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• Database design grouping contacts by lists and companies

  - by Serge

  Hi, I'm wondering what would be the best way to group contacts by their company. Right now a user can group their contacts by custom created lists but I'd like to be able to group contacts by their company as well as store the contact's position (i.e. Project Manager of XYZ company). Database wise this is what I have for grouping contacts into lists contact [id_contact] [int] PK NOT NULL, [lastName] [varchar] (128) NULL, [firstName] [varchar] (128) NULL, ...... contact_list [id_contact] [int] FK, [id_list] [int] FK, list [id_list] [int] PK [id_user] [int] FK [list_name] [varchar] (128) NOT NULL, [description] [TEXT] NULL Should I implement something similar for grouping contacts by company? If so how would I store the contact's position in that company and how can I prevent data corruption if a user modifies a contact's company name. For instance John Doe changed companies but the other co-workers are still in the old company. I doubt that will happen often (might not even happen at all) but better be safe than sorry. I'm also keeping an audit trail so in a way the contact would still need to be linked to the old company as well as the new one but without confusing what company he's actually working at the moment. I hope that made sense... Has anyone encountered such a problem? UPDATE Would something like this make sense contact_company [id_contact_company] [int] PK [id_contact] [int] FK [id_company] [int] FK [contact_title] [varchar] (128) company [id_company] [int] PK NOT NULL, [company_name] [varchar] (128) NULL, [company_description] [varchar] (300) NULL, [created_date] [datetime] NOT NULL This way a contact can work for more than one company and contacts can be grouped by companies

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• applicationWillTerminate Appears to be Inconsistent

  - by Lauren Quantrell

  This one has me batty. In applicationWillTerminate I am doing two things: saving some settings to the app settings plist file and updating any changed data to the SQLite database referenced in the managedObjectContext. Problem is it works sometimes and not others. Same issue in the simulator and on the device. If I hit the home button while the app is running, I can only sometimes get the data to store in the plist and into the CoreData store. It seems that it's both works or neither works, and it makes no difference if I switch the execution order (saveState, managedObjectContext or managedObjectContext, saveState). I can't figure out how this can happen. Any help is greatly appreciated. lq AppDelegate.m @synthesize rootViewController; - (void)applicationWillTerminate:(UIApplication *)application { [rootViewController saveState]; NSError *error; if (managedObjectContext != nil) { if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) { // Handle error exit(-1); // Fail } } } RootViewController.m - (void)saveState { NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults]; [userDefaults setInteger:self.someInteger forKey:kSomeNumber]; [userDefaults setObject:self.someArray forKey:kSomeArray]; }

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• OAuth secrets in mobile apps

  - by Felixyz

  When using the OAuth protocol, you need a secret string obtained from the service you want to delegate to. If you are doing this in a web app, you can simply store the secret in your data base or on the file system, but what is the best way to handle it in a mobile app (or a desktop app for that matter)? Storing the string in the app is obviously not good, as someone could easily find it and abuse it. Another approach would be to store it on you server, and have the app fetch it on every run, never storing it on the phone. This is almost as bad, because you have to include the URL in the app. I don't believe using https is any help. The only workable solution I can come up with is to first obtain the Access Token as normal (preferably using a web view inside the app), and then route all further communication through our server, where a script would append the secret to the request data and communicates with the provider. Then again, I'm a security noob, so I'd really like to hear some knowledgeable peoples' opinions on this. It doesn't seem to me that most apps are going to these lengths to guarantee security (for example, Facebook Connect seems to assume that you put the secret into a string right in your app). Another thing: I don't believe the secret is involved in initially requesting the Access Token, so that could be done without involving our own server. Am I correct?

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• Appending data to NSFetchedResultsController during find or create loop

  - by Justin Williams

  I have a table view that is managed by an NSFetchedResultsController. I am having an issue with a find-or-create operation, however. When the user hits the bottom of my table view, I am querying my server for another batch of content. If it doesn't exist in the local cache, we create it and store it. If it does exist, however, I want to append that data to the fetched results controller and display it. I can't quite figure that part out. Here's what I'm doing thus far: Passing the returned array of values from my server to an NSOperation to process. In the operation, create a new managed object context to work with. In the operation, I iterate through the array and execute a fetch request to see if the object exists (based on its server id). If the object doesn't exist, we create it and insert it into the operations' managed object context. After the iteration completes, we save the managed object context, which triggers a merge notification on my main thread. At this point, any objects that weren't locally cached in my Core Data store before will appear, but the ones that previously existed do not come along for the ride. I feel like it's something simple I'm missing, and could use a nudge in the right direction.

