/* * Let's me introduce my own implementation * of the shared_ptr smart pointer. * This pointer counts references * and deletes object if there is no more */ #include #include //size_t #include template class smart_ptr { // counter of references std::size_t *counter; // inner ptr T *ptr; public: smart_ptr() :counter(new std::size_t(1)), ptr(nullptr) {} explicit smart_ptr(T *ptr) :counter(new std::size_t(1)), ptr(ptr) {} smart_ptr(smart_ptr& ptr); smart_ptr& operator=(smart_ptr& ptr); T& operator*() const; T* operator->() const; operator bool() const; ~smart_ptr(); //deleted members smart_ptr(smart_ptr&& ptr) = delete; smart_ptr& operator=(smart_ptr&& ptr) = delete; }; int main() { using std::cout; using std::endl; using std::string; smart_ptr s1(new string("Smart string")); smart_ptr s2; s2 = s1; cout << "string: " << *s2 << endl; cout << "string->size(): " << s2->size() << endl; { smart_ptr s3; s3 = s2; } // check operator bool if(s1) { cout << "pointer s1 is not null" << endl; } return 0; } template smart_ptr::smart_ptr(smart_ptr& ptr) :counter(new std::size_t(1)) { this->ptr = ptr.ptr; if(*counter == 1) { delete counter; } ++*ptr.counter; counter = ptr.counter; } template smart_ptr& smart_ptr::operator=(smart_ptr& ptr) { this->ptr = ptr.ptr; if(*counter == 1) { delete counter; } ++*ptr.counter; counter = ptr.counter; return *this; } template inline T& smart_ptr::operator*() const { return *ptr; } template inline T* smart_ptr::operator->() const { return ptr; } template inline smart_ptr::operator bool() const { return ptr; } template smart_ptr::~smart_ptr() { //debug cout to check value of the counter std::cout << "counter: " << *counter << std::endl; --*counter; if(*counter == 0) { delete ptr; delete counter; ptr = nullptr; counter = nullptr; } //debug output std::cout << ((ptr) ? "not null" : "null") << std::endl; }

Smart pointer class template