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CRC64 Check

Last updated: 2022-01-24 12:28:54

    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 Description

    SDK APIs get CRC64 values from response headers. When files are uploaded, the SDK verifies the CRC64 values by default.

    Note:

    The COS Go SDK version should not be earlier than v0.7.23.

    Sample request

    package main
    import (
       "context"
       "fmt"
       "github.com/tencentyun/cos-go-sdk-v5"
       "net/http"
       "net/url"
       "strings"
    )
    func main() {
       // Replace examplebucket-1250000000 and COS_REGION with the actual information
       u, _ := url.Parse("https://examplebucket-1250000000.cos.COS_REGION.myqcloud.com")
       b := &cos.BaseURL{BucketURL: u}
       client := cos.NewClient(b, &http.Client{
           Transport: &cos.AuthorizationTransport{
               SecretID:  "SECRETID",  // Replace it with the actual SecretId, which can be viewed and managed at https://console.tencentcloud.com/cam/capi
               SecretKey: "SECRETKEY", // Replace it with the actual SecretKey, which can be viewed and managed at https://console.tencentcloud.com/cam/capi
           },
       })
       // Disable CRC64 verification. CRC64 verification is enabled by default. You are strongly advised not to disable CRC64 verification.
       // client.Conf.EnableCRC = false
        name := "exampleobject"
       // Upload the object with a string
       f := strings.NewReader("test")
       // The SDK automatically verifies the CRC64 value
       resp, err := client.Object.Put(context.Background(), name, f, nil)
       if err != nil {
           // ERROR
       }
       // Get the CRC64 value from the response header
       fmt.Printf("CRC64: %v\n", resp.Header.Get("x-cos-hash-crc64ecma"))
    }
    

    Response description

    Parameter Description Type
    Response HTTP response Struct
    Response.Header HTTP response header Struct
    Response.Body HTTP response data Struct
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