C#基础-FileStream实现多线程断点续传

一、前言

网上有许多的多线程断点续传操作，但总是写的很云里雾里，或者写的比较坑长。由于这几个月要负责公司的在线升级项目，所以正好顺便写了一下

代码如下：

  1 using System;
  2 using System.Collections.Generic;
  3 using System.IO;
  4 using System.Threading.Tasks;
  5 
  6 namespace TestCenter
  7 {
  8     class Program
  9     {
 10         static void Main(string[] args)
 11         {
 12             string LocalSavePath = @"E:\Test\TestFile\Local\1.msi";  //本地目标文件路径
 13 
 14             FileInfo SeverFilePath = new FileInfo(@"E:\Test\TestFile\Server\1.msi"); //服务器待文件路径
 15             long FileLength = SeverFilePath.Length; //待下载文件大小
 16 
 17 
 18             Console.WriteLine("Start Configuration");
 19             int PackCount = 0;  //初始化数据包个数
 20 
 21             long PackSize = 1024000; //数据包大小
 22 
 23             if (FileLength % PackSize > 0)
 24             {
 25                 PackCount = (int)(FileLength / PackSize) + 1;
 26             }
 27 
 28             else
 29             {
 30                 PackCount = (int)(FileLength / PackSize);
 31             }
 32 
 33 
 34             Console.WriteLine("Start Recieve");
 35             var tasks = new Task[PackCount];  //多线程任务
 36 
 37             for (int index = 0; index < PackCount; index++)
 38             {
 39 
 40 
 41                 int Threadindex = index; //这步很关键，在Task()里的绝对不能直接使用index
 42                 var task = new Task(() =>
 43                 {
 44                     string tempfilepath = @"E:\Test\TestFile\Temp\" + "QS_" + Threadindex + "_" + PackCount; //临时文件路径
 45 
 46                     using (FileStream tempstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write))
 47                     {
 48                         int length = (int)Math.Min(PackSize, FileLength - Threadindex * PackSize);
 49 
 50                         var bytes = GetFile(Threadindex*PackCount, length);
 51 
 52                         tempstream.Write(bytes, 0, length);
 53                         tempstream.Flush();
 54                         tempstream.Close();
 55                         tempstream.Dispose();
 56                     }
 57                 });
 58                 tasks[Threadindex] = task;
 59                 task.Start();
 60             }
 61 
 62             Task.WaitAll(tasks); //等待所有线程完成
 63             Console.WriteLine("Recieve End");
 64 
 65 
 66             //检测有哪些数据包未下载
 67             Console.WriteLine("Start Compare");
 68             DirectoryInfo TempDir = new DirectoryInfo(@"E:\Test\TestFile\temp"); //临时文件夹路径
 69             List<string> Comparefiles = new List<string>();
 70 
 71             for (int i = 0; i < PackCount; i++)
 72             {
 73                 bool hasfile = false;
 74                 foreach (FileInfo Tempfile in TempDir.GetFiles())
 75                 {
 76                     if (Tempfile.Name.Split('_')[1] == i.ToString())
 77                     {
 78                         hasfile = true;
 79                         break;
 80                     }
 81                 }
 82                 if (hasfile == false)
 83                 {
 84                     Comparefiles.Add(i.ToString());
 85                 }
 86             }
 87 
 88             //最后补上这些缺失的文件
 89             if (Comparefiles.Count > 0)
 90             {
 91                 foreach (string com_index in Comparefiles)
 92                 {
 93                     string tempfilepath = @"E:\Test\TestFile\Temp\" + "QS_" + com_index+ "_" + PackCount;
 94                     using (FileStream Compstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write))
 95                     {
 96                         int length = (int)Math.Min(PackSize, FileLength - Convert.ToInt32(com_index) * PackSize);
 97                         var bytes = GetFile(Convert.ToInt32(com_index)*PackCount, length);
 98                         Compstream.Write(bytes, 0, length);
 99                         Compstream.Flush();
100                         Compstream.Close();
101                         Compstream.Dispose();
102                     }
103                 }
104 
105             }
106             Console.WriteLine("Compare End");
107 
108 
109             //准备将临时文件融合并写到1.msi中
110             Console.WriteLine("Start Write");
111             using (FileStream writestream = new FileStream(LocalSavePath, FileMode.Create, FileAccess.Write, FileShare.Write))
112             {
113                 foreach (FileInfo Tempfile in TempDir.GetFiles())
114                 {
115                     using (FileStream readTempStream = new FileStream(Tempfile.FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
116                     {
117                         long onefileLength = Tempfile.Length;
118                         byte[] buffer = new byte[Convert.ToInt32(onefileLength)];
119                         readTempStream.Read(buffer, 0, Convert.ToInt32(onefileLength));
120                         writestream.Write(buffer, 0, Convert.ToInt32(onefileLength));
121                     }
122                 }
123                 writestream.Flush();
124                 writestream.Close();
125                 writestream.Dispose();
126             }
127             Console.WriteLine("Write End");
128 
129 
130 
131             //删除临时文件
132             Console.WriteLine("Start Delete Temp Files");
133             foreach (FileInfo Tempfile in TempDir.GetFiles())
134             {
135                 Tempfile.Delete();
136             }
137             Console.WriteLine("Delete Success");
138             Console.ReadKey();
139         }
140 
141 
142         //这个方法可以放到Remoting或者WCF服务中去，然后本地调用该方法即可实现多线程断点续传
143         public static byte[] GetFile(int start, int length)
144         {
145             string SeverFilePath = @"E:\Test\TestFile\Server\1.msi";
146             using (FileStream ServerStream = new FileStream(SeverFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 1024*80, true))
147             {
148                 byte[] buffer = new byte[length];
149                 ServerStream.Position = start;
150                 //ServerStream.Seek(start, SeekOrigin.Begin);
151                 ServerStream.Read(buffer, 0, length);
152                 return buffer;
153             }
154         }
155     }
156 }

二、讨论

1）需要注意的是第44行，不能直接使用index变量在Task()里进行操作，而是要将它赋给Threadindex，让Threadindex在Task()里，不然会直接报错，为什么呢？

链接：http://bbs.csdn.net/topics/390769774

2）70至108行代码可以在外面再套一层while循环，循环检测临时文件是否下完整了，然后再定义一个检测最大上限，超过这个上限就放弃本次更新，当用户的网络恢复正常后下次再做更新操作。所以说放临时文件的文件夹最好要包含版本信息，不会把2.0.0的临时文件和1.0.0的临时文件搞混。

3） FileStream.Position 与 FileStream.Seek(long offset, SeekOrigin seekorigin) 的作用都是获取流的指针位置，当文件路径使用绝对路径时使用Position；相对路径时使用Seek方法

链接：https://stackoverflow.com/questions/7238929/stream-seek0-seekorigin-begin-or-position-0

posted on 2016-08-01 20:29 airforce094 阅读(2926) 评论(0) 编辑收藏举报