@Throws(IOException::class)
  internal fun cancelStreamIfNecessary() {
    lock.assertNotHeld()

    val open: Boolean
    val cancel: Boolean
    this.withLock {
      cancel = !source.finished && source.closed && (sink.finished || sink.closed)
      open = isOpen
    }
    if (cancel) {
      // RST this stream to prevent additional data from being sent. This is safe because the input