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  • how to cast an array of char into a single integer number?

    - by SepiDev
    Hi guys, i'm trying to read contents of PNG file. As you may know, all data is written in a 4-byte manner in png files, both text and numbers. so if we have number 35234 it is save in this way: [1000][1001][1010][0010]. but sometimes numbers are shorter, so the first bytes are zero, and when I read the array and cast it from char* to integer I get wrong number. for example [0000] [0000] [0001] [1011] sometimes numbers are misinterpreted as negative numbers and simetimes as zero! let me give you an intuitive example: char s_num[4] = {120, 80, 40, 1}; int t_num = 0; t_num = int(s_num); => 3215279148 ?????? the result should be 241 but the output is 3215279148? I wish I could explain my problem well! how can i cast such arrays into a single integer value?

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  • Forcibly clear memory in java

    - by MBennett
    I am writing an application in java that I care about being secure. After encrypting a byte array, I want to forcibly remove from memory anything potentially dangerous such as the key used. In the following snippet key is a byte[], as is data. SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec); byte[] encData = cipher.doFinal(data, 0, data.length); Arrays.fill(key, (byte)0); As far as I understand, the last line above overwrites the key with 0s so that it no longer contains any dangerous data, but I can't find a way to overwrite or evict secretKeySpec or cipher similarly. Is there any way to forcibly overwrite the memory held by secretKeySpec and cipher, so that if someone were to be able to view the current memory state (say, via a cold boot attack), they would not get access to this information?

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  • Dynamically creating/inserting into an associative array in PHP

    - by emil.mp
    I'm trying to build an associative array in PHP dynamically, and not quite getting my strategy right. Basically, I want to insert a value at a certain depth in the array structure, for instance: $array['first']['second']['third'] = $val; Now, the thing is, I'm not sure if that depth is available, and if it isn't, I want to create the keys (and arrays) for each level, and finally insert the value at the correct level. Since I'm doing this quite a lot in my code, I grew tired of doing a whole bunch of "array_key_exists", so I wanted to do a function that builds the array for me, given a list of the level keys. Any help on a good strategy for this is appreciated. I'm sure there is a pretty simple way, I'm just not getting it...

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  • set arraylist element as null

    - by Jessy
    The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ if(choice.get(0).equals(null)) System.out.println("I am empty"); //it doesn't print this output } }

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  • divide the image into 3*3 blocks

    - by Jayanth Silesh
    I have a matrix that does not happen to have dimensions that are multiples of 3 or it might. How can we divide the entire image into blocks of 3*3 matrices. (Can ignore the last ones which does not come under the 3*3 multiples. Also, the 3*3 matrices can be be saved in arrays. a=3; b=3; %window size x=size(f,1)/a; y=size(f,2)/b; %f is the original image m=a*ones(1,x); n=b*ones(1,y); I=mat2cell(f,m,n);

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  • Convert String containing several numbers into integers

    - by GobiasKoffi
    I realize that this question may have been asked several times in the past, but I am going to continue regardless. I have a program that is going to get a string of numbers from keyboard input. The numbers will always be in the form "66 33 9" Essentially, every number is separated with a space, and the user input will always contain a different amount of numbers. I'm aware that using 'sscanf' would work if the amount of numbers in every user-entered string was constant, but this is not the case for me. Also, because I'm new to C++, I'd prefer dealing with 'string' variables rather than arrays of chars.

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  • Radio buttons + array elements

    - by Mark
    I have a form that can be dynamically duplicated (with JS) so that the user can enter as much data as he wants. This works great for text inputs, because I just leave the name attribute the same (ending with a []) and then when the values are posted, it just returns me an array. Now I just realized that this doesn't work so well for radio buttons, because the names actually need to be unique for each set. But from the data standpoint, each set only returns one value, so retrieving the data from the POST data wouldn't be a problem, it just screws up the functionality of my form. There's no way around this, is there? I'm just screwed and I can't use arrays?

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  • Pass in Dynamic number of parameters to a stored procedure

    - by xrum
    Hi, I have a function in my .NET application, that needs to do a search of an unknown number of parameters. for example: select * from tbl where x=1 or x=2 or x=3 or x=4 is it possible to do in .NEt and SQL? how do i go about creating dynamic parameters in .NET (I was thinking doing it with a loop) but then how do i declare them in my stored procedure? does sql have arrays? please help. thank you!

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  • Convert bit vector (array of booleans) to an integer, and integer to bit vector, in Java.

    - by dreeves
    What's the best way to unstub the following functions? // Convert a bit-vector to an integer. int bitvec2int(boolean[] b) { [CODE HERE] } // Convert an integer x to an n-element bit-vector. boolean[] int2bitvec(int x, int n) { [CODE HERE] } Or is there a better way to do that sort of thing than passing boolean arrays around? This comes up in an Android app where we need an array of 20 booleans to persist and the easiest way to do that is to write an integer or string to the key-value store. I'll post the way we (Bee and I) wrote the above as an answer. Thanks!

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  • Why is this loop over mysql resultset slow? (1.4ms per cycle)

    - by pawpro
    The $res contains around 488k rows the whole loop takes 61s! that's over 1.25ms per cycle! What is taking all that time? while($row = $res->fetch_assoc()) { $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['std'] = $row['cost_std']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['ecn'] = $row['cost_ecn']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['wnd'] = $row['cost_wnd']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['other_destination'] = $row['destination_id']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['carrier_destination'] = $row['carrier_destination_id']; } Now resultset of 10 rows, smaller arrays and performance 30 times higher (0.041ms) not the fastest still but better. while($row = $res->fetch_assoc()) { $customer[$row['id']]['name'] = $row['name']; $customer[$row['id']]['code'] = $row['customer']; }

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  • Class properties vs NSArray / NSDictionary

    - by Frank Martin
    I want a custom class object to hold data and have somehow the feeling that creating about 80 properties is not the best way of doing it. Most of the properties would be bool values, so i'm thinking about creating Arrays (keys / values) or (probably better) a NSDictionary attached to the object for holding the data. Does that make sense or should i stay with the properties? Extra: Are there general pros and cons for the different approaches? And what keywords / concepts do i have to search for to find discussions about that somehow general question? Thanks in advance

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  • How can I write faster JavaScript?

    - by a paid nerd
    I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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  • In scala can I pass repeated parameters to other methods?

    - by Fred Haslam
    Here is something I can do in java, take the results of a repeated parameter and pass it to another method: public void foo(String ... args){bar(args);} public void bar(String ... args){System.out.println("count="+args.length);} In scala it would look like this: def foo(args:String*) = bar(args) def bar(args:String*) = println("count="+args.length) But this won't compile, the bar signature expects a series of individual strings, and the args passed in is some non-string structure. For now I'm just passing around arrays. It would be very nice to use starred parameters. Is there some way to do it?

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  • OpenGL Mapping Textures to a Grid Stored Inside Vertex Array

    - by Matthew Hoggan
    I am writing a test to verify something. This is not production code, just verification code. So I would appreciate it if the specific question was answered. I have code that uses indices and vertices to draw a set of triangles in the shape of a grid. All the vertices are drawn using glDrawElements(). Now for each vertex I will set its corresponding Texture Coordinates to 0 or 1 for each set of triangles that form a square in the grid. Basically I want to draw a collage of random textures in each one of the "squares" (consisting of two triangles). I can do this using the glBegin() and glEnd() method calls inside a for loop using the fixed functional pipeline, but I would like to know how to do this using Vertex Arrays.

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  • What exactly does a self-describing type in .Net mean?

    - by tzup
    Given this MSDN article, we learn that the Common Type System in .Net has this classification of reference types: "Reference types can be self-describing types, pointer types, or interface types. The type of a reference type can be determined from values of self-describing types. Self-describing types are further split into arrays and class types." So an array, for instance, is a self-describing type because we can determine it's type from its values? How? Is that it, or is there more to this definition?

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  • How do I change the number of thumbnails seen in the Android sample Home application?

    - by Todd
    I am working with the sample Home application project on http://developer.android.com/resources/samples/Home/index.html I've added another value to the THUMBS_IDS and IMAGE_IDS Integer arrays in the Wallpaper class for a total of four wallpaper options. When I run the application with Device API version 7, Skin: HVGA, hw.lcd.density: 160, in portrait layout, the fourth wallpaper option is not shown. I need to use the directional keys in the emulator to see the 4th wallpaper option, because the first option is centered. I have modified only the wallpaper.xml file with a variety of android:layout_* options with no success at this point. How do I show all four of my wallpaper options?

