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• question about joGL (glTexImage2D)

  - by Nour

  Hi everybody I was trying to load a texture using joGL library but it seems that something is missing when using this method glTexImage2D at : IOStream wdis = new IOStream(fileName); wdis.skipBytes(18); int width = wdis.readIntW(); // dis.skipBytes(2); int height = wdis.readIntW(); // dis.skipBytes(2); wdis.skipBytes(28); byte buf[] = new byte[wdis.available()]; wdis.read(buf); wdis.close(); gl.glBindTexture(GL.GL_TEXTURE_2D, BMPtextures[index]); gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, 3, width, height, 0, GL.GL_BGR, GL.GL_UNSIGNED_BYTE, buf); gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR); gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR); as IOStream is a class that extends DataInputStream it shows a message that glTexImage2D(int,int,int,int,int,int,int,int,byte[]) is not found at javax.media.opengl.GL I couldn't figure the problem her because it's an open source code and it seems to work perfectly with my friends but unfortunately not with me even though we are using the same library and the same JDK version what shall I do ??

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• Upload image from J2ME client to a Servlet

  - by Akash

  I want to send an image from a J2ME client to a Servlet. I am able to get a byte array of the image and send it using HTTP POST. conn = (HttpConnection) Connector.open(url, Connector.READ_WRITE, true); conn.setRequestMethod(HttpConnection.POST); conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); os.write(bytes, 0, bytes.length); // bytes = byte array of image This is the Servlet code: String line; BufferedReader r1 = new BufferedReader(new InputStreamReader(in)); while ((line = r1.readLine()) != null) { System.out.println("line=" + line); buf.append(line); } String s = buf.toString(); byte[] img_byte = s.getBytes(); But the problem I found is, when I send bytes from the J2ME client, some bytes are lost. Their values are 0A and 0D hex. Exactly, the Carriage Return and Line Feed. Thus, either POST method or readLine() are not able to accept 0A and 0D values. Any one have any idea how to do this, or how to use any another method?

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• How to convert an InputStream to a DataHandler?

  - by pcorey

  I'm working on a java web application in which files will be stored in a database. Originally we retrieved files already in the DB by simply calling getBytes on our result set: byte[] bytes = resultSet.getBytes(1); ... This byte array was then converted into a DataHandler using the obvious constructor: dataHandler=new DataHandler(bytes,"application/octet-stream"); This worked great until we started trying to store and retrieve larger files. Dumping the entire file contents into a byte array and then building a DataHandler out of that simply requires too much memory. My immediate idea is to retrieve a stream of the data in the database with getBinaryStream and somehow convert that InputStream into a DataHandler in a memory-efficient way. Unfortunately it doesn't seem like there's a direct way to convert an InputStream into a DataHandler. Another idea I've been playing with is reading chunks of data from the InputStream and writing them to the OutputStream of the DataHandler. But... I can't find a way to create an "empty" DataHandler that returns a non-null OutputStream when I call getOutputStream... Has anyone done this? I'd appreciate any help you can give me or leads in the right direction.

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• Serial Communication between Java RXTX and Arduino

  - by SharpBarb

  I'm trying to communicate between my PC (Windows 7 using Netbeans and RXTX) with an Arduino Pro, using the serial port. The Arduino is actually connected to the PC using an FTDI cable. The code is based on the Java SimpleRead.Java found here. Currently the Arduino simply prints out a string when it starts up. My Java program should print the number of bytes that have been read and then print out the contents. The Java program works, sort of... If the string is long (10 bytes or so) the output will get broken up. So if on the Arduino I print Serial.println("123456789123456789"); //20 bytes including '\r' and '\n' The output of my Java program may look something like: Number of Bytes: 15 1234567891234 Number of Bytes: 5 56789 or Number of Bytes: 12 1234567891 Number of Bytes: 8 23456789 I'm thinking it's a timing problem, because when I manually go through the code using the debugger, the result string is always what it should be: one 20 byte string. I've been messing with various things but I haven't been able to fix the problem. Here is the part of the code that is giving me problems: static int baudrate = 9600, dataBits = SerialPort.DATABITS_8, stopBits = SerialPort.STOPBITS_1, parity = SerialPort.PARITY_NONE; byte[] readBuffer = new byte[128]; ... ... public void serialEvent(SerialPortEvent event) { if (event.getEventType() == SerialPortEvent.DATA_AVAILABLE) { try { if (input.available() > 0) { //Read the InputStream and return the number of bytes read numBytes = input.read(readBuffer); String result = new String(readBuffer,0,numBytes); System.out.println("Number of Bytes: " + numBytes); System.out.println(result); } } catch (IOException e) { System.out.println("Data Available Exception"); } }

