[ViewVC] Diff of: cvs/IO-AIO/AIO.pm

Comparing IO-AIO/AIO.pm (file contents):
Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC vs.
Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC

…		…
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
		31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		32	use AnyEvent::AIO;
		33
30	# AnyEvent integration	34	# EV integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";	35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33		36
34	# Event integration	37	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,	38	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',	39	poll => 'r',
37	cb => \&IO::AIO::poll_cb);	40	cb => \&IO::AIO::poll_cb);
…		…
50		53
51	=head1 DESCRIPTION	54	=head1 DESCRIPTION
52		55
53	This module implements asynchronous I/O using whatever means your	56	This module implements asynchronous I/O using whatever means your
54	operating system supports.	57	operating system supports.
		58
		59	Asynchronous means that operations that can normally block your program
		60	(e.g. reading from disk) will be done asynchronously: the operation
		61	will still block, but you can do something else in the meantime. This
		62	is extremely useful for programs that need to stay interactive even
		63	when doing heavy I/O (GUI programs, high performance network servers
		64	etc.), but can also be used to easily do operations in parallel that are
		65	normally done sequentially, e.g. stat'ing many files, which is much faster
		66	on a RAID volume or over NFS when you do a number of stat operations
		67	concurrently.
		68
		69	While most of this works on all types of file descriptors (for
		70	example sockets), using these functions on file descriptors that
		71	support nonblocking operation (again, sockets, pipes etc.) is very
		72	inefficient. Use an event loop for that (such as the L<Event\|Event>
		73	module): IO::AIO will naturally fit into such an event loop itself.
55		74
56	In this version, a number of threads are started that execute your	75	In this version, a number of threads are started that execute your
57	requests and signal their completion. You don't need thread support	76	requests and signal their completion. You don't need thread support
58	in perl, and the threads created by this module will not be visible	77	in perl, and the threads created by this module will not be visible
59	to perl. In the future, this module might make use of the native aio	78	to perl. In the future, this module might make use of the native aio
60	functions available on many operating systems. However, they are often	79	functions available on many operating systems. However, they are often
61	not well-supported or restricted (Linux doesn't allow them on normal	80	not well-supported or restricted (GNU/Linux doesn't allow them on normal
62	files currently, for example), and they would only support aio_read and	81	files currently, for example), and they would only support aio_read and
63	aio_write, so the remaining functionality would have to be implemented	82	aio_write, so the remaining functionality would have to be implemented
64	using threads anyway.	83	using threads anyway.
65		84
66	Although the module will work with in the presence of other (Perl-)	85	Although the module will work in the presence of other (Perl-) threads,
67	threads, it is currently not reentrant in any way, so use appropriate	86	it is currently not reentrant in any way, so use appropriate locking
68	locking yourself, always call C<poll_cb> from within the same thread, or	87	yourself, always call C<poll_cb> from within the same thread, or never
69	never call C<poll_cb> (or other C<aio_> functions) recursively.	88	call C<poll_cb> (or other C<aio_> functions) recursively.
		89
		90	=head2 EXAMPLE
		91
		92	This is a simple example that uses the Event module and loads
		93	F</etc/passwd> asynchronously:
		94
		95	use Fcntl;
		96	use Event;
		97	use IO::AIO;
		98
		99	# register the IO::AIO callback with Event
		100	Event->io (fd => IO::AIO::poll_fileno,
		101	poll => 'r',
		102	cb => \&IO::AIO::poll_cb);
		103
		104	# queue the request to open /etc/passwd
		105	aio_open "/etc/passwd", O_RDONLY, 0, sub {
		106	my $fh = shift
		107	or die "error while opening: $!";
		108
		109	# stat'ing filehandles is generally non-blocking
		110	my $size = -s $fh;
		111
		112	# queue a request to read the file
		113	my $contents;
		114	aio_read $fh, 0, $size, $contents, 0, sub {
		115	$_[0] == $size
		116	or die "short read: $!";
		117
		118	close $fh;
		119
		120	# file contents now in $contents
		121	print $contents;
		122
		123	# exit event loop and program
		124	Event::unloop;
		125	};
		126	};
		127
		128	# possibly queue up other requests, or open GUI windows,
		129	# check for sockets etc. etc.
		130
		131	# process events as long as there are some:
		132	Event::loop;
70		133
71	=head1 REQUEST ANATOMY AND LIFETIME	134	=head1 REQUEST ANATOMY AND LIFETIME
72		135
73	Every C<aio_*> function creates a request. which is a C data structure not	136	Every C<aio_*> function creates a request. which is a C data structure not
74	directly visible to Perl.	137	directly visible to Perl.
…		…
116	Request has reached the end of its lifetime and holds no resources anymore	179	Request has reached the end of its lifetime and holds no resources anymore
117	(except possibly for the Perl object, but its connection to the actual	180	(except possibly for the Perl object, but its connection to the actual
118	aio request is severed and calling its methods will either do nothing or	181	aio request is severed and calling its methods will either do nothing or
119	result in a runtime error).	182	result in a runtime error).
120		183
		184	=back
		185
121	=cut	186	=cut
122		187
123	package IO::AIO;	188	package IO::AIO;
		189
		190	use Carp ();
124		191
125	no warnings;	192	no warnings;
126	use strict 'vars';	193	use strict 'vars';
127		194
128	use base 'Exporter';	195	use base 'Exporter';
129		196
130	BEGIN {	197	BEGIN {
131	our $VERSION = '2.0';	198	our $VERSION = '3.19';
132		199
133	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
134	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
135	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
136	aio_group aio_nop);	203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
		204	aio_rename aio_link aio_move aio_copy aio_group
		205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		206	aio_chmod aio_utime aio_truncate);
		207
137	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139	min_parallel max_parallel nreqs);	210	min_parallel max_parallel max_idle
		211	nreqs nready npending nthreads
		212	max_poll_time max_poll_reqs);
		213
		214	push @AIO_REQ, qw(aio_busy); # not exported
140		215
141	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142		217
143	require XSLoader;	218	require XSLoader;
144	XSLoader::load ("IO::AIO", $VERSION);	219	XSLoader::load ("IO::AIO", $VERSION);
145	}	220	}
146		221
147	=head1 FUNCTIONS	222	=head1 FUNCTIONS
148		223
149	=head2 AIO FUNCTIONS	224	=head2 AIO REQUEST FUNCTIONS
150		225
151	All the C<aio_*> calls are more or less thin wrappers around the syscall	226	All the C<aio_*> calls are more or less thin wrappers around the syscall
152	with the same name (sans C<aio_>). The arguments are similar or identical,	227	with the same name (sans C<aio_>). The arguments are similar or identical,
153	and they all accept an additional (and optional) C<$callback> argument	228	and they all accept an additional (and optional) C<$callback> argument
154	which must be a code reference. This code reference will get called with	229	which must be a code reference. This code reference will get called with
155	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike
156	perl, which usually delivers "false") as it's sole argument when the given	231	perl, which usually delivers "false") as its sole argument after the given
157	syscall has been executed asynchronously.	232	syscall has been executed asynchronously.
