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• Using runtime generic type reflection to build a smarter DAO

  - by kerry

  Have you ever wished you could get the runtime type of your generic class? I wonder why they didn’t put this in the language. It is possible, however, with reflection: Consider a data access object (DAO) (note: I had to use brackets b/c the arrows were messing with wordpress): public interface Identifiable { public Long getId(); } public interface Dao { public T findById(Long id); public void save(T obj); public void delete(T obj); } Using reflection, we can create a DAO implementation base class, HibernateDao, that will work for any object: import java.lang.reflect.Field; import java.lang.reflect.ParameterizedType; public class HibernateDao implements Dao { private final Class clazz; public HibernateDao(Session session) { // the magic ParameterizedType parameterizedType = (ParameterizedType) clazz.getGenericSuperclass(); return (Class) parameterizedType.getActualTypeArguments()[0]; } public T findById(Long id) { return session.get(clazz, id); } public void save(T obj) { session.saveOrUpdate(obj); } public void delete(T obj) { session.delete(obj); } } Then, all we have to do is extend from the class: public class BookDaoHibernateImpl extends HibernateDao { }

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• A generic Re-usable C# Property Parser utility [on hold]

  - by Shyam K Pananghat

  This is about a utility i have happened to write which can parse through the properties of a data contracts at runtime using reflection. The input required is a look like XPath string. since this is using reflection, you dont have to add the reference to any of your data contracts thus making pure generic and re- usable.. you can read about this and get the full c# sourcecode here. Property-Parser-A-C-utility-to-retrieve-values-from-any-Net-Data-contracts-at-runtime Now about the doubts which i have about this utility. i am using this utility enormously i many places of my code I am using Regex repeatedly inside a recursion method. does this affect the memmory usage or GC collection badly ?do i have to dispose this manually. if yes how ?. The statements like obj.GetType().GetProperty() and obj.GetType().GetField() returns .net "object" which makes difficult or imposible to introduce generics here. Does this cause to have any overheads like boxing ? on an overall, please suggest to make this utility performance efficient and more light weight on memmory

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• Generic Pop and Push for List<T>

  - by Bil Simser

  Here's a little snippet I use to extend a generic List class to have similar capabilites to the Stack class. The Stack<T> class is great but it lives in its own world under System.Object. Wouldn't it be nice to have a List<T> that could do the same? Here's the code: .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: Consolas, "Courier New", Courier, Monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 1: public static class ExtensionMethods 2: { 3: public static T Pop<T>(this List<T> theList) 4: { 5: var local = theList[theList.Count - 1]; 6: theList.RemoveAt(theList.Count - 1); 7: return local; 8: } 9:   10: public static void Push<T>(this List<T> theList, T item) 11: { 12: theList.Add(item); 13: } 14: } It's a simple extension but I've found it useful, hopefully you will too! Enjoy.

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• ASP.NET Client to Server communication

  - by Nelson

  Can you help me make sense of all the different ways to communicate from browser to client in ASP.NET? I have made this a community wiki so feel free to edit my post to improve it. Specifically, I'm trying to understand in which scenario to use each one by listing how each works. I'm a little fuzzy on UpdatePanel vs CallBack (with ViewState): I know UpdatePanel always returns HTML while CallBack can return JSON. Any other major differences? ...and CallBack (without ViewState) vs WebMethod. CallBack goes through most of the Page lifecycle, WebMethod doesn't. Any other major differences? IHttpHandler Custom handler for anything (page, image, etc.) Only does what you tell it to do (light server processing) Page is an implementation of IHttpHandler If you don't need what Page provides, create a custom IHttpHandler If you are using Page but overriding Render() and not generating HTML, you probably can do it with a custom IHttpHandler (e.g. writing binary data such as images) By default can use the .axd or .ashx file extensions -- both are functionally similar .ashx doesn't have any built-in endpoints, so it's preferred by convention Regular PostBack (System.Web.UI.Page : IHttpHandler) Inherits Page Full PostBack, including ViewState and HTML control values (heavy traffic) Full Page lifecycle (heavy server processing) No JavaScript required Webpage flickers/scrolls since everything is reloaded in browser Returns full page HTML (heavy traffic) UpdatePanel (Control) Control inside Page Full PostBack, including ViewState and HTML control values (heavy traffic) Full Page lifecycle (heavy server processing) Controls outside the UpdatePanel do Render(NullTextWriter) Must use ScriptManager If no client-side JavaScript, it can fall back to regular PostBack with no JavaScript (?) No flicker/scroll since it's an async call, unless it falls back to regular postback. Can be used with master pages and user controls Has built-in support for progress bar Returns HTML for controls inside UpdatePanel (medium traffic) Client CallBack (Page, System.Web.UI.ICallbackEventHandler) Inherits Page Most of Page lifecycle (heavy server processing) Takes only data you specify (light traffic) and optionally ViewState (?) (medium traffic) Client must support JavaScript and use ScriptManager No flicker/scroll since it's an async call Can be used with master pages and user controls Returns only data you specify in format you specify (e.g. JSON, XML...) (?) (light traffic) WebMethod Class implements System.Web.Service.WebService HttpContext available through this.Context Takes only data you specify (light traffic) Server only runs the called method (light server processing) Client must support JavaScript No flicker/scroll since it's an async call Can be used with master pages and user controls Returns only data you specify, typically JSON (light traffic) Can create instance of server control to render HTML and sent back as string, but events, paging in GridView, etc. won't work PageMethods Essentially a WebMethod contained in the Page class, so most of WebMethod's bullet's apply Method must be public static, therefore no Page instance accessible HttpContext available through HttpContext.Current Accessed directly by URL Page.aspx/MethodName (e.g. with XMLHttpRequest directly or with library such as jQuery) Setting ScriptManager property EnablePageMethods="True" generates a JavaScript proxy for each WebMethod Cannot be used directly in user controls with master pages and user controls Any others?

