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  • API Class with intensive network requests

    - by Marco Acierno
    I'm working an API which works as "intermediary" between a REST API and the developer. In this way, when the programmer do something like this: User user = client.getUser(nickname); it will execute a network request to download from the service the data about the user and then the programmer can use the data by doing things like user.getLocation(); user.getDisplayName(); and so on. Now there are some methods like getFollowers() which execute another network request and i could do it in two ways: Download all the data in the getUser method (and not only the most important) but in this way the request time could be very long since it should execute the request to various urls Download the data when the user calls the method, it looks like the best way and to improve it i could cache the result so the next call to getFollowers returns immediately with the data already download instead of execute again the request. What is the best way? And i should let methods like getUser and getFollowers stop the code execution until the data is ready or i should implement a callback so when the data is ready the callback gets fired? (this looks like Javascript)

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  • Stacks in C++

    - by MarkPearl
    So some more basics… One of the things you will be taught at any college after conquering arrays is different derivatives of collections. Stack is one of the simplest of those and very useful… A stack is a LIFO (last in first out) data structure and has at least two basic method calls – push & pop. Push, “pushes” an item on the top of the stack. Pop, removes the top most item off the stack. Because all elements on a stack are of the same type, one can use an array to implement a stack or a linked list. With the array based approach, the first element in a stack would be the first element in the array, the second on the stack would be the second on the array, etc. One limitation with an array implementation of a stack is that unless the array is dynamic, one would have to have a preset max stack size (based on the bounds of the array). Linked lists is another approach that gets past this boundary by allowing you to dynamically grow or shrink a collection of data. Stacks have many applications… a typical computer science example would be Postfix Expression Calculator, where the LIFO principle is maintained.

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  • Prevent Click Fraud in Advertisement system with PHP and Javascript

    - by CodeDevelopr
    I would like to build an Advertising project with PHP, MySQL, and Javascript. I am talking about something like... Google Adsense BuySellAds.com Any other advertising platform My question is mainly, what do I need to look out for to prevent people cheating the system and any other issues I may encounter? My design concept. An Advertisement is a record in the Database, when a page is loaded, using Javascript, it calls my server which in turn will use a PHP script to query the Database and get a random Advertisement. (It may do kore like get an ad based on demographics or other criteria as well) The PHP script will then return the Advertisement to the server/website that is calling it and show it on the page as an Image that will have a special tracking link. I will need to... Count all impressions (when the Advertisement is shown on the page) Count all clicks on the Advertisement link Count all Unique clicks on the Advertisement link My question is purely on the query and displaying of the Advertisement and nothing to do with the administration side. If there is ever money involved with my Advertisement buying/selling of adspace, then the stats need to be accurate and make sure people can't easily cheat the system. Is tracking IP address really the only way to try to prevent click fraud? I am hoping someone with some experience can clarify I am on the right track? As well as give me any advice, tips, or anything else I should know about doing something like this?

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  • How to implement smart card authentication with a .NET Fat client?

    - by John Nevermore
    I know very little about smart card authentication in general so please point out or correct me if anything below doesn't make sense. Lets say i have: A Certificate Authority "X"-s smart card (non-exportable private key) Drivers for that smart card written in C A smart card reader CA-s authentication OCSP web service A requirement to implement user authentication in a .NET fat client application via a smart card, that was given out by the CA "X". I tried searching info on the web but no prevail. What would the steps be ? My first thought was: Set up a web service, that would allow saving of (for example) scores of a ping pong game for each user. Each time someone tries to submit a score via the client application, he can only do so by inserting the smart card into the reader. Then the public key is read from the smart card by native c calls through .NET and sent to my custom web service, which in return uses the CA-s authentication OCSP web service to prove the validity of the public key/public certificate (?). If the public key is okay and valid, encrypt a random sequence of bytes with the public key and send it to the client application. If the client application sends back the correctly decrypted random sequence of bytes along with the score of the ping pong game, then the score is saved in the database for the given user. My question is, is this the correct way to do it ? What else should i know about smart card authentication ?

