MemoryReader.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "HAL/UnrealMemory.h"
#include "Math/UnrealMathUtility.h"
#include "Memory/MemoryView.h"
#include "Containers/UnrealString.h"
#include "Serialization/MemoryArchive.h"
#include "Containers/ArrayView.h"
 
/**
 * Archive for reading arbitrary data from the specified memory location
 */
class FMemoryReader : public FMemoryArchive
{
public:
    /**
     * Returns the name of the Archive.  Useful for getting the name of the package a struct or object
     * is in when a loading error occurs.
     *
     * This is overridden for the specific Archive Types
     **/
    virtual FString GetArchiveName() const override
    {
        return TEXT("FMemoryReader");
    }
 
    virtual int64 TotalSize() override
    {
        return FMath::Min((int64)Bytes.Num(), LimitSize);
    }
 
    void Serialize( void* Data, int64 Num )
    {
        if (Num && !IsError())
        {
            // Only serialize if we have the requested amount of data
            if (Offset + Num <= TotalSize())
            {
                FMemory::Memcpy( Data, &Bytes[(int32)Offset], Num );
                Offset += Num;
            }
            else
            {
                SetError();
            }
        }
    }
 
    explicit FMemoryReader( const TArray<uint8>& InBytes, bool bIsPersistent = false )
        : Bytes    (InBytes)
        , LimitSize(INT64_MAX)
    {
        this->SetIsLoading(true);
        this->SetIsPersistent(bIsPersistent);
    }
 
    /** With this method it's possible to attach data behind some serialized data. */
    void SetLimitSize(int64 NewLimitSize)
    {
        LimitSize = NewLimitSize;
    }
 
private:
    const TArray<uint8>& Bytes;
    int64                LimitSize;
};
 
/**
 * Archive for reading arbitrary data from the specified memory view
 */
class FMemoryReaderView : public FMemoryArchive
{
public:
    /**
     * Returns the name of the Archive.  Useful for getting the name of the package a struct or object
     * is in when a loading error occurs.
     *
     * This is overridden for the specific Archive Types
     **/
    virtual FString GetArchiveName() const override
    {
        return TEXT("FMemoryReaderView");
    }
 
    virtual int64 TotalSize() override
    {
        return FMath::Min(static_cast<int64>(Bytes.GetSize()), LimitSize);
    }
 
    void Serialize(void* Data, int64 Num)
    {
        if (Num && !IsError())
        {
            // Only serialize if we have the requested amount of data
            if (Offset + Num <= TotalSize())
            {
                FMutableMemoryView(Data, static_cast<uint64>(Num)).CopyFrom(Bytes.Mid(Offset, Num));
                Offset += Num;
            }
            else
            {
                SetError();
            }
        }
    }
 
    explicit FMemoryReaderView(TArrayView<const uint8> InBytes, bool bIsPersistent = false)
        : FMemoryReaderView(MakeMemoryView(InBytes), bIsPersistent)
    {
    }
 
    explicit FMemoryReaderView(FMemoryView InBytes, bool bIsPersistent = false)
        : Bytes(InBytes)
        , LimitSize(INT64_MAX)
    {
        this->SetIsLoading(true);
        this->SetIsPersistent(bIsPersistent);
    }
 
    /** With this method it's possible to attach data behind some serialized data. */
    void SetLimitSize(int64 NewLimitSize)
    {
        LimitSize = NewLimitSize;
    }
 
private:
    FMemoryView          Bytes;
    int64                LimitSize;
};