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  • What does this pointer-heavy C code do?

    - by justRadojko
    Could someone explain to me what should two following lines do: s.httpheaderline[s.httpheaderlineptr] = *(char *)uip_appdata; ++((char *)uip_appdata); This is taken from uIP code for microcontrollers. s - structure httpheaderline - http packet presented as a string httpheadrlineptr - integer value uip_appdata - received ethernet packet (string) If some more info is needed please let me know. BTW. Eclipse is reporting an error on the second line with message Invalid lvalue in increment so i'm trying to figure out how to solve this.

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  • Cast A primitive type pointer to A structure pointer - Alignment and Padding?

    - by Seçkin Savasçi
    Just 20 minutes age when I answered a question, I come up with an interesting scenario that I'm not sure of the behavior: Let me have an integer array of size n, pointed by intPtr; int* intPtr; and let me also have a struct like this: typedef struct { int val1; int val2; //and less or more integer declarations goes on like this(not any other type) }intStruct; My question is if I do a cast intStruct* structPtr = (intStruct*) intPtr; Am I sure to get every element correctly if I traverse the elements of the struct? Is there any possibility of miss-alignment(possible because of padding) in any architecture/compiler?

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  • javascript function pointer and "this"

    - by Justin808
    I'm passing a method as a variable to be used as a callback. When its called, the "this" is not the object the method is a member of. How do I go about getting access to the method's object instance so I can get access to it variables and other member functions? I have no control over the callback call method, its a separate library. All I do is call the binding from my object init method. I would have expected this inside my _connection method to have been its object. jsPlumb.bind('connection', this._connection);

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  • Void pointer cast C++ and GTK

    - by Tarantula
    See this GTK callback function: static gboolean callback(GtkWidget *widget, GdkEventButton *event, gpointer *data) { AnyClass *obj = (AnyClass*) data; // using obj works } (please note the gpointer* on the data). And then the signal is connected using: AnyClass *obj2 = new AnyClass(); gtk_signal_connect(/*GTK params (...)*/, callback, obj2); See that the *AnyClass is going to be cast to gpointer* (void**). In fact, this is working now. The callback prototype in GTK documentation is "gpointer data" and not "gpointer *data" as shown in code, what I want to know is: how this can work ? Is this safe ?

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  • Misaligned Pointer Performance

    - by Elite Mx
    Aren't misaligned pointers (in the BEST possible case) supposed to slow down performance and in the worst case crash your program (assuming the compiler was nice enough to compile your invalid c program). Well, the following code doesn't seem to have any performance differences between the aligned and misaligned versions. Why is that? /* brutality.c */ #ifdef BRUTALITY xs = (unsigned long *) ((unsigned char *) xs + 1); #endif ... /* main.c */ #include <stdio.h> #include <stdlib.h> #define size_t_max ((size_t)-1) #define max_count(var) (size_t_max / (sizeof var)) int main(int argc, char *argv[]) { unsigned long sum, *xs, *itr, *xs_end; size_t element_count = max_count(*xs) >> 4; xs = malloc(element_count * (sizeof *xs)); if(!xs) exit(1); xs_end = xs + element_count - 1; sum = 0; for(itr = xs; itr < xs_end; itr++) *itr = 0; #include "brutality.c" itr = xs; while(itr < xs_end) sum += *itr++; printf("%lu\n", sum); /* we could free the malloc-ed memory here */ /* but we are almost done */ exit(0); } Compiled and tested on two separate machines using gcc -pedantic -Wall -O0 -std=c99 main.c for i in {0..9}; do time ./a.out; done

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  • question regarding "this" pointer in c++

    - by sil3nt
    hello there, i have been given class with int variables x and y in private, and an operator overload function, class Bag{ private: int x; int y; public: Bag(); ~Bag(); //....... //.....etc }; Bag operator+ (Bag new) const{ Bag result(*this); //what does this mean? result.x += new.x; result.y += new.y; } What is the effect of having "Bag result(*this);" there?.

