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Revision 1.185 by root, Sat Dec 11 19:06:07 2010 UTC vs.
Revision 1.286 by root, Sun Jul 22 20:39:19 2018 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
…		…
58	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
59	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
60	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
61	using threads anyway.	61	using threads anyway.
62		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
63	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
64	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
65	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
66	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
67		71
68	=head2 EXAMPLE	72	=head2 EXAMPLE
69		73
70	This is a simple example that uses the EV module and loads	74	This is a simple example that uses the EV module and loads
71	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
72		76
73	use Fcntl;
74	use EV;	77	use EV;
75	use IO::AIO;	78	use IO::AIO;
76		79
77	# register the IO::AIO callback with EV	80	# register the IO::AIO callback with EV
78	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
…		…
95		98
96	# file contents now in $contents	99	# file contents now in $contents
97	print $contents;	100	print $contents;
98		101
99	# exit event loop and program	102	# exit event loop and program
100	EV::unloop;	103	EV::break;
101	};	104	};
102	};	105	};
103		106
104	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
105	# check for sockets etc. etc.	108	# check for sockets etc. etc.
106		109
107	# process events as long as there are some:	110	# process events as long as there are some:
108	EV::loop;	111	EV::run;
109		112
110	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
111		114
112	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
113	directly visible to Perl.	116	directly visible to Perl.
…		…
168	use common::sense;	171	use common::sense;
169		172
170	use base 'Exporter';	173	use base 'Exporter';
171		174
172	BEGIN {	175	BEGIN {
173	our $VERSION = '3.7';	176	our $VERSION = 4.42;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
179	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
180	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
182	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
183	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
184		190
185	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187	min_parallel max_parallel max_idle	193	min_parallel max_parallel max_idle idle_timeout
188	nreqs nready npending nthreads	194	nreqs nready npending nthreads
189	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
190	sendfile fadvise madvise	196	sendfile fadvise madvise
191	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
192		198
193	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
194		200
195	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
196		202
…		…
200		206
201	=head1 FUNCTIONS	207	=head1 FUNCTIONS
202		208
203	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
204		210
205	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
206	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
207	documentation.	213	documentation.
208		214
		215	aio_wd $pathname, $callback->($wd)
209	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
210	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
211	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
215	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
216	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
217	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
218	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219	aio_chown $fh_or_path, $uid, $gid, $callback->($status)	227	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		228	aio_chmod $fh_or_path, $mode, $callback->($status)
220	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
221	aio_chmod $fh_or_path, $mode, $callback->($status)	230	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		231	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
222	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
223	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
224	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
225	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
226	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
		237	aio_realpath $pathname, $callback->($path)
227	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
228	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
229	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
230	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
231	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN	245	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		246	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
234	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
235	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
236	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
237	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238	aio_rmtree $path, $callback->($status)	250	aio_rmtree $pathname, $callback->($status)
		251	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		252	aio_ioctl $fh, $request, $buf, $callback->($status)
239	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
240	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
241	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
242	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
244	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
245	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
248	aio_group $callback->(...)	263	aio_group $callback->(...)
249	aio_nop $callback->()	264	aio_nop $callback->()
…		…
258	IO::AIO::max_poll_reqs $nreqs	273	IO::AIO::max_poll_reqs $nreqs
259	IO::AIO::max_poll_time $seconds	274	IO::AIO::max_poll_time $seconds
260	IO::AIO::min_parallel $nthreads	275	IO::AIO::min_parallel $nthreads
261	IO::AIO::max_parallel $nthreads	276	IO::AIO::max_parallel $nthreads
262	IO::AIO::max_idle $nthreads	277	IO::AIO::max_idle $nthreads
		278	IO::AIO::idle_timeout $seconds
263	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
264	IO::AIO::nreqs	280	IO::AIO::nreqs
265	IO::AIO::nready	281	IO::AIO::nready
266	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
267		285
268	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
269	IO::AIO::fadvise $fh, $offset, $len, $advice	287	IO::AIO::fadvise $fh, $offset, $len, $advice
		288	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		289	IO::AIO::munmap $scalar
		290	IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
270	IO::AIO::madvise $scalar, $offset, $length, $advice	291	IO::AIO::madvise $scalar, $offset, $length, $advice
271	IO::AIO::mprotect $scalar, $offset, $length, $protect	292	IO::AIO::mprotect $scalar, $offset, $length, $protect
272	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
273	IO::AIO::munlockall	294	IO::AIO::munlockall
274		295
275	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
276		297
277	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
278	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
279	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
280	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
281	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
282	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
283	syscall has been executed asynchronously.	304	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		305	most syscalls return C<-1> on error, unlike perl, which usually delivers
		306	"false").
		307
		308	Some requests (such as C<aio_readdir>) pass the actual results and
		309	communicate failures by passing C<undef>.
284		310
285	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
286	internally until the request has finished.	312	internally until the request has finished.
287		313
288	All functions return request objects of type L<IO::AIO::REQ> that allow	314	All functions return request objects of type L<IO::AIO::REQ> that allow
289	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
290		316
291	The pathnames you pass to these routines I<must> be absolute and	317	The pathnames you pass to these routines I<should> be absolute. The
292	encoded as octets. The reason for the former is that at the time the	318	reason for this is that at the time the request is being executed, the
293	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
294	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
295	current working directory anywhere in the program and then use relative	321	in the program and then use relative paths. You can also take advantage
296	paths.	322	of IO::AIOs working directory abstraction, that lets you specify paths
		323	relative to some previously-opened "working directory object" - see the
		324	description of the C<IO::AIO::WD> class later in this document.
297		325
298	To encode pathnames as octets, either make sure you either: a) always pass	326	To encode pathnames as octets, either make sure you either: a) always pass
299	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
300	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	328	tinkering, b) are in your native filesystem encoding, c) use the Encode
301	your pathnames to the locale (or other) encoding in effect in the user	329	module and encode your pathnames to the locale (or other) encoding in
302	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	330	effect in the user environment, d) use Glib::filename_from_unicode on
303	use something else to ensure your scalar has the correct contents.	331	unicode filenames or e) use something else to ensure your scalar has the
		332	correct contents.
304		333
305	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	334	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
306	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
307		338
308	=over 4	339	=over 4
309		340
310	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
311		342
…		…
341		372
342		373
343	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
344		375
345	Asynchronously open or create a file and call the callback with a newly	376	Asynchronously open or create a file and call the callback with a newly
346	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
347		378
348	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	379	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
349	for an explanation.	380	for an explanation.
350		381
351	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	382	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
367	} else {	398	} else {
368	die "open failed: $!\n";	399	die "open failed: $!\n";
369	}	400	}
370	};	401	};
371		402
		403	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		404	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		405	following POSIX and non-POSIX constants are available (missing ones on
		406	your system are, as usual, C<0>):
		407
		408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
		411
372		412
373	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
374		414
375	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
376	code.	416	code.
…		…
385	Or in other words: the file descriptor will be closed, but it will not be	425	Or in other words: the file descriptor will be closed, but it will not be
386	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
387		427
388	=cut	428	=cut
389		429
		430	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		431
		432	Seeks the filehandle to the new C<$offset>, similarly to perl's
		433	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		434	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		435	C<IO::AIO::SEEK_END>).
		436
		437	The resulting absolute offset will be passed to the callback, or C<-1> in
		438	case of an error.
		439
		440	In theory, the C<$whence> constants could be different than the
		441	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		442	so don't panic.
		443
		444	As a GNU/Linux (and maybe Solaris) extension, also the constants
		445	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		446	could be found. No guarantees about suitability for use in C<aio_seek> or
		447	Perl's C<sysseek> can be made though, although I would naively assume they
		448	"just work".
		449
390	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
391		451
392	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
393		453
394	Reads or writes C<$length> bytes from or to the specified C<$fh> and	454	Reads or writes C<$length> bytes from or to the specified C<$fh> and
395	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	455	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
396	and calls the callback without the actual number of bytes read (or -1 on	456	calls the callback with the actual number of bytes transferred (or -1 on
397	error, just like the syscall).	457	error, just like the syscall).
398		458
399	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	459	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
400	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
401		461
…		…
426		486
427	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	487	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
428	reading at byte offset C<$in_offset>, and starts writing at the current	488	reading at byte offset C<$in_offset>, and starts writing at the current
429	file offset of C<$out_fh>. Because of that, it is not safe to issue more	489	file offset of C<$out_fh>. Because of that, it is not safe to issue more
430	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	490	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
431	other.	491	other. The same C<$in_fh> works fine though, as this function does not
		492	move or use the file offset of C<$in_fh>.
