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• Finding N contiguous zero bits in an integer to the left of the MSB position of another integer

  - by James Morris

  The problem is: given an integer val1 find the position of the highest bit set (Most Significant Bit) then, given a second integer val2 find a contiguous region of unset bits, with the minimum number of zero bits given by width to the left of the position (ie, in the higher bits). Here is the C code for my solution: typedef unsigned int t; unsigned const t_bits = sizeof(t) * CHAR_BIT; _Bool test_fit_within_left_of_msb( unsigned width, t val1, t val2, unsigned* offset_result) { unsigned offbit = 0; unsigned msb = 0; t mask; t b; while(val1 >>= 1) ++msb; while(offbit + width < t_bits - msb) { mask = (((t)1 << width) - 1) << (t_bits - width - offbit); b = val2 & mask; if (!b) { *offset_result = offbit; return true; } if (offbit++) /* this conditional bothers me! */ b <<= offbit - 1; while(b <<= 1) offbit++; } return false; } Aside from faster ways of finding the MSB of the first integer, the commented test for a zero offbit seems a bit extraneous, but necessary to skip the highest bit of type t if it is set. I have also implemented similar algorithms but working to the right of the MSB of the first number, so they don't require this seemingly extra condition. How can I get rid of this extra condition, or even, are there far more optimal solutions? Edit: Some background not strictly required. The offset result is a count of bits from the high bit, not from the low bit as maybe expected. This will be part of a wider algorithm which scans a 2D array for a 2D area of zero bits. Here, for testing, the algorithm has been simplified. val1 represents the first integer which does not have all bits set found in a row of the 2D array. From this the 2D version would scan down which is what val2 represents. Here's some output showing success and failure: t_bits:32 t_high: 10000000000000000000000000000000 ( 2147483648 ) --------- ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000010000000 ( 128 ) val2: 01000001000100000000100100001001 ( 1091569929 ) msb: 7 offbit:0 + width: 8 = 8 mask: 11111111000000000000000000000000 ( 4278190080 ) b: 01000001000000000000000000000000 ( 1090519040 ) offbit:8 + width: 8 = 16 mask: 00000000111111110000000000000000 ( 16711680 ) b: 00000000000100000000000000000000 ( 1048576 ) offbit:12 + width: 8 = 20 mask: 00000000000011111111000000000000 ( 1044480 ) b: 00000000000000000000000000000000 ( 0 ) offbit:12 iters:10 ***** found room for width:8 at offset: 12 ***** ----------------------------------- *** fit within left of msb test *** ----------------------------------- val1: 00000000000000000000000001000000 ( 64 ) val2: 00010000000000001000010001000001 ( 268469313 ) msb: 6 offbit:0 + width: 13 = 13 mask: 11111111111110000000000000000000 ( 4294443008 ) b: 00010000000000000000000000000000 ( 268435456 ) offbit:4 + width: 13 = 17 mask: 00001111111111111000000000000000 ( 268402688 ) b: 00000000000000001000000000000000 ( 32768 ) ***** mask: 00001111111111111000000000000000 ( 268402688 ) offbit:17 iters:15 ***** no room found for width:13 ***** (iters is the count of iterations of the inner while loop)

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• ArgumentError: Error #1063: Argument count mismatch on com.flashden::MenuItem(). Expected 1, got 0.

  - by Suzanne

  I keep getting the below error only in firefox ArgumentError: Error #1063: Argument count mismatch on com.flashden::MenuItem(). Expected 1, got 0. at flash.display::Sprite/constructChildren() at flash.display::Sprite() at flash.display::MovieClip() at com.flashden::Preview() Below is my menu script: package com.flashden { import flash.display.MovieClip; import flash.text.; import flash.events.MouseEvent; import flash.events.; import flash.net.URLRequest; import flash.display.Loader; public class MenuItem extends MovieClip { private var scope; public var closedX :Number public static const OPEN_MENU = "openMenu"; function callLink(event:MouseEvent):void { public function MenuItem(scope) { // set scope to talk back to -------------------------------// this.scope = scope; // disable all items not to be clickable -------------------// txt_label.mouseEnabled = false; menuItemShine.mouseEnabled = false; menuItemArrow.mouseEnabled = false; // make background clip the item to be clicked (button) ----// menuItemBG.buttonMode = true; // add click event listener to the header background -------// menuItemBG.addEventListener(MouseEvent.CLICK, clickHandler); } private function clickHandler (e:MouseEvent) { scope.openMenuItem(this); } public function loadContent (contentURL:String) { var loader:Loader = new Loader(); configureListeners(loader.contentLoaderInfo); var request:URLRequest = new URLRequest(contentURL); loader.load(request); // place x position of content at the bottom of the header so the top is not cut off ----// loader.x = 35; // we add the content at level 1, because the background clip is at level 0 ----// addChildAt(loader, 0); } private function configureListeners(dispatcher:IEventDispatcher):void { dispatcher.addEventListener(Event.COMPLETE, completeHandler); dispatcher.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler); dispatcher.addEventListener(Event.INIT, initHandler); dispatcher.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler); dispatcher.addEventListener(Event.OPEN, openHandler); dispatcher.addEventListener(ProgressEvent.PROGRESS, progressHandler); dispatcher.addEventListener(Event.UNLOAD, unLoadHandler); } private function completeHandler(event:Event):void { //trace("completeHandler: " + event); // remove loader animation ----------------// removeChild(getChildByName("mc_preloader")); } private function httpStatusHandler(event:HTTPStatusEvent):void { // trace("httpStatusHandler: " + event); } private function initHandler(event:Event):void { //trace("initHandler: " + event); } private function ioErrorHandler(event:IOErrorEvent):void { //trace("ioErrorHandler: " + event); } private function openHandler(event:Event):void { //trace("openHandler: " + event); } private function progressHandler(event:ProgressEvent):void { //trace("progressHandler: bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal); } private function unLoadHandler(event:Event):void { //trace("unLoadHandler: " + event); } } } Any idea why this is happening?

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• Who calls the Destructor of the class when operator delete is used in multiple inheritance.

