public void finishRow() throws IOException {
    int length = output.getLength() - rowBeginPos;
    output.writeInt(rowBeginPos - 4, length);
    if (output.getLength() > THRESHOLD) {
      fileOutputStream.write(output.getData(), 0, output.getLength());
      totalWriteLength += output.getLength();
      output.reset();
    }
  }
An eager bytes container that puts row bytes to an output stream.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/rowbytescontainer/VectorRowBytesContainer.java