Int128.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Serialization/Archive.h"
 
class FUInt128
{
private:
    uint64 Hi;
    uint64 Lo;
 
    inline uint32 AddInternal(uint32 A, uint32 B, uint32& Carry)
    {
        uint64 Result = (uint64)A + (uint64)B + (uint64)Carry;
        Carry = (Result >> 32) & 1;
        return (uint32)Result;
    }
 
    inline uint32 MultiplyInternal(uint32 Multiplicand, uint32 Multiplier, uint32& Carry)
    {
        uint64 Result;
        Result = ((uint64)Multiplicand * (uint64)Multiplier) + (uint64)Carry;
        Carry = Result >> 32;
        return (uint32)Result;
    }
 
    inline uint32 DivideInternal(uint32 Dividend, uint32 Divisor, uint32& Remainder)
    {
        uint64 Value = ((uint64)Remainder << 32) | Dividend;
        Remainder = Value % Divisor;
        return (uint32)(Value / Divisor);
    }
 
public:
    [[nodiscard]] inline uint32 GetQuadPart(uint32 Part) const
    {
        switch (Part)
        {
        case 3: return Hi >> 32;
        case 2: return (uint32)Hi;
        case 1: return Lo >> 32;
        case 0: return (uint32)Lo;
        default: check(0);
        }
        return 0;
    }
 
    inline void SetQuadPart(uint32 Part, uint32 Value)
    {
        switch (Part)
        {
        case 3: Hi = (Hi & 0x00000000ffffffffull) | ((uint64)Value << 32); break;
        case 2: Hi = (Hi & 0xffffffff00000000ull) | Value; break;
        case 1: Lo = (Lo & 0x00000000ffffffffull) | ((uint64)Value << 32); break;
        case 0: Lo = (Lo & 0xffffffff00000000ull) | Value; break;
        default: check(0);
        }
    }
 
    UE_FORCEINLINE_HINT void Zero()
    {
        Hi = Lo = 0;
    }
 
    inline void Set(uint64 InHi, uint64 InLo)
    {
        Hi = InHi;
        Lo = InLo;
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT FUInt128(const FUInt128&) = default;
    [[nodiscard]] UE_FORCEINLINE_HINT FUInt128(FUInt128&&) = default;
    UE_FORCEINLINE_HINT FUInt128& operator=(FUInt128 const&) = default;
    UE_FORCEINLINE_HINT FUInt128& operator=(FUInt128&&) = default;
 
    [[nodiscard]] inline FUInt128()
        : Hi(0)
        , Lo(0)
    {}
 
    [[nodiscard]] inline FUInt128(uint64 A)
        : Hi(0)
        , Lo(A)
    {}
 
    [[nodiscard]] inline FUInt128(uint64 A, uint64 B)
        : Hi(A)
        , Lo(B)
    {}
 
    [[nodiscard]] inline FUInt128(uint32 A, uint32 B, uint32 C, uint32 D)
        : Hi(((uint64)A << 32) | B)
        , Lo(((uint64)C << 32) | D)
    {}
 
    [[nodiscard]] inline bool IsGreater(const FUInt128& Other) const
    {
        if (Hi == Other.Hi)
        {
            return Lo > Other.Lo;
        }
        return Hi > Other.Hi;
    }
 
    [[nodiscard]] inline bool IsGreaterOrEqual(const FUInt128& Other) const
    {
        if (Hi == Other.Hi)
        {
            return Lo >= Other.Lo;
        }
        return Hi >= Other.Hi;
    }
 
    [[nodiscard]] inline bool IsLess(const FUInt128& Other) const
    {
        if (Hi == Other.Hi)
        {
            return Lo < Other.Lo;
        }
        return Hi < Other.Hi;
    }
 
