Finding the next in round-robin scheduling by bit twiddling

Question

Consider the following problem. You have a bit-string that represents the current scheduled slave in one-hot encoding. For example, \"00000100\" (with the leftmost bit being #7

Answer 1

Assuming twos complement representation, call your two words mask and current, in C:

mask_lo = (current << 1) - 1; // the bits to the right and including current
mask_hi = ~mask_lo;           // the bits to the left of current
                              // the left bits, otherwise right:
next = (mask & mask_hi) ? (mask & mask_hi) : (mask & mask_lo);
return (next & -next);        // the least significant bit set