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C#實(shí)現(xiàn)http斷點(diǎn)續(xù)傳上傳和下載的實(shí)現(xiàn)示例

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2024年3月12日 21:55 本文熱度 496

斷點(diǎn)續(xù)傳是一種可以在文件傳輸過(guò)程中出現(xiàn)斷電、網(wǎng)絡(luò)故障等情況時(shí)，能夠保證傳輸內(nèi)容不會(huì)全部丟失，而是可以從已傳輸?shù)奈恢美^續(xù)傳輸?shù)臋C(jī)制。在文件傳輸較大、較復(fù)雜的情況下，使用斷點(diǎn)續(xù)傳可以提高傳輸質(zhì)量、穩(wěn)定性和效率。

在C#中，可以使用HTTP協(xié)議的Range頭部域來(lái)實(shí)現(xiàn)斷點(diǎn)續(xù)傳。使用HTTP Range頭部域，可以控制取哪個(gè)字節(jié)范圍內(nèi)的字節(jié)。具體實(shí)現(xiàn)方法，在HTTP請(qǐng)求頭中填寫(xiě)Range頭部信息，指明下載區(qū)間：

Range: bytes=[start]-[end]

start和end的值為0和文件大小減1，表示下載全部數(shù)據(jù)；若要實(shí)現(xiàn)斷點(diǎn)續(xù)傳，則start的值為當(dāng)前已下載的數(shù)據(jù)大小，end的值不變。

在本篇文章中，我們將詳細(xì)介紹如何使用C#實(shí)現(xiàn)HTTP協(xié)議的斷點(diǎn)續(xù)傳功能，并提供了完整的代碼示例。

實(shí)現(xiàn)步驟

C#實(shí)現(xiàn)斷點(diǎn)續(xù)傳功能的步驟，簡(jiǎn)要描述如下：

1.定義HTTP請(qǐng)求，并填寫(xiě)Range頭部信息，指明下載區(qū)間信息。

2.執(zhí)行HTTP請(qǐng)求，接收服務(wù)端返回的字節(jié)流，并將流寫(xiě)入本地文件。

3.檢查最終下載文件的大小，與服務(wù)端的文件大小是否一致，若不一致則下載失敗。

4.上傳文件時(shí)，同樣需制定Range信息，然后發(fā)送PUT請(qǐng)求進(jìn)行上傳。

代碼實(shí)現(xiàn)

我們將使用HttpClient來(lái)執(zhí)行請(qǐng)求，使用FileStream來(lái)讀寫(xiě)文件。下面是代碼實(shí)現(xiàn)的詳細(xì)過(guò)程。

1.下載文件

下載文件時(shí)，首先需要判斷本地是否已經(jīng)存在相同的文件，如果存在，則需要計(jì)算出當(dāng)前已下載數(shù)據(jù)的大?。雌鹗嘉恢胹tartPosition），否則從頭開(kāi)始下載。

下載時(shí)，需要在HTTP請(qǐng)求頭中填寫(xiě)Range頭部信息，指明下載區(qū)間。同時(shí)，需要注意控制下載緩沖區(qū)大小，以避免內(nèi)存不足的情況。

最后，需要檢查下載完成后文件的大小是否與服務(wù)端的文件大小一致，若不一致，則下載失敗。

代碼示例：

  private static async Task DownloadFileAsync(Uri uri, string filename, CancellationToken cancellationToken = default)
  {
      long startPosition;
      var fileInfo = new FileInfo(filename);
   
      if (fileInfo.Exists)
      {
          startPosition = fileInfo.Length;
          if (startPosition == uri.GetFileSize())
        {
            Console.WriteLine($"The file '{filename}' has already been downloaded.");
            return;
        }
    }
    else
    {
        startPosition = 0;
    }

    using var fs = new FileStream(filename, startPosition == 0 ? FileMode.Create : FileMode.Append);

    var rangeHeader = new RangeHeaderValue(startPosition, null);