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  • Interview Questions in OOP

    - by Fero
    Hi all, I faced the below interview questions in OOP under PHP language. Kindly clear my clarifications regarding this. I am very confused. As i am a beginner to OOP i got too confused. Could anyone clarify these things clearly? Difference between Abstract class and interface. Interviewer : Let us consider abstract class contains three abstract methods such as a,b,c and interface contains three methods a,b,c. In this case these do the same functionality. Then why are going for abstract and why are we going for interface. Me : ? static keyword. Interviewer: We call static method without creating object by using scope resolution operator in PHP. As well as we can able to call concrete methods also. Then what is need of static keyword there? Me : .... final keyword. Interviewer: Give me any scenario of using final keyword. Me : For db connection related method Interviewer: Other than that? Me: ... Constructor. Interviewer: What is the use of constructor? Me : There is no need for object to access this. It will call automatically when the class calls. Interviewer: Other than that? Me : .... Thanks in advance...

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  • Explicitly pass context object versus injecting with IoC

    - by SonOfPirate
    I have a layered service application where the service layer delegates operations into the domain layer for execution. Many of these operations need to know the context under which they are operation. (The context included the identity of the current user, culture information, etc. received from the caller.) For example, I have an API method that returns a list of announcements. The list is based on the current user's role and each announcement is localized to their culture. The API is a thin-facade that delegates to an Application Service in my domain layer. The Application Service method obviously needs to know the context of the current request/operation as another call to the same API from another user should result in a different list. Within this method, we also have logging that uses some of the context information so we a clear understanding of the context when the operation was performed (this is especially useful if something goes wrong.) While this is a contrived example, in the real world, my Application Services will coordinate operations with many collaborative components, any number of them also needing the context information. My choice is to pass the context to the Application Service which would then pass it with any calls to collaborators or have the IoC container satisfy the dependency the Application Service and any collaborators have on the context. I am wondering if it is considered good/bad, best practices/code smell, etc. if I pass the context object as a parameter to the domain methods or if injecting the context via an IoC container is preferred. (EDIT: I should mention that the context object is instantiated per-request.)

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  • How does font rendering actually work?

    - by Andrea
    I realize that I know essentially nothing about the way fonts get rendered in my computer. From what I can observe, font rendering is generally made in a consistent way throughout the system. For instance, the subpixel font hinting settings that I configure in my DE control panel have influence on text which appears on window borders, in my browser, in my text editor and so on. (I should observe that some Java applications show a noticeable difference, so I guess they are using a different font rendering mechanism). What I get from the above is that probably all applications that need font rendering make use of some OS (or DE)-wide library. On the other hand, browsers usually manage their own rendering through a rendering engine, that takes care of positioning various items - including text - according to specific flow rules. I am not sure how these two facts are compatible. I would assume that the browser would have to ask the OS to draw a glyph at a given position, but how can it manage the flow of text without knowing beforehand how much space the glyph will take? Are there separate calls to determine the glyph sizes, so that the browser can manage the flow as if characters were little boxes that are later filled in by the OS? (Although this does not take care of kerning). Or is the OS responsible for drawing a whole text area, including text flow? Does the OS return the rendered glyph as a bitmap and leaves it to the application to draw that on the screen?

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  • What functionality should a (basic) mock framework have?

    - by user1175327
    If i would start on writing a simple Mock framework, then what are the things that a basic mock framework MUST have? Obviously mocking any object, but what about assertions and perhaps other things? When I think of how I would write my own mock framework then I realise how much I really know (or don't know) and what I would trip up on. So this is more for educational purposes. Of course I did research and this is what i've come up with that a minimal mocking framework should be able to do. Now my question in this whole thing is, am I missing some important details in my ideas? Mocking Mocking a class: Should be able to mock any class. The Mock should preserve the properties and their original values as they were set in the original class. All method implementations are empty. Calls to methods of Mock: The Mock framework must be able to define what a mocked method must return. IE: $MockObj->CallTo('SomeMethod')->Returns('some value'); Assertions To my understanding mocking frameworks also have a set of assertions. These are the ones I think are most important (taken from SimpleTest). expect($method, $args) Arguments must match if called expectAt($timing, $method, $args) Arguments must match when called on the $timing'th time expectCallCount($method, $count) The method must be called exactly this many times expectMaximumCallCount($method, $count) Call this method no more than $count times expectMinimumCallCount($method, $count) Must be called at least $count times expectNever($method) Must never be called expectOnce($method, $args) Must be called once and with the expected arguments if supplied expectAtLeastOnce($method, $args) Must be called at least once, and always with any expected arguments And that's basically, as far as I understand, what a mock framework should be able to do. But is this really everything? Because it currently doesn't seem like a big deal to build something like this. But that's also the reason why I have the feeling that i'm missing some important details about such a framework. So is my understanding right about a mock framework? Or am i missing alot of details?