432		493
433	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than	494	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
434	are written, and there is no way to find out how many bytes have been read	495	are written, and there is no way to find out how many more bytes have been
435	from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of	496	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
436	bytes written to C<$out_fh>. Only if the result value equals C<$length>	497	number of bytes written to C<$out_fh>. Only if the result value equals
437	one can assume that C<$length> bytes have been read.	498	C<$length> one can assume that C<$length> bytes have been read.
438		499
439	Unlike with other C<aio_> functions, it makes a lot of sense to use	500	Unlike with other C<aio_> functions, it makes a lot of sense to use
440	C<aio_sendfile> on non-blocking sockets, as long as one end (typically	501	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
441	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while	502	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
442	the socket I/O will be non-blocking. Note, however, that you can run into	503	the socket I/O will be non-blocking. Note, however, that you can run
443	a trap where C<aio_sendfile> reads some data with readahead, then fails	504	into a trap where C<aio_sendfile> reads some data with readahead, then
444	to write all data, and when the socket is ready the next time, the data	505	fails to write all data, and when the socket is ready the next time, the
445	in the cache is already lost, forcing C<aio_sendfile> to again hit the	506	data in the cache is already lost, forcing C<aio_sendfile> to again hit
446	disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage	507	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
447	much better.	508	resource usage.
448		509
449	This call tries to make use of a native C<sendfile> syscall to provide	510	This call tries to make use of a native C<sendfile>-like syscall to
450	zero-copy operation. For this to work, C<$out_fh> should refer to a	511	provide zero-copy operation. For this to work, C<$out_fh> should refer to
451	socket, and C<$in_fh> should refer to an mmap'able file.	512	a socket, and C<$in_fh> should refer to an mmap'able file.
452		513
453	If a native sendfile cannot be found or it fails with C<ENOSYS>,	514	If a native sendfile cannot be found or it fails with C<ENOSYS>,
454	C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,	515	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
455	it will be emulated, so you can call C<aio_sendfile> on any type of	516	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
456	filehandle regardless of the limitations of the operating system.	517	type of filehandle regardless of the limitations of the operating system.
		518
		519	As native sendfile syscalls (as practically any non-POSIX interface hacked
		520	together in a hurry to improve benchmark numbers) tend to be rather buggy
		521	on many systems, this implementation tries to work around some known bugs
		522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
		523	so you really really should check the return value of C<aio_sendfile> -
		524	fewer bytes than expected might have been transferred.
457		525
458		526
459	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
460		528
461	C<aio_readahead> populates the page cache with data from a file so that	529	C<aio_readahead> populates the page cache with data from a file so that
…		…
465	whole pages, so that offset is effectively rounded down to a page boundary	533	whole pages, so that offset is effectively rounded down to a page boundary
466	and bytes are read up to the next page boundary greater than or equal to	534	and bytes are read up to the next page boundary greater than or equal to
467	(off-set+length). C<aio_readahead> does not read beyond the end of the	535	(off-set+length). C<aio_readahead> does not read beyond the end of the
468	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
469		537
470	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	538	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
471	emulated by simply reading the data, which would have a similar effect.	539	be emulated by simply reading the data, which would have a similar effect.
472		540
473		541
474	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
475		543
476	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
…		…
483	for an explanation.	551	for an explanation.
484		552
485	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	553	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
486	error when stat'ing a large file, the results will be silently truncated	554	error when stat'ing a large file, the results will be silently truncated
487	unless perl itself is compiled with large file support.	555	unless perl itself is compiled with large file support.
		556
		557	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		558	following constants and functions (if not implemented, the constants will
		559	be C<0> and the functions will either C<croak> or fall back on traditional
		560	behaviour).
		561
		562	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		563	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		564	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
488		565
489	Example: Print the length of F</etc/passwd>:	566	Example: Print the length of F</etc/passwd>:
490		567
491	aio_stat "/etc/passwd", sub {	568	aio_stat "/etc/passwd", sub {
492	$_[0] and die "stat failed: $!";	569	$_[0] and die "stat failed: $!";
…		…
536	namemax => 255,	613	namemax => 255,
537	frsize => 1024,	614	frsize => 1024,
538	fsid => 1810	615	fsid => 1810
539	}	616	}
540		617
541
542	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	618	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
543		619
544	Works like perl's C<utime> function (including the special case of $atime	620	Works like perl's C<utime> function (including the special case of $atime
545	and $mtime being undef). Fractional times are supported if the underlying	621	and $mtime being undef). Fractional times are supported if the underlying
546	syscalls support them.	622	syscalls support them.
…		…
573	=item aio_truncate $fh_or_path, $offset, $callback->($status)	649	=item aio_truncate $fh_or_path, $offset, $callback->($status)
574		650
575	Works like truncate(2) or ftruncate(2).	651	Works like truncate(2) or ftruncate(2).
576		652
577		653
		654	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		655
		656	Allocates or frees disk space according to the C<$mode> argument. See the
		657	linux C<fallocate> documentation for details.
		658
		659	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		660	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		661	to deallocate a file range.
		662
		663	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		664	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		665	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		666	to unshare shared blocks (see your L<fallocate(2)> manpage).
		667
		668	The file system block size used by C<fallocate> is presumably the
		669	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		670	can dictate other limitations.
		671
		672	If C<fallocate> isn't available or cannot be emulated (currently no
		673	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		674
		675
578	=item aio_chmod $fh_or_path, $mode, $callback->($status)	676	=item aio_chmod $fh_or_path, $mode, $callback->($status)
579		677
580	Works like perl's C<chmod> function.	678	Works like perl's C<chmod> function.
581		679
582		680
…		…
584		682
585	Asynchronously unlink (delete) a file and call the callback with the	683	Asynchronously unlink (delete) a file and call the callback with the
586	result code.	684	result code.
587		685
588		686
589	=item aio_mknod $path, $mode, $dev, $callback->($status)	687	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
590		688
591	[EXPERIMENTAL]	689	[EXPERIMENTAL]
592		690
593	Asynchronously create a device node (or fifo). See mknod(2).	691	Asynchronously create a device node (or fifo). See mknod(2).
594		692
595	The only (POSIX-) portable way of calling this function is:	693	The only (POSIX-) portable way of calling this function is:
596		694
597	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	695	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
598		696
		697	See C<aio_stat> for info about some potentially helpful extra constants
		698	and functions.
599		699
600	=item aio_link $srcpath, $dstpath, $callback->($status)	700	=item aio_link $srcpath, $dstpath, $callback->($status)
601		701
602	Asynchronously create a new link to the existing object at C<$srcpath> at	702	Asynchronously create a new link to the existing object at C<$srcpath> at
603	the path C<$dstpath> and call the callback with the result code.	703	the path C<$dstpath> and call the callback with the result code.
…		…
607		707
608	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	708	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
609	the path C<$dstpath> and call the callback with the result code.	709	the path C<$dstpath> and call the callback with the result code.
610		710
611		711
612	=item aio_readlink $path, $callback->($link)	712	=item aio_readlink $pathname, $callback->($link)
613		713
614	Asynchronously read the symlink specified by C<$path> and pass it to	714	Asynchronously read the symlink specified by C<$path> and pass it to
615	the callback. If an error occurs, nothing or undef gets passed to the	715	the callback. If an error occurs, nothing or undef gets passed to the
616	callback.	716	callback.
617		717
618		718
		719	=item aio_realpath $pathname, $callback->($path)
		720
		721	Asynchronously make the path absolute and resolve any symlinks in
		722	C<$path>. The resulting path only consists of directories (same as
		723	L<Cwd::realpath>).
		724
		725	This request can be used to get the absolute path of the current working
		726	directory by passing it a path of F<.> (a single dot).
		727
		728
619	=item aio_rename $srcpath, $dstpath, $callback->($status)	729	=item aio_rename $srcpath, $dstpath, $callback->($status)
620		730
621	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	731	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
622	rename(2) and call the callback with the result code.	732	rename(2) and call the callback with the result code.
		733
		734	On systems that support the AIO::WD working directory abstraction
		735	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		736	of failing, C<rename> is called on the absolute path of C<$wd>.
