Function RoundWithPositiveScale

cpp/src/gandiva/precompiled/decimal_ops.cc:615–640

Modify the scale and round.

// Modify the scale and round.
static BasicDecimal128 RoundWithPositiveScale(const BasicDecimalScalar128& x,
                                              int32_t out_precision, int32_t out_scale,
                                              RoundType round_type, bool* overflow) {
  DCHECK_GE(out_scale, 0);

  auto scaled = ModifyScaleAndPrecision(x, out_precision, out_scale, overflow);
  if (*overflow) {
    return 0;
  }

  auto delta = ComputeRoundingDelta(x.value(), x.scale(), out_scale, round_type);
  if (delta == 0) {
    return scaled;
  }

  // If there is a rounding delta, the output scale must be less than the input scale.
  // That means at least one digit is dropped after the decimal. The delta add can add
  // utmost one digit before the decimal. So, overflow will occur only if the output
  // precision has changed.
  DCHECK_GT(x.scale(), out_scale);
  auto result = scaled + delta;
  DECIMAL_OVERFLOW_IF(out_precision < x.precision() &&
                          BasicDecimal128::Abs(result) > GetMaxValue(out_precision),
                      overflow);
  return result;
}

// Modify scale to drop all digits to the right of the decimal and round.
// Then, zero out 'rounding_scale' number of digits to the left of the decimal point.