Method ToRealPositive

cpp/src/arrow/util/decimal.cc:1415–1431

  /// Here "exact value" means the closest representable value by Real.
  template <typename Real>
  static Real ToRealPositive(const Decimal256& decimal, int32_t scale) {
    const auto parts_le = decimal.little_endian_array();
    if (scale <= 0 || (parts_le[3] == 0 && parts_le[2] == 0 && parts_le[1] == 0 &&
                       parts_le[0] < RealTraits<Real>::kMaxPreciseInteger)) {
      // No need to split the decimal if it is already an integer (scale <= 0) or if it
      // can be precisely represented by Real
      return ToRealPositiveNoSplit<Real>(decimal, scale);
    }

    // Split the decimal into whole and fractional parts to avoid precision loss
    BasicDecimal256 whole_decimal, fraction_decimal;
    decimal.GetWholeAndFraction(scale, &whole_decimal, &fraction_decimal);

    Real whole = ToRealPositiveNoSplit<Real>(whole_decimal, 0);
    Real fraction = ToRealPositiveNoSplit<Real>(fraction_decimal, scale);
    return whole + fraction;
  }
};

}  // namespace