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• Why doesn't java.util.Set have get(int index)?

  - by Marty Pitt

  I'm sure there's a good reason, but could someone please explain why the java.util.Set interface lacks get(int Index), or any similar get() method? It seems that sets are great for putting things into, but I can't find an elegant way of retrieving a single item from it. If I know I want the first item, I can use set.iterator().next(), but otherwise it seems I have to cast to an Array to retrieve an item at a specific index? What are the appropriate ways of retrieving data from a set? (other than using an iterator) I'm sure the fact that it's excluded from the API means there's a good reason for not doing this -- could someone please enlighten me? EDIT: Some extremely great answers here, and a few saying "more context". The specific scneario was a dbUnit test, where I could reasonalby assert that the returned set from a query had only 1 item, and I was trying to access that item. However, the question is more valid without the scenario, as it remains more focussed : What's the difference between set & list. Thanks to all for the fantastic answers below.

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• Sending files from server to client in Java

  - by Lee Jacobson

  Hi, I'm trying to find a way to send files of different file types from a server to a client. I have this code on the server to put the file into a byte array: File file = new File(resourceLocation); byte[] b = new byte[(int) file.length()]; FileInputStream fileInputStream; try { fileInputStream = new FileInputStream(file); try { fileInputStream.read(b); } catch (IOException ex) { System.out.println("Error, Can't read from file"); } for (int i = 0; i < b.length; i++) { fileData += (char)b[i]; } } catch (FileNotFoundException e) { System.out.println("Error, File Not Found."); } I then send fileData as a string to the client. This works fine for txt files but when it comes to images I find that although it creates the file fine with the data in, the image won't open. I'm not sure if I'm even going about this the right way. Thanks for the help.

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• Finding character in String in Vector.

  - by SoulBeaver

  Judging from the title, I kinda did my program in a fairly complicated way. BUT! I might as well ask anyway xD This is a simple program I did in response to question 3-3 of Accelerated C++, which is an awesome book in my opinion. I created a vector: vector<string> countEm; That accepts all valid strings. Therefore, I have a vector that contains elements of strings. Next, I created a function int toLowerWords( vector<string> &vec ) { for( int loop = 0; loop < vec.size(); loop++ ) transform( vec[loop].begin(), vec[loop].end(), vec[loop].begin(), ::tolower ); that splits the input into all lowercase characters for easier counting. So far, so good. I created a third and final function to actually count the words, and that's where I'm stuck. int counter( vector<string> &vec ) { for( int loop = 0; loop < vec.size(); loop++ ) for( int secLoop = 0; secLoop < vec[loop].size(); secLoop++ ) { if( vec[loop][secLoop] == ' ' ) That just looks ridiculous. Using a two-dimensional array to call on the characters of the vector until I find a space. Ridiculous. I don't believe that this is an elegant or even viable solution. If it was a viable solution, I would then backtrack from the space and copy all characters I've found in a separate vector and count those. My question then is. How can I dissect a vector of strings into separate words so that I can actually count them? I thought about using strchr, but it didn't give me any epiphanies.

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• Get location of element you just pushed into vector C++

  - by Satchmo Brown

  I am curious about how pushing back into a vector works. I want a way to push back an element and then be able to add it's location in the vector to a double array serving as a type of map. Something like this: // Create a bomb Bomb b; b.currentTime = SDL_GetTicks(); b.explodeTime = SDL_GetTicks() + 3000; b.owner = player; b.power = 2; b.x = x; b.y = y; bombVec.push_back(b); bombs[y][x] = THIS_IS_WHAT_I_WANT; This way when I explode the bomb, I can check the map and then have an ID in the vector to deal with. Every non bomb square will have a -1. Also, just curious. Imagine I have 3 elements in a vector. I delete the second one and then add another. Does the new element go in the same location as the one that was deleted? Thanks!

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• Javascript getElementsByTagName broken firefox?

