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  • Delete throws "deleted object would be re-saved by cascade"

    - by Greg
    I have following model: <class name="Person" table="Person" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <!-- plus some properties here --> </class> <class name="Event" table="Event" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <!-- plus some properties here --> </class> <class name="PersonEventRegistration" table="PersonEventRegistration" optimistic-lock="version"> <id name="Id" type="Int32" unsaved-value="0"> <generator class="native" /> </id> <property name="IsComplete" type="Boolean" not-null="true" /> <property name="RegistrationDate" type="DateTime" not-null="true" /> <many-to-one name="Person" class="Person" column="PersonId" foreign-key="FK_PersonEvent_PersonId" cascade="all-delete-orphan" /> <many-to-one name="Event" class="Event" column="EventId" foreign-key="FK_PersonEvent_EventId" cascade="all-delete-orphan" /> </class> There are no properties pointing to PersonEventRegistration either in Person nor in Event. When I try to delete an entry from PersonEventRegistration, I get the following error: "deleted object would be re-saved by cascade" The problem is, I don't store this object in any other collection - the delete code looks like this: public bool UnregisterFromEvent(Person person, Event entry) { var registrationEntry = this.session .CreateCriteria<PersonEventRegistration>() .Add(Restrictions.Eq("Person", person)) .Add(Restrictions.Eq("Event", entry)) .Add(Restrictions.Eq("IsComplete", false)) .UniqueResult<PersonEventRegistration>(); bool result = false; if (null != registrationEntry) { using (ITransaction tx = this.session.BeginTransaction()) { this.session.Delete(registrationEntry); tx.Commit(); result = true; } } return result; } What am I doing wrong here?

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  • Atomic int writes on file

    - by Waneck
    Hello! I'm writing an application that will have to be able to handle many concurrent accesses to it, either by threads as by processes. So no mutex'es or locks should be applied to this. To make the use of locks go down to a minimum, I'm designing for the file to be "append-only", so all data is first appended to disk, and then the address pointing to the info it has updated, is changed to refer to the new one. So I will need to implement a small lock system only to change this one int so it refers to the new address. How is the best way to do it? I was thinking about maybe putting a flag before the address, that when it's set, the readers will use a spin lock until it's released. But I'm afraid that it isn't at all atomic, is it? e.g. a reader reads the flag, and it is unset on the same time, a writer writes the flag and changes the value of the int the reader may read an inconsistent value! I'm looking for locking techniques but all I find is either for thread locking techniques, or to lock an entire file, not fields. Is it not possible to do this? How do append-only databases handle this? Thanks! Cauê

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  • How did this happen?? Git error? Some other fluke?

    - by marfarma
    Every file in this Rails project is duplicated with a -e and again with a -e-e tacked onto the end of it, like the following. It's that way in my GitHub repository too. But I can't figure out how it happened. Any clue? Google searching comes up empty. -rw-r--r--@ 1 usrname staff 959 Jan 7 02:13 Gemfile -rw-r--r-- 1 usrname staff 958 Jan 5 01:10 Gemfile-e -rw-r--r-- 1 usrname staff 958 Jan 5 01:09 Gemfile-e-e -rw-r--r-- 1 usrname staff 6650 Jan 7 02:13 Gemfile.lock -rw-r--r-- 1 usrname staff 6650 Jan 5 01:10 Gemfile.lock-e -rw-r--r-- 1 usrname staff 6650 Jan 5 01:09 Gemfile.lock-e-e lrwxr-xr-x 1 usrname staff 18 Jan 5 00:37 README.rdoc - doc/README_FOR_APP -rw-r--r-- 1 usrname staff 283 Jan 5 01:10 Rakefile -rw-r--r-- 1 usrname staff 283 Jan 5 01:10 Rakefile-e -rw-r--r-- 1 usrname staff 283 Jan 5 01:09 Rakefile-e-e drwxr-xr-x 6 usrname staff 204 Jan 5 00:37 app drwxr-xr-x 5 usrname staff 170 Jan 5 01:10 autotest drwxr-xr-x 28 usrname staff 952 Jan 5 01:15 config -rw-r--r-- 1 usrname staff 173 Jan 5 01:10 config.ru -rw-r--r-- 1 usrname staff 173 Jan 5 01:10 config.ru-e -rw-r--r-- 1 usrname staff 173 Jan 5 01:09 config.ru-e-e

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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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  • File Locked by Services (after service code reading the text file)

    - by rvpals
    I have a windows services written in C# .NET. The service is running on a internal timer, every time the interval hits, it will go and try to read this log file into a String. My issue is every time the log file is read, the service seem to lock the log file. The lock on that log file will continue until I stop the windows service. At the same time the service is checking the log file, the same log file needs to be continuously updated by another program. If the file lock is on, the other program could not update the log file. Here is the code I use to read the text log file. private string ReadtextFile(string filename) { string res = ""; try { System.IO.FileStream fs = new System.IO.FileStream(filename, System.IO.FileMode.Open, System.IO.FileAccess.Read); System.IO.StreamReader sr = new System.IO.StreamReader(fs); res = sr.ReadToEnd(); sr.Close(); fs.Close(); } catch (System.Exception ex) { HandleEx(ex); } return res; } Thank you.