158		233
159	All functions expecting a filehandle keep a copy of the filehandle	234	All functions expecting a filehandle keep a copy of the filehandle
160	internally until the request has finished.	235	internally until the request has finished.
161		236
162	All requests return objects of type L<IO::AIO::REQ> that allow further	237	All functions return request objects of type L<IO::AIO::REQ> that allow
163	manipulation of those requests while they are in-flight.	238	further manipulation of those requests while they are in-flight.
164		239
165	The pathnames you pass to these routines I<must> be absolute and	240	The pathnames you pass to these routines I<must> be absolute and
166	encoded in byte form. The reason for the former is that at the time the	241	encoded as octets. The reason for the former is that at the time the
167	request is being executed, the current working directory could have	242	request is being executed, the current working directory could have
168	changed. Alternatively, you can make sure that you never change the	243	changed. Alternatively, you can make sure that you never change the
169	current working directory.	244	current working directory anywhere in the program and then use relative
		245	paths.
170		246
171	To encode pathnames to byte form, either make sure you either: a)	247	To encode pathnames as octets, either make sure you either: a) always pass
172	always pass in filenames you got from outside (command line, readdir	248	in filenames you got from outside (command line, readdir etc.) without
173	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
174	your pathnames to the locale (or other) encoding in effect in the user	250	your pathnames to the locale (or other) encoding in effect in the user
175	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176	use something else.	252	use something else to ensure your scalar has the correct contents.
		253
		254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		255	handles correctly whether it is set or not.
177		256
178	=over 4	257	=over 4
179		258
180	=item aioreq_pri $pri	259	=item $prev_pri = aioreq_pri [$pri]
181		260
182	Sets the priority for the next aio request. The default priority	261	Returns the priority value that would be used for the next request and, if
		262	C<$pri> is given, sets the priority for the next aio request.
		263
183	is C<0>, the minimum and maximum priorities are C<-4> and C<4>,	264	The default priority is C<0>, the minimum and maximum priorities are C<-4>
184	respectively. Requests with higher priority will be serviced first.	265	and C<4>, respectively. Requests with higher priority will be serviced
		266	first.
185		267
186	The priority will be reset to C<0> after each call to one of the C<aio_>	268	The priority will be reset to C<0> after each call to one of the C<aio_*>
187	functions.	269	functions.
188		270
189	Example: open a file with low priority, then read something from it with	271	Example: open a file with low priority, then read something from it with
190	higher priority so the read request is serviced before other low priority	272	higher priority so the read request is serviced before other low priority
191	open requests (potentially spamming the cache):	273	open requests (potentially spamming the cache):
…		…
198	aio_read $_[0], ..., sub {	280	aio_read $_[0], ..., sub {
199	...	281	...
200	};	282	};
201	};	283	};
202		284
		285
203	=item aioreq_nice $pri_adjust	286	=item aioreq_nice $pri_adjust
204		287
205	Similar to C<aioreq_pri>, but subtracts the given value from the current	288	Similar to C<aioreq_pri>, but subtracts the given value from the current
206	priority, so effects are cumulative.	289	priority, so the effect is cumulative.
		290
207		291
208	=item aio_open $pathname, $flags, $mode, $callback->($fh)	292	=item aio_open $pathname, $flags, $mode, $callback->($fh)
209		293
210	Asynchronously open or create a file and call the callback with a newly	294	Asynchronously open or create a file and call the callback with a newly
211	created filehandle for the file.	295	created filehandle for the file.
…		…
217	list. They are the same as used by C<sysopen>.	301	list. They are the same as used by C<sysopen>.
218		302
219	Likewise, C<$mode> specifies the mode of the newly created file, if it	303	Likewise, C<$mode> specifies the mode of the newly created file, if it
220	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	304	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
221	except that it is mandatory (i.e. use C<0> if you don't create new files,	305	except that it is mandatory (i.e. use C<0> if you don't create new files,
222	and C<0666> or C<0777> if you do).	306	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		307	by the umask in effect then the request is being executed, so better never
		308	change the umask.
223		309
224	Example:	310	Example:
225		311
226	aio_open "/etc/passwd", O_RDONLY, 0, sub {	312	aio_open "/etc/passwd", O_RDONLY, 0, sub {
227	if ($_[0]) {	313	if ($_[0]) {
…		…
230	} else {	316	} else {
231	die "open failed: $!\n";	317	die "open failed: $!\n";
232	}	318	}
233	};	319	};
234		320
		321
235	=item aio_close $fh, $callback->($status)	322	=item aio_close $fh, $callback->($status)
236		323
237	Asynchronously close a file and call the callback with the result	324	Asynchronously close a file and call the callback with the result
238	code. I<WARNING:> although accepted, you should not pass in a perl	325	code.
239	filehandle here, as perl will likely close the file descriptor another
240	time when the filehandle is destroyed. Normally, you can safely call perls
241	C<close> or just let filehandles go out of scope.
242		326
243	This is supposed to be a bug in the API, so that might change. It's	327	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
244	therefore best to avoid this function.	328	closing the file descriptor associated with the filehandle itself.
		329
		330	Therefore, C<aio_close> will not close the filehandle - instead it will
		331	use dup2 to overwrite the file descriptor with the write-end of a pipe
		332	(the pipe fd will be created on demand and will be cached).
		333
		334	Or in other words: the file descriptor will be closed, but it will not be
		335	free for reuse until the perl filehandle is closed.
		336
		337	=cut
245		338
246	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
247		340
248	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
249		342
250	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	343	Reads or writes C<$length> bytes from or to the specified C<$fh> and
251	into the scalar given by C<data> and offset C<dataoffset> and calls the	344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>
252	callback without the actual number of bytes read (or -1 on error, just	345	and calls the callback without the actual number of bytes read (or -1 on
253	like the syscall).	346	error, just like the syscall).
		347
		348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		349	offset plus the actual number of bytes read.
		350
		351	If C<$offset> is undefined, then the current file descriptor offset will
		352	be used (and updated), otherwise the file descriptor offset will not be
		353	changed by these calls.
