static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['static int test_mod_exp(int round)\n{\n    BN_CTX *ctx;\n    unsigned char c;\n    int ret = 0;\n    BIGNUM *r_mont = NULL;\n    BIGNUM *r_mont_const = NULL;\n    BIGNUM *r_recp = NULL;\n    BIGNUM *r_simple = NULL;\n    BIGNUM *a = NULL;\n    BIGNUM *b = NULL;\n    BIGNUM *m = NULL;\n    if (!TEST_ptr(ctx = BN_CTX_new()))\n        goto err;\n    if (!TEST_ptr(r_mont = BN_new())\n        || !TEST_ptr(r_mont_const = BN_new())\n        || !TEST_ptr(r_recp = BN_new())\n        || !TEST_ptr(r_simple = BN_new())\n        || !TEST_ptr(a = BN_new())\n        || !TEST_ptr(b = BN_new())\n        || !TEST_ptr(m = BN_new()))\n        goto err;\n    RAND_bytes(&c, 1);\n    c = (c % BN_BITS) - BN_BITS2;\n    BN_rand(a, NUM_BITS + c, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY);\n    RAND_bytes(&c, 1);\n    c = (c % BN_BITS) - BN_BITS2;\n    BN_rand(b, NUM_BITS + c, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY);\n    RAND_bytes(&c, 1);\n    c = (c % BN_BITS) - BN_BITS2;\n    BN_rand(m, NUM_BITS + c, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ODD);\n    if (!TEST_true(BN_mod(a, a, m, ctx))\n        || !TEST_true(BN_mod(b, b, m, ctx))\n        || !TEST_true(BN_mod_exp_mont(r_mont, a, b, m, ctx, NULL))\n        || !TEST_true(BN_mod_exp_recp(r_recp, a, b, m, ctx))\n        || !TEST_true(BN_mod_exp_simple(r_simple, a, b, m, ctx))\n        || !TEST_true(BN_mod_exp_mont_consttime(r_mont_const, a, b, m, ctx, NULL)))\n        goto err;\n    if (!TEST_BN_eq(r_simple, r_mont)\n        || !TEST_BN_eq(r_simple, r_recp)\n        || !TEST_BN_eq(r_simple, r_mont_const)) {\n        if (BN_cmp(r_simple, r_mont) != 0)\n            TEST_info("simple and mont results differ");\n        if (BN_cmp(r_simple, r_mont_const) != 0)\n            TEST_info("simple and mont const time results differ");\n        if (BN_cmp(r_simple, r_recp) != 0)\n            TEST_info("simple and recp results differ");\n        BN_print_var(a);\n        BN_print_var(b);\n        BN_print_var(m);\n        BN_print_var(r_simple);\n        BN_print_var(r_recp);\n        BN_print_var(r_mont);\n        BN_print_var(r_mont_const);\n        goto err;\n    }\n    ret = 1;\n err:\n    BN_free(r_mont);\n    BN_free(r_mont_const);\n    BN_free(r_recp);\n    BN_free(r_simple);\n    BN_free(a);\n    BN_free(b);\n    BN_free(m);\n    BN_CTX_free(ctx);\n    return ret;\n}', 'int BN_div(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num, const BIGNUM *divisor,\n           BN_CTX *ctx)\n{\n    int ret;\n    if (BN_is_zero(divisor)) {\n        BNerr(BN_F_BN_DIV, BN_R_DIV_BY_ZERO);\n        return 0;\n    }\n    if (divisor->d[divisor->top - 1] == 0) {\n        BNerr(BN_F_BN_DIV, BN_R_NOT_INITIALIZED);\n        return 0;\n    }\n    ret = bn_div_fixed_top(dv, rm, num, divisor, ctx);\n    if (ret) {\n        if (dv != NULL)\n            bn_correct_top(dv);\n        if (rm != NULL)\n            bn_correct_top(rm);\n    }\n    return ret;\n}', 'int bn_div_fixed_top(BIGNUM *dv, BIGNUM *rm, const BIGNUM *num,\n                     const BIGNUM *divisor, BN_CTX *ctx)\n{\n    int norm_shift, i, j, loop;\n    BIGNUM *tmp, *snum, *sdiv, *res;\n    BN_ULONG *resp, *wnum, *wnumtop;\n    BN_ULONG d0, d1;\n    int num_n, div_n;\n    assert(divisor->top > 0 && divisor->d[divisor->top - 1] != 0);\n    bn_check_top(num);\n    bn_check_top(divisor);\n    bn_check_top(dv);\n    bn_check_top(rm);\n    BN_CTX_start(ctx);\n    res = (dv == NULL) ? BN_CTX_get(ctx) : dv;\n    tmp = BN_CTX_get(ctx);\n    snum = BN_CTX_get(ctx);\n    sdiv = BN_CTX_get(ctx);\n    if (sdiv == NULL)\n        goto err;\n    if (!BN_copy(sdiv, divisor))\n        goto err;\n    norm_shift = bn_left_align(sdiv);\n    sdiv->neg = 0;\n    if (!(bn_lshift_fixed_top(snum, num, norm_shift)))\n        goto err;\n    div_n = sdiv->top;\n    num_n = snum->top;\n    if (num_n <= div_n) {\n        if (bn_wexpand(snum, div_n + 1) == NULL)\n            goto err;\n        memset(&(snum->d[num_n]), 0, (div_n - num_n + 1) * sizeof(BN_ULONG));\n        snum->top = num_n = div_n + 1;\n    }\n    loop = num_n - div_n;\n    wnum = &(snum->d[loop]);\n    wnumtop = &(snum->d[num_n - 1]);\n    d0 = sdiv->d[div_n - 1];\n    d1 = (div_n == 1) ? 