shared pointer in C++

shared_ptr.cpp

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#include <iostream>
#include <atomic>
#include <utility>

template <typename T>
class SharedPtr {
  private:
  
  T* ptr;
  std::atomic<unsigned>* ref_count;
  
  void release() {
      if (ref_count) {
          if (--(*ref_count) == 0) {
              delete ptr;
              delete ref_count;
          }
      }
  }
  
  public:
  
  SharedPtr() : ptr(nullptr), ref_count(nullptr) {}
  
  explicit SharedPtr(T* raw_ptr) : ptr(raw_ptr), ref_count(new std::atomic<unsigned>(1)) {
  }

  // Copy constructor
  SharedPtr(const SharedPtr& other) : ptr(other.ptr), ref_count(other.ref_count) {
      if (ref_count) {
          ++(*ref_count);
      }
  }

  // Move constructor
  SharedPtr(SharedPtr&& other) noexcept : ptr(other.ptr), ref_count(other.ref_count) {
    other.ptr = nullptr;
    other.ref_count = nullptr;
  }
  
  // Copy assignment operator
  SharedPtr& operator=(const SharedPtr& other) {
     if (this != other) {
         release();
         ptr = other.ptr;
         ref_count = other.ref_count;
         if (ref_count) {
             ++(*ref_count);
         }
     }
     return *this;
  }
  
  // Move assignment operator
  SharedPtr& operator=(SharedPtr&& other) noexcept {
      if (this != &other) {
          release();
          ptr = other.ptr;
          ref_count = other.ref_count;
          other.ptr = nullptr;
          other.ref_count = nullptr;
      }
  }
  
  ~SharedPtr() {
      release();
  }
  
  unsigned use_count() const {
      return ref_count ? ref_count->load() : 0;
  }

};

int main()
{
    SharedPtr<int> sp1(new int(10));
    std::cout << "Reference count: " << sp1.use_count() << "\n";

    {
        SharedPtr<int> sp2 = sp1; // Copy constructor
        std::cout << "Reference count after copy: " << sp1.use_count() << "\n";

        SharedPtr<int> sp3 = std::move(sp1); // Move constructor
        std::cout << "Reference count after move: " << sp3.use_count() << "\n";
    }

    std::cout << "Reference count after block: " << sp1.use_count() << "\n";

    return 0;
}