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Revision 1.203 by root, Thu Jul 7 22:36:18 2011 UTC vs.
Revision 1.298 by root, Thu Nov 29 21:48:44 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 = '3.93';	176	our $VERSION = 4.6;
174		177
175	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
176	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
177	aio_scandir aio_symlink aio_readlink aio_realpath 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_fallocate	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
179	aio_pathsync aio_readahead	182	aio_pathsync aio_readahead aio_fiemap aio_allocate
180	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
181	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
182	aio_chmod aio_utime aio_truncate	185	aio_chmod aio_utime aio_truncate
183	aio_msync aio_mtouch aio_mlock aio_mlockall	186	aio_msync aio_mtouch aio_mlock aio_mlockall
184	aio_statvfs);	187	aio_statvfs
		188	aio_slurp
		189	aio_wd);
185		190
186	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
187	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
188	min_parallel max_parallel max_idle idle_timeout	193	min_parallel max_parallel max_idle idle_timeout
189	nreqs nready npending nthreads	194	nreqs nready npending nthreads
190	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
191	sendfile fadvise madvise	196	sendfile fadvise madvise
192	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
193		198
194	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
195		200
196	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
197		202
…		…
201		206
202	=head1 FUNCTIONS	207	=head1 FUNCTIONS
203		208
204	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
205		210
206	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
207	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
208	documentation.	213	documentation.
209		214
		215	aio_wd $pathname, $callback->($wd)
210	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
211	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
212	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
214	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
215	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
216	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
217	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
218	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
219	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
220	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)
221	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
222	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)
223	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
224	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
225	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
226	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
227	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
228	aio_realpath $path, $callback->($link)	237	aio_realpath $pathname, $callback->($path)
229	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
230	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
231	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
232	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
233	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
234	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
235	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)
236	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
237	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
238	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
239	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
240	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)
241	aio_sync $callback->($status)	253	aio_sync $callback->($status)
		254	aio_syncfs $fh, $callback->($status)
242	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
243	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
244	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
245	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
246	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
247	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
248	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
249	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
250	aio_group $callback->(...)	263	aio_group $callback->(...)
251	aio_nop $callback->()	264	aio_nop $callback->()
…		…
265	IO::AIO::idle_timeout $seconds	278	IO::AIO::idle_timeout $seconds
266	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
267	IO::AIO::nreqs	280	IO::AIO::nreqs
268	IO::AIO::nready	281	IO::AIO::nready
269	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
270		285
271	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
272	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]
273	IO::AIO::madvise $scalar, $offset, $length, $advice	291	IO::AIO::madvise $scalar, $offset, $length, $advice
274	IO::AIO::mprotect $scalar, $offset, $length, $protect	292	IO::AIO::mprotect $scalar, $offset, $length, $protect
275	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
276	IO::AIO::munlockall	294	IO::AIO::munlockall
277		295
278	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
279		297
280	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
281	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
282	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
283	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
284	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
285	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
286	syscall has been executed asynchronously.	304	error occured, in C<$!>) - 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>.
287		310
288	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
289	internally until the request has finished.	312	internally until the request has finished.
290		313
291	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
292	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
293		316
294	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
295	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
296	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
297	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
298	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
299	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.
300		325
301	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
302	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
303	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
304	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
305	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
306	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.
307		333
308	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
309	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
310		338
311	=over 4	339	=over 4
312		340
313	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
314		342
…		…
344		372
345		373
346	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
347		375
348	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
349	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
350		378
351	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,
352	for an explanation.	380	for an explanation.
353		381
354	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
…		…
377	following POSIX and non-POSIX constants are available (missing ones on	405	following POSIX and non-POSIX constants are available (missing ones on
378	your system are, as usual, C<0>):	406	your system are, as usual, C<0>):
379		407
380	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,	408	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
381	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,	409	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
382	C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.	410	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, C<O_TTY_INIT> and C<O_ACCMODE>.
383		411
384		412
385	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
386		414
387	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
…		…
397	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
398	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
399		427
400	=cut	428	=cut
401		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
402	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
403		451
404	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
405		453
406	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
407	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
408	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
409	error, just like the syscall).	457	error, just like the syscall).
410		458
411	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
412	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
413		461
…		…
471	As native sendfile syscalls (as practically any non-POSIX interface hacked	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
472	together in a hurry to improve benchmark numbers) tend to be rather buggy	520	together in a hurry to improve benchmark numbers) tend to be rather buggy
473	on many systems, this implementation tries to work around some known bugs	521	on many systems, this implementation tries to work around some known bugs
474	in Linux and FreeBSD kernels (probably others, too), but that might fail,	522	in Linux and FreeBSD kernels (probably others, too), but that might fail,
475	so you really really should check the return value of C<aio_sendfile> -	523	so you really really should check the return value of C<aio_sendfile> -
476	fewre bytes than expected might have been transferred.	524	fewer bytes than expected might have been transferred.
477		525
478		526
479	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
480		528
481	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
…		…
485	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
486	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
487	(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
488	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
489		537
490	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
491	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.
492		540
493		541
494	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
495		543
496	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
497		545
498	Works like perl's C<stat> or C<lstat> in void context. The callback will	546	Works almost exactly like perl's C<stat> or C<lstat> in void context. The
499	be called after the stat and the results will be available using C<stat _>	547	callback will be called after the stat and the results will be available
500	or C<-s _> etc...	548	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		549	and C<-T>).
501		550
502	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,	551	The pathname passed to C<aio_stat> must be absolute. See API NOTES, above,
503	for an explanation.	552	for an explanation.
504		553
505	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	554	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
…		…
512	behaviour).	561	behaviour).
513		562
514	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,	563	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
515	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,	564	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
516	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.	565	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
		566
		567	To access higher resolution stat timestamps, see L<SUBSECOND STAT TIME
		568	ACCESS>.
517		569
518	Example: Print the length of F</etc/passwd>:	570	Example: Print the length of F</etc/passwd>:
519		571
520	aio_stat "/etc/passwd", sub {	572	aio_stat "/etc/passwd", sub {
521	$_[0] and die "stat failed: $!";	573	$_[0] and die "stat failed: $!";
…		…
565	namemax => 255,	617	namemax => 255,
566	frsize => 1024,	618	frsize => 1024,
567	fsid => 1810	619	fsid => 1810
568	}	620	}
569		621
570
571	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	622	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
572		623
573	Works like perl's C<utime> function (including the special case of $atime	624	Works like perl's C<utime> function (including the special case of $atime
574	and $mtime being undef). Fractional times are supported if the underlying	625	and $mtime being undef). Fractional times are supported if the underlying
575	syscalls support them.	626	syscalls support them.
576		627
577	When called with a pathname, uses utimes(2) if available, otherwise	628	When called with a pathname, uses utimensat(2) or utimes(2) if available,
578	utime(2). If called on a file descriptor, uses futimes(2) if available,	629	otherwise utime(2). If called on a file descriptor, uses futimens(2)
579	otherwise returns ENOSYS, so this is not portable.	630	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		631	portable.
580		632
581	Examples:	633	Examples:
582		634
583	# set atime and mtime to current time (basically touch(1)):	635	# set atime and mtime to current time (basically touch(1)):
584	aio_utime "path", undef, undef;	636	aio_utime "path", undef, undef;
…		…
602	=item aio_truncate $fh_or_path, $offset, $callback->($status)	654	=item aio_truncate $fh_or_path, $offset, $callback->($status)
603		655
604	Works like truncate(2) or ftruncate(2).	656	Works like truncate(2) or ftruncate(2).
605		657
606		658
		659	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		660
		661	Allocates or frees disk space according to the C<$mode> argument. See the
		662	linux C<fallocate> documentation for details.
		663
		664	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		665	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		666	to deallocate a file range.
		667
		668	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		669	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		670	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		671	to unshare shared blocks (see your L<fallocate(2)> manpage).
		672
		673	The file system block size used by C<fallocate> is presumably the
		674	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		675	can dictate other limitations.
		676
		677	If C<fallocate> isn't available or cannot be emulated (currently no
		678	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		679
		680
607	=item aio_chmod $fh_or_path, $mode, $callback->($status)	681	=item aio_chmod $fh_or_path, $mode, $callback->($status)
608		682
609	Works like perl's C<chmod> function.	683	Works like perl's C<chmod> function.
610		684
611		685
…		…
613		687
614	Asynchronously unlink (delete) a file and call the callback with the	688	Asynchronously unlink (delete) a file and call the callback with the
615	result code.	689	result code.
