C++编程思想 第2卷 第4章 输入输出流 输入输出流缓冲

好的设计原则指出，无论何时创建一个新类，都应该尽最大努力隐藏实现细节

重要的是产生和消耗数据的输入输出流部分进行通信

每个输出流对象包含一个指向streambuf对象的指针，并且streambuf对象拥有可供
调用的成员函数

程序打开文件把文件中的内容送到标准输出

//: C04:Stype.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Type a file to standard output.
#include <fstream>
#include <iostream>
#include "../require.h"
using namespace std;

int main() {
  ifstream in("Stype.cpp");
  assure(in, "Stype.cpp");
  cout << in.rdbuf(); // Outputs entire file
  getchar();
} ///:~

输出 stype.cpp 放目录
//: C04:Stype.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Type a file to standard output.
#include <fstream>
#include <iostream>
#include "../require.h"
using namespace std;

int main() {
  ifstream in("Stype.cpp");
  assure(in, "Stype.cpp");
  cout << in.rdbuf(); // Outputs entire file
} ///:~

这里使用程序源代码作为参数创建了一个ifstream对象

一种形式的get()函数直接把数据写入另一个对象的streambuf中

这个函数的第1个参数是目标streambuf的引用，第2个参数是使函数get()停止
执行的结束字符

还有一种将文件发送到标准输出的方法

//: C04:Sbufget.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Copies a file to standard output.
#include <fstream>
#include <iostream>
#include "../require.h"
using namespace std;

int main() {
  ifstream in("Sbufget.cpp");
  assure(in);
  streambuf& sb = *cout.rdbuf();
  while(!in.get(sb).eof()) {
    if(in.fail())          // Found blank line
      in.clear();
    cout << char(in.get()); // Process '\n'
  }
  getchar();
} ///:~

输出 Sbufget.cpp 放工程目录
//: C04:Sbufget.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Copies a file to standard output.
#include <fstream>
#include <iostream>
#include "../require.h"
using namespace std;

int main() {
  ifstream in("Sbufget.cpp");
  assure(in);
  streambuf& sb = *cout.rdbuf();
  while(!in.get(sb).eof()) {
    if(in.fail())          // Found blank line
      in.clear();
    cout << char(in.get()); // Process '\n'
  }
} ///:~

函数rdbuf()返回一个指针，必须解除引用 dereference,满足函数查看对象的需要