HTTP协议 HttpWebRequest和 Socket的一点总结

相信接触过网络开发的人对HTTP、HttpWebRequest、Socket这些东西都不陌生吧。它们之间的一些介绍和关系我这里都忽略了。开我们平时开发过程中也是很少有机会接触大什么大并发这个东东,一般大并发我们都需要考虑异步和多线程以及对象池,这个我们以一个简单demo来讲解吧。

主要的调用关系图如下:

HTTP协议 HttpWebRequest和 Socket的一点总结_第1张图片

类的结构图如下:

HTTP协议 HttpWebRequest和 Socket的一点总结_第2张图片

一:这里我们依次对这些类做一个简单的说明

HttpRequestInfo:

public string Url:http请求的url字符串,如http://www.baidu.com/
public byte[] PostData:Post请求中的数据
public WebHeaderCollection Headers:请求的头部数据
public bool AllowAutoRedirect :是否允许301、302自动跳转,如果你想获取请求返回的头部信息,建议一般设置为false
public Dictionary<string, string> ExternalData :请求过程中附加的数据(如数据记录的ID),便于在成功或失败回调函数中调用
public Action<HttpContextInfo> ActionCompleted :请求成功后所调用的函数
public Action<HttpRequestException> ActionException:请求失败所调用函数
public HttpRequestInfo Clone():返回当前对象的一个副本。

HttpResponseInfo

public Stream ResponseContent :Http请求返回内容(除头部信息)的对象流
public HttpStatusCode StatusCode:Http返回的状态
public string StatusDescription :Http状态描述
public WebHeaderCollection Headers:Http返回的头部信息
public string GetString(Encoding coding):把http返回体中数据流转换为字符串,转换编码就是我们所传参数。

   public interface IHttpRequest
    {
        void GetResponseAsync(HttpRequestInfo request);
        bool IsBusy { set; get; }
    }

在IHttpRequest接口中,IsBusy属性主要是判断当前对象是否正在使用中,GetResponseAsync方法是真正完成Http请求的方法。

这里我们主要看看HttpRequestFactory的封装吧,管理对象实例的个数,相当于一个对象池,这里的代码主要是基于。net framework2.0的,

首先我们需要2个集合分别管理HttpRequestInfo请求实例和IHttpRequest处理请求实例,

  static Queue<HttpRequestInfo> requestTask = new Queue<HttpRequestInfo>();
   static List<IHttpRequest> Handlers = new List<IHttpRequest>();

而我们暴露给外部的一个主要方法就是AddRequestTask,

  public static void AddRequestTask(HttpRequestInfo info)
        {
            if (!string.IsNullOrEmpty(info.Url))
            {
                lock (Lockobj)
                {
                    Interlocked.Increment(ref requestCount);
                    requestTask.Enqueue(info);
                }
            }
        }
那么这些请求在什么时候被处理了,在一个叫Process方法中处理,

private static void Process(object obj)
        {
            while (true)
            {
                IHttpRequest handler = GetAvailableHttpRequest();
                while (handler == null)
                {
                    Thread.Sleep(100);
                    handler = GetAvailableHttpRequest();
                }
                HttpRequestInfo task = GetTask();
                while (task == null)
                {
                    Thread.Sleep(100);
                    task = GetTask();
                }
                if (task != null && handler != null)
                {
                    Interlocked.Decrement(ref requestCount);
                    handler.GetResponseAsync(task);
                }
                // Thread.Sleep(10);
            }
        }

在这个方法中我们需要调用GetAvailableHttpRequest来获取IHttpRequest处理对象实例,调用GetTask来获取HttpRequestInfo请求实例。如果这2个实例都存在我们调用    IHttpRequest.GetResponseAsync(HttpRequestInfo);方法开始处理http请求。

GetAvailableHttpRequest如下:

  private static IHttpRequest GetAvailableHttpRequest()
        {
            lock (Lockobj)
            {
                for (int i = 0; i < Handlers.Count; i++)
                {
                    if (!Handlers[i].IsBusy)
                    {
                        return Handlers[i];
                    }
                }
                if (Handlers.Count <= MaxRequestCount)
                {
                    IHttpRequest handler = (IHttpRequest)Activator.CreateInstance(_httpRequestType);
                    Handlers.Add(handler);
                    return handler;
                }
            }
            return null;
            //return GetAvailableHttpRequest();
        }

GetAvailableHttpRequest方法中,我们首先在处理对象集合中查找是否有空闲对象,如果有就返回,否则检查当前对象实例个数个数是否达到最大个数,如果没有我们则创建新实例,且加入到集合中,再返回,否者返回null。所以在Process方法中有一个检查,看啊看你返回的IHttpRequest是否为null,请注意这里一定不要用递归来返回有效的IHttpRequest,建议用一个死循环来处理,如果用递归一般不会出现什么问题,但是递归层次嵌套太深就会出现栈溢出错误,我在测试的时候曾经出现过这个问题。GetTask和GetAvailableHttpRequest处理一样。

那么这里的Process方法有在什么地方调用了,在HttpRequestFactory的静态构造函数中调用。

    static HttpRequestFactory()
        {
            MaxRequestCount = 10;
            ThreadPool.QueueUserWorkItem(new WaitCallback(Process));
        }
到这里我们的一个对象池就构造玩了。

二 现在我们来看看RequestHttpWebRequest是如何处理HTTP请求的。它主要使用HttpWebRequest来处理请求。

这里我们主要使用HttpWebRequest的异步方法,因此我们需要构造一个状态对象StateObjectInfo

   class StateObjectInfo : HttpContextInfo
        {
            internal byte[] Buffer { set; get; } //把返回的流写到HttpResponseInfo.ResponseContent 时用到的暂存数组
            internal Stream ReadStream { set; get; }//把返回的流写到HttpResponseInfo.ResponseContent
            internal HttpWebRequest HttpWebRequest { set; get; }
            internal RequestHttpWebRequest RequestHandler { set; get; }//主要便于后面改IsBusy属性。
        }

其GetResponseAsync实现如下:

public void GetResponseAsync(HttpRequestInfo info)
        {
            HttpWebRequest webRequest;
            StateObjectInfo state;
            InitWebRequest(info, out webRequest, out state);
            try
            {
                if (IsHttpPost)
                {
                    webRequest.Method = "POST";
                    webRequest.ContentType = "application/x-www-form-urlencoded";
                    webRequest.BeginGetRequestStream(EndRequest, state);
                }
                else { webRequest.BeginGetResponse(EndResponse, state); }

            }
            catch (Exception ex)
            {
                HandException(ex, state);
            }
        }

其中InitWebRequest的实现如下:

  private void InitWebRequest(HttpRequestInfo info, out HttpWebRequest webRequest, out StateObjectInfo state)
        {
            IsBusy = true;
            if (info.PostData != null && info.PostData.Length > 0)
            {
                IsHttpPost = true;
            }
            else
            {
                IsHttpPost = false;
            }
            if (info.Url.ToLower().Trim().StartsWith("https"))
            {
                IsHttps = true;
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
            }
            else
            {
                IsHttps = false; }
            webRequest = HttpWebRequest.CreateDefault(new Uri(info.Url)) as HttpWebRequest;
            if (IsHttps)
            {
                /*基础连接已经关闭: 发送时发生错误 */
                /*无法从传输连接中读取数据: 远程主机强迫关闭了一个现有的连接*/
                webRequest.KeepAlive = false;
                webRequest.ProtocolVersion = HttpVersion.Version10;
                webRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)";
            }
            webRequest.AllowAutoRedirect = info.AllowAutoRedirect;
            if (info.Headers != null && info.Headers.Count > 0)
            {
                foreach (string key in info.Headers.Keys)
                {
                    webRequest.Headers.Add(key, info.Headers[key]);
                }
            }
            //webRequest.Proxy = WebProxy.GetDefaultProxy();   
            //webRequest.Proxy.Credentials = CredentialCache.DefaultCredentials;     
            //webResponse.Headers.Get("Set-Cookie");   
            state = new StateObjectInfo
            {
                Buffer = new byte[1024 * 1024],
                HttpWebRequest = webRequest,
                RequestHandler = this,
                RequestInfo = info,
                ResponseInfo = new HttpResponseInfo()