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• C# wrapper and Callbacks

  - by fergs

  I'm in the process of writing a C# wrapper for Dallmeier Common API light (Camera & Surviellance systems) and I've never written a wrapper before, but I have used the Canon EDSDK C# wrapper. So I'm using the Canon wrapper as a guide to writing the Dallmeier wrapper. I'm currently having issues with wrapping a callback. In the API manual it has the following: dlm_connect int(unsigned long uLWindowHandle, const char * strIP, const char* strUser1, const char* strPwd1, const char* strUser2, const char* strPwd2, void (*callback)(void *pParameters, void *pResult, void *pInput), void * pInput) Arguments - ulWindowhandle - handle of the window that is passed to the ViewerSDK to display video and messages there - strUser1/2 - names of the users to log in. If only single user login is used strUser2 is - NULL - strPwd1/2 - passwords of both users. If strUser2 is NULL strPwd2 is ignored. Return This function creates a SessionHandle that has to be passed Callback pParameters will be structured: - unsigned long ulFunctionID - unsigned long ulSocketHandle, //handle to socket of the established connection - unsigned long ulWindowHandle, - int SessionHandle, //session handle of the session created - const char * strIP, - const char* strUser1, - const char* strPwd1, - const char* strUser2, - const char * strPWD2 pResult is a pointer to an integer, representing the result of the operation. Zero on success. Negative values are error codes. So from what I've read on the Net and Stack Overflow - C# uses delegates for the purpose of callbacks. So I create a my Callback function : public delegate uint DallmeierCallback(DallPparameters pParameters, IntPtr pResult, IntPtr pInput); I create the connection function [DllImport("davidapidis.dll")] public extern static int dlm_connect(ulong ulWindowHandle, string strIP, string strUser1, string strPwd1, string strUser2, string strPwd2, DallmeierCallback inDallmeierFunc And (I think) the DallPParameters as a struct : [StructLayout(LayoutKind.Sequential)] public struct DallPParameters { public ulong ulfunctionID; public ulong ulsocketHandle; public ulong ulWindowHandle; ... } All of this is in my wrapper class. Am I heading in the right direction or is this completely wrong?

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• WCF Callbacks often break

  - by cdecker

  I'm having quite some trouble with the WCF Callback mechanism. They sometimes work but most of the time they don't. I have a really simple Interface for the callbacks to implement: public interface IClientCallback { [OperationContract] void Log(string content); } I then implmenent that interface with a class on the client: [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)] [ServiceContract] internal sealed class ClientCallback : IClientCallback { public void Log(String content){ Console.Write(content); } } And on the client I finally connect to the server: NetTcpBinding tcpbinding = new NetTcpBinding(SecurityMode.Transport); EndpointAddress endpoint = new EndpointAddress("net.tcp://127.0.0.1:1337"); ClientCallback callback= new ClientCallback(); DuplexChannelFactory<IServer> factory = new DuplexChannelFactory<IServer>(callback,tcpbinding, endpoint); factory.Open(); _connection = factory.CreateChannel(); ((ICommunicationObject)_connection).Faulted += new EventHandler(RecreateChannel); try { ((ICommunicationObject)_connection).Open(); } catch (CommunicationException ce) { Console.Write(ce.ToString()); } To invoke the callback I use the following: OperationContext.Current.GetCallbackChannel().Log("Hello World!"); But it just hangs there, and after a while the client complains about timeouts. Is there a simple solution as to why?

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• A Generic, IDisposable WCF Service Client

