Function ModifyScaleAndPrecision

cpp/src/gandiva/precompiled/decimal_ops.cc:536–553

Helper function to modify the scale and/or precision of a decimal value.

// Helper function to modify the scale and/or precision of a decimal value.
static BasicDecimal128 ModifyScaleAndPrecision(const BasicDecimalScalar128& x,
                                               int32_t out_precision, int32_t out_scale,
                                               bool* overflow) {
  int32_t delta_scale = out_scale - x.scale();
  if (delta_scale >= 0) {
    // check if multiplying by delta_scale will cause an overflow.
    DECIMAL_OVERFLOW_IF(
        BasicDecimal128::Abs(x.value()) > GetMaxValue(out_precision - delta_scale),
        overflow);
    return x.value().IncreaseScaleBy(delta_scale);
  } else {
    // Do not do any rounding, that is handled by the caller.
    auto result = x.value().ReduceScaleBy(-delta_scale, false);
    DECIMAL_OVERFLOW_IF(BasicDecimal128::Abs(result) > GetMaxValue(out_precision),
                        overflow);
    return result;
  }
}

enum RoundType {
  kRoundTypeCeil,         // +1 if +ve and trailing value is > 0, else no rounding.