/*      row_seek(offset)     */
static VALUE row_seek(VALUE obj, VALUE offset)
{
    MYSQL_ROW_OFFSET prev_offset;
    if (CLASS_OF(offset) != cMysqlRowOffset)
        rb_raise(rb_eTypeError, "wrong argument type %s (expected Mysql::RowOffset)", rb_obj_classname(offset));
    check_free(obj);
    prev_offset = mysql_row_seek(GetMysqlRes(obj), DATA_PTR(offset));
    return Data_Wrap_Struct(cMysqlRowOffset, 0, NULL, prev_offset);
}