Append upload (C++ SDK)

Notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.

• This topic demonstrates creating an OSSClient instance with an OSS endpoint. For alternative configurations, such as using a custom domain or authenticating with credentials from Security Token Service (STS), see Create an OssClient instance.

• If the object to which you want to append content does not exist, the AppendObject operation creates an appendable object.

• If the object to which you want to append content exists:

  • If the object is an appendable object and the specified position from which the append operation starts is equal to the current object size, the data is appended to the end of the object.

  • If the object is an appendable object and the specified position from which the append operation starts is not equal to the current object size, the PositionNotEqualToLength error is returned.

  • If the object is not an appendable object, the ObjectNotAppendable error is returned.

Permissions

By default, an Alibaba Cloud account has full permissions. RAM users or RAM roles under an Alibaba Cloud account do not have any permissions by default. The Alibaba Cloud account or account administrator must grant operation permissions through RAM policies or Bucket Policy.

Sample code

The following code provides an example of how to append data to an object:

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

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, for example, examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. The full path cannot contain the bucket name. For 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 running 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);

    auto meta = ObjectMetaData();
    meta.setContentType("text/plain");

    /* The position for the first append operation is 0. The return value indicates the position for the next append operation. The position for subsequent append operations is the length of the object before the append. */
    std::shared_ptr<std::iostream> content1 = std::make_shared<std::stringstream>();
    *content1 <<"Thank you for using Alibaba Cloud Object Storage Service!";
    AppendObjectRequest request(BucketName, ObjectName, content1, meta);
    request.setPosition(0L);

    /* Append data to the object for the first time. */
    auto result = client.AppendObject(request);

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

    std::shared_ptr<std::iostream> content2 = std::make_shared<std::stringstream>();
    *content2 <<"Thank you for using Alibaba Cloud Object Storage Service!";
    auto position = result.result().Length();
    AppendObjectRequest appendObjectRequest(BucketName, ObjectName, content2);
    appendObjectRequest.setPosition(position);

    /* Append data to the object for the second time. */
    auto outcome = client.AppendObject(appendObjectRequest);

    if (!outcome.isSuccess()) {
        /* Handle exceptions. */
        std::cout << "AppendObject 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 complete sample code for append uploads, see the GitHub example.

• For more information about the API operation that you can call to perform append upload, see AppendObject.