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• Copy constructor called even when returning by reference?

  - by Johnyy

  Hi, I am testing the return of local objects by reference. My original test went well but something else happens unexpected. #include <iostream> using namespace std; class MyInt { public: MyInt(int i){ value = new int(i); } ~MyInt(){ delete value; } int getValue(){ return *value; } MyInt(const MyInt &b){ cout<<"Copy"<<endl; } private: int* value; }; MyInt& returnref(){ MyInt a(10); cout<<"Returning from returnref()"<<endl; return a; } int main(){ MyInt a = returnref(); cout<<a.getValue()<<endl; return 0; } My console prints "Returning from ..." then "Copy" then a random value. My understanding of pass by reference is that it does not need to make any copy. Why is it not doing what I expected?

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• Cant display button on specific rows of UITableView properly for iPhone

  - by varunwg

  Hi, I am trying to have a button for selected rows of my table. Here is the example code I am using: - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *ControlRowIdentifier = @"ControlRowIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ControlRowIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:ControlRowIdentifier] autorelease]; } if ([indexPath row] > 5) { UIImage *buttonUpImage = [UIImage imageNamed:@"button_up.png"]; UIImage *buttonDownImage = [UIImage imageNamed:@"button_down.png"]; UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; button.frame = CGRectMake(0.0, 0.0, buttonUpImage.size.width, buttonUpImage.size.height); [button setBackgroundImage:buttonUpImage forState:UIControlStateNormal]; [button setBackgroundImage:buttonDownImage forState:UIControlStateHighlighted]; [button setTitle:@"Tap" forState:UIControlStateNormal]; [button addTarget:self action:@selector(buttonTapped:) forControlEvents:UIControlEventTouchUpInside]; cell.accessoryView = button; } NSUInteger row = [indexPath row]; NSString *rowTitle = [list objectAtIndex:row]; cell.textLabel.text = rowTitle; return cell; } This code works absolutely fine when loaded for 1st time. So, as per the logic it shows 'Tap' button for all rows greater than 5. Problem occurs when I scroll up and down. Once I do that it just starts putting that button at any random row. I dont understand why it does that and it'll be really helpful if someone can give some tips on this. Thanks.

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• Cant print contents of a custom file

  - by ZaZu

  Hello, Im trying to scan contents from a random file into an array in a structure. Then I want to print those contents on screen. (NOTE: The following code is from a bigger program, this is just a sample, but all structures and arrays used are needed as declared ) The contents of the file being tested are simply: 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); int trialdisplay(trial *test); main(){ trial test; trialtest(&test); trialdisplay(&test); } int trialtest(trial *test){ int z,x,i; FILE *inputf; inputf=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(inputf,"%f",&(*test).what[z][x]); } fclose(inputf); return 0; } int trialdisplay(trial *test){ int i,z,x; printf("printing\n\n\n"); for (i=0;i<10;i++){ printf("%f",(*test).what[z][x]); } return 0; } The problem is, I get this error whenever I run the code .. I cant really understand whats going on : Any suggestions ? Thanks alot !

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• Android: How to put ListView in XML?

  - by FloIancu

  I want to make a simple app that shows a list of contacts (name, surname). My code: package lista.android; import java.util.*; import android.app.ListActivity; import android.os.Bundle; import android.widget.*; class Contact{ String nume; String prenume; Contact(String nume, String prenume){ this.nume=nume; this.prenume=prenume; } public String toString(){ return prenume +" "+ nume; } } public class Lista1Activity extends ListActivity { /** Called when the activity is first created. */ ArrayList <Contact> lista; ArrayAdapter <Contact> adaptor; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); setListAdapter(adaptor); lista=new ArrayList<Contact>(); adaptor=new ArrayAdapter<Contact>(this, R.id.element, lista); adaugaContact("Florian", "Iancu"); adaugaContact("Ioana", "Constantina"); } public void adaugaContact(String nume, String prenume){ lista.add(new Contact(nume, prenume)); adaptor.notifyDataSetChanged(); } } In the XML I have the LinearLayout and a TextView that is the list element. When I run it, the simulator says "Sorry, the application [...] has stopped unexpectedly. Please try again." The LogCat tells me I have to have a ListView whose id is android.R.id.lista. If I create a random ListView field in the XML file and give it the "lista" id, it still doesn't work. How to I call that ListView from XML to match something in my Java code? In other words, I know I'm wrong, but where and how do I fix it?

