throws Throwable
  public static String chunk_split(String body,                                   @Optional("76") int chunkLen,                                   @Optional("\"\\r\\n\"") String end)    throws Throwable  {    if (chunkLen < 1) // XXX: real exn      throw new IllegalArgumentException(L.l("bad value {0}", chunkLen));    StringBuilder sb = new StringBuilder();    int i = 0;    for (; i + chunkLen <= body.length(); i += chunkLen) {      sb.append(body.substring(i, i + chunkLen));      sb.append(end);    }    if (i < body.length()) {      sb.append(body.substring(i));      sb.append(end);    }    return sb.toString();  }