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• Parsing JPEG file format: Format of entropy-coded segment (ECS) segments?

  - by me2

  I'm having difficulty understanding the ITU-T T.81 spec for the JPEG file format. Hopefully someone else here has tried to parse JPEG files and/or knows about the details of this file format. The spec indiates that the ECS0 segment starts after the SOS segment but I can't find where in the spec it actually talks about the format of the ECS0 segment or how do detect its start. Simple JPEG implementations online are of limited help because they assume many things about the JPEGs they parse. Can anyone point me in the right direction?

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• ado.net managing connections

  - by madlan

  Hi, I'm populating a listview with a list of databases on a selected SQL instance, then retrieving a value from each database (It's internal product version, column doesn't always exist) I'm calling the below function to populate the second column of the listview: item.SubItems.Add(DBVersionCheck(serverName, database.Name)) Function DBVersionCheck(ByVal SelectedInstance As String, ByVal SelectedDatabase As String) Dim m_Connection As New SqlConnection("Server=" + SelectedInstance + ";User Id=sa;Password=password;Database=" + SelectedDatabase) Dim db_command As New SqlCommand("select Setting from SystemSettings where [Setting] = 'version'", m_Connection) Try m_Connection.Open() Return db_command.ExecuteScalar().trim m_Connection.Dispose() Catch ex As Exception 'MessageBox.Show(ex.Message) Return "NA" Finally m_Connection.Dispose() End Try End Function This works fine except it's creating a connection to each database and leaving it open. My understanding is the close()\dispose() releases only the connection from the pool in ado rather than the actual connection to sql. How would I close the actual connections after I've retrieved the value? Leaving these open will create hundreds of connections to databases that will probably not be used for that session.

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• A question about some code from TBB book, Thanks.

  - by Jackie

  I am reading the book: Intel Threading Building Blocks. I often have difficulties understanding them. For example,the following code is from the book(page 112): Node* AllocateNode() { Node* n; FreeListMutexType::scoped_lock lock; lock.acquire(FreeListMutex); n=FreeList; if(n) Freelist=n->next; lock.release(); if(!n) n=new Node(); return n; } There is other introduction regarding this code. I can not understand it. What does it means? How can I understand this book better? Thanks.

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• Strange thing about .NET 4.0 filesystem enumeration functionality

  - by codymanix

  I just read a page of "Whats new .NET Framework 4.0". I have trouble understanding the last paragraph: To remove open handles on enumerated directories or files Create a custom method (or function in Visual Basic) to contain your enumeration code. Apply the MethodImplAttribute attribute with the NoInlining option to the new method. For example: [MethodImplAttribute(MethodImplOptions.NoInlining)] Private void Enumerate() Include the following method calls, to run after your enumeration code: * The GC.Collect() method (no parameters). * The GC.WaitForPendingFinalizers() method. Why the attribute NoInlining? What harm would inlining do here? Why call the garbage collector manually, why not making the enumerator implement IDisposable in the first place? I suspect they use FindFirstFile()/FindNextFile() API calls for the imlementation, so FindClose() has to be called in any case if the enumeration is done.

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• Why & When should I use SPARSE COLUMN? (SQL SERVER 2008)

  - by priyanka.sarkar

  After going thru some tutorials on SQL SERVER 2008's new feature SPARSE COLUMN, I have found that it doesn't take any space if the column value is 0 or null but when there is a value, it takes 4 times the space a regular(non sparse) column holds. If my understanding is correct, then why I will go for that at the time of database design? And if I use that, then at what situation so I be? Also out of curiosity, how come no space get's reserve when a column is defined as sparse column(I mean to say, what is the internal implementation for that) Thanks in advance

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• How do I create SEO-Friendly urls in ASP.Net-MVC

  - by blesh

  I'm getting myself acquainted with ASP.Net-MVC, and I was trying to accomplish some common tasks I've accomplished in the past with webforms and other functionality. On of the most common tasks I need to do is create SEO-friendly urls, which in the past has meant doing some url rewriting to build the querystring into the directory path. for example: www.somesite.com/productid/1234/widget rather than: www.somesite.com?productid=1234&name=widget What method do I use to accomplish this in ASP.Net-MVC? I've search around, and all I've found is this, which either I'm not understanding properly, or doesn't really answer my question: http://stackoverflow.com/questions/734583/seo-urls-with-asp-net-mvc

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• Expression Tree

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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• Difference between 'scope' and 'namespace'?

