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• Why is a database always represented with a cylinder?

  - by Creepy Gnome

  This question came up today and I couldn't find any historical answer as to why a database is always represented as a cylinder. I am hoping someone in the stack world would know why and have a link or something backing it up.

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• Marshal.PtrToStructure (and back again) and generic solution for endianness swapping

  - by cgyDeveloper

  I have a system where a remote agent sends serialized structures (from and embedded C system) for me to read and store via IP/UDP. In some cases I need to send back the same structure types. I thought I had a nice setup using Marshal.PtrToStructure (receive) and Marshal.StructureToPtr (send). However, a small gotcha is that the network big endian integers need to be converted to my x86 little endian format to be used locally. When I'm sending them off again, big endian is the way to go. Here are the functions in question: private static T BytesToStruct<T>(ref byte[] rawData) where T: struct { T result = default(T); GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); result = (T)Marshal.PtrToStructure(rawDataPtr, typeof(T)); } finally { handle.Free(); } return result; } private static byte[] StructToBytes<T>(T data) where T: struct { byte[] rawData = new byte[Marshal.SizeOf(data)]; GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned); try { IntPtr rawDataPtr = handle.AddrOfPinnedObject(); Marshal.StructureToPtr(data, rawDataPtr, false); } finally { handle.Free(); } return rawData; } And a quick example structure that might be used like this: byte[] data = this.sock.Receive(ref this.ipep); Request request = BytesToStruct<Request>(ref data); Where the structure in question looks like: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)] private struct Request { public byte type; public short sequence; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)] public byte[] address; } What (generic) way can I swap the endianness when marshalling the structures? My need is such that the locally stored 'public short sequence' in this example will be little-endian for displaying to the user. I don't want to have to swap the endianness on a structure-specific way. My first thought was to use Reflection, but I'm not very familiar with that feature. Also, I hoped that there would be a better solution out there that somebody could point me towards. Thanks in advance :)

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• is it right to assigning multiple variable like this a = b = c = d = 5 in ruby?

  - by Salil

  a = b = c = d = 5 puts (a) >> 5 puts (b) >> 5 puts (b) >> 5 puts (b) >> 5 a= a+1 puts (a) >> 6 puts (b) >> 5 i found there is no problem with the assigning value like this. my question is should one assign like the one given above or a , b, c, d = 5, 5, 5, 5

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• "Access 2002 vs SQL Server 200*" as DB for sharepoint

  - by Jake

  I work with a team that has a sharepoint site currently runnning and its lists are linked to an access DB. My question is really on the investment level, what would be the reasons to upgrade DB to sharepoint if only a few 100 users access this site. Is there a real benefit to replacing the DB with a version of SQL Server, escpecially if about to replace Access 2002 with 2007 some day. I know SQL Server can handle more memory and traffic for more users, but I'm looking for more reasons than that if there are any.

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• Need to check uptime on a large file being hosted

  - by trustfundbaby

  I have a dynamically generated rss feed that is about 150M in size (don't ask) The problem is that it keeps crapping out sporadically and there is no way to monitor it without downloading the entire feed to get a 200 status. Pingdom times out on it and returns a 'down' error. So my question is, how do I check that this thing is up and running

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• Impact of Multiple .ToUpper()'ing

  - by Kyle Rozendo

  Hi All, This is not a question of premature optimization per se. On the garbage collector and memory in general, what would hundreds of ToUpper() operations (many could be duplicated) do to a program, mainly in regard to the immutability of strings? Thanks, Kyle

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• ASP.Net webapplication, keep in mind things for performance ,scalability

  - by Radhi

  what are the things a developer should keep in mind or should take care when depeloping a web application. web application e.g. social networking web app. which are the things which must be implemented to get good performance and scalability. please provide any article or blogs or suggestions for this kind of question if you have -thanks in advance

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• Adobe AIR - Write a file and specify as read-only

  - by Mauricio

  Hey Stack Overflow community, Another Adobe AIR question for you: Can we write files to the file system and leave them as read-only in Adobe AIR? In the future, we would overwrite these files (or delete them and write a new one). Thanks, Mauricio

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• Modeling a cellphone bill: should I use single-table inheritance or polymorphic associations?