  - by Steve Wilkes

  WCF clients need to be cleaned up properly, but as they're usually auto-generated they don't implement IDisposable. I've been doing a fair bit of WCF work recently, so I wrote a generic WCF client wrapper which effectively gives me a disposable service client. The ServiceClientWrapper is constructed using a WebServiceConfig instance, which contains a Binding, an EndPointAddress, and whether the client should ignore SSL certificate errors - pretty useful during testing! The Binding can be created based on configuration data or entirely programmatically - that's not the client's concern. Here's the service client code: using System; using System.Net; using System.Net.Security; using System.ServiceModel; public class ServiceClientWrapper<TService, TChannel> : IDisposable     where TService : ClientBase<TChannel>     where TChannel : class {     private readonly WebServiceConfig _config;     private TService _serviceClient;     public ServiceClientWrapper(WebServiceConfig config)     {         this._config = config;     }     public TService CreateServiceClient()     {         this.DisposeExistingServiceClientIfRequired();         if (this._config.IgnoreSslErrors)         {             ServicePointManager.ServerCertificateValidationCallback =                 (obj, certificate, chain, errors) => true;         }         else         {             ServicePointManager.ServerCertificateValidationCallback =                 (obj, certificate, chain, errors) => errors == SslPolicyErrors.None;         }         this._serviceClient = (TService)Activator.CreateInstance(             typeof(TService),             this._config.Binding,             this._config.Endpoint);         if (this._config.ClientCertificate != null)         {             this._serviceClient.ClientCredentials.ClientCertificate.Certificate =                 this._config.ClientCertificate;         }         return this._serviceClient;     }     public void Dispose()     {         this.DisposeExistingServiceClientIfRequired();     }     private void DisposeExistingServiceClientIfRequired()     {         if (this._serviceClient != null)         {             try             {                 if (this._serviceClient.State == CommunicationState.Faulted)                 {                     this._serviceClient.Abort();                 }                 else                 {                     this._serviceClient.Close();                 }             }             catch             {                 this._serviceClient.Abort();             }             this._serviceClient = null;         }     } } A client for a particular service can then be created something like this: public class ManagementServiceClientWrapper :     ServiceClientWrapper<ManagementServiceClient, IManagementService> {     public ManagementServiceClientWrapper(WebServiceConfig config)         : base(config)     {     } } ...where ManagementServiceClient is the auto-generated client class, and the IManagementService is the auto-generated WCF channel class - and used like this: using(var serviceClientWrapper = new ManagementServiceClientWrapper(config)) {     serviceClientWrapper.CreateServiceClient().CallService(); } The underlying WCF client created by the CreateServiceClient() will be disposed after the using, and hey presto - a disposable WCF service client.

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• Engine Rendering pipeline : Making shaders generic

  - by fakhir

  I am trying to make a 2D game engine using OpenGL ES 2.0 (iOS for now). I've written Application layer in Objective C and a separate self contained RendererGLES20 in C++. No GL specific call is made outside the renderer. It is working perfectly. But I have some design issues when using shaders. Each shader has its own unique attributes and uniforms that need to be set just before the main draw call (glDrawArrays in this case). For instance, in order to draw some geometry I would do: void RendererGLES20::render(Model * model) { // Set a bunch of uniforms glUniformMatrix4fv(.......); // Enable specific attributes, can be many glEnableVertexAttribArray(......); // Set a bunch of vertex attribute pointers: glVertexAttribPointer(positionSlot, 2, GL_FLOAT, GL_FALSE, stride, m->pCoords); // Now actually Draw the geometry glDrawArrays(GL_TRIANGLES, 0, m->vertexCount); // After drawing, disable any vertex attributes: glDisableVertexAttribArray(.......); } As you can see this code is extremely rigid. If I were to use another shader, say ripple effect, i would be needing to pass extra uniforms, vertex attribs etc. In other words I would have to change the RendererGLES20 render source code just to incorporate the new shader. Is there any way to make the shader object totally generic? Like What if I just want to change the shader object and not worry about game source re-compiling? Any way to make the renderer agnostic of uniforms and attributes etc?. Even though we need to pass data to uniforms, what is the best place to do that? Model class? Is the model class aware of shader specific uniforms and attributes? Following shows Actor class: class Actor : public ISceneNode { ModelController * model; AIController * AI; }; Model controller class: class ModelController { class IShader * shader; int textureId; vec4 tint; float alpha; struct Vertex * vertexArray; }; Shader class just contains the shader object, compiling and linking sub-routines etc. In Game Logic class I am actually rendering the object: void GameLogic::update(float dt) { IRenderer * renderer = g_application->GetRenderer(); Actor * a = GetActor(id); renderer->render(a->model); } Please note that even though Actor extends ISceneNode, I haven't started implementing SceneGraph yet. I will do that as soon as I resolve this issue. Any ideas how to improve this? Related design patterns etc? Thank you for reading the question.

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• Handy Generic JQuery Functions

  - by Steve Wilkes

  I was a bit of a late-comer to the JQuery party, but now I've been using it for a while it's given me a host of options for adding extra flair to the client side of my applications. Here's a few generic JQuery functions I've written which can be used to add some neat little features to a page. Just call any of them from a document ready function. Apply JQuery Themeroller Styles to all Page Buttons   The JQuery Themeroller is a great tool for creating a theme for a site based on colours and styles for particular page elements. The JQuery.UI library then provides a set of functions which allow you to apply styles to page elements. This function applies a JQuery Themeroller style to all the buttons on a page - as well as any elements which have a button class applied to them - and then makes the mouse pointer turn into a cursor when you mouse over them: function addCursorPointerToButtons() {     $("button, input[type='submit'], input[type='button'], .button") .button().css("cursor", "pointer"); } Automatically Remove the Default Value from a Select Box   Required drop-down select boxes often have a default option which reads 'Please select...' (or something like that), but once someone has selected a value, there's no need to retain that. This function removes the default option from any select boxes on the page which have a data-val-remove-default attribute once one of the non-default options has been chosen: function removeDefaultSelectOptionOnSelect() {     $("select[data-val-remove-default='']").change(function () {         var sel = $(this);         if (sel.val() != "") { sel.children("option[value='']:first").remove(); }     }); } Automatically add a Required Label and Stars to a Form   It's pretty standard to have a little * next to required form field elements. This function adds the text * Required to the top of the first form on the page, and adds *s to any element within the form with the class editor-label and a data-val-required attribute: function addRequiredFieldLabels() {     var elements = $(".editor-label[data-val-required='']");     if (!elements.length) { return; }     var requiredString = "<div class='editor-required-key'>* Required</div>";     var prependString = "<span class='editor-required-label'> * </span>"; var firstFormOnThePage = $("form:first");     if (!firstFormOnThePage.children('div.editor-required-key').length) {         firstFormOnThePage.prepend(requiredString);     }     elements.each(function (index, value) { var formElement = $(this);         if (!formElement.children('span.editor-required-label').length) {             formElement.prepend(prependString);         }     }); } I hope those come in handy :)

