[JonChesterfield]

If it's a power of two, you don't need the branch at all. Let the unsigned index wrap.

[loeg]

You ultimately need a mask to access the correct slot in the ring. But it's true that you can leave unmasked values in your reader/writer indices.

[dalvrosa]

Interesting, I've never heard about anybody using this. Maybe a bit unreadable? But yeah, should work :)

[mandarax8]

See https://fgiesen.wordpress.com/2012/07/21/the-magic-ring-buff... which takes it even further :)

[dalvrosa]

Nice one!

[loeg]

I believe ConcurrencyKit's impl does this.

https://github.com/concurrencykit/ck/blob/master/include/ck_...