zeroshade commented on code in PR #43957:
URL: https://github.com/apache/arrow/pull/43957#discussion_r1763455692
##########
cpp/src/arrow/util/decimal.cc:
##########
@@ -742,6 +1106,78 @@ static inline uint64_t UInt64FromBigEndian(const uint8_t*
bytes, int32_t length)
return ::arrow::bit_util::FromBigEndian(result);
}
+Result<Decimal32> Decimal32::FromBigEndian(const uint8_t* bytes, int32_t
length) {
+ static constexpr int32_t kMinDecimalBytes = 1;
+ static constexpr int32_t kMaxDecimalBytes = 4;
+
+ if (ARROW_PREDICT_FALSE(length < kMinDecimalBytes || length >
kMaxDecimalBytes)) {
+ return Status::Invalid("Length of byte array passed to
Decimal32::FromBigEndian was ",
+ length, ", but must be between ", kMinDecimalBytes,
" and ",
+ kMaxDecimalBytes);
+ }
+
+ const bool is_negative = static_cast<int8_t>(bytes[0]) < 0;
+
+ uint32_t result = 0;
+ memcpy(reinterpret_cast<uint8_t*>(&result) + kMaxDecimalBytes - length,
bytes, length);
+
+ const auto value = bit_util::FromBigEndian(result);
+ const int32_t bits_offset = std::max(0, length - kMaxDecimalBytes);
+ if (bits_offset == 8) {
Review Comment:
i've added some comments to better explain this
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