616		690
617		691
618	=item aio_mknod $path, $mode, $dev, $callback->($status)	692	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
619		693
620	[EXPERIMENTAL]	694	[EXPERIMENTAL]
621		695
622	Asynchronously create a device node (or fifo). See mknod(2).	696	Asynchronously create a device node (or fifo). See mknod(2).
623		697
624	The only (POSIX-) portable way of calling this function is:	698	The only (POSIX-) portable way of calling this function is:
625		699
626	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	700	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
627		701
628	See C<aio_stat> for info about some potentially helpful extra constants	702	See C<aio_stat> for info about some potentially helpful extra constants
629	and functions.	703	and functions.
630		704
631	=item aio_link $srcpath, $dstpath, $callback->($status)	705	=item aio_link $srcpath, $dstpath, $callback->($status)
…		…
638		712
639	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	713	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
640	the path C<$dstpath> and call the callback with the result code.	714	the path C<$dstpath> and call the callback with the result code.
641		715
642		716
643	=item aio_readlink $path, $callback->($link)	717	=item aio_readlink $pathname, $callback->($link)
644		718
645	Asynchronously read the symlink specified by C<$path> and pass it to	719	Asynchronously read the symlink specified by C<$path> and pass it to
646	the callback. If an error occurs, nothing or undef gets passed to the	720	the callback. If an error occurs, nothing or undef gets passed to the
647	callback.	721	callback.
648		722
649		723
650	=item aio_realpath $path, $callback->($path)	724	=item aio_realpath $pathname, $callback->($path)
651		725
652	Asynchronously make the path absolute and resolve any symlinks in	726	Asynchronously make the path absolute and resolve any symlinks in
653	C<$path>. The resulting path only consists of directories (Same as	727	C<$path>. The resulting path only consists of directories (same as
654	L<Cwd::realpath>).	728	L<Cwd::realpath>).
655		729
656	This request can be used to get the absolute path of the current working	730	This request can be used to get the absolute path of the current working
657	directory by passing it a path of F<.> (a single dot).	731	directory by passing it a path of F<.> (a single dot).
658		732
659		733
660	=item aio_rename $srcpath, $dstpath, $callback->($status)	734	=item aio_rename $srcpath, $dstpath, $callback->($status)
661		735
662	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	736	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
663	rename(2) and call the callback with the result code.	737	rename(2) and call the callback with the result code.
		738
		739	On systems that support the AIO::WD working directory abstraction
		740	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		741	of failing, C<rename> is called on the absolute path of C<$wd>.
		742
		743
		744	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		745
		746	Basically a version of C<aio_rename> with an additional C<$flags>
		747	argument. Calling this with C<$flags=0> is the same as calling
		748	C<aio_rename>.
		749
		750	Non-zero flags are currently only supported on GNU/Linux systems that
		751	support renameat2. Other systems fail with C<ENOSYS> in this case.
		752
		753	The following constants are available (missing ones are, as usual C<0>),
		754	see renameat2(2) for details:
		755
		756	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		757	and C<IO::AIO::RENAME_WHITEOUT>.
664		758
665		759
666	=item aio_mkdir $pathname, $mode, $callback->($status)	760	=item aio_mkdir $pathname, $mode, $callback->($status)
667		761
668	Asynchronously mkdir (create) a directory and call the callback with	762	Asynchronously mkdir (create) a directory and call the callback with
…		…
673	=item aio_rmdir $pathname, $callback->($status)	767	=item aio_rmdir $pathname, $callback->($status)
674		768
675	Asynchronously rmdir (delete) a directory and call the callback with the	769	Asynchronously rmdir (delete) a directory and call the callback with the
676	result code.	770	result code.
677		771
		772	On systems that support the AIO::WD working directory abstraction
		773	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		774	C<rmdir> is called on the absolute path of C<$wd>.
		775
678		776
679	=item aio_readdir $pathname, $callback->($entries)	777	=item aio_readdir $pathname, $callback->($entries)
680		778
681	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	779	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
682	directory (i.e. opendir + readdir + closedir). The entries will not be	780	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
686	array-ref with the filenames.	784	array-ref with the filenames.
687		785
688		786
689	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	787	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
690		788
691	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	789	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
692	behaviour and output format. In case of an error, C<$entries> will be	790	tune behaviour and output format. In case of an error, C<$entries> will be
693	C<undef>.	791	C<undef>.
694		792
695	The flags are a combination of the following constants, ORed together (the	793	The flags are a combination of the following constants, ORed together (the
696	flags will also be passed to the callback, possibly modified):	794	flags will also be passed to the callback, possibly modified):
697		795
698	=over 4	796	=over 4
699		797
700	=item IO::AIO::READDIR_DENTS	798	=item IO::AIO::READDIR_DENTS
701		799
702	When this flag is off, then the callback gets an arrayref consisting of	800	Normally the callback gets an arrayref consisting of names only (as
703	names only (as with C<aio_readdir>), otherwise it gets an arrayref with	801	with C<aio_readdir>). If this flag is set, then the callback gets an
704	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	802	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
705	entry in more detail.	803	single directory entry in more detail:
706		804
707	C<$name> is the name of the entry.	805	C<$name> is the name of the entry.
708		806
709	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	807	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
710		808
711	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	809	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
712	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	810	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
713	C<IO::AIO::DT_WHT>.	811	C<IO::AIO::DT_WHT>.
714		812
715	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	813	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
716	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	814	to know, you have to run stat yourself. Also, for speed/memory reasons,
717	scalars are read-only: you can not modify them.	815	the C<$type> scalars are read-only: you must not modify them.
718		816
719	C<$inode> is the inode number (which might not be exact on systems with 64	817	C<$inode> is the inode number (which might not be exact on systems with 64
720	bit inode numbers and 32 bit perls). This field has unspecified content on	818	bit inode numbers and 32 bit perls). This field has unspecified content on
721	systems that do not deliver the inode information.	819	systems that do not deliver the inode information.
722		820
…		…
733	short names are tried first.	831	short names are tried first.
734		832
735	=item IO::AIO::READDIR_STAT_ORDER	833	=item IO::AIO::READDIR_STAT_ORDER
736		834
737	When this flag is set, then the names will be returned in an order	835	When this flag is set, then the names will be returned in an order
738	suitable for stat()'ing each one. That is, when you plan to stat()	836	suitable for stat()'ing each one. That is, when you plan to stat() most or
739	all files in the given directory, then the returned order will likely	837	all files in the given directory, then the returned order will likely be
740	be fastest.	838	faster.
741		839
742	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	840	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
743	the likely dirs come first, resulting in a less optimal stat order.	841	then the likely dirs come first, resulting in a less optimal stat order
		842	for stat'ing all entries, but likely a more optimal order for finding
		843	subdirectories.
744		844
745	=item IO::AIO::READDIR_FOUND_UNKNOWN	845	=item IO::AIO::READDIR_FOUND_UNKNOWN
746		846
747	This flag should not be set when calling C<aio_readdirx>. Instead, it	847	This flag should not be set when calling C<aio_readdirx>. Instead, it
748	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	848	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
749	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	849	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
750	C<$type>'s are known, which can be used to speed up some algorithms.	850	C<$type>'s are known, which can be used to speed up some algorithms.
751		851
752	=back	852	=back
753		853
754		854
		855	=item aio_slurp $pathname, $offset, $length, $data, $callback->($status)
		856
		857	Opens, reads and closes the given file. The data is put into C<$data>,
		858	which is resized as required.
		859
		860	If C<$offset> is negative, then it is counted from the end of the file.
		861
		862	If C<$length> is zero, then the remaining length of the file is
		863	used. Also, in this case, the same limitations to modifying C<$data> apply
		864	as when IO::AIO::mmap is used, i.e. it must only be modified in-place
		865	with C<substr>. If the size of the file is known, specifying a non-zero
		866	C<$length> results in a performance advantage.
		867
		868	This request is similar to the older C<aio_load> request, but since it is
		869	a single request, it might be more efficient to use.
		870
		871	Example: load F</etc/passwd> into C<$passwd>.
		872
		873	my $passwd;
		874	aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
		875	$_[0] >= 0
		876	or die "/etc/passwd: $!\n";
		877
		878	printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
		879	print $passwd;
		880	};
		881	IO::AIO::flush;
		882
		883
755	=item aio_load $path, $data, $callback->($status)	884	=item aio_load $pathname, $data, $callback->($status)
756		885
757	This is a composite request that tries to fully load the given file into	886	This is a composite request that tries to fully load the given file into
758	memory. Status is the same as with aio_read.	887	memory. Status is the same as with aio_read.
