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CRC64 Check

Terakhir diperbarui:2022-01-23 14:33:34

    Overview

    Errors may occur when data is transferred between the client and the server. COS can not only verify data integrity through MD5 and custom attributes, but also the CRC64 check code.

    COS will calculate the CRC64 value of the newly uploaded object and store the result as object attributes. It will carry x-cos-hash-crc64ecma in the returned response header, which indicates the CRC64 value of the uploaded object calculated according to ECMA-182 standard. If an object already has a CRC64 value stored before this feature is activated, COS will not calculate its CRC64 value, nor will it be returned when the object is obtained.

    Description

    APIs that currently support CRC64 include:

    • APIs for simple upload
    • Multipart upload APIs
      • Upload Part: you can compare and verify the CRC64 value returned by COS against the value calculated locally.
      • Complete Multipart Upload: returns a CRC64 value for the entire object only if each part has a CRC64 attribute. Otherwise, no value is returned.
    • The Upload Part - Copy operation returns a corresponding CRC64 value.
    • When you call the PUT Object - Copy, the CRC64 value is returned only if the source object has one.
    • The HEAD Object and GET Object operations return the CRC64 value provided the object has one. You can compare and verify the CRC64 value returned by COS against that calculated locally.

    SDK API References

    For the parameters and method descriptions of all the APIs in the SDK, see SDK API Reference.

    SDK Description

    You can get the CRC64 value from the response header after a successful upload or download.

    Note:

    The COS Android SDK version should not be earlier than v5.7.5.

    Upload request sample

    // 1. Initialize TransferService. You should use the same TransferService for the same configuration
    TransferConfig transferConfig = new TransferConfig.Builder()
           .build();
    TransferService transferService = new TransferService(cosXmlService, transferConfig);
    // 2. Initialize PutObjectRequest
    // Bucket name in the format of BucketName-APPID (APPID is required), which can be viewed in the COS console at https://console.intl.cloud.tencent.com/cos5/bucket
    String bucket = "examplebucket-1250000000";
    String cosPath = "exampleobject"; // Location identifier of the object in the bucket, i.e., the object key
    String srcPath = "examplefilepath"; // Absolute path to the local file
    PutObjectRequest putObjectRequest = new PutObjectRequest(bucket,
           cosPath, srcPath);
    // 3. Call the upload method to upload the file
    final COSUploadTask uploadTask = transferService.upload(putObjectRequest);
    uploadTask.setCosXmlResultListener(new CosXmlResultListener() {
       @Override
       public void onSuccess(CosXmlRequest request, CosXmlResult result) {
           // You can get the CRC64 value of the file after the upload is successful
           String crc64 = result.getHeader("x-cos-hash-crc64ecma");
       }
        // If you use the Kotlin language to call this, please note that the exception in the callback method is nullable; otherwise, the onFail method will not be called back, that is:
       // clientException is of type CosXmlClientException? and serviceException is of type CosXmlServiceException?
       @Override
       public void onFail(CosXmlRequest request,
                          @Nullable CosXmlClientException clientException,
                          @Nullable CosXmlServiceException serviceException) {
           if (clientException != null) {
               clientException.printStackTrace();
           } else {
               serviceException.printStackTrace();
           }
       }
    });
    
    Note:

    For more samples, please visit GitHub.

    Samples for download requests

    // 1. Initialize TransferService. You should use the same TransferService for the same configuration
    TransferConfig transferConfig = new TransferConfig.Builder()
           .build();
    TransferService transferService = new TransferService(cosXmlService, transferConfig);
    // 2. Initialize GetObjectRequest
    // Bucket name in the format of BucketName-APPID (APPID is required), which can be viewed in the COS console at https://console.intl.cloud.tencent.com/cos5/bucket
    String bucket = "examplebucket-1250000000";
    String cosPath = "exampleobject"; // Location identifier of the object in the bucket, i.e., the object key
    String savePathDir = context.getCacheDir().toString(); // Local directory path
    // File name saved locally. If not specified (null), it will be the same as the COS file name
    String savedFileName = "exampleobject";
    GetObjectRequest getObjectRequest = new GetObjectRequest(bucket,
           cosPath, savePathDir, savedFileName);
    // 3. Call the download method to download the file
    final COSDownloadTask downloadTask = transferService.download(getObjectRequest);
    downloadTask.setCosXmlResultListener(new CosXmlResultListener() {
       @Override
       public void onSuccess(CosXmlRequest request, CosXmlResult result) {
           // You can get the CRC64 value of the file after the download is successful
           String cosCRC64 = result.getHeader("x-cos-hash-crc64ecma");
       }
        // If you use the Kotlin language to call this, please note that the exception in the callback method is nullable; otherwise, the onFail method will not be called back, that is:
       // clientException is of type CosXmlClientException? and serviceException is of type CosXmlServiceException?
       @Override
       public void onFail(CosXmlRequest request,
                          @Nullable CosXmlClientException clientException,
                          @Nullable CosXmlServiceException serviceException) {
           if (clientException != null) {
               clientException.printStackTrace();
           } else {
               serviceException.printStackTrace();
           }
       }
    });
    
    Note:

    For more samples, please visit GitHub.

    CRC64 check

    When you use TransferService for upload or download, the SDK verifies the data by default. If you still want to perform CRC64 check yourself, refer to the following code.

    // 1. Refer to the above upload or download request sample code to get the CRC64 value of the file on COS
    String cosCRC64 = "examplecoscrc64";
    // 2. Calculate the CRC64 value of the local file
    File localFile = new File("examplefilepath");
    String localCRC64 = DigestUtils.getCRC64String(localFile);
    // 3. Check whether localCRC64 and cosCRC64 are the same
    if (localCRC64.equals(cosCRC64)) {
       // CRC64 values are the same
    }
    
    Note:

    For more samples, please visit GitHub.

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