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• Repaint() not calling paint() in Java

  - by Joshua Auriemma

  Let me start off by saying I know I've violated some basic Java principles in this messy code, but I'm desperately trying to finish a program by Tuesday for a social science experiment, and I don't know Java, so I'm basically just fumbling through it for now. With that disclaimer out of the way, I have a separate program working where a circle is moving around the screen and the user must click on it. It works fine when its in its own separate class file, but when I add the code to my main program, it's no longer working. I don't even really understand why repaint() calls my paint() function — as far as I'm concerned, it's magic, but I've noticed that repaint() calls paint() in my test program, but not in the more complicated actual program, and I assume that's why the circle is no longer painting on my program. Entire code is below: import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Rectangle; import javax.swing.*; import java.awt.event.*; import java.awt.geom.Ellipse2D; import java.io.FileReader; import java.io.IOException; import java.util.Calendar; public class Reflexology1 extends JFrame{ private static final long serialVersionUID = -1295261024563143679L; private Ellipse2D ball = new Ellipse2D.Double(0, 0, 25, 25); private Timer moveBallTimer; int _ballXpos, _ballYpos; JButton button1, button2; JButton movingButton; JTextArea textArea1; int buttonAClicked, buttonDClicked; private long _openTime = 0; private long _closeTime = 0; JPanel thePanel = new JPanel(); JPanel thePlacebo = new JPanel(); final JFrame frame = new JFrame("Reflexology"); final JFrame frame2 = new JFrame("The Test"); JLabel label1 = new JLabel("Press X and then click the moving dot as fast as you can."); public static void main(String[] args){ new Reflexology1(); } public Reflexology1(){ frame.setSize(600, 475); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setTitle("Reflexology 1.0"); frame.setResizable(false); frame2.setSize(600, 475); frame2.setLocationRelativeTo(null); frame2.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame2.setTitle("Reflexology 1.0"); frame2.setResizable(false); button1 = new JButton("Accept"); button2 = new JButton("Decline"); //movingButton = new JButton("Click Me"); ListenForAcceptButton lForAButton = new ListenForAcceptButton(); ListenForDeclineButton lForDButton = new ListenForDeclineButton(); button1.addActionListener(lForAButton); button2.addActionListener(lForDButton); //movingButton.addActionListener(lForMButton); JTextArea textArea1 = new JTextArea(24, 50); textArea1.setText("Tracking Events\n"); textArea1.setLineWrap(true); textArea1.setWrapStyleWord(true); textArea1.setSize(15, 50); textArea1.setEditable(false); FileReader reader = null; try { reader = new FileReader("EULA.txt"); textArea1.read(reader, "EULA.txt"); } catch (IOException exception) { System.err.println("Problem loading file"); exception.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException exception) { System.err.println("Error closing reader"); exception.printStackTrace(); } } } JScrollPane scrollBar1 = new JScrollPane(textArea1, JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER); AdjustmentListener listener = new MyAdjustmentListener(); thePanel.add(scrollBar1); thePanel.add(button1); thePanel.add(button2); frame.add(thePanel); ListenForMouse lForMouse = new ListenForMouse(); thePlacebo.addMouseListener(lForMouse); thePlacebo.add(label1); frame2.add(thePlacebo); ListenForWindow lForWindow = new ListenForWindow(); frame.addWindowListener(lForWindow); frame2.addKeyListener(new KeyAdapter() { public void keyPressed(KeyEvent e){ if(e.getKeyChar() == 'X' || e.getKeyChar() == 'x') {moveBallTimer.start();} } }); frame.setVisible(true); moveBallTimer = new Timer(1000, new ActionListener() { public void actionPerformed(ActionEvent e) { moveBall(); System.out.println("Timer started!"); repaint(); } }); addKeyListener(new KeyAdapter() { public void keyPressed(KeyEvent e) { if(frame2.isVisible()){ moveBallTimer.start(); } } }); } private class ListenForAcceptButton implements ActionListener{ public void actionPerformed(ActionEvent e){ if (e.getSource() == button1){ Calendar ClCDateTime = Calendar.getInstance(); System.out.println(ClCDateTime.getTimeInMillis() - _openTime); _closeTime = ClCDateTime.getTimeInMillis() - _openTime; //frame.getContentPane().remove(thePanel); //thePlacebo.addKeyListener(lForKeys); //frame.getContentPane().add(thePlacebo); //frame.repaint(); //moveBallTimer.start(); frame.setVisible(false); frame2.setVisible(true); frame2.revalidate(); frame2.repaint(); } } } private class ListenForDeclineButton implements ActionListener{ public void actionPerformed(ActionEvent e){ if (e.getSource() == button2){ JOptionPane.showMessageDialog(Reflexology1.this, "You've declined the license agreement. DO NOT RESTART the program. Please go inform a researcher that you have declined the agreement.", "WARNING", JOptionPane.INFORMATION_MESSAGE); System.exit(0); } } } private class ListenForWindow implements WindowListener{ public void windowActivated(WindowEvent e) { //textArea1.append("Window is active"); } // if this.dispose() is called, this is called: public void windowClosed(WindowEvent arg0) { } // When a window is closed from a menu, this is called: public void windowClosing(WindowEvent arg0) { } // Called when the window is no longer the active window: public void windowDeactivated(WindowEvent arg0) { //textArea1.append("Window is NOT active"); } // Window gone from minimized to normal state public void windowDeiconified(WindowEvent arg0) { //textArea1.append("Window is in normal state"); } // Window has been minimized public void windowIconified(WindowEvent arg0) { //textArea1.append("Window is minimized"); } // Called when the Window is originally created public void windowOpened(WindowEvent arg0) { //textArea1.append("Let there be Window!"); Calendar OlCDateTime = Calendar.getInstance(); _openTime = OlCDateTime.getTimeInMillis(); //System.out.println(_openTime); } } private class MyAdjustmentListener implements AdjustmentListener { public void adjustmentValueChanged(AdjustmentEvent arg0) { AdjustmentEvent scrollBar1; //System.out.println(scrollBar1.getValue())); } } public void paint(Graphics g) { //super.paint(g); frame2.paint(g); Graphics2D g2d = (Graphics2D) g; g2d.setColor(Color.RED); g2d.fill(ball); System.out.println("Calling fill()"); } protected void moveBall() { //System.out.println("I'm in the moveBall() function!"); int width = getWidth(); int height = getHeight(); int min, max, randomX, randomY; min =200; max = -200; randomX = min + (int)(Math.random() * ((max - min)+1)); randomY = min + (int)(Math.random() * ((max - min)+1)); //System.out.println(randomX + ", " + randomY); Rectangle ballBounds = ball.getBounds(); //System.out.println(ballBounds.x + ", " + ballBounds.y); if (ballBounds.x + randomX < 0) { randomX = 200; } else if (ballBounds.x + ballBounds.width + randomX > width) { randomX = -200; } if (ballBounds.y + randomY < 0) { randomY = 200; } else if (ballBounds.y + ballBounds.height + randomY > height) { randomY = -200; } ballBounds.x += randomX; ballBounds.y += randomY; _ballXpos = ballBounds.x; _ballYpos = ballBounds.y; ball.setFrame(ballBounds); } public void start() { moveBallTimer.start(); } public void stop() { moveBallTimer.stop(); } private class ListenForMouse implements MouseListener{ // Called when the mouse is clicked public void mouseClicked(MouseEvent e) { //System.out.println("Mouse Panel pos: " + e.getX() + " " + e.getY() + "\n"); if (e.getX() >=_ballXpos && e.getX() <= _ballXpos + 25 && e.getY() <=_ballYpos && e.getY() >= _ballYpos - 25 ) { System.out.println("TRUE"); } System.out.println("{e.getX(): " + e.getX() + " / " + "_ballXpos: " + _ballXpos + " | " + "{e.getY(): " + e.getY() + " / " + "_ballYpos: " + _ballYpos); } public void mouseEntered(MouseEvent arg0) { // TODO Auto-generated method stub } public void mouseExited(MouseEvent arg0) { // TODO Auto-generated method stub } public void mousePressed(MouseEvent arg0) { // TODO Auto-generated method stub } public void mouseReleased(MouseEvent arg0) { // TODO Auto-generated method stub } } // System.out.println("e.getX(): " + e.getX() + " / " + "_ballXpos: " + _ballXpos); // Mouse over public void mouseEntered(MouseEvent arg0) { // TODO Auto-generated method stub } // Mouse left the mouseover area: public void mouseExited(MouseEvent arg0) { // TODO Auto-generated method stub } public void mousePressed(MouseEvent arg0) { // TODO Auto-generated method stub } public void mouseReleased(MouseEvent arg0) { // TODO Auto-generated method stub } } Could anyone tell me what I need to do to get repaint() to call the paint() method in the above program? I'm assuming the multiple frames is causing the problem, but that's just a guess. Thanks.

