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• VB6 app not executing as scheduled task unless user is logged on

  - by Tedd Hansen

  Hi Would greatly apprechiate some help on this one! It may be a tricky one. :) Problem I have an VB6 application which is set up as scheduled task. It starts every time, but when executing CreateObject it fails if user is not logged on to computer. I am looking for information on what could cause this. Primary suspicion is that some Windows API fails. Key points Behaviour confirmed on Windows 2000, 2003, 2008 and Vista. The application executes as user X at scheduled time, executed by Windows Task Scheduler. It executes every time. Application does start! -- If user X is logged on via RDP it runs perfectly. (Note that user doesn't need to be connected, only logged on) -- If user X is not logged on to computer the application fails. Failure point Application fails when using CreateObject() to instansiate a DCOM object which is also part of the application. The DCOM objects declare .dll-references at startup (globally/on top of .bas-file) and run a small startup function. Failure must be during startup, possibly in one of the .dll-declarations. Thoughts After some Googling my initial suspicion was directed at MAPI. From what I could see MAPI required user to be logged on. The application has MAPI references. But even with all MAPI references removed it still does not work. What is the difference if an user is logged on? Registry mapping? Environment? explorer.exe is running. Isn't the user logged on when application executes as the user? What info would help? A definitive answer would be truly great. Any information regarding any VB6 feature/Windows API that could act differently depending on wether user is logged on or not would definitively help. Similar experiences may lead me in the right direction. Tips on debuggin this. Thanks! :)

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• SVN directories not showing up in localhost when using WAMP

  - by JsusSalv

  Hi: I recently installed WAMP for actual local use. I've worked on live development servers but now am working on localhost. I've managed to get multiple virtual hosts setup on my WAMP/Vista 64-bit box but am having difficulty with directories pulled from SVN. I have four vhosts setup. Two work well and they are not tied to any SVN just yet. I'm also using TortoiseSVN in case it makes any difference. However, the other projects are coming from SVN repositories. When I view these two projects I get the following error: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, admin@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error. More information about this error may be available in the server error log. The way I setup the vhosts is as follows: httpd.conf # Multiple Virtual Hosts <VirtualHost 127.0.0.1> ServerName localhost DocumentRoot "C:/wamp/www/" </VirtualHost> <VirtualHost 127.0.1.0> ServerName testone.local DocumentRoot "C:/wamp/www/root/projectone/" </VirtualHost> <VirtualHost 127.0.2.0> ServerName testtwo.local DocumentRoot "C:/wamp/www/root/projecttwo/" </VirtualHost> <VirtualHost 127.0.3.0> ServerName testthree.local DocumentRoot "C:/wamp/www/root/projectthree/" </VirtualHost> <VirtualHost 127.0.3.1> ServerName testfour.local DocumentRoot "C:/wamp/www/root/projectfour/" </VirtualHost> And here's the 'hosts' file: # Localhost 127.0.0.1 localhost ::1 localhost # Project One 127.0.1.0 testone.local # Project Two 127.0.2.0 testtwo.local # Project Three 127.0.3.0 testthree.local # Project Four 127.0.3.1 testfour.local Everything works just fine. So if you want to tell me I'm doing something wrong then by all means point out a few things. But as it stands, it works and I'm content using different IPs and/or named-based vhosts. The problem comes in not being able to see the directories and files in the projects that are tied to an SVN. Whenever I visit http://testxxxx.local I get the error message at the top of this post. Please provide some suggestions. Thank you!

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• Would Like Multiple Checkboxes to Update World PNG Image Using Mogrify to FloodFill Countries With C

  - by socrtwo

  Hi. I'm seeing in another forum if the best way to do this is with Javascript or Ajax but I'm wondering if there is an even easier simpler way. I'm trying to create a web service where users can check which countries they have visited from a list of 175 or so and a World map image would then instantly update with a filled color. There are other similar services, but I'm envisioning mine to be both updating from checks in checkboxes and by clicking on the target country in the displayed image say with an imagemap. Additionally other solutions display all the visited countries in the same color. I would like different colors for different countries or at least for those countries that touch. Eventually I would like to include a feature that enables the choice of which colors to assign countries. I found a Sourceforge project called pwmfccd. It's simply an open source image of the world and the coordinates on the PNG image for all the countries. You can use mogrify from ImageMagick and floodfill to fill the countries with color. I have done this successfully, locally with batch files. My ISP has told me where mogrify is located, basically "/usr/bin/mogrify". I now have a horrendously complicated cgi script which if it worked is set to redraw the world map image with each checkbox. It's here. It also redraws the whole web page with each check. The web page starts here. Of course this is not at all efficient, and I think probably the real way to go is Ajax or Javascript, so that maybe just the image gets changed and redrawn, not the whole web page. Sorry I don't even know the difference between Javascript and Ajax and their relative merits at this point. I suppose you could make just one part of the image update with each check or click on the image instead of even just the image redrawing, but I have never even heard of a hint at being able to do that for irregularly shaped image elements like countries. So I guess an Image map and sister checkbox entries tied to mogrify events redrawing the user's personal copy of the image with an image refresh would be the only way to go. So how do you do this with something other than Javascript or Ajax or is that definitely the way to go and if so, how would you do it? Or can you after all cut up a web based image into irregular puzzle shaped piece which you can redraw individually at will. Thanks in advance for reading and considering answering this post.