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  • Help with validation rules

    - by George Garman
    I am trying to figure out how to validate a section of a form using php. If at least one of value 1-5 is checked, then at least one of value A-E must be checked. Value's A-E cannot be allowed without at least one of 1-5 being checked. Multiple values in each section can be selected, as long as there is at least one value in each section checked. I have tried individual IF statements and arrays without success. Does anyone have any suggestions or examples? I am missing something and I am certain it is pretty obvious, right in my face.

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  • NSArray : release its objects, but keep a pointer to it.

    - by Leo
    Hello, I declare an NSArray in my code then building the array from another array. I process my NSArray and when I'm finished, I would like to release the objects, but I'm reusing this pointer to NSAarray again later to do the same process (creating the array from another array, process then releasing).. So I need to keep the pointer. What should I do ? Here is roughly what I want to do, the buildArray is creating and returning an autoreleased NSArray : NSArray *myArray; for (int i = 0, i < 10, i++){ [myArray arrayWithArray:[self buildArray]]; // Here I process myArray [myArray = nil] // is my guess } I need to keep a pointer to my NSArray, in order to reuse later in the loop, but what is happening to the objects created with [self buildArray]? What is the best to do in order not to keep unused object and arrays ? Or maybe the best solution is simply to removeAllObject of the array..? Thank you!

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  • Incompatible format types

    - by nebffa
    I'm playing around with strncpy in C and am having some trouble. The code is as follows: #include <stdio.h> #include <string.h> int main(int argc, char *argv[]) { char src[] = "Benjamin Franklin"; char dest[5]; strncpy(src, dest, sizeof(dest) / sizeof(char)); dest[5] = '\0'; printf("%s\n", dest); return 0; } which compiles with no errors using: gcc -Wall -g -Werror test.c -o test and prints out gibberish like p4?? I cannot really understand what I'm doing wrong especially since I have played around with it a lot and been looking online for answers. Perhaps since I am using arrays I am passing the address to printf without realising it?

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  • Fortran - String with unknown characters into substrings

    - by Masoud
    I am trying to put an input string into sub-string arrays. The number of data in the input file are less than 10 but unknown. The number of spaces between each data is also unclear. Example: Asd B Cwqe21 Ddsw Eww I am quite novice to Fortran, so I do not know which format I should use. My problem is that I do not know the number of data (here I assumed that there are 5), so how can I make the code work? I tried the following which did not work: CHARACTER (LEN=100), DIMENSION(10) :: string READ (1,*) (string,I=1,10) It seems that the error I got was because there was no 6th string to read and put into string(6). I tried using the "Index" to find the space, but since I do not know how many spaces are in the string, it did not help me.

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  • Java: ListA.addAll(ListB) fires NullPointerException?

    - by HH
    The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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  • Large amount of constants in Java

    - by Lars D
    I need to include about 1 MByte of data in a Java application, for very fast and easy access in the rest of the source code. My main background is not Java, so my initial idea was to convert the data directly to Java source code, defining 1MByte of constant arrays, classes (instead of C++ struct) etc., something like this: public final/immutable/const MyClass MyList[] = { { 23012, 22, "Hamburger"} , { 28375, 123, "Kieler"} }; However, it seems that Java does not support such constructs. Is this correct? If yes, what is the best solution to this problem?

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  • from JS to iphone dev - what's the best language to start with?

    - by Enkai
    I am a total beginner and would like to eventually learn to develop for the iphone. I have just done a beginner's CS course where the language we learned was JavaScript. We studied basic concepts like: variables, arrays, loops (for,while,if,if..else..), properties and functions. I'm wondering if I am starting in the right/wrong place by following this book: Learn C on the Mac by Dave Mark? I have read a few chapters and am finding it a bit hard to get my head around the way that C works, for example the way that Strings are printed seems overly complicated as compared to JS. Do you think that JS was the wrong language to start off with and would I be better to go from JS straight to Objective-C rather than to C? I have tried to read up on previous threads on the merits/demerits of learning C first but haven't found any that relate JS to learning C/Obj C/ Cocoa. Any advice appreciated as I am very new to this. Thanks

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  • What can cause reset connection when running PHP script?

    - by marcin_koss
    I've developed a web application with CodeIgniter that works perfectly on my local machines (one with windows and one with Linux). When I moved it to my hosting server, connection gets reset when running one particular PHP script that does a few MySQL queries and some operations on arrays. The data I'm querying is small, just a few tables with up to 25 records. Firefox returns "The connection was reset" after maybe 2-3 seconds. I checked the servers error logs but there was nothing there. Unfortunately I don't have access to Apache error logs. What can cause this behavior?

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