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  • How to understand computer science as a whole?

    - by MrCellophane
    I am a college student in Computer Science, I have been studying CS for a long time. But even till today, I still feel so confused about a lot of things. First of all, I have solid foundation in alg, data structure, and OOP, but I don't have a clear understanding of the whole system of the subject. I studied database, alg, data structure, OOP, network, software engineering, OS, and a lot of courses. I know what they are, but I don't know how to connect them together. Is there a way to have a clear understanding of the architecture of the subject? And is there a way to know what technology is used to do what? For example, in interviews, when people ask me alg, data str, Java, OS or any other specific field, I could answer, but when they ask some other very general about the field, I have no idea. Well, I know my question maybe a little bit confusing, but what my situation is I don't even know how to ask a clear question. I don't know my question, it's totally a mess in my head. Is there a way to make it clear?

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  • Should components have sub-components in a component-based system like Artemis?

    - by Daniel Ingraham
    I am designing a game using Artemis, although this is more of philosophical question about component-based design in general. Let's say I have non-primitive data which applies to a given component (a Component "animal" may have qualities such as "teeth" or "diet"). There are three ways to approach this in data-driven design, as I see it: 1) Generate classes for these qualities using "traditional" OOP. I imagine this has negative implications for performance, as systems then must be made aware of these qualities in order to process them. It also seems counter to the overall philosophy of data-driven design. 2) Include these qualities as sub-components. This seems off, in that we are now confusing the role of components with that of entities. Moreover out of the box Artemis isn't capable of mapping these subcomponents onto their parent components. 3) Add "teeth", "diet", etc. as components to the overall entity alongside "animal". While this feels odd hierarchically, it may simply be a peculiarity of component-based systems. I suspect 3 is the correct way to think about things, but I was curious about other ideas.

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  • 9 Gigapixel Photo Captures 84 Million Stars

    - by Jason Fitzpatrick
    The European Southern Observatory has released an absolutely enormous picture of the center of the Milky Way captured by their VISTA telescope–the image is 9 gigapixels and captures over 84 million stars. From the press release: The large mirror, wide field of view and very sensitive infrared detectors of ESO’s 4.1-metre Visible and Infrared Survey Telescope for Astronomy (VISTA) make it by far the best tool for this job. The team of astronomers is using data from the VISTA Variables in the Via Lactea programme (VVV), one of six public surveys carried out with VISTA. The data have been used to create a monumental 108 200 by 81 500 pixel colour image containing nearly nine billion pixels. This is one of the biggest astronomical images ever produced. The team has now used these data to compile the largest catalogue of the central concentration of stars in the Milky Way ever created. Want to check out all 9 billion glorious pixels in their uncompressed state? Be prepared to wait a bit, the uncompressed image is available for download but it weighs in at a massive 24.6GB. 84 Million Stars and Counting [via Wired] How Hackers Can Disguise Malicious Programs With Fake File Extensions Can Dust Actually Damage My Computer? What To Do If You Get a Virus on Your Computer

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  • asp.net Multiple Page_Load events for a user control when using URL Routing

    - by Paul Hutson
    Hello, I've recently set up an ASP.net site (not using MVC.net) to use URL Routing (more on the code below) - when using user controls on the site (i.e I've created a "menu" user control to hold menu information) the page_load event for that control will fire twice when URLs have more than one variable passed over. i.e. pageName/VAR1 : will only fire the page_load event once. while pageName/VAR1/VAR2 : will fire the page_load event twice. *Multiple extra VARs added on the end will still only fire the page_load event twice*. Below are the code snippits from the files, the first is the MapPageRoute, located in the Global.asax : // Register a route for the Example page, with the NodeID and also the Test123 variables allowed. // This demonstrates how to have several items linked with the page routes. routes.MapPageRoute( "Multiple Data Example", // Route name "Example/{NodeID}/{test123}/{variable}", // Route URL - note the NodeID bit "~/Example.aspx", // Web page to handle route true, // Check for physical access new System.Web.Routing.RouteValueDictionary { { "NodeID", "1" }, // Default Node ID { "test123", "1" }, // Default addtional variable value { "variable", "hello"} // Default test variable value } ); Next is the way I've directed to the page in the menu item, this is a list item within a UL tag : <li class="TopMenu_ListItem"><a href="<%= Page.GetRouteUrl("Multiple Data Example", new System.Web.Routing.RouteValueDictionary { { "NodeID", "4855" }, { "test123", "2" } }) %>">Example 2</a></li> And finally the control that gets hit multiple times on a page load : // For use when the page loads. protected void Page_Load(object sender, EventArgs e) { // Handle the routing variables. // this handles the route data value for NodeID - if the page was reached using URL Routing. if (Page.RouteData.Values["NodeID"] != null) { nodeID = Page.RouteData.Values["NodeID"] as string; }; // this handles the route data value for Test123 - if the page was reached using URL Routing. if (Page.RouteData.Values["Test123"] != null) { ExampleOutput2.Text = "I am the output of the third variable : " + Page.RouteData.Values["Test123"] as string; }; // this handles the route data value for variable - if the page was reached using URL Routing. if (Page.RouteData.Values["variable"] != null) { ExampleOutput3.Text = "I say " + Page.RouteData.Values["variable"] as string; }; } Note, that when I'm just hitting the page and it uses the default values for items, the reloads do not happen. Any help or guidance that anyone can offer would be very much appreciated! EDIT : The User Control is only added to the page once. I've tested the load sequence by putting a breakpoint in the page_load event - it only hits twice when the extra routes are added. Thanks in Advance, Paul Hutson

