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  • SQL SERVER – SQL in Sixty Seconds – 5 Videos from Joes 2 Pros Series – SQL Exam Prep Series 70-433

    - by pinaldave
    Joes 2 Pros SQL Server Learning series is indeed fun. Joes 2 Pros series is written for beginners and who wants to build expertise for SQL Server programming and development from fundamental. In the beginning of the series author Rick Morelan is not shy to explain the simplest concept of how to open SQL Server Management Studio. Honestly the book starts with that much basic but as it progresses further Rick discussing about various advanced concepts from query tuning to Core Architecture. This five part series is written with keeping SQL Server Exam 70-433. Instead of just focusing on what will be there in exam, this series is focusing on learning the important concepts thoroughly. This book no way take short cut to explain any concepts and at times, will go beyond the topic at length. The best part is that all the books has many companion videos explaining the concepts and videos. Every Wednesday I like to post a video which explains something in quick few seconds. Today we will go over five videos which I posted in my earlier posts related to Joes 2 Pros series. Introduction to XML Data Type Methods – SQL in Sixty Seconds #015 The XML data type was first introduced with SQL Server 2005. This data type continues with SQL Server 2008 where expanded XML features are available, most notably is the power of the XQuery language to analyze and query the values contained in your XML instance. There are five XML data type methods available in SQL Server 2008: query() – Used to extract XML fragments from an XML data type. value() – Used to extract a single value from an XML document. exist() – Used to determine if a specified node exists. Returns 1 if yes and 0 if no. modify() – Updates XML data in an XML data type. node() – Shreds XML data into multiple rows (not covered in this blog post). [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Error Actions – SQL in Sixty Seconds #014 Most people believe that when SQL Server encounters an error severity level 11 or higher the remaining SQL statements will not get executed. In addition, people also believe that if any error severity level of 11 or higher is hit inside an explicit transaction, then the whole statement will fail as a unit. While both of these beliefs are true 99% of the time, they are not true in all cases. It is these outlying cases that frequently cause unexpected results in your SQL code. To understand how to achieve consistent results you need to know the four ways SQL Error Actions can react to error severity levels 11-16: Statement Termination – The statement with the procedure fails but the code keeps on running to the next statement. Transactions are not affected. Scope Abortion – The current procedure, function or batch is aborted and the next calling scope keeps running. That is, if Stored Procedure A calls B and C, and B fails, then nothing in B runs but A continues to call C. @@Error is set but the procedure does not have a return value. Batch Termination – The entire client call is terminated. XACT_ABORT – (ON = The entire client call is terminated.) or (OFF = SQL Server will choose how to handle all errors.) [Detailed Blog Post] | [Quiz with Answer] Introduction to Basics of a Query Hint – SQL in Sixty Seconds #013 Query hints specify that the indicated hints should be used throughout the query. Query hints affect all operators in the statement and are implemented using the OPTION clause. Cautionary Note: Because the SQL Server Query Optimizer typically selects the best execution plan for a query, it is highly recommended that hints be used as a last resort for experienced developers and database administrators to achieve the desired results. [Detailed Blog Post] | [Quiz with Answer] Introduction to Hierarchical Query – SQL in Sixty Seconds #012 A CTE can be thought of as a temporary result set and are similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. A CTE is generally considered to be more readable than a derived table and does not require the extra effort of declaring a Temp Table while providing the same benefits to the user. However; a CTE is more powerful than a derived table as it can also be self-referencing, or even referenced multiple times in the same query. A recursive CTE requires four elements in order to work properly: Anchor query (runs once and the results ‘seed’ the Recursive query) Recursive query (runs multiple times and is the criteria for the remaining results) UNION ALL statement to bind the Anchor and Recursive queries together. INNER JOIN statement to bind the Recursive query to the results of the CTE. [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Server Security – SQL in Sixty Seconds #011 Let’s get some basic definitions down first. Take the workplace example where “Tom” needs “Read” access to the “Financial Folder”. What are the Securable, Principal, and Permissions from that last sentence? A Securable is a resource that someone might want to access (like the Financial Folder). A Principal is anything that might want to gain access to the securable (like Tom). A Permission is the level of access a principal has to a securable (like Read). [Detailed Blog Post] | [Quiz with Answer] Please leave a comment explain which one was your favorite video as that will help me understand what works and what needs improvement. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video

