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  • Not sure I am using inheritance/polymorphism issue?

    - by planker1010
    So for this assignment I have to create a car class(parent) and a certifiedpreowned (child) and I need to have the parent class have a method to check if it is still under warranty. *checkWarrantyStatus(). that method calls the boolean isCoveredUnderWarranty() to veryify if the car still has warranty. My issue is in the certifiedpreowned class I have to call the isCoveredUnderWarranty() as well to see if it is covered under the extended warranty and then have it be called via the checkWarrantyStatus() in the car method. I hope this makes sense. So to sum it up I need to in the child class have it check the isCoveredUnderWarranty with extended warranty info. Then it has to move to the parent class so it can be called via checkWarrantyStatus. Here is my code, I have 1 error. public class Car { public int year; public String make; public String model; public int currentMiles; public int warrantyMiles; public int warrantyYears; int currentYear =java.util.Calendar.getInstance().get(java.util.Calendar.YEAR); /** construct car object with specific parameters*/ public Car (int y, String m, String mod, int mi){ this.year = y; this.make = m; this.model = mod; this.currentMiles = mi; } public int getWarrantyMiles() { return warrantyMiles; } public void setWarrantyMiles(int warrantyMiles) { this.warrantyMiles = warrantyMiles; } public int getWarrantyYears() { return warrantyYears; } public void setWarrantyYears(int warrantyYears) { this.warrantyYears = warrantyYears; } public boolean isCoveredUnderWarranty(){ if (currentMiles < warrantyMiles){ if (currentYear < (year+ warrantyYears)) return true; } return false; } public void checkWarrantyStatus(){ if (isCoveredUnderWarranty()){ System.out.println("Your car " + year+ " " + make+ " "+ model+ " With "+ currentMiles +" is still covered under warranty"); } else System.out.println("Your car " + year+ " " + make+ " "+ model+ " With "+ currentMiles +" is out of warranty"); } } public class CertifiedPreOwnCar extends Car{ public CertifiedPreOwnCar(int y, String m, String mod, int mi) { super(mi, m, mod, y); } public int extendedWarrantyYears; public int extendedWarrantyMiles; public int getExtendedWarrantyYears() { return extendedWarrantyYears; } public void setExtendedWarrantyYears(int extendedWarrantyYears) { this.extendedWarrantyYears = extendedWarrantyYears; } public int getExtendedWarrantyMiles() { return extendedWarrantyMiles; } public void setExtendedWarrantyMiles(int extendedWarrantyMiles) { this.extendedWarrantyMiles = extendedWarrantyMiles; } public boolean isCoveredUnderWarranty() { if (currentMiles < extendedWarrantyMiles){ if (currentYear < (year+ extendedWarrantyYears)) return true; } return false; } } public class TestCar { public static void main(String[] args) { Car car1 = new Car(2014, "Honda", "Civic", 255); car1.setWarrantyMiles(60000); car1.setWarrantyYears(5); car1.checkWarrantyStatus(); Car car2 = new Car(2000, "Ferrari", "F355", 8500); car2.setWarrantyMiles(20000); car2.setWarrantyYears(7); car2.checkWarrantyStatus(); CertifiedPreOwnCar car3 = new CertifiedPreOwnCar(2000, "Honda", "Accord", 65000); car3.setWarrantyYears(3); car3.setWarrantyMiles(30000); car3.setExtendedWarrantyMiles(100000); car3.setExtendedWarrantyYears(7); car3.checkWarrantyStatus(); } }

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  • Use of select or multithread for almost 80 or more clients?

    - by Tushar Goel
    I am working on one project in which i need to read from 80 or more clients and then write their o/p into a file continuously and then read these new data for another task. My question is what should i use select or multithreading? Also I tried to use multi threading using read/fgets and write/fputs call but as they are blocking calls and one operation can be performed at one time so it is not feasible. Any idea is much appreciated. update 1: I have tried to implement the same using condition variable. I able to achieve this but it is writing and reading one at a time.When another client tried to write then it cannot able to write unless i quit from the 1st thread. I do not understand this. This should work now. What mistake i am doing? Update 2: Thanks all .. I am able to succeeded to get this model implemented using mutex condition variable. updated Code is as below: **header file******* char *mailbox ; pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER ; pthread_cond_t writer = PTHREAD_COND_INITIALIZER; int main(int argc,char *argv[]) { pthread_t t1 , t2; pthread_attr_t attr; int fd, sock , *newfd; struct sockaddr_in cliaddr; socklen_t clilen; void *read_file(); void *update_file(); //making a server socket if((fd=make_server(atoi(argv[1])))==-1) oops("Unable to make server",1) //detaching threads pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED); ///opening thread for reading pthread_create(&t2,&attr,read_file,NULL); while(1) { clilen = sizeof(cliaddr); //accepting request sock=accept(fd,(struct sockaddr *)&cliaddr,&clilen); //error comparison against failire of request and INT if(sock==-1 && errno != EINTR) oops("accept",2) else if ( sock ==-1 && errno == EINTR) oops("Pressed INT",3) newfd = (int *)malloc(sizeof(int)); *newfd = sock; //creating thread per request pthread_create(&t1,&attr,update_file,(void *)newfd); } free(newfd); return 0; } void *read_file(void *m) { pthread_mutex_lock(&lock); while(1) { printf("Waiting for lock.\n"); pthread_cond_wait(&writer,&lock); printf("I am reading here.\n"); printf("%s",mailbox); mailbox = NULL ; pthread_cond_signal(&writer); } } void *update_file(int *m) { int sock = *m; int fs ; int nread; char buffer[BUFSIZ] ; if((fs=open("database.txt",O_RDWR))==-1) oops("Unable to open file",4) while(1) { pthread_mutex_lock(&lock); write(1,"Waiting to get writer lock.\n",29); if(mailbox != NULL) pthread_cond_wait(&writer,&lock); lseek(fs,0,SEEK_END); printf("Reading from socket.\n"); nread=read(sock,buffer,BUFSIZ); printf("Writing in file.\n"); write(fs,buffer,nread); mailbox = buffer ; pthread_cond_signal(&writer); pthread_mutex_unlock(&lock); } close(fs); }

