auto_scope.cpp

//
// Created by light on 19-12-9.
//
#include "../RAII/shape.h"
template <typename T> class auto_ptr {
public:
  explicit auto_ptr(T *ptr = nullptr) noexcept : ptr_(ptr) {}

  ~auto_ptr() noexcept { delete ptr_; }

  T &operator*() const noexcept { return *ptr_; }

  T *operator->() const noexcept { return ptr_; }

  operator bool() const noexcept { return ptr_; }

  T *get() const noexcept { return ptr_; }

  // 拷贝构造,被复制放释放原来指针的所有权,交给复制方
  // 始终只有一个对象管理一块空间
  auto_ptr(auto_ptr &other) noexcept { ptr_ = other.release(); }

  // copy and swap  始终只有一个对象有管理这块空间的权限
  auto_ptr &operator=(auto_ptr &rhs) noexcept {
    //        auto_ptr tmp(rhs.release());
    //        tmp.swap(*this);
    // s上述两行等价于下面一行
    auto_ptr(rhs.release()).swap(*this);
    return *this;
  }

  // 原来的指针释放所有权
  T *release() noexcept {
    T *ptr = ptr_;
    ptr_ = nullptr;
    return ptr;
  }

  void swap(auto_ptr &rhs) noexcept {
    using std::swap;
    swap(ptr_, rhs.ptr_); // 转移指针所有权
  }

private:
  T *ptr_;
};

template <typename T> void swap(auto_ptr<T> &lhs, auto_ptr<T> &rhs) noexcept {
  lhs.swap(rhs);
}

template <class T>
class scoped_ptr // noncopyable
{

public:
  explicit scoped_ptr(T *ptr = 0) noexcept : ptr_(ptr) {}

  ~scoped_ptr() noexcept { delete ptr_; }

  void reset(T *p = 0) noexcept { scoped_ptr(p).swap(*this); }

  T &operator*() const noexcept { return *ptr_; }

  T *operator->() const noexcept { return ptr_; }

  T *get() const noexcept { return ptr_; }

  void swap(scoped_ptr &rhs) noexcept {
    using std::swap;
    swap(ptr_, rhs.ptr_);
  }

private:
  T *ptr_;

  scoped_ptr(scoped_ptr const &);
  scoped_ptr &operator=(scoped_ptr const &);
};

template <typename T>
void swap(scoped_ptr<T> &lhs, scoped_ptr<T> &rhs) noexcept {
  lhs.swap(rhs);
}

int main() {
  auto_ptr<shape> ptr1{create_shape(shape_type::circle)};
  auto_ptr<shape> ptr2{ptr1};
  if (ptr1.get() == nullptr && ptr2.get())
    cout << "拷贝构造：ptr1释放了所有权,ptr2获得了所有权" << endl;
  ptr1 = ptr1;

  auto_ptr<shape> ptr3{create_shape(shape_type::rectangle)};
  ptr1 = ptr3;
  if (ptr3.get() == nullptr && ptr1.get())
    cout << "赋值操作：始终只有一个对象管理一个区块!ptr3释放了所有权,"
            "ptr1获得了所有权"
         << endl;

  scoped_ptr<shape> sptr1{create_shape(shape_type::circle)};
  //    scoped_ptr<shape> sptr2{sptr1};       // error  不可拷贝
}