code: String scanString()
      throws IOException
    {
      int ch = read();
      
      switch (ch) {
      case 'N':
        return null;
        
      case 0x00: case 0x01: case 0x02: case 0x03:
      case 0x04: case 0x05: case 0x06: case 0x07:
      case 0x08: case 0x09: case 0x0a: case 0x0b:
      case 0x0c: case 0x0d: case 0x0e: case 0x0f:
        
      case 0x10: case 0x11: case 0x12: case 0x13:
      case 0x14: case 0x15: case 0x16: case 0x17:
      case 0x18: case 0x19: case 0x1a: case 0x1b:
      case 0x1c: case 0x1d: case 0x1e: case 0x1f:
        return readString(ch - 0x00);
        
      default:
        throw new UnsupportedOperationException(getClass().getName());
      }
    }
docs: Reads the Hessian value as an object.