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  • Eclipse gives me a weird error when compiling...

    - by Legend
    I have this function which returns a datatype InetAddress[] public InetAddress [] lookupAllHostAddr(String host) throws UnknownHostException { Name name = null; try { name = new Name(host); } catch (TextParseException e) { throw new UnknownHostException(host); } Record [] records = null; if (preferV6) records = new Lookup(name, Type.AAAA).run(); if (records == null) records = new Lookup(name, Type.A).run(); if (records == null && !preferV6) records = new Lookup(name, Type.AAAA).run(); if (records == null) throw new UnknownHostException(host); InetAddress[] array = new InetAddress[records.length]; for (int i = 0; i < records.length; i++) { Record record = records[i]; if (records[i] instanceof ARecord) { ARecord a = (ARecord) records[i]; array[i] = a.getAddress(); } else { AAAARecord aaaa = (AAAARecord) records[i]; array[i] = aaaa.getAddress(); } } return array; } Eclipse complains that the return type should be byte[][] but when I change the return type to byte[][], it complains that the function is returning the wrong data type. I'm stuck in a loop. Does anyone know what is happening here?

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  • How do I display java.lang.* object allocations in Eclipse profiler?

    - by Martin Wickman
    I am profiling an application using the Eclipse profiler. I am particularly interested in number of allocated object instances of classes from java.lang (for instance java.lang.String or java.util.HashMap). I also want to know stuff like number of calls to String.equals() etc. I use the "Object Allocations" tab and I shows all classes in my application and a count. It also shows all int[], byte[], long[] etc, but there is no mention of any standard java classes. For instance, this silly code: public static void main(String[] args) { Object obj[] = new Object[1000]; for (int i = 0; i < 1000; i++) { obj[i] = new StringBuffer("foo" + i); } System.out.println (obj[30]); } Shows up in the Object Allocations tab as 7 byte[]s, 4 char[]s and 2 int[]s. It doesn't matter if I use 1000 or 1 iterations. It seems the profiler simply ignores everything that is in any of the java.* packages. The same applies to Execution Statistics as well. Any idea how to display instances of java.* in the Eclipse Profiler?

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  • how do I deconstruct COUNT()?

    - by user151841
    I have a view with some joins in it. I'm doing a select from that view with COUNT(*) as one of the columns of the select. I'm surprised by the number it's returning. Note that there is no GROUP BY nor aggregate column statement in the source view that the query is drawing from. How can I take it apart to see how it arrives at this number? I have three columns in the GROUP BY clause. SELECT column1, column2, column3, COUNT(*) FROM View GROUP BY column1, column2, column3 I get a result like +---------+---------+---------+----------+ | column1 | column2 | column3 | COUNT(*) | +---------+---------+---------+----------+ | value1 | valueA | value_a | 103 | +---------+---------+---------+----------+ | value2 | valueB | value_b | 56 | +---------+---------+---------+----------+ etc. I'd like to see how it arrives at that 103, 26, etc. In other words, I want to run a query that returns 103 rows of something, so that I know that I've expressed the query properly. I'm double-checking my work. I'm not saying that I think COUNT(*) doesn't work ( I know that "SELECT is not broken" ), what I want to double-check is exactly what I'm expressing in my query, because I think I've expressed the wrong thing, which would be why I'm getting unexpected values. I need to see more what I'm actually directing MySQL to count. So should I take them one by one, and try out each value in a WHERE clause? In other words, should I do SELECT column1 FROM View WHERE column1 = 'first_grouped_value' SELECT column1 FROM View WHERE column1 = 'second_grouped_value' SELECT column2 FROM View WHERE column1 = 'first_grouped_value' SELECT column2 FROM View WHERE column1 = 'second_grouped_value' and see the row count returned matches the COUNT(*) value in the grouped results? Because of confidentiality, I won't be able to post any of the query or database structure. All I'm asking for is a general technique to see what COUNT(*) is actually counting.