		888
		889	Using C<aio_slurp> might be more efficient, as it is a single request.
759		890
760	=cut	891	=cut
761		892
762	sub aio_load($$;$) {	893	sub aio_load($$;$) {
763	my ($path, undef, $cb) = @_;	894	my ($path, undef, $cb) = @_;
…		…
783	=item aio_copy $srcpath, $dstpath, $callback->($status)	914	=item aio_copy $srcpath, $dstpath, $callback->($status)
784		915
785	Try to copy the I<file> (directories not supported as either source or	916	Try to copy the I<file> (directories not supported as either source or
786	destination) from C<$srcpath> to C<$dstpath> and call the callback with	917	destination) from C<$srcpath> to C<$dstpath> and call the callback with
787	a status of C<0> (ok) or C<-1> (error, see C<$!>).	918	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		919
		920	Existing destination files will be truncated.
788		921
789	This is a composite request that creates the destination file with	922	This is a composite request that creates the destination file with
790	mode 0200 and copies the contents of the source file into it using	923	mode 0200 and copies the contents of the source file into it using
791	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	924	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
792	uid/gid, in that order.	925	uid/gid, in that order.
…		…
895	};	1028	};
896		1029
897	$grp	1030	$grp
898	}	1031	}
899		1032
900	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1033	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
901		1034
902	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1035	Scans a directory (similar to C<aio_readdir>) but additionally tries to
903	efficiently separate the entries of directory C<$path> into two sets of	1036	efficiently separate the entries of directory C<$path> into two sets of
904	names, directories you can recurse into (directories), and ones you cannot	1037	names, directories you can recurse into (directories), and ones you cannot
905	recurse into (everything else, including symlinks to directories).	1038	recurse into (everything else, including symlinks to directories).
906		1039
907	C<aio_scandir> is a composite request that creates of many sub requests_	1040	C<aio_scandir> is a composite request that generates many sub requests.
908	C<$maxreq> specifies the maximum number of outstanding aio requests that	1041	C<$maxreq> specifies the maximum number of outstanding aio requests that
909	this function generates. If it is C<< <= 0 >>, then a suitable default	1042	this function generates. If it is C<< <= 0 >>, then a suitable default
910	will be chosen (currently 4).	1043	will be chosen (currently 4).
911		1044
912	On error, the callback is called without arguments, otherwise it receives	1045	On error, the callback is called without arguments, otherwise it receives
…		…
936	Then entries will be sorted into likely directories a non-initial dot	1069	Then entries will be sorted into likely directories a non-initial dot
937	currently) and likely non-directories (see C<aio_readdirx>). Then every	1070	currently) and likely non-directories (see C<aio_readdirx>). Then every
938	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1071	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
939	in order of their inode numbers. If that succeeds, it assumes that the	1072	in order of their inode numbers. If that succeeds, it assumes that the
940	entry is a directory or a symlink to directory (which will be checked	1073	entry is a directory or a symlink to directory (which will be checked
941	seperately). This is often faster than stat'ing the entry itself because	1074	separately). This is often faster than stat'ing the entry itself because
942	filesystems might detect the type of the entry without reading the inode	1075	filesystems might detect the type of the entry without reading the inode
943	data (e.g. ext2fs filetype feature), even on systems that cannot return	1076	data (e.g. ext2fs filetype feature), even on systems that cannot return
944	the filetype information on readdir.	1077	the filetype information on readdir.
945		1078
946	If the known number of directories (link count - 2) has been reached, the	1079	If the known number of directories (link count - 2) has been reached, the
…		…
962		1095
963	my $grp = aio_group $cb;	1096	my $grp = aio_group $cb;
964		1097
965	$maxreq = 4 if $maxreq <= 0;	1098	$maxreq = 4 if $maxreq <= 0;
966		1099
967	# stat once	1100	# get a wd object
968	aioreq_pri $pri;	1101	aioreq_pri $pri;
969	add $grp aio_stat $path, sub {	1102	add $grp aio_wd $path, sub {
		1103	$_[0]
970	return $grp->result () if $_[0];	1104	or return $grp->result ();
971	my $now = time;
972	my $hash1 = join ":", (stat _)[0,1,3,7,9];
973		1105
974	# read the directory entries	1106	my $wd = [shift, "."];
		1107
		1108	# stat once
975	aioreq_pri $pri;	1109	aioreq_pri $pri;
976	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1110	add $grp aio_stat $wd, sub {
977	my $entries = shift
978	or return $grp->result ();	1111	return $grp->result () if $_[0];
		1112	my $now = time;
		1113	my $hash1 = join ":", (stat _)[0,1,3,7,9];
979		1114
980	# stat the dir another time	1115	# read the directory entries
981	aioreq_pri $pri;	1116	aioreq_pri $pri;
		1117	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1118	my $entries = shift
		1119	or return $grp->result ();
		1120
		1121	# stat the dir another time
		1122	aioreq_pri $pri;
982	add $grp aio_stat $path, sub {	1123	add $grp aio_stat $wd, sub {
983	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1124	my $hash2 = join ":", (stat _)[0,1,3,7,9];
984		1125
985	my $ndirs;	1126	my $ndirs;
986		1127
987	# take the slow route if anything looks fishy	1128	# take the slow route if anything looks fishy
988	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1129	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
989	$ndirs = -1;	1130	$ndirs = -1;
990	} else {	1131	} else {
991	# if nlink == 2, we are finished	1132	# if nlink == 2, we are finished
992	# for non-posix-fs's, we rely on nlink < 2	1133	# for non-posix-fs's, we rely on nlink < 2
993	$ndirs = (stat _)[3] - 2	1134	$ndirs = (stat _)[3] - 2
994	or return $grp->result ([], $entries);	1135	or return $grp->result ([], $entries);
995	}	1136	}
996		1137
997	my (@dirs, @nondirs);	1138	my (@dirs, @nondirs);
998		1139
999	my $statgrp = add $grp aio_group sub {	1140	my $statgrp = add $grp aio_group sub {
1000	$grp->result (\@dirs, \@nondirs);	1141	$grp->result (\@dirs, \@nondirs);
1001	};	1142	};
1002		1143
1003	limit $statgrp $maxreq;	1144	limit $statgrp $maxreq;
1004	feed $statgrp sub {	1145	feed $statgrp sub {
1005	return unless @$entries;	1146	return unless @$entries;
1006	my $entry = shift @$entries;	1147	my $entry = shift @$entries;
1007		1148
1008	aioreq_pri $pri;	1149	aioreq_pri $pri;
		1150	$wd->[1] = "$entry/.";
1009	add $statgrp aio_stat "$path/$entry/.", sub {	1151	add $statgrp aio_stat $wd, sub {
1010	if ($_[0] < 0) {	1152	if ($_[0] < 0) {
1011	push @nondirs, $entry;	1153	push @nondirs, $entry;
1012	} else {	1154	} else {
1013	# need to check for real directory	1155	# need to check for real directory
1014	aioreq_pri $pri;	1156	aioreq_pri $pri;
		1157	$wd->[1] = $entry;
1015	add $statgrp aio_lstat "$path/$entry", sub {	1158	add $statgrp aio_lstat $wd, sub {
1016	if (-d _) {	1159	if (-d _) {
1017	push @dirs, $entry;	1160	push @dirs, $entry;
1018		1161
1019	unless (--$ndirs) {	1162	unless (--$ndirs) {
1020	push @nondirs, @$entries;	1163	push @nondirs, @$entries;
1021	feed $statgrp;	1164	feed $statgrp;
		1165	}
		1166	} else {
		1167	push @nondirs, $entry;
1022	}	1168	}
1023	} else {
1024	push @nondirs, $entry;
1025	}	1169	}
1026	}	1170	}
1027	}	1171	};
1028	};	1172	};
1029	};	1173	};
1030	};	1174	};
1031	};	1175	};
1032	};	1176	};
1033		1177
1034	$grp	1178	$grp
1035	}	1179	}
1036		1180
1037	=item aio_rmtree $path, $callback->($status)	1181	=item aio_rmtree $pathname, $callback->($status)
1038		1182
1039	Delete a directory tree starting (and including) C<$path>, return the	1183	Delete a directory tree starting (and including) C<$path>, return the
1040	status of the final C<rmdir> only. This is a composite request that	1184	status of the final C<rmdir> only. This is a composite request that
1041	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1185	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1042	everything else.	1186	everything else.
