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• What constitutes a development environment, and how do you document it?

  - by Joel Coehoorn

  What items go into a software shop's development environment, how do you document it, and what processes do you follow to make changes? I thinking about this from the standpoint where I want to make it easier to bring new hires up to speed quickly by having all this on a checklist we follow when setting them up, and then while I'm at it making it easier for the new hires or existing team members to bring new powerful toolkits and ideas into the environment without disrupting things. I want to keep this platform agnostic, so even though I'm currently at a microsoft shop where Visual Studio would be assumed I'll go ahead and list compiler/IDE as one of the items: Here are some ideas for part 1: [edit]: I'm keeping this updated based on the better suggestions. Source Control access Issue/Bug/Project tracker System Documention, or references to find the system documentation in source control or in a wiki, including: build document/environment covered by this question design documents / technical notes Coding Style guidelines Deploy for review/testing/QA/staging/production procedures Licensing details for your tools and your product Team Calendar, including the project schedule(s), deadlines, vacation time, and support/on-call schedule (if required) compiler/IDE compiler/IDE extensions (things like source control plugins or visual studio add-ins) 3rd party SDKs/toolkits Database connection and tools Testing Frameworks Internal libraries communication tools (chat, wiki, etc) Static analysis tools (FxCop, FlawFinder, etc) Virtual machines (holding dev environment or for testing) Specialized editors (modeling, xml, etc) Other tools What else goes in this list, and how do you document it and vet changes?

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• POST XML to server, receive PDF

  - by Shaggy Frog

  Similar to this question, we are developing a Web app where the client clicks a button to receive a PDF from the server. Right now we're using the .ajax() method with jQuery to POST the data the backend needs to generate the PDF (we're sending XML) when the button is pressed, and then the backend is generating the PDF entirely in-memory and sending it back as application/pdf in the HTTP response. One answer to that question requires the server-side save the PDF to disk so it can give back a URL for the client to GET. But I don't want the backend caching content at all. The other answer suggests the use of a jQuery plugin, but when you look at its code, it's actually generating a form element and then submitting the form. That method will not work for us since we are sending XML data in the body of the HTTP request. Is there a way to have the browser open up the PDF without caching the PDF server-side, and without requiring us to throw out our send-data-to-the-server-using-XML solution? (I'd like the browser to behave like it does when a form element is submitted -- a POST is made and then the browser looks at the Content-type header to determine what to do next, like load the PDF in the browser window, a la Safari)

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• How do I change the base class at runtime in C#?

  - by MatthewMartin

  I may be working on mission impossible here, but I seem to be getting close. I want to extend a ASP.NET control, and I want my code to be unit testable. Also, I'd like to be able to fake behaviors of a real Label (namely things like ID generation, etc), which a real Label can't do in an nUnit host. Here a working example that makes assertions on something that depends on a real base class and something that doesn't-- in a more realistic unit test, the test would depend on both --i.e. an ID existing and some custom behavior. Anyhow the code says it better than I can: public class LabelWrapper : Label //Runtime //public class LabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } //Ugh, now I have to test FakeLabelWrapper public class FakeLabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } [TestFixture] public class UnitTest { [Test] public void Test() { //Wish this was LabelWrapper label = new LabelWrapper(new FakeBase()) LabelWrapper label = new LabelWrapper(); //FakeLabelWrapper label = new FakeLabelWrapper(); label.Text = "ToUpper"; Assert.AreEqual("TOUPPER",label.Text); StringWriter stringWriter = new StringWriter(); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); label.RenderControl(writer); Assert.AreEqual(1,label.ID); Assert.AreEqual("<span>TOUPPER</span>", stringWriter.ToString()); } } public class FakeLabel { virtual public string Text { get; set; } public void RenderControl(TextWriter writer) { writer.Write("<span>" + Text + "</span>"); } } //System Under Test internal class LabelLogic { internal string ProcessGetText(string value) { return value.ToUpper(); } internal string ProcessSetText(string value) { return value.ToUpper(); } }

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• Several Objective-C objects become Invalid for no reason, sometimes.

  - by farnsworth

  - (void)loadLocations { NSString *url = @"<URL to a text file>"; NSStringEncoding enc = NSUTF8StringEncoding; NSString *locationString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:url] usedEncoding:&enc error:nil]; NSArray *lines = [locationString componentsSeparatedByString:@"\n"]; for (int i=0; i<[lines count]; i++) { NSString *line = [lines objectAtIndex:i]; NSArray *components = [line componentsSeparatedByString:@", "]; Restaurant *res = [byID objectForKey:[components objectAtIndex:0]]; if (res) { NSString *resAddress = [components objectAtIndex:3]; NSArray *loc = [NSArray arrayWithObjects:[components objectAtIndex:1], [components objectAtIndex:2]]; [res.locationCoords setObject:loc forKey:resAddress]; } else { NSLog([[components objectAtIndex:0] stringByAppendingString:@" res id not found."]); } } } There are a few weird things happening here. First, at the two lines where the NSArray lines is used, this message is printed to the console- *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSCFDictionary count]: method sent to an uninitialized mutable dictionary object' which is strange since lines is definitely not an NSMutableDictionary, definitely is initialized, and because the app doesn't crash. Also, at random points in the loop, all of the variables that the debugger can see will become Invalid. Local variables, property variables, everything. Then after a couple lines they will go back to their original values. setObject:forKey never has an effect on res.locationCoords, which is an NSMutableDictionary. I'm sure that res, res.locationCoords, and byId are initialized. I also tried adding a retain or copy to lines, same thing. I'm sure there's a basic memory management principle I'm missing here but I'm at a loss.

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• Thoughts on GoGrid vs EC2

  - by Jason

  I am currently hosting my SaaS application at GoGrid (Microsoft stack). Here's what I have: Database Server - physical box, 12 GB RAM, 2 X Quad Core CPU (2.13 GHz Xeon E5506) 2 Web / App servers - cloud servers, 2 GB RAM, 2 VCPUs 300 GB monthly bandwidth I am paying around $900 / month for this. My web / app servers are busting at the seams and need to be upgraded to 4 GB of RAM. I also need a firewall, and GoGrid just added this service for an additional $200. After the upgrade, I will be paying around $1,400. I started looking at Amazon EC2, specifically this config: Database server - "High Memory Double Extra Large Instance" - 34 GB RAM, 13 EC2 compute units 2 Web / App servers - "Large Instance" - 7.5 GB RAM, 4 EC2 compute units If I go with 1 year reserved instances, my upfront cost would be $4,500 and my monthly would be $700. This comes to $1,075 / month when amortized. Amazon also includes a firewall for free. Here are my questions: Do any of you have experience running a database (especially SQL Server) on an EC2 instance? How did it perform compared to a dedicated machine? One of my major concerns is with disk I/O. Amazon's description of a compute unit is fairly vague. Any ideas on how the CPU performance on the database servers would compare? I am hoping that the Amazon solution will provide significantly better performance than my current or even improved GoGrid setup. Having a virtual database server would also be nice in terms of availability. Right now I would be in serious trouble if I had any hardware issues. Thanks for any insight...

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• ExpertPDF and Caching of URLs

  - by Josh

  We are using ExpertPDF to take URLs and turn them into PDFs. Everything we do is through memory, so we build up the request and then read the stream into ExpertPDF and then write the bits to file. All the files we have been requesting so far are just plain HTML documents. Our designers update CSS files or change the HTML and rerequest the documents as PDFs, but often times, things are getting cached. Take, for example, if I rename the only CSS file and view the HTML page through a web browser, the page looks broke because the CSS doesn't exist. But if I request that page through the PDF Generator, it still looks ok, which means somewhere the CSS is cached. Here's the relevant PDF creation code: // Create a request HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url); request.UserAgent = "IE 8.0"; request.ContentType = "application/x-www-form-urlencoded"; request.Method = "GET"; // Send the request HttpWebResponse resp = (HttpWebResponse)request.GetResponse(); if (resp.IsFromCache) { System.Web.HttpContext.Current.Trace.Write("FROM THE CACHE!!!"); } else { System.Web.HttpContext.Current.Trace.Write("not from cache"); } // Read the response pdf.SavePdfFromHtmlStream(resp.GetResponseStream(), System.Text.Encoding.UTF8, "Output.pdf"); When I check the trace file, nothing is being loaded from cache. I checked the IIS log file and found a 200 response coming from the request, even after a file had been updated (I would expect a 302). We've tried putting the No-Cache attribute on all HTML pages, but still no luck. I even turned off all caching at the IIS level. Is there anything in ExpertPDF that might be caching somewhere or something I can do to the request object to do a hard refresh of all resources? UPDATE I put ?foo at the end of my style href links and this updates the CSS everytime. Is there a setting someplace that can prevent stylesheets from being cached so I don't have to do this inelegant solution?