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• How can I lookup data about a book from its barcode number?

  - by Joel Spolsky

  I'm building the world's simplest library application. All I want to be able to do is scan in a book's UPC (barcode) using a typical scanner (which just types the numbers of the barcode into a field) and then use it to look up data about the book... at a minimum, title, author, year published, and either the Dewey Decimal or Library of Congress catalog number. The goal is to print out a tiny sticker ("spine label") with the card catalog number that I can stick on the spine of the book, and then I can sort the books by card catalog number on the shelves in our company library. That way books on similar subjects will tend to be near each other, for example, if you know you're looking for a book about accounting, all you have to do is find SOME book about accounting and you'll see the other half dozen that we have right next to it which makes it convenient to browse the library. There seem to be lots of web APIs to do this, including Amazon and the Library of Congress. But those are all extremely confusing to me. What I really just want is a single higher level function that takes a UPC barcode number and returns some basic data about the book.

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• Why is my panel not positioned correctly even after setting the boundaries?

  - by nutellafella

  I'm trying to make a simple GUI with radio buttons and I grouped them into one panel. I wanted it positioned on the leftmost side so I used the setBounds method. Whatever numbers I put on the parameters, the panel won't move. Are panels not affected by the setBounds method? Or is there another way to position my panel. Here's the snippet of my code: JPanel radioPanel = new JPanel(); radioPanel.setLayout(new GridLayout(3,1)); JRadioButton Rbutton1 = new JRadioButton("Credit Card"); JRadioButton Rbutton2 = new JRadioButton("E-Funds"); JRadioButton Rbutton3 = new JRadioButton("Check"); Rbutton3.setSelected(true); ButtonGroup Bgroup = new ButtonGroup(); Bgroup.add(Rbutton1); Bgroup.add(Rbutton2); Bgroup.add(Rbutton3); radioPanel.add(Rbutton1); radioPanel.add(Rbutton2); radioPanel.add(Rbutton3); radioPanel.setBounds(10,50,50,40); //this is where I'm trying to position the panel with the radio buttons paymentPanel.add(radioPanel); contentPane.add(paymentPanel); //contentPane is the frame contentPane.setVisible(true);

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• Add leading zeros to this javascript countdown script?

  - by eddjedi

  I am using the following countdown script which works great, but I can't figure out how to add leading zeros to the numbers (eg so it displays 09 instead of 9.) Can anybody help me out please? Here's the current script: function countDown(id, end, cur){ this.container = document.getElementById(id); this.endDate = new Date(end); this.curDate = new Date(cur); var context = this; var formatResults = function(day, hour, minute, second){ var displayString = [ '<div class="stat statBig">',day,'</div>', '<div class="stat statBig">',hour,'</div>', '<div class="stat statBig">',minute,'</div>', '<div class="stat statBig">',second,'</div>' ]; return displayString.join(""); } var update = function(){ context.curDate.setSeconds(context.curDate.getSeconds()+1); var timediff = (context.endDate-context.curDate)/1000; // Check if timer expired: if (timediff<0){ return context.container.innerHTML = formatResults(0,0,0,0); } var oneMinute=60; //minute unit in seconds var oneHour=60*60; //hour unit in seconds var oneDay=60*60*24; //day unit in seconds var dayfield=Math.floor(timediff/oneDay); var hourfield=Math.floor((timediff-dayfield*oneDay)/oneHour); var minutefield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour)/oneMinute); var secondfield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour-minutefield*oneMinute)); context.container.innerHTML = formatResults(dayfield, hourfield, minutefield, secondfield); // Call recursively setTimeout(update, 1000); }; // Call the recursive loop update(); }

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• WSACONNREFUSED when connecting to server

  - by Robert Mason

  I'm currently working on a server. I know that the client side is working (I can connect to www.google.com on port 80, for example), but the server is not functioning correctly. The socket has socket()ed, bind()ed, and listen()ed successfully and is on an accept loop. The only problem is that accept() doesn't seem to work. netstat shows that the server connection is running fine, as it prints the PID of the server process as LISTENING on the correct port. However, accept never returns. Accept just keeps running, and running, and if i try to connect to the port on localhost, i get a 10061 WSACONNREFUSED. I tried looping the connection, and it just keeps refusing connections until i hit ctrl+c. I put a breakpoint directly after the call to accept(), and no matter how many times i try to connect to that port, the breakpoint never fires. Why is accept not accepting connections? Has anyone else had this problem before? Known: [breakpoint0] if ((new_fd = accept(sockint, NULL, NULL)) == -1) { throw netlib::error("Accept Error"); //netlib::error : public std::exception } else { [breakpoint1] code...; } breakpoint0 is reached (and then continued through), no exception is thrown, and breakpoint1 is never reached. The client code is proven to work. Netstat shows that the socket is listening. If it means anything, i'm connecting to 127.0.0.1 on port 5842 (random number). The server is configured to run on 5842, and netstat confirms that the port is correct.