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• jeditable cancel button callback?

  - by Haroldo

  the solution here: http://stackoverflow.com/questions/1128760/jeditable-cancel-callback-from-ajax-callback using onreset() doesnt seem to work... any ideas?

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• WCF service and COM interop callback

  - by Sjblack

  I have a COM object that creates an instance of a WCF service and passes a handle to itself as a callback. The com object is marked/initialized as MTA. The problem being every instance of the WCF service that makes a call to the callback occurs on the same thread so they are being processed one at a time which is causing session timeouts under a heavy load. The WCF service is session based not sure if that makes any difference.

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• Updating a gridview based on dundas chart callback

  - by Daud

  I have a dundas pie chart which when clicked issues a client callback which updates another chart associated with it. Basically its like a drill down thing. I also want to update my gridview based on the user's selection of the pie. But since the update of chart is being done using dundas client callback I'm unable to rebind my Gridview. Is there any way to do it? .

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• node.js callback getting unexpected value for variable

  - by defrex

  I have a for loop, and inside it a variable is assigned with var. Also inside the loop a method is called which requires a callback. Inside the callback function I'm using the variable from the loop. I would expect that it's value, inside the callback function, would be the same as it was outside the callback during that iteration of the loop. However, it always seems to be the value from the last iteration of the loop. Am I misunderstanding scope in JavaScript, or is there something else wrong? The program in question here is a node.js app that will monitor a working directory for changes and restart the server when it finds one. I'll include all of the code for the curious, but the important bit is the parse_file_list function. var posix = require('posix'); var sys = require('sys'); var server; var child_js_file = process.ARGV[2]; var current_dir = __filename.split('/'); current_dir = current_dir.slice(0, current_dir.length-1).join('/'); var start_server = function(){ server = process.createChildProcess('node', [child_js_file]); server.addListener("output", function(data){sys.puts(data);}); }; var restart_server = function(){ sys.puts('change discovered, restarting server'); server.close(); start_server(); }; var parse_file_list = function(dir, files){ for (var i=0;i<files.length;i++){ var file = dir+'/'+files[i]; sys.puts('file assigned: '+file); posix.stat(file).addCallback(function(stats){ sys.puts('stats returned: '+file); if (stats.isDirectory()) posix.readdir(file).addCallback(function(files){ parse_file_list(file, files); }); else if (stats.isFile()) process.watchFile(file, restart_server); }); } }; posix.readdir(current_dir).addCallback(function(files){ parse_file_list(current_dir, files); }); start_server(); The output from this is: file assigned: /home/defrex/code/node/ejs.js file assigned: /home/defrex/code/node/templates file assigned: /home/defrex/code/node/web file assigned: /home/defrex/code/node/server.js file assigned: /home/defrex/code/node/settings.js file assigned: /home/defrex/code/node/apps file assigned: /home/defrex/code/node/dev_server.js file assigned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js stats returned: /home/defrex/code/node/main_urls.js For those from the future: node.devserver.js

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• Javascript callback function does not work in IE8!

  - by Abhishek

  I have a callback function in my open social application which fetches remote date. This works perfect on Crome and Mozila browers but not in IE8. Following is the example for the same, help will be appriciated: This funcation: gadgets.io.makeRequest(url, response, params) makes the callback call and following function process the responce: function response(obj) { var str = obj.text; var offerDtlPg = str.substr(0, str.length); document.getElementById('pplOfrDetls').innerHTML = offerDtlPg; };

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• Form validation with optional File Upload field callback

