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• What could trigger a change of http status to 500 on the client's end?

  - by VexedPanda

  We have a PHP web application that posts data to itself, and either displays an updated page based on that data, or redirects to another page. An example of this is a script with a paged list on it, where clicking on the Next link causes a post to the same page, which then returns an updated version of the page showing the new set of list items. One client is reporting that IE is displaying friendly error messages when the page updates itself instead of the correct behavior of displaying the updated page. Turning friendly error messages off "corrects" this problem, and displays the updated page normally, indicating no actual server error occurred. When testing from any location other than this client's our web app does not produce any http error statuses, and in this specific situation only produces 200 statuses. (According to Fiddler.) What could be interfering with the HTTP POST and changing the response's http status code to 500 (or another code that would trigger friendly errors in IE)? Are there certain proxies or other network tools that could be misconfigured or buggy in this manner? Is there any way we can alter our application (apart from avoiding posts to the same script, which is not feasible) to get around this misbehavior?

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• What could possibly be causing this NPE in onCreate?

  - by Adam Johns

  I am getting an NPE in onCreate of the following file (MySubActivity): public class MySubActivity extends MySuperActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); myTextView.setText(getResources().getString(R.string.myString)); } } MySuperActivity: public class MySuperActivity extends Activity { protected TextView myTextView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.my_layout); myTextView = (TextView)findViewById(R.id.myTextViewid); } } The strange thing is that I have never seen this crash while testing the app. The page works fine when I test it. However I got a crash report from Google notifying me of the crash. I cannot reproduce it, and I have no idea under what scenario this crash could happen. Seeing as how it works for me, the resource ids and string names etc. must be correct. The only thing that came across my mind was that maybe the user had their phone set to a different language, so it couldn't properly pull the resources. However, there are default resources for all of them, and I tested changing the language of my emulator and it didn't crash. Any ideas?

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• Multiple "ObjectChangeTracker" getting created, can it be avoided?

  - by user555937

  Hi, We are working on a POC where we have following architecture (MVVM), WPF(Client) + WCF + Model(DataAccess)+ ADO.Net Entity Framework 4.0 (with SQL Server 2008 R2 as DB) All are different projects. In the DataAccess layer we have created different Entity Models(edmx) based on the functionality. The tables under perticular flow are grouped and created different entity models. We are using self tracking entities to and fro to communicate with the WPF client through wcf service. For Single model everything works fine. But when we created a Multiple models then few issues started coming. Mutliple models have few duplicate tables/entities. Two probels are, 1) When we try to access entities from different models mutiple objects "ObjectChangeTracker" are getting created. E.g. CompanyModel(edmx) - Company(Entity) - ObjectChangeTracker, ObjectState ProductModel(edmx) - Customer(Entity) - ObjectChangeTracker1, ObjectState1 OrderModel(edmx) - Oder(Entity) - ObjectChangeTracker2, ObjectState2 Is there any way to avoid this? 2) There are few tables which shared across the Models, E.g. Company(Entity) is used in All above mdoels. During compile time it does not thow any error. But run time It gives error saying "Schema specified is not valid. Errors: The mapping of CLR type to EDM type is ambiguous because multiple CLR types match the EDM type "Company"".. To resolve this, we renamed the entities with some prefix to make them Unique. Is there any other way we can resolve this without changing the name of the entity in the same assembly? Thanks in advance and appreciate if anyone has approach for these issues. Thanks, Kiran

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• How do I put my return data from an asmx into JSON?

  - by jphenow

  I want to return an array of javascript objects from my asp.net asmx file. ie. variable = [ { *value1*: 'value1', *value2*: 'value2', ..., }, { . . } ]; I seem have been having trouble reaching this. I'd put this into code but I've been hacking away at it so much it'd probably do more harm than good in having this answered. Basically I am using a web service to find names as people type the name. I'd use a regular text file or something but its a huge database that's always changing - and don't worry I've indexed the names so searching can be a little snappier - but I would really prefer to stick with this method and just figure out how to get usable JSON back to javascript. I've seen a few that sort of attempt to describe how one would approach this but I honestly think microsofts articles are damn near unreadable. Thanks in advance for assistance. EDIT: I'm using the $.ajax() function from jQuery - I've had it working but it seems like I was doing it in bad practice not returning and using actual JSON. Previously I'd take a string back and insert it into html to use the variable it set - very roundabout.