1043		1187
1044	=cut	1188	=cut
1045		1189
…		…
1067	};	1211	};
1068		1212
1069	$grp	1213	$grp
1070	}	1214	}
1071		1215
		1216	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1217
		1218	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1219
		1220	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1221	they execute asynchronously and pass the return value to the callback.
		1222
		1223	Both calls can be used for a lot of things, some of which make more sense
		1224	to run asynchronously in their own thread, while some others make less
		1225	sense. For example, calls that block waiting for external events, such
		1226	as locking, will also lock down an I/O thread while it is waiting, which
		1227	can deadlock the whole I/O system. At the same time, there might be no
		1228	alternative to using a thread to wait.
		1229
		1230	So in general, you should only use these calls for things that do
		1231	(filesystem) I/O, not for things that wait for other events (network,
		1232	other processes), although if you are careful and know what you are doing,
		1233	you still can.
		1234
		1235	The following constants are available (missing ones are, as usual C<0>):
		1236
		1237	C<F_DUPFD_CLOEXEC>,
		1238
		1239	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1240
		1241	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1242
		1243	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1244	C<FS_IOC_FIEMAP>.
		1245
		1246	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1247	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1248
		1249	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1250	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1251	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1252	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1253	C<FS_FL_USER_MODIFIABLE>.
		1254
		1255	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1256	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1257	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1258	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1259
1072	=item aio_sync $callback->($status)	1260	=item aio_sync $callback->($status)
1073		1261
1074	Asynchronously call sync and call the callback when finished.	1262	Asynchronously call sync and call the callback when finished.
1075		1263
1076	=item aio_fsync $fh, $callback->($status)	1264	=item aio_fsync $fh, $callback->($status)
…		…
1083	Asynchronously call fdatasync on the given filehandle and call the	1271	Asynchronously call fdatasync on the given filehandle and call the
1084	callback with the fdatasync result code.	1272	callback with the fdatasync result code.
1085		1273
1086	If this call isn't available because your OS lacks it or it couldn't be	1274	If this call isn't available because your OS lacks it or it couldn't be
1087	detected, it will be emulated by calling C<fsync> instead.	1275	detected, it will be emulated by calling C<fsync> instead.
		1276
		1277	=item aio_syncfs $fh, $callback->($status)
		1278
		1279	Asynchronously call the syncfs syscall to sync the filesystem associated
		1280	to the given filehandle and call the callback with the syncfs result
		1281	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1282	errno to C<ENOSYS> nevertheless.
1088		1283
1089	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1284	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1090		1285
1091	Sync the data portion of the file specified by C<$offset> and C<$length>	1286	Sync the data portion of the file specified by C<$offset> and C<$length>
1092	to disk (but NOT the metadata), by calling the Linux-specific	1287	to disk (but NOT the metadata), by calling the Linux-specific
…		…
1096	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1291	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1097	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1292	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1098	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1293	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1099	manpage for details.	1294	manpage for details.
1100		1295
1101	=item aio_pathsync $path, $callback->($status)	1296	=item aio_pathsync $pathname, $callback->($status)
1102		1297
1103	This request tries to open, fsync and close the given path. This is a	1298	This request tries to open, fsync and close the given path. This is a
1104	composite request intended to sync directories after directory operations	1299	composite request intended to sync directories after directory operations
1105	(E.g. rename). This might not work on all operating systems or have any	1300	(E.g. rename). This might not work on all operating systems or have any
1106	specific effect, but usually it makes sure that directory changes get	1301	specific effect, but usually it makes sure that directory changes get
…		…
1137	};	1332	};
1138		1333
1139	$grp	1334	$grp
1140	}	1335	}
1141		1336
1142	=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1337	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
1143		1338
1144	This is a rather advanced IO::AIO call, which only works on mmap(2)ed	1339	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1145	scalars (see the C<IO::AIO::mmap> function, although it also works on data	1340	scalars (see the C<IO::AIO::mmap> function, although it also works on data
1146	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the	1341	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1147	scalar must only be modified in-place while an aio operation is pending on	1342	scalar must only be modified in-place while an aio operation is pending on
…		…
1149		1344
1150	It calls the C<msync> function of your OS, if available, with the memory	1345	It calls the C<msync> function of your OS, if available, with the memory
1151	area starting at C<$offset> in the string and ending C<$length> bytes	1346	area starting at C<$offset> in the string and ending C<$length> bytes
1152	later. If C<$length> is negative, counts from the end, and if C<$length>	1347	later. If C<$length> is negative, counts from the end, and if C<$length>
1153	is C<undef>, then it goes till the end of the string. The flags can be	1348	is C<undef>, then it goes till the end of the string. The flags can be
1154	a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and	1349	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
1155	C<IO::AIO::MS_SYNC>.	1350	C<IO::AIO::MS_INVALIDATE>.
1156		1351
1157	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	1352	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1158		1353
1159	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1354	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1160	scalars.	1355	scalars.
1161		1356
1162	It touches (reads or writes) all memory pages in the specified	1357	It touches (reads or writes) all memory pages in the specified
1163	range inside the scalar. All caveats and parameters are the same	1358	range inside the scalar. All caveats and parameters are the same
1164	as for C<aio_msync>, above, except for flags, which must be either	1359	as for C<aio_msync>, above, except for flags, which must be either
1165	C<0> (which reads all pages and ensures they are instantiated) or	1360	C<0> (which reads all pages and ensures they are instantiated) or
1166	C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and	1361	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
1167	writing an octet from it, which dirties the page).	1362	writing an octet from it, which dirties the page).
1168		1363
1169	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1364	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1170		1365
1171	This is a rather advanced IO::AIO call, which works best on mmap(2)ed	1366	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
…		…
1190	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;	1385	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1191	aio_mlock $data; # mlock in background	1386	aio_mlock $data; # mlock in background
1192		1387
1193	=item aio_mlockall $flags, $callback->($status)	1388	=item aio_mlockall $flags, $callback->($status)
1194		1389
1195	Calls the C<mlockall> function with the given C<$flags> (a combination of	1390	Calls the C<mlockall> function with the given C<$flags> (a
1196	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).	1391	combination of C<IO::AIO::MCL_CURRENT>, C<IO::AIO::MCL_FUTURE> and
		1392	C<IO::AIO::MCL_ONFAULT>).
1197		1393
1198	On systems that do not implement C<mlockall>, this function returns C<-1>	1394	On systems that do not implement C<mlockall>, this function returns C<-1>
1199	and sets errno to C<ENOSYS>.	1395	and sets errno to C<ENOSYS>. Similarly, flag combinations not supported
		1396	by the system result in a return value of C<-1> with errno being set to
		1397	C<EINVAL>.
1200		1398
1201	Note that the corresponding C<munlockall> is synchronous and is	1399	Note that the corresponding C<munlockall> is synchronous and is
1202	documented under L<MISCELLANEOUS FUNCTIONS>.	1400	documented under L<MISCELLANEOUS FUNCTIONS>.
1203		1401
1204	Example: asynchronously lock all current and future pages into memory.	1402	Example: asynchronously lock all current and future pages into memory.
1205		1403
1206	aio_mlockall IO::AIO::MCL_FUTURE;	1404	aio_mlockall IO::AIO::MCL_FUTURE;
		1405
		1406	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1407
		1408	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1409	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1410	the ioctl is not available on your OS, then this request will fail with
		1411	C<ENOSYS>.
		1412
		1413	C<$start> is the starting offset to query extents for, C<$length> is the
		1414	size of the range to query - if it is C<undef>, then the whole file will
		1415	be queried.
		1416
		1417	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1418	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1419	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1420	the data portion.
		1421
		1422	C<$count> is the maximum number of extent records to return. If it is
		1423	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1424	case, if it is C<0>, then the callback receives the number of extents
		1425	instead of the extents themselves (which is unreliable, see below).
		1426
		1427	If an error occurs, the callback receives no arguments. The special
		1428	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1429
		1430	Otherwise, the callback receives an array reference with extent
		1431	structures. Each extent structure is an array reference itself, with the
		1432	following members:
		1433
		1434	[$logical, $physical, $length, $flags]
		1435
		1436	Flags is any combination of the following flag values (typically either C<0>
		1437	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1438
		1439	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1440	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1441	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1442	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1443	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1444	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1445
		1446	At the time of this writing (Linux 3.2), this request is unreliable unless
		1447	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1448	it to return all extents of a range for files with a large number of
		1449	extents. The code (only) works around all these issues if C<$count> is
		1450	C<undef>.
1207		1451
1208	=item aio_group $callback->(...)	1452	=item aio_group $callback->(...)
