static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int BN_GF2m_mod_exp_arr(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,\n                        const int p[], BN_CTX *ctx)\n{\n    int ret = 0, i, n;\n    BIGNUM *u;\n    bn_check_top(a);\n    bn_check_top(b);\n    if (BN_is_zero(b))\n        return BN_one(r);\n    if (BN_abs_is_word(b, 1))\n        return (BN_copy(r, a) != NULL);\n    BN_CTX_start(ctx);\n    if ((u = BN_CTX_get(ctx)) == NULL)\n        goto err;\n    if (!BN_GF2m_mod_arr(u, a, p))\n        goto err;\n    n = BN_num_bits(b) - 1;\n    for (i = n - 1; i >= 0; i--) {\n        if (!BN_GF2m_mod_sqr_arr(u, u, p, ctx))\n            goto err;\n        if (BN_is_bit_set(b, i)) {\n            if (!BN_GF2m_mod_mul_arr(u, u, a, p, ctx))\n                goto err;\n        }\n    }\n    if (!BN_copy(r, u))\n        goto err;\n    bn_check_top(r);\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\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_GF2m_mod_sqr_arr(BIGNUM *r, const BIGNUM *a, const int p[],\n                        BN_CTX *ctx)\n{\n    int i, ret = 0;\n    BIGNUM *s;\n    bn_check_top(a);\n    BN_CTX_start(ctx);\n    if ((s = BN_CTX_get(ctx)) == NULL)\n        goto err;\n    if (!bn_wexpand(s, 2 * a->top))\n        goto err;\n    for (i = a->top - 1; i >= 0; i--) {\n        s->d[2 * i + 1] = SQR1(a->d[i]);\n        s->d[2 * i] = SQR0(a->d[i]);\n    }\n    s->top = 2 * a->top;\n    bn_correct_top(s);\n    if (!BN_GF2m_mod_arr(r, s, p))\n        goto err;\n    bn_check_top(r);\n    ret = 1;\n err:\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}', 'int BN_GF2m_mod_mul_arr(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,\n                        const int p[], BN_CTX *ctx)\n{\n    int zlen, i, j, k, ret = 0;\n    BIGNUM *s;\n    BN_ULONG x1, x0, y1, y0, zz[4];\n    bn_check_top(a);\n    bn_check_top(b);\n    if (a == b) {\n        return BN_GF2m_mod_sqr_arr(r, a, p, ctx);\n    }\n    BN_CTX_start(ctx);\n    if ((s = BN_CTX_get(ctx)) == NULL)\n        goto err;\n    zlen = a->top + b->top + 4;\n    if (!bn_wexpand(s, zlen))\n        goto err;\n    s->top = zlen;\n    for (i = 0; i < zlen; i++)\n        s->d[i] = 0;\n    for (j = 0; j < b->top; j += 2) {\n        y0 = b->d[j];\n        y1 = ((j + 1) == b->top) ? 0 : b->d[j + 1];\n        for (i = 0; i < a->top; i += 2) {\n            x0 = a->d[i];\n            x1 = ((i + 1) == a->top) ? 0 : a->d[i + 1];\n            bn_GF2m_mul_2x2(zz, x1, x0, y1, y0);\n            for (k = 0; k < 4; k++)\n                s->d[i + j + k] ^= zz[k];\n        }\n    }\n    bn_correct_top(s);\n    if (BN_GF2m_mod_arr(r, s, p))\n        ret = 1;\n    bn_check_top(r);\n err:\n    BN_CTX_end(ctx);\n    return ret;\n}', 'static unsigned int BN_STACK_pop(BN_STACK *st)\n{\n    return st->indexes[--(st->depth)];\n}']