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• How to Create Deterministic Guids

  - by desigeek

  In our application we are creating Xml files with an attribute that has a Guid value. This value needed to be consistent between file upgrades. So even if everything else in the file changes, the guid value for the attribute should remain the same. One obvious solution was to create a static dictionary with the filename and the Guids to be used for them. Then whenever we generate the file, we look up the dictionary for the filename and use the corresponding guid. But this is not feasible coz we might scale to 100's of files and didnt want to maintain big list of guids. So another approach was to make the Guid the same based on the path of the file. Since our file paths and application directory structure are unique, the Guid should be unique for that path. So each time we run an upgrade, the file gets the same guid based on its path. I found one cool way to generate such 'Deterministic Guids' (Thanks Elton Stoneman). It basically does this: private Guid GetDeterministicGuid(string input) { //use MD5 hash to get a 16-byte hash of the string: MD5CryptoServiceProvider provider = new MD5CryptoServiceProvider(); byte[] inputBytes = Encoding.Default.GetBytes(input); byte[] hashBytes = provider.ComputeHash(inputBytes); //generate a guid from the hash: Guid hashGuid = new Guid(hashBytes); return hashGuid; } So given a string, the Guid will always be the same. Are there any other approaches or recommended ways to doing this? What are the pros or cons of that method?

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• StackOverFlowException - but oviously NO recursion/endless loop

  - by user567706

  Hi there, I'm now blocked by this problem the entire day, read thousands of google results, but nothing seems to reflect my problem or even come near to it... i hope any of you has a push into the right direction for me. I wrote a client-server-application (so more like 2 applications) - the client collects data about his system, as well as a screenshot, serializes all this into a XML stream (the picture as a byte[]-array]) and sends this to the server in regular intervals. The server receives the stream (via tcp), deserializes the xml to an information-object and shows the information on a windows form. This process is running stable for about 20-25 minutes at a submission interval of 3 seconds. When observing the memory usage there's nothing significant to see, also kinda stable. But after these 20-25 mins the server throws a StackOverflowException at the point where it deserializes the tcp-stream, especially when setting the Image property from the byte[]-array. I thoroughly searched for recursive or endless loops, and regarding the fact that it occurs after thousands of sucessfull intervals, i could hardly imagine that. public byte[] ImageBase { get { MemoryStream ms = new MemoryStream(); _screen.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); return ms.GetBuffer(); } set { if (_screen != null) _screen.Dispose(); //preventing well-known image memory leak MemoryStream ms = new MemoryStream(value); try { _screen = Image.FromStream(ms); //<< EXCEPTION THROWING HERE } catch (StackOverflowException ex) //thx to new CLR management this wont work anymore -.- { Console.WriteLine(ex.Message + Environment.NewLine + ex.StackTrace); } ms.Dispose(); ms = null; } } I hope that more code would be unnecessary, or it could get very complex... Please help, i have no clue at all anymore thx Chris

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• nasm/yasm arguments, linkage to C++

  - by arionik

  Hello everybody, I've got a question concerning nasm and its linkage to C++. I declare a litte test function as extern "C" void __cdecl myTest( byte i1, byte i2, int stride, int *width ); and I call it like this: byte i1 = 1, i2 = 2; int stride = 3, width = 4; myTest( i1, i2, stride, &width ); the method only serves to debug assembly and have a look at how the stack pointer is used to get the arguments. beyond that, the pointer arguments value shall be set to 7, to figure out how that works. This is implemented like this: global _myTest _myTest: mov eax, [esp+4] ; 1 mov ebx, [esp+8] ; 2 mov ecx, dword [esp+16] ; width mov edx, dword [esp+12] ; stride mov eax, dword [esp+16] mov dword [eax], 7 ret and compiled via yasm -f win32 -g cv8 -m x86 -o "$(IntDir)\$(InputName).obj" "$(InputPath)" , then linked to the c++ app. In debug mode, everything works fine. the function is called a couple of times and works as expected, whereas in release mode the function works once, but subsequent programm operations fail. It seems to me that something's wrong with stack/frame pointers, near/far, but I'm quite new to this subject and need a little help. thanks in advance! a.

