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• ANSI C as core of a C# project? Is this possible?

  - by Nektarios

  I'm writing a NON-GUI app which I want to be cross platform between OS X and Windows. I'm looking at the following architecture, but I don't know if it will work on the windows side: (Platform specific entry point) - ANSI C main loop = ANSI C model code doing data processing / logic = (Platform specific helpers) So the core stuff I'm planning to write in regular ANSI C, because A) it should be platform independent, B) I'm extremely comfortable with C, C) It can do the job and do it well (Platform specific entry point) can be written in whatever necessary to get the job done, this is a small amount of code, doesn't matter to me. (Platform specific helpers) is the sticky thing. This is stuff like parsing XML, accessing databases, graphics toolkit stuff, whatever. Things that aren't easy in C. Things that modern languages/frameworks will give for free. On OS X this code will be written in Objective-C interfacing with Cocoa. On Windows I'm thinking my best bet is to use C# So on Windows my architecture (simplified) looks like (C# or C?) - ANSI C - C# Is this possible? Some thoughts/suggestions so far.. 1) Compile my C core as a .dll -- this is fine, but seems there's no way to call my C# helpers unless I can somehow get function pointers and pass them to my core, but that seems unlikely 2) Compile a C .exe and a C# .exe and have them talk via shared memory or some kind of IPC. I'm not entirely opposed to this but it obviously introduces a lot of complexity so it doesn't seem ideal 3) Instead of C# use C++, it gets me some nice data management stuff and nice helper code. And I can mix it pretty easily. And the work I do could probably easily port to Linux. But I really don't like C++, and I don't want this to turn in to a 3rd-party-library-fest. Not that it's a huge deal, but it's 2010.. anything for basic data management should be built in. And targetting Linux is really not a priority. Note that no "total" alternatives are OK as suggested in other similar questions on SO I've seen; java, RealBasic, mono.. this is an extremely performance intensive application doing soft realtime for game/simulation purposes, I need C & friends here to do it right (maybe you don't, but I do)

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• What can cause System.Move to occasionaly give wrong results?

  - by Fredrik Loftheim

  The last few days we have had some strange problems with our database components developed by a third party. There has been no changes to these components for months. The code that HAS changed the last few days is our own code and we have also updated our gui-components developed by another third party. After debugging I have found that a call to System.Move in one of the database component procedures occationaly gives wrong results! Please take a look at the code below from the database components and read my comments. How can this inconsistent behaviour happen? Can anyone give me an idea of how to procede to find the cause of this inconsistent behaviour? NB! I dont think there is anything wrong with THIS code, it is only shown to explain the problem "symptoms". My guess is that there is some sort of memory corruption or something, caused by our code or the updated gui-component-code. Edit: Take a look at the blogpost linked below. It seems that it could be related to my problem. At least as I read it it confirms that System.Move can give wrong results: http://blog.excastle.com/2007/08/28/delphi-bug-of-the-day-fpu-stack-leak/ Procedure InternalDescribe; var cbufl: sb4; //sb4=LongInt cbuf: array[0..30] of char; cbufp: PChar; //.... begin //..Some code repeat //...Some code to initialize cbufp and cbufl //On the 15. iteration the values immediately Before Move are always these: //cbufp = 'STDPRODUCTSTOREDELEMENTSCOUNT' //cbuf = ('S', 'T', 'A', 'T', 'U', 'S', #0, 'E', 'V', 'A', 'R', 'R', 'E', 'C', 'I', 'D', #0, 'D', 'U', 'C', 'T', 'I', 'D', #0, #0, #0, #0, #0, #0, #0, #0) //cbufl = 29 Move(cbufp^, cbuf, cbufl); //Values immediately After Move should then be: //cbuf = ('S', 'T', 'D', 'P', 'R', 'O', 'D', 'U', 'C', 'T', 'S', 'T', 'O', 'R', 'E', 'D', 'E', 'L', 'E', 'M', 'E', 'N', 'T', 'S', 'C', 'O', 'U', 'N', 'T', #0, #0) //But sometimes this Move results in this value( 1 in 5..15 times): //cbuf = ('S', 'T', 'D', 'P', 'R', 'O', 'D', 'U', 'C', 'T', 'S', 'T', 'O', 'R', 'E', 'D', #0, #0, #0, #0, #0, 'N', 'T', 'S', 'C', 'O', 'U', 'N', 'T', #0, #0) } until SomeCondition; //...Some more code end;

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• How to Transfer Large File from MS Word Add-In (VBA) to Web Server?

  - by Ian Robinson

  Overview I have a Microsoft Word Add-In, written in VBA (Visual Basic for Applications), that compresses a document and all of it's related contents (embedded media) into a zip archive. After creating the zip archive it then turns the file into a byte array and posts it to an ASMX web service. This mostly works. Issues The main issue I have is transferring large files to the web site. I can successfully upload a file that is around 40MB, but not one that is 140MB (timeout/general failure). A secondary issue is that building the byte array in the VBScript Word Add-In can fail by running out of memory on the client machine if the zip archive is too large. Potential Solutions I am considering the following options and am looking for feedback on either option or any other suggestions. Option One Opening a file stream on the client (MS Word VBA) and reading one "chunk" at a time and transmitting to ASMX web service which assembles the "chunks" into a file on the server. This has the benefit of not adding any additional dependencies or components to the application, I would only be modifying existing functionality. (Fewer dependencies is better as this solution should work in a variety of server environments and be relatively easy to set up.) Question: Are there examples of doing this or any recommended techniques (either on the client in VBA or in the web service in C#/VB.NET)? Option Two I understand WCF may provide a solution to the issue of transferring large files by "chunking" or streaming data. However, I am not very familiar with WCF, and am not sure what exactly it is capable of or if I can communicate with a WCF service from VBA. This has the downside of adding another dependency (.NET 3.0). But if using WCF is definitely a better solution I may not mind taking that dependency. Questions: Does WCF reliably support large file transfers of this nature? If so, what does this involve? Any resources or examples? Are you able to call a WCF service from VBA? Any examples?

