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• Copy a LinkedList that has a Random Pointer in it

  - by Bragaadeesh

  Hi, First of all this is not a homework, this is an interview question that I got from a company I attended today. You have a singly linked list with the Node structure as the following class Node{ int data; Node next; Node random; } You have a typical singly linked list of length n. The random pointer in each node in the linkedlist randomly points to some Node within the linked list. The Question is to create a copy of the linked list efficiently into a different LinkedList. I said that I will first calculate the Random pointer's position in the linked list and store it in an array. Then create a new linked list normally. Then iterate through the linked list by setting the random pointer where they belong by reading the values stored from the array. I know its a very brute force technique and the interviewer asked me to come up with a better solution but I couldnt. Please can someone answer this? I can explain if the question is not clear.

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• multiple models in Rails with a shared interface

  - by dfondente

  I'm not sure of the best structure for a particular situation in Rails. We have several types of workshops. The administration of the workshops is the same regardless of workshop type, so the data for the workshops is in a single model. We collect feedback from participants about the workshops, and the questionnaire is different for each type of workshop. I want to access the feedback about the workshop from the workshop model, but the class of the associated model will depend on the type of workshop. If I was doing this in something other than Rails, I would set up an abstract class for WorkshopFeedback, and then have subclasses for each type of workshop: WorkshopFeedbackOne, WorkshopFeedbackTwo, WorkshopFeedbackThree. I'm unsure how to best handle this with Rails. I currently have: class Workshop < ActiveRecord::Base has_many :workshop_feedbacks end class Feedback < ActiveRecord::Base belongs_to :workshop has_many :feedback_ones has_many :feedback_twos has_many :feedback_threes end class FeedbackOne < ActiveRecord::Base belongs_to :feedback end class FeedbackTwo < ActiveRecord::Base belongs_to :feedback end class FeedbackThree < ActiveRecord::Base belongs_to :feedback end This doesn't seem like to the cleanest way to access the feedback from the workshop model, as accessing the correct feedback will require logic investigating the Workshop type and then choosing, for instance, @workshop.feedback.feedback_one. Is there a better way to handle this situation? Would it be better to use a polymorphic association for feedback? Or maybe using a Module or Mixin for the shared Feedback interface? Note: I am avoiding using Single Table Inheritance here because the FeedbackOne, FeedbackTwo, FeedbackThree models do not share much common data, so I would end up with a large sparsely populated table with STI.

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• Getting memory leak at NSURL connection in Iphone sdk.

  - by monish

  Hi guys, Here Im getting leak at the NSURL connection in my libxml parser can anyone tell how to resolve it. The code where leak generates is: - (BOOL)parseWithLibXML2Parser { BOOL success = NO; ZohoAppDelegate *appDelegate = (ZohoAppDelegate*) [ [UIApplication sharedApplication] delegate]; NSString* curl; if ([cName length] == 0) { curl = @"https://invoice.zoho.com/api/view/settings/currencies?ticket="; curl = [curl stringByAppendingString:appDelegate.ticket]; curl = [curl stringByAppendingString:@"&apikey="]; curl = [curl stringByAppendingString:appDelegate.apiKey]; curl = [curl stringByReplacingOccurrencesOfString:@"\n" withString:@""]; } NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:curl]]; NSLog(@"the request parserWithLibXml2Parser %@",theRequest); NSURLConnection *con = [[[NSURLConnection alloc] initWithRequest:theRequest delegate:self] autorelease];//Memory leak generated here at this line of code. //self.connection = con; //[con release]; // This creates a context for "push" parsing in which chunks of data that are // not "well balanced" can be passed to the context for streaming parsing. // The handler structure defined above will be used for all the parsing. The // second argument, self, will be passed as user data to each of the SAX // handlers. The last three arguments are left blank to avoid creating a tree // in memory. _xmlParserContext = xmlCreatePushParserCtxt(&simpleSAXHandlerStruct, self, NULL, 0, NULL); if(con != nil) { do { [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; } while (!_done && !self.error); } if(self.error) { //NSLog(@"parsing error"); [self.delegate parser:self encounteredError:nil]; } else { success = YES; } return success; } Anyone's help will be muck appreciated . Thank you, Monish.

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• C# ? Can anyone explain the strange behaviour?

  - by partizan

  Hi, guys. Here is the example with comments: class Program { // first version of structure public struct D1 { public double d; public int f; } // during some changes in code then we got D2 from D1 // Field f type became double while it was int before public struct D2 { public double d; public double f; } static void Main(string[] args) { // Scenario with the first version D1 a = new D1(); D1 b = new D1(); a.f = b.f = 1; a.d = 0.0; b.d = -0.0; bool r1 = a.Equals(b); // gives true, all is ok // The same scenario with the new one D2 c = new D2(); D2 d = new D2(); c.f = d.f = 1; c.d = 0.0; d.d = -0.0; bool r2 = c.Equals(d); // false, oops! this is not the result i've expected for } } So, what do you think about this?

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• How do software projects go over budget and under-deliver?

  - by Carlos

  I've come across this story quite a few times here in the UK: NHS Computer System Summary: We're spunking £12 Billion on some health software with barely anything working. I was sitting the office discussing this with my colleagues, and we had a little think about. From what I can see, all the NHS needs is a database + middle tier of drugs/hospitals/patients/prescriptions objects, and various GUIs for doctors and nurses to look at. You'd also need to think about security and scalability. And you'd need to sit around a hospital/pharmacy/GPs office for a bit to figure out what they need. But, all told, I'd say I could knock together something with that kind of structure in a couple of days, and maybe throw in a month or two to make it work in scale. If I had a few million quid, I could probably hire some really excellent designers to make a maintainable codebase, and also buy appropriate hardware to run the system on. I hate to trivialize something that seems to have caused to much trouble, but to me it looks like just a big distributed CRUD + UI system. So how on earth did this project bloat to £12B without producing much useful software? As I don't think the software sounds so complicated, I can only imagine that something about how it was organised caused this mess. Is it outsourcing that's the problem? Is it not getting the software designers to understand the medical business that caused it? What are your experiences with projects gone over budget, under delivered? What are best practices for large projects? Have you ever worked on such a project?

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• Echoing variable construct instead of content

  - by danp

  I'm merging two different versions of a translations array. The more recent version has a lot of changes, over several thousand lines of code. To do this, I loaded and evaluated the new file (which uses the same structure and key names), then loaded and evaluated the older version, overwriting the new untranslated values in the array with the values we already have translated. So far so good! However, I want to be able to echo out the constructor for this new merged array so I can cut and paste it into the new translation file, and have job done (apart from completing the rest of the translations..). The code looks like this (lots of different keys, not just index): $lang["index"]["chart1_label1"] = "Subscribed"; $lang["index"]["chart1_label2"] = "Unsubscribed"; And the old.. $lang["index"]["chart1_label1"] = "Subscrito"; $lang["index"]["chart1_label2"] = "Não subscrito"; After loading the two files, I end up with a merged $lang array, which I then want to echo out in the same form, so it can be used by the project. However, when I do something like this.. foreach ($lang as $key => $value) { if (is_array($value)) { foreach ($value as $key2 => $value2) { echo "$lang['".$key."']"; // ... etc etc } } } ..obviously I get "ArrayIndex" etc etc instead of "$lang". How to echo out $lang without it being evaluated..? Once this is working, can add in the rest of the brackets etc (I realise they are missing), but just want to make this part work first. If there's a better way to do this, all ears too! Thanks.

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• Two floating div's, one underneath. works in every browser except IE

  - by Veltar

  So I have an html-structure that looks like this: <div id="contact-wrapper"> <div> <h4>België</h4> <p>Tuinwijklaan 79<br /> 9000 Gent<br /> Tel. 0468/115967<br /> [email protected]<br /> </p> </div> <div> <h4>Nederland</h4> <p>Kerkstraat 423-C<br /> 1017 HX Amsterdam<br /> Tel: +32 468 11 59 67<br /> [email protected] </p> </div><br /> <a id="link-contact" href="#">Contacteer ons</a> </div> The two div's are displayed next to each other, and the link under it, like this: But in ie9 it shows like this: This is my css for the divs: footer div#contact-wrapper, footer h1 { float: left; } footer div#contact-wrapper div { margin: 16px 0px 0px 45px; float: left; } footer div#contact-wrapper div:first-of-type { padding-right: 30px; margin-left: 60px; border-right: 1px dashed #a3b0b9; } footer div#contact-wrapper a#link-contact { display: inline-block; background: #ffffff url('../img/contact-arrow.gif') no-repeat 95% center; border: 4px solid #bbc2c7; font-size: 12px; color: #bbc2c7; margin: 5px 0px 0px 60px; padding: 3px 0px 3px 5px; width: 150px; }

