private void SetAttribute(int attrib) {
Debug.Assert(0 <= attrib && attrib < this.attributeCount);
Debug.Assert(0 <= attrib && attrib < this.attributeList.Count);
Debug.Assert(this.attributeList[attrib] is BuilderInfo);
this.currentIndex = attrib;
this.currentInfo = (BuilderInfo) this.attributeList[attrib];
}