/// <summary>
        /// Reads record at specified offset, does not change cursor position
        /// </summary>
        /// <param name="offset"></param>
        /// <returns></returns>
        public XlsBiffRecord ReadAt(int offset)
        {
            XlsBiffRecord rec = XlsBiffRecord.GetRecord(bytes, (uint)offset);

            if (m_offset + rec.Size > m_size)
            {
                return(null);
            }
            return(rec);
        }
        public XlsBiffRecord Read()
        {
            XlsBiffRecord rec = XlsBiffRecord.GetRecord(bytes, (uint)m_offset);

            m_offset += rec.Size;
            if (m_offset > m_size)
            {
                return(null);
            }
            return(rec);
        }