  - by MotiveKyle

  I have a form with some input fields and a file upload field in the same form. I am trying to include a callback into the form validation to check for file upload errors. Here is the controller for adding and the callback: public function add() { if ($this->ion_auth->logged_in()): //validate form input $this->form_validation->set_rules('title', 'title', 'trim|required|max_length[66]|min_length[2]'); // link url $this->form_validation->set_rules('link', 'link', 'trim|required|max_length[255]|min_length[2]'); // optional content $this->form_validation->set_rules('content', 'content', 'trim|min_length[2]'); $this->form_validation->set_rules('userfile', 'image', 'callback_validate_upload'); $this->form_validation->set_error_delimiters('<small class="error">', '</small>'); // if form was submitted, process form if ($this->form_validation->run()) { // add pin $pin_id = $this->pin_model->create(); $slug = strtolower(url_title($this->input->post('title'), TRUE)); // path to pin folder $file_path = './uploads/' . $pin_id . '/'; // if folder doesn't exist, create it if (!is_dir($file_path)) { mkdir($file_path); } // file upload config variables $config['upload_path'] = $file_path; $config['allowed_types'] = 'jpg|png'; $config['max_size'] = '2048'; $config['max_width'] = '1920'; $config['max_height'] = '1080'; $config['encrypt_name'] = TRUE; $this->load->library('upload', $config); // upload image file if ($this->upload->do_upload()) { $this->load->model('file_model'); $image_id = $this->file_model->insert_image_to_db($pin_id); $this->file_model->add_image_id_to_pin($pin_id, $image_id); } } // build page else: // User not logged in redirect("login", 'refresh'); endif; } The callback: function validate_upload() { if ($_FILES AND $_FILES['userfile']['name']): if ($this->upload->do_upload()): return true; else: $this->form_validation->set_message('validate_upload', $this->upload->display_errors()); return false; endif; else: return true; endif; } I am getting the error Fatal error: Call to a member function do_upload() on a non-object on line 92 when I try to run this. Line 92 is the if ($this->upload->do_upload()): line in the validate_upload callback. Am I going about this the right way? What's triggering this error?

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• callback in android?

  - by androidbase Praveen

  in android application development, i frequently go through the word "CALLBACK" in many places. i want to know want it means to tell us technically. and how i can manage the callback of the applications. i would need a guidance to understand about it....

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• How to initiate JavaScript Callback with MVC2 using RenderAction

  - by Zacho

  I am building a dashboard where I am iterating through a list of controls to render, and I need to initiate a general callback both after each control and after they are all completed. I was curious what the best way to handle this is. I can get the control specific callback fired off by placing myUserControlCallback(); in the user control itself. I'm just not sure how to run something like allControlsRendered();. Any ideas?

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• PHP Curl progress bar (callback returning percentage)

  - by WarDoGG

  I have implemented the curl progress bar using curl_setopt($curl, CURLOPT_PROGRESSFUNCTION, 'callback'); curl_setopt($curl, CURLOPT_BUFFERSIZE,64000); curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true); and a callback function. problem is, the script is outputting the percentage on my html everytime like this : 0 0.1 0.2 0.2 0.3 0.4 .. .. .. 1 1.1 How do i combine this with CSS to show a changing progress bar ?

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• callback for each for loop iteration

  - by SWKK

  Hi Guys, a bit of a naive question, but nonetheless. I am trying to break up a for loop in which a 2d Matrix is being read. I would like to write a callback function to consume row-wise/col-wise chunks per row/col iteration. Any hints on how to tie up the callback function with iteration?

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• How to implement a timer callback that executes in the same execution context

  - by Waldorf

  Some programming environments like C++ builder have timer components with a callback function which executes in the same execution contexts as where the timer object is created. I was wondering how to do something similar in plain c++ with threading. Or are there any other ways to have a callback which is periodically called to perform some task and runs in the same execution context as the calling thread?

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• getJSON callback not firing

  - by Marty Trenouth

  I'm making the call using the following script which is called on click of an anchor tag function GetToken(videoId) { debugger; var json = $.getJSON("/Vod/RequestAccessToken/"+videoId, function(result){ alert("token recieved: " + result.token); }); } In the server application I recieve the call so I know it is a valid URL, but the callback is not being invoked. If i set though the jquery code (f11/f10) the callback is called??!!!?

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• When I shutdown the computer, it restarts

