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• Entities used to serialize data have changed. How can the serialized data be upgraded for the new entities?

  - by i8abug

  Hi, I have a bunch of simple entity instances that I have serialized to a file. In the future, I know that the structure of these entities (ie, maybe I will rename Name to Header or something). The thing is, I don't want to lose the data that I have saved in all these old files. What is the proper way to either load the data from the old entities into new entities upgrade the old files so that they can be used with new entities Note: I think I am stuck with binary serialization, not xml serialization. Thanks in advance! Edit: So I have an answer for the case I have described. I can use a dataContractSerializer and do something like [DataMember("bar")] private string foo; and change the name in the code and keep the same name that was used for serialization. But what about the following additional cases: The original entity has new members which can be serialized Some serialized members that were in the original entity are removed Some members have actually changed in function (suppose that the original class had a FirstName and LastName member and it has been refactored to have only a FullName member which combines the two) To handle these, I need some sort of interpreter/translator deserialization class but I have no idea what I should use

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• multi-threading in MFC

  - by kiddo

  Hello all,in my application there is a small part of function,in which it will read files to get some information,the number of filecount would be utleast 50,So I thought of implementing threading.Say if the user is giving 50 files,I wanted to separate it as 5 *10, 5 thread should be created,so that each thread can handle 10 files which can speed up the process.And also from the below code you can see that some variables are common.I read some articles about threading and I am aware that only one thread should access a variable/contorl at a me(CCriticalStiuation can be used for that).For me as a beginner,I am finding hard to imlplement what I have learned about threading.Somebody please give me some idea with code shown below..thanks in advance file read function:// void CMyClass::GetWorkFilesInfo(CStringArray& dataFilesArray,CString* dataFilesB, int* check,DWORD noOfFiles,LPWSTR path) { CString cFilePath; int cIndex =0; int exceptionInd = 0; wchar_t** filesForWork = new wchar_t*[noOfFiles]; int tempCheck; int localIndex =0; for(int index = 0;index < noOfFiles; index++) { tempCheck = *(check + index); if(tempCheck == NOCHECKBOX) { *(filesForWork+cIndex) = new TCHAR[MAX_PATH]; wcscpy(*(filesForWork+cIndex),*(dataFilesB +index)); cIndex++; } else//CHECKED or UNCHECKED { dataFilesArray.Add(*(dataFilesB+index)); *(check + localIndex) = *(check + index); localIndex++; } } WorkFiles(&cFilePath,dataFilesArray,filesForWork, path, cIndex); dataFilesArray.Add(cFilePath); *(check + localIndex) = CHECKED; }

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• New to JEE; architecture suggestions for a service/daemon?

  - by Kate

  I am brand new to the JEE world. As an exercise to try and familiarize myself with JEE, I'm trying to create a tiered web-app, but I'm getting a little stuck on what the best way is to spin up a service in the background that does work. Parameters of the service: It must open and hold a socket connection and receive information from the connected server. There is a 1-to-1 correlation between a user and a new socket connection. So the idea is the user presses a button on the web-page, and somewhere on the server a socket connection is opened. For the remainder of the users session (or until the user presses some sort of disconnect button) the socket remains open and pushes received information to some sort of centralized store that servlets can query and return to the user via AJAX. Is there a JEE type way to handle this situation? Naturally what I would think to do is to just write a Java application that listens on a port that the servlets can connect to and spawns new threads that open these sockets, but that seems very ad-hoc to me. (PS: I am also new to Stack Overflow, so forgive me if it takes me some time to figure the site out!)

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• j_security_check to SSO in different module under Oracle App Server?

  - by thebearinboulder

  I have an existing j2ee application running on Oracle App Server. It is targeted towards paying customers so the content is secured and a SSO module properly intercepts all requests for secured content. Now the company is adding a unbranded public-facing module with a number of unsecured pages. At one point the user is expected to register for a free account and log in to proceed further. Think doctors adding a public-facing site with information for potential patients, or lawyers adding a public-facing site with information for potential clients. There's some information on the session and the usual approach would be to authenticate the user, persist the session information using the now-known user id, invalidate the existing session (to prevent certain types of attacks), the reload the session information before returning to the user. I can't just persist it under the session id since that's about to change. The glitch is that the existing application already has an SSO module and I get a 404 error every time I try to direct to j_security_check. I've tried that, /sso/j_security_check, even http://localhost/sso/j_security_check, all without success. I noticed that an earlier question said that tomcat requires access to a secured page before j_security_check is even visible. I don't know if that's the case with Oracle AS. Ideas? Or is the best approach to continue arguing that we have a different user base so it would be better to handle authentication in our own module anyway?