  - by katriel

  What is the difference, in general, between the concepts of namespaces and scope? To my understanding, both describe the parts of a program in which a variable/object/method/function will be accessible. I understand that 'scope' tends to be a property of the variable (e.g., "This variable has global scope"), while a 'namespace' is a property of the program (e.g., "A Python function creates a local namespace"). Are there other differences? Global scope vs global namespace addresses a slightly narrower question: global namespaces in C++. http://www.alan-g.me.uk/tutor/tutname.htm states, There are a few very subtle differences between the terms but only a Computer Scientist pedant would argue with you, and for our purposes namespace and scope are identical. What are those subtle differences? Under what circumstances or with which kinds of languages do people use each concept?

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• How does this ruby custom accessor work

  - by ennuikiller

  So the method below in class_eval dynamically creates accessors for attributes defined at runtime. It can be used, for example, to create configuration objects with attributes read from a config file (and unknown until runtime). I understanding all of it except for the else branch. If I am correct the else branch returns the attribute value (val[0]) if there is one value passed in *val. However the way its written I would expect it to return an array (val) if there is more then one value passed in *var. In particular, if I have something like the following: value = 5 then from reading the code I would expect "#{@value}" to be [=,5]. However "#{@value}" returns 5 and not the array [=,5]. How is this possible? class Module def dsl_accessor(*symbols) symbols.each do |sym| class_eval %{ def #{sym}(*val) if val.empty? @#{sym} else @#{sym} = val.size == 1 ? val[0] : val end end } end end end

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• java keytool question

  - by user384706

  Hi, I created a java keystore programmatically of type jks (i.e. default type). It is initially empty so I created a DSA certificate. keytool -genkey -alias myCert -v -keystore trivial.keystore How can I see the public and private keys? I.e. is there a command that prints the private key of my certificate? I could only find keytool -certreq which in my understanding prints the certificate as a whole: -----BEGIN NEW CERTIFICATE REQUEST----- MIICaTCCAicCAQAwZTELMAkGA1UEBhMCR1IxDzANBgNVBAgTBkdyZWVjZTEPMA0GA1UEBxMGQXRo BQADLwAwLAIUQZbY/3Qq0G26fsBbWiHMbuVd3VICFE+gwtUauYiRbHh0caAtRj3qRTwl -----END NEW CERTIFICATE REQUEST----- I assume this is the whole certificate. How can I see private (or public key) via keytool? Thank you

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• WHERE clause confusion with PDO

  - by Greg

  I'm having some trouble understanding how to use prepared statements, when you need to match one value against several columns at once. In other words what instead of doing this: $stmt = $dbh-prepare("SELECT * FROM REGISTRY where name = ?"); $stmt-bindParam(':name', $name); I wanted to do this: $stmt = $dbh-prepare("SELECT * FROM REGISTRY where firstname = ? or lastname = ?"); with both '?' representing the same string.

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• concurrency in Java

  - by p1

  1]What is Non-blocking Concurrency and how is it different. 2] I have heard that this is available in Java. Are there any particular scenarios we should use this feature 3] Is there a difference/advantage of using one of these methods for a collection. What are the trade offs class List { private final ArrayList<String> list = new ArrayList<String>(); void add(String newValue) { synchronized (list) { list.add(newValue); } } } OR private final ArrayList<String> list = Collections.synchronizedMap(); The questions are more from a learning/understanding point of view. Thanks for attention.

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• Separation of logic from presentation: HTTP variable names?

