@Override
    public boolean seekTo() throws IOException {
      if (reader == null) {
        return false;
      }

      if (reader.getTrailer().getEntryCount() == 0) {
        // No data blocks.
        return false;
      }

      long firstDataBlockOffset = reader.getTrailer().getFirstDataBlockOffset();
      if (curBlock != null && curBlock.getOffset() == firstDataBlockOffset) {
        return processFirstDataBlock();
      }

      readAndUpdateNewBlock(firstDataBlockOffset);
      return true;
    }
Positions this scanner at the start of the file.
@return false if empty file; i.e. a call to next would return false and the current key and
        value are undefined.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java