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：
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using System;using System.Collections.Generic;using System.IO;using System.Threading.Tasks;namespace TestCenter{ class Program { static void Main(string[] args) { string LocalSavePath = @"E:\Test\TestFile\Local\1.msi"; //本地目标文件路径 FileInfo SeverFilePath = new FileInfo(@"E:\Test\TestFile\Server\1.msi"); //服务器待文件路径 long FileLength = SeverFilePath.Length; //待下载文件大小 Console.WriteLine("Start Configuration"); int PackCount = 0; //初始化数据包个数 long PackSize = 1024000; //数据包大小 if (FileLength % PackSize > 0) { PackCount = (int)(FileLength / PackSize) + 1; } else { PackCount = (int)(FileLength / PackSize); } Console.WriteLine("Start Recieve"); var tasks = new Task[PackCount]; //多线程任务 for (int index = 0; index < PackCount; index++) { int Threadindex = index; //这步很关键，在Task()里的绝对不能直接使用index var task = new Task(() => { string tempfilepath = @"E:\Test\TestFile\Temp\" + "QS_" + Threadindex + "_" + PackCount; //临时文件路径 using (FileStream tempstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write)) { int length = (int)Math.Min(PackSize, FileLength - Threadindex * PackSize); var bytes = GetFile(Threadindex*PackCount, length); tempstream.Write(bytes, 0, length); tempstream.Flush(); tempstream.Close(); tempstream.Dispose(); } }); tasks[Threadindex] = task; task.Start(); } Task.WaitAll(tasks); //等待所有线程完成 Console.WriteLine("Recieve End"); //检测有哪些数据包未下载 Console.WriteLine("Start Compare"); DirectoryInfo TempDir = new DirectoryInfo(@"E:\Test\TestFile\temp"); //临时文件夹路径 List<string> Comparefiles = new List<string>(); for (int i = 0; i < PackCount; i++) { bool hasfile = false; foreach (FileInfo Tempfile in TempDir.GetFiles()) { if (Tempfile.Name.Split('_')[1] == i.ToString()) { hasfile = true; break; } } if (hasfile == false) { Comparefiles.Add(i.ToString()); } } //最后补上这些缺失的文件 if (Comparefiles.Count > 0) { foreach (string com_index in Comparefiles) { string tempfilepath = @"E:\Test\TestFile\Temp\" + "QS_" + com_index+ "_" + PackCount; using (FileStream Compstream = new FileStream(tempfilepath, FileMode.Create, FileAccess.Write, FileShare.Write)) { int length = (int)Math.Min(PackSize, FileLength - Convert.ToInt32(com_index) * PackSize); var bytes = GetFile(Convert.ToInt32(com_index)*PackCount, length); Compstream.Write(bytes, 0, length); Compstream.Flush(); Compstream.Close(); Compstream.Dispose(); } } } Console.WriteLine("Compare End"); //准备将临时文件融合并写到1.msi中 Console.WriteLine("Start Write"); using (FileStream writestream = new FileStream(LocalSavePath, FileMode.Create, FileAccess.Write, FileShare.Write)) { foreach (FileInfo Tempfile in TempDir.GetFiles()) { using (FileStream readTempStream = new FileStream(Tempfile.FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)) { long onefileLength = Tempfile.Length; byte[] buffer = new byte[Convert.ToInt32(onefileLength)]; readTempStream.Read(buffer, 0, Convert.ToInt32(onefileLength)); writestream.Write(buffer, 0, Convert.ToInt32(onefileLength)); } } writestream.Flush(); writestream.Close(); writestream.Dispose(); } Console.WriteLine("Write End"); //删除临时文件 Console.WriteLine("Start Delete Temp Files"); foreach (FileInfo Tempfile in TempDir.GetFiles()) { Tempfile.Delete(); } Console.WriteLine("Delete Success"); Console.ReadKey(); } //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 public static byte[] GetFile(int start, int length) { string SeverFilePath = @"E:\Test\TestFile\Server\1.msi"; using (FileStream ServerStream = new FileStream(SeverFilePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 1024*80, true)) { byte[] buffer = new byte[length]; ServerStream.Position = start; //ServerStream.Seek(start, SeekOrigin.Begin); ServerStream.Read(buffer, 0, length); return buffer; } } }} |
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？查看链接
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，查看链接
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://www.cnblogs.com/lovecsharp094/p/5727141.html