  - by Sheldon Ross

  I'm getting the weirdest issues with Javascript in Firefox today. I'm trying to manipulate some table rows, but .getElementsByTagName("tr"); is pulling back junk. dynamicTable.tableBody = dynamicTable.getElementsByTagName("tbody")[0]; var tableRows = dynamicTable.tableBody.getElementsByTagName("TR"); var actualTableRows = new Array(); for(var i in tableRows) { var row = tableRows[i]; alert(row.tagName); if(row.tagName == "TR"){ actualTableRows.push(row); } } dynamicTable.bodyRows = actualTableRows; The puzzling part of course is my temporary hack to fix the error. For some reason .getElementsByTagName("tr") is pulling back some functions also. Incidently the alert above goes something like this TR TR TR TR undefined undefined undefined. The code I wanted was something like this dynamicTable.bodyRows = dynamicTable.tableBody.getElementsByTagName("tr"); But then bodyrows does not contain just tr elements it has the aforementioned junk in it. Any thoughts?

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• How do I perform this MutliArray setup in Java?

  - by Andy Barlow

  I come from a PHP background and I'm just getting my teeth into some Java. I was wondering how I could implement the following in Java as simply as possible, just echoing the results to a terminal via the usual "System.out.print()" method. <?php $Results[0]['title'] = "No Country for Old Men"; $Results[0]['run_time'] = "122 mins"; $Results[0]['cert'] = "15"; $Results[1]['title'] = "Old School"; $Results[1]['run_time'] = "88 mins"; $Results[1]['cert'] = "18"; // Will basically show the above in order. foreach($Results as value) { echo $Results[$value]['title']; echo $Results[$value]['run_time']; echo $Results[$value]['cert']; } // Lets add some more as I need to do this in Java too $Results[2]['title'] = "Saving Private Ryan"; $Results[2]['run_time'] = "153 mins"; $Results[2]['cert'] = "15"; // Lets remove the first one as an example of another need $Results[0] = null; ?> I hear there are "list iterators" or something that are really good for rolling through data like this. Perhaps it could be implemented with that? A fully working .java file would be most handy in this instance, including how to add and remove items from the array like the above. P.S. I do plan on using this for an Android App in the distant future, so, hopefully it should all work on Android fine too, although, I imagine this sort of thing works on anything Java related :).

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• OpenCL Matrix Multiplication - Getting wrong answer

  - by Yash

  here's a simple OpenCL Matrix Multiplication kernel which is driving me crazy: __kernel void matrixMul( __global int* C, __global int* A, __global int* B, int wA, int wB){ int row = get_global_id(1); //2D Threas ID x int col = get_global_id(0); //2D Threas ID y //Perform dot-product accumulated into value int value; for ( int k = 0; k < wA; k++ ){ value += A[row*wA + k] * B[k*wB+col]; } C[row*wA+col] = value; //Write to the device memory } Where (inputs) A = [72 45 75 61] B = [26 53 46 76] Output I am getting: C = [3942 7236 3312 5472] But the output should be: C = [3943 7236 4756 8611] The problem I am facing here is that for any dimension array the elements of the first row of the resulting matrix is correct. The elements of all the other rows of the resulting matrix is wrong. By the way I am using pyopencl. I don't know what I mistake I am doing here. I have spent the entire day with no luck. Please help me with this

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• How do I know which Object I clicked?

  - by Nick

  Here's the deal: I'm working on a personal portfolio in AS3 and I've run into a problem which I can't seem to find a logical answer to. I want everything (well, most of it) to be editable with an XML file, including my menu. My menu is just a Sprite with some text on it and a Tweener-tween, no big deal. But, I forgot to think of a way how I can determine which menu-item I have clicked. This is in my Main.as private function xmlLoaded(e:Event):void { xml = e.target.xml; menu = new Menu(xml); menu.x = 0; menu.y = stage.stageHeight / 2 - menu.height / 2; addChild(menu); } In Menu.as public function Menu(xml:XML) { for each (var eachMenuItem:XML in xml.menu.item) { menuItem = new MenuItem(eachMenuItem); menuItem.y += yPos; addChild(menuItem); yPos += menuItem.height + 3; } } and in my MenuItem.as, everything works - I have a fancy tween when I hover over it, but when I click a menu-item, I want something to appear ofcourse. How do I know which one I clicked? I've tried with pushing everything in an array, but that didn't work out well (or maybe I'm doing it wrong). Also tried a global counter, but that's not working either because the value will always be amount of items in my XML file. Also tried e.currentTarget in my click-function, but when I trace that, all of them are "Object Sprite".. I need something so I can give each a unique "name"? Thanks in advance!