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  • Doubt regarding usage of array as a pointer in C

    - by Som
    For eg. I have an array of structs 'a' as below: struct mystruct{ int b int num; }; struct bigger_struct { struct my_struct a[10]; } struct bigger_struct *some_var; i know that the name of an array when used as a value implicitly refers to the address of the first element of the array.(Which is how the array subscript operator works at-least) Can i know do the other way around i.e if i do: some_var->a->b, it should be equivalent to some_var->a[0]->b, am i right? I have tested this and it seems to work , but is this semantically 100% correct?

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  • Why do I get a Null Pointer Exception?

    - by Roman
    I have this code: Manager manager = new Manager("Name"); MyWindowListener windowListener = new MyWindowListener(); manager.addWindowListener(windowListener); Eclipse writes that I have a NullPointerException in the last line. What can be the reason for that. I do have constructors in the Manager and MyWindowListener. If it's important MyWindowListener implements WindowListener.

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  • C/C++ opaque pointer library

    - by aaa
    hello Is there library/header already written to manage C++ objects from C using opaque pointers/handles? I can write one myself, but I would rather use already made solution, especially if it has fortran bindings. Thanks

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  • Extract inputs from a pointer to array of characters in C / C++

    - by user2066884
    I am writing a command line utility but I cannot find a way to store the commands and arguments. so far I have the following but I get a Segmentation fault: int main(void) { char *command; char *args[MAX_LINE/2 + 1]; int should_run = 1; do{ cout << "cmd> "; int counter = 0; while(cin >> command) { strcpy(args[counter],command); counter++; } cout << args[0] << "\n"; } }

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  • Obtaining frame pointer in C

    - by assketchum
    I'm trying to get the FP in my C program, I tried two different ways, but they both differ from what I get when I run GDB. The first way I tried, I made a protocol function in C for the Assembly function: int* getEbp(); and my code looks like this: int* ebp = getEbp(); printf("ebp: %08x\n", ebp); // value i get here is 0xbfe2db58 while( esp <= ebp ) esp -= 4; printf( "ebp: %08x, esp" ); //value i get here is 0xbfe2daec My assembly code getEbp: movl %ebp, %eax ret I tried making the prototype function to just return an int, but that also doesn't match up with my GDB output. We are using x86 assembly. EDIT: typos, and my getEsp function looks exactly like the other one: getEsp: movl %esp, %eax ret

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  • Changing Value of Array Pointer When Passed to a Function

    - by ZAX
    I have a function which receives both the array, and a specific instance of the array. I try to change the specific instance of the array by accessing one of its members "color", but it does not actually change it, as can be seen by debugging (checking the value of color after function runs in the main program). I am hoping someone can help me to access this member and change it. Essentially I need the instance of the array I'm specifying to be passed by reference if nothing else, but I'm hoping there is an easier way to accomplish what I'm trying to do. Here's the structures: typedef struct adjEdge{ int vertex; struct adjEdge *next; } adjEdge; typedef struct vertex{ int sink; int source; int color; //0 will be white, 1 will be grey, 5 will be black int number; adjEdge *nextVertex; } vertex; And here is the function: void walk(vertex *vertexArray, vertex v, int source, maxPairing *head) { int i; adjEdge *traverse; int moveVertex; int sink; traverse = vertexArray[v.number-1].nextVertex; if(v.color != 5 && v.sink == 5) { sink = v.number; v.color = 5; addMaxPair(head, source, sink); } else { walk(vertexArray, vertexArray[traverse->vertex-1], source, head); } } In particular, v.color needs to be changed to a 5, that way later after recursion the if condition blocks it.

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  • cant figure out pointer assignment in c

    - by vadiklk
    int add(char *var1, char *var2, char **var3) { int num1, num2, length1 = strlen(var1), length2 = strlen(var2), length = max(length1, length2) + 1; char *result = (char*) calloc(length, sizeof(char)); ... free(*var3); *var3 = result; return 0; } out side of the function i get its still nothing(var3); more detail: int addSubCommand(char **vars, int isAdd) { ... return add(vars[index1], var2, &(vars[index3])); } that's where i call add. the char** vars goes from every function to the other.