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  • iphone problem receiving UDP packets

    - by SooDesuNe
    I'm using sendto() and recvfrom() to send some simple packets via UDP over WiFI. I've tried using two phones, and a simulator, the results I'm getting are: Packets sent from phones - recieved by simulator Packets sent from simulator - simulator recvfrom remains blocking. Packets sent from phones - other phone recvfrom remains blocking. I'm not sure how to start debugging this one, since the simulator/mac is able to receive the the packets, but the phones don't appear to be getting the message. A slight aside, do I need to keep my packets below the MTU for my network? Or is fragmentation handled by the OS or some other lower level software? UPDATE: I forgot to include the packet size and structure. I'm transmitting: typedef struct PacketForTransmission { int32_t packetTypeIdentifier; char data[64]; // size to fit my biggest struct } PacketForTransmission; of which the char data[64] is: typedef struct PacketHeader{ uint32_t identifier; uint32_t datatype; } PacketHeader; typedef struct BasePacket{ PacketHeader header; int32_t cardValue; char sendingDeviceID[41]; //dont forget to save room for the NULL terminator! } BasePacket; typedef struct PositionPacket{ BasePacket basePacket; int32_t x; int32_t y; } PositionPacket; sending packet is like: PositionPacket packet; bzero(&packet, sizeof(packet)); //fill packet with it's associated data PacketForTransmission transmissionPacket; transmissionPacket.packetTypeIdentifier = kPositionPacketType; memcpy(&transmissionPacket.data, (void*)&packet, sizeof(packet)); //put the PositionPacket into data[64] size_t sendResult = sendto(_socket, &transmissionPacket, sizeof(transmissionPacket), 0, [address bytes], [address length]); NSLog(@"packet sent of size: %i", sendResult); and recieving packets is like: while(1){ char dataBuffer[8192]; struct sockaddr addr; socklen_t socklen = sizeof(addr); ssize_t len = recvfrom(_socket, dataBuffer, sizeof(dataBuffer), 0, &addr, &socklen); //continues blocking here NSLog(@"packet recieved of length: %i", len); //do some more stuff }

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  • How to remove a box2d body when collision happens?

    - by Ayham
    I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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  • Need advice on framework design: how to make extending easy

    - by beginner_
    I'm creating a framework/library for a rather specific use-case (data type). It uses diverse spring components, including spring-data. The library has a set of entity classes properly set up and according service and dao layers. The main work or main benefit of the framework lies in the dao and service layer. Developers using the framework should be able to extend my entity classes to add additional fields they require. Therefore I made dao and service layer generic so it can be used by such extended entity classes. I now face an issue in the IO part of the framework. It must be able to import the according "special data type" into the database. In this part I need to create a new entity instance and hence need the actual class used. My current solution is to configure in spring a bean of the actual class used. The problem with this is that an application using the framework could only use 1 implementation of the entity (the original one from me or exactly 1 subclass but not 2 different classes of the same hierarchy. I'm looking for suggestions / desgins for solving this issue. Any ideas?