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• SQL 2008: Using separate tables for each datatype to return single row

  - by Thomas C

  Hi all I thought I'd be flexible this time around and let the users decide what contact information the wish to store in their database. In theory it would look as a single row containing, for instance; name, adress, zipcode, Category X, Listitems A. Example FieldType table defining the datatypes available to a user: FieldTypeID, FieldTypeName, TableName 1,"Integer","tblContactInt" 2,"String50","tblContactStr50" ... A user the define his fields in the FieldDefinition table: FieldDefinitionID, FieldTypeID, FieldDefinitionName 11,2,"Name" 12,2,"Adress" 13,1,"Age" Finally we store the actual contact data in separate tables depending on its datatype. Master table, only contains the ContactID tblContact: ContactID 21 22 tblContactStr50: ContactStr50ID,ContactID,FieldDefinitionID,ContactStr50Value 31,21,11,"Person A" 32,21,12,"Adress of person A" 33,22,11,"Person B" tblContactInt: ContactIntID,ContactID,FieldDefinitionID,ContactIntValue 41,22,13,27 Question: Is it possible to return the content of these tables in two rows like this: ContactID,Name,Adress,Age 21,"Person A","Adress of person A",NULL 22,"Person B",NULL,27 I have looked into using the COALESCE and Temp tables, wondering if this is at all possible. Even if it is: maybe I'm only adding complexity whilst sacrificing performance for benefit in datastorage and user definition option. What do you think? Best Regards /Thomas C

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• List of objects or parallel arrays of properties?

  - by Headcrab

  The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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• Neo4j Reading data / performing shortest path calculations on stored data

  - by paddydub

  I'm using the Batch_Insert example to insert Data into the database How can i read this data back from the database. I can't find any examples of how i do this. public static void CreateData() { // create the batch inserter BatchInserter inserter = new BatchInserterImpl( "var/graphdb", BatchInserterImpl.loadProperties( "var/neo4j.props" ) ); Map<String,Object> properties = new HashMap<String,Object>(); properties.put( "name", "Mr. Andersson" ); properties.put( "age", 29 ); long node1 = inserter.createNode( properties ); properties.put( "name", "Trinity" ); properties.remove( "age" ); long node2 = inserter.createNode( properties ); inserter.createRelationship( node1, node2, DynamicRelationshipType.withName( "KNOWS" ), null ); inserter.shutdown(); } I would like to store graph data in the database, graph.makeEdge( "s", "c", "cost", (double) 7 ); graph.makeEdge( "c", "e", "cost", (double) 7 ); graph.makeEdge( "s", "a", "cost", (double) 2 ); graph.makeEdge( "a", "b", "cost", (double) 7 ); graph.makeEdge( "b", "e", "cost", (double) 2 ); Dijkstra<Double> dijkstra = getDijkstra( graph, 0.0, "s", "e" ); What is the best method to store this kind data with 10000's of edges. Then run the Dijskra algorighm to find shortest path calculations using the stored graph data.

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• OutOfMemoryException

  - by Andrew

  I have an application that is pretty memory hungry. It holds a large amount of data in some big arrays. I have recently been noticing the occasional OutOfMemoryException. These OutOfMemoryExceptions are occurring long before my application (ASP.Net) has used up the 800mb available to it. I have track the issue down to the area of code where the array is resized. The array contains a structure that is 74bytes in size. (I know that you shouldn't create struct's that are bigger than 16bytes), but this application is a port from a Vb6 application). I have tried changing the struct to a class and this appears to have fixed the problem for now. I think the reason that changing to a class solves the problem has to do with the fact that when using a struct and the array is resized, a segment of memory that is large enough to store the new array needs to be reserved (e.g. (currentArraySize + increaseBySize)*74) cannot be found. This leads to the OutOfMemoryException. This isn't the case with a class as each element of the array only needs 8bytes to store a pointer to the new object. Is my thinking correct here?