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• How to encrypt/decrypt a file in Java?

  - by Petike

  Hello, I am writing a Java application which can "encrypt" and consequently "decrypt" whatever binary file. I am just a beginner in the "cryptography" area so I would like to write a very simple application for the beginning. For reading the original file, I would probably use the java.io.FileInputStream class to get the "array of bytes" byte originalBytes[] of the file. Then I would probably use some very simple cipher, for example "shift up every byte by 1" and then I would get the "encrypted" bytes byte encryptedBytes[] and let's say that I would also set a "password" for it, for example "123456789". Next, when somebody wants to "decrypt" that file, he has to enter the password ("123456789") first and after that the file could be decrypted (thus "shift down every byte by 1") and consequently saved to the output file via java.io.FileOutputStream I am just wondering how to "store" the password information to the encrypted file so that the decrypting application knows if the entered password and the "real" password equals? Probably it would be silly to add the password (for example the ASCII ordinal numbers of the password letters) to the beginning of the file (before the encrypted data). So my main question is how to store the password information to the encrypted file?

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• Asp MVC - "The Id field is required" validation message on Create; Id not set to [Required]

  - by burnt_hand

  This is happening when I try to create the entity using a Create style action in Asp.Net MVC 2. The POCO has the following properties: public int Id {get;set;} [Required] public string Message {get; set} On the creation of the entity, the Id is set automatically, so there is no need for it on the Create action. The ModelState says that "The Id field is required", but I haven't set that to be so. Is there something automatic going on here? EDIT - Reason Revealed The reason for the issue is answered by Brad Wilson via Paul Speranza in one of the comments below where he says (cheers Paul): You're providing a value for ID, you just didn't know you were. It's in the route data of the default route ("{controller}/{action}/{id}"), and its default value is the empty string, which isn't valid for an int. Use the [Bind] attribute on your action parameter to exclude ID. My default route was: new { controller = "Customer", action = "Edit", id = " " } // Parameter defaults EDIT - Update Model technique I actually changed the way I did this again by using TryUpdateModel and the exclude parameter array asscoiated with that. [HttpPost] public ActionResult Add(Venue collection) { Venue venue = new Venue(); if (TryUpdateModel(venue, null, null, new[] { "Id" })) { _service.Add(venue); return RedirectToAction("Index", "Manage"); } return View(collection); }

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• High Runtime for Dictionary.Add for a large amount of items

  - by aaginor

  Hi folks, I have a C#-Application that stores data from a TextFile in a Dictionary-Object. The amount of data to be stored can be rather large, so it takes a lot of time inserting the entries. With many items in the Dictionary it gets even worse, because of the resizing of internal array, that stores the data for the Dictionary. So I initialized the Dictionary with the amount of items that will be added, but this has no impact on speed. Here is my function: private Dictionary<IdPair, Edge> AddEdgesToExistingNodes(HashSet<NodeConnection> connections) { Dictionary<IdPair, Edge> resultSet = new Dictionary<IdPair, Edge>(connections.Count); foreach (NodeConnection con in connections) { ... resultSet.Add(nodeIdPair, newEdge); } return resultSet; } In my tests, I insert ~300k items. I checked the running time with ANTS Performance Profiler and found, that the Average time for resultSet.Add(...) doesn't change when I initialize the Dictionary with the needed size. It is the same as when I initialize the Dictionary with new Dictionary(); (about 0.256 ms on average for each Add). This is definitely caused by the amount of data in the Dictionary (ALTHOUGH I initialized it with the desired size). For the first 20k items, the average time for Add is 0.03 ms for each item. Any idea, how to make the add-operation faster? Thanks in advance, Frank

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• Trying to create a .NET DLL to be used with Non-.NET Application

