Удаление информации из файла

struct Parcel {
    AnsiString type;
    AnsiString weight;
    AnsiString dispatch_date;
    AnsiString arrival_date;
    AnsiString status;
    AnsiString f_name, s_name;
    AnsiString p_number;
};
 
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    Parcel p_in_file;
 
    fstream File;
    File.open("file.txt", ios::app);
 
    p_in_file.type = Form1->Edit1->Text;
    p_in_file.weight = Form1->Edit2->Text;
    p_in_file.dispatch_date = Form1->DateTimePicker1->Date.FormatString("dd.mm.yyyy");
    p_in_file.arrival_date = Form1->DateTimePicker2->Date.FormatString("dd.mm.yyyy");
    p_in_file.status = Form1->Edit5->Text;
    p_in_file.f_name = Form1->Edit6->Text;
    p_in_file.s_name = Form1->Edit7->Text;
    p_in_file.p_number = Form1->Edit8->Text;
    File << p_in_file.type << "\n" << p_in_file.weight << "\n" << p_in_file.dispatch_date << "\n" << p_in_file.arrival_date << "\n" << p_in_file.status << "\n" << p_in_file.f_name << "\n" << p_in_file.s_name << "\n" << p_in_file.p_number << "\n";
 
}

void __fastcall TForm3::Button3Click(TObject *Sender)
{
    EditForm->Show();
    EditForm->Memo1->Lines->LoadFromFile("file.txt");
    EditForm->Memo2->Lines->LoadFromFile("file.txt");
}

void __fastcall TEditForm::Button1Click(TObject *Sender)
{
    ofstream File("file.txt", ios::trunc);
    File.close();
    EditForm->Memo1->Lines->SaveToFile("file.txt");
    ofstream log("log_file.txt", ios::app);
    for (int i = 7; i < Memo2->Lines->Count; i+7) {
        bool flag = true;
        for (int j = 7; j < Memo1->Lines->Count; j+7) {
            if (Memo2->Lines->Strings[i] == Memo1->Lines->Strings[j]) {
                flag = false;
                break;
            }
        }
        if (flag == true) {
            for (int k = i - 7; k <= i; k++) {
                String buffer = Memo2->Lines->Strings[k];
                log << buffer.c_str();
            }
        }
    }
}