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  • Parsing concatenated, non-delimited XML messages from TCP-stream using C#

    - by thaller
    I am trying to parse XML messages which are send to my C# application over TCP. Unfortunately, the protocol can not be changed and the XML messages are not delimited and no length prefix is used. Moreover the character encoding is not fixed but each message starts with an XML declaration <?xml>. The question is, how can i read one XML message at a time, using C#. Up to now, I tried to read the data from the TCP stream into a byte array and use it through a MemoryStream. The problem is, the buffer might contain more than one XML messages or the first message may be incomplete. In these cases, I get an exception when trying to parse it with XmlReader.Read or XmlDocument.Load, but unfortunately the XmlException does not really allow me to distinguish the problem (except parsing the localized error string). I tried using XmlReader.Read and count the number of Element and EndElement nodes. That way I know when I am finished reading the first, entire XML message. However, there are several problems. If the buffer does not yet contain the entire message, how can I distinguish the XmlException from an actually invalid, non-well-formed message? In other words, if an exception is thrown before reading the first root EndElement, how can I decide whether to abort the connection with error, or to collect more bytes from the TCP stream? If no exception occurs, the XmlReader is positioned at the start of the root EndElement. Casting the XmlReader to IXmlLineInfo gives me the current LineNumber and LinePosition, however it is not straight forward to get the byte position where the EndElement really ends. In order to do that, I would have to convert the byte array into a string (with the encoding specified in the XML declaration), seek to LineNumber,LinePosition and convert that back to the byte offset. I try to do that with StreamReader.ReadLine, but the stream reader gives no public access to the current byte position. All this seams very inelegant and non robust. I wonder if you have ideas for a better solution. Thank you. EDIT: I looked around and think that the situation is as follows (I might be wrong, corrections are welcome): I found no method so that the XmlReader can continue parsing a second XML message (at least not, if the second message has an XmlDeclaration). XmlTextReader.ResetState could do something similar, but for that I would have to assume the same encoding for all messages. Therefor I could not connect the XmlReader directly to the TcpStream. After closing the XmlReader, the buffer is not positioned at the readers last position. So it is not possible to close the reader and use a new one to continue with the next message. I guess the reason for this is, that the reader could not successfully seek on every possible input stream. When XmlReader throws an exception it can not be determined whether it happened because of an premature EOF or because of a non-wellformed XML. XmlReader.EOF is not set in case of an exception. As workaround I derived my own MemoryBuffer, which returns the very last byte as a single byte. This way I know that the XmlReader was really interested in the last byte and the following exception is likely due to a truncated message (this is kinda sloppy, in that it might not detect every non-wellformed message. However, after appending more bytes to the buffer, sooner or later the error will be detected. I could cast my XmlReader to the IXmlLineInfo interface, which gives access to the LineNumber and the LinePosition of the current node. So after reading the first message I remember these positions and use it to truncate the buffer. Here comes the really sloppy part, because I have to use the character encoding to get the byte position. I am sure you could find test cases for the code below where it breaks (e.g. internal elements with mixed encoding). But up to now it worked for all my tests. The parser class follows here -- may it be useful (I know, its very far from perfect...) class XmlParser { private byte[] buffer = new byte[0]; public int Length { get { return buffer.Length; } } // Append new binary data to the internal data buffer... public XmlParser Append(byte[] buffer2) { if (buffer2 != null && buffer2.Length > 0) { // I know, its not an efficient way to do this. // The EofMemoryStream should handle a List<byte[]> ... byte[] new_buffer = new byte[buffer.Length + buffer2.Length]; buffer.CopyTo(new_buffer, 0); buffer2.CopyTo(new_buffer, buffer.Length); buffer = new_buffer; } return this; } // MemoryStream which returns the last byte of the buffer individually, // so that we know that the buffering XmlReader really locked at the last // byte of the stream. // Moreover there is an EOF marker. private class EofMemoryStream: Stream { public bool EOF { get; private set; } private MemoryStream mem_; public override bool CanSeek { get { return false; } } public override bool CanWrite { get { return false; } } public override bool CanRead { get { return true; } } public override long Length { get { return mem_.Length; } } public override long Position { get { return mem_.Position; } set { throw new NotSupportedException(); } } public override void Flush() { mem_.Flush(); } public override long Seek(long offset, SeekOrigin origin) { throw new NotSupportedException(); } public override void SetLength(long value) { throw new NotSupportedException(); } public override void Write(byte[] buffer, int offset, int count) { throw new NotSupportedException(); } public override int Read(byte[] buffer, int offset, int count) { count = Math.Min(count, Math.Max(1, (int)(Length - Position - 1))); int nread = mem_.Read(buffer, offset, count); if (nread == 0) { EOF = true; } return nread; } public EofMemoryStream(byte[] buffer) { mem_ = new MemoryStream(buffer, false); EOF = false; } protected override void Dispose(bool disposing) { mem_.Dispose(); } } // Parses the first xml message from the stream. // If the first message is not yet complete, it returns null. // If the buffer contains non-wellformed xml, it ~should~ throw an exception. // After reading an xml message, it pops the data from the byte array. public Message deserialize() { if (buffer.Length == 0) { return null; } Message message = null; Encoding encoding = Message.default_encoding; //string xml = encoding.GetString(buffer); using (EofMemoryStream sbuffer = new EofMemoryStream (buffer)) { XmlDocument xmlDocument = null; XmlReaderSettings settings = new XmlReaderSettings(); int LineNumber = -1; int LinePosition = -1; bool truncate_buffer = false; using (XmlReader xmlReader = XmlReader.Create(sbuffer, settings)) { try { // Read to the first node (skipping over some element-types. // Don't use MoveToContent here, because it would skip the // XmlDeclaration too... while (xmlReader.Read() && (xmlReader.NodeType==XmlNodeType.Whitespace || xmlReader.NodeType==XmlNodeType.Comment)) { }; // Check for XML declaration. // If the message has an XmlDeclaration, extract the encoding. switch (xmlReader.NodeType) { case XmlNodeType.XmlDeclaration: while (xmlReader.MoveToNextAttribute()) { if (xmlReader.Name == "encoding") { encoding = Encoding.GetEncoding(xmlReader.Value); } } xmlReader.MoveToContent(); xmlReader.Read(); break; } // Move to the first element. xmlReader.MoveToContent(); // Read the entire document. xmlDocument = new XmlDocument(); xmlDocument.Load(xmlReader.ReadSubtree()); } catch (XmlException e) { // The parsing of the xml failed. If the XmlReader did // not yet look at the last byte, it is assumed that the // XML is invalid and the exception is re-thrown. if (sbuffer.EOF) { return null; } throw e; } { // Try to serialize an internal data structure using XmlSerializer. Type type = null; try { type = Type.GetType("my.namespace." + xmlDocument.DocumentElement.Name); } catch (Exception e) { // No specialized data container for this class found... } if (type == null) { message = new Message(); } else { // TODO: reuse the serializer... System.Xml.Serialization.XmlSerializer ser = new System.Xml.Serialization.XmlSerializer(type); message = (Message)ser.Deserialize(new XmlNodeReader(xmlDocument)); } message.doc = xmlDocument; } // At this point, the first XML message was sucessfully parsed. // Remember the lineposition of the current end element. IXmlLineInfo xmlLineInfo = xmlReader as IXmlLineInfo; if (xmlLineInfo != null && xmlLineInfo.HasLineInfo()) { LineNumber = xmlLineInfo.LineNumber; LinePosition = xmlLineInfo.LinePosition; } // Try to read the rest of the buffer. // If an exception is thrown, another xml message appears. // This way the xml parser could tell us that the message is finished here. // This would be prefered as truncating the buffer using the line info is sloppy. try { while (xmlReader.Read()) { } } catch { // There comes a second message. Needs workaround for trunkating. truncate_buffer = true; } } if (truncate_buffer) { if (LineNumber < 0) { throw new Exception("LineNumber not given. Cannot truncate xml buffer"); } // Convert the buffer to a string using the encoding found before // (or the default encoding). string s = encoding.GetString(buffer); // Seek to the line. int char_index = 0; while (--LineNumber > 0) { // Recognize \r , \n , \r\n as newlines... char_index = s.IndexOfAny(new char[] {'\r', '\n'}, char_index); // char_index should not be -1 because LineNumber>0, otherwise an RangeException is // thrown, which is appropriate. char_index++; if (s[char_index-1]=='\r' && s.Length>char_index && s[char_index]=='\n') { char_index++; } } char_index += LinePosition - 1; var rgx = new System.Text.RegularExpressions.Regex(xmlDocument.DocumentElement.Name + "[ \r\n\t]*\\>"); System.Text.RegularExpressions.Match match = rgx.Match(s, char_index); if (!match.Success || match.Index != char_index) { throw new Exception("could not find EndElement to truncate the xml buffer."); } char_index += match.Value.Length; // Convert the character offset back to the byte offset (for the given encoding). int line1_boffset = encoding.GetByteCount(s.Substring(0, char_index)); // remove the bytes from the buffer. buffer = buffer.Skip(line1_boffset).ToArray(); } else { buffer = new byte[0]; } } return message; } }