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  • pass arraylist bean from android to webservice php

    - by user1547432
    i'm newbie in android with web service i'm trying to pass arraylist from android to webservice php server here's my bean code: public class ExpressionBean { public static final String EXPRESSION_ID = "expressionID"; public static final String EXPRESSION_TEXT = "expressionText"; public static final String ANS_TEXT1 = "ansText1"; public static final String ANS_TEXT2 = "ansText2"; public static final String ASSESSEE_ANSWER = "assesseeAnswer"; private String expressionID; private String expressionText; private String ansText1; private String ansText2; private String assesseeAnswer; public String getExpressionID() { return expressionID; } public void setExpressionID(String expressionID) { this.expressionID = expressionID; } public String getExpressionText() { return expressionText; } public void setExpressionText(String expressionText) { this.expressionText = expressionText; } public String getAnsText1() { return ansText1; } public void setAnsText1(String ansText1) { this.ansText1 = ansText1; } public String getAnsText2() { return ansText2; } public void setAnsText2(String ansText2) { this.ansText2 = ansText2; } public String getAssesseeAnswer() { return assesseeAnswer; } public void setAssesseeAnswer(String assesseeAnswer) { this.assesseeAnswer = assesseeAnswer; } } and here's my doInBackround on async task : protected Boolean doInBackground(Void... params) { // TODO: attempt authentication against a network service. boolean result = false; // test = new TestBean(); // int resultTest = 0; UserFunctions userFunction = new UserFunctions(); Log.d(TAG, "UID : " + mEmail); // Log.d(TAG, "resultTest : " + resultTest); JSONObject jsonTest = userFunction.storeTest(mEmail); Log.d(TAG, "After JSON TEST "); try { if (jsonTest.getString(KEY_SUCCESS) != null) { String res = jsonTest.getString(KEY_SUCCESS); JSONObject testData = jsonTest.getJSONObject(TAG_TEST); test = new TestBean(); test.setTestid(testData.getInt(TAG_TEST_ID)); test.setUid(testData.getInt(TAG_UID)); JSONArray list = new JSONArray(); String list2; for (int position = 0; position < expressionList.size(); position++) { Gson gson = new Gson(); list.put(gson.toJson(expressionList.get(position))); } Log.d(TAG, "JSONArray list coy : " + list); UserFunctions uf = new UserFunctions(); JSONObject jsonHistoryList = new JSONObject(); jsonHistoryList = uf.storeHistoryList(list.toString()); if (Integer.parseInt(res) == 1) { result = true; finish(); } else { result = false; } } } catch (JSONException e) { e.printStackTrace(); return false; } // TODO: register the new account here. return result; } and here's storeHistoryList Method : public JSONObject storeHistoryList(String list) { // Building Parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); params.add(new BasicNameValuePair("tag", storeHistory_tag)); params.add(new BasicNameValuePair("list", list)); JSONObject json = jsonParser.getJSONFromUrl(URL, params); return json; } i want to pass list to web service list is an arraylist ExpressionBean i used gson for convert bean to json but when i execute, the log said "error parsing data... jsonarray cannot be converted to jsonobject what i must to do? thanks

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  • C Program not running as intended, hangs after input

