异或校验
    :param t:
    :type t:
    :return:
    :rtype:

def xorsum(t):
    """
    异或校验
    :param t:
    :type t:
    :return:
    :rtype:
    """
    _b = t[0]
    for i in t[1:]:
        _b = _b ^ i
        _b &= 0xff
    return _b