code: private void init(int bitWidth) {
      Preconditions.checkArgument(bitWidth >= 0 && bitWidth <= 32, "bitWidth must be >= 0 and <= 32");
      this.bitWidth = bitWidth;
      this.bytesWidth = BytesUtils.paddedByteCountFromBits(bitWidth);
      this.packer = Packer.LITTLE_ENDIAN.newBytePacker(bitWidth);
    }
docs: Initializes the internal state for decoding ints of `bitWidth`.