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• .Net oracle parameter order

  - by jkrebsbach

  Using the ODAC (Oracle Data Access Components) downloaded from Oracle to talk to a handfull of Oracle DBs - Was putting together my DAL to update the DB, and things weren't working as I hoped - UPDATE foo SET bar = :P_BAR WHERE bap = :P_BAP I assign my parameters - objCmd.Parameters.Add(objBap); objCmd.Parameters.Add(objBar);   Execute update command - int result = objCmd.ExecuteNonQuery() and result is zero! ...  Is my filter incorrect? SELECT count(*) FROM foo WHERE bap = :P_BAP ...result is one... Is my new value incorrect?  Am I using Char instead of Varchar somewhere and need an RTRIM?  Is there a transaction getting involved?  An error thrown and not caught? The answer: Order of parameters.   The order parameters are added to the Oracle Command object must match the order the parameters are referenced in the SQL statement.  I was adding the parameters for the WHERE clause before adding the SET value parameters, and for that reason although no error was being thrown, no value was updated either. Flip parameter collection around to match order of params in the SQL statement, and ExecuteNonQuery() is back to returning the number of rows affected.

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• Can't read .cso files but I can read their .hlsl versions?

  - by Jader J Rivera

  Well I've been trying to read a .cso file to use as a shader for a DirectX program I'm currently making. Problem is no matter how I implemented a way to read the file it never worked. And after fidgeting around I discover that it's only the .cso files I can't read. I can read anything else (which means it works) even their .hlsl files. Which is strange because the .hlsl (high level shader language) files are supposed to turn into .cso (compiled shader object) files. What I'm currently doing is: vector<byte> Read(string File){ vector<byte> Text; fstream file(File, ios::in | ios::ate | ios::binary); if(file.is_open()){ Text.resize(file.tellg()); file.seekg(0 , ios::beg); file.read(reinterpret_cast<char*>(&Text[0]), Text.size()); file.close(); } return Text; }; If I then implement it. Read("VertexShader.hlsl"); //Works Read("VertexShader.cso"); //Doesn't Works?!?! And I need the .cso version of the shader to draw my sexy triangles. Without it my life and application will never continue and I have no idea what could be wrong. (I've also asked this at stack overflow but still no answers.)

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• How to use Pixel Bender (pbj) in ActionScript3 on large Vectors to make fast calculations?

  - by Arthur Wulf White

  Remember my old question: 2d game view camera zoom, rotation & offset using 'Filter' / 'Shader' processing? I figured I could use a Pixel Bender Shader to do the computation for any large group of elements in a game to save on processing time. At least it's a theory worth checking. I also read this question: Pass large array to pixel shader Which I'm guessing is about accomplishing the same thing in a different language. I read this tutorial: http://unitzeroone.com/blog/2009/03/18/flash-10-massive-amounts-of-3d-particles-with-alchemy-source-included/ I am attempting to do some tests. Here is some of the code: private const SIZE : int = Math.pow(10, 5); private var testVectorNum : Vector.<Number>; private function testShader():void { shader.data.ab.value = [1.0, 8.0]; shader.data.src.input = testVectorNum; shader.data.src.width = SIZE/400; shader.data.src.height = 100; shaderJob = new ShaderJob(shader, testVectorNum, SIZE / 4, 1); var time : int = getTimer(), i : int = 0; shaderJob.start(true); trace("TEST1 : ", getTimer() - time); } The problem is that I keep getting a error saying: [Fault] exception, information=Error: Error #1000: The system is out of memory. Update: I managed to partially workaround the problem by converting the vector into bitmapData: (Using this technique I still get a speed boost of 3x using Pixel Bender) private function testShader():void { shader.data.ab.value = [1.0, 8.0]; var time : int = getTimer(), i : int = 0; testBitmapData.setVector(testBitmapData.rect, testVectorInt); shader.data.src.input = testBitmapData; shaderJob = new ShaderJob(shader, testBitmapData); shaderJob.start(true); testVectorInt = testBitmapData.getVector(testBitmapData.rect); trace("TEST1 : ", getTimer() - time); }

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• Script language native extensions - avoiding name collisions and cluttering others' namespace

