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• Easiest way to combine a dataset and other data in a single file?

  - by Tim Gradwell

  I have a dataset in C# which I can serialise using dataset.WriteXml(filename); but I want the file to contain other data as well (essentially some meta data about the dataset). I could add another table to the dataset which contained the metadata, but I'd prefer to keep it separate, if at all possible. Essentially I think I want to create a 'combination of files' file, that looks something like this: size_of_file1 file1 size_of_file2 file2 ... etc Then, I'd like to load the file into memory, and split the file into separate streams, so that I can feed the dataset into dataset.ReadXml(stream); and the metadata into something else. Sound possible? Can anyone tell me how I can do it? Thanks Tim

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• Problem with detecting phone orientation change in Symbian/Qt

  - by trex279

  I want to do some custom processing when the orientation of the phone changes. I have re-implemented the resizeEvent(QResizeEvent*) virtual function in my class. The strange thing is, for the first one time when the phone orientation is changed, this function is actually called, and works fine. But all subsequent orientation changes, this function isn't even called? Why does this happen? Are there any other ways to detect phone orientation change? Thanks.

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• Could someone give me their two cents on this optimization strategy

  - by jimstandard

  Background: I am writing a matching script in python that will match records of a transaction in one database to names of customers in another database. The complexity is that names are not unique and can be represented multiple different ways from transaction to transaction. Rather than doing multiple queries on the database (which is pretty slow) would it be faster to get all of the records where the last name (which in this case we will say never changes) is "Smith" and then have all of those records loaded into memory as you go though each looking for matches for a specific "John Smith" using various data points. Would this be faster, is it feasible in python, and if so does anyone have any recommendations for how to do it?

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• Is it faster to use a complicated boolean to limit a ResultSet at the MySQL end or at the Java end?

  - by javanix

  Lets say I have a really big table filled with lots of data (say, enough not to fit comfortably in memory), and I want to analyze a subset of the rows. Is it generally faster to do: SELECT (column1, column2, ... , columnN) FROM table WHERE (some complicated boolean clause); and then use the ResultSet, or is it faster to do: SELECT (column1, column2, ... , columnN) FROM table; and then iterate over the ResultSet, accepting different rows based on a java version of your boolean condition? I think it comes down to whether the Java iterator/boolean evaluator is faster than the MySQL boolean evaluator.

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• Retrieving data from an encrypted text file?

  - by user

  Let's say I have a text file contains my data. data : ab bc de - encrypted data on text file : ba cb ed I want to find bc from text file, so I have to decrypt the text file with this code : SL:=TStringList.create; SL.LoadFromFile(textfile) SLtemp:=TStringList.create; for I := 0 to SL.Count - 1 do SLtemp.Add(ReverseString(SL[i])); //decrypt SL.Free; for I := 0 to SLtemp.Count - 1 do if SLtemp[i] = 'bc' then begin showmessage('found'); break; end; SLtemp.Free; I think my way is wasting resources. I have to load whole file to memory and decrypt them. I need some suggestions here to find quickly a specific line from an encrypted text. Thanks.

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• session_start() Hangs The Server

  - by Narcissus

  Totally confused by this one... We have a WAMPServer installation set up, running a number of virtual hosts from various document roots. Just recently, one particular domain has started hanging the server. We traced it down to session_start(). If we comment it out, there are no problems (except, of course, for the fact that we can't do anything with the session). With it uncommented, it will hang the page load and, with enough reloads, will hang the entire server. All of the other sites still work perfectly with their sessions. As far as I know, there is nothing different with the way sessions are being worked with. I am looking further into it (in case someone changed something) but right now I'm hoping for some direction :) So, any thoughts?

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• Best Practices for a Web App Staging Server (on a budget)

  - by fig-gnuton

  I'd like to set up a staging server for a Rails app. I use git & github, Cap, and have a VPS with Apache/Passenger. I'm curious as to the best practices for a staging setup, as far as both the configuration of the staging server as well as the processes for interacting with it. I do know it should be as identical to the production server as possible, but restricting public access to it will limit that, so tips on securing it only for my use would also be great. Another specific question would be whether I could just create a virtual host on the VPS, so that the staging server could reside alongside the production one. I have a feeling there may be reasons to avoid this, though.

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• In C, as free() knows an array size, why isn't there a function that gets the array size? [closed]

  - by user354959

  Possible Duplicate: If free() knows the length of my array, why can’t I ask for it in my own code? Searching around (including here at stackoverflow), I got that malloc() allocates an array and also creates a header to control the array info. In this header, there's also the array size. free() use such information to know how to deallocate that array. So, if the array size info is "there" (somewhere in the memory), why there isn't a function that returns an array size, looking for this at the array header? Or am I missing something?