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  • Any way to turn off quips in OOWeb?

    - by Misha Koshelev
    http://ooweb.sourceforge.net/tutorial.html Not really a question, but I can't seem to stop writing stuff like this. Maybe someone will find it useful. I know rewriting an HTTP server is not the way to turn off the quips ;) /* Copyright 2010 Misha Koshelev. All Rights Reserved. */ package com.mksoft.common; import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.IOException; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import java.net.URLDecoder; import java.text.SimpleDateFormat; import java.util.Date; import java.util.LinkedHashMap; import java.net.ServerSocket; import java.net.Socket; /** * Simple HTTP Server. * * @author Misha Koshelev */ public class HttpServer extends Thread { /* * Constants */ /** * 404 Not Found Result */ protected final static String result404NotFound="<html><head><title>404 Not Found</title></head><body bgcolor='#ffffff'><h1>404 Not Found</h1></body></html>"; /* * Variables */ /** * Port on which HTTP server handles requests. */ protected int port; public int getPort() { return port; } public void setPort(int _port) { port=_port; } /* * Constructors */ public HttpServer(int _port) { setPort(_port); } /* * Helpers */ /** * Errors */ protected void error(String message) { System.err.println(message); System.err.flush(); } /** * Debugging */ protected boolean debugOutput=true; protected void debug(String message) { if (debugOutput) { error(message); } } /** * Lock object */ private Object lock=new Object(); /** * Should we quit? */ protected boolean doQuit=false; /** * Are we done? */ protected boolean areWeDone=false; /** * Process POST request headers */ protected String processPostRequest(String url,LinkedHashMap<String,String> headers,String inputLine) { debug("HttpServer.processPostRequest: url=\""+url); if (debugOutput) { for (String key: headers.keySet()) { debug("HttpServer.processPostRequest: headers."+key+"=\""+headers.get(key)+"\""); } } debug("HttpServer.processPostRequest: inputLine=\""+inputLine+"\""); try { inputLine=new URLDecoder().decode(inputLine,"UTF-8"); } catch (UnsupportedEncodingException uee) { uee.printStackTrace(); } String[] keyValues=inputLine.split("&"); LinkedHashMap<String,String> post=new LinkedHashMap<String,String>(); for (int i=0;i<keyValues.length;i++) { String keyValue=keyValues[i]; int equals=keyValue.indexOf('='); String key=keyValue.substring(0,equals); String value=keyValue.substring(equals+1); post.put(key,value); } return post(url,headers,post); } /** * Server loop (here for exception handling purposes) */ protected void serverLoop() throws IOException { /* Start server socket */ ServerSocket serverSocket=null; try { serverSocket=new ServerSocket(getPort()); } catch (IOException ioe) { ioe.printStackTrace(); System.exit(1); } Socket clientSocket=null; while (true) { /* Quit if necessary */ if (doQuit) { break; } /* Accept incoming connections */ try { clientSocket=serverSocket.accept(); } catch (IOException ioe) { ioe.printStackTrace(); System.exit(1); } /* Read request */ BufferedReader in=null; String inputLine=null; String firstLine=null; String blankLine=null; LinkedHashMap<String,String> headers=new LinkedHashMap<String,String>(); try { in=new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); while (true) { if (blankLine==null) { inputLine=in.readLine(); } else { /* POST request, read Content-length bytes */ int contentLength=new Integer(headers.get("Content-Length")).intValue(); StringBuilder sb=new StringBuilder(contentLength); for (int i=0;i<contentLength;i++) { sb.append((char)in.read()); } inputLine=sb.toString(); break; } if (firstLine==null) { firstLine=inputLine; } else if (blankLine==null) { if (inputLine.equals("")) { if (firstLine.startsWith("GET ")) { break; } blankLine=inputLine; } else { int colon=inputLine.indexOf(": "); String key=inputLine.substring(0,colon); String value=inputLine.substring(colon+2); headers.put(key,value); } } } } catch (IOException ioe) { ioe.printStackTrace(); } /* Process request */ String result=null; firstLine=firstLine.replaceAll(" HTTP/.*",""); if (firstLine.startsWith("GET ")) { result=get(firstLine.replaceFirst("GET ",""),headers); } else if (firstLine.startsWith("POST ")) { result=processPostRequest(firstLine.replaceFirst("POST ",""),headers,inputLine); } else { error("HttpServer.ServerLoop: Unhandled request \""+firstLine+"\""); } debug("HttpServer.ServerLoop: result=\""+result+"\""); /* Send response */ PrintWriter out=null; try { out=new PrintWriter(clientSocket.getOutputStream(),true); } catch (IOException ioe) { ioe.printStackTrace(); } if (result!=null) { out.println("HTTP/1.1 200 OK"); } else { out.println("HTTP/1.0 404 Not Found"); result=result404NotFound; } Date now=new Date(); out.println("Date: "+new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss z").format(now)); out.println("Content-Type: text/html; charset=UTF-8"); out.println("Content-Length: "+result.length()); out.println(""); out.print(result); /* Clean up */ out.close(); if (in!=null) { in.close(); } clientSocket.close(); } serverSocket.close(); areWeDone=true; synchronized(lock) { lock.notifyAll(); } } /* * Methods */ /** * Run server on port specified in constructor. */ public void run() { try { serverLoop(); } catch (IOException ioe) { ioe.printStackTrace(); System.exit(1); } } /** * Process GET request (should be overwritten). */ public String get(String url,LinkedHashMap<String,String> headers) { debug("HttpServer.get: url=\""+url+"\""); if (debugOutput) { for (String key: headers.keySet()) { debug("HttpServer.get: headers."+key+"=\""+headers.get(key)+"\""); } } if (url.equals("/")) { return "<html><head><title>HttpServer GET Test Page</title></head>\r\n"+ "<body bgcolor='#ffffff'>\r\n"+ "<center><h1>HttpServer GET Test Page</h1></center>\r\n"+ "<hr />\r\n"+ "<center><table>\r\n"+ "<form method='post' action='/'>\r\n"+ "<tr><td align=right>Test 1:</td>\r\n"+ " <td><input type='text' name='text 1' value='test me !!! !@#$'></td></tr>\r\n"+ "<tr><td align=right>Test 2:</td>\r\n"+ " <td><input type='text' name='text 2' value='type smthng'></td></tr>\r\n"+ "<tr><td>&nbsp;</td>\r\n"+ " <td align=right><input type='submit' value='Submit'></td></tr>\r\n"+ "</form>\r\n"+ "</table></center>\r\n"+ "<hr />\r\n"+ "<center><a href='/quit'>Shutdown Server</a></center>\r\n"+ "</html>"; } else if (url.equals("/quit")) { quit(); return ""; } else { return null; } } /** * Process POST request (should be overwritten). */ public String post(String url,LinkedHashMap<String,String> headers,LinkedHashMap<String,String> post) { debug("HttpServer.post: url=\""+url+"\""); if (debugOutput) { for (String key: headers.keySet()) { debug("HttpServer.post: headers."+key+"=\""+headers.get(key)+"\""); } } if (url.equals("/")) { String result="<html><head><title>HttpServer Post Test Page</title></head>\r\n"+ "<body bgcolor='#ffffff'>\r\n"+ "<center><h1>HttpServer Post Test Page</h1></center>\r\n"+ "<hr />\r\n"+ "<center><table>\r\n"+ "<tr><th>Key</th><th>Value</th></tr>\r\n"; for (String key: post.keySet()) { result+="<tr><td align=right>"+key+"</td><td align=left>"+post.get(key)+"</td></tr>\r\n"; } result+="</table></center>\r\n"+ "</html>"; return result; } else { return null; } } /** * Wait for server to quit. */ public void waitForCompletion() { while (areWeDone==false) { synchronized(lock) { try { lock.wait(); } catch (InterruptedException ie) { } } } } /** * Shutdown server. */ public void quit() { doQuit=true; } }

