Object Storage Service: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.

• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient by using custom domain names or Security Token Service (STS), see Create an OSSClient instance.

MD5 validation

If you configure Content-MD5 in an object upload request, OSS calculates the MD5 hash of the uploaded object. If the calculated MD5 hash is different from the MD5 hash configured in the upload request, InvalidDigest is returned. This allows OSS to ensure data integrity for object uploads. If InvalidDigest is returned, you need to upload the object again.

The following sample code provides an example on how to 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 in object upload, download, and copy operations to check data integrity.

The following code shows how to perform CRC-64 validation when you download a file:

#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;
}