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  • Mobile redirect strategy

    - by Kevin
    Looking for help on deciding how to redirect users to a mobile optimized version of my site (m.mysite.com). Looking at two methods: Server configuration (.htaccess or even varnish) Webapp (php) The problem I see with #1 is with the "view full site" link on the mobile site. If a user clicks that link and they go to mysite.com won't the server just redirect them back to m.mysite.com? For #2 I could create a cookie that is checked in addition to the user agent. Any suggestions/comments? Is there a better way to "remember" if the user clicked "visit full site"? Thanks, Kevin

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  • Displaying XML data using XSLT transformations in an ASP.Net site

    - by nikolaosk
    In this post, I will try to show you how to display xml data in asp.net website after making some xslt transformations. You will need to know a few things about XSLT. The best place to find out about XSLT is this link . I am going to explain a few things about XSLT elements and functions in this post, anyway. You will see the namespaces we are going to use and some of the main classes and methods.All these come with the FCL (Framework class library) and we just have to know what they do. We will...(read more)

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  • General approach to isometrics

    - by MrThys
    I am currently discovering the world of isometrics, now I found out there are two approaches to creating the tilemap; Just create 2:1 ratio tile-images and draw those. Creating squares and transforming them to the 2:1 ratio. What is the general approach on developing an isometric game? Now I was wondering a few things; How do more known games like AOE1/2 do this? What are the pros/cons of both methods? Which method is preferred to be used in this day and age? Edit added more general question

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  • T4Toolbox and Visual Studio 2010

    - by Ben Griswold
    I’ve been using the T4Toolbox to help generate my ASP.NET MVC models and scaffolding for a while now.  Another developer tried using my generator project last week and ran into troubles due to a breaking change around the RenderCore() and TransformText() methods in support for VS 2010.  If you upgraded to the latest version of T4Toolbox and receive a build error similar to the following, you are probably in the same boat: GeneratedTextTransformation.[Template].RenderCore(): no suitable method found to override We took the easy way out.  I had him uninstall the latest version of T4Toolbox and install version 9.7.25.1 which my templates were initially coded against.  For now, that worked great, but it sounds like I’ll be doing some rework of the 20+ templates in my project to support Visual Studio 2010 when we migrate later this month.

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  • Using your own gameloop logic on iphone?

    - by kkan
    I'm currently working on moving some android-ndk code to the iphone and have hit a wall. I'm new to iphone development, and from looking at some samples it seems that the main loop is handled for you and all you've got to do is override the render method on the view to handle the rendering and add a selector to handle the update methods. The render method itself lookslike it's attached to the windows refresh. But in android I've got my own game loop that controls the rendering and updates using c++ time.h. is it possible to implement the same here bypassing apple's loop? I'd really like the keep the structures of the code similar. Thanks!

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  • Getting to grips with the stack in nasm

