// If the field is fully contained by CurWord, return it quickly.
if (BitsInCurWord >= NumBits) {
uint32_t R = CurWord & ((1U << NumBits)-1);
// If the field is fully contained by CurWord, return it quickly.
if (BitsInCurWord >= NumBits) {
uint32_t R = CurWord & ((1U << NumBits)-1);