public void sendResponseHeaders(int rCode, long contentLen) throws IOException {
   if (sentHeaders) {
     throw new IOException("headers already sent");
   }
   this.rcode = rCode;
   String statusLine = "HTTP/1.1 " + rCode + Code.msg(rCode) + "\r\n";
   OutputStream tmpout = new BufferedOutputStream(ros);
   PlaceholderOutputStream o = getPlaceholderResponseBody();
   tmpout.write(bytes(statusLine, 0), 0, statusLine.length());
   boolean noContentToSend = false; // assume there is content
   rspHdrs.set("Date", df.format(new Date()));
   if (contentLen == 0) {
     if (http10) {
       o.setWrappedStream(new UndefLengthOutputStream(this, ros));
       close = true;
     } else {
       rspHdrs.set("Transfer-encoding", "chunked");
       o.setWrappedStream(new ChunkedOutputStream(this, ros));
     }
   } else {
     if (contentLen == -1) {
       noContentToSend = true;
       contentLen = 0;
     }
     /* content len might already be set, eg to implement HEAD resp */
     if (rspHdrs.getFirst("Content-length") == null) {
       rspHdrs.set("Content-length", Long.toString(contentLen));
     }
     o.setWrappedStream(new FixedLengthOutputStream(this, ros, contentLen));
   }
   write(rspHdrs, tmpout);
   this.rspContentLen = contentLen;
   tmpout.flush();
   tmpout = null;
   sentHeaders = true;
   if (noContentToSend) {
     WriteFinishedEvent e = new WriteFinishedEvent(this);
     server.addEvent(e);
     closed = true;
   }
   server.logReply(rCode, req.requestLine(), null);
 }
 static {
   String pattern = "EEE, dd MMM yyyy HH:mm:ss zzz";
   tz = TimeZone.getTimeZone("GMT");
   df = new SimpleDateFormat(pattern, Locale.US);
   df.setTimeZone(tz);
 }