  - by Horace Loeb

  In my domain: Users have many Bills Bills have many BillItems (and therefore Users have many BillItems through Bills) Every BillItem is one of: Call SMS (text message) MMS (multimedia message) Data Here are the properties of each individual BillItem (some are common): My question is whether I should model this arrangement with single-table inheritance (i.e., one "bill_items" table with a "type" column) or polymorphism (separate tables for each BillItem type), and why.

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• Convert .net String object into base64 encoded string

  - by chester89

  I have a question, which Unicode encoding to use while encoding .NET string into base64? I know strings are UTF-16 encoded on Windows, so is my way of encoding is the right one? public static String ToBase64String(this String source) { return Convert.ToBase64String(Encoding.Unicode.GetBytes(source)); }

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• What are void pointers for in C++?

  - by Dr. Acula

  My question is simple: What are void pointers for in C++? (Those things you declare with void* myptr;) What is their use? Can I make them point to a variable of any type?

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• Extraneous Library Linkage

  - by gmatt

  I have a question which may be somewhat silly because I'm pretty sure I may know the answer already. Suppose you have static library A, and dynamic shared object library B and your program C under linux. Suppose that library A calls functions from library B and your program calls functions from library A. Now suppose that all functions that C calls in A make no use of functions in B. To compile C will it be enough to link just A and omit B and furthermore can your program C be run on a system without library B installed?

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• Iterate Multi-Dimensional Array with Nested Foreach Statement

  - by Tyler Murry

  I think this might be a pretty simple question, but I haven't been able to figure it out yet. If I've got a 2-dimensional array like so: int[,] = new int[2,3] { {1, 2, 3}, {4, 5, 6} }; What's the best way to iterate through each dimension of the array with a nested foreach statement?

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• ajaxToolkit:DropDownExtender where is items ?

  - by nCdy

  <asp:TextBox ID="TextBox5" runat="server" Height="30px" Width="68px"></asp:TextBox> <ajaxToolkit:DropDownExtender ID="TextBox5_DropDownExtender" runat="server" DynamicServicePath="" Enabled="True" TargetControlID="TextBox5"> </ajaxToolkit:DropDownExtender> //this.TextBox5_DropDownExtender ???? YearList.Items.Add(DateTime.Today.AddYears(-i).ToString("yyyy")); Question : where is items for this DropDownExtender ?

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• Automatically charge PayPal account?

  - by Mark

  I'd like to automatically charge my members a variable amount of money based on the services they use on my website. They would accumulate a balance owing, and then every week they would be charged for that amount. Is there a way I can do this without having to store their credit card information in my database? (Similar to my last question, but I just realized I don't really want to go through the headaches and liability issues of having to safely store CC info)

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• Why did Matz choose to make Strings mutable by default in Ruby?

  - by Seth Tisue

  It's the reverse of this question: http://stackoverflow.com/questions/93091/why-cant-strings-be-mutable-in-java-and-net Was this choice made in Ruby only because operations (appends and such) are efficient on mutable strings, or was there some other reason? (If it's only efficiency, that would seem peculiar, since the design of Ruby seems otherwise to not put a high premium on faciliating efficient implementation.)

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• Good C# Interview Questions for a Senior Dev Position

  - by kronoz

  I know there have been a great deal of interview questions posed on SO, however I wondered what sort of questions people here ask at C# interviews, interviewing for a senior developer position. In order to keep this in line with SO principles, please provide a list of questions (or a single question) rather than discussion.

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• Using ListViews on the Android?