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  • Hijacking ASP.NET Sessions

    - by Ricardo Peres
    So, you want to be able to access other user’s session state from the session id, right? Well, I don’t know if you should, but you definitely can do that! Here is an extension method for that purpose. It uses a bit of reflection, which means, it may not work with future versions of .NET (I tested it with .NET 4.0/4.5). 1: public static class HttpApplicationExtensions 2: { 3: private static readonly FieldInfo storeField = typeof(SessionStateModule).GetField("_store", BindingFlags.NonPublic | BindingFlags.Instance); 4:  5: public static ISessionStateItemCollection GetSessionById(this HttpApplication app, String sessionId) 6: { 7: var module = app.Modules["Session"] as SessionStateModule; 8:  9: if (module == null) 10: { 11: return (null); 12: } 13:  14: var provider = storeField.GetValue(module) as SessionStateStoreProviderBase; 15:  16: if (provider == null) 17: { 18: return (null); 19: } 20:  21: Boolean locked; 22: TimeSpan lockAge; 23: Object lockId; 24: SessionStateActions actions; 25:  26: var data = provider.GetItem(HttpContext.Current, sessionId.Trim(), out locked, out lockAge, out lockId, out actions); 27:  28: if (data == null) 29: { 30: return (null); 31: } 32:  33: return (data.Items); 34: } 35: } As you can see, it extends the HttpApplication class, that is because we need to access the modules collection, for the Session module. Use with care!

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  • The MDM Journey: From the Customer Perspective

    - by Mala Narasimharajan
    Master Data Management is more than just about a single version of  the truth or providing a 360 degree view of the customer.  It spans multiple domains ranging from customers to suppliers to products and beyond.  MDM is pivotal to providing a solid customer experience - one that results in repeat business, continued loyalty and last but not least - high customer satisfaction.  Customer experience is not only defined as accurate information about the customer for the enterprise, but also presenting the customer with the right information about products, orders, product availability, etc.   Let's take a look at a couple of customer use cases with Oracle MDM. Below is a picture from a recent customer panel: Oracle MDM is a key platform for increasing upsell/cross-sell opportunities, improve targeting of customers and uncover new sales opportunies, reduce inaccuracies in mailing marketing materials to prospects, as well as to tap into and uncover the full value of a customer across business units more accurately.  A leading investment and private bank leverages Oracle MDM to do a better job of identifying clients, their levels of investment as well as consistently manage them through a series of areas such as credit, risk, new accounts, etc. Ultimately, they are looking to understand client investments and touchpoints across the company's offerings.  Another use case for Oracle MDM is with a major financial and insurance services company with clients worldwide, looking to resolve customer data inaccuracies and client information stored differently across mulitiple systems.  For more information on Oracle Master Data Management, click here.  

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  • Oracle as a Service in the Cloud

    - by Jason Williamson
    This should really be a Tweet, but I guess I'm writing a bit more. In theme of data migration and legacy modernization, I am seeing more and more of a push to consolidate data sources, especially from non-oracle to oracle in an effort to save dollars. From a modernization perspective, this fits in quite well. We are able to migrate things like Terradata, Sybase and DB2 and put that all into an Oracle database and then provide that as a OaaS (Oracle as a Service) Cloud offering. This seems to be a growing trend, and not unlike the cool RDS Amazon Database cloud being built on Oracle as well. We again find ourselves back in the similar theme of migration, however. The target technology sounds like a winner (COBOL to Java/SOA...DB2/Datacom/Adabas to Oracle) but the age-old problem of how to get there still persists. It it not trivial to migrate large amounts of pre-relational or "devolved" relational data. To do this, we again must revert back to a tight roadmap to migration and leverage the growing tools and services that we have. I'm working on a couple of new sections and chapters for a book that Tom and Prakash and I are writing around Database Migration and Consolidation. I'll share some snipits shortly.

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  • What to do when TDD tests reveal new functionality that is needed that also needs tests?