		354
		355	If C<$length> is undefined in C<aio_write>, use the remaining length of
		356	C<$data>.
		357
		358	If C<$dataoffset> is less than zero, it will be counted from the end of
		359	C<$data>.
254		360
255	The C<$data> scalar I<MUST NOT> be modified in any way while the request	361	The C<$data> scalar I<MUST NOT> be modified in any way while the request
256	is outstanding. Modifying it can result in segfaults or WW3 (if the	362	is outstanding. Modifying it can result in segfaults or World War III (if
257	necessary/optional hardware is installed).	363	the necessary/optional hardware is installed).
258		364
259	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	365	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
260	offset C<0> within the scalar:	366	offset C<0> within the scalar:
261		367
262	aio_read $fh, 7, 15, $buffer, 0, sub {	368	aio_read $fh, 7, 15, $buffer, 0, sub {
263	$_[0] > 0 or die "read error: $!";	369	$_[0] > 0 or die "read error: $!";
264	print "read $_[0] bytes: <$buffer>\n";	370	print "read $_[0] bytes: <$buffer>\n";
265	};	371	};
266		372
267	=item aio_move $srcpath, $dstpath, $callback->($status)
268
269	Try to move the I<file> (directories not supported as either source or
270	destination) from C<$srcpath> to C<$dstpath> and call the callback with
271	the C<0> (error) or C<-1> ok.
272
273	This is a composite request that tries to rename(2) the file first. If
274	rename files with C<EXDEV>, it creates the destination file with mode 0200
275	and copies the contents of the source file into it using C<aio_sendfile>,
276	followed by restoring atime, mtime, access mode and uid/gid, in that
277	order, and unlinking the C<$srcpath>.
278
279	If an error occurs, the partial destination file will be unlinked, if
280	possible, except when setting atime, mtime, access mode and uid/gid, where
281	errors are being ignored.
282
283	=cut
284
285	sub aio_move($$$) {
286	my ($src, $dst, $cb) = @_;
287
288	my $grp = aio_group $cb;
289
290	add $grp aio_rename $src, $dst, sub {
291	if ($_[0] && $! == EXDEV) {
292	add $grp aio_open $src, O_RDONLY, 0, sub {
293	if (my $src_fh = $_[0]) {
294	my @stat = stat $src_fh;
295
296	add $grp aio_open $dst, O_WRONLY, 0200, sub {
297	if (my $dst_fh = $_[0]) {
298	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
299	close $src_fh;
300
301	if ($_[0] == $stat[7]) {
302	utime $stat[8], $stat[9], $dst;
303	chmod $stat[2] & 07777, $dst_fh;
304	chown $stat[4], $stat[5], $dst_fh;
305	close $dst_fh;
306
307	add $grp aio_unlink $src, sub {
308	$grp->result ($_[0]);
309	};
310	} else {
311	my $errno = $!;
312	add $grp aio_unlink $dst, sub {
313	$! = $errno;
314	$grp->result (-1);
315	};
316	}
317	};
318	} else {
319	$grp->result (-1);
320	}
321	},
322
323	} else {
324	$grp->result (-1);
325	}
326	};
327	} else {
328	$grp->result ($_[0]);
329	}
330	};
331
332	$grp
333	}
334		373
335	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	374	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
336		375
337	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
338	reading at byte offset C<$in_offset>, and starts writing at the current	377	reading at byte offset C<$in_offset>, and starts writing at the current
…		…
352	C<$in_fh> than are written, and there is no way to find out how many	391	C<$in_fh> than are written, and there is no way to find out how many
353	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
354	provides the number of bytes written to C<$out_fh>. Only if the result	393	provides the number of bytes written to C<$out_fh>. Only if the result
355	value equals C<$length> one can assume that C<$length> bytes have been	394	value equals C<$length> one can assume that C<$length> bytes have been
356	read.	395	read.
		396
357		397
358	=item aio_readahead $fh,$offset,$length, $callback->($retval)	398	=item aio_readahead $fh,$offset,$length, $callback->($retval)
359		399
360	C<aio_readahead> populates the page cache with data from a file so that	400	C<aio_readahead> populates the page cache with data from a file so that
361	subsequent reads from that file will not block on disk I/O. The C<$offset>	401	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
367	file. The current file offset of the file is left unchanged.	407	file. The current file offset of the file is left unchanged.
368		408
369	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be
370	emulated by simply reading the data, which would have a similar effect.	410	emulated by simply reading the data, which would have a similar effect.
371		411
		412
372	=item aio_stat $fh_or_path, $callback->($status)	413	=item aio_stat $fh_or_path, $callback->($status)
373		414
374	=item aio_lstat $fh, $callback->($status)	415	=item aio_lstat $fh, $callback->($status)
375		416
376	Works like perl's C<stat> or C<lstat> in void context. The callback will	417	Works like perl's C<stat> or C<lstat> in void context. The callback will
…		…
389	aio_stat "/etc/passwd", sub {	430	aio_stat "/etc/passwd", sub {
390	$_[0] and die "stat failed: $!";	431	$_[0] and die "stat failed: $!";
391	print "size is ", -s _, "\n";	432	print "size is ", -s _, "\n";
392	};	433	};
393		434
		435
		436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		437
		438	Works like perl's C<utime> function (including the special case of $atime
		439	and $mtime being undef). Fractional times are supported if the underlying
		440	syscalls support them.
		441
		442	When called with a pathname, uses utimes(2) if available, otherwise
		443	utime(2). If called on a file descriptor, uses futimes(2) if available,
		444	otherwise returns ENOSYS, so this is not portable.
		445
		446	Examples:
		447
		448	# set atime and mtime to current time (basically touch(1)):
		449	aio_utime "path", undef, undef;
		450	# set atime to current time and mtime to beginning of the epoch:
		451	aio_utime "path", time, undef; # undef==0
		452
		453
		454	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		455
		456	Works like perl's C<chown> function, except that C<undef> for either $uid
		457	or $gid is being interpreted as "do not change" (but -1 can also be used).
		458
		459	Examples:
		460
		461	# same as "chown root path" in the shell:
		462	aio_chown "path", 0, -1;
		463	# same as above:
		464	aio_chown "path", 0, undef;
		465
		466
		467	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		468
		469	Works like truncate(2) or ftruncate(2).
		470
		471
		472	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		473
		474	Works like perl's C<chmod> function.
		475
		476
394	=item aio_unlink $pathname, $callback->($status)	477	=item aio_unlink $pathname, $callback->($status)
395		478
396	Asynchronously unlink (delete) a file and call the callback with the	479	Asynchronously unlink (delete) a file and call the callback with the
397	result code.	480	result code.
398		481
		482
		483	=item aio_mknod $path, $mode, $dev, $callback->($status)
		484
		485	[EXPERIMENTAL]
		486
		487	Asynchronously create a device node (or fifo). See mknod(2).
		488
		489	The only (POSIX-) portable way of calling this function is:
		490
		491	aio_mknod $path, IO::AIO::S_IFIFO \| $mode, 0, sub { ...
