问打印输出在c++中居中对齐的解决方案

EN

//Prints Text in the center of width, when possible
int printCenter(FILE *out, const char *str, size_t width)
{
  size_t l=strlen(str); //Find out how long the text is
  if(l<width) // only print padding chars when we can align the text
  {
    size_t p=(width-l)/2;
    //Need to convert p to a int, only do that when p is small enough
    //use UINT_MAX in #if because p is <=SIZE_MAX/2. This avoids the
    //Check when size_t and int have the same rank
    #if SIZE_MAX>UINT_MAX
    if(p>INT_MAX)
    {
      errno=ERANGE;
      return -1;
    }
    #endif
    //print the padding chars to the left
    if(fprintf(out,"%*s",(int)p,"")<0) return -1;
  }
  return fprintf(out,"%s\n",str);
}

typedef struct
{
    char *string;
    int (*handler)(const int, const char *, void *);
}menu_type;

void print_menu(int width, const menu_type *menu)
{
    int pos = 1;
    printf("%*spress :\n",width, "");
    while(menu -> string)
    {
        printf("%*d.) %s\n", width, pos++, menu -> string);
        menu++;
    }
}

const menu_type mm[] = 
{
    {"Display all existing products:", NULL},
    {"Add new product details:", NULL},
    {"Edit a existing product:", NULL},
    {"Make a purchase.", NULL},
    {"Delete a list :", NULL},
    {"Display Profit/loss is sales:", NULL},
    {"Display all product with zero quantity", NULL},
    {"Display all product with highest quantity", NULL},
    {"Change user password.", NULL},
    {"Exit the program.", NULL},
    {NULL, NULL},
};

int main(void)
{
    print_menu(40, mm);
}