    - by MarkPearl
    Today I spent a good part of my day getting to grips with the stack and nasm. After looking at my notes on nasm I think this is one area for the course I am doing they could focus more on… So here are some snippets I have put together that have helped me understand a little bit about the stack… Simplest example of the stack You will probably see examples like the following in circulation… these demonstrate the simplest use of the stack… org 0x100 bits 16 jmp main main: push 42h push 43h push 44h mov ah,2h ;set to display characters pop dx    ;get the first value int 21h   ;and display it pop dx    ;get 2nd value int 21h   ;and display it pop dx    ;get 3rd value int 21h   ;and display it int 20h The output from above code would be… DCB Decoupling code using “call” and “ret” This is great, but it oversimplifies what I want to use the stack for… I do not know if this goes against the grain of assembly programmers or not, but I want to write loosely coupled assembly code – and I want to use the stack as a mechanism for passing values into my decoupled code. In nasm we have the call and return instructions, which provides a mechanism for decoupling code, for example the following could be done… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h mov dx,41h int 21h ret ;---------------------------------------- main: call displayChar int 20h   This would output the following to the console A So, it would seem that call and ret allow us to jump to segments of our code and then return back to the calling position – a form of segmenting the code into what we would called in higher order languages “functions” or “methods”. The only issue is, in higher order languages there is a way to pass parameters into the functions and return results. Because of the primitive nature of the call and ret instructions, this does not seem to be obvious. We could of course use the registers to pass values into the subroutine and set values coming out, but the problem with this is we… Have a limited number of registers Are threading our code with tight coupling (it would be hard to migrate methods outside of their intended use in a particular program to another one) With that in mind, I turn to the stack to provide a loosely coupled way of calling subroutines… First attempt with the Stack Initially I thought this would be simple… we could use code that looks as follows to achieve what I want… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov ah,2h pop dx int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h   However running this application does not give the desired result, I want an ‘A’ to be returned, and I am getting something totally different (you will to). Reading up on the call and ret instructions a discovery is made… they are pushing and popping things onto and off the stack as well… When the call instruction is executed, the current value of IP (the address of the instruction to follow) is pushed onto the stack, when ret is called, the last value on the stack is popped off into the IP register. In effect what the above code is doing is as follows with the stack… push 41h push current value of ip pop current value of ip to dx pop 41h to ip This is not what I want, I need to access the 41h that I pushed onto the stack, but the call value (which is necessary) is putting something in my way. So, what to do? Remember we have other registers we can use as well as a thing called indirect addressing… So, after some reading around, I came up with the following approach using indirect addressing… org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h call displayChar int 20h In essence, what I have done here is used a trick with the stack pointer… it goes as follows… Push 41 onto the stack Make the call to the function, which will push the IP register onto the stack and then jump to the displayChar label Move the value in the stack point to the bp register (sp currently points at IP register) Move the at the location of bp minus 2 bytes to dx (this is now the value 41h) display it, execute the ret instruction, which pops the ip value off the stack and goes back to the calling point This approach is still very raw, some further reading around shows that I should be pushing the value of bp onto the stack before replacing it with sp, but it is the starting thread to getting loosely coupled subroutines. Let’s see if you get what the following output would be? org 0x100 bits 16 jmp main ;---------------------------------------- displayChar: mov bp,sp mov ah,2h mov dx,[bp+4] int 21h mov dx,[bp+2] int 21h ret ;---------------------------------------- main: push 41h push 42h call displayChar int 20h The output is… AB Where to from here? If by any luck some assembly programmer comes along and see this code and notices that I have made some fundamental flaw in my logic… I would like to know, so please leave a comment… appreciate any feedback!

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  • Windows Azure End to End Examples

    - by BuckWoody
    I’m fascinated by the way people learn. I’m told there are several methods people use to understand new information, from reading to watching, from experiencing to exploring. Personally, I use multiple methods of learning when I encounter a new topic, usually starting with reading a bit about the concepts. I quickly want to put those into practice, however, especially in the technical realm. I immediately look for examples where I can start trying out the concepts. But I often want a “real” example – not just something that represents the concept, but something that is real-world, showing some feature I could actually use. And it’s no different with the Windows Azure platform – I like finding things I can do now, and actually use. So when I started learning Windows Azure, I of course began with the Windows Azure Training Kit – which has lots of examples and labs, presentations and so on. But from there, I wanted more examples I could learn from, and eventually teach others with. I was asked if I would write a few of those up, so here are the ones I use. CodePlex CodePlex is Microsoft’s version of an “Open Source” repository. Anyone can start a project, add code, documentation and more to it and make it available to the world, free of charge, using various licenses as they wish. Microsoft also uses this location for most of the examples we publish, and sample databases for SQL Server. If you search in CodePlex for “Azure”, you’ll come back with a list of projects that folks have posted, including those of us at Microsoft. The source code and documentation are there, so you can learn using actual examples of code that will do what you need. There’s everything from a simple table query to a full project that is sort of a “Corporate Dropbox” that uses Windows Azure Storage. The advantage is that this code is immediately usable. It’s searchable, and you can often find a complete solution to meet your needs. The disadvantage is that the code is pretty specific – it may not cover a huge project like you’re looking for. Also, depending on the author(s), you might not find the documentation level you want. Link: http://azureexamples.codeplex.com/site/search?query=Azure&ac=8    Tailspin Microsoft Patterns and Practices is a group here that does an amazing job at sharing standard ways of doing IT – from operations to coding. If you’re not familiar with this resource, make sure you read up on it. Long before I joined Microsoft I used their work in my daily job – saved a ton of time. It has resources not only for Windows Azure but other Microsoft software as well. The Patterns and Practices group also publishes full books – you can buy these, but many are also online for free. There’s an end-to-end example for Windows Azure using a company called “Tailspin”, and the work covers not only the code but the design of the full solution. If you really want to understand the thought that goes into a Platform-as-a-Service solution, this is an excellent resource. The advantages are that this is a book, it’s complete, and it includes a discussion of design decisions. The disadvantage is that it’s a little over a year old – and in “Cloud” years that’s a lot. So many things have changed, improved, and have been added that you need to treat this as a resource, but not the only one. Still, highly recommended. Link: http://msdn.microsoft.com/en-us/library/ff728592.aspx Azure Stock Trader Sometimes you need a mix of a CodePlex-style application, and a little more detail on how it was put together. And it would be great if you could actually play with the completed application, to see how it really functions on the actual platform. That’s the Azure Stock Trader application. There’s a place where you can read about the application, and then it’s been published to Windows Azure – the production platform – and you can use it, explore, and see how it performs. I use this application all the time to demonstrate Windows Azure, or a particular part of Windows Azure. The advantage is that this is an end-to-end application, and online as well. The disadvantage is that it takes a bit of self-learning to work through.  Links: Learn it: http://msdn.microsoft.com/en-us/netframework/bb499684 Use it: https://azurestocktrader.cloudapp.net/

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  • Reset the controls within asp placeholder

    - by alaa9jo
    I use placeholders very much in many projects,but in one of the projects I was asked to reset the controls within a specific placeholder to their original state after the user has finished from inserting his/her data. As everyone of us know,to keep the controls within a placeholder from disappearing after postbacks you have to recreate them,we add such a code in i.e. page_load,the controls will be recreated and their values will be loaded from viewstate (for some of them like textbox,checkboxs,..etc) automatically,that placeholder contains only textboxs so what I need is to block/ loading/clear that viewstate after inserting the data. First thought: Customizing placeholder I thought about it and tried overriding many methods but no success at all...maybe I'm missing something not sure. Second thought: recreate the controls 2 times: In page_load,I recreate the controls within that placeholder then in button click (the button that saves user's data) I recreate them once more and it worked! I just thought of sharing my experience in that case with everyone in case anyone needed it,any better suggestion(s) is welcomed.

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  • How properly perform passing operation result to View

    - by atomAltera
    I'm developing web site on self made MVC engine. I have actionController that handles operations like register, login, post submit and etc. actionController receives operation name and parameters. Of course it mast handle errors such user with same nick already exists or password is to short about which action handler have to notify user. The question is which is the best way to organize errors, such that View could easily get localized user notification message. I see two ways First one: define error constants like ERR_NICK_BUSY = '1' ERR_NICK_INVALID = '2' ... and localization map local[ERR_NICK_BUSY] = 'User with the same nick already registered' local[ERR_NICK_INVALID ] = 'Nick, you entered is invalid' ... And second one: define abstract constants like ERR_FIELD_BUSY = '1' ERR_FIELD_INVALID = '2' ... and pass them with field name. In this case localization looks like local['nick_'+ERR_FIELD_BUSY] = 'User with the same nick already registered' ... I don't like both this methods. Can you advise something else?

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  • How do I set a touch listener in a child scene in AndEngine?

    - by Siddharth
    In my game, I want to implement touch listener for my child scene objects. Basically I tried all the possible way to implement this that I have usually done for my normal scenes, but those methods do not work here. Could somebody provide some guidance for setting touch area listener in child scene? Here is my code: menuScene.setTouchAreaBindingEnabled(true); menuScene.registerTouchArea(resumeButtonSprite); menuScene.registerTouchArea(retryButtonSprite); menuScene.registerTouchArea(exitButtonSprite); menuScene.setOnAreaTouchListener(new IOnAreaTouchListener() { @Override public boolean onAreaTouched(TouchEvent pSceneTouchEvent, ITouchArea pTouchArea, float pTouchAreaLocalX, float pTouchAreaLocalY) { System.out.println("Touch"); return true; } }); In this code, menuScene was a child scene activity. Also after research I found that my engine was stopped while the child scene was activated so the touch event is not detected. I want to implement a pause menu in my game so any desirable solution for a pause menu implementation would help.