  - by Robert

  Hey everyone, I am just getting started with the Android SDK and I had a quick question. I am trying to set up a ListView with a rectangle of color on the left and then a bit of text for each row. I also want to make it so I can click each entry in the list and open a new activity to display some information (similar to the contact list). Anyone have any examples to help me out? Thanks a ton, Robert Hill

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• Is daisy chaining xslt an accepted practice?

  - by Stephen

  I have a situation where I think I need to daisy chain my xslt transformation (i.e. that output of one xslt transform being input into another). The first transform is rather complex with lots of xsl:choice and ancestor xpaths. My thought is to transform the xml into xml that can then be easily transformed to html. My question is 'Is this standard practice or am I missing something?' Thanks in advance. Stephen

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• What is a "Decentralized Uniqueness Algorithm"?

  - by Tony

  The function in COM to create a GUID (CoCreateGUID) uses a "Decentralized Uniqueness Algorithm", but my question is, what is it? Can anybody explain?

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• Java - Common Gotchas

  - by Alan

  In the same spirit of other platforms, it seemed logical to follow up with this question: What are common non-obvious mistakes in Java? Things that seem like they ought to work, but don't. I won't give guidelines as to how to structure answers, or what's "too easy" to be considered a gotcha, since that's what the voting is for. See also: Perl - Common gotchas .NET - Common gotchas

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• ASP.NET Web Service - how to handle special characters in strings?

  - by Vlorg

  To show this fundamental issue in .NET and the reason for this question, I have written a simple test web service with one method (EditString), and a consumer console app that calls it. They are both standard web service/console applications created via File/New Project, etc., so I won't list the whole code - just the methods in question: Web method: [WebMethod] public string EditString(string s, bool useSpecial) { return s + (useSpecial ? ((char)19).ToString() : ""); } [You can see it simply returns the string s if useSpecial is false. If useSpecial is true, it returns s + char 19.] Console app: TestService.Service1 service = new SCTestConsumer.TestService.Service1(); string response1 = service.EditString("hello", false); Console.WriteLine(response1); string response2 = service.EditString("hello", true); // fails! Console.WriteLine(response2); [The second response fails, because the method returns hello + a special character (ascii code 19 for argument's sake).] The error is: There is an error in XML document (1, 287) Inner exception: "'', hexadecimal value 0x13, is an invalid character. Line 1, position 287." A few points worth mentioning: The web method itself WORKS FINE when browsing directly to the ASMX file (e.g. http://localhost:2065/service1.asmx), and running the method through this (with the same parameters as in the console application) - i.e. displays XML with the string hello + char 19. Checking the serialized XML in other ways shows the special character is being encoded properly (the SERVER SIDE seems to be ok which is GOOD) So it seems the CLIENT SIDE has the issue - i.e. the .NET generated proxy class code doesn't handle special characters This is part of a bigger project where objects are passed in and out of the web methods - that contain string attributes - these are what need to work properly. i.e. we're de/serializing classes. Any suggestions for a workaround and how to implement it? Or have I completely missed something really obvious!!? Thanks in advance... PS. I've not had much luck with getting it to use CDATA tags (does .NET support these out of the box?).

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• client-side synchronous service invocation

  - by qkrsppopcmpt

  I am talking about synchronous on the client side. That means, the service requester is blocking after sending a message to the service. my question is: is it related to the -a -s parameter of wsdl2java tool, Since -a generate async style code and -s generate sync style code. Or the client side blocking or not is totally controlled by the client logic? Thanks

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• Asynchronous vs Synchronous vs Threading in an iPhone App