1209		1453
1210	This is a very special aio request: Instead of doing something, it is a	1454	This is a very special aio request: Instead of doing something, it is a
1211	container for other aio requests, which is useful if you want to bundle	1455	container for other aio requests, which is useful if you want to bundle
…		…
1248	like sleep and file handle readable/writable, the overhead this creates is	1492	like sleep and file handle readable/writable, the overhead this creates is
1249	immense (it blocks a thread for a long time) so do not use this function	1493	immense (it blocks a thread for a long time) so do not use this function
1250	except to put your application under artificial I/O pressure.	1494	except to put your application under artificial I/O pressure.
1251		1495
1252	=back	1496	=back
		1497
		1498
		1499	=head2 IO::AIO::WD - multiple working directories
		1500
		1501	Your process only has one current working directory, which is used by all
		1502	threads. This makes it hard to use relative paths (some other component
		1503	could call C<chdir> at any time, and it is hard to control when the path
		1504	will be used by IO::AIO).
		1505
		1506	One solution for this is to always use absolute paths. This usually works,
		1507	but can be quite slow (the kernel has to walk the whole path on every
		1508	access), and can also be a hassle to implement.
		1509
		1510	Newer POSIX systems have a number of functions (openat, fdopendir,
		1511	futimensat and so on) that make it possible to specify working directories
		1512	per operation.
		1513
		1514	For portability, and because the clowns who "designed", or shall I write,
		1515	perpetrated this new interface were obviously half-drunk, this abstraction
		1516	cannot be perfect, though.
		1517
		1518	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1519	object. This object stores the canonicalised, absolute version of the
		1520	path, and on systems that allow it, also a directory file descriptor.
		1521
		1522	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1523	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1524	object and a pathname instead (or the IO::AIO::WD object alone, which
		1525	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1526	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1527	to that IO::AIO::WD object.
		1528
		1529	For example, to get a wd object for F</etc> and then stat F<passwd>
		1530	inside, you would write:
		1531
		1532	aio_wd "/etc", sub {
		1533	my $etcdir = shift;
		1534
		1535	# although $etcdir can be undef on error, there is generally no reason
		1536	# to check for errors here, as aio_stat will fail with ENOENT
		1537	# when $etcdir is undef.
		1538
		1539	aio_stat [$etcdir, "passwd"], sub {
		1540	# yay
		1541	};
		1542	};
		1543
		1544	The fact that C<aio_wd> is a request and not a normal function shows that
		1545	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1546	which is why it is done asynchronously.
		1547
		1548	To stat the directory obtained with C<aio_wd> above, one could write
		1549	either of the following three request calls:
		1550
		1551	aio_lstat "/etc" , sub { ... # pathname as normal string
		1552	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1553	aio_lstat $wd , sub { ... # shorthand for the previous
		1554
		1555	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1556	object and the pathname string, so you could write the following without
		1557	causing any issues due to C<$path> getting reused:
		1558
		1559	my $path = [$wd, undef];
		1560
		1561	for my $name (qw(abc def ghi)) {
		1562	$path->[1] = $name;
		1563	aio_stat $path, sub {
		1564	# ...
		1565	};
		1566	}
		1567
		1568	There are some caveats: when directories get renamed (or deleted), the
		1569	pathname string doesn't change, so will point to the new directory (or
		1570	nowhere at all), while the directory fd, if available on the system,
		1571	will still point to the original directory. Most functions accepting a
		1572	pathname will use the directory fd on newer systems, and the string on
		1573	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1574	the string form of the pathname.
		1575
		1576	So this functionality is mainly useful to get some protection against
		1577	C<chdir>, to easily get an absolute path out of a relative path for future
		1578	reference, and to speed up doing many operations in the same directory
		1579	(e.g. when stat'ing all files in a directory).
		1580
		1581	The following functions implement this working directory abstraction:
		1582
		1583	=over 4
		1584
		1585	=item aio_wd $pathname, $callback->($wd)
		1586
		1587	Asynchonously canonicalise the given pathname and convert it to an
		1588	IO::AIO::WD object representing it. If possible and supported on the
		1589	system, also open a directory fd to speed up pathname resolution relative
		1590	to this working directory.
		1591
		1592	If something goes wrong, then C<undef> is passwd to the callback instead
		1593	of a working directory object and C<$!> is set appropriately. Since
		1594	passing C<undef> as working directory component of a pathname fails the
		1595	request with C<ENOENT>, there is often no need for error checking in the
		1596	C<aio_wd> callback, as future requests using the value will fail in the
		1597	expected way.
		1598
		1599	=item IO::AIO::CWD
		1600
		1601	This is a compiletime constant (object) that represents the process
		1602	current working directory.
		1603
		1604	Specifying this object as working directory object for a pathname is as if
		1605	the pathname would be specified directly, without a directory object. For
		1606	example, these calls are functionally identical:
		1607
		1608	aio_stat "somefile", sub { ... };
		1609	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1610
		1611	=back
		1612
		1613	To recover the path associated with an IO::AIO::WD object, you can use
		1614	C<aio_realpath>:
		1615
		1616	aio_realpath $wd, sub {
		1617	warn "path is $_[0]\n";
		1618	};
		1619
		1620	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1621	sometimes, fall back to using an absolue path.
1253		1622
1254	=head2 IO::AIO::REQ CLASS	1623	=head2 IO::AIO::REQ CLASS
1255		1624
1256	All non-aggregate C<aio_*> functions return an object of this class when	1625	All non-aggregate C<aio_*> functions return an object of this class when
1257	called in non-void context.	1626	called in non-void context.
…		…
1375		1744
1376	Sets a feeder/generator on this group: every group can have an attached	1745	Sets a feeder/generator on this group: every group can have an attached
1377	generator that generates requests if idle. The idea behind this is that,	1746	generator that generates requests if idle. The idea behind this is that,
1378	although you could just queue as many requests as you want in a group,	1747	although you could just queue as many requests as you want in a group,
1379	this might starve other requests for a potentially long time. For example,	1748	this might starve other requests for a potentially long time. For example,
1380	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1749	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1381	delaying any later requests for a long time.	1750	requests, delaying any later requests for a long time.
1382		1751
1383	To avoid this, and allow incremental generation of requests, you can	1752	To avoid this, and allow incremental generation of requests, you can
1384	instead a group and set a feeder on it that generates those requests. The	1753	instead a group and set a feeder on it that generates those requests. The
1385	feed callback will be called whenever there are few enough (see C<limit>,	1754	feed callback will be called whenever there are few enough (see C<limit>,
1386	below) requests active in the group itself and is expected to queue more	1755	below) requests active in the group itself and is expected to queue more
…		…
1418	The default value for the limit is C<0>, but note that setting a feeder	1787	The default value for the limit is C<0>, but note that setting a feeder
1419	automatically bumps it up to C<2>.	1788	automatically bumps it up to C<2>.
1420		1789
1421	=back	1790	=back
1422		1791
		1792
1423	=head2 SUPPORT FUNCTIONS	1793	=head2 SUPPORT FUNCTIONS
1424		1794
1425	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1795	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1426		1796
1427	=over 4	1797	=over 4
…		…
1435		1805
1436	See C<poll_cb> for an example.	1806	See C<poll_cb> for an example.
1437		1807
1438	=item IO::AIO::poll_cb	1808	=item IO::AIO::poll_cb
1439		1809
1440	Process some outstanding events on the result pipe. You have to call	1810	Process some requests that have reached the result phase (i.e. they have
		1811	been executed but the results are not yet reported). You have to call
		1812	this "regularly" to finish outstanding requests.
		1813
1441	this regularly. Returns C<0> if all events could be processed (or there	1814	Returns C<0> if all events could be processed (or there were no
1442	were no events to process), or C<-1> if it returned earlier for whatever	1815	events to process), or C<-1> if it returned earlier for whatever
1443	reason. Returns immediately when no events are outstanding. The amount of	1816	reason. Returns immediately when no events are outstanding. The amount
1444	events processed depends on the settings of C<IO::AIO::max_poll_req> and	1817	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
1445	C<IO::AIO::max_poll_time>.	1818	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
1446		1819
1447	If not all requests were processed for whatever reason, the filehandle	1820	If not all requests were processed for whatever reason, the poll file
1448	will still be ready when C<poll_cb> returns, so normally you don't have to	1821	descriptor will still be ready when C<poll_cb> returns, so normally you
1449	do anything special to have it called later.	1822	don't have to do anything special to have it called later.