  - by dicaprio-leonard

  This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

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• Possible bug with tabified QDockWidget and setFloating()

  - by krunk

  I've run into some odd behavior with tabified QDockWidgets, below is an example program with comments that demonstrates the behavior. Is this a bug or is it expected behavior and I'm missing some nuance in QDockWidget that causes this? Directly, since this does not work, how would one properly "undock" a hidden QDockWidget then display it? #include <QApplication> #include <QMainWindow> #include <QAction> #include <QDockWidget> #include <QMenu> #include <QSize> #include <QMenuBar> using namespace std; int main (int argc, char* argv[]) { QApplication app(argc, argv); QMainWindow window; QDockWidget dock1(&window); QDockWidget dock2(&window); QMenu menu("View"); dock1.setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea); dock2.setAllowedAreas(Qt::LeftDockWidgetArea | Qt::RightDockWidgetArea); dock1.setWindowTitle("Dock One"); dock2.setWindowTitle("Dock Two"); window.addDockWidget(Qt::RightDockWidgetArea, &dock1); window.addDockWidget(Qt::RightDockWidgetArea, &dock2); window.menuBar()->addMenu(&menu); window.setMinimumSize(QSize(800, 600)); window.tabifyDockWidget(&dock1, &dock2); dock1.hide(); dock2.hide(); menu.addAction(dock1.toggleViewAction()); menu.addAction(dock2.toggleViewAction()); window.show(); // Below is where the oddness starts. It seems to only exhibit the // behavior if the dock widgets are tabified. // Odd behavior here // This does not work. the window never shows, though its menu action shows // checked. Not only does this window not show up, but all toggle actions // for all dock windows (e.g. dock1 and dock2) are broken for the duration // of the application loop. // dock1.setFloating(true); // dock1.show(); // This does work. . . of course only if you do _not_ run the above first. // however, you can often get a little lag or "blip" in the rendering as // the dock is shown docked before setFloating is set to true. dock1.show(); dock1.setFloating(true); return app.exec(); }

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• System.MissingMemberException was unhandled by user code

  - by AmRoSH

  I'm using this code: Dim VehiclesTable1 = dsVehicleList.Tables(0) Dim VT1 = (From d In VehiclesTable1.AsEnumerable _ Select VehicleTypeName = d.Item("VehicleTypeName") _ , VTypeID = d.Item("VTypeID") _ , ImageURL = d.Item("ImageURL") _ , DailyRate = d.Item("DailyRate") _ , RateID = d.Item("RateID")).Distinct its linq to dataset and I Take Data on THis Rotator: <telerik:RadRotator ID="RadRotatorVehicleType" runat="server" Width="620px" Height="145" ItemWidth="155" ItemHeight="145" ScrollDirection="Left" FrameDuration="1" RotatorType="Buttons"> <ItemTemplate> <div style="text-align: center; cursor: pointer; width: 150px"> <asp:Image ID="ImageVehicleType" runat="server" Width="150" ImageUrl='<%# Container.DataItem("ImageURL") %>' /> <asp:Label ID="lblVehicleType" runat="server" Text='<%# Container.DataItem("VehicleTypeName") %>' Font-Bold="true"></asp:Label> <br /> <asp:Label ID="lblDailyRate" runat="server" Text='<%# Container.DataItem("DailyRate") %>' Visible="False"></asp:Label> <input id="HiddenVehicleTypeID" type="hidden" value='<%# Container.DataItem("VTypeID") %>' name="HiddenVehicleTypeID" runat="server" /> <input id="HiddenRateID" type="hidden" value='<%# Container.DataItem("RateID") %>' name="HiddenRateID" runat="server" /> </div> </ItemTemplate> <ControlButtons LeftButtonID="img_left" RightButtonID="img_right" /> </telerik:RadRotator> and I got this Exception: No default member found for type 'VB$AnonymousType_0(Of Object,Object,Object,Object,Object)'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.MissingMemberException: No default member found for type 'VB$AnonymousType_0(Of Object,Object,Object,Object,Object)'. I don't know whats up ? Any help please. Thanks for who tried to solve this but I got solution: using '<%# DataBinder.Eval(Container.DataItem,"ImageURL") %>' instead of '<%# Container.DataItem("RateID") %>' Thanks,

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• LsaAddAccountRights not working for me

  - by SteveL

  Using: Delphi 2010 and the JEDI Windows API and JWSCL I am trying to assign the Logon As A Service privilege to a user using LsaAddAccountRights function but it does not work ie. after the function returns, checking in Group Policy Editor shows that the user still does not have the above mentioned privilege. I'm running the application on Windows XP. Would be glad if someone could point out what is wrong in my code: unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, JwaWindows, JwsclSid; type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} function AddPrivilegeToAccount(AAccountName, APrivilege: String): DWORD; var lStatus: TNTStatus; lObjectAttributes: TLsaObjectAttributes; lPolicyHandle: TLsaHandle; lPrivilege: TLsaUnicodeString; lSid: PSID; lSidLen: DWORD; lTmpDomain: String; lTmpDomainLen: DWORD; lTmpSidNameUse: TSidNameUse; lPrivilegeWStr: String; begin ZeroMemory(@lObjectAttributes, SizeOf(lObjectAttributes)); lStatus := LsaOpenPolicy(nil, lObjectAttributes, POLICY_LOOKUP_NAMES, lPolicyHandle); if lStatus <> STATUS_SUCCESS then begin Result := LsaNtStatusToWinError(lStatus); Exit; end; try lTmpDomainLen := DNLEN; // In 'clear code' this should be get by LookupAccountName SetLength(lTmpDomain, lTmpDomainLen); lSidLen := SECURITY_MAX_SID_SIZE; GetMem(lSid, lSidLen); try if LookupAccountName(nil, PChar(AAccountName), lSid, lSidLen, PChar(lTmpDomain), lTmpDomainLen, lTmpSidNameUse) then begin lPrivilegeWStr := APrivilege; lPrivilege.Buffer := PChar(lPrivilegeWStr); lPrivilege.Length := Length(lPrivilegeWStr) * SizeOf(Char); lPrivilege.MaximumLength := lPrivilege.Length; lStatus := LsaAddAccountRights(lPolicyHandle, lSid, @lPrivilege, 1); Result := LsaNtStatusToWinError(lStatus); end else Result := GetLastError; finally FreeMem(lSid); end; finally LsaClose(lPolicyHandle); end; end; procedure TForm1.Button1Click(Sender: TObject); begin AddPrivilegeToAccount('Sam', 'SeServiceLogonRight'); end; end. Thanks in advance.

