presto-rcfile/src/main/java/io/prestosql/rcfile/text/DecimalEncoding.java/DecimalEncoding/parseLong
class DecimalEncoding:    private long parseLong(Slice slice, int offset, int length)
    {
        BigDecimal decimal = parseBigDecimal(slice, offset, length);
        return decimal.unscaledValue().longValue();
    }