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• Need some advice on Core Data modeling strategy

  - by Andy

  I'm working on an iPhone app and need a little advice on modeling the Core Data schema. My idea is a utility that allows the user to speed-dial their contacts using user-created rules based on the time of day. In other words, I would tell the app that my wife is commuting from 6am to 7am, at work from 7am to 4pm, commuting from 4pm to 5pm, and home from 5pm to 6am, Monday through Friday. Then, when I tap her name in my app, it would select the number to dial based on the current day and time. I have the user interface nearly complete (thanks in no small part to help I've received here), but now I've got some questions regarding the persistent store. The user can select start- and stop-times in 5-minute increments. This means there are 2,016 possible "time slots" in week (7 days * 24 hours * 12 5-minute intervals per hour). I see a few options for setting this up. Option #1: One array of time slots, with 2,016 entries. Each entry would be a dictionary containing a contact identifier and an associated phone number to dial. I think this means I'd need a "Contact" entity to store the contact information, and a "TimeSlot" entity for each of the 2,016 possible time slots. Option #2: Each Contact has its own array of time slots, each with 2,016 entries. Each array entry would simply be a string indicating which phone number to dial. Option #3: Each Contact has a dictionary of time slots. An entry would only be added to the dictionary for time slots with an active rule. If a search for, say, time slot 1,299 (Friday 12:15pm) didn't find a key @"1299" in the dictionary, then a default number would be dialed instead. I'm not sure any of these is the "right" way or the "best" way. I'm not even sure I need to use Core Data to manage it; maybe just saving arrays would be simpler. Any input you can offer would be appreciated.

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• Simple CalendarStore query puts application into infinite loop!?

  - by Frank R.

  Hi, I've been looking at adding iCal support to my new application and everything seemed just fine and worked on my Mac OS X 10.6 Snow Leopard development machine without a hitch. Now it looks like depending on what is in your calendar the very simple query below: - (NSArray*) fetchCalendarEventsForNext50Minutes { NSLog(@"fetchCalendarEventsForNext50Minutes"); NSTimeInterval start = [NSDate timeIntervalSinceReferenceDate]; NSDate* startDate = [[NSDate alloc] init]; NSDate* endDate = [startDate addTimeInterval: 50.0 * 60.0]; NSPredicate *eventsForTheNext50Minutes = [CalCalendarStore eventPredicateWithStartDate:startDate endDate:endDate calendars:[[CalCalendarStore defaultCalendarStore] calendars]]; // Fetch all events for this year NSArray *events = [[CalCalendarStore defaultCalendarStore] eventsWithPredicate: eventsForTheNext50Minutes]; NSLog( @"fetch took: %f seconds", [NSDate timeIntervalSinceReferenceDate] - start ); return events; } produces a beachball thrash even with quite limited events in the calendar store. Am I missing something crucial here? The code snippet is pretty much exactly from the documentation at: // Create a predicate to fetch all events for this year NSInteger year = [[NSCalendarDate date] yearOfCommonEra]; NSDate *startDate = [[NSCalendarDate dateWithYear:year month:1 day:1 hour:0 minute:0 second:0 timeZone:nil] retain]; NSDate *endDate = [[NSCalendarDate dateWithYear:year month:12 day:31 hour:23 minute:59 second:59 timeZone:nil] retain]; NSPredicate *eventsForThisYear = [CalCalendarStore eventPredicateWithStartDate:startDate endDate:endDate calendars:[[CalCalendarStore defaultCalendarStore] calendars]]; // Fetch all events for this year NSArray *events = [[CalCalendarStore defaultCalendarStore] eventsWithPredicate:eventsForThisYear]; It looks like it has something to do with the recurrence rules, but as far as I can see there are no other ways of fetching events from the calendar store anyway. Has anybody else come across this? Best regards, Frank

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• QueryReadStore loads JSON into DataGrid, but JsonRestStore does not (from the same source)

