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• PulpCore music playback - loop sound and animate volume

  - by Peter Perhác

  I have been experimenting with PulpCore, trying to create my own tower defence game (not-playable yet), and I am enjoying it very much I ran into a problem that I can't quite figure out. I extended PulpCore with the JOrbis thing to allow OGG files to be played. Works fine. However, pulpCore seems to have a problem with looping the sound WHILE animating the volume level. I tried this with wav file too, to make sure it isn't jOrbis that breaks it. The code is like this: Sound bgMusic = Sound.load("music/music.ogg"); Playback musicPlayback; ... musicVolume = new Fixed(0.75); musicPlayback = bgMusic.loop(musicVolume); //TODO figure out why it's NOT looping when volume is animated // musicVolume.animate(0, musicVolume.get(), FADE_IN_TIME); This code, for as long as the last line is commented out, plays the music.ogg again and again in an endless loop (which I can stop by calling stop on the Playback object returned from loop(). However, I would like the music to fade in smoothly, so following the advice of the PulpCore API docs, I added the last line which will create the fade-in but the music will only play once and then stop. I wonder why is that? Here is a bit of the documentation: Playback pulpcore.sound.Sound.loop(Fixed level) Loops this sound clip with the specified volume level (0.0 to 1.0). The level may have a property animation attached. Parameters: level Returns: a Playback object for this unique sound playback (one Sound can have many simultaneous Playback objects) or null if the sound could not be played. So what could be the problem? I repeat, with the last line, the sound fades in but doesn't loop, without it it loops but starts with the specified 0.75 volume level. Why can't I animate the volume of the looped music playback? What am I doing wrong? Anyone has any experience with pulpCore and has come across this problem? Anyone could please download PulpCore and try to loop music which fades-in (out)? note: I need to keep a reference to the Playback object returned so I can kill music later.

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• C#: BackgroundWorker cloning resources?

  - by Dav

  The problem I've been struggling with this partiular problem for two days now and just run out of ideas. A little... background: we have a WinForms app that needs to access a database, construct a list of related in-memory objects from that data, and then display on a DataGridView. Important point is that we first populate an app-wide cache (List), and then create a mirror of the cache local to the form on which the DGV lives (using List constructor param). Because fetching the data takes a good few seconds (DB sits on a LAN server) to load, we decided to use a BackgroundWorker, and only refresh the DGV once the data is loaded. However, it seems that doing the loading via a BGW results in some memory leak... or an error on my part. When loaded using a blocking method call, the app consumes about 30MB of RAM; with a BGW this jumps to 80MB! While it may not seem as much anyway, our clients are not too happy about it. Relevant code Form private void MyForm_Load(object sender, EventArgs e) { MyRepository.Instance.FinishedEvent += RefreshCache; } private void RefreshCache(object sender, EventArgs e) { dgvProducts.DataSource = new List<MyDataObj>(MyRepository.Products); } Repository private static List<MyDataObj> Products { get; set; } public event EventHandler ProductsLoaded; public void GetProductsSync() { List<MyDataObj> p; using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString)) { p = db.PRODUCTS .Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR}) .ToList(); } Products = p; // tell the form to refresh UI if (ProductsLoaded != null) ProductsLoaded(this, null); } public void GetProductsAsync() { using (BackgroundWorker myWorker = new BackgroundWorker()) { myWorker.DoWork += delegate { List<MyDataObj> p; using (MyL2SDb db = new MyL2SDb(MyConfig.ConnectionString)) { p = db.PRODUCTS .Select(p => new MyDataObj {Id = p.ID, Description = p.DESCR}) .ToList(); } Products = p; }; // tell the form to refresh UI when finished myWorker.RunWorkerCompleted += GetProductsCompleted; myWorker.RunWorkerAsync(); } } private void GetProductsCompleted(object sender, RunWorkerCompletedEventArgs e) { if (ProductsLoaded != null) ProductsLoaded(this, null); } End! GetProductsSync or GetProductsAsync are called on the main thread, not shown above. Could it be that the GarbageCollector just gets lost with two threads? Or is it the task manager that shows incorrect values? Will be greateful for any responses, suggestions, criticism.

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• input type="text" not clickable in a jcarousel (jQuery based carousel) element

  - by AkaiKen

  Hello ! I work on a website where almost all objects are in a jCarousel element : <div> <ul id="mycarousel"> <li>object 1</li> <li>object 2</li> </ul> </div> is the "written" code, and : <div class=" jcarousel-skin-tango"> <div class="jcarousel-container jcarousel-container-horizontal" style="display: block;"> <div class="jcarousel-prev jcarousel-prev-horizontal jcarousel-prev-disabled jcarousel-prev-disabled-horizontal" style="display: block;" disabled="true"></div> <div class="jcarousel-next jcarousel-next-horizontal" style="display: block;" disabled="false"></div> <div class="jcarousel-clip jcarousel-clip-horizontal"> <ul class=" jcarousel-list jcarousel-list-horizontal" id="mycarousel" style="width: 2853px; left: 0px;"> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-1 jcarousel-item-1-horizontal" jcarouselindex="1" style="width: 307px;"> object 1 </li> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-1 jcarousel-item-1-horizontal" jcarouselindex="1" style="width: 307px;"> object 2 </li> </ul> </div> </div> is the generated code (here it lacks the ultimate </div>, maybe a number of rows limitation ?). I'm sorry I can't provide a link, I work on a local server currently. It works perfectly =) but... my problem is : an <input type="text" /> won't be clickable in this environment. I tried the others type of input, radio, checkbox, file : works. But text does not. I can specify a value on my input (it's its purpose on my work : a search in a database for datas to be modified and reinjected in database). In fact, I can access to the text input by clicking-right in then left. But it's pretty 'unergonomic', and in my project it's unthinkable. Ah, and I tried to style this input with a style="z-index:1000;", no changes, I think it's not a CSS problem. Does anybody have an idea ? Thank you very much in advance.

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• NHibernate criteria query question

  - by Chris

  I have 3 related objects (Entry, GamePlay, Prize) and I'm trying to find the best way to query them for what I need using NHibernate. When a request comes in, I need to query the Entries table for a matching entry and, if found, get a) the latest game play along with the first game play that has a prize attached. Prize is a child of GamePlay and each Entry object has a GamePlays property (IList). Currently, I'm working on a method that pulls the matching Entry and eagerly loads all game plays and associated prizes, but it seems wasteful to load all game plays just to find the latest one and any that contain a prize. Right now, my query looks like this: var entry = session.CreateCriteria<Entry>() .Add(Restrictions.Eq("Phone", phone)) .AddOrder(Order.Desc("Created")) .SetFetchMode("GamePlays", FetchMode.Join) .SetMaxResults(1).UniqueResult<Entry>(); Two problems with this: It loads all game plays up front. With 365 days of data, this could easily balloon to 300k of data per query. It doesn't eagerly load the Prize child property for each game. Therefore, my code that loops through the GamePlays list looking for a non-null Prize must make a call to load each Prize property I check. I'm not an nhibernate expert, but I know there has to be a better way to do this. Ideally, I'd like to do the following (pseudocode): entry = findEntry(phoneNumber) lastPlay = getLatestGamePlay(Entry) firstWinningPlay = getFirstWinningGamePlay(Entry) The end result of course is that I have the entry details, the latest game play, and the first winning game play. The catch is that I want to do this in as few database calls as possible, otherwise I'd just execute 3 separate queries. The object definitions look like: public class Entry { public Guid Id {get;set;} public string Phone {get;set;} public IList<GamePlay> GamePlays {get;set;} // ... other properties } public class GamePlay { public Guid Id {get;set;} public Entry Entry {get;set;} public Prize Prize {get;set;} // ... other properties } public class Prize { public Guid Id {get;set;} // ... other properties } The proper NHibernate mappings are in place, so I just need help figuring out how to set up the criteria query (not looking for HQL, don't use it).

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• Making a Grid in an NSView

  - by Hooligancat

  I currently have an NSView that draws a grid pattern (essentially a guide of horizontal and vertical lines) with the idea being that a user can change the spacing of the grid and the color of the grid. The purpose of the grid is to act as a guideline for the user when lining up objects. Everything works just fine with one exception. When I resize the NSWindow by dragging the resize handle, if my grid spacing is particularly small (say 10 pixels). the drag resize becomes lethargic in nature. My drawRect code for the grid is as follows: -(void)drawRect:(NSRect)dirtyRect { NSRect thisViewSize = [self bounds]; // Set the line color [[NSColor colorWithDeviceRed:0 green:(255/255.0) blue:(255/255.0) alpha:1] set]; // Draw the vertical lines first NSBezierPath * verticalLinePath = [NSBezierPath bezierPath]; int gridWidth = thisViewSize.size.width; int gridHeight = thisViewSize.size.height; int i; while (i < gridWidth) { i = i + [self currentSpacing]; NSPoint startPoint = {i,0}; NSPoint endPoint = {i, gridHeight}; [verticalLinePath setLineWidth:1]; [verticalLinePath moveToPoint:startPoint]; [verticalLinePath lineToPoint:endPoint]; [verticalLinePath stroke]; } // Draw the horizontal lines NSBezierPath * horizontalLinePath = [NSBezierPath bezierPath]; i = 0; while (i < gridHeight) { i = i + [self currentSpacing]; NSPoint startPoint = {0,i}; NSPoint endPoint = {gridWidth, i}; [horizontalLinePath setLineWidth:1]; [horizontalLinePath moveToPoint:startPoint]; [horizontalLinePath lineToPoint:endPoint]; [horizontalLinePath stroke]; } } I suspect this is entirely to do with the way that I am drawing the grid and am open to suggestions on how I might better go about it. I can see where the inefficiency is coming in, drag-resizing the NSWindow is constantly calling the drawRect in this view as it resizes, and the closer the grid, the more calculations per pixel drag of the parent window. I was thinking of hiding the view on the resize of the window, but it doesn't feel as dynamic. I want the user experience to be very smooth without any perceived delay or flickering. Does anyone have any ideas on a better or more efficient method to drawing the grid? All help, as always, very much appreciated.

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• Does this MSDN article violate MVVM?

  - by rasx

  This may be old news but back in March 2009, this article, “Model-View-ViewModel In Silverlight 2 Apps,” has a code sample that includes DataServiceEntityBase: // COPIED FROM SILVERLIGHTCONTRIB Project for simplicity /// <summary> /// Base class for DataService Data Contract classes to implement /// base functionality that is needed like INotifyPropertyChanged. /// Add the base class in the partial class to add the implementation. /// </summary> public abstract class DataServiceEntityBase : INotifyPropertyChanged { /// <summary> /// The handler for the registrants of the interface's event /// </summary> PropertyChangedEventHandler _propertyChangedHandler; /// <summary> /// Allow inheritors to fire the event more simply. /// </summary> /// <param name="propertyName"></param> protected void FirePropertyChanged(string propertyName) { if (_propertyChangedHandler != null) { _propertyChangedHandler(this, new PropertyChangedEventArgs(propertyName)); } } #region INotifyPropertyChanged Members /// <summary> /// The interface used to notify changes on the entity. /// </summary> event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged { add { _propertyChangedHandler += value; } remove { _propertyChangedHandler -= value; } } #endregion What this class implies is that the developer intends to bind visuals directly to data (yes, a ViewModel is used but it defines an ObservableCollection of data objects). Is this design diverging too far from the guidance of MVVM? Now I can see some of the reasons Why would we go this way: what we can do with DataServiceEntityBase is this sort of thing (which is intimate with the Entity Framework): // Partial Method to support the INotifyPropertyChanged interface public partial class Game : DataServiceEntityBase { #region Partial Method INotifyPropertyChanged Implementation // Override the Changed partial methods to implement the // INotifyPropertyChanged interface // This helps with the Model implementation to be a mostly // DataBound implementation partial void OnDeveloperChanged() { base.FirePropertyChanged("Developer"); } partial void OnGenreChanged() { base.FirePropertyChanged("Genre"); } partial void OnListPriceChanged() { base.FirePropertyChanged("ListPrice"); } partial void OnListPriceCurrencyChanged() { base.FirePropertyChanged("ListPriceCurrency"); } partial void OnPlayerInfoChanged() { base.FirePropertyChanged("PlayerInfo"); } partial void OnProductDescriptionChanged() { base.FirePropertyChanged("ProductDescription"); } partial void OnProductIDChanged() { base.FirePropertyChanged("ProductID"); } partial void OnProductImageUrlChanged() { base.FirePropertyChanged("ProductImageUrl"); } partial void OnProductNameChanged() { base.FirePropertyChanged("ProductName"); } partial void OnProductTypeIDChanged() { base.FirePropertyChanged("ProductTypeID"); } partial void OnPublisherChanged() { base.FirePropertyChanged("Publisher"); } partial void OnRatingChanged() { base.FirePropertyChanged("Rating"); } partial void OnRatingUrlChanged() { base.FirePropertyChanged("RatingUrl"); } partial void OnReleaseDateChanged() { base.FirePropertyChanged("ReleaseDate"); } partial void OnSystemNameChanged() { base.FirePropertyChanged("SystemName"); } #endregion } Of course MSDN code can seen as “toy code” for educational purposes but is anyone doing anything like this in the real world of Silverlight development?

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• ASP.NET Web Service - how to handle special characters in strings?

  - by Vlorg

  To show this fundamental issue in .NET and the reason for this question, I have written a simple test web service with one method (EditString), and a consumer console app that calls it. They are both standard web service/console applications created via File/New Project, etc., so I won't list the whole code - just the methods in question: Web method: [WebMethod] public string EditString(string s, bool useSpecial) { return s + (useSpecial ? ((char)19).ToString() : ""); } [You can see it simply returns the string s if useSpecial is false. If useSpecial is true, it returns s + char 19.] Console app: TestService.Service1 service = new SCTestConsumer.TestService.Service1(); string response1 = service.EditString("hello", false); Console.WriteLine(response1); string response2 = service.EditString("hello", true); // fails! Console.WriteLine(response2); [The second response fails, because the method returns hello + a special character (ascii code 19 for argument's sake).] The error is: There is an error in XML document (1, 287) Inner exception: "'', hexadecimal value 0x13, is an invalid character. Line 1, position 287." A few points worth mentioning: The web method itself WORKS FINE when browsing directly to the ASMX file (e.g. http://localhost:2065/service1.asmx), and running the method through this (with the same parameters as in the console application) - i.e. displays XML with the string hello + char 19. Checking the serialized XML in other ways shows the special character is being encoded properly (the SERVER SIDE seems to be ok which is GOOD) So it seems the CLIENT SIDE has the issue - i.e. the .NET generated proxy class code doesn't handle special characters This is part of a bigger project where objects are passed in and out of the web methods - that contain string attributes - these are what need to work properly. i.e. we're de/serializing classes. Any suggestions for a workaround and how to implement it? Or have I completely missed something really obvious!!? Thanks in advance... PS. I've not had much luck with getting it to use CDATA tags (does .NET support these out of the box?).

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• Linked List Design

  - by Jim Scott

  The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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• Uses of a C++ Arithmetic Promotion Header

  - by OlduvaiHand

  I've been playing around with a set of templates for determining the correct promotion type given two primitive types in C++. The idea is that if you define a custom numeric template, you could use these to determine the return type of, say, the operator+ function based on the class passed to the templates. For example: // Custom numeric class template <class T> struct Complex { Complex(T real, T imag) : r(real), i(imag) {} T r, i; // Other implementation stuff }; // Generic arithmetic promotion template template <class T, class U> struct ArithmeticPromotion { typedef typename X type; // I realize this is incorrect, but the point is it would // figure out what X would be via trait testing, etc }; // Specialization of arithmetic promotion template template <> class ArithmeticPromotion<long long, unsigned long> { typedef typename unsigned long long type; } // Arithmetic promotion template actually being used template <class T, class U> Complex<typename ArithmeticPromotion<T, U>::type> operator+ (Complex<T>& lhs, Complex<U>& rhs) { return Complex<typename ArithmeticPromotion<T, U>::type>(lhs.r + rhs.r, lhs.i + rhs.i); } If you use these promotion templates, you can more or less treat your user defined types as if they're primitives with the same promotion rules being applied to them. So, I guess the question I have is would this be something that could be useful? And if so, what sorts of common tasks would you want templated out for ease of use? I'm working on the assumption that just having the promotion templates alone would be insufficient for practical adoption. Incidentally, Boost has something similar in its math/tools/promotion header, but it's really more for getting values ready to be passed to the standard C math functions (that expect either 2 ints or 2 doubles) and bypasses all of the integral types. Is something that simple preferable to having complete control over how your objects are being converted? TL;DR: What sorts of helper templates would you expect to find in an arithmetic promotion header beyond the machinery that does the promotion itself?

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• Create links programmatically inside an EmberJS view

  - by Michael Gallego

  I have a pretty complex view to render which involves some kind of recursion (the typical folder/file nested list). The fact that it contains heterogeneous objects (folders and files) make it even harder to write Handlebars templates. Therefore, the only solution I've found is to create a view, and manually fill the render buffer. I came with the following solution: App.LibraryContentList = Ember.View.extend({ tagName: 'ol', classNames: ['project-list', 'dd-list'], nameChanged: function() { this.rerender(); }.observes('[email protected]'), render: function(buffer) { // We only start with depth of zero var content = this.get('content').filterProperty('depth', 0); content.forEach(function(item) { this.renderItem(buffer, item); }, this); }, renderItem: function(buffer, item) { switch (item.constructor.toString()) { case 'Photo.Folder': this.renderFolder(buffer, item); break; case 'Photo.File': this.renderFile(buffer, item); break; } }, renderFolder: function(buffer, folder) { buffer.push('<li class="folder dd-item">'); buffer.push('<span class="dd-handle">' + folder.get('name') + '</span>'); // Merge sub folders and files, and sort them by sort order var content = this.mergeAndSort(); if (content.get('length') > 0) { buffer.push('<ol>'); content.forEach(function(item) { this.renderItem(buffer, item); }, this); buffer.push('</ol>'); } buffer.push('</li>'); }, renderFile: function(buffer, album) { buffer.push('<li class="album dd-item">'); buffer.push('<span class="dd-handle">' + file.get('name') + '</span>'); buffer.push('</li>'); } }); Now, what I'd like is to be able to add links so that each folder and each file is clickable and redirect to another route. But how am I supposed to do that, as I don't have access to the linkTo helper? I've tried to play with the LinkView view, but without any success. Should I register handlers manually for each item? I've also thought about breaking that with a CollectionView instead, and splitting the content by depth so that I could render it using templates, but it seems more complicated. Any thoughts?

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• Corner Cases, Unexpected and Unusual Matlab

  - by Mikhail

  Over the years, reading others code, I encountered and collected some examples of Matlab syntax which can be at first unusual and counterintuitive. Please, feel free to comment or complement this list. I verified it r2006a. set([], 'Background:Color','red') Matlab is very forgiving sometimes. In this case, setting properties to an array of objects works also with nonsense properties, at least when the array is empty. myArray([1,round(end/2)]) This use of end keyword may seem unclean but is sometimes very handy instead of using length(myArray). any([]) ~= all([]) Surprisigly any([]) returns false and all([]) returns true. And I always thought that all is stronger then any. EDIT: with not empty argument all() returns true for a subset of values for which any() returns true (e.g. truth table). This means that any() false implies all() false. This simple rule is being violated by Matlab with [] as argument. Loren also blogged about it. Select(Range(ExcelComObj)) Procedural style COM object method dispatch. Do not wonder that exist('Select') returns zero! [myString, myCell] Matlab makes in this case an implicit cast of string variable myString to cell type {myString}. It works, also if I would not expect it to do so. [double(1.8), uint8(123)] => 2 123 Another cast example. Everybody would probably expect uint8 value being cast to double but Mathworks have another opinion. a = 5; b = a(); It looks silly but you can call a variable with round brackets. Actually it makes sense because this way you can execute a function given its handle. a = {'aa', 'bb' 'cc', 'dd'}; Surprsisingly this code neither returns a vector nor rises an error but defins matrix, using just code layout. It is probably a relict from ancient times. set(hobj, {'BackgroundColor','ForegroundColor'},{'red','blue'}) This code does what you probably expect it to do. That function set accepts a struct as its second argument is a known fact and makes sense, and this sintax is just a cell2struct away. Equvalence rules are sometimes unexpected at first. For example 'A'==65 returns true (although for C-experts it is self-evident). About which further unexpected/unusual Matlab features are you aware?

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• ASP.Net JSON Web Service Post Form Data

  - by Will D

  I have a ASP.NET web service decorated with System.Web.Script.Services.ScriptService() so it can return json formatted data. This much is working for me, but ASP.Net has a requirement that parameters to the web service must be in json in order to get json out. I'm using jquery to run my ajax calls and there doesn't seem to be an easy way to create a nice javascript object from the form elements. I have looked at serialiseArray in the json2 library but it doesn't encode the field names as property name in the object. If you have 2 form elements like this <input type="text" name="namefirst" id="namefirst" value="John"/> <input type="text" name="namelast" id="namelast" value="Doe"/> calling $("form").serialize() will get you the standard query string namefirst=John&namelast=Doe calling JSON.stringify($("form").serializeArray()) will get you the (bulky) json representation [{"name":"namefirst","value":"John"},{"name":"namelast","value":"Doe"}] This will work when passing to the web service but its ugly as you have to have code like this to read it in: Public Class NameValuePair Public name As String Public value As String End Class <WebMethod()> _ Public Function GetQuote(ByVal nvp As NameValuePair()) As String End Function You would also have to wrap that json text inside another object nameed nvp to make the web service happy. Then its more work as all you have is an array of NameValuePair when you want an associative array. I might be kidding myself but i imagined something more elegant when i started this project - more like this Public Class Person Public namefirst As String Public namelast As String End Class which would require the json to look something like this: {"namefirst":"John","namelast":"Doe"} Is there an easy way to do this? Obviously it is simple for a form with two parameters but when you have a very large form concatenating strings gets ugly. Having nested objects would also complicate things The cludge I have settled on for the moment is to use the standard name value pair format stuffed inside a json object. This is compact and fast {"q":"namefirst=John&namelast=Doe"} then have a web method like this on the server that parses the query string into an associate array. <WebMethod()> _ Public Function AjaxForm(ByVal q As String) as string Dim params As NameValueCollection = HttpUtility.ParseQueryString(q) 'do stuff return "Hello" End Sub As far a cludges go this one seems reasonably elegant in terms of amount of code, but my question is: is there a better way? Is there a generally accepted way of passing form data to asp.net web/script services?

