// what we did get (such as a 4xx response) without ever transmitting the request body.
        if ("100-continue".equals(request.header("Expect"), ignoreCase = true)) {
          exchange.flushRequest()
          responseBuilder = exchange.readResponseHeaders(expectContinue = true)
          exchange.responseHeadersStart()
          invokeStartEvent = false
        }
        if (responseBuilder == null) {

  @Throws(IOException::class)
  fun writeRequestHeaders(request: Request)

  /** Flush the request to the underlying socket. */
  @Throws(IOException::class)
  fun flushRequest()

  /** Flush the request to the underlying socket and signal no more bytes will be transmitted. */
  @Throws(IOException::class)
  fun finishRequest()

  /**

    val rawRequestBody = codec.createRequestBody(request, contentLength)
    return RequestBodySink(rawRequestBody, contentLength)
  }

  @Throws(IOException::class)
  fun flushRequest() {
    try {
      codec.flushRequest()
    } catch (e: IOException) {
      eventListener.requestFailed(call, e)
      trackFailure(e)
      throw e
    }
  }

  @Throws(IOException::class)
  fun finishRequest() {

    }
    stream!!.readTimeout().timeout(chain.readTimeoutMillis.toLong(), TimeUnit.MILLISECONDS)
    stream!!.writeTimeout().timeout(chain.writeTimeoutMillis.toLong(), TimeUnit.MILLISECONDS)
  }

  override fun flushRequest() {
    http2Connection.flush()
  }

  override fun finishRequest() {
    stream!!.sink.close()
  }

  override fun readResponseHeaders(expectContinue: Boolean): Response.Builder? {

    }
    check(state == STATE_READING_RESPONSE_BODY || state == STATE_CLOSED) {
      "Trailers cannot be read because the state is $state"
    }
    return trailers
  }

  override fun flushRequest() {
    socket.sink.flush()
  }

  override fun finishRequest() {
    socket.sink.flush()
  }

  /** Returns bytes of a request header for sending on an HTTP transport. */
  fun writeRequest(