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  • May volatile be in user defined types to help writing thread-safe code

    - by David Rodríguez - dribeas
    I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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  • MIN() and MAX() in Swift and converting Int to CGFloat

    - by gotnull
    I'm getting some errors with the following methods: 1) How do I return screenHeight / cellCount as a CGFLoat for the first method? 2) How do I use the equivalent of ObjC's MIN() and MAX() in the second method? func tableView(tableView: UITableView!, heightForRowAtIndexPath indexPath: NSIndexPath!) -> CGFloat { var cellCount = Int(self.tableView.numberOfRowsInSection(indexPath.section)) return screenHeight / cellCount as CGFloat } // #pragma mark - UIScrollViewDelegate func scrollViewDidScroll(scrollView: UIScrollView) { let height = CGFloat(scrollView.bounds.size.height) let position = CGFloat(MAX(scrollView.contentOffset.y, 0.0)) let percent = CGFloat(MIN(position / height, 1.0)) blurredImageView.alpha = percent }

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  • Exposing C# COM server events to Delphi client applications

    - by hectorsosajr
    My question is very similar to these two: http://stackoverflow.com/questions/1140984/c-component-events http://stackoverflow.com/questions/1638372/c-writing-a-com-server-events-not-firing-on-client However, what worked for them is not working for me. The type library file, does not have any hints of events definitions, so Delphi doesn't see it. The class works fine for other C# applications, as you would expect. COM Server tools: Visual Studio 2010 .NET 4.0 Delphi applications: Delphi 2010 Delphi 7 Here's a simplified version of the code: /// <summary> /// Call has arrived delegate. /// </summary> [ComVisible(false)] public delegate void CallArrived(object sender, string callData); /// <summary> /// Interface to expose SimpleAgent events to COM /// </summary> [ComVisible(true)] [GuidAttribute("1FFBFF09-3AF0-4F06-998D-7F4B6CB978DD")] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IAgentEvents { ///<summary> /// Handles incoming calls from the predictive manager. ///</summary> ///<param name="sender">The class that initiated this event</param> ///<param name="callData">The data associated with the incoming call.</param> [DispId(1)] void OnCallArrived(object sender, string callData); } /// <summary> /// Represents the agent side of the system. This is usually related to UI interactions. /// </summary> [ComVisible(true)] [GuidAttribute("EF00685F-1C14-4D05-9EFA-538B3137D86C")] [ClassInterface(ClassInterfaceType.None)] [ComSourceInterfaces(typeof(IAgentEvents))] public class SimpleAgent { /// <summary> /// Occurs when a call arrives. /// </summary> public event CallArrived OnCallArrived; public SimpleAgent() {} public string AgentName { get; set; } public string CurrentPhoneNumber { get; set; } public void FireOffCall() { if (OnCallArrived != null) { OnCallArrived(this, "555-123-4567"); } } } The type library file has the definitions for the properties and methods, but no events are visible. I even opened the type library in Delphi's viewer to make sure. The Delphi app can see and use any property, methods, and functions just fine. It just doesn't see the events. I would appreciate any pointers or articles to read. Thanks!

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  • Asp.Net MVC missing style and defaults to logon page

    - by user279750
    I just setup an out of the box "W2K8 R2 Web" server and installed IIS 7 out of the box. Then I installed the .NET4 framework and ran "aspnet_regiis -i" command. I created a site using .NET 4.0 Integrated app pool. I created an MVC application using the default MVC project template, without modifying I compiled the project and deploy the files using (Publish) to the virtual directory. I can pull the site up, but the styles are missing from the page and for some reason it routing to the /Account/LogOn?ReturnUrl=/

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  • Older iPhone/ iPod frame rate?

    - by Adam
    Do older iPods and iPhones have a frame rate of 60fps? I'm finding that all the methods for calculating time intervals on iPhone (cftimeinterval, nstimer, timesince1970, etc) are all giving me bad data, so I've decided assume a frame rate of 60, just not sure if older apple devices can run at this.

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  • VC++ Charts using Chart X

    - by Arjun
    Hi, I'm new to drawing the chart using chartfx can you give me the meanings of teh following methods, they are kinda confusing...I did not find documentation anywhere. GetValue ( ) GetXValue ( ) PutItem() Thanks, Arjun

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  • How to bind set of reports to report viwer ?

    - by prasad
    Hi all , I want to print a set of invoice for my application. So I need to display all invoices in report viewer before they print. are there any methods to bind multiple reports to same report viewer using crystal reports or rdlc. I try rdlc but I couldn't find any way to do that. please any one can provide code sample or instruction in C#.net it's worth for me. thank you.......

