private static BitSet toBitset(byte[] nulls) {
    BitSet bitset = new BitSet();
    int bits = nulls.length * 8;
    for (int i = 0; i < bits; i++) {
      bitset.set(i, (nulls[i / 8] & MASKS[i % 8]) != 0);
    }
    return bitset;
  }
Get a subset of this ColumnBuffer, starting from the 1st value.

@param end index after the last value to include
serde/src/java/org/apache/hadoop/hive/serde2/thrift/ColumnBuffer.java