  - by Allan Jardine

  Hello all, This could probably be considered an academic question, rather than a real world one - but throwing it out to see if anyone has any great ideas! We all know that keeping the business logic of an application separate from the presentation is a good idea (I'm looking at web-apps atm), but there needs to be an understanding between the business logic for what HTTP variables to expect (and then process) and the variable names which are sent by the presentation layer. Is this simply a matter of telling the designer what variable names to use in a template? The template doesn't need to know what the variable names are (unless using them for JS/CSS selectors), so why should they be 'hardcoded' in there. Or should the business logic put the names into variables to be printed out? Another layer of complexity for the templates? Does anyone have any experience of this, or thoughts on how to deal with it? Thanks, Allan

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• JavaFX layouts question.

  - by Jhonghee

  I am having some problem understanding layouts in JavaFX. Consider following code. Stage { title: "ListView test" scene: Scene { width: 400 height: 400 content: [ VBox { content: [ ListView { height: 200 width: 200 items: ["item1", "item2"] } ] } ] } } I was expecting ListView showing up in 200 x 200 dimension but no matter how I tried to fix this, the width and height of ListView seemed fixed. But following code works for showing ListView as I intended. Stage { title: "ListView test" scene: Scene { width: 400 height: 400 content: [ ListView { height: 200 width: 200 items: ["item1", "item2"] } ] } } So, what is the problem here? I cannot use ListView within layouts?

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• Can someone explain me implicit parameters in Scala?

  - by Oscar Reyes

  And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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• What is going on with the "return fibonacci( number-1 ) + fibonacci( number-2 )"?

  - by user1478598

  I have problem understanding what the return fibonacci( number-1 ) + fibonacci( number-2 ) does in the following program: import sys def fibonacci( number ): if( number <= 2 ): return 1 else: return fibonacci( number-1 ) + fibonacci( number-2 ) The problem is that I can't imagine how this line works: return fibonacci( number-1 ) + fibonacci( number-2 ) Does the both of the "fibonacci( number-1 )" and "fibonacci( number-2 )" being processed at the same time? or the "fibonacci( number-1 )" is the first to be processed and then the second one? I only see that processing both of them would eventually return '1' so the last result I expect to see it is a '1 + 1' = '2' I would appreciate a lot, If someone can elaborately explain the process of its calculation. I think this is a very newb question but I can't really get a picture of its process.

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• Front End Developer positions for Recent Graduates

  - by Rajat

  Is it just me or there is a serious dearth of Front End Web Developer positions for recent grads. I have been working as one for the last 6 months now after my graduation and I understand that most of the front-end skills are not taught at academia and the profession requires a lot of discipline and patience to learn them on your own. I see a plethora of opportunities for recent grads for back-end positions but very few for front end positions. Does the industry have an understanding that Front-End positions require more expertise than back-end positions? Just my thoughts but not many people seem to keen to hire recent grads for front-end positions.

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• PHP app with cookie less session does not work

  - by iama

  I am trying to use PHP session without using cookies. I have enabled session.use_trans_sid and disabled session.use_cookies in my php.ini file. I have also disabled cookies in my firefox browser. Now, when I browse my home page, I do not see the HTTP set cookie header in the server response to my page request (using Live HTTP headers). My understanding is that PHP will append session IDs to my request URL when cookies are disabled. Am I doing something wrong? BTW, I am aware using session IDs is not a recommended approach.

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• CSS class equivalent for LaTeX

  - by Ryan Scott Bardsley

  I am trying to figure out if there is a way to apply the CSS methodology to the LaTeX template I am building. What I would like to do is to have a set of classes that apply a specific style treatment to the bracketed words. For example: If I have three paragraphs of text, I want to have all of the paragraphs have [0.5cm] of spacing after the last line without having to add \\[0.5cm] after each paragraph. Is there a LaTeX equivalent of defining the treatment for all paragraphs in the preamble so that it cascades throughout my document? The equivalent of: <style> p {padding-bottom:0.5cm} </style> I want to be able to specify multiple version of these CSS-like LaTeX classes throughout my document, so I don't need a specific solution. I need help understanding how to add custom labels/names/classes to the preamble and an example of how to use them in the document itself. Thanks! Ryan

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• grails metaprogramming

  - by Don

  Hi, My understanding is that there are two obvious places in a Grails app where one can do meta-programming: The init closure of Bootstrap.groovy The doWithDynamicMethods closure of a plugin The meta-programming I'm referring to here should be visible throughout the metaprogramming, typical examples include adding (or replacing) methods of 3rd party classes. String.metaClass.myCustomMethod = { /* implementation omitted */ } The disadvantage of (1), is that the metaprogramming won't be applied when the application is dynamically reloaded. The disadvantage of (2) is that I need to create and maintain an entire plugin just for the sake of a little metaprogramming. Is there a better place to do this kind of metaprogramming? Thanks, Don

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• What considerations need to be made when transitioning an application to support?

