Imagine we had four bit integers and a three cell array. Stepping from 7 (= 1 mod 3) to 8 (= 2 mod 3) winds up stepping instead to 0 (= 0 mod 3) because overflow, which would reuse cells inappropriately.
> It's unclear to me why the focus on a 2^n sized buffer just so you can use & for the mask.
In fact it is required for correctness to use the approach he specified with any choice of masking operation.
Write index of 8 = 1000
Masking those together to create a write position 1000 & 0100 = 0
Doesn't work out correctly, got 0, would expect to get 2. In fact, you could never get a write position of 1, 2, or 3 with an array size of 5.
You are assuming still using &, which is very obviously incorrect with a very obvious fix (%5) which is still wrong because of behavior at overflow.
[EDIT] Resolved internal concerns about size calculations.