            };
        }

关于该类的EndRequest、EndResponse我想就没什么说的了,其中ReadCallBack的实现如下:

   void ReadCallBack(IAsyncResult ar)
        {
            StateObjectInfo state = ar.AsyncState as StateObjectInfo;
            try
            {
                int read = state.ReadStream.EndRead(ar);
                if (read > 0)
                {
                    state.ResponseInfo.ResponseContent.Write(state.Buffer, 0, read);
                    state.ReadStream.BeginRead(state.Buffer, 0, state.Buffer.Length, ReadCallBack, state);
                }
                else
                {
                    state.ReadStream.Close();
                    state.HttpWebRequest.Abort();
                    if (state.RequestInfo.ActionCompleted != null)
                    {
                        state.ResponseInfo.ResponseContent.Seek(0, SeekOrigin.Begin); state.RequestInfo.ActionCompleted(state); }
                    state.Buffer = null;
                    state.RequestHandler.IsBusy = false;
                }
            }
            catch (Exception ex)
            {
                HandException(ex, state);
            }
        }

这里还有一个HandException方法需要我们注意:

   private void HandException(Exception ex, StateObjectInfo state)
        {
            if (state.ReadStream != null)
                state.ReadStream.Close();
            if (state.HttpWebRequest != null)
                state.HttpWebRequest.Abort();
            state.Buffer = null;
            if (state.RequestInfo.ActionException != null)
            {
                state.RequestInfo.ActionException(new HttpRequestException(state, ex));
            }
            state.RequestHandler.IsBusy = false;
        }

这里我们在使用HttpWebRequest的时候,在完成使用后一定要关闭请求流

在我们来看看一个简单的调用把:

  public static void DownLoadFile(string remoteurl, string destinationFilePath, string id)
        {
            try
            {
                if (HasIllegalCharacters(destinationFilePath, false))
                {
                    SetFileCopyed(id, "400", "HasIllegalCharacters");
                    return;
                }
                DirectoryInfo dir = new DirectoryInfo(destinationFilePath);
                FileInfo destinationFile = new FileInfo(destinationFilePath);
                if (!destinationFile.Directory.Exists)
                {
                    destinationFile.Directory.Create();
                }
                HttpRequestInfo request = new HttpRequestInfo(remoteurl);
             request.ActionCompleted = new Action<HttpContextInfo>(x =>
                {
                    if (x.ResponseInfo.StatusCode == HttpStatusCode.OK)
                    {
                        using (Stream wr = File.Open(destinationFilePath, FileMode.OpenOrCreate, FileAccess.Write), sr = x.ResponseInfo.ResponseContent)
                        {                   
                            byte[] data = new byte[1024 * 1024];
                            int readcount = sr.Read(data, 0, data.Length);
                            while (readcount > 0)
                            {
                                wr.Write(data, 0, readcount);
                                readcount = sr.Read(data, 0, data.Length);
                            }
                        }
                        SetFileCopyed(id, "200", string.Empty);
                    }
                    else
                    {
                        SetFileCopyed(id, ((int)x.ResponseInfo.StatusCode).ToString(), x.ResponseInfo.StatusDescription);
                        string message = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + " : " + remoteurl + " : " + x.ResponseInfo.StatusDescription;
                        LogManager.LogException(message);
                    }
                });
               request.ActionException = new Action<HttpRequestException>(ex =>
                {
                    Regex reg = new Regex(@"\d{3}",RegexOptions.Compiled);
                    string message = ex.Message;
                    Match m = reg.Match(message);
                    if (m.Success)
                    {
                        SetFileCopyed(id, m.Value, message);
                    }
                    else
                    {
                        SetFileCopyed(id, "503", message);
                        HttpRequestInfo newRequest = ex.HttpContextInfo.RequestInfo.Clone();
                        request.ActionCompleted = null;
                        request.ActionException = null;
                       HttpRequestFactory.AddRequestTask(newRequest);
                    }
                    message = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + " : " + ex.HttpContextInfo.RequestInfo.Url + " : " + message;
                    LogManager.LogException(message);
                });
             
