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  • Linux C debugging library to detect memory corruptions

    - by calandoa
    When working sometimes ago on an embedded system with a simple MMU, I used to program dynamically this MMU to detect memory corruptions. For instance, at some moment at runtime, the foo variable was overwritten with some unexpected data (probably by a dangling pointer or whatever). So I added the additional debugging code : at init, the memory used by foo was indicated as a forbidden region to the MMU; each time foo was accessed on purpose, access to the region was allowed just before then forbidden just after; a MMU irq handler was added to dump the master and the address responsible of the violation. This was actually some kind of watchpoint, but directly self-handled by the code itself. Now, I would like to reuse the same trick, but on a x86 platform. The problem is that I am very far from understanding how is working the MMU on this platform, and how it is used by Linux, but I wonder if any library/tool/system call already exist to deal with this problem. Note that I am aware that various tools exist like Valgrind or GDB to manage memory problems, but as far as I know, none of these tools car be dynamically reconfigured by the debugged code. I am mainly interested for user space under Linux, but any info on kernel mode or under Windows is also welcome!

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  • How do I use a custom cookie session serializer in Rack?

    - by Damien Wilson
    Hello SO. I'm currently integrating Warden into a new Rack application I'm building. I'd like to implement a recent patch to Rack that allows me to specify how sessions are serialized; specifically, I'd like to use Rack::Session::Cookie::Identity as the session processor. Unfortunately, the documentation is a little unclear as to what syntax I should use to configure Rack::Session::Cookie in my rackup file, can anyone here tell me what I'm doing wrong? config.ru require 'my_sinatra_app' app = self use Rack::Session::Cookie.new(app, Rack::Session::Cookie::Identity.new), {:key => "auth_token"} use Warden::Manager do |warden| # Must come AFTER Rack::Session warden.default_strategies :password warden.failure_app Jelli::Auth.run! end run MySinatraApp error message from thin !! Unexpected error while processing request: undefined method `new' for #<Rack::Session::Cookie:0x00000110124128> PS: I'm using bundler to manage my gem dependencies and I've likewise included rack's master branch as the desired version. Update: As suggested in the comments below, I have read the documentation; sadly the suggested syntax in the docs is not working. Update: Still no luck on my end; offering up a bounty to whoever can help me figure this out.

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  • How to solve the delay problem in animation of sprites ?

    - by srikanth rongali
    My problem is, I did coding for a sprite. It should change it should change it's image from( 1, 2, 3). It should look like count down time to start a game. 1, 2, 3 are 3 png images. But the images are not displayed in equal intervals of time. I mean time between (1 - 2), (2 - 3) is not same. It is random. Please help me with my problem. Help me if there is better solution than what I am doing.(My animation should be like, before any game starts we see count down 1 then 2 then 3 then GO). -(id)init { if((self = [super init])) { [[CCDirector sharedDirector] setAnimationInterval:60.0/60]; [[CCDirector sharedDirector] setDisplayFPS:NO]; CCAnimation* numberAnimation = [CCAnimation animationWithName:@"countDown" delay: 60.0/60]; for( int i=1;i<4;i++) [numberAnimation addFrameWithFilename: [NSString stringWithFormat:@"number_%02d.png", i]]; id numberAction = [CCAnimate actionWithAnimation: numberAnimation restoreOriginalFrame:NO]; id action2 = [CCFadeOut actionWithDuration:0.5f]; CCSprite *number; number = [CCSprite spriteWithFile:@"number.png"]; .... } }

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  • Getting around IBActions limited scope

    - by Septih
    Hello, I have an NSCollectionView and the view is an NSBox with a label and an NSButton. I want a double click or a click of the NSButton to tell the controller to perform an action with the represented object of the NSCollectionViewItem. The Item View is has been subclassed, the code is as follows: #import <Cocoa/Cocoa.h> #import "WizardItem.h" @interface WizardItemView : NSBox { id delegate; IBOutlet NSCollectionViewItem * viewItem; WizardItem * wizardItem; } @property(readwrite,retain) WizardItem * wizardItem; @property(readwrite,retain) id delegate; -(IBAction)start:(id)sender; @end #import "WizardItemView.h" @implementation WizardItemView @synthesize wizardItem, delegate; -(void)awakeFromNib { [self bind:@"wizardItem" toObject:viewItem withKeyPath:@"representedObject" options:nil]; } -(void)mouseDown:(NSEvent *)event { [super mouseDown:event]; if([event clickCount] > 1) { [delegate performAction:[wizardItem action]]; } } -(IBAction)start:(id)sender { [delegate performAction:[wizardItem action]]; } @end The problem I've run into is that as an IBAction, the only things in the scope of -start are the things that have been bound in IB, so delegate and viewItem. This means that I cannot get at the represented object to send it to the delegate. Is there a way around this limited scope or a better way or getting hold of the represented object? Thanks.

