根据文件内存字节数，返回文件占用内存大小：单位：T，G，M，K，B

    auto format = [](uint64_t b) {
        std::stringstream ss;
        ss << std::setprecision(4);
        if (b >> 40) {
            ss << double(b) / double(1ULL << 40) << " TB";
        } else if (b >> 30) {
            ss << double(b) / double(1ULL << 30) << " GB";
        } else if (b >> 20) {
            ss << double(b) / double(1ULL << 20) << " MB";
        } else if (b >> 10) {
            ss << double(b) / double(1ULL << 10) << " KB";
        } else {
            ss << b << " Bytes";
        }
        return ss.str();
    };

返回： 10.55 MB