p12.cpp

#include <cstring>
#include <fstream>
#include <iostream>
using namespace std;

typedef struct student {
    int rollNo;
    char name[50];
    char div;
    char address[100];
} student;

class studentDatabase {
    string fileName = "student_data.dat";

   public:
    studentDatabase() {
        fstream fileObj(fileName);
        if (fileObj.fail()) {
            fileObj.open(fileName, ios::out);
            cout << "New file created." << endl;
        } else {
            cout << "File already exists." << endl;
        }
        fileObj.close();
    }

    void addStudent();
    void searchStudent();
    void deleteStudent();
    void displayAll();
};

void studentDatabase::searchStudent() {
    int roll;
    student s;
    bool status = false;

    // take input of roll number to delete
    cout << "Roll number to search:\t";
    cin >> roll;

    // opening files to delete a record
    ifstream readFile;
    readFile.open(fileName, ios::in | ios::binary);

    // looking for record
    while (readFile.read((char*)&s, sizeof(student))) {
        if (s.rollNo == roll) {
            status = true;
            break;
        }
    }
    
    readFile.close();

    if (status) {
        cout << "--- RECORD FOUND ---" << endl;
        cout << "Roll number:\t" << s.rollNo << endl;
        cout << "Name:\t" << s.name << endl;
        cout << "Division:\t" << s.div << endl;
        cout << "Address:\t" << s.address << endl;
        cout << "--- END OF RECORD ---" << endl;
    } else {
        cout << "Record not found." << endl;
    }
}

void studentDatabase::deleteStudent() {
    int roll;
    student s;
    bool status = false;

    // take input of roll number to delete
    cout << "Roll number to delete:\t";
    cin >> roll;

    // opening files to delete a record
    ifstream readFile;
    readFile.open(fileName, ios::in | ios::binary);
    ofstream writeFile;
    writeFile.open("~" + fileName, ios::out | ios::binary);
    writeFile.clear();

    // looking for record
    while (readFile.read((char*)&s, sizeof(student))) {
        if (s.rollNo == roll) {
            status = true;
        } else {
            writeFile.write((char*)&s, sizeof(student)) << flush;
        }
    }
    readFile.close();
    writeFile.close();

    // moving temp file back to original file
    if (status) {
        readFile.open("~" + fileName, ios::in | ios::binary);
        writeFile.open(fileName, ios::out | ios::binary);
        writeFile.clear();

        writeFile << readFile.rdbuf();
        readFile.close();
        writeFile.close();

        // remove("~"+fileName);
        cout << "Record deleted." << endl;
    } else {
        cout << "Record not found." << endl;
    }
}

void studentDatabase::addStudent() {
    student s;
    cout << "Roll number:\t";
    cin >> s.rollNo;
    cout << "Name:\t";
    cin.ignore();
    cin.getline(s.name, 50);
    cout << "Division:\t";
    // cin.ignore();
    cin >> s.div;
    cout << "Address:\t";
    cin.ignore();
    cin.getline(s.address, 100);
    // cin.ignore();
    ofstream file(fileName, ios::out | ios::binary | ios::app);
    // file.seekp(ios::end);
    file.write((char*)&s, sizeof(student)) << flush;
    if (file.fail()) {
        cout << "Failed to add student record." << endl;
    } else {
        cout << "Student added successfully." << endl;
    }
    file.close();
}

void studentDatabase::displayAll() {
    ifstream file;
    student s;
    int count = 0;
    file.open(fileName, ios::in | ios::binary);
    while (file.read((char*)&s, sizeof(student))) {
        count++;
        cout << count << ") ";
        cout << s.rollNo << "|";
        cout << s.name << "|";
        cout << s.div << "|";
        cout << s.address << endl;
    }
    if (count == 0) {
        cout << "No records found." << endl;
    }
    file.close();
}
int main() {
    int ch;
    studentDatabase db;

    // loop
    do {
        cout << endl;
        cout << "--- MAIN MENU ---" << endl;
        cout << "1 -> Add record" << endl;
        cout << "2 -> Delete record" << endl;
        cout << "3 -> Search record" << endl;
        cout << "4 -> Display all records" << endl;
        cout << "0 -> Exit" << endl << endl;
        cout << "Choose an option (0-4):\t";
        cin >> ch;
        switch (ch) {
            case 0:
                cout << "\n\n// END OF CODE\n\n" << endl;
                break;
            case 1:
                db.addStudent();
                break;
            case 2:
                db.deleteStudent();
                break;
            case 3:
                db.searchStudent();
                break;
            case 4:
                cout << "All records are:\t" << endl;
                db.displayAll();
                break;

            default:
                cout << "Please choose a valid option (0-4):\t" << endl;
                break;
        }
    } while (ch != 0);

    return 0;
}
// END OF CODE