		492
		493
399	=item aio_link $srcpath, $dstpath, $callback->($status)	494	=item aio_link $srcpath, $dstpath, $callback->($status)
400		495
401	Asynchronously create a new link to the existing object at C<$srcpath> at	496	Asynchronously create a new link to the existing object at C<$srcpath> at
402	the path C<$dstpath> and call the callback with the result code.	497	the path C<$dstpath> and call the callback with the result code.
403		498
		499
404	=item aio_symlink $srcpath, $dstpath, $callback->($status)	500	=item aio_symlink $srcpath, $dstpath, $callback->($status)
405		501
406	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
407	the path C<$dstpath> and call the callback with the result code.	503	the path C<$dstpath> and call the callback with the result code.
408		504
		505
		506	=item aio_readlink $path, $callback->($link)
		507
		508	Asynchronously read the symlink specified by C<$path> and pass it to
		509	the callback. If an error occurs, nothing or undef gets passed to the
		510	callback.
		511
		512
409	=item aio_rename $srcpath, $dstpath, $callback->($status)	513	=item aio_rename $srcpath, $dstpath, $callback->($status)
410		514
411	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
412	rename(2) and call the callback with the result code.	516	rename(2) and call the callback with the result code.
413		517
		518
		519	=item aio_mkdir $pathname, $mode, $callback->($status)
		520
		521	Asynchronously mkdir (create) a directory and call the callback with
		522	the result code. C<$mode> will be modified by the umask at the time the
		523	request is executed, so do not change your umask.
		524
		525
414	=item aio_rmdir $pathname, $callback->($status)	526	=item aio_rmdir $pathname, $callback->($status)
415		527
416	Asynchronously rmdir (delete) a directory and call the callback with the	528	Asynchronously rmdir (delete) a directory and call the callback with the
417	result code.	529	result code.
		530
418		531
419	=item aio_readdir $pathname, $callback->($entries)	532	=item aio_readdir $pathname, $callback->($entries)
420		533
421	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
422	directory (i.e. opendir + readdir + closedir). The entries will not be	535	directory (i.e. opendir + readdir + closedir). The entries will not be
423	sorted, and will B<NOT> include the C<.> and C<..> entries.	536	sorted, and will B<NOT> include the C<.> and C<..> entries.
424		537
425	The callback a single argument which is either C<undef> or an array-ref	538	The callback is passed a single argument which is either C<undef> or an
426	with the filenames.	539	array-ref with the filenames.
		540
		541
		542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		543
		544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune
		545	behaviour and output format. In case of an error, C<$entries> will be
		546	C<undef>.
		547
		548	The flags are a combination of the following constants, ORed together (the
		549	flags will also be passed to the callback, possibly modified):
		550
		551	=over 4
		552
		553	=item AIO::READDIR_DENTS
		554
		555	When this flag is off, then the callback gets an arrayref with of names
		556	only (as with C<aio_readdir>), otherwise it gets an arrayref with
		557	C<[$name, $inode, $type]> arrayrefs, each describing a single directory
		558	entry in more detail.
		559
		560	C<$name> is the name of the entry.
		561
		562	C<$inode> is the inode number (which might not be exact on systems with 64
		563	bit inode numbers and 32 bit perls). On systems that do not deliver the
		564	inode information, this will always be zero.
		565
		566	C<$type> is one of the C<AIO::DT_xxx> constants:
		567
		568	C<AIO::DT_UNKNOWN>, C<AIO::DT_FIFO>, C<AIO::DT_CHR>, C<AIO::DT_DIR>,
		569	C<AIO::DT_BLK>, C<AIO::DT_REG>, C<AIO::DT_LNK>, C<AIO::DT_SOCK>,
		570	C<AIO::DT_WHT>.
		571
		572	C<AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		573	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		574	scalars are read-only: you can not modify them.
		575
		576	=item AIO::READDIR_DIRS_FIRST
		577
		578	When this flag is set, then the names will be returned in an order where
		579	likely directories come first. This is useful when you need to quickly
		580	find directories, or you want to find all directories while avoiding to
		581	stat() each entry.
		582
		583	=item AIO::READDIR_STAT_ORDER
		584
		585	When this flag is set, then the names will be returned in an order
		586	suitable for stat()'ing each one. That is, when you plan to stat()
		587	all files in the given directory, then the returned order will likely
		588	be fastest.
		589
		590	If both this flag and IO::READDIR_DIRS_FIRST are specified, then the
		591	likely dirs come first, resulting in a less optimal stat order.
		592
		593	=item AIO::READDIR_FOUND_UNKNOWN
		594
		595	This flag should not be set when calling C<aio_readdirx>. Instead, it
		596	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		597	C<AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all
		598	C<$type>'s are known, which can be used to speed up some algorithms.
		599
		600	=back
		601
		602
		603	=item aio_load $path, $data, $callback->($status)
		604
		605	This is a composite request that tries to fully load the given file into
		606	memory. Status is the same as with aio_read.
		607
		608	=cut
		609
		610	sub aio_load($$;$) {
		611	my ($path, undef, $cb) = @_;
		612	my $data = \$_[1];
		613
		614	my $pri = aioreq_pri;
		615	my $grp = aio_group $cb;
		616
		617	aioreq_pri $pri;
		618	add $grp aio_open $path, O_RDONLY, 0, sub {
		619	my $fh = shift
		620	or return $grp->result (-1);
		621
		622	aioreq_pri $pri;
		623	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		624	$grp->result ($_[0]);
		625	};
		626	};
		627
		628	$grp
		629	}
		630
		631	=item aio_copy $srcpath, $dstpath, $callback->($status)
		632
		633	Try to copy the I<file> (directories not supported as either source or
		634	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		635	the C<0> (error) or C<-1> ok.
		636
		637	This is a composite request that creates the destination file with
		638	mode 0200 and copies the contents of the source file into it using
		639	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
		640	uid/gid, in that order.
		641
		642	If an error occurs, the partial destination file will be unlinked, if
		643	possible, except when setting atime, mtime, access mode and uid/gid, where
		644	errors are being ignored.
		645
		646	=cut
		647
		648	sub aio_copy($$;$) {
		649	my ($src, $dst, $cb) = @_;
		650
		651	my $pri = aioreq_pri;
		652	my $grp = aio_group $cb;
		653
		654	aioreq_pri $pri;
		655	add $grp aio_open $src, O_RDONLY, 0, sub {
		656	if (my $src_fh = $_[0]) {
		657	my @stat = stat $src_fh; # hmm, might bock over nfs?
