Очередь с защитой от ошибок

#include <iostream>

using namespace  std;

struct queue
{
    uint32_t   cursor_start = 0;
    uint32_t   cursor_end   = 0;
    int64_t    array[100000];

    //////////////////
    void push(const int64_t& n)
    {
        array[cursor_end++] = n;
    }
    //////////////////
    int64_t pop()
    {
        return array[cursor_start++];
    }
    /////////////////
    int64_t front()
    {
        return array[cursor_start];
    }
    ///////////////////
    int64_t size()
    {
        return cursor_end-cursor_start;
    }
    ////////////////
    void clear()
    {
        cursor_start = 0;
        cursor_end   = 0;
    }
};
int main() {
    queue primer;
    string stroka;
    while (cin >> stroka)
        if (stroka == "push")
        {
            int64_t vr;
            cin >> vr;
            primer.push(vr);
            cout << "ok" << endl;
        }
        else if(stroka == "pop")
        {
            if(primer.size() == 0)
            {
                cout << "error" << endl;
            }
            else
            {
                cout << primer.pop() << endl;
            }
        }
        else if(stroka == "front")
        {
            if(primer.size() == 0)
            {
                cout << "error" << endl;
            }
            else
            {
                cout << primer.front() << endl;
            }
        }
        else if(stroka == "size")
        {
            cout << primer.size() << endl;
        }
        else if(stroka == "clear")
        {
            primer.clear();
            cout << "ok" << endl;
        }
        else if(stroka == "exit")
        {
            cout << "bye";
            break;
        }
    return 0;
}