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• Loaded OBJ Model Will Not Display in OpenGL / C++ Project

  - by Drake Summers

  I have been experimenting with new effects in game development. The programs I have written have been using generic shapes for the visuals. I wanted to test the effects on something a bit more complex, and wrote a resource loader for Wavefront OBJ files. I started with a simple cube in blender, exported it to an OBJ file with just vertices and triangulated faces, and used it to test the resource loader. I could not get the mesh to show up in my application. The loader never gave me any errors, so I wrote a snippet to loop through my vertex and index arrays that were returned from the loader. The data is exactly the way it is supposed to be. So I simplified the OBJ file by editing it directly to just show a front facing square. Still, nothing is displayed in the application. And don't worry, I did check to make sure that I decreased the value of each index by one while importing the OBJ. - BEGIN EDIT I also tested using glDrawArrays(GL_TRIANGLES, 0, 3 ); to draw the first triangle and it worked! So the issue could be in the binding of the VBO/IBO items. END EDIT - INDEX/VERTEX ARRAY OUTPUT: GLOBALS AND INITIALIZATION FUNCTION: GLuint program; GLint attrib_coord3d; std::vector<GLfloat> vertices; std::vector<GLushort> indices; GLuint vertexbuffer, indexbuffer; GLint uniform_mvp; int initialize() { if (loadModel("test.obj", vertices, indices)) { GLfloat myverts[vertices.size()]; copy(vertices.begin(), vertices.end(), myverts); GLushort myinds[indices.size()]; copy(indices.begin(), indices.end(), myinds); glGenBuffers(1, &vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(myverts), myverts, GL_STATIC_DRAW); glGenBuffers(1, &indexbuffer); glBindBuffer(GL_ARRAY_BUFFER, indexbuffer); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(myinds), myinds, GL_STATIC_DRAW); // OUTPUT DATA FROM NEW ARRAYS TO CONSOLE // ERROR HANDLING OMITTED FOR BREVITY } GLint link_result = GL_FALSE; GLuint vert_shader, frag_shader; if ((vert_shader = create_shader("tri.v.glsl", GL_VERTEX_SHADER)) == 0) return 0; if ((frag_shader = create_shader("tri.f.glsl", GL_FRAGMENT_SHADER)) == 0) return 0; program = glCreateProgram(); glAttachShader(program, vert_shader); glAttachShader(program, frag_shader); glLinkProgram(program); glGetProgramiv(program, GL_LINK_STATUS, &link_result); // ERROR HANDLING OMITTED FOR BREVITY const char* attrib_name; attrib_name = "coord3d"; attrib_coord3d = glGetAttribLocation(program, attrib_name); // ERROR HANDLING OMITTED FOR BREVITY const char* uniform_name; uniform_name = "mvp"; uniform_mvp = glGetUniformLocation(program, uniform_name); // ERROR HANDLING OMITTED FOR BREVITY return 1; } RENDERING FUNCTION: glm::mat4 model = glm::translate(glm::mat4(1.0f), glm::vec3(0.0, 0.0, -4.0)); glm::mat4 view = glm::lookAt(glm::vec3(0.0, 0.0, 4.0), glm::vec3(0.0, 0.0, 3.0), glm::vec3(0.0, 1.0, 0.0)); glm::mat4 projection = glm::perspective(45.0f, 1.0f*(screen_width/screen_height), 0.1f, 10.0f); glm::mat4 mvp = projection * view * model; int size; glUseProgram(program); glUniformMatrix4fv(uniform_mvp, 1, GL_FALSE, glm::value_ptr(mvp)); glClearColor(0.5, 0.5, 0.5, 1.0); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); glEnableVertexAttribArray(attrib_coord3d); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer(attrib_coord3d, 3, GL_FLOAT, GL_FALSE, 0, 0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexbuffer); glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &size); glDrawElements(GL_TRIANGLES, size/sizeof(GLushort), GL_UNSIGNED_SHORT, 0); glDisableVertexAttribArray(attrib_coord3d); VERTEX SHADER: attribute vec3 coord3d; uniform mat4 mvp; void main(void) { gl_Position = mvp * vec4(coord3d, 1.0); } FRAGMENT SHADER: void main(void) { gl_FragColor[0] = 0.0; gl_FragColor[1] = 0.0; gl_FragColor[2] = 1.0; gl_FragColor[3] = 1.0; } OBJ RESOURCE LOADER: bool loadModel(const char * path, std::vector<GLfloat> &out_vertices, std::vector<GLushort> &out_indices) { std::vector<GLfloat> temp_vertices; std::vector<GLushort> vertexIndices; FILE * file = fopen(path, "r"); // ERROR HANDLING OMITTED FOR BREVITY while(1) { char lineHeader[128]; int res = fscanf(file, "%s", lineHeader); if (res == EOF) { break; } if (strcmp(lineHeader, "v") == 0) { float _x, _y, _z; fscanf(file, "%f %f %f\n", &_x, &_y, &_z ); out_vertices.push_back(_x); out_vertices.push_back(_y); out_vertices.push_back(_z); } else if (strcmp(lineHeader, "f") == 0) { unsigned int vertexIndex[3]; int matches = fscanf(file, "%d %d %d\n", &vertexIndex[0], &vertexIndex[1], &vertexIndex[2]); out_indices.push_back(vertexIndex[0] - 1); out_indices.push_back(vertexIndex[1] - 1); out_indices.push_back(vertexIndex[2] - 1); } else { ... } } // ERROR HANDLING OMITTED FOR BREVITY return true; } I can edit the question to provide any further info you may need. I attempted to provide everything of relevance and omit what may have been unnecessary. I'm hoping this isn't some really poor mistake, because I have been at this for a few days now. If anyone has any suggestions or advice on the matter, I look forward to hearing it. As a final note: I added some arrays into the code with manually entered data, and was able to display meshes by using those arrays instead of the generated ones. I do not understand!

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• How can I render multiple windows with DirectX 9 in C++?

  - by Friso1990

  I'm trying to render multiple windows, using DirectX 9 and swap chains, but even though I create 2 windows, I only see the first one that I've created. My RendererDX9 header is this: #include <d3d9.h> #include <Windows.h> #include <vector> #include "RAT_Renderer.h" namespace RAT_ENGINE { class RAT_RendererDX9 : public RAT_Renderer { public: RAT_RendererDX9(); ~RAT_RendererDX9(); void Init(RAT_WindowManager* argWMan); void CleanUp(); void ShowWin(); private: LPDIRECT3D9 renderInterface; // Used to create the D3DDevice LPDIRECT3DDEVICE9 renderDevice; // Our rendering device LPDIRECT3DSWAPCHAIN9* swapChain; // Swapchain to make multi-window rendering possible WNDCLASSEX wc; std::vector<HWND> hwindows; void Render(int argI); }; } And my .cpp file is this: #include "RAT_RendererDX9.h" static LRESULT CALLBACK MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ); namespace RAT_ENGINE { RAT_RendererDX9::RAT_RendererDX9() : renderInterface(NULL), renderDevice(NULL) { } RAT_RendererDX9::~RAT_RendererDX9() { } void RAT_RendererDX9::Init(RAT_WindowManager* argWMan) { wMan = argWMan; // Register the window class WNDCLASSEX windowClass = { sizeof( WNDCLASSEX ), CS_CLASSDC, MsgProc, 0, 0, GetModuleHandle( NULL ), NULL, NULL, NULL, NULL, "foo", NULL }; wc = windowClass; RegisterClassEx( &wc ); for (int i = 0; i< wMan->getWindows().size(); ++i) { HWND hWnd = CreateWindow( "foo", argWMan->getWindow(i)->getName().c_str(), WS_OVERLAPPEDWINDOW, argWMan->getWindow(i)->getX(), argWMan->getWindow(i)->getY(), argWMan->getWindow(i)->getWidth(), argWMan->getWindow(i)->getHeight(), NULL, NULL, wc.hInstance, NULL ); hwindows.push_back(hWnd); } // Create the D3D object, which is needed to create the D3DDevice. renderInterface = (LPDIRECT3D9)Direct3DCreate9( D3D_SDK_VERSION ); // Set up the structure used to create the D3DDevice. Most parameters are // zeroed out. We set Windowed to TRUE, since we want to do D3D in a // window, and then set the SwapEffect to "discard", which is the most // efficient method of presenting the back buffer to the display. And // we request a back buffer format that matches the current desktop display // format. D3DPRESENT_PARAMETERS deviceConfig; ZeroMemory( &deviceConfig, sizeof( deviceConfig ) ); deviceConfig.Windowed = TRUE; deviceConfig.SwapEffect = D3DSWAPEFFECT_DISCARD; deviceConfig.BackBufferFormat = D3DFMT_UNKNOWN; deviceConfig.BackBufferHeight = 1024; deviceConfig.BackBufferWidth = 768; deviceConfig.EnableAutoDepthStencil = TRUE; deviceConfig.AutoDepthStencilFormat = D3DFMT_D16; // Create the Direct3D device. Here we are using the default adapter (most // systems only have one, unless they have multiple graphics hardware cards // installed) and requesting the HAL (which is saying we want the hardware // device rather than a software one). Software vertex processing is // specified since we know it will work on all cards. On cards that support // hardware vertex processing, though, we would see a big performance gain // by specifying hardware vertex processing. renderInterface->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwindows[0], D3DCREATE_SOFTWARE_VERTEXPROCESSING, &deviceConfig, &renderDevice ); this->swapChain = new LPDIRECT3DSWAPCHAIN9[wMan->getWindows().size()]; this->renderDevice->GetSwapChain(0, &swapChain[0]); for (int i = 0; i < wMan->getWindows().size(); ++i) { renderDevice->CreateAdditionalSwapChain(&deviceConfig, &swapChain[i]); } renderDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW); // Set cullmode to counterclockwise culling to save resources renderDevice->SetRenderState(D3DRS_AMBIENT, 0xffffffff); // Turn on ambient lighting renderDevice->SetRenderState(D3DRS_ZENABLE, TRUE); // Turn on the zbuffer } void RAT_RendererDX9::CleanUp() { renderDevice->Release(); renderInterface->Release(); } void RAT_RendererDX9::Render(int argI) { // Clear the backbuffer to a blue color renderDevice->Clear( 0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB( 0, 0, 255 ), 1.0f, 0 ); LPDIRECT3DSURFACE9 backBuffer = NULL; // Set draw target this->swapChain[argI]->GetBackBuffer(0, D3DBACKBUFFER_TYPE_MONO, &backBuffer); this->renderDevice->SetRenderTarget(0, backBuffer); // Begin the scene renderDevice->BeginScene(); // End the scene renderDevice->EndScene(); swapChain[argI]->Present(NULL, NULL, hwindows[argI], NULL, 0); } void RAT_RendererDX9::ShowWin() { for (int i = 0; i < wMan->getWindows().size(); ++i) { ShowWindow( hwindows[i], SW_SHOWDEFAULT ); UpdateWindow( hwindows[i] ); // Enter the message loop MSG msg; while( GetMessage( &msg, NULL, 0, 0 ) ) { if (PeekMessage( &msg, NULL, 0U, 0U, PM_REMOVE ) ) { TranslateMessage( &msg ); DispatchMessage( &msg ); } else { Render(i); } } } } } LRESULT CALLBACK MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ) { switch( msg ) { case WM_DESTROY: //CleanUp(); PostQuitMessage( 0 ); return 0; case WM_PAINT: //Render(); ValidateRect( hWnd, NULL ); return 0; } return DefWindowProc( hWnd, msg, wParam, lParam ); } I've made a sample function to make multiple windows: void RunSample1() { //Create the window manager. RAT_ENGINE::RAT_WindowManager* wMan = new RAT_ENGINE::RAT_WindowManager(); //Create the render manager. RAT_ENGINE::RAT_RenderManager* rMan = new RAT_ENGINE::RAT_RenderManager(); //Create a window. //This is currently needed to initialize the render manager and create a renderer. wMan->CreateRATWindow("Sample 1 - 1", 10, 20, 640, 480); wMan->CreateRATWindow("Sample 1 - 2", 150, 100, 480, 640); //Initialize the render manager. rMan->Init(wMan); //Show the window. rMan->getRenderer()->ShowWin(); } How do I get the multiple windows to work?

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• Class Mapping Error: 'T' must be a non-abstract type with a public parameterless constructor

  - by Amit Ranjan

  Hi, While mapping class i am getting error 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. Below is my SqlReaderBase Class public abstract class SqlReaderBase<T> : ConnectionProvider { #region Abstract Methods protected abstract string commandText { get; } protected abstract CommandType commandType { get; } protected abstract Collection<IDataParameter> GetParameters(IDbCommand command); **protected abstract MapperBase<T> GetMapper();** #endregion #region Non Abstract Methods /// <summary> /// Method to Execute Select Queries for Retrieveing List of Result /// </summary> /// <returns></returns> public Collection<T> ExecuteReader() { //Collection of Type on which Template is applied Collection<T> collection = new Collection<T>(); // initializing connection using (IDbConnection connection = GetConnection()) { try { // creates command for sql operations IDbCommand command = connection.CreateCommand(); // assign connection to command command.Connection = connection; // assign query command.CommandText = commandText; //state what type of query is used, text, table or Sp command.CommandType = commandType; // retrieves parameter from IDataParameter Collection and assigns it to command object foreach (IDataParameter param in GetParameters(command)) command.Parameters.Add(param); // Establishes connection with database server connection.Open(); // Since it is designed for executing Select statements that will return a list of results // so we will call command's execute reader method that return a Forward Only reader with // list of results inside. using (IDataReader reader = command.ExecuteReader()) { try { // Call to Mapper Class of the template to map the data to its // respective fields MapperBase<T> mapper = GetMapper(); collection = mapper.MapAll(reader); } catch (Exception ex) // catch exception { throw ex; // log errr } finally { reader.Close(); reader.Dispose(); } } } catch (Exception ex) { throw ex; } finally { connection.Close(); connection.Dispose(); } } return collection; } #endregion } What I am trying to do is , I am executine some command and filling my class dynamically. The class is given below: namespace FooZo.Core { public class Restaurant { #region Private Member Variables private int _restaurantId = 0; private string _email = string.Empty; private string _website = string.Empty; private string _name = string.Empty; private string _address = string.Empty; private string _phone = string.Empty; private bool _hasMenu = false; private string _menuImagePath = string.Empty; private int _cuisine = 0; private bool _hasBar = false; private bool _hasHomeDelivery = false; private bool _hasDineIn = false; private int _type = 0; private string _restaurantImagePath = string.Empty; private string _serviceAvailableTill = string.Empty; private string _serviceAvailableFrom = string.Empty; public string Name { get { return _name; } set { _name = value; } } public string Address { get { return _address; } set { _address = value; } } public int RestaurantId { get { return _restaurantId; } set { _restaurantId = value; } } public string Website { get { return _website; } set { _website = value; } } public string Email { get { return _email; } set { _email = value; } } public string Phone { get { return _phone; } set { _phone = value; } } public bool HasMenu { get { return _hasMenu; } set { _hasMenu = value; } } public string MenuImagePath { get { return _menuImagePath; } set { _menuImagePath = value; } } public string RestaurantImagePath { get { return _restaurantImagePath; } set { _restaurantImagePath = value; } } public int Type { get { return _type; } set { _type = value; } } public int Cuisine { get { return _cuisine; } set { _cuisine = value; } } public bool HasBar { get { return _hasBar; } set { _hasBar = value; } } public bool HasHomeDelivery { get { return _hasHomeDelivery; } set { _hasHomeDelivery = value; } } public bool HasDineIn { get { return _hasDineIn; } set { _hasDineIn = value; } } public string ServiceAvailableFrom { get { return _serviceAvailableFrom; } set { _serviceAvailableFrom = value; } } public string ServiceAvailableTill { get { return _serviceAvailableTill; } set { _serviceAvailableTill = value; } } #endregion public Restaurant() { } } } For filling my class properties dynamically i have another class called MapperBase Class with following methods: public abstract class MapperBase<T> where T : new() { protected T Map(IDataRecord record) { T instance = new T(); string fieldName; PropertyInfo[] properties = typeof(T).GetProperties(); for (int i = 0; i < record.FieldCount; i++) { fieldName = record.GetName(i); foreach (PropertyInfo property in properties) { if (property.Name == fieldName) { property.SetValue(instance, record[i], null); } } } return instance; } public Collection<T> MapAll(IDataReader reader) { Collection<T> collection = new Collection<T>(); while (reader.Read()) { collection.Add(Map(reader)); } return collection; } } There is another class which inherits the SqlreaderBaseClass called DefaultSearch. Code is below public class DefaultSearch: SqlReaderBase<Restaurant> { protected override string commandText { get { return "Select Name from vw_Restaurants"; } } protected override CommandType commandType { get { return CommandType.Text; } } protected override Collection<IDataParameter> GetParameters(IDbCommand command) { Collection<IDataParameter> parameters = new Collection<IDataParameter>(); parameters.Clear(); return parameters; } protected override MapperBase<Restaurant> GetMapper() { MapperBase<Restaurant> mapper = new RMapper(); return mapper; } } But whenever I tried to build , I am getting error 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. Even T here is Restaurant has a Parameterless Public constructor.

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• Project Euler #15

  - by Aistina

  Hey everyone, Last night I was trying to solve challenge #15 from Project Euler: Starting in the top left corner of a 2×2 grid, there are 6 routes (without backtracking) to the bottom right corner. How many routes are there through a 20×20 grid? I figured this shouldn't be so hard, so I wrote a basic recursive function: const int gridSize = 20; // call with progress(0, 0) static int progress(int x, int y) { int i = 0; if (x < gridSize) i += progress(x + 1, y); if (y < gridSize) i += progress(x, y + 1); if (x == gridSize && y == gridSize) return 1; return i; } I verified that it worked for a smaller grids such as 2×2 or 3×3, and then set it to run for a 20×20 grid. Imagine my surprise when, 5 hours later, the program was still happily crunching the numbers, and only about 80% done (based on examining its current position/route in the grid). Clearly I'm going about this the wrong way. How would you solve this problem? I'm thinking it should be solved using an equation rather than a method like mine, but that's unfortunately not a strong side of mine. Update: I now have a working version. Basically it caches results obtained before when a n×m block still remains to be traversed. Here is the code along with some comments: // the size of our grid static int gridSize = 20; // the amount of paths available for a "NxM" block, e.g. "2x2" => 4 static Dictionary<string, long> pathsByBlock = new Dictionary<string, long>(); // calculate the surface of the block to the finish line static long calcsurface(long x, long y) { return (gridSize - x) * (gridSize - y); } // call using progress (0, 0) static long progress(long x, long y) { // first calculate the surface of the block remaining long surface = calcsurface(x, y); long i = 0; // zero surface means only 1 path remains // (we either go only right, or only down) if (surface == 0) return 1; // create a textual representation of the remaining // block, for use in the dictionary string block = (gridSize - x) + "x" + (gridSize - y); // if a same block has not been processed before if (!pathsByBlock.ContainsKey(block)) { // calculate it in the right direction if (x < gridSize) i += progress(x + 1, y); // and in the down direction if (y < gridSize) i += progress(x, y + 1); // and cache the result! pathsByBlock[block] = i; } // self-explanatory :) return pathsByBlock[block]; } Calling it 20 times, for grids with size 1×1 through 20×20 produces the following output: There are 2 paths in a 1 sized grid 0,0110006 seconds There are 6 paths in a 2 sized grid 0,0030002 seconds There are 20 paths in a 3 sized grid 0 seconds There are 70 paths in a 4 sized grid 0 seconds There are 252 paths in a 5 sized grid 0 seconds There are 924 paths in a 6 sized grid 0 seconds There are 3432 paths in a 7 sized grid 0 seconds There are 12870 paths in a 8 sized grid 0,001 seconds There are 48620 paths in a 9 sized grid 0,0010001 seconds There are 184756 paths in a 10 sized grid 0,001 seconds There are 705432 paths in a 11 sized grid 0 seconds There are 2704156 paths in a 12 sized grid 0 seconds There are 10400600 paths in a 13 sized grid 0,001 seconds There are 40116600 paths in a 14 sized grid 0 seconds There are 155117520 paths in a 15 sized grid 0 seconds There are 601080390 paths in a 16 sized grid 0,0010001 seconds There are 2333606220 paths in a 17 sized grid 0,001 seconds There are 9075135300 paths in a 18 sized grid 0,001 seconds There are 35345263800 paths in a 19 sized grid 0,001 seconds There are 137846528820 paths in a 20 sized grid 0,0010001 seconds 0,0390022 seconds in total I'm accepting danben's answer, because his helped me find this solution the most. But upvotes also to Tim Goodman and Agos :) Bonus update: After reading Eric Lippert's answer, I took another look and rewrote it somewhat. The basic idea is still the same but the caching part has been taken out and put in a separate function, like in Eric's example. The result is some much more elegant looking code. // the size of our grid const int gridSize = 20; // magic. static Func<A1, A2, R> Memoize<A1, A2, R>(this Func<A1, A2, R> f) { // Return a function which is f with caching. var dictionary = new Dictionary<string, R>(); return (A1 a1, A2 a2) => { R r; string key = a1 + "x" + a2; if (!dictionary.TryGetValue(key, out r)) { // not in cache yet r = f(a1, a2); dictionary.Add(key, r); } return r; }; } // calculate the surface of the block to the finish line static long calcsurface(long x, long y) { return (gridSize - x) * (gridSize - y); } // call using progress (0, 0) static Func<long, long, long> progress = ((Func<long, long, long>)((long x, long y) => { // first calculate the surface of the block remaining long surface = calcsurface(x, y); long i = 0; // zero surface means only 1 path remains // (we either go only right, or only down) if (surface == 0) return 1; // calculate it in the right direction if (x < gridSize) i += progress(x + 1, y); // and in the down direction if (y < gridSize) i += progress(x, y + 1); // self-explanatory :) return i; })).Memoize(); By the way, I couldn't think of a better way to use the two arguments as a key for the dictionary. I googled around a bit, and it seems this is a common solution. Oh well.

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• what is the problem in ATM machine program

  - by Have alook

  in this prigramm when the account number is uncorrect it should display a message to write a gain but when i wrote a gain by corrrect account number always it diplay the result of first account also there is aproblem in PIN number ,the use have only three time to try if he enter wrong numbe and if enter three times wrong it should stop the program but it complete to the last part I dont know why pleas help me this is my proram import java.util.*; class assignment2_70307{ public static void main(String args[]){ Scanner m=new Scanner(System.in); int i; i=0; int [] accountNo =new int[7] ;//declear the Accont number array accountNo [0] =1111; accountNo [1] =2222; accountNo [2] =3333; accountNo [3] =4444; accountNo [4] =5555; accountNo [5] =6666; accountNo [6] =7777; int [] PINno =new int[7]; //declear the PIN number array PINno [0] =1234; PINno [1] =5678; PINno [2] =9874; PINno [3] =6523; PINno [4] =1236; PINno [5] =4569; PINno [6] =8521; String [] CusomerNm =new String[7]; //dclear the customer name CusomerNm [0] ="Ali"; CusomerNm [1] ="Ahmed"; CusomerNm [2] ="Amal"; CusomerNm [3] ="Said"; CusomerNm [4] ="Rashid"; CusomerNm [5] ="Fatema"; CusomerNm [6] ="Mariam"; double [] Balance =new double[7]; //declear the Balane array Balance [0] =100.50; Balance [1] =5123.00; Balance [2] =12.00; Balance [3] =4569.00; Balance [4] =1020.25; Balance [5] =0.00; Balance [6] =44.10; System.out.println("Wellcome to mini ATM Machine"); int accountno,pino; accountno=0; pino=0; System.out.println("Please Enter your account number: or -1 to stop" ); accountno=m.nextInt(); if (accountno==accountNo[0]) System.out.print("Customer Name: "+CusomerNm [0]+ "\n" ); else if (accountno==accountNo[1]) System.out.print("Customer Name: "+CusomerNm [1]+ "\n" ); else if (accountno==accountNo[2]) System.out.print("Customer Name: "+CusomerNm [2]+ "\n" ); else if (accountno==accountNo[3]) System.out.print("Customer Name: "+CusomerNm [3]+ "\n" ); else if (accountno==accountNo[4]) System.out.print("Customer Name: "+CusomerNm [4]+ "\n" ); else if (accountno==accountNo[5]) System.out.print("Customer Name: "+CusomerNm [5]+ "\n" ); else if (accountno==accountNo[6]) System.out.print("Customer Name: "+CusomerNm [6]+ "\n" ); // else if (accountNo[0]==-1) //break; else { System.out.println("The account dose not exist,please try again"); //accountNo[i]=m.nextInt(); accountno=m.nextInt(); if(accountNo[i]==accountno) System.out.println("Customer Name: "+CusomerNm[i] ); else System.out.println("The account dose not exist,please try again"); accountno=m.nextInt(); System.out.println("Customer Name: "+CusomerNm[i] ); } System.out.print("Enter your PIN number:"); PINno[i]=m.nextInt(); if(PINno[i]==1234) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [0]+ "Rial"); //return 0; } else if(PINno[i]==5678) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [1]+ "Rial"); // return 1; } else if(PINno[i]==9874) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [2]+ "Rial"); // return 2; } else if(PINno[i]==6523) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [3]+ "Rial"); // return 3; } else if(PINno[i]==1236) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [4]+ "Rial"); // return 4; } else if(PINno[i]==4569) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [5]+ "Rial"); // return 5; } else if(PINno[i]==8521) { System.out.println(PINno[i]); System.out.println("Balance:"+Balance [6]+ "Rial"); // return 6; } else {System.out.println("try again"); //return 7; //if its wrong u can enter PIN number three times only for( i=0;i<2;i++) { System.out.println("enter pin again"); PINno[i]=m.nextInt(); String ss; //ss = "MAnal"; // goto ss ; } } //ss = "m"; int x; x=0; System.out.println("Enter the option from the list /n 1.Deposit /n 2.Withdraw /n 3.Balance"); x=m.nextInt(); double balance,amount; balance=0; amount=0; double deposit ,Withdraw; deposit=0; Withdraw=0; if (x==1){ System.out.println("Enter the amont you want to deposit:"+amount); amount=m.nextDouble(); Balance [i]=Balance [i]+amount; System.out.println("your balance ="+Balance [i]); } else if (x==2) { System.out.println("Enter the amont to withdraw:"); amount=m.nextDouble(); System.out.print(amount); if(Withdraw<=Balance [i]) { Balance [i]=Balance [i]-amount; System.out.println("your balance ="+Balance [i]); } else { System.out.println("sorry,please enter the amont less or equal your balance"); System.out.println(Balance [i]); } } else { if(x==1) { Balance [i]=Balance [i]+deposit; System.out.println("your current balance is :" +Balance [i]); } else { Balance [i]=Balance [i]-Withdraw; System.out.println("your current balance is :"+Balance [i]); } System.out.println("Thank you"); // err() } } }

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• SocketChannel in Java sends data, but it doesn't get to destination application

  - by Peterson

  Hi Everybody, I'm suffering a lot to create a simple ChatServer in Java, using the NIO libraries. Wonder if someone could help me. I am doing that by using SocketChannel and Selector to handle multiple clients in a single thread. The problem is: I am able to accept new connections and get it's data, but when I try to send data back, the SocketChannel simply doesn't work. In the method write(), it returns a integer that is the same size of the data i'm passing to it, but the client never receives that data. Strangely, when I close the server application, the client receives the data. It's like the socketchannel maintains a buffer, and it only get flushed when I close the application. Here are some more details, to give you more information to help. I'm handling the events in this piece of code: private void run() throws IOException { ServerSocketChannel ssc = ServerSocketChannel.open(); // Set it to non-blocking, so we can use select ssc.configureBlocking( false ); // Get the Socket connected to this channel, and bind it // to the listening port this.serverSocket = ssc.socket(); InetSocketAddress isa = new InetSocketAddress( this.port ); serverSocket.bind( isa ); // Create a new Selector for selecting this.masterSelector = Selector.open(); // Register the ServerSocketChannel, so we can // listen for incoming connections ssc.register( masterSelector, SelectionKey.OP_ACCEPT ); while (true) { // See if we've had any activity -- either // an incoming connection, or incoming data on an // existing connection int num = masterSelector.select(); // If we don't have any activity, loop around and wait // again if (num == 0) { continue; } // Get the keys corresponding to the activity // that has been detected, and process them // one by one Set keys = masterSelector.selectedKeys(); Iterator it = keys.iterator(); while (it.hasNext()) { // Get a key representing one of bits of I/O // activity SelectionKey key = (SelectionKey)it.next(); // What kind of activity is it? if ((key.readyOps() & SelectionKey.OP_ACCEPT) == SelectionKey.OP_ACCEPT) { // Aceita a conexão Socket s = serverSocket.accept(); System.out.println( "LOG: Conexao TCP aceita de " + s.getInetAddress() + ":" + s.getPort() ); // Make sure to make it non-blocking, so we can // use a selector on it. SocketChannel sc = s.getChannel(); sc.configureBlocking( false ); // Registra a conexao no seletor, apenas para leitura sc.register( masterSelector, SelectionKey.OP_READ ); } else if ( key.isReadable() ) { SocketChannel sc = null; // It's incoming data on a connection, so // process it sc = (SocketChannel)key.channel(); // Verifica se a conexão corresponde a um cliente já existente if((clientsMap.getClient(key)) != null){ boolean closedConnection = !processIncomingClientData(key); if(closedConnection){ int id = clientsMap.getClient(key); closeClient(id); } } else { boolean clientAccepted = processIncomingDataFromNewClient(key); if(!clientAccepted){ // Se o cliente não foi aceito, sua conexão é simplesmente fechada sc.socket().close(); sc.close(); key.cancel(); } } } } // We remove the selected keys, because we've dealt // with them. keys.clear(); } } This piece of code is simply handles new clients that wants to connect to the chat. So, a client makes a TCP connection to the server, and once it gets accepted, it sends data to the server following a simply text protocol, informing his id and asking to get registrated to the server. I handle this in the method processIncomingDataFromNewClient(key). I'm also keeping a map of clients and its connections in a data structure similar to a hashtable. I? doing that because I need to recover a client Id from a connection and a connection from a client Id. This is can be shown in: clientsMap.getClient(key). But the problem itself resides in the method processIncomingDataFromNewClient(key). There, I simply read the data that the client sent to me, validate it, and if it's ok, I send a message back to the client to tell that it is connected to the chat server. Here is a similar piece of code: private boolean processIncomingDataFromNewClient(SelectionKey key){ SocketChannel sc = (SocketChannel) key.channel(); String connectionOrigin = sc.socket().getInetAddress() + ":" + sc.socket().getPort(); int id = 0; //id of the client buf.clear(); int bytesRead = 0; try { bytesRead = sc.read(buf); if(bytesRead<=0){ System.out.println("Conexão fechada pelo: " + connectionOrigin); return false; } System.out.println("LOG: " + bytesRead + " bytes lidos de " + connectionOrigin); String msg = new String(buf.array(),0,bytesRead); // Do validations with the client sent me here // gets the client id }catch (Exception e) { e.printStackTrace(); System.out.println("LOG: Oops. Cliente não conhece o protocolo. Fechando a conexão: " + connectionOrigin); System.out.println("LOG: Primeiros 10 caracteres enviados pelo cliente: " + msg); return false; } } } catch (IOException e) { System.out.println("LOG: Erro ao ler dados da conexao: " + connectionOrigin); System.out.println("LOG: "+ e.getLocalizedMessage()); System.out.println("LOG: Fechando a conexão..."); return false; } // If it gets to here, the protocol is ok and we can add the client boolean inserted = clientsMap.addClient(key, id); if(!inserted){ System.out.println("LOG: Não foi possível adicionar o cliente. Ou ele já está conectado ou já têm clientes demais. Id: " + id); System.out.println("LOG: Fechando a conexão: " + connectionOrigin); return false; } System.out.println("LOG: Novo cliente conectado! Enviando mesnsagem de confirmação. Id: " + id + " Conexao: " + connectionOrigin); /* Here is the error */ sendMessage(id, "Servidor pet: connection accepted"); System.out.println("LOG: Novo cliente conectado! Id: " + id + " Conexao: " + connectionOrigin); return true; } And finally, the method sendMessage(SelectionKey key) looks like this: private void sendMessage(int destId, String msg) { Charset charset = Charset.forName("ISO-8859-1"); CharBuffer charBuffer = CharBuffer.wrap(msg, 0, msg.length()); ByteBuffer bf = charset.encode(charBuffer); //bf.flip(); int bytesSent = 0; SelectionKey key = clientsMap.getClient(destId); SocketChannel sc = (SocketChannel) key.channel(); try { / int total_bytes_sent = 0; while(total_bytes_sent < msg.length()){ bytesSent = sc.write(bf); total_bytes_sent += bytesSent; } System.out.println("LOG: Bytes enviados para o cliente " + destId + ": "+ total_bytes_sent + " Tamanho da mensagem: " + msg.length()); } catch (IOException e) { System.out.println("LOG: Erro ao mandar mensagem para: " + destId); System.out.println("LOG: " + e.getLocalizedMessage()); } } So, what is happening is that the server, when send a message, prints something like this: LOG: Bytes sent to the client: 28 Size of the message: 28 So, it tells that it sent the data, but the chat client keeps blocking, waiting in the recv() method. So, the data never gets to it. When I close the server application, though, all the data appears in the client. I wonder why. It is important to say that the client is in C and the server JAVA, and I'm running both in the same machine, an Ubuntu Guest in virtualbox under windows. I also run both under windows host and under linuxes hosts, and keep getting the same strange problem. I'm sorry for the great lenght of this question, but I already searched a lot of places for an answer, found a lot of tutorials and questions, including here at StackOverflow, but coundn't find a reasonable explanation. I am really not liking this Java NIO, and i saw a lot of people complaining about it too. I am thinking that if I had done that in C it would have been a lot easier :-D So, if someone could help me and even discuss this behavor, it would be great! :-) Thanks everybody in advance, Péterson

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• Adding Polynomials (Linked Lists)......Bug Help

  - by Brian

  I have written a program that creates nodes that in this class are parts of polynomials and then the two polynomials get added together to become one polynomial (list of nodes). All my code compiles so the only problem I am having is that the nodes are not inserting into the polynomial via the insert method I have in polynomial.java and when running the program it does create nodes and displays them in the 2x^2 format but when it comes to add the polynomials together it displays o as the polynomials, so if anyone can figure out whats wrong and what I can do to fix it it would be much appreciated. Here is the code: import java.util.Scanner; class Polynomial{ public termNode head; public Polynomial() { head = null; } public boolean isEmpty() { return (head == null); } public void display() { if (head == null) System.out.print("0"); else for(termNode cur = head; cur != null; cur = cur.getNext()) { System.out.println(cur); } } public void insert(termNode newNode) { termNode prev = null; termNode cur = head; while (cur!=null && (newNode.compareTo(cur)<0)) { prev = null; cur = cur.getNext(); } if (prev == null) { newNode.setNext(head); head = newNode; } else { newNode.setNext(cur); prev.setNext(newNode); } } public void readPolynomial(Scanner kb) { boolean done = false; double coefficient; int exponent; termNode term; head = null; //UNLINK ANY PREVIOUS POLYNOMIAL System.out.println("Enter 0 and 0 to end."); System.out.print("coefficient: "); coefficient = kb.nextDouble(); System.out.println(coefficient); System.out.print("exponent: "); exponent = kb.nextInt(); System.out.println(exponent); done = (coefficient == 0 && exponent == 0); while(!done) { Polynomial poly = new Polynomial(); term = new termNode(coefficient,exponent); System.out.println(term); poly.insert(term); System.out.println("Enter 0 and 0 to end."); System.out.print("coefficient: "); coefficient = kb.nextDouble(); System.out.println(coefficient); System.out.print("exponent: "); exponent = kb.nextInt(); System.out.println(exponent); done = (coefficient==0 && exponent==0); } } public static Polynomial add(Polynomial p, Polynomial q) { Polynomial r = new Polynomial(); double coefficient; int exponent; termNode first = p.head; termNode second = q.head; termNode sum = r.head; termNode term; while (first != null && second != null) { if (first.getExp() == second.getExp()) { if (first.getCoeff() != 0 && second.getCoeff() != 0); { double addCoeff = first.getCoeff() + second.getCoeff(); term = new termNode(addCoeff,first.getExp()); sum.setNext(term); first.getNext(); second.getNext(); } } else if (first.getExp() < second.getExp()) { sum.setNext(second); term = new termNode(second.getCoeff(),second.getExp()); sum.setNext(term); second.getNext(); } else { sum.setNext(first); term = new termNode(first.getNext()); sum.setNext(term); first.getNext(); } } while (first != null) { sum.setNext(first); } while (second != null) { sum.setNext(second); } return r; } } Here is my Node class: class termNode implements Comparable { private int exp; private double coeff; private termNode next; public termNode(double coefficient, int exponent) { coeff = coefficient; exp = exponent; next = null; } public termNode(termNode inTermNode) { coeff = inTermNode.coeff; exp = inTermNode.exp; } public void setData(double coefficient, int exponent) { coefficient = coeff; exponent = exp; } public double getCoeff() { return coeff; } public int getExp() { return exp; } public void setNext(termNode link) { next = link; } public termNode getNext() { return next; } public String toString() { if (exp == 0) { return(coeff + " "); } else if (exp == 1) { return(coeff + "x"); } else { return(coeff + "x^" + exp); } } public int compareTo(Object other) { if(exp ==((termNode) other).exp) return 0; else if(exp < ((termNode) other).exp) return -1; else return 1; } } And here is my Test class to run the program. import java.util.Scanner; class PolyTest{ public static void main(String [] args) { Scanner kb = new Scanner(System.in); Polynomial r; Polynomial p = new Polynomial(); System.out.println("Enter first polynomial."); p.readPolynomial(kb); Polynomial q = new Polynomial(); System.out.println(); System.out.println("Enter second polynomial."); q.readPolynomial(kb); r = Polynomial.add(p,q); System.out.println(); System.out.print("The sum of "); p.display(); System.out.print(" and "); q.display(); System.out.print(" is "); r.display(); } }

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• Different behavior of functors (copies, assignments) in VS2010 (compared with VS2005)

  - by Patrick

  When moving from VS2005 to VS2010 we noticed a performance decrease, which seemed to be caused by additional copies of a functor. The following code illustrates the problem. It is essential to have a map where the value itself is a set. On both the map and the set we defined a comparison functor (which is templated in the example). #include <iostream> #include <map> #include <set> class A { public: A(int i, char c) : m_i(i), m_c(c) { std::cout << "Construct object " << m_c << m_i << std::endl; } A(const A &a) : m_i(a.m_i), m_c(a.m_c) { std::cout << "Copy object " << m_c << m_i << std::endl; } ~A() { std::cout << "Destruct object " << m_c << m_i << std::endl; } void operator= (const A &a) { m_i = a.m_i; m_c = a.m_c; std::cout << "Assign object " << m_c << m_i << std::endl; } int m_i; char m_c; }; class B : public A { public: B(int i) : A(i, 'B') { } static const char s_c = 'B'; }; class C : public A { public: C(int i) : A(i, 'C') { } static const char s_c = 'C'; }; template <class X> class compareA { public: compareA() : m_i(999) { std::cout << "Construct functor " << X::s_c << m_i << std::endl; } compareA(const compareA &a) : m_i(a.m_i) { std::cout << "Copy functor " << X::s_c << m_i << std::endl; } ~compareA() { std::cout << "Destruct functor " << X::s_c << m_i << std::endl; } void operator= (const compareA &a) { m_i = a.m_i; std::cout << "Assign functor " << X::s_c << m_i << std::endl; } bool operator() (const X &x1, const X &x2) const { std::cout << "Comparing object " << x1.m_i << " with " << x2.m_i << std::endl; return x1.m_i < x2.m_i; } private: int m_i; }; typedef std::set<C, compareA<C> > SetTest; typedef std::map<B, SetTest, compareA<B> > MapTest; int main() { int i = 0; std::cout << "--- " << i++ << std::endl; MapTest mapTest; std::cout << "--- " << i++ << std::endl; SetTest &setTest = mapTest[0]; std::cout << "--- " << i++ << std::endl; } If I compile this code with VS2005 I get the following output: --- 0 Construct functor B999 Copy functor B999 Copy functor B999 Destruct functor B999 Destruct functor B999 --- 1 Construct object B0 Construct functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Copy object B0 Copy functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Copy object B0 Copy functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Destruct functor C999 Destruct object B0 Destruct functor C999 Destruct object B0 --- 2 If I compile this with VS2010, I get the following output: --- 0 Construct functor B999 Copy functor B999 Copy functor B999 Destruct functor B999 Destruct functor B999 --- 1 Construct object B0 Construct functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Copy object B0 Copy functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Copy functor C999 Assign functor C999 Assign functor C999 Destruct functor C999 Copy object B0 Copy functor C999 Copy functor C999 Copy functor C999 Destruct functor C999 Destruct functor C999 Copy functor C999 Assign functor C999 Assign functor C999 Destruct functor C999 Destruct functor C999 Destruct object B0 Destruct functor C999 Destruct object B0 --- 2 The output for the first statement (constructing the map) is identical. The output for the second statement (creating the first element in the map and getting a reference to it), is much bigger in the VS2010 case: Copy constructor of functor: 10 times vs 8 times Assignment of functor: 2 times vs. 0 times Destructor of functor: 10 times vs 8 times My questions are: Why does the STL copy a functor? Isn't it enough to construct it once for every instantiation of the set? Why is the functor constructed more in the VS2010 case than in the VS2005 case? (didn't check VS2008) And why is it assigned two times in VS2010 and not in VS2005? Are there any tricks to avoid the copy of functors? I saw a similar question at http://stackoverflow.com/questions/2216041/prevent-unnecessary-copies-of-c-functor-objects but I'm not sure that's the same question. Thanks in advance, Patrick

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• C sockets, chat server and client, problem echoing back.

  - by wretrOvian

  Hi This is my chat server : #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define LISTEN_Q 20 #define MSG_SIZE 1024 struct userlist { int sockfd; struct sockaddr addr; struct userlist *next; }; int main(int argc, char *argv[]) { // declare. int listFD, newFD, fdmax, i, j, bytesrecvd; char msg[MSG_SIZE], ipv4[INET_ADDRSTRLEN]; struct addrinfo hints, *srvrAI; struct sockaddr_storage newAddr; struct userlist *users, *uptr, *utemp; socklen_t newAddrLen; fd_set master_set, read_set; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // create a user list users = (struct userlist *)malloc(sizeof(struct userlist)); users->sockfd = -1; //users->addr = NULL; users->next = NULL; // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo("localhost", argv[1], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((listFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // bind socket bind(listFD, srvrAI->ai_addr, srvrAI->ai_addrlen); // listen on socket if(listen(listFD, LISTEN_Q) == -1) { perror("* ERROR | listen()\n"); exit(1); } // add listfd to master_set FD_SET(listFD, &master_set); // initialize fdmax fdmax = listFD; while(1) { // equate read_set = master_set; // run select if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()\n"); exit(1); } // query all sockets for(i = 0; i <= fdmax; i++) { if(FD_ISSET(i, &read_set)) { // found active sockfd if(i == listFD) { // new connection // accept newAddrLen = sizeof newAddr; if((newFD = accept(listFD, (struct sockaddr *)&newAddr, &newAddrLen)) == -1) { perror("* ERROR | select()\n"); exit(1); } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&newAddr)->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } fprintf(stdout, "* Client Connected | %s\n", ipv4); // add to master list FD_SET(newFD, &master_set); // create new userlist component utemp = (struct userlist*)malloc(sizeof(struct userlist)); utemp->next = NULL; utemp->sockfd = newFD; utemp->addr = *((struct sockaddr *)&newAddr); // iterate to last node for(uptr = users; uptr->next != NULL; uptr = uptr->next) { } // add uptr->next = utemp; // update fdmax if(newFD > fdmax) fdmax = newFD; } else { // existing sockfd transmitting data // read if((bytesrecvd = recv(i, msg, MSG_SIZE, 0)) == -1) { perror("* ERROR | recv()\n"); exit(1); } msg[bytesrecvd] = '\0'; // find out who sent? for(uptr = users; uptr->next != NULL; uptr = uptr->next) { if(i == uptr->sockfd) break; } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&(uptr->addr))->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } // print fprintf(stdout, "%s\n", msg); // send to all for(j = 0; j <= fdmax; j++) { if(FD_ISSET(j, &master_set)) { if(send(j, msg, strlen(msg), 0) == -1) perror("* ERROR | send()"); } } } // handle read from client } // end select result handle } // end looping fds } // end while return 0; } This is my client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define MSG_SIZE 1024 int main(int argc, char *argv[]) { // declare. int newFD, bytesrecvd, fdmax; char msg[MSG_SIZE]; fd_set master_set, read_set; struct addrinfo hints, *srvrAI; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo(argv[1], argv[2], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((newFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // connect to server if(connect(newFD, srvrAI->ai_addr, srvrAI->ai_addrlen) == -1) { perror("* ERROR | connect()\n"); exit(1); } // add to master, and add keyboard FD_SET(newFD, &master_set); FD_SET(STDIN_FILENO, &master_set); // initialize fdmax if(newFD > STDIN_FILENO) fdmax = newFD; else fdmax = STDIN_FILENO; while(1) { // equate read_set = master_set; if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()"); exit(1); } // check server if(FD_ISSET(newFD, &read_set)) { // read data if((bytesrecvd = recv(newFD, msg, MSG_SIZE, 0)) < 0 ) { perror("* ERROR | recv()"); exit(1); } msg[bytesrecvd] = '\0'; // print fprintf(stdout, "%s\n", msg); } // check keyboard if(FD_ISSET(STDIN_FILENO, &read_set)) { // read data from stdin if((bytesrecvd = read(STDIN_FILENO, msg, MSG_SIZE)) < 0) { perror("* ERROR | read()"); exit(1); } msg[bytesrecvd] = '\0'; // send if((send(newFD, msg, bytesrecvd, 0)) == -1) { perror("* ERROR | send()"); exit(1); } } } return 0; } The problem is with the part where the server recv()s data from an FD, then tries echoing back to all [send() ]; it just dies, w/o errors, and my client is left looping :(

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• What would be a correct implemantation of JSF Converter if I need to get an Integer to run a query?

  - by Ignacio

  HI here's my code: List.xhmtl <h:selectOneMenu value="#{produtosController.items}"> <f:selectItems value="#{produtosController.itemsAvailableSelectOne}"/> </h:selectOneMenu> <h:commandButton action="#{produtosController.createByCodigos}" value="Buscar" /> My Controller Class with innner Converter implemantation @ManagedBean (name="produtosController") @SessionScoped public class ProdutosController { private Produtos current; private DataModel items = null; @EJB private controladores.ProdutosFacade ejbFacade; private PaginationHelper pagination; private int selectedItemIndex; public ProdutosController() { } public Produtos getSelected() { if (current == null) { current = new Produtos(); selectedItemIndex = -1; } return current; } private ProdutosFacade getFacade() { return ejbFacade; } public PaginationHelper getPagination() { if (pagination == null) { pagination = new PaginationHelper(10) { @Override public int getItemsCount() { return getFacade().count(); } @Override public DataModel createPageDataModel() { return new ListDataModel(getFacade().findRange(new int[]{getPageFirstItem(), getPageFirstItem()+getPageSize()})); } }; } return pagination; } public String prepareList() { recreateModel(); return "List"; } public String prepareView() { current = (Produtos)getItems().getRowData(); selectedItemIndex = pagination.getPageFirstItem() + getItems().getRowIndex(); return "View"; } public String prepareCreate() { current = new Produtos(); selectedItemIndex = -1; return "Create"; } public String create() { try { getFacade().create(current); JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("ProdutosCreated")); return prepareCreate(); } catch (Exception e) { JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured")); return null; } } public String createByMarcas() { items = new ListDataModel(ejbFacade.findByMarcas(current.getIdMarca())); updateCurrentItem(); return "List"; } public String createByModelos() { items = new ListDataModel(ejbFacade.findByModelos(current.getIdModelo())); updateCurrentItem(); return "List"; } public String createByCodigos(){ items = new ListDataModel(ejbFacade.findByCodigo(current.getCodigo())); updateCurrentItem(); return "List"; } public String prepareEdit() { current = (Produtos)getItems().getRowData(); selectedItemIndex = pagination.getPageFirstItem() + getItems().getRowIndex(); return "Edit"; } public String update() { try { getFacade().edit(current); JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("ProdutosUpdated")); return "View"; } catch (Exception e) { JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured")); return null; } } public String destroy() { current = (Produtos)getItems().getRowData(); selectedItemIndex = pagination.getPageFirstItem() + getItems().getRowIndex(); performDestroy(); recreateModel(); return "List"; } public String destroyAndView() { performDestroy(); recreateModel(); updateCurrentItem(); if (selectedItemIndex >= 0) { return "View"; } else { // all items were removed - go back to list recreateModel(); return "List"; } } private void performDestroy() { try { getFacade().remove(current); JsfUtil.addSuccessMessage(ResourceBundle.getBundle("/Bundle").getString("ProdutosDeleted")); } catch (Exception e) { JsfUtil.addErrorMessage(e, ResourceBundle.getBundle("/Bundle").getString("PersistenceErrorOccured")); } } private void updateCurrentItem() { int count = getFacade().count(); if (selectedItemIndex >= count) { // selected index cannot be bigger than number of items: selectedItemIndex = count-1; // go to previous page if last page disappeared: if (pagination.getPageFirstItem() >= count) { pagination.previousPage(); } } if (selectedItemIndex >= 0) { current = getFacade().findRange(new int[]{selectedItemIndex, selectedItemIndex+1}).get(0); } } public DataModel getItems() { if (items == null) { items = getPagination().createPageDataModel(); } return items; } private void recreateModel() { items = null; } public String next() { getPagination().nextPage(); recreateModel(); return "List"; } public String previous() { getPagination().previousPage(); recreateModel(); return "List"; } public SelectItem[] getItemsAvailableSelectMany() { return JsfUtil.getSelectItems(ejbFacade.findAll(), false); } public SelectItem[] getItemsAvailableSelectOne() { return JsfUtil.getSelectItems(ejbFacade.findAll(), true); } @FacesConverter(forClass=Produtos.class) public static class ProdutosControllerConverter implements Converter{ public Object getAsObject(FacesContext facesContext, UIComponent component, String value) { if (value == null || value.length() == 0) { return null; } ProdutosController controller = (ProdutosController)facesContext.getApplication().getELResolver(). getValue(facesContext.getELContext(), null, "produtosController"); return controller.ejbFacade.find(getKey(value)); } java.lang.Integer getKey(String value) { java.lang.Integer key; key = Integer.decode(value); return key; } String getStringKey(java.lang.Integer value) { StringBuffer sb = new StringBuffer(); sb.append(value); return sb.toString(); } public String getAsString(FacesContext facesContext, UIComponent component, Object object) { if (object == null) { return null; } if (object instanceof Produtos) { Produtos o = (Produtos) object; return getStringKey(o.getCodigo()); } else { throw new IllegalArgumentException("object " + object + " is of type " + object.getClass().getName() + "; expected type: "+ProdutosController.class.getName()); } } } } and my EJB @Entity @ViewScoped @Table(name = "produtos") @NamedQueries({ @NamedQuery(name = "Produtos.findAll", query = "SELECT p FROM Produtos p"), @NamedQuery(name = "Produtos.findById", query = "SELECT p FROM Produtos p WHERE p.id = :id"), @NamedQuery(name = "Produtos.findByCodigo", query = "SELECT p FROM Produtos p WHERE p.codigo = :codigo"), @NamedQuery(name = "Produtos.findByDescripcion", query = "SELECT p FROM Produtos p WHERE p.descripcion = :descripcion"), @NamedQuery(name = "Produtos.findByImagen", query = "SELECT p FROM Produtos p WHERE p.imagen = :imagen"), @NamedQuery(name = "Produtos.findByMarcas", query="SELECT m FROM Produtos m WHERE m.idMarca.id = :idMarca"), @NamedQuery(name = "Produtos.findByModelos", query="SELECT m FROM Produtos m WHERE m.idModelo.id = :idModelo")}) public class Produtos implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Basic(optional = false) @Column(name = "id") private Integer id; @Column(name = "codigo") private Integer codigo; @Column(name = "descripcion") private String descripcion; @Column(name = "imagen") private String imagen; @JoinColumn(name = "id_modelo", referencedColumnName = "id") @ManyToOne(optional = false) private Modelos idModelo; @JoinColumn(name = "id_marca", referencedColumnName = "id") @ManyToOne(optional = false) private Marcas idMarca; public Produtos() { } public Produtos(Integer id) { this.id = id; } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public Integer getCodigo() { return codigo; } public void setCodigo(Integer codigo) { this.codigo = codigo; } public String getDescripcion() { return descripcion; } public void setDescripcion(String descripcion) { this.descripcion = descripcion; } public String getImagen() { return imagen; } public void setImagen(String imagen) { this.imagen = imagen; } public Modelos getIdModelo() { return idModelo; } public void setIdModelo(Modelos idModelo) { this.idModelo = idModelo; } public Marcas getIdMarca() { return idMarca; } public void setIdMarca(Marcas idMarca) { this.idMarca = idMarca; } @Override public int hashCode() { int hash = 0; hash += (id != null ? id.hashCode() : 0); return hash; } @Override public boolean equals(Object object) { // TODO: Warning - this method won't work in the case the id fields are not set if (!(object instanceof Produtos)) { return false; } Produtos other = (Produtos) object; if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) { return false; } return true; } @Override public String toString() { return "" + codigo + ""; } }

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• Flash AS3 Mysterious Blinking MovieClip

  - by Ben

  This is the strangest problem I've faced in flash so far. I have no idea what's causing it. I can provide a .swf if someone wants to actually see it, but I'll describe it as best I can. I'm creating bullets for a tank object to shoot. The tank is a child of the document class. The way I am creating the bullet is: var bullet:Bullet = new Bullet(); (parent as MovieClip).addChild(bullet); The bullet itself simply moves itself in a direction using code like this.x += 5; The problem is the bullets will trace for their creation and destruction at the correct times, however the bullet is sometimes not visible until half way across the screen, sometimes not at all, and sometimes for the whole traversal. Oddly removing the timer I have on bullet creation seems to solve this. The timer is implemented as such: if(shot_timer == 0) { shoot(); // This contains the aforementioned bullet creation method shot_timer = 10; My enter frame handler for the tank object controls the timer and decrements it every frame if it is greater than zero. Can anyone suggest why this could be happening? EDIT: As requested, full code: Bullet.as package { import flash.display.MovieClip; import flash.events.Event; public class Bullet extends MovieClip { public var facing:int; private var speed:int; public function Bullet():void { trace("created"); speed = 10; addEventListener(Event.ADDED_TO_STAGE,addedHandler); } private function addedHandler(e:Event):void { addEventListener(Event.ENTER_FRAME,enterFrameHandler); removeEventListener(Event.ADDED_TO_STAGE,addedHandler); } private function enterFrameHandler(e:Event):void { //0 - up, 1 - left, 2 - down, 3 - right if(this.x > 720 || this.x < 0 || this.y < 0 || this.y > 480) { removeEventListener(Event.ENTER_FRAME,enterFrameHandler); trace("destroyed"); (parent as MovieClip).removeChild(this); return; } switch(facing) { case 0: this.y -= speed; break; case 1: this.x -= speed; break; case 2: this.y += speed; break; case 3: this.x += speed; break; } } } } Tank.as: package { import flash.display.MovieClip; import flash.events.KeyboardEvent; import flash.events.Event; import flash.ui.Keyboard; public class Tank extends MovieClip { private var right:Boolean = false; private var left:Boolean = false; private var up:Boolean = false; private var down:Boolean = false; private var facing:int = 0; //0 - up, 1 - left, 2 - down, 3 - right private var horAllowed:Boolean = true; private var vertAllowed:Boolean = true; private const GRID_SIZE:int = 100; private var shooting:Boolean = false; private var shot_timer:int = 0; private var speed:int = 2; public function Tank():void { addEventListener(Event.ADDED_TO_STAGE,stageAddHandler); addEventListener(Event.ENTER_FRAME, enterFrameHandler); } private function stageAddHandler(e:Event):void { stage.addEventListener(KeyboardEvent.KEY_DOWN,checkKeys); stage.addEventListener(KeyboardEvent.KEY_UP,keyUps); removeEventListener(Event.ADDED_TO_STAGE,stageAddHandler); } public function checkKeys(event:KeyboardEvent):void { if(event.keyCode == 32) { //trace("Spacebar is down"); shooting = true; } if(event.keyCode == 39) { //trace("Right key is down"); right = true; } if(event.keyCode == 38) { //trace("Up key is down"); // lol up = true; } if(event.keyCode == 37) { //trace("Left key is down"); left = true; } if(event.keyCode == 40) { //trace("Down key is down"); down = true; } } public function keyUps(event:KeyboardEvent):void { if(event.keyCode == 32) { event.keyCode = 0; shooting = false; //trace("Spacebar is not down"); } if(event.keyCode == 39) { event.keyCode = 0; right = false; //trace("Right key is not down"); } if(event.keyCode == 38) { event.keyCode = 0; up = false; //trace("Up key is not down"); } if(event.keyCode == 37) { event.keyCode = 0; left = false; //trace("Left key is not down"); } if(event.keyCode == 40) { event.keyCode = 0; down = false; //trace("Down key is not down") // O.o } } public function checkDirectionPermissions(): void { if(this.y % GRID_SIZE < 5 || GRID_SIZE - this.y % GRID_SIZE < 5) { horAllowed = true; } else { horAllowed = false; } if(this.x % GRID_SIZE < 5 || GRID_SIZE - this.x % GRID_SIZE < 5) { vertAllowed = true; } else { vertAllowed = false; } if(!horAllowed && !vertAllowed) { realign(); } } public function realign():void { if(!horAllowed) { if(this.x % GRID_SIZE < GRID_SIZE / 2) { this.x -= this.x % GRID_SIZE; } else { this.x += (GRID_SIZE - this.x % GRID_SIZE); } } if(!vertAllowed) { if(this.y % GRID_SIZE < GRID_SIZE / 2) { this.y -= this.y % GRID_SIZE; } else { this.y += (GRID_SIZE - this.y % GRID_SIZE); } } } public function enterFrameHandler(Event):void { //trace(shot_timer); if(shot_timer > 0) { shot_timer--; } movement(); firing(); } public function firing():void { if(shooting) { if(shot_timer == 0) { shoot(); shot_timer = 10; } } } public function shoot():void { var bullet = new Bullet(); bullet.facing = facing; //0 - up, 1 - left, 2 - down, 3 - right switch(facing) { case 0: bullet.x = this.x; bullet.y = this.y - this.height / 2; break; case 1: bullet.x = this.x - this.width / 2; bullet.y = this.y; break; case 2: bullet.x = this.x; bullet.y = this.y + this.height / 2; break; case 3: bullet.x = this.x + this.width / 2; bullet.y = this.y; break; } (parent as MovieClip).addChild(bullet); } public function movement():void { //0 - up, 1 - left, 2 - down, 3 - right checkDirectionPermissions(); if(horAllowed) { if(right) { orient(3); realign(); this.x += speed; } if(left) { orient(1); realign(); this.x -= speed; } } if(vertAllowed) { if(up) { orient(0); realign(); this.y -= speed; } if(down) { orient(2); realign(); this.y += speed; } } } public function orient(dest:int):void { //trace("facing: " + facing); //trace("dest: " + dest); var angle = facing - dest; this.rotation += (90 * angle); facing = dest; } } }

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• On screen orientation loads again data with Async Task

  - by Zookey

  I make Android application with master/detail pattern. So I have ListActivity class which is FragmentActivity and ListFragment class which is Fragment It all works perfect, but when I change screen orientation it calls again AsyncTask and reload all data. Here is the code for ListActivity class where I handle all logic: @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_list); getActionBar().setDisplayHomeAsUpEnabled(true); getActionBar().setHomeButtonEnabled(true); getActionBar().setTitle("Dnevni horoskop"); if(findViewById(R.id.details_container) != null){ //Tablet mTwoPane = true; //Fragment stuff FragmentManager fm = getSupportFragmentManager(); FragmentTransaction ft = fm.beginTransaction(); DetailsFragment df = new DetailsFragment(); ft.add(R.id.details_container, df); ft.commit(); } pb = (ProgressBar) findViewById(R.id.pb_list); tvNoConnection = (TextView) findViewById(R.id.tv_no_internet); ivNoConnection = (ImageView) findViewById(R.id.iv_no_connection); list = (GridView) findViewById(R.id.gv_list); if(mTwoPane == true){ list.setNumColumns(1); //list.setPadding(16,16,16,16); } adapter = new CustomListAdapter(); list.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) { pos = position; if(mTwoPane == false){ Bundle bundle = new Bundle(); bundle.putSerializable("zodiac", zodiacFeed); Intent i = new Intent(getApplicationContext(), DetailsActivity.class); i.putExtra("position", position); i.putExtras(bundle); startActivity(i); overridePendingTransition(R.anim.right_in, R.anim.right_out); } else if(mTwoPane == true){ DetailsFragment fragment = (DetailsFragment) getSupportFragmentManager().findFragmentById(R.id.details_container); fragment.setHoroscopeText(zodiacFeed.getItem(position).getText()); fragment.setLargeImage(zodiacFeed.getItem(position).getLargeImage()); fragment.setSign("Dnevni horoskop - "+zodiacFeed.getItem(position).getName()); fragment.setSignDuration(zodiacFeed.getItem(position).getDuration()); // inflate menu from xml /*if(menu != null){ MenuItem item = menu.findItem(R.id.share); Toast.makeText(getApplicationContext(), item.getTitle().toString(), Toast.LENGTH_SHORT).show(); }*/ } } }); if(!Utils.isConnected(getApplicationContext())){ pb.setVisibility(View.GONE); tvNoConnection.setVisibility(View.VISIBLE); ivNoConnection.setVisibility(View.VISIBLE); } //Calling AsyncTask to load data Log.d("TAG", "loading"); HoroscopeAsyncTask task = new HoroscopeAsyncTask(pb); task.execute(); } @Override public void onConfigurationChanged(Configuration newConfig) { // TODO Auto-generated method stub super.onConfigurationChanged(newConfig); } class CustomListAdapter extends BaseAdapter { private LayoutInflater layoutInflater; public CustomListAdapter() { layoutInflater = (LayoutInflater) getBaseContext().getSystemService( Context.LAYOUT_INFLATER_SERVICE); } public int getCount() { // TODO Auto-generated method stub // Set the total list item count return names.length; } public Object getItem(int arg0) { // TODO Auto-generated method stub return null; } public long getItemId(int arg0) { // TODO Auto-generated method stub return 0; } public View getView(int position, View convertView, ViewGroup parent) { // Inflate the item layout and set the views View listItem = convertView; int pos = position; zodiacItem = zodiacList.get(pos); if (listItem == null && mTwoPane == false) { listItem = layoutInflater.inflate(R.layout.list_item, null); } else if(mTwoPane == true){ listItem = layoutInflater.inflate(R.layout.tablet_list_item, null); } // Initialize the views in the layout ImageView iv = (ImageView) listItem.findViewById(R.id.iv_horoscope); iv.setScaleType(ScaleType.CENTER_CROP); TextView tvName = (TextView) listItem.findViewById(R.id.tv_zodiac_name); TextView tvDuration = (TextView) listItem.findViewById(R.id.tv_duration); iv.setImageResource(zodiacItem.getImage()); tvName.setText(zodiacItem.getName()); tvDuration.setText(zodiacItem.getDuration()); Animation animation = AnimationUtils.loadAnimation(getBaseContext(), R.anim.push_up); listItem.startAnimation(animation); animation = null; return listItem; } } private void getHoroscope() { String urlString = "http://balkanandroid.com/download/horoskop/examples/dnevnihoroskop.php"; try { HttpClient client = new DefaultHttpClient(); HttpPost post = new HttpPost(urlString); HttpResponse response = client.execute(post); resEntity = response.getEntity(); response_str = EntityUtils.toString(resEntity); if (resEntity != null) { Log.i("RESPONSE", response_str); runOnUiThread(new Runnable() { public void run() { try { Log.d("TAG", "Response from server : n " + response_str); } catch (Exception e) { e.printStackTrace(); } } }); } } catch (Exception ex) { Log.e("TAG", "error: " + ex.getMessage(), ex); } } private class HoroscopeAsyncTask extends AsyncTask<String, Void, Void> { public HoroscopeAsyncTask(ProgressBar pb1){ pb = pb1; } @Override protected void onPreExecute() { pb.setVisibility(View.VISIBLE); super.onPreExecute(); } @Override protected Void doInBackground(String... params) { getHoroscope(); try { Log.d("TAG", "test u try"); JSONObject jsonObject = new JSONObject(response_str); JSONArray jsonArray = jsonObject.getJSONArray("horoscope"); for(int i=0;i<jsonArray.length();i++){ Log.d("TAG", "test u for"); JSONObject horoscopeObj = jsonArray.getJSONObject(i); String horoscopeSign = horoscopeObj.getString("name_sign"); String horoscopeText = horoscopeObj.getString("txt_hrs"); zodiacItem = new ZodiacItem(horoscopeSign, horoscopeText, duration[i], images[i], largeImages[i]); zodiacList.add(zodiacItem); zodiacFeed.addItem(zodiacItem); //Treba u POJO klasu ubaciti sve. Log.d("TAG", "ZNAK: "+zodiacItem.getName()+" HOROSKOP: "+zodiacItem.getText()); } } catch (JSONException e) { // TODO Auto-generated catch block e.printStackTrace(); Log.e("TAG", "error: " + e.getMessage(), e); } return null; } @Override protected void onPostExecute(Void result) { pb.setVisibility(View.GONE); list.setAdapter(adapter); adapter.notifyDataSetChanged(); super.onPostExecute(result); } } Here is the code for ListFragment class: public class ListFragment extends Fragment { @Override public void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub // Retain this fragment across configuration changes. setRetainInstance(true); super.onCreate(savedInstanceState); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // TODO Auto-generated method stub View view = inflater.inflate(R.layout.fragment_list, container, false); return view; } }

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• File using .net sockets, transferring problem

  - by Sergei

  I have a client and server, client sending file to server. When i transfer files on my computer(in local) everything is ok(try to sen file over 700mb). When i try to sent file use Internet to my friend in the end of sending appears error on server "Input string is not in correct format".This error appears in this expression fSize = Convert::ToUInt64(tokenes[0]); - and i don't mind wht it's appear. File should be transfered and wait other transferring ps: sorry for too much code, but i want to find solution private: void CreateServer() { try{ IPAddress ^ipAddres = IPAddress::Parse(ipAdress); listener = gcnew System::Net::Sockets::TcpListener(ipAddres, port); listener->Start(); clientsocket =listener->AcceptSocket(); bool keepalive = true; array<wchar_t,1> ^split = gcnew array<wchar_t>(1){ '\0' }; array<wchar_t,1> ^split2 = gcnew array<wchar_t>(1){ '|' }; statusBar1->Text = "Connected" ; // while (keepalive) { array<Byte>^ size1 = gcnew array<Byte>(1024); clientsocket->Receive(size1); System::String ^notSplited = System::Text::Encoding::GetEncoding(1251)->GetString(size1); array<String^> ^ tokenes = notSplited->Split(split2); System::String ^fileName = tokenes[1]->ToString(); statusBar1->Text = "Receiving file" ; unsigned long fSize = 0; //IN THIS EXPRESSIN APPEARS ERROR fSize = Convert::ToUInt64(tokenes[0]); if (!Directory::Exists("Received")) Directory::CreateDirectory("Received"); System::String ^path = "Received\\"+ fileName; while (File::Exists(path)) { int dotPos = path->LastIndexOf('.'); if (dotPos == -1) { path += "[1]"; } else { path = path->Insert(dotPos, "[1]"); } } FileStream ^fs = gcnew FileStream(path, FileMode::CreateNew, FileAccess::Write); BinaryWriter ^f = gcnew BinaryWriter(fs); //bytes received unsigned long processed = 0; pBarFilesTr->Visible = true; pBarFilesTr->Minimum = 0; pBarFilesTr->Maximum = (int)fSize; // Set the initial value of the ProgressBar. pBarFilesTr->Value = 0; pBarFilesTr->Step = 1024; //loop for receive file array<Byte>^ buffer = gcnew array<Byte>(1024); while (processed < fSize) { if ((fSize - processed) < 1024) { int bytes ; array<Byte>^ buf = gcnew array<Byte>(1024); bytes = clientsocket->Receive(buf); if (bytes != 0) { f->Write(buf, 0, bytes); processed = processed + (unsigned long)bytes; pBarFilesTr->PerformStep(); } break; } else { int bytes = clientsocket->Receive(buffer); if (bytes != 0) { f->Write(buffer, 0, 1024); processed = processed + 1024; pBarFilesTr->PerformStep(); } else break; } } statusBar1->Text = "File was received" ; array<Byte>^ buf = gcnew array<Byte>(1); clientsocket->Send(buf,buf->Length,SocketFlags::None); f->Close(); fs->Close(); SystemSounds::Beep->Play(); } }catch(System::Net::Sockets::SocketException ^es) { MessageBox::Show(es->ToString()); } catch(System::Exception ^es) { MessageBox::Show(es->ToString()); } } private: void CreateClient() { clientsock = gcnew System::Net::Sockets::TcpClient(ipAdress, port); ns = clientsock->GetStream(); sr = gcnew StreamReader(ns); statusBar1->Text = "Connected" ; } private:void Send() { try{ OpenFileDialog ^openFileDialog1 = gcnew OpenFileDialog(); System::String ^filePath = ""; System::String ^fileName = ""; //file choose dialog if (openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK) { filePath = openFileDialog1->FileName; fileName = openFileDialog1->SafeFileName; } else { MessageBox::Show("You must select a file", "Error", MessageBoxButtons::OK, MessageBoxIcon::Exclamation); return; } statusBar1->Text = "Sending file" ; NetworkStream ^writerStream = clientsock->GetStream(); System::Runtime::Serialization::Formatters::Binary::BinaryFormatter ^format = gcnew System::Runtime::Serialization::Formatters::Binary::BinaryFormatter(); array<Byte>^ buffer = gcnew array<Byte>(1024); FileStream ^fs = gcnew FileStream(filePath, FileMode::Open); BinaryReader ^br = gcnew BinaryReader(fs); //file size unsigned long fSize = (unsigned long)fs->Length; //transfer file size + name bFSize = Encoding::GetEncoding(1251)->GetBytes(Convert::ToString(fs->Length+"|"+fileName+"|")); writerStream->Write(bFSize, 0, bFSize->Length); //status bar pBarFilesTr->Visible = true; pBarFilesTr->Minimum = 0; pBarFilesTr->Maximum = (int)fSize; pBarFilesTr->Value = 0; // Set the initial value of the ProgressBar. pBarFilesTr->Step = 1024; //bytes transfered unsigned long processed = 0; int bytes = 1024; //loop for transfer while (processed < fSize) { if ((fSize - processed) < 1024) { bytes = (int)(fSize - processed); array<Byte>^ buf = gcnew array<Byte>(bytes); br->Read(buf, 0, bytes); writerStream->Write(buf, 0, buf->Length); pBarFilesTr->PerformStep(); processed = processed + (unsigned long)bytes; break; } else { br->Read(buffer, 0, 1024); writerStream->Write(buffer, 0, buffer->Length); pBarFilesTr->PerformStep(); processed = processed + 1024; } } array<Byte>^ bufsss = gcnew array<Byte>(100); writerStream->Read(bufsss,0,bufsss->Length); statusBar1->Text = "File was sent" ; btnSend->Enabled = true; fs->Close(); br->Close(); SystemSounds::Beep->Play(); newThread->Abort(); } catch(System::Net::Sockets::SocketException ^es) { MessageBox::Show(es->ToString()); } } UPDATE: ok, i can add checking if clientsocket->Receive(size1); equal zero, but why he begin receiving data again , in the ending of receiving. UPDATE:After adding this checking problem remains. AND WIN RAR SAY TO OPENING ARCHIVE - unexpected end of file! UPDATE:http://img153.imageshack.us/img153/3760/erorr.gif I think it continue receiving some bytes from client(that remains in the stream), but why existes cicle while (processed < fSize)

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• File using sockets .net, tranfering problem

  - by Sergei

  I have a client and server, client sending file to server. When i transfer files on my computer(in local) everything is ok(try to sen file over 700mb). When i try to sent file use Internet to my friend in the end of sending appears error on server "Input string is not in correct format".This error appears in this expression fSize = Convert::ToUInt64(tokenes[0]); - and i don't mind wht it's appear. File should be transfered and wait other transferring ps: sorry for too much code, but i want to find solution private: void CreateServer() { try{ IPAddress ^ipAddres = IPAddress::Parse(ipAdress); listener = gcnew System::Net::Sockets::TcpListener(ipAddres, port); listener->Start(); clientsocket =listener->AcceptSocket(); bool keepalive = true; array<wchar_t,1> ^split = gcnew array<wchar_t>(1){ '\0' }; array<wchar_t,1> ^split2 = gcnew array<wchar_t>(1){ '|' }; statusBar1->Text = "Connected" ; // while (keepalive) { array<Byte>^ size1 = gcnew array<Byte>(1024); clientsocket->Receive(size1); System::String ^notSplited = System::Text::Encoding::GetEncoding(1251)->GetString(size1); array<String^> ^ tokenes = notSplited->Split(split2); System::String ^fileName = tokenes[1]->ToString(); statusBar1->Text = "Receiving file" ; unsigned long fSize = 0; //IN THIS EXPRESSIN APPEARS ERROR fSize = Convert::ToUInt64(tokenes[0]); if (!Directory::Exists("Received")) Directory::CreateDirectory("Received"); System::String ^path = "Received\\"+ fileName; while (File::Exists(path)) { int dotPos = path->LastIndexOf('.'); if (dotPos == -1) { path += "[1]"; } else { path = path->Insert(dotPos, "[1]"); } } FileStream ^fs = gcnew FileStream(path, FileMode::CreateNew, FileAccess::Write); BinaryWriter ^f = gcnew BinaryWriter(fs); //bytes received unsigned long processed = 0; pBarFilesTr->Visible = true; pBarFilesTr->Minimum = 0; pBarFilesTr->Maximum = (int)fSize; // Set the initial value of the ProgressBar. pBarFilesTr->Value = 0; pBarFilesTr->Step = 1024; //loop for receive file array<Byte>^ buffer = gcnew array<Byte>(1024); while (processed < fSize) { if ((fSize - processed) < 1024) { int bytes ; array<Byte>^ buf = gcnew array<Byte>(1024); bytes = clientsocket->Receive(buf); if (bytes != 0) { f->Write(buf, 0, bytes); processed = processed + (unsigned long)bytes; pBarFilesTr->PerformStep(); } break; } else { int bytes = clientsocket->Receive(buffer); if (bytes != 0) { f->Write(buffer, 0, 1024); processed = processed + 1024; pBarFilesTr->PerformStep(); } else break; } } statusBar1->Text = "File was received" ; array<Byte>^ buf = gcnew array<Byte>(1); clientsocket->Send(buf,buf->Length,SocketFlags::None); f->Close(); fs->Close(); SystemSounds::Beep->Play(); } }catch(System::Net::Sockets::SocketException ^es) { MessageBox::Show(es->ToString()); } catch(System::Exception ^es) { MessageBox::Show(es->ToString()); } } private: void CreateClient() { clientsock = gcnew System::Net::Sockets::TcpClient(ipAdress, port); ns = clientsock->GetStream(); sr = gcnew StreamReader(ns); statusBar1->Text = "Connected" ; } private:void Send() { try{ OpenFileDialog ^openFileDialog1 = gcnew OpenFileDialog(); System::String ^filePath = ""; System::String ^fileName = ""; //file choose dialog if (openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK) { filePath = openFileDialog1->FileName; fileName = openFileDialog1->SafeFileName; } else { MessageBox::Show("You must select a file", "Error", MessageBoxButtons::OK, MessageBoxIcon::Exclamation); return; } statusBar1->Text = "Sending file" ; NetworkStream ^writerStream = clientsock->GetStream(); System::Runtime::Serialization::Formatters::Binary::BinaryFormatter ^format = gcnew System::Runtime::Serialization::Formatters::Binary::BinaryFormatter(); array<Byte>^ buffer = gcnew array<Byte>(1024); FileStream ^fs = gcnew FileStream(filePath, FileMode::Open); BinaryReader ^br = gcnew BinaryReader(fs); //file size unsigned long fSize = (unsigned long)fs->Length; //transfer file size + name bFSize = Encoding::GetEncoding(1251)->GetBytes(Convert::ToString(fs->Length+"|"+fileName+"|")); writerStream->Write(bFSize, 0, bFSize->Length); //status bar pBarFilesTr->Visible = true; pBarFilesTr->Minimum = 0; pBarFilesTr->Maximum = (int)fSize; pBarFilesTr->Value = 0; // Set the initial value of the ProgressBar. pBarFilesTr->Step = 1024; //bytes transfered unsigned long processed = 0; int bytes = 1024; //loop for transfer while (processed < fSize) { if ((fSize - processed) < 1024) { bytes = (int)(fSize - processed); array<Byte>^ buf = gcnew array<Byte>(bytes); br->Read(buf, 0, bytes); writerStream->Write(buf, 0, buf->Length); pBarFilesTr->PerformStep(); processed = processed + (unsigned long)bytes; break; } else { br->Read(buffer, 0, 1024); writerStream->Write(buffer, 0, buffer->Length); pBarFilesTr->PerformStep(); processed = processed + 1024; } } array<Byte>^ bufsss = gcnew array<Byte>(100); writerStream->Read(bufsss,0,bufsss->Length); statusBar1->Text = "File was sent" ; btnSend->Enabled = true; fs->Close(); br->Close(); SystemSounds::Beep->Play(); newThread->Abort(); } catch(System::Net::Sockets::SocketException ^es) { MessageBox::Show(es->ToString()); } }

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• Logic error for Gauss elimination

  - by iwanttoprogram

  Logic error problem with the Gaussian Elimination code...This code was from my Numerical Methods text in 1990's. The code is typed in from the book- not producing correct output... Sample Run: SOLUTION OF SIMULTANEOUS LINEAR EQUATIONS USING GAUSSIAN ELIMINATION This program uses Gaussian Elimination to solve the system Ax = B, where A is the matrix of known coefficients, B is the vector of known constants and x is the column matrix of the unknowns. Number of equations: 3 Enter elements of matrix [A] A(1,1) = 0 A(1,2) = -6 A(1,3) = 9 A(2,1) = 7 A(2,2) = 0 A(2,3) = -5 A(3,1) = 5 A(3,2) = -8 A(3,3) = 6 Enter elements of [b] vector B(1) = -3 B(2) = 3 B(3) = -4 SOLUTION OF SIMULTANEOUS LINEAR EQUATIONS The solution is x(1) = 0.000000 x(2) = -1.#IND00 x(3) = -1.#IND00 Determinant = -1.#IND00 Press any key to continue . . . The code as copied from the text... //Modified Code from C Numerical Methods Text- June 2009 #include <stdio.h> #include <math.h> #define MAXSIZE 20 //function prototype int gauss (double a[][MAXSIZE], double b[], int n, double *det); int main(void) { double a[MAXSIZE][MAXSIZE], b[MAXSIZE], det; int i, j, n, retval; printf("\n \t SOLUTION OF SIMULTANEOUS LINEAR EQUATIONS"); printf("\n \t USING GAUSSIAN ELIMINATION \n"); printf("\n This program uses Gaussian Elimination to solve the"); printf("\n system Ax = B, where A is the matrix of known"); printf("\n coefficients, B is the vector of known constants"); printf("\n and x is the column matrix of the unknowns."); //get number of equations n = 0; while(n <= 0 || n > MAXSIZE) { printf("\n Number of equations: "); scanf ("%d", &n); } //read matrix A printf("\n Enter elements of matrix [A]\n"); for (i = 0; i < n; i++) for (j = 0; j < n; j++) { printf(" A(%d,%d) = ", i + 1, j + 1); scanf("%lf", &a[i][j]); } //read {B} vector printf("\n Enter elements of [b] vector\n"); for (i = 0; i < n; i++) { printf(" B(%d) = ", i + 1); scanf("%lf", &b[i]); } //call Gauss elimination function retval = gauss(a, b, n, &det); //print results if (retval == 0) { printf("\n\t SOLUTION OF SIMULTANEOUS LINEAR EQUATIONS\n"); printf("\n\t The solution is"); for (i = 0; i < n; i++) printf("\n \t x(%d) = %lf", i + 1, b[i]); printf("\n \t Determinant = %lf \n", det); } else printf("\n \t SINGULAR MATRIX \n"); return 0; } /* Solves the system of equations [A]{x} = {B} using */ /* the Gaussian elimination method with partial pivoting. */ /* Parameters: */ /* n - number of equations */ /* a[n][n] - coefficient matrix */ /* b[n] - right-hand side vector */ /* *det - determinant of [A] */ int gauss (double a[][MAXSIZE], double b[], int n, double *det) { double tol, temp, mult; int npivot, i, j, l, k, flag; //initialization *det = 1.0; tol = 1e-30; //initial tolerance value npivot = 0; //mult = 0; //forward elimination for (k = 0; k < n; k++) { //search for max coefficient in pivot row- a[k][k] pivot element for (i = k + 1; i < n; i++) { if (fabs(a[i][k]) > fabs(a[k][k])) { //interchange row with maxium element with pivot row npivot++; for (l = 0; l < n; l++) { temp = a[i][l]; a[i][l] = a[k][l]; a[k][l] = temp; } temp = b[i]; b[i] = b[k]; b[k] = temp; } } //test for singularity if (fabs(a[k][k]) < tol) { //matrix is singular- terminate flag = 1; return flag; } //compute determinant- the product of the pivot elements *det = *det * a[k][k]; //eliminate the coefficients of X(I) for (i = k; i < n; i++) { mult = a[i][k] / a[k][k]; b[i] = b[i] - b[k] * mult; //compute constants for (j = k; j < n; j++) //compute coefficients a[i][j] = a[i][j] - a[k][j] * mult; } } //adjust the sign of the determinant if(npivot % 2 == 1) *det = *det * (-1.0); //backsubstitution b[n] = b[n] / a[n][n]; for(i = n - 1; i > 1; i--) { for(j = n; j > i + 1; j--) b[i] = b[i] - a[i][j] * b[j]; b[i] = b[i] / a[i - 1][i]; } flag = 0; return flag; } The solution should be: 1.058824, 1.823529, 0.882353 with det as -102.000000 Any insight is appreciated...

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• c# Unable to open file for reading

  - by Maks

  I'm writing a program that uses FileSystemWatcher to monitor changes to a given directory, and when it recieves OnCreated or OnChanged event, it copies those created/changed files to a specified directorie(s). At first I had problems with the fact that OnChanged/OnCreated events can be sent twice (not acceptable in case it needed to process 500MB file) but I made a way around this and with what I'm REALLY STUCKED with is getting the following IOException: The process cannot access the file 'C:\Where are Photos\bookmarks (11).html' because it is being used by another process. Thus, preventing the program from copying all the files it should. So as I mentioned, when user uses this program he/she specifes monitored directory, when user copies/creates/changes file in that directory, program should get OnCreated/OnChanged event and then copy that file to few other directories. Above error happens in all casess, if user copies few files that needs to owerwrite other ones in folder being monitored or when copying bulk of several files or even sometimes when copying one file in a monitored directory. Whole program is quite big so I'm sending the most important parts. OnCreated: private void OnCreated(object source, FileSystemEventArgs e) { AddLogEntry(e.FullPath, "created", ""); // Update last access data if it's file so the same file doesn't // get processed twice because of sending another event. if (fileType(e.FullPath) == 2) { lastPath = e.FullPath; lastTime = DateTime.Now; } // serves no purpose now, it will be remove soon string fileName = GetFileName(e.FullPath); // copies file from source to few other directories Copy(e.FullPath, fileName); Console.WriteLine("OnCreated: " + e.FullPath); } OnChanged: private void OnChanged(object source, FileSystemEventArgs e) { // is it directory if (fileType(e.FullPath) == 1) return; // don't mind directory changes itself // Only if enough time has passed or if it's some other file // because two events can be generated int timeDiff = ((TimeSpan)(DateTime.Now - lastTime)).Seconds; if ((timeDiff < minSecsDiff) && (e.FullPath.Equals(lastPath))) { Console.WriteLine("-- skipped -- {0}, timediff: {1}", e.FullPath, timeDiff); return; } // Update last access data for above to work lastPath = e.FullPath; lastTime = DateTime.Now; // Only if size is changed, the rest will handle other handlers if (e.ChangeType == WatcherChangeTypes.Changed) { AddLogEntry(e.FullPath, "changed", ""); string fileName = GetFileName(e.FullPath); Copy(e.FullPath, fileName); Console.WriteLine("OnChanged: " + e.FullPath); } } fileType: private int fileType(string path) { if (Directory.Exists(path)) return 1; // directory else if (File.Exists(path)) return 2; // file else return 0; } Copy: private void Copy(string srcPath, string fileName) { foreach (string dstDirectoy in paths) { string eventType = "copied"; string error = "noerror"; string path = ""; string dirPortion = ""; // in case directory needs to be made if (srcPath.Length > fsw.Path.Length) { path = srcPath.Substring(fsw.Path.Length, srcPath.Length - fsw.Path.Length); int pos = path.LastIndexOf('\\'); if (pos != -1) dirPortion = path.Substring(0, pos); } if (fileType(srcPath) == 1) { try { Directory.CreateDirectory(dstDirectoy + path); //Directory.CreateDirectory(dstDirectoy + fileName); eventType = "created"; } catch (IOException e) { eventType = "error"; error = e.Message; } } else { try { if (!overwriteFile && File.Exists(dstDirectoy + path)) continue; // create new dir anyway even if it exists just to be sure Directory.CreateDirectory(dstDirectoy + dirPortion); // copy file from where event occured to all specified directories using (FileStream fsin = new FileStream(srcPath, FileMode.Open, FileAccess.Read, FileShare.Read)) { using (FileStream fsout = new FileStream(dstDirectoy + path, FileMode.Create, FileAccess.Write)) { byte[] buffer = new byte[32768]; int bytesRead = -1; while ((bytesRead = fsin.Read(buffer, 0, buffer.Length)) > 0) fsout.Write(buffer, 0, bytesRead); } } } catch (Exception e) { if ((e is IOException) && (overwriteFile == false)) { eventType = "skipped"; } else { eventType = "error"; error = e.Message; // attempt to find and kill the process locking the file. // failed, miserably System.Diagnostics.Process tool = new System.Diagnostics.Process(); tool.StartInfo.FileName = "handle.exe"; tool.StartInfo.Arguments = "\"" + srcPath + "\""; tool.StartInfo.UseShellExecute = false; tool.StartInfo.RedirectStandardOutput = true; tool.Start(); tool.WaitForExit(); string outputTool = tool.StandardOutput.ReadToEnd(); string matchPattern = @"(?<=\s+pid:\s+)\b(\d+)\b(?=\s+)"; foreach (Match match in Regex.Matches(outputTool, matchPattern)) { System.Diagnostics.Process.GetProcessById(int.Parse(match.Value)).Kill(); } Console.WriteLine("ERROR: {0}: [ {1} ]", e.Message, srcPath); } } } AddLogEntry(dstDirectoy + path, eventType, error); } } I checked everywhere in my program and whenever I use some file I use it in using block so even writing event to log (class for what I ommited since there is probably too much code already in post) wont lock the file, that is it shouldn't since all operations are using using statement block. I simply have no clue who's locking the file if not my program "copy" process from user through Windows or something else. Right now I have two possible "solutions" (I can't say they are clean solutions since they are hacks and as such not desireable). Since probably the problem is with fileType method (what else could lock the file?) I tried changing it to this, to simulate "blocking-until-ready-to-open" operation: fileType: private int fileType(string path) { FileStream fs = null; int ret = 0; bool run = true; if (Directory.Exists(path)) ret = 1; else { while (run) { try { fs = new FileStream(path, FileMode.Open); ret = 2; run = false; } catch (IOException) { } finally { if (fs != null) { fs.Close(); fs.Dispose(); } } } } return ret; } This is working as much as I could tell (test), but... it's hack, not to mention other deficients. The other "solution" I could try (I didn't test it yet) is using GC.Collect() somewhere at the end of fileType() method. Maybe even worse "solution" than previous one. Can someone pleas tell me, what on earth is locking the file, preventing it from opening and how can I fix that? What am I missing to see? Thanks in advance.

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• Capturing and Transforming ASP.NET Output with Response.Filter

  - by Rick Strahl

  During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

  - by mortezam

  This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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• Read XML Files using LINQ to XML and Extension Methods

  - by psheriff

  In previous blog posts I have discussed how to use XML files to store data in your applications. I showed you how to read those XML files from your project and get XML from a WCF service. One of the problems with reading XML files is when elements or attributes are missing. If you try to read that missing data, then a null value is returned. This can cause a problem if you are trying to load that data into an object and a null is read. This blog post will show you how to create extension methods to detect null values and return valid values to load into your object. The XML Data An XML data file called Product.xml is located in the \Xml folder of the Silverlight sample project for this blog post. This XML file contains several rows of product data that will be used in each of the samples for this post. Each row has 4 attributes; namely ProductId, ProductName, IntroductionDate and Price. <Products>  <Product ProductId="1"           ProductName="Haystack Code Generator for .NET"           IntroductionDate="07/01/2010"  Price="799" />  <Product ProductId="2"           ProductName="ASP.Net Jumpstart Samples"           IntroductionDate="05/24/2005"  Price="0" />  ...  ...</Products> The Product Class Just as you create an Entity class to map each column in a table to a property in a class, you should do the same for an XML file too. In this case you will create a Product class with properties for each of the attributes in each element of product data. The following code listing shows the Product class. public class Product : CommonBase{  public const string XmlFile = @"Xml/Product.xml";   private string _ProductName;  private int _ProductId;  private DateTime _IntroductionDate;  private decimal _Price;   public string ProductName  {    get { return _ProductName; }    set {      if (_ProductName != value) {        _ProductName = value;        RaisePropertyChanged("ProductName");      }    }  }   public int ProductId  {    get { return _ProductId; }    set {      if (_ProductId != value) {        _ProductId = value;        RaisePropertyChanged("ProductId");      }    }  }   public DateTime IntroductionDate  {    get { return _IntroductionDate; }    set {      if (_IntroductionDate != value) {        _IntroductionDate = value;        RaisePropertyChanged("IntroductionDate");      }    }  }   public decimal Price  {    get { return _Price; }    set {      if (_Price != value) {        _Price = value;        RaisePropertyChanged("Price");      }    }  }} NOTE: The CommonBase class that the Product class inherits from simply implements the INotifyPropertyChanged event in order to inform your XAML UI of any property changes. You can see this class in the sample you download for this blog post. Reading Data When using LINQ to XML you call the Load method of the XElement class to load the XML file. Once the XML file has been loaded, you write a LINQ query to iterate over the “Product” Descendants in the XML file. The “select” portion of the LINQ query creates a new Product object for each row in the XML file. You retrieve each attribute by passing each attribute name to the Attribute() method and retrieving the data from the “Value” property. The Value property will return a null if there is no data, or will return the string value of the attribute. The Convert class is used to convert the value retrieved into the appropriate data type required by the Product class. private void LoadProducts(){  XElement xElem = null;   try  {    xElem = XElement.Load(Product.XmlFile);     // The following will NOT work if you have missing attributes    var products =         from elem in xElem.Descendants("Product")        orderby elem.Attribute("ProductName").Value        select new Product        {          ProductId = Convert.ToInt32(            elem.Attribute("ProductId").Value),          ProductName = Convert.ToString(            elem.Attribute("ProductName").Value),          IntroductionDate = Convert.ToDateTime(            elem.Attribute("IntroductionDate").Value),          Price = Convert.ToDecimal(elem.Attribute("Price").Value)        };     lstData.DataContext = products;  }  catch (Exception ex)  {    MessageBox.Show(ex.Message);  }} This is where the problem comes in. If you have any missing attributes in any of the rows in the XML file, or if the data in the ProductId or IntroductionDate is not of the appropriate type, then this code will fail! The reason? There is no built-in check to ensure that the correct type of data is contained in the XML file. This is where extension methods can come in real handy. Using Extension Methods Instead of using the Convert class to perform type conversions as you just saw, create a set of extension methods attached to the XAttribute class. These extension methods will perform null-checking and ensure that a valid value is passed back instead of an exception being thrown if there is invalid data in your XML file. private void LoadProducts(){  var xElem = XElement.Load(Product.XmlFile);   var products =       from elem in xElem.Descendants("Product")      orderby elem.Attribute("ProductName").Value      select new Product      {        ProductId = elem.Attribute("ProductId").GetAsInteger(),        ProductName = elem.Attribute("ProductName").GetAsString(),        IntroductionDate =            elem.Attribute("IntroductionDate").GetAsDateTime(),        Price = elem.Attribute("Price").GetAsDecimal()      };   lstData.DataContext = products;} Writing Extension Methods To create an extension method you will create a class with any name you like. In the code listing below is a class named XmlExtensionMethods. This listing just shows a couple of the available methods such as GetAsString and GetAsInteger. These methods are just like any other method you would write except when you pass in the parameter you prefix the type with the keyword “this”. This lets the compiler know that it should add this method to the class specified in the parameter. public static class XmlExtensionMethods{  public static string GetAsString(this XAttribute attr)  {    string ret = string.Empty;     if (attr != null && !string.IsNullOrEmpty(attr.Value))    {      ret = attr.Value;    }     return ret;  }   public static int GetAsInteger(this XAttribute attr)  {    int ret = 0;    int value = 0;     if (attr != null && !string.IsNullOrEmpty(attr.Value))    {      if(int.TryParse(attr.Value, out value))        ret = value;    }     return ret;  }   ...  ...} Each of the methods in the XmlExtensionMethods class should inspect the XAttribute to ensure it is not null and that the value in the attribute is not null. If the value is null, then a default value will be returned such as an empty string or a 0 for a numeric value. Summary Extension methods are a great way to simplify your code and provide protection to ensure problems do not occur when reading data. You will probably want to create more extension methods to handle XElement objects as well for when you use element-based XML. Feel free to extend these extension methods to accept a parameter which would be the default value if a null value is detected, or any other parameters you wish. NOTE: You can download the complete sample code at my website. http://www.pdsa.com/downloads. Choose “Tips & Tricks”, then "Read XML Files using LINQ to XML and Extension Methods" from the drop-down. Good Luck with your Coding,Paul D. Sheriff  

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• Minecraft Style Chunk building problem

  - by David Torrey

  I'm having some problems with speed in my chunk engine. I timed it out, and in its current state it takes a total ~5 seconds per chunk to fill each face's list. I have a check to see if each face of a block is visible and if it is not visible, it skips it and moves on. I'm using a dictionary (unordered map) because it makes sense memorywise to just not have an entry if there is no block. I've tracked my problem down to testing if there is an entry, and accessing an entry if it does exist. If I remove the tests to see if there is an entry in the dictionary for an adjacent block, or if the block type itself is seethrough, it runs within about 2-4 milliseconds. so here's my question: Is there a faster way to check for an entry in a dictionary than .ContainsKey()? As an aside, I tried TryGetValue() and it doesn't really help with the speed that much. If I remove the ContainsKey() and keep the test where it does the IsSeeThrough for each block, it halves the time, but it's still about 2-3 seconds. It only drops to 2-4ms if I remove BOTH checks. Here is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Runtime.InteropServices; using OpenTK; using OpenTK.Graphics.OpenGL; using System.Drawing; namespace Anabelle_Lee { public enum BlockEnum { air = 0, dirt = 1, } [StructLayout(LayoutKind.Sequential,Pack=1)] public struct Coordinates<T1> { public T1 x; public T1 y; public T1 z; public override string ToString() { return "(" + x + "," + y + "," + z + ") : " + typeof(T1); } } public struct Sides<T1> { public T1 left; public T1 right; public T1 top; public T1 bottom; public T1 front; public T1 back; } public class Block { public int blockType; public bool SeeThrough() { switch (blockType) { case 0: return true; } return false ; } public override string ToString() { return ((BlockEnum)(blockType)).ToString(); } } class Chunk { private Dictionary<Coordinates<byte>, Block> mChunkData; //stores the block data private Sides<List<Coordinates<byte>>> mVBOVertexBuffer; private Sides<int> mVBOHandle; //private bool mIsChanged; private const byte mCHUNKSIZE = 16; public Chunk() { } public void InitializeChunk() { //create VBO references #if DEBUG Console.WriteLine ("Initializing Chunk"); #endif mChunkData = new Dictionary<Coordinates<byte> , Block>(); //mIsChanged = true; GL.GenBuffers(1, out mVBOHandle.left); GL.GenBuffers(1, out mVBOHandle.right); GL.GenBuffers(1, out mVBOHandle.top); GL.GenBuffers(1, out mVBOHandle.bottom); GL.GenBuffers(1, out mVBOHandle.front); GL.GenBuffers(1, out mVBOHandle.back); //make new list of vertexes for each face mVBOVertexBuffer.top = new List<Coordinates<byte>>(); mVBOVertexBuffer.bottom = new List<Coordinates<byte>>(); mVBOVertexBuffer.left = new List<Coordinates<byte>>(); mVBOVertexBuffer.right = new List<Coordinates<byte>>(); mVBOVertexBuffer.front = new List<Coordinates<byte>>(); mVBOVertexBuffer.back = new List<Coordinates<byte>>(); #if DEBUG Console.WriteLine("Chunk Initialized"); #endif } public void GenerateChunk() { #if DEBUG Console.WriteLine("Generating Chunk"); #endif for (byte i = 0; i < mCHUNKSIZE; i++) { for (byte j = 0; j < mCHUNKSIZE; j++) { for (byte k = 0; k < mCHUNKSIZE; k++) { Random blockLoc = new Random(); Coordinates<byte> randChunk = new Coordinates<byte> { x = i, y = j, z = k }; mChunkData.Add(randChunk, new Block()); mChunkData[randChunk].blockType = blockLoc.Next(0, 1); } } } #if DEBUG Console.WriteLine("Chunk Generated"); #endif } public void DeleteChunk() { //delete VBO references #if DEBUG Console.WriteLine("Deleting Chunk"); #endif GL.DeleteBuffers(1, ref mVBOHandle.left); GL.DeleteBuffers(1, ref mVBOHandle.right); GL.DeleteBuffers(1, ref mVBOHandle.top); GL.DeleteBuffers(1, ref mVBOHandle.bottom); GL.DeleteBuffers(1, ref mVBOHandle.front); GL.DeleteBuffers(1, ref mVBOHandle.back); //clear all vertex buffers ClearPolyLists(); #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void UpdateChunk() { #if DEBUG Console.WriteLine("Updating Chunk"); #endif ClearPolyLists(); //prepare buffers //for every entry in mChunkData map foreach(KeyValuePair<Coordinates<byte>,Block> feBlockData in mChunkData) { Coordinates<byte> checkBlock = new Coordinates<byte> { x = feBlockData.Key.x, y = feBlockData.Key.y, z = feBlockData.Key.z }; //check for polygonson the left side of the cube if (checkBlock.x > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x - 1, checkBlock.y, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } //check for polygons on the right side of the cube if (checkBlock.x < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x + 1, checkBlock.y, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } if (checkBlock.y > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y - 1, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } //check for polygons on the right side of the cube if (checkBlock.y < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y + 1, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } if (checkBlock.z > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z - 1)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } //check for polygons on the right side of the cube if (checkBlock.z < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z + 1)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } BuildBuffers(); #if DEBUG Console.WriteLine("Chunk Updated"); #endif } public void RenderChunk() { } public void LoadChunk() { #if DEBUG Console.WriteLine("Loading Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void SaveChunk() { #if DEBUG Console.WriteLine("Saving Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Saved"); #endif } private bool IsVisible(int pX,int pY,int pZ) { Block testBlock; Coordinates<byte> checkBlock = new Coordinates<byte> { x = Convert.ToByte(pX), y = Convert.ToByte(pY), z = Convert.ToByte(pZ) }; if (mChunkData.TryGetValue(checkBlock,out testBlock )) //if data exists { if (testBlock.SeeThrough() == true) //if existing data is not seethrough { return true; } } return true; } private void AddPoly(byte pX, byte pY, byte pZ, int BufferSide) { //create temp array GL.BindBuffer(BufferTarget.ArrayBuffer, BufferSide); if (BufferSide == mVBOHandle.front) { //front face mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.right) { //back face mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.top) { //left face mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.bottom) { //right face mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.front) { //top face mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.back) { //bottom face mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); } } private void BuildBuffers() { #if DEBUG Console.WriteLine("Building Chunk Buffers"); #endif GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.front); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.front.Count), mVBOVertexBuffer.front.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.back); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.back.Count), mVBOVertexBuffer.back.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.left); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.left.Count), mVBOVertexBuffer.left.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.right); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.right.Count), mVBOVertexBuffer.right.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.top); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.top.Count), mVBOVertexBuffer.top.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.bottom); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.bottom.Count), mVBOVertexBuffer.bottom.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer,0); #if DEBUG Console.WriteLine("Chunk Buffers Built"); #endif } private void ClearPolyLists() { #if DEBUG Console.WriteLine("Clearing Polygon Lists"); #endif mVBOVertexBuffer.top.Clear(); mVBOVertexBuffer.bottom.Clear(); mVBOVertexBuffer.left.Clear(); mVBOVertexBuffer.right.Clear(); mVBOVertexBuffer.front.Clear(); mVBOVertexBuffer.back.Clear(); #if DEBUG Console.WriteLine("Polygon Lists Cleared"); #endif } }//END CLASS }//END NAMESPACE

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• Windows Azure Service Bus Splitter and Aggregator

  - by Alan Smith

  This article will cover basic implementations of the Splitter and Aggregator patterns using the Windows Azure Service Bus. The content will be included in the next release of the “Windows Azure Service Bus Developer Guide”, along with some other patterns I am working on. I’ve taken the pattern descriptions from the book “Enterprise Integration Patterns” by Gregor Hohpe. I bought a copy of the book in 2004, and recently dusted it off when I started to look at implementing the patterns on the Windows Azure Service Bus. Gregor has also presented an session in 2011 “Enterprise Integration Patterns: Past, Present and Future” which is well worth a look. I’ll be covering more patterns in the coming weeks, I’m currently working on Wire-Tap and Scatter-Gather. There will no doubt be a section on implementing these patterns in my “SOA, Connectivity and Integration using the Windows Azure Service Bus” course. There are a number of scenarios where a message needs to be divided into a number of sub messages, and also where a number of sub messages need to be combined to form one message. The splitter and aggregator patterns provide a definition of how this can be achieved. This section will focus on the implementation of basic splitter and aggregator patens using the Windows Azure Service Bus direct programming model. In BizTalk Server receive pipelines are typically used to implement the splitter patterns, with sequential convoy orchestrations often used to aggregate messages. In the current release of the Service Bus, there is no functionality in the direct programming model that implements these patterns, so it is up to the developer to implement them in the applications that send and receive messages. Splitter A message splitter takes a message and spits the message into a number of sub messages. As there are different scenarios for how a message can be split into sub messages, message splitters are implemented using different algorithms. The Enterprise Integration Patterns book describes the splatter pattern as follows: How can we process a message if it contains multiple elements, each of which may have to be processed in a different way? Use a Splitter to break out the composite message into a series of individual messages, each containing data related to one item. The Enterprise Integration Patterns website provides a description of the Splitter pattern here. In some scenarios a batch message could be split into the sub messages that are contained in the batch. The splitting of a message could be based on the message type of sub-message, or the trading partner that the sub message is to be sent to. Aggregator An aggregator takes a stream or related messages and combines them together to form one message. The Enterprise Integration Patterns book describes the aggregator pattern as follows: How do we combine the results of individual, but related messages so that they can be processed as a whole? Use a stateful filter, an Aggregator, to collect and store individual messages until a complete set of related messages has been received. Then, the Aggregator publishes a single message distilled from the individual messages. The Enterprise Integration Patterns website provides a description of the Aggregator pattern here. A common example of the need for an aggregator is in scenarios where a stream of messages needs to be combined into a daily batch to be sent to a legacy line-of-business application. The BizTalk Server EDI functionality provides support for batching messages in this way using a sequential convoy orchestration. Scenario The scenario for this implementation of the splitter and aggregator patterns is the sending and receiving of large messages using a Service Bus queue. In the current release, the Windows Azure Service Bus currently supports a maximum message size of 256 KB, with a maximum header size of 64 KB. This leaves a safe maximum body size of 192 KB. The BrokeredMessage class will support messages larger than 256 KB; in fact the Size property is of type long, implying that very large messages may be supported at some point in the future. The 256 KB size restriction is set in the service bus components that are deployed in the Windows Azure data centers. One of the ways of working around this size restriction is to split large messages into a sequence of smaller sub messages in the sending application, send them via a queue, and then reassemble them in the receiving application. This scenario will be used to demonstrate the pattern implementations. Implementation The splitter and aggregator will be used to provide functionality to send and receive large messages over the Windows Azure Service Bus. In order to make the implementations generic and reusable they will be implemented as a class library. The splitter will be implemented in the LargeMessageSender class and the aggregator in the LargeMessageReceiver class. A class diagram showing the two classes is shown below. Implementing the Splitter The splitter will take a large brokered message, and split the messages into a sequence of smaller sub-messages that can be transmitted over the service bus messaging entities. The LargeMessageSender class provides a Send method that takes a large brokered message as a parameter. The implementation of the class is shown below; console output has been added to provide details of the splitting operation. public class LargeMessageSender {     private static int SubMessageBodySize = 192 * 1024;     private QueueClient m_QueueClient;       public LargeMessageSender(QueueClient queueClient)     {         m_QueueClient = queueClient;     }       public void Send(BrokeredMessage message)     {         // Calculate the number of sub messages required.         long messageBodySize = message.Size;         int nrSubMessages = (int)(messageBodySize / SubMessageBodySize);         if (messageBodySize % SubMessageBodySize != 0)         {             nrSubMessages++;         }           // Create a unique session Id.         string sessionId = Guid.NewGuid().ToString();         Console.WriteLine("Message session Id: " + sessionId);         Console.Write("Sending {0} sub-messages", nrSubMessages);           Stream bodyStream = message.GetBody<Stream>();         for (int streamOffest = 0; streamOffest < messageBodySize;             streamOffest += SubMessageBodySize)         {                                     // Get the stream chunk from the large message             long arraySize = (messageBodySize - streamOffest) > SubMessageBodySize                 ? SubMessageBodySize : messageBodySize - streamOffest;             byte[] subMessageBytes = new byte[arraySize];             int result = bodyStream.Read(subMessageBytes, 0, (int)arraySize);             MemoryStream subMessageStream = new MemoryStream(subMessageBytes);               // Create a new message             BrokeredMessage subMessage = new BrokeredMessage(subMessageStream, true);             subMessage.SessionId = sessionId;               // Send the message             m_QueueClient.Send(subMessage);             Console.Write(".");         }         Console.WriteLine("Done!");     }} The LargeMessageSender class is initialized with a QueueClient that is created by the sending application. When the large message is sent, the number of sub messages is calculated based on the size of the body of the large message. A unique session Id is created to allow the sub messages to be sent as a message session, this session Id will be used for correlation in the aggregator. A for loop in then used to create the sequence of sub messages by creating chunks of data from the stream of the large message. The sub messages are then sent to the queue using the QueueClient. As sessions are used to correlate the messages, the queue used for message exchange must be created with the RequiresSession property set to true. Implementing the Aggregator The aggregator will receive the sub messages in the message session that was created by the splitter, and combine them to form a single, large message. The aggregator is implemented in the LargeMessageReceiver class, with a Receive method that returns a BrokeredMessage. The implementation of the class is shown below; console output has been added to provide details of the splitting operation.   public class LargeMessageReceiver {     private QueueClient m_QueueClient;       public LargeMessageReceiver(QueueClient queueClient)     {         m_QueueClient = queueClient;     }       public BrokeredMessage Receive()     {         // Create a memory stream to store the large message body.         MemoryStream largeMessageStream = new MemoryStream();           // Accept a message session from the queue.         MessageSession session = m_QueueClient.AcceptMessageSession();         Console.WriteLine("Message session Id: " + session.SessionId);         Console.Write("Receiving sub messages");           while (true)         {             // Receive a sub message             BrokeredMessage subMessage = session.Receive(TimeSpan.FromSeconds(5));               if (subMessage != null)             {                 // Copy the sub message body to the large message stream.                 Stream subMessageStream = subMessage.GetBody<Stream>();                 subMessageStream.CopyTo(largeMessageStream);                   // Mark the message as complete.                 subMessage.Complete();                 Console.Write(".");             }             else             {                 // The last message in the sequence is our completeness criteria.                 Console.WriteLine("Done!");                 break;             }         }                     // Create an aggregated message from the large message stream.         BrokeredMessage largeMessage = new BrokeredMessage(largeMessageStream, true);         return largeMessage;     } }   The LargeMessageReceiver initialized using a QueueClient that is created by the receiving application. The receive method creates a memory stream that will be used to aggregate the large message body. The AcceptMessageSession method on the QueueClient is then called, which will wait for the first message in a message session to become available on the queue. As the AcceptMessageSession can throw a timeout exception if no message is available on the queue after 60 seconds, a real-world implementation should handle this accordingly. Once the message session as accepted, the sub messages in the session are received, and their message body streams copied to the memory stream. Once all the messages have been received, the memory stream is used to create a large message, that is then returned to the receiving application. Testing the Implementation The splitter and aggregator are tested by creating a message sender and message receiver application. The payload for the large message will be one of the webcast video files from http://www.cloudcasts.net/, the file size is 9,697 KB, well over the 256 KB threshold imposed by the Service Bus. As the splitter and aggregator are implemented in a separate class library, the code used in the sender and receiver console is fairly basic. The implementation of the main method of the sending application is shown below.   static void Main(string[] args) {     // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Use the MessagingFactory to create a queue client     QueueClient queueClient = factory.CreateQueueClient(AccountDetails.QueueName);       // Open the input file.     FileStream fileStream = new FileStream(AccountDetails.TestFile, FileMode.Open);       // Create a BrokeredMessage for the file.     BrokeredMessage largeMessage = new BrokeredMessage(fileStream, true);       Console.WriteLine("Sending: " + AccountDetails.TestFile);     Console.WriteLine("Message body size: " + largeMessage.Size);     Console.WriteLine();         // Send the message with a LargeMessageSender     LargeMessageSender sender = new LargeMessageSender(queueClient);     sender.Send(largeMessage);       // Close the messaging facory.     factory.Close();  } The implementation of the main method of the receiving application is shown below. static void Main(string[] args) {       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Use the MessagingFactory to create a queue client     QueueClient queueClient = factory.CreateQueueClient(AccountDetails.QueueName);       // Create a LargeMessageReceiver and receive the message.     LargeMessageReceiver receiver = new LargeMessageReceiver(queueClient);     BrokeredMessage largeMessage = receiver.Receive();       Console.WriteLine("Received message");     Console.WriteLine("Message body size: " + largeMessage.Size);       string testFile = AccountDetails.TestFile.Replace(@"\In\", @"\Out\");     Console.WriteLine("Saving file: " + testFile);       // Save the message body as a file.     Stream largeMessageStream = largeMessage.GetBody<Stream>();     largeMessageStream.Seek(0, SeekOrigin.Begin);     FileStream fileOut = new FileStream(testFile, FileMode.Create);     largeMessageStream.CopyTo(fileOut);     fileOut.Close();       Console.WriteLine("Done!"); } In order to test the application, the sending application is executed, which will use the LargeMessageSender class to split the message and place it on the queue. The output of the sender console is shown below. The console shows that the body size of the large message was 9,929,365 bytes, and the message was sent as a sequence of 51 sub messages. When the receiving application is executed the results are shown below. The console application shows that the aggregator has received the 51 messages from the message sequence that was creating in the sending application. The messages have been aggregated to form a massage with a body of 9,929,365 bytes, which is the same as the original large message. The message body is then saved as a file. Improvements to the Implementation The splitter and aggregator patterns in this implementation were created in order to show the usage of the patterns in a demo, which they do quite well. When implementing these patterns in a real-world scenario there are a number of improvements that could be made to the design. Copying Message Header Properties When sending a large message using these classes, it would be great if the message header properties in the message that was received were copied from the message that was sent. The sending application may well add information to the message context that will be required in the receiving application. When the sub messages are created in the splitter, the header properties in the first message could be set to the values in the original large message. The aggregator could then used the values from this first sub message to set the properties in the message header of the large message during the aggregation process. Using Asynchronous Methods The current implementation uses the synchronous send and receive methods of the QueueClient class. It would be much more performant to use the asynchronous methods, however doing so may well affect the sequence in which the sub messages are enqueued, which would require the implementation of a resequencer in the aggregator to restore the correct message sequence. Handling Exceptions In order to keep the code readable no exception handling was added to the implementations. In a real-world scenario exceptions should be handled accordingly.

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• Inside the Concurrent Collections: ConcurrentDictionary

  - by Simon Cooper

  Using locks to implement a thread-safe collection is rather like using a sledgehammer - unsubtle, easy to understand, and tends to make any other tool redundant. Unlike the previous two collections I looked at, ConcurrentStack and ConcurrentQueue, ConcurrentDictionary uses locks quite heavily. However, it is careful to wield locks only where necessary to ensure that concurrency is maximised. This will, by necessity, be a higher-level look than my other posts in this series, as there is quite a lot of code and logic in ConcurrentDictionary. Therefore, I do recommend that you have ConcurrentDictionary open in a decompiler to have a look at all the details that I skip over. The problem with locks There's several things to bear in mind when using locks, as encapsulated by the lock keyword in C# and the System.Threading.Monitor class in .NET (if you're unsure as to what lock does in C#, I briefly covered it in my first post in the series): Locks block threads The most obvious problem is that threads waiting on a lock can't do any work at all. No preparatory work, no 'optimistic' work like in ConcurrentQueue and ConcurrentStack, nothing. It sits there, waiting to be unblocked. This is bad if you're trying to maximise concurrency. Locks are slow Whereas most of the methods on the Interlocked class can be compiled down to a single CPU instruction, ensuring atomicity at the hardware level, taking out a lock requires some heavy lifting by the CLR and the operating system. There's quite a bit of work required to take out a lock, block other threads, and wake them up again. If locks are used heavily, this impacts performance. Deadlocks When using locks there's always the possibility of a deadlock - two threads, each holding a lock, each trying to aquire the other's lock. Fortunately, this can be avoided with careful programming and structured lock-taking, as we'll see. So, it's important to minimise where locks are used to maximise the concurrency and performance of the collection. Implementation As you might expect, ConcurrentDictionary is similar in basic implementation to the non-concurrent Dictionary, which I studied in a previous post. I'll be using some concepts introduced there, so I recommend you have a quick read of it. So, if you were implementing a thread-safe dictionary, what would you do? The naive implementation is to simply have a single lock around all methods accessing the dictionary. This would work, but doesn't allow much concurrency. Fortunately, the bucketing used by Dictionary allows a simple but effective improvement to this - one lock per bucket. This allows different threads modifying different buckets to do so in parallel. Any thread making changes to the contents of a bucket takes the lock for that bucket, ensuring those changes are thread-safe. The method that maps each bucket to a lock is the GetBucketAndLockNo method: private void GetBucketAndLockNo( int hashcode, out int bucketNo, out int lockNo, int bucketCount) { // the bucket number is the hashcode (without the initial sign bit) // modulo the number of buckets bucketNo = (hashcode & 0x7fffffff) % bucketCount; // and the lock number is the bucket number modulo the number of locks lockNo = bucketNo % m_locks.Length; } However, this does require some changes to how the buckets are implemented. The 'implicit' linked list within a single backing array used by the non-concurrent Dictionary adds a dependency between separate buckets, as every bucket uses the same backing array. Instead, ConcurrentDictionary uses a strict linked list on each bucket: This ensures that each bucket is entirely separate from all other buckets; adding or removing an item from a bucket is independent to any changes to other buckets. Modifying the dictionary All the operations on the dictionary follow the same basic pattern: void AlterBucket(TKey key, ...) { int bucketNo, lockNo; 1: GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, m_buckets.Length); 2: lock (m_locks[lockNo]) { 3: Node headNode = m_buckets[bucketNo]; 4: Mutate the node linked list as appropriate } } For example, when adding another entry to the dictionary, you would iterate through the linked list to check whether the key exists already, and add the new entry as the head node. When removing items, you would find the entry to remove (if it exists), and remove the node from the linked list. Adding, updating, and removing items all follow this pattern. Performance issues There is a problem we have to address at this point. If the number of buckets in the dictionary is fixed in the constructor, then the performance will degrade from O(1) to O(n) when a large number of items are added to the dictionary. As more and more items get added to the linked lists in each bucket, the lookup operations will spend most of their time traversing a linear linked list. To fix this, the buckets array has to be resized once the number of items in each bucket has gone over a certain limit. (In ConcurrentDictionary this limit is when the size of the largest bucket is greater than the number of buckets for each lock. This check is done at the end of the TryAddInternal method.) Resizing the bucket array and re-hashing everything affects every bucket in the collection. Therefore, this operation needs to take out every lock in the collection. Taking out mutiple locks at once inevitably summons the spectre of the deadlock; two threads each hold a lock, and each trying to acquire the other lock. How can we eliminate this? Simple - ensure that threads never try to 'swap' locks in this fashion. When taking out multiple locks, always take them out in the same order, and always take out all the locks you need before starting to release them. In ConcurrentDictionary, this is controlled by the AcquireLocks, AcquireAllLocks and ReleaseLocks methods. Locks are always taken out and released in the order they are in the m_locks array, and locks are all released right at the end of the method in a finally block. At this point, it's worth pointing out that the locks array is never re-assigned, even when the buckets array is increased in size. The number of locks is fixed in the constructor by the concurrencyLevel parameter. This simplifies programming the locks; you don't have to check if the locks array has changed or been re-assigned before taking out a lock object. And you can be sure that when a thread takes out a lock, another thread isn't going to re-assign the lock array. This would create a new series of lock objects, thus allowing another thread to ignore the existing locks (and any threads controlling them), breaking thread-safety. Consequences of growing the array Just because we're using locks doesn't mean that race conditions aren't a problem. We can see this by looking at the GrowTable method. The operation of this method can be boiled down to: private void GrowTable(Node[] buckets) { try { 1: Acquire first lock in the locks array // this causes any other thread trying to take out // all the locks to block because the first lock in the array // is always the one taken out first // check if another thread has already resized the buckets array // while we were waiting to acquire the first lock 2: if (buckets != m_buckets) return; 3: Calculate the new size of the backing array 4: Node[] array = new array[size]; 5: Acquire all the remaining locks 6: Re-hash the contents of the existing buckets into array 7: m_buckets = array; } finally { 8: Release all locks } } As you can see, there's already a check for a race condition at step 2, for the case when the GrowTable method is called twice in quick succession on two separate threads. One will successfully resize the buckets array (blocking the second in the meantime), when the second thread is unblocked it'll see that the array has already been resized & exit without doing anything. There is another case we need to consider; looking back at the AlterBucket method above, consider the following situation: Thread 1 calls AlterBucket; step 1 is executed to get the bucket and lock numbers. Thread 2 calls GrowTable and executes steps 1-5; thread 1 is blocked when it tries to take out the lock in step 2. Thread 2 re-hashes everything, re-assigns the buckets array, and releases all the locks (steps 6-8). Thread 1 is unblocked and continues executing, but the calculated bucket and lock numbers are no longer valid. Between calculating the correct bucket and lock number and taking out the lock, another thread has changed where everything is. Not exactly thread-safe. Well, a similar problem was solved in ConcurrentStack and ConcurrentQueue by storing a local copy of the state, doing the necessary calculations, then checking if that state is still valid. We can use a similar idea here: void AlterBucket(TKey key, ...) { while (true) { Node[] buckets = m_buckets; int bucketNo, lockNo; GetBucketAndLockNo( key.GetHashCode(), out bucketNo, out lockNo, buckets.Length); lock (m_locks[lockNo]) { // if the state has changed, go back to the start if (buckets != m_buckets) continue; Node headNode = m_buckets[bucketNo]; Mutate the node linked list as appropriate } break; } } TryGetValue and GetEnumerator And so, finally, we get onto TryGetValue and GetEnumerator. I've left these to the end because, well, they don't actually use any locks. How can this be? Whenever you change a bucket, you need to take out the corresponding lock, yes? Indeed you do. However, it is important to note that TryGetValue and GetEnumerator don't actually change anything. Just as immutable objects are, by definition, thread-safe, read-only operations don't need to take out a lock because they don't change anything. All lockless methods can happily iterate through the buckets and linked lists without worrying about locking anything. However, this does put restrictions on how the other methods operate. Because there could be another thread in the middle of reading the dictionary at any time (even if a lock is taken out), the dictionary has to be in a valid state at all times. Every change to state has to be made visible to other threads in a single atomic operation (all relevant variables are marked volatile to help with this). This restriction ensures that whatever the reading threads are doing, they never read the dictionary in an invalid state (eg items that should be in the collection temporarily removed from the linked list, or reading a node that has had it's key & value removed before the node itself has been removed from the linked list). Fortunately, all the operations needed to change the dictionary can be done in that way. Bucket resizes are made visible when the new array is assigned back to the m_buckets variable. Any additions or modifications to a node are done by creating a new node, then splicing it into the existing list using a single variable assignment. Node removals are simply done by re-assigning the node's m_next pointer. Because the dictionary can be changed by another thread during execution of the lockless methods, the GetEnumerator method is liable to return dirty reads - changes made to the dictionary after GetEnumerator was called, but before the enumeration got to that point in the dictionary. It's worth listing at this point which methods are lockless, and which take out all the locks in the dictionary to ensure they get a consistent view of the dictionary: Lockless: TryGetValue GetEnumerator The indexer getter ContainsKey Takes out every lock (lockfull?): Count IsEmpty Keys Values CopyTo ToArray Concurrent principles That covers the overall implementation of ConcurrentDictionary. I haven't even begun to scratch the surface of this sophisticated collection. That I leave to you. However, we've looked at enough to be able to extract some useful principles for concurrent programming: Partitioning When using locks, the work is partitioned into independant chunks, each with its own lock. Each partition can then be modified concurrently to other partitions. Ordered lock-taking When a method does need to control the entire collection, locks are taken and released in a fixed order to prevent deadlocks. Lockless reads Read operations that don't care about dirty reads don't take out any lock; the rest of the collection is implemented so that any reading thread always has a consistent view of the collection. That leads us to the final collection in this little series - ConcurrentBag. Lacking a non-concurrent analogy, it is quite different to any other collection in the class libraries. Prepare your thinking hats!

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• Quick Quips on QR Codes

  - by Tim Dexter

  Yes, I'm an alliterating all-star; I missed my calling as a newspaper headline writer. I have recently received questions from several folks on support for QR codes. You know them they are everywhere you look, even here! How does Publisher handle QR codes then? In theory, exactly the same way we handle any other 2D barcode font. We need the font file, a mapping entry and an encoding class. With those three pieces we can embed QR codes into any output. To test the theory, I went off to IDAutomation, I have worked with them and many customers over the years and their fonts and encoders have worked great and have been very reliable. They kindly provide demo fonts which has made my life so much easier to be able to write posts like this. Their QR font and encoder is a little tough to find. I started here and then hit the Demo Now button. On the next page I hit the right hand Demo Now button. In the resulting zip file you'll need two files: AdditionalFonts.zip >> Automation2DFonts >> TrueType >> IDAutomation2D.ttf Java Class Encoder >> IDAutomation_JavaFontEncoder_QRCode.jar - the QRBarcodeExample.java is useful to see how to call the encoder. The font file needs to be installed into the windows/fonts directory, just copy and paste it in using file explorer and windows will install it for you. Remember, we are using the demo font here and you'll see if you get your phones decoder to looks a the font above there is a fixed string 'DEMO' at the beginning. You want that removed? Go buy the font from the IDAutomation folks. The Encoder Next you need to create your encoding wrapper class. Publisher does ship a class but its compiled and I do not recommend trying to modify it, you can just build your own. I have loaded up my class here. You do not need to be a java guru, its pretty straightforward. I'd recommend a java IDE like JDeveloper from a convenience point of view. I have annotated my class and added a main method to it so you can test your encoders from JDeveloper without having to deploy them first. You can load up the project form the zip file straight into JDeveloper.Next, take a look at IDAutomation's example java class and you'll see: QRCodeEncoder qre=new QRCodeEncoder();  String DataToEncode = "IDAutmation Inc.";  boolean ApplyTilde = false;  int EncodingMode = 0;  int Version = 0;  int ErrorCorrectionLevel = 0;  System.out.println( qre.FontEncode(DataToEncode, ApplyTilde, EncodingMode, Version, ErrorCorrectionLevel) ); You'll need to check what settings you need to set for the ApplyTilde, EncodingMode, Version and ErrorCorrectionLevel. They are covered in the user guide from IDAutomation here. If you do not want to hard code the values in the encoder then you can quite easily externalize them and read the values from a text file. I have not covered that scenario here, I'm going with IDAutomation's defaults and my phone app is reading the fonts no problem. Now you know how to call the encoder, you need to incorporate it into your encoder wrapper class. From my sample class:       Class[] clazz = new Class[] { "".getClass() };        ENCODERS.put("code128a",mUtility.getClass().getMethod("code128a", clazz));       ENCODERS.put("code128b",mUtility.getClass().getMethod("code128b", clazz));       ENCODERS.put("code128c",mUtility.getClass().getMethod("code128c", clazz));       ENCODERS.put("qrcode",mUtility.getClass().getMethod("qrcode", clazz)); I just added a new entry to register the encoder method 'qrcode' (in red). Then I created a new method inside the class to call the IDAutomation encoder. /** Call to IDAutomations QR Code encoder. Passing the data to encode      Returning the encoded string to the template for formatting **/ public static final String qrcode (String DataToEncode) {   QRCodeEncoder qre=new QRCodeEncoder();    boolean ApplyTilde = false;    int EncodingMode = 0;    int Version = 0;    int ErrorCorrectionLevel = 0; return qre.FontEncode(DataToEncode, ApplyTilde, EncodingMode, Version, ErrorCorrectionLevel); } Almost the exact same code in their sample class. The DataToEncode string is passed in rather than hardcoded of course. With the class done you can now compile it, but you need to ensure that the IDAutomation_JavaFontEncoder_QRCode.jar is in the classpath. In JDeveloper, open the project properties >> Libraries and Classpaths and then add the jar to the list. You'll need the publisher jars too. You can find those in the jlib directory in your Template Builder for Word directory.Note! In my class, I have used package oracle.psbi.barcode; As my package spec, yours will be different but you need to note it for later. Once you have it compiling without errors you will need to generate a jar file to keep it in. In JDeveloper highlight your project node >> New >> Deployment Profile >> JAR file. Once you have created the descriptor, just take the defaults. It will tell you where the jar is located. Go get it and then its time to copy it and the IDAutomation jar into the Template Builder for Word directory structure. Deploying the jars On your windows machine locate the jlib directory under the Template Builder for Word install directory. On my machine its here, F:\Program Files\Oracle\BI Publisher\BI Publisher Desktop\Template Builder for Word\jlib. Copy both of the jar files into the directory. The next step is to get the jars into the classpath for the Word plugin so that Publisher can find your wrapper class and it can then find the IDAutomation encoder. The most consistent way I have found so far, is to open up the RTF2PDF.jar in the same directory and make some mods. First make a backup of the jar file then open it using winzip or 7zip or similar and get into the META-INF directory. In there is a file, MANIFEST.MF. This contains the classpath for the plugin, open it in an editor and add the jars to the end of the classpath list. In mine I have: Manifest-Version: 1.0 Class-Path: ./activation.jar ./mail.jar ./xdochartstyles.jar ./bicmn.jar ./jewt4.jar ./share.jar ./bipres.jar ./xdoparser.jar ./xdocore.jar ./xmlparserv2.jar ./xmlparserv2-904.jar  ./i18nAPI_v3.jar ./versioninfo.jar ./barcodejar.jar ./IDAutomation_JavaFontEncoder_QRCode.jar Main-Class: RTF2PDF I have put in carriage returns above to make the Class-Path: entry more readable, make sure yours is all on one line. Be sure to use the ./ as a prefix to the jar name. Ensure the file is saved inside the jar file 7zip and winzip both have popups asking if you want to update the file in the jar file.Now you have the jars on the classpath, the Publisher plugin will be able to find our classes at run time. Referencing the Font The next step is to reference the font location so that the rendering engine can find it and embed a subset into the PDF output. Remember the other output formats rely on the font being present on the machine that is opening the document. The PDF is the only truly portable format. Inside the config directory under the Template Builder for Word install directory, mine is here, F:\Program Files\Oracle\BI Publisher\BI Publisher Desktop\Template Builder for Word\config. You'll find the file, 'xdo example.cfg'. Rename it to xdo.cfg and open it in a text editor. In the fonts section, create a new entry:       <font family="IDAutomation2D" style="normal" weight="normal">              <truetype path="C:\windows\fonts\IDAutomation2D.ttf" />       </font> Note, 'IDAutomation2D' (in red) is the same name as you can see when you open MSWord and look for the QRCode font. This must match exactly. When Publisher looks at the fonts in the RTF template at runtime it will see 'IDAutomation2D' it will then look at its font mapping entries to find where that font file resides on the disk. If the names do not match or the font is not present then the font will not get used and it will fall back on Helvetica. Building the Template Now you have the data encoder and the font in place and mapped; you can use it in the template. The two commands you will need to have present are: <?register-barcode-vendor:'ENCODER WRAPPER CLASS'; 'ENCODER NAME'?> for my encoder I have: <?register-barcode-vendor:'oracle.psbi.barcode.BarcodeUtil'; 'MyBarcodeEncoder'?> Notice the two parameters for the command. The first provides the package 'path' and class name (remember I said you need to remember that above.)The second is the name of the encoder, in my case 'MyBarcodeEncoder'. Check my full encoder class in the zip linked below to see where I named it. You can change it to something else, no problem.This command needs to be near the top of the template. The second command is the encoding command: <?format-barcode:DATAT_TO_ENCODE;'ENCODER_METHOD_NAME';'ENCODER_NAME'?> for my command I have <?format-barcode:DATATEXT;'qrcode';'MyBarcodeEncoder'?>DATATEXT is the XML element that contains the text to be encoded. If you want to hard code a piece of text just surround it with single quotes. qrcode is the name of my encoder method that calls the IDAutomation encoder. Remember this.MyBarcodeEncoder is the name of my encoder. Repetition? Yes but its needed again. Both of these commands are put inside their own form fields. Do not apply the QRCode font to the second field just yet. Lets make sure the encoder is working. Run you template with some data and you should get something like this for your encoded data: AHEEEHAPPJOPMOFADIPFJKDCLPAHEEEHA BNFFFNBPJGMDIDJPFOJGIGBLMPBNFFFNB APIBOHFJCFBNKHGGBMPFJFJLJBKGOMNII OANKPJFFLEPLDNPCLMNGNIJIHFDNLJFEH FPLFLHFHFILKFBLOIGMDFCFLGJGOPJJME CPIACDFJPBGDODOJCHALJOBPECKMOEDDF MFFNFNEPKKKCHAIHCHPCFFLDAHFHAGLMK APBBBPAPLDKNKJKKGIPDLKGMGHDDEPHLN HHHHHHHPHPHHPHPPHPPPPHHPHHPHPHPHP Grooovy huh? If you do not get the encoded text then go back and check that your jars are in the right spot and that you have the MANIFEST.MF file updated correctly. Once you do get the encoded text, highlight the field and apply the IDAutomation2D font to it. Then re-run the report and you will hopefully see the QR code in your output. If not, go back and check the xdo.cfg entry and make sure its in the right place and the font location is correct. That's it, you now have QR codes in Publisher outputs. Everything I have written above, has been tested with the 5.6.3, 10.1.3.4.2 codelines. I'll be testing the 11g code in the next day or two and will update you with any changes. One thing I have not covered yet and will do in the next few days is how to deploy all of this to your server. Look out for a follow up post. One note on the apparent white lines in the font (see the image above). Once printed they disappear and even viewing the code on a screen with the white lines, my phone app is still able to read and interpret the contents no problem. I have zipped up my encoder wrapper class as a JDeveloper 11.1.1.6 project here. Just dig into the src directories to find the BarcodeUtil.java file if you just want the code. I have put comments into the file to hopefully help the novice java programmer out. Happy QR'ing!

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• Shell Script if else

  - by user34104

  #!/bin/bash echo "Int. a number" read num1 echo "Int. another numer" read num2 if ["$num1"="$num2"]; then echo "Equals" else echo "Dif" fi if["$num1"<0]; then echo "The number $num1 is negative" else if ["$num2"<0]; then echo "The number $num2 is negative" fi # this code is not working, i've something wrong when i see if the number is < 0. thanks

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• programatically check if a domain is availible?

  - by acidzombie24

  Using this solution http://serverfault.com/questions/98940/bot-check-if-a-domain-name-is-availible/98956#98956 I wrote a quick script (pasted below) in C# to check if the domain MIGHT be available. A LOT of results come up with taken domains. It looks like all 2 and 3 letter .com domains are taken and it looks like all 3 letter are taken (not including numbers which many are available). Is there a command or website to take my list of domains and check if they are registered or available? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Text.RegularExpressions; using System.Diagnostics; using System.IO; namespace domainCheck { class Program { static void Main(string[] args) { var sw = (TextWriter)File.CreateText(@"c:\path\aviliableUrlsCA.txt"); int countIndex = 0; int letterAmount=3; char [] sz = new char[letterAmount]; for(int z=0; z<letterAmount; z++) { sz[z] = '0'; } //*/ List<string> urls = new List<string>(); //var sz = "df3".ToCharArray(); int i=0; while (i <letterAmount) { if (sz[i] == '9') sz[i] = 'a'; else if (sz[i] == 'z') { if (i != 0 && i != letterAmount - 1) sz[i] = '-'; else { sz[i] = 'a'; i++; continue; } } else if (sz[i] == '-') { sz[i] = 'a'; i++; continue; } else sz[i]++; string uu = new string(sz); string url = uu + ".ca"; Console.WriteLine(url); Process p = new Process(); p.StartInfo.UseShellExecute = false; p.StartInfo.RedirectStandardError = true; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.FileName = "nslookup "; p.StartInfo.Arguments = url; p.Start(); var res = ((TextReader) new StreamReader( p.StandardError.BaseStream)).ReadToEnd(); if (res.IndexOf("Non-existent domain") != -1) { sw.WriteLine(uu); if (++countIndex >= 100) { sw.Flush(); countIndex = 0; } urls.Add(uu); Console.WriteLine("Found domain {0}", url); } i = 0; } Console.WriteLine("Writing out list of urls"); foreach (var u in urls) Console.WriteLine(u); sw.Close(); } } }

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