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  • std::conditional compile-time branch evaluation

    - by cmannett85
    Compiling this: template < class T, class Y, class ...Args > struct isSame { static constexpr bool value = std::conditional< sizeof...( Args ), typename std::conditional< std::is_same< T, Y >::value, isSame< Y, Args... >, // Error! std::false_type >::type, std::is_same< T, Y > >::type::value; }; int main() { qDebug() << isSame< double, int >::value; return EXIT_SUCCESS; } Gives me this compiler error: error: wrong number of template arguments (1, should be 2 or more) The issue is that isSame< double, int > has an empty Args parameter pack, so isSame< Y, Args... > effectively becomes isSame< Y > which does not match the signature. But my question is: Why is that branch being evaluated at all? sizeof...( Args ) is false, so the inner std:conditional should not be evaluated. This isn't a runtime piece of code, the compiler knows that sizeof..( Args ) will never be true with the given template types. If you're curious, it's supposed to be a variadic version of std::is_same, not that it works...

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  • What exactly is the GNU tar ././@LongLink "trick"?

    - by Cheeso
    I read that a tar entry type of 'L' (76) is used by gnu tar and gnu-compliant tar utilities to indicate that the next entry in the archive has a "long" name. In this case the header block with the entry type of 'L' usually encodes the name ././@LongLink . My question is: where is the format of the next block described? The format of a tar archive is very simple: it is just a series of 512-byte blocks. In the normal case, each file in a tar archive is represented as a series of blocks. The first block is a header block, containing the file name, entry type, modified time, and other metadata. Then the raw file data follows, using as many 512-byte blocks as required. Then the next entry. If the filename is longer than will fit in the space allocated in the header block, gnu tar apparently uses what's known as "the ././@LongLink trick". I can't find a precise description for it. When the entry type is 'L', how do I know how long the "long" filename is? Is the long name limited to 512 bytes, in other words, whatever fits in one block? Most importantly: where is this documented?

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  • Managed .NET Equivalent to CreateFile & WriteFile from WinBase (kernel32.dll)

    - by StevenH
    I am working with a legacy file format. The file is created using unmanaged C++ that utilizes the WinBase.h CreateFile() & WriteFile() functions (found in the kernel32.dll). I have been using P/Invoke interop to access these native functions like so: [DllImport("kernel32.dll")] public static extern bool WriteFile( IntPtr hFile, byte[] lpBuffer, uint nNumberOfBytesToWrite, out uint lpNumberOfBytesWritten, [In] ref NativeOverlapped lpOverlapped); [DllImport("kernel32.dll", SetLastError = true)] public static extern bool WriteFileEx( IntPtr hFile, byte[] lpBuffer, uint nNumberOfBytesToWrite, [In] ref NativeOverlapped lpOverlapped, WriteFileCompletionDelegate lpCompletionRoutine); [DllImport("kernel32.dll", SetLastError = true)] public static extern IntPtr CreateFile( string lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile); [DllImport("kernel32.dll", SetLastError = true)] public static extern bool CloseHandle(IntPtr hObject); public delegate void WriteFileCompletionDelegate( UInt32 dwErrorCode, UInt32 dwNumberOfBytesTransfered, ref NativeOverlapped lpOverlapped); The issue with this is when I call WriteFile(), the file is always overwritten by the proceeding call. I need to find a compatible .NET equivalent that would allow me to produce the exact same format of output. Thanks.

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  • jQuery ajax post of jpg image to .net webservice. Image results corrupted

    - by sosergio
    I have a phonegap jquery app that opens the camera and take a picture. I then POST this picture to a .net webservice, wich I've coded. I can't use phonegap FileTransfer because such isn't supported by Bada os, wich is a requirement. I believe I've successfully loaded the image from phonegap FileSystem API, I've attached it into an .ajax type:post, I've even received it from .net side, but when .net save the image into the server, the image results corrupted. It seems to me that two sides of the communication have different data type. Has anyone experience in this? Any help will be appreciated. This is my code: //PHONEGAP CAMERA ACCESS (summed up) navigator.camera.getPicture(onGetPictureSuccess, onGetPictureFail, { quality: 50, destinationType:Camera.DestinationType.FILE_URI }); window.resolveLocalFileSystemURI(imageURI, onResolveFileSystemURISuccess, onResolveFileSystemURIError); fileEntry.file(gotFileSuccess, gotFileError); new FileReader().readAsDataURL(file); //UPLOAD FILE function onDataReadSuccess(evt) { var image_data = evt.target.result; var filename = unique_id(); var filext = "jpg"; $.ajax({ type : 'POST', url : SERVICE_BASE_URL+"/fotos/"+filename+"?ext="+filext, cache: false, timeout: 100000, processData: false, data: image_data, contentType: 'image/jpeg', success : function(data) { console.log("Data Uploaded with success. Message: "+ data); $.mobile.hidePageLoadingMsg(); $.mobile.changePage("ok.html"); } }); } On my .net Web Service this is the method that gets invoked: public string FotoSave(string filename, string extension, Stream fileContent) { string filePath = HttpContext.Current.Server.MapPath("~/foto_data/") + "\\" + filename; FileStream writeStream = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Write); int Length = 256; Byte[] buffer = new Byte[Length]; int bytesRead = readStream.Read(buffer, 0, Length); // write the required bytes while (bytesRead > 0) { writeStream.Write(buffer, 0, bytesRead); bytesRead = readStream.Read(buffer, 0, Length); } readStream.Close(); writeStream.Close(); }

