static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP *group,\n                                               const EC_POINT *point,\n                                               BIGNUM *x, BIGNUM *y,\n                                               BN_CTX *ctx)\n{\n    BN_CTX *new_ctx = NULL;\n    BIGNUM *Z, *Z_1, *Z_2, *Z_3;\n    const BIGNUM *Z_;\n    int ret = 0;\n    if (EC_POINT_is_at_infinity(group, point)) {\n        ECerr(EC_F_EC_GFP_SIMPLE_POINT_GET_AFFINE_COORDINATES,\n              EC_R_POINT_AT_INFINITY);\n        return 0;\n    }\n    if (ctx == NULL) {\n        ctx = new_ctx = BN_CTX_new();\n        if (ctx == NULL)\n            return 0;\n    }\n    BN_CTX_start(ctx);\n    Z = BN_CTX_get(ctx);\n    Z_1 = BN_CTX_get(ctx);\n    Z_2 = BN_CTX_get(ctx);\n    Z_3 = BN_CTX_get(ctx);\n    if (Z_3 == NULL)\n        goto err;\n    if (group->meth->field_decode) {\n        if (!group->meth->field_decode(group, Z, point->Z, ctx))\n            goto err;\n        Z_ = Z;\n    } else {\n        Z_ = point->Z;\n    }\n    if (BN_is_one(Z_)) {\n        if (group->meth->field_decode) {\n            if (x != NULL) {\n                if (!group->meth->field_decode(group, x, point->X, ctx))\n                    goto err;\n            }\n            if (y != NULL) {\n                if (!group->meth->field_decode(group, y, point->Y, ctx))\n                    goto err;\n            }\n        } else {\n            if (x != NULL) {\n                if (!BN_copy(x, point->X))\n                    goto err;\n            }\n            if (y != NULL) {\n                if (!BN_copy(y, point->Y))\n                    goto err;\n            }\n        }\n    } else {\n        if (!group->meth->field_inv(group, Z_1, Z_, ctx)) {\n            ECerr(EC_F_EC_GFP_SIMPLE_POINT_GET_AFFINE_COORDINATES,\n                  ERR_R_BN_LIB);\n            goto err;\n        }\n        if (group->meth->field_encode == 0) {\n            if (!group->meth->field_sqr(group, Z_2, Z_1, ctx))\n                goto err;\n        } else {\n            if (!BN_mod_sqr(Z_2, Z_1, group->field, ctx))\n                goto err;\n        }\n        if (x != NULL) {\n            if (!group->meth->field_mul(group, x, point->X, Z_2, ctx))\n                goto err;\n        }\n        if (y != NULL) {\n            if (group->meth->field_encode == 0) {\n                if (!group->meth->field_mul(group, Z_3, Z_2, Z_1, ctx))\n                    goto err;\n            } else {\n                if (!BN_mod_mul(Z_3, Z_2, Z_1, group->field, ctx))\n                    goto err;\n            }\n            if (!group->meth->field_mul(group, y, point->Y, Z_3, ctx))\n                goto err;\n        }\n    }\n    ret = 1;\n err:\n    BN_CTX_end(ctx);\n    BN_CTX_free(new_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}', '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}']