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Revision 1.208 by root, Mon Sep 26 20:19:08 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 = '4.0';	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	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
178	aio_fsync aio_syncfs 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
185	aio_wd);	189	aio_wd);
186		190
187	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	191	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
188	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	192	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
189	min_parallel max_parallel max_idle idle_timeout	193	min_parallel max_parallel max_idle idle_timeout
190	nreqs nready npending nthreads	194	nreqs nready npending nthreads
191	max_poll_time max_poll_reqs	195	max_poll_time max_poll_reqs
192	sendfile fadvise madvise	196	sendfile fadvise madvise
193	mmap munmap munlock munlockall);	197	mmap munmap mremap munlock munlockall);
194		198
195	push @AIO_REQ, qw(aio_busy); # not exported	199	push @AIO_REQ, qw(aio_busy); # not exported
196		200
197	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	201	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
198		202
…		…
202		206
203	=head1 FUNCTIONS	207	=head1 FUNCTIONS
204		208
205	=head2 QUICK OVERVIEW	209	=head2 QUICK OVERVIEW
206		210
207	This section simply lists the prototypes of the most important functions	211	This section simply lists the prototypes most of the functions for
208	for quick reference. See the following sections for function-by-function	212	quick reference. See the following sections for function-by-function
209	documentation.	213	documentation.
210		214
211	aio_wd $pathname, $callback->($wd)	215	aio_wd $pathname, $callback->($wd)
212	aio_open $pathname, $flags, $mode, $callback->($fh)	216	aio_open $pathname, $flags, $mode, $callback->($fh)
213	aio_close $fh, $callback->($status)	217	aio_close $fh, $callback->($status)
		218	aio_seek $fh,$offset,$whence, $callback->($offs)
214	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	219	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
215	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	220	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
216	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	221	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
217	aio_readahead $fh,$offset,$length, $callback->($retval)	222	aio_readahead $fh,$offset,$length, $callback->($retval)
218	aio_stat $fh_or_path, $callback->($status)	223	aio_stat $fh_or_path, $callback->($status)
219	aio_lstat $fh, $callback->($status)	224	aio_lstat $fh, $callback->($status)
220	aio_statvfs $fh_or_path, $callback->($statvfs)	225	aio_statvfs $fh_or_path, $callback->($statvfs)
221	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	226	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
222	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)
223	aio_truncate $fh_or_path, $offset, $callback->($status)	229	aio_truncate $fh_or_path, $offset, $callback->($status)
224	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)
225	aio_unlink $pathname, $callback->($status)	232	aio_unlink $pathname, $callback->($status)
226	aio_mknod $path, $mode, $dev, $callback->($status)	233	aio_mknod $pathname, $mode, $dev, $callback->($status)
227	aio_link $srcpath, $dstpath, $callback->($status)	234	aio_link $srcpath, $dstpath, $callback->($status)
228	aio_symlink $srcpath, $dstpath, $callback->($status)	235	aio_symlink $srcpath, $dstpath, $callback->($status)
229	aio_readlink $path, $callback->($link)	236	aio_readlink $pathname, $callback->($link)
230	aio_realpath $path, $callback->($link)	237	aio_realpath $pathname, $callback->($path)
231	aio_rename $srcpath, $dstpath, $callback->($status)	238	aio_rename $srcpath, $dstpath, $callback->($status)
		239	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
232	aio_mkdir $pathname, $mode, $callback->($status)	240	aio_mkdir $pathname, $mode, $callback->($status)
233	aio_rmdir $pathname, $callback->($status)	241	aio_rmdir $pathname, $callback->($status)
234	aio_readdir $pathname, $callback->($entries)	242	aio_readdir $pathname, $callback->($entries)
235	aio_readdirx $pathname, $flags, $callback->($entries, $flags)	243	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
236	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST	244	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
237	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)
238	aio_load $path, $data, $callback->($status)	247	aio_load $pathname, $data, $callback->($status)
239	aio_copy $srcpath, $dstpath, $callback->($status)	248	aio_copy $srcpath, $dstpath, $callback->($status)
240	aio_move $srcpath, $dstpath, $callback->($status)	249	aio_move $srcpath, $dstpath, $callback->($status)
241	aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
242	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)
243	aio_sync $callback->($status)	253	aio_sync $callback->($status)
244	aio_syncfs $fh, $callback->($status)	254	aio_syncfs $fh, $callback->($status)
245	aio_fsync $fh, $callback->($status)	255	aio_fsync $fh, $callback->($status)
246	aio_fdatasync $fh, $callback->($status)	256	aio_fdatasync $fh, $callback->($status)
247	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	257	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
248	aio_pathsync $path, $callback->($status)	258	aio_pathsync $pathname, $callback->($status)
249	aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	259	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
250	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)	260	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
251	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	261	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
252	aio_mlockall $flags, $callback->($status)	262	aio_mlockall $flags, $callback->($status)
253	aio_group $callback->(...)	263	aio_group $callback->(...)
