Simple queue implementation in C++ using templates

queue.cpp

template <class T>
class queue {
    T *buffer;
    int buf_size;
    int front_index;
    int back_index;
    int buf_grow_factor;
    void realloc() {
        T *tmp = new T[buf_size*buf_grow_factor];
        int size = 0;
        if (front_index <= back_index) {
            for (int i = 0; i < buf_size; i++)
                tmp[size++] = buffer[i];
        } else {
            for (int i = front_index; i < buf_size; i++)
                tmp[size++] = buffer[i];
            for (int i = 0; i < back_index; i++)
                tmp[size++] = buffer[i];
        }
        front_index = 0;
        back_index = buf_size;
        delete[] buffer;
        buffer = tmp;
        buf_size *= buf_grow_factor;
    }
    public:
    queue(int init_size, int grow_factor) {
        buf_grow_factor = grow_factor;
        buffer = new T[init_size];
        buf_size = init_size;
        back_index = 0;
        front_index = 0;
    }
    ~queue() {
        delete[] buffer;
    }
    void push_back(T item) {
        buffer[back_index++] = item;
        if (back_index == buf_size)
            back_index = 0;
        if (back_index == front_index)
            realloc();
    }
    void pop_front() {
        // Decrement back_index; if it turns negative, wrap around the end
        front_index++;
        if (front_index == buf_size)
            front_index = 0;
    }

    T front() {
        return buffer[front_index];
    }
    int size() {
        if (front_index <= back_index)
            return back_index - front_index;
        return buf_size - (front_index - back_index);
    }
    bool empty() {
        return size() == 0;
    }
};

int main() {
    queue<int> q(4, 2);
    for(int i = 0; i < 10; i++)
        q.push_back(i);
    while (!q.empty())
    {
        cout << q.front() << endl;
        q.pop_front();
    }
    return 0;
}