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  • Can someone describe the nested set model from a C#/LINQ perspective?

    - by Chad
    I know the nested set model doesn't pertain to the C# language or LINQ directly... it's what I'm using to develop my web app. For hierarchical data (categories with sub-categories in my case), I'm currently using something similar to the Adjacency List model. At the moment, I've only got 2 levels of categories, but I'd like to take it further and allow for n levels of categories using the nested set model. I'm not quite clear on how to use it in a C# context. Here's the article I'm reading on the nested set model. Though this article cleared up my confusion some, I still have a big ?? in my head: - Is inserting, updating or deleting categories tedious? It looks like the left and right numbers would require re-numbering... what would the LINQ queries look like for the following scenarios? Delete a child node (re-number all node's left/right values) Delete a parent node (what do you do with the orphans?) Move a child node to a different parent node (renumber again) If my understanding is correct, at all times the child node's left/right values will always be between the parent node's left/right values, am I correct? Seems easy enough, if only the categories were static... most likely I need to spend more time to get my head around the concept. Any help is greatly appreciated!

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  • how to better (inambiguaously) use the terms CAPTCHA and various types of interactions?

    - by vgv8
    I am working on survey of state-of-the-art and trends of spam prevention techniques. I observe that non-intrusive, transparent to visitor spam prevention techniques (like context-based filtering or honey traps) are frequently called non-captcha. Is it correct understanding of term CAPTCHA which is "type of challenge-response [ 2 ]test used in computing to ensure that the response is not generated by a compute" [ 1 ] and challenge-response does not seem to imply obligatory human involvement. So, which understanding (definition) of term and classification I'd better to stick with? How would I better call CAPTCHA without direct human interaction in order to avoid ambiguity and confusion of terms understnding? How would I better (succinctly and unambiguously) coin the term for captchas requiring human interaction but without typing into textbox? How would I better (succinctly and unambiguously) coin the terms to mark the difference between human interaction with images (playing, drag&dropping, rearranging, clicking with images) vs. just recognizing them (and then typing into a textbox the answer without interaction with images)? PS. The problem is that recognition of a wiggled word in an image or typing the answer to question is also interaction and when I start to use the terms "interaction", "interactive", "captcha", "protection", "non-captcha", "non-interactive", "static", "dynamic", "visible", "hidden" the terms overlap ambiguously with which another (especailly because the definitions or their actual practice of usage are vague or contradictive). [ 1 ] http://en.wikipedia.org/wiki/CAPTCHA

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  • Has Twisted changed its dependencies?

    - by cdecker
    Hi all, I'm currently working on a Python/Twisted project which is to be distributed and tested on Planetlab. For some reason my code was working on friday and now that I wanted to test a minor change it refuses to work at all: Traceback (most recent call last): File "acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/__init__.py", line 18, in <module> from twisted.python import compat File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/compat.py", line 146, in <module> import operator File "/home/cdecker/dev/acn/acn_a4/src/operator.py", line 7, in <module> File "/home/cdecker/acn_a4/src/node.py", line 6, in <module> from twisted.internet.protocol import DatagramProtocol File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/internet/protocol.py", line 20, in <module> from twisted.python import log, failure, components File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/log.py", line 19, in <module> from twisted.python import util, context, reflect File "/usr/lib/python2.5/site-packages/Twisted-10.0.0-py2.5-linux-i686.egg/twisted/python/util.py", line 5, in <module> import os, sys, hmac, errno, new, inspect, warnings File "/usr/lib/python2.5/inspect.py", line 32, in <module> from operator import attrgetter ImportError: cannot import name attrgetter And since I'm pretty new to python I have no idea what could have caused this problem. All suggestions are welcome :-)

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  • Maven webapp with Eclipse and WTP plugin deploy files in stranges ways in Tomcat

    - by hokkos
    Hi, I use Eclipse J2EE 3.5 with Maven and tomcat. To deploy my maven webapp with WTP I added a Dynamic Web Module facet and changed the "org.eclipse.wst.common.component" file of the project because the webapp is not in a WebContent directory, here is the content of the file: <?xml version="1.0" encoding="UTF-8"?> <project-modules id="moduleCoreId" project-version="1.5.0"> <wb-module deploy-name="tkey-ca-web"> <wb-resource deploy-path="/" source-path="/src/main/webapp"/> <wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/java"/> <wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/resources"/> <property name="context-root" value="toto"/> <property name="java-output-path" value="/toto/target/classes"/> </wb-module> </project-modules> But it never deploy the content correctly, in "workspace.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\toto\" the directory structure is correct with WEB-INF and META-INF but empty, the jsp, html, css files are in "workspace.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\toto\WEB-INF\classes\" with another WEB-INF and META-INF structure but with the files. I don't understand this at all, thanks.

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  • Forking in PHP on Windows

    - by Doug Kavendek
    We are running PHP on a Windows server (a source of many problems indeed, but migrating is not an option currently). There are a few points where a user-initiated action will need to kick off a few things that take a while and about which the user doesn't need to know if they succeed or fail, such as sending off an email or making sure some third-party accounts are updated. If I could just fork with pcntl_fork(), this would be very simple, but the PCNTL functions are not available in Windows. It seems the closest I can get is to do something of this nature: exec( 'php-cgi.exe somescript.php' ); However, this would be far more complicated. The actions I need to kick off rely on a lot of context that already will exist in the running process; to use the above example, I'd need to figure out the essential data and supply it to the new script in some way. If I could fork, it'd just be a matter of letting the parent process return early, leaving the child to work on a few more things. I've found a few people talking about their own work in getting various PCNTL functions compiled on Windows, but none seemed to have anything available (broken links, etc). Despite this question having practically the same name as mine, it seems the problem was more execution timeout than needing to fork. So, is my best option to just refactor a bit to deal with calling php-cgi, or are there other options? Edit: It seems exec() won't work for this, at least not without me figuring some other aspect of it, as it waits until the call returns. I figured I could use START, sort of like exec( 'start php-cgi.exe somescript.php' );, but it still waits until the other script finishes.

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  • Entity framework entity class mapping with plain .net class

    - by Elan
    I have following in entity framework Table - Country Fields List item Country_ID Dialing_Code ISO_Alpha2 ISO_Alpha3 ISO_Full I would like to map only selected fields from this entity model to my domain class. My domain model class is public class DomainCountry { public int Country_ID { get; set; } public string Dialing_Code { get; set; } public string ISO_3166_1_Alpha_2 { get; set; } } The following will work however insert or update is not possible. In order to get insert or update we need to use ObjectSet< but it will not support in my case. IQueryable<DomainCountry> countries = context.Countries.Select( c => new DomainCountry { Country_ID = c.Country_Id, Dialing_Code = c.Dialing_Code, ISO_3166_1_Alpha_2 = c.ISO_3166_1_Alpha_2 }); It will be really fantastic could someone provide a nice solution for this. Ideally it will be kind of proxy class which will support all the futures however highly customizable i.e. only the columns we want to expose to the outer world

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  • Calling SubmitChanges on DataContext does not update database.

    - by drasto
    In C# ASP.NET MVC application I use Link to SQL to provide data for my application. I have got simple database schema like this: In my controller class I reference this data context called Model (as you can see on the right side of picture in properties) like this: private Model model = new Model(); I've got a table (List) of Series rendered on my page. It renders properly and I was able to add delete functionality to delete Series like this: public ActionResult Delete(int id) { model.Series.DeleteOnSubmit(model.Series.SingleOrDefault(s => s.ID == id)); model.SubmitChanges(); return RedirectToAction("Index"); } Where appropriate action link looks like this: <%: Html.ActionLink("Delete", "Delete", new { id=item.ID })%> Also create (implemented in similar way) works fine. However edit does not work. My edit looks like this: public ActionResult Edit(int id) { return View(model.Series.SingleOrDefault(s => s.ID == id)); } [HttpPost] public ActionResult Edit(Series series) { if (ModelState.IsValid) { UpdateModel(series); series.Title = series.Title + " some string to ensure title has changed"; model.SubmitChanges(); return RedirectToAction("Index"); } I have controlled that my database has a primary key set up correctly. I debugged my application and found out that everything works as expected until the line with model.SubmitChanges();. This command does not apply the changes of Title property(or any other) against the database. Please help.

