static void copyStreamWithPrints(InputStream in, OutputStream out, S pat) ctex {
  byte[] buf = new byte[65536];
  int total = 0;
  while (true) {
    int n = in.read(buf);
    if (n <= 0) return;
    out.write(buf, 0, n);
    if ((total+n)/100000 > total/100000)
      print(pat.replace("{*}", str(roundDownTo(100000, total))));
    total += n;
  }
}

Began life as a copy of #1000844