1450		1823
1451	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes	1824	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
1452	ready, it can be beneficial to call this function from loops which submit	1825	ready, it can be beneficial to call this function from loops which submit
1453	a lot of requests, to make sure the results get processed when they become	1826	a lot of requests, to make sure the results get processed when they become
1454	available and not just when the loop is finished and the event loop takes	1827	available and not just when the loop is finished and the event loop takes
…		…
1463	poll => 'r', async => 1,	1836	poll => 'r', async => 1,
1464	cb => \&IO::AIO::poll_cb);	1837	cb => \&IO::AIO::poll_cb);
1465		1838
1466	=item IO::AIO::poll_wait	1839	=item IO::AIO::poll_wait
1467		1840
1468	If there are any outstanding requests and none of them in the result	1841	Wait until either at least one request is in the result phase or no
1469	phase, wait till the result filehandle becomes ready for reading (simply	1842	requests are outstanding anymore.
1470	does a C<select> on the filehandle. This is useful if you want to	1843
1471	synchronously wait for some requests to finish).	1844	This is useful if you want to synchronously wait for some requests to
		1845	become ready, without actually handling them.
1472		1846
1473	See C<nreqs> for an example.	1847	See C<nreqs> for an example.
1474		1848
1475	=item IO::AIO::poll	1849	=item IO::AIO::poll
1476		1850
…		…
1487		1861
1488	Strictly equivalent to:	1862	Strictly equivalent to:
1489		1863
1490	IO::AIO::poll_wait, IO::AIO::poll_cb	1864	IO::AIO::poll_wait, IO::AIO::poll_cb
1491	while IO::AIO::nreqs;	1865	while IO::AIO::nreqs;
		1866
		1867	This function can be useful at program aborts, to make sure outstanding
		1868	I/O has been done (C<IO::AIO> uses an C<END> block which already calls
		1869	this function on normal exits), or when you are merely using C<IO::AIO>
		1870	for its more advanced functions, rather than for async I/O, e.g.:
		1871
		1872	my ($dirs, $nondirs);
		1873	IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
		1874	IO::AIO::flush;
		1875	# $dirs, $nondirs are now set
1492		1876
1493	=item IO::AIO::max_poll_reqs $nreqs	1877	=item IO::AIO::max_poll_reqs $nreqs
1494		1878
1495	=item IO::AIO::max_poll_time $seconds	1879	=item IO::AIO::max_poll_time $seconds
1496		1880
…		…
1523	poll => 'r', nice => 1,	1907	poll => 'r', nice => 1,
1524	cb => &IO::AIO::poll_cb);	1908	cb => &IO::AIO::poll_cb);
1525		1909
1526	=back	1910	=back
1527		1911
		1912
1528	=head3 CONTROLLING THE NUMBER OF THREADS	1913	=head3 CONTROLLING THE NUMBER OF THREADS
1529		1914
1530	=over	1915	=over
1531		1916
1532	=item IO::AIO::min_parallel $nthreads	1917	=item IO::AIO::min_parallel $nthreads
…		…
1597		1982
1598	This is a very bad function to use in interactive programs because it	1983	This is a very bad function to use in interactive programs because it
1599	blocks, and a bad way to reduce concurrency because it is inexact: Better	1984	blocks, and a bad way to reduce concurrency because it is inexact: Better
1600	use an C<aio_group> together with a feed callback.	1985	use an C<aio_group> together with a feed callback.
1601		1986
1602	It's main use is in scripts without an event loop - when you want to stat	1987	Its main use is in scripts without an event loop - when you want to stat
1603	a lot of files, you can write somehting like this:	1988	a lot of files, you can write something like this:
1604		1989
1605	IO::AIO::max_outstanding 32;	1990	IO::AIO::max_outstanding 32;
1606		1991
1607	for my $path (...) {	1992	for my $path (...) {
1608	aio_stat $path , ...;	1993	aio_stat $path , ...;
…		…
1619	The default value for C<max_outstanding> is very large, so there is no	2004	The default value for C<max_outstanding> is very large, so there is no
1620	practical limit on the number of outstanding requests.	2005	practical limit on the number of outstanding requests.
1621		2006
1622	=back	2007	=back
1623		2008
		2009
1624	=head3 STATISTICAL INFORMATION	2010	=head3 STATISTICAL INFORMATION
1625		2011
1626	=over	2012	=over
1627		2013
1628	=item IO::AIO::nreqs	2014	=item IO::AIO::nreqs
…		…
1645	Returns the number of requests currently in the pending state (executed,	2031	Returns the number of requests currently in the pending state (executed,
1646	but not yet processed by poll_cb).	2032	but not yet processed by poll_cb).
1647		2033
1648	=back	2034	=back
1649		2035
		2036
		2037	=head3 SUBSECOND STAT TIME ACCESS
		2038
		2039	Both C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> functions can
		2040	generally find access/modification and change times with subsecond time
		2041	accuracy of the system supports it, but perl's built-in functions only
		2042	return the integer part.
		2043
		2044	The following functions return the timestamps of the most recent
		2045	stat with subsecond precision on most systems and work both after
		2046	C<aio_stat>/C<aio_lstat> and perl's C<stat>/C<lstat> calls. Their return
		2047	value is only meaningful after a successful C<stat>/C<lstat> call, or
		2048	during/after a successful C<aio_stat>/C<aio_lstat> callback.
		2049
		2050	This is similar to the L<Time::HiRes> C<stat> functions, but can return
		2051	full resolution without rounding and work with standard perl C<stat>,
		2052	alleviating the need to call the special C<Time::HiRes> functions, which
		2053	do not act like their perl counterparts.
		2054
		2055	On operating systems or file systems where subsecond time resolution is
		2056	not supported or could not be detected, a fractional part of C<0> is
		2057	returned, so it is always safe to call these functions.
		2058
		2059	=over 4
		2060
		2061	=item $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
		2062
		2063	Return the access, modication, change or birth time, respectively,
		2064	including fractional part. Due to the limited precision of floating point,
		2065	the accuracy on most platforms is only a bit better than milliseconds
		2066	for times around now - see the I<nsec> function family, below, for full
		2067	accuracy.
		2068
		2069	File birth time is only available when the OS and perl support it (on
		2070	FreeBSD and NetBSD at the time of this writing, although support is
		2071	adaptive, so if your OS/perl gains support, IO::AIO can take avdantage of
		2072	it). On systems where it isn't available, C<0> is currently returned, but
		2073	this might change to C<undef> in a future version.
		2074
		2075	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
		2076
		2077	Returns access, modification, change and birth time all in one go, and
		2078	maybe more times in the future version.
		2079
		2080	=item $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
		2081
		2082	Return the fractional access, modifcation, change or birth time, in nanoseconds,
		2083	as an integer in the range C<0> to C<999999999>.
		2084
		2085	Note that no accessors are provided for access, modification and
		2086	change times - you need to get those from C<stat _> if required (C<int
		2087	IO::AIO::st_atime> and so on will I<not> generally give you the correct
		2088	value).
		2089
		2090	=item $seconds = IO::AIO::st_btimesec
		2091
		2092	The (integral) seconds part of the file birth time, if available.
		2093
		2094	=item ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
		2095
		2096	Like the functions above, but returns all four times in one go (and maybe
		2097	more in future versions).
		2098
		2099	=item $counter = IO::AIO::st_gen
		2100
		2101	Returns the generation counter (in practice this is just a random number)
		2102	of the file. This is only available on platforms which have this member in
		2103	their C<struct stat> (most BSDs at the time of this writing) and generally
		2104	only to the root usert. If unsupported, C<0> is returned, but this might
		2105	change to C<undef> in a future version.
		2106
		2107	=back
		2108
		2109	Example: print the high resolution modification time of F</etc>, using
		2110	C<stat>, and C<IO::AIO::aio_stat>.
		2111
		2112	if (stat "/etc") {
		2113	printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
		2114	}
		2115
		2116	IO::AIO::aio_stat "/etc", sub {
		2117	$_[0]
		2118	and return;
		2119
		2120	printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
		2121	};
		2122
		2123	IO::AIO::flush;
		2124
		2125	Output of the awbove on my system, showing reduced and full accuracy:
		2126
		2127	stat(/etc) mtime: 1534043702.020808
		2128	aio_stat(/etc) mtime: 1534043702.020807792
		2129
		2130
1650	=head3 MISCELLANEOUS FUNCTIONS	2131	=head3 MISCELLANEOUS FUNCTIONS
1651		2132
1652	IO::AIO implements some functions that might be useful, but are not	2133	IO::AIO implements some functions that are useful when you want to use
1653	asynchronous.	2134	some "Advanced I/O" function not available to in Perl, without going the
		2135	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2136	counterpart.
