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  • Strange layout behaviour

    - by andrii
    I am a little bit confused. Here is an small web page. There are two main div-s: top and mainBlock. First contain image. The problem is that firebug shows that div#top's height is equal to 0 and because of that the next div mainBlock moves up. If I would delete this peace of code: div#logo{ float: left; } everything will start working fine and div#mainBlock will be below the div#top. Could you, please, explain me how it works and how to avoid this in proper way? Here is my code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/> <title>Paralab - Website &amp; interface design, web apps development, usability</title> <style text="text/css"> html, body{ } div#logo{ float: left; } #top{ width: 100%; } #mainBlock{ width:100%; } </style> </head> <body> <div id="top"> <div id="logo"> <img alt="logo" src="img/logo.png" /> </div> </div> <div id="mainBlock"> Contact Us </div> </body> </html>

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  • Drupal Studs help me with my form_alter hook ( I am almost there)

    - by user363036
    So I think I am almost there conceptually but need some missing pointers. Objective is to add a few more fields to the normal user registration form, style it a little, then submit it with storing the extra fields in a table. This is what I have so far. Can someone give me the final nudge and get me going. Please help me. Also how do I apply some minor styling like aligning the new form fields ? Thank you so much !!!!!!!!! function module_menu() { $items = array(); $items['school/registration'] = array( 'title' = 'Upgraded Registration Form', 'page callback' ='module_school_register', 'type' = MENU_CALLBACK ); return $items; }//end of the function function module_school_register(){ return drupal_get_form('form_school_register'); }//end of the function function module_school_form_alter(&$form, $form_state, $form_id) { dsm($form_id); if ($form_id == 'user_registration_form') { // modify the "#submit" form property by prepending another submit handler array $form['#submit'] = array_merge( array('_module_registration_submit' = array()), $form['#submit'] ); } } function _module_registration_submit($form_id, $form_values) { // store extra data in different table } function module_registration_validate($form, &$form_state) { $error=0; //Validation stuff here, set $error to true if something went wrong, or however u want to do this. Completely up to u in how u set errors. if ($error) { form_set_error('new_field_name', 'AHH SOMETHING WRONG!'); } }

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  • Passive and active sockets

    - by davsan
    Quoting from this socket tutorial: Sockets come in two primary flavors. An active socket is con­nect­ed to a remote active socket via an open data con­nec­tion... A passive socket is not con­nect­ed, but rather awaits an in­com­ing con­nec­tion, which will spawn a new active socket once a con­nec­tion is es­tab­lished ... Each port can have a single passive socket binded to it, await­ing in­com­ing con­nec­tions, and mul­ti­ple active sockets, each cor­re­spond­ing to an open con­nec­tion on the port. It's as if the factory worker is waiting for new mes­sages to arrive (he rep­re­sents the passive socket), and when one message arrives from a new sender, he ini­ti­ates a cor­re­spon­dence (a con­nec­tion) with them by del­e­gat­ing someone else (an active socket) to ac­tu­al­ly read the packet and respond back to the sender if nec­es­sary. This permits the factory worker to be free to receive new packets. ... Then the tutorial explains that, after a connection is established, the active socket continues receiving data until there are no remaining bytes, and then closes the connection. What I didn't understand is this: Suppose there's an incoming connection to the port, and the sender wants to send some little data every 20 minutes. If the active socket closes the connection when there are no remaining bytes, does the sender have to reconnect to the port every time it wants to send data? How do we persist a once established connection for a longer time? Can you tell me what I'm missing here? My second question is, who determines the limit of the concurrently working active sockets?

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  • Query notation for the sitecore 'source' field in template builder

    - by M.R.
    I am trying to set the the source field of a template using the query notation (or xpath - whichever works), but none of them seems to be working. My content tree is a multisite content tree: France --Page 1 ----Page1A -------Page1AA --Page 2 --Page 3 --METADATA ----Regions US --Page 1 ----Page1A -------Page1AA --Page 2 --Page 3 --METADATA ----Regions Each site has its own METADATA folder, and I want it so that when adding a page inside each of the main country nodes, I want the values to reflect whatever is in the METADATA of that site. I have two different fields for now - a droplink and a treelistex field. So I thought I can just get the parent item that is a country site, and get the metadata folder for that. When I put the following query in both the fields, I get different results: query:./ancestor::*[@@templatename='CountryHome']/METADATA/Regions/* For the droplink field, I get only the first Region (one item) For the treelistex field, I get the entire content tree I then tried to modify the query a little bit and took the 'query' notation out ./ancestor::*[@@templatename='CountryHome']/METADATA/Regions/* If I go to the developer center/xpath builder, and set the context node to any item underneath the main country site, it returns me exactly what I need, but when I put this in the source, I get the entire content tree in both the cases. Help!

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  • Using data binding on value which is a FrameworkElement

    - by JaredPar
    One of my data sources produces a collection of values which are typed to the following interface public interface IData { string Name { get; } FrameworkElement VisualElement { get; } } I'd like to use data binding in WPF to display a collection of IData instances in a TabControl where the Name value becomes the header of the tab and the VisualElement value is displayed as the content of the corresponding tab. Binding the header is straight forward. I'm stuck though on how to define a template which allows me to display the VisualElement value. I've tried a number of solutions with little success. My best attempt is as follows. <TabControl ItemsSource="{Binding}"> <TabControl.ItemTemplate> <DataTemplate> <Label Content="{Binding Name}"/> </DataTemplate> </TabControl.ItemTemplate> <TabControl.ContentTemplate> <DataTemplate> How do I display VisualElement here? </DataTemplate> </TabControl.ContentTemplate> </TabControl> I'm still very new to WPF so I could be missing the obvious here.

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  • Unobtrusive, self-hosted comments function to put onto existing web pages

    - by Pekka
    I am building a new site which will consist of a mix of dynamic and static pages. I would like to add commenting functionality to those pages with as little work as possible. I'm curious as to whether such a solution exists in PHP. The ideal set of features would be: Completely independent from the surrounding page / site: PHP code gets dropped into page, a page ID is added, done. Simple "write a comment" form Comments for each page are displayed using a PHP function Nice, clean output of <ul><li>.... that can be styled by the surrounding site Optional Captcha Optional Gravatar sensitivity Minimalistic administration area to moderate/delete comments, no ACL, can protect it using .htaccess The ideal integreation would be like this: <?php show_comments("my_page_name"); ?> this would 1. display a form to add a new comment that gets automatically associtated with my_page_name; and 2. display all comments that were made through this form using this ID. Does anybody know a solution like this? Bounty I am setting up a bounty because while there were some good suggestions, they all point to external services. I'm really curious to see whether there isn't anything self-hosted around. If this doesn't exist yet, it sure would be great to see as an Open Source project.

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  • Point data structure for a sketching application

    - by bebraw
    I am currently developing a little sketching application based on HTML5 Canvas element. There is one particular problem I haven't yet managed to find a proper solution for. The idea is that the user will be able to manipulate existing stroke data (points) quite freely. This includes pushing point data around (ie. magnet tool) and manipulating it at whim otherwise (ie. altering color). Note that the current brush engine is able to shade by taking existing stroke data in count. It's a quick and dirty solution as it just iterates the points in the current stroke and checks them against a distance rule. Now the problem is how to do this in a nice manner. It is extremely important to be able to perform efficient queries that return all points within given canvas coordinate and radius. Other features, such as space usage, should be secondary to this. I don't mind doing some extra processing between strokes while the user is not painting. Any pointers are welcome. :)

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  • Should I use two queries, or is there a way to JOIN this in MySQL/PHP?

    - by Jack W-H
    Morning y'all! Basically, I'm using a table to store my main data - called 'Code' - a table called 'Tags' to store the tags for each code entry, and a table called 'code_tags' to intersect it. There's also a table called 'users' which stores information about the users who submitted each bit of code. On my homepage, I want 5 results returned from the database. Each returned result needs to list the code's title, summary, and then fetch the author's firstname based on the ID of the person who submitted it. I've managed to achieve this much so far (woot!). My problem lies when I try to collect all the tags as well. At the moment this is a pretty big query and it's scaring me a little. Here's my problematic query: SELECT code.*, code_tags.*, tags.*, users.firstname AS authorname, users.id AS authorid FROM code, code_tags, tags, users WHERE users.id = code.author AND code_tags.code_id = code.id AND tags.id = code_tags.tag_id ORDER BY date DESC LIMIT 0, 5 What it returns is correct looking data, but several repeated rows for each tag. So for example if a Code entry has 3 tags, it will return an identical row 3 times - except in each of the three returned rows, the tag changes. Does that make sense? How would I go about changing this? Thanks! Jack

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  • How to manage sessions in NHibernate unit tests?