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  • Capturing and Transforming ASP.NET Output with Response.Filter

    - by Rick Strahl
    During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • DirectX: Render to a screen buffer without using a render target

    - by knight666
    Hello, I'm writing an open source 2D game engine, and I want to support as many devices and platforms as possible. I currently only have Windows Mobile though. I'm rendering using DirectX Mobile, with DirectDraw as a fallback path. However, I've run into a bit of trouble. It seems that while the reference driver supports createRenderTarget, many many many physical devices do not. I need some way to render to the screen without using a render target, because I render sprites using textured quads, but I also need to be able to draw individual pixels. This is how I do it right now: // save old values if (Error::Failed(m_D3DDevice->GetRenderTarget(&m_D3DOldTarget))) { ERROR_EXPLAIN("Could not retrieve backbuffer."); return false; } // clear render surface if (Error::Failed(m_D3DDevice->SetRenderTarget(m_D3DRenderSurface, NULL))) { ERROR_EXPLAIN("Could not set render target to render texture."); return false; } if (Error::Failed (m_D3DDevice->Clear( 0, NULL, // target rectangle D3DMCLEAR_TARGET, D3DMCOLOR_XRGB(0, 0, 0), // clear color 1.0f, 0 ) ) ) { ERROR_EXPLAIN("Failed to clear render texture."); return false; } D3DMLOCKED_RECT render_rect; if (Error::Failed(m_D3DRenderSurface->LockRect(&render_rect, NULL, NULL))) { ERROR_EXPLAIN("Failed to lock render surface pixels."); } else { m_D3DBackSurf->SetBuffer((Pixel*)render_rect.pBits); m_D3DRenderSurface->UnlockRect(); } // begin scene if (Error::Failed(m_D3DDevice->BeginScene())) { ERROR_EXPLAIN("Failed to start rendering."); return false; } // ===================== // example rendering // ===================== // some other stuff, but the most important part of rendering a sprite: device->SetTexture(0, m_Texture)); device->SetStreamSource(0, m_VertexBuffer, sizeof(Vertex)); device->DrawPrimitive(D3DMPT_TRIANGLELIST, 0, 2); // plotting a pixel Surface* target = (Surface*)Device::GetRenderMethod()->GetRenderTarget(); buffer = target->GetBuffer(); buffer[somepixel] = MAKECOLOR(255, 0, 0); // end scene if (Error::Failed(device->EndScene())) { ERROR_EXPLAIN("Failed to end scene."); return false; } // clear screen if (Error::Failed(device->SetRenderTarget(m_D3DOldTarget, NULL))) { ERROR_EXPLAIN("Couldn't set render target to backbuffer."); return false; } if (Error::Failed(device->GetBackBuffer ( 0, D3DMBACKBUFFER_TYPE_MONO, &m_D3DBack ) ) ) { ERROR_EXPLAIN("Couldn't retrieve backbuffer."); return false; } RECT dest = { 0, 0, Device::GetWidth(), Device::GetHeight() }; if (Error::Failed( device->StretchRect ( m_D3DRenderSurface, NULL, m_D3DBack, &dest, D3DMTEXF_NONE ) ) ) { ERROR_EXPLAIN("Failed to stretch render texture to backbuffer."); return false; } if (Error::Failed(device->Present(NULL, NULL, NULL, NULL))) { ERROR_EXPLAIN("Failed to present device."); return false; } I'm looking for a way to do the same thing (render sprites using hardware acceleration and plot pixels on a buffer) without using a render target. Thanks in advance.

