手撕c++ shared

#include <iostream> #include <memory> using namespace std; namespace smart_pointer { template <typename T> struct defaultDeleter { void operator()(const T *ptr) { if(ptr) { delete ptr; ptr = nullptr; } } }; template <typename T, typename Deleter=defaultDeleter<T> > class shared_ptr { public: shared_ptr(); shared_ptr(T *ptr); shared_ptr(const shared_ptr &sp); //拷贝构造 shared_ptr(shared_ptr &&sp); //移动构造 ~shared_ptr(); T* operator ->() const; T& operator *() const; operator bool() const; shared_ptr &operator =(const shared_ptr &sp); shared_ptr &operator =(shared_ptr &&sp); T* get() const; void reset(T *ptr); void swap(shared_ptr &sp); int count(); private: atomic<int> *use_count; T *ptr; }; template <typename T, typename Deleter> shared_ptr<T, Deleter>::shared_ptr() {} template <typename T, typename Deleter> shared_ptr<T, Deleter>::shared_ptr(T *_ptr) : ptr(_ptr), use_count(new atomic<int>(1)) {} template <typename T, typename Deleter> shared_ptr<T, Deleter>::shared_ptr(const shared_ptr &sp) : ptr(sp.ptr), use_count(sp.use_count) { ++*use_count; } template <typename T, typename Deleter> shared_ptr<T, Deleter>::shared_ptr(shared_ptr &&sp) { std::swap(ptr, sp.ptr); std::swap(use_count, sp.use_count); } template <typename T, typename Deleter> shared_ptr<T, Deleter>::~shared_ptr() { if(ptr) { --*use_count; if(*use_count <= 0) { Deleter()(ptr); delete use_count; cout << "shared_ptr dctor" << endl; } } } template <typename T, typename Deleter> T *shared_ptr<T, Deleter>::operator-> () const { return ptr; } template <typename T, typename Deleter> T& shared_ptr<T, Deleter>::operator* () const { return *ptr; } template <typename T, typename Deleter> shared_ptr<T, Deleter>::operator bool() const { return ptr!=nullptr; } /* 异常安全赋值 */ template <typename T, typename Deleter> shared_ptr<T, Deleter> &shared_ptr<T, Deleter>::operator= (const shared_ptr<T, Deleter> &sp) { #if 1 //copy and swap shared_ptr<T, Deleter> tmp(sp); swap(tmp); return *this; #else //自我赋值 if(sp.ptr == ptr) return *this; ptr = sp.ptr; use_count = sp.use_count; ++*use_count; return *this; #endif } template <typename T, typename Deleter> shared_ptr<T, Deleter> &shared_ptr<T, Deleter>::operator= (shared_ptr<T, Deleter> &&sp) { std::swap(ptr, sp.ptr); std::swap(use_count, sp.use_count); return *this; } template <typename T, typename Deleter> T* shared_ptr<T, Deleter>::get() const { return ptr; } template <typename T, typename Deleter> void shared_ptr<T, Deleter>::reset(T *_ptr) { shared_ptr<T, Deleter>().swap(*this); ptr = _ptr; use_count = new atomic<int>(1); } template <typename T, typename Deleter> void shared_ptr<T, Deleter>::swap(shared_ptr<T, Deleter> &sp) { std::swap(ptr, sp.ptr); std::swap(use_count, sp.use_count); } template <typename T, typename Deleter> int shared_ptr<T, Deleter>::count() { return *use_count; } }; //namespace smart_pointer int main(int argc, char *argv[]) { { smart_pointer::shared_ptr<int> p(new int(12)); smart_pointer::shared_ptr<int> p1(p); *p1 = 2; cout << *p << endl; cout << p.count() << endl; //异常安全测试 p = p; cout << *p << endl; cout << p.count() << endl; } { smart_pointer::shared_ptr<int> p(new int(12)); p.reset(new int(13)); cout << *p << endl; //右值赋值测试 p = smart_pointer::shared_ptr<int>(new int(14)); cout << *p << endl; //移动构造测试 smart_pointer::shared_ptr<int> p1(smart_pointer::shared_ptr<int>(new int(15))); cout << *p1 << endl; } return 0; }