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• Inorder tree traversal in binary tree in C

  - by srk

  In the below code, I'am creating a binary tree using insert function and trying to display the inserted elements using inorder function which follows the logic of In-order traversal.When I run it, numbers are getting inserted but when I try the inorder function( input 3), the program continues for next input without displaying anything. I guess there might be a logical error.Please help me clear it. Thanks in advance... #include<stdio.h> #include<stdlib.h> int i; typedef struct ll { int data; struct ll *left; struct ll *right; } node; node *root1=NULL; // the root node void insert(node *root,int n) { if(root==NULL) //for the first(root) node { root=(node *)malloc(sizeof(node)); root->data=n; root->right=NULL; root->left=NULL; } else { if(n<(root->data)) { root->left=(node *)malloc(sizeof(node)); insert(root->left,n); } else if(n>(root->data)) { root->right=(node *)malloc(sizeof(node)); insert(root->right,n); } else { root->data=n; } } } void inorder(node *root) { if(root!=NULL) { inorder(root->left); printf("%d ",root->data); inorder(root->right); } } main() { int n,choice=1; while(choice!=0) { printf("Enter choice--- 1 for insert, 3 for inorder and 0 for exit\n"); scanf("%d",&choice); switch(choice) { case 1: printf("Enter number to be inserted\n"); scanf("%d",&n); insert(root1,n); break; case 3: inorder(root1); break; default: break; } } }

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• Memory management of objects returned by methods (iOS / Objective-C)

  - by iOSNewb

  I am learning Objective-C and iOS programming through the terrific iTunesU course posted by Stanford (http://www.stanford.edu/class/cs193p/cgi-bin/drupal/) Assignment 2 is to create a calculator with variable buttons. The chain of commands (e.g. 3+x-y) is stored in a NSMutableArray as "anExpression", and then we sub in random values for x and y based on an NSDictionary to get a solution. This part of the assignment is tripping me up: The final two [methods] “convert” anExpression to/from a property list: + (id)propertyListForExpression:(id)anExpression; + (id)expressionForPropertyList:(id)propertyList; You’ll remember from lecture that a property list is just any combination of NSArray, NSDictionary, NSString, NSNumber, etc., so why do we even need this method since anExpression is already a property list? (Since the expressions we build are NSMutableArrays that contain only NSString and NSNumber objects, they are, indeed, already property lists.) Well, because the caller of our API has no idea that anExpression is a property list. That’s an internal implementation detail we have chosen not to expose to callers. Even so, you may think, the implementation of these two methods is easy because anExpression is already a property list so we can just return the argument right back, right? Well, yes and no. The memory management on this one is a bit tricky. We’ll leave it up to you to figure out. Give it your best shot. Obviously, I am missing something with respect to memory management because I don't see why I can't just return the passed arguments right back. Thanks in advance for any answers!

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• Combining two-part SQL query into one query

  - by user332523

  Hello, I have a SQL query that I'm currently solving by doing two queries. I am wondering if there is a way to do it in a single query that makes it more efficient. Consider two tables: Transaction_Entries table and Transactions, each one defined below: Transactions - id - reference_number (varchar) Transaction_Entries - id - account_id - transaction_id (references Transactions table) Notes: There are multiple transaction entries per transaction. Some transactions are related, and will have the same reference_number string. To get all transaction entries for Account X, then I would do SELECT E.*, T.reference_number FROM Transaction_Entries E JOIN Transactions T ON (E.transaction_id=T.id) where E.account_id = X The next part is the hard part. I want to find all related transactions, regardless of the account id. First I make a list of all the unique reference numbers I found in the previous result set. Then for each one, I can query all the transactions that have that reference number. Assume that I hold all the rows from the previous query in PreviousResultSet UniqueReferenceNumbers = GetUniqueReferenceNumbers(PreviousResultSet) // in Java foreach R in UniqueReferenceNumbers // in Java SELECT * FROM Transaction_Entries where transaction_id IN (SELECT * FROM Transactions WHERE reference_number=R Any suggestions how I can put this into a single efficient query?

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• How is this Perl code selecting two different elements from an array?

  - by Mike

  I have inherited some code from a guy whose favorite past time was to shorten every line to its absolute minimum (and sometimes only to make it look cool). His code is hard to understand but I managed to understand (and rewrite) most of it. Now I have stumbled on a piece of code which, no matter how hard I try, I cannot understand. my @heads = grep {s/\.txt$//} OSA::Fast::IO::Ls->ls($SysKey,'fo','osr/tiparlo',qr{^\d+\.txt$}) || (); my @selected_heads = (); for my $i (0..1) { $selected_heads[$i] = int rand scalar @heads; for my $j (0..@heads-1) { last if (!grep $j eq $_, @selected_heads[0..$i-1]); $selected_heads[$i] = ($selected_heads[$i] + 1) % @heads; #WTF? } my $head_nr = sprintf "%04d", $i; OSA::Fast::IO::Cp->cp($SysKey,'',"osr/tiparlo/$heads[$selected_heads[$i]].txt","$recdir/heads/$head_nr.txt"); OSA::Fast::IO::Cp->cp($SysKey,'',"osr/tiparlo/$heads[$selected_heads[$i]].cache","$recdir/heads/$head_nr.cache"); } From what I can understand, this is supposed to be some kind of randomizer, but I never saw a more complex way to achieve randomness. Or are my assumptions wrong? At least, that's what this code is supposed to do. Select 2 random files and copy them. === NOTES === The OSA Framework is a Framework of our own. They are named after their UNIX counterparts and do some basic testing so that the application does not need to bother with that.