  - by labratmatt

  I'm building a Dojo DataGrid from JSON data provided by my REST interface. The DataGrid loads the data fine using a QueryReadStore, but doesn't seem to work with the same same data piped into a JsonRestStore. I'm using the following Dojo libs with Dojo 1.4.1: dojo.require("dojox.data.JsonRestStore"); dojo.require("dojox.grid.DataGrid"); dojo.require("dojox.data.QueryReadStore"); dojo.require("dojo.parser"); I declare my stores in the following manner: var storeJRS = new dojox.data.JsonRestStore({target:"api/collaborations.php/1", idAttribute: 'items[].id'}); var storeQRS = new dojox.data.QueryReadStore({url:"api/collaborations.php/1", requestMethod:"get"}); I create my grid layout like this: var gridLayout = [ new dojox.grid.cells.RowIndex({ name: "Row #", width: 5, styles: "text-align: left;" }), { name: "Name", field: "name", styles: "text-align:right;", width:20 }, { name: "Description", field: "description", width:30 } ]; I create my DataGrid as follows: The above works, but if I use QueryReadStore as my store, the grid is created with the headers (Name, Description), but it isn't populated with any rows: <div dojoType="dojox.grid.DataGrid" jsid="grid3" store="storeQRS" structure="gridLayout" style="height:500px; width:1000px;"></div> Using FireBug, I can see that QueryReadStore is getting my JSON data from my REST interface. It looks like the following: {"numRows":6,"items":[{"name":"My Super Cool Collab","description":"This is for all the super cool people in the super cool group","id":1},{"name":"My Other Super Cool","description":"This is for all the other super cool people","id":3},{"name":"This is another coll","description":"This is just some other collab","id":4},{"name":"some new collab","description":"this is a new collab","id":5},{"name":"yet another new coll","description":"uh huh","id":6},{"name":"asdf","description":"asdf","id":7}]} Any ideas? Thanks.

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• Databinding combobox selected item to settings

  - by Tuukka

  I store user specified settings using application settings properties and databinding. It has been working fine, until i want user selected to font for combobox. Databinding between user settings and combobox not working. I want to store font family name. App.XML <Application.Resources> <ResourceDictionary> <properties:Settings x:Key="Settings" /> </ResourceDictionary> </Application.Resources> Window.XML <ComboBox Name="Families" ItemsSource="{x:Static Fonts.SystemFontFamilies}" <!-- This line --> SelectedItem="{Binding Source={StaticResource Settings}, Path=Default.Font, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Margin="57,122,199,118"> <ComboBox.ItemTemplate> <DataTemplate> <TextBlock Text="{Binding}" FontFamily="{Binding}"/> </DataTemplate> </ComboBox.ItemTemplate> </ComboBox> Settings: font String User Arial

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• storing/retrieving data for graph with long continuous stretches

  - by james

  i have a large 2-dimensional data set which i would like to graph. the graph is displayed in a browser and the data is retrieved via ajax. long stretches of this graph will be continuous - e.g., for x=0 through x=1000, y=9, then for x=1001 through x=1100, y=80, etc. the approach i'm considering is to send (from the server) and store (in the browser) only the points where the data changes. so for the example above, i would say data[0] = 9, then data[1001] = 80. then given x=999 for example, retrieving data[999] would actually look up data[0]. the problem that arises is finding a dictionary-like data structure which behaves like this. the approach i'm considering is to store the data in a traditional dictionary object, then also maintain a sorted array of key for that object. when given x=999, it would look at the mid-point of this array, determine whether the nearest lower key is left or right of that midpoint, then repeat with the correct subsection, etc.. does anyone have thoughts on this problem/approach?

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• How to architect Rails site that can be edited while running?

  - by Chris Kimpton

  Hi, I am writing a Rails app that "scrapes/navigates" some other websites and webservices for content. I am using Mechanize and Savon to do the heavylifting. But given the dynamic nature of the web, I'd like to make my calls to these editable by the admin users of the site - rather than requiring me to release a new version of the site. The actual scraping thread happens async to the website, using the daemons gem. My requirements are: Thinking that the scraping/webservice calling code is quite simple, the easiest route is to make the whole class editable by the admins. Keep a history of the scraping code - so that we can fairly easily revert if we introduce a problem. Initially use the code from the file system, but as soon as thats been edited and stored somewhere, to use that code instead. I am thinking my options are: Store the code in the db (with a history table for the old versions) Store the code in a private git repo somewhere and access that for the history/latest versions. I am thinking the git route might be easiest, given its raison d'etre is to track file history... But perhaps there is a gem/plugin that does all this for me, out of the box? Thanks in advance for any tips/advice. ~chris