          HttpRequestFactory.AddRequestTask(request);
            }
            catch (Exception ex)
            {
                SetFileCopyed(id, "-1", ex.Message);
                string message = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + " : " + remoteurl + " : " + ex.Message;
                LogManager.LogException(message);
            }
        }

        internal static bool HasIllegalCharacters(string path, bool checkAdditional)
        {
            for (int i = 0; i < path.Length; i++)
            {
                int num2 = path[i];
                if (((num2 == 0x22) || (num2 == 60)) || (((num2 == 0x3e) || (num2 == 0x7c)) || (num2 < 0x20)))
                {
                    return true;
                }
                if (checkAdditional && ((num2 == 0x3f) || (num2 == 0x2a)))
                {
                    return true;
                }
            }
            return false;
        }

对于这个调用的demo我这里就不多说,不过在调用的时候偶尔会出现:

 /*基础连接已经关闭: 发送时发生错误 */
/*无法从传输连接中读取数据: 远程主机强迫关闭了一个现有的连接*/

这样的错误,网上有一些什么改良方法,我测试后都不管用,个人猜测是与网络有关的,即使我用socket来做偶尔也会有一些问题。所以当我们遇到这些网络问题的时候,我们把我们的请求再次加入请求队列中 HttpRequestFactory.AddRequestTask(newRequest);。这一很重要的哦

HttpWebRequest类对我们做http请求做了很多封装,我们使用也很方便。但是它的性能比我们自己用socket要低很多,同时在一些处理上违背了我们的操作习惯。如我们上面的调用代码:

如果我们http返回状态是403、404...(除200以外)程序没有进入我的else,而是进入我的ActionException方法里面了,这点让我很是不爽。于是萌生了用socket来做http请求的念头

三  现在我们来看看SocketHttpRequest是如何处理HTTP请求的。它主要使用Socket来处理请求。

SocketHttpRequest和RequestHttpWebRequest一样都是采用对象的异步模式,那么也需要一个状态对象:
        class RequestSockeStateObject : HttpContextInfo
        {
            internal SocketHttpRequest RequestHandler { set; get; }
            internal Socket _socket { set; get; } //普通http请求采用socket
            internal List<byte> HeaderBuffer { set; get; }
            internal byte[] Buffer { set; get; }
            internal int ContentLength { set; get; }//http需要接收的数据长度
            internal int ReceiveLength { set; get; }//http已经接收的数据长度
            internal SslStream SslStream { set; get; }//https请求采用TcpClient,这里需要用到SslStream
        }

  public void GetResponseAsync(HttpRequestInfo info)
        {
            RequestSockeStateObject _state;
            InitRequestSockeStateObject(info, out _state);
            SocketConnection(_state);
        }

这里的InitRequestSockeStateObject和RequestHttpWebRequest的InitWebRequest方法差不多,就不在累赘了。

主要看看SocketConnection方法:

   void SocketConnection(RequestSockeStateObject _state)
        {
            try
            {
               Uri uri = new Uri(_state.RequestInfo.Url);
                IPHostEntry hostEntry = Dns.GetHostEntry(uri.Host);
                if (IsHttps)
                {
                   TcpClient tcpclient = new TcpClient();
                    tcpclient.Connect(hostEntry.AddressList, uri.Port);
                    _state._socket = tcpclient.Client;
                   SslStream sslStream = new SslStream(tcpclient.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);
                    sslStream.AuthenticateAsClient(hostEntry.HostName, new X509CertificateCollection(), SslProtocols.Ssl3 | SslProtocols.Tls, false);
                    _state.SslStream = sslStream;
                    Begin_Write(_state);
                }
                else
                {
                    Socket client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); client.Connect(hostEntry.AddressList, uri.Port);
                    _state._socket = client;
                    BeginSend(_state);
                }
            }
            catch (Exception ex)
            {
                HandException(ex, _state);
            }
        }

socket连接是需要IP和端口的,这里我们借用 Uri来获取所需端口,但是一台计算机的ip可能有很多个,实际只有一两个可以连接,所以我们这里需要调用 client.Connect(hostEntry.AddressList, uri.Port)方法,传递一个ip集合。如果是https的话,直接用socket我没有搞定,最后用SslStream搞定,不知道大家有没有其他方法。

