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• How do I prevent programmatically the "Program Compatibility Assistant" in Vista (and Windows 7) fro

  - by Asaf

  I develop a C++ program which might use adobe flash, although it is not essential. I use CoCreateInstance to create the flash object, and if it fails, I know flash is not installed so I don't use it. However, in Vista (and I think Windows 7 as well), when flash is not installed, after leaving the application, the "Program Compatibility Assistant" pops up a message saying that "This program requires a missing Windows component" specifying the flash.ocx. Is there a way to prevent this message from appearing? I don't want to force any user to install flash (especially since it's the IE ActiveX, and FireFox users might not have it installed), and my application can operate well without the flash. Plus this message is really annoying when it appears after every run. I don't mean of course disabling the PCA on the user's machine, but programmatically disable this specific appearance on all machines. Any thoughts? Thanks [EDIT:] I followed Shay's lead (thanks), and did some more digging of my own. I added the following XML to the application's manifest: <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2"> <security> <requestedPrivileges> <requestedExecutionLevel level="asInvoker" uiAccess="false"> </requestedExecutionLevel> </requestedPrivileges> </security> </trustInfo> (see also: msdn.microsoft.com/en-us/library/bb756929.aspx) This solved the problem on Vista 64. To solve the same problem on Windows 7, I added the following: <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1"> <application> <!--The ID below indicates application support for Windows Vista --> <supportedOS Id="{e2011457-1546-43c5-a5fe-008deee3d3f0}"/> <!--The ID below indicates application support for Windows 7 --> <supportedOS Id="{35138b9a-5d96-4fbd-8e2d-a2440225f93a}"/> </application> </compatibility> (See also: blogs.msdn.com/yvesdolc/archive/2009/09/22/the-new-compatibility-section-in-the-application-manifest.aspx) Solved Windows 7. But for some reason, it still happens in Vista 32... I also tried editing the manifest of the specific DLL which causes the problem, but it had no effect. Only the executable's manifest itself affected the problem. So... Vista 32?

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• error C2065: 'CComQIPtr' : undeclared identifier

  - by Ken Smith

  I'm still feeling my way around C++, and am a complete ATL newbie, so I apologize if this is a basic question. I'm starting with an existing VC++ executable project that has functionality I'd like to expose as an ActiveX object (while sharing as much of the source as possible between the two projects). I've approached this by adding an ATL project to the solution in question, and in that project have referenced all the .h and .cpp files from the executable project, added all the appropriate references, and defined all the preprocessor macros. So far so good. But I'm getting a compiler error in one file (HideDesktop.cpp). The relevant parts look like this: #include "stdafx.h" #define WIN32_LEAN_AND_MEAN #include <Windows.h> #include <WinInet.h> // Shell object uses INTERNET_MAX_URL_LENGTH (go figure) #if _MSC_VER < 1400 #define _WIN32_IE 0x0400 #endif #include <atlbase.h> // ATL smart pointers #include <shlguid.h> // shell GUIDs #include <shlobj.h> // IActiveDesktop #include "stdhdrs.h" struct __declspec(uuid("F490EB00-1240-11D1-9888-006097DEACF9")) IActiveDesktop; #define PACKVERSION(major,minor) MAKELONG(minor,major) static HRESULT EnableActiveDesktop(bool enable) { CoInitialize(NULL); HRESULT hr; CComQIPtr<IActiveDesktop, &IID_IActiveDesktop> pIActiveDesktop; // <- Problematic line (throws errors 2065 and 2275) hr = pIActiveDesktop.CoCreateInstance(CLSID_ActiveDesktop, NULL, CLSCTX_INPROC_SERVER); if (!SUCCEEDED(hr)) { return hr; } COMPONENTSOPT opt; opt.dwSize = sizeof(opt); opt.fActiveDesktop = opt.fEnableComponents = enable; hr = pIActiveDesktop->SetDesktopItemOptions(&opt, 0); if (!SUCCEEDED(hr)) { CoUninitialize(); // pIActiveDesktop->Release(); return hr; } hr = pIActiveDesktop->ApplyChanges(AD_APPLY_REFRESH); CoUninitialize(); // pIActiveDesktop->Release(); return hr; } This code is throwing the following compiler errors: error C2065: 'CComQIPtr' : undeclared identifier error C2275: 'IActiveDesktop' : illegal use of this type as an expression error C2065: 'pIActiveDesktop' : undeclared identifier The two weird bits: (1) CComQIPtr is defined in atlcomcli.h, which is included in atlbase.h, which is included in HideDesktop.cpp; and (2) this file is only throwing these errors when it's referenced in my new ATL/AX project: it's not throwing them in the original executable project, even though they have basically the same preprocessor definitions. (The ATL AX project, naturally enough, defines _ATL_DLL, but I can't see where that would make a difference.) My current workaround is to use a normal "dumb" pointer, like so: IActiveDesktop *pIActiveDesktop; HRESULT hr = ::CoCreateInstance(CLSID_ActiveDesktop, NULL, // no outer unknown CLSCTX_INPROC_SERVER, IID_IActiveDesktop, (void**)&pIActiveDesktop); And that works, provided I remember to release it. But I'd rather be using the ATL smart stuff. Any thoughts?

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• Problem with final branch in a parallel activity

  - by Dan Revell

  This might seem like a silly thing to say, the final branch in a parallel activity so I'll clarify. It's a parallel activity with three branches each containing a simple create task, on task changed and complete task. The branch containing the task that is last to complete seems to break. So every task works in it's own right, but the last one encounters a problem. Say the user clicks the final tasks link to open the attached infopath form and submits that. Execution gets to the event handler for that onTaskChanged where a taskCompleted variable gets set to true which will exit the while loop. I've successfully hit a breakpoint on this line so I know that happens. However the final activity in that branch, the completeTask doesn't get hit. When submit is clicked in the final form, the operation in progess screen says of for quite a while before returning to the workflow status page. The task that was opened and submitted says "Not Started". I can disable any of the branches to leave only two, but the same problem happens with the last to be completed. Earlier on in the workflow I do essencially the same thing. I have another 3 branch parallel activity with each brach containing a task. This one works correctly which leads me to believe that it might be a problem with having two parallel activites in the same sequential workflow. I've considered the possibility that it might be a correlation token problem. The token that every task branch uses is unique to that branch and it's owner activity name is est to that of the branch. It stands to reason that if the task complete variable is indeed getting set to true but the while loop isn't being exited, then there's a wire crossing with the variable somewhere. However I'd still have thought that the task status back on the workflow status page would at least say that the task is in progress. This is a frustrating show stopper of a bug for me. Any thoughts or suggestions would be much appricated so I can investigate them.