  - by Coocoo4Cocoa

  I'm in the design stage for an app which will utilize a REST web service and sort of have a dilemma in as far as using asynchronous vs synchronous vs threading. Here's the scenario. Say you have three options to drill down into, each one having its own REST-based resource. I can either lazily load each one with a synchronous request, but that'll block the UI and prevent the user from hitting a back navigation button while data is retrieved. This case applies almost anywhere except for when your application requires a login screen. I can't see any reason to use synchronous HTTP requests vs asynchronous because of that reason alone. The only time it makes sense is to have a worker thread make your synchronous request, and notify the main thread when the request is done. This will prevent the block. The question then is bench marking your code and seeing which has more overhead, a threaded synchronous request or an asynchronous request. The problem with asynchronous requests is you need to either setup a smart notification or delegate system as you can have multiple requests for multiple resources happening at any given time. The other problem with them is if I have a class, say a singleton which is handling all of my data, I can't use asynchronous requests in a getter method. Meaning the following won't go: - (NSArray *)users { if(users == nil) users = do_async_request // NO GOOD return users; } whereas the following: - (NSArray *)users { if(users == nil) users == do_sync_request // OK. return users; } You also might have priority. What I mean by priority is if you look at Apple's Mail application on the iPhone, you'll notice they first suck down your entire POP/IMAP tree before making a second request to retrieve the first 2 lines (the default) of your message. I suppose my question to you experts is this. When are you using asynchronous, synchronous, threads -- and when are you using either async/sync in a thread? What kind of delegation system do you have setup to know what to do when a async request completes? Are you prioritizing your async requests? There's a gamut of solutions to this all too common problem. It's simple to hack something out. The problem is, I don't want to hack and I want to have something that's simple and easy to maintain.

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• load Javascript object from file

  - by megapool020

  Hi there, I asked a question in this thread Stackoverflow, and it works perfect. So tnx to all the users who gave me a reply. But now I have a other question. I would like to have the object in a seperate file, so I only need to update the file in stead of the JS file (otherwise it will be very big). I'm using JQUERY. I now looks like this (with all the info in the JS file). IBANInfo is used to fill a selectbox var IBANInfo = { "ccAL":{ countryCode:"AL", countryName:"Albani&euml;", IBANlength:"28", bankFormCode:"0 8n 0 ", accountNum:"0 16 0 " }, "ccAD":{ countryCode:"AD", countryName:"Andorra", IBANlength:"24", bankFormCode:"0 4n 4n", accountNum:"0 12 0 " }, "ccBE":{ countryCode:"BE", countryName:"Belgi&euml;", IBANlength:"16", bankFormCode:"0 3n 0 ", accountNum:"0 7n 2n" } }; //---- then this function is used to build the selectList function createSelect(){ var selectList = ''; var key; selectList += "<option value=''>Kies een land</option>\n"; for (key in IBANInfo) { if (IBANInfo.hasOwnProperty(key)) { var countryInfo = IBANInfo[key]; selectList += "<option value='"+countryInfo.countryCode+"'>"+countryInfo.countryName+"</option>\n"; } } $('#selectBox').html(selectList); } I thought I could do it like this, but I get the message undefined in my selectbox. var IBANInfo = $.get('include/countryCodes.txt'); // also tried var IBANInfo = $.getJSON('include/countryCodes.txt'); //---- then this function is used to build the selectList function createSelect(){ var selectList = ''; var key; selectList += "<option value=''>Kies een land</option>\n"; for (key in IBANInfo) { if (IBANInfo.hasOwnProperty(key)) { var countryInfo = IBANInfo[key]; selectList += "<option value='"+countryInfo.countryCode+"'>"+countryInfo.countryName+"</option>\n"; } } $('#selectBox').html(selectList); } /* the countryCodes.txt file is like this: { "ccAL":{ countryCode:"AL", countryName:"Albani&euml;", IBANlength:"28", bankFormCode:"0 8n 0 ", accountNum:"0 16 0 " }, "ccAD":{ countryCode:"AD", countryName:"Andorra", IBANlength:"24", bankFormCode:"0 4n 4n", accountNum:"0 12 0 " }, "ccBE":{ countryCode:"BE", countryName:"Belgi&euml;", IBANlength:"16", bankFormCode:"0 3n 0 ", accountNum:"0 7n 2n" } } */ What am I doing wrong. Tnx in advance

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