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  • How to use the buffer on SocketAsyncEventArgs object

    - by Rob
    We're stuck with using buffers on the SocketAsyncEventArgs object. With the old socket method we'd cast our state object, like this: clientState cs = (clientState)asyncResult.AsyncState; However, the 3.5 framework is different. With have strings arriving from the client in chunks and we can't seem to work out how the buffers work so we can process an entire string when we find a char3. Code at the moment: private void ProcessReceive(SocketAsyncEventArgs e) { string content = string.Empty; // Check if the remote host closed the connection. if (e.BytesTransferred > 0) { if (e.SocketError == SocketError.Success) { Socket s = e.UserToken as Socket; //asyncResult.AsyncState; Int32 bytesTransferred = e.BytesTransferred; // Get the message received from the listener. content += Encoding.ASCII.GetString(e.Buffer, e.Offset, bytesTransferred); if (content.IndexOf(Convert.ToString((char)3)) > -1) { e.BufferList = null; // Increment the count of the total bytes receive by the server. Interlocked.Add(ref this.totalBytesRead, bytesTransferred); } else { content += Encoding.ASCII.GetString(e.Buffer, e.Offset, bytesTransferred); ProcessReceive(e); } } else { this.CloseClientSocket(e); } } }

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  • scipy.io typeerror:buffer too small for requested array

    - by kartiku
    I have a problem in python. I'm using scipy, where i use scipy.io to load a .mat file. The .mat file was created using MATLAB. listOfFiles = os.listdir(loadpathTrain) for f in listOfFiles: fullPath = loadpathTrain + '/' + f mat_contents = sio.loadmat(fullPath) print fullPath Here's the error: Traceback (most recent call last): File "tryRankNet.py", line 1112, in demo() File "tryRankNet.py", line 645, in demo mat_contents = sio.loadmat(fullPath) File "/usr/lib/python2.6/dist-packages/scipy/io/matlab/mio.py", line 111, in loadmat matfile_dict = MR.get_variables() File "/usr/lib/python2.6/dist-packages/scipy/io/matlab/miobase.py", line 356, in get_variables getter = self.matrix_getter_factory() File "/usr/lib/python2.6/dist-packages/scipy/io/matlab/mio5.py", line 602, in matrix_getter_factory return self._array_reader.matrix_getter_factory() File "/usr/lib/python2.6/dist-packages/scipy/io/matlab/mio5.py", line 274, in matrix_getter_factory tag = self.read_dtype(self.dtypes['tag_full']) File "/usr/lib/python2.6/dist-packages/scipy/io/matlab/miobase.py", line 171, in read_dtype order='F') TypeError: buffer is too small for requested array The whole thing is in a loop, and I checked the size of the file where it gives the error by loading it interactively in IDLE. The size is (9,521), which is not at all huge. I tried to find if I'm supposed to clear the buffer after each iteration of the loop, but I could not find anything. Any help would be appreciated. Thanks.