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• Java Recursion Triangle Standing on Tip

  - by user1629075

  I was wondering how to create triangle out of asterisks on its tip rather than on its base. I have the code for making it stand on its base: public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = printTriangle(count - 1); p = p + "*"; System.out.print(p); System.out.print("\n"); return p; } But then I'm stuck on how to have the greatest number of stars on the top, and then the next least, and so on. I was thinking something along the terms of having (count - p) to have the input of rows be subtracted from the amount of decrease, but then i was confused by this idea because p is string. EDIT: I tried changing the position of printTriangle(count - 1) using my original method without iterations and got 1 star per each line; how can I fix this? public class triangles { public static void main(String[] args) { printTriangle(5); } public static String printTriangle (int count) { if( count <= 0 ) return ""; String p = ""; p = p + "*"; System.out.print(p); System.out.print("\n"); p = printTriangle(count - 1); return p; } }

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• 3 websites 1 Project

  - by godz-gift05

  Hey Guys, OK. we are currently on a plan to develop a website for 3 same company. The main difference would be just the look and maybe a couple of extra question for one or two company. Currently each company have their own website and when they required a new function we have to re-code all three website or when one wants a new function just one website update. What we wanna accomplish is to create ONE website that could house all these 3 website. Most of these website function are the same like 90% function is the same I figure out the different look which can be done changing the website style-theme.. But we have problem tackling the functionality of if one company wanted to add something. So if we wanted to update a function we just wanna do a change in one function and that should apply for all.. And if one function is required for one company then just add the new fucntion and assign it to 1 company... How do u structure something like this.. We wanna be able to control what being displayed based on the company and also the fucntions available. THANK YOU. I just need some direction on how to do this, Right now Inheritance is on my head to solve all this problem.

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• jQuery - How to animate click function without clicking (Slide-show like) - Is this possible?

  - by iamtheratio

  Hello, I have created a jQuery script (with help) that works great however I need it to automate/animate itself without using the click function, I just want to know is this possible and if so, how? Similar to a slide-show. Basically the code allows me to click on an image and hide/show a DIV, while changing a list of elements such as class/id name. Here's my code: JQUERY: jQuery(document).ready(function(){ //if this is not the first tab, hide it jQuery(".imgs:not(:first)").hide(); //to fix u know who jQuery(".imgs:first").show(); //when we click one of the tabs jQuery(".img_selection a").click(function(){ //get the ID of the element we need to show stringref = jQuery(this).attr("href").split('#')[1]; // adjust css on tabs to show active tab $('.img_selection a').removeAttr('id'); // remove all ids $(this).attr('id', this.className + "_on") // create class+_on as this id. //hide the tabs that doesn't match the ID jQuery('.imgs:not(#'+stringref+')').hide(); //fix if (jQuery.browser.msie && jQuery.browser.version.substr(0,3) == "6.0") { jQuery('.imgs#' + stringref).show(); } else //display our tab fading it in jQuery('.imgs#' + stringref).show(); //stay with me return false; }); });

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• Best way of showing more results with javascript/css

  - by Ricardo Neves

  I'm developing a website and i'm having troubles showing the search results to the user the way I want. Basically, after the user search, the page makes a couple of ajax requests and as soon as a response arrive it appends the info to a specific element on my page. Each results is shown as a line... The problem is that in most case there are going to be more than 1000 results and this would make the page have a large scroll. My idea was to show only the first 15 results and when the user clicks "show more" the element would expand and show the next 15 results and so on... This would be easier to do if the website wasn't responsive, but because it is I can't find the proper way of implementing what I want without lowering the website perfomance. I have "2 ideas": The first is by using something like #element .div:nth-child(-n+15) on my css and figure a way of changing the "15" to how much results I want to show... I don't know if this can be done. Is it possible to call css rules with parameters? Maybe with less css? The second option is probably a bad option if i don't want to lower the website performance. Using javascript I would check if there is a specific css class(like .show-15 .show30 .show45) and add that class to my element and if it don't exist, create it somehow.. Any help would be appreciated.

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• java label setText and setBounds clashing?

  - by java

  I would like to have a JLabel changint color to a random one, while jumping to a random position, and while changing its text. but the setText and setBounds seem to clash and i don't know why. if you comment out the setText then the setBounds will work, but they won't work together. import java.awt.*; import java.util.*; import javax.swing.*; public class test2 extends JFrame { private static JLabel label = new JLabel("0"); private static Random gen = new Random(); public test2() { JPanel panel = new JPanel(); panel.add(label); this.add(panel); } public static void move() { for (int i = 0; i < 10; i++) { int n = gen.nextInt(254)+1; int nn = gen.nextInt(254)+1; int nnn = gen.nextInt(254)+1; label.setText(""+i); //the setBounds command will not work with the setText command. why? label.setBounds(n*2, nn*2, 20, 20); label.setForeground(new Color(n, nn, nnn)); try { Thread.sleep(200); } catch (Exception e) {} } } public static void main(String[] args) { test2 frame = new test2(); frame.setVisible(true); frame.setSize(600, 600); frame.setResizable(true); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); move(); } }

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• What prevents a user from adding controls to an ASP.NET page client side?

