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• Is it Bad Practice to use C++ only for the STL containers?

  - by gmatt

  First a little background ... In what follows, I use C,C++ and Java for coding (general) algorithms, not gui's and fancy program's with interfaces, but simple command line algorithms and libraries. I started out learning about programming in Java. I got pretty good with Java and I learned to use the Java containers a lot as they tend to reduce complexity of book keeping while guaranteeing great performance. I intermittently used C++, but I was definitely not as good with it as with Java and it felt cumbersome. I did not know C++ enough to work in it without having to look up every single function and so I quickly reverted back to sticking to Java as much as possible. I then made a sudden transition into cracking and hacking in assembly language, because I felt I was concentrated too much attention on a much too high level language and I needed more experience with how a CPU interacts with memory and whats really going on with the 1's and 0's. I have to admit this was one of the most educational and fun experiences I've had with computers to date. For obviously reasons, I could not use assembly language to code on a daily basis, it was mostly reserved for fun diversions. After learning more about the computer through this experience I then realized that C++ is so much closer to the "level of 1's and 0's" than Java was, but I still felt it to be incredibly obtuse, like a swiss army knife with far too many gizmos to do any one task with elegance. I decided to give plain vanilla C a try, and I quickly fell in love. It was a happy medium between simplicity and enough "micromanagent" to not abstract what is really going on. However, I did miss one thing about Java: the containers. In particular, a simple container (like the stl vector) that expands dynamically in size is incredibly useful, but quite a pain to have to implement in C every time. Hence my code currently looks like almost entirely C with containers from C++ thrown in, the only feature I use from C++. I'd like to know if its consider okay in practice to use just one feature of C++, and ignore the rest in favor of C type code?

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• Keeping Velocity Constant and Player in Position - Sidescrolling

  - by user2904951

  I'm working on a Little Mobile Game with Cocos2D-X and Box2D. The Point where I got stuck is the movement of a box2d-body (the main actor) and the according Sprite. Now I want to : move this Body with a constant velocity along the x-axis, no matter if it's rolling (it's a circleshape) upwards or downwards keep the body nearly sticking to the ground on which it's rolling keep the Body and the according Sprite in the Center of the Screen. What I tried : in the update()- method I used body->SetLinearVelocity(b2Vec2(x,y)) to higher/lower values, if the Body was passing a constant value for his velocity I used to set very high y-Values in body->SetLinearVelocity(b2Vec2(x,y)) First tried to use CCFollow with my playerSprite, which was also Scrolling along the y-axis, as i only need to scroll along the x-axis, so I decided to move the whole layer which is containing the ambience (platforms etc.) to the left of my Screen and my Player Body & Player sprite to the right of the Screen, adjusting the speed values to Keep the Player in the Center of the Screen. Well... ...didn't work as i wanted it to, because each time i set the velocity manually (I also tried to use body->applyLinearImpulse(...) when the Body is moving upwards just as playing around with the value of velocityIterations in world->Step(...)) there's a small delay, which pushes the player Body more or less further of the Center of the Screen. ... didn't also work as I expected it to, because I needed to adjust the x-Values, when the Body was moving upwards to Keep it not getting slowed down, this made my Body even less sticky to the ground.... ... CCFollow did a good Job, except that I didn't want to scroll along the y-axis also and it Forces the overgiven sprite to start in the Center of the Screen. Moving the whole Layer even brought no good results, I have tried a Long time to adjust values of the movement Speed of the layer and the Body to Keep it negating each other, that the player stays nearly in the Center of the Screen.... So my question is : Does anyone of you have any Kind of new Approach for me to solve this cohesive bunch of Problems ? Cheers, Seb

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• Commitment to Zend Framework - any arguments against?

  - by Pekka

  I am refurbishing a big CMS that I have been working on for quite a number of years now. The product itself is great, but some components, the Database and translation classes for example, need urgent replacing - partly self-made as far back as 2002, grown into a bit of a chaos over time, and might have trouble surviving a security audit. So, I've been looking closely at a number of frameworks (or, more exactly, component Libraries, as I do not intend to change the basic structure of the CMS) and ended up with liking Zend Framework the best. They offer a solid MVC model but don't force you into it, and they offer a lot of professional components that have obviously received a lot of attention (Did you know there are multiple plurals in Russian, and you can't translate them using a simple ($number == 0) or ($number > 1) switch? I didn't, but Zend_Translate can handle it. Just to illustrate the level of thorougness the library seems to have been built with.) I am now literally at the point of no return, starting to replace key components of the system by the Zend-made ones. I'm not really having second thoughts - and I am surely not looking to incite a flame war - but before going onward, I would like to step back for a moment and look whether there is anything speaking against tying a big system closely to Zend Framework. What I like about Zend: As far as I can see, very high quality code Extremely well documented, at least regarding introductions to how things work (Haven't had to use detailed API documentation yet) Backed by a company that has an interest in seeing the framework prosper Well received in the community, has a considerable user base Employs coding standards I like Comes with a full set of unit tests Feels to me like the right choice to make - or at least, one of the right choices - in terms of modern, professional PHP development. I have been thinking about encapsulating and abstracting ZF's functionality into own classes to be able to switch frameworks more easily, but have come to the conclusion that this would not be a good idea because: it would be an unnecessary level of abstraction it could cost performance the big advantage of using a framework - the existence of a developer base that is familiar with its components - would partly be cancelled out therefore, the commitment to ZF would be a deep one. Thus my question: Is there anything substantial speaking against committing to the Zend Framework? Do you have insider knowledge of plans of Zend Inc.'s to go evil in 2011, and make it a closed source library? Is Zend Inc. run by vampires? Are there conceptual flaws in the code base you start to notice when you've transitioned all your projects to it? Is the appearance of quality code an illusion? Does the code look good, but run terribly slow on anything below my quad-core workstation?