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  • Alternatives to Pessimistic Locking in Cluster Applications

    - by amphibient
    I am researching alternatives to database-level pessimistic locking to achieve transaction isolation in a cluster of Java applications going against the same database. Synchronizing concurrent access in the application tier is clearly not a solution in the present configuration because the same database transaction can be invoked from multiple JVMs concurrently. Currently, we are subject to occasional race conditions which, due to the optimistic locking we have in place via Hibernate, cause a StaleObjectStateException exception and data loss. I have a moderately large transaction within the scope of my refactoring project. Let's describe it as updating one top-level table row and then making various related inserts and/or updates to several of its child entities. I would like to insure exclusive access to the top-level table row and all of the children to be affected but I would like to stay away from pessimistic locking at the database level for performance reasons mostly. We use Hibernate for ORM. Does it make sense to start a single (perhaps synchronous) message queue application into which this method could be moved to insure synchronized access as opposed to each cluster node using its own, which is a clear race condition hazard? I am mentioning this approach even though I am not confident in it because both the top-level table row and its children could also be updated from other system calls, not just the mentioned transaction. So I am seeking to design a solution where the top-level table row and its children will all somehow be pseudo-locked (exclusive transaction isolation) but at the application and not the database level. I am open to ideas and suggestions, I understand this is not a very cut and dried challenge.

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  • CA For A Large Intranet

    - by Tim Post
    I'm managing what has become a very large intranet (over 100 different hosts / services) and will be stepping down from my role in the near future. I want to make things easy for the next victim person who takes my place. All hosts are secured via SSL. This includes various portals, wikis, data entry systems, HR systems and other sensitive things. We're using self signed certificates which worked o.k. in the past, but are now problematic because: Browsers make it harder for users to understand exactly what is going on when a self signed certificate is encountered, much less accept them. Putting up a new host means 100 phone calls asking what "Add an exception" means What we were doing is just importing the self signed certs when we set up a new workstation. This was fine when we only had a dozen to deal with, but now its just overwhelming. Our I.T. Department has classified this as ya all's problem, all we get from them is support for switch and router configurations. Beyond the user having connectivity, everything else is up to the intranet administrators. We have a mix of Ubuntu and Windows workstations. We'd like to set up our own self signed CA root, which can sign certificates for each host that we deploy on the intranet. Client browsers would of course be told to trust our CA. My question is, would this be dangerous and would we be better off going with intermediate certificates from someone like Verisign? Either way, I still have to import the root for the intermediate CA, so I really don't see what the difference is? Other than charging us money, what would Verisign be doing that we could not, beyond protecting the root CA cert so it can't be used to make forgeries?

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  • ORM and component-based architecture

    - by EagleBeek
    I have joined an ongoing project, where the team calls their architecture "component-based". The lowest level is one big database. The data access (via ORM) and business layers are combined into various components, which are separated according to business logic. E.g., there's a component for handling bank accounts, one for generating invoices, etc. The higher levels of service contracts and presentation are irrelevant for the question, so I'll omit them here. From my point of view the separation of the data access layer into various components seems counterproductive, because it denies us the relational mapping capabilities of the ORM. E.g., when I want to query all invoices for one customer I have to identify the customer with the "customers" component and then make another call to the "invoices" component to get the invoices for this customer. My impression is that it would be better to leave the data access in one component and separate it from business logic, which may well be cut into various components. Does anybody have some advice? Have I overlooked something?

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  • How to implement child-parent aggregation link in C++?

    - by Giorgio
    Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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  • Javascript MVC in principle

    - by Michael
    Suppose I want to implement MVC in JavaScript. I am not asking about MVC frameworks. I am asking how to build it in principle. Let's consider a search page of an e-commerce site, which works s follows: User chooses a product and its attributes and press a "search" button. Application sends the search request to the server, receives a list of products. Application displays the list in the web page. I think the Model holds a Query and list of Product objects and "publishes" such events as "query updated", "list of products updated", etc. The Model is not aware of DOM and server, or course. View holds the entire DOM tree and "subscribes" to the Model events to update the DOM. Besides, it "publishes" such events as "user chose a product", "user pressed the search button" etc. Controller does not hold any data. It "subscribes" to the View events, calls the server and updates the Model. Does it make sense?

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  • Why would Java app make RPC call to itself?

    - by amphibient
    I am working with a multithreaded homegrown multi-module app in my new job. We use the the Thrift protocol to communicate RPC calls between different stand-alone applications in a distributed system. One of them listens on multiple ports and I just noticed that it actually makes an RPC call to itself from one thread invoked from one socket it listens to (web service call) to another port within the same app. I verified that it could accomplish the same thing if it just went and directly called the method that the remote procedure ultimately invokes as it is all within the same application, same JVM. To make it even more mysterious, the call is completely synchronous, i.e. no callbacks involved. The first thread totally sits and waits until it makes a call across the wire to itself and comes back. Now, I am perplexed why anybody would do it this way. It seems like calling somebody on the phone that sits in the same room as you do. Can anybody provide an explanation why the developer before me would come up with the above mentioned model? Maybe there is a reason and I am missing something.

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  • SSIS Catalog: How to use environment in every type of package execution

    - by Kevin Shyr
    Here is a good blog on how to create a SSIS Catalog and setting up environments.  http://sqlblog.com/blogs/jamie_thomson/archive/2010/11/13/ssis-server-catalogs-environments-environment-variables-in-ssis-in-denali.aspx Here I will summarize 3 ways I know so far to execute a package while using variables set up in SSIS Catalog environment. First way, we have SSIS project having reference to environment, and having one of the project parameter using a value set up in the environment called "Development".  With this set up, you are limited to calling the packages by right-clicking on the packages in the SSIS catalog list and select Execute, but you are free to choose absolute or relative path of the environment. The following screenshot shows the 2 available paths to your SSIS environments.  Personally, I use absolute path because of Option 3, just to keep everything simple for myself. The second option is to call through SQL Job.  This does require you to configure your project to already reference an environment and use its variable.  When a job step is set up, the configuration part will require you to select that reference again.  This is more useful when you want to automate the same package that needs to be run in different environments. The third option is the most important to me as I have a SSIS framework that calls hundreds of packages.  The main part of the stored procedure is in this post (http://geekswithblogs.net/LifeLongTechie/archive/2012/11/14/time-to-stop-using-ldquoexecute-package-taskrdquondash-a-way-to.aspx).  But the top part had to be modified to include the logic to use environment reference. CREATE PROCEDURE [AUDIT].[LaunchPackageExecutionInSSISCatalog] @PackageName NVARCHAR(255) , @ProjectFolder NVARCHAR(255) , @ProjectName NVARCHAR(255) , @AuditKey INT , @DisableNotification BIT , @PackageExecutionLogID INT , @EnvironmentName NVARCHAR(128) = NULL , @Use32BitRunTime BIT = FALSE AS BEGIN TRY DECLARE @execution_id BIGINT = 0; -- Create a package execution IF @EnvironmentName IS NULL BEGIN   EXEC [SSISDB].[catalog].[create_execution]     @package_name=@PackageName,     @execution_id=@execution_id OUTPUT,     @folder_name=@ProjectFolder,     @project_name=@ProjectName,     @use32bitruntime=@Use32BitRunTime; END ELSE BEGIN   DECLARE @EnvironmentID AS INT   SELECT @EnvironmentID = [reference_id]    FROM SSISDB.[internal].[environment_references] WITH(NOLOCK)    WHERE [environment_name] = @EnvironmentName     AND [environment_folder_name] = @ProjectFolder      EXEC [SSISDB].[catalog].[create_execution]     @package_name=@PackageName,     @execution_id=@execution_id OUTPUT,     @folder_name=@ProjectFolder,     @project_name=@ProjectName,     @reference_id=@EnvironmentID,     @use32bitruntime=@Use32BitRunTime; END

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  • Learning OO for a C Programmer

    - by Holysmoke
    I've been programming professionally in C, and only C, for around 10 years in a variety of roles. As would be normal to expect, I understand the idioms of the language fairly well and beyond that also some of the design nuances - which APIs to make public, who calls what, who does what, what is supposed to reentrant and so on. I grew up reading 'Writing Solid Code', it's early C edition, not the one based on C++. However, I've never ever programmed in an OO language. Now, I want to migrate to writing applications for iPhone (maybe android), so want to learn to use Objective-C and use it with a degree of competence fitting a professional programmer. How do I wrap my head around the OO stuff? What would be your smallest reading list suggestion to me. Is there a book that carries some sort of relatively real world example OO design Objective-C? Besides, the reading what source code would you recommend me to go through. How to learn OO paradigm using Objective-C?

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  • The Correct Usage of DLLs with a DirectX Game?

    - by smoth190
    I'm using DirectX 10 (in C++) to make a game engine, and a test driver program on top of it. Now that I've written many messy rough drafts of an engine, I want to make the final (or sorta final) clean version. I choose to follow how I've seen other engines do it, and that's to have all the core nasty messy crap in a DLL, and then you can create games with just a few functions (well, not really :D). However, I'm unsure of what nasty messy crap to put in that DLL. I don't know about speed restrictions with DLLs. What I've done is put my winproc in the DLL, and have a class that takes the messages, and sends them through to the program using the DLL. Then that program does what it needs to do, and calls a rendering functions back in the DLL that renders everything. Only problem is it gets very low FPS (2, to be exact...). I've looked through everything, and I don't know if the way I'm using DLLs in causing this, or its something different. Whether it's the DLLs or not, I still want to know how to use a DLL correctly with a game engine. I like being neat, I hate having to see all those long names of DirectX classes. I use typedef a lot.

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  • XNA hlsl tex2D() only reads 3 channels from normal maps and specular maps

    - by cubrman
    Our engine uses deferred rendering and at the main draw phase gathers plenty of data from the objects it draws. In order to save on tex2D calls, we packed our objects' specular maps with all sorts of data, so three out of four channels are already taken. To make it clear: I am talking about the assets that come with the models and are stored in their material's Specular Level channel, not about the RenderTarget. So now I need another information to be stored in the alpha channel, but I cannot make the shader to read it properly! Nomatter what I write into alpha it ends up being 1 (255)! I tried: saving the textures in PNG/TGA formats. turning off pre-computed alpha in model's properties. Out of every texture available to me (we use Diffuse map, Normal Map and Specular Map) I was only able to read alpha successfully from the Diffuse Map! Here is how I add specular and normal maps to my model's material in the content processor: if (geometry.Material.Textures.ContainsKey(normalMapKey)) { ExternalReference<TextureContent> texRef = geometry.Material.Textures[normalMapKey]; geometry.Material.Textures.Remove("NormalMap"); geometry.Material.Textures.Add("NormalMap", texRef); } ... foreach (KeyValuePair<String, ExternalReference<TextureContent>> texture in material.Textures) { if ((texture.Key == "Texture") || (texture.Key == "NormalMap") || (texture.Key == "SpecularMap")) mat.Textures.Add(texture.Key, texture.Value); } In the shader I obviously use: float4 data = tex2D(specularMapSampler, TexCoords); so data.a is always 1 in my case, could you suggest a reason?

