CSV Parsing with c++

Question

I\'m trying to create a code that will parse through a csv database with stock information. Currently, I have the code generated so that it will search with a keyword and pr

Answer 1

First a comma should be parsed as whitespace. You can do this by changing the internal std::ctype facet in the stream's locale:

struct csv_classification : std::ctype {
    csv_classification() : ctype(make_table()) { }
private:
    static mask* make_table() {
        const mask* classic = classic_table();
        static std::vector v(classic, classic + table_size);
        v[','] |= space;
        v[' '] &= ~space;
        return &v[0];
    }
};

Then set the locale using:

ifs.imbue(std::locale(ifs.getloc(), new csv_classification));

Next make a manipulator that checks to see if you're at the end of the line. If you are it sets the std::ios_base::failbit flag in the stream state. Also use internal storage to tell if the record belongs as a key or value in the map. Borrowing a bit from Dietmar...

static int row_end = std::ios_base::xalloc();

std::istream& record(std::istream& is) {
    while (std::isspace(is.peek())) {
        int c(is.peek());
        is.ignore();

        if (c == '\n') {
            is.iword(row_end) = !is.iword(row_end);
            is.setstate(std::ios_base::failbit);
        }
    }
    return is;
}

Then you can do:

std::vector keys, values;

for (std::string item;;) {
    if (ifs >> record >> item)
        keys.push_back(item);
    else if (ifs.eof())
        break;
    else if (ifs.iword(row_end)) {
        ifs.clear();
        while (ifs >> record >> item)
            values.push_back(item);
    }
    else
        break;
}

Now we need to apply both the keys and values and print them out. We can create a new algorithm for that:

template
void for_each_binary_range(Iter1 first1, Iter1 last1,
                           Iter2 first2, Iter2 last2, Function f)
{
    assert(std::distance(first1, last1) <= std::distance(first2, last2));

    while (first1 != last1) {
        f(*first1++, *first2++);
    }
}

Finally we do:

for_each_binary_range(std::begin(keys),   std::end(keys),
                      std::begin(values), std::end(values),
[&] (std::string const& key, std::string const& value)
{
    std::cout << key << ": " << value << std::endl;
}

Live Demo