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  • recommendation systems and the cold start problem

    - by Hellnar
    Hello, I am curious what are the methods / approaches to overcome the "cold start" problem where when a new user or an item enters the system, due to lack of info about this new entity, making recommendation is a problem. I can think of doing some prediction based recommendation (like gender, nationality and so on). Thanks

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  • Fancybox force scroll to top

    - by Bradley Herman
    I'm using the jQuery Fancybox plugin to display some content on a website. Unfortunately, when a link is clicked, the lightbox that is loaded starts at the same scroll position as the previous one. I tried using self.scrollTo(0,0) $.scrollTo(0) $('#top').scrollTo(); and a few others methods to push it back to the top, but none have seemed to work. Any help on this?

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  • WCF web service: response is 200/ok, but response body is empty

    - by user1021224
    I am creating a WCF web api service. My problem is that some methods return a 200/OK response, but the headers and the body are empty. In setting up my web service, I created an ADO.NET Entity Data Model. I chose ADO.NET DbContext Generator when I added a code generation item. In the Model.tt document, I changed HashSet and ICollection to List. I built my website. It used to be that when I coded a method to return a List of an entity (like List<Customer> or List<Employee> in the Northwind database), it worked fine. Over time, I could not return a List of any of those, and could only grab one entity. Now, it's gotten to a point where I can return a List<string> or List<int>, but not a List or an instance of any entity. When I try to get a List<AnyEntity>, the response is 200/OK, but the response headers and body are empty. I have tried using the debugger and Firefox's Web Console. Using FF's WC, I could only get an "undefined" status code. I am not sure where to go from here. EDIT: In trying to grab all Areas from the database, I do this: [WebGet(UriTemplate = "areas")] public List<a1Areas> AllAreas() { return context.a1Areas.ToList(); } I would appreciate any more methods for debugging this. Thanks in advance. Found the answer, thanks to Merlyn! In my Global.asax file, I forgot to comment out two lines that took care of proxies and disposing of my context object. The code is below: void Application_BeginRequest(object sender, EventArgs e) { var context = new AssignmentEntities(); context.Configuration.ProxyCreationEnabled = false; HttpContext.Current.Items["_context"] = context; } void Application_EndRequest(object sender, EventArgs e) { var context = HttpContext.Current.Items["_context"] as AssignmentEntities; if (context != null) { context.Dispose(); } }

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  • ip based ssl certificate

    - by user121196
    I have two domain names pointing to the same ip, I am currently not using virtual host in my apache configuration. I simply use /var/www/html/ as root of the app. do I need to buy 2 godaddy certificates, one for each domain? It seems that godaddy certificate is tied to a domain, not ip, can someone clarify?

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  • Filtering out page content with AJAX in Sitecore

    - by RaYell
    I have a page in Sitecore that displays the list of clients. There's a form with two select boxes that should filter out clients not matching specified criterias. Clients list should be refreshed via AJAX everytime user changes one of the values in the form or after clicking Submit button if JS is disabled. What is the suggested approach I should take to have this working in Sitecore? I'm not sure about Sitecore part, I know how to call AJAX methods/

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  • Colour instead of color?

    - by Jookia
    I'm working on a game engine in C++ and I have methods like setColour and things that use british grammar. While I was thinking how C++ compilers mostly use the english language (correct me if I'm wrong) and how most APIs use american grammar, should I go with the flow and continue the unofficial standard in the grammar programmer high council or be a rebel? I'm not sure which.

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  • objective C NSString retain

    - by Amarsh
    If I create a String with [NSString StringWithFormat], do I have to [retain] it? My understanding is that convenience methods add the objects to autorelease pool. If that is the case, shouldnt we retain the object so that it doesnt get drained with pool at the end of the event loop?

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  • BlackBerry : How to Parse XML file ?

    - by yakub_moriss
    Hi, All I want to know how to parse xml data in blackberry. and also want to know diferent methods available. as i read somewhere that JSON is good method to parse xml data. is there any tutorials to parse xml data using JSON. Simple parsing method tutorial is also acceptable... plz help me out... Thanks in advance...

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  • Java declarations (ordering)

    - by incrediman
    In Java, what's generally the most accepted way to organize a class in terms of the order in which declared data members and methods should be listed in the class file, keeping in mind the following and anything else you can think of for each one: its visibility whether it's a constructor, method, or member if it's a method, does it overload, or override other method(s)?

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  • Block users using auto-clickers

    - by James Simpson
    I'm having some problems with users cheating my online game by using macros to automatically click certain spots on the screen in a certain order to automate various tasks without having to actually be playing the game. Are there any methods that can be used to block this kind of activity without having to plaster CAPTCHAs all over the site and ruin the experience for the honest users?

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  • Legacy exchange MAPI help?

    - by Zenox
    I'm working with some legacy exchange code and I am having trouble finding information about some methods/constants. A google search reveals others using similar code, but with no explanations. Does anyone have any ideas where I can find proper docs? One constant I am looking for is: SYNC_ASSOCIATED.

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