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  • Iphone Core Data Internal Inconsistency

    - by kiyoshi
    This question has something to do with the question I posted here: http://stackoverflow.com/questions/1230858/iphone-core-data-crashing-on-save however the error is different so I am making a new question. Now I get this error when trying to insert new objects into my managedObjectContext: *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '"MailMessage" is not a subclass of NSManagedObject.' But clearly it is: @interface MailMessage : NSManagedObject { .... And when I run this code: NSManagedObjectModel *managedObjectModel = [[self.managedObjectContext persistentStoreCoordinator] managedObjectModel]; NSEntityDescription *entity =[[managedObjectModel entitiesByName] objectForKey:@"MailMessage"]; NSManagedObject *newObject = [[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:self.managedObjectContext]; It runs fine when I do not present an MFMailComposeViewController, but if I run this code in the - (void)mailComposeController:(MFMailComposeViewController*)controller didFinishWithResult:(MFMailComposeResult)result error:(NSError*)error { method, it throws the above error when creating the newObject variable. The entity object when I use print object produces the following: (<NSEntityDescription: 0x1202e0>) name MailMessage, managedObjectClassName MailMessage, renamingIdentifier MailMessage, isAbstract 0, superentity name (null), properties { in both cases, so I don't think the managedObjectContext is completely invalid. I have no idea why it would say MailMessage is not a subclass of NSManagedObject at that point, and not at the other. Any help would be appreciated, thanks in advance.

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  • Cannot make a static reference to the non-static type MyRunnable

    - by kaiwii ho
    Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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  • pthread_create followed by pthread_detach still results in possibly lost error in Valgrind.

    - by alesplin
    I'm having a problem with Valgrind telling me I have some memory possible lost: ==23205== 544 bytes in 2 blocks are possibly lost in loss record 156 of 265 ==23205== at 0x6022879: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==23205== by 0x540E209: allocate_dtv (in /lib/ld-2.12.1.so) ==23205== by 0x540E91D: _dl_allocate_tls (in /lib/ld-2.12.1.so) ==23205== by 0x623068D: pthread_create@@GLIBC_2.2.5 (in /lib/libpthread-2.12.1.so) ==23205== by 0x758D66: MTPCreateThreadPool (MTP.c:290) ==23205== by 0x405787: main (MServer.c:317) The code that creates these threads (MTPCreateThreadPool) basically gets an index into a block of waiting pthread_t slots, and creates a thread with that. TI becomes a pointer to a struct that has a thread index and a pthread_t. (simplified/sanitized): for (tindex = 0; tindex < NumThreads; tindex++) { int rc; TI = &TP->ThreadInfo[tindex]; TI->ThreadID = tindex; rc = pthread_create(&TI->ThreadHandle,NULL,MTPHandleRequestsLoop,TI); /* check for non-success that I've omitted */ pthread_detach(&TI->ThreadHandle); } Then we have a function MTPDestroyThreadPool that loops through all the threads we created and cancels them (since the MTPHandleRequestsLoop doesn't exit). for (tindex = 0; tindex < NumThreads; tindex++) { pthread_cancel(TP->ThreadInfo[tindex].ThreadHandle); } I've read elsewhere (including other questions here on SO) that detaching a thread explicitly would prevent this possibly lost error, but it clearly isn't. Any thoughts?

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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • ASP.Net MVC: Change Routes dynamically

    - by Frank
    Hi, usually, when I look at a ASP.Net MVC application, the Route table gets configured at startup and is not touched ever after. I have a couple of questions on that but they are closely related to each other: Is it possible to change the route table at runtime? How would/should I avoid threading issues? Is there maybe a better way to provide a dynamic URL? I know that IDs etc. can appear in the URL but can't see how this could be applicable in what I want to achieve. How can I avoid that, even though I have the default controller/action route defined, that default route doesn't work for a specific combination, e.g. the "Post" action on the "Comments" controller is not available through the default route? Background: Comment Spammers usually grab the posting URL from the website and then don't bother to go through the website anymore to do their automated spamming. If I regularly modify my post URL to some random one, spammers would have to go back to the site and find the correct post URL to try spamming. If that URL changes constantly I'd think that that could make the spammers' work more tedious, which should usually mean that they give up on the affected URL.

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  • mysql select update

    - by Tillebeck
    Hi I have read quite a few selcet+update questions in here but cannot understand how to do it. So will have to ask from the beginning. I would like to update a table based on data in another table. Setup is like this: - TABLE a ( int ; string ) ID WORD 1 banana 2 orange 3 apple - TABLE b ( "comma separated" string ; string ) WORDS TEXTAREA 0 banana -> 0,1 0 orange apple apple -> BEST:0,2,3 ELSE 0,2,3,3 0 banana orange apple -> 0,1,2,3 Now I would like to for each word in TABLE a append ",a.ID" to b.WORDS like: SELECT id, word FROM a (for each) -> UPDATE b SET words = CONCAT(words, ',', a.id) WHERE b.textarea like %a.word% Or even better: replace the word found in b.textarea with ",a.id" so it is the b.textarea that ends up beeing a comma separeted string of id's... But I do not know if that is possible.

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  • Adding new records in Access without wrecking the form

    - by Matt Parker
    I'm working on a simple Access 2003 application to keep track of things that need to be done for clients for some colleagues. Each colleague has a set of clients, and each client has a set of actions that need to be taken by a certain date. I've set up a form that consists of a combobox for client ID (indexed), a drop-down for the person who is handling that client's case, and a button for adding new clients (a standard Access-created Add Record button). The actions are listed in a subform below these three elements. The problem I've run into is that the first person I tested this on clicked the button to add a new record, then didn't fill it out and tried to select another client from the drop-down list. Access interprets this as an attempt to set the selected Client ID as the ID for the new record and rightfully throws an error for duplicate primary keys. I can think of a couple of ways around this problem, but I'd much rather hear your elegant solutions than kludge together some junk in a language I don't know. Let me know if you have any questions. Thank you.

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  • Using boost::random to select from an std::list where elements are being removed

    - by user144182
    See this related question on more generic use of the Boost Random library. My questions involves selecting a random element from an std::list, doing some operation, which could potentally include removing the element from the list, and then choosing another random element, until some condition is satisfied. The boost code and for loop look roughly like this: // create and insert elements into list std::list<MyClass> myList; //[...] // select uniformly from list indices boost::uniform_int<> indices( 0, myList.size()-1 ); boost::variate_generator< boost::mt19937, boost::uniform_int<> > selectIndex(boost::mt19937(), indices); for( int i = 0; i <= maxOperations; ++i ) { int index = selectIndex(); MyClass & mc = myList.begin() + index; // do operations with mc, potentially removing it from myList //[...] } My problem is as soon as the operations that are performed on an element result in the removal of an element, the variate_generator has the potential to select an invalid index in the list. I don't think it makes sense to completely recreate the variate_generator each time, especially if I seed it with time(0).

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  • Python-based password tracker (or dictionary)

    - by Arrieta
    Hello: Where we work we need to remember about 10 long passwords which need to change every so often. I would like to create a utility which can potentially save these passwords in an encrypted file so that we can keep track of them. I can think of some sort of dictionary passwd = {'host1':'pass1', 'host2':'pass2'}, etc, but I don't know what to do about encryption (absolutely zero experience in the topic). So, my question is really two questions: Is there a Linux-based utility which lets you do that? If you were to program it in Python, how would you go about it? A perk of approach two, would be for the software to update the ssh public keys after the password has been changed (you know the pain of updating ~15 tokens once you change your password). As it can be expected, I have zero control over the actual network configuration and the management of scp keys. I can only hope to provide a simple utility to me an my very few coworkers so that, if we need to, we can retrieve a password on demand. Cheers.

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  • How to create a desktop shortcut to a website with website logo as icon?

    - by Wbdvlpr
    Hi I need a solution which allows users to create a desktop shortcut to a website, preferably with website logo as shortcut icon. There are ways users can create shortcut such as drag drop favicon or right click create new shortcut etc. This works but also creates the shortcut with default IE icon on windows. I am trying to avoid this method for this icon and some other reasons. I thought of creating a website-title.URL file, and tell users to download and save file to their desktop, again this works but doesn't solve the icon problem as the website logo (.ico) has to be at local disk and at a pre-specified location [IconFile=path]. I was wondering if it is possible to create a some sort of installer or windows application which users can download from the website. Once its executed by user, it creates this .URL file on user desktop which have IconFile path pre-specified, and copy the website-logo.ico at path specified in .URL file etc. So my questions are - Is it possible to create such a solution? What programming languages can be used to achieve this? Can this installer/app be made to work on non-windows machines as well? From developments point of view how big project it is? if I have to hire a programmer to do this. Please let me know if you need more information. Thanks

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  • LINQ EF not saving to database...

    - by Keith Barrows
    I guess this is a continuation of the last question I asked: http://stackoverflow.com/questions/2587542/bulk-insert-and-update-with-ado-net-entity-framework. I am not getting any errors while doing inserts yet no data is actually going into my DB. My DB is a SDF file (SQL CE). Any ideas what to check? My app.config looks like: <?xml version="1.0" encoding="utf-8"?> <configuration> <configSections> </configSections> <connectionStrings> <add name="Lab_Use_Billing.Properties.Settings.LabUseConnectionString" connectionString="Data Source=|DataDirectory|\Models\LabUse.sdf" providerName="Microsoft.SqlServerCe.Client.3.5" /> <add name="LabUseEntities" connectionString="metadata=res://*/Models.LabUseEntities.csdl|res://*/Models.LabUseEntities.ssdl|res://*/Models.LabUseEntities.msl; provider=System.Data.SqlServerCe.3.5; provider connection string=&quot;Data Source=|DataDirectory|\Models\LabUse.sdf&quot;" providerName="System.Data.EntityClient" /> </connectionStrings> </configuration> TIA

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  • Why C++ is (one of) the best language to learn at first [closed]

    - by AlexV
    C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's the one who will reward the most in long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Why C++ is for you (one of) the best language to learn at first. Since it's subjective, I've marked this question as community wiki.

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  • Browser timing out attempting to load images

    - by notJim
    I've got a page on a webapp that has about 13 images that are generated by my application, which is written in the Kohana PHP framework. The images are actually graphs. They are cached so they are only generated once, but the first time the user visits the page, and the images all have to be generated, about half of the images don't load in the browser. Once the page has been requested once and images are cached, they all load successfully. Doing some ad-hoc testing, if I load an individual image in the browser, it takes from 450-700 ms to load with an empty cache (I checked this using Google Chrome's resource tracking feature). For reference, it takes around 90-150 ms to load a cached image. Even if the image cache is empty, I have the data and some of the application's startup tasks cached, so that after the first request, none of that data needs to be fetched. My questions are: Why are the images failing to load? It seems like the browser just decides not to download the image after a certain point, rather than waiting for them all to finish loading. What can I do to get them to load the first time, with an empty cache? Obviously one option is to decrease the load times, and I could figure out how to do that by profiling the app, but are there other options? As I mentioned, the app is in the Kohana PHP framework, and it's running on Apache. As an aside, I've solved this problem for now by fetching the page as soon as the data is available (it comes from a batch process), so that the images are always cached by the time the user sees them. That feels like a kludgey solution to me, though, and I'm curious about what's actually going on.

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  • Updating a composite primary key

    - by VBCSharp
    I am struggling with the philosophical discussions about whether or not to use composite primary keys on my SQL Server database. I have always used the surrogate keys in the past and I am challenging myself by leaving my comfort zone to try something different. I have read many discussion but can't come to any kind of solution yet. The struggle I am having is when I have to update a record with the composite PK. For example, the record in questions is like this: ContactID, RoleID, EffectiveDate, TerminationDT. The PK in this case is the ContactID, RoleID, and EffectiveDate. TerminationDT can be null. If in my UI, the user changes the RoleID and then I need to update the record. Using the surrogate key I can do an Update Table Set RoleID = 1 WHERE surrogateID = Z. However, using the Composite Key way, once one of the fields in the composite key changes I have no way to reference the old record to update it without now maintaining somewhere in the UI a reference to the old values. I do not bind datasources in my UI. I open a connection, get the data and store it in a bucket, then close the connection. What are everyone's opinions? Thanks.

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  • Best way to run multiple queries per second on database, performance wise?

    - by Michael Joell
    I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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  • Why can’t PHP script write a file on server 2008 via command line or task scheduler?

    - by rg89
    I created a question on serverfault.com, and it was recommended that I ask here. http://serverfault.com/questions/140669/why-cant-php-script-write-a-file-on-server-2008-via-command-line-or-task-schedul I have a PHP script. It runs well when I use a browser. It writes an XML file in the same directory. The script takes ~60 seconds to run, and the resulting XML file is ~16 MB. I am running PHP 5.2.13 via FastCGI on Windows Server Web edition SP1 64 bit. The code pulls inventory from SQL server, runs a loop to build an XML file for a third party. I created a task in task scheduler to run c:\php5\php.exe "D:\inetpub\tools\build.php" The task scheduler shows a time lapse of about a minute, which is how long the script takes to run in a browser. No error returned, but no file created. Each time I make a change to the scheduled task properties, a user password box comes up and I enter the administrator account password. If I run this same path and argument at a command line it does not error and does not create the file. When I right click run command prompt as an administrator, the file is still not created. I get my echo statement "file published" that is after the file creation and no error is returned. I am doing a simple fopen fwrite fclose to save the contents of a php variable to a .xml file, and the file only gets created when the script is run through the browser. Here's what happens after the xml-building loop: $feedContent .= "</feed"; sqlsrv_close( $conn ); echo "<p>feed built</p>"; $feedFile = "feed.xml"; $handler = fopen($feedFile, 'w'); fwrite( $handler, $feedContent ); fclose( $handler ); echo "<p>file published</p>"; Thanks

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  • Fast find object by string property

    - by Andrew Kalashnikov
    Hello, colleagues. I've got task to fast find object by its string property. Object: class DicDomain { public virtual string Id{ get; set; } public virtual string Name { get; set; } } For storing my object I use List[T] dictionary where T is DicDomain for now . I've got 5-10 such lists, which contain about 500-20000 at each one. Task is find objects by its Name. I use next code now: List<T> entities = dictionary.FindAll(s => s.Name.Equals(word, StringComparison.OrdinalIgnoreCase)); I've got some questions: Is my search speed optimal. I think now. Data structure. It List good for this task. What about hashtable,sorted... Method Find. May be i should use string intern?? I haven't much exp at these tasks. Can u give me good advice for increase perfomance. Thanks

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  • How can I run some common code from both (a) scheduled via Windows Task & (b) manually from within W

    - by Greg
    Hi, QUESTION - How can I run some common code from both (a) scheduled via Windows Task & (b) manually from within WinForms app? BACKGROUND: This follows on from the http://stackoverflow.com/questions/2489999/how-can-i-schedule-tasks-in-a-winforms-app thread REQUIREMENTS C# .NETv3.5 project using VS2008 There is an existing function which I want to run both (a) manually from within the WinForms application, and (b) scheduled via Windows Task. APPROACHES So what I'm trying to understand is what options are there to make this work eg Is it possible for a windows task to trigger a function to run within a running/existing WinForms application? (doesn't sound solid I guess) Split code out into two projects and duplicate for both console application that the task manager would run AND code that the winforms app would run Create a common library and re-use this for both the above-mentioned projects in the bullet above Create a service with an interface that both the task manager can access plus the winforms app can manage Actually each of these approaches sounds quite messy/complex - would be really nice to drop back to have the code only once within the one project in VS2008, the only reason I ask about this is I need to have a scheduling function and the suggestion has been to use http://taskscheduler.codeplex.com/ as the means to do this, which takes the scheduling out of my VS2008 project... thanks

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  • CodeModel help needed for right-hand singleton.getinstance() assignment.

    - by antarti
    I've been able to generate 99% of what I need with the CodeModel API, but I am stumped here... Using the various "directXX" methods does not add import statements to the generated code, and I can work without the "directXXX" type of methods except for one place in a generated class. Suppose I desire a generated method like: /** * Copies data from this Value-Obj instance, to the returned PERSON instance. * * @return PERSON * */ public PERSON mapVOToPERSON() throws MappingException { Mapper mapper = (com.blah.util.MapperSingleton.getMapperInstance()); return mapper.map(this, PERSON.class); } You can see the right hand of the Mapper assignment in parens. Emitting the entire package+class was the only way I could find to just declare "SomeSingleton.someMethod()" on the right hand side and have the generated code compile. Without the MapperSingleton being added to the object model, there is no import generated... Questions: 1) Is there a way to force an import to be generated? 2) How to declare an expression that gives me the right side of the Mapper assignment within the object model (so that an import of MapperSingleton gets generated. Any help appreciated...

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  • forcing a download using PHP / jQuery

    - by Dirty-flow
    I know there are already many questions about forcing a download with PHP, but I can't find what I'm doing wrong and what should I do. I'm having an list with filenames, and I want to download one of them by clicking a button. My jQuery: $(".MappeDownload").on("click",function(e){ e.stopPropagation(); fileId=$(this).val() $.post("ajax/DownloadFile.php",{ id : fileId}) }) and on the server side I have a table with the file names and the file path. $sql = "SELECT vUploadPfad, vUploadOriginname FROM tabUpload WHERE zUploadId='$_POST[id]'"; $result = mysql_query($sql) or die(""); $file = mysql_fetch_array($result); $localfile = $file["vUploadPfad"]; $name=$file["vUploadOriginname"]; $fp = fopen($localfile, 'rb'); header("Cache-Control: "); header("Pragma: "); header("Content-Type: application/octet-stream"); header("Content-Length: " . filesize($localfile)); header("Content-Disposition: attachment; filename='".$name."';"); header("Content-Transfer-Encoding: binary\n"); fpassthru($fp); exit; The AJAX request is successful, I'm getting the right header(filesize, filename etc...) but the download are not starting.

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  • Security of Flex for payment website

    - by Mario
    So, it's been about 3 years since I wrote and went live with my company's main internet facing website. Originally written in php, I've since just been making minor changes here and there to progress the site as we've needed to. I've wanted to rewrite it from the ground up in the last year or so and now, we want to add some major features so this is a perfect time. The website in question is as close to a banking website as you'd get (without being a bank; sorry for the obscurity, but the less info I can give out, the better). For the rewrite, I want to separate the presentation layer from the processing layer as much as I can. I want the end user to be stuck in a box and not be able to get out so to speak (this is all because of PCI complacency, being PEN tested every 3 months, etc...) So, being probed every 3 months has increasingly made me nervous. We haven't failed yet and there hasen't been a breach yet, but I want to make sure I continue to pass (as much as I can anyways) So, I'm considering rewriting the presentation layer in Adobe Flex and do all the processing in PHP (effectively IMO, separating presentation from processing) - I would do all my normal form validation in flex (as opposed to javascript or php) and do my reads and writes to the db via php. My questions are: I know Flash has something like 99% market penetration - do people find this to be true? Has anyone seen on their own sites being in flash that someone couldn't access it? Flash in general has come under alot of attacks about security and the like - i know this. I would use a swf encryptor - disable debugging (which i got snagged on once on a different application), continue to use https and any other means i can think of. At the end of the day, everyone knows if someone wants in to the data bad enough, their going to find a ways in; i just wanna make it as difficult for them as i can. Any thoughts are appreciated. -Mario

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  • PHP – Slow String Manipulation

    - by Simon Roberts
    I have some very large data files and for business reasons I have to do extensive string manipulation (replacing characters and strings). This is unavoidable. The number of replacements runs into hundreds of thousands. It's taking longer than I would like. PHP is generally very quick but I'm doing so many of these string manipulations that it's slowing down and script execution is running into minutes. This is a pain because the script is run frequently. I've done some testing and found that str_replace is fastest, followed by strstr, followed by preg_replace. I've also tried individual str_replace statements as well as constructing arrays of patterns and replacements. I'm toying with the idea of isolating string manipulation operation and writing in a different language but I don't want to invest time in that option only to find that improvements are negligible. Plus, I only know Perl, PHP and COBOL so for any other language I would have to learn it first. I'm wondering how other people have approached similar problems? I have searched and I don't believe that this duplicates any existing questions.

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  • Generic applet style system for publishing mathematics demonstrations?

    - by Alex
    Anyone who's tried to study mathematics using online resources will have come across these Java applets that demonstrate a particular mathematical idea. Examples: http://www.math.ucla.edu/~tao/java/Mobius.html http://www.mathcs.org/java/programs/FFT/index.html I love the idea of this interactive approach because I believe it is very helpful in conveying mathematical principles. I'd like to create a system for visually designing and publishing these 'mathlets' such that they can be created by teachers with little programming experience. So in order to create this app, i'll need a GUI and a 'math engine'. I'll probably be working with .NET because thats what I know best and i'd like to start experimenting with F#. Silverlight appeals to me as a presentation framework for this project (im not worried about interoperability right now). So my questions are: does anything like this exist already in full form? are there any GUI frameworks for displaying mathematical objects such as graphs & equations? are there decent open source libraries that exposes a mathematical framework (Math.NET looks good, just wondering if there is anything else out there) is there any existing work on taking mathematical models/demos built with maple/matlab/octave/mathematica etc and publishing them to the web?

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  • Qt display image in a new window

    - by user312543
    Hi, I am naive to Qt and GUI programming. http://stackoverflow.com/questions/1357960/qt-jpg-image-display/2605463#2605463 The procedure given for displaying an image is working fine and thank you for providing that. But I want to display an image when I click on radiobutton. I created a slot, and I connected the button click event to the slot (dispImage is my slot). My slot consists only the code which is working to display an image (First answer in this link). I am able to compile it and run it. But the o/p is not as we desire. On button click, image windoe flashes for a sec and disappears. One more point to share is, I tried the same with windowsflags example present in qt examples. In this example I want to display the image on the preview window created by us. Even this is also not worked for me. Please provide me the solution. Thanks in advance.

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  • Why doesn't String's hashCode() cache 0?

    - by polygenelubricants
    I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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