code: static int calculateChecksum(ByteBuf data, int offset, int length) {
          Crc32c crc32 = new Crc32c();
          try {
              crc32.update(data, offset, length);
              return maskChecksum((int) crc32.getValue());
          } finally {
              crc32.reset();
          }
      }
docs: Computes the CRC32C checksum of the supplied data and performs the "mask" operation
  on the computed checksum
  
  @param data The input data to calculate the CRC32C checksum of