zeroshade commented on code in PR #43957:
URL: https://github.com/apache/arrow/pull/43957#discussion_r1763429117
##########
cpp/src/arrow/util/decimal.cc:
##########
@@ -697,8 +919,150 @@ Status DecimalFromString(const char* type_name,
std::string_view s, Decimal* out
return Status::OK();
}
+template <typename DecimalClass>
+Status SimpleDecimalFromString(const char* type_name, std::string_view s,
+ DecimalClass* out, int32_t* precision, int32_t*
scale) {
+ if (s.empty()) {
+ return Status::Invalid("Empty string cannot be converted to ", type_name);
+ }
+
+ DecimalComponents dec;
+ if (!ParseDecimalComponents(s.data(), s.size(), &dec)) {
+ return Status::Invalid("The string '", s, "' is not a valid ", type_name,
" number");
+ }
+
+ // count number of significant digits (without leading zeros)
+ size_t first_non_zero = dec.whole_digits.find_first_not_of('0');
+ size_t significant_digits = dec.fractional_digits.size();
+ if (first_non_zero != std::string::npos) {
+ significant_digits += dec.whole_digits.size() - first_non_zero;
+ }
+ int32_t parsed_precision = static_cast<int32_t>(significant_digits);
+
+ int32_t parsed_scale = 0;
+ if (dec.has_exponent) {
+ auto adjusted_exponent = dec.exponent;
+ parsed_scale =
+ -adjusted_exponent +
static_cast<int32_t>(dec.fractional_digits.size());
+ } else {
+ parsed_scale = static_cast<int32_t>(dec.fractional_digits.size());
+ }
+
+ if (out != nullptr) {
+ if constexpr (std::is_same_v<Decimal32, DecimalClass>) {
Review Comment:
the `ShiftAndAdd` function handles the math for shifting `dec.whole_digits`
before adding `dec.fractional_digits`
but if we want to just do that here explicitly rather than having a 32-bit
overload for `ShiftAndAdd` i can do that.
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