    - by Joshua Harris
    What do you do when you are writing a test and you get to the point where you need to make the test pass and you realize that you need an additional piece of functionality that should be separated into its own function? That new function needs to be tested as well, but the TDD cycle says to Make a test fail, make it pass then refactor. If I am on the step where I am trying to make my test pass I'm not supposed to go off and start another failing test to test the new functionality that I need to implement. For example, I am writing a point class that has a function WillCollideWith(LineSegment): public class Point { // Point data and constructor ... public bool CollidesWithLine(LineSegment lineSegment) { Vector PointEndOfMovement = new Vector(Position.X + Velocity.X, Position.Y + Velocity.Y); LineSegment pointPath = new LineSegment(Position, PointEndOfMovement); if (lineSegment.Intersects(pointPath)) return true; return false; } } I was writing a test for CollidesWithLine when I realized that I would need a LineSegment.Intersects(LineSegment) function. But, should I just stop what I am doing on my test cycle to go create this new functionality? That seems to break the "Red, Green, Refactor" principle. Should I just write the code that detects that lineSegments Intersect inside of the CollidesWithLine function and refactor it after it is working? That would work in this case since I can access the data from LineSegment, but what about in cases where that kind of data is private?

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  • Stored procedure error when use computed column for ID

    - by Hari
    I got the error: Procedure or function usp_User_Info3 has too many arguments specified When I run the program. I don't know the error in SP or in C# code. I have to display the Vendor_ID after the user clicks the submit button. Where the thing going wrong here ? Table structure : CREATE TABLE User_Info3 ( SNo int Identity (2000,1) , Vendor_ID AS 'VEN' + CAST(SNo as varchar(16)) PERSISTED PRIMARY KEY, UserName VARCHAR(16) NOT NULL, User_Password VARCHAR(12) NOT NULL, User_ConPassword VARCHAR(12) NOT NULL, User_FirstName VARCHAR(25) NOT NULL, User_LastName VARCHAR(25) SPARSE NULL, User_Title VARCHAR(35) NOT NULL, User_EMail VARCHAR(35) NOT NULL, User_PhoneNo VARCHAR(14) NOT NULL, User_MobileNo VARCHAR(14)NOT NULL, User_FaxNo VARCHAR(14)NOT NULL, UserReg_Date DATE DEFAULT GETDATE() ) Stored Procedure : ALTER PROCEDURE [dbo].[usp_User_Info3] @SNo INT OUTPUT, @Vendor_ID VARCHAR(10) OUTPUT, @UserName VARCHAR(30), @User_Password VARCHAR(12), @User_ConPassword VARCHAR(12), @User_FirstName VARCHAR(25), @User_LastName VARCHAR(25), @User_Title VARCHAR(35), @User_OtherEmail VARCHAR(30), @User_PhoneNo VARCHAR(14), @User_MobileNo VARCHAR(14), @User_FaxNo VARCHAR(14) AS BEGIN SET NOCOUNT ON; INSERT INTO User_Info3 (UserName,User_Password,User_ConPassword,User_FirstName, User_LastName,User_Title,User_OtherEmail,User_PhoneNo,User_MobileNo,User_FaxNo) VALUES (@UserName,@User_Password,@User_ConPassword,@User_FirstName,@User_LastName, @User_Title,@User_OtherEmail,@User_PhoneNo,@User_MobileNo,@User_FaxNo) SET @SNo = Scope_Identity() SELECT Vendor_ID From User_Info3 WHERE SNo = @SNo END C# Code : protected void BtnUserNext_Click(object sender, EventArgs e) { cmd.CommandType = CommandType.StoredProcedure; cmd.CommandText = "usp_User_Info3"; System.Data.SqlClient.SqlParameter SNo=cmd.Parameters.Add("@SNo",System.Data.SqlDbType.Int); System.Data.SqlClient.SqlParameter Vendor_ID=cmd.Parameters.Add("@Vendor_ID", System.Data.SqlDbType.VarChar,10); cmd.Parameters.Add("@UserName", SqlDbType.VarChar).Value = txtUserName.Text; cmd.Parameters.Add("@User_Password", SqlDbType.VarChar).Value = txtRegPassword.Text; cmd.Parameters.Add("@User_ConPassword", SqlDbType.VarChar).Value = txtRegConPassword.Text; cmd.Parameters.Add("@User_FirstName", SqlDbType.VarChar).Value = txtRegFName.Text; cmd.Parameters.Add("@User_LastName", SqlDbType.VarChar).Value = txtRegLName.Text; cmd.Parameters.Add("@User_Title", SqlDbType.VarChar).Value = txtRegTitle.Text; cmd.Parameters.Add("@User_OtherEmail", SqlDbType.VarChar).Value = txtOtherEmail.Text; cmd.Parameters.Add("@User_PhoneNo", SqlDbType.VarChar).Value =txtRegTelephone.Text; cmd.Parameters.Add("@User_MobileNo", SqlDbType.VarChar).Value =txtRegMobile.Text; cmd.Parameters.Add("@User_FaxNo", SqlDbType.VarChar).Value =txtRegFax.Text; cmd.Connection = SqlCon; try { Vendor_ID.Direction = System.Data.ParameterDirection.Output; SqlCon.Open(); cmd.ExecuteNonQuery(); string VendorID = cmd.ExecuteScalar() as string; } catch (Exception ex) { throw new Exception(ex.Message); } finally { string url = "../CompanyBasicInfo.aspx?Parameter=" + Server.UrlEncode(" + VendorID + "); SqlCon.Close(); } }