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• Blackberry ListField Text Wrapping - only two lines.

  - by Diego Tori

  Within my ListField, I want to be able to take any given long String, and just be able to wrap the first line within the width of the screen, and just take the remaining string and display it below and ellipsis the rest. Right now, this is what I'm using to detect wrapping within my draw paint call: int totalWidth = 0; int charWidth = 0; int lastIndex = 0; int spaceIndex = 0; int lineIndex = 0; String firstLine = ""; String secondLine = ""; boolean isSecondLine = false; for (int i = 0; i < longString.length(); i++){ charWidth = Font.getDefault().getAdvance(String.valueOf(longString.charAt(i))); //System.out.println("char width: " + charWidth); if(longString.charAt(i) == ' ') spaceIndex = i; if((charWidth + totalWidth) > (this.getWidth()-32)){ //g.drawText(longString.substring(lastIndex, spaceIndex), xpos, y +_padding, DrawStyle.LEFT, w - xpos); lineIndex++; System.out.println("current lines to draw: " + lineIndex); /*if (lineIndex = 2){ int idx = i; System.out.println("first line " + longString.substring(lastIndex, spaceIndex)); System.out.println("second line " + longString.substring(spaceIndex+1, longString.length())); }*/ //firstLine = longString.substring(lastIndex, spaceIndex); firstLine = longString.substring(0, spaceIndex); //System.out.println("first new line: " +firstLine); //isSecondLine=true; //xpos = 0; //y += Font.getDefault().getHeight(); i = spaceIndex + 1; lastIndex = i; System.out.println("Rest of string: " + longString.substring(lastIndex, longString.length())); charWidth = 0; totalWidth = 0; } totalWidth += charWidth; System.out.println("total width: " + totalWidth); //g.drawText(longString.substring(lastIndex, i+1), xpos, y + (_padding*3)+4, DrawStyle.ELLIPSIS, w - xpos); //secondLine = longString.substring(lastIndex, i+1); secondLine = longString.substring(lastIndex, longString.length()); //isSecondLine = true; } Now this does a great job of actually wrapping any given string (assuming the y values were properly offsetted and it only drew the text after the string width exceeded the screen width, as well as the remaining string afterwards), however, every time I try to get the first two lines, it always ends up returning the last two lines of the string if it goes beyond two lines. Is there a better way to do this sort of thing, since I am fresh out of ideas?

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• programming question

  - by shivam

  using System; using System.Data; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.SqlClient; namespace datasynchronization { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { string connectString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseA;Integrated Security=True"; using (var srcCon = new SqlConnection(connectString)) //connection to source table { srcCon.Open();//source table connection open SqlCommand cmd = new SqlCommand();// sqlobject for source table cmd.Connection = srcCon; string connectionString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseB;Integrated Security=True"; using (var tgtCon = new SqlConnection(connectionString)) //connection to target table { tgtCon.Open(); //target table connection open SqlCommand objcmd1 = new SqlCommand();//sqlobject for target table objcmd1.Connection = tgtCon; objcmd1.CommandText = "SELECT MAX(date) FROM Table_2"; //query to findout the max date from target table var maxdate = objcmd1.ExecuteScalar(); // store the value of max date into the variable maxdate cmd.CommandText = string.Format("SELECT id,date,name,city,salary,region FROM Table_1 where date >'{0}'", maxdate); //select query to fetch rows from source table using (var reader = cmd.ExecuteReader()) { SqlCommand objcmd = new SqlCommand(); objcmd.Connection = tgtCon; objcmd.CommandText = "INSERT INTO Table_2(id,date,name,city,salary,region)VALUES(@id,@date,@name,@city,@salary,@region)"; objcmd.Parameters.Add("@id", SqlDbType.Int); objcmd.Parameters.Add("@date", SqlDbType.DateTime); objcmd.Parameters.Add("@name", SqlDbType.NVarChar); objcmd.Parameters.Add("@city", SqlDbType.NVarChar); objcmd.Parameters.Add("@salary", SqlDbType.Int); objcmd.Parameters.Add("@region", SqlDbType.Char); while (reader.Read()) { var order1 = reader[0].ToString(); var order2 = reader[1].ToString(); var order3 = reader[2].ToString(); var order4 = reader[3].ToString(); var order5 = reader[4].ToString(); var order6 = reader[5].ToString(); objcmd.Parameters["@id"].Value = order1; objcmd.Parameters["@date"].Value = order2; objcmd.Parameters["@name"].Value = order3; objcmd.Parameters["@city"].Value = order4; objcmd.Parameters["@salary"].Value = order5; objcmd.Parameters["@region"].Value = order6; objcmd.ExecuteNonQuery(); } } tgtCon.Close(); } srcCon.Close(); } } } } how can i organize the above written code in an efficient way?

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• Is do-notation specific to "base:GHC.Base.Monad"?

  - by yairchu

  The idea that the standard Monad class is flawed and that it should actually extend Functor or Pointed is floating around. I'm not necessarily claiming that it is the right thing to do, but suppose that one was trying to do it: import Prelude hiding (Monad(..)) class Functor m => Monad m where return :: a -> m a join :: m (m a) -> m a join = (>>= id) (>>=) :: m a -> (a -> m b) -> m b a >>= t = join (fmap t a) (>>) :: m a -> m b -> m b a >> b = a >>= const b So far so good, but then when trying to use do-notation: whileM :: Monad m => m Bool -> m () whileM iteration = do done <- iteration if done then return () else whileM iteration The compiler complains: Could not deduce (base:GHC.Base.Monad m) from the context (Monad m) Question: Does do-notation work only for base:GHC.Base.Monad? Is there a way to make it work with an alternative Monad class? Extra context: What I really want to do is replace base:Control.Arrow.Arrow with a "generalized" Arrow class: {-# LANGUAGE TypeFamilies #-} class Category a => Arrow a where type Pair a :: * -> * -> * arr :: (b -> c) -> a b c first :: a b c -> a (Pair a b d) (Pair a c d) second :: a b c -> a (Pair a d b) (Pair a d c) (***) :: a b c -> a b' c' -> a (Pair a b b') (Pair a c c') (&&&) :: a b c -> a b c' -> a b (Pair a c c') And then use the Arrow's proc-notation with my Arrow class, but that fails like in the example above of do-notation and Monad. I'll use mostly Either as my pair type constructor and not the (,) type constructor as with the current Arrow class. This might allow to make the code of my toy RTS game (cabal install DefendTheKind) much prettier.