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  • Command not write in buffer with Expect

    - by Romuald
    Hello, I try to backup a Linkproof device with expect script and i have some trouble. It's my first script in expect and i have reach my limits ;) #!/usr/bin/expect spawn ssh @IPADDRESS expect "username:" # Send the username, and then wait for a password prompt. send "@username\r" expect "password:" # Send the password, and then wait for a shell prompt. send "@password\r" expect "#" # Send the prebuilt command, and then wait for another shell prompt. send "system config immediate\r" #Send space to pass the pause expect -re "^ *--More--\[^\n\r]*" send "" expect -re "^ *--More--\[^\n\r]*" send "" expect -re "^ *--More--\[^\n\r]*" send "" # Capture the results of the command into a variable. This can be displayed, or written to disk. sleep 10 expect -re .* set results $expect_out(buffer) # Copy buffer in a file set config [open linkproof.txt w] puts $config $results close $config # Exit the session. expect "#" send "logout\r" expect eof The content of the output file: The authenticity of host '@IP (XXX.XXX.XXX.XXX)' can't be established. RSA key fingerprint is XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX. Are you sure you want to continue connecting (yes/no)? @username Please type 'yes' or 'no': @password Please type 'yes' or 'no': system config immediate Please type 'yes' or 'no': Like you can see, the result of the command is not in the file. Could you, please, help me to understantd why ? Thanks for your help. Romuald

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  • OpenGL depth buffer on Android

    - by kayahr
    I'm currently learning OpenGL ES programming on Android (2.1). I started with the obligatory rotating cube. It's rotating fine but I can't get the depth buffer to work. The polygons are always displayed in the order the GL commands render them. I do this during initialization of GL: gl.glClearColor(.5f, .5f, .5f, 1); gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearDepthf(1f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); On surface-change I do this: gl.glViewport(0, 0, width, height); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); GLU.gluPerspective(gl, 45.0f, (float) width / (float) height, 0.1f, 100f); When I enable backface culling then everything looks correct. But backface culling is only a speed-optimization so it should also work with only the depth buffer or not? So what is missing here?

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  • Silverlight Socket Constantly Returns With Empty Buffer

    - by Benny
    I am using Silverlight to interact with a proxy application that I have developed but, without the proxy sending a message to the Silverlight application, it executes the receive completed handler with an empty buffer ('\0's). Is there something I'm doing wrong? It is causing a major memory leak. this._rawBuffer = new Byte[this.BUFFER_SIZE]; SocketAsyncEventArgs receiveArgs = new SocketAsyncEventArgs(); receiveArgs.SetBuffer(_rawBuffer, 0, _rawBuffer.Length); receiveArgs.Completed += new EventHandler<SocketAsyncEventArgs>(ReceiveComplete); this._client.ReceiveAsync(receiveArgs); if (args.SocketError == SocketError.Success && args.LastOperation == SocketAsyncOperation.Receive) { // Read the current bytes from the stream buffer int bytesRecieved = this._client.ReceiveBufferSize; // If there are bytes to process else the connection is lost if (bytesRecieved > 0) { try { //Find out what we just received string messagePart = UTF8Encoding.UTF8.GetString(_rawBuffer, 0, _rawBuffer.GetLength(0)); //Take out any trailing empty characters from the message messagePart = messagePart.Replace('\0'.ToString(), ""); //Concatenate our current message with any leftovers from previous receipts string fullMessage = _theRest + messagePart; int seperator; //While the index of the seperator (LINE_END defined & initiated as private member) while ((seperator = fullMessage.IndexOf((char)Messages.MessageSeperator.Terminator)) > 0) { //Pull out the first message available (up to the seperator index string message = fullMessage.Substring(0, seperator); //Queue up our new message _messageQueue.Enqueue(message); //Take out our line end character fullMessage = fullMessage.Remove(0, seperator + 1); } //Save whatever was NOT a full message to the private variable used to store the rest _theRest = fullMessage; //Empty the queue of messages if there are any while (this._messageQueue.Count > 0) { ... } } catch (Exception e) { throw e; } // Wait for a new message if (this._isClosing != true) Receive(); } } Thanks in advance.

