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• Is a switch statment ok for 30 or so conditions?

  - by DeanMc

  I am in the final stages of creating an MP4 tag parser in .Net. For those who have experience with tagging music you would be aware that there are an average of 30 or so tags. If tested out different types of loops and it seems that a switch statement with Const values seems to be the way to go with regard to catching the tags in binary. The switch allows me to search the binary without the need to know which order the tags are stored or if there are some not present but I wonder if anyone would be against using a switch statement for so many conditionals. Any insight is much appreciated.

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• Where does output of print in kernel go?

  - by apoorv020

  I am debugging a driver for linux (specifically ubuntu server 9.04), and there are several printf statements in the code. Where can I view the output of these statements? EDIT1: What i'm trying to do is write to kernel using the proc file-system. The print code is static int proc_fractel_config_write(struct file *file, const char *argbuf, unsigned long count, void *data) { printk(KERN_DEBUG "writing fractel config\n"); ... In kern.log when I see the following message when i try to overwrite the file /proc/net/madwifi/ath1/fractel_config (with varying time of course). [ 8671.924873] proc write [ 8671.924919] Any explainations?

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• encryption problem for wlan profile

  - by Jassi

  i am trying to encrypt keyMaterial element from wireless profile. so I want to convert byte array into OLECHAR but it is giving me wrong output not key sea the below code you may know the solution... DATA_BLOB in; DATA_BLOB out; BYTE pin=(BYTE)"FIPL2"; DWORD din=strlen((char*)pin)+1; in.pbData = pin; in.cbData = din; if(CryptProtectData(&in,L"what is it",NULL,NULL,NULL,0,&out)) { BYTE *b=out.pbData; USES_CONVERSION; bstr=SysAllocString(W2BSTR((const WCHAR *)b)); HRCALL(peSubS222->put_text(bstr), ""); SysFreeString(bstr); bstr=NULL; } else { cout<<"NOOOOOOOOOOOOOOOO :("; } what is missing please help me out

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• pointer delegate in STL set.

  - by ananth

  hi. Im kinda stuck with using a set with a pointer delegate. my code is as follows: void Graph::addNodes (NodeSet& nodes) { for (NodeSet::iterator pos = nodes.begin(); pos != nodes.end(); ++pos) { addNode(*pos); } } Here NodeSet is defined as: typedef std::set NodeSet; The above piece of code works perfectly on my windows machine, but when i run the same piece of code on a MAC, it gives me the following error: no matching function for call to 'Graph::addNode(const boost::shared_ptr&)' FYI, Node_ptr is of type: typedef boost::shared_ptr Node_ptr; can somebody plz tell me why this is happening?

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• BigInteger.ToString() returns more than 50 decimal digits.

  - by brickner

  I'm using .NET 4 System.Numerics.BigInteger Structure and I'm getting results different from the documentation. In the documentation of BigInteger.ToString() Method It says: The ToString() method supports 50 decimal digits of precision. That is, if the BigInteger value has more than 50 digits, only the 50 most significant digits are preserved in the output string; all other digits are replaced with zeros. I have some code that takes a 60 decimal digits BigInteger and converts it to a string. The 60 significant decimal digits string didn't lose any significant digits: const string vString = "123456789012345678901234567890123456789012345678901234567890"; Assert.AreEqual(60, vString.Length); BigInteger v = BigInteger.Parse(vString); Assert.AreEqual(60, v.ToString().Length); Assert.AreEqual('9', v.ToString()[58]); Assert.AreEqual('1', v.ToString()[0]); Assert.AreEqual(vString, v.ToString()); All the asserts pass. What exactly does the quoted part of the documentation mean?

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• += Overloading in C++ problem.

  - by user69514

  I am trying to overload the += operator for my rational number class, but I don't believe that it's working because I always end up with the same result: RationalNumber RationalNumber::operator+=(const RationalNumber &rhs){ int den = denominator * rhs.denominator; int a = numerator * rhs.denominator; int b = rhs.numerator * denominator; int num = a+b; RationalNumber ratNum(num, den); return ratNum; } Inside main //create two rational numbers RationalNumber a(1, 3); a.print(); RationalNumber b(6, 7); b.print(); //test += operator a+=(b); a.print(); After calling a+=(b), a is still 1/3, it should be 25/21. Any ideas what I am doing wrong?

