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• calling constructor of the class in the destructor of the same class

  - by dicaprio

  Experts !! I know this question is one of the lousy one , but still I dared to open my mind , hoping I would learn from all. I was trying some examples as part of my routine and did this horrible thing, I called the constructor of the class from destructor of the same class. I don't really know if this is ever required in real programming , I cant think of any real time scenarios where we really need to call functions/CTOR in our destructor. Usually , destructor is meant for cleaning up. If my understanding is correct, why the compiler doesn't complain ? Is this because it is valid for some good reasons ? If so what are they ? I tried on Sun Forte, g++ and VC++ compiler and none of them complain about it. using namespace std; class test{ public: test(){ cout<<"CTOR"<<endl; } ~test() {cout<<"DTOR"<<endl; test(); }};

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• Why would one want to use the public constructors on Boolean and similar immutable classes?

  - by Robert J. Walker

  (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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• Purpose of singletons in programming

  - by thecoshman

  This is admittedly a rather loose question. My current understanding of singletons is that they are a class that you set up in such a way that only one instance is ever created. This sounds a lot like a static class to me. The main differnce being that with a static class you don't / can't instance it, you just use it such as Math.pi(). With a singletong class, you would still need to do something like singleton mySingleton = new singleton(); mysingleton.set_name("foo"); singleton otherSingleton = new singleton(); // correct me if i am wrong, but mysingleton == othersingleton right now, yes? // this the following should happen? otherSingleston.set_name("bar"); mysingleton.report_name(); // will output "bar" won't it? Please note, I am asking this language independently, more about the concept. So I am not so worried about actually how to coed such a class, but more why you would wan't to and what thing you would need to consider.

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• trying to reenter IT field after a break of over 5 years

  - by josephj1989

  Hello I have had some misfortune in life - I was unwell and had to stay out of work for an extended period of about 5 years.Before that I used to work as an Oracle/Oracle Ebusiness suite consultant (I was charging very good contract rates). But now I am fully recovered ,feeling sharper than ever. But there arent many opportunities in my areas of expertise in a small market like New Zealand and the long absence is no help either. So for the last 5 months I have been training myself in C# ,ASP .NET,WEB technologies like HTML,JQuery,CSS and also SQL Server.I had some previous experience with JAVA and VB .NET (few months). But I am fully confident of my abilities and believe I can hit the ground running given a chance.I used to be an expert with SQL and C language and these skills are portable to SQL Server and C#. Another problem I face is my age- I am over 50. What is your opinion - Am I doing the right thing. Can I get back into an IT career-I am willing to start all over again at a junior level, I am really facing a crisis in my life.

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• Pick up relevant information from a string using regular expression C#3.0

  - by Newbie

  Hi, I have a situation. I have been given some file name which can be like <filename>YYYYMMDD<fileextension> some valid file names that will satisfy the above pattern are as under xxx20100326.xls, xxx2v20100326.csv, x_20100326.xls, xy2z_abc_20100326_xyz.csv, abc.xyz.20100326.doc, ab2.v.20100326.doc, abc.v.20100326_xyz.xls In what ever be the above defined case, I need to pick up the dates only. So for all the cases, the output will be 20100326. I am trying to achieve the same but no luck. Here is what I have done so far string testdata = "x2v20100326.csv"; string strYYYY = @"\d{4}"; string strMM = @"(1[0-2]|0[1-9])"; string strDD = @"(3[0-1]|[1-2][0-9]|0[1-9])"; string regExPattern = @"\A" + strYYYY + strMM + strDD + @"\Z"; Regex regex = new Regex(regExPattern); Match match = regex.Match(testdata); if (match.Success) { string result = match.Groups[0].Value; } I am using c#3.0 and dotnet framework 3.5 Please help. It is very urgent Thanks in advance.

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• Sync data between a windows desktop app and windows mobile client app

  - by Chris W

  I need to knock up a very quick prototype/proof of concept application to demo to someone within the next couple of days so I've minimal time to research this as fully as I normally would. The set-up is a very simple database application running on a laptop - will only ever be a single user updating a couple of tables so I was thinking of knocking up a basic Win Forms app against SQL Compact. Visual Studio's auto generated data grid edit screens will be fine with a little customisation. The second aspect is to then add a windows mobile client application that can pull data from both tables stored on the laptop, edit some data and insert some extra rows before sending the changes back to the laptop copy of the database. I've not done any WinMo development so what's the best approach for me to look at. Is it easy enough to sync data between the two databases when the WinMo device is connected to the laptop with USB? Most of the samples I've looked at so far seem to be syncing SQL Compact with SQL Standard using IIS which seems a bit overkill. The volumes of data to be synced are so small that I can easily write some manual sync code if it's easy for me to query/update the Compact DB from the laptop application when the device is connected.

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• Are we in demand?

  - by dotnetdev

  I was made redundant in the end of November. This wasn't because I lacked required skills (although I'm a youngster and in career levels a junior dev - though I knew a lot more than was called for in my job). Anyway, I was laid off due to the whole recession/credit crunch thing going on. I worked for a small company and money got tight and I had to go. I haven't made a thread about this but I have seen threads about others being laid off and experiencing a similar fate. This leads me to the question: What is the job market like for developers? Are we in demand? I ask this question on a global level, but I live in London UK (in case anyone comes across this thread from the same area). I am a .NET dev but my secondary skillset is Flex (actionscript too) and Java, which my personal portfolio is made with. I hope to be strong enough in this to do this commercially, with a few more months of practise. Then I will have more jobs applicable to me. Unfortunately, I use agencies and sites like Jobserve/Monster.com but no new jobs are ever posted on there so when you apply to all the relevant jobs, then what? Whatsmore, a lot of companies are putting a freeze on recruitment. Thanks

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• Should I *always* import my file references into the database in drupal?

  - by sprugman

  I have a cck type with an image field, and a unique_id text field. The file name of the image is based on the unique_id. All of the content, including the image itself is being generated automatically via another process, and I'm parsing what that generates into nodes. Rather than creating separate fields for the id and the image, and doing an official import of the image into the files table, I'm tempted to only create the id field and create the file reference in the theme layer. I can think of pros and cons: 1) Theme Layer Approach Pros: makes the import process much less complex don't have to worry about syncing the db with the file system as things change more flexible -- I can move my images around more easily if I want Cons: maybe not as much The Drupal Way™ not as pure -- I'll wind up with more logic on the theme side. 2) Import Approach Pros: import method is required if we ever wanted to make the files private (we won't.) safer? Maybe I'll know if there's a problem with the image at import time, rather than view time. Since I'll be bulk importing, that might make a difference. if I delete a node through the admin interface, drupal might be able to delete the file for me, as well. Con: more complex import and maintenance All else being equal, simpler is always better, so I'm leaning toward #1. Are there any other issues I'm missing? (Since this is an open ended question, I guess I'll make it a community wiki, whatever that means.)

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• How to retrieve content via .load() or $.get() with this line

  - by Sin

  hello :) I posted a question a day or two ago about how to retrieve php via ajax method in this modal I was using. I kinda found out the right way to go about it, but there's still something I'm not doing right (obviously lol) Here's the section thats giving me the issues: jQuery('div that holds content').fadeIn(200).css({ 'width': Number( popWidth ) }); $('').load('/something/somewhere/this #content'); So, im using safari, and a local server (mamp), when I check activity in my browser, it shows that it is loading the content with every click, AND the pop up pops up, but no content. When I simply retrieve content via hidden div, ofcourse, i get it. This is what I'm trying to avoid. right now I have that div in my footer stashed as hidden. I'd rather just make a call when its needed, instead of loading it every single time a page is accessed. you can go here to see the whole script i posted in my last question: How to use ajax to show php in a modal pop up Anyone have any idea? I read that .load() has the ability to grab specific content from a request, but im not sure the major difference between that and $.get() I've tried both, and I get the same results. Im using wordpress, and wordpress's ajax requests run smooth as ever, so I know its not a local problem, i'ts my coding lol Ok....Im done typing :)

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• Optimization of a c++ matrix/bitmap class

  - by Andrew

  I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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• Caching vector addition over changing collections

  - by DRMacIver

  I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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• [PHP, CSS, & ?] fixed width div, resizing text on the fly based on length

  - by Andrew Heath

  Let's say you've got a simple fixed-width layout that pulls a title from a MySQL database. CSS: #wrapper { width: 800px; } h1 { width: 100%; } HTML: <html> <body> <div id="wrapper"> <h1> $titleString </h1> </div> </body> </html> But the catch is, the length of the title string pulled from your MySQL database varies wildly. Sometimes it might be 10 characters, sometimes it might be 80. It's possible to establish a min & max character count. How, if at all possible, do I get the text-size of my <h1>$titleString</h1> to enlarge/decrease on-the-fly such that the string is only ever on one line and best fit to that line length? I've seen a lot of questions about resizing the div - but in my case the div must always be 100% (800px) and I want to best-fit the title. Obviously a maximum text-size value would have to be set so 5 character strings don't become gargantuan. Does anyone have a suggestion? I'm only using PHP/MySQL/CSS on this page at the moment, but incorporation of another language is fine if it means I can solve the problem. The only thing I can think of is a bruteforce approach whereby through trial and error I establish acceptable string character count ranges matched with CSS em sizes, but that'd be a pretty ugly implementation from the code side.

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• Database/Object Mapping

  - by Eric

  Hello everyone, This is a beginner question, but it's been frustrating me... I am using C#, by the way. I'd like to make a few classes, each with their own properties and methods. I would also like to have a database to store certain instances of these classes in case I would ever need to look at them again. So, for example... class Polygon { String name; Double perimiter; int numSides; public Double GetArea() { // ... } } class Circle { String name; Double radius; public void PrintName() { // ... } } Say I've got these classes. I also want a database that has the TABLES "Polygon" and "Circle" with the COLUMNS "name" "perimeter" "radius" etc. And I want an easy way to save a class instance into the database, or pull a class instance out of the database. I have previously been using MS Access for my database stuff, which I don't mind using, but I would prefer if nothing other than .NET need to be installed. I've been researching online a bit, but I wanted to get some opinions on here. I have looked at Linq-to-Sql, but it seems you need Sql-Server. Is this true? If so, I'd really rather not use it because I don't want to have to have it installed everywhere. Anway, I'm just fishing for some ideas/insights/suggestions/etc. so please help me out if you can. Thanks.

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• Why does a MFC application behaves mysteriously in encrypted hard drive environment.

  - by MauriceL

  I'm working on a bug where I have an MFC application that does weird things when installed in when Sophos Safeguard hard drive encryption is installed. I'm sorry to be so vague here, but I'm writing this away from the office so this is all from my (poor) memory. Three things I've noticed: AfxGetResourceHandle() doesn't return a consistent resource handle. There is a single case where we try to load a string resource, and for some reason, the resource handle that we get from this method is different to all the other stings. Can't construct a CDocumentTemplate. There is a trace error which I cant seem to recall. Will edit and post when I'm in tomorrow. This behaviour appears to manifest in a Visual Studio 2005 version of the project, but not a Visual Studio 2008 version. Unfortunately moving to the 2008 version is not an option. The bug is not always reproducable if I step through with a debugger. Also, bringing up debug message boxes changes the behaviuor, which leads me to think that either there is some kind of race condition going on with the way MFC events are being handled, but I'm not sure how I'll ever know for sure, or even what I can do about it if I did. I think there's some underlying reason that the app is behaving weirdly, but what I've posted are more symptoms. Can anyone think of what I should check for? I've run Windows update on the test environment to ensure everything was up to date, and I've examined the process in procmon to see if the disk encryption stuff was getting in the way and conflicting with files - it didn't appear to be, but it does appear to be involved in some way as our app accesses Sophos related paths in the temp directory.

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• Android SDK: Hello World won't run !

  - by RedRoses

  Hello, This is a very very beginner question regarding Android Development I am trying to create and run the Hello world example from the Android SDK website, but I can't see anything appearing on the screen. It appears to me that Eclipse just hangs at this point: [2010-11-05 09:55:47 - HelloAndroid] ------------------------------ [2010-11-05 09:55:47 - HelloAndroid] Android Launch! [2010-11-05 09:55:47 - HelloAndroid] adb is running normally. [2010-11-05 09:55:47 - HelloAndroid] Performing com.example.helloandroid.HelloAndroid activity launch [2010-11-05 09:55:48 - HelloAndroid] Automatic Target Mode: launching new emulator with compatible AVD 'AVD2' [2010-11-05 09:55:48 - HelloAndroid] Launching a new emulator with Virtual Device 'AVD2' [2010-11-05 09:55:51 - HelloAndroid] New emulator found: emulator-5554 [2010-11-05 09:55:51 - HelloAndroid] Waiting for HOME ('android.process.acore') to be launched... [2010-11-05 09:57:10 - HelloAndroid] WARNING: Application does not specify an API level requirement! [2010-11-05 09:57:10 - HelloAndroid] Device API version is 8 (Android 2.2) [2010-11-05 09:57:10 - HelloAndroid] HOME is up on device 'emulator-5554' [2010-11-05 09:57:10 - HelloAndroid] Uploading HelloAndroid.apk onto device 'emulator-5554' [2010-11-05 09:57:12 - HelloAndroid] Installing HelloAndroid.apk... [2010-11-05 09:59:33 - HelloAndroid] Success! [2010-11-05 09:59:33 - HelloAndroid] Starting activity com.example.helloandroid.HelloAndroid on device emulator-5554 So it says "Starting activity ..." but nothing ever starts and it's already been more than 30 mins. What could be wrong?? Thanks !

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• Retrieving my own data via FaceBook API

  - by goggin13

  I am building a website for a comedy group which uses Facebook as one of their marketing platforms; one of the requirements for the new site is to display all of their Facebook events on a calendar. Currently, I am just trying to put together a Python script which can pull some data from my own Facebook account, like a list of all my friends. I presume once I can accomplish this I can move to pulling more complicated data out of my clients account (since they have given me access to their account). I have looked at many of the posts here, and also went through the Facebook API documentation, including Facebook Connect, but am really beating my head against the wall. Everything I have read seems like overkill, as it involves setting up a good deal of infrastructure to allow my app to set up connections to any arbitrary user's account (who authorizes me). Shouldn't it be much simpler, given I only ever need to access 1 account? I cannot find a way to retrieve data without having to display the Facebook login window. I have a script which will retrieve all my friends, but it includes a redirect where I have to physically log myself in to Facebook. Would appreciate any advice or links, I just feel like I must be missing something simple. Thank you!

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• Can a conforming C# compiler optimize away a local (but unused) variable if it is the only strong re

  - by stakx

  The title says it all, but let me explain: void Case_1() { var weakRef = new WeakReference(new object()); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. if (weakRef.IsAlive) ... } In this code example, I obviously have to plan for the possibility that the new'ed object is reclaimed by the garbage collector; therefore the if statement. (Note that I'm using weakRef for the sole purpose of checking if the new'ed object is still around.) void Case_2() { var unusedLocalVar = new object(); var weakRef = new WeakReference(unusedLocalVar); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. Debug.Assert(weakReferenceToUseless.IsAlive); } The main change in this code example from the previous one is that the new'ed object is strongly referenced by a local variable (unusedLocalVar). However, this variable is never used again after the weak reference (weakRef) has been created. Question: Is a conforming C# compiler allowed to optimize the first two lines of Case_2 into those of Case_1 if it sees that unusedLocalVar is only used in one place, namely as an argument to the WeakReference constructor? i.e. is there any possibility that the assertion in Case_2 could ever fail?

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• EXC_BAD_ACCESS in NSURLConnection: how to debug?

  - by baswell

  I have an iPhone app that downloads URLs. (PDFs to display) Easy: self.conn = [NSURLConnection connectionWithRequest:self.request delegate:self]; where self.conn is a retained property. For specific URLs, this throws EXC_BAD_ACCESS. The URL is valid and is constructed in the same way as URLs that do work. (90% of URLs are fine) These ones work: http://www.airservicesaustralia.com/publications/current/ersa/FAC_YARG_11-Mar-2010.pdf http://www.airservicesaustralia.com/publications/current/ersa/FAC_YARK_11-Mar-2010.pdf These don't: http://www.airservicesaustralia.com/publications/current/ersa/FAC_YAMK_11-Mar-2010.pdf http://www.airservicesaustralia.com/publications/current/ersa/FAC_YATN_11-Mar-2010.pdf Spot the difference? Yeah, me neither. Also no difference in response headers from the server for them. To clarify, the ones that work ALWAYS work, the ones that don't NEVER work. So not some random release/retain issue it seems. For the ones that don't work, none of the methods in my delegate are ever called, it fails hard before that. And with no error message, just EXC_BAD_ACCESS. Sooo.... Any way to debug what is going on inside NSURLConnection?

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• Stopping at my Front-End abilities... good career move?

  - by R. H.

  Just curious about what other front-end and back-end people think, career wise. Here's the details: I'm a 30 yr old mom who is pretty good at front end development - that's my day job at an interactive agency. Don't have the money or time to go back to school or lots of high priced training sessions. I started out as a graphic designer ten years ago or so, then moved into database-backed web stuff, like CMS. I'm great at transforming PSD to a working html and css structure, especially for Wordpress themes. I enjoy this part of the process, probably because it's easy and fun, and as I learn a little more about jQuery and PHP, I can make it even better if I want or need. I'm not sure where I should stop though, as far as my career goes. I don't know that I'll ever get to the point that I'm a great PHP developer or jQuery master. Is it lame to just be a front-end designer/developer? Can that be a successful career all its own? Or, should I obligate myself to learning the harder programming, if I'm capable? Any advice or points any of you may have is appreciated!

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• Is it possible to have WAMP run httpd.exe as user [myself] instead of local SYSTEM?

  - by Olivier H

  Hello! I run a django application over apache with mod_wsgi, using WAMP. A certain URL allows me to stream the content of image files, the paths of which are stored in database. The files can be located whether on local machine or under network drive (\my\network\folder). With the development server (manage.py runserver), I have no trouble at all reading and streaming the files. With WAMP, and with network drive files, I get a IOError : obviously because the httpd instance does not have read permission on said drive. In the task manager, I see that httpd.exe is run by SYSTEM. I would like to tell WAMP to run the server as [myself] as I have read and write permissions on the shared folder. (eventually, the production server should be run by a 'www-admin' user having the permissions) Mapping the network shared folder on a drive letter (Z: for instance) does not solve this at all. The User/Group directives in httpd.conf do not seem to have any kind of influence on Apache's behaviour. I've also regedited : I tried to duplicate the HKLM[...]\wampapache registry key under HK_CURRENT_USER\ and rename the original key, but then the new key does not seem to be found when I cmd this > httpd.exe -n wampapache -k start or when I run WAMP. I've run out of ideas :) Has anybody ever had the same issue?

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• Does Monitor.Wait ensure that fields are re-read?

  - by Marc Gravell

  It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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• Hide elements for current visit only

  - by deanloh

  I need to display a banner that sticks to the bottom of the browser. So I used these codes: $(document).ready(function(){ $('#footie').css('display','block'); $('#footie').hide().slideDown('slow'); $('#footie_close').click(function(){ $('#footie_close').hide(); $('#footie').slideUp('slow'); }); }); And here's the HTML: <div id="footie"> {banner here} <a id="footie_close">Close</a> </div> I added the close link there to let user have the option to close the banner. How ever, when user navigates to next page, the banner shows up again. What can I do to set the banner to remained hidden just for this visit? In other words, as long as the browser remained open, the banner will not show up again. But if user returns to the same website another time, the banner should load again. Thanks in advance for any help!

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• What do I do about a Java program that spawned two instaces of itself?

  - by user288915

  I have a java JAR file that is triggered by a SQL server job. It's been running successfully for months. The process pulls in a structured flat file to a staging database then pushes that data into an XML file. However yesterday the process was triggered twice at the same time. I can tell from a log file that gets created, it looks like the process ran twice simultaneously. This caused a lot of issues and the XML file that it kicked out was malformed and contained duplicate nodes etc. My question is, is this a known issue with Java JVM's spawning multiple instances of itself? Or should I be looking at sql server as the culprit? I'm looking into 'socket locking' or file locking to prevent multiple instances in the future. This is the first instance of this issue that I've ever heard of. More info: The job is scheduled to run every minute. The job triggers a .bat file that contains the java.exe - jar filename.jar The java program runs, scans a directory for a file and then executes a loop to process if the file if it finds one. After it processes the file it runs another loop that kicks out XML messages. I can provide code samples if that would help. Thank you, Kevin

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• [c++] accessing the hidden 'this' pointer

  - by Kyle

  I have a GUI architecture wherein elements fire events like so: guiManager->fireEvent(BUTTON_CLICKED, this); Every single event fired passes 'this' as the caller of the event. There is never a time I dont want to pass 'this', and further, no pointer except for 'this' should ever be passed. This brings me to a problem: How can I assert that fireEvent is never given a pointer other than 'this', and how can I simplify (and homogenize) calls to fireEvent to just: guiManager->fireEvent(BUTTON_CLICKED); At this point, I'm reminded of a fairly common compiler error when you write something like this: class A { public: void foo() {} }; class B { void oops() { const A* a = new A; a->foo(); } }; int main() { return 0; } Compiling this will give you ../src/sandbox.cpp: In member function ‘void B::oops()’: ../src/sandbox.cpp:7: error: passing ‘const A’ as ‘this’ argument of ‘void A::foo()’ discards qualifiers because member functions pass 'this' as a hidden parameter. "Aha!" I say. This (no pun intended) is exactly what I want. If I could somehow access the hidden 'this' pointer, it would solve both issues I mentioned earlier. The problem is, as far as I know you can't (can you?) and if you could, there would be outcries of "but it would break encapsulation!" Except I'm already passing 'this' every time, so what more could it break. So, is there a way to access the hidden 'this', and if not are there any idioms or alternative approaches that are more elegant than passing 'this' every time?

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• Why can't we just use a hash of passphrase as the encryption key (and IV) with symmetric encryption algorithms?

  - by TX_

  Inspired by my previous question, now I have a very interesting idea: Do you really ever need to use Rfc2898DeriveBytes or similar classes to "securely derive" the encryption key and initialization vector from the passphrase string, or will just a simple hash of that string work equally well as a key/IV, when encrypting the data with symmetric algorithm (e.g. AES, DES, etc.)? I see tons of AES encryption code snippets, where Rfc2898DeriveBytes class is used to derive the encryption key and initialization vector (IV) from the password string. It is assumed that one should use a random salt and a shitload of iterations to derive secure enough key/IV for the encryption. While deriving bytes from password string using this method is quite useful in some scenarios, I think that's not applicable when encrypting data with symmetric algorithms! Here is why: using salt makes sense when there is a possibility to build precalculated rainbow tables, and when attacker gets his hands on hash he looks up the original password as a result. But... with symmetric data encryption, I think this is not required, as the hash of password string, or the encryption key, is never stored anywhere. So, if we just get the SHA1 hash of password, and use it as the encryption key/IV, isn't that going to be equally secure? What is the purpose of using Rfc2898DeriveBytes class to generate key/IV from password string (which is a very very performance-intensive operation), when we could just use a SHA1 (or any other) hash of that password? Hash would result in random bit distribution in a key (as opposed to using string bytes directly). And attacker would have to brute-force the whole range of key (e.g. if key length is 256bit he would have to try 2^256 combinations) anyway. So either I'm wrong in a dangerous way, or all those samples of AES encryption (including many upvoted answers here at SO), etc. that use Rfc2898DeriveBytes method to generate encryption key and IV are just wrong.

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