public void set(byte[] newData, int offset, int len) {
    bytes = newData;
    start = offset;
    length = len;
    lazyDecompressObj = null;
  }
readFields() will corrupt the array. So use the set method whenever
possible.

@see #readFields(DataInput)
serde/src/java/org/apache/hadoop/hive/serde2/columnar/BytesRefWritable.java