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• C++ destructors causing crash's

  - by larsonator

  ok, so i got a some what intricate program that simulates the uni systems of students, units, and students enrolling in units. Students are stored in a binary search tree, Units are stored in a standard list. Student has a list of Unit Pointers, to store which units he/she is enrolled in Unit has a list of Student pointers, to store students which are enrolled in that unit. The unit collections (storing units in a list) as made as a static variable where the main function is, as is the Binary search tree of students. when its finaly time to close the program, i call the destructors of each. but at some stage, during the destructors on the unit side, Unhandled exception at 0x002e4200 in ClassAllocation.exe: 0xC0000005: Access violation reading location 0x00000000. UnitCollection destructor: UnitCol::~UnitCol() { list<Unit>::iterator itr; for(itr = UnitCollection.begin(); itr != UnitCollection.end();) { UnitCollection.pop_front(); itr = UnitCollection.begin(); } } Unit Destructor Unit::~Unit() { } now i got the same sorta problem on the student side of things BST destructors void StudentCol::Destructor(const BTreeNode * r) { if(r!= 0) { Destructor(r->getLChild()); Destructor(r->getRChild()); delete r; } } StudentCol::~StudentCol() { Destructor(root); } Student Destructor Student::~Student() { } so yeah any help would be greatly appreciated

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• NullPointerException with Servlet

  - by RonaDona

  I am calling a Servlet using its URL address. This is the URL I am typing http://localhost:7001/ryan/olympics?action=selectCatalog&id=1 This is the Servlet's URL for sure; if I change the address I get page not found This is the code for the Servlet. public class Servlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { private static final long serialVersionUID = 1L; public Servlet() { super(); } public void init(ServletConfig config) throws ServletException { System.out.println("*** initializing controller servlet."); super.init(config); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String action = request.getParameter("action"); if (action.equals("selectCatalog")) { String categoryId = request.getParameter("id"); ProductModelDAO dao4 = new ProductModelDAOImpl("jpac"); if (categoryId != null && !categoryId.trim().equals("")) { CategoryDAO dao1 = new CategoryDAOImpl("jpac"); try { Category category = dao1.getCategoryName(categoryId); request.setAttribute("category", category); } catch (Exception e) { e.printStackTrace(); } } try { @SuppressWarnings("unchecked") List<Product> products = dao4 .getProductsByCategory(categoryId); request.setAttribute("products", products); } catch (Exception e) { e.printStackTrace(); } url = "SelectCatalog.jsp"; RequestDispatcher requestDispatcher = getServletContext().getRequestDispatcher(url); requestDispatcher.forward(request, response); I get the NullPointerException pointing to the RequestDispatcher's line. Any help?

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• Where is the "ListViewItemPlaceholderBackgroundThemeBrush" located?

  - by Dimi Toulakis

  I have a problem understanding one style definition in Windows 8 metro apps. When you create a metro style application with VS, there is also a folder named Common created. Inside this folder there is file called StandardStyles.xaml Now the following snippet is from this file: <!-- Grid-appropriate 250 pixel square item template as seen in the GroupedItemsPage and ItemsPage --> <DataTemplate x:Key="Standard250x250ItemTemplate"> <Grid HorizontalAlignment="Left" Width="250" Height="250"> <Border Background="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}"> <Image Source="{Binding Image}" Stretch="UniformToFill"/> </Border> <StackPanel VerticalAlignment="Bottom" Background="{StaticResource ListViewItemOverlayBackgroundThemeBrush}"> <TextBlock Text="{Binding Title}" Foreground="{StaticResource ListViewItemOverlayForegroundThemeBrush}" Style="{StaticResource TitleTextStyle}" Height="60" Margin="15,0,15,0"/> <TextBlock Text="{Binding Subtitle}" Foreground="{StaticResource ListViewItemOverlaySecondaryForegroundThemeBrush}" Style="{StaticResource CaptionTextStyle}" TextWrapping="NoWrap" Margin="15,0,15,10"/> </StackPanel> </Grid> </DataTemplate> What I do not understand here is the static resource definition, e.g. for the Border Background="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}" It is not about how you work with templates and binding and resources. Where is this ListViewItemPlaceholderBackgroundThemeBrush located? Many thanks for your help. Dimi

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• Get an array of structures from native dll to c# application

  - by PaulH

  I have a C# .NET 2.0 CF project where I need to invoke a method in a native C++ DLL. This native method returns an array of type TableEntry. At the time the native method is called, I do not know how large the array will be. How can I get the table from the native DLL to the C# project? Below is effectively what I have now. // in C# .NET 2.0 CF project [StructLayout(LayoutKind.Sequential)] public struct TableEntry { [MarshalAs(UnmanagedType.LPWStr)] public string description; public int item; public int another_item; public IntPtr some_data; } [DllImport("MyDll.dll", CallingConvention = CallingConvention.Winapi, CharSet = CharSet.Auto)] public static extern bool GetTable(ref TableEntry[] table); SomeFunction() { TableEntry[] table = null; bool success = GetTable( ref table ); // at this point, the table is empty } // In Native C++ DLL std::vector< TABLE_ENTRY > global_dll_table; extern "C" __declspec(dllexport) bool GetTable( TABLE_ENTRY* table ) { table = &global_dll_table.front(); return true; } Thanks, PaulH

