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• Calling from C# to C function which accept a struct array allocated by caller

  - by lifey

  I have the following C struct struct XYZ { void *a; char fn[MAX_FN]; unsigned long l; unsigned long o; }; And I want to call the following function from C#: extern "C" int func(int handle, int *numEntries, XYZ *xyzTbl); Where xyzTbl is an array of XYZ of size numEntires which is allocated by the caller I have defined the following C# struct: [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential, CharSet = System.Runtime.InteropServices.CharSet.Ansi)] public struct XYZ { public System.IntPtr rva; [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = 128)] public string fn; public uint l; public uint o; } and a method: [System.Runtime.InteropServices.DllImport(@"xyzdll.dll", CallingConvention = CallingConvention.Cdecl)] public static extern Int32 func(Int32 handle, ref Int32 numntries, [MarshalAs(UnmanagedType.LPArray)] XYZ[] arr); Then I try to call the function : XYZ xyz = new XYZ[numEntries]; for (...) xyz[i] = new XYZ(); func(handle,numEntries,xyz); Of course it does not work. Can someone shed light on what I am doing wrong ?

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• C++ Suppress Automatic Initialization and Destruction

  - by Travis G

  How does one suppress the automatic initialization and destruction of a type? While it is wonderful that T buffer[100] automatically initializes all the elements of buffer, and destroys them when they fall out of scope, this is not the behavior I want. #include <iostream> static int created = 0, destroyed = 0; struct S { S() { ++created; } ~S() { ++destroyed; } }; template <typename T, size_t KCount> class Array { private: T m_buffer[KCount]; public: Array() { // some way to suppress the automatic initialization of m_buffer } ~Array() { // some way to suppress the automatic destruction of m_buffer } }; int main() { { Array<S, 100> arr; } std::cout << "Created:\t" << created << std::endl; std::cout << "Destroyed:\t" << destroyed << std::endl; return 0; } The output of this program is: Created: 100 Destroyed: 100 I would like it to be: Created: 0 Destroyed: 0 My only idea is to make m_buffer some trivially constructed and destructed type like char and then rely on operator[] to wrap the pointer math for me, although this seems like a horribly hacked solution. Another solution would be to use malloc and free, but that gives a level of indirection that I do not want.

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• Is this overly clever or unsafe?

  - by Liberalkid

  I was working on some code recently and decided to work on my operator overloading in c++, because I've never really implemented it before. So I overloaded the comparison operators for my matrix class using a compare function that returned 0 if LHS was less than RHS, 1 if LHS was greater than RHS and 2 if they were equal. Then I exploited the properties of logical not in c++ on integers, to get all of my compares in one line: inline bool Matrix::operator<(Matrix &RHS){ return ! (compare(*this,RHS)); } inline bool Matrix::operator>(Matrix &RHS){ return ! (compare((*this),RHS)-1); } inline bool Matrix::operator>=(Matrix &RHS){ return compare((*this),RHS); } inline bool Matrix::operator<=(Matrix &RHS){ return compare((*this),RHS)-1; } inline bool Matrix::operator!=(Matrix &RHS){ return compare((*this),RHS)-2; } inline bool Matrix::operator==(Matrix &RHS){ return !(compare((*this),RHS)-2); } Obviously I should be passing RHS as a const, I'm just probably not going to use this matrix class again and I didn't feel like writing another function that wasn't a reference to get the array index values solely for the comparator operation.

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• Simple average calculation

  - by sasquatch90

  I'm trying to write program calculating average of given numbers stored in an array. Amount of numbers should be not more than 100, and user should input them until a !int variable is given : #include <iostream> #include <conio.h> using namespace std; double average(int tab[], int i){ int sum=0; for(int j=0; j<i; ++j){ sum+=tab[j]; } return (double)sum/i; } int main() { int tab[100]; int n=0; int number=0; do { if(n < 100){ cout << "Give " << n+1 << " number : "; cin >> number; tab[n]=number; number=0; ++n; } else{ break; } } while( !isdigit(number) ); cout << average(tab, n) << endl; getch(); return 0; } Why after giving char, it prints me 'Give n number:' for all empty cells of my array ? It should end and use only given numbers.

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• C++ design related question

  - by Kotti

  Hi! Here is the question's plot: suppose I have some abstract classes for objects, let's call it Object. It's definition would include 2D position and dimensions. Let it also have some virtual void Render(Backend& backend) const = 0 method used for rendering. Now I specialize my inheritance tree and add Rectangle and Ellipse class. Guess they won't have their own properties, but they will have their own virtual void Render method. Let's say I implemented these methods, so that Render for Rectangle actually draws some rectangle, and the same for ellipse. Now, I add some object called Plane, which is defined as class Plane : public Rectangle and has a private member of std::vector<Object*> plane_objects; Right after that I add a method to add some object to my plane. And here comes the question. If I design this method as void AddObject(Object& object) I would face trouble like I won't be able to call virtual functions, because I would have to do something like plane_objects.push_back(new Object(object)); and this should be push_back(new Rectangle(object)) for rectangles and new Circle(...) for circles. If I implement this method as void AddObject(Object* object), it looks good, but then somewhere else this means making call like plane.AddObject(new Rectangle(params)); and this is generally a mess because then it's not clear which part of my program should free the allocated memory. ["when destroying the plane? why? are we sure that calls to AddObject were only done as AddObject(new something).] I guess the problems caused by using the second approach could be solved using smart pointers, but I am sure there have to be something better. Any ideas?

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• Are C++ exceptions sufficient to implement thread-local storage?

  - by Potatoswatter

  I was commenting on an answer that thread-local storage is nice and recalled another informative discussion about exceptions where I supposed The only special thing about the execution environment within the throw block is that the exception object is referenced by rethrow. Putting two and two together, wouldn't executing an entire thread inside a function-catch-block of its main function imbue it with thread-local storage? It seems to work fine: #include <iostream> #include <pthread.h> using namespace std; struct thlocal { string name; thlocal( string const &n ) : name(n) {} }; thlocal &get_thread() { try { throw; } catch( thlocal &local ) { return local; } } void print_thread() { cerr << get_thread().name << endl; } void *kid( void *local_v ) try { thlocal &local = * static_cast< thlocal * >( local_v ); throw local; } catch( thlocal & ) { print_thread(); return NULL; } int main() try { thlocal local( "main" ); throw local; } catch( thlocal & ) { print_thread(); pthread_t th; thlocal kid_local( "kid" ); pthread_create( &th, NULL, &kid, &kid_local ); pthread_join( th, NULL ); print_thread(); return 0; } Is this novel or well-characterized? Was my initial premise correct? What kind of overhead does get_thread incur in, say, GCC and VC++? It would require throwing only exceptions derived from struct thlocal, but altogether this doesn't feel like an unproductive insomnia-ridden Sunday morning…

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• C# Multidimensional Array Definition

  - by Blaenk

  Can someone help me convert this to C#. I've already spent more time than I would have liked trying to do it myself and it's preventing me from actually getting any work done. I guess it seems like C# has a limitation regarding how one can define arrays. I think somewhere inside I have to keep doing new int[] but I'm not sure exactly where. You don't have to convert the whole thing, just enough so I can understand how to do it. I would really appreciate it. I would like to use integers instead of characters, by the way. Thanks again // Pieces definition char mArray [7][4][5][5] = { // Square { { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} } }, // and so on and so forth, for 6 more };

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• How to change the meaning of pointer access operator

  - by kumar_m_kiran

  Hi All, This may be very obvious question, pardon me if so. I have below code snippet out of my project, #include <stdio.h> class X { public: int i; X() : i(0) {}; }; int main(int argc,char *arv[]) { X *ptr = new X[10]; unsigned index = 5; cout<<ptr[index].i<<endl; return 0; } Question Can I change the meaning of the ptr[index] ? Because I need to return the value of ptr[a[index]] where a is an array for subindexing. I do not want to modify existing source code. Any new function added which can change the behavior is needed. Since the access to index operator is in too many places (536 to be precise) in my code, and has complex formulas inside the index subscript operator, I am not inclined to change the code in many locations. PS : 1. I tried operator overload and came to conclusion that it is not possible. 2. Also p[i] will be transformed into *(p+i). I cannot redefine the basic operator '+'. So just want to reconfirm my understanding and if there are any possible short-cuts to achieve. Else I need fix it by royal method of changing every line of code :) .

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• How to make command-line options mandatory with GLib?

  - by ahe

  I use GLib to parse some command-line options. The problem is that I want to make two of those options mandatory so that the program terminates with the help screen if the user omits them. My code looks like this: static gint line = -1; static gint column = -1; static GOptionEntry options[] = { {"line", 'l', 0, G_OPTION_ARG_INT, &line, "The line", "L"}, {"column", 'c', 0, G_OPTION_ARG_INT, &column, "The column", "C"}, {NULL} }; ... int main(int argc, char** argv) { GError *error = NULL; GOptionContext *context; context = g_option_context_new ("- test"); g_option_context_add_main_entries (context, options, NULL); if (!g_option_context_parse(context, &argc, &argv, &error)) { usage(error->message, context); } ... return 0; } If I omit one of those parameters or both on the command-line g_option_context_parse() still succeeds and the values in question (line and or column) are still -1. How can I tell GLib to fail parsing if the user doesn't pass both options on the command-line? Maybe I'm just blind but I couldn't find a flag I can put into my GOptionEntry data structure to tell it to make those fields mandatory. Of course I could check if one of those variables is still -1 but then the user could just have passed this value on the command-line and I want to print a separate error message if the values are out of range.

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• Fibonacci in C works great with 1 - 18 but 19 does nothing at all...

  - by shevron

  Yeah right... we are forced to programm some good old C at our university... ;) So here's my problem: We got the assignment to program a little program that show a fibonacci sequence from 1 to n 1 to 18 works great. But from 19 the program does nothing at all and just exit as it's done. I can not find the error... so please give me a hint. :) #include #include #include #include int main(int argc, char **argv) { pid_t pid; int fib[argc]; int i, size; size = strtol(argv[1], NULL, 0L); fib[0] = 0; fib[1] = 1; pid = fork(); printf("size = %d \n", size); if(pid == 0){ for(i = 2; i 0){ // Parent, because pid 0 wait(NULL); printf("\n"); exit(1); } } Thanks already!

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• C++ CRTP(template pattern) question

  - by aaa

  following piece of code does not compile, the problem is in T::rank not be inaccessible (I think) or uninitialized in parent template. Can you tell me exactly what the problem is? is passing rank explicitly the only way? or is there a way to query tensor class directly? Thank you #include <boost/utility/enable_if.hpp> template<class T, // size_t N, class enable = void> struct tensor_operator; // template<class T, size_t N> template<class T> struct tensor_operator<T, typename boost::enable_if_c< T::rank == 4>::type > { tensor_operator(T &tensor) : tensor_(tensor) {} T& operator()(int i,int j,int k,int l) { return tensor_.layout.element_at(i, j, k, l); } T &tensor_; }; template<size_t N, typename T = double> // struct tensor : tensor_operator<tensor<N,T>, N> { struct tensor : tensor_operator<tensor<N,T> > { static const size_t rank = N; }; I know the workaround, however am interested in mechanics of template instantiation for self-education

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• Objective-C ref count and autorelease

  - by turbovince

  Hey guys, suppose the following code: int main (int argc, const char * argv[]) { //[...] Rectangle* myRect = [[Rectangle alloc] init]; Vector2* newOrigin = [[[Vector2 alloc] init] autorelease]; // ref count 1 [newOrigin setX: 50.0f]; [myRect setOrigin: newOrigin]; // ref count 2 [myRect.origin setXY: 25.0f :100.0f]; // ref count goes to 3... why ? [myRect release]; [pool drain]; return 0; } Rectangle's origin is declared as a (retain) synthesized property. Just wondering 2 things: Why does ref count goes to 3 when using the getter accessor of Rectangle's origin? Am I doing something wrong ? With a ref count of 3, I don't understand how this snippet of code cannot leak. Calling release on myRect will make it go down to 2 since I call release on the origin in dealloc(). But then, when does autorelease take effect? Thanks!

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• Sending data in a GTK Callback

  - by snostorm

  How can I send data through a GTK callback? I've Googled, and with the information I found created this: #include <gtk/gtk.h> #include <stdio.h> void button_clicked( GtkWidget *widget, GdkEvent *event, gchar *data); int main( int argc, char *argv[]){ GtkWidget *window; GtkWidget *button; gtk_init (&argc, &argv); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); button = gtk_button_new_with_label("Go!"); gtk_container_add(GTK_CONTAINER(window), button); g_signal_connect_swapped(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL); g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(button_clicked),"test" ); gtk_widget_show(window); gtk_widget_show(button); gtk_main(); return 0; } void button_clicked( GtkWidget *widget, GdkEvent *event, gchar *data){ printf("%s \n", (gchar *) data); return; } But it just Segfaults when I press the button. What is the right way to do this?