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  • WPF create a list of controls that can be scrolled via the mouse but still remain functional

    - by Mark
    I have a list of controls that I am displaying via a WrapPanel and it horizontally oriented. I have implemented a "Click and Drag" scrolling technique so that the user scrolls with the mouse via clicking and dragging. Like so: <Canvas x:Name="ParentCanvas" PreviewMouseDown="Canvas_MouseDown" MouseMove="Canvas_MouseMove"> <WrapPanel> <WrapPanel.RenderTransform> <TranslateTransform /> </WrapPanel.RenderTransform> <!-- controls are all in here ... --> </WrapPanel> </Canvas> Then in the code behind: private Point _mousePosition; private Point _lastMousePosition; private void Canvas_MouseDown(object sender, MouseButtonEventArgs e) { _lastMousePosition = e.GetPosition(ParentCanvas); e.Handled = true; } private void Canvas_MouseMove(object sender, MouseEventArgs e) { _mousePosition = e.GetPosition(ParentCanvas); var delta = _mousePosition - _lastMousePosition; if(e.LeftButton == MouseButtonState.Pressed && delta.X != 0) { var transform = ((TranslateTransform)_wrapPanel.RenderTransform).Clone(); transform.X += delta.X; _wrapPanel.RenderTransform = transform; _lastMousePosition = _mousePosition; } } This all works fine But what I want to do is make it so that when a users clicks to drag, the items within the WrapPanel dont respond (i.e. the user is only browsing), but when the user clicks (as in a full click) then they do respond to the click. Just like how the iphone works, when you press and drag directly on an app, it does not open the app, but rather scrolls the screen, but when you tap the app, it starts... I hope this makes sense. Cheers, Mark

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  • How can I set a Java applet transparency to show contents behind it?