		658
		659	aioreq_pri $pri;
		660	add $grp aio_open $dst, O_CREAT \| O_WRONLY \| O_TRUNC, 0200, sub {
		661	if (my $dst_fh = $_[0]) {
		662	aioreq_pri $pri;
		663	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
		664	if ($_[0] == $stat[7]) {
		665	$grp->result (0);
		666	close $src_fh;
		667
		668	my $ch = sub {
		669	aioreq_pri $pri;
		670	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		671	aioreq_pri $pri;
		672	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		673	aioreq_pri $pri;
		674	add $grp aio_close $dst_fh;
		675	}
		676	};
		677	};
		678
		679	aioreq_pri $pri;
		680	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		681	if ($_[0] < 0 && $! == ENOSYS) {
		682	aioreq_pri $pri;
		683	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
		684	} else {
		685	$ch->();
		686	}
		687	};
		688	} else {
		689	$grp->result (-1);
		690	close $src_fh;
		691	close $dst_fh;
		692
		693	aioreq $pri;
		694	add $grp aio_unlink $dst;
		695	}
		696	};
		697	} else {
		698	$grp->result (-1);
		699	}
		700	},
		701
		702	} else {
		703	$grp->result (-1);
		704	}
		705	};
		706
		707	$grp
		708	}
		709
		710	=item aio_move $srcpath, $dstpath, $callback->($status)
		711
		712	Try to move the I<file> (directories not supported as either source or
		713	destination) from C<$srcpath> to C<$dstpath> and call the callback with
		714	the C<0> (error) or C<-1> ok.
		715
		716	This is a composite request that tries to rename(2) the file first; if
		717	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
		718	that is successful, unlinks the C<$srcpath>.
		719
		720	=cut
		721
		722	sub aio_move($$;$) {
		723	my ($src, $dst, $cb) = @_;
		724
		725	my $pri = aioreq_pri;
		726	my $grp = aio_group $cb;
		727
		728	aioreq_pri $pri;
		729	add $grp aio_rename $src, $dst, sub {
		730	if ($_[0] && $! == EXDEV) {
		731	aioreq_pri $pri;
		732	add $grp aio_copy $src, $dst, sub {
		733	$grp->result ($_[0]);
		734
		735	if (!$_[0]) {
		736	aioreq_pri $pri;
		737	add $grp aio_unlink $src;
		738	}
		739	};
		740	} else {
		741	$grp->result ($_[0]);
		742	}
		743	};
		744
		745	$grp
		746	}
427		747
428	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	748	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
429		749
430	Scans a directory (similar to C<aio_readdir>) but additionally tries to	750	Scans a directory (similar to C<aio_readdir>) but additionally tries to
431	efficiently separate the entries of directory C<$path> into two sets of	751	efficiently separate the entries of directory C<$path> into two sets of
…		…
433	recurse into (everything else, including symlinks to directories).	753	recurse into (everything else, including symlinks to directories).
434		754
435	C<aio_scandir> is a composite request that creates of many sub requests_	755	C<aio_scandir> is a composite request that creates of many sub requests_
436	C<$maxreq> specifies the maximum number of outstanding aio requests that	756	C<$maxreq> specifies the maximum number of outstanding aio requests that
437	this function generates. If it is C<< <= 0 >>, then a suitable default	757	this function generates. If it is C<< <= 0 >>, then a suitable default
438	will be chosen (currently 6).	758	will be chosen (currently 4).
439		759
440	On error, the callback is called without arguments, otherwise it receives	760	On error, the callback is called without arguments, otherwise it receives
441	two array-refs with path-relative entry names.	761	two array-refs with path-relative entry names.
442		762
443	Example:	763	Example:
…		…
477	as those tend to return 0 or 1 as link counts, which disables the	797	as those tend to return 0 or 1 as link counts, which disables the
478	directory counting heuristic.	798	directory counting heuristic.
479		799
480	=cut	800	=cut
481		801
482	sub aio_scandir($$$) {	802	sub aio_scandir($$;$) {
483	my ($path, $maxreq, $cb) = @_;	803	my ($path, $maxreq, $cb) = @_;
484		804
		805	my $pri = aioreq_pri;
		806
485	my $grp = aio_group $cb;	807	my $grp = aio_group $cb;
486		808
487	$maxreq = 6 if $maxreq <= 0;	809	$maxreq = 4 if $maxreq <= 0;
488		810
489	# stat once	811	# stat once
		812	aioreq_pri $pri;
490	add $grp aio_stat $path, sub {	813	add $grp aio_stat $path, sub {
491	return $grp->result () if $_[0];	814	return $grp->result () if $_[0];
492	my $now = time;	815	my $now = time;
493	my $hash1 = join ":", (stat _)[0,1,3,7,9];	816	my $hash1 = join ":", (stat _)[0,1,3,7,9];
494		817
495	# read the directory entries	818	# read the directory entries
		819	aioreq_pri $pri;
496	add $grp aio_readdir $path, sub {	820	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {
497	my $entries = shift	821	my $entries = shift
498	or return $grp->result ();	822	or return $grp->result ();
499		823
500	# stat the dir another time	824	# stat the dir another time
		825	aioreq_pri $pri;
501	add $grp aio_stat $path, sub {	826	add $grp aio_stat $path, sub {
502	my $hash2 = join ":", (stat _)[0,1,3,7,9];	827	my $hash2 = join ":", (stat _)[0,1,3,7,9];
503		828
504	my $ndirs;	829	my $ndirs;
505		830
…		…
529	limit $statgrp $maxreq;	854	limit $statgrp $maxreq;
530	feed $statgrp sub {	855	feed $statgrp sub {
531	return unless @$entries;	856	return unless @$entries;
532	my $entry = pop @$entries;	857	my $entry = pop @$entries;
533		858
		859	aioreq_pri $pri;
534	add $statgrp aio_stat "$path/$entry/.", sub {	860	add $statgrp aio_stat "$path/$entry/.", sub {
535	if ($_[0] < 0) {	861	if ($_[0] < 0) {
536	push @nondirs, $entry;	862	push @nondirs, $entry;
537	} else {	863	} else {
538	# need to check for real directory	864	# need to check for real directory
		865	aioreq_pri $pri;
539	add $statgrp aio_lstat "$path/$entry", sub {	866	add $statgrp aio_lstat "$path/$entry", sub {
540	if (-d _) {	867	if (-d _) {
541	push @dirs, $entry;	868	push @dirs, $entry;
542		869
543	unless (--$ndirs) {	870	unless (--$ndirs) {
…		…
556	};	883	};
557		884
558	$grp	885	$grp
559	}	886	}
560		887
		888	=item aio_rmtree $path, $callback->($status)
		889
		890	Delete a directory tree starting (and including) C<$path>, return the
		891	status of the final C<rmdir> only. This is a composite request that
		892	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		893	everything else.