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• How do I detect whether the sample supplied by VideoSink.OnSample() is right-side up?

  - by Ken Smith

  We're currently using the Silverlight VideoSink to capture video from users' local webcams, kinda like so: protected override void OnSample(long sampleTime, long frameDuration, byte[] sampleData) { if (FrameShouldBeSubmitted()) { byte[] resampledData = ResizeFrame(sampleData); mediaController.SetVideoFrame(resampledData); } } Now, on most of the machines that we've tested, the video sample provided in the byte[] sampleData parameter is upside-down, i.e., if you try to take the RGBA data and turn it into, say, a WriteableBitmap, the bitmap will be upside-down. That's odd, but fairly easy to correct, of course -- you just have to reverse the array as you encode it. The problem is that at least on some machines (e.g., the single Macintosh in our test environment), the video sample provided is no longer upside-down, but right-side up, and hence, flipping the image actually results in an image that's received upside-down on the far side. I reported this to MS as a bug, but their (terse) response was that it was "As Designed". Further attempts at clarification have so far been ignored. Now, I'll grant that it's kinda entertaining to imagine the discussions behind this design decision: "OK, just to make it interesting, let's play the video rightside up on a Mac, but let's turn it upside down for Windows!" "Great idea!" "Yeah, that'll keep those developers guessing!" But beyond that, I can't find this, umm, "feature" documented anywhere, nor can I find any documentation on how one is supposed to be able to tell that a given video sample is upside down or rightside up. Any thoughts on how to tell this?

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• Convert 4 bytes to int

  - by Oscar Reyes

  I'm reading a binary file like this: InputStream in = new FileInputStream( file ); byte[] buffer = new byte[1024]; while( ( in.read(buffer ) > -1 ) { int a = // ??? } What I want to do it to read up to 4 bytes and create a int value from those but, I don't know how to do it. I kind of feel like I have to grab 4 bytes at a time, and perform one "byte" operation ( like << & FF and stuff like that ) to create the new int What's the idiom for this? EDIT Ooops this turn out to be a bit more complex ( to explain ) What I'm trying to do is, read a file ( may be ascii, binary, it doesn't matter ) and extract the integers it may have. For instance suppose the binary content ( in base 2 ) : 00000000 00000000 00000000 00000001 00000000 00000000 00000000 00000010 The integer representation should be 1 , 2 right? :- / 1 for the first 32 bits, and 2 for the remaining 32 bits. 11111111 11111111 11111111 11111111 Would be -1 and 01111111 11111111 11111111 11111111 Would be Integer.MAX_VALUE ( 2147483647 )

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• VB.net Saving an MetaFile / EMF as a bitmap ( .tiff)

  - by pehaada

  Currently I have a third party control that generates a Metafile. I can save the .wmf file to disk with out issue. The problem is how do I render the Metafile as a Tiff file. Currently I have the following code to get my metafile and save it. Dim mf As Metafile = page.GetImage(TXTextControl.Page.PageContent.All) Dim enhMetafileHandle As IntPtr = mf.GetHenhmetafile() Dim h As IntPtr Dim bufferSize As UInteger = GetEnhMetaFileBits(enhMetafileHandle, 0, h) Dim buffer(CInt(bufferSize)) As Byte GetEnhMetaFileBits(enhMetafileHandle, bufferSize, buffer) Dim msMetafileStream As New MemoryStream msMetafileStream.Write(buffer, 0, CInt(bufferSize)) Dim baMetafileData() As Byte baMetafileData = msMetafileStream.ToArray Dim g As Graphics = Graphics.FromImage(mf) mf.Dispose() File.WriteAllBytes("c:\a.wmf", baMetafileData) end sub _ Public Shared Function GetEnhMetaFileBits( ByVal hEMF As System.IntPtr, ByVal nSize As UInteger, ByVal lpData As IntPtr) As UInteger End Function <System.Runtime.InteropServices.DllImportAttribute("gdi32.dll", EntryPoint:="GetEnhMetaFileBits")> _ Public Shared Function GetEnhMetaFileBits(<System.Runtime.InteropServices.InAttribute()> ByVal hEMF As System.IntPtr, ByVal nSize As UInteger, ByVal lpData() As Byte) As UInteger End Function I've tried all sort of IMAGE and Graphic calls and just can't save the meta file as a .tiff. Any suggestions would be great. I even tried to create a new bitmap and draw the metafile onto it. I always end up with a GDI exception being thrown.

