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  • fread() behaves weird

    - by Cres
    hi, I have a problem in a C program of mine where after I use fread(), the file pointer goes to the end of the file sometimes. I'll try to explain better - the code looks something like: dummy = ftell(fp); fread(&buf, sizeof(unsigned char), 8, fp); dummy = ftell(fp); where fp is a file pointer to an opened file (opened it with "w+", I'm using it as a binary file and I know i'm supposed to have a "b" in there too, but I heard its not really important to add it..), dummy is just an unsigned long variable, and buf is unsigned char[8] now, when debugging, at the ftell before the fread, dummy is 262062 at the ftell after the fread, dummy is 262640 even though I only 'moved' 8 bytes.. does anyone have any idea what can be the cause of this..? thanks for your help :)

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  • C++ interface inheritance problem

    - by james t
    Hey, i'm trying to create a c++ stomp client, my client constructor is : Client(std::string &server, short port, std::string &login, std::string &pass, Listener &listener); it gets a listener object which when Listener is the following interface : class Listener { virtual void message(StmpMessage message) =0; }; now i attempt to instantiate a client in a test class : class test : public virtual Listener { public: void message(StmpMessage message) { message.prettyPrint(); } int main(int argc, char* argv[]) { Client client("127.0.0.1", 61613, *this); return 0; } }; i'm sending this to the client because this is a listener object, i get the following error : /Users/mzruya/Documents/STOMPCPP/main.cpp:18: error: no matching function for call to 'Client::Client(const char [10], int, test&)' /Users/mzruya/Documents/STOMPCPP/Client.h:43: note: candidates are: Client::Client(std::string&, short int, std::string&, std::string&, Listener&) /Users/mzruya/Documents/STOMPCPP/Client.h:37: note: Client::Client(const Client&)

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  • Template type deduction with a non-copyable class

    - by Evan Teran
    Suppose I have an autolocker class which looks something like this: template <T> class autolocker { public: autolocker(T *l) : lock(l) { lock->lock(); } ~autolocker() { lock->unlock(); } private: autolocker(const autolocker&); autolocker& operator=(const autolocker&); private: T *lock; } Obviously the goal is to be able to use this autolocker with anything that has a lock/unlock method without resorting to virtual functions. Currently, it's simple enough to use like this: autolocker<some_lock_t> lock(&my_lock); // my_lock is of type "some_lock_t" but it is illegal to do: autolocker lock(&my_lock); // this would be ideal Is there anyway to get template type deduction to play nice with this (keep in my autolocker is non-copyable). Or is it just easiest to just specify the type?

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  • How do I send telnet option codes?

    - by Matt
    I've written a socket listener in Java that just sends some data to the client. If I connect to the server using telnet, I want the server to send some telnet option codes. Do I just send these like normal messages? Like, if I wanted the client to print "hello", I would do this: PrintWriter out = new PrintWriter(clientSocket.getOutputStream()); out.print("hello"); out.flush(); But when I try to send option codes, the client just prints them. Eg, the IAC char (0xff) just gets printed as a strange y character when I do this: PrintWriter out = new PrintWriter(clientSocket.getOutputStream()); out.print((char)0xff); out.flush();

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  • Viewing array of pointers to structures in Visual Studio in the debugger

    - by Fozi
    I'm having a problem displaying the contents of a pointer array with its contents in the debugger. If I just add the pointer to the watch only the fist entry is visible. But if I add the length to it the debugger assumes that I have something like array[length][length]. Picture The first entry is the broken one, looks the same with ,2 or with any ,2 x. The second one is what I would like to see, but for more entries. Edit: The two entries displayed as [x][1] are invalid. I'm using VS 2005 but I think I had this problem on 2008 as well. Is this a bug or am I doing something wrong?

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  • How to load an RSA key from binary data to an RSA structure using the OpenSSL C Library?

    - by Andreas Bonini
    Currently I have my private key saved in a file, private.key, and I use the following function to load it: RSA *r = PEM_read_RSAPrivateKey("private.key", NULL, NULL, NULL); This works perfectly but I'm not happy with the file-based format; I want to save my key in pure binary form (ie, no base64 or similar) in a char* variable and load/save the key from/to it. This way I have much more freedom: I'll be able to store the key directly into the application const char key[] { 0x01, 0x02, ... };, send it over a network socket, etc. Unfortunately though I haven't found a way to do that. The only way to save and load a key I know of reads/saves it to a file directly.

