instead of doing something, it is a
1182	container for other aio requests, which is useful if you want to bundle	1446	container for other aio requests, which is useful if you want to bundle
…		…
1219	like sleep and file handle readable/writable, the overhead this creates is	1483	like sleep and file handle readable/writable, the overhead this creates is
1220	immense (it blocks a thread for a long time) so do not use this function	1484	immense (it blocks a thread for a long time) so do not use this function
1221	except to put your application under artificial I/O pressure.	1485	except to put your application under artificial I/O pressure.
1222		1486
1223	=back	1487	=back
		1488
		1489
		1490	=head2 IO::AIO::WD - multiple working directories
		1491
		1492	Your process only has one current working directory, which is used by all
		1493	threads. This makes it hard to use relative paths (some other component
		1494	could call C<chdir> at any time, and it is hard to control when the path
		1495	will be used by IO::AIO).
		1496
		1497	One solution for this is to always use absolute paths. This usually works,
		1498	but can be quite slow (the kernel has to walk the whole path on every
		1499	access), and can also be a hassle to implement.
		1500
		1501	Newer POSIX systems have a number of functions (openat, fdopendir,
		1502	futimensat and so on) that make it possible to specify working directories
		1503	per operation.
		1504
		1505	For portability, and because the clowns who "designed", or shall I write,
		1506	perpetrated this new interface were obviously half-drunk, this abstraction
		1507	cannot be perfect, though.
		1508
		1509	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1510	object. This object stores the canonicalised, absolute version of the
		1511	path, and on systems that allow it, also a directory file descriptor.
		1512
		1513	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1514	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1515	object and a pathname instead (or the IO::AIO::WD object alone, which
		1516	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1517	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1518	to that IO::AIO::WD object.
		1519
		1520	For example, to get a wd object for F</etc> and then stat F<passwd>
		1521	inside, you would write:
		1522
		1523	aio_wd "/etc", sub {
		1524	my $etcdir = shift;
		1525
		1526	# although $etcdir can be undef on error, there is generally no reason
		1527	# to check for errors here, as aio_stat will fail with ENOENT
		1528	# when $etcdir is undef.
		1529
		1530	aio_stat [$etcdir, "passwd"], sub {
		1531	# yay
		1532	};
		1533	};
		1534
		1535	The fact that C<aio_wd> is a request and not a normal function shows that
		1536	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1537	which is why it is done asynchronously.
		1538
		1539	To stat the directory obtained with C<aio_wd> above, one could write
		1540	either of the following three request calls:
		1541
		1542	aio_lstat "/etc" , sub { ... # pathname as normal string
		1543	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1544	aio_lstat $wd , sub { ... # shorthand for the previous
		1545
		1546	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1547	object and the pathname string, so you could write the following without
		1548	causing any issues due to C<$path> getting reused:
		1549
		1550	my $path = [$wd, undef];
		1551
		1552	for my $name (qw(abc def ghi)) {
		1553	$path->[1] = $name;
		1554	aio_stat $path, sub {
		1555	# ...
		1556	};
		1557	}
		1558
		1559	There are some caveats: when directories get renamed (or deleted), the
		1560	pathname string doesn't change, so will point to the new directory (or
		1561	nowhere at all), while the directory fd, if available on the system,
		1562	will still point to the original directory. Most functions accepting a
		1563	pathname will use the directory fd on newer systems, and the string on
		1564	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1565	the string form of the pathname.
		1566
		1567	So this functionality is mainly useful to get some protection against
		1568	C<chdir>, to easily get an absolute path out of a relative path for future
		1569	reference, and to speed up doing many operations in the same directory
		1570	(e.g. when stat'ing all files in a directory).
		1571
		1572	The following functions implement this working directory abstraction:
		1573
		1574	=over 4
		1575
		1576	=item aio_wd $pathname, $callback->($wd)
		1577
		1578	Asynchonously canonicalise the given pathname and convert it to an
		1579	IO::AIO::WD object representing it. If possible and supported on the
		1580	system, also open a directory fd to speed up pathname resolution relative
		1581	to this working directory.
