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• Small-o(n^2) implementation of Polynomial Multiplication

  - by AlanTuring

  I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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• LaTeX book class: Twosided document with wrong margins

  - by fgysin

  I am trying to write my thesis in latex... Cannot get the layout straight though :? I'm using the following document class: \documentclass[11pt,a4paper,twoside,openright]{book} My problem is: on the odd numbered pages there is a big margin right, and a small margin left - it should be the other way round... (for binding & stuff) I am a little puzzled by this - am I just to stupid to see the obvious? The odd page numbers appear on the 'right' page of a bound document, so there needs to be a larger margin left for bindin. Right? Why does LaTeX not behave like this? Here is the full code to produce a small Tex file that shows my problem: \documentclass[11pt,a4paper,twoside,openright]{book} \begin{document} \chapter{blah} Lorem ipsum ius et accumsan tractatos, aliquip deterruisset cu usu. Ea soleat eirmod nostrud eum, est ceteros similique ad, at mea tempor petentium. At decore neglegentur quo, ea ius doming dictas facilis, duo ut porro nostrum suavitate. \end{document}

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• A queue in C using structs and dynamic memory allocation (linked list)

  - by Martin Pugh

  I am tasked with making a queue data structure in C, as a linked list. Our lecturer gave us a large amount of code to implement a stack, but we have to adapt it to create a queue. The code our lecturer gave us ends up not compiling and segfaulting at the exact same point as the code I wrote for the queue. I'm very new to structs, malloc and C in general, so there could be something painfully obvious I've overlooked. Here is the code I am using: #include <stdio.h> #include <stdlib.h> struct node{ int data; //contains the actual data struct node *prev; //pointer to previous node (Closer to front) struct node *next; //pointer to next node (Closer to back) }; typedef struct node *Nodepointer; struct queue{ Nodepointer front; Nodepointer back; }; typedef struct queue *Queuepointer; main(){ Queuepointer myqueue; //create a queue called myqueue init(myqueue); //initialise the queue Nodepointer new = (Nodepointer)malloc(sizeof(struct node)); myqueue->front = new; } int init(Queuepointer q){ q = (Queuepointer)malloc(sizeof(struct queue)); q->front = NULL; q->back = NULL; } The idea is that the queue struct 'contains' the first and last nodes in a queue, and when a node is created, myqueue is updated. However, I cannot even get to that part (pop and push are written but omitted for brevity). The code is segfaulting at the line myqueue->front = new; with the following gdb output: Program received signal SIGSEGV, Segmentation fault. 0x08048401 in main () at queue.c:27 27 myqueue->front = new; Any idea what I'm doing wrong?

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• Code Golf: Shortest Turing-complete interpreter.

  - by ilya n.

  I've just tried to create the smallest possible language interpreter. Would you like to join and try? Rules of the game: You should specify a programming language you're interpreting. If it's a language you invented, it should come with a list of commands in the comments. Your code should start with example program and data assigned to your code and data variables. Your code should end with output of your result. It's preferable that there are debug statements at every intermediate step. Your code should be runnable as written. You can assume that data are 0 and 1s (int, string or boolean, your choice) and output is a single bit. The language should be Turing-complete in the sense that for any algorithm written on a standard model, such as Turing machine, Markov chains, or similar of your choice, it's reasonably obvious (or explained) how to write a program that after being executred by your interpreter performs the algorithm. The length of the code is defined as the length of the code after removal of input part, output part, debug statements and non-necessary whitespaces. Please add the resulting code and its length to the post. You can't use functions that make compiler execute code for you, such as eval(), exec() or similar. This is a Community Wiki, meaning neither the question nor answers get the reputation points from votes. But vote anyway!

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• How does one target all divs of any webpage but differentiate them in javascript?

  - by Chaz

  So I am trying to create an extension in Chrome (a prototype for a project that I am doing) that targets all of the <div> tags of any web page, hides them or rather doesn't display them until the user clicks the mouse (further explained below). So typing a url into the browser yields a white page. The person clicks, and the first <div> appears (probably the mast head or menu). The user clicks again and the second <div> appears. I have gotten to the point where I can hide or show all <div>'s (the obvious easy part) but I am not sure how to go about targeting each since every website has different id's for them while still using the <div> tag. This is what I need the most help with. This is part of a grander operation called the Web Crank. It's just a physical crank that controls the speed by which a web page loads. Each time you make one full rotation of the crank, one section (the first <div>) of the web page loads. The faster you go, the quicker the page loads. I hope this is clear enough. I am a newbie when it comes to this, but I have done some minor coding in the past and it's not such a big deal. Thanks for your help!