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  • UIScrollView Infinite Scrolling

    - by Ben Robinson
    I'm attempting to setup a scrollview with infinite (horizontal) scrolling. Scrolling forward is easy - I have implemented scrollViewDidScroll, and when the contentOffset gets near the end I make the scrollview contentsize bigger and add more data into the space (i'll have to deal with the crippling effect this will have later!) My problem is scrolling back - the plan is to see when I get near the beginning of the scroll view, then when I do make the contentsize bigger, move the existing content along, add the new data to the beginning and then - importantly adjust the contentOffset so the data under the view port stays the same. This works perfectly if I scroll slowly (or enable paging) but if I go fast (not even very fast!) it goes mad! Heres the code: - (void) scrollViewDidScroll:(UIScrollView *)scrollView { float pageNumber = scrollView.contentOffset.x / 320; float pageCount = scrollView.contentSize.width / 320; if (pageNumber > pageCount-4) { //Add 10 new pages to end mainScrollView.contentSize = CGSizeMake(mainScrollView.contentSize.width + 3200, mainScrollView.contentSize.height); //add new data here at (320*pageCount, 0); } //*** the problem is here - I use updatingScrollingContent to make sure its only called once (for accurate testing!) if (pageNumber < 4 && !updatingScrollingContent) { updatingScrollingContent = YES; mainScrollView.contentSize = CGSizeMake(mainScrollView.contentSize.width + 3200, mainScrollView.contentSize.height); mainScrollView.contentOffset = CGPointMake(mainScrollView.contentOffset.x + 3200, 0); for (UIView *view in [mainContainerView subviews]) { view.frame = CGRectMake(view.frame.origin.x+3200, view.frame.origin.y, view.frame.size.width, view.frame.size.height); } //add new data here at (0, 0); } //** MY CHECK! NSLog(@"%f", mainScrollView.contentOffset.x); } As the scrolling happens the log reads: 1286.500000 1285.500000 1284.500000 1283.500000 1282.500000 1281.500000 1280.500000 Then, when pageNumber<4 (we're getting near the beginning): 4479.500000 4479.500000 Great! - but the numbers should continue to go down in the 4,000s but the next log entries read: 1278.000000 1277.000000 1276.500000 1275.500000 etc.... Continiuing from where it left off! Just for the record, if scrolled slowly the log reads: 1294.500000 1290.000000 1284.500000 1280.500000 4476.000000 4476.000000 4473.000000 4470.000000 4467.500000 4464.000000 4460.500000 4457.500000 etc.... Any ideas???? Thanks Ben.

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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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  • thick client migration to web based application

    - by user1151597
    This query is related to application design the technology that I should consider during migration. The Scenario: I have a C#.net Winform application which communicates with a device. One of the main feature of this application is monitoring cyclic data(rate 200ms) sent from the device to the application. The request to start the cyclic data is sent only once in the beginning and then the application starts receiving data from the device until it sends a stop request. Now this same application needs to be deployed over the web in a intranet. The application is composed of a business logic layer and a communication layer which communicates with the device through UDP ports. I am trying to look at a solution which will allow me to have a single instance of the application on the server so that the device thinks that it is connected as usual and then from the business logic layer I can manage the clients. I want to reuse the code of the business layer and the communication layer as much as possible. Please let me know if webserives/WCF/ etc what i should consider to design the migration. Thanks in advance.

