How to subtract two unsigned ints with wrap around or overflow

Question

There are two unsigned ints (x and y) that need to be subtracted. x is always larger than y. However, both x and y can wrap around; for example, if they were both bytes, af

Answer 1

The problem should be stated as follows:

Let's assume the position (angle) of two pointers a and b of a clock is given by an uint8_t. The whole circumerence is devided into the 256 values of an uint8_t. How can the smaller distance between the two pointer be calculated efficiently?

A solution is:

uint8_t smaller_distance = abs( (int8_t)( a - b ) );

I suspect there is nothing more effient as otherwise there would be something more efficient than abs().