    [[nodiscard]] inline bool IsLessOrEqual(const FUInt128& Other) const
    {
        if (Hi == Other.Hi)
        {
            return Lo <= Other.Lo;
        }
        return Hi <= Other.Hi;
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool IsEqual(const FUInt128& Other) const
    {
        return (Hi == Other.Hi) && (Lo == Other.Lo);
    }
 
    inline FUInt128 Add(uint32 Value)
    {
        uint32 Carry = 0;
 
        FUInt128 Result;
        Result.SetQuadPart(0, AddInternal(GetQuadPart(0), Value, Carry));
        Result.SetQuadPart(1, AddInternal(GetQuadPart(1), 0, Carry));
        Result.SetQuadPart(2, AddInternal(GetQuadPart(2), 0, Carry));
        Result.SetQuadPart(3, AddInternal(GetQuadPart(3), 0, Carry));
        return Result;
    }
 
    /* Subtract an unsigned 32bit value */
    inline FUInt128 Sub(uint32 Value)
    {
        uint32 Carry = 0;
 
        uint32 AddValue = ~Value + 1;
        uint32 SignExtend = (AddValue >> 31) ? ~0 : 0;
 
        FUInt128 Result;
        Result.SetQuadPart(0, AddInternal(GetQuadPart(0), AddValue, Carry));
        Result.SetQuadPart(1, AddInternal(GetQuadPart(1), SignExtend, Carry));
        Result.SetQuadPart(2, AddInternal(GetQuadPart(2), SignExtend, Carry));
        Result.SetQuadPart(3, AddInternal(GetQuadPart(3), SignExtend, Carry));
        return Result;
    }
 
    inline FUInt128 Multiply(uint32 Multiplier)
    {
        uint32 Carry = 0;
 
        FUInt128 Result;
        Result.SetQuadPart(0, MultiplyInternal(GetQuadPart(0), Multiplier, Carry));
        Result.SetQuadPart(1, MultiplyInternal(GetQuadPart(1), Multiplier, Carry));
        Result.SetQuadPart(2, MultiplyInternal(GetQuadPart(2), Multiplier, Carry));
        Result.SetQuadPart(3, MultiplyInternal(GetQuadPart(3), Multiplier, Carry));
        return Result;
    }
 
    inline FUInt128 Divide(uint32 Divisor, uint32& Remainder)
    {
        Remainder = 0;
 
        FUInt128 Result;
        Result.SetQuadPart(3, DivideInternal(GetQuadPart(3), Divisor, Remainder));
        Result.SetQuadPart(2, DivideInternal(GetQuadPart(2), Divisor, Remainder));
        Result.SetQuadPart(1, DivideInternal(GetQuadPart(1), Divisor, Remainder));
        Result.SetQuadPart(0, DivideInternal(GetQuadPart(0), Divisor, Remainder));
        return Result;
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator>(const FUInt128& Other) const
    {
        return IsGreater(Other);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator>=(const FUInt128& Other) const
    {
        return IsGreaterOrEqual(Other);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator==(const FUInt128& Other) const
    {
        return IsEqual(Other);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator<(const FUInt128& Other) const
    {
        return IsLess(Other);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool operator<=(const FUInt128& Other) const
    {
        return IsLessOrEqual(Other);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool IsZero() const
    {
        return !(Hi | Lo);
    }
 
    [[nodiscard]] UE_FORCEINLINE_HINT bool IsGreaterThanZero() const
    {
        return !IsZero();
    }
 
    inline FUInt128& operator+=(uint32 Other)
    {
        *this = Add(Other);
        return *this;
    }
 
    inline FUInt128& operator-=(uint32 Other)
    {
        *this = Sub(Other);
        return *this;
    }
 
    inline FUInt128& operator*=(uint32 Other)
    {
        *this = Multiply(Other);
        return *this;
    }
 
    inline FUInt128& operator/=(uint32 Other)
    {
        uint32 Remainder;
        *this = Divide(Other, Remainder);
        return *this;
    }
 
    friend FArchive& operator<<(FArchive& Ar, FUInt128& Value)
    {
        return Ar << Value.Hi << Value.Lo;
    }
};