presto-spi/src/main/java/io/prestosql/spi/type/UnscaledDecimal128Arithmetic.java/UnscaledDecimal128Arithmetic/setNegative
class UnscaledDecimal128Arithmetic:    private static void setNegative(Slice decimal, boolean negative)
    {
        setRawInt(decimal, SIGN_INT_INDEX, getInt(decimal, SIGN_INT_INDEX) | (negative ? SIGN_INT_MASK : 0));
    }