其中Begin_Write、End_Write、Complete_Read方法是sslStream异步中所必需的方法,BeginSend、Send_Completed、Receive_Completed、RepeatReceive是socket异步中所需方法。其中Complete_Read和Receive_Completed方法相似。

  protected virtual void Complete_Read(IAsyncResult ar)
        {
            RequestSockeStateObject state = ar.AsyncState as RequestSockeStateObject;
            try
            {
                int byteCount = state.SslStream.EndRead(ar);
                if (state.ResponseInfo.Headers.Count < 1)
                {
                  SetResponseHeaders(state, byteCount); if ((state.ReceiveLength == state.ContentLength && state.ContentLength > 0))
                    {
                        EndReceive(state);
                    }
                    else
                    {
                        state.SslStream.BeginRead(state.Buffer, 0, state.Buffer.Length, Complete_Read, state);
                    }
                }
                else
                {
                    if (byteCount > 0 && byteCount==state.Buffer.Length)
                    {
                        state.ResponseInfo.ResponseContent.Write(state.Buffer, 0, byteCount);
                        state.SslStream.BeginRead(state.Buffer, 0, state.Buffer.Length, Complete_Read, state);
                    }
                    else
                    {
                        state.ResponseInfo.ResponseContent.Write(state.Buffer, 0, byteCount);
                        EndReceive(state);
                    }
                }

            }
            catch (Exception ex)
            {
                HandException(ex, state);
            }
        }

 如果是第一次接收数据流,我们必须把数据流中http头部信息取出来,再把头部信息以外的数据流写到HttpResponseInfo.ResponseContent中,如果我们已经接收的数据等于我们需要接收的数据,就表示我们已经接收完毕了。如果没有就继续接收数据。在第二次及以后所接收数据过程中,我们需要判断接收数据长度是否小于接收数组的长度,如果小于就表示接收完毕了,否则继续接收。这里的EndReceive方法如下:

 void EndReceive(RequestSockeStateObject state)
        {
            /*
             * if (state.RequestInfo.AllowAutoRedirect &&
                                   (state.ResponseInfo.StatusCode == HttpStatusCode.Found || state.ResponseInfo.StatusCode == HttpStatusCode.MovedPermanently))
                {
                    string location = state.ResponseInfo.Headers["Location"];
                    state.RequestInfo.Url = location;
                    state.RequestInfo.Headers = state.ResponseInfo.Headers;
                    state.RequestInfo.Headers.Remove("Location");
                    state.RequestInfo.Headers.Add("Referer", location);
                    Begin_Write(state);
                }
             */
            if (IsHttps)
            {
               state.SslStream.Close(); state.SslStream = null;
            }
            else
            {
                state._socket.Shutdown(SocketShutdown.Both); state._socket.Close(); state._socket = null;
            }
            if (state.RequestInfo.ActionCompleted != null)
            {
                state.ResponseInfo.ResponseContent.Seek(0, SeekOrigin.Begin); state.RequestInfo.ActionCompleted(state); }
            state.RequestHandler.IsBusy = false;

        }

EndReceive方法主要是关闭socket或则SslStream数据流,然后调用ActionCompleted方法。在这里 state.ResponseInfo.ResponseContent.Seek(0, SeekOrigin.Begin);这个方法非常重要,不然在外面的调用方法就必须调用Stream.Seek(0, SeekOrigin.Begin)来吧数据流定位开始位置。

 在SocketHttpRequest这个类中,我们是如何来获取发送的http请求信息以及如何解析http返回的header信息了?

首先来看一个GetRequestData方法,它主要是通过RequestInfo实例来获取请求信息:

 byte[] GetRequestData(RequestSockeStateObject _state)
        {
            StringBuilder bufRequest = new StringBuilder();

            Uri uri = new Uri(_state.RequestInfo.Url);
            if (!IsHttpPost)
            {
                bufRequest.Append("GET ").Append(uri.OriginalString).AppendLine(" HTTP/1.1");
            }
            else
            {
                bufRequest.Append("POST ").Append(uri.OriginalString).AppendLine(" HTTP/1.1");
                string contentLengthkey = "Content-Length";
                string contentTypekey = "Content-Type";
                List<string> headerKeys = new List<string>(_state.RequestInfo.Headers.AllKeys);
                if (headerKeys.Contains(contentLengthkey))
                {
                    _state.RequestInfo.Headers.Remove(contentLengthkey);
                }
                if (headerKeys.Contains(contentTypekey))
                {
                    _state.RequestInfo.Headers.Remove(contentTypekey);
                }
                _state.RequestInfo.Headers.Add(contentTypekey, "application/x-www-form-urlencoded");
                _state.RequestInfo.Headers.Add(contentLengthkey, _state.RequestInfo.PostData.Length.ToString());
            }
            _state.RequestInfo.Headers.Add("Host", uri.Host);
            _state.RequestInfo.Headers.Add("Connection", "keep-alive");
            if (_state.RequestInfo.Headers.Count > 0)
            {
             bufRequest.Append(_state.RequestInfo.Headers.ToString());
            }
            byte[] byteData = Encoding.ASCII.GetBytes(bufRequest.ToString());

            if (!IsHttpPost)
            {
                return byteData;
            }
            else
            {
                byte[] sendData = new byte[byteData.Length + _state.RequestInfo.PostData.Length];
              Array.Copy(byteData, 0, sendData, 0, byteData.Length);
                Array.Copy(_state.RequestInfo.PostData, 0, sendData, byteData.Length, _state.RequestInfo.PostData.Length);
                return sendData;
            }
        }

有关请求和header信息的字符串建议不要自己拼接,用WebHeaderCollection实例的ToString方法来生成,并且它把最后那个回车换行也生成

那么如何更具换回的流中的数据来设置它的返回头信息了,这里我们有一个方法SetResponseHeaders:

 void SetResponseHeaders(RequestSockeStateObject state, int bytesRead)
        {
            try
            {
                byte[] tempArray = new byte[bytesRead];
                Array.Copy(state.Buffer, 0, tempArray, 0, bytesRead);
                state.HeaderBuffer.AddRange(tempArray);
                tempArray = state.HeaderBuffer.ToArray();
                string headerSpilt = "\r\n\r\n";
                byte[] headerbyte = Encoding.ASCII.GetBytes(headerSpilt);
                int contentindex = DestTag(tempArray, headerbyte, 0, tempArray.Length);
                if (contentindex > 0)
                {
                    string headerStr = Encoding.ASCII.GetString(tempArray, 0, contentindex);
                    int startIndex = contentindex + headerbyte.Length;
                    SetResponseHeaders(headerStr, state);
                    state.ReceiveLength = tempArray.Length - startIndex;
                    state.ResponseInfo.ResponseContent.Write(tempArray, startIndex, tempArray.Length - startIndex);
                    state.HeaderBuffer.Clear();
                }
            }
            catch (Exception ex)
            {
                HandException(ex, state);
            }
        }

这里的bytesRead时我第一次接收的数据流长度,首先我们需要在返回流中找到连续的\r\n\r\n 信息,它前面是返回头信息,后面的时返回体信息。这里我们用自定义的DestTag方法来查找。SetResponseHeaders方法如下:

  void SetResponseHeaders(string headerStr, RequestSockeStateObject state)
        {
            try
            {
                string[] headers = headerStr.Split(new string[] { "\r\n" }, StringSplitOptions.RemoveEmptyEntries);
                string statline = headers[0];
               state.ResponseInfo.StatusCode = GetStatusCode(statline);
                for (int i = 1; i < headers.Length; i++)
                {
                    int index = headers[i].IndexOf(":");
                    if (index > 1)
                    {
                        string key = headers[i].Substring(0, index);
                        string value = headers[i].Substring(index + 1);
                        state.ResponseInfo.Headers.Add(key.Trim(), value.Trim());
                    }
                }
                string contentLength = state.ResponseInfo.Headers["Content-Length"];
                state.ContentLength = int.Parse(contentLength);
                state.ReceiveLength = 0;
            }
            catch (Exception ex)
            {
                HandException(ex, state);
            }
        }

以上就是这个类的主要方法,目前SocketHttpRequest对301、302暂不支持。

完整的代码如下:

SocketHttpRequest代码:

 调用代码:

 有不对的地方还请大家拍砖!

 

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