		737
		738
		739	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		740
		741	Basically a version of C<aio_rename> with an additional C<$flags>
		742	argument. Calling this with C<$flags=0> is the same as calling
		743	C<aio_rename>.
		744
		745	Non-zero flags are currently only supported on GNU/Linux systems that
		746	support renameat2. Other systems fail with C<ENOSYS> in this case.
		747
		748	The following constants are available (missing ones are, as usual C<0>),
		749	see renameat2(2) for details:
		750
		751	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		752	and C<IO::AIO::RENAME_WHITEOUT>.
623		753
624		754
625	=item aio_mkdir $pathname, $mode, $callback->($status)	755	=item aio_mkdir $pathname, $mode, $callback->($status)
626		756
627	Asynchronously mkdir (create) a directory and call the callback with	757	Asynchronously mkdir (create) a directory and call the callback with
…		…
632	=item aio_rmdir $pathname, $callback->($status)	762	=item aio_rmdir $pathname, $callback->($status)
633		763
634	Asynchronously rmdir (delete) a directory and call the callback with the	764	Asynchronously rmdir (delete) a directory and call the callback with the
635	result code.	765	result code.
636		766
		767	On systems that support the AIO::WD working directory abstraction
		768	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		769	C<rmdir> is called on the absolute path of C<$wd>.
		770
637		771
638	=item aio_readdir $pathname, $callback->($entries)	772	=item aio_readdir $pathname, $callback->($entries)
639		773
640	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	774	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
641	directory (i.e. opendir + readdir + closedir). The entries will not be	775	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
645	array-ref with the filenames.	779	array-ref with the filenames.
646		780
647		781
648	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	782	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
649		783
650	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	784	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
651	behaviour and output format. In case of an error, C<$entries> will be	785	tune behaviour and output format. In case of an error, C<$entries> will be
652	C<undef>.	786	C<undef>.
653		787
654	The flags are a combination of the following constants, ORed together (the	788	The flags are a combination of the following constants, ORed together (the
655	flags will also be passed to the callback, possibly modified):	789	flags will also be passed to the callback, possibly modified):
656		790
657	=over 4	791	=over 4
658		792
659	=item IO::AIO::READDIR_DENTS	793	=item IO::AIO::READDIR_DENTS
660		794
661	When this flag is off, then the callback gets an arrayref with of names	795	Normally the callback gets an arrayref consisting of names only (as
662	only (as with C<aio_readdir>), otherwise it gets an arrayref with	796	with C<aio_readdir>). If this flag is set, then the callback gets an
663	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	797	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
664	entry in more detail.	798	single directory entry in more detail:
665		799
666	C<$name> is the name of the entry.	800	C<$name> is the name of the entry.
667		801
668	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	802	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
669		803
670	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	804	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
671	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	805	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
672	C<IO::AIO::DT_WHT>.	806	C<IO::AIO::DT_WHT>.
673		807
674	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	808	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
675	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	809	to know, you have to run stat yourself. Also, for speed/memory reasons,
676	scalars are read-only: you can not modify them.	810	the C<$type> scalars are read-only: you must not modify them.
677		811
678	C<$inode> is the inode number (which might not be exact on systems with 64	812	C<$inode> is the inode number (which might not be exact on systems with 64
679	bit inode numbers and 32 bit perls). This field has unspecified content on	813	bit inode numbers and 32 bit perls). This field has unspecified content on
680	systems that do not deliver the inode information.	814	systems that do not deliver the inode information.
681		815
682	=item IO::AIO::READDIR_DIRS_FIRST	816	=item IO::AIO::READDIR_DIRS_FIRST
683		817
684	When this flag is set, then the names will be returned in an order where	818	When this flag is set, then the names will be returned in an order where
685	likely directories come first. This is useful when you need to quickly	819	likely directories come first, in optimal stat order. This is useful when
686	find directories, or you want to find all directories while avoiding to	820	you need to quickly find directories, or you want to find all directories
687	stat() each entry.	821	while avoiding to stat() each entry.
688		822
689	If the system returns type information in readdir, then this is used	823	If the system returns type information in readdir, then this is used
690	to find directories directly. Otherwise, likely directories are files	824	to find directories directly. Otherwise, likely directories are names
691	beginning with ".", or otherwise files with no dots, of which files with	825	beginning with ".", or otherwise names with no dots, of which names with
692	short names are tried first.	826	short names are tried first.
693		827
694	=item IO::AIO::READDIR_STAT_ORDER	828	=item IO::AIO::READDIR_STAT_ORDER
695		829
696	When this flag is set, then the names will be returned in an order	830	When this flag is set, then the names will be returned in an order
697	suitable for stat()'ing each one. That is, when you plan to stat()	831	suitable for stat()'ing each one. That is, when you plan to stat() most or
698	all files in the given directory, then the returned order will likely	832	all files in the given directory, then the returned order will likely be
699	be fastest.	833	faster.
700		834
701	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	835	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
702	the likely dirs come first, resulting in a less optimal stat order.	836	then the likely dirs come first, resulting in a less optimal stat order
		837	for stat'ing all entries, but likely a more optimal order for finding
		838	subdirectories.
703		839
704	=item IO::AIO::READDIR_FOUND_UNKNOWN	840	=item IO::AIO::READDIR_FOUND_UNKNOWN
705		841
706	This flag should not be set when calling C<aio_readdirx>. Instead, it	842	This flag should not be set when calling C<aio_readdirx>. Instead, it
707	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	843	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
708	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	844	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
709	C<$type>'s are known, which can be used to speed up some algorithms.	845	C<$type>'s are known, which can be used to speed up some algorithms.
710		846
711	=back	847	=back
712		848
713		849
		850	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		851
		852	Opens, reads and closes the given file. The data is put into C<$data>,
		853	which is resized as required.
		854
		855	If C<$offset> is negative, then it is counted from the end of the file.
		856
		857	If C<$length> is zero, then the remaining length of the file is
		858	used. Also, in this case, the same limitations to modifying C<$data> apply
		859	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		860	with C<substr>. If the size of the file is known, specifying a non-zero
		861	C<$length> results in a performance advantage.
		862
		863	This request is similar to the older C<aio_load> request, but since it is
		864	a single request, it might be more efficient to use.
		865
		866	Example: load F</etc/passwd> into C<$passwd>.
		867
		868	my $passwd;
		869	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		870	$_[0] >= 0
		871	or die "/etc/passwd: $!\n";
		872
		873	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		874	print $passwd;
		875	};
		876	IO::AIO::flush;
		877
		878
714	=item aio_load $path, $data, $callback->($status)	879	=item aio_load $pathname, $data, $callback->($status)
715		880
716	This is a composite request that tries to fully load the given file into	881	This is a composite request that tries to fully load the given file into
717	memory. Status is the same as with aio_read.	882	memory. Status is the same as with aio_read.
		883
		884	Using C<aio_slurp> might be more efficient, as it is a single request.
718		885
719	=cut	886	=cut
720		887
721	sub aio_load($$;$) {	888	sub aio_load($$;$) {
722	my ($path, undef, $cb) = @_;	889	my ($path, undef, $cb) = @_;
…		…
742	=item aio_copy $srcpath, $dstpath, $callback->($status)	909	=item aio_copy $srcpath, $dstpath, $callback->($status)
743		910
744	Try to copy the I<file> (directories not supported as either source or	911	Try to copy the I<file> (directories not supported as either source or
745	destination) from C<$srcpath> to C<$dstpath> and call the callback with	912	destination) from C<$srcpath> to C<$dstpath> and call the callback with
746	a status of C<0> (ok) or C<-1> (error, see C<$!>).	913	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		914
		915	Existing destination files will be truncated.
747		916
748	This is a composite request that creates the destination file with	917	This is a composite request that creates the destination file with
749	mode 0200 and copies the contents of the source file into it using	918	mode 0200 and copies the contents of the source file into it using
750	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	919	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
751	uid/gid, in that order.	920	uid/gid, in that order.
