code: static void validateChecksum(int expectedChecksum, ByteBuf data) {
          validateChecksum(expectedChecksum, data, data.readerIndex(), data.readableBytes());
      }
docs: Computes the CRC32C checksum of the supplied data, performs the "mask" operation
  on the computed checksum, and then compares the resulting masked checksum to the
  supplied checksum.
  
  @param expectedChecksum The checksum decoded from the stream to compare against
  @param data The input data to calculate the CRC32C checksum of
  @throws DecompressionException If the calculated and supplied checksums do not match