uffer = NULL;
    return TRUE;
}

HRESULT CSequentialStream::PreAllocBuffer( ULONG uSize )
{
    if( m_uBufferSize < uSize )
    {
        m_uBufferSize = uSize;
        m_pBuffer = CoTaskMemRealloc( m_pBuffer, m_uBufferSize );
        if( m_pBuffer == NULL )
        {
            Clear( );
            return STG_E_INSUFFICIENTMEMORY;
        }
    }
    return S_OK;
}

HRESULT CSequentialStream::Read( void* pv, ULONG cb, ULONG* pcbRead )
{
    ( pcbRead != NULL ? ( * pcbRead = 0U ) : 0 );
    if( pv == NULL ) { return STG_E_INVALIDPOINTER; }
    if( cb == 0U ) { return S_OK; }

    ASSERT( m_uPosition <= m_uBufferUsed );
    ULONG uBytesLeft = m_uBufferUsed - m_uPosition;

    if( uBytesLeft == 0U ) { return S_FALSE; } //no more bytes

    ULONG uBytesRead = ( cb > uBytesLeft ? uBytesLeft : cb );
    memcpy( pv, ( BYTE* )m_pBuffer + m_uPosition, uBytesRead );
    m_uPosition += uBytesRead;

    ( pcbRead != NULL ? ( * pcbRead = uBytesRead ) : 0 );
    return ( cb != uBytesRead ? S_FALSE : S_OK );
}

HRESULT CSequentialStream::Write( const void* pv, ULONG cb, ULONG* pcbWritten )
{
    if( pv == NULL ) { return STG_E_INVALIDPOINTER; }
    ( pcbWritten != NULL ? ( * pcbWritten = 0U ) : 0 );
    if( cb == 0U ){ return S_OK; }

    ASSERT( m_uPosition <= m_uBufferUsed );
    if( m_uBufferSize < m_uPosition + cb )
    {
        m_uBufferSize = m_uPosition + cb;
        m_pBuffer = CoTaskMemRealloc( m_pBuffer, m_uBufferSize );
        if( m_pBuffer == NULL )
        {
            Clear( );
            return STG_E_INSUFFICIENTMEMORY;
        }
    }
    m_uBufferUsed = m_uPosition + cb;
    memcpy( ( BYTE* )m_pBuffer + m_uPosition, pv, cb );
    m_uPosition += cb;
    ( pcbWritten != NULL ? ( * pcbWritten = cb ) : 0 );
    return S_OK;
}

下面我们开始往一个包含ntext字段的表中添加记录。假设这个表（News）的结构为：I