rdbuf 在批量数据测试中的应用

1. 改变cin输入流

#include <iostream>
#include <fstream>

using namespace std;

int main( )
{

	int a,b,c,d;

	// 从main.txt中读取数据
	ifstream infile("c://main.txt");

	// 为恢复cin备份
	streambuf *inrecover = cin.rdbuf();
	
	// 指定cin输入源为流infile，即为main.txt
	cin.rdbuf ( infile.rdbuf() );

	// 程序自动接收数据a,b,c
	cin >> a >> b;
	cin >> c;
	cout << a + b << endl;
	cout << c << endl;
	
	// 恢复cin输入源
	cin.rdbuf ( inrecover );

	// 等待从键盘输入数据
	cin >> d;
	cout << d;

	getchar();
	return 0;
}

2. 改变cout输出流

ofstream outf("out.txt");  
streambuf *strm_buf = cout.rdbuf();  
cout.rdbuf( outf.rdbuf() );  
cout << "write something to file";  
cout.rdbuf(strm_buf); //recover  
cout << "display something on screen";