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• What's a nice explanation for pointers?

  - by Macneil

  In your own studies (on your own, or for a class) did you have an "ah ha" moment when you finally, really understood pointers? Do you have an explanation you use for beginner programmers that seems particularly effective? For example, when beginners first encounter pointers in C, they might just add &s and *s until it compiles (as I myself once did). Maybe it was a picture, or a really well motivated example, that made pointers "click" for you or your student. What was it, and what did you try before that didn't seem to work? Were any topics prerequisites (e.g. structs, or arrays)? In other words, what was necessary to understand the meaning of &s and *, when you could use them with confidence? Learning the syntax and terminology or the use cases isn't enough, at some point the idea needs to be internalized. Update: I really like the answers so far; please keep them coming. There are a lot of great perspectives here, but I think many are good explanations/slogans for ourselves after we've internalized the concept. I'm looking for the detailed contexts and circumstances when it dawned on you. For example: I only somewhat understood pointers syntactically in C. I heard two of my friends explaining pointers to another friend, who asked why a struct was passed with a pointer. The first friend talked about how it needed to be referenced and modified, but it was just a short comment from the other friend where it hit me: "It's also more efficient." Passing 4 bytes instead of 16 bytes was the final conceptual shift I needed.

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• Compiling kernal problem

  - by James

  Hi, I have a hp pavilion dm3t with intel HD graphics running ubuntu 10.10 64 bit. I'm trying to compile and install a patched kernel according to this, https://launchpad.net/~kamalmostafa/+archive/linux-kamal-mjgbacklight So I downloaded the tarball from here (linked to from the page above): http://kernel.ubuntu.com/git?p=kamal/ubuntu-maverick.git;a=shortlog;h=refs/heads/mjg-backlight I untar'd it to a directory, entered the directory and did: make defconfig which was successful, so I did: make which seemed to work fine until it gave these errors: ubuntu/ndiswrapper/iw_ndis.c:1966: error: unknown field ‘num_private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1966: warning: initialization makes pointer from integer without a cast ubuntu/ndiswrapper/iw_ndis.c:1967: error: unknown field ‘num_private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: excess elements in struct initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: (near initialization for ‘ndis_handler_def’) ubuntu/ndiswrapper/iw_ndis.c:1970: error: unknown field ‘private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1970: warning: initialization makes integer from pointer without a cast ubuntu/ndiswrapper/iw_ndis.c:1970: error: initializer element is not computable at load time ubuntu/ndiswrapper/iw_ndis.c:1970: error: (near initialization for ‘ndis_handler_def.num_standard’) ubuntu/ndiswrapper/iw_ndis.c:1971: error: unknown field ‘private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1971: warning: initialization from incompatible pointer type make[2]: *** [ubuntu/ndiswrapper/iw_ndis.o] Error 1 make[1]: *** [ubuntu/ndiswrapper] Error 2 make: *** [ubuntu] Error 2 How can I compile and install this kernel successfully? I'm new to this and would appreciate any help.

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• How do I draw a single Triangle with XNA and fill it with a Texture?

  - by Deukalion

  I'm trying to wrap my head around: http://msdn.microsoft.com/en-us/library/bb196409.aspx I'm trying to create a method in XNA that renders a single Triangle, then later make a method that takes a list of Triangles and renders them also. But it isn't working. I'm not understanding what all the things does and there's not enough information. My methods: // Triangle is a struct with A, B, C (didn't include) A, B, C = Vector3 public static void Render(GraphicsDevice device, List<Triangle> triangles, Texture2D texture) { foreach (Triangle triangle in triangles) { Render(device, triangle, texture); } } public static void Render(GraphicsDevice device, Triangle triangle, Texture2D texture) { BasicEffect _effect = new BasicEffect(device); _effect.Texture = texture; _effect.VertexColorEnabled = true; VertexPositionColor[] _vertices = new VertexPositionColor[3]; _vertices[0].Position = triangle.A; _vertices[1].Position = triangle.B; _vertices[2].Position = triangle.B; foreach (var pass in _effect.CurrentTechnique.Passes) { pass.Apply(); device.DrawUserIndexedPrimitives<VertexPositionColor> ( PrimitiveType.TriangleList, _vertices, 0, _vertices.Length, new int[] { 0, 1, 2 }, // example has something similiar, no idea what this is 0, 3 // 3 = gives me an error, 1 = works but no results ); } }

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• XNA shield effect with a Primative sphere problem

  - by Sparky41

  I'm having issue with a shield effect i'm trying to develop. I want to do a shield effect that surrounds part of a model like this: http://i.imgur.com/jPvrf.png I currently got this: http://i.imgur.com/Jdin7.png (The red likes are a simple texture a black background with a red cross in it, for testing purposes: http://i.imgur.com/ODtzk.png where the smaller cross in the middle shows the contact point) This sphere is drawn via a primitive (DrawIndexedPrimitives) This is how i calculate the pieces of the sphere using a class i've called Sphere (this class is based off the code here: http://xbox.create.msdn.com/en-US/education/catalog/sample/primitives_3d) public class Sphere { // During the process of constructing a primitive model, vertex // and index data is stored on the CPU in these managed lists. List vertices = new List(); List indices = new List(); // Once all the geometry has been specified, the InitializePrimitive // method copies the vertex and index data into these buffers, which // store it on the GPU ready for efficient rendering. VertexBuffer vertexBuffer; IndexBuffer indexBuffer; BasicEffect basicEffect; public Vector3 position = Vector3.Zero; public Matrix RotationMatrix = Matrix.Identity; public Texture2D texture; /// <summary> /// Constructs a new sphere primitive, /// with the specified size and tessellation level. /// </summary> public Sphere(float diameter, int tessellation, Texture2D text, float up, float down, float portstar, float frontback) { texture = text; if (tessellation < 3) throw new ArgumentOutOfRangeException("tessellation"); int verticalSegments = tessellation; int horizontalSegments = tessellation * 2; float radius = diameter / 2; // Start with a single vertex at the bottom of the sphere. AddVertex(Vector3.Down * ((radius / up) + 1), Vector3.Down, Vector2.Zero);//bottom position5 // Create rings of vertices at progressively higher latitudes. for (int i = 0; i < verticalSegments - 1; i++) { float latitude = ((i + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude / up);//(up)5 float dxz = (float)Math.Cos(latitude); // Create a single ring of vertices at this latitude. for (int j = 0; j < horizontalSegments; j++) { float longitude = j * MathHelper.TwoPi / horizontalSegments; float dx = (float)(Math.Cos(longitude) * dxz) / portstar;//port and starboard (right)2 float dz = (float)(Math.Sin(longitude) * dxz) * frontback;//front and back1.4 Vector3 normal = new Vector3(dx, dy, dz); AddVertex(normal * radius, normal, new Vector2(j, i)); } } // Finish with a single vertex at the top of the sphere. AddVertex(Vector3.Up * ((radius / down) + 1), Vector3.Up, Vector2.One);//top position5 // Create a fan connecting the bottom vertex to the bottom latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(0); AddIndex(1 + (i + 1) % horizontalSegments); AddIndex(1 + i); } // Fill the sphere body with triangles joining each pair of latitude rings. for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; AddIndex(1 + i * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); } } // Create a fan connecting the top vertex to the top latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(CurrentVertex - 1); AddIndex(CurrentVertex - 2 - (i + 1) % horizontalSegments); AddIndex(CurrentVertex - 2 - i); } //InitializePrimitive(graphicsDevice); } /// <summary> /// Adds a new vertex to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddVertex(Vector3 position, Vector3 normal, Vector2 texturecoordinate) { vertices.Add(new VertexPositionNormal(position, normal, texturecoordinate)); } /// <summary> /// Adds a new index to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddIndex(int index) { if (index > ushort.MaxValue) throw new ArgumentOutOfRangeException("index"); indices.Add((ushort)index); } /// <summary> /// Queries the index of the current vertex. This starts at /// zero, and increments every time AddVertex is called. /// </summary> protected int CurrentVertex { get { return vertices.Count; } } public void InitializePrimitive(GraphicsDevice graphicsDevice) { // Create a vertex declaration, describing the format of our vertex data. // Create a vertex buffer, and copy our vertex data into it. vertexBuffer = new VertexBuffer(graphicsDevice, typeof(VertexPositionNormal), vertices.Count, BufferUsage.None); vertexBuffer.SetData(vertices.ToArray()); // Create an index buffer, and copy our index data into it. indexBuffer = new IndexBuffer(graphicsDevice, typeof(ushort), indices.Count, BufferUsage.None); indexBuffer.SetData(indices.ToArray()); // Create a BasicEffect, which will be used to render the primitive. basicEffect = new BasicEffect(graphicsDevice); //basicEffect.EnableDefaultLighting(); } /// <summary> /// Draws the primitive model, using the specified effect. Unlike the other /// Draw overload where you just specify the world/view/projection matrices /// and color, this method does not set any renderstates, so you must make /// sure all states are set to sensible values before you call it. /// </summary> public void Draw(Effect effect) { GraphicsDevice graphicsDevice = effect.GraphicsDevice; // Set our vertex declaration, vertex buffer, and index buffer. graphicsDevice.SetVertexBuffer(vertexBuffer); graphicsDevice.Indices = indexBuffer; graphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass effectPass in effect.CurrentTechnique.Passes) { effectPass.Apply(); int primitiveCount = indices.Count / 3; graphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, vertices.Count, 0, primitiveCount); } graphicsDevice.BlendState = BlendState.Opaque; } /// <summary> /// Draws the primitive model, using a BasicEffect shader with default /// lighting. Unlike the other Draw overload where you specify a custom /// effect, this method sets important renderstates to sensible values /// for 3D model rendering, so you do not need to set these states before /// you call it. /// </summary> public void Draw(Camera camera, Color color) { // Set BasicEffect parameters. basicEffect.World = GetWorld(); basicEffect.View = camera.view; basicEffect.Projection = camera.projection; basicEffect.DiffuseColor = color.ToVector3(); basicEffect.TextureEnabled = true; basicEffect.Texture = texture; GraphicsDevice device = basicEffect.GraphicsDevice; device.DepthStencilState = DepthStencilState.Default; if (color.A < 255) { // Set renderstates for alpha blended rendering. device.BlendState = BlendState.AlphaBlend; } else { // Set renderstates for opaque rendering. device.BlendState = BlendState.Opaque; } // Draw the model, using BasicEffect. Draw(basicEffect); } public virtual Matrix GetWorld() { return /*world */ Matrix.CreateScale(1f) * RotationMatrix * Matrix.CreateTranslation(position); } } public struct VertexPositionNormal : IVertexType { public Vector3 Position; public Vector3 Normal; public Vector2 TextureCoordinate; /// <summary> /// Constructor. /// </summary> public VertexPositionNormal(Vector3 position, Vector3 normal, Vector2 textCoor) { Position = position; Normal = normal; TextureCoordinate = textCoor; } /// <summary> /// A VertexDeclaration object, which contains information about the vertex /// elements contained within this struct. /// </summary> public static readonly VertexDeclaration VertexDeclaration = new VertexDeclaration ( new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0), new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0), new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0) ); VertexDeclaration IVertexType.VertexDeclaration { get { return VertexPositionNormal.VertexDeclaration; } } } A simple call to the class to initialise it. The Draw method is called in the master draw method in the Gamecomponent. My current thoughts on this are: The direction of the weapon hitting the ship is used to get the middle position for the texture Wrap a texture around the drawn sphere based on this point of contact Problem is i'm not sure how to do this. Can anyone help or if you have a better idea please tell me i'm open for opinion? :-) Thanks.