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• Java downcasting dilemma

  - by Shades88

  please have a look at this code here. class Vehicle { public void printSound() { System.out.print("vehicle"); } } class Car extends Vehicle { public void printSound() { System.out.print("car"); } } class Bike extends Vehicle{ public void printSound() { System.out.print("bike"); } } public class Test { public static void main(String[] args) { Vehicle v = new Car(); Bike b = (Bike)v; v.printSound(); b.printSound(); Object myObj = new String[]{"one", "two", "three"}; for (String s : (String[])myObj) System.out.print(s + "."); } } Executing this code will give ClassCastException saying inheritance.Car cannot be cast to inheritance.Bike. Now look at the line Object myObj = new String[]{"one", "two", "three"};. This line is same as Vehicle v = new Car(); right? In both lines we are assigning sub class object to super class reference variable. But downcasting String[]myObj is allowed but (Bike)v is not. Please help me understand what is going on around here.

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• setBit java method using bit shifting and hexadecimal code - question

  - by somewhat_confused

  I am having trouble understanding what is happening in the two lines with the 0xFF7F and the one below it. There is a link here that explains it to some degree. http://www.herongyang.com/java/Bit-String-Set-Bit-to-Byte-Array.html I don't know if 0xFF7FposBit) & oldByte) & 0x00FF are supposed to be 3 values 'AND'ed together or how this is supposed to be read. If anyone can clarify what is happening here a little better, I would greatly appreciate it. private static void setBit(byte[] data, final int pos, final int val) { int posByte = pos/8; int posBit = pos%8; byte oldByte = data[posByte]; oldByte = (byte) (((0xFF7F>>posBit) & oldByte) & 0x00FF); byte newByte = (byte) ((val<<(8-(posBit+1))) | oldByte); data[posByte] = newByte; } passed into this method as parameters from a selectBits method was setBit(out,i,val); out = is byte[] out = new byte[numOfBytes]; (numOfBytes can be 7 in this situation) i = which is number [57], the original number from the PC1 int array holding the 56-integers. val = which is the bit taken from the byte array from the getBit() method.

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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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• Using Quartz to draw every second via NSTimer (iPhone)

  - by stuartloxton

  Hi, I'm relatively new to Objective-C + Quartz and am running into what is probably a very simple issue. I have a custom UIView sub class which I am using to draw simple rectangles via Quartz. However I am trying to hook up an NSTimer so that it draws a new object every second, the below code will draw the first rectangle but will never draw again. The function is being called (the NSLog is run) but nothing is draw. Code: - (void)drawRect:(CGRect)rect { context = UIGraphicsGetCurrentContext(); [self step:self]; [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)(2) target:self selector:@selector(step:) userInfo:nil repeats:TRUE]; } - (void) step:(id) sender { static double trans = 0.5f; CGContextSetRGBFillColor(context, 1, 0, 0, trans); CGContextAddRect(context, CGRectMake(10, 10, 10, 10)); CGContextFillPath(context); NSLog(@"Trans: %f", trans); trans += 0.01; } context is in my interface file as: CGContextRef context; Any help will be greatly appreciated!

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• How do I debug into an ILMerged assembly?

  - by Rory Becker

  Summary I want to alter the build process of a 2-assembly solution, such that a call to ILMerge is invoked, and the build results in a single assembly. Further I would like to be able to debug into the resultant assembly. Preparation - A simple example New Solution - ClassLibrary1 Create a static function 'GetMessage' in Class1 which returns the string "Hello world" Create new console app which references the ClassLibrary. Output GetMessage from main() via the console. You now have a 2 assembly app which outputs "Hello World" to the console. So what next..? I would like to alter the Console app build process, to include a post build step which uses ILMerge, to merge the ClassLibrary assembly into the Console assembly After this step I should be able to: Run the Console app directly with no ClassLibrary1.dll present Run the Console app via F5 (or F11) in VS and be able to debug into each of the 2 projects. Limited Success I read this blogpost and managed to achieve the merge I was after with a post-build command of... "$(ProjectDir)ILMerge.bat" "$(TargetDir)" $(ProjectName) ...and an ILMerge.bat file which read... CD %1 Copy %2.exe temp.exe ILMerge.exe /out:%2.exe temp.exe ClassLibrary1.dll Del temp.exe Del ClassLibrary1.* This works fairly well, and does in fact produce an exe which runs outside the VS environment as required. However it does not appear to produce symbols (.pdb file) which VS is able to use in order to debug into the code. I think this is the last piece of the puzzle. Does anyone know how I can make this work? FWIW I am running VS2010 on an x64 Win7 x64 machine.