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  • Cocos2d v2.0 and OpenGL 2.0/1.0: where to start

    - by mm24
    I started developing my very first game 3 months ago using Cocos2d 2.0 for iPhone. I am now in the stage where I'd like to add some cool effects to the bullets and some special weapons (see my waveforms question here). I got a good answer in the cocos2d-iphone forum (see this one). Unfortunately I am a bit paralized now. I don't know if I will be overdoing by learning OpengGL 2.0 or if I should just stick ot the old 1.0. There is a good intro on various tutorial's written in Steffen Itterheims blog (see this post). I would like to add to my game: a blur effect to the bullets (here is a tutorial for OpenGL 1.0) a waveform (see above) some realistic water ripples (here is a nice sample code) So now, given that I don't want to overdo things but at the same time I want to achieve those effects, from where should I start? Should I discard the OpenGL 1.0 tutorials? OR should I use only OpenGL 1.0 code? How can I avoid confusion? I mean, it seems that the compiler recognizes both, but that there are some conflictual calls in some circumnstances, I am fairly sure this has some explanation, is there some reference to this somewhere?

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  • It could be worse....

    - by Darryl Gove
    As "guest" pointed out, in my file I/O test I didn't open the file with O_SYNC, so in fact the time was spent in OS code rather than in disk I/O. It's a straightforward change to add O_SYNC to the open() call, but it's also useful to reduce the iteration count - since the cost per write is much higher: ... #define SIZE 1024 void test_write() { starttime(); int file = open("./test.dat",O_WRONLY|O_CREAT|O_SYNC,S_IWGRP|S_IWOTH|S_IWUSR); ... Running this gave the following results: Time per iteration 0.000065606310 MB/s Time per iteration 2.709711563906 MB/s Time per iteration 0.178590114758 MB/s Yup, disk I/O is way slower than the original I/O calls. However, it's not a very fair comparison since disks get written in large blocks of data and we're deliberately sending a single byte. A fairer result would be to look at the I/O operations per second; which is about 65 - pretty much what I'd expect for this system. It's also interesting to examine at the profiles for the two cases. When the write() was trapping into the OS the profile indicated that all the time was being spent in system. When the data was being written to disk, the time got attributed to sleep. This gives us an indication how to interpret profiles from apps doing I/O. It's the sleep time that indicates disk activity.

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  • How to convince a client to switch to a framework *now*; also examples of great, large-scale php applications.

    - by cbrandolino
    Hi everybody. I'm about to start working on a very ambitious project that, in my opinion, has some great potential for what concerns the basic concept and the implementation ideas (implementation as in how this ideas will be implemented, not as in programming). The state of the code right now is unluckily subpar. It's vanilla php, no framework, no separation between application and visualization logic. It's been done mostly by amateur students (I know great amateur/student programmers, don't get me wrong: this was not the case though). The clients are really great, and they know the system won't scale and needs a redesign. The problem is, they would like to launch a beta ASAP and then think of rebuilding. Since just the basic functionalities are present now, I suggested it would be a great idea if we (we're a three-people shop, all very proficient) ported that code to some framework (we like CodeIgniter) before launching. We would reasonably be able to do that in < 10 days. Problem is, they don't think php would be a valid long-term solution anyway, so they would prefer to just let it be and fix the bugs for now (there's quite a bit) and then directly switch to some ruby/python based system. Porting to CI now will make future improvements incredibly easier, the current code more secure, changing the style - still being discussed with the designers - a breeze (reminder: there are database calls in template files right now); the biggest obstacle is the lack of trust in php as a valid, scalable technology. So well, I need some examples of great php applications (apart from facebook) and some suggestions on how to try to convince them to port soon. Again, they're great people - it's not like they would like ruby cause it's so hot right now; they just don't trust php since us cool programmers like bashing it, I suppose, but I'm sure going on like this for even one more day would be a mistake. Also, we have some weight in the decision process.