    - by user41419
    The program I am writing to take a number and display that number as a calculator would display it (shown below) is compiling with no issues, but when I try to run it, I am able to input my number, but nothing happens. It seems like it is "hanging", since no further output is shown as I would have expected. Might anyone know what the problem is? #include <stdio.h> #define MAX_DIGITS 20 char segments[10][7] = /* seven segment array */ {{'1','1','1','1','1','1','0'}, /* zero */ {'0','1','1','0','0','0','0'}, /* one */ {'1','1','0','1','1','0','1'}, /* two */ {'1','1','1','1','0','0','1'}, /* three */ {'0','1','1','0','0','1','1'}, /* four */ {'1','0','1','1','0','1','1'}, /* five */ {'1','0','1','1','1','1','1'}, /* six */ {'1','1','1','0','0','0','0'}, /* seven */ {'1','1','1','1','1','1','1'}, /* eight */ {'1','1','1','0','0','1','1'}};/* nine */ char digits[3][MAX_DIGITS * 4]; /* digits array */ int i, j; /* count variables */ int adjust; /* output formatting */ int main(void) { clear_digits_array(); int digit[20]; for (i = 0; i < 20; i++) { digit[i] = 0; } int count = 20; int position = 0; printf("Enter a number: "); int number = scanf("%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d", &digit[0], &digit[1], &digit[2], &digit[3], &digit[4], &digit[5], &digit[6], &digit[7], &digit[8], &digit[9], &digit[10], &digit[11], &digit[12], &digit[13], &digit[14], &digit[15], &digit[16], &digit[17], &digit[18], &digit[19]); //NOTHING HAPPENS AFTER HERE printf("Got input, number is %d", number); while (count > 0) { printf("Reading digits, count is %d", count); process_digit(digit[20 - count], position); position++; count--; } print_digits_array(); printf("\n"); return 0; } void clear_digits_array(void) { /* fill all positions in digits array with blank spaces */ for (i = 0; i < 3; i++) { for (j = 0; j < (MAX_DIGITS * 4); j++) { digits[i][j] = ' '; } } } void process_digit(int digit, int position) { /* check each segment to see if segment should be filled in for given digit */ for (i = 0; i < 7; i++) { printf("Processing digit %d at position %d, i is %d", digit, position, i); if (segments[digit][i] == 1) { switch (i) { case 0: digits[0][(position * 4) + 1] = '_'; break; case 1: digits[1][(position * 4) + 2] = '|'; break; case 2: digits[2][(position * 4) + 2] = '|'; break; case 3: digits[2][(position * 4) + 1] = '_'; break; case 4: digits[2][(position * 4) + 0] = '|'; break; case 5: digits[1][(position * 4) + 0] = '|'; break; case 6: digits[1][(position * 4) + 1] = '_'; break; } } } } void print_digits_array(void) { /* print each character in digits array */ for (i = 0; i < 3; i++) { for (j = 0; j < (MAX_DIGITS * 4); j++) { printf("%c", digits[i][j]); } printf("/n"); } }

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  • linked list problem (with insert)

    - by JohnWong
    The problem appears with the insert function that I wrote. 3 conditions must work, I tested b/w 1 and 2, b/w 2 and 3 and as last element, they worked. But b/w 3 and 4, it did not work. It only display up to the new added record, and did not show the fourth element. Efficiency is not my concern here (not yet). Please guide me through this debug process. Thank you very much. #include<iostream> #include<string> using namespace std; struct List // we create a structure called List { string name; string tele; List *nextAddr; }; void populate(List *); void display(List *); void insert(List *); int main() { const int MAXINPUT = 3; char ans; List * data, * current, * point; // create two pointers data = new List; current = data; for (int i = 0; i < (MAXINPUT - 1); i++) { populate(current); current->nextAddr = new List; current = current->nextAddr; } // last record we want to do it sepeartely populate(current); current->nextAddr = NULL; cout << "The current list consists of the following data records: " << endl; display(data); // now ask whether user wants to insert new record or not cout << "Do you want to add a new record (Y/N)?"; cin >> ans; if (ans == 'Y' || ans == 'y') { /* To insert b/w first and second, use point as parameter between second and third uses point->nextAddr between third and fourth uses point->nextAddr->nextAddr and insert as last element, uses current instead */ point = data; insert(()); display(data); } return 0; } void populate(List *data) { cout << "Enter a name: "; cin >> data->name; cout << "Enter a phone number: "; cin >> data->tele; return; } void display(List *content) { while (content != NULL) { cout << content->name << " " << content->tele; content = content->nextAddr; cout << endl; // we skip to next line } return; } void insert(List *last) { List * temp = last->nextAddr; //save the next address to temp last->nextAddr = new List; // now modify the address pointed to new allocation last = last->nextAddr; populate(last); last->nextAddr = temp; // now link all three together, eg 1-NEW-2 return; }

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  • Problem in arranging contents of Class in JAVA