  - by H2CO3

  I have developed a small scripting language and I've just started writing the very first native library bindings. This is practically the first time I'm writing a native extension to a script language, so I've run into a conceptual issue. I'd like to write glue code for popular libraries so that they can be used from this language, and because of the design of the engine I've written, this is achieved using an array of C structs describing the function name visible by the virtual machine, along with a function pointer. Thus, a native binding is really just a global array variable, and now I must obviously give it a (preferably good) name. In C, it's idiomatic to put one's own functions in a "namespace" by prepending a custom prefix to function names, as in myscript_parse_source() or myscript_run_bytecode(). The custom name shall ideally describe the name of the library which it is part of. Here arises the confusion. Let's say I'm writing a binding for libcURL. In this case, it seems reasonable to call my extension library curl_myscript_binding, like this: MYSCRIPT_API const MyScriptExtFunc curl_myscript_lib[10]; But now this collides with the curl namespace. (I have even thought about calling it curlmyscript_lib but unfortunately, libcURL does not exclusively use the curl_ prefix -- the public APIs contain macros like CURLCODE_* and CURLOPT_*, so I assume this would clutter the namespace as well.) Another option would be to declare it as myscript_curl_lib, but that's good only as long as I'm the only one who writes bindings (since I know what I am doing with my namespace). As soon as other contributors start to add their own native bindings, they now clutter the myscript namespace. (I've done some research, and it seems that for example the Perl cURL binding follows this pattern. Not sure what I should think about that...) So how do you suggest I name my variables? Are there any general guidelines that should be followed?

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• How can I resolve component types in a way that supports adding new types relatively easily?

  - by John

  I am trying to build an Entity Component System for an interactive application developed using C++ and OpenGL. My question is quite simple. In my GameObject class I have a collection of Components. I can add and retrieve components. class GameObject: public Object { public: GameObject(std::string objectName); ~GameObject(void); Component * AddComponent(std::string name); Component * AddComponent(Component componentType); Component * GetComponent (std::string TypeName); Component * GetComponent (<Component Type Here>); private: std::map<std::string,Component*> m_components; }; I will have a collection of components that inherit from the base Components class. So if I have a meshRenderer component and would like to do the following GameObject * warship = new GameObject("myLovelyWarship"); MeshRenderer * meshRenderer = warship->AddComponent(MeshRenderer); or possibly MeshRenderer * meshRenderer = warship->AddComponent("MeshRenderer"); I could be make a Component Factory like this: class ComponentFactory { public: static Component * CreateComponent(const std::string &compTyp) { if(compTyp == "MeshRenderer") return new MeshRenderer; if(compTyp == "Collider") return new Collider; return NULL; } }; However, I feel like I should not have to keep updating the Component Factory every time I want to create a new custom Component but it is an option. Is there a more proper way to add and retrieve these components? Is standard templates another solution?

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• Ray Tracing concers: Efficient Data Structure and Photon Mapping

  - by Grieverheart

  I'm trying to build a simple ray tracer for specific target scenes. An example of such scene can be seen below. I'm concerned as to what accelerating data structure would be most efficient in this case since all objects are touching but on the other hand, the scene is uniform. The objects in my ray tracer are stored as a collection of triangles, thus I also have access to individual triangles. Also, when trying to find the bounding box of the scene, how should infinite planes be handled? Should one instead use the viewing frustum to calculate the bounding box? A few other questions I have are about photon mapping. I've read the original paper by Jensen and many more material. In the compact data structure for the photon they introduce, they store photon power as 4 chars, which from my understanding is 3 chars for color and 1 for flux. But I don't understand how 1 char is enough to store a flux of the order of 1/n, where n is the number of photons (I'm also a bit confused about flux vs power). The other question about photon mapping is, if it would be more efficient in my case to store photons per object (or even per Object's triangle) instead of using a balanced kd-tree. Also, same question about bounding box of the scene but for photon mapping. How should one find a bounding box from the pov of the light when infinite planes are involved?

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• Accessing second hard drive

  - by Jonathan

  Hi, So I recently installed Ubuntu 10.10 64-bit on my computer. I installed it on my 60gb SSD hard drive, and in the installation it never acknowledged the existence of my second hard drive. The hard drive that I keep all my files on, and which I want to make my home folder if I can, is a Western Digital Caviar Black 1TB SATA 6Gb/s 64MB cache (WD1002FAEX). I've read the following: https://help.ubuntu.com/community/Mount but honestly cannot work out how to access the hard drive from my Ubuntu installation. I did have Windows 7 64-bit prior to installing Ubuntu. I have backed up all the files on the hard drive, but if I could just access them straight off that would be super cool. Does anyone know how I can use the second hard drive? Thank you for your help EDIT: The following directories are currently in my /dev/ folder: ati/, block/, bsg/, bus/, char/, cpu/, isk/, input/, mapper/, net/, pktcdvd/, pts/, shm/, snd/, and usb/ EDIT: Result from sudo fdisk -l Disk /dev/sda: 60.0 GB, 60022480896 bytes 255 heads, 63 sectors/track, 7297 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000d2dfd Device Boot Start End Blocks Id System /dev/sda1 * 1 6994 56174592 83 Linux /dev/sda2 6994 7298 2438145 5 Extended /dev/sda5 6994 7298 2438144 82 Linux swap / Solaris

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• Unrealscript splitting a string

  - by burntsugar

  Note, this is repost from stackoverflow - I have only just discovered this site :) I need to split a string in Unrealscript, in the same way that Java's split function works. For instance - return the string "foo" as an array of char. I have tried to use the SplitString function: array SplitString( string Source, optional string Delimiter=",", optional bool bCullEmpty ) Wrapper for splitting a string into an array of strings using a single expression. as found at http://udn.epicgames.com/Three/UnrealScriptFunctions.html but it returns the entire String. simulated function wordDraw() { local String inputString; inputString = "trolls"; local string whatwillitbe; local int b; local int x; local array<String> letterArray; letterArray = SplitString(inputString,, false); for (x = 0; x < letterArray.Length; x++) { whatwillitbe = letterArray[x]; `log('it will be '@whatwillitbe); b = letterarray.Length; `log('letterarray length is '@b); `log('letter number '@x); } } Output is: b returns: 1 whatwillitbe returns: trolls However I would like b to return 6 and whatwillitbe to return each character individually. I have had a few answers proposed, however, I would still like to properly understand how the SplitString function works. For instance, if the Delimiter parameter is optional, what does the function use as a delimiter by default?

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• OpenGL ES rotate texture

  - by 0xSina

  I just got started with OpenGL ES... I have a fragment: const char * sFragment = _STRINGIFY( varying highp vec2 coordinate; precision mediump float; uniform vec4 maskC; uniform float threshold; uniform sampler2D videoframe; uniform sampler2D videosprite; uniform vec4 mask; uniform vec4 maskB; uniform int recording; vec3 normalize(vec3 color, float meanr) { return color*vec3(0.75 + meanr, 1., 1. - meanr); } void main() { float d; float dB; float dC; float meanr; float meanrB; float meanrC; float minD; vec4 pixelColor; vec4 spriteColor; pixelColor = texture2D(videoframe, coordinate); spriteColor = texture2D(videosprite, coordinate); meanr = (pixelColor.r + mask.r)/8.; meanrB = (pixelColor.r + maskB.r)/8.; meanrC = (pixelColor.r + maskC.r)/8.; d = distance(normalize(pixelColor.rgb, meanr), normalize(mask.rgb, meanr)); dB = distance(normalize(pixelColor.rgb, meanrB), normalize(maskB.rgb, meanrB)); dC = distance(normalize(pixelColor.rgb, meanrC), normalize(maskC.rgb, meanrC)); minD = min(d, dB); minD = min(minD, dC); gl_FragColor = spriteColor; if (minD > threshold) { gl_FragColor = pixelColor; } } Now, depending on wether recording is 0 or 1, I want to rotate uniform sampler2D videosprite 180 degrees (reflection in x-axis, flip vertically). How can I do that? I found the function glRotatef(), but how do i specify that I want to rotate video sprite and not videoframe? Thanks

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• forward motion car physics - gradual slow

  - by spartan2417

  Im having trouble creating realistic car movements in xna 4. Right now i have a car going forward and hitting a terminal velocity which is fine but when i release the up key i need to the car to slow down gradually and then come to a stop. Im pretty sure this is easy code but i cant seem to get it to work the code - update if (Keyboard.GetState().IsKeyDown(Keys.Up)) { double elapsedTime = gameTime.ElapsedGameTime.Milliseconds; CalcTotalForce(); Acceleration = Vector2.Divide(CalcTotalForce(), MASS); Velocity = Vector2.Add(Velocity, Vector2.Multiply(Acceleration, (float)(elapsedTime))); Position = Vector2.Add(Position, Vector2.Multiply(Velocity, (float)(elapsedTime))); } added functions public Vector2 CalcTraction() { //Traction force = vector direction * engine force return Vector2.Multiply(forwardDirection, ENGINE_FORCE); } public Vector2 CalcDrag() { //Drag force = constdrag * velocity * speed return Vector2.Multiply(Vector2.Multiply(Velocity, DRAG_CONST), Velocity.Y); } public Vector2 CalcRoll() { //roll force = const roll * velocity return Vector2.Multiply(Velocity, ROLL_CONST); } public Vector2 CalcTotalForce() { //total force = traction + (-drag) + (-rolling) return Vector2.Add(CalcTraction(), Vector2.Add(-CalcDrag(), -CalcRoll())); } anyone have any ideas?

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• OpenGL ES 2 on Android: native window

  - by ThreaderSlash

  According to OGLES specification, we have the following definition: EGLSurface eglCreateWindowSurface(EGLDisplay display, EGLConfig config, NativeWindowType native_window, EGLint const * attrib_list) More details, here: http://www.khronos.org/opengles/documentation/opengles1_0/html/eglCreateWindowSurface.html And also by definition: int32_t ANativeWindow_setBuffersGeometry(ANativeWindow* window, int32_t width, int32_t height, int32_t format); More details, here: http://mobilepearls.com/labs/native-android-api I am running Android Native App on OGLES 2 and debugging it in a Samsung Nexus device. For setting up the 3D scene graph environment, the following variables are defined: struct android_app { ... ANativeWindow* window; }; android_app* mApplication; ... mApplication=&pApplication; And to initialize the App, we run the commands in the code: ANativeWindow_setBuffersGeometry(mApplication->window, 0, 0, lFormat); mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); Funny to say is that, the command ANativeWindow_setBuffersGeometry behaves as expected and works fine according to its definition, accepting all the parameters sent to it. But the eglCreateWindowSurface does no accept the parameter mApplication-window, as it should accept according to its definition. Instead, it looks for the following input: EGLNativeWindowType hWnd; mSurface = eglCreateWindowSurface(mDisplay,lConfig,hWnd,NULL); As an alternative, I considered to use instead: NativeWindowType hWnd=android_createDisplaySurface(); But debugger says: Function 'android_createDisplaySurface' could not be resolved Is 'android_createDisplaySurface' compatible only for OGLES 1 and not for OGLES 2? Can someone tell if there is a way to convert mApplication-window? In a way that the data from the android_app get accepted to the window surface?

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• GSL Uniform Random Number Generator

  - by Jamaia

  I want to use GSL's uniform random number generator. On their website, they include this sample code: #include <stdio.h> #include <gsl/gsl_rng.h> int main (void) { const gsl_rng_type * T; gsl_rng * r; int i, n = 10; gsl_rng_env_setup(); T = gsl_rng_default; r = gsl_rng_alloc (T); for (i = 0; i < n; i++) { double u = gsl_rng_uniform (r); printf ("%.5f\n", u); } gsl_rng_free (r); return 0; } However, this does not rely on any seed and so, the same random numbers will be produced each time. They also specify the following: The generator itself can be changed using the environment variable GSL_RNG_TYPE. Here is the output of the program using a seed value of 123 and the multiple-recursive generator mrg, $ GSL_RNG_SEED=123 GSL_RNG_TYPE=mrg ./a.out But I don't understand how to implement this. Any ideas as to what modifications I can make to the above code to incorporate the seed?

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• Importing tab delimited file into array in Visual Basic 2013 [migrated]

  - by JaceG

  I am needing to import a tab delimited text file that has 11 columns and an unknown number of rows (always minimum 3 rows). I would like to import this text file as an array and be able to call data from it as needed, throughout my project. And then, to make things more difficult, I need to replace items in the array, and even add more rows to it as the project goes on (all at runtime). Hopefully someone can suggest code corrections or useful methods. I'm hoping to use something like the array style sMyStrings(3,2), which I believe would be the easiest way to control my data. Any help is gladly appreciated, and worthy of a slab of beer. Here's the coding I have so far: Imports System.IO Imports Microsoft.VisualBasic.FileIO Public Class Main Dim strReadLine As String Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim sReader As IO.StreamReader = Nothing Dim sRawString As String = Nothing Dim sMyStrings() As String = Nothing Dim intCount As Integer = -1 Dim intFullLoop As Integer = 0 If IO.File.Exists("C:\MyProject\Hardware.txt") Then ' Make sure the file exists sReader = New IO.StreamReader("C:\MyProject\Hardware.txt") Else MsgBox("File doesn't exist.", MsgBoxStyle.Critical, "Error") End End If Do While sReader.Peek >= 0 ' Make sure you can read beyond the current position sRawString = sReader.ReadLine() ' Read the current line sMyStrings = sRawString.Split(New Char() {Chr(9)}) ' Separate values and store in a string array For Each s As String In sMyStrings ' Loop through the string array intCount = intCount + 1 ' Increment If TextBox1.Text <> "" Then TextBox1.Text = TextBox1.Text & vbCrLf ' Add line feed TextBox1.Text = TextBox1.Text & s ' Add line to debug textbox If intFullLoop > 14 And intCount > -1 And CBool((intCount - 0) / 11 Mod 0) Then cmbSelectHinge.Items.Add(sMyStrings(intCount)) End If Next intCount = -1 intFullLoop = intFullLoop + 1 Loop End Sub

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• X Error of failed request: BadMatch [migrated]

  - by Andrew Grabko

  I'm trying to execute some "hello world" opengl code: #include <GL/freeglut.h> void displayCall() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); ... Some more code here glutSwapBuffers(); } int main(int argc, char *argv[]) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH); glutInitWindowSize(500, 500); glutInitWindowPosition(300, 200); glutInitContextVersion(4, 2); glutInitContextFlags(GLUT_FORWARD_COMPATIBLE); glutCreateWindow("Hello World!"); glutDisplayFunc(displayCall); glutMainLoop(); return 0; } As a result I get: X Error of failed request: BadMatch (invalid parameter attributes) Major opcode of failed request: 128 (GLX) Minor opcode of failed request: 34 () Serial number of failed request: 39 Current serial number in output stream: 40 Here is the stack trace: fghCreateNewContext() at freeglut_window.c:737 0x7ffff7bbaa81 fgOpenWindow() at freeglut_window.c:878 0x7ffff7bbb2fb fgCreateWindow() at freeglut_structure.c:106 0x7ffff7bb9d86 glutCreateWindow() at freeglut_window.c:1,183 0x7ffff7bbb4f2 main() at AlphaTest.cpp:51 0x4007df Here is the last piece of code, after witch the program crashes: createContextAttribs = (CreateContextAttribsProc) fghGetProcAddress("glXCreateContextAttribsARB" ); if ( createContextAttribs == NULL ) { fgError( "glXCreateContextAttribsARB not found" ); } context = createContextAttribs( dpy, config, share_list, direct, attributes ); "glXCreateContextAttribsARB" address is obtained successfully, but the program crashes on its invocation. If I specify OpenGL version less than 4.2 in "glutInitContextVersion()" program runs without errors. Here is my glxinfo's OpelGL version: OpenGL version string: 4.2.0 NVIDIA 285.05.09 I would be very appreciate any further ideas.

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• Information about how much time in spent in a function, based on the input of this function

  - by olchauvin

  Is there a (quantitative) tool to measure performance of functions based on its input? So far, the tools I used to measure performance of my code, tells me how much time I spent in functions (like Jetbrain Dottrace for .Net), but I'd like to have more information about the parameters passed to the function in order to know which parameters impact the most the performance. Let's say that I have function like that: int myFunction(int myParam1, int myParam 2) { // Do and return something based on the value of myParam1 and myParam2. // The code is likely to use if, for, while, switch, etc.... } If would like a tool that would allow me to tell me how much time is spent in myFunction based on the value of myParam1 and myParam2. For example, the tool would give me a result looking like this: For "myFunction" : value | value | Number of | Average myParam1 | myParam2 | call | time ---------|----------|-----------|-------- 1 | 5 | 500 | 301 ms 2 | 5 | 250 | 1253 ms 3 | 7 | 1268 | 538 ms ... That would mean that myFunction has been call 500 times with myParam1=1 and myParam2=5, and that with those parameters, it took on average 301ms to return a value. The idea behind that is to do some statistical optimization by organizing my code such that, the blocs of codes that are the most likely to be executed are tested before the one that are less likely to be executed. To put it bluntly, if I know which values are used the most, I can reorganize the if/while/for etc.. structure of the function (and the whole program) to optimize it. I'd like to find such tools for C++, Java or.Net. Note: I am not looking for technical tips to optimize the code (like passing parameters as const, inlining functions, initializing the capacity of vectors and the like).

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• SDL mouse wheel not picking up

  - by Chris

  Running Ubuntu 11.04, SDL 1.2 trying to pickup mouse wheel up/down movement with this (stripped down) code: int main( int argc, char **argv ) { SDL_MouseButtonEvent *mousebutton = NULL; while ( !done ) { if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_LEFT) yrot += 0.75f; else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_RIGHT) yrot -= 0.75f; else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_WHEELUP){ xrot += 0.75f; }else if(mousebutton != NULL && mousebutton->button == SDL_BUTTON_WHEELDOWN){ xrot -= 0.75f; } while ( SDL_PollEvent( &event ) ) { switch( event.type ) { case SDL_MOUSEBUTTONDOWN: mousebutton = &event.button; break; case SDL_MOUSEBUTTONUP: mousebutton = NULL; break; default: break; } } } return 0; } strange thing is, scrolling with the mouse button does nothing, but if I hold down a mouse button or two and then move the mouse it hits the SDL_BUTTON_WHEEL code occasionally. This honestly reeks of a pointer issue, which would make sense since I've been spoiled with C# for the past couple years, but I am just not seeing it. How do i correctly find mouse scroll events in SDL?

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• Why are embedded device apps still written in C/C++? Why not Java programming language?

  - by hinkmond

  At the recent Black Hat 2014 conference in Sin City, the Black Hatters were focusing on Embedded Devices and IoT. You know? Make your networked-toaster burn your bread 10,000 miles away, over the Web for grins and giggles. Well, apparently the Black Hatters say it can be done pretty easily these days, which is scary. See: Securing Embedded Devices & IoT Here's a quote: All these devices are still written in C and C++. The challenges associated with developing securely in these languages have been fought for nearly two decades. "You often hear people say, 'Well, why don't we just get rid of the C and C++ language if it's so problematic. Why don't we just write everything in C# or Java, or something that is a little safer to develop in?'," DeMott says. Gah! Why are all these IoT devices still using C/C++? Of course they should be using Java SE Embedded technology! It's a natural fit to use for better security on embedded devices. Or, I guess, developers really don't mind if their networked-toasters do char their breakfast. If it can be burned, it will be... That's what I say. Unless they use Java. Hinkmond

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• Thoughts on type aliases/synonyms?

  - by Rei Miyasaka

  I'm going to try my best to frame this question in a way that doesn't result in a language war or list, because I think there could be a good, technical answer to this question. Different languages support type aliases to varying degrees. C# allows type aliases to be declared at the beginning of each code file, and they're valid only throughout that file. Languages like ML/Haskell use type aliases probably as much as they use type definitions. C/C++ are sort of a Wild West, with typedef and #define often being used seemingly interchangeably to alias types. The upsides of type aliasing don't invoke too much dispute: It makes it convenient to define composite types that are described naturally by the language, e.g. type Coordinate = float * float or type String = [Char]. Long names can be shortened: using DSBA = System.Diagnostics.DebuggerStepBoundaryAttribute. In languages like ML or Haskell, where function parameters often don't have names, type aliases provide a semblance of self-documentation. The downside is a bit more iffy: aliases can proliferate, making it difficult to read and understand code or to learn a platform. The Win32 API is a good example, with its DWORD = int and its HINSTANCE = HANDLE = void* and its LPHANDLE = HANDLE FAR* and such. In all of these cases it hardly makes any sense to distinguish between a HANDLE and a void pointer or a DWORD and an integer etc.. Setting aside the philosophical debate of whether a king should give complete freedom to their subjects and let them be responsible for themselves or whether they should have all of their questionable actions intervened, could there be a happy medium that would allow the benefits of type aliasing while mitigating the risk of its abuse? As an example, the issue of long names can be solved by good autocomplete features. Visual Studio 2010 for instance will alllow you to type DSBA in order to refer Intellisense to System.Diagnostics.DebuggerStepBoundaryAttribute. Could there be other features that would provide the other benefits of type aliasing more safely?

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• C++ and system exceptions

  - by Abyx

  Why standard C++ doesn't respect system (foreign or hardware) exceptions? E.g. when null pointer dereference occurs, stack isn't unwound, destructors aren't called, and RAII doesn't work. The common advice is "to use system API". But on certain systems, specifically Win32, this doesn't work. To enable stack unwinding for this C++ code // class Foo; // void bar(const Foo&); bar(Foo(1, 2)); one should generate something like this C code Foo tempFoo; Foo_ctor(&tempFoo); __try { bar(&tempFoo); } __finally { Foo_dtor(&tempFoo); } Foo_dtor(&tempFoo); and it's impossible to implement this as C++ library. Upd: Standard doesn't forbid handling system exceptions. But it seems that popular compilers like g++ doesn't respect system exceptions on any platforms just because standard doesn't require this. The only thing that I want - is to use RAII to make code readable and program reliable. I don't want to put hand-crafted try\finally around every call to unknown code. For example in this reusable code, AbstractA::foo is such unknown code: void func(AbstractA* a, AbstractB* b) { TempFile file; a->foo(b, file); } Maybe one will pass to func such implementation of AbstractA, which every Friday will not check if b is NULL, so access violation will happen, application will terminate and temporary file will not be deleted. How many months uses will suffer because of this issue, until either author of func or author of AbstractA will do something with it? Related: Is `catch(...) { throw; }` a bad practice?

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• Why the clip space in OpenGL has 4 dimensions?

  - by user827992

  I will use this as a generic reference, but the more i browser online docs and books, the less i understand about this. const float vertexPositions[] = { 0.75f, 0.75f, 0.0f, 1.0f, 0.75f, -0.75f, 0.0f, 1.0f, -0.75f, -0.75f, 0.0f, 1.0f, }; in this online book there is an example about how to draw the first and classic hello world for OpenGL about making a triangle. The vertex structure for the triangle is declared as stated in the code above. The book, as all the other sources about this, stress the point that the Clip Space is a 4D structure that is used to basically decide what will be rasterized and rendered to the screen. Here I have my questions: i can't imagine something in 4D, i don't think that a human can do that, what is a 4D for this Clip space ? the most human-readable doc that i have read speaks about a camera, which is just an abstraction over the clipping concept, and i get that, the problem is, why not using the concept of a camera in the first place which is a more familiar 3D structure? The only problem with the concept of a camera is that you need to define the prospective in other way and so you basically have to add another statement about what kind of camera you wish to have. How i'm supposed to read this 0.75f, 0.75f, 0.0f, 1.0f ? All i get is that they are all float values and i get the meaning of the first 3 values, what does it mean the last one?

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• relationship between the model and the renderer

  - by acrilige

  I tried to build a simple graphics engine, and faced with this problems: i have a list of models that i need to draw, and object (renderer) that implements IRenderer interface with method DrawObject(Object* obj). Implementation of renderer depends on using graphics library (opengl/directx). 1st question: model should not know nothing about renderer implementation, but in this case where can i hold (cache) information that depends on renderer implementation? For example, if model have this definition: class Model { public: Model(); Vertex* GetVertices() const; private: Vertex* m_vertices; }; what is the best way to cache, for example, vertex buffer of this model for dx11? Hold it in renderer object? 2nd question: what is the best way for model to say renderer HOW it must be rendered (for example with texture, bump mapping, or may be just in one color). I thought it can be done with flags, like this: model-SetRenderOptions(RENDER_TEXTURE | RENDER_BUMPMAPPING | RENDER_LIGHTING); and in Renderer::DrawModel method check for each flag. But looks like it will become uncomfortable with the options count growth...

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• Reconstruct a file from a TCP stream

  - by Abhishek Chanda

  I have a client and a server and a third box which sees all packets from the server to the client (but not the other way around). Now when the client requests a file from the server (over HTTP), the third box sees the response. I am trying to reconstruct the file there. I am using libpcap to capture TCP datagrams and trying to reconstruct the file there. Here is what I did Listen for packets on an interface Group all packets which have the same ACK number Sort the group based on SEQ number Extract data from each packet and combine them and write to the disk The problem is, the file thus generated is not exactly the same as the original file. Does everything sound correct here? Some more details: I am using C++ The packet data is being stored as std::vector<char> I did change the byte order while reading the ack number and seq number from the packet using ntohl I am not sure if I need to change the byte order for the data as well. I tried to reverse the data from each packet before combining them, even that did not work. Is there something I am missing?

