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• Have I taken a wrong path in programming by being excessively worried about code elegance and style?

  - by Ygam

  I am in a major stump right now. I am a BSIT graduate, but I only started actual programming less than a year ago. I observed that I have the following attitude in programming: I tend to be more of a purist, scorning unelegant approaches to solving problems using code I tend to look at anything in a large scale, planning everything before I start coding, either in simple flowcharts or complex UML charts I have a really strong impulse on refactoring my code, even if I miss deadlines or prolong development times I am obsessed with good directory structures, file naming conventions, class, method, and variable naming conventions I tend to always want to study something new, even, as I said, at the cost of missing deadlines I tend to see software development as something to engineer, to architect; that is, seeing how things relate to each other and how blocks of code can interact (I am a huge fan of loose coupling) i.e the OOP thinking I tend to combine OOP and procedural coding whenever I see fit I want my code to execute fast (thus the elegant approaches and refactoring) This bothers me because I see my colleagues doing much better the other way around (aside from the fact that they started programming since our first year in college). By the other way around I mean, they fire up coding, gets the job done much faster because they don't have to really look at how clean their codes are or how elegant their algorithms are, they don't bother with OOP however big their projects are, they mostly use web APIs, piece them together and voila! Working code! CLients are happy, they get paid fast, at the expense of a really unmaintainable or hard-to-read code that lacks structure and conventions, or slow executions of certain actions (which the common reasoning against would be that internet connections are much faster these days, hardware is more powerful). The excuse I often receive is clients don't care about how you write the code, but they do care about how long you deliver it. If it works then all is good. Now, did my "purist" approach to programming may have been the wrong way to start programming? Should I just dump these purist concepts and just code the hell up because I have seen it: clients don't really care how beautifully coded it is?

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• How can I fix this clang warning: "Object with +0 retain counts returned to caller where +1 (owning)

  - by mipadi

  I have a piece of Objective-C code that looks like the following: - (NSString *)copyData:(NSData *)data { NSString *path = [[[self outputDirectory] stringByAppendingPathComponent:@"archive"] stringByAppendingPathExtension:@"zip"]; NSLog(@"Copying data to %@", path); [data writeToFile:path atomically:NO]; return path; } The code is called from an initializer that looks like this: - (id)initWithData:(NSData *)data { if ((self = [super init]) != nil) { NSString *path = [self copyData:data]; // Line 41 (referenced in warning, shown below) return [self initWithContentsOfFile:path]; } return self; } When running the clang static analyzer, I get the following warnings for the path variable: Potential leak of an object allocated on line 41 and stored into 'path' Object with +0 retain counts returned to caller where +1 (owning) retain count is expected I'm confused. My understanding is that stringByAppendingPathComponent should not return an autoreleased string, so it should have a net retain count of 0. (Obviously I don't want to retain it.) I've tried altering copyData: to return the following, but it didn't get rid of the warning: return [[path retain] autorelease]; So what's the deal with this warning?

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• Dynamic memory inside a struct

  - by Maximilien

  Hello, I'm editing a piece of code, that is part of a big project, that uses "const's" to initialize a bunch of arrays. Because I want to parametrize these const's I have to adapt the code to use "malloc" in order to allocate the memory. Unfortunately there is a problem with structs: I'm not able to allocate dynamic memory in the struct itself. Doing it outside would cause to much modification of the original code. Here's a small example: int globalx,globaly; struct bigStruct{ struct subStruct{ double info1; double info2; bool valid; }; double data; //subStruct bar[globalx][globaly]; subStruct ** bar=(subStruct**)malloc(globalx*sizeof(subStruct*)); for(int i=0;i<globalx;i++) bar[i]=(*subStruct)malloc(globaly*sizeof(subStruct)); }; int main(){ globalx=2; globaly=3; bigStruct foo; for(int i=0;i<globalx;i++) for(int j=0;j<globaly;j++){ foo.bar[i][j].info1=i+j; foo.bar[i][j].info2=i*j; foo.bar[i][j].valid=(i==j); } return 0; } Note: in the program code I'm editing globalx and globaly were const's in a specified namespace. Now I removed the "const" so they can act as parameters that are set exactly once. Summarized: How can I properly allocate memory for the substruct inside the struct? Thank you very much! Max

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• My 3D object (opengl es) is disappearing behind the iPhone camera view

  - by KLC

  I have an augmented reality iPhone app that I am converting from Core Animation to OpenGL ES 1.1. I have added code that has been modified from the Apple OpenGL template. My problem is that my 3D object , when translating along the negative Z-axis (away from the user), appears to disappear into the camera view, until its completely gone. I have experimented with several solutions, but to no avail. What I have determined: Using the 3D icosahedron from Jeff Lamarche's blog here, the object starts it at 0,0,0 and then translates with decreasing z coordinates. By the time the z value reaches -2.0f, the object is gone. It appears as if it is disappearing behind the camera view. This is how I set my frustrum & viewport (unchanged from Apple's code) glMatrixMode(GL_PROJECTION); size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); //Grab the size of the screen CGRect rect = self.bounds; glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar); glViewport(0, 0, rect.size.width, rect.size.height); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); What I have tried: The camera view is the main view and several other views are added to it as subviews, including the openGLView. I have commented those views out for test purposes. I have applied CATransforms to move the openGLView in the z direction -500 and +500, and done the same to the camera view. I have also changed the zFar in the above code to 1.0f, and it still disappears at z position of -2.0, which doesn't make sense (shouldn't it disappear at z=1.0?) My experimentation has got me more confused than when I started ( which usually means I am missing a key piece, but I can't figure out what). Thanks for your help.

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• Using bitwise operators on > 32 bit integers

  - by dqhendricks

  I am using bitwise operations in order to represent many access control flags within one integer. ADMIN_ACCESS = 1; EDIT_ACCOUNT_ACCESS = 2; EDIT_ORDER_ACCESS = 4; var myAccess = 3; // ie: ( ADMIN_ACCESS | EDIT_ACCOUNT_ACCESS ) if ( myAccess & EDIT_ACCOUNT_ACCESS ) { // check for correct access // allow for editing of account } Most of this is occurring on the PHP side of my project. There is one piece however where Javascript is used to join several access flags using | when saving someone's access level. This works fine to a point. I have found that once an integer (flag) gets too large ( 32bit), it no longer works correctly with bitwise operators in Javascript. For instance: alert( 4294967296 | 1 ); // equals 1, but should equal 4294967297 I am trying to find a workaround for this so that I do not have to limit my number of access control flags to 32. Each access control flag is two times the previous control flag so that each control flag will not interfere with other control flags. dec(4) = bin(100) dec(8) = bin(1000) dec(16) = bin(10000) I have noticed that when adding two of these flags together with a simple +, it seems to come out with the same answer as a bitwise or operation, but am having trouble wrapping my head around whether this is a simple substitution, or if there might be problems with doing this. Can anyone comment on the validity of this workaround? Example: (4294967296 | 262144 | 524288) == (4294967296 + 262144 + 524288)

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• How do I get 3 lines of text from a paragraph in C#

  - by Keltex

  I'm trying to create an "snippet" from a paragraph. I have a long paragraph of text with a word hilighted in the middle. I want to get the line containing the word before that line and the line after that line. I have the following piece of information: The text (in a string) The lines are deliminated by a NEWLINE character \n I have the index into the string of the text I want to hilight A couple other criteria: If my word falls on first line of the paragraph, it should show the 1st 3 lines If my word falls on the last line of the paragraph, it should show the last 3 lines Should show the entire paragraph in the degenative cases (the paragraph only has 1 or 2 lines) Here's an example: This is the 1st line of CAT text in the paragraph This is the 2nd line of BIRD text in the paragraph This is the 3rd line of MOUSE text in the paragraph This is the 4th line of DOG text in the paragraph This is the 5th line of RABBIT text in the paragraph Example, if my index points to BIRD, it should show lines 1, 2, & 3 as one complete string like this: This is the 1st line of CAT text in the paragraph This is the 2nd line of BIRD text in the paragraph This is the 3rd line of MOUSE text in the paragraph If my index points to DOG, it should show lines 3, 4, & 5 as one complete string like this: This is the 3rd line of MOUSE text in the paragraph This is the 4th line of DOG text in the paragraph This is the 5th line of RABBIT text in the paragraph etc. Anybody want to help tackle this?

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• Yet another "What is this code doing"-type of Perl code

  - by Mike

  I have inherited some code from a guy whose favorite past time was to shorten every line to its absolute minimum (and sometimes only to make it look cool). His code is hard to understand but I managed to understand (and rewrite) most of it. Now I have stumbled on a piece of code which, no matter how hard I try, I cannot understand. my @heads = grep {s/\.txt$//} OSA::Fast::IO::Ls->ls($SysKey,'fo','osr/tiparlo',qr{^\d+\.txt$}) || (); my @selected_heads = (); for my $i (0..1) { $selected_heads[$i] = int rand scalar @heads; for my $j (0..@heads-1) { last if (!grep $j eq $_, @selected_heads[0..$i-1]); $selected_heads[$i] = ($selected_heads[$i] + 1) % @heads; #WTF? } my $head_nr = sprintf "%04d", $i; OSA::Fast::IO::Cp->cp($SysKey,'',"osr/tiparlo/$heads[$selected_heads[$i]].txt","$recdir/heads/$head_nr.txt"); OSA::Fast::IO::Cp->cp($SysKey,'',"osr/tiparlo/$heads[$selected_heads[$i]].cache","$recdir/heads/$head_nr.cache"); } From what I can understand, this is supposed to be some kind of randomizer, but I never saw a more complex way to achieve randomness. Or are my assumptions wrong? At least, that's what this code is supposed to do. Select 2 random files and copy them. === NOTES === The OSA Framework is a Framework of our own. They are named after their UNIX counterparts and do some basic testing so that the application does not need to bother with that.

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• when an autoreleased object is actually released?

  - by psebos

  Hi, I am new in objective-c and I am trying to understand memory management to get it right. After reading the excellent Memory Management Programming Guide for Cocoa by apple my only concern is when actually an autoreleased object is released in an iphone/ipod application. My understanding is at the end of a run loop. But what defines a run loop in the application? So I was wondering whether the following piece of code is right. Assume an object @implementation Test - (NSString *) functionA { NSString *stringA; stringA = [[NSString alloc] initWithString:@"Hello" autorelease] return stringA; } - (NSString *) functionB { NSString *stringB; stringB = [self functionA]; return stringB; } - (NSString *) functionC { NSString *stringC; stringC = [self functionB]; return stringC; } - (void)viewDidLoad { [super viewDidLoad]; (NSString *) p = [self functionC]; NSLog(@"string is %@",p); } @end Is this code valid? From the apple text I understand that the NSString returned from functionA is valid in the scope of functionB. I am not sure whether it is valid in functionC and in viewDidLoad. Thanks!

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• How can I make an even more random number in ActionScript 2.0

  - by Theo

  I write a piece of software that runs inside banner ads which generates millions of session IDs every day. For a long time I've known that the random number generator in Flash is't random enough to generate sufficiently unique IDs, so I've employed a number of tricks to get even more random numbers. However, in ActionScript 2.0 it's not easy, and I'm seeing more and more collisions, so I wonder if there is something I've overlooked. As far as I can tell the problem with Math.random() is that it's seeded by the system time, and when you have sufficient numbers of simultaneous attempts you're bound to see collisions. In ActionScript 3.0 I use the System.totalMemory, but there's no equivalent in ActionScript 2.0. AS3 also has Font.enumerateFonts, and a few other things that are different from system to system. On the server side I also add the IP address to the session ID, but even that isn't enough (for example, many large companies use a single proxy server and that means that thousands of people all have the same IP -- and since they tend to look at the same sites, with the same ads, roughly at the same time, there are many session ID collisions). What I need isn't something perfectly random, just something that is random enough to dilute the randomness I get from Math.random(). Think of it this way: there is a certain chance that two people will generate the same random number sequence using only Math.random(), but the chance of two people generating the same sequence and having, say, the exact same list of fonts is significantly lower. I cannot rely on having sufficient script access to use ExternalInterface to get hold of things like the user agent, or the URL of the page. I don't need suggestions of how to do it in AS3, or any other system, only AS2 -- using only what's available in the standard APIs. The best I've come up with so far is to use the list of microphones (Microphone.names), but I've also tried to make some fingerprinting using some of the properties in System.capabilities, I'm not sure how much randomness I can get out of that though so I'm not using that at the moment. I hope I've overlooked something.

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• Actual element tags are not getting captured.

  - by user323719

  I am using the below piece of XSL code to construct a span tag calling a javascript function on mouseover. The input to the javascipt should be a html table. The output from the variable "showContent" gives just the text content but not along with the table tags. How can this be resolved. XSL: <xsl:variable name="aTable" as="element()*"> <table border="0" cellspacing="0" cellpadding="0"> <xsl:for-each select="$capturedTags"> <tr><td><xsl:value-of select="node()" /></td></tr> </xsl:for-each> </table> </xsl:variable> <xsl:variable name="start" select='concat("Tip(&#39;", "")'></xsl:variable> <xsl:variable name="end" select='concat("&#39;)", "")'></xsl:variable> <xsl:variable name="showContent"> <xsl:value-of select='concat($start,$aTable,$end)'/> </xsl:variable> <span xmlns="http://www.w3.org/1999/xhtml" onmouseout="{$hideContent}" onmouseover="{$showContent}" id="{$textNodeId}"><xsl:value-of select="$textNode"></xsl:value-of></span> Actual Output: <span onmouseout="UnTip()" onmouseover="Tip('content1')" id="d1t14"is my </span Expected output: <span onmouseout="UnTip()" onmouseover="Tip('<table><tr><td>content1</td></tr>')" id="d1t14">is my </span> What is the change that needs to done in the above XSL for the table, tr and td tags to get passed?

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• code to ping websites works sometimes ...

  - by trustfundbaby

  I'm testing out a piece of code to ping a bunch of websites I own on a regular basis, to make sure they're up. I'm using rails and so far I have this hideous test action that I'm using to try it out (see below). The problem though, is that sometimes it works, and other times it won't ... sometimes it runs through the code just fine, other times, it seems to completely ignore the begin/rescue block ... a. I need help figuring out what the problem is b. And refactoring this to make it look respectable. Your help is much appreciated. require 'net/http' require 'uri' def ping @sites = NewsSource.all @sites.each do |site| if site.uri and !site.uri.empty? uri = URI.parse(site.uri) response = nil path = uri.path.blank? ? '/' : uri.path path = uri.query.blank? ? path : "#{path}?#{uri.query}" begin Net::HTTP.start(uri.host, uri.port) {|http| http.open_timeout = 30 http.read_timeout = 30 response = http.head(path) } if response.code.eql?('200') or response.code.eql?('301') or response.code.eql?('302') site.up = true else site.up = false end site.up_check_msg = response.message site.up_check_code = response.code rescue Errno::EBADF rescue Timeout::Error site.up = false site.up_check_msg = 'timeout' site.up_check_code = '408' end site.up_check_time = 0.seconds.ago site.save end end end

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• Discover generic types

  - by vittore

  Thanks @dtb for help, he advised really need piece of code for generic service locator static class Locator { private static class LocatorEntry<T> where T : ... { public static IDataManager<T> instance; } public static void Register<T>(IDataManager<T> instance) where T : ... { LocatorEntry<T>.instance = instance; } public static IDataManager<T> GetInstance<T>() where T : ... { return LocatorEntry<T>.instance; } } However in my previous version I used reflection on assembly to discover a hundred of DataManager's I want to write an method discover like the following void Discover() { var pManager = new ProtocolSQLDataManager(); Register(pManager); var rManager = new ResultSQLDataManager(); Register(rManager); var gType = typeof(ISQLDataAccessManager<>); foreach (Type type in Assembly.GetExecutingAssembly().GetTypes()) { if (type.IsSubclassOf(gType) && !type.IsAbstract)) { var manager = Activator.CreateInstance(type); // put something here in order to make next line of code works Register<T>(manager); } } } How to cast type to appropriate type in order to make Register working( and call appropriate Register ?

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• Equivalent Carbon 32-bit call for using in 64-bit application - GetApplicationEventTarget().

  - by Dheeraj

  Hi All, I'm writing a 64-bit Cocoa application. I need to register for global key events. So I wrote this piece of code : - (void)awakeFromNib { EventHotKeyRef gMyHotKeyRef; EventHotKeyID gMyHotKeyID; EventTypeSpec eventType; eventType.eventClass=kEventClassKeyboard; eventType.eventKind=kEventHotKeyPressed; eventType.eventClass=kEventClassKeyboard; eventType.eventKind=kEventHotKeyPressed; InstallApplicationEventHandler(&MyHotKeyHandler,1,&eventType,NULL,NULL); gMyHotKeyID.signature='htk1'; gMyHotKeyID.id=1; RegisterEventHotKey(49, cmdKey+optionKey, gMyHotKeyID, **GetApplicationEventTarget**(), 0, &gMyHotKeyRef); } But since GetApplicationEventTarget() is not supported for 64-bit applications I'm getting errors. If I declare it, then I don't get any errors but the application crashes. Is there any equivalent method for GetApplicationEventTarget() (defined in Carbon framework) to use in 64-bit applications. Or is there any way to get the global key events using cocoa calls? Any help is appreciated. Thanks, Dheeraj.

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• call addsubview again causes slowdown

  - by Tom

  hi guys, i am writing a little music-game for the iphone. I am almost done, this is the only issue which keeps me from rolling it out. any help to solve this is much appreciated. this is what i do: at my appDelegate I add my menu-view-screen to the window. the menu-view-screen acts as a container and controls which view gets presented to the user. means, on the menu-view-screen I got 4 buttons (new game, options, faq, highscore). when the user clicks on a button something as this happens: if (self.gameViewController == nil) { GameViewController *viewController = [[GameViewController alloc] initWithNibName:@"GameViewController" bundle:nil]; self.gameViewController = viewController; [viewController release]; } [self.view addSubview:self.gameViewController.view]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleSwitchViewNotificationFromGameView:) name:@"SwitchView" object:gameViewController]; when the user returns to the menu, this piece of code gets executed: [[NSNotificationCenter defaultCenter] removeObserver:self]; [self.gameViewController viewWillDisappear:YES]; [self.gameViewController.view removeFromSuperview]; this works fine for all screens but not for the gamescreen(well this is the only one with heaps of user-interaction) means the responsiveness of the iphone(when playing tones) gets really slow. The performance is fine when I display the gameview for the first time. it starts getting slower as soon as I add it to the menu-views-container-subviews again (addsubview) (basically open up a new game) any ideas what causes(or to get around) this? thanks heaps Best regards Tom

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• Java: easiest way to package both Java 1.5 and 1.6 code

  - by WizardOfOdds

  I want to package a piece of code that absolutely must run on Java 1.5. There's one part of the code where the program can be "enhanced" if the VM is an 1.6 VM. Basically it's this method: private long[] findDeadlockedThreads() { // JDK 1.5 only supports the findMonitorDeadlockedThreads() // method, so you need to comment out the following three lines if (mbean.isSynchronizerUsageSupported()) return mbean.findDeadlockedThreads(); else return mbean.findMonitorDeadlockedThreads(); } What would be easiest way to have this compile on 1.5 and yet do the 1.6 method calls when on 1.6 ? In the past I've done something similar by compiling a unique 1.6 class that I would package with my app and instantiate using a ClassLoader when on 1.6 (because an 1.6 JVM is perfectly fine mixing 0x32 and 0x31 classes), but I think it's a bit overkill (and a bit painful because during the build process you have to build both 0x31 and 0x32 .class files). How should I go if I wanted to compile the above method on 1.5? Maybe using reflection but then how (I'm not familiar at all with reflection) Note: if you're curious, the above method comes from this article: http://www.javaspecialists.eu/archive/Issue130.html (but I don't want to "comment the three lines" like in the article, I want this to compile and run on both 1.5 and 1.6)

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• Display image background fully for last repeat in a div

  - by Stiggler

  I have a 700x300 background repeating seamlessly under the main content-div. Now I'd like to attach a div at the bottom of the content-div, containing a continuation-to-end of the background image, connecting seamlessly with the background above it. Due to the nature of the pattern, unless the full 300px height of the background image is visible in the last repeat of the content-div's backround, the background in the div below won't seamlessly connect. Basically, I need the content div's height to be a multiple of 300px under all circumstances. What's a good approach to this sort of problem? I've tried resizing the content-div on loading the page, but this only works as long as the content div doesn't contain any resizing, dynamic content, which is not my case: function adjustContentHeight() { // Setting content div's height to nearest upper multiple of column backgrounds height, // forcing it not to be cut-off when repeated. var contentBgHeight = 300; var contentHeight = $("#content").height(); var adjustedHeight = Math.ceil(contentHeight / contentBgHeight); $("#content").height(adjustedHeight * contentBgHeight); } $(document).ready(adjustContentHeight); What I'm looking for there is a way to respond to a div resizing event, but there doesn't seem to be such a thing. Also, please assume I have no access to the JS controlling the resizing of content in the content-div, though this is potentially a way of solving the problem. Another potential solution I was thinking off was to offset the background image in the bottom div by a certain amount depending on the height of the content-div. Again, the missing piece seems to be the ability to respond to a resize event.

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• Using Reflection.Emit to emit a "using (x) { ... }" block?

  - by Lasse V. Karlsen

  I'm trying to use Reflection.Emit in C# to emit a using (x) { ... } block. At the point I am in code, I need to take the current top of the stack, which is an object that implements IDisposable, store this away in a local variable, implement a using block on that variable, and then inside it add some more code (I can deal with that last part.) Here's a sample C# piece of code I tried to compile and look at in Reflector: public void Test() { TestDisposable disposable = new TestDisposable(); using (disposable) { throw new Exception("Test"); } } This looks like this in Reflector: .method public hidebysig instance void Test() cil managed { .maxstack 2 .locals init ( [0] class LVK.Reflection.Tests.UsingConstructTests/TestDisposable disposable, [1] class LVK.Reflection.Tests.UsingConstructTests/TestDisposable CS$3$0000, [2] bool CS$4$0001) L_0000: nop L_0001: newobj instance void LVK.Reflection.Tests.UsingConstructTests/TestDisposable::.ctor() L_0006: stloc.0 L_0007: ldloc.0 L_0008: stloc.1 L_0009: nop L_000a: ldstr "Test" L_000f: newobj instance void [mscorlib]System.Exception::.ctor(string) L_0014: throw L_0015: ldloc.1 L_0016: ldnull L_0017: ceq L_0019: stloc.2 L_001a: ldloc.2 L_001b: brtrue.s L_0024 L_001d: ldloc.1 L_001e: callvirt instance void [mscorlib]System.IDisposable::Dispose() L_0023: nop L_0024: endfinally .try L_0009 to L_0015 finally handler L_0015 to L_0025 } I have no idea how to deal with that ".try ..." part at the end there when using Reflection.Emit. Can someone point me in the right direction?

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• Looking for fast, minimal, preferrably free disc cloning software [closed]

  - by Dave

  We have to test our application installation and functionality on many Windows operating system versions and languages (XP, Vista, Win7; English, Spanish, Portuguese, etc; 32-bit & b4-bit.) While we can do much of this in virtual machines, we have noticed that VM's sometimes hide problems, or raise false bugs. So, we need to do "bare metal" OS installation for much of our testing. I have been using Acronis True Image for the past year, and am not impressed. It often gives random errors which require a reboot, and is really slow. For example, when trying to restore an image, it goes through a "Locking partition" cycle about three times (once after you click OK on each step of the wizard), each of which can take 5 minutes to complete. This all happens BEFORE it actually starts the image copy, which is sometimes quick (3-5 minutes), sometimes long (hours). The size of all of our images are roughly the same, so that is not related. So, anyway, I'm looking to switch to something else: I only need very basic functionality--just creating images of entire discs, and then restoring those images onto the exact same hard drive at a later date. That's it. I'm not opposed to paying for a good piece of software, but if there is something free out there that does the job well, that would be a preference. My OS on which the imaging software would run is Windows Vista, but a bootable media (into a Linux flavor) would be fine also, as long as its quick to use and reliable. Recommendations? (Also, moderators, if this should be a CW, I'll be happy to mark it as such; unclear about the rules there.)

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• How to make safe frequent DataSource switches for AbstractRoutingDataSource?

  - by serg555

  I implemented Dynamic DataSource Routing for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query. Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use: public class CustomerContextHolder { private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>(); public static void setCustomerType(CustomerType customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType); } public static CustomerType getCustomerType() { return (CustomerType) contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } } It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel: CustomerContextHolder.setCustomerType(CustomerType.GOLD); //<another user will switch customer type here to CustomerType.SILVER in another request> List<Item> goldItems = catalog.getItems(); Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true. How to make sure that nobody else will switch datasource until I run required query for current user? Thanks.

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• Why am I getting "(304) Not Modified" error on some links when using HttpWebRequest?

  - by Greg

  Hi, Any ideas why on some links that I try to access using HttpWebRequest I am getting "The remote server returned an error: (304) Not Modified." in the code? The code I'm using is from Jeff's post here. Note the concept of the code is a simple proxy server, so I'm pointing my browser at this locally running piece of code, which gets my browsers request, and then proxies it on by creating a new HttpWebRequest, as you'll see in the code. It works great for most sites/links, but for some this error comes up. You will see one key bit in the code is where it seems to copy the http header settings from the browser request to it's request out to the site, and it copies in the header attributes. Not sure if the issue is something to do with how it mimics this aspect of the request and then what happens as the result comes back? case "If-Modified-Since": request.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]); break; I get the issue for example from http://en.wikipedia.org/wiki/Main_Page thanks

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• onSubmit returning false is not working

  - by StuckOnSubmit

  I'm completely confused ... I'd swear this was working yesterday ... I woke up this morning and all my forms stopped to work in my project. All the forms have a "onsubmit" to a function that returns false since it's an ajax call, so the form is never sent. After a lot of tests, I simplified the question to this piece of code: <html> <head> <script type="text/javascript"> function sub() { alert ("MIC!"); return false; } </script> </head> <body> <form method = "post" id = "form1" onsubmit = "return sub()"> input: <input type="text" name="input1" > <a href="#" onClick="document.getElementById('form1').submit();">button</a> </form> </body> </html> I would swear that this works perfectly, but today is nor working :D Why if I press the button the form is sent ? I know it's a total newbie question, but I'm stuck Thank you !

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• I am confused -- Will this code always work?

  - by Shekhar

  Hello, I have written this piece of code public class Test{ public static void main(String[] args) { List<Integer> list = new ArrayList<Integer>(); for(int i = 1;i<= 4;i++){ new Thread(new TestTask(i, list)).start(); } while(list.size() != 4){ // this while loop required so that all threads complete their work } System.out.println("List "+list); } } class TestTask implements Runnable{ private int sequence; private List<Integer> list; public TestTask(int sequence, List<Integer> list) { this.sequence = sequence; this.list = list; } @Override public void run() { list.add(sequence); } } This code works and prints all the four elements of list on my machine. My question is that will this code always work. I think there might be a issue in this code when two/or more threads add element to this list at the same point. In that case it while loop will never end and code will fail. Can anybody suggest a better way to do this? I am not very good at multithreading and don't know which concurrent collection i can use? Thanks Shekhar

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• Updating a specific key/value inside of an array field with MongoDB

  - by Jesta

  As a preface, I've been working with MongoDB for about a week now, so this may turn out to be a pretty simple answer. I have data already stored in my collection, we will call this collection content, as it contains articles, news, etc. Each of these articles contains another array called author which has all of the author's information (Address, Phone, Title, etc). The Goal - I am trying to create a query that will update the author's address on every article that the specific author exists in, and only the specified author block (not others that exist within the array). Sort of a "Global Update" to a specific article that affects his/her information on every piece of content that exists. Here is an example of what the content with the author looks like. { "_id" : ObjectId("4c1a5a948ead0e4d09010000"), "authors" : [ { "user_id" : null, "slug" : "joe-somebody", "display_name" : "Joe Somebody", "display_title" : "Contributing Writer", "display_company_name" : null, "email" : null, "phone" : null, "fax" : null, "address" : null, "address2" : null, "city" : null, "state" : null, "zip" : null, "country" : null, "image" : null, "url" : null, "blurb" : null }, { "user_id" : null, "slug" : "jane-somebody", "display_name" : "Jane Somebody", "display_title" : "Editor", "display_company_name" : null, "email" : null, "phone" : null, "fax" : null, "address" : null, "address2" : null, "city" : null, "state" : null, "zip" : null, "country" : null, "image" : null, "url" : null, "blurb" : null }, ], "tags" : [ "tag1", "tag2", "tag3" ], "title" : "Title of the Article" } I can find every article that this author has created by running the following command: db.content.find({authors: {$elemMatch: {slug: 'joe-somebody'}}}); So theoretically I should be able to update the authors record for the slug joe-somebody but not jane-somebody (the 2nd author), I am just unsure exactly how you reach in and update every record for that author. I thought I was on the right track, and here's what I've tried. b.content.update( {authors: {$elemMatch: {slug: 'joe-somebody'} } }, {$set: {address: '1234 Avenue Rd.'} }, false, true ); I just believe there's something I am missing in the $set statement to specify the correct author and point inside of the correct array. Any ideas? **Update** I've also tried this now: b.content.update( {authors: {$elemMatch: {slug: 'joe-somebody'} } }, {$set: {'authors.$.address': '1234 Avenue Rd.'} }, false, true );

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• requesting ajax via HttpWebRequest

  - by Sami Abdelgadir Mohammed

  Hi guys: I'm writing a simple application that will download some piece of data from a website then I can use it later for any purpose The following is the request and response copied from Firebug as the browser did that... when u type http://x5.travian.com.sa/ajax.php?f=k7&x=18&y=-186&xx=12&yy=-192 you will get a php file has some data.. But when I make a request with HttpWebRequest I get wrong data (some unknown letters) Can anyone help me in that.. and if I have to make some encodings or what?? I will be so appreciated.. Response Server nginx Date Tue, 04 Jan 2011 23:03:49 GMT Content-Type application/json; charset=UTF-8 Transfer-Encoding chunked Connection keep-alive X-Powered-By PHP/5.2.8 Expires Mon, 26 Jul 1997 05:00:00 GMT Last-Modified Tue, 04 Jan 2011 23:03:49 GMT Cache-Control no-store, no-cache, must-revalidate, post-check=0, pre-check=0 Pragma no-cache Content-Encoding gzip Vary Accept-Encoding Request Host x5.travian.com.sa User-Agent Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13 Accept text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 Accept-Language en-us,en;q=0.5 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 115 Connection keep-alive Cookie CAD=57878984%231292375897%230%230%23%230; T3E=%3DImYykTN2EzMmhjO5QTM2QDN2oDM1ITOyoDOxIjM4EDN5ITM6gjO4MDOxIWZyQWMipTZu9metl2ctl2c6MDNxADN6MDNxADNjMDNxADNjMDNxADN; orderby_b1=0; orderby_b=0; orderby2=0; orderby=0

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• Java webapp: how to implement a web bug (1x1 pixel)?

  - by NoozNooz42

  In the accepted answer in the following question, a SO regular with 13K+ rep suggests to use a "web bug" (non-cacheable 1x1 img) to be able to track requests in the logs: http://stackoverflow.com/questions/1784893 How can I do this in Java? Basically, I've got two issues: how to make sure the 1x1 image is not cacheable (how to set the header)? how to make sure the query for these 1x1 image will appear in the logs? I'm looking for exact piece of code because I know how to write a .jsp/servlet and I know how to serve an 1x1 image :) My question is really about the exact .jsp/servlet that I should write and how/what needs to be done so that Tomcat logs the request. For example I plan to use the following mapping: <servlet-mapping> <servlet-name>WebBugServlet</servlet-name> <url-pattern>/webbug*</url-pattern> </servlet-mapping> and then use an img tag referencing a "webbug.png" (or .gif), so how do I write the .jsp/servlet? What/where should I look for in the logs?

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