code: public boolean addSourceFile(FileSystem fs, PolicyInfo info, FileStatus src,
        RaidState.Checker checker, long now, int targetReplication)
        throws IOException {
      RaidState state = checker.check(info, src, now, false);
      Counters counters = stateToSourceCounters.get(state);
      counters.inc(src);
      if (state == RaidState.RAIDED) {
        incRaided(src);
        long paritySize = computeParitySize(src, targetReplication);
        estimatedParitySize += paritySize;
        estimatedDoneParitySize += paritySize;
        estimatedDoneSourceSize += src.getLen() * targetReplication;
        return false;
      }
      if (state == RaidState.NOT_RAIDED_BUT_SHOULD) {
        estimatedDoneParitySize += computeParitySize(src, targetReplication);
        estimatedDoneSourceSize += src.getLen() * targetReplication;
        return true;
      }
      return false;
    }
docs: Collect the statistics of a source file. Return true if the file should be
  raided but not.