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  • Is my DFD accurate?

    - by Dummy Derp
    This is my first ever DFD that I made after my fair share of learning but I have no way of verifying whether it is correct or not. Although I have taken utmost care to make sure it is right, I may be wrong. Here is the scenario: Bebop Records is a mail-order company that distributes CDs and tapes at discount prices to record club members. When an order processing clerk receives an order form, he or she verifies that the sender is a club member by checking the Member file. If the sender is not a member, the clerk returns the order along with a membership application form. If the customer is a member, the clerk verifies the order item data by checking the Item file. Then the clerk enters the order data and saves it to the Daily Order file. The clerk also prints an invoice and shipping list for each order, which are forwarded to Order Fulfilment. And here is my diagram:

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  • Fastest way to document software architecture and design

    - by Karsten
    We are a small team of 5 developers and I'm looking for some great advices about how to document the software architecture and design. I'm going for the sweet spot, where the time invested pays off. I don't want to use more time documenting than necessary. I'll quickly give you my thoughts. What are the diagrams I should made? I'm thinking an overall diagram showing the various applications and services. And then some sequence diagrams showing the most important or complicated processes. About the code it self, I really don't see much value in describing or making diagrams for the code outside the .cs files them self. About text documents, I'm a bit uncertain about when to put down on paper. Most developers don't like to either write or read long documents.

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  • Simultaneously calling multiple methods on a WCF service from silverlight

    - by ola karlsson
    A while back I had to debug some performance issues in an existing Silverlight app, as the problem / solution was a bit obscure and finding info about it was quite tricky, I thought I’d share, maybe it can help the next person with this problem. The App On start, the app would do a number of calls to different methods on a WCF service, this to populate the UI with the necessary data. Recently one of those services had been changed and was now taking quite a bit longer than it used to. This was resulting in quite a long loading time for the whole UI, which was set up so it wouldn’t let the user interact with anything, until all the service calls had finished. First I broke out the longer running service call from the others, then removed the constraint that it had to be loaded for the UI in general to become responsive. I also added a loading indicator just on that area of the UI, thinking that the main UI would load while this particular section could keep loading independently. The Problem However this is where things started to get a bit strange. I found that even after these changes, the main UI wouldn’t activate until the long running call returned. So now, I did what I should have done to start with, I got Fiddler out and had a look at what was really happening. What I found was that, once the call to the long running service method was placed, all subsequent call were waiting for that one to return before executing. Not having really worked with WCF previously or knowing much about it in general, I was stumped… I knew of the issues where Silverlight is restricted by the browsers networking features in regards to number of simultaneous connections etc. However that just didn’t seem to be the issue here, you can clearly see in Fiddler that there’s numerous calls, but they’re just not returning. I thought of the problem maybe being in the WCF service, but the calls were really not that complicated and surely the service should be able to handle a lot more than what I was throwing at it! So I did what every developer does in this type of scenario, I hit the search engines. I did a whole bunch of searching on things like “multiple simultaneous WCF calls from Silverlight” and “Calling long running WCF services from Silverlight” etc. etc. This however, pretty much got me nowhere, I found a whole heap of resources on how to do WCF calls from Silverlight but most of them were very basic and of no use what so ever. The fog is clearing It wasn’t until I came across the term “ WCF blocking calls” and started incorporating that in my searches I started to get somewhere. Those searches quite quickly brought me to the following thread in the Silverlight forum “Long-running WCF call blocking subsequent calls” which discussed the exact problem I was facing and the best part, one of the guys there had the solution! The short answer is in the forum post and the guys answering, has also done a more extensive blog post about it called “Silverlight, WCF, and ASP.Net Configuration Gotchas” which covers it very well.  So come on what’s the solution?! I heard you ask, unless you’ve already gone to the links and looked it up ;) The Solution Well, it turns out that the issue is founded in a mix of Silverlight, Asp.Net and WCF, basically if you’re doing multiple calls to a single WCF web-service and you have Asp.Net session state enabled, the calls will be executed sequentially by the service, hence any long running calls will block subsequent ones. So why is Asp.Net session state effecting us, we’re working in Silverlight, right? We'll as mentioned earlier, by default Silverlight uses the browsers networking stack when doing service calls, hence to the WCF service, the call looks like it might as well be coming from a normal Asp.Net. To get around this, we look to a feature introduced in Silverlight 3, namely the Client HTTP Stack. The Client HTTP Stack to the rescue By using the following syntax (for example in our App.xaml.cs, Application_Startup method) WebRequest.RegisterPrefix("http://", WebRequestCreator.ClientHttp); we can set our Silverlight application to use the Client HTTP Stack, which incidentally solves our problem! By using Silverlights own networking stack, rather than that of the browser, we get around the Asp.Net - WCF session state issue. The above code specifies that all calls to addresses starting with “http://” should go through the client stack, this can actually be set more granular and you can specify it to be used only for certain domains etc. Summary The actual solution is well covered in the forum and blog posts I link to above. This post is more about sharing my experience, hopefully helping to spread the word about this and maybe make it a bit easier for the next poor guy with this issue to find the solution. Until next time, Ola

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  • Thanks to NxtGenUG Manchester - Hyper-V for Developers presentation now available for download

    - by Liam Westley
    Thanks to Steve and Andy at NxtGenUG Manchester for making me very welcome and for the guys who didn't head down the pub for a Guinness for St Patrick's Day and came to NxtGen instead.  I hope you all got something from the presentation, if not technical insights, at least a can of Guinness of Tunnocks caramel wafer as swag. As promised here is the presentation in both PowerPoint and Adobe PDF format (with speaker notes), http://www.tigernews.co.uk/blog-twickers/nxtgenugmanc/hyperv4devs-ppt.zip http://www.tigernews.co.uk/blog-twickers/nxtgenugmanc/hyperv4devs-pdf.zip Since I gave the presentation Microsoft has released XP Mode (Windows Virtual PC for use under Windows 7) without the requirement for hardware virtualisation. Read more about that here, http://blogs.msdn.com/Virtual_PC_Guy/ For anyone who has seen this presentation at other user groups, there is a new section at the end of the presentation dealing with the various networking configurations under Hyper-V; not connected, private network, internal network and external network.  This includes details of what these mean, and a Venn diagram to aid understanding of the implications.

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  • CLR via C# 3rd Edition is out

    - by Abhijeet Patel
    Time for some book news update. CLR via C#, 3rd Edition seems to have been out for a little while now. The book was released in early Feb this year, and needless to say my copy is on it’s way. I can barely wait to dig in and chew on the goodies that one of the best technical authors and software professionals I respect has in store. The 2nd edition of the book was an absolute treat and this edition promises to be no less. Here is a brief description of what’s new and updated from the 2nd edition. Part I – CLR Basics Chapter 1-The CLR’s Execution Model Added about discussion about C#’s /optimize and /debug switches and how they relate to each other. Chapter 2-Building, Packaging, Deploying, and Administering Applications and Types Improved discussion about Win32 manifest information and version resource information. Chapter 3-Shared Assemblies and Strongly Named Assemblies Added discussion of TypeForwardedToAttribute and TypeForwardedFromAttribute. Part II – Designing Types Chapter 4-Type Fundamentals No new topics. Chapter 5-Primitive, Reference, and Value Types Enhanced discussion of checked and unchecked code and added discussion of new BigInteger type. Also added discussion of C# 4.0’s dynamic primitive type. Chapter 6-Type and Member Basics No new topics. Chapter 7-Constants and Fields No new topics. Chapter 8-Methods Added discussion of extension methods and partial methods. Chapter 9-Parameters Added discussion of optional/named parameters and implicitly-typed local variables. Chapter 10-Properties Added discussion of automatically-implemented properties, properties and the Visual Studio debugger, object and collection initializers, anonymous types, the System.Tuple type and the ExpandoObject type. Chapter 11-Events Added discussion of events and thread-safety as well as showing a cool extension method to simplify the raising of an event. Chapter 12-Generics Added discussion of delegate and interface generic type argument variance. Chapter 13-Interfaces No new topics. Part III – Essential Types Chapter 14-Chars, Strings, and Working with Text No new topics. Chapter 15-Enums Added coverage of new Enum and Type methods to access enumerated type instances. Chapter 16-Arrays Added new section on initializing array elements. Chapter 17-Delegates Added discussion of using generic delegates to avoid defining new delegate types. Also added discussion of lambda expressions. Chapter 18-Attributes No new topics. Chapter 19-Nullable Value Types Added discussion on performance. Part IV – CLR Facilities Chapter 20-Exception Handling and State Management This chapter has been completely rewritten. It is now about exception handling and state management. It includes discussions of code contracts and constrained execution regions (CERs). It also includes a new section on trade-offs between writing productive code and reliable code. Chapter 21-Automatic Memory Management Added discussion of C#’s fixed state and how it works to pin objects in the heap. Rewrote the code for weak delegates so you can use them with any class that exposes an event (the class doesn’t have to support weak delegates itself). Added discussion on the new ConditionalWeakTable class, GC Collection modes, Full GC notifications, garbage collection modes and latency modes. I also include a new sample showing how your application can receive notifications whenever Generation 0 or 2 collections occur. Chapter 22-CLR Hosting and AppDomains Added discussion of side-by-side support allowing multiple CLRs to be loaded in a single process. Added section on the performance of using MarshalByRefObject-derived types. Substantially rewrote the section on cross-AppDomain communication. Added section on AppDomain Monitoring and first chance exception notifications. Updated the section on the AppDomainManager class. Chapter 23-Assembly Loading and Reflection Added section on how to deploy a single file with dependent assemblies embedded inside it. Added section comparing reflection invoke vs bind/invoke vs bind/create delegate/invoke vs C#’s dynamic type. Chapter 24-Runtime Serialization This is a whole new chapter that was not in the 2nd Edition. Part V – Threading Chapter 25-Threading Basics Whole new chapter motivating why Windows supports threads, thread overhead, CPU trends, NUMA Architectures, the relationship between CLR threads and Windows threads, the Thread class, reasons to use threads, thread scheduling and priorities, foreground thread vs background threads. Chapter 26-Performing Compute-Bound Asynchronous Operations Whole new chapter explaining the CLR’s thread pool. This chapter covers all the new .NET 4.0 constructs including cooperative cancelation, Tasks, the aralle class, parallel language integrated query, timers, how the thread pool manages its threads, cache lines and false sharing. Chapter 27-Performing I/O-Bound Asynchronous Operations Whole new chapter explaining how Windows performs synchronous and asynchronous I/O operations. Then, I go into the CLR’s Asynchronous Programming Model, my AsyncEnumerator class, the APM and exceptions, Applications and their threading models, implementing a service asynchronously, the APM and Compute-bound operations, APM considerations, I/O request priorities, converting the APM to a Task, the event-based Asynchronous Pattern, programming model soup. Chapter 28-Primitive Thread Synchronization Constructs Whole new chapter discusses class libraries and thread safety, primitive user-mode, kernel-mode constructs, and data alignment. Chapter 29-Hybrid Thread Synchronization Constructs Whole new chapter discussion various hybrid constructs such as ManualResetEventSlim, SemaphoreSlim, CountdownEvent, Barrier, ReaderWriterLock(Slim), OneManyResourceLock, Monitor, 3 ways to solve the double-check locking technique, .NET 4.0’s Lazy and LazyInitializer classes, the condition variable pattern, .NET 4.0’s concurrent collection classes, the ReaderWriterGate and SyncGate classes.

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  • Operating systems theory -- using minimum number of semaphores

    - by stackuser
    This situation is prone to deadlock of processes in an operating system and I'd like to solve it with the minimum of semaphores. Basically there are three cooperating processes that all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. Semaphores should be used to synchronize: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'm sure that any kernel programmers that happen on this can knock this out in a minute or 2. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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  • ASP.NET WebAPI Security 2: Identity Architecture

    - by Your DisplayName here!
    Pedro has beaten me to the punch with a detailed post (and diagram) about the WebAPI hosting architecture. So go read his post first, then come back so we can have a closer look at what that means for security. The first important takeaway is that WebAPI is hosting independent-  currently it ships with two host integration implementations – one for ASP.NET (aka web host) and WCF (aka self host). Pedro nicely shows the integration into the web host. Self hosting is not done yet so we will mainly focus on the web hosting case and I will point out security related differences when they exist. The interesting part for security (amongst other things of course) is the HttpControllerHandler (see Pedro’s diagram) – this is where the host specific representation of an HTTP request gets converted to the WebAPI abstraction (called HttpRequestMessage). The ConvertRequest method does the following: Create a new HttpRequestMessage. Copy URI, method and headers from the HttpContext. Copies HttpContext.User to the Properties<string, object> dictionary on the HttpRequestMessage. The key used for that can be found on HttpPropertyKeys.UserPrincipalKey (which resolves to “MS_UserPrincipal”). So the consequence is that WebAPI receives whatever IPrincipal has been set by the ASP.NET pipeline (in the web hosting case). Common questions are: Are there situations where is property does not get set? Not in ASP.NET – the DefaultAuthenticationModule in the HTTP pipeline makes sure HttpContext.User (and Thread.CurrentPrincipal – more on that later) are always set. Either to some authenticated user – or to an anonymous principal. This may be different in other hosting environments (again more on that later). Why so generic? Keep in mind that WebAPI is hosting independent and may run on a host that materializes identity completely different compared to ASP.NET (or .NET in general). This gives them a way to evolve the system in the future. How does WebAPI code retrieve the current client identity? HttpRequestMessage has an extension method called GetUserPrincipal() which returns the property as an IPrincipal. A quick look at self hosting shows that the moral equivalent of HttpControllerHandler.ConvertRequest() is HttpSelfHostServer.ProcessRequestContext(). Here the principal property gets only set when the host is configured for Windows authentication (inconsisteny). Do I like that? Well – yes and no. Here are my thoughts: I like that it is very straightforward to let WebAPI inherit the client identity context of the host. This might not always be what you want – think of an ASP.NET app that consists of UI and APIs – the UI might use Forms authentication, the APIs token based authentication. So it would be good if the two parts would live in a separate security world. It makes total sense to have this generic hand off point for identity between the host and WebAPI. It also makes total sense for WebAPI plumbing code (especially handlers) to use the WebAPI specific identity abstraction. But – c’mon we are running on .NET. And the way .NET represents identity is via IPrincipal/IIdentity. That’s what every .NET developer on this planet is used to. So I would like to see a User property of type IPrincipal on ApiController. I don’t like the fact that Thread.CurrentPrincipal is not populated. T.CP is a well established pattern as a one stop shop to retrieve client identity on .NET.  That makes a lot of sense – even if the name is misleading at best. There might be existing library code you want to call from WebAPI that makes use of T.CP (e.g. PrincipalPermission, or a simple .Name or .IsInRole()). Having the client identity as an ambient property is useful for code that does not have access to the current HTTP request (for calling GetUserPrincipal()). I don’t like the fact that that the client identity conversion from host to WebAPI is inconsistent. This makes writing security plumbing code harder. I think the logic should always be: If the host has a client identity representation, copy it. If not, set an anonymous principal on the request message. Btw – please don’t annoy me with the “but T.CP is static, and static is bad for testing” chant. T.CP is a getter/setter and, in fact I find it beneficial to be able to set different security contexts in unit tests before calling in some logic. And, in case you have wondered – T.CP is indeed thread static (and the name comes from a time where a logical operation was bound to a thread – which is not true anymore). But all thread creation APIs in .NET actually copy T.CP to the new thread they create. This is the case since .NET 2.0 and is certainly an improvement compared to how Win32 does things. So to sum it up: The host plumbing copies the host client identity to WebAPI (this is not perfect yet, but will surely be improved). or in other words: The current WebAPI bits don’t ship with any authentication plumbing, but solely use whatever authentication (and thus client identity) is set up by the host. WebAPI developers can retrieve the client identity from the HttpRequestMessage. Hopefully my proposed changes around T.CP and the User property on ApiController will be added. In the next post, I will detail how to add WebAPI specific authentication support, e.g. for Basic Authentication and tokens. This includes integrating the notion of claims based identity. After that we will look at the built-in authorization bits and how to improve them as well. Stay tuned.

