Trouble determining proper decoding of a REST response from an existing REST service using IHttpModule and response filters.

First a little background on what I am trying to achieve.

I have an application that is utilizing REST services served by ArcGIS Server and IIS7. The REST services return data in one of several different formats. I am requesting a JSON response. I want to be able to modify the response (remove or add parameters) before the response is sent to the client.

However, I am having difficulty converting the stream to a string that I can modify. To that end, I have implemented the following code in order to try to inspect the stream.

SecureModule.cs

using System;
using System.Web;

namespace SecureModuleTest
{
    public class SecureModule : IHttpModule
    {
        public void Init(HttpApplication context)
        {
            context.BeginRequest += new EventHandler(OnBeginRequest);
        }

        public void Dispose()
        {
        }

        public void OnBeginRequest(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication) sender;
            HttpContext context = application.Context;
            HttpRequest request = context.Request;
            HttpResponse response = context.Response;

            response.Filter = new ServicesFilter(response.Filter);
        }
    }
}

ServicesFilter.cs

using System;
using System.IO;
using System.Text;

namespace SecureModuleTest
{
    class ServicesFilter : MemoryStream
    {
        private readonly Stream _outputStream;
        private StringBuilder _content;

        public ServicesFilter(Stream output)
        {
            _outputStream = output;
            _content = new StringBuilder();
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            _content.Append(Encoding.UTF8.GetString(buffer, offset, count));

            using (TextWriter textWriter = new StreamWriter(@"C:\temp\content.txt", true))
            {
                textWriter.WriteLine(String.Format("Buffer: {0}", _content.ToString()));
                textWriter.WriteLine(String.Format("Length: {0}", buffer.Length));
                textWriter.WriteLine(String.Format("Offset: {0}", offset));
                textWriter.WriteLine(String.Format("Count: {0}", count));
                textWriter.WriteLine("");
                textWriter.Close();
            }

            // Modify response

            _outputStream.Write(buffer, offset, count);
        }
    }
}

The module is installed in the /ArcGIS/rest/ virtual directory and is executed via the following GET request.

http://localhost/ArcGIS/rest/services/?f=json&pretty=true

The web page displays the expected response, however, the text file tells a very different (encoded?) story.

Expect Response

{"currentVersion" : "10.0", 
  "folders" : [], 
  "services" : [

  ]
}

Text File Contents

Buffer: �      �`I�%&/m�{J�J��t��`$ؐ@������iG#)�*��eVe]f@�흼��{���{���;�N'���?\fdl��J�ɞ!���?~|?"~�G�u]���'�)��G��ݝ��G��7N����W��{��Ϛ��,��|�OR����q�
Length: 4096
Offset: 0
Count: 168

Buffer: �      �`I�%&/m�{J�J��t��`$ؐ@������iG#)�*��eVe]f@�흼��{���{���;�N'���?\fdl��J�ɞ!���?~|?"~�G�u]���'�)��G��ݝ��G��7N����W��{��Ϛ��,��|�OR����q�K���!P   
Length: 4096
Offset: 0
Count: 11

Interestingly, Fiddler depicts a similar picture.

Fiddler Request

GET http://localhost/ArcGIS/rest/services/?f=json&amp;pretty=true HTTP/1.1
Host: localhost
Connection: keep-alive
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.70 Safari/533.4
Referer: http://localhost/ArcGIS/rest/services
Cache-Control: no-cache
Pragma: no-cache
Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
Cookie: a=mWz_JFOusuGPnS3w5xx1BSUuyKGB3YZo92Dy2SUntP2MFWa8MaVq6a4I_IYBLKuefXDZANQMeqvxdGBgQoqTKz__V5EQLHwxmKlUNsaK7do.

Fiddler Response - Before Clicking Decode

HTTP/1.1 200 OK
Content-Type: text/plain;charset=utf-8
Content-Encoding: gzip
ETag: 719143506
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Thu, 10 Jun 2010 01:08:43 GMT
Content-Length: 179

��������`I�%&/m�{J�J��t��`$ؐ@������iG#)�*��eVe]f@�흼��{���{���;�N'���?\fdl��J�ɞ!���?~|?"~�G�u]���'�)��G��ݝ��G��7N����W��{��Ϛ��,��|�OR����q�K���!
P���

Fiddler Response - After Clicking Decode

HTTP/1.1 200 OK
Content-Type: text/plain;charset=utf-8
ETag: 719143506
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Thu, 10 Jun 2010 01:08:43 GMT
Content-Length: 80

{"currentVersion" : "10.0", 
  "folders" : [], 
  "services" : [

  ]
}

I think that the problem may be a result of compression and/or chunking of data (this might be why I am receiving two calls to ServicesFilter.Write(...), however, I have not yet been able to solve the issue.

How might I decode, unzip, and otherwise convert the byte stream into the string I know it should be for modification by my filter?

ansaurus

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Trouble determining proper decoding of a REST response from an existing REST service using IHttpModule and response filters.

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