Object Storage Service:Download progress bar (C++ SDK)

Usage notes

• The examples in this topic use the public endpoint for the China (Hangzhou) region. To access OSS from another Alibaba Cloud service in the same region, use an internal endpoint instead. For region-specific endpoint values, see Regions and endpoints.

• The examples create an OSSClient instance using an OSS endpoint. To create an OSSClient using a custom domain name or Security Token Service (STS), see Create an OSSClient instance.

Sample code

The callback receives three parameters on every invocation.

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

void ProgressCallback(size_t increment, int64_t transfered, int64_t total, void* userData)
{
    // increment: bytes received in this callback invocation
    // transfered: cumulative bytes received so far
    // total: total size of the object being downloaded
    std::cout << "ProgressCallback[" << userData << "] => " <<
                 increment <<" ," << transfered << "," << total << std::endl;
}

int main(void )
{
    /* Initialize the OSS account information. */

    /* Set yourEndpoint to the endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set yourRegion to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the region to cn-hangzhou. */
    std::string Region = "yourRegion";
    /* Specify the bucket name. Example: examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. The full path cannot contain the bucket name. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

    /* Initialize network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    conf.signatureVersion = SignatureVersionType::V4;
    /* Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);
    client.SetRegion(Region);

    /* Attach the progress callback to the download request. */
    GetObjectRequest request(BucketName, ObjectName);
    TransferProgress progressCallback = { ProgressCallback , nullptr };
    request.setTransferProgress(progressCallback);

    auto outcome = client.GetObject(request);

    if (!outcome.isSuccess()) {
        /* Handle the exception. */
        std::cout << "getObject fail" <<
        ",code:" << outcome.error().Code() <<
        ",message:" << outcome.error().Message() <<
        ",requestId:" << outcome.error().RequestId() << std::endl;
         return -1;
    }

    /* Release network resources. */
    ShutdownSdk();
    return 0;
}

References

For the complete sample code that shows how to use a progress bar for file downloads, see GitHub example.