…		…
841	if ($_[0] && $! == EXDEV) {	1010	if ($_[0] && $! == EXDEV) {
842	aioreq_pri $pri;	1011	aioreq_pri $pri;
843	add $grp aio_copy $src, $dst, sub {	1012	add $grp aio_copy $src, $dst, sub {
844	$grp->result ($_[0]);	1013	$grp->result ($_[0]);
845		1014
846	if (!$_[0]) {	1015	unless ($_[0]) {
847	aioreq_pri $pri;	1016	aioreq_pri $pri;
848	add $grp aio_unlink $src;	1017	add $grp aio_unlink $src;
849	}	1018	}
850	};	1019	};
851	} else {	1020	} else {
…		…
854	};	1023	};
855		1024
856	$grp	1025	$grp
857	}	1026	}
858		1027
859	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1028	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
860		1029
861	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1030	Scans a directory (similar to C<aio_readdir>) but additionally tries to
862	efficiently separate the entries of directory C<$path> into two sets of	1031	efficiently separate the entries of directory C<$path> into two sets of
863	names, directories you can recurse into (directories), and ones you cannot	1032	names, directories you can recurse into (directories), and ones you cannot
864	recurse into (everything else, including symlinks to directories).	1033	recurse into (everything else, including symlinks to directories).
865		1034
866	C<aio_scandir> is a composite request that creates of many sub requests_	1035	C<aio_scandir> is a composite request that generates many sub requests.
867	C<$maxreq> specifies the maximum number of outstanding aio requests that	1036	C<$maxreq> specifies the maximum number of outstanding aio requests that
868	this function generates. If it is C<< <= 0 >>, then a suitable default	1037	this function generates. If it is C<< <= 0 >>, then a suitable default
869	will be chosen (currently 4).	1038	will be chosen (currently 4).
870		1039
871	On error, the callback is called without arguments, otherwise it receives	1040	On error, the callback is called without arguments, otherwise it receives
…		…
895	Then entries will be sorted into likely directories a non-initial dot	1064	Then entries will be sorted into likely directories a non-initial dot
896	currently) and likely non-directories (see C<aio_readdirx>). Then every	1065	currently) and likely non-directories (see C<aio_readdirx>). Then every
897	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1066	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
898	in order of their inode numbers. If that succeeds, it assumes that the	1067	in order of their inode numbers. If that succeeds, it assumes that the
899	entry is a directory or a symlink to directory (which will be checked	1068	entry is a directory or a symlink to directory (which will be checked
900	seperately). This is often faster than stat'ing the entry itself because	1069	separately). This is often faster than stat'ing the entry itself because
901	filesystems might detect the type of the entry without reading the inode	1070	filesystems might detect the type of the entry without reading the inode
902	data (e.g. ext2fs filetype feature), even on systems that cannot return	1071	data (e.g. ext2fs filetype feature), even on systems that cannot return
903	the filetype information on readdir.	1072	the filetype information on readdir.
904		1073
905	If the known number of directories (link count - 2) has been reached, the	1074	If the known number of directories (link count - 2) has been reached, the
…		…
921		1090
922	my $grp = aio_group $cb;	1091	my $grp = aio_group $cb;
923		1092
924	$maxreq = 4 if $maxreq <= 0;	1093	$maxreq = 4 if $maxreq <= 0;
925		1094
926	# stat once	1095	# get a wd object
927	aioreq_pri $pri;	1096	aioreq_pri $pri;
928	add $grp aio_stat $path, sub {	1097	add $grp aio_wd $path, sub {
		1098	$_[0]
929	return $grp->result () if $_[0];	1099	or return $grp->result ();
930	my $now = time;
931	my $hash1 = join ":", (stat _)[0,1,3,7,9];
932		1100
933	# read the directory entries	1101	my $wd = [shift, "."];
		1102
		1103	# stat once
934	aioreq_pri $pri;	1104	aioreq_pri $pri;
935	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1105	add $grp aio_stat $wd, sub {
936	my $entries = shift
937	or return $grp->result ();	1106	return $grp->result () if $_[0];
		1107	my $now = time;
		1108	my $hash1 = join ":", (stat _)[0,1,3,7,9];
938		1109
939	# stat the dir another time	1110	# read the directory entries
940	aioreq_pri $pri;	1111	aioreq_pri $pri;
		1112	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1113	my $entries = shift
		1114	or return $grp->result ();
		1115
		1116	# stat the dir another time
		1117	aioreq_pri $pri;
941	add $grp aio_stat $path, sub {	1118	add $grp aio_stat $wd, sub {
942	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1119	my $hash2 = join ":", (stat _)[0,1,3,7,9];
943		1120
944	my $ndirs;	1121	my $ndirs;
945		1122
946	# take the slow route if anything looks fishy	1123	# take the slow route if anything looks fishy
947	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1124	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
948	$ndirs = -1;	1125	$ndirs = -1;
949	} else {	1126	} else {
950	# if nlink == 2, we are finished	1127	# if nlink == 2, we are finished
951	# for non-posix-fs's, we rely on nlink < 2	1128	# for non-posix-fs's, we rely on nlink < 2
952	$ndirs = (stat _)[3] - 2	1129	$ndirs = (stat _)[3] - 2
953	or return $grp->result ([], $entries);	1130	or return $grp->result ([], $entries);
954	}	1131	}
955		1132
956	my (@dirs, @nondirs);	1133	my (@dirs, @nondirs);
957		1134
958	my $statgrp = add $grp aio_group sub {	1135	my $statgrp = add $grp aio_group sub {
959	$grp->result (\@dirs, \@nondirs);	1136	$grp->result (\@dirs, \@nondirs);
960	};	1137	};
961		1138
962	limit $statgrp $maxreq;	1139	limit $statgrp $maxreq;
963	feed $statgrp sub {	1140	feed $statgrp sub {
964	return unless @$entries;	1141	return unless @$entries;
965	my $entry = shift @$entries;	1142	my $entry = shift @$entries;
966		1143
967	aioreq_pri $pri;	1144	aioreq_pri $pri;
		1145	$wd->[1] = "$entry/.";
968	add $statgrp aio_stat "$path/$entry/.", sub {	1146	add $statgrp aio_stat $wd, sub {
969	if ($_[0] < 0) {	1147	if ($_[0] < 0) {
970	push @nondirs, $entry;	1148	push @nondirs, $entry;
971	} else {	1149	} else {
972	# need to check for real directory	1150	# need to check for real directory
973	aioreq_pri $pri;	1151	aioreq_pri $pri;
		1152	$wd->[1] = $entry;
974	add $statgrp aio_lstat "$path/$entry", sub {	1153	add $statgrp aio_lstat $wd, sub {
975	if (-d _) {	1154	if (-d _) {
976	push @dirs, $entry;	1155	push @dirs, $entry;
977		1156
978	unless (--$ndirs) {	1157	unless (--$ndirs) {
979	push @nondirs, @$entries;	1158	push @nondirs, @$entries;
980	feed $statgrp;	1159	feed $statgrp;
		1160	}
		1161	} else {
		1162	push @nondirs, $entry;
981	}	1163	}
982	} else {
983	push @nondirs, $entry;
984	}	1164	}
985	}	1165	}
986	}	1166	};
987	};	1167	};
988	};	1168	};
989	};	1169	};
990	};	1170	};
991	};	1171	};
992		1172
993	$grp	1173	$grp
994	}	1174	}
995		1175
996	=item aio_rmtree $path, $callback->($status)	1176	=item aio_rmtree $pathname, $callback->($status)
997		1177
998	Delete a directory tree starting (and including) C<$path>, return the	1178	Delete a directory tree starting (and including) C<$path>, return the
999	status of the final C<rmdir> only. This is a composite request that	1179	status of the final C<rmdir> only. This is a composite request that
1000	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1180	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1001	everything else.	1181	everything else.
1002		1182
1003	=cut	1183	=cut
1004		1184
…		…
1026	};	1206	};
1027		1207
1028	$grp	1208	$grp
1029	}	1209	}
1030		1210
		1211	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1212
		1213	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1214
		1215	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1216	they execute asynchronously and pass the return value to the callback.
		1217
		1218	Both calls can be used for a lot of things, some of which make more sense
		1219	to run asynchronously in their own thread, while some others make less
		1220	sense. For example, calls that block waiting for external events, such
		1221	as locking, will also lock down an I/O thread while it is waiting, which
		1222	can deadlock the whole I/O system. At the same time, there might be no
		1223	alternative to using a thread to wait.
		1224
		1225	So in general, you should only use these calls for things that do
		1226	(filesystem) I/O, not for things that wait for other events (network,
		1227	other processes), although if you are careful and know what you are doing,
		1228	you still can.
		1229
		1230	The following constants are available (missing ones are, as usual C<0>):
		1231
		1232	C<F_DUPFD_CLOEXEC>,
		1233
		1234	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1235
		1236	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1237
		1238	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1239	C<FS_IOC_FIEMAP>.
		1240
		1241	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1242	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1243
		1244	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1245	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1246	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1247	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1248	C<FS_FL_USER_MODIFIABLE>.
