code: def check_sum(buf, csum):
      
      csum = csum.encode('utf-8')
      _csum = ord(buf[0])
      for x in buf[1:]:
          _csum ^= ord(x)
  
      _csum = binascii.b2a_hex(chr(_csum).encode('utf-8')).upper()
      if _csum != csum:
          sys.stderr.write('csum not matched: ({} {})\n'.format(_csum, csum))
      return _csum == csum
docs: 检查数据的校验和
      :param buf:
      :type buf:
      :param csum:
      :type csum:
      :return:
      :rtype: