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• When and why will an OS initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?

  - by LeopardSkinPillBoxHat

  I know that the OS will sometimes initialise memory with certain patterns such as 0xCD and 0xDD. What I want to know is when and why this happens. When Is this specific to the compiler used? Do malloc/new and free/delete work in the same way with regard to this? Is it platform specific? Will it occur on other operating systems, such as Linux or VxWorks? Why My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions. Can you give any practical examples as to how this initialisation is useful? I remember reading something (maybe in Code Complete 2) that it is good to initialise memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger. How portable is this?

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• Can you use data binding with the Content property of a WPF Frame?

  - by dthrasher

  I can use data binding to set the initial Content of a WPF Frame, but subsequent changes to the the bound property (implemented using INotifyPropertyChange) do not seem to change the content. Also, does anyone know if binding directly to the Content property in this way will cause the bound item to appear in the Frame or NavigationWindow's journal? Some context: I realize that I should probably be using the NavigationService to interact with the Frame, but I'm attempting to follow the MVVM pattern. It seems like it would be much simpler to databind to the Content property...

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• Image reflection in Silverlight 4

  - by Phani Kumar PV

  I am developing a product scrolling feature where products info( product image, Name, price)will be shown side by side horizontally. i need to show the image of the product and also its reflection. under the reflected image i need to show the Prod Name and its price. The problem here is i dont want to show the complete reflected image. the oputput should be something like this Image Height-100% Reflected Image Height-20% Product name Product Price The above pattern will repeat horizontally. I am able to get the desired output with some problem. The reflected image is shown up with hieght 100% and the sapce between the actual image and product name is very high. My reflected image should be a rotated image of the actual image and only half part of the actual image should be shown. Any pointers even is highly appreciated

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• creative way for implementing Data object with it's corespanding buisness logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity reasons lets call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I loose my hierarchy freedom, does any of you have any creative solution for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• Rails: common approach for handling exceptions in restful actions on objects that have been destroye

  - by Greg

  It is very common in Rails for an objects_controller controller to have RESTful edit and destroy actions like so: def edit @object = Object.find(params[:id]) end def destroy @object = Object.find(params[:id]) @object.destroy redirect_to :back end With an associated view that provides edit and destroy links like so: <%= link_to "Edit the Object", edit_object_path(object) %> <%= link_to "Delete", object, :confirm => 'Are you sure?', :method => :delete %> And it is easy to blow this up. If I open two browser windows, A and B, destroy an object with the "Delete" link in browser A and then press the "Edit" link in browser B, the find() in the edit action throws an exception. Obviously there are several ways to deal with this in the edit action: catch the exception and recover gracefully use @object = find(:first, "conditions... etc. and test the @object before going further But seeing as this is such a common pattern, I would love to know how other folks deal with this situation.

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• modrewrite RewriteRule problem

  - by timpone

  I am using Apache 2.2 and mod_rewrite. I would like to take the following urls and map them to another url. The pattern is simple and like this: http://domain/test/ex1.html - http://domain/app/index.php/content/?name=ex1 I tried the following in an .htaccess file: RewriteEngine On RewriteBase /app/ RewriteRule (.*)\.html index.php/content/?name=$1 and RewriteEngine On RewriteRule (.*)\.html /app/index.php/content/?name=$1 I wasn't sure if the backreference was correct so set to $0 and $2 but never seemed to help. I also tried setting the RewriteLogLevel to 9. There is a step where it is almost there: rewrite 'ex1.html' - 'index.php/content/?name=ex1' The last line of the rewrite log is as follows: [perdir /var/www/domain/htdocs/test/] internal redirect with /app/index.php/content/ [INTERNAL REDIRECT] How can I get this to rewrite to /app/index.php/content/?name=ex1 ? thanks

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• How to access File over the Network

  - by Polo

  Hi! I am having a hard time on this one, I have a folder over the network with public access (no credential restriction). I am trying to do a File.Exist or Directory.Exist and I keep on having a exception. Can someone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\\agoodip\Public") or File.exist(@"\\agoodip\Public\test.txt") The exception I get is Path not found. EDIT 2 : I am using Silverlight 3, Is there any security pattern to be aware of to lookup file on the network? Thanks!

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• Pass a captured named regular expression to URL dictionary in generic view

  - by Trent Jurewicz

  I am working with a generic view in Django. I want to capture a named group parameter in the URL and pass the value to the URL pattern dictionary. For example, in the URLConf below, I want to capture the parent_slug value in the URL and pass it to the queryset dictionary value like so: urlpatterns = patterns('django.views.generic.list_detail', (r'^(?P<parent_slugs>[-\w])$', 'object_list', {'queryset':Promotion.objects.filter(category=parent_slug)}, 'promo_promotion_list'), ) Is this possible to do in one URLConf entry, or would it be wiser if I create a custom view to capture the value and pass the queryset directly to the generic view from my overridden view?

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• Regular expressions and matching URLs with metacharacters

  - by James P.

  I'm having trouble finding a regular expression that matches the following String. Korben;http://feeds.feedburner.com/KorbensBlog-UpgradeYourMind?format=xml;1 One problem is escaping the question mark. Java's pattern matcher doesn't seem to accept \? as a valid escape sequence but it also fails to work with the tester at myregexp.com. Here's what I have so far: ([a-zA-Z0-9])+;http://([a-zA-Z0-9./-]+);[0-9]+ Any suggestions? Edit: The original intent was to match all URLs that could be found after the first semi colon.

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• Django - Tips to avoid repeating code in views

  - by D Roddis

  I'm moving from a PHP background into Django development via python, mostly for the sake of tackling a MVC (or MVT) that I feel makes the most sense, although in this pattern I've started to notice a lot of repeated code in my views. For example, when logged in I have information regarding the user that I would like to appear on every page, although when using render_to_response and in every view this is required I have to grab the information and pass it to the render_to_response function. I'm wondering what would be the most efficient way to cut down on the duplicate code which would in essence be required in all views in a particular app. Thanks in advance.

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• Looking for a good explanation of the table generation macro idiom

  - by detly

  I want to make this clear up front : I know how this trick works, what I want is a link to a clear explanation to share with others. One of the answers to a C macro question talks about the "X macro" or "not yet defined macro" idiom. This involves defining something like: #define MAGIC_LIST \ X(name_1, default_1) \ X(name_2, default_2) \ ... Then to create, say, an array of values with named indices you do: typedef enum { #define X(name, val) name, MAGIC_LIST #undef X } NamedDefaults; You can repeat the procedure with a different #define for X() to create an array of values, and maybe debugging strings, etc. I'd like a link to a clear explanation of how this works, pitched at someone who is passably familiar with C. I have no idea what everyone usually calls this pattern, though, so my attempts to search the web for it have failed thus far. (If there is such an explanation on SO, that'd be fine...)

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• How should I implement items that are normalized in the Database, in Object Oriented Design?

  - by Jonas

  How should I implement items that are normalized in the Database, in Object Oriented classes? In the database I have a big table of items and a smaller of groups. Each item belong to one group. This is how my database design look like: +----------------------------------------+ | Inventory | +----+------+-------+----------+---------+ | Id | Name | Price | Quantity | GroupId | +----+------+-------+----------+---------+ | 43 | Box | 34.00 | 456 | 4 | | 56 | Ball | 56.50 | 3 | 6 | | 66 | Tin | 23.00 | 14 | 4 | +----+------+-------+----------+---------+ Totally 3000 lines +----------------------+ | Groups | +---------+------+-----+ | GroupId | Name | VAT | +---------+------+-----+ | 4 | Mini | 0.2 | | 6 | Big | 0.3 | +---------+------+-----+ Totally 10 lines I will use the OOP classes in a GUI, where the user can edit Items and Groups in the inventory. It should also be easy to do calculations with a bunch of items. The group information like VAT are needed for the calculations. I will write an Item class, but do I need a Group class? and if I need it, should I keep them in a global location or how do I access it when I need it for Item-calculations? Is there any design pattern for this case?

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• VB.net: Custom ' TODO: List on an Interface

  - by Shiftbit

  How do I add my own todo and comments list to appear on Interfaces? I want it to pop up like IDisposable does: Public Class Foo : Implements IDisposable Private disposedValue As Boolean = False ' To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub #Region " IDisposable Support " ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub #End Region End Class Whenever I enter my own comments and todo list they are never autogenerated like IDisposable Interface does. I would like my own Interfaces to preserve the comments so that I can share my Interfaces with in source documentation.

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• How would MVVM be for games?

  - by Benny Jobigan

  Particularly for 2d games, and particularly silverlight/wpf games. If you think about it, you can divide a game object into its view (the graphic on the screen) and a view-model/model (the state, ai, and other data for the object). In silverlight, it seems common to make each object a user control, putting the model and view into a single object. I suppose the advantage of this is simplicity. But, perhaps it's less clean or has some disadvantages in terms of the underlying "game engine". What are your thoughts on this matter? What are some advantages and disadvantages of using the MVVM pattern for game development? How about performance? All thoughts are welcome.

