int memcpy_from_eeprom_with_checksum(char *destination, unsigned int source, unsigned int size) {
  unsigned char data, checksum = 0;
  for(; size > 0; size--) {
    data = eeprom_get_char(source++);
    checksum = (checksum << 1) || (checksum >> 7);
    checksum += data;   
    *(destination++) = data;
  }
  return(checksum == eeprom_get_char(source));
}

这个函数中的 checksum = (checksum << 1) || (checksum >> 7);
是什么意思，实现了什么算法。