BufferReader.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Misc/AssertionMacros.h"
#include "HAL/UnrealMemory.h"
#include "Serialization/Archive.h"
#include "Containers/UnrealString.h"
 
/**
* Similar to FMemoryReader, but able to internally
* manage the memory for the buffer.
*/
class FBufferReaderBase : public FArchive
{
public:
    /**
    * Constructor
    *
    * @param Data Buffer to use as the source data to read from
    * @param Size Size of Data
    * @param bInFreeOnClose If true, Data will be FMemory::Free'd when this archive is closed
    * @param bIsPersistent Uses this value for SetIsPersistent()
    * @param bInSHAVerifyOnClose It true, an async SHA verification will be done on the Data buffer (bInFreeOnClose will be passed on to the async task)
    */
    FBufferReaderBase(void* Data, int64 Size, bool bInFreeOnClose, bool bIsPersistent = false)
        : ReaderData(Data)
        , ReaderPos(0)
        , ReaderSize(Size)
        , bFreeOnClose(bInFreeOnClose)
    {
        this->SetIsLoading(true);
        this->SetIsPersistent(bIsPersistent);
    }
 
    // Abstract to force implementors to call Close() themselves, since it's a virtual function.
    virtual ~FBufferReaderBase() = 0;
 
    virtual bool Close() override
    {
        if (bFreeOnClose)
        {
            FMemory::Free(ReaderData);
            ReaderData = nullptr;
        }
        return !IsError();
    }
    void Serialize(void* Data, int64 Num) final
    {
        check(ReaderPos >= 0);
        check(ReaderPos + Num <= ReaderSize);
        FMemory::Memcpy(Data, (uint8*)ReaderData + ReaderPos, Num);
        ReaderPos += Num;
    }
    int64 Tell() final
    {
        return ReaderPos;
    }
    int64 TotalSize() final
    {
        return ReaderSize;
    }
    void Seek(int64 InPos) final
    {
        check(InPos >= 0);
        check(InPos <= ReaderSize);
        ReaderPos = InPos;
    }
    bool AtEnd() final
    {
        return ReaderPos >= ReaderSize;
    }
    /**
    * 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 { return TEXT("FBufferReaderBase"); }
protected:
    void*       ReaderData;
    int64       ReaderPos;
    int64       ReaderSize;
    bool    bFreeOnClose;
};
 
inline FBufferReaderBase::~FBufferReaderBase()
{
}
 
/**
 * Similar to FMemoryReader, but able to internally
 * manage the memory for the buffer.
 */
class FBufferReader final : public FBufferReaderBase
{
public:
    /**
     * Constructor
     * 
     * @param Data Buffer to use as the source data to read from
     * @param Size Size of Data
     * @param bInFreeOnClose If true, Data will be FMemory::Free'd when this archive is closed
     * @param bIsPersistent Uses this value for SetIsPersistent()
     * @param bInSHAVerifyOnClose It true, an async SHA verification will be done on the Data buffer (bInFreeOnClose will be passed on to the async task)
     */
    FBufferReader( void* Data, int64 Size, bool bInFreeOnClose, bool bIsPersistent = false )
        : FBufferReaderBase(Data, Size, bInFreeOnClose, bIsPersistent)
    {
    }
 
    virtual ~FBufferReader() override
    {
        Close();
    }
 
    virtual FString GetArchiveName() const { return TEXT("FBufferReader"); }
};