/**
   * Remove an outstanding piece data request.
   *
   * @param piece_number
   * @param piece_offset
   * @param length
   */
  public void removePieceRequest(int piece_number, int piece_offset, int length) {
    if (destroyed) return;

    DiskManagerReadRequest dmr =
        peer.getManager().getDiskManager().createReadRequest(piece_number, piece_offset, length);

    try {
      lock_mon.enter();

      if (requests.contains(dmr)) {
        requests.remove(dmr);
        return;
      }

      if (loading_messages.contains(dmr)) {
        loading_messages.remove(dmr);
        return;
      }

      for (Iterator i = queued_messages.entrySet().iterator(); i.hasNext(); ) {
        Map.Entry entry = (Map.Entry) i.next();
        if (entry.getValue().equals(dmr)) { // it's already been queued
          BTPiece msg = (BTPiece) entry.getKey();
          if (outgoing_message_queue.removeMessage(msg, true)) {
            i.remove();
          }
          break; // do manual listener notify
        }
      }
    } finally {
      lock_mon.exit();
    }

    outgoing_message_queue.doListenerNotifications();
  }
        public void readFailed(DiskManagerReadRequest request, Throwable cause) {
          try {
            lock_mon.enter();

            if (!loading_messages.contains(request) || destroyed) { // was canceled
              return;
            }
            loading_messages.remove(request);

          } finally {
            lock_mon.exit();
          }
        }
        public void readCompleted(DiskManagerReadRequest request, DirectByteBuffer data) {
          try {
            lock_mon.enter();

            if (!loading_messages.contains(request) || destroyed) { // was canceled
              data.returnToPool();
              return;
            }
            loading_messages.remove(request);

            BTPiece msg =
                new BTPiece(request.getPieceNumber(), request.getOffset(), data, piece_version);
            queued_messages.put(msg, request);

            outgoing_message_queue.addMessage(msg, true);
          } finally {
            lock_mon.exit();
          }

          outgoing_message_queue.doListenerNotifications();
        }