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• VirtualHost configuration

  - by Hari

  Hi, I need to configure two name-based virtual hosts in my ubuntu pc. If I type the address "http://mypage1" in browser, it should display my first customized html page and if I type the address "http://mypage2", it should display my second customized html page. I tried out the following: 1. installed apache 2. created a file mypage1 inside sites-available with the contents as follows: VirtualHost *:80 ServerName mypage1 ServerAlias http://mypage1 DocumentRoot /var/www/mypage1/html /VirtualHost 3. created a similar file mypage2 inside sites-available 4. ran the commands "a2ensite mypage1" and "a2ensite mypage2" to generate soft links inside sites-enabled. 5. restarted apache using "sudo /etc/init.d/apache2 restart" After doing the above steps, when I type mypage1 in firefox, I get dns_unresolved_hostname error. Kindly help me how to resolve this problem.

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• Instance where embedded C++ compilers don't support multiple inheritance?

  - by Nathan

  I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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• how can i set mTextView to show on button click

  - by Ajay Pandey

  i have a UITextView object which i have created in interface builder with it's hidden property unmarked.Now i want this textView to be invisible when my application launches and first view appears.Further i want it to be displayed when a particular method is called.Now this is what i have written in view did load [mTextView setHidden:YES]; self.mTextView=[[UITextView alloc] init]; it hides the textView ats the first view appears but when my desired method is called and i write [mTextView setHidden:NO]; it does not show it again.. Is it like we cant change the appearance of a textView once it is assigned because after assigning memory as self.mTextView=[[UITextView alloc] init]; and then writing [mTextView setHidden:YES]; it does not hide textView in viwDidLoad either.....

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• How are a session identifiers generated?

  - by Asaf R

  Most web applications depend on some kind of session with the user (for instance, to retain login status). The session id is kept as a cookie in the user's browser and sent with every request. To make it hard to guess the next user's session these session-ids need to be sparse and somewhat random. The also have to be unique. The question is - how to efficiently generate session ids that are sparse and unique? This question has a good answer for unique random numbers, but it seems not scalable for a large range of numbers, simply because the array will end up taking a lot of memory.

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• How to handle this type of model validation in Ruby on Rails

  - by randombits

  I have a controller/model hypothetically named Pets. Pets has the following declarations: :belongs_to owner :has_many dogs :has_many cats Not the best example, but again, it demonstrates what I'm trying to solve. Now when a request comes in as an HTTP POST to http://127.0.0.1/pets, I want to create an instance of Pets. The restriction here is, if the user doesn't submit at least one dog or one cat, it should fail validation. It can have both, but it can't be missing both. How does one handle this in Ruby on Rails? Dogs don't care if cats exists and the inverse is also true. Can anyone show some example code of what the Pets model would look like to ensure that one or the other exists, or fail otherwise? errors.add also takes an attribute, in this case, there is no particular attribute that's failing. It's almost a 'virtual' combination that's missing.

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• What segments does C compiled program use?

  - by b-gen-jack-o-neill

  Hi, I read on OSDev wiki, that protected mode of x86 architecture allow you to create separate segments for code and data, while you cannot write into code section. That Windows (yes, this is the platform) loads new code into code segment, and data are created on data segment. But, if this is the case, how does program know it must switch segments to the data segment? Becouse if I understand it right, all adress instructions point to the segment you run the code from, unless you switch the descriptor. But I also read, that so colled flat memory model allows you to run code and data within one segment. But I read this only in connection to assembler. So, please, what is the case with C compiled code on Windows? Thanks.

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• storing an integer constant other than zero in a pointer variable

  - by benjamin button

  int main() { int *d=0; printf("%d\n",*d); return 0; } this works fine. >cc legal.c > ./a.out 0 if i change the statement int *d=0; to int *d=1; i see the error. cc: "legal.c", line 6: error 1522: Cannot initialize a pointer with an integer constant other than zero. so its obvious that it will allow only zero.i want to know what happens inside the memory when we do this int *d=0 which is making it valid syntax. I am just asking this out of curiosity!

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• IO.Directory.Exists always returns true

  - by roygbiv

  I am executing a IO.Directory.Exists on a network share from an ASP.NET application running under a specific Application Pool with a specific user account. The call always returns true. I have tried several variations: \\server\share$\directory \\192.168.0.1\share$\directory H:\directory I have checked that directory and share permissions are available to the account. The path does have spaces in it \\server\share$\directory\name name\test test, which should make no difference, however I have read otherwise. I will continue to check permissions, as it does work from my local machine (with the built in VS web-server and I am an administrator on the network), but when deployed to the IIS 6.0 virtual directory, and run under the Application Pool, it does not work.