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• Checking instance of non-class constrained type parameter for null in generic method

  - by casperOne

  I currently have a generic method where I want to do some validation on the parameters before working on them. Specifically, if the instance of the type parameter T is a reference type, I want to check to see if it's null and throw an ArgumentNullException if it's null. Something along the lines of: // This can be a method on a generic class, it does not matter. public void DoSomething<T>(T instance) { if (instance == null) throw new ArgumentNullException("instance"); Note, I do not wish to constrain my type parameter using the class constraint. I thought I could use Marc Gravell's answer on "How do I compare a generic type to its default value?", and use the EqualityComparer<T> class like so: static void DoSomething<T>(T instance) { if (EqualityComparer<T>.Default.Equals(instance, null)) throw new ArgumentNullException("instance"); But it gives a very ambiguous error on the call to Equals: Member 'object.Equals(object, object)' cannot be accessed with an instance reference; qualify it with a type name instead How can I check an instance of T against null when T is not constrained on being a value or reference type?

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• Different users get the same cookie - value in .ASPXANONYMOUS

  - by Malcolm Frexner

  My site allows anonymous users. I saw that under heavy load user get sometimes profile values from other users. This happens for anonymous users. I logged the access to profile data: /// <summary> /// /// </summary> /// <param name="controller"></param> /// <returns></returns> public static string ProfileID(this Controller controller ) { if (ApplicationConfiguration.LogProfileAccess) { StringBuilder sb = new StringBuilder(); (from header in controller.Request.Headers.ToPairs() select string.Concat(header.Key, ":", header.Value, ";")).ToList().ForEach(x => sb.Append(x)); string log = string.Format("ip:{0} url:{1} IsAuthenticated:{2} Name:{3} AnonId:{4} header:{5}", controller.Request.UserHostAddress, controller.Request.Url.ToString(), controller.Request.IsAuthenticated, controller.User.Identity.Name, controller.Request.AnonymousID, sb); _log.Debug(log); } return controller.Request.IsAuthenticated ? controller.User.Identity.Name : controller.Request.AnonymousID; } I can see in the log that user realy get the same cookievalue for .ASPXANONYMOUS even if they have different IP. Just to be safe I removed dependency injection for the FormsAuthentication. I dont use OutputCaching. My web.config has this setting for authentication: <anonymousIdentification enabled="true" cookieless="UseCookies" cookieName=".ASPXANONYMOUS" cookieTimeout="30" cookiePath="/" cookieRequireSSL="false" cookieSlidingExpiration="true" /> <authentication mode="Forms"> <forms loginUrl="~/de/Account/Login" /> </authentication> Does anybody have an idea what else I could log or what I should have a look at?

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• iphone table view check mark accessory problem

  - by Pankaj Kainthla

  I have a table with 50 rows. I want to select particular rows with checkmark accessory but when i select some rows and scroll down the table then i see pre checked rows. I know that table cell are reused but i want to emit this problem what can i do about this? - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // return [array count]; return 50; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; TableViewCell *cell = (TableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[TableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text=[NSString stringWithFormat:@"%i",[indexPath row]]; return cell; } // Override to support row selection in the table view. - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath]; if (cell.accessoryType == UITableViewCellAccessoryNone) { cell.accessoryType = UITableViewCellAccessoryCheckmark; } else { cell.accessoryType = UITableViewCellAccessoryNone; }

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• Including partial views when applying the Mode-View-ViewModel design pattern

  - by Filip Ekberg

  Consider that I have an application that just handles Messages and Users I want my Window to have a common Menu and an area where the current View is displayed. I can only work with either Messages or Users so I cannot work simultaniously with both Views. Therefore I have the following Controls MessageView.xaml UserView.xaml Just to make it a bit easier, both the Message Model and the User Model looks like this: Name Description Now, I have the following three ViewModels: MainWindowViewModel UsersViewModel MessagesViewModel The UsersViewModel and the MessagesViewModel both just fetch an ObserverableCollection<T> of its regarding Model which is bound in the corresponding View like this: <DataGrid ItemSource="{Binding ModelCollection}" /> The MainWindowViewModel hooks up two different Commands that have implemented ICommand that looks something like the following: public class ShowMessagesCommand : ICommand { private ViewModelBase ViewModel { get; set; } public ShowMessagesCommand (ViewModelBase viewModel) { ViewModel = viewModel; } public void Execute(object parameter) { var viewModel = new ProductsViewModel(); ViewModel.PartialViewModel = new MessageView { DataContext = viewModel }; } public bool CanExecute(object parameter) { return true; } public event EventHandler CanExecuteChanged; } And there is another one a like it that will show Users. Now this introduced ViewModelBase which only holds the following: public UIElement PartialViewModel { get { return (UIElement)GetValue(PartialViewModelProperty); } set { SetValue(PartialViewModelProperty, value); } } public static readonly DependencyProperty PartialViewModelProperty = DependencyProperty.Register("PartialViewModel", typeof(UIElement), typeof(ViewModelBase), new UIPropertyMetadata(null)); This dependency property is used in the MainWindow.xaml to display the User Control dynamicly like this: <UserControl Content="{Binding PartialViewModel}" /> There are also two buttons on this Window that fires the Commands: ShowMessagesCommand ShowUsersCommand And when these are fired, the UserControl changes because PartialViewModel is a dependency property. I want to know if this is bad practice? Should I not inject the User Control like this? Is there another "better" alternative that corresponds better with the design pattern? Or is this a nice way of including partial views?

