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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • Video works with 'Try me' but not after install. What is the difference? U12.04LTS,

    - by HarveyP
    My hard drive got corrupted so I did a reinstall. Tested Youtube in FF during 'try me' and it worked - jerky, but it worked. Instal without all the updates (576 outstanding now) in order to get ff installed as per the demo - to no avail. In 'try me' mode ff NEVER crashed! After install ff crashed whilst I was typing in 'youtube' in the address field. When I finally got to youtube - no video. What is the difference between ff in try me and ff after install? Off to try some selected updates now to see if I can see it for myself. In previous installation I had several profiles and aliased ff with -safe-mode switch to simplify startup of most stable ff. Also found that ff startup in graphic mode worked better (but still without video) with all of the extensions disabled and all of the plugins set to "ask" and always denied ... I have SiS graphic card in SiS Motherboard for XP and ancient Hyundai ImageQuest QV770 monitor. I have Ubuntu 12.04.01 LTS 1 day after install with only the immediate upgrades requested to language pack (English UK). Using FR Alternative keyboard. Connected with domestic wifi network from Orange (FT) I really want to use Skype, but won't bother installing it (again) without video as I can do my sms on FB - whilst ff is not crashed ... Update ... Is something overflowing? I have just had to reboot in order to get ff to restart in any way shape or form - restart on crash form generates new crash form, etc. It was however a good half hour before it crashed so some improvement over conditions before disk corruption. I have now installed all of the critical updates (332 recommended updates still outstanding) which included some relating to ff. Still no video. Still crashing - especially when on Grepolis website. Since the re-install I have had a lovely 1024x768 screen, but after last ff crash and reboot I got a message about 'low graphics mode' and 'setting things myself'. I was not sufficiently tuned in at the time to take proper note - I have no doubt I shall see it again and shall report accordingly. I still have only laptop options for my screen and do not know how to rectify this. Spent a few days with ubuntu on a different, newer machine which has now suffered a graphics breakdown. Returned to this old one again, but with new flat screen Monitor. Found SIS drivers for my graphics BUT it is intended for Red Hat 7.2. I chose this over the version for 7.0 because I thought what the hell, I might not be able to do anything with either of them but this is the later one ... The file will not open with software manager - found a similar problem on Overclock but it has not helped me to install this driver. File name is sis_drv.o-410 and it is currently idling away in my Downloads folder ... I have tried the solution offered on another sis problem, but this shows that my xserver-xorg-video-sis driver is up to date. I am now at a loss as to how to proceed if I can't install the latest sis driver from sis ... Does nobody know how FF changes from "try-me" to "installed"? Any time I MUST have video I reboot from the disk again, but this is tedious! Also one of the things I mock most about MS is the constant rebooting ... UPDATE 10/6/2014 I have installed chromium-browser - worse, crashes even more often than ff.I have installed epiphany - better; Video works but not the associated soundtrack.FireFox is version 14.01 in 'try me' and version 29.0 from my install. Would it be useful to try to downgrade FireFox in order to get video?

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  • Cloud Fact for Business Managers #3: Where You Data Is, and Who Has Access to It Might Surprise You

    - by yaldahhakim
    Written by: David Krauss While data security and operational risk conversations usually happen around the desk of a CCO/CSO (chief compliance and/or security officer), or perhaps the CFO, since business managers are now selecting cloud providers, they need to be able to at least ask some high-level questions on the topic of risk and compliance.  While the report found that 76% of adopters were motivated to adopt cloud apps because of quick access to software, most of these managers found that after they made a purchase decision their access to exciting new capabilities in the cloud could be hindered due to performance and scalability constraints put forth  by their cloud provider.  If you are going to let your business consume their mission critical business applications as a service, then it’s important to understand who is providing those cloud services and what kind of performance you are going to get.  Different types of departments, companies and industries will all have unique requirements so it’s key to take this also into consideration.   Nothing puts a CEO in a bad mood like a public data breach or finding out the company lost money when customers couldn’t buy a product or service because your cloud service provider had a problem.  With 42% of business managers having seen a data security breach in their department associated directly with the use of cloud applications, this is happening more than you think.   We’ve talked about the importance of being able to avoid information silos through a unified cloud approach and platform.  This is also important when keeping your data safe and secure, and a key conversation to have with your cloud provider.  Your customers want to know that their information is protected when they do business with you, just like you want your own company information protected.   This is really hard to do when each line of business is running different cloud application services managed by different cloud providers, all with different processes and controls.   It only adds to the complexity, and the more complex, the more risky and the chance that something will go wrong. What about compliance? Depending on the cloud provider, it can be difficult at best to understand who has access to your data, and were your data is actually stored.  Add to this multiple cloud providers spanning multiple departments and it becomes very problematic when trying to comply with certain industry and country data security regulations.  With 73% of business managers complaining that having cloud data handled externally by one or more cloud vendors makes it hard for their department to be compliant, this is a big time suck for executives and it puts the organization at risk. Is There A Complete, Integrated, Modern Cloud Out there for Business Executives?If you are a business manager looking to drive faster innovation for your business and want a cloud application that your CIO would approve of, I would encourage you take a look at Oracle Cloud.  It’s everything you want from a SaaS based application, but without compromising on functionality and other modern capabilities like embedded business intelligence, social relationship management (for your entire business), and advanced mobile.  And because Oracle Cloud is built and managed by Oracle, you can be confident that your cloud application services are enterprise-grade.  Over 25 Million users and 10 thousands companies around the globe rely on Oracle Cloud application services everyday – maybe your business should too.  For more information, visit cloud.oracle.com. Additional Resources •    Try it: cloud.oracle.com•    Learn more: http://www.oracle.com/us/corporate/features/complete-cloud/index.html•    Research Report: Cloud for Business Managers: The Good, the Bad, and the Ugly

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  • The long road to bug-free software

    - by Tony Davis
    The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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  • JQuery Json error: Object doesn't support this property or method

    - by Abu Hamzah
    ERROR: Microsoft JScript runtime error: Object doesn't support this property or method i am using WCF service to pull the data and its very simple for the purpose of test and it does returning me the data from wcf service but it fails on json2.js on line number 314-316 // We split the first stage into 4 regexp operations in order to work around // crippling inefficiencies in IE's and Safari's regexp engines. First we // replace all backslash pairs with '@' (a non-JSON character). Second, we // replace all simple value tokens with ']' characters. Third, we delete all // open brackets that follow a colon or comma or that begin the text. Finally, // we look to see that the remaining characters are only whitespace or ']' or // ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval. if (/^[\],:{}\s]*$/.test(text.replace(/\\["\\\/bfnrtu]/g, '@'). replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']'). replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) { here is what i am doing function serviceProxy(wjOrderServiceURL) { var _I = this; this.ServiceURL = wjOrderServiceURL; // *** Call a wrapped object this.invoke = function (options) { // Default settings var settings = { serviceMethod: '', data: null, callback: null, error: null, type: "POST", processData: false, contentType: "application/json", dataType: "text", bare: false }; if (options) { $.extend(settings, options); } function GetFederalHolidays() { $("#dContacts1").empty().html('Searching for Active Contacts...'); ContactServiceProxy.invoke({ serviceMethod: "Holidays", callback: function (response) { // ProcessActiveContacts1(response); debugger }, error: function (xhr, errorMsg, thrown) { postErrorAndUnBlockUI(xhr, errorMsg, thrown); } }); } any help what iam doing wrong? i try to change from dataType: text to json but i get the same error above.

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  • Interpret Objective C scripts at runtime on iPhone?

    - by Brad Parks
    Is there anyway to load an objective c script at runtime, and run it against the classes/methods/objects/functions in the current iPhone app? The reason i ask is that I've been playing around with iPhone wax, a lua interpreter that can be embedded in an iPhone app, and it works very nicely, in the sense that any object/method/function that's publically available in your Objective C code is automatically bridged, and available in lua. This allows you to rapidly prototype applications by simply making the core of your app be lua files that are in the users documents directory. Just reload the app, and you can test out changes to your lua files without needing to rebuild the app in XCode - a big time saver! But, with Apples recent 3.1.3 SDK stuff, it got me thinking that the safest approach for doing this type of rapid prototypeing would be if you could use Objective C as the interpreted code... That way, worst case scenario, you could just compile it into your app before your release, instead. I have heard that the lua source can be compiled to byte code, and linked in at build time, but I think the ultimate safe thing would be if the scripted source was in objective c, not lua. This leads me to wondering (i've searched, but come up with nothing) if there are any examples on how to embed an Objective C Interpreter in an iPhone app? This would allow you to rapidly prototype your app against the current classes that are built into your binary, and, when your about to deploy your app, instead of running the classes through the in app interpreter, you compile them in instead.

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  • Is this a good implementation of DefaultHttpClient and ThreadSafeClientConnManager in Android?

    - by johnrock
    In my Android app I am sharing one httpclient for all activities/threads. All requests are made by callling getHttpClient().execute(httpget) or getHttpClient().execute(httppost). Is this implementation complete/correct and safe for multiple threads? Is there anything else missing i.e. Do I have to worry about releasing connections at all? private static HttpClient httpclient ; public static HttpClient getHttpClient() { if(httpclient == null){ return getHttpClientNew(); } else{ return httpclient; } } public static synchronized HttpClient getHttpClientNew() { HttpParams params = new BasicHttpParams(); ConnManagerParams.setMaxTotalConnections(params, 100); HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1); HttpProtocolParams.setContentCharset(params, "UTF_8"); HttpProtocolParams.setUseExpectContinue(params, false); HttpConnectionParams.setConnectionTimeout(params, 10000); HttpConnectionParams.setSoTimeout(params, 10000); SchemeRegistry schemeRegistry = new SchemeRegistry(); schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80)); ClientConnectionManager cm = new ThreadSafeClientConnManager(params, schemeRegistry); httpclient = new DefaultHttpClient(cm, params); return httpclient; } This is an example of how the httpclient is used: private void update() { HttpGet httpget = new HttpGet(URL); httpget.setHeader(USER_AGENT, userAgent); httpget.setHeader(CONTENT_TYPE, MGUtils.APP_XML); HttpResponse response; try { response = getHttpClient().execute(httpget); HttpEntity entity = response.getEntity(); if (entity != null) { // parse stuff } } catch (Exception e) { } }

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  • XNA Xbox 360 Content Manager Thread freezing Draw Thread

    - by Alikar
    I currently have a game that takes in large images, easily bigger than 1MB, to serve as backgrounds. I know exactly when this transition is supposed to take place, so I made a loader class to handle loading these large images in the background, but when I load the images it still freezes the main thread where the drawing takes place. Since this code runs on the 360 I move the thread to the 4th hardware thread, but that doesn't seem to help. Below is the class I am using. Any thoughts as to why my new content manager which should be in its own thread is interrupting the draw in my main thread would be appreciated. namespace FileSystem { /// <summary> /// This is used to reference how many objects reference this texture. /// Everytime someone references a texture we increase the iNumberOfReferences. /// When a class calls remove on a specific texture we check to see if anything /// else is referencing the class, if it is we don't remove it. If there isn't /// anything referencing the texture its safe to dispose of. /// </summary> class TextureContainer { public uint uiNumberOfReferences = 0; public Texture2D texture; } /// <summary> /// This class loads all the files from the Content. /// </summary> static class FileManager { static Microsoft.Xna.Framework.Content.ContentManager Content; static EventWaitHandle wh = new AutoResetEvent(false); static Dictionary<string, TextureContainer> Texture2DResourceDictionary; static List<Texture2D> TexturesToDispose; static List<String> TexturesToLoad; static int iProcessor = 4; private static object threadMutex = new object(); private static object Texture2DMutex = new object(); private static object loadingMutex = new object(); private static bool bLoadingTextures = false; /// <summary> /// Returns if we are loading textures or not. /// </summary> public static bool LoadingTexture { get { lock (loadingMutex) { return bLoadingTextures; } } } /// <summary> /// Since this is an static class. This is the constructor for the file loadeder. This is the version /// for the Xbox 360. /// </summary> /// <param name="_Content"></param> public static void Initalize(IServiceProvider serviceProvider, string rootDirectory, int _iProcessor ) { Content = new Microsoft.Xna.Framework.Content.ContentManager(serviceProvider, rootDirectory); Texture2DResourceDictionary = new Dictionary<string, TextureContainer>(); TexturesToDispose = new List<Texture2D>(); iProcessor = _iProcessor; CreateThread(); } /// <summary> /// Since this is an static class. This is the constructor for the file loadeder. /// </summary> /// <param name="_Content"></param> public static void Initalize(IServiceProvider serviceProvider, string rootDirectory) { Content = new Microsoft.Xna.Framework.Content.ContentManager(serviceProvider, rootDirectory); Texture2DResourceDictionary = new Dictionary<string, TextureContainer>(); TexturesToDispose = new List<Texture2D>(); CreateThread(); } /// <summary> /// Creates the thread incase we wanted to set up some parameters /// Outside of the constructor. /// </summary> static public void CreateThread() { Thread t = new Thread(new ThreadStart(StartThread)); t.Start(); } // This is the function that we thread. static public void StartThread() { //BBSThreadClass BBSTC = (BBSThreadClass)_oData; FileManager.Execute(); } /// <summary> /// This thread shouldn't be called by the outside world. /// It allows the File Manager to loop. /// </summary> static private void Execute() { // Make sure our thread is on the correct processor on the XBox 360. #if WINDOWS #else Thread.CurrentThread.SetProcessorAffinity(new int[] { iProcessor }); Thread.CurrentThread.IsBackground = true; #endif // This loop will load textures into ram for us away from the main thread. while (true) { wh.WaitOne(); // Locking down our data while we process it. lock (threadMutex) { lock (loadingMutex) { bLoadingTextures = true; } bool bContainsKey = false; for (int con = 0; con < TexturesToLoad.Count; con++) { // If we have already loaded the texture into memory reference // the one in the dictionary. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(TexturesToLoad[con]); } if (bContainsKey) { // Do nothing } // Otherwise load it into the dictionary and then reference the // copy in the dictionary else { TextureContainer TC = new TextureContainer(); TC.uiNumberOfReferences = 1; // We start out with 1 referece. // Loading the texture into memory. try { TC.texture = Content.Load<Texture2D>(TexturesToLoad[con]); // This is passed into the dictionary, thus there is only one copy of // the texture in memory. // There is an issue with Sprite Batch and disposing textures. // This will have to wait until its figured out. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(TexturesToLoad[con]); Texture2DResourceDictionary.Add(TexturesToLoad[con], TC); } // We don't have the find the reference to the container since we // already have it. } // Occasionally our texture will already by loaded by another thread while // this thread is operating. This mainly happens on the first level. catch (Exception e) { // If this happens we don't worry about it since this thread only loads // texture data and if its already there we don't need to load it. } } Thread.Sleep(100); } } lock (loadingMutex) { bLoadingTextures = false; } } } static public void LoadTextureList(List<string> _textureList) { // Ensuring that we can't creating threading problems. lock (threadMutex) { TexturesToLoad = _textureList; } wh.Set(); } /// <summary> /// This loads a 2D texture which represents a 2D grid of Texels. /// </summary> /// <param name="_textureName">The name of the picture you wish to load.</param> /// <returns>Holds the image data.</returns> public static Texture2D LoadTexture2D( string _textureName ) { TextureContainer temp; lock (Texture2DMutex) { bool bContainsKey = false; // If we have already loaded the texture into memory reference // the one in the dictionary. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(_textureName); if (bContainsKey) { temp = Texture2DResourceDictionary[_textureName]; temp.uiNumberOfReferences++; // Incrementing the number of references } // Otherwise load it into the dictionary and then reference the // copy in the dictionary else { TextureContainer TC = new TextureContainer(); TC.uiNumberOfReferences = 1; // We start out with 1 referece. // Loading the texture into memory. try { TC.texture = Content.Load<Texture2D>(_textureName); // This is passed into the dictionary, thus there is only one copy of // the texture in memory. } // Occasionally our texture will already by loaded by another thread while // this thread is operating. This mainly happens on the first level. catch(Exception e) { temp = Texture2DResourceDictionary[_textureName]; temp.uiNumberOfReferences++; // Incrementing the number of references } // There is an issue with Sprite Batch and disposing textures. // This will have to wait until its figured out. Texture2DResourceDictionary.Add(_textureName, TC); // We don't have the find the reference to the container since we // already have it. temp = TC; } } } // Return a reference to the texture return temp.texture; } /// <summary> /// Go through our dictionary and remove any references to the /// texture passed in. /// </summary> /// <param name="texture">Texture to remove from texture dictionary.</param> public static void RemoveTexture2D(Texture2D texture) { foreach (KeyValuePair<string, TextureContainer> pair in Texture2DResourceDictionary) { // Do our references match? if (pair.Value.texture == texture) { // Only one object or less holds a reference to the // texture. Logically it should be safe to remove. if (pair.Value.uiNumberOfReferences <= 1) { // Grabing referenc to texture TexturesToDispose.Add(pair.Value.texture); // We are about to release the memory of the texture, // thus we make sure no one else can call this member // in the dictionary. Texture2DResourceDictionary.Remove(pair.Key); // Once we have removed the texture we don't want to create an exception. // So we will stop looking in the list since it has changed. break; } // More than one Object has a reference to this texture. // So we will not be removing it from memory and instead // simply marking down the number of references by 1. else { pair.Value.uiNumberOfReferences--; } } } } /*public static void DisposeTextures() { int Count = TexturesToDispose.Count; // If there are any textures to dispose of. if (Count > 0) { for (int con = 0; con < TexturesToDispose.Count; con++) { // =!THIS REMOVES THE TEXTURE FROM MEMORY!= // This is not like a normal dispose. This will actually // remove the object from memory. Texture2D is inherited // from GraphicsResource which removes it self from // memory on dispose. Very nice for game efficency, // but "dangerous" in managed land. Texture2D Temp = TexturesToDispose[con]; Temp.Dispose(); } // Remove textures we've already disposed of. TexturesToDispose.Clear(); } }*/ /// <summary> /// This loads a 2D texture which represnets a font. /// </summary> /// <param name="_textureName">The name of the font you wish to load.</param> /// <returns>Holds the font data.</returns> public static SpriteFont LoadFont( string _fontName ) { SpriteFont temp = Content.Load<SpriteFont>( _fontName ); return temp; } /// <summary> /// This loads an XML document. /// </summary> /// <param name="_textureName">The name of the XML document you wish to load.</param> /// <returns>Holds the XML data.</returns> public static XmlDocument LoadXML( string _fileName ) { XmlDocument temp = Content.Load<XmlDocument>( _fileName ); return temp; } /// <summary> /// This loads a sound file. /// </summary> /// <param name="_fileName"></param> /// <returns></returns> public static SoundEffect LoadSound( string _fileName ) { SoundEffect temp = Content.Load<SoundEffect>(_fileName); return temp; } } }

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  • Multithreading recommendation based on program description

    - by user260197
    I would like to describe some specifics of my program and get feedback on what the best multithreading model to use would be most applicable. I've spent a lot of time now reading on ThreadPool, Threads, Producer/Consumer, etc. and have yet to come to solid conclusions. I have a list of files (all the same format) but with different contents. I have to perform work on each file. The work consists of reading the file, some processing that takes about 1-2 minutes of straight number crunching, and then writing large output files at the end. I would like the UI interface to still be responsive after I initiate the work on the specified files. Some questions: What model/mechanisms should I use? Producer/Consumer, WorkPool, etc. Should I use a BackgroundWorker in the UI for responsiveness or can I launch the threading from within the Form as long as I leave the UI thread alone to continue responding to user input? How could I take results or status of each individual work on each file and report it to the UI in a thread safe way to give user feedback as the work progresses (there can be close to 1000 files to process) Update: Great feedback so far, very helpful. I'm adding some more details that are asked below: Output is to multiple independent files. One set of output files per "work item" that then themselves gets read and processed by another process before the "work item" is complete The work items/threads do not share any resources. The work items are processed in part using a unmanaged static library that makes use of boost libraries.

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  • Problem with Informix JDBC, MONEY and decimal separator in string literals

    - by Michal Niklas
    I have problem with JDBC application that uses MONEY data type. When I insert into MONEY column: insert into _money_test (amt) values ('123.45') I got exception: Character to numeric conversion error The same SQL works from native Windows application using ODBC driver. I live in Poland and have Polish locale and in my country comma separates decimal part of number, so I tried: insert into _money_test (amt) values ('123,45') And it worked. I checked that in PreparedStatement I must use dot separator: 123.45. And of course I can use: insert into _money_test (amt) values (123.45) But some code is "general", it imports data from csv file and it was safe to put number into string literal. How to force JDBC to use DBMONEY (or simply dot) in literals? My workstation is WinXP. I have ODBC and JDBC Informix client in version 3.50 TC5/JC5. I have set DBMONEY to just dot: DBMONEY=. EDIT: Test code in Jython: import sys import traceback from java.sql import DriverManager from java.lang import Class Class.forName("com.informix.jdbc.IfxDriver") QUERY = "insert into _money_test (amt) values ('123.45')" def test_money(driver, db_url, usr, passwd): try: print("\n\n%s\n--------------" % (driver)) db = DriverManager.getConnection(db_url, usr, passwd) c = db.createStatement() c.execute("delete from _money_test") c.execute(QUERY) rs = c.executeQuery("select amt from _money_test") while (rs.next()): print('[%s]' % (rs.getString(1))) rs.close() c.close() db.close() except: print("there were errors!") s = traceback.format_exc() sys.stderr.write("%s\n" % (s)) print(QUERY) test_money("com.informix.jdbc.IfxDriver", 'jdbc:informix-sqli://169.0.1.225:9088/test:informixserver=ol_225;DB_LOCALE=pl_PL.CP1250;CLIENT_LOCALE=pl_PL.CP1250;charSet=CP1250', 'informix', 'passwd') test_money("sun.jdbc.odbc.JdbcOdbcDriver", 'jdbc:odbc:test', 'informix', 'passwd') Results when I run money literal with dot and comma: C:\db_examples>jython ifx_jdbc_money.py insert into _money_test (amt) values ('123,45') com.informix.jdbc.IfxDriver -------------- [123.45] sun.jdbc.odbc.JdbcOdbcDriver -------------- there were errors! Traceback (most recent call last): File "ifx_jdbc_money.py", line 16, in test_money c.execute(QUERY) SQLException: java.sql.SQLException: [Informix][Informix ODBC Driver][Informix]Character to numeric conversion error C:\db_examples>jython ifx_jdbc_money.py insert into _money_test (amt) values ('123.45') com.informix.jdbc.IfxDriver -------------- there were errors! Traceback (most recent call last): File "ifx_jdbc_money.py", line 16, in test_money c.execute(QUERY) SQLException: java.sql.SQLException: Character to numeric conversion error sun.jdbc.odbc.JdbcOdbcDriver -------------- [123.45]

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  • Silverlight and Encryption, how to store/generate they key/iv pair?

    - by cmaduro
    I have a Silverlight app that connects to a php webservice. I want to encrypt the communication between the webservice and the Silverlight client. I'm not relying on SSL. I'm encrypting/decrypting the POST string myself using AES 256bit Key and IV. The big questions then are: How do I generate a random unique key/iv pair in PHP. How do I share this key/iv pair between the web service and silverlight client in a secure way. It seems impossible without having some kind of hard coded key or iv on the client. Which would compromise security. This is a public website, there are no logins. Just the requirement of secure communication. I can hard code the seed for the key/iv (which is hashed with SHA256 with a time stamp salt and then assigned as the key or iv) in PHP source code, that's on the server so that is pretty safe. However on the client the seed for the key/iv pair would be visible, if it is hard coded. Further more using a time stamp as the basis for uniqueness/randomness is definitely not ok, since timestamps are predictable. It does however provide a common factor between the C# code and the PHP code. The only other option that I can think of would be to have a 3rd service involved that provides the key/iv to the Silverlight client, as well as the php webservice. This of course start the cycle anew, with the question of how to store the credentials for accessing the key/iv distribution service on the Silverlight client. Sounds like the solution is then asymmetric encryption, since sensitive data will be viewed only on the administrative back end of the website. Unfortunately Silverlight has no asymmetric encryption classes. The solution? Roll my own Diffie-Hellman key exchange! Plug that key into AES256!

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  • Horizontal page curl in iPhone - I have - But Valid ?

    - by sagar
    Hello ! Every one. I was googling for applying horizontal page curl in iPhone. I also tried this, but it wasn't appropriate for me (To change orientation & work in different ori.). I tried to google more. Finally I got a link or link . From Where, I could Understand the horizontal page curl. But when I went to code deeply, I found some confusing points. Let me list down. Please download attached code - it's not my code. ( I am not selling any code, but Direct project link would be better than placing multiple codes here. ) extern NSString *kCAFilterPageCurl; // From QuartzCore.framework is it valid to use internal variable ? ( as it's mentioned - from QuartzCore ) CAFilter *previousFilter = [[CAFilter filterWithType:kCAFilterPageCurl] retain]; Above statement is giving warning ( not error ) - no '+filterWithType:' method found Might be using internal (apple's private) method. [previousFilter setDefaults]; Above statement is giving warning ( not error ) - no '-setDefaults:' method found Might be using internal (apple's private) method. Now My queries. I have above doubts in the project ( that might be using apple's private methods ). Is this code safe for apple store approval ? If 2's answer is wrong, what should be done for horizontal page curl ? In short, I want a horizontal page curl, But Need your suggestions for having the proper solution, which might not trouble me in future. Thanks in advance for your great help. Sagar.

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  • Full JSON-RPC specifications

    - by Artyom
    Hello, I'm going to implement JSON-PRC web service. I need specifications for this. So far I had found only one resource that can be called as real specifications: JSON-RPC 1.0 http://json-rpc.org/wiki/specification Proposal of JSON-PRC 2.0: http://groups.google.com/group/json-rpc/web/json-rpc-2-0 (why is it on google groups?) However I've seen that JavaScript frameworks like Dojo actively use JSON-RPC SMD Service Mapping Description proposal But it requires JSON Schema specifications, but it redirects to incorrect URL as reference. So far I had found following: http://tools.ietf.org/html/draft-zyp-json-schema-02 And it is still draft... Can anybody point me to spome actual specifications... At least something official updated? Because it looks like that implementing JSON-RPC 1.0 and 2.0 would not be enought, at least for frameworks like Dojo. Or am I wrong? Questions: Is it enough to implement JSON-RPC 1.0 specifications and 2.0 draft to be on safe side, would this work for most JSON-RPC clients? If I should implement SMD, or it is recommended can somebody point to official specifications of Json Schema and Service Mapping Description or links I found are really "specifications?" Note: do not suggest existing JSON-RPC service implementations.

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  • How do I get folder size with Exchange Web Services 2010 Managed API?

    - by Adam Tuttle
    I'm attempting to use EWS 2010 Managed API to get the total size of a user's mailbox. I haven't found a web service method to get this data, so I figured I would try to calculate it. I found one seemingly-applicable question on another site about finding mailbox sizes with EWS 2007, but either I'm not understanding what it's asking me to do, or that method just doesn't work with EWS 2010. Noodling around in the code insight, I was able to write what I thought was a method that would traverse the folder structure recursively and result in a combined total for all folders inside the Inbox: private int traverseChildFoldersForSize(Folder f) { int folderSizeSum = 0; if (f.ChildFolderCount > 0) { foreach (Folder c in f.FindFolders(new FolderView(10000))) { folderSizeSum += traverseChildFoldersForSize(c); } } folderSizeSum += (int)f.ManagedFolderInformation.FolderSize; return folderSizeSum; } (Assumes there aren't more than 10,000 folders inside a given folder. Figure that's a safe bet...) Unfortunately, this doesn't work. I'm initiating the recursion with this code: Folder root = Folder.Bind(svc, WellKnownFolderName.Inbox); int totalSize = traverseChildFoldersForSize(root); But a Null Pointer Exception is thrown, essentially saying that [folder].ManagedFolderInformation is a null object reference. For clarity, I also attempted to just get the size of the root folder: Console.Write(root.ManagedFolderInformation.FolderSize.ToString()); Which threw the same NPE exception, so I know that it's not just that once you get to a certain depth in the directory tree that ManagedFolderInformation doesn't exist. Any ideas on how to get the total size of the user's mailbox? Am I barking up the wrong tree?

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  • Visual Studio 2010 Can no longer build .NET v3.5

    - by Adam Driscoll
    I have a 2010 project that is targeting .NET v3.5. Inexplicably I can no longer build v3.5 projects. The project doesn't have ANY references added. It won't even let me add a reference to System.Core as it is added by the 'build system'. warning CS1685: The predefined type 'System.Func' is defined in multiple assemblies in the global alias; using definition from 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll' IFilter.cs(82,49): error CS0433: The type 'System.Func' exists in both 'c:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\v3.5\System.Core.dll' and 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll' Looks like something is grabbing onto 4.0 but I'm not quite sure how to fix it. Any one else run into this? Coworker had this same issue. It took a reinstall of Windows to correct the problem I've opened a bug on this one: https://connect.microsoft.com/VisualStudio/feedback/details/558245/warning-cs1685-when-compiling-a-v3-5-net-application-in-visual-studio-2010 If the compiler is set to verbose I see this: FrameworkPathOverride = C:\Windows\Microsoft.NET\Framework\v4.0.30319 which is defined as: Specifies the location of mscorlib.dll and microsoft.visualbasic.dll. This parameter is equivalent to the /sdkpath switch of the vbc.exe compiler. Some other interesting tidbits: I've created a new project all together and cannot build v3.5 at all. I can build 2.0, 3.0, 3.5 Client Profile, 4.0 and 4.0 Client Profile with no problem. VB.NET can build v3.5 but C# cannot. I've tried a reinstall of .NET 3.5, 4.0 and Visual Studio 2010 with no success. Visual Studio debug logs shown nothing interesting and Safe Mode does not work. Trying to avoid a Windows reinstall...

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  • powershell / runspace in a thread

    - by Vincent
    Hello ! I'm running the following code : RunspaceConfiguration config = RunspaceConfiguration.Create(); PSSnapInException warning; config.AddPSSnapIn("Microsoft.Exchange.Management.PowerShell.Admin", out warning); if (warning != null) throw warning; Runspace thisRunspace = RunspaceFactory.CreateRunspace(config); thisRunspace.Open(); string alias = usr.AD.CN.Replace(' ', '.'); string letter = usr.AD.CN.Substring(0, 1); string email = alias + "@" + (!usr.Mdph ? Constantes.AD_DOMAIN : Constantes.MDPH_DOMAIN) + "." + Constantes.AD_LANG; string db = "CN=IS-" + letter + ",CN=SG-" + letter + ",CN=InformationStore,CN=" + ((char)letter.ToCharArray()[0] < 'K' ? Constantes.EXC_SRVC : Constantes.EXC_SRVD) + Constantes.EXC_DBMEL; string cmd = "Enable-Mailbox -Identity \"" + usr.AD.CN + "\" -Alias " + alias + " -PrimarySmtpAddress " + email + " -DisplayName \"" + usr.AD.CN + "\" -Database \"" + db + "\""; Pipeline thisPipeline = thisRunspace.CreatePipeline(cmd); thisPipeline.Invoke(); The code is running in a thread created that way : t.WorkThread = new Thread(cu.CreerUser); t.WorkThread.Start(); If I run the code directly (not through a thread), it's working. When in a thread it throws the following exception : ObjectDisposedException "The safe handle has been closed." (Translated from french) I then replaced "Open" wirh "OpenAsync" which helped not getting the previous exception. But when on Invoke I get the following exception : InvalidRunspaceStateException "Unable to call the pipeline because its state of execution is not Opened. Its current state is Opening." (Also translated from french) I'm clueless... Any help welcome !!! Thanks !!!

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  • malloc: error checking and freeing memory

    - by yCalleecharan
    Hi, I'm using malloc to make an error check of whether memory can be allocated or not for the particular array z1. ARRAY_SIZE is a predefined with a numerical value. I use casting as I've read it's safe to do so. long double *z1 = (long double *)malloc(sizeof (long double) * ARRAY_SIZE); if(z1 == NULL){ printf("Out of memory\n"); exit(-1); } The above is just a snippet of my code, but when I add the error checking part (contained in the if statement above), I get a lot of compile time errors with visual studio 2008. It is this error checking part that's generating all the errors. What am I doing wrong? On a related issue with malloc, I understand that the memory needs to be deallocated/freed after the variable/array z1 has been used. For the array z1, I use: free(z1); z1 = NULL; Is the second line z1 = NULL necessary? Thanks a lot...

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  • Saving record in Subsonic 3 using Active Record

    - by singfoom
    I'm having trouble saving a record in Subsonic 3 using Active record. I've generated my objects using the DALs and tts and everything seems fine because the following test passes. I think that my connection string is correct or the generation wouldn't have succeeded. [Test] public void TestSavingAnEmail() { Email testEmail = new Email(); testEmail.EmailAddress = "[email protected]"; testEmail.Subscribed = true; testEmail.Save(); Assert.AreEqual(1, Email.All().Count()); } On the live side, the following code fails: protected void btEmailSubmit_Click(object sender, EventArgs e) { Email email = new Email(); email.EmailAddress = txtEmail.Text; email.Subscribed = chkSubscribe.Checked; email.Save(); } with a message of: Need to specify Values or a Select query to insert - can't go on! at the following line repo.Add(this,provider); line in my ActiveRecord.cs: public void Add(IDataProvider provider){ var key=KeyValue(); if(key==null){ var newKey=_repo.Add(this,provider); this.SetKeyValue(newKey); }else{ _repo.Add(this,provider); } SetIsNew(false); OnSaved(); } Am I doing something horribly wrong here? The save and add methods have parameterless overloads that I thought were safe to use. Do I need to pass a provider? I've googled around for this for a while and was unable to come up with anything specific to my situation. Thanks in advance for any kind of answer.

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  • Debugging StoreKit functionality without a device

    - by Rolf Staflin
    Hi! I'm porting an app with in-app purchase functionality from the iPhone to the iPad, but the simulator doesn't handle any StoreKit calls (they fail immediately with a warning). Since there are no iPads available yet, I can't use a device for debugging. I have thought of a few alternatives: Use the iPhone code as is. This is the safe bet since everything already works on the iPhone, but it will not feel right on the iPad (there are several ViewControllers in a NavigationController involved on the iPhone, but everything could fit on one screen on the pad). Write a test framework for StoreKit. I actually started doing this, but I won't be able to finish it in time. Submit untested code and pray. Nah, just kidding -- that's not an option :) So, any thoughts? Has anyone else written a test framework for this kind of thing? I googled a bit but couldn't find anything. I'm grateful for any thoughts on this!

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  • How to get current Joomla user with external PHP script

    - by Joey Adams
    I have a couple PHP scripts used for AJAX queries, but I want them to be able to operate under the umbrella of Joomla's authentication system. Is the following safe? Are there any unnecessary lines? joomla-auth.php (located in the same directory as Joomla's index.php): <?php define( '_JEXEC', 1 ); define('JPATH_BASE', dirname(__FILE__)); define( 'DS', DIRECTORY_SEPARATOR ); require_once ( JPATH_BASE .DS.'includes'.DS.'defines.php' ); require_once ( JPATH_BASE .DS.'includes'.DS.'framework.php' ); /* Create the Application */ $mainframe =& JFactory::getApplication('site'); /* Make sure we are logged in at all. */ if (JFactory::getUser()->id == 0) die("Access denied: login required."); ?> test.php: <?php include 'joomla-auth.php'; echo 'Logged in as "' . JFactory::getUser()->username . '"'; /* We then proceed to access things only the user of that name has access to. */ ?>

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  • Hadoop safemode recovery - taking lot of time

    - by Algorist
    Hi, We are running our cluster on Amazon EC2. we are using cloudera scripts to setup hadoop. On the master node, we start below services. 609 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start namenode' 610 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start secondarynamenode' 611 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start jobtracker' 612 613 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop dfsadmin -safemode wait' On the slave machine, we run the below services. 625 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start datanode' 626 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start tasktracker' The main problem we are facing is, hdfs safemode recovery is taking more than an hour and this is causing delays in our job completion. Below are the main log messages. 1. domU-12-31-39-0A-34-61.compute-1.internal 10/05/05 20:44:19 INFO ipc.Client: Retrying connect to server: ec2-184-73-64-64.compute-1.amazonaws.com/10.192.11.240:8020. Already tried 21 time(s). 2. The reported blocks 283634 needs additional 322258 blocks to reach the threshold 0.9990 of total blocks 606499. Safe mode will be turned off automatically. The first message is thrown in task trackers log because, job tracker is not started. job tracker didn't start because of hdfs safemode recovery. The second message is thrown during the recovery process. Is there something I am doing wrong? How much time does normal hdfs safemode recovery takes? Will there be any speedup, by not starting task trackers till job tracker is started? Are there any known hadoop problems on amazon cluster? Thanks for your help. Regards Bala Mudiam

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  • System.Web.Caching vs. Enterprise Library Caching Block

    - by ESV
    For a .NET component that will be used in both web applications and rich client applications, there seem to be two obvious options for caching: System.Web.Caching or the Ent. Lib. Caching Block. What do you use? Why? System.Web.Caching Is this safe to use outside of web apps? I've seen mixed information, but I think the answer is maybe-kind-of-not-really. a KB article warning against 1.0 and 1.1 non web app use The 2.0 page has a comment that indicates it's OK: http://msdn.microsoft.com/en-us/library/system.web.caching.cache(VS.80).aspx Scott Hanselman is creeped out by the notion The 3.5 page includes a warning against such use Rob Howard encouraged use outside of web apps I don't expect to use one of its highlights, SqlCacheDependency, but the addition of CacheItemUpdateCallback in .NET 3.5 seems like a Really Good Thing. Enterprise Library Caching Application Block other blocks are already in use so the dependency already exists cache persistence isn't necessary; regenerating the cache on restart is OK Some cache items should always be available, but be refreshed periodically. For these items, getting a callback after an item has been removed is not very convenient. It looks like a client will have to just sleep and poll until the cache item is repopulated. Memcached for Win32 + .NET client What are the pros and cons when you don't need a distributed cache?

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  • How to get PHP command line to work with PDO?

    - by Sabya
    I want to work with PDO, through PHP command line. It works perfect through the PHP web API, but not through the command line. But when I execute the command: php test.php, it says unknown class PDO. I think it has something to do with the thread-safety difference. Because, when I execute the above command, the following warnings come: - F:\shema\htdocs>php test.php PHP Warning: PHP Startup: soap: Unable to initialize module Module compiled with module API=20060613, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=1 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: sockets: Unable to initialize module Module compiled with module API=20060613, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=1 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: mysql: Unable to initialize module Module compiled with module API=20060613, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=1 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: pdo_mysql: Unable to initialize module Module compiled with module API=20060613, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=1 These options need to match in Unknown on line 0 PHP Warning: PHP Startup: pdo_pgsql: Unable to initialize module Module compiled with module API=20060613, debug=0, thread-safety=0 PHP compiled with module API=20060613, debug=0, thread-safety=1 These options need to match in Unknown on line 0 PHP Fatal error: Class 'PDO' not found in F:\shema\htdocs\test.php on line 2 PHP version: 5.2.9-2, downloaded from here. OS: Windows Vista If the problem is with the modules, where do I get the thread safe modules for those modules?

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  • Problem reading from two separate InputStreams

    - by Emil H
    I'm building a Yammer client for Android in Scala and have encountered the following issue. When two AsyncTasks try to parse an XML response (not the same, each task has it's own InputStream) from the Yammer API the underlying stream throws a IOException with the message "null SSL pointer", as seen below: Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception java.lang.RuntimeException: An error occured while executing doInBackground() at android.os.AsyncTask$3.done(AsyncTask.java:200) at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258) at java.util.concurrent.FutureTask.run(FutureTask.java:122) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) at java.lang.Thread.run(Thread.java:1060) Caused by: java.io.IOException: null SSL pointer at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.nativeread(Native Method) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.access$300(OpenSSLSocketImpl.java:55) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl$SSLInputStream.read(OpenSSLSocketImpl.java:524) at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103) at org.apache.http.impl.io.AbstractSessionInputBuffer.read(AbstractSessionInputBuffer.java:134) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:174) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:188) at org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:178) at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:504) at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:467) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:329) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:286) at javax.xml.parsers.SAXParser.parse(SAXParser.java:361) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:28) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:12) ..... Searching for the error didn't give much clarity. Does this have something to do with the response from the server? Or is it something else? Complete code can be found at: http://github.com/archevel/YammerTime I get no error if I wait until the first repsponse is finished and then let the other complete. The request is made with the DefaultHttpClient, but this is supposedly thread safe. What am I missing? If anything needs to be clarified just ask :) Cheers, Emil H

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  • Hidden features of Perl?

    - by Adam Bellaire
    What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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