anchor.diff:    Tid.
   
   %% @private Get the latest cached entry which has timestamp before the given Ts.
  --spec latest_cached_entry_before_ts(cache(), os_sec(), logid(), logid(), logid()) ->
  -        entry().
  +-spec latest_cached_entry_before_ts(cache(), os_sec(), logid(), logid(), logid()) -> entry().
   latest_cached_entry_before_ts(Tid, _Ts, LogId, _Hi, LogId) ->
     lookup_cache(Tid, LogId);
   latest_cached_entry_before_ts(Tid, Ts, Lo, Hi, LogId) ->
  
positive.code:                  false                                 -> LogIdHi;
                   ?ENTRY(LogId2_, _Ts2, _SegId2, _Pos2) -> LogId2_
                 end,
        %% Then run another binary search in the file to locate the
        %% first log entry of timestamp >= Ts
        find_first_logid_since_in_file(Dir, Ts, SegId1, LogId1+1, LogId2)
    end.
  
negative.code:     false when Ts > TsHi -> false;   %% no log since the given ts
      false ->                       %% in between
        LogIdMid = (LogIdLo + LogIdHi) bsr 1,
        %% First, run a quick binary search (in cache) to locate
        %% the latest logid which has timestamp < Ts
        ?ENTRY(LogId1, Ts1, SegId1, _Pos1) =
          latest_cached_entry_before_ts(Tid, Ts, LogIdLo, LogIdHi, LogIdMid),
        true = (Ts1 < Ts), %% assert
  