Reading from a CSV file in C++

Question

I wrote this code to read from a CSV text file (containing data such as 12,3,568,48,3,8 with no more than 3 digits to each number). It stores the numbers as char arrays in the vector values. However, this does seem like a clumsy way of doing this with resizing the vector and copying the chars. Is there a neater/more succinct way of doing this?

#include <iostream>
#include <fstream>
#include <assert.h>
#include <vector>
int main() {
 using namespace std;
 ifstream in;
 in.open("Data.txt");
 assert(in.is_open());
 vector<char*> values;
 const int MAXSIZE = 4;
 char thisVal[MAXSIZE];
 while(in.getline(thisVal,MAXSIZE,',')) {
 values.resize(values.size() + 1);
 values.back() = new char[MAXSIZE];
 strcpy(values.back(), thisVal);
 }
 in.close();
 for (char* cp: values) cout<<*cp<<endl;
 return 0;
}

Answer 1

Storing char* in a vector leads to leaks. instead use std::string, which will manage its own buffer and delete it as needed.

vector<string> values;

inserting to the back of a vector can be done with push_back or you can construct in place with emplace_back in C++11:

while(in.getline(thisVal,MAXSIZE,',')) {
 string str(thisVal);
 values.push_back(std::move(str));
 //std::move signals that I won't be using str anymore and that the underlying buffer can just be passed through to the new element. 
 // After this str will not be valid. You can still assign to it normally but until you do any result of calling a method on it will be implementation defined.
}

or

while(in.getline(thisVal,MAXSIZE,',')) {
 values.emplace_back(thisVal);
}

Failing to open a file is common enough to use an explicit if and print an error message instead of asserting (which won't do anything when compiled as a release version):

if(!in.is_open()){
 cerr << "failed to open file.";
 return 1; 
}

I return 1 here to signal to the OS that the program didn't finish successfully and a script using it can then react to it.