static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int BN_mod_exp_recp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,\n                    const BIGNUM *m, BN_CTX *ctx)\n{\n    int i, j, bits, ret = 0, wstart, wend, window, wvalue;\n    int start = 1;\n    BIGNUM *aa;\n    BIGNUM *val[TABLE_SIZE];\n    BN_RECP_CTX recp;\n    if (BN_get_flags(p, BN_FLG_CONSTTIME) != 0\n            || BN_get_flags(a, BN_FLG_CONSTTIME) != 0\n            || BN_get_flags(m, BN_FLG_CONSTTIME) != 0) {\n        BNerr(BN_F_BN_MOD_EXP_RECP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);\n        return 0;\n    }\n    bits = BN_num_bits(p);\n    if (bits == 0) {\n        if (BN_abs_is_word(m, 1)) {\n            ret = 1;\n            BN_zero(r);\n        } else {\n            ret = BN_one(r);\n        }\n        return ret;\n    }\n    BN_CTX_start(ctx);\n    aa = BN_CTX_get(ctx);\n    val[0] = BN_CTX_get(ctx);\n    if (val[0] == NULL)\n        goto err;\n    BN_RECP_CTX_init(&recp);\n    if (m->neg) {\n        if (!BN_copy(aa, m))\n            goto err;\n        aa->neg = 0;\n        if (BN_RECP_CTX_set(&recp, aa, ctx) <= 0)\n            goto err;\n    } else {\n        if (BN_RECP_CTX_set(&recp, m, ctx) <= 0)\n            goto err;\n    }\n    if (!BN_nnmod(val[0], a, m, ctx))\n        goto err;\n    if (BN_is_zero(val[0])) {\n        BN_zero(r);\n        ret = 1;\n        goto err;\n    }\n    window = BN_window_bits_for_exponent_size(bits);\n    if (window > 1) {\n        if (!BN_mod_mul_reciprocal(aa, val[0], val[0], &recp, ctx))\n            goto err;\n        j = 1 << (window - 1);\n        for (i = 1; i < j; i++) {\n            if (((val[i] = BN_CTX_get(ctx)) == NULL) ||\n                !BN_mod_mul_reciprocal(val[i], val[i - 1], aa, &recp, ctx))\n                goto err;\n        }\n    }\n    start = 1;\n    wvalue = 0;\n    wstart = bits - 1;\n    wend = 0;\n    if (!BN_one(r))\n        goto err;\n    for (;;) {\n        if (BN_is_bit_set(p, wstart) == 0) {\n            if (!start)\n                if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))\n                    goto err;\n            if (wstart == 0)\n                break;\n            wstart--;\n            continue;\n        }\n        j = wstart;\n        wvalue = 1;\n        wend = 0;\n        for (i = 1; i < window; i++) {\n            if (wstart - i < 0)\n                break;\n            if (BN_is_bit_set(p, wstart - i)) {\n                wvalue <<= (i - wend);\n                wvalue |= 1;\n                wend = i;\n            }\n        }\n        j = wend + 1;\n        if (!start)\n            for (i = 0; i < j; i++) {\n                if (!BN_mod_mul_reciprocal(r, r, r, &recp, ctx))\n                    goto err;\n            }\n        if (!BN_mod_mul_reciprocal(r, r, val[wvalue >> 1], &recp, ctx))\n            goto err;\n        wstart -= wend + 1;\n        wvalue = 0;\n        start = 0;\n        if (wstart < 0)\n            break;\n    }\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\n    BN_RECP_CTX_free(&recp);\n    bn_check_top(r);\n    return ret;\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}', 'BIGNUM *BN_CTX_get(BN_CTX *ctx)\n{\n    BIGNUM *ret;\n    CTXDBG("ENTER BN_CTX_get()", ctx);\n    if (ctx->err_stack || ctx->too_many)\n        return NULL;\n    if ((ret = BN_POOL_get(&ctx->pool, ctx->flags)) == NULL) {\n        ctx->too_many = 1;\n        BNerr(BN_F_BN_CTX_GET, BN_R_TOO_MANY_TEMPORARY_VARIABLES);\n        return NULL;\n    }\n    BN_zero(ret);\n    ret->flags &= (~BN_FLG_CONSTTIME);\n    ctx->used++;\n    CTXDBG("LEAVE BN_CTX_get()", ctx);\n    return ret;\n}', 'int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)\n{\n    if (!