Generate the Norwegian equivalent to social security numbers

Question

This is just a little hobby project I've been working on. I've been using it to learn/improve my knowledge of C++.

The program generate Norwegian personal-numbers (11 digits) for males born a given year. It works just fine, but I'd like some input on how to improve the code. For now I have a basic class structure.

Norwegian personal-numbers is built up like this.

#include <iostream>

using namespace std;

const int DATE_LENGTH = 6;
const int BUFFER = 30;

class ID {
    private:
        int date[DATE_LENGTH];
        int i1, i2, i3;
        int k1, k2;
        int year;
    public:
        ID(int i1 = 0, int i2 = 0, int i3 = 0, int k1 = 0, int k2 = 0) {
            for (int i = 0; i < DATE_LENGTH; i++) { date[i] = 0; }
        }

        int *getDate() { return date; }

        void setYear(int year) {
            this->year = year;
        }

        int getYear() {
            return year;
        }

        void individSiffer() {
            static int individ = -1;
            if(year >= 1900 && year <= 1999 ){
                    individ++;
                    i1 = i2 = i3 = 0;
                }
                i3 = individ % 10;
                if(individ < 100){
                    i1 = 0;
                    i2 = individ / 10 % 10;
                }else if(individ < 10){
                    i1 = i2 = 0;
                }else{
                    i1 = individ / 100 % 10;
                    i2 = individ / 10 % 10;
                }
        }

        void generate() {
            k1 = 11 - ((3*date[0] + 7*date[1] + 6*date[2] + 1*date[3] + 8*date[4] + 9*date[5] + 4*i1 + 5*i2 + 2*i3) % 11); 
            if(k1 == 11){
                k1 = 0;
            }
            k2 = 11 - ((5*date[0] + 4*date[1] + 3*date[2] + 2*date[3] + 7*date[4] + 6*date[5] + 5*i1 + 4*i2 + 3*i3 + 2*k1) % 11);
            if(k2 == 11){
                k2 = 0;
            }
            if((i3 != 0 && i3 != 2 && i3 !=4 && i3 !=6 && i3 !=8) && (k1 != 10 && k2 !=10)){
                for (int i = 0; i < DATE_LENGTH; i++) {
                    printf("%d", date[i]);
                }
                printf("%d%d%d%d%d\n", i1, i2, i3, k1, k2);
            }   
        }
};

int main(int argc, char *argv[]) {
    char dateString[BUFFER];
    int i = 0;
    ID generator;

    printf("%s", "Your date of birth (DDMMYY): ");
    cin.getline(dateString, BUFFER);

    for(int i = 0; i < DATE_LENGTH; i++){
        *(generator.getDate() + i) = int(dateString[i]-'0');
    }
    generator.setYear(1900 + (*(generator.getDate() + 4) * 10) + *(generator.getDate() + 5));
    while(i < 500){
        generator.individSiffer();
        generator.generate();
        i++;
    }
    cout << "\n\n\n";
    return 0;
}

Answer 1

Comment on C++ interface:

You are doing work outside of ID that belongs as part of the class:

ID generator;

for(int i = 0; i < DATE_LENGTH; i++){
    *(generator.getDate() + i) = int(dateString[i]-'0');
}

generator.setYear(1900 + (*(generator.getDate() + 4) * 10) + *(generator.getDate() + 5));

while(i < 500){
    generator.individSiffer();
    generator.generate();
    i++;
}

Because this work is not part of a method you are exposing implementation details of your ID class via getter methods. All of which is bad:

A better interface would have been:

std::string date = getDate(); // Get a valid date or throw.
ID          generator(date);

std::cout << generator;

Comments on Code

Don't use this interface. What happens if the user types an extra long line of stuff.

cin.getline(dateString, BUFFER);

Its not going to crash but you are left with lots of crap on the input stream. User input is line based so read a line from the user and then try and parse the line. Because a line can be any length don't use that version of get line.

std::string line;
while(std::getline(std::cin, line))
{
    // Valid line has been read.
    if (validDate(line))
    {    return line;
    }
    std::cerr << "Invalid date please try again\n";
}
throw std::runtime_error("The user give up trying to enter a date correctly");

Comments on C functions

C based functions for printing printf() are dangerous, because they are not type safe. Prefer to use the C++ type safe streams.

Comments on Data values

generator.setYear(1900 + (*(generator.getDate() + 4) * 10) + *(generator.getDate() + 5));

What about people born after 31st Dec 1999?

Comments on Loop structures

while(i < 500){
    // STUFF
    i++;
}

// This kind of loop is better written as a for:

for(int loop=0; loop < 500; ++loop) {
    // STUFF
}

Also notice that I am declaring my loop variable as close to the point of usage as possible. Do not use the C style of putting all the variables at the top of the function. Put your variables where you can see there declaration and type easily.