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  • Core-Plot crash only in Release Configuration

    - by denbec
    Hey everyone, I really don't know a solution or even an idea to get around the following failure. It only happens in Release Configuration on the Device - Simulator and Debug Configuration work fine. It also only appears on the second launch. So if I have the phone connected to my mac, build the application and run it, everything works fine. If I then close the app and restart, it crashes. After long search, it seems that the error comes from the following line: x.majorIntervalLength = CPDecimalFromFloat(2.0f); The code before: CPLayerHostingView *chartView = [[CPLayerHostingView alloc] initWithFrame:CGRectMake(0, 0, 320, 160)]; [self addSubview:chartView]; // create an CPXYGraph and host it inside the view CPTheme *theme = [CPTheme themeNamed:kCPPlainWhiteTheme]; CPXYGraph *graph = (CPXYGraph *)[theme newGraph]; chartView.hostedLayer = graph; graph.paddingLeft = 20.0; graph.paddingTop = 10.0; graph.paddingRight = 10.0; graph.paddingBottom = 20.0; CPXYPlotSpace *plotSpace = (CPXYPlotSpace *)graph.defaultPlotSpace; plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0) length:CPDecimalFromFloat(100)]; plotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(0) length:CPDecimalFromFloat(10)]; CPXYAxisSet *axisSet = (CPXYAxisSet *)graph.axisSet; CPXYAxis *x = axisSet.xAxis; x.majorIntervalLength = CPDecimalFromFloat(2.0f); If I comment the last line, everything works fine (off course the interval length is not correct). I would appreciate any help! Thanks in advance!

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  • Yii CGridView and dropdown filter

    - by Dmitriy Gunchenko
    I created dropdown filter, it's display, but don't worked right. As I anderstand trouble in search() method view: $this->widget('zii.widgets.grid.CGridView', array( 'dataProvider'=>$model->search(), 'filter' => $model, 'columns'=>array( array( 'name' => 'client_id', 'filter' => CHtml::listData(Client::model()->findAll(), 'client_id', 'name'), 'value'=>'$data->client->name' ), 'task' ) )); I have to tables, and they relations are shown down model: public function relations() { // NOTE: you may need to adjust the relation name and the related // class name for the relations automatically generated below. return array( 'client' => array(self::BELONGS_TO, 'Client', 'client_id'), ); } public function search() { // Warning: Please modify the following code to remove attributes that // should not be searched. $criteria=new CDbCriteria; $criteria->with = array('client'); $criteria->compare('task_id',$this->task_id); $criteria->compare('client_id',$this->client_id); $criteria->compare('name',$this->client->name); $criteria->compare('task',$this->task,true); $criteria->compare('start_date',$this->start_date,true); $criteria->compare('end_date',$this->end_date,true); $criteria->compare('complete',$this->complete); return new CActiveDataProvider($this, array( 'criteria'=>$criteria, )); }

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  • Using pointers to adjust global objects in objective-c