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• Ruby - encrypted_strings

  - by Tom Andersen

  A bit of a Ruby newbie here - should be an easy question: I want to use the encrypted_strings gem to create a password encrypted string: (from http://rdoc.info/projects/pluginaweek/encrypted_strings) Question is: Everything works fine, but how come I don't need the password to decrypt the string? Say I want to store the string somewhere for a while,like the session. Is the password also stored with it? (which would seem very strange?). And no, I'm not planning on using 'secret-key' or any similar hack as a password. I am planning on dynamically generating a class variable @@password using a uuid, which I don't store other than in memory, and can change from one running of the program to the next. Symmetric: >> password = 'shhhh' => "shhhh" >> crypted_password = password.encrypt(:symmetric, :password => 'secret_key') => "qSg8vOo6QfU=\n" >> crypted_password.class => String >> crypted_password == 'shhhh' => true >> password = crypted_password.decrypt => "shhhh"

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• Autologin for web application

  - by Maulin

  We want to AutoLogin feature to allow user directly login using link into our Web Application. What is the best way achieve this? We have following approches in our mind. 1) Store user credentials(username/password) in cookie. Send cookie for authentication. e.g. http: //www.mysite.com/AutoLogin (here username/password will be passed in cookie) OR Pass user credentials in link URL. http: //www.mysite.com/AutoLogin?userid=<&password=< 2) Generate randon token and store user random token and user IP on server side database. When user login using link, validate token and user IP on server. e.g. http: //www.mysite.com/AutoLogin?token=< The problem with 1st approach is if hacker copies link/cookie from user machine to another machine he can login. The problem with 2nd approach is the user ip will be same for all users of same organization behind proxy. Which one is better from above from security perspective? If there is better solution which is other than mentioned above, please let us know.

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• How to create Dictionary object in AppDelegate to access objectkey in another ViewController

  - by TechFusion

  Hello, I have created Window Based application and tab bar controller as root controller. My objective is to store Text Field data values in one tab bar VC and will be accessible and editable by other VC and also retrievable when application start. I am looking to use NSDictionary class in AppDelegate so that I can access stroed Data Values with keys. //TestAppDelegate.h @interface { ..... .... NSDictionary *Data; } @property (nonatomic, retain) NSDictionary *Data; //TestAppDelegate.m #import "TestAppDelegate.h" NSString *kNamekey =@"Namekey"; NSString *kUserIDkey =@"UserIDkey"; NSString *kPasswordkey =@"Passwordkey"; @implemetation TestAppDelegate @synthesize Data; -(void)applicationDidFinishLaunching:(UIApplication)application { NSString *NameDefault; NSString *UserIDdefault; NSString *Passworddefault; NSString *testvalue = [[NSUserDefaults standardUserDefaults] stringForKey: kNamekey]; if(testvalue == nil) { NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys: NameDefault, kNamekey, UserIdefault kUserIDkey, Passwordefault kPasswordkey, nil]; self.Data = appDefaults; [[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults]; [[NSUserDefaults standardUserDefaults] synchronize]; } else { } } Here ViewController is ViewController of Navigation Controller which is attached with one tab bar.. I have attached xib file with ViewController //ViewController.h @interface IBOutlet UITextField *Name; IBOutlet UITextField *UserId; IBOutlet UITextField *Password; } @property(retain,nonatomic) IBOutlet UITextField *Name @property(retain,nonatomic) IBOutlet UITextField *UserId; @property(retain,nonatomic) IBOutlet UITextField *Password; -(IBAction)Save:(id)sender; @end Here in ViewController.m I want to store Text Field input data with key which are defined in AppDelegate. I have linked Save Barbutton with action. Here I am not getting how to access NSDictionary class with object and keys in ViewController. //ViewController.m -(IBAction)Save:(id)sender{ TestAppDelegate *appDelegate = (TestAppDelegate*)[[UIApplication sharedApplication] delegate]; //Here how to access knamekey here to set object(Name.test) value with key } Please guide me about this. Thanks,

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• PHP OOP: Providing Domain Entities with "Identity"

  - by sunwukung

  Bit of an abstract problem here. I'm experimenting with the Domain Model pattern, and barring my other tussles with dependencies - I need some advice on generating Identity for use in an Identity Map. In most examples for the Data Mapper pattern I've seen (including the one outlined in this book: http://apress.com/book/view/9781590599099) - the user appears to manually set the identity for a given Domain Object using a setter: $UserMapper = new UserMapper; //returns a fully formed user object from record sets $User = $UserMapper->find(1); //returns an empty object with appropriate properties for completion $UserBlank = $UserMapper->get(); $UserBlank->setId(); $UserBlank->setOtherProperties(); Now, I don't know if I'm reading the examples wrong - but in the first $User object, the $id property is retrieved from the data store (I'm assuming $id represents a row id). In the latter case, however, how can you set the $id for an object if it has not yet acquired one from the data store? The problem is generating a valid "identity" for the object so that it can be maintained via an Identity Map - so generating an arbitrary integer doesn't solve it. My current thinking is to nominate different fields for identity (i.e. email) and demanding their presence in generating blank Domain Objects. Alternatively, demanding all objects be fully formed, and using all properties as their identity...hardly efficient. (Or alternatively, dump the Domain Model concept and return to DBAL/DAO/Transaction Scripts...which is seeming increasingly elegant compared to the ORM implementations I've seen...)