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• dynamic button in jsp

  - by kawtousse

  hi everyone, in my jsp i have a table constructed dynamically like the following: retour.append("<tr>"); try { s= HibernateUtil.currentSession(); tx=s.beginTransaction(); Query query = s.createQuery(HQL_QUERY); for(Iterator it=query.iterate();it.hasNext();) { if(it.hasNext()){ Dailytimesheet object=(Dailytimesheet)it.next(); retour.append("<td>" +object.getActivity() +"</td>"); retour.append("<td>" +object.getProjectCode() + "</td>"); retour.append("<td>" +object.getWAName() + "</td>"); retour.append("<td>" +object.getTaskCode() +"</td>"); retour.append("<td>" +object.getTimeFrom() +"</td>"); retour.append("<td>" +object.getTimeSpent() + "</td>"); retour.append("<td>" +object.getPercentTaskComplete() + "</td>"); if (droitdaccess) { retour.append(""); retour.append(""); retour.append(""); retour.append("<td bordercolor=#FFFFFF>"); retour.append("<input type=\"hidden\" id=\"id_"+nomTab+"_"+compteur+"\" value=\""+object.getIdDailyTimeSheet()+"\"/>"); retour.append("<img src=\"icon_delete.gif\" onClick=\"deletearowById('id_"+nomTab+"_"+compteur+"')\" style=\"cursor:pointer\" name=\"action\" value=\"deleting\" />"); retour.append("</td>"); } } compteur++; retour.append("</tr>"); } //terminer la table. retour.append ("</table>"); next to the table i want to display a button named send in order to send the table content. I do not really want to dispaly this button where the table is empty. So at least if the table is populated by nly one record i want that button being displayed. How should i deal in this case. Thanks.

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• how can we make class with Linked list recursion ...

  - by epsilon_G

  Hi , I'm newbee in The C++ heaven and the OOP, ... I'd like to make some stuffs with the Data structures ... However,I'd like to merge two linked listes ... I made a class before "List" wich contain all what I need to programme something with List ... Add , Display .. The probleme is that I programmed the function "Merge2lists" which give us the third list .. How can I display the third list in the main program after using "Merge2lists" Plz , my prob with the Class and the OOP syntaxe ... try to give me the implementation in the main program ??? Otherwise,How can I apply function given pointer in main program wich declared in class .. Thankx class Liste { private: struct node { int elem ; node *next; }*p; public: LLC(); void Merge2lists (node* a, node * b,node *&result); ~LLC(); }; void List::Merge2lists (node* a, node * b,node *&result) { result = NULL; if (a==NULL) { result=b; return;} else if (b==NULL) { result=a; return;} if (a->elem <= b->elem) { result = a; Merge2lists(a->next, b,result->next); } else { result = b; Merge2lists(a, b->next,result->next); } return; } int main() { liste a ; a.Aff_Val(46); a.Aff_Val(54); a.add_as_first(2); a.add_as_first(1); a.Display(); /*This to displat the elemnts ... Don't care about it it's easy to make*/ list liste2; b.Add(2); b.Add(14); b.Add(16); list result; Merge2lists (a,b,result); /*The probleme is here , how can I use this in my program */

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• Interoperability between two AES algorithms

  - by lpfavreau

  Hello, I'm new to cryptography and I'm building some test applications to try and understand the basics of it. I'm not trying to build the algorithms from scratch but I'm trying to make two different AES-256 implementation talk to each other. I've got a database that was populated with this Javascript implementation stored in Base64. Now, I'm trying to get an Objective-C method to decrypt its content but I'm a little lost as to where the differences in the implementations are. I'm able to encrypt/decrypt in Javascript and I'm able to encrypt/decrypt in Cocoa but cannot make a string encrypted in Javascript decrypted in Cocoa or vice-versa. I'm guessing it's related to the initialization vector, nonce, counter mode of operation or all of these, which quite frankly, doesn't speak to me at the moment. Here's what I'm using in Objective-C, adapted mainly from this and this: @implementation NSString (Crypto) - (NSString *)encryptAES256:(NSString *)key { NSData *input = [self dataUsingEncoding: NSUTF8StringEncoding]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:TRUE]; return [Base64 encode:output]; } - (NSString *)decryptAES256:(NSString *)key { NSData *input = [Base64 decode:self]; NSData *output = [NSString cryptoAES256:input key:key doEncrypt:FALSE]; return [[[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding] autorelease]; } + (NSData *)cryptoAES256:(NSData *)input key:(NSString *)key doEncrypt:(BOOL)doEncrypt { // 'key' should be 32 bytes for AES256, will be null-padded otherwise char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused) bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding) // fetch key data [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; NSUInteger dataLength = [input length]; // See the doc: For block ciphers, the output size will always be less than or // equal to the input size plus the size of one block. // That's why we need to add the size of one block here size_t bufferSize = dataLength + kCCBlockSizeAES128; void* buffer = malloc(bufferSize); size_t numBytesCrypted = 0; CCCryptorStatus cryptStatus = CCCrypt(doEncrypt ? kCCEncrypt : kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode | kCCOptionPKCS7Padding, keyPtr, kCCKeySizeAES256, nil, // initialization vector (optional) [input bytes], dataLength, // input buffer, bufferSize, // output &numBytesCrypted ); if (cryptStatus == kCCSuccess) { // the returned NSData takes ownership of the buffer and will free it on deallocation return [NSData dataWithBytesNoCopy:buffer length:numBytesCrypted]; } free(buffer); // free the buffer; return nil; } @end Of course, the input is Base64 decoded beforehand. I see that each encryption with the same key and same content in Javascript gives a different encrypted string, which is not the case with the Objective-C implementation that always give the same encrypted string. I've read the answers of this post and it makes me believe I'm right about something along the lines of vector initialization but I'd need your help to pinpoint what's going on exactly. Thank you!