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  • How to decrypt a string encrypted with HMACSHA1?

    - by Bob
    I'm an encryption novice trying to pass some values back and forth between systems. I can encrypt the value, but can't seem to figure out how to decrypt on the other end. I've created a simple Windows Forms application using VB.NET. Trying to input a value and a key, encrypt and then decrypt to get the original value. Here's my code so far. Any help greatly appreciated. Thanks. Imports System Imports System.IO Imports System.Security.Cryptography Imports System.Text Public Class Form1 Private Sub btnEncode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncode.Click Dim hmacsha1 As New HMACSHA1(Encoding.ASCII.GetBytes(txtKey.Text)) Dim hashValue As Byte() = hmacsha1.ComputeHash(Encoding.ASCII.GetBytes(txtValue.Text)) txtResult.Text = BytesToHexString(hashValue) hmacsha1.Clear() End Sub Private Sub btnDecode_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDecode.Click '??? End Sub Private Function BytesToHexString(ByVal bytes As Byte()) As String Dim output As String = String.Empty Dim i As Integer = 0 Do While i < bytes.Length output += bytes(i).ToString("X2") i += 1 Loop Return output End Function End Class

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  • Problem with loading a PNG image in JApplet.

    - by Bruce
    Hi there, I'm trying to load a PNG image from JAR file when running JApplet. The file is, I think, loaded properly - there are no errors. However it is not displayed. img.png is placed in the same directory as MainClass.java file. Here is the code: InputStream imageURL = this.getClass().getResourceAsStream("img.png" ); byte[] bytes = null; try {bytes = new byte[imageURL.available()]; System.out.println(imageURL.available()); imageURL.read(bytes);} catch(Exception e) {System.out.println("bleah");} Image image = Toolkit.getDefaultToolkit().createImage(bytes); Image imageScaled = me.getScaledInstance( 100, 150, Image.SCALE_SMOOTH ); jLabel6 = new javax.swing.JLabel( new ImageIcon( imageScaled) ); and the HTML exerpt: <APPLET codebase="classes" code="myapplet/MainClass.class" archive ="LittleApplet.jar" width=700 height=500> The image, as I wrote, is probably read, but not displayed in JLabel. What am I missing/doing wrong? Thanks in advance for the reply!

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  • Problem with displaying image from DB using asp.net MVC 2

    - by Renato
    Hello! I'm having trouble with displaying image from db. I think that method for saving image is working, because I see in DB that varbinary fields have some value, and that image type is correct. Also the size of image. But when I want to display image for product i don't get anything. Just blank space.. here is my code... public byte[] GetImage(int productID) { Product product = products.GetByID(productID); byte[] imageData = product.ImageData.ToArray(); return imageData; } That code is in my controller. Second is code from view : <% if (product.ImageData != null) { %> <img src='/product/getimage/<%= Html.Encode(product.ID) %>' alt=""/> <% } %> I tried some solutions found here on stack overflow, and everyone do it like this, but it's working for them. I dont have any idea why images aren't displayed. When i look at source code of page at debugging i have : <img src='/product/getimage/18' alt=""/> I'm using .net 4.0, MVC 2, VS 2010... Thanks in advance

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  • IntelliJ Doesn't Notice Changes in Interface

    - by yar
    [I've decided to give IntelliJ another go (to replace Eclipse), since its Groovy support is supposed to be the best. But back to Java...] I have an Interface that defines a constant public static final int CHANNEL_IN = 1; and about 20 classes in my Module that implement that interface. I've decided that this constant was a bad idea so I did what I do in Eclipse: I deleted the entire line. This should cause the Project tree to light up like a Christmas tree and all classes that implement that interface and use that constant to break. Instead, this is not happening. If I don't actually double-click on the relevant classes -- which I find using grep -- the module even builds correctly (using Build - Make Module). If I double-click on a relevant class, the error is shown both in the Project Tree and in the Editor. I am not able to replicate this behavior in small tests, but in large modules it works (incorrectly) this way. Is there some relevant setting in IntelliJ for this?

