Function MaskLeastSignificant

Bcore/src/main/cpp/base/bit_utils.h:390–399

// msb                           lsb
template <typename T = size_t>
inline static constexpr std::make_unsigned_t<T> MaskLeastSignificant(size_t bits) {
  DCHECK_GE(BitSizeOf<T>(), bits) << "Bits out of range for type T";
  using unsigned_T = std::make_unsigned_t<T>;
  if (bits >= BitSizeOf<T>()) {
    return std::numeric_limits<unsigned_T>::max();
  } else {
    auto kOne = static_cast<unsigned_T>(1);  // Do not truncate for T>size_t.
    return static_cast<unsigned_T>((kOne << bits) - kOne);
  }
}

// Clears the bitfield starting at the least significant bit "lsb" with a bitwidth of 'width'.
// (Equivalent of ARM BFC instruction).