static unsigned int BN_STACK_pop(BN_STACK *st)
{
    return st->indexes[--(st->depth)];
}
['int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,\n                             const unsigned char *buf, size_t len,\n                             BN_CTX *ctx)\n{\n    point_conversion_form_t form;\n    int y_bit;\n    BN_CTX *new_ctx = NULL;\n    BIGNUM *x, *y, *yxi;\n    size_t field_len, enc_len;\n    int ret = 0;\n    if (len == 0) {\n        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);\n        return 0;\n    }\n    form = buf[0];\n    y_bit = form & 1;\n    form = form & ~1U;\n    if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)\n        && (form != POINT_CONVERSION_UNCOMPRESSED)\n        && (form != POINT_CONVERSION_HYBRID)) {\n        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n        return 0;\n    }\n    if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {\n        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n        return 0;\n    }\n    if (form == 0) {\n        if (len != 1) {\n            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n            return 0;\n        }\n        return EC_POINT_set_to_infinity(group, point);\n    }\n    field_len = (EC_GROUP_get_degree(group) + 7) / 8;\n    enc_len =\n        (form ==\n         POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;\n    if (len != enc_len) {\n        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\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    x = BN_CTX_get(ctx);\n    y = BN_CTX_get(ctx);\n    yxi = BN_CTX_get(ctx);\n    if (yxi == NULL)\n        goto err;\n    if (!BN_bin2bn(buf + 1, field_len, x))\n        goto err;\n    if (BN_ucmp(x, group->field) >= 0) {\n        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n        goto err;\n    }\n    if (form == POINT_CONVERSION_COMPRESSED) {\n        if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))\n            goto err;\n    } else {\n        if (!BN_bin2bn(buf + 1 + field_len, field_len, y))\n            goto err;\n        if (BN_ucmp(y, group->field) >= 0) {\n            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n            goto err;\n        }\n        if (form == POINT_CONVERSION_HYBRID) {\n            if (!group->meth->field_div(group, yxi, y, x, ctx))\n                goto err;\n            if (y_bit != BN_is_odd(yxi)) {\n                ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);\n                goto err;\n            }\n        }\n        if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))\n            goto err;\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}']