protected void setNonSeekedState() {
      reset();
      blockBuffer = null;
      currKeyLen = 0;
      currValueLen = 0;
      currMemstoreTS = 0;
      currMemstoreTSLen = 0;
      currTagsLen = 0;
    }
Scans blocks in the "scanned" section of the {@link HFile} until the next data block is
found.
@return the next block, or null if there are no more data blocks
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java