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  • emule algorithm and how to get fast download speed.

    - by Benjamin
    Actually, I use amule in ubuntu. Because emule users are much more, I wrote emule in this title. But whatever emule or amule, it's okay. Both of them are very similar. I want to get fast-download speed as much as I can. But I don't understand emule(or amule)'s detail functions and algorithms. These are always very qurious to me. If I provide higher upload-speed or more valuable files to other people, can I get benefit?(My download speed) Is serverlist important? Does it cause my download-speed? I captured a image for my amule. Please explain these columns and let me know your tips for getting fast speed. What does 8/9+23 mean in the Source column? What does 294/300(1) mean in the Source column? What does QR:608(0) mean in the Priority? What do I do for getting fast download speed as much as I can get? You can also explain other columns.

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  • Do PHP Framworks Speed Up the Development Process?

    - by Jacob
    I recently started working for a web firm as a freelancer taking my hobby of coding in PHP to a career level, and since then I have been overwhelmed by the amount of work that needs to be done within short time frames. The problem isn't being able to do what is asked, but being able to do it all as quickly as is needed of me. I never used any PHP frameworks, but if I started using one, would that speed up the entire development process? If so, how drastically? Also which framework would be best for my purpose? If it matters, what I do is mostly build back end cms's and tie that with front end functionality for small business client sites.

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  • PHP, ImageMagick, Google's Page Speed, & JPG File Size Optimization

    - by Sonny
    I have photo gallery code that does image re-sizing and thumbnail creation. I use ImageMagick to do this. I ran a gallery page through Google's Page Speed tool and it revealed that the re-sized images and thumbnails both have about an extra 10KB of data (JPEG files specifically). What can I add to my scripts to optimize the file size? ADDITIONAL INFORMATION I am using the imagick::FILTER_LANCZOS filter with a blur setting of 0.9 when calling the resizeImage() function. JPEGs have a quality setting of 80.

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  • JPG File Size Optimization - PHP, ImageMagick, & Google's Page Speed

    - by Sonny
    I have photo gallery code that does image re-sizing and thumbnail creation. I use ImageMagick to do this. I ran a gallery page through Google's Page Speed tool and it revealed that the re-sized images and thumbnails both have about an extra 10KB of data (JPEG files specifically). What can I add to my scripts to optimize the file size? ADDITIONAL INFORMATION I am using the imagick::FILTER_LANCZOS filter with a blur setting of 0.9 when calling the resizeImage() function. JPEGs have a quality setting of 80.

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  • Speed improvements for Perl's chameneos-redux in the Computer Language Benchmarks Game

    - by Robert P
    Ever looked at the Computer Language Benchmarks Game (formerly known as the Great Language Shootout)? Perl has some pretty healthy competition there at the moment. It also occurs to me that there's probably some places that Perl's scores could be improved. The biggest one is in the chameneos-redux script right now—the Perl version runs the worst out of any language: 1,626 times slower than the C baseline solution! There are some restrictions on how the programs can be made and optimized, and there is Perl's interpreted runtime penalty, but 1,626 times? There's got to be something that can get the runtime of this program way down. Taking a look at the source code and the challenge, how can the speed be improved?

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  • Let system time determine animation speed, not program FPS

    - by Anders
    I'm writing a card game in ActionScript 3. Each card is represented by an instance of a class extending movieclip exported from Flash CS4 that contains the card graphics and a flip animation. When I want to flip a card I call gotoAndPlay on this movieclip. When the frame rate slows down all animations take longer to finish. It seems Flash will by default animate movieclips in a way that makes sure all frames in the clip will be drawn. Therefor, when the program frame rate goes below the frame rate of the clip, the animation will be played at a slower pace. I would like to have an animation always play at the same speed and as a consequence always be shown on the screen for the same amount of time. If the frame rate is too slow to show all frames, frames are dropped. Is is possible to tell Flash to animate in this way? If not, what is the easiest way to program this behavior myself?

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  • Speed improvements for Perl's chameneos-redux script in the Computer Language Benchmarks Game

    - by Robert P
    Ever looked at the Computer Language Benchmarks Game, (formerly known as the Great Language Shootout)? Perl has some pretty healthy competition there at the moment. It also occurs to me that there's probably some places that Perl's scores could be improved. The biggest one is in the chameneos-redux script right now - the Perl version runs the worst out of any language : 1,626 times slower than the C baseline solution! There are some restrictions on how the programs can be made and optimized, and there is Perl's interpreted runtime penalty, but 1,626 times? There's got to be something that can get the runtime of this program way down. Taking a look at the source code and the challenge, what do you think could be done to reduce this runtime speed?

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  • Is Code Completion speed improved in Delphi 2010?

    - by Holgerwa
    I am working with Delphi 2009 Pro and just tried to find out why code completion is so slow in my setup. Whenever code completion is invoked, the IDE locks up for up to 30s, which really interrupts any workflow. When working with BDS 2006, code completion was incredibly fast compared to Delphi 2009. After reading this post it seems to be normal for Delphi 2009, but just turning off the automatic code completion is not anything I want to do. My question is: If I switch to Delphi 2010, will I have the same slow speed for code completion or was it improved to a point to be usable?

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  • speed up a sql query to mysql?

    - by fayer
    in my mysql database i've got the geonames database, containing all countries, states and cities. i am using this to create a cascading menu so the user could select where he is from: country - state - county - city. but the main problem is that the query will search through all the 7 millions rows in that table each time i want to get the list of children rows, and that is taking a while 10-15 seconds. i wonder how i could speed this up: caching? table views? reorganizing table structure somehow? and most important, how do i do these things? are there good tutorials you could link to me? i appreciate all help and feedback discussing smart ways of handling this issue!

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  • Play a beep that loop and change the frequency/speed

    - by Bono
    Hi all, I am creating an iphone application that use audio. I want to play a beep sound that loop indefinitely. I found an easy way to do that using the upper layer AVAudioPlayer and the numberOfLoops set to "-1". It works fine. But now I want to play this audio and be able to change the rate / speed. It may works like the sound played by a car when approaching an obstacle. At the beginning the beep has a low frequency and this frequency accelerate till reaching a continuous sound biiiiiiiiiiiip ... It seems this is not feasible using the high layer AVAudioPlayer, but even looking at AudioToolBox I found no solution. Does anybody have informations about how to do that? Thanks a lot for helping me!

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  • Java paint speed relative to color model

    - by Jon
    I have a BufferedImage with an IndexColorModel. I need to paint that image onto the screen, but I've noticed that this is slow when using an IndexColorModel. However, if I run the BufferedImage through an identity affine transform it creates an image with a DirectColorModel and the painting is significantly faster. Here's the code I'm using AffineTransformOp identityOp = new AffineTransformOp(new AffineTransform(), AffineTransformOp.TYPE_BILINEAR); displayImage = identityOp.filter(displayImage, null); I have three questions 1. Why is painting the slower on an IndexColorModel? 2. Is there any way to speed up the painting of an IndexColorModel? 3. If the answer to 2. is no, is this the most efficient way to convert from an IndexColorModel to a DirectColorModel? I've noticed that this conversion is dependent on the size of the image, and I'd like to remove that dependency. Thanks for the help

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  • making use of c++ to speed up php

    - by Ygam
    I saw this post on Sitepoint quoting a statement by Rasmus Lerdorf which goes (according to Sitepoint) as follows: "How can you make PHP fast? Well, you can’t" was his quick answer. PHP is simply not fast enough to scale to Yahoo levels. PHP was never meant for those sorts of tasks. "Any script based language is simply not fast enough". To get the speed that is necessary for truly massive web systems you have to use compiled C++ extensions to get true, scaleable architecture. That is what Yahoo does and so do many other PHP heavyweights. Intrigued by the statement (not to mention the fact that up to now, all I was doing in PHP was small database-based apps), I was wondering how I could "use compiled C++ extensions" with PHP. Any ideas or resources?

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