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Articles indexed Monday March 15 2010

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  • How to make Stack.Pop threadsafe

    - by user260197
    I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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  • Force full garbage collection when memory occupation goes beyond a certain threshold

    - by Silvio Donnini
    I have a server application that, in rare occasions, can allocate large chunks of memory. It's not a memory leak, as these chunks can be claimed back by the garbage collector by executing a full garbage collection. Normal garbage collection frees amounts of memory that are too small: it is not adequate in this context. The garbage collector executes these full GCs when it deems appropriate, namely when the memory footprint of the application nears the allotted maximum specified with -Xmx. That would be ok, if it wasn't for the fact that these problematic memory allocations come in bursts, and can cause OutOfMemoryErrors due to the fact that the jvm is not able to perform a GC quickly enough to free the required memory. If I manually call System.gc() beforehand, I can prevent this situation. Anyway, I'd prefer not having to monitor my jvm's memory allocation myself (or insert memory management into my application's logic); it would be nice if there was a way to run the virtual machine with a memory threshold, over which full GCs would be executed automatically, in order to release very early the memory I'm going to need. Long story short: I need a way (a command line option?) to configure the jvm in order to release early a good amount of memory (i.e. perform a full GC) when memory occupation reaches a certain threshold, I don't care if this slows my application down every once in a while. All I've found till now are ways to modify the size of the generations, but that's not what I need (at least not directly). I'd appreciate your suggestions, Silvio P.S. I'm working on a way to avoid large allocations, but it could require a long time and meanwhile my app needs a little stability

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  • Nullable ToString()

    - by StupidDeveloper
    I see everywhere constructions like: int? myVar = null; string test = myVar.HasValue ? myVar.Value.ToString() : string.Empty; Why not use simply: string test = myVar.ToString(); Isn't that exactly the same ? At least Reflector says that: public override string ToString() { if (!this.HasValue) { return ""; } return this.value.ToString(); } So, is that correct (the shorter version) or am I missing something?

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  • xhtml validation javascript

    - by Jason
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> onmouseover="text.show('<br /><b>XXXXXX</b><br />')" Validation Output: Error: character "<" is the first character of a delimiter but occurred as data How can I fix it? thanks

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  • variables in assembler

    - by stupid_idiot
    hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake?

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  • Reporting Services keeps erasing my dataset parameters

    - by Dustin Brooks
    I'm using a web service and every time I change something on the dataset, it erases all my parameters. The weird thing is, I can execute the web service call from the data tab and it prompts for all my parameters, but if I click to edit the data the list is empty or if I try to preview the report it blows up because parameters are missing. Just wondering if anyone else has experienced this and if there is a way to prevent this behavior. Here is a copy of the dataset, not that I think it matters. This has to be the most annoying bug (if its a bug) ever. I can't even execute the dataset from the designer without it erasing my parameter list. When you have about 10 parameters and you are making all kinds of changes to a new report, it becomes very tedious to be constantly re-typing the same list over and over. If anything, studio should at least be able to pre-populate with the parameters the service is asking for. sigh Wheres my stress ball... <Query> <Method Namespace="http://www.abc.com/" Name="TWRPerformanceSummary"/> <SoapAction>http://www.abc.com/TWRPerformanceSummary</SoapAction> <ElementPath IgnoreNamespaces="true"> TWRPerformanceSummaryResponse/TWRPerformanceSummaryResult/diffgram/NewDataSet/table{StockPerc,RiskBudget,Custodian,ProductName,StartValue(decimal),EndValue(decimal),CostBasis(decimal)} </ElementPath> </Query>

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  • How to get a Canvas' width when auto sizing is set?

    - by ThePower
    Hi, I'm using silverlight and I have created a Canvas, it has Auto Width and Height. But I require the Actual Width and Height in code. Is there a way I can do this? I don't want to use .Parent.Width, because the parents width may also be set to auto to replicate its parents height. Thanks again Lloyd

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  • Reusing service proxies

    - by Hadi Eskandari
    I have a set of webservices that I connect to using Silverlight Client. I use proxies generated by "Add service reference" or SLSVCUTIL.exe tool to connect to this service. So far, I have only used one single service. Now I want to use another service on the same server. The problem is that, first service generated set of proxy classes for me, and second service will reuse the same set of classes (plus extra services/classes), e.g. CustomerService.SaveCustomer(Customer customer); OrderService.CheckCustomerLevel(Customer customer); The problem is when I add reference to the second service, I can not reuse the same namespace for the second one (VS error), and when I use a different namespace, the generated classes, although are essentially the same, reside in different namespace, hence different and I end up with two Customer classes in two different namespaces. Anyway around this? I just neeed to have two set of services, reusing the Customer class. I have already tried "reuse types in assembly / all assemblies" check mark when generating proxy classes, but it seems to have no effect. any help is greatly appreciated.

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  • vs2008 mystery: Quick macro record and playback shortcuts not allowed?

    - by gerryLowry
    in vs2008, Tools, Macros, Record TemporaryMacro keyboard shortcut toggle is Ctrl+Shift+R; Run TemporaryMacro keyboard shorcut is Ctrl+Shift+P for playback. I've used them before, but they've stopped working. If I open Tools, Options, Keyboard, then navigate to a command like Tools.Run that has no assigned keyboard shortcut, I can experiment by pretending to assign a keyboard shorcut: I simply click inside the "Press shortcut keys:" textbox and try different keystroke combinations. Examples: Ctrl+p: currently assigned to File.Print Ctrl+r: currently assigned to various uses Ctrl+Shift+Q: available Ctrl+Shift+B: currently assigned to Build.BuildSolution BUT vs2008 will not even allow me to type either of Ctrl+Shift+P or Ctrl+Shift+R in the "Press shortcut keys:" textbox. When I type those combinations, nothing appears in the "Press shortcut keys:" textbox. Please note: I can record and playback a temporary macro by using the menu commands, however, the mouse is like a turtle when compared to the keyboard. Any ideas why this very useful vs2008 feature is broken? Thank you. Regards ~~ Gerry (Lowry)

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  • Optional Navigation Controller

    - by Kevin Sylvestre
    I have an application containing a variety of view controllers linked together in different ways (Welcome Browse Preview OR Browse Preview OR Settings Splash). The first view controller is presented modally using a navigation controller from a main controller, then the next set of view controllers are added using pop and push. This works correctly, but I need to be able to define my 'UINavigationBar' and 'UIToolbar' within interface builder, so they still work as expected if they are presented without using a navigation controller. Is this possible? Currently I get this if I try:

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  • Map NHibernate entity to multiple tables based on parent

    - by Programming Hero
    I'm creating a domain model where entities often (but not always) have a member of type ActionLog. ActionLog is a simple class which allows for an audit trail of actions being performed on an instance. Each action is recorded as an ActionLogEntry instance. ActionLog is implemented (approximately) as follows: public class ActionLog { public IEnumerable<ActionLogEntry> Entries { get { return EntriesCollection; } } protected ICollection<ActionLogEntry> EntriesCollection { get; set; } public void AddAction(string action) { // Append to entries collection. } } What I would like is to re-use this class amongst my entities and have the entries map to different tables based on which class they are logged against. For example: public class Customer { public ActionLog Actions { get; protected set; } } public class Order { public ActionLog Actions { get; protected set; } } This design is suitable for me in the application, however I can't see a clear way to map this scenario to a database with NHibernate. I typically use Fluent NHibernate for my configuration, but I'm happy to accept answers in more general HBM xml.

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  • Equivalents to Z80 DJNZ instruction on other architectures?

    - by Justin Ethier
    First a little background. The z80 CPU has an instruction called DJNZ which can be used in a similar manner as a for loop. Basically DJNZ decrements the B register and jumps to a label if not zero. For example: ld b,96 ; erase all of the line disp_version_erase_loop: call _vputblank ; erase pixels at cursor (uses b reg) djnz disp_version_erase_loop ; loop Of course you can do the same thing using regular comparison and jump instructions, but often it is handy to use the single instruction. With that out of the way, my question is, do other CPU architectures include a similar control instruction?

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  • Viewing array of pointers to structures in Visual Studio in the debugger

    - by Fozi
    I'm having a problem displaying the contents of a pointer array with its contents in the debugger. If I just add the pointer to the watch only the fist entry is visible. But if I add the length to it the debugger assumes that I have something like array[length][length]. Picture The first entry is the broken one, looks the same with ,2 or with any ,2 x. The second one is what I would like to see, but for more entries. Edit: The two entries displayed as [x][1] are invalid. I'm using VS 2005 but I think I had this problem on 2008 as well. Is this a bug or am I doing something wrong?

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  • Rate limiting a ruby file stream

    - by Matthew Savage
    I am working on a project which involves uploading flash video files to a S3 bucket from a number of geographically distributed nodes. The video files are about 2-3mb each, and we are only sending one file (per node) every ten minutes, however the bandwidth we consume needs to be rate limited to ~20k/s, as these nodes are delivering streaming media to a CDN, and due to the locations we are only able to get 512k max upload. I have been looking into the ASW-S3 gem and while it doesn't offer any kind of rate limiting I am aware that you can pass in a IO Stream. Given this I am wondering if it might be possible to create a rate-limited stream which overrides the read method, adds in the rate limiting logic (e.g. in its simplest form a call to sleep between reads) and then call out to the super of the overridden method. Another option I considered is hacking the code for Net::HTTP and putting the rate limiting into the send_request_with_body_stream method which is using a while loop, but I'm not entirely sure which would be the best option. I have attempted at extending the IO class, however that didn't work at all, simply inheriting from the class with class ThrottledIO < IO didn't do anything. Any suggestions will be greatly appreciated.

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  • Making JSON Feed Work Server to Server

    - by Oscar Godson
    I have a JSON feed (which I don't directly control, I have to ask the server admins to update it), that is returning NULL, or otherwise not working when I try to access it from another server. The actual feed works fine, but I can't get it to work like a normal API. Why can I use Flickr, WhitePages, Twitter, etc's JSON APIs, but for: http://portlandoregon.gov/shared/cfm/json.cfm It returns NULL in the browser when using JS. If I call it on the same server, it's fine though. If this is a server issue, what do I ask the admins to change, and if this is a local (browser) based issue, what am I doing wrong for this one feed that works for every other JSON API?

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  • 2.6.9 Kernel on virtual server (non upgradable) - any expected problems?

    - by chris_l
    Hi, I'm considering to rent a virtual server (for me personally). The product I'm currently looking at offers IMO fair pricing, very good hardware etc. The only problem is, that I won't be able to do an upgrade to a newer kernel than 2.6.9 (running Debian Etch). Also, I can't install my own kernel modules. (The server runs with Virtuozzo, so as far as I understand it, it just does some chroot instead of a real virtualization (?)) I want to run GlassFish, Postgres, Subversion, Trac and maybe some other things on it. It will also have to employ a firewall, and provide OpenSSL for https. Ideally, it would also be able to do AIO (asynchronous IO), which could speed up some server I/O. Should I expect problems with that old kernel version, in conjunction with the software I want to install (I'd like to use current versions of the software)? One thing I already found out, is that you can't do everything with iptables, since some kernel modules are missing/things are not build into the kernel. GlassFish v3 appears to run fine at first glance. I was able to test the server for a few hours. Installing my whole setup wasn't feasible in that time, but what I can say is, that it's amazingly fast for an entry-level vserver, especially hard disk and network performance (averaging at ca. 400MBit/s). So if the kernel won't be a problem, I'd really like to take it. Thanks, Chris PS Exact kernel version: 2.6.9-023stab051.3-smp

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  • How do I install .NET framework 1.1 for Windows 7

    - by Extrakun
    The problem: Lord of the Rings Online required .NET framework 1.1 to be installed. It will not recongize other higher versions. Downloading the standalone installer yields exceptions at the end of the installation process. The error message is "Application has generated an exception that could not be handled" What could I do about this?

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  • Oracle Linked Servers on Windows Server 2008 R2

    - by John Paul Cook
    Oracle hasn’t yet released versions of its client software for Windows Server 2008 R2. If you need to create an Oracle linked server, that’s a problem. You’ll see this installation block when attempting to install the Oracle client software for Windows Server 2008: It’s very simple to fix. Check the first checkbox to make the installer ignore the version check. Click Next and ignore the warning you’ll see. The installation should complete successfully. Windows does offer various strategies for mitigating...(read more)

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  • Codeigniter Session Data not available in other pages after login

    - by jswat
    So, I have set up a login page that verifies the user's credentials, and then sets codeigniter session data 'email' and 'is_logged_in' and a few other items. The first page after the login, the data is accessible. After that page, I can no longer access the session data. In fact, if I try reloading that first page, the session data is gone. I have tried storing it in the database, storing it unencrypted (bad idea I know, but it was for troubleshooting), and storing it encrypted. I have autoloaded the session library in config.php. Here's an example of the code I'm using to set the session data: $data = array( 'email' => $this->input->post('username'), 'is_logged_in' => true ); $this->session->set_userdata($data); And to retrieve it, I'm using : $this->session->userdata('email'); Or $this->session->userdata('is_logged_in'); I've done lots of work with PHP and cookies, and sessions before, but this is my first project with Codeigniter and I'm perplexed. Could it have something to do with directory issues? I have the login page and process controlled by a 'login' controller, and then it redirects to a 'site' controller. Thanks for your help, and please let me know if I need to clarify anything.

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  • Optimizing sorting container of objects with heap-allocated buffers - how to avoid hard-copying buff

    - by Kache4
    I was making sure I knew how to do the op= and copy constructor correctly in order to sort() properly, so I wrote up a test case. After getting it to work, I realized that the op= was hard-copying all the data_. I figure if I wanted to sort a container with this structure (its elements have heap allocated char buffer arrays), it'd be faster to just swap the pointers around. Is there a way to do that? Would I have to write my own sort/swap function? #include <deque> //#include <string> //#include <utility> //#include <cstdlib> #include <cstring> #include <iostream> //#include <algorithm> // I use sort(), so why does this still compile when commented out? #include <boost/filesystem.hpp> #include <boost/foreach.hpp> using namespace std; namespace fs = boost::filesystem; class Page { public: // constructor Page(const char* path, const char* data, int size) : path_(fs::path(path)), size_(size), data_(new char[size]) { // cout << "Creating Page..." << endl; strncpy(data_, data, size); // cout << "done creating Page..." << endl; } // copy constructor Page(const Page& other) : path_(fs::path(other.path())), size_(other.size()), data_(new char[other.size()]) { // cout << "Copying Page..." << endl; strncpy(data_, other.data(), size_); // cout << "done copying Page..." << endl; } // destructor ~Page() { delete[] data_; } // accessors const fs::path& path() const { return path_; } const char* data() const { return data_; } int size() const { return size_; } // operators Page& operator = (const Page& other) { if (this == &other) return *this; char* newImage = new char[other.size()]; strncpy(newImage, other.data(), other.size()); delete[] data_; data_ = newImage; path_ = fs::path(other.path()); size_ = other.size(); return *this; } bool operator < (const Page& other) const { return path_ < other.path(); } private: fs::path path_; int size_; char* data_; }; class Book { public: Book(const char* path) : path_(fs::path(path)) { cout << "Creating Book..." << endl; cout << "pushing back #1" << endl; pages_.push_back(Page("image1.jpg", "firstImageData", 14)); cout << "pushing back #3" << endl; pages_.push_back(Page("image3.jpg", "thirdImageData", 14)); cout << "pushing back #2" << endl; pages_.push_back(Page("image2.jpg", "secondImageData", 15)); cout << "testing operator <" << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[1]? " < " : " > ") << pages_[1].path().string() << endl; cout << pages_[1].path().string() << (pages_[1] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << "sorting" << endl; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; sort(pages_.begin(), pages_.end()); cout << "done sorting\n"; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; cout << "checking datas" << endl; BOOST_FOREACH (Page p, pages_) { char data[p.size() + 1]; strncpy((char*)&data, p.data(), p.size()); data[p.size()] = '\0'; cout << p.path().string() << " " << data << endl; } cout << "done Creating Book" << endl; } private: deque<Page> pages_; fs::path path_; }; int main() { Book* book = new Book("/some/path/"); }

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  • Can I attach a .NET TraceListener to an externally running process?

    - by BBlake
    I am developing an application scheduling program that will run other applications using System.Diagnostics.Process. The external applications are of various types (some .NET and some not). For those external apps that have trace logging enabled, is there a way that I can attach the tracelistener of the parent/calling application to listen to and record all the trace output from the child/called application to the parent application's trace output? This is not primarily for debugging purposes. This is more to track trace output from all the various scheduled applications by collecting it into one place as much as possible. The scheduler app is still in the early design stages, but will be .NET, and I'm trying to clear up potential design issues before I get into it too far.

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