254	aio_nop $callback->()	264	aio_nop $callback->()
…		…
268	IO::AIO::idle_timeout $seconds	278	IO::AIO::idle_timeout $seconds
269	IO::AIO::max_outstanding $maxreqs	279	IO::AIO::max_outstanding $maxreqs
270	IO::AIO::nreqs	280	IO::AIO::nreqs
271	IO::AIO::nready	281	IO::AIO::nready
272	IO::AIO::npending	282	IO::AIO::npending
		283	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		284	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
273		285
274	IO::AIO::sendfile $ofh, $ifh, $offset, $count	286	IO::AIO::sendfile $ofh, $ifh, $offset, $count
275	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]
276	IO::AIO::madvise $scalar, $offset, $length, $advice	291	IO::AIO::madvise $scalar, $offset, $length, $advice
277	IO::AIO::mprotect $scalar, $offset, $length, $protect	292	IO::AIO::mprotect $scalar, $offset, $length, $protect
278	IO::AIO::munlock $scalar, $offset = 0, $length = undef	293	IO::AIO::munlock $scalar, $offset = 0, $length = undef
279	IO::AIO::munlockall	294	IO::AIO::munlockall
280		295
281	=head2 AIO REQUEST FUNCTIONS	296	=head2 API NOTES
282		297
283	All the C<aio_*> calls are more or less thin wrappers around the syscall	298	All the C<aio_*> calls are more or less thin wrappers around the syscall
284	with the same name (sans C<aio_>). The arguments are similar or identical,	299	with the same name (sans C<aio_>). The arguments are similar or identical,
285	and they all accept an additional (and optional) C<$callback> argument	300	and they all accept an additional (and optional) C<$callback> argument
286	which must be a code reference. This code reference will get called with	301	which must be a code reference. This code reference will be called after
287	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	302	the syscall has been executed in an asynchronous fashion. The results
288	perl, which usually delivers "false") as its sole argument after the given	303	of the request will be passed as arguments to the callback (and, if an
289	syscall has been executed asynchronously.	304	error occured, in C<$!>) - 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>.
290		310
291	All functions expecting a filehandle keep a copy of the filehandle	311	All functions expecting a filehandle keep a copy of the filehandle
292	internally until the request has finished.	312	internally until the request has finished.
293		313
294	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
295	further manipulation of those requests while they are in-flight.	315	further manipulation of those requests while they are in-flight.
296		316
297	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
298	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
299	request is being executed, the current working directory could have	319	current working directory could have changed. Alternatively, you can
300	changed. Alternatively, you can make sure that you never change the	320	make sure that you never change the current working directory anywhere
301	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
302	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.
303		325
304	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
305	in filenames you got from outside (command line, readdir etc.) without	327	in filenames you got from outside (command line, readdir etc.) without
306	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
307	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
308	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
309	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.
310		333
311	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
312	handles correctly whether it is set or not.	335	handles correctly whether it is set or not.
		336
		337	=head2 AIO REQUEST FUNCTIONS
313		338
314	=over 4	339	=over 4
315		340
316	=item $prev_pri = aioreq_pri [$pri]	341	=item $prev_pri = aioreq_pri [$pri]
317		342
…		…
347		372
348		373
349	=item aio_open $pathname, $flags, $mode, $callback->($fh)	374	=item aio_open $pathname, $flags, $mode, $callback->($fh)
350		375
351	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
352	created filehandle for the file.	377	created filehandle for the file (or C<undef> in case of an error).
353		378
354	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,
355	for an explanation.	380	for an explanation.
356		381
357	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
…		…
380	following POSIX and non-POSIX constants are available (missing ones on	405	following POSIX and non-POSIX constants are available (missing ones on
381	your system are, as usual, C<0>):	406	your system are, as usual, C<0>):
382		407
383	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>,
384	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>,
385	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>.
386		411
387		412
388	=item aio_close $fh, $callback->($status)	413	=item aio_close $fh, $callback->($status)
389		414
390	Asynchronously close a file and call the callback with the result	415	Asynchronously close a file and call the callback with the result
…		…
400	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
401	free for reuse until the perl filehandle is closed.	426	free for reuse until the perl filehandle is closed.
402		427
403	=cut	428	=cut
404		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
405	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
406		451
407	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	452	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
408		453
409	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
410	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
411	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
412	error, just like the syscall).	457	error, just like the syscall).
413		458
414	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
415	offset plus the actual number of bytes read.	460	offset plus the actual number of bytes read.
416		461
…		…
474	As native sendfile syscalls (as practically any non-POSIX interface hacked	519	As native sendfile syscalls (as practically any non-POSIX interface hacked
475	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
476	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
477	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,
478	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> -
479	fewre bytes than expected might have been transferred.	524	fewer bytes than expected might have been transferred.
480		525
481		526
482	=item aio_readahead $fh,$offset,$length, $callback->($retval)	527	=item aio_readahead $fh,$offset,$length, $callback->($retval)
483		528
484	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
…		…
488	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
489	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
490	(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
491	file. The current file offset of the file is left unchanged.	536	file. The current file offset of the file is left unchanged.
492		537
493	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
494	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.
495		540
496		541
497	=item aio_stat $fh_or_path, $callback->($status)	542	=item aio_stat $fh_or_path, $callback->($status)
498		543
499	=item aio_lstat $fh, $callback->($status)	544	=item aio_lstat $fh, $callback->($status)
500		545
501	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
502	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
503	or C<-s _> etc...	548	using C<stat _> or C<-s _> and other tests (with the exception of C<-B>
		549	and C<-T>).
504		550
505	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,
506	for an explanation.	552	for an explanation.
507		553
508	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
…		…
515	behaviour).	561	behaviour).
516		562
517	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>,
518	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>,
519	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>.
520		569
521	Example: Print the length of F</etc/passwd>:	570	Example: Print the length of F</etc/passwd>:
522		571
523	aio_stat "/etc/passwd", sub {	572	aio_stat "/etc/passwd", sub {
524	$_[0] and die "stat failed: $!";	573	$_[0] and die "stat failed: $!";
…		…
568	namemax => 255,	617	namemax => 255,
569	frsize => 1024,	618	frsize => 1024,
570	fsid => 1810	619	fsid => 1810
571	}	620	}
572		621
573
574	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	622	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
575		623
576	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
577	and $mtime being undef). Fractional times are supported if the underlying	625	and $mtime being undef). Fractional times are supported if the underlying
578	syscalls support them.	626	syscalls support them.
579		627
580	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,
581	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)
582	otherwise returns ENOSYS, so this is not portable.	630	or futimes(2) if available, otherwise returns ENOSYS, so this is not
		631	portable.
583		632
584	Examples:	633	Examples:
585		634
586	# set atime and mtime to current time (basically touch(1)):	635	# set atime and mtime to current time (basically touch(1)):
587	aio_utime "path", undef, undef;	636	aio_utime "path", undef, undef;
…		…
605	=item aio_truncate $fh_or_path, $offset, $callback->($status)	654	=item aio_truncate $fh_or_path, $offset, $callback->($status)
606		655
607	Works like truncate(2) or ftruncate(2).	656	Works like truncate(2) or ftruncate(2).
608		657
609		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
610	=item aio_chmod $fh_or_path, $mode, $callback->($status)	681	=item aio_chmod $fh_or_path, $mode, $callback->($status)
611		682
612	Works like perl's C<chmod> function.	683	Works like perl's C<chmod> function.
613		684
614		685
…		…
616		687
617	Asynchronously unlink (delete) a file and call the callback with the	688	Asynchronously unlink (delete) a file and call the callback with the
618	result code.	689	result code.
619		690
620		691
621	=item aio_mknod $path, $mode, $dev, $callback->($status)	692	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
622		693
623	[EXPERIMENTAL]	694	[EXPERIMENTAL]
624		695
625	Asynchronously create a device node (or fifo). See mknod(2).	696	Asynchronously create a device node (or fifo). See mknod(2).
626		697
627	The only (POSIX-) portable way of calling this function is:	698	The only (POSIX-) portable way of calling this function is:
628		699
629	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	700	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
630		701
631	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
632	and functions.	703	and functions.
633		704
634	=item aio_link $srcpath, $dstpath, $callback->($status)	705	=item aio_link $srcpath, $dstpath, $callback->($status)
…		…
641		712
642	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
643	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.
644		715
645		716
646	=item aio_readlink $path, $callback->($link)	717	=item aio_readlink $pathname, $callback->($link)
647		718
648	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
649	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
650	callback.	721	callback.
651		722
652		723
653	=item aio_realpath $path, $callback->($path)	724	=item aio_realpath $pathname, $callback->($path)
654		725
655	Asynchronously make the path absolute and resolve any symlinks in	726	Asynchronously make the path absolute and resolve any symlinks in
656	C<$path>. The resulting path only consists of directories (Same as	727	C<$path>. The resulting path only consists of directories (same as
657	L<Cwd::realpath>).	728	L<Cwd::realpath>).
658		729
659	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
660	directory by passing it a path of F<.> (a single dot).	731	directory by passing it a path of F<.> (a single dot).
661		732
662		733
663	=item aio_rename $srcpath, $dstpath, $callback->($status)	734	=item aio_rename $srcpath, $dstpath, $callback->($status)
664		735
665	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
666	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>.
667		758
668		759
669	=item aio_mkdir $pathname, $mode, $callback->($status)	760	=item aio_mkdir $pathname, $mode, $callback->($status)
670		761
671	Asynchronously mkdir (create) a directory and call the callback with	762	Asynchronously mkdir (create) a directory and call the callback with
…		…
676	=item aio_rmdir $pathname, $callback->($status)	767	=item aio_rmdir $pathname, $callback->($status)
677		768
678	Asynchronously rmdir (delete) a directory and call the callback with the	769	Asynchronously rmdir (delete) a directory and call the callback with the
679	result code.	770	result code.
680		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
681		776
682	=item aio_readdir $pathname, $callback->($entries)	777	=item aio_readdir $pathname, $callback->($entries)
683		778
684	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
685	directory (i.e. opendir + readdir + closedir). The entries will not be	780	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
700		795
701	=over 4	796	=over 4
702		797
703	=item IO::AIO::READDIR_DENTS	798	=item IO::AIO::READDIR_DENTS
704		799
705	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
706	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
707	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	802	arrayref with C<[$name, $type, $inode]> arrayrefs, each describing a
708	entry in more detail.	803	single directory entry in more detail:
709		804
710	C<$name> is the name of the entry.	805	C<$name> is the name of the entry.
711		806
712	C<$type> is one of the C<IO::AIO::DT_xxx> constants:	807	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
713		808
714	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,	809	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
715	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,	810	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
716	C<IO::AIO::DT_WHT>.	811	C<IO::AIO::DT_WHT>.
717		812
718	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to	813	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need
719	know, you have to run stat yourself. Also, for speed reasons, the C<$type>	814	to know, you have to run stat yourself. Also, for speed/memory reasons,
720	scalars are read-only: you can not modify them.	815	the C<$type> scalars are read-only: you must not modify them.
721		816
722	C<$inode> is the inode number (which might not be exact on systems with 64	817	C<$inode> is the inode number (which might not be exact on systems with 64
723	bit inode numbers and 32 bit perls). This field has unspecified content on	818	bit inode numbers and 32 bit perls). This field has unspecified content on
724	systems that do not deliver the inode information.	819	systems that do not deliver the inode information.
725		820
…		…
736	short names are tried first.	831	short names are tried first.
737		832
738	=item IO::AIO::READDIR_STAT_ORDER	833	=item IO::AIO::READDIR_STAT_ORDER
739		834
740	When this flag is set, then the names will be returned in an order	835	When this flag is set, then the names will be returned in an order
741	suitable for stat()'ing each one. That is, when you plan to stat()	836	suitable for stat()'ing each one. That is, when you plan to stat() most or
742	all files in the given directory, then the returned order will likely	837	all files in the given directory, then the returned order will likely be
743	be fastest.	838	faster.
744		839
745	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then	840	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified,
746	the likely dirs come first, resulting in a less optimal stat order.	841	then the likely dirs come first, resulting in a less optimal stat order
		842	for stat'ing all entries, but likely a more optimal order for finding
		843	subdirectories.
747		844
748	=item IO::AIO::READDIR_FOUND_UNKNOWN	845	=item IO::AIO::READDIR_FOUND_UNKNOWN
749		846
750	This flag should not be set when calling C<aio_readdirx>. Instead, it	847	This flag should not be set when calling C<aio_readdirx>. Instead, it
751	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	848	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
…		…
753	C<$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.
754		851
755	=back	852	=back
756		853
757		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
758	=item aio_load $path, $data, $callback->($status)	884	=item aio_load $pathname, $data, $callback->($status)
759		885
760	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
761	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.
762		890
763	=cut	891	=cut
764		892
765	sub aio_load($$;$) {	893	sub aio_load($$;$) {
766	my ($path, undef, $cb) = @_;	894	my ($path, undef, $cb) = @_;
…		…
786	=item aio_copy $srcpath, $dstpath, $callback->($status)	914	=item aio_copy $srcpath, $dstpath, $callback->($status)
787		915
788	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
789	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
790	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.
791		921
792	This is a composite request that creates the destination file with	922	This is a composite request that creates the destination file with
793	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
794	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	924	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
795	uid/gid, in that order.	925	uid/gid, in that order.
…		…
898	};	1028	};
899		1029
900	$grp	1030	$grp
901	}	1031	}
902		1032
903	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1033	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
904		1034
905	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1035	Scans a directory (similar to C<aio_readdir>) but additionally tries to
906	efficiently separate the entries of directory C<$path> into two sets of	1036	efficiently separate the entries of directory C<$path> into two sets of
907	names, directories you can recurse into (directories), and ones you cannot	1037	names, directories you can recurse into (directories), and ones you cannot
908	recurse into (everything else, including symlinks to directories).	1038	recurse into (everything else, including symlinks to directories).
909		1039
910	C<aio_scandir> is a composite request that creates of many sub requests_	1040	C<aio_scandir> is a composite request that generates many sub requests.
