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c#https下载文件每次read只有4096,像是被限速,怎么解决

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[已解决问题]
        public const int MaxLength = 104857600;         //100M
        private const string DefaultUserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36";
        public string Url { get; set; }                 //下载链接
        public string SavePath { get; set; }            //保存的完整路径
        public long ContentLength { get; private set; }                  //本次下载的总长度,并非文件总长度
        private int unitDownloadLength = MaxLength;
        bool isStop;
        private int Offset { get; set; }
        private WebResponse Response;
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Url);
if (Url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
{
     ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CertificateValidationCallback);
     req.ProtocolVersion = HttpVersion.Version11;
     req.UserAgent = DefaultUserAgent;
}
 if(RecievedSize > 0)
     req.AddRange(RecievedSize);
Response = (HttpWebResponse)req.GetResponse();
using (Stream stream = Response.GetResponseStream())
{
     if (State == DownloadState.Stoping) return;                                        //判断停止
     using (FileStream fs = new FileStream(SavePath, FileMode.Create, FileAccess.Write))
     {
          using (BinaryReader br = new BinaryReader(stream))
          {
               byte[] b = new byte[MaxLength];
               while (!isStop && (Offset = br.Read(b, 0, (unitDownloadLength = unitDownloadLength > ContentLength - Offset ? (int)(ContentLength - Offset) : unitDownloadLength))) > 0)  //offset等于0时完成下载
               {
                    fs.Write(b, 0, Offset);
                    b = new byte[MaxLength];
                    RecievedSize += Offset;
                    ProgressChanged?.Invoke(null, new DownloadEventArgs(this));
                    Thread.Sleep(50);
                }
           }
     }
}

每次br.read()只read出4096个字节,大概10多次就出一次12288字节,无论我怎么设置单次读取长度都会一直这样

HotSky的主页 HotSky | 菜鸟二级 | 园豆:235
提问于:2017-11-25 10:37
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最佳答案
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你看下http响应中有没有chunked标志,其次你那个byte数组用的姿势不对,没必要再循环中重新实例化,只需要在最后写到fs中告知其offset和count即可,这样开销会小很多的。

奖励园豆:5
Daniel Cai | 大侠五级 |园豆:9048 | 2017-11-25 12:29

 没有chunked标志,byte数组因为每次读取的的长度可能不一样,如果不重新实例化,那么可能会影响下次读取的byte数组

HotSky | 园豆:235 (菜鸟二级) | 2017-11-25 14:20

@HotSky: 读取的长度是看BinaryReader返回值,你byte数组在这块是做个buffer而已,你前面已经申明了足够大的空间,在每次写入底层文件时只是通过Write方法告知这块是从这个buffer区域中的哪儿开始读取多少

Daniel Cai | 园豆:9048 (大侠五级) | 2017-11-25 14:35

@Daniel Cai: OK,谢谢!我发现我速度慢是因为用了睡眠-_-||

HotSky | 园豆:235 (菜鸟二级) | 2017-11-25 15:50
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