    var request = new HttpRequestMessage(HttpMethod.Get, uri);
    request.Headers.Range = rangeHeader;

    using var response = await HttpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
    var contentLength = response.Content.Headers.ContentLength;
    if (!contentLength.HasValue)
    {
        throw new InvalidOperationException("The server did not provide the content length.");
    }

    var totalSize = contentLength.Value + startPosition;

    using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
   await stream.CopyToAsync(fs);

    if (fs.Length != totalSize)
    {
        fileInfo.Refresh();
        if (fileInfo.Length < totalSize)
        {
            throw new InvalidOperationException($"The file '{filename}' was not downloaded correctly.");
        }
    }

    Console.WriteLine($"The file '{filename}' has been downloaded.");
}

2.上傳文件

上傳文件與下載文件相似，同樣需要在HTTP請(qǐng)求頭中填寫(xiě)Range頭部信息，以限制上傳的范圍。同時(shí)，需要指定Content-Type，以明確上傳數(shù)據(jù)的類(lèi)型。

上傳文件需要注意的一點(diǎn)是，如果文件較大，則需要分多次上傳?？梢詫⑽募指畛啥鄠€(gè)大小相同的片段，逐個(gè)上傳，確保操作的穩(wěn)定性和效率。

上傳完成后，會(huì)收到服務(wù)端的響應(yīng)。如果響應(yīng)碼為2xx，則表示上傳成功；否則，表示上傳失敗。

代碼示例：

  public static async Task UploadFileAsync(Uri uri, string filename, int bufferSize = 4096, CancellationToken cancellationToken = default)
  {
      long startPosition;
      var fileInfo = new FileInfo(filename);
   
      if (fileInfo.Exists)
      {
          startPosition = fileInfo.Length;
      }
    else
    {
        throw new FileNotFoundException("The file was not found.", filename);
    }

    using var fs = new FileStream(filename, FileMode.Open);

    var rangeHeader = new RangeHeaderValue(startPosition, fs.Length - 1);

    var request = new HttpRequestMessage(HttpMethod.Put, uri);
    request.Headers.Range = rangeHeader;
    request.Headers.TryAddWithoutValidation("Content-Type", "application/octet-stream");

    var content = new StreamContent(fs, bufferSize);
    request.Content = content;

    using var response = await HttpClient.SendAsync(request, cancellationToken);

    if (!response.IsSuccessStatusCode)
    {
        var responseMessage = await response.Content.ReadAsStringAsync();
        throw new InvalidOperationException($"Failed to upload file: {response.StatusCode} {responseMessage}");
    }

    Console.WriteLine($"The file '{filename}' has been uploaded.");
}

完整代碼

上述代碼僅為示例，仍然需要加入部分邊界檢查、異常處理等邏輯，以保證代碼的健壯性。下面是完整的實(shí)現(xiàn)代碼，包含了斷點(diǎn)續(xù)傳功能的完整實(shí)現(xiàn)。

  using System;
  using System.IO;
  using System.Net.Http;
  using System.Net.Http.Headers;
  using System.Threading;
  using System.Threading.Tasks;
   
  namespace ConsoleApp
  {
    internal static class Program
    {
        private static readonly HttpClient HttpClient = new HttpClient();

        private static async Task Main(string[] args)
        {
            var uri = new Uri("https://download.visualstudio.microsoft.com/download/pr/26246709-5c10-4383-ad1a-f22f3e8e5e15/23e2d41d2e57b81fc0f9c72068994e70/vc_redist.x64.exe");

            var filename = Path.Combine(Path.GetTempPath(), "vc_redist.x64.exe");

            Console.WriteLine("Start downloading the file...");

            try
            {
                await DownloadFileAsync(uri, filename, CancellationToken.None);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Failed to download the file: {ex.Message}");
                return;
            }

            Console.WriteLine("\nStart uploading the file...\n");

            try
            {
                await UploadFileAsync(uri, filename, 4096, CancellationToken.None);
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Failed to upload the file: {ex.Message}");
                return;
            }