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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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• Negamax implementation doesn't appear to work with tic-tac-toe

  - by George Jiglau

  I've implemented Negamax as it can be found on wikipedia, which includes alpha/beta pruning. However, it seems to favor a losing move, which should be an invalid result. The game is Tic-Tac-Toe, I've abstracted most of the game play so it should be rather easy to spot an error within the algorithm. Here is the code, nextMove, negamax or evaluate are probably the functions that contain the fault: #include <list> #include <climits> #include <iostream> //#define DEBUG 1 using namespace std; struct Move { int row, col; Move(int row, int col) : row(row), col(col) { } Move(const Move& m) { row = m.row; col = m.col; } }; struct Board { char player; char opponent; char board[3][3]; Board() { } void read(istream& stream) { stream >> player; opponent = player == 'X' ? 'O' : 'X'; for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { char playa; stream >> playa; board[row][col] = playa == '_' ? 0 : playa == player ? 1 : -1; } } } void print(ostream& stream) { for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { switch(board[row][col]) { case -1: stream << opponent; break; case 0: stream << '_'; break; case 1: stream << player; break; } } stream << endl; } } void do_move(const Move& move, int player) { board[move.row][move.col] = player; } void undo_move(const Move& move) { board[move.row][move.col] = 0; } bool isWon() { if (board[0][0] != 0) { if (board[0][0] == board[0][1] && board[0][1] == board[0][2]) return true; if (board[0][0] == board[1][0] && board[1][0] == board[2][0]) return true; } if (board[2][2] != 0) { if (board[2][0] == board[2][1] && board[2][1] == board[2][2]) return true; if (board[0][2] == board[1][2] && board[1][2] == board[2][2]) return true; } if (board[1][1] != 0) { if (board[0][1] == board[1][1] && board[1][1] == board[2][1]) return true; if (board[1][0] == board[1][1] && board[1][1] == board[1][2]) return true; if (board[0][0] == board[1][1] && board[1][1] == board[2][2]) return true; if (board[0][2] == board [1][1] && board[1][1] == board[2][0]) return true; } return false; } list<Move> getMoves() { list<Move> moveList; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board[row][col] == 0) moveList.push_back(Move(row, col)); return moveList; } }; ostream& operator<< (ostream& stream, Board& board) { board.print(stream); return stream; } istream& operator>> (istream& stream, Board& board) { board.read(stream); return stream; } int evaluate(Board& board) { int score = board.isWon() ? 100 : 0; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board.board[row][col] == 0) score += 1; return score; } int negamax(Board& board, int depth, int player, int alpha, int beta) { if (board.isWon() || depth <= 0) { #if DEBUG > 1 cout << "Found winner board at depth " << depth << endl; cout << board << endl; #endif return player * evaluate(board); } list<Move> allMoves = board.getMoves(); if (allMoves.size() == 0) return player * evaluate(board); for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, -player); int val = -negamax(board, depth - 1, -player, -beta, -alpha); board.undo_move(*it); if (val >= beta) return val; if (val > alpha) alpha = val; } return alpha; } void nextMove(Board& board) { list<Move> allMoves = board.getMoves(); Move* bestMove = NULL; int bestScore = INT_MIN; for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, 1); int score = -negamax(board, 100, 1, INT_MIN + 1, INT_MAX); board.undo_move(*it); #if DEBUG cout << it->row << ' ' << it->col << " = " << score << endl; #endif if (score > bestScore) { bestMove = &*it; bestScore = score; } } if (!bestMove) return; cout << bestMove->row << ' ' << bestMove->col << endl; #if DEBUG board.do_move(*bestMove, 1); cout << board; #endif } int main() { Board board; cin >> board; #if DEBUG cout << "Starting board:" << endl; cout << board; #endif nextMove(board); return 0; } Giving this input: O X__ ___ ___ The algorithm chooses to place a piece at 0, 1, causing a guaranteed loss, do to this trap(nothing can be done to win or end in a draw): XO_ X__ ___ Perhaps it has something to do with the evaluation function? If so, how could I fix it?

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• How can I use the dualforward parameter in my unity shader to use lightmaps and normal maps together?

  - by Raphaeltm

  I'm using the free version of unity and I would like to combine lightmaps with specularity and normal maps. After doing a -bunch- of research, I've figured out that there doesn't seem to be any easy way to do this in the free version of unity, which doesn't support deferred rendering/easy use of dual lightmaps. However, it looks like it's possible, by writing a custom shader, using the "dualforward" parameter in a shader, switching the lightmapping mode to "dual lightmaps" and turning on "Use in forward ren." (basically, writing a shader that specifies the use of dual lightmaps, which should allow for a combination of lightmaps and normal maps) So I downloaded the source code for the default shaders (because all I need is a normal specular bumped shader) and added "dualforward" to the parameters: Shader "Bumped Specular Dual Lightmaps" { Properties { _Color ("Main Color", Color) = (1,1,1,1) _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1) _Shininess ("Shininess", Range (0.03, 1)) = 0.078125 _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {} _BumpMap ("Normalmap", 2D) = "bump" {} } SubShader { Tags { "RenderType"="Opaque" } LOD 400 CGPROGRAM #pragma surface surf BlinnPhong dualforward sampler2D _MainTex; sampler2D _BumpMap; fixed4 _Color; half _Shininess; struct Input { float2 uv_MainTex; float2 uv_BumpMap; }; void surf (Input IN, inout SurfaceOutput o) { fixed4 tex = tex2D(_MainTex, IN.uv_MainTex); o.Albedo = tex.rgb * _Color.rgb; o.Gloss = tex.a; o.Alpha = tex.a * _Color.a; o.Specular = _Shininess; o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap)); } ENDCG } FallBack "Specular" } This, however, doesn't seem to work. When I keep the "dualforward" param, every object that uses it seems to be lit by the one directional light in the scene. When I remove the "dualforward" param, it they look like normal lightmapped objects with no normal maps or specularity. I noticed that the support for "dualforward" seems to be new in v.3.4.2, so I made sure to download it (I was running 3.4.1), but it still doesn't work. Anybody have any advice for me?

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• Benefits of classic OOP over Go-like language

  - by tylerl

  I've been thinking a lot about language design and what elements would be necessary for an "ideal" programming language, and studying Google's Go has led me to question a lot of otherwise common knowledge. Specifically, Go seems to have all of the interesting benefits from object oriented programming without actually having any of the structure of an object oriented language. There are no classes, only structures; there is no class/structure inheritance -- only structure embedding. There aren't any hierarchies, no parent classes, no explicit interface implementations. Instead, type casting rules are based on a loose system similar to duck-typing, such that if a struct implements the necessary elements of a "Reader" or a "Request" or an "Encoding", then you can cast it and use it as one. Does such a system obsolete the concept of OOP? Or is there something about OOP as implemented in C++ and Java and C# that is inherently more capable, more maintainable, somehow more powerful that you have to give up when moving to a language like Go? What benefit do you have to give up to gain the simplicity that this new paradigm represents?

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• the correct way to deal with gtk_events_pending and gtk_main_iteration

  - by abd alsalam

  I have program that send files and i want to make a progress bar for it, but that progress bar just updated after the transferring complete,so i putted a gtk_events_pending() and gtk_main_iteration() functions in the sending loop to go back to the gtk main loop to update the progress bar but also it seems to not work here is a EDIT: the send function is in a separated thread snippet from my code float Percent = 0.0 ; float Interval = 0.0 ; the sending function gint SendTheFile ( ) { char FileBlockBuffer[512]; bzero(FileBlockBuffer, 512); int FileBlockSize ; FILE * FilePointer ; int filesize = 0 ; FilePointer = fopen(LocalFileName , "r"); struct stat st; stat(LocalFileName, &st); filesize = st.st_size; Interval = (512 / (float)filesize) ; while((FileBlockSize = fread(FileBlockBuffer,sizeof(char),512,FilePointer))>0) { send(SocketDiscriptor , FileBlockBuffer , FileBlockSize,0); bzero(FileBlockBuffer, 512); Percent = Percent + Interval ; if (Percent > 1.0)Percent = 0.0; while(gtk_events_pending() ) { gtk_main_iteration(); } } update progress bar function gint UpdateProgressBar(gpointer data) { gtk_progress_bar_set_fraction(GTK_PROGRESS_BAR(data),Percent); } updating progress bar in the main function g_timeout_add(50,(GSourceFunc)UpdateProgressBar,SendFileProgressBar);

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• Is goto to improve DRY-ness OK?

  - by Marco Scannadinari

  My code has many checks to detect errors in various cases (many conditions would result in the same error), inside a function returning an error struct. Instead of looking like this: err_struct myfunc(...) { err_struct error = { .error = false }; ... if(something) { error.error = true; error.description = "invalid input"; return error; } ... case 1024: error.error = true; error.description = "invalid input"; // same error, but different detection scenario return error; break; // don't comment on this break please (EDIT: pun unintended) ... Is use of goto in the following context considered better than the previous example? err_struct myfunc(...) { err_struct error = { .error = false }; ... if(something) goto invalid_input; ... case 1024: goto invalid_input; break; return error; invalid_input: error.error = true; error.description = "invalid input"; return error;

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• How can I ensure my Collada model fits on an iPhone screen?

  - by rakeshNS

  Hi I am new to game development. I see many examples and tried myself like displaying triangle, cube etc. Now I am looking to render a Collada object. So I created a Collada object using Google Sketch up and trying to render that now. But the thing I am not understanding is, in all examples the vertices are between -1.0 and +1.0 values. But when I looked into that Collada file, the vertices were ranging from -30.0 to 90.0. I know any vertices greater than 1.0 will not display on iPhone. So can you pleas tell my the secret behind converting Object coordinate to normalized vector coordinate? My previous triangle defined as struct Vertex{ float Position[3]; float Color[4]; }; const Vertex Vertices[] = { {{-0.5, -0.866}, {1, 1, 0.5f, 1}}, {{0.5, -0.866}, {1, 1, 0.5, 1}}, {{0, 1}, {1, 1, 0.5, 1}}, {{-0.5, -0.866}, {0.5f, 0.5f, 0.5f}}, {{0.5, -0.866}, {0.5f, 0.5f, 0.5f}}, {{0, -0.4f}, {0.5f, 0.5f, 0.5f}}, }; And now triangle from collada is const Vertex Vertices[] = { {{39.4202092, 90.1263924, 0.0000000}, {1, 1, 0.5f, 1}}, {{-20.2205588, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 176.3763924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 176.3763924, 0.0000000}, {1, 1, 0.5, 1}}, {{-20.2205588, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, {{39.4202092, 90.1263924, 0.0000000}, {1, 1, 0.5, 1}}, };

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• Modular Architecture for Processing Pipeline

  - by anjruu

  I am trying to design the architecture of a system that I will be implementing in C++, and I was wondering if people could think of a good approach, or critique the approach that I have designed so far. First of all, the general problem is an image processing pipeline. It contains several stages, and the goal is to design a highly modular solution, so that any of the stages can be easily swapped out and replaced with a piece of custom code (so that the user can have a speed increase if s/he knows that a certain stage is constrained in a certain way in his or her problem). The current thinking is something like this: struct output; /*Contains the output values from the pipeline.*/ class input_routines{ public: virtual foo stage1(...){...} virtual bar stage2(...){...} virtual qux stage3(...){...} ... } output pipeline(input_routines stages); This would allow people to subclass input_routines and override whichever stage they wanted. That said, I've worked in systems like this before, and I find the subclassing and the default stuff tends to get messy, and can be difficult to use, so I'm not giddy about writing one myself. I was also thinking about a more STLish approach, where the different stages (there are 6 or 7) would be defaulted template parameters. Can anyone offer a critique of the pattern above, thoughts on the template approach, or any other architecture that comes to mind?

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• Should I learn the easier framework as a start? [closed]

  - by gunbuster363

  I've been a programmer for 2 years. I learned Java SE, C from college and learned Cobol from the workplace. I've noticed that there is a hype about framework and I actually don't know what is a framework. It is so cool that my colleague once said you cannot find a new job without knowing something like struct spring hibernate. And we should know Java EE too because it was aimed for enterprise application. I've never code something such as server-client web application, and I think I need to try it out. But which language should I code in? I can't decide between the following 2: 1) Java. It is heavily used by many company so I could easily reuse the experience gained. But Java and its related framework are pretty heavy (for the machine and operation). It is on-demand. 2) ROR. It is cool. The syntax of ruby is simple. I can get a better hand on it. And maybe I can learn the concept easily and possibly correctly. However, not much company here would use it. All the job ads are about J2EE/C#. Should I learn the easy one or the difficult one? Not to mention there are a lot of frameworks out there for Java, which makes the decision much more difficult.

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• Convert collections of enums to collection of strings and vice versa

  - by Michael Freidgeim

  Recently I needed to convert collections of  strings, that represent enum names, to collection of enums, and opposite,  to convert collections of   enums  to collection of  strings. I didn’t find standard LINQ extensions.However, in our big collection of helper extensions I found what I needed - just with different names: /// <summary> /// Safe conversion, ignore any unexpected strings/// Consider to name as Convert extension /// </summary> /// <typeparam name="EnumType"></typeparam> /// <param name="stringsList"></param> /// <returns></returns> public static List<EnumType> StringsListAsEnumList<EnumType>(this List<string> stringsList) where EnumType : struct, IComparable, IConvertible, IFormattable     { List<EnumType> enumsList = new List<EnumType>(); foreach (string sProvider in stringsList)     {     EnumType provider;     if (EnumHelper.TryParse<EnumType>(sProvider, out provider))     {     enumsList.Add(provider);     }     }     return enumsList;     }/// <summary> /// Convert each element of collection to string /// </summary> /// <typeparam name="T"></typeparam> /// <param name="objects"></param> /// <returns></returns> public static IEnumerable<string> ToStrings<T>(this IEnumerable<T> objects) {//from http://www.c-sharpcorner.com/Blogs/997/using-linq-to-convert-an-array-from-one-type-to-another.aspx return objects.Select(en => en.ToString()); }

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• Getting the total number of processors a computer has (c#)

  - by mbcrump

  Here is a code snippet for getting the total number of processors a computer has without using Environment.ProcessorCount. I found out that Environment.ProcessorCount is not necessary returning the correct value on some Intel based CPU’s.   using System; usingSystem.Collections.Generic; usingSystem.Linq; usingSystem.Text; usingSystem.Globalization; usingSystem.Runtime.InteropServices; namespaceConsoleApplication4 {     classProgram    {         static voidMain(string[] args)         {             int c = ProcessorCount;             Console.WriteLine("The computer has {0} processors", c);             Console.ReadLine();         }         private static classNativeMethods        {             [StructLayout(LayoutKind.Sequential)]             internal struct SYSTEM_INFO            {                 public ushort wProcessorArchitecture;                 public ushort wReserved;                 public uint dwPageSize;                 publicIntPtr lpMinimumApplicationAddress;                 publicIntPtr lpMaximumApplicationAddress;                 publicUIntPtr dwActiveProcessorMask;                 public uint dwNumberOfProcessors;                 public uint dwProcessorType;                 public uint dwAllocationGranularity;                 public ushort wProcessorLevel;                 public ushort wProcessorRevision;             }             [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]             internal static extern voidGetNativeSystemInfo(refSYSTEM_INFOlpSystemInfo);         }         public static int ProcessorCount         {             get            {                 NativeMethods.SYSTEM_INFOlpSystemInfo = newNativeMethods.SYSTEM_INFO();                 NativeMethods.GetNativeSystemInfo(reflpSystemInfo);                 return(int)lpSystemInfo.dwNumberOfProcessors;             }         }     } }

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• Are Vala and desktopcouch ready?

  - by pavolzetor

  Hi, I have started writting rss reader in Vala, but I don't know, what database system should I use, I cannot connect to couchdb and sqlite works fine, but I would like use couchdb because of ubuntu one. I have natty with latest updates public CouchDB.Session session; public CouchDB.Database db; public string feed_table = "feed"; public string item_table = "item"; public struct field { string name; string val; } // constructor public Database() { try { this.session = new CouchDB.Session(); } catch (Error e) { stderr.printf ("%s a\n", e.message); } try { this.db = new CouchDB.Database (this.session, "test"); } catch (Error e) { stderr.printf ("%s a\n", e.message); } try { this.session.get_database_info("test"); } catch (Error e) { stderr.printf ("%s aa\n", e.message); } try { var newdoc = new CouchDB.Document (); newdoc.set_boolean_field ("awesome", true); newdoc.set_string_field ("phone", "555-VALA"); newdoc.set_double_field ("pi", 3.14159); newdoc.set_int_field ("meaning_of_life", 42); this.db.put_document (newdoc); // store document } catch (Error e) { stderr.printf ("%s aaa\n", e.message); } reports $ ./xml_parser rss.xmlCannot connect to destination (127.0.0.1) aa Cannot connect to destination (127.0.0.1) aaa

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• Image mapping using lookup tables [on hold]

  - by jblasius

  I have an optimization problem. I'm using a look-up table to map a pixel in an image: for (uint32_t index = 0u; index < imgSize; index++) { img[ lt[ index ] ] = val; } Is there a faster way to do this, perhaps using a reinterpret_cast or something like that? I am accessing two different memory addresses, so what is the compiler doing? One solution is to do a set of reads to access adjacent memory addresses. struct mblock { uint32_t buf[10u]; }; mblock mb; for (uint32_t index = 0u; index < imgSize; index += 10u) { mb = *reinterpret_cast<mblock*>(lt + index)); for (uint8_t i = 0u; i < 10u; i ++) { mb.buf[i] += img; } for (uint8_t i = 0u; i < 10u; i ++) { *( mb.buf[i] ) = val; } } This speeds up the code because I'm separating the image access from the table look-up; the positions in the look-up table are adjacent. I still get the image access problem as it is accessing random address positions.

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• loading a heightmap as texture in shader

  - by wtherapy

  I have a height map of 256x256, containing, foreach cell, not only height as a normal float value ( not 0-1 ) and also 2 gradient values ( for X and Y ), also as normal float values ( not 0-1 ). I have uploaded the texture via normal texture loading: glEnable( GL_TEXTURE_2D ); glGenTextures( 1, &m_uglID ); DEBUG_OUTPUT("Err %x\n", glGetError()); glBindTexture( GL_TEXTURE_2D , m_uglID ); DEBUG_OUTPUT("Err %x\n", glGetError()); glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB32F, unW + 1, unH + 1, 0, GL_RGB, GL_FLOAT, pvBytes ); DEBUG_OUTPUT("Err %x\n", glGetError()); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_LINEAR); DEBUG_OUTPUT("Err %x\n", glGetError()); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_LINEAR); DEBUG_OUTPUT("Err %x\n", glGetError()); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); DEBUG_OUTPUT("Err %x\n", glGetError()); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); DEBUG_OUTPUT("Err %x\n", glGetError()); as a parenthesis, the debug output is: Err 500 Err 0 Err 0 Err 0 Err 500 Err 500 Err 0 Err 0 pvBytes is a 256x256 array of typedef struct _tGradientHeightCell { float v; float px; float py; } TGradientHeightCell, *LPTGradientHeightCell; then, m_ugl_HeightMapTexture = glGetUniformLocation(m_uglProgram, "TexHeightMap"); I load it via: glEnable(GL_TEXTURE_2D ); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D , pTexture->GetID()); glUniform1i(m_ugl_HeightMapTexture, 0); in shader, I just access it: uniform sampler2D TexHeightMap; vec4 GetVertCellParameters( uint i, uint j ) { return texture( TexHeightMap, vec2( i, j ) ); } vec4 vH00 = GetVertCellParameters( i, j ); My problem is that, when passing negative values in one of the values in TGradientHeightCell ( v, px, py ), the texture is corrupted. I need the values to be passed exact as I have them in memory. Any help appreciated.

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• How do you make a precise countdown timer using clock_gettime? [migrated]

  - by Joshun

  Could somebody please explain how to make a countdown timer using clock_gettime, under Linux. I know you can use the clock() function to get cpu time, and multiply it by CLOCKS_PER_SEC to get actual time, but I'm told the clock() function is not well suited for this. So far I have attempted this (a billion is to pause for one second) #include <stdio.h> #include <time.h> #define BILLION 1000000000 int main() { struct timespec rawtime; clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime); unsigned long int current = ( rawtime.tv_sec + rawtime.tv_nsec ); unsigned long int end = (( rawtime.tv_sec + rawtime.tv_nsec ) + BILLION ); while ( current < end ) { clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime); current = ( rawtime.tv_sec + rawtime.tv_nsec ); } return 0; } I know this wouldn't be very useful on its own, but once I've found out how to time correctly I can use this in my projects. I know that sleep() can be used for this purpose, but I want to code the timer myself so that I can better integrate it in my projects - such as the possibility of it returning the time left, as opposed to pausing the whole program.

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• Free memory outside function [migrated]

  - by Dev Bag

  Can you please help with this issue, is the below gonna leak memory or is it ok? and please let me know if there is something else that I need to pay attention to typedef struct { int len; UC * message; }pack; pack * prepare_packet_to_send(const int length,const unsigned char tag,const int numargs, ... ) { pack *layer= malloc(sizeof(pack)); va_list listp; va_start( listp, numargs ); int step = 0; layer->message = (unsigned char *) malloc(length); layer->len = length; int i = 0; int len = 0; unsigned char *source_message ; for( i = 0 ; i < numargs; i++ ) { source_message = va_arg( listp, unsigned char *); len = va_arg( listp, long); memcpy(layer->message+step, source_message, (long) len); step+=len; } va_end( listp ); return layer; } main() { pack *test = call prepare_packet_to_send(sizeof(var1)+sizeof(var2),any tag,any args) // are following two frees correct/enough? or is there something else i need to do to prevent mem leak? free(test->message); free(test); }

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• a c++ program for task scheduling [closed]

  - by scheduling

  This is the code which I made but I am not able to correct the mistake in the code. Please correct the mistake in my code. #include<unistd.h> #include<stdio.h> #include<stdlib.h> #include<time.h> #include<string.h> int main() { char *timetoken; char currtime[7]; char schedtime[7]; int i; struct tm *localtimeptr; strcpy(schedtime,"15:25:00"); while(6!=9) { time_t lt; sleep(1); lt = time(NULL); localtimeptr = localtime(<); timetoken=strtok(asctime(localtimeptr)," "); for(i=1;i<5;i++) timetoken=strtok('\0'," "); if(i==3) { strcpy(currtime,timetoken); } } printf("The current time is: %s\n",currtime); printf("We are waiting for: %s\n",schedtime); if(!strcmp(currtime,schedtime)) { printf("Time to do stuff \n"); system("C:\PROJECT X"); } getch(); return 0; }

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• a c++ code for scheduling tasks [closed]

  - by scheduling

  This code has no errors but then when i execute it, there is no output and the program automatically shuts down saying the program has stopped working. #include<unistd.h> #include<stdio.h> #include<stdlib.h> #include<time.h> #include<string.h> int main() { char *timetoken; char currtime[7]; char schedtime[7]; int i; struct tm *localtimeptr; strcpy(schedtime,"15:25:00"); while(6!=9) { time_t lt; sleep(1); lt = time(NULL); localtimeptr = localtime(lt); timetoken=strtok(asctime(localtimeptr)," "); for(i=1;i<5;i++) timetoken=strtok('\0'," "); if(i==3) { strcpy(currtime,timetoken); } } printf("The current time is: %s\n",currtime); printf("We are waiting for: %s\n",schedtime); if(!strcmp(currtime,schedtime)) { printf("Time to do stuff \n"); system("C:\PROJECT X"); } getch(); return 0; }

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• OBJ model loaded in LWJGL has a black area with no texture