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  • Concurrency pattern of logger in multithreaded application

    - by Dipan Mehta
    The context: We are working on a multi-threaded (Linux-C) application that follows a pipeline model. Each module has a private thread and encapsulated objects which do processing of data; and each stage has a standard form of exchanging data with next unit. The application is free from memory leak and is threadsafe using locks at the point where they exchange data. Total number of threads is about 15- and each thread can have from 1 to 4 objects. Making about 25 - 30 odd objects which all have some critical logging to do. Most discussion I have seen about different levels as in Log4J and it's other translations. The real big questions is about how the overall logging should really happen? One approach is all local logging does fprintf to stderr. The stderr is redirected to some file. This approach is very bad when logs become too big. If all object instantiate their individual loggers - (about 30-40 of them) there will be too many files. And unlike above, one won't have the idea of true order of events. Timestamping is one possibility - but it is still a mess to collate. If there is a single global logger (singleton) pattern - it indirectly blocks so many threads while one is busy putting up logs. This is unacceptable when processing of the threads are heavy. So what should be the ideal way to structure the logging objects? What are some of the best practices in actual large scale applications? I would also love to learn from some of the real designs of large scale applications to get inspirations from!

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  • Best design for a "Command Executer" class

    - by Justin984
    Sorry for the vague title, I couldn't think of a way to condense the question. I am building an application that will run as a background service and intermittently collect data about the system its running on. A second Android controller application will query the system over tcp/ip for statistics about the system. Currently, the background service has a tcp listener class that reads/writes bytes from a socket. When data is received, it raises an event to notify the service. The service takes the bytes, feeds them into a command parser to figure out what is being requested, and then passes the parsed command to a command executer class. When the service receives a "query statistics" command, it should return statistics over the tcp/ip connection. Currently, all of these classes are fully decoupled from each other. But in order for the command executer to return statistics, it will obviously need access to the socket somehow. For reasons I can't completely articulate, it feels wrong for the command executer to have a direct reference to the socket. I'm looking for strategies and/or design patterns I can use to return data over the socket while keeping the classes decoupled, if this is possible. Hopefully this makes sense, please let me know if I can include any info that would make the question easier to understand.

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  • Http handler for classic ASP application for introducing a layer between client and server

    - by JPReddy
    I've a huge classic ASP application where in thousands of users manage their company/business data. Currently this is not multi-user so that application users can create users and authorize them to access certain areas in the system. I'm thinking of writing a handler which will act as middle man between client and server and go through every request and find out who the user is and whether he is authorized to access the data he is trying to. For the moment ignore about the part how I'm going to check the authorization and all that stuff. Just want to know whether I can implement a ASP.net handler and use it as middle man for the requests coming for a asp website? I just want to read the url and see what is the page user is trying to access and what are the parameters he is passing in the url the posted data. Is this possible? I read that Asp.net handler cannot be used with asp website and I need to use isapi filter or extensions for that and that can be developed only c/c++. Can anybody through some light on this and guide me whether I'm in the right direction or not?

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  • Implementing a scalable and high-performing web app

    - by Christopher McCann
    I have asked a few questions on here before about various things relating to this but this is more of a consolidation question as I would like to check I have got the gist of everything. I am in the middle of developing a social media web app and although I have a lot of experience coding in Java and in PHP I am trying things a bit different this time. I have modularised each component of the application. So for example one component of the application allows users to private message each other and I have split this off into its own private messaging service. I have also created a user data service the purpose of which is to return data about the user for example their name, address, age etc etc from the database. Their is also another service, the friends service, which will work off the neo4j database to create a social graph. My reason for doing all this is to allow me up to update seperate modules when I need to - so while they mostly all run off MySQL right now I could move one to Cassandra later if I thought it approriate. The actual code of the web app is really just used for the final construction. The modules behind it dont really follow any strict REST or SOAP protocol. Basically each method on our API is turned into a PHP procedural script. This then may make calls to other back-end code which tends to be OO. The web app makes CURL requests to these pages and POSTs data to them or GETs data from them. These pages then return JSON where data is required. I'm still a little mixed up about how I actually identify which user is logged in at that moment. Do I just use sessions for that? Like if we called the get-messages.php script which equates to the getMessages() method for that user - returning all the private messages for that user - how would the back-end code know which user it is as posting the users ID to the script would not be secure. Anyone could do that and get all the messages. So I thought I would use sessions for it. Am I correct on this? Can anyone spot any other problems with what I am doing here? Thanks

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  • Why do I need a framework?

    - by lvictorino
    First of all I know my question may sounds idiot but I am no "beginner". In fact I work as game developer for several years now and I know some things about code :) But as this is no related to game development I am a bit lost. I am writing a big script (something about GIS) in Python, using a lot of data stored in a database. I made a first version of my script, and now, I'd like to re-design the whole thing. I read some advice about using a framework (like Django) for database queries. But as my script only "SELECT" informations I was wondering about the real benefits to use a framework. It seems that it adds a lot of complexity and useless embedded features (useless for my specific script) for the benefits that it will bring. Am I wrong? EDIT: few spec of this "script". Its purpose is to get GIS data on an enormous database (if you ever worked with openstreetmap you know what I mean ~= 200Go) and to manipulate this data in order to produce nice map images. Queries are not numerous (select streets, select avenues, select waterways, select forests... and so on for a specific area) but query results may be more than 10.000 rows. I'd like to sell this script as a service, so yes it's meant to stay.

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  • How to store bitmaps in memory?

    - by Geotarget
    I'm working with general purpose image rendering, and high-performance image processing, and so I need to know how to store bitmaps in-memory. (24bpp/32bpp, compressed/raw, etc) I'm not working with 3D graphics or DirectX / OpenGL rendering and so I don't need to use graphics card compatible bitmap formats. My questions: What is the "usual" or "normal" way to store bitmaps in memory? (in C++ engines/projects?) How to store bitmaps for high-performance algorithms, such that read/write times are the fastest? (fixed array? with/without padding? 24-bpp or 32-bpp?) How to store bitmaps for applications handling a lot of bitmap data, to minimize memory usage? (JPEG? or a faster [de]compression algorithm?) Some possible methods: Use a fixed packed 24-bpp or 32-bpp int[] array and simply access pixels using pointer access, all pixels are allocated in one continuous memory chunk (could be 1-10 MB) Use a form of "sparse" data storage so each line of the bitmap is allocated separately, reusing more memory and requiring smaller contiguous memory segments Store bitmaps in its compressed form (PNG, JPG, GIF, etc) and unpack only when its needed, reducing the amount of memory used. Delete the unpacked data if its not used for 10 secs.

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  • Is there a canonical source supporting "all-surrogates"?

    - by user61852
    Background The "all-PK-must-be-surrogates" approach is not present in Codd's Relational Model or any SQL Standard (ANSI, ISO or other). Canonical books seems to elude this restrictions too. Oracle's own data dictionary scheme uses natural keys in some tables and surrogate keys in other tables. I mention this because these people must know a thing or two about RDBMS design. PPDM (Professional Petroleum Data Management Association) recommend the same canonical books do: Use surrogate keys as primary keys when: There are no natural or business keys Natural or business keys are bad ( change often ) The value of natural or business key is not known at the time of inserting record Multicolumn natural keys ( usually several FK ) exceed three columns, which makes joins too verbose. Also I have not found canonical source that says natural keys need to be immutable. All I find is that they need to be very estable, i.e need to be changed only in very rare ocassions, if ever. I mention PPDM because these people must know a thing or two about RDBMS design too. The origins of the "all-surrogates" approach seems to come from recommendations from some ORM frameworks. It's true that the approach allows for rapid database modeling by not having to do much business analysis, but at the expense of maintainability and readability of the SQL code. Much prevision is made for something that may or may not happen in the future ( the natural PK changed so we will have to use the RDBMS cascade update funtionality ) at the expense of day-to-day task like having to join more tables in every query and having to write code for importing data between databases, an otherwise very strightfoward procedure (due to the need to avoid PK colisions and having to create stage/equivalence tables beforehand ). Other argument is that indexes based on integers are faster, but that has to be supported with benchmarks. Obviously, long, varying varchars are not good for PK. But indexes based on short, fix-length varchar are almost as fast as integers. The questions - Is there any canonical source that supports the "all-PK-must-be-surrogates" approach ? - Has Codd's relational model been superceded by a newer relational model ?