    - by Rob
    Ok, so I am working with two sets of data that are extremely similar, and at the same time, these data sets are both global NSMutableArrays within the object. data_set_one = [[NSMutableArray alloc] init]; data_set_two = [[NSMutableArray alloc] init]; Two new NSMutableArrays are loaded, which need to be added to the old, existing data. These Arrays are also global. xml_dataset_one = [[NSMutableArray alloc] init]; xml_dataset_two = [[NSMutableArray alloc] init]; To reduce code duplication (and because these data sets are so similar) I wrote a void method within the class to handle the data combination process for both Arrays: -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str Now, I have a decent understanding of object oriented programming, so I was thinking that if I were to invoke the method with the global Arrays in the data like so... [self constructData:data_set_one fromDownloadArray:xml_dataset_one withMatchSelector:@"id"]; Then the global NSMutableArrays (data_set_one) would reflect the changes that happen to "array" within the method. Sadly, this is not the case, data_set_one doesn't reflect the changes (ex: new objects within the Array) outside of the method. Here is a code snippet of the problem // data_set_one is empty // xml_dataset_one has a few objects [constructData:(NSMutableArray *)data_set_one fromDownloadArray:(NSMutableArray *)xml_dataset_one withMatchSelector:(NSString *)@"id"]; // data_set_one should now be xml_dataset_one, but when echoed to screen, it appears to remain empty And here is the gist of the code for the method, any help is appreciated. -(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str { if ([data count] == 0) { data = down; // set data equal to downloaded data } else if ([down count] == 0) { // download yields no results, do nothing } else { // combine the two arrays here } } This project is not ARC enabled. Thanks for the help guys! Rob

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  • Problem: How to display a Wordpress RSS feed in a browser that doesn't have a built in RSS reader?

    - by StephenMeehan
    If I can, i'd rather not use a service like FeedBurner. My setup: I've setup a RSS feed link on a self-hosted Wordpress website, clicking the RSS link in Safari shows the feed - because Safari has a built in RSS reader. Great. Unfortunately clicking the same RSS link in Chrome displays the raw XML feed. I know why this happens - Chrome doesn't have a built in RSS reader. I also assume this will be the same in older versions of Internet Explorer. Possible solution? I've noticed http://www.bbc.co.uk/news has a nice solution: Click the RSS feed (top tight of the page) in a RSS enabled browser (Safari) and it uses the built in RSS reader to display the RSS feed. Click the same RSS feed link in Chrome (Chrome has no built in RSS reader) it displays the RSS feed using what looks like a custom page. Is there a way to check if a browser has a built in RSS reader? How would I provide alternative content (like the BBC site) to a browser that doesn't have a RSS reader installed? Any help on this would be brilliant, thanks for taking the time to read this. Stephen

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  • Rexml - Parsing Data

    - by Paddy
    I have a XML File in the following format: <?xml version='1.0' encoding='UTF-8'?> <entry xmlns='http://www.w3.org/2005/Atom' xmlns:gwo='http://schemas.google.com/analytics/websiteoptimizer/2009' xmlns:app='http://www.w3.org/2007/app' xmlns:gd='http://schemas.google.com/g/2005' gd:etag='W/&quot;DUYGRX85fCp7I2A9WxFWEkQ.&quot;'><id>https://www.google.com/analytics/feeds/websiteoptimizer/experiments/1025910</id><updated>2010-05-31T02:12:04.124-07:00</updated><app:edited>2010-05-31T02:12:04.124-07:00</app:edited><title>Flow Experiment</title><link rel='gwo:goalUrl' type='text/html' href='http://cart.personallifemedia.com/dlg/download.php'/><link rel='alternate' type='text/html' href='https://www.google.com/websiteoptimizer'/><link rel='self' type='application/atom+xml' href='https://www.google.com/analytics/feeds/websiteoptimizer/experiments/1025910'/><gwo:analyticsAccountId>16334726</gwo:analyticsAccountId><gwo:autoPruneMode>None</gwo:autoPruneMode><gwo:controlScript>..... I have to parse and get the data for gd:etag and how do I do it? I was able to get the value using SimpleXML, but i wanted to achieve it in ReXML. Please do advice.

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  • Error copying file from app bundle

    - by Michael Chen
    I used the FireFox add-on SQLite Manager, created a database, which saved to my desktop as "DB.sqlite". I copied the file into my supporting files for the project. But when I run the app, immediately I get the error "Assertion failure in -[AppDelegate copyDatabaseIfNeeded], /Users/Mac/Desktop/Note/Note/AppDelegate.m:32 2014-08-19 23:38:02.830 Note[28309:60b] Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create writable database file with message 'The operation couldn’t be completed. (Cocoa error 4.)'.' First throw call stack: "... Here is the App Delegate Code where the error takes place -(void) copyDatabaseIfNeeded { NSFileManager *fileManager = [NSFileManager defaultManager]; NSError *error; NSString *dbPath = [self getDBPath]; BOOL success = [fileManager fileExistsAtPath:dbPath]; if (!success) { NSString *defaultDBPath = [[ [NSBundle mainBundle ] resourcePath] stringByAppendingPathComponent:@"DB.sqlite"]; success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error]; if (!success) NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]); } } I am very new to Sqlite, so I maybe I didn't create a database correctly in the FireFox Sqlite manager, or maybe I didn't "properly" copy the .sqlite file in? (I did check the target membership in the sqlite and it correctly has my project selected. Also, the .sqlite file names all match up perfectly.)

