string ReadUTF8Z(long recPosEnd)
        {
            if (reader.Position > recPosEnd)
            {
                return(null);
            }
            var bytes = reader.ReadBytesUntilByte(0);

            if (bytes == null)
            {
                return(null);
            }
            var s = Encoding.UTF8.GetString(bytes);

            reader.Position++;
            return(s);
        }