0 : sdiv->d[div_n - 2];\n    if (!bn_wexpand(res, loop))\n        goto err;\n    res->neg = (num->neg ^ divisor->neg);\n    res->top = loop;\n    res->flags |= BN_FLG_FIXED_TOP;\n    resp = &(res->d[loop]);\n    if (!bn_wexpand(tmp, (div_n + 1)))\n        goto err;\n    for (i = 0; i < loop; i++, wnumtop--) {\n        BN_ULONG q, l0;\n# if defined(BN_DIV3W)\n        q = bn_div_3_words(wnumtop, d1, d0);\n# else\n        BN_ULONG n0, n1, rem = 0;\n        n0 = wnumtop[0];\n        n1 = wnumtop[-1];\n        if (n0 == d0)\n            q = BN_MASK2;\n        else {\n            BN_ULONG n2 = (wnumtop == wnum) ? 0 : wnumtop[-2];\n#  ifdef BN_LLONG\n            BN_ULLONG t2;\n#   if defined(BN_LLONG) && defined(BN_DIV2W) && !defined(bn_div_words)\n            q = (BN_ULONG)(((((BN_ULLONG) n0) << BN_BITS2) | n1) / d0);\n#   else\n            q = bn_div_words(n0, n1, d0);\n#   endif\n#   ifndef REMAINDER_IS_ALREADY_CALCULATED\n            rem = (n1 - q * d0) & BN_MASK2;\n#   endif\n            t2 = (BN_ULLONG) d1 *q;\n            for (;;) {\n                if (t2 <= ((((BN_ULLONG) rem) << BN_BITS2) | n2))\n                    break;\n                q--;\n                rem += d0;\n                if (rem < d0)\n                    break;\n                t2 -= d1;\n            }\n#  else\n            BN_ULONG t2l, t2h;\n            q = bn_div_words(n0, n1, d0);\n#   ifndef REMAINDER_IS_ALREADY_CALCULATED\n            rem = (n1 - q * d0) & BN_MASK2;\n#   endif\n#   if defined(BN_UMULT_LOHI)\n            BN_UMULT_LOHI(t2l, t2h, d1, q);\n#   elif defined(BN_UMULT_HIGH)\n            t2l = d1 * q;\n            t2h = BN_UMULT_HIGH(d1, q);\n#   else\n            {\n                BN_ULONG ql, qh;\n                t2l = LBITS(d1);\n                t2h = HBITS(d1);\n                ql = LBITS(q);\n                qh = HBITS(q);\n                mul64(t2l, t2h, ql, qh);\n            }\n#   endif\n            for (;;) {\n                if ((t2h < rem) || ((t2h == rem) && (t2l <= n2)))\n                    break;\n                q--;\n                rem += d0;\n                if (rem < d0)\n                    break;\n                if (t2l < d1)\n                    t2h--;\n                t2l -= d1;\n            }\n#  endif\n        }\n# endif\n        l0 = bn_mul_words(tmp->d, sdiv->d, div_n, q);\n        tmp->d[div_n] = l0;\n        wnum--;\n        l0 = bn_sub_words(wnum, wnum, tmp->d, div_n + 1);\n        q -= l0;\n        for (l0 = 0 - l0, j = 0; j < div_n; j++)\n            tmp->d[j] = sdiv->d[j] & l0;\n        l0 = bn_add_words(wnum, wnum, tmp->d, div_n);\n        (*wnumtop) += l0;\n        assert((*wnumtop) == 0);\n        *--resp = q;\n    }\n    snum->neg = num->neg;\n    snum->top = div_n;\n    snum->flags |= BN_FLG_FIXED_TOP;\n    if (rm != NULL)\n        bn_rshift_fixed_top(rm, snum, norm_shift);\n    BN_CTX_end(ctx);\n    return 1;\n err:\n    bn_check_top(rm);\n    BN_CTX_end(ctx);\n    return 0;\n}', 'void BN_CTX_start(BN_CTX *ctx)\n{\n    CTXDBG("ENTER BN_CTX_start()", ctx);\n    if (ctx->err_stack || ctx->too_many)\n        ctx->err_stack++;\n    else if (!BN_STACK_push(&ctx->stack, ctx->used)) {\n        BNerr(BN_F_BN_CTX_START, BN_R_TOO_MANY_TEMPORARY_VARIABLES);\n        ctx->err_stack++;\n    }\n    CTXDBG("LEAVE BN_CTX_start()", ctx);\n}', 'void BN_CTX_end(BN_CTX *ctx)\n{\n    CTXDBG("ENTER BN_CTX_end()", ctx);\n    if (ctx->err_stack)\n        ctx->err_stack--;\n    else {\n        unsigned int fp = BN_STACK_pop(&ctx->stack);\n        if (fp < ctx->used)\n            BN_POOL_release(&ctx->pool, ctx->used - fp);\n        ctx->used = fp;\n        ctx->too_many = 0;\n    }\n    CTXDBG("LEAVE BN_CTX_end()", ctx);\n}', 'static unsigned int BN_STACK_pop(BN_STACK *st)\n{\n    return st->indexes[--(st->depth)];\n}']