WriteBufferRedirect.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
// HEADER_UNIT_SKIP - Internal
 
#include "Trace/Detail/Writer.inl"
 
namespace UE {
namespace Trace {
namespace Private {
 
extern thread_local FWriteBuffer* GTlsWriteBuffer;
 
template <int BufferSize>
class TWriteBufferRedirect
{
public:
    enum : uint16 { ActiveRedirection = 0xffff };
 
                    TWriteBufferRedirect();
                    ~TWriteBufferRedirect();
    void            Close();
    void            Abandon();
    uint8*          GetData();
    uint32          GetSize() const;
    uint32          GetCapacity() const;
    void            Reset();
 
private:
    FWriteBuffer*   PrevBuffer;
    uint8           Data[BufferSize];
    FWriteBuffer    Buffer;
};
 
template <int BufferSize>
inline TWriteBufferRedirect<BufferSize>::TWriteBufferRedirect()
{
    Reset();
    PrevBuffer = GTlsWriteBuffer;
    GTlsWriteBuffer = &Buffer;
    Buffer.Size = uint16(BufferSize);
    Buffer.ThreadId = ActiveRedirection;
}
 
template <int BufferSize>
inline TWriteBufferRedirect<BufferSize>::~TWriteBufferRedirect()
{
    Close();
}
 
template <int BufferSize>
inline void TWriteBufferRedirect<BufferSize>::Close()
{
    if (PrevBuffer == nullptr)
    {
        return;
    }
 
    GTlsWriteBuffer = PrevBuffer;
    PrevBuffer = nullptr;
}
 
template <int BufferSize>
inline void TWriteBufferRedirect<BufferSize>::Abandon()
{
    PrevBuffer = nullptr;
}
 
template <int BufferSize>
inline uint8* TWriteBufferRedirect<BufferSize>::GetData()
{
    return Buffer.Reaped;
}
 
template <int BufferSize>
inline uint32 TWriteBufferRedirect<BufferSize>::GetSize() const
{
    return uint32(Buffer.Committed - Buffer.Reaped);
}
 
template <int BufferSize>
inline uint32 TWriteBufferRedirect<BufferSize>::GetCapacity() const
{
    return BufferSize;
}
 
template <int BufferSize>
inline void TWriteBufferRedirect<BufferSize>::Reset()
{
    Buffer.Cursor = Data + sizeof(uint32);
    Buffer.Committed = Buffer.Cursor;
    Buffer.Reaped = Buffer.Cursor;
}
 
} // namespace Private
} // namespace Trace
} // namespace UE