File Handling c++: using this pointer to read objects - c++

Question

Is this correct?
Here Update is member function of Product class.
I am using this pointer(pointing to calling product object) to read objects stored in file over and over.
file.read((char *)this, sizeof(product));
Here if the class(see the update member function):
class product
{
int product_num;
string product_name;
int quantity;
float sell_p;
float buy_p;
int gst;
float total;
float profit;
public:
void calculate()
{
this->total = this->quantity * (this->sell_p);
this->profit = this->total - (this->buy_p * this->quantity) * (1 + this->gst / 100);
}
product()
{
product_num = 0;
product_name = "\0";
}
product(int p_num, string name, int quantity, float sell_p, float buy_p, int gst)
{
this->product_num = p_num;
this->product_name = name;
this->quantity = quantity;
this->sell_p = sell_p;
this->buy_p = buy_p;
this->gst = gst;
calculate();
}
void get_data()
{
cout << "Enter Serial Number: ";
cin >> this->product_num;
cout << "Enter Product Name(MAX LENGTH: 20): ";
cin>>this->product_name;
cout << "Enter Quantity: ";
cin >> this->quantity;
cout << "Enter Buying Price: ";
cin >> this->buy_p;
cout << "Enter GST: ";
cin >> this->gst;
cout << "Enter Selling Price: (Selling Price should be greater than " << (this->buy_p + (this->gst / 100) * this->buy_p) << " to turn profit)";
cin >> this->sell_p;
calculate();
}
void show_product()
{
cout << "Serial: " << this->product_num
<< "\nName: " << this->product_name
<< "\nQuantity: " << this->quantity
<< "\nSelling Price: " << this->sell_p
<< "\nBuying Price: " << this->buy_p
<< "\nGST: " << this->gst << endl;
}
bool remove_product(int x)
{
if (x > this->quantity)
return false;
this->quantity -= x;
return true;
}
int getSerialNumber()
{
return this->product_num;
}
string getName()
{
return this->product_name;
}
int getQuantity()
{
return this->quantity;
}
int getGST()
{
return this->gst;
}
float getTotal()
{
return this->total;
}
float getProfit()
{
return this->profit;
}
float getSellPrice()
{
return this->sell_p;
}
float getBuyPrice()
{
return this->buy_p;
}
bool isValid()
{
if (product_num == 0 || product_name == "\0")
return false;
return true;
}
void save()
{
ofstream fout;
fout.open("product.dat", ios::binary | ios::app);
if (!fout)
{
cout << "Failed To Open File!!\nExiting..";
exit(0);
}
else
{
fout.write((char *)this, sizeof(product));
}
fout.close();
}
void update()
{
int s_num = this->product_num;
fstream file;
file.open("product.dat", ios::binary | ios::ate | ios::in | ios::out);
if (!file)
{
cout << "Failed to open file!!!\nExiting...." << endl;
exit(0);
}
else
{
file.seekg(0);
file.read((char *)this, sizeof(product));
while (!file.eof())
{
if (s_num == this->product_num)
{
cout << "Product Detail: ";
this->show_product();
cout << "Enter the Values: " << endl;
cout << "Note: IF DONT WISH TO CHANGE KINDLY ENTER SAME VALUE.";
this->get_data();
file.seekp(-(sizeof(product)),ios::cur);
file.write((char *)this, sizeof(product));
break;
}
file.read((char *)this, sizeof(product));
}
}
file.close();
}
void remove_it()
{
int s_num = this->product_num;
ofstream fout;
ifstream fin;
fin.open("product.dat", ios::in | ios::binary);
if (!fin)
{
cout << "Failed to open file!!\nExiting...";
exit(0);
}
else
{
fout.open("temp.dat", ios::binary | ios::out);
fin.read((char *)this, sizeof(product));
while (!fin.eof())
{
if (!(s_num == this->product_num))
{
fout.write((char *)this, sizeof(product));
}
fin.read((char *)this, sizeof(product));
}
fin.close();
fout.close();
if(remove("product.dat") == 0)
cout<<"Sucessfully Deleted file\n";
else
cout<<"File Removal Failed\n";
if(rename("temp.dat", "product.dat") == 0)
cout<<"Successfully Renamed\n";
else
cout<<"Failed to Rename\n";
}
}
};