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• MVC 2 AntiForgeryToken - Why symmetric encryption + IPrinciple?

  - by Brad R

  We recently updated our solution to MVC 2, and this has updated the way that the AntiForgeryToken works. Unfortunately this does not fit with our AJAX framework any more. The problem is that MVC 2 now uses symmetric encryption to encode some properties about the user, including the user's Name property (from IPrincipal). We are able to securely register a new user using AJAX, after which subsequent AJAX calls will be invalid as the anti forgery token will change when the user has been granted a new principal. There are also other cases when this may happen, such as a user updating their name etc. My main question is why does MVC 2 even bother using symmetric encryption? Any then why does it care about the user name property on the principal? If my understanding is correct then any random shared secret will do. The basic principle is that the user will be sent a cookie with some specific data (HttpOnly!). This cookie is then required to match a form variable sent back with each request that may have side effects (POST's usually). Since this is only meant to protect from cross site attacks it is easy to craft up a response that would easily pass the test, but only if you had full access to the cookie. Since a cross site attacker is not going to have access to your user cookies you are protected. By using symmetric encryption, what is the advantage in checking the contents of the cookie? That is, if I already have sent an HttpOnly cookie the attacker cannot override it (unless a browser has a major security issue), so why do I then need to check it again? After having a think about it it appears to be one of those 'added layer of security' cases - but if your first line of defence has fallen (HttpOnly) then the attacker is going to get past the second layer anyway as they have full access to the users cookie collection, and could just impersonate them directly, instead of using an indirect XSS/CSRF attack. Of course I could be missing a major issue, but I haven't found it yet. If there are some obvious or subtle issues at play here then I would like to be aware of them.

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• Can't setup Facebook Login on my website..

  - by Mark

  I am trying to experiment with the new facebook authentication system, and I can't getthe login to work. I'm getting the following error message: API Error Code: 100 API Error Description: Invalid parameter Error Message: next is not owned by the application. The url that is being sent to facebook is: http://www.facebook.com/connect/uiserver.php?app_id=444444444444444&next=http%3A%2F%2Fstatic.ak.fbcdn.net%2Fconnect%2Fxd_proxy.php%23%3F%3D%26cb%3Df357eceb0361a8a%26origin%3Dhttp%253A%252F%252Fwww.mysite.com%252Ff38fea4f9ea573%26relation%3Dopener%26transport%3Dpostmessage%26frame%3Df23b800f8a78%26result%3DxxRESULTTOKENxx&display=popup&channel=http%3A%2F%2Fwww.mysite.com%2Ffbtester.php&cancel=http%3A%2F%2Fstatic.ak.fbcdn.net%2Fconnect%2Fxd_proxy.php%23%3F%3D%26cb%3Df6095a98598be8%26origin%3Dhttp%253A%252F%252Fwww.mysite.com%252Ff38fea4f9ea573%26relation%3Dopener%26transport%3Dpostmessage%26frame%3Df23b800f8a78%26result%3DxxRESULTTOKENxx&locale=en_US&return_session=1&session_version=3&fbconnect=1&canvas=0&legacy_return=1&method=permissions.request Note that the 'Next' variable in the url is: next=http%3A%2F%2Fstatic.ak.fbcdn.net%2Fconnect%2Fxd_proxy.php%23%3F%3D%26cb%3Df357eceb0361a8a%26origin%3Dhttp%253A%252F%252Fwww.mysite.com%252Ff38fea4f9ea573%26relation%3Dopener%26transport%3Dpostmessage%26frame%3Df23b800f8a78%26result%3DxxRESULTTOKENxx Any ideas what could be going wrong? All I've done is copy and paste the facebook login demo code from facebook's website: define('FACEBOOK_APP_ID', 'your application id'); define('FACEBOOK_SECRET', 'your application secret'); function get_facebook_cookie($app_id, $application_secret) { $args = array(); parse_str(trim($COOKIE['fbs' . $app_id], '\"'), $args); ksort($args); $payload = ''; foreach ($args as $key = $value) { if ($key != 'sig') { $payload .= $key . '=' . $value; } } if (md5($payload . $application_secret) != $args['sig']) { return null; } return $args; } $cookie = get_facebook_cookie(FACEBOOK_APP_ID, FACEBOOK_SECRET); ? Your user ID is <div id="fb-root"></div> <script src="http://connect.facebook.net/en_US/all.js"></script> <script> FB.init({appId: '<?= FACEBOOK_APP_ID ?>', status: true, cookie: true, xfbml: true}); FB.Event.subscribe('auth.login', function(response) { window.location.reload(); }); </script> Thanks for the help!

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• Declare private static members in F#?

  - by acidzombie24

  I decided to port the class in C# below to F# as an exercise. It was difficult. I only notice three problems 1) Greet is visible 2) I can not get v to be a static class variable 3) I do not know how to set the greet member in the constructor. How do i fix these? The code should be similar enough that i do not need to change any C# source. ATM only Test1.v = 21; does not work C# using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace CsFsTest { class Program { static void Main(string[] args) { Test1.hi("stu"); new Test1().hi(); Test1.v = 21; var a = new Test1("Stan"); a.hi(); a.a = 9; Console.WriteLine("v = {0} {1} {2}", a.a, a.b, a.NotSTATIC()); } } class Test1 { public int a; public int b { get { return a * 2; } } string greet = "User"; public static int v; public Test1() {} public Test1(string name) { greet = name; } public static void hi(string greet) { Console.WriteLine("Hi {0}", greet); } public void hi() { Console.WriteLine("Hi {0} #{1}", greet, v); } public int NotSTATIC() { return v; } } } F# namespace CsFsTest type Test1 = (* public int a; public int b { get { return a * 2; } } string greet = "User"; public static int v; *) [<DefaultValue>] val mutable a : int member x.b = x.a * 2 member x.greet = "User" (*!! Needs to be private *) [<DefaultValue>] val mutable v : int (*!! Needs to be static *) (* public Test1() {} public Test1(string name) { greet = name; } *) new () = {} new (name) = { } (* public static void hi(string greet) { Console.WriteLine("Hi {0}", greet); } public void hi() { Console.WriteLine("Hi {0} #{1}", greet, v); } public int NotSTATIC() { return v; } *) static member hi(greet) = printfn "hi %s" greet member x.hi() = printfn "hi %s #%i" x.greet x.v member x.NotSTATIC() = x.v

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• Is this way of storing typed objects in memory good?

