Azure 存儲(chǔ)的斷點(diǎn)續(xù)傳與 MD5 校驗(yàn)

Azure 存儲(chǔ)的斷點(diǎn)續(xù)傳與 MD5 校驗(yàn)

問(wèn)題分析

首先關(guān)于 Azure 存儲(chǔ)中 MD5 的描述，我們已經(jīng)有相關(guān)的介紹文檔，如果對(duì)于存儲(chǔ)中 MD5 的描述不熟悉，可以先參考 Azure Blob 存儲(chǔ)基于 MD5 的完整性檢查的內(nèi)容。

如果直接將文件上傳到 Blob 中可以在上傳的方法中配置 BlobRequestOptions 類，將該類的 StoreBlobContentMD5 參數(shù)設(shè)置為 true，即可在上傳時(shí)自動(dòng)計(jì)算 MD5 值并將此值寫(xiě)入到請(qǐng)求頭部（ContentMD5）中（可以參考 BlobRequestOptions.StoreBlobContentMD5 Property 此文檔的描述）。 但是如果使用斷點(diǎn)續(xù)傳的方法，是將文件分為多個(gè)塊上傳，之后通過(guò) PubBlockList 請(qǐng)求完成組合，那么想要上傳 MD5 值，需要在 PubBlockList 請(qǐng)求的頭部添加 xmsblobcontentmd5 參數(shù)，但是在 sdk 相關(guān)的方法中，BlobRequestOptions 中并沒(méi)有關(guān)于該參數(shù)的屬性，所以如果使用斷點(diǎn)續(xù)傳，采用 sdk 的 PubBlockList() 方法無(wú)法將 MD5 值上傳上去，本篇文檔即要解決如何在斷點(diǎn)續(xù)傳時(shí)上傳 MD5 值的問(wèn)題。

解決方案

可以通過(guò)使用 REST API 的方式來(lái)解決此問(wèn)題:

1.首先我們需要計(jì)算出文件的 MD5 值：

string contentHash = md5()(File.ReadAllBytes(sourcePath));

2.將文件分塊上傳：

public async Task PutBlobAsync(String containerName, String blobName, byte[] blobContent, String blobid, bool error = false)

{

  String requestMethod = PUT;

  String urlPath = String.Format({0}/{1}, containerName, blobName) +  comp=blockblockid= + blobid;

  String storageServiceVersion = 20150221;

  String dateInRfc1123Format = DateTime.UtcNow.ToString(R, CultureInfo.InvariantCulture);

  Int32 blobLength = blobContent.Length;

  //headers

  String canonicalizedHeaders = String.Format(

    \nxmsdate:{0}\nxmsversion:{1},

    dateInRfc1123Format,

    storageServiceVersion);

  //resources

  String canonicalizedResource = String.Format(/{0}/{1}, AzureConstants.Account, String.Format({0}/{1}, containerName, blobName) + \nblockid: + blobid + \ncomp:block);

  String stringToSign = String.Format(

  {0}\n\n\n{1}\n\n\n\n\n\n\n\n{2}\n{3},

  requestMethod,

  blobLength,

  canonicalizedHeaders,

  canonicalizedResource);

  string authorizationHeader = CreateAuthorizationHeader(stringToSign);

  //上傳url

  Uri uri = new Uri(BlobEndPoint + urlPath);

  HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

  request.Method = requestMethod;

  request.Headers[xmsdate] = dateInRfc1123Format;

  request.Headers[xmsversion] = storageServiceVersion;

  request.Headers[Authorization] = authorizationHeader;

  request.ContentLength = blobLength;

  try {

    using (Stream requestStream = await request.GetRequestStreamAsync()) {

      requestStream.Write(blobContent, 0, blobLength);

    }

    using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync()) {

      String ETag = response.Headers[ETag];

      System.Console.WriteLine(ETag);

    }

    error = false;

  }

  catch (WebException ex) {

    System.Console.WriteLine(An error occured. Status code: + ((HttpWebResponse)ex.Response).StatusCode);

    System.Console.WriteLine(Error information:);

    error = true;

    using (Stream stream = ex.Response.GetResponseStream()) {

      using (StreamReader sr = new StreamReader(stream)) {

        var s = sr.ReadToEnd();

        System.Console.WriteLine(s);

      }

    }

  }

}

3.在 PutBlobListAsync() 方法中將 MD5 值和 xmsblobcontentmd5 寫(xiě)入到請(qǐng)求頭中：

public async Task PutBlobListAsync(String containerName, String blobName, Liststring blobIdList, string md5, bool error = false)

{

  String requestMethod = PUT;

  String urlPath = String.Format({0}/{1}, containerName, blobName) + ?comp=blocklist;

  String storageServiceVersion = 20150221;

  String dateInRfc1123Format = DateTime.UtcNow.ToString(R, CultureInfo.InvariantCulture);

  String canonicalizedHeaders = String.Format(

    \nxmsblobcontentmd5:{0}\nxmsdate:{1}\nxmsversion:{2},

    md5,

    dateInRfc1123Format,

    storageServiceVersion);

  StringBuilder stringbuilder = new StringBuilder();

  stringbuilder.Append(BlockList);

  foreach (string item in blobIdList) {

    stringbuilder.Append( Latest + item + /Latest);

  }

  stringbuilder.Append(/BlockList);

  byte[] data = Encoding.UTF8.GetBytes(stringbuilder.ToString());

  Int32 blobLength = data.Length;

  String canonicalizedResource = String.Format(/{0}/{1}, AzureConstants.Account, String.Format({0}/{1}, containerName, blobName) + \ncomp:blocklist);

  String stringToSign = String.Format(

    {0}\n\n\n{1}\n\n\n\n\n\n\n\n{2}\n{3},

    requestMethod,

    blobLength,

    canonicalizedHeaders,

    canonicalizedResource);

  String authorizationHeader = CreateAuthorizationHeader(stringToSign);

  Uri uri = new Uri(BlobEndPoint + urlPath);

  HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);

  request.Method = requestMethod;

  request.Headers[xmsblobcontentmd5] = md5;

  request.Headers[xmsdate] = dateInRfc1123Format;

  request.Headers[xmsversion] = storageServiceVersion;

  request.Headers[Authorization] = authorizationHeader;

  request.ContentLength = blobLength;

  try {

    using (Stream requestStream = await request.GetRequestStreamAsync()) {

      requestStream.Write(data, 0, blobLength);

    }

    using (HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync()) {

      String ETag = response.Headers[ETag];

      System.Console.WriteLine(ETag);

    }

    error = false;

  }

  catch (WebException ex) {

    System.Console.WriteLine(An error occured. Status code: + ((HttpWebResponse)ex.Response).StatusCode);

    System.Console.WriteLine(Error information:);

    error = true;

    using (Stream stream = ex.Response.GetResponseStream()) {

      using (StreamReader sr = new StreamReader(stream)) {

        var s = sr.ReadToEnd();

        System.Console.WriteLine(s);

      }

    }

  }

}

完整示例請(qǐng)參考示例代碼。

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