private set

  /** The total number of bytes acknowledged by outgoing `WINDOW_UPDATE` frames. */
  var acknowledged: Long = 0L
    private set

  val unacknowledged: Long
    @Synchronized get() = total - acknowledged

  @Synchronized
  fun update(
    total: Long = 0,
    acknowledged: Long = 0,
  ) {
    check(total >= 0)
    check(acknowledged >= 0)

    this.total += total

                    .execute()) {
                final Map<String, Object> contentMap = response.getContent(OpenSearchCurl.jsonParser());
                if (!Constants.TRUE.equalsIgnoreCase(contentMap.get("acknowledged").toString())) {
                    throw new DictionaryException("Failed to update " + dictFile.getPath());
                }
            } catch (final IOException e) {

#### Shared reader thread