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• Am I going the right way to make login system secure with this simple password salting?

  - by LoVeSmItH

  I have two fields in login table password salt And I have this little function to generate salt function random_salt($h_algo="sha512"){ $salt1=uniqid(rand(),TRUE); $salt2=date("YmdHis").microtime(true); if(function_exists('dechex')){ $salt2=dechex($salt2); } $salt3=$_SERVER['REMOTE_ADDR']; $salt=$salt1.$salt2.$salt3; if(function_exists('hash')){ $hash=(in_array($h_algo,hash_algos()))?$h_algo:"sha512"; $randomsalt=hash($hash,md5($salt)); //returns 128 character long hash if sha512 algorithm is used. }else{ $randomsalt=sha1(md5($salt)); //returns 40 characters long hash } return $randomsalt; } Now to create user password I have following $userinput=$_POST["password"] //don't bother about escaping, i have done it in my real project. $static_salt="THIS-3434-95456-IS-RANDOM-27883478274-SALT"; //some static hard to predict secret salt. $salt=random_salt(); //generates 128 character long hash. $password =sha1($salt.$userinput.$static_salt); $salt is saved in salt field of database and $password is saved in password field. My problem, In function random_salt(), I m having this FEELING that I'm just making things complicated while this may not generate secure salt as it should. Can someone throw me a light whether I m going in a right direction? P.S. I do have an idea about crypt functions and like such. Just want to know is my code okay? Thanks.

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• Why SetMinimumSize sets the minimal heights but not width?

  - by Roman

  Here is my code: import javax.swing.*; import java.awt.*; public class PanelModel { public static void main(String[] args) { JFrame frame = new JFrame("Colored Trails"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel mainPanel = new JPanel(); mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS)); JPanel firstPanel = new JPanel(); firstPanel.setLayout(new GridLayout(4, 4)); firstPanel.setMaximumSize(new Dimension(4*100, 4*100)); firstPanel.setMinimumSize(new Dimension(4*100, 4*100)); JButton btn; for (int i=1; i<=4; i++) { for (int j=1; j<=4; j++) { btn = new JButton(); btn.setPreferredSize(new Dimension(100, 100)); firstPanel.add(btn); } } mainPanel.add(firstPanel); frame.add(mainPanel); frame.setSize(520,600); //frame.setMinimumSize(new Dimension(520,600)); frame.setVisible(true); } } When I increase the size of the window (by mouse) I see that my panel does not increase its size. It is the expected behavior (because I set the maximal size of the panel). However, when I decrease the size of the window, I see that width of the panel is decreased too (while the height is constant). So, the setMinimumSize works only partially. Why is that?

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• How do I patch a Windows API at runtime so that it to returns 0 in x64?

  - by Jorge Vasquez

  In x86, I get the function address using GetProcAddress() and write a simple XOR EAX,EAX; RET; in it. Simple and effective. How do I do the same in x64? bool DisableSetUnhandledExceptionFilter() { const BYTE PatchBytes[5] = { 0x33, 0xC0, 0xC2, 0x04, 0x00 }; // XOR EAX,EAX; RET; // Obtain the address of SetUnhandledExceptionFilter HMODULE hLib = GetModuleHandle( _T("kernel32.dll") ); if( hLib == NULL ) return false; BYTE* pTarget = (BYTE*)GetProcAddress( hLib, "SetUnhandledExceptionFilter" ); if( pTarget == 0 ) return false; // Patch SetUnhandledExceptionFilter if( !WriteMemory( pTarget, PatchBytes, sizeof(PatchBytes) ) ) return false; // Ensures out of cache FlushInstructionCache(GetCurrentProcess(), pTarget, sizeof(PatchBytes)); // Success return true; } static bool WriteMemory( BYTE* pTarget, const BYTE* pSource, DWORD Size ) { // Check parameters if( pTarget == 0 ) return false; if( pSource == 0 ) return false; if( Size == 0 ) return false; if( IsBadReadPtr( pSource, Size ) ) return false; // Modify protection attributes of the target memory page DWORD OldProtect = 0; if( !VirtualProtect( pTarget, Size, PAGE_EXECUTE_READWRITE, &OldProtect ) ) return false; // Write memory memcpy( pTarget, pSource, Size ); // Restore memory protection attributes of the target memory page DWORD Temp = 0; if( !VirtualProtect( pTarget, Size, OldProtect, &Temp ) ) return false; // Success return true; } This example is adapted from code found here: http://www.debuginfo.com/articles/debugfilters.html#overwrite .