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• Fastest PNG decoder for .NET

  - by sboisse

  Our web server needs to process many compositions of large images together before sending the results to web clients. This process is performance critical because the server can receive several thousands of requests per hour. Right now our solution loads PNG files (around 1MB each) from the HD and sends them to the video card so the composition is done on the GPU. We first tried loading our images using the PNG decoder exposed by the XNA API. We saw the performance was not too good. To understand if the problem was loading from the HD or the decoding of the PNG, we modified that by loading the file in a memory stream, and then sending that memory stream to the .NET PNG decoder. The difference of performance using XNA or using System.Windows.Media.Imaging.PngBitmapDecoder class is not significant. We roughly get the same levels of performance. Our benchmarks show the following performance results: Load images from disk: 37.76ms 1% Decode PNGs: 2816.97ms 77% Load images on Video Hardware: 196.67ms 5% Composition: 87.80ms 2% Get composition result from Video Hardware: 166.21ms 5% Encode to PNG: 318.13ms 9% Store to disk: 3.96ms 0% Clean up: 53.00ms 1% Total: 3680.50ms 100% From these results we see that the slowest parts are when decoding the PNG. So we are wondering if there wouldn't be a PNG decoder we could use that would allow us to reduce the PNG decoding time. We also considered keeping the images uncompressed on the hard disk, but then each image would be 10MB in size instead of 1MB and since there are several tens of thousands of these images stored on the hard disk, it is not possible to store them all without compression.

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• How can I randomly iterate through a large Range?

  - by void

  I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: class Array def shuffle ret = dup j = length i = 0 while j > 1 r = i + rand(j) ret[i], ret[r] = ret[r], ret[i] i += 1 j -= 1 end ret end end (0..9).to_a.shuffle.each{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle is used to efficiently provide random ordering. My problem is that shuffle needs to operate on an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. Imagine replacing (0..9) with (0..99**99). This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do? [Edit1]: Why do I want to do this? I'm trying to exhaust the search space of a hash algorithm for a N-length input string looking for partial collisions. Each number I generate is equivalent to a unique input string, entropy and all. Basically, I'm "counting" using a custom alphabet. [Edit2]: This means that f(x) in the above examples is a method that generates a hash and compares it to a constant, target hash for partial collisions. I do not need to store the value of x after I call f(x) so memory should remain constant over time. [Edit3/4/5/6]: Further clarification/fixes.

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• CouchDB, HDFS, HBase or which is right for my situation?

  - by Lucas

  Hello all, This question is regarding data storage systems such as CouchDB, HDFS and HBase, specifically, which is right. I am looking at making a simple and customized Document Management System for my organization. Basically, we need the ability to store some Word Documents, PDFs and other similar files. I also want to store metadata about these files (e.g., Author, Dates, etc). Usage permissions would also be handy, but that can probably be built using meta-data. I would also need the ability to full-text index. The ability to version, while not required would be extremely useful. I would like the ability to simply add hardware to expand the resources of the system and the system must support Network Attached Storage over the CIFS or NFS protocol(s). I have read about CouchDB, HDFS and HBase. My preferred programming language is C# as all of my end-users will be running Windows machines and I will want to make both web and winforms client implementations. My question is which solution best fits my needs? Based on my research it appears that CouchDB (utilizing the CouchDB-Lounge and CouchDB-Lucene) perfectly fits my needs. However, I am worried that since I have worked with CouchDB that I might be overlooking something useful for my needs in HDFS or HBase or something similar due to a bias. Any and all opinions are welcome as I am looking for the community input as I really do not want to make the wrong choice at the start of my project. Please ask if you need more information. I thank you all for your time, input and assistance.