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• How to alter image pixels of a wild life bird?

  - by NoobScratcher

  Hello so I was hoping someone knew how to move or change color and position actual image pixels and could explain and show the code to do so. I know how to write pixels on a surface or screen-surface usigned int *ptr = static_cast <unsigned int *> (screen-pixels); int offset = y * (screen->pitch / sizeof(unsigned int)); ptr[offset + x] = color; But I don't know how to alter or manipulate a image pixel of a png image my thoughts on this was How do I get the values and locations of pixels and what do I have to write to make it happen? Then how do I actually change the values or locations of those gotten pixels and how do I make that happen? any ideas tip suggestions are also welcome! int main(int argc , char *argv[]) { SDL_Surface *Screen = SDL_SetVideoMode(640,480,32,SDL_SWSURFACE); SDL_Surface *Image; Image = IMG_Load("image.png"); bool done = false; SDL_Event event; while(!done) { SDL_FillRect(Screen,NULL,(0,0,0)); SDL_BlitSurface(Image,NULL,Screen,NULL); while(SDL_PollEvent(&event)) { switch(event.type) { case SDL_QUIT: return 0; break; } } SDL_Flip(Screen); } return 0; }

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• Accessing second hard drive

  - by Jonathan

  So I recently installed Ubuntu 10.10 64-bit on my computer. I installed it on my 60gb SSD hard drive, and in the installation it never acknowledged the existence of my second hard drive. The hard drive that I keep all my files on, and which I want to make my home folder if I can, is a Western Digital Caviar Black 1TB SATA 6Gb/s 64MB cache (WD1002FAEX). I've read the following: https://help.ubuntu.com/community/Mount but honestly cannot work out how to access the hard drive from my Ubuntu installation. I did have Windows 7 64-bit prior to installing Ubuntu. I have backed up all the files on the hard drive, but if I could just access them straight off that would be super cool. Does anyone know how I can use the second hard drive? Thank you for your help EDIT: The following directories are currently in my /dev/ folder: ati/, block/, bsg/, bus/, char/, cpu/, isk/, input/, mapper/, net/, pktcdvd/, pts/, shm/, snd/, and usb/ EDIT: Result from sudo fdisk -l Disk /dev/sda: 60.0 GB, 60022480896 bytes 255 heads, 63 sectors/track, 7297 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000d2dfd Device Boot Start End Blocks Id System /dev/sda1 * 1 6994 56174592 83 Linux /dev/sda2 6994 7298 2438145 5 Extended /dev/sda5 6994 7298 2438144 82 Linux swap / Solaris @djeykib So very close to fixing it.. unfortunately on the last command you gave it says this: $ sudo apt-get install linux-lts-backport-natty Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package linux-lts-backport-natty Checking on http://www.ubuntuupdates.org/ppas reveals that it is only available for 10.04. Looks like I'll have to unplug and re-plug hardware if I want it working still :(

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• How to pass one float as four unsigned chars to shader by glVertexPointAttrib?

  - by Kog

  For each vertex I use two floats as position and four unsigned bytes as color. I want to store all of them in one table, so I tried casting those four unsigned bytes to one float, but I am unable to do that correctly... All in all, my tests came to one point: GLfloat vertices[] = { 1.0f, 0.5f, 0, 1.0f, 0, 0 }; glEnableVertexAttribArray(0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), vertices); // VER1 - draws red triangle // unsigned char colors[] = { 0xff, 0, 0, 0xff, 0xff, 0, 0, 0xff, 0xff, 0, 0, // 0xff }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors); // VER2 - draws greenish triangle (not "pure" green) // float f = 255 << 24 | 255; //Hex:0xff0000ff // float colors2[] = { f, f, f }; // glEnableVertexAttribArray(1); // glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), // colors2); // VER3 - draws red triangle int i = 255 << 24 | 255; //Hex:0xff0000ff int colors3[] = { i, i, i }; glEnableVertexAttribArray(1); glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 4 * sizeof(GLubyte), colors3); glDrawArrays(GL_TRIANGLES, 0, 3); Above code is used to draw one simple red triangle. My question is - why do versions 1 and 3 work correctly, while version 2 draws some greenish triangle? Hex values are one I read by marking variable during debug. They are equal for version 2 and 3 - so what causes the difference?

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