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• Where is the errnos defined? Example linux c/c++ program for i2c.

  - by Johan

  Hi When something goes wrong in a classic linux c/c++ software we have the magic variable errno that gives us a clue on what just went wrong. But where is those errors defined? Let's take a example (it's actually a piece from a Qt app, therefore the qDebug()). if (ioctl(file, I2C_SLAVE, address) < 0) { int err = errno; qDebug() << __FILE__ << __FUNCTION__ << __LINE__ << "Can't set address:" << address << "Errno:" << err << strerror(err); .... The next step is to look at what that errno was so we can decide if we just quit or try to do something about the problem. So we maybe add a if or switch at this point. if (err == 9) { // do something... } else { //do someting else } And my question is where to find the errors that "9" represents? I don't like that kind of magic numbers in my code. /Thanks

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• Best practices for encrypting continuous/small UDP data

  - by temp

  Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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• Looking for a 'pick a-or-b' voting system script

  - by user324455

  Apologies: this is my first time on stackoverflow and I'm starting with a question and seeking advice. Sorry. Caveats: I know HTML and CSS pretty well. Javascript and PHP are not completely alien, but I'm really pretty basic on those. That said, I'm pretty sharp and willing to search for explanations independently. Ok, so my question is this: I want to create a site with a voting system very much like the one on kittenwar.com - the page loads 2 random images from a db of some sort and you click on the one you want to 'win'. Ranked pairs kind of deal. Then there is a leaderboard of those images which have the highest win-loss ratio. There also needs to be an uploader for peeps to upload their own images and have them go into an approval workflow, and from there into the db that feeds the voting thing. I tried a pre-made solution ('photo battle') but found it was completely standalone, so trying to integrate it or change any of the options was a nightmare, plus it was buggy. i'm sure there has to be a relatively easy way to do this, right? Ideally I'd like to build my site in Joomla and integrate this functionality somehow. I'd be very grateful for any advice on this. Thanks Tom

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• Can't understand sessions in Rails

  - by ciss

  Hello everyone. Please don't bit my for my misunderstanding. The sessions are very new for me, and i have some problems. Okay i read many information about sessions and especially rails session. But this don't give me right imagine about sessions. Did i understand right, when users send request to server (get) - Server create a new session (and store this some file in hard drive with session id), session id - is a random generated num? so, server create a new session (and store session on drive) after this server send back answer to client and set session_id in cookies? Ok, i debug some params and see some results: debug(session): {:_csrf_token=>"jeONIfNxFmnpDn/xt6I0icNK1m3EB3CzT9KMntNk7KU=", :session_id=>"06c5628155efaa6446582c491499af6d", "flash"=>{}} debug(cookies): {"remember_user_token"=>"1::3GFRFyXb83lffzwPDPQd", "_blog_session"=>"BAh7CDoQX2NzcmZfdG9rZW4iMWplT05JZk54Rm1ucERuL3h0NkkwaWNOSzFtM0VCM0N6VDlLTW50Tms3S1U9Og9zZXNzaW9uX2lkIiUwNmM1NjI4MTU1ZWZhYTY0NDY1ODJjNDkxNDk5YWY2ZCIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA==--348c88b594e98f4bf6389d94383134fbe9b03095"} Okay, i know, what _csrf_token helps to prevent csrf. session_id - is id of the session which stored on hard drive (by default) but what is _blog_session in cookies? also, remeber_user_token containes my id (1::*) and what about second part, what is it? Sorry for this stupid questions, i know what i can easy use any nice auth-plugins (authlogic/clearance/devise), but i want to fully understand sessions. Thank you. (also sorry for my english, this is not my native language)

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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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• Syntax for documenting JSON structure

