/**
   * Parses custom packet serialized by hessian marshaller.
   *
   * @param ses Session.
   * @param buf Buffer containing not parsed bytes.
   * @param state Parser state.
   * @return Parsed message.
   * @throws IOException If packet parsing or deserialization failed.
   */
  @Nullable
  private GridClientMessage parseCustomPacket(GridNioSession ses, ByteBuffer buf, ParserState state)
      throws IOException {
    assert state.packetType() == PacketType.GRIDGAIN;
    assert state.packet() == null;

    ByteArrayOutputStream tmp = state.buffer();

    int len = state.index();

    while (buf.remaining() > 0) {
      byte b = buf.get();

      if (len == 0) {
        tmp.write(b);

        if (tmp.size() == 4) {
          len = U.bytesToInt(tmp.toByteArray(), 0);

          tmp.reset();

          if (len == 0) return PING_MESSAGE;
          else if (len < 0)
            throw new IOException(
                "Failed to parse incoming packet (invalid packet length) [ses="
                    + ses
                    + ", len="
                    + len
                    + ']');

          state.index(len);
        }
      } else {
        tmp.write(b);

        if (tmp.size() == len) return marshaller.unmarshal(tmp.toByteArray());
      }
    }

    return null;
  }
  /** {@inheritDoc} */
  @Override
  public ByteBuffer encode(GridNioSession ses, GridClientMessage msg)
      throws IOException, GridException {
    assert msg != null;

    if (msg instanceof GridTcpRestPacket) return encodeMemcache((GridTcpRestPacket) msg);
    else if (msg == PING_MESSAGE) return ByteBuffer.wrap(PING_PACKET);
    else {
      byte[] data = marshaller.marshal(msg);

      assert data.length > 0;

      ByteBuffer res = ByteBuffer.allocate(data.length + 5);

      res.put(GRIDGAIN_REQ_FLAG);
      res.put(U.intToBytes(data.length));
      res.put(data);

      res.flip();

      return res;
    }
  }
 /** {@inheritDoc} */
 public String toString() {
   return S.toString(
       GridTcpRestParser.class, this, "clientMarshaller", marshaller.getClass().getSimpleName());
 }