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  • C# DynamicPDF Merging causing "Index out of bounds" error

    - by Dining Philanderer
    Greetings, We use DynamicPDF to merge multiple PDF documents stored in a MSSQL database. The vast majority of times it works wonderfully, but occasionally one of these documents will fail to merge generating the exception message "Index was outside the bounds of the array." I think I have isolated the problem to PDF files that are greater than 8.5 x 11.0. Does anyone know if this is a known issue with DynamicPDF? The merging code is posted here. What would be ideal is if there is a way to resize the PDF files to the correct size so this is not a concern at all... for (int docs = 0; docs < dsPDFInfo.Tables[0].Rows.Count; docs++) { byte[] bytePDFArray = (byte[])dsPDFInfo.Tables[0].Rows[docs]["Content"]; int iContentSize = Convert.ToInt32(dsPDFInfo.Tables[0].Rows[docs]["ContentSize"]); MemoryStream ms = new MemoryStream(bytePDFArray, 0, iContentSize); ceTe.DynamicPDF.Merger.PdfDocument pdfdoc = new ceTe.DynamicPDF.Merger.PdfDocument(ms); ceTe.DynamicPDF.Merger.MergeDocument mergedoc = new ceTe.DynamicPDF.Merger.MergeDocument(pdfdoc); docCombinedPDF.Append(mergedoc); } Thanks....

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  • why is a minus sign prepended to my biginteger?

    - by kyrogue
    package ewa; import java.io.UnsupportedEncodingException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.logging.Level; import java.util.logging.Logger; import java.math.BigInteger; /** * * @author Lotus */ public class md5Hash { public static void main(String[] args) throws NoSuchAlgorithmException { String test = "abc"; MessageDigest md = MessageDigest.getInstance("MD5"); try { md.update(test.getBytes("UTF-8")); byte[] result = md.digest(); BigInteger bi = new BigInteger(result); String hex = bi.toString(16); System.out.println("Pringting result"); System.out.println(hex); } catch (UnsupportedEncodingException ex) { Logger.getLogger(md5Hash.class.getName()).log(Level.SEVERE, null, ex); } } } i am testing conversion of byte to hex and when done, the end result has a minus sign on the beginning of the string, why does this happen? i have read the docs and it says it will add a minus sign, however i do not understand it. And will the minus sign affect the hash result? because i am going to implement it to hash password stored on my database

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  • Problem painting JLabel class to another JPanel class

    - by jjpotter
    I have created a class that extends JLabel to use as my object moving around a JPanel for a game. import javax.swing.*; public class Head extends JLabel { int xpos; int ypos; int xvel; int yvel; ImageIcon chickie = new ImageIcon("C:\\Users\\jjpotter.MSDOM1\\Pictures\\clavalle.jpg"); JLabel myLabel = new JLabel(chickie); public Head(int xpos, int ypos, int xvel, int yvel){ this.xpos = xpos; this.ypos = ypos; this.xvel = xvel; this.yvel = yvel; } public void draw(){ myLabel.setLocation(xpos, ypos); } public double getXpos() { return xpos; } public double getYpos() { return ypos; } public int getXvel() { return xvel; } public int getYvel() { return yvel; } public void setPos(int x, int y){ xpos = x; ypos = y; } } I am then trying to add it onto my JPanel. From here I will randomly have it increment its x and y coordinates to float it around the screen. I can not get it to paint itself onto the JPanel. I know there is a key concept I am missing here that involves painting components on different panels. Here is what I have in my GamePanel class import java.awt.Dimension; import java.util.Random; import javax.swing.*; public class GamePanel extends JPanel { Random myRand = new Random(); Head head = new Head(20,20,0,0); public GamePanel(){ this.setSize(new Dimension(640, 480)); this.add(head); } } Any suggestions on how to get this to add to the JPanel? Also, is this a good way to go about having the picture float around the screen randomly for a game?