    - by yuri
    I've got a web page with an applet inside. This applet is a drop target on a drag and drop action from the OS, I simply take an image from a folder, drag it on the applet and something happens. I give this webpage to a graphic designer and he ask to if he can put an image behind the java applet so he can simulate to change the background using CSS (it is a skinned app and graphic design can change during execution). Practically i supposed to do: <div> <applet width="50" height="50" /> </div> with this CSS: div { width:50px; height:50px; background-image: url(image.jpg) center center no-repeat; } But it doesn't work (background is opaque). It is possible to set transparency to the applet without loosing drag and drop capabilities ? I'm searching something similar to flash wmode parameter. Better solutions implies only changes on the CSS/HTML without recompiling java class so the designing team can change the page structure without changing the Java.

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  • How to deserialize implementation classes in OSGi

    - by Daniel Schneller
    In an eRCP OSGi based application the user can push a button and go to a lock screen similar to that of Windows or Mac OS X. When this happens, the current state of the application is serialized to a file and control is handed over to the lock screen. In this mobile application memory is very tight, so we need to get rid of the original view/controller when the lock screen comes up. This works fine and we end up with a binary serialized file. Once the user logs back in, the file is read in again and the original state of the application restored. This works fine as well, except when the controller that was serialized contained a reference to an object which comes from a different bundle. In my concrete case the original controller (from bundle A) can call a web service and gets a result back. Nothing fancy, just some Strings and Numbers in a simple value holder class. However the controller only sees this as a Result interface; the actual runtime object (ResultImpl) is defined and created in a different bundle (bundle B, the webservice client implementation) and returned via a service call. When the deserialization now tries to thaw the controller from the file, it throws a ClassNotFound exception, complaining about not being able to deserialize the result object, because deserialization is called from bundle A, which cannot see the ResultImpl class from bundle B. Any ideas on how to work around that? The only thing I could come up with is to clone all the individual values into another object, defined in the controller's bundle, but this seems like quite a hassle.

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  • How to improve multi-threaded access to Cache (custom implementation)

    - by Andy
    I have a custom Cache implementation, which allows to cache TCacheable<TKey> descendants using LRU (Least Recently Used) cache replacement algorithm. Every time an element is accessed, it is bubbled up to the top of the LRU queue using the following synchronized function: // a single instance is created to handle all TCacheable<T> elements public class Cache() { private object syncQueue = new object(); private void topQueue(TCacheable<T> el) { lock (syncQueue) if (newest != el) { if (el.elder != null) el.elder.newer = el.newer; if (el.newer != null) el.newer.elder = el.elder; if (oldest == el) oldest = el.newer; if (oldest == null) oldest = el; if (newest != null) newest.newer = el; el.newer = null; el.elder = newest; newest = el; } } } The bottleneck in this function is the lock() operator, which limits cache access to just one thread at a time. Question: Is it possible to get rid of lock(syncQueue) in this function while still preserving the queue integrity?

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  • Sharing a COM port over TCP

    - by guinness
    What would be a simple design pattern for sharing a COM port over TCP to multiple clients? For example, a local GPS device that could transmit co-ordinates to remote hosts in realtime. So I need a program that would open the serial port and accept multiple TCP connections like: class Program { public static void Main(string[] args) { SerialPort sp = new SerialPort("COM4", 19200, Parity.None, 8, StopBits.One); Socket srv = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); srv.Bind(new IPEndPoint(IPAddress.Any, 8000)); srv.Listen(20); while (true) { Socket soc = srv.Accept(); new Connection(soc); } } } I would then need a class to handle the communication between connected clients, allowing them all to see the data and keeping it synchronized so client commands are received in sequence: class Connection { static object lck = new object(); static List<Connection> cons = new List<Connection>(); public Socket socket; public StreamReader reader; public StreamWriter writer; public Connection(Socket soc) { this.socket = soc; this.reader = new StreamReader(new NetworkStream(soc, false)); this.writer = new StreamWriter(new NetworkStream(soc, true)); new Thread(ClientLoop).Start(); } void ClientLoop() { lock (lck) { connections.Add(this); } while (true) { lock (lck) { string line = reader.ReadLine(); if (String.IsNullOrEmpty(line)) break; foreach (Connection con in cons) con.writer.WriteLine(line); } } lock (lck) { cons.Remove(this); socket.Close(); } } } The problem I'm struggling to resolve is how to facilitate communication between the SerialPort instance and the threads. I'm not certain that the above code is the best way forward, so does anybody have another solution (the simpler the better)?

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  • How to clear wxpython frame content when dragging a panel?