    - by Ben
    I am a little unsure as to how to manage sessions within my nunit test fixtures. In the following test fixture, I am testing a repository. My repository constructor takes in an ISession (since I will be using session per request in my web application). In my test fixture setup I configure NHibernate and build the session factory. In my test setup I create a clean SQLite database for each test executed. [TestFixture] public class SimpleRepository_Fixture { private static ISessionFactory _sessionFactory; private static Configuration _configuration; [TestFixtureSetUp] // called before any tests in fixture are executed public void TestFixtureSetUp() { _configuration = new Configuration(); _configuration.Configure(); _configuration.AddAssembly(typeof(SimpleObject).Assembly); _sessionFactory = _configuration.BuildSessionFactory(); } [SetUp] // called before each test method is called public void SetupContext() { new SchemaExport(_configuration).Execute(true, true, false); } [Test] public void Can_add_new_simpleobject() { var simpleObject = new SimpleObject() { Name = "Object 1" }; using (var session = _sessionFactory.OpenSession()) { var repo = new SimpleObjectRepository(session); repo.Save(simpleObject); } using (var session =_sessionFactory.OpenSession()) { var repo = new SimpleObjectRepository(session); var fromDb = repo.GetById(simpleObject.Id); Assert.IsNotNull(fromDb); Assert.AreNotSame(simpleObject, fromDb); Assert.AreEqual(simpleObject.Name, fromDb.Name); } } } Is this a good approach or should I be handling the sessions differently? Thanks Ben

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  • Is there a limit for the number of files in a directory on an SD card?

    - by jamesh
    I have a project written for Android devices. It generates a large number of files, each day. These are all text files and images. The app uses a database to reference these files. The app is supposed to clear up these files after a little use (perhaps after a few days), but this process may or may not be working. This is not the subject of this question. Due to a historic accident, the organization of the files are somewhat naive: everything is in the same directory; a .hidden directory which contains a zero byte .nomedia file to prevent the MediaScanner indexing it. Today, I am seeing an error reported: java.io.IOException: Cannot create: /sdcard/.hidden/file-4200.html at java.io.File.createNewFile(File.java:1263) Regarding the sdcard, I see it has plenty of storage left, but counting $ cd /Volumes/NO_NAME/.hidden $ ls | wc -w 9058 Deleting a number of files seems to have allowed the file creation for today to proceed. Regrettably, I did not try touching a new file to try and reproduce the error on a commandline; I also deleted several hundred files rather than a handful. However, my question is: are there hard limits on filesize or number of files in a directory? am I even on the right track here? Nota Bene: The SD card is as-is - i.e. I haven't formatted it, so I would guess it would be a FAT-* format. The FAT-32 format has hard limits of filesize of 2GB (well above the filesizes I am dealing with) and a limit of number of files in the root directory. I am definitely not writing files in the root directory.

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  • A monkey could do this better - Access to and availability of private member functions in C++

    - by David
    I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

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  • Is there a way to implement Caliburn-like co-routines in VB.NET since there's no yield keyword

    - by Miroslav Popovic
    Note that I'm aware of other yield in vb.net questions here on SO. I'm playing around with Caliburn lately. Bunch of great stuff there, including co-routines implementation. Most of the work I'm doing is C# based, but now I'm also creating an architecture guideline for a VB.NET only shop, based on Rob's small MVVM framework. Everything looks very well except using co-routines from VB. Since VB 10 is used, we can try something like Bill McCarthy's suggestion: Public Function Lines(ByVal rdr as TextReader) As IEnumerable(Of String) Return New GenericIterator(Of String) (Function(ByRef nextItem As String) As Boolean nextItem = rdr.ReadLine Return nextItem IsNot Nothing End Function) End Function I'm just failing to comprehend how a little more complex co-routine method like the one below (taken from Rob's GameLibrary) could be written in VB: public IEnumerable<IResult> ExecuteSearch() { var search = new SearchGames { SearchText = SearchText }.AsResult(); yield return Show.Busy(); yield return search; var resultCount = search.Response.Count(); if (resultCount == 0) SearchResults = _noResults.WithTitle(SearchText); else if (resultCount == 1 && search.Response.First().Title == SearchText) { var getGame = new GetGame { Id = search.Response.First().Id }.AsResult(); yield return getGame; yield return Show.Screen<ExploreGameViewModel>() .Configured(x => x.WithGame(getGame.Response)); } else SearchResults = _results.With(search.Response); yield return Show.NotBusy(); } Any idea how to achieve that, or any thoughts on using Caliburn co-routines in VB?

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  • Help me choose a web development framework/platform that will make me learn something

    - by Sergio Tapia
    I'm having a bit of an overload of information these past two days. I'm planning to start my own website that will allow local businesses to list their items on sale, and then users can come in and search for "Abercrombie t-shirt" and the stores that sell them will be listed. It's a neat little project I'm really excited for and I'm sure it'll take off, but I'm having problems from the get go. Sure I could use ASP.Net for it, I'm a bit familiar with it and the IDE for ASP.Net pages is bar-none, but I feel this is a great chance for me to learn something new to branch out a bit and not regurgitate .NET like a robot. I've been looking and asking around but it's all just noise and I can't make an educated decision. Can you help me choose a framework/platform that will make me learn something that's a nice thing to know in the job market, but also nice for me to grow as a professional? So far I've looked at: Ruby on Rails Kohana CakePHP CodeIgniter Symfony But they are all very esoteric to me, and I have trouble even finding out which IDE to use to that will let me use auto-complete for the proprietary keywords/methods. Thank you for your time.

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  • Playing video and audio in iPhone not working...

    - by Scott
    So we have buttons linked up to display images/videos/audio on click depending on a check we do earlier. That part works fine. It knows which one to play, however, when we click the buttons for video and audio, nothing happens. The image one works fine. The video and audio are being taken for a URL online, they are not local, but everywhere said this was still possible. Here is a little snippet of the code where we play the two files: if ( [fName hasSuffix:@".png"]) { NSLog(@"PICTURE"); NSURL *url = [NSURL URLWithString: fName]; UIImage *image = [UIImage imageWithData: [NSData dataWithContentsOfURL:url]]; self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; // self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"MainBG.jpg"]]; [self.view addSubview:[[UIImageView alloc] initWithImage:image]]; } if ( [fName hasSuffix:@".mp4"]) { NSLog(@"VIDEO"); //NSString *path = [[NSBundle mainBundle] pathForResource:fName ofType:@"mp4"]; //NSLog(path); NSURL *url = [NSURL fileURLWithPath:fName]; MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:url]; [player play]; } if ( [fName hasSuffix:@".mp3"]) { NSLog(@"AUDIO"); NSURL *url = [NSURL fileURLWithPath:fName]; NSData *soundData = [NSData dataWithContentsOfURL:url]; AVAudioPlayer *avPlayer = [[AVAudioPlayer alloc] initWithData:soundData error: nil]; [avPlayer play]; } See anything wrong? By the way it compiles and runs, but nothing happens when we hit the button that executes that code.

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  • How to embed XBase expressions in an Xtext DSL

    - by Marcus Mathioudakis
    I am writing a simple little DSL for specifying constraints on messages, and Have been trying without success for a while to embed XBase expressions into the language. The Grammar looks like this: grammar org.xtext.businessrules.BusinessRules with org.eclipse.xtext.xbase.Xbase //import "http://www.eclipse.org/xtext/xbase/Xbase" as xbase import "http://www.eclipse.org/xtext/common/JavaVMTypes" as jvmTypes generate businessRules "http://www.xtext.org/businessrules/BusinessRules" Start: rules+=Constraint*; Constraint: {Constraint} 'FOR' 'PAYLOAD' payload=PAYLOAD 'ELEMENT' element=ID 'CONSTRAINED BY' constraint=XExpression; PAYLOAD: "SimulationSessionEvents" |"stacons" |"any" ; Range: 'above' min=INT ('below' max=INT)? |'below' max=INT ('above' min=INT)? ; When trying to parse a file such as: FOR PAYLOAD SimulationSessionEvents ELEMENT matrix CONSTRAINED BY ... I can't get it to work for ... = any kind of Arithmetic expression, although it works for ...= loop or if expression, or even just a number. As soon as I do something like '-5' or '4-5' it says Couldn't resolve reference to JvmIdentifiableElement '-', even though the Xbase.xtext Grammar looks like it allows these expressions. I don't think I'm missing any Jars, as it doesn't complain when I run the mwe workflow, but only when trying to parse the input file. Any help would be much appreciated.

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  • How can I map stored procedure result into a custom class with linq-to-sql?

