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• How Can I Implement This Function?

  - by hoora

  I'm a beginner and I want to write Java code in eclipse. This program takes two LinkedLists of integers (for example, a and b) and makes a LinkedList (for example d) in which every element is the sum of elements from a and b. However, I can't add these two elements from a and b because they are Objects Example: a=[3,4,6,7,8] b=[4,3,7,5,3,2,1] ------ d=[7,7,13,12,11,2,1]

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• Slowdowns when reading from an urlconnection's inputstream (even with byte[] and buffers)

  - by user342677

  Ok so after spending two days trying to figure out the problem, and reading about dizillion articles, i finally decided to man up and ask to for some advice(my first time here). Now to the issue at hand - I am writing a program which will parse api data from a game, namely battle logs. There will be A LOT of entries in the database(20+ million) and so the parsing speed for each battle log page matters quite a bit. The pages to be parsed look like this: http://api.erepublik.com/v1/feeds/battle_logs/10000/0. (see source code if using chrome, it doesnt display the page right). It has 1000 hit entries, followed by a little battle info(lastpage will have <1000 obviously). On average, a page contains 175000 characters, UTF-8 encoding, xml format(v 1.0). Program will run locally on a good PC, memory is virtually unlimited(so that creating byte[250000] is quite ok). The format never changes, which is quite convenient. Now, I started off as usual: //global vars,class declaration skipped public WebObject(String url_string, int connection_timeout, int read_timeout, boolean redirects_allowed, String user_agent) throws java.net.MalformedURLException, java.io.IOException { // Open a URL connection java.net.URL url = new java.net.URL(url_string); java.net.URLConnection uconn = url.openConnection(); if (!(uconn instanceof java.net.HttpURLConnection)) { throw new java.lang.IllegalArgumentException("URL protocol must be HTTP"); } conn = (java.net.HttpURLConnection) uconn; conn.setConnectTimeout(connection_timeout); conn.setReadTimeout(read_timeout); conn.setInstanceFollowRedirects(redirects_allowed); conn.setRequestProperty("User-agent", user_agent); } public void executeConnection() throws IOException { try { is = conn.getInputStream(); //global var l = conn.getContentLength(); //global var } catch (Exception e) { //handling code skipped } } //getContentStream and getLength methods which just return'is' and 'l' are skipped Here is where the fun part began. I ran some profiling (using System.currentTimeMillis()) to find out what takes long ,and what doesnt. The call to this method takes only 200ms on avg public InputStream getWebPageAsStream(int battle_id, int page) throws Exception { String url = "http://api.erepublik.com/v1/feeds/battle_logs/" + battle_id + "/" + page; WebObject wobj = new WebObject(url, 10000, 10000, true, "Mozilla/5.0 " + "(Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 ( .NET CLR 3.5.30729)"); wobj.executeConnection(); l = wobj.getContentLength(); // global variable return wobj.getContentStream(); //returns 'is' stream } 200ms is quite expected from a network operation, and i am fine with it. BUT when i parse the inputStream in any way(read it into string/use java XML parser/read it into another ByteArrayStream) the process takes over 1000ms! for example, this code takes 1000ms IF i pass the stream i got('is') above from getContentStream() directly to this method: public static Document convertToXML(InputStream is) throws ParserConfigurationException, IOException, SAXException { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document doc = db.parse(is); doc.getDocumentElement().normalize(); return doc; } this code too, takes around 920ms IF the initial InputStream 'is' is passed in(dont read into the code itself - it just extracts the data i need by directly counting the characters, which can be done thanks to the rigid api feed format): public static parsedBattlePage convertBattleToXMLWithoutDOM(InputStream is) throws IOException { // Point A BufferedReader br = new BufferedReader(new InputStreamReader(is)); LinkedList ll = new LinkedList(); String str = br.readLine(); while (str != null) { ll.add(str); str = br.readLine(); } if (((String) ll.get(1)).indexOf("error") != -1) { return new parsedBattlePage(null, null, true, -1); } //Point B Iterator it = ll.iterator(); it.next(); it.next(); it.next(); it.next(); String[][] hits_arr = new String[1000][4]; String t_str = (String) it.next(); String tmp = null; int j = 0; for (int i = 0; t_str.indexOf("time") != -1; i++) { hits_arr[i][0] = t_str.substring(12, t_str.length() - 11); tmp = (String) it.next(); hits_arr[i][1] = tmp.substring(14, tmp.length() - 9); tmp = (String) it.next(); hits_arr[i][2] = tmp.substring(15, tmp.length() - 10); tmp = (String) it.next(); hits_arr[i][3] = tmp.substring(18, tmp.length() - 13); it.next(); it.next(); t_str = (String) it.next(); j++; } String[] b_info_arr = new String[9]; int[] space_nums = {13, 10, 13, 11, 11, 12, 5, 10, 13}; for (int i = 0; i < space_nums.length; i++) { tmp = (String) it.next(); b_info_arr[i] = tmp.substring(space_nums[i] + 4, tmp.length() - space_nums[i] - 1); } //Point C return new parsedBattlePage(hits_arr, b_info_arr, false, j); } I have tried replacing the default BufferedReader with BufferedReader br = new BufferedReader(new InputStreamReader(is), 250000); This didnt change much. My second try was to replace the code between A and B with: Iterator it = IOUtils.lineIterator(is, "UTF-8"); Same result, except this time A-B was 0ms, and B-C was 1000ms, so then every call to it.next() must have been consuming some significant time.(IOUtils is from apache-commons-io library). And here is the culprit - the time taken to parse the stream to string, be it by an iterator or BufferedReader in ALL cases was about 1000ms, while the rest of the code took 0ms(e.g. irrelevant). This means that parsing the stream to LinkedList, or iterating over it, for some reason was eating up a lot of my system resources. question was - why? Is it just the way java is made...no...thats just stupid, so I did another experiment. In my main method I added after the getWebPageAsStream(): //Point A ba = new byte[l]; // 'l' comes from wobj.getContentLength above bytesRead = is.read(ba); //'is' is our URLConnection original InputStream offset = bytesRead; while (bytesRead != -1) { bytesRead = is.read(ba, offset - 1, l - offset); offset += bytesRead; } //Point B InputStream is2 = new ByteArrayInputStream(ba); //Now just working with 'is2' - the "copied" stream The InputStream-byte[] conversion took again 1000ms - this is the way many ppl suggested to read an InputStream, and stil it is slow. And guess what - the 2 parser methods above (convertToXML() and convertBattlePagetoXMLWithoutDOM(), when passed 'is2' instead of 'is' took, in all 4 cases, under 50ms to complete. I read a suggestion that the stream waits for connection to close before unblocking, so i tried using HttpComponentsClient 4.0 (http://hc.apache.org/httpcomponents-client/index.html) instead, but the initial InputStream took just as long to parse. e.g. this code: public InputStream getWebPageAsStream2(int battle_id, int page) throws Exception { String url = "http://api.erepublik.com/v1/feeds/battle_logs/" + battle_id + "/" + page; HttpClient httpclient = new DefaultHttpClient(); HttpGet httpget = new HttpGet(url); HttpParams p = new BasicHttpParams(); HttpConnectionParams.setSocketBufferSize(p, 250000); HttpConnectionParams.setStaleCheckingEnabled(p, false); HttpConnectionParams.setConnectionTimeout(p, 5000); httpget.setParams(p); HttpResponse response = httpclient.execute(httpget); HttpEntity entity = response.getEntity(); l = (int) entity.getContentLength(); return entity.getContent(); } took even longer to process(50ms more for just the network) and the stream parsing times remained the same. Obviously it can be instantiated so as to not create HttpClient and properties every time(faster network time), but the stream issue wont be affected by that. So we come to the center problem - why does the initial URLConnection InputStream(or HttpClient InputStream) take so long to process, while any stream of same size and content created locally is orders of magnitude faster? I mean, the initial response is already somewhere in RAM, and I cant see any good reasong why it is processed so slowly compared to when a same stream is just created from a byte[]. Considering I have to parse million of entries and thousands of pages like that, a total processing time of almost 1.5s/page seems WAY WAY too long. Any ideas? P.S. Please ask in any more code is required - the only thing I do after parsing is make a PreparedStatement and put the entries into JavaDB in packs of 1000+, and the perfomance is ok ~ 200ms/1000entries, prb could be optimized with more cache but I didnt look into it much.

