presto-rcfile/src/main/java/io/prestosql/rcfile/binary/DecimalEncoding.java/DecimalEncoding/getValueLength
class DecimalEncoding:    @Override
    public int getValueLength(Slice slice, int offset)
    {
        // first vint is scale
        int scaleLength = decodeVIntSize(slice, offset);

        // second vint is data length
        int dataLengthLength = decodeVIntSize(slice, offset + scaleLength);
        int dataLength = toIntExact(readVInt(slice, offset + scaleLength));

        return scaleLength + dataLengthLength + dataLength;
    }