学步园

// RightValue.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <algorithm>商账追收
#include <vector>
#include <ctime>
using namespace std;

class CMyObj{ TCSTAR7034
protected:
    unsigned m_iBufferSize;
    char* m_pBuffer;
public:
    CMyObj():m_iBufferSize(0),m_pBuffer(NULL){}
    CMyObj(unsigned int iBufSize):
        m_iBufferSize(iBufSize)斜庞克发型怎么剪
        {
            m_pBuffer = new char[iBufSize];
            memset(m_pBuffer,0,m_iBufferSize);
        }
    CMyObj(const CMyObj& objSrc){
        m_iBufferSize = objSrc.m_iBufferSize;
        if(m_iBufferSize > 0){
            m_pBuffer = new char[m_iBufferSize];
            memcpy(m_pBuffer,objSrc.m_pBuffer,m_iBufferSize);
        }
    }
    ~CMyObj(){
        if(m_pBuffer) delete m_pBuffer;
        m_pBuffer = NULL;
    }
};

class CMyObjWithMoveConstructor:public CMyObj
{
public:
    CMyObjWithMoveConstructor():CMyObj(){}
    CMyObjWithMoveConstructor(int iBufSize)
        :CMyObj(iBufSize){}
    //copy constructor
    CMyObjWithMoveConstructor(const CMyObjWithMoveConstructor& myObj)
        :CMyObj(myObj){}

    //move constructor
    CMyObjWithMoveConstructor(CMyObjWithMoveConstructor&& myObj){
        m_iBufferSize = myObj.m_iBufferSize;
        m_pBuffer = myObj.m_pBuffer;

        myObj.m_pBuffer = NULL;
        myObj.m_iBufferSize = 0;
    }

};

int _tmain(int argc, _TCHAR* argv[])
{
    static int iBufSize = 1024*1024*2; //2M
    static int iObjCnt = 100;

    clock_t t1,t2;
    double times;

    vector<CMyObj> vec;
    t1 = clock();
    //没有右值引用
    for( int i = 0; i < iObjCnt; i ++){ //加入100个元素
        vec.push_back( CMyObj(iBufSize));
    }
    t2 = clock();
    times = (double)(t2-t1)/CLOCKS_PER_SEC;
    cout<<"without move constructor:"<<times<<endl;
   
    vector<CMyObjWithMoveConstructor> vec2;
    t1 = clock();
    //有右值引用
    for( int j = 0; j < iObjCnt; j ++){ //加入100个元素
        vec2.push_back( CMyObjWithMoveConstructor(iBufSize));
    }
    t2 = clock();
    times = (double)(t2-t1)/CLOCKS_PER_SEC;
    cout<<"with move constructor:"<<times<<endl;

    return 0;
}

//最后结果：
//without move constructor:1.48
//with move constructor:0.16
//相差了9.25倍