911	C<$maxreq> specifies the maximum number of outstanding aio requests that	1041	C<$maxreq> specifies the maximum number of outstanding aio requests that
912	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
913	will be chosen (currently 4).	1043	will be chosen (currently 4).
914		1044
915	On error, the callback is called without arguments, otherwise it receives	1045	On error, the callback is called without arguments, otherwise it receives
…		…
965		1095
966	my $grp = aio_group $cb;	1096	my $grp = aio_group $cb;
967		1097
968	$maxreq = 4 if $maxreq <= 0;	1098	$maxreq = 4 if $maxreq <= 0;
969		1099
970	# stat once	1100	# get a wd object
971	aioreq_pri $pri;	1101	aioreq_pri $pri;
972	add $grp aio_stat $path, sub {	1102	add $grp aio_wd $path, sub {
		1103	$_[0]
973	return $grp->result () if $_[0];	1104	or return $grp->result ();
974	my $now = time;
975	my $hash1 = join ":", (stat _)[0,1,3,7,9];
976		1105
977	# read the directory entries	1106	my $wd = [shift, "."];
		1107
		1108	# stat once
978	aioreq_pri $pri;	1109	aioreq_pri $pri;
979	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1110	add $grp aio_stat $wd, sub {
980	my $entries = shift
981	or return $grp->result ();	1111	return $grp->result () if $_[0];
		1112	my $now = time;
		1113	my $hash1 = join ":", (stat _)[0,1,3,7,9];
982		1114
983	# stat the dir another time	1115	# read the directory entries
984	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;
985	add $grp aio_stat $path, sub {	1123	add $grp aio_stat $wd, sub {
986	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1124	my $hash2 = join ":", (stat _)[0,1,3,7,9];
987		1125
988	my $ndirs;	1126	my $ndirs;
989		1127
990	# take the slow route if anything looks fishy	1128	# take the slow route if anything looks fishy
991	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1129	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
992	$ndirs = -1;	1130	$ndirs = -1;
993	} else {	1131	} else {
994	# if nlink == 2, we are finished	1132	# if nlink == 2, we are finished
995	# for non-posix-fs's, we rely on nlink < 2	1133	# for non-posix-fs's, we rely on nlink < 2
996	$ndirs = (stat _)[3] - 2	1134	$ndirs = (stat _)[3] - 2
997	or return $grp->result ([], $entries);	1135	or return $grp->result ([], $entries);
998	}	1136	}
999		1137
1000	my (@dirs, @nondirs);	1138	my (@dirs, @nondirs);
1001		1139
1002	my $statgrp = add $grp aio_group sub {	1140	my $statgrp = add $grp aio_group sub {
1003	$grp->result (\@dirs, \@nondirs);	1141	$grp->result (\@dirs, \@nondirs);
1004	};	1142	};
1005		1143
1006	limit $statgrp $maxreq;	1144	limit $statgrp $maxreq;
1007	feed $statgrp sub {	1145	feed $statgrp sub {
1008	return unless @$entries;	1146	return unless @$entries;
1009	my $entry = shift @$entries;	1147	my $entry = shift @$entries;
1010		1148
1011	aioreq_pri $pri;	1149	aioreq_pri $pri;
		1150	$wd->[1] = "$entry/.";
1012	add $statgrp aio_stat "$path/$entry/.", sub {	1151	add $statgrp aio_stat $wd, sub {
1013	if ($_[0] < 0) {	1152	if ($_[0] < 0) {
1014	push @nondirs, $entry;	1153	push @nondirs, $entry;
1015	} else {	1154	} else {
1016	# need to check for real directory	1155	# need to check for real directory
1017	aioreq_pri $pri;	1156	aioreq_pri $pri;
		1157	$wd->[1] = $entry;
1018	add $statgrp aio_lstat "$path/$entry", sub {	1158	add $statgrp aio_lstat $wd, sub {
1019	if (-d _) {	1159	if (-d _) {
1020	push @dirs, $entry;	1160	push @dirs, $entry;
1021		1161
1022	unless (--$ndirs) {	1162	unless (--$ndirs) {
1023	push @nondirs, @$entries;	1163	push @nondirs, @$entries;
1024	feed $statgrp;	1164	feed $statgrp;
		1165	}
		1166	} else {
		1167	push @nondirs, $entry;
1025	}	1168	}
1026	} else {
1027	push @nondirs, $entry;
1028	}	1169	}
1029	}	1170	}
1030	}	1171	};
1031	};	1172	};
1032	};	1173	};
1033	};	1174	};
1034	};	1175	};
1035	};	1176	};
1036		1177
1037	$grp	1178	$grp
1038	}	1179	}
1039		1180
1040	=item aio_rmtree $path, $callback->($status)	1181	=item aio_rmtree $pathname, $callback->($status)
1041		1182
1042	Delete a directory tree starting (and including) C<$path>, return the	1183	Delete a directory tree starting (and including) C<$path>, return the
1043	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
1044	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
1045	everything else.	1186	everything else.