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  • How to move files in C drive using MoveFileEx APi

    - by rajivpradeep
    Hi, when i use MoveFileEx to move files in C drive, but i am getting the ERROR that ACCESS DENIED. Any solutions int i ; DWORD dw ; String^ Source = "C:\Folder\Program\test.exe" ; String^ Destination = "C:\test.exe"; // move to program Files Folder pin_ptr<const wchar_t> WSource = PtrToStringChars(Source); pin_ptr<const wchar_t> WDestination = PtrToStringChars(Destination); i = MoveFileEx( WSource, WDestination ,MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED ) ; dw = GetLastError() ;

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  • use callback function to report stack backtrace

    - by user353394
    Assume I have the following: typedef struct { char *name; char binding; int address; } Fn_Symbol //definition of function symbol static Fn_Symbol *fnSymbols; //array of function symbols in a file statc int total; //number of symbol functions in the array and file static void PrintBacktrace(int sigum, siginfo_t * siginfo, void *context) { printf("\nSignal received %d (%s)\n", signum, strsignal(signum)); const int eip_index = 14; void *eip = (void *)((struct ucontext *)context)->uc_mcontext.gregs[eip_index]; printf("Error at [%p] %s (+0x%x), eip, fnName, offset from start); //????? exit(0); } I have this so far, but what is the best way using the fnSymbols static global pointer to identify the function where the error occured and then back trace through the stack to identify each calling function by address, name, and offset?

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  • Duplicates in a sorted java array

    - by Max Frazier
    I have to write a method that takes an array of ints that is already sorted in numerical order then remove all the duplicate numbers and return an array of just the numbers that have no duplicates. That array must then be printed out so I can't have any null pointer exceptions. The method has to be in O(n) time, can't use vectors or hashes. This is what I have so far but it only has the first couple numbers in order without duplicates and then just puts the duplicates in the back of the array. I can't create a temporary array because it gives me null pointer exceptions. public static int[] noDups(int[] myArray) { int j = 0; for (int i = 1; i < myArray.length; i++) { if (myArray[i] != myArray[j]) { j++; myArray[j] = myArray[i]; } } return myArray; }

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  • Valid signed Hex to long function

    - by Ben
    I am trying to convert a 24bit Hexadecimal string (6 characters) signed in two's complement to a long int in C. This is the function I have come up with: long int hex2li (char string[]) { char *pEnd; long int result = strtol (string, &pEnd, 16); if (strcmp (pEnd, "") == 0) { if (toupper (string[0]) == 'F') { return result - 16777216; } else { return result; } } return LONG_MIN; } Is it valid? Is there a better way of doing this?

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  • Javascript pass reference by value

    - by Carlos R. Batista
    Im having this weird reference issue when im trying to get a JSON file through query: var themeData; $.getJSON("json/sample.js", function(data) { themeData = data.theme; console.log(themeData.sample[0].description); }); console.log(themeData.sample[0].description); The first console.log works, the second doesnt. Im guessing because "data" already expired by the time the script gets there and themeData is just a mere pointer to "data". Is there a ways I can make sure themeData gets a duplicate of "data" and not just a pointer to it?

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  • Can this rectangle to rectangle intersection code still work?

    - by Jeremy Rudd
    I was looking for a fast performing code to test if 2 rectangles are intersecting. A search on the internet came up with this one-liner (WOOT!), but I don't understand how to write it in Javascript, it seems to be written in an ancient form of C++. Can this thing still work? Can you make it work? struct { LONG left; LONG top; LONG right; LONG bottom; } RECT; bool IntersectRect(const RECT * r1, const RECT * r2) { return ! ( r2->left > r1->right || r2->right left || r2->top > r1->bottom || r2->bottom top ); }

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  • Why doesn't this work?

