Without this, the byte is cast as follows (in bits) if the top
byte is set:
10000010 -> 1000000000000000000000000000010
This works because we then always shift at least one bit left,
and only look at the bottom 8 bits of the result. It's confusing
though. It's clearer if the cast to int gives just adds zeros to
the front, like:
10000010 -> 0000000000000000000000010000010