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• Problems using wxWidgets (wxMSW) within multiple DLL instances

  Preface I'm developing VST-plugins which are DLL-based software modules and loaded by VST-supporting host applications. To open a VST-plugin the host applications loads the VST-DLL and calls an appropriate function of the plugin while providing a native window handle, which the plugin can use to draw it's GUI. I managed to port my original VSTGUI code to the wxWidgets-Framework and now all my plugins run under wxMSW and wxMac but I still have problems under wxMSW to find a correct way to open and close the plugins and I am not sure if this is a wxMSW-only issue. Problem If I use any VST-host application I can open and close multiple instances of one of my VST-plugins without any problems. As soon as I open another of my VST-plugins besides my first VST-plugin and then close all instances of my first VST-plugin the application crashes after a short amount of time within the wxEventHandlerr::ProcessEvent function telling me that the wxTheApp object isn't valid any longer during execution of wxTheApp-FilterEvent (see below). So it seems to be that the wxTheApp objects was deleted after closing all instances of the first plugin and is no longer available for the second plugin. bool wxEvtHandler::ProcessEvent(wxEvent& event) { // allow the application to hook into event processing if ( wxTheApp ) { int rc = wxTheApp->FilterEvent(event); if ( rc != -1 ) { wxASSERT_MSG( rc == 1 || rc == 0, _T("unexpected wxApp::FilterEvent return value") ); return rc != 0; } //else: proceed normally } .... } Preconditions 1.) All my VST-plugins a dynamically linked against the C-Runtime and wxWidgets libraries. With regard to the wxWidgets forum this seemed to be the best way to run multiple instances of the software side by side. 2.) The DllMain of each VST-Plugin is defined as follows: // WXW #include "wx/app.h" #include "wx/defs.h" #include "wx/gdicmn.h" #include "wx/image.h" #ifdef __WXMSW__ #include <windows.h> #include "wx/msw/winundef.h" BOOL APIENTRY DllMain ( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved ) { switch (ul_reason_for_call) { case DLL_PROCESS_ATTACH: { wxInitialize(); ::wxInitAllImageHandlers(); break; } case DLL_THREAD_ATTACH: break; case DLL_THREAD_DETACH: break; case DLL_PROCESS_DETACH: wxUninitialize(); break; } return TRUE; } #endif // __WXMSW__ class Application : public wxApp {}; IMPLEMENT_APP_NO_MAIN(Application) Question How can I prevent this behavior respectively how can I properly handle the wxTheApp object if I have multiple instances of different VST-plugins (DLL-modules), which are dynamically linked against the C-Runtime and wxWidgets libraries? Best reagards, Steffen

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• Segmentation fault in std function std::_Rb_tree_rebalance_for_erase ()

  - by Sarah

  I'm somewhat new to programming and am unsure how to deal with a segmentation fault that appears to be coming from a std function. I hope I'm doing something stupid (i.e., misusing a container), because I have no idea how to fix it. The precise error is Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address: 0x000000000000000c 0x00007fff8062b144 in std::_Rb_tree_rebalance_for_erase () (gdb) backtrace #0 0x00007fff8062b144 in std::_Rb_tree_rebalance_for_erase () #1 0x000000010000e593 in Simulation::runEpidSim (this=0x7fff5fbfcb20) at stl_tree.h:1263 #2 0x0000000100016078 in main () at main.cpp:43 The function that exits successfully just before the segmentation fault updates the contents of two containers. One is a boost::unordered_multimap called carriage; it contains one or more struct Infection objects that contain two doubles. The other container is of type std::multiset< Event, std::less< Event EventPQ called ce. It is full of Event structs. void Host::recover( int s, double recoverTime, EventPQ & ce ) { // Clearing all serotypes in carriage // and their associated recovery events in ce // and then updating susceptibility to each serotype double oldRecTime; int z; for ( InfectionMap::iterator itr = carriage.begin(); itr != carriage.end(); itr++ ) { z = itr->first; oldRecTime = (itr->second).recT; EventPQ::iterator epqItr = ce.find( Event(oldRecTime) ); assert( epqItr != ce.end() ); ce.erase( epqItr ); immune[ z ]++; } carriage.clear(); calcSusc(); // a function that edits an array cout << "Done with sync_recovery event." << endl; } The last cout << line appears immediately before the seg fault. I hope this is enough (but not too much) information. My idea so far is that the rebalancing is being attempting on ce after this function, but I am unsure why it would be failing. (It's unfortunately very hard for me to test this code by removing particular lines, since they would create logical inconsistencies and further problems, but if experienced programmers still think this is the way to go, I'll try.)

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• Help with storing/accessing user access roles C# Winforms

  - by user222453

  Hello, firstly I would like to thank you in advance for any assistance provided. I am new to software development and have designed several Client/Server applications over the last 12 months or so, I am currently working on a project that involves a user logging in to gain access to the application and I am looking at the most efficient and "simple" method of storing the users permissions once logged in to the application which can be used throughout restricting access to certain tabs on the main form. I have created a static class called "User" detailed below: static class User { public static int _userID; public static string _moduleName; public static string _userName; public static object[] UserData(object[] _dataRow) { _userID = (int)_dataRow[0]; _userName = (string)_dataRow[1]; _moduleName = (string)_dataRow[2]; return _moduleName; } } When the user logs in and they have been authenticated, I wish to store the _moduleName objects in memory so I can control which tabs on the main form tab control they can access, for example; if the user has been assigned the following roles in the database: "Sales Ledger", "Purchase Ledger" they can only see the relevant tabs on the form, by way of using a Switch - Case block once the login form is hidden and the main form is instantiated. I can store the userID and userName variables in the main form once it loads by means of say for example: Here we process the login data from the user: DataAccess _dal = new DataAccess(); switch (_dal.ValidateLogin(txtUserName.Text, txtPassword.Text)) { case DataAccess.ValidationCode.ConnectionFailed: MessageBox.Show("Database Server Connection Failed!"); break; case DataAccess.ValidationCode .LoginFailed: MessageBox.Show("Login Failed!"); _dal.RecordLogin(out errMsg, txtUserName.Text, workstationID, false); break; case DataAccess.ValidationCode .LoginSucceeded: frmMain frmMain = new frmMain(); _dal.GetUserPrivList(out errMsg,2); //< here I access my DB and get the user permissions based on the current login. frmMain.Show(); this.Hide(); break; default: break; } private void frmMain_Load(object sender, EventArgs e) { int UserID = User._userID; } That works fine, however the _modules object contains mutiple permissions/roles depending on what has been set in the database, how can I store the multiple values and access them via a Switch-Case block? Thank you again in advance.