    - by user146780
    I'v tried to solve a memory leak in the GLU callback by creating a global variable but now it dos not draw anything: GLdouble *gluptr = NULL; void CALLBACK combineCallback(GLdouble coords[3], GLdouble *vertex_data[4], GLfloat weight[4], GLdouble **dataOut) { GLdouble *vertex; if(gluptr == NULL) { gluptr = (GLdouble *) malloc(6 * sizeof(GLdouble)); } vertex = (GLdouble*)gluptr; vertex[0] = coords[0]; vertex[1] = coords[1]; vertex[2] = coords[2]; for (int i = 3; i < 6; i++) { vertex[i] = weight[0] * vertex_data[0][i] + weight[1] * vertex_data[0][i] + weight[2] * vertex_data[0][i] + weight[3] * vertex_data[0][i]; } *dataOut = vertex; } basically instead of doing malloc each time in the loop (thus the memory leak) im using a global pointer, but this doesn't work (drawing to the screen). Why would using malloc to a pointer created in the function work any different than a global variable? Thanks

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  • Store return value of function in reference C++

    - by Ruud v A
    Is it valid to store the return value of an object in a reference? class A { ... }; A myFunction() { A myObject; return A; } //myObject goes out of scope here void mySecondFunction() { A& mySecondObject = myFunction(); } Is it possible to do this in order to avoid copying myObject to mySecondObject? myObject is not needed anymore and should be exactly the same as mySecondObject so it would in theory be faster just to pass ownership of the object from one object to another. (This is also possible using boost shared pointer but that has the overhead of the shared pointer.) Thanks in advance.

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  • How to move the mouse

    - by GroundZero
    I'm making a little bot in C#. At the moment it works pretty well, it can load text from a file and type it for you. But for now, I need to manualy click the textfield to put the focus on it, remaximize my form and then click the Type-button. After the typing, I need to manualy slide the scorebar and press submit. I'd like to know how I can move my mouse with C# and if possible, if possible I'd like to load the mouse positions from a xml-file. I need to move to the textfield, click in it to focus on it, start the type script, move to the slider, hold the mouse down on it while dragging, releasing it on the correct position & clicking on the submitbutton This is what I have for now: To load in the variables, I'm using this script: private void Initialize() { XmlTextReader reader = new XmlTextReader(Application.StartupPath + @"..\..\..\CursorPositions.xml"); while (reader.Read()) { switch (reader.NodeType) { case XmlNodeType.Element: // The node is an element. element = reader.Value; break; case XmlNodeType.Text: //Display the text in each element. switch (element) { case "Textbox-X": textX = int.Parse(reader.Value); break; case "Textbox-Y": textY = int.Parse(reader.Value); break; case "SliderBegin-X": sliderX = int.Parse(reader.Value); break; case "SliderBegin-Y": sliderY = int.Parse(reader.Value); break; case "SubmitButton-X": submitX = int.Parse(reader.Value); break; case "SubmitButton-Y": submitY = int.Parse(reader.Value); break; } break; } } This is the xml-file: <?xml version="1.0" encoding="utf-8" ?> <CursorPositions> <Textbox-X>430</Textbox-X> <Textbox-Y>270</Textbox-Y> <SliderBegin-X>430</SliderBegin-X> <SliderBegin-Y>470</SliderBegin-Y> <SubmitButton-X>860</SubmitButton-X> <SubmitButton-Y>365</SubmitButton-Y> </CursorPositions> To move the mouse I'm using this piece of code: public partial class FrmMain : Form { [System.Runtime.InteropServices.DllImport("user32.dll")] public static extern void mouse_event(int dwFlags, int dx, int dy, int cButtons, int dwExtraInfo); public const int MOUSEEVENTF_LEFTDOWN = 0x0002; public const int MOUSEEVENTF_LEFTUP = 0x0004; public const int MOUSEEVENTF_RIGHTDOWN = 0x0008; public const int MOUSEEVENTF_RIGHTUP = 0x0010; ... private void btnStart_Click(object sender, EventArgs e) { // start button (de)activates loop if (!running) { btnStart.Text = "Stop"; btnStart.Cursor = Cursors.No; running = true; } else { btnStart.Text = "Start"; btnStart.Cursor = Cursors.AppStarting; running = false; } while (running) { // move to textbox & type Cursor.Position = new Point(textX, textY); mouse_event(MOUSEEVENTF_LEFTDOWN, textX, textY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, textX, textY, 0, 0); Type(); // wait 90 seconds till slider available Thread.Sleep(90 * 1000); // move to slider & slide according to score Cursor.Position = new Point(sliderX, sliderY); mouse_event(MOUSEEVENTF_LEFTDOWN, sliderX, sliderY, 0, 0); Cursor.Position = new Point(sliderX + 345 / 10 * score, sliderY); mouse_event(MOUSEEVENTF_LEFTUP, sliderX + 345 / 10 * score, sliderY, 0, 0); // submit Cursor.Position = new Point(submitX, submitY); mouse_event(MOUSEEVENTF_LEFTDOWN, submitX, submitY, 0, 0); mouse_event(MOUSEEVENTF_LEFTUP, submitX, submitY, 0, 0); // wait 10 sec to be sure it's submitted Thread.Sleep(10 * 1000); // refresh page SendKeys.SendWait("{F5}"); // get new text NewText(); // wait 10 sec to refresh and load song Thread.Sleep(10 * 1000); } } } PS: I get the coordinates via my form. I've got 2 labels that show my X & Y coordinates. To capture them outside the form, I press and hold my Left Mouse Button and 'drag' it outside the form to the correct place. This way I get the coordinates of my mouse outside the form