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  • Simple Preferred time control using silverlight 3.

    - by mohanbrij
    Here I am going to show you a simple preferred time control, where you can select the day of the week and the time of the day. This can be used in lots of place where you may need to display the users preferred times. Sample screenshot is attached below. This control is developed using Silverlight 3 and VS2008, I am also attaching the source code with this post. This is a very basic example. You can download and customize if further for your requirement if you want. I am trying to explain in few words how this control works and what are the different ways in which you can customize it further. File: PreferredTimeControl.xaml, in this file I have just hardcoded the controls and their positions which you can see in the screenshot above. In this example, to change the start day of the week and time, you will have to go and change the design in XAML file, its not controlled by your properties or implementation classes. You can also customize it to change the start day of the week, Language, Display format, styles, etc, etc. File: PreferredTimeControl.xaml.cs, In this control using the code below, first I am taking all the checkbox from my form and store it in the Global Variable, which I can use across my page. List<CheckBox> checkBoxList; #region Constructor public PreferredTimeControl() { InitializeComponent(); GetCheckboxes();//Keep all the checkbox in List in the Load itself } #endregion #region Helper Methods private List<CheckBox> GetCheckboxes() { //Get all the CheckBoxes in the Form checkBoxList = new List<CheckBox>(); foreach (UIElement element in LayoutRoot.Children) { if (element.GetType().ToString() == "System.Windows.Controls.CheckBox") { checkBoxList.Add(element as CheckBox); } } return checkBoxList; } Then I am exposing the two methods which you can use in the container form to get and set the values in this controls. /// <summary> /// Set the Availability on the Form, with the Provided Timings /// </summary> /// <param name="selectedTimings">Provided timings comes from the DB in the form 11,12,13....37 /// Where 11 refers to Monday Morning, 12 Tuesday Morning, etc /// Here 1, 2, 3 is for Morning, Afternoon and Evening respectively, and for weekdays /// 1,2,3,4,5,6,7 where 1 is for Monday, Tuesday, Wednesday, Thrusday, Friday, Saturday and Sunday respectively /// So if we want Monday Morning, we can can denote it as 11, similarly for Saturday Evening we can write 36, etc /// </param> public void SetAvailibility(string selectedTimings) { foreach (CheckBox chk in checkBoxList) { chk.IsChecked = false; } if (!String.IsNullOrEmpty(selectedTimings)) { string[] selectedString = selectedTimings.Split(','); foreach (string selected in selectedString) { foreach (CheckBox chk in checkBoxList) { if (chk.Tag.ToString() == selected) { chk.IsChecked = true; } } } } } /// <summary> /// Gets the Availibility from the selected checkboxes /// </summary> /// <returns>String in the format of 11,12,13...41,42...31,32...37</returns> public string GetAvailibility() { string selectedText = string.Empty; foreach (CheckBox chk in GetCheckboxes()) { if (chk.IsChecked == true) { selectedText = chk.Tag.ToString() + "," + selectedText; } } return selectedText; }   In my example I am using the matrix format for Day and Time, for example Monday=1, Tuesday=2, Wednesday=3, Thursday = 4, Friday = 5, Saturday = 6, Sunday=7. And Morning = 1, Afternoon =2, Evening = 3. So if I want to represent Morning-Monday I will have to represent it as 11, Afternoon-Tuesday as 22, Morning-Wednesday as 13, etc. And in the other way to set the values in the control I am passing the values in the control in the same format as preferredTimeControl.SetAvailibility("11,12,13,16,23,22"); So this will set the checkbox value for Morning-Monday, Morning-Tuesday, Morning-Wednesday, Morning-Saturday, Afternoon of Tuesday and Afternoon of Wednesday. To implement this control, first I have to import this control in xmlns namespace as xmlns:controls="clr-namespace:PreferredTimeControlApp" and finally put in your page wherever you want, <Grid x:Name="LayoutRoot" Style="{StaticResource LayoutRootGridStyle}"> <Border x:Name="ContentBorder" Style="{StaticResource ContentBorderStyle}"> <controls:PreferredTimeControl x:Name="preferredTimeControl"></controls:PreferredTimeControl> </Border> </Grid> And in the code behind you can just include this code: private void InitializeControl() { preferredTimeControl.SetAvailibility("11,12,13,16,23,22"); } And you are ready to go. For more details you can refer to my code attached. I know there can be even simpler and better way to do this. Let me know if any other ideas. Sorry, Guys Still I have used Silverlight 3 and VS2008, as from the system I am uploading this is still not upgraded, but still you can use the same code with Silverlight 4 and VS2010 without any changes. May be just it will ask you to upgrade your project which will take care of rest. Download Source Code.   Thanks ~Brij