    - by LuckySlevin
    Hi, I have some classes and I'm trying to fill the objects of this class. Here is what i've tried. (Question is at the below) public class Team { private String clubName; private String preName; private ArrayList<String> branches; public Team(String clubName, String preName) { this.clubName = clubName; this.preName = preName; branches = new ArrayList<String>(); } public Team() { // TODO Auto-generated constructor stub } public String getClubName() { return clubName; } public String getPreName() { return preName; } public ArrayList<String> getBranches() { return branches; } public void setClubName(String clubName) { this.clubName = clubName; } public void setPreName(String preName) { this.preName = preName; } public void setBranches(ArrayList<String> branches) { this.branches = branches; } } public class Branch { private ArrayList<Player> players = new ArrayList<Player>(); String brName; public Branch() {} public void setBr(String brName){this.brName = brName;} public String getBr(){return brName;} public ArrayList<Player> getPlayers() { return players; } public void setPlayers(ArrayList<Player> players) { this.players = players; } } //TEST CLASS public class test { /** * @param args * @throws IOException */ public static void main(String[] args) throws IOException { String a,b,c; String q = "q"; int brCount = 0, tCount = 0; BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); Team[] teams = new Team[30]; Branch[] myBranch = new Branch[30]; for(int z = 0 ; z <30 ;z++) { teams[z] = new Team(); myBranch[z] = new Branch(); } ArrayList<String> tmp = new ArrayList<String>(); int k = 0; int secim = Integer.parseInt(input.readLine()); while(secim != 0) { if(k!=0) secim = Integer.parseInt(input.readLine()); k++; switch(secim) { case 1 : brCount = 0; a = input.readLine(); teams[tCount].setClubName(a); b= input.readLine(); teams[tCount].setPreName(b); c = input.readLine(); while(c.equals(q) == false) { if(brCount != 0) {c = input.readLine();} if(c.equals(q)== false){ myBranch[brCount].brName = c; tmp.add(myBranch[brCount].brName); brCount++; } System.out.println(brCount); } teams[tCount].setBranches(tmp); for(int i=0;i<=tCount;i++ ){ System.out.print("a :" + teams[i].getClubName()+ " " + teams[i].getPreName()+ " "); System.out.println(teams[i].getBranches());} tCount++; break; case 2: String src = input.readLine();//LATERRRRRRRr } } } } The problem is one of my class elements. I have an arraylist as an element of a class. When i enter: AAA as preName BBB as clubName c d e as Branches Then as a second element www as preName GGG as clubName a b as branches The result is coming like: AAA BBB c,d,e,a,b GGG www c,d,e,a,b Which means ArrayList part of the class is putting it on and on. I tried to use clear() method but caused problems. Any ideas.

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  • save as .txt format

    - by user1180492
    I made a NotePad program. The problem is it doesn't save in .txt format, It save as a file with no format. But it can open .txt files. How can i fix it? Here is my work. import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.util.Scanner; import java.io.*; public class NotePad extends JFrame { private JTextArea noteArea; public static void main(String[] args) { NotePad p = new NotePad(); p.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); p.setSize(500,300); p.setVisible(true); } public NotePad() { super("Java Notepad"); setLayout(new BorderLayout()); noteArea = new JTextArea("",20,20); noteArea.setWrapStyleWord(true); noteArea.setLineWrap(true); Font font = new Font("sanserif", Font.BOLD,14); noteArea.setFont(font); JScrollPane scroller = new JScrollPane(noteArea); scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS); scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER); add(scroller,BorderLayout.CENTER); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenuItem openMenu = new JMenuItem("Open"); openMenu.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent ae) { JFileChooser openFile = new JFileChooser(); openFile.showOpenDialog(new NotePad()); loadFile(openFile.getSelectedFile()); } }); JMenuItem saveMenu = new JMenuItem("Save"); saveMenu.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent ae) { JFileChooser saveFile = new JFileChooser(); saveFile.showSaveDialog(new NotePad()); fileSaved(saveFile.getSelectedFile()); } }); JMenuItem exitMenu = new JMenuItem("Close"); exitMenu.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent ae) { System.exit(0); } }); fileMenu.add(openMenu); fileMenu.add(saveMenu); fileMenu.add(exitMenu); menuBar.add(fileMenu); this.setJMenuBar(menuBar); } public void loadFile(File file) { noteArea.setText(""); try { BufferedReader read = new BufferedReader(new FileReader(file)); String line = null; while((line =read.readLine())!=null) { noteArea.append(line +"\n"); } read.close(); } catch (Exception e) { System.out.println("Error " + e.toString()); } } public void fileSaved(File file) { try { PrintWriter writer = new PrintWriter(file); String[] lines = noteArea.getText().split("\\n"); for (String ) { writer.println(words); } writer.close(); } catch (Exception e) { System.out.println("Error " + e.toString()); } } } btw I can't post my question because of not explaning the scenario according to the site. So there. Thanks for the help

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  • How to mix C++ Qt objects and Qt Jambi objects

    - by Dan
    Hi, I'm trying to combine some existing Qt code written in C++ with some code written in Java using Qt Jambi, but I'm not quite sure how to do it. I'm basically trying to acieve two things: Pass a QObject from C++ to Java using JNI Pass a Qt Jambi QObject from Java to C++ It looks like I can pass the pointer directly and then wrap it in QNativePointer on the Java side, but I can't figure out how to turn a QNativePointer back into the original object, wrapped by Qt Jambi. Eg: I can pass a QWidget* as a long to Java and then create a QNativePointer in Java, but how can I then construct a QWidget out of this? QJambiObject and QObject dont seem to have a "setNativePointer" method and I'm not sure how to convert it. In C++: QWidget* widget = ... jclass cls = env->FindClass("Test"); jmethodID mid = env->GetStaticMethodID(cls, "test", "(I)V"); env->CallStaticVoidMethod(cls, mid, int(widget)); In Java: public class Test { public static void test (int ptr) { QNativePointer pointer = new QNativePointer(QNativePointer.Type.Int); pointer.setIntValue(ptr); QWidget widget = ... Thanks!