  - by Curtis White

  This goes back to my other question which I thought was sufficiently answers but upon reflect am not sure that it was (sorry). Backgrounder: I am generating a form dynamically. I am pulling from the database the controls. I must associate each control with a database ID which is not the user's session id. I do this currently by storing my ID in the ID for the web control with some other stuff to make it unique/clear what I am doing. On the post back, I iterate through all the controls on my web page checking for my special identifier, ie, MyGeneratedTextBox_ID_Unique. This process enables for 2 important steps, identifying the control was one I generated and also getting the ID for this input field. And, all of this works but I'm still concerned about the security of it. I do not see a security issue with showing the actual database ID's in this case, although agree it is not desirable. However, I am concerned of the following possibilities: If a user could add a nefarious control to my collection and use that for a SQL injection attack. More academic, but if a user could somehow store data for fields they do not have access too by changing the id's. I agree this is a "hack" of a way to do it. But my question is, is it a security risk and is there an 'easy' way to do it in a less hack way? I assume that only the controls that are created/instantiated on the page are added to the controls list.. thus all controls must be created server side and thus the security issue is address but just wanted to validate. Thanks again. PS: I could see adding a property for each control and encrypting the viewstate would be a little more secure.

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• PHP Header redirection problem within page called by cURL

  - by Das123

  I have a site that uses cURL to access some pages, stores the returned results in variables, and then uses these variables within its own page. The script works well except where the target cURL page has a header('Location: ...') command inside it. It seems to just ignore this header command. The cURL command is as follows... //Load result page into variable so portions can be allocated to correct variables $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); # URL to post to curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 ); # return into a variable curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_POST, true); curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields); $loaded_result = curl_exec( $ch ); # run! curl_close($ch); I've tried changing the CURLOPT_HEADER to 1 but it doesn't do anything. So how can I allow script redirection within the target urls using cURL to grab the results? By the way, the pages work fine if accessed other than via cURL but iFrames are not an option in this instance.

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• PHP class to C# class?

  - by LordSauron

  I work for a company that makes application's in C#. recently we got a customer asking us to look in to rebuilding an application written in PHP. This application receives GPS data from car mounted boxes and processes that into workable information. The manufacturer for the GPS device has a PHP class that parses the received information and extracts coordinates. We were looking in to rewriting the PHP class to a C# class so we can use it and adapt it. And here it comes, on the manufacturers website there is a singel line of text that got my skin krawling: "The encoding format and contents of the transmitted data are subject to constant changes. This is caused by implementations of additional features by new module firmware versions which makes it virtually impossible to document it and for you to properly decode it yourself." So i am now looking for a option to use the "constantly changing" PHP class and access it in C#. Some thing link a shell only exposing some function's i need. Except i have no idea how i can do this. Can any one help me find a solution for this.

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• Importing package as a submodule

  - by wecac

  Hi, I have a package 3rd party open source package "foo"; that is in beta phase and I want to tweak it to my requirements. So I don't want to get it installed in /usr/local/lib/python or anywhere in current sys.path as I can't make frequent changes in top level packages. foo/ __init__.py fmod1.py import foo.mod2 fmod2.py pass I want to install the the package "foo" as a sub package of my namespace say "team.my_pkg". So that the "fullname" of the package becomes "team.my_pkg.foo" without changing the code in inner modules that refer "team.my_pkg.foo" as "foo". team/ __init__.py my_pkg/ __init__.py foo/ fmod1.py import foo.mod2 fmod2.py pass One way to do this is to do this in team.my_pkg.init.py: import os.path import sys sys.path.append(os.path.dirname(__file__)) But I think it is very unsafe. I hope there is some way that only fmod1.py and fmod2.py can call "foo" by its short name everything else should use its complete name "team.my_pkg.foo" I mean this should fail outside team/my_pkg/foo: import team.my_pkg import foo But this should succeed outside team/my_pkg/foo: import team.my_pkg.foo

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• Numbers localization

  - by Reza

  How can I set the variant of Arabic numeral without changing number characters ? Eastern Arabic ? ? ? ? ? ? ? ? ? ? Persian variant ? ? ? ? ? ? ? ? ? ? Western Arabic 0 1 2 3 4 5 6 7 8 9 here is a sample code: <!DOCTYPE html> <html> <meta charset="utf-8"> <head> <title></title> </head> <body> <div lang="fa">123456789</div> <div lang="ar">123456789</div> <div lang="en">123456789</div> </body> </html> Also note that in Windows text boxes (e.g. Run) numbers are displayed correctly according to surrounding text languages.

