Chapter 1, Problem 4PA

Program Plan Intro

Extended Case Study for maintaining the record order while insertion:

Program plan:

• Include the required header files in your program.
• Define a class “Personal” with the following functions.
  • Define the default constructor “Personal()” that initializes the member variables.
  • Define the constructor “Personal()” with arguments that initializes the member variables.
  • Define the function “writeToFile()” to write a record to the output stream.
  • Define the function “readFromFile()” to read a record from the input stream.
  • Define the function “readKey()” to read SSN from console.
  • Define the function “size()” to get the size of a record.
  • Define the function “operator==()” to check the equality of the two records.
  • Define the function “operator<()” to check the current record is less than passed record.
  • Define the function “writeLegibly()” to write a record to the output stream.
  • Define the function “operator<<()” to write a record to the output stream.
  • Define the function “readFromConsole()” to read a record from the input stream.
  • Define the function “operator>>()” to read a record from the output stream.
• Define a class “Student” with the following functions.
  • Define the default constructor “Student()” that initializes the member variables.
  • Define the constructor “Student()” with arguments that initializes the member variables.
  • Define the function “writeToFile()” to write a record to the output stream.
  • Define the function “readFromFile()” to read a record from the input stream.
  • Define the function “size()” to get the size of a record.
  • Define the function “writeLegibly()” to write a record to the output stream.
  • Define the function “operator<<()” to write a record to the output stream.
  • Define the function “readFromConsole()” to read a record from the input stream.
  • Define the function “operator>>()” to read a record from the output stream.
• Define a class “Database” with the following functions.
  • Define the default constructor “Database()” that initializes the member variables.
  • Define the function “run()” that processes the user wishes.
  • Define the function “add()” to add a record to the database.
  • Define the function “find()” to find a record in the database.
  • Define the function “modify()” to modify the existing record.
  • Define the function “operator<<()” to write the database to the output stream.
  • Define the function “print()” to display the database.
• Define the function “main()”.
  • Create a database for “Personal” and call the function “run()”.

Program Description Answer

This program Extends the case study for inserting records in sorted order.

Explanation of Solution

Program:

//personal.h.

#ifndef PERSONAL

#define PERSONAL

// Include the required header files

#include<iostream>

#include <fstream>

#include <cstring>

using namespace std;

//Personal class declaration.

class Personal

{

//Access Specifier.

public:

  //constructor.

  Personal();

  //Argumented constructor.

  Personal(char*,char*,char*,int,long);

  //Function to write Person data to file.

  void writeToFile(fstream&) const;

  //Function to read Person data from file.

  void readFromFile(fstream&);

  //Function read SSN

  void readKey();

  //Function that returns the size of a record.

  int size() const

  {

  //Sum all the fields length and return it.

return 9 + nameLen + cityLen + sizeof(year) + sizeof(salary);

  }

/*Function to check the passed the record is equal to the current record.*/

  bool operator==(const Personal& pr) const

  {

  //Compare the SSN's of current record and pr.

/*If they equal the function return true. otherwise it return false.*/

  return strncmp(pr.SSN,SSN,9) == 0;

  }

/*Function to check the passed record's SSN is less than the current record.*/

  bool operator<(const Personal& pr) const

  {

  //Compare the SSN's of current record and pr.

/*If SSN's of current record less than pr.SSN then the function return true, otherwise return false*/

  return strncmp(SSN,pr.SSN,9)<0;

  }

//Access specifier.

protected:

  //Declare variables.

  const int nameLen, cityLen;

  char SSN[10], *name, *city;

  int year;

  long salary;

  //Function to write the record to the output stream.

  ostream& writeLegibly(ostream&);

/*Overload the operator << to write to the output stream.*/

  friend ostream& operator<<(ostream& out, Personal& pr)

  {

  //Call the member function to write.

  return pr.writeLegibly(out);

  }

  //Function to read a record from the input stream.

  istream& readFromConsole(istream&);

/*Overload the operator >> to read fromo the input stream.*/

  friend istream& operator>>(istream& in, Personal& pr)

  {

  //Call the member function to read.

  return pr.readFromConsole(in);

  }

};

#endif

//personal.cpp

//Include the header files.

#include "personal.h"

//Constructor that fixes the length for name and city.

Personal::Personal() : nameLen(10), cityLen(10)

{

/*Create the character array for name and city with specified size.*/

  name = new char[nameLen+1];

  city = new char[cityLen+1];

}

//Constructor with input arguments.