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• Lock thread using somthing other than a object

  - by Scott Chamberlain

  when using a lock does the thing you are locking on have to be a object. For example is this legal static DateTime NextCleanup = DateTime.Now; const TimeSpan CleanupInterval = new TimeSpan(1, 0, 0); private static void DoCleanup() { lock ((object)NextCleanup) { if (NextCleanup < DateTime.Now) { NextCleanup = DateTime.Now.Add(CleanupInterval); System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(cleanupThread)); } } return; } EDIT-- From reading SLaks' responce I know the above code would be not valid but would this be? static MyClass myClass = new MyClass(); private static void DoCleanup() { lock (myClass) { // } return; }

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• Cant free memory.

  - by atch

  In code: int a[3][4] = {1,2,3,4, 5,6,7,8, 9,10,11,12}; template<class T, int row, int col> void invert(T a[row][col]) { T* columns = new T[col]; T* const free_me = columns; for (int i = 0; i < col; ++i) { for (int j = 0; j < row; ++j) { *columns = a[j][i]; ++columns;//SOMETIMES VALUE IS 0 } } delete[] free_me;//I'M GETTING ERROR OF HEAP ABUSE IN THIS LINE } int main(int argc, char* argv[]) { invert<int,3,4>(a); } I've observed that while iterating, value of variable columns equals zero and I think thats the problem. Thanks for your help.

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• Is there a way to serialize automatically enums as int?

  - by FireAphis

  Hello, Is there a way to serialize enums automatically as int? Every time I define a new enum and write std::stringstream stream; stream << myenum1; stream >> myenum2; the compiler complains that the operators << and are not defined. Do you know a way to tell the compiler to treat enums as plain int's? What makes the problem harder is that, actually, the serialization is inside a template. Something like this: template <typename T> void serialize(const T& value) { std::stringstream stream; stream << value; } So I cannot add any casts :( Maybe I can specialize it somehow? Thank you.

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• When do I need to deallocate memory? C++

  - by extintor

  I am using this code inside a class to make a webbrowser control visit a website: void myClass::visitWeb(const char *url) { WCHAR buffer[MAX_LEN]; ZeroMemory(buffer, sizeof(buffer)); MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, url, strlen(url), buffer, sizeof(buffer)-1); VARIANT vURL; vURL.vt = VT_BSTR; vURL.bstrVal = SysAllocString(buffer); // webbrowser navigate code... VariantClear(&vURL); } Do I need to do some memory deallocation here?, I see vURL is being deallocated by VariantClear but should I deallocate memory for buffer? I've been told that in another bool I have in the same app I shouldn't deallocate anything because everything clear out when the bool return true/false, but what happens on this void?

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• Magick++ in VS2010 - unresolved external symbol

  - by FlashFan

  Hey guys! I'm trying to use ImageMagick Magick++ for a C++ Project in VS2010. I installed the Library from here: klick Then in my Project, I added c:/program files/ImageMagick-6.6.6-Q16/include to the include folders. Then I tried to use Magick++ with this code: #include <Magick++.h> void main(int argc, char ** argv){ InitializeMagick(*argv); } But this does not work! VS2010 returns the following errors: error LNK2001: unresolved external symbol "__declspec(dllimport) void __cdecl Magick::InitializeMagick(char const *)" (__imp_?InitializeMagick@Magick@@YAXPBD@Z) error LNK1120: 1 unresolved externals What am I doing wrong? Thanks very much for your help!

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• hierarchical html listbox with mimicking file explorer level folding

  - by collapsar

  hello everybody, i'm looking for a technique to adapt a html listbox to hierarchical content with an unlimited number of levels ( const 1 would be sufficient ). hierarchy levels should be collapsible as in the usual file explorer views. the html listbox behaviour should be preserved / mimicked as comprehensively as possible. do you have a hint on where to find or how to implement this ? jquery solutions are fine. firefox 3.5+, ie 8+, safari 5 must be supported; opera 11, chrome 9 would be nice. as far as i understand the issue, listbox contents are rendered inside their own browser window sporting none of the standard window adornments. a hint on how to obtain a handle on this window in js would be a sufficient starting point, as well as correcting me in case i misconceived the browser behaviour. thanks in advance for your efforts, best regards, carsten

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• How to use the boost lexical_cast library for just for checking input

  - by Inverse

  I use the boost lexical_cast library for parsing text data into numeric values quite often. In several situations however, I only need to check if values are numeric; I don't actually need or use the conversion. So, I was thinking about writing a simple function to test if a string is a double: template<typename T> bool is_double(const T& s) { try { boost::lexical_cast<double>(s); return true; } catch (...) { return false; } } My question is, are there any optimizing compilers that would drop out the lexical_cast here since I never actually use the value? Is there a better technique to use the lexical_cast library to perform input checking?