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• "bin/sh: can't access tty; job control turned off” error when running shellcode"

  - by Nosrettap

  I'm writing shellcode to exploit a buffer overflow vulnerability on a server. To do so I have port binding shellcode that I send to the server and then I run (from a linux terminal) the command telnet serverAdress 4444 where 4444 is the port which I have opened up. The hope is that I will receive a shell back that I can use to execute commands. However, I always end up with the command bin/sh: can't access tty; job control turned off I can't change any of the server code, and I believe the shellcode is correct because I got it from this website (http://www.tsirogiannis.com/exploits-vulnerabilities-videos-papers-shellcode/linuxx86-port-binding-shellcode-xor-encoded-152-bytes/). From my research, it appears that this may have to do with the mode that my terminal is running in (something called interactive mode...or something like that). All computers involved are linux machines and the machine that I am on is running the latest version of Ubuntu. Any ideas what this job control error means and how I can fix it?

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• C/C++: Who uses the logical operator macros from iso646.h and why?

  - by Jaime Soto

  There has been some debate at work about using the merits of using the alternative spellings for C/C++ logical operators in iso646.h: and && and_eq &= bitand & bitor | compl ~ not ! not_eq != or || or_eq |= xor ^ xor_eq ^= According to Wikipedia, these macros facilitate typing logical operators in international (non-US English?) and non-QWERTY keyboards. All of our development team is in the same office in Orlando, FL, USA and from what I have seen we all use the US English QWERTY keyboard layout; even Dvorak provides all the necessary characters. Supporters of using the iso646.h macros claim we should them because they are part of the C and C++ standards. I think this argument is moot since digraphs and trigraphs are also part of these standards and they are not even supported by default in many compilers. My rationale for opposing these macros in our team is that we do not need them since: Everybody on our team uses the US English QWERTY keyboard layout; C and C++ programming books from the US barely mention iso646.h, if at all; and new developers may not be familiar with iso646.h (this is expected if they are from the US). /rant Finally, to my set of questions: Does anyone in this site use the iso646.h logical operator macros? Why? What is your opinion about using the iso646.h logical operator macros in code written and maintained on US English QWERTY keyboards? Is my digraph and trigraph analogy a valid argument against using iso646.h with US English QWERTY keyboard layouts? EDIT: I missed two similar questions in StackOverflow: Is anybody using the named boolean operators? Which C++ logical operators do you use: and, or, not and the ilk or C style operators? why?

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• Alternatives to Component Based Architecture?

  - by Ben Lakey

  Usually when I develop a game I will use an architecture like what you see below. What other architectures are popular for simple game development? I'm concerned about having a narrow view of what exists out there for architectures beyond this. Is this an example of component-based architecture? Or is this something else? What would that look like? What alternatives exist? public abstract class ComponentBase { protected final Collection<ComponentBase> subComponents = new LinkedList<ComponentBase>(); private boolean enableInput; private boolean isVisible; protected ComponentBase(boolean enableInput, boolean isVisible) { this.enableInput = enableInput; this.isVisible = isVisible; } public void render(Graphics2D graphics) { for(ComponentBase gameComponent : this.subComponents) { if(gameComponent.isVisible()) { gameComponent.render(graphics); } } } public void input(InputData input) { for(ComponentBase gameComponent : this.subComponents) { if(gameComponent.inputIsEnabled()) { gameComponent.input(input); } } } ... getters/setters ... public void update(long elapsedTimeMillis) { for(ComponentBase gameComponent : this.subComponents) { gameComponent.update(elapsedTimeMillis); } } }

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• Android 2D terrain scrolling

  - by Nikola Ninkovic

  I want to make infinite 2D terrain based on my algorithm.Then I want to move it along Y axis (to the left) This is how I did it : public class Terrain { Queue<Integer> _bottom; Paint _paint; Bitmap _texture; Point _screen; int _numberOfColumns = 100; int _columnWidth = 20; public Terrain(int screenWidth, int screenHeight, Bitmap texture) { _bottom = new LinkedList<Integer>(); _screen = new Point(screenWidth, screenHeight); _numberOfColumns = screenWidth / 6; _columnWidth = screenWidth / _numberOfColumns; for(int i=0;i<=_numberOfColumns;i++) { // Generate terrain point and put it into _bottom queue } _paint = new Paint(); _paint.setStyle(Paint.Style.FILL); _paint.setShader(new BitmapShader(texture, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT)); } public void update() { _bottom.remove(); // Algorithm calculates next point _bottom.add(nextPoint); } public void draw(Canvas canvas) { Iterator<Integer> i = _bottom.iterator(); int counter = 0; Path path = new Path(); path.moveTo(0, _screen.y); while (i.hasNext()) { path.lineTo(counter, _screen.y-i.next()); counter += _columnWidth; } path.lineTo(_screen.x, _screen.y); path.lineTo(0, _screen.y); canvas.drawPath(path2, _paint); } } The problem is that the game is too 'fast', so I tried with pausing thread with Thread.sleep(50); in run() method of my game thread but then it looks too torn. Well, is there any way to slow down drawing of my terrain ?

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• Which are the best ways to organize view hierarchies in GUI interfaces?

  - by none

  I'm currently trying to figure out the best techniques for organizing GUI view hierarchies, that is dividing a window into several panels which are in turn divided into other components. I've given a look to the Composite Design Pattern, but I don't know if I can find better alternatives, so I'd appreciate to know if using the Composite is a good idea, or it would be better looking for some other techniques. I'm currently developing in Java Swing, but I don't think that the framework or the language can have a great impact on this. Any help will be appreciated. ---------EDIT------------ I was currently developing a frame containing three labels, one button and a text field. At the button pressed, the content inside the text field would be searched, and the results written inside the three labels. One of my typical structure would be the following: MainWindow | Main panel | Panel with text field and labels. | Panel with search button Now, as the title explains, I was looking for a suitable way of organizing both the MainPanel and the other two panels. But here came problems, since I'm not sure whether organizing them like attributes or storing inside some data structure (i.e. LinkedList or something like this). Anyway, I don't really think that both my solution are really good, so I'm wondering if there are really better approaches for facing this kind of problems. Hope it helps

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• Creating a Serializable mock with Mockito error

  - by KwintenP

  I'm trying to create a mock object with Mockito that can be serialized. The object is an interface implementation. When this method is called, I receive an object that I want to pass to another object, hence using the doAnswer(...)-method. This is my code. InterfaceClass obj = mock(InterfaceClass.class, withSettings().serializable()); doAnswer(new Answer<Object>() { public Object answer(InvocationOnMock invocation) throws Throwable { Object[] args = invocation.getArguments(); //Here I do something with the arguments } }).when(obj).someMethod( any(someObject.class)); ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutput out = null; try { out = new ObjectOutputStream(bos); out.writeObject(obj); byte[] yourBytes = bos.toByteArray(); } finally { out.close(); bos.close(); } As far as I can tell this should be correct (I'm fairly new to Mockito). But when Serializing my object I get this error: java.io.NotSerializableException: com.trust1t.ocs.signcore.test.InvalidInputTestCase$1 at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1165) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:329) at java.util.concurrent.ConcurrentLinkedQueue.writeObject(ConcurrentLinkedQueue.java:644) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:950) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1482) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1535) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:329) at java.util.LinkedList.writeObject(LinkedList.java:943) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:950) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1482) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1535) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1535) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1535) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1535) at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496) at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413) at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:329) at com.trust1t.ocs.signcore.test.InvalidInputTestCase.certificateValidationTest(InvalidInputTestCase.java:117) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) at org.junit.runners.ParentRunner.run(ParentRunner.java:309) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) The invalidInputTestCase class is the class containing the test where I'm using this code. It looks as if the mock object references this TestCase somewhere (can't find it though). Am I not correctly implementing this or better ideas to mock?

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• C++ - Unwanted characters printed in output file.

  - by Gabe

  This is the last part of the program I am working on. I want to output a tabular list of songs to cout. And then I want to output a specially formatted list of song information into fout (which will be used as an input file later on). Printing to cout works great. The problem is that tons of extra character are added when printing to fout. Any ideas? Here's the code: void Playlist::printFile(ofstream &fout, LinkedList<Playlist> &allPlaylists, LinkedList<Songs*> &library) { fout.open("music.txt"); if(fout.fail()) { cout << "Output file failed. Information was not saved." << endl << endl; } else { if(library.size() > 0) fout << "LIBRARY" << endl; for(int i = 0; i < library.size(); i++) // For Loop - "Incremrenting i"-Loop to go through library and print song information. { fout << library.at(i)->getSongName() << endl; // Prints song name. fout << library.at(i)->getArtistName() << endl; // Prints artist name. fout << library.at(i)->getAlbumName() << endl; // Prints album name. fout << library.at(i)->getPlayTime() << " " << library.at(i)->getYear() << " "; fout << library.at(i)->getStarRating() << " " << library.at(i)->getSongGenre() << endl; } if(allPlaylists.size() <= 0) fout << endl; else if(allPlaylists.size() > 0) { int j; for(j = 0; j < allPlaylists.size(); j++) // Loops through all playlists. { fout << "xxxxx" << endl; fout << allPlaylists.at(j).getPlaylistName() << endl; for(int i = 0; i < allPlaylists.at(j).listSongs.size(); i++) { fout << allPlaylists.at(j).listSongs.at(i)->getSongName(); fout << endl; fout << allPlaylists.at(j).listSongs.at(i)->getArtistName(); fout << endl; } } fout << endl; } } } Here's a sample of the output to music.txt (fout): LIBRARY sadljkhfds dfgkjh dfkgh 3 3333 3 Rap sdlkhs kjshdfkh sdkjfhsdf 3 33333 3 Rap xxxxx PayröÈöè÷÷(÷H÷h÷÷¨÷È÷èøø(øHøhøø¨øÈøèùù(ùHùhùù¨ùÈùèúú(úHúhúú¨úÈúèûû(ûHûhûû¨ûÈûèüü(üHühüü¨üÈüèýý(ýHýhý ! sdkjfhsdf!õüöýÄõ¼5! sadljkhfds!þõÜö|ö\ þx þ  þÈ þð ÿ ÿ@ ÿh ÿ ÿ¸ ÿà 0 X ¨ Ð ø enter code here enter code here

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• Help in building an 16 bit os

  - by Barshan Das

  I am trying to build an old 16 bit dos like os. My bootloader code: ; This is not my code. May be of Fritzos. I forgot the source. ORG 7c00h jmp Start drive db 0 msg db " Loader Initialization",0 msg2 db "ACos Loaded",0 print: lodsb cmp al, 0 je end mov ah, 0Eh int 10h jmp print end: ret Start: mov [ drive ], dl ; Get the floppy OS booted from ; Update the segment registers xor ax, ax ; XOR ax mov ds, ax ; Mov AX into DS mov si,msg call print ; Load Kernel. ResetFloppy: mov ax, 0x00 ; Select Floppy Reset BIOS Function mov dl, [ drive ] ; Select the floppy ADos booted from int 13h ; Reset the floppy drive jc ResetFloppy ; If there was a error, try again. ReadFloppy: mov bx, 0x9000 ; Load kernel at 9000h. mov ah, 0x02 ; Load disk data to ES:BX mov al, 17 ; Load two floppy head full's worth of data. mov ch, 0 ; First Cylinder mov cl, 2 ; Start at the 2nd Sector to load the Kernel mov dh, 0 ; Use first floppy head mov dl, [ drive ] ; Load from the drive kernel booted from. int 13h ; Read the floppy disk. jc ReadFloppy ; Error, try again. ; Clear text mode screen mov ax, 3 int 10h ;print starting message mov si,msg2 call print mov ax, 0x0 mov ss, ax mov sp, 0xFFFF jmp 9000h ; This part makes sure the bootsector is 512 bytes. times 510-($-$$) db 0 ;bootable sector signature dw 0xAA55 My example kernel code: asm(".code16\n"); void putchar(char); int main() { putchar('A'); return 0; } void putchar(char val) { asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"r"(val) ) ; } This is how I compile it : nasm -f bin -o ./bin/boot.bin ./source/boot.asm gcc -nostdinc -fno-builtin -I./include -c -o ./bin/kernel.o ./source/kernel.c ld -Ttext=0x9000 -o ./bin/kernel.bin ./bin/kernel.o -e 0x0 dd if=/dev/zero of=./bin/empty.bin bs=1440K count=1 cat ./bin/boot.bin ./bin/kernel.bin ./bin/empty.bin|head -c 1440K > ./bin/os rm ./bin/empty.bin and I run it in virtual machine. When I make the putchar function ( in kernel code ) for constant value ....i.e like this: void putchar() { char val = 'A'; asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"r"(val) ) ; } then it works fine. But when I pass argument to it ( That is in the previous code ) , then it prints a space for any character. What should I do?

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• CodePlex Daily Summary for Wednesday, March 16, 2011

  CodePlex Daily Summary for Wednesday, March 16, 2011Popular ReleasesuComponents: uComponents v2.1 RTM: What's new in v2.1? 5 new DataTypes JSON Datasource DropDown Multiple Textstring Similarity Text Image XPath DropDownList Please note that the release of DataType Grid has been postponed until v2.2. 3 new XSLT extensions Media Nodes Search Multi-node tree picker updates XPath start node selectors From Global or Relative start node selectors Max & Min node selection limits Bug fixes If you find a bug or have an issue, please raise a ticket here on CodePlex for us and we'l...Facebook C# SDK: 5.0.6 (BETA): This is seventh BETA release of the version 5 branch of the Facebook C# SDK. Remember this is a BETA build. Some things may change or not work exactly as planned. We are absolutely looking for feedback on this release to help us improve the final 5.X.X release. New in this release: Version 5.0.6 is almost completely backward compatible with 4.2.1 and 5.0.3 (BETA) Bug fixes and helpers to simplify many common scenarios For more information about this release see the following blog posts: F...SQLCE Code Generator: Build 1.0.3: New beta of the SQLCE Code Generator. New features: - Generates an IDataRepository interface that contains the generated repository interfaces that represents each table - Visual Studio 2010 Custom Tool Support Custom Tool: The custom tool is called SQLCECodeGenerator. Write this in the Custom Tool field in the Properties Window of an SDF file included in your project, this should create a code-behind file for the generated data access codeKooboo CMS: Kooboo 3.0 RC: Bug fixes Inline editing toolbar positioning for websites with complicate CSS. Inline editing is turned on by default now for the samplesite template. MongoDB version content query for multiple filters. . Add a new 404 page to guide users to login and create first website. Naming validation for page name and datarule name. Files in this download kooboo_CMS.zip: The Kooboo application files Content_DBProvider.zip: Additional content database implementation of MSSQL,SQLCE, RavenDB ...SQL Monitor - tracking sql server activities: SQL Monitor 3.2: 1. introduce sql color syntax highlighting with http://www.codeproject.com/KB/edit/FastColoredTextBox_.aspxUmbraco CMS: Umbraco 4.7.0: Service release fixing 50+ issues! Getting Started A great place to start is with our Getting Started Guide: Getting Started Guide: http://umbraco.codeplex.com/Project/Download/FileDownload.aspx?DownloadId=197051 Make sure to check the free foundation videos on how to get started building Umbraco sites. They're available from: Introduction for webmasters: http://umbraco.tv/help-and-support/video-tutorials/getting-started Understand the Umbraco concepts: http://umbraco.tv/help-and-support...ProDinner - ASP.NET MVC EF4 Code First DDD jQuery Sample App: first release: ProDinner is an ASP.NET MVC sample application, it uses DDD, EF4 Code First for Data Access, jQuery and MvcProjectAwesome for Web UI, it has Multi-language User Interface Features: CRUD and search operations for entities Multi-Language User Interface upload and crop Images (make thumbnail) for meals pagination using "more results" button very rich and responsive UI (using Mvc Project Awesome) Multiple UI themes (using jQuery UI themes)BEPUphysics: BEPUphysics v0.15.0: BEPUphysics v0.15.0!LiveChat Starter Kit: LCSK v1.1: This release contains couple of new features and bug fixes including: Features: Send chat transcript via email Operator can now invite visitor to chat (pro-active chat request) Bug Fixes: Operator management (Save and Delete) bug fixes Operator Console chat small fixesIronRuby: 1.1.3: IronRuby 1.1.3 is a servicing release that keeps on improving compatibility with Ruby 1.9.2 and includes IronRuby integration to Visual Studio 2010. We decided to drop 1.8.6 compatibility mode in all post-1.0 releases. We recommend using IronRuby 1.0 if you need 1.8.6 compatibility. The main purpose of this release is to sync with IronPython 2.7 release, i.e. to keep the Dynamic Language Runtime that both these languages build on top shareable. This release also fixes a few bugs: 5763 Use...SQL Server PowerShell Extensions: 2.3.2.1 Production: Release 2.3.2.1 implements SQLPSX as PowersShell version 2.0 modules. SQLPSX consists of 13 modules with 163 advanced functions, 2 cmdlets and 7 scripts for working with ADO.NET, SMO, Agent, RMO, SSIS, SQL script files, PBM, Performance Counters, SQLProfiler, Oracle and MySQL and using Powershell ISE as a SQL and Oracle query tool. In addition optional backend databases and SQL Server Reporting Services 2008 reports are provided with SQLServer and PBM modules. See readme file for details.IronPython: 2.7: On behalf of the IronPython team, I'm very pleased to announce the release of IronPython 2.7. This release contains all of the language features of Python 2.7, as well as several previously missing modules and numerous bug fixes. IronPython 2.7 also includes built-in Visual Studio support through IronPython Tools for Visual Studio. IronPython 2.7 requires .NET 4.0 or Silverlight 4. To download IronPython 2.7, visit http://ironpython.codeplex.com/releases/view/54498. Any bugs should be report...XML Explorer: XML Explorer 4.0.2: Changes in 4.0: This release is built on the Microsoft .NET Framework 4 Client Profile. Changed XSD validation to use the schema specified by the XML documents. Added a VS style Error List, double-clicking an error takes you to the offending node. XPathNavigator schema validation finally gives SourceObject (was fixed in .NET 4). Added Namespaces window and better support for XPath expressions in documents with a default namespace. Added ExpandAll and CollapseAll toolbar buttons (in a...Mobile Device Detection and Redirection: 1.0.0.0: Stable Release 51 Degrees.mobi Foundation has been in beta for some time now and has been used on thousands of websites worldwide. We’re now highly confident in the product and have designated this release as stable. We recommend all users update to this version. New Capabilities MappingsTo improve compatibility with other libraries some new .NET capabilities are now populated with wurfl data: “maximumRenderedPageSize” populated with “max_deck_size” “rendersBreaksAfterWmlAnchor” populated ...ASP.NET MVC Project Awesome, jQuery Ajax helpers (controls): 1.7.3: A rich set of helpers (controls) that you can use to build highly responsive and interactive Ajax-enabled Web applications. These helpers include Autocomplete, AjaxDropdown, Lookup, Confirm Dialog, Popup Form, Popup and Pager added interactive search for the lookupWPF Inspector: WPF Inspector 0.9.7: New Features in Version 0.9.7 - Support for .NET 3.5 and 4.0 - Multi-inspection of the same process - Property-Filtering for multiple keywords e.g. "Height Width" - Smart Element Selection - Select Controls by clicking CTRL, - Select Template-Parts by clicking CTRL+SHIFT - Possibility to hide the element adorner (over the context menu on the visual tree) - Many bugfixes??????????: All-In-One Code Framework ??? 2011-03-10: http://download.codeplex.com/Project/Download/FileDownload.aspx?ProjectName=1codechs&DownloadId=216140 ??，????。??????????All-In-One Code Framework ???，??20?Sample！！????，?????。http://i3.codeplex.com/Project/Download/FileDownload.aspx?ProjectName=1code&DownloadId=128165 ASP.NET ??： CSASPNETBingMaps VBASPNETRemoteUploadAndDownload CS/VBASPNETSerializeJsonString CSASPNETIPtoLocation CSASPNETExcelLikeGridView ....... Winform??： FTPDownload FTPUpload MultiThreadedWebDownloader...Rawr: Rawr 4.1.0: Note: This release may say 4.0.21 in the version bar. This is a typo and the version is actually 4.1.0, not to be confused with 4.0.10 which was released a while back. Rawr is now web-based. The link to use Rawr4 is: http://elitistjerks.com/rawr.phpThis is the Cataclysm Release. More details can be found at the following link http://rawr.codeplex.com/Thread/View.aspx?ThreadId=237262 As of the 4.0.16 release, you can now also begin using the new Downloadable WPF version of Rawr!This is a Relea...PHP Manager for IIS: PHP Manager 1.1.2 for IIS 7: This is a localization release of PHP Manager for IIS 7. It contains all the functionality available in 56962 plus a few bug fixes (see change list for more details). Most importantly this release is translated into five languages: German - the translation is provided by Christian Graefe Dutch - the translation is provided by Harrie Verveer Turkish - the translation is provided by Yusuf Oztürk Japanese - the translation is provided by Kenichi Wakasa Russian - the translation is provid...TweetSharp: TweetSharp v2.0.0: Documentation for this release may be found at http://tweetsharp.codeplex.com/wikipage?title=UserGuide&referringTitle=Documentation. Beta ChangesAdded user streams support Serialization is not attempted for Twitter 5xx errors Fixes based on feedback Third Party Library VersionsHammock v1.2.0: http://hammock.codeplex.com Json.NET 4.0 Release 1: http://json.codeplex.comNew ProjectsABSC - Automatic Battle System Configurator: ABSC - Automatic Battle System Configurator Este é um aplicativo que auxilia os usuários na configuração de diversos script's de batalha disponíveis atualmente para o Rpg Maker. O aplicativo irá gerar um script com toda a configuração especificada pelo usuário.Active Directory Monkey: Designed for IS support teams to easily reset active directoy passwords.Ag-Light: Artesis projectAnito.ORM: Anito ORMblogengine customizations: Customizations for dotnetblogengineCool Tool: Cool Tool is a Visual studio add-in for generating business entities. Generator provides functionality to be able easily and comfortable generate class elements and implement chosen interfaces. Project is developed in VS 2010 (C# 4.0). Enjoy!csmpfit - A Least Squares Optimization Library in C# (C Sharp): A C# port of the C-based mpfit Levenberg Marquardt solver at Argonne National Labs (http://cow.physics.wisc.edu/~craigm/idl/cmpfit.html), including both desktop .NET and Silverlight project libraries.DirectX 11 Framework for Experimentation: Basic Framework for DirectX 11 (without DXUT) containing basic stuffs like Text Rendering, Quad Render, Model Loading, basic Skinning animation, Shader framework (substitute for the effect API) and lots of random stuffs !!!Doanvien code project: DoanVien code projectdtweet - a dashing way of tweeting: dtweet is developed in ASP.NET MVC 3 RTM (Razor) C# JQuery 1.5.1FormMail.NET: This is a project to support emailing form data from a .NET page, and storing that form data in an XML file.LRU Cache: This project implements the LRU Cache using C#. It uses a Dictionary and a LinkedList. Dictionary ensures fast access to the data, and the linkedlist controls which objects are to be removed first.Magelia WebStore Open-source e-commerce software: Magelia WebStore is a customizable, multilingual and multi-currency open-source e-commerce software for the .net environment. WebStore was developped C# and Aspx and only requires an SQL Server Express. MDA.Net: MDA.Net is the .Net/Silverlight port of mda-vst instruments and effects. Currently it includes just the MDA piano and an overdrive with basic interfaces to build on. Just PM me if you have some time to help - we are in no rush, aim to migrate everything one-by-one. MVC NGShop: NGShop ????????????，????Asp.net MVC 2.0 + Jquery + SQL Server 2008， ???Castle Windsor IOC、entity framework，??????visual studio 2010??，??????vs2010，?????js???。Orchard - Photo Albums module: This module allows you to create photo albums with various effects: lightbox, slideshow, etc. PowerShell Workflow: PowerShell Workflow helps organizations to define their operational processes through the power of Workflow and Powershell. Project Dark: Early version of our project. Made in Torque 3dReFSharp: ReFSharp is pretty printer, analyzing tool and translator source code texts between F#, C# and Java. Current version has full functional pretty printer for F# and pre-alpha translator of C# to F#.Relate Intranet Templates: <project name> is an open source package for EPiServer Relate which creates a foundation for an intranet.Service monitor: Service monitor is a simple utility that lets you monitor and manage the states of services of multiple machines. It allows starting/stopping and restarting. It is Windows 7 UAC aware.Sharp Console: Sharp Console is a Windows Command Line (WCL)alternative written in C#. It targets those who lack access to the WCL or simply wish to use the NET framework instead. It aims to provide the same (and more!) functionality as the WCL. Contribute anything you feel will make it better!Stone2: New version of Stone, but using TFS for versioningStudent Database Management System: Student Database Management System is a sample Online Web based and also desktop application which helps school to maintain their records free online. this project is open source project and Free available for all schools to check and send their response..

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• How to do RLE (run length encoding) in C# on a byte array?

  - by CuriousCoder

  I am trying to XOR two bitmap files (their byte arrays) to produce a byte array that can be used to change image A into image B or vice versa. I am sending this over the network so I would like to do some basic compression before this happens. Is there a way to do RLE (run length encoding) in C# (using a built-in, or fast reliable 3rd party library) on a byte array for this purpose? Notes: If you are going to suggest an alternative to my approach please keep in mind that the decompression and transformation on the remote machine has to be as quick and efficient as possible.

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• org.hibernate.MappingException: No Dialect mapping for JDBC type: 2002

  - by Moli

  Hi at all, I'm having a issue trying to get working a JPA nativeQuery. I'm having a org.hibernate.MappingException: No Dialect mapping for JDBC type: 2002 when a try to do a nativeQuery and get a geometry field type. I use oracle and org.hibernatespatial.oracle.OracleSpatial10gDialect. The geom fields is mapped as: @Column(name="geometry") @Type(type = "org.hibernatespatial.GeometryUserType") private Geometry geometry; List<Object> listFeatures= new LinkedList<Object>(); Query query= entityManager.createNativeQuery( "SELECT "+ slots +" , geometry FROM edtem_features feature, edtem_dades dada WHERE" + " feature."+ tematic.getIdGeomField() +" = dada."+ tematic.getIdDataField()+ " AND dada.capesid= "+ tematic.getCapa().getId() + " AND feature.geometriesid= "+ tematic.getGeometria().getId()); listFeatures.addAll( query.getResultList()); Anybody knows a solution? or how to force the type of the geometry to get wroking this... MANY Thanks in advance. Moli

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• CSS regression tool?

  - by ronaldwidha

  I'm looking for a visual regression testing tool for CSS refactoring and see whether or not there are any unintended cascading behavior in a website. Ideally, the tool that can crawl a website (even locally) and grab snapshots of each page and store it in a single repository. When run for the second time, it will show the pages that are visually different since the last time it was run. Even better: if it can show the overlapper XOR view of the 2 version of the page. compare rendering results of different browsers (almost like an automated Microsoft Expression Web compare feature). Thanks

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• determine if parity bit representation in MIPS

  - by Hristo

  Is there some instruction in MIPS that will determine the parity of a certain bit representation? I know to determine whether a "number" has an even parity or an odd parity is to XOR the individual bits of the binary representation together, but that seems computationally-intensive for a set of MIPS instructions... and I need to do this as quick as possible. Also, the number I'm working in is represented in Grey Code... just to throw that in there. So is there some pseudo-instruction in MIPS to determine the parity of a "number" or do I have to do it by hand? Thanks, Hristo

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• "call" instruction that seemingly jumps into itself

  - by Checkers

  I have gcc 4 compiling some C++ code into the following (from objdump): 00000030 <func()>: 30: 55 push %ebp 31: 89 e5 mov %esp,%ebp 33: 56 push %esi 34: 31 f6 xor %esi,%esi 36: 53 push %ebx 37: bb 00 00 00 00 mov $0x0,%ebx 3c: 83 ec 40 sub $0x40,%esp 3f: c7 04 24 01 00 00 00 movl $0x1,(%esp) 46: e8 fc ff ff ff call 47 <func()+0x17> 4b: 8d 55 ec lea 0xffffffec(%ebp),%edx 4e: 89 14 24 mov %edx,(%esp) 51: 89 5c 24 04 mov %ebx,0x4(%esp) 55: 89 74 24 08 mov %esi,0x8(%esp) 59: 89 44 24 0c mov %eax,0xc(%esp) ; the rest of the function is omitted I can't understand the operand of call instruction here, why does it call into itself, but with one byte off?

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• One position right barrel shift using ALU Operators?

  - by Tomek

  I was wondering if there was an efficient way to perform a shift right on an 8 bit binary value using only ALU Operators (NOT, OR, AND, XOR, ADD, SUB) Example: input: 00110101 output: 10011010 I have been able to implement a shift left by just adding the 8 bit binary value with itself since a shift left is equivalent to multiplying by 2. However, I can't think of a way to do this for shift right. The only method I have come up with so far is to just perform 7 left barrel shifts. Is this the only way?

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• ASM programming, how to use loop?

  - by chris

  Hello. Im first time here.I am a college student. I've created a simple program by using assembly language. And im wondering if i can use loop method to run it almost samething as what it does below the program i posted. and im also eager to find someome who i can talk through MSN messanger so i can ask you questions right away.(if possible) ok thank you .MODEL small .STACK 400h .data prompt db 10,13,'Please enter a 3 digit number, example 100:',10,13,'$' ;10,13 cause to go to next line first_digit db 0d second_digit db 0d third_digit db 0d Not_prime db 10,13,'This number is not prime!',10,13,'$' prime db 10,13,'This number is prime!',10,13,'$' question db 10,13,'Do you want to contine Y/N $' counter dw 0d number dw 0d half dw ? .code Start: mov ax, @data ;establish access to the data segment mov ds, ax mov number, 0d LetsRoll: mov dx, offset prompt ; print the string (please enter a 3 digit...) mov ah, 9h int 21h ;execute ;read FIRST DIGIT mov ah, 1d ;bios code for read a keystroke int 21h ;call bios, it is understood that the ascii code will be returned in al mov first_digit, al ;may as well save a copy sub al, 30h ;Convert code to an actual integer cbw ;CONVERT BYTE TO WORD. This takes whatever number is in al and ;extends it to ax, doubling its size from 8 bits to 16 bits ;The first digit now occupies all of ax as an integer mov cx, 100d ;This is so we can calculate 100*1st digit +10*2nd digit + 3rd digit mul cx ;start to accumulate the 3 digit number in the variable imul cx ;it is understood that the other operand is ax ;AND that the result will use both dx::ax ;but we understand that dx will contain only leading zeros add number, ax ;save ;variable <number> now contains 1st digit * 10 ;---------------------------------------------------------------------- ;read SECOND DIGIT, multiply by 10 and add in mov ah, 1d ;bios code for read a keystroke int 21h ;call bios, it is understood that the ascii code will be returned in al mov second_digit, al ;may as well save a copy sub al, 30h ;Convert code to an actual integer cbw ;CONVERT BYTE TO WORD. This takes whatever number is in al and ;extends it to ax, boubling its size from 8 bits to 16 bits ;The first digit now occupies all of ax as an integer mov cx, 10d ;continue to accumulate the 3 digit number in the variable mul cx ;it is understood that the other operand is ax, containing first digit ;AND that the result will use both dx::ax ;but we understand that dx will contain only leading zeros. Ignore them add number, ax ;save -- nearly finished ;variable <number> now contains 1st digit * 100 + second digit * 10 ;---------------------------------------------------------------------- ;read THIRD DIGIT, add it in (no multiplication this time) mov ah, 1d ;bios code for read a keystroke int 21h ;call bios, it is understood that the ascii code will be returned in al mov third_digit, al ;may as well save a copy sub al, 30h ;Convert code to an actual integer cbw ;CONVERT BYTE TO WORD. This takes whatever number is in al and ;extends it to ax, boubling its size from 8 bits to 16 bits ;The first digit now occupies all of ax as an integer add number, ax ;Both my variable number and ax are 16 bits, so equal size mov ax, number ;copy contents of number to ax mov cx, 2h div cx ;Divide by cx mov half, ax ;copy the contents of ax to half mov cx, 2h; mov ax, number; ;copy numbers to ax xor dx, dx ;flush dx jmp prime_check ;jump to prime check print_question: mov dx, offset question ;print string (do you want to continue Y/N?) mov ah, 9h int 21h ;execute mov ah, 1h int 21h ;execute cmp al, 4eh ;compare je Exit ;jump to exit cmp al, 6eh ;compare je Exit ;jump to exit cmp al, 59h ;compare je Start ;jump to start cmp al, 79h ;compare je Start ;jump to start prime_check: div cx; ;Divide by cx cmp dx, 0h ;reset the value of dx je print_not_prime ;jump to not prime xor dx, dx; ;flush dx mov ax, number ;copy the contents of number to ax cmp cx, half ;compare half with cx je print_prime ;jump to print prime section inc cx; ;increment cx by one jmp prime_check ;repeat the prime check print_prime: mov dx, offset prime ;print string (this number is prime!) mov ah, 9h int 21h ;execute jmp print_question ;jumps to question (do you want to continue Y/N?) this is for repeat print_not_prime: mov dx, offset Not_prime ;print string (this number is not prime!) mov ah, 9h int 21h ;execute jmp print_question ;jumps to question (do you want to continue Y/N?) this is for repeat Exit: mov ah, 4ch int 21h ;execute exit END Start

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• C question: Padding bits in unsigned integers and bitwise operations (C89)

  - by Anonymous Question Guy

  I have a lot of code that performs bitwise operations on unsigned integers. I wrote my code with the assumption that those operations were on integers of fixed width without any padding bits. For example an array of 32 bit unsigned integers of which all 32 bits available for each integer. I'm looking to make my code more portable and I'm focused on making sure I'm C89 compliant (in this case). One of the issues that I've come across is possible padded integers. Take this extreme example, taken from the GMP manual: However on Cray vector systems it may be noted that short and int are always stored in 8 bytes (and with sizeof indicating that) but use only 32 or 46 bits. The nails feature can account for this, by passing for instance 8*sizeof(int)-INT_BIT. I've also read about this type of padding in other places. I actually read of a post on SO last night (forgive me, I don't have the link and I'm going to cite something similar from memory) where if you have, say, a double with 60 usable bits the other 4 could be used for padding and those padding bits could serve some internal purpose so they cannot be modified. So let's say for example my code is compiled on a platform where an unsigned int type is sized at 4 bytes, each byte being 8 bits, however the most significant 2 bits are padding bits. Would UINT_MAX in that case be 0x3FFFFFFF (1073741823) ? #include <stdio.h> #include <stdlib.h> /* padding bits represented by underscores */ int main( int argc, char **argv ) { unsigned int a = 0x2AAAAAAA; /* __101010101010101010101010101010 */ unsigned int b = 0x15555555; /* __010101010101010101010101010101 */ unsigned int c = a ^ b; /* ?? __111111111111111111111111111111 */ unsigned int d = c << 5; /* ?? __111111111111111111111111100000 */ unsigned int e = d >> 5; /* ?? __000001111111111111111111111111 */ printf( "a: %X\nb: %X\nc: %X\nd: %X\ne: %X\n", a, b, c, d, e ); return 0; } is it safe to XOR two integers with padding bits? wouldn't I XOR whatever the padding bits are? I can't find this behavior covered in C89. furthermore is the c var guaranteed to be 0x3FFFFFFF or if for example the two padding bits were both on in a or b would c be 0xFFFFFFFF ? same question with d and e. am i manipulating the padding bits by shifting? I would expect to see this below, assuming 32 bits with the 2 most significant bits used for padding, but I want to know if something like this is guaranteed: a: 2AAAAAAA b: 15555555 c: 3FFFFFFF d: 3FFFFFE0 e: 01FFFFFF Also are padding bits always the most significant bits or could they be the least significant bits? Thanks guys EDIT 12/19/2010 5PM EST: Christoph has answered my question. Thanks! I had also asked (above) whether padding bits are always the most significant bits. This is cited in the rationale for the C99 standard, and the answer is no. I am playing it safe and assuming the same for C89. Here is specifically what the C99 rationale says for §6.2.6.2 (Representation of Integer Types): Padding bits are user-accessible in an unsigned integer type. For example, suppose a machine uses a pair of 16-bit shorts (each with its own sign bit) to make up a 32-bit int and the sign bit of the lower short is ignored when used in this 32-bit int. Then, as a 32-bit signed int, there is a padding bit (in the middle of the 32 bits) that is ignored in determining the value of the 32-bit signed int. But, if this 32-bit item is treated as a 32-bit unsigned int, then that padding bit is visible to the user’s program. The C committee was told that there is a machine that works this way, and that is one reason that padding bits were added to C99. Footnotes 44 and 45 mention that parity bits might be padding bits. The committee does not know of any machines with user-accessible parity bits within an integer. Therefore, the committee is not aware of any machines that treat parity bits as padding bits. EDIT 12/28/2010 3PM EST: I found an interesting discussion on comp.lang.c from a few months ago. Bitwise Operator Effects on Padding Bits (VelocityReviews reader) Bitwise Operator Effects on Padding Bits (Google Groups alternate link) One point made by Dietmar which I found interesting: Let's note that padding bits are not necessary for the existence of trap representations; combinations of value bits which do not represent a value of the object type would also do.

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• [ebp + 6] instead of +8 in a JIT compiler

  - by David Titarenco

  I'm implementing a simplistic JIT compiler in a VM I'm writing for fun (mostly to learn more about language design) and I'm getting some weird behavior, maybe someone can tell me why. First I define a JIT "prototype" both for C and C++: #ifdef __cplusplus typedef void* (*_JIT_METHOD) (...); #else typedef (*_JIT_METHOD) (); #endif I have a compile() function that will compile stuff into ASM and stick it somewhere in memory: void* compile (void* something) { // grab some memory unsigned char* buffer = (unsigned char*) malloc (1024); // xor eax, eax // inc eax // inc eax // inc eax // ret -> eax should be 3 /* WORKS! buffer[0] = 0x67; buffer[1] = 0x31; buffer[2] = 0xC0; buffer[3] = 0x67; buffer[4] = 0x40; buffer[5] = 0x67; buffer[6] = 0x40; buffer[7] = 0x67; buffer[8] = 0x40; buffer[9] = 0xC3; */ // xor eax, eax // mov eax, 9 // ret 4 -> eax should be 9 /* WORKS! buffer[0] = 0x67; buffer[1] = 0x31; buffer[2] = 0xC0; buffer[3] = 0x67; buffer[4] = 0xB8; buffer[5] = 0x09; buffer[6] = 0x00; buffer[7] = 0x00; buffer[8] = 0x00; buffer[9] = 0xC3; */ // push ebp // mov ebp, esp // mov eax, [ebp + 6] ; wtf? shouldn't this be [ebp + 8]!? // mov esp, ebp // pop ebp // ret -> eax should be the first value sent to the function /* WORKS! */ buffer[0] = 0x66; buffer[1] = 0x55; buffer[2] = 0x66; buffer[3] = 0x89; buffer[4] = 0xE5; buffer[5] = 0x66; buffer[6] = 0x66; buffer[7] = 0x8B; buffer[8] = 0x45; buffer[9] = 0x06; buffer[10] = 0x66; buffer[11] = 0x89; buffer[12] = 0xEC; buffer[13] = 0x66; buffer[14] = 0x5D; buffer[15] = 0xC3; // mov eax, 5 // add eax, ecx // ret -> eax should be 50 /* WORKS! buffer[0] = 0x67; buffer[1] = 0xB8; buffer[2] = 0x05; buffer[3] = 0x00; buffer[4] = 0x00; buffer[5] = 0x00; buffer[6] = 0x66; buffer[7] = 0x01; buffer[8] = 0xC8; buffer[9] = 0xC3; */ return buffer; } And finally I have the main chunk of the program: void main (int argc, char **args) { DWORD oldProtect = (DWORD) NULL; int i = 667, j = 1, k = 5, l = 0; // generate some arbitrary function _JIT_METHOD someFunc = (_JIT_METHOD) compile(NULL); // windows only #if defined _WIN64 || defined _WIN32 // set memory permissions and flush CPU code cache VirtualProtect(someFunc,1024,PAGE_EXECUTE_READWRITE, &oldProtect); FlushInstructionCache(GetCurrentProcess(), someFunc, 1024); #endif // this asm just for some debugging/testing purposes __asm mov ecx, i // run compiled function (from wherever *someFunc is pointing to) l = (int)someFunc(i, k); // did it work? printf("result: %d", l); free (someFunc); _getch(); } As you can see, the compile() function has a couple of tests I ran to make sure I get expected results, and pretty much everything works but I have a question... On most tutorials or documentation resources, to get the first value of a function passed (in the case of ints) you do [ebp+8], the second [ebp+12] and so forth. For some reason, I have to do [ebp+6] then [ebp+10] and so forth. Could anyone tell me why?

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• Using an array in embedded x86 assembly??

  - by Mark V.

  Hey all I have a method (C++) that returns a character and takes an array of characters as its parameters. I'm messing with assembly for the first time and just trying to return the first character of the array in the dl register. Here's what I have so far: char returnFirstChar(char arrayOfLetters[]) { char max; __asm { push eax push ebx push ecx push edx mov dl, 0 mov eax, arrayOfLetters[0] xor edx, edx mov dl, al mov max, dl pop edx pop ecx pop ebx pop eax } return max; } For some reason this method returns a ? Any idea whats going on? Thanks

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• How to get predecessor and successors from an adjacency matrix

  - by NickTFried

  Hi I am am trying to complete an assignment, where it is ok to consult the online community. I have to create a graph class that ultimately can do Breadth First Search and Depth First Search. I have been able to implement those algorithms successfully however another requirement is to be able to get the successors and predecessors and detect if two vertices are either predecessors or successors for each other. I'm having trouble thinking of a way to do this. I will post my code below, if anyone has any suggestions it would be greatly appreciated. import java.util.ArrayList; import java.util.Iterator; import java.util.LinkedList; import java.util.Queue; import java.util.Stack; public class Graph<T> { public Vertex<T> root; public ArrayList<Vertex<T>> vertices=new ArrayList<Vertex<T>>(); public int[][] adjMatrix; int size; private ArrayList<Vertex<T>> dfsArrList; private ArrayList<Vertex<T>> bfsArrList; public void setRootVertex(Vertex<T> n) { this.root=n; } public Vertex<T> getRootVertex() { return this.root; } public void addVertex(Vertex<T> n) { vertices.add(n); } public void removeVertex(int loc){ vertices.remove(loc); } public void addEdge(Vertex<T> start,Vertex<T> end) { if(adjMatrix==null) { size=vertices.size(); adjMatrix=new int[size][size]; } int startIndex=vertices.indexOf(start); int endIndex=vertices.indexOf(end); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public void removeEdge(Vertex<T> v1, Vertex<T> v2){ int startIndex=vertices.indexOf(v1); int endIndex=vertices.indexOf(v2); adjMatrix[startIndex][endIndex]=1; adjMatrix[endIndex][startIndex]=1; } public int countVertices(){ int ver = vertices.size(); return ver; } /* public boolean isPredecessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ /* public boolean isSuccessor( Vertex<T> a, Vertex<T> b){ for() return true; }*/ public void getSuccessors(Vertex<T> v1){ } public void getPredessors(Vertex<T> v1){ } private Vertex<T> getUnvisitedChildNode(Vertex<T> n) { int index=vertices.indexOf(n); int j=0; while(j<size) { if(adjMatrix[index][j]==1 && vertices.get(j).visited==false) { return vertices.get(j); } j++; } return null; } public Iterator<Vertex<T>> bfs() { Queue<Vertex<T>> q=new LinkedList<Vertex<T>>(); q.add(this.root); printVertex(this.root); root.visited=true; while(!q.isEmpty()) { Vertex<T> n=q.remove(); Vertex<T> child=null; while((child=getUnvisitedChildNode(n))!=null) { child.visited=true; bfsArrList.add(child); q.add(child); } } clearVertices(); return bfsArrList.iterator(); } public Iterator<Vertex<T>> dfs() { Stack<Vertex<T>> s=new Stack<Vertex<T>>(); s.push(this.root); root.visited=true; printVertex(root); while(!s.isEmpty()) { Vertex<T> n=s.peek(); Vertex<T> child=getUnvisitedChildNode(n); if(child!=null) { child.visited=true; dfsArrList.add(child); s.push(child); } else { s.pop(); } } clearVertices(); return dfsArrList.iterator(); } private void clearVertices() { int i=0; while(i<size) { Vertex<T> n=vertices.get(i); n.visited=false; i++; } } private void printVertex(Vertex<T> n) { System.out.print(n.label+" "); } }

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• Redundancy algorithm for reading noisy bitstream

  - by Tedd Hansen

  I'm reading a lossy bit stream and I need a way to recover as much usable data as possible. There can be 1's in place of 0's and 0's in palce of 1's, but accuracy is probably over 80%. A bonus would be if the algorithm could compensate for missing/too many bits as well. The source I'm reading from is analogue with noise (microphone via FFT), and the read timing could vary depending on computer speed. I remember reading about algorithms used in CD-ROM's doing this in 3? layers, so I'm guessing using several layers is a good option. I don't remember the details though, so if anyone can share some ideas that would be great! :) Edit: Added sample data Best case data: in: 0000010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111 out: 0010101000010110100101101100111000000100100101101100111000000100100001100000010000101110101001101100111000101110000001001111011001100110000001001100111011110110101011100111011000100110000001000010111011 Bade case (timing is off, samples are missing): out: 00101010000101101001011011001110000001001001011011001110000001001000011000000100001011101010011011001 in: 00111101001011111110010010111111011110000010010000111000011101001101111110000110111011110111111111101 Edit2: I am able to controll the data being sent. Currently attempting to implement simple XOR checking (though it won't be enough).

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• how can c# help in drawing using memory layers concept?

  - by moon

  hello all i am facing problem in drawing dynamically in a picture box. i works very good when the drawing objects are few but as the drawing objects increases the response time of my GUI is getting worse and worse, my GUI works very well up to 90 drawing objects but i have to support more than 1000 so this technique didn't work for me. know i have decided to adopt layers mechanism, i mean i will draw different layers of drawing in memory and then XOR them to load the final image to my display. the question is "i Can play directly with memory do draw layers using C# (Examples needed?)" other ideas are also appreciated, (Drawing objects means the shapes line,circles etc. that i have to draw on my GUI) thanx in advance

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• Implementig Java Iterable<E> interface

  - by Metz

  Hi, i wrote this code: public class C1 implements Iterable<NC1> { private LinkedList<NC1> list; public static class NC1 { ... } ... x public Iterator<NC1> iterator() { return list.iterator(); } } but eclipse whines (at the x-ed line): - The return type is incompatible with Iterable<NC1>.iterator() - implements java.lang.Iterable<NC1>.iterator i don't understand where the mistake is. thanks in advance.

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