		894
		895	=cut
		896
		897	sub aio_rmtree;
		898	sub aio_rmtree($;$) {
		899	my ($path, $cb) = @_;
		900
		901	my $pri = aioreq_pri;
		902	my $grp = aio_group $cb;
		903
		904	aioreq_pri $pri;
		905	add $grp aio_scandir $path, 0, sub {
		906	my ($dirs, $nondirs) = @_;
		907
		908	my $dirgrp = aio_group sub {
		909	add $grp aio_rmdir $path, sub {
		910	$grp->result ($_[0]);
		911	};
		912	};
		913
		914	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		915	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		916
		917	add $grp $dirgrp;
		918	};
		919
		920	$grp
		921	}
		922
		923	=item aio_sync $callback->($status)
		924
		925	Asynchronously call sync and call the callback when finished.
		926
561	=item aio_fsync $fh, $callback->($status)	927	=item aio_fsync $fh, $callback->($status)
562		928
563	Asynchronously call fsync on the given filehandle and call the callback	929	Asynchronously call fsync on the given filehandle and call the callback
564	with the fsync result code.	930	with the fsync result code.
565		931
…		…
568	Asynchronously call fdatasync on the given filehandle and call the	934	Asynchronously call fdatasync on the given filehandle and call the
569	callback with the fdatasync result code.	935	callback with the fdatasync result code.
570		936
571	If this call isn't available because your OS lacks it or it couldn't be	937	If this call isn't available because your OS lacks it or it couldn't be
572	detected, it will be emulated by calling C<fsync> instead.	938	detected, it will be emulated by calling C<fsync> instead.
		939
		940	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		941
		942	Sync the data portion of the file specified by C<$offset> and C<$length>
		943	to disk (but NOT the metadata), by calling the Linux-specific
		944	sync_file_range call. If sync_file_range is not available or it returns
		945	ENOSYS, then fdatasync or fsync is being substituted.
		946
		947	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		948	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		949	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		950	manpage for details.
		951
		952	=item aio_pathsync $path, $callback->($status)
		953
		954	This request tries to open, fsync and close the given path. This is a
		955	composite request intended to sync directories after directory operations
		956	(E.g. rename). This might not work on all operating systems or have any
		957	specific effect, but usually it makes sure that directory changes get
		958	written to disc. It works for anything that can be opened for read-only,
		959	not just directories.
		960
		961	Passes C<0> when everything went ok, and C<-1> on error.
		962
		963	=cut
		964
		965	sub aio_pathsync($;$) {
		966	my ($path, $cb) = @_;
		967
		968	my $pri = aioreq_pri;
		969	my $grp = aio_group $cb;
		970
		971	aioreq_pri $pri;
		972	add $grp aio_open $path, O_RDONLY, 0, sub {
		973	my ($fh) = @_;
		974	if ($fh) {
		975	aioreq_pri $pri;
		976	add $grp aio_fsync $fh, sub {
		977	$grp->result ($_[0]);
		978
		979	aioreq_pri $pri;
		980	add $grp aio_close $fh;
		981	};
		982	} else {
		983	$grp->result (-1);
		984	}
		985	};
		986
		987	$grp
		988	}
573		989
574	=item aio_group $callback->(...)	990	=item aio_group $callback->(...)
575		991
576	This is a very special aio request: Instead of doing something, it is a	992	This is a very special aio request: Instead of doing something, it is a
577	container for other aio requests, which is useful if you want to bundle	993	container for other aio requests, which is useful if you want to bundle
…		…
689	Their lifetime, simplified, looks like this: when they are empty, they	1105	Their lifetime, simplified, looks like this: when they are empty, they
690	will finish very quickly. If they contain only requests that are in the	1106	will finish very quickly. If they contain only requests that are in the
691	C<done> state, they will also finish. Otherwise they will continue to	1107	C<done> state, they will also finish. Otherwise they will continue to
692	exist.	1108	exist.
693		1109
694	That means after creating a group you have some time to add requests. And	1110	That means after creating a group you have some time to add requests
695	in the callbacks of those requests, you can add further requests to the	1111	(precisely before the callback has been invoked, which is only done within
696	group. And only when all those requests have finished will the the group	1112	the C<poll_cb>). And in the callbacks of those requests, you can add
697	itself finish.	1113	further requests to the group. And only when all those requests have
		1114	finished will the the group itself finish.
698		1115
699	=over 4	1116	=over 4
700		1117
701	=item add $grp ...	1118	=item add $grp ...
702		1119
…		…
714	itself. Useful when you queued a lot of events but got a result early.	1131	itself. Useful when you queued a lot of events but got a result early.
715		1132
716	=item $grp->result (...)	1133	=item $grp->result (...)
717		1134
718	Set the result value(s) that will be passed to the group callback when all	1135	Set the result value(s) that will be passed to the group callback when all
719	subrequests have finished. By default, no argument will be passed.	1136	subrequests have finished and set the groups errno to the current value
		1137	of errno (just like calling C<errno> without an error number). By default,
		1138	no argument will be passed and errno is zero.
		1139
		1140	=item $grp->errno ([$errno])
		1141
		1142	Sets the group errno value to C<$errno>, or the current value of errno
		1143	when the argument is missing.
		1144
		1145	Every aio request has an associated errno value that is restored when
		1146	the callback is invoked. This method lets you change this value from its
		1147	default (0).
		1148
		1149	Calling C<result> will also set errno, so make sure you either set C<$!>
		1150	before the call to C<result>, or call c<errno> after it.
720		1151
721	=item feed $grp $callback->($grp)	1152	=item feed $grp $callback->($grp)
722		1153
723	Sets a feeder/generator on this group: every group can have an attached	1154	Sets a feeder/generator on this group: every group can have an attached
724	generator that generates requests if idle. The idea behind this is that,	1155	generator that generates requests if idle. The idea behind this is that,
725	although you could just queue as many requests as you want in a group,	1156	although you could just queue as many requests as you want in a group,
726	this might starve other requests for a potentially long time. For	1157	this might starve other requests for a potentially long time. For example,
727	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1158	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,
728	requests, delaying any later requests for a long time.	1159	delaying any later requests for a long time.
729		1160
730	To avoid this, and allow incremental generation of requests, you can	1161	To avoid this, and allow incremental generation of requests, you can
731	instead a group and set a feeder on it that generates those requests. The	1162	instead a group and set a feeder on it that generates those requests. The
732	feed callback will be called whenever there are few enough (see C<limit>,	1163	feed callback will be called whenever there are few enough (see C<limit>,
733	below) requests active in the group itself and is expected to queue more	1164	below) requests active in the group itself and is expected to queue more
…		…
737	not impose any limits).	1168	not impose any limits).