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• IE7 - jquery addClass() breaks floating elements

  - by Patrick

  I have this nav that uses addClass('hover') when the mouse is rolled over an item. This works fine except in IE7 when the addClass function is called every element with float:left stops floating and the page totally loses its structure. This is my JS: _this.position_sub_menus = function(){ $('#header #nav > ul > li').mouseenter( function(e){ pos = $(this).offset(); height = $(this).height(); lvl2 = '#' + $(this).attr('id') + '-submenu'; if( $(this).position().left > ($('#nav').width()/2)){ pos.left = pos.left - $(lvl2).width() + $(this).width(); } $(this).addClass('hover'); $(lvl2).show(); $(lvl2).css( { 'left' : (pos.left - 12) + 'px', 'top' : pos.top + height + 'px'}); } ); This is the CSS of the of the elements that break: display: inline; float: left; margin-left: 10px; margin-right: 10px; position: relative; It's CSS from the 960 grid system. When I comment out the $(this).addClass('hover'); line the floated elements dont break. Is anyone familiar with this IE7 problem? Thanks guys

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• JSF2: Re-render all components on page that have a given ID, without absolute paths

  - by tlind

  Is there any way in JSF 2.0/PrimeFaces of re-rendering all components (using the PrimeFaces update="id1 id2..." attribute or the <f:ajax render="..."/> tag) that have got a given ID, regardless of whether they are in the same form that contains the button triggering the AJAX re-render or not? For example, I want my button to re-render all sections on a page that visualize the user's current shopping basket. Right now, I always have to specify the absolute path to the components that I want to get updated, e.g. update=":header:basket :left-sidebar:menu:basket" which is rather impractical if the structure of the page changes (besides, I have not been able to figure out the correct path for one of these components). I already tried to implement a custom EL function like this, which traverses the component tree: update="{utilBean.findAllComponentsMatchingId('basket')}" but at the time that function is evaluated, apparently not the entire component tree has been set up as it doesn't contain the components I am looking for. How can I deal with this? There certainly must be an easy way of doing AJAX-based updates of sections of the page that are not part of the current <h:form>? Thanks!

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• [javascript] Populating jsTree based on XML data uploaded to server folder

  - by PFM

  tl:dr How can I populate jsTree based on a folder location instead of an exact XML url? I'm looking for a little direction on this project. Currently I am trying to copy file structures of hard drives as XML files and recreate them using jsTree on the webserver for a completely independent version of the file structure. I have some python script that outputs XML files that are formed to jsTree and automatically uploads to a folder on the server. The problem is now I am a little lost because I have to manually enter each XML file into jsTree code for it to display so I have multiple entries like this: $("#tree1") .jstree({ "plugins" : [ "themes", "xml_data", "ui", "search", "types" ], "xml_data" : { "ajax" : { "url" : "./XML_DATA/DRIVE1.xml" }, "xsl" : "nest" }, I see in the documentation that instead of populated by the direct file the folders are populated by "server.php" but no where in the php code does it point to any directories or files. After considering the problem I thought of a few solutions and could use some advice on them: Should I be trying to write php code to automatically look through my XML_DATA folder to upload each XML file? Should I just upload all the XML to mySQL and populate my tree based on that? Should the javascript be the code looking through the server's folder for XML files? All the XML is formed the same way but the number of XML files on the server will increase and will have to be refreshed as well as they will be overwritten with changes. Any direction would be appreciated, thanks.

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• Reducing Duplicated Code

  - by cam

  I have some code that works on the color structure like this public void ChangeColor() { thisColor.R = thisColor.R + 5; } Now I need to make a method that changes a different variable depending on what it is passed. Here is what the code looks like now. public void ChangeColor(int RGBValue) { switch(RGBValue) { case 1: thisColor.R = thisColor.R + 5; break; case 2: thiscolor.B = thisColor.B + 5; break; } } Now, this is something I would normally never question, I'd just throw a #region statement around it and call it a day, but this is just an example of what I have, the actual function is quite long. I want it to look like this: public void ChangeColor(int RGBValue) { thiscolor.RGBValue = thiscolor.RGBValue; } So essentially the value would refer to the variable being used. Is there a name for this? Is this what Reflection is for? Or something like that... Is there a way to do this?

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• Pointer inside a struct / thread

  - by bruno

  Hi! I have this warning "warning: assignment from incompatible pointer type " in this line: data1->transformed_block[l] = &transformed_block[l]; - void print_message_function ( void *ptr ) { dt *data; data = (dt *) ptr; printf("Dentro da thread Numero0: %ld\n", data->L_norm_NewBlock); pthread_exit(0); } typedef struct data_thread { long L_norm_NewBlock; int Bsize_X; int Bsize_Y; int *transformed_block[MAX_LEVEL]; long L_norm_OrigBlock; } dt; void function() { int *transformed_block[MAX_LEVEL]; pthread_t thread1; dt *data1; pthread_attr_t attr; pthread_attr_init(&attr); //Fills structure data1 = (dt *) malloc(sizeof(dt)); data1->transformed_block[l] = &transformed_block[l]; data1->L_norm_NewBlock=0; data1->Bsize_Y = Bsize_Y; data1->Bsize_X = Bsize_X; pthread_create(&thread1, &attr, (void *) &print_message_function, (void *) &data1); } I want to get rid of that warning, and the values i get inside the thread are wrong. For example data1-L_norm_NewBlock=0; in the thread guives me a differente value (not 0 like it should be).

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• How do I handle freeing unmanaged structures on application close?

  - by LostKaleb

  I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } }

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• Extra NotifyIcon shown in system tray

  - by Kettch19

  I'm having an issue with an app where my NotifyIcon displays an extra icon. The steps to reproduce it are easy, but the problem is that the extra icon shows up after any of the actual codebehind we've added fires. Put simply, clicking a button triggers execution of method FooBar() which runs all the way through fine but its primary duty is to fire a backgroundworker to log into another of our apps. It only appears if this particular button is clicked. Strangely enough, we have a WndProc method override and if I step through until the extra NotifyIcon appears, it always appears during this method so something else beyond the codebehind must be triggering the behavior. Our WndProc method is currently (although I don't think it's caused by the WndProc): Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message) 'Check for WM_COPYDATA message from other app or drag/drop action and handle message If m.Msg = NativeMethods.WM_COPYDATA Then ' get the standard message structure from lparam Dim CD As NativeMethods.COPYDATASTRUCT = m.GetLParam(GetType(NativeMethods.COPYDATASTRUCT)) 'setup byte array Dim B(CD.cbData) As Byte 'copy data from memory into array Runtime.InteropServices.Marshal.Copy(New IntPtr(CD.lpData), B, 0, CD.cbData) 'Get message as string and process ProcessWMCopyData(System.Text.Encoding.Default.GetString(B)) 'empty array Erase B 'set message result to 'true', meaning message handled m.Result = New IntPtr(1) End If 'pass on result and all messages not handled by this app MyBase.WndProc(m) End Sub The only place in the code where the NotifyIcon in question is manipulated at all is in the following event handler (again, don't think this is the culprit, but just for more info): Private Sub TrayIcon_MouseDoubleClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles TrayIcon.MouseDoubleClick If Me.Visible Then Me.Hide() Else PositionBottomRight() Me.Show() End If End Sub The backgroundworker's DoWork is as follows (just a class call to log in to our other app, but again just for info): Private Sub LoginBackgroundWorker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles LoginBackgroundWorker.DoWork Settings.IsLoggedIn = _wdService.LogOn(Settings.UserName, Settings.Password) End Sub Does anyone else have ideas on what might be causing this or how to possibly further debug this? I've been banging my head on this without seeing a pattern so another set of eyes would be extremely appreciated. :) I've posted this on MSDN winforms forums as well and have had no luck there so far either.