  - by Changeling

  I am trying to create a .NET DLL so I can use the cryptographic functions with my non .NET application. I have created a class library so far with this code: namespace AESEncryption { public class EncryptDecrypt { private static readonly byte[] optionalEntropy = { 0x21, 0x05, 0x07, 0x08, 0x27, 0x02, 0x23, 0x36, 0x45, 0x50 }; public interface IEncrypt { string Encrypt(string data, string filePath); }; public class EncryptDecryptInt:IEncrypt { public string Encrypt(string data, string filePath) { byte[] plainKey; try { // Read in the secret key from our cipher key store byte[] cipher = File.ReadAllBytes(filePath); plainKey = ProtectedData.Unprotect(cipher, optionalEntropy, DataProtectionScope.CurrentUser); // Convert our plaintext data into a byte array byte[] plainTextBytes = Encoding.ASCII.GetBytes(data); MemoryStream ms = new MemoryStream(); Rijndael alg = Rijndael.Create(); alg.Mode = CipherMode.CBC; alg.Key = plainKey; alg.IV = optionalEntropy; CryptoStream cs = new CryptoStream(ms, alg.CreateEncryptor(), CryptoStreamMode.Write); cs.Write(plainTextBytes, 0, plainTextBytes.Length); cs.Close(); byte[] encryptedData = ms.ToArray(); return Convert.ToString(encryptedData); } catch (Exception ex) { return ex.Message; } } } } } In my VC++ application, I am using the #import directive to import the TLB file created from the DLL, but the only available functions are _AESEncryption and LIB_AES etc I don't see the interface or the function Encrypt. When I try to instantiate so I can call the functions in my VC++ program, I use this code and get the following error: HRESULT hr = CoInitialize(NULL); IEncryptPtr pIEncrypt(__uuidof(EncryptDecryptInt)); error C2065: 'IEncryptPtr': undeclared identifier error C2146: syntax error : missing ';' before identifier 'pIEncrypt'

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• Like posts over Facebook graph api

  - by Sima

  HI! I have little problem with facebook PHP SDK..I want to like a post, or something else via facebook PHP SDK..I am doing this code, I think it should be right, but  apparently it's not working..The given error code is, the PHP SDK dont know this kind of POST request(the generated link is definitely alright). What I have seen on Facebook Developers page is about the same..There is an example of Curl command, and I the PHP SDK is doing this requests over Curl (propably). $this->getFacebook()->api("/"+$id+"/likes", 'post'); This is what I am using in my code and it's not working(Facebook API Exception unsupported post request). Maybe, I have bad syntax in my code, but, for example, when I want to post a status to my Profile, it's working..Another cause which confused me, was when I tried to fetch these data over Graph api(on the documentation page is written, I should use address like graph.facebook.com/POST_ID/likes)... You can comment on or like a post by posting to https://graph.facebook.com/POST_ID/comments and https://graph.facebook.com/POST_ID/likes,respectively: curl -F 'access_token=...' \ https://graph.facebook.com/313449204401/likes <=this is from facebook documentation And all these requests or commands(liking ones, comments have I not yet tried) are putting me back a JSON array which contents any already existing likes, but my like is nowhere. Does anyone know what to do?How to like a post from PHP..There are other SKDs like FQL, but I haven't any knowlegde with it, so I like rather to use the standard PHP SDK(but if is there some possibility how to call for example FQL from PHP SDK, here I am:)) Please help..

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• PHP Notice: Undefined property: stdClass:

  - by 4D

  I've got an array coming back from a Flash app created in Flash Builder 4. I have a service setup that queries and brings data back from the DB successfully, however the Update script is generating the Undefined Property errors. I'm still learning both PHP and Flash Builder, and don't fully understand what the $this- commands do. If anyone can suggest where this script is going wrong, it is basically just generated by Flash Builder and is not something I've developed myself, I would appreciate it? Also if someone can explain $this- to me that would be awesome too? I've seen them before, but then I've seen scripts doing the same thing that do not use them, so is this an old way of doing things? Really appreciate any input anyone can give. public function updateItem($item) { // TODO Auto-generated method stub // Update an existing record in the database and return the item // Sample code \' $this->connect(); $sql = "UPDATE tbltrust SET inst_code = '$item->inst_code', trust_name = '$item->trust_name', trust_code = '$item->trust_code' WHERE trust_key = '$item->trust_key'"; mysqli_query($this->connection, $sql) or die('Query failed: ' . mysqli_error($this->connection)); mysqli_close($this->connection); }

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• Generate and download a text file in javascript