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  • 3 Ways to Make Steam Even Faster

    - by Chris Hoffman
    Have you ever noticed how slow Steam’s built-in web browser can be? Do you struggle with slow download speeds? Or is Steam just slow in general? These tips will help you speed it up. Steam isn’t a game itself, so there are no 3D settings to change to achieve maximum performance. But there are some things you can do to speed it up dramatically. Speed Up the Steam Web Browser Steam’s built-in web browser — used in both the Steam store and in Steam’s in-game overlay to provide a web browser you can quickly use within games – can be frustratingly slow on many systems. Rather than the typical speed we’ve come to expect from Chrome, Firefox, or even Internet Explorer, Steam seems to struggle. When you click a link or go to a new page, there’s a noticeable delay before the new page appears — something that doesn’t happen in desktop browsers. Many people seem to have made peace with this slowness, accepting that Steam’s built-in browser is just bad. However, there’s a trick that will eliminate this delay on many systems and make the Steam web browser fast. This problem seems to arise from an incompatibility with the Automatically Detect Proxy Settings option, which is enabled by default on Windows. This is a compatibility option that very few people should actually need, so it’s safe to disable it. To disable this option, open the Internet Options dialog — press the Windows key to access the Start menu or Start screen, type Internet Options, and click the Internet Options shortcut. Select the Connections tab in the Internet Options window and click the LAN settings button. Uncheck the Automatically detect settings option here, then click OK to save your settings. If you experienced a significant delay every time a web page loaded in Steam’s web browser, it should now be gone. In the unlikely event that you encounter some sort of problem with your network connection, you could always re-enable this option. Increase Steam’s Game Download Speed Steam attempts to automatically select the nearest download server to your location. However, it may not always select the ideal download server. Or, in the case of high-traffic events like big seasonal sales and huge game launches, you may benefit from selecting a less-congested server. To do this, open Steam’s settings by clicking the Steam menu in Steam and selecting Settings. Click over to the Downloads tab and select the closest download server from the Download Region box. You should also ensure that Steam’s download bandwidth isn’t limited from here. You may want to restart Steam and see if your download speeds improve after changing this setting. In some cases, the closest server might not be the fastest. One a bit farther away could be faster if your local server is more congested, for example. Steam once provided information about content server load, which allowed you to select a regional server that wasn’t under high-load, but this information no longer seems to be available. Steam still provides a page that shows you the amount of download activity happening in different regions, including statistics about the difference in download speeds in different US states, but this information isn’t as useful. Accelerate Steam and Your Games One way to speed up all your games — and Steam itself —  is by getting a solid-state drive and installing Steam to it. Steam allows you to easily move your Steam folder — at C:\Program Files (x86)\Steam by default — to another hard drive. Just move it like you would any other folder. You can then launch the Steam.exe program as if you had never moved Steam’s files. Steam also allows you to configure multiple game library folders. This means that you can set up a Steam library folder on a solid-state drive and one on your larger magnetic hard drive. Install your most frequently played games to the solid-state drive for maximum speed and your less frequently played ones to the slower magnetic hard drive to save SSD space. To set up additional library folders, open Steam’s Settings window and click the Downloads tab. You’ll find the Steam Library Folders option here. Click the Add Library Folder button and create a new game library on another hard drive. When you install a game in Steam, you’ll be asked which library folder you want to install it to. With the proxy compatibility option disabled, the correct download server chosen, and Steam installed to a fast SSD, it should be a speed demon. There’s not much more you can do to speed up Steam, short of upgrading other hardware like your computer’s CPU. Image Credit: Andrew Nash on Flickr     

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  • Is context inheritance, as shown by Head First Design Patterns' Duck example, irrelevant to strategy pattern?

    - by Korey Hinton
    In Head First Design Patterns it teaches the strategy pattern by using a Duck example where different subclasses of Duck can be assigned a particular behavior at runtime. From my understanding the purpose of the strategy pattern is to change an object's behavior at runtime. Emphasis on "an" meaning one. Could I further simplify this example by just having a Duck class (no derived classes)? Then when implementing one duck object it can be assigned different behaviors based on certain circumstances that aren't dependent on its own object type. For example: FlyBehavior changes based on the weather or QuackBehavior changes based on the time of day or how hungry a duck is. Would my example above constitute the strategy pattern as well? Is context inheritance (Duck) irrelevant to the strategy pattern or is that the reason for the strategy pattern? Here is the UML diagram from the Head First book:

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  • Design Code Outside of an IDE (C#)?

    - by ryanzec
    Does anyone design code outside of an IDE? I think that code design is great and all but the only place I find myself actually design code (besides in my head) is in the IDE itself. I generally think about it a little before hand but when I go to type it out, it is always in the IDE; no UML or anything like that. Now I think having UML of your code is really good because you are able to see a lot more of the code on one screen however the issue I have is that once I type it in UML, I then have to type the actual code and that is just a big duplicate for me. For those who work with C# and design code outside of Visual Studio (or at least outside Visual Studio's text editor), what tools do you use? Do those tools allow you to convert your design to actual skeleton code? It is also possible to convert code to the design (when you update the code and need an updated UML diagram or whatnot)?