		1249
		1250	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1251	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1252	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1253	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1254
1031	=item aio_sync $callback->($status)	1255	=item aio_sync $callback->($status)
1032		1256
1033	Asynchronously call sync and call the callback when finished.	1257	Asynchronously call sync and call the callback when finished.
1034		1258
1035	=item aio_fsync $fh, $callback->($status)	1259	=item aio_fsync $fh, $callback->($status)
…		…
1042	Asynchronously call fdatasync on the given filehandle and call the	1266	Asynchronously call fdatasync on the given filehandle and call the
1043	callback with the fdatasync result code.	1267	callback with the fdatasync result code.
1044		1268
1045	If this call isn't available because your OS lacks it or it couldn't be	1269	If this call isn't available because your OS lacks it or it couldn't be
1046	detected, it will be emulated by calling C<fsync> instead.	1270	detected, it will be emulated by calling C<fsync> instead.
		1271
		1272	=item aio_syncfs $fh, $callback->($status)
		1273
		1274	Asynchronously call the syncfs syscall to sync the filesystem associated
		1275	to the given filehandle and call the callback with the syncfs result
		1276	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1277	errno to C<ENOSYS> nevertheless.
1047		1278
1048	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1279	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1049		1280
1050	Sync the data portion of the file specified by C<$offset> and C<$length>	1281	Sync the data portion of the file specified by C<$offset> and C<$length>
1051	to disk (but NOT the metadata), by calling the Linux-specific	1282	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1055	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1286	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1056	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1287	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1057	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1288	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1058	manpage for details.	1289	manpage for details.
1059		1290
1060	=item aio_pathsync $path, $callback->($status)	1291	=item aio_pathsync $pathname, $callback->($status)
1061		1292
1062	This request tries to open, fsync and close the given path. This is a	1293	This request tries to open, fsync and close the given path. This is a
1063	composite request intended to sync directories after directory operations	1294	composite request intended to sync directories after directory operations
1064	(E.g. rename). This might not work on all operating systems or have any	1295	(E.g. rename). This might not work on all operating systems or have any
1065	specific effect, but usually it makes sure that directory changes get	1296	specific effect, but usually it makes sure that directory changes get
…		…
1096	};	1327	};
1097		1328
1098	$grp	1329	$grp
1099	}	1330	}
1100		1331
1101	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1332	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1102		1333
1103	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1334	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1104	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1335	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1105	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1336	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1106	scalar must only be modified in-place while an aio operation is pending on	1337	scalar must only be modified in-place while an aio operation is pending on
…		…
1108		1339
1109	It calls the C<msync> function of your OS, if available, with the memory	1340	It calls the C<msync> function of your OS, if available, with the memory
1110	area starting at C<$offset> in the string and ending C<$length> bytes	1341	area starting at C<$offset> in the string and ending C<$length> bytes
1111	later. If C<$length> is negative, counts from the end, and if C<$length>	1342	later. If C<$length> is negative, counts from the end, and if C<$length>
1112	is C<undef>, then it goes till the end of the string. The flags can be	1343	is C<undef>, then it goes till the end of the string. The flags can be
1113	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1344	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1114	C<IO::AIO::MS_SYNC>.	1345	C<IO::AIO::MS_INVALIDATE>.
1115		1346
1116	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1347	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1117		1348
1118	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1349	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1119	scalars.	1350	scalars.
1120		1351
1121	It touches (reads or writes) all memory pages in the specified	1352	It touches (reads or writes) all memory pages in the specified
1122	range inside the scalar. All caveats and parameters are the same	1353	range inside the scalar. All caveats and parameters are the same
1123	as for C<aio_msync>, above, except for flags, which must be either	1354	as for C<aio_msync>, above, except for flags, which must be either
1124	C<0> (which reads all pages and ensures they are instantiated) or	1355	C<0> (which reads all pages and ensures they are instantiated) or
1125	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1356	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1126	writing an octet from it, which dirties the page).	1357	writing an octet from it, which dirties the page).
1127		1358
1128	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1359	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1129		1360
1130	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1361	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1161	documented under L<MISCELLANEOUS FUNCTIONS>.	1392	documented under L<MISCELLANEOUS FUNCTIONS>.
1162		1393
1163	Example: asynchronously lock all current and future pages into memory.	1394	Example: asynchronously lock all current and future pages into memory.
1164		1395
1165	aio_mlockall IO::AIO::MCL_FUTURE;	1396	aio_mlockall IO::AIO::MCL_FUTURE;
		1397
		1398	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1399
		1400	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1401	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1402	the ioctl is not available on your OS, then this request will fail with
		1403	C<ENOSYS>.
		1404
		1405	C<$start> is the starting offset to query extents for, C<$length> is the
		1406	size of the range to query - if it is C<undef>, then the whole file will
		1407	be queried.
		1408
		1409	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1410	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1411	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1412	the data portion.
		1413
		1414	C<$count> is the maximum number of extent records to return. If it is
		1415	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1416	case, if it is C<0>, then the callback receives the number of extents
		1417	instead of the extents themselves (which is unreliable, see below).
		1418
		1419	If an error occurs, the callback receives no arguments. The special
		1420	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1421
		1422	Otherwise, the callback receives an array reference with extent
		1423	structures. Each extent structure is an array reference itself, with the
		1424	following members:
		1425
		1426	[$logical, $physical, $length, $flags]
		1427
		1428	Flags is any combination of the following flag values (typically either C<0>
		1429	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1430
		1431	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1432	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1433	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1434	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1435	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1436	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1437
		1438	At the time of this writing (Linux 3.2), this request is unreliable unless
		1439	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1440	it to return all extents of a range for files with a large number of
		1441	extents. The code (only) works around all these issues if C<$count> is
		1442	C<undef>.
1166		1443
1167	=item aio_group $callback->(...)	1444	=item aio_group $callback->(...)
1168		1445
1169	This is a very special aio request: Instead of doing something, it is a	1446	This is a very special aio request: Instead of doing something, it is a
1170	container for other aio requests, which is useful if you want to bundle	1447	container for other aio requests, which is useful if you want to bundle
…		…
1207	like sleep and file handle readable/writable, the overhead this creates is	1484	like sleep and file handle readable/writable, the overhead this creates is
1208	immense (it blocks a thread for a long time) so do not use this function	1485	immense (it blocks a thread for a long time) so do not use this function
1209	except to put your application under artificial I/O pressure.	1486	except to put your application under artificial I/O pressure.
1210		1487
1211	=back	1488	=back
		1489
		1490
		1491	=head2 IO::AIO::WD - multiple working directories
		1492
		1493	Your process only has one current working directory, which is used by all
		1494	threads. This makes it hard to use relative paths (some other component
		1495	could call C<chdir> at any time, and it is hard to control when the path
		1496	will be used by IO::AIO).
		1497
		1498	One solution for this is to always use absolute paths. This usually works,
		1499	but can be quite slow (the kernel has to walk the whole path on every
		1500	access), and can also be a hassle to implement.
		1501
		1502	Newer POSIX systems have a number of functions (openat, fdopendir,
		1503	futimensat and so on) that make it possible to specify working directories
		1504	per operation.
		1505
		1506	For portability, and because the clowns who "designed", or shall I write,
		1507	perpetrated this new interface were obviously half-drunk, this abstraction
		1508	cannot be perfect, though.
		1509
		1510	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1511	object. This object stores the canonicalised, absolute version of the
		1512	path, and on systems that allow it, also a directory file descriptor.
		1513
		1514	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1515	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1516	object and a pathname instead (or the IO::AIO::WD object alone, which
		1517	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1518	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1519	to that IO::AIO::WD object.
		1520
		1521	For example, to get a wd object for F</etc> and then stat F<passwd>
		1522	inside, you would write:
		1523
		1524	aio_wd "/etc", sub {
		1525	my $etcdir = shift;
		1526
		1527	# although $etcdir can be undef on error, there is generally no reason
		1528	# to check for errors here, as aio_stat will fail with ENOENT
		1529	# when $etcdir is undef.
		1530
		1531	aio_stat [$etcdir, "passwd"], sub {
		1532	# yay
		1533	};
		1534	};
		1535
		1536	The fact that C<aio_wd> is a request and not a normal function shows that
		1537	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1538	which is why it is done asynchronously.