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• Rails scalar query

  - by Craig

  I need to display a UI element (e.g. a star or checkmark) for employees that are 'favorites' of the current user (another employee). The Employee model has the following relationship defined to support this: has_and_belongs_to_many :favorites, :class_name => "Employee", :join_table => "favorites", :association_foreign_key => "favorite_id", :foreign_key => "employee_id" The favorites has two fields: employee_id, favorite_id. If I were to write SQL, the following query would give me the results that I want: SELECT id, account, IF( ( SELECT favorite_id FROM favorites WHERE favorite_id=p.id AND employee_id = ? ) IS NULL, FALSE, TRUE) isFavorite FROM employees Where the '?' would be replaced by the session[:user_id]. How do I represent the isFavorite scalar query in Rails? Another approach would use a query like this: SELECT id, account, IF(favorite_id IS NULL, FALSE, TRUE) isFavorite FROM employees e LEFT OUTER JOIN favorites f ON e.id=f.favorite_id AND employee_id = ? Again, the '?' is replaced by the session[:user_id] value. I've had some success writing this in Rails: ee=Employee.find(:all, :joins=>"LEFT OUTER JOIN favorites ON employees.id=favorites.favorite_id AND favorites.employee_id=1", :select=>"employees.*,favorites.favorite_id") Unfortunately, when I try to make this query 'dynamic' by replacing the '1' with a '?', I get errors. ee=Employee.find(:all, :joins=>["LEFT OUTER JOIN favorites ON employees.id=favorites.favorite_id AND favorites.employee_id=?",1], :select=>"employees.*,favorites.favorite_id") Obviously, I have the syntax wrong, but can :joins expressions be 'dynamic'? Is this a case for a Lambda expression? I do hope to add other filters to this query and use it with will_paginate and acts_as_taggable_on, if that makes a difference. edit errors from trying to make :joins dynamic: ActiveRecord::ConfigurationError: Association named 'LEFT OUTER JOIN favorites ON employees.id=favorites.favorite_id AND favorites.employee_id=?' was not found; perhaps you misspelled it? from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/associations.rb:1906:in `build' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/associations.rb:1911:in `build' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/associations.rb:1910:in `each' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/associations.rb:1910:in `build' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/associations.rb:1830:in `initialize' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1789:in `new' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1789:in `add_joins!' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1686:in `construct_finder_sql' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1548:in `find_every' from /Users/craibuc/.gem/ruby/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:615:in `find'

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• converting code from not CPS to CPS (CPS aka Continuation Passing Style aka Continuations)

  - by Delirium tremens

  before: function sc_startSiteCompare(){ var visitinguri; var validateduri; var downloaduris; var compareuris; var tryinguri; sc_setstatus('started'); visitinguri = sc_getvisitinguri(); validateduri = sc_getvalidateduri(visitinguri); downloaduris = new Array(); downloaduris = sc_generatedownloaduris(validateduri); compareuris = new Array(); compareuris = sc_generatecompareuris(validateduri); tryinguri = 0; sc_finishSiteCompare(downloaduris, compareuris, tryinguri); } function sc_getvisitinguri() { var visitinguri; visitinguri = content.location.href; return visitinguri; } after (I'm trying): function sc_startSiteCompare(){ var visitinguri; sc_setstatus('started'); visitinguri = sc_getvisitinguri(sc_startSiteComparec1); } function sc_startSiteComparec1 (visitinguri) { var validateduri; validateduri = sc_getvalidateduri(visitinguri, sc_startSiteComparec2); } function sc_startSiteComparec2 (visitinguri, c) { var downloaduris; downloaduris = sc_generatedownloaduris(validateduri, sc_startSiteComparec3); } function sc_startSiteComparec3 (validateduri, c) { var compareuris; compareuris = sc_generatecompareuris(downloaduris, validateduri, sc_startSiteComparec4); } function sc_startSiteComparec4 (downloaduris, compareuris, validateduri, c) { var tryinguri; tryinguri = 0; sc_finishSiteCompare(downloaduris, compareuris, tryinguri); } function sc_getvisitinguri(c) { var visitinguri; visitinguri = content.location.href; c(visitinguri); } What should the code above become? I need CPS, because I have XMLHttpRequests when validating uris, then downloading pages, but I can't use return statements, because I use asynchronous calls. Is there an alternative to CPS? Also, I'm having to pass lots of arguments to functions now. global in procedural code look like this / self in modular code. Any difference? Will I really have to convert from procedural to modular too? It's looking like a lot of work ahead.

