Poly1305.clamp_mask: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/spec/crypto/poly1305.bend as Poly1305
Lines 76-87 of bend-collections@1.0.0.0/spec/crypto/poly1305.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/spec/crypto/poly1305.bend&start_line=76&end_line=87

import Base

# clamp(r): r &= 0x0ffffffc0ffffffc0ffffffc0fffffff, i.e. r[3], r[7], r[11]
# and r[15] keep their low four bits, r[4], r[8] and r[12] lose their low two.
def clamp_mask(i: Nat) -> U32:
  match i:
    case 3n: 15
    case 7n: 15
    case 11n: 15
    case 15n: 15
    case 4n: 252
    case 8n: 252
    case 12n: 252
    case _: 255

Uses (2):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32