@Override
      public ExtendedCell getCell() {
        if (atEnd) {
          return null;
        }

        return delegate.getCell();
      }
Creates a half file reader for a hfile referred to by an hfilelink.
@param context   Reader context info
@param fileInfo  HFile info
@param cacheConf CacheConfig
@param r         original reference file (contains top or bottom)
@param conf      Configuration
hbase-server/src/main/java/org/apache/hadoop/hbase/io/HalfStoreFileReader.java