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• Should I add try/catch around when casting on an attribute of JSP implicit object?

  - by Michael Mao

  Hi all: Basically what I mean is like this: List<String[]> routes = (List<String[]>)application.getAttribute("routes"); For the above code, it tries to get an attribute named "routes" from the JSP implicit object - application. But as everyone knows, after this line of code, routes may very well contains a null - which means this application hasn't got an attribute named "routes". Is this "casting on null" good programming practice in Java or not? Basically I try to avoid exceptions such as java.io.InvalidCastException I reckon things like this are more as "heritage" of Java 1.4 when generic types were not introduced to this language. So I guess everything stored in application attributes as Objects (Similar to traditional ArrayList). And when you do "downcast", there might be invalid casts. What would you do in this case? Update: Just found that although in the implicit object application I did store a List of String arrays, when I do this : List<double[]> routes = (List<double[]>)application.getAttribute("routes"); It doesn't produce any error... And I felt not comfortable already... And even with this code: out.print(routes.get(0)); It does print out something strange : [Ljava.lang.String;@18b352f Am I printing a "pointer to String"? I can finally get an exception like this: out.print(routes.get(0)[1]); with error : java.lang.ClassCastException: [Ljava.lang.String; Because it was me to add the application attribute, I know which type should it be cast to. I feel this is not "good enough", what if I forget the exact type? I know there are still some cases where this sort of thing would happen, such as in JSP/Servlet when you do casting on session attributes. Is there a better way to do this? Before you say:"OMG, why you don't use Servlets???", I should justify my reason as this: - because my uni sucks, its server can only work with Servlets generated by JSP, and I don't really want to learn how to fix issues like that. look at my previous question on this , and this is uni homework, so I've got no other choice, forget all about war, WEB-INF,etc, but "code everything directly into JSP" - because the professors do that too. :)

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• C++ program Telephone Directory from a file

  - by Stacy Doyle

  I am writing a program for a phone directory. The user inputs a name and the program searches the file and either outputs the number or an error because the persons name is not in the file. The program should also ask the user if they would like to continue using the program and look up another number. So far runs and asks for the name and then prints the error message that I put in place saying that the name is not in the database. I am guessing that I must not really be having my program look in the file but not sure what to do also don't know how to get the program to run again if the user chooses to continue. #include <iostream> #include <fstream> #include <string> #include <iomanip> using namespace std; char chr; int main() { string first; string last; string number; string firstfile; string lastfile; string numberfile; int cont; ifstream infile; infile.open("name and numbers.dat"); //opening the file infile>>firstfile>>lastfile>>numberfile; cout<<"Enter a first and last name."<<endl; //Asking user for the input cin>>first>>last; //input the data { if(first==firstfile && last==lastfile) //if the entered information matches the information in the file cout<<first<<" "<<last<<"'s number is "<<numberfile<<endl; //this is printed else cout<<"Sorry that is not in our database."<<endl; //if the information doesn't match this is printed } cout<<"Would you like to search for another name? Y or N"<<endl; //user is asked if they would like to continue cin>>cont; infile.close(); //close file cin>>chr; return 0; }

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• Turning temporary stringstream to c_str() in single statement

  - by AshleysBrain

  Consider the following function: void f(const char* str); Suppose I want to generate a string using stringstream and pass it to this function. If I want to do it in one statement, I might try: f((std::ostringstream() << "Value: " << 5).str().c_str()); // error This gives an error: 'str()' is not a member of 'basic_ostream'. OK, so operator<< is returning ostream instead of ostringstream - how about casting it back to an ostringstream? 1) Is this cast safe? f(static_cast<std::ostringstream&>(std::ostringstream() << "Value: " << 5).str().c_str()); // incorrect output Now with this, it turns out for the operator<<("Value: ") call, it's actually calling ostream's operator<<(void*) and printing a hex address. This is wrong, I want the text. 2) Why does operator<< on the temporary std::ostringstream() call the ostream operator? Surely the temporary has a type of 'ostringstream' not 'ostream'? I can cast the temporary to force the correct operator call too! f(static_cast<std::ostringstream&>(static_cast<std::ostringstream&>(std::ostringstream()) << "Value: " << 5).str().c_str()); This appears to work and passes "Value: 5" to f(). 3) Am I relying on undefined behavior now? The casts look unusual. I'm aware the best alternative is something like this: std::ostringstream ss; ss << "Value: " << 5; f(ss.str().c_str()); ...but I'm interested in the behavior of doing it in one line. Suppose someone wanted to make a (dubious) macro: #define make_temporary_cstr(x) (static_cast<std::ostringstream&>(static_cast<std::ostringstream&>(std::ostringstream()) << x).str().c_str()) // ... f(make_temporary_cstr("Value: " << 5)); Would this function as expected?

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• How can I have a Makefile automatically rebuild source files that include a modified header file? (I

  - by Nicholas Flynt

  I have the following makefile that I use to build a program (a kernel, actually) that I'm working on. Its from scratch and I'm learning about the process, so its not perfect, but I think its powerful enough at this point for my level of experience writing makefiles. AS = nasm CC = gcc LD = ld TARGET = core BUILD = build SOURCES = source INCLUDE = include ASM = assembly VPATH = $(SOURCES) CFLAGS = -Wall -O -fstrength-reduce -fomit-frame-pointer -finline-functions \ -nostdinc -fno-builtin -I $(INCLUDE) ASFLAGS = -f elf #CFILES = core.c consoleio.c system.c CFILES = $(foreach dir,$(SOURCES),$(notdir $(wildcard $(dir)/*.c))) SFILES = assembly/start.asm SOBJS = $(SFILES:.asm=.o) COBJS = $(CFILES:.c=.o) OBJS = $(SOBJS) $(COBJS) build : $(TARGET).img $(TARGET).img : $(TARGET).elf c:/python26/python.exe concat.py stage1 stage2 pad.bin core.elf floppy.img $(TARGET).elf : $(OBJS) $(LD) -T link.ld -o $@ $^ $(SOBJS) : $(SFILES) $(AS) $(ASFLAGS) $< -o $@ %.o: %.c @echo Compiling $<... $(CC) $(CFLAGS) -c -o $@ $< #Clean Script - Should clear out all .o files everywhere and all that. clean: -del *.img -del *.o -del assembly\*.o -del core.elf My main issue with this makefile is that when I modify a header file that one or more C files include, the C files aren't rebuilt. I can fix this quite easily by having all of my header files be dependencies for all of my C files, but that would effectively cause a complete rebuild of the project any time I changed/added a header file, which would not be very graceful. What I want is for only the C files that include the header file I change to be rebuilt, and for the entire project to be linked again. I can do the linking by causing all header files to be dependencies of the target, but I cannot figure out how to make the C files be invalidated when their included header files are newer. I've heard that GCC has some commands to make this possible (so the makefile can somehow figure out which files need to be rebuilt) but I can't for the life of me find an actual implementation example to look at. Can someone post a solution that will enable this behavior in a makefile? EDIT: I should clarify, I'm familiar with the concept of putting the individual targets in and having each target.o require the header files. That requires me to be editing the makefile every time I include a header file somewhere, which is a bit of a pain. I'm looking for a solution that can derive the header file dependencies on its own, which I'm fairly certain I've seen in other projects.

