code: public static FileSplit getCurrentSplit(JobConf job) {
      String path = job.get("map.input.file");
      if (path == null) {
        return null;
      }
      Path p = new Path(path);
      long start = Long.parseLong(job.get("map.input.start"));
      long length = Long.parseLong(job.get("map.input.length"));
      return new FileSplit(p, start, length, job);
    }
docs: JobConf helpers