Insert Sort on Struct

#include <stdio.h>
#include <stdlib.h>
typedef struct {
  unsigned char *pref_name;
  unsigned int poplation;
} pref_t;

static pref_t *init_pref(void) {
  pref_t *p = (pref_t *) malloc(sizeof(pref_t));
  p->pref_name = (unsigned char *) malloc(BUFSIZ);
  return p;
}

static void print_pref(pref_t **data, size_t len) {
  for (int i = 0; i < len; i++) {
    printf("%s %d\n", data[i]->pref_name, data[i]->poplation);
  }
}

static void insert_sort_pref(pref_t **data, size_t len) {
  for (int i = 1; i < len; i++) {
    pref_t *p = data[i];
    if (data[i - 1]->poplation > p->poplation) {
      int j = i;
      do {
        data[j] = data[j - 1];
        j--;
      } while (j > 0 && data[j - 1]->poplation > p->poplation);
      data[j] = p;
    }
  }
}

int main(int argc, char **argv) {
  FILE *in;
  if (argc > 1) in = fopen(argv[1], "r");
  else in = stdin;
  char header[BUFSIZ];
  fgets(header, BUFSIZ, in); // ignore header
  pref_t *data[BUFSIZ];
  size_t len = 0;
  for (int i = 0; i < BUFSIZ; i++) {
    data[i] = init_pref();
    if (fscanf(in, "%s%d", data[i]->pref_name, &(data[i]->poplation)) == EOF) {
      len = i;
      break;
    }
  }
  fclose(in);
  printf("Before:\n");
  print_pref(data, len);
  printf("\n");
  insert_sort_pref(data, len);
  printf("After:\n");
  print_pref(data, len);
  return EXIT_SUCCESS;
}