线程安全智能指针

线程安全的share指针

1. 代码部分

#include <iostream>
#include <mutex>
using namespace std;

class Counter{
public:
    Counter(): m_Counter(0) {}
    Counter(const Counter&) = delete;
    Counter& operator=(const Counter&) = delete;
    ~Counter() {}
    void reset() { m_Counter = 0; }
    unsigned int get() const { return m_Counter; }
    void operator++() { m_Counter++; }
    void operator++(int) { m_Counter++; }
    void operator--() { m_Counter--; }
    void operator--(int) { m_Counter--; }

private:
    unsigned int m_Counter{}; // 花括号也可以初始化
};

template<typename T>
class SharedPtr{
public:
    explicit SharedPtr(T *ptr = nullptr): // explicit
        pData(ptr),
        pCounter(new Counter()),
        pMutex(new std::mutex)
    {
        if (ptr) {
            addCount();
        }
    }

    SharedPtr(const SharedPtr<T>& sp) {
        pData = sp.pData;
        pCounter = sp.pCounter;
        pMutex = sp.pMutex;
        addCount();
    }

    SharedPtr<T>& operator=(const SharedPtr<T>& sp) {
        if (pData != sp.pData) {
            subCount();
            pData = sp.pData;
            pCounter = sp.pCounter;
            pMutex = sp.pMutex;
            addCount();
        }
    }

    T* operator->() { return pData; }

    T& operator*() { return *pData; }

    T* get() { return pData; }

    unsigned int getCount() { return pCounter->get(); }

    ~SharedPtr() { subCount(); }

private:
    void addCount() {
        pMutex->lock();
        ++(*pCounter);
        pMutex->unlock();
    }

    void subCount() {
        bool deleteflag = false;
        pMutex->lock();
        --(*pCounter);
        if (pCounter->get() == 0) {
            delete pCounter;
            delete pData;
            deleteflag = true;
        }
        pMutex->unlock();
        if (deleteflag == true) delete pMutex;
    }

private:
    T *pData;
    std::mutex *pMutex;
    Counter *pCounter;
};

class MyClass {
public:
    MyClass() {
        cout << "Constructor" << endl;
    }
    ~MyClass() {
        cout << "Destructor" << endl;
    }
};

int main() {
    SharedPtr<MyClass> p(new MyClass());
    SharedPtr<MyClass> p2 = p;
    cout << "END" << endl;
    return 0;
}

2. 参考资料

• 1. 线程安全智能指针
• 2. 智能指针