@Test
    public void test_bigInt_4() throws Exception {
        String str = "-1.2345678901234567890";
        char[] chars = str.toCharArray();
        BigDecimal decimal = new BigDecimal(str);

        // isneg ? -1 : 1
        bigInt(chars, -1, 10, 1, chars.length);

        assertEquals(-1, signum);
        assertEquals(mag2, -1420514932);
        assertEquals(mag3, -350287150);
    }
This mask is used to obtain the value of an int as if it were unsigned.
core/src/test/java/com/alibaba/fastjson2/read/BigIntTest.java