zeroshade commented on code in PR #43957:
URL: https://github.com/apache/arrow/pull/43957#discussion_r1761537759
##########
cpp/src/arrow/util/basic_decimal.h:
##########
@@ -166,6 +167,317 @@ class ARROW_EXPORT GenericBasicDecimal {
}
};
+template <typename BaseType>
+class ARROW_EXPORT BasicDecimal {
+ public:
+ static_assert(
+ std::is_same_v<BaseType, int32_t> || std::is_same_v<BaseType, int64_t>,
+ "for bitwidths larger than 64 bits use BasicDecimal128 and
BasicDecimal256");
+
+ static constexpr int kMaxPrecision = std::numeric_limits<BaseType>::digits10;
+ static constexpr int kMaxScale = kMaxPrecision;
+ static constexpr int kBitWidth = sizeof(BaseType) * CHAR_BIT;
+ static constexpr int kByteWidth = sizeof(BaseType);
+
+ /// \brief Empty constructor creates a decimal with a value of 0.
+ constexpr BasicDecimal() noexcept : value_(0) {}
+
+ /// \brief Create a decimal from any integer not wider than 64 bits.
+ template <typename T,
+ typename = typename std::enable_if<
+ std::is_integral<T>::value && (sizeof(T) <= sizeof(int64_t)),
T>::type>
+ constexpr BasicDecimal(T value) noexcept // NOLINT(runtime/explicit)
+ : value_(static_cast<BaseType>(value)) {}
+
+ /// \brief Create a decimal from an array of bytes.
+ ///
+ /// Bytes are assumed to be in native-endian byte order.
+ explicit BasicDecimal(const uint8_t* bytes) { memcpy(&value_, bytes,
sizeof(value_)); }
+
+ const uint8_t* native_endian_bytes() const {
+ return reinterpret_cast<const uint8_t*>(&value_);
+ }
+
+ uint8_t* mutable_native_endian_bytes() { return
reinterpret_cast<uint8_t*>(&value_); }
+
+ /// \brief Return the raw bytes of the value in native-endian byte order.
+ std::array<uint8_t, kByteWidth> ToBytes() const {
+ std::array<uint8_t, kByteWidth> out{{0}};
+ memcpy(out.data(), &value_, kByteWidth);
+ return out;
+ }
+
+ /// \brief Copy the raw bytes of the value in native-endian byte order
+ void ToBytes(uint8_t* out) const { memcpy(out, &value_, kByteWidth); }
+
+ /// \brief Return 1 if positive or 0, -1 if strictly negative
+ int64_t Sign() const { return 1 | (value_ >> (sizeof(kBitWidth) - 1)); }
+
+ bool IsNegative() const { return value_ < 0; }
+
+ explicit operator bool() const { return value_ != 0; }
+
+ friend bool operator==(const BasicDecimal& left, const BasicDecimal& right) {
+ return left.value_ == right.value_;
+ }
+
+ friend bool operator!=(const BasicDecimal& left, const BasicDecimal& right) {
+ return left.value_ != right.value_;
+ }
+
+ BaseType value() const { return value_; }
+
+ /// \brief count hte number of leading binary zeroes.
+ int32_t CountLeadingBinaryZeros() const;
+
+ constexpr uint64_t low_bits() const { return static_cast<uint64_t>(value_); }
+
+ protected:
+ BaseType value_;
+};
+
+class BasicDecimal64;
+
+class ARROW_EXPORT BasicDecimal32 : public BasicDecimal<int32_t> {
+ public:
+ using BasicDecimal<int32_t>::BasicDecimal;
+ using ValueType = int32_t;
+
+ /// \brief Negate the current value (in-place)
+ BasicDecimal32& Negate();
+ /// \brief Absolute value (in-place)
+ BasicDecimal32& Abs();
+ /// \brief Absolute value
+ static BasicDecimal32 Abs(const BasicDecimal32& left);
+ /// \brief Add a number to this one. The result is truncated to 32 bits.
+ BasicDecimal32& operator+=(const BasicDecimal32& right);
+ /// \brief Subtract a number from this one. The result is truncated to 32
bits.
+ BasicDecimal32& operator-=(const BasicDecimal32& right);
+ /// \brief Multiply this number by another. The result is truncated to 32
bits.
+ BasicDecimal32& operator*=(const BasicDecimal32& right);
Review Comment:
I tried using CRTP, still gives a compiler error that it can't initialize a
reference to the derived class from the base class :smile:. probably because
`*this` is still the type of the base class, not the derived
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