@Override
  public void readFields(DataInput in) throws IOException {
    String inputSplitClassName = in.readUTF();
    int numSplits = in.readInt();
    inputSplits = new InputSplit[numSplits];
    for (int i = 0; i < numSplits; i++) {
      try {
        inputSplits[i] = (InputSplit) ReflectionUtil.newInstance(conf
            .getClassByName(inputSplitClassName), conf);
      } catch (Exception e) {
        throw new IOException(
            "Cannot create an instance of InputSplit class = "
                + inputSplitClassName + ":" + e.getMessage());
      }
      inputSplits[i].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/BucketizedHiveInputSplit.java