71 lines
1.8 KiB
C++
71 lines
1.8 KiB
C++
//
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// Created by light on 19-12-12.
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//
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#include "../RAII/shape.h"
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template <typename T> class unique_ptr {
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public:
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explicit unique_ptr(T *ptr = nullptr) noexcept : ptr_(ptr) {}
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~unique_ptr() noexcept { delete ptr_; }
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T &operator*() const noexcept { return *ptr_; }
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T *operator->() const noexcept { return ptr_; }
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operator bool() const noexcept { return ptr_; }
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T *get() const noexcept { return ptr_; }
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unique_ptr(unique_ptr &&other) noexcept {
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cout << "move ctor" << endl;
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ptr_ = other.release();
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}
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template <typename U> unique_ptr(unique_ptr<U> &&other) noexcept {
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cout << "U move ctor" << endl;
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ptr_ = other.release();
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}
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// copy and swap 始终只有一个对象有管理这块空间的权限
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unique_ptr &operator=(unique_ptr rhs) noexcept {
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rhs.swap(*this);
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return *this;
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}
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// 原来的指针释放所有权
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T *release() noexcept {
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T *ptr = ptr_;
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ptr_ = nullptr;
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return ptr;
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}
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void swap(unique_ptr &rhs) noexcept {
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using std::swap;
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swap(ptr_, rhs.ptr_); // 转移指针所有权
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}
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private:
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T *ptr_;
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};
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template <typename T> void swap(unique_ptr<T> &lhs, unique_ptr<T> &rhs) {
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lhs.swap(rhs);
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}
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int main() {
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unique_ptr<shape> ptr1{create_shape(shape_type::circle)};
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// unique_ptr<shape> ptr2{ptr1}; // error
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unique_ptr<shape> ptr2_2{std::move(ptr1)}; // ok
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if (ptr2_2.get() != nullptr && ptr1.get() == nullptr)
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ptr2_2.get()->print();
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unique_ptr<shape> ptr3{create_shape(shape_type::rectangle)};
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// ptr1 = ptr3; // error
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ptr3 = std::move(ptr1); // ok
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// unique_ptr<circle> cl{create_shape(shape_type::circle)}; // error
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// 因为create_shape返回的是shape 不能基类转子类
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unique_ptr<circle> cl{new circle()};
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unique_ptr<shape> ptr5(std::move(cl)); // ok unique<circle>转unique<circle>
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} |