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• LiveView plugin template creates lots of errors?

  - by Shedo Surashu

  I'm trying to get the LiveView plugin template to work but upon import of the project into Eclipse, I already have 13 errors and 2 warnings. I have already downloaded SDK for Android 1.6 which I believe is what it requires. The errors are as follows: The method startPlugin() of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 173 Java Problem The method stopPlugin() of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 182 Java Problem The method onSharedPreferenceChanged(SharedPreferences, String) of type new SharedPreferences.OnSharedPreferenceChangeListener(){} must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 360 Java Problem The method onServiceDisconnected(ComponentName) of type new ServiceConnection(){} must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 345 Java Problem The method onServiceConnected(ComponentName, IBinder) of type new ServiceConnection(){} must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 318 Java Problem The method screenMode(int) of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 230 Java Problem The method openInPhone(String) of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 221 Java Problem The method run() of type SandboxPluginService.Rotator must override a superclass method SandboxPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins/sandbox line 254 Java Problem The method onUnregistered() of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 216 Java Problem The method run() of type SandboxPluginService.Timer must override a superclass method SandboxPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins/sandbox line 235 Java Problem The method displayCaps(int, int) of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 206 Java Problem The method button(String, boolean, boolean) of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 196 Java Problem The method getPluginName() of type AbstractPluginService.LiveViewCallback must override a superclass method AbstractPluginService.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/src/com/sonyericsson/extras/liveview/plugins line 191 Java Problem and the warnings: The method getInterfaceDescriptor() from the type IPluginServiceV1.Stub.Proxy is never used locally IPluginServiceV1.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/gen/com/sonyericsson/extras/liveview line 242 Java Problem The method getInterfaceDescriptor() from the type IPluginServiceCallbackV1.Stub.Proxy is never used locally IPluginServiceCallbackV1.java /com.sonyericsson.extras.liveview.plugins.PluginPreferences/gen/com/sonyericsson/extras/liveview line 130 Java Problem These all occur fresh from the ZIP file from Sony Mobile's Developer World. No code has been changed. Any thoughts?

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• DatagridView loses current edit on Background update

  - by yoni.s

  Here's my problem : I have a DataGridView bound to a BindingList of custom objects. A background thread is constantly updating a value of these objects. The udpates are showing correctly, and everything is fine except for one thing - If you try to edit a different field while the background-updated field is being updated, it loses the entered value. Here is a code sample that demonstrates this behavior: (for new form, drop a new DataGridView on:) using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; namespace WindowsFormsApplication2 { public partial class Form1 : Form { private BindingList<foo> flist; private Thread thrd; private BindingSource b; public Form1() { InitializeComponent(); flist = new BindingList<foo> { new foo(){a =1,b = 1, c=1}, new foo(){a =1,b = 1, c=1}, new foo(){a =1,b = 1, c=1}, new foo(){a =1,b = 1, c=1} }; b = new BindingSource(); b.DataSource = flist; dataGridView1.DataSource = b; thrd = new Thread(new ThreadStart(updPRoc)); thrd.Start(); } private void upd() { flist.ToList().ForEach(f=>f.c++); } private void updPRoc() { while (true) { this.BeginInvoke(new MethodInvoker(upd)); Thread.Sleep(1000); } } } public class foo:INotifyPropertyChanged { private int _c; public int a { get; set; } public int b { get; set; } public int c { get {return _c;} set { _c = value; if (PropertyChanged!= null) PropertyChanged(this,new PropertyChangedEventArgs("c")); } } #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; #endregion } } So, you edit column a or b, you will see that the column c update causes you to lose your entry. Any thoughts appreciated.

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• How to best integrate generated code

  - by Arne

  I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code. I've got something like this in mind: model Aircraft has state x1, x2; state x3; input double : u; input bool : flag1, flag2; algebraic double : x1x2; model Engine : tw1, tw2; model Gear : gear; model ISA : isa; trim routine HorizontalFight; trim routine OnGround, General; constant double : c1, c2; constant int : ci1; begin differential equations x1' = x1 + 2.*x2; x2' = x2 + x1x2; begin algebraic equations x1x2 = x1*x2 + x1'; end model It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated. My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places [File Aircarft.h] class Aircraft { public: void Aircraft(..); // hand-written constructor void ReadParameters(string &file_name); // hand-written private: /* more hand wirtten boiler-plate code */ /* generate declarations follow */ #include "Aircraft.generated.decl" }; [File Aircraft.cpp] Aircarft::Aircraft(..) { /* hand-written constructer implementation */ } /* more hand-written implementation code */ /* generated implementation code follows */ #include "Aircraft.generated.impl" Any thoughts or suggestions?