  - by gambiting

  I have a problem with loading an .obj file in LWJGL and its textures. The object is a tree(it's a paid model from TurboSquid, so I can't post it here,but here's the link if you want to see how it should look like): http://www.turbosquid.com/FullPreview/Index.cfm/ID/701294 I wrote a custom OBJ loader using the LWJGL tutorial from their wiki. It looks like this: public class OBJLoader { public static Model loadModel(File f) throws FileNotFoundException, IOException { BufferedReader reader = new BufferedReader(new FileReader(f)); Model m = new Model(); String line; Texture currentTexture = null; while((line=reader.readLine()) != null) { if(line.startsWith("v ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); float z = Float.valueOf(line.split(" ")[3]); m.verticies.add(new Vector3f(x,y,z)); }else if(line.startsWith("vn ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); float z = Float.valueOf(line.split(" ")[3]); m.normals.add(new Vector3f(x,y,z)); }else if(line.startsWith("vt ")) { float x = Float.valueOf(line.split(" ")[1]); float y = Float.valueOf(line.split(" ")[2]); m.texVerticies.add(new Vector2f(x,y)); }else if(line.startsWith("f ")) { Vector3f vertexIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[0]), Float.valueOf(line.split(" ")[2].split("/")[0]), Float.valueOf(line.split(" ")[3].split("/")[0])); Vector3f textureIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[1]), Float.valueOf(line.split(" ")[2].split("/")[1]), Float.valueOf(line.split(" ")[3].split("/")[1])); Vector3f normalIndicies = new Vector3f(Float.valueOf(line.split(" ")[1].split("/")[2]), Float.valueOf(line.split(" ")[2].split("/")[2]), Float.valueOf(line.split(" ")[3].split("/")[2])); m.faces.add(new Face(vertexIndicies,textureIndicies,normalIndicies,currentTexture.getTextureID())); }else if(line.startsWith("g ")) { if(line.length()>2) { String name = line.split(" ")[1]; currentTexture = TextureLoader.getTexture("PNG", ResourceLoader.getResourceAsStream("res/" + name + ".png")); System.out.println(currentTexture.getTextureID()); } } } reader.close(); System.out.println(m.verticies.size() + " verticies"); System.out.println(m.normals.size() + " normals"); System.out.println(m.texVerticies.size() + " texture coordinates"); System.out.println(m.faces.size() + " faces"); return m; } } Then I create a display list for my model using this code: objectDisplayList = GL11.glGenLists(1); GL11.glNewList(objectDisplayList, GL11.GL_COMPILE); Model m = null; try { m = OBJLoader.loadModel(new File("res/untitled4.obj")); } catch (Exception e1) { e1.printStackTrace(); } int currentTexture=0; for(Face face: m.faces) { if(face.texture!=currentTexture) { currentTexture = face.texture; GL11.glBindTexture(GL11.GL_TEXTURE_2D, currentTexture); } GL11.glColor3f(1f, 1f, 1f); GL11.glBegin(GL11.GL_TRIANGLES); Vector3f n1 = m.normals.get((int) face.normal.x - 1); GL11.glNormal3f(n1.x, n1.y, n1.z); Vector2f t1 = m.texVerticies.get((int) face.textures.x -1); GL11.glTexCoord2f(t1.x, t1.y); Vector3f v1 = m.verticies.get((int) face.vertex.x - 1); GL11.glVertex3f(v1.x, v1.y, v1.z); Vector3f n2 = m.normals.get((int) face.normal.y - 1); GL11.glNormal3f(n2.x, n2.y, n2.z); Vector2f t2 = m.texVerticies.get((int) face.textures.y -1); GL11.glTexCoord2f(t2.x, t2.y); Vector3f v2 = m.verticies.get((int) face.vertex.y - 1); GL11.glVertex3f(v2.x, v2.y, v2.z); Vector3f n3 = m.normals.get((int) face.normal.z - 1); GL11.glNormal3f(n3.x, n3.y, n3.z); Vector2f t3 = m.texVerticies.get((int) face.textures.z -1); GL11.glTexCoord2f(t3.x, t3.y); Vector3f v3 = m.verticies.get((int) face.vertex.z - 1); GL11.glVertex3f(v3.x, v3.y, v3.z); GL11.glEnd(); } GL11.glEndList(); The currentTexture is an int - it contains the ID of the currently used texture. So my model looks absolutely fine without textures: (sorry I cannot post hyperlinks since I am a new user) i.imgur.com/VtoK0.png But look what happens if I enable GL_TEXTURE_2D: i.imgur.com/z8Kli.png i.imgur.com/5e9nn.png i.imgur.com/FAHM9.png As you can see an entire side of the tree appears to be missing - and it's not transparent, since it's not in the colour of the background - it's rendered black. It's not a problem with the model - if I load it using Kanji's OBJ loader it works fine(but the thing is,that I need to write my own OBJ loader) i.imgur.com/YDATo.png this is my OpenGL init section: //init display try { Display.setDisplayMode(new DisplayMode(Support.SCREEN_WIDTH, Support.SCREEN_HEIGHT)); Display.create(); Display.setVSyncEnabled(true); } catch (LWJGLException e) { e.printStackTrace(); System.exit(0); } GL11.glLoadIdentity(); GL11.glEnable(GL11.GL_TEXTURE_2D); GL11.glClearColor(1.0f, 0.0f, 0.0f, 1.0f); GL11.glShadeModel(GL11.GL_SMOOTH); GL11.glEnable(GL11.GL_DEPTH_TEST); GL11.glDepthFunc(GL11.GL_LESS); GL11.glDepthMask(true); GL11.glEnable(GL11.GL_NORMALIZE); GL11.glMatrixMode(GL11.GL_PROJECTION); GLU.gluPerspective (90.0f,800f/600f, 1f, 500.0f); GL11.glMatrixMode(GL11.GL_MODELVIEW); GL11.glEnable(GL11.GL_CULL_FACE); GL11.glCullFace(GL11.GL_BACK); //enable lighting GL11.glEnable(GL11.GL_LIGHTING); ByteBuffer temp = ByteBuffer.allocateDirect(16); temp.order(ByteOrder.nativeOrder()); GL11.glMaterial(GL11.GL_FRONT, GL11.GL_DIFFUSE, (FloatBuffer)temp.asFloatBuffer().put(lightDiffuse).flip()); GL11.glMaterialf(GL11.GL_FRONT, GL11.GL_SHININESS,(int)material_shinyness); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_DIFFUSE, (FloatBuffer)temp.asFloatBuffer().put(lightDiffuse2).flip()); // Setup The Diffuse Light GL11.glLight(GL11.GL_LIGHT2, GL11.GL_POSITION,(FloatBuffer)temp.asFloatBuffer().put(lightPosition2).flip()); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_AMBIENT,(FloatBuffer)temp.asFloatBuffer().put(lightAmbient).flip()); GL11.glLight(GL11.GL_LIGHT2, GL11.GL_SPECULAR,(FloatBuffer)temp.asFloatBuffer().put(lightDiffuse2).flip()); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_CONSTANT_ATTENUATION, 0.1f); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_LINEAR_ATTENUATION, 0.0f); GL11.glLightf(GL11.GL_LIGHT2, GL11.GL_QUADRATIC_ATTENUATION, 0.0f); GL11.glEnable(GL11.GL_LIGHT2); Could somebody please help me?

