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L<perl(1)> |
L<perl(1)> |
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L<http://stackoverflow.com/questions/149617/how-could-i-guess-a-checksum-algorithm> |
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=head1 AUTHOR |
=head1 AUTHOR |
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Dobrica Pavlinusic <dpavlin@rot13.org> L<http://www.rot13.org/~dpavlin/> |
Dobrica Pavlinusic <dpavlin@rot13.org> L<http://www.rot13.org/~dpavlin/> |
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my @tags; |
my @tags; |
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push @tags, substr($tags, $_ * 8, 8) foreach ( 0 .. $nr - 1 ); |
push @tags, substr($tags, $_ * 8, 8) foreach ( 0 .. $nr - 1 ); |
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warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags ); |
warn "## tags ",as_hex($tags), " [$tl] = ",dump( $tags ) if $debug; |
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print "seen $nr tags: ", join(',', map { unpack('H16', $_) } @tags ) , "\n"; |
print "seen $nr tags: ", join(',', map { unpack('H16', $_) } @tags ) , "\n"; |
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} |
} |
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) } |
) } |
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foreach my $str ( @_ ) { |
foreach my $str ( @_ ) { |
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my $hex = unpack( 'H*', $str ); |
my $hex = unpack( 'H*', $str ); |
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$hex =~ s/(..)/$1 /g if length( $str ) > 2; |
$hex =~ s/(..)/$1 /g if length( $str ) > 2; |
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$hex =~ s/\s+$//; |
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push @out, $hex; |
push @out, $hex; |
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} |
} |
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return join(' ', @out); |
return join(' | ', @out); |
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} |
} |
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sub read_bytes { |
sub read_bytes { |
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} |
} |
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} |
} |
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use Digest::CRC; |
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sub crcccitt { |
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my $bytes = shift; |
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my $crc = Digest::CRC->new( |
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# midified CCITT to xor with 0xffff instead of 0x0000 |
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width => 16, init => 0xffff, xorout => 0xffff, refout => 0, poly => 0x1021, refin => 0, |
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) or die $!; |
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$crc->add( $bytes ); |
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pack('n', $crc->digest); |
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} |
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# my $checksum = checksum( $bytes ); |
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# my $checksum = checksum( $bytes, $original_checksum ); |
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sub checksum { |
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my ( $bytes, $checksum ) = @_; |
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my $xor = crcccitt( substr($bytes,1) ); # skip D6 |
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warn "## checksum ",dump( $bytes, $xor, $checksum ) if $debug; |
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if ( defined $checksum && $xor ne $checksum ) { |
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print "checksum doesn't match: ", as_hex($xor), " != ", as_hex($checksum), " data: ", as_hex($bytes), "\n"; |
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} |
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} |
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sub readchunk { |
sub readchunk { |
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my ( $parser ) = @_; |
my ( $parser ) = @_; |
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my $length = read_bytes( 1, 'length' ); |
my $length = read_bytes( 1, 'length' ); |
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my $len = ord($length); |
my $len = ord($length); |
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my $data = read_bytes( $len, 'data' ); |
my $data = read_bytes( $len, 'data' ); |
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my ( $cmd ) = unpack('C', $data ); |
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my $payload = substr( $data, 0, -2 ); |
my $payload = substr( $data, 0, -2 ); |
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my $payload_len = length($data); |
my $payload_len = length($data); |
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warn "## payload too short $payload_len != $len\n" if $payload_len != $len; |
warn "## payload too short $payload_len != $len\n" if $payload_len != $len; |
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my $checksum = substr( $data, -2, 2 ); |
my $checksum = substr( $data, -2, 2 ); |
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# FIXME check checksum |
checksum( $header . $length . $payload, $checksum ); |
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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"; |
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$assert->{len} = $len; |
$assert->{len} = $len; |
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$assert->{payload} = $payload; |
$assert->{payload} = $payload; |
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$assert->{checksum} = $checksum; |
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$parser->( $len, $payload, $checksum ) if $parser && ref($parser) eq 'CODE'; |
$parser->( $len, $payload ) if $parser && ref($parser) eq 'CODE'; |
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return $data; |
return $data; |
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} |
} |