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• JSF 2.0: Preserving component state across multiple views

  - by tlind

  The web application I am developing using MyFaces 2.0.3 / PrimeFaces 2.2RC2 is divided into a content and a navigation area. In the navigation area, which is included into multiple pages using templating (i.e. <ui:define>), there are some widgets (e.g. a navigation tree, collapsible panels etc.) of which I want to preserve the component state across views. For example, let's say I am on the home page. When I navigate to a product details page by clicking on a product in the navigation tree, my Java code triggers a redirect using navigationHandler.handleNavigation(context, null, "/detailspage.jsf?faces-redirect=true") Another way of getting to that details page would be by directly clicking on a product teaser that is shown on the home page. The corresponding <h:link> would lead us to the details page. In both cases, the expansion state of my navigation tree (a PrimeFaces tree component) and my collapsible panels is lost. I understand this is because the redirect / h:link results in the creation of a new view. What is the best way of dealing with this? I am already using MyFaces Orchestra in my project along with its conversation scope, but I am not sure if this is of any help here (since I'd have to bind the expansion/collapsed state of the widgets to a backing bean... but as far as I know, this is not possible). Is there a way of telling JSF which component states to propagate to the next view, assuming that the same component exists in that view? I guess I could need a pointer into the right direction here. Thanks! Update 1: I just tried binding the panels and the tree to a session-scoped bean, but this seems to have no effect. Also, I guess I would have to bind all child components (if any) manually, so this doesn't seem like the way to go. Update 2: Binding UI components to non-request scoped beans is not a good idea (see link I posted in a comment below). If there is no easier approach, I might have to proceed as follows: When a panel is collapsed or the tree is expanded, save the current state in a session-scoped backing bean (!= the UI component itself) The components' states are stored in a map. The map key is the component's (hopefully) unique, relative ID. I cannot use the whole absolute component path here, since the IDs of the parent naming containers might change if the view changes, assuming these IDs are generated programmatically. As soon as a new view gets constructed, retrieve the components' states from the map and apply them to the components. For example, in case of the panels, I can set the collapsed attribute to a value retrieved from my session-scoped backing bean.

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• properies profile when writing word file

  - by avani-nature

  Hai frnds i am new to php i am having following problems in my coding... 1.Actually i am opening word document with com object and storing it in textarea. 2.when content gets opened in textarea i am editing that content and saving the document 3.actually when i edited that file and done save after that if i open word document then file properties-custom the old content getting removed i wannt to retain that even if i edited the word document..please do the needful i am using below code <?php $filename = 'C:/xampp/htdocs/mts/sites/default/files/a.doc'; //echo $filename; if(isset($_REQUEST['Save'])){ $somecontent = stripslashes($_POST['somecontent']); // Let's make sure the file exists and is writable first. if (is_writable($filename)) { // In our example we're opening $filename in append mode. // The file pointer is at the bottom of the file hence // that's where $somecontent will go when we fwrite() it. if (!$handle = fopen($filename, 'w')) { echo "Cannot open file ($filename)"; exit; } // Write $somecontent to our opened fi<form action="" method="get"></form>le. if (fwrite($handle, $somecontent) === FALSE) { echo "Cannot write to file ($filename)"; exit; } echo "Success, wrote ($somecontent) to file ($filename) <a href=".$_SERVER['PHP_SELF']."> - Continue - "; fclose($handle); } else { echo "The file $filename is not writable"; } } else{ // get contents of a file into a string $handle = fopen($filename, "r"); $somecontent = fread($handle, filesize($filename)); $word = new COM("word.application") or die ("Could not initialise MS Word object."); $word->Documents->Open(realpath("$filename")); // Extract content. $somecontent = (string) $word->ActiveDocument->Content; //echo $somecontent; $word->ActiveDocument->Close(false); $word->Quit(); $word = null; unset($word); fclose($handle); } ?> <h6>Edit file --------><? $filenam=explode("/",$filename);$filename=$filename[7]; echo $filename ;?></h6> <form name="form1" method="post" action=""> <p> <textarea name="somecontent" cols="100" rows="20"><? echo $somecontent ;?></textarea> </p> <div style='padding-left:250px;'><input type="submit" name="Save" value="Save"></div> </p> </form> <? } ?>

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• Two seperate tm structs mirroring each other