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• reading a file of unknown length with a function

  - by Faken

  I'm trying to write a short function that will let me quickly read in a file of unknown size and return pointer to the array of data and the length of that array but it seems my code isn't working. What am i doing wrong? int readIn(int* pointer, param parameters, string description) { string fileName = parameters.fileName + " " + description + ".bin"; ifstream readFile; readFile.open(fileName.c_str(), ios::in|ios::binary|ios::ate); int size = readFile.tellg(); int length = size / 4; int* output = new int [length]; readFile.seekg (0, ios::beg); readFile.read(reinterpret_cast<char*>(output), (size)); readFile.close(); pointer = output; // link new array with the pointer return length; } and in the main function: int* testList; int numEntries = readIn(testList, parameters, "test"); I end up with an error saying that my testList variable was used and not initialized. What am i doing wrong?

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• ISO C90 forbids mixed declarations and code sscanf

  - by Need4Sleep

  I'm getting a strange error attempting to compile my unit test code,. For some reason the compiler treats my sscanf call as a mixed declaration? I don't quite understand, here is the entire error: cc1: warnings being treated as errors /home/brlcad/brlcad/src/libbn/tests/bn_complex.c: In function 'main': /home/brlcad/brlcad/src/libbn/tests/bn_complex.c:53: error: ISO C90 forbids mixed declarations and code make[2]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/bn_complex.c.o] Error 1 make[1]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/all] Error 2 make: *** [all] Error 2 int main(int argc, char *argv[]) { double expRe1, expIm2, expSqRe1, expSqIm2; double actRe1, actIm2, actSqRe1, actSqIm2; actRe1 = actIm2 = actSqRe1 = actSqIm2 = expRe1 = expIm2 = expSqRe1 = expSqIm2 = 0.0; bn_complex_t com1,com2; //a struct that holds two doubles if(argc < 5) bu_exit(1, "ERROR: Invalid parameters[%s]\n", argv[0]); sscanf(argv[1], "%lf,%lf", &com1.re, &com1.im); /* Error is HERE */ sscanf(argv[2], "%lf,%lf", &com2.re, &com2.im); sscanf(argv[3], "%lf,%lf", &expRe1, &expIm2); sscanf(argv[4], "%lf,%lf", &expSqRe1, &expSqIm2); test_div(com1, com2, &actRe1, &actIm2); test_sqrt(com1,com2, &actSqRe1, &actSqIm2); if((fabs(actRe1 - expRe1) < 0.00001) || (fabs(actIm2 - expIm2) < 0.00001)){ printf("Division failed...\n"); return 1; } if((fabs(actSqRe1 - expSqRe1) < 0.00001) || (fabs(actSqIm2 - expSqIm2) < 0.00001)){ printf("Square roots failed...\n"); return 1; } return 0; }

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• C++ socket protocol design issue (ring inclusion)

  - by Martin Lauridsen

  So I have these two classes, mpqs_client and client_protocol. The mpqs_client class handles a Boost socket connection to a server (sending and receiving messages with some specific format. Upon receiving a message, it calls a static method, parse_message(..), in the class client_protocol, and this method should analyse the message received and perform some corresponding action. Given some specific input, the parse_message method needs to send some data back to the server. As mentioned, this happens through the class mpqs_client. So I could, from mpqs_client, pass "this" to parse_message(..) in client_protocol. However, this leads to a two-way association relationship between the two classes. Something which I reckon is not desireable. Also, to implement this, I would need to include the other in each one, and this gives me a terrible pain. I am thinking this is more of a design issue. What is the best solution here? Code is posted below. Class mpqs_client: #include "mpqs_client.h" mpqs_client::mpqs_client(boost::asio::io_service& io_service, tcp::resolver::iterator endpoint_iterator) : io_service_(io_service), socket_(io_service) { ... } ... void mpqs_client::write(const network_message& msg) { io_service_.post(boost::bind(&mpqs_client::do_write, this, msg)); } Class client_protocol: #include "../network_message.hpp" #include "../protocol_consts.h" class client_protocol { public: static void parse_message(network_message& msg, mpqs_sieve **instance_, mpqs_client &client_) { ... switch (type) { case MPQS_DATA: ... break; case POLYNOMIAL_DATA: ... break; default: break; } }

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• How to wrap a C function whose parameters are pointer to structs, so that it can be called from Lua?

  - by pierr

  I have the follwing C function. How should I wrap it so it can be called from a Lua script? typedef struct tagT{ int a ; int b ; } type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapr it if the function parameter type were int or char *. Should I use table type for a C structure? EDIT: I am using SWIG for the wraping , according to this doc, It seems that I should automatically have this funtion new_type_t(2,3) , but it is not the case. If you wrap a C structure, it is also mapped to a Lua userdata. By adding a metatable to the userdata, this provides a very natural interface. For example, struct Point{ int x,y; }; is used as follows: p=example.new_Point() p.x=3 p.y=5 print(p.x,p.y) 3 5 Similar access is provided for unions and the data members of C++ classes. C structures are created using a function new_Point(), but for C++ classes are created using just the name Point().

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• Sql Server 2005 multiple insert with c#

  - by bottlenecked

  Hello. I have a class named Entry declared like this: class Entry{ string Id {get;set;} string Name {get;set;} } and then a method that will accept multiple such Entry objects for insertion into the database using ADO.NET: static void InsertEntries(IEnumerable<Entry> entries){ //build a SqlCommand object using(SqlCommand cmd = new SqlCommand()){ ... const string refcmdText = "INSERT INTO Entries (id, name) VALUES (@id{0},@name{0});"; int count = 0; string query = string.Empty; //build a large query foreach(var entry in entries){ query += string.Format(refcmdText, count); cmd.Parameters.AddWithValue(string.Format("@id{0}",count), entry.Id); cmd.Parameters.AddWithValue(string.Format("@name{0}",count), entry.Name); count++; } cmd.CommandText=query; //and then execute the command ... } } And my question is this: should I keep using the above way of sending multiple insert statements (build a giant string of insert statements and their parameters and send it over the network), or should I keep an open connection and send a single insert statement for each Entry like this: using(SqlCommand cmd = new SqlCommand(){ using(SqlConnection conn = new SqlConnection(){ //assign connection string and open connection ... cmd.Connection = conn; foreach(var entry in entries){ cmd.CommandText= "INSERT INTO Entries (id, name) VALUES (@id,@name);"; cmd.Parameters.AddWithValue("@id", entry.Id); cmd.Parameters.AddWithValue("@name", entry.Name); cmd.ExecuteNonQuery(); } } } What do you think? Will there be a performance difference in the Sql Server between the two? Are there any other consequences I should be aware of? Thank you for your time!

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• How is an AppDelegate instanciated?

  - by pwny

  I have an iOS application for which I want to create a ViewController programmatically. I started an empty XCode project and modified the main method so it looks like this int main(int argc, char *argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, @"MyAppDelegate_iPad"); [pool release]; return retVal; } The app is a Universal Application, MyAppDelegate_iPad is a subclass of MyAppDelegate, which is a subclass of NSObject <UIApplicationDelegate>. My problem is that the applicationDidFinishLoading method I've overridden in MyAppDelegate_iPad is never called (break point on the first line never hits). The method looks like this -(void) applicationDidFinishLaunching:(UIApplication *)application { window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; if(!window) { [self release]; return; } window.backgroundColor = [UIColor whiteColor]; rootController = [[MyViewController alloc] init]; [window addSubview:rootController.view]; [window makeKeyAndVisible]; [window layoutSubviews]; } I removed the line to link to a nib file from my plist file (I used to get the default "My Universal app on iPad" white screen) and now all that is displayed is a black screen. applicationDidFinishLoading is still not being called. Am I doing something wrong? How should I properly create my AppDelegate instance?

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• finding N contiguous zero bits in an integer to the left of the MSB from another

  - by James Morris

  First we find the MSB of the first integer, and then try to find a region of N contiguous zero bits within the second number which is to the left of the MSB from the first integer. 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?

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• Static Logger in seperate thread?

  - by SirLenz0rlot

  Hi all, I've made my Logger, that logs a string, a static class with a static so I can call it from my entire project without having to make an instance of it. quite nice, but I want to make it run in a seperate thread, since accessing the file costs time is that possible somehow and what's the best way to do it? Its a bit of a short discription, but I hope the idea is clear. if not, please let me know. Thanks in advance! btw: any other improvements on my code are welcome as well, i have the feeling not everthing is as efficient as it can be: internal static class MainLogger { internal static void LogStringToFile(string logText) { DateTime timestamp = DateTime.Now; string str = timestamp.ToString("dd-MM-yy HH:mm:ss ", CultureInfo.InvariantCulture) + "\t" + logText + "\n"; const string filename = Constants.LOG_FILENAME; FileInfo fileInfo = new FileInfo(filename); if (fileInfo.Exists) { if (fileInfo.Length > Constants.LOG_FILESIZE) { File.Create(filename).Dispose(); } } else { File.Create(filename).Dispose(); } int i = 0; while(true) { try { using (StreamWriter writer = File.AppendText(filename)) { writer.WriteLine(str); } break; } catch (IOException) { Thread.Sleep(10); i++; if (i >= 8) { throw new IOException("Log file \"" + Constants.LOG_FILENAME + "\" not accessible after 5 tries"); } } } } } enter code here

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• How do you safely wrap a JS string variable in double quote chars?

  - by incombinative

  Obviously when you're creating an actual string literal yourself, you backslash escape the double quote characters yourself. var foo = "baz\"bat"; Just as you would with the handful of other control characters, like linebreaks and backslashes. var bar = "baz\\bat"; but when you already have a variable, and you're wrapping that existing variable in quote characters, there's some confusion. Obviously you have to escape any potential double quote characters that are in the string. (Assuming whatever system you're giving the explicitly quoted string to, needs to be able to parse them correctly. =) var doubleQuoteRe = /\"/g; var quoted = unquoted.replace(escaper, '\\\"'); However from there opinions diverge a little. In particular, according to some you also have to worry about escaping literal backslash characters in the variable. // now say i have a string bar, that has both single backslash character in it, // as well as a double-quote character in it. // the following code ONLY worries about escaping the double quote char. var quoted = bar.replace(doubleQuoteRe, '\\\"'); The above seems fine to me. But is there a problem im not seeing?

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• What goes into main function?

  - by Woltan

  I am looking for a best practice tip of what goes into the main function of a program using c++. Currently I think two approaches are possible. (Although the "margins" of those approaches can be arbitrarily close to each other) 1: Write a "Master"-class that receives the parameters passed to the main function and handle the complete program in that "Master"-class (Of course you also make use of other classes). Therefore the main function would be reduced to a minimum of lines. #include "MasterClass.h" int main(int args, char* argv[]) { MasterClass MC(args, argv); } 2: Write the "complete" program in the main function making use of user defined objects of course! However there are also global functions involved and the main function can get somewhat large. I am looking for some general guidelines of how to write the main function of a program in c++. I came across this issue by trying to write some unit test for the first approach, which is a little difficult since most of the methods are private. Thx in advance for any help, suggestion, link, ...

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• Strange Access Denied warning when running the simplest C++ program.

  - by DaveJohnston

  I am just starting to learn C++ (coming from a Java background) and I have come across something that I can't explain. I am working through the C++ Primer book and doing the exercises. Every time I get to a new exercise I create a new .cpp file and set it up with the main method (and any includes I think I will need) e.g.: #include <list> #include <vector> int main(int argc, char **args) { } and just to make sure I go to the command prompt and compile and run: g++ whatever.cpp a.exe Normally this works just fine and I start working on the exercise, but I just did it and got a strange error. It compiles fine, but when I run it it says Access Denied and AVG pops up telling me that a threat has been detected 'Trojan Horse Generic 17.CKZT'. I tried compiling again using the Microsoft Compiler (cl.exe) and it runs fines. So I went back, and added: #include <iostream> compiled using g++ and ran. This time it worked fine. So can anyone tell me why AVG would report an empty main method as a trojan horse but if the iostream header is included it doesn't?

