Radix Conversion

#include <stdio.h>
#include <stdlib.h>

const char digitmap[] = "0123456789abcdef";

char *num_to_s(int val, int base) {
  char *ret = (char *)malloc(BUFSIZ);
  ret = ret + BUFSIZ;
  *--ret = '\0';
  do {
    *--ret = digitmap[(int )(val % base)];
  } while (val /= base);
  return ret;
}

int main(void) {
  int val, base;
  printf("number base ? ");
  scanf("%d%d", &val, &base);
  printf("%d base %d = %s\n", val, base, num_to_s(val, base));
  return EXIT_SUCCESS;
}