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• How is IObservable<double>.Average supposed to work?

  - by Dan Tao

  Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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• How to produce precisely-timed tone and silence?

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution.

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• How to pass ctor args in Activator.CreateInstance?

  - by thames

  I need a performance enhanced Activator.CreateInstance() and came across this article by Miron Abramson that uses a factory to create the instance in IL and then cache it. (I've included code below from Miron Abramson's site in case it somehow disappears). I'm new to IL Emit code and anything beyond Activator.CreateInstance() for instantiating a class and any help would be much appreciative. My problem is that I need to create an instance of an object that takes a ctor with a parameter. I see there is a way to pass in the Type of the parameter, but is there a way to pass in the value of the ctor parameter as well? If possible, I would like to use a method similar to CreateObjectFactory<T>(params object[] constructorParams) as some objects I want to instantiate may have more than 1 ctor param. // Source: http://mironabramson.com/blog/post/2008/08/Fast-version-of-the-ActivatorCreateInstance-method-using-IL.aspx public static class FastObjectFactory { private static readonly Hashtable creatorCache = Hashtable.Synchronized(new Hashtable()); private readonly static Type coType = typeof(CreateObject); public delegate object CreateObject(); /// /// Create an object that will used as a 'factory' to the specified type T /// public static CreateObject CreateObjectFactory() where T : class { Type t = typeof(T); FastObjectFactory.CreateObject c = creatorCache[t] as FastObjectFactory.CreateObject; if (c == null) { lock (creatorCache.SyncRoot) { c = creatorCache[t] as FastObjectFactory.CreateObject; if (c != null) { return c; } DynamicMethod dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + t.Name, typeof(object), null, t); ILGenerator ilGen = dynMethod.GetILGenerator(); ilGen.Emit(OpCodes.Newobj, t.GetConstructor(Type.EmptyTypes)); ilGen.Emit(OpCodes.Ret); c = (CreateObject)dynMethod.CreateDelegate(coType); creatorCache.Add(t, c); } } return c; } } Update to Miron's code from commentor on his post 2010-01-11 public static class FastObjectFactory2<T> where T : class, new() { public static Func<T> CreateObject { get; private set; } static FastObjectFactory2() { Type objType = typeof(T); var dynMethod = new DynamicMethod("DM$OBJ_FACTORY_" + objType.Name, objType, null, objType); ILGenerator ilGen = dynMethod.GetILGenerator(); ilGen.Emit(OpCodes.Newobj, objType.GetConstructor(Type.EmptyTypes)); ilGen.Emit(OpCodes.Ret); CreateObject = (Func<T>) dynMethod.CreateDelegate(typeof(Func<T>)); } }

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• How can I resolve this one application coming up with an "You don't have permission to use the application" error?

  - by morgant

  I've got a Mac OS X 10.6 Snow Leopard Server Open Directory Master with a user who's getting Mobility & Application managed preferences from a group (the only group they're a member of). The workstation is also running Mac OS X 10.6 Snow Leopard, when the user logs in and tries to run our primary application which they're explicitly allowed to run (via the group's preferences), it says "You don't have permission to use the application 'Blah'". Now, the application is added to the group's list of always allowed applications, unsigned (so a minor difference in application version or file contents shouldn't disallow it). It even lives in a subdirectory of /Applications which is in the list of folders to allow applications. I've run into this when logging this user into new workstations and the following usually works: Log them out Remove the following files from their mobile home folder on the workstation: /Library/Managed\ Preferences/, ~/.FileSync, ~/Library/Preferences/com.apple.finder.plist, and ~/Library/Preferences/com.apple.MCX.plist. Remove the following files from their network home folder on the server: ~/.FileSync, ~/Library/Preferences/com.apple.finder.plist, and ~/Library/Preferences/com.apple.MCX.plist. Log them back in on the workstation. However, this no longer resolves the issue. Their Home Sync preferences are set (on the group) to sync ~, but not the following files (manually, at login, and at logout... no background sync here): ~/.SymAVQSFile ~/NAVMac800QSFile ~/Library ~/.FileSync ~/.account Their Preferences Sync preferences are set (also on the group) to sync ~/Library & ~/Documents/Microsoft User Data, but not the following files (also manually, at login, and at logout... no background sync): ~/.SymAVQSFile ~/.Trash ~/.Trashes ~/Documents/Microsoft User Data/Entourage Temp ~/Library/Application Support/SyncServices ~/Library/Application Support/MobileSync ~/Library/Caches ~/Library/Calendars/Calendar Cache ~/Library/Logs ~/Library/Mail/AvailableFeeds ~/Library/Mail/Envelope Index ~/Library/Preferences/Macromedia/ ~/Library/Printers ~/Library/PubSub/Database ~/Library/PubSub/Downloads ~/Library/PubSub/Feeds ~/Library/Safari/Icons.db ~/Library/Safari/HistoryIndex.sk ~/Library/iTunes/iPhone Software Updates IMAP-* Exchange-* EWS-* Mac-* ~/Library/Preferences/ByHost ~/Library/Preferences/com.apple.dock.plist ~/Library/Preferences/com.apple.sitebarlists.plist ~/Library/Application Support/4D ~/Library/Preferences/com.apple.MCX.plist ~/.FileSync ~/.account Even with ~/Library/Preferences/com.apple.MCX.plist prevented from syncing during a Preferences Sync, it still seems to show up in the network home on the server frequently. Are there any other files other than ~/Library/Preferences/com.apple.MCX.plist that contain application Managed Preferences that might be causing this one app to be showing up as not allowed? Any ideas on how ~/Library/Preferences/com.apple.MCX.plist keeps getting sync'd back up the network home folder on the server? Update: I thought I had found a workaround this morning, but it also seemed to be extremely temporary. Basically, loking at /Library/Managed\ Preferences/[shortname]/com.apple.applicationaccess.new.plist I discovered that it didn't have an entry for the application in question, but /Library/Managed\ Preferences/[shortname]/complete.plist did. Naturally, I deleted com.apple.applicationaccess.new.plist, logged in again, and it worked... on one workstation. It failed on others, and after logging out & back in a couple more times it started failing on all of them again, even after further deletions of com.apple.applicationaccess.new.plist. Oddly, com.apple.applicationaccess.new.plist & complete.plist do both contain an entry for the application in question now, but it still says it's not allowed. Further Update: Okay, so I now have a reproducible workaround which seems to be required after every reboot of the workstation: Log in as the user (you'll discover you cannot launch the application in question). Fast User Switch to the local admin account on the workstation (we always have one on every machine). From that local admin account, run sudo mcxrefresh -n 'shortname' (logging out and back in as the user in question will not work). Fast User Switch back to the user (you'll still not be allowed to run the application). Log the user out and back in (you'll now be able to run the application in question.) Fast User Switch back to the local admin account, log it out, and log back in as the user in question. If you do all that exactly as described it'll keep working through log out & log back in, but NOT through a reboot. If, after a reboot, you try something like logging in as the local admin account, running sudo mcxrefresh -n 'shortname', logging out, then logging in as the user in question, it will NOT work. Yet Another Update We don't have any computer groups in our Open Directory, so it shouldn't be getting any conflicting settings from there. I ran sudo mcxquery -format xml -user shortname -group groupname before & after performing the aforementioned process to allow the application in question to be run and the results were identical (saved the result to files & diff'd... I'm not just guessing here). One Step Forward, Half a Step Back: When the Mac OS X 10.6.5 Server update was released, we upgraded our Open Directory Master to it as the changes included the following managed preferences fixes which I hoped might address this issue: Addresses an issue that could prevent managed preferences from being applied when a user logs in on a workstation that has been idle. Fixes an issue that could prevent administrators from bypassing client management settings on a workstation. This seemed to improve the situation slightly. The application in question now usually launches without error. If, and when it does launch with the "You don't have permission to use the application" error, logging the user out and back in seems to correct it. That said, we've since had to add a couple of applications to the user's ~/Applications/ directory and those are still prevented from launching. The workstations are running Mac OS X 10.6.4, the OD Master (which the workstations are bound to) is running Mac OS 10.6.5 Server (although there are two OD Replicas still running 10.6.4 Server), and we're using Workgroup Manager 10.6.3 (which is included with the Server Admin Tools 10.6.5 upgrade) to add the applications (unsigned, as always). This time, I've caught the following in /var/log/system.log when attempting to launch one of the allowed applications from ~/Applications: Dec 22 17:36:24 hostname parentalcontrolsd[43221]: -[ActivityTracker checkApp:csFlags:] [954:username] -- *** Incoming app appears to be masquerading as white listed app and failed signature validation: /Users/username/Applications/FileMaker Pro 5.5/FileMaker Pro.app/Contents/MacOS/FileMaker Pro. Note: This may be a valid app of a different version than what was whitelisted (on a different volume?) Dec 22 17:36:24 hostname [0x0-0xa42a42].com.filemaker.filemakerpro[43304]: launch of /Users/username/Applications/FileMaker Pro 5.5/FileMaker Pro.app/Contents/MacOS/FileMaker Pro was blocked Dec 22 17:36:24 hostname com.apple.launchd.peruser.1340[6375] ([0x0-0xa42a42].com.filemaker.filemakerpro[43304]): Exited with exit code: 255 Dec 22 17:36:24 hostname parentalcontrolsd[43221]: -[ActivityTracker(Private) _removeAppFromWhiteList:] [1362:username] -- *** Couldn't find local user record Running sudo mcxquery -format xml -user username -group groupname includes the following entry for FileMaker Pro 5.5 (and appears to include a full integration of the user's application whitelist & group's application whitelist): <dict> <key>bundleID</key> <string>com.filemaker.filemakerpro</string> <key>displayName</key> <string>FileMaker Pro</string> </dict> Note the lack of <key>appID</key><data> ... </data> which seems to specify a signed application. While whitelisted directories also appear to be correctly listed in the results, they too do not actually allow the applications to be run either. What is going on here?! Where else should I be looking?

