FunctionX Tutorials

Object Serialization

Introduction

The C++ language provides a somewhat limited support for file processing. This is probably based on the time it was conceived and put to use. Many languages that were developed after C++, such as (Object) Pascal and Java provide a better support, probably because their libraries were implemented as the demand was made obvious. Based on this, C++ supports saving only values of primitive types such as short, int, char double. This can be done by using either the C FILE structure or C++' own fstream class.

 

Binary Serialization

Object serialization consists of saving the values that are part of an object, mostly the value gotten from declaring a variable of a class. AT the current standard, C++ doesn't inherently support object serialization. To perform this type of operation, you can use a technique known as binary serialization.

When you decide to save a value to a medium, the fstream class provides the option to save the value in binary format. This consists of saving each byte to the medium by aligning bytes in a contiguous manner, the same way the variables are stored in binary numbers.

To indicate that you want to save a value as binary, when declaring the ofstream variable, specify the ios option as binary. Here is an example:

#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);



	return 0;

}

Writing to the Stream

The ios::binary option lets the compiler know how the value will be stored. This declaration also initiates the file. To write the values to a stream, you can call the fstream::write() method.

After calling the write() method, you can write the value of the variable to the medium. Here is an example:

#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;

}
 

Reading From the Stream

Reading an object saved in binary format is as easy as writing it. To read the value, call the ifstream::read() method. Here is an example:

#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;

}

 

 

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