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• Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

  - by ke3pup

  Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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• How to access a named element in a control that inherits from a templated control

  - by Mrt

  Hello this is similar to http://stackoverflow.com/questions/2620165/how-to-access-a-named-element-of-a-derived-user-control-in-silverlight with the difference is inheriting from a templated control, not a user control. I have a templated control called MyBaseControl <Style TargetType="Problemo:MyBaseControl"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="Problemo:MyBaseControl"> <Grid x:Name="LayoutRoot" Background="White"> <Border Name="HeaderControl" Background="Red" /> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> public class MyBaseControl : Control { public UIElement Header { get; set; } public MyBaseControl() { DefaultStyleKey = typeof(MyBaseControl); } public override void OnApplyTemplate() { base.OnApplyTemplate(); var headerControl = GetTemplateChild("HeaderControl") as ContentPresenter; if (headerControl != null) headerControl.Content = Header; } } I have another control called myControl which inherits from MyBaseControl Control <me:MyBaseControl x:Class="Problemo.MyControl" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" xmlns:me="clr-namespace:Problemo" d:DesignHeight="300" d:DesignWidth="400"> <me:MyBaseControl.Header> <TextBlock Name="xxx" /> </me:MyBaseControl.Header> </me:MyBaseControl> public partial class MyControl : MyBaseControl { public string Text { get; set; } public MyControl(string text) { InitializeComponent(); Text = text; Loaded += MyControl_Loaded; } void MyControl_Loaded(object sender, RoutedEventArgs e) { base.ApplyTemplate(); xxx.Text = Text; } } The issue is xxx is null. How do I access the xxx control in the code behind ?

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• CSS selectors : should I make my CSS easier to read or optimise the speed

  - by Laurent Bourgault-Roy

  As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It make my .css file harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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• Heroku Push Problem part 2 - Postgresql - PGError Relations does not exist - Ruby on Rails

  - by bgadoci

  Ok so got through my last problem with the difference between Postgresql and SQLite and seems like Heroku is telling me I have another one. I am new to ruby and rails so a lot of this stuff I can't decipher at first. Looking for a little direction here. The error message and PostsController Index are below. I checked my routes.rb file and all seems well there but I could be missing something. I will post if you need. Processing PostsController#index (for 99.7.50.140 at 2010-04-23 15:19:22) [GET] ActiveRecord::StatementInvalid (PGError: ERROR: relation "tags" does not exist : SELECT a.attname, format_type(a.atttypid, a.atttypmod), d.adsrc, a.attnotnull FROM pg_attribute a LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum WHERE a.attrelid = '"tags"'::regclass AND a.attnum > 0 AND NOT a.attisdropped ORDER BY a.attnum ): PostsController#index def index @tag_counts = Tag.count(:group => :tag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @ugtag_counts = Ugtag.count(:group => :ugctag_name, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes @vote_counts = Vote.count(:group => :post_title, :order => 'count_all DESC', :limit => 20) conditions, joins = {}, :votes unless(params[:tag_name] || "").empty? conditions = ["tags.tag_name = ? ", params[:tag_name]] joins = [:tags, :votes] end @posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id, posts.id ", :order => "created_at DESC", :page => params[:page], :per_page => 5) @popular_posts=Post.paginate( :select => "posts.*, count(*) as vote_total", :joins => joins, :conditions=> conditions, :group => "votes.post_id, posts.id", :order => "vote_total DESC", :page => params[:page], :per_page => 3) respond_to do |format| format.html # index.html.erb format.xml { render :xml => @posts } format.json { render :json => @posts } format.atom end end

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• Floating point vs integer calculations on modern hardware

  - by maxpenguin

  I am doing some performance critical work in C++, and we are currently using integer calculations for problems that are inherently floating point because "its faster". This causes a whole lot of annoying problems and adds a lot of annoying code. Now, I remember reading about how floating point calculations were so slow approximately circa the 386 days, where I believe (IIRC) that there was an optional co-proccessor. But surely nowadays with exponentially more complex and powerful CPUs it makes no difference in "speed" if doing floating point or integer calculation? Especially since the actual calculation time is tiny compared to something like causing a pipeline stall or fetching something from main memory? I know the correct answer is to benchmark on the target hardware, what would be a good way to test this? I wrote two tiny C++ programs and compared their run time with "time" on Linux, but the actual run time is too variable (doesn't help I am running on a virtual server). Short of spending my entire day running hundreds of benchmarks, making graphs etc. is there something I can do to get a reasonable test of the relative speed? Any ideas or thoughts? Am I completely wrong? The programs I used as follows, they are not identical by any means: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { int accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += rand( ) % 365; } std::cout << accum << std::endl; return 0; } Program 2: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { float accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += (float)( rand( ) % 365 ); } std::cout << accum << std::endl; return 0; } Thanks in advance!

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• Java Hardware Acceleration