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• Should I put actors in the Domain-Model/Class-Diagram?

  - by devoured elysium

  When designing both the domain-model and class-diagrams I am having some trouble understanding what to put in them. I'll give an example of what I mean: I am doing a vacations scheduler program, that has an Administrator and End-Users. The Administrator does a couple of things like registering End-Users in the program, changing their previleges, etc. The End-User can choose his vacations days, etc. I initially defined an Administrator and End-User as concepts in the domain-model, and later as classes in the class-diagram. In the class-diagram, both classes ended up having a couple of methods like Administrator.RegisterNewUser(); Administrator.UnregisterUser(int id); etc. Only after some time I realised that actually both Administrator and End-User are actors, and maybe I got this design totally wrong. Instead of filling Administrator and End-User classes with methods to do what my Use-Cases request, I could define other classes from the domain to do them, and have controllers handle the Use-Cases(actually, I decided to do one for each Use-Case). I could have a UserDatabase.RegisterNewUser() and UserDatabase.UnregisterUser(int id);, for example, instead of having those methods on the Administrator class. The idea would be to try to think of the whole vacation-scheduler as a "closed-program" that has a set of features and doesn't bother with things such as authentication, that should be internal/protected, being that the only public things I'd let the outside world see would be its controllers. Is this the right approach? Or am I getting this totally wrong? Is it generally bad idea to put Actors in the domain-model/class-diagrams? What are good rules of thumb for this? My lecturer is following Applying UML and Patterns, which I find awful, so I'd like to know where I could look up more info on this described actor-models situation. I'm still a bit confused about all of this, as this new approach is radically different from anything I've done before.

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• To NOLOCK or NOT to NOLOCK, that is the question

  - by Limey

  Hi all, This is really more of a discussion than a specific question about nolock. I took over an app recently that almost every query (and there are lots of them) has the nolock option on them. Now I am pretty new to SQL server (used Oracle for 10 years) but yet I find this pretty disturbing. So this weekend I was talking with one of my friends who runs a rather large ecommerce site (name will be withheld to protect the guilty) and he says he has to do this with all of his SQL servers cause he will always end in deadlocks. Is this just a huge short fall with SQL server? Is this just a failure in the DB design (mine is not 3rd level, but its close) Is anybody out there running an SQL server app without nolocks? These are issues that Oracle handles better with more grandulare recordlocks. Is SQL server just not able to handle big loads? Is there some better workaround than reading uncommited data? I would love to hear what people think. Thanks

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• OCR combined with font recognition?

  - by Adam

  I have a bold idea where a user could take an image like the following and in a few seconds of processing, be able to edit a document which looks roughly the same. The software would use WhatTheFont (or something similar) to recognize the fonts used, and OCR and other software to handle the font size, color, line-spacing, and of course the text content itself. In the case of the example image, there would be three separate "textboxes" produced, each starting at the upper left corner of the text, and extending as far to the bottom right as it could before running into another text box. So the user would then see something like this: (The rectangles are just used to show the boundaries of each textbox.) From here, the user would be able to edit the text in each of these boxes to create a new document. Of course there are tons of obvious uses for such an application, especially on a mobile phone with a built in camera. So my questions are the following: I doubt the answer is yes, but does anything do this already? If I'm going to try to build this, what should I write it in? Can I use Python? What would be the best OCR libraries to start with? Is there a service other than WhatTheFont for font recognition that has better API support? Anybody want to help me build it? :) etc. etc. Update: One thing I wanted to mention (but forgot) is I would also like the background to be preserved. In other words, if the example above had an image behind the text, I'd like the document to use that image with text removed. I know this complicates things a lot because that would require some image editing techniques too (something akin to Photoshop CS5' "content-aware fill"). But if we can solve diminished reality on iPhones, I think we can figure this out!

