docs: @Override
  	public Integer getPrefixLengthForSingleBlock() {
  		if(!hasNoPrefixCache()) {
  			Integer result = prefixCache.cachedEquivalentPrefix;
  			if(result != null) {
  				if(result < 0) {
  					return null;
  				}
  				return result;
  			}
  		}
  		Integer res = super.getPrefixLengthForSingleBlock();
  		if(res == null) {
  			prefixCache.cachedEquivalentPrefix = NO_PREFIX_LENGTH;
  			return null;
  		}
  		return prefixCache.cachedEquivalentPrefix = res;
  	}