  - by Prabu

  I am unable to shutdown. Whenever I try to shutdown, it reboots. I am running Ubuntu 12.10. I have run the boot-repair and this is the result: Boot Info Script 0.61.full + Boot-Repair extra info [Boot-Info November 20th 2012] ============================= Boot Info Summary: =============================== => Grub2 (v2.00) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for (,msdos1)/boot/grub. sda1: __________________________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 12.10 Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/i386-pc/core.img sda2: __________________________________________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: sda5: __________________________________________________________________________ File system: swap Boot sector type: - Boot sector info: ============================ Drive/Partition Info: ============================= Drive: sda _____________________________________________________________________ Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 2,048 1,936,809,983 1,936,807,936 83 Linux /dev/sda2 1,936,812,030 1,953,523,711 16,711,682 5 Extended /dev/sda5 1,936,812,032 1,953,523,711 16,711,680 82 Linux swap / Solaris "blkid" output: ________________________________________________________________ Device UUID TYPE LABEL /dev/loop0 squashfs /dev/sda1 229a5484-7659-4ce1-98ce-2f05f61a1ffa ext4 /dev/sda5 6c6dca25-ab67-4de4-8602-26fdb6154781 swap /dev/sr0 iso9660 Ubuntu 12.10 amd64 ================================ Mount points: ================================= Device Mount_Point Type Options /dev/loop0 /rofs squashfs (ro,noatime) /dev/sr0 /cdrom iso9660 (ro,noatime) =========================== sda1/boot/grub/grub.cfg: =========================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=auto load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_US insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=10 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "${linux_gfx_mode}" != "text" ]; then load_video; fi menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi linux /boot/vmlinuz-3.5.0-19-generic root=UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa ro quiet splash acpi=force $vt_handoff initrd /boot/initrd.img-3.5.0-19-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { menuentry 'Ubuntu, with Linux 3.5.0-19-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-19-generic-advanced-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi echo 'Loading Linux 3.5.0-19-generic ...' linux /boot/vmlinuz-3.5.0-19-generic root=UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa ro quiet splash acpi=force $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-19-generic } menuentry 'Ubuntu, with Linux 3.5.0-19-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-19-generic-recovery-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { recordfail insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi echo 'Loading Linux 3.5.0-19-generic ...' linux /boot/vmlinuz-3.5.0-19-generic root=UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-19-generic } menuentry 'Ubuntu, with Linux 3.5.0-17-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-advanced-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa ro quiet splash acpi=force $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } menuentry 'Ubuntu, with Linux 3.5.0-17-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-recovery-229a5484-7659-4ce1-98ce-2f05f61a1ffa' { recordfail insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 229a5484-7659-4ce1-98ce-2f05f61a1ffa else search --no-floppy --fs-uuid --set=root 229a5484-7659-4ce1-98ce-2f05f61a1ffa fi linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### -------------------------------------------------------------------------------- =============================== sda1/etc/fstab: ================================ -------------------------------------------------------------------------------- # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sda1 during installation UUID=229a5484-7659-4ce1-98ce-2f05f61a1ffa / ext4 errors=remount-ro 0 1 # swap was on /dev/sda5 during installation UUID=6c6dca25-ab67-4de4-8602-26fdb6154781 none swap sw 0 0 -------------------------------------------------------------------------------- =================== sda1: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) 200.155235291 = 214.915047424 boot/grub/grub.cfg 1 40.280788422 = 43.251167232 boot/initrd.img-3.5.0-17-generic 1 2.468288422 = 2.650304512 boot/initrd.img-3.5.0-19-generic 1 200.149234772 = 214.908604416 boot/vmlinuz-3.5.0-17-generic 1 1.990135193 = 2.136891392 boot/vmlinuz-3.5.0-19-generic 1 2.468288422 = 2.650304512 initrd.img 1 1.990135193 = 2.136891392 vmlinuz 1 1.990135193 = 2.136891392 vmlinuz.old 1 =============================== StdErr Messages: =============================== cat: write error: Broken pipe File descriptor 8 (/proc/6297/mounts) leaked on lvscan invocation. Parent PID 13390: bash No volume groups found ADDITIONAL INFORMATION : =================== log of boot-repair 2012-12-17__01h53 =================== boot-repair version : 3.197~ppa1~quantal boot-sav version : 3.197~ppa1~quantal glade2script version : 3.2.2~ppa45~quantal boot-sav-extra version : 3.197~ppa1~quantal boot-repair is executed in live-session (Ubuntu 12.10, quantal, Ubuntu, x86_64) CPU op-mode(s): 32-bit, 64-bit file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity =================== os-prober: /dev/sda1:Ubuntu 12.10 (12.10):Ubuntu:linux =================== blkid: /dev/loop0: TYPE="squashfs" /dev/sr0: LABEL="Ubuntu 12.10 amd64" TYPE="iso9660" /dev/sda1: UUID="229a5484-7659-4ce1-98ce-2f05f61a1ffa" TYPE="ext4" /dev/sda5: UUID="6c6dca25-ab67-4de4-8602-26fdb6154781" TYPE="swap" 1 disks with OS, 1 OS : 1 Linux, 0 MacOS, 0 Windows, 0 unknown type OS. Warning: extended partition does not start at a cylinder boundary. DOS and Linux will interpret the contents differently. =================== sda1/etc/default/grub : # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: # info -f grub -n 'Simple configuration' GRUB_DEFAULT=0 GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force" GRUB_CMDLINE_LINUX="" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" =================== sda1/etc/grub.d/ : drwxr-xr-x 2 root root 4096 Oct 17 14:59 grub.d total 72 -rwxr-xr-x 1 root root 7541 Oct 14 17:36 00_header -rwxr-xr-x 1 root root 5488 Oct 4 09:30 05_debian_theme -rwxr-xr-x 1 root root 10891 Oct 14 17:36 10_linux -rwxr-xr-x 1 root root 10258 Oct 14 17:36 20_linux_xen -rwxr-xr-x 1 root root 1688 Oct 11 14:10 20_memtest86+ -rwxr-xr-x 1 root root 10976 Oct 14 17:36 30_os-prober -rwxr-xr-x 1 root root 1426 Oct 14 17:36 30_uefi-firmware -rwxr-xr-x 1 root root 214 Oct 14 17:36 40_custom -rwxr-xr-x 1 root root 216 Oct 14 17:36 41_custom -rw-r--r-- 1 root root 483 Oct 14 17:36 README =================== UEFI/Legacy mode: This live-session is not in EFI-mode. SecureBoot maybe enabled. =================== PARTITIONS & DISKS: sda1 : sda, not-sepboot, grubenv-ok grub2, grub-pc , update-grub, 64, with-boot, is-os, not--efi--part, fstab-without-boot, fstab-without-efi, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, apt-get, grub-install, with--usr, fstab-without-usr, not-sep-usr, standard, farbios, /mnt/boot-sav/sda1. sda : not-GPT, BIOSboot-not-needed, has-no-EFIpart, not-usb, has-os, 2048 sectors * 512 bytes =================== parted -l: Model: ATA ST1000DM003-1CH1 (scsi) Disk /dev/sda: 1000GB Sector size (logical/physical): 512B/4096B Partition Table: msdos Number Start End Size Type File system Flags 1 1049kB 992GB 992GB primary ext4 boot 2 992GB 1000GB 8556MB extended 5 992GB 1000GB 8556MB logical linux-swap(v1) Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only. Error: Can't have a partition outside the disk! =================== parted -lm: BYT; /dev/sda:1000GB:scsi:512:4096:msdos:ATA ST1000DM003-1CH1; 1:1049kB:992GB:992GB:ext4::boot; 2:992GB:1000GB:8556MB:::; 5:992GB:1000GB:8556MB:linux-swap(v1)::; Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only. Error: Can't have a partition outside the disk! =================== mount: /cow on / type overlayfs (rw) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) /dev/sr0 on /cdrom type iso9660 (ro,noatime) /dev/loop0 on /rofs type squashfs (ro,noatime) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) tmpfs on /tmp type tmpfs (rw,nosuid,nodev) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755) gvfsd-fuse on /run/user/ubuntu/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=ubuntu) /dev/sda1 on /mnt/boot-sav/sda1 type ext4 (rw) =================== ls: /sys/block/sda (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro sda1 sda2 sda5 size slaves stat subsystem trace uevent /sys/block/sr0 (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro size slaves stat subsystem trace uevent /dev (filtered): alarm ashmem autofs binder block bsg btrfs-control bus cdrom cdrw char console core cpu cpu_dma_latency disk dri dvd dvdrw ecryptfs fb0 fd full fuse fw0 hidraw0 hidraw1 hpet input kmsg kvm log mapper mcelog mei mem net network_latency network_throughput null oldmem port ppp psaux ptmx pts random rfkill rtc rtc0 sda sda1 sda2 sda5 sg0 sg1 shm snapshot snd sr0 stderr stdin stdout uinput urandom usb vga_arbiter vhost-net zero ls /dev/mapper: control =================== df -Th: Filesystem Type Size Used Avail Use% Mounted on /cow overlayfs 3.9G 100M 3.8G 3% / udev devtmpfs 3.9G 12K 3.9G 1% /dev tmpfs tmpfs 1.6G 864K 1.6G 1% /run /dev/sr0 iso9660 763M 763M 0 100% /cdrom /dev/loop0 squashfs 717M 717M 0 100% /rofs tmpfs tmpfs 3.9G 32K 3.9G 1% /tmp none tmpfs 5.0M 4.0K 5.0M 1% /run/lock none tmpfs 3.9G 176K 3.9G 1% /run/shm none tmpfs 100M 52K 100M 1% /run/user /dev/sda1 ext4 910G 26G 838G 3% /mnt/boot-sav/sda1 =================== fdisk -l: Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x000da1e9 Device Boot Start End Blocks Id System /dev/sda1 * 2048 1936809983 968403968 83 Linux /dev/sda2 1936812030 1953523711 8355841 5 Extended Partition 2 does not start on physical sector boundary. /dev/sda5 1936812032 1953523711 8355840 82 Linux swap / Solaris Partition outside the disk detected. =================== Recommended repair Recommended-Repair This setting will reinstall the grub2 of sda1 into the MBR of sda. Additional repair will be performed: unhide-bootmenu-10s Unhide GRUB boot menu in sda1/etc/default/grub grub-install (GRUB) 2.00-7ubuntu11,grub-install (GRUB) 2. Reinstall the GRUB of sda1 into the MBR of sda Installation finished. No error reported. grub-install /dev/sda: exit code of grub-install /dev/sda:0 chroot /mnt/boot-sav/sda1 update-grub Generating grub.cfg ... Found linux image: /boot/vmlinuz-3.5.0-19-generic Found initrd image: /boot/initrd.img-3.5.0-19-generic Found linux image: /boot/vmlinuz-3.5.0-17-generic Found initrd image: /boot/initrd.img-3.5.0-17-generic Found memtest86+ image: /boot/memtest86+.bin Unhide GRUB boot menu in sda1/boot/grub/grub.cfg Boot successfully repaired. You can now reboot your computer.

