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  • C++, generic programming and virtual functions. How do I get what I want?

    - by carleeto
    This is what I would like to do using templates: struct op1 { virtual void Method1() = 0; } ... struct opN { virtual void MethodN() = 0; } struct test : op1, op2, op3, op4 { virtual void Method1(){/*do work1*/}; virtual void Method2(){/*do work2*/}; virtual void Method3(){/*do work3*/}; virtual void Method4(){/*do work4*/}; } I would like to have a class that simply derives from a template class that provides these method declarations while at the same time making them virtual. This is what I've managed to come up with: #include <iostream> template< size_t N > struct ops : ops< N - 1 > { protected: virtual void DoStuff(){ std::cout<<N<<std::endl; }; public: template< size_t i > void Method() { if( i < N ) ops<i>::DoStuff(); } //leaving out compile time asserts for brevity } struct test : ops<6> { }; int main( int argc, char ** argv ) { test obj; obj.Method<3>(); //prints 3 return 0; } However, as you've probably guessed, I am unable to override any of the 6 methods I have inherited. I'm obviously missing something here. What is my error? No, this isn't homework. This is curiosity.

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  • Can I execute a "variable statements" within a function and without defines.

    - by René Nyffenegger
    I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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  • faking a filesystem / virtual filesystem

    - by attwad
    I have a web service to which users upload python scripts that are run on a server. Those scripts process files that are on the server and I want them to be able to see only a certain hierarchy of the server's filesystem (best: a temporary folder on which I copy the files I want processed and the scripts). The server will ultimately be a linux based one but if a solution is also possible on Windows it would be nice to know how. What I though of is creating a user with restricted access to folders of the FS - ultimately only the folder containing the scripts and files - and launch the python interpreter using this user. Can someone give me a better alternative? as relying only on this makes me feel insecure, I would like a real sandboxing or virtual FS feature where I could run safely untrusted code.

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  • How to share cookies across multiple Apache Virtual Hosts

    - by puk
    This question is generally phrased as "How to share cookies across multiple subdomains" and the answer is generally to use the leading dot like so setcookie( 'id', 0, time()+30*3600, '/', '.example.com' ); which means that the cookie is available to all subdomains of example.com. However, the / path I suspect adds the constraint that all subdomains must be physically under the same tree. The PHP documentation states path The path on the server in which the cookie will be available on. If set to '/', the cookie will be available within the entire domain. If set to '/foo/', the cookie will only be available within the /foo/ directory and all sub-directories such as /foo/bar/ of domain. The default value is the current directory that the cookie is being set in. Is it possible to share cookies if one has two (Apache) Virtual Hosts set up with document roots at, for example www.one.example.com ? /var/www/example1 www.two.example.com ? /var/www/example2

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  • Issues in Convergence of Sequential minimal optimization for SVM

    - by Amol Joshi
    I have been working on Support Vector Machine for about 2 months now. I have coded SVM myself and for the optimization problem of SVM, I have used Sequential Minimal Optimization(SMO) by Mr. John Platt. Right now I am in the phase where I am going to grid search to find optimal C value for my dataset. ( Please find details of my project application and dataset details here http://stackoverflow.com/questions/2284059/svm-classification-minimum-number-of-input-sets-for-each-class) I have successfully checked my custom implemented SVM`s accuracy for C values ranging from 2^0 to 2^6. But now I am having some issues regarding the convergence of the SMO for C 128. Like I have tried to find the alpha values for C=128 and it is taking long time before it actually converges and successfully gives alpha values. Time taken for the SMO to converge is about 5 hours for C=100. This huge I think ( because SMO is supposed to be fast. ) though I`m getting good accuracy? I am screwed right not because I can not test the accuracy for higher values of C. I am actually displaying number of alphas changed in every pass of SMO and getting 10, 13, 8... alphas changing continuously. The KKT conditions assures convergence so what is so weird happening here? Please note that my implementation is working fine for C<=100 with good accuracy though the execution time is long. Please give me inputs on this issue. Thank You and Cheers.

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  • How do I render 3d model into directshow virtual camera output

    - by Mr Bell
    I want to provide a virtual webcam via DirectShow that will use the video feed from an existing camera running some tracking software against it to find the users face and then overlay a 3d model oriented just that it appears to move the users face. I am using a third party api to do the face tracking and thats working great. I get position and rotation data from that api. My question is whats the best way to render the 3d model and get into the video feed and out to direct show? I am using c++ on windows xp.