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  • Binding mousemove within mousedown function with jQuery

    - by colinjameswebb
    I am trying to bind a mousemove event to a div when the left mousebutton is down, and unbind when it is released. This code should be fairly self-explainatory. function handleMouseDown(e, sbar){ if (e.button == 0){ console.log(sbar); //firebug sbar.bind('mousemove', function(event){ handleMouseMove(event, sbar); }); } } function handleMouseUp(e, sbar){ sbar.unbind('mousemove'); } function handleMouseMove(e, sbar){ // not sure it this will work yet, but unimportant $(".position").html(e.pageX); } $(document).ready(function (){ var statusbar = $(".statusbar"); statusbar.mousedown(function(event){ handleMouseDown(event, this); }); statusbar.mouseup(function(event){ handleMouseUp(event, this); }); }); The important part of the HTML looks like this <div id="main"> <div class="statusbar"> <p class="position"></p> </div> </div> Firebug says that the bind methods are undefined on the variable sbar within handleMouseDown and handleMouseUp. The firebug console prints out <div class="statusbar"> for the line commented //firebug. I'm doing something wrong, probably when binding the mousedown and mouseup... but what?! I'm using jQuery v1.4.2, if that helps?

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  • SSL signed certificates for internal use

    - by rogueprocess
    I have a distributed application consisting of many components that communicate over TCP (for examle JMS) and HTTP. All components run on internal hardware, with internal IP addresses, and are not accessible to the public. I want to make the communication secure using SSL. Does it make sense to purchase signed certificates from a well-known certificate authority? Or should I just use self-signed certs? My understanding of the advantage of trusted certs is that the authority is an entity that can be trusted by the general public - but that is only an issue when the general public needs to be sure that the entity at a particular domain is who they say they are. Therefore, in my case, where the same organization is responsible for the components at both ends of the communication, and everything in between, a publicly trusted authority would be pointless. In other words, if I generate and sign a certificate for my own server, I know that it's trustworthy. And no one from outside the organization will ever be asked to trust this certificate. That is my reasoning - am I correct, or is there some potential advantage to using certs from a known authority?

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  • How do I push another viewController onto the navigationController from within a tabviewController?

    - by user207788
    Hi, I have a project set up using these two tutorials. http://twilloapp.blogspot.com/2009/03/how-to-embed-navigation-controller.html and the link for the second tutorial is at the bottom of the first. The tutorial is slightly outdated but I managed to get it to work as advertised. Now I want to push a new detailedView onto the NavigationController when a user touches a row in the table view. So I added this to my MyTableViewController.m file. - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. SecondViewController *detailViewController = [[SecondViewController alloc] initWithNibName:@"SecondViewController.xib" bundle:nil]; // ... // Pass the selected object to the new view controller. [self.navigationController pushViewController:detailViewController animated:YES]; [detailViewController release]; } Now when I run this project and touch a row in my table view I am getting an error: asm_Terminating_due_to_uncaught_exception IT seems to be having an issue loading the SecondViewController from nib, however I checked the detailViewController and it is not nil. I know I am missing something and it is more than likely something simple. Please help. Thanks, Bruce

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  • rspec and ruby 1.9.1: problem with dummy controller and routes

