docs: @Override
  	public Integer getPrefixLengthForSingleBlock() {
  		int count = getDivisionCount();
  		int totalPrefix = 0;
  		for(int i = 0; i < count; i++) {
  			AddressDivisionBase div = getDivision(i);
  			Integer divPrefix = div.getPrefixLengthForSingleBlock();
  			if(divPrefix == null) {
  				return null;
  			}
  			totalPrefix += divPrefix;
  			if(divPrefix < div.getBitCount()) {
  				//remaining segments must be full range or we return null
  				for(i++; i < count; i++) {
  					AddressDivisionBase laterDiv = getDivision(i);
  					if(!laterDiv.isFullRange()) {
  						return null;
  					}
  				}
  			}
  		}
  		return cacheBits(totalPrefix);
  	}