1046		1187
1047	=cut	1188	=cut
1048		1189
…		…
1070	};	1211	};
1071		1212
1072	$grp	1213	$grp
1073	}	1214	}
1074		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
1075	=item aio_sync $callback->($status)	1260	=item aio_sync $callback->($status)
1076		1261
1077	Asynchronously call sync and call the callback when finished.	1262	Asynchronously call sync and call the callback when finished.
1078		1263
1079	=item aio_fsync $fh, $callback->($status)	1264	=item aio_fsync $fh, $callback->($status)
…		…
1106	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>,
1107	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1292	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1108	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
1109	manpage for details.	1294	manpage for details.
1110		1295
1111	=item aio_pathsync $path, $callback->($status)	1296	=item aio_pathsync $pathname, $callback->($status)
1112		1297
1113	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
1114	composite request intended to sync directories after directory operations	1299	composite request intended to sync directories after directory operations
1115	(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
1116	specific effect, but usually it makes sure that directory changes get	1301	specific effect, but usually it makes sure that directory changes get
…		…
1147	};	1332	};
1148		1333
1149	$grp	1334	$grp
1150	}	1335	}
1151		1336
1152	=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)
1153		1338
1154	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
1155	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
1156	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
1157	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
…		…
1159		1344
1160	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
1161	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
1162	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>
1163	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
1164	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
1165	C<IO::AIO::MS_SYNC>.	1350	C<IO::AIO::MS_INVALIDATE>.
1166		1351
1167	=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)
1168		1353
1169	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
1170	scalars.	1355	scalars.
1171		1356
1172	It touches (reads or writes) all memory pages in the specified	1357	It touches (reads or writes) all memory pages in the specified
1173	range inside the scalar. All caveats and parameters are the same	1358	range inside the scalar. All caveats and parameters are the same
1174	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
1175	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
1176	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
1177	writing an octet from it, which dirties the page).	1362	writing an octet from it, which dirties the page).
1178		1363
1179	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)	1364	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1180		1365
1181	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
…		…
1200	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;
1201	aio_mlock $data; # mlock in background	1386	aio_mlock $data; # mlock in background
1202		1387
1203	=item aio_mlockall $flags, $callback->($status)	1388	=item aio_mlockall $flags, $callback->($status)
1204		1389
1205	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
1206	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>).
1207		1393
1208	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>
1209	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>.
1210		1398
1211	Note that the corresponding C<munlockall> is synchronous and is	1399	Note that the corresponding C<munlockall> is synchronous and is
1212	documented under L<MISCELLANEOUS FUNCTIONS>.	1400	documented under L<MISCELLANEOUS FUNCTIONS>.
1213		1401
1214	Example: asynchronously lock all current and future pages into memory.	1402	Example: asynchronously lock all current and future pages into memory.
1215		1403
1216	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>.
1217		1451
1218	=item aio_group $callback->(...)	1452	=item aio_group $callback->(...)
1219		1453
1220	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
1221	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
…		…
1258	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
1259	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
1260	except to put your application under artificial I/O pressure.	1494	except to put your application under artificial I/O pressure.
1261		1495
1262	=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.
1263		1622
1264	=head2 IO::AIO::REQ CLASS	1623	=head2 IO::AIO::REQ CLASS
1265		1624
1266	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
1267	called in non-void context.	1626	called in non-void context.
…		…
1385		1744
1386	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
1387	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,
1388	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,
1389	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,
1390	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>
1391	delaying any later requests for a long time.	1750	requests, delaying any later requests for a long time.
1392		1751
1393	To avoid this, and allow incremental generation of requests, you can	1752	To avoid this, and allow incremental generation of requests, you can
1394	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
1395	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>,
1396	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
…		…
1428	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
1429	automatically bumps it up to C<2>.	1788	automatically bumps it up to C<2>.
1430		1789
1431	=back	1790	=back
1432		1791
		1792
1433	=head2 SUPPORT FUNCTIONS	1793	=head2 SUPPORT FUNCTIONS
1434		1794
1435	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	1795	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1436		1796
1437	=over 4	1797	=over 4
…		…
1445		1805
1446	See C<poll_cb> for an example.	1806	See C<poll_cb> for an example.
1447		1807
1448	=item IO::AIO::poll_cb	1808	=item IO::AIO::poll_cb
1449		1809
1450	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
1451	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
1452	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
1453	reason. Returns immediately when no events are outstanding. The amount of	1816	reason. Returns immediately when no events are outstanding. The amount
1454	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>,
1455	C<IO::AIO::max_poll_time>.	1818	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
1456		1819
1457	If not all requests were processed for whatever reason, the filehandle	1820	If not all requests were processed for whatever reason, the poll file
1458	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
1459	do anything special to have it called later.	1822	don't have to do anything special to have it called later.