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  • Fastest way to document software architecture and design

    - by Karsten
    We are a small team of 5 developers and I'm looking for some great advices about how to document the software architecture and design. I'm going for the sweet spot, where the time invested pays off. I don't want to use more time documenting than necessary. I'll quickly give you my thoughts. What are the diagrams I should made? I'm thinking an overall diagram showing the various applications and services. And then some sequence diagrams showing the most important or complicated processes. About the code it self, I really don't see much value in describing or making diagrams for the code outside the .cs files them self. About text documents, I'm a bit uncertain about when to put down on paper. Most developers don't like to either write or read long documents.

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  • Finding rows that intersect with a date period

    - by DavidWimbush
    This one is mainly a personal reminder but I hope it helps somebody else too. Let's say you have a table that covers something like currency exchange rates with columns for the start and end dates of the period each rate was applicable. Now you need to list the rates that applied during the year 2009. For some reason this always fazes me and I have to work it out with a diagram. So here's the recipe so I never have to do that again: select  * from    ExchangeRate where   StartDate < '31-DEC-2009'         and EndDate > '01-JAN-2009'   That is all!

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  • What is a best practice tier structure of a Java EE 6/7 application?

    - by James Drinkard
    I was attempting to find a best practice for modeling the tiers in a Java EE application yesterday and couldn't come up with anything current. In the past, say java 1.4, it was four tiers: Presentation Tier Web Tier Business Logic Tier DAL (Data Access Layer ) which I always considered a tier and not a layer. After working with Web Services and SOA I thought to add in a services tier, but that may fall under 3. the business logic tier. I did searches for quite a while and reading articles. It seems like Domain Driven Design is becoming more popular, but I couldn't find a diagram on it's tier structure. Anyone have ideas or diagrams on what the proper tier structure is for newer Java EE applications or is it really the same, but more items are ranked under the four I've mentioned?

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  • Goto for the Java Programming Language

    - by darcy
    Work on JDK 8 is well-underway, but we thought this late-breaking JEP for another language change for the platform couldn't wait another day before being published. Title: Goto for the Java Programming Language Author: Joseph D. Darcy Organization: Oracle. Created: 2012/04/01 Type: Feature State: Funded Exposure: Open Component: core/lang Scope: SE JSR: 901 MR Discussion: compiler dash dev at openjdk dot java dot net Start: 2012/Q2 Effort: XS Duration: S Template: 1.0 Reviewed-by: Duke Endorsed-by: Edsger Dijkstra Funded-by: Blue Sun Corporation Summary Provide the benefits of the time-testing goto control structure to Java programs. The Java language has a history of adding new control structures over time, the assert statement in 1.4, the enhanced for-loop in 1.5,and try-with-resources in 7. Having support for goto is long-overdue and simple to implement since the JVM already has goto instructions. Success Metrics The goto statement will allow inefficient and verbose recursive algorithms and explicit loops to be replaced with more compact code. The effort will be a success if at least twenty five percent of the JDK's explicit loops are replaced with goto's. Coordination with IDE vendors is expected to help facilitate this goal. Motivation The goto construct offers numerous benefits to the Java platform, from increased expressiveness, to more compact code, to providing new programming paradigms to appeal to a broader demographic. In JDK 8, there is a renewed focus on using the Java platform on embedded devices with more modest resources than desktop or server environments. In such contexts, static and dynamic memory footprint is a concern. One significant component of footprint is the code attribute of class files and certain classes of important algorithms can be expressed more compactly using goto than using other constructs, saving footprint. For example, to implement state machines recursively, some parties have asked for the JVM to support tail calls, that is, to perform a complex transformation with security implications to turn a method call into a goto. Such complicated machinery should not be assumed for an embedded context. A better solution is just to expose to the programmer the desired functionality, goto. The web has familiarized users with a model of traversing links among different HTML pages in a free-form fashion with some state being maintained on the side, such as login credentials, to effect behavior. This is exactly the programming model of goto and code. While in the past this has been derided as leading to "spaghetti code," spaghetti is a tasty and nutritious meal for programmers, unlike quiche. The invokedynamic instruction added by JSR 292 exposes the JVM's linkage operation to programmers. This is a low-level operation that can be leveraged by sophisticated programmers. Likewise, goto is a also a low-level operation that should not be hidden from programmers who can use more efficient idioms. Some may object that goto was consciously excluded from the original design of Java as one of the removed feature from C and C++. However, the designers of the Java programming languages have revisited these removals before. The enum construct was also left out only to be added in JDK 5 and multiple inheritance was left out, only to be added back by the virtual extension method methods of Project Lambda. As a living language, the needs of the growing Java community today should be used to judge what features are needed in the platform tomorrow; the language should not be forever bound by the decisions of the past. Description From its initial version, the JVM has had two instructions for unconditional transfer of control within a method, goto (0xa7) and goto_w (0xc8). The goto_w instruction is used for larger jumps. All versions of the Java language have supported labeled statements; however, only the break and continue statements were able to specify a particular label as a target with the onerous restriction that the label must be lexically enclosing. The grammar addition for the goto statement is: GotoStatement: goto Identifier ; The new goto statement similar to break except that the target label can be anywhere inside the method and the identifier is mandatory. The compiler simply translates the goto statement into one of the JVM goto instructions targeting the right offset in the method. Therefore, adding the goto statement to the platform is only a small effort since existing compiler and JVM functionality is reused. Other language changes to support goto include obvious updates to definite assignment analysis, reachability analysis, and exception analysis. Possible future extensions include a computed goto as found in gcc, which would replace the identifier in the goto statement with an expression having the type of a label. Testing Since goto will be implemented using largely existing facilities, only light levels of testing are needed. Impact Compatibility: Since goto is already a keyword, there are no source compatibility implications. Performance/scalability: Performance will improve with more compact code. JVMs already need to handle irreducible flow graphs since goto is a VM instruction.

