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• Socket programming question

  - by dfddf

  I am given the following declaration: char inbuff[500], *ptr; int n, bufferlen; Write a program segement to receive a message having 500 bits from the TCP socket sock and store this message in inbuff. My answer is: n = recv( sock, inbuff, strlen( inbuff ), 0 ); However, I am not sure why *ptr is given in the declaration. So, I would like ask, what is the purpose of the pointer in this question?? Or my program segement is wrong? Thank you for all of yours help first!

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• Copying a 14bit grayscale image (saved in long[]) to a pictureBox

  - by Itsik

  My camera gives me 14bit grayscale images, but the API's function returns a long* to the image data. (so i'm assuming 4 bytes for each pixel) My application is written in C++/CLI, and the pictureBox is of .NET type. I am currently using the BitmapData.LockBits() mechanism to gain pointer access to the image data, and using memcpy(bmpData.Scan0.ToPointer(), imageData, sizeof(long)*height*width) to copy the image data to the Bitmap. For now, the only PixelFormat that is working is 32bit RGB, and the image appears in shades of blue with contours. Trying to initialize the Bitmap as 16bppGrayscale isn't working. I would ideally want to cast the array from long to word and using a 16bit format (hoping the the 14bit data will be displayed properly) but I'm not sure if this works. Also, I don't want to iterate over the image data, so finding the min/max and then histogram stretching to [0..255] isnt an option for me (the display must be as efficient as possible) Thanks

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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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• What's the purpose of having a separate "operator new[]" ?

  - by sharptooth

  Looks like operator new and operator new[] have exactly the same signature: void* operator new( size_t size ); void* operator new[]( size_t size ); and do exactly the same: either return a pointer to a big enough block of raw (not initialized in any way) memory or throw an exception. Also operator new is called internally when I create an object with new and operator new[] - when I create an array of objects with new[]. Still the above two special functions are called by C++ internally in exactly the same manner and I don't se how the two calls can have different meanings. What's the purpose of having two different functions with exactly the same signatures and exactly the same behavior?

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• ASP.NET MVC, JSON & non JavaScript clients

  - by redsquare

  I need to ensure that an application I am developing is accessable and also works with JavaScript turned off. I just need a pointer to assist with the following. I had 3 'chained' select boxes and I wanted JavaScript enabled clients to have a nice Ajax experience. I can easily write the required functionality to populate the chained boxes on the change event of the preceeding select using jQuery and JSON with a WCF service. However what about the non JavaScript client? Would I wrap a submit next to the select and place these inside their own form to post back with a certain action or different querstring parameter? Can the same controller give me a partial JSON response as well as feeding the full HTML response. Can anyone point me to a good demo that utilises both JSON and normal HTTP posts to produce the same result in ASP.NET MVC. All ASP.NET MVC demo/examples I see forget about the non JavaScript enabled client.

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• Avoiding Nested Blocks

  - by Helium3

  If there is a view controller that wants to execute a number of block based tasks one at a time, how can the control be given back to the view controller after a completion block has executed. Lets say ViewControllerOne wants to execute a number of tasks, each relying on the result of the previous one, how would this control be given back to the viewcontroller after each completion block has been executed? I started thinking about this and I was heading towards a deeply nested block pattern that will surely only cause confusion to whoever else reads or tests it. A task executes and the completion block returns the result or error which is needed by the next task, which has its own completion task, that the next task relies on and so forth. How can the control be managed in one place, the viewcontroller? Would the completion block just call the next function that handles the next task, using a pointer to the view controller?

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• Django sys.path.append for project *and* app needed under WSGI

  - by GerardJP

  Hi all, Could somebody give me a pointer on why I need to add my project root path to the python path as well as the application itself in my WSGI file? Project base is called 'djapp', the application is called 'myapp'. sys.path.append(os.path.dirname(os.path.abspath(__file__)) + '/..') sys.path.append(os.path.dirname(os.path.abspath(__file__)) + '/../djapp') os.environ['DJANGO_SETTINGS_MODULE'] = 'djapp.settings' If I omit the line with "/../djapp/" the log tells my that 'myapp' can not be imported, even though 'djapp.settings' is. (validating 'djapp' was imported) It al runs properly with the ./manage.py command. there's a __init__ in the project folder. For testings sake, I see the same issue using addsitedir: site.addsitedir('/home/user/web/project/') site.addsitedir('/home/user/web/project/djapp') Thanx a lot. Gerard.