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  • Microsoft Unity 2.0 Released

    - by shiju
    Microsoft's dependency injection framework Unity Application Block (Unity) has reached version 2.0. The release available on Codeplex at http://unity.codeplex.com/ Unity 2.0  Change LogRelease Notes - Unity 2 for DesktopRelease Notes - Unity 2 for SilverlightOfficial Download - Unity 2.0Official Download - Unity 2.0 for SilverlightAdditional Materials DownloadMigration GuideVideos UnityContainer Fluent InterfaceUnity 2.0 provides a fluent interface for type configuration. Now you can call all the methods in a single statement, as shown in the following code.  IUnityContainer container = new UnityContainer() .RegisterType<IFormsAuthentication, FormsAuthenticationService>() .RegisterType<IMembershipService, AccountMembershipService>() .RegisterInstance<MembershipProvider>(Membership.Provider) .RegisterType<IDinnerRepository, DinnerRepository>();    

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  • Ubuntu Desktop Password

    - by doug
    I inherited a machine with Ubuntu desktop installed. It has a password in place and I have no idea what the password may be. I cannot get to the command line to use the methods I have found online. No matter how many times I press "Shift" during the boot process it still goes all the way to the desktop login. I never see grub. I am not sure which version I have but I think may be 9 or 10. Thanks Doug

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  • How to Share Files Online with Ubuntu One

    - by Chris Hoffman
    Ubuntu One, Ubuntu’s built-in cloud file storage service, allows you to make files publically available online or share them privately with others. You can share files over the Internet right from Ubuntu’s file browser. Ubuntu One has two file-sharing methods: Publish, which makes a file publically available on the web to anyone who knows its address, and Share, which shares a folder with other Ubuntu One users. HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux

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  • Low level Linux graphics

    - by math4tots
    For educational purposes, I'd like to write an application on a Linux environment that can process keyboard events and draw graphics without huge dependencies like X or SDL. I presume that this must be possible, because X and SDL are just programs themselves, so they must rely on other methods inherent to the environment. Is this understanding correct? If so, where might I learn to write such a program? My limited experience tells me that it would involve making calls to the kernel, and/or writing to special files; however, I haven't been able to find any tutorials on the matter (I am not even sure what to Google). Also, in case it is relevant, I am running Debian Squeeze on Virtualbox. I have used a netinst cd without networking, so there isn't much installed on it currently. I will install gcc, but I am hoping I can get by with nothing more.

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  • Hide 'Your profile could not be opened correctly'

    - by B. Roland
    Hello! I have a small public internet cafe, with Ubuntu 10.04 and 10.10. I'm using Google Chrome 7.0.517.44 (64615), with AutoScroll - Version: 2.7.5; AdBlock is removed because of high CPU loads, and unconfortable speed of machine. "Your profile could not be opened correctly" error is displayed: This image is only an illustration. The reason is that I changed permissions of some config files, to don't remember the history, there are no setting in options, to don't use history. I've been removed write permission to: ~/.config/google-chrome$ find . -group nopasswdlogin ./Default/Archived History ./Default/History ./Default/Visited Links When I solved all of my problem, I'll remove some other write permission, this is a public place. What methods are known to HIDE this message? Thanks!

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  • Addressing a variable in VB

    - by Jeff
    Why doesn't Visual Basic.NET have the addressof operator like C#? In C#, one can int i = 123; int* addr = &i; But VB has no equivalent counter part. It seems like it should be important. UPDATE Since there's some interest, Im copying my response to Strilanc below. The case I ran into didnt necessitate pointers by any means, but I was trying to trouble shoot a unit test that was failing and there was some confusion over whether or not an object being used at one point in the stack was the same object as an object several methods away.

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  • APress Deal of the Day 10/August/2014 - Pro ASP.NET Web API Security

    - by TATWORTH
    Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2014/08/10/apress-deal-of-the-day-10august2014---pro-asp.net-web.aspxToday’s $10 Deal of the Day from APress at http://www.apress.com/9781430257820 is Pro ASP.NET Web API Security. “ASP.NET Web API is a key part of ASP.NET MVC 4. It has become the platform of choice for building RESTful services. Securing ASP.NET Web API applications requires a move away from traditional WCF-based techniques in favor of new SOAP-less methods. The evaluation, selection and analysis of these new techniques is the focus of this book.”

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  • Complexity of a web application

    - by Dominik G
    I am currently writing my Master's Thesis on maintainability of a web application. I found some methods like the "Maintainability Index" by Coleman et.al. or the "Software Maintainability Index" by Muthanna et.al. For both of them one needs to calculate the cyclomatic complexity. So my question is: Is it possible to measure the cyclomatic complexity of a web application? In my opinion there are three parts to a web application: Server code (PHP, C#, Python, Perl, etc.) Client code (JavaScript) HTML (links and forms as operators, GET-parameters and form fields as operands!?) What do you think? Is there another point of view on the complexity of web application? Did I miss something?

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  • Telerik Releases the Data Service Wizard

    After a great beta cycle, Telerik is proud to announce today the commercial availability of the OpenAccess Data Service Wizard. You can download it and install it with Telerik OpenAccess Q1 2010 for both Visual Studio 2008 and 2010 RTM. If you are new to the Data Service Wizard, it is a great tool that will allow you to point a wizard at your OpenAccess generated data access classes and automatically build an WCF, Astoria (WCF Data Services), REST or ATOMPub collection endpoint, complete with the CRUD methods if applicable. If you are familiar with the Data Service Wizard already, there will be two new surprises in the release version. If you generated a domain model with the new OpenAccess Visual Entity Designer, you have only one file added to your project, mydomainmodel.rlinq for example. The first surprise of the new Data Service Wizard is that if you right click on the domain model in Visual Studio, ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Googlebot fetches my pages very frequent, rel-nofollow, meta-noindex or robots.txt-disallow

    - by trante
    Googlebot fetches pages in my site very frequently. And this slowens my website. I don't want Googlebot to crawl too frequent. I decreased crawl rate from Google webmaster tools. But I'm supposing to use these three tools: Adding rel="nofollow" to my inner pages. So Googlebot won't crawl and index them. Adding meta tag "noindex" so Google will remove this page from index and won't get it again. Adding Disallow: /mySomeFolder/ to robots.txt and Googlebot won't crawl that pages. I'm planning to use these methods for my 56.000 pages, except the most important 6-7 pages. Which method would you prefer and what would be disadvantages or advantages ? Or won't it change my website speed etc..

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  • Gradual approaches to dependency injection

    - by JW01
    I'm working on making my classes unit-testable, using dependency injection. But some of these classes have a lot of clients, and I'm not ready to refactor all of them to start passing in the dependencies yet. So I'm trying to do it gradually; keeping the default dependencies for now, but allowing them to be overridden for testing. One approach I'm conisdering is just moving all the "new" calls into their own methods, e.g.: public MyObject createMyObject(args) { return new MyObject(args); } Then in my unit tests, I can just subclass this class, and override the create functions, so they create fake objects instead. Is this a good approach? Are there any disadvantages? More generally, is it okay to have hard-coded dependencies, as long as you can replace them for testing? I know the preferred approach is to explicitly require them in the constructor, and I'd like to get there eventually. But I'm wondering if this is a good first step.

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  • libssh2 and simultaneous connections

    - by Florian Margaine
    I'm writing a node.js C++ module using the C library libssh2. The module is supposed to be a bridge to connect to SSH over HTTPS. Right now, I'm still in the design/learning phase of v8 API and C++, and I have a design question: libssh2 is a C library, all its methods are global. From what I see in the examples, libssh2 can only handle one connection at a time. If I want to allow simultaneous connections to different SSH servers, do I have to fork a process to completely separate the libssh2 "instances", or is forking a thread enough? I don't know enough of the separation limit used there. Any idea on how to handle this is appreciated.

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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