  - by Roman A. Taycher

  So I'm trying to document the format of the json returned by an api I am writing against and I'd like to know if there is any popular format for the documentation of json structure. Note I'm not trying to to test or validate anything, I'm just using this for documentation. Also some ways to add comments to non-constants(items always returned w/ the same value) would be nice. This the not totally thought out scheme I'm currently using: Plain names refer to identifiers or types. Some types have type-comment Strings that appear to be constant(always returned for that type of request) strings are "str" Constant Numbers would be just the number Constant null is null Booleans are true/false for constant booleans or Boolean otherwise [a,b,c] are lists with 3 items a,b,c [... ...] is a list of repeating elements of some types/constants/patterns {a:A,b:B,c:c} and {... ...} is the same for a dictionary. example: story := [header,footer] header := {"data":realHeader,"kind":"Listing"} realHeader := {"after": null, "before": null, "children": [{"data": realRealHeader, "kind": "t3"}], "modhash": ""} footer := {"data":AlmostComments,"kind":"Listing"} AlmostComments := {"data": {"after": null, "before": null, "children": comments, "modhash": ""}, "kind": "t1"} comments := [...{"data":comment, "kind":"t1"}...] realRealHeader := {"author": string, "clicked": boolean, "created": int, "created_utc": int, "domain": "code.reddit.com", "downs": int, "hidden": boolean, "id": string-id, "is_self": boolean, "levenshtein": null, "likes": null, "media": null, "media_embed": { }, "name": string-id, "num_comments": int, "over_18": false, "permalink": string-urlLinkToStoryStartingFrom/r, "saved": false, "score": int, "selftext": string, "selftext_html": string-html, "subreddit": string-subredditname, "subreddit_id": string-id, "thumbnail": "", "title": string, "ups": int, "url": "http://code.reddit.com/" } comments := { "author": string, "body": string-body_html-wout-html, "body_html": string-html-formated, "created": int, "created_utc": int, "downs": int, "id": string-id, "levenshtein": null, "likes": null, "link_id": string-id, "name": string-id", "parent_id": string-id, "replies": AlmostComments or null, "subreddit": string-subredditname, "subreddit_id": string-id, "ups": int }

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• What is the best Design/Way to keep user connected ?

  - by Fasih Hansmukh

  Am working on a POC for self learning in which I want to keep my user connected in LIVE pattern. For example, A game in which 4 user can play at a time , here I need to keep this user connected to my game . M not good at Socket type of programming and love to do that in Services way.What i wana know is 'What is the best way of doing this'. According to my initial Brain Storming, I have decided that I will use SilverLight(In Browser Or Out of Browser) as Front end [I have no issue in that]. I m more concern in back end. Either I make an handler or make a WCF service or use full duplex service and use pooling mechanism for that. As a random thought I come up with a Timer type logic that will fire every after 10 seconds at clients end and get status like Is it now Its turn to roll a dice Home many user left (in case if some of them left) What are connected user status in game like there score/points ect and update game view according to this at his end Kindly place your best answers here that will help me to learn this. Regards and thanks in Advance EDIT: Starting Bounty as i need more feedback. FH

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• algorithm - How to sort a 0/1 array with 2n/3 comparisons?

  - by Jackson Tale

  In Algorithm Design Manual, there is such an excise 4-26 Consider the problem of sorting a sequence of n 0’s and 1’s using comparisons. For each comparison of two values x and y, the algorithm learns which of x < y, x = y, or x y holds. (a) Give an algorithm to sort in n - 1 comparisons in the worst case. Show that your algorithm is optimal. (b) Give an algorithm to sort in 2n/3 comparisons in the average case (assuming each of the n inputs is 0 or 1 with equal probability). Show that your algorithm is optimal. For (a), I think it is fairly easy. I can choose a[n-1] as pivot, then do something like in quicksort partition, scan 0 to n - 2, find the middle point where left side is all 0 and right side is all 1, this take n - 1 comparisons. But for (b), I can't get a clue. It says "each of the n inputs is 0 or 1 with equal probability", so I guess I can assume the numbers of 0 and 1 equal? But how can I get a result which is related to 1/3? divide the whole array into 3 groups? Thanks

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• Animate and form rows, arrays, AS3

  - by VideoDnd

  Question How can I animate and form rows together? Explanation One 'for loop' is for animation, the other 'for loop' is for making rows. I want to understand how to use arrays and create a row of sprite animations. 'for loop' for animation //FRAMES ARRAY //THIS SETS UP MY ANIMATION FOR TIMER EVENT var frames:Array = [ new Frame1(), new Frame2(), new Frame3(), new Frame4(), new Frame5(), new Frame6(), new Frame7(), new Frame8(), new Frame9(), new Frame0(), ]; for each (var frame:Sprite in frames) { addChild(frame); } 'for loop' for rows //THIS MAKES A ROW OF DISPLAY OBJECTS var numberOfClips:Number = 11; var xStart:Number = 0; var yStart:Number = 0; var xVal:Number = xStart; var xOffset:Number = 2; for (var $:Number=0; $<numberOfClips; $++) { //DUDE ARRAY var dude:Array = frames; dude.y = yStart +11; dude.x = xVal +55; xVal = dude.x + dude.width + this.xOffset; } timer var timer:Timer = new Timer(100); timer.addEventListener(TimerEvent.TIMER, countdown); function countdown(event:TimerEvent) { var currentFrame:int = timer.currentCount % frames.length; for (var i:int = 0; i < frames.length; ++i) { frames[i].visible = (i == currentFrame); } } timer.start(); counter experiment My new class I'm working on loops through 10 different display objects that are numbers. For those following, I'm trying to make something like NumbersView.