  - by BSchlinker

  Here is my current situation: I have two tm structs, both set to the current time I make a change to the hour in one of the structs The change is occurring in the other struct magically.... How do I prevent this from occurring? I need to be able to compare and know the number of seconds between two different times -- the current time and a time in the future. I've been using difftime and mktime to determine this. I recognize that I don't technically need two tm structs (the other struct could just be a time_t loaded with raw time) but I'm still interested in understanding why this occurs. void Tracker::monitor(char* buffer){ // time handling time_t systemtime, scheduletime, currenttime; struct tm * dispatchtime; struct tm * uiuctime; double remainingtime; // let's get two structs operating with current time dispatchtime = dispatchtime_tm(); uiuctime = uiuctime_tm(); // set the scheduled parameters dispatchtime->tm_hour = 5; dispatchtime->tm_min = 05; dispatchtime->tm_sec = 14; uiuctime->tm_hour = 0; // both of these will now print the same time! (0:05:14) // what's linking them?? // print the scheduled time printf ("Current Time : %2d:%02d:%02d\n", uiuctime->tm_hour, uiuctime->tm_min, uiuctime->tm_sec); printf ("Scheduled Time : %2d:%02d:%02d\n", dispatchtime->tm_hour, dispatchtime->tm_min, dispatchtime->tm_sec); } struct tm* Tracker::uiuctime_tm(){ time_t uiucTime; struct tm *ts_uiuc; // give currentTime the current time time(&uiucTime); // change the time zone to UIUC putenv("TZ=CST6CDT"); tzset(); // get the localtime for the tz selected ts_uiuc = localtime(&uiucTime); // set back the current timezone unsetenv("TZ"); tzset(); // set back our results return ts_uiuc; } struct tm* Tracker::dispatchtime_tm(){ time_t currentTime; struct tm *ts_dispatch; // give currentTime the current time time(&currentTime); // get the localtime for the tz selected ts_dispatch = localtime(&currentTime); // set back our results return ts_dispatch; }

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• HTML: order of divs and a tags for href

  - by user2962389

  I'm busy with HTML and CSS and got stuck with this. I have created a button with :hover and :active options, which is centered on the page. Clicking on this button needs to lead to a website. My HTML is: <div> <a href="website"><div id="button">Text</div></a> </div> The CSS is: body, html { height: 100%; } a { text-decoration: none; } #button { text-transform: uppercase; font-size: 18px; text-align: center; padding: 1em 0.5em 0.8em; background-color: white; font-family: Myriad Pro, Source Sans Pro, Helvetica, Arial, sans-serif; color: #ff4700; cursor: pointer; width: 150px; -webkit-border-radius: 5px; -moz-border-radius: 5px; border-radius: 5px; border: 1px solid #ff4700; margin-left: auto; margin-right: auto; margin-bottom: 50px; -webkit-transition: all .1s ease; -moz-transition: all .1s ease; -ms-transition: all .1s ease; -o-transition: all .1s ease; transition: all .1s ease; } #button:hover { background-color: #ff4700; color: white; border: 1px solid white; } #button:active { background-color: #cc3900; } The problem lies in the fact that the whole width of the page is clickable at the height of the button and not only the button itself that is 150px wide and is centered on the page. I think I have my divs mixed up and it needs other formatting and precedence, but I'm not sure. Thanks for your help! P.S. First time on StackOverflow, sorry if I formatted something wrong.

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• C program using inotify to monitor multiple directories along with sub-directories?

  - by lakshmipathi

  I have program which monitors a directory (/test) and notify me. I want to improve this to monitor another directory (say /opt). And also how to monitor it's subdirectories , current i'll get notified if any changes made to files under /test . but i'm not getting any inotifcation if changes made sub-directory of /test, that is touch /test/sub-dir/files.txt .. Here my current code - hope this will help /* Simple example for inotify in Linux. inotify has 3 main functions. inotify_init1 to initialize inotify_add_watch to add monitor then inotify_??_watch to rm monitor.you the what to replace with ??. yes third one is inotify_rm_watch() */ #include <sys/inotify.h> int main(){ int fd,wd,wd1,i=0,len=0; char pathname[100],buf[1024]; struct inotify_event *event; fd=inotify_init1(IN_NONBLOCK); /* watch /test directory for any activity and report it back to me */ wd=inotify_add_watch(fd,"/test",IN_ALL_EVENTS); while(1){ //read 1024 bytes of events from fd into buf i=0; len=read(fd,buf,1024); while(i<len){ event=(struct inotify_event *) &buf[i]; /* check for changes */ if(event->mask & IN_OPEN) printf("%s :was opened\n",event->name); if(event->mask & IN_MODIFY) printf("%s : modified\n",event->name); if(event->mask & IN_ATTRIB) printf("%s :meta data changed\n",event->name); if(event->mask & IN_ACCESS) printf("%s :was read\n",event->name); if(event->mask & IN_CLOSE_WRITE) printf("%s :file opened for writing was closed\n",event->name); if(event->mask & IN_CLOSE_NOWRITE) printf("%s :file opened not for writing was closed\n",event->name); if(event->mask & IN_DELETE_SELF) printf("%s :deleted\n",event->name); if(event->mask & IN_DELETE) printf("%s :deleted\n",event->name); /* update index to start of next event */ i+=sizeof(struct inotify_event)+event->len; } } }

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• Efficient list compacting

  - by Patrik

  Suppose you have a list of unsigned ints. Suppose some elements are equal to 0 and you want to push them back. Currently I use this code (list is a pointer to a list of unsigned ints of size n for (i = 0; i < n; ++i) { if (list[i]) continue; int j; for (j = i + 1; j < n && !list[j]; ++j); int z; for (z = j + 1; z < n && list[z]; ++z); if (j == n) break; memmove(&(list[i]), &(list[j]), sizeof(unsigned int) * (z - j))); int s = z - j + i; for(j = s; j < z; ++j) list[j] = 0; i = s - 1; } Can you think of a more efficient way to perform this task? The snippet is purely theoretical, in the production code, each element of list is a 64 bytes struct EDIT: I'll post my solution. Many thanks to Jonathan Leffler. void RemoveDeadParticles(int * list, int * n) { int i, j = *n - 1; for (; j >= 0 && list[j] == 0; --j); for (i = 0; i < j; ++i) { if (list[i]) continue; memcpy(&(list[i]), &(list[j]), sizeof(int)); list[j] = 0; for (; j >= 0 && list[j] == 0; --j); if (i == j) break; } *n = i + 1; }

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• Can't get InputStream read to block...