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• Any way to avoid a filesort when order by is different to where clause?

  - by Julian

  I have an incredibly simple query (table type InnoDb) and EXPLAIN says that MySQL must do an extra pass to find out how to retrieve the rows in sorted order. SELECT * FROM `comments` WHERE (commentable_id = 1976) ORDER BY created_at desc LIMIT 0, 5 exact explain output: table select_type type extra possible_keys key key length ref rows comments simple ref using where; using filesort common_lookups common_lookups 5 const 89 commentable_id is indexed. Comments has nothing trick in it, just a content field. The manual suggests that if the order by is different to the where, there is no way filesort can be avoided. http://dev.mysql.com/doc/refman/5.0/en/order-by-optimization.html I also tried order by id as well as it's equivalent but makes no difference, even if I add id as an index (which I understand is not required as id is indexed implicitly in MySQL). thanks in advance for any ideas!

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• How to fill a section within c++ string?

  - by stacker

  Having a string of whitespaces: string *str = new string(); str->resize(width,' '); I'd like to fill length chars at a position. In C it would look like memset(&str[pos],'#', length ); How can i achieve this with c++ string, I tried string& assign( const string& str, size_type index, size_type len ); but this seems to truncat the original string. Is there an easy C++ way to do this? Thanks.

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• class which cannot be derived

  - by benjamin button

  I found this code here class Usable; class Usable_lock { friend class Usable; private: Usable_lock() {} Usable_lock(const Usable_lock&) {} }; class Usable : public virtual Usable_lock { // ... public: Usable(); Usable(char*); // ... }; Usable a; class DD : public Usable { }; DD dd; // error: DD::DD() cannot access // Usable_lock::Usable_lock(): private member Could anybody explain me this code?

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• Context Menu event with QGraphicsWidget

  - by onurozcelik

  In my application I subclass QGraphicsWidget In paint I am drawing a line with pen width 4. I reimplemented boundingRect() and shape(). But I can't catch context menu event every time I click right mouse button. What is the problem.(Pen Width ? ) //Sample code for boundingRect() and shape() QRectF boundingRect() const { qreal rectLeft = x1 < x2 ? x1 : x2; qreal rectTop = y1 < y2 ? y1 : y2; qreal rectWidth = (x1 - x2) != 0 ? abs(x1-x2) : 4; qreal rectHeight = (y1 - y2) != 0 ? abs(y1 -y2) : 4; return QRectF(rectLeft,rectTop,rectWidth,rectHeigt); } QPainterPath shape() { QPainterPath path; path.addRect(boundingRect()); return path; }

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• C++ cin returns 0 for integer no matter what the user inputs

  - by kevin dappah

  No matter the cin it continues to to output 0 for score. Why is that? I tried returning the "return 0;" but still no go :/ #include "stdafx.h" #include <iostream> using namespace std; // Variables int enemiesKilled; const int KILLS = 150; int score = enemiesKilled * KILLS; int main() { cout << "How many enemies did you kill?" << endl; cin >> enemiesKilled; cout << "Your score: " << score << endl; return 0; }

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• Call a C++ constructor from an Objective C class

  - by syvex

  How can I call a C++ constructor from inside an Objective C class? class CppClass { public: CppClass(int arg1, const std::string& arg2): _arg1(arg1), _arg2(arg2) { } // ... private: int _arg1; std::string _arg2; }; @interface ObjC: NSObject { CppClass _cppClass; } @end @implementation ObjC - (id)init { self = [super init]; if ( self ) { // what is the syntax to call CppClass::CppClass(5, "hello") on _cppClass? } return self; } @end

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• Calling some functions before main in C

  - by minjang

  I'd like to do some stuffs before main function. I have multiple source files. In each file, there is some work that needs to be done before main. It was no problem in C++, but problematic with C. In C++, this can be done by two ways: Exploiting a constructor of a global class/struct. Calling a function to a global variable For example, static const int __register_dummy_ = __AddRegisterMetaInfo(...); However, in C, either ways is impossible. Obviously, there is no constructor. So, the first option is inherently impossible. I thought that the second option would be possible, but not compiled in C (I tested only with Visual C++. It gives C2099.). C only allows a constant to a non-automatic variable. Is there any way to call some functions before main?