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  • Learning about the low level

    - by Anoners
    I'm interested in learning more about the PC from a lower (machine) level. I graduated from a school which taught us concepts using the Java language which abstracted out that level almost completely. As a result I only learned a bit from the one required assembly language course. In order to cram in ASM and quite a few details about architecture, it was hard to get a very deep picture of what is going on there. At work I focus on unix socket programming in C, so i'm much closer to the hardware now, but I feel I should learn a bit more about what streams really are, how memory management and paging works, what goes on when you call "paint()" on a graphics buffer, etc. I missed out on a lot of this and i'm looking for a good resource to get me started. I've heard a lot about the "Pink Book" by Peter Norton (Programmer's Guide to the IBM PC, Programmer's Guide to inside the PC, etc). It seems like this is on the right track, however the original is quite out dated and the newer ones have had conflicting reviews, with many people saying to stay away from it. I'm not sure what the SO crowd thinks about this book or if they have some suggestions for similar books, online resources, etc that may be good primers for this sort of thing. Any suggestions would be appreciated.

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  • Python/X11: find out if user switches virtual desktops

    - by Philip
    Hello everyone, I'm looking for a way to determine if the user switches virtual desktops under X11. I'm using Python with X11 libraries and PyGTK. I found some working examples in C, but I lack the expertise to translate them into Python, and I read the source code of several X11 pager applications (fbpanel, pypanel), but I can't seem to find what I'm looking for. Do I have to register for a signal? Using X11 or GTK? Do I have to busy-wait? I'm completely new to both X11 and GTK, so any hints/help would be greatly appreciated. Greets, Philip PS: My current efforts can be found here.

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  • What AOP tools exist for doing aspect-oriented programming at the assembly language level against x8

    - by JohnnySoftware
    Looking for a tool I can use to do aspect-oriented programming at the assembly language level. For experimentation purposes, I would like the code weaver to operate native application level executable and dynamic link libraries. I have already done object-oriented AOP. I know assembly language for x86 and so forth. I would like to be able to do logging and other sorts of things using the familiar before/after/around constructs. I would like to be able to specify certain instructions or sequences/patterns of consecutive instructions as what to do a pointcut on since assembly/machine language is not exactly the most semantically rich computer language on the planet. If debugger and linker symbols are available, naturally, I would like to be able to use them to identify subroutines' entry points , branch/call/jump target addresses, symbolic data addresses, etc. I would like the ability to send notifications out to other diagnostic tools. Thus, support for sending data through connection-oriented sockets and datagrams is highly desirable. So is normal logging to files, UI, etc. This can be done using the action part of an aspect to make a function call, but then there are portability issues so the tool needs to support a flexible, well-abstracted logging/notifying mechanism with a clean, simple yet flexible. The goal is rapid-QA. The idea is to be able to share aspect source code braodly within communties as well as publicly. So, there needs to be a declarative security policy file that users can share. This insures that nothing untoward that is hidden directly or indirectly in an aspect source file slips by the execution manager. The policy file format needs to be simple to read, write, modify, understand, type-in, edit, and generate. Sort of like Java .policy files. Think the exact opposite of anything resembling XML Schema files and you get the idea. Is there such a tool in existence already?

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  • Reference app relative virtual paths in .css file

    - by bravo9
    Assume I have an "images" folder directory under the root of my application. How can I, from within a .css file, reference an image in this directory using an ASP.NET app relative path. Example: When in development, the path of ~/Images/Test.gif might resolve to /MyApp/Images/Test.gif while, in production, it might resolve to /Images/Test.gif (depending on the virtual directory for the application). I, obviously, want to avoid having to modify the .css file between environments. I know you can use Page.ResolveClientUrl to inject a url into a control's Style collection dynamically at render time. I would like to avoid doing this.

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  • Virtual dedicated surver repetitive draining RAM, OOM constantly

    - by Deerly
    My linux (fedora red hat 7) virtual dedicated server has been experiencing OOM multiple times a day for the past several days. I thought the issue was with spamd/spamassassin but after disabling this the errors remains. The highest usage displayed on ps faux --cumulative: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 28412 8.7 0.5 309572 109308 ? Sl 22:15 0:17 /usr/java/jdk1. mysql 7716 0.0 0.0 136256 18000 ? Sl 22:12 0:00 _ /usr/libexe named 17697 0.0 0.0 120904 15316 ? Ssl 22:09 0:00 /usr/sbin/named I'm not running any java applications so I'm not sure why the top issue is showing up. It is frustrating as I barely have anything running on the server and use the tiniest fraction of bandwidth. Any help or suggestions on zeroing in on the source of the drain would be much appreciated! Thanks!

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  • SharePoint Virtual Directories Sitemap

    - by Edison
    I have created and asp.net web site utilizing a web.sitemap file to help with navigation. The site needs to be deployed within a virtual directory inside of our SharePoint intranet site. The problem that I am running in to is that when I request the SiteMap.CurrentNode property, it is returning information from SharePoint's sitemap. Specifically, when i try to get my sitemap's title or description, I am getting information from SharePoint. I have tried re-naming my sitemap and declaring a new Sitemap provider within the web.config. After creating the new sitemap provider and requesting the SiteMap.currentNode, I receive an error message saying that it can't find the web.sitemap file. Any help you can provide would be greatly appreciated.

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  • Loading machinecode from file into memory and executing in C -- mprotect failing

    - by chartreusekitsune
    Hi I'm trying to load raw machine code into memory and run it from within a C program, right now when the program executes it breaks when trying to run mprotect on the memory to make it executable. I'm also not entirely sure that if the memory does get set right it will execute. What I currently have is the following: #include <memory.h> #include <sys/mman.h> #include <stdio.h> int main ( int argc, char **argv ) { FILE *fp; int sz = 0; char *membuf; int output = 0; fp = fopen(argv[1],"rb"); if(fp == NULL) { printf("Failed to open file, aborting!\n"); exit(1); } fseek(fp, 0L, SEEK_END); sz = ftell(fp); fseek(fp, 0L, SEEK_SET); membuf = (char *)malloc(sz*sizeof(char)); if(membuf == NULL) { printf("Failed to allocate memory, aborting!\n"); exit(1); } memset(membuf, 0x90, sz*sizeof(char)); if( mprotect(membuf, sz*sizeof(char), PROT_EXEC | PROT_READ | PROT_WRITE) == -1) { printf("mprotect failed!!! aborting!\n"); exit(1); } if((sz*sizeof(char)) != fread(membuf, sz*sizeof(char), 1, fp)) { printf("Read failed, aborting!\n"); exit(1); } __asm__ ( "call %%eax;" : "=a" (output) : "a" (membuf) ); printf("Output = %x\n", output); return 0; }

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  • C# System.IO.FileInfo gets virtual address which has sessions key

    - by Anicho
    Okay so the following line returns null because its path cannot be found: System.IO.FileInfo fi = di.GetFiles()[position]; What I am currently doing is: <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <ctl:Gallery runat="server" ID="Gallery1" FolderUrl="~/images/1/" Size="100" /> When this is invoked System.IO.FileInfo fi = di.GetFiles()[position]; it has the value similar to this: C:\Users\SomeUsername\Desktop\Tiamo\(S(mr1h0l55ycuixfbtqxbmttek))\images\1 Any idea how I can return the virtual path without actually having the session key in there? Thank you in advanced for any help you may give :) much appreciated.

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  • Virtual dedicated server repetitive draining RAM, OOM constantly

    - by Deerly
    My linux (fedora red hat 7) virtual dedicated server has been experiencing OOM multiple times a day for the past several days. I thought the issue was with spamd/spamassassin but after disabling this the errors remains. The highest usage displayed on ps faux --cumulative: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 28412 8.7 0.5 309572 109308 ? Sl 22:15 0:17 /usr/java/jdk1. mysql 7716 0.0 0.0 136256 18000 ? Sl 22:12 0:00 _ /usr/libexe named 17697 0.0 0.0 120904 15316 ? Ssl 22:09 0:00 /usr/sbin/named I'm not running any java applications so I'm not sure why the top issue is showing up. It is frustrating as I barely have anything running on the server and use the tiniest fraction of bandwidth. Any help or suggestions on zeroing in on the source of the drain would be much appreciated! Thanks!

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  • Retrieve a list of the most popular GET param variations for a given URL?

    - by jamtoday
    I'm working on building intelligence around link propagation, and because I need to deal with many short URL services where a reverse-lookup from an exact URL address is required, I need to be able to resolve multiple approximate versions of the same URL. An example would be a URL like http://www.example.com?ref=affil&hl=en&ct=0 Of course, changing GET params in certain circumstances can refer to a completely different page, especially if the GET params in question refer to a profile or content ID. But a quick parse of the page would quickly determine how similar the pages were to each other. Using a bit of machine learning, it could quickly become clear which GET params don't effect the content of the pages returned for a given site. I'm assuming a service to send a URL and get a list of very similar URLs could only be offered by the likes of Google or Yahoo (or Twitter), but they don't seem to offer this feature, and I haven't found any other services that do. If you know of any services that do cluster together groups of almost identical URLs in the aforementioned way, please let me know. My bounty is a hug.

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  • Cross Browser Testing on Virtual Machines - Issues?

    - by codemate2112
    I am part of an organization in which there is contention amongst some very competent folks as to whether or not testing cross-browser behavior for JavaScript applications on virtual machines (for IE6/7/8, FF2/3, Chrome on XP/Vista/7) is reliable. This is using VMWare server on a Linux box host. While the discrepancies seen are few, there are cases in which it has proven difficult to tell if it is a product of virtualization or just different machine configurations. My question to the community is, what is people experience with this? Is there any credence to the claim that VM pose inconsistencies, or are they generally spot-on reliable? Can we trust them?

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  • Virtual Mode List View Click 1 Selects More Than One Items

    - by Samir
    I have a list view with virtual mode set to true and other things. It doing ok. But 1) Say there are 25 items and 15 of them are visible, that is to see the rest of 10 items need to scroll down. 2) Before scrolling swap two items, say myItems[0], it must be visible & myItems[20], it must be not visible scroll required. 3) Now select the first item, it was swapped, you now have two items selected, both 0 indexed and 20 indexed ones. When after swap, those two list view items are of same Position and same Bounds. But before 20-indexed item's Position was (-1, -1) and Bounds was (0,0,0,0). How come 0-indexed item didn't change its position & size? How to solve this ?

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  • redirecting to multiple virtual subdomains using htaccess

    - by Gerald Ferreira
    Hi Everyone I am trying to create subdomains via htaccess. The code below does exactly want I want It takes http://domain.com and redirect it to http://www.domain.com Options -Indexes DirectoryIndex index.html index.htm index.asp index.php ErrorDocument 401 http://www.domain.com ErrorDocument 403 http://www.domain.com ErrorDocument 404 http://www.domain.com ErrorDocument 500 http://www.domain.com ErrorDocument 507 http://www.domain.com RewriteEngine On RewriteCond %{HTTP_HOST} ^domain.com$ RewriteRule ^(.*) http://www.domain.com/$1 [QSA,L,R=301] AddType text/html .html .htm .asp This is the part I am not to sure of: RewriteCond %{HTTP_HOST} ^domain.com/nl$ RewriteRule ^(.*) http://nl.domain.com/$1 [QSA,L,R=301] How can I create virtual subdomains so that if someone goes to http://nl.domain.com it would stay on http://nl.domain.com if someone types http://www.nl.domain.com it would take out the http://www.nl.domain.com and make it http://nl.domain.com also the directory structure for the subdomain would be http://www.domain.com/nl (This is where the actual files will be sitting). so if someone goes to http://www.domain.com/nl it should also redirect to http://nl.domain.com. Thanks in advance for any advice and pointers

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  • Rails - building an absolute url in a model's virtual attribute without url helper

    - by Nick
    I have a model that has paperclip attachments. The model might be used in multiple rails apps I need to return a full (non-relative) url to the attachment as part of a JSON API being consumed elsewhere. I'd like to abstract the paperclip aspect and have a simple virtual attribute like this: def thumbnail_url self.photo.url(:thumb) end This however only gives me the relative path. Since it's in the model I can't use the URL helper methods, right? What would be a good approach to prepending the application root url since I don't have helper support? I would like to avoid hardcoding something or adding code to the controller method that assembles my JSON. Thank you

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