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• Session is Closed! NHibernate shouldn't be trying to grab data

  - by Jeremy Holovacs

  I have a UnitOfWork/Service pattern where I populate my model using NHibernate before sending it to the view. For some reason I still get the YSOD, and I don't understand why the object collection is not already populated. My controller method looks like this: public ActionResult PendingRegistrations() { var model = new PendingRegistrationsModel(); using (var u = GetUnitOfWork()) { model.Registrations = u.UserRegistrations.GetRegistrationsPendingAdminApproval(); } return View(model); } The service/unit of work looks like this: public partial class NHUserRegistrationRepository : IUserRegistrationRepository { public IEnumerable<UserRegistration> GetRegistrationsPendingAdminApproval() { var r = from UserRegistration ur in _Session.Query<UserRegistration>() where ur.Status == AccountRegistrationStatus.PendingAdminReview select ur; NHibernateUtil.Initialize(r); return r; } } What am I doing wrong?

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• How can I expose a service bus by a wcf service to be consumed by a silverlight client

  - by illdev

  In a Silverlight application, instead of consuming and writing (wcf) wrappers around messages that finally get sent to the bus, I want to send use my message bus as directly as possible. My idea was to expose the service bus directly as a wcf service, or, in other terms, I want to bidirectionally pub/sub over the wire. Has this been done already? Is bi-directionality doable at all? After all, we are (are we restricted to that?) in the http domain? Lots of questions. Some head start would be greatly appreciated! I am in .NET land, with using Rhino Service Bus, but the pattern should apply to different platforms.

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• Customizing UISlider look

  - by tcurdt

  To customize the visual look of a UISlider you can set the thumb and track images. Part of the track images gets stretched to the appropriate with. From the documentation: A stretchable region sits between two end cap regions. The end caps define the portions of the image that remain as is and are not stretched. The stretchable region is a 1-point wide area between the end caps that can be replicated to make the image appear longer. Now the problem I have is that my stretchable region needs to be more than 1-point wide. (It's a pattern) Unfortunately the 1-point width seems to be hard coded in the SDK. Anyone having an idea how to work around this? Or will I have to write my own slider from scratch for this?

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• Insert A Line At The Beginning Of A File

  - by thebourneid

  I'm trying to insert/add a line 'COMMENT DUMMY' at the beginnig of a file as a first row if /PATTERN/ not found. I know how to do this with OPEN CLOSE function. Probably after reading the file it should look something like this: open F, ">", $fn or die "could not open file: $!"; ; print F "COMMENT DUMMY\n", @array; close F; But I have a need to implement this with the use of the Tie::File function and don't know how. use strict; use warnings; use Tie::File; my $fn = 'test.txt'; tie my @lines, 'Tie::File', $fn or die "could not tie file: $!"; untie @lines;

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• Can this be done with single SQL query

  - by Ghostrider

  I'm using MySQL. I have a table Type SubType 1 1 1 5 1 6 1 8 2 2 2 3 3 1 3 2 3 3 For each type there is some number of subtypes. For every subtype in a type there is a corresponding subtype in the next type: (1,1) => (2,2) (1,5) => (2,3) (1,6) => (2,2) (1,8) => (2,3) (2,2) => (3,1) (2,3) => (3,2) In case you haven't seen the pattern, here it is: you sort both current and next types by subtype, then in the next type you get subtype in the same position as your current subtype in current type is. If there are more subtypes in the current type that in the next one, you warp around and start from the first subtype in the next type. Is it possible to construct a query that takes current type and subtype and returns corresponding subtype in the next type?

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• Problem Rewriting URL's from HTTPS to HTTP using IIS7 URL Rewriter, when using Webforms ReturnURL=

  - by theminesgreg

  I took Jeff's Re-write rules from this post and the HTTP to HTTPS conversion works great. However, going back to HTTP is giving me problems because of the ReturnUrl= in the URL (I'm using webforms). Here's an example of the url: https://localhost/Login.aspx?ReturnUrl=%2f Here's the rewrite rule I'm using: <rule name="HTTPS to HTTP redirect for all other pages" stopProcessing="true"> <match url="^login\.aspx$" ignoreCase="true" negate="true" /> <conditions> <add input="{SERVER_PORT}" pattern="^443$" /> </conditions> <action type="Redirect" redirectType="Found" url="http://{HTTP_HOST}{REQUEST_URI}" /> </rule> Here's the resulting re-written URL: http://localhost/,/ Has anyone found a work around for this?

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• System.Timers.Timer leaking due to "direct delegate roots"

  - by alimbada

  Apologies for the rather verbose and long-winded post, but this problem's been perplexing me for a few weeks now so I'm posting as much information as I can in order to get this resolved quickly. We have a WPF UserControl which is being loaded by a 3rd party app. The 3rd party app is a presentation application which loads and unloads controls on a schedule defined by an XML file which is downloaded from a server. Our control, when it is loaded into the application makes a web request to a web service and uses the data from the response to display some information. We're using an MVVM architecture for the control. The entry point of the control is a method that is implementing an interface exposed by the main app and this is where the control's configuration is set up. This is also where I set the DataContext of our control to our MainViewModel. The MainViewModel has two other view models as properties and the main UserControl has two child controls. Depending on the data received from the web service, the main UserControl decides which child control to display, e.g. if there is a HTTP error or the data received is not valid, then display child control A, otherwise display child control B. As you'd expect, these two child controls bind two separate view models each of which is a property of MainViewModel. Now child control B (which is displayed when the data is valid) has a RefreshService property/field. RefreshService is an object that is responsible for updating the model in a number of ways and contains 4 System.Timers.Timers; a _modelRefreshTimer a _viewRefreshTimer a _pageSwitchTimer a _retryFeedRetrievalOnErrorTimer (this is only enabled when something goes wrong with retrieving data). I should mention at this point that there are two types of data; the first changes every minute, the second changes every few hours. The controls' configuration decides which type we are using/displaying. If data is of the first type then we update the model quite frequently (every 30 seconds) using the _modelRefreshTimer's events. If the data is of the second type then we update the model after a longer interval. However, the view still needs to be refreshed every 30 seconds as stale data needs to be removed from the view (hence the _viewRefreshTimer). The control also paginates the data so we can see more than we can fit on the display area. This works by breaking the data up into Lists and switching the CurrentPage (which is a List) property of the view model to the right List. This is done by handling the _pageSwitchTimer's Elapsed event. Now the problem My problem is that the control, when removed from the visual tree doesn't dispose of it's timers. This was first noticed when we started getting an unusually high number of requests on the web server end very soon after deploying this control and found that requests were being made at least once a second! We found that the timers were living on and not stopping hours after the control had been removed from view and that the more timers there were the more requests piled up at the web server. My first solution was to implement IDisposable for the RefreshService and do some clean up when the control's UnLoaded event was fired. Within the RefreshServices Dispose method I've set Enabled to false for all the timers, then used the Stop() method on all of them. I've then called Dispose() too and set them to null. None of this worked. After some reading around I found that event handlers may hold references to Timers and prevent them from being disposed and collected. After some more reading and researching I found that the best way around this was to use the Weak Event Pattern. Using this blog and this blog I've managed to work around the shortcomings in the Weak Event pattern. However, none of this solves the problem. Timers are still not being disabled or stopped (let alone disposed) and web requests are continuing to build up. Mem Profiler tells me that "This type has N instances that are directly rooted by a delegate. This can indicate the delegate has not been properly removed" (where N is the number of instances). As far as I can tell though, all listeners of the Elapsed event for the timers are being removed during the cleanup so I can't understand why the timers continue to run. Thanks for reading. Eagerly awaiting your suggestions/comments/solutions (if you got this far :-p)

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• How to check connection leak using regular expression ?

  - by gauravkarnatak

  I have to check connection leak in my application i.e. open connections which have not been closed. After searching, after I found out that a thousands times connections have been opened but I can't manually go to each and every code fragment and check for connection close thing. I think, it could be possible using a regular expression but the fact is, I am not that well versed with regex that I could write one. Please suggest a regular expression for checking in a no of java files that a opened connection has been closed or not. My code pattern is something like this. try { /* Some code goes here */ con = EJBUtil.getConnection(JNDI_NAME); /* Some code goes here */ } finally { /* Some code goes here */ DBUtil.close(con); or closeConnection.close(con); /* Some code goes here */ }

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• htaccess Redirect - First Segment to PHP File, Second Segment as Parameter

  - by Steve

  My htaccess redirect knowledge is somewhat weak, so I was hoping to get some help here. I currently have the following redirect, which works well: # remove trailing slash RewriteRule ^(.*)/$ /$1 [L,R=301] # redirect to clean URL RewriteCond /%{REQUEST_FILENAME}.php -f RewriteRule ^([a-zA-Z0-9_-\s]+)$ /$1.php This takes a URL like www.mysite.com/about to www.mysite.com/about.php Now I would like to keep this behavior, but add parameters (if applicable), as such: www.mysite.com/about = www.mysite.com/about.php www.mysite.com/gallery/1 = www.mysite.com/gallery.php?id=1 If possible, I might like to expand this system to 2 or more parameters, as such: www.mysite.com/gallery/1/2 = www.mysite.com/gallery.php?id=1&section=2 So the pattern would be: First URL segment redirects to a PHP file (Optionally) the second segment gets added as the id parameter (Optionally) the third segment gets added as the section parameter

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