def mask

bend-collections-laws-crypto@1.0.0.0 · src/math/random/rand.bend:99

import Base
import bend-collections-laws-crypto@1.0.0.0/src/math/u64.bend as W
import bend-collections-laws-crypto@1.0.0.0/src/math/w64.bend as X

99def mask(-S: Data, +n: W.U64, p: W.U64 & S) -> W.U64 & S:
100  (+x, s) = p
101  (and64(x, X.sub(n, W.U64{1, 0})), s)