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• MyController class must produce class according to the enum type.

  - by programmerist

  GenoTipController must produce class according to the enum type. i have 3 class: _Company,_Muayene,_Radyoloji. Also i have CompanyView Class GetPersonel method. if you look GenoTipController my codes need refactoring. Can you understand me? i need a class according to ewnum type must me produce class. For example; case DataModelType.Radyoloji it must return radyoloji= new Radyoloji . Everything must be one switch case? public class GenoTipController { public _Company GenerateCompany(DataModelType modeltype) { _Company company = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: company = new Company(); break; default: break; } return company; } public _Muayene GenerateMuayene(DataModelType modeltype) { _Muayene muayene = null; switch (modeltype) { case DataModelType.Radyoloji: break; case DataModelType.Satis: break; case DataModelType.Muayene: muayene = new Muayene(); break; case DataModelType.Company: break; default: break; } return muayene; } public _Radyoloji GenerateRadyoloji(DataModelType modeltype) { _Radyoloji radyoloji = null; switch (modeltype) { case DataModelType.Radyoloji: radyoloji = new Radyoloji(); break; case DataModelType.Satis: break; case DataModelType.Muayene: break; case DataModelType.Company: break; default: break; } return radyoloji; } } public class CompanyView { public static List GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.GenerateCompany(DataModelType.Company); return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company } }

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• What if a large number of objects are passed to my SwingWorker.process() method?

  - by Trejkaz

  I just found an interesting situation. Suppose you have some SwingWorker (I've made this one vaguely reminiscent of my own): public class AddressTreeBuildingWorker extends SwingWorker<Void, NodePair> { private DefaultTreeModel model; public AddressTreeBuildingWorker(DefaultTreeModel model) { } @Override protected Void doInBackground() { // Omitted; performs variable processing to build a tree of address nodes. } @Override protected void process(List<NodePair> chunks) { for (NodePair pair : chunks) { // Actually the real thing inserts in order. model.insertNodeInto(parent, child, parent.getChildCount()); } } private static class NodePair { private final DefaultMutableTreeNode parent; private final DefaultMutableTreeNode child; private NodePair(DefaultMutableTreeNode parent, DefaultMutableTreeNode child) { this.parent = parent; this.child = child; } } } If the work done in the background is significant then things work well - process() is called with relatively small lists of objects and everything is happy. Problem is, if the work done in the background is suddenly insignificant for whatever reason, process() receives a huge list of objects (I have seen 1,000,000, for instance) and by the time you process each object, you have spent 20 seconds on the Event Dispatch Thread, exactly what SwingWorker was designed to avoid. In case it isn't clear, both of these occur on the same SwingWorker class for me - it depends on the input data, and the type of processing the caller wanted. Is there a proper way to handle this? Obviously I can intentionally delay or yield the background processing thread so that a smaller number might arrive each time, but this doesn't feel like the right solution to me.

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• Immutable classes in C++

  - by ereOn

  Hi, In one of my projects, I have some classes that represent entities that cannot change once created, aka. immutable classes. Example : A class RSAKey that represent a RSA key which only has const methods. There is no point changing the existing instance: if you need another one, you just create one. My objects sometimes are heavy and I enforced the use of smart pointers to avoid copy. So far, I have the following pattern for my classes: class RSAKey : public boost::noncopyable, public boost::enable_shared_from_this<RSAKey> { public: /** * \brief Some factory. * \param member A member value. * \return An instance. */ static boost::shared_ptr<const RSAKey> createFromMember(int member); /** * \brief Get a member. * \return The member. */ int getMember() const; private: /** * \brief Constructor. * \param member A member. */ RSAKey(int member); /** * \brief Member. */ const int m_member; }; So you can only get a pointer (well, a smart pointer) to a const RSAKey. To me, it makes sense, because having a non-const reference to the instance is useless (it only has const methods). Do you guys see any issue regarding this pattern ? Are immutable classes something common in C++ or did I just created a monster ? Thank you for your advices !

