Simplified algorithm for calculating remaining space in a circular buffer?

Question

I was wonder if there is a simpler (single) way to calculate the remaining space in a circular buffer than this?

int remaining = (end > start)
                ? end-start
                : bufferSize - start + end;

Answer 1

If you're worried about poorly-predicted conditionals slowing down your CPU's pipeline, you could use this:

int remaining = (end - start) + (-((int) (end <= start)) & bufferSize);

But that's likely to be premature optimisation (unless you have really identified this as a hotspot). Stick with your current technique, which is much more readable.

Answer 2

Hmmm....

int remaining = (end - start + bufferSize) % bufferSize;

13 tokens, do I win?