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• Implementing an async "read all currently available data from stream" operation

  - by Jon

  I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a console's standard output Stream. Console output streams are of type FileStream; the implementation can cast to that, if needed. There is also an associated StreamReader already present to leverage. There is only one thing I need to implement in this class to achieve my desired functionality: an async "read all the data available this moment" operation. Reading to the end of the stream is not viable because the stream will not end unless the process closes the console output handle, and it will not do that because it is interactive and expecting input before continuing. I will be using that hypothetical async operation to implement event-based notification, which will be more convenient for my callers. The public interface of the class is this: public class ConsoleAutomator { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Remember that the goal here is to read all of the chunk and call event subscribers exactly once for each chunk. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream. private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer (in which case we know that there was no more data to be read during the last read operation), all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Never more than one event for each time data is available to be read Is almost agnostic to the buffer size The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this. Update: I definitely did not communicate the scenario well in my initial writeup. I have since revised the writeup quite a bit, but to be extra sure: The question is about how to implement an async "read all the data available this moment" operation. My apologies to the people who took the time to read and answer without me making my intent clear enough.

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• Jquery append input for 2 different input-sections

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  Hi i use the following simple jquery script to append input. Source http://muiomuio.com/web-design/add-remove-items-with-jquery <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Add and Remove - jQuery tutorial</title> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { var i = $('input').size() + 1; $('a.add').click(function() { $('<p><input type="text" value="input ' + i + '" name="input_field'+ i +'" /></p>').animate({ opacity: "show" }, "slow").appendTo('#inputs'); i++; }); $('a.remove').click(function() { if(i > 2) { $('input:last').animate({opacity:"hide"}, "slow").remove(); i--; } }); $('a.reset').click(function() { while(i > 2) { $('input:last').remove(); i--; } }); }); </script> </head> <body> <h1>Add / remove text fields from webform</h1> <a href="#" class="add"><img src="add.png" width="24" height="24" alt="add" title="add input" /></a> <a href="#" class="remove"><img src="remove.png" width="24" height="24" alt="remove input" /></a> <a href="#" class="reset"><img src="reset.png" width="24" height="24" alt="reset" /></a> <div id="inputs"> <p> <input type="text" value="input 1" name="input_field1"> </p> </div> </div> </body> </html> I know want to add more input fields so i add this html <div id="outputs"> <p> <input type="text" value="output 1" name="output_field1"> </p> how can i achieve that the var i = $('input').size() + 1; will be individually for every input section? EDITED: the full script is the following. copy and paste will get you a full clone of mine. Problem still exists <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Add and Remove - jQuery tutorial</title> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script> <script type="text/javascript"> $(function() { var i = $('input').size() + 1; $('a.add').click(function() { $('<p><input type="text" value="input ' + i + '" name="input_field'+ i +'" /></p>').animate({ opacity: "show" }, "slow").appendTo('#inputs'); i++; }); $('a.remove').click(function() { if(i > 2) { $('input:last').animate({opacity:"hide"}, "slow").remove(); i--; } }); $('a.reset').click(function() { while(i > 2) { $('input:last').remove(); i--; } }); $('a.add_o').click(function() { $('<p><input type="text" value="output ' + i + '" name="input_field'+ i +'" /></p>').animate({ opacity: "show" }, "slow").appendTo('#outputs'); i++; }); $('a.remove_o').click(function() { if(i > 2) { $('input:last').animate({opacity:"hide"}, "slow").remove(); i--; } }); $('a.reset_o').click(function() { while(i > 2) { $('input:last').remove(); i--; } }); }); </script> <style rel="stylesheet" type="text/css"> h1 { font-family:"Trebuchet MS", Arial, Helvetica, sans-serif;} .hide {visibility:hidden;} img {border:none;} input { width:500px; height:20px; padding:10px; background:#f7f7f7; border:1px solid #f0f0f0; color:#333; font-size:20px; text-align:center; line-height:120px; margin:0; -moz-border-radius:5px; -webkit-border-radius:5px; } #inputs { width:520px; padding:0px 20px; border:1px solid #f0f0f0; -moz-border-radius:20px; -webkit-border-radius:20px; } </style> </head> <body> <h1>Add / remove text fields from webform</h1> <a href="#" class="add"><img src="http://muiomuio.com/tutorials/jquery/add-remove/add.png" width="24" height="24" alt="add" title="add input" /></a> <a href="#" class="remove"><img src="http://muiomuio.com/tutorials/jquery/add-remove/remove.png" width="24" height="24" alt="remove input" /></a> <a href="#" class="reset"><img src="http://muiomuio.com/tutorials/jquery/add-remove/reset.png" width="24" height="24" alt="reset" /></a> <div id="inputs"> <p> <input type="text" value="input 1" name="input_field1"> </p> </div> <a href="#" class="add_o"><img src="http://muiomuio.com/tutorials/jquery/add-remove/add.png" width="24" height="24" alt="add" title="add input" /></a> <a href="#" class="remove_o"><img src="http://muiomuio.com/tutorials/jquery/add-remove/remove.png" width="24" height="24" alt="remove input" /></a> <a href="#" class="reset_o"><img src="http://muiomuio.com/tutorials/jquery/add-remove/reset.png" width="24" height="24" alt="reset" /></a> <div id="outputs"> <p> <input type="text" value="output 1" name="output_field1"> </p> </div> </body> </html>

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