docs: public void writeBytes(byte value, int len) throws IOException {
      if (len > buf.length - pos) {
        //not enough space remaining
        byte[] arr = new byte[len];
        Arrays.fill(arr, value);
        write(arr, 0, len);
        return;
      }
  
      for (int i = pos; i < pos + len; i++) {
        buf[i] = value;
      }
      pos += len;
    }