Function keccak_round 

pub fn keccak_round(state: KeccakState, round: b5) -> KeccakState

Apply one Keccak-f[1600] round selected at runtime.

round must be in 0..24. Values 24 through 31 intentionally select the last constant; the iterative engine never generates those values. The Rho shifts and Pi destinations are all literal/static; only the 64-bit Iota constant is selected by round.