文件的分割下载

 HttpFile类：

public class HttpFile
    {
        public Form1 formm;
        public int threadh;//线程代号
        public string filename;//文件名
        public string strUrl;//接收文件的URL
        public FileStream fs;
        public HttpWebRequest request;
        public System.IO.Stream ns;
        public byte[] nbytes;//接收缓冲区
        public int nreadsize;//接收字节数

        public HttpFile(Form1 form, int thread)//构造方法
        {
            formm = form;
            threadh = thread;
        }
        public HttpFile()//析构方法
        {
            formm.Dispose();
        }

        public void receive()//接收线程
        {
            filename = formm.filenamew[threadh];
            strUrl = formm.strurl;
            ns = null;
            nbytes = new byte[512];
            nreadsize = 0;
            fs = new FileStream(filename, System.IO.FileMode.Create);
            try
            {
                request = (HttpWebRequest)HttpWebRequest.Create(strUrl);
                //接收的起始位置及接收的长度 
                request.AddRange(formm.filestartw[threadh],
                formm.filestartw[threadh] + formm.filesizew[threadh]);
                ns = request.GetResponse().GetResponseStream();//获得接收流
                nreadsize = ns.Read(nbytes, 0, 512);
                while (nreadsize > 0)
                {
                    fs.Write(nbytes, 0, nreadsize);
                    nreadsize = ns.Read(nbytes, 0, 512);
                }
                fs.Close();
                ns.Close();
            }
            catch (Exception er)
            {
                string message=(er.Message);
                fs.Close();
            }
            formm.threadw[threadh] = true;
        }
    }

 

窗体代码：

        public bool[] threadw; //每个线程结束标志
        public string[] filenamew;//每个线程接收文件的文件名
        public int[] filestartw;//每个线程接收文件的起始位置
        public int[] filesizew;//每个线程接收文件的大小
        public string strurl;//接受文件的URL
        public bool hb;//文件合并标志
        public int thread;//进程数 


        /// <summary>
        /// 下载
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            lblMessage.Text = "正在下载...";
            strurl = textBox2.Text.Trim().ToString();
            WebRequest request;
            long filesize = 0;
            try
            {
                request = (HttpWebRequest)HttpWebRequest.Create(strurl);
                filesize = request.GetResponse().ContentLength;//取得目标文件的长度
                request.Abort();
            }
            catch (Exception er)
            {
                MessageBox.Show(er.Message);
            }
            // 接收线程数
            thread = Convert.ToInt32(textBox4.Text.Trim().ToString(), 10);
            //根据线程数初始化数组
            threadw = new bool[thread];
            filenamew = new string[thread];
            filestartw = new int[thread];
            filesizew = new int[thread];

            //计算每个线程应该接收文件的大小
            int filethread = (int)filesize / thread;//平均分配
            int filethreade = filethread + (int)filesize % thread;//剩余部分由最后一个线程完成
            //为数组赋值
            for (int i = 0; i < thread; i++)
            {
                threadw[i] = false;//每个线程状态的初始值为假
                filenamew[i] = i.ToString() + ".dat";//每个线程接收文件的临时文件名
                if (i < thread - 1)
                {
                    filestartw[i] = filethread * i;//每个线程接收文件的起始点
                    filesizew[i] = filethread - 1;//每个线程接收文件的长度
                }
                else
                {
                    filestartw[i] = filethread * i;
                    filesizew[i] = filethreade - 1;
                }
            }
            //定义线程数组，启动接收线程
            Thread[] threadk = new Thread[thread];
            HttpFile[] httpfile = new HttpFile[thread];
            for (int j = 0; j < thread; j++)
            {
                httpfile[j] = new HttpFile(this, j);
                threadk[j] = new Thread(new ThreadStart(httpfile[j].receive));
                threadk[j].Start();
            }
            //启动合并各线程接收的文件线程
            Thread hbth = new Thread(new ThreadStart(hbfile));
            hbth.Start();
        }


        /// <summary>
        /// 合并的方法
        /// </summary>
        public void hbfile()
        {
            if (this.InvokeRequired)
            {
                while (true)//等待
                {
                    hb = true;
                    for (int i = 0; i < thread; i++)
                    {
                        if (threadw[i] == false)//有未结束线程，等待
                        {
                            hb = false;
                            Thread.Sleep(100);
                            break;
                        }
                    }
                    if (hb == true)//所有线程均已结束，停止等待，
                    {
                        break;
                    }
                }
                FileStream fs;//开始合并
                FileStream fstemp;
                int readfile;
                byte[] bytes = new byte[512];
                fs = new FileStream(textBox3.Text.Trim().ToString(), System.IO.FileMode.Create);
                for (int k = 0; k < thread; k++)
                {
                    fstemp = new FileStream(filenamew[k], System.IO.FileMode.Open);
                    while (true)
                    {
                        readfile = fstemp.Read(bytes, 0, 512);
                        if (readfile > 0)
                        {
                            fs.Write(bytes, 0, readfile);
                        }
                        else
                        {
                            break;
                        }
                    }
                    fstemp.Close();
                }
                fs.Close();
                this.lblMessage.Invoke(new ThreadStart(Show) );
            }
        }
        private void Show()
        {
            lblMessage.Text = "下载完成。";
        }