		1539
		1540	To stat the directory obtained with C<aio_wd> above, one could write
		1541	either of the following three request calls:
		1542
		1543	aio_lstat "/etc" , sub { ... # pathname as normal string
		1544	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1545	aio_lstat $wd , sub { ... # shorthand for the previous
		1546
		1547	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1548	object and the pathname string, so you could write the following without
		1549	causing any issues due to C<$path> getting reused:
		1550
		1551	my $path = [$wd, undef];
		1552
		1553	for my $name (qw(abc def ghi)) {
		1554	$path->[1] = $name;
		1555	aio_stat $path, sub {
		1556	# ...
		1557	};
		1558	}
		1559
		1560	There are some caveats: when directories get renamed (or deleted), the
		1561	pathname string doesn't change, so will point to the new directory (or
		1562	nowhere at all), while the directory fd, if available on the system,
		1563	will still point to the original directory. Most functions accepting a
		1564	pathname will use the directory fd on newer systems, and the string on
		1565	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1566	the string form of the pathname.
		1567
		1568	So this functionality is mainly useful to get some protection against
		1569	C<chdir>, to easily get an absolute path out of a relative path for future
		1570	reference, and to speed up doing many operations in the same directory
		1571	(e.g. when stat'ing all files in a directory).
		1572
		1573	The following functions implement this working directory abstraction:
		1574
		1575	=over 4
		1576
		1577	=item aio_wd $pathname, $callback->($wd)
		1578
		1579	Asynchonously canonicalise the given pathname and convert it to an
		1580	IO::AIO::WD object representing it. If possible and supported on the
		1581	system, also open a directory fd to speed up pathname resolution relative
		1582	to this working directory.
		1583
		1584	If something goes wrong, then C<undef> is passwd to the callback instead
		1585	of a working directory object and C<$!> is set appropriately. Since
		1586	passing C<undef> as working directory component of a pathname fails the
		1587	request with C<ENOENT>, there is often no need for error checking in the
		1588	C<aio_wd> callback, as future requests using the value will fail in the
		1589	expected way.
		1590
		1591	=item IO::AIO::CWD
		1592
		1593	This is a compiletime constant (object) that represents the process
		1594	current working directory.
		1595
		1596	Specifying this object as working directory object for a pathname is as if
		1597	the pathname would be specified directly, without a directory object. For
		1598	example, these calls are functionally identical:
		1599
		1600	aio_stat "somefile", sub { ... };
		1601	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1602
		1603	=back
		1604
		1605	To recover the path associated with an IO::AIO::WD object, you can use
		1606	C<aio_realpath>:
		1607
		1608	aio_realpath $wd, sub {
		1609	warn "path is $_[0]\n";
		1610	};
		1611
		1612	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1613	sometimes, fall back to using an absolue path.
1212		1614
1213	=head2 IO::AIO::REQ CLASS	1615	=head2 IO::AIO::REQ CLASS
1214		1616
1215	All non-aggregate C<aio_*> functions return an object of this class when	1617	All non-aggregate C<aio_*> functions return an object of this class when
1216	called in non-void context.	1618	called in non-void context.
…		…
1334		1736
1335	Sets a feeder/generator on this group: every group can have an attached	1737	Sets a feeder/generator on this group: every group can have an attached
1336	generator that generates requests if idle. The idea behind this is that,	1738	generator that generates requests if idle. The idea behind this is that,
1337	although you could just queue as many requests as you want in a group,	1739	although you could just queue as many requests as you want in a group,
1338	this might starve other requests for a potentially long time. For example,	1740	this might starve other requests for a potentially long time. For example,
1339	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1741	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1340	delaying any later requests for a long time.	1742	requests, delaying any later requests for a long time.
1341		1743
1342	To avoid this, and allow incremental generation of requests, you can	1744	To avoid this, and allow incremental generation of requests, you can
1343	instead a group and set a feeder on it that generates those requests. The	1745	instead a group and set a feeder on it that generates those requests. The
1344	feed callback will be called whenever there are few enough (see C<limit>,	1746	feed callback will be called whenever there are few enough (see C<limit>,
1345	below) requests active in the group itself and is expected to queue more	1747	below) requests active in the group itself and is expected to queue more
…		…
1394		1796
1395	See C<poll_cb> for an example.	1797	See C<poll_cb> for an example.
1396		1798
1397	=item IO::AIO::poll_cb	1799	=item IO::AIO::poll_cb
1398		1800
1399	Process some outstanding events on the result pipe. You have to call this	1801	Process some requests that have reached the result phase (i.e. they have
1400	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1802	been executed but the results are not yet reported). You have to call
1401	returned earlier for whatever reason. Returns immediately when no events	1803	this "regularly" to finish outstanding requests.
1402	are outstanding. The amount of events processed depends on the settings of
1403	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1404		1804
		1805	Returns C<0> if all events could be processed (or there were no
		1806	events to process), or C<-1> if it returned earlier for whatever
		1807	reason. Returns immediately when no events are outstanding. The amount
		1808	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1809	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1810
1405	If not all requests were processed for whatever reason, the filehandle	1811	If not all requests were processed for whatever reason, the poll file
1406	will still be ready when C<poll_cb> returns, so normally you don't have to	1812	descriptor will still be ready when C<poll_cb> returns, so normally you
1407	do anything special to have it called later.	1813	don't have to do anything special to have it called later.
		1814
		1815	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1816	ready, it can be beneficial to call this function from loops which submit
		1817	a lot of requests, to make sure the results get processed when they become
		1818	available and not just when the loop is finished and the event loop takes
		1819	over again. This function returns very fast when there are no outstanding
		1820	requests.
1408		1821
1409	Example: Install an Event watcher that automatically calls	1822	Example: Install an Event watcher that automatically calls
1410	IO::AIO::poll_cb with high priority (more examples can be found in the	1823	IO::AIO::poll_cb with high priority (more examples can be found in the
1411	SYNOPSIS section, at the top of this document):	1824	SYNOPSIS section, at the top of this document):
1412		1825
…		…
1414	poll => 'r', async => 1,	1827	poll => 'r', async => 1,
1415	cb => \&IO::AIO::poll_cb);	1828	cb => \&IO::AIO::poll_cb);
1416		1829
1417	=item IO::AIO::poll_wait	1830	=item IO::AIO::poll_wait
1418		1831
1419	If there are any outstanding requests and none of them in the result	1832	Wait until either at least one request is in the result phase or no
1420	phase, wait till the result filehandle becomes ready for reading (simply	1833	requests are outstanding anymore.
1421	does a C<select> on the filehandle. This is useful if you want to	1834
1422	synchronously wait for some requests to finish).	1835	This is useful if you want to synchronously wait for some requests to
		1836	become ready, without actually handling them.
1423		1837
1424	See C<nreqs> for an example.	1838	See C<nreqs> for an example.
1425		1839
1426	=item IO::AIO::poll	1840	=item IO::AIO::poll
1427		1841
…		…
1514		1928
1515	Under normal circumstances you don't need to call this function.	1929	Under normal circumstances you don't need to call this function.
1516		1930
1517	=item IO::AIO::max_idle $nthreads	1931	=item IO::AIO::max_idle $nthreads
1518		1932
1519	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1933	Limit the number of threads (default: 4) that are allowed to idle
1520	threads that did not get a request to process within 10 seconds). That	1934	(i.e., threads that did not get a request to process within the idle
1521	means if a thread becomes idle while C<$nthreads> other threads are also	1935	timeout (default: 10 seconds). That means if a thread becomes idle while
1522	idle, it will free its resources and exit.	1936	C<$nthreads> other threads are also idle, it will free its resources and
		1937	exit.
1523		1938
1524	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1939	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1525	to allow for extremely high load situations, but want to free resources	1940	to allow for extremely high load situations, but want to free resources
1526	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1941	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1527		1942
1528	The default is probably ok in most situations, especially if thread	1943	The default is probably ok in most situations, especially if thread
1529	creation is fast. If thread creation is very slow on your system you might	1944	creation is fast. If thread creation is very slow on your system you might
1530	want to use larger values.	1945	want to use larger values.
1531		1946
		1947	=item IO::AIO::idle_timeout $seconds
		1948
		1949	Sets the minimum idle timeout (default 10) after which worker threads are
		1950	allowed to exit. SEe C<IO::AIO::max_idle>.
		1951
1532	=item IO::AIO::max_outstanding $maxreqs	1952	=item IO::AIO::max_outstanding $maxreqs
		1953
		1954	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1955	you do queue up more than this number of requests, the next call to
		1956	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1957	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1958	longer exceeded.