		1582
		1583	If something goes wrong, then C<undef> is passwd to the callback instead
		1584	of a working directory object and C<$!> is set appropriately. Since
		1585	passing C<undef> as working directory component of a pathname fails the
		1586	request with C<ENOENT>, there is often no need for error checking in the
		1587	C<aio_wd> callback, as future requests using the value will fail in the
		1588	expected way.
		1589
		1590	=item IO::AIO::CWD
		1591
		1592	This is a compiletime constant (object) that represents the process
		1593	current working directory.
		1594
		1595	Specifying this object as working directory object for a pathname is as if
		1596	the pathname would be specified directly, without a directory object. For
		1597	example, these calls are functionally identical:
		1598
		1599	aio_stat "somefile", sub { ... };
		1600	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1601
		1602	=back
		1603
		1604	To recover the path associated with an IO::AIO::WD object, you can use
		1605	C<aio_realpath>:
		1606
		1607	aio_realpath $wd, sub {
		1608	warn "path is $_[0]\n";
		1609	};
		1610
		1611	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1612	sometimes, fall back to using an absolue path.
1224		1613
1225	=head2 IO::AIO::REQ CLASS	1614	=head2 IO::AIO::REQ CLASS
1226		1615
1227	All non-aggregate C<aio_*> functions return an object of this class when	1616	All non-aggregate C<aio_*> functions return an object of this class when
1228	called in non-void context.	1617	called in non-void context.
…		…
1346		1735
1347	Sets a feeder/generator on this group: every group can have an attached	1736	Sets a feeder/generator on this group: every group can have an attached
1348	generator that generates requests if idle. The idea behind this is that,	1737	generator that generates requests if idle. The idea behind this is that,
1349	although you could just queue as many requests as you want in a group,	1738	although you could just queue as many requests as you want in a group,
1350	this might starve other requests for a potentially long time. For example,	1739	this might starve other requests for a potentially long time. For example,
1351	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1740	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1352	delaying any later requests for a long time.	1741	requests, delaying any later requests for a long time.
1353		1742
1354	To avoid this, and allow incremental generation of requests, you can	1743	To avoid this, and allow incremental generation of requests, you can
1355	instead a group and set a feeder on it that generates those requests. The	1744	instead a group and set a feeder on it that generates those requests. The
1356	feed callback will be called whenever there are few enough (see C<limit>,	1745	feed callback will be called whenever there are few enough (see C<limit>,
1357	below) requests active in the group itself and is expected to queue more	1746	below) requests active in the group itself and is expected to queue more
…		…
1406		1795
1407	See C<poll_cb> for an example.	1796	See C<poll_cb> for an example.
1408		1797
1409	=item IO::AIO::poll_cb	1798	=item IO::AIO::poll_cb
1410		1799
1411	Process some outstanding events on the result pipe. You have to call	1800	Process some requests that have reached the result phase (i.e. they have
		1801	been executed but the results are not yet reported). You have to call
		1802	this "regularly" to finish outstanding requests.
		1803
1412	this regularly. Returns C<0> if all events could be processed (or there	1804	Returns C<0> if all events could be processed (or there were no
1413	were no events to process), or C<-1> if it returned earlier for whatever	1805	events to process), or C<-1> if it returned earlier for whatever
1414	reason. Returns immediately when no events are outstanding. The amount of	1806	reason. Returns immediately when no events are outstanding. The amount
1415	events processed depends on the settings of C<IO::AIO::max_poll_req> and	1807	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
1416	C<IO::AIO::max_poll_time>.	1808	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
1417		1809
1418	If not all requests were processed for whatever reason, the filehandle	1810	If not all requests were processed for whatever reason, the poll file
1419	will still be ready when C<poll_cb> returns, so normally you don't have to	1811	descriptor will still be ready when C<poll_cb> returns, so normally you
1420	do anything special to have it called later.	1812	don't have to do anything special to have it called later.
1421		1813
1422	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes	1814	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
1423	ready, it can be beneficial to call this function from loops which submit	1815	ready, it can be beneficial to call this function from loops which submit
1424	a lot of requests, to make sure the results get processed when they become	1816	a lot of requests, to make sure the results get processed when they become
1425	available and not just when the loop is finished and the event loop takes	1817	available and not just when the loop is finished and the event loop takes
…		…
1434	poll => 'r', async => 1,	1826	poll => 'r', async => 1,
1435	cb => \&IO::AIO::poll_cb);	1827	cb => \&IO::AIO::poll_cb);
1436		1828
1437	=item IO::AIO::poll_wait	1829	=item IO::AIO::poll_wait
1438		1830
1439	If there are any outstanding requests and none of them in the result	1831	Wait until either at least one request is in the result phase or no
1440	phase, wait till the result filehandle becomes ready for reading (simply	1832	requests are outstanding anymore.