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• multiple-to-one relationship mysql, submissions

  - by Yulia

  Hello, I have the following problem. Basically I have a form with an option to submit up to 3 images. Right now, after each submission it creates 3 records for album table and 3 records for images. I need it to be one record for album and 3 for images, plus to link images to the album. I hope it all makes sense... Here is my structure. TABLE `albums` ( `id` int(11) NOT NULL auto_increment, `title` varchar(50) NOT NULL, `fullname` varchar(40) NOT NULL, `email` varchar(100) NOT NULL, `created_at` datetime NOT NULL, `theme_id` int(11) NOT NULL, `description` int(11) NOT NULL, `vote_cache` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=20 ; TABLE `images` ( `id` int(11) NOT NULL auto_increment, `album_id` int(11) NOT NULL, `name` varchar(30) NOT NULL, and my code function create_album($params) { db_connect(); $query = sprintf("INSERT INTO albums set albums.title = '%s', albums.email = '%s', albums.discuss_url = '%s', albums.theme_id = '%s', albums.fullname = '%s', albums.description = '%s', created_at = NOW()", mysql_real_escape_string($params['title']), mysql_real_escape_string($params['email']), mysql_real_escape_string($params['theme_id']), mysql_real_escape_string($params['fullname']), mysql_real_escape_string($params['description']) ); $result = mysql_query($query); if(!$result) { return false; } $album_id = mysql_insert_id(); return $album_id; } if(!is_uploaded_file($_FILES['userfile']['tmp_name'][$i])) { $warning = 'No file uploaded'; } elseif is_valid_file_size($_FILES['userfile']['size'][$i])) { $_POST['album']['theme_id'] = $theme['id']; create_album($_POST['album']); mysql_query("INSERT INTO images(name) VALUES('$newName')"); copy($_FILES['userfile']['tmp_name'][$i], './photos/'.$original_dir.'/' .$newName.'.jpg');

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• Python NameError when attempting to use a user-defined class

  - by Michael Herold

  I'm getting a weird instance of a NameError when attempting to use a class I wrote. In a directory, I have the following file structure: dir/ ReutersParser.py test.py reut-xxx.sgm Where my custom class is defined in ReutersParser.py and I have a test script defined in test.py. The ReutersParser looks something like this: from sgmllib import SGMLParser class ReutersParser(SGMLParser): def __init__(self, verbose=0): SGMLParser.__init__(self, verbose) ... rest of parser if __name__ == '__main__': f = open('reut2-short.sgm') s = f.read() p = ReutersParser() p.parse(s) It's a parser to deal with SGML files of Reuters articles. The test works perfectly. Anyway, I'm going to use it in test.py, which looks like this: from ReutersParser import ReutersParser def main(): parser = ReutersParser() if __name__ == '__main__': main() When it gets to that parser line, I'm getting this error: Traceback (most recent call last): File "D:\Projects\Reuters\test.py", line 34, in <module> main() File "D:\Projects\Reuters\test.py", line 19, in main parser = ReutersParser() File "D:\Projects\Reuters\ReutersParser.py", line 38, in __init__ SGMLParser.__init__(self, verbose) NameError: global name 'sgmllib' is not defined For some reason, when I try to use my ReutersParser in test.py, it throws an error that says it cannot find sgmllib, which is a built-in module. I'm at my wits' end trying to figure out why the import won't work. What's causing this NameError? I've tried importing sgmllib in my test.py and that works, so I don't understand why it can't find it when trying to run the constructor for my ReutersParser.

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• [Ruby on Rails] complex model relationship

  - by siulamvictor

  I am not sure am I doing these correct. I have 3 models, Account, User, and Event. Account contains a group of Users. Each User have its own username and password for login, but they can access the same Account data under the same Account. Events is create by a User, which other Users in the same Account can also read or edit it. I created the following migrations and models. User migration class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.integer :account_id t.string :username t.string :password t.timestamps end end def self.down drop_table :users end end Account migration class CreateAccounts < ActiveRecord::Migration def self.up create_table :accounts do |t| t.string :name t.timestamps end end def self.down drop_table :accounts end end Event migration class CreateEvents < ActiveRecord::Migration def self.up create_table :events do |t| t.integer :account_id t.integer :user_id t.string :name t.string :location t.timestamps end end def self.down drop_table :events end end Account model class Account < ActiveRecord::Base has_many :users has_many :events end User model class User < ActiveRecord::Base belongs_to :account end Event model class Event < ActiveRecord::Base belongs_to :account belongs_to :user end so.... Is this setting correct? Every time when a user create a new account, the system will as for the user information, i.e. username and password. How can I add them into correct tables? How can I add a new event? I am sorry for such a long question. I am not very understand the rails way in handling such data structure. Thank you guys for answering me. :)

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• Within a DLL, how is the function table structured?