		1959
		1960	In other words, this setting does not enforce a queue limit, but can be
		1961	used to make poll functions block if the limit is exceeded.
1533		1962
1534	This is a very bad function to use in interactive programs because it	1963	This is a very bad function to use in interactive programs because it
1535	blocks, and a bad way to reduce concurrency because it is inexact: Better	1964	blocks, and a bad way to reduce concurrency because it is inexact: Better
1536	use an C<aio_group> together with a feed callback.	1965	use an C<aio_group> together with a feed callback.
1537		1966
1538	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1967	Its main use is in scripts without an event loop - when you want to stat
1539	do queue up more than this number of requests, the next call to the	1968	a lot of files, you can write something like this:
1540	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1541	function will block until the limit is no longer exceeded.
1542		1969
1543	The default value is very large, so there is no practical limit on the	1970	IO::AIO::max_outstanding 32;
1544	number of outstanding requests.
1545		1971
1546	You can still queue as many requests as you want. Therefore,	1972	for my $path (...) {
1547	C<max_outstanding> is mainly useful in simple scripts (with low values) or	1973	aio_stat $path , ...;
1548	as a stop gap to shield against fatal memory overflow (with large values).	1974	IO::AIO::poll_cb;
		1975	}
		1976
		1977	IO::AIO::flush;
		1978
		1979	The call to C<poll_cb> inside the loop will normally return instantly, but
		1980	as soon as more thna C<32> reqeusts are in-flight, it will block until
		1981	some requests have been handled. This keeps the loop from pushing a large
		1982	number of C<aio_stat> requests onto the queue.
		1983
		1984	The default value for C<max_outstanding> is very large, so there is no
		1985	practical limit on the number of outstanding requests.
1549		1986
1550	=back	1987	=back
1551		1988
1552	=head3 STATISTICAL INFORMATION	1989	=head3 STATISTICAL INFORMATION
1553		1990
…		…
1575		2012
1576	=back	2013	=back
1577		2014
1578	=head3 MISCELLANEOUS FUNCTIONS	2015	=head3 MISCELLANEOUS FUNCTIONS
1579		2016
1580	IO::AIO implements some functions that might be useful, but are not	2017	IO::AIO implements some functions that are useful when you want to use
1581	asynchronous.	2018	some "Advanced I/O" function not available to in Perl, without going the
		2019	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2020	counterpart.
1582		2021
1583	=over 4	2022	=over 4
		2023
		2024	=item $numfd = IO::AIO::get_fdlimit
		2025
		2026	This function is I<EXPERIMENTAL> and subject to change.
		2027
		2028	Tries to find the current file descriptor limit and returns it, or
		2029	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2030	the highest valid file descriptor number.
		2031
		2032	=item IO::AIO::min_fdlimit [$numfd]
		2033
		2034	This function is I<EXPERIMENTAL> and subject to change.
		2035
		2036	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2037	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2038	is missing, it will try to set a very high limit, although this is not
		2039	recommended when you know the actual minimum that you require.
		2040
		2041	If the limit cannot be raised enough, the function makes a best-effort
		2042	attempt to increase the limit as much as possible, using various
		2043	tricks, while still failing. You can query the resulting limit using
		2044	C<IO::AIO::get_fdlimit>.
		2045
		2046	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2047	true.
1584		2048
1585	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2049	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1586		2050
1587	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2051	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1588	but is blocking (this makes most sense if you know the input data is	2052	but is blocking (this makes most sense if you know the input data is
…		…
1593		2057
1594	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2058	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1595		2059
1596	Simply calls the C<posix_fadvise> function (see its	2060	Simply calls the C<posix_fadvise> function (see its
1597	manpage for details). The following advice constants are	2061	manpage for details). The following advice constants are
1598	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2062	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1599	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2063	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1600	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2064	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1601		2065
1602	On systems that do not implement C<posix_fadvise>, this function returns	2066	On systems that do not implement C<posix_fadvise>, this function returns
1603	ENOSYS, otherwise the return value of C<posix_fadvise>.	2067	ENOSYS, otherwise the return value of C<posix_fadvise>.
1604		2068
1605	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2069	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1606		2070
1607	Simply calls the C<posix_madvise> function (see its	2071	Simply calls the C<posix_madvise> function (see its
1608	manpage for details). The following advice constants are	2072	manpage for details). The following advice constants are
1609	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2073	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1610	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2074	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2075	C<IO::AIO::MADV_DONTNEED>.
		2076
		2077	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2078	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2079	will be reduced to fit into the C<$scalar>.
1611		2080
1612	On systems that do not implement C<posix_madvise>, this function returns	2081	On systems that do not implement C<posix_madvise>, this function returns
1613	ENOSYS, otherwise the return value of C<posix_madvise>.	2082	ENOSYS, otherwise the return value of C<posix_madvise>.
1614		2083
1615	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2084	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1616		2085
1617	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2086	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1618	$scalar (see its manpage for details). The following protect	2087	$scalar (see its manpage for details). The following protect
1619	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2088	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1620	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2089	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2090
		2091	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2092	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2093	will be reduced to fit into the C<$scalar>.
1621		2094
1622	On systems that do not implement C<mprotect>, this function returns	2095	On systems that do not implement C<mprotect>, this function returns
1623	ENOSYS, otherwise the return value of C<mprotect>.	2096	ENOSYS, otherwise the return value of C<mprotect>.
1624		2097
1625	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2098	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1626		2099
1627	Memory-maps a file (or anonymous memory range) and attaches it to the	2100	Memory-maps a file (or anonymous memory range) and attaches it to the
1628	given C<$scalar>, which will act like a string scalar.	2101	given C<$scalar>, which will act like a string scalar. Returns true on
		2102	success, and false otherwise.
1629		2103
		2104	The scalar must exist, but its contents do not matter - this means you
		2105	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2106	the scalar first.
		2107
1630	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2108	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1631	change the string length, and most read-only operations such as copying it	2109	which don't change the string length, and most read-only operations such
1632	or searching it with regexes and so on.	2110	as copying it or searching it with regexes and so on.
1633		2111
1634	Anything else is unsafe and will, at best, result in memory leaks.	2112	Anything else is unsafe and will, at best, result in memory leaks.
1635		2113
1636	The memory map associated with the C<$scalar> is automatically removed	2114	The memory map associated with the C<$scalar> is automatically removed
1637	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2115	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1638	C<IO::AIO::munmap> functions are called.	2116	or C<IO::AIO::munmap> functions are called on it.
1639		2117
1640	This calls the C<mmap>(2) function internally. See your system's manual	2118	This calls the C<mmap>(2) function internally. See your system's manual
1641	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2119	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1642		2120
1643	The C<$length> must be larger than zero and smaller than the actual	2121	The C<$length> must be larger than zero and smaller than the actual
1644	filesize.	2122	filesize.
1645		2123
1646	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2124	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1647	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2125	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1648		2126
1649	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2127	C<$flags> can be a combination of
1650	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2128	C<IO::AIO::MAP_SHARED> or
1651	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2129	C<IO::AIO::MAP_PRIVATE>,
		2130	or a number of system-specific flags (when not available, the are C<0>):
1652	(which is set to C<MAP_ANON> if your system only provides this	2131	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1653	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2132	C<IO::AIO::MAP_LOCKED>,
1654	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2133	C<IO::AIO::MAP_NORESERVE>,
		2134	C<IO::AIO::MAP_POPULATE>,
1655	C<IO::AIO::MAP_NONBLOCK>	2135	C<IO::AIO::MAP_NONBLOCK>,
		2136	C<IO::AIO::MAP_FIXED>,
		2137	C<IO::AIO::MAP_GROWSDOWN>,
		2138	C<IO::AIO::MAP_32BIT>,
		2139	C<IO::AIO::MAP_HUGETLB> or
		2140	C<IO::AIO::MAP_STACK>.
1656		2141
1657	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2142	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1658		2143
1659	C<$offset> is the offset from the start of the file - it generally must be	2144	C<$offset> is the offset from the start of the file - it generally must be
1660	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2145	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1674		2159
1675	=item IO::AIO::munmap $scalar	2160	=item IO::AIO::munmap $scalar
1676		2161
1677	Removes a previous mmap and undefines the C<$scalar>.	2162	Removes a previous mmap and undefines the C<$scalar>.
1678		2163
		2164	=item IO::AIO::mremap $scalar, $new_length, $flags = 0[, $new_address = 0]
		2165
		2166	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2167	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2168	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2169
		2170	Returns true if successful, and false otherwise. If the underlying mmapped
		2171	region has changed address, then the true value has the numerical value
		2172	C<1>, otherwise it has the numerical value C<0>:
		2173
		2174	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2175	or die "mremap: $!";
		2176
		2177	if ($success*1) {
		2178	warn "scalar has chanegd address in memory\n";
		2179	}
		2180
		2181	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2182	implemented, but not supported and might go away in a future version.
