when {
      !response.promisesBody() -> 0L
      response.isChunked -> -1L
      else -> response.headersContentLength()
    }

  override fun openResponseBodySource(response: Response): Source =
    when {
      !response.promisesBody() -> newFixedLengthSource(response.request.url, 0)
      response.isChunked -> newChunkedSource(response.request.url)
      else -> {