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  • maintaining a large list in python

    - by Oren
    I need to maintain a large list of python pickleable objects that will quickly execute the following algorithm: The list will have 4 pointers and can: Read\Write each of the 4 pointed nodes Insert new nodes before the pointed nodes Increase a pointer by 1 Pop nodes from the beginning of the list (without overlapping the pointers) Add nodes at the end of the list The list can be very large (300-400 MB), so it shouldnt be contained in the RAM. The nodes are small (100-200 bytes) but can contain various types of data. The most efficient way it can be done, in my opinion, is to implement some paging-mechanism. On the harddrive there will be some database of a linked-list of pages where in every moment up to 5 of them are loaded in the memory. On insertion, if some max-page-size was reached, the page will be splitted to 2 small pages, and on pointer increment, if a pointer is increased beyond its loaded page, the following page will be loaded instead. This is a good solution, but I don't have the time to write it, especially if I want to make it generic and implement all the python-list features. Using a SQL tables is not good either, since I'll need to implement a complex index-key mechanism. I tried ZODB and zc.blist, which implement a BTree based list that can be stored in a ZODB database file, but I don't know how to configure it so the above features will run in reasonable time. I don't need all the multi-threading\transactioning features. No one else will touch the database-file except for my single-thread program. Can anyone explain me how to configure the ZODB\zc.blist so the above features will run fast, or show me a different large-list implementation?

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  • Delegates in .NET: how are they constructed ?

    - by Saulius
    While inspecting delegates in C# and .NET in general, I noticed some interesting facts: Creating a delegate in C# creates a class derived from MulticastDelegate with a constructor: .method public hidebysig specialname rtspecialname instance void .ctor(object 'object', native int 'method') runtime managed { } Meaning that it expects the instance and a pointer to the method. Yet the syntax of constructing a delegate in C# suggests that it has a constructor new MyDelegate(int () target) where I can recognise int () as a function instance (int *target() would be a function pointer in C++). So obviously the C# compiler picks out the correct method from the method group defined by the function name and constructs the delegate. So the first question would be, where does the C# compiler (or Visual Studio, to be precise) pick this constructor signature from ? I did not notice any special attributes or something that would make a distinction. Is this some sort of compiler/visualstudio magic ? If not, is the T (args) target construction valid in C# ? I did not manage to get anything with it to compile, e.g.: int () target = MyMethod; is invalid, so is doing anything with MyMetod, e.g. calling .ToString() on it (well this does make some sense, since that is technically a method group, but I imagine it should be possible to explicitly pick out a method by casting, e.g. (int())MyFunction. So is all of this purely compiler magic ? Looking at the construction through reflector reveals yet another syntax: Func CS$1$0000 = new Func(null, (IntPtr) Foo); This is consistent with the disassembled constructor signature, yet this does not compile! One final interesting note is that the classes Delegate and MulticastDelegate have yet another sets of constructors: .method family hidebysig specialname rtspecialname instance void .ctor(class System.Type target, string 'method') cil managed Where does the transition from an instance and method pointer to a type and a string method name occur ? Can this be explained by the runtime managed keywords in the custom delegate constructor signature, i.e. does the runtime do it's job here ?

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  • Accessing Firefox tab element in nsIWebProgressListener::OnStateChange using C++

    - by Vaibhav Gade
    Hi All, I am developing extension for Firefox 3.0-3.5 versions using VS2008. I want to set attribute to a tab once the document load request completes within that tab window. So in OnStateChange method, I am checking for document load. I have used STATE_STOP & STATE_IS_DOCUMENT for it. I want to determine which tab window has been associated with particular document request. I have valid DOM Document pointer got from nsIWebProgress *aWebProgress which is 1st input parameter of OnStateChange. if ((aStateFlags & STATE_STOP) && (aStateFlags & STATE_IS_DOCUMENT)) { nsCOMPtr<nsIDOMWindow> domwin; nsCOMPtr<nsIDOMDocument> domDoc; aWebProgress->GetDOMWindow(getter_AddRefs(domwin)); domwin->GetDocument(getter_AddRefs(domDoc)); } I have tried to get nsIDOMDocumentXBL pointer by QIing nsIDOMDocument pointer(domDoc in my example) but it fails with Error code 0x80004002 (2147500034) i.e.NS_ERROR_NO_INTERFACE. How do I get the tab element corresponding to document load request. Could any one please help me? Thanks in Advance, Vaibhav D. Gade.

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  • Why so much stack space used for each recursion?