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  • Silverlight 3 ArcSegment to always draw circle's

    - by kapaboo
    Hi everyone, Ok, my arcSegment must always draw Circle's. For this reason I calculate the Arc's Width with the following formula: arcXRadius = (4 * Math.Pow(height, 2) + Math.Pow(distanceArcPoints, 2)) / (8 * height); so Arcs.Size = (arcXRadius,height) But seems that the height is scaled down when drawn. I want to add a small Circle to the Arc's middle (highest point) so when you drag it it changes the arc Height but also changes the Width so it will remain a circle. Here's how I calculate the Circle's (highest) point: Point middlePoint = GetMiddlePoint(arcPointA,arcPointB); double arcYRadius = arcSegment.Size.Height; if (arcYRadius <= 0) return middlePoint; double angle = arcSegment.RotationAngle; Point ellinewPoint = new Point(); ellinewPoint.X = Math.Cos((angle + 90) * Math.PI / 180) * arcYRadius + middlePoint.X; ellinewPoint.Y = Math.Sin((angle + 90) * Math.PI / 180) * arcYRadius + middlePoint.Y; Until Arc's.Size.Height Property gets Closer to the Width my Circle is not at the right Point. So maybe someone can give me a hint or tell me what am I doing wrong. Cheers, kapaboo

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  • Problem with sprintf function, last parameters are wrong when written

    - by Apoc
    So I use sprintf sprintf(buffer,"%f|%f|%f|%f|%f|%f|%d|%f|%d", x, y, z, u, v, w, nID,dDistance, nConfig) But when I print the buffer I get the 2 last parameters wrong, they are lets suppose to be 35.0000 and 0 and in the string they are 0.00000 and 10332430 and my buffer is long enough and all the other parameters are good in the string Any idea? Is there a length limit to sprintf or something^ I checked the types of all the numbers and they are right, but what seems to be the problem is the dDistance. When I remove it from the sprint, the nConfig gets the right value in the string, but when I remove nConfig, dDistance still doesn't get the right value. I checked and dDistance is a double. Any idea? Since people don't seem to believe me I did this : char test[255]={0}; int test1 = 2; double test2=35.00; int test3 = 0; sprintf(test,"%d|%f|%d",test1,test2,test3); and I get this in my string: 2|0.000000|1078034432

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  • Could I do this blind relative to absolute path conversion (for perforce depot paths) better?

    - by wonderfulthunk
    I need to "blindly" (i.e. without access to the filesystem, in this case the source control server) convert some relative paths to absolute paths. So I'm playing with dotdots and indices. For those that are curious I have a log file produced by someone else's tool that sometimes outputs relative paths, and for performance reasons I don't want to access the source control server where the paths are located to check if they're valid and more easily convert them to their absolute path equivalents. I've gone through a number of (probably foolish) iterations trying to get it to work - mostly a few variations of iterating over the array of folders and trying delete_at(index) and delete_at(index-1) but my index kept incrementing while I was deleting elements of the array out from under myself, which didn't work for cases with multiple dotdots. Any tips on improving it in general or specifically the lack of non-consecutive dotdot support would be welcome. Currently this is working with my limited examples, but I think it could be improved. It can't handle non-consecutive '..' directories, and I am probably doing a lot of wasteful (and error-prone) things that I probably don't need to do because I'm a bit of a hack. I've found a lot of examples of converting other types of relative paths using other languages, but none of them seemed to fit my situation. These are my example paths that I need to convert, from: //depot/foo/../bar/single.c //depot/foo/docs/../../other/double.c //depot/foo/usr/bin/../../../else/more/triple.c to: //depot/bar/single.c //depot/other/double.c //depot/else/more/triple.c And my script: begin paths = File.open(ARGV[0]).readlines puts(paths) new_paths = Array.new paths.each { |path| folders = path.split('/') if ( folders.include?('..') ) num_dotdots = 0 first_dotdot = folders.index('..') last_dotdot = folders.rindex('..') folders.each { |item| if ( item == '..' ) num_dotdots += 1 end } if ( first_dotdot and ( num_dotdots > 0 ) ) # this might be redundant? folders.slice!(first_dotdot - num_dotdots..last_dotdot) # dependent on consecutive dotdots only end end folders.map! { |elem| if ( elem !~ /\n/ ) elem = elem + '/' else elem = elem end } new_paths << folders.to_s } puts(new_paths) end