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• jQuery remove SELECT options based on another SELECT selected on change and on load

  - by John Sieber

  I'm using the following jQuery code to remove options from a select and it is working well. But instead of it only executing when the theOption2 select is changed I would also like it to work when the page is loaded depending on the selected item that is selected. I tried using the a copy of the script and changing the .change to .load and also tried using (window).load without the desired results. Essentially, I need the script to execute on change of the Options1 and on the loading of the page. Any help with this would be greatly appreciated. <script type="text/javascript"> $(document).ready(function() { //copy the second select, so we can easily reset it var selectClone = $('#theOptions2').clone(); $('#theOptions1').change(function() { var val = parseInt($(this).val()); //reset the second select on each change $('#theOptions2').html(selectClone.html()) switch(val) { //if 2 is selected remove C case 2 : $('#theOptions2').find('option:contains(c)').remove();break; //if 3 is selected remove A case 3 : $('#theOptions2').find('option:contains(a)').remove();break; } }); }); </script> <select id="theOptions1"> <option value="1">1</option> <option value="2" selected="selected">2</option> <option value="3">3</option> </select> <br /> <select id="theOptions2"> <option>a</option> <option>b</option> <option>c</option> </select>

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• StructureMap Configuration Per Thread/Request for the Full Dependency Chain

  - by Phil Sandler

  I've been using Structuremap for a few months now, and it has worked great on some smaller (green field) projects. Most of the configurations I have had to set up involve a single implementation per interface. In the cases where I needed to choose a specific implementation at runtime, I created a factory class that used ObjectFactory.GetNamedInstance<(). In the smaller projects, there were few enough of these cases where I was comfortable with the references to ObjectFactory. My understanding is that you want to limit these references as much as possible, and ideally only reference the ObjectFactory once. I am working to refactor a larger codebase to use IOC/StructureMap, and am finding that I may need many of these factory classes with ObjectFactory references to get what I need. Essentially, I am creating a "root service" with the ObjectFactory, so that everything in the dependency chain is managed by the container. The root service is created by name (i.e. "BuildCar", "BuildTruck"), and the services needed deeper in the dependency chain could also be constructed using the same name--so the "IAttachWheels" service could vary based on whether a car or truck is being built. Since the class that depends on IAttachWheels is the same in both configurations, I don't think I can use ConstructedBy in the registry to choose the implementation. Also, to be clear, the IAttachWheels implementations need to be managed by the container as well, because the dependency chain runs fairly deep. I looked briefly at Profiles as an option, but read (here on StackOverflow) that changing profiles essentially changes implementations for all threads. Is there a feature that is similar to profiles that is thread/request specific? Is the factory class that references ObjectFactory approach the right way to go? Any thoughts would be appreciated.

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• MPI Odd/Even Compare-Split Deadlock

  - by erebel55

  I'm trying to write an MPI version of a program that runs an odd/even compare-split operation on n randomly generated elements. Process 0 should generated the elements and send nlocal of them to the other processes, (keeping the first nlocal for itself). From here, process 0 should print out it's results after running the CompareSplit algorithm. Then, receive the results from the other processes run of the algorithm. Finally, print out the results that it has just received. I have a large chunk of this already done, but I'm getting a deadlock that I can't seem to fix. I would greatly appreciate any hints that people could give me. Here is my code http://pastie.org/3742474 Right now I'm pretty sure that the deadlock is coming from the Send/Recv at lines 134 and 151. I've tried changing the Send to use "tag" instead of myrank for the tag parameter..but when I did that I just keep getting a "MPI_ERR_TAG: invalid tag" for some reason. Obviously I would also run the algorithm within the processors 0 but I took that part out for now, until I figure out what is going wrong. Any help is appreciated.

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• In Rails, how would I include a section of a page only if the rest of the page doesn't match a certain regexp?

  - by Simon

  We have a site with a lot of user-generated content, and we'd like to show Google ads on it. Some of the content is such that we mustn't show the ads on pages containing that content, or else the whole site gets banned. We've come up with a regexp which we think will match all the offending content. So, three approaches come to mind: Render the page once without the ad section, and then insert the ad section into it if it's clean Render the page as normal, and do the insertion in client-side javascript Render the page above the ad section, capturing only the parts of the page that change; make sure there are no changing parts afterwards. Only show the ads if the captured text is clean, and make sure the unchanging, uncaptured parts are well-vetted in advance. The first one seems like it might delay the page rendering for too long; the second seems like it might delay showing the ads too long; and the third seems too fragile. Is there a better approach? If not, which one is the best solution of the three?

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• Repeated host lookups failing in urllib2

  - by reve_etrange

  I have code which issues many HTTP GET requests using Python's urllib2, in several threads, writing the responses into files (one per thread). During execution, it looks like many of the host lookups fail (causing a name or service unknown error, see appended error log for an example). Is this due to a flaky DNS service? Is it bad practice to rely on DNS caching, if the host name isn't changing? I.e. should a single lookup's result be passed into the urlopen? Exception in thread Thread-16: Traceback (most recent call last): File "/usr/lib/python2.6/threading.py", line 532, in __bootstrap_inner self.run() File "/home/da/local/bin/ThreadedDownloader.py", line 61, in run page = urllib2.urlopen(url) # get the page File "/usr/lib/python2.6/urllib2.py", line 126, in urlopen return _opener.open(url, data, timeout) File "/usr/lib/python2.6/urllib2.py", line 391, in open response = self._open(req, data) File "/usr/lib/python2.6/urllib2.py", line 409, in _open '_open', req) File "/usr/lib/python2.6/urllib2.py", line 369, in _call_chain result = func(*args) File "/usr/lib/python2.6/urllib2.py", line 1170, in http_open return self.do_open(httplib.HTTPConnection, req) File "/usr/lib/python2.6/urllib2.py", line 1145, in do_open raise URLError(err) URLError: <urlopen error [Errno -2] Name or service not known>

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• Trouble swapping values as keys in generic java BST class

  - by user1729869

  I was given a generic binary search tree class with the following declaration: public class BST<K extends Comparable<K>, V> I was asked to write a method that reverses the BST such that the values become the keys and keys become values. When I call the following method (defined in the class given) reverseDict.put(originalDict.get(key), key); I get the following two error messages from Netbeans: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: BST.put And also: no suitable method found for put(V,K) method BST.put(BST<K,V>.Node,K,V) is not applicable (actual and formal argument lists differ in length) method BST.put(K,V) is not applicable (actual argument V cannot be converted to K by method invocation conversion) where V,K are type-variables: V extends Object declared in method <K,V>reverseBST(BST<K,V>) K extends Comparable<K> declared in method <K,V>reverseBST(BST<K,V>) From what the error messages are telling me, since my values do not extend Comparable I am unable to use them as keys. If I am right, how can I get around that without changing the class given (maybe a cast)?

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• Why does Python's 'for ... in' work differently on a list of values vs. a list of dictionaries?

  - by Code Duck

  I'm wondering about some details of how for ... in works in Python. My understanding is for var in iterable on each iteration creates a variable, var, bound to the current value of iterable. So, if you do for c in cows; c = cows[whatever], but changing c within the loop does not affect the original value. However, it seems to work differently if you're assigning a value to a dictionary key. cows=[0,1,2,3,4,5] for c in cows: c+=2 #cows is now the same - [0,1,2,3,4,5] cows=[{'cow':0},{'cow':1},{'cow':2},{'cow':3},{'cow':4},{'cow':5}] for c in cows: c['cow']+=2 # cows is now [{'cow': 2}, {'cow': 3}, {'cow': 4}, {'cow': 5}, {'cow': 6}, {'cow': 7} #so, it's changed the original, unlike the previous example I see one can use enumerate to make the first example work, too, but that's a different story, I guess. cows=[0,1,2,3,4,5] for i,c in enumerate(cows): cows[i]+=1 # cows is now [1, 2, 3, 4, 5, 6] Why does it affect the original list values in the second example but not the first?

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• Once an HTML document has a manifest (cache.manifest), how can you remove it?

  - by Michael F

  It seems that once you have a manifest entry, a la: <html manifest="cache.manifest"> Then that page (the master entry in the cache) will always be cached (at least by Safari) until the user does something to remove the cache, even if you later remove the manifest attribute from the html tag and update the manifest (by changing something within it), forcing the master entry to be reloaded along with everything else. In other words, if you have: index.html (with manifest defined) file1.js (referenced in manifest) file2.js (referenced in manifest) cache.manifest (lists the two js files) -- removing the manifest entry from index.html and modifying the manifest (so it gets expired by the browser and all content reloaded) will not stop this page from behaving as if it's still fully cached. If you view source on index.html you won't see the manifest listed anymore, but the browser will still request only the cache.manifest file, and unless that file's content is changed, no other changes to any files will be shown to the user. It seems like a pretty glaring bug, and it's present on iOS as well as Mac versions of Safari. Has anyone found a way of resetting the page and getting rid of the cache without requiring user intervention?

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• Benefits of "Don't Fragment" on TCP Packets?

  - by taspeotis

  One of our customers is having trouble submitting data from our application (on their PC) to a server (different geographical location). When sending packets under 1100 bytes everything works fine, but above this we see TCP retransmitting the packet every few seconds and getting no response. The packets we are using for testing are about 1400 bytes (but less than 1472). I can send an ICMP ping to www.google.com that is 1472 bytes and get a response (so it's not their router/first few hops). I found that our application sets the DF flag for these packets, and I believe a router along the way to the server has an MTU less than/equal to 1100 and dropping the packet. This affects 1 client in 5000, but since everybody's routes will be different this is expected. The data is a SOAP envelope and we expect a SOAP response back. I can't justify WHY we do it, the code to do this was written by a previous developer. So... Are there are benefits OR justification to setting the DF flag on TCP packets for application data? I can think of reasons it is needed for network diagnostics applications but not in our situation (we want the data to get to the endpoint, fragmented or not). One of our sysadmins said that it might have something to do with us using SSL, but as far as I know SSL is like a stream and regardless of fragmentation, as long as the stream is rebuilt at the end, there's no problem. If there's no good justification I will be changing the behaviour of our application. Thanks in advance.

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• C++: inheritance problem

  - by Helltone

  It's quite hard to explain what I'm trying to do, I'll try: Imagine a base class A which contains some variables, and a set of classes deriving from A which all implement some method bool test() that operates on the variables inherited from A. class A { protected: int somevar; // ... }; class B : public A { public: bool test() { return (somevar == 42); } }; class C : public A { public: bool test() { return (somevar > 23); } }; // ... more classes deriving from A Now I have an instance of class A and I have set the value of somevar. int main(int, char* []) { A a; a.somevar = 42; Now, I need some kind of container that allows me to iterate over the elements i of this container, calling i::test() in the context of a... that is: std::vector<...> vec; // push B and C into vec, this is pseudo-code vec.push_back(&B); vec.push_back(&C); bool ret = true; for(i = vec.begin(); i != vec.end(); ++i) { // call B::test(), C::test(), setting *this to a ret &= ( a .* (&(*i)::test) )(); } return ret; } How can I do this? I've tried two methods: forcing a cast from B::* to A::*, adapting a pointer to call a method of a type on an object of a different type (works, but seems to be bad); using std::bind + the solution above, ugly hack; changing the signature of bool test() so that it takes an argument of type const A& instead of inheriting from A, I don't really like this solution because somevar must be public.

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• How to access variables in shared memory

  - by user1723361

  I am trying to create a shared memory segment containing three integers and an array. The segment is created and a pointer is attached, but when I try to access the values of the variables (whether changing, printing, etc.) I get a segmentation fault. Here is the code I tried: #include <stdio.h> #include <stdbool.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #define SIZE 10 int* shm_front; int* shm_end; int* shm_count; int* shm_array; int shm_size = 3*sizeof(int) + sizeof(shm_array[SIZE]); int main(int argc, char* argsv[]) { int shmid; //create shared memory segment if((shmid = shmget(IPC_PRIVATE, shm_size, 0644)) == -1) { printf("error in shmget"); exit(1); } //obtain the pointer to the segment if((shm_front = (int*)shmat(shmid, (void *)0, 0)) == (void *)-1) { printf("error in shmat"); exit(1); } //move down the segment to set the other pointers shm_end = shm_front + 1; shm_count = shm_front + 2; shm_array = shm_front + 3; //tests on shm //*shm_end = 10; //gives segmentation fault //printf("\n%d", *shm_front); //gives segmentation fault //clean-up //get rid of shared memory shmdt(shm_front); shmctl(shmid, IPC_RMID, NULL); //printf("\n\n"); return 0; } I tried accessing the shared memory by dereferencing the pointer to the struct, but got a segmentation fault each time.

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