int BN_hex2bn(BIGNUM **bn, const char *a)
{
    BIGNUM *ret = NULL;
    BN_ULONG l = 0;
    int neg = 0, h, m, i, j, k, c;
    int num;
    if ((a == NULL) || (*a == '\0'))
        return (0);
    if (*a == '-') {
        neg = 1;
        a++;
    }
    for (i = 0; i <= (INT_MAX/4) && isxdigit((unsigned char)a[i]); i++)
        continue;
    if (i == 0 || i > INT_MAX/4)
        goto err;
    num = i + neg;
    if (bn == NULL)
        return (num);
    if (*bn == NULL) {
        if ((ret = BN_new()) == NULL)
            return (0);
    } else {
        ret = *bn;
        BN_zero(ret);
    }
    if (bn_expand(ret, i * 4) == NULL)
        goto err;
    j = i;
    m = 0;
    h = 0;
    while (j > 0) {
        m = ((BN_BYTES * 2) <= j) ? (BN_BYTES * 2) : j;
        l = 0;
        for (;;) {
            c = a[j - m];
            k = OPENSSL_hexchar2int(c);
            if (k < 0)
                k = 0;
            l = (l << 4) | k;
            if (--m <= 0) {
                ret->d[h++] = l;
                break;
            }
        }
        j -= (BN_BYTES * 2);
    }
    ret->top = h;
    bn_correct_top(ret);
    *bn = ret;
    bn_check_top(ret);
    if (ret->top != 0)
        ret->neg = neg;
    return (num);
 err:
    if (*bn == NULL)
        BN_free(ret);
    return (0);
}
['static int test_hex2bn()\n{\n    BIGNUM *bn = NULL;\n    int ret, st = 0;\n    ret = parseBN(&bn, "0");\n    if (ret != 1 || !BN_is_zero(bn) || BN_is_negative(bn)) {\n        fprintf(stderr, "BN_hex2bn(0) gave a bad result.\\n");\n        goto err;\n    }\n    BN_free(bn);\n    ret = parseBN(&bn, "256");\n    if (ret != 3 || !BN_is_word(bn, 0x256) || BN_is_negative(bn)) {\n        fprintf(stderr, "BN_hex2bn(256) gave a bad result.\\n");\n        goto err;\n    }\n    BN_free(bn);\n    ret = parseBN(&bn, "-42");\n    if (ret != 3 || !BN_abs_is_word(bn, 0x42) || !BN_is_negative(bn)) {\n        fprintf(stderr, "BN_hex2bn(-42) gave a bad result.\\n");\n        goto err;\n    }\n    BN_free(bn);\n    ret = parseBN(&bn, "-0");\n    if (ret != 2 || !BN_is_zero(bn) || BN_is_negative(bn)) {\n        fprintf(stderr, "BN_hex2bn(-0) gave a bad result.\\n");\n        goto err;\n    }\n    BN_free(bn);\n    ret = parseBN(&bn, "abctrailing garbage is ignored");\n    if (ret != 3 || !BN_is_word(bn, 0xabc) || BN_is_negative(bn)) {\n        fprintf(stderr, "BN_hex2bn(abctrail...) gave a bad result.\\n");\n        goto err;\n    }\n    st = 1;\nerr:\n    BN_free(bn);\n    return st;\n}', 'static int parseBN(BIGNUM **out, const char *in)\n{\n    *out = NULL;\n    return BN_hex2bn(out, in);\n}', "int BN_hex2bn(BIGNUM **bn, const char *a)\n{\n    BIGNUM *ret = NULL;\n    BN_ULONG l = 0;\n    int neg = 0, h, m, i, j, k, c;\n    int num;\n    if ((a == NULL) || (*a == '\\0'))\n        return (0);\n    if (*a == '-') {\n        neg = 1;\n        a++;\n    }\n    for (i = 0; i <= (INT_MAX/4) && isxdigit((unsigned char)a[i]); i++)\n        continue;\n    if (i == 0 || i > INT_MAX/4)\n        goto err;\n    num = i + neg;\n    if (bn == NULL)\n        return (num);\n    if (*bn == NULL) {\n        if ((ret = BN_new()) == NULL)\n            return (0);\n    } else {\n        ret = *bn;\n        BN_zero(ret);\n    }\n    if (bn_expand(ret, i * 4) == NULL)\n        goto err;\n    j = i;\n    m = 0;\n    h = 0;\n    while (j > 0) {\n        m = ((BN_BYTES * 2) <= j) ? (BN_BYTES * 2) : j;\n        l = 0;\n        for (;;) {\n            c = a[j - m];\n            k = OPENSSL_hexchar2int(c);\n            if (k < 0)\n                k = 0;\n            l = (l << 4) | k;\n            if (--m <= 0) {\n                ret->d[h++] = l;\n                break;\n            }\n        }\n        j -= (BN_BYTES * 2);\n    }\n    ret->top = h;\n    bn_correct_top(ret);\n    *bn = ret;\n    bn_check_top(ret);\n    if (ret->top != 0)\n        ret->neg = neg;\n    return (num);\n err:\n    if (*bn == NULL)\n        BN_free(ret);\n    return (0);\n}"]