  - by Pindatjuh

  This is an "is this okay, or can it be done better" question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical possition when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignement. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 11111111 11111111 11111111 11111111 Data Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 11111111 11111111 11111111 11111111 Is this okay, or can it be done better?

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• Calculating CPU frequency in C with RDTSC always returns 0

  - by Nazgulled

  Hi, The following piece of code was given to us from our instructor so we could measure some algorithms performance: #include <stdio.h> #include <unistd.h> static unsigned cyc_hi = 0, cyc_lo = 0; static void access_counter(unsigned *hi, unsigned *lo) { asm("rdtsc; movl %%edx,%0; movl %%eax,%1" : "=r" (*hi), "=r" (*lo) : /* No input */ : "%edx", "%eax"); } void start_counter() { access_counter(&cyc_hi, &cyc_lo); } double get_counter() { unsigned ncyc_hi, ncyc_lo, hi, lo, borrow; double result; access_counter(&ncyc_hi, &ncyc_lo); lo = ncyc_lo - cyc_lo; borrow = lo > ncyc_lo; hi = ncyc_hi - cyc_hi - borrow; result = (double) hi * (1 << 30) * 4 + lo; return result; } However, I need this code to be portable to machines with different CPU frequencies. For that, I'm trying to calculate the CPU frequency of the machine where the code is being run like this: int main(void) { double c1, c2; start_counter(); c1 = get_counter(); sleep(1); c2 = get_counter(); printf("CPU Frequency: %.1f MHz\n", (c2-c1)/1E6); printf("CPU Frequency: %.1f GHz\n", (c2-c1)/1E9); return 0; } The problem is that the result is always 0 and I can't understand why. I'm running Linux (Arch) as guest on VMware. On a friend's machine (MacBook) it is working to some extent; I mean, the result is bigger than 0 but it's variable because the CPU frequency is not fixed (we tried to fix it but for some reason we are not able to do it). He has a different machine which is running Linux (Ubuntu) as host and it also reports 0. This rules out the problem being on the virtual machine, which I thought it was the issue at first. Any ideas why this is happening and how can I fix it?

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• Html Agility Pack: DescendantsOrSelf() not returning HTML element

  - by Program.X

  I have some HTML, eg: <%@ Page Title="About Us" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeBehind="ContentManagedTargetPage.aspx.cs" Inherits="xxx.ContentManagedTargetPage" %> <%@ Register TagPrefix="CxCMS" Namespace="xxx.ContentManagement.ASPNET.UI" Assembly="xxx.ContentManagement.ASPNET" %> <asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent"> </asp:Content> <asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent"> <h2> Content Managed </h2> <p> Put content here. [<CxCMS:ContentManagedPlaceHolder Key="keyThingy" runat="server" />] </p> </asp:Content> And I want to find all the instances of the CxCMS:ContentManagedPlaceHolder element. I'm using HTML Agility Pack, which seems the best fit. However, despite looking at the [meagre] documentation, I can't get my code to work. I would expect the following to work: string searchForElement = "CxCMS:ContentManagedPlaceHolder"; IEnumerable<HtmlNode> contentPlaceHolderHtmlNodes = HtmlDocument.DocumentNode.Descendants(searchForElement); int count = contentPlaceHolderHtmlNodes.Count(); But I get nothing back. If I change to DescendantsOrSelf, I get the document node back, "#document" - which is incorrect: string searchForElement = "CxCMS:ContentManagedPlaceHolder"; IEnumerable<HtmlNode> contentPlaceHolderHtmlNodes = HtmlDocument.DocumentNode.DescendantsOrSelf(searchForElement); int count = contentPlaceHolderHtmlNodes.Count(); I also tried using LINQ: string searchForElement = "CxCMS:ContentManagedPlaceHolder"; IEnumerable<HtmlNode> contentPlaceHolderHtmlNodes = HtmlDocument.DocumentNode.DescendantsOrSelf().Where(q=>q.Name==searchForElement); int count = contentPlaceHolderHtmlNodes.Count(); As neither of these methods work, I moved onto using SelectNodes, instead: string searchForElement = "CxCMS:ContentManagedPlaceHolder"; string xPath="//"+searchForElement // "//CxCMS:ContentManagedPlaceHolder" var nodes= HtmlDocument.DocumentNode.SelectNodes(xPath); This just throws the exception: "Namespace Manager or XsltContext needed. This query has a prefix, variable, or user-defined function.". I can't find any way of adding namespace management to the HtmlDocument object. What am I missing, here? The DescendantsOrSelf() method works if using a "standard" HTML tag, such as "p", but not the one I have. Surely it should work? (It needs to!)

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• How to use CFNetwork to get byte array from sockets?

  - by Vic

  Hi, I'm working in a project for the iPad, it is a small program and I need it to communicate with another software that runs on windows and act like a server; so the application that I'm creating for the iPad will be the client. I'm using CFNetwork to do sockets communication, this is the way I'm establishing the connection: char ip[] = "192.168.0.244"; NSString *ipAddress = [[NSString alloc] initWithCString:ip]; /* Build our socket context; this ties an instance of self to the socket */ CFSocketContext CTX = { 0, self, NULL, NULL, NULL }; /* Create the server socket as a TCP IPv4 socket and set a callback */ /* for calls to the socket's lower-level connect() function */ TCPClient = CFSocketCreate(NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketDataCallBack, (CFSocketCallBack)ConnectCallBack, &CTX); if (TCPClient == NULL) return; /* Set the port and address we want to listen on */ struct sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_len = sizeof(addr); addr.sin_family = AF_INET; addr.sin_port = htons(PORT); addr.sin_addr.s_addr = inet_addr([ipAddress UTF8String]); CFDataRef connectAddr = CFDataCreate(NULL, (unsigned char *)&addr, sizeof(addr)); CFSocketConnectToAddress(TCPClient, connectAddr, -1); CFRunLoopSourceRef sourceRef = CFSocketCreateRunLoopSource(kCFAllocatorDefault, TCPClient, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), sourceRef, kCFRunLoopCommonModes); CFRelease(sourceRef); CFRunLoopRun(); And this is the way I sent the data, which basically is a byte array /* The native socket, used for various operations */ // TCPClient is a CFSocketRef member variable CFSocketNativeHandle sock = CFSocketGetNative(TCPClient); Byte byteData[3]; byteData[0] = 0; byteData[1] = 4; byteData[2] = 0; send(sock, byteData, strlen(byteData)+1, 0); Finally, as you may have noticed, when I create the server socket, I registered a callback for the kCFSocketDataCallBack type, this is the code. void ConnectCallBack(CFSocketRef socket, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { // SocketsViewController is the class that contains all the methods SocketsViewController *obj = (SocketsViewController*)info; UInt8 *unsignedData = (UInt8 *) CFDataGetBytePtr(data); char *value = (char*)unsignedData; NSString *text = [[NSString alloc]initWithCString:value length:strlen(value)]; [obj writeToTextView:text]; [text release]; } Actually, this callback is being invoked in my code, the problem is that I don't know how can I get the data that the windows client sent me, I'm expecting to receive an array of bytes, but I don't know how can I get those bytes from the data param. If anyone can help me to find a way to do this, or maybe me point me to another way to get the data from the server in my client application I would really appreciate it. Thanks.