1441	does a C<select> on the filehandle. This is useful if you want to	1833
1442	synchronously wait for some requests to finish).	1834	This is useful if you want to synchronously wait for some requests to
		1835	become ready, without actually handling them.
1443		1836
1444	See C<nreqs> for an example.	1837	See C<nreqs> for an example.
1445		1838
1446	=item IO::AIO::poll	1839	=item IO::AIO::poll
1447		1840
…		…
1555	Sets the minimum idle timeout (default 10) after which worker threads are	1948	Sets the minimum idle timeout (default 10) after which worker threads are
1556	allowed to exit. SEe C<IO::AIO::max_idle>.	1949	allowed to exit. SEe C<IO::AIO::max_idle>.
1557		1950
1558	=item IO::AIO::max_outstanding $maxreqs	1951	=item IO::AIO::max_outstanding $maxreqs
1559		1952
		1953	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1954	you do queue up more than this number of requests, the next call to
		1955	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1956	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1957	longer exceeded.
		1958
		1959	In other words, this setting does not enforce a queue limit, but can be
		1960	used to make poll functions block if the limit is exceeded.
		1961
1560	This is a very bad function to use in interactive programs because it	1962	This is a very bad function to use in interactive programs because it
1561	blocks, and a bad way to reduce concurrency because it is inexact: Better	1963	blocks, and a bad way to reduce concurrency because it is inexact: Better
1562	use an C<aio_group> together with a feed callback.	1964	use an C<aio_group> together with a feed callback.
1563		1965
1564	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1966	Its main use is in scripts without an event loop - when you want to stat
1565	do queue up more than this number of requests, the next call to the	1967	a lot of files, you can write something like this:
1566	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1567	function will block until the limit is no longer exceeded.
1568		1968
1569	The default value is very large, so there is no practical limit on the	1969	IO::AIO::max_outstanding 32;
1570	number of outstanding requests.
1571		1970
1572	You can still queue as many requests as you want. Therefore,	1971	for my $path (...) {
1573	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1972	aio_stat $path , ...;
1574	as a stop gap to shield against fatal memory overflow (with large values).	1973	IO::AIO::poll_cb;
		1974	}
		1975
		1976	IO::AIO::flush;
		1977
		1978	The call to C<poll_cb> inside the loop will normally return instantly, but
		1979	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1980	some requests have been handled. This keeps the loop from pushing a large
		1981	number of C<aio_stat> requests onto the queue.
		1982
		1983	The default value for C<max_outstanding> is very large, so there is no
		1984	practical limit on the number of outstanding requests.
1575		1985
1576	=back	1986	=back
1577		1987
1578	=head3 STATISTICAL INFORMATION	1988	=head3 STATISTICAL INFORMATION
1579		1989
…		…
1601		2011
1602	=back	2012	=back
1603		2013
1604	=head3 MISCELLANEOUS FUNCTIONS	2014	=head3 MISCELLANEOUS FUNCTIONS
1605		2015
1606	IO::AIO implements some functions that might be useful, but are not	2016	IO::AIO implements some functions that are useful when you want to use
1607	asynchronous.	2017	some "Advanced I/O" function not available to in Perl, without going the
		2018	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2019	counterpart.
1608		2020
1609	=over 4	2021	=over 4
		2022
		2023	=item $numfd = IO::AIO::get_fdlimit
		2024
		2025	This function is I<EXPERIMENTAL> and subject to change.
		2026
		2027	Tries to find the current file descriptor limit and returns it, or
		2028	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2029	the highest valid file descriptor number.
		2030
		2031	=item IO::AIO::min_fdlimit [$numfd]
		2032
		2033	This function is I<EXPERIMENTAL> and subject to change.
		2034
		2035	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2036	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2037	is missing, it will try to set a very high limit, although this is not
		2038	recommended when you know the actual minimum that you require.