    - by aF
    Hello, I have 3 panels and I want to make drags on them. The problem is that when I do a drag on one this happens: How can I refresh the frame to happear its color when the panel is no longer there? This is the code that I have to make the drag: def onMouseMove(self, event): (self.pointWidth, self.pointHeight) = event.GetPosition() (self.width, self.height) = self.GetSizeTuple() if (self.pointWidth>100 and self.pointWidth<(self.width-100) and self.pointHeight < 15) or self.parent.dragging: self.SetCursor(wx.StockCursor(wx.CURSOR_SIZING)) """implement dragging""" if not event.Dragging(): self.w = 0 self.h = 0 return self.CaptureMouse() if self.w == 0 and self.h == 0: (self.w, self.h) = event.GetPosition() else: (posw, posh) = event.GetPosition() displacement = self.h - posh self.SetPosition( self.GetPosition() - (0, displacement)) else: self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW)) def onDraggingDown(self, event): if self.pointWidth>100 and self.pointWidth<(self.width-100) and self.pointHeight < 15: self.parent.dragging = 1 self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW)) self.SetBackgroundColour('BLUE') self.parent.SetTransparent(220) self.Refresh() def onDraggingUp(self, event): self.parent.dragging = 0 self.parent.SetTransparent(255) self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW)) and this are the binds for this events: self.Bind(wx.EVT_MOTION, self.onMouseMove) self.Bind(wx.EVT_LEFT_DOWN, self.onDraggingDown) self.Bind(wx.EVT_LEFT_UP, self.onDraggingUp) With this, if I click on the top of the panel, and move down or up, the panel position changes (I drag the panel) to the position of the mouse.

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  • Update a list of things without hitting every entry

    - by bobobobo
    I have a list in a database that the user should be able to order. itemname| order value (int) --------+--------------------- salad | 1 mango | 2 orange | 3 apples | 4 On load from the database, I simply order by order_value. By drag 'n drop, he should be able to move apples so that it appears at the top of the list.. itemname| order value (int) --------+--------------------- apples | 4 salad | 1 mango | 2 orange | 3 Ok. So now internally I have to update EVERY LIST ITEM! If the list has 20 or 100 items, that's a lot of updates for a simple drag operation. itemname| order value (int) --------+--------------------- apples | 1 salad | 2 mango | 3 orange | 4 I'd rather do it with only one update. One way I thought of is if "internal Order" is a double value. itemname| order value (double) --------+--------------------- salad | 1.0 mango | 2.0 orange | 3.0 apples | 4.0 SO after the drag n' drop operation, I assign apples has a value that is less than the item it is to appear in front of: itemname| order value (double) --------+--------------------- apples | 0.5 salad | 1.0 mango | 2.0 orange | 3.0 .. and if an item is dragged into the middle somewhere, its order_value is bigger than the one it appears after .. here I moved orange to be between salad and mango: itemname| order value (double) --------+--------------------- apples | 0.5 salad | 1.0 orange | 1.5 mango | 2.0 Any thoughts on better ways to do this?

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  • Fastest inline-assembly spinlock

    - by sigvardsen
    I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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  • Stop Observing Events with JS Prototype not working with .bind(this)

    - by PeterBelm
    I'm working on a Javascript class based on the Prototype library. This class needs to observe an event to perform a drag operation (the current drag-drop controls aren't right for this situation), but I'm having problems making it stop observing the events. Here's a sample that causes this problem: var TestClass = Class.create({ initialize: function(element) { this.element = element; Event.observe(element, 'mousedown', function() { Event.observe(window, 'mousemove', this.updateDrag.bind(this)); Event.observe(window, 'mouseup', this.stopDrag.bind(this)); }); }, updateDrag: function(event) { var x = Event.pointerX(event); var y = Event.pointerY(event); this.element.style.top = y + 'px'; this.element.style.left = x + 'px'; }, stopDrag: function(event) { console.log("stopping drag"); Event.stopObserving(window, 'mousemove', this.updateDrag.bind(this)); Event.stopObserving(window, 'mouseup', this.stopDrag.bind(this)); } }); Without .bind(this) then this.element is undefined, but with it the events don't stop being observed (the console output does occur though).

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  • Sequential access to asynchronous sockets

    - by Lars A. Brekken
    I have a server that has several clients C1...Cn to each of which there is a TCP connection established. There are less than 10,000 clients. The message protocol is request/response based, where the server sends a request to a client and then the client sends a response. The server has several threads, T1...Tm, and each of these may send requests to any of the clients. I want to make sure that only one of these threads can send a request to a specific client at any one time, while the other threads wanting to send a request to the same client will have to wait. I do not want to block threads from sending requests to different clients at the same time. E.g. If T1 is sending a request to C3, another thread T2 should not be able to send anything to C3 until T1 has received its response. I was thinking of using a simple lock statement on the socket: lock (c3Socket) { // Send request to C3 // Get response from C3 } I am using asynchronous sockets, so I may have to use Monitor instead: Monitor.Enter(c3Socket); // Before calling .BeginReceive() And Monitor.Exit(c3Socket); // In .EndReceive I am worried about stuff going wrong and not letting go of the monitor and therefore blocking all access to a client. I'm thinking that my heartbeat thread could use Monitor.TryEnter() with a timeout and throw out sockets that it cannot get the monitor for. Would it make sense for me to make the Begin and End calls synchronous in order to be able to use the lock() statement? I know that I would be sacrificing concurrency for simplicity in this case, but it may be worth it. Am I overlooking anything here? Any input appreciated.