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• Problems saving a photo to a file

  - by Peter vdL

  Man, I am still not able to save a picture when I send an intent asking for a photo to be taken. Here's what I am doing: Make a URI representing the pathname android.content.Context c = getApplicationContext(); String fname = c.getFilesDir().getAbsolutePath()+"/parked.jpg"; java.io.File file = new java.io.File( fname ); Uri fileUri = Uri.fromFile(file); Create the Intent (don't forget the pkg name!) and start the activity private static int TAKE_PICTURE = 22; Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE ); intent.putExtra("com.droidstogo.boom1." + MediaStore.EXTRA_OUTPUT, fileUri); startActivityForResult( intent, TAKE_PICTURE ); The camera activity starts, and I can take a picture, and approve it. My onActivityResult() then gets called. But my file doesn't get written. The URI is: file:///data/data/com.droidstogo.boom1/files/parked.jpg I can create thumbnail OK (by not putting the extra into the Intent), and can write that file OK, and later read it back). Can anyone see what simple mistake I am making? Nothing obvious shows up in the logcat - the camera is clearly taking the picture. Thanks, Peter

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• How does a java web project architecture look like without EJB3 ?

  - by Hendrik

  A friend and I are building a fairly complex website based on java. (PHP would have been more obvious but we chose for java because the educational aspect of this project is important to us) We have already decided to use JSF (with richfaces) for the front end and JPA for the backend and so far we have decided not to use EJB3 for the business layer. The reason we've decided not to use EJB3 is because - and please correct me if I am wrong - if we use EJB3 we can only run it on a full blown java application server like jboss and if we don't use EJB3 we can still run it on a lightweight server like tomcat. We want to keep speed and cost of our future web server in mind. So far i've worked on two JEE projects and both used the full stack with web business logic factories/persistence service entities with every layer a seperate module. Now here is my question, if you dont use EJB3 in the business logic layer. What does the layer look like? Please tell what is common practice when developing java web projects without ejb3? Do you think business logic layer can be thrown out altogether and have business logic in the backing beans? If you keep the layer, do you have all business methods static? Or do you initialize each business class as needed in the backing beans in every session as needed?

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• Properly using Log4r in Ruby Application

  - by Spencer

  I must really be missing something obvious, but I'm having trouble with general use of Log4r in my Ruby application. I am able to log without issue, but the overhead seems clunky the way I have it setup. I'm basically passing the full path to a filename to log in each class in my application. The ruby script that is called pulls the log file from one of the arguments in ARGV which is then passed around and set in each class that I call in ruby. In each class I use the patternFormatter to insert the class/file name into the log statement. Is there a better way to make this work? It feels like no matter what I think of will require something to be passed to each class in my ruby application. I could set the log file in a yaml configuration file instead, but then I would be passing around the configuration file to each class as well. Any advice? If this doesn't make sense I could try and post some more specific code samples to further explain what I mean. Thanks!

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• Why can't I install psycopg2? (Python 2.6.4, PostgreSQL 8.4, OS X 10.6.3)

  - by cojadate

  UPDATE: After updating all my software, the error message has changed. Now, when I run "python setup.py install" I get the following: Warning: Unable to find 'pg_config' filebuilding 'psycopg2._psycopg' extension gcc-4.0 -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.2.1 (dt dec ext pq3)" -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -DHAVE_PQPROTOCOL3=1 -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -I. -c psycopg/psycopgmodule.c -o build/temp.macosx-10.3-fat-2.6/psycopg/psycopgmodule.o followed by a very long list of other error messages. After running python setup.py install I get the following: Warning: Unable to find 'pg_config' filebuilding 'psycopg2._psycopg' extension gcc-4.0 -arch ppc -arch i386 -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 - DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.2.1 (dt dec ext pq3)" -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -DHAVE_PQPROTOCOL3=1 -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -I. -c psycopg/psycopgmodule.c -o build/temp.macosx-10.3-fat-2.6/psycopg/psycopgmodule.o unable to execute gcc-4.0: No such file or directory error: command 'gcc-4.0' failed with exit status 1 There's probably something screamingly obvious there to anyone who knows the first thing about back-end web programming, but unfortunately it's all gobbledegook to me. The psycopg2 documentation was not helpful.