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• Windows debugging - WinDbg

  - by Santhosh77

  Hi, I got the following error while debuggging a process with its core dump. 0:000 !lmi test.exe Loaded Module Info: [test.exe] Module: test Base Address: 00400000 Image Name: test.exe Machine Type: 332 (I386) Time Stamp: 4a3a38ec Thu Jun 18 07:54:04 2009 Size: 27000 CheckSum: 54c30 Characteristics: 10f Debug Data Dirs: Type Size VA Pointer MISC 110, 0, 21000 [Debug data not mapped] FPO 50, 0, 21110 [Debug data not mapped] CODEVIEW 31820, 0, 21160 [Debug data not mapped] - Can't validate symbols, if present. Image Type: FILE - Image read successfully from debugger. test.exe Symbol Type: CV - Symbols loaded successfully from image path. Load Report: cv symbols & lines Does any body know what the error "CODEVIEW 31820, 0, 21160 [Debug data not mapped] - Can't validate symbols, if present." really mean? Is this error meant that i can't read public/private symbols from the executable? If it is not so, why does the WinDbg debugger throws this typr of error? Thanks in advance, Santhosh.

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• When to pass by value?

  - by Dervin Thunk

  Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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• Flipping around a div using Javascript

  - by Isaac Copper

  Flip is a great JQuery plugin for flipping blocks, but it doesn't preserve the background while it animates the flip. For example, I have this pretty background, here, before I flip. While flipping, it gets ugly: here. Is there a way I can flip this div nicely, keeping the pretty background I have, and maybe even achieve a smoother animation than I can get with Flip? If I need to dive into this headfirst and code my own function for flipping a div, that's also doable, and I'd really appreciate some pointer there, if that's what I must do. Thanks so much!

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• What was that tutorial on pointers?

  - by pecker

  Hello, I once read a tutorial/article on Pointers somewhere. It was not a general tutorial but it explained how to clearly understand the complex & confusing pointers (especially like the ones that are usually asked in interview). It was more like http://www.codeweblog.com/right-left-rule-complex-pointer-analysis/ I'm unable to find it. Could any one post it here. PS: I did tried to google it but couldn't find. I'm asking it here because I thought it was popular.

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• multiple C++ deletion of a memory pointed by multiple objects

  - by elgcom

  Another c++ pointer deletion question is in the following example: class Foo { public: int *p; ~Foo() { delete p; p = NULL; } }; Foo *f1 = new Foo(); Foo *f2 = new Foo(); f1->p = new int(1); f2->p = f1->p; delete f2; // ok delete f1; // no error? Why I did not get error when calling "delete f1"? didn't I delete the same address (*p) twice? If I directly delete the pointers in the last 2 lines of code, I will get error. delete f2->p; // ok delete f1->p; // error!! *** glibc detected *** double free or corruption (fasttop) ***

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• Jquery toggle should expand after Page reload

  - by James123

  I wrote below code for Collapse/Expand some section. It is working fine. Finally If I click "Save" button and I am re-loading page again in asp.net. So then sections are going default Colleapse again. I need them back to expand. How can I do that? $(function() { $('tr.subCategory') .css("cursor", "pointer") .attr("title", "Click to expand/collapse") .click(function() { $(this).siblings('.RegText-' + this.id).toggle(); }); $('tr[@class^=RegText-]').hide().children('td'); })

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• Best way to reverse bitmap data that is upside down

  - by Wladimir

  Hello, I have a method that I call and it returns bitmap data from a capture device. It returns a pointer to the buffer data as an IntPtr and the buffer length as an int. I know in advance that this bitmap is a 24bpp and its width and height. The problem is that the buffer contains the bitmap data upside down and I need this data to be in the right order (reverse it). What I do is create a for loop and using CopyMemory, I copy each line (stride) of this data from bottom to up to a newly allocated memory space. Is there any way to make it faster than creating more memory each time I receive a new frame? It makes the application get a bit slow and consumes more memory as each bitmap is pretty big. I do this because I use another component that analyses the bitmaps and it doesn't work propertly if the bitmaps are upside down. I'm using .net, c# thanks!

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• How do I modify the -encoding argument to javac in the Android Ant build system

  - by Paul Butcher

  Apologies if this is a stupid question - I'm an Android and Ant newbie. I have utf8 encoded source files that I need to compile with the Android Ant build system. By default, the encoding is set to ascii. I'd be very grateful for a pointer to whatever I need to do to let the build system know that my files are utf8. Incidentally, it works fine if I build in Eclipse, but I need to build from the command line. Thanks!

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• STL map containing references does not compile

  - by MTsoul

  The following: std::map<int, ClassA &> test; gives: error C2101: '&' on constant While the following std::map<ClassA &, int> test; gives error C2528: '_First' : pointer to reference is illegal The latter seems like map cannot contain a reference for the key value, since it needs to instantiate the class sometimes and a reference cannot be instantiated without an object. But why does the first case not work?

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• Removing a UIView from its superView and expanding its frame to full screen

  - by Magic Bullet Dave

  I have an object that is a subclass of UIView that can be added to a view hierarchy as a subView. I want to be able to remove the UIView from its superView and add it as a subView of the main window and then expand to full screen. Something along the lines of: // Remove from superView and add to mainWindow [self retain]; [self removeFromSuperView]; [self addSubView:mainWindow]; // Animate to full screen [UIView beginAnimations:@"expandToFullScreen" context:nil]; [UIView setAnimationDuration:1.0]; self.frame = [[UIScreen mainScreen] applicationFrame]; [UIView commitAnimations]; [self release]; Firstly am I on the right lines? Secondly, is there an easily way for the object to get a pointer to the mainWindow? Thanks Dave

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• How to set up a Bitmap with unmanaged data?

  - by Danvil

  I have int width, height; and IntPtr data; which comes from a unmanaged unsigned char* pointer and I would like to create a Bitmap to show the image data in a GUI. Please consider, that width must not be a multiple of 4, i do not have a "stride" and my image data is aligned as BGRA. The following code works: byte[] pixels = new byte[4*width*height]; System.Runtime.InteropServices.Marshal.Copy(data, pixels, 0, pixels.Length); var bmp = new Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppArgb); for(int i=0; i<height; i++) { for(int j=0; j<width; j++) { int p = 4*(width*i + j); bmp.SetPixel(j, i, Color.FromArgb(pixels[p+3], pixels[p+2], pixels[p+1], pixels[p+0])); } } Is there a more direct way to copy the data?

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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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• how to open many files simultaneously for reading in c

  - by monkeyking

  I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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• Treat a void function as a value

  - by Brendan Long

  I'm writing some terrible, terrible code, and I need a way to put a free() in the middle of a statement. The actual code is: int main(){ return printf("%s", isPalindrome(fgets(malloc(1000), 1000, stdin))?"Yes!\n":"No!\n") >= 0; // leak 1000 bytes of memory } I was using alloca(), but I can't be sure that will actually work on my target computer. My problem is that free returns void, so my code has this error message: error: void value not ignored as it ought to be The obvious idea I had was: int myfree(char *p){ free(p); return 0; } Which is nice in that it makes the code even more unreadable, but I'd prefer not to add another function. I also briefly tried treating free() as a function pointer, but I don't know if that would work, and I don't know enough about C to do it properly. Note: I know this is a terrible idea. Don't try this at home kids.

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• To capture Tv tuner/webcam output

  - by mawia

  Hi! all, We are developting a tool for live video streaming in which we want to broadcast the output of tv tuner on a network.Our project is at it's nascent stage.Our main concern at this moment is to how to capture the output of a tv tuner card.Plz guide us regarding this or provide a pointer where I can detail about the topic. All help will be highly appreciated. Thanks Mawia ps:project is for cross-platform but at the moment even if you tell me of any one platform it will be enough!

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• which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project?

  - by Greg

  Hi, Which lightweight SQL Server type could I use on my Dev machine for a C# VS2010 project? (e.g. sql server express, sql server ce, full version etc). That is, I'm running on a VMWare fusion instance on my MacBook, and just want something to develop against for a C# VS2010 project. I'm planning on having a simple database (not many tables) but will use Entity Framework. I haven't used SQL Server before so a quick pointer re what is the best database admin interface/app to use for the version you recommend (e.g. to create database, tables etc).

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• C++ - Opening a file inside a function using fopen

  - by Josh

  I am using Visual Studio 2005 (C++). I am passing a string into a function as a char array. I want to open the file passed in as a parameter and use it. I know my code works to an extent, because if I hardcode the filename as the first parameter it works perfectly. I do notice if I look at the value as a watch, the value includes the address aside the string literal. I have tried passing in the filename as a pointer, but it then complains about type conversion with __w64. As I said before it works fine with "filename.txt" in place of fileName. I am stumped. void read(char fileName[50],int destArray[MAX_R][MAX_C],int demSize[2]) { int rows=0; int cols=0; int row=0; int col=0; FILE * f = fopen(fileName,"r"); ...

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• Insert XML node before specific node using c#

  - by sam

  This is my XML file <employee> <name ref="a1" type="xxx"></name> <name ref="a2" type="yyy"></name> <name ref="a3" type="zzz"></name> </employee> Using C#, I need to insert this node <name ref="b2" type="aaa"></name> between the "a2" and "a3" nodes. Any pointer how to sort this out?

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