I'm trying to implement a Queue where you pass to it an Object to be added to the Queue.
struct Node {
T data;
Node *next, *prev;
};
// Push data to the back of the list.
template <class T> T& CircularQueue<T>::push_back(const T&& new_data)
{
Node* new_node = new Node();
new_node->data = std::move(new_data);
link_node(new_node, m_head);
return new_node->data;
}
The problem with my current approach is there is too much overhead (as i come from C these things bothers me). for example image i will add an object from MyClass:
CircularQueue<MyClass> list;
list.push_back(MyClass(arg1, arg2));
The first problem is that the MyClass needs to have a constructor without argument to be used in Node* new_node = new Node(); since creating a Node structure will call the constructor of the object inside it which is MyClass. i tried with std::vector and it didn't require this.
The second problem is too much overhead, list.push_back(MyClass(arg1, arg2)); will create an rvalue object in the stack then send to push_back, it then creates a new object (with no argument list) in the heap then move all of its members to the new object using move assignment, is there any faster solution ?
you can emplace_back your Node
template <class T>
class CircularQueue {
template<typename... U>
T &emplace_back(U&&... u)
{
Node *new_node = new Node{{std::forward<U>(u)...}}; // <data is created here
// link_node(new_node, m_head);
return new_node->data;
}
};
void foo() {
CircularQueue<Data> x;
// Do not create a Data, pass the parameters you need to create
x.emplace_back(10, 20);
// If you actually need to, you can of course copy or move an existing Data
Data y(20, 30);
x.emplace_back(y); // copies y
x.emplace_back(std::move(y)); // moves y
}