            Console.WriteLine("Done.");
        }

        private static async Task DownloadFileAsync(Uri uri, string filename, CancellationToken cancellationToken = default)
        {
            long startPosition;
            var fileInfo = new FileInfo(filename);

            if (fileInfo.Exists)
            {
                startPosition = fileInfo.Length;
                if (startPosition == uri.GetFileSize())
                {
                    Console.WriteLine($"The file '{filename}' has already been downloaded.");
                    return;
                }
            }
            else
            {
                startPosition = 0;
            }

            using var fs = new FileStream(filename, startPosition == 0 ? FileMode.Create : FileMode.Append);

            var rangeHeader = new RangeHeaderValue(startPosition, null);

            var request = new HttpRequestMessage(HttpMethod.Get, uri);
            request.Headers.Range = rangeHeader;

            using var response = await HttpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, cancellationToken);
            var contentLength = response.Content.Headers.ContentLength;
            if (!contentLength.HasValue)
            {
                throw new InvalidOperationException("The server did not provide the content length.");
            }

            var totalSize = contentLength.Value + startPosition;

            using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
            await stream.CopyToAsync(fs);

            if (fs.Length != totalSize)
            {
                fileInfo.Refresh();
                if (fileInfo.Length < totalSize)
                {
                    throw new InvalidOperationException($"The file '{filename}' was not downloaded correctly.");
                }
            }

            Console.WriteLine($"The file '{filename}' has been downloaded.");
        }

        public static async Task UploadFileAsync(Uri uri, string filename, int bufferSize = 4096, CancellationToken cancellationToken = default)
        {
            long startPosition;
                   var fileInfo = new FileInfo(filename);
        
                   if (fileInfo.Exists)
                   {
                       startPosition = fileInfo.Length;
                   }
                   else
                   {
                       throw new FileNotFoundException("The file was not found.", filename);
                   }
        
                   using var fs = new FileStream(filename, FileMode.Open);
        
                   var rangeHeader = new RangeHeaderValue(startPosition, fs.Length - 1);
        
                   var request = new HttpRequestMessage(HttpMethod.Put, uri);
                   request.Headers.Range = rangeHeader;
                   request.Headers.TryAddWithoutValidation("Content-Type", "application/octet-stream");
        
                   var content = new StreamContent(fs, bufferSize);
                   request.Content = content;
        
                   using var response = await HttpClient.SendAsync(request, cancellationToken);
        
                   if (!response.IsSuccessStatusCode)
                   {
                       var responseMessage = await response.Content.ReadAsStringAsync();
                       throw new InvalidOperationException($"Failed to upload file: {response.StatusCode} {responseMessage}");
                   }
        
                   Console.WriteLine($"The file '{filename}' has been uploaded.");
               }
           }
        
           public static class UriExtensions
           {
               public static long GetFileSize(this Uri uri)
               {
                   using var client = new HttpClient();
                   using var response = client.Send(new HttpRequestMessage(HttpMethod.Head, uri));
                   var contentLength = response.Content.Headers.ContentLength;
                   if (!contentLength.HasValue)
                   {
                       throw new InvalidOperationException("The server did not provide the content length.");
                   }
        
                   return contentLength.Value;
               }
           }
       }

總結(jié)

斷點(diǎn)續(xù)傳功能可以在文件傳輸?shù)倪^(guò)程中，提高傳輸質(zhì)量和效率，確保數(shù)據(jù)傳輸?shù)陌踩院头€(wěn)定性。在本文中，我們介紹了C#中實(shí)現(xiàn)HTTP協(xié)議斷點(diǎn)續(xù)傳的方法，并提供了完整的代碼示例。希望讀者通過(guò)本文的介紹，能夠成功實(shí)現(xiàn)斷點(diǎn)續(xù)傳功能，并在實(shí)際工作中應(yīng)用到相應(yīng)的場(chǎng)景中去。

該文章在 2024/3/12 23:35:13 編輯過(guò)

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