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  • How do you dive into large code bases?

    - by miku
    What tools and techniques do you use for exploring and learning an unknown code base? I am thinking of tools like grep, ctags, unit-tests, functional test, class-diagram generators, call graphs, code metrics like sloccount and so on. I'd be interested in your experiences, the helpers you used or wrote yourself and the size of the codebase, with which you worked with. I realize, that this is also a process (happening over time) and that learning can mean "can give a ten minute intro" to "can refactor and shrink this to 30% of the size". Let's leave that open for now.

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  • Script to only execute during first install of a package

    - by Jeroen
    I recently started packaging up some of my software and publishing it on Launchpad. The installation and removal works fine, but upgrading the package form one version to the next version is problematic. The problem is that there are some scripts that only need to run during the first installation of the package. These scripts populate the DB, create a user, etc. They are currently called in the package.postinst configure) section. However this results in them being called during an upgrade as well as shown in the diagram. Is there a way to include a maintainer script in a .deb package that only executes during the first installation of the package and not during an upgrade? Or what would be an elegant way to include some initial setup scripts in a .deb package?

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  • Processing Binary Data in SOA Suite 11g

    - by Ramkumar Menon
    SOA Suite 11g provides a variety of ways to exchange binary data amongst applications and endpoints. The illustration below is a bird's-eye view of all the features in SOA Suite to facilitate such exchanges. Handling Binary data in SOA Suite 11g Composites Samples and Step-by-Step Tutorials A few step-by-step tutorials have been uploaded to java.net that illustrate key concepts related to Binary content handling within SOA composites. Each sample consists of a fully built composite project that can be deployed and tested, together with a Readme doc with screenshots to build the project from scratch. Binary Content Handling within File Adapter Samples [Opaque, Streaming, Attachments] SOAP with Attachments [SwA] Sample MTOM Sample Mediator Pass-through for attachments Sample For detailed information on binary content and large document handling within SOA Suite, refer to Chapter 42 of the SOA Suite Developer's Guide. Handling Binary data in Oracle B2B The following diagram illustrates how Oracle B2B facilitates exchange of binary documents between SOA Suite and Trading Partners.

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  • Why enumerator structs are a really bad idea

    - by Simon Cooper
    If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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  • How do you dive into large code bases?

    - by miku
    What tools and techniques do you use for exploring and learning an unknown code base? I am thinking of tools like grep, ctags, unit-tests, functional test, class-diagram generators, call graphs, code metrics like sloccount and so on. I'd be interested in your experiences, the helpers you used or wrote yourself and the size of the codebase, with which you worked with. I realize, that this is also a process (happening over time) and that learning can mean "can give a ten minute intro" to "can refactor and shrink this to 30% of the size". Let's leave that open for now.

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  • Operating systems -- using minimum number of semaphores

    - by stackuser
    The three cooperating processes all read data from the same input device. Each process, when it gets the input device, must read two consecutive data. I want to use mutual exclusion to do this. The declaration and initialization that I think would work here are: semaphore s=1 sa1 = 0, sa2 = 0, sb1 = 0, sb2 = 0, sc1 = 0, sc2 = 0 I'd like to use semaphores to synchronize the following processes: P1: P2: P3: input(a1,a2) input (b1,b2) input(c1,c2) Y=a1+c1 W=b2+c2 Z=a2+b1 Print (X) X=Z-Y+W I'm wondering how to use the minimum number of semaphores to solve this. Diagram of cooperating Processes and one input device: It seems like P1 and P2 would start something like: wait(s) input (a1/b1, a2/b2) signal(s)

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  • For normal mapping, why can we not simply add the tangent normal to the surface normal?

    - by sebf
    I am looking at implementing bump mapping (which in all implementations I have seen is really normal mapping), and so far all I have read says that to do this, we create a matrix to convert from world-space to tangent-space, in order to transform the lights and eye direction vectors into tangent space, so that the vectors from the normal map may be used directly in place of those passed through from the vertex shader. What I do not understand though, is why we cannot just use the normalised sum of the sampled-normal vector, and the surface-normal? (assuming we already transform and pass through the surface normal for the existing lighting functions) Take the diagram below; the normal is simply the deviation from the 'reference normal' for any given coordinate system, correct? And transforming the surface normal of a mapped surface from world space to tangent space makes it equivalent to the tangent space 'reference normal', no? If so, why do we transform all lighting vectors into tangent space, instead of simply transforming the sampled tangent once in the pixel shader?

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  • How to design application for scaling the application?

