ClickHouse/base/common/Decimal.h

#pragma once
#include "common/extended_types.h"

#if !defined(NO_SANITIZE_UNDEFINED)
#if defined(__clang__)
    #define NO_SANITIZE_UNDEFINED __attribute__((__no_sanitize__("undefined")))
#else
    #define NO_SANITIZE_UNDEFINED
#endif
#endif

namespace DB
{
template <class> struct Decimal;
class DateTime64;

using Decimal32 = Decimal<Int32>;
using Decimal64 = Decimal<Int64>;
using Decimal128 = Decimal<Int128>;
using Decimal256 = Decimal<Int256>;

template <class T>
concept is_decimal =
    std::is_same_v<T, Decimal32>
    || std::is_same_v<T, Decimal64>
    || std::is_same_v<T, Decimal128>
    || std::is_same_v<T, Decimal256>
    || std::is_same_v<T, DateTime64>;

template <class T>
concept is_over_big_int =
    std::is_same_v<T, Int128>
    || std::is_same_v<T, UInt128>
    || std::is_same_v<T, Int256>
    || std::is_same_v<T, UInt256>
    || std::is_same_v<T, Decimal128>
    || std::is_same_v<T, Decimal256>;

template <class T> struct NativeTypeT { using Type = T; };
template <is_decimal T> struct NativeTypeT<T> { using Type = typename T::NativeType; };
template <class T> using NativeType = typename NativeTypeT<T>::Type;

/// Own FieldType for Decimal.
/// It is only a "storage" for decimal.
/// To perform operations, you also have to provide a scale (number of digits after point).
template <typename T>
struct Decimal
{
    using NativeType = T;

    constexpr Decimal() = default;
    constexpr Decimal(Decimal<T> &&) = default;
    constexpr Decimal(const Decimal<T> &) = default;

    constexpr Decimal(const T & value_): value(value_) {}

    template <typename U>
    constexpr Decimal(const Decimal<U> & x): value(x.value) {}

    constexpr Decimal<T> & operator = (Decimal<T> &&) = default;
    constexpr Decimal<T> & operator = (const Decimal<T> &) = default;

    constexpr operator T () const { return value; }

    template <typename U>
    constexpr U convertTo() const
    {
        if constexpr (is_decimal<U>)
            return convertTo<typename U::NativeType>();
        else
            return static_cast<U>(value);
    }

    const Decimal<T> & operator += (const T & x) { value += x; return *this; }
    const Decimal<T> & operator -= (const T & x) { value -= x; return *this; }
    const Decimal<T> & operator *= (const T & x) { value *= x; return *this; }
    const Decimal<T> & operator /= (const T & x) { value /= x; return *this; }
    const Decimal<T> & operator %= (const T & x) { value %= x; return *this; }

    template <typename U> const Decimal<T> & operator += (const Decimal<U> & x) { value += x.value; return *this; }
    template <typename U> const Decimal<T> & operator -= (const Decimal<U> & x) { value -= x.value; return *this; }
    template <typename U> const Decimal<T> & operator *= (const Decimal<U> & x) { value *= x.value; return *this; }
    template <typename U> const Decimal<T> & operator /= (const Decimal<U> & x) { value /= x.value; return *this; }
    template <typename U> const Decimal<T> & operator %= (const Decimal<U> & x) { value %= x.value; return *this; }

    /// This is to avoid UB for sumWithOverflow()
    void NO_SANITIZE_UNDEFINED addOverflow(const T & x) { value += x; }

    T value;
};

template <typename T> inline bool operator< (const Decimal<T> & x, const Decimal<T> & y) { return x.value < y.value; }
template <typename T> inline bool operator> (const Decimal<T> & x, const Decimal<T> & y) { return x.value > y.value; }
template <typename T> inline bool operator<= (const Decimal<T> & x, const Decimal<T> & y) { return x.value <= y.value; }
template <typename T> inline bool operator>= (const Decimal<T> & x, const Decimal<T> & y) { return x.value >= y.value; }
template <typename T> inline bool operator== (const Decimal<T> & x, const Decimal<T> & y) { return x.value == y.value; }
template <typename T> inline bool operator!= (const Decimal<T> & x, const Decimal<T> & y) { return x.value != y.value; }

template <typename T> inline Decimal<T> operator+ (const Decimal<T> & x, const Decimal<T> & y) { return x.value + y.value; }
template <typename T> inline Decimal<T> operator- (const Decimal<T> & x, const Decimal<T> & y) { return x.value - y.value; }
template <typename T> inline Decimal<T> operator* (const Decimal<T> & x, const Decimal<T> & y) { return x.value * y.value; }
template <typename T> inline Decimal<T> operator/ (const Decimal<T> & x, const Decimal<T> & y) { return x.value / y.value; }
template <typename T> inline Decimal<T> operator- (const Decimal<T> & x) { return -x.value; }

/// Distinguishable type to allow function resolution/deduction based on value type,
/// but also relatively easy to convert to/from Decimal64.
class DateTime64 : public Decimal64
{
public:
    using Base = Decimal64;
    using Base::Base;
    using NativeType = Base::NativeType;

    constexpr DateTime64(const Base & v): Base(v) {}
};
}

constexpr DB::UInt64 max_uint_mask = std::numeric_limits<DB::UInt64>::max();

namespace std
{
    template <typename T>
    struct hash<DB::Decimal<T>>
    {
        size_t operator()(const DB::Decimal<T> & x) const { return hash<T>()(x.value); }
    };

    template <>
    struct hash<DB::Decimal128>
    {
        size_t operator()(const DB::Decimal128 & x) const
        {
            return std::hash<DB::Int64>()(x.value >> 64)
                ^ std::hash<DB::Int64>()(x.value & max_uint_mask);
        }
    };

    template <>
    struct hash<DB::DateTime64>
    {
        size_t operator()(const DB::DateTime64 & x) const
        {
            return std::hash<DB::DateTime64::NativeType>()(x);
        }
    };

    template <>
    struct hash<DB::Decimal256>
    {
        size_t operator()(const DB::Decimal256 & x) const
        {
            // FIXME temp solution
            return std::hash<DB::Int64>()(static_cast<DB::Int64>(x.value >> 64 & max_uint_mask))
                ^ std::hash<DB::Int64>()(static_cast<DB::Int64>(x.value & max_uint_mask));
        }
    };
}