kevin-Y

public class SyncDownloader
    {
        
        public delegate byte[] DownloadBytesHandle(string pFileName, long pPosition, int pMaxSize);

        System.IO.FileStream write = null;
        long pos = 0;
        int lastReceiveSize = 0;
        int bufferVersion = 0;
        SyncDownloadItem curDown;
        public SyncDownloader()
        {
            
        }
        private ManualResetEvent timeoutObject = new ManualResetEvent(false);
        
        public bool StartDownload(string fileName, string localFullPath)
        {
            int buffersize = 50000;//默认500K一次   25000 12500 6000 3000  1500   
            bufferVersion = 0;
            pos = 0;
            lastReceiveSize = buffersize;//默认与最大的一致
            bool isOk = false;
            int timeoutTimes = 0;//超时20次退出下载。
            
            try
            {
                System.IO.FileInfo file = new FileInfo(localFullPath);
                if (!file.Directory.Exists)
                    file.Directory.Create();
                write = new FileStream(localFullPath, FileMode.Create);                
                while (true)
                {                    
                    timeoutObject.Reset();
                    if (lastReceiveSize < buffersize)
                        break;
                    bufferVersion++;
                               
                    //异步下载
                    DownloadBytesHandle fh = new DownloadBytesHandle(this.dwonloadBytes);
                    AsyncCallback callback = new AsyncCallback(this.downloadCallback);
                    IAsyncResult ar = fh.BeginInvoke(fileName, pos, buffersize, callback, bufferVersion);

                    if (!timeoutObject.WaitOne(10000))//10秒应能下载完成
                    {
                        timeoutTimes++;
                        Console.Write("_{0}", timeoutTimes);  //超时加下划线                      
                        if (timeoutTimes > 20)
                            break;
                        //超时
                        if (buffersize > 3000)//10秒无论如何都应能下载1.5K
                            buffersize = buffersize / 2;//超时下载尺寸减半。                        
                    }
                    else
                    {                        
                        byte[] buffer = fh.EndInvoke(ar);
                        Console.Write(".");//不断的加点
                        write.Write(buffer, 0, buffer.Length);
                        pos += buffer.Length;
                        lastReceiveSize = buffer.Length;
                    }
                }
                isOk = true;
            }
            catch (Exception ex)
            {
                isOk = false;
                GeneralMethod.HandleException(ex);
            }
            finally
            {
                if (write != null)
                    write.Close();
            }
            return isOk;
        }
        public void downloadCallback(IAsyncResult ar)
        {
            int dbVer = Convert.ToInt32(ar.AsyncState);           
            if (dbVer == this.bufferVersion)//只有当次调用才释放
                timeoutObject.Set();
        }

        public byte[] dwonloadBytes(string pFileName, long pPosition, int pMaxSize)
        {
            //System.Threading.Thread.Sleep(11000);//睡11秒。判断是否还会执行。
            byte[] buffer = null;
            try
            {                
                buffer = Factory.AreaIssueFacade.DownFromTestPool(pFileName, pPosition, pMaxSize);
            }
            catch { }//忽略所有错误
            return buffer;
        }
    }