code: public Path getSpillIndexFile(TaskAttemptID mapTaskId, int spillNumber)
      throws IOException {
      return lDirAlloc.getLocalPathToRead(TaskTracker.getIntermediateOutputDir(
                         jobId.toString(), mapTaskId.toString())
                         + "/spill" + 
                         spillNumber + ".out.index", conf);
    }
docs: Return a local map spill index file created earlier
  @param mapTaskId a map task id
  @param spillNumber the number