多线程复制下载文件参考代码
1 多线程下载文件原理
其实就是把一个文件分成几个部分,不同线程(或者进程)负责下载文件的不同的部分。各种下载工具的底层原理应该和此相同,但由于是复杂的网络环境,实际会远比这复杂。
2 模拟代码实现。
[csharp]
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
namespace ConsoleTest
{
class Program
{
private static int ThreadCount = 20;
static void Main(string[] args)
{
for (int i = 0; i < ThreadCount; i++)
{
Thread thread = new Thread(DoWork);
thread.Name = "Thread"+i;
Console.WriteLine("Thread" + i + "Start");
thread.Start(i);
}
System.Console.ReadLine();
}
public static void DoWork(object threadIndex)
{
Console.WriteLine(Thread.CurrentThread.Name);
string oldPath = @"F:\Reflector7.3.rar";
string newPath = @"F:\Reflector7.rar";
int fileLength = (int)(new FileInfo(oldPath).Length);//需要拷贝的文件大小
int lengthPerThread = (fileLength/ThreadCount + 1);//计算平均每个线程需要复制的文件内容大小
int startIndex = (int)threadIndex * lengthPerThread;//计算开始读取文件的位置
Console.WriteLine(Thread.CurrentThread.Name + "start write startIndex=" + startIndex);
int hasRead = 0; //
using (var oldFileReader = File.Open(oldPath, FileMode.Open, FileAccess.Read, FileShare.Read))
{
oldFileReader.Seek(startIndex, SeekOrigin.Begin);//移动到需要读取的位置
byte[] array = new byte[100];
using (var newFileWriter = File.Open(newPath, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite))
{
int read = oldFileReader.Read(array, 0, 100);
newFileWriter.Seek(startIndex, SeekOrigin.Begin);//移动到需要写入的位置
while (read > 0 && hasRead <= lengthPerThread)//
{
hasRead += read;
newFileWriter.Write(array, 0, read);
read = oldFileReader.Read(array, 0, 100);
Random random = new Random();
int next= random.Next(1, 10);
if(next==5)//生成随机数,制造多线程不按生成顺序结束
{
Console.WriteLine(Thread.CurrentThread.Name + "Sleep");
Thread.Sleep(50);
}
}
}
}
Console.WriteLine(Thread.CurrentThread.Name +" end write" + (startIndex + hasRead));
}
}
}
摘自 xuexiaodong2009的专栏
补充:软件开发 , 其他 ,