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• Converting "A* Search" code from C++ to Java [on hold]

  - by mr5

  Updated! I get this code from this site It's A* Search Algorithm(finding shortest path with heuristics) I modify most of variable names and some if conditions from the original version to satisfy my syntactic taste. It works in C++ (as I can't see any trouble with it) but fails in Java version. Java Code: String findPath(int startX, int startY, int finishX, int finishY) { @SuppressWarnings("unchecked") LinkedList<Node>[] nodeList = (LinkedList<Node>[]) new LinkedList<?>[2]; nodeList[0] = new LinkedList<Node>(); nodeList[1] = new LinkedList<Node>(); Node n0; Node m0; int nlIndex = 0; // queueList index // reset the node maps for(int y = 0;y < ROW_COUNT; ++y) { for(int x = 0;x < COL_COUNT; ++x) { close_nodes_map[y][x] = 0; open_nodes_map[y][x] = 0; } } // create the start node and push into list of open nodes n0 = new Node( startX, startY, 0, 0 ); n0.updatePriority( finishX, finishY ); nodeList[nlIndex].push( n0 ); open_nodes_map[startY][startX] = n0.getPriority(); // mark it on the open nodes map // A* search while( !nodeList[nlIndex].isEmpty() ) { LinkedList<Node> pq = nodeList[nlIndex]; // get the current node w/ the highest priority // from the list of open nodes n0 = new Node( pq.peek().getX(), pq.peek().getY(), pq.peek().getIterCount(), pq.peek().getPriority()); int x = n0.getX(); int y = n0.getY(); nodeList[nlIndex].pop(); // remove the node from the open list open_nodes_map[y][x] = 0; // mark it on the closed nodes map close_nodes_map[y][x] = 1; // quit searching when the goal state is reached //if((*n0).estimate(finishX, finishY) == 0) if( x == finishX && y == finishY ) { // generate the path from finish to start // by following the directions String path = ""; while( !( x == startX && y == startY) ) { int j = dir_map[y][x]; int c = '0' + ( j + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; path = (char)c + path; x += DIR_X[j]; y += DIR_Y[j]; } return path; } // generate moves (child nodes) in all possible directions for(int i = 0; i < Node.DIRECTION_COUNT; ++i) { int xdx = x + DIR_X[i]; int ydy = y + DIR_Y[i]; // boundary check if (!(xdx >= 0 && xdx < COL_COUNT && ydy >= 0 && ydy < ROW_COUNT)) continue; if ( ( gridMap.getData( ydy, xdx ) == GridMap.WALKABLE || gridMap.getData( ydy, xdx ) == GridMap.FINISH) && close_nodes_map[ydy][xdx] != 1 ) { // generate a child node m0 = new Node( xdx, ydy, n0.getIterCount(), n0.getPriority() ); m0.nextLevel( i ); m0.updatePriority( finishX, finishY ); // if it is not in the open list then add into that if( open_nodes_map[ydy][xdx] == 0 ) { open_nodes_map[ydy][xdx] = m0.getPriority(); nodeList[nlIndex].push( m0 ); // mark its parent node direction dir_map[ydy][xdx] = ( i + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; } else if( open_nodes_map[ydy][xdx] > m0.getPriority() ) { // update the priority info open_nodes_map[ydy][xdx] = m0.getPriority(); // update the parent direction info dir_map[ydy][xdx] = ( i + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; // replace the node // by emptying one queueList to the other one // except the node to be replaced will be ignored // and the new node will be pushed in instead while( !(nodeList[nlIndex].peek().getX() == xdx && nodeList[nlIndex].peek().getY() == ydy ) ) { nodeList[1 - nlIndex].push( nodeList[nlIndex].pop() ); } nodeList[nlIndex].pop(); // remove the wanted node // empty the larger size queueList to the smaller one if( nodeList[nlIndex].size() > nodeList[ 1 - nlIndex ].size() ) nlIndex = 1 - nlIndex; while( !nodeList[nlIndex].isEmpty() ) { nodeList[1 - nlIndex].push( nodeList[nlIndex].pop() ); } nlIndex = 1 - nlIndex; nodeList[nlIndex].push( m0 ); // add the better node instead } } } } return ""; // no route found } Output1: Legends . = PATH ? = START X = FINISH 3,2,1 = OBSTACLES (Misleading path) Output2: Changing these lines: n0 = new