    - by Remnant
    I have a stored procedure that returns a result set (4 columns x n Rows). The data is based on multiple tables within my database and provides a summary for each department within a corporate. Here is sample: usp_GetDepartmentSummary DeptName EmployeeCount Male Female HR 12 5 7 etc... I am using linq-to-sql to retrieve data from my database (nb - have to use sproc as it is something I have inherited). I would like to call the above sproc and map into a department class: public class Department { public string DeptName {get; set;} public int EmployeeCount {get; set;} public int MaleCount {get; set;} public int FemaleCount {get; set;} } In VS2008, I can drag and drop my sproc onto the methods pane of the linq-to-sql designer. When I examine the designer.cs the return type for this sproc is defined as: ISingleResult<usp_GetDepartmentSummaryResult> What I would like to do is amend this somehow so that it returns a Department type so that I can pass the results of the sproc as a strongly typed view: <% foreach (var dept in Model) { %> <ul> <li class="deptname"><%= dept.DeptName %></li> <li class="deptname"><%= dept.EmployeeCount %></li> etc... Any ideas how to achieve this? NB - I have tried amending the designer.cs and dbml xml file directly but with limited success. I admit to being a little out of my depth when it comes to updating those files directly and I am not sure it is best practice? Would be good to get some diretion. Thanks much

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  • Which Table Should be Master and Child in Database Design

    - by Jason
    I am quickly learning the ins and outs of database design (something that, as of a week ago, was new to me), but I am running across some questions that don't seem immediately obvious, so I was hoping to get some clarification. The question I have right is about foreign keys. As part of my design, I have a Company table. Originally, I had included address information directly within the table, but, as I was hoping to achieve 3NF, I broke out the address information into its own table, Address. In order to maintain data integrity, I created a row in Company called "addressId" as an INT and the Address table has a corresponding addressId as its primary key. What I'm a little bit confused about (or what I want to make sure I'm doing correctly) is determining which table should be the master (referenced) table and which should be the child (referencing) table. When I originally set this up, I made the Address table the master and the Company the child. However, I now believe this is wrong due to the fact that there should be only one address per Company and, if a Company row is deleted, I would want the corresponding Address to be removed as well (CASCADE deletion). I may be approaching this completely wrong, so I would appreciate any good rules of thumb on how to best think about the relationship between tables when using foreign keys. Thanks!

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  • Html.ListBox() and MultiselectList

    - by Ivan90
    Hi guys, I've a little problem with an Html.ListBox! I am developing a personal blog in ASP.NET MVC 1.0 and I created an adminpanel where I can add and edit a post! During this two operations, I can add also tags! I think of use an Html.ListBox() helper to list all tags, and so I can select multiple tags to add in a post! The problem isn't during the add mode, but in the edit mode, where I have to pre-select post's tags! I read that I have to use a MultiSelectList and so in its constructor pass, tags' list and tag's list(pre-selected value). But I don't know how to use this class! I post, some code: This is my models method that get all list tags in selectlist public IEnumerable<SelectListItem> GetTagsListBox() { return from t in db.Tags orderby t.IDTag descending select new SelectListItem { Text = t.TagName, Value = t.IDTag.ToString(), }; } So in Edit (Get and Post), Add(Get and Post) I use a ViewData to pass this list in Html.ListBox(). ViewData["Tags"] = tagdb.GetTagsListBox(); And in my view <%=Html.ListBox("Tags",ViewData["Tags"] as SelectList) %> So with this code it's ok in Add Mode! But in Edit Mode I need to pre-select those values! So Now, of course I have to create a method that get all tagsbypostid! and then in ViewData what Must I to pass? Any suggest?

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  • How does a client find the port number of a server?

    - by Jonathan
    Hello all, I am currently learning about basic networking in java. I have been playing around with the server and client relationship between two of my computers. However, I cannot figure out how distributed programs (say, a videogame), can not only find the 'host' computer, but also the port number on which the server is running in order to create a Socket between the two computers. The only way I really see to create a Socket is with an already known IP Address, and with a known port number. How do you search a LAN network for another computer (host) searching for clients? How do you determine what port the server is located on without 'pinging' all available ports for a response (which, I understand, is bad form... Something about 'server attack'...)? In such a situation as a video game, there can be any number of computers on the same network, and any number of them might be attempting to host, or otherwise running the application. Any other important information, or perhaps reference to a more detailed tutorial than the one I am using, regarding making connections on so very little information on the client side would be appreciated. Many thanks, Jonathan

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  • fgets in c don't return a portion of an string

    - by Marc
    Hi! I'm totally new in C, and I'm trying to do a little application that searches a string into a file, my problem is that I need to open a big file (more than 1GB) with just one line inside and fgets return me the entire file (I'm doing test with a 10KB file). actually this is my code: #include <stdio.h> #include <string.h> int main(int argc, char *argv[]) { char *search = argv[argc-1]; int retro = strlen(search); int pun = 0; int sortida; int limit = 10; char ara[20]; FILE *fp; if ((fp = fopen ("SEARCHFILE", "r")) == NULL){ sortida = -1; exit (1); } while(!feof(fp)){ if (fgets(ara, 20, fp) == NULL){ break; } //this must be a 20 bytes line, but it gets the entyre 10Kb file printf("%s",ara); } sortida = 1; if(fclose(fp) != 0){ sortida = -2; exit (1); } return 0; } What can I do to find an string into a file? I'v tried with GREP but it don't helps, because it returns the position:ENTIRE_STRING. I'm open to ideas. Thanks in advance!

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  • Constructor and Destructors in C++ [Not a question] [closed]

    - by Jack
    I am using gcc. Please tell me if I am wrong - Lets say I have two classes A & B class A { public: A(){cout<<"A constructor"<<endl;} ~A(){cout<<"A destructor"<<endl;} }; class B:public A { public: B(){cout<<"B constructor"<<endl;} ~B(){cout<<"B destructor"<<endl;} }; 1) The first line in B's constructor should be a call to A's constructor ( I assume compiler automatically inserts it). Also the last line in B's destructor will be a call to A's destructor (compiler does it again). Why was it built this way? 2) When I say A * a = new B(); compiler creates a new B object and checks to see if A is a base class of B and if it is it allows 'a' to point to the newly created object. I guess that is why we don't need any virtual constructors. ( with help from @Tyler McHenry , @Konrad Rudolph) 3) When I write delete a compiler sees that a is an object of type A so it calls A's destructor leading to a problem which is solved by making A's destructor virtual. As user - Little Bobby Tables pointed out to me all destructors have the same name destroy() in memory so we can implement virtual destructors and now the call is made to B's destructor and all is well in C++ land. Please comment.

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  • Prototypal inheritance should save memory, right?

    - by Techpriester
    Hi Folks, I've been wondering: Using prototypes in JavaScript should be more memory efficient than attaching every member of an object directly to it for the following reasons: The prototype is just one single object. The instances hold only references to their prototype. Versus: Every instance holds a copy of all the members and methods that are defined by the constructor. I started a little experiment with this: var TestObjectFat = function() { this.number = 42; this.text = randomString(1000); } var TestObjectThin = function() { this.number = 42; } TestObjectThin.prototype.text = randomString(1000); randomString(x) just produces a, well, random String of length x. I then instantiated the objects in large quantities like this: var arr = new Array(); for (var i = 0; i < 1000; i++) { arr.push(new TestObjectFat()); // or new TestObjectThin() } ... and checked the memory usage of the browser process (Google Chrome). I know, that's not very exact... However, in both cases the memory usage went up significantly as expected (about 30MB for TestObjectFat), but the prototype variant used not much less memory (about 26MB for TestObjectThin). I also checked: The TestObjectThin instances contain the same string in their "text" property, so they are really using the property of the prototype. Now, I'm not so sure what to think about this. The prototyping doesn't seem to be the big memory saver at all. I know that prototyping is a great idea for many other reasons, but I'm specifically concerned with memory usage here. Any explanations why the prototype variant uses almost the same amount of memory? Am I missing something?

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  • Is this the right way to organize my database tables?

    - by Moss
    So I'm making a website that allows users to build contact lists. So their are users, the users have lists, and the lists have contacts. It seems to me that I need 3 tables for this but I just want to make sure. There would be a User table of course, and then a "List of Lists" table that has the username, and listname, as primary key along with whatever other info we want to attach to the lists as a whole. Finally, for lack of a better word, the List table which would again have the username/listname p.k., then the contact ID and notes and such that the user attaches to that contact on that specific list. I hope that is a clear explanation. For some reason I feel unsure about this arrangement. For one thing if the website becomes popular the List table could swell to billions of rows. And it also feels a little weird that everybody's list info is all jumbled up in the same table. I suppose I could create separate tables for each user and even for each list but that seems like a bad idea for other reasons. My db explanation assumes I can use foreign keys on my tables which at the moment isn't actually an option. If I can't get InnoDB tables enabled I will probably use ID's for the lists instead of depending on a compound key. Maybe I should do this anyway?

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  • Are there pitfalls to using static class/event as an application message bus

    - by Doug Clutter
    I have a static generic class that helps me move events around with very little overhead: public static class MessageBus<T> where T : EventArgs { public static event EventHandler<T> MessageReceived; public static void SendMessage(object sender, T message) { if (MessageReceived != null) MessageReceived(sender, message); } } To create a system-wide message bus, I simply need to define an EventArgs class to pass around any arbitrary bits of information: class MyEventArgs : EventArgs { public string Message { get; set; } } Anywhere I'm interested in this event, I just wire up a handler: MessageBus<MyEventArgs>.MessageReceived += (s,e) => DoSomething(); Likewise, triggering the event is just as easy: MessageBus<MyEventArgs>.SendMessage(this, new MyEventArgs() {Message="hi mom"}); Using MessageBus and a custom EventArgs class lets me have an application wide message sink for a specific type of message. This comes in handy when you have several forms that, for example, display customer information and maybe a couple forms that update that information. None of the forms know about each other and none of them need to be wired to a static "super class". I have a couple questions: fxCop complains about using static methods with generics, but this is exactly what I'm after here. I want there to be exactly one MessageBus for each type of message handled. Using a static with a generic saves me from writing all the code that would maintain the list of MessageBus objects. Are the listening objects being kept "alive" via the MessageReceived event? For instance, perhaps I have this code in a Form.Load event: MessageBus<CustomerChangedEventArgs>.MessageReceived += (s,e) => DoReload(); When the Form is Closed, is the Form being retained in memory because MessageReceived has a reference to its DoReload method? Should I be removing the reference when the form closes: MessageBus<CustomerChangedEventArgs>.MessageReceived -= (s,e) => DoReload();

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  • How can I overlay images over one another in Java?

    - by Sam
    So I have been posting all over and have yet to get a solid answer: I have created an image resizing class, with a crop method. The cropping works great. The issue that I am having is the background color that I specify in the drawImage function of Graphics is not working correctly. It defaults to black as the background regardless of what I supply (in this case Color.WHITE). Also, the overlaying image or top most image (comes from a file) is being inverted (I think it is) or otherwise discolored. Just so you can conceptualize this a little bit better, I am taking a jpeg and overlaying it on top of a new BufferedImage, the new buffered image's background is not being set. Here is the code below that I am working with: public void Crop(int Height, int Width, int SourceX, int SourceY) throws Exception { //output height and width int OutputWidth = this.OutputImage.getWidth(); int OutputHeight = this.OutputImage.getHeight(); //create output streams ByteArrayOutputStream MyByteArrayOutputStream = new ByteArrayOutputStream(); MemoryCacheImageOutputStream MyMemoryCacheImageOutputStream = new MemoryCacheImageOutputStream(MyByteArrayOutputStream); //Create a new BufferedImage BufferedImage NewImage = new BufferedImage(Width, Height, BufferedImage.TYPE_INT_RGB); Graphics MyGraphics = NewImage.createGraphics(); MyGraphics.drawImage(this.OutputImage, -SourceX, -SourceY, OutputWidth, OutputHeight, Color.WHITE, null); // Get Writer and set compression Iterator MyIterator = ImageIO.getImageWritersByFormatName("png"); if (MyIterator.hasNext()) { //get image writer ImageWriter MyImageWriter = (ImageWriter)MyIterator.next(); //get params ImageWriteParam MyImageWriteParam = MyImageWriter.getDefaultWriteParam(); //set outputstream MyImageWriter.setOutput(MyMemoryCacheImageOutputStream); //create new ioimage IIOImage MyIIOImage = new IIOImage(NewImage, null, null); //write new image MyImageWriter.write(null, MyIIOImage, MyImageWriteParam); } //convert output stream back to inputstream ByteArrayInputStream MyByteArrayInputStream = new ByteArrayInputStream(MyByteArrayOutputStream.toByteArray()); MemoryCacheImageInputStream MyMemoryCacheImageInputStream = new MemoryCacheImageInputStream(MyByteArrayInputStream); //resassign as a buffered image this.OutputImage = ImageIO.read(MyMemoryCacheImageInputStream); }

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