public void Decode()
{
byte[] bytes = AlphabetMapper.TranslateMetroidStringToComputerBytes(Encoded);
byte checksum = bytes[ChecksumByte - 1];
byte shift = bytes[ShiftByte - 1];
byte[] decoded = new byte[ChecksumByteCount];
Buffer.BlockCopy(bytes, 0, decoded, 0, ChecksumByteCount);
decoded = decoded.RotateLeft(shift);
byte verifyChecksum = CalculateChecksum(decoded, shift);
if (verifyChecksum != checksum)
{
throw new ChecksumException("Invalid Metroid password");
}
// The bitpacking we use assumes that information is packed from the left which means that it makes a big difference for a byte full of bools
// Information is actually packed from the right of the byte
// Ergo we just have to flip each byte
// However first we handle the only 32-bit value (which can't be fixed by a naive flip)
if (!BitConverter.IsLittleEndian)
{
// The game age value comes in little-endian format
Swap(decoded, GameAgeStartByteIndex, GameAgeEndByteIndex);
Swap(decoded, GameAgeStartByteIndex + 1, GameAgeEndByteIndex - 1);
}
for (int i = 0; i < decoded.Length; i++)
{
if (i >= GameAgeStartByteIndex && i <= GameAgeEndByteIndex)
{
continue;
}
decoded[i] = decoded[i].ReverseBits();
}
var reader = new PackedBitReader(decoded);
var serializer = new PackedBitSerializer(typeof(PasswordProperties));
Properties = serializer.Deserialize(reader) as PasswordProperties;
Properties.Checksum = checksum;
Properties.Shift = shift;
}
public void Encode()
{
var writer = new PackedBitWriter();
var serializer = new PackedBitSerializer(typeof(PasswordProperties));
serializer.Serialize(writer, Properties);
byte[] bytes = writer.ToArray();
// The bitpacking we use assumes that information is packed from the left which means that it makes a big difference for a byte full of bools
// Information is actually packed from the right of the byte
// Ergo we just have to flip each byte
// However first we handle the only 32-bit value (which can't be fixed by a naive flip)
if (!BitConverter.IsLittleEndian)
{
// The game age value comes in little-endian format
Swap(bytes, GameAgeStartByteIndex, GameAgeEndByteIndex);
Swap(bytes, GameAgeStartByteIndex + 1, GameAgeEndByteIndex - 1);
}
for (int i = 0; i < ChecksumByteCount; i++)
{
if (i >= GameAgeStartByteIndex && i <= GameAgeEndByteIndex)
{
continue;
}
bytes[i] = bytes[i].ReverseBits();
}
byte checksum = CalculateChecksum(bytes, Properties.Shift);
Properties.Checksum = checksum;
if (Properties.Shift > 0)
{
bytes = bytes.RotateRight(Properties.Shift);
}
byte[] encoded = new byte[ChecksumByte];
Buffer.BlockCopy(bytes, 0, encoded, 0, ChecksumByteCount);
encoded[ShiftByte - 1] = Properties.Shift;
encoded[ChecksumByte - 1] = Properties.Checksum;
Encoded = AlphabetMapper.TranslateComputerBytesToMetroidString(encoded);
}