  - by mark dufresne

  I would like the input stream read to block instead of reading end of stream (-1). Is there a way to configure the stream to do this? Here's my Servlet code: PrintWriter out = response.getWriter(); BufferedReader in = request.getReader(); try { String line; int loop = 0; while (loop < 20) { line = in.readLine(); lgr.log(Level.INFO, line); out.println("<" + loop + "html>"); Thread.sleep(1000); loop++; // } } catch (InterruptedException ex) { lgr.log(Level.SEVERE, null, ex); } finally { out.close(); } Here's my Midlet code: private HttpConnection conn; InputStream is; OutputStream os; private boolean exit = false; public void run() { String url = "http://localhost:8080/WebApplication2/NewServlet"; try { conn = (HttpConnection) Connector.open(url); is = conn.openInputStream(); os = conn.openOutputStream(); StringBuffer sb = new StringBuffer(); int c; while (!exit) { os.write("<html>\n".getBytes()); while ((c = is.read()) != -1) { sb.append((char) c); } System.out.println(sb.toString()); sb.delete(0, sb.length() - 1); try { Thread.sleep(1000); } catch (InterruptedException ex) { ex.printStackTrace(); } } os.close(); is.close(); conn.close(); } catch (IOException ex) { ex.printStackTrace(); } } I've tried InputStream.read, but it doesn't block either, it returns -1 as well. I'm trying to keep the I/O streams on either side alive. I want the servlet to wait for input, process the input, then send back a response. In the code above it should do this 20 times. thanks for any help

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• Error in Print Function in Bubble Sort MIPS?

  - by m00nbeam360

  Sorry that this is such a long block of code, but do you see any obvious syntax errors in this? I feel like the problem is that the code isn't printing correctly since the sort and swap methods were from my textbook. Please help if you can! .data save: .word 1,2,4,2,5,6 size: .word 6 .text swap: sll $t1, $a1, 2 #shift bits by 2 add $t1, $a1, $t1 #set $t1 address to v[k] lw $t0, 0($t1) #load v[k] into t1 lw $t2, 4($t1) #load v[k+1] into t1 sw $t2, 0($t1) #swap addresses sw $t0, 4($t1) #swap addresses jr $ra #return sort: addi $sp, $sp, -20 #make enough room on the stack for five registers sw $ra, 16($sp) #save the return address on the stack sw $s3, 12($sp) #save $s3 on the stack sw $s2, 8($sp) #save Ss2 on the stack sw $s1, 4($sp) #save $s1 on the stack sw $s0, 0($sp) #save $s0 on the stack move $s2, $a0 #copy the parameter $a0 into $s2 (save $a0) move $s3, $a1 #copy the parameter $a1 into $s3 (save $a1) move $s0, $zero #start of for loop, i = 0 for1tst: slt $t0, $s0, $s3 #$t0 = 0 if $s0 S $s3 (i S n) beq $t0, $zero, exit1 #go to exit1 if $s0 S $s3 (i S n) addi $s1, $s0, -1 #j - i - 1 for2tst: slti $t0, $s1, 0 #$t0 = 1 if $s1 < 0 (j < 0) bne $t0, $zero, exit2 #$t0 = 1 if $s1 < 0 (j < 0) sll $t1, $s1, 2 #$t1 = j * 4 (shift by 2 bits) add $t2, $s2, $t1 #$t2 = v + (j*4) lw $t3, 0($t2) #$t3 = v[j] lw $t4, 4($t2) #$t4 = v[j+1] slt $t0, $t4, $t3 #$t0 = 0 if $t4 S $t3 beq $t0, $zero, exit2 #go to exit2 if $t4 S $t3 move $a0, $s2 #1st parameter of swap is v(old $a0) move $a1, $s1 #2nd parameter of swap is j jal swap #swap addi $s1, $s1, -1 j for2tst #jump to test of inner loop j print exit2: addi $s0, $s0, 1 #i = i + 1 j for1tst #jump to test of outer loop exit1: lw $s0, 0($sp) #restore $s0 from stack lw $s1, 4($sp) #resture $s1 from stack lw $s2, 8($sp) #restore $s2 from stack lw $s3, 12($sp) #restore $s3 from stack lw $ra, 16($sp) #restore $ra from stack addi $sp, $sp, 20 #restore stack pointer jr $ra #return to calling routine .data space:.asciiz " " # space to insert between numbers head: .asciiz "The sorted numbers are:\n" .text print:add $t0, $zero, $a0 # starting address of array add $t1, $zero, $a1 # initialize loop counter to array size la $a0, head # load address of print heading li $v0, 4 # specify Print String service syscall # print heading out: lw $a0, 0($t0) # load fibonacci number for syscall li $v0, 1 # specify Print Integer service syscall # print fibonacci number la $a0, space # load address of spacer for syscall li $v0, 4 # specify Print String service syscall # output string addi $t0, $t0, 4 # increment address addi $t1, $t1, -1 # decrement loop counter bgtz $t1, out # repeat if not finished jr $ra # return

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• Cleaning up a dynamic array of Objects in C++

  - by Dr. Monkey

  I'm a bit confused about handling an array of objects in C++, as I can't seem to find information about how they are passed around (reference or value) and how they are stored in an array. I would expect an array of objects to be an array of pointers to that object type, but I haven't found this written anywhere. Would they be pointers, or would the objects themselves be laid out in memory in an array? In the example below, a custom class myClass holds a string (would this make it of variable size, or does the string object hold a pointer to a string and therefore take up a consistent amount of space. I try to create a dynamic array of myClass objects within a myContainer. In the myContainer.addObject() method I attempt to make a bigger array, copy all the objects into it along with a new object, then delete the old one. I'm not at all confident that I'm cleaning up my memory properly with my destructors - what improvements could I make in this area? class myClass { private string myName; public unsigned short myAmount; myClass(string name, unsigned short amount) { myName = name; myAmount = amount; } //Do I need a destructor here? I don't think so because I don't do any // dynamic memory allocation within this class } class myContainer { int numObjects; myClass * myObjects; myContainer() { numObjects = 0; } ~myContainer() { //Is this sufficient? //Or do I need to iterate through myObjects and delete each // individually? delete [] myObjects; } void addObject(string name, unsigned short amount) { myClass newObject = new myClass(name, amount); myClass * tempObjects; tempObjects = new myClass[numObjects+1]; for (int i=0; i<numObjects; i++) tempObjects[i] = myObjects[i]); tempObjects[numObjects] = newObject; numObjects++; delete newObject; //Will this delete all my objects? I think it won't. //I'm just trying to delete the old array, and have the new array hold // all the objects plus the new object. delete [] myObjects; myObjects = tempObjects; } }

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