		2039
		2040	If the limit cannot be raised enough, the function makes a best-effort
		2041	attempt to increase the limit as much as possible, using various
		2042	tricks, while still failing. You can query the resulting limit using
		2043	C<IO::AIO::get_fdlimit>.
		2044
		2045	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2046	true.
1610		2047
1611	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2048	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1612		2049
1613	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2050	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1614	but is blocking (this makes most sense if you know the input data is	2051	but is blocking (this makes most sense if you know the input data is
…		…
1619		2056
1620	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2057	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1621		2058
1622	Simply calls the C<posix_fadvise> function (see its	2059	Simply calls the C<posix_fadvise> function (see its
1623	manpage for details). The following advice constants are	2060	manpage for details). The following advice constants are
1624	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2061	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1625	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2062	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1626	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2063	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1627		2064
1628	On systems that do not implement C<posix_fadvise>, this function returns	2065	On systems that do not implement C<posix_fadvise>, this function returns
1629	ENOSYS, otherwise the return value of C<posix_fadvise>.	2066	ENOSYS, otherwise the return value of C<posix_fadvise>.
1630		2067
1631	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2068	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1632		2069
1633	Simply calls the C<posix_madvise> function (see its	2070	Simply calls the C<posix_madvise> function (see its
1634	manpage for details). The following advice constants are	2071	manpage for details). The following advice constants are
1635	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2072	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1636	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2073	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2074	C<IO::AIO::MADV_DONTNEED>.
		2075
		2076	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2077	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2078	will be reduced to fit into the C<$scalar>.
1637		2079
1638	On systems that do not implement C<posix_madvise>, this function returns	2080	On systems that do not implement C<posix_madvise>, this function returns
1639	ENOSYS, otherwise the return value of C<posix_madvise>.	2081	ENOSYS, otherwise the return value of C<posix_madvise>.
1640		2082
1641	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2083	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1642		2084
1643	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2085	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1644	$scalar (see its manpage for details). The following protect	2086	$scalar (see its manpage for details). The following protect
1645	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2087	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1646	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2088	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2089
		2090	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2091	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2092	will be reduced to fit into the C<$scalar>.
1647		2093
1648	On systems that do not implement C<mprotect>, this function returns	2094	On systems that do not implement C<mprotect>, this function returns
1649	ENOSYS, otherwise the return value of C<mprotect>.	2095	ENOSYS, otherwise the return value of C<mprotect>.
1650		2096
1651	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2097	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1652		2098
1653	Memory-maps a file (or anonymous memory range) and attaches it to the	2099	Memory-maps a file (or anonymous memory range) and attaches it to the
1654	given C<$scalar>, which will act like a string scalar.	2100	given C<$scalar>, which will act like a string scalar. Returns true on
		2101	success, and false otherwise.
1655		2102
		2103	The scalar must exist, but its contents do not matter - this means you
		2104	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2105	the scalar first.
		2106
1656	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2107	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1657	change the string length, and most read-only operations such as copying it	2108	which don't change the string length, and most read-only operations such
1658	or searching it with regexes and so on.	2109	as copying it or searching it with regexes and so on.
1659		2110
1660	Anything else is unsafe and will, at best, result in memory leaks.	2111	Anything else is unsafe and will, at best, result in memory leaks.
1661		2112
1662	The memory map associated with the C<$scalar> is automatically removed	2113	The memory map associated with the C<$scalar> is automatically removed
1663	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2114	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1664	C<IO::AIO::munmap> functions are called.	2115	or C<IO::AIO::munmap> functions are called on it.
1665		2116
1666	This calls the C<mmap>(2) function internally. See your system's manual	2117	This calls the C<mmap>(2) function internally. See your system's manual
1667	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2118	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1668		2119
1669	The C<$length> must be larger than zero and smaller than the actual	2120	The C<$length> must be larger than zero and smaller than the actual
1670	filesize.	2121	filesize.
