code: private void closeBlock(ByteBuf out) {
          final Bzip2BlockCompressor blockCompressor = this.blockCompressor;
          if (!blockCompressor.isEmpty()) {
              blockCompressor.close(out);
              final int blockCRC = blockCompressor.crc();
              streamCRC = (streamCRC << 1 | streamCRC >>> 31) ^ blockCRC;
          }
      }
docs: Close current block and update {@link #streamCRC}.