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  • How to mmap the stack for the clone() system call on linux?

    - by Joseph Garvin
    The clone() system call on Linux takes a parameter pointing to the stack for the new created thread to use. The obvious way to do this is to simply malloc some space and pass that, but then you have to be sure you've malloc'd as much stack space as that thread will ever use (hard to predict). I remembered that when using pthreads I didn't have to do this, so I was curious what it did instead. I came across this site which explains, "The best solution, used by the Linux pthreads implementation, is to use mmap to allocate memory, with flags specifying a region of memory which is allocated as it is used. This way, memory is allocated for the stack as it is needed, and a segmentation violation will occur if the system is unable to allocate additional memory." The only context I've ever heard mmap used in is for mapping files into memory, and indeed reading the mmap man page it takes a file descriptor. How can this be used for allocating a stack of dynamic length to give to clone()? Is that site just crazy? ;) In either case, doesn't the kernel need to know how to find a free bunch of memory for a new stack anyway, since that's something it has to do all the time as the user launches new processes? Why does a stack pointer even need to be specified in the first place if the kernel can already figure this out?

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  • iPhone UIView Animation Disables UIButton Subview

    - by bensnider
    So I've got a problem with buttons and animations. Basically, I'm animating a view using the UIView animations while also trying to listen for taps on the button inside the view. The view is just as large as the button, and the view is actually a subclass of UIImageView with an image below the button. The view is a subview of a container view placed in Interface Builder with user interaction enabled and clipping enabled. All the animation and button handling is done in this UIImageView subclass, while the startFloating message is sent from a separate class as needed. If I do no animation, the buttonTapped: message gets sent correctly, but during the animation it does not get sent. I've also tried implementing the touchesEnded method, and the same behavior occurs. UIImageView subclass init (I have the button filled with a color so I can see the frame gets set properly, which it does): - (id)initWithImage:(UIImage *)image { self = [super initWithImage:image]; if (self != nil) { // ...stuffs UIButton *tapBtn = [UIButton buttonWithType:UIButtonTypeCustom]; tapBtn.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height); [tapBtn addTarget:self action:@selector(buttonTapped:) forControlEvents:UIControlEventTouchUpInside]; tapBtn.backgroundColor = [UIColor cyanColor]; [self addSubview:tapBtn]; self.userInteractionEnabled = YES; } return self; } Animation method that starts the animation (if I don't call this the button works correctly): - (void)startFloating { [UIView beginAnimations:@"floating" context:nil]; [UIView setAnimationDelegate:self]; [UIView setAnimationCurve:UIViewAnimationCurveLinear]; [UIView setAnimationDuration:10.0f]; self.frame = CGRectMake(self.frame.origin.x, -self.frame.size.height, self.frame.size.width, self.frame.size.height); [UIView commitAnimations]; } So, to be clear: Using the UIView animation effectively disables the button. Disabling the animation causes the button to work. The button is correctly sized and positioned on screen, and moves along with the view correctly.

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  • Namespace Problem

    - by Tarik
    Hello, Normally we all do use using System.Linq; and using System.Data.Linq; for example on the code-behind and expect we can reach the members of these namespaces from Source Code like <%= Something.First()%> but when I wrote it, asp.net said it couldn't find First() in the context and I had to add <%@ Import Namespace="System.Linq" which looked very weird to me but it worked out. Since they are targeting at the same class why they both need separate namespace importing. Code-behind : using System; using System.Data.Linq; using System.Linq; using System.Text namespace Something { class Items : System.Web.UI { //... } } but also I need to add the same Linq namespace on the Html Source part <%@Import Namespace="System.Linq"%> Do I know something wrong or this is some kind of bug in asp.net. I thought when the page is compiling, asp.net combines these two classes and converts html source code into cs class and indicates the control in Control c= new Control(); hierarchy. Thanks in advance.

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  • Should programmers do Pro Bono work? where are the code public defenders?

    - by Tj Kellie
    How many projects are people doing based on the Bro Bono publico ideals versus working for the highest wage or potential for a cash-in-buy-out payday? For years lawyers have been called out for excessive gathering of wealth from high bill rates and huge settlement deals, hiring out their knowledge and skills to the highest bidders. People call for them to do more for free, use the laws and their time to defend or further some cause thats in the public's best interest. Is professional software development that different? So many bright people and so much knowledge of complex systems. Do you think that there is enough of a "Pro Bono" movement to solve the social and public problems in the industry right now? If so what are the examples to point to? OLPC? NOTE: Saying that open source software is the same as pro bono misses the point completely. I was looking for specific projects with a social context, not just group-sourcing for free software. Just because your not making anyone pay for your software does not mean its doing anyone any good. I'm not calling out manual enforcement of pro bono work for programmers, really just want some objective opinions and concrete examples of social-minded software/tech development projects like the One Laptop Per Child project. I'm sure open source would be a natural tie-in for some.

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  • How best to embed multiple Flash Player instances using swfobject via a usercontrol?

    - by panamack
    I have a ListView on a Page within a MasterPage and some very ugly ugly autogenerated IDs. Such as..."ctl00_workbenchPlaceHolder_ListView1_ctrl1_LibItem2One" Using swfobject.embedSWF(...) requires me to hand over the id of a div on my page that can be replaced with object/embed markup depending on the browser context. My aim is to show the user a collection of video's they have uploaded to their website so they can review them and change some related data if desired. Hence the ListView which is populated via a SQLDataSource which currently provides a number of URLs pointing to .flv files. But it ain't gonna work if I put a <div id="replaceme"></div>' in my user control because I may then have more than one id="replaceme" and poor swfobject won't like it. So my evil solution is to put an <asp:Literal> in my usercontrol and build the script, function name and div tag id as a string. ApplyVideoConfiguration is called if the library object retreived from the database is a video and switches to the relevant View of a MultiView control. protected void ApplyVideoConfiguration() { MultiViewLibItem.ActiveViewIndex = 3; string functionName = "MakeFlashFor_" + this.ClientID; string divId = "fp" + this.ClientID; VideoScriptLiteral.Text = "<script type=\"text/javascript\">" + "Sys.Application.add_load(" + functionName + ");" + "function " + functionName + "(){" + "swfobject.embedSWF('PanamaVideoThumbnail.swf', '" + divId + "', '140', '127', '10');" + "};" + "</script>" + "<div id=\"" + divId + "\" ></div>" ; } I was wondering, just how bad a solution is this, I'm really completely inexperienced when it comes to best practices but my instincts are telling me this is bad, although it does succeed in the aim of embedding some Flash Player instances. Can anyone help me make it beautiful?

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  • iPhone: TableView inside UIScrollview, show vaccillating scrollbars around

    - by karim
    Hi, I have added some table and other vies in a scrollview. scrolling in tables are working fine. But in the parent scrollview, when scrolling, a vacillating vertical scrollbars are shown, sometimes it even come to the middle of the screen. sometime show at the left side of the screen. and not limited to the vertical scrollbar region. When I set tje showsVerticalScrollIndicator = NO, it is not shown. But do you know why the scrollbar is moving around. DashboardView is a subclass of UIScrollView. dashboard=[[DashboardView alloc] initWithFrame:fullScreenRect]; dashboard.contentSize = CGSizeMake(320,700); // must do! dashboard.showsVerticalScrollIndicator = YES; dashboard.bounces = YES; self.view = dashboard; @implementation DashboardView (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } (void)drawRect:(CGRect)rect { // Drawing code } (void) layoutSubviews{ NSArray *views = self.subviews; [UIView beginAnimations:@"CollapseExpand" context:nil]; [UIView setAnimationDuration:0.5]; [UIView setAnimationBeginsFromCurrentState:YES]; [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; UIView *view = [views objectAtIndex: 0]; CGRect rect = view.frame; for (int i = 1; i < [views count]; i++ ) { view = [views objectAtIndex:i]; view.frame = CGRectMake(rect.origin.x, rect.origin.y + rect.size.height, view.frame.size.width, view.frame.size.height); rect = view.frame; } [UIView commitAnimations]; }

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  • Issue intercepting property in Silverlight application

    - by joblot
    I am using Ninject as DI container in a Silverlight application. Now I am extending the application to support interception and started integrating DynamicProxy2 extension for Ninject. I am trying to intercept call to properties on a ViewModel and ending up getting following exception: “Attempt to access the method failed: System.Reflection.Emit.DynamicMethod..ctor(System.String, System.Type, System.Type[], System.Reflection.Module, Boolean)” This exception is thrown when invocation.Proceed() method is called. I tried two implementations of the interceptor and they both fail public class NotifyPropertyChangedInterceptor: SimpleInterceptor { protected override void AfterInvoke(IInvocation invocation) { var model = (IAutoNotifyPropertyChanged)invocation.Request.Proxy; model.OnPropertyChanged(invocation.Request.Method.Name.Substring("set_".Length)); } } public class NotifyPropertyChangedInterceptor: IInterceptor { public void Intercept(IInvocation invocation) { invocation.Proceed(); var model = (IAutoNotifyPropertyChanged)invocation.Request.Proxy; model.OnPropertyChanged(invocation.Request.Method.Name.Substring("set_".Length)); } } I want to call OnPropertyChanged method on the ViewModel when property value is set. I am using Attribute based interception. [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)] public class NotifyPropertyChangedAttribute : InterceptAttribute { public override IInterceptor CreateInterceptor(IProxyRequest request) { if(request.Method.Name.StartsWith("set_")) return request.Context.Kernel.Get<NotifyPropertyChangedInterceptor>(); return null; } } I tested the implementation with a Console Application and it works alright. I also noted in Console Application as long as I had Ninject.Extensions.Interception.DynamicProxy2.dll in same folder as Ninject.dll I did not have to explicitly load DynamicProxy2Module into the Kernel, where as I had to explicitly load it for Silverlight application as follows: IKernel kernel = new StandardKernel(new DIModules(), new DynamicProxy2Module()); Could someone please help? Thanks

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  • Extend base type and automatically update audit information on Entity

    - by Nix
    I have an entity model that has audit information on every table (50+ tables) CreateDate CreateUser UpdateDate UpdateUser Currently we are programatically updating audit information. Ex: if(changed){ entity.UpdatedOn = DateTime.Now; entity.UpdatedBy = Environment.UserName; context.SaveChanges(); } But I am looking for a more automated solution. During save changes, if an entity is created/updated I would like to automatically update these fields before sending them to the database for storage. Any suggestion on how i could do this? I would prefer to not do any reflection, so using a text template is not out of the question. A solution has been proposed to override SaveChanges and do it there, but in order to achieve this i would either have to use reflection (in which I don't want to do ) or derive a base class. Assuming i go down this route how would I achieve this? For example EXAMPLE_DB_TABLE CODE NAME --Audit Tables CREATE_DATE CREATE_USER UPDATE_DATE UPDATE_USER And if i create a base class public abstract class IUpdatable{ public virtual DateTime CreateDate {set;} public virtual string CreateUser { set;} public virtual DateTime UpdateDate { set;} public virtual string UpdateUser { set;} } The end goal is to be able to do something like... public overrride void SaveChanges(){ //Go through state manager and update audit infromation //FOREACH changed entity in state manager if(entity is IUpdatable){ //If state is created... update create audit. //if state is updated... update update audit } } But I am not sure how I go about generating the code that would extend the interface.

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  • Aliasing Resources (WPF)

    - by Noldorin
    I am trying to alias a resource in XAML, as follows: <UserControl.Resources> <StaticResourceExtension x:Key="newName" ResourceKey="oldName"/> </UserControl.Resources> oldName simply refers to a resource of type Image, defined in App.xaml. As far as I understand, this is the correct way to do this, and should work fine. However, the XAML code gives me the superbly unhelpful error: "The application XAML file failed to load. Fix errors in the application XAML before opening other XAML files." This appears when I hover over the StaticResourceExtension line in the code (which has a squiggly underline). Several other errors are generated in the actual Error List, but seem to be fairly irrelevant and nonsenical (such messages as "The name 'InitializeComponent' does not exist in the current context"), as they all disappear when the line is removed. I'm completely stumped here. Why is WPF complaining about this code? Any ideas as to a resolution please? Note: I'm using WPF in .NET 3.5 SP1. Update 1: I should clairfy that I do receive compiler errors (the aforementioned messages in the Error List), so it's not just a designer problem. Update 2: Here's the relevant code in full... In App.xaml (under Application.Resource): <Image x:Key="bulletArrowUp" Source="Images/Icons/bullet_arrow_up.png" Stretch="None"/> <Image x:Key="bulletArrowDown" Source="Images/Icons/bullet_arrow_down.png" Stretch="None"/> And in MyUserControl.xaml (under UserControl.Resources): <StaticResourceExtension x:Key="columnHeaderSortUpImage" ResourceKey="bulletArrowUp"/> <StaticResourceExtension x:Key="columnHeaderSortDownImage" ResourceKey="bulletArrowDown"/> These are the lines that generate the errors, of course.

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  • Red5 Unable to Start Distribution.

    - by Iscariot
    I have installed subclipse, Ant, IvyDE, Red5 Plugin for eclipse, All of the Environmental variables are set and the necessary elements have been added to the path. I am attempting to create a Red5 Distribution by using eclipse, opening Build.xml right clicking dist [default] in the outline window and running as and selecting Ant Builder. Eclipse says that the build is Successful. I first stop the Red5 Service, and then I attempt to run the build I create in eclipse it fails, below are the errors that display in the command prompt. I was hoping someone else might have run into a similar issue before. Starting Red5 Red5 root: C:/Users/Admin/workspace/temp/red5_server/dist Configuation root: C:/Users/Admin/workspace/temp/red5_server/dist/conf Setting temp directory to C:\Users\Admin\AppData\localLow Exception in thread "main" java.lang.Error: Unresolved compilation problems: The import org.slf4j.bridge cannot be resolved The import org.springframework.context.support.FileSystemXmlApplicationC ontext cannot be resolved SLF4JBridgeHandler cannot be resolved FileSystemXmlApplicationContext cannot be resolved to a type FileSystemXmlApplicationContext cannot be resolved to a type at org.red5.server.Launcher.<init>(Launcher.java:25) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct orAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC onstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at java.lang.Class.newInstance0(Class.java:355) at java.lang.Class.newInstance(Class.java:308) at org.red5.server.Bootstrap.bootStrap(Bootstrap.java:132) at org.red5.server.Bootstrap.main(Bootstrap.java:50) Press any key to continue . . .

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  • Lightweight spinlocks built from GCC atomic operations?

    - by Thomas
    I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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  • The "first past the post election" query problem

    - by MPelletier
    This problem may seem like school work, but it isn't. At best it is self-imposed school work. I encourage any teachers to take is as an example if they wish. "First past the post" elections are single-round, meaning that whoever gets the most votes win, no second rounds. Suppose a table for an election. CREATE TABLE ElectionResults ( DistrictHnd INTEGER NOT NULL, PartyHnd INTEGER NOT NULL, CandidateName VARCHAR2(100) NOT NULL, TotalVotes INTEGER NOT NULL, PRIMARY KEY DistrictHnd, PartyHnd); The table has two foreign keys: DistrictHnd points to a District table (lists all the different electoral districts) and PartyHnd points to a Party table (lists all the different political parties). I won't bother with other tables here, joining them is trivial. This is just a wee bit of context. The question: What SQL query will return a table listing the DistrictHnd, PartyHnd, CandidateName and TotalVotes of the winners (max votes) in each District? This does not suppose any particular database system. If you wish to stick to a particular implementation of SQL, go the way of SQLite and MySQL. If you can devise a better schema (or an easier one), that is acceptable too. Criteria: simplicity, portability to other databases.

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  • Animate multiple UIView in a cicle

    - by Giovanni
    Hi all, i'm creating a card game on iphone. My problem is that i want to animate the cards at the beginning of the game making the cards animate from a point to another point in a deck. I move my cards that are UIView, in afor cicle. this is what i do With this code, alla tha cards move together, i need to move the cards separately one after another CGPoint point; // Create the deck of playing cards for (int i = 0; i < 28; i++) { CardView *aCardView = [self.mazzo objectAtIndex:i]; point.x = -100; point.y = 200; aCardView.center = point; aCardView.zPosition = i; [self.viewGioco addSubview:aCardView]; [aCardView release]; //Here i call the method to position the card [aCardView positionCard]; } in the card view there are this methods -(void)positionCard{ [self performSelector:@selector(_positionCard) withObject:nil afterDelay:0.0]; } -(void)_positionCard{ [UIView beginAnimations:@"posizionacarta" context:nil]; [UIView setAnimationCurve:UIViewAnimationCurveEaseIn]; [UIView setAnimationDuration:0.3f]; CGPoint point; point.x = 280 + ((arc4random() % 2) - 1); point.y = 240 + ((arc4random() % 2) - 1); self.center = point; [UIView commitAnimations]; [self setNeedsLayout]; }

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  • How to specify selector when CAKeyframeAnimation is finished?

    - by darenchow
    I'm using a CAKeyframeAnimation to animate a view along a CGPath. When the animation is done, I'd like to be able to call some other method to perform another action. Is there a good way to do this? I've looked at using UIView's setAnimationDidStopSelector:, however from the docs this looks like it only applies when used within a UIView animation block (beginAnimations and commitAnimations). I also gave it a try just in case, but it doesn't seem to work. Here's some sample code (this is within a custom UIView sub-class method): // These have no effect since they're not in a UIView Animation Block [UIView setAnimationDelegate:self]; [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)]; // Set up path movement CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"path"]; pathAnimation.calculationMode = kCAAnimationPaced; pathAnimation.fillMode = kCAFillModeForwards; pathAnimation.removedOnCompletion = NO; pathAnimation.duration = 1.0f; CGMutablePathRef path = CGPathCreateMutable(); CGPathMoveToPoint(path, NULL, self.center.x, self.center.y); // add all points to the path for (NSValue* value in myPoints) { CGPoint nextPoint = [value CGPointValue]; CGPathAddLineToPoint(path, NULL, nextPoint.x, nextPoint.y); } pathAnimation.path = path; CGPathRelease(path); [self.layer addAnimation:pathAnimation forKey:@"pathAnimation"]; A workaround I was considering that should work, but doesn't seem like the best way, is to use NSObject's performSelector:withObject:afterDelay:. As long as I set the delay equal to the duration of the animation, then it should be fine. Is there a better way? Thanks!

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  • Cooperative/Non-preemptive threading avoiding threadlooks?

    - by Wayne
    Any creative ideas to avoid deadlocks on a yield or sleep with cooperative/non-preemptive multitasking without doing an O/S Thread.Sleep(10)? Typically the yield or sleep call will call back into the scheduler to run other tasks. But this can sometime produce deadlocks. Some background: This application has enormous need for speed and, so far, it's extremely fast as compared to other systems in the same industry. One of the speed techniques is cooperative/non-preemptive threading rather then the cost of a context switch from O/S threads. The high level design a priority manager which calls out to tasks depending on priority and processing time. Each task does one "iteration" of work and returns to wait its turn again in the priority queue. The tricky thing with non-preemptive threading is what to do when you want to a particular task to stop in the middle of work and wait for some other event from a different task before continuing. In this case, we have 3 tasks, A B and C where A is a controller that must synchronize the activity of B and C. First, A starts both B and C. Then B yields so C gets invoked. When C yields, A sees they are both inactive, decides it's time for B to run but not time for C yet. Well B is now stuck in a yield that has called C, so it can never run. Sincerely, Wayne

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  • How can I do batch image processing with ImageJ in Java or clojure?

    - by Robert McIntyre
    I want to use ImageJ to do some processing of several thousand images. Is there a way to take any general imageJ plugin and apply it to hundreds of images automatically? For example, say I want to take my thousand images and apply a polar transformation to each--- A polar transformation plugin for ImageJ can be found here: http://rsbweb.nih.gov/ij/plugins/polar-transformer.html Great! Let's use it. From: [http://albert.rierol.net/imagej_programming_tutorials.html#How%20to%20automate%20an%20ImageJ%20dialog] I find that I can apply a plugin using the following: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" ""))) This is good because it suppresses the dialog which would otherwise pop up for every image. But running this always brings up a window containing the transformed image, when what I want is to simply return the transformed image. The stupidest way to do what I want is to just close the window that comes up and return the image which it was displaying. Does what I want but is absolutely retarded: (defn x-polar [imageP] (let [thread (Thread/currentThread) options ""] (.setName thread "Run$_polar-transform") (Macro/setOptions thread options) (IJ/runPlugIn imageP "Polar_Transformer" "") (let [return-image (IJ/getImage)] (.hide return-image) return-image))) I'm obviously missing something about how to use imageJ plugins in a programming context. Does anyone know the right way to do this? Thanks, --Robert McIntyre

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  • PHP/Java Bridge - Access Java objects in PHP

    - by Omer Hassan
    I have a Red5 application which defines some public Java methods. When I start the server, an object of the application class gets created. I am trying to call the public methods of the application class from PHP using the existing instance of the Java application class. So here's my Java application: public class App extends org.red5.server.adapter.ApplicationAdapter { public boolean appStart(IScope app) { // This method gets called when the application starts // and an object of this App class is created. return true; } // This is the method I would like to call from PHP. public void f() { } } From PHP, I would like to get access to the App object that is created and call the method f() on it. I have tried playing around with this thing called "context". So in the Java method App.appStart(), I did this: // Save a reference to this App object to be retrieved later in PHP. new PhpScriptContextFactory().getContext().put("x", this); And in PHP, I tried to access the saved object like this: require_once("http://localhost:5080/JavaBridge/java/Java.inc"); var_dump(java_is_null(java_context()->get("x"))); Unfortunately, the java_is_null() function in PHP returns true. I also tried saving the App object in a static variable of App class but when I access that variable in PHP, its value is null.

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  • Spring security with GAE

    - by xybrek
    I'm trying to implement Spring security for my GAE application however I'm getting this error: No bean named 'springSecurityFilterChain' is defined I added this configuration on my application web.xml: <filter> <filter-name>springSecurityFilterChain</filter-name> <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> </filter> <filter-mapping> <filter-name>springSecurityFilterChain</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> And in the servlet-context: <!-- Configure security --> <security:http auto-config="true"> <security:intercept-url pattern="/**" access="ROLE_USER" /> </security:http> <security:authentication-manager alias="authenticationManager"> <security:authentication-provider> <security:user-service> <security:user name="jimi" password="jimi" authorities="ROLE_USER, ROLE_ADMIN" /> <security:user name="bob" password="bob" authorities="ROLE_USER" /> </security:user-service> </security:authentication-provider> </security:authentication-manager> What could be causing the error?

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