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• Passing Flash variables to PHP.

  - by user340553

  Hi, I have a simple standalone application written in Visual Basic that I'm porting to a browser based application using PHP/javascript. The original VB application has some simple embedded flash games with token and point counters. The token and point values are being passed as variables between the application and the game. I'm trying to achieve the same effect in my PHP port without modifying the actionscript code( using the variables in actionscript that already exist). Below is Visual Basic code that's loading a value from a database and posting that value to flash using FlashVars: Private Sub loadPlayer() Try If CtblPoints.CheckPointsByID(mCard) Then objPoints = CtblPoints.GettblPointsByID(mCard) objPlayerAc = CtblPlayerAccount.GettblPlayerAccountByPlayerID(objPoints.AccountId) objPlayer = CtblPlayer.GettblPlayerByID(objPlayerAc.PlayerID) objPlayerBal = CtblPlayerBalance.GettblPlayerBalanceByID(objPlayerAc.PlayerID) objPlayerAcDetail = CtblPlayerAccountDetail.GettblPlayerAccountDetailByAmount(objPoints.AccountId) strTotalPoints = Convert.ToString(objPlayerAc.Points) strTotalWin = Convert.ToString(objPlayerBal.TokenAmount) 'Dim intTokenAmount As Decimal = Convert.ToDecimal(objPlayerBal.TokenAmount) 'strTotalWin = Convert.ToString(Convert.ToInt64(intTokenAmount * 100)) flashPlayer.Size = panelGame.Size flashPlayer.FlashVars = "totalEntries=" & strTotalPoints & "&credit=" & strTotalWin flashPlayer.LoadMovie(0, strGameFile) flashPlayer.Play() Else Me.Close() Dim frmInvCrd As New frmInvalidCard frmInvCrd.ShowDialog() End If Catch ex As Exception End Try I'm trying to recreate this in PHP, but I'm at a loss as to how to begin implementing it. The variables in flash are declared publicly, and global imports used: import com.atticmedia.console.*; import flash.display.*; import flash.events.*; import flash.geom.*; import flash.media.*; import flash.net.*; import flash.system.*; import flash.utils.*; First declaration of variable 'totalEntries' is: public var totalEntries:int = 0; and this is a snip of totalEntries being used in the actionscript public function notifyServerOfUnwonCredits(param1) { var remainder:* = param1; if (this.useServer) { this.targetWinAmount = 0; this.cancelUpdateOverTime = F9.setEnterFrame(this.updateOverTime); fscommand("OverTime", "" + remainder); this.flashVarsUpdatedAction = function () { originalTotalWin = totalWin; return; }// end function ; } else { this.setTotalEntries(100000); this.setTotalWin(0); } return; }// end function Eventually I'll be passing these values back to a mySQL database. Any insight into this would be extremely helpful, Thanks!

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• change password code error.......

  - by shimaTun

  I've created a code to change a password. Now it seem contain an error. When before I fill in the form to change password.the error is: Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\xampp\htdocs\e-Complaint(FYP)\userChangePass.php:7) in C:\Program Files\xampp\htdocs\e-Complaint(FYP)\userChangePass.php on line 126 the code: <?php # userChangePass.php //this page allows logged in user to change their password. $page_title='Change Your Password'; //if no first_name variable exists, redirect the user if(!isset($_SESSION['userid'])){ header("Location: http://" .$_SERVER['HTTP_HOST']. dirname($_SERVER['PHP_SELF'])."/index.php"); ob_end_clean(); exit(); }else{ if(isset($_POST['submit'])) {//handle form. require_once('connectioncomplaint.php'); //connec to the database //check for a new password and match againts the confirmed password. if(eregi ("^[[:alnum:]]{4,20}$", stripslashes(trim($_POST['password1'])))){ if($_POST['password1'] == $_POST['password2']){ $p =escape_data($_POST['password1']); }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Your password did not match the confirmed password!</font></p>'; } }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Please Enter a valid password!</font></p>'; } if($p){ //if everything OK. //make the query $query="UPDATE access SET password=PASSWORD('$p') WHERE userid={$_SESSION['userid']}"; $result=@mysql_query($query);//run the query. if(mysql_affected_rows() == 1) {//if it run ok. //send an email,if desired. echo '<p><b>your password has been changed.</b></p>'; //include('templates/footer.inc');//include the HTML footer. exit(); }else{//if it did not run ok $message= '<p>Your password could not be change due to a system error.We apolpgize for any inconvenience.</p><p>' .mysql_error() .'</p>'; } mysql_close();//close the database connection. }else{//failed the validation test. echo '<p><font color="red" size="+1"> Please try again.</font></p>'; } }//end of the main Submit conditional. } ?> the error at this line:- header("Location: http://" .$_SERVER['HTTP_HOST']. dirname($_SERVER['PHP_SELF'])."/index.php"); please help me guy...