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• How big can I make an Android application's canvas in terms of pixels?

  - by user279112

  I've determined an estimate of the size of my Android emulator's screen in pixels, although I think its resolution can be changed to other numbers. Quite frankly though that doesn't eliminate the general problem of not knowing how many pixels on each axis I have to work with on my Android applications in general. The main problem I'm trying to solve is this: How do I make sure I don't use a faulty resolution on Android applications if I want to keep things' sizes constant (so that if the application screen shrinks, for instances, objects will still show up just as big - there just won't be as many of them being shown) if I wish to do this with a single universal resolution for each program? Failing that, how do I make sure everything's alright if I try to do everything the same way with maybe a few different pre-set resolutions? Mainly it seems like a relevant question that must be answered before I can come across a complete answer for the general problem is how big can I always make my application in pixels, NOT regarding if and when a user resizes the application's screen to something smaller than the maximum size permitted by the phone and its operating system. I really want to try to keep this simple. If I were doing this for a modern desktop, for instance, I know that if I design the application with a 800x600 canvas, the user can still shrink the application to the point they're not doing themselves any favors, but at least I can basically count on it working right and not being too big for the monitor or something. Is there such a magic resolution for Android, assuming that I'm designing for API levels 3+ (Android 1.5+)? Thanks

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• What is the minimal licensable source code?

  - by Hernán Eche

  Let's suppose I want to "protect" this code about being used without attribution, patenting it, or through any open source licence... #include<stdio.h> int main (void) { int version=2; printf("\r\n.Hello world, ver:(%d).", version); return 0; } It's a little obvious or just a language definition example.. When a source stop being "trivial, banal, commonplace, obvious", and start to be something that you may claim "rights"? Perhaps it depends on who read it, something that could be great geniality for someone that have never programmed, could be just obvious for an expert. It's easy when watching two sources there are 10000 same lines of code, that's a theft.. but that's not always so obvious. How to measure amount of "ownness", it's about creativity? line numbers? complexity? I can't imagine objetive answers for that, only some patches. For example perhaps the complexity, It's not fair to replace "years of engeneering" with "copy and paste". But is there any objetive index for objetive determination of this subject? (In a funny way I imagine this criterion: If the licence is longer than the code, then there is no owner, just to punish not caring storage space and world resources =P)

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• Shuffle Two NSMutableArray independently

  - by Superman

  I'm creating two NSMutableArray in my viewDidLoad, I add it in a NSMutableDictionary. When I tried shuffling it with one array, It is okay. But the problem is when Im shuffling two arrays independently its not working,somehow the indexes got mixed up. Here is my code for my array (I have two of these): self.items1 = [NSMutableArray new]; for(int i = 0; i <= 100; i++) { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); NSString *documentsDir = [paths objectAtIndex:0]; NSString *savedImagePath = [documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"[Images%d.png", i]]; if([[NSFileManager defaultManager] fileExistsAtPath:savedImagePath]){ self.container = [[NSMutableDictionary alloc] init]; [container setObject:[UIImage imageWithContentsOfFile:savedImagePath] forKey:@"items1"]; [container setObject:[NSNumber numberWithInt:i] forKey:@"index1"]; [items1 addObject:container]; } } NSLog(@"Count : %d", [items1 count]); [items1 enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL *stop) { NSLog(@"%@ images at index %d", object, index); }]; then my shuffle code(Which I tried duplicating for the other array,but not working also): srandom(time(NULL)); NSUInteger count = [items1 count]; for (NSUInteger i = 0; i < count; ++i) { int nElements = count - i; int n = (random() % nElements) + i; [items1 exchangeObjectAtIndex:i withObjectAtIndex:n]; } How am I going to shuffle it using above code (or if you have other suggestions) with two arrays? Thanks My other problem is when I tries subclassing the class for the shuffle method or either use the above code, their index mixed. For example: Object: apple, ball, carrots, dog Indexes: 1 2 3 4 but in my View when shuffled: Object: carrots, apple, dog, balle Indexes: 2 4 1 3

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