Visual C++中使用OLE DB读写SQL Server简明指南

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实现如下：

CSequentialStream::CSequentialStream( ) : m_uRefCount( 0U ), m_pBuffer( NULL ), m_uBufferUsed( 0U ), m_uBufferSize( 0U ), m_uPosition( 0U )
{
    AddRef( );
}

CSequentialStream::~CSequentialStream( )
{
    Clear( );
}

HRESULT CSequentialStream::QueryInterface( REFIID riid, void** ppv )
{
    if( riid == IID_IUnknown || riid == IID_ISequentialStream )
    {
        * ppv = this;
        ( ( IUnknown* )*ppv )->AddRef( );
        return S_OK;
    }
    * ppv = NULL;
    return E_NOINTERFACE;
}

BOOL CSequentialStream::Seek( ULONG uPosition )
{
    ASSERT( uPosition < m_uBufferUsed );
    m_uPosition = uPosition;
    return TRUE;
}

BOOL CSequentialStream::Clear( )
{
    m_uBufferUsed = 0U;
    m_uBufferSize = 0U;
    m_uPosition = 0U;
    ( m_pBuffer != NULL ? CoTaskMemFree( m_pBuffer ) : 0 );
    m_pBuffer = NULL;
    return TRUE;
}

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