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• Java queue and multi-dimension array

  - by javaLearner.java

  First of all, this is my code (just started learning java): Queue<String> qe = new LinkedList<String>(); qe.add("b"); qe.add("a"); qe.add("c"); qe.add("d"); qe.add("e"); My question: Is it possible to add element to the queue with two values, like: qe.add("a","1"); // where 1 is integer So, that I know element "a" have value 1. If I want to add a number let say "2" to element a, I will have like a = 3. If this cant be done, what else in java classes that can handle this? I tried to use multi-dimention array, but its kinda hard to do the queue, like pop, push etc. (Maybe I am wrong) How to call specific element in the queue? Like, call element a, to check its value. [Note] Please don't give me links that ask me to read java docs. I was reading, and I still dont get it. The reason why I ask here is because, I know I can find the answer faster and easier.

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• How to filter List<T> with LINQ and Reflection

  - by Ehsan Sajjad

  i am getting properties via reflection and i was doing like this to iterate on the list. private void HandleListProperty(object oldObject, object newObject, string difference, PropertyInfo prop) { var oldList = prop.GetValue(oldObject, null) as IList; var newList = prop.GetValue(newObject, null) as IList; if (prop.PropertyType == typeof(List<DataModel.ScheduleDetail>)) { List<DataModel.ScheduleDetail> ScheduleDetailsOld = oldList as List<DataModel.ScheduleDetail>; List<DataModel.ScheduleDetail> ScheduleDetailsNew = newList as List<DataModel.ScheduleDetail>; var groupOldSchedules = ScheduleDetailsOld .GroupBy(x => x.HomeHelpID) .SelectMany(s => s.DistinctBy(d => d.HomeHelpID) .Select(h => new { h.HomeHelpID, h.HomeHelpName })); } } Now i am making it generic because there will be coming different types of Lists and i don't want to put if conditions this way i want to write generic code to handle any type of list. I came up with this way: private void HandleListProperty(object oldObject, object newObject, string difference, PropertyInfo prop) { var oldList = prop.GetValue(oldObject, null) as IList; var newList = prop.GetValue(newObject, null) as IList; var ListType = prop.PropertyType; var MyListInstance = Activator.CreateInstance(ListType); MyListInstance = oldList; } i am able to get the items in MyListInstance but as the type will come at runtime i am not getting how to write linq query to filter them, any ideah how to do.

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• How do I subtract two dates in Django/Python?

  - by Ryan

  Hi! I'm working on a little fitness tracker in order to teach myself Django. I want to graph my weight over time, so I've decided to use the Python Google Charts Wrapper. Google charts require that you convert your date into a x coordinate. To do this I want to take the number of days in my dataset by subtracting the first weigh-in from the last weigh-in and then using that to figure out the x coords (for example, I could 100 by the result and increment the x coord by the resulting number for each y coord.) Anyway, I need to figure out how to subtract Django datetime objects from one another and so far, I am striking out on both google and here at the stack. I know PHP, but have never gotten a handle on OO programming, so please excuse my ignorance. Here is what my models look like: class Goal(models.Model): goal_weight = models.DecimalField("Goal Weight",max_digits=4, decimal_places=1) target_date = models.DateTimeField("Target Date to Reach Goal") set_date = models.DateTimeField("When did you set your goal?") comments = models.TextField(blank=True) def __unicode__(self): return unicode(self.goal_weight) class Weight(models.Model): """Weight at a given date and time """ goal = models.ForeignKey(Goal) weight = models.DecimalField("Current Weight",max_digits=4, decimal_places=1) weigh_date = models.DateTimeField("Date of Weigh-In") comments = models.TextField(blank=True) def __unicode__(self): return unicode(self.weight) def recorded_today(self): return self.date.date() == datetime.date.today() Any ideas on how to proceed in the view? Thanks so much!