  - by Freezerburn

  I have been spending some time looking into the hardware acceleration features of Java, and I am still a bit confused as none of the sites that I found online directly and clearly answered some of the questions I have. So here are the questions I have for hardware acceleration in Java: 1) In Eclipse version 3.6.0, with the most recent Java update for Mac OS X (1.6u10 I think), is hardware acceleration enabled by default? I read somewhere that someCanvas.getGraphicsConfiguration().getBufferCapabilities().isPageFlipping() is supposed to give an indication of whether or not hardware acceleration is enabled, and my program reports back true when that is run on my main Canvas instance for drawing to. If my hardware acceleration is not enabled now, or by default, what would I have to do to enable it? 2) I have seen a couple articles here and there about the difference between a BufferedImage and VolatileImage, mainly saying that VolatileImage is the hardware accelerated image and is stored in VRAM for fast copy-from operations. However, I have also found some instances where BufferedImage is said to be hardware accelerated as well. Is BufferedImage hardware accelerated as well in my environment? What would be the advantage of using a VolatileImage if both types are hardware accelerated? My main assumption for the advantage of having a VolatileImage in the case of both having acceleration is that VolatileImage is able to detect when its VRAM has been dumped. But if BufferedImage also support acceleration now, would it not have the same kind of detection built into it as well, just hidden from the user, in case that the memory is dumped? 3) Is there any advantage to using someGraphicsConfiguration.getCompatibleImage/getCompatibleVolatileImage() as opposed to ImageIO.read() In a tutorial I have been reading for some general concepts about setting up the rendering window properly (tutorial) it uses the getCompatibleImage method, which I believe returns a BufferedImage, to get their "hardware accelerated" images for fast drawing, which ties into question 2 about if it is hardware accelerated. 4) This is less hardware acceleration, but it is something I have been curious about: do I need to order which graphics get drawn? I know that when using OpenGL via C/C++ it is best to make sure that the same graphic is drawn in all the locations it needs to be drawn at once to reduce the number of times the current texture needs to be switch. From what I have read, it seems as if Java will take care of this for me and make sure things are drawn in the most optimal fashion, but again, nothing has ever said anything like this clearly. 5) What AWT/Swing classes support hardware acceleration, and which ones should be used? I am currently using a class that extends JFrame to create a window, and adding a Canvas to it from which I create a BufferStrategy. Is this good practice, or is there some other type of way I should be implementing this? Thank you very much for your time, and I hope I provided clear questions and enough information for you to answer my several questions.

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• [solved] PHP-called hyperlink stopped showing when CSS table implemented

  - by Luke

  EDIT: Solved - was not flutter's tag stripping, should work as advertised. I'm using Flutter (which creates custom fields) in Wordpress to display profile information entered as a Post. Before I implemented the CSS tables the link showed up and was clickable. Now I get nothing returned, even when I try to call the link outside the table. If you know anything about this, here's my code in the index.php file and I remain available for any questions. <?php if (in_category('Profile')) { ?> <table id="mytable" cellspacing="0"> -snip- <tr> <th class="row1" valign="top">Website </td> <td>Link: <a href="<?php echo get_post_meta($post->ID, 'FrWebsite', $single=true) ?>"> <?php echo get_post_meta($post->ID, 'FrWebsite', $single=true) ?></a></td> </tr> -snip- </table> Thanks, L Edit: @Josh - there is a foreach looping construct in the table and it is reading and displaying the code correctly, I see what you're getting at now: <tr> <th class="row2" valign="top">Specialities </td> <td class="alt" valign="top"><?php $my_array = get('Expertise'); $output = ""; foreach($my_array as $check) { $output .= "<span>$check</span><br/> "; } echo $output; ?></td> </tr> Edit - @Josh - here's the old code as far as I can remember it, there was no major difference just a <td> tag where there now stands a <th>, there wasn't the class="" and there was no "Link:" and FrWebsite was called Website, but it still didn't work when called Website so I changed to see if that was the error. <tr> <td width="200" valign="top">Website </td> <td><a href="<?php echo get_post_meta($post->ID, 'Website', $single=true) ?>"><?php echo get_post_meta($post->ID, 'Website', $single=true) ?></a></td> </tr>

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• GCC, -O2, and bitfields - is this a bug or a feature?

  - by Rooke

  Today I discovered alarming behavior when experimenting with bit fields. For the sake of discussion and simplicity, here's an example program: #include <stdio.h> struct Node { int a:16 __attribute__ ((packed)); int b:16 __attribute__ ((packed)); unsigned int c:27 __attribute__ ((packed)); unsigned int d:3 __attribute__ ((packed)); unsigned int e:2 __attribute__ ((packed)); }; int main (int argc, char *argv[]) { Node n; n.a = 12345; n.b = -23456; n.c = 0x7ffffff; n.d = 0x7; n.e = 0x3; printf("3-bit field cast to int: %d\n",(int)n.d); n.d++; printf("3-bit field cast to int: %d\n",(int)n.d); } The program is purposely causing the 3-bit bit-field to overflow. Here's the (correct) output when compiled using "g++ -O0": 3-bit field cast to int: 7 3-bit field cast to int: 0 Here's the output when compiled using "g++ -O2" (and -O3): 3-bit field cast to int: 7 3-bit field cast to int: 8 Checking the assembly of the latter example, I found this: movl $7, %esi movl $.LC1, %edi xorl %eax, %eax call printf movl $8, %esi movl $.LC1, %edi xorl %eax, %eax call printf xorl %eax, %eax addq $8, %rsp The optimizations have just inserted "8", assuming 7+1=8 when in fact the number overflows and is zero. Fortunately the code I care about doesn't overflow as far as I know, but this situation scares me - is this a known bug, a feature, or is this expected behavior? When can I expect gcc to be right about this? Edit (re: signed/unsigned) : It's being treated as unsigned because it's declared as unsigned. Declaring it as int you get the output (with O0): 3-bit field cast to int: -1 3-bit field cast to int: 0 An even funnier thing happens with -O2 in this case: 3-bit field cast to int: 7 3-bit field cast to int: 8 I admit that attribute is a fishy thing to use; in this case it's a difference in optimization settings I'm concerned about.