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• Finding users whose birtday is today with JPA

  - by Jeduan Cornejo

  Hi, I have a table with users and are trying to get a list with the people who have birthday today so the app can send an email. The User is defined as @Entity public class User { @Size(max = 30) @NotNull private String name; [...] @Temporal(TemporalType.DATE) @DateTimeFormat(style = "S-") protected Date birthday; } and I've got a method which returns the people which were born today like so @SuppressWarnings("unchecked") public static List<User> findUsersWithBirthday() { List<User> users = entityManager().createQuery("select u from User u where u.birthday = :date") .setParameter("date", new Date(), TemporalType.DATE) .getResultList(); return users; } This is fine and all for finding people which were born today, however tha's not really that useful, so I've been struggling for a way to find all the users that were born today, independent of the year. Using MySQL there's functions I can use like select month(curdate()) as month, dayofmonth(curdate()) as day However I've been struggling to find a JPA equivalent to that. I'm using Spring 3.0.1 and Hibernate 3.3.2

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• Comparing all properties of an object using expression trees

  - by stringargs

  Hi, I'm trying to write a simple generator that uses an expression tree to dynamically generate a method that compares all properties of an instance of a type to the properties of another instance of that type. This works fine for most properties, like int an string, but fails for DateTime? (and presumably other nullable value types). The method: static Delegate GenerateComparer(Type type) { var left = Expression.Parameter(type, "left"); var right = Expression.Parameter(type, "right"); Expression result = null; foreach (var p in type.GetProperties()) { var leftProperty = Expression.Property(left, p.Name); var rightProperty = Expression.Property(right, p.Name); var equals = p.PropertyType.GetMethod("Equals", new[] { p.PropertyType }); var callEqualsOnLeft = Expression.Call(leftProperty, equals, rightProperty); result = result != null ? (Expression)Expression.And(result, callEqualsOnLeft) : (Expression)callEqualsOnLeft; } var method = Expression.Lambda(result, left, right).Compile(); return method; } On a DateTime? property it fails with: Expression of type 'System.Nullable`1[System.DateTime]' cannot be used for parameter of type 'System.Object' of method 'Boolean Equals(System.Object)' OK, so it finds an overload of Equals that expects object. So why can't I pass a DateTime? into that, as it's convertible to object? If I look at Nullable<T>, it indeed has an override of Equals(object o). PS: I realize that this isn't a proper generator yet as it can't deal with null values, but I'll get to that :)

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• Using libgrib2c in c++ application, linker error "Undefined reference to..."

