How to write/output a dynamic data structure to/from a file?

Question

C++ / C#

Hello everyone . I have a dynamic structure, I need the user to enter the data and display the data on a new start. I managed to make it only write one element, and output one too. How to make it record multiple elements? How to find out how many elements are written in a document?
This is how I implemented writing to the document.

/* Запись в документ */
    fwrite(&temper, sizeof(int), 1, file);
    fwrite(p_film, sizeof(p_film), 1, file);
    fclose(file);
  }
    fread(&temper, sizeof(int), 1, file);
  fread(p_film, sizeof(p_film), temper, file);
  fclose(file);

temper is a counter.
p_film is a pointer to a dynamic array.

Reading data from a document.

file = fopen("data.bin", "r");
  if (file == NULL) {
    file = fopen("data.bin", "w");
    fclose(file);
    file = fopen("data.txt", "r");
  }
    fread(&temper, sizeof(int), 1, file);
  fread(p_film, sizeof(p_film), temper, file);
  fclose(file);

Full code

Додавання элемента

void add_new_item(films *p_film) {
  /* variables */
  char text[100];
  strcpy(text, "Додавання нового елемента");
  //
    print_table(text);
    file = fopen("data.bin", "a");
    printf("Введіть назву кінострічки:"); scanf_s("%s", &p_film->name_film,100);
    printf("Введіть режисера(ім'я та прізвище): "); scanf_s("%s %s", &p_film->producer_surname, 100, &p_film->producer_name, 100);
    printf("Введіть рік виходу в прокат. Формат(2000.04.05): "); scanf_s("%i.%i.%i", &p_film->date_i.year, &p_film->date_i.month, &p_film->date_i.day);
    printf("Введіть назву країни:"); scanf_s("%s", &p_film->name_country, 100);
    printf("Введіть вартість:"); scanf_s("%i", &p_film->price);
    printf("Введіть дохід:"); scanf_s("%i", &p_film->income);
    printf("Введіть прибуток:"); scanf_s("%i", &p_film->profit);
    printf("Введіть жанр:"); scanf_s("%s", &p_film->genre, 100);
    /* Запись в документ */
    fwrite(&temper, sizeof(int), 1, file);
    fwrite(p_film, sizeof(p_film), 1, file);
    //fwrite(p_film, sizeof(films), tz, file);
    fclose(file);
    SetConsoleTextAttribute(hConsole, (WORD)((0 << 4) | 2));
    printf("Успішно додано!\n");
    SetConsoleTextAttribute(hConsole, (WORD)((0 << 4) | 7));
    end_table();
    Sleep(2000);
  temper++;
  main_menu();
}

Чтения файла

int main() {
  SetConsoleCP(1251);
  //p_film[0] = { "Білгоград", "Сторожевський","Миколай", 1992,01,9, "Україна", 200, 200, 200, "Ужастик" };
  file = fopen("data.bin", "r");
  if (file == NULL) {
    file = fopen("data.bin", "w");
    fclose(file);
    file = fopen("data.txt", "r");
  }
    fread(&temper, sizeof(int), 1, file);
  fread(p_film, sizeof(p_film), temper, file);
  fclose(file);
  //
  SetConsoleOutputCP(1251);
  system("color 0F");
  main_menu();
  free(p_film);
  system("pause");
  retur

Link to the whole project

Answer 1

First, write a header to the file, in which, among other things, indicate the number of elements.