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• Giving event control back to xaml/callee to access check/uncheck

  - by dovholuk

  Hi All, I've scoured the Internet but my search-foo must not work if it's out there cause I just can't find the proper search terms to get me the answer I am looking for. So I turn to the experts here as a last resort to point me in the right direction. What I'm trying to do is create a composite control of a text box and a list box but I want to allow the control consumer to decide what to do when say the checkbox is checked/unchecked and I just can't figure it out... Maybe i'm going about it all wrong. What I've done thus far is to: create a custom control that extends ListBox expose a custom DP named "Text" (for the Text box but it's not the important part) craft the generic.xaml so that the list items have a default ItemTemplate/DataTemplate inside the DataTemplate I'm trying to set the "Checked" or "Unchecked" events expose 'wrapper' events as DPs in the custom control that would get 'set' via the template when instatiated As soon as I try something like the following (inside generic.xaml): <DataTemplate> <...> <CheckBox Checked="{TemplateBinding MyCheckedDP}"/> <...> </DataTemplate> I get runtime exceptions, the designer - vs2010 - pukes out a LONG list of errors that are all very similar and nothing I do can make it work. I went so far as to try using the VisualTreeHelper but no magic combination I could find would work nor would it allow me to traverse the tree because when the OnApplyTemplate method fires the listbox items don't exist yet and aren't in the tree. So hopefully this all makes sense but if not please let me know and I'll edit the post for clarifications. Thanks to all for any pointers or thoughts... Like I said maybe I'm heading about it in the wrong way from the start... EDIT (Request for xaml) generic.xaml datatemplate: <DataTemplate > <StackPanel Orientation="Horizontal" > <local:FilterCheckbox x:Name="chk"> <TextBlock Text="{Binding Path=Display}" /> </local:FilterCheckbox> </StackPanel> </DataTemplate> usercontrol.xaml (invocation of custom control) <local:MyControl FancyName="This is the fancy name" ItemChecked="DoThisWhenACheckboxIsChecked" <-- this is where the consumer "ties" to the checkbox events ItemsSource="{Binding Source={StaticResource someDataSource}}" />

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• What Can I Do To One Of My Team Number (Good Friend As Well) Who Lost His Passion.

  - by skyflyer

  It seems this question is not program related, but there are lot of similar questions. So please bear with me! By the way, I am programmer and my team is also charging a software project. And SO is the only place which solved me lot of thorny troubles!THANK YOU GUYS! I joined my company with him years ago. At that time he was quite passionate on his job which is a front-end development. He gave us lot of useful suggestions concerning his work like design. And I believed he was a smart guy. I believe he still is smart too by the way. One years later, however, he seemed lost his passion and fooling around every day, did not care about his work any more and produced poorwork. Even worse he literally stopped learning new skills and honing his work related skills. For me it is horrible, we got to keep abreast with new technology development, otherwise we will be throw out. Since we were just coworkers, I did not care about it too much except mentioned my thoughts several times. But last month, we resembled a new group and assigned very important project. And I am the team leader, sadly! My boss gave me lot of support and expectation as well. I did a pretty good job before and I am very optimism to our future. But as a team, if my team does not work hard, we will be doomed to failure no matter how hard I work and push. In order to revitalize his passion, I tried couple of ways like talking to him about my concern and my boss's angry. I offered his new task which is quite new to him. I even persuaded my boss to give him new incentive package. But all of them knocked wall. His reaction was just he did not care. Even worse he did not want to talk about his situation. I want to be hard on him, but since we are friends and coworkers, I really can not see it will work. Even it works, I can not so quickly change my self from friend and coworker into manager. As a novice in management, I am really overwhelmed! I do not want get him fired, we are friends and I do not see him fired as my team number. What can I do? Thank you guys!

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• XSLT: Display unique rows of filtered XML recordset

  - by Chris G.

  I've got a recordset that I'm filtering on a particular field (i.e. Manager ="Frannklin"). Now I'd like to group the results of that filtered recordset based on another field (Client). I can't seem to get Muenchian grouping to work right. Any thoughts? TIA! CG My filter looks like this: <xsl:key name="k1" match="Row" use="@Manager"/> <xsl:param name="dvt_filterval">Frannklin</xsl:param> <xsl:variable name="Rows" select="/dsQueryResponse/Rows/Row" /> <xsl:variable name="FilteredRowsAttr" select="$Rows[normalize-space(@*[name()=$FieldNameNoAtSign])=$dvt_filterval ]" /> Templates <xsl:apply-templates select="$FilteredRowsAttr[generate-id() = generate-id(key('k1',@Manager))]" mode="g1000a"> </xsl:apply-templates> <xsl:template match="Row" mode="g1000a"> Client: <xsl:value-of select="@Client"/> </xsl:template> Results I'm getting Client: Beta Client: Beta Client: Beta Client: Gamma Client: Delta Results I want Client: Beta Client: Gamma Client: Delta Sample recordset <dsQueryResponse> <Rows> <Row Manager="Smith" Client="Alpha " Project_x0020_Name="Annapolis" PM_x0023_="00123" /> <Row Manager="Ford" Client="Alpha " Project_x0020_Name="Brown" PM_x0023_="00124" /> <Row Manager="Cronkite" Client="Beta " Project_x0020_Name="Gannon" PM_x0023_="00129" /> <Row Manager="Clinton, Bill" Client="Beta " Project_x0020_Name="Harvard" PM_x0023_="00130" /> <Row Manager="Frannklin" Client="Beta " Project_x0020_Name="Irving" PM_x0023_="00131" /> <Row Manager="Frannklin" Client="Beta " Project_x0020_Name="Jakarta" PM_x0023_="00132" /> <Row Manager="Frannklin" Client="Beta " Project_x0020_Name="Vassar" PM_x0023_="00135" /> <Row Manager="Jefferson" Client="Gamma " Project_x0020_Name="Stamford" PM_x0023_="00141" /> <Row Manager="Cronkite" Client="Gamma " Project_x0020_Name="Tufts" PM_x0023_="00142" /> <Row Manager="Frannklin" Client="Gamma " Project_x0020_Name="UCLA" PM_x0023_="00143" /> <Row Manager="Jefferson" Client="Gamma " Project_x0020_Name="Villanova" PM_x0023_="00144" /> <Row Manager="Carter" Client="Delta " Project_x0020_Name="Drexel" PM_x0023_="00150" /> <Row Manager="Clinton" Client="Delta " Project_x0020_Name="Iona" PM_x0023_="00151" /> <Row Manager="Frannklin" Client="Delta " Project_x0020_Name="Temple" PM_x0023_="00152" /> <Row Manager="Ford" Client="Epsilon " Project_x0020_Name="UNC" PM_x0023_="00157" /> <Row Manager="Clinton" Client="Epsilon " Project_x0020_Name="Berkley" PM_x0023_="00158" /> </Rows> </dsQueryResponse>

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• C socket programming: connect() hangs

  - by Fantastic Fourier

  Hey all, I'm about to rip my hair out. I have this client that tries to connect to a server, everything seems to be fine, using gethostbyname(), socket(), bind(), but when trying toconnect()` it just hangs there and the server doesn't see anything from the client. I know that the server works because another client (also in C) can connect just fine. What causes the server to not see this incoming connection? I'm at the end of my wits here. The two different clients are pretty similar too so I'm even more lost. if (argc == 2) { host = argv[1]; // server address } else { printf("plz read the manual\n"); exit(1); } hserver = gethostbyname(host); if (hserver) { printf("host found: %p\n", hserver); printf("host found: %s\n", hserver->h_name ); } else { printf("host not found\n"); exit(1); } bzero((char * ) &server_address, sizeof(server_address)); // copy zeroes into string server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(hserver->h_addr); server_address.sin_port = htons(SERVER_PORT); bzero((char * ) &client_address, sizeof(client_address)); // copy zeroes into string client_address.sin_family = AF_INET; client_address.sin_addr.s_addr = htonl(INADDR_ANY); client_address.sin_port = htons(SERVER_PORT); sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) exit(1); else { printf("socket is opened: %i \n", sockfd); info.sock_fd = sockfd; rv = fcntl(sockfd, F_SETFL, O_NONBLOCK); // socket set to NONBLOCK if(rv < 0) printf("nonblock failed: %i %s\n", errno, strerror(errno)); else printf("socket is set nonblock\n"); } timeout.tv_sec = 0; // seconds timeout.tv_usec = 500000; // micro seconds ( 0.5 seconds) setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(struct timeval)); rv = bind(sockfd, (struct sockaddr *) &client_address, sizeof(client_address)); if (rv < 0) { printf("MAIN: ERROR bind() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("socket is bound\n"); rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); Any thoughts or insights are deeply greatly humongously appreciated. -Fourier

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• Under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope T

  - by Triynko

  What does it mean for an SqlConnection to be "enlisted" in a transaction? Does it simply mean that commands I execute on the connection will participate in the transaction? If so, under what circumstances is an SqlConnection automatically enlisted in an ambient TransactionScope Transaction? See questions in code comments. My guess to each question's answer follows each question in parenthesis. Scenario 1: Opening connections INSIDE a transaction scope using (TransactionScope scope = new TransactionScope()) using (SqlConnection conn = ConnectToDB()) { // Q1: Is connection automatically enlisted in transaction? (Yes?) // // Q2: If I open (and run commands on) a second connection now, // with an identical connection string, // what, if any, is the relationship of this second connection to the first? // // Q3: Will this second connection's automatic enlistment // in the current transaction scope cause the transaction to be // escalated to a distributed transaction? (Yes?) } Scenario 2: Using connections INSIDE a transaction scope that were opened OUTSIDE of it //Assume no ambient transaction active now SqlConnection new_or_existing_connection = ConnectToDB(); //or passed in as method parameter using (TransactionScope scope = new TransactionScope()) { // Connection was opened before transaction scope was created // Q4: If I start executing commands on the connection now, // will it automatically become enlisted in the current transaction scope? (No?) // // Q5: If not enlisted, will commands I execute on the connection now // participate in the ambient transaction? (No?) // // Q6: If commands on this connection are // not participating in the current transaction, will they be committed // even if rollback the current transaction scope? (Yes?) // // If my thoughts are correct, all of the above is disturbing, // because it would look like I'm executing commands // in a transaction scope, when in fact I'm not at all, // until I do the following... // // Now enlisting existing connection in current transaction conn.EnlistTransaction( Transaction.Current ); // // Q7: Does the above method explicitly enlist the pre-existing connection // in the current ambient transaction, so that commands I // execute on the connection now participate in the // ambient transaction? (Yes?) // // Q8: If the existing connection was already enlisted in a transaction // when I called the above method, what would happen? Might an error be thrown? (Probably?) // // Q9: If the existing connection was already enlisted in a transaction // and I did NOT call the above method to enlist it, would any commands // I execute on it participate in it's existing transaction rather than // the current transaction scope. (Yes?) }

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• Sanity check on this idea for an Image Viewer in a web app

  - by Charlie Flowers

  I have an approach in mind for an image viewer in a web app, and want to get a sanity check and any thoughts you stackoverflowers might have. Here's the whirlwind nutshell summary: I'm working on an ASP.NET MVC application that will run in my company's retail stores. Even though it is a web application, we own the store machines and have control over them. We have a "windows agent" running on the store machine which we can talk to via http post (it is a WCF service, and our web app has permission to talk to it from the browser). One of the web pages needs to be an "image viewer" page with some common things like Rotate & Zoom. Now, there are some WebForms controls that offer Rotate and Zoom. However, they take up server resources and generate a good bit of traffic between the server and the browser. For example, the Rotate function would cause an ajax call to the server, which would then generate a new image written to a .NET Canvas object, which would then be written to a file on the server, which would then be returned from the ajax call and refreshed inside the browser. Normally, that's a pretty good way of doing things. But in our case, we have code running on the store machine that we can communicate with. This leads me to consider the following approach: When the user asks to view an image, we tell our "windows agent" to download it from our image server to the store machine. We then redirect our browser to our image viewer page, which will pull the image from the local file we just wrote to the store machine. When the user clicks "Rotate", we cause JavaScript code in the browser to call our "windows agent" software, asking it to perform the "Rotate" function. The "windows agent" does the rotation using the same kind of imaging control that would formerly have been used on the server, but it does so now on the store machine. Javascript in the browser then refreshes the image on the page to show the newly rotated image. Zoom and similar features would be implemented the same way. This seems to be much more efficient, scalable, and responsive for the end-users. However, I've never heard of anything like it being done, mostly because it's rare to have this combination of a web app plus a "windows agent" on the client machine. What do you think? Feasible? Reasonable? Any pitfalls I overlooked or improvements / suggestions you can see? Has anyone done anything like this who would like to offer the wisdom of experience? Thanks!

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• PHP: How to implement a __get-like method for local function variables

  - by Tom Frost

  I'm no stranger to __get(), and have used it to make some very convenient libraries in the past. However, I'm faced with a new challenge (PHP 5.3, abbreviated and simplified my code for this question): <?php namespace test; class View { function __construct($filename, $varArray) { $this->filename = $filename; $this->varArray = $varArray; } function display() { include($this->filename); } function __get($varName) { if (isset($this->varArray[$varName])) return $this->varArray[$varName]; return "?? $varname ??"; } } ?> Above is a very, very simplified system for loading a View. This code would call the view and display it: <?php require_once("View.php"); use test\View; $view = new View("views/myview.php", array("user" => "Tom")); $view->display(); ?> My goal for this code is to allow the view "myview.php" to contain code like this: <p> Hello <?php echo $user; ?>! Your E-mail is <?php echo $email; ?> </p> And, used with the above code, this would output "Hello Tom! Your E-mail is ?? email ??" However, this won't work. The view is being included within a class method, so when it refers to $user and $email, it's looking for local function variables -- not variables belonging to the View class. For this reason, __get never gets triggered. I could change all my view's variables to things like $this-user and $this-email, but that would be a messy and unintuitive solution. I'd love to find a way where I can reference variables directly WITHOUT having PHP throw an error when an undefined variable is used. Thoughts? Is there a clean way to do this, or am I forced to resort to hacky solutions?

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• Help with Arrays in Objective C.

  - by NJTechie

  Problem : Take an integer as input and print out number equivalents of each number from input. I hacked my thoughts to work in this case but I know it is not an efficient solution. For instance : 110 Should give the following o/p : one one zero Could someone throw light on effective usage of Arrays for this problem? #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int input, i=0, j,k, checkit; int temp[i]; NSLog(@"Enter an integer :"); scanf("%d", &input); checkit = input; while(input > 0) { temp[i] = input%10; input = input/10; i++; } if(checkit != 0) { for(j=i-1;j>=0;j--) { //NSLog(@" %d", temp[j]); k = temp[j]; //NSLog(@" %d", k); switch (k) { case 0: NSLog(@"zero"); break; case 1: NSLog(@"one"); break; case 2: NSLog(@"two"); break; case 3: NSLog(@"three"); break; case 4: NSLog(@"four"); break; case 5: NSLog(@"five"); break; case 6: NSLog(@"six"); break; case 7: NSLog(@"seven"); break; case 8: NSLog(@"eight"); break; case 9: NSLog(@"nine"); break; default: break; } } } else NSLog(@"zero"); [pool drain]; return 0; }

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• What to Return? Error String, Bool with Error String Out, or Void with Exception

  - by Ranger Pretzel

  I spend most of my time in C# and am trying to figure out which is the best practice for handling an exception and cleanly return an error message from a called method back to the calling method. For example, here is some ActiveDirectory authentication code. Please imagine this Method as part of a Class (and not just a standalone function.) bool IsUserAuthenticated(string domain, string user, string pass, out errStr) { bool authentic = false; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; // No exception thrown? We must be good, then. authentic = true; } catch (Exception e) { errStr = e.Message().ToString(); } return authentic; } The advantages of doing it this way are a clear YES or NO that you can embed right in your If-Then-Else statement. The downside is that it also requires the person using the method to supply a string to get the Error back (if any.) I guess I could overload this method with the same parameters minus the "out errStr", but ignoring the error seems like a bad idea since there can be many reasons for such a failure... Alternatively, I could write a method that returns an Error String (instead of using "out errStr") in which a returned empty string means that the user authenticated fine. string AuthenticateUser(string domain, string user, string pass) { string errStr = ""; try { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } catch (Exception e) { errStr = e.Message().ToString(); } return errStr; } But this seems like a "weak" way of doing things. Or should I just make my method "void" and just not handle the exception so that it gets passed back to the calling function? void AuthenticateUser(string domain, string user, string pass) { // Instantiate Directory Entry object DirectoryEntry entry = new DirectoryEntry("LDAP://" + domain, user, pass); // Force connection over network to authenticate object nativeObject = entry.NativeObject; } This seems the most sane to me (for some reason). Yet at the same time, the only real advantage of wrapping those 2 lines over just typing those 2 lines everywhere I need to authenticate is that I don't need to include the "LDAP://" string. The downside with this way of doing it is that the user has to put this method in a try-catch block. Thoughts? Is there another way of doing this that I'm not thinking of?

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• Optimize date query for large child tables: GiST or GIN?

  - by Dave Jarvis

  Problem 72 child tables, each having a year index and a station index, are defined as follows: CREATE TABLE climate.measurement_12_013 ( -- Inherited from table climate.measurement_12_013: id bigint NOT NULL DEFAULT nextval('climate.measurement_id_seq'::regclass), -- Inherited from table climate.measurement_12_013: station_id integer NOT NULL, -- Inherited from table climate.measurement_12_013: taken date NOT NULL, -- Inherited from table climate.measurement_12_013: amount numeric(8,2) NOT NULL, -- Inherited from table climate.measurement_12_013: category_id smallint NOT NULL, -- Inherited from table climate.measurement_12_013: flag character varying(1) NOT NULL DEFAULT ' '::character varying, CONSTRAINT measurement_12_013_category_id_check CHECK (category_id = 7), CONSTRAINT measurement_12_013_taken_check CHECK (date_part('month'::text, taken)::integer = 12) ) INHERITS (climate.measurement) CREATE INDEX measurement_12_013_s_idx ON climate.measurement_12_013 USING btree (station_id); CREATE INDEX measurement_12_013_y_idx ON climate.measurement_12_013 USING btree (date_part('year'::text, taken)); (Foreign key constraints to be added later.) The following query runs abysmally slow due to a full table scan: SELECT count(1) AS measurements, avg(m.amount) AS amount FROM climate.measurement m WHERE m.station_id IN ( SELECT s.id FROM climate.station s, climate.city c WHERE -- For one city ... -- c.id = 5182 AND -- Where stations are within an elevation range ... -- s.elevation BETWEEN 0 AND 3000 AND 6371.009 * SQRT( POW(RADIANS(c.latitude_decimal - s.latitude_decimal), 2) + (COS(RADIANS(c.latitude_decimal + s.latitude_decimal) / 2) * POW(RADIANS(c.longitude_decimal - s.longitude_decimal), 2)) ) <= 50 ) AND -- -- Begin extracting the data from the database. -- -- The data before 1900 is shaky; insufficient after 2009. -- extract( YEAR FROM m.taken ) BETWEEN 1900 AND 2009 AND -- Whittled down by category ... -- m.category_id = 1 AND m.taken BETWEEN -- Start date. (extract( YEAR FROM m.taken )||'-01-01')::date AND -- End date. Calculated by checking to see if the end date wraps -- into the next year. If it does, then add 1 to the current year. -- (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date GROUP BY extract( YEAR FROM m.taken ) The sluggishness comes from this part of the query: m.taken BETWEEN /* Start date. */ (extract( YEAR FROM m.taken )||'-01-01')::date AND /* End date. Calculated by checking to see if the end date wraps into the next year. If it does, then add 1 to the current year. */ (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date The HashAggregate from the plan shows a cost of 10006220141.11, which is, I suspect, on the astronomically huge side. There is a full table scan on the measurement table (itself having neither data nor indexes) being performed. The table aggregates 237 million rows from its child tables. Question What is the proper way to index the dates to avoid full table scans? Options I have considered: GIN GiST Rewrite the WHERE clause Separate year_taken, month_taken, and day_taken columns to the tables What are your thoughts? Thank you!

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• Impersonation on Windows 2000 to Windows XP Leaves Connections Open

  - by Tallek

  I'm running on a Windows 2000 Pro SP4 box (off domain) and trying to impersonate a local user on a Windows XP box (on domain). I'm using code very similar to the WindowsImpersonationContextFacade in the question posted here: http://stackoverflow.com/questions/879704/how-can-i-temporarily-impersonate-a-user-to-open-a-file. I am using impersonation to remotely start and stop windows services as well as access network shares (for some automated integration tests). To get this working, i had to use LOGON32_PROVIDER_DEFAULT and LOGON32_LOGON_NEW_CREDENTIALS when calling LogonUser. Everything worked beautifully ( Windows XP on domain to Windows XP on domain, Windows XP on domain to Windows Server 2003 off domain, and even Windows XP on domain to Windows 2000 off domain). The one issue was running on Windows 2000 Pro SP4 off the domain and trying to impersonate a local user on a Windows XP box running on the domain. To get the Windows 2000 piece working, i had to use LOGON32_PROVIDER_WINNT50 and LOGON32_LOGON_NEW_CREDENTIALS when calling LogonUser. This seemed to get me 95% of the way there, i could now impersonate the local user on the XP box and start/stop services as well as access a network share using the impersonated credentials. I'm running in to one problem though, calling Undo impersonation and closing the token handle seems to leave the connection to the remote box open. After about 10 or so impersonation calls, further impersonation attempts will fail with an error saying something about too many connections are currently open. If i look at the Computer Management - System Tools - Shared Folders - Sessions on my remote Windows XP box, i can see about 10 sessions open to the Windows 2000 box. I can manually close these (i think they may eventually close themselves, but not very quickly) and then impersonation begins working again few more times. This open session issue doesn't seem to be a problem in any of my other test scenarios, just when running locally on a Windows 2000 box. Any ideas? Edit 1: After some more testing and trying out many different things, this seems to be an issue with open sessions not being reused. On Windows 2000 only, every call to LogonUser to get a token and then using that token to impersonate seems to result in a new session being created. I'm guessing Windows XP & Windows Server 2003 are reusing open sessions since i don't seem to be having any issues with them. If I call LogonUser once, then cache the token, I seem to be able to make as many calls to impersonate as I need using the cached token without running in to the "too many connections" issue. This seems like an ugly work around though since i can't call CloseHandle() on my token every time i perform impersonation. Anybody have any thoughts or ideas, or am i stuck with this ugly hack? Thanks

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• Which MarkDown (WMD) javascript editor should I use?

  - by Edan Maor

  Background I'm working on an application which requires user-entered content, and I've decided to use a StackOverflow-style MarkDown editor. After researching this topic for the last few days, I realize there are numerous forks of the base WMD editor, some with a few basic enhancements and some with serious differences from the StackOverflow one. Since this will be the heart of the application, I'd like to start with the best code base I can. I'd be happy if anyone can recommend which one of the many solutions out there best fits my needs. Below is requirements, plus what I've managed to find already. I'm hoping this question will help me decide which version to go with, and maybe help me discover a port out there that's an even better fit for my needs. The requirements for my project Live Preview Multiple editors on the same page (not know how many in advance, since the user can dynamically add another editing box). Ability to extend with extra buttons (I'd like a button to upload a picture, instead of just adding an img url). Ability to dynamically show/hide the edit box (and only see the preview box). Not an absolute must, but I'd prefer to stick as close to StackOverflow's look and feel, since it's well known. Don't know if this matters, but the backend is written in Django. Editors I've looked at Here are a few of the code bases I've looked at, with thoughts. Obviously, I might be missing another solution out there. The derobins version. From what I can tell, this is the official StackOverflow version. Seems like it doesn't support multiple editors on one page. JQuery.MarkEdit. Looks very good, but is pretty different from the StackOverflow version. MooWMD. Looks like the winner right now, but I'm a little concerned since it looks less active/hackable than MarkEdit. The wmd-new version. Not sure, looks like an old codebase without much use. The SocialSite branch. Seems like it's not for public use.

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• Calculating a Sample Covariance Matrix for Groups with plyr

  - by John A. Ramey

  I'm going to use the sample code from http://gettinggeneticsdone.blogspot.com/2009/11/split-apply-and-combine-in-r-using-plyr.html for this example. So, first, let's copy their example data: mydata=data.frame(X1=rnorm(30), X2=rnorm(30,5,2), SNP1=c(rep("AA",10), rep("Aa",10), rep("aa",10)), SNP2=c(rep("BB",10), rep("Bb",10), rep("bb",10))) I am going to ignore SNP2 in this example and just pretend the values in SNP1 denote group membership. So then, I may want some summary statistics about each group in SNP1: "AA", "Aa", "aa". Then if I want to calculate the means for each variable, it makes sense (modifying their code slightly) to use: > ddply(mydata, c("SNP1"), function(df) data.frame(meanX1=mean(df$X1), meanX2=mean(df$X2))) SNP1 meanX1 meanX2 1 aa 0.05178028 4.812302 2 Aa 0.30586206 4.820739 3 AA -0.26862500 4.856006 But what if I want the sample covariance matrix for each group? Ideally, I would like a 3D array, where the I have the covariance matrix for each group, and the third dimension denotes the corresponding group. I tried a modified version of the previous code and got the following results that have convinced me that I'm doing something wrong. > daply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) , , = 1 SNP1 1 2 aa 1.4961210 -0.9496134 Aa 0.8833190 -0.1640711 AA 0.9942357 -0.9955837 , , = 2 SNP1 1 2 aa -0.9496134 2.881515 Aa -0.1640711 2.466105 AA -0.9955837 4.938320 I was thinking that the dim() of the 3rd dimension would be 3, but instead, it is 2. Really this is a sliced up version of the covariance matrix for each group. If we manually compute the sample covariance matrix for aa, we get: [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 Using plyr, the following gives me what I want in list() form: > dlply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) $aa [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 $Aa [,1] [,2] [1,] 0.8833190 -0.1640711 [2,] -0.1640711 2.4661046 $AA [,1] [,2] [1,] 0.9942357 -0.9955837 [2,] -0.9955837 4.9383196 attr(,"split_type") [1] "data.frame" attr(,"split_labels") SNP1 1 aa 2 Aa 3 AA But like I said earlier, I would really like this in a 3D array. Any thoughts on where I went wrong with daply() or suggestions? Of course, I could typecast the list from dlply() to a 3D array, but I'd rather not do this because I will be repeating this process many times in a simulation. As a side note, I found one method (http://www.mail-archive.com/[email protected]/msg86328.html) that provides the sample covariance matrix for each group, but the outputted object is bloated. Thanks in advance.

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• Square Peg Web: Gets you the traffic to where it matters most: Your Website!

  - by demetriusalwyn

  Have you decided to start your business online or is your business not reaching the targeted audience? Come to Square Peg Web; where you will find what you want to make your business reach new heights. The team at Square Peg Web is professionals who understand what you want and make sure you get it right. Our confidence stems from the fact of thousands of satisfied clients who keep referring friends and business associates to us and we do not let our clients down. Many companies promise the sky but how far is does their work live up to the promises? We do not know about the others however, we are sure that we strive to put together all our ideas and thoughts to make your website rank among the top. Web hosting is something that needs to have a personal touch; Square Peg Web customizes everything to suit your requirements so that you do not have to look further. With Square Peg Web you have a host of features to make your Business go viral. Some of the product details that are offered with Square Peg Web are unlimited product options/ variants/ properties giving you an option on price modifiers. You get unlimited customized input fields for your products and you can also Customer-define the prices. Square Peg Web provides you an option of using multiple product images with zoom features and one can also list a particular product in several categories. There are other aspects which make Square Peg Web the best choice for your website needs; every sale of yours’ is important to you and to us. We make sure that each sale is tracked by the product and also the list of bestsellers that appeal to the audience. Other comprehensive statistics of Square Peg Web includes searchable order data, an interface for shipments and order fulfillments, export sales & customer data for usage in a spreadsheet and the ability to export orders to QuickBooks format. With Square Peg Web; Admin Panel is a lot simpler. Administrative access is completely password protected and any changes done are all in real-time. You can have absolute control on the cart from anywhere around the world using your web browser and the topping on the cake is the unlimited amount of admin accounts that can be created for you. Square Peg Web offers you a world of experience with the options of choosing from marketing websites to e-commerce and from customized applications to community oriented sites. Some of the projects which appear in the portfolio of Square Peg Web are Online Marketing Web Sites, E-Commerce Web Sites, customized web applications, Blog designing and programming, video sharing and the option of downloading web sites, online advertisements, flash animation, customer and product support web sites, web site re-designing and planning and complete information architecture.

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• Another C datatypes question

  - by b-gen-jack-o-neill

  Hello. Well, I completely get the most basic datatypes of C, like short, int, long, float, to be exact, all numerical types.These types are needed to be known perform right operations with right numbers. For example to use FPU to add two float numbers. So the compiler must know what the type is. But, when it comes to characters I am little bit off. I know that basic C datatype char is there for ASCII characters coding. But what I don´t know is, why you even need another datatype for characters. Why could not you just use 1 byte integer value to store ASCII character. If you call printf, you apecify the datatype in the call, so you could say to printf that the integer represents ASCII character. I dont know how cout resolves datatype, but I guess you could just specify it somehow. Another thing is, when you want to use Unicode, you must use datatype wchar. But, what if I would like to use some another, for example ISO, or Windows coding instead of UTF? Becouse wchar codes characters as UTF-16 or UTF-32 (I read its compiler specific). And, what if I would want to use for example some imaginary new 8 byte text coding? What datatype should I use for it? I am actually pretty confused of this, becouse I always expected that if I want to use UTF-32 instead of ASCII, I just tell compiler "get UTF-32 value of the character I typed and save it into 4 char field." I thought that text coding is to be dealt with by the end, print function for example. That I just need to specify the coding for the compiler to use, since Windows doesent use ASCII in win32 apps, I guess C compiler must convert the char I typed to ASCII from whatever the type is that windows sends to the C editor. And the last thing is, what if I want to use for example 25 Byte integer for some high math operations? C has no specify-yourself datatype. Yes, I know that this would be difficult since all the math operations would need to be changed, becouse CPU can not add 25 Bytes numbers together. But is there a way to do it? Or is there some math library for it? What if I want to compute Pi to 1000000000000000 digits? :) I know my question is pretty long, but I just wanted to explain my thoughts the best I can in English, since its not my native language it is difficult. And I believe there is simple answer to my question(s), something I missed that explains everything. I read lot about text coding, C tutorials, but nothing about his. Thank you for your time.

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• Multiprogramming in Django, writing to the Database

  - by Marcus Whybrow

  Introduction I have the following code which checks to see if a similar model exists in the database, and if it does not it creates the new model: class BookProfile(): # ... def save(self, *args, **kwargs): uniqueConstraint = {'book_instance': self.book_instance, 'collection': self.collection} # Test for other objects with identical values profiles = BookProfile.objects.filter(Q(**uniqueConstraint) & ~Q(pk=self.pk)) # If none are found create the object, else fail. if len(profiles) == 0: super(BookProfile, self).save(*args, **kwargs) else: raise ValidationError('A Book Profile for that book instance in that collection already exists') I first build my constraints, then search for a model with those values which I am enforcing must be unique Q(**uniqueConstraint). In addition I ensure that if the save method is updating and not inserting, that we do not find this object when looking for other similar objects ~Q(pk=self.pk). I should mention that I ham implementing soft delete (with a modified objects manager which only shows non-deleted objects) which is why I must check for myself rather then relying on unique_together errors. Problem Right thats the introduction out of the way. My problem is that when multiple identical objects are saved in quick (or as near as simultaneous) succession, sometimes both get added even though the first being added should prevent the second. I have tested the code in the shell and it succeeds every time I run it. Thus my assumption is if say we have two objects being added Object A and Object B. Object A runs its check upon save() being called. Then the process saving Object B gets some time on the processor. Object B runs that same test, but Object A has not yet been added so Object B is added to the database. Then Object A regains control of the processor, and has allready run its test, even though identical Object B is in the database, it adds it regardless. My Thoughts The reason I fear multiprogramming could be involved is that each Object A and Object is being added through an API save view, so a request to the view is made for each save, thus not a single request with multiple sequential saves on objects. It might be the case that Apache is creating a process for each request, and thus causing the problems I think I am seeing. As you would expect, the problem only occurs sometimes, which is characteristic of multiprogramming or multiprocessing errors. If this is the case, is there a way to make the test and set parts of the save() method a critical section, so that a process switch cannot happen between the test and the set?

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• Double Buffering for Game objects, what's a nice clean generic C++ way?

  - by Gary

  This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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• Constructor Injection and when to use a Service Locator

  - by Simon

  I'm struggling to understand parts of StructureMap's usage. In particular, in the documentation a statement is made regarding a common anti-pattern, the use of StructureMap as a Service Locator only instead of constructor injection (code samples straight from Structuremap documentation): public ShippingScreenPresenter() { _service = ObjectFactory.GetInstance<IShippingService>(); _repository = ObjectFactory.GetInstance<IRepository>(); } instead of: public ShippingScreenPresenter(IShippingService service, IRepository repository) { _service = service; _repository = repository; } This is fine for a very short object graph, but when dealing with objects many levels deep, does this imply that you should pass down all the dependencies required by the deeper objects right from the top? Surely this breaks encapsulation and exposes too much information about the implementation of deeper objects. Let's say I'm using the Active Record pattern, so my record needs access to a data repository to be able to save and load itself. If this record is loaded inside an object, does that object call ObjectFactory.CreateInstance() and pass it into the active record's constructor? What if that object is inside another object. Does it take the IRepository in as its own parameter from further up? That would expose to the parent object the fact that we're access the data repository at this point, something the outer object probably shouldn't know. public class OuterClass { public OuterClass(IRepository repository) { // Why should I know that ThingThatNeedsRecord needs a repository? // that smells like exposed implementation to me, especially since // ThingThatNeedsRecord doesn't use the repo itself, but passes it // to the record. // Also where do I create repository? Have to instantiate it somewhere // up the chain of objects ThingThatNeedsRecord thing = new ThingThatNeedsRecord(repository); thing.GetAnswer("question"); } } public class ThingThatNeedsRecord { public ThingThatNeedsRecord(IRepository repository) { this.repository = repository; } public string GetAnswer(string someParam) { // create activeRecord(s) and process, returning some result // part of which contains: ActiveRecord record = new ActiveRecord(repository, key); } private IRepository repository; } public class ActiveRecord { public ActiveRecord(IRepository repository) { this.repository = repository; } public ActiveRecord(IRepository repository, int primaryKey); { this.repositry = repository; Load(primaryKey); } public void Save(); private void Load(int primaryKey) { this.primaryKey = primaryKey; // access the database via the repository and set someData } private IRepository repository; private int primaryKey; private string someData; } Any thoughts would be appreciated. Simon

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• Escaping Code for Different Shells

  - by Jon Purdy

  Question: What characters do I need to escape in a user-entered string to securely pass it into shells on Windows and Unix? What shell differences and version differences should be taken into account? Can I use printf "%q" somehow, and is that reliable across shells? Backstory (a.k.a. Shameless Self-Promotion): I made a little DSL, the Vision Web Template Language, which allows the user to create templates for X(HT)ML documents and fragments, then automatically fill them in with content. It's designed to separate template logic from dynamic content generation, in the same way that CSS is used to separate markup from presentation. In order to generate dynamic content, a Vision script must defer to a program written in a language that can handle the generation logic, such as Perl or Python. (Aside: using PHP is also possible, but Vision is intended to solve some of the very problems that PHP perpetuates.) In order to do this, the script makes use of the @system directive, which executes a shell command and expands to its output. (Platform-specific generation can be handled using @unix or @windows, which only expand on the proper platform.) The problem is obvious, I should think: test.htm: <!-- ... --> <form action="login.vis" method="POST"> <input type="text" name="USERNAME"/> <input type="password" name="PASSWORD"/> </form> <!-- ... --> login.vis: #!/usr/bin/vision # Think USERNAME = ";rm -f;" @system './login.pl' { USERNAME; PASSWORD } One way to safeguard against this kind of attack is to set proper permissions on scripts and directories, but Web developers may not always set things up correctly, and the naive developer should get just as much security as the experienced one. The solution, logically, is to include a @quote directive that produces a properly escaped string for the current platform. @system './login.pl' { @quote : USERNAME; @quote : PASSWORD } But what should @quote actually do? It needs to be both cross-platform and secure, and I don't want to create terrible problems with a naive implementation. Any thoughts?

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