int BN_sub_word(BIGNUM *a, BN_ULONG w)
{
    int i;
    bn_check_top(a);
    w &= BN_MASK2;
    if (!w)
        return 1;
    if (BN_is_zero(a)) {
        i = BN_set_word(a, w);
        if (i != 0)
            BN_set_negative(a, 1);
        return i;
    }
    if (a->neg) {
        a->neg = 0;
        i = BN_add_word(a, w);
        a->neg = 1;
        return i;
    }
    if ((a->top == 1) && (a->d[0] < w)) {
        a->d[0] = w - a->d[0];
        a->neg = 1;
        return 1;
    }
    i = 0;
    for (;;) {
        if (a->d[i] >= w) {
            a->d[i] -= w;
            break;
        } else {
            a->d[i] = (a->d[i] - w) & BN_MASK2;
            i++;
            w = 1;
        }
    }
    if ((a->d[i] == 0) && (i == (a->top - 1)))
        a->top--;
    bn_check_top(a);
    return 1;
}
['static int test_check_public_key(void)\n{\n    int ret = 0;\n    BIGNUM *n = NULL, *e = NULL;\n    RSA *key = NULL;\n    ret = TEST_ptr(key = RSA_new())\n          && TEST_false(rsa_sp800_56b_check_public(key))\n          && TEST_ptr(e = bn_load_new(cav_e, sizeof(cav_e)))\n          && TEST_ptr(n = bn_load_new(cav_n, sizeof(cav_n)))\n          && TEST_true(RSA_set0_key(key, n, e, NULL));\n    if (!ret) {\n        BN_free(e);\n        BN_free(n);\n        goto end;\n    }\n    ret = TEST_true(rsa_sp800_56b_check_public(key))\n          && TEST_true(BN_add_word(n, 1))\n          && TEST_false(rsa_sp800_56b_check_public(key))\n          && TEST_true(BN_sub_word(n, 1))\n          && TEST_true(BN_lshift1(n, n))\n          && TEST_false(rsa_sp800_56b_check_public(key))\n          && TEST_true(BN_rshift1(n, n))\n          && TEST_true(BN_add_word(e, 1))\n          && TEST_false(rsa_sp800_56b_check_public(key))\n          && TEST_true(BN_sub_word(e, 1))\n          && TEST_true(BN_add_word(n, 2))\n          && TEST_false(rsa_sp800_56b_check_public(key));\nend:\n    RSA_free(key);\n    return ret;\n}', 'static BIGNUM *bn_load_new(const unsigned char *data, int sz)\n{\n    BIGNUM *ret = BN_new();\n    if (ret != NULL)\n        BN_bin2bn(data, sz, ret);\n    return ret;\n}', 'BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)\n{\n    unsigned int i, m;\n    unsigned int n;\n    BN_ULONG l;\n    BIGNUM *bn = NULL;\n    if (ret == NULL)\n        ret = bn = BN_new();\n    if (ret == NULL)\n        return NULL;\n    bn_check_top(ret);\n    for ( ; len > 0 && *s == 0; s++, len--)\n        continue;\n    n = len;\n    if (n == 0) {\n        ret->top = 0;\n        return ret;\n    }\n    i = ((n - 1) / BN_BYTES) + 1;\n    m = ((n - 1) % (BN_BYTES));\n    if (bn_wexpand(ret, (int)i) == NULL) {\n        BN_free(bn);\n        return NULL;\n    }\n    ret->top = i;\n    ret->neg = 0;\n    l = 0;\n    while (n--) {\n        l = (l << 8L) | *(s++);\n        if (m-- == 0) {\n            ret->d[--i] = l;\n            l = 0;\n            m = BN_BYTES - 1;\n        }\n    }\n    bn_correct_top(ret);\n    return ret;\n}', 'int BN_add_word(BIGNUM *a, BN_ULONG w)\n{\n    BN_ULONG l;\n    int i;\n    bn_check_top(a);\n    w &= BN_MASK2;\n    if (!w)\n        return 1;\n    if (BN_is_zero(a))\n        return BN_set_word(a, w);\n    if (a->neg) {\n        a->neg = 0;\n        i = BN_sub_word(a, w);\n        if (!BN_is_zero(a))\n            a->neg = !(a->neg);\n        return i;\n    }\n    for (i = 0; w != 0 && i < a->top; i++) {\n        a->d[i] = l = (a->d[i] + w) & BN_MASK2;\n        w = (w > l) ? 1 : 0;\n    }\n    if (w && i == a->top) {\n        if (bn_wexpand(a, a->top + 1) == NULL)\n            return 0;\n        a->top++;\n        a->d[i] = w;\n    }\n    bn_check_top(a);\n    return 1;\n}', 'int BN_sub_word(BIGNUM *a, BN_ULONG w)\n{\n    int i;\n    bn_check_top(a);\n    w &= BN_MASK2;\n    if (!w)\n        return 1;\n    if (BN_is_zero(a)) {\n        i = BN_set_word(a, w);\n        if (i != 0)\n            BN_set_negative(a, 1);\n        return i;\n    }\n    if (a->neg) {\n        a->neg = 0;\n        i = BN_add_word(a, w);\n        a->neg = 1;\n        return i;\n    }\n    if ((a->top == 1) && (a->d[0] < w)) {\n        a->d[0] = w - a->d[0];\n        a->neg = 1;\n        return 1;\n    }\n    i = 0;\n    for (;;) {\n        if (a->d[i] >= w) {\n            a->d[i] -= w;\n            break;\n        } else {\n            a->d[i] = (a->d[i] - w) & BN_MASK2;\n            i++;\n            w = 1;\n        }\n    }\n    if ((a->d[i] == 0) && (i == (a->top - 1)))\n        a->top--;\n    bn_check_top(a);\n    return 1;\n}']