  - by Rich

  EDIT: If you're going to be doing things with GRIB files I would recommend the GDAL library which is backed by the Open Source Geospatial Foundation. You will save yourself a lot of headache :) I'm using Qt creator in Ubuntu creating a c++ app. I am attempting to use an external lib, libgrib2c.a, that has a header grib2.h. Everything compiles, but when it tries to link I get the error: undefined reference to 'seekgb(_IO_FILE*, long, long, long*, long*) I have tried wrapping the header file with: extern "C"{ #include "grib2.h" } But it didn't fix anything so I figured that was not my problem. In the .pro file I have the line: include($${ROOT}/Shared/common/commonLibs.pri) and in commonLibs.pri I have: INCLUDEPATH+=$${ROOT}/external_libs/g2clib/include LIBS+=-L$${ROOT}/external_libs/g2clib/lib LIBS+=-lgrib2c I am not encountering an error finding the library. If I do a nm command on the libgrib2c.a I get: nm libgrib2c.a | grep seekgb seekgb.o: 00000000 T seekgb And when I run qmake with the additional argument of LIBS+=-Wl,--verbose I can find the lib file in the output: attempt to open /usr/lib/libgrib2c.so failed attempt to open /usr/lib/libgrib2c.a failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.so failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.a failed attempt to open ..//Shared/Config/lib/libgrib2c.so failed attempt to open ..//Shared/Config/lib/libgrib2c.a failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.so failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.a failed attempt to open ..//external_libs/openssl/lib/libgrib2c.so failed attempt to open ..//external_libs/openssl/lib/libgrib2c.a failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.so failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.a succeeded Although it doesn't show any of the .o files in the library is this because it is a c library in my c++ app? in the .cpp file that I am trying to use the library I have: #include "gribreader.h" #include <stdio.h> #include <stdlib.h> #include <external_libs/g2clib/include/grib2.h> #include <Shared/logging/Logger.hpp> //------------------------------------------------------------------------------ /// Opens a GRIB file from disk. /// /// This function opens the grib file and searches through it for how many GRIB /// messages are contained as well as their starting locations. /// /// \param a_filePath. The path to the file to be opened. /// \return True if successful, false if not. //------------------------------------------------------------------------------ bool GRIBReader::OpenGRIB(std::string a_filePath) { LOG(notification)<<"Attempting to open grib file: "<< a_filePath; if(isOpen()) { CloseGRIB(); } m_filePath = a_filePath; m_filePtr = fopen(a_filePath.c_str(), "r"); if(m_filePtr == NULL) { LOG(error)<<"Unable to open file: " << a_filePath; return false; } LOG(notification)<<"Successfully opened GRIB file"; g2int currentMessageSize(1); g2int seekPosition(0); g2int lengthToBeginningOfGrib(0); g2int seekLength(32000); int i(0); int iterationLimit(300); m_GRIBMessageLocations.clear(); m_GRIBMessageSizes.clear(); while(i < iterationLimit) { seekgb(m_filePtr, seekPosition, seekLength, &lengthToBeginningOfGrib, &currentMessageSize); if(currentMessageSize != 0) { LOG(verbose) << "Adding GRIB message location " << lengthToBeginningOfGrib << " with length " << currentMessageSize; m_GRIBMessageLocations.push_back(lengthToBeginningOfGrib); m_GRIBMessageSizes.push_back(currentMessageSize); seekPosition = lengthToBeginningOfGrib + currentMessageSize; LOG(verbose) << "GRIB seek position moved to " << seekPosition; } else { LOG(notification)<<"End of GRIB file found, after "<< i << " GRIB messages."; break; } } if(i >= iterationLimit) { LOG(warning) << "The iteration limit of " << iterationLimit << "was reached while searching for GRIB messages"; } return true; } And the header grib2.h is as follows: #ifndef _grib2_H #define _grib2_H #include<stdio.h> #define G2_VERSION "g2clib-1.4.0" #ifdef __64BIT__ typedef int g2int; typedef unsigned int g2intu; #else typedef long g2int; typedef unsigned long g2intu; #endif typedef float g2float; struct gtemplate { g2int type; /* 3=Grid Defintion Template. */ /* 4=Product Defintion Template. */ /* 5=Data Representation Template. */ g2int num; /* template number. */ g2int maplen; /* number of entries in the static part */ /* of the template. */ g2int *map; /* num of octets of each entry in the */ /* static part of the template. */ g2int needext; /* indicates whether or not the template needs */ /* to be extended. */ g2int extlen; /* number of entries in the template extension. */ g2int *ext; /* num of octets of each entry in the extension */ /* part of the template. */ }; typedef struct gtemplate gtemplate; struct gribfield { g2int version,discipline; g2int *idsect; g2int idsectlen; unsigned char *local; g2int locallen; g2int ifldnum; g2int griddef,ngrdpts; g2int numoct_opt,interp_opt,num_opt; g2int *list_opt; g2int igdtnum,igdtlen; g2int *igdtmpl; g2int ipdtnum,ipdtlen; g2int *ipdtmpl; g2int num_coord; g2float *coord_list; g2int ndpts,idrtnum,idrtlen; g2int *idrtmpl; g2int unpacked; g2int expanded; g2int ibmap; g2int *bmap; g2float *fld; }; typedef struct gribfield gribfield; /* Prototypes for unpacking API */ void seekgb(FILE *,g2int ,g2int ,g2int *,g2int *); g2int g2_info(unsigned char *,g2int *,g2int *,g2int *,g2int *); g2int g2_getfld(unsigned char *,g2int ,g2int ,g2int ,gribfield **); void g2_free(gribfield *); /* Prototypes for packing API */ g2int g2_create(unsigned char *,g2int *,g2int *); g2int g2_addlocal(unsigned char *,unsigned char *,g2int ); g2int g2_addgrid(unsigned char *,g2int *,g2int *,g2int *,g2int ); g2int g2_addfield(unsigned char *,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *); g2int g2_gribend(unsigned char *); /* Prototypes for supporting routines */ extern double int_power(double, g2int ); extern void mkieee(g2float *,g2int *,g2int); void rdieee(g2int *,g2float *,g2int ); extern gtemplate *getpdstemplate(g2int); extern gtemplate *extpdstemplate(g2int,g2int *); extern gtemplate *getdrstemplate(g2int); extern gtemplate *extdrstemplate(g2int,g2int *); extern gtemplate *getgridtemplate(g2int); extern gtemplate *extgridtemplate(g2int,g2int *); extern void simpack(g2float *,g2int,g2int *,unsigned char *,g2int *); extern void compack(g2float *,g2int,g2int,g2int *,unsigned char *,g2int *); void misspack(g2float *,g2int ,g2int ,g2int *, unsigned char *, g2int *); void gbit(unsigned char *,g2int *,g2int ,g2int ); void sbit(unsigned char *,g2int *,g2int ,g2int ); void gbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); void sbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); int pack_gp(g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *); #endif /* _grib2_H */ I have been scratching my head for two days on this. If anyone has an idea on what to do or can point me in some sort of direction, I'm stumped. Also, if you have any comments on how I can improve this post I'd love to hear them, kinda new at this posting thing. Usually I'm able to find an answer in the vast stores of knowledge already contained on the web.