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• Primary language - QtC++, C#, Java?

  - by Airjoe

  I'm looking for some input, but let me start with a bit of background (for tl;dr skip to end). I'm an IT major with a concentration in networking. While I'm not a CS major nor do I want to program as a vocation, I do consider myself a programmer and do pretty well with the concepts involved. I've been programming since about 6th grade, started out with a proprietary game creation language that made my transition into C++ at college pretty easy. I like to make programs for myself and friends, and have been paid to program for local businesses. A bit about that- I wrote some programs for a couple local businesses in my senior year in high school. I wrote management systems for local shops (inventory, phone/pos orders, timeclock, customer info, and more stuff I can't remember). It definitely turned out to be over my head, as I had never had any formal programming education. It was a great learning experience, but damn was it crappy code. Oh yeah, by the way, it was all vb6. So, I've used vb6 pretty extensively, I've used c++ in my classes (intro to programming up to algorithms), used Java a little bit in another class (had to write a ping client program, pretty easy) and used Java for some simple Project Euler problems to help learn syntax and such when writing the program for the class. I've also used C# a bit for my own simple personal projects (simple programs, one which would just generate an HTTP request on a list of websites and notify if one responded unexpectedly or not at all, and another which just held a list of things to do and periodically reminded me to do them), things I would've written in vb6 a year or two ago. I've just started using Qt C++ for some undergrad research I'm working on. Now I've had some formal education, I [think I] understand organization in programming a lot better (I didn't even use classes in my vb6 programs where I really should have), how it's important to structure code, split into functions where appropriate, document properly, efficiency both in memory and speed, dynamic and modular programming etc. I was looking for some input on which language to pick up as my "primary". As I'm not a "real programmer", it will be mostly hobby projects, but will include some 'real' projects I'm sure. From my perspective: QtC++ and Java are cross platform, which is cool. Java and C# run in a virtual machine, but I'm not sure if that's a big deal (something extra to distribute, possibly a bit slower? I think Qt would require additional distributables too, right?). I don't really know too much more than this, so I appreciate any help, thanks! TL;DR Am an avocational programmer looking for a language, want quick and straight forward development, liked vb6, will be working with database driven GUI apps- should I go with QtC++, Java, C#, or perhaps something else?

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• Different behavior of reflected generic delegates with and without debugger

  - by Andrew_B

  Hello. We have encountered some strange things while calling reflected generic delegates. In some cases with attatched debuger we can make impossible call, while without debugger we cannot catch any exception and application fastfails. Here is the code: using System; using System.Windows.Forms; using System.Reflection; namespace GenericDelegate { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private delegate Class2 Delegate1(); private void button1_Click(object sender, EventArgs e) { MethodInfo mi = typeof (Class1<>).GetMethod("GetClass", BindingFlags.NonPublic | BindingFlags.Static); if (mi != null) { Delegate1 del = (Delegate1) Delegate.CreateDelegate(typeof (Delegate1), mi); MessageBox.Show("1"); try { del(); } catch (Exception) { MessageBox.Show("No, I can`t catch it"); } MessageBox.Show("2"); mi.Invoke(null, new object[] {});//It's Ok, we'll get exception here MessageBox.Show("3"); } } class Class2 { } class Class1<T> : Class2 { internal static Class2 GetClass() { Type type = typeof(T); MessageBox.Show("Type name " + type.FullName +" Type: " + type + " Assembly " + type.Assembly); return new Class1<T>(); } } } } There are two problems: Behavior differs with debugger and without You cannot catch this error without debugger by clr tricks. It's just not the clr exception. There are memory acces vialation, reading zero pointer inside of internal code. Use case: You develop something like plugins system for your app. You read external assembly, find suitable method in some type, and execute it. And we just forgot about that we need to check up is the type generic or not. Under VS (and .net from 2.0 to 4.0) everything works fine. Called function does not uses static context of generic type and type parameters. But without VS application fails with no sound. We even cannot identify call stack attaching debuger. Tested with .net 4.0 The question is why VS catches but runtime do not?

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• Technical non-terminating condition in a loop

  - by Snarfblam

  Most of us know that a loop should not have a non-terminating condition. For example, this C# loop has a non-terminating condition: any even value of i. This is an obvious logic error. void CountByTwosStartingAt(byte i) { // If i is even, it never exceeds 254 for(; i < 255; i += 2) { Console.WriteLine(i); } } Sometimes there are edge cases that are extremely unlikeley, but technically constitute non-exiting conditions (stack overflows and out-of-memory errors aside). Suppose you have a function that counts the number of sequential zeros in a stream: int CountZeros(Stream s) { int total = 0; while(s.ReadByte() == 0) total++; return total; } Now, suppose you feed it this thing: class InfiniteEmptyStream:Stream { // ... Other members ... public override int Read(byte[] buffer, int offset, int count) { Array.Clear(buffer, offset, count); // Output zeros return count; // Never returns -1 (end of stream) } } Or more realistically, maybe a stream that returns data from external hardware, which in certain cases might return lots of zeros (such as a game controller sitting on your desk). Either way we have an infinite loop. This particular non-terminating condition stands out, but sometimes they don't. A completely real-world example as in an app I'm writing. An endless stream of zeros will be deserialized into infinite "empty" objects (until the collection class or GC throws an exception because I've exceeded two billion items). But this would be a completely unexpected circumstance (considering my data source). How important is it to have absolutely no non-terminating conditions? How much does this affect "robustness?" Does it matter if they are only "theoretically" non-terminating (is it okay if an exception represents an implicit terminating condition)? Does it matter whether the app is commercial? If it is publicly distributed? Does it matter if the problematic code is in no way accessible through a public interface/API? Edit: One of the primary concerns I have is unforseen logic errors that can create the non-terminating condition. If, as a rule, you ensure there are no non-terminating conditions, you can identify or handle these logic errors more gracefully, but is it worth it? And when? This is a concern orthogonal to trust.

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• nodejs async.waterfall method

  - by user1513388

  Update 2 Complete code listing var request = require('request'); var cache = require('memory-cache'); var async = require('async'); var server = '172.16.221.190' var user = 'admin' var password ='Passw0rd' var dn ='\\VE\\Policy\\Objects' var jsonpayload = {"Username": user, "Password": password} async.waterfall([ //Get the API Key function(callback){ request.post({uri: 'http://' + server +'/sdk/authorize/', json: jsonpayload, headers: {'content_type': 'application/json'} }, function (e, r, body) { callback(null, body.APIKey); }) }, //List the credential objects function(apikey, callback){ var jsonpayload2 = {"ObjectDN": dn, "Recursive": true} request.post({uri: 'http://' + server +'/sdk/Config/enumerate?apikey=' + apikey, json: jsonpayload2, headers: {'content_type': 'application/json'} }, function (e, r, body) { var dns = []; for (var i = 0; i < body.Objects.length; i++) { dns.push({'name': body.Objects[i].Name, 'dn': body.Objects[i].DN}) } callback(null, dns, apikey); }) }, function(dns, apikey, callback){ // console.log(dns) var cb = []; for (var i = 0; i < dns.length; i++) { //Retrieve the credential var jsonpayload3 = {"CredentialPath": dns[i].dn, "Pattern": null, "Recursive": false} console.log(dns[i].dn) request.post({uri: 'http://' + server +'/sdk/credentials/retrieve?apikey=' + apikey, json: jsonpayload3, headers: {'content_type': 'application/json'} }, function (e, r, body) { // console.log(body) cb.push({'cl': body.Classname}) callback(null, cb, apikey); console.log(cb) }); } } ], function (err, result) { // console.log(result) // result now equals 'done' }); Update: I'm building a small application that needs to make multiple HTTP calls to a an external API and amalgamates the results into a single object or array. e.g. Connect to endpoint and get auth key - pass auth key to step 2 Connect to endpoint using auth key and get JSON results - create an object containing summary results and pass to step 3. Iterate over passed object summary results and call API for each item in the object to get detailed information for each summary line Create a single JSON data structure that contains the summary and detail information. The original question below outlines what I've tried so far! Original Question: Will the async.waterfall method support multiple callbacks? i.e. Iterate over an array thats passed from a previous item in the chain, then invoke multiple http requests each of which would have their own callbacks. e.g, sync.waterfall([ function(dns, key, callback){ var cb = []; for (var i = 0; i < dns.length; i++) { //Retrieve the credential var jsonpayload3 = {"Cred": dns[i].DN, "Pattern": null, "Recursive": false} console.log(dns[i].DN) request.post({uri: 'http://' + vedserver +'/api/cred/retrieve?apikey=' + key, json: jsonpayload3, headers: {'content_type': 'application/json'} }, function (e, r, body) { console.log(body) cb.push({'cl': body.Classname}) callback(null, cb, key); }); } }

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• how to set footer image in this video screen?

  - by bala

  hi my problem is how to create footer image in this video screen while playing.... how to create this format. now i am give my description: • 1) Header image, a stretched background image. The location of this external image comes from the application xml; • 2) Footer image, a stretched background image. The location of this external image comes from the application xml; 2.a) the copyright, disclaimer and buy block, this block contains links to popup windows that contain a copyright and or disclaimer. And an option to buy the application for the advertisement less version. The content of this block is fed trough the application XML feed. The color of the text is fed by the application xml plus the popup links and texts itself; • 3) Carousel image, a stretched background image. The location of this external image comes from the application xml; 3.a) the carousel contains objects that can flow from right to left, possibly trough a animation (a soft break of the slide). The first object is centered in the middle of the carousel. This is the first element in the video feed. All the subsequent video object are added to the right of the centered object; 4) Total Video object, this object links to window two with the corresponding video of this object. This object is visually build out of the following sub parts:o 4.a) Thumb object (possible playing video thumb); 4.b) Reflection of the Thumb; 4.c) Textual Explanation of Thumb. 1) Video stream, this is the video stream coming from a external server streamed to the television (maybe up scaled) as 720p stream; 2) Advertisement, the type of advertisement shown overlaid on the video is based on previous settings in the video feed. This could mean that Admob, Adsense or a third party image plus URL could be shown. When the advertisement is selected trough navigation (it will highlight in a different color as a border around the advertisement. The color an thickness can be managed trough the application xml), when clicked a browser will open with the associated site (the application will be pushed to the background process, when the user is finished it will return to the app); 3) A back button, an image and navigational element. The location of the image comes from the application xml. The button is only shown when a cursor is moved (a button is pressed on the remote) it will highlight when selected and when pressed will forward the screen to the main window. When the main window is opened the video will be removed from cache and memory and cannot be start from the point it was exited. please give me your idea....

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• DataGridView live display of datatable using virtual mode

  - by Chris

  I have a DataGridView that will display records (log entries) from a database. The amount of records that can exist at a time is very large. I would like to use the virtual mode feature of the DataGridView to display a page of data, and to minimize the amount of data that has to be transferred across a network at a given time. Polling for data is out of the question. There will be several clients running at a time, all of which are on the same network and viewing the records. If they all poll for data, the network will run very slowly. The data is read-only to the user; they won't be able to edit any of it, just view it. I need to know when updates occur in the database, and I need to update the screen with those updates accordingly using virtual mode. If a page of data a user is viewing contains data that has change, he/she will see those updates on that page. If updates were made to data in the database, but not in the data the user is viewing, then not much really changes on the user screen (Maybe just the scroll bar if records were added or removed). My current approach is using SQL server change tracking with the sync framework. Each client has a local SQL Server CE instance and database file that is kept in sync with the main database server. I use the information from the synchronization event to see if any changes were made to the main database and were sync'ed to the client. I need to use the DataGridView virtual mode here because I can't have thousands of records loaded into the DataGridView at once, otherwise memory usage goes through the roof. The main challenge right now is knowing how to use virtual mode to provide a seamless experience to the user by allowing them to scroll up and down through the records, and also have records update on the fly without interfering with the user inappropriately. Has anybody dealt with this issue before, and if so, where I can see how they did it? I've gone through some of the MSDN documentation and examples on virtual mode. So far, I haven't found documentation and/or examples on their site that explains how to do what I am trying to accomplish.

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• C - What is the proper format to allow a function to show an error was encountered?

  - by BrainSteel

  I have a question about what a function should do if the arguments to said function don't line up quite right, through no fault of the function call. Since that sentence doesn't make much sense, I'll offer my current issue. To keep it simple, here is the most relevant and basic function I have. float getYValueAt(float x, PHYS_Line line, unsigned short* error) *error = 0; if(x < line.start.x || x > line.end.x){ *error = 1; return -1; } if(line.slope.value != 0){ //line's equation: y - line.start.y = line.slope.value(x - line.start.x) return line.slope.value * (x - line.start.x) + line.start.y; } else if(line.slope.denom == 0){ if(line.start.x == x) return line.start.y; else{ *error = 1; return -1; } } else if(line.slope.num == 0){ return line.start.y; } } The function attempts to find the point on a line, given a certain x value. However, under some circumstances, this may not be possible. For example, on the line x = 3, if 5 is passed as a value, we would have a problem. Another problem arises if the chosen x value is not within the interval the line is on. For this, I included the error pointer. Given this format, a function call could work as follows: void foo(PHYS_Line some_line){ unsigned short error = 0; float y = getYValueAt(5, some_line, &error); if(error) fooey(); else do_something_with_y(y); } My question pertains to the error. Note that the value returned is allowed to be negative. Returning -1 does not ensure that an error has occurred. I know that it is sometimes preferred to use the following method to track an error: float* getYValueAt(float x, PHYS_Line line); and then return NULL if an error occurs, but I believe this requires dynamic memory allocation, which seems even less sightly than the solution I was using. So, what is standard practice for an error occurring?

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• Ajax progress with PHP session

  - by FFish

  I have an app that processes images and use jQuery to display progress to the user. I done this with writing to a textfile each time and image is processed and than read this status with a setInterval. Because no images are actually written in the processing (I do it in PHP's memory) I thought a log.txt would be a solution, but I am not sure about all the fopen and fread's. Is this prone to issues? I tried also with PHP sessions, but can't seem to get it to work, I don't get why.. HTML: <a class="download" href="#">request download</a> <p class="message"></p> JS: $('a.download').click(function() { var queryData = {images : ["001.jpg", "002.jpg", "003.jpg"]}; $("p.message").html("initializing..."); var progressCheck = function() { $.get("dynamic-session-progress.php", function(data) { $("p.message").html(data); } ); }; $.post('dynamic-session-process.php', queryData, function(intvalId) { return function(data) { $("p.message").html(data); clearInterval(intvalId); } } (setInterval(progressCheck, 1000)) ); return false; }); process.php: // session_start(); $arr = $_POST['images']; $arr_cnt = count($arr); $filename = "log.txt"; for ($i = 1; $i <= $arr_cnt; $i++) { $content = "processing $val ($i/$arr_cnt)"; $handle = fopen($filename, 'w'); fwrite($handle, $content); fclose($handle); // $_SESSION['counter'] = $content; sleep(3); // to mimic image processing } echo "<a href='#'>download zip</a>"; progress.php: // session_start(); $filename = "log.txt"; $handle = fopen($filename, "r"); $contents = fread($handle, filesize($filename)); fclose($handle); echo $contents; // echo $_SESSION['counter'];

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• Rewrite code from Threads to AnyEvent

  - by user1779868

  I wrote a code: use LWP::UserAgent; use HTTP::Cookies; use threads; use threads::shared; $| = 1; $threads = 50; my @urls : shared = loadf('url.txt'); my @thread_list = (); $thread_list[$_] = threads->create(\&thread) for 0 .. $threads - 1; $_->join for @thread_list; thread(); sub thread { my ($web, $ck) = browser(); while(1) { my $url = shift @urls; if(!$url) { last; } $code = $web->get($url)->code; print "[+] $url - code: $code\n"; if($code == 200) { open F, ">>200.txt"; print F $url."\n"; close F; } elsif($code == 301) { open F, ">>301.txt"; print F $url."\n"; close F; } else { open F, ">>else.txt"; print F "$url code - $code\n"; close F; } } } sub loadf { open (F, "<".$_[0]) or erroropen($_[0]); chomp(my @data = <F>); close F; return @data; } sub browser { my $web = new LWP::UserAgent; my $ck = new HTTP::Cookies; $web->cookie_jar($ck); $web->agent('Opera/9.80 (Windows 7; U; en) Presto/2.9.168 Version/11.50'); $web->timeout(5); return $web, $ck; } After its working for some time physical storage is full. Can u help me to re-write it with AnyEvent. I tried but my code didn't work. I read that it will help me to safe some memory. Thanks a lot to any helpers.

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• How can I run an android frame animation without it skewing?

  - by GameDev123

  I have a small state machine that runs a series of frame by frame animations in an ImageView, in a nested hierarchy of layouts. There is more than adequate space to display each frame of the animation. Each frame of the animation is cropped to fit the minimum amount of area, in order to save memory. If a frame only contains 50x50 worth of pixels then the png is 50x50. There is no transparent padding to keep them the same size. The ImageView is directly within a RelativeLayout, and is anchored to the bottom left with some padding. The general idea being that the character in the animation performs some action, which results in individual frames of the animation growing or shrinking. The issue is that individual frames of animation are skewed, and there does not appear to be any way of preventing this. If I set the source of the imageview directly to one of the frames of animation, it displays fine in the layout manager. I have tried this with Adjust View Bounds set to true, false, and undefined. I have tried using the background and the src attribute of imageview to set the animation drawable, I have tried every configuration of layout manager and setting minimum/maximum size that I can think of, and it still stretches the character on various frames depending on the size of the source png. In essence, all I want to do is say "I want this ImageView to anchor in the bottom left and then display any frame that happens to be in it without stretching or skewing it in any way aside from that which occurred when the frame png's were loaded." Seems simple, but I have yet to come across any way of doing it. Here is the layout of the imageview as of my last test, I had to remove bits of the XML to get it to display but nothing pertinent: RelativeLayout android:orientation="horizontal" android:layout_above="@+id/MenuOptions" android:layout_width="fill_parent" android:id="@+id/AnimationLayout" android:clipChildren="false" android:minHeight="180dp" android:layout_height="fill_parent" android:layout_below="@+id/GameBarLayout" ImageView android:id="@+id/animatedImg" android:layout_height="wrap_content" android:layout_width="wrap_content" android:visibility="visible" android:baselineAlignBottom="true" android:minHeight="180dp" android:minWidth="200dp" android:adjustViewBounds="true" android:layout_alignParentBottom="true" android:paddingLeft="30dp" android:paddingBottom="10dp" android:src="@drawable/idle01"/ImageView /RelativeLayout Here is how an animation is set up: animationDrawable = new AnimationDrawable(); animationDrawable.addFrame(res.getDrawable(R.drawable.idle01), 16); animationDrawable.addFrame(res.getDrawable(R.drawable.idle02), 16); animationDrawable.addFrame(res.getDrawable(R.drawable.idle03), 16);

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• C++ Vector vs Array (Time)

  - by vsha041

  I have got here two programs with me, both are doing exactly the same task. They are just setting an boolean array / vector to the value true. The program using vector takes 27 seconds to run whereas the program involving array with 5 times greater size takes less than 1 s. I would like to know the exact reason as to why there is such a major difference ? Are vectors really that inefficient ? Program using vectors #include <iostream> #include <vector> #include <ctime> using namespace std; int main(){ const int size = 2000; time_t start, end; time(&start); vector<bool> v(size); for(int i = 0; i < size; i++){ for(int j = 0; j < size; j++){ v[i] = true; } } time(&end); cout<<difftime(end, start)<<" seconds."<<endl; } Runtime - 27 seconds Program using Array #include <iostream> #include <ctime> using namespace std; int main(){ const int size = 10000; // 5 times more size time_t start, end; time(&start); bool v[size]; for(int i = 0; i < size; i++){ for(int j = 0; j < size; j++){ v[i] = true; } } time(&end); cout<<difftime(end, start)<<" seconds."<<endl; } Runtime - < 1 seconds Platform - Visual Studio 2008 OS - Windows Vista 32 bit SP 1 Processor Intel(R) Pentium(R) Dual CPU T2370 @ 1.73GHz Memory (RAM) 1.00 GB Thanks Amare

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• Better way to write an object generator for an RAII template class?

  - by Dan

  I would like to write an object generator for a templated RAII class -- basically a function template to construct an object using type deduction of parameters so the types don't have to be specified explicitly. The problem I foresee is that the helper function that takes care of type deduction for me is going to return the object by value, which will result in a premature call to the RAII destructor when the copy is made. Perhaps C++0x move semantics could help but that's not an option for me. Anyone seen this problem before and have a good solution? This is what I have: template<typename T, typename U, typename V> class FooAdder { private: typedef OtherThing<T, U, V> Thing; Thing &thing_; int a_; // many other members public: FooAdder(Thing &thing, int a); ~FooAdder(); void foo(T t, U u); void bar(V v); }; The gist is that OtherThing has a horrible interface, and FooAdder is supposed to make it easier to use. The intended use is roughly like this: FooAdder(myThing, 2) .foo(3, 4) .foo(5, 6) .bar(7) .foo(8, 9); The FooAdder constructor initializes some internal data structures. The foo and bar methods populate those data structures. The ~FooAdder dtor wraps things up and calls a method on thing_, taking care of all the nastiness. That would work fine if FooAdder wasn't a template. But since it is, I would need to put the types in, more like this: FooAdder<Abc, Def, Ghi>(myThing, 2) ... That's annoying, because the types can be inferred based on myThing. So I would prefer to create a templated object generator, similar to std::make_pair, that will do the type deduction for me. Something like this: template<typename T, typename U, typename V> FooAdder<T, U, V> AddFoo(Thing &thing, int a) { return FooAdder<T, U, V>(thing, a); } That seems problematic: because it returns by value, the stack temporary object will be destructed, which will cause the RAII dtor to run prematurely. One thought I had was to give FooAdder a copy ctor with move semantics, kinda like std::auto_ptr. But I would like to do this without dynamic memory allocation, so I thought the copy ctor could set a flag within FooAdder indicating the dtor shouldn't do the wrap-up. Like this: FooAdder(FooAdder &rhs) // Note: rhs is not const : thing_(rhs.thing_) , a_(rhs.a_) , // etc... lots of other members, annoying. , moved(false) { rhs.moved = true; } ~FooAdder() { if (!moved) { // do whatever it would have done } } Seems clunky. Anyone got a better way?

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• Javascript to add cdata section on the fly?

  - by Chris G.

  I'm having trouble with special characters that exist in an xml node attribute. To combat this, I'm trying to render the attributes as child nodes and, where necessary, using cdata sections to get around the special characters. The problem is, I can't seem to get the cdata section appended to the node correctly. I'm iterating over the source xml node's attributes and creating new nodes. If the attribute.name = "description" I want to put the attribute.text() in a cdata section and append the new node. That's where I jump the track. // newXMLData is the new xml document that I've created in memory for (var ctr =0;ctr< this.attributes.length;ctr++){ // iterate over the attributes if( this.attributes[ctr].name =="Description"){ // if the attribute name is "Description" add a CDATA section var thisNodeName = this.attributes[ctr].name; newXMLDataNode.append("<"+thisNodeName +"></"+ thisNodeName +">" ); var cdata = newXMLData.createCDATASection('test'); // here's where it breaks. } else { // It's not "Description" so just append the new node. newXMLDataNode.append("<"+ this.attributes[ctr].name +">" + $(this.attributes[ctr]).text() + "</"+ this.attributes[ctr].name +">" ); } } Any ideas? Is there another way to add a cdata section? Here's a sample snippet of the source... <row pSiteID="4" pSiteTile="Test Site Name " pSiteURL="http://www.cnn.com" ID="1" Description="<div>blah blah blah since June 2007.&amp;nbsp; T<br>&amp;nbsp;<br>blah blah blah blah&amp;nbsp; </div>" CreatedDate="2010-09-20 14:46:18" Comments="Comments example.&#10;" > here's what I'm trying to create... <Site> <PSITEID>4</PSITEID> <PSITETILE>Test Site Name</PSITETILE> <PSITEURL>http://www.cnn.com</PSITEURL> <ID>1</ID> <DESCRIPTION><![CDATA[<div>blah blah blah since June 2007.&amp;nbsp; T<br>&amp;nbsp;<br>blah blah blah blah&amp;nbsp; </div ]]></DESCRIPTION> <CREATEDDATE>2010-09-20 14:46:18</CREATEDDATE> <COMMENTS><![CDATA[ Comments example.&#10;]]></COMMENTS> </Site>

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• Calling managed code from unmanaged win32 assembly dll - crash

  - by JustGreg

  I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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• Is it possible to create a C++ factory system that can create an instance of any "registered" object

  - by chrensli

  Hello, I've spent my entire day researching this topic, so it is with some scattered knowledge on the topic that i come to you with this inquiry. Please allow me to describe what I am attempting to accomplish, and maybe you can either suggest a solution to the immediate question, or another way to tackle the problem entirely. I am trying to mimic something related to how XAML files work in WPF, where you are essentially instantiating an object tree from an XML definition. If this is incorrect, please inform. This issue is otherwise unrelated to WPF, C#, or anything managed - I solely mention it because it is a similar concept.. So, I've created an XML parser class already, and generated a node tree based on ObjectNode objects. ObjectNode objects hold a string value called type, and they have an std::vector of child ObjectNode objects. The next step is to instantiate a tree of objects based on the data in the ObjectNode tree. This intermediate ObjectNode tree is needed because the same ObjectNode tree might be instantiated multiple times or delayed as needed. The tree of objects that is being created is such that the nodes in the tree are descendants of a common base class, which for now we can refer to as MyBase. Leaf nodes can be of any type, not necessarily derived from MyBase. To make this more challenging, I will not know what types of MyBase derived objects might be involved, so I need to allow for new types to be registered with the factory. I am aware of boost's factory. Their docs have an interesting little design paragraph on this page: o We may want a factory that takes some arguments that are forwarded to the constructor, o we will probably want to use smart pointers, o we may want several member functions to create different kinds of objects, o we might not necessarily need a polymorphic base class for the objects, o as we will see, we do not need a factory base class at all, o we might want to just call the constructor - without #new# to create an object on the stack, and o finally we might want to use customized memory management. I might not be understanding this all correctly, but that seems to state that what I'm trying to do can be accomplished with boost's factory. But all the examples I've located, seem to describe factories where all objects are derived from a base type. Any guidance on this would be greatly appreciated. Thanks for your time!

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• Defined variables and arrays vs functions in php

  - by Frank Presencia Fandos

  Introduction I have some sort of values that I might want to access several times each page is loaded. I can take two different approaches for accessing them but I'm not sure which one is 'better'. Three already implemented examples are several options for the Language, URI and displaying text that I describe here: Language Right now it is configured in this way: lang() is a function that returns different values depending on the argument. Example: lang("full") returns the current language, "English", while lang() returns the abbreviation of the current language, "en". There are many more options, like lang("select"), lang("selectact"), etc that return different things. The code is too long and irrelevant for the case so if anyone wants it just ask for it. Url The $Url array also returns different values depending on the request. The whole array is fully defined in the beginning of the page and used to get shorter but accurate links of the current page. Example: $Url['full'] would return "http://mypage.org/path/to/file.php?page=1" and $Url['file'] would return "file.php". It's useful for action="" within the forms and many other things. There are more values for $Url['folder'], $Url['file'], etc. Same thing about the code, if wanted, just request it. Text [You can skip this section] There's another array called $Text that is defined in the same way than $Url. The whole array is defined at the beginning, making a mysql call and defining all $Text[$i] for current page with a while loop. I'm not sure if this is more efficient than multiple calls for a single mysql cell. Example: $Text['54'] returns "This is just a test array!" which this could perfectly be implemented with a function like text(54). Question With the 3 examples you can see that I use different methods to do almost the same function (no pun intended), but I'm not sure which one should become the standard one for my code. I could create a function called url() and other called text() to output what I want. I think that working with functions in those cases is better, but I'm not sure why. So I'd really appreciate your opinions and advice. Should I mix arrays and functions in the way I described or should I just use funcions? Please, base your answer in this: The source needs to be readable and reusable by other developers Resource consumption (processing, time and memory). The shorter the code the better. The more you explain the reasons the better. Thank you PS, now I know the differences between $Url and $Uri.

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• Controlling the USB from Windows

  - by b-gen-jack-o-neill

  Hi, I know this probably is not the easiest thing to do, but I am trying to connect Microcontroller and PC using USB. I dont want to use internal USART of Microcontroller or USB to RS232 converted, its project indended to help me understand various principles. So, getting the communication done from the Microcontroller side is piece of cake - I mean, when I know he protocol, its relativelly easy to implement it on Micro, becouse I am in direct control of evrything, even precise timing. But this is not the case of PC. I am not very familiar with concept of Windows handling the devices connected. In one of my previous question I ask about how Windows works with devices thru drivers. I understood that for internal use of Windows, drivers must have some default set of functions available to OS. I mean, when OS wants to access HDD, it calls HDD driver (which is probably internal in OS), with specific "questions" so that means that HDD driver has to be written to cooperate with Windows, to have write function in the proper place to be called by the OS. Something similiar is for GPU, Even DirectX, I mean DirectX must call specific functions from drivers, so drivers must be written to work with DX. I know, many functions from WinAPI works on their own, but even "simple" window must be in the end written into framebuffer, using MMIO to adress specified by drivers. Am I right? So, I expected that Windows have internal functions, parts of WinAPI designed to work with certain comonly used things. To call manufacturer-designed drivers. But this seems to not be entirely true becouse Windows has no way to communicate thru Paralel port. I mean, there is no function in the WinAPI to work with serial port, but there are funcions to work with HDD,GPU and so. But now there comes the part I am getting very lost at. So, I think Windows must have some built-in functions to communicate thru USB, becouse for example it handles USB flash memory. So, is there any WinAPI function designed to let user to operate USB thru that function, or when I want to use USB myself, do I have to call desired USB-driver function myself? Becouse all you need to send to USB controller is device adress and the infromation right? I mean, I don´t have to write any new drivers, am I right? Just to call WinAPI function if there is such, or directly call original USB driver. Does any of this make some sense?

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• Java template classes using generator or similar?

  - by Hugh Perkins

  Is there some library or generator that I can use to generate multiple templated java classes from a single template? Obviously Java does have a generics implementation itself, but since it uses type-erasure, there are lots of situations where it is less than adequate. For example, if I want to make a self-growing array like this: class EasyArray { T[] backingarray; } (where T is a primitive type), then this isn't possible. This is true for anything which needs an array, for example high-performance templated matrix and vector classes. It should probably be possible to write a code generator which takes a templated class and generates multiple instantiations, for different types, eg for 'double' and 'float' and 'int' and 'String'. Is there something that already exists that does this? Edit: note that using an array of Object is not what I'm looking for, since it's no longer an array of primitives. An array of primitives is very fast, and uses only as much space a sizeof(primitive) * length-of-array. An array of object is an array of pointers/references, that points to Double objects, or similar, which could be scattered all over the place in memory, require garbage collection, allocation, and imply a double-indirection for access. Edit2: good god, voted down for asking for something that probably doesn't currently exist, but is technically possible and feasible? Does that mean that people looking for ways to improve things have already left the java community? Edit3: Here is code to show the difference in performance between primitive and boxed arrays: int N = 10*1000*1000; double[]primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } Object[] objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } tic(); primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } toc(); tic(); objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } toc(); Results: double[] array: 148 ms Double[] array: 4614 ms Not even close!

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• Solve a maze using multicores?

  - by acidzombie24

  This question is messy, i dont need a working solution, i need some psuedo code. How would i solve this maze? This is a homework question. I have to get from point green to red. At every fork i need to 'spawn a thread' and go that direction. I need to figure out how to get to red but i am unsure how to avoid paths i already have taken (finishing with any path is ok, i am just not allowed to go in circles). Heres an example of my problem, i start by moving down and i see a fork so one goes right and one goes down (or this thread can take it, it doesnt matter). Now lets ignore the rest of the forks and say the one going right hits the wall, goes down, hits the wall and goes left, then goes up. The other thread goes down, hits the wall then goes all the way right. The bottom path has been taken twice, by starting at different sides. How do i mark this path has been taken? Do i need a lock? Is this the only way? Is there a lockless solution? Implementation wise i was thinking i could have the maze something like this. I dont like the solution because there is a LOT of locking (assuming i lock before each read and write of the haveTraverse member). I dont need to use the MazeSegment class below, i just wrote it up as an example. I am allowed to construct the maze however i want. I was thinking maybe the solution requires no connecting paths and thats hassling me. Maybe i could split the map up instead of using the format below (which is easy to read and understand). But if i knew how to split it up i would know how to walk it thus the problem. How do i walk this maze efficiently? The only hint i receive was dont try to conserve memory by reusing it, make copies. However that was related to a problem with ordering a list and i dont think the hint was a hint for this. class MazeSegment { enum Direction { up, down, left, right} List<Pair<Direction, MazeSegment*>> ConnectingPaths; int line_length; bool haveTraverse; } MazeSegment root; class MazeSegment { enum Direction { up, down, left, right} List<Pair<Direction, MazeSegment*>> ConnectingPaths; bool haveTraverse; } void WalkPath(MazeSegment segment) { if(segment.haveTraverse) return; segment.haveTraverse = true; foreach(var v in segment) { if(v.haveTraverse == false) spawn_thread(v); } } WalkPath(root);

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• probelm with recv() on a tcp connection

  - by michael

  Hi, I am simulating TCP communication on windows in C I have sender and a receiver communicating. sender sends packets of specific size to receiver. receiver gets them and send an ACK for each packet it received back to the sender. If the sender didn't get a specific packet (they are numbered in a header inside the packet) it sends the packet again to the receiver. Here is the getPacket function on the receiver side: //get the next packet from the socket. set the packetSize to -1 //if it's the first packet. //return: total bytes read // return: 0 if socket has shutdown on sender side, -1 error, else number of bytes received int getPakcet(char *chunkBuff,int packetSize,SOCKET AcceptSocket){ int totalChunkLen = 0; int bytesRecv=-1; bool firstTime=false; if (packetSize==-1) { packetSize=MAX_PACKET_LENGTH; firstTime=true; } int needToGet=packetSize; do { char* recvBuff; recvBuff = (char*)calloc(needToGet,sizeof(char)); if(recvBuff == NULL){ fprintf(stderr,"Memory allocation problem\n"); return -1; } bytesRecv = recv(AcceptSocket, recvBuff, needToGet, 0); if (bytesRecv == SOCKET_ERROR){ fprintf(stderr,"recv() error %ld.\n", WSAGetLastError()); totalChunkLen=-1; return -1; } if (bytesRecv == 0){ fprintf(stderr,"recv(): socket has shutdown on sender side"); return 0; } else if(bytesRecv > 0) { memcpy(chunkBuff + totalChunkLen,recvBuff,bytesRecv); totalChunkLen+=bytesRecv; } needToGet-=bytesRecv; } while ((totalChunkLen < packetSize) && (!firstTime)); return totalChunkLen; } i use firstTime because for the first time the receiver doesn't know the normal package size that the sender is going to send to it, so i use a MAX_PACKET_LENGTH to get a package and then set the normal package size to the num of bytes i have received my problem is the last package. it's size is less than the package size so lets say last package size is 2 and the normal package size is 4. so recv() gets two bytes, continues to the while condition, then totalChunkLen < packetSize because 2<4 so it iterates the loop again and the gets stuck in recv() because it's blocking because the sender has nothing to send. on the sender side i can't close the connection because i didn't ACK back, so it's kind of a deadlock. receiver is stuck because it's waiting for more packages but sender has nothing to send. i don't want to use a timeout for recv() or to insert a special character to the package header to mark that it is the last one what can i do ? thanks

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• new operator overwriting an existing object

  - by dvpdiner2

  I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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• iOS dynamic object creation

  - by Abdul Ahmad

  I've worked with Xcode and iOS on a few personal projects and have always used non-object-oriented designs for everything... just because I've been doing mostly learning/experimenting with things. Now I've been trying to implement some object oriented design into one game I've made previously. The idea is, I have a space ship that can shoot bullets. In the past I basically added the UIImageView to the storyboard and then connected it to the .h file and from there did things on it like move it around or whatever (using CGPointMake). The idea now is to make a method (and a whole other class soon) that will create a UIImageView programmatically, allocate it, add it to the superview etc... I've got this working so far, easy stuff, but the next part is a bit harder. Where do I store this local variable "bullet"? I've been saving it to an NSMutableArray and doing the following: (actually here are the methods that I have) -(void)movement { for (int i = 0; i < [array1 count]; i ++) { UIImageView *a = [array1 objectAtIndex:i]; a.center = CGPointMake(a.center.x + 2, a.center.y); if (a.center.x > 500) { [array1 removeObjectAtIndex:i]; [a removeFromSuperview]; } } } -(void)getBullet { UIImageView *bullet = [[UIImageView alloc] initWithFrame:CGRectMake(ship.center.x + 20, ship.center.y - 2, 15, 3)]; bullet.image = [UIImage imageNamed:@"bullet2.png"]; bullet.hidden = NO; [self.view addSubview:bullet]; [array1 addObject:bullet]; } (by the way, array1 is declared in the .h file) and theres a timer that controls the movement method timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(movement) userInfo:nil repeats:YES]; first question is: what is the correct way of doing this? Storing a bullet for example until it is removed from the superview, should I store it another way? and another question is, when I remove a UIImageView from the superview, does that remove it from memory so its not using up system resources? Thank you for the help! (will update if I Think of other questions

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