procedure TForm1.Clear1Click(Sender: TObject);
begin
  Memo1.Clear;
end;

Function WriteToFile(mFile: String; pText: AnsiString): Boolean;
Var
  FileHandle    : THandle;
  Len           : Cardinal;
  BW            : Cardinal;
Begin
  Result := False;
  Len := Length(pText);
  FileHandle := CreateFile(pChar(mFile), GENERIC_WRITE, FILE_SHARE_WRITE, NIL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
  If FileHandle = INVALID_HANDLE_VALUE Then
    Exit;
  WriteFile(FileHandle, pText, Len, BW, NIL);
  CloseHandle(FileHandle);
  if (BW = Len) Then
    Result := True;
End;

Function ReWriteToFile(rFile: String; rText: AnsiString): Boolean;
Var
  FileHandle     : THandle;
  Len            : Cardinal;
  BW             : Cardinal;
Begin
  Result := False;
  FileHandle := CreateFile(pChar(rFile), GENERIC_WRITE, FILE_SHARE_WRITE, NIL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
  if FileHandle = INVALID_HANDLE_VALUE Then
    Exit;
  SetFilePointer(FileHandle, 0, NIL, FILE_END);
  WriteFile(FileHandle, rText, Len, BW, NIL);
  if (BW = Len) Then
    Result := True;
End;

procedure TForm1.Sav1Click(Sender: TObject);
Var
  Enc         : TRC4;
  Data        : String;
  constFile   : String;
begin
  Data := form1.Memo1.Text;
  Data := #13#10 + ' Detta är en ny logg my friend' + Data;
  constFile := 'D:\test.log';
  If WriteToFile(constFile, Data) Then
    Form1.Caption := 'Text encrypted and saved!';

  if FileExists(constFile) Then
    if ReWriteToFile(constFile, Data) Then
      Form1.Caption := 'Text encrypted and saved to the existing file';

end;

end.