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• Multiple generic parameters on a html helper extension method

  - by WestDiscGolf

  What I'm trying to do is create an extension method for the HtmlHelper to create a specific output and associated details like TextBoxFor<. What I want to do is specify the property from the model class as per TextBoxFor<, then an associated controller action and other parameters. So far the signature of the method looks like: public static MvcHtmlString Create<TModel, TProperty, TController>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, Expression<Action<TController>> action, object htmlAttributes) where TController : Controller where TModel : class The issue occurs when I go to call it. In my view if I call it as per the TextBoxFor without specifying the Model type I am able to specify the lambda expression to set the property which it's for, but when I go to specify the action I am unable to. However, when I specify the controller type Html.Create<HomeController>( ... ) I am unable to specify the model property that the control is to be created for. I want to be able to call it like <%= Html.Create(x => x.Title, controller => controller.action, null) %> I've been hitting my head for a few hours now on this issue over the past day, can anyone point me in the right direction?

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• How to print a page when a JButton is pressed in java swing using PrinterJob?

  - by Prayag Upd

  I tried the following code AWT but at runtime shows multiple print dialogs repeatedly.... package printerjob; import java.awt.BasicStroke; import java.awt.Frame; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.event.WindowAdapter; import java.awt.print.PageFormat; import java.awt.print.Printable; import java.awt.print.PrinterException; import java.awt.print.PrinterJob; /** * * @author pragX */ public class FramePrinterJob extends Frame implements Printable{ public void start(){ add(button); } @Override public void paint(Graphics graphics){ PrinterJob printerJob=PrinterJob.getPrinterJob(); printerJob.setPrintable(this); if(printerJob.printDialog()){ try{ printerJob.print(); }catch(PrinterException printerException){ //printerException.printStackTrace(); System.out.println("Error Printing." + printerException); } } } public int print(Graphics graphics, PageFormat pageFormat, int pageIndex) throws PrinterException { //throw new UnsupportedOperationException("Not supported yet."); if(pageIndex>=1){ return Printable.NO_SUCH_PAGE; } graphics.translate((int) pageFormat.getImageableX(), (int)pageFormat.getImageableY()); Graphics2D graphics2D=(Graphics2D)graphics; graphics2D.setStroke(new BasicStroke(4f)); graphics2D.drawLine(20, 20, 20, 120); graphics2D.drawLine(40, 20, 40, 120); graphics2D.drawLine(20, 70, 40, 70); graphics2D.drawLine(60, 70, 60, 120); graphics2D.drawLine(60, 40, 60, 45); return Printable.PAGE_EXISTS; } public static void main(String args[]){ Frame frame=new FramePrinterJob(); frame.addWindowListener(new WindowAdapter() { public void windowClosing(){System.exit(0);}}); frame.setSize(300,400); frame.setVisible(true); } }

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• Why do the outputs differ when I run this code using Netbeans 6.8 and Eclipse?

  - by Vimal Basdeo

  When I am running the following codes using Eclipse and Netbeans 6.8. I want to see the available COM ports on my computer. When running in Eclipse it is returning me all available COm ports but when running t in Netbeans, it does not seem to find any ports .. public static void test(){ Enumeration lists=CommPortIdentifier.getPortIdentifiers(); System.out.println(lists.hasMoreElements()); while (lists.hasMoreElements()){ CommPortIdentifier cn=(CommPortIdentifier)lists.nextElement(); if ((CommPortIdentifier.PORT_SERIAL==cn.getPortType())){ System.out.println("Name is serail portzzzz "+cn.getName()+" Owned status "+cn.isCurrentlyOwned()); try{ SerialPort port1=(SerialPort)cn.open("ComControl",800000); port1.setSerialPortParams(9600, SerialPort.DATABITS_8, SerialPort.STOPBITS_1, SerialPort.PARITY_NONE); System.out.println("Before get stream"); OutputStream out=port1.getOutputStream(); InputStream input=port1.getInputStream(); System.out.println("Before write"); out.write("AT".getBytes()); System.out.println("After write"); int sample=0; //while((( sample=input.read())!=-1)){ System.out.println("Before read"); //System.out.println(input.read() + "TEsting "); //} System.out.println("After read"); System.out.println("Receive timeout is "+port1.getReceiveTimeout()); }catch(Exception e){ System.err.println(e.getMessage()); } } else{ System.out.println("Name is parallel portzzzz "+cn.getName()+" Owned status "+cn.isCurrentlyOwned()+cn.getPortType()+" "); } } } Output with Netbeans false Output using Eclipse true Name is serail portzzzz COM1 Owned status false Before get stream Before write After write Before read After read Receive timeout is -1 Name is serail portzzzz COM2 Owned status false Before get stream Before write After write Before read After read Receive timeout is -1 Name is parallel portzzzz LPT1 Owned status false2 Name is parallel portzzzz LPT2 Owned status false2

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