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• Is it possible to store controls(Panel) as object, serialize it and store it as a file?

  - by ikky

  The topic says it all. Using Compact Framework C# I'm tiling (order/sequence is important) some images that i download from an url, into a Panel(each image is a PictureBox). This can be a huge process, and may take some time. Therefor i only want the user to download the images and tile them once. So the next time the user uses the Tile Application, the Panel that was created the first time is already stored in a file and is loaded from that file. So what i want is a method to store a Panel as a file. Is this possible, or do you think i should do it another way? I've tried something like this: BinaryWriter panelStorage = new BinaryWriter(new FileStream("imagePanel.panel", FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)); Byte[] bImageObject = new Byte[20000]; bImageObject = (byte[])(object)this.imagePanel; panelStorage .Write(bMapObject); panelStorage .Close(); But the casting was not very legal :P "InvalidCastException" Can anyone help me with this problem? Thank you in advance!

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• udp can not receive any data

  - by StoneHeart

  Here is my code Socket sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); sck.Bind(new IPEndPoint(IPAddress.Any, 0)); // Broadcast to find server string msg = "Imlookingforaserver:" + udp_listen_port; byte[] sendBytes4 = Encoding.ASCII.GetBytes(msg); IPEndPoint groupEP = new IPEndPoint(IPAddress.Parse("255.255.255.255"), server_port); sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1); sck.SendTo(sendBytes4, groupEP); //Wait response from server Socket sck2 = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); sck2.Bind(new IPEndPoint(IPAddress.Any, udp_listen_port)); byte[] buffer = new byte[128]; EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, udp_listen_port); sck2.ReceiveFrom(buffer, ref remoteEndPoint); //<<< I never pass this line I use above code to try find a server. First I broadcast a message and then I wait for a response from the server. A test I made with the server written in C++ and running in Windows Vista, client written in C# and run on the same machine with server. Problem is: The server can receive message which client broadcast, but client can not receive anything from server. I try to write a client with C++ and it work like a charm, I think my problem is in C# client.

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• Best way to pass image to server?

  - by Chris

  I have an SL3 application that needs to be able to pass an image to the server, and then the server will generate a PDF file with the image in it, and display it to the user. What I already have in place are the following: (1) Code to convert image to byte array (2) Code to generate PDF file with image The main problem that I am running into is the following: In order to bypass the pop-up blocker, which is a requirement for my application, I am using the following code: var button = new NavigationButton(); button.NavigateUri = new Uri("http://localhost:3616/PrintReport.aspx?ReportIndex=11&ActionType=Get&ReportIdentifier=" + reportIdentifier.ToString() + ""); button.TargetName = "_blank"; button.PerformClick(); Initially, I would pass the image to a WCF web service (as a byte array), and then "navigate" to the ASP.NET page that would display the report. However, if I do this, then I can not use my custom HyperlinkButton class, and, certain browsers, including Safari, will block a new window from opening up. Therefore, it appears that the only option is to use the HyperlinkButton class. What I need to be able to do is to somehow pass the image, as a byte array or some other data type, to the server, such that it can temporarily store the image, even if it is in a server variable, and then immediately retrieve it when I navigate to the PrintReport.aspx page. If I upload the image to an ASP.NET form and then use the HyperlinkButton class to navigate to the PrintReport page, it doesn't work, as the app navigates to the PrintReport page before the system has finished uploading the image. I can't pass it to a web service, as that would require that I navigate to the PrintReport.aspx page in the callback code of the web method that I would be passing the image to, and the HyperlinkButton will not allow that, based on security rules. Any help or ideas would be appreciated. Thanks. Chris

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• Java File IO Compendium

  - by Warren Taylor

  I've worked in and around Java for nigh on a decade, but have managed to ever avoid doing serious work with files. Mostly I've written database driven applications, but occasionally, even those require some file io. Since I do it so rarely, I end up googling around for quite some time to figure out the exact incantation that Java requires to read a file into a byte[], char[], String or whatever I need at the time. For a 'once and for all' list, I'd like to see all of the usual ways to get data from a file into Java, or vice versa. There will be a fair bit of overlap, but the point is to define all of the subtle different variants that are out there. For example: Read/Write a text file from/to a single String. Read a text file line by line. Read/Write a binary file from/to a single byte[]. Read a binary file into a byte[] of size x, one chunk at a time. The goal is to show concise ways to do each of these. Samples do not need to handle missing files or other errors, as that is generally domain specific. Feel free to suggest more IO tasks that are somewhat common and I have neglected to mention.

