alt Hacker News> The author says that non-power-of-two is not possible, but I'm pretty sure it is if you use a conditional instead of integer modulus.
I don't see why it wouldn't be, it's just computationally expensive to take the modulo value of the pointer rather than just masking off the appropriate number of bits.
Replacing just the mask operation is not enough.
The problem is incrementing past the index integer type limit.
Consider a simple example with ring buffer size 9, and 16bit indices:
When you increment the write index from 0xffff to 0, your "masked index" jumps from 6 (0xffff % 9) to 0 (instead of 7).
There is no elegant fix that I'm aware of (using a very wide index type, like possibly a uint64, is extremely non-elegant).