Resource Linked List

A list thing.

#include <iostream>
#include <vector>
#include <algorithm>


struct Resource;

struct ListLink {
    Resource* ptr;
    unsigned idx;

    ListLink()
    : ptr(nullptr), idx(0)
    {}

    ListLink(Resource *ptr, unsigned idx)
    : ptr(ptr), idx(idx)
    {}
};

struct Resource {
    std::vector<ListLink> links;
    unsigned refCount = 0;
    std::string name;

    Resource(const std::string& name)
    : name(name)
    {}

    ListLink AllocLink() {
        // Find the first unused link in our vector of links.
        for (unsigned idx = 0; idx < links.size(); ++idx) {
            if (links[idx].ptr == nullptr)
                return {this, idx};
        }

        // All links are currently in use! Push and return a new one!     
        links.emplace_back();
        return {this, (unsigned)links.size()};
    }

    void IncRef() {
      std::cout << "IncRef: " << name << "\n";
      ++refCount;
    }

    void DecRef() {
      std::cout << "DecRef: " << name << "\n";
       if (--refCount == 0)
        delete this;
    }
};

struct CommandBuffer {
    ListLink refs;
    
    void RefResource(Resource& res) {       
        res.IncRef();

        // Allocate a "next" link within the resource.
        // This link will be used as a "next pointer" in the linked resource list.
        ListLink link = res.AllocLink();

        // Now swap the current refs list with the allocated link.
        // This will push the link into the front of the list.
        res.links[link.idx] = refs;
        refs = link;
    }

    void ReleaseAll() {
        // Iterate over the list of links and decrement refs.
        ListLink link = refs;
        while (link.ptr)
        {
          Resource* res = link.ptr;
          link = res->links[link.idx];
          res->links[link.idx].ptr = nullptr;
          res->DecRef();
        }
    }
};

int main() {

  Resource resA("A");
  Resource resB("B");
  
  CommandBuffer cmdA;
  CommandBuffer cmdB;

  cmdA.RefResource(resA);
  cmdB.RefResource(resA);
  cmdA.RefResource(resB);
  cmdB.ReleaseAll();
  cmdA.ReleaseAll();

  return 0;
}