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• Why can't I use __getattr__ with Django models?

  - by Joshmaker

  I've seen examples online of people using __getattr__ with Django models, but whenever I try I get errors. (Django 1.2.3) I don't have any problems when I am using __getattr__ on normal objects. For example: class Post(object): def __getattr__(self, name): return 42 Works just fine... >>> from blog.models import Post >>> p = Post() >>> p.random 42 Now when I try it with a Django model: from django.db import models class Post(models.Model): def __getattr__(self, name): return 42 And test it on on the interpreter: >>> from blog.models import Post >>> p = Post() ERROR: An unexpected error occurred while tokenizing input The following traceback may be corrupted or invalid The error message is: ('EOF in multi-line statement', (6, 0)) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/josh/project/ in () /Users/josh/project/lib/python2.6/site-packages/django/db/models/base.pyc in init(self, *args, **kwargs) 338 if kwargs: 339 raise TypeError("'%s' is an invalid keyword argument for this function" % kwargs.keys()[0]) -- 340 signals.post_init.send(sender=self.class, instance=self) 341 342 def repr(self): /Users/josh/project/lib/python2.6/site-packages/django/dispatch/dispatcher.pyc in send(self, sender, **named) 160 161 for receiver in self._live_receivers(_make_id(sender)): -- 162 response = receiver(signal=self, sender=sender, **named) 163 responses.append((receiver, response)) 164 return responses /Users/josh/project/python2.6/site-packages/photologue/models.pyc in add_methods(sender, instance, signal, *args, **kwargs) 728 """ 729 if hasattr(instance, 'add_accessor_methods'): -- 730 instance.add_accessor_methods() 731 732 # connect the add_accessor_methods function to the post_init signal TypeError: 'int' object is not callable Can someone explain what is going on? EDIT: I may have been too abstract in the examples, here is some code that is closer to what I actually would use on the website: class Post(models.Model): title = models.CharField(max_length=255) slug = models.SlugField() date_published = models.DateTimeField() content = RichTextField('Content', blank=True, null=True) # Etc... Class CuratedPost(models.Model): post = models.ForeignKey('Post') position = models.PositiveSmallIntegerField() def __getattr__(self, name): ''' If the user tries to access a property of the CuratedPost, return the property of the Post instead... ''' return self.post.name # Etc... While I could create a property for each attribute of the Post class, that would lead to a lot of code duplication. Further more, that would mean anytime I add or edit a attribute of the Post class I would have to remember to make the same change to the CuratedPost class, which seems like a recipe for code rot.

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• get_or_create generic relations in Django & python debugging in general

  - by rabidpebble

  I ran the code to create the generically related objects from this demo: http://www.djangoproject.com/documentation/models/generic_relations/ Everything is good intially: >>> bacon.tags.create(tag="fatty") <TaggedItem: fatty> >>> tag, newtag = bacon.tags.get_or_create(tag="fatty") >>> tag <TaggedItem: fatty> >>> newtag False But then the use case that I'm interested in for my app: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome") Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 123, in get_or_create return self.get_query_set().get_or_create(**kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 343, in get_or_create raise e IntegrityError: app_taggeditem.content_type_id may not be NULL I tried a bunch of random things after looking at other code: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem) ValueError: Cannot assign "<class 'generics.app.models.TaggedItem'>": "TaggedItem.content_type" must be a "ContentType" instance. or: >>> tag, newtag = bacon.tags.get_or_create(tag="wholesome", content_type=TaggedItem.content_type) InterfaceError: Error binding parameter 3 - probably unsupported type. etc. I'm sure somebody can give me the correct syntax, but the real problem here is that I have no idea what is going on. I have developed in strongly typed languages for over ten years (x86 assembly, C++ and C#) but am new to Python. I find it really difficult to follow what is going on in Python when things like this break. In the languages I mentioned previously it's fairly straightforward to figure things like this out -- check the method signature and check your parameters. Looking at the Django documentation for half an hour left me just as lost. Looking at the source for get_or_create(self, **kwargs) didn't help either since there is no method signature and the code appears very generic. A next step would be to debug the method and try to figure out what is happening, but this seems a bit extreme... I seem to be missing some fundamental operating principle here... what is it? How do I resolve issues like this on my own in the future?

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• Best Practice: Legitimate Cross-Site Scripting

  - by Ryan

  While cross-site scripting is generally regarded as negative, I've run into several situations where it's necessary. I was recently working within the confines of a very limiting content management system. I needed to include database code within the page, but the hosting server didn't have anything usable available. I set up a couple barebones scripts on my own server, originally thinking that I could use AJAX to import the contents of my scripts directly into the template of the CMS (thus retaining dynamic images, menu items, CSS, etc.). I was wrong. Due to the limitations of XMLHttpRequest objects, it's not possible to grab content from a different domain. So I thought "iFrame" - even though I'm not a fan of frames, I thought that I could create a frame that matched the width and height of the content, so that it would appear native. Again, I was blocked by cross-site scripting "protections." While I could indeed load a remote file into the iFrame, I couldn't execute JavaScript to modify its size on either the host page or inside the loaded page. In this particular scenario, I wasn't able to point a subdomain to my server. I also couldn't create a script on the CMS server that could proxy content from my server, so my last thought was to use a remote JavaScript. A remote JavaScript works. It breaks when the user has JavaScript disabled, which is a downside; but it works. The "problem" I was having with using a remote JavaScript was that I had to use the JS function document.write() to output any content. Any output that isn't JS causes script errors. In addition to using document.write() for every line, you also have to ensure that the content is escaped - or else you end up with more script errors. My solution was as follows: My script received a GET parameter ("page") and then looked for the file ({$page}.php), and read the contents into a variable. However, I had to use awkward buffering techniques in order to actually execute the included scripts (for things like database interaction) then strip the final content of all line break characters ("\n") followed by escaping all required characters. The end result is that my original script (which outputs JavaScript) accesses seemingly "standard" scripts on my server and converts their standard output to JavaScript for displaying within the CMS template. While this solution works, it seems like there may be a better way to accomplish the same thing. What is the best way to make cross-site scripting work specifically for the purpose of including content from a completely different domain?

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• Binding CoreData Managed Object to NSTextFieldCell subclass

  - by ndg

  I have an NSTableView which has its first column set to contain a custom NSTextFieldCell. My custom NSTextFieldCell needs to allow the user to edit a "desc" property within my Managed Object but to also display an "info" string that it contains (which is not editable). To achieve this, I followed this tutorial. In a nutshell, the tutorial suggests editing your Managed Objects generated subclass to create and pass a dictionary of its contents to your NSTableColumn via bindings. This works well for read-only NSCell implementations, but I'm looking to subclass NSTextFieldCell to allow the user to edit the "desc" property of my Managed Object. To do this, I followed one of the articles comments, which suggests subclassing NSFormatter to explicitly state which Managed Object property you would like the NSTextFieldCell to edit. Here's the suggested implementation: @implementation TRTableDescFormatter - (BOOL)getObjectValue:(id *)anObject forString:(NSString *)string errorDescription:(NSString **)error { if (anObject != nil){ *anObject = [NSDictionary dictionaryWithObject:string forKey:@"desc"]; return YES; } return NO; } - (NSString *)stringForObjectValue:(id)anObject { if (![anObject isKindOfClass:[NSDictionary class]]) return nil; return [anObject valueForKey:@"desc"]; } - (NSAttributedString*)attributedStringForObjectValue:(id)anObject withDefaultAttributes:(NSDictionary *)attrs { if (![anObject isKindOfClass:[NSDictionary class]]) return nil; NSAttributedString *anAttributedString = [[NSAttributedString alloc] initWithString: [anObject valueForKey:@"desc"]]; return anAttributedString; } @end I assign the NSFormatter subclass to my cell in my NSTextFieldCell subclass, like so: - (void)awakeFromNib { TRTableDescFormatter *formatter = [[[TRTableDescFormatter alloc] init] autorelease]; [self setFormatter:formatter]; } This seems to work, but falls down when editing multiple rows. The behaviour I'm seeing is that editing a row will work as expected until you try to edit another row. Upon editing another row, all previously edited rows will have their "desc" value set to the value of the currently selected row. I've been doing a lot of reading on this subject and would really like to get to the bottom of this. What's more frustrating is that my NSTextFieldCell is rendering exactly how I would like it to. This editing issue is my last obstacle! If anyone can help, that would be greatly appreciated.

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• Temporarily impersonate and enable privileges?

  - by Luke

  We maintain a DLL that does a lot of system-related things; traversing the file system, registry, etc. The callers of this DLL may or may not be using impersonation. In order to better support all possible scenarios I'm trying to modify it to be smarter. I'll use the example of deleting a file. Currently we just call DeleteFile(), and if that fails that's the end of that. I've come up with the following: BOOL TryReallyHardToDeleteFile(LPCTSTR lpFileName) { // 1. caller without privilege BOOL bSuccess = DeleteFile(lpFileName); DWORD dwError = GetLastError(); if(!bSuccess && dwError == ERROR_ACCESS_DENIED) { // failed with access denied; try with privilege DWORD dwOldRestorePrivilege = 0; BOOL bHasRestorePrivilege = SetPrivilege(SE_RESTORE_NAME, SE_PRIVILEGE_ENABLED, &dwOldRestorePrivilege); if(bHasRestorePrivilege) { // 2. caller with privilege bSuccess = DeleteFile(lpFileName); dwError = GetLastError(); SetPrivilege(SE_RESTORE_NAME, dwOldRestorePrivilege, NULL); } if(!bSuccess && dwError == ERROR_ACCESS_DENIED) { // failed with access denied; if caller is impersonating then try as process HANDLE hToken = NULL; if(OpenThreadToken(GetCurrentThread(), TOKEN_QUERY | TOKEN_IMPERSONATE, TRUE, &hToken)) { if(RevertToSelf()) { // 3. process without privilege bSuccess = DeleteFile(lpFileName); dwError = GetLastError(); if(!bSuccess && dwError == ERROR_ACCESS_DENIED) { // failed with access denied; try with privilege bHasRestorePrivilege = SetPrivilege(SE_RESTORE_NAME, SE_PRIVILEGE_ENABLED, &dwOldRestorePrivilege); if(bHasRestorePrivilege) { // 4. process with privilege bSuccess = DeleteFile(lpFileName); dwError = GetLastError(); SetPrivilege(SE_RESTORE_NAME, dwOldRestorePrivilege, NULL); } } SetThreadToken(NULL, hToken); } CloseHandle(hToken); hToken = NULL; } } } if(!bSuccess) { SetLastError(dwError); } return bSuccess; } So first it tries as the caller. If that fails with access denied, it temporarily enables privileges in the caller's token and tries again. If that fails with access denied and the caller is impersonating, it temporarily unimpersonates and tries again. If that fails with access denied, it temporarily enables privileges in the process token and tries again. I think this should handle pretty much any situation, but I was wondering if there was a better way to achieve this? There are a lot of operations that we would potentially want to use this method (i.e. pretty much any operation that accesses securable objects).

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• Connect ps/2->usb keyboard to linux?

  - by Daniel

  I have a lovely ancient ergonomic keyboard (no name SK - 6000) connected via a DIN-ps/2 adapter to a ps/2-usb adapter to my docking station. After Grub it stops working. It takes either suspending and waking up or replugging it while Linux is running to get it to work. No extra kernel modules get loaded for this. When it works and I restart without power off, it will work immediately. Even when it does not work, it is visible (lsusb device number varies but output is identical whether working or not): $ lsusb -v -s 001:006 Bus 001 Device 006: ID 0a81:0205 Chesen Electronics Corp. PS/2 Keyboard+Mouse Adapter Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 1.10 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 8 idVendor 0x0a81 Chesen Electronics Corp. idProduct 0x0205 PS/2 Keyboard+Mouse Adapter bcdDevice 0.10 iManufacturer 1 CHESEN iProduct 2 PS2 to USB Converter iSerial 0 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 59 bNumInterfaces 2 bConfigurationValue 1 iConfiguration 2 PS2 to USB Converter bmAttributes 0xa0 (Bus Powered) Remote Wakeup MaxPower 100mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 3 Human Interface Device bInterfaceSubClass 1 Boot Interface Subclass bInterfaceProtocol 1 Keyboard iInterface 0 HID Device Descriptor: bLength 9 bDescriptorType 33 bcdHID 1.10 bCountryCode 0 Not supported bNumDescriptors 1 bDescriptorType 34 Report wDescriptorLength 64 Report Descriptors: ** UNAVAILABLE ** Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 10 Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 1 bAlternateSetting 0 bNumEndpoints 1 bInterfaceClass 3 Human Interface Device bInterfaceSubClass 1 Boot Interface Subclass bInterfaceProtocol 2 Mouse iInterface 0 HID Device Descriptor: bLength 9 bDescriptorType 33 bcdHID 1.10 bCountryCode 0 Not supported bNumDescriptors 1 bDescriptorType 34 Report wDescriptorLength 148 Report Descriptors: ** UNAVAILABLE ** Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 10 Device Status: 0x0000 (Bus Powered) $ ll -R /sys/bus/hid/drivers/ /sys/bus/hid/drivers/: total 0 drwxr-xr-x 2 root root 0 Jul 8 2012 generic-usb/ /sys/bus/hid/drivers/generic-usb: total 0 lrwxrwxrwx 1 root root 0 Jul 7 23:33 0003:046D:C03D.0003 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.2/1-1.2.2:1.0/0003:046D:C03D.0003/ lrwxrwxrwx 1 root root 0 Jul 7 23:33 0003:0A81:0205.0001 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/ lrwxrwxrwx 1 root root 0 Jul 7 23:33 0003:0A81:0205.0002 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.1/0003:0A81:0205.0002/ --w------- 1 root root 4096 Jul 7 23:32 bind lrwxrwxrwx 1 root root 0 Jul 7 23:33 module -> ../../../../module/usbhid/ --w------- 1 root root 4096 Jul 7 23:32 new_id --w------- 1 root root 4096 Jul 8 2012 uevent --w------- 1 root root 4096 Jul 7 23:32 unbind When replugging, dmesg shows this (which except for the 1st line and different input numbers already came at boot time): [ 1583.295385] usb 1-1.2.1: new low-speed USB device number 6 using ehci_hcd [ 1583.446514] input: CHESEN PS2 to USB Converter as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/input/input17 [ 1583.446817] generic-usb 0003:0A81:0205.0001: input,hidraw0: USB HID v1.10 Keyboard [CHESEN PS2 to USB Converter] on usb-0000:00:1a.0-1.2.1/input0 [ 1583.454764] input: CHESEN PS2 to USB Converter as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.1/input/input18 [ 1583.455534] generic-usb 0003:0A81:0205.0002: input,hidraw1: USB HID v1.10 Mouse [CHESEN PS2 to USB Converter] on usb-0000:00:1a.0-1.2.1/input1 [ 1583.455578] usbcore: registered new interface driver usbhid [ 1583.455584] usbhid: USB HID core driver So I tried $ sudo udevadm test /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0 run_command: calling: test adm_test: version 175 This program is for debugging only, it does not run any program, specified by a RUN key. It may show incorrect results, because some values may be different, or not available at a simulation run. parse_file: reading '/lib/udev/rules.d/40-crda.rules' as rules file parse_file: reading '/lib/udev/rules.d/40-fuse.rules' as rules file ... parse_file: reading '/lib/udev/rules.d/40-usb-media-players.rules' as rules file parse_file: reading '/lib/udev/rules.d/40-usb_modeswitch.rules' as rules file ... parse_file: reading '/lib/udev/rules.d/42-qemu-usb.rules' as rules file ... parse_file: reading '/lib/udev/rules.d/69-cd-sensors.rules' as rules file add_rule: IMPORT found builtin 'usb_id', replacing /lib/udev/rules.d/69-cd-sensors.rules:76 ... parse_file: reading '/lib/udev/rules.d/77-mm-usb-device-blacklist.rules' as rules file ... parse_file: reading '/lib/udev/rules.d/85-usbmuxd.rules' as rules file ... parse_file: reading '/lib/udev/rules.d/95-upower-hid.rules' as rules file parse_file: reading '/lib/udev/rules.d/95-upower-wup.rules' as rules file parse_file: reading '/lib/udev/rules.d/97-bluetooth-hid2hci.rules' as rules file udev_rules_new: rules use 271500 bytes tokens (22625 * 12 bytes), 44331 bytes buffer udev_rules_new: temporary index used 76320 bytes (3816 * 20 bytes) udev_device_new_from_syspath: device 0x7f78a5e4d2d0 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0' udev_device_new_from_syspath: device 0x7f78a5e5f820 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0' udev_device_read_db: device 0x7f78a5e5f820 filled with db file data udev_device_new_from_syspath: device 0x7f78a5e60270 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001' udev_device_new_from_syspath: device 0x7f78a5e609c0 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0' udev_device_new_from_syspath: device 0x7f78a5e61160 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1' udev_device_new_from_syspath: device 0x7f78a5e61960 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2' udev_device_new_from_syspath: device 0x7f78a5e62150 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1' udev_device_new_from_syspath: device 0x7f78a5e62940 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1' udev_device_new_from_syspath: device 0x7f78a5e630f0 has devpath '/devices/pci0000:00/0000:00:1a.0' udev_device_new_from_syspath: device 0x7f78a5e638a0 has devpath '/devices/pci0000:00' udev_event_execute_rules: no node name set, will use kernel supplied name 'hidraw0' udev_node_add: creating device node '/dev/hidraw0', devnum=251:0, mode=0600, uid=0, gid=0 udev_node_mknod: preserve file '/dev/hidraw0', because it has correct dev_t udev_node_mknod: preserve permissions /dev/hidraw0, 020600, uid=0, gid=0 node_symlink: preserve already existing symlink '/dev/char/251:0' to '../hidraw0' udev_device_update_db: created empty file '/run/udev/data/c251:0' for '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0' ACTION=add DEVNAME=/dev/hidraw0 DEVPATH=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0 MAJOR=251 MINOR=0 SUBSYSTEM=hidraw UDEV_LOG=6 USEC_INITIALIZED=969079051 The later lines sound like it's already there. And none of these awakes the keyboard: $ sudo udevadm trigger --verbose --sysname-match=usb* /sys/devices/pci0000:00/0000:00:1a.0/usb1 /sys/devices/pci0000:00/0000:00:1a.0/usbmon/usbmon1 /sys/devices/pci0000:00/0000:00:1d.0/usb2 /sys/devices/pci0000:00/0000:00:1d.0/usbmon/usbmon2 /sys/devices/virtual/usbmon/usbmon0 $ sudo udevadm trigger --verbose --sysname-match=hidraw0 /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0 $ sudo udevadm trigger I also tried this to no avail: # echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/bind ksh: echo: write to 1 failed [No such device] # echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/unbind # echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/bind # echo usb1 >/sys/bus/usb/drivers/usb/unbind # echo usb1 >/sys/bus/usb/drivers/usb/bind What else should I try to get the same result as replugging or suspending, by just issuing a command?

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