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• Decoding tcp packets using python

  - by mikip

  Hello I am trying to decode data received over a tcp connection. The packets are small, no more than 100 bytes. However when there is a lot of them I receive some of the the packets joined together. Is there a way to prevent this. I am using python I have tried to separate the packets, my source is below. The packets start with STX byte and end with ETX bytes, the byte following the STX is the packet length, (packet lengths less than 5 are invalid) the checksum is the last bytes before the ETX def decode(data): while True: start = data.find(STX) if start == -1: #no stx in message pkt = '' data = '' break #stx found , next byte is the length pktlen = ord(data[1]) #check message ends in ETX (pktken -1) or checksum invalid if pktlen < 5 or data[pktlen-1] != ETX or checksum_valid(data[start:pktlen]) == False: print "Invalid Pkt" data = data[start+1:] continue else: pkt = data[start:pktlen] data = data[pktlen:] break return data , pkt I use it like this #process reports try: data = sock.recv(256) except: continue else: while data: data, pkt = decode(data) if pkt: process(pkt) Also if there are multiple packets in the data stream, is it best to return the packets as a collection of lists or just return the first packet I am not that familiar with python, only C, is this method OK. Any advice would be most appreciated. Thanks in advance Thanks

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• rs232 communication, general timing question

  - by Sunny Dee

  Hi, I have a piece of hardware which sends out a byte of data representing a voltage signal at a frequency of 100Hz over the serial port. I want to write a program that will read in the data so I can plot it. I know I need to open the serial port and open an inputstream. But this next part is confusing me and I'm having trouble understanding the process conceptually: I create a while loop that reads in the data from the inputstream 1 byte at a time. How do I get the while loop timing so that there is always a byte available to be read whenever it reaches the readbyte line? I'm guessing that I can't just put a sleep function inside the while loop to try and match it to the hardware sample rate. Is it just a matter of continuing reading the inputstream in the while loop, and if it's too fast then it won't do anything (since there's no new data), and if it's too slow then it will accumulate in the inputstream buffer? Like I said, i'm only trying to understand this conceptually so any guidance would be much appreciated! I'm guessing the idea is independent of which programming language I'm using, but if not, assume it is for use in Java. Thanks!

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• How Can I Generate Equivalent Output Using the CryptoAPI and the .NET Encryption (TripleDESCryptoSer

  - by S. Butts

  I have some C#/.NET code that encrypts and decrypts data using TripleDES encryption. It sticks to the sample code provided at MSDN pretty closely. The encryption piece looks like the following: TripleDESCryptoServiceProvider _desProvider = new TripleDESCryptoServiceProvider(); //bytes for key and initialization vector //keyBytes is 24 bytes of stuff, vectorBytes is 8 bytes of stuff byte[] keyBytes; byte[] vectorBytes; FileStream fStream = File.Open(locationOfFile, FileMode.Create, FileAccess.Write); CryptoStream cStream = new CryptoStream(fStream, _desProvider.CreateEncryptor(keyBytes, vectorBytes), CryptoStreamMode.Write); BinaryWriter bWriter = new BinaryWriter(cStream); //write out encrypted data //raw data is a few bytes of binary information byte[] rawData; bWriter.Write(rawData); With encrypting and decrypting in C#, this all works like a charm. The problem is I need to write a small Win32 utility that will duplicate the encryption above. I have tried several methods using the CryptoAPI, and I simply do not get output that the .NET piece can decrypt, no matter what I do. Can someone please tell me what the equivalent C++ code is that will produce the same output? I am not certain just what methods of the CryptoAPI the .NET functions use to encrypt the data. What options are used, and what method of generating the key is used? Before someone suggests that I just write it in C# anyway, or create some common library bridge for them, those options are unfortunately off the table. It really has to work in Win32 with .NET and without using a DLL. I have some leeway in changing the C# code. I apologize in advance if this is bone-headed, as I am new to encryption.

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• Why This Maintainability Index Increase?