1654		2137
1655	=over 4	2138	=over 4
		2139
		2140	=item $numfd = IO::AIO::get_fdlimit
		2141
		2142	This function is I<EXPERIMENTAL> and subject to change.
		2143
		2144	Tries to find the current file descriptor limit and returns it, or
		2145	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2146	the highest valid file descriptor number.
		2147
		2148	=item IO::AIO::min_fdlimit [$numfd]
		2149
		2150	This function is I<EXPERIMENTAL> and subject to change.
		2151
		2152	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2153	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2154	is missing, it will try to set a very high limit, although this is not
		2155	recommended when you know the actual minimum that you require.
		2156
		2157	If the limit cannot be raised enough, the function makes a best-effort
		2158	attempt to increase the limit as much as possible, using various
		2159	tricks, while still failing. You can query the resulting limit using
		2160	C<IO::AIO::get_fdlimit>.
		2161
		2162	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2163	true.
1656		2164
1657	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2165	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1658		2166
1659	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,	2167	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1660	but is blocking (this makes most sense if you know the input data is	2168	but is blocking (this makes most sense if you know the input data is
…		…
1665		2173
1666	=item IO::AIO::fadvise $fh, $offset, $len, $advice	2174	=item IO::AIO::fadvise $fh, $offset, $len, $advice
1667		2175
1668	Simply calls the C<posix_fadvise> function (see its	2176	Simply calls the C<posix_fadvise> function (see its
1669	manpage for details). The following advice constants are	2177	manpage for details). The following advice constants are
1670	avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,	2178	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1671	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,	2179	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1672	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.	2180	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1673		2181
1674	On systems that do not implement C<posix_fadvise>, this function returns	2182	On systems that do not implement C<posix_fadvise>, this function returns
1675	ENOSYS, otherwise the return value of C<posix_fadvise>.	2183	ENOSYS, otherwise the return value of C<posix_fadvise>.
1676		2184
1677	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2185	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1678		2186
1679	Simply calls the C<posix_madvise> function (see its	2187	Simply calls the C<posix_madvise> function (see its
1680	manpage for details). The following advice constants are	2188	manpage for details). The following advice constants are
1681	avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2189	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1682	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2190	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2191	C<IO::AIO::MADV_DONTNEED>.
		2192
		2193	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2194	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2195	will be reduced to fit into the C<$scalar>.
1683		2196
1684	On systems that do not implement C<posix_madvise>, this function returns	2197	On systems that do not implement C<posix_madvise>, this function returns
1685	ENOSYS, otherwise the return value of C<posix_madvise>.	2198	ENOSYS, otherwise the return value of C<posix_madvise>.
1686		2199
1687	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2200	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1688		2201
1689	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed	2202	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1690	$scalar (see its manpage for details). The following protect	2203	$scalar (see its manpage for details). The following protect
1691	constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2204	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1692	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2205	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2206
		2207	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2208	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2209	will be reduced to fit into the C<$scalar>.
1693		2210
1694	On systems that do not implement C<mprotect>, this function returns	2211	On systems that do not implement C<mprotect>, this function returns
1695	ENOSYS, otherwise the return value of C<mprotect>.	2212	ENOSYS, otherwise the return value of C<mprotect>.
1696		2213
1697	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2214	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1698		2215
1699	Memory-maps a file (or anonymous memory range) and attaches it to the	2216	Memory-maps a file (or anonymous memory range) and attaches it to the
1700	given C<$scalar>, which will act like a string scalar.	2217	given C<$scalar>, which will act like a string scalar. Returns true on
		2218	success, and false otherwise.
1701		2219
		2220	The scalar must exist, but its contents do not matter - this means you
		2221	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2222	the scalar first.
		2223
1702	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2224	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1703	change the string length, and most read-only operations such as copying it	2225	which don't change the string length, and most read-only operations such
1704	or searching it with regexes and so on.	2226	as copying it or searching it with regexes and so on.
1705		2227
1706	Anything else is unsafe and will, at best, result in memory leaks.	2228	Anything else is unsafe and will, at best, result in memory leaks.
1707		2229
1708	The memory map associated with the C<$scalar> is automatically removed	2230	The memory map associated with the C<$scalar> is automatically removed
1709	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2231	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1710	C<IO::AIO::munmap> functions are called.	2232	or C<IO::AIO::munmap> functions are called on it.
1711		2233
1712	This calls the C<mmap>(2) function internally. See your system's manual	2234	This calls the C<mmap>(2) function internally. See your system's manual
1713	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2235	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1714		2236
1715	The C<$length> must be larger than zero and smaller than the actual	2237	The C<$length> must be larger than zero and smaller than the actual
1716	filesize.	2238	filesize.
1717		2239
1718	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2240	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1719	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2241	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1720		2242
1721	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2243	C<$flags> can be a combination of
1722	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2244	C<IO::AIO::MAP_SHARED> or
1723	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2245	C<IO::AIO::MAP_PRIVATE>,
		2246	or a number of system-specific flags (when not available, the are C<0>):
1724	(which is set to C<MAP_ANON> if your system only provides this	2247	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1725	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2248	C<IO::AIO::MAP_LOCKED>,
1726	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2249	C<IO::AIO::MAP_NORESERVE>,
		2250	C<IO::AIO::MAP_POPULATE>,
1727	C<IO::AIO::MAP_NONBLOCK>	2251	C<IO::AIO::MAP_NONBLOCK>,
		2252	C<IO::AIO::MAP_FIXED>,
		2253	C<IO::AIO::MAP_GROWSDOWN>,
		2254	C<IO::AIO::MAP_32BIT>,
		2255	C<IO::AIO::MAP_HUGETLB> or
		2256	C<IO::AIO::MAP_STACK>.
1728		2257
1729	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2258	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1730		2259
1731	C<$offset> is the offset from the start of the file - it generally must be	2260	C<$offset> is the offset from the start of the file - it generally must be
1732	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.	2261	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
…		…
1746		2275
1747	=item IO::AIO::munmap $scalar	2276	=item IO::AIO::munmap $scalar
1748		2277
1749	Removes a previous mmap and undefines the C<$scalar>.	2278	Removes a previous mmap and undefines the C<$scalar>.
1750		2279
		2280	=item IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[, $new_address = 0]
		2281
		2282	Calls the Linux-specific mremap(2) system call. The C<$scalar> must have
		2283	been mapped by C<IO::AIO::mmap>, and C<$flags> must currently either be
		2284	C<0> or C<IO::AIO::MREMAP_MAYMOVE>.
		2285
		2286	Returns true if successful, and false otherwise. If the underlying mmapped
		2287	region has changed address, then the true value has the numerical value
		2288	C<1>, otherwise it has the numerical value C<0>:
		2289
		2290	my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
		2291	or die "mremap: $!";
		2292
		2293	if ($success*1) {
		2294	warn "scalar has chanegd address in memory\n";
		2295	}
		2296
		2297	C<IO::AIO::MREMAP_FIXED> and the C<$new_address> argument are currently
		2298	implemented, but not supported and might go away in a future version.
		2299
		2300	On systems where this call is not supported or is not emulated, this call
		2301	returns falls and sets C<$!> to C<ENOSYS>.
		2302
		2303	=item IO::AIO::mlockall $flags
		2304
		2305	Calls the C<eio_mlockall_sync> function, which is like C<aio_mlockall>,
		2306	but is blocking.
		2307
1751	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2308	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1752		2309
1753	Calls the C<munlock> function, undoing the effects of a previous	2310	Calls the C<munlock> function, undoing the effects of a previous
1754	C<aio_mlock> call (see its description for details).	2311	C<aio_mlock> call (see its description for details).
1755		2312
…		…
1757		2314
1758	Calls the C<munlockall> function.	2315	Calls the C<munlockall> function.
1759		2316
1760	On systems that do not implement C<munlockall>, this function returns	2317	On systems that do not implement C<munlockall>, this function returns
1761	ENOSYS, otherwise the return value of C<munlockall>.	2318	ENOSYS, otherwise the return value of C<munlockall>.
		2319
		2320	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2321
		2322	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2323	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2324	should be the file offset.
		2325
		2326	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2327	silently corrupt the data in this case.
		2328
		2329	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2330	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2331	C<IO::AIO::SPLICE_F_GIFT>.
		2332
		2333	See the C<splice(2)> manpage for details.
		2334
		2335	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2336
		2337	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2338	description for C<IO::AIO::splice> above for details.