  - by Eric U.

  I will be taking on the role of support for a complex application that is transitioning from the development team. This application is a sharepoint solution that connects to several (7) web services. The development team is rolling off almost immediately and will be available only for small questions. I'm new to this role so I'm wondering what suggestions you have for me as I take on this large project. What are some considerations that should be made so that the transition to support is smooth and uninterupted? I've been reading the documentation but I can already see some gaps that need to be filled. The applicaiton is very (perhaps overly) configurable and there is lots of injected code. Stepping through the code is about the only way I can gain an understanding of what is actually happening. At this point I'm a little over whelmed and appreciate any suggestions or advice. Thanks!

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• Unreachable code detected by using const variables

  - by Anton Roth

  I have following code: private const FlyCapture2Managed.PixelFormat f7PF = FlyCapture2Managed.PixelFormat.PixelFormatMono16; public PGRCamera(ExamForm input, bool red, int flags, int drawWidth, int drawHeight) { if (f7PF == FlyCapture2Managed.PixelFormat.PixelFormatMono8) { bpp = 8; // unreachable warning } else if (f7PF == FlyCapture2Managed.PixelFormat.PixelFormatMono16){ bpp = 16; } else { MessageBox.Show("Camera misconfigured"); // unreachable warning } } I understand that this code is unreachable, but I don't want that message to appear, since it's a configuration on compilation which just needs a change in the constant to test different settings, and the bits per pixel (bpp) change depending on the pixel format. Is there a good way to have just one variable being constant, deriving the other from it, but not resulting in an unreachable code warning? Note that I need both values, on start of the camera it needs to be configured to the proper Pixel Format, and my image understanding code needs to know how many bits the image is in. So, is there a good workaround, or do I just live with this warning?

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• Database Replication OOD Pattern

  - by MrOnigiri

  Greetings fellow overflowers, After reading on MSDN about correct strategies on how to perform database replication, and understanding their suggestion on Master-Subordinate Incremental Replication. It left me wondering, what OOD design pattern should I use on this... The main elements of this strategy are the Acquirer, the Manipulator and the Writer. The first fetches data from the database and passes on to the second which might perform simple transformations to the data, before handling it to the final element, the writer, that writes the desired data on the destination Database. I thought about using the Chain of Responsibility pattern, but the Acquirer, Manipulator and Writer don't share a common role among theme, so It makes no sense. Should these elements be written as separate classes, or methods inside my service? Of course I'll be creating a DB Helper class as well, but that doesn't constitutes a problem. Wondering what your opinions on this are! Thanks for your replies

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• Can someone explain me implicit conversions in Scala?

  - by Oscar Reyes

  And more specifically how does the BigInt works for convert int to BigInt? In the source code it reads: ... implicit def int2bigInt(i: Int): BigInt = apply(i) ... How is this code invoked? I can understand how this other sample: "Date literals" works. In. val christmas = 24 Dec 2010 Defined by: implicit def dateLiterals(date: Int) = new { import java.util.Date def Dec(year: Int) = new Date(year, 11, date) } When int get's passed the message Dec with an int as parameter, the system looks for another method that can handle the request, in this case Dec(year:Int) Q1. Am I right in my understanding of Date literals? Q2. How does it apply to BigInt? Thanks

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• Argument passing regarding ivars

  - by StoneBreaker

  I am passing an iVar into a function. The iVar is a double. The value of the iVar inside the function is correct, but the value of the iVar outside the function is not changed. This must have something to do with the way that I am receiving the iVar into the function. How do I pass a double iVar in so that its value is changed in the object and not only in the function? I do the same thing with pointers and the results are as expected, so I think I am not understanding scalar argument passing in c/objective-c.

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