1671		2122
1672	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2123	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1673	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2124	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1674		2125
1675	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2126	C<$flags> can be a combination of
1676	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2127	C<IO::AIO::MAP_SHARED> or
1677	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2128	C<IO::AIO::MAP_PRIVATE>,
		2129	or a number of system-specific flags (when not available, the are C<0>):
1678	(which is set to C<MAP_ANON> if your system only provides this	2130	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1679	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2131	C<IO::AIO::MAP_LOCKED>,
1680	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2132	C<IO::AIO::MAP_NORESERVE>,
		2133	C<IO::AIO::MAP_POPULATE>,
1681	C<IO::AIO::MAP_NONBLOCK>	2134	C<IO::AIO::MAP_NONBLOCK>,
		2135	C<IO::AIO::MAP_FIXED>,
		2136	C<IO::AIO::MAP_GROWSDOWN>,
		2137	C<IO::AIO::MAP_32BIT>,
		2138	C<IO::AIO::MAP_HUGETLB> or
		2139	C<IO::AIO::MAP_STACK>.
1682		2140
1683	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2141	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1684		2142
1685	C<$offset> is the offset from the start of the file - it generally must be	2143	C<$offset> is the offset from the start of the file - it generally must be
1686	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2144	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1711		2169
1712	Calls the C<munlockall> function.	2170	Calls the C<munlockall> function.
1713		2171
1714	On systems that do not implement C<munlockall>, this function returns	2172	On systems that do not implement C<munlockall>, this function returns
1715	ENOSYS, otherwise the return value of C<munlockall>.	2173	ENOSYS, otherwise the return value of C<munlockall>.
		2174
		2175	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2176
		2177	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2178	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2179	should be the file offset.
		2180
		2181	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2182	silently corrupt the data in this case.
		2183
		2184	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2185	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2186	C<IO::AIO::SPLICE_F_GIFT>.
		2187
		2188	See the C<splice(2)> manpage for details.
		2189
		2190	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2191
		2192	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2193	description for C<IO::AIO::splice> above for details.
		2194
		2195	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2196
		2197	Attempts to query or change the pipe buffer size. Obviously works only
		2198	on pipes, and currently works only on GNU/Linux systems, and fails with
		2199	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2200	size on other systems, drop me a note.
		2201
		2202	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2203
		2204	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2205	C<$flags> is missing or C<0>, then this should be the same as a call to
		2206	perl's built-in C<pipe> function and create a new pipe, and works on
		2207	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2208	(..., 4096, O_BINARY)>.
		2209
		2210	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2211	the given flags (Linux 2.6.27, glibc 2.9).
		2212
		2213	On success, the read and write file handles are returned.
		2214
		2215	On error, nothing will be returned. If the pipe2 syscall is missing and
		2216	C<$flags> is non-zero, fails with C<ENOSYS>.
		2217
		2218	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2219	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2220	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2221
		2222	Example: create a pipe race-free w.r.t. threads and fork:
		2223
		2224	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2225	or die "pipe2: $!\n";
		2226
		2227	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2228
		2229	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2230	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2231
		2232	On success, the new eventfd filehandle is returned, otherwise returns
		2233	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2234
		2235	Please refer to L<eventfd(2)> for more info on this call.
		2236
		2237	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2238	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2239
		2240	Example: create a new eventfd filehandle:
		2241
		2242	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2243	or die "eventfd: $!\n";
		2244
		2245	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2246
		2247	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2248	(unhelpful) default for C<$flags> is C<0>.
		2249
		2250	On success, the new timerfd filehandle is returned, otherwise returns
		2251	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2252
		2253	Please refer to L<timerfd_create(2)> for more info on this call.
		2254
		2255	The following C<$clockid> values are
		2256	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2257	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2258	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2259	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2260
		2261	The following C<$flags> values are available (Linux
		2262	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2263
		2264	Example: create a new timerfd and set it to one-second repeated alarms,
		2265	then wait for two alarms:
		2266
		2267	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2268	or die "timerfd_create: $!\n";
		2269
		2270	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2271	or die "timerfd_settime: $!\n";
		2272
		2273	for (1..2) {
		2274	8 == sysread $fh, my $buf, 8
		2275	or die "timerfd read failure\n";
		2276
		2277	printf "number of expirations (likely 1): %d\n",
		2278	unpack "Q", $buf;
		2279	}
		2280
		2281	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2282
		2283	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2284	call. Please refer to its manpage for more info on this call.
		2285
		2286	The new itimerspec is specified using two (possibly fractional) second
		2287	values, C<$new_interval> and C<$new_value>).