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• jQuery .ajax call to bit.ly returns results in IE but not FF or Chrome

  - by Ian Quigley

  I am trying to call to the bit.ly URL shortening service using jQuery with an .ajax call. <html><head> <script type="text/javascript" src="http://www.twipler.com/settings/scripts/jquery.1.4.min.js"></script> <script type="text/javascript"> jQuery.fn.shorten = function(url) { var resultUrl = url; $.ajax( { url: "http://api.bit.ly/shorten?version=2.0.1&login=twipler&apiKey=R_4e618e42fadbb802cf95c6c2dbab3763&longUrl=" + url, async: false, dataType: 'json', data: "", type: "GET", success: function (json) { resultUrl = json.results[url].shortUrl; } }); return resultUrl; } ; </script></head><body> <a href="#" onclick="alert($().shorten('http://amiconnectedtotheinternet.com'));"> Shorten</a> </body> </html> This works in IE8 but does not work in FireFox (3.5.9) nor in Chrome. In both cases 'json' is null. Headers in IE8 GET http://api.bit.ly/shorten?ver..[SNIP]..dtotheinternet.com HTTP/1.1 Accept: application/json, text/javascript, */* Accept-Language: en-US Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; Media Center PC 6.0; InfoPath.2; .NET CLR 1.1.4322; .NET CLR 3.5.30729; .NET CLR 3.0.30729) Host: api.bit.ly Connection: Keep-Alive Headers in Chrome GET http://api.bit.ly/shorten?versio..[SNIP]..nectedtotheinternet.com HTTP/1.1 Host: api.bit.ly Connection: keep-alive User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.1.249.1045 Safari/532.5 Origin: file:// Accept: application/json, text/javascript, */* Accept-Encoding: gzip,deflate,sdch Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 So the only obvious difference is that Chrome is sending "Origin: file://" and I've no idea how to stop it doing that.

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• H.264 over RTP - Identify SPS and PPS Frames

  - by Toby

  I have a raw H.264 Stream from an IP Camera packed in RTP frames. I want to get raw H.264 data into a file so I can convert it with ffmpeg. So when I want to write the data into my raw H.264 file I found out it has to look like this: 00 00 01 [SPS] 00 00 01 [PPS] 00 00 01 [NALByte] [PAYLOAD RTP Frame 1] // Payload always without the first 2 Bytes -> NAL [PAYLOAD RTP Frame 2] [... until PAYLOAD Frame with Mark Bit received] // From here its a new Video Frame 00 00 01 [NAL BYTE] [PAYLOAD RTP Frame 1] .... So I get the SPS and the PPS from the Session Description Protocol out of my preceding RTSP communication. Additionally the camera sends the SPS and the PPSin two single messages before starting with the video stream itself. So I capture the messages in this order: 1. Preceding RTSP Communication here ( including SDP with SPS and PPS ) 2. RTP Frame with Payload: 67 42 80 28 DA 01 40 16 C4 // This is the SPS 3. RTP Frame with Payload: 68 CE 3C 80 // This is the PPS 4. RTP Frame with Payload: ... // Video Data Then there come some Frames with Payload and at some point a RTP Frame with the Marker Bit = 1. This means ( if I got it right) that I have a complete video frame. Afer this I write the Prefix Sequence ( 00 00 01 ) and the NALfrom the payload again and go on with the same procedure. Now my camera sends me after every 8 complete Video Frames the SPS and the PPS again. ( Again in two RTP Frames, as seen in the example above ). I know that especially the PPS can change in between streaming but that's not the problem. My questions are now: 1. Do I need to write the SPS/PPS every 8th Video Frame? If my SPS and my PPS don't change it should be enough to have them written at the very beginning of my file and nothing more? 2. How to distinguish between SPS/PPS and normal RTP Frames? In my C++ Code which parses the transmitted data I need make a difference between the RTP Frames with normal Payload an the ones carrying the SPS/PPS. How can I distinguish them? Okay the SPS/PPS frames are usually way smaller, but that's not a save call to rely on. Because if I ignore them I need to know which data I can throw away, or if I need to write them I need to put the 00 00 01 Prefix in front of them. ? Or is it a fixed rule that they occur every 8th Video Frame?

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• notification scheduling question

  - by sims

  Hi Stackers! I'm building an app that needs to send out notifications to users depending on user definable "notifications". So the notifications are not per event. They are arbitrary. A cron job should query the database and send out emails when it finds an event with matching criterion. The is a scheduling app. So naturally, one of the criterion is time. I think I've figured it out, but I'm sure there are better ideas out there as it seems to be a fairly common thing to do. I think I'll limit the users ability to "minutes before hand" to get notified as opposed to seconds or hours. So I have an eventA and notificationA. notificationA should be triggered if an event is due within 45 minutes. So eventA starts at 17:30. The user should be notified at 16:45. But the cron job might not run exactly at 00 seconds. So when the difference is not 45 minutes and 0 seconds it is, say, 45 minutes and 5 seconds. Notification time is past. Email doesn't get sent. User misses event. Shugar. We should also take into account that the cron job might take a long time to run. So maybe we should only trigger it every 5 minutes. So we need a bigger interval maybe. So then my guess would be to say that: if ((eventDueTime - now notificationTimeValue - interval) && (eventDueTime - now < notificationTimeValue + interval)) sendTheFrikinNotificationAlready(); It seems kind of risky if the there are thousands of notifications to send out. I guess I could make a thread for each notification and then a thread for each event that matches the criterion. That might help. Does that make sense? Any other ideas? Thanks!

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• Cannot populate form with ajax and populate jquery plugin

  - by Azriel_

  I'm trying to populate a form with jquery's populate plugin, but using $.ajax The idea is to retrieve data from my database according to the id in the links (ex of link: get_result_edit.php?id=34), reformulate it to json, return it to my page and fill up the form up with the populate plugin. But somehow i cannot get it to work. Any ideas: here's the code: $('a').click(function(){ $('#updatediv').hide('slow'); $.ajax({ type: "GET", url: "get_result_edit.php", success: function(data) { var $response=$(data); $('#form1').populate($response); } }); $('#updatediv').fadeIn('slow'); return false; whilst the php file states as follow: <?php $conn = new mysqli('localhost', 'XXXX', 'XXXXX', 'XXXXX'); @$query = 'Select * FROM news WHERE id ="'.$_GET['id'].'"'; $stmt = $conn->query($query) or die ($mysql->error()); if ($stmt) { $results = $stmt->fetch_object(); // get database data $json = json_encode($results); // convert to JSON format echo $json; } ?> Now first thing is that the mysql returns a null in this way: is there something wrong with he declaration of the sql statement in the $_GET part? Second is that even if i put a specific record to bring up, populate doesn't populate. Update: I changed the populate library with the one called "PHP jQuery helper functions" and the difference is that finally it says something. finally i get an error saying NO SUCH ELEMENT AS i wen into the library to have a look and up comes the following function function populateFormElement(form, name, value) { // check that the named element exists in the form var name = name; // handle non-php naming var element = form[name]; if(element == undefined) { debug('No such element as ' + name); return false; } // debug options if(options.debug) { _populate.elements.push(element); } } Now looking at it one can see that it should print out also the name, but its not printing it out. so i'm guessing that retrieving the name form the json is not working correctly. Link is at http://www.ocdmonline.org/michael/edit%5Fnews.php with username: Testing and pass:test123 Any ideas?

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• Git/Mercurial (hg) opinion

  - by Richard

  First, let me say I'm not a professional programmer, but an engineer who had a need for it and had to learn. I was always working alone, so it was just me and my seven splitted personalities ... and we worked okey as a team :) Most of my stuff is done in C/Fortran/Matlab and so far I've been learning git to manage it all. However, although I've had no unsolvable problems with it, I've never been "that" happy with it ... for everything I cannot do, I hae to look up a book. And, for some time now I've been hearning a lot of good stuff about hg. Now, a coleague of mine will have to work with me on a project (I almost feel sorry for him) and he's started learning hg (says he likes it more), and I'm considering the switch myself. We work almost exclusivly on Windows platform (although I manage relatively ok using unix tools and things that come from that part of the world). So, I was wondering, in a described scenario, what problems could I expect with the switch. I heard that hg is rather more user friendly towards windows users, regarding the user interfaces. How does it handle repositories ? Does it create them the same way as git does (just one subdirectory in a working directory) and can I just copy the whole project directory (including git repo) and just carry them somewhere with no extra thinking ? (I really liked that when I was choosing over git/svn). Are there any good books on it that you can recommend (something like Pro Git, only for Hg). What are good ways to implement hg into Visual Studio/GVim for Windows, or into Windows Explorer so I can work relatively easily (I would like to avoid using the command line for everything regarding it, like in git shell). Is there something else I should be aware of (please, on this don't point me to other questions ... they just give me a ton of info, and I'm not sure what is it that I should take as important, and what to disregard). I'm trying to cut some time, since I cannot spend all that time relearning hg, like I did for git. I've also heard git is c project, while mercurial is python ... is there any noticeable difference in speed. git was pretty speedy ... will I encounter some waiting while working. Notice: All my projects are of let's say, middle size ... mostly numerical simulations ... 10-15000 lines (medium size?)

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• Efficiency of data structures in C99 (possibly affected by endianness)

  - by Ninefingers

  Hi All, I have a couple of questions that are all inter-related. Basically, in the algorithm I am implementing a word w is defined as four bytes, so it can be contained whole in a uint32_t. However, during the operation of the algorithm I often need to access the various parts of the word. Now, I can do this in two ways: uint32_t w = 0x11223344; uint8_t a = (w & 0xff000000) >> 24; uint8_t b = (w & 0x00ff0000) >> 16; uint8_t b = (w & 0x0000ff00) >> 8; uint8_t d = (w & 0x000000ff); However, part of me thinks that isn't particularly efficient. I thought a better way would be to use union representation like so: typedef union { struct { uint8_t d; uint8_t c; uint8_t b; uint8_t a; }; uint32_t n; } word32; Using this method I can assign word32 w = 0x11223344; then I can access the various parts as I require (w.a=11 in little endian). However, at this stage I come up against endianness issues, namely, in big endian systems my struct is defined incorrectly so I need to re-order the word prior to it being passed in. This I can do without too much difficulty. My question is, then, is the first part (various bitwise ands and shifts) efficient compared to the implementation using a union? Is there any difference between the two generally? Which way should I go on a modern, x86_64 processor? Is endianness just a red herring here? I could inspect the assembly output of course, but my knowledge of compilers is not brilliant. I would have thought a union would be more efficient as it would essentially convert to memory offsets, like so: mov eax, [r9+8] Would a compiler realise that is what happening in the bit-shift case above? If it matters, I'm using C99, specifically my compiler is clang (llvm). Thanks in advance.

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• Historical / auditable database

  - by Mark

  Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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• Button.MouseDown

  - by Gilad

  Hi Guys, I'm relatively new with WPF. I'm trying to understand the difference between MouseDownEvent and PreviewMouseDownEvent. I understand the WPF event strategies and i understand that the MouseDown event is a bubbling event and the PreviewMouseDown is a tunneling event. I also understand the order of which these events are being fired - according to this MSDN overview http://msdn.microsoft.com/en-us/library/ms742806.aspx#routing (there is a diagram with example there). So i tried to code some my self, check this for example: <Grid x:Name="grid" Width="250"> <StackPanel Mouse.MouseDown="StackPanel_MouseDown" PreviewMouseDown="StackPanel_PreviewMouseDown"> <WPFVisualizerExample:MyButton x:Name="B1" PreviewMouseDown="B1_PreviewMouseDown" MouseDown="B1_MouseDown" Margin="5,5,5,5"> <WPFVisualizerExample:MyButton x:Name="B2" PreviewMouseDown="B2_PreviewMouseDown" MouseDown="B2_MouseDown" Margin="5,5,5,5"> <WPFVisualizerExample:MyButton x:Name="B3" PreviewMouseDown="B3_PreviewMouseDown" MouseDown="B3_MouseDown" Margin="5,5,5,5">Click Me</WPFVisualizerExample:MyButton> </WPFVisualizerExample:MyButton> </WPFVisualizerExample:MyButton> </StackPanel> </Grid> I have an event handler for each of the events (the preview and non-preview) and i wanted to see what is happening, which of the event is being thrown (i have a message box shown for each event). The 'MyButton' user control simply extends the base Button and override the OnMouseDown and OnPreviewMouseDown to set the e.Handled false: protected override void OnMouseDown(System.Windows.Input.MouseButtonEventArgs e) { base.OnMouseDown(e); e.Handled = false; } protected override void OnPreviewMouseDown(System.Windows.Input.MouseButtonEventArgs e) { base.OnPreviewMouseDown(e); e.Handled = false; } (tried with this and without this). According to the MSDN overview (in the link above), if i have 3 elements then the events route should be as follows: PreviewMouseDown (tunnel) on root element. PreviewMouseDown (tunnel) on intermediate element #1. PreviewMouseDown (tunnel) on source element #2. MouseDown (bubble) on source element #2. MouseDown (bubble) on intermediate element #1. MouseDown (bubble) on root element. So I expected the the message boxes to be shown according to the above. From some reason - which I don't understand only the preview events are being thrown (according to what the MSDN says Preview_B1=Preview_B2=Preview_B3). My expectations were: Preview_B1=Preview_B2=Preview_B3=NonPreview_B3=NonPreview_B2=NonPreview_B1. But the non-preview events are not being thrown at all. So basically I don't understand the route of the events, from MSDN overview I understood that the route starts from the root element, goes down (tunnel) to the source element and then back up (bubble) to the root element, but this is not what happening in practice. It is really important for me to understand how this events are working, i probably miss-understand something basic here, your help will be appreciated. THANX!! -Gili

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• VS 2008 irritating copy constructor link dependency

  - by Paul Hollingsworth

  Hi guys, I've run into the following annoying and seemingly incorrect behaviour in the Visual Studio 2008 C++ compiler: Suppose I have a class library - Car.lib - that uses a "Car" class, with a header called "Car.h": class Car { public: void Drive() { Accelerate(); } void Accelerate(); }; What I'm actually trying to do is use the Car headers (for some other functions), but without having to link with Car.lib itself (the actual class is not called "Car" but I am sanitising this example). If I #include "Car.h" in the .cpp file used to build a managed C++ .dll, but never refer to Car, everything compiles and links fine. This is because I never instantiate a Car object. However, the following: namespace { class Car { public: Car(const Car& rhs) { Accelerate(); } void Accelerate(); }; } leaves me with the link error: Error 2 error LNK2001: unresolved external symbol "public: void __thiscall `anonymous namespace'::Car::Accelerate(void)" (?Accelerate@Car@?A0xce3bb5ed@@$$FQAEXXZ) CREObjectWrapper.obj CREObjectBuilderWrapper Note I've declared the whole thing inside an anonymous namespace so there's no way that the Car functions could be exported from the .DLL in any case. Declaring the copy constructor out-of-line makes no difference. i.e. the following also fails to link: class Car { public: Car(const Car& rhs); void Accelerate(); }; Car::Car(const Car& rhs) { Accelerate(); } It's something specifically to do with the copy constructor note, because the following, for example, does link: class Car { public: Car() { Accelerate(); } void Accelerate(); }; I am not a C++ standards guru but this doesn't seem correct to me. Surely the compiler still should not have had to even generate any code that calls the Car copy constructor. Can anyone confirm if this behaviour is correct? It's been a while since I used C++ - but I don't think this used to be an issue with Visual Studio 6.0 for example. Can anyone suggest a workaround that allows one to "re-use" the Accelerate method from within the copy constructor and still have the copy constructor declared inline?

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• Would Apache running on port 8080 prevent dynamically loaded scripts in JavaScript?

  - by editor

  Had a nice PHP/HTML/JS prototype working on my personal Linode, then tried to throw it into a work machine. The page adds a script tag dynamically with some JavaScript. It's a bunch of Google charts that update based on different timeslices. That code looks something like this: // jQuery $.post to send the beginning and end timestamps $.post("channel_functions.php", data_to_post, function(data){ // the data that's returned is the javascript I want to load var script = document.createElement('script'); var head= document.getElementsByTagName('head')[0]; var script= document.createElement('script'); var text = document.createTextNode(data); script.type= 'text/javascript'; script.id = 'chart_data'; script.appendChild(text); // Adding script tag to page head.appendChild(script); // Call the function I know were present in the script tag loadTheCharts(); }); function loadTheCharts() { // These are the functions that were loaded dynamically // By this point the script tag is supposed be loaded, added and eval'd function1(); function2(); } Function1() and function2() don't exist until they get added to the dom, but I don't call loadTheCharts() until after the $.post has run so this doesn't seem to be a problem. I'm one of those dirty PHP coders you mother warned you about, so I'm not well versed in JavaScript beyond what I've read in the typical go-to O'Reilly books. But this code worked fine on my personal dev server, so I'm wondering why it wouldn't work on this new machine. The only difference in setup, from what I can tell, is that the new machine is running on port 8080, so it's 192.168.blah.blah:8080/index.php instead of nicedomain.com/index.php. I see the code was indeed added to the dom when I use webmaster tools to "view generated source" but in Firebug I get an error like "function2() is undefined" even though my understanding was that all script tags are eval'ed when added to . My question: Given what I've laid out, and that the machine is running on :8080, is there a reason anyone can think of as to why a dynamically loaded function like function2() would be defined on the Linode and not on the machine running Apache on 8080?

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• Data aggregation mongodb vs mysql

  - by Dimitris Stefanidis

  I am currently researching on a backend to use for a project with demanding data aggregation requirements. The main project requirements are the following. Store millions of records for each user. Users might have more than 1 million entries per year so even with 100 users we are talking about 100 million entries per year. Data aggregation on those entries must be performed on the fly. The users need to be able to filter on the entries by a ton of available filters and then present summaries (totals , averages e.t.c) and graphs on the results. Obviously I cannot precalculate any of the aggregation results because the filter combinations (and thus the result sets) are huge. Users are going to have access on their own data only but it would be nice if anonymous stats could be calculated for all the data. The data is going to be most of the time in batch. e.g the user will upload the data every day and it could like 3000 records. In some later version there could be automated programs that upload every few minutes in smaller batches of 100 items for example. I made a simple test of creating a table with 1 million rows and performing a simple sum of 1 column both in mongodb and in mysql and the performance difference was huge. I do not remember the exact numbers but it was something like mysql = 200ms , mongodb = 20 sec. I have also made the test with couchdb and had much worse results. What seems promising speed wise is cassandra which I was very enthusiastic about when I first discovered it. However the documentation is scarce and I haven't found any solid examples on how to perform sums and other aggregate functions on the data. Is that possible ? As it seems from my test (Maybe I have done something wrong) with the current performance its impossible to use mongodb for such a project although the automated sharding functionality seems like a perfect fit for it. Does anybody have experience with data aggregation in mongodb or have any insights that might be of help for the implementation of the project ? Thanks, Dimitris

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• .NET Impersonate and file upload issues

  - by Jagd

  I have a webpage that allows a user to upload a file to a network share. When I run the webpage locally (within VS 2008) and try to upload the file, it works! However, when I deploy the website to the webserver and try to upload the file through the webpage, it doesn't work! The error being returned to me on the webserver says "Access to the path '\05prd1\emp\test.txt' is denied. So, obviously, this is a permissions issue. The network share is configured to allow full access both to me (NT authentication) and to the NETWORK SERVICE (which is .NET's default account and what we have set in our IIS application pool as the default user for this website). I have tried this with and without impersonation upon the webserver and neither way works, yet both ways work on my local machine (in other words, with and without impersonation works on my local machine). The code that does the file upload is below. Please note that the code below includes impersonation, but like I said above, I've tried it with and without impersonation and it's made no difference. if (fuCourses.PostedFile != null && fuCourses.PostedFile.ContentLength > 0) { System.Security.Principal.WindowsImpersonationContext impCtx; impCtx = ((System.Security.Principal.WindowsIdentity)User.Identity).Impersonate(); try { lblMsg.Visible = true; // The courses file to be uploaded HttpPostedFile file = fuCourses.PostedFile; string fName = file.FileName; string uploadPath = "\\\\05prd1\\emp\\"; // Get the file name if (fName.Contains("\\")) { fName = fName.Substring( fName.LastIndexOf("\\") + 1); } // Delete the courses file if it is already on \\05prd1\emp FileInfo fi = new FileInfo(uploadPath + fName); if (fi != null && fi.Exists) { fi.Delete(); } // Open new file stream on \\05prd1\emp and read bytes into it from file upload FileStream fs = File.Create(uploadPath + fName, file.ContentLength); using (Stream stream = file.InputStream) { byte[] b = new byte[4096]; int read; while ((read = stream.Read(b, 0, b.Length)) > 0) { fs.Write(b, 0, read); } } fs.Close(); lblMsg.Text = "File Successfully Uploaded"; lblMsg.ForeColor = System.Drawing.Color.Green; } catch (Exception ex) { lblMsg.Text = ex.Message; lblMsg.ForeColor = System.Drawing.Color.Red; } finally { impCtx.Undo(); } } Any help on this would be very appreciated!

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