  - by Timothy

  I would be appreciative if someone could explain to me the difference between the following two pieces of code in terms of Visual Studio's Code Metrics rules. Why does the Maintainability Index increase slightly if I don't encapsulate everything within using ( )? Sample 1 (MI score of 71) public static String Sha1(String plainText) { using (SHA1Managed sha1 = new SHA1Managed()) { Byte[] text = Encoding.Unicode.GetBytes(plainText); Byte[] hashBytes = sha1.ComputeHash(text); return Convert.ToBase64String(hashBytes); } } Sample 2 (MI score of 73) public static String Sha1(String plainText) { Byte[] text, hashBytes; using (SHA1Managed sha1 = new SHA1Managed()) { text = Encoding.Unicode.GetBytes(plainText); hashBytes = sha1.ComputeHash(text); } return Convert.ToBase64String(hashBytes); } I understand metrics are meaningless outside of a broader context and understanding, and programmers should exercise discretion. While I could boost the score up to 76 with return Convert.ToBase64String(sha1.ComputeHash(Encoding.Unicode.GetBytes(plainText))), I shouldn't. I would clearly be just playing with numbers and it isn't truly any more readable or maintainable at that point. I am curious though as to what the logic might be behind the increase in this case. It's obviously not line-count.

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• C# - parse content away from structure in a binary file

  - by Jeff Godfrey

  Using C#, I need to read a packed binary file created using FORTRAN. The file is stored in an "Unformatted Sequential" format as described here (about half-way down the page in the "Unformatted Sequential Files" section): http://www.tacc.utexas.edu/services/userguides/intel8/fc/f_ug1/pggfmsp.htm As you can see from the URL, the file is organized into "chunks" of 130 bytes or less and includes 2 length bytes (inserted by the FORTRAN compiler) surrounding each chunk. So, I need to find an efficient way to parse the actual file payload away from the compiler-inserted formatting. Once I've extracted the actual payload from the file, I'll then need to parse it up into its varying data types. That'll be the next exercise. My first thoughts are to slurp up the entire file into a byte array using File.ReadAllBytes. Then, just iterate through the bytes, skipping the formatting and transferring the actual data to a second byte array. In the end, that second byte array should contain the actual file contents minus all the formatting, which I'd then need to go back through to get what I need. As I'm fairly new to C#, I thought there might be a better, more accepted way of tackling this. Also, in case it's helpful, these files could be fairly large (say 30MB), though most will be much smaller...

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• GCC - How to realign stack?

  - by psihodelia

  I try to build an application which uses pthreads and __m128 SSE type. According to GCC manual, default stack alignment is 16 bytes. In order to use __m128, the requirement is the 16-byte alignment. My target CPU supports SSE. I use a GCC compiler which doesn't support runtime stack realignment (e.g. -mstackrealign). I cannot use any other GCC compiler version. My test application looks like: #include <xmmintrin.h> #include <pthread.h> void *f(void *x){ __m128 y; ... } int main(void){ pthread_t p; pthread_create(&p, NULL, f, NULL); } The application generates an exception and exits. After a simple debugging (printf "%p", &y), I found that the variable y is not 16-byte aligned. My question is: how can I realign the stack properly (16-byte) without using any GCC flags and attributes (they don't help)? Should I use GCC inline Assembler within this thread function f()?

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• how is data stored at bit level according to "Endianness" ?

  - by bakra

  I read about Endianness and understood squat... so I wrote this main() { int k = 0xA5B9BF9F; BYTE *b = (BYTE*)&k; //value at *b is 9f b++; //value at *b is BF b++; //value at *b is B9 b++; //value at *b is A5 } k was equal to "A5 B9 BF 9F" and (byte)pointer "walk" o/p was "9F BF b9 A5" so I get it bytes are stored backwards...ok. ~ so now I thought how is it stored at BIT level... I means is "9f"(1001 1111) stored as "f9"(1111 1001)? so I wrote this int _tmain(int argc, _TCHAR* argv[]) { int k = 0xA5B9BF9F; void *ptr = &k; bool temp= TRUE; cout<<"ready or not here I come \n"< for(int i=0;i<32;i++) { temp = *( (bool*)ptr + i ); if( temp ) cout<<"1 "; if( !temp) cout<<"0 "; if(i==7||i==15||i==23) cout<<" - "; } } I get some random output even for nos. like "32" I dont get anything sensible. why ?

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• What am I doing wrong with HttpResponse content and headers when downloading a file?