		2183
		2184	On systems where this call is not supported or is not emulated, this call
		2185	returns falls and sets C<$!> to C<ENOSYS>.
		2186
1679	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2187	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1680		2188
1681	Calls the C<munlock> function, undoing the effects of a previous	2189	Calls the C<munlock> function, undoing the effects of a previous
1682	C<aio_mlock> call (see its description for details).	2190	C<aio_mlock> call (see its description for details).
1683		2191
…		…
1685		2193
1686	Calls the C<munlockall> function.	2194	Calls the C<munlockall> function.
1687		2195
1688	On systems that do not implement C<munlockall>, this function returns	2196	On systems that do not implement C<munlockall>, this function returns
1689	ENOSYS, otherwise the return value of C<munlockall>.	2197	ENOSYS, otherwise the return value of C<munlockall>.
		2198
		2199	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2200
		2201	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2202	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2203	should be the file offset.
		2204
		2205	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2206	silently corrupt the data in this case.
		2207
		2208	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2209	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2210	C<IO::AIO::SPLICE_F_GIFT>.
		2211
		2212	See the C<splice(2)> manpage for details.
		2213
		2214	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2215
		2216	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2217	description for C<IO::AIO::splice> above for details.
		2218
		2219	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2220
		2221	Attempts to query or change the pipe buffer size. Obviously works only
		2222	on pipes, and currently works only on GNU/Linux systems, and fails with
		2223	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2224	size on other systems, drop me a note.
		2225
		2226	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2227
		2228	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2229	C<$flags> is missing or C<0>, then this should be the same as a call to
		2230	perl's built-in C<pipe> function and create a new pipe, and works on
		2231	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2232	(..., 4096, O_BINARY)>.
		2233
		2234	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2235	the given flags (Linux 2.6.27, glibc 2.9).
		2236
		2237	On success, the read and write file handles are returned.
		2238
		2239	On error, nothing will be returned. If the pipe2 syscall is missing and
		2240	C<$flags> is non-zero, fails with C<ENOSYS>.
		2241
		2242	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2243	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2244	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2245
		2246	Example: create a pipe race-free w.r.t. threads and fork:
		2247
		2248	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2249	or die "pipe2: $!\n";
		2250
		2251	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2252
		2253	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2254	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2255
		2256	On success, the new eventfd filehandle is returned, otherwise returns
		2257	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2258
		2259	Please refer to L<eventfd(2)> for more info on this call.
		2260
		2261	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2262	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2263
		2264	Example: create a new eventfd filehandle:
		2265
		2266	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2267	or die "eventfd: $!\n";
		2268
		2269	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2270
		2271	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2272	(unhelpful) default for C<$flags> is C<0>.
		2273
		2274	On success, the new timerfd filehandle is returned, otherwise returns
		2275	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2276
		2277	Please refer to L<timerfd_create(2)> for more info on this call.
		2278
		2279	The following C<$clockid> values are
		2280	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2281	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2282	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2283	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2284
		2285	The following C<$flags> values are available (Linux
		2286	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2287
		2288	Example: create a new timerfd and set it to one-second repeated alarms,
		2289	then wait for two alarms:
		2290
		2291	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2292	or die "timerfd_create: $!\n";
		2293
		2294	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2295	or die "timerfd_settime: $!\n";
		2296
		2297	for (1..2) {
		2298	8 == sysread $fh, my $buf, 8
		2299	or die "timerfd read failure\n";
		2300
		2301	printf "number of expirations (likely 1): %d\n",
		2302	unpack "Q", $buf;
		2303	}
		2304
		2305	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2306
		2307	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2308	call. Please refer to its manpage for more info on this call.
		2309
		2310	The new itimerspec is specified using two (possibly fractional) second
		2311	values, C<$new_interval> and C<$new_value>).
		2312
		2313	On success, the current interval and value are returned (as per
		2314	C<timerfd_gettime>). On failure, the empty list is returned.
		2315
		2316	The following C<$flags> values are
		2317	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2318	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2319
		2320	See C<IO::AIO::timerfd_create> for a full example.
		2321
		2322	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2323
		2324	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2325	call. Please refer to its manpage for more info on this call.
		2326
		2327	On success, returns the current values of interval and value for the given
		2328	timerfd (as potentially fractional second values). On failure, the empty
		2329	list is returned.
1690		2330
1691	=back	2331	=back
1692		2332
1693	=cut	2333	=cut
1694		2334
…		…
1729	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>	2369	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1730	\&IO::AIO::poll_cb);	2370	\&IO::AIO::poll_cb);
1731		2371
1732	=head2 FORK BEHAVIOUR	2372	=head2 FORK BEHAVIOUR
1733		2373
1734	This module should do "the right thing" when the process using it forks:	2374	Usage of pthreads in a program changes the semantics of fork
		2375	considerably. Specifically, only async-safe functions can be called after
		2376	fork. Perl doesn't know about this, so in general, you cannot call fork
		2377	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2378	pthreads, so this applies, but many other extensions and (for inexplicable
		2379	reasons) perl itself often is linked against pthreads, so this limitation
		2380	applies to quite a lot of perls.
1735		2381
1736	Before the fork, IO::AIO enters a quiescent state where no requests	2382	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1737	can be added in other threads and no results will be processed. After	2383	only works in the process that loaded it. Forking is fully supported, but
1738	the fork the parent simply leaves the quiescent state and continues	2384	using IO::AIO in the child is not.
1739	request/result processing, while the child frees the request/result queue
1740	(so that the requests started before the fork will only be handled in the
1741	parent). Threads will be started on demand until the limit set in the
1742	parent process has been reached again.
1743		2385
1744	In short: the parent will, after a short pause, continue as if fork had	2386	You might get around by not I<using> IO::AIO before (or after)
1745	not been called, while the child will act as if IO::AIO has not been used	2387	forking. You could also try to call the L<IO::AIO::reinit> function in the
1746	yet.	2388	child:
		2389
		2390	=over 4
		2391
		2392	=item IO::AIO::reinit
		2393
		2394	Abandons all current requests and I/O threads and simply reinitialises all
		2395	data structures. This is not an operation supported by any standards, but
		2396	happens to work on GNU/Linux and some newer BSD systems.
		2397
		2398	The only reasonable use for this function is to call it after forking, if
		2399	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2400	the process will result in undefined behaviour. Calling it at any time
		2401	will also result in any undefined (by POSIX) behaviour.
		2402
		2403	=back
		2404
		2405	=head2 LINUX-SPECIFIC CALLS
		2406
		2407	When a call is documented as "linux-specific" then this means it
		2408	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2409	availability and compatibility of such calls regardless of the platform
		2410	it is compiled on, so platforms such as FreeBSD which often implement
		2411	these calls will work. When in doubt, call them and see if they fail wth
		2412	C<ENOSYS>.
1747		2413
1748	=head2 MEMORY USAGE	2414	=head2 MEMORY USAGE
1749		2415
1750	Per-request usage:	2416	Per-request usage:
1751		2417
…		…
1764	temporary buffers, and each thread requires a stack and other data	2430	temporary buffers, and each thread requires a stack and other data
1765	structures (usually around 16k-128k, depending on the OS).	2431	structures (usually around 16k-128k, depending on the OS).
1766		2432
1767	=head1 KNOWN BUGS	2433	=head1 KNOWN BUGS
1768		2434
1769	Known bugs will be fixed in the next release.	2435	Known bugs will be fixed in the next release :)
		2436
		2437	=head1 KNOWN ISSUES
		2438
		2439	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2440	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2441	non-created hash slots or other scalars I didn't think of. It's best to
		2442	avoid such and either use scalar variables or making sure that the scalar
		2443	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2444
		2445	I am not sure anything can be done about this, so this is considered a
		2446	known issue, rather than a bug.
1770		2447
1771	=head1 SEE ALSO	2448	=head1 SEE ALSO
1772		2449
1773	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2450	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1774	more natural syntax.	2451	more natural syntax.

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