		2339
		2340	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2341
		2342	Attempts to query or change the pipe buffer size. Obviously works only
		2343	on pipes, and currently works only on GNU/Linux systems, and fails with
		2344	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2345	size on other systems, drop me a note.
		2346
		2347	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2348
		2349	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2350	C<$flags> is missing or C<0>, then this should be the same as a call to
		2351	perl's built-in C<pipe> function and create a new pipe, and works on
		2352	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2353	(..., 4096, O_BINARY)>.
		2354
		2355	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2356	the given flags (Linux 2.6.27, glibc 2.9).
		2357
		2358	On success, the read and write file handles are returned.
		2359
		2360	On error, nothing will be returned. If the pipe2 syscall is missing and
		2361	C<$flags> is non-zero, fails with C<ENOSYS>.
		2362
		2363	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2364	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2365	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2366
		2367	Example: create a pipe race-free w.r.t. threads and fork:
		2368
		2369	my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
		2370	or die "pipe2: $!\n";
		2371
		2372	=item $fh = IO::AIO::eventfd [$initval, [$flags]]
		2373
		2374	This is a direct interface to the Linux L<eventfd(2)> system call. The
		2375	(unhelpful) defaults for C<$initval> and C<$flags> are C<0> for both.
		2376
		2377	On success, the new eventfd filehandle is returned, otherwise returns
		2378	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2379
		2380	Please refer to L<eventfd(2)> for more info on this call.
		2381
		2382	The following symbol flag values are available: C<IO::AIO::EFD_CLOEXEC>,
		2383	C<IO::AIO::EFD_NONBLOCK> and C<IO::AIO::EFD_SEMAPHORE> (Linux 2.6.30).
		2384
		2385	Example: create a new eventfd filehandle:
		2386
		2387	$fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
		2388	or die "eventfd: $!\n";
		2389
		2390	=item $fh = IO::AIO::timerfd_create $clockid[, $flags]
		2391
		2392	This is a direct interface to the Linux L<timerfd_create(2)> system call. The
		2393	(unhelpful) default for C<$flags> is C<0>.
		2394
		2395	On success, the new timerfd filehandle is returned, otherwise returns
		2396	C<undef>. If the eventfd syscall is missing, fails with C<ENOSYS>.
		2397
		2398	Please refer to L<timerfd_create(2)> for more info on this call.
		2399
		2400	The following C<$clockid> values are
		2401	available: C<IO::AIO::CLOCK_REALTIME>, C<IO::AIO::CLOCK_MONOTONIC>
		2402	C<IO::AIO::CLOCK_CLOCK_BOOTTIME> (Linux 3.15)
		2403	C<IO::AIO::CLOCK_CLOCK_REALTIME_ALARM> (Linux 3.11) and
		2404	C<IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM> (Linux 3.11).
		2405
		2406	The following C<$flags> values are available (Linux
		2407	2.6.27): C<IO::AIO::TFD_NONBLOCK> and C<IO::AIO::TFD_CLOEXEC>.
		2408
		2409	Example: create a new timerfd and set it to one-second repeated alarms,
		2410	then wait for two alarms:
		2411
		2412	my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
		2413	or die "timerfd_create: $!\n";
		2414
		2415	defined IO::AIO::timerfd_settime $fh, 0, 1, 1
		2416	or die "timerfd_settime: $!\n";
		2417
		2418	for (1..2) {
		2419	8 == sysread $fh, my $buf, 8
		2420	or die "timerfd read failure\n";
		2421
		2422	printf "number of expirations (likely 1): %d\n",
		2423	unpack "Q", $buf;
		2424	}
		2425
		2426	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
		2427
		2428	This is a direct interface to the Linux L<timerfd_settime(2)> system
		2429	call. Please refer to its manpage for more info on this call.
		2430
		2431	The new itimerspec is specified using two (possibly fractional) second
		2432	values, C<$new_interval> and C<$new_value>).
		2433
		2434	On success, the current interval and value are returned (as per
		2435	C<timerfd_gettime>). On failure, the empty list is returned.
		2436
		2437	The following C<$flags> values are
		2438	available: C<IO::AIO::TFD_TIMER_ABSTIME> and
		2439	C<IO::AIO::TFD_TIMER_CANCEL_ON_SET>.
		2440
		2441	See C<IO::AIO::timerfd_create> for a full example.
		2442
		2443	=item ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
		2444
		2445	This is a direct interface to the Linux L<timerfd_gettime(2)> system
		2446	call. Please refer to its manpage for more info on this call.
		2447
		2448	On success, returns the current values of interval and value for the given
		2449	timerfd (as potentially fractional second values). On failure, the empty
		2450	list is returned.
1762		2451
1763	=back	2452	=back
1764		2453
1765	=cut	2454	=cut
1766		2455
…		…
1804	=head2 FORK BEHAVIOUR	2493	=head2 FORK BEHAVIOUR
1805		2494
1806	Usage of pthreads in a program changes the semantics of fork	2495	Usage of pthreads in a program changes the semantics of fork
1807	considerably. Specifically, only async-safe functions can be called after	2496	considerably. Specifically, only async-safe functions can be called after
1808	fork. Perl doesn't know about this, so in general, you cannot call fork	2497	fork. Perl doesn't know about this, so in general, you cannot call fork
1809	with defined behaviour in perl. IO::AIO uses pthreads, so this applies,	2498	with defined behaviour in perl if pthreads are involved. IO::AIO uses
1810	but many other extensions and (for inexplicable reasons) perl itself often	2499	pthreads, so this applies, but many other extensions and (for inexplicable
1811	is linked against pthreads, so this limitation applies.	2500	reasons) perl itself often is linked against pthreads, so this limitation
		2501	applies to quite a lot of perls.
1812		2502
1813	Some operating systems have extensions that allow safe use of fork, and	2503	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1814	this module should do "the right thing" on those, and tries on others. At	2504	only works in the process that loaded it. Forking is fully supported, but
1815	the time of this writing (2011) only GNU/Linux supports these extensions	2505	using IO::AIO in the child is not.
1816	to POSIX.	2506
		2507	You might get around by not I<using> IO::AIO before (or after)
		2508	forking. You could also try to call the L<IO::AIO::reinit> function in the
		2509	child:
		2510
		2511	=over 4
		2512
		2513	=item IO::AIO::reinit
		2514
		2515	Abandons all current requests and I/O threads and simply reinitialises all
		2516	data structures. This is not an operation supported by any standards, but
		2517	happens to work on GNU/Linux and some newer BSD systems.
		2518
		2519	The only reasonable use for this function is to call it after forking, if
		2520	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2521	the process will result in undefined behaviour. Calling it at any time
		2522	will also result in any undefined (by POSIX) behaviour.
		2523
		2524	=back
		2525
		2526	=head2 LINUX-SPECIFIC CALLS
		2527
		2528	When a call is documented as "linux-specific" then this means it
		2529	originated on GNU/Linux. C<IO::AIO> will usually try to autodetect the
		2530	availability and compatibility of such calls regardless of the platform
		2531	it is compiled on, so platforms such as FreeBSD which often implement
		2532	these calls will work. When in doubt, call them and see if they fail wth
		2533	C<ENOSYS>.
1817		2534
1818	=head2 MEMORY USAGE	2535	=head2 MEMORY USAGE
1819		2536
1820	Per-request usage:	2537	Per-request usage:
1821		2538
…		…
1834	temporary buffers, and each thread requires a stack and other data	2551	temporary buffers, and each thread requires a stack and other data
1835	structures (usually around 16k-128k, depending on the OS).	2552	structures (usually around 16k-128k, depending on the OS).
1836		2553
1837	=head1 KNOWN BUGS	2554	=head1 KNOWN BUGS
1838		2555
1839	Known bugs will be fixed in the next release.	2556	Known bugs will be fixed in the next release :)
		2557
		2558	=head1 KNOWN ISSUES
		2559
		2560	Calls that try to "import" foreign memory areas (such as C<IO::AIO::mmap>
		2561	or C<IO::AIO::aio_slurp>) do not work with generic lvalues, such as
		2562	non-created hash slots or other scalars I didn't think of. It's best to
		2563	avoid such and either use scalar variables or making sure that the scalar
		2564	exists (e.g. by storing C<undef>) and isn't "funny" (e.g. tied).
		2565
		2566	I am not sure anything can be done about this, so this is considered a
		2567	known issue, rather than a bug.
1840		2568
1841	=head1 SEE ALSO	2569	=head1 SEE ALSO
1842		2570
1843	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a	2571	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
1844	more natural syntax.	2572	more natural syntax.

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