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  • Problem with finding the next word in RichTextBox

    - by paradisonoir
    As I enter a character in my RichTextBox, I want to get the next character from the its TextRange. So here is how I do it: TextPointer ptr1= RichTextBox.CaretPosition; char nextChar = GetNextChar(); while (char.IsWhiteSpace(nextChar)) { ptr1= ptr1.GetNextInsertionPosition(LogicalDirection.Forward); nextChar = GetCharacterAt(Ptr1); } then I get the ptr1 of the next character and from the TextPointer, I get the TextRange, and do my changes. So here is the problem? when the next word is spelled correctly, I have no problem, but if it's not spelled properly then ptr1 would not point to the first character of the next word (the second character), and if I use GetNextContextPosition(LogicalDirection.Forward) it would give me the first letter of the next word if it's misspelled. So depending on the spelling only one of them works? I was just wondering if you have any idea about this problem? Is there anything wrong I am doing here?

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  • What's the performance penalty of weak_ptr?

    - by Kornel Kisielewicz
    I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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  • Fseek on C problem

    - by Pedro
    i'm testing this code, but doesn't work, it always says that an error occurred :S int main(int argc, char **argv) { FILE *file_pointer; file_pointer = fopen("text.txt","r"); if(fseek(file_pointer, 0, -1)) { puts("An error occurred"); } else { char buffer[100]; fgets(buffer, 100, file_pointer); puts("The first line of the file is:"); puts(buffer); } fclose(file_pointer); return 0; }

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  • Boost multiindex complex struct

    - by StrifeLow
    In boost multiindex example complex_structs, it use one key in the car_manufacturer struct for car_table. If car_manufacturer have been modify to have 2 ID struct car_manufacturer { std::string name; int cm_code; car_manufacturer(const std::string& name_, const int& cm_code_):name(name_), cm_code(cm_code_){} }; What will be the key_from_key struct looks like? Have try to add another KeyExtractor or use composite index inside key_from_key, but still cannot compile. Please help on this. Thanks.

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  • While making an RSS reader which saves articles, how can I prevent duplicates?

    - by Koning Baard
    Lets say I have a RSS feed which lists the 3 newest questions on SO. At 1 o'clock, the feed looks like this: While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ How to deploy a Java Swing application with an embedded JavaDB database? At 2 o'clock, this feed looks like: django url from another template than the one associated with the view-function While making an RSS reader which saves articles, how can I prevent duplicates? Convert char array to UNICODE in MFC C++ (duplicate articles are bold) I want to download the RSS feed every 5 minutes, parse it and save the articles that aren't already saved, but I do not want duplicates (items that remain in the new, updated feed like the examples above). What can I use to determine if an article is already saved? Thanks

