学步园

      C++语言对文件的处理有一些限制，对于后来出现的一些语言，如Pascal 和Java都提供了对对象进行序列化的支持，而C++只能通过C FILE s结构 或 C++自己的fstream 类来保存程序中变量的值。

 二进制序列化

     对象序列化包含保存对象中的某些值，这些值是来自类当中的成员变量。在目前的标准当中，C++不存在内在的对象序列化，为了达到对象序列化，可以用二进制序列化来实现。

   如果你想保存一个值到文件，fstream
 类提供了以二进制形式保存该值的方法。当你想用二进制的形式保存一个变量，在定义ofstream变量的时候，要指定iso::binary.

例子如下：

将对象保存在stream

#include <fstream>

#include <iostream>

using namespace std;



class Student

{

public:

	char   FullName[40];

	char   CompleteAddress[120];

	char   Gender;

	double Age;

	bool   LivesInASingleParentHome;

};



int main()

{

	Student one;



	strcpy(one.FullName, "Ernestine Waller");

	strcpy(one.CompleteAddress, "824 Larson Drv, Silver Spring, MD 20910");

	one.Gender = 'F';

	one.Age = 16.50;

	one.LivesInASingleParentHome = true;

	

	ofstream ofs("fifthgrade.ros", ios::binary);



	ofs.write((char *)&one, sizeof(one));



	return 0;

}

从stream流中读取对象

#include <fstream>

#include <iostream>

using namespace std;



class Student

{

public:

	char   FullName[40];

	char   CompleteAddress[120];

	char   Gender;

	double Age;

	bool   LivesInASingleParentHome;

};



int main()

{

/*	Student one;



	strcpy(one.FullName, "Ernestine Waller");

	strcpy(one.CompleteAddress, "824 Larson Drv, Silver Spring, MD 20910");

	one.Gender = 'F';

	one.Age = 16.50;

	one.LivesInASingleParentHome = true;

	

	ofstream ofs("fifthgrade.ros", ios::binary);



	ofs.write((char *)&one, sizeof(one));

*/

	Student two;



	ifstream ifs("fifthgrade.ros", ios::binary);

	ifs.read((char *)&two, sizeof(two));



	cout << "Student Information\n";

	cout << "Student Name: " << two.FullName << endl;

	cout << "Address:      " << two.CompleteAddress << endl;

	if( two.Gender == 'f' || two.Gender == 'F' )

		cout << "Gender:       Female" << endl;

	else if( two.Gender == 'm' || two.Gender == 'M' )

		cout << "Gender:       Male" << endl;

	else

		cout << "Gender:       Unknown" << endl;

	cout << "Age:          " << two.Age << endl;

	if( two.LivesInASingleParentHome == true )

		cout << "Lives in a single parent home" << endl;

	else

		cout << "Doesn't live in a single parent home" << endl;

	

	cout << "\n";



	return 0;

}