code: private Set<Integer> matchWithClosestAisMessageIfBufferLargeEnough(
  			long arrivalTime, Integer earliestTimestampLineIndex) {
  		String timestampLine = getLine(earliestTimestampLineIndex);
  		long time = getLineTime(earliestTimestampLineIndex);
  		log.debug("ts=" + timestampLine + ",time=" + time);
  		Set<Integer> removeThese;
  		if (arrivalTime - time > MAXIMUM_ARRIVAL_TIME_DIFFERENCE_MS) {
  			removeThese = matchWithClosestAisMessageAndFindIndexesToRemove(
  					earliestTimestampLineIndex, timestampLine, time);
  		} else
  			removeThese = findExpiredIndexesBeforeIndex(earliestTimestampLineIndex);
  		return removeThese;
  	}
docs: Finds matches and reports them to the listeners if buffer has a sufficent
  span of time in it. Returns the indexes that should be removed from the
  buffer.
  
  @param arrivalTime
  @param earliestTimestampLineIndex
  @return