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  • Threading models when talking to hardware devices

    - by Fuzz
    When writing an interface to hardware over a communication bus, communications timing can sometimes be critical to the operation of a device. As such, it is common for developers to spin up new threads to handle communications. It can also be a terrible idea to have a whole bunch of threads in your system, an in the case that you have multiple hardware devices you may have many many threads that are out of control of the main application. Certainly it can be common to have two threads per device, one for reading and one for writing. I am trying to determine the pros and cons of the two different models I can think of, and would love the help of the Programmers community. Each device instance gets handles it's own threads (or shares a thread for a communication device). A thread may exist for writing, and one for reading. Requested writes to a device from the API are buffered and worked on by the writer thread. The read thread exists in the case of blocking communications, and uses call backs to pass read data to the application. Timing of communications can be handled by the communications thread. Devices aren't given their own threads. Instead read and write requests are queued/buffered. The application then calls a "DoWork" function on the interface and allows all read and writes to take place and fire their callbacks. Timing is handled by the application, and the driver can request to be called at a given specific frequency. Pros for Item 1 include finer grain control of timing at the communication level at the expense of having control of whats going on at the higher level application level (which for a real time system, can be terrible). Pros for Item 2 include better control over the timing of the entire system for the application, at the expense of allowing each driver to handle it's own business. If anyone has experience with these scenarios, I'd love to hear some ideas on the approaches used.

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  • Is it considered poor programming to do this with xna components?

    - by Rob
    I created my own Menu System that is event driven. In order to have a loading screen and multithreaded loading to work, I devised this sort of implementation: //Let's check if the game is done loading. if (_game != null) { _gameLoaded = _game.DoneLoading; } //This means the game is loading still, //therefore the loading screen should be active. if (!_gameLoaded && _gameActive) { _gameScreenList[2].UpdateMenu(); } //The loading screen was selected. if (_gameScreenList[2].CurrentState == GameScreen.State.Shown && !_gameActive) { Components.Add(_game = new ParadoxGame(this)); _game.Initialize(); //Initializes the Game so that the loading can begin. _gameActive = true; } In the XNA Game Component that contains the actual game, in the LoadContent method I simply created a new Thread that calls another method ThreadLoad that has all the actual loading. I also have a boolean variable called DoneLoading in the XNA Game Component that is set to true at the end of the ThreadLoad. I am wondering if this is a poor implementation.

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  • The Importance of Fully Specifying a Problem

    - by Alan
    I had a customer call this week where we were provided a forced crashdump and asked to determine why the system was hung. Normally when you are looking at a hung system, you will find a lot of threads blocked on various locks, and most likely very little actually running on the system (unless it's threads spinning on busy wait type locks). This vmcore showed none of that. In fact we were seeing hundreds of threads actively on cpu in the second before the dump was forced. This prompted the question back to the customer: What exactly were you seeing that made you believe that the system was hung? It took a few days to get a response, but the response that I got back was that they were not able to ssh into the system and when they tried to login to the console, they got the login prompt, but after typing "root" and hitting return, the console was no longer responsive. This description puts a whole new light on the "hang". You immediately start thinking "name services". Looking at the crashdump, yes the sshds are all in door calls to nscd, and nscd is idle waiting on responses from the network. Looking at the connections I see a lot of connections to the secure ldap port in CLOSE_WAIT, but more interestingly I am seeing a few connections over the non-secure ldap port to a different LDAP server just sitting open. My feeling at this point is that we have an either non-responding LDAP server, or one that is responding slowly, the resolution being to investigate that server. Moral When you log a service ticket for a "system hang", it's great to get the forced crashdump first up, but it's even better to get a description of what you observed to make to believe that the system was hung.

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  • Eris Update to 2.1 &ndash; No Problems

    - by Bunch
    I updated my Eris to Android’s 2.1 OS last night and everything went pretty well. I had wanted to update the phone mainly for two reasons. The first was to have the Navigation feature of the Google Maps application and to make YouTube work again. YouTube used to work on the phone and then stopped a few weeks ago. But before I started I looked around various forums and blogs to see what doom and gloom folks were talking about the update. Based on what I read and some common sense I used the following steps: Made sure there was a good charge on the phone. Connected to our WiFi (the download is about 77 megs, not very 3G friendly). Checked that the contacts were synced with the GMail account. As a precaution I copied off any music and pictures from the SD card to my laptop. Started the update process and waited for the download and installation to complete. It took maybe 30 minutes to do everything. After the update I re-synced the contacts and tested out the phone (it does make calls after all). I did need to download the text to speech application to get the Maps Navigation to work but that was easy enough since the application prompted me to download it. And now the YouTube application works again. Technorati Tags: Android

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