code: func (r *Rollsum32Base) GetSum(b []byte) {
  	value := uint32((r.a & FULL_BYTES_16) + ((r.b & FULL_BYTES_16) << 16))
  	binary.LittleEndian.PutUint32(b, value)
  }
docs: // Puts the sum into b. Avoids allocation. b must have length >= 4