Node( a, b, c, d ); m0 = new Node( e, f, g, h ); to n0.set( a, b, c, d ); m0.set( e, f, g, h ); I get (I'm really confused) C++ Code: std::string A_Star::findPath(int startX, int startY, int finishX, int finishY) { typedef std::queue<Node> List_Container; List_Container nodeList[2]; // list of open (not-yet-tried) nodes Node n0; Node m0; int pqIndex = 0; // nodeList index // reset the node maps for(int y = 0;y < ROW_COUNT; ++y) { for(int x = 0;x < COL_COUNT; ++x) { close_nodes_map[y][x] = 0; open_nodes_map[y][x] = 0; } } // create the start node and push into list of open nodes n0 = Node( startX, startY, 0, 0 ); n0.updatePriority( finishX, finishY ); nodeList[pqIndex].push( n0 ); open_nodes_map[startY][startX] = n0.getPriority(); // mark it on the open nodes map // A* search while( !nodeList[pqIndex].empty() ) { List_Container &pq = nodeList[pqIndex]; // get the current node w/ the highest priority // from the list of open nodes n0 = Node( pq.front().getX(), pq.front().getY(), pq.front().getIterCount(), pq.front().getPriority()); int x = n0.getX(); int y = n0.getY(); nodeList[pqIndex].pop(); // remove the node from the open list open_nodes_map[y][x] = 0; // mark it on the closed nodes map close_nodes_map[y][x] = 1; // quit searching when the goal state is reached //if((*n0).estimate(finishX, finishY) == 0) if( x == finishX && y == finishY ) { // generate the path from finish to start // by following the directions std::string path = ""; while( !( x == startX && y == startY) ) { int j = dir_map[y][x]; char c = '0' + ( j + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; path = c + path; x += DIR_X[j]; y += DIR_Y[j]; } return path; } // generate moves (child nodes) in all possible directions for(int i = 0; i < DIRECTION_COUNT; ++i) { int xdx = x + DIR_X[i]; int ydy = y + DIR_Y[i]; // boundary check if (!( xdx >= 0 && xdx < COL_COUNT && ydy >= 0 && ydy < ROW_COUNT)) continue; if ( ( pGrid->getData(ydy,xdx) == WALKABLE || pGrid->getData(ydy, xdx) == FINISH) && close_nodes_map[ydy][xdx] != 1 ) { // generate a child node m0 = Node( xdx, ydy, n0.getIterCount(), n0.getPriority() ); m0.nextLevel( i ); m0.updatePriority( finishX, finishY ); // if it is not in the open list then add into that if( open_nodes_map[ydy][xdx] == 0 ) { open_nodes_map[ydy][xdx] = m0.getPriority(); nodeList[pqIndex].push( m0 ); // mark its parent node direction dir_map[ydy][xdx] = ( i + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; } else if( open_nodes_map[ydy][xdx] > m0.getPriority() ) { // update the priority info open_nodes_map[ydy][xdx] = m0.getPriority(); // update the parent direction info dir_map[ydy][xdx] = ( i + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; // replace the node // by emptying one nodeList to the other one // except the node to be replaced will be ignored // and the new node will be pushed in instead while ( !( nodeList[pqIndex].front().getX() == xdx && nodeList[pqIndex].front().getY() == ydy ) ) { nodeList[1 - pqIndex].push( nodeList[pqIndex].front() ); nodeList[pqIndex].pop(); } nodeList[pqIndex].pop(); // remove the wanted node // empty the larger size nodeList to the smaller one if( nodeList[pqIndex].size() > nodeList[ 1 - pqIndex ].size() ) pqIndex = 1 - pqIndex; while( !nodeList[pqIndex].empty() ) { nodeList[1-pqIndex].push(nodeList[pqIndex].front()); nodeList[pqIndex].pop(); } pqIndex = 1 - pqIndex; nodeList[pqIndex].push( m0 ); // add the better node instead } } } } return ""; // no route found } Output: Legends . = PATH ? = START X = FINISH 3,2,1 = OBSTACLES (Just right) From what I read about Java's documentation, I came up with the conclusion: C++'s std::queue<T>::front() == Java's LinkedList<T>.peek() Java's LinkedList<T>.pop() == C++'s std::queue<T>::front() + std::queue<T>::pop() What might I be missing in my Java version? In what way does it became different algorithmically from the C++ version?

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