How do I write intrusive containers for game development?

Intrusive containers are a powerful way to manage collections of objects in C++ game development, allowing objects to be part of the container without needing additional memory allocations. This approach provides performance advantages in terms of memory usage and cache efficiency, which are critical in game development where performance is paramount.

What are Intrusive Containers?

Intrusive containers store objects that themselves carry their connectivity data. This means that the container does not need to maintain separate pointers to the objects it stores. Instead, the objects themselves contain the necessary pointers to link to each other. This approach is particularly useful for scenarios where the overhead of dynamic memory allocation is a concern.

Example of an Intrusive List

Here’s a simple example of an intrusive list implementation:

#include 

class Node {
public:
    Node* next = nullptr; // next pointer for the intrusive list

    // Some data the node holds
    int value;

    Node(int val) : value(val) {}
};

class IntrusiveList {
private:
    Node* head = nullptr;

public:
    void push_front(Node* node) {
        node->next = head;
        head = node;
    }

    void print() {
        Node* current = head;
        while (current) {
            std::cout << current->value << " ";
            current = current->next;
        }
        std::cout << std::endl;
    }
};

int main() {
    IntrusiveList list;
    Node node1(10);
    Node node2(20);
    Node node3(30);

    list.push_front(&node1);
    list.push_front(&node2);
    list.push_front(&node3);

    list.print(); // Output: 30 20 10

    return 0;
}