  - by Mark B

  All my research so far suggests this can't be done, but I'm hoping someone here has some cunning ideas. I have a form on a website which allows users to bulk upload lots of URLs to add to a list on the server. There's quite a lot of server-side processing to do on each URL, so to avoid timeouts and to display progress, I've implemented the upload using jQuery to submit the URLs one at a time using ajax. This is all working nicely. However, part of the processing on each URL is deduplicating it against the complete list. The ajax call returns a status indicating either a successful upload or a rejection due to duplication. As the upload progresses, I tell the user how many URLs have been rejected as duplicates (along with overall progress and ETA). The problem now is how to give the user a complete list of the failed duplicate URLs. I've kept them in an array in my jQuery, and would like the user to be able to click on a link on the form to download a text file containing those URLs. Is this possible just using client-side processing? The server-side processing basically handles a single keyword at a time. I'd rather not have to store the duplicates in a database table with some kind of session key which gets sent with every ajax call, and is then used at the end to generate the text file server-side (and then gets cleaned up some time later). I can see how to do this, but it seems very clunky and a bit 20th century.

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• Low Level Console Input

  - by Soulseekah

  I'm trying to send commands to to the input of a cmd.exe application using the low level read/write console functions. I have no trouble reading the text (scraping) using the ReadConsole...() and WriteConsole() functions after having attached to the process console, but I've not figured out how to write for example "dir" and have the console interpret it as a sent command. Here's a bit of my code: CreateProcess(NULL, "cmd.exe", NULL, NULL, FALSE, CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi); AttachConsole(pi.dwProcessId); strcpy(buffer, "dir"); WriteConsole(GetStdHandle(STD_INPUT_HANDLE), buffer, strlen(buffer), &charRead, NULL); STARTUPINFO attributes of the process are all set to zero, except, of course, the .cb attribute. Nothing changes on the screen, however I'm getting an Error 6: Invalid Handle returned from WriteConsole to STD_INPUT_HANDLE. If I write to (STD_OUTPUT_HANDLE) I do get my dir written on the screen, but nothing of course happens. I'm guessing SetConsoleMode() might be of help, but I've tried many mode combinations, nothing helped. I've also created a quick console application that waits for input (scanf()) and echoes back whatever goes in, didn't work. I've also tried typing into the scanf() promp and then peek into the input buffer using PeekConsoleInput(), returns 0, but the INPUT_RECORD array is empty. I'm aware that there is another way around this using WriteConsoleInput() to directly inject INPUT_RECORD structured events into the console, but this would be way too long, I'll have to send each keypress into it. I hope the question is clear. Please let me know if you need any further information. Thanks for your help.

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• Are there any security issues to avoid when providing a email-or-username-can-act-as-username login

  - by Tchalvak

  I am in the process of moving from a "username/password" system to one that uses email for login. I don't think that there's any horrible problem with allowing either email or username for login, and I remember seeing sites that I consider somewhat respectable doing it as well, but I'd like to be aware of any major security flaws that I may be introducing. More specifically, here is the pertinent function (the query_row function parameterizes the sql). function authenticate($p_user, $p_pass) { $user = (string)$p_user; $pass = (string)$p_pass; $returnValue = false; if ($user != '' && $pass != '') { // Allow login via username or email. $sql = "SELECT account_id, account_identity, uname, player_id FROM accounts join account_players on account_id=_account_id join players on player_id = _player_id WHERE lower(account_identity) = lower(:login) OR lower(uname) = lower(:login) AND phash = crypt(:pass, phash)"; $returnValue = query_row($sql, array(':login'=>$user, ':pass'=>$pass)); } return $returnValue; } Notably, I have added the WHERE lower(account_identity) = lower(:login) OR lower(uname) = lower(:login) ...etc section to allow graceful backwards compatibility for users who won't be used to using their email for the login procedure. I'm not completely sure that that OR is safe, though. Are there some ways that I should tighten the security of the php code above?