738		1169
739	If the feed does not queue more requests when called, it will be	1170	If the feed does not queue more requests when called, it will be
740	automatically removed from the group.	1171	automatically removed from the group.
741		1172
742	If the feed limit is C<0>, it will be set to C<2> automatically.	1173	If the feed limit is C<0> when this method is called, it will be set to
		1174	C<2> automatically.
743		1175
744	Example:	1176	Example:
745		1177
746	# stat all files in @files, but only ever use four aio requests concurrently:	1178	# stat all files in @files, but only ever use four aio requests concurrently:
747		1179
…		…
759	Sets the feeder limit for the group: The feeder will be called whenever	1191	Sets the feeder limit for the group: The feeder will be called whenever
760	the group contains less than this many requests.	1192	the group contains less than this many requests.
761		1193
762	Setting the limit to C<0> will pause the feeding process.	1194	Setting the limit to C<0> will pause the feeding process.
763		1195
		1196	The default value for the limit is C<0>, but note that setting a feeder
		1197	automatically bumps it up to C<2>.
		1198
764	=back	1199	=back
765		1200
766	=head2 SUPPORT FUNCTIONS	1201	=head2 SUPPORT FUNCTIONS
		1202
		1203	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
767		1204
768	=over 4	1205	=over 4
769		1206
770	=item $fileno = IO::AIO::poll_fileno	1207	=item $fileno = IO::AIO::poll_fileno
771		1208
…		…
776		1213
777	See C<poll_cb> for an example.	1214	See C<poll_cb> for an example.
778		1215
779	=item IO::AIO::poll_cb	1216	=item IO::AIO::poll_cb
780		1217
781	Process all outstanding events on the result pipe. You have to call this	1218	Process some outstanding events on the result pipe. You have to call this
782	regularly. Returns the number of events processed. Returns immediately	1219	regularly. Returns C<0> if all events could be processed, or C<-1> if it
783	when no events are outstanding.	1220	returned earlier for whatever reason. Returns immediately when no events
		1221	are outstanding. The amount of events processed depends on the settings of
		1222	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
		1223
		1224	If not all requests were processed for whatever reason, the filehandle
		1225	will still be ready when C<poll_cb> returns, so normally you don't have to
		1226	do anything special to have it called later.
784		1227
785	Example: Install an Event watcher that automatically calls	1228	Example: Install an Event watcher that automatically calls
786	IO::AIO::poll_cb with high priority:	1229	IO::AIO::poll_cb with high priority:
787		1230
788	Event->io (fd => IO::AIO::poll_fileno,	1231	Event->io (fd => IO::AIO::poll_fileno,
789	poll => 'r', async => 1,	1232	poll => 'r', async => 1,
790	cb => \&IO::AIO::poll_cb);	1233	cb => \&IO::AIO::poll_cb);
791		1234
		1235	=item IO::AIO::max_poll_reqs $nreqs
		1236
		1237	=item IO::AIO::max_poll_time $seconds
		1238
		1239	These set the maximum number of requests (default C<0>, meaning infinity)
		1240	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1241	the maximum amount of time (default C<0>, meaning infinity) spent in
		1242	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1243	of time C<poll_cb> is allowed to use).
		1244
		1245	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1246	syscall per request processed, which is not normally a problem unless your
		1247	callbacks are really really fast or your OS is really really slow (I am
		1248	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1249
		1250	Setting these is useful if you want to ensure some level of
		1251	interactiveness when perl is not fast enough to process all requests in
		1252	time.
		1253
		1254	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
		1255
		1256	Example: Install an Event watcher that automatically calls
		1257	IO::AIO::poll_cb with low priority, to ensure that other parts of the
		1258	program get the CPU sometimes even under high AIO load.
		1259
		1260	# try not to spend much more than 0.1s in poll_cb
		1261	IO::AIO::max_poll_time 0.1;
		1262
		1263	# use a low priority so other tasks have priority
		1264	Event->io (fd => IO::AIO::poll_fileno,
		1265	poll => 'r', nice => 1,
		1266	cb => &IO::AIO::poll_cb);
		1267
792	=item IO::AIO::poll_wait	1268	=item IO::AIO::poll_wait
793		1269
		1270	If there are any outstanding requests and none of them in the result
794	Wait till the result filehandle becomes ready for reading (simply does a	1271	phase, wait till the result filehandle becomes ready for reading (simply
795	C<select> on the filehandle. This is useful if you want to synchronously wait	1272	does a C<select> on the filehandle. This is useful if you want to
796	for some requests to finish).	1273	synchronously wait for some requests to finish).
797		1274
798	See C<nreqs> for an example.	1275	See C<nreqs> for an example.
799		1276
		1277	=item IO::AIO::poll
		1278
		1279	Waits until some requests have been handled.
		1280
		1281	Returns the number of requests processed, but is otherwise strictly
		1282	equivalent to:
		1283
		1284	IO::AIO::poll_wait, IO::AIO::poll_cb
		1285
800	=item IO::AIO::nreqs	1286	=item IO::AIO::flush
801		1287
802	Returns the number of requests currently outstanding (i.e. for which their	1288	Wait till all outstanding AIO requests have been handled.
803	callback has not been invoked yet).
804		1289
805	Example: wait till there are no outstanding requests anymore:	1290	Strictly equivalent to:
806		1291
807	IO::AIO::poll_wait, IO::AIO::poll_cb	1292	IO::AIO::poll_wait, IO::AIO::poll_cb
808	while IO::AIO::nreqs;	1293	while IO::AIO::nreqs;
809		1294
810	=item IO::AIO::flush	1295	=back
811		1296
812	Wait till all outstanding AIO requests have been handled.	1297	=head3 CONTROLLING THE NUMBER OF THREADS
813		1298
814	Strictly equivalent to:	1299	=over
815
816	IO::AIO::poll_wait, IO::AIO::poll_cb
817	while IO::AIO::nreqs;
818
819	=item IO::AIO::poll
820
821	Waits until some requests have been handled.
822
823	Strictly equivalent to:
824
825	IO::AIO::poll_wait, IO::AIO::poll_cb
826	if IO::AIO::nreqs;
827		1300
828	=item IO::AIO::min_parallel $nthreads	1301	=item IO::AIO::min_parallel $nthreads
829		1302
830	Set the minimum number of AIO threads to C<$nthreads>. The current	1303	Set the minimum number of AIO threads to C<$nthreads>. The current
831	default is C<8>, which means eight asynchronous operations can execute	1304	default is C<8>, which means eight asynchronous operations can execute
832	concurrently at any one time (the number of outstanding requests,	1305	concurrently at any one time (the number of outstanding requests,
833	however, is unlimited).	1306	however, is unlimited).