  - by Willi Ballenthin

  I've been looking into the implementation of a device library that doesn't explicitly support my operating system. In particular, I have a disassembled DLL, and a fair amount of supporting source code. Now, how is the function table/export table structured? My understanding is that the first structure of the .data section is a table of VRAs. Next is a table of strings linked by index to that first address table. This makes sense to me, as a linker could translate between symbols and addresses. How do functions referenced by ordinals fit into this picture? How does one know which function has such and such ordinal number, and how does the linker resolve this? In other words, given that some other DLL imports SOME_LIBRARY_ordinal_7, how does the linker know which function to work with? Thanks, all! edit More information... Im working with the FTDI libraries, and would like to resolve which function is being invoked. In particular, I see something like: extern FTD2XX_Ordinal_28: near how might I go about determining which function is being referenced, and how does the linker do this?

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• Is there a way to create subdatabases as a kind of subfolders in sql server?

  - by user193655

  I am creating an application where there is main DB and where other data is stored in secondary databases. The secondary databases follow a "plugin" approach. I use SQL Server. A simple installation of the application will just have the mainDB, while as an option one can activate more "plug-ins" and for every plug-in there will be a new database. Now why I made this choice is because I have to work with an exisiting legacy system and this is the smartest thing I could figure to implement the plugin system. MainDB and Plugins DB have exactly the same schema (basically Plugins DB have some "special content", some important data that one can use as a kind of template - think to a letter template for example - in the application). Plugin DBs are so used in readonly mode, they are "repository of content". The "smart" thing is that the main application can also be used by "plugin writers", they just write a DB inserting content, and by making a backup of the database they creaetd a potential plugin (this is why all DBs has the same schema). Those plugins DB are downloaded from internet as there is a content upgrade available, every time the full PlugIn DB is destroyed and a new one with the same name is creaetd. This is for simplicity and even because the size of this DBs is generally small. Now this works, anyway I would prefer to organize the DBs in a kind of Tree structure, so that I can force the PlugIn DBs to be "sub-DBs" of the main application DB. As a workaround I am thinking of using naming rules, like: ApplicationDB (for the main application DB) ApplicationDB_PlugIn_N (for the N-th plugin DB) When I search for plugin 1 I try to connect to ApplicationDB_PlugIn_1, if I don't find the DB i raise an error. This situation can happen for example if som DBA renamed ApplicationDB_Plugin_1. So since those Plugin DBs are really dependant on ApplicationDB only I was trying to "do the subfolder trick". Can anyone suggest a way to do this? Can you comment on this self-made plugin approach I decribed above?

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• Codeigniter: how should I restructure db schema?

  - by Kevin Brown

  I don't even know if that's the right term. May it be known that I'm a major novice! I have three tables: users, profiles, and survey. Each one has user_id as it's first field, (auto-increment for users), and they're all tied by a foreign key constraint, CASCADE on DELETE. Currently, for each user, let's say user_id 1, they have a corresponding db entry in the other tables. For profiles it lists all their information, and the survey table holds all their survey information. Now I must change things...darn scope creep. Users need the ability to have multiple survey results. I imagine that this would be similar to a comment table for a blog... My entire app runs around the idea that a single user is linked to a constraining profile and survey. How should I structure my db? How should I design my app's db so that a user can have multiple tests/profiles for the test? Please assist! Any advice, information and personal-knowledge is appreciated! Right now the only way I know how to accompany my client is to create a pseudo-user for each test (so unnecessary) and list them in a view table (called "your tests")-- these are obtained from the db by saying: where user_id=manager_id

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• Best solution for __autoload

  - by tpk

  As our PHP5 OO application grew (in both size and traffic), we decided to revisit the __autoload() strategy. We always name the file by the class definition it contains, so class Customer would be contained within Customer.php. We used to list the directories in which a file can potentially exist, until the right .php file was found. This is quite inefficient, because you're potentially going through a number of directories which you don't need to, and doing so on every request (thus, making loads of stat() calls). Solutions that come to my mind... -use a naming convention that dictates the directory name (similar to PEAR). Disadvantages: doesn't scale too great, resulting in horrible class names. -come up with some kind of pre-built array of the locations (propel does this for its __autoload). Disadvantage: requires a rebuild before any deploy of new code. -build the array "on the fly" and cache it. This seems to be the best solution, as it allows for any class names and directory structure you want, and is fully flexible in that new files just get added to the list. The concerns are: where to store it and what about deleted/moved files. For storage we chose APC, as it doesn't have the disk I/O overhead. With regards to file deletes, it doesn't matter, as you probably don't wanna require them anywhere anyway. As to moves... that's unresolved (we ignore it as historically it didn't happen very often for us). Any other solutions?

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• Counting a cell up per Objects

  - by Auro

  hey i got a problem once again :D a little info first: im trying to copy data from one table to an other table(structure is the same). now one cell needs to be incremented, beginns per group at 1 (just like a histroy). i have this table: create table My_Test/My_Test2 ( my_Id Number(8,0), my_Num Number(6,0), my_Data Varchar2(100)); (my_Id, my_Num is a nested PK) if i want to insert a new row, i need to check if the value in my_id already exists. if this is true then i need to use the next my_Num for this Id. i have this in my Table: My_Id My_Num My_Data 1 1 'test1' 1 2 'test2' 2 1 'test3' if i add now a row for my_Id 1, the row would look like this: i have this in my Table: My_Id My_Num My_Data 1 3 'test4' this sounds pretty easy ,now i need to make it in a SQL and on SQL Server i had the same problem and i used this: Insert Into My_Test (My_Id,My_Num,My_Data) SELECT my_Id, ( SELECT CASE ( CASE MAX(a.my_Num) WHEN NULL THEN 0 Else Max(A.My_Num) END) + b.My_Num WHEN NULL THEN 1 ELSE ( CASE MAX(a.My_Num) WHEN NULL THEN 0 Else Max(A.My_Num) END) + b.My_Num END From My_Test A where my_id = 1 ) ,My_Data From My_Test2 B where my_id = 1; this Select gives null back if no Rows are found in the subselect is there a way so i could use max in the case? and if it give null back it should use 0 or 1? greets Auro

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• Array Indexing Properties of A Class

  - by Chris

  I have a class that has several properties: class Person { string Name; int Age; DateTime BirthDate; } Then I have a sort of wrapper class with a List<Person>. Within this wrapper class I want to be able to do something like Wrapper["Name"] that returns a new List<string> using .Select(x=>x.Name). How do I create a wrapper class around an IEnumerable that supports mapping a string to the Property name? Something like the pseudo code below, but obviously it doesn't work. I'm 99.9% sure the solution will have to use Reflection and thats fine. class Wrapper { List<Person> PersonList; List<dynamic> this[string Column] { return PersonList.Select(x => x.[Column]).ToList(); } } This may not seem like a good design, but its a fix to eventually enable the correct design from .NET 2.0 days. As I have it right now, the data is stored in Columns, so there is actually a List of Lists within my class right now. Using the above example there would be three ILists (with a string Title) Name, Age, and Birthdate. Everything is currently predicated on addressing the columns by their "string" name. I'm trying to convert the data structure to row based with an IEnumberable interface to allow Linq eventually while still maintaining the functionality of my current code. Is converting the code to a Row based IEnumberable a good idea?

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• In Silverlight, what structures, aside of the ListBox, can be used for binding?

  - by Aidenn

  I need to simply provide the content of a property to a custom User Control in Silverlight. My control is something like this: <UserControl x:Class="SilverlightApplication.Header" 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" d:DesignWidth="300" d:DesignHeight="120"> <Grid x:Name="Header_Layout"> <StackPanel x:Name="hiHeaderContent" Width="Auto" Margin="73,8,8,8"> <TextBlock x:Name="User:" Text="{Binding name}" /> </StackPanel> </Grid> I try to use this User Control from another control where I try to pass the parameter "name" to the previous UserControl ("Header"). I don't need to create a "ListBox" as I will only have 1 header, so I try to avoid doing: <ListBox x:Name="HeaderListBox" Grid.Row="0"> <ListBox.ItemTemplate> <DataTemplate> <SilverlightApplication:Header/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> in order to send the "User" account using: HeaderListBox.ItemsSource = name; Is there any other structure I can use instead of the ListBox to pass the parameter just once? It won't be a list, it's just a header... Thank you!

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• Fast serialization/deserialization of structs

  - by user256890

  I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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