[aws-sdk-cpp][s3] Downloading binary file with getObject

I've being tried to write some codes to download binary files from AWS S3 server.

I wrote that code right below and It looks like okay about ~200MB binary files, so I thought it worked.

but for big files like 200MB~, it would be downloaded but only front part of files.

for example, a video file (1.2GB) downloaded only front part(460MB ~ 700MB).

Why this can be happened? It's about ofstream features?

// 3. file download from s3
{
    string strTargetPath = hThis->m_strTargetPath;
    Aws::SDKOptions options;
    options.loggingOptions.logLevel = Aws::Utils::Logging::LogLevel::Trace;
    Aws::InitAPI(options);
    {
        // Download from s3 using GetObject

        char *bucket_name = "mybucket";
        std::string key_name = strTargetPath;

        Aws::Client::ClientConfiguration clientConfig;
        clientConfig.region = "ap-northeast-2";

        //Aws::S3::S3Client s3_client;
        std::unique_ptr< Aws::S3::S3Client > s3_client(new Aws::S3::S3Client(clientConfig));
        Aws::S3::Model::GetObjectRequest object_request;
        object_request.WithBucket(bucket_name).WithKey(key_name.c_str());

        // parse file name from path
        string str_arr[1000];
        int str_cnt = 0;

        char *str_buff = new char[1000];
        strcpy(str_buff, strTargetPath.c_str());

        char *tok = strtok(str_buff, "/");
        while (tok != nullptr) {
            str_arr[str_cnt++] = string(tok);
            tok = strtok(nullptr, "/");
        }

        string fileName = str_arr[str_cnt - 1];

        auto get_object_outcome = s3_client.get()->GetObject(object_request);

        if (get_object_outcome.IsSuccess())
        {
            Aws::OFStream local_file;
            std::string strFileName = fileName;
            hThis->m_origFileNameString = strFileName;
            hThis->m_origFileName = strFileName.c_str();

            // Writing file downloaded
            local_file.open(hThis->m_origFileName, std::ios::out | std::ios::binary);
            local_file << get_object_outcome.GetResult().GetBody().rdbuf();
            hThis->Logger(CPrePackagerDlg::currentDateTime() + "download is done\n");

            TCHAR programpath[_MAX_PATH];
            GetCurrentDirectory(_MAX_PATH, programpath);
            hThis->m_valOriginFolderPath.Format(_T("%s\\"), programpath);
            hThis->m_valOriginFolderPath += hThis->m_origFileName;
        }
        else
        {
            hThis->Logger(CPrePackagerDlg::currentDateTime() + "s3 download error: " +
                get_object_outcome.GetError().GetExceptionName() + " " +
                get_object_outcome.GetError().GetMessage() + "\n");
            hThis->runSignal = CPrePackagerDlg::RunSignal::STAT_RUN_STOP;
        }


    }
    Aws::ShutdownAPI(options);

}

Even now, I don't know exactly Why it doesn't work.

Because in your initial example it storing the whole file in memory. In your second code snippet you did the right thing by using fstream as the response stream. So it now writes to disk right away.