Personal::Personal(char *ssn, char *n, char *c, int y, long s) :

nameLen(10), cityLen(10)

{

/*Create the character array for name and city with specified size.*/

  name = new char[nameLen+1];

  city = new char[cityLen+1];

  //Copy the passed SSN

  strcpy(SSN,ssn);

  //Copy the name.

  strcpy(name,n);

  //Copy the city.

  strcpy(city,c);

  //store the year.

  year = y;

  //Store the salary.

  salary = s;

}

//Function to write the record into the output stream.

void Personal::writeToFile(fstream& out) const

{

  //Write the SSN.

  out.write(SSN,9);

  //Write the name.

  out.write(name,nameLen);

  //Write the city.

  out.write(city,cityLen);

/*Convert the year into char* and write it on the output.*/

out.write(reinterpret_cast<const char*>(&year),sizeof(int));

/*Convert the salary into char* and write it on the output.*/

out.write(reinterpret_cast<const char*>(&salary),sizeof(int));

}

//Function to read a record from the input stream.

void Personal::readFromFile(fstream& in)

{

  //Read the SSN

  in.read(SSN,9);

  //Read the name.

  in.read(name,nameLen);

  //Read the city.

  in.read(city,cityLen);

  //Convert the char* to int and store it in year.

  in.read(reinterpret_cast<char*>(&year),sizeof(int));

  //Convert the char* to int and store it in salary.

  in.read(reinterpret_cast<char*>(&salary),sizeof(int));

}

//Function to read the SSN from the user.

void Personal::readKey()

{

  //Declare the variables.

  char s[80];

  //Prompt the user.

  cout << "Enter SSN: ";

  //Read the SSN

  cin.getline(s,80);

  //copy the SSN.

  strncpy(SSN,s,9);

}

//Function to write the record to the console.

ostream& Personal::writeLegibly(ostream& out)

{

  //Terminate the strings.

  SSN[9] = name[nameLen] = city[cityLen] = '\0';

  //Write SSN, name, year, city, salary to the console.

out << "SSN = " << SSN << ", name = " << name<< ", city = " << city << ", year = " << year<< ", salary = " << salary;

  //Return the output stream.

  return out;

}

//Function to read a record from the console.

istream& Personal::readFromConsole(istream& in)

{

  //Terminate the strings.

  SSN[9] = name[nameLen] = city[cityLen] = '\0';

  char s[80];

  //Read SSN in variable 's'.

  cout << "SSN: ";

  in.getline(s,80);

  //Copy the SSN from 's'.

  strncpy(SSN,s,9);

  //Read name in variable 's'.

  cout << "Name: ";

  in.getline(s,80);

  //Copy the name from 's'.

  strncpy(name,s,nameLen);

  //Read the city in 's'.

  cout << "City: ";

  in.getline(s,80);

  //Copy the city from 's'.

  strncpy(city,s,cityLen);

  //Read the year.

  cout << "Birthyear: ";

  in >> year;

  //Read the salary.

  cout << "Salary: ";

  in >> salary;

  in.ignore();

  //Return the input stream.

  return in;

}

//student.h

//Defining the header file.

#ifndef STUDENT

#define STUDENT

//Include the header file

#include "personal.h"

//Derive the class Student from Personal

class Student : public Personal

{

//Access specifier.

public:

  //Constructor

  Student();

  //Constructor with arguments*/

  Student(char*,char*,char*,int,long,char*);

  //Function to write record to the output stream.

  void writeToFile(fstream&) const;

  //Function to read a Student record from input stream.

  void readFromFile(fstream&);

  //Function to get the size of the Student record.

  int size() const

  {

/*Call the base call method to find the record size.*/

  return Personal::size() + majorLen;

  }

//Access specifier.

protected:

  //Declare variables.

  char *major;

  const int majorLen;

  //Function to write the record to the output stream.

  ostream& writeLegibly(ostream&);

/*Overaloaded operator << to write to the output stream.*/

  friend ostream& operator<<(ostream& out, Student& sr)

  {

  //Call member function to write the record.

  return sr.writeLegibly(out);

  }

  //Function to read a record from the input stream.

  istream& readFromConsole(istream&);

//Overload the operator >> to read fromo the input stream.

  friend istream& operator>>(istream& in, Student& sr)

  {

  //Call the member function to read.

  return sr.readFromConsole(in);

  }

};

#endif

//student.cpp

//Include the header files.

#include "student.h"

//Constructor to initialize the variables.

Student::Student() : majorLen(10)

{

  //Call base call constructor for initialization.

  Personal();

  //Create the character array for the major.

  major = new char[majorLen+1];

}

//Constructor to initialize all the variables. This constructor takes arguments*/

Student::Student(char *ssn, char *n, char *c, int y, long s, char *m) :

majorLen(11)

{

  //Call baseclass constructor.