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• Converting non-delimited text into name/value pairs in Delphi

  - by robsoft

  I've got a text file that arrives at my application as many lines of the following form: <row amount="192.00" store="10" transaction_date="2009-10-22T12:08:49.640" comp_name="blah " comp_ref="C65551253E7A4589A54D7CCD468D8AFA" name="Accrington "/> and I'd like to turn this 'row' into a series of name/value pairs in a given TStringList (there could be dozens of these <row>s in the file, so eventually I will want to iterate through the file breaking each row into name/value pairs in turn). The problem I've got is that the data isn't obviously delimited (technically, I suppose it's space delimited). Now if it wasn't for the fact that some of the values contain leading or trailing spaces, I could probably make a few reasonable assumptions and code something to break a row up based on spaces. But as the values themselves may or may not contain spaces, I don't see an obvious way to do this. Delphi' TStringList.CommaText doesn't help, and I've tried playing around with Delimiter but I get caught-out by the spaces inside the values each time. Does anyone have a clever Delphi technique for turning the sample above into something resembling this? ; amount="192.00" store="10" transaction_date="2009-10-22T12:08:49.640" comp_name="blah " comp_ref="C65551253E7A4589A54D7CCD468D8AFA" name="Accrington " Unfortunately, as is usually the case with this kind of thing, I don't have any control over the format of the data to begin with - I can't go back and 'make' it comma delimited at source, for instance. Although I guess I could probably write some code to turn it into comma delimited - would rather find a nice way to work with what I have though. This would be in Delphi 2007, if it makes any difference.

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• Can't connect to HTTPS using X509 client certificate

  - by wows

  Hi - I'm new to cryptography and I'm a bit stuck: I'm trying to connect (from my development environment) to a web service using HTTPS. The web service requires a client certificate - which I think I've installed correctly. They have supplied me with a .PFX file. In Windows 7, I double clicked the file to install it into my Current User - Personal certificate store. I then exported a X509 Base-64 encoded .cer file from the certificate entry in the store. It didn't have a private key associate with it. Then, in my app, I'm attempting to connect to the service like this: var certificate = X509Certificate.CreateFromCertFile("xyz.cer")); var serviceUrl = "https://xyz"; var request = (HttpWebRequest) WebRequest.Create(serviceUrl); request.ClientCertificates.Add(certificate); request.Method = WebRequestMethods.Http.Post; request.ContentType = "application/x-www-form-urlencoded"; I get a 502 Connection failed when I connect. Is there anything you can see wrong with this method? Our production environment seems to work with a similar configuration, but it's running Windows Server 2003. Thanks!

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• Getting a users Facebook profile url

  - by Greg Pabst

  I am creating a registry site so similar people can find each other easily. I don't want to use Facebook Connect as the primary log in method or use Facebook to store their information. I'll be creating a database on my end to store that info. For security reasons I won't be displaying the users address, phone number or email address so I wanted to provide the next best way for people to connect with each other, this is where Facebook comes in. Normally I would just ask them to type their Facebook URL in a text box but I don't think most people know what their url is which is why I think I need to use Facebook Connect. So here is my idea..when the users signs up there is a check box that when checked signifies they are allowing people to find them on Facebook. I assume once they click the register button that a Facebook Connect popup will show up asking for permission to access their Facebook account. When they "allow" it, then I can get their profile url. All I need is their Facebook profile url, I don't want any other Facebook features or information. Is Facebook Connect the best thing to use for this scenario? Is there an easier way? Several months ago on the Facebook Connect site their used to be examples of doing this, but all the documentation has been rearranged and changed and I can't seem to find the information. Any help you can provide would be great!

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• How to create database records for a financial year

  - by David A Gibson

  Hello, I need to create entities (specifically contracts) in a database table that are associated with a financial year. These contracts will be applied to projects. Any contract variation will be recorded by creating a new contract record for the same financial year but the original will remain associated with the project as a history. The projects can last several years and so at any one time a project will have a live contract record for each year as well as any number of historic contracts for that year. All of which is incidental but I'm trying to provide some context. If the contracts where for the year - it would be easy and I'd just store the Year either as a date field with the 1st of January or just an Integer. However the contracts run for financial years and I don't know how to approach this. I don't want a separate table containing the financial years as I don't want the users to have to maintain this. I don't want to store the financial year as a string "2009/2010" as this is not ideal for sorting/extracting the data. Any ideas will be helpful, my best so far is to have starting and ending year in 2 columns and just "KNOW" that starting is April of the year etc Thanks

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