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• Turtle Graphics as a Haskell Monad

  - by iliis

  I'm trying to implement turtle graphis in Haskell. The goal is to be able to write a function like this: draw_something = do fordward 100 right 90 forward 100 ... and then have it produce a list of points (maybe with additional properties): > draw_something (0,0) 0 -- start at (0,0) facing east (0 degrees) [(0,0), (0,100), (-100,100), ...] I have all this working in a 'normal' way, but I fail to implement it as a Haskell Monad and use the do-notation. The basic code: data State a = State (a, a) a -- (x,y), angle deriving (Show, Eq) initstate :: State Float initstate = State (0.0,0.0) 0.0 -- constrain angles to 0 to 2*pi fmod :: Float -> Float fmod a | a >= 2*pi = fmod (a-2*pi) | a < 0 = fmod (a+2*pi) | otherwise = a forward :: Float -> State Float -> [State Float] forward d (State (x,y) angle) = [State (x + d * (sin angle), y + d * (cos angle)) angle] right :: Float -> State Float -> [State Float] right d (State pos angle) = [State pos (fmod (angle+d))] bind :: [State a] -> (State a -> [State a]) -> [State a] bind xs f = xs ++ (f (head $ reverse xs)) ret :: State a -> [State a] ret x = [x] With this I can now write > [initstate] `bind` (forward 100) `bind` (right (pi/2)) `bind` (forward 100) [State (0.0,0.0) 0.0,State (0.0,100.0) 0.0,State (0.0,100.0) 1.5707964,State (100.0,99.99999) 1.5707964] And get the expected result. However I fail to implement this as an instance of Monad. instance Monad [State] where ... results in `State' is not applied to enough type arguments Expected kind `*', but `State' has kind `* -> *' In the instance declaration for `Monad [State]' And if I wrap the list in a new object data StateList a = StateList [State a] instance Monad StateList where return x = StateList [x] I get Couldn't match type `a' with `State a' `a' is a rigid type variable bound by the type signature for return :: a -> StateList a at logo.hs:38:9 In the expression: x In the first argument of `StateList', namely `[x]' In the expression: StateList [x] I tried various other versions but I never got it to run as I'd like to. What am I doing wrong? What do I understand incorrectly?

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• NSTimer as a self-targeting ivar.

  - by Matt Wilding

  I have come across an awkward situation where I would like to have a class with an NSTimer instance variable that repeatedly calls a method of the class as long as the class is alive. For illustration purposes, it might look like this: // .h @interface MyClock : NSObject { NSTimer* _myTimer; } - (void)timerTick; @end - // .m @implementation MyClock - (id)init { self = [super init]; if (self) { _myTimer = [[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(timerTick) userInfo:nil repeats:NO] retain]; } return self; } - (void)dealloc { [_myTimer invalidate]; [_myTImer release]; [super dealloc]; } - (void)timerTick { // Do something fantastic. } @end That's what I want. I don't want to to have to expose an interface on my class to start and stop the internal timer, I just want it to run while the class exists. Seems simple enough. But the problem is that NSTimer retains its target. That means that as long as that timer is active, it is keeping the class from being dealloc'd by normal memory management methods because the timer has retained it. Manually adjusting the retain count is out of the question. This behavior of NSTimer seems like it would make it difficult to ever have a repeating timer as an ivar, because I can't think of a time when an ivar should retain its owning class. This leaves me with the unpleasant duty of coming up with some method of providing an interface on MyClock that allows users of the class to control when the timer is started and stopped. Besides adding unneeded complexity, this is annoying because having one owner of an instance of the class invalidate the timer could step on the toes of another owner who is counting on it to keep running. I could implement my own pseudo-retain-count-system for keeping the timer running but, ...seriously? This is way to much work for such a simple concept. Any solution I can think of feels hacky. I ended up writing a wrapper for NSTimer that behaves exactly like a normal NSTimer, but doesn't retain its target. I don't like it, and I would appreciate any insight.

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• POD global object initialization

  - by paercebal

  I've got bitten today by a bug. The following source can be copy/pasted (and then compiled) into a main.cpp file #include <iostream> // The point of SomeGlobalObject is for its // constructor to be launched before the main // ... struct SomeGlobalObject { SomeGlobalObject() ; } ; // ... // Which explains the global object SomeGlobalObject oSomeGlobalObject ; // A POD... I was hoping it would be constructed at // compile time when using an argument list struct MyPod { short m_short ; const char * const m_string ; } ; // declaration/Initialization of a MyPod array MyPod myArrayOfPod[] = { { 1, "Hello" }, { 2, "World" }, { 3, " !" } } ; // declaration/Initialization of an array of array of void * void * myArrayOfVoid[][2] = { { (void *)1, "Hello" }, { (void *)2, "World" }, { (void *)3, " !" } } ; // constructor of the global object... Launched BEFORE main SomeGlobalObject::SomeGlobalObject() { std::cout << "myArrayOfPod[0].m_short : " << myArrayOfPod[0].m_short << std::endl ; std::cout << "myArrayOfVoid[0][0] : " << myArrayOfVoid[0][0] << std::endl ; } // main... What else ? int main(int argc, char* argv[]) { return 0 ; } MyPod being a POD, I believed there would be no constructors. Only initialization at compile time. Thus, the global object SomeGlobalObject would have no problem to use the global array of PODs upon its construction. The problem is that in real life, nothing is so simple. On Visual C++ 2008 (I did not test on other compilers), upon execution myArrayOfPodis not initialized, even ifmyArrayOfVoid` is initialized. So my questions is: Are C++ compilers not supposed to initialize global PODs (including POD structures) at compilation time ? Note that I know global variable are evil, and I know that one can't be sure of the order of creation of global variables declared in different compilation units. The problem here is really the POD C-like initialization which seems to call a constructor (the default, compiler-generated one?). And to make everyone happy: This is on debug. On release, the global array of PODs is correctly initialized.

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• Prototype JS swallows errors in dom:loaded, and ajax callbacks?

  - by WishCow

  I can't figure out why prototype suppressess the error messages in the dom:loaded event, and in AJAX handlers. Given the following piece of HTML: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Conforming XHTML 1.1 Template</title> <script type="text/javascript" src="prototype.js"></script> <script type="text/javascript"> document.observe('dom:loaded', function() { console.log('domready'); console.log(idontexist); }); </script> </head> <body> </body> </html> The domready event fires, I see the log in the console, but there is no indication of any errors whatsoever. If you move the console.log(idontexist); line out of the handler, you get the idontexist is not defined error in the console. I find it a little weird, that in other event handlers, like 'click', you get the error message, it seems that it's only the dom:loaded that has this problem. The same goes for AJAX handlers: new Ajax.Request('/', { method: 'get', onComplete: function(r) { console.log('xhr complete'); alert(youwontseeme); } }); You won't see any errors. This is with prototype.js 1.6.1, and I can't find any indication of this behavior in the docs, nor a way to enable error reporting in these handlers. I have tried stepping through the code with FireBug's debugger, and it seems to jump to a function on line 53 named K, when it encounters the missing variable in the dom:loaded handler: K: function(x) { return x } But how? Why? When? I can't see any try/catch block there, how does the program flow end up there? I know that I can make the errors visible by packing my dom:ready handler(s) in try/catch blocks, but that's not a very comfortable option. Same goes for registering a global onException handler for the AJAX calls. Why does it even suppress the errors? Did someone encounter this before?

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• Help with a logic problem

  - by Stradigos

  I'm having a great deal of difficulty trying to figure out the logic behind this problem. I have developed everything else, but I really could use some help, any sort of help, on the part I'm stuck on. Back story: *A group of actors waits in a circle. They "count off" by various amounts. The last few to audition are thought to have the best chance of getting the parts and becoming stars. Instead of actors having names, they are identified by numbers. The "Audition Order" in the table tells, reading left-to-right, the "names" of the actors who will be auditioned in the order they will perform.* Sample output: etc, all the way up to 10. What I have so far: using System; using System.Collections; using System.Text; namespace The_Last_Survivor { class Program { static void Main(string[] args) { //Declare Variables int NumOfActors = 0; System.DateTime dt = System.DateTime.Now; int interval = 3; ArrayList Ring = new ArrayList(10); //Header Console.Out.WriteLine("Actors\tNumber\tOrder"); //Add Actors for (int x = 1; x < 11; x++) { NumOfActors++; Ring.Insert((x - 1), new Actor(x)); foreach (Actor i in Ring) { Console.Out.WriteLine("{0}\t{1}\t{2}", NumOfActors, i, i.Order(interval, x)); } Console.Out.WriteLine("\n"); } Console.In.Read(); } public class Actor { //Variables protected int Number; //Constructor public Actor(int num) { Number = num; } //Order in circle public string Order(int inter, int num) { //Variable string result = ""; ArrayList myArray = new ArrayList(num); //Filling Array for (int i = 0; i < num; i++) myArray.Add(i + 1); //Formula foreach (int element in myArray) { if (element == inter) { result += String.Format(" {0}", element); myArray.RemoveAt(element); } } return result; } //String override public override string ToString() { return String.Format("{0}", Number); } } } } The part I'm stuck on is getting some math going that does this: Can anyone offer some guidance and/or sample code?

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• Ada: Adding an exception in a separate procedure when reading a file

  - by yCalleecharan

  This is a follow-up of this question: Ada: reading from a file . I would like to add an exception that checks if the file that I'm opening actually exists or not. I have made a separate procedure to avoid code clutter. Here is the main code test_read.adb: with Ada.Text_IO; use Ada.Text_IO; with Ada.Long_Float_Text_IO; with Ada.Float_Text_IO; procedure Test_Read is Input_File : File_Type; Value : Long_Float; procedure Open_Data (File : in Ada.Text_IO.File_Type; Name : in String) is separate; begin Ada.Text_IO.Open (File => Input_File, Mode => Ada.Text_IO.In_File, Name => "fx.txt"); while not End_Of_File (Input_File) loop Ada.Long_Float_Text_IO.Get (File => Input_File, Item => Value); Ada.Long_Float_Text_IO.Put (Item => value, Fore => 3, Aft => 5, Exp => 0); Ada.Text_IO.New_Line; end loop; Ada.Text_IO.Close (File => Input_File); end Test_Read; And here is the separate body test_read-open_data.adb of the procedure Open_Data: separate(test_read) procedure Open_Data (File : in Ada.Text_IO.File_Type; Name : in String) is --this procedure prepares a file for reading begin begin Ada.Text_IO.Open (File => File, Mode => Ada.Text_IO.In_File, Name => Name); exception when Ada.Text_IO.Name_Error => Ada.Text_IO.Put(File => Standard_Error, Item => "File not found."); end; end Open_Data; On compilation I get an error message in the separate body test_read-open_data.adb: actual for "File" must be a variable How to fix this? Thanks a lot...

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• Flex - Problem with auto resizing datagrid

  - by Marty Pitt

  Hi All I'm trying to create a datagrid which will resize vertically to ensure all the renderers are displayed in full. Additionally, Renderers are of variable height Renderers can resize themselves Generally speaking, the flow of events is as follows : One of the item renderers resizes itself (normally in response to a user click etc) It dispatches a bubbling event which the parent datagrid picks up The DataGrid attempts to resize to ensure that all renderers remain visible in full. I'm currently using this code within the datagrid to calculate the height: height = measureHeightOfItems(0, dataProvider.length ) + headerHeight; This appears to get an incorrect height. I've tried a number of variations including callLater ( to ensure the resize has completed so measure can work correctly), and overriding meausre() and calling invalidateSize() / validateSize(), but neither works. Below are 3 classes which will illustrate the problem. Clicking the button in the item renderers resizes the renderer. The grid should also expand so that all of the 3 renderers are shown in their entirety. Any suggestions would be greatly appreciated. Regards Marty DataGridProblem.mxml (Application file) <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" xmlns:view="view.*"> <mx:ArrayCollection id="dataProvider"> <mx:String>Item A</mx:String> <mx:String>Item B</mx:String> <mx:String>Item C</mx:String> </mx:ArrayCollection> <view:TestDataGrid id="dg" dataProvider="{ dataProvider }" width="400"> <view:columns> <mx:DataGridColumn dataField="text" /> <mx:DataGridColumn itemRenderer="view.RendererButton" /> </view:columns> </view:TestDataGrid> </mx:Application> view.TestDataGrid.as package view { import flash.events.Event; import mx.controls.DataGrid; import mx.core.ScrollPolicy; public class TestDataGrid extends DataGrid { public function TestDataGrid() { this.verticalScrollPolicy = ScrollPolicy.OFF; this.variableRowHeight = true; this.addEventListener( RendererButton.RENDERER_RESIZE , onRendererResize ); } private function onRendererResize( event : Event ) : void { resizeDatagrid(); } private function resizeDatagrid():void { height = measureHeightOfItems(0, dataProvider.length ) + headerHeight; } } } view.RendererButton.mxml <?xml version="1.0" encoding="utf-8"?> <mx:HBox xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Button width="50" height="50" click="onClick()" /> <mx:Script> <![CDATA[ public static const RENDERER_RESIZE : String = "resizeRenderer"; private function onClick() : void { this.height += 20; dispatchEvent( new Event( RENDERER_RESIZE , true ) ); } ]]> </mx:Script> </mx:HBox>

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• simple jquery dropdown - clearTimeout, setTimeout issues

  - by user210757

  HTML: <ul class="topnav"> <li><a href="#"><span>One</span></a></li> <li><a href="#"><span>Two</span></a></li> <li> <li><a href="#"><span>Three</span></a></li> <ul class="subnav"> <li><a href="#">A</a></li> <li><a href="#">B</a></li> <li><a href="#">C</a></li> </ul> </li> </ul> jquery: var timeout = null; $(document).ready(function() { $("ul.topnav li").mouseover(function() { if (timeout) clearTimeout(timeout); $(this).find("ul.subnav").slideDown('fast').show(); }).mouseout(function() { timeout = setTimeout(closemenu, 500); }); // sub menu mouseovers keep dropdown open $("ul.subnav li").mouseover(function() { if (timeout) clearTimeout(timeout); } ).mouseout(function() { timeout = setTimeout(closemenu, 500); // alert(timeout); }); // any click closes $(document).click(closemenu); }); // Closes all open menus function closemenu() { $('ul.subnav:visible').hide(); if (timeout) clearTimeout(timeout); } I'm having issues with timeout. In use, if i mouseover "Three", the dropdown stays out forever. if i mouseover "A", dropdown will stay out forever, but if I mouseover "B" or anything lower, the menu will close on me. if you uncomment "// alert(timeout);" it gets there for B, (and A) but timeout will have a value. why is this? i thought clearTimeout would null the timeout variable?

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• Using a type parameter and a pointer to the same type parameter in a function template

  - by Darel

  Hello, I've written a template function to determine the median of any vector or array of any type that can be sorted with sort. The function and a small test program are below: #include <algorithm> #include <vector> #include <iostream> using namespace::std; template <class T, class X> void median(T vec, size_t size, X& ret) { sort(vec, vec + size); size_t mid = size/2; ret = size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } int main() { vector<double> v; v.push_back(2); v.push_back(8); v.push_back(7); v.push_back(4); v.push_back(9); double a[5] = {2, 8, 7, 4, 9}; double r; median(v.begin(), v.size(), r); cout << r << endl; median(a, 5, r); cout << r << endl; return 0; } As you can see, the median function takes a pointer as an argument, T vec. Also in the argument list is a reference variable X ret, which is modified by the function to store the computed median value. However I don't find this a very elegant solution. T vec will always be a pointer to the same type as X ret. My initial attempts to write median had a header like this: template<class T> T median(T *vec, size_t size) { sort(vec, vec + size); size_t mid = size/2; return size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } I also tried: template<class T, class X> X median(T vec, size_t size) { sort(vec, vec + size); size_t mid = size/2; return size % 2 == 0 ? (vec[mid] + vec[mid-1]) / 2 : vec[mid]; } I couldn't get either of these to work. My question is, can anyone show me a working implementation of either of my alternatives? Thanks for looking!

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• NSOutlineView not refreshing when objects added to managed object context from NSOperations

  - by John Gallagher

  Background Cocoa app using core data Two processes - daemon and a main UI Daemon constantly writing to a data store UI process reads from same data store NSOutlineView in UI is bound to an NSTreeController which is bound to Application with key path of delegate.interpretedMOC What I want When the UI is activated, the outline view should update with the latest data inserted by the daemon. The Problem Main Thread Approach I fetch all the entities I'm interested in, then iterate over them, doing refreshObject:mergeChanges:YES. This works OK - the items get refreshed correctly. However, this is all running on the main thread, so the UI locks up for 10-20 seconds whilst it refreshes. Fine, so let's move these refreshes to NSOperations that run in the background instead. NSOperation Multithreaded Approach As soon as I move the refreshObject:mergeChanges: call into an NSOperation, the refresh no longer works. When I add logging messages, it's clear that the new objects are loaded in by the NSOperation subclass and refreshed. Not only that, but they are What I've tried I've messed around with this for 2 days solid and tried everything I can think of. Passing objectIDs to the NSOperation to refresh instead of an entity name. Resetting the interpretedMOC at various points - after the data refresh and before the outline view reload. I'd subclassed NSOutlineView. I discarded my subclass and set the view back to being an instance of NSOutlineView, just in case there was any funny goings on here. Added a rearrangeObjects call to the NSTreeController before reloading the NSOutlineView data. Made sure I had set the staleness interval to 0 on all managed object contexts I was using. I've got a feeling this problem is somehow related to caching core data objects in memory. But I've totally exhausted all my ideas on how I get this to work. I'd be eternally grateful of any ideas anyone else has. Code Main Thread Approach // In App Delegate -(void)applicationDidBecomeActive:(NSNotification *)notification { // Delay to allow time for the daemon to save [self performSelector:@selector(refreshTrainingEntriesAndGroups) withObject:nil afterDelay:3]; } -(void)refreshTrainingEntriesAndGroups { NSSet *allTrainingGroups = [[[NSApp delegate] interpretedMOC] fetchAllObjectsForEntityName:kTrainingGroup]; for(JGTrainingGroup *thisTrainingGroup in allTrainingGroups) [interpretedMOC refreshObject:thisTrainingGroup mergeChanges:YES]; NSError *saveError = nil; [interpretedMOC save:&saveError]; [windowController performSelectorOnMainThread:@selector(refreshTrainingView) withObject:nil waitUntilDone:YES]; } // In window controller class -(void)refreshTrainingView { [trainingViewTreeController rearrangeObjects]; // Didn't really expect this to have any effect. And it didn't. [trainingView reloadData]; } NSOperation Multithreaded Approach // In App Delegate -(void)refreshTrainingEntriesAndGroups { JGRefreshEntityOperation *trainingGroupRefresh = [[JGRefreshEntityOperation alloc] initWithEntityName:kTrainingGroup]; NSOperationQueue *refreshQueue = [[NSOperationQueue alloc] init]; [refreshQueue setMaxConcurrentOperationCount:1]; [refreshQueue addOperation:trainingGroupRefresh]; while ([[refreshQueue operations] count] > 0) { [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:0.05]]; [windowController performSelectorOnMainThread:@selector(refreshTrainingView) withObject:nil waitUntilDone:YES]; } // JGRefreshEntityOperation.m @implementation JGRefreshEntityOperation @synthesize started; @synthesize executing; @synthesize paused; @synthesize finished; -(void)main { [self startOperation]; NSSet *allEntities = [imoc fetchAllObjectsForEntityName:entityName]; for(id thisEntity in allEntities) [imoc refreshObject:thisEntity mergeChanges:YES]; [self finishOperation]; } -(void)startOperation { [self willChangeValueForKey:@"isExecuting"]; [self willChangeValueForKey:@"isStarted"]; [self setStarted:YES]; [self setExecuting:YES]; [self didChangeValueForKey:@"isExecuting"]; [self didChangeValueForKey:@"isStarted"]; imoc = [[NSManagedObjectContext alloc] init]; [imoc setStalenessInterval:0]; [imoc setUndoManager:nil]; [imoc setPersistentStoreCoordinator:[[NSApp delegate] interpretedPSC]]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(mergeChanges:) name:NSManagedObjectContextDidSaveNotification object:imoc]; } -(void)finishOperation { saveError = nil; [imoc save:&saveError]; if (saveError) { NSLog(@"Error saving. %@", saveError); } imoc = nil; [self willChangeValueForKey:@"isExecuting"]; [self willChangeValueForKey:@"isFinished"]; [self setExecuting:NO]; [self setFinished:YES]; [self didChangeValueForKey:@"isExecuting"]; [self didChangeValueForKey:@"isFinished"]; } -(void)mergeChanges:(NSNotification *)notification { NSManagedObjectContext *mainContext = [[NSApp delegate] interpretedMOC]; [mainContext performSelectorOnMainThread:@selector(mergeChangesFromContextDidSaveNotification:) withObject:notification waitUntilDone:YES]; } -(id)initWithEntityName:(NSString *)entityName_ { [super init]; [self setStarted:false]; [self setExecuting:false]; [self setPaused:false]; [self setFinished:false]; [NSThread setThreadPriority:0.0]; entityName = entityName_; return self; } @end // JGRefreshEntityOperation.h @interface JGRefreshEntityOperation : NSOperation { NSString *entityName; NSManagedObjectContext *imoc; NSError *saveError; BOOL started; BOOL executing; BOOL paused; BOOL finished; } @property(readwrite, getter=isStarted) BOOL started; @property(readwrite, getter=isPaused) BOOL paused; @property(readwrite, getter=isExecuting) BOOL executing; @property(readwrite, getter=isFinished) BOOL finished; -(void)startOperation; -(void)finishOperation; -(id)initWithEntityName:(NSString *)entityName_; -(void)mergeChanges:(NSNotification *)notification; @end

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• Queue ExternalInterface calls to Flash Object in UpdatePanel - Needs Improvement?

  - by Laramie

  A Flash (actually Flex) object is created on an ASP.Net page within an Update Panel using a modified version of the embedCallAC_FL_RunContent.js script so it can be written in dynamically. It is re-created with this script with each partial postback to that panel. There are also other Update Panels on the page. With some postbacks (partial and full), External Interface calls such as $get('FlashObj').ExternalInterfaceFunc('arg1', 0, true); are prepared server-side and added to the page using ScriptManager.RegisterStartupScript. They're embedded in a function and stuffed into Sys.Application's load event, for example Sys.Application.add_load(funcContainingExternalInterfaceCalls). The problem is that because the Flash object's state state may change with each partial postback, the Flash (Flex) object and/or External Interface may not be ready or even exist yet in the DOM when the JavaScript - Flash External Interface call is made. It results in an "Object doesn't support this property or method" exception. I have a working strategy to make the ExternalInterface calls immediately if Flash is ready or else queue them until such time that Flash announces its readiness. //Called when the Flash object is initialized and can accept ExternalInterfaceCalls var flashReady = false; //Called by Flash when object is fully initialized function setFlashReady() { flashReady = true; //Make any queued ExternalInterface calls, then dequeue while (extIntQueue.length > 0) (extIntQueue.shift())(); } var extIntQueue = []; function callExternalInterface(flashObjName, funcName, args) { //reference to the wrapped ExternalInterface Call var wrapped = extWrap(flashObjName, funcName, args); //only procede with ExternalInterface call if the global flashReady variable has been set if (flashReady) { wrapped(); } else { //queue the function so when flashReady() is called next, the function is called and the aruments are passed. extIntQueue.push(wrapped); } } //bundle ExtInt call and hold variables in a closure function extWrap(flashObjName, funcName, args) { //put vars in closure return function() { var funcCall = '$get("' + flashObjName + '").' + funcName; eval(funcCall).apply(this, args); } } I set the flashReady var to dirty whenever I update the Update Panel that contains the Flash (Flex) object. ScriptManager.RegisterClientScriptBlock(parentContainer, parentContainer.GetType(), "flashReady", "flashReady = false;", true); I'm pleased that I got it to work, but it feels like a hack. I am still on the learning curve with respect to concepts like closures why "eval()" is apparently evil, so I'm wondering if I'm violating some best practice or if this code should be improved, if so how? Thanks.

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• Javascript closures with google geocoder

  - by DaNieL

  Hi all, i still have some problems with javascript closures, and input/output variables. Im playing with google maps api for a no profit project: users will place the marker into a gmap, and I have to save the locality (with coordinates) in my db. The problem comes when i need to do a second geocode in order to get a unique pairs of lat and lng for a location: lets say two users place the marker in the same town but in different places, I dont want to have the same locality twice in the database with differents coords. I know i can do the second geocode after the user select the locality, but i want to understand what am i mistaking here: // First geocoding, take the marker coords to get locality. geocoder.geocode( { 'latLng': new google.maps.LatLng($("#lat").val(), $("#lng").val()), 'language': 'it' }, function(results_1, status_1){ // initialize the html var inside this closure var html = ''; if(status_1 == google.maps.GeocoderStatus.OK) { // do stuff here for(i = 0, geolen = results_1[0].address_components.length; i != geolen) { // Second type of geocoding: for each location from the first geocoding, // i want to have a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, function(results_2, status_2){ // Here come the problem. I need to have the long_name here, and // 'html' var should increment. coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality'; } ); } // Finally, insert the 'html' variable value into my dom... //but it never gets updated! } else { alert("Error from google geocoder:" + status_1) } } ); I tryed with: // Second type of geocoding: for each location from the first geocoding, i want // to have a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, (function(results_2, status_2, long_name){ // But in this way i'll never get results_2 or status_2, well, results_2 // get long_name value, status_2 and long_name is undefined. // However, html var is correctly updated. coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality'; })(results_1[0].address_components[i].long_name) ); And with: // Second type of geocoding: for each location from the first geocoding, i want to have // a unique [lat,lan] geocoder.geocode( { 'address': results_1[0].address_components[i].long_name }, (function(results_2, status_2, long_name){ // But i get an obvious "results_2 is not defined" error (same for status_2). coords = results_2[0].geometry.location.toUrlValue(); html += 'some html to let the user choose the locality, that can be more than one'; })(results_2, status_2, results_1[0].address_components[i].long_name) ); Any suggestion? EDIT: My problem is how to pass an additional arguments to the geocoder inner function: function(results_2, status_2, long_name){ //[...] } becose if i do that with a clousure, I mess with the original parameters (results_2 and status_2)

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• how to read values from the remote OPC Server

  - by Shailesh Jaiswal

  I have created one asp.net web service. In this web service I am using the web method as follows. The web service is related to the OPC ( OLE for process control) public string ReadServerItems(string ServerName) { string txt = ""; ArrayList obj = new ArrayList(); XmlServer Srv = new XmlServer("XDAGW.CS.WCF.Eval.1"); RequestOptions opt = new RequestOptions(); ReadRequestItemList iList = new ReadRequestItemList(); iList.Items = new ReadRequestItem[3]; iList.Items[0] = new ReadRequestItem(); iList.Items[0].ItemName = "ServerInfo.ConnectedClients"; iList.Items[1] = new ReadRequestItem(); iList.Items[1].ItemName = "ServerInfo.TotalGroups"; iList.Items[2] = new ReadRequestItem(); iList.Items[2].ItemName = "EventSources.Area1.Tracking"; ReplyItemList rslt; OPCError[] err; ReplyBase reply = Srv.Read(opt, iList, out rslt, out err); if ((rslt == null)) txt += err[0].Text; else { foreach (xmldanet.xmlda.ItemValue iv in rslt.Items) { txt += iv.ItemName; if (iv.ResultID == null) // success { txt += " = " + iv.Value.ToString() + "\r\n"; obj.Add(txt); } else txt += " : Error: " + iv.ResultID.Name + "\r\n"; } } return txt; } I am using the namespaces as follows using xmldanet; using xmldanet.xmlda; I have installed XMLDA.NET client component evaluation. In this there is an in built Test client which successfully reads the values of these data items from the remote OPC server. I also provides the template through which we can build the OPC based applications. In the above code I am trying to read the values of the data items but i am not able to read the values. I have applied the breakpoint. In that I can see that the condition if (iv.ResultID == null) becomes false & also there is null values in the variable rslt. Please tell me where I am doing mistake ? how should I correct my mistake ? can provide me the correct code ?

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• How to produce precisely-timed tone and silence?

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution.

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• May volatile be in user defined types to help writing thread-safe code

  - by David Rodríguez - dribeas

  I know, it has been made quite clear in a couple of questions/answers before, that volatile is related to the visible state of the c++ memory model and not to multithreading. On the other hand, this article by Alexandrescu uses the volatile keyword not as a runtime feature but rather as a compile time check to force the compiler into failing to accept code that could be not thread safe. In the article the keyword is used more like a required_thread_safety tag than the actual intended use of volatile. Is this (ab)use of volatile appropriate? What possible gotchas may be hidden in the approach? The first thing that comes to mind is added confusion: volatile is not related to thread safety, but by lack of a better tool I could accept it. Basic simplification of the article: If you declare a variable volatile, only volatile member methods can be called on it, so the compiler will block calling code to other methods. Declaring an std::vector instance as volatile will block all uses of the class. Adding a wrapper in the shape of a locking pointer that performs a const_cast to release the volatile requirement, any access through the locking pointer will be allowed. Stealing from the article: template <typename T> class LockingPtr { public: // Constructors/destructors LockingPtr(volatile T& obj, Mutex& mtx) : pObj_(const_cast<T*>(&obj)), pMtx_(&mtx) { mtx.Lock(); } ~LockingPtr() { pMtx_->Unlock(); } // Pointer behavior T& operator*() { return *pObj_; } T* operator->() { return pObj_; } private: T* pObj_; Mutex* pMtx_; LockingPtr(const LockingPtr&); LockingPtr& operator=(const LockingPtr&); }; class SyncBuf { public: void Thread1() { LockingPtr<BufT> lpBuf(buffer_, mtx_); BufT::iterator i = lpBuf->begin(); for (; i != lpBuf->end(); ++i) { // ... use *i ... } } void Thread2(); private: typedef vector<char> BufT; volatile BufT buffer_; Mutex mtx_; // controls access to buffer_ };

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• Issue with angular gradient algorithm

  - by user146780

  I have an angular gradient algorithm: GLuint OGLENGINEFUNCTIONS::CreateAngularGradient( std::vector<ARGBCOLORF> &input,POINTFLOAT start, POINTFLOAT end, int width, int height ) { std::vector<GLubyte> pdata(width * height * 4); float pi = 3.1415; float cx; float cy; float r1; float r2; float ang; float px; float py; float t; cx = start.x; cy = start.y; r1 = 0; r2 = 500; ang = end.x / 100; ARGBCOLORF color; for (unsigned int i = 0; i < height; i++) { for (unsigned int j = 0; j < width; j++) { px = j; py = i; if( px * px + py * py <= r2 * r2 && px * px + py * py >= r1 * r1 ) { t= atan2(py-cy,px-cx) + ang; t= t+ pi; if (t > 2* pi) { t=t-2*pi; t=t/(2*pi); } } //end + start color.r = (0 * t) + (120 * (1 - t)); color.g = (50 * t) + (255 * (1 - t)); color.b = (0 * t) + (50 * (1 - t)); color.a = (255 * t) + (200 * (1 - t)); pdata[i * 4 * width + j * 4 + 0] = (GLubyte) color.r; pdata[i * 4 * width + j * 4 + 1] = (GLubyte) color.g; pdata[i * 4 * width + j * 4 + 2] = (GLubyte) 12; pdata[i * 4 * width + j * 4 + 3] = (GLubyte) 255; } } It works fine except the ang variable only controls the end sweep, not the start sweep. The start sweep is always facing the middle left as seen here: http://img810.imageshack.us/img810/9623/uhoh.png Basically I have no control over the end one going this <- way. How could I control this one? Thanks

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