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：
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 = ; //初始化数据包个数 long PackSize = ; //数据包大小 if (FileLength % PackSize > )
{
PackCount = (int)(FileLength / PackSize) + ;
} else
{
PackCount = (int)(FileLength / PackSize);
} Console.WriteLine("Start Recieve");
var tasks = new Task[PackCount]; //多线程任务 for (int index = ; 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, , 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 = ; i < PackCount; i++)
{
bool hasfile = false;
foreach (FileInfo Tempfile in TempDir.GetFiles())
{
if (Tempfile.Name.Split('_')[] == 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 > )
{
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, , 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, , Convert.ToInt32(onefileLength));
writestream.Write(buffer, , 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, *, true))
{
byte[] buffer = new byte[length];
ServerStream.Position = start;
//ServerStream.Seek(start, SeekOrigin.Begin);
ServerStream.Read(buffer, , 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？
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