cpp_prac/refcount/main.cc

#include <iostream>

/* RefCounter. Analogous to std::shared_ptr. */
template <typename T>
class Rc {
    T *data;
    std::size_t *refs;

  public:
    explicit Rc(const T &); // Copy ctor
    explicit Rc(T &&);      // Move ctor

    Rc(const Rc &); // Copy ctor
    Rc(Rc &&);      // Move ctor

    void operator=(const Rc &); // Copy assign
    void operator=(Rc &&);      // Move assign

    ~Rc();
    const T &borrow() noexcept;
    T &borrow_mut() noexcept;
};

template <typename T>
Rc<T>::Rc(const T &data)
    : Rc(std::move(data)) {}

template <typename T>
Rc<T>::Rc(T &&data)
    : data(new T(std::move(data)))
    , refs(new std::size_t(1)) {}

template <typename T>
Rc<T>::Rc(const Rc &other)
    : data(other.data)
    , refs(other.refs) {
    refs++;
}

template <typename T>
Rc<T>::Rc(Rc &&other)
    : data(other.data)
    , refs(other.refs) {
    other.refs = nullptr;
    other.data = nullptr;
}

template <typename T>
void Rc<T>::operator=(const Rc &other) {}

template <typename T>
void Rc<T>::operator=(Rc &&other) {}

template <typename T>
Rc<T>::~Rc() {
    if (--refs == 0)
        delete data;
}

template <typename T>
const T &Rc<T>::borrow() noexcept {
    return *data;
}

template <typename T>
T &Rc<T>::borrow_mut() noexcept {
    return *data;
}

int main() {
    std::cout << "Template" << std::endl;
    Rc<int> a = Rc(10);
    auto b = Rc(10);
    b.borrow_mut()++;
    std::cout << a.borrow() << std::endl;
    std::cout << b.borrow() << std::endl;

    a = b;
}