--- 3m-810.pl	2008/09/28 18:19:37	6
+++ 3m-810.pl	2008/10/03 08:53:57	17
@@ -39,6 +39,8 @@
 
 L<perl(1)>
 
+L<http://stackoverflow.com/questions/149617/how-could-i-guess-a-checksum-algorithm>
+
 =head1 AUTHOR
 
 Dobrica Pavlinusic <dpavlin@rot13.org> L<http://www.rot13.org/~dpavlin/>
@@ -102,26 +104,40 @@
 			die "wrong length $tl for $nr tags: ",dump( $tags ) if $tl =! $nr * 8;
 
 			my @tags;
-			push @tags, substr($tags, $_ * 8, 8) foreach ( 0 .. $nr - 1 );
-			warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags );
-			print "seen $nr tags: ", join(',', map { unpack('H16', $_) } @tags ) , "\n";
+			push @tags, uc(unpack('H16', substr($tags, $_ * 8, 8))) foreach ( 0 .. $nr - 1 );
+			warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags ) if $debug;
+			print "seen $nr tags: ", join(',', @tags ) , "\n";
+
+			# XXX read first tag
+			read_tag( @tags );
+
 		}
 ) }
 
 ) foreach ( 1 .. 100 );
 
-cmd( 'D6 00  0D  02      E00401003123AA26   00   03     1CC4', 'read offset: 0 blocks: 3' );
+my $read_cached;
 
-#     D6 00  1F  02 00   E00401003123AA26   03   00 00   04 11 00 01   01 00   30 30 30 30   02 00   30 30 30 30    E5F4
-warn "D6 00  1F  02 00   E00401003123AA26   03   00 00   04 11 00 01   01 00   31 32 33 34   02 00   35 36 37 38    531F\n";
+sub read_tag {
+	my ( $tag ) = @_;
 
-cmd( 'D6 00  0D  02      E00401003123AA26   03   04     3970', 'read offset: 3 blocks: 4' );
+	print "read_tag $tag\n";
+	return if $read_cached->{ $tag }++;
 
-#     D6 00  25  02 00   E00401003123AA26   04                         03 00   30 30 00 00   04 00   00 00 00 00   
-#                                                                      05 00   00 00 00 00   06 00   00 00 00 00    B9BA
-warn "D6 00  25  02 00   E00401003123AA26   04                         03 00   39 30 31 32   04 00   33 34 35 36
-                                                                       05 00   00 00 00 00   06 00   00 00 00 00    524B\n";
-warn "D6 00  0F  FE  00 00  05 01   E00401003123AA26  941A ##### ready?\n";
+	cmd(    "D6 00  0D  02      $tag   00   03     1CC4", 'read offset: 0 blocks: 3' );
+
+	#        D6 00  1F  02 00   $tag   03   00 00   04 11 00 01   01 00   30 30 30 30   02 00   30 30 30 30    E5F4
+	warn "?? D6 00  1F  02 00   $tag   03   00 00   04 11 00 01   01 00   31 32 33 34   02 00   35 36 37 38    531F\n";
+if (0) {
+	cmd(    "D6 00  0D  02      $tag   03   04     3970", 'read offset: 3 blocks: 4' );
+
+	#        D6 00  25  02 00   $tag   04                         03 00   30 30 00 00   04 00   00 00 00 00   
+	#                           $tag                              05 00   00 00 00 00   06 00   00 00 00 00    B9BA
+	warn "?? D6 00  25  02 00   $tag   04                         03 00   39 30 31 32   04 00   ....\n";
+}
+	warn "?? D6 00  0F  FE  00 00  05 01   $tag  941A ##### ready?\n";
+
+}
 
 for ( 1 .. 3 ) {
 
@@ -161,9 +177,10 @@
 	foreach my $str ( @_ ) {
 		my $hex = unpack( 'H*', $str );
 		$hex =~ s/(..)/$1 /g if length( $str ) > 2;
+		$hex =~ s/\s+$//;
 		push @out, $hex;
 	}
-	return join('  ', @out);
+	return join(' | ', @out);
 }
 