    - by Muhammad
    I have one application which handles hardware events connected on the same computer's PCIe slots. The maximum number of PCIe slots on motherboard are two. I have utilized both slots. Now for scaling the application I need either more PCIe slots in same computer or I use another computer. So consider I am using another computer with same application and hardware connected on the PCIe Slots. Now my problem is that I want to design application over it which can access both computers hardware devices and does the process on it. The processed data should be send back to the respective PC's hardware. Please refer the attached diagram for expansion.

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  • Reference Data Management and Master Data: Are Relation ?

    - by Mala Narasimharajan
    Submitted By:  Rahul Kamath  Oracle Data Relationship Management (DRM) has always been extremely powerful as an Enterprise Master Data Management (MDM) solution that can help manage changes to master data in a way that influences enterprise structure, whether it be mastering chart of accounts to enable financial transformation, or revamping organization structures to drive business transformation and operational efficiencies, or restructuring sales territories to enable equitable distribution of leads to sales teams following the acquisition of new products, or adding additional cost centers to enable fine grain control over expenses. Increasingly, DRM is also being utilized by Oracle customers for reference data management, an emerging solution space that deserves some explanation. What is reference data? How does it relate to Master Data? Reference data is a close cousin of master data. While master data is challenged with problems of unique identification, may be more rapidly changing, requires consensus building across stakeholders and lends structure to business transactions, reference data is simpler, more slowly changing, but has semantic content that is used to categorize or group other information assets – including master data – and gives them contextual value. In fact, the creation of a new master data element may require new reference data to be created. For example, when a European company acquires a US business, chances are that they will now need to adapt their product line taxonomy to include a new category to describe the newly acquired US product line. Further, the cross-border transaction will also result in a revised geo hierarchy. The addition of new products represents changes to master data while changes to product categories and geo hierarchy are examples of reference data changes.1 The following table contains an illustrative list of examples of reference data by type. Reference data types may include types and codes, business taxonomies, complex relationships & cross-domain mappings or standards. Types & Codes Taxonomies Relationships / Mappings Standards Transaction Codes Industry Classification Categories and Codes, e.g., North America Industry Classification System (NAICS) Product / Segment; Product / Geo Calendars (e.g., Gregorian, Fiscal, Manufacturing, Retail, ISO8601) Lookup Tables (e.g., Gender, Marital Status, etc.) Product Categories City à State à Postal Codes Currency Codes (e.g., ISO) Status Codes Sales Territories (e.g., Geo, Industry Verticals, Named Accounts, Federal/State/Local/Defense) Customer / Market Segment; Business Unit / Channel Country Codes (e.g., ISO 3166, UN) Role Codes Market Segments Country Codes / Currency Codes / Financial Accounts Date/Time, Time Zones (e.g., ISO 8601) Domain Values Universal Standard Products and Services Classification (UNSPSC), eCl@ss International Classification of Diseases (ICD) e.g., ICD9 à IC10 mappings Tax Rates Why manage reference data? Reference data carries contextual value and meaning and therefore its use can drive business logic that helps execute a business process, create a desired application behavior or provide meaningful segmentation to analyze transaction data. Further, mapping reference data often requires human judgment. Sample Use Cases of Reference Data Management Healthcare: Diagnostic Codes The reference data challenges in the healthcare industry offer a case in point. Part of being HIPAA compliant requires medical practitioners to transition diagnosis codes from ICD-9 to ICD-10, a medical coding scheme used to classify diseases, signs and symptoms, causes, etc. The transition to ICD-10 has a significant impact on business processes, procedures, contracts, and IT systems. Since both code sets ICD-9 and ICD-10 offer diagnosis codes of very different levels of granularity, human judgment is required to map ICD-9 codes to ICD-10. The process requires collaboration and consensus building among stakeholders much in the same way as does master data management. Moreover, to build reports to understand utilization, frequency and quality of diagnoses, medical practitioners may need to “cross-walk” mappings -- either forward to ICD-10 or backwards to ICD-9 depending upon the reporting time horizon. Spend Management: Product, Service & Supplier Codes Similarly, as an enterprise looks to rationalize suppliers and leverage their spend, conforming supplier codes, as well as product and service codes requires supporting multiple classification schemes that may include industry standards (e.g., UNSPSC, eCl@ss) or enterprise taxonomies. Aberdeen Group estimates that 90% of companies rely on spreadsheets and manual reviews to aggregate, classify and analyze spend data, and that data management activities account for 12-15% of the sourcing cycle and consume 30-50% of a commodity manager’s time. Creating a common map across the extended enterprise to rationalize codes across procurement, accounts payable, general ledger, credit card, procurement card (P-card) as well as ACH and bank systems can cut sourcing costs, improve compliance, lower inventory stock, and free up talent to focus on value added tasks. Change Management: Point of Sales Transaction Codes and Product Codes In the specialty finance industry, enterprises are confronted with usury laws – governed at the state and local level – that regulate financial product innovation as it relates to consumer loans, check cashing and pawn lending. To comply, it is important to demonstrate that transactions booked at the point of sale are posted against valid product codes that were on offer at the time of booking the sale. Since new products are being released at a steady stream, it is important to ensure timely and accurate mapping of point-of-sale transaction codes with the appropriate product and GL codes to comply with the changing regulations. Multi-National Companies: Industry Classification Schemes As companies grow and expand across geographies, a typical challenge they encounter with reference data represents reconciling various versions of industry classification schemes in use across nations. While the United States, Mexico and Canada conform to the North American Industry Classification System (NAICS) standard, European Union countries choose different variants of the NACE industry classification scheme. Multi-national companies must manage the individual national NACE schemes and reconcile the differences across countries. Enterprises must invest in a reference data change management application to address the challenge of distributing reference data changes to downstream applications and assess which applications were impacted by a given change. References 1 Master Data versus Reference Data, Malcolm Chisholm, April 1, 2006.