834		1307
835	IO::AIO starts threads only on demand, when an AIO request is queued and	1308	IO::AIO starts threads only on demand, when an AIO request is queued and
836	no free thread exists.	1309	no free thread exists. Please note that queueing up a hundred requests can
		1310	create demand for a hundred threads, even if it turns out that everything
		1311	is in the cache and could have been processed faster by a single thread.
837		1312
838	It is recommended to keep the number of threads relatively low, as some	1313	It is recommended to keep the number of threads relatively low, as some
839	Linux kernel versions will scale negatively with the number of threads	1314	Linux kernel versions will scale negatively with the number of threads
840	(higher parallelity => MUCH higher latency). With current Linux 2.6	1315	(higher parallelity => MUCH higher latency). With current Linux 2.6
841	versions, 4-32 threads should be fine.	1316	versions, 4-32 threads should be fine.
…		…
855	This module automatically runs C<max_parallel 0> at program end, to ensure	1330	This module automatically runs C<max_parallel 0> at program end, to ensure
856	that all threads are killed and that there are no outstanding requests.	1331	that all threads are killed and that there are no outstanding requests.
857		1332
858	Under normal circumstances you don't need to call this function.	1333	Under normal circumstances you don't need to call this function.
859		1334
		1335	=item IO::AIO::max_idle $nthreads
		1336
		1337	Limit the number of threads (default: 4) that are allowed to idle (i.e.,
		1338	threads that did not get a request to process within 10 seconds). That
		1339	means if a thread becomes idle while C<$nthreads> other threads are also
		1340	idle, it will free its resources and exit.
		1341
		1342	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1343	to allow for extremely high load situations, but want to free resources
		1344	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1345
		1346	The default is probably ok in most situations, especially if thread
		1347	creation is fast. If thread creation is very slow on your system you might
		1348	want to use larger values.
		1349
860	=item $oldnreqs = IO::AIO::max_outstanding $nreqs	1350	=item IO::AIO::max_outstanding $maxreqs
861		1351
862	[REMOVED]	1352	This is a very bad function to use in interactive programs because it
		1353	blocks, and a bad way to reduce concurrency because it is inexact: Better
		1354	use an C<aio_group> together with a feed callback.
863		1355
864	Pre-2.x versions used max_outstanding for a crude request queue length limit.
865
866	In 2.x+ you are advised to use a group and a feeder to limit
867	concurrency. The max_outstanding feature ran very unstable (endless
868	recursions causing segfaults, bad interaction with groups etc.) and was
869	removed.
870
871	I am deeply sorry, but I am still on the hunt for a good limiting interface.
872
873	Original description was as follows:
874
875	Sets the maximum number of outstanding requests to C<$nreqs>. If you try	1356	Sets the maximum number of outstanding requests to C<$nreqs>. If you
876	to queue up more than this number of requests, the caller will block until	1357	do queue up more than this number of requests, the next call to the
877	some requests have been handled.	1358	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
		1359	function will block until the limit is no longer exceeded.
		1360
		1361	The default value is very large, so there is no practical limit on the
		1362	number of outstanding requests.
		1363
		1364	You can still queue as many requests as you want. Therefore,
		1365	C<max_outstanding> is mainly useful in simple scripts (with low values) or
		1366	as a stop gap to shield against fatal memory overflow (with large values).
878		1367
879	=back	1368	=back
880		1369
		1370	=head3 STATISTICAL INFORMATION
		1371
		1372	=over
		1373
		1374	=item IO::AIO::nreqs
		1375
		1376	Returns the number of requests currently in the ready, execute or pending
		1377	states (i.e. for which their callback has not been invoked yet).
		1378
		1379	Example: wait till there are no outstanding requests anymore:
		1380
		1381	IO::AIO::poll_wait, IO::AIO::poll_cb
		1382	while IO::AIO::nreqs;
		1383
		1384	=item IO::AIO::nready
		1385
		1386	Returns the number of requests currently in the ready state (not yet
		1387	executed).
		1388
		1389	=item IO::AIO::npending
		1390
		1391	Returns the number of requests currently in the pending state (executed,
		1392	but not yet processed by poll_cb).
		1393
		1394	=back
		1395
881	=cut	1396	=cut
882		1397
883	# support function to convert a fd into a perl filehandle
884	sub _fd2fh {
885	return undef if $_[0] < 0;
886
887	# try to generate nice filehandles
888	my $sym = "IO::AIO::fd#$_[0]";
889	local *$sym;
890
891	open *$sym, "+<&=$_[0]" # usually works under any unix
892	or open *$sym, "<&=$_[0]" # cygwin needs this
893	or open *$sym, ">&=$_[0]" # or this
894	or return undef;
895
896	*$sym
897	}
898
899	min_parallel 8;	1398	min_parallel 8;
900		1399
901	END {	1400	END { flush }
902	max_parallel 0;
903	}
904		1401
905	1;	1402	1;
906		1403
907	=head2 FORK BEHAVIOUR	1404	=head2 FORK BEHAVIOUR
908		1405
…		…
928	bytes of memory. In addition, stat requests need a stat buffer (possibly	1425	bytes of memory. In addition, stat requests need a stat buffer (possibly
929	a few hundred bytes), readdir requires a result buffer and so on. Perl	1426	a few hundred bytes), readdir requires a result buffer and so on. Perl
930	scalars and other data passed into aio requests will also be locked and	1427	scalars and other data passed into aio requests will also be locked and
931	will consume memory till the request has entered the done state.	1428	will consume memory till the request has entered the done state.
932		1429
933	This is now awfully much, so queuing lots of requests is not usually a	1430	This is not awfully much, so queuing lots of requests is not usually a
934	problem.	1431	problem.
935		1432
936	Per-thread usage:	1433	Per-thread usage:
937		1434
938	In the execution phase, some aio requests require more memory for	1435	In the execution phase, some aio requests require more memory for
…		…
943		1440
944	Known bugs will be fixed in the next release.	1441	Known bugs will be fixed in the next release.
945		1442
946	=head1 SEE ALSO	1443	=head1 SEE ALSO
947		1444
948	L<Coro::AIO>.	1445	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		1446	more natural syntax.
949		1447
950	=head1 AUTHOR	1448	=head1 AUTHOR
951		1449
952	Marc Lehmann <schmorp@schmorp.de>	1450	Marc Lehmann <schmorp@schmorp.de>
953	http://home.schmorp.de/	1451	http://home.schmorp.de/

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Comparing IO-AIO/AIO.pm (file contents): Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC vs. Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC

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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.77 by root, Wed Oct 25 17:57:30 2006 UTC vs.
Revision 1.148 by root, Sat Jun 6 17:25:13 2009 UTC