code: public void write(DataOutput out) throws IOException {
      WritableUtils.writeVInt(out, splits.length);
      for (InputSplit s : splits) {
        Text.writeString(out, s.getClass().getName());
      }
      for (InputSplit s : splits) {
        s.write(out);
      }
    }
docs: Write splits in the following format.
  {@code
  <count><class1><class2>...<classn><split1><split2>...<splitn>
  }