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• How can I load a SQLITE database from a buffer with the C API ?

  - by rockeye

  Hello, I am trying to load a database from the memory instead of opening a .sqlite file. I have read the C/C++ API reference but I can not find the proper method. The buffer I am trying to load is simply an sqlite file loaded in memory. I just want to use this buffer (a const char* array) without using the filesystem (I could have saved this buffer in a file, then load the file, but no). First, I create a memory DB : mErrorCode = sqlite3_open_v2(":memory:", &mSqlDatabase, lMode, NULL); This returns SQLITE_OK, then I tried to use the buffer as a statement and call preparev2(MyDB, MyBufferData, MyBufferLength, MyStatement, NULL) but it's not really a statement, and it returns an error. Same result if I call directly exec(MyDB, MyBufferData, NULL, NULL, NULL); I guess there is an appropriate method to achieve this as it might be common to load a DB from a stream or from decrypted data... Thanks.

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• Is there any way to pass an anonymous array as an argument in C++?

  - by Jeremy Friesner

  Hi all, I'd like to be able to declare an array as a function argument in C++, as shown in the example code below (which doesn't compile). Is there any way to do this (other than declaring the array separately beforehand)? #include <stdio.h> static void PrintArray(int arrayLen, const int * array) { for (int i=0; i<arrayLen; i++) printf("%i -> %i\n", i, array[i]); } int main(int, char **) { PrintArray(5, {5,6,7,8,9} ); // doesn't compile return 0; }

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• Any side effect of not using USES_CONVERSION

  - by Yan Cheng CHEOK

  Recently, I have a utilities function of // T2CA #include "ATLCONV.H" std::string Utils::CString2String(const CString& cString) { #if _MSC_VER > 1200 // Convert a TCHAR string to a LPCSTR // construct a std::string using the LPCSTR input CT2CA tmp(cString); std::string strStd (tmp); #else // Deprecated in VC2008. // construct a std::string using the LPCSTR input std::string strStd (T2CA (cString)); #endif return strStd; } I do several simple test it seems work fine. However, when I google around, I see most usage of T2CA in VC6, before they call, they will invoke USES_CONVERSION; Is there any thing I had missed out? Shall I invoke my function by : #else // Deprecated in VC2008. // construct a std::string using the LPCSTR input USES_CONVERSION; std::string strStd (T2CA (cString)); #endif

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• boost timer usage question

  - by stefita

  I have a really simple question, yet I can't find an answer for it. I guess I am missing something in the usage of the boost timer.hpp. Here is my code, that unfortunately gives me an error message: include <boost/timer.hpp> int main() { boost::timer t; } And the error messages are as follows: /usr/include/boost/timer.hpp: In member function ‘double boost::timer::elapsed_max() const’: /usr/include/boost/timer.hpp:59: error: ‘numeric_limits’ is not a member of ‘std’ /usr/include/boost/timer.hpp:59: error: ‘::max’ has not been declared /usr/include/boost/timer.hpp:59: error: expected primary-expression before ‘double’ /usr/include/boost/timer.hpp:59: error: expected `)' before ‘double’ The used library is boost 1.36 (SUSE 11.1). Thanks in advance!

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• Objective C: App freezes when using a timer

  - by Chris

  It took me hours to figure out how to implement a timer into my program, but when it runs, the app doesn't load completely as it did before the timer. In my main.m: int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; OutLauncher *theLauncher = [[OutLauncher alloc] init]; NSTimer *theTimer = [theLauncher getTimer]; [theTimer retain]; [[NSRunLoop currentRunLoop] addTimer: theTimer forMode: NSDefaultRunLoopMode]; [[NSRunLoop currentRunLoop] run]; [pool release]; return 0; } The file OutLauncher is being imported into that, which looks like this: - (void)doStuff { NSLog( @"Doing Stuff"); } - (NSTimer *)getTimer{ NSTimer *theTimer; theTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector: @selector(doStuff) userInfo:nil repeats:YES]; return [theTimer autorelease]; } The timer works, the console updates every second with the phrase "doing stuff" but the rest of the program just won't load. It will if I comment out the code I added to int main though

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