		2288
		2289	On success, the current interval and value are returned (as per
		2290	C<timerfd_gettime>). On failure, the empty list is returned.
		2291
		2292	The following C<$flags> values are
		2293	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2294	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2295
		2296	See C<IO::AIO::timerfd_create> for a full example.
		2297
		2298	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2299
		2300	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2301	call. Please refer to its manpage for more info on this call.
		2302
		2303	On success, returns the current values of interval and value for the given
		2304	timerfd (as potentially fractional second values). On failure, the empty
		2305	list is returned.
1716		2306
1717	=back	2307	=back
1718		2308
1719	=cut	2309	=cut
1720		2310
…		…
1755	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2345	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1756	\&IO::AIO::poll_cb);	2346	\&IO::AIO::poll_cb);
1757		2347
1758	=head2 FORK BEHAVIOUR	2348	=head2 FORK BEHAVIOUR
1759		2349
1760	This module should do "the right thing" when the process using it forks:	2350	Usage of pthreads in a program changes the semantics of fork
		2351	considerably. Specifically, only async-safe functions can be called after
		2352	fork. Perl doesn't know about this, so in general, you cannot call fork
		2353	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2354	pthreads, so this applies, but many other extensions and (for inexplicable
		2355	reasons) perl itself often is linked against pthreads, so this limitation
		2356	applies to quite a lot of perls.
1761		2357
1762	Before the fork, IO::AIO enters a quiescent state where no requests	2358	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1763	can be added in other threads and no results will be processed. After	2359	only works in the process that loaded it. Forking is fully supported, but
1764	the fork the parent simply leaves the quiescent state and continues	2360	using IO::AIO in the child is not.
1765	request/result processing, while the child frees the request/result queue
1766	(so that the requests started before the fork will only be handled in the
1767	parent). Threads will be started on demand until the limit set in the
1768	parent process has been reached again.
1769		2361
1770	In short: the parent will, after a short pause, continue as if fork had	2362	You might get around by not I<using> IO::AIO before (or after)
1771	not been called, while the child will act as if IO::AIO has not been used	2363	forking. You could also try to call the L<IO::AIO::reinit> function in the
1772	yet.	2364	child:
		2365
		2366	=over 4
		2367
		2368	=item IO::AIO::reinit
		2369
		2370	Abandons all current requests and I/O threads and simply reinitialises all
		2371	data structures. This is not an operation supported by any standards, but
		2372	happens to work on GNU/Linux and some newer BSD systems.
		2373
		2374	The only reasonable use for this function is to call it after forking, if
		2375	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2376	the process will result in undefined behaviour. Calling it at any time
		2377	will also result in any undefined (by POSIX) behaviour.
		2378
		2379	=back
		2380
		2381	=head2 LINUX-SPECIFIC CALLS
		2382
		2383	When a call is documented as "linux-specific" then this means it
		2384	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2385	availability and compatibility of such calls regardless of the platform
		2386	it is compiled on, so platforms such as FreeBSD which often implement
		2387	these calls will work. When in doubt, call them and see if they fail wth
		2388	C<ENOSYS>.
1773		2389
1774	=head2 MEMORY USAGE	2390	=head2 MEMORY USAGE
1775		2391
1776	Per-request usage:	2392	Per-request usage:
1777		2393
…		…
1790	temporary buffers, and each thread requires a stack and other data	2406	temporary buffers, and each thread requires a stack and other data
1791	structures (usually around 16k-128k, depending on the OS).	2407	structures (usually around 16k-128k, depending on the OS).
1792		2408
1793	=head1 KNOWN BUGS	2409	=head1 KNOWN BUGS
1794		2410
1795	Known bugs will be fixed in the next release.	2411	Known bugs will be fixed in the next release :)
		2412
		2413	=head1 KNOWN ISSUES
		2414
		2415	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2416	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2417	non-created hash slots or other scalars I didn't think of. It's best to
		2418	avoid such and either use scalar variables or making sure that the scalar
		2419	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2420
		2421	I am not sure anything can be done about this, so this is considered a
		2422	known issue, rather than a bug.
1796		2423
1797	=head1 SEE ALSO	2424	=head1 SEE ALSO
1798		2425
1799	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2426	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1800	more natural syntax.	2427	more natural syntax.

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