 sub read_bytes {
@@ -218,6 +235,41 @@
 	}
 }
 
+use Digest::CRC;
+
+sub crcccitt {
+	my $bytes = shift;
+	my $crc = Digest::CRC->new(
+		# midified CCITT to xor with 0xffff instead of 0x0000
+		width => 16, init => 0xffff, xorout => 0xffff, refout => 0, poly => 0x1021, refin => 0,
+	) or die $!;
+	$crc->add( $bytes );
+	pack('n', $crc->digest);
+}
+
+# my $checksum = checksum( $bytes );
+# my $checksum = checksum( $bytes, $original_checksum );
+sub checksum {
+	my ( $bytes, $checksum ) = @_;
+
+	my $xor = crcccitt( substr($bytes,1) );	# skip D6
+	warn "## checksum ",dump( $bytes, $xor, $checksum ) if $debug;
+
+	my $len = ord(substr($bytes,2,1));
+	my $len_real = length($bytes) - 1;
+
+	if ( $len_real != $len ) {
+		print "length wrong: $len_real != $len\n";
+		$bytes = substr($bytes,0,2) . chr($len_real) . substr($bytes,4);
+	}
+
+	if ( defined $checksum && $xor ne $checksum ) {
+		print "checksum doesn't match: ", as_hex($xor), " != ", as_hex($checksum), " data: ", as_hex($bytes), "\n";
+		return $bytes . $xor;
+	}
+	return $bytes . $checksum;
+}
+
 sub readchunk {
 	my ( $parser ) = @_;
 
@@ -228,21 +280,20 @@
 	my $length = read_bytes( 1, 'length' );
 	my $len = ord($length);
 	my $data = read_bytes( $len, 'data' );
-	my ( $cmd ) = unpack('C', $data );
 
 	my $payload  = substr( $data, 0, -2 );
 	my $payload_len = length($data);
 	warn "## payload too short $payload_len != $len\n" if $payload_len != $len;
+
 	my $checksum = substr( $data, -2, 2 );
-	# FIXME check checksum
+	checksum( $header . $length . $payload, $checksum );
 
-	print "<< ",as_hex( $header ), " [$len] ", as_hex( $payload ), "checksum: ", as_hex( $checksum ),"\n";
+	print "<< ",as_hex( $header ), " [$len] ", as_hex( $payload ), " | sum: ",as_hex($checksum),"\n";
 
 	$assert->{len}      = $len;
 	$assert->{payload}  = $payload;
-	$assert->{checksum} = $checksum;
 
-	$parser->( $len, $payload, $checksum ) if $parser && ref($parser) eq 'CODE';
+	$parser->( $len, $payload ) if $parser && ref($parser) eq 'CODE';
 
 	return $data;
 }
@@ -250,10 +301,9 @@
 sub str2bytes {
 	my $str = shift || confess "no str?";
 	my $b = $str;
-	$b =~ s/\s+(\S\S)(\S\S)+\s*/ $1 $2/;	# fix checksum
-	$b =~ s/\s+$//;
-	$b =~ s/\s+/\\x/g;
-	$b = '"\x' . $b . '"';
+	$b =~ s/\s+//g;
+	$b =~ s/(..)/\\x$1/g;
+	$b = "\"$b\"";
 	my $bytes = eval $b;
 	die $@ if $@;
 	warn "## str2bytes( $str ) => $b => ",as_hex($bytes) if $debug;
@@ -264,6 +314,9 @@
 	my ( $cmd, $cmd_desc, $expect, $expect_desc, $coderef ) = @_;
 	my $bytes = str2bytes( $cmd );
 
+	# fix checksum if needed
+	$bytes = checksum( substr( $bytes, 0, -2 ), substr( $bytes, -2, 2 ) );
+
 	warn ">> ", as_hex( $bytes ), "\t## $cmd_desc\n";
 	$assert->{send} = $cmd;
 	writechunk( $bytes );