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  • base64-Encoding breaks smime-encrypted emaildata

    - by Streuner
    I'm using Mime::Lite to create and send E-Mails. Now I need to add support for S/Mime-encryption and finally could encrypt my E-Mail (the only Perllib I could install seems broken, so I'm using a systemcall and openssl smime), but when I try to create a mime-object with it, the E-Mail will be broken as soon as I set the Content-Transfer-Encoding to base64. To make it even more curious, it happens only if I set it via $myMessage->attr. If I'm using the constructor -new everything is fine, besides a little warning which I suppress by using MIME::Lite->quiet(1); Is it a bug or my fault? Here are the two ways how I create the mime-object. Setting the Content-Transfer-Encoding via construtor and suppress the warning: MIME::Lite->quiet(1); my $msgEncr = MIME::Lite->new(From =>'[email protected]', To => '[email protected]', Subject => 'SMIME Test', Data => $myEncryptedMessage, 'Content-Transfer-Encoding' => 'base64'); $msgEncr->attr('Content-Disposition' => 'attachment'); $msgEncr->attr('Content-Disposition.filename' => 'smime.p7m'); $msgEncr->attr('Content-Type' => 'application/x-pkcs7-mime'); $msgEncr->attr('Content-Type.smime-type' => 'enveloped-data'); $msgEncr->attr('Content-Type.name' => 'smime.p7m'); $msgEncr->send; MIME::Lite->quiet(0); Setting the Content-Transfer-Encoding via $myMessage->attr which breaks the encrypted Data, but won't cause a warning: my $msgEncr = MIME::Lite->new(From => '[email protected]', To => '[email protected]', Subject => 'SMIME Test', Data => $myEncryptedMessage); $msgEncr->attr('Content-Disposition' => 'attachment'); $msgEncr->attr('Content-Disposition.filename' => 'smime.p7m'); $msgEncr->attr('Content-Type' => 'application/x-pkcs7-mime'); $msgEncr->attr('Content-Type.smime-type' => 'enveloped-data'); $msgEncr->attr('Content-Type.name' => 'smime.p7m'); $msgEncr->attr('Content-Transfer-Encoding' => 'base64'); $msgEncr->send; I just don't get why my message is broken when I'm using the attribute-setter. Thanks in advance for your help! Besides that i'm unable to attach any file to this E-Mail without breaking the encrypted message again.

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  • java multipart POST library

    - by tom
    Is there a multipart POST library out there that achieve the same effect of doing a POST from a html form? for example - upload a file programmingly in Java versus upload the file using a html form. And on the server side, it just blindly expect the request from client side to be a multipart POST request and parse out the data as appropriate. Has anyone tried this? specifically, I am trying to see if I can simulate the following with Java The user creates a blob by submitting an HTML form that includes one or more file input fields. Your app sets blobstoreService.createUploadUrl() as the destination (action) of this form, passing the function a URL path of a handler in your app. When the user submits the form, the user's browser uploads the specified files directly to the Blobstore. The Blobstore rewrites the user's request and stores the uploaded file data, replacing the uploaded file data with one or more corresponding blob keys, then passes the rewritten request to the handler at the URL path you provided to blobstoreService.createUploadUrl(). This handler can do additional processing based on the blob key. Finally, the handler must return a headers-only, redirect response (301, 302, or 303), typically a browser redirect to another page indicating the status of the blob upload. Set blobstoreService.createUploadUrl as the form action, passing the application path to load when the POST of the form is completed. <body> <form action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data"> <input type="file" name="myFile"> <input type="submit" value="Submit"> </form> </body> Note that this is how the upload form would look if it were created as a JSP. The form must include a file upload field, and the form's enctype must be set to multipart/form-data. When the user submits the form, the POST is handled by the Blobstore API, which creates the blob. The API also creates an info record for the blob and stores the record in the datastore, and passes the rewritten request to your app on the given path as a blob key.

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  • What are my choices for server side sandboxed scripting?

    - by alfa64
    I'm building a public website where users share data and scripts to run over some data. The scripts are run serverside in some sort of sandbox without other interaction this cycle: my Perl program reads from a database a User made script, adds the data to be processed into the script ( ie: a JSON document) then calls the interpreter, it returns the response( a JSON document or plain text), i save it to the database with my perl script. The script should be able to have some access to built in functions added to the scripting language by myself, but nothing more. So i've stumbled upon node.js as a javascript interpreter, and and hour or so ago with Google's V8(does v8 makes sense for this kind of thing?). CoffeeScript also came to my mind, since it looks nice and it's still Javascript. I think javascript is widespread enough and more "sandboxeable" since it doesn't have OS calls or anything remotely insecure ( i think ). by the way, i'm writing the system on Perl and Php for the front end. To improve the question: I'm choosing Javascript because i think is secure and simple enough to implement with node.js, but what other alternatives are for achieving this kind of task? Lua? Python? I just can't find information on how to run a sandboxed interpreter in a proper way.

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