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  • Boost Asio UDP retrieve last packet in socket buffer

    - by Alberto Toglia
    I have been messing around Boost Asio for some days now but I got stuck with this weird behavior. Please let me explain. Computer A is sending continuos udp packets every 500 ms to computer B, computer B desires to read A's packets with it own velocity but only wants A's last packet, obviously the most updated one. It has come to my attention that when I do a: mSocket.receive_from(boost::asio::buffer(mBuffer), mEndPoint); I can get OLD packets that were not processed (almost everytime). Does this make any sense? A friend of mine told me that sockets maintain a buffer of packets and therefore If I read with a lower frequency than the sender this could happen. ¡? So, the first question is how is it possible to receive the last packet and discard the ones I missed? Later I tried using the async example of the Boost documentation but found it did not do what I wanted. http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/tutorial/tutdaytime6.html From what I could tell the async_receive_from should call the method "handle_receive" when a packet arrives, and that works for the first packet after the service was "run". If I wanted to keep listening the port I should call the async_receive_from again in the handle code. right? BUT what I found is that I start an infinite loop, it doesn't wait till the next packet, it just enters "handle_receive" again and again. I'm not doing a server application, a lot of things are going on (its a game), so my second question is, do I have to use threads to use the async receive method properly, is there some example with threads and async receive? Thanks for you attention.

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  • Flushing writes in buffer of Memory Controller to DDR device

    - by Rohit
    At some point in my code, I need to push the writes in my code all the way to the DIMM or DDR device. My requirement is to ensure the write reaches the row,ban,column of the DDR device on the DIMM. I need to read what I've written to the main memory. I do not want caching to get me the value. Instead after writing I want to fetch this value from main memory(DIMM's). So far I've been using Intel's x86 instruction wbinvd(write back and invalidate cache). However this means the caches and TLB are flushed. Write-back requests go to the main memory. However, there is a reasonable amount of time this data might reside in the write buffer of the Memory Controller( Intel calls it integrated memory controller or IMC). The Memory Controller might take some more time depending on the algorithm that runs in the Memory Controller to handle writes. Is there a way I force all existing or pending writes in the write buffer of the memory controller to the DRAM devices ?? What I am looking for is something more direct and more low-level than wbinvd. If you could point me to right documents or specs that describe this I would be grateful. Generally, the IMC has a several registers which can be written or read from. From looking at the specs for that for the chipset I could not find anything useful. Thanks for taking the time to read this.

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  • Open an Emacs buffer when a command tries to open an editor in shell-mode

    - by Chris Conway
    I like to use Emacs' shell mode, but it has a few deficiencies. One of those is that it's not smart enough to open a new buffer when a shell command tries to invoke an editor. For example with the environment variable VISUAL set to vim I get the following from svn propedit: $ svn propedit svn:externals . "svn-prop.tmp" 2L, 149C[1;1H ~ [4;1H~ [5;1H~ [6;1H~ [7;1H~ ... (It may be hard to tell from the representation, but it's a horrible, ugly mess.) With VISUAL set to "emacs -nw", I get $ svn propedit svn:externals . emacs: Terminal type "dumb" is not powerful enough to run Emacs. It lacks the ability to position the cursor. If that is not the actual type of terminal you have, use the Bourne shell command `TERM=... export TERM' (C-shell: `setenv TERM ...') to specify the correct type. It may be necessary to do `unset TERMINFO' (C-shell: `unsetenv TERMINFO') as well.svn: system('emacs -nw svn-prop.tmp') returned 256 (It works with VISUAL set to just emacs, but only from inside an Emacs X window, not inside a terminal session.) Is there a way to get shell mode to do the right thing here and open up a new buffer on behalf of the command line process?

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  • Can I move the Flash temp folder/buffer (Win64)

    - by xciter
    I need to move the folder in which the Flash plugin saves its temporary files (so NOT the browser cache folder). Normally, the plugin saves its buffered content in the default temporary folder of the operating system. However, I do not want to move that folder. In other words, I only need to change the folder which flash uses. My operating system is Windows 7 64-bit. I am using the latest version of the flash plugin.

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  • Debian tuning for increasing read/write buffer.

    - by Claudiu
    Is there a way to modify Debian settings so the memory could be used more for disk read/write caching ? I am already using RAID 0 but thats not enough for multiple users, and the disk is almost struggled. Torrents use the disk very much and rTorrent doesn't have cache settings.

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  • How to measure Citrix receiver video buffer framerate?