    - by giorgian
    I want to test a module that basically executes some verify statements, to ensure that actions are invoked with the correct method. # /lib/rest_verification.rb module RestVerification def self.included(base) # :nodoc: base.extend(ClassMethods) end module ClassMethods def verify_rest_actions verify :method => :post, :only => [:create], :redirect_to => { :action => :new } ... end end end I tried this: describe RestVerification do class FooController < ActionController::Base include RestVerification verify_rest_actions def new ; end def index ; end def create ; end def edit ; end def update ; end def destroy ; end end # controller_name 'foo' # this only works with ruby 1.8.7 : 1.9.1 says "uninitialized constant FooController" tests FooController # this works with both before(:each) do ActionController::Routing::Routes.draw do |map| map.resources :foo end end after(:each) do ActionController::Routing::Routes.reload! end it ':create should redirect to :new if invoked with wrong verb' do [:get, :put, :delete].each do |verb| send verb, :create response.should redirect_to(new_foo_url) end end ... end When testing: $ ruby -v ruby 1.8.7 (2010-01-10 patchlevel 249) [i486-linux] $ rake RestVerification :create should redirect to :new if invoked with wrong verb Finished in 0.175586 seconds $ rvm use 1.9.1 Using ruby 1.9.1 p378 $ rake RestVerification :create should redirect to :new if invoked with wrong verb (FAILED - 1) 1) 'RestVerification :create should redirect to :new if invoked with wrong verb' FAILED expected redirect to "http://test.host/foo/new", got redirect to "http://test.host/spec/rails/example/controller_example_group/subclass_1/foo/new" Is this a known issue? Is there a workaround?

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  • Delphi fastMM doesn't work with operator "IS"

    - by Joc02
    I work on Delphi project who interac with many other small libraries. I use FastMM4 and I would like work with complex classes passed on dll parameter. So for exemple I send my form to my dll. Into the dll I test the type of parameter with the operator "IS". But into the Dll the operator "IS" return always "false" Exemple library Dll; uses FastMM4, System.SysUtils, System.Classes, Vcl.Dialogs, Vcl.Forms; {$R *.res} procedure Complex(L : TObject);stdcall; begin if L is TForm then showmessage('Ok') else showmessage('Pas ok') ; if L is TCustomFrame then showmessage('Ok') else showmessage('Pas ok') end; exports Complex; begin end. And the call procedure TffsIsOperator.Button2Click(Sender: TObject); var MaDLL : THandle; Proc : procedure (l : TForm); begin try MaDLL := LoadLibrary(PChar('Dll.dll')); @Proc := GetProcAddress(MaDLL, 'Complex'); Proc(self); finally FreeLibrary(MaDLL); end; end;

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  • Good strategy for copying a "sliding window" of data from a table?

    - by chiborg
    I have a MySQL table from a third-party application that has millions of rows and only one index - the timestamp of each entry. Now I want to do some heavy self-joins and queries on the data using fields other than the timestamp. Doing the query on the original table would bring the database to a crawl, adding indexes to the table is not an option. Additionally, I only need entries that are newer than one week. My current strategy for doing the queries efficiently is to use a separate table (aux_table) that has the necessary indexes. My questions are: Is there another way to do the queries? and if not, How do I update the data in the indexed table efficiently? So far I have found two approaches for updating aux_table: Truncate aux_table and insert the desired data from the original table. Not very efficient because all the indexes must be re-crated. Check for the biggest timestamp in aux_table and insert all entries with a greater or equal timestamp from the original table. Occasionally drop older entries. Only copying entries with greater timestamp leads to dropped entries (because of entries with same timestamp that were inserted into the original table after the last update).

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  • NSTimer Reset Not Working

    - by user355900
    hi, i have a nstimer and it works perfectly counting down from 2:00 but when i hit the reset button it does not work it just stops the timer and when i press start again it will carry on with the timer as if it had never been stopped. Here is my code `@implementation TimerAppDelegate @synthesize window; (void)applicationDidFinishLaunching:(UIApplication *)application { timerLabel.text = @"2:00"; seconds = 120; // Override point for customization after application launch [window makeKeyAndVisible]; } (void)viewDidLoad { [timer invalidate]; } (void)countDownOneSecond { seconds--; int currentTime = [timerLabel.text intValue]; int newTime = currentTime - 1; int displaySeconds = !(seconds % 60) ? 0 : seconds < 60 ? seconds : seconds - 60; int displayMinutes = floor(seconds / 60); NSString *time = [NSString stringWithFormat:@"%d:%@%d", displayMinutes, [[NSString stringWithFormat:@"%d", displaySeconds] length] == 1 ? @"0" : @"", displaySeconds ]; timerLabel.text = time; if(seconds == 0) { [timer invalidate]; } } (void)startOrStopTimer { if(timerIsRunning){ [timer invalidate]; [startOrStopButton setTitle:@"Start" forState:UIControlStateNormal]; } else { timer = [[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(countDownOneSecond) userInfo:nil repeats:YES] retain]; [startOrStopButton setTitle:@"Stop" forState:UIControlStateNormal]; } timerIsRunning = !timerIsRunning; } (void)resetTimer { [timer invalidate]; [startOrStopButton setTitle:@"Start" forState:UIControlStateNormal]; [timer invalidate]; timerLabel.text = @"2:00"; } (void)dealloc { [window release]; [super dealloc]; } @end` thanks

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  • How to add images while moving finger across UIView?

    - by Luke Irvin
    I am having issues adding an image across a view while moving finger across the screen. Currently it is adding the image multiple times but squeezing them too close together and not really following my touch. Here is what I am trying: -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch * touch = [touches anyObject]; touchPoint = [touch locationInView:imageView]; if (touchPoint.x > 0 && touchPoint.y > 0) { _aImageView = [[UIImageView alloc] initWithImage:aImage]; _aImageView.multipleTouchEnabled = YES; _aImageView.userInteractionEnabled = YES; [_aImageView setFrame:CGRectMake(touchPoint.x, touchPoint.y, 80.0, 80.0)]; [imageView addSubview:_aImageView]; [_aImageView release]; } } -(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [self touchesBegan:touches withEvent:event]; } Any suggestions is much appreciated. EDIT: What I want: After taking or choosing an image, the user can then select another image from a list. I want the user to touch and move their finger across the view and the selected image will appear where they drag their finger, without overlapping, in each location.

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  • What does it mean to double license?

    - by Adrian Panasiuk
    What does it mean to double license code? I can't just put both licenses in the source files. That would mean that I mandate users to follow the rules of both of them, but the licenses will probably be contradictory (otherwise there'd be no reason to double license). I guess this is something like in cryptographic chaining, cipher = crypt_2(crypt_1(clear)) (generally) means, that cipher is neither the output of crypt_2 on clear nor the output of crypt_1 on clear. It's the output of the composition. Likewise, in double-licensing, in reality my code has one license, it's just that this new license says please follow all of the rules of license1, or all of the rules of license2, and you are hereby granted the right to redistribute this application under this "double" license, license1 or license2, or any license under which license1 or license2 allow you to redistribute this software, in which case you shall replace the relevant licensing information in this application with that of the new license. (Does this mean that before someone may use the app under license1, he has to perform the operation of redistributing to self? How would he document the fact that he did that operation?) Am I correct. What LICENSE file and what text to put in the source files would I need if I wanted to double license on, for the sake of example, Apachev2 and GPLv3 ?

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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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  • Rails runner command not saving to cache

    - by mark
    Hi I'm having a bit of a problem with a cron task generated by rails whenever plugin that should store remote data in the rails cache for display. What I have is this: schedule.rb set :path, '/var/www/apps/tuexplore/current' every 1.hour do runner "Weather.cache_remote", :environment => :production end calls this model class Weather def self.cache_remote Rails.cache.write('weather_data', Net::HTTP.get_response(URI.parse(WEATHER_URL)).body) end end Calling whenever returns this PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/deploy/.gem/ruby/1.8/bin 0 * * * * /var/www/apps/tuexplore/current/script/runner -e production "Weather.cache_remote" This doesn't work. Calling the weather model method from a controller works fine, but I need to schedule it hourly. The cron task causes a "Cache write: weather_data" entry to appear in the production log but data isn't stored nor output into the page. Additional information, I can log into production console and run Weather.cache_remote, then read the data from the rails cache. I'd be really appreciative if someone could point out the error of my ways. If further explanation is needed please ask. Thanks in advance for any pointers.

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  • Ruby: Why is Array.sort slow for large objects?

    - by David Waller
    A colleague needed to sort an array of ActiveRecord objects in a Rails app. He tried the obvious Array.sort! but it seemed surprisingly slow, taking 32s for an array of 3700 objects. So just in case it was these big fat objects slowing things down, he reimplemented the sort by sorting an array of small objects, then reordering the original array of ActiveRecord objects to match - as shown in the code below. Tada! The sort now takes 700ms. That really surprised me. Does Ruby's sort method end up copying objects about the place rather than just references? He's using Ruby 1.8.6/7. def self.sort_events(events) event_sorters = Array.new(events.length) {|i| EventSorter.new(i, events[i])} event_sorters.sort! event_sorters.collect {|es| events[es.index]} end private # Class used by sort_events class EventSorter attr_reader :sqn attr_reader :time attr_reader :index def initialize(index, event) @index = index @sqn = event.sqn @time = event.time end def <=>(b) @time != b.time ? @time <=> b.time : @sqn <=> b.sqn end end

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  • iPhone SDK: App crashing when trying to scroll through table

    - by iPhone Developer
    I have a view controller with a table on it. When the app starts, it loads the first 5 visble cells. That works as expected. My problem is that, when I try to scroll down the app crashes with this error. Any help appreciated. 2010-06-06 12:25:42.547 iphoneos[18238:207] * -[NSCFString tableView:cellForRowAtIndexPath:]: unrecognized selector sent to instance 0x451a980 2010-06-06 12:25:42.549 iphoneos[18238:207] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '** -[NSCFString tableView:cellForRowAtIndexPath:]: unrecognized selector sent to instance 0x451a980' Here is my code to load cells. UITableViewCell * cell = nil; NSInteger index = [indexPath indexAtPosition:1]; NSLog(@"WHAT IS INDEX %i", indexPath); RoundedGradientTableViewCell *retailerCell = (RoundedGradientTableViewCell *)[tb dequeueReusableCellWithIdentifier:@"RET"]; if(!retailerCell){ retailerCell = [[[RoundedGradientTableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:@"RET"] autorelease]; } [retailerCell setArcSize:5.0]; [retailerCell setStrokeSize:1.0]; [retailerCell setStrokeColor:[UIColor clearColor]]; [retailerCell setBackgroundFillColor:[UIColor clearColor]]; [retailerCell setBackgroundColor:[UIColor clearColor]]; Retailer *retailer = [self retailerAtIndex:index]; if(retailer){ [[retailerCell textLabel] setText:[retailer name]]; if([retailer hasImage]){ [[retailerCell contentImageView] setImage:[retailer image]]; } } else { [[retailerCell textLabel] setText:@"No title"]; } cell = retailerCell; [cell setSelectionStyle:UITableViewCellSelectionStyleNone]; NSLog(@"retailer: %@ ", [retailer name]); NSLog(@"log: %i ", index); return cell;

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  • Determining polygon intersection and containment

    - by Victor Liu
    I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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  • Ruby: how does constant-lookup work in instance_eval/class_eval?

    - by Alan O'Donnell
    I'm working my way through Pickaxe 1.9, and I'm a bit confused by constant-lookup in instance/class_eval blocks. I'm using 1.9.2. It seems that Ruby handles constant-lookup in *_eval blocks the same way it does method-lookup: look for a definition in receiver.singleton_class (plus mixins); then in receiver.singleton_class.superclass (plus mixins); then continue up the eigenchain until you get to #<Class:BasicObject>; whose superclass is Class; and then up the rest of the ancestor chain (including Object, which stores all the constants you define at the top-level), checking for mixins along the way Is this correct? The Pickaxe discussion is a bit terse. Some examples: class Foo CONST = 'Foo::CONST' class << self CONST = 'EigenFoo::CONST' end end Foo.instance_eval { CONST } # => 'EigenFoo::CONST' Foo.class_eval { CONST } # => 'EigenFoo::CONST', not 'Foo::CONST'! Foo.new.instance_eval { CONST } # => 'Foo::CONST' In the class_eval example, Foo-the-class isn't a stop along Foo-the-object's ancestor chain! And an example with mixins: module M CONST = "M::CONST" end module N CONST = "N::CONST" end class A include M extend N end A.instance_eval { CONST } # => "N::CONST", because N is mixed into A's eigenclass A.class_eval { CONST } # => "N::CONST", ditto A.new.instance_eval { CONST } # => "M::CONST", because A.new.class, A, mixes in M

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