@Override
    protected void onSerialize(Serializer buf) {
        super.onSerialize(buf);
        buf.putLong(null, xor);
    }
Sets the current xor value.

@param xor The value to set.
@return This, to allow chaining.
searchlib/src/main/java/com/yahoo/searchlib/aggregation/XorAggregationResult.java