正在从boost::tuples::tuple检索字符串

Question

在https://www.boost.org/doc/libs/1_67_0/libs/tuple/doc/html/tuple_users_guide.html上阅读了这篇文章后，下面的说明对我来说是一个问题。请注意，使用std::string或C样式字符串元素提取元组通常不起作用，因为流式元组表示可能不是明确可解析的。我应该使用什么类型来明确地将流中的字符串解析为元组？

从元组中检索std::string时，字符串由空格分隔。这不是我们想要的！设置分隔符(例如，数字符号(#))无济于事。

// typedef tuple
typedef std::string td_current_gmt, td_remote_endpoint, 
    td_request, td_response, td_elapsed_time;
typedef boost::tuples::tuple<td_current_gmt, td_remote_endpoint, 
    td_request, td_response, td_elapsed_time> tuple_logging;
// store in tuple
tuple_logging tl{ current_gmt, remote_endpoint, 
    request, response, elapsed_time };
// write tuple to file
tl = boost::tuples::make_tuple(current_gmt, remote_endpoint,
    request, response, elapsed_time);
boost::filesystem::path p = { "logging" };
boost::filesystem::ofstream ofs{ p };
ofs << /*boost::tuples::set_delimiter('#') <<*/ tl;
ofs.close();
// read tuple from file
tuple_logging tlin{ current_gmt, remote_endpoint,
    request, response, elapsed_time };
boost::filesystem::ifstream ifs{ p };
//ifs >> boost::tuples::set_delimiter('#');
ifs >> tlin;

输出是(Fri，Aug 16 201906:28:05)，但实际上必须是(Fri，Aug 16 201906:28:05 GMT 192.168.178.14:52832 TRACE /HTTP/1.1HTTP/1.1200 OK 8.936800)

Answer 1

这是代码。

void parse_logfile(
boost::filesystem::ifstream& ifs,
const boost::filesystem::path& p,
std::vector<tuple_logging>& vector_with_tuples

){类型定义函数std::string one_line_from_logging；

one_line_from_logging str;
tuple_logging tlin;

// clear vector
vector_with_tuples.clear();

// open log file for reading
ifs.open(p);

// read one line from log file, until eof
while (std::getline(ifs, str))
{
    size_t sBegin = 0, sEnd = 0;
    // 1
    // first character on a line is '(',
    // start at sBegin = 1
    sBegin = sEnd + 1;
    sEnd = str.find('#', sBegin);
    std::string current_gmt_ = str.substr(sBegin, sEnd - sBegin);
    // 2
    sBegin = sEnd + 1;
    sEnd = str.find('#', sBegin);
    std::string remote_endpoint_ = str.substr(sBegin, sEnd - sBegin);
    // 3
    sBegin = sEnd + 1;
    sEnd = str.find('#', sBegin);
    std::string request_ = str.substr(sBegin, sEnd - sBegin);
    // 4
    sBegin = sEnd + 1;
    sEnd = str.find('#', sBegin);
    std::string response_ = str.substr(sBegin, sEnd - sBegin);
    // 5
    sBegin = sEnd + 1;
    // last character on a line is ')'
    sEnd = str.find(')', sBegin);
    std::string elapsed_time_ = str.substr(sBegin, sEnd - sBegin);

    // create tuple from parsed log data out of file
    tlin = boost::tuples::make_tuple(
        current_gmt_,
        remote_endpoint_,
        request_,
        response_,
        elapsed_time_
    );

    // set tuple into vector
    vector_with_tuples.push_back(tlin);
}

// close log file
ifs.close();

}