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• Python ctypes in_dll string assignment

  - by ackdesha

  I could use some help assigning to a global C variable in DLL using ctypes. The following is an example of what I'm trying: test.c contains the following #include <stdio.h> char name[60]; void test(void) { printf("Name is %s\n", name); } On windows (cygwin) I build a DLL (Test.dll) as follows: gcc -g -c -Wall test.c gcc -Wall -mrtd -mno-cygwin -shared -W1,--add-stdcall-alias -o Test.dll test.o When trying to modify the name variable and then calling the C test function using the ctypes interface I get the following... >>> from ctypes import * >>> dll = windll.Test >>> dll <WinDLL 'Test', handle ... at ...> >>> f = c_char_p.in_dll(dll, 'name') >>> f c_char_p(None) >>> f.value = 'foo' >>> f c_char_p('foo') >>> dll.test() Name is Name is 48+? 13 Why does the test function print garbage in this case?

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• RewitePath on IIS7 with .Net 3.5 or 4.0 - The resource cannot be found.

  - by Renso

  In Global.asax handle errors by trying to redirect users to another page without changing the url in the address bar, that's why I am using RewritePath and not Redirect. void Application_Error(object sender, EventArgs e) { // Code that runs when an unhandled error occurs Context.RewritePath("~/Error.aspx", false); } Error.apsx in same root folder as About.aspx, and Default.aspx pages which of course work. Not sure I am having this issue. Have the following web.config file settings that I thought may be relevant: IIS7 settings: Application "TestRewriteUrl" under Default Web Site on DefaultAppPool. This example my seem trivial but I cannot use IIS7 HTTP Redirect as I actually was using this example to keep it simple. What I want to ultimately do is have a user type in http://www.somesite.com/myownpage and have it rewrite the path to another page in the same application directory by looking up the "myownpage" in the database to see what database id they have and redirect them to the correct "microsite" based on that without the user noticing a url change. Kind of like when you go to a blogging engine and no matter where in your blog you go the url remains the same. I don't want the user to go from http://www.mysite.com/tomshardware to http://www.mysite.com?id=8734656856. So that is why I used the simply example above to try and understand why the rewrite path does not work.

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• Selective replication with CouchDB

  - by FRotthowe

  I'm currently evaluating possible solutions to the follwing problem: A set of data entries must be synchonized between multiple clients, where each client may only view (or even know about the existence of) a subset of the data. Each client "owns" some of the elements, and the decision who else can read or modify those elements may only be made by the owner. To complicate this situation even more, each element (and each element revision) must have an unique identifier that is equal for all clients. While the latter sounds like a perfect task for CouchDB (and a document based data model would fit my needs perfectly), I'm not sure if the authentication/authorization subsystem of CouchDB can handle these requirements: While it should be possible to restict write access using validation functions, there doesn't seem to be a way to authorize read access. All solutions I've found for this problem propose to route all CouchDB requests through a proxy (or an application layer) that handles authorization. So, the question is: Is it possible to implement an authorization layer that filters requests to the database so that access is granted only to documents that the requesting client has read access to and still use the replication mechanism of CouchDB? Simplified, this would be some kind of "selective replication" where only some of the documents, and not the whole database is replicated. I would also be thankful for directions to some detailed information about how replication works. The CouchDB wiki and even the "Definite Guide" Book are not too specific about that.

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• Creating Thread in Win32

  - by Dave18

  Does ThreadFunc() gets called two times here? sometimes I notice a single call and sometimes none at all. #include <windows.h> #include <stdio.h> DWORD WINAPI ThreadFunc(LPVOID); int main() { HANDLE hThread; DWORD threadld; hThread = CreateThread(NULL, 0, ThreadFunc, 0, 0, &threadld ); printf("Thread is running\n"); } DWORD WINAPI ThreadFunc(LPVOID p) { printf("In ThreadFunc\n"); return 0; } Output 1 Thread is running In ThreadFunc In ThreadFunc Press any key to continue . . . Output 2 Thread is running In ThreadFunc Press any key to continue . . . Output 3 Thread is running Press any key to continue . . .

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• Perl : In splice() type of arg1 must be array, cannot be scalar dereference. How to fix?