  Personal(ssn,n,c,y,s);

  //Create the character array for the major.

  major = new char[majorLen+1];

  //Copy the major.

  strcpy(major,m);

}

//Function to write the record to the output stream.

void Student::writeToFile(fstream& out) const

{

/*Call base class method to write the name, city, SSN, year, salary.*/

  Personal::writeToFile(out);

  //Write the major.

  out.write(major,majorLen);

}

//Function to read a record from the input stream.

void Student::readFromFile(fstream& in)

{

/*Call baseclass method to read the name,city, SSN,  year,salary.*/

  Personal::readFromFile(in);

  //Read the major.

  in.read(major,majorLen);

}

/*Function to write the student record to the output stream.*/

ostream& Student::writeLegibly(ostream& out)

{

/*Call baseclass method to write the name,city, SSN,  year,salary.*/

  Personal::writeLegibly(out);

  major[majorLen] = '\0';

  //Write the major.

  out << ", major = " << major;

  //Return the output stream.

  return out;

}

//Function to read a record from the input stream console.

istream& Student::readFromConsole(istream& in)

{

/*Call base class method to read name, city, year, SSN, salary from console.*/

  Personal::readFromConsole(in);

  char s[80];

  //Prompt the user to enter the major.

  cout << "Major: ";

  //read the major in variable 's'.

  in.getline(s,80);

  //Copy the major from 's'.

  strncpy(major,s,9);

  //Return the input stream.

  return in;

}

//database.h

//Define the header file.

#ifndef DATABASE

#define DATABASE

//Create the template class.

template<class T>

//Create the class Database

class Database

{

//Access Specifier.

public:

  //Construtor.

  Database();

/*Function that displays the menu and proceeds as per user wish.*/

  void run();

//Access Specifier.

private:

  /* Declare variables*/

  fstream database;

  char fName[20];

  //Function to display the database

  ostream& print(ostream&);

  //Function to add a record into the database.

  void add(T&);

/*Function to find a particular record in the database.*/

  bool find(const T&);

  //Function to modify the record in the database.

  void modify(const T&);

/*Overloaded operator << to print the given database to the output stream.*/

  friend ostream& operator<<(ostream& out, Database& db)

  {

  //Call the method to print the database.

  return db.print(out);

  }

};

#endif

//database.cpp

#include <iostream>

#include <vector>

#include "student.h"

#include "personal.h"

#include "database.h"

//No argumented constructor.

template<class T>

Database<T>::Database()

{

}

//Function to add a record into the database.

template<class T>

void Database<T>::add(T& d)

{

  //Declare the variables.

  T tmp;

  int rCnt=0;

/*Create a vector to store the records after 'd' record.*/

  vector<Personal> per;

  //Declare the flag to indicate the record inserted.

  int flag=0;

  //Open the database.

  database.open(fName,ios::in|ios::out|ios::binary);

/*Inifinite loop that runs until record is inserted in the database.*/

  while (true)

  {

  //Read a record from the file.

  tmp.readFromFile(database);

  //Increment the record count.

  rCnt++;

/*Check database is null. If so exit from the loop.*/

  if (database.eof())

  break;

  //Check tmp exists the 'd'

  if ((d<tmp))

  {

  //Go back to the start of the tmp.

  database.seekp(-d.size(),ios::cur);

/*Infinite loop to read the record from tmp to database end.*/

  while(true)

  {

  //Read a record.

  tmp.readFromFile(database);

/*Check database is null. If so, return. */

  if (database.eof())

  break;

  //Push the tmp into per.

  per.push_back(tmp);

  }

  //Clear the pointers.

  database.clear();

  //Move to the file beginning.

  database.seekg(0);

  //Goto the violating record position.

  database.seekp((rCnt-1)*d.size(),ios::beg);

  //Write d in that position.

  d.writeToFile(database);

/*Loop to write back the vector of records into database. */

  for(int kk=0;kk<per.size();kk++)

  {

  //Write kkth record into database.

per.at(kk).writeToFile(database);

  }

  //Close the database.

  database.close();

  //Return statement.

  return;

  }

  }

  //If record is not inserted.

  if(flag==0)

  {

  //Open the database.

database.open(fName,ios::in|ios::out|ios::binary);

  //Clear the file pointers.

  database.clear();

  //Goto the file end.

  database.seekp(0,ios::end);

  //Write 'd' to the database.

  d.writeToFile(database);

  }

  //Close the database.

  database.close();

}

//Function to modify the existing record in the database.

template<class T>

void Database<T>::modify(const T& d)

{

  //Declare the variable.

