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  • Good computer science lecture series

    - by joemoe
    Since we have a thread on books.. what are your recommendations of publicly accessible video lecture series related to programming, computer science, or mathematics? Please post specific courses, not websites with courses. :) This is the video equivalent of this thread: http://stackoverflow.com/questions/194812/list-of-freely-available-programming-books

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  • C++/CLI HTTP Proxy problems...

    - by darkantimatter
    Hi, I'm trying(very hard) to make a small HTTP Proxy server which I can use to save all communications to a file. Seeing as I dont really have any experience in the area, I used a class from codeproject.com and some associated code to get started (It was made in the old CLI syntax, so I converted it). I couldn't get it working, so I added lots more code to make it work (threads etc), and now it sort of works. Basically, it recieves something from a client (I just configured Mozilla Firefox to route its connections through this proxy) and then routes it to google.com. After it sends Mozilla's data to google, recieves a responce, and sends that to Mozilla. This works fine, but then the proxy fails to recieve any data from Mozilla. It just loops in the Sleep(50) section. Anyway, heres the code: ProxyTest.cpp: #include "stdafx.h" #include "windows.h" #include "CHTTPProxy.h" public ref class ClientThread { public: System::Net::Sockets::TcpClient ^ pClient; CHttpProxy ^ pProxy; System::Int32 ^ pRecieveBufferSize; System::Threading::Thread ^ Thread; ClientThread(System::Net::Sockets::TcpClient ^ sClient, CHttpProxy ^ sProxy, System::Int32 ^ sRecieveBufferSize) { pClient = sClient; pProxy = sProxy; pRecieveBufferSize = sRecieveBufferSize; }; void StartReading() { Thread = gcnew System::Threading::Thread(gcnew System::Threading::ThreadStart(this,&ClientThread::ThreadEntryPoint)); Thread->Start(); }; void ThreadEntryPoint() { char * bytess; bytess = new char[(int)pRecieveBufferSize]; memset(bytess, 0, (int)pRecieveBufferSize); array<unsigned char> ^ bytes = gcnew array<unsigned char>((int)pRecieveBufferSize); array<unsigned char> ^ sendbytes; do { if (pClient->GetStream()->DataAvailable) { try { do { Sleep(100); //Lets wait for whole packet to get cached (If it even does...) unsigned int k = pClient->GetStream()->Read(bytes, 0, (int)pRecieveBufferSize); //Read it for(unsigned int i=0; i<(int)pRecieveBufferSize; i++) bytess[i] = bytes[i]; Console::WriteLine("Packet Received:\n"+gcnew System::String(bytess)); pProxy->SendToServer(bytes,pClient->GetStream()); //Now send it to google! pClient->GetStream()->Flush(); } while(pClient->GetStream()->DataAvailable); } catch (Exception ^ e) { break; } } else { Sleep(50); //It just loops here because it thinks mozilla isnt sending anything if (!(pClient->Connected)) break; }; } while (pClient->GetStream()->CanRead); delete [] bytess; pClient->Close(); }; }; int main(array<System::String ^> ^args) { System::Collections::Generic::Stack<ClientThread ^> ^ Clients = gcnew System::Collections::Generic::Stack<ClientThread ^>(); System::Net::Sockets::TcpListener ^ pTcpListener = gcnew System::Net::Sockets::TcpListener(8080); pTcpListener->Start(); System::Net::Sockets::TcpClient ^ pTcpClient; while (1) { pTcpClient = pTcpListener->AcceptTcpClient(); //Wait for client ClientThread ^ Client = gcnew ClientThread(pTcpClient, gcnew CHttpProxy("www.google.com.au", 80), pTcpClient->ReceiveBufferSize); //Make a new object for this client Client->StartReading(); //Start the thread Clients->Push(Client); //Add it to the list }; pTcpListener->Stop(); return 0; } CHTTPProxy.h, from http://www.codeproject.com/KB/IP/howtoproxy.aspx with a lot of modifications: //THIS FILE IS FROM http://www.codeproject.com/KB/IP/howtoproxy.aspx. I DID NOT MAKE THIS! BUT I HAVE MADE SEVERAL MODIFICATIONS! #using <mscorlib.dll> #using <SYSTEM.DLL> using namespace System; using System::Net::Sockets::TcpClient; using System::String; using System::Exception; using System::Net::Sockets::NetworkStream; #include <stdio.h> ref class CHttpProxy { public: CHttpProxy(System::String ^ szHost, int port); System::String ^ m_host; int m_port; void SendToServer(array<unsigned char> ^ Packet, System::Net::Sockets::NetworkStream ^ sendstr); }; CHttpProxy::CHttpProxy(System::String ^ szHost, int port) { m_host = gcnew System::String(szHost); m_port = port; } void CHttpProxy::SendToServer(array<unsigned char> ^ Packet, System::Net::Sockets::NetworkStream ^ sendstr) { TcpClient ^ tcpclnt = gcnew TcpClient(); try { tcpclnt->Connect(m_host,m_port); } catch (Exception ^ e ) { Console::WriteLine(e->ToString()); return; } // Send it if ( tcpclnt ) { NetworkStream ^ networkStream; networkStream = tcpclnt->GetStream(); int size = Packet->Length; networkStream->Write(Packet, 0, size); array<unsigned char> ^ bytes = gcnew array<unsigned char>(tcpclnt->ReceiveBufferSize); char * bytess = new char[tcpclnt->ReceiveBufferSize]; Sleep(500); //Wait for responce do { unsigned int k = networkStream->Read(bytes, 0, (int)tcpclnt->ReceiveBufferSize); //Read from google for(unsigned int i=0; i<k; i++) { bytess[i] = bytes[i]; if (bytess[i] == 0) bytess[i] = ' '; //Dont terminate the string if (bytess[i] < 8) bytess[i] = ' '; //Somethings making the computer beep, and its not 7?!?! }; Console::WriteLine("\n\nAbove packet sent to google. Google Packet Received:\n"+gcnew System::String(bytess)); sendstr->Write(bytes,0,k); //Send it to mozilla Console::WriteLine("\n\nAbove packet sent to client..."); //Sleep(1000); } while(networkStream->DataAvailable); delete [] bytess; } return; } Any help would be much appreciated, I've tried for hours.

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  • Which is more robust and scalable method?

    - by Dhruv Arya
    I am implementing a distributed chat system, in this system we have the following options : Make the client and server running at each node run as separate threads. The server acting as the receiver will be running as the daemon thread and the client taking the user input as a normal thread. Fork two processes one for the client and one for the server. I am not able to reason out with which one to proceed. Any insight would be great !

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  • SQL ORDER BY thing1 ASC, thing2 DESC not working

    - by William
    it puts item1 down as DESC for some reason. edit: $sql_result = mysql_query("SELECT post, name, trip, Thread, sticky FROM (SELECT MIN(ID) AS min_id, MAX(ID) AS max_id, MAX(Date) AS max_date FROM test_posts GROUP BY Thread ) t_min_max INNER JOIN test_posts ON test_posts.ID = t_min_max.min_id WHERE Board=".$board." ORDER BY sticky ASC, max_date DESC", $db); http://prime.programming-designs.com/test_forum/viewboard.php?board=0&page=3

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  • Implementing the procducer-consumer pattern with .NET 4.0

    - by bitbonk
    With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing/enqueuing task items and another thread executes/dequeues these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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  • Is it multitasking?

    - by Newbie
    Consider the below program myThread = new Thread( new ThreadStart( delegate { Method1(); Method2(); } ) ); Is it that 2 threads are getting called parallely(multitasking) or a single thread is calling the methods sequentially? It's urgent.

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  • How to change label content with timers throwing InvalidOperationException.

    - by Guru
    Hi there, I'm making an application and I'm using a timer in that application to change label content in WPF C# .NET. In timer elapsed event I'm writing the following code lblTimer.Content = "hello"; but its throwing an InvalidOperationException and gives a message "The calling thread cannot access this object because a different thread owns it." I'm using .NET framework 3.5 and WPF with C#. Please help me. Thanks in advance.

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  • NSThread and memory management

    - by misfit153
    Imagine I create and execute an NSThread object using detachNewThreadSelector:toTarget:withObject:. The method executed by the thread might look like this: - (void)search { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // perform a lengthy search here. [pool release]; } I then might use the cancel method to kill the thread while it's running, before the pool gets released. What happens to the NSAutoreleasePool object? I suppose it will leak, won't it?

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  • Dynamically loading modules in Python (+ threading question)

    - by morpheous
    I am writing a Python package which reads the list of modules (along with ancillary data) from a configuration file. I then want to iterate through each of the dynamically loaded modules and invoke a do_work() function in it which will spawn a new thread, so that the code runs in a separate thread. At the moment, I am importing the list of all known modules at the beginning of my main script - this is a nasty hack I feel, and is not very flexible, as well as being a maintenance pain. This is the function that spawns the threads. I will like to modify it to dynamically load the module when it is encountered. The key in the dictionary is the name of the module containing the code: def do_work(work_info): for (worker, dataset) in work_info.items(): #import the module defined by variable worker here... t = threading.Thread(target=worker.do_work, args=[dataset]) # I'll NOT dameonize since spawned children need to clean up on shutdown # Since the threads will be holding resources #t.daemon = True t.start() Question 1 When I call the function in my script (as written above), I get the following error: AttributeError: 'str' object has no attribute 'do_work' Which makes sense, since the dictionary key is a string (name of the module to be imported). When I add the statement: import worker before spawning the thread, I get the error: ImportError: No module named worker This is strange, since the variable name rather than the value it holds are being used - when I print the variable, I get the value (as I expect) whats going on? Question 2 As I mentioned in the comments section, I realize that the do_work() function written in the spawned children needs to cleanup after itself. My understanding is to write a clean_up function that is called when do_work() has completed successfully, or an unhandled exception is caught - is there anything more I need to do to ensure resources don't leak or leave the OS in an unstable state? Question 3 If I comment out the t.daemon flag statement, will the code stil run ASYNCHRONOUSLY?. The work carried out by the spawned children are pretty intensive, and I don't want to have to be waiting for one child to finish before spawning another child. BTW, I am aware that threading in Python is in reality, a kind of time sharing/slicing - thats ok Lastly is there a better (more Pythonic) way of doing what I'm trying to do?

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  • c++ volatile multithreading variables

    - by anon
    I'm writing a C++ app. I have a class variable that more than one thread is writing to. In C++, anything that can be modified without the compiler "realizing" that it's being changed needs to be marked volatile right? So if my code is multi threaded, and one thread may write to a var while another reads from it, do I need to mark the var volaltile? [I don't have a race condition since I'm relying on writes to ints being atomic] Thanks!

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  • Java Synchronized function

    - by leon
    Hi I have a question. In the following code, if a thread were blocked at wait statement, and another thread attempts to execute foo(), would the hello wolrd message be printed? and Why? Many Thanks synchronized foo(){ system.out.println("hello world"); ..... wait(); ..... }

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  • Managed c++ cross threading

    - by Nitroglycerin
    I got a thread: static void TestThread(System::Object ^obj) { Bot ^ob = (Bot^) obj; while( ob->Threads[0]->IsAlive ){ ob->textBox->text = "test"; // Cross threading error... Thread::Sleep(100); } } Dont know what to do i read about InvokeRequired and Invoke but didnt understand it.. Please help

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  • Get ahold of session in command object in Grails

    - by UltraVi01
    How can I get the session from within a command object? I have tried: import org.springframework.security.context.SecurityContextHolder as SCH class MyCommand { def session = RCH.currentRequestAttributes().getSession() } This throws java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.

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  • How to reconcile my support of open-source software and need to feed and house myself?

    - by Guzba
    I have a bit of a dilemma and wanted to get some other developers' opinions on it and maybe some guidance. So I have created a 2D game for Android from the ground up, learning and re factoring as I went along. I did it for the experience, and have been proud of the results. I released it for free as ad supported with AdMob not really expecting much out of it, but curious to see what would happen. Its been a few of months now since release, and it has become very popular (250k downloads!). Additionally, the ad revenue is great and is driving me to make more good games and even allowing me to work less so that I can focus on my own works. When I originally began working on the game, I was pretty new to concurrency and completely new to Android (had Java experience though). The standard advice I got for starting an Android game was to look at the sample games from Google (Snake, Lunar Lander, ...) so I did. In my opinion, these Android sample games from Google are decent to see in general what your code should look like, but not actually all that great to follow. This is because some of their features don't work (saving game state), the concurrency is both unexplained and cumbersome (there is no real separation between the game thread and the UI thread since they sync lock each other out all the time and the UI thread runs game thread code). This made it difficult for me as a newbie to concurrency to understand how it was organized and what was really running what code. Here is my dilemma: After spending this past few months slowly improving my code, I feel that it could be very beneficial to developers who are in the same position that I was in when I started. (Since it is not a complex game, but clearly coded in my opinion.) I want to open up the source so that others can learn from it but don't want to lose my ad revenue stream, which, if I did open the source, I fear I would when people released versions with the ad stripped, or minor tweaks that would fragment my audience, etc. I am a CS undergrad major in college and this money is giving me the freedom to work less at summer job, thus giving me the time and will to work on more of my own projects and improving my own skills while still paying the bills. So what do I do? Open the source at personal sacrifice for the greater good, or keep it closed and be a sort of hypocritical supporter of open source?

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  • Java: Multithreading & UDP Socket Programming

    - by Ravi
    I am new to multithreading & socket programming in Java. I would like to know what is the best way to implement 2 threads - one for receiving a socket and one for sending a socket. If what I am trying to do sounds absurd, pls let me know why! The code is largely inspired from Sun's tutorials online.I want to use Multicast sockets so that I can work with a multicast group. class server extends Thread { static protected MulticastSocket socket = null; protected BufferedReader in = null; public InetAddress group; private static class receive implements Runnable { public void run() { try { byte[] buf = new byte[256]; DatagramPacket pkt = new DatagramPacket(buf,buf.length); socket.receive(pkt); String received = new String(pkt.getData(),0,pkt.getLength()); System.out.println("From server@" + received); Thread.sleep(1000); } catch (IOException e) { System.out.println("Error:"+e); } catch (InterruptedException e) { System.out.println("Error:"+e); } } } public server() throws IOException { super("server"); socket = new MulticastSocket(4446); group = InetAddress.getByName("239.231.12.3"); socket.joinGroup(group); } public void run() { while(1>0) { try { byte[] buf = new byte[256]; DatagramPacket pkt = new DatagramPacket(buf,buf.length); //String msg = reader.readLine(); String pid = ManagementFactory.getRuntimeMXBean().getName(); buf = pid.getBytes(); pkt = new DatagramPacket(buf,buf.length,group,4446); socket.send(pkt); Thread t = new Thread(new receive()); t.start(); while(t.isAlive()) { t.join(1000); } sleep(1); } catch (IOException e) { System.out.println("Error:"+e); } catch (InterruptedException e) { System.out.println("Error:"+e); } } //socket.close(); } public static void main(String[] args) throws IOException { new server().start(); //System.out.println("Hello"); } }

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  • Android Thumbnail Loading Problem

    - by y ramesh rao
    I'm using a thumbnail loader in my project the one mentioned below. The problem is that the it loads all the thumbnails properly except the ones who's size is of about 40K. When our back end is giving that sort of thumbnails are not generated and sometimes this eventually leads to a Crash too. What m I supposed to do with this ? public class ThumbnailManager { private final Map<String, Bitmap> drawableMap; public static Context context; private Resources res; private int thumbnail_size; public ThumbnailManager() { drawableMap = new HashMap<String, Bitmap >(); res = new Resources(context.getAssets(), null, null); thumbnail_size = res.getInteger(R.ThumbnailManager.THUMBNAIL_SIZE); } public Bitmap fetchBitmap(String urlString) { if(drawableMap.containsKey(urlString)) { return (drawableMap.get(urlString)); } //Log.d(getClass().getSimpleName(), " Image URL :: "+ urlString); try { InputStream is = fetch(urlString); android.util.Log.v("ThumbnailManager", "ThumbnailManager " + urlString); drawableMap.put(urlString, BitmapFactory.decodeStream(is));//Bitmap.createScaledBitmap(BitmapFactory.decodeStream(is), thumbnail_size, thumbnail_size, false)); return drawableMap.get(urlString); } catch(Exception e) { android.util.Log.v("EXCEPTION", "EXCEPTION" + urlString); return null; } } public void fetchBitmapOnThread(final String urlString, final ImageView imageView) { if(drawableMap.containsKey(urlString)) { imageView.setImageBitmap(drawableMap.get(urlString)); return; } if(urlString.compareTo("AUDIO") == 0) { Bitmap audioThumb = BitmapFactory.decodeResource(context.getResources(), R.drawable.timeline_audio_thumb); drawableMap.put(urlString, Bitmap.createScaledBitmap(audioThumb, thumbnail_size, thumbnail_size, false)); imageView.setImageBitmap(drawableMap.get(urlString)); return; } final Handler handler = new Handler() { public void handleMessage(Message message) { imageView.setImageBitmap((Bitmap) message.obj); } }; Thread thread = new Thread() { public void run() { Bitmap urlBitmap = fetchBitmap(urlString); Message message = handler.obtainMessage(1, urlBitmap); handler.sendMessage(message); } }; thread.start(); } public InputStream fetch(String urlString) throws IOException, MalformedURLException { final URL url = new URL(urlString); final URLConnection conn = url.openConnection(); HttpURLConnection httpConn = (HttpURLConnection) conn; httpConn.setAllowUserInteraction(true); httpConn.setInstanceFollowRedirects(true); httpConn.setRequestMethod("GET"); httpConn.connect(); return(conn.getInputStream()); } }

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  • Getting huge lags when downloading files via Service

    - by Copa
    I have a Service which receives URLs to download. The Service than downloads these URLs and save them to a file on the SD Card. When I put more than 2 items in the download queue my device is unusable. It nearly freezes. Huge lags and so on. Any idea? Sourcecode: private static boolean downloading = false; private static ArrayList<DownloadItem> downloads = new ArrayList<DownloadItem>(); /** * called once when the service started */ public static void start() { Thread thread = new Thread(new Runnable() { @Override public void run() { while (true) { if (downloads.size() > 0 && !downloading) { downloading = true; DownloadItem item = downloads.get(0); downloadSingleFile(item.getUrl(), item.getFile()); } } } }); thread.start(); } public static void addDownload(DownloadItem item) { downloads.add(item); } private static void downloadSuccessfullFinished() { if (downloads.size() > 0) downloads.get(0).setDownloaded(true); downloadFinished(); } private static void downloadFinished() { // remove the first entry; it has been downloaded if (downloads.size() > 0) downloads.remove(0); downloading = false; } private static void downloadSingleFile(String url, File output) { final int maxBufferSize = 4096; HttpResponse response = null; try { response = new DefaultHttpClient().execute(new HttpGet(url)); if (response != null && response.getStatusLine().getStatusCode() == 200) { // request is ok InputStream is = response.getEntity().getContent(); BufferedInputStream bis = new BufferedInputStream(is); RandomAccessFile raf = new RandomAccessFile(output, "rw"); ByteArrayBuffer baf = new ByteArrayBuffer(maxBufferSize); long current = 0; long i = 0; // read and write 4096 bytes each time while ((current = bis.read()) != -1) { baf.append((byte) current); if (++i == maxBufferSize) { raf.write(baf.toByteArray()); baf = new ByteArrayBuffer(maxBufferSize); i = 0; } } if (i > 0) // write the last bytes to the file raf.write(baf.toByteArray()); baf.clear(); raf.close(); bis.close(); is.close(); // download finished get start next download downloadSuccessfullFinished(); return; } } catch (Exception e) { // not successfully downloaded downloadFinished(); return; } // not successfully downloaded downloadFinished(); return; }

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  • some fields of "content//sms/"

    - by soclose
    Hi, I query "content//sms/" and don't know what some fields are. They are - Thread ID Protocol Status Reply_Path_Present Service_Center I check them in LogCat. I find them like below Thread ID : 1 to 6 etc.. Protocol : null / 0 Status : -1 Reply_Path_Present : null / 0 Service_Center : null Please tell me what they are.

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