* 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 if they're ready. May be empty. */

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

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