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• ASP.NET Event delegation between user controls

  - by Ishan

  Give the following control hierarchy on a ASP.NET page: Page HeaderControl       (User Control) TitleControl       (Server Control) TabsControl       (User Control) other controls I'm trying to raise an event (or some notification) in the TitleControl that bubbles to the Page level. Then, I'd like to (optionally) register an event handler at the Page codebehind that will take the EventArgs and modify the TabsControl in the example above. The important thing to note is that this design will allow me to drop these controls into any Page and make the entire system work seamlessly if the event handler is wired up. The solution should not involve a call to FindControl() since that becomes a strong association. If no handler is defined in the containing Page, the event is still raised by TitleControl but is not handled. My basic goal is to use event-based programming so that I can decouple the user controls from each other. The event from TitleControl is only raised in some instances, and this seemed to be (in my head) the preferred approach. However, I can't seem to find a way to cleanly achieve this. Here are my (poor) attempts: Using HttpContext.Current.Items Add the EventArgs to the Items collection on TitleControl and pick it up on the TabsControl. This works but it's fundamentally hard to decipher since the connection between the two controls is not obvious. Using Reflection Instead of passing events, look for a function on the container Page directly within TitleControl as in: Page.GetType().GetMethod("TabControlHandler").Invoke(Page, EventArgs); This will work, but the method name will have to be a constant that all Page instances will have to defined verbatim. I'm sure that I'm over-thinking this and there must be a prettier solution using delegation, but I can't seem to think of it. Any thoughts?

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• Forms/AD Authentication with Sharepoint

  - by David Lively

  All, I'm configuring Sharepoint to use forms authentication with LDAP/Active Directory. I'm new to Sharepoint, so if this is obvious, please point me in the right direction. Whenever I attempt to log in with a bad account or password, I get the very friendly (and correct) error message, The server could not sign you in. Make sure your user name and password are correct, and then try again. ... which implies that Sharepoint is able to communicate with AD. If I log in with a valid account, I get a page that says: (I added the grey bar to cover up the login name) Any suggestions? The account I'm logging in with is an administrator and has been granted full control in central administration. Also, interesting note: If I click the "sign in as a different user" link, and attempt to sign in using with the same credentials I just used, the site just redirects back to the login page, with no error or status message. If I then manually enter the site url, it again shows the "Error: Access Denied" page. Argh.

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• Object created in Interface Builder getting dealloc'ed too soon

  - by Collin Allen

  The Project I'm working on a relatively simple iPhone OS project that's navigation controller based, with a root table view and a detail table view. Tap an item in the main list to see its details in a pushed table view. The Setup I broke out the data source for both views into their own objects so as not to muddy the purpose of a view controller. Having done this, the table views no longer have data sources since those methods are now in separate files, so I created an instance of each data source class in the appropriate XIB files with the Object item (dragged it in, then set its class). Then, to actually connect the tableviews to their data sources, I set the dataSource outlet of each tableview to the yellow data source object in Interface Builder. The table view delegates are still set to their view controllers. The Problem The root table view works just fine, but when you tap a row to push to the detail view, the data source object gets instantiated as expected, then immediately dealloc'ed, causing a crash (numberOfSectionsInTableView: gets called on the freed object). I can't figure out why the data source is getting automatically dealloc-ed when I need it right then and there for the detail view, as indicated by my data source object creation and tableview connection in Interface Builder. What's more perplexing is that the very approach works fine for the root tableview! The Question Is there anything obvious I'm missing that would cause this to happen? Or, is this even the right way to instantiate a data source for a table view controller? It seems like poor object oriented programming to do it from within the view controller, which should only be concerned with the view. I could cram everything in two table view controller classes and it would probably work, but it would not be as modular as I'd like. Thanks!

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• Django: how to cleanup form fields and avoid code duplication

  - by Alexander Konstantinov

  Quite often I need to filter some form data before using it (saving to database etc.) Let's say I want to strip whitespaces and replace repeating whitespaces with a single one in most of the text fields, in many forms. It's not difficult to do this using clean_<fieldname> methods: # Simplified model with two text fields class MyModel(models.Model): title = models.CharField() description = models.CharField() # Model-based form class MyForm(forms.ModelForm): class Meta: model = MyModel def clean_title(self): title = self.cleaned_data['title'] return re.sub(r'\s{2,}', ' ', title.strip()) def clean_description(self): description = self.cleaned_data['description'] return re.sub(r'\s{2,}', ' ', description.strip()) It does exactly what I need, and has a nice side effect which I like: if user enters only whitespaces, the field will be considered empty and therefore invalid (if it is required) and I don't even have to throw a ValidationError. The obvious problem here is code duplication. Even if I'll create some function for that, say my_text_filter, I'll have to call it for every text field in all my forms: from myproject.filters import my_text_filter class MyForm(forms.ModelForm): class Meta: model = MyModel def clean_title(self): return my_text_filter(self.cleaned_data['title']) def clean_description(self): return my_text_filter(self.cleaned_data['description']) The question: is there any standard and simple way in Django (I use version 1.2 if that matters) to do this (like, for example, by adding property validators = {'title': my_text_filter, 'description': my_text_filter} to MyModel), or at least some more or less standard workaround? I've read about form validation and validators in the documentation, but couldn't find what I need there.

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• Can Castle.Windsor do automatic resolution of concrete types

  - by Anthony

  We are evaluating IoC containers for C# projects, and both Unity and Castle.Windsor are standing out. One thing that I like about Unity (NInject and StructureMap also do this) is that types where it is obvious how to construct them do not have to be registered with the IoC Container. Is there way to do this in Castle.Windsor? Am I being fair to Castle.Windsor to say that it does not do this? Is there a design reason to deliberately not do this, or is it an oversight, or just not seen as important or useful? I am aware of container.Register(AllTypes... in Windsor but that's not quite the same thing. It's not entirely automatic, and it's very broad. To illustrate the point, here are two NUnit tests doing the same thing via Unity and Castle.Windsor. The Castle.Windsor one fails. : namespace SimpleIocDemo { using NUnit.Framework; using Castle.Windsor; using Microsoft.Practices.Unity; public interface ISomeService { string DoSomething(); } public class ServiceImplementation : ISomeService { public string DoSomething() { return "Hello"; } } public class RootObject { public ISomeService SomeService { get; private set; } public RootObject(ISomeService service) { SomeService = service; } } [TestFixture] public class IocTests { [Test] public void UnityResolveTest() { UnityContainer container = new UnityContainer(); container.RegisterType<ISomeService, ServiceImplementation>(); // Root object needs no registration in Unity RootObject rootObject = container.Resolve<RootObject>(); Assert.AreEqual("Hello", rootObject.SomeService.DoSomething()); } [Test] public void WindsorResolveTest() { WindsorContainer container = new WindsorContainer(); container.AddComponent<ISomeService, ServiceImplementation>(); // fails with exception "Castle.MicroKernel.ComponentNotFoundException: // No component for supporting the service SimpleIocDemo.RootObject was found" // I could add // container.AddComponent<RootObject>(); // but that approach does not scale RootObject rootObject = container.Resolve<RootObject>(); Assert.AreEqual("Hello", rootObject.SomeService.DoSomething()); } } }

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• Mocking Autofac's "Resolve" extension method with TypeMock

  - by Lockshopr

  I'm trying to mock an Autofac resolve, such as: using System; using Autofac; using TypeMock.ArrangeActAssert; class Program { static void Main(string[] args) { var inst = Isolate.Fake.Instance<IContainer>(); Isolate.Fake.StaticMethods(typeof(ResolutionExtensions), Members.ReturnNulls); Isolate.WhenCalled(() => inst.Resolve<IRubber>()).WillReturn(new BubbleGum()); Console.Out.WriteLine(inst.Resolve<IRubber>()); } } public interface IRubber {} public class BubbleGum : IRubber {} Coming from Moq, the syntax and exceptions from TypeMock confuse me a great deal. Having initially run this in a TestMethod, I kept getting an exception resembling "WhenCalled cannot be run without a complementing behavior". I tried defining behaviors for everyone and their mothers, but to no avail. Then I debug stepped through the test run, and saw that an actual exception was fired from Autofac: IRubber has not been registered. So it's obvious that the static Resolve function isn't being faked, and I can't get it to be faked, no matter how I go about hooking it up. Isolate.WhenCalled(() => ResolutionExtensions.Resolve<IRubber>(null)).WillReturn(new BubbleGum()); ... throws an exception from Autofac complaining that the IComponentContext cannot be null. Feeding it the presumably faked IContainer (or faking an IComponentContext instead) gets me back to the "IRubber not registered" error.

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• LINQ to SQL and DataPager

  - by Jonathan S.

  I'm using LINQ to SQL to search a fairly large database and am unsure of the best approach to perform paging with a DataPager. I am aware of the Skip() and Take() methods and have those working properly. However, I'm unable to use the count of the results for the datapager, as they will always be the page size as determined in the Take() method. For example: var result = (from c in db.Customers where c.FirstName == "JimBob" select c).Skip(0).Take(10); This query will always return 10 or fewer results, even if there are 1000 JimBobs. As a result, the DataPager will always think there's a single page, and users aren't able to navigate across the entire result set. I've seen one online article where the author just wrote another query to get the total count and called that. Something like: int resultCount = (from c in db.Customers where c.FirstName == "JimBob" select c).Count(); and used that value for the DataPager. But I'd really rather not have to copy and paste every query into a separate call where I want to page the results for obvious reasons. Is there an easier way to do this that can be reused across multiple queries? Thanks.

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• target-action uicontrolevents

  - by Fabrizio Farinelli

  I must be missing something obvious here but ... UIControl has a method - (void)addTarget:(id)target action:(SEL)action forControlEvents: (UIControlEvents)controlEvents which lets you add an action to be called when any of the given controlEvents occur. ControlEvents are a bitmask of events which tell you if a touch went down, or up inside, or was dragged etc., there's about 16 of them, you or them together and get called when any of them occur. The selector can have one of the following signatures - (void)action - (void)action:(id)sender - (void)action:(id)sender forEvent:(UIEvent *) none of those tell you what the control event bitmask was. The UIEvent is something slightly different, it's related to the actual touch event and doesn't (I think) contain the UIControlEvent. The sender (UIControl) doesn't have a way to find the control events either. I'd like to have one method which deals with a number of control events as I have some common code regardless of which event or events happened but I still need to know what the UIControlEvents were for some specific processing. Am I missing a way to find out what UIControlEvents were used when the action was called or do I really have to separate my code into -(void)actionWithUIControlEventX; -(void)actionWithUIControlEventY;

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• AppEngine JDO-QL : Problem with multiple AND and OR in query

  - by KlasE

  Hi, I'm working with App Engine(Java/JDO) and are trying to do some querying with lists. So I have the following class: @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true") public class MyEntity { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) Key key; @Persistent List<String> tags = new ArrayList<String>(); @Persistent String otherVar; } The following JDO-QL works for me: ( tags.contains('a') || tags.contains('b') || tags.contains('c') || tags.contains('d') ) && otherVar > 'a' && otherVar < 'z' This seem to return all results where tags has one or more strings with one or more of the given values and together with the inequality search on otherVar But the following do not work: (tags.contains('a') || tags.contains('_a')) && (tags.contains('b') || tags.contains('_b')) && otherVar > 'a' && otherVar < 'z' In this case I want all hits where there is at least one a (either a or _a) and one b (either b or _b) together with the inequality search as before. But the problem is that I also get back the results where there is a but no b, which is not what I want. Maybe I have missed something obvious, or done a coding error, or possibly there is a restriction on how you can write these queries in appengine, so any tips or help would be very welcome. Regards Klas

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• Enable cross app redirects

  - by Gogster

  Hi all, We have load balancing set up on out two web server, however, a few users are being asked to login when they are being re-directed to a particular server to upload a document (we are trying to keep all uploaded documents on one server only), here is the code from web.config: <authentication mode="Forms"> <forms name="EAAAuthCookie" loginUrl="/login" defaultUrl="/members/home" protection="All" path="/" timeout="60000" slidingExpiration="true" enableCrossAppRedirects="true" /> </authentication> <machineKey decryption="AES" validation="SHA1" decryptionKey="7B4EC5B0C83631DF25D5B179EDDBF91B1C175B81C6F52102267D3D097FBF272A" validationKey="7D1F50788629CC342EE4985D85DE3D14F10654695912C0FFD439F54BED64F76A57A2D5E8180BC6FF052E0385C30558F5527D6C197C577A7F32DD8FF1CAC9F794" /> Here is the transfer code to the upload form: $('#addReport').click(function() { if ($.cookie('TransferURL') != '') { $("#iframeUploadReport").attr('src', $.cookie('TransferURL')); }; $('#overlay').fadeIn('slow'); }); <script type="text/C#" runat="server"> void Page_Load() { string cookieName = FormsAuthentication.FormsCookieName; string userName = Request.Cookies["HiddenUsername"].ToString(); string cookieValue = FormsAuthentication.GetAuthCookie(userName, false).Value; Response.Cookies["TransferURL"].Value = "http://eaa.cms.necinteractive.net/members/media-upload" + String.Format("?{0}={1}", cookieName, cookieValue); } </script> <iframe id="iframeUploadReport" src="http://eaa.cms.necinteractive.net/members/media-upload" width="500px" height="336px" frameborder="0" scrolling="no"></iframe> Can you see any obvious step we are missing? Thanks

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• Get directory path by fd

  - by tylerl

  I've run into the need to be able refer to a directory by path given its file descriptor in Linux. The path doesn't have to be canonical, it just has to be functional so that I can pass it to other functions. So, taking the same parameters as passed to a function like fstatat(), I need to be able to call a function like getxattr() which doesn't have a f-XYZ-at() variant. So far I've come up with these solutions; though none are particularly elegant. The simplest solution is to avoid the problem by calling openat() and then using a function like fgetxattr(). This works, but not in every situation. So another method is needed to fill the gaps. The next solution involves looking up the information in proc: if (!access("/proc/self/fd",X_OK)) { sprintf(path,"/proc/self/fd/%i/",fd); } This, of course, totally breaks on systems without proc, including some chroot environments. The last option, a more portable but potentially-race-condition-prone solution, looks like this: DIR* save = opendir("."); fchdir(fd); getcwd(path,PATH_MAX); fchdir(dirfd(save)); closedir(save); The obvious problem here is that in a multithreaded app, changing the working directory around could have side effects. However, the fact that it works is compelling: if I can get the path of a directory by calling fchdir() followed by getcwd(), why shouldn't I be able to just get the information directly: fgetcwd() or something. Clearly the kernel is tracking the necessary information. So how do I get to it?

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• JQuery: Dynamically-generated form fields not submitted and event handlers appear to fire multiple t

  - by Bob

  Hi, I'm new to JQuery, so I apologise if there's something which should be obvious which I'm unaware of. I seem to be having a couple of issues some JQuery I'm trying to implement: Code: http://pastebin.ca/1843496 (the editor didn't seem to like HTML tags) post_test.php simply contains: [?php print_r($_POST); ?] in an attempt to find out what's actually being submitted. The first issue I'm having is that only the hidden form fields are actually being submitted. If I insert tags into the container DIV manually it works as expected, but when done as above the text field doesn't get posted. From what I've read, I gather it's to do with the fact that the DOM is being modified after it's loaded, but the thing that's puzzling me is why, in that case, there are no issues referencing the other added hidden fields or the tag. I've experimented with changing the event handler for a.save to '.live('click', function ...' and also using LiveQuery to no avail. The other issue is that when a.save is clicked, before the form is actually submitted, as far as I can tell the event handler is running again, replacing the value entered into the text field with the value of editable.text(), which is what ultimately gets submitted. I'm sorry if any of this is unclear. Regards,

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• How to implement Session timeout in Web Server Side?

  - by Morgan Cheng

  I beheld a web framework implementing in-memory session in this way. The session object is added to Cache with timeout. When the time is out, the session is removed from Cache automatically. To protect race condition, each request should acquire lock on given session object to proceed. Each request will "touch" the session in Cache to refresh the timeout. Everything looks fine, until this scenario is discovered. Say, one operation takes a long time, longer than timeout. Another request comes and wait on session lock which is currently hold by the long-time request. Finally, the long-time request is over, it releases the lock. But, since it already takes longer time than timeout, the session object is already removed from Cache. This is obvious because the only request holding the lock doesn't have a chance to "touch" the session object in cache. The second request gets the lock but cannot retrieve the expired Session object. Oops... To fix this issue, the second request has to re-create the Session object. But, this is just like digging a buried dead body from tomb and try to bring it back to life. It causes buggy code. I'm wondering what's the best way to implement timeout in session to handle such scenario. I know that current platform must have good session mechanism. I just want to know the under-the-hood how.

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• Version control - stubs and mocks

  - by Tesserex

  For the sake of this question, I don't care about the difference between stubs, mocks, dummies, fakes, etc. Let's say I'm working on a project with one other person. I'm working on component A and he is working on component B. They work together, so I stub out B for testing, and he stubs out A. We're working in a DVCS, let's say Git, because that's actually the case here. When it comes time to merge our components together, we need to get the "real" files from my A and his B, but throw away all the fake stuff. During development, it's likely (unless I need to learn how to properly stub things) that the fakes have the same file names and class names as the real thing. So my question is: what is the proper procedure for doing version control on the fakes, and how are the components correctly merged, making sure to grab the real thing and not the fake? I would guess that one way is just do the merge, expect it to say CONFLICT, and then manually delete all the fake code out of the half-merged files. But this sounds tedious and inefficient. Should the fake things not go under VC at all? Should they be ripped out just before merging? Sorry if the answer to this should be obvious or trivial, I'm just looking for a "suggested practice" here.

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• What do these errors mean? ISOC++ forbids assignment of arrays...

  - by xunlinkx

  I'm trying to compile some code on one of our systems for our DBA...I've edited the makefiles to include the pertinent libraries listed in the documentation, but I keep getting these errors... Can you discern any obvious problems from my command lines in reference to the errors listed? Thank you! make -f /u01/app/banner/ban8/TEST3/links/Makefile_tm_linux64_redhat5_ban8.mk gcc -m64 -D_NOFIXARGPTR -fpic -shared -DTMCILIB_EXPORTS -D_TMUNICODE -I/usr/local/ban_icu -I/usr/local/src/icu/source/i18n/ -I/usr/local/src/icu/source/common/ -I/usr/local/src/icu/source/extra/ustdio/ -I/usr/local/src/icu/source/io -L/usr/lib64 -L/usr/lib -L/usr/local/src/icu/source/data/ -L/usr/local/src/icu/source/data/out/ -L/usr/local/src/icu/source/tools/toolutil/ -L/usr/lib/im/icuconv/ -L/usr/local/lib/ -L. -licui18n -licudata -licuuc -licu-toolutil -licuio msgfmttm.cpp umsgtm.cpp tmcilib.cpp -o /u01/app/banner/ban8/TEST3/general/exe/libtmciuc.so umsgtm.cpp: In function ‘void fixArgPtr(const UChar*, __va_list_tag (*)[1])’: umsgtm.cpp:158: error: array must be initialized with a brace-enclosed initializer umsgtm.cpp:194: error: ISO C++ forbids assignment of arrays umsgtm.cpp: In function ‘int32_t tmumsg_vformat(void*, UChar, int32_t, __va_list_tag*, UErrorCode*)’: umsgtm.cpp:305: error: cannot convert ‘__va_list_tag**’ to ‘__va_list_tag ()[1]’ for argument ‘2’ to ‘void fixArgPtr(const UChar, __va_list_tag (*)[1])’ tmcilib.cpp: In function ‘int tmprintf(TMBundle*, const UChar*, ...)’: tmcilib.cpp:743: error: array must be initialized with a brace-enclosed initializer tmcilib.cpp: In function ‘int tmfprintf(TMBundle*, UFILE*, const UChar*, ...)’: tmcilib.cpp:757: error: array must be initialized with a brace-enclosed initializer tmcilib.cpp: In function ‘int tmsprintf(TMBundle*, UChar*, const UChar*, ...)’: tmcilib.cpp:808: error: array must be initialized with a brace-enclosed initializer

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• Managing resource closure in a servlet container

  - by Steven Schlansker

  I'm using Tomcat as a servlet container, and have many WARs deployed. Many of the WARs share common base classes, which are replicated in each context due to the different classloaders, etc. How can I ensure resource cleanup on context destruction, without hooking each and every web.xml file to add context listeners? Ideally, I'd like something along the lines of class MyResourceHolder implements SomeListenerInterface { private SomeResource resource; { SomeContextThingie.registerDestructionListener(this); } public void onDestroy() { resource.close(); } } I could put something in each web.xml, but since there are potentially many WARs and only ones that actually initialize the resource need to clean it up, it seems more natural to register for cleanup when the resource is initialized rather than duplicating a lot of XML configuration and then maybe cleaning up. (In this particular case, I'm initiating an orderly shutdown of a SQL connection pool. But I see this being useful in many other situations as well...) I'm sure there's some blisteringly obvious solution out there, but my Google-fu is failing me right now. Thanks!

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