* response code. Otherwise this method never returns null.
   */
  @Throws(IOException::class)
  fun readResponseHeaders(expectContinue: Boolean): Response.Builder?

  @Throws(IOException::class)
  fun reportedContentLength(response: Response): Long

  @Throws(IOException::class)
  fun openResponseBodySource(response: Response): Source

  /** Returns the trailers after the HTTP response. May be empty. */
  @Throws(IOException::class)

    return if (expectContinue && responseBuilder.code == HTTP_CONTINUE) {
      null
    } else {
      responseBuilder
    }
  }

  override fun reportedContentLength(response: Response): Long {
    return when {
      !response.promisesBody() -> 0L
      else -> response.headersContentLength()
    }
  }

  }

  @Throws(IOException::class)
  fun openResponseBody(response: Response): ResponseBody {
    try {
      val contentType = response.header("Content-Type")
      val contentLength = codec.reportedContentLength(response)
      val rawSource = codec.openResponseBodySource(response)
      val source = ResponseBodySource(rawSource, contentLength)
      return RealResponseBody(contentType, contentLength, source.buffer())

   */
  override fun writeRequestHeaders(request: Request) {
    val requestLine = RequestLine.get(request, carrier.route.proxy.type())
    writeRequest(request.headers, requestLine)
  }

  override fun reportedContentLength(response: Response): Long {
    return when {
      !response.promisesBody() -> 0L
      response.isChunked -> -1L
      else -> response.headersContentLength()
    }
  }