  - by Slauma

  I want to download a PDF file from a SQL Server database which is stored in a binary column. There is a LinkButton on an aspx page. The event handler of this button looks like this: protected void LinkButtonDownload(object sender, EventArgs e) { ... byte[] aByteArray; // Read binary data from database into this ByteArray // aByteArray has the size: 55406 byte Response.ClearHeaders(); Response.ClearContent(); Response.BufferOutput = true; Response.AddHeader("Content-Disposition", "attachment; filename=" + "12345.pdf"); Response.ContentType = "application/pdf"; using (BinaryWriter aWriter = new BinaryWriter(Response.OutputStream)) { aWriter.Write(aByteArray, 0, aByteArray.Length); } } A "File Open/Save dialog" is offered in my browser. When I store this file "12345.pdf" to disk, the file has a size of 71523 Byte. The additional 16kB at the end of the PDF file are the HTML code of my page (as I can see when I view the file in an editor). I am confused because I was believing that ClearContent and ClearHeaders would ensure that the page content is not sent together with the file content. What am I doing wrong here? Thanks for help!

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• Retrieving dll version info via Win32 - VerQueryValue(...) crashes under Win7 x64

  - by user256890

  The respected open source .NET wrapper implementation (SharpBITS) of Windows BITS services fails identifying the underlying BITS version under Win7 x64. Here is the source code that fails. NativeMethods are native Win32 calls wrapped by .NET methods and decorated via DllImport attribute. private static BitsVersion GetBitsVersion() { try { string fileName = Path.Combine( System.Environment.SystemDirectory, "qmgr.dll"); int handle = 0; int size = NativeMethods.GetFileVersionInfoSize(fileName, out handle); if (size == 0) return BitsVersion.Bits0_0; byte[] buffer = new byte[size]; if (!NativeMethods.GetFileVersionInfo(fileName, handle, size, buffer)) { return BitsVersion.Bits0_0; } IntPtr subBlock = IntPtr.Zero; uint len = 0; if (!NativeMethods.VerQueryValue(buffer, @"\VarFileInfo\Translation", out subBlock, out len)) { return BitsVersion.Bits0_0; } int block1 = Marshal.ReadInt16(subBlock); int block2 = Marshal.ReadInt16((IntPtr)((int)subBlock + 2 )); string spv = string.Format( @"\StringFileInfo\{0:X4}{1:X4}\ProductVersion", block1, block2); string versionInfo; if (!NativeMethods.VerQueryValue(buffer, spv, out versionInfo, out len)) { return BitsVersion.Bits0_0; } ... The implementation follows the MSDN instructions by the letter. Still during the second VerQueryValue(...) call, the application crashes and kills the debug session without hesitation. Just a little more debug info right before the crash: spv = "\StringFileInfo\040904B0\ProductVersion" buffer = byte[1900] - full with binary data block1 = 1033 block2 = 1200 I looked at the targeted "C:\Windows\System32\qmgr.dll" file (The implementation of BITS) via Windows. It says that the Product Version is 7.5.7600.16385. Instead of crashing, this value should return in the verionInfo string. Any advice?

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• Why should the "prime-based" hashcode implmentation be used instead of the "naive" one?

  - by Wilhelm

  I have seen that a prime number implmentation of the GetHashCode function is being recommend, for example here. However using the following code (in VB, sorry), it seems as if that implementation gives the same hash density as a "naive" xor implementation. If the density is the same, I would suppose there is the same probability of cllision in both implementations. Am I missing anything on why is the prime approach preferred? I am supossing that if the hash code is a byte I do not lose generality for the integer case. Sub Main() Dim XorHashes(255) As Integer Dim PrimeHashes(255) As Integer For i = 0 To 255 For j = 0 To 255 For k = 0 To 255 XorHashes(GetXorHash(i, j, k)) += 1 PrimeHashes(GetPrimeHash(i, j, k)) += 1 Next Next Next For i = 0 To 255 Console.WriteLine("{0}: {1}, {2}", i, XorHashes(i), PrimeHashes(i)) Next Console.ReadKey() End Sub Public Function GetXorHash(ByVal valueOne As Integer, ByVal valueTwo As Integer, ByVal valueThree As Integer) As Byte Return CByte((valueOne Xor valueTwo Xor valueThree) Mod 256) End Function Public Function GetPrimeHash(ByVal valueOne As Integer, ByVal valueTwo As Integer, ByVal valueThree As Integer) As Byte Dim TempHash = 17 TempHash = 31 * TempHash + valueOne TempHash = 31 * TempHash + valueTwo TempHash = 31 * TempHash + valueThree Return CByte(TempHash Mod 256) End Function

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