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• iphone table view check mark accessory problem

  - by Pankaj Kainthla

  I have a table with 50 rows. I want to select particular rows with checkmark accessory but when i select some rows and scroll down the table then i see pre checked rows. I know that table cell are reused but i want to emit this problem what can i do about this? - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // return [array count]; return 50; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; TableViewCell *cell = (TableViewCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[TableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } cell.textLabel.text=[NSString stringWithFormat:@"%i",[indexPath row]]; return cell; } // Override to support row selection in the table view. - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath]; if (cell.accessoryType == UITableViewCellAccessoryNone) { cell.accessoryType = UITableViewCellAccessoryCheckmark; } else { cell.accessoryType = UITableViewCellAccessoryNone; }

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• Java/JAXB: Accessing property of object in a list

  - by Mark Lewis

  Hello Using JAXB I've created a series of classes which represent my XML schema. Validating against the schema an XML file has thus become a 'tree' of java objects representing the XML. Now I'd like to access, delete and add an object of one the created types in my tree. If I've got classes' methods arranged like this: RootType class has: public List<FQType> getFq() { // and setter return fq; } FQType class has: public RemapType getRemap() { // and setter return remap; } RemapType class has: public String getSource() { // and setter return source; } What's the most concise way to code reading and writing of the 'source' member of a RemapType instance in an FQType instance with, say, fqtypeID=1, in an array of type RootType (in which RootType instances also each have rootID)? Currently I'm using a for loop Iterator in which is an if rootID = mySelectedRootID. In the if I nest a second for loop Iterator over the contained FQType instances and in that a second if fqTypeID = mySelectedFQTypeID. IE for loop iterator/if statement pairs to recognise the object of desire. With all the bells and whistles this way is nearly 15 lines of code to access a data type - can I do this in one line? Thanks

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• Determine image src in onload and onerror event handlers in IE

  - by Bill

  How can I determine the image src of the image that triggered the event in the onload and onerror event handlers in IE? This example code I threw together: <script language="javascript" type="text/javascript" src="jquery.js"></script> <script language="javascript" type="text/javascript"> function loadImages() { var goodImage = new Image(); var missingImage = new Image(); $(goodImage).bind('load', function(event){ $("#log").append( $(event.target).attr('src') + ' WAS FOUND <br>'); }); $(missingImage).bind('load', function(event){ $("#log").append( $(event.target).attr('src') + ' WAS FOUND <br>' ); }); $(goodImage).bind('error', function(event){ $("#log").append( $(event.target).attr('src') + ' IS MISSING <br>'); }); $(missingImage).bind('error', function(event){ $("#log").append( $(event.target).attr('src') + ' IS MISSING <br>'); }); goodImage.src = 'GOOD-IMAGE.GIF'; // this image exists missingImage.src = 'MISSING-IMAGE.GIF'; // this image doesn't exist } </script> </head> <body onload="loadImages();"> <div id="log"></div> works in FF but in IE8 it prints out undefined for the $(event.target).attr('src') part. I thought jQuery was supposed to normalize the event object for IE so that it acted like other browsers? I've tried a number of permutations but haven't been able to get anything to work in IE8. Anyway if anyone has a suggestion on how to figure out the image src in the onload and onerror event handlers that works in IE I would really appreciate it. Or even how to figure out after the images have loaded which have loaded and which haven't (but not graphically - I need to generate an array containing the filenames of the images that didn't load). Thanks!

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• Alignment in assembly

  - by jena

  Hi, I'm spending some time on assembly programming (Gas, in particular) and recently I learned about the align directive. I think I've understood the very basics, but I would like to gain a deeper understanding of its nature and when to use alignment. For instance, I wondered about the assembly code of a simple C++ switch statement. I know that under certain circumstances switch statements are based on jump tables, as in the following few lines of code: .section .rodata .align 4 .align 4 .L8: .long .L2 .long .L3 .long .L4 .long .L5 ... .align 4 aligns the following data on the next 4-byte boundary which ensures that fetching these memory locations is efficient, right? I think this is done because there might be things happening before the switch statement which caused misalignment. But why are there actually two calls to .align? Are there any rules of thumb when to call .align or should it simply be done whenever a new block of data is stored in memory and something prior to this could have caused misalignment? In case of arrays, it seems that alignment is done on 32-byte boundaries as soon as the array occupies at least 32 byte. Is it more efficient to do it this way or is there another reason for the 32-byte boundary? I'd appreciate any explanation or hint on literature.

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• Projective transformation

  - by mcwehner

  Given two image buffers (assume it's an array of ints of size width * height, with each element a color value), how can I map an area defined by a quadrilateral from one image buffer into the other (always square) image buffer? I'm led to understand this is called "projective transformation". I'm also looking for a general (not language- or library-specific) way of doing this, such that it could be reasonably applied in any language without relying on "magic function X that does all the work for me". An example: I've written a short program in Java using the Processing library (processing.org) that captures video from a camera. During an initial "calibrating" step, the captured video is output directly into a window. The user then clicks on four points to define an area of the video that will be transformed, then mapped into the square window during subsequent operation of the program. If the user were to click on the four points defining the corners of a door visible at an angle in the camera's output, then this transformation would cause the subsequent video to map the transformed image of the door to the entire area of the window, albeit somewhat distorted.

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• Runing bcdedit from python in Windows 2008 SP2

  - by Lee-Man

  I do not know windows well, so that may explain my dilemma ... I am trying to run bcdedit in Windows 2008R2 from Python 2.6. My Python routine to run a command looks like this: def run_program(cmd_str): """Run the specified command, returning its output as an array of lines""" dprint("run_program(%s): entering" % cmd_str) cmd_args = cmd_str.split() subproc = subprocess.Popen(cmd_args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True) (outf, errf) = (subproc.stdout, subproc.stderr) olines = outf.readlines() elines = errf.readlines() if Options.debug: if elines: dprint('Error output:') for line in elines: dprint(line.rstrip()) if olines: dprint('Normal output:') for line in olines: dprint(line.rstrip()) errf.close() outf.close() res = subproc.wait() dprint('wait result=', res) return (res, olines) I call this function thusly: (res, o) = run_program('bcdedit /set {current} MSI forcedisable') This command works when I type it from a cmd window, and it works when I put it in a batch file and run it from a command window (as Administrator, of course). But when I run it from Python (as Administrator), Python claims it can't find the command, returning: bcdedit is not recognized as an internal or external command, operable program or batch file Also, if I trying running my batch file from Python (which works from the command line), it also fails. I've also tried it with the full path to bcdedit, with the same results. What is it about calling bcdedit from Python that makes it not found? Note that I can call other EXE files from Python, so I have some level of confidence that my Python code is sane ... but who knows. Any help would be most appreciated.

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• Serializing and deserializing a map with key as string

  - by Grace K

  Hi! I am intending to serialize and deserialize a hashmap whose key is a string. From Josh Bloch's Effective Java, I understand the following. P.222 "For example, consider the case of a harsh table. The physical representation is a sequence of hash buckets containing key-value entries. Which bucket an entry is placed in is a function of the hash code of the key, which is not, in general guaranteed to be the same from JVM implementation to JVM implementation. In fact, it isn't even guranteed to be the same from run to run on the same JVM implementation. Therefore accepting the default serialized form for a hash table would constitute a serious bug. Serializing and deserializing the hash table could yield an object whose invariants were seriously corrupt." My questions are: 1) In general, would overriding the equals and hashcode of the key class of the map resolve this issue and the map can be correctly restored? 2) If my key is a String and the String class is already overriding the hashCode() method, would I still have problem described above. (I am seeing a bug which makes me think this is probably still a problem even though the key is String with overriding hashCode.) 3)Previously, I get around this issue by serializing an array of entries (key, value) and when deserializing I would reconstruct the map. I am wondering if there is a better approach. 4) If the answers to question 1 and 2 are that I still can't be guaranteed. Could someone explain why? If the hashCodes are the same would they go to the same buckets across JVMs? Thanks, Grace

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• Editing a remote file on-the-fly with PHP

  - by user275074

  Hi, I have a requirement to edit a remote text file on-the-fly, the content of which currently stands at ~1Mb. I have tried a couple of approaches and both seem to be clunky or hog memory which I can't rely on. Thinking out logically what I'm trying to achieve is: FTP to a remote server. Download a copy of the file for backup purposes and store it somewhere locally. Open the remote file and add the necessary lines required. Remove lines from the remote file as per an array of un-required data generated from the local server. Is this possible? I've managed to code steps 1 and 2 but I'm having difficult with 3 and 4. The way I'm doing it now is to use fgets and return the whole string. Really, I don't want to do this as it involves manipulating and re-generating the whole string (and it's large) and then re-inserting it in between two markers in the remote file. Is there no way of manipulating the lines of text in the file on-the-fly?

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