public Object readFully() throws IOException {
      Object val = null;
      for (itemsRead = 0; iterator.hasNext(); itemsRead++) {
        val = iterator.next();
      }
      return val;
    }
Reads blocks off of an {@link HFileBlockChannelPositionIterator}, counting them as it does.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestHFileBlockHeaderCorruption.java