上传大文件问题

Question

在网上找到一个上传大文件的方法，有些不明白的地方，请大家指教：

public void Application_BeginRequest(object sender, EventArgs e)
        {
            HttpApplication application = sender as HttpApplication;
            HttpWorkerRequest workRequest = GetWorkerRequest(application.Context);

            if (workRequest != null)
            {
                HttpRequest request = application.Request;
                byte[] tempBuffer;

                //tempBuffer为何总是为null?
                tempBuffer = workRequest.GetPreloadedEntityBody();

                if (IsUploadRequest(request))
                {
                    Encoding encode = request.ContentEncoding;
                   

                    int bytesRead = 0;
                    int read = 0;
                    int count = 8192;
                    byte[] buffer;
                    //为何当上传的文件很大的时候（我用了几百M、1.+G、3.+G的做测试，当用3.+G做测试时）length为负
                    long length = long.Parse(workRequest.GetKnownRequestHeader(HttpWorkerRequest.HeaderContentLength));
                    tempBuffer = tempBuffer == null ? new byte[count] : tempBuffer;

                    buffer = new byte[length];
                    count = tempBuffer.Length;

                    bytesRead = tempBuffer.Length;

                    while (workRequest.IsClientConnected() && !workRequest.IsEntireEntityBodyIsPreloaded() && bytesRead < length)
                    {
                        if (bytesRead + count > length)
                        {
                            count = (int)(length - bytesRead);
                            tempBuffer = new byte[count];
                        }

                        read = workRequest.ReadEntityBody(tempBuffer, count);

                        Buffer.BlockCopy(tempBuffer, 0, buffer, bytesRead, read);

                        bytesRead += read;
                    }

                    if (workRequest.IsClientConnected() && !workRequest.IsEntireEntityBodyIsPreloaded())
                    {
                        // 传入已上传完的数据
                        //
                        InjectTextParts(workRequest, buffer);
                    }
                }
            }
        }

public HttpWorkerRequest GetWorkerRequest(HttpContext context)
        {
            IServiceProvider provider = (IServiceProvider)HttpContext.Current;
            return (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));
        }

        /// <summary>
        /// 是否为附件上传
        /// 判断的根据是ContentType中有无multipart/form-data
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        public bool IsUploadRequest(HttpRequest request)
        {
            string s1 = request.ContentType, s2 = "multipart/form-data";
            return (string.Compare(s1, 0, s2, 0, s2.Length, true, CultureInfo.InvariantCulture) == 0);
        }

        /// <summary>
        /// 传入已上传完的数据
        /// </summary>
        /// <param name="request"></param>
        /// <param name="textParts"></param>
        public void InjectTextParts(HttpWorkerRequest request, byte[] textParts)
        {
            BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.NonPublic;

            Type type = request.GetType();

            while ((type != null) && (type.FullName != "System.Web.Hosting.ISAPIWorkerRequest"))
            {
                type = type.BaseType;
            }

            if (type != null)
            {
                type.GetField("_contentAvailLength", bindingFlags).SetValue(request, textParts.Length);
                type.GetField("_contentTotalLength", bindingFlags).SetValue(request, textParts.Length);
                type.GetField("_preloadedContent", bindingFlags).SetValue(request, textParts);
                type.GetField("_preloadedContentRead", bindingFlags).SetValue(request, true);
            }
        }

 主要有以下三个问题：
1、tempBuffer = workRequest.GetPreloadedEntityBody();----tempBuffer为何总是为null?
2、long length = long.Parse(workRequest.GetKnownRequestHeader(HttpWorkerRequest.HeaderContentLength));为何当上传的文件很大的时候（我用了几百M、1.+G、3.+G的做测试，当用3.+G做测试时）length为负
3、这样上传能上传多大的文件，我只上传了几十M就上传不了了，长度太大

关于第一个问题，网上有人说要用IIS，不用vs自带的服务器，我IIS7还是不行
希望大家不吝赐教

Answer 1

Please try the following coding:

  protected void Application_BeginRequest(object sender, EventArgs e)
        {
            HttpRequest request = HttpContext.Current.Request;
            if (request.ContentType.Contains("multipart/form-data") && request.ContentLength > 4194304)//4096000 is maxRequestLength
            {
                HttpApplication app = sender as HttpApplication;
                HttpContext context = app.Context;

                //HttpWorkerRequest workerRequest = (HttpWorkerRequest)(context.GetType().GetProperty("WorkerRequest", BindingFlags.Instance | BindingFlags.NonPublic).GetValue(context, null));

                IServiceProvider provider = (IServiceProvider)HttpContext.Current;
                HttpWorkerRequest workerRequest = (HttpWorkerRequest)provider.GetService(typeof(HttpWorkerRequest));


                if (workerRequest.HasEntityBody())
                {

                    //int contentlen = Convert.ToInt32(wr.GetKnownRequestHeader(HttpWorkerRequest.HeaderContentLength));
                    //buffer = wr.GetPreloadedEntityBody();
                    //int received = buffer.Length;
                    //int totalrecv = received;


                    // get the total body length
                    int requestLength = workerRequest.GetTotalEntityBodyLength();
                    // Get the initial bytes loaded
                    int initialBytes = 0;

                    if (workerRequest.GetPreloadedEntityBody() != null)
                        initialBytes = workerRequest.GetPreloadedEntityBody().Length;

                    if (!workerRequest.IsEntireEntityBodyIsPreloaded())
                    {
                        byte[] buffer = new byte[52000];
                        // Set the received bytes to initial bytes before start reading
                        int receivedBytes = initialBytes;
                        while (requestLength - receivedBytes >= initialBytes)
                        {
                            // Read another set of bytes
                            initialBytes = workerRequest.ReadEntityBody(buffer, buffer.Length);

                            // Update the received bytes
                            receivedBytes += initialBytes;
                        }

                        initialBytes = workerRequest.ReadEntityBody(buffer, requestLength - receivedBytes);
                    }
                }

                context.Response.Redirect("../UploadError.aspx");//Redirect to custom error page.
            }
        }

Answer 2

你好，

一般上述代码用来避免上传大文件时出现一些不可预测的错误的。

比如我们在web.config中配置了上传的最大限制，如果你超过了这个限制，你会看到一个似乎服务器没响应的页面，什么连接有问题的页面。

这时我们可以自定义一个HttpModule，调用花雨透提供的代码，对传过来的数据进行预处理，以避免出现上述情况。

在上面代码中，你可以选择保存该数据，也可以忽略它，但是必须要把传过来的数据过一遍，否则还是会报错。

即必须要至少要有下面这段代码：

while (requestLength - receivedBytes >= initialBytes)
                        {
                            // Read another set of bytes
                            initialBytes = workerRequest.ReadEntityBody(buffer, buffer.Length);

                            // Update the received bytes
                            receivedBytes += initialBytes;
                        }

你可以在上面的代码中保存数据。

 建议你用花雨透 的方法试试。

 

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