    - by Harvey
    I have a simple recursive function RCompare() that calls a more complex function Compare() which returns before the recursive call. Each recursion level uses 248 bytes of stack space which seems like way more than it should. Here is the recursive function: void CMList::RCompare(MP n1) // RECURSIVE and Looping compare function { auto MP ne=n1->mf; while(StkAvl() && Compare(n1=ne->mb)) RCompare(n1); // Recursive call ! } StkAvl() is a simple stack space check function that compares the address of an auto variable to the value of an address near the end of the stack stored in a static variable. It seems to me that the only things added to the stack in each recursion are two pointer variables (MP is a pointer to a structure) and the stuff that one function call stores, a few saved registers, base pointer, return address, etc., all 32-bit (4 byte) values. There's no way that is 248 bytes is it? I don't no how to actually look at the stack in a meaningful way in Visual Studio 2008. Thanks

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  • c - strncpy issue

    - by Joe
    Hi there, I am getting segmentation fault when using strncpy and (pointer-to-struct)-(member) notation: I have simplified my code. I initialise a struct and set all of it's tokens to an empty string. Then a declare a pointer to a struct and assign the address of the struct to it. I pass the pointer to a function. I can print out the contents of the struct at the beginning of the function, but if I try to use the tp - mnemonic in a strncpy function, I get seg fault. Can anyone tell me what I am doing wrong? typedef struct tok { char* label; char* mnem; char* operand; }Tokens; Tokens* tokenise(Tokens* tp, char* line) { // This prints fine printf("Print this - %s\n", tp -> mnem); // This function gives me segmentation fault strncpy(tp -> mnem, line, 4); return tp; } int main() { char* line = "This is a line"; Tokens tokens; tokens.label = ""; tokens.mnem = "load"; tokens.operand = ""; Tokens* tp = &tokens; tp = tokenise(tp, line); return 0; } I have used printf statements to confirm that the code definitely stops executing at the strncpy function. Can anyone tell me where I am going wrong? Many thanks Joe

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  • Why does std::cout convert volatile pointers to bool?

    - by Joseph Garvin
    If you try to cout a volatile pointer, even a volatile char pointer where you would normally expect cout to print the string, you will instead simply get '1' (assuming the pointer is not null I think). I assume output stream operator<< is template specialized for volatile pointers, but my question is, why? What use case motivates this behavior? Example code: #include <iostream> #include <cstring> int main() { char x[500]; std::strcpy(x, "Hello world"); int y; int *z = &y; std::cout << x << std::endl; std::cout << (char volatile*)x << std::endl; std::cout << z << std::endl; std::cout << (int volatile*)z << std::endl; return 0; } Output: Hello world 1 0x8046b6c 1

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  • should std::auto_ptr<>::operator = reset / deallocate its existing pointee ?

    - by afriza
    I read here about std::auto_ptr<::operator= Notice however that the left-hand side object is not automatically deallocated when it already points to some object. You can explicitly do this by calling member function reset before assigning it a new value. However, when I read the source code for header file C:\Program Files\Microsoft Visual Studio 8\VC\ce\include\memory template<class _Other> auto_ptr<_Ty>& operator=(auto_ptr<_Other>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr<_Ty>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr_ref<_Ty> _Right) _THROW0() { // assign compatible _Right._Ref (assume pointer) _Ty **_Pptr = (_Ty **)_Right._Ref; _Ty *_Ptr = *_Pptr; *_Pptr = 0; // release old reset(_Ptr); // set new return (*this); } What is the correct/standard behavior? How do other STL implementations behave?

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  • What's correct way to remove a boost::shared_ptr from a list?

    - by Catskul
    I have a std::list of boost::shared_ptr<T> and I want to remove an item from it but I only have a pointer of type T* which matches one of the items in the list. However I cant use myList.remove( tPtr ) I'm guessing because shared_ptr does not implement == for its template argument type. My immediate thought was to try myList.remove( shared_ptr<T>(tPtr) ) which is syntactically correct but it will crash from a double delete since the temporary shared_ptr has a separate use_count. std::list< boost::shared_ptr<T> > myList; T* tThisPtr = new T(); // This is wrong; only done for example code. // stand-in for actual code in T using // T's actual "this" pointer from within T { boost::shared_ptr<T> toAdd( tThisPtr ); // typically would be new T() myList.push_back( toAdd ); } { //T has pointer to myList so that upon a certain action, // it will remove itself romt the list //myList.remove( tThisPtr); //doesn't compile myList.remove( boost::shared_ptr<T>(tThisPtr) ); // compiles, but causes // double delete } The only options I see remaining are to use std::find with a custom compare, or to loop through the list brute force and find it myself, but it seems there should be a better way. Am I missing something obvious, or is this just too non-standard a use to be doing a remove the clean/normal way?

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  • What is the correct JNA mapping for UniChar on Mac OS X?

