code: BlockCrcInfoWritable getNextRecord() throws IOException {
      // By calling getBucketIdForNextRecord(), we make sure the next field
      // to read is the next record (if there is any record left in the file)
      // Also, by checking the return value, we know whether we've finished
      // the file.
      if (moveToNextRecordAndGetItsBucketId() == -1) {
        return null;
      }
  
      BlockCrcInfoWritable crcInfo = new BlockCrcInfoWritable();
      crcInfo.readFields(in);
      numRecordsReadInBucket++;
      return crcInfo;
    }
docs: Get information for the next blockCRC record. NULL if not more left.
  @return
  @throws IOException