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

Here it is your solution (the most close to what you requested):

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>

using namespace std;

typedef std::vector<std::string> record;

std::istream&
operator>>(
  std::istream& is,
  record&       r)
{
  r.clear();

  string line;
  getline(is, line);

  istringstream iss(line);
  string field;

  while (getline(iss, field, ',' ))
    r.push_back(field);

  return is;
}

int
main()
{

  ifstream file("Stock Database.csv");
  record headers, r;

  if (file.good())
    file >> headers;

  while (file >> r)
  {
    for (int i = 0; i < r.size(); i++)
      cout << headers[i] <<  ":\t" << r[i] << endl;

    cout << "------------------------------" << endl;
  }

  return 0;
}

// EOF

The content of the "Stock Database.csv" file is:

Symbol,Name,Price,High Today,Low Today,52 Week Low
GOOG,Google Inc.,$568.77 ,$570.25 ,$560.35
AAPL,Apple Inc.,$93.28 ,$63.89 ,$99.44

Just do with the record whatever you want. The first read from the file suppose to bring you headers. Every next read fill each record with csv values.

Answer 2

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

struct csv_classification : std::ctype<char> {
    csv_classification() : ctype(make_table()) { }
private:
    static mask* make_table() {
        const mask* classic = classic_table();
        static std::vector<mask> 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<std::string> 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<class Iter1, class Iter2, class Function>
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