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• Fix hard-coded display setting without source (24-bit, need 32-bit)

  - by FerretallicA

  I wrote a program about 10 years ago in Visual Basic 6 which was basically a full-screen game similar to Breakout / Arkanoid but had 'demoscene'-style backgrounds. I found the program, but not the source code. Back then I hard-coded the display mode to 800x600x24, and the program crashes whenever I try to run it as a result. No virtual machine seems to support 24-bit display when the host display mode is 16/32-bit. It uses DirectX 7 so DOSBox is no use. I've tried all sorts of decompiler and at best they give me the form names and a bunch of assembly calls which mean nothing to me. The display mode setting was a DirectX 7 call but there's no clear reference to it in the decompilation. In this situation, is there any pointers on how I can: pin-point the function call in the program which is setting the display mode to 800x600x24 (ResHacker maybe?) and change the value being passed to it so it sets 800x600x32 view/intercept DirectX calls being made while it's running or if that's not possible, at least run the program in an environment that emulates a 24-bit display I don't need to recover the source code (as nice as it would be) so much as just want to get it running.

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• activemessaging with stomp and activemq.prefetchSize=1

  - by Clint Miller

  I have a situation where I have a single activemq broker with 2 queues, Q1 and Q2. I have two ruby-based consumers using activemessaging. Let's call them C1 and C2. Both consumers subscribe to each queue. I'm setting activemq.prefetchSize=1 when subscribing to each queue. I'm also setting ack=client. Consider the following sequence of events: 1) A message that triggers a long-running job is published to queue Q1. Call this M1. 2) M1 is dispatched to consumer C1, kicking off a long operation. 3) Two messages that trigger short jobs are published to queue Q2. Call these M2 and M3. 4) M2 is dispatched to C2 which quickly runs the short job. 5) M3 is dispatched to C1, even though C1 is still running M1. It's able to dispatch to C1 because prefetchSize=1 is set on the queue subscription, not on the connection. So the fact that a Q1 message has already been dispatched doesn't stop one Q2 message from being dispatched. Since activemessaging consumers are single-threaded, the net result is that M3 sits and waits on C1 for a long time until C1 finishes processing M1. So, M3 is not processed for a long time, despite the fact that consumer C2 is sitting idle (since it quickly finishes with message M2). Essentially, whenever a long Q1 job is run and then a whole bunch of short Q2 jobs are created, exactly one of the short Q2 jobs gets stuck on a consumer waiting for the long Q1 job to finish. Is there a way to set prefetchSize at the connection level rather than at the subscription level? I really don't want any messages dispatched to C1 while it is processing M1. The other alternative is that I could create a consumer dedicated to processing Q1 and then have other consumers dedicated to processing Q2. But, I'd rather not do that since Q1 messages are infrequent--Q1's dedicated consumers would sit idle most of the day tying up memory.

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• Trouble with Unions in C program.

  - by Jordan S

  I am working on a C program that uses a Union. The union definition is in FILE_A header file and looks like this... // FILE_A.h**************************************************** xdata union { long position; char bytes[4]; }CurrentPosition; If I set the value of CurrentPosition.position in FILE_A.c and then call a function in FILE_B.c that uses the union, the data in the union is back to Zero. This is demonstrated below. // FILE_A.c**************************************************** int main.c(void) { CurrentPosition.position = 12345; SomeFunctionInFileB(); } // FILE_B.c**************************************************** void SomeFunctionInFileB(void) { // After the following lines execute I see all zeros in the flash memory. WriteByteToFlash(CurrentPosition.bytes[0]; WriteByteToFlash(CurrentPosition.bytes[1]; WriteByteToFlash(CurrentPosition.bytes[2]; WriteByteToFlash(CurrentPosition.bytes[3]; } Now, If I pass a long to SomeFunctionInFileB(long temp) and then store it into CurrentPosition.bytes within that function, and finally call WriteBytesToFlash(CurrentPosition.bytes[n]... it works just fine. It appears as though the CurrentPosition Union is not global. So I tried changing the union definition in the header file to include the extern keyword like this... extern xdata union { long position; char bytes[4]; }CurrentPosition; and then putting this in the source (.c) file... xdata union { long position; char bytes[4]; }CurrentPosition; but this causes a compile error that says: C:\SiLabs\Optec Programs\AgosRot\MotionControl.c:76: error 91: extern definition for 'CurrentPosition' mismatches with declaration. C:\SiLabs\Optec Programs\AgosRot\/MotionControl.h:48: error 177: previously defined here So what am I doing wrong? How do I make the union global?

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• Cache data in SQL CE database

  - by user93422

  Background I have an SQL CE database, that is constantly updated (every second). I have a (web) application that allows a user to look at the data in real-time. At some point a user can click "take a snapshot" button, and it will open the snapshot in a different window. And then on that form, there is "print" and "download" buttons that will either generate a page for printing, or will stream the data as CSV file - but same data snapshot has to be used, i.e. I can't go to the DB to get latest data for that. Details SQL CE dabatase is exposed through WCF web service. Snapshot consists of up to 500 records, 10 columns each. Expiration time on the snapshot of 2 hours is sufficient. It is a low-traffic application, so I don't expect more than few (5) connections at the same time. Loosing snapshot is not a big deal, user can simply generate new one. database is accessed by self-hosted WCF web service using Linq-to-SQL. Web site is ASP.NET MVC hosted on UltiDev Cassini. database, and web site are most likely be on the same box, when deployed. The entire app is intranet bound. Problem I need to cache the snapshot of the data at the moment user pressed "take a snapshot" button, so that I can use same data to generate print page, or generate a file for download. Solution 1: Each time there is a need to generate a snapshot, I will create a table in the database. Since there are no temp tables in SQL CE, I will need to clean it up myself. Solution 2: Cache the snapshot in-memory on either DB server, or web server. Question: Is there anything wrong with proposed solutions? Any different solution suggestions?

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• PHP GD imagecreatefromstring discards transparency

  - by meustrus

  I've been trying to get transparency to work with my application (which dynamically resizes images before storing them) and I think I've finally narrowed down the problem after much misdirection about imagealphablending and imagesavealpha. The source image is never loaded with proper transparency! // With this line, the output image has no transparency (where it should be // transparent, colors bleed out randomly or it's completely black, depending // on the image) $img = imagecreatefromstring($fileData); // With this line, it works as expected. $img = imagecreatefrompng($fileName); // Blah blah blah, lots of image resize code into $img2 goes here; I finally // tried just outputting $img instead. header('Content-Type: image/png'); imagealphablending($img, FALSE); imagesavealpha($img, TRUE); imagepng($img); imagedestroy($img); It would be some serious architectural difficulty to load the image from a file; this code is being used with a JSON API that gets queried from an iPhone app, and it's easier in this case (and more consistent) to upload images as base64-encoded strings in the POST data. Do I absolutely need to somehow store the image as a file (just so that PHP can load it into memory again)? Is there maybe a way to create a Stream from $fileData that can be passed to imagecreatefrompng?

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• Can I get rid of this read lock?

  - by Pieter

  I have the following helper class (simplified): public static class Cache { private static readonly object _syncRoot = new object(); private static Dictionary<Type, string> _lookup = new Dictionary<Type, string>(); public static void Add(Type type, string value) { lock (_syncRoot) { _lookup.Add(type, value); } } public static string Lookup(Type type) { string result; lock (_syncRoot) { _lookup.TryGetValue(type, out result); } return result; } } Add will be called roughly 10/100 times in the application and Lookup will be called by many threads, many of thousands of times. What I would like is to get rid of the read lock. How do you normally get rid of the read lock in this situation? I have the following ideas: Require that _lookup is stable before the application starts operation. The could be build up from an Attribute. This is done automatically through the static constructor the attribute is assigned to. Requiring the above would require me to go through all types that could have the attribute and calling RuntimeHelpers.RunClassConstructor which is an expensive operation; Move to COW semantics. public static void Add(Type type, string value) { lock (_syncRoot) { var lookup = new Dictionary<Type, string>(_lookup); lookup.Add(type, value); _lookup = lookup; } } (With the lock (_syncRoot) removed in the Lookup method.) The problem with this is that this uses an unnecessary amount of memory (which might not be a problem) and I would probably make _lookup volatile, but I'm not sure how this should be applied. (John Skeets' comment here gives me pause.) Using ReaderWriterLock. I believe this would make things worse since the region being locked is small. Suggestions are very welcome.

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• smallest mysql type that accomodates single decimal

  - by donpal

  Database newbie here. I'm setting up a mysql table. One of the fields will accept a value in increment of a 0.5. e.g. 0.5, 1.0, 1.5, 2.0, .... 200.5, etc. I've tried int but it doesn't capture the decimals. `value` int(10), What would be the smallest type that can accommodate this value, considering it's only a single decimal. I also was considering that because the decimal will always be 0.5 if at all, I could store it in a separate boolean field? So I would have 2 fields instead. Is this a stupid or somewhat over complicated idea? I don't know if it really saves me any memory, and it might get slower now that I'm accessing 2 fields instead of 1 `value` int(10), `half` bool, //or something similar to boolean What are your suggestions guys? Is the first option better, and what's the smallest data type in that case that would get me the 0.5?

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• Winsock WSAAsyncSelect sending without an infinite buffer

  - by Xexr

  Hi, This is more of a design question than a specific code question, I'm sure I am missing the obvious, I just need another set of eyes. I am writing a multi-client server based on WSAAsyncSelect, each connection is made into an object of a connection class I have written which contains associated settings and buffers etc. My question concerns FD_WRITE, I understand how it operates: One FD_WRITE is sent immediately after a connection is established. Thereafter, you should send until WSAEWOULDBLOCK is received at which point you store what is left to send in a buffer, and wait to be told that it is ok to send again. This is where I have a problem, how large do I make this holding buffer within each connections object? The amount of time until a new FD_WRITE is received is unknown, I could be attempting to send a lot of stuff during this period, all the time adding to my outgoing buffer. If I make the buffer dynamic, memory usage could spiral out of control if for whatever reason, I am unable to send() and reduce the buffer. So my question is how do you generally handle this situation? Note I am not talking about the network buffer itself which winsock uses, but one of my own creation used to "queue" up sends. Hope I explained that well enough, thanks all!

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• [WEB] Local/Dev/Live deployment - best workflow

  - by Adam Kiss

  Hello, situation We our little company with 3 people, each has a localhost webserver and most projects (previous and current) are on one PC network shared disk. We have virtual server, where some of our clients' sites and our site. Our standard workflow is: Coder PC ? Programmer localhost ? dev domain (client.company.com) ? live version (client.com) It often happens, that there are two or three guys working on same projects at the same time - one is on dev version, two are on localhost. When finished, we try to synchronize the files on dev version and ideally not to mess (thanks ILMV:]) up any files, which *knock knock * doesn't happen often. And then one of us deploys dev version on live webserver. question we are looking for a way to simplify this workflow while updating websites - ideally some sort of diff uploader or VCS probably (Git/SVN/VCS/...), but we are not completely sure where to begin or what way would be ideal, therefore I ask you, fellow stackoverflowers for your experience with website / application deployment and recommended workflow. We probably will also need to use Mac in process, so if it won't be a problem, that would be even better. Thank you

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• .Net lambda expression-- where did this parameter come from?

  - by larryq

  I'm a lambda newbie, so if I'm missing vital information in my description please tell me. I'll keep the example as simple as possible. I'm going over someone else's code and they have one class inheriting from another. Here's the derived class first, along with the lambda expression I'm having trouble understanding: class SampleViewModel : ViewModelBase { private ICustomerStorage storage = ModelFactory<ICustomerStorage>.Create(); public ICustomer CurrentCustomer { get { return (ICustomer)GetValue(CurrentCustomerProperty); } set { SetValue(CurrentCustomerProperty, value); } } private int quantitySaved; public int QuantitySaved { get { return quantitySaved; } set { if (quantitySaved != value) { quantitySaved = value; NotifyPropertyChanged(p => QuantitySaved); //where does 'p' come from? } } } public static readonly DependencyProperty CurrentCustomerProperty; static SampleViewModel() { CurrentCustomerProperty = DependencyProperty.Register("CurrentCustomer", typeof(ICustomer), typeof(SampleViewModel), new UIPropertyMetadata(ModelFactory<ICustomer>.Create())); } //more method definitions follow.. Note the call to NotifyPropertyChanged(p => QuantitySaved) bit above. I don't understand where the "p" is coming from. Here's the base class: public abstract class ViewModelBase : DependencyObject, INotifyPropertyChanged, IXtremeMvvmViewModel { public event PropertyChangedEventHandler PropertyChanged; protected virtual void NotifyPropertyChanged<T>(Expression<Func<ViewModelBase, T>> property) { MvvmHelper.NotifyPropertyChanged(property, PropertyChanged); } } There's a lot in there that's not germane to the question I'm sure, but I wanted to err on the side of inclusiveness. The problem is, I don't understand where the 'p' parameter is coming from, and how the compiler knows to (evidently?) fill in a type value of ViewModelBase from thin air? For fun I changed the code from 'p' to 'this', since SampleViewModel inherits from ViewModelBase, but I was met with a series of compiler errors, the first one of which statedInvalid expression term '=>' This confused me a bit since I thought that would work. Can anyone explain what's happening here?

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• Why are references compacted inside Perl lists?

  - by parkan

  Putting a precompiled regex inside two different hashes referenced in a list: my @list = (); my $regex = qr/ABC/; push @list, { 'one' => $regex }; push @list, { 'two' => $regex }; use Data::Dumper; print Dumper(\@list); I'd expect: $VAR1 = [ { 'one' => qr/(?-xism:ABC)/ }, { 'two' => qr/(?-xism:ABC)/ } ]; But instead we get a circular reference: $VAR1 = [ { 'one' => qr/(?-xism:ABC)/ }, { 'two' => $VAR1->[0]{'one'} } ]; This will happen with indefinitely nested hash references and shallowly copied $regex. I'm assuming the basic reason is that precompiled regexes are actually references, and references inside the same list structure are compacted as an optimization (\$scalar behaves the same way). I don't entirely see the utility of doing this (presumably a reference to a reference has the same memory footprint), but maybe there's a reason based on the internal representation Is this the correct behavior? Can I stop it from happening? Aside from probably making GC more difficult, these circular structures create pretty serious headaches. For example, iterating over a list of queries that may sometimes contain the same regular expression will crash the MongoDB driver with a nasty segfault (see https://rt.cpan.org/Public/Bug/Display.html?id=58500)

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• C/C++: feedback in analyzing a code example

  - by KaiserJohaan

  Hello, I have a piece of code from an assignment I am uncertain about. I feel confident that I know the answer, but I just want to double-check with the community incase there's something I forgot. The title is basically secure coding and the question is just to explain the results. int main() { unsigned int i = 1; unsigned int c = 1; while (i > 0) { i = i*2; c++; } printf("%d\n", c); return 0; } My reasoning is this: At first glance you could imagine the code would run forever, considering it's initialized to a positive value and ever increasing. This of course is wrong because eventually the value will grow so large it will cause an integer overflow. This in turn is not entirely true either, because eventally it will force the variable 'i' to be signed by making the last bit to 1 and therefore regarded as a negative number, therefore terminating the loop. So it is not writing to unallocated memory and therefore cause integer overflow, but rather violating the data type and therefore causing the loop to terminate. I am quite sure this is the reason, but I just want to double check. Any opinions?

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• Is there really such a thing as a char or short in modern programming?

  - by Dean P

  Howdy all, I've been learning to program for a Mac over the past few months (I have experience in other languages). Obviously that has meant learning the Objective C language and thus the plainer C it is predicated on. So I have stumbles on this quote, which refers to the C/C++ language in general, not just the Mac platform. With C and C++ prefer use of int over char and short. The main reason behind this is that C and C++ perform arithmetic operations and parameter passing at integer level, If you have an integer value that can fit in a byte, you should still consider using an int to hold the number. If you use a char, the compiler will first convert the values into integer, perform the operations and then convert back the result to char. So my question, is this the case in the Mac Desktop and IPhone OS environments? I understand when talking about theses environments we're actually talking about 3-4 different architectures (PPC, i386, Arm and the A4 Arm variant) so there may not be a single answer. Nevertheless does the general principle hold that in modern 32 bit / 64 bit systems using 1-2 byte variables that don't align with the machine's natural 4 byte words doesn't provide much of the efficiency we may expect. For instance, a plain old C-Array of 100,000 chars is smaller than the same 100,000 ints by a factor of four, but if during an enumeration, reading out each index involves a cast/boxing/unboxing of sorts, will we see overall lower 'performance' despite the saved memory overhead?

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• How do I rewrite a for loop with a shared dependency using actors

  - by Thomas Rynne

  We have some code which needs to run faster. Its already profiled so we would like to make use of multiple threads. Usually I would setup an in memory queue, and have a number of threads taking jobs of the queue and calculating the results. For the shared data I would use a ConcurrentHashMap or similar. I don't really want to go down that route again. From what I have read using actors will result in cleaner code and if I use akka migrating to more than 1 jvm should be easier. Is that true? However, I don't know how to think in actors so I am not sure where to start. To give a better idea of the problem here is some sample code: case class Trade(price:Double, volume:Int, stock:String) { def value(priceCalculator:PriceCalculator) = (priceCalculator.priceFor(stock)-> price)*volume } class PriceCalculator { def priceFor(stock:String) = { Thread.sleep(20)//a slow operation which can be cached 50.0 } } object ValueTrades { def valueAll(trades:List[Trade], priceCalculator:PriceCalculator):List[(Trade,Double)] = { trades.map { trade => (trade,trade.value(priceCalculator)) } } def main(args:Array[String]) { val trades = List( Trade(30.5, 10, "Foo"), Trade(30.5, 20, "Foo") //usually much longer ) val priceCalculator = new PriceCalculator val values = valueAll(trades, priceCalculator) } } I'd appreciate it if someone with experience using actors could suggest how this would map on to actors.

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• Test Driven Development with C++: How to test a class which depends on other classes?

  - by Nikhil

  Suppose I have a class A which depends on 3 other classes X, Y and Z, either A uses these through a reference or a pointer or say A is templated to be instantiated with X, Y and Z doesn't matter, the key is that in order to test A, I need to have X, Y and Z. So I need to have fakes for A, B and C. Suppose I write them. Now, how do I swap real and fake objects easily? I can see that this works very easily in the case of templates. In order to make it work when A depends on X, Y and Z through a reference or a pointer, I would need to have a base class say X_Interface from which I can inherit X_Real and X_Fake. So basically, I would end up in having 3 times the number of classes for every class that would need to have a fake. I am most likely missing something. There has to be a simpler way to do this. Having a base class X_Interface is also quite expensive as I will be using more space and making virtual calls. I guess I could use CRTP as I know whether its a X_Real or X_Fake at compile time but still there must be a better way.

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• How to efficiently convert String, integer, double, datetime to binary and vica versa?

  - by Ben

  Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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• Can't get screen pixel from a specific full screen game with any language?

  - by user1007059

  Okay, I know this might seem like I'm posting a duplicate question since I've asked something similar like a day ago HOWEVER, if anyone sees any problem with this, please read my question first before judging: Yesterday I tried getting a specific pixel from a fullscreen game in C#. I thought my C# code was faulty but when I tried with multiple full screen games today they all worked except for that specific game. I literally tried with 10 different full screen games, a couple being mmofps, mmorpg, mmotps, regular rpg games, regular shooters, regular action adventure games, etc. I tried with multiple programming languages, and with every game except that specific game I'm dealing with, it returns the pixel color to me like I wanted. So let me explain what I tried: first I tried returning an IntPtr with C# using GetDC(IntPtr.Zero) before invoking GetPixel(int x, int y) and then getting the color out of it. Then I tried using the Robot class in Java and using the getPixelColor(int x, int y) method. I also tried using GetDC(0) to return an HDC object in C++ and then invoking GetPixel(int x, int y) before again extracting the color. These three methods worked EXACTLY the same in every single game except that specific game I was talking about. They returned the pixel perfectly, and extracted the exact same color perfectly. I don't feel it's necessary to tell you the game name or anything, since you probably don't even know it, but what could possibly be causing this malfunction in 1 specific game? PS: The game ALWAYS returns an RGB color of: A = 255, R = 0, G = 0, B = 0. Also, I tried taking a snapshot of the game with the 3 programming languages, and then getting the pixel which actually works in all 3 languages, but since I need to get this pixel every 30 ms, it kind of makes my game lag a bit (+ I think it takes up a lot of memory)

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• Unhandled Exception error message

  - by Joshua Green

  Does anyone know why including a term such as: t = PL_new_term_ref(); would cause an Unhandled Exception error message: 0xC0000005: Access violation reading location 0x0000000c. (Visual Studio 2008) I have a header file: class UserTaskProlog : public ArAction { public: UserTaskProlog( const char* name = " sth " ); ~UserTaskProlog( ); AREXPORT virtual ArActionDesired *fire( ArActionDesired currentDesired ); private: term_t t; }; and a cpp file: UserTaskProlog::UserTaskProlog( const char* name ) : ArAction( name, " sth " ) { char** argv; argv[ 0 ] = "libpl.dll"; PL_initialise( 1, argv ); PlCall( "consult( 'myProg.pl' )" ); } UserTaskProlog::~UserTaskProlog( ) { } ArActionDesired *UserTaskProlog::fire( ArActionDesired currentDesired ) { cout << " something " << endl; t = PL_new_term_ref( ); } Without t=PL_new_term_ref() everything works fine, but when I start adding my Prolog code (declarations first, such as t=PL_new_term_ref), I get this Access Violation error message. I'd appreciate any help. Thanks,

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• How to deserialize implementation classes in OSGi

  - by Daniel Schneller

  In an eRCP OSGi based application the user can push a button and go to a lock screen similar to that of Windows or Mac OS X. When this happens, the current state of the application is serialized to a file and control is handed over to the lock screen. In this mobile application memory is very tight, so we need to get rid of the original view/controller when the lock screen comes up. This works fine and we end up with a binary serialized file. Once the user logs back in, the file is read in again and the original state of the application restored. This works fine as well, except when the controller that was serialized contained a reference to an object which comes from a different bundle. In my concrete case the original controller (from bundle A) can call a web service and gets a result back. Nothing fancy, just some Strings and Numbers in a simple value holder class. However the controller only sees this as a Result interface; the actual runtime object (ResultImpl) is defined and created in a different bundle (bundle B, the webservice client implementation) and returned via a service call. When the deserialization now tries to thaw the controller from the file, it throws a ClassNotFound exception, complaining about not being able to deserialize the result object, because deserialization is called from bundle A, which cannot see the ResultImpl class from bundle B. Any ideas on how to work around that? The only thing I could come up with is to clone all the individual values into another object, defined in the controller's bundle, but this seems like quite a hassle.

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