  T tmp;

  //Open the database.

  database.open(fName,ios::in|ios::out|ios::binary);

  //Read a record from the file.

  tmp.readFromFile(database);

  //Check database is null. If so exit from the loop.

  if (database.eof())

  {

  //Close the database.

  database.close();

  //Return statement.

  return;

  }

  //Read  until tmp less than d.

  while (tmp<d)

  {

  //Read the record from the database.

  tmp.readFromFile(database);

  }

  //Check tmp matches d.

  if (tmp == d)

  {

  //Read the record

  cin >> tmp;

  //Seek to the record's position.

  database.seekp(-d.size(),ios::cur);

  //Write the record to the file.

  tmp.writeToFile(database);

  //Close the database.

  database.close();

  //Exit from the function.

  return;

  }

  //Close the database.

  database.close();

  //Print the message indicating record not found.

cout << "The record to be modified is not in the database\n";

}

//Function to find the given record in the database.

template<class T>

bool Database<T>::find(const T& d)

{

  //Declare the variable.

  T tmp;

  //Open the database.

  database.open(fName,ios::in|ios::binary);

  //Read a record from the file.

  tmp.readFromFile(database);

  //Check database is null. If so exit from the loop.

  if (database.eof())

  {

  //Close the database.

  database.close();

  //Record not found, so return false.

  return false;

  }

  //Read  until tmp less than d.

  while (tmp<d)

  {

  //Read the record from the database.

  tmp.readFromFile(database);

  }

  //Check tmp matches d.

  if (tmp == d)

  {

  //Close the database.

  database.close();

  //Record found, so return true.

  return true;

  }

  //Close the database.

  database.close();

  //Record not found, so return false.

  return false;

}

template<class T>

ostream& Database<T>::print(ostream& out)

{

  //Declare the variable.

T tmp;

//Open the database.

  database.open(fName,ios::in|ios::binary);

  //Infinite loop.

  while (true)

  {

  //Read a record from the file.

  tmp.readFromFile(database);

/*Check database is null. If so exit from the loop.*/

  if (database.eof())

  //Exit from the loop.

  break;

  //Write the record tmp to the output stream.

  out << tmp << endl;

  }

  //Close the database.

  database.close();

  //Return the output stream.

  return out;

}

//Function to process the user wish.

template<class T>

void Database<T>::run()

{

  //Get the database filename.

  cout << "File name: ";

  cin >> fName;

  //Declare variables.

  char option[5];

  T rec;

  //Display menu.

cout << "1. Add 2. Find 3. Modify a record; 4. Exit\n";

  //Get option.

  cout << "Enter an option: ";

  cin.getline(option,4);

  //Infinite loop ends until user wishes to exit.

  while (cin.getline(option,4))

  {

  //If user wants to add a record.

  if (*option == '1')

  {

  //Get the record.

  cin >> rec;

  //Write the record into the database.

  add(rec);

  }

  //If user wants to find a record,

  else if (*option == '2')

  {

  //Read the SSN

  rec.readKey();

  //Display record is found or not.

  cout << "The record is ";

  //Check finding record returns false.

  if (find(rec) == false)

  cout << "not ";

  cout << "in the database\n";

  }

/*If user wants to modify a record in the database,*/

  else if (*option == '3')

  {

  //Read the SSN of the record to be modified.

  rec.readKey();

  //Call the method modify()

  modify(rec);

  }

  //If user enters wrong option.

  else if (*option != '4')

  //Print wrong input.

  cout << "Wrong option\n";

  //Otherwise exit from the loop.

  else

  //Return to the main function.

  return;

  //Display the database.

  cout << *this;

  //Ask the user for an option.

  cout << "Enter an option: ";

  }

}

//main() method.

int main()

{

/*Creating the database with Personal objects and call the function run().*/

  Database<Personal>().run();

  //To pause the console window.

  system("pause");

  return 0;

}

Sample Output

Output:

File name: student.txt

1. Add 2. Find 3. Modify a record; 4. Exit

Enter an option: 1

SSN: 456

Name: Mullen

City: Bangalore

Birthyear: 2015

Salary: 1000

SSN = 456, name = Mullen, city = Bangalore, year = 2015, salary = 1000

Enter an option: 1

SSN: 123

Name: Arlen

City: Delhi

Birthyear: 2000

Salary: 40000

SSN = 123, name = Arlen, city = Delhi, year = 2000, salary = 40000

SSN = 456, name = Mullen, city = Bangalore, year = 2015, salary = 1000

Enter an option: 2

Enter SSN: 456

The record is in the database

SSN = 123, name = Arlen, city = Delhi, year = 2000, salary = 40000

SSN = 456, name = Mullen, city = Bangalore, year = 2015, salary = 1000

Enter an option: 3

Enter SSN: 456

SSN: 456

Name: Mullen

City: Bangalore

Birthyear: 2005

Salary: 10000

SSN = 123, name = Arlen, city = Delhi, year = 2000, salary = 40000

SSN = 456, name = Mullen, city = Bangalore, year = 2005, salary = 10000

Enter an option: 4

Press any key to continue . . .

After running of the program, the file has been changed as follows,

student.txt: