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  • EasyHook Windows Hooking problem/.dll injection

    - by Tom
    Ok can someone try and find the error with this code, it should produce all the registry keys every time something accesses them but i keep getting: System.MissingMethodException: The given method does not exist at EasyHook.LocalHook.GetProcAdress(String InModule, String InChannelName) An example code can be found here: http://www.codeproject.com/KB/DLL/EasyHook64.aspx I can get the CcreateFileW example to work! My code is here: public class Main : EasyHook.IEntryPoint { FileMon.FileMonInterface Interface; LocalHook LocalHook; Stack<String> Queue = new Stack<String>(); public Main(RemoteHooking.IContext InContext,String InChannelName) { // connect to host... Interface = RemoteHooking.IpcConnectClient<FileMon.FileMonInterface>(InChannelName); Interface.Ping(); } public void Run(RemoteHooking.IContext InContext,String InChannelName) { // install hook... try { LocalHook localHook = LocalHook.Create(LocalHook.GetProcAddress("Advapi32.dll", "RegOpenKeyExW"),new DMyRegOpenKeyExW(MyRegOpenKeyExW),this); localHook.ThreadACL.SetExclusiveACL(new int[] { }); } catch (Exception ExtInfo) { Interface.ReportException(ExtInfo); return; } Interface.IsInstalled(RemoteHooking.GetCurrentProcessId()); RemoteHooking.WakeUpProcess(); // wait for host process termination... try { while (true) { Thread.Sleep(500); // transmit newly monitored file accesses... if (Queue.Count > 0) { String[] Package = null; lock (Queue) { Package = Queue.ToArray(); Queue.Clear(); } Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package); } else Interface.Ping(); } } catch { // Ping() will raise an exception if host is unreachable } } [DllImport("Advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true, CallingConvention = CallingConvention.StdCall)] static extern int RegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode, SetLastError = true)] delegate int DMyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); int MyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult) { Console.WriteLine(string.Format("Accessing: {0}", subKey)); return RegOpenKeyExW(hKey, subKey, ulOptions, samDesired, out hkResult); } }

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  • Timer Service in ejb 3.1 - schedule calling timeout problem

    - by Greg
    Hi Guys, I have created simple example with @Singleton, @Schedule and @Timeout annotations to try if they would solve my problem. The scenario is this: EJB calls 'check' function every 5 secconds, and if certain conditions are met it will create single action timer that would invoke some long running process in asynchronous fashion. (it's sort of queue implementation type of thing). It then continues to check, but as long as long running process is there it won't start another one. Below is the code I came up with, but this solution does not work, because it looks like asynchronous call I'm making is in fact blocking my @Schedule method. @Singleton @Startup public class GenerationQueue { private Logger logger = Logger.getLogger(GenerationQueue.class.getName()); private List<String> queue = new ArrayList<String>(); private boolean available = true; @Resource TimerService timerService; @Schedule(persistent=true, minute="*", second="*/5", hour="*") public void checkQueueState() { logger.log(Level.INFO,"Queue state check: "+available+" size: "+queue.size()+", "+new Date()); if (available) { timerService.createSingleActionTimer(new Date(), new TimerConfig(null, false)); } } @Timeout private void generateReport(Timer timer) { logger.info("!!--timeout invoked here "+new Date()); available = false; try { Thread.sleep(1000*60*2); // something that lasts for a bit } catch (Exception e) {} available = true; logger.info("New report generation complete"); } What am I missing here or should I try different aproach? Any ideas most welcome :) Testing with Glassfish 3.0.1 latest build - forgot to mention

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  • What does it mean to say "Instance variables are not over-rided" in java?

    - by Ankit
    I am aware of the concept called field hiding in java. But still I am having a confusion in relation to instance variable being not over-ridden. According to my present knowledge, overriding a method of super-class means that the JVM will call the sub-class's over-ridden method though the super-class's method is available to the sub-class. And I read the similar thing for field hiding via the link:- Hiding Fields So, in any case we are over-ridding the instance if we change the values of the inherited instance variable in the sub-class. I am confused please help. I am using the following super-class:- public class Animal{ File picture; String food; int hunger; int width, height; int xcoord, ycoord; public void makeNoise(){ ......... } public void eat(){ ............. } public void sleep(){ .......... } public void roam(){ ............. } } It has sub-classes like Tiger, cat, dog,hippo etc. The sub-classes over-ride the makeNoise(), eat and roam() method. But each sub-class also uses a different set of values for instance variables. So as per my confusion, I am kind-of overriding all the instance variables and 3 methods of the super-class Animal; and I still have the super-class instance variables available to the sub-class with the use of the super keyword.

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  • .NET Splash screen issues

    - by CODe
    I have a splash screen for my C# database application that is called via the Shown event. The splash screen contains some information that is preprocessed when the main form's constructor is called, hence why I'm using the Shown event, because that information should be available. However, when the splash screen is shown, the main form is whited out, and the menu bar, bottom menu bar, and even the gray background are all white and invisible. It looks like the program is hanging, but after the 5 second delay I have built in, the banner goes away and the program is shown normally. Also, on the banner, I have labels that are not shown when the splash screen displays... Here is my code, some reasoning behind why it isn't working would help greatly. SPLASH SCREEN CODE : public partial class StartupBanner : Form { public StartupBanner(int missingNum, int expiredNum) { InitializeComponent(); missingLabel.Text = missingNum.ToString() + " MISSING POLICIES"; expiredLabel.Text = expiredNum.ToString() + " EXPIRED POLICIES"; } } CALLING CODE : private void MainForm_Shown(object sender, EventArgs e) { StartupBanner startup = new StartupBanner(missingPoliciesNum, expiredPoliciesNum); startup.MdiParent = this; startup.Show(); Thread.Sleep(5000); startup.Close(); } Using startup.ShowDialog() shows the correct label information on the splash screen, but that locks up the application, and I need the splash to go away after about 5 seconds, which is why it's a splash. ;)

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  • How can I return the number of rows affected in sqlplus to a shell script?

    - by jessica
    Here is my shell script: # Deletes data from the 'sample' table starting August 30, 2011. # This is done in stages with a 7 second break every # 2 seconds or so to free up the database for other users. # The message "Done." will be printed when there are # no database entries left to delete. user="*****" pass="*****" while(true); do starttime=`date +%s` while [[ $((`date +%s` - $starttime)) -lt 2 ]]; do sqlplus $user/$pass@//blabla <<EOF whenever sqlerror exit 1 delete from sample where sampletime >= to_date('08-30-2011','mm-dd-yyyy') and rownum <= 2; commit; EOF rows = ??? if [ $rows -eq 0 ] ; then echo "Done." exit 0; fi done sleep 7 done If there is no way to get the number of rows, maybe I can use an error code returned by sqlplus to figure out when to end the script? Any thoughts? Thank you!

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  • Improving my first Clojure program

    - by StackedCrooked
    After a few weekends exploring Clojure I came up with this program. It allows you to move a little rectangle in a window. Here's the code: (import java.awt.Color) (import java.awt.Dimension) (import java.awt.event.KeyListener) (import javax.swing.JFrame) (import javax.swing.JPanel) (def x (ref 0)) (def y (ref 0)) (def panel (proxy [JPanel KeyListener] [] (getPreferredSize [] (Dimension. 100 100)) (keyPressed [e] (let [keyCode (.getKeyCode e)] (if (== 37 keyCode) (dosync (alter x dec)) (if (== 38 keyCode) (dosync (alter y dec)) (if (== 39 keyCode) (dosync (alter x inc)) (if (== 40 keyCode) (dosync (alter y inc)) (println keyCode))))))) (keyReleased [e]) (keyTyped [e]))) (doto panel (.setFocusable true) (.addKeyListener panel)) (def frame (JFrame. "Test")) (doto frame (.add panel) (.pack) (.setDefaultCloseOperation JFrame/EXIT_ON_CLOSE) (.setVisible true)) (defn drawRectangle [p] (doto (.getGraphics p) (.setColor (java.awt.Color/WHITE)) (.fillRect 0 0 100 100) (.setColor (java.awt.Color/BLUE)) (.fillRect (* 10 (deref x)) (* 10 (deref y)) 10 10))) (loop [] (drawRectangle panel) (Thread/sleep 10) (recur)) Despite being an experienced C++ programmer I found it very challenging to write even a simple application in a language that uses a radically different style than what I'm used to. On top of that, this code probably sucks. I suspect the globalness of the various values is a bad thing. It's also not clear to me if it's appropriate to use references here for the x and y values. Any hints for improving this code are welcome.

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  • Java - If statement with String comparison fails

    - by Andrea
    I really don't know why the if statement below is not executing: if (s == "/quit") { System.out.println("quitted"); } Below is the whole class. It is probably a really stupid logic problem but I have been pulling my hair out over here not being able to figure this out. Thanks for looking :) class TextParser extends Thread { public void run() { while (true) { for(int i = 0; i < connectionList.size(); i++) { try { System.out.println("reading " + i); Connection c = connectionList.elementAt(i); Thread.sleep(200); System.out.println("reading " + i); String s = ""; if (c.in.ready() == true) { s = c.in.readLine(); //System.out.println(i + "> "+ s); if (s == "/quit") { System.out.println("quitted"); } if(! s.equals("")) { for(int j = 0; j < connectionList.size(); j++) { Connection c2 = connectionList.elementAt(j); c2.out.println(s); } } } } catch(Exception e){ System.out.println("reading error"); } } } } }

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  • Updating ToolStripProgressBar and ToolStripStatusLabel along with with an action

    - by TChristian
    In a Windows Form, I have a search box that fires an event to search a remote database and display some results. The query is pretty fast, usually just a fraction of a second, but in case the delay is noticeable there is a progress bar and label in the form's status bar. When the user clicks "Search" the status label should appear and the progress bar show some progress. Then when the result comes back the label should disappear and the progress bar should be full. Pretty basic response. The problem is, I can't get those actions to happen in that order. Using the code below, I click "Search", nothing happens until the results are displayed, and then the progress bar fills up from 0 to 100. The label never appears. I even threw in a sleep command immediately after the event to be sure I wasn't just missing it, but it's as if the first 2 statements are not being executed. What am I doing wrong here? private void searchButton_Click(object sender, EventArgs e) { toolStripStatusLabel1.Visible = true; toolStripProgressBar1.Value = 20; m_changeRequestedEvents.Fire<String>("SearchTerm", searchTextBox.Text); toolStripProgressBar1.Value = 100; toolStripStatusLabel1.Visible = false; }

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  • What programming language is this?

    - by Richard M.
    I recently stumbled over a very odd source listing on a rather old programming-related site (lost it somewhere in my browser history as I didn't care about it at first). I think that this is part of a simple (console-based?) snake game. I searched and searched but didn't find a language that looked somwhat like this. This seems like a mix of Python, Ruby and C++. What the hell? What programming-language is the below source listing written in? Maybe you can figure it out? my Snake.hasProps { length parts xDir yDir } & hasMethods { init: length = 0 parts[0].x,y = 5 move: parts[ 0 ].x,y.!add xDir | yDir # Move the head map parts(i,v): parts[ i ] = parts[ i + 1 ] checkBiteSelf checkFeed checkBiteSelf: part } my SnakePart.hasProps { x y } fork SnakePart to !Feed my Game.hasProps { frameTime = 30 } & hasMethods { init: mainloop mainloop: sys.util.sleep frameTime Snake.move Field.getInput -> Snake.xDir | Snake.yDir Field.reDraw with Snake & Feed & Game # For FPS } main.isMethod { game.init }

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  • App hosting Report Viewer crashes on exit after export

    - by Paul Sasik
    We have a .NET Winforms application that hosts the Crystal Reports Viewer control (Version XI). It works well for the most part but when an export of data from the viewer is performed the application will crash on exit and in unmanaged code. The error message is not very useful and just says that an incorrect memory location was accessed. No other info such a specific DLL etc. is provided. This only happens after the viewer is used to export a report to CSV, XML etc. My guess is that at some point in the export process Crystal creates a resource that attempts an action on shut down to a parent window (perhaps) that no longer exists. I've seen a number of memory leak and shut down issues with Crystal but this one's new. Has anyone seen it and come up with a workaround or has ideas for workarounds? So far we've tried explicitly disposing of all crystal-related objects, setting to null and even setting a Thread.Sleep cycle on shut down to "give Crystal time to clean up." Update: The crash happens only on shut down (so not immediate) All export formats work All export files are created properly CR is installed on the same machine as the hosting .NET app not sure about exporting from the IDE... is that even possible?

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  • Check if TIFF file is complete

    - by Davi
    I have a FileSystemWatcher monitoring a directory that receives TIF files from a scanning device. Its necessary to check if the scanning process is done and then read a multipage TIF file, otherwise, the FileSystemWatcher will raise the event before the file be fully scanned. I have something like: private void OnFileCreated(...) { while(IsFileLocked(path)) Thread.Sleep(time); // OK to read } This is what is happening: - Scanner creates the file - FileSystemWatcher detects the file, but its in use - Scanner reads the first page to the file - Scanner releases the file - My code leaves the while(FileInUse(path)) - My code reads the incomplete file (problem) - Scanner adds more pages to the file Let's say the scanner is scanning 100 pages, then, when "OK to read", the file will be incomplete (99 pages left). So, its necessary to know if the file is complete or not. Maybe waiting some time to see if the file is modified, but this time span can be up to hours, because the scanner can get idle scanning the same TIF. Other solution would be checking some flag in the TIF file that indicates that the file is not complete(I've looked for this but don't found anything).

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  • why does entity framework+mysql provider enumeration returns partial results with no exceptions

    - by Freddy Rios
    I'm trying to make sense of a situation I have using entity framework on .net 3.5 sp1 + MySQL 6.1.2.0 as the provider. It involves the following code: Response.Write("Products: " + plist.Count() + "<br />"); var total = 0; foreach (var p in plist) { //... some actions total++; //... other actions } Response.Write("Total Products Checked: " + total + "<br />"); Basically the total products is varying on each run, and it isn't matching the full total in plist. Its varies widely, from ~ 1/5th to half. There isn't any control flow code inside the foreach i.e. no break, continue, try/catch, conditions around total++, anything that could affect the count. As confirmation, there are other totals captured inside the loop related to the actions, and those match the lower and higher total runs. I don't find any reason to the above, other than something in entity framework or the mysql provider that causes it to end the foreach when retrieving an item. The body of the foreach can have some good variation in time, as the actions involve file & network access, my best shot at the time is that when the .net code takes beyond certain threshold there is some type of timeout in the underlying framework/provider and instead of causing an exception it is silently reporting no more items for enumeration. Can anyone give some light in the above scenario and/or confirm if the entity framework/mysql provider has the above behavior? Update: I can't reproduce the behavior by using Thread.Sleep in a simple foreach in a test project, not sure where else to look for this weird behavior :(.

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  • ~1 second TcpListener Pending()/AcceptTcpClient() lag

    - by cpf
    Probably just watch this video: http://screencast.com/t/OWE1OWVkO As you see, the delay between a connection being initiated (via telnet or firefox) and my program first getting word of it. Here's the code that waits for the connection public IDLServer(System.Net.IPAddress addr,int port) { Listener = new TcpListener(addr, port); Listener.Server.NoDelay = true;//I added this just for testing, it has no impact Listener.Start(); ConnectionThread = new Thread(ConnectionListener); ConnectionThread.Start(); } private void ConnectionListener() { while (Running) { while (Listener.Pending() == false) { System.Threading.Thread.Sleep(1); }//this is the part with the lag Console.WriteLine("Client available");//from this point on everything runs perfectly fast TcpClient cl = Listener.AcceptTcpClient(); Thread proct = new Thread(new ParameterizedThreadStart(InstanceHandler)); proct.Start(cl); } } (I was having some trouble getting the code into a code block) I've tried a couple different things, could it be I'm using TcpClient/Listener instead of a raw Socket object? It's not a mandatory TCP overhead I know, and I've tried running everything in the same thread, etc.

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

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

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  • using a While loop to control the value of a keyframe in a timeline in Javafx

    - by dragoknight
    i want to create an animation where the ball will move in one of the 4 sectors of a circle randomly.this will happen 5 times.so,i create a while loop(i<5) and call the random function.i then create an if loop and attach some x and y values according to the random fn value.i then create an timeline object inside the while loop and in the key frame value,i use these x and y values.but when i run the program,what happens is that all the values are being created(x and y values seen through println) but only the last x and y value(for i=5)is being rendered in the screen.the animations for the previous values(1<=i<=4)are not being rendered.Please advise where have i gone wrong? public function run(args:String[]) { var i=0; while(i<5) { var z=gety(); println(z); // var relativeTime:Duration=0s; if(z==1) {xbind=120; ybind=80; } else if(z==2) {xbind=120; ybind=120; } else if(z==3) { xbind=80; ybind=120; } else if(z==4) { xbind=80; ybind=80; } var t:Timeline=Timeline{ //time: bind pos with inverse; repeatCount: Timeline.INDEFINITE autoReverse: true keyFrames: [ KeyFrame{ time: 0s values: [ x => 100.0,y => 100.0]}, KeyFrame{time: 2s values:[x => xbind tween Interpolator.LINEAR, y => ybind tween Interpolator.LINEAR,] }, ] }//end timeline i++; t.play(); Thread.sleep(2000); }//end while }

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  • sqlite3 'database is locked' won't go away with retries

    - by Azarias
    I have a sqlite3 database that is accessed by a few threads (3-4). I am aware of the general limitations of sqlite3 with regards to concurrency as stated http://www.sqlite.org/faq.html#q6 , but I am convinced that is not the problem. All of the threads both read and write from this database. Whenever I do a write, I have the following construct: try: Cursor.execute(q, params) Connection.commit() except sqlite3.IntegrityError: Notify except sqlite3.OperationalError: print sys.exc_info() print("DATABASE LOCKED; sleeping for 3 seconds and trying again") time.sleep(3) Retry On some runs, I won't even hit this block, but when I do, it never comes out of it (keeps retrying, but I keep getting the 'database is locked' error from exc_info. If I understand the reader/writer lock usage correctly, some amount of waiting should help with the contention. What this sounds like is deadlock, but I do not use any transactions in my code, and every SELECT or INSERT is simply a one off. Some threads, however, keep the same connection when they do their operation (which includes a mix of SELECTS and INSERTS and other modifiers). I would appericiate it if you could shade a light on this, and also ways around fixing it (besides using a different database engine.)

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  • Checking if a console application is still running using the Process class

    - by Ced
    I'm making an application that will monitor the state of another process and restart it when it stops responding, exits, or throws an error. However, I'm having trouble to make it reliably check if the process (Being a C++ Console window) has stopped responding. My code looks like this: public void monitorserver() { while (true) { server.StartInfo = new ProcessStartInfo(textbox_srcdsexe.Text, startstring); server.Start(); log("server started"); log("Monitor started."); while (server.Responding) { if (server.HasExited) { log("server exitted, Restarting."); break; } log("server is running: " + server.Responding.ToString()); Thread.Sleep(1000); } log("Server stopped responding, terminating.."); try { server.Kill(); } catch (Exception) { } } } The application I'm monitoring is Valve's Source Dedicated Server, running Garry's Mod, and I'm over stressing the physics engine to simulate it stopping responding. However, this never triggers the process class recognizing it as 'stopped responding'. I know there are ways to directly query the source server using their own protocol, but i'd like to keep it simple and universal (So that i can maybe use it for different applications in the future). Any help appreciated

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  • How to play mpg/3gp 5 sec video at start of application?

    - by Asad Ahmed
    I am developing an application in which i want to play a short 5 seconds video at the startup. which is the best format 3gp, mpg or something else? i have generated a title activity. I wanted to play the video before title. Help please!!! Below is the code of my title activity. public class Title extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.title); setTitle("M.I.S.T"); this.setTitleColor(Color.BLUE); View title = getWindow().findViewById(android.R.id.title); View titleBar = (View) title.getParent(); titleBar.setBackgroundColor(Color.YELLOW); Thread timer = new Thread(){ public void run(){ try{ sleep(3000); }catch (InterruptedException e){ e.printStackTrace(); }finally{ Intent open= new Intent("com.congestion6.asad.MENU"); startActivity(open); } } }; timer.start(); } protected void onPause() { // TODO Auto-generated method stub super.onPause(); finish(); } }

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  • Java Concurrency in practice sample question

    - by andy boot
    I am reading "Java Concurrency in practice" and looking at the example code on page 51. According to the book this piece of code is at risk of of failure if it has not been published properly. Because I like to code examples and break them to prove how they work. I have tried to make it throw an AssertionError but have failed. (Leading me to my previous question) Can anyone post sample code so that an AssertionError is thrown? Rule: Do not modify the Holder class. public class Holder{ private int n; public Holder(int n){ this.n = n; } public void assertSanity(){ if (n != n) { throw new AssertionError("This statement is false"); } } } I have modified the class to make it more fragile but I still can not get an AssertionError thrown. class Holder2{ private int n; private int n2; public Holder2(int n) throws InterruptedException{ this.n = n; Thread.sleep(200); this.n2 = n; } public void assertSanity(){ if (n != n2) { throw new AssertionError("This statement is false"); } } } Is it possible to make either of the above classes throw an AssertionError? Or do we have to accept that they may occasionally do so and we can't write code to prove it?

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  • PHP curl timing mismatch

    - by JonoB
    I am running a php script that: queries a local database to retrieve an amount executes a curl statement to update an external database with the above amount + x queries the local database again to insert a new row reflecting that the curl statement has been executed. One of the problems that I am having is that the curl statement takes 2-4 seconds to execute, so I have two different users from the same company running the same script at the same time, the execution time of the curl command can cause a mismatch in what should be updated in the external database. This is the because the curl statement has not yet returned from the first user...so the second user is working off incorrect figures. I am not sure of the best options here, but basically I need to prevent two or more curl statements being run at the same time. I thought of storing a value in the database that indicates that the curl statement is being executed at that time, and prevent any other curl statements being run until its completed. Once the first curl statement has been executed, then the database flag is updated and the next one can run. If this field is 'locked', then I could loop through the code and sleep for (5) seconds, and then check again if the flag has been reset. If after (3) loops, then reset the flag automatically (i've never seen the curl take longer than 5 seconds) and continue processing. Are there any other (more elegant) ways of approaching this?

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  • SQLite transaction doesn't work as expected

    - by troll
    I prepared 2 files, "1.php" and "2.php". "1.php" is like this. <?php $dbh = new PDO('sqlite:test1'); $dbh->beginTransaction(); print "aaa<br>"; sleep(55); $dbh->commit(); print "bbb"; ?> and "2.php" is like this. <?php $dbh = new PDO('sqlite:test1'); $dbh->beginTransaction(); print "ccc<br>"; $dbh->commit(); print "ddd"; ?> and I excute "1.php". It starts a transaction and waits 55 seconds. So when I immediately excute "2.php", my expectation is this: "1.php" is getting transaction and "1" holds a database lock "2" can not begin a transaction "2" can not get database lock so "2" have to wait 55 seconds BUT, but the test went another way. When I excute "2",then "2" immediately returned it's result "2" did not wait so I have to think that "1" could not get transaction, or could not get database lock. Can anyone help?

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  • Avoiding a fork()/SIGCHLD race condition

    - by larry
    Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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  • What is an efficient strategy for multiple threads posting jobs and waiting for response from a single thread?

    - by jakewins
    In java, what is an efficient solution to the following problem: I have multiple threads (10-20 or so) generating jobs ("Job Creators"), and a single thread capable of performing them ("The worker"). Once a job creator has posted a job, it should wait for the job to finish, yielding no result other than "it's done", before it keeps going. For sending the jobs to the worker thread, I think a ring buffer or similar standard fan-in setup would perhaps be a good approach? But for a Job Creator to find out that her job has been done, I'm not so sure.. The job creators could sleep, and the worker interrupt them when done.. Or each job creator could have an atomic boolean that it checks, and that the worker sets. I dunno, neither of those feel very nice. I'd like to do it with as few (none, if possible) locks as absolutely possible. So to be clear: What I'm looking for is speed, not necessarily simplicity. Does anyone have any suggestions? Links to reading about concurrency strategies would also be very welcome!

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  • how to update UI controls in cocoa application from background thread

    - by AmitSri
    following is .m code: #import "ThreadLabAppDelegate.h" @interface ThreadLabAppDelegate() - (void)processStart; - (void)processCompleted; @end @implementation ThreadLabAppDelegate @synthesize isProcessStarted; - (void)awakeFromNib { //Set levelindicator's maximum value [levelIndicator setMaxValue:1000]; } - (void)dealloc { //Never called while debugging ???? [super dealloc]; } - (IBAction)startProcess:(id)sender { //Set process flag to true self.isProcessStarted=YES; //Start Animation [spinIndicator startAnimation:nil]; //perform selector in background thread [self performSelectorInBackground:@selector(processStart) withObject:nil]; } - (IBAction)stopProcess:(id)sender { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } - (void)processStart { int counter = 0; while (counter != 1000) { NSLog(@"Counter : %d",counter); //Sleep background thread to reduce CPU usage [NSThread sleepForTimeInterval:0.01]; //set the level indicator value to showing progress [levelIndicator setIntValue:counter]; //increment counter counter++; } //Notify main thread for process completed [self performSelectorOnMainThread:@selector(processCompleted) withObject:nil waitUntilDone:NO]; } - (void)processCompleted { //Stop Animation [spinIndicator stopAnimation:nil]; //set process flag to false self.isProcessStarted=NO; } @end I need to clear following things as per the above code. How to interrupt/cancel processStart while loop from UI control? I also need to show the counter value in main UI, which i suppose to do with performSelectorOnMainThread and passing argument. Just want to know, is there anyother way to do that? When my app started it is showing 1 thread in Activity Monitor, but when i started the processStart() in background thread its creating two new thread,which makes the total 3 thread until or unless loop get finished.After completing the loop i can see 2 threads. So, my understanding is that, 2 thread created when i called performSelectorInBackground, but what about the thrid thread, from where it got created? What if thread counts get increases on every call of selector.How to control that or my implementation is bad for such kind of requirements? Thanks

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  • nServiceBus - Not all commands being received by handler

    - by SimonB
    In a test project based of the nServiceBus pub/sub sample, I've replace the bus.publish with bus.send in the server. The server sends 50 messages with a 1sec wait after each 5 (ie 10 burst of 5 messages). The client does not get all the messages. The soln has 3 projects - Server, Client, and common messages. The server and client are hosted via the nServiceBus generic host. Only a single bus is defined. Both client and server are configured to use StructureMap builder and BinarySerialisation. Server Endpoint: public class EndPointConfig : AsA_Publisher, IConfigureThisEndpoint, IWantCustomInitialization { public void Init() { NServiceBus.Configure.With() .StructureMapBuilder() .BinarySerializer(); } } Server Code : for (var nextId = 1; nextId <= 50; nextId++) { Console.WriteLine("Sending {0}", nextId); IDataMsg msg = new DataMsg { Id = nextId, Body = string.Format("Batch Msg #{0}", nextId) }; _bus.SendLocal(msg); Console.WriteLine(" ...sent {0}", nextId); if ((nextId % 5) == 0) Thread.Sleep(1000); } Client Endpoint: public class EndPointConfig : AsA_Client, IConfigureThisEndpoint, IWantCustomInitialization { public void Init() { NServiceBus.Configure.With() .StructureMapBuilder() .BinarySerializer(); } } Client Clode: public class DataMsgHandler : IMessageHandler<IDataMsg> { public void Handle(IDataMsg msg) { Console.WriteLine("DataMsgHandler.Handle({0}, {1}) - ({2})", msg.Id, msg.Body, Thread.CurrentThread.ManagedThreadId); } } Client and Server App.Config: <MsmqTransportConfig InputQueue="nsbt02a" ErrorQueue="error" NumberOfWorkerThreads="1" MaxRetries="5" /> <UnicastBusConfig DistributorControlAddress="" DistributorDataAddress=""> <MessageEndpointMappings> <add Messages="Test02.Messages" Endpoint="nsbt02a" /> </MessageEndpointMappings> </UnicastBusConfig> All run via VisualStudio 2008. All 50 messages are sent - but after the 1st or 2nd batch. only 1 msg per batch is sent? Any ideas? I'm assuming config or misuse but ....?

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