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  • Android shared library which is not JNI based

    - by Mondain
    I am developing a library for Android applications which does not use native code (JNI). I have tried suppling the library as an external jar in my Android projects but this method does not include the library contents in the apk and thus throws class not found errors when run in the emulator or device. I have also tried creating the library as an Android project in itself and this does work, but only for public static properties (not methods). With the library and application both being in separate apk's I can see that the VM notices references to the library and can read some properties, but when an attempt to instantiate a class in the library is executed I get class not found even though I can read the public static properties from it (very frustrating!!). I realize that Davlik byte code is not the same as Java byte code but I am having trouble even finding good information about how to solve what would seem to be a very simple issue in Android. I am looking into the old PlatformLibrary stuff right now but I am not convinced this will work either since the sample has been removed from the Android site :( So help me out if you can, if I find the answer before this happens I will share it. viva la Android!

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  • UDP server doesnt accept calls from outside.

    - by rayman
    Hi, ive implement simple udp server on my Android device.(sdk 1.5) it works fine when i am runnning a local client on the phone sends through it trigger to my server. but when i try to get udp call from an outside server to my phone, it doesnt work. already make sure the outside server isnt blocked by firewall and it's sending the udp trigger to the right port, which my phone is listening to. i used natstat on the phone and checked that the phone is realy listening to the it's local ip and the port ive setted it to. here is my code of the server:(on the device) // server will listen to one client try { Thread udpServerThread = new Thread() { @Override public void run() { try { // Retrieve the ServerName InetAddress serverAddr = InetAddress .getByName("localhost"); Log.d("UDP", "S: Connecting..."); // Create new UDP-Socket socket = new DatagramSocket(SERVERPORT,serverAddr); byte[] buf = new byte[17]; // * Prepare a UDP-Packet that can contain the data we // * want to receive DatagramPacket packet = new DatagramPacket(buf, buf.length); Log.d("UDP", "S: Receiving..."); // wait to Receive the UDP-Packet socket.receive(packet); Log.d("UDP", "S: Received: '" + new String(packet.getData()) + "'"); acceptedMsg=new String(packet.getData()); notifyService(acceptedMsg); Log.d("UDP", "S: Done."); } catch (Exception e) { Log.e("UDP", "S: Error", e); } } }; udpServerThread.start(); } catch (Exception E) { Log.e("r",E.getMessage()) ; } so as i said, when i try it with local client(seperate thread) which sends udp trigger it works fine, but when i take this client implementation and put it on an outside real server, after UDP being sent, the phone doesnt respond to it. any idea? thanks, ray.

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  • python crc32 woes

    - by lazyr
    I'm writing a python program to extract data from the middle of a 6 GB bz2 file. A bzip2 file is made up of independently decryptable blocks of data, so I only need to find a block (they are delimited by magic bits), then create a temporary one-block bzip2 file from it in memory, and finally pass that to the bz2.decompress function. Easy, no? The bzip2 format has a crc32 checksum for the file at the end. No problem, binascii.crc32 to the rescue. But wait. The data to be checksummed does not necessarily end on a byte boundary, and the crc32 function operates on a whole number of bytes. My plan: use the binascii.crc32 function on all but the last byte, and then a function of my own to update the computed crc with the last 1-7 bits. But hours of coding and testing has left me bewildered, and my puzzlement can be boiled down to this question: how come crc32("\x00") is not 0x00000000? Shouldn't it be, according to the wikipedia article? You start with 0b00000000 and pad with 32 0's, then do polynomial division with 0x04C11DB7 until there are no ones left in the first 8 bits, which is immediately. Your last 32 bits is the checksum, and how can that not be all zeroes? I've searched google for answers and looked at the code of several crc32 implementations without finding any clue to why this is so.

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  • What is the difference between Inversion of Control and Dependency injection in C++?

