OutputDeviceMemory.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/Array.h"
#include "CoreTypes.h"
#include "HAL/CriticalSection.h"
#include "Logging/LogVerbosity.h"
#include "Misc/OutputDevice.h"
#include "Serialization/Archive.h"
#include "UObject/NameTypes.h"
 
/**
 * Memory output device. Logs only into pre-allocated memory buffer.
 */
class FOutputDeviceMemory : public FOutputDevice
{
    class FOutputDeviceMemoryProxyArchive : public FArchive
    {
        FOutputDeviceMemory& OutputDevice;
    public:
        FOutputDeviceMemoryProxyArchive(FOutputDeviceMemory& InOutputDevice)
            : OutputDevice(InOutputDevice)
        {}
        virtual void Serialize(void* V, int64 Length) override
        {
            OutputDevice.SerializeToBuffer((ANSICHAR*)V, Length / sizeof(ANSICHAR));
        }
    } ArchiveProxy;
 
public:
    /** 
     * Constructor, initializing member variables.
     *
     * @param InPreserveSize    Bytes of the rung buffer not to overwrite (startup info etc)
     * @param InBufferSize      Maximum size of the memory ring buffer
     */
    FOutputDeviceMemory(int32 InPreserveSize = 256 * 1024, int32 InBufferSize = 2048 * 1024, bool bInSuppressEventTag = false);
 
    /** Dumps the contents of the buffer to an archive */
    virtual void Dump(FArchive& Ar) override;
 
    //~ Begin FOutputDevice Interface.
    /**
     * Closes output device and cleans up. This can't happen in the destructor
     * as we have to call "delete" which cannot be done for static/ global
     * objects.
     */
    virtual void TearDown() override;
 
    /**
     * Flush the write cache so the file isn't truncated in case we crash right
     * after calling this function.
     */
    virtual void Flush() override;
 
    virtual void Serialize( const TCHAR* Data, ELogVerbosity::Type Verbosity, const class FName& Category, const double Time ) override;
    virtual void Serialize( const TCHAR* Data, ELogVerbosity::Type Verbosity, const class FName& Category) override;
    virtual bool CanBeUsedOnAnyThread() const override
    {
        return true;
    }
    virtual bool CanBeUsedOnPanicThread() const override
    {
        return true;
    }
    virtual bool IsMemoryOnly() const override
    {
        return true;
    }
    //~ End FOutputDevice Interface.
 
private:
 
    /** Serialize cast data to the actual memory buffer */
    void SerializeToBuffer(ANSICHAR* Data, int32 Length);
 
    /** Ring buffer */
    TArray<ANSICHAR> Buffer;
    /** Position where data starts in the buffer */
    int32 BufferStartPos;
    /** Used data size */
    int32 BufferLength;
    /** Amount of data not to overwrite */
    int32 PreserveSize;
    /** Sync object for the buffer pos */
    FCriticalSection BufferPosCritical;
};