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• Garbage Collection Java

  - by simion

  On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• Book resources for x86/x64 assembly programming on Win platform

  - by Scott Davies

  Hello, I ran a search for assembly language resources on stackoverflow.com and found some interesting results, but they seemed to boil down to two groups: 1) Assembly references to old ia32 architecture, such as the 80386 to Pentium 2) Windows agnostic books. Most of the commenters make the point that assembler is CPU dependent and that the OS is irrelevant, but it seems pointless to me to pick a book that has assembly examples that refer to MS-DOS interrupts and memory layouts. Likewise, learning assembler on Linux would seem to produce Linux executables Are there any: 1) Modern 2) x86/x64 3) on Windows platform - book resources available ? The reason I am targeting the Win platform is I would like to do low-level, OS internals programming, to supplement my Win C/C++ work. Thanks

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• Knowing the fundamentals of Java what is the right approach to learn Groovy?

  - by Liuh

  As my question already implies I want to learn a new language and have read several articles about groovy and its more pragmatic syntax. SO I have choosen Groovy as the language of my choice. What is a good way to learn a new language like Groovy when I already know the fundamentals of Java. When I understand correctly Groovy will be running in the Java Virtual Machine and allows me to always rely on what I know from Java when I don't know how to solve the problem in Groovy. I am looking for hints on how to organize a learning track to learn this language. I found that page explaining the differences: http://groovy.codehaus.org/Differences+from+Java But what I am looking for is more a tutorial where I can get through and get introduced to the differences.

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• How do I write raw binary data in Python?

  - by Chris B.

  I've got a Python program that stores and writes data to a file. The data is raw binary data, stored internally as str. I'm writing it out through a utf-8 codec. However, I get UnicodeDecodeError: 'charmap' codec can't decode byte 0x8d in position 25: character maps to <undefined> in the cp1252.py file. This looks to me like Python is trying to interpret the data using the default code page. But it doesn't have a default code page. That's why I'm using str, not unicode. I guess my questions are: How do I represent raw binary data in memory, in Python? When I'm writing raw binary data out through a codec, how do I encode/unencode it?

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• Create fake subdirectories with htaccess and php AND keep existing directories as is.

  - by Arseni

  I have a website, which has numerous subdirectories already. (All existing in server's filesystem) I want to create new "virtual" sub-dirs with htaccess, but I only want the htaccess rule work for directories, listed in DB, and not existing in filesystem. i.e. File system has: /dir1/ & /dir2/ MySQL database has record for 'dir3' & 'dir4' And I want: A: mysite.com/dir1/ and mysite.com/dir2/ display existing old content B: mysite.com/dir3/ and mysite.com/dir4/ display content from MySQL provided by PHP sctipt via redirect like: mysite.com/myscript.php?dir=dir3 C: mysite.com/dir5/ display 404 error (Dir does not exist in DB nor in Database) Basically I want .htaccess to work like this: IF DIR Exists in DB - apply the rewrite rule and show content from myscript.php?dir=DIR ELSE don't apply any rule. I can create a separate php script, which can return 0/1 when given dir name exist in DB or not, but how do I make mod_rewrite get the data from that script? Is it possible with htaccess/PHP at all?

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• Inheriting database connection in PHP OOP

  - by vrode

  My abstract class Database is made for database interaction and any child of this class (UserDatabase, ActionDatabase, EventDatabase) inherits its database connection which is defined as static. `abstract class Database { static $connection = mysql_connect( ); } class UserDatabase extends Database { ... public function __construct( ) { $connection ? "connected" : "not connected"; $this-table = "users"; mysql_query( "FROM " . $this-table . " SELECT *" ); } } ` Does that mean, that my database connection is only set up and stored in memory once and passed on to subclasses as reference without being replicated for each instance? Is this how you would implement you OOP-correct database interface?

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• OpenGL texture not showing up on some computers, problem with auxDIBImageLoad?

  - by CptanPanic

  I have a simple openGL GUI that has uses a bmp as a texture. The problem is on some computers the texture doesn't show up. But on ones with newer OpenGL drivers it works. How can I make it more compatible. I think the problem may be with auxDIBImageLoad. When I inspect the result, I see the x,y correct, but the data pointer points to memory bank with all zeros. What could be wrong?

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• Quick way to do data lookup in PHP

  - by Ghostrider

  I have a data table with 600,000 records that is around 25 megabytes large. It is indexed by a 4 byte key. Is there a way to find a row in such dataset quickly with PHP without resorting to MySQL? The website in question is mostly static with minor PHP code and no database dependencies and therefore fast. I would like to add this data without having to use MySQL if possible. In C++ I would memory map the file and do a binary search in it. Is there a way to do something similar in PHP?

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• Will .NET 4.0 apps work on Win 2008 R2 Server Core?

  - by markus

  When Windows Server 2008 R2 was launched, the "server core" edition started to become useful to me, because it lets me deploy .NET background applications isolated on their own virtual machine instance with only a small fraction of all the disk space overhead of a default Windows Server installation, and very few Windows Updates. It comes with a subset of .NET 3.5 SP1 integrated (as an optional feature). Now that .NET 4.0 is released, the redistributables explicitly state that it's not support on Server Core. Any chance that there will be a separate download available for Server Core (e. g. without WPF) any time soon, has anybody heard about it?

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