1自己實現一個智能指針的功能

#include <iostream>

#include <string>

#include <vector>

#include <algorithm>

#include <functional>

#include <stdlib.h>

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using namespace std;

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template<class T>

class pmy

{

public:

??? pmy()

??? {}

??? pmy(T *t)

??? {

??????? p = t;

??? }

??? ~pmy()

??? {

??????? if (p != nullptr)

??????? {

??????????? delete p;

??????? }

??? }

??? T operator *()

??? {

??????? return *p;

??? }

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private:

??? T *p = nullptr;

};

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class Test

{

public:

??? Test()

??? {

??????? cout << "Test? create" << endl;

??? }

??? ~Test()

??? {

??????? cout << "Testdelete"<< endl;

??? }

};

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void run()

{

??? pmy<Test> p(new Test);//智能指針，智能釋放

??? //*p;

}

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void main()

{

??? run();

??? cin.get();

}

運行結果：

2.boost:scoped_ptr智能指針,獨占內存，并且會自動釋放內存，也就是說這片內存不用共享給別人用的時候可以用這個智能指針

#include <iostream>

#include <boost/scoped_ptr.hpp>

//#include<boost/scoped_array.hpp>

//#include<boost/shared_ptr.hpp>

//#include<boost/shared_array.hpp>

//#include<boost/weak_ptr.hpp>

//#include<windows.h>

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using namespace std;

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void main()

{

??? //scoped_ptr(作用于指針，特點是獨享)就是一個智能指針

??? //p用（new int）來初始化

??? boost::scoped_ptr<int> p(new int);//自動釋放內存

??? *p = 12;

??? //get()獲取指針指向的內容

??? cout << *p.get() << endl;

??? //reset()的作用是將原來的內存空間自動釋放

??? p.reset(new int);

??? *p.get() = 3;

??? //獨占內存，也可以用nullptr的方式進行初始化

??? boost::scoped_ptr<int> pA(nullptr);

??? cout << *p.get() << endl;

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??? cin.get();

??? //運行結果：

??? //12

??? //3

}

2. boost::scoped_array，通過它來智能管理數組

#include <iostream>

//#include<boost/scoped_ptr.hpp>

#include <boost/scoped_array.hpp>

//#include<boost/shared_ptr.hpp>

//#include<boost/shared_array.hpp>

//#include<boost/weak_ptr.hpp>

//#include<windows.h>

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using namespace std;

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void main()

{

??? //某些情況下可以用作用域數組：管理數組比較方便，可以有效的釋放數組

??? //同樣會自動釋放數組

??? boost::scoped_array<int> p(new int[10]);

??? //下面的方式是錯的，因為這個指針是獨享的，不可以共享給別的指針

??? //boost::scoped_array<int> pA(p);

???

??? *p.get() = 1;

??? p[3] = 2;

??? //結果為2

??? cout << p[3] << endl;

??? //重新分配內存，這種指針獨享指針，自動釋放內存

??? p.reset(new int[5]);

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??? cin.get();

}

3.共享指針boost::shared_ptr

#include <iostream>

#include <vector>

//#include<boost/scoped_ptr.hpp>

//#include<boost/scoped_array.hpp>

#include <boost/shared_ptr.hpp>

#include <boost/shared_array.hpp>

#include <algorithm>

//#include<boost/weak_ptr.hpp>

//#include<windows.h>

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using namespace std;

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//boost::shared_ptr<int>p共享一個指針

void show(boost::shared_ptr<int> p)

{

??? cout << *p << endl;

}

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void main()

{

??? vector<boost::shared_ptr<int>> v;

??? boost::shared_ptr<int> p1(new int(11));

??? boost::shared_ptr<int> p2(new int(12));

??? boost::shared_ptr<int> p3(p2);//拷貝

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??? v.push_back(p1);

??? v.push_back(p2);

??? v.push_back(p3);

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??? for_each(v.begin(),v.end(),show);

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??? cin.get();

??? //運行結果：

??? //11

??? //12

??? //12

}

4. boost::shared_array，共享指針數組

#include <iostream>

#include <vector>

//#include<boost/scoped_ptr.hpp>

//#include<boost/scoped_array.hpp>

#include <boost/shared_ptr.hpp>

#include <boost/shared_array.hpp>

#include <algorithm>

//#include<boost/weak_ptr.hpp>

//#include<windows.h>

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using namespace std;

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class runclass

{

public:

??? int? i = 0;

public:

??? runclass(int num) :i(num)

??? {

??????? cout << "i create" << i << endl;

??? }

??? runclass()

??? {

??????? cout << "i create" << i << endl;

??? }

??? ~runclass()

??? {

??????? cout << "i delete" << i << endl;

??? }

??? void print()

??? {

??????? cout << "i =" << i << endl;

??? }

};

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void testfun()

{

??? boost::shared_ptr<runclass>? p1(new runclass(10));

??? boost::shared_ptr<runclass>? p2(p1);? //淺拷貝

??? boost::shared_ptr<runclass>? p3(p1);

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??? p1.reset(new runclass(12));

??? p1->print();

??? p2->print();

??? p3->print();

}

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void testfunarray()

{

??? boost::shared_array<runclass> p1(new runclass[5]);

??? boost::shared_array<runclass> p2(p1);

}

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void main()

{

??? testfun();

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??? cout << "--------" << endl;

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??? testfunarray();

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??? cin.get();

}

運行指針：

5.弱指針（協助共享指針的管理）

#include <iostream>

//#include<vector>

//#include<boost/scoped_ptr.hpp>

//#include<boost/scoped_array.hpp>

#include <boost/shared_ptr.hpp>

//#include<boost/shared_array.hpp>

//#include<algorithm>

#include<boost/weak_ptr.hpp>

#include <windows.h>

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using namespace std;

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//DWORD在：#include<windows.h>中,其本質是unsignedlong

DWORD? WINAPI reset(LPVOID p)

{

??? boost::shared_ptr<int > *sh = static_cast<boost::shared_ptr<int > *> (p);

??? sh->reset();//指針的重置,釋放內存

??? std::cout << "指針執行釋放" << endl;

??? return 0;

}

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DWORD WINAPI print(LPVOID p)

{

??? boost::weak_ptr<int > * pw = static_cast<boost::weak_ptr<int > *>(p);

??? boost::shared_ptr<int > sh = pw->lock();//鎖定不可以釋放

??? Sleep(5000);

??? if (sh)

??? {

??????? std::cout << *sh << endl;

??? }

??? else

??? {

??????? std::cout << "指針已經被釋放" << endl;

??? }

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??? return 0;

}

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void main()

{

??? boost::shared_ptr<int> sh(new int(99));

??? boost::weak_ptr<int > pw(sh);

??? HANDLE threads[2];

??? threads[0] = CreateThread(0, 0, reset, &sh, 0, 0);//創建一個線程

??? threads[1] = CreateThread(0, 0, print, &pw, 0, 0);

??? Sleep(1000);

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??? WaitForMultipleObjects(2, threads, TRUE, INFINITE);//等待線程結束

??? cin.get();

}

運行結果：

指針執行釋放

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總結

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