@Override
    public void readFields(DataInput in) throws IOException {
      String inputSplitClassName = in.readUTF();
      try {
        inputSplit = (InputSplit) ReflectionUtil.newInstance(conf
            .getClassByName(inputSplitClassName), conf);
      } catch (Exception e) {
        throw new IOException(
            "Cannot create an instance of InputSplit class = "
            + inputSplitClassName + ":" + e.getMessage(), e);
      }
      inputSplit.readFields(in);
      inputFormatClassName = in.readUTF();
    }
The position of the first byte in the file to process.
ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java