@Override
  public int enumerateEx(byte @NotNull [] hash) throws IOException {
    //RC: this is not thread-safe -- but the only use from PFSContentAccessor is under the lock, so
    //    no reason to introduce additional lock here.
    int largestId = getLargestId();
    int id = enumerate(hash);
    if (id > largestId) {
      return id;
    }
    else {
      return -id;
    }
  }
@Override
  public int enumerateEx(byte @NotNull [] hash)