public HFileBlockChannelPosition next() {
      if (current == null) {
        throw new NoSuchElementException();
      }
      HFileBlockChannelPosition ret = current;
      current = null;
      return ret;
    }
A simplified wrapper over an {@link HFileBlock.BlockIterator} that looks a lot like an
{@link java.util.Iterator}.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestHFileBlockHeaderCorruption.java