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Articles indexed Monday April 5 2010

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  • Cassandra instead of MySQL for social networking app

    - by Christopher McCann
    I am in the middle of building a new app which will have very similar features to Facebook and although obviously it wont ever have to deal with the likes of 400,000,000 million users it will still be used by a substantial user base and most of them will demand it run very very quickly. I have extensive experience with MySQL but a social app offers complexities which MySQL is not well suited too. I know Facebook, Twitter etc have moved towards Cassandra for a lot of their data but I am not sure how far to go with it. For example would you store such things as user data - username, passwords, addresses etc in Cassandra? Would you store e-mails, comments, status updates etc in Cassandra? I have also read alot that something like neo4j is much better for representing the friend relationships used by social apps as it is a graph database. I am only just starting down the NoSQL route so any guidance is greatly appreciated. Would anyone be able to advise me on this? I hope I am not being too general!

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  • Does (size_t)((char *)0) ever not evaluate to 0?

    - by Bruce Christensen
    According to the responses in "Why subtract null pointer in offsetof()?" (and my reading of K&R), the C standard doesn't require that (size_t)((char *)0) == 0. Still, I've never seen a situation where casting a null pointer to an integer type evaluates to anything else. If there is a compiler or scenario where (size_t)((char *)0) != 0, what is it?

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  • Ninject: Singleton binding syntax?

    - by Rosarch
    I'm using Ninject 2.0 for the .Net 3.5 framework. I'm having difficulty with singleton binding. I have a class UserInputReader which implements IInputReader. I only want one instance of this class to ever be created. public class MasterEngineModule : NinjectModule { public override void Load() { // using this line and not the other two makes it work //Bind<IInputReader>().ToMethod(context => new UserInputReader(Constants.DEFAULT_KEY_MAPPING)); Bind<IInputReader>().To<UserInputReader>(); Bind<UserInputReader>().ToSelf().InSingletonScope(); } } static void Main(string[] args) { IKernel ninject = new StandardKernel(new MasterEngineModule()); MasterEngine game = ninject.Get<MasterEngine>(); game.Run(); } public sealed class UserInputReader : IInputReader { public static readonly IInputReader Instance = new UserInputReader(Constants.DEFAULT_KEY_MAPPING); // ... public UserInputReader(IDictionary<ActionInputType, Keys> keyMapping) { this.keyMapping = keyMapping; } } If I make that constructor private, it breaks. What am I doing wrong here?

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  • how to auto log onto form authentication from desktop app

    - by user156144
    I have an asp website that uses form authentication to protect certain resources. I am developing a desktop winform application that accesses the protected resource. How do I take id and password from user on the desktop app and pass it to the site? I initially thought WebRequest.Credentials can be used to achieve this but I was wrong. Thanks!

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  • Maximum depth of a B-tree

    - by Phenom
    How do you figure out the maximum depth of a B-tree? Say you had a B-tree of order 1625, meaning each node has 1625 pointers and 1624 elements. What is the maximum depth of the tree if it contains 85,000,000 keys?

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  • Visual Web Developer 2008 Express and XHTML 1.1 (not applying)

    - by Mike Valeriano
    Hello. I may be missing something since I'm not used to work with IDEs for web development, so please understand if I'm doing something stupid. I've picked a copy of Beginning ASP.NET 3.5 in C# and VB to try and learn this thing quickly. I'm no HTML guru, but I know something about the DTDs and I want to either use XHTML 1.0 Strict or XHTML 1.1 while learning the ins and outs of ASP.NET. Following the book (just started actually), I'm not having any trouble understanding the concepts, since I have a C# background, but what I don't understand is how VWD goes about applying the schema you select for validation. The book explains that the drop-down list on the toolbar is enough to set this, so that's what I did: I've selected XHTML 1.1 (since there is no 1.0 strict option, what I find really odd) and then started the project. The thing is that the code generated automatically for the Default page had the XHTML 1.0 transitional DTD. Every other page added had the same DTD, even though XHTML 1.1 is still the selected schema in the drop-down list. I decided to test it out and there it was: inserting some text in the design view and then applying a bold formatting just inserted < b tags on the code. Changing color does add a span tag with added CSS though. What I want to know is: if I want strict XHTML (or 1.1) should I just code it manually? Or is there a "fix" for this problem (having a schema selected but not applied by the IDE)? Am I missing something really easy and dumb? I have no problem with coding it manually - I actually prefer doing that. The thing is that I really wanna try this WYSIWYG approach for once, since some developers swear by it. Plus I don't know yet if I'll need special tags for ASP.NET, so I think having them inserted automatically should be the best practice. I couldn't find any similar problems around (MSDN, Google, here), and as far as the book goes (up to the point I've read), this is the expected VWD behavior, which I find suspect at least. Sorry for the long text (and poor English - not my primary language). Thanks in advance for any help/tips.

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  • C++ Newbie: Passing an fstream to a function to read data

    - by vgm64
    I have a text file named num.txt who's only contents is the line 123. Then I have the following: void alt_reader(ifstream &file, char* line){ file.read(line, 3); cout << "First Time: " << line << endl; } int main() { ifstream inFile; int num; inFile.open("num.txt"); alt_reader(inFile, (char*)&num); cout << "Second Time: " << num << endl; } The output is: First Time: 123 Second Time: 3355185 Can you help me figure out how to get an fstream that is read in a function still assign the variable in main? I'm doing this because alt_reader really has a lot more to it, but this is the part I'm stuck on. Thanks a lot for the help.

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  • How to change rows in a table based on other table rows in mysql?

    - by understack
    I've a table which has 3 columns: id, a_id and b_id. Suppose rows are like this: 1, a1, b1 2, a1, b2 3, a1, b3 4, a2, b4 5, a2, b5 6, a2, b6 I want to convert it to 1, a1, b1 2, a1, b1 3, a1, b1 4, a2, b4 5, a2, b4 6, a2, b4 So I want to make all the b_id corresponding to a_id same, and equal to the one which is found first. How can I do this? For simplicity, I've removed other columns from table. So please ignore row duplication here.

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  • .Net Custom Components "disappear" after file save

    - by EatATaco
    I might have a hard time explaining this because I am at a total loss for what is happening so I am just looking for some guidance. I might be a bit wordy because I don't know exactly what is the relevant information. I am developing a GUI for a project that I am working on in using .Net (C#) Part of the interface mimics, exactly, what we do in another product. For consistency reasons, my boss wants me to make it look the same way. So I got the other software and basically copied and pasted the components into my new GUI. This required me to introduce a component library (the now defunct Graphics Server GSNet, so I can't go to them for help) so I could implement some simple graphs and temperature/pressure "widgets." The components show up fine, and when I compile, everything seems to work fine. However, at some point during my programming it just breaks. Sometimes the tab that these components are on starts throwing exceptions when I view the designer page (A missing method exception) so it won't display. Sometimes JUST those components from the GSNet library don't show up. Sometimes, if I try to run it, I get a not-instantiated exception on one of their lines of code in the designer code file. Sometimes I can't view the designer at all. No matter what I do I can't reverse it. Even if I undo what I just did it won't fix it. If it happens, I have to revert to a backup and start over again. So I started to backup pretty much every step. I compile it and it works. I comment out a line of code, save it, and then uncomment that same line of code (so I am working with the same exact code) and the components all disappear. It doesn't matter what line of code I actually comment out, as long as it is in the same project that these components are being used. I pretty much have to use the components. . . so does anyone have any suggestion or where I can look to debug this?

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  • fwbuilder/iptables manually scripted + autogenerated rules at startup?

    - by Jakobud
    Fedora 11 Our previous IT-guy setup iptable rules on our firewall in a way that is confusing me and he didn't document any of it. I was hoping someone could help me make some sense of it. The iptables service is obviously starting at startup, but the /etc/sysconfig/iptables file was untouched (default values). I found in /etc/rc.local he was doing this: # We have multiple ISP connections on our network. # The following is about 50+ rules to route incoming and outgoing # information. For example, certain internal hosts are specified here # to use ISP A connection while everyone else on the network uses # ISP B connection when access the internet. ip rule add from 99.99.99.99 table Whatever_0 ip rule add from 99.99.99.98 table Whatever_0 ip rule add from 99.99.99.97 table Whatever_0 ip rule add from 99.99.99.96 table Whatever_0 ip rule add from 99.99.99.95 table Whatever_0 ip rule add from 192.168.1.103 table ISB_A ip rule add from 192.168.1.105 table ISB_A ip route add 192.168.0.0/24 dev eth0 table ISB_B # etc... and then near the end of the file, AFTER all the ip rules he just declared, he has this: /root/fw/firewall-rules.fw He's executing the firewall rules file that was auto-generated by fwbuilder. Some questions Why is he declaring all these ip rules in rc.local instead of declaring them in fwbuilder like all the other rules? Any advantage or necessity to this? Or is this just a poorly organized way to implement firewall rules? Why is he declaring ip rules BEFORE executing the fwbuilder script? I would assume that one of the first things the fwbuilder script does it get rid of any existing rules before declaring all the new ones. Am I wrong about this? If that was the case, the fwbuilder script would basically just delete all the ip rules that were defined in rc.local. Does this make any sense? Why is he executing all this stuff at startup in rc.local instead of just using iptables-save to keep the firewall settings at /etc/sysconfig/iptables that will get implemented at runtime?

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  • Upgrade Debian to unstable on VirtualBox: udev problem

    - by Ken
    I'm running Debian stable on VirtualBox on Windows Vista 64-bit Ultimate. It's been running great, but I needed some newer packages, so I put sid in my sources.list to upgrade to unstable (as I've done a dozen times on various Linux boxes over the years). When I upgraded, something went screwy and it asked me to run apt-get -f install to fix them, which gave this: (Reading database ... 77846 files and directories currently installed.) Preparing to replace udev 0.125-7+lenny3 (using .../archives/udev_151-3_amd64.deb) ... Since release 150, udev requires that support for the CONFIG_SYSFS_DEPRECATED feature is disabled in the running kernel. Please upgrade your kernel before or while upgrading udev. AT YOUR OWN RISK, you can force the installation of this version of udev WHICH DOES NOT WORK WITH YOUR RUNNING KERNEL AND WILL BREAK YOUR SYSTEM AT THE NEXT REBOOT by creating the /etc/udev/kernel-upgrade file. There is always a safer way to upgrade, do not try this unless you understand what you are doing! dpkg: error processing /var/cache/apt/archives/udev_151-3_amd64.deb (--unpack): subprocess new pre-installation script returned error exit status 1 insserv: warning: current start runlevel(s) (2 3 4 5) of script `vboxadd-x11' overwrites defaults (empty). insserv: warning: current stop runlevel(s) (0 1 6) of script `vboxadd-x11' overwrites defaults (empty). insserv: warning: current start runlevel(s) (2 3 4 5) of script `vboxadd-x11' overwrites defaults (empty). insserv: warning: current stop runlevel(s) (0 1 6) of script `vboxadd-x11' overwrites defaults (empty). Errors were encountered while processing: /var/cache/apt/archives/udev_151-3_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) I have the VirtualBox extensions installed, and it looks like the udev install doesn't know what to make of them. But I don't know exactly where/how they're installed (I just ran the VBoxLinuxAdditions-amd64.run script, basically), so I don't know how to disable them. Any ideas? Thanks!

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  • My pivot chart has the wrong Y axis values but correct data point values

    - by Mark Harnett
    I created a pivot chart based on some raw data for the x axis (dates) and 4 calculated fields for the Y values. The values on resulting lines are correct (see the data label at the end of the line) but the Y axis is off by about 100, but not off by any consistent amount. I have played with auto axis on and off, turn log scale on and off. All to no avail. Does anybody have any thoughts? Image link

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  • Personal wiki on usb / the cloud?

    - by drby
    I'm looking for a personal wiki that can be installed on an usb stick and (more importantly) somewhere on the cloud (dropbox). I've looked at the Wiki Matrix, but I really don't care that much about any of the options, so I end up with a choice between ~50 wikis at the end. Tried out TiddlyWiki but there are some things that really annoy me like the fact that all pages get opened on the same page. It really looks like it'd turn into a giant mess pretty quickly. I'd like to have something that's pretty close in terms of appearance and usability to wikipedia. Hierarchical categories for organization would be really nice. And accessible storage (in case I ever want to convert it to something else).

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  • Dragging a shape in Photoshop doesn't show outline

    - by nevan
    I've created a shape in Photoshop with the Rounded Rectangle tool. Now I want to reposition it. When I use the Path Selection tool to move it, Photoshop doesn't seem to pick up the shape. When I let go of the mouse button, the shape moves to wherever I've moved the mouse. I'm used to there being an outline as I drag, so I can position the shape in its final place but this outline isn't showing up. Is there some setting like "Show outline when dragging" that I've changed by mistake?

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  • What Would Google Do?

    - by David Dorf
    Last year I read Jeff Jarvis' book What Would Google Do? and found it very interesting. Jeff is a long-time journalist that's been studying technology, and more specifically the internet. He used his skills to reverse-engineer Google into a list of "Google rules," then goes on to describe a futuristic world driven by these rules. Its an interesting look at crowd-sourcing, openness, and collaboration across many industries, including retail (Google Shops). This year Jeff Jarvis will be a keynote speaker at CrossTalk, Oracle's user conference dedicated to the retail industry. This year's theme is... Retail Redefined: Redesign. Reinvigorate. Reimagine. I think that's pretty appropriate given the massive changes the industry has undergone during the last three years. The thing I really like about this conference is that we try to let the retailers do most of the talking. I'm very interested in hearing about the innovative projects they've got brewing, and where they think our industry is heading. I'll be speaking, but I'm not sure about what so let me know of any interesting topics.

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  • INetCfgComponent::RaisePropertyUi arguments

    - by Soo Wei Tan
    I'm trying to do some COM interop and attempting to invoke the INetCfgComponent::RaisePropertyUi method. I've gotten to the point where I can enumerate devices and get a valid INetCfgComponent for the adapter that I want to display the UI for. However, I'm a COM newbie (let alone COM interop) so I have no idea what the third argument in RaisePropertyUi() is meant to be. I've tried passing in the INetCfgComponent object that I have, but that just results in a InvalidCastException. MSDN has the following to say about the argument: Pointer to the IUnknown interface. RaisePropertyUi retrieves from IUnknown the interface of the context in which to display a network component's property sheet. RaisePropertyUi uses this interface to restrict the display of the property sheet to the context of a connection.

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  • Brute force characters into a textbox in c#

    - by Fred Dunly
    Hey everyone, I am VERY new to programming and the only language I know is C# So I will have to stick with that... I want to make a program that "test passwords" to see how long they would take to break with a basic brute force attack. So what I did was make 2 text boxes. (textbox1 and textbox2) and wrote the program so if the text boxes had the input, a "correct password" label would appear, but i want to write the program so that textbox2 will run a brute force algorithm in it, and when it comes across the correct password, it will stop. I REALLY need help, and if you could just post my attached code with the correct additives in it that would be great. The program so far is extremely simple, but I am very new to this, so. Thanks in advance. private void textBox2_TextChanged(object sender, EventArgs e) { } private void button1_Click(object sender, EventArgs e) { if (textBox2.Text == textBox1.Text) { label1.Text = "Password Correct"; } else { label1.Text = "Password Wrong"; } } private void label1_Click(object sender, EventArgs e) { } } } `

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  • Why am I not getting the expected results with fread() in C?

    - by mauvehead
    Here is my code: #include <stdio.h> int main(void) { FILE *fp; unsigned int i; char bytes[512]; fp = fopen("myFile","r"); for(i = 0;i <= 512;i++) { fread(&bytes, sizeof(bytes), 1, fp); printf("bytes[%d]: %x\n", i, bytes[i]); } } Here is the expected output $ hexdump myFile 0000000 aa55 aa55 0060 0000 0a17 0000 b1a5 a2ea 0000010 0000 0000 614c 7563 616e 0000 0000 0000 0000020 0000 0000 0a68 0000 1001 421e 0000 0000 0000030 f6a0 487d ffff ffff 0040 0000 002f 0000 But here is what I see from my program bytes[0]: 55 bytes[1]: 8 bytes[2]: ffffffc8 bytes[3]: ffffffdd bytes[4]: 22 bytes[5]: ffffffc8 bytes[6]: ffffff91 bytes[7]: 63 bytes[8]: ffffff82 My obvious guess is that I'm either addressing something incorrectly and receiving the wrong data back or I am printing it incorrectly and viewing it the wrong way.

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  • Good .net4 profiler

    - by Martin
    What is a good profiler for .NET 4.0? I'm willing to spend some money, but not too much (say up to £50) I'm developing games for windows phone and xbox using XNA, which means that the projects are commercial. I mention it because I've seen several which are free for non commercial use. Extra points for Visual studio integration. Nb. I'm using Visual Studio Professional 2010

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  • Perl CGI that sends a temporary loading page to client then later sends the actual results page

    - by Kurt W. Leucht
    I've wasted at least a half day of my company's time searching the Internet for an answer and I'm getting wrapped around the axle here. I can't figure out the difference between all the different technology choices (long polling, ajax streaming, comet, XMPP, etc.) and I can't get a simple hello world example working on my PC. I am running Apache 2.2 and ActivePerl 5.10.0. JavaScript is completely acceptable for this solution. All I want to do is write a simple Perl CGI script that when accessed, it immediately returns some HTML that tells the user to wait or maybe sends an animated GIF. Then without any user intervention (no mouse clicks or anything) I want the CGI script to at some time later replace the wait message or the animated GIF with the actual HTML results from their query. I know this is simple stuff and websites do it all the time, but I can't find a single working example that I can cut and paste onto my machine that will work. Here is my simple Hello World example that I've compiled from various Internet sources, but it doesn't seem to work. When I refresh this CGI URL in my web browser it prints nothing for 5 seconds, then it prints the PLEASE BE PATIENT web page, but not the results web page. What am I doing wrong? #!C:\Perl\bin\perl.exe use CGI; use CGI::Carp qw/fatalsToBrowser warningsToBrowser/; sub Create_HTML { my $html = <<EOHTML; <html> <head> <meta http-equiv="pragma" content="no-cache" /> <meta http-equiv="expires" content="-1" /> <script type="text/javascript" > var xmlhttp=false; /*@cc_on @*/ /*@if (@_jscript_version >= 5) // JScript gives us Conditional compilation, we can cope with old IE versions. // and security blocked creation of the objects. try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (E) { xmlhttp = false; } } @end @*/ if (!xmlhttp && typeof XMLHttpRequest!='undefined') { try { xmlhttp = new XMLHttpRequest(); } catch (e) { xmlhttp=false; } } if (!xmlhttp && window.createRequest) { try { xmlhttp = window.createRequest(); } catch (e) { xmlhttp=false; } } </script> <title>Ajax Streaming Connection Demo</title> </head> <body> Some header text. <p> <div id="response">PLEASE BE PATIENT</div> <p> Some footer text. </body> </html> EOHTML return $html; } my $cgi = new CGI; print $cgi->header; print Create_HTML(); sleep(5); print "<script type=\"text/javascript\">\n"; print "\$('response').innerHTML = 'Here are your results!';\n"; print "</script>\n";

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  • ASP.NET Writing to the Bin directory, access denied when anonymous user

    - by LeeW
    Hi all I have a program that creates a small file in the Bin directory for the purpose of tracking a license (that's the intention), all works fine when debugging but I've just realized that when I run it on a IIS server under the anonymous user account (IUSR) the file isn't created as IUSR only has read permission (I know this is correct but drat!). Can I write to another location under IUSR account or can I run my code under 'Local Service' account? Thanks

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