  - by Michael Mao

  I am trying to comprehend the reference/dereference system in Perl. What I am trying to do is to remove an element by using reference: my $ref= \@{$collection{$_[0]}}; # delete($$ref[$i]); # delete works, I've tested that already splice($$ref, $i, 1); # this wouldn't do. I first tried the delete() subroutine, it works; however, it doesn't shift the index after the removed elements forward by 1, so I cannot continue working on other stuff. I then Googled and found the splice() subroutine which does delete and shift in one go. But the error feedback tells me that "Type of arg 1 to splice must be array (not scalar dereference)..." I then tried something like this: splice(@{$$ref}, $i, 1); That resulted in another error like this: "Not a SCALAR reference at...(pointing at that line)" So I am a bit puzzled, how could I handle this issue? I prefer not using any CPAN or additional library for the solution, if possible.

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• Reading and writing to files simultaneously?

  - by vipersnake005

  Moved the question here. Suppose, I want to store 1,000,000,000 integers and cannot use my memory. I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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• Why does my code fail to create a directory in "C:\Program Files" under Windows 7?

  - by sunil.nishad87

  I am using Windows 7 and I have to run one program in that windows but that program working in Windows XP. This is a Visual C++ program and I am using Visual Studio 2008 for this. When I am running my application, it does not throw any errors, but it does not create a directory in "c:\program files\". So can anyone help me to create directory and exe file? This is the code I am using: char szAppPath[MAX_PATH]; char szFileName[MAX_PATH]; DWORD dwResult; WIN32_FIND_DATA FindFileData; HANDLE hFind; dwResult = ExpandEnvironmentStrings( NULL, szAppPath, MAX_PATH); // "%ProgramFiles%" // do same for NSim directory strcat(szAppPath,"\\NSim"); hFind = FindFirstFile(szAppPath, &FindFileData); if (hFind == INVALID_HANDLE_VALUE) { //Directory Does't Exists create New if(!CreateDirectory(szAppPath,NULL)) //Throw Error { MessageBox("Unable to Create N-SIM directory","NSim Installer"); return ; } } else { //check if is directory or not if(!(FindFileData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)) { MessageBox("Can't Create N-SIM directory\n Another file with same name exists","NSim Installer"); return ; } FindClose(hFind); } //***************************************N-SIM Application**************************** strcpy(szFileName, szAppPath); HRSRC hRes; if( bRegister == FALSE) { strcat(szFileName,"\\NSim.exe"); //make same name of the Client & Server in program file hRes = FindResource(NULL, MAKEINTRESOURCE(IDR_LANSIMSERVER),RT_RCDATA); if(flagUpgrade ==0) { CString trial = installationDate(); //----- Detemine Expiry Date ----- setRegistry(trial); } }

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• A better solution than element.Elements("Whatever").First()?

  - by codeka

  I have an XML file like this: <SiteConfig> <Sites> <Site Identifier="a" /> <Site Identifier="b" /> <Site Identifier="c" /> </Sites> </SiteConfig> The file is user-editable, so I want to provide reasonable error message in case I can't properly parse it. I could probably write a .xsd for it, but that seems kind of overkill for a simple file. So anyway, when querying for the list of <Site> nodes, there's a couple of ways I could do it: var doc = XDocument.Load(...); var siteNodes = from siteNode in doc.Element("SiteConfig").Element("SiteUrls").Elements("Sites") select siteNode; But the problem with this is that if the user has not included the <SiteUrls> node (say) it'll just throw a NullReferenceException which doesn't really say much to the user about what actually went wrong. Another possibility is just to use Elements() everywhere instead of Element(), but that doesn't always work out when coupled with calls to Attribute(), for example, in the following situation: var siteNodes = from siteNode in doc.Elements("SiteConfig") .Elements("SiteUrls") .Elements("Sites") where siteNode.Attribute("Identifier").Value == "a" select siteNode; (That is, there's no equivalent to Attributes("xxx").Value) Is there something built-in to the framework to handle this situation a little better? What I would prefer is a version of Element() (and of Attribute() while we're at it) that throws a descriptive exception (e.g. "Looking for element <xyz> under <abc> but no such element was found") instead of returning null. I could write my own version of Element() and Attribute() but it just seems to me like this is such a common scenario that I must be missing something...

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• How to do something when AVQueuePlayer finishes the last playeritem

  - by user1634529

  I've got an AVQueuePlayer which I'm creating from an array of 4 AVPlayerItems, and it all plays fine. I want to do something when the last item in the queue finishes playing, I've looked a load of answers on here and this is the one that looks most promising for what I want: The best way to execute code AFTER a sound has finished playing In my button handler i have this code: static const NSString *ItemStatusContext; [thePlayerItemA addObserver:self forKeyPath:@"status" options:0 context:&ItemStatusContext]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playerItemDidReachEnd) name:AVPlayerItemDidPlayToEndTimeNotification object:thePlayerItemA]; theQueuePlayer = [AVQueuePlayer playerWithPlayerItem:thePlayerItemA]; [theQueuePlayer play]; and then I have a function to handle playerItemDidReachEnd: - (void)playerItemDidReachEnd:(NSNotification *)notification { // Do stuff here NSLog(@"IT REACHED THE END"); } But when I run this I get an Internal Inconsistency Exception: An -observeValueForKeyPath:ofObject:change:context: message was received but not handled. Key path: status Observed object: <AVPlayerItem: 0x735a130, asset = <AVURLAsset: 0x73559c0, URL = file://localhost/Users/mike/Library/Application%20Support/iPhone%20Simulator/5.0/Applications/A0DBEC13-2DA6-4887-B29D-B43A78E173B8/Phonics%2001.app/yes.mp3>> Change: { kind = 1; } What am I doing wrong?

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• Qt: QStackedWidget solution

  - by Martin

  I'm building a Qt application that have about 30 different views (QWidgets). My idea is to use a QStackedWidget to make it easy to switch between the different views in the application. I have two different solutions of how to implement this and use as little memory as possible when the user navigates through the application. Solution 1: Everytime I need to show a view I check if it is already in the stack. (The user might open the same view many times, maybe a view showing an item from a database). If the view is in the stack already it doesn't need to be created again and I can just show the view. The good thing with this solution is that I reuse the views (widgets) so they only need to be created once. This is good as the UI and other stuff should look the same everytime the user show a view, so why not reuse it? The problem with this solution is that every view has childrens. Maybe an object, a QList with objects or other things. A good thing with Qt is that you can use the parent-children mechanism so that the children will be deleted when the parent is deleted. As I never delete the parent (view) I need to handle this myself as the children might need to be deleted from different times when the view is shown. (Maybe the view show a list with objects and the list should be updated from a database each time the view is shown.) Solution 2: Everytime I need to show a QWidget I create a new one and show it. When it is not shown anymore, I delete it from memory. This is a quite easy solution. And as I delete the views when they are not shown both the view and it's children should be deleted from memory so it shouldn't increase memory, am I right? Which one of the solutions do you recommend?

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• NULL pointer dereference in swiotlb_unmap_sg_attrs() on disk IO

  - by Inductiveload

  I'm getting an error I really don't understand when reading or writing files using a PCIe block device driver. I seem to be hitting an issue in swiotlb_unmap_sg_attrs(), which appears to be doing a NULL dereference of the sg pointer, but I don't know where this is coming from, as the only scatterlist I use myself is allocated as part of the device info structure and persists as long as the driver does. There is a stacktrace to go with the problem. It tends to vary a bit in exact details, but it always crashes in swiotlb_unmap_sq_attrs(). I think it's likely I have a locking issue, as I am not sure how to handle the locks around the IO functions. The lock is already held when the request function is called, I release it before the IO functions themselves are called, as they need an (MSI) IRQ to complete. The IRQ handler updates a "status" value, which the IO function is waiting for. When the IO function returns, I then take the lock back up and return to request queue handling. The crash happens in blk_fetch_request() during the following: if (!__blk_end_request(req, res, bytes)){ printk(KERN_ERR "%s next request\n", DRIVER_NAME); req = blk_fetch_request(q); } else { printk(KERN_ERR "%s same request\n", DRIVER_NAME); } where bytes is updated by the request handler to be the total length of IO (summed length of each scatter-gather segment).

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• Writing my own implementation of stl-like Iterator in C++.

  - by Negai

  Good evening everybody, I'm currently trying to understand the intrinsics of iterators in various languages i.e. the way they are implemented. For example, there is the following class exposing the list interface. template<class T> class List { public: virtual void Insert( int beforeIndex, const T item ) throw( ListException ) =0 ; virtual void Append( const T item ) =0; virtual T Get( int position ) const throw( ListException ) =0; virtual int GetLength() const =0; virtual void Remove( int position ) throw( ListException ) =0; virtual ~List() =0 {}; }; According to GoF, the best way to implement an iterator that can support different kinds of traversal is to create the base Iterator class (friend of List) with protected methods that can access List's members. The concrete implementations of Iterator will handle the job in different ways and access List's private and protected data through the base interface. From here forth things are getting confusing. Say, I have class LinkedList and ArrayList, both derived from List, and there are also corresponding iterators, each of the classes returns. How can I implement LinkedListIterator? I'm absolutely out of ideas. And what kind of data can the base iterator class retrieve from the List (which is a mere interface, while the implementations of all the derived classes differ significantly) ? Sorry for so much clutter. Thanks.

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• My method is too specific. How can I make it more generic?

  - by EricBoersma

  I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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• mvc design in a card game

  - by Hong

  I'm trying to make a card game. some classes I have are: CardModel, CardView; DeckModel, DeckView. The deck model has a list of card model, According to MVC, if I want to send a card to a deck, I can add the card model to the deck model, and the card view will be added to the deck view by a event handler. So I have a addCard(CardModel m) in the DeckModel class, but if I want to send a event to add the card view of that model to the deck view, I only know let the model has a reference to view. So the question is: If the card model and deck model have to have a reference to their view classes to do it? If not, how to do it better? Update, the code: public class DeckModel { private ArrayList<CardModel> cards; private ArrayList<EventHandler> actionEventHandlerList; public void addCard(CardModel card){ cards.add(card); //processEvent(event x); //must I pass a event that contain card view here? } CardModel getCards(int index){ return cards.get(index); } public synchronized void addEventHandler(EventHandler l){ if(actionEventHandlerList == null) actionEventHandlerList = new ArrayList<EventHandler>(); if(!actionEventHandlerList.contains(l)) actionEventHandlerList.add(l); } public synchronized void removeEventHandler(EventHandler l){ if(actionEventHandlerList!= null && actionEventHandlerList.contains(l)) actionEventHandlerList.remove(l); } private void processEvent(Event e){ ArrayList list; synchronized(this){ if(actionEventHandlerList!= null) list = (ArrayList)actionEventHandlerList.clone(); else return; } for(int i=0; i<actionEventHandlerList.size(); ++i){ actionEventHandlerList.get(i).handle(e); } } }

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• How does an ASP.NET programmer go from working on/developing existing sites, to creating one from sc

  - by SLC

  I've been an ASP.NET developer for some time, always working on existing ASP.NET pages, modifying functionality, adding features, tweaking things etc. but have never built a site up from scratch. I've read books on ASP.NET, and they generally talk you through the various features of ASP.NET with a mock up site, but it's always very basic and they jump straight in. The time has come however, to write a site from scratch for a client. I've never done this before. There are design considerations, but like a lot of ASP.NET sites, the basic idea is, you have a site, where users can log in, and save some information like their name and password and address. The site has some functionality, but that's the basic design of a majority of (business-related) asp.net websites I would wager. I know how to program in ASP.NET already on an existing site, but I don't know how to design my own properly that meets the criteria above. I guess the main worry is security. I don't know the best way to handle a simple log-in system that stores user information like their name and password. I understand there are a few approaches to this, but the catch with this project is that it has to be absolutely bulletproof. Maximum security. All those good practices for security, it needs to have them all. I'm not asking what they are, but I am asking where to begin. What should be the first steps after I do File New Project ? Where can I look for information about setting up a secure ASP.NET website? I'll figure out the content and page layout later, it's the framework that is the big thing. Any and all advice would be welcome. I really want to get my first from-scratch project right from the beginning. Just to confuse things, it's possible I will be using MVC, I am not sure if this has any impact.

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