Need help implementing a copy constructor for a doubly linked stack.

class DLinkedStack : public StackInterface { private: Node *headPtr; // Pointer to first node in the chain;  Node *topPtr; // Pointer to (last) node in the chain that contains the stack's top  

template DLinkedStack::DLinkedStack() : headPtr(nullptr), topPtr(nullptr) { } //default constructor template DLinkedStack::DLinkedStack(const DLinkedStack &aStack) { //code } //copy constructor