docs: public long getInt64(int index) throws IOException
      {
          validateIndex(index, 8);
  
          if (_isMotorolaByteOrder) {
              // Motorola - MSB first
              return ((long)getByte(index    ) << 56 & 0xFF00000000000000L) |
                     ((long)getByte(index + 1) << 48 & 0xFF000000000000L) |
                     ((long)getByte(index + 2) << 40 & 0xFF0000000000L) |
                     ((long)getByte(index + 3) << 32 & 0xFF00000000L) |
                     ((long)getByte(index + 4) << 24 & 0xFF000000L) |
                     ((long)getByte(index + 5) << 16 & 0xFF0000L) |
                     ((long)getByte(index + 6) << 8  & 0xFF00L) |
                     ((long)getByte(index + 7)       & 0xFFL);
          } else {
              // Intel ordering - LSB first
              return ((long)getByte(index + 7) << 56 & 0xFF00000000000000L) |
                     ((long)getByte(index + 6) << 48 & 0xFF000000000000L) |
                     ((long)getByte(index + 5) << 40 & 0xFF0000000000L) |
                     ((long)getByte(index + 4) << 32 & 0xFF00000000L) |
                     ((long)getByte(index + 3) << 24 & 0xFF000000L) |
                     ((long)getByte(index + 2) << 16 & 0xFF0000L) |
                     ((long)getByte(index + 1) << 8  & 0xFF00L) |
                     ((long)getByte(index    )       & 0xFFL);
          }
      }