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  • Books or help on OO Analysis

    - by Pat
    I have this course where we learn about the domain model, use cases, contracts and eventually leap into class diagrams and sequence diagrams to define good software classes. I just had an exam and I got trashed, but part of the reason is we barely have any practical material, I spent at least two good months without drawing a single class diagram by myself from a case study. I'm not here to blame the system or the class I'm in, I'm just wondering if people have some exercise-style books that either provide domain models with glossaries, system sequence diagrams and ask you to use GRASP to make software classes? I could really use some alone-time practicing going from analysis to conception of software entities. I'm almost done with Larman's book called "Applying UML and Patterns An Introduction to Object-Oriented Analysis and Design and Iterative Development, Third Edition". It's a good book, but I'm not doing anything by myself since it doesn't come with exercises. Thanks.

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  • Oracle GoldenGate 12c - Leading Enterprise Replication

    - by Doug Reid
    Oracle GoldenGate 12c released  on October 17th and includes several new cutting edge features that firmly establishes GoldenGate's leader position in the data replication space.   In fact, this release more than doubles the performance of data delivery, supports Oracle's new multitenant database feature,  it's more secure, has more options for high availability, and has made great strides to simplify the configuration and deployment of the product.     Read through the press release if you haven't already and do not miss the quote from Cern's Eva Dafonte Perez, regarding Oracle GoldenGate 12c "….performs five times faster compared to previous GoldenGate versions and simplifies the management of a multi-tier environment" There are a variety of new and improved features in the Oracle GoldenGate 12c.  Here are the highlights: Optimized for Oracle Database 12c -  GoldenGate 12c is custom tailored to the unique capabilities of Oracle database 12c and out of the box GoldenGate 12c supports multitenant (pluggable database (PDB)) and non-consolidated deployments of Oracle Database 12c.   The naming convention used by database 12c is now in three parts (PDB-name, schema-name, and object name).  We have made changes to the GoldenGate capture process to support the new naming convention and streamlined the whole process so a single GoldenGate capture process is being used at the container level rather than at each individual PDB.  By having the capture process at the container level resource usage and the number of processes are reduced. To view a conceptual architecture diagram click here. Integrated Delivery for the Oracle Database - Leveraging a lightweight streaming API built exclusively for Oracle GoldenGate 12c, this process distributes load, auto tunes the degree of parallelism, scales better, and delivers blinding rates of changed data delivery to the Oracle database.  One of the goals for Oracle GoldenGate 12c was to reduce IT costs by simplifying the configuration and reduce the time to manage complex infrastructures.  In previous versions of Oracle GoldenGate, customers would split transaction loads by grouping tables into multiple different delivery processes (click here to view the previous method). Each delivery process executed independently and without any interaction or knowledge of other delivery processes.  This setup was complicated to configure and time consuming as the developer needed in-depth knowledge of the source and target schemas and the transaction profile. With GoldenGate 12c and Integrated Delivery we have made it easier to configure and faster to deploy.  To view a conceptual architecture diagram of integrated delivery click here Coordinated Delivery for Non-Oracle Databases - Coordinated Delivery orchestrates high-speed apply processes and simplifies the configuration of GoldenGate for non-Oracle targets. In Oracle GoldenGate 12c a single delivery process is used with multiple threads (click here) and key events, such as primary key updates, event markers, DDL, etc, are coordinated between the various threads to insure that the transactions are applied in the same sequence as they were captured, all while delivery improved performance.  Replication Between On-Premises and Cloud-Based systems. - The trend for business to utilize both on-premises and cloud-based systems is rising and businesses need to replicate data back and forth.   GoldenGate 12c can be configured in a variety of ways to provide real-time replication when unrestricted or restricted (limited ports or HTTP tunneling) networks are between on-premises and cloud-based systems.    Expanded Heterogeneity - It wouldn't be a GoldenGate release without new and improved platform support.   Release 1 includes support for MySQL 5.6 and Sybase 15.7.   Upcoming in the next release GoldenGate, support will be expanded for MS SQL Server, DB2, and Teradata. Tighter Security - Oracle GoldenGate 12c is integrated with the Oracle wallet to shield usernames and passwords using strong encryption and aliases.   Customers accustomed to using the Oracle Wallet with other Oracle products will instantly be familiar with how to use this great new feature Expanded Oracle Application and Technology Support -   GoldenGate can be used along with Oracle Coherence to enable real-time changed data feeds to the Coherence cache using Toplink and the Oracle GoldenGate JMS adapter.     Plus,  Oracle Advanced Customer Services (ACS) now offers a low downtime E-Business Suite platform and database migrations using GoldenGate as the enabling technology.  Keep tuned for more blogs on the new features and the upcoming launch webcast where we will go into these new features in more detail.   In the mean time make sure to read through our white paper "Oracle GoldenGate 12c Release 1 New Features Overview"

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