    - by Trejkaz
    I have a C struct like this: struct HFSUniStr255 { UInt16 length; UniChar unicode[255]; }; I have mapped this in the expected way: public class HFSUniStr255 extends Structure { public UInt16 length; // UInt16 is just an IntegerType with length 2 for convenience. public /*UniChar*/ char[] unicode = new char[255]; //public /*UniChar*/ byte[] unicode = new byte[255*2]; //public /*UniChar*/ UInt16[] unicode = new UInt16[255]; public HFSUniStr255() { } public HFSUniStr255(Pointer pointer) { super(pointer); } } If I use this version, I get every second character of the string into my char[] ("aits D" for "Macintosh HD".) I am assuming that this is something to do with being on a 64-bit platform and JNA mapping the value to a 32-bit wchar_t but then chopping off the high 16 bits on each wchar_t on copying them back. If I use the byte[] version, I get data which decodes correctly using the UTF-16LE charset. If I use the UInt16[] version, I get the right code point for each character but it is then inconvenient to convert them back into a string. Is there some way I can define my type as char[], and yet have it convert correctly?

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  • COM-Objects containing maps / content error(0)

    - by Florian Berzsenyi
    I'm writing a small wrapper to get familiar with some important topics in C++ (WinAPI, COM, STL,OOP). For now, my class shall be able to create a (child) window. Mainly, this window is connected to a global message loop that distribute messages to a local loop of the right instance (global is static, local is virtual). Obviously, there are surely better ways to do that but I'm using std::maps to store HWND and their instance pointer in pairs (the Global loop looks for the pointer with the HWND-parameter, gets itself the pointer from the map and calls then the local loop). Now, it appears that the map does not accept any values because of a unknown reason. It seems to allocate enough space but something went wrong anyway [ (error) 0 is displayed instead of the entries in visual C++). I've looked that up in google as well and found out that maps cause some trouble when used in classes AND DLLs. May this be the reason and is there any solution?? Protected scope of class: static std::map<HWND,MAP_BASE_OBJECT*> m_LoopBuf Implementation in .cpp-file: std::map<HWND,MAP_BASE_OBJECT*> HWindow::m_LoopBuf;

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  • Defining an implementation independent version of the global object in JavaScript

    - by Aadit M Shah
    I'm trying to define the global object in JavaScript in a single line as follows: var global = this.global || this; The above statement is in the global scope. Hence in browsers the this pointer is an alias for the window object. Assuming that it's the first line of JavaScript to be executed in the context of the current web page, the value of global will always be the same as that of the this pointer or the window object. In CommonJS implementations, such as RingoJS and node.js the this pointer points to the current ModuleScope. However, we can access the global object through the property global defined on the ModuleScope. Hence we can access it via the this.global property. Hence this code snippet works in all browsers and in at least RingoJS and node.js, but I have not tested other CommomJS implementations. Thus I would like to know if this code will not yield correct results when run on any other CommonJS implementation, and if so how I may fix it. Eventually, I intend to use it in a lambda expression for my implementation independent JavaScript framework as follows (idea from jQuery): (function (global) { // javascript framework })(this.global || this);

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  • Qt/C++, Problems with large QImage

    - by David Günzel
    I'm pretty new to C++/Qt and I'm trying to create an application with Visual Studio C++ and Qt (4.8.3). The application displays images using a QGraphicsView, I need to change the images at pixel level. The basic code is (simplified): QImage* img = new QImage(img_width,img_height,QImage::Format_RGB32); while(do_some_stuff) { img->setPixel(x,y,color); } QGraphicsPixmapItem* pm = new QGraphicsPixmapItem(QPixmap::fromImage(*img)); QGraphicsScene* sc = new QGraphicsScene; sc->setSceneRect(0,0,img->width(),img->height()); sc->addItem(pm); ui.graphicsView->setScene(sc); This works well for images up to around 12000x6000 pixel. The weird thing happens beyond this size. When I set img_width=16000 and img_height=8000, for example, the line img = new QImage(...) returns a null image. The image data should be around 512,000,000 bytes, so it shouldn't be too large, even on a 32 bit system. Also, my machine (Win 7 64bit, 8 GB RAM) should be capable of holding the data. I've also tried this version: uchar* imgbuf = (uchar*) malloc(img_width*img_height*4); QImage* img = new QImage(imgbuf,img_width,img_height,QImage::Format_RGB32); At first, this works. The img pointer is valid and calling img-width() for example returns the correct image width (instead of 0, in case the image pointer is null). But as soon as I call img-setPixel(), the pointer becomes null and img-width() returns 0. So what am I doing wrong? Or is there a better way of modifying large images on pixel level? Regards, David

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  • Common lisp, CFFI, and instantiating c structs

    - by andrew
    Hi, I've been on google for about, oh, 3 hours looking for a solution to this "problem." I'm trying to figure out how to instantiate a C structure in lisp using CFFI. I have a struct in c: struct cpVect{cpFloat x,y;} Simple right? I have auto-generated CFFI bindings (swig, I think) to this struct: (cffi:defcstruct #.(chipmunk-lispify "cpVect" 'classname) (#.(chipmunk-lispify "x" 'slotname) :double) (#.(chipmunk-lispify "y" 'slotname) :double)) This generates a struct "VECT" with slots :X and :Y, which foreign-slot-names confirms (please note that I neither generated the bindings or programmed the C library (chipmunk physics), but the actual functions are being called from lisp just fine). I've searched far and wide, and maybe I've seen it 100 times and glossed over it, but I cannot figure out how to create a instance of cpVect in lisp to use in other functions. Note the function: cpShape *cpPolyShapeNew(cpBody *body, int numVerts, cpVect *verts, cpVect offset) Takes not only a cpVect, but also a pointer to a set of cpVects, which brings me to my second question: how do I create a pointer to a set of structs? I've been to http://common-lisp.net/project/cffi/manual/html_node/defcstruct.html and tried the code, but get "Error: Unbound variable: PTR" (I'm in Clozure CL), not to mention that looks to only return a pointer, not an instance. I'm new to lisp, been going pretty strong so far, but this is the first real problem I've hit that I can't figure out. Thanks!