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  • Protecting critical sections based on a condition in C#

    - by NAADEV
    Hello, I'm dealing with a courious scenario. I'm using EntityFramework to save (insert/update) into a SQL database in a multithreaded environment. The problem is i need to access database to see whether a register with a particular key has been already created in order to set a field value (executing) or it's new to set a different value (pending). Those registers are identified by a unique guid. I've solved this problem by setting a lock since i do know entity will not be present in any other process, in other words, i will not have same guid in different processes and it seems to be working fine. It looks something like that: static readonly object LockableObject = new object(); static void SaveElement(Entity e) { lock(LockableObject) { Entity e2 = Repository.FindByKey(e); if (e2 != null) { Repository.Insert(e2); } else { Repository.Update(e2); } } } But this implies when i have a huge ammount of requests to be saved, they will be queued. I wonder if there is something like that (please, take it just as an idea): static void SaveElement(Entity e) { (using ThisWouldBeAClassToProtectBasedOnACondition protector = new ThisWouldBeAClassToProtectBasedOnACondition(e => e.UniqueId) { Entity e2 = Repository.FindByKey(e); if (e2 != null) { Repository.Insert(e2); } else { Repository.Update(e2); } } } The idea would be having a kind of protection that protected based on a condition so each entity e would have its own lock based on e.UniqueId property. Any idea?

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  • Powershell finding services using a cmdlet dll

    - by bartonm
    I need to upgrade a dll assemblies, written in C#, in our installation. Before I replace the DLL file, I want to check if the file has a lock and if so display a message. How do I implement this in powershell? I was thinking iterate through Get-Process checking dependencies. Solved. I iterated through list looking a file path match. function IsCaradigmPowershellDLLFree() { # The list of DLLs to check for locks by running processes. $DllsToCheckForLocks = "$env:ProgramFiles\Caradigm Platform\System 3.0\Platform\PowerShell\Caradigm.Platform.Powershell.dll", "$env:ProgramFiles\Caradigm Platform\System 3.0\Platform\PowerShell\Caradigm.Platform.Powershell.InternalPlatformSetup.dll"; # Assume true, then check all process dependencies $result = $true; # Iterate through each process and check module dependencies foreach ($p in Get-Process) { # Iterate through each dll used in a given process foreach ($m in Get-Process -Name $p.ProcessName -Module -ErrorAction SilentlyContinue) { # Check if dll dependency match any DLLs in list foreach ($dll in $DllsToCheckForLocks) { # Compare the fully-qualified file paths, # if there's a match then a lock exists. if ( ($m.FileName.CompareTo($dll) -eq 0) ) { $pName = $p.ProcessName.ToString() Write-Error "$dll is locked by $pName. This dll must be have zero locked prior to upgrade. Stop this service to release this lock on $m1." $result = $false; } } } } return $result; }

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  • Do something else if ReadWriteSlimlock is held

    - by user43838
    Hi everyone, I have implemented ReaderWriterLockSlim, Now i don't want it to wait at the lock. I want to do something else if the lock is held. I considered using is isWriterLockHeld but it does not makes much sense to me, Since if two threads come in at the same time and enter the if statement at the same time one will still be waiting at the lock here is my code. ReaderWriterLockSlim rw = GetLoadingLock(parameters); rw = GetLoadingLock(parameters); try { rw.EnterWriteLock(); item = this.retrieveCacheItem(parameters.ToString(), false); if (item != null) { parameters.DataCameFromCache = true; // if the data was found in the cache, return it immediately return item.data; } else { try { object loaditem = null; itemsLoading[parameters.ToString()] = true; loaditem = this.retrieveDataFromStore(parameters); return loaditem; } finally { itemsLoading.Remove(parameters.ToString()); } } } finally { rw.ExitWriteLock(); } Can anyone please guide me in the right direction with this. Thanks

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  • Why would paperclip not assign an ID to my uploaded photos?

    - by Trip
    I just deployed to a cluster server, and my delayed_jobs recipe was overwritten in the process. I solved that, delayed_jobs is up and running but can't find the ID of images that are uploaded. The images are saved correctly : Processing PhotosController#create (for 173.161.167.41 at 2010-06-01 05:09:14) [POST] Parameters: {"Filename"="1.jpg", "gallery_id"="1298", "action"="create", "amp"=nil, "authenticity_token"="qmbnpwFY8a5E3YtS/4fMWF/Z8evCE4hMxqKVJw0I7Ek=", "Upload"="Submit Query", "controller"="photos", "organization_id"="470", "_hq_channel_session"="BAh7CSIYdXNlcl9jcmVkZW50aWFsc19pZGkHIhV1c2VyX2NyZWRlbnRpYWxzIgGAOGRlZDc0NGJlOWU3NTNlNDFlYmVlMDdjMzIzYjA1ZjQxNGE5ZDY4YjNmYjFmNjNkMDQ2OWY2ZDQyOTljZDhiMDFlNmRkMDljNThmMzBmOWJhMTIwNDhkMDI5MTMxYmU5MDczYjIxZmI4YmQxMDVlMTBmNjZmOWFhODE1ZTBjMGM6EF9jc3JmX3Rva2VuIjFxbWJucHdGWThhNUUzWXRTLzRmTVdGL1o4ZXZDRTRoTXhxS1ZKdzBJN0VrPToPc2Vzc2lvbl9pZCIlMjAwMDQ3ZDQ3ZWUyZTgzODIxYzdjOGI3OTdmZGJiMDM=--ac6aa580262938bf5a4d6b9a740722b680eb5d48", "Filedata"=#} [paperclip] Saving attachments. [paperclip] saving /data/HQ_Channel/releases/20100530153454/public/system/photos/9253/original/1.jpg [paperclip] Saving attachments. [paperclip] Saving attachments. Completed in 127ms (View: 2, DB: 91) | 200 OK [http://invent.hqchannel.com/organizations/470/media/galleries/1298/photos?_hq_channel_session=BAh7CSIYdXNlcl9jcmVkZW50aWFsc19pZGkHIhV1c2VyX2NyZWRlbnRpYWxzIgGAOGRlZDc0NGJlOWU3NTNlNDFlYmVlMDdjMzIzYjA1ZjQxNGE5ZDY4YjNmYjFmNjNkMDQ2OWY2ZDQyOTljZDhiMDFlNmRkMDljNThmMzBmOWJhMTIwNDhkMDI5MTMxYmU5MDczYjIxZmI4YmQxMDVlMTBmNjZmOWFhODE1ZTBjMGM6EF9jc3JmX3Rva2VuIjFxbWJucHdGWThhNUUzWXRTLzRmTVdGL1o4ZXZDRTRoTXhxS1ZKdzBJN0VrPToPc2Vzc2lvbl9pZCIlMjAwMDQ3ZDQ3ZWUyZTgzODIxYzdjOGI3OTdmZGJiMDM%3D--ac6aa580262938bf5a4d6b9a740722b680eb5d48&authenticity_token=qmbnpwFY8a5E3YtS%2F4fMWF%2FZ8evCE4hMxqKVJw0I7Ek%3D] And then delayed_jobs keeps spinning around in circles on this one : 2010-06-01T05:09:02-0700: * [Worker(delayed_job host:ip-10-251-197-159 pid:19994)] acquired lock on PhotoJob 2010-06-01T05:09:02-0700: * [JOB] delayed_job host:ip-10-251-197-159 pid:19994 failed with ActiveRecord::RecordNotFound: Couldn't find Photo with ID=9247 - 0 failed attempts 2010-06-01T05:09:02-0700: * [Worker(delayed_job host:ip-10-251-197-159 pid:19994)] acquired lock on PhotoJob 2010-06-01T05:09:02-0700: * [JOB] delayed_job host:ip-10-251-197-159 pid:19994 failed with ActiveRecord::RecordNotFound: Couldn't find Photo with ID=9245 - 0 failed attempts 2010-06-01T05:09:02-0700: * [Worker(delayed_job host:ip-10-251-197-159 pid:19994)] acquired lock on PhotoJob So what I get is that the photos are not being assigned ID's by paperclip. Anyone know where I could poke and pry from here? UPDATE: I created a clone application on a single server. And there are no problems. The images on the cluster do show up (occassionally). If I keep clicking on the folders that lead to photos, it will 50% of the time return a 404 with it not being able to find the photo, and the other half it will present the photo. So the problem has got to be with the server interaction between the ActiveRecord through multiple servers.

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  • Is there any reason why jQuery Sortable would work in IE/Chrome but not Firefox?

    - by DNS
    I have a fairly straightforward list of horizontally floated items, like this: <div class="my-widget-container"> <div class="my-widget-column">...</div> ... </div> Both the container and each column have a fixed width, set using jQuery's .width(). The container is position: relative and the column is float: left and overflow: hidden. Not sure if any other styles/properties are relevant. When I apply a jQuery-UI sortable to this, the result is exactly what I'd expect in Chome 8 and IE 8; the columns can be dragged around to change their order. But in Firefox 3.6 I can click an item and drag to create a new sort-helper, yet the actual sort never happens; the real item's position in the DOM never changes. I dug around a little in Sortable, and added a debug print to _intersectsWithPointer. Whenever the drag helper moves, Sortable runs through its list of elements and uses this method to determine whether the drag helper has passed over one. What I saw was that item.left had the same value for all my columns, which is obviously not correct, and probably the source of the problem. It looks like all columns had a left position corresponding to that of the first column. I'm using jQuery 1.4.3 and jQuery UI Sortable 1.8. Those aren't the very latest versions, but they're pretty recent, and I don't see anything in the Sortable release notes that indicates any such problem has been fixed. Does anyone know what might be happening here, or have any ideas for further debugging?

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  • svg mouseup event not fired in IE9, unless the debugger is open

    - by Roberto Lupi
    I am using d3 to build a simple chart that the user can edit interactively with the mouse. It works on in all modern common browser (Chrome, Firefox, Safari), except for Internet Explorer 9 where I can start to drag an item but I never get the mouseup event. The strangest bit is that, if I open the debugger, the page works percetly on Internet Explorer 9 as well. My code looks like this: item.append("svg:circle") .attr("class", "handle") .attr("opacity",0.5) .attr("stroke","gray") .attr("cx", bx(0.5)-bx(0)) .attr("r", 10) .style("cursor", "crosshair") .style("pointer-events", "all") .call(d3.behavior.drag() .on("dragstart", function() { dragTarget = d3.select(this); }) .on("drag", function() { this.parentNode.appendChild(this); // put us on the front, not really needed var dragTarget = d3.select(this); dragTarget .attr("cy", function() { return d3.event.dy + parseInt(dragTarget.attr("cy"))}); }) .on("dragend", function(d, i) { newY = parseInt(d3.select(this).attr("cy")); newValue = y.invert(newY); var serieNo = this.__data__.serieNo; console.log([serieNo+1,i+1]); data[serieNo+1][i+1] = newValue; updateBarChart(); onchange(); }) );

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  • Subquery with multiple results combined into a single field?

    - by Todd
    Assume I have these tables, from which i need to display search results in a browser: Table: Containers id | name 1 Big Box 2 Grocery Bag 3 Envelope 4 Zip Lock Table: Sale id | date | containerid 1 20100101 1 2 20100102 2 3 20091201 3 4 20091115 4 Table: Items id | name | saleid 1 Barbie Doll 1 2 Coin 3 3 Pop-Top 4 4 Barbie Doll 2 5 Coin 4 I need output that looks like this: itemid itemname saleids saledates containerids containertypes 1 Barbie Doll 1,2 20100101,20100102 1,2 Big Box, Grocery Bag 2 Coin 3,4 20091201,20091115 3,4 Envelope, Zip Lock 3 Pop-Top 4 20091115 4 Zip Lock The important part is that each item type only gets one record/row in the return on the screen. I accomplished this in the past by returning multiple rows of the same item and using a scripting language to limit the output. However, this makes the ui overly complicated and loopy. So, I'm hoping I can get the database to spit out only as many records as there are rows to display. This example may be a bit extreme because of the 2 joins needed to get to the container from the item (through the sale table). I'd be happy for just an example query that outputs this: itemid itemname saleids saledates 1 Barbie Doll 1,2 20100101,20100102 2 Coin 3,4 20091201,20091115 3 Pop-Top 4 20091115 I can only return a single result in a subquery, so I'm not sure how to do this.

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  • I just discovered why all ASP.Net websites are slow, and I am trying to work out what to do about it

    - by James
    I just discovered that every request in an ASP.Net web application gets a Session lock at the begging of a request, and then releases it at the end of the request!!! I mean, WTF Microsoft! In case the implication is lost on you, as it was from me at first, this basically means the following: Anytime an ASP.Net webpage is taking a long time to load (maybe due to a slow database call or whatever), and the user decides they want to navigate to a different page because they are tired of waiting, THEY CANT! The ASP.Net session lock forces the new page request to wait until the original request has finished its painfully slow load. Arrrgh. Anytime an UpdatePanel is loading slowly, and the user decides to navigate to a different page before the UpdadePanel has finished updating... THEY CANT! The ASP.Net session lock forces the new page request to wait until the original request has finished its painfully slow load. Double Arrrgh! So what are the options? So far I have come up with: Implement a Custom SessionStateDataStore, which ASP.Net supports. I haven't found too many out there to copy, and it seems kind of high risk and easy to mess up. Keep track of all requests in progress, and if a request comes in from the same user, cancel the original request. Seems kind of extreme, but it would work (I think) Don't user Session! When I need some kind of state for the user, I could just user Cache instead, and key items on the authenticated user's name, or some such thing. Again seems kind of extreme I really can't believe that the ASP.Net Microsoft team would have left such a huge performance bottleneck in the framework at version 4.0! Am I missing something obvious? How hard would it be to use a ThreadSafe collection for the Session? Arrrrghhhhhh. Any advice much appreciated.

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  • Write-Only Reference in C++?

    - by Robert Mason
    Is there a way to code a write-only reference to an object? For example, suppose there was a mutex class: template <class T> class mutex { protected: T _data; public: mutex(); void lock(); //locks the mutex void unlock(); //unlocks the mutex T& data(); //returns a reference to the data, or throws an exception if lock is unowned }; Is there a way to guarantee that one couldn't do this: mutex<type> foo; T& ref; foo.lock(); ref = foo.data(); foo.unlock(); //I have a unguarded reference to foo now On the other hand, is it even worth it? I know that some people assume that programmers won't deliberately clobber the system, but then, why do we have private variables in the first place, eh? It'd be nice to just say it's "Undefined Behavior", but that just seems a little bit too insecure.

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