presto-spi/src/main/java/io/prestosql/spi/type/UnscaledDecimal128Arithmetic.java/UnscaledDecimal128Arithmetic/getLong
class UnscaledDecimal128Arithmetic:    public static long getLong(Slice decimal, int index)
    {
        long value = getRawLong(decimal, index);
        if (index == SIGN_LONG_INDEX) {
            return unpackUnsignedLong(value);
        }
        return value;
    }