sdk/samples/all in on code/Visual Studio 2010/CSWebDownloader/DownloaderHelper.cs

   1 /****************************** Module Header ******************************\
   2  * Module Name:  DownloaderHelper.cs
   3  * Project:      CSWebDownloader
   4  * Copyright (c) Microsoft Corporation.
   5  *
   6  * This class supplies the methods to
   7  * 1. Initialize a HttpWebRequest object.
   8  * 2. Check the url and initialize some properties of a downloader.
   9  * 3. Check whether the destination file exists. If not, create a file with
  10  *    the same size as the file to be downloaded.
  11  *
  12  *
  13  * This source is subject to the Microsoft Public License.
  14  * See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
  15  * All other rights reserved.
  16  *
  17  * THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
  18  * EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
  20 \***************************************************************************/
  21
  22 using System;
  23 using System.Net;
  24 using System.Text.RegularExpressions;
  25 using System.IO;
  26
  27 namespace CSWebDownloader
  28 {
  29     public static class DownloaderHelper
  30     {
  31
  32         public static HttpWebRequest InitializeHttpWebRequest(IDownloader downloader)
  33         {
  34             var webRequest = (HttpWebRequest)WebRequest.Create(downloader.Url);
  35
  36             if (downloader.Credentials != null)
  37             {
  38                 webRequest.Credentials = downloader.Credentials;
  39             }
  40             else
  41             {
  42                 webRequest.Credentials = CredentialCache.DefaultCredentials;
  43             }
  44
  45             if (downloader.Proxy != null)
  46             {
  47                 webRequest.Proxy = downloader.Proxy;
  48             }
  49             else
  50             {
  51                 webRequest.Proxy = WebRequest.DefaultWebProxy;
  52             }
  53
  54             return webRequest;
  55         }
  56
  57         /// <summary>
  58         /// Check the URL to download, including whether it supports Range,
  59         /// </summary>
  60         /// <param name="downloader"></param>
  61         /// <returns></returns>
  62         public static string CheckUrl(IDownloader downloader)
  63         {
  64             string fileName = string.Empty;
  65
  66             // Check the file information on the remote server.
  67             var webRequest = InitializeHttpWebRequest(downloader);
  68
  69             using (var response = webRequest.GetResponse())
  70             {
  71                 foreach (var header in response.Headers.AllKeys)
  72                 {
  73                     if (header.Equals("Accept-Ranges", StringComparison.OrdinalIgnoreCase))
  74                     {
  75                         downloader.IsRangeSupported = true;
  76                     }
  77
  78                     if (header.Equals("Content-Disposition", StringComparison.OrdinalIgnoreCase))
  79                     {
  80                         string contentDisposition = response.Headers[header];
  81
  82                         string pattern = ".[^;]*;\\s+filename=\"(?<file>.*)\"";
  83                         Regex r = new Regex(pattern);
  84                         Match m = r.Match(contentDisposition);
  85                         if (m.Success)
  86                         {
  87                             fileName = m.Groups["file"].Value;
  88                         }
  89                     }
  90                 }
  91
  92                 downloader.TotalSize = response.ContentLength;
  93
  94                 if (downloader.TotalSize <= 0)
  95                 {
  96                     throw new ApplicationException(
  97                         "The file to download does not exist!");
  98                 }
  99
 100                 if (!downloader.IsRangeSupported)
 101                 {
 102                     downloader.StartPoint = 0;
 103                     downloader.EndPoint = int.MaxValue;
 104                 }
 105             }
 106
 107             if (downloader.IsRangeSupported &&
 108                 (downloader.StartPoint != 0 || downloader.EndPoint != long.MaxValue))
 109             {
 110                 webRequest = InitializeHttpWebRequest(downloader);
 111
 112                 if (downloader.EndPoint != int.MaxValue)
 113                 {
 114                     webRequest.AddRange(downloader.StartPoint, downloader.EndPoint);
 115                 }
 116                 else
 117                 {
 118                     webRequest.AddRange(downloader.StartPoint);
 119                 }
 120                 using (var response = webRequest.GetResponse())
 121                 {
 122                     downloader.TotalSize = response.ContentLength;
 123                 }
 124             }
 125
 126             return fileName;
 127         }
 128
 129
 130         /// <summary>
 131         /// Check whether the destination file exists. If not, create a file with the same
 132         /// size as the file to be downloaded.
 133         /// </summary>
 134         public static void CheckFileOrCreateFile(IDownloader downloader, object fileLocker)
 135         {
 136             // Lock other threads or processes to prevent from creating the file.
 137             lock (fileLocker)
 138             {
 139                 FileInfo fileToDownload = new FileInfo(downloader.DownloadPath);
 140                 if (fileToDownload.Exists)
 141                 {
 142
 143                     // The destination file should have the same size as the file to be downloaded.
 144                     if (fileToDownload.Length != downloader.TotalSize)
 145                     {
 146                         throw new ApplicationException(
 147                             "The download path already has a file which does not match"
 148                             + " the file to download. ");
 149                     }
 150                 }
 151
 152                 // Create a file.
 153                 else
 154                 {
 155                     if (downloader.TotalSize == 0)
 156                     {
 157                         throw new ApplicationException("The file to download does not exist!");
 158                     }
 159
 160                     using (FileStream fileStream = File.Create(downloader.DownloadPath))
 161                     {
 162                         long createdSize = 0;
 163                         byte[] buffer = new byte[4096];
 164                         while (createdSize < downloader.TotalSize)
 165                         {
 166                             int bufferSize = (downloader.TotalSize - createdSize) < 4096
 167                                 ? (int)(downloader.TotalSize - createdSize) : 4096;
 168                             fileStream.Write(buffer, 0, bufferSize);
 169                             createdSize += bufferSize;
 170                         }
 171                     }
 172                 }
 173             }
 174         }
 175     }
 176 }