return FixedLengthSource(length)
  }

  private fun newChunkedSource(url: HttpUrl): Source {
    check(state == STATE_OPEN_RESPONSE_BODY) { "state: $state" }
    state = STATE_READING_RESPONSE_BODY
    return ChunkedSource(url)
  }

  private fun newUnknownLengthSource(): Source {
    check(state == STATE_OPEN_RESPONSE_BODY) { "state: $state" }
    state = STATE_READING_RESPONSE_BODY
    carrier.noNewExchanges()