Question

I’m more of a hardware person, but the chip design tools I’m using require me to write some C++ code. I am not familiar with object-oriented programming; although I have a good handle on C. What I’m asking is for an explanation of how to structure my class (called cq) to accomplish the task at hand.

I would like to be able to generate a queue of a specified data type and specified size (which should not change after being generated). Ideally, this would be accomplished like this…

my_queue = new cq(uint8_t, 6);

…which would generate an array (or vector) of six 8-bit unsigned integers.

Then, I would like a method to both insert an element to an end and return the element at the head of the queue as follows.

uint8_t front;
front = my_queue.advance(28);

What kind of structure do I need to accomplish this? Do I need a template since the data types are variable? Or should I have a generic class and have a class for each data type inherit its structure?

Thank you!

Edit: using input from the answers below, I’ve come up with the following:

template <class type>
template <class size>
class CQ {

    private:
        // Allocates a queue with type and size
        // specified by template arguments.
        std::queue<type> cycle_queue(size, 0);

    public:
        // Inserts input to the end of the queue;
        // removes and returns the front element.
        type advance(type in){
            type out = cycle_queue.front();
            cycle_queue.push_back(in);
            cycle_queue.pop_front();
            return out;
        }

}

My question then becomes… how do I instantiate this in my main C++ program? I tried this, but it did not work:

CQ<uint8_t><6> my_queue;
my_queue.advance(28);

Thanks again!

Answer 1

This looks like a perfect application for STL containers. You could write your own queue class (as a template class, since you want to be able to specify data type), but why re-invent the wheel?

You’re looking probably for: std::list, for a FIFO queue. For your particular example:

std::list<uint8_t> my_queue;
my_queue.push_back(28);            // push an element
uint8_t front = my_queue.front();  // get the element on the front of the queue
my_queue.pop_front();              // and then pop it

---

If you’re not already somewhat familiar with OOP and C++, writing your own template classes might be a bit out of reach for now. There are good references all over the ‘net though if you want to try: e.g. http://www.cplusplus.com/doc/tutorial/templates/