IoOffsetLength.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "HAL/UnrealMemory.h"
 
struct FIoOffsetAndLength
{
    FIoOffsetAndLength() = default;
 
    explicit FIoOffsetAndLength(const uint64 Offset, const uint64 Length)
    {
        SetOffset(Offset);
        SetLength(Length);
    }
 
    inline uint64 GetOffset() const
    {
        return OffsetAndLength[4]
            | (uint64(OffsetAndLength[3]) << 8)
            | (uint64(OffsetAndLength[2]) << 16)
            | (uint64(OffsetAndLength[1]) << 24)
            | (uint64(OffsetAndLength[0]) << 32)
            ;
    }
 
    inline uint64 GetLength() const
    {
        return OffsetAndLength[9]
            | (uint64(OffsetAndLength[8]) << 8)
            | (uint64(OffsetAndLength[7]) << 16)
            | (uint64(OffsetAndLength[6]) << 24)
            | (uint64(OffsetAndLength[5]) << 32)
            ;
    }
 
    inline void SetOffset(uint64 Offset)
    {
        OffsetAndLength[0] = uint8(Offset >> 32);
        OffsetAndLength[1] = uint8(Offset >> 24);
        OffsetAndLength[2] = uint8(Offset >> 16);
        OffsetAndLength[3] = uint8(Offset >>  8);
        OffsetAndLength[4] = uint8(Offset >>  0);
    }
 
    inline void SetLength(uint64 Length)
    {
        OffsetAndLength[5] = uint8(Length >> 32);
        OffsetAndLength[6] = uint8(Length >> 24);
        OffsetAndLength[7] = uint8(Length >> 16);
        OffsetAndLength[8] = uint8(Length >> 8);
        OffsetAndLength[9] = uint8(Length >> 0);
    }
 
    inline bool IsValid() const
    {
        return !FMemory::MemIsZero(OffsetAndLength, 10);
    }
 
private:
    // We use 5 bytes for offset and size, this is enough to represent
    // an offset and size of 1PB
    uint8 OffsetAndLength[5 + 5];
};