(BN_mod(r, m, d, ctx)))\n        return 0;\n    if (!r->neg)\n        return 1;\n    return (d->neg ? BN_sub : BN_add) (r, r, d);\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_mod_mul_reciprocal(BIGNUM *r, const BIGNUM *x, const BIGNUM *y,\n                          BN_RECP_CTX *recp, BN_CTX *ctx)\n{\n    int ret = 0;\n    BIGNUM *a;\n    const BIGNUM *ca;\n    BN_CTX_start(ctx);\n    if ((a = BN_CTX_get(ctx)) == NULL)\n        goto err;\n    if (y != NULL) {\n        if (x == y) {\n            if (!BN_sqr(a, x, ctx))\n                goto err;\n        } else {\n            if (!BN_mul(a, x, y, ctx))\n                goto err;\n        }\n        ca = a;\n    } else\n        ca = x;\n    ret = BN_div_recp(NULL, r, ca, recp, ctx);\n err:\n    BN_CTX_end(ctx);\n    bn_check_top(r);\n    return ret;\n}', 'int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)\n{\n    int ret = bn_sqr_fixed_top(r, a, ctx);\n    bn_correct_top(r);\n    bn_check_top(r);\n    return ret;\n}', 'int bn_sqr_fixed_top(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)\n{\n    int max, al;\n    int ret = 0;\n    BIGNUM *tmp, *rr;\n    bn_check_top(a);\n    al = a->top;\n    if (al <= 0) {\n        r->top = 0;\n        r->neg = 0;\n        return 1;\n    }\n    BN_CTX_start(ctx);\n    rr = (a != r) ? r : BN_CTX_get(ctx);\n    tmp = BN_CTX_get(ctx);\n    if (rr == NULL || tmp == NULL)\n        goto err;\n    max = 2 * al;\n    if (bn_wexpand(rr, max) == NULL)\n        goto err;\n    if (al == 4) {\n#ifndef BN_SQR_COMBA\n        BN_ULONG t[8];\n        bn_sqr_normal(rr->d, a->d, 4, t);\n#else\n        bn_sqr_comba4(rr->d, a->d);\n#endif\n    } else if (al == 8) {\n#ifndef BN_SQR_COMBA\n        BN_ULONG t[16];\n        bn_sqr_normal(rr->d, a->d, 8, t);\n#else\n        bn_sqr_comba8(rr->d, a->d);\n#endif\n    } else {\n#if defined(BN_RECURSION)\n        if (al < BN_SQR_RECURSIVE_SIZE_NORMAL) {\n            BN_ULONG t[BN_SQR_RECURSIVE_SIZE_NORMAL * 2];\n            bn_sqr_normal(rr->d, a->d, al, t);\n        } else {\n            int j, k;\n            j = BN_num_bits_word((BN_ULONG)al);\n            j = 1 << (j - 1);\n            k = j + j;\n            if (al == j) {\n                if (bn_wexpand(tmp, k * 2) == NULL)\n                    goto err;\n                bn_sqr_recursive(rr->d, a->d, al, tmp->d);\n            } else {\n                if (bn_wexpand(tmp, max) == NULL)\n                    goto err;\n                bn_sqr_normal(rr->d, a->d, al, tmp->d);\n            }\n        }\n#else\n        if (bn_wexpand(tmp, max) == NULL)\n            goto err;\n        bn_sqr_normal(rr->d, a->d, al, tmp->d);\n#endif\n    }\n    rr->neg = 0;\n    rr->top = max;\n    rr->flags |= BN_FLG_FIXED_TOP;\n    if (r != rr && BN_copy(r, rr) == NULL)\n        goto err;\n    ret = 1;\n err:\n    bn_check_top(rr);\n    bn_check_top(tmp);\n    BN_CTX_end(ctx);\n    return ret;\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}']