    - by rlbond
    I've been reading recently about DI and IoC in C++. I am a little confused (even after reading related questions here on SO) and was hoping for some clarification. It seems to me that being familiar with the STL and Boost leads to use of dependency injection quite a bit. For example, let's say I made a function that found the mean of a range of numbers: template <typename Iter> double mean(Iter first, Iter last) { double sum = 0; size_t number = 0; while (first != last) { sum += *(first++); ++number; } return sum/number; }; Is this dependency injection? Inversion of control? Neither? Let's look at another example. We have a class: class Dice { public: typedef boost::mt19937 Engine; Dice(int num_dice, Engine& rng) : n_(num_dice), eng_(rng) {} int roll() { int sum = 0; for (int i = 0; i < num_dice; ++i) sum += boost::uniform_int<>(1,6)(eng_); return sum; } private: Engine& eng_; int n_; }; This seems like dependency injection. But is it inversion of control? Also, if I'm missing something, can someone help me out?

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  • How to send a future email using AT command.

    - by BHare
    I just need to send one email into the future, so I figured i'd be best at using at rather than using cron. This is what I have so far, its messy and ugly and not that great at escaping: <pre> <?php $out = array(); // Where is the email going? $email = "[email protected]"; // What is the body of the email (make sure to escape any double-quotes) $body = "This is what is actually emailed to me"; $body = escapeshellcmd($body); $body = str_replace('!', '\!', $body); // What is the subject of the email (make sure to escape any double-quotes) $subject = "It's alive!"; $subject = escapeshellcmd($subject); $subject = str_replace('!', '\!', $subject); // How long from now should this email be sent? IE: 1 minute, 32 days, 1 month 2 days. $when = "1 minute"; $command= <<<END echo " echo \"$body\" > /tmp/email; mail -s \"$subject\" $email < /tmp/email; rm /tmp/email; " | at now + $when; END; $ret = exec($command, $out); print_r($out); ?> </pre> The output should be something like warning: commands will be executed using /bin/sh job 60 at Thu Dec 30 19:39:00 2010 However I am doing something wrong with exec and not getting the result? The main thing is this seem very messy. Is there any alternative better methods for doing this? PS: I had to add apache's user (www-data for me) to /etc/at.allow ...Which I don't like, but I can live with it.

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  • Semi-generic function

    - by Fredrik Ullner
    I have a bunch of overloaded functions that operate on certain data types such as int, double and strings. Most of these functions perform the same action, where only a specific set of data types are allowed. That means I cannot create a simple generic template function as I lose type safety (and potentially incurring a run-time problem for validation within the function). Is it possible to create a "semi-generic compile time type safe function"? If so, how? If not, is this something that will come up in C++0x? An (non-valid) idea; template <typename T, restrict: int, std::string > void foo(T bar); ... foo((int)0); // OK foo((std::string)"foobar"); // OK foo((double)0.0); // Compile Error Note: I realize I could create a class that has overloaded constructors and assignment operators and pass a variable of that class instead to the function.

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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  • MSVC 2003 doesn't see any definitions from a nested include file

    - by ezpresso
    I have a piece of code with COM class declaration as follows: #include "PathTypes.h" MIDL_INTERFACE("552C7555-0555-4444-BA86-56CF39AAFFFF") IPathCalc : public IUnknown { virtual HRESULT STDMETHODCALLTYPE GetLocation( /* [retval][out] */ GeoLocation* pLoc) = 0; virtual HRESULT STDMETHODCALLTYPE SetLocation( /* [in] */ GeoLocation* pLoc) = 0; ... }; Below is the contents of PathTypes.h file: #if !defined(PATHCALC_TYPES_INCLUDED) #define PATHCALC_TYPES_INCLUDED #include "libastro/AstronomyStructs.h" #endif And the libastro/AstronomyStructs.h from an external cross-platform library: #ifndef _ASTRONOMY_STRUCTS_INCLUDED #define _ASTRONOMY_STRUCTS_INCLUDED typedef struct { double lattitude; double longitude; } GeoLocation; ... #endif /* _ASTRONOMY_STRUCTS_INCLUDED */ When I'm trying to build this code with g++ everything goes well. That's not the case with MSVC 2003 which returns error C2061: syntax error : identifier 'GeoLocation'. Seems like MSVC doesn't "see" the definitions from the libastro/AstronomyStructs.h file. When I replace #include "PathTypes.h" with #include "libastro/AstronomyStructs.h" the code compiles without errors. How to make MSVC 2003 to actually "see" the definitions from the nested include files?

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