def low_bytes

bend-collections-laws-crypto@1.0.0.0 · spec/crypto/blake/blake3.bend:160

import Base

160# A block holding len bytes (len <= 64) is zero past them: the word at byte
161# offset pos keeps its min(4, len - pos) low bytes.
162def low_bytes(w: U32, k: Nat) -> U32:
163  match k:
164    case 0n: 0
165    case 1n: U32.and(w,255)
166    case 2n: U32.and(w,65535)
167    case 3n: U32.and(w,16777215)
168    case 4n+q: w