1460		1823
1461	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
1462	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
1463	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
1464	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
…		…
1473	poll => 'r', async => 1,	1836	poll => 'r', async => 1,
1474	cb => \&IO::AIO::poll_cb);	1837	cb => \&IO::AIO::poll_cb);
1475		1838
1476	=item IO::AIO::poll_wait	1839	=item IO::AIO::poll_wait
1477		1840
1478	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
1479	phase, wait till the result filehandle becomes ready for reading (simply	1842	requests are outstanding anymore.
1480	does a C<select> on the filehandle. This is useful if you want to	1843
1481	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.
1482		1846
1483	See C<nreqs> for an example.	1847	See C<nreqs> for an example.
1484		1848
1485	=item IO::AIO::poll	1849	=item IO::AIO::poll
1486		1850
…		…
1497		1861
1498	Strictly equivalent to:	1862	Strictly equivalent to:
1499		1863
1500	IO::AIO::poll_wait, IO::AIO::poll_cb	1864	IO::AIO::poll_wait, IO::AIO::poll_cb
1501	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
1502		1876
1503	=item IO::AIO::max_poll_reqs $nreqs	1877	=item IO::AIO::max_poll_reqs $nreqs
1504		1878
1505	=item IO::AIO::max_poll_time $seconds	1879	=item IO::AIO::max_poll_time $seconds
1506		1880
…		…
1533	poll => 'r', nice => 1,	1907	poll => 'r', nice => 1,
1534	cb => &IO::AIO::poll_cb);	1908	cb => &IO::AIO::poll_cb);
1535		1909
1536	=back	1910	=back
1537		1911
		1912
1538	=head3 CONTROLLING THE NUMBER OF THREADS	1913	=head3 CONTROLLING THE NUMBER OF THREADS
1539		1914
1540	=over	1915	=over
1541		1916
1542	=item IO::AIO::min_parallel $nthreads	1917	=item IO::AIO::min_parallel $nthreads
…		…
1607		1982
1608	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
1609	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
1610	use an C<aio_group> together with a feed callback.	1985	use an C<aio_group> together with a feed callback.
1611		1986
1612	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
1613	a lot of files, you can write somehting like this:	1988	a lot of files, you can write something like this:
1614		1989
1615	IO::AIO::max_outstanding 32;	1990	IO::AIO::max_outstanding 32;
1616		1991
1617	for my $path (...) {	1992	for my $path (...) {
1618	aio_stat $path , ...;	1993	aio_stat $path , ...;
…		…
1629	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
1630	practical limit on the number of outstanding requests.	2005	practical limit on the number of outstanding requests.
1631		2006
1632	=back	2007	=back
1633		2008
		2009
1634	=head3 STATISTICAL INFORMATION	2010	=head3 STATISTICAL INFORMATION
1635		2011
1636	=over	2012	=over
1637		2013
1638	=item IO::AIO::nreqs	2014	=item IO::AIO::nreqs
…		…
1655	Returns the number of requests currently in the pending state (executed,	2031	Returns the number of requests currently in the pending state (executed,
1656	but not yet processed by poll_cb).	2032	but not yet processed by poll_cb).
1657		2033
1658	=back	2034	=back
1659		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
1660	=head3 MISCELLANEOUS FUNCTIONS	2131	=head3 MISCELLANEOUS FUNCTIONS
1661		2132
1662	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
1663	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.
1664		2137
1665	=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.
1666		2164
1667	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count	2165	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1668		2166
1669	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>,
1670	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
…		…
1687	=item IO::AIO::madvise $scalar, $offset, $len, $advice	2185	=item IO::AIO::madvise $scalar, $offset, $len, $advice
1688		2186
1689	Simply calls the C<posix_madvise> function (see its	2187	Simply calls the C<posix_madvise> function (see its
1690	manpage for details). The following advice constants are	2188	manpage for details). The following advice constants are
1691	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,	2189	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1692	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.	2190	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2191	C<IO::AIO::MADV_DONTNEED>.
		2192
		2193	If C<$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>.
1693		2196
1694	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
1695	ENOSYS, otherwise the return value of C<posix_madvise>.	2198	ENOSYS, otherwise the return value of C<posix_madvise>.
1696		2199
1697	=item IO::AIO::mprotect $scalar, $offset, $len, $protect	2200	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
…		…
1699	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
1700	$scalar (see its manpage for details). The following protect	2203	$scalar (see its manpage for details). The following protect
1701	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,	2204	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1702	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.	2205	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
1703		2206
		2207	If C<$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>.
		2210
1704	On systems that do not implement C<mprotect>, this function returns	2211	On systems that do not implement C<mprotect>, this function returns
1705	ENOSYS, otherwise the return value of C<mprotect>.	2212	ENOSYS, otherwise the return value of C<mprotect>.
1706		2213
1707	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]	2214	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1708		2215
1709	Memory-maps a file (or anonymous memory range) and attaches it to the	2216	Memory-maps a file (or anonymous memory range) and attaches it to the
1710	given C<$scalar>, which will act like a string scalar.	2217	given C<$scalar>, which will act like a string scalar. Returns true on
		2218	success, and false otherwise.