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  • UInt32 to IntPtr

    - by ffenix
    I have the following problem: public class ListenThread : SocketInvoke { [DllImport("Ws2_32", CharSet = CharSet.Auto)] public unsafe static extern UInt32 WSAWaitForMultipleEvents(UInt32 cEvents, IntPtr hEventObject, UInt32 fWaitAll, UInt32 dwTimeout, Boolean fAlertable); public void ListenConnections(NetSharedData data) { while (true) { unsafe { if (WSAWaitForMultipleEvents((UInt32)1, data.signal, (UInt32)0, (UInt32)100, false) != WSA_WAIT_TIMEOUT) { } } } } data.signal is a UInt32 how i can cast it to IntPtr?, i try: IntPtr signal = (IntPtr)data.signal; but it doesn't work because i need a pointer to data.signal (UInt32) type and not the int value as an pointer, that will make a memory exception. An C++ example of what i need: int signal = 0; int* psignal = &signal;

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  • In Python, how to use a C++ function which returns an allocated array of structs via a ** parameter?

    - by Jon-Eric
    I'd like to use some existing C++ code, NvTriStrip, in a Python tool. SWIG easily handles the functions with simple parameters, but the main function, GenerateStrips, is much more complicated. What do I need to put in the SWIG interface file to indicate that primGroups is really an output parameter and that it must be cleaned up with delete[]? /////////////////////////////////////////////////////////////////////////// // GenerateStrips() // // in_indices: input index list, the indices you would use to render // in_numIndices: number of entries in in_indices // primGroups: array of optimized/stripified PrimitiveGroups // numGroups: number of groups returned // // Be sure to call delete[] on the returned primGroups to avoid leaking mem // bool GenerateStrips( const unsigned short* in_indices, const unsigned int in_numIndices, PrimitiveGroup** primGroups, unsigned short* numGroups, bool validateEnabled = false ); FYI, here is the PrimitiveGroup declaration: enum PrimType { PT_LIST, PT_STRIP, PT_FAN }; struct PrimitiveGroup { PrimType type; unsigned int numIndices; unsigned short* indices; PrimitiveGroup() : type(PT_STRIP), numIndices(0), indices(NULL) {} ~PrimitiveGroup() { if(indices) delete[] indices; indices = NULL; } };

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  • Simple question about C++ constant syntax

    - by WilliamLou
    Here is some code copied from Thinking in C++ Vol1 Chapter 10. #include <iostream> using namespace std; int x = 100; class WithStatic { static int x; static int y; public: void print() const { cout << "WithStatic::x = " << x << endl; cout << "WithStatic::y = " << y << endl; } }; what's the meaning of const for the function print()? Thanks!

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  • "Ambiguous template specialization" problem

    - by Setien
    I'm currently porting a heap of code that has previously only been compiled with Visual Studio 2008. In this code, there's an arrangement like this: template <typename T> T convert( const char * s ) { // slow catch-all std::istringstream is( s ); T ret; is >> ret; return ret; } template <> inline int convert<int>( const char * s ) { return (int)atoi( s ); } Generally, there are a lot of specializations of the templated function with different return types that are invoked like this: int i = convert<int>( szInt ); The problem is, that these template specializations result in "Ambiguous template specialization". If it was something besides the return type that differentiated these function specializations, I could obviously just use overloads, but that's not an option. How do I solve this without having to change all the places the convert functions are called?

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  • Why does accessing a member of a malloced array of structs seg fault?

    - by WSkinner
    I am working through Learn C The Hard Way and am stumped on something. I've written a simplified version of the problem I am running into to make it easier to get down to it. Here is the code: #include <stdlib.h> #define GROUP_SIZE 10 #define DATA_SIZE 64 struct Dummy { char *name; }; struct Group { struct Dummy **dummies; }; int main() { struct Group *group1 = malloc(sizeof(struct Group)); group1->dummies = malloc(sizeof(struct Dummy) * GROUP_SIZE); struct Dummy *dummy1 = group1->dummies[3]; // Why does this seg fault? dummy1->name = (char *) malloc(DATA_SIZE); return 0; } when I try to set the name pointer on one of my dummies I get a seg fault. Using valgrind it tells me this is uninitialized space. Why is this?

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