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  • The Implications of Modern Day Software Development Abstractions

    - by Andreas Grech
    I am currently doing a dissertation about the implications or dangers that today's software development practices or teachings may have on the long term effects of programming. Just to make it clear: I am not attacking the use abstractions in programming. Every programmer knows that abstractions are the bases for modularity. What I want to investigate with this dissertation are the positive and negative effects abstractions can have in software development. As regards the positive, I am sure that I can find many sources that can confirm this. But what about the negative effects of abstractions? Do you have any stories to share that talk about when certain abstractions failed on you? The main concern is that many programmers today are programming against abstractions without having the faintest idea of what the abstraction is doing under-the-covers. This may very well lead to bugs and bad design. So, in you're opinion, how important is it that programmers actually know what is going below the abstractions? Taking a simple example from Joel's Back to Basics, C's strcat: void strcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); } The above function hosts the issue that if you are doing string concatenation, the function is always starting from the beginning of the dest pointer to find the null terminator character, whereas if you write the function as follows, you will return a pointer to where the concatenated string is, which in turn allows you to pass this new pointer to the concatenation function as the *dest parameter: char* mystrcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); return --dest; } Now this is obviously a very simple as regards abstractions, but it is the same concept I shall be investigating. Finally, what do you think about the issue that schools are preferring to teach Java instead of C and Lisp ? Can you please give your opinions and your says as regards this subject? Thank you for your time and I appreciate every comment.

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  • Atomic swap in GNU C++

    - by Steve
    I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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  • What is the purpose of the s==NULL case for mbrtowc?

    - by R..
    mbrtowc is specified to handle a NULL pointer for the s (multibyte character pointer) argument as follows: If s is a null pointer, the mbrtowc() function shall be equivalent to the call: mbrtowc(NULL, "", 1, ps) In this case, the values of the arguments pwc and n are ignored. As far as I can tell, this usage is largely useless. If ps is not storing any partially-converted character, the call will simply return 0 with no side effects. If ps is storing a partially-converted character, then since '\0' is not valid as the next byte in a multibyte sequence ('\0' can only be a string terminator), the call will return (size_t)-1 with errno==EILSEQ. and leave ps in an undefined state. The intended usage seems to have been to reset the state variable, particularly when NULL is passed for ps and the internal state has been used, analogous to mbtowc's behavior with stateful encodings, but this is not specified anywhere as far as I can tell, and it conflicts with the semantics for mbrtowc's storage of partially-converted characters (if mbrtowc were to reset state when encountering a 0 byte after a potentially-valid initial subsequence, it would be unable to detect this dangerous invalid sequence). If mbrtowc were specified to reset the state variable only when s is NULL, but not when it points to a 0 byte, a desirable state-reset behavior would be possible, but such behavior would violate the standard as written. Is this a defect in the standard? As far as I can tell, there is absolutely no way to reset the internal state (used when ps is NULL) once an illegal sequence has been encountered, and thus no correct program can use mbrtowc with ps==NULL.

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  • C standard addressing simplification inconsistency

    - by Chris Lutz
    Section §6.5.3.2 "Address and indirection operators" ¶3 says (relevant section only): The unary & operator returns the address of its operand. ... If the operand is the result of a unary * operator, neither that operator nor the & operator is evaluated and the result is as if both were omitted, except that the constraints on the operators still apply and the result is not an lvalue. Similarly, if the operand is the result of a [] operator, neither the & operator nor the unary * that is implied by the [] is evaluated and the result is as if the & operator were removed and the [] operator were changed to a + operator. ... This means that this: int *i = NULL; printf("%p", (void *) (&*i) ); printf("%p", (void *) (&i[10]) ); Should be perfectly legal, printing the null pointer (probably 0) and the null pointer plus 10 (probably 10). The standard seems very clear that both of those cases are required to be optimized. However, it doesn't seem to require the following to be optimized: struct { int a; short b; } *s = 0; printf("%p", (void *) (&s->b) ); This seems awfully inconsistent. I can see no reason that the above code shouldn't print the null pointer plus sizeof(int) (possibly 4). Simplifying a &-> expression is going to be the same conceptually (IMHO) as &[], a simple address-plus-offset. It's even an offset that's going to be determinable at compile time, rather than potentially runtime with the [] operator. Is there anything in the rationale about why this is so seemingly inconsistent?

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