Data validation (C++ SDK)

Usage 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.

MD5 validation

When you include Content-MD5 in an upload request, OSS compares the MD5 hash of the received data against the value you provided. If they do not match, OSS returns an InvalidDigest error and you must re-upload the object.

Configure MD5 verification in a PutObject operation:

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

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set Endpoint to the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set Region to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set 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 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);
    std::shared_ptr<std::iostream> content = std::make_shared<std::stringstream>();
    *content << "test cpp sdk";
    PutObjectRequest request(BucketName, ObjectName, content);

    /* Set MD5 validation. */
    std::string contentMd5 = ComputeContentMD5(*content);
    request.setContentMd5(contentMd5);

    /* Upload the file. */
    auto outcome = client.PutObject(request);

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

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

CRC-64 validation

CRC-64 verification is enabled by default for object upload, download, and copy operations.

The following sample code shows how to perform CRC-64 validation when you download an object:

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

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set Endpoint to the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set Region to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set 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 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);

    /* Get the file to local memory. */
    GetObjectRequest request(BucketName, ObjectName);
    /* By default, CRC-64 validation is enabled in the C++ SDK. */
    /* If CRC-64 validation fails, the "Crc64 validation failed" error is reported. */    
    auto outcome = client.GetObject(request);
    if (outcome.isSuccess()) {    
        std::cout << "getObjectToBuffer" << "server crc:" << outcome.result().Metadata().HttpMetaData().at("x-oss-hash-crc64ecma") << std::endl; 
    }
    else {
        /* Handle the exception. */
        std::cout << "getObjectToBuffer fail" <<
        ",code:" << outcome.error().Code() <<
        ",message:" << outcome.error().Message() <<
        ",requestId:" << outcome.error().RequestId() << std::endl;
        return -1;
    }

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