1711		2219
		2220	The scalar must exist, but its contents do not matter - this means you
		2221	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2222	the scalar first.
		2223
1712	The only operations allowed on the scalar are C<substr>/C<vec> that don't	2224	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
1713	change the string length, and most read-only operations such as copying it	2225	which don't change the string length, and most read-only operations such
1714	or searching it with regexes and so on.	2226	as copying it or searching it with regexes and so on.
1715		2227
1716	Anything else is unsafe and will, at best, result in memory leaks.	2228	Anything else is unsafe and will, at best, result in memory leaks.
1717		2229
1718	The memory map associated with the C<$scalar> is automatically removed	2230	The memory map associated with the C<$scalar> is automatically removed
1719	when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or	2231	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
1720	C<IO::AIO::munmap> functions are called.	2232	or C<IO::AIO::munmap> functions are called on it.
1721		2233
1722	This calls the C<mmap>(2) function internally. See your system's manual	2234	This calls the C<mmap>(2) function internally. See your system's manual
1723	page for details on the C<$length>, C<$prot> and C<$flags> parameters.	2235	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1724		2236
1725	The C<$length> must be larger than zero and smaller than the actual	2237	The C<$length> must be larger than zero and smaller than the actual
1726	filesize.	2238	filesize.
1727		2239
1728	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,	2240	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1729	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,	2241	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1730		2242
1731	C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or	2243	C<$flags> can be a combination of
1732	C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when	2244	C<IO::AIO::MAP_SHARED> or
1733	not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>	2245	C<IO::AIO::MAP_PRIVATE>,
		2246	or a number of system-specific flags (when not available, the are C<0>):
1734	(which is set to C<MAP_ANON> if your system only provides this	2247	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
1735	constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,	2248	C<IO::AIO::MAP_LOCKED>,
1736	C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or	2249	C<IO::AIO::MAP_NORESERVE>,
		2250	C<IO::AIO::MAP_POPULATE>,
1737	C<IO::AIO::MAP_NONBLOCK>	2251	C<IO::AIO::MAP_NONBLOCK>,
		2252	C<IO::AIO::MAP_FIXED>,
		2253	C<IO::AIO::MAP_GROWSDOWN>,
		2254	C<IO::AIO::MAP_32BIT>,
		2255	C<IO::AIO::MAP_HUGETLB> or
		2256	C<IO::AIO::MAP_STACK>.
1738		2257
1739	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.	2258	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1740		2259
1741	C<$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
1742	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>.
…		…
1756		2275
1757	=item IO::AIO::munmap $scalar	2276	=item IO::AIO::munmap $scalar
1758		2277
1759	Removes a previous mmap and undefines the C<$scalar>.	2278	Removes a previous mmap and undefines the C<$scalar>.
1760		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
1761	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef	2308	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1762		2309
1763	Calls the C<munlock> function, undoing the effects of a previous	2310	Calls the C<munlock> function, undoing the effects of a previous
1764	C<aio_mlock> call (see its description for details).	2311	C<aio_mlock> call (see its description for details).
1765		2312
…		…
1767		2314
1768	Calls the C<munlockall> function.	2315	Calls the C<munlockall> function.
1769		2316
1770	On systems that do not implement C<munlockall>, this function returns	2317	On systems that do not implement C<munlockall>, this function returns
1771	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.
1772		2451
1773	=back	2452	=back
1774		2453
1775	=cut	2454	=cut
1776		2455
…		…
1842	the process will result in undefined behaviour. Calling it at any time	2521	the process will result in undefined behaviour. Calling it at any time
1843	will also result in any undefined (by POSIX) behaviour.	2522	will also result in any undefined (by POSIX) behaviour.
1844		2523
1845	=back	2524	=back
1846		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>.
		2534
1847	=head2 MEMORY USAGE	2535	=head2 MEMORY USAGE
1848		2536
1849	Per-request usage:	2537	Per-request usage:
1850		2538
1851	Each aio request uses - depending on your architecture - around 100-200	2539	Each aio request uses - depending on your architecture - around 100-200
…		…
1863	temporary buffers, and each thread requires a stack and other data	2551	temporary buffers, and each thread requires a stack and other data
1864	structures (usually around 16k-128k, depending on the OS).	2552	structures (usually around 16k-128k, depending on the OS).
1865		2553
1866	=head1 KNOWN BUGS	2554	=head1 KNOWN BUGS
1867		2555
1868	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.
1869		2568
1870	=head1 SEE ALSO	2569	=head1 SEE ALSO
1871		2570
1872	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
1873	more natural syntax.	2572	more natural syntax.

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