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• Strategies for invoking subclass methods on generic objects

  - by Brad Patton

  I've run into this issue in a number of places and have solved it a bunch of different ways but looking for other solutions or opinions on how to address. The scenario is when you have a collection of objects all based off of the same superclass but you want to perform certain actions based only on instances of some of the subclasses. One contrived example of this might be an HTML document made up of elements. You could have a superclass named HTMLELement and subclasses of Headings, Paragraphs, Images, Comments, etc. To invoke a common action across all of the objects you declare a virtual method in the superclass and specific implementations in all of the subclasses. So to render the document you could loop all of the different objects in the document and call a common Render() method on each instance. It's the case where again using the same generic objects in the collection I want to perform different actions for instances of specific subclass (or set of subclasses). For example (an remember this is just an example) when iterating over the collection, elements with external links need to be downloaded (e.g. JS, CSS, images) and some might require additional parsing (JS, CSS). What's the best way to handle those special cases. Some of the strategies I've used or seen used include: Virtual methods in the base class. So in the base class you have a virtual LoadExternalContent() method that does nothing and then override it in the specific subclasses that need to implement it. The benefit being that in the calling code there is no object testing you send the same message to each object and let most of them ignore it. Two downsides that I can think of. First it can make the base class very cluttered with methods that have nothing to do with most of the hierarchy. Second it assumes all of the work can be done in the called method and doesn't handle the case where there might be additional context specific actions in the calling code (i.e. you want to do something in the UI and not the model). Have methods on the class to uniquely identify the objects. This could include methods like ClassName() which return a string with the class name or other return values like enums or booleans (IsImage()). The benefit is that the calling code can use if or switch statements to filter objects to perform class specific actions. The downside is that for every new class you need to implement these methods and can look cluttered. Also performance could be less than some of the other options. Use language features to identify objects. This includes reflection and language operators to identify the objects. For example in C# there is the is operator that returns true if the instance matches the specified class. The benefit is no additional code to implement in your object hierarchy. The only downside seems to be the lack of using something like a switch statement and the fact that your calling code is a little more cluttered. Are there other strategies I am missing? Thoughts on best approaches?

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• Generic Adjacency List Graph implementation

  - by DmainEvent

  I am trying to come up with a decent Adjacency List graph implementation so I can start tooling around with all kinds of graph problems and algorithms like traveling salesman and other problems... But I can't seem to come up with a decent implementation. This is probably because I am trying to dust the cobwebs off my data structures class. But what I have so far... and this is implemented in Java... is basically an edgeNode class that has a generic type and a weight-in the event the graph is indeed weighted. public class edgeNode<E> { private E y; private int weight; //... getters and setters as well as constructors... } I have a graph class that has a list of edges a value for the number of Vertices and and an int value for edges as well as a boolean value for whether or not it is directed. The brings up my first question, if the graph is indeed directed, shouldn't I have a value in my edgeNode class? Or would I just need to add another vertices to my LinkedList? That would imply that a directed graph is 2X as big as an undirected graph wouldn't it? public class graph { private List<edgeNode<?>> edges; private int nVertices; private int nEdges; private boolean directed; //... getters and setters as well as constructors... } Finally does anybody have a standard way of initializing there graph? I was thinking of reading in a pipe-delimited file but that is so 1997. public graph GenereateGraph(boolean directed, String file){ List<edgeNode<?>> edges; graph g; try{ int count = 0; String line; FileReader input = new FileReader("C:\\Users\\derekww\\Documents\\JavaEE Projects\\graphFile"); BufferedReader bufRead = new BufferedReader(input); line = bufRead.readLine(); count++; edges = new ArrayList<edgeNode<?>>(); while(line != null){ line = bufRead.readLine(); Object edgeInfo = line.split("|")[0]; int weight = Integer.parseInt(line.split("|")[1]); edgeNode<String> e = new edgeNode<String>((String) edges.add(e); } return g; } catch(Exception e){ return null; } } I guess when I am adding edges if boolean is true I would be adding a second edge. So far, this all depends on the file I write. So if I wrote a file with the following Vertices and weights... Buffalo | 18 br Pittsburgh | 20 br New York | 15 br D.C | 45 br I would obviously load them into my list of edges, but how can I represent one vertices connected to the other... so on... I would need the opposite vertices? Say I was representing Highways connected to each city weighted and un-directed (each edge is bi-directional with weights in some fictional distance unit)... Would my implementation be the best way to do that? I found this tutorial online Graph Tutorial that has a connector object. This appears to me be a collection of vertices pointing to each other. So you would have A and B each with there weights and so on, and you would add this to a list and this list of connectors to your graph... That strikes me as somewhat cumbersome and a little dismissive of the adjacency list concept? Am I wrong and that is a novel solution? This is all inspired by steve skiena's Algorithm Design Manual. Which I have to say is pretty good so far. Thanks for any help you can provide.

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• Twitter oauth_callback parameter being ignored!

  - by Astrofaes

  Hi guys, I'm trying to get Twitter authentication working on my ASP.NET site. When you create the app on the Twitter website, you have to specify a callback URL, which for sake of argument, I have set to http://mydomain.com I've read the oAuth 1.0a spec, and to override this callback URL with your own custom one you have to send the oauth_callback parameter in the request_token phase (url-encoded of course). So my request URL looks like this: http://twitter.com/oauth/request_token?oauth_callback_url=http%3A%2F%2Fmydomain.com%2Ftwittercallback Supposedly, if all goes to plan, in your response data, you are supposed to receive a new parameter of oauth_callback_confirmed=true in addition to your token and token secret parameters. However, my response comes through as: oauth_token=MYTOKEN&oauth_token_secret=MYTOKENSECRET I know I haven't given you guys the greatest amount to go on, but I'm at my wits end as to why I am not receiving the oauth_callback_confirmed parameter. Without this, my application keeps defaulting back to the callback URL hard-coded on the Twitter website. Please if anyone could help me out, I will be eternally grateful! Thanks, A.

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