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• Recommended integration mechanism for bi-directional, authenticated, encrypted connection in C clien

  - by rcampbell

  Let me first give an example. Imagine you have a single server running a JVM application. This server keeps a collection of N equations, once for each client: Client #1: 2x Client #2: 1 + y Client #3: z/4 This server includes an HTTP interface so that random visitors can type https://www.acme.com/client/3 int their browsers and see the latest evaluated result of z/4. The tricky part is that either the client or the server may change the variable value at any time, informing the other party immediately. More specifically, Client #3 - a C app - can initially tell the server that z = 20. An hour later that same client informs the server that z = 23. Likewise the server can later inform the client that z = 28. As caf pointed out in the comments, there can be a race condition when values are changed by the client and server simultaneously. The solution would be for both client and server to send the operation performed in their message, which would need to be executed by the other party. To keep things simple, let's limit the operations to (commutative) addition, allowing us to disregard message ordering. For example, the client seeds the server with z = 20: server:z=20, client:z=20 server sends {+3} message (so z=23 locally) & client sends {-2} message (so z=18 locally) at the exact same time server receives {-2} message at some point, adds to his local copy so z=21 client receives {+3} message at some point, adds to his local copy so z=21 As long as all messages are eventually evaluated by both parties, the correct answer will eventually be given to the users of the client and server since we limited ourselves to commutative operations (addition of 3 and -2). This does mean that both client and server can be returning incorrect answers in the time it takes for messages to be exchanged and processed. While undesirable, I believe this is unavoidable. Some possible implementations of this idea include: Open an encrypted, always on TCP socket connection for communication Pros: no additional infrastructure needed, client and server know immediately if there is a problem (disconnect) with the other party, fairly straightforward (except the the encryption), native support from both JVM and C platforms Cons: pretty low-level so you end up writing a lot yourself (protocol, delivery verification, retry-on-failure logic), probably have a lot of firewall headaches during client app installation Asynchronous messaging (ex: ActiveMQ) Pros: transactional, both C & Java integration, free up the client and server apps from needing retry logic or delivery verification, pretty straightforward encryption, easy extensibility via message filters/routers/etc Cons: need additional infrastructure (message server) which must never fail, Database or file system as asynchronous integration point Same pros/cons as above but messier RESTful Web Service Pros: simple, possible reuse of the server's existing REST API, SSL figures out the encryption problem for you (maybe use RSA key a la GitHub for authentication?) Cons: Client now needs to run a C HTTP REST server w/SSL, client and server need retry logic. Axis2 has both a Java and C version, but you may be limited to SOAP. What other techniques should I be evaluating? What real world experiences have you had with these mechanisms? Which do you recommend for this problem and why?

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• Modelling deterministic and nondeterministic data separately

  - by Superstringcheese

  I'm working with the Microsoft ADO.NET Entity Framework for a game project. Following the advice of other posters on SO, I'm considering modelling deterministic and nondeterministic data separately. The idea for this came from a discussion on multiplayer games, but it seemed to make sense in a single-player scenario as well. Deterministic (things that aren't going to change during gameplay) Attributes (Strength, Agility, etc.) and their descriptions Skills and their descriptions and requirements Races, Factions, Equipment, etc. Base Attribute/Skill/Equipment loadouts for monsters Nondeterministic (things that will change a lot during gameplay) Beings' current AttributeModifers (Potion of Might = +10 Strength), current health and mana, etc. Player inventory, cash, experience, level Player quests states Player FactionRelationships ...and so on. My deterministic model would serve as a set of constants. My nondeterministic model would provide my on-the-fly operable data and would be serialized to a savegame file to maintain game state between play sessions. The data store will be an embedded SQL Compact database. So I might want to create relations between my Attributes table (deterministic model) and my BeingAttributeModifiers table (nondeterministic model), but how do I set that up across models? Det model/db Nondet model/db ____________ ________________________ |Attributes | |PlayerAttributeModifiers| |------------| |------------------------| |Id | |Id | |Name | |AttributeId | |Description | |SourceId | ------------ |Value | ------------------------ Should I use two separate models (edmx) that transact with a single database containing both deterministic-type and nondeterministic-type tables? Or should/can I use two separate databases in one model? Or two models each with their own database? With distinct models/dbs it seems like this will get really complicated and I'll end up fighting EF a lot, rolling my own transaction code, and generally losing out on a lot of the advantages of the framework. I know these are vague questions, I'm just looking for a sanity check before I forge ahead any further.

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• How to register application for existing file types using WiX installer?

  - by Marek

  related to this: http://stackoverflow.com/questions/138550/how-to-register-file-types-extensions-with-a-wix-installer but not a duplicate. I need to handle existing file types (.jpg files). I do not want to be the default handler for .jpg, I would just like to extend the "Open with" menu with a link to my app. I see HKCR\.jpg\OpenWithList\ and HKCR\.jpg\OpenWithProgIds\ in the registry but I am not sure whether to write to these and how to do it correctly with WiX. Should I use something like this? <ProgId Id='??what here?' Description='Jpeg handled by my App'> <Extension Id='jpg' ContentType='image/jpeg'> <Verb Id='openwithmyapp' Sequence='10' Command='OpenWithMyApp' Target='[!FileId]' Argument='"%1"' /> </Extension> </ProgId> There are many ways how to fail here (like Photo Mechanics did, the HKCR for image file types is a real mess after I have installed this software) How to do this correctly with WiX?

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• How to handle large dataset with JPA (or at least with Hibernate)?

  - by Roman

  I need to make my web-app work with really huge datasets. At the moment I get either OutOfMemoryException or output which is being generated 1-2 minutes. Let's put it simple and suppose that we have 2 tables in DB: Worker and WorkLog with about 1000 rows in the first one and 10 000 000 rows in the second one. Latter table has several fields including 'workerId' and 'hoursWorked' fields among others. What we need is: count total hours worked by each user; list of work periods for each user. The most straightforward approach (IMO) for each task in plain SQL is: 1) select Worker.name, sum(hoursWorked) from Worker, WorkLog where Worker.id = WorkLog.workerId group by Worker.name; //results of this query should be transformed to Multimap<Worker, Long> 2) select Worker.name, WorkLog.start, WorkLog.hoursWorked from Worker, WorkLog where Worker.id = WorkLog.workerId; //results of this query should be transformed to Multimap<Worker, Period> //if it was JDBC then it would be vitally //to set resultSet.setFetchSize (someSmallNumber), ~100 So, I have two questions: how to implement each of my approaches with JPA (or at least with Hibernate); how would you handle this problem (with JPA or Hibernate of course)?

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• Emulating Visual Studio's Web Application "publish" at the command line

  - by cbp

  Hi, I am trying to automate my deployment process and am now thoroughly confused. I know that there are many questions on stackoverflow about this, but they all have different solutions and none of them work. I have a Web Application project which I usually publish by right-clicking and selecting "Publish". I get a dialog box where I use the following options: Build configuration: Release Publish method: File system Target location: C:\Deployments\MyWebsite Replace matching files with local copies I should mention that in the properties of the project I have "Items to deploy" set to "Only files needed to run this application". After running this, my entire solution is built, dependencies are resolved, build events are run, web.config transformations are applied and the website is copied to C:\Deployments\MyWebsite, although non-required files such as code-behind files are not copied. I have not been able to replicate this... in fact at this stage I'm not even sure which command line tool am I supposed to be using - msbuild, msdeploy or aspnet_compiler? This guy asks almost the same question but his solution doesn't work at all. For example, build events do not run correctly because the macros are not resolved. Whats more, the files do not get copied into the correct directory at all... I can't even begin to explain what happens!

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• How do I work with constructs in PHPUnit?

  - by Ben Dauphinee

  I am new into PHPUnit, and just digging through the manual. I cannot find a decent example of how to build a complete test from end to end though, and so, am left with questions. One of these is how can I prep my environment to properly test my code? I am trying to figure out how to properly pass various configuration values needed for both the test setup/teardown methods, and the configs for the class itself. // How can I set these variables on testing start? protected $_db = null; protected $_config = null; // So that this function runs properly? public function setUp(){ $this->_acl = new acl( $this->_db, // The database connection for the class passed // from whatever test construct $this->_config // Config values passed in from construct ); } // Can I just drop in a construct like this, and have it work properly? // And if so, how can I set the construct call properly? public function __construct( Zend_Db_Adapter_Abstract $db, $config = array(), $baselinedatabase = NULL, $databaseteardown = NULL ){ $this->_db = $db; $this->_config = $config; $this->_baselinedatabase = $baselinedatabase; $this->_databaseteardown = $databaseteardown; } // Or is the wrong idea to be pursuing?

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• C# reflection instantiation

  - by NickLarsen

  I am currently trying to create a generic instance factory for which takes an interface as the generic parameter (enforced in the constructor) and then lets you get instantiated objects which implement that interface from all types in all loaded assemblies. The current implementation is as follows:     public class InstantiationFactory     {         protected Type Type { get; set; }         public InstantiationFactory()         {             this.Type = typeof(T);             if (!this.Type.IsInterface)             {                 // is there a more descriptive exception to throw?                 throw new ArgumentException(/* Crafty message */);             }         }         public IEnumerable GetLoadedTypes()         {             // this line of code found in other stack overflow questions             var types = AppDomain.CurrentDomain.GetAssemblies()                 .SelectMany(a = a.GetTypes())                 .Where(/* lambda to identify instantiable types which implement this interface */);             return types;         }         public IEnumerable GetImplementations(IEnumerable types)         {             var implementations = types.Where(/* lambda to identify instantiable types which implement this interface */                 .Select(x = CreateInstance(x));             return implementations;         }         public IEnumerable GetLoadedImplementations()         {             var loadedTypes = GetLoadedTypes();             var implementations = GetImplementations(loadedTypes);             return implementations;         }         private T CreateInstance(Type type)         {             T instance = default(T);             var constructor = type.GetConstructor(Type.EmptyTypes);             if (/* valid to instantiate test */)             {                 object constructed = constructor.Invoke(null);                 instance = (T)constructed;             }             return instance;         }     } It seems useful to me to have my CreateInstance(Type) function implemented as an extension method so I can reuse it later and simplify the code of my factory, but I can't figure out how to return a strongly typed value from that extension method. I realize I could just return an object:     public static class TypeExtensions     {         public object CreateInstance(this Type type)         {             var constructor = type.GetConstructor(Type.EmptyTypes);             return /* valid to instantiate test */ ? constructor.Invoke(null) : null;         }     } Is it possible to have an extension method create a signature per instance of the type it extends? My perfect code would be this, which avoids having to cast the result of the call to CreateInstance():     Type type = typeof(MyParameterlessConstructorImplementingType);     MyParameterlessConstructorImplementingType usable = type.CreateInstance();

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• Same jQuery code returns two different results – Submit Button Text

  - by Lijo

  I have two jQuery codes - http://jsfiddle.net/Lijo/CXGX7/7/ and http://jsfiddle.net/Lijo/CXGX7/8/ . The first code returns undefined whereas the second code returns text of button. QUESTIONS What is the reason for this difference in result? Why is the first code not returning expected text of button? Note: I verified that both are using same version of jQuery (by an alert of jQuery) alert($.fn.jquery); CODE <html xmlns="http://www.w3.org/1999/xhtml"> <head><title> </title> <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.8.1.js"></script> <script type="text/javascript"> alert($('.myButton').attr("value")); </script> </head> <body> <form method="post" action="Test.aspx" id="form1"> <div class="aspNetHidden"> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwULLTE0MDM4MzYxMjNkZMycQvsYQ+GPFsQHoQ8j/8vEo2vQbqkhfgPc60kxXaQO" /> </div> <div class="aspNetHidden"> <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWAwKqxqqrCgLi/JazDQKM54rGBqgaroRQTXJkD1LyUlVxAmLRCNfTGVe73swQBMemBtvN" /> </div> <div> <input name="txtEmpName" type="text" id="txtEmpName" /> <input type="submit" name="Button1" value="Submit" id="Button1" class="myButton" /> </div> </form> </body> </html> REFERENCES Retrieve Button value with jQuery How to determine and print jQuery version?

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• Can you have a Dynamic Data Field which consists of a list of fields?

  - by Telos

  This is a purely theoretical question (at least until I start trying to implement it) but here goes. I wrote a web form a long time ago which has a configurable section for getting information. Basically for some customers there are no fields, for other customers there are up to 20 fields. I got it working by dynamically creating the fields at just the right time in the page lifecycle and going through a lot of headaches. 2 years later, I need to make some pretty big updates to this web form and there are some nifty new technologies. I've worked with ASP.NET Dynamic Data just a bit and, well, I half-crazed plan just occurred to me: The Ticket object has a one-to-many relationship to ExtendedField, we'll call that relationship Fields for brevity. Using that, the idea would be to create a FieldTemplate that dynamically generated the list of fields and displayed it. The big questions here would probably be: 1) Can a single field template resolve to multiple web controls without breaking things? 2) Can dynamic data handle updating/inserting multiple rows in such a fashion? 3) There was a third question I had a few minutes ago, but coworkers interrupted me and I forgot. So now the third question is: what is the third question? So basically, does this sound like it could work or am I missing a better/more obvious solution?

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• URL naming conventions

  - by LookitsPuck

  So, this may be a can of worms. But I'm curious what your practices are? For example, let's say your website consists of the following needs (very basic): A landing page An information page for an event (static) A listing of places for that event (dynamic) An information page for each place With that said, how would you design your URLs? Typically, I'd do something like the following: www.domain.com/ - landing page [also accessible via www.domain.com/home] www.domain.com/event - event information page www.domain.com/places - listing of all places www.domain.com/places/{id} - place information page Now, here's a question. Just grammatically speaking, I have a hangup of referring to a given place in a url as being plural. Shouldn't it make more sense to go with this: www.domain.com/place/{id} as opposed to www.domain.com/places/{id} In some frameworks, you have a convention to follow (for example, ASP.NET MVC) by default. Yes, you can define custom routes to have /place/{id} route to the PlacesController. However, I'm just trying to keep this a bit abstract in discussion. With that being said, let's see for instance on another page of your site, you have a link, that when clicked, would open a modal popup populated with place information. Where you place that information? We could go with something like this: www.domain.com/ajax/places/{id} OR www.domain.com/places/{id} and serve based on the request header (that is, if requesting JSON, return JSON?}. Finally, for SEO reasons, typically I use a slug associated with a given resource. So, something like such: www.domain.com/ajax/places/{id}/london Where london is only there to add decoration to the link for SEO reasons. Is this sound? I ask all of these questions, because these are practices that I've been using for awhile, and I'd just like to see what other developers are doing or if I'm approaching things incorrectly. Thanks!

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• com.sun.org.apache.xerces.internal.dom.DocumentImpl cannot be cast to org.codehaus.plexus.util.xml.X

  - by Random

  Afetr using the Model library (see this) for my Maven pom.xml during this weeks I jumped on this error while attempting to write a ConfiguratonContainer into the pom.xml. The javadoc for Model says: public void setConfiguration(Object configuration) Set the configuration as DOM object. Parameters: configuration - So I made some xml with Document (org.w3c.dom.Document) and the xml parser standar javax library. You know the code (it's through all the net) but I paste it here... DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder parser = factory.newDocumentBuilder(); Document doc =parser.newDocument(); And then you fill the code with Element declaration,a lot of appendChild and such. And tried to make it work. Doesn't seem to do well. First tried using plugin.setConfiguration(doc); But it didn't work. Then I tried Obejct obj = doc; plugin.setConfiguration(obj); But it didn't work. Then I searched the net for answers, and guess... It didn't work. There are like 0 people using this library (maven.model) in all the net. So here am I again, asking the senseis for help. Where is my error? I have downloaded the source code of the library trying to see where is the error, but it seems to be ok (as should). I add the stackrace for reference java.lang.ClassCastException: com.sun.org.apache.xerces.internal.dom.DocumentImpl cannot be cast to org.codehaus.plexus.util.xml.Xpp3Dom at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writePlugin(MavenXpp3Writer.java:1472) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writeBuild(MavenXpp3Writer.java:326) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.writeModel(MavenXpp3Writer.java:1093) at org.apache.maven.model.io.xpp3.MavenXpp3Writer.write(MavenXpp3Writer.java:102) at com.mapfre.mutua.PDA.model.GeneratePOM.createPOM(GeneratePOM.java:28) at com.mapfre.mutua.PDA.prueba.MavenPOM.generatePOMWAR(MavenPOM.java:681) at com.mapfre.mutua.PDA.prueba.GenerarPOMMapfreAction.execute(GenerarPOMMapfreAction.java:36) at org.apache.struts.chain.commands.servlet.ExecuteAction.execute(ExecuteAction.java:58) at org.apache.struts.chain.commands.AbstractExecuteAction.execute(AbstractExecuteAction.java:67) at org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51) at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191) at org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305) at org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191) at org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:873) at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689) at java.lang.Thread.run(Unknown Source)

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• Cross compiling from MinGW on Fedora 12 to Windows - console window?

  - by elcuco

  After reading this article http://lukast.mediablog.sk/log/?p=155 I decided to use mingw on linux to compile windows applications. This means I can compile, test, debug and release directly from Linux. I hacked this build script which will cross compile the application and even package it in a ZIP file. Note that I am using out of source builds for QMake (did you even know this is supported? wow...). Also note that the script will pull the needed DLLs automagically. Here is the script for you all internets to use and abuse: #! /bin/sh set -x set -e VERSION=0.1 PRO_FILE=blabla.pro BUILD_DIR=mingw_build DIST_DIR=blabla-$VERSION-win32 # clean up old shite rm -fr $BUILD_DIR mkdir $BUILD_DIR cd $BUILD_DIR # start building QMAKESPEC=fedora-win32-cross qmake-qt4 QT_LIBINFIX=4 config=\"release\ quiet\" ../$PRO_FILE #qmake-qt4 -spec fedora-win32-cross make DLLS=`i686-pc-mingw32-objdump -p release/*.exe | grep dll | awk '{print $3}'` for i in $DLLS mingwm10.dll ; do f=/usr/i686-pc-mingw32/sys-root/mingw/bin/$i if [ ! -f $f ]; then continue; fi cp -av $f release done mkdir -p $DIST_DIR mv release/*.exe $DIST_DIR mv release/*.dll $DIST_DIR zip -r ../$DIST_DIR.zip $DIST_DIR The compiled binary works on the Windows7 machine I tested. Now to the questions: When I execute the application on Windows, the theme is not the Windows7 theme. I assume I am missing a style module, I am not really sure yet. The application gets a console window for some reason. The second point (the console window) is critical. How can I remove this background window? Please note that the extra config lines are not working for me, what am I missing there?

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• FluentNHibernate, getting 1 column from another table

  - by puffpio

  We're using FluentNHibernate and we have run into a problem where our object model requires data from two tables like so: public class MyModel { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual int FooId { get; set; } public virtual string FooName { get; set; } } Where there is a MyModel table that has Id, Name, and FooId as a foreign key into the Foo table. The Foo tables contains Id and FooName. This problem is very similar to another post here: http://stackoverflow.com/questions/1896645/nhibernate-join-tables-and-get-single-column-from-other-table but I am trying to figure out how to do it with FluentNHibernate. I can make the Id, Name, and FooId very easily..but mapping FooName I am having trouble with. This is my class map: public class MyModelClassMap : ClassMap<MyModel> { public MyModelClassMap() { this.Id(a => a.Id).Column("AccountId").GeneratedBy.Identity(); this.Map(a => a.Name); this.Map(a => a.FooId); // my attempt to map FooName but it doesn't work this.Join("Foo", join => join.KeyColumn("FooId").Map(a => a.FooName)); } } with that mapping I get this error: The element 'class' in namespace 'urn:nhibernate-mapping-2.2' has invalid child element 'join' in namespace 'urn:nhibernate-mapping-2.2'. List of possible elements expected: 'joined-subclass, loader, sql-insert, sql-update, sql-delete, filter, resultset, query, sql-query' in namespace 'urn:nhibernate-mapping-2.2'. any ideas?

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• Jquery Show Fields depending on Select Menu value but on page load

  - by Tim

  Hello, This question refers to the question http://stackoverflow.com/questions/835259/jquery-show-hide-fields-depening-on-select-value <select id="viewSelector"> <option value="0">-- Select a View --</option> <option value="view1">view1</option> <option value="view2">view2</option> <option value="view3">view3</option> </select> <div id="view1"> <!-- content --> </div> <div id="view2a"> <!-- content --> </div> <div id="view2b"> <!-- content --> </div> <div id="view3"> <!-- content --> </div> $(document).ready(function() { $.viewMap = { '0' : $([]), 'view1' : $('#view1'), 'view2' : $('#view2a, #view2b'), 'view3' : $('#view3') }; $('#viewSelector').change(function() { // hide all $.each($.viewMap, function() { this.hide(); }); // show current $.viewMap[$(this).val()].show(); }); }); When I select the 2nd item in the menu it shows the corresponding field. The exception to this is when the on page load the select menu already has the 2nd menu item selected, the field does not show. As you may be able to tell, I am new to jquery and could definetly use some help with adjusting this code so that the selected item's field is shown on page load. Thanks, Tim

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• Return value from Object match

  - by Hito_kun

  I'm, by no means, JS fluent, so forgive me if im asking for some really basic stuff, but I've not being able to find a proper answer to my question. Im writting my first Node.js (plus Extra Framework and Socket.io) app and Im having some fun setting up the server side of a FB-like messenger (surprise!!!). So, let's say I have this data structure to store online users(This is a JSON Array, but I'm not sure it is the best way to do it or should I go with Javascript Objects): [ { "site": 45, "users": [ { "idUser": 5, "idSocket": "qwe87r7w8qwe", "name": "Carlos Ray Norris" }, { "idUser": 6, "idSocket": "v8d9d0fgfs7d", "name": "John Connor" } ] }, { "site": 48, "users": [ { "idUser": 22, "idSocket": "qwe87r7w8qwe", "name": "David Bowie" }, { "idUser": 23, "idSocket": "v8d9d0fgfs7d", "name": "Barack H. Obama" } ] } ] What I want to do is to search in the array for x value given y. In this case, retrieving the idSocket knowing the idUser WITHOUT having to run through the array values. So I have basically 2 questions: first, what would be the proper way to store users online? and secondly, how to find values matching with the values I already know (find the idSocket that has a given idUser). I would like a pure JS approach(or using some of the tools given by Node, Socket.io or Express), but if that's not possible then I can look for some JQuery.

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• Practical rules for premature optimization

  - by DougW

  It seems that the phrase "Premature Optimization" is the buzz-word of the day. For some reason, iphone programmers in particular seem to think of avoiding premature optimization as a pro-active goal, rather than the natural result of simply avoiding distraction. The problem is, the term is beginning to be applied more and more to cases that are completely inappropriate. For example, I've seen a growing number of people say not to worry about the complexity of an algorithm, because that's premature optimization (eg http://stackoverflow.com/questions/2190275/help-sorting-an-nsarray-across-two-properties-with-nssortdescriptor/2191720#2191720). Frankly, I think this is just laziness, and appalling to disciplined computer science. But it has occurred to me that maybe considering the complexity and performance of algorithms is going the way of assembly loop unrolling, and other optimization techniques that are now considered unnecessary. What do you think? Are we at the point now where deciding between an O(n^n) and O(n!) complexity algorithm is irrelevant? What about O(n) vs O(n*n)? What do you consider "premature optimization"? What practical rules do you use to consciously or unconsciously avoid it? This is a bit vague, but I'm curious to hear other peoples' opinions on the topic.

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• Delphi Client-Server Application using Firebird 2.5 embedded connection error

  - by Japster

  0 down vote favorite 1 share [fb] share [tw] I have got a lengthy question to ask. First of all Im still very new when it comes to Delphi programming and my experience has beem mostly developing small single user database applications using ADO and an Access database. I need to take the transition now to a client server application and this is where the problem starts. I decided to use Firebird 2.5 embeded as my database, as it is open source, and it is can be used with the interbase components in Delphi and that multiple clients can access the database simultanously. So I followed the interbase tutorial in Delphi. I managed to connect the client to the server and see the data in the example (While both are running on my pc), but when i tried to move the client to another pc, keeping the server on mine and running it to see if I can connect to the server it gave me the following error. Exception EIdSocketError in module clientDemo.exe at 0029DCAC. Socket Error # 10061 Connection refused. I understand that this might be because the host is defined as localhost in the client. But here is my first question. In the TSQLConncetion you can set die hostname under Driver-Hostname. The thing I want to know is how do you do this at run time, as I cannot get the property when I try and make an edit box to allow the user to enter the value and then set it via code like for example: SQLConncetion1.Driver.Hostname := edtHost.text; This cannot be done this way and the only way I see you can set the hostname is with the object inspector, but that is not available at runtime and I need to set the hostname on the client when the program is running the first time, so how do you set the hostname/IP address at runtime? Im using Delphi XE2 There is still a lot of questions to come especially when it comes to deployment, but I will take this piece by piece and I appreciate the advice.

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• Router 2wire, Slackware desktop in DMZ mode, iptables policy aginst ping, but still pingable

  - by skriatok

  I'm in DMZ mode, so I'm firewalling myself, stealthy all ok, but I get faulty test results from Shields Up that there are pings. Yesterday I couldn't make a connection to game servers work, because ping block was enabled (on the router). I disabled it, but this persists even due to my firewall. What is the connection between me and my router in DMZ mode (for my machine, there is bunch of others too behind router firewall)? When it allows router affecting if I'm pingable or not and if router has setting not blocking ping, rules in my iptables for this scenario do not work. Please ignore commented rules, I do uncomment them as I want. These two should do the job right? iptables -A INPUT -p icmp --icmp-type echo-request -j DROP echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all Here are my iptables: #!/bin/sh # Begin /bin/firewall-start # Insert connection-tracking modules (not needed if built into the kernel). #modprobe ip_tables #modprobe iptable_filter #modprobe ip_conntrack #modprobe ip_conntrack_ftp #modprobe ipt_state #modprobe ipt_LOG # allow local-only connections iptables -A INPUT -i lo -j ACCEPT # free output on any interface to any ip for any service # (equal to -P ACCEPT) iptables -A OUTPUT -j ACCEPT # permit answers on already established connections # and permit new connections related to established ones (eg active-ftp) iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT #Gamespy&NWN #iptables -A INPUT -p tcp -m tcp -m multiport --ports 5120:5129 -j ACCEPT #iptables -A INPUT -p tcp -m tcp --dport 6667 --tcp-flags SYN,RST,ACK SYN -j ACCEPT #iptables -A INPUT -p tcp -m tcp --dport 28910 --tcp-flags SYN,RST,ACK SYN -j ACCEPT #iptables -A INPUT -p tcp -m tcp --dport 29900 --tcp-flags SYN,RST,ACK SYN -j ACCEPT #iptables -A INPUT -p tcp -m tcp --dport 29901 --tcp-flags SYN,RST,ACK SYN -j ACCEPT #iptables -A INPUT -p tcp -m tcp --dport 29920 --tcp-flags SYN,RST,ACK SYN -j ACCEPT #iptables -A INPUT -p udp -m udp -m multiport --ports 5120:5129 -j ACCEPT #iptables -A INPUT -p udp -m udp --dport 6500 -j ACCEPT #iptables -A INPUT -p udp -m udp --dport 27900 -j ACCEPT #iptables -A INPUT -p udp -m udp --dport 27901 -j ACCEPT #iptables -A INPUT -p udp -m udp --dport 29910 -j ACCEPT # Log everything else: What's Windows' latest exploitable vulnerability? iptables -A INPUT -j LOG --log-prefix "FIREWALL:INPUT" # set a sane policy: everything not accepted > /dev/null iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT DROP iptables -A INPUT -p icmp --icmp-type echo-request -j DROP # be verbose on dynamic ip-addresses (not needed in case of static IP) echo 2 > /proc/sys/net/ipv4/ip_dynaddr # disable ExplicitCongestionNotification - too many routers are still # ignorant echo 0 > /proc/sys/net/ipv4/tcp_ecn #ping death echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all # If you are frequently accessing ftp-servers or enjoy chatting you might # notice certain delays because some implementations of these daemons have # the feature of querying an identd on your box for your username for # logging. Although there's really no harm in this, having an identd # running is not recommended because some implementations are known to be # vulnerable. # To avoid these delays you could reject the requests with a 'tcp-reset': #iptables -A INPUT -p tcp --dport 113 -j REJECT --reject-with tcp-reset #iptables -A OUTPUT -p tcp --sport 113 -m state --state RELATED -j ACCEPT # To log and drop invalid packets, mostly harmless packets that came in # after netfilter's timeout, sometimes scans: #iptables -I INPUT 1 -p tcp -m state --state INVALID -j LOG --log-prefix \ "FIREWALL:INVALID" #iptables -I INPUT 2 -p tcp -m state --state INVALID -j DROP # End /bin/firewall-start Active ruleset: bash-4.1# iptables -L -n -v Chain INPUT (policy DROP 38 packets, 2228 bytes) pkts bytes target prot opt in out source destination 0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 844 542K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 38 2228 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4 prefix `FIREWALL:INPUT' 0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 38 2228 LOG all -- * * 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4 prefix `FIREWALL:INPUT' Chain FORWARD (policy DROP 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy DROP 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 1158 111K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 Active ruleset: (after editing iptables into below sugested form) bash-4.1# iptables -L -n -v Chain INPUT (policy DROP 2567 packets, 172K bytes) pkts bytes target prot opt in out source destination 49 4157 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 412K 441M ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 2567 172K LOG all -- * * 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4 prefix `FIREWALL:INPUT' 0 0 DROP icmp -- * * 0.0.0.0/0 0.0.0.0/0 icmp type 8 Chain FORWARD (policy DROP 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 312K packets, 25M bytes) pkts bytes target prot opt in out source destination ping and syslog simultaneous screenshots from phone (pinger) and from laptop (being pinged) http://dl.dropbox.com/u/4160051/slckwr/pingfrom%20mobile.jpg http://dl.dropbox.com/u/4160051/slckwr/tailsyslog.jpg

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• C# Hiding, overriding and calling function from base class.

  - by Lukasz Lysik

  I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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• Advanced Linq query using into

  - by dilbert789

  I have this query that someone else wrote, it's over my head so I'm looking for some direction. What is happening currently is that it's taking numbers where there is a goal and no history entered, or history and no goal, this screws up the calculations as both goal and history for the same item are required on each. The three tables involved are: KPIType Goal KPIHistory What I need: Need all rows from KPIType. Need all goals where there is a matching KPIHistory row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 1 Need all kpiHistory’s where there is a matching Goal row (Goal.KPItypeID == KPIHistory.KPItypeID ) into results 2 Current query: var query = from t in dcs.KPIType.Where(k => k.ID <= 23) join g in dcs.Goal.Where(g => g.Dealership.ID == dealershipID && g.YearMonth >= beginDate && g.YearMonth <= endDate ) on t.ID equals g.KPITypeID into results1 join h in dcs.KPIHistory.Where(h => h.Dealership.ID == dealershipID && h.ForDate >= beginDate && h.ForDate <= endDate ) on t.ID equals h.KPIType.ID into results2 orderby t.DisplayOrder select new { t, Goal = results1, KPIHistory = results2 }; query.ToList().ForEach(q => { results.Add(q.t); }); Thanks, I'm happy to answer questions if more info needed.

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• R: extracting "clean" UTF-8 text from a web page scraped with RCurl

  - by SlowLearner

  Using R, I am trying to scrape a web page save the text, which is in Japanese, to a file. Ultimately this needs to be scaled to tackle hundreds of pages on a daily basis. I already have a workable solution in Perl, but I am trying to migrate the script to R to reduce the cognitive load of switching between multiple languages. So far I am not succeeding. Related questions seem to be this one on saving csv files and this one on writing Hebrew to a HTML file. However, I haven't been successful in cobbling together a solution based on the answers there. The pages are from Yahoo! Japan Finance and my Perl code that looks like this. use strict; use HTML::Tree; use LWP::Simple; #use Encode; use utf8; binmode STDOUT, ":utf8"; my @arr_links = (); $arr_links[1] = "http://stocks.finance.yahoo.co.jp/stocks/detail/?code=7203"; $arr_links[2] = "http://stocks.finance.yahoo.co.jp/stocks/detail/?code=7201"; foreach my $link (@arr_links){ $link =~ s/"//gi; print("$link\n"); my $content = get($link); my $tree = HTML::Tree->new(); $tree->parse($content); my $bar = $tree->as_text; open OUTFILE, ">>:utf8", join("","c:/", substr($link, -4),"_perl.txt") || die; print OUTFILE $bar; } This Perl script produces a CSV file that looks like the screenshot below, with proper kanji and kana that can be mined and manipulated offline: My R code, such as it is, looks like the following. The R script is not an exact duplicate of the Perl solution just given, as it doesn't strip out the HTML and leave the text (this answer suggests an approach using R but it doesn't work for me in this case) and it doesn't have the loop and so on, but the intent is the same. require(RCurl) require(XML) links <- list() links[1] <- "http://stocks.finance.yahoo.co.jp/stocks/detail/?code=7203" links[2] <- "http://stocks.finance.yahoo.co.jp/stocks/detail/?code=7201" txt <- getURL(links, .encoding = "UTF-8") Encoding(txt) <- "bytes" write.table(txt, "c:/geturl_r.txt", quote = FALSE, row.names = FALSE, sep = "\t", fileEncoding = "UTF-8") This R script generates the output shown in the screenshot below. Basically rubbish. I assume that there is some combination of HTML, text and file encoding that will allow me to generate in R a similar result to that of the Perl solution but I cannot find it. The header of the HTML page I'm trying to scrape says the chartset is utf-8 and I have set the encoding in the getURL call and in the write.table function to utf-8, but this alone isn't enough. The question How can I scrape the above web page using R and save the text as CSV in "well-formed" Japanese text rather than something that looks like line noise? Edit: I have added a further screenshot to show what happens when I omit the Encoding step. I get what look like Unicode codes, but not the graphical representation of the characters. So it may be some kind of locale-related issue, but in the exact same locale the Perl script does provide useful output. So this is still puzzling.

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• How to deploy a number of disparate project types?

  - by niteice

  This question is similar to http://stackoverflow.com/questions/1900269/whats-the-best-way-to-deploy-an-executable-process-on-a-web-server. The situation is this: I'm developing a product that needs to be deployed to a web server. It consists of 4 website projects, a background service, a couple of command-line tools, and two assemblies shared by all of these components. Now, I also happen to administer the server that this product will be deployed on. So I'm familiar with everything that may need to be done to perform an update: Copy website files Replace the service binary Install updated components in the GAC Configure IIS Update database schema After some research it seems that, to reduce deployment time and to be able to let the other sysadmins handle deployment, I want to deploy all of these as an MSI, except that I don't know a thing about installers. I know VS can generate web deployment projects, but where do I go from there? Being able to simply click Next a few times on an installer is my goal for deploying updates. It would also be nice to modularize it, so for example, I could distribute the four websites among multiple servers and have everything appear as individual components in the installer, and as one entity in Add/Remove Programs. Is all of this too much to ask in a single package?

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• An Ideal Keyboard Layout for Programming

  - by Jon Purdy

  I often hear complaints that programming languages that make heavy use of symbols for brevity, most notably C and C++ (I'm not going to touch APL), are difficult to type because they require frequent use of the shift key. A year or two ago, I got tired of it myself, downloaded Microsoft's Keyboard Layout Creator, made a few changes to my layout, and have not once looked back. The speed difference is astounding; with these few simple changes I am able to type C++ code around 30% faster, depending of course on how hairy it is; best of all, my typing speed in ordinary running text is not compromised. My questions are these: what alternate keyboard layouts have existed for programming, which have gained popularity, are any of them still in modern use, do you personally use any altered layout, and how can my layout be further optimised? I made the following changes to a standard QWERTY layout. (I don't use Dvorak, but there is a programmer Dvorak layout worth mentioning.) Swap numbers with symbols in the top row, because long or repeated literal numbers are typically replaced with named constants; Swap backquote with tilde, because backquotes are rare in many languages but destructors are common in C++; Swap minus with underscore, because underscores are common in identifiers; Swap curly braces with square brackets, because blocks are more common than subscripts; and Swap double quote with single quote, because strings are more common than character literals. I suspect this last is probably going to be the most controversial, as it interferes the most with running text by requiring use of shift to type common contractions. This layout has significantly increased my typing speed in C++, C, Java, and Perl, and somewhat increased it in LISP and Python.

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• Encapsulate update method inside of object or have method which accepts an object to update

  - by Tom

  Hi, I actually have 2 questions related to each other: I have an object (class) called, say MyClass which holds data from my database. Currently I have a list of these objects ( List < MyClass ) that resides in a singleton in a "communal area". I feel it's easier to manage the data this way and I fail to see how passing a class around from object to object is beneficial over a singleton (I would be happy if someone can tell me why). Anyway, the data may change in the database from outside my program and so I have to update the data every so often. To update the list of the MyClass I have a method called say, Update, written in another class which accepts a list of MyClass. This updates all the instances of MyClass in the list. However would it be better instead to encapulate the Update() method inside the MyClass object, so instead I would say foreach(MyClass obj in MyClassList) { obj.update(); } What is a better implementation and why? The update method requires a XML reader. I have written an XML reader class which is basically a wrapper over the standard XML reader the language natively provides which provides application specific data collection. Should the XML reader class be in anyway in the "inheritance path" of the MyClass object - the MyClass objects inherits from the XML reader because it uses a few methods. I can't see why it should. I don't like the idea of declaring an instance of the XML Reader class inside of MyClass and an MyClass object is meant to be a simple "record" from the database and I feel giving it loads of methods, other object instances is a bit messy. Perhaps my XML reader class should be static but C#'s native XMLReader isn't static.? Any comments would be greatly appreciated Thanks Thomas

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• Delphi Performance: Case Versus If

  - by Andreas Rejbrand

  I guess there might be some overlapping with previous SO questions, but I could not find a Delphi-specific question on this topic. Suppose that you want to check if an unsigned 32-bit integer variable "MyAction" is equal to any of the constants ACTION1, ACTION2, ... ACTIONn, where n is - say 1000. I guess that, besides being more elegant, case MyAction of ACTION1: {code}; ACTION2: {code}; ... ACTIONn: {code}; end; if much faster than if MyAction = ACTION1 then // code else if MyAction = ACTION2 then // code ... else if MyAction = ACTIONn then // code; I guess that the if variant takes time O(n) to complete (i.e. to find the right action) if the right action ACTIONi has a high value of i, whereas the case variant takes a lot less time (O(1)?). Am I correct that switch is much faster? Am I correct that the time required to find the right action in the switch case actually is independent of n? I.e. is it true that it does not really take any longer to check a million cases than to check 10 cases? How, exactly, does this work?

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