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• Execution plan issue requires reset on SQL Server 2005, how to determine cause?

  - by Tony Brandner

  We have a web application that delivers training to thousands of corporate students running on top of SQL Server 2005. Recently, we started seeing that a single specific query in the application went from 1 second to about 30 seconds in terms of execution time. The application started throwing timeouts in that area. Our first thought was that we may have incorrect indexes, so we reviewed the tables and indexes. However, similar queries elsewhere in the application also run quickly. Reviewing the indexes showed us that they were configured as expected. We were able to narrow it down to a single query, not a stored procedure. Running this query in SQL Studio also runs quickly. We tried running the application in a different server environment. So a different web server with the same query, parameters and database. The query still ran slow. The query is a fairly large one related to determining a student's current list of training. It includes joins and left joins on a dozen tables and subqueries. A few of the tables are fairly large (hundreds of thousands of rows) and some of the other tables are small lookup tables. The query uses a grouping clause and a few where conditions. A few of the tables are quite active and the contents change often but the volume of added rows doesn't seem extreme. These symptoms led us to consider the execution plan. First off, as soon as we reset the execution plan cache with the SQL command 'DBCC FREEPROCCACHE', the problem went away. Unfortunately, the problem started to reoccur within a few days. The problem has continued to plague us for awhile now. It's usually the same query, but we did appear to see the problem occur in another single query recently. It happens enough to be a nuisance. We're having a heck of a time trying to fix it since we can't reproduce it in any other environment other than production. I have downloaded the High Availability guide from Red Gate and I read up more on execution plans. I hope to run the profiler on the live server, but I'm a bit concerned about impact. I would like to ask - what is the best way to figure out what is triggering this problem? Has anyone else seen this same issue?

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• casting doubles to integers in order to gain speed

  - by antirez

  Hello all, in Redis (http://code.google.com/p/redis) there are scores associated to elements, in order to take this elements sorted. This scores are doubles, even if many users actually sort by integers (for instance unix times). When the database is saved we need to write this doubles ok disk. This is what is used currently: snprintf((char*)buf+1,sizeof(buf)-1,"%.17g",val); Additionally infinity and not-a-number conditions are checked in order to also represent this in the final database file. Unfortunately converting a double into the string representation is pretty slow. While we have a function in Redis that converts an integer into a string representation in a much faster way. So my idea was to check if a double could be casted into an integer without lost of data, and then using the function to turn the integer into a string if this is true. For this to provide a good speedup of course the test for integer "equivalence" must be fast. So I used a trick that is probably undefined behavior but that worked very well in practice. Something like that: double x = ... some value ... if (x == (double)((long long)x)) use_the_fast_integer_function((long long)x); else use_the_slow_snprintf(x); In my reasoning the double casting above converts the double into a long, and then back into an integer. If the range fits, and there is no decimal part, the number will survive the conversion and will be exactly the same as the initial number. As I wanted to make sure this will not break things in some system, I joined #c on freenode and I got a lot of insults ;) So I'm now trying here. Is there a standard way to do what I'm trying to do without going outside ANSI C? Otherwise, is the above code supposed to work in all the Posix systems that currently Redis targets? That is, archs where Linux / Mac OS X / *BSD / Solaris are running nowaday? What I can add in order to make the code saner is an explicit check for the range of the double before trying the cast at all. Thank you for any help.

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• Akka framework support for finding duplicate messages

  - by scala_is_awesome

  I'm trying to build a high-performance distributed system with Akka and Scala. If a message requesting an expensive (and side-effect-free) computation arrives, and the exact same computation has already been requested before, I want to avoid computing the result again. If the computation requested previously has already completed and the result is available, I can cache it and re-use it. However, the time window in which duplicate computation can be requested may be arbitrarily small. e.g. I could get a thousand or a million messages requesting the same expensive computation at the same instant for all practical purposes. There is a commercial product called Gigaspaces that supposedly handles this situation. However there seems to be no framework support for dealing with duplicate work requests in Akka at the moment. Given that the Akka framework already has access to all the messages being routed through the framework, it seems that a framework solution could make a lot of sense here. Here is what I am proposing for the Akka framework to do: 1. Create a trait to indicate a type of messages (say, "ExpensiveComputation" or something similar) that are to be subject to the following caching approach. 2. Smartly (hashing etc.) identify identical messages received by (the same or different) actors within a user-configurable time window. Other options: select a maximum buffer size of memory to be used for this purpose, subject to (say LRU) replacement etc. Akka can also choose to cache only the results of messages that were expensive to process; the messages that took very little time to process can be re-processed again if needed; no need to waste precious buffer space caching them and their results. 3. When identical messages (received within that time window, possibly "at the same time instant") are identified, avoid unnecessary duplicate computations. The framework would do this automatically, and essentially, the duplicate messages would never get received by a new actor for processing; they would silently vanish and the result from processing it once (whether that computation was already done in the past, or ongoing right then) would get sent to all appropriate recipients (immediately if already available, and upon completion of the computation if not). Note that messages should be considered identical even if the "reply" fields are different, as long as the semantics/computations they represent are identical in every other respect. Also note that the computation should be purely functional, i.e. free from side-effects, for the caching optimization suggested to work and not change the program semantics at all. If what I am suggesting is not compatible with the Akka way of doing things, and/or if you see some strong reasons why this is a very bad idea, please let me know. Thanks, Is Awesome, Scala

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• Implementing Object Oriented: ansi-C approach

  - by No Money

  Hey there, I am an Intermediate programmer in Java and know some of the basics in C++. I recently started to scam over "C language" [please note that i emphasized on C language and want to stick with C as i found it to be a perfect tool, so no need for suggestions focusing on why should i move back to C++ or Java or any other crappy language (e.g: C#)]. Moving on, I code an Object Oriented approach in C but kindda scramble with the pointers part. Please understand that I am just a noob trying to extend my knowledge beyond what i learned in High School. Here is my code..... #include <stdio.h> typedef struct per{ int privateint; char *privateString; struct per (*New) (); void (*deleteperOBJ) (struct t_person *); void (*setperNumber) ((struct*) t_person,int); void (*setperString) ((struct*) t_person,char *); void (*dumpperState) ((struct*) t_person); }t_person; void setperNumber(t_person *const per,int num){ if(per==NULL) return; per->privateint=num; } void setperString(t_person *const per,char *string){ if(per==NULL) return; per->privateString=string; } void dumpperState(t_person *const per){ if(per==NULL) return; printf("value of private int==%d\n", per->privateint); printf("value of private string==%s\n", per->privateString); } void deleteperOBJ(struct t_person *const per){ free((void*)t_person->per); t_person ->per = NULL; } main(){ t_person *const per = (struct*) malloc(sizeof(t_person)); per = t_person -> struct per -> New(); per -> setperNumber (t_person *per, 123); per -> setperString(t_person *per, "No money"); dumpperState(t_person *per); deleteperOBJ(t_person *per); } Just to warn you, this program has several errors and since I am a beginner I couldn't help except to post this thread as a question. I am looking forward for assistance. Thanks in advance.

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• Making a grid on iPhone using Opengl

  - by TheGambler

  I'm trying to make a grid similar to what you would see in these geo games(geoDefense/geometry wars). I'm wanting to apply separate transformation matrixes to each to create different effects. So, it makes since to me that I need to draw each square separately to that I can apply a different transformation to each one. The problem I'm having is mapping these grids out or connecting the squares. The coordinate systems is still confusing to me. I know it would be easy just to create a huge triangle strip but I'm not able to figure out a way to apply separate transformations to each square( quad ) if I use triangle strips. So first question: Can you apply different transformations to quads if you use a triangle strip to draw a huge grid? If so, any tips suggestions on how to do so? If not, how does one usually connect textures without using triangle strips? Here is my coord setup: const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0; GLfloat size; glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); CGRect rect = view.bounds; glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar); glViewport(0, 0, rect.size.width, rect.size.height); Here is my draw: - (void)drawView:(GLView*)view; { int loop; //glColor4f(1.0, 1.0, 1.0, 0.5); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Grid Loop for( loop = 0; loop < kNumberSectionsInGrid; loop++ ) { //glLoadIdentity(); static Matrix3D shearMatrix; Matrix3DSetShear(shearMatrix, 0.2, 0.2); static Matrix3D finalMatrix; //Matrix3DMultiply(temp2Matrix, shearMatrix, finalMatrix); glLoadMatrixf(shearMatrix); glTranslatef(-1.0f,(float)loop,-3.0f); glScalef(0.1, 0.1, 0.0); Vertex3D vertices[] = { {-1.0, 1.0, 0.5}, { 1.0, 1.0, 0.5}, { -1.0, -1.0, 0.5}, { 1.0, -1.0, 0.5} }; static const Vector3D normals[] = { {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0}, {0.0, 0.0, 1.0}, }; GLfloat texCoords[] = { 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0 }; glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_NORMAL_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glBindTexture(GL_TEXTURE_2D, texture[0]); glVertexPointer(3, GL_FLOAT, 0, vertices); glNormalPointer(GL_FLOAT, 0, normals); glTexCoordPointer(2, GL_FLOAT, 0, texCoords); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDisableClientState(GL_VERTEX_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); glDisableClientState(GL_TEXTURE_COORD_ARRAY); } } glMatrixMode(GL_MODELVIEW);

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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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• PHP problems when transfering code from Windows to OS X

  - by Makka95

  I have recently bought a new MacBook Pro. Before I had my MacBook Pro I was working on a website on my desktop computer. And now I want to transfer this code to my new MacBook Pro. The problem is that when I transfered the code (I put it on Dropbox and simply downloaded it on my MacBook Pro) I started to see lots of error messages in my PHP code. The error message I”m receiving is: Warning: Cannot modify header information - headers already sent by (output started at /some/file.php:1) in /some/file.php on line 23 I have done some research on this and it seems that this error is most frequently caused by a new line, simple whitespace or any output before the <?php sign. I have looked through all the places where I have cookies that are being sent in the HTTP request and also where I'm using the header() function. I haven’t detected any output or whitespace that possibly could interfere and cause this problem. Noteworthy is that the error always says that the output is started at line 1. Which got me thinking if there is some kind of coding differences in the way that the Mac OS X and Windows operating systems handle new lines or white spaces? Or could the Dropbox transfer messed something up? The code on one of the sites(login.php) which produces the error: <?php include "mysql_database.php"; login(); $id = $_SESSION['Loggedin']; setcookie("login", $id, (time()+60*60*24*30)); header('Location: ' . $_SERVER['HTTP_REFERER']); ?> login function: function login() { $connection = connecttodatabase(); $pass = ""; $user = ""; $query = ""; if (isset($_POST['user']) && $_POST['user'] != null) { $user = $_POST['user']; if (isset($_POST['pass']) && $_POST['pass'] != null) { $pass = md5($_POST['pass']); $query = "SELECT ID FROM Anvandare WHERE Nickname='$user' AND Password ='$pass'"; } } if ($query != "") { $id = $connection->query($query); $id = mysqli_fetch_assoc($id); $id = $id['ID']; $_SESSION['Loggedin'] = $id; } closeconnection($connection); } Complete error: Warning: Cannot modify header information - headers already sent by (output started at /Users/name/GitHub/website/login.php:1) in /Users/namn/GitHub/website/login.php on line 9

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• JPanels, JFrames, and Windows, Oh my!

  - by Jonathan

  Simply stated, I am trying to make a game I am working on full-screen. I have the following code I am trying to use: GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment(); GraphicsDevice gs = ge.getDefaultScreenDevice(); if(!gs.isFullScreenSupported()) { System.out.println("full-screen not supported"); } Frame frame = new Frame(gs.getDefaultConfiguration()); Window win = new Window(frame); try { // Enter full-screen mode gs.setFullScreenWindow(win); win.validate(); } Problem with this is that I am working within a class that extends JPanel, and while I have a variable of type Frame, I have none of type Window within the class. My understanding of JPanel is that it is a Window of sorts, but I cannot pass 'this' into gs.setFullScreenWindow(Window win)... How should I go about doing this? Is there any easy way of calling that, or a similar method, using a JPanel? Is there a way I can get something of type Window from my JPanel? - EDIT: The following method changes the state of JFrame and is called every 10ms: public void paintScreen() { Graphics g; try{ g = this.getGraphics(); //get Panel's graphic context if(g == null) { frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setExtendedState(frame.getExtendedState()|JFrame.MAXIMIZED_BOTH); frame.add(this); frame.pack(); frame.setResizable(false); frame.setTitle("Game Window"); frame.setVisible(true); } if((g != null) && (dbImage != null)) { g.drawImage(dbImage, 0, 0, null); } Toolkit.getDefaultToolkit().sync(); //sync the display on some systems g.dispose(); } catch (Exception e) { if(blockError) { blockError = false; } else { System.out.println("Graphics context error: " + e); } } } I anticipate that there may be a few redundancies or unnecessary calls after the if(g==null) statement (all the frame.somethingOrOther()s), any cleanup advice would be appreciated... Also, the block error is what it seems. I am ignoring an error. The error only occurs once, and this works fine when setup to ignore the first instance of the error... For anyone interested I can post additional info there if anyone wants to see if that block can be removed, but i'm not concerned... I might look into it later.

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• A two player game over the intranet..

  - by Santwana

  Hi everybody.. I am a student of 3rd year engineering and only a novice in my programming skills. I need some help with my project.. I wish to develop a two player game to be played over the network (Intranet). I want to develop a simple website with a few html pages for this.My ideas for the project run as follows: 1.People can log in from different systems and check who ever is online on the network currently. the page also shows who is playing with whom. 2.If a person is interested in playing with a player who is currently online, he sends a request of which the other player is somehow notified( using a message or an alert on his profile page..) 3.If the player accepts the request, a game is started. This is exactly where I am clueless.. How can I make them play the game? I need to develop a turn based game with two players, eg chessboard.. how can I do this? The game has to be played live.. and it is time tracked. i need your help with coding the above.. the other features i wish to include are: 4.The game could not be abruptly terminated by any one if the users.The request to terminate the game should be sent to the other player first and only if he accepts can the game be terminated. Whoever wins the game would get a plus 10 on their credit and if he terminated he gets a minus 10. The credits remains constant even if he loses but the success percentage is reduced. 6.The player with highest winning percentage is projected as the player of the week on the home page and he can post a challenge to all others.. I only have an intermediate knowledge of core java and know the basics of Swing and Awt. I am not at all familiar with networking in java right now. I have 5 to 6 weeks of time for developing the project but I hope to learn the things before I start my project. i would prefer to use a lan to illustrate the project and I know only java,jsp,oracle,html and bit of xml to develop my proj. Also I wish to know if I can code this within 6 weeks, would it be too difficult or complicated? Please spare some time to tell me. Please.. please.. I need your suggestions and help.. thank you so much..

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• Missing part of the image when taking screenshot while supporting Retina Display

  - by Spaft

  I'm currently working on enabling support for retina display for my game. In the game, we have a feature that the user can take screenshot. We are using these part of code we found online a while ago and it's working fine when we are not supporting retina display: CCDirector* director = [CCDirector sharedDirector]; CGSize size = [director winSizeInPixels]; //Create buffer for pixels GLuint bufferLength = size.width * size.height * 4; GLubyte* buffer = (GLubyte*)malloc(bufferLength); //Read Pixels from OpenGL glReadPixels(0, 100, size.width, size.height, GL_RGBA, GL_UNSIGNED_BYTE, buffer); //Make data provider with data. CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, bufferLength, NULL); //Configure image int bitsPerComponent = 8; int bitsPerPixel = 32; int bytesPerRow = 4 * size.width; CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB(); CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault; CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault; CGImageRef iref = CGImageCreate(size.width, size.height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent); uint32_t* pixels = (uint32_t*)malloc(bufferLength); CGContextRef context = CGBitmapContextCreate(pixels, size.width, size.height, 8, size.width * 4, CGImageGetColorSpace(iref), kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); CGContextTranslateCTM(context, 0, size.height); CGContextScaleCTM(context, 1.0f, -1.0f); switch (director.deviceOrientation) { case CCDeviceOrientationPortrait: break; case CCDeviceOrientationPortraitUpsideDown: CGContextRotateCTM(context, CC_DEGREES_TO_RADIANS(180)); CGContextTranslateCTM(context, -size.width, -size.height); break; case CCDeviceOrientationLandscapeLeft: CGContextRotateCTM(context, CC_DEGREES_TO_RADIANS(-90)); CGContextTranslateCTM(context, -size.width, 0); break; case CCDeviceOrientationLandscapeRight: CGContextRotateCTM(context, CC_DEGREES_TO_RADIANS(90)); CGContextTranslateCTM(context, size.width * 0.5f, -size.height); break; } CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), iref); UIImage *outputImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)]; //Dealloc CGDataProviderRelease(provider); CGImageRelease(iref); CGContextRelease(context); free(buffer); free(pixels); return outputImage; But when we enabled retina display in cocos 0.99.5. This functionality is a little messed up since it will miss a little left part of the image while the high is still correct. So I'm wondering if there is anything wrong with the code or am I doing anything wrong here? Thank you in advance for any reply!

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• Can a process have two pid's?

  - by limp_chimp

  I'm studying computer systems and I've made this very simple function which uses fork() to create a child process. fork() returns a pid_t that is 0 if it's a child process. But calling the getpid() function within this child process returns a different, nonzero pid. In the code I have below, is newPid only meaningful in the context of the program, and not to the operating system? Is it possibly only a relative value, measured against the pid of the parent? #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <string.h> #include <errno.h> #include <stdlib.h> void unixError(char* msg) { printf("%s: %s\n", msg, strerror(errno)); exit(0); } pid_t Fork() { pid_t pid; if ((pid = fork()) < 0) unixError("Fork error"); return pid; } int main(int argc, const char * argv[]) { pid_t thisPid, parentPid, newPid; int count = 0; thisPid = getpid(); parentPid = getppid(); printf("thisPid = %d, parent pid = %d\n", thisPid, parentPid); if ((newPid = Fork()) == 0) { count++; printf("I am teh child. My pid is %d, my other pid is %d\n", getpid(), newPid); exit(0); } printf("I am the parent. My pid is %d\n", thisPid); return 0; } Output: thisPid = 30050, parent pid = 30049 I am the parent. My pid is 30050 I am teh child. My pid is 30052, my other pid is 0 Lastly, why is the child's pid 2 higher than the parent's, and not 1? The difference between the main function's pid and its parent is 1, but when we create a child it increments the pid by 2. Why is that?

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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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• AudioTrack lag: obtainBuffer timed out

  - by BTR

  I'm playing WAVs on my Android phone by loading the file and feeding the bytes into AudioTrack.write() via the FileInputStream BufferedInputStream DataInputStream method. The audio plays fine and when it is, I can easily adjust sample rate, volume, etc on the fly with nice performance. However, it's taking about two full seconds for a track to start playing. I know AudioTrack has an inescapable delay, but this is ridiculous. Every time I play a track, I get this: 03-13 14:55:57.100: WARN/AudioTrack(3454): obtainBuffer timed out (is the CPU pegged?) 0x2e9348 user=00000960, server=00000000 03-13 14:55:57.340: WARN/AudioFlinger(72): write blocked for 233 msecs, 9 delayed writes, thread 0xba28 I've noticed that the delayed write count increases by one every time I play a track -- even across multiple sessions -- from the time the phone has been turned on. The block time is always 230 - 240ms, which makes sense considering a minimum buffer size of 9600 on this device (9600 / 44100). I've seen this message in countless searches on the Internet, but it usually seems to be related to not playing audio at all or skipping audio. In my case, it's just a delayed start. I'm running all my code in a high priority thread. Here's a truncated-yet-functional version of what I'm doing. This is the thread callback in my playback class. Again, this works (only playing 16-bit, 44.1kHz, stereo files right now), it just takes forever to start and has that obtainBuffer/delayed write message every time. public void run() { // Load file FileInputStream mFileInputStream; try { // mFile is instance of custom file class -- this is correct, // so don't sweat this line mFileInputStream = new FileInputStream(mFile.path()); } catch (FileNotFoundException e) {} BufferedInputStream mBufferedInputStream = new BufferedInputStream(mFileInputStream, mBufferLength); DataInputStream mDataInputStream = new DataInputStream(mBufferedInputStream); // Skip header try { if (mDataInputStream.available() > 44) mDataInputStream.skipBytes(44); } catch (IOException e) {} // Initialize device mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, ConfigManager.SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_STEREO, AudioFormat.ENCODING_PCM_16BIT, ConfigManager.AUDIO_BUFFER_LENGTH, AudioTrack.MODE_STREAM); mAudioTrack.play(); // Initialize buffer byte[] mByteArray = new byte[mBufferLength]; int mBytesToWrite = 0; int mBytesWritten = 0; // Loop to keep thread running while (mRun) { // This flag is turned on when the user presses "play" while (mPlaying) { try { // Check if data is available if (mDataInputStream.available() > 0) { // Read data from file and write to audio device mBytesToWrite = mDataInputStream.read(mByteArray, 0, mBufferLength); mBytesWritten += mAudioTrack.write(mByteArray, 0, mBytesToWrite); } } catch (IOException e) { } } } } If I can get past the artificially long lag, I can easily deal with the inherit latency by starting my write at a later, predictable position (ie, skip past the minimum buffer length when I start playing a file).

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• How should I ethically approach user password storage for later plaintext retrieval?

  - by Shane

  As I continue to build more and more websites and web applications I am often asked to store user's passwords in a way that they can be retrieved if/when the user has an issue (either to email a forgotten password link, walk them through over the phone, etc.) When I can I fight bitterly against this practice and I do a lot of ‘extra’ programming to make password resets and administrative assistance possible without storing their actual password. When I can’t fight it (or can’t win) then I always encode the password in some way so that it at least isn’t stored as plaintext in the database—though I am aware that if my DB gets hacked that it won’t take much for the culprit to crack the passwords as well—so that makes me uncomfortable. In a perfect world folks would update passwords frequently and not duplicate them across many different sites—unfortunately I know MANY people that have the same work/home/email/bank password, and have even freely given it to me when they need assistance. I don’t want to be the one responsible for their financial demise if my DB security procedures fail for some reason. Morally and ethically I feel responsible for protecting what can be, for some users, their livelihood even if they are treating it with much less respect. I am certain that there are many avenues to approach and arguments to be made for salting hashes and different encoding options, but is there a single ‘best practice’ when you have to store them? In almost all cases I am using PHP and MySQL if that makes any difference in the way I should handle the specifics. Additional Information for Bounty I want to clarify that I know this is not something you want to have to do and that in most cases refusal to do so is best. I am, however, not looking for a lecture on the merits of taking this approach I am looking for the best steps to take if you do take this approach. In a note below I made the point that websites geared largely toward the elderly, mentally challenged, or very young can become confusing for people when they are asked to perform a secure password recovery routine. Though we may find it simple and mundane in those cases some users need the extra assistance of either having a service tech help them into the system or having it emailed/displayed directly to them. In such systems the attrition rate from these demographics could hobble the application if users were not given this level of access assistance, so please answer with such a setup in mind. Thanks to Everyone This has been a fun questions with lots of debate and I have enjoyed it. In the end I selected an answer that both retains password security (I will not have to keep plain text or recoverable passwords), but also makes it possible for the user base I specified to log into a system without the major drawbacks I have found from normal password recovery. As always there were about 5 answers that I would like to have marked correct for different reasons, but I had to choose the best one--all the rest got a +1. Thanks everyone!

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• Device drivers and Windows

  - by b-gen-jack-o-neill

  Hi, I am trying to complete the picture of how the PC and the OS interacts together. And I am at point, where I am little out of guess when it comes to device drivers. Please, don´t write things like its too complicated, or you don´t need to know when using high programming laguage and winapi functions. I want to know, it´s for study purposes. So, the very basic structure of how OS and PC (by PC I mean of course HW) is how I see it is that all other than direct CPU commands, which can CPU do on itself (arithmetic operation, its registers access and memory access) must pass thru OS. Mainly becouse from ring level 3 you cannot use in and out intructions which are used for acesing other HW. I know that there is MMIO,but it must be set by port comunication first. It was not like this all the time. Even I am bit young to remember MSDOS, I know you could access HW directly, becouse there ws no limitation, no ring mode. So you could to write string to diplay use wheather DOS function, or directly acess video card memory and write it by yourself. But as OS developed, there is no longer this possibility. But it is fine, since OS now handles all the HW comunication, and frankly it more convinient and much more safe (I would say the only option) in multitasking environment. So nowdays you instead of using int instructions to use BIOS mapped function or DOS function you call dll which internally than handles everything you don´t need to know about. I understand this. I also undrstand that device drivers is the piece of code that runs in ring level 0, so it can do all the HW interactions. But what I don´t understand is connection between OS and device driver. Let´s take a example - I want to make a sound card make a sound. So I call windows API to acess sound card, but what happens than? Does windows call device drivers to do so? But if it does call device driver, does it mean, that all device drivers which can be called by winAPI function, must have routines named in some specific way? I mean, when I have new sound card, must its drivers have functions named same as the old one? So Windows can actually call the same function from its perspective? But if Windows have predefined sets of functions requored by device drivers, that it cannot use new drivers that doesent existed before last version of OS came out. Please, help me understand this mess. I am really getting mad. Thanks.

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• Table row height in Internet Explorer

  - by Fritz H

  I have the following table: <table> <tr> <td style="height: 7px; width: 7px"> A1 </td> <td style="height: 7px"> B1 </td> <td style="height: 7px; width: 7px"> C1 </td> </tr> <tr> <td style="width: 7px"> A2 </td> <td> B2 </td> <td style="width: 7px"> C2 </td> </tr> <tr> <td style="height: 7px; width: 7px"> A3 </td> <td style="height: 7px"> B3 </td> <td style="height: 7px; width: 7px"> C3 </td> </tr> </table> The basic idea is that the first row must be 7 pixels high. The left- and rightmost cells (A1 and C1) must be 7px wide, and the middle cell (B1) must scale according to the width of the table. The same goes for the bottom row (A3, B3, C3). The middle row, however, needs to scale in height - in other words, it needs to be (tableheight - 14px). The left- and rightmost cells (A2, C2) need to be 7 pixels wide. An example: 7px x 7px |------|-------------------------|------| --- +------+-------------------------+------+ | | | | | | 7px | | | | | | | | | --- +------+-------------------------+------+ | | | | | | | | | | | | | | | | | | | | | y | | | | | | | | | | | | | | | | | | | | | | | | --- +------+-------------------------+------+ | | | | | | 7px | | | | | | | | | --- +------+-------------------------+------+ HOWEVER: In Internet Explorer, the widths work fine (columns A and C are 7px, column B scales dynamically) - but the heights don't. Rows 1, 2 and 3 turn out to be exactly 33% of the height of the table, no matter what I do. Unfortunately I have to use this table, so replacing it with a set of DIVs is not an option. I have the following DOCTYPE: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> I need to keep this, as some other elements on the page rely on some complex CSS-based layouts. Can anyone point me in the right direction to whip this into shape for IE? EDIT: Should have mentioned earlier - this table is resized on the fly using javascript.

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• Getting caught in loops - R

  - by user334898

  I am looking at whether or not certain 'systems' for betting really do work as claimed, namely, that they have a positive expectation. One such system is based on the rebate on loss. You basically have a large master pot, say $1 million. Your bankroll for each game is $50k. The way it works, is as follows: 1) Start with $50k, always bet on banker 2) If you win, add the money to the master pot. Then play again with $50k. 3) If you lose(now you're at $30k) play till you either: (a) hit 0, you get a rebate of 10%. Begin playing again with $50k+5k=$55k. (b) If you win more than the initial bankroll, add the money to the master pot. Then play again with $50k. 4) Continue until you double the master pot. I just cant find an easy way of programming out the possible cases in R, since you can eventually go down an improbable path. For example, you start at 50k, lose 20, win 19, now you're at 49, now you lose 20, lose 20, now youre at 9, you either lose 9 and get back 5k or you win and this cycle continues until you either end up with more than 50k or hit 0 and get the rebate on the 50k and start again with $50k +5k. Here's some code i started, but i havent figured out a good way of handling the cases where you get stuck and keeping track of the number of games played. Thanks again for your help. Obviously, I understand you may be busy and not have time. p.loss <- .4462466 p.win <- .4585974 p.tie <- 1 - (p.win+p.loss) prob <- c(p.win,p.tie,p.loss) bet<-20 x <- c(19,0,-20) r <- 10 # rebate = 20% br.i <- 50 br<-200 #for(i in 1:100){ # cbr.i<-0 y <- sample(x,1,replace=T,prob) cbr.i<-y+br.i if(cbr.i > br.i){ br<-br+(cbr.i-br.i); cbr.i<-br.i; }else{ y <- sample(x,2,replace=T,prob); if( sum(y)< cbr.i ){ cbr.i<-br.i+(1/r)*br.i; br<-br-br.i} cbr.i<-y+ }else{ cbr.i<- sum(y) + cbr.i; }if(cbr.i <= bet){ y <- sample(x,1,replace=T,prob) if(abs(y)>cbr.i){ cbr.i<-br.i+(1/r)*br.i } }

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• c# video equivalent to image.fromstream? Or changing the scope of the following script to allow vide

  - by Daniel

  The following is a part of an upload class in a c# script. I'm a php programmer, I've never messed with c# much but I'm trying to learn. This upload script will not handle anything except images, I need to adapt this class to handle other types of media also, or rewrite it all together. If I'm correct, I realize that using (Image image = Image.FromStream(file.InputStream)) basically says that the scope of the following is Image, only an image can be used or the object is discarded? And also that the variable image is being created from an Image from the file stream, which I understand to be, like... the $_FILES array in php? I dunno, I don't really care about making thumbnails right now either way, so if this can be taken out and still process the upload I'm totally cool with that, I just haven't had any luck getting this thing to take anything but images, even when commenting out that whole part of the class... protected void Page_Load(object sender, EventArgs e) { string dir = Path.Combine(Request.PhysicalApplicationPath, "files"); if (Request.Files.Count == 0) { // No files were posted Response.StatusCode = 500; } else { try { // Only one file at a time is posted HttpPostedFile file = Request.Files[0]; // Size limit 100MB if (file.ContentLength > 102400000) { // File too large Response.StatusCode = 500; } else { string id = Request.QueryString["userId"]; string[] folders = userDir(id); foreach (string folder in folders) { dir = Path.Combine(dir, folder); if (!Directory.Exists(dir)) Directory.CreateDirectory(dir); } string path = Path.Combine(dir, String.Concat(Request.QueryString["batchId"], "_", file.FileName)); file.SaveAs(path); // Create thumbnail int dot = path.LastIndexOf('.'); string thumbpath = String.Concat(path.Substring(0, dot), "_thumb", path.Substring(dot)); using (Image image = Image.FromStream(file.InputStream)) { // Find the ratio that will create maximum height or width of 100px. double ratio = Math.Max(image.Width / 100.0, image.Height / 100.0); using (Image thumb = new Bitmap(image, new Size((int)Math.Round(image.Width / ratio), (int)Math.Round(image.Height / ratio)))) { using (Graphics graphic = Graphics.FromImage(thumb)) { // Make sure thumbnail is not crappy graphic.SmoothingMode = SmoothingMode.HighQuality; graphic.InterpolationMode = InterpolationMode.High; graphic.CompositingQuality = CompositingQuality.HighQuality; // JPEG ImageCodecInfo codec = ImageCodecInfo.GetImageEncoders()[1]; // 90% quality EncoderParameters encode = new EncoderParameters(1); encode.Param[0] = new EncoderParameter(Encoder.Quality, 90L); // Resize graphic.DrawImage(image, new Rectangle(0, 0, thumb.Width, thumb.Height)); // Save thumb.Save(thumbpath, codec, encode); } } } // Success Response.StatusCode = 200; } } catch { // Something went wrong Response.StatusCode = 500; } } }

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• C# .NET Why does my inherited listview keep drawing in LargeIcon View ?? Because Microsoft is Evil!!

  - by Bugz R us

  I have a inherited Listview which standard has to be in Tile Mode. When using this control, the DrawItem gives e.bounds which are clearly bounds of largeIcon view ?? When debugging to check the view it is actually set to, it says it's in Tile view ?? Yet e.DrawText draws LargeIcon view ?? ......... Edit: ................. This seems only to happen when the control is placed upon another usercontrol? ......... Edit 2: ................. It gets stranger ... When i add buttons next to the list to change the view at runtime, "Tile" is the same as "LargeIcon", and "List" view is the same as "SmallIcons" ??? I've also completely removed the ownerdraw ... .......... Edit 3: ................. MSDN Documentation: Tile view Each item appears as a full-sized icon with the item label and subitem information to the right of it. The subitem information that appears is specified by the application. This view is available only on Windows XP and the Windows Server 2003 family. On earlier operating systems, this value is ignored and the ListView control displays in the LargeIcon view. Well I am on XP ya damn liars ?!? Apparently if the control is within a usercontrol, this value is ignored too ... pff I'm getting enough of this Microsoft crap .... you just keep on hitting bugs ... another day down the drain ... public class InheritedListView : ListView { //Hiding members ... mwuahahahahaha //yeah i was still laughing then [BrowsableAttribute(false)] public new View View { get { return base.View; } } public InheritedListView() { base.View = View.Tile; this.OwnerDraw = true; base.DrawItem += new DrawListViewItemEventHandler(DualLineGrid_DrawItem); } void DualLineGrid_DrawItem(object sender, DrawListViewItemEventArgs e) { View v = this.View; //**when debugging, v is Tile, however e.DrawText() draws in LargeIcon mode, // e.Bounds also reflects LargeIcon mode ???? ** }

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• Is 4-5 years the “Midlife Crisis” for a programming career?

  - by Jeffrey

  I’ve been programming C# professionally for a bit over 4 years now. For the past 4 years I’ve worked for a few small/medium companies ranging from “web/ads agencies”, small industry specific software shops to a small startup. I've been mainly doing "business apps" that involves using high-level programming languages (garbage collected) and my overall experience was that all of the works I’ve done could have been more professional. A lot of the things were done incorrectly (in a rush) mainly due to cost factor that people always wanted something “now” and with the smallest amount of spendable money. I kept on thinking maybe if I could work for a bigger companies or a company that’s better suited for programmers, or somewhere that's got the money and time to really build something longer term and more maintainable I may have enjoyed more in my career. I’ve never had a “mentor” that guided me through my 4 years career. I am pretty much blog / google / self taught programmer other than my bachelor IT degree. I’ve also observed another issue that most so called “senior” programmer in “my working environment” are really not that senior skill wise. They are “senior” only because they’ve been a long time programmer, but the code they write or the decisions they make are absolutely rubbish! They don't want to learn, they don't want to be better they just want to get paid and do what they've told to do which make sense and most of us are like that. Maybe that’s why they are where they are now. But I don’t want to become like them I want to be better. I’ve run into a mental state that I no longer intend to be a programmer for my future career. I started to think maybe there are better things out there to work on. The more blogs I read, the more “best practices” I’ve tried the more I feel I am drifting away from “my reality”. But I am not a great programmer otherwise I don't think I am where I am now. I think 4-5 years is a stage that can be a step forward career wise or a step out of where you are. I just wanted to hear what other have to say about what I’ve mentioned above and whether you’ve experienced similar situation in your past programming career and how you dealt with it. Thanks.

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• C# - periodic data reading and Thread.Sleep()

  - by CaldonCZE

  Hello, my C# application reads data from special USB device. The data are read as so-called "messages", each of them having 24 bytes. The amount of messages that must be read per second may differ (maximal frequency is quite high, about 700 messages per second), but the application must read them all. The only way to read the messages is by calling function "ReadMessage", that returns one message read from the device. The function is from external DLL and I cannot modify it. My solution: I've got a seperate thread, that is running all the time during the program run and it's only job is to read the messages in cycle. The received messages are then processed in main application thread. The function executed in the "reading thread" is the following: private void ReadingThreadFunction() { int cycleCount; try { while (this.keepReceivingMessages) { cycleCount++; TRxMsg receivedMessage; ReadMessage(devHandle, out receivedMessage); //...do something with the message... } } catch { //... catch exception if reading failed... } } This solution works fine and all messages are correctly received. However, the application consumes too much resources, the CPU of my computer runs at more than 80%. Therefore I'd like to reduce it. Thanks to the "cycleCount" variable I know that the "cycling speed" of the thread is about 40 000 cycles per second. This is unnecessarily too much, since I need to receive maximum 700 messagges/sec. (and the device has buffer for about 100 messages, so the cycle speed can be even a little lower) I tried to reduce the cycle speed by suspending the thread for 1 ms by Thread.Sleep(1); command. Of course, this didn't work and the cycle speed became about 70 cycles/second which was not enough to read all messages. I know that this attempt was silly, that putting the thread to sleep and then waking him up takes much longer than 1 ms. However, I don't know what else to do: Is there some other way how to slow the thread execution down (to reduce CPU consumption) other than Thread.Sleep? Or am I completely wrong and should I use something different for this task instead of Thread, maybe Threading.Timer or ThreadPool? Thanks a lot in advance for all suggestions. This is my first question here and I'm a beginner at using threads, so please excuse me if it's not clear enough.

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• When to use new layouts and when to use new activities?

  - by cmdfrg

  I'm making a game in Android and I'm trying to add a set of menu screens. Each screen takes up the whole display and has various transitions available to other screens. As a rough summary, the menu screens are: Start screen Difficult select screen Game screen. Pause screen. Game over screen. And there are several different ways you can transition between screen: 1 - 2 2 - 3 3 - 4 (pause game) 4 - 1 (exit game) 4 - 3 (resume game) 3 - 5 (game ends) Obviously, I need some stored state when moving between screens, such as the difficulty level select when starting a game and what the player's score is when the game over screen is shown. Can anyone give me some advice for the easiest way to implement the above screens and transitions in Android? All the create/destroy/pause/resume methods make me nervous about writing brittle code if I'm not careful. I'm not fond of using an Activity for each screen. It seems too heavy weight, having to pass data around using intents seems like a real pain and each screen isn't a useful module by itself. As the "back" button doesn't always go back to the previous screen either, my menu layout doesn't seem to fit the activity model well. At the moment, I'm representing each screen as an XML layout file and I have one activity. I set the different buttons on each layout to call setContentView to update the screen the main activity is showing (e.g. the pause button changes the layout to the pause screen). The activity holds onto all the state needed (e.g. the current difficulty level and the game high score), which makes it easy to share data between screens. This seems roughly similar to the LunarLander sample, except I'm using multiple screens. Does what I have at the moment sound OK or am I not doing things the typical Android way? Is there a class I can use (e.g. something like ViewFlipper) that could make my life easier? By the way, my game screen is implemented as a SurfaceView that stores the game state. I need the state in this view to persist between calls to setContentView (e.g. to resume from paused). Is the right idea to create the game view when the activity starts, keep a reference to it and then use this reference with setContentView whenever I want the game screen to appear?

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