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• Drag-n-Drop on contentEditable elements

  - by Raybiez

  There are numerous WYSIWYG editors available on the internet, but I'm yet to find one that implements some form of drag-n-drop implementation. It is easy to create one's own editor, but I want to the user to be able to drag elements (ie. tokens) from outside the editable area and have them drop it at a location of their choice inside the editable area. It is easy to inject html at a specific location of an editable element, but how do one determine where the caret should be when the user is dragging a DIV over some element in the editable area. To better illustrate what I'm trying to explain, see the following scenario. The editable area (either an IFRAME in edit mode or a DIV with its contentEditable attribute set to true) already contains the following text: "Dear , please take note of ...." The user now drags an element representing some token from a list of elements, over the editable area, moving the cursor over the text until the caret appear just before the comma (,) in the text as shown above. When the user releases the mouse button at that location, HTML will be injected which could result in something like this: "Dear {UserFirstName}, please take note of ...". I do not know if anyone has ever done anything similar to this, or at least know of how one would go about doing this using JavaScript. Any help will be greatly appreciated.

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• Hibernate: order multiple one-to-many relations

  - by Markos Fragkakis

  I have a search screen, using JSF, JBoss Seam and Hibernate underneath. There are columns for A, B and C, where the relations are as follows: A (1< -- ) B (1< -- ) C A has a List< B and B has a List< C (both relations are one-to-many). The UI table supports ordering by any column (ASC or DESC), so I want the results of the query to be ordered. This is the reason I used Lists in the model. However, I got an exception that Hibernate cannot eagerly fetch multiple bags (it considers both lists to be bags). There is an interesting blog post here, and they identify the following solutions: Use @IndexColumn annotation (there is none in my DB, and what's more, I want the position of results to be determined by the ordering, not by an index column) Fetch lazily (for performance reasons, I need eager fetching) Change List to Set So, I changed the List to Set, which by the way is more correct, model-wise. First, if don't use @OrderBy, the PersistentSet returned by Hibernate wraps a HashSet, which has no ordering. Second, If I do use @OrderBy, the PersistentSet wraps a LinkedHashSet, which is what I would like, but the OrderBy property is hardcoded, so all other ordering I perform through the UI comes after it. I tried again with Sets, and used SortedSet (and its implementation, TreeSet), but I have some issues: I want ordering to take place in the DB, and not in-memory, which is what TreeSet does (either through a Comparator, or through the Comparable interface of the elements). Second, I found that there is the Hibernate annotation @Sort, which has a SortOrder.UNSORTED and you can also set a Comparator. I still haven't managed to make it compile, but I am still not convinced it is what I need. Any advice?

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• my MKAnnotationVIew is not showing the title

  - by hydev

  Hi, I am new to iPhone programming and I can't understand why the MKAnnotationView is not showing the title's of my annotation's. Below is the code that is used to display it on the map. - (void)mapView:(MKMapView *)mv didAddAnnotationViews:(NSArray *)views { NSLog(@"Entered didAddAnnotationViews"); MKAnnotationView *annotationView = [views objectAtIndex:0]; id <MKAnnotation> mp = [annotationView annotation]; MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance([mp coordinate], 250, 250); [mv setRegion:region animated:YES]; } Here is where I am defining my annotations: MapPoint *mp = [[MapPoint alloc] initWithCoordinate:[newLocation coordinate] title:[locationTitleField text]]; [mapView addAnnotation:mp]; [mp release]; mp is a class I have created to keep track of all the map points: #import "MapPoint.h" @implementation MapPoint @synthesize coordinate, title; - (id)initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t { [super init]; coordinate = c; [self setTitle:t]; return self; } - (void)dealloc { [title release]; [super dealloc]; } @end I am beginner so go easy, and all help greatly appreciated. Mike

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• P6 Architecture - Register renaming aside, does the limited user registers result in more ops spent

  - by mrjoltcola

  I'm studying JIT design with regard to dynamic languages VM implementation. I haven't done much Assembly since the 8086/8088 days, just a little here or there, so be nice if I'm out of sorts. As I understand it, the x86 (IA-32) architecture still has the same basic limited register set today that it always did, but the internal register count has grown tremendously, but these internal registers are not generally available and are used with register renaming to achieve parallel pipelining of code that otherwise could not be parallelizable. I understand this optimization pretty well, but my feeling is, while these optimizations help in overall throughput and for parallel algorithms, the limited register set we are still stuck with results in more register spilling overhead such that if x86 had double, or quadruple the registers available to us, there may be significantly less push/pop opcodes in a typical instruction stream? Or are there other processor optmizations that also optimize this away that I am unaware of? Basically if I've a unit of code that has 4 registers to work with for integer work, but my unit has a dozen variables, I've got potentially a push/pop for every 2 or so instructions. Any references to studies, or better yet, personal experiences?

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• Reliable strtotime() result for different languages

  - by Maksee

  There was always a strange bug in Joomla when adding new article with back-end displayed with a language other than English (for me it's Russian). The field "Finish Publishing" started to be current date instead of "Never" equivalent in Russian. For a site in php4 finally found that strtotime function returns different results for arbitrary words. For "Never" it always -1 and joomla relies on this result in the JDate implementation. But in other case it sometimes returns a valid date. For russian translation of Never (???????) it is the case, but also for single "N" it is the case, so if one decided to change the string to some other he or she would face the same issue. So the code below <?php echo "Res:".strtotime("N")."<br>"; echo "Res:".strtotime("Nev")."<br>"; echo "Res:".strtotime("Neve")."<br>"; echo "Res:".strtotime("Never")."<br>"; ?> Outputs: Res:1271120400 Res:-1 Res:-1 Res:-1 So what are the solutions would be in this case? I would like not to write language-specific date.php handler, but to modify date method of JDate class, but what are language-neutral changes would be in order to detect invalid string. Thank you

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• LINQ to SQL - Left Outer Join with multiple join conditions

  - by dan

  I have the following SQL which I am trying to translate to LINQ: SELECT f.value FROM period as p LEFT OUTER JOIN facts AS f ON p.id = f.periodid AND f.otherid = 17 WHERE p.companyid = 100 I have seen the typical implementation of the left outer join (ie. into x from y in x.DefaultIfEmpty() etc.) but am unsure how to introduce the other join condition ('AND f.otherid = 17') EDIT Why is the 'AND f.otherid = 17' condition part of the JOIN instead of in the WHERE clause? Because f may not exist for some rows and I still want these rows to be included. If the condition is applied in the WHERE clause, after the JOIN - then I don't get the behaviour I want. Unfortunately this: from p in context.Periods join f in context.Facts on p.id equals f.periodid into fg from fgi in fg.DefaultIfEmpty() where p.companyid == 100 && fgi.otherid == 17 select f.value seems to be equivalent to this: SELECT f.value FROM period as p LEFT OUTER JOIN facts AS f ON p.id = f.periodid WHERE p.companyid = 100 && AND f.otherid = 17 which is not quite what I'm after.

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• UIScrollview calling superviews layoutSubviews when scrolling?

  - by marchinram

  Hello, I added a UITableView as a subview to a custom UIView class I'm working on. However I noticed that whenever I scroll the table it calls my classes layoutSubviews. I'm pretty sure its the UIScrollview that the table is inheriting from which is actually doing this but wanted to know if there is a way to disable this functionality and if not why is it happening? I don't understand why when you scroll a scrollview it needs its superview to layout its subviews. Code: @implementation CustomView - (id)initWithFrame:(CGRect)frame { if ((self = [super initWithFrame:frame])) { self.clipsToBounds = YES; UITableView *tableView = [[UITableView alloc] initWithFrame:CGRectMake(0.0, 15.0, 436.0, 132.0) style:UITableViewStylePlain]; tableView.dataSource = self; tableView.delegate = self; tableView.separatorStyle = UITableViewCellSeparatorStyleNone; tableView.backgroundColor = [UIColor clearColor]; tableView.showsVerticalScrollIndicator = NO; tableView.contentInset = UIEdgeInsetsMake(kRowHeight, 0.0, kRowHeight, 0.0); tableView.tag = componentIndex; [self addSubview:tableView]; [tableView release]; } return self; } - (void)layoutSubviews { // This is called everytime I scroll the tableview } @end

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• Read-only view of a Java list with more general type parameter

  - by Michael Rusch

  Suppose I have class Foo extends Superclass. I understand why I can't do this: List<Foo> fooList = getFooList(); List<Superclass> supList = fooList; But, it would seem reasonable for me to do that if supList were somehow "read-only". Then, everything would be consistent as everything that would come out of an objList would be a Foo, which is a Superclass. I could probably write a List implementation that would take an underlying list and a more general type parameter, and would then return everything as the more general type instead of the specific type. It would work like the return of Collections.unmodifiableList() except that the type would be made more general. Is there an easier way? The reason I'm considering doing this is that I am implementing an interface that requires that I return an (unmodifiable) List<Superclass>, but internally I need to use Foos, so I have a List<Foo>. I can't just cast.

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• C# TCP Async EndReceive() throws InvalidOperationException ONLY on Windows XP 32-bit

  - by James Farmer

  I have a simple C# Async Client using a .NET socket that waits for timed messages from a local Java server used for automating commands. The messages come in asynchronously and is written to a ring buffer. This implementation seems to work fine on Windows Vista/7/8 and OSX, but will randomly throw this exception while it's receiving a message from the local Java server: Unhandled Exception: System.InvalidOperationException: EndReceive can only be called once for each asynchronous operation.     at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult, SocketError& errorCode)     at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)     at SocketTest.Controller.RecvAsyncCallback(IAsyncResult ar)     at System.Net.LazyAsyncResult.Complete(IntPtr userToken)     ... I've looked online for this error, but have found nothing really helpful. This is the code where it seems to break: /// <summary> /// Callback to receive socket data /// </summary> /// <param name="ar">AsyncResult to pass to End</param> private void RecvAsyncCallback(IAsyncResult ar) { // The exception will randomly happen on this call int bytes = _socket.EndReceive(_recvAsyncResult); // check for connection closed if (bytes == 0) { return; } _ringBuffer.Write(_buffer, 0, bytes); // Checks buffer CheckBuffer(); _recvAsyncResult = _sock.BeginReceive(_buffer, 0, _buffer.Length, SocketFlags.None, RecvAsyncCallback, null); } The error doesn't happen on any particular moment except in the middle of receiving a message. The message itself can be any length for this to happen, and the exception can happen right away, or sometimes even up to a minute of perfect communication. I'm pretty new with sockets and network communication, and I feel I might be missing something here. I've tested on at least 8 different computers, and the only similarity with the computers that throw this exception is that their OS is Windows XP 32-bit.

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• How to avoid using this in a contructor

  - by Paralife

  I have this situation: interface MessageListener { void onMessageReceipt(Message message); } class MessageReceiver { MessageListener listener; public MessageReceiver(MessageListener listener, other arguments...) { this.listener = listener; } loop() { Message message = nextMessage(); listener.onMessageReceipt(message); } } and I want to avoid the following pattern: (Using the this in the Client constructor) class Client implements MessageListener { MessageReceiver receiver; MessageSender sender; public Client(...) { receiver = new MessageReceiver(this, other arguments...); sender = new Sender(...); } . . . @Override public void onMessageReceipt(Message message) { if(Message.isGood()) sender.send("Congrtulations"); else sender.send("Boooooooo"); } } The reason why i need the above functionality is because i want to call the sender inside the onMessageReceipt() function, for example to send a reply. But I dont want to pass the sender into a listener, so the only way I can think of is containing the sender in a class that implements the listener, hence the above resulting Client implementation. Is there a way to achive this without the use of 'this' in the constructor? It feels bizare and i dont like it, since i am passing myself to an object(MessageReceiver) before I am fully constructed. On the other hand, the MessageReceiver is not passed from outside, it is constructed inside, but does this 'purifies' the bizarre pattern? I am seeking for an alternative or an assurance of some kind that this is safe, or situations on which it might backfire on me.

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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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• Is android's motion event handling accurate??

  - by Peterdk

  Bug I have a weird bug in my piano app. Sometimes keys (and thus notes) hang. I did a lot of debugging and narrowed it down to what looks like androids inaccuracy of motion event handling: DEBUG/(2091): ACTION_DOWN A4 DEBUG/(2091): KeyDown: A4 DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_MOVE A4 => A4 DEBUG/(2091): ACTION_MOVE ignoring DEBUG/(2091): ACTION_UP B4 //HOW CAN THIS BE???? DEBUG/(2091): KeyUp: B4 DEBUG/(2091): Stream is null, can't stop DEBUG/(2091): Hanging Note: A4 X=240-287 EventX=292 Y=117-200 EventY=164 DEBUG/(2091): KeyUp Note: B4 X=288-335 EventX=292 Y=117-200 EventY=164 Clearly it can be seen here that out of nowhere I suddenly have an ACTION_UP for another note. Shouldn't I definitely get a ACTION_MOVE first? As shown in the end of the log, it's definitely not an error in region detection, since the ACTION_UP event is clearly in the B4 region. Logging Implementation details Every onTouchEvent() call is logged, so the log is accurate. The relevant pseudo-code for the ACTION_MOVE logging is: Key oldKey = Key.get(event.getHistoricalX(), event.getHistoricalY()); Key newKey = Key.get(event.getX(), event.getY()); Question Is this normal behaviour for Android (the jumping in coordinates)? Am I missing something?

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• Unable to call RESTful web services methods

  - by Alessandro

  Hello, I'm trying to dive into the RESTful web services world and have started with the following template: [ServiceContract] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)] public class Test { // TODO: Implement the collection resource that will contain the SampleItem instances [WebGet(UriTemplate = ""), OperationContract] public List<SampleItem> GetCollection() { // TODO: Replace the current implementation to return a collection of SampleItem instances return new List<SampleItem>() {new SampleItem() {Id = 1, StringValue = "Hello"}}; } [WebInvoke(UriTemplate = "", Method = "POST"), OperationContract] public SampleItem Create(SampleItem instance) { // TODO: Add the new instance of SampleItem to the collection throw new NotImplementedException(); } [WebGet(UriTemplate = "{id}"), OperationContract] public SampleItem Get(string id) { // TODO: Return the instance of SampleItem with the given id throw new NotImplementedException(); } [WebInvoke(UriTemplate = "{id}", Method = "PUT"), OperationContract] public SampleItem Update(string id, SampleItem instance) { return new SampleItem { Id = 99, StringValue = "Done" }; } [WebInvoke(UriTemplate = "{id}", Method = "DELETE"), OperationContract] public void Delete(string id) { // TODO: Remove the instance of SampleItem with the given id from the collection throw new NotImplementedException(); } } I am able to perform the GET operation but I am unable to perform PUT, POST or DELETE requests. Can anyone explain me how to perform these operations and how to create the correct URLs? Best regards Alessandro

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• TLS with SNI in Java clients

  - by ftrotter

  There is an ongoing discussion on the security and trust working group for NHIN Direct regarding the IP-to-domain mapping problem that is created with traditional SSL. If an HISP (as defined by NHIN Direct) wants to host thousands of NHIN Direct "Health Domains" for providers, then it will an "artificially inflated cost" to have to purchase an IP for each of those domains. Because Apache and OpenSSL have recently released TLS with support for the SNI extension, it is possible to use SNI as a solution to this problem on the server side. However, if we decide that we will allow server implementations of the NHINDirect transport layer to support TLS+SNI, then we must require that all clients support SNI too. OpenSSL based clients should do this by default and one could always us stunnel to implement an TLS+SNI aware client to proxy if your given programming language SSL implementation does not support SNI. It appears that native Java applications using OpenJDK do not yet support SNI, but I cannot get a straight answer out of that project. I know that there are OpenSSL Java libraries available but I have no idea if that would be considered viable. Can you give me a "state of the art" summary of where TLS+SNI support is for Java clients? I need a Java implementers perspective on this.

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• Is there any way to access files in your source tree in Android?

  - by Chris Thompson

  Hi all, This is a bit unorthodox but I'm trying to figure out if there's a way to access files stored in the src tree of my applications apk in Android. I'm trying to use i-Jetty (Jetty implementation for Android) and rather than use it as a separate application and manually download my war file, I'd rather just bake i-jetty in. However, in order to use (easily) standard html/jsp I need to be able to give it a document root, preferably within my application's apk file. I know Android specifically works to prevent you from accessing (freely) the stuff on the actual system so this may not be possible, but I'm thinking it might be possible to access something within the apk. One option to work around this would be to have all of the files stored in the res directory and then copy them to the sdcard on startup but this wouldn't allow me to automatically remove the files on uninstall. To give you an idea of what I've tried, currently, the html files are stored in org.webtext.android Context rootContext = new Context(server_, "/", Context.SESSIONS); rootContext.setResourceBase("org/webtext/webapp"); Returns a 404 error. final URL url = this.getClassLoader().getResource("org/webtext/webapp"); Context html = new WebAppContext(url.toExternalForm(), "/"); Blows up with a NullPointerException because no URL is returned from the getResource call. Any thoughts would be greatly appreciated! Thanks, Chris

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• FluentNHibernate SQLite configuration exception - after switching to .net4

  - by stiank81

  I get an exception thrown when trying to use Fluent to configure my NHibernate connection to SQLite. The code I use to configure is as follows: var cfg = Fluently.Configure(). Database(SQLiteConfiguration.Standard.ShowSql().UsingFile("MyDb.db")). Mappings(m => m.FluentMappings.AddFromAssemblyOf<MappingsPersistenceModel>()); _sessionFactory = cfg.BuildSessionFactory(); A HibernateException is thrown when BuildSessionFactory() is called, saying: Could not create the driver from NHibernate.Driver.SQLite20Driver, NHibernate, Version=2.1.2.4000, Culture=neutral, PublicKeyToken=aa95f207798dfdb4. It has an InnerException: Exception has been thrown by the target of an invocation. Which again has an InnerException: The IDbCommand and IDbConnection implementation in the assembly System.Data.SQLite could not be found. Ensure that the assembly System.Data.SQLite is located in the application directory or in the Global Assembly Cache. If the assembly is in the GAC, use element in the application configuration file to specify the full name of the assembly. Now - to me it sounds like it doesn't find System.Data.SQLite.dll, but I can't understand this. Everywhere this is referenced I have "Copy Local", and I have verified that it is in every build folder for projects using SQLite. I have also copied it manually to every Debug folder of the solution - without luck. What can be causing this? Any ideas? My suspicion is that it is related to .Net4 somehow. The reason is that it worked just fine when I used .Net3.5, and then I changed to .Net4, and the problem started. You can also check out this other question for a more general approach towards Fluent-.Net4 compatibility.

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• How do I pass a callback function to sqlite3_exec on iOS 5.1?

  - by John Doh

  I am new to both xcode/iOS/Objective-C and sqlite. I am trying to teach myself the basics - and I would like to use the sqlite3 wrapper "sqlite3_exec" for a select query. For some reason, I can't find a simple example anywhere of someone doing this. Basically, the method has a parameter (the third one) for a callback function: int sqlite3_exec( sqlite3*, /* An open database */ const char *sql, /* SQL to be evaluated */ int (*callback)(void*,int,char**,char**), /* Callback function */ void *, /* 1st argument to callback */ char **errmsg /* Error msg written here */ ); That's fine. I'm no stranger to callbacks. However, I just can't seem to get the syntax down right. I took over one of the view controllers in my iPad (iOS 5.1) xcode (4.3) project, and made the changes shown below: #import "SecondViewController.h" #import "sqlite3.h" #import "AppState.h" @interface SecondViewController () @end @implementation SecondViewController - (int)myCallback:(void *)a_parm argc:(int)argc argv:(char **)argv column:(char **)column { return 0; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //grab questionnaire names char *sql = "select * from QST2Main order by [Name]"; char *err = nil; sqlite3 *db = [[AppState sharedManager] getgCn]; sqlite3_exec(db, sql, myCallback, nil, &err); } Essentially, I want to run a query when this view first loads, to store some data for later use. But, XCode doesn't like the "myCallback" usage at the bottom there. It says: Undeclared Use of Identifier 'myCallback.' That method is declared in the header file, and I've even tried making it static. Nothing seems to make this error go away. I know I must be doing something fundamentally wrong here, but for the life of me I can't figure out what - I can't even find other code samples in this area that could help me figure out what I'm missing. Many thanks!

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• How can I build something like Amazon S3 in Perl?

  - by Joel G

  I am looking to code a file storage application in perl similar to amazon s3. I already have a amazon s3 clone that I found online called parkplace but its in ruby and is old also isn't built for high loads. I am not really sure what modules and programs I should use so id like some help picking them out. My requirements are listed below (yes I know there are lots but I could start simple then add more once I get it going): Easy API implementation for client side apps. (maybe REST (?) Centralized database server for the USERDB (maybe PostgreSQL (?). Logging of all connections, bandwidth used, well pretty much everything to a centralized server (maybe PostgreSQL again (?). Easy server side configuration (config file(s) stored on the servers). Web based control panel for admin(s) and user(s) to show logs. (could work just running queries from the databases) Fast High Uptime Low memory usage Some sort of load distribution/load balancer (maybe a dns based or pound or perlbal or something else (?). Maybe a cache of some sort (memcached or parlbal or something else (?). Thanks in advance

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• Basic jUnit Questions

  - by Epitaph

  I was testing a String multiplier class with a multiply() method that takes 2 numbers as inputs (as String) and returns the result number (as String) `public String multiply(String num1, String num2); I have done the implementation and created a test class with the following test cases involving the input String parameter as 1) valid numbers 2) characters 3) special symbol 4) empty string 5) Null value 6) 0 7) Negative number 8) float 9) Boundary values 10) Numbers that are valid but their product is out of range 11) numbers will + sign (+23) 1) I'd like to know if "each and every" assertEquals() should be in it's own test method? Or, can I group similar test cases like testInvalidArguments() to contains all asserts involving invalid characters since ALL of them throw the same NumberFormatException ? 2) If testing an input value like character ("a"), do I need to include test cases for ALL scenarios? "a" as the first argument "a" as the second argument "a" and "b" as the 2 arguments 3) As per my understanding, the benefit of these unit tests is to find out the cases where the input from a user might fail and result in an exception. And, then we can give the user with a meaningful message (asking them to provide valid input) instead of an exception. Is that the correct? And, is it the only benefit? 4) Are the 11 test cases mentioned above sufficient? Did I miss something? Did I overdo? When is enough? 5) Following from the above point, have I successfully tested the multiply() method?

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• .NET Membership with Repository Pattern

  - by Zac

  My team is in the process of designing a domain model which will hide various different data sources behind a unified repository abstraction. One of the main drivers for this approach is the very high probability that these data sources will undergo significant change in the near future and we don't want to be re-writing business logic when this happens. One data source will be our membership database which was originally implemented using the default ASP.Net Membership Provider. The membership provider is tied to the System.Web.Security namespace but we have a design guideline requiring that our domain model layer is not dependent upon System.Web (or any other implementation/environment dependency) as it will be consumed in different environments - nor do we want our websites directly communicating with databases. I am considering what would be a good approach to reconciling the MembershipProvider approach with our abstracted n-tier architecture. My initial feeling is that we could create a "DomainMembershipProvider" which interacts with the domain model and then implement objects in the model which deal with the repository and handle validation/business logic. The repository would then implement data access using our (as-yet undecided) ORM/data access tool. Are there are any glaring holes in this approach - I haven't worked closely with the MembershipProvider class so may well be missing something. Alternatively, is there an approach that you think will better serve the requirements I described above? Thanks in advance for your thoughts and advice. Regards, Zac

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• Memory mapped files and "soft" page faults. Unavoidable?

  - by Robert Oschler

  I have two applications (processes) running under Windows XP that share data via a memory mapped file. Despite all my efforts to eliminate per iteration memory allocations, I still get about 10 soft page faults per data transfer. I've tried every flag there is in CreateFileMapping() and CreateFileView() and it still happens. I'm beginning to wonder if it's just the way memory mapped files work. If anyone there knows the O/S implementation details behind memory mapped files I would appreciate comments on the following theory: If two processes share a memory mapped file and one process writes to it while another reads it, then the O/S marks the pages written to as invalid. When the other process goes to read the memory areas that now belong to invalidated pages, this causes a soft page fault (by design) and the O/S knows to reload the invalidated page. Also, the number of soft page faults is therefore directly proportional to the size of the data write. My experiments seem to bear out the above theory. When I share data I write one contiguous block of data. In other words, the entire shared memory area is overwritten each time. If I make the block bigger the number of soft page faults goes up correspondingly. So, if my theory is true, there is nothing I can do to eliminate the soft page faults short of not using memory mapped files because that is how they work (using soft page faults to maintain page consistency). What is ironic is that I chose to use a memory mapped file instead of a TCP socket connection because I thought it would be more efficient. Note, if the soft page faults are harmless please note that. I've heard that at some point if the number is excessive, the system's performance can be marred. If soft page faults intrinsically are not significantly harmful then if anyone has any guidelines as to what number per second is "excessive" I'd like to hear that. Thanks.

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• Detecting Xml namespace fast

  - by Anna Tjsoken

  Hello there, This may be a very trivial problem I'm trying to solve, but I'm sure there's a better way of doing it. So please go easy on me. I have a bunch of XSD files that are internal to our application, we have about 20-30 Xml files that implement datasets based off those XSDs. Some Xml files are small (<100Kb), others are about 3-4Mb with a few being over 10Mb. I need to find a way of working out what namespace these Xml files are in order to provide (something like) intellisense based off the XSD. The implementation of this is not an issue - another developer has written the code for this. But I'm not sure the best (and fastest!) way of detecting the namespace is without the use of XmlDocument (which does a full parse). I'm using C# 3.5 and the documents come through as a Stream (some are remote files). All the files are *.xml (I can detect if it was extension based) but unfortunately the Xml namespace is the only way. Right now I've tried XmlDocument but I've found it to be innefficient and slow as the larger documents are awaiting to be parsed (even the 100Kb docs). public string GetNamespaceForDocument(Stream document); Something like the above is my method signature - overloads include string for "content". Would a RegEx (compiled) pattern be good? How does Visual Studio manage this so efficiently? Another college has told me to find a fast Xml parser in C/C++, parse the content and have a stub that gives back the namespace as its slower in .NET, is this a good idea?

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• How do you create a non-Thread-based Guice custom Scope?

  - by Russ

  It seems that all Guice's out-of-the-box Scope implementations are inherently Thread-based (or ignore Threads entirely): Scopes.SINGLETON and Scopes.NO_SCOPE ignore Threads and are the edge cases: global scope and no scope. ServletScopes.REQUEST and ServletScopes.SESSION ultimately depend on retrieving scoped objects from a ThreadLocal<Context>. The retrieved Context holds a reference to the HttpServletRequest that holds a reference to the scoped objects stored as named attributes (where name is derived from com.google.inject.Key). Class SimpleScope from the custom scope Guice wiki also provides a per-Thread implementation using a ThreadLocal<Map<Key<?>, Object>> member variable. With that preamble, my question is this: how does one go about creating a non-Thread-based Scope? It seems that something that I can use to look up a Map<Key<?>, Object> is missing, as the only things passed in to Scope.scope() are a Key<T> and a Provider<T>. Thanks in advance for your time.

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• Graph limitations - Should I use Decorator?

  - by Nick Wiggill

  I have a functional AdjacencyListGraph class that adheres to a defined interface GraphStructure. In order to layer limitations on this (eg. acyclic, non-null, unique vertex data etc.), I can see two possible routes, each making use of the GraphStructure interface: Create a single class ("ControlledGraph") that has a set of bitflags specifying various possible limitations. Handle all limitations in this class. Update the class if new limitation requirements become apparent. Use the decorator pattern (DI, essentially) to create a separate class implementation for each individual limitation that a client class may wish to use. The benefit here is that we are adhering to the Single Responsibility Principle. I would lean toward the latter, but by Jove!, I hate the decorator Pattern. It is the epitome of clutter, IMO. Truthfully it all depends on how many decorators might be applied in the worst case -- in mine so far, the count is seven (the number of discrete limitations I've recognised at this stage). The other problem with decorator is that I'm going to have to do interface method wrapping in every... single... decorator class. Bah. Which would you go for, if either? Or, if you can suggest some more elegant solution, that would be welcome. EDIT: It occurs to me that using the proposed ControlledGraph class with the strategy pattern may help here... some sort of template method / functors setup, with individual bits applying separate controls in the various graph-canonical interface methods. Or am I losing the plot?

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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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