    - by Rex Hardin
    How can I measure Citrix receiver framerate at the client end? I've tried FRAPS, but that doesn't seem to work. Is there a way to determine how many "frames" are sent per second from the client side? Assume a Windows 7 client connecting to a Windows 7 VM using the Citrix web plugin. To restate the question, how could I potentially measure the Citrix client's frame display rate for some 200px^2 area? Assume that the remote VM will try and play back a frame sequence at 24fps. Will any frames drop?

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  • Trying to make changes to the size of the events buffer in prelude-ids auditd plugin

    - by tharris
    I am running systems using the prelude-ids plugin for auditd. When the manager is up every thing works fine however I have a requirement that when the clients can't talk to the manager they should store no more than 250MB of messages, and when they hit that point they should start deleting the oldest events. All I can find is that audispd can be set to an overflow action of ignore,syslog,suspend,single, and halt none of which meet my requirement, and several of which I really cannot use. Does anyone know a way to do this? I know the events get stored in /var/spool/prelude/auditd/global, but I can't find anything about configuring how things are stored here. There are usually several files in the global directory but only 2 of them ever go above 0 in size, data0 and data0.journal.

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  • How do I increase copy/paste buffer size in Linux

    - by Thrawn
    Hi all, I'm trying to copy and paste lines of code to the linux terminal. However, I've noticed that when the copied text is too long (let's say, 60 or more lines), it gets trimmed and altered in an apparently random way (e.g. some characters missing). I found the same problem in Ubuntu Karmic Koala, Fedora 10 and Ubuntu Jaunty Jackalope. Any clue why this happens and if I can increase the size of safely copy/pasteable text? Thanks!

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  • less maximum buffer size?

    - by Tyzoid
    I was messing around with my system and found a novel way to use up memory, but it seems that the less command only holds a limited amount of data before stopping/killing the command. To test, run (careful! uses lots of system memory very fast!) $ cat /dev/zero | less From my testing, it looks like the command is killed after less reaches 2.5 gigabytes of memory, but I can't find anything in the man page that suggests that it would limit it in such a way. In addition, I couldn't find any documentation via the google on the subject. Any light to this quite surprising discovery would be great! System Information: Quad core intel i7, 8gb ram. $ uname -a Linux Tyler-Work 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux $ less --version less 458 (GNU regular expressions) Copyright (C) 1984-2012 Mark Nudelman less comes with NO WARRANTY, to the extent permitted by law. For information about the terms of redistribution, see the file named README in the less distribution. Homepage: http://www.greenwoodsoftware.com/less $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 14.04 LTS Release: 14.04 Codename: trusty

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  • wm_concat function and small characer buffer

    - by Ruslan
    Hi, i have select like: select substr(account,1,4), currency, amount, module,count(*) quan, wm_concat(id) ids from all_transactions group by substr(account,1,4), currency, amount, module But sometimes COUNT(*) is more then 600. In that case i get: 'ORA-06502: PL/SQL: : character string buffer too small' Is there any way out to keep wm_concat(id) for all records? Because excluding this function for entries with big COUNT(*) is the way out.

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  • Linux Kernel - traverse to buffer heads

    - by CodeRanger
    In the Linux kernel, is there a way to traverse down to the buffer_heads from within a module? I can see how to get to struct bio (task_struct macro: current-bio). But how can I get to the buffer heads? The buffer_head struct holds some information I'd like to obtain at any point regarding physical block numbers.

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  • Dereferencing within a buffer

    - by kaykun
    Let's say I had a char pointer pointing to a buffer that contained these values (in hex): 12 34 56 78 00 00 80 00 I want to modify the last two bytes to a short value of 42. So I would think I would have to do something like this: (short)*(pointer+6)=42; The compiler doesn't complain but it does not do what I'm expecting it to do. Can someone tell me the correct way to assign the value?

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  • OpenGL Motion blur with the accumulation buffer

    - by Klaus
    Hello, I'm trying to achieve a motion blur effect in my OpenGL application. I read somewhere this solution, using